Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Space Suits”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,099 records · Page 61Linked to original sources
PubMed2002

Europa as an abode of life.

Life as we know it on Earth depends on liquid water, a suite of 'biogenic' elements (most famously carbon) and a useful source of free energy. Here we review Europa's suitability for life from the perspective of these three requirements. It is likely, though not yet certain, that Europa harbors a subsurface ocean of liquid water whose volume is about twice that of Earth's oceans. Little is known about Europa's inventory of carbon, nitrogen, and other biogenic elements, but lower bounds on these can be placed by considering the role of commentary delivery over Europa's history. Sources of free energy are challenging for a world covered with an ice layer kilometers thick, but it is possible that hydrothermal activity and/or organics and oxidants provided by the action of radiation chemistry at Europa's surface and subsequent mixing into Europa's ocean could provide the electron donors and acceptors needed to power a Europan ecosystem. It is not premature to draw lessons from the search for life on Mars with the Viking spacecraft for planning exobiological missions to Europa.

Carbon↗
PubMed1998

Search for life on Mars.

A multi-user integrated suite of instruments designed to optimize the search for evidence of life on Mars is described. The package includes: -Surface inspection and surface environment analysis to identify the potential Mars landing sites, to inspect the surface geology and mineralogy, to search for visible surficial microbial macrofossils, to study the surface radiation budget and surface oxidation processes, to search for niches for extant life. -Subsurface sample acquisition by core drilling -Analysis of surface and subsurface minerals and organics to characterize the surface mineralogy, to analyse the surface and subsurface oxidants, to analyse the mineralogy of subsurface aliquots, to analyse the organics present in the subsurface aliquots (elemental and molecular composition, isotopes, chirality). -Macroscopic and microscopic inspection of subsurface aliquots to search for life's indicators (paleontological, biological, mineralogical) and to characterize the mineralogy of the subsurface aliquots. The study is led by ESA Manned Spaceflight and Microgravity Directorate.

Europe↗
PubMed1995

Reciprocity of hemodynamic changes during lower body negative and positive pressure.

Lower body negative pressure (LBNP) and lower body positive pressure (LBPP) are two opposite environments for the lower abdomen and lower extremities. We examined RR interval (RRI), blood pressure, forearm blood flow, cardiac output, plasma atrial natriuretic factor, and plasma catecholamines during sequentially administered LBNP and LBPP in order to define the cardiovascular and neuroendocrine reciprocity of these models of orthostasis (LBNP) and anti-orthostasis (LBPP). Six healthy young men were studied with a ramped onset of LBNP followed by a similarly ramped LBPP, spaced between periods of data acquisition during rest. Forearm blood flow decreased during LBNP and increased during LBPP. However, LBNP and LBPP did not produce reciprocal changes in cardiac output. No reciprocal changes were found in plasma catecholamines and plasma atrial natriuretic factor. The variability of RRI and systolic/diastolic blood pressures were analyzed within two bandwidths of interest: the low bandwidth, corresponding to the frequency of baroreflex-mediated variability (0.04 to 0.12 Hz), and the high bandwidth, representative of parasympathetically mediated variability at the frequency of respiration (0.22 to 0.28 Hz). The ratio of high to low bandwidth RRI variability was reciprocally diminished during LBNP and increased during LBPP, reflecting a relative decrease in the level of parasympathetic tone during LBNP and an increase during LBPP. In addition, the variability of the DBP within the low baroreflex bandwidth increased during LBNP and decreased during LBPP. The phase lag of RRI variability in relation to BP variability did not change reciprocally.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2002

Insulin: discovery and controversy.

During the first two decades of the 20th century, several investigators prepared extracts of pancreas that were often successful in lowering blood sugar and reducing glycosuria in test animals. However, they were unable to remove impurities, and toxic reactions prevented its use in humans with diabetes. In the spring of 1921, Frederick G. Banting, a young Ontario orthopedic surgeon, was given laboratory space by J.J.R. Macleod, the head of physiology at the University of Toronto, to investigate the function of the pancreatic islets. A student assistant, Charles Best, and an allotment of dogs were provided to test Banting's hypothesis that ligation of the pancreatic ducts before extraction of the pancreas, destroys the enzyme-secreting parts, whereas the islets of Langerhans, which were believed to produce an internal secretion regulating sugar metabolism, remained intact. He believed that earlier failures were attributable to the destructive action of trypsin. The name "insuline" had been introduced in 1909 for this hypothetic substance. Their experiments produced an extract of pancreas that reduced the hyperglycemia and glycosuria in dogs made diabetic by the removal of their pancreases. They next developed a procedure for extraction from the entire pancreas without the need for duct ligation. This extract, now made from whole beef pancreas, was successful for treating humans with diabetes. Facilitating their success was a development in clinical chemistry that allowed blood sugar to be frequently and accurately determined in small volumes of blood. Success with purification was largely the work of J.B. Collip. Yield and standardization were improved by cooperation with Eli Lilly and Company. When the Nobel Prize was awarded to Banting and Macleod for the discovery of insulin, it aggravated the contentious relationship that had developed between them during the course of the investigation. Banting was outraged that Macleod and not Best had been selected, and he briefly threatened to refuse the award. He immediately announced that he was giving one-half of his share of the prize money to Best and publicly acknowledged Best's contribution to the discovery of insulin. Macleod followed suit and gave one-half of his money award to Collip. Years later, the official history of the Nobel Committee admitted that Best should have been awarded a share of the prize.

Animals↗
PubMed2006

[Adult lateral meniscus].

Meniscal lesion does not mean meniscectomy and this is particularly true for the lateral meniscus. The reputation of mildness of the meniscectomy is usurped. The rate of joint space narrowing after lateral meniscectomy is of 40% at a follow-up of 13 years compared to 28% for the medial meniscus (symposium SFA 1996). Several arguments explain those results: biomechanical: the lateral meniscus contributes to the congruence; particularly the lateral meniscus is the zone where antero-posterior translational during knee flexion is 12 mm. The pejorative effects of lateral meniscectomy have conducted, more though to the medial meniscus, to the concept of meniscal economy. Lateral meniscectomy must be as partial as possible. Particularly, a discoid meniscus presenting a complete tear should be treated by a meniscoplasty in order to shape the meniscus in a more anatomic form than a total meniscectomy. Lateral meniscectomy is indicated in complex or horizontal cleavage, symptomatic, on stable knees. A particular case is the cyst of the lateral meniscus. It is a cystic subcutaneous formation, usual consequence of a horizontal cleaved meniscus of which the particularity is that it opens besides the articulation. The strategy must not consist in the isolated treatment of the cyst. This pathology should be addressed by an arthroscopic meniscectomy reaching the meniscosynovial junction at the level of the cyst. Meniscal repair must be proposed every time if possible. Criteria of reparability are better studied on MRI. Preoperatively MRI is the first choice radiological exam. Two essential indications can be held back: the vertical peripheral longitudinal lesion is on the non-vascularized area, and the horizontal cleaving of the junior athlete (if the cleaving remains purely intra meniscal). Meniscal repair is highly performed when the meniscal tear is associated to a rupture of the ACL (simultaneous reconstruction of the LCA). Postoperative outcome is different of that of a "simple" arthroscopic meniscectomy. The healing process being slow, it suits to protect the suture by a splint in the first month, and with an exclusion of sports with knee torsion during 6 months. Functional results (absence of secondary meniscectomy) and anatomical results (reality of the cicatrisation) are good in 77% of cases (symposium of the French Society of Arthroscopy 2003) at a follow-up of 55 months. Survivorship analysis indicates that majority of the failures occur within two years: this testifies a default of primary cicatrisation. At the studied follow-up, meniscal repair was efficient to protect the cartilage. Lateral meniscus results are better that medial meniscus one. Those data support indications: All suspicion of meniscal lesion must have an MRI preoperatively to confirm the lesion, to localize her and to search criteria of reparability; All vertical longitudinal peripheral lesions can and must be repaired especially in young patients and children; All horizontal cleaving of the junior athletes should be treated by open repair; surgical abstention must be proposed when the lesion is non symptomatic, or when lesion is limited and associated to an ACL tear (in that case isolated ACL reconstruction is proposed), or when clinical symptoms are minimal; Meniscectomy, always arthroscopic, is proposed for a symptomatic lesion in the avascular zone or for a deep horizontal cleavage or a complex tear; Tear of the discoid meniscus should be treated by meniscoplasty. A painful knee after lateral meniscectomy might be due to a too limited initial meniscectomy: an iterative meniscectomy may be indicated or lateral femorotibial arthritis, especially after subtotal or total meniscectomy. In this last case and after failure of usual medical treatment such as viscosupplementation surgery may be indicated. Osteotomy in order to unload the lateral femorotibial compartment gives a partial response as the shearing forces remain. This osteotomy is indicated only if the lower limb axis is normal or in valgus. Meniscal allograft is an option in young patients in grade I or II arthritis. Results are promising. Rene Verdonk's series show a survivorship analysis of 75% at 7 years. Early diagnosis of a postmeniscectomy syndrome before cartilaginous lesions occur is essential for an adapted treatment. In conclusion, lateral meniscectomy are less frequent than those of the medial meniscus but their prognosis is less favorable. They should be early diagnosed (MRI). Treatment options are various: abstention, meniscectomy, and repair. Painful post lateral meniscectomy syndrome may be treated by a new surgical option: meniscal allograft.

Cysts↗
PubMedDate not supplied

Measuring eye movements during locomotion: filtering techniques for obtaining velocity signals from a video-based eye monitor.

Video-based eye-tracking systems are especially suited to studying eye movements during naturally occurring activities such as locomotion, but eye velocity records suffer from broad band noise that is not amenable to conventional filtering methods. We evaluated the effectiveness of combined median and moving-average filters by comparing prefiltered and postfiltered records made synchronously with a video eye-tracker and the magnetic search coil technique, which is relatively noise free. Root-mean-square noise was reduced by half, without distorting the eye velocity signal. To illustrate the practical use of this technique, we studied normal subjects and patients with deficient labyrinthine function and compared their ability to hold gaze on a visual target that moved with their heads (cancellation of the vestibulo-ocular reflex). Patients and normal subjects performed similarly during active head rotation but, during locomotion, patients held their eyes more steadily on the visual target than did subjects.

Adult↗
PubMed1979

The reproductive ecology of the house mouse.

This paper attempts to integrate the physiological and ecological perspectives of the reproductive biology of the house mouse (Mus musculus). The endeavor is made within a larger context to provide a prototype for mammalian reproductive ecology in general. Specifically, the environmental regulation of the reproduction of Mus musculus is examined in relation to its ecological opportunism and, in particular, in relation to its history of global colonization. House mice can live as commensals of man or under totally feral conditions. Stable, high density, commensal populations are characterized by an insular division of the living space into demeterritories, each dominated by a single male. Feral populations typically are characterized by temporal, spatial, and social instability. Territoriality is improbable under such conditions, particularly given the necessity for large home ranges in most feral habitats. In both feral and commensal populations, however, male aggressiveness promotes the large-scale dispersal of young, all of which are potential colonizers. Of the ten or so environmental factors known to influence reproduction in house mice, seven probably are of routine importance in natural populations: diurnal modulation by daily light:dark cycles; caloric intake; nutrition; extreme temperature; agaonistic stimuli; socio-tactile cues; and priming pheronomes. The last two factors named operate directly on the secretion of luteinizing hormone or prolactin; the others act at many points in the reproductive system. Reproduction in the house mouse seems divorced from photoperiodically induced seasonality; indeed, this species breeds well even in constant darkness. Seasonal breeding may or may not then occur, depending upon dietary considerations, with or without a secondary interaction with variation in ambient temperature. There is no evidence for a dependence upon secondary plant compounds. Some of the effects of priming pheromones that have been observed previously in laboratory mice probably play no meaningful role in wild populations. The remaining pheromonal phenomena can be conceptualized as a single cueing system that has three components: (a) urinary cues of socially dominant males can accelerate ovulation in females, adult or prepubertal; (b) female urinary cues may elevate pheromonal potency in adult males, thereby forming a feedback loop by which the females elicit their own ovulation; and (c) the male's action on prepubertal females can be blocked by urinary cues emanating from other females. When all of the above is viewed in toto, the reproductive biology of the house mouse seems uniquely suited to support ecological opportunism. The relatively few environmental inhibitors of reproduction in this species should enhance the ability of dispersing young to colonize an exceptionally wide variety of habitats and climates...

Animals↗
PubMed1988

Decompression sickness and bubble formation in females exposed to a simulated 7.8 psia suit environment.

The purpose of this study was to measure female susceptibility to decompression sickness (DCS) during simulated extravehicular activity (EVA) at a candidate (7.8 psia) suit pressure. Thirty female volunteer subjects, in groups of three, were exposed to three consecutive daily EVA simulations at 7.8 psia (5,031 m altitude equivalent) continuously for 6 h. During each altitude exposure, the subjects breathed a gas mixture of 50% oxygen/50% nitrogen, and participated in exercise workloads similar to those expected to be experienced by astronauts during a typical EVA scenario. Precordial Doppler bubble monitoring was accomplished after each cycle of exercise workload simulations. During at least 1 of the 3 days (d) of exposure, 43% of the subjects experienced intravenous bubbling. Of the 30 subjects, 17 (57%) did not experience detectable bubbling on any of the 3 d of exposure and 5 (17%) developed decompression sickness (DCS) during the study. Two cases were delayed, occurring after recompression to ground level; and three subjects required hyperbaric oxygen treatment. The results of this study suggest that female subjects may suffer more delayed DCS symptoms, necessitating hyperbaric oxygen treatment, than their male counterparts under the same experimental conditions. Female subjects did not experience intravenous bubbling as frequently as male subjects when exposed to these study conditions.

Adult↗
PubMed1995

MR imaging of the retroperitoneum.

The diagnosis of retroperitoneal pathology has historically presented a challenge to physicians. The signs and symptoms of retroperitoneal diseases are myriad and often subtle. Cross-sectional imaging techniques have therefore had a major impact on retroperitoneal diagnosis. Computed tomography (CT) is currently the standard imaging technique for evaluating the retroperitoneum. Magnetic resonance (MR) imaging is also well suited for retroperitoneal imaging and has several advantages over CT. MR imaging is the preferred technique in patients with contraindications to iodinated contrast material due to renal dysfunction or allergy. It excels at evaluating the blood vessels, providing a reliable assessment of vessel patency, aneurysm, or dissection. The ability of MR imaging to acquire images without exposure to ionizing radiation facilitates imaging of obstetric and pediatric patients. The ability to acquire images in any plane is a distinct advantage for assessing the extent and origin of retroperitoneal pathology, although this can now be accomplished with spiral CT as well as MR imaging. The spatial resolution of CT is currently superior to MR imaging for most retroperitoneal studies, but this may change with continued technological advances such as improved phased array coil systems (Bidgood WD Jr, Schiebler ML. Retroperitoneum and mesentery. In: Ros PR, Bidgood WD Jr, eds. Abdominal magnetic resonance imaging. St. Louis: Mosby Year Book, 1993:310-47). Finally, MR imaging provides the flexibility to tailor each examination to the specific clinical question. With few exceptions, anything CT can do in the retroperitoneum, MR imaging can do as well or better.

Aortic Diseases↗
PubMed2006

Understanding the origin of metal-sulfur vibrations in an oxo-molybdenum dithiolene complex: relevance to sulfite oxidase.

X-ray crystallography and resonance Raman (rR) spectroscopy have been used to further characterize (Tp*)MoO(qdt) (Tp* is hydrotris(3,5-dimethyl-1-pyrazolyl)borate and qdt is 2,3-quinoxalinedithiolene), which represents an important benchmark oxomolybdenum mono-dithiolene model system relevant to various pyranopterin Mo enzyme active sites, including sulfite oxidase. The compound (Tp*)MoO(qdt) crystallizes in the triclinic space group, P1, where a = 9.8424 (7) A, b = 11.2323 (8) A, c = 11.9408 (8) A, alpha = 92.7560 (10) degrees, beta = 98.9530 (10) degrees, and gamma = 104.1680 (10) degrees. The (Tp*)MoO(qdt) molecule exhibits the distorted six-coordinate geometry characteristic of related oxo-Mo(V) systems possessing a single coordinated dithiolene ligand. The first coordination sphere bond lengths and angles in (Tp*)MoO(qdt) are very similar to the corresponding structural parameters for (Tp*)MoO(bdt) (bdt is 1,2-benzenedithiolene). The relatively small inner-sphere structural variations observed between (Tp*)MoO(qdt) and (Tp*)MoO(bdt) strongly suggest that geometric effects are not a major contributor to the significant electronic structural differences reported for these two oxo-Mo(V) dithiolenes. Therefore, the large differences observed in the reduction potential and first ionization energy between the two molecules appear to derive primarily from differences in the effective nuclear charges of their respective sulfur donors. However, a subtle perturbation to Mo-S bonding is implied by the nonplanarity of the dithiolene chelate ring, which is defined by the fold angle. This angular distortion (theta = 29.5 degrees in (Tp*)MoO(qdt); 21.3 degrees in (Tp*)MoO(bdt)) observed between the MoS2 and S-C=C-S planes may contribute to the electronic structure of these oxo-Mo dithiolene systems by controlling the extent of S p-Mo d orbital overlap. In enzymes, the fold angle may be dynamically modulated by the pyranopterin, thereby functioning as a transducer of vibrational energy associated with protein conformational changes directly to the active site via changes in the fold angle. This process could effectively mediate charge redistribution at the active site during the course of atom- and electron-transfer processes. The rR spectrum shows bands at 348 and 407 cm(-1). From frequency analysis of the normal modes of the model, [(NH3)3MoO(qdt)]1+, using the Gaussian03 suite of programs, these bands are assigned as mixed-mode Mo-S vibrations of the five-membered Mo-ditholene core structure. Raman spectroscopy has also provided additional evidence for an in-plane pseudo-sigma dithiolene S-Mo d(xy) covalent bonding interaction in (Tp*)MoO(qdt) and related oxo-Mo-dithiolenes that has implications for electron-transfer regeneration of the active site in sulfite oxidase involving the pyranopterin dithiolene.

Crystallography, X-Ray↗
PubMed1997

The present and future role of intraoperative MRI in neurosurgical procedures.

OBJECTIVE: We have worked in conjunction with scientists from the General Electric Corporation over 6 years to develop an open-bore MR imaging system (0.5 T) enabling optimal vertical access of surgeon and assistant to the patient, and real-time imaging during major neurosurgical procedures. METHODS: The intraoperative MR system (MRT) is located in a specially modified operative suite that combines the features of an MR-imaging suite with a fully functional operating room. An MR-compatible anesthesia machine and patient-monitoring device are located next to the magnet. The position of instruments, platforms and supports may be mapped in the operative field using 3 charge-coupled device video cameras mounted in the overhead support truncheon that follow various light-emitting diodes on the devices (Pixsys). The MR image plane can be defined as the axial, coronal or sagittal views through a point along the vector beneath the Pixsys tripod. A variety of surface coils were designed to take full advantage of full open patient access. The software, implemented by a technologist located outside the MR room, is now equivalent to that available on the commercial 0.5-tesla Signa Advantage system. Development of very robust 3-dimensional software in conjunction with the Surgical Planning Laboratory (SPL) at the Brigham & Women's Hospital is the subject of significant effort. The MRT system has been shown to possess imaging capabilities comparable, or even slightly superior (by 10%), to a conventional 0.5-tesla MR scanner. Two modified liquid-crystal display screens are mounted on the magnet housing for the surgeon to monitor the images during the procedures. Projection into larger screens or the operating microscope is under development. RESULTS: We have performed 110 neurosurgical cases in MRT as of January 29, 1997, including 47 biopsies, 6 catheter placements, 4 cyst drainages, 47 craniotomies for resection, 3 spinal cases (1 syrinx drainage), and 3 laser tumor ablations. CONCLUSIONS: MRT is especially useful in guiding biopsies and resections near cysts, ventricles and critical vascular structures where preoperative images with framed/frameless techniques would be inadequate to show anatomic changes during the procedure. Real-time images of a biopsy needle within the abnormal area are very useful in cases of subtle pathologic change. More complete resection of infiltrative tumor is readily accomplished. SPL image fusion of SPECT and neurofunctional data (e.g. from magnetic stimulation preoperatively) into the imaging space enables the surgeon to better visualize tumor invasion or neural function in real-time imaging during resection. Imaging of thermal gradients for cryoprobe or laser ablation, and combination with endoscopy and robotics will offer additional benefit in the performance of difficult neurosurgical procedures.

Biopsy↗
PubMed1999

Taxane-induced apoptosis decompresses blood vessels and lowers interstitial fluid pressure in solid tumors: clinical implications.

Elevated tumor interstitial fluid pressure (IFP) is partly responsible for the poor penetration and distribution of therapeutic agents in solid tumors. The etiology of tumor interstitial hypertension is poorly understood. We have postulated that the solid stress generated by tumor cells growing in a confined space compresses blood vessels and increases tumor microvascular pressure and IFP. To test the hypothesis that neoplastic cell loss would decompress blood vessels and lower IFP, we induced apoptosis in tumors with paclitaxel and docetaxel. Taxanes inhibited the growth of the murine mammary carcinoma (MCa-IV) and of the human soft tissue sarcoma (HSTS-26T). Taxanes induced apoptosis and reduced the density of intact neoplastic cells in both MCa-IV and HSTS-26T. To determine whether neoplastic cell loss decompressed blood vessels, we measured the diameter of tumor vessels in HSTS-26T tumors implanted in transparent dorsal skin fold chambers. At 48 and 96 h after paclitaxel, the diameter of tumor vessels was significantly increased. The increase in vascular diameters was associated with reductions in microvascular pressure and IFP. The changes in neoplastic cell density and IFP were also correlated. In the human glioblastoma U87, which is resistant to paclitaxel, the IFP and cellular density were not modified by paclitaxel treatment. Collectively, these results support the hypothesis that solid stress generated by neoplastic cell proliferation increases vascular resistance and IFP. The increase in vessel diameter induced by paclitaxel and docetaxel suggests that taxanes could improve tumor response by increasing the vascular surface area for delivery of therapeutic agents.

Animals↗
PubMed1996

Competition in a spatially heterogeneous environment: modelling the risk of spread of a genetically engineered population.

In recent years regulations have been developed to address the risks of releasing genetically engineered organisms into the natural environment. These risks are generally considered to be proportional to the exposure multiplied by the hazard. Exposure is, in part, determined by the spatial spread of the organisms, a component of risk suited to mathematical analysis. In this paper we exampine a mathematical model describing the spread of organisms introduced into a hetereogeneous environment, focusing on the risk of spread and plausibility of containment strategies. Two competing populations are assumed, one the natural species and the other an engineered species or strain, both of which move randomly in a spatially heterogenous environment consisting of alternating favourable and unfavourable patches. The classical Lotka-Volterra competition model with diffusion is used. Analyses of the possible spread and invasion of engineered organisms are thus reduced to finding periodic travelling wave solutions to the model equations. We focus on whether a very small number of engineered organisms can spatially invade a natural population. Initially we investigate the problem for spatially periodic diffusion coefficients and demonstrate that, under the right circumstances and a large enough unfavourable patch, invasion does not succeed. However, if spatially periodic carrying capacities are assumed along with spatially varying diffusion rates, the situation is far more complex. In this case containment of the engineered species is no longer only a simple function of the unfavourable patch length. By using perturbation solutions to the nonuniform steady states, approximate invasion conditions are obtained.

DNA, Recombinant↗
PubMedDate not supplied

The vascular endothelium: a survey of some newly evolving biochemical and physiological features.

The morphological, biochemical and functional characterization of the vascular endothelium has become possible through the broad use of electron microscopic methods, the successful elaboration and application of techniques for the isolation and cultivation of endothelial cells in vitro and through sophisticated studies on vessel and organ preparations, both in vitro and in vivo. In this survey emphasis is placed on certain methodological aspects of endothelial cell culture as well as on biochemical, physiological and pathophysiological features of the vascular endothelium. Endothelial cells can be propagated in culture dishes, the most commonly applied method, on suspended microbeads (dextrane, polyacrylamide), a technique giving large yields, or on thin porous membranes, a procedure suited for the study of transport processes across the endothelial layer. Different structural, biochemical and functional properties of the luminal (apical) and abluminal (basal) cell membrane determine important polarity features of the endothelium. Endothelial cells exhibit a variety of biochemical pathways and are characterized by high metabolic activities. Of particular interest is the large content of ATP in endothelial cells of different vascular origin. The rapid intracellular degradation of adenine nucleotides to nucleosides and bases, which are constantly released, is balanced by synthesis, mainly via salvage pathways. In endothelial cells of microvascular origin uric acid predominates by far as the final purine degradative because of the presence of xanthine dehydrogenase in these cells; in the macrovascular endothelium purine breakdown proceeds only to hypoxanthine, since xanthine dehydrogenase is lacking. In this connection interrelations between nucleotide catabolism in myocardial tissue and in coronary endothelial cells are discussed, also with respect to the participation of endothelial xanthine oxidase in the formation of oxygen radicals during post-ischemic reperfusion of the heart. Vascular endothelial cells of different origin are also capable of a rapid extracellular degradation of ATP, ADP and AMP to adenosine by means of specific ecto-nucleotidases. The subsequent fate of extracellularly formed adenosine appears to be different for endothelial cells of microvascular (preferential adenosine uptake) and macrovascular origin (preferential extracellular adenosine accumulation), thus implying functional consequences for platelet aggregation.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenine Nucleotides↗
PubMed2005

Factors governing the substrate recognition by GroEL chaperone: a sequence correlation approach.

The chaperonin GroEL binds to a large number of polypeptides, prevents their self-association, and mediates appropriate folding in a GroES and adenosine triphosphate-dependent manner. But how the GroEL molecule actually recognizes the polypeptide and what are the exact GroEL recognition sites in the substrates are still poorly understood. We have examined more than 50 in vivo substrates as well as well-characterized in vitro substrates, for their binding characteristics with GroEL. While addressing the issue, we have been driven by the basic concept that GroES, being the cochaperonin of GroEL, is the best-suited substrate for GroEL, as well as by the fact that polypeptide substrate and GroES occupy the same binding sites on the GroEL apical domain. GroES interacts with GroEL through selective hydrophobic residues present on its mobile loop region, and we have considered the group of residues on the GroES mobile loop as the key element in choosing a substrate for GroEL. Considering the hydrophobic region on the GroES mobile loop as the standard, we have attempted to identify the homologous region on the peptide sequences in the proteins of our interest. Polypeptides have been judged as potential GroEL substrates on the basis of the presence of the GroES mobile loop-like hydrophobic segments in their amino acid sequences. We have observed 1 or more GroES mobile loop-like hydrophobic patches in the peptide sequence of some of the proteins of our interest, and the hydropathy index of most of these patches also seems to be approximately close to that of the standard. It has been proposed that the presence of hydrophobic patches having substantial degree of hydropathy index as compared with the standard segment is a necessary condition for a peptide sequence to be recognized by GroEL molecules. We also observed that the overall hydrophobicity is also close to 30% in these substrates, although this is not the sufficient criterion for a polypeptide to be assigned as a substrate for GroEL. We found that the binding of aconitase, alpha-lactalbumin, and murine dihydrofolate reductase to GroEL falls in line with our present model and have also predicted the exact regions of their binding to GroEL. On the basis of our GroEL substrate prediction, we have presented a model for the binding of apo form of some proteins to GroEL and the eventual formation of the holo form. Our observation also reveals that in most of the cases, the GroES mobile loop-like hydrophobic patch is present in the unstructured region of the protein molecule, specifically in the loop or beta-sheeted region. The outcome of our study would be an essential feature in identifying a potential substrate for GroEL on the basis of the presence of 1 or more GroES mobile loop-like hydrophobic segments in the amino acid sequence of those polypeptides and their location in three-dimensional space.

Amino Acid Sequence↗
PubMed1991

Recurrent group A streptococcal carriage in a health care worker associated with widely separated nosocomial outbreaks.

Nine postpartum infections (five bacteremias, three cases of endometritis without bacteremia, and one infected episiotomy site) caused by an M-nontypable, T-28 strain of group A Streptococcus occurred during a 9-week period in 1987. Seven cases were cared for by one obstetrician, who was also present in the delivery suite when the remaining patients delivered. This individual was found to be an anal carrier of group A Streptococcus with the same M and T types. During the cluster, the attack rate for vaginal deliveries performed by this individual was 18% (6 of 34 patients). The individual was treated with penicillin V (500 mg four times a day for 10 days), rifampin (600 mg twice a day for 5 days), and hexachlorophene showers. Surveillance cultures of the physician were negative 1 week, 1 month, and 3 months after completion of therapy. No additional cases were identified among the next 210 vaginal deliveries performed by this individual. Fourteen months after therapy, four new cases occurred during 2 days. The physician was found to be heavily colonized once again with the original strain of group A Streptococcus and was treated with rifampin (600 mg twice a day) and oral vancomycin (250 mg four times a day) for 7 days. An open-ended regimen of penicillin V (250 mg/day) and periodic surveillance cultures was begun. During the next 19 months, this physician performed 275 vaginal deliveries, one of which resulted in an M-nontypable, T-28 group A streptococcal infection, at a time when the physician's surveillance cultures were negative. It is unclear how long a colonized health care worker who causes nosocomial group A streptococcal disease must be treated or monitored, but there is some risk after more than a year. Long-term surveillance or prophylaxis may be useful in some circumstances.

Carrier State↗
PubMed1992

Heterogeneity and sampling volume dependence of epicardial adenosine concentrations.

Rapid steady-state estimates of interstitial fluid (ISF) adenosine concentrations (ADOi) in the left ventricular epicardium of anesthetized dogs were obtained by the epicardial porous disc (EPD) method described herein. Because of the high temporal and spatial resolution of this method, it was ideally suited to test the hypothesis that ADOi may vary in these domains. Variance in steady-state EPD solute concentrations was quantified statistically by the coefficient of variation (CV = standard deviation/mean), which we used as an index of heterogeneity. A significant temporal variation in steady-state EPD adenosine concentrations was observed when samples were sequentially collected from one epicardial location (CV = 42.9 +/- 3.5%). When steady-state sample pairs (n = 45) were collected simultaneously from two distinct epicardial locations, a 2.6 +/- 0.3-fold mean difference in their respective adenosine concentrations was measured. About 25% of this variation was inherent in procedural methodology, based on the variability of steady-state EPD concentrations of extracellularly-equilibrated 14C sucrose (CV = 12.7 +/- 1.2%) and the variability of steady-state concentrations of both solutes measured using in vitro preparations (mean CV = 9.7 +/- 1.2%). Thus, we contend that endogenous myocardial ISF adenosine is temporally and perhaps spatially heterogeneous. Our estimates of steady-state ADOi obtained with the EPD method ranged from 0.47 to 0.99 microM. Using modifications of the EPD technique and the epicardial chamber, we also demonstrated that the adenosine concentration in 'steady-state' epicardial samples is reduced when the volume/surface area ratio of the sample buffer is increased. We hypothesize that sampling-induced decreases in steady-state ADOi underlie these observations, because losses of ISF adenosine to high volumes of sample buffer can be greater than the myocardial cells are capable of replacing. However, with the very low volume/surface area ratio of a single EPD (7.5 microliters/cm2), steady-state ADOi may remain constant during sampling, allowing for accurate determinations of ADOi with this method.

Adenosine↗
PubMedDate not supplied

[Current malaria situation in the Republic of Kazakhstan].

The Republic of Kazakhstan is situated in the northern hemisphere on the boundary of two continents--Europe and Asia--at a longitude of 45 degrees E--87 degrees E and a latitude of 40 degrees N--55 degrees N. The total area of the republic is 2,724,900 square kilometers. Kazakhstan shares a border with the Russian Federation to the north-west, north and east: the border between the two countries is almost 6500 km long. To the south, Kazakhstan shares a border with the Central Asian states of Turkmenistan (380 km), Uzbekistan (2300 km) and Kyrgystan (980 km). To the south-east, it shares a border with China (1460 km): to the west is the Caspian Sea (600 km). Thus, the total length of Kazakhstan's external borders is 12,000 km. Because of the geographical, natural and climatic features prevailing throughout most of the Republic, there is a potential danger that local transmission of malaria may begin again if the disease is imported from abroad. The areas most at risk are the Panfilov and Uigur raions of Almaty oblast, which share a border with malaria-endemic regions of China, and the Saryagash and Makhtaral' raions of South Kazakhstan oblast along the border with Uzbekistan. The Government of the Republic of Kazakhstan places particular emphasis on malaria prevention and control, taking into account the historical data about the prevalence of malaria from the late 1920s to the early 1940s, amounting to hundreds of thousands of cases every year. Government Decree No. 840 entitled "Urgent Measures to Protect the Population from Blood-Sucking Insects and Ticks Dangerous to Humans", which lays down measures for the control of malarial mosquitoes in the areas most susceptible to malaria resurgence, was adopted in 1996. The Ministry of Health of the Republic of Kazakhstan issued instructions in 1998 and 1999 which were designed to motivate all health facilities in the field of malaria prevention and control. At present, as part of the directives developed by the Republican Health Epidemiology Posts, work is being done on the planning of malaria control measures in Kazakhstan for the period 2001-2003. In 1994 a programme of epidemiological malaria surveillance was introduced, which has enabled us to improve our monitoring of the epidemiological situation of malaria. The number of cases of imported malaria has declined: in 1997, there were 102 cases, in 1998-87 and in 1999-52. There have been occasional local cases in some years, and in 1998 there were four local cases in the south and north-west of the country: two cases in Almaty oblast, one case in Zhambyl oblast and one in West Kazakhstan oblast (see Fig. 1). Most malaria infections are imported from Tajikistan and Azerbaijan, with occasional cases from Pakistan, India, Turkey and Afghanistan. Analysis of the occupational status of patients shows that around 45% are military personnel who have served on the Tajik-Afghan border. The others are refugees, merchants, unemployed people or students. The overall aetiological structure of malaria cases is dominated by P. vivax malaria. For example, in 1999, there were 48 cases of P. vivax malaria (90.5% of the total), one case of tropical malaria (1.9%), two cases of quartan malaria (3.8%) and two cases of P. vivax + P. malariae (3.8%). In order to prevent indigenous malaria occurring within the country, a system of malaria screening has been set up; screening is carried out every year on groups who have visited neighbouring or more distant malaria-endemic countries and for patients with a persistent fever who are suspected of suffering from malaria. The area of water throughout the country within communities or within a 3-5 km radius of them which is susceptible to colonization by the Anopheles mosquito amounts to over 5000 hectares, according to the certification system in force. In addition, approximately 70,000 hectares in three oblasts used for rice cultivation also provide a habitat for Anopheles. The main malaria vector, An. messeae, is found throughout the country: in a few areas An. hyrcanus and An. claviger are found and, in the south, An. pulcherrimus. Data from recent years show the presence of An. superpictus, An. plumbeus and An. algeriensis. In 1999, from data collected during systematic observations of the phenology and seasonal variations in the number of Anopheles at 114 observation posts, the average seasonal numerical indicators for the mosquito imago reached a maximum of between 21 and 46.5 adult mosquitoes per cattle shed, up to 2.7-3.3 adult mosquitoes per residential building and 30-67.3 larvae per square metre of surface water. According to the results of large scale trapping programmes (486 communities were screened in 1999), the maximum value of the numerical indicator was 16.8-74.1 adult mosquitoes per cattle shed and 4.1-3.8 adult mosquitoes per residential building. In 1999, compared with 1998, the number of malarial mosquitoes detected throughout the country declined encouragingly, or stayed at the same level, which is one of the factors responsible for the country's favourable epidemiological situation with regard to malaria. According to data going back many years, there has been a significant increase in the number of mosquitoes at some observation posts in Almaty, East Kazakhstan and Kyzlorda oblasts. There is a tendency everywhere for the numbers of imagos detected in residential buildings to increase, which presents a definite epidemiological risk that indigenous malaria will re-emerge if the disease is imported into Kazakhstan from countries which suffer from it. If we consider the species of mosquito present in the country and the temperature factor (the number of days in the year when the average daily temperature is over 16 degrees C), the country can be divided, on the basis of incomplete 1999 data, into zones at very high risk of re-emergence of malaria (Almaty, Zhambyl and South Kazakhstan oblasts), high risk (Karaganda oblasts and Almaty city), medium risk (Aktyubinsk and Akmolinsk oblasts), and low risk (Kostanay oblast). The malaria risk of the other oblasts has been calculated using data from earlier years (map attached) [Translator's Note: map missing]. Preventive malaria control measures in Kazakhstan are divided into three categories to suit three different groups of communities. One hundred and seventy-nine communities have been allocated to the first group, at high risk of malaria resurgence; 1377 communities to the second group, at medium risk; and the remainder to the third group, at little or no risk of malaria resurgence. The following factors were used to categorize communities according to the risk that malaria might become reestablished if the disease should be imported from elsewhere: species of malarial mosquito present; changes in mosquito numbers and in the area of water susceptible to population by Anopheles; temperature conditions and, consequently, the length of the malaria transmission season and the season of effective susceptibility of the mosquito to infection; population migration; quality of laboratory testing for the diagnosis of malaria. Measures aimed at the destruction of mosquitoes are intended to reduce the numbers of Anopheles in the communities most at risk of malaria resurgence, i.e. those in group 1 above and the actual foci of malaria infection. Because of the economic crisis and financial difficulties, fewer areas have been treated in recent years. In 1999, 1387 hectares of water and 450,000 square metres of buildings were treated (see Fig. 2). Measures to control biting flies in health establishments, recreation areas, etc. Certainly also help to protect people from malarial mosquitoes. In 1999, 12,501 hectares of water and land were treated from the ground or the air (see Fig. 3). In the present situation, the main reasons for the difficulties affecting the malaria control and prevention campaign are as follows. Staff numbers in the Republic's parasitology service have been unjustifiably reduced. For example, the number of entomologists and entomology assistants employed is 58% and 48%, respectively, of the number laid down in Ministry of Health directives. At the health epidemiology posts, the number of disinfectors has been reduced to a minimum, and practically all engineer/water engineer posts have been abolished. The country does not possess the necessary education base for initial training or continuing education of staff for the parasitology service. The lack of basic scientific information about the problems of malaria control and prevention and parasitology in general. There is no research to test or introduce the most effective, safe and low-cost malaria control products and insecticides. The methodological literature required to use certain modern insecticides is not available. Entomologists are not provided with specialist insect control equipment. Entomological surveys are left incomplete because of shortages of transport and fuel at the health epidemiology posts. Because of the economic crisis and the high cost of the radical water engineering measures necessary to combat malaria, these measures cannot be implemented on the scale required. The equipment and materials stocks of the parasitology laboratories are highly inadequate: there is a lack of modern laboratory equipment, as well as a lack of opportunities for high-level professional training for staff. The exchange of information between the CIS countries is unsatisfactory, and there is no common information space: nor is there any systematic data available from other foreign countries. In the period 2000-2003, Kazakhstan plans to carry out malaria control activities (mosquito destruction) over an area of 2000 hectares of water and 1.5 million square metres of buildings.

Animals↗