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At least 1,063 records · Page 59Linked to original sources
PubMed2003

Structure and magnetic properties of the two-dimensional ferrimagnet (NEt4)[[Mn(salen)]2Fe(CN)6]: investigation of magnetic anisotropy on a single crystal.

The title compound, (NEt(4))[[Mn(salen)](2)Fe(CN)(6)] (1), was synthesized via a 1:1 reaction of [Mn(salen)(H(2)O)]ClO(4) with (NEt(4))(3)[Fe(CN)(6)] in a methanol/ethanol medium (NEt(4)(+) = tetraethylammonium cation, salen(2)(-) = N,N'-ethylenebis(salicylidene)iminate). The two-dimensional layered structure of 1 was revealed by X-ray crystallographic analysis: 1 crystallizes in monoclinic space group P2(1)/c with cell dimensions of a = 12.3660(8) A, b = 15.311(1) A, c = 12.918(1) A, beta = 110.971(4) degrees, Z = 2 and is isostructural to the previously synthesized compound, (NEt(4))[[Mn(5-Clsalen)](2)Fe(CN)(6)] (5-Clsalen(2-) = N,N'-ethylenebis(5-chlorosalicylidene)iminate; Miyasaka, H.; Matsumoto, N.; Re, N.; Gallo, E.; Floriani, C. Inorg. Chem. 1997, 36, 670). The Mn ion is surrounded by an equatorial salen quadridentate ligand and two axial nitrogen atoms from the [Fe(CN)(6)](3-) unit, the four Fe[bond]CN groups of which coordinate to the Mn ions of [Mn(salen)](+) units, forming a two-dimensional network having [[bond]Mn[bond]NC[bond]Fe[bond]CN[bond]](4) cyclic repeating units. The network is spread over the bc-plane of the unit cell, and the layers are stacked along the a-axis. The countercation NEt(4)(+) is located between the layers. Compound 1 is a ferrimagnet with T(c) = 7.7 K and exhibits hysteresis with a remnant magnetization of 13.44 cm(3).mol(-1) (M/N mu(B) = 2.4) at zero field and a coercivity of 1000 Oe when the powder sample was measured at 1.9 K. Magnetic measurements of a direction-arranged single crystal were also carried out. The orientation of the crystallographic axes of a selected single crystal was determined by X-ray analysis, and magnetization was measured when an external field was applied in the a*, b, and c directions. The magnetization in the a* direction increased more easily than those in the b and c directions below the critical temperature. No hysteresis was observed only for the measurement in the a* direction, indicating the presence of strong structural anisotropy with potential anisotropy on Mn(III) ions.

Journal Article↗
PubMed1983

A review of radiation accidents involving whole body exposure and the relevance to the LD50/60 for man.

The absorbed dose of low LET radiation that would be lethal (due to bone marrow failure) to 50% of an exposed human population is a matter for concern in planning for the consequences of an accident to a nuclear reactor and in the event of nuclear war. Since accidents with radiation-generating equipment or in the nuclear fuel processing industry might provide relevant human data, published accounts of these are reviewed. Two accidents, one in the USA, the other in Yugoslavia, both involving exposure to neutrons as well as gamma-rays, are identified as possibly satisfying the criteria of uniformity of dose, magnitude of dose and dose rate necessary to provide useful information on the value of LD50/60 for man. The symptomatology of the exposed individuals is discussed in terms of the published doses. Detailed examination of the dosimetry for these two accidents revealed possible ambiguities and a thorough re-examination has been carried out, the results of which are reported in detail in the Appendix. This indicates considerable and largely unresolvable uncertainty in the magnitude of the dose to exposed individuals when expressed as the low LET equivalent dose in bone marrow. It is also shown that the relationship between severity of effects and dose to exposed individuals is not the same for both accidents and it is argued that the experience from the Yugoslavian accident is more relevant to the determination of the sensitivity to radiation of an exposed human population. Given the uncertain nature of the accident data and the small amount of other relevant human data at present available, the uncertainty of current knowledge of man's sensitivity to the acute effects of exposure to ionising radiation is discussed.

Accidents, Occupational↗
PubMed1989

Percussion of the chest re-visited: a comparison of the diagnostic value of ausculatory and conventional chest percussion.

Percussion of the chest is thought to be insensitive in detecting small or deeply situated chest lesions. A newer technique, ausculatory percussion, has been reported as having a far higher sensitivity. In a controlled blind study the diagnostic value of conventional chest percussion compared with ausculatory percussion was defined using the chest x-ray as a gold standard. The prevalence of disease in 100 lung fields was 26%. The majority of lesions were not detected by either technique resulting in very low sensitivities of 15.4% for conventional percussion and 19.2% for ausculatory percussion. A positive result with ausculatory percussion was twice as likely to be false as true (positive predictive value 31.2%). The technique did not add to the diagnostic value of conventional percussion. Both techniques have major limitations. Patients with suspected lung disease still require chest x-ray examination if percussion is normal.

Auscultation↗
PubMed2005

Silk implants for the healing of critical size bone defects.

Bone (re)-generation and bone fixation strategies utilize biomaterial implants, which are gradually replaced by autologous tissues. Ideally, these biomaterials should be biodegradable, osteoconductive, and provide mechanical strength and integrity until newly formed host tissues can maintain function. Some protein-based biomaterials such as collagens are promising because of their biological similarities to natural proteins on bone surfaces. However, their use as bone implant materials is largely hampered by poor mechanical properties. In contrast, silks offer distinguishing mechanical properties that are tailorable, along with slow degradability to permit adequate time for remodeling. To assess the suitability of silk-based biomaterials as implants for bone healing, we explored the use of novel porous silk fibroin scaffolds as templates for the engineering of bone tissues starting from human bone marrow derived stem cells cultured under osteogenic conditions for up to 5 weeks. The slowly degrading protein matrix permitted adequate temporal control of hydroxyapatite deposition and resulted in the formation of a trabecular-like bone matrix in bioreactor studies. The organic and inorganic components of the engineered bone tissues resembled those of bone, as shown by gene expression analysis, biochemical assays, and X-ray diffractometry. Implantation of the tissue-engineered bone implants (grown in bioreactors for 5 weeks prior to implantation) into calvarial critical size defects in mice demonstrated the capacity of these systems to induce advanced bone formation within 5 weeks, whereas the implantation of stem cell loaded silk scaffolds, and scaffolds alone resulted in less bone formation. These results demonstrate the feasibility of silk-based implants with engineered bone for the (re-)generation of bone tissues and expand the class of protein-based bone-implant materials with a mechanically stable and durable option.

Animals↗
PubMed1986

Comparison of the structure of human intervertebral discs in the cervical, thoracic and lumbar regions of the spine.

Posterior and anterior heights, cross-sectional area and shape were measured for all the intervertebral discs in four spines from elderly human cadavers. Disc height was a minimum at the T4-5 level; thoracic discs were less wedge-shaped than those in the cervical and lumbar regions. Cross-sectional area increased from the cranial to caudal extremity; at the L5-S1 level the nucleus pulposus occupied a high proportion of this area. Cervical discs tended to have an elliptical cross-sectional shape, thoracic discs were more circular and lumbar discs tended to have an elliptical cross-section which was flattened or re-entrant posteriorly. This shape distribution was quantified by defining a shape index which had a maximum value of 1 for a circular cross-section. Orientations of the reinforcing fibres in the outer lamellae of the anterior annulus fibrosus were measured from 27 discs by X-ray diffraction. For these measurements, C3-4, T7-8 and L2-3 were chosen as representative of cervical, thoracic and lumbar discs. The fibre tilt, with respect to the axis of the spine, was significantly less in the cervical discs (at 65 degrees) than in the thoracic and lumbar discs (about 70 degrees). These findings are interpreted in relation to differing functional requirements and possible mechanisms of failure in the cervical, thoracic and lumbar regions of the spine in the light of current knowledge on the biomechanics of the intervertebral disc.

Humans↗
PubMed2003

Bone mineral density changes in women with systemic lupus erythematosus.

The aim of this study was to analyse the heterogeneity of bone mineral density (BMD) reduction across measurement sites in female systemic lupus erythematosus (SLE) patients on glucocorticoid (CS) treatment. The study population consisted of two subgroups: 32 women at a mean (SD) age of 43.2 (12.0) years, SLE duration of 13.4 (6.2) years, treated with a mean cumulative prednisone dose of 34.4 g; and 16 women at a mean age of 36.1 (9.0) years, SLE duration of 3.2 (2.0) years, never treated with glucocorticoids (control group). The participants underwent a standardised interview, medical record review, blood sampling and BMD examination of the lumbar spine, femoral neck and distal forearm by dual-energy X-ray absorptiometry. CS-treated participants were supplemented with daily calcium (1200 mg) and vitamin D (500 UI). During the study mean daily glucocorticoid dose was 10 mg prednisone equivalent. The controls did not receive either corticosteroids or calcium and vitamin D. BMD and laboratory parameters were re-examined at the end of the second year. At baseline 22 (68.7%) of the CS-treated participants had osteoporosis at least at one major site, compared to 18.8% of the controls. The BMD reduction was proportional to the trabecular bone content at the specific measurement site. At baseline mean T scores in the CS-treated group were the highest at the forearm (-1.03 +/- 1.13), followed by the hip (-1.32 +/- 1.26), AP spine (-1.87 +/- 1.46) and lateral spine (-2.90 +/- 1.50). At follow-up lateral spine bone loss was 5.54% per year, the total hip and the forearm lost 3.59% and 0.33%, respectively, compared to annual losses of 1.02% (AP spine), 1.30% (lateral spine), 0.83% (total hip) and 0.11% (forearm) in the control group. The heterogeneity of BMD reduction in our SLE population emphasises the need for the targeted use of bone densitometry in steroid-treated patients. Attention should be paid to trabecular-rich sites, and fracture risk should be specifically determined.

Absorptiometry, Photon↗
PubMed2006

Phylogenetic conservation of chromosome numbers in Actinopterygiian fishes.

The genomes of ray-finned fishes (Actinopterygii) are well known for their evolutionary dynamism as reflected by drastic alterations in DNA content often via regional and whole-genome duplications, differential patterns of gene silencing or loss, shifts in the insertion-to-deletion ratios of genomic segments, and major re-patternings of chromosomes via non-homologous recombination. In sharp contrast, chromosome numbers in somatic karyotypes have been highly conserved over vast evolutionary timescales - a histogram of available counts is strongly leptokurtic with more than 50% of surveyed species displaying either 48 or 50 chromosomes. Here we employ comparative phylogenetic analyses to examine the evolutionary history of alterations in fish chromosome numbers. The most parsimonious ancestral state for major actinopterygiian clades is 48 chromosomes. When interpreted in a phylogenetic context, chromosome numbers evidence many recent instances of polyploidization in various lineages but there is no clear indication of a singular polyploidization event that has been hypothesized to have immediately preceded the teleost radiation. After factoring out evident polyploidizations, a correlation between chromosome numbers and genome sizes across the Actinopterygii is marginally statistically significant (p = 0.012) but exceedingly weak (R (2) = 0.0096). Overall, our phylogenetic analysis indicates a mosaic evolutionary pattern in which the forces that govern labile features of fish genomes must operate largely independently of those that operate to conserve chromosome numbers.

Amphibians↗
PubMed2005

Management of esophageal symptoms following fundoplication.

Laparoscopic antireflux surgery has emerged as a widely used and effective management option for the properly selected patient with gastroesophageal reflux disease. Poor symptomatic outcomes occur even in the best of hands, the most common being recurrent or persistent heartburn (or atypical symptoms) and dysphagia. When heartburn predominates, the initial management step is an anatomical and physiologic evaluation to determine whether acid reflux is controlled and if the postoperative neoanatomy is appropriate. If anatomical evaluation indicates surgical failure (eg, slipped or loose fundoplication, recurrent hiatal hernia), earlier re- operation may be warranted. Objective evidence of ongoing acid reflux or a reflux-symptom association despite anatomical integrity indicates reintroduction of antireflux medical therapy. Evidence favoring physiologic and anatomical success should direct treatment toward functional heartburn, including the use of tricyclic antidepressants. Dysphagia in the immediate postoperative setting mandates reassurance, as conservative measures alone often suffice while postoperative changes resolve. With persistent dysphagia, anatomical and physiologic evaluation is again indicated in the search for a mechanical-, motility-, or reflux-related symptom basis. Dilation techniques can prevent the need for re-operation, but persistent dysphagia associated with distorted postoperative anatomy will likely require surgical intervention. Regardless of the indication, re-operation carries substantial morbidity and reduced success rates compared with the initial procedure. These procedures mandate careful patient selection and referral to a center with thorough surgical experience.

Journal Article↗
PubMed1987

Effects of low or high doses of short wavelength ultraviolet light (UVB) on Langerhans cells and skin allograft survival.

Since Langerhans cells (LC) are normally the only cells within the epidermis to express the class II major histocompatibility complex (MHC) transplantation antigens, depletion of LC could be expected to prolong skin allograft survival by reducing the antigenic disparity between host and recipient. To assess this hypothesis, donor C57BL mouse shaved dorsal trunk or tail skin was exposed to high (200 mJ/cm2) or low (40 mJ/cm2) doses of short wavelength ultraviolet light (UVB) before grafting on to the thorax of BALB/c mouse recipients of the same sex. These strains have different major and minor transplantation antigens. The effects of UVB treatments on LC were determined by electronmicroscopy. Skin grafted 1-14 days following a single high dose of UVB irradiation was ultrastructurally depleted of LC and survived significantly longer than unirradiated skin before being rejected. After a 21-day interval between exposure and grafting when LC were again present in the epidermis there was no significant difference between treated and control graft survival. Exposure to low dose UVB irradiation only significantly increased graft survival for skin transplanted 1-3 days after irradiation; skin grafted 4 days following irradiation survived for a similar period to unirradiated control skin grafts. Electronmicroscopy showed that the low UVB dose did not deplete LC from the epidermis. We conclude that after low dose UVB treatment the class II MHC antigens on the LC plasma membrane were lost temporarily, thus prolonging graft survival, but when the plasma membrane antigens were re-expressed graft survival returned to normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[Artificial respiration in the prone position in a case of acute respiratory distress syndrome].

A patient is presented in whom an acute respiratory distress syndrome (ARDS) developed after severe lung contusion. Exchange of gas was markedly restricted under aggressive respiration (FiO2 = 1.0, PEEP = 10 mmHg, breathing time quotient = 0.5, respiratory minute volume = 16 litres; gas exchange values: PaO2 = 67 mmHg, PaCO2 = 45 mmHg, PA-aO2 = 461 mmHg). After control of the computed tomogram of the lungs showed marked densifications in those parts of the lung that are lower most by gravitation according to the positioning of the patient at a particular time the patient was ventilated in ventricumbent (prone) position for 60 hours. After having remained in this position for 48 hours, there was a significant improvement in the gas exchange (PaO2 = 89 mmHg, PaCO2 = 36 mmHg, PA-aO2 = 77 mmHg at FiO2 = 0.3, PEEP = 6 mmHg, breathing time quotient = 0.5 and respiratory minute volume = 9 litres). The control CT in dorsal position showed that the dorsal densifications had disappeared completely. Five days later the patient could be extubated. Respiration in ventricumbent (prone) position may considerably improve oxygenation by perfusion of well-ventilated regions of the lung that are lower-most by gravitation according to the relative positioning of the patient. Besides regions not well ventilated or not ventilated at all (according to the patient's position) may be better ventilated or re-opened and made accessible to ventilation by this method.

Adult↗
PubMed1986

Primary brain stem haemorrhages: clinico-radiological considerations on five cases observed.

Five patients with primary brain stem haemorrhage are reported, of whom four survived. One died from complications involving other organs. The diagnosis was made by computerized tomography which also allowed the temporal evolution of the lesion to be followed. The importance of haemorrhagic lesions in brain stem vascular pathology with regard to ischaemic lesions is re-evaluated.

Aged↗
PubMed1988

Calculation of protein conformation by the build-up procedure. Application to bovine pancreatic trypsin inhibitor using limited simulated nuclear magnetic resonance data.

Low-energy conformations of a set of tetrapeptides derived from the small protein bovine pancreatic trypsin inhibitor (BPTI) were generated by a build-up procedure from the low-energy conformations of single amino acid residues. At each stage, various-size fragments were built up from all combinations of smaller ones, the total energies were then minimized, and the low-energy conformations were retained for the next stage. The energies of the tetrapeptides were re-ordered by including the effects of hydration. No information other than the amino acid sequence was used to obtain the low-energy conformations of the hydrated tetrapeptides. The latter were then supplemented with a limited set of simulated NMR distance information, derived from the X-ray structure of BPTI, to provide a basis for building the rest of the whole protein molecule by the same procedure. A total of 189 upper bounds, plus 12 pairs of upper and lower bounds pertaining to the location of the three disulfide bonds in this molecule, were used. Four sets of conformations of the entire molecule were generated by utilizing different combinations of smaller fragments. It was possible to obtain low-energy conformations with small rms deviations, 1.1 to 1.4 A for the alpha-carbons, from the structure derived by X-ray diffraction. The average deviations of the backbone dihedral angles were also low, viz. 23 degrees to 26 degrees.

Amino Acid Sequence↗
PubMed1981

Cimetidine treatment of recurrent ulcer after proximal gastric vagotomy.

Twenty-one patients with endoscopically confirmed recurrent ulceration after proximal gastric vagotomy entered an open trial of treatment with cimetidine, 1.0 g/day. Twenty patients completed 6 weeks' treatment, and repeat endoscopy showed ulcer healing in 18 of 20 patients. One patient's ulcer was found to be healed on X-ray examination, and the other patient had a healed ulcer after an additional 2 weeks' treatment. Eighteen of the patients with healed ulcer entered a maintenance trial of cimetidine, 400 mg at night. During the 1-year follow-up period the occurrence of symptoms led to re-endoscopy in 11 patients. Re-ulceration was confirmed in six patients (33%), and mean time to ulcer recurrence was 18.2 weeks. Ulcer recurrence was treated with an increased dose of cimetidine and antacids. All the ulcers then healed again, and the patients remained well on a maintenance dose of cimetidine, 800 mg/day. None of the patients had to be operated on during the trial. Two patients developed gynaecomastia during maintenance treatment with 400 mg cimetidine a day. No serious untoward signs or symptoms occurred that necessitated withdrawal from the trial. It seems as if recurrent ulcers after proximal gastric vagotomy respond to cimetidine treatment approximately as do peptic ulcers in unoperated patients.

Adult↗
PubMed2001

[Thrombosis of great pulmonary vessels causing severe pulmonary hypertension in systemic lupus erythematosus].

We describe a 34 year old male patient with systemic lupus erythematosus (SLE) who developed pulmonary hypertension (PHT) associated with anticardiolipin antibodies. Ten years after diagnosis, an helical CT scan revealed thrombosis of the major pulmonary arteries, which was confirmed by digital pulmonary angiography. An inferior caval vein filter was placed and oral anticoagulation was begun. The patient refused pulmonary thromboendarterectomy and died soon thereafter. Even though PHT is widely described associated with SLE, proximal thrombosis of pulmonary arteries is exceptional. We describe such a patient review the different etiologies, incidence and diagnostic approach of PHT in SLE, focusing on those patients with an effective treatment.

Adult↗
PubMed2002

[Flat-panel detector technology -State-of-the-art and future prospects-].

A flat-panel detector (FPD) is a long-awaited technology to implement the digital X-ray imaging technology into the radiological department. This paper describes the state-of-the-art technology and future prospects on the FPD technology. State-of-the-art technology was reviewed taking the CXDI series as an example. Several FPD-based systems have been introduced into the Japanese market since CXDI-11 opened it in November 1998. Accompanying CXDI-C2 for control, CXDI-22 for table position and CXDI-31 for portable, the CXDI series fulfills the requirement of the radiography room being a fully digitalized room. The FPD on the CXDI series is comprised of a scintillator (Gd(2)O(2)S:Tb(3+)) as a primary sensor in which the X-ray is captured and an amorphous silicon detector (LANMIT) as a secondary sensor in which the fluorescent light is detected. Since the scintillator is identical to that of the screen-film systems, it can be said as proven, durable and chemically stable and it is expected to produce the same image quality as the screen-film systems. CXDI-31, a portable FPD-based system, was developed targeting thinner dimensions, lightweight, durability and high spatial resolution. Thoroughly re-designing the mechanical structure and reducing the power consumption at the readout IC realized thinner dimensions. Introducing the portable note PC technologies successfully combined lightweight with durability. Improving the sensor process and re-designing the layout made the sensor high resolution without compromising the signal-to-noise ratio. Future prospects were overviewed in the aspect of technology and applications. Sensitivity, spatial resolution, frame rate and portability were described as the upcoming technology. Increasing gain and reducing noise will realize higher sensitivity, especially by adopting the PbI(2), HgI(2) or such photoconductor materials as the primary sensor. Pixelized amplifier will also achieve higher sensitivity. Layered sensor designed such that TFT layer and sensitive layer are constructed separately will decrease the pixel pitch lower than 100 microm. The FPD has been applied in radiography, mammography and angiography. It will expand the applications into low-dose fluoroscopy to replace the X-ray image intensifiers and into cone-beam computer tomography. What the FPD brought was mainly the efficient workflow of the X-ray technologist. However, diagnosis efficiency and patient benefit must be improved further more by combining FPD technology into computer-aided diagnosis, tele-radiography or other IT-based technologies. Such prospect may come true in the near future.

Fluoroscopy↗