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PubMed1999

Dual-energy X-ray absorptiometry: a review.

Dual-energy X-ray absorptiometry (DXA) has been recently used for body composition analysis in dialysis patients. It is based on the principle that X-rays passed through various body tissues have different attenuation and, therefore, can be differentiated. By using X-rays at two different energy levels, better tissue differentiation is possible compared with single energy systems. This article will review the evolution of DXA scanners and the role DXA has in assessing body composition in dialysis patients. Overall, this technique has excellent precision and holds promise for use in the serial evaluation of body composition and nutritional evaluation of dialysis patients.

Absorptiometry, Photon↗
PubMedDate not supplied

Derivation of the mammalian skull vault.

This review describes the evolutionary history of the mammalian skull vault as a basis for understanding its complex structure. Current information on the developmental tissue origins of the skull vault bones (mesoderm and neural crest) is assessed for mammals and other tetrapods. This information is discussed in the context of evolutionary changes in the proportions of the skull vault bones at the sarcopterygian-tetrapod transition. The dual tissue origin of the skull vault is considered in relation to the molecular mechanisms underlying osteogenic cell proliferation and differentiation in the sutural growth centres and in the proportionate contributions of different sutures to skull growth.

Animals↗
PubMed2004

Bone fractal analysis.

Fractal analysis is a quantitative method used to evaluate complex anatomic findings in their elementary component. Its application to biologic images, particularly to cancellous bones, has been well practiced within the past few years. The aims of these applications are to assess changes in bone and the loss of spongious architecture, indicate bone fragility, and to show the increased risk for fracture in primary or secondary osteoporosis. The applications are very promising to help complete the studies that can define bone density (bone mineral density by dual energy x-ray absorptiometry or quantitative computed tomography), and also have the capacity to distinguish the patients with a high or low risk for fracture. Their extension to the clinical fields, to define a test for fracture risk, is still limited by difficult application to the medical quantitative imaging of bones, between correct application at superficial bones and unreliable application to deep bones. The future evolution and validity do not depend upon fractal methods but upon well-detailed imaging of the bones in clinical conditions.

Absorptiometry, Photon↗
PubMed2002

Transfer of space technologies past and present: the Russian case.

Since the end of the 1980's transfer of government sponsored high technology space goods and services to other sectors, industry, and eventually non-government use has been a growing concern of the Russian policy makers. Today the real and functional transformation of this field is on the agenda. The paper is organized as follows. The first section analyzes the evolution of the common approach to technology transfer, looks at the main obstacles to this processes as a whole, and in the space sector in particular. The second section examines the Russian space R&D sector from the point of view of its role and place in the Russian scientific and technological base. New mechanisms of technology transfer are then considered. Here, problems of conversion, commercialization, dual-use, and internationalization are examined in the context of space technology transfer. Furthermore, issues of innovation in technology transfer are discussed. The new networks that are forming through which technologies diffuse is considered. The paper then turns to legislative and regulatory problems, including the discussion of the main principles of the Russian space transfer code, which is now being drafted. It is necessary to underline, that in the Russian case, official statistics still do not help analyze the question of technology transfer.

Government Agencies↗
PubMed2006

The evolution of weight and body composition in renal transplant recipients: Two-year longitudinal study.

UNLABELLED: Previous series have reported weight gain after kidney transplantation. However few studies have investigated the body composition after kidney transplantation, particularly during longitudinal follow-up. In this prospective study, we assessed the changes in body composition after kidney transplantation. We also analyzed the effect of steroid withdrawal from the immunosuppressive regimen on weight gain and body composition. METHODS: Thirty-eight cadaveric kidney transplant recipients were followed for 2 years posttransplant. Total and segmental body composition were measured by dual energy X-ray absorptiometry (DEXA) at the time of transplantation as well as 3, 6, 12, and 24 months later. RESULTS: In 28 patients (group A), prednisone was stopped by month 6, whereas, in 10 patients (group B), it was continued throughout the study. In the overall patient group, there were no significant changes in body weight. However, a trend to increased weight was observed in group B. In this group, patients showed an early increase in total body fat with a central accumulation of fat mass that was maintained during the follow-up period. On the other hand, total lean mass increased significantly in group A but did not change significantly in group B. CONCLUSION: In summary, overall the group showed no major changes in body weight during the 2 years after transplantation. Steroid withdrawal in kidney transplant recipients may have a significant positive effect on body composition.

Absorptiometry, Photon↗
PubMed2005

A new scrambled gene in the ciliate Uroleptus.

In the germline micronucleus of spirotrichous ciliates, the gene segments, or macronuclear destined sequences (MDSs), that give rise to the somatic macronucleus are interrupted by internal eliminated sequences (IESs). For some genes, the MDSs are not arranged sequentially, but rather are scrambled, in the micronucleus. Three scrambled genes have been extensively studied in many species: actin I, alpha-telomere binding protein, and DNA polymerase alpha. However, in the past decade, no new scrambled genes have been reported, and the prevalence of scrambled genes is still an important question. To screen for scrambled genes, we completely sequenced 11 macronuclear chromosomes in the spirotrich Uroleptus sp., and then pursued their micronuclear organization. This allowed us to identify new scrambled genes, which also display novel features. In this study we describe one of these newly discovered scrambled genes. This gene, tentatively named USG1 (Unknown Scrambled Gene 1), encodes a putative protein of 1016 aa. While the function of this protein product is not clear, dN/dS calculated from the two alleles suggests the encoded protein is under purifying selection. USG1 consists of 16 germline MDSs, of which 14 are located on one locus. The other locus, which is at least 3 kb away from the main locus, contains two scrambled MDSs separated by a nonscrambled IES. Curiously, one MDS and its outgoing (3') pointer (direct repeat) overlap intron splice sites, indicating that these DNA sequences may be under dual (or multiple) constraints. Our findings identify a new scrambled gene in the micronuclear genome of a spirotrichous ciliate, and suggest that even more complicated structures may be present.

Animals↗
PubMed2000

Adherens junctions and beta-catenin-mediated cell signalling in a non-metazoan organism.

Mechanical forces between cells have a principal role in the organization of animal tissues. Adherens junctions are an important component of these tissues, connecting cells through their actin cytoskeleton and allowing the assembly of tensile structures. At least one adherens junction protein, beta-catenin, also acts as a signalling molecule, directly regulating gene expression. To date, adherens junctions have only been detected in metazoa, and therefore we looked for them outside the animal kingdom to examine their evolutionary origins. The non-metazoan Dictyostelium discoideum forms a multicellular, differentiated structure. Here we describe the discovery of actin-associated intercellular junctions in Dictyostelium. We have isolated a gene encoding a beta-catenin homologue, aardvark, which is a component of the junctional complex, and, independently, is required for cell signalling. Our discovery of adherens junctions outside the animal kingdom shows that the dual role of beta-catenin in cell-cell adhesion and cell signalling evolved before the origins of metazoa.

Actins↗
PubMed2005

Molecular signaling aptamers for real-time fluorescence analysis of protein.

Aptamers are a new class of nucleic acids that are selected in vitro for binding target molecules with high affinity and selectivity. They are promising protein-binding molecular probes that rival conventional antibodies for protein analysis. There have been recent advances in the development of molecular signaling aptamers that can transduce target protein binding to sensitive fluorescence signal changes. This facilitates the real time protein monitoring in homogenous solution as well as potentially in vivo. Different signaling strategies of using dual labeled aptamers based on fluorescence resonance energy transfer (FRET), one fluorophore labeled aptamers based on fluorescence anisotropy assay, or other label-free aptamers are reviewed.

Anisotropy↗
PubMed2001

Progressive and reproducible focal cortical ischemia with or without late spontaneous reperfusion generated by a ring-shaped, laser-driven photothrombotic lesion in rats.

Clinical stroke is mostly of thromboembolic origin, in which the magnitude of brain damage resulting from arterial occlusions depends on the degree and duration of the concomitant ischemia. To facilitate more controllable and reproducible study of stroke-related pathophysiological mechanisms, a photothrombotic ring stroke model was initially developed in adult rats. The ring interior zone comprises an anatomically well confined cortical region-at-risk which is gradually encroached by progressive hypoperfusion, thus mimicking the situation (albeit in inverse fashion) of an ischemic penumbra or stroke-in-evolution. Modification of this model using a thinner ring irradiation beam resulted in late spontaneous reperfusion in the cortical region-at-risk and a remarkable morphological tissue recovery in this ostensibly critically injured region. On the other hand, doubling the thin irradiating beam intensity facilitates a complementary situation in which lack of reperfusion in the region-at-risk after stroke induction leads to tissue pannecrosis. The dual photothrombotic ring stroke model, effectuated either with or without reperfusion and thereby tissue recovery or pannecrosis, may be well suited for the study of events related to postischemic survival or cell death in the penumbra region. To popularize the photothrombotic ring stroke model, we present a detailed protocol of how this model is induced in either version as well as protocols for transcardial carbon black perfusion and laser-Doppler flowmetry experiments.

Animals↗
PubMed1996

[Preoperative instrumental diagnosis in secondary hyperparathyroidism].

There is a very high incidence of hyperparathyroidism secondary to chronic renal insufficiency in dialysed patients (67%). When medical therapy can no longer control the evolution of disease, an appropriate surgical strategy must be defined for the clinical case. Instrumental tests play an important role during the preoperative phase in the possible "localisation" of ectopic parathyroids (10% of cases) and the identification of those glands with a more pronounced hyperplastic appearance. The authors examine and describe the most useful tests for a preoperative study, namely ultrasonography, echo-colour Doppler, scintigraphy using a dual tracer and image subtraction, computerised xial tomography (CT), magnetic resonance (MR), digital angiography and intraoperative ultrasonography. In conclusion, it can be said that all the methods examined present similar sensitivity levels for the study of parathyroid, but the combination of more than one technique considerably improves diagnostic accuracy.

Angiography, Digital Subtraction↗
PubMed1995

The gene for pyruvate, orthophosphate dikinase in C4 plants: structure, regulation and evolution.

Pyruvate, orthophosphate dikinase (PPDK; EC 2.7.9.1) is a key enzyme in photosynthesis in plants that exploit the C4 photosynthetic pathway for the fixation of CO2. This review focuses on the structure, regulation and evolution of the C4-type ppdk gene in the maize genome. The C4-ppdk gene in maize consists of 19 exons spanning about 12 kbp. The gene is transcribed from two different initiation sites under the control of two promoters to produce two mRNAs of different sizes. The larger one contains the exon 1 sequence that encodes the chloroplast transit peptide and its product acts as C4-PPDK in chloroplasts, while the smaller one does not contain the sequence and its product may function as a C3-enzyme in the cytosol. This unusual dual promoter system is not unique to the maize C4-type ppdk gene since the same organization is also observed in the rice (C3 plant) ppdk gene and in Flaveria. Thus, the two-promoter system is common to plant ppdk genes from C3 and C4, monocot and dicot plants. A discussion is also presented of the generation of a system for regulation of the expression of the C4-type ppdk gene. A chimeric gene consisting of a reporter gene under the control of the promoter of maize C4-ppdk is exclusively expressed in photosynthetic tissues and not in roots or stems of transgenic rice. The expression of the introduced gene is also regulated by light: it is low in etiolated leaves and is enhanced by illumination. These results indicate that the regulatory system that controls ppdk expression in maize is not unique to C4 plants.

Amino Acid Sequence↗
PubMed1999

Short-term evolution of new multiple sclerosis lesions enhancing on standard and triple dose gadolinium-enhanced brain MRI scans.

We compared the short-term magnetic resonance imaging (MRI) evolution of new multiple sclerosis (MS) lesions enhancing after single dose (SD) (0.1 mmol/kg) or triple dose (TD) (0.3 mmol/kg) gadolinium-DTPA (Gd) to explore possible differences in the pathological substrates of acute MS lesions. Brain MRI scans were obtained at baseline and every 4 weeks for a 3-month period in 18 relapsing-remitting MS patients. At each time point, using two separate sessions, we obtained dual echo and T1-weighted scans before and after SD and TD of Gd. New enhancing lesions detected at month 1 and 2 were entered into the analysis. The presence of corresponding hypointense lesions on unenhanced T1-weighted scans and hyperintense lesions on T2/proton density (PD)-weighted images was assessed on the same scan and on the scans performed 1 month before and 1 month after the new lesion development. Persistence of enhancement was evaluated on the SD and TD scans obtained 1 month after new lesion appearance. One-hundred and sixty lesions were studied. Of these, 97 lesions were enhancing after both SD and TD (group A) and 63 lesions only after TD (group B). Thirty (31%) of the lesions enhancing after both SD and TD and ten (16%) of the lesions enhancing only after TD had corresponding T1-weighted lesions (P = 0.03). Of these lesions, 87% in group A and 40% in group B (P = 0.003) were not hypointense on the previous scans. No differences were found in the frequencies of corresponding T2/PD-weighted abnormalities (92% in Group A vs. 87% in Group B lesions). Of these hyperintense areas, 62% in group A and 56% in group B were not present on the previous scans. On follow-up scans, 52% of the lesions enhancing after SD and TD and 70% of the lesions enhancing only after TD did not show enhancement after the injection of both the doses of Gd (P = 0.02). The frequencies of corresponding T2/PD and T1-weighted abnormalities were higher in Group A than in Group B lesions, but the differences were not statistically significant. Our findings suggest that the pathological process is less severe in MS lesions enhancing only after TD injection than in those enhancing after the SD.

Adult↗
PubMed2001

Nutritional status after short-term dietary supplementation in hospitalized malnourished geriatric patients.

AIM: To examine the evolution of different parameters of the nutritional status after short-term oral protein-energy supplementation in moderately malnourished geriatric patients. METHODS: Seventeen hospitalized malnourished elderly patients and 12 healthy adults received dietary supplements for 10 days. A group of six malnourished elderly subjects served as controls. Spontaneous oral intakes, biological and biophysical markers of the nutritional status were measured. Fat-free mass (FFM) was assessed using Dual energy X-ray absorptiometry (DXA), bio-impedance analysis (BIA) and anthropometry. RESULTS: In elderly subjects, the supplementation significantly increased both dietary intake (energy +32%, protein +65%) and FFM (+1.3 kg, P<0.001) as assessed using DXA. BIA and anthropometric data correlated with DXA measurements in the elderly (BIA: r=0.68--0.80, anthropometry: r=0.80--0.89), but failed to reflect accurately the changes measured in FFM. Supplementation had no notable effect on biological markers in any of the groups. IGF-I and hand-grip strength were not significantly influenced by the supplementation despite trends towards an improvement. CONCLUSIONS: Monitoring short-term changes in nutritional status in malnourished elderly individuals is a problem in routine clinical management. Our data put in the limelight the changes in IGF-I values related to dietary supplementation, and, chiefly, suggest a prime role for the assessment of dietary intake and FFM, as assessed by DXA, as indicators of short-term efficacy of refeeding. Nevertheless larger studies are necessary to confirm the clinical and prognostic significance of the changes.

Absorptiometry, Photon↗
PubMed1993

Dual-perspective analysis of vascular formations in sickle cell retinopathy.

OBJECTIVE: To examine the sickle cell retina in dual perspective (vascular patterns en bloc and structure in serial sections) to gain new insights into sickle cell retinopathy. METHODS: We analyzed the retinas of two patients with sickle cell disease (a 54-year-old patient with hemoglobin SC, heterozygous for the S and C mutation in the beta chain of the globin gene, and a 20-month-old patient with sickle cell anemia [SS], homozygous for the S mutation) using the previously described adenosine diphosphatase flat-embedding technique. RESULTS: The dual-perspective analysis afforded by our technique revealed that the primary site of occlusions was located at the precapillary level. An unusual neovascular formation, the hairpin loop, was observed in both patients' retinas and appeared to result from recanalization of the wall of an occluded vessel. Many autoinfarcted pre-retinal neovascular formations were observed in the older SC patient. Two patent preretinal formations were studied in detail and their evolution appeared to be influenced by mechanical factors. The vessels appeared to have been extruded from the retina, perhaps owing to hydrostatic pressure secondary to downstream occlusions. Small pigmented lesions consisting of retinal pigment epithelial cells ensheathing channels that resembled autoinfarcted vessels were found in the eye of the SC patient. CONCLUSIONS: This study illustrates unusual morphological features of intraretinal and preretinal neovascularization and of chorioretinal lesions in sickle cell retinopathy and suggests alternative mechanisms for their formation.

Adult↗
PubMed2000

Selective versus non-selective laser photocoagulation of placental vessels in twin-to-twin transfusion syndrome.

OBJECTIVE: We have recently described a surgical technique for the treatment of twin-to-twin transfusion syndrome (TTTS) that allows precise identification of vascular anastomoses (selective laser photocoagulation of communicating vessels, or S-LPCV). The purpose of this study was to compare S-LPCV with the previous non-selective technique (NS-LPCV) that targeted all vessels crossing the dividing membrane. MATERIALS AND METHODS: Patients with TTTS were treated with NS-LPCV from May 1994 to June 1997 and with S-LPCV from July 1997 to December 1999. TTTS was defined as polyhydramnios of > or = 8 cm maximum vertical pocket (MVP) in the recipient twin and oligohydramnios of < or = 2 cm MVP in the donor twin. Outcome was measured as survival per number of pregnancies and per number of fetuses together with limited morbidity data. RESULTS: NS-LPCV was used in 18 patients and 74 were treated with S-LPCV. Three patients interrupted their pregnancies electively after surgery (S-LPCV) and were removed from further analysis. Survival of at least one fetus was higher in S-LPCV (83.1%) than in NS-LPCV (61.1%) (P = 0.04), mostly due to a lower rate of dual intra-uterine fetal demise in S-LPCV (5.6%) than in NS-LPCV (22%) (P = 0.05). There were more hydropic fetuses in the NS-LPCV group (27%) than in the S-LPCV group (5.4%), but this difference did not account for the results. There was no difference in the survival per number of fetuses between the two groups. CONCLUSIONS: S-LPCV represents an important evolution in the surgical treatment of TTTS. The use of this technique by all centers should allow better comparison of fetal survival and morbidity rates. S-LPCV should be the standard technique in trials comparing amniocentesis versus laser for the treatment of severe TTTS.

Arteriovenous Anastomosis↗
PubMed2005

Matching-pursuit/split-operator Fourier-transform simulations of nonadiabatic quantum dynamics.

A rigorous and practical approach for simulations of nonadiabatic quantum dynamics is introduced. The algorithm involves a natural extension of the matching-pursuitsplit-operator Fourier-transform (MPSOFT) method [Y. Wu and V. S. Batista, J. Chem. Phys. 121, 1676 (2004)] recently developed for simulations of adiabatic quantum dynamics in multidimensional systems. The MPSOFT propagation scheme, extended to nonadiabatic dynamics, recursively applies the time-evolution operator as defined by the standard perturbation expansion to first-, or second-order, accuracy. The expansion is implemented in dynamically adaptive coherent-state representations, generated by an approach that combines the matching-pursuit algorithm with a gradient-based optimization method. The accuracy and efficiency of the resulting propagation method are demonstrated as applied to the canonical model systems introduced by Tully for testing simulations of dual curve-crossing nonadiabatic dynamics.

Journal Article↗
PubMed2004

Progression from frontal-parietal to mesial-temporal epilepsy after fluid percussion injury in the rat.

We recently described an in vivo model of post-traumatic epilepsy (PTE) in the rat where chronic spontaneous recurrent seizures appear following a single episode of fluid percussion injury (FPI). PTE, studied during the first 2 months post-injury, was focal and seizures originated predominantly from the frontal-parietal neocortex at or around the injury site. However, rarer bilateral seizures originating from a different and undefined focus were also observed. To shed light on the Posttraumatic Epileptogenic mechanisms and on the generation of bilateral seizures, we studied rats up to 7 months post-injury. In vivo paired epidural and depth-electrode recordings indicated that the anterior hippocampus evolves into an epileptic focus which initiates bilateral seizures. The rate of frontal-parietal seizures remained constant over time after 2 weeks post-injury, while the rate of hippocampal seizures greatly increased over time, suggesting that different mechanisms mediate neocortical and hippocampal post-traumatic epileptogenesis. Because of different temporal evolution of these foci, the epileptic syndrome was characterized by predominant frontal-parietal seizures early after injury, but by predominant mesio-temporal seizures at later time points. Pathological analysis demonstrated progressive hippocampal and temporal cortex pathology that paralleled the increase in frequency and duration of bilateral seizures. These results demonstrate that FPI-induced frontal-parietal epilepsy (FPE) progresses to mesial-temporal lobe epilepsy (MTLE) with dual pathology. These observations establish numerous similarities between FPI-induced and human PTE and further validate it as a clinically relevant model of PTE.

Animals↗
PubMed1988

Bunyavirus-vector interactions.

Recent advances in the genetics and molecular biology of bunyaviruses have been applied to understanding bunyavirus-vector interactions. Such approaches have revealed which virus gene and gene products are important in establishing infections in vectors and in transmission of viruses. However, much more information is required to understand the molecular mechanisms of persistent infections of vectors which are lifelong but apparently exert no untoward effect. In fact, it seems remarkable that LAC viral antigen can be detected in almost every cell in an ovarian follicle, yet no untoward effect on fecundity and no teratology is seen. Similarly the lifelong infection of the vector would seem to provide ample opportunity for bunyavirus evolution by genetic drift and, under the appropriate circumstances, by segment reassortment. The potential for bunyavirus evolution by segment reassortment in vectors certainly exists. For example the Group C viruses in a small forest in Brazil seem to constitute a gene pool, with the 6 viruses related alternately by HI/NT and CF reactions, which assay respectively M RNA and S RNA gene products (Casals and Whitman, 1960; Shope and Causey, 1962). Direct evidence for naturally occurring reassortant bunyaviruses has also been obtained. Oligonucleotide fingerprint analyses of field isolates of LAC virus and members of the Patois serogroup of bunyaviruses have demonstrated that reassortment does occur in nature (El Said et al., 1979; Klimas et al., 1981; Ushijima et al., 1981). Determination of the genotypic frequencies of viruses selected by the biological interactions of viruses and vectors after dual infection and segment reassortment is an important issue. Should a virus result that efficiently interacts with alternate vector species, the virus could be expressed in different circumstances with serious epidemiologic consequences. Dual infection of vectors with different viruses is not unlikely, because many bunyaviruses are sympatric in nature. For example, the Ae. trivittatus-cottontail rabbit and the Ae. triseriatus-squirrel arbovirus cycles are sympatric in the ecotone between their respective grassland and forest ecosystems (LeDuc, 1979). Should a LaCrosse virus variant or reassortant evolve that was efficiently vectored by Ae. trivittatus mosquitoes, significantly more human infections with La Crosse virus would likely occur. Unlike Ae. triseriatus, Ae. trivittatus mosquitoes are not restricted to forested areas and consequently are more likely to encounter and to feed upon humans.(ABSTRACT TRUNCATED AT 400 WORDS)

Aedes↗