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Biomedical subjects

M C Webb

Publications and source records attributed to M C Webb.

At least 19 recordsLinked to original sources
PubMed1995

Simian AIDS type D serogroup 2 retrovirus: isolation of an infectious molecular clone and sequence analyses of its envelope glycoprotein gene and 3' long terminal repeat.

We describe the molecular cloning of a serogroup 2 simian retrovirus (SRV; D2/RHE/OR) and present the sequence of its envelope (env) glycoprotein gene and 3' long terminal repeat region. This report documents the first infectious molecular clone of a serogroup 2 SRV and provides env sequence verification of genetic diversity among serogroup 2 SRV isolates.

Amino Acid Sequence↗
PubMed1993

Quantitative cerebral anatomy in depression. A controlled magnetic resonance imaging study.

Magnetic resonance imaging was used to examine cerebral anatomy in 48 inpatients with severe depression who were referred for electroconvulsive therapy and in 76 normal control subjects. The magnetic resonance imaging measures included determinations of regional cerebral volumes and ratings of the frequency and severity of cortical atrophy, lateral ventricular enlargement, and subcortical hyperintensity. The mean total frontal lobe volume was found to be 7% smaller in the inpatients with severe depression (235.88 mL) than in the normal control subjects (254.32 mL)--a difference that was statistically significant even after adjusting for the effects of age, sex, education, and intracranial size. No group differences were observed in the volumes of the cerebral hemispheres, the temporal lobes, or the amygdala-hippocampal complex, nor in the frequency of cortical atrophy. Neither did the groups differ with respect to the total volumes of the lateral and third ventricles, nor in the frequency of lateral ventricular enlargement. Patients with depression had a significantly higher frequency of subcortical hyperintensity in the periventricular white matter, with an odds ratio of 5.32.

Adult↗
PubMed1993

Buccal mucous membrane-fat graft in the management of the contracted socket.

A new surgical technique for reconstructing severely contracted sockets using an autogenous buccal mucous membrane-fat graft is presented. The buccal mucosa provides replacement of deficient conjunctival surface area; the fat in the underlying substantia propria of the buccal mucosa replenishes moderate volume deficiency in a single procedure. A custom-designed conformer is used in the immediate postoperative period to maintain reconstructed vertical fornices. We present four consecutive patients with contracted sockets having both a volume deficit and severe conjunctival contracture who were successfully rehabilitated using this technique.

Adipose Tissue↗
PubMed1992

Quantitative cerebral anatomy of the aging human brain: a cross-sectional study using magnetic resonance imaging.

Seventy-six healthy adults underwent magnetic resonance imaging (1.5 T) to investigate the effects of age on regional cerebral volumes and on the frequency and severity of cortical atrophy, lateral ventricular enlargement, and subcortical hyperintensity. Increasing age was associated with (1) decreasing volumes of the cerebral hemispheres (0.23% per year), the frontal lobes (0.55% per year), the temporal lobes (0.28% per year), and the amygdala-hippocampal complex (0.30% per year); (2) increasing volumes of the third ventricle (2.8% per year) and the lateral ventricles (3.2% per year); and (3) increasing odds of cortical atrophy (8.9% per year), lateral ventricular enlargement (7.7% per year), and subcortical hyperintensity in the deep white matter (6.3% per year) and the pons (8.1% per year). Many elderly subjects did not exhibit cortical atrophy or lateral ventricular enlargement, however, indicating that such changes are not inevitable consequences of advancing age. These data should provide a useful clinical context within which to interpret changes in regional brain size associated with "abnormal" aging.

Adult↗
PubMed1990

Cardiovascular response to unilateral electroconvulsive therapy.

Few studies have examined the cardiovascular response to pulse unilateral electroconvulsive therapy (ECT) performed using modern techniques. In this study of 30 patients (mean age 62 years) with major depression, we determined the effects of pulse unilateral ECT on cardiac work load using the rate-pressure product (RPP), a product of pulse and systolic blood pressure. The mean RPP across all ECT treatments increased by an average of 96% from pre-ECT baseline, with the maximal RPP occurring typically during the seizure. The amount of increase in RPP did not differ significantly over the course of treatments. The increase in RPP was significantly and inversely related to baseline RPP, such that subjects with the highest baseline RPPs actually had smaller increases in RPP during the ECT treatments. The mean percent change in RPP was not associated with age, sex, presence of cardiovascular disease, ECT stimulus charge, EEG seizure duration, or amnestic side effects. There was a trend (p = 0.06), however, for the mean increase in RPP to be greater in responders (100% increase, n = 25) than in nonresponders (76% increase, n = 5). The potential relationship of clinical outcome to the increase in RPP suggests that both factors may be manifestations of the physiological intensity of the ECT-induced seizure.

Adult↗
PubMed1979

A murine leukemia virus mutant with a temperature-sensitive defect in membrane glycoprotein synthesis.

Cells infected with a temperature-sensitive mutant (ts-26) of Rauscher murine leukemia virus (R-MuLV) or with wild-type virus were labeled with 35S-methionine, and cell extracts were examined for radioactive polypeptides which could be precipitated by monospecific antisera to viral proteins. When shifted from permissive (31 degrees C) to nonpermissive (39 degrees C) temperature, cells infected with ts-26 rapidly begin to accumulate gPr90enr, the glycoprotein precursor to the membrane envelope glycoprotein gp70 and to the membrane-associated protein p15E. Simultaneously, formation of these mature virion proteins ceases. In addition, lactoperoxidase-catalyzed surface labeling with 125I--iodine indicates that the plasma membrane of cells infected with ts-26 becomes depleted of gp70 antigens at 39 degrees C. Nevertheless, at 39 degrees C these cells release defective MuLVs which lack gp70 and p15E but contain an outer membrane. The released particles also contain an aberrantly processed form of the major virion core protein p30, and many of these virion cores have an unusual immature crescent shape. It has previously been reported that cells infected with the ts-26 mutant of R-MuLV process a 65,000 dalton precursor (Pr65gag) of the virion core proteins more slowly at 39 degrees C than do cells infected with wild-type virus (Stephenson, Tronick and Aaronson, 1975). Although we have confirmed these results, this effect is relatively small and it is known that various alterations of MuLV assembly can lead secondarily to inhibited processing of Pr65gag. We propose that the ts-26 mutant has a primary temperature-sensitive defect in membrane glycoprotein synthesis and that this change causes pleiotropic effects on core morphogenesis.

Genes↗
PubMed1977

Fine structural changes in the gastro-intestinal tract of the hypoxic puppy: a study of natural history.

The present study demonstrates that a 2 hr period of sustained hypoxia results in a focally destructive process, a process which resolves by 5 days. That the changes described in earlier work are not overwhelming to the animal suggest that an early, focal, and reversible stage of the development of acute enterocolitis in the puppy can be described with the aid of electron microsocpy.

Animals↗
PubMed1977

Microcirculatory changes in the lung of the hypoxic and hypovolemic puppy: an electron microscope study.

The effect of systemic hypoxemia and hypovolemia on pulmonary fine structure was studied and compared in 12 Labrador puppies 6 days to 3 weeks old. Central venous and arterial pressures were monitored and arterial pH, PCO2 and PO2 recorded serially. In 4 puppies lung biopsies were taken after a two hour period of breathing 7% oxygen. Four other puppies were made hypovolemic by acute hemorrhage of 50% of the calculated blood volume and lung biopsies taken after one hour. Four control puppies were maintained under anesthesia for two hours, breathing an atmosphere of 20% oxygen before lung biopsies were taken. Both hypoxemia and hypovolemia resulted in similar pulmonary ultrastructural changes. These changes which occurred more frequently in areas where the air spaces and blood vessels were expanded, were characterized by aggregation of platelets and leucocytes in the vascular space, focal endothelial cell disruption, interstitial edema and type I epithelial cell discontinuities with exudation of plasma into the alveolar air spaces.

Animals↗
PubMed1976

Pulmonary fine structural changes in children with tissue hypoxia.

Six children have undergone lung biopsy for evaluation of fine structure. Four children demonstrated increased DAVO2 preoperatively and had marked ultrastructural changes in their lungs. Such changes appear to result from embolization of microthrombi or microaggregates to the lung from under-oxygenated tissue.

Adolescent↗
PubMed1975

Microcirculatory changes in the gastrointestinal tract of the hypoxic puppy: an electron microscope study.

Hypoxia and hypovolemia result in similar ultrastructural changes. These changes are characterized by aggregation of platelets and leukocytes in the vascular space, focal endothelial cell disruption, and appearance of increased amounts of perivascular edema, and loss of ultrastructural organization of the mucosal cell. These changes appear to relate to variations in blood flow to the mucosa of different areas of the bowel and to follow the distribution observed for necrotizing enterocolitis in the human infant.

Animals↗
PubMed1975

Filtration characteristics of three new in-line blood transfusion filters.

Three types of microemboli filters were examined with the scanning electron microscope. The single layer 40 mu pore filter traps aggregates in the pores. The aggregates are extruded and pass on with the blood and can be demonstrated in a Dacron wool filter downstream. The polyurethane foam filter is an in depth multiple pore filter of variable pore size. This filter allows many aggregates to escape through the pores in the beginning of a transfusion and these aggregates were seen in a Dacron wool filter downstream. As aggregates become trapped, the pore sizes decrease, filtration improves, and flow through the filter becomes reduced. The Dacron wool filter absorbs the particulate material to the fibers of wool. This filter has a large capacity and was not observed to leak aggregates even when subjected to high filtration pressures.

Animals↗