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Biomedical subjects

M E Taylor

Publications and source records attributed to M E Taylor.

At least 91 records · Page 5Linked to original sources
PubMed1986

Genetic variation in HTLV-III/LAV over time in patients with AIDS or at risk for AIDS.

In a study of genetic variation in the AIDS virus, HTLV-III/LAV, sequential virus isolates from persistently infected individuals were examined by Southern blot genomic analysis, molecular cloning, and nucleotide sequencing. Four to six virus isolates were obtained from each of three individuals over a 1-year or 2-year period. Changes were detected throughout the viral genomes and consisted of isolated and clustered nucleotide point mutations as well as short deletions or insertions. Results from genomic restriction mapping and nucleotide sequence comparisons indicated that viruses isolated sequentially had evolved in parallel from a common progenitor virus. The rate of evolution of HTLV-III/LAV was estimated to be at least 10(-3) nucleotide substitutions per site per year for the env gene and 10(-4) for the gag gene, values a millionfold greater than for most DNA genomes. Despite this relatively rapid rate of sequence divergence, virus isolates from any one patient were all much more related to each other than to viruses from other individuals. In view of the substantial heterogeneity among most independent HTLV-III/LAV isolates, the repeated isolation from a given individual of only highly related viruses raises the possibility that some type of interference mechanism may prevent simultaneous infection by more than one major genotypic form of the virus.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Human serum contains a lectin which inhibits hepatic uptake of glycoproteins.

Human serum will inhibit the specific uptake of N-acetylglucosamine-terminated glycoproteins by isolated rat hepatic sinusoidal cells. The serum inhibitors are not glycoproteins that bind to the hepatic mannose/N-acetylglucosamine receptor but have the properties of lectins which bind to mannose/N-acetylglucosamine-terminated glycoproteins. They can be isolated from serum by affinity chromatography. The predominant lectin, with a molecular mass of less than 35 kDa, will inhibit the sinusoidal cell uptake of glycoproteins in vitro.

Animals↗
PubMed1984

Reconstitution of purified halorhodopsin.

Asolectin lipid vesicles containing halorhodopsin show light-induced acidification in the presence of proton ionophores. This effect is abolished by triphenyltin chloride, a chloride/hydroxyl antiporter, and is greatly diminished by valinomycin in the presence of potassium ions, which collapse the membrane potential. This indicates that halorhodopsin orients in the lipid vesicles preferentially inside out, pumping chloride into the extravesicular compartment. The absorption maximum of halorhodopsin in asolectin vesicles in 3 M NaCl is at 567 nm, and the action spectrum for the light-induced pH changes followed closely the absorption spectrum. Replacement of chloride by acetate or sulfate causes a shift in the absorption maximum to approximately equal to 559 nm and renders the pump inactive. The different photocycles of the two forms were used to show that 80% of the molecules have the extracellular side exposed to the vesicle interior and that the halide-binding site(s) associated with the spectral transition is accessible from the extracellular side of the molecule. The data presented demonstrate that the purified chromoprotein is the light-driven chloride pump in Halobacterium halobium.

Bacteriorhodopsins↗
PubMed1984

Evidence for a directional correspondence between eye movements and dream imagery in REM sleep.

We examined the relationship between eye movement direction in REM sleep recorded by electrooculograph (EOG) and gaze direction in dream imagery. In a double-blind protocol, carefully screened and trained subjects were awakened subsequent to direct coupled EOG activity that was either predominantly horizontal or vertical. Following a target eye movement that fulfilled predetermined amplitude and directional criteria, a brief period of ocular quiescence was allowed to transpire before the subject was awakened. The dream narratives and EOG activity occurring prior to the REM awakenings were each reduced to a series of quantitatively scaled ratings. Analyses of variance demonstrated that when the confidence level of the experimenters' prediction is taken into account, statistically significant relationships exist between the number and direction of shifts of gaze in the dream report and scaled measurements of the corresponding EOG. When given dream narratives and the corresponding EOG recordings in sets of four, judges were unable to match them correctly better than by chance. However, in the above matching, judges significantly paired the dream narratives with EOG recordings that were in the same axis of gaze.

Adult↗
PubMed1984

Effects of iron loading and bacillus Calmette-Guerin on a glycoprotein recognition system on rat hepatic sinusoidal cells.

Experiments were performed to determine the effects of agents that modify Kupffer cells on the mannose-N-acetylglucosamine-glycoprotein receptor on hepatic sinusoidal cells. Cells were prepared by collagenase liver perfusion, centrifugation on Percoll gradients, and centrifugal elutriation. The uptake of 125I-labeled agalacto-orosomucoid (125I-AGOR), an N-acetylglucosamine-terminated glycoprotein, was greatest (53% of total uptake) by elutriator fractions containing equal proportions of endothelial and Kupffer cells ("mixed cell" fraction). Uptake was specific and time and concentration dependent. The apparent Km (0.4 mumol/L) and the patterns of inhibition by monosaccharides were similar in all the elutriator fractions, suggesting that only one class of receptor was present. The highest apparent maximal velocity (18 pmol/hr/5 X 10(6) cells) was found in the mixed cell fraction, indicating this fraction contained the highest proportion of receptor-bearing cells. Latex (0.8 micron) and bacillus Calmette-Guerin pretreatments did not influence the hepatic uptake of the glycoprotein in vivo. Iron sorbitol significantly reduced hepatic glycoprotein uptake and caused a twofold increase in the proportion of the ligand remaining in the circulation. Uptake of 125I-agalacto-orosomucoid by cells from latex-treated rats was similar to controls, but uptake by bacillus Calmette-Guerin-treated rat cells was only 25% of control uptake. This was related to a marked increase in sinusoidal cell number caused by bacillus Calmette-Guerin. In contrast, iron sorbitol caused a selective suppression of 125I-agalacto-orosomucoid uptake (10% of control uptake) by cells in the mixed cell fraction. This study showed that maximal uptake of 125I-agalacto-orosomucoid was by elutriator fractions containing equal proportions of endothelial and Kupffer cells and that iron sorbitol suppressed ligand uptake by these cells, possibly by influencing the mannose-N-acetylglucosamine receptor on Kupffer cells.

Animals↗
PubMed1983

Purification of photochemically active halorhodopsin.

We have developed a procedure for the purification of halorhodopsin in a photochemically active state. Solubilization of membranes from a bacteriorhodopsin-negative Halobacterium strain with octyl glucoside was followed by chromatography on hydroxylapatite and octyl-Sepharose gels. All steps were carried out in high-ionic-strength solutions. The procedure resulted in 270-fold enrichment with a 35% yield. The eluted pigment had an absorption maximum at 575 nm and an A280/A575 ratio of 2. On removal of the detergent by dialysis, the purified halorhodopsin was chemically bleached, regenerated with [3H]retinal, and reduced with cyanoborohydride. Such samples showed one main and one satellite band after staining or fluorography of NaDodSO4/polyacrylamide gels. The apparent molecular weight of the main band was 25,000. Purified halorhodopsin underwent a photocycle after excitation with pulsed laser light and showed a 9-nm blue shift (at neutral pH) on removal of chloride ion. The pigment also underwent a photoreversible shift at alkaline pH to a form absorbing maximally at 410 nm. All three reactions closely resembled those of membrane-bound halorhodopsin.

Bacterial Proteins↗
PubMed1983

Metabolism of prolonged shock.

Dogs in shock due to controlled cardiac tamponade for 4 or 12 h were studied to determine which of the metabolic changes characteristic of early shock persisted if the shock state was prolonged. Moderate hyperglycemia and severe lactacidemia were present in the first few hours but the levels returned to near normal values by the end of 12 h. The entry rate of lactic acid into the circulation as well as the rate of glycogenolysis was high in the first 4 h but decreased thereafter even though skeletal muscle glycogen stores were not exhausted. In early but not in late shock glycogen accumulated in the heart. Glucose entry and exit rates were significantly elevated in early shock only. Increased protein utilization and decreased fatty acid mobilization persisted throughout the experimental period. Both in early and late shock the incorporation of labeled free fatty acid into tissue lipids was decreased in most organs. In the diaphragm free fatty acid incorporation only decreased in late shock. In the heart and lung, incorporation was higher than normal in the early stages but was at control levels after 12 h of shock.

Ammonia↗
PubMed1977

Antigenic and morphologic regeneration of epidermal basement membrane in short term organ culture of human skin.

In fetal life the development of bullous pemphigoid antigen is preceded by a morphologically detectable basement membrane zone (BMZ). The present study investigated the possibility that similar morphologic and antigenic changes of the BMZ occur in short term organ culture of human skin. Twenty small pieces from each of four neonatal foreskin specimens were cultured under standard conditions. At regular intervals two pieces from each specimen were removed. One piece was frozen and cryostat sections were processed for indirect immunofluorescence using a patient's serum that was proven to have circulating pemphigoid IgG antibodies. Additional sections were stained with periodic acid-Schiff and hematoxylin and eosin. The other piece was processed for electron microscopic examination. Morphologically the BMZ started degenerating after 24 hours. Regeneration started on the 4th day and reached an optimal level on the 5th day. Chance of the immunofluorescence line at the BMZ began with a slight weakening at 24 hours followed by progressive widening and breakage until the 4th day when fluorescence was no longer detectable. Except for a few punctate areas immunofluorescence remained absent on the 5th day. Sixth day specimens, however, revealed reappearance of the immunofluorescence line in a continuous pattern. By the 7th day a second morphologic and antigenic degeneration started at the BMZ. This lag between the morphologic and antigenic regeneration of the BMZ in organ culture although shorter is comparable to the one observed during the development of the BMZ in fetal life.

Antigens↗
PubMed1976

The functional anatomy of the hindlimb of some African Viverridae (Carnivora).

The functional anatomy of the hindlimb of 12 species of viverrids was studied with relation to locomotion. The animals were allocated to primary locomotor categories on the basis of their anatomy and locomotion. The climbing, arboreal walking category (Nandinia binotata) is characterized by a small sacroiliac articulation, the iliopsoas inserts onto a medially located lesser trochanter and the femoral condyles are not posteriorly placed. The hindfoot is plantigrade and its structure permits considerable movement. The pads are soft and the claws retractile. Representatives of the arboreal and terrestrial walking and jumping category (Genetta genetta, G. servalina, G. tigrina) have a plantigrade forefoot and digitigrade hindfoot. The lesser trochanter is more posteriorly placed than in the climbing category. A previously undescribed muscle, the caudofemoralis profundus extends from several anterior caudal vertebrae to the femur. The tibio-astragular joint restricts supination of the foot. There is little mediolateral movement in the digitidgrade foot. The claws are retractile. In the general terrestrial walking and scrambling group (Helogale parvula, Mungos mungo, Atilax paludinosus, Bdeogale crassicauda, Herpestes ichneumon, H. sanguineus) the animals have essentially similar hindlimbs except for size differences and modifications to the feet. Helogale and Mungos have large medial epicondyles on the humerus and large terminal phalanges. Bdeogale has a vestigial first metatarsal, while Atilax can splay its digits. In all species the distal phalanges are non-retractile. The trotting category (Civettictis civetta, Ichneumia albicauda) is characterized by longer epipodials and metapodials and a more proximal position of muscle bellies. Most of the adaptations minimize rotation, adduction and abduction of the leg and supination of the foot. The metatarsals are closely adjoined and the distal phalanx is stout and non-retractile. There appear to be two levels of locomotory adaptation. Major adaptations affect the whole appendicular skeleton and are used to assign animals to primary locomotor categories. Minor adaptations occur mainly in the foot and indicate the more specific habits of the animal.

Africa↗
PubMed1976

Preservation of specific fluorescence by sealing with nail polish.

Semipermanent mounting media and postfixation of immunofluorescence (IF) slides in alcohol have been effective in preserving specific fluorescence (SF). In the present study the efficacy of such mounting was compared with a simpler technique of sealing the routinely mounted IF slides with nail polish. Frozen sections of skin lesions of systemic lupus erythematosus and lichen planus, and patients' sera known to have pemphigus or pemphigoid antibodies were used for IF procedures. SF was equally detectable with both techniques for over 8 months. Control slides similarly processed but not sealed lost most of their SF within a few weeks.

Alcohols↗