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Biomedical subjects

G R Taylor

Publications and source records attributed to G R Taylor.

At least 109 records · Page 6Linked to original sources
PubMed1986

Hematological changes following repetitive decompressions during simulated extravehicular activity.

A study was performed to evaluate decompression procedures suggested for use prior to Space Shuttle extravehicular activity. Hematological parameters were measured in 12 male human subjects before and after exposure in an altitude chamber to a 3-day staged decompression schedule, with simulated extravehicular activity. Following the exposure, significant increases occurred in white blood cell count and activated partial thromboplastin time, and platelet aggregate ratio was significantly decreased. Pre-exposure samples from subjects who were susceptible to formation of venous gas emboli (VGE) exhibited a significantly lower degree of ADP-induced platelet aggregation and a significantly higher amount of lymphocyte blastogenic transformation in response to the mitogen phytohemagglutinin than samples from VGE-resistant subjects. The results indicate that, following this decompression profile, small but significant changes occur in several hematological parameters, and that levels of certain parameters may be related to susceptibility to VGE formation during decompression.

Adult↗
PubMed1986

Recovery and measurement of specific RNA species from postmortem brain tissue: a general reduction in Alzheimer's disease detected by molecular hybridization.

The recovery of RNA from postmortem (PM) brain tissues was quantified by molecular hybridization. RNA degradation rates postmortem were faster in mice with herpes encephalitis than with uninfected mice, but clear ribosomal peaks could be seen up to 72 hr after death. In a comparison between frontal cortex samples from neurologically normal and Alzheimer's disease cases a reduction in ribosomal, poly A, preproenkephalin, and preprosomatostatin RNA levels was observed in the Alzheimer's disease group. This general reduction may be influenced by the cause of death as well as the pathology.

Alzheimer Disease↗
PubMed1986

Viruses in human brains: a search for cytomegalovirus and herpes virus 1 DNA in necropsy tissue from normal and neuropsychiatric cases.

DNA was extracted from the brains of patients with Alzheimer-type dementia, schizophrenia, Huntington's chorea and from patients without neurological disease, and examined for the presence of herpes simplex virus type 1 and human cytomegalovirus sequences. By selecting cloned virus DNA fragments which do not hybridize to normal human DNA we were able to achieve a detection level assessed on reconstruction experiments of 1 virus genome per 50 cells. Screening at such sensitivity did not detect virus sequences in the higher CNS, except in cases of encephalitis or immunosuppression. We conclude that, at this level of sensitivity, these viruses cannot be regarded as normal residents of the higher CNS, and at the time of death they do not appear to be associated with these neuropsychiatric conditions.

Aged↗
PubMed1986

Induction of intrachromosomal recombination in yeast by inhibition of thymidylate biosynthesis.

The biosynthesis of thymidylate in the yeast Saccharomyces cerevisiae can be inhibited by antifolate drugs. We have found that antifolate treatment enhances the formation of leucine prototrophs in a haploid strain of yeast carrying, on the same chromosome, two different mutant leu2 alleles separated by Escherichia coli plasmid sequences. That this effect is a consequence of thymine nucleotide depletion was verified by the finding that provision of exogenous thymidylate eliminates the increased production of Leu+ colonies. DNA hybridization analysis revealed that recombination, including reciprocal exchange, gene conversion and unequal sister-chromatid crossing over, between the duplicated genes gave rise to the induced Leu+ segregants. Although gene conversion unaccompanied by crossing over was responsible for the major fraction of leucine prototrophs, events involving reciprocal exchange exhibited the largest increase in frequency. These data show that recombination is induced between directly repeated DNA sequences under conditions of thymine nucleotide depletion. In addition, the results of this and previous studies are consistent with the possibility that inhibition of thymidylate biosynthesis in yeast may create a metabolic condition that provokes all forms of mitotic recombination.

Genotype↗
PubMed1986

Immunological analyses of U.S. Space Shuttle crewmembers.

We have previously reported changes in the immunoresponsiveness of "T" lymphocytes following space flight. Additional data collected before and after 11 Shuttle space flights show that absolute lymphocyte numbers, lymphocyte blastogenic capability, and eosinophil percent in the peripheral blood of crewmembers are generally depressed postflight. These responses resemble those associated with physical and emotional stress and may not be related to flight per se. Additional data from Space Shuttle flights 41B and 41D, involving 11 crewmembers, indicate a postflight decrease in cells reacting with "B" lymphocyte and monocyte monoclonal antibody tags. Further, the loss of "T" lymphocyte blast capability interacts with the decreased monocyte count (correlation coefficient = 0.697). This finding implies that the previously reported loss of blastogenic capability may be a function of decreased monocyte control, as noted in several non-spaceflight related studies.

Adult↗
PubMed1985

Southern transfer of native DNA using nylon membranes.

Transfer of native or denatured DNA from gels or filter manifolds was compared using nylon or nitrocellulose membranes. The results were comparable when denatured DNA was used, but only nylon membranes were able to retain native DNA. Although retention of the native DNA was less efficient the bound DNA could be rapidly denatured in situ, avoiding the need to soak gels in alkaline denaturation solution and neutralizing buffer.

Collodion↗
PubMed1985

Mating-type switching in yeast is induced by thymine nucleotide depletion.

Thymidylate biosynthesis was inhibited in a haploid heterothallic strain of Saccharomyces cerevisiae. When the treated cells were mixed with a haploid strain of the same mating-type, there was an increase in the recovery of diploid colonies. Genetic and biochemical analyses demonstrated that the diploid clones arose as a consequence of induced mating-type interconversion.

Crosses, Genetic↗
PubMed1985

Cytopathogenic cerebrospinal fluid from neurological and psychiatric patients.

Cerebrospinal fluids (CSFs) were examined for the presence of a cytopathogenic component by an in vitro assay. No abnormal proteins were detected in CSF which produced cytopathic effects. The cytopathic effect was associated with high-molecular-weight material which was resistant to enzyme treatment. The effect persisted after extensive ultraviolet irradiation. The presence of the cytopathic effect was associated with increased CSF enolase levels.

Cells, Cultured↗
PubMed1985

A comparison of the effects of cytotoxic cerebrospinal fluid on cell cultures with other cytopathogenic agents.

Protein synthesis, antigen synthesis, and cell membrane permeability were analyzed after inoculating human diploid fibroblasts with control or cytotoxic CSF, herpes simplex virus type 1 (HSV 1), poliovirus 3, or Clostridium difficile toxin. Whereas protein synthesis and membrane permeability were affected by the viruses, and virus antigens detectable by pooled human serum were synthesized, the bacterial toxin and cytotoxic CSF did not induce any new proteins or antigens, although the cytotoxic CSF reduced cellular protein synthesis levels and caused an increase in the permeability of the cell membranes. The effect of the cytotoxic CSF in cell culture resembles that of a toxin rather than a replicating virus.

Animals↗
PubMed1985

Herpes simplex virus encephalitis. Neuroanatomical and neurochemical selectivity.

Intracerebral infection of mice with HSV-1 was found to produce a 2-3-fold increase in dopamine and serotonin metabolism in cortex, striatum, diencephalon and brain stem. Neurochemical markers of GABA and acetylcholine neurones, and neurotransmitter receptor binding sites were unchanged. The immunohistochemical distribution of virus antigen revealed high levels of immunoreactivity in s. nigra, ventral tegmental area, locus coeruleus and dorsal raphe nucleus, whilst other areas of brain stem were clear of virus antigen. The changes in monoamine metabolism observed in experimental HSV encephalitis may be related to the concentration of virus in monoamine neurones.

Acetylcholine↗
PubMed1985

Search for cytomegalovirus in postmortem brain tissue from patients with Huntington's chorea and other psychiatric disease by molecular hybridization using cloned DNA.

Postmortem human brain extracts were examined for the presence of human cytomegalovirus (CMV) DNA by molecular hybridization using a dot blot technique. The method was able to detect picogram quantities of homologous DNA, but CMV specific hybridization was detected in only one of 83 brains examined. The positive case came from a patient who had received immunosuppressive therapy. We were not able to confirm the report that CMV is present in the brains of patients with Huntington's chorea, nor was CMV detected in the temporal cortex of brains from schizophrenic patients. Our findings are discussed in relation to the methodology for investigating a possible viral etiology of some neuropsychiatric diseases.

Adult↗
PubMed1985

Nine-year microflora study of an isolator-maintained immunodeficient child.

A male child, maintained in a controlled environment, was monitored each month for bacteria, yeasts, and filamentous fungi recovered from the mouth, nasal passages, feces, and nine body surface sites. Three natural microbial categories became apparent. Incident microorganisms were recovered from within the isolator but did not establish permanent residence. Of the 53 incident types isolated, 20 were filamentous fungi and 4 were yeasts. Some genera, such as Fusobacterium, Lactobacillus, Neisseria, and Rothia, which were commonly found in the reference group, did not become permanent inhabitants. Transient microorganisms were repeatedly recovered but could not be demonstrated within the isolated environment at the end of the study. The loss of only a few of the 19 transient species could be associated with antimicrobial therapy. Permanent microorganisms consisted of Pencillium citrinum and 17 bacterial types, of which alpha-hemolytic streptococci, Staphylococcus edpidermidis subgroups II and V, Micrococcus groups 1 and 2, Clostridium bifermentans, and Propionibacterium acnes were recovered throughout the entire 9 years of the study. The number of CFUs recovered from each sample type was generally not unlike that from the reference group of healthy male adults. Also, the number of different aerobic species recovered from the feces was within the normal range of that of the reference group. In contrast, the number of different species recovered from all other samples was less than that commonly found in the reference group.

Aerobiosis↗