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Biomedical subjects

A C Taylor

Publications and source records attributed to A C Taylor.

At least 19 recordsLinked to original sources
PubMed1994

The use of museum specimens to reconstruct the genetic variability and relationships of extinct populations.

In this review, we discuss the use of DNA from museum specimens to address conservation genetic questions. We provide four examples from our previous studies of the northern hairy-nosed wombat, African wild dog, Ethiopian wolf and red wolf. These species were genetically surveyed using two molecular approaches: first, analysis of short sequences in the mitochondrial genome using species-specific primers, and second, analysis of hypervariable microsatellite loci. The studies demonstrate that museum-derived DNA adds an important dimension to the genetic study of extant populations. Inaccessible populations can be studied, and both the loss of genetic variation and its distribution over space and time can be better understood. Finally, analysis of additional museum material provides definitive evidence for a hybrid origin of the red wolf.

Animals↗
PubMed1994

Effect of the psychoactive metabolite of marijuana, delta 9-tetrahydrocannabinol (THC), on the synthesis of tumor necrosis factor by human large granular lymphocytes.

The natural killer cell (NK)/3polymorphonuclear neutrophil axis has recently been identified to be important in early defense against the opportunistic fungi, Candida albicans. Repression of this system is therefore likely to contribute to susceptibility to opportunistic infections. delta 9-Tetrahydrocannabinol (THC), an active constituent of marijuana, has been reported to be immunosuppressive at concentrations that exceed attainable plasma levels. In this report, we examine the possibility that human large granular lymphocytes (LGL) can be immunosuppressed by exposure to THC at physiologically relevant concentrations and probed two functions associated with LGL, i.e., cytokine production and tumoricidal activity. We find that these low levels of THC inhibit tumor necrosis factor-alpha (TNF) induction from LGL by C. albicans and are dependent upon THC dose (0.005-5.0 micrograms/ml) and length of exposure (0.05-3.0 hr). Northern blot analysis indicates that the downregulation of TNF production from LGL by THC resides at the mRNA level. Moreover, exposure of LGL to physiological THC concentrations (0.01-2.0 micrograms/ml) diminishes their cytolytic activity against K562 tumor cells.

Candida albicans↗
PubMed1994

Genetic variation of microsatellite loci in a bottlenecked species: the northern hairy-nosed wombat Lasiorhinus krefftii.

We investigate the utility of hypervariable microsatellite loci to measure genetic variability remaining in the northern hairy-nosed wombat, one of Australia's rarest mammals. This species suffered a dramatic range and population reduction over the past 120 years and now exists as a single colony of about 70 individuals at Epping Forest National Park, central Queensland. Because our preliminary research on mitochondrial DNA and multilocus DNA fingerprints did not reveal informative variation in this population, we chose to examine variation in microsatellite repeats, a class of loci known to be highly polymorphic in mammals. To assess the suitability of various wombat populations as a reference for comparisons of genetic variability and subdivision we further analysed mitochondrial DNA cytochrome b sequence, using phylogenetic methods. Our results show that appreciable levels of variation still exist in the Epping Forest colony although it has only 41% of the heterozygosity shown in a population of a closely-related species. From museum specimens collected in 1884, we also assessed microsatellite variation in an extinct population of the northern hairy-nosed wombat, from Deniliquin, New South Wales, 2000 km to the south of the extant population. The apparent loss of variation in the Epping Forest colony is consistent with an extremely small effective population size throughout its 120-year decline.

Animals↗
PubMed1992

An association between ADH protein levels and polymorphic nucleotide variation in the Adh gene of Drosophila melanogaster.

Southern analysis of the Adh region of 212 Drosophila melanogaster lines collected from the Tahbilk winery revealed linkage disequilibrium between a 37-bp insertion [designated delta 2 by Kreitman (1983)] and the fast electrophoretic variant of alcohol dehydrogenase (ADH-F). Among these lines 34% contained the insert and encoded ADH-F, 33.5% encoded ADH-F and did not have the insert, and 32.5% encoded the slow electrophoretic variant of alcohol dehydrogenase (ADH-S). Strong linkage association between this insert and ADH-F is evident worldwide. Twenty-nine of the second chromosome lines were characterized for ADH protein quantity by using radial immunodiffusion. ADH quantity was estimated in both larvae and adult males raised in the presence and absence of alcohol supplement to each of two different food media. Analyses of variance indicated higher levels of ADH protein in larvae from lines with the insert (all ADH-F), compared with those without (both ADH-F and ADH-S), independent of either dietary alcohol or media type. No such difference in ADH quantity between insert- and noninsert-containing ADH-F lines was detected in adults, although the expected higher levels occurred in ADH-F lines compared with ADH-S lines. Given the high levels of linkage disequilibrium in the Adh region, these data suggest that either polymorphic nucleotide-site variants positively associated with delta 2 on the second chromosome or delta 2 itself increases larval levels of ADH protein.

Alcohol Dehydrogenase↗
PubMed1991

Conservation genetics of the koala (Phascolarctos cinereus). II. Limited variability in minisatellite DNA sequences.

We have examined variability in TaqI and EcoRI restriction fragment sizes of DNA from the koala (Phascolarctos cinereus) using six HVR (hypervariable region) probes which reveal complex, individual-specific restriction patterns in humans and other species. Frequency of band-sharing among unrelated koalas was extremely high. This result is likely to be a consequence of the history of near-extinction and artificial recolonization of the populations we have studied, rather than a general marsupial or koala-wide phenomenon.

Animals↗
PubMed1990

Whither the professions?

I must confess to having been a little surprised at being asked to give The Dental School Founders' and Benefactors' Lecture this year. It is manifest to all that I am not a founder of the School and as chairman of the Health Authority I have not always been perceived to be a benefactor. Nevertheless I accepted your Dean's invitation and I hope my status may improve. There has been some uncertainty in relation to my title 'Whither the professions?' as to whether it expresses a question or an exhortation. It was certainly intended to be a question.

Dentistry↗
PubMed1986

A serological survey of scrub, tick, and endemic typhus in Sabah, East Malaysia.

A seroepidemiological survey of 837 people and 383 febrile patients was performed in rural areas of Sabah. We determined that the rickettsial diseases scrub typhus and endemic typhus were uncommon causes of febrile illness, as was tick typhus, except in forest dwelling peoples. The rate of occurrence of SFGR specific antibody was 16.5% among 412 forest dwellers, indicating that tick typhus may be a frequent cause of illness in this population.

Adolescent↗
PubMed1985

Oxygen consumption by Palaemon elegans (Rathke) in response to temperature change: a determinant of distribution.

The distribution of the intertidal rock pool prawn Palaemon elegans Rathke, on a rocky shore of the Isle of Cumbrae in west Scotland, was investigated. Prawns of all sizes were abundant in the mid- to high-shore pools throughout the summer until September when the largest individuals began to dissappear from the shore. Small and large P. elegans were found to be distributed on the shore in different ways. The small prawns found on the shore during the winter exhibited a much altered behaviour. In the laboratory, the effect of temperature change on oxygen consumption was assessed as was the role of temperature acclimation in determining the rate of oxygen consumption. Oxygen consumption calculated as a weight specific rate (Mo2) could be negatively correlated with body weight. This relationship between body weight and oxygen consumption was different in prawns acclimated to 10 and 23 degrees C and is considered to be an acclimatory response. The acute response, of prawns acclimated to a given temperature, to changes in temperature was similar in different sized prawns. After an acclimatory period of between 1 and 2 weeks small prawns exhibited positive acclimation of oxygen consumption whereas the larger prawns appeared to be unable to acclimate. This variable size dependent, response is discussed as a determinant of distribution and behaviour.

Acclimatization↗
PubMed1981

A universal computer and interface system for the disabled (UNICAID).

A prototype text handling and computing system using microprocessor technology has been developed for the severely handicapped user. The input uses a serial 'suck-puff' code (TWC code version DR2). In addition to the usual video display and full editing and printout facilities of a word processor, the unit acts as a terminal for other computers and can also function as a stand-alone microcomputer using commercial software. The 'bus' structure allows simple expansion to incorporate additional functions, and a remote control link is used for the input. The prototype is currently being evaluated by a tetraplegic student.

Communication Devices for People with Disabilities↗
PubMed1976

The cardiac responses to shell opening and closure in the bivalve Arctica islandica (L.).

Shell closure in Arctica islandica is followed by an exponential decrease in the oxygen tension of the mantle cavity water and is accompanied by an initial increase in heart rate which is followed at lower oxygen tensions by a bradycardia. Prior to shell opening there is a slight increase in heart rate before any movement of the shell valves can be detected. However, once the shell opens and pumping activity recommences there is a rapid increase in heart rate, often to levels above normal. Perfusion of the mantle cavity with water of high and low oxygen tension resulted in the cardiac responses normally associated with shell opening and closure. Recordings of the PO2 of the blood in the ventricle, made simultaneously with cardiac recordings, showed that the changes in heart rate were recorded only after the PO2 of the blood had changed. These experiments suggest that changes in the PO2 of the mantle cavity water may be primarily responsible for the cardiac responses to shell closure in Arctica.

Animals↗
PubMed1976

The respiratory responses of Carcinus maenas to declining oxygen tension.

The degree of respiratory independence shown by Carcinus under conditions of declining oxygen tension is dependent on the animal's level of activity. Inactive Carcinus are capable of maintaining respiratory independence down to a Po2 of 60-80 mmHg. This is achieved primarily by an increase in ventilation volume such that the amount of oxygen made available at the respiratory surfaces remains constant over a wide range of oxygen tension. The Po2 at which this can no longer be maintained corresponds closely to the Po2 at which respiratory independence is lost. Under normoxic conditions the Po2 of the post- and prebranchial blood was 97 and 18 mmHg respectively. At the high oxygen tensions prevailing in the postbranchial blood the respiratory pigment is fully saturated. Under conditions of declining oxygen tension the heart rate remains more or less constant until the Po2 reaches 60-80 mmHg, the onset of bradycardia coinciding with the loss of saturation of the haemocyanin. Although cardiac output falls during hypoxia, the capacity rate ratio remains approximately constant, which enables the effectiveness of oxygen uptake by the blood to remain at a high level.

Animals↗