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Biomedical subjects

C Clark

Publications and source records attributed to C Clark.

At least 37 records · Page 2Linked to original sources
PubMed1990

Diversity of Conus neuropeptides.

Conus venoms contain a remarkable diversity of pharmacologically active small peptides. Their targets are ion channels and receptors in the neuromuscular system. The venom of Conus geographus contains high-affinity peptides that act on voltage-sensitive calcium channels, sodium channels, N-methyl-D-aspartate (NMDA) receptors, acetylcholine receptors, and vasopressin receptors; many more peptides with still uncharacterized receptor targets are present in this venom. It now seems that the Conus species (approximately 500 in number) will each use a distinctive assortment of peptides and that the pharmacological diversity in Conus venoms may be ultimately comparable to that of plant alkaloids or secondary metabolites of microorganisms. The cone snails may generate this diverse spectrum of venom peptides by a "fold-lock-cut" synthetic pathway. These peptides are specific enough to discriminate effectively between closely related receptor subtypes and can be used for structure-function correlations.

Amino Acid Sequence↗
PubMed1990

A model for teaching periodontal surgery.

A simple laboratory-made model is described for periodontal surgical technique exercises. It has proved useful for tutor demonstration and student practice of all aspects of flap management.

Humans↗
PubMed1990

Regional cerebral glucose metabolism in Turner syndrome.

Regional cerebral glucose metabolism was examined in females with Turner syndrome, a sex chromosome abnormality. Previous studies have found a visual/spatial cognitive anomaly in these women but, to date, no abnormalities in brain structure or function have been associated with the condition. In the present study, decreases in regional metabolism were found in the occipital and parietal cortex. The involvement of the occipital cortex, although consistent with the observed cognitive anomalies, has not been suggested previously as an area dysfunction. Because the occipital cortex is a primary sensory cortex, the reduction of glucose metabolism in the parietal cortex may reflect a lack of innervation from the occipital cortex. Besides insight into the functional specialization of the brain, these findings are also consistent with previous reports on animals regarding the effects of estrogen in brain maturation.

Adult↗
PubMed1990

Implications of olfactory agnosia for understanding sex differences in schizophrenia.

In our studies, 50 percent of the male patients with schizophrenia have an olfactory agnosia. This finding is of interest because the olfactory neuroanatomical network involves brain regions found to be abnormal in patients with schizophrenia, and this olfactory deficit appears to be sex dependent. This article reviews conceptual models for assessing olfactory function, describes the neuroanatomical structures involved, and reviews the findings of olfactory performance in patients with neurological dysfunction. The findings are then integrated with neuropathological studies of patients with schizophrenia. Finally, as there is increasing evidence for a sex difference in patients with schizophrenia, a model is suggested to account for these differences based on neuro-developmental and latent lesion hypotheses.

Agnosia↗
PubMed1990

Personality types of family practice residents in the 1980s.

This study was based on a nationwide sample of 778 family practice residents in the mid-1980s and was conducted to determine the personality types that were most common among those residents. The results showed that the single most common personality type was that in which the individual prefers to see the world in terms of challenges and future possibilities and to make decisions based upon his or her subjective values. These results showed that the sample differed significantly in Myers-Briggs personality type from both the general practitioners of the 1950s and the early family practice residents of the 1970s, who preferred to see the world in terms of the immediate facts of experience and to make decisions objectively. There were also significant differences between the civilian and military family practice residents, but not between the community-based and university-based residents. Implications regarding future practice styles, physicians' personal values, and manpower needs are discussed.

Career Choice↗
PubMed1990

Inhaled fentanyl as a method of analgesia.

A study was undertaken to investigate the use of fentanyl by aerosol for postoperative analgesia. Seven patients had placebo, six received fentanyl 100 micrograms and seven were given fentanyl 300 micrograms. A significant improvement in postoperative pain, as assessed by linear visual analogue scale, was achieved in the higher dose group, and in both fentanyl groups the time to alternative analgesia was significantly longer than in the control group. Serum fentanyl levels after inhalation of 100 micrograms reached a plateau around 0.04 ng/ml and after 300 micrograms at around 0.1 ng/ml after 15 minutes. Inhaled fentanyl may have a useful analgesic effect despite these low serum levels; this supports the hypothesis that the mode of analgesia from inhaled opioids may be different from that after other routes of administration. There were no adverse effects such as respiratory depression, bronchospasm, nausea or drowsiness.

Adolescent↗
PubMed1990

Human immunodeficiency virus pseudotypes with expanded cellular and species tropism.

One mechanism for expanding the cellular tropism of a virus is through the formation of phenotypically mixed particles or pseudotypes, a process commonly occurring during viral assembly in cells infected with two or more viruses. We report here that dual infection of cells with human immunodeficiency virus (HIV) and a murine amphotropic retrovirus leads to the production of HIV pseudotypes that have acquired the host range of the amphotropic retrovirus and are capable of infecting not only CD4- human cells but also mouse cells. The replication of the HIV pseudotypes in the various CD4- cells was determined by measuring the appearance of HIV antigens in the supernatants, by cocultivation of CD4+ CEM cells with the infected CD4- cells, and in some cases by assaying the culture supernatants directly for infectious virus. Of the cells tested, human foreskin fibroblasts were the best host cells, and by in situ cytohybridization, we were able to document that all cells in the culture were infected. In addition, the temporal appearance of HIV-specific proteins in the HIV pseudotype-infected fibroblasts was similar to that seen in CD4+ CEM cells. If the human fibroblasts were first infected with the amphotropic retrovirus, they demonstrated the property of superinfection exclusion and were resistant to subsequent infection by the HIV pseudotype. In other cell lines, including the human glioblastoma-derived cell line U373MG, HeLa cells, BALB/c mouse embryo cells, and SC-1 wild mouse cells, although the HIV pseudotype infection appeared to be less efficient, substantial amounts of HIV were nevertheless produced. These results indicate that the HIV (amphotropic retrovirus) pseudotypes may be useful for studying the molecular biology of HIV infections in a wide range of cells.

Animals↗
PubMed1990

An empirical model for analysing and interpreting ventricular measures.

Given the abundant and, at times, contradictory studies of ventricular enlargement in neurological and psychiatric disorders, the current study was carried out to provide an empirical basis for analysing and interpreting these measures. A sample of CT scans on 100 control subject was drawn from the files of the University of British Columbia Department of Radiology and 19 measures of ventricular and head diameter or area were made. The interrelationships of these measures were then examined using factor analytic procedures. Three ventricular dimensions were found. To validate these three dimensions, the relationship of each with age was examined and then the age-corrected scores of seven clinical groups were compared on each of these dimensions. The magnitude of the relationship between these dimensions and age was impressive and each dimension contributed unique information regarding these age-related changes. Moreover, the analysis of the clinical groups suggested that differential patterns of ventricular change were present dependent upon the disease. These results are discussed with a view to integrating the findings of previous studies and planning future studies.

Adult↗
PubMed1990

Regional cerebral glucose metabolism in major depressive disorder.

Six subjects with DSM-III defined unipolar major depressive disorder had positron emission tomography scans using 18F-2-fluoro-2-deoxy-D-glucose (2FDG) before and after treatment with imipramine. Their 12 scans were compared to the scans of six controls matched for age. Significant reductions in metabolism for subjects in the depressed group were found on scans for both the anterior and right frontal regions. significant reductions in metabolism occurred more often in the right hemisphere than the left. No significant changes in metabolism could be attributed to imipramine. In addition, absolute metabolic rates were not related to the degree of depression pre- and post-treatment. The findings suggest that hypometabolism in the frontal cortex and right hemisphere may occur in major depressive disorders.

Adult↗
PubMed1990

Family factors affecting adjustment in Japanese immigrant housewives.

Data obtained from 130 questionnaires distributed to immigrant Japanese housewives were analyzed to determine if family factors were associated with poor adjustment, and in particular with depressive symptoms. It was possible to identify women who had no major adjustment problems in adapting to life in Canada (n = 70), transitional adjustment problems (n = 30), late onset adjustment problems (n = 7) and chronic adjustment problems (n = 23). These categories were determined by self-report and validated by symptom identification. Style of marriage, communication with spouse and mother-child interactions were hypothesized to be related to adjustment problems. A 16 item questionnaire was developed to assess the degree to which these factors affected adjustment. The only factor which affected degree of adjustment was communication with the spouse. These results are discussed within the context of traditional hypotheses concerning adaptation to a new culture and the implication for treatment.

Acculturation↗
PubMed1990

The fluid mechanics of a sac-type ventricular assist device.

Flow visualisation and velocity measurement studies have been carried out on the liquid side of a sac-type VAD. The objectives have been to identify both good (e.g. short residence times) and bad (e.g. high turbulence levels) flow characteristics. The flow was visualised using polystyrene micro-spheres illuminated with white light on selected transverse planes across the pumping chamber and its inlet and outlet connections. These results then served as a guide for velocity measurements using laser-Doppler anemometry. Flow tests were run using water or a water/glycerol mixture. Operating conditions were determined from the appropriate fluid mechanics modelling laws to ensure dynamical similarity. Initially, steady flow behaviour was investigated including the effects of removal and insertion of the tilting-disc inlet and outlet valves. In subsequent full pumping tests, using a pneumatic driver, regions of high shear, separation, and high turbulence intensity have been identified.

Blood Flow Velocity↗
PubMed1989

Positron emission tomography in manganese intoxication.

We employed 6-fluorodopa to study the integrity of the nigrostriatal dopaminergic projection by positron emission tomography in 4 subjects with clinical features of mild parkinsonism caused by exposure to manganese. The 6-fluorodopa scans were normal. This finding suggests that in early manganism sufficient to cause parkinsonian deficits, damage may occur in pathways postsynaptic to the nigrostriatal system, probably involving striatal or pallidal neurons. Fluorodeoxyglucose scans showed decreased cortical glucose metabolism, the significance of which is discussed.

Adult↗
PubMed1989

Linkage in a family with X-linked Charcot-Marie-Tooth disease.

The gene for the X-linked form of Charcot-Marie-Tooth disease (CMT Peroneal Muscular Atrophy, X-linked: McKusick No. 30280) has been shown in a single family to be linked to DXYS1 with a lod score of 4.55 at a recombination fraction of 0.03 and to PGK1 with a lod score of 3.34 at zero recombination. This is in agreement with previous work based on several families. Pooled data from this family and 7 previously reported families give a maximum lod score of 12.04 at theta max of 0.05 for linkage between CMTX and DXYS1 loci.

Charcot-Marie-Tooth Disease↗