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Biomedical subjects

M Clarke

Publications and source records attributed to M Clarke.

At least 289 records · Page 16Linked to original sources
PubMed1984

Ambulatory electrocardiographic monitoring in patients with transient focal cerebral ischaemia.

Sixty-four patients with transient ischaemic attacks were investigated for the presence of an associated cardiac arrhythmia. 24-hour ambulatory monitoring showed arrhythmia in 41% of patients where the standard ECG had shown arrhythmia in only 25%. Significant arrhythmias were found in 21% of patients with focal transient ischaemic attacks on prolonged monitoring as compared to 7% in a control group. Where arrhythmias were specifically treated there was abolition or improvement of neurological symptoms.

Aged↗
PubMed1984

Identification of the human T cell lymphoma virus in B cell lines established from patients with adult T cell leukemia.

Cell lines were established from the peripheral blood of two patients with adult T cell leukemia. In contrast to our previous experience, where all such lines expressed T cell markers, these two cell lines expressed B cell antigens and Ig light chains (kappa on CF-2, lambda on HS). Human T cell lymphoma proviral (HTLV) sequences were demonstrated in both cell lines. Since only a portion of the cells in culture expressed Ig light chains, experiments were carried out to exclude the possibility that the cultures were not a mixture of B and T or non-B cells. Cells that expressed kappa- or lambda-light chains were separated by cell sorting from kappa- or lambda-negative cells and replaced in culture. Light chain negative cells reexpressed light chains after time in culture. After 5-azacytidine treatment of the cell lines, all cells expressed Ig light chains. These studies show that the human retrovirus HTLV, which has been demonstrated to be associated with certain T cell malignancies, can infect B cells or B cell precursors.

Adult↗
PubMed1984

The elderly at home: health and social status.

The health, social status and contacts with services of all people over the age of seventy-five living at home in and around Melton Mowbray was assessed by interview. Nearly half the sample (46%) lived alone, and just over a third (37%) were married. Most respondents were able to complete the basic activities of daily living without any assistance. The apparent prevalence of dementia at 1.6% was lower than had been found in previous population studies. The levels of social contact were similar to those reported previously. While service provision compared well with that found in other studies, only a relatively small proportion of the population were in receipt of nursing, paramedical and social services.

Activities of Daily Living↗
PubMed1983

Surveys of rubella antibodies in young adults and children.

22 000 serum samples from university students and young adult blood donors collected between 1969 and 1980 were tested for antibody to rubella virus. Of the women born in 1956 and after (i.e., those eligible for rubella vaccine at school) the proportions seronegative ranged from 3% to 6% in different years, compared with 12-20% in men of the same age groups. Serum samples from schoolchildren were also tested: 40-50% of girls and boys aged 10-11 years were seronegative--percentages similar to those before the introduction of vaccine. However, only 2-6% of 15-year-old girls (who would have been offered vaccine) were seronegative compared with 20-30% of 15-year-old boys. These results indicate that the rubella vaccination programme in the U.K. is having a significant impact on the immunological status of young women of childbearing age but that a large number of women remain potentially susceptible.

Adolescent↗
PubMed1983

Quality of obstetric care provided for Asian immigrants in Leicestershire.

Between 1976 and 1981 some 939 perinatal deaths occurred to women living in Leicestershire, of which 128 (14%) were to Asian women. The qualifications of the general practitioners, the gestation at which women start antenatal care, and perinatal death were used as structural, process, and outcome measures for evaluating the services provided to Asian immigrants within this population. Perinatal deaths were divided into four groups: congenital malformation, macerated stillbirth, asphyxia in labour, and immaturity. Asian mothers had one and a half times the risk of perinatal mortality when social class, parity, height, legitimacy, and the general practitioner's qualifications were taken into account. Asian and non-Asian mothers with general practitioners who were not on the obstetric list had more than twice the risk of a perinatal death when a similar adjustment was made. Recommendations include priority allocation of community midwives to practitioners not on the obstetric list, the establishment of postgraduate courses for such doctors, and the continued evaluation of the effect of such proposals on perinatal mortality.

Asia↗
PubMed1983

Evidence for a trans-dominant regulator of purine nucleoside phosphorylase expression in rat hepatoma cells.

Purine nucleoside phosphorylase (PNP) levels are modulated during the growth cycle of rat hepatoma cells and increase two- to three-fold as cells go from early exponential growth phase to stationary growth phase. A mutant of these hepatoma cells has been isolated which is deficient in PNP activity. Quantitative immunoprecipitation tests indicate that the decrease in enzyme activity is due to a decrease in the number of PNP molecules. The low level of PNP enzyme produced by the mutant, however, is indistinguishable from the wild-type enzyme, suggesting that the mutant may be defective in the ability to modulate PNP levels. Fusion of the mutant cells to wild-type parental cells results in hybrids that express the mutant phenotype. Segregants that arise from the hybrids show chromosome loss and reexpression of the wild-type parental phenotype, the mutant parental phenotype, and a 2S wild-type phenotype. These indicate the following about the defect in modulation in the mutant PNP-100: (1) it is trans dominant to the wild-type; (2) its effect is negative; (3) some genomic element is required for its continued effect; and (4) it does not act by obliterating its functioning counterpart in hybrid cells.

Animals↗
PubMed1983

Radiometric assay of S-adenosylmethionine:calmodulin(lysine)N-methyltransferase by calcium-dependent hydrophobic interaction chromatography.

A radiometric assay for S-adenosylmethionine:calmodulin(lysine)N-methyltransferase in tissue extracts has been developed. This assay utilizes the non-N-methylated calmodulin from Dictyostelium discoideum as a substrate and calcium-dependent hydrophobic interaction chromatography to isolate the reaction product, N-methylated calmodulin. The assay measures the transfer of 3H-labeled methyl groups from [methyl-3H]S-adenosylmethionine to calmodulin. Methylated calmodulin is eluted from phenyl-Sepharose columns with EDTA and protein carboxylmethyl esters are removed by heat treatment prior to liquid scintillation counting of [methyl-3H]calmodulin. This assay is more specific, more sensitive, and more precise than the acid-precipitation assay previously employed and lends itself more readily to the assay of large numbers of samples.

Animals↗
PubMed1983

Relationship between axenic growth of Dictyostelium discoideum strains and their track morphology on substrates coated with gold particles.

Amoebae of Dictyostelium discoideum produce tracks with two distinct morphologies on gold-coated coverslips. The wild-type strain and other strains that feed only by phagocytosis produced indistinct, fuzzy tracks, whereas mutants capable of axenic growth produced clear, sharp tracks. The sharp track morphology was found to be a recessive phenotype that segregates with axenicity and probably requires a previously unidentified axenic mutation. Axenic and nonaxenic strains also differed in their ability to pinocytose. When the two types of cells were shifted from bacterial growth plates to nutrient media, within 24 h the axenic strain established a rapid rate of pinocytosis, approximately 100-fold higher than the low rate detectable for the nonaxenic strain. However, track formation did not appear to be directly related to endocytosis. Electron microscopic examination of cells during track formation showed that both axenic and nonaxenic strains accumulated gold particles on their surfaces, but neither strain internalized the gold to any significant degree. Observation of living cells revealed that axenic strains collected all particles that they contacted, whereas wild-type strains left many particles undisturbed. The size of the gold particle clusters discarded by the cells also contributed to track morphology.

Dictyostelium↗
PubMed1983

Institutional care for the elderly: the impact and implications of the ageing population.

Two cross-sectional studies three years apart assessed functional capacity in everyone aged 65 years and over in any ward, hospital, home or hostel in a defined geographical area. Comparison of the proportion of patients aged 65-74 years, 75-84 years and 85 years and over within these institutions showed that a higher proportion of the very elderly were in homes for the elderly and a lower proportion in National Health Service (NHS) geriatric hospital beds in the later time period. Greater proportions of all age groups of the elderly were in NHS acute hospital beds. Levels of incapacity in these people had increased between 1976 and 1979. In continuously resident people the proportion remaining unchanged fell and the extent of deterioration increased with greater age: among recent admissions significant increases in incapacity were only seen in patients in NHS geriatric hospitals. At present the demands of the ageing population are such that old people will be admitted where places are available even if the setting is not entirely appropriate to their needs. Restrictive admission policies on the part of residential homes will not reduce levels of incapacity if they continue to admit older residents.

Activities of Daily Living↗
PubMed1982

Motility mutants of Dictyostelium discoideum.

We describe six motility mutants of Dictyostelium discoideum in this report. They were identified among a group of temperature-sensitive growth (Tsg) mutants that had been previously isolated using an enrichment for phagocytosis-defective cells. The Tsg mutants were screened for their ability to produce tracks on gold-coated cover slips, and several strains were found that were temperature-sensitive for migration in this assay. Analysis of spontaneous Tsg+ revertants of 10 migration-defective strains identified six strains that co-reverted the Tsg and track formation phenotypes. Characterization of these six strains indicated that they were defective at restrictive temperature in track formation, phagocytosis of bacteria, and pseudopodial and filopodial activity, while retaining normal rates of oxygen consumption and viability. Because they had lost this group of motile capabilities, these strains were designated motility mutants. The Tsg+ revertants of these mutants, which coordinately recovered all of the motile activities, were found at frequencies consistent with single genetic events. Analysis of the motility mutants and their revertants suggests a relationship between the motility mutations in some of these strains and genes affecting axenic growth.

Dictyostelium↗
PubMed1981

Characterization of a novel calmodulin from Dictyostelium discoideum.

We have purified calmodulin from the eukaryotic microorganism Dictyostelium discoideum (Clarke, M., Bazari, W. L., and Kayman, S. C. (1980) J. Bacteriol. 141, 397-400) and have compared it to calmodulin purified from bovine brain. The two proteins behaved almost identically during fractionation on ion exchange and gel filtration columns and on isoelectric focusing gels. Dictyostelium calmodulin had one-third the specific activity of brain calmodulin in the Ca2+-dependent activation of brain cyclic nucleotide phosphodiesterase; this activation was inhibited for both proteins by 25 microM trifluoperazine. Dictyostelium calmodulin also activated erythrocyte (Ca2+ + Mg2+)-ATPase and interacted with the inhibitory subunit of skeletal muscle troponin. Competition radioimmune assays showed that Dictyostelium calmodulin could compete with brain calmodulin for antibodies to brain calmodulin. These similarities indicate a close relationship between Dictyostelium and brain calmodulin and suggest that the functional capabilities of the protein have been conserved even among evolutionarily distant species. However, substantial differences in primary structure were detected by amino acid analyses and peptide mapping. Most interesting is the lack of trimethyllysine in Dictyostelium calmodulin. This unusual amino acid, which is commonly found in calmodulins, is therefore not essential for interaction between calmodulin and the calmodulin-regulated proteins tested here.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗