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Biomedical subjects

M Williamson

Publications and source records attributed to M Williamson.

At least 91 records · Page 5Linked to original sources
PubMed1990

A bacteriological study of purulent meningitis in children.

There was an increase in incidence of meningitis in children within the last three years at the Bai Yamunabai Laxman Rao Nair Charitable Hospital in Bombay. Out of 270 purulent samples, 60 (22.22 percent) were culture positive. Neisseria meningitidis showed an increase from one case in 1985 to 11 cases by the end of 1987. Staphylococcus aureus was isolated from 6 percent cases, Streptococcus pneumoniae 15 percent, and Gram negative bacilli were predominant, isolation rate being 57 percent. Salmonella species were isolated from 6 (10 percent) cases. They were multidrug resistant type, some belonging to the rare zoonotic species.

Cerebrospinal Fluid↗
PubMed1989

Natural extinction on islands.

Almost all recent extinction of species or subspecies on islands comes from human activities. On the other hand, in local populations there is much natural extinction and immigration, i.e. turnover, on small islands. Most of this turnover occurs in locally rare species, and attests to the phenomenon of minimum viable population size. The MacArthur-Wilson theory is based on this turnover which, from an ecological point of view, is generally trivial. More useful theories of minimum viable population size are being developed. Rarity is the precursor of extinction, and species can be rare in several ways. Models of these phenomena are still primitive, particularly those that relate habitat availability to population density. Models of interactive communities show phenomena that may be relevant to the understanding of extinction in the geological record. Lotka-Volterra equations indicate considerable sensitivity to invasions, sometimes producing a cascade of extinction. Chemostat equations show that the behaviour of food chains can change dramatically with small changes in parameters, suggesting that small environmental effects can sometimes cause large ecological changes, including extinctions, in interactive biotic communities.

Animals↗
PubMed1989

31P NMR studies of the kinetics of bisalkylation by isophosphoramide mustard: comparisons with phosphoramide mustard.

31P nuclear magnetic resonance spectroscopy was used to measure the pKa (4.28 +/- 0.2) of isophosphoramide mustard (IPM) at 20 degrees C and to study the kinetics and products of the decomposition of IPM at a solution pH value of ca. 7.4 and at temperatures between 20 and 47 degrees C in the presence of nucleophilic trapping agents. At 37 degrees C, the half-life for the first alkylation was ca. 77 min and ca. 171 min for the second alkylation; these data may be compared with those for phosphoramide mustard (Engle, T.W.; Zon, G.; Egan, W.J. Med. Chem. 1982, 25, 1347), wherein the half-lives for the first and second alkylations are approximately the same (18 min). The rate of fragmentation of aldoifosfamide to IPM and acrolein was also studied by NMR spectroscopy (pH 7.0; 37 degrees C; 0.07 M phosphate); under the noted conditions, the half-life of aldoifosfamide was found to be ca. 60 min.

Alkylating Agents↗
PubMed1987

Primary structure and differential expression of beta-amylase in normal and mutant barleys.

The primary structure of barley endosperm beta-amylase, an enzyme which catalyses the liberation of maltose from 1,4-alpha-D-glucans, has been deduced from the nucleotide sequence of a cloned full-length cDNA. The mRNA is 1754 nucleotides long [excluding the poly(A) tail] and codes for a polypeptide of 535 amino acids with a relative molecular mass of 59,663. The deduced amino acid sequence was compared with the sequences of ten peptides obtained from the purified enzyme and unambiguous identification was obtained. The N-terminal region of the deduced sequence was identical to a 12-residue cyanogen-bromide-peptide sequence, indicating that beta-amylase is synthesized as the mature protein. A graphic matrix homology plot shows four glycine-rich repeats, each of 11 residues, preceding the C-terminus. Southern blotting of genomic DNA demonstrates that beta-amylase is encoded by a small gene family, while cDNA sequence analysis indicates the presence of at least two types of mRNA in the endosperm. Dot and northern blot analysis show that Hiproly barley contains greatly increased levels of beta-amylase mRNA compared to the normal cultivar Sundance, whereas Risø mutant 1508 contains only trace amounts. These results correlate well with the deposition of beta-amylase during endosperm development in these lines. Low but similar amounts of beta-amylase mRNAs sequences were detected in leaves and shoots from normal and mutant barleys, demonstrating that the mutant lys3a (1508) and lysl (Hiproly) genes do not affect the expression of beta-amylase in these tissues.

Amino Acid Sequence↗
PubMed1986

Interactions of virulent and avirulent leptospires with primary cultures of renal epithelial cells.

A primary culture system for the cells of mouse renal-tubular epithelium was established and used to observe the adhesion of leptospires. Virulent strains of serovars copenhageni and ballum attached themselves to epithelial cells within 3 h of infection whereas an avirulent variant of serovar copenhageni did not adhere to epithelial cells at all within the experimental period of 24 h. The saprophytic Leptospira biflexa serovar patoc became attached non-specifically to inert glass surfaces as well as to the cells. The adhesion of leptospires to epithelial cells was not inhibited by homologous antibody.

Adhesiveness↗
PubMed1986

Diabetes mellitus and open heart surgery. A simple, practical closed-loop insulin infusion system for blood glucose control.

A method, based on bedside determinations of blood glucose by nursing staff, was designed to control the administration of insulin to diabetic patients during and following open heart surgery. A computer-controlled intravenous infusion pump was used to deliver the insulin. Excellent control of the hyperglycaemia normally associated with open heart surgery was achieved, with 84 percent of measured blood glucose values falling within 2 mmol/litre of the target value of 6 mmol/litre. The method proved to be simple, effective, and safe.

Adult↗
PubMed1986

Mineralization in in vitro cultures of rabbit marrow stromal cells.

Localized regions of mineralization were found in confluent cultures of rabbit marrow fibroblastic cells. The mineralized tissue developed within clusters of giant fat cells in the spaces between the cells. Investigations with light and electron microscopy demonstrated that in these sites there was some differentiation of the fibroblastic cells in an osteogenic direction, shown by changes to more polygonal shapes, and the synthesis of well-banded collagen similar to that found in bone tissue. Differentiation may be due, in part, to increased cell density in a confined space. Growth of the mineralized tissue was observed in the living cultures with a fluorescence microscope. Electron probe microanalysis confirmed that the mineral formed was hydroxyapatite. Initiating sites of mineralization included membranous vesicular bodies, lipid, and products of cellular degeneration. Once initiated, mineralization appeared to spread rapidly into adjacent collagenous and other structures, suggesting the appearance of a mixture of skeletal-type and dystrophic mineralization.

Animals↗
PubMed1985

Family management in the prevention of morbidity of schizophrenia. Clinical outcome of a two-year longitudinal study.

Environmental stress may contribute to the clinical morbidity of established cases of schizophrenia treated with optimal neuroleptic drugs. A family-based approach that aimed to enhance the problem-solving capacity of the index patient and his family caregivers was compared with a patient-oriented approach of similar intensity over a two-year period. Thirty-six patients who returned to stressful parental households after florid episodes of schizophrenia (CATEGO and DSM-III) were stabilized with optimal neuroleptics before being randomly assigned to family or individual therapy in a comprehensive community management program. After nine months, family-managed patients had fewer exacerbations of schizophrenia, lower ratings of schizophrenic psychopathology, fewer hospital admissions, and a trend toward lower deficit symptoms and reduced neuroleptic dosage. This reduced clinical morbidity was sustained throughout the second year of less intensive follow-up. The relative efficacy of the family approach in this clinical management study did not appear to be due to prognostic factors, rater bias, stressful life events, or the effectiveness of pharmacotherapy. Definitive tests of these findings with respect to efficacy require further well-designed studies.

Adolescent↗
PubMed1985

Characterization of cells with high alkaline phosphatase activity derived from human bone and marrow: preliminary assessment of their osteogenicity.

Confluent cellular layers are reproducibly obtained (from 21 of 24 specimens) by outgrowth from composite pieces of human trabecular bone and marrow. The cells resemble fibroblasts in terms of morphology, esterase profile, and production of collagen type 1. However, the cells displayed some osteoblastlike features. Both the primary outgrowths and passaged cultures had high alkaline phosphatase activities (37 nmols min-1 X microgram DNA-1) in the range displayed by embryonic osteoblastlike cells. The cellular alkaline phosphatase activity, which showed similarity to the bone isoenzyme on kinetic criteria, was stimulated by 1,25-dihydroxyvitamin D3 but decreased by PTH (1-34). In addition, the cell preparations were shown to increase osteocalcin (bone Gla protein) production in response to 1,25-dihydroxyvitamin D3. The osteogenic potential of the bone and marrow-derived cells has been assessed in an in vivo diffusion chamber assay in which congenitally athymic (nude) mice were used as hosts. None of the 25 chambers examined showed evidence of osteogenesis, although the cells remained viable and fibroblastlike. The alkaline phosphatase activities decreased to less than 1% of the original, high in vitro values. The findings question the hypothesis that bone and marrow-derived cells are osteoblasts or osteoblastlike cells, rather than a mixture of cell lines of the bone and marrow stromal system.

Adolescent↗
PubMed1985

Practical closed-loop insulin infusion.

A method was designed to control the insulin infusion given to diabetic patients at the time of open-heart surgery. Excellent control of the blood glucose concentration was achieved, with eighty-four percent of blood glucose values falling between 4 and 8 mmol/l.

Adult↗
PubMed1984

The interaction of the potential-sensitive molecular probe merocyanine 540 with phosphorylating beef heart submitochondrial particles under equilibrium and time-resolved conditions.

The interaction of the potential-sensitive extrinsic molecular probe merocyanine 540 ( M540 ) with phosphorylating submitochondrial particles has been investigated under equilibrium and time-resolved conditions. The addition of ATP to a M540 -membrane suspension produces oligomycin and CCCP-sensitive spectral changes with absolute maxima near 490, 530, and 565 nm; a 1- to 2-nm red shift of the dye absorption spectrum is also evident in the longer-wavelength region of the spectrum. In fixed-wavelength work, the energy-dependent optical signals were increased by the addition of nigericin and NH4Cl, and could be subsequently restored to the control level by valinomycin or KSCN, respectively. These observations suggest that M540 is specifically sensitive to the membrane-potential portion of the electrochemical gradient presumably present in the submitochondrial particle system in the presence of substrate. Binding analyses based on the Langmuir adsorption isotherm and the direct linear method indicate that the M540 dissociation constant is decreased by the presence of ATP with little or no change in the maximum number of binding sites. The M540 dissociation constant was markedly decreased when 0.1 M NaCl was present in the medium, suggesting that the association of this probe with the membrane may be subject to considerable surface charge repulsion. Results from the binding analyses indicate that the origin of the energy-dependent spectral changes may be an enhanced association of M540 with the submitochondrial particle membrane resulting from the transfer of dye from the aqueous phase to membrane-binding sites. The time course of the NADH-, ATP-, or succinate-induced signal developed slowly, on a time scale of tens of seconds, and follows a second-order rate law, suggesting that the rate-limiting step in the development of the ATP-induced M540 signal may be the transfer of dye from the aqueous phase to membrane-binding sites. The enhanced passive binding of M540 to the submitochondrial particle membrane in the presence of NaCl reduces the concentration of free dye apparently available to redistribute to the membrane when substrate is present, with a concomitant reduction in the observed pseudo-first-order and the second-order rate constants. If the effective free dye concentration is estimated from binding data and used in the plot from which the latter rate constant is obtained, the value of this constant compares favorably with the obtained in the absence of the electrolyte.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗
PubMed1984

Chromosome fragility in Alzheimer's disease.

We present cytogenetic findings for 12 patients with Alzheimer's Disease (AD) mean age 75.8 +/- 6.01 years and 35 normal age and sex matched controls (mean age 74.8 +/- 4.04 years). The study, undertaken due to reports of increased fragments and chromosome breakage in individuals with AD, was performed blind on coded peripheral blood specimens and the allocation of AD or control was not known to the cytogenetic staff until the end of the study. Both the AD group and the controls have been very carefully selected and both underwent the same clinical assessment and screening procedures which included CT scanning. Chromosomes were analysed after 72 h cultures, using deprived medium TC199 which is known to enhance the appearance of fragile sites. A minimum of 50 cells was examined in each case and any rearrangement found was classified as ctg, csg , ctb , csb and the chromosome in which it occurred was recorded. Analysis of results showed that there was no statistically significant difference between the AD group and the controls for either the total occurrence of breaks, the type of aberration or the chromosome(s) involved. In both groups the commonest break was in 3p .

Aged↗
PubMed1983

Phenylalanine intakes of 1- to 6-year-old children with phenylketonuria undergoing therapy.

Mean of median phenylalanine intakes of 1- to 6-yr-old treated phenylketonuria patients who were growing normally were evaluated by age, sex, and treatment group assignment. Total daily means of median phenylalanine intakes of subjects in treatment group 1 were significantly different from those of subjects in treatment group 2 except at the median age of 69 months. Total daily phenylalanine intakes varied from 285 +/- 10 to 453 +/- 30 mg (mean +/- SEM) by subjects in treatment group 1. Total daily phenylalanine intakes of subjects in treatment group 2 varied from 349 +/- 12 to 530 +/- 42 mg (mean +/- SEM). Mean, median phenylalanine intakes by males ranged from 30 mg/kg of body weight by the younger to 23 mg/kg of body weight by the older subjects. Means of median phenylalanine intakes of females varied from 32 mg/kg of body weight by the younger to 21 mg/kg of body weight by the older subjects. No child had a median phenylalanine intake below 10 mg/kg of body weight.

Age Factors↗
PubMed1983

Chromosome aneuploidy in Alzheimer's disease.

We present cytogenetic findings in 9 patients with Alzheimer's disease (AD) and 35 normal age matched controls. The study was undertaken due to reports of increased aneuploidy in individuals with AD. Coded peripheral blood chromosome preparations were evaluated for aneuploidy; there were 4.5% hypomodal cells in AD patients compared with 5.5% in controls. There were no hypermodal cells in the AD group and only 0.7% among the controls. Statistical analyses of the results did not show any differences between AD patients and controls in these data. There was a statistically significant increase in the loss of C group chromosomes in the old controls which we attribute to ageing.

Aged↗