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Biomedical subjects

M Webb

Publications and source records attributed to M Webb.

At least 19 recordsLinked to original sources
PubMed1992

Female twin with Hunter disease due to nonrandom inactivation of the X-chromosome: a consequence of twinning.

We report the occurrence of Hunter disease (mucopolysaccharidosis type II) in a karyotypically normal girl who was one of identical twins. Molecular studies showed nonrandom X-inactivation in both her fibroblasts and lymphocytes, while her normal twin showed equal usage of both X chromosomes. In view of previous reports of 7 pairs of identical female twins in which one had Duchenne muscular dystrophy, it seems that twinning may be strongly associated with nonrandom X-inactivation, and is not specific to the properties of the disease causing gene.

DNA Probes↗
PubMed1992

Monoclonal antibodies reveal molecular differences between terminal fields in the rat dentate gyrus.

We have derived a number of monoclonal antibodies which detect molecular differences correlating with the afferent inputs to the molecular layer of the adult rat hippocampal dentate gyrus. One group, dubbed OM-1 to OM-4, strongly stain the outer zone of the molecular layer, which receives its major innervation from the ipsilateral entorhinal cortex. A second group, IM-1 and IM-2, show a complementary pattern and preferentially stain the inner molecular layer, which receives inputs from the ipsilateral and contralateral hippocampus. These antigens are not, however, restricted to these layers, being found outside the hippocampus in several other areas of neuropil in the adult brain. In the developing brain the IM-1 antigen appears ubiquitously from the earliest age studied, embryonic day 12. Within the dentate gyrus, its restriction to the inner terminal field of the molecular layer only occurs during the second postnatal week. In contrast, OM staining appears only sparsely and late in the prenatal brain, appearing in developing cortical white matter between embryonic days 18 and 20. The outer dentate molecular layer becomes OM-positive from birth onwards, corresponding to the time of arrival of entorhinal axons during the first postnatal week. These two groups of monoclonal antibodies recognize a number of different glycoproteins. Ultrastructural immunohistochemistry shows they are cell surface molecules, and as such may be involved in the recognition events required for the establishment of specific patterns of neuronal connectivity.

Animals↗
PubMed1992

Expression of functional bradykinin receptors in Xenopus oocytes.

mRNA prepared from various tissues and cultured cells was injected into Xenopus laevis oocytes. Three to five days after injection, the response of the oocytes to the peptide bradykinin was monitored. The oocytes were voltage clamped and the membrane currents generated on application of agonist were recorded. mRNA from NG108-15, rat uterus, and human fibroblast cell line WI38 gave similar responses to bradykinin (1 microM), with an initial inward current (10-20 nA) followed by a prolonged period of membrane current oscillations. The same pattern of response was given by total RNA from rat dorsal root ganglia. No response to bradykinin (10 microM) was recorded from oocytes injected with rat brain mRNA, although these oocytes gave peak inward currents of about 75 nA in response to serotonin (10 microM). mRNA from both NG108-15 cells and rat uterus was fractionated on sucrose gradients. This resulted in an approximately five-fold increase in the size of the response compared to that given by unfractionated mRNA. The largest responses were given by mRNA fractions with a size of approximately 4.5 kb. Data were obtained consistent with the expression of both B1 and B2 receptors by WI38 human fibroblasts and with the expression of only the B2 type of receptor by NG108-15 cells.

Animals↗
PubMed1992

Effects of extended speaking on resonance of patients with cleft palate.

Groups of listeners and rating scales were used to study the effects of extended speaking on resonance and voice quality in eight adults with cleft palate and mild to moderate hypernasality and a matched group of noncleft adults, with normal resonance and voice quality. Authors interpret their findings as indicating that resonance changes were greater and vocal quality changes less, for the cleft group, but that changes were not extensive nor always in the direction of increased hypernasality or decreased vocal quality.

Adolescent↗
PubMed1991

Potential availability of cadaver organs for transplantation.

OBJECTIVE: To determine the potential number of cadaver kidney donors by applying defined donor criteria to people dying in hospital. DESIGN: Prospective study of all deaths occurring in 21 hospitals from 1 September 1988 to 31 August 1989. Questionnaires were administered to medical and nursing staff and families of potential donors aged 1-69. SETTING: Acute care hospitals in Gwent, South Glamorgan, Mid Glamorgan, West Glamorgan, Pembrokeshire, and East Dyfed health authorities, serving a population of 2.2 million. MAIN OUTCOME MEASURES: Cause of death, age, ventilation at time of death, diagnosis of brain death, and consideration of consent. RESULTS: Adequate data were available for 9840 of 10,095 hospital deaths (97.5% coverage). 188 patients aged 0-69 were identified as potential organ donors (widest definition), and of these 108 died without being ventilated at the time of death. Tests of brain stem death were formally completed in 57 cases, and organ donation was considered by the families of 47 of these potential donors. 26 patients became organ donors. Patients aged 50-69 with stroke were less likely to be ventilated than those aged less than or equal to 49 (21/96 v 24/34). Families of potential donors aged 20-39 were least likely to give permission. CONCLUSIONS: The supply of donor organs (specifically kidneys) could be increased by altering the management of patients aged 50-69 dying of severe cerebrovascular disease in general medical wards, in particular by increasing the proportion ventilated. The ethics of elective ventilation for the purposes of organ donation require discussion.

Adolescent↗
PubMed1991

Eight-year outcome of problem drinking among medical inpatients.

Male medical inpatients rated alcoholic on the Michigan Alcoholism Screening Test in 1982 were compared with non-alcoholic controls admitted to medical wards in the same year. By 1990 the alcoholic subjects had moderated their drinking, although peak consumption at follow-up was twice that of controls. A similar number of health and social disabilities occurred during the follow-up period among alcoholics and controls. Untraced and dead alcoholics had scored highly on MAST and the Severity of Alcohol Dependence Questionnaire in 1982.

Adult↗
PubMed1991

d-fenfluramine/prolactin response throughout the menstrual cycle: evidence for an oestrogen-induced alteration.

The prolactin (PRL) response to fenfluramine (FEN), a serotonin (5-HT) releasing agent, is used as an index of 5-HT sensitivity in studying disorders associated with central 5-HT abnormality. Plasma oestrogen levels are known to augment PRL responses to a variety of stimuli. In order to examine the effect that ovarian steroids have on this response nine, healthy women were tested twice at three time points in the menstrual cycle: early follicular, mid-cycle and late luteal phase with either d-FEN, a more specific 5-HT agent than the racemic mixture, or placebo. Responses to d-FEN were maximal at mid-cycle, lowest during the early follicular phase, with responses premenstrually being intermediate between the two. Responses to placebo did not vary. Plasma oestradiol levels fluctuated in parallel with neuroendocrine responses to d-FEN. The possible mechanisms are discussed, including an effect that oestradiol may exert at central serotonin sites.

Adult↗
PubMed1979

Complex formation between selenium and methylmercury.

Methylmercury, after incubation at 3k7 degrees C and pH 7.0 with selenite in the presence of rat erythrocytes, can be extracted into benzene as an unstable 2 : 1 complex with selenium. The same complex, possibly bis-methylmercury selenide, is formed when methylmercury is treated with hydrogen selenide at pH 7.0 in the absence of erythrocytes.

Animals↗
PubMed1979

Acute effects of cadmium on the pregnant rat and embryo-fetal development.

In rats, of the Wistar-Porton strain, a single intravenous injection of 1.25 mg Cd2+ between days 9 and 15 of gestation results in a high incidence (80% of hydrocephalus, together with other malformations in the fetuses, examined on day 20. This dose is critical, since 1.1 mg Cd2+/kg is not teratogenic, while 1.35 mg Cd2+/kg kills all the embryos. Intravenous injection of Cd2+ to the pregnant rat on day 12 causes a dose-dependent inhibition of placental Zn2+ transport. At the teratogenic dose, Zn2+ transport is inhibited by about 75% at 4 hr. Thereafter, inhibition decreases with time but is still significant at 48 hr. At 20 hr after administration of Cd2+ the embryonic concentration of Zn2+ is depressed by 33%. In the whole embryo the activity of the Zn2+-dependent thymidine kinase is inhibited by about 60% at 4 hr and at 20 hr the DNA concentration is reduced significantly. Placental transport of 14C-leucine and 14C-uridine, as well as the embryonic incorporation of these precursors into protein and RNA is unaffected at least at short times after the administration of Cd2+. It is possible therefore, that the teratogenic effects of Cd2+ may be related to the inhibition of DNA synthesis in the embryo.

Abnormalities, Drug-Induced↗
PubMed1978

Maleate induced change in the kidney binding of mercury in rats pretreated with cadmium.

The kidney uptake of Hg2+ was increased by Cd2+-pretreatment when Hg2+ was given intraperitoneally but not subcutaneously. Subsequent s.c. administration of maleate increased Hg2+ release from the kidneys only if Hg2+ was given subcutaneously. Neither the effect of Cd2+, nor that of maleate, on the distribution of Hg2+ among the renal soluble protein fractions was affected by the route of Hg2+ administration. The protective effect of Cd2+-pretreatment against the nephrotoxic effect of Hg2+ was also independent of the route of Hg2+ administration. Maleate given in nephrotoxic doses removed Hg2+ and copper, but not Cd2+ from the renal metallothionein fraction. Mercury in the urine, however, was not complexed by proteins with the molecular weight of thionein, but was bound to high molecular weight proteins and diffusible molecules. These findings are discussed in relation to the role of metallothionein in the interaction between Cd2+ and Hg2+.

Animals↗
PubMed1978

Theoretical and practical considerations on the problem of metal--metal interaction.

The interaction between two metals, which can be either synergistic or antagonistic, implies that the behavior of one is changed by the presence of the other. Possible mechanisms of these interactions, which include chemical association, competition for carriers, metabolic changes, induction of binding proteins, membrane alterations are discussed.

Animals↗
PubMed1977

The effect of selenium on the brain uptake of methylmercury.

Twenty-four h after the subcutaneous administration of 0.5 mumoles selenite labelled with 75Se to rats of 200 g body weight, the retention of selenium at the injection site was significantly increased by the presence of equimolar amounts of methylmercury in the injection solution. The retention of Me203HgCl was not affected by the presence of selenite. The most significant shift caused by interaction was a decrease in the blood content and an increase in the brain content of 203Hg. The brain content of 75Se was also increased to a lesser extent. The shift in the distribution--which was the same whether the two metals were injected at the same site or separately--continuously decreased from 6-48 h. The same interaction pattern was observed when methylmercury and selenite were administered by gastric gavage and differences in distribution increased when the dose was increased from 1.25 mumoles/kg to 2.5 mumoles/kg. The increase in the brain content of mercury caused by selenite was not restricted to simultaneous administration and occurred when selenite was given 2-7 days after methylmercury.

Animals↗