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Biomedical subjects

S M Hall

Publications and source records attributed to S M Hall.

At least 163 records · Page 9Linked to original sources
PubMed1985

Vesicular demyelination induced by raised intracellular calcium.

Incubation of nerve with high concentrations of the divalent cation ionophore A23187 produces myelin vesiculation (Schlaepfer 1977). This observation has now been extended using segments of rat ventral or dorsal root incubated with high (19 microM, 10 micrograms/ml) or low (1-1.5 microM) concentrations of A23187, or another divalent ionophore, ionomycin. Low concentrations of A23187 induced no vesiculation within a 2-h period. However, subsequent incubation of these roots in fresh, ionophore-free medium for 20 h, resulted in a prominent vesicular demyelination at the Schmidt-Lanterman incisures and paranodes of many fibres. At this time (22 h) the Schwann cells associated with some demyelinating internodes appeared vital upon ultrastructural examination: the cells also excluded the nuclear dye nigrosin. High concentrations of A23187 induced a similar vesicular demyelination in affected fibres within only 15-20 min. While the Schwann cells continued to exclude nigrosin for a further 4 h, their ultrastructural appearance indicated that they were probably in the early stages of necrosis. Incubation of moribund root with the ionophore produced no myelin vesiculation. At all ionophore concentrations, the myelin vesiculation was dependent upon the presence of extracellular Ca2+, and could be modulated in severity by varying this concentration. Other divalent cations (Ba2+, Co2+, Mg2+, Mn2+, Ni2+, Sr2+) could not substitute for Ca2+. The vesiculation induced by A23187 could be entirely prevented by the addition of Zn2+ (greater than or equal to 1 microM), Ni2+ (greater than or equal to 1-10 microM), Co2+ (greater than or equal to 100 microM) or Mn2+ (greater than or equal to 100 microM) to the bathing medium. A23187 applied to only part of an isolated internode resulted in a localization of the myelin disruption to that region. Ionomycin (greater than or equal to 1 microM), an ionophore with a greater selectivity for Ca2+ than A23187, also induced a prompt Ca2+-dependent myelin vesiculation. We conclude that vesicular demyelination can be initiated in vital Schwann cells by a raised intracellular Ca2+ concentration. Such demyelination does not necessarily lead to Schwann cell death. The possible relevance of the findings to vesicular demyelinating neuropathies is discussed, and a hypothesis regarding the mechanism of demyelination is advanced.

Animals↗
PubMed1985

Effects of challenge dose on the clinical and immune responses of cattle vaccinated with reduced doses of Brucella abortus strain 19.

Fifty-seven pregnant beef heifers that were unvaccinated or previously vaccinated with Brucella abortus S19, at a dose of either 10(9) or 10(10) colony-forming units (CFU), were challenge-exposed intraconjunctivally with virulent B. abortus S2308 at a dose of 9.4 X 10(6) CFU (Experiment 1) or 5.2 X 10(7) CFU (Experiment 2). In Experiment 1, S19 afforded significant protection (P less than 0.01) against challenge exposure in that 8 of 9 unvaccinated heifers, 1 of 11 vaccinated with 10(9) CFU, and 3 of 10 vaccinated with 10(10) CFU aborted or delivered weak, non-viable calves. In Experiment 2, vaccination did not afford significant protection (P greater than 0.05) in that 9 of 9 unvaccinated heifers, 8 of 10 vaccinated with 10(9) CFU, and 8 of 8 vaccinated with 10(10) CFU aborted. Serologic responses to B. abortus were determined by three standard tests, as well as a quantitative fluorometric immunoassay (FIAX) and an enzyme-linked immunosorbent assay. In Experiment 1, the early serologic response, 0-8 weeks after challenge, appeared greater for controls than for vaccinates, but in Experiment 2, the early response, 0-6 weeks after challenge exposure, appeared greater for vaccinates than for controls. The lymphocyte blast transformation assay, using heat-killed B. abortus as an antigen, was performed sequentially after challenge exposure. In general, mean responses were significantly higher (P less than 0.05) for vaccinated than for non-vaccinated heifers. For individual heifers, an association could not be established between the lymphocyte blast transformation assay and the clinical response to challenge exposure.

Abortion, Veterinary↗
PubMed1985

Effect of high-frequency positive-pressure ventilation on halothane ablation of hypoxic pulmonary vasoconstriction.

High-frequency positive-pressure ventilation (HFPPV) was compared to intermittent positive-pressure ventilation (IPPV) during unilateral atelectasis with and without halothane anesthesia. Dogs with electromagnetic flow probes chronically implanted on their main (Qt) and left (Ql) pulmonary arteries were ventilated via Carlen's dual-lumen endotracheal tubes. In eight closed-chest dogs, about 43% of the cardiac output perfused the left lung during bilateral ventilation by either a Harvard animal respirator (IPPV) or a Health-dyne model 300 high-frequency ventilator (HFPPV). Unilateral atelectasis decreased blood flow (Ql/Qt) to that lung. Ql/Qt was 19 +/- 1% with HFPPV during left-lung atelectasis and right-lung ventilation, compared to 32 +/- 1% with unilateral IPPV. This suggests that HFPPV permits stronger hypoxic pulmonary vasoconstriction. Addition of 1% halothane increased blood flow to the atelectatic left lung during unilateral ventilation with IPPV but not with HFPPV. This suggests that halothane decreases the effects of hypoxic pulmonary vasoconstriction during conventional ventilation but not during HFPPV.

Animals↗
PubMed1985

A hospital outbreak of Clostridium difficile?

An increase in numbers of patients with Clostridium difficile and its toxin in their stools at a hospital in South-west London led to closure of a ward to admissions and to an investigation of a possible nosocomial outbreak. The findings suggested that the increase was not due to an outbreak of related cases but to increased investigation. The cost of the episode both in financial terms and in the effect on patient care, was considerable. This study highlights the need for caution in interpreting the significance of Cl. difficile in stool specimens. Laboratory data can only alert clinicians to the possibility of colitis; decisions about treatment and control of spread of infection should also be based on clinical criteria.

Age Factors↗
PubMed1985

Transient enhancement of the serum antibody response to Brucella abortus strain 19 in cattle treated with levamisole.

Two experiments were done on 57 steers. These cattle were allotted to 8 groups (4 groups/experiment) and vaccinated with 1 to 3 X 10(9) colony-forming units of Brucella abortus strain 19. Cattle in 3 of the 4 groups/experiment were given 6 mg of levamisole/kg, subcutaneously, either at the time of vaccination (day 0), 7 days later, or at both times. Serum antibody titers to B abortus were measured sequentially for 28 days in experiment 1 and for 56 days in experiment 2, using the card test, Rivanol test, complement-fixation test, fluorometric immunoassay, and an enzyme-linked immunosorbent assay. In general, the highest mean antibody titers, as determined by all serologic tests, occurred in steers treated with levamisole at 7 days after vaccination or in those treated at the time of vaccination and 7 days later. By the card test on day 56, there was a significantly (P less than 0.05) greater number of seropositive cattle among those given levamisole 7 days after seropositive cattle among those given strain 19 alone. Simultaneous administration of strain 19 and levamisole did not alter antibody responses to B abortus.

Adjuvants, Immunologic↗
PubMed1984

Methadone dose decreases and anxiety reduction.

This research evaluated the efficacy of an Anxiety Reduction program designed to reduce anxiety early in methadone detoxification and thereby facilitate dose reduction. Major outcome variables were methadone dose, alcohol and illicit drug use, and withdrawal symptomatology. Fifty-three subjects were recruited and randomly assigned to Anxiety Reduction or Control conditions, and were followed for 48 weeks after study start. Statistically significant differences in dose between Anxiety Reduction subjects and Controls occurred early in treatment, and could only be interpreted when initial dose and initial mood disturbance were taken into account. The differences were not of sufficient magnitude to be of clinical importance, and reflected differences in the small number of subjects who changed dose, rather than overall group trends. Anxiety Reduction subjects reported less alcohol use at treatment termination and at follow-ups, and fewer withdrawal symptoms at termination. They were also less likely to be dropped from treatment for disciplinary reasons. High initial anxiety about detoxification was related to minimal dose reduction in both conditions. Also, in both conditions, anxiety increased with decreasing dose.

Adult↗
PubMed1984

Joiners and non-joiners in smoking treatment: a comparison of psychosocial variables.

Treatment joiners were differentiated from non-joiners in a smoking cessation clinic. Subjects were 108 smokers who attended an orientation session for a smoking cessation program. The primary variable of interest was perceived self-efficacy. Other variables studied were demographic characteristics, tobacco and drug use, anxiety, and health locus of control. Non-joiners were found to be more anxious, less educated, and had a lower self-efficacy expectation than treatment joiners.

Adult↗
PubMed1984

An outbreak of erythema infectiosum associated with human parvovirus infection.

Erythema infectiosum (EI) or fifth disease is a mild, acute exanthematous disease, occurring mainly among children, for which a causative virus has long been sought. In May 1983 an outbreak of exanthematous illness was reported in a primary school in North London. Children attending the school were investigated by questionnaire and 162 (43.9%) reported an illness with the features of EI. In each of 36 cases investigated virologically the illness was associated with parvovirus infection. Moreover, pre-existing antibody to parvovirus was correlated with protection from EI in 16 of 17 close family contacts of cases. We propose therefore that EI is the common manifestation of infection with the human parvovirus.

Adult↗
PubMed1984

Blood cotinine levels as indicators of smoking treatment outcome.

Pretreatment blood cotinine levels, expired carbon monoxide levels, and self-reported cigarette consumption were evaluated as predictors of smoking treatment outcome in 114 patients. Of these indices of nicotine intake, blood cotinine level was the most useful predictor. High blood cotinine level was the best predictor of dropping out before completion of treatment and of smoking at the end of treatment and at follow-ups. The usefulness of cotinine as a marker of tobacco dependence is discussed.

Adult↗