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Biomedical subjects

J A Bell

Publications and source records attributed to J A Bell.

At least 145 records · Page 8Linked to original sources
PubMed1984

Disruption of passive avoidance learning in the rat by electrical stimulation of the hippocampus.

The effect of electrical stimulation to discrete regions of the dorsal hippocampus on passive avoidance was examined in five experiments. Rats stepped from a brightly lit, white compartment to a dark compartment. Following footshock in the dark compartment, step-through latencies were recorded 1 min, 24 hr, and 48 hr after footshock. When given 20 step-through trials prior to footshock, dentate-stimulated animals exhibited lack of passive avoidance with particularly short latencies at 1 min, and CA1 rats showed reduced latencies compared with latencies of cortical and nonoperated controls. In Experiment 2, rats given stimulation in the same regions performed the avoidance task without prior step-through experience. All groups showed less passive avoidance than the control group in Experiment 1, and there were no significant differences between groups. With a single step-through trial before the footshock trial, longer avoidance latencies were recorded, but again groups did not differ significantly. Dentate-implanted animals, given 20 prior exposure trials but with stimulation at different stages of the task sequence, demonstrated a passive avoidance deficit at 1 min after footshock. The results are discussed in terms of the generation of expectancy that the black compartment was a safe place and the effects of brain stimulation on the expectancy, with particular reference to Vinogradova's (1975) theory of hippocampal function.

Animals↗
PubMed1984

Factors influencing referrals for prenatal cytogenetic diagnosis.

This paper reports the results of an investigation into factors influencing the referral of women for prenatal cytogenetic diagnosis, following mid-second-trimester amniocentesis. The overall diagnostic amniocentesis rate for women over the age of 35 years was 16.8%. One hundred and forty consecutive Brisbane women referred to the 2 Queensland laboratories offering chromosome analysis of amniotic fluid cells were included in this study. 72% were referred for advanced maternal age. The socioeconomic status (SES) of the 140 women was skewed very significantly towards the professional and semiprofessional classes (Classes A and B on the Congalton Australian Four-point Scale). Twenty seven percent of all women are in SES Class D in the Brisbane population, but only 7.4% of such women (SES Class D) were within the group studied. Forty nine percent of women indicated that they themselves raised the question of prenatal diagnosis with their doctor. Diagnostic amniocentesis is not acceptable to a certain proportion of couples, but it is estimated that 60% would accept it if there were medical indications, and if it were offered. Our studies have indicated that of those women who are at increased risk of having a child with a significant chromosomal abnormality (including those over the age of 35 years) and to whom prenatal diagnosis is acceptable, 28% are actually receiving it in current practice. Those who do are a well informed, self-motivated upper and middle class group.

Adult↗
PubMed1983

Register of chromosomal abnormalities in Queensland.

The development and use of the computer-aided retrieval of karyotypes (CAROK), a register of chromosomal abnormalities in Queensland, is described. The six independent cytogenetic laboratories serving the population of 2.2 million contribute data to the register which provides total population information on the occurrence of chromosomal abnormalities, without selection. CAROK policy on confidentiality, security, access, and safety of data is described in detail. A cytogenetic register such as this ensures a reliable permanent file of results, facilitates research, and provides a data base which will enable questions of clustering or secular trends to be answered efficiently. The register is complete for the years 1976-1981, and contains information on 880 consecutive abnormal cases; in this sense, the data constitute an unselected six-year series of diagnosed chromosomal abnormalities in Queensland. These figures show an average incidence figure (over a six-year period) for newly diagnosed cases of chromosomal abnormality of 6.61/100 000 general population per year.

Aneuploidy↗
PubMed1983

Enterotoxemia in the goat: the humoral response and local tissue reaction following vaccination with two different bacterin-toxoids.

A vaccination trial involving 72 goats was designed to compare the epsilon antitoxin titres and local reactions at the injection sites, of two commercial enterotoxemia vaccines. Three dosage regimens were used for each vaccine (12 goats per group). Although no significant differences were noted in humoral immune response between the two vaccines (P = 0.05), one vaccine regime resulted in low titres (P = 0.05) on two occasions. Local tissue reactions at injection sites persisted for six months in 53% of the goats regardless of vaccine used or dosage administered. No immunological basis for the reported differences in vaccine efficacy between sheep and goats was observed in this trial.

Animals↗
PubMed1982

Cortical depth changes in enriched and isolated mice.

The occipital cortical depth was determined in laboratory mice at both 14 and 20 days of age and after various periods of postweaning exposure to enrichment or isolation. The depth was found to be maximal at 20 days of age. It declined thereafter, irrespective of environment, but the isolate cortical depth decreased faster than the enriched. The postweaning depth of the occipital cortex appears to be determined by an inevitable age-related decrease whose rate of decline may be attenuated by sensory stimulation. The postweaning cortical depth may reflect the extent of cortical neuronal development and associated metabolic activity.

Age Factors↗
PubMed1982

A trial of prophylactic mexiletine in home coronary care.

A double blind randomised study was undertaken comparing the effects of oral mexiletine and placebo given by general practitioners at home in the early stages of suspected acute myocardial infarction, and continued for six weeks. The study comprised 216 patients. In 59 the diagnosis of acute myocardial infarction was not confirmed. Of the 72 patients with confirmed myocardial infarction treated with mexiletine, 11 (15.3%) died, compared with 19 (22.4%) of the 85 patients given the placebo, and significantly fewer of the former compared with the latter had frequent ventricular ectopics or ventricular tachycardia recorded on 24 hour electrocardiograms. Numbers of patients transferred to hospital or withdrawn from the trial because of arrhythmia or heart failure were similar in the two treated groups. Ten (13.9%) of the patients taking mexiletine had the drug withdrawn because of side effects attributed to it, compared with three (3.5%) of the group taking the placebo. A further five patients (all on mexiletine) also had treatment withdrawn because of side effects but infarction was not later confirmed. The results indicate that oral mexiletine can be given safely to patients with suspected myocardial infarction at home by their general practitioners in the absence of a positive electrocardiographic diagnosis. The frequency of ventricular tachycardia is significantly reduced; but there is no evidence of reduced mortality.

Aged↗
PubMed1981

Electron transport across glycerol monooleate bilayer lipid membranes facilitated by magnesium etiochlorin.

The transport of electrons across biological membranes is believed to play an important role in many biophenomena. Although there have been many examples of systems which may be transporting electrons across Mueller-Rudin bilayer lipid membranes (blm), none has been well characterized. The system we describe here comprises a glycerol monooleate blm containing a magnesium etiochlorin (Mg-C) separating two aqueous phases each containing ferricyanide, ferrocyanide, KCl, and a platinum electrode. The E0s for the Mg-C+/Mg-C and ferri-/ferrocyanide couples are 0.22 and 0.24 V vs. SCE. Thus the MG-C+/Mb-C system is easily poised by the ferri-/ferrocyanide system. When the potentials of the ferri-/ferrocyanide couples are different on each side of the blm we show that the open-circuit membrane potential nearly equals the difference between the redox potentials. This is unequivocal evidence that electrons are being transferred across the blm from one aqueous phase to the other. On the basis of these experiments we deduce that electron transport is the major charge transport mechanism. When redox potentials are the same on each side of the blm, the conductance of the membrane can be greater than 10(-3) S/cm2. The conductance is proportional to the second power of the concentration of Mg-C in the membrane-forming mixture. A number of additional experiments are described which attempt to elucidate the mechanism of electron transfer. We believe that our data are consistent with the idea of an electron-hopping mechanism in which the transmembrane electron transport occurs by a series of second-order electron transfers between membrane-bound electron donors (Mg-C) and acceptors (Mg-C+). Alternative explanations are presented.

Electron Transport↗
PubMed1981

Prenatal diagnosis of chromosomal abnormalities: analysis of 1000 consecutive amniotic fluids.

Cytogenetic studies have been performed on 1,000 amniotic fluid specimens referred for prenatal diagnosis. Two-thirds of the patients had strong clinical indications for prenatal chromosome studies and the remaining one-third were referred because of maternal anxiety or a family history of neural tube defect. A total of 18 affected fetuses were detected in this series (1.8%) and these included 3 male fetuses in patients with a history of sex-linked disorder and 15 fetuses with chromosome abnormalities. The overall culture success rate was 97.4% and the average time taken to obtain sufficient material for initial chromosome analysis was 13 days. Fetal loss within 4 weeks of the amniocentesis was 1.2%.

Abortion, Habitual↗
PubMed1981

Applications of high-voltage paper electrophoresis for the characterization of drug metabolites.

1. The application of high-voltage paper electrophoresis (h.v.p.e.) to the identification of drug metabolites in urine and bile has been investigated. 2. The major urinary metabolite of [3H]salbutamol in man had an electrophoretic mobility indicative of a sulphate ester. 3. A metabolite of [14C]ranitidine present in rat bile was shown to contain an ionized group with a pKa corresponding to a carboxylic acid. 4. The electrophoretic mobility-pH profile of a metabolite of radiolabelled N"-cyano-N-[2-[5-(dimethylaminomethyl)-2-furanylmethylthio]ethyl]-N-methylguanidine (14C-AH 18801) excreted in dog urine suggested that oxidation of the tertiary amine group of the compound had occurred. 5. H.v.p.e. provided valuable information on the structure of both phases I and phase II metabolites at a stage when the material was insufficiently pure for identification by other techniques.

Albuterol↗
PubMed1980

Depressant and excitant effects of intraspinal microinjections of morphine and methionine-enkephalin in the cat.

The effects of intraspinal microinjectins of morphine (10 microgram) and methionine-enkephalin (Met-enkephalin) (5 microgram) on the C-fiber and polysynaptic reflexes in the acute decerebrate low spinal cat were investigated. Microinjected into the dorsal horn, morphine and Met-enkephalin depressed the nociceptive C-fiber reflex (CFR) without altering the short latency polysynaptic reflex. Microinjected into the ventral horn, morphine and Met-enkephalin facilitated the C-fiber and polysynaptic reflexes. Pretreatment of the cats with intravenous naltrexone (2 mg/kg) antagonized the depressant effects produced by dorsal horn intraspinal microinjections of morphine and Met-enkephalin. The excitant effects of ventral horn microinjections of morphine were not antagonized by naltrexone (2 mg/kg). These results support a hypothesis that the analgesic effects of morphine at the spinal cord level are due to interactions with opiate receptors in the dorsal horn.

Animals↗