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Biomedical subjects

L Simons

Publications and source records attributed to L Simons.

31 records · Page 2Linked to original sources
PubMed1992

A rapid method for diagnosis of the Lebanese allele in the low-density lipoprotein receptor gene.

The Lebanese allele in the low-density lipoprotein receptor gene is one of the alleles which results in the disease familial hypercholesterolemia. We describe a rapid method for detection of the Lebanese allele, using the polymerase chain reaction to amplify part of exon 13, intron 14 and all of exon 14. The amplified DNA is then digested with HinfI which distinguishes between the normal and Lebanese alleles. A previously unidentified HinfI site is described in the intron. HinfI fragments are separated using polyacrylamide gel electrophoresis, and visualized by ethidium bromide staining.

Alleles↗
PubMed1991

The toxic effect of deltamethrin on linyphiid and erigonid spiders in connection with ambient temperature, humidity, and predation.

The first part of this study concerns the effect of temperature and air humidity on the toxicity of deltamethrin to the erigonid Oedothorax apicatus. The second part concerns the effect of deltamethrin on behavior of linyphiids and erigonids with respect to their ability to escape from predators and to select between unfavorable (dry) and favorable (moist) habitat conditions. The toxic effect of deltamethrin was highest at the combination of high temperature and low air humidity. It was concluded that the spider's sensitivity to drought is increased by this pyrethroid. Affected spiders, however, are less able to select moist habitat conditions than unaffected ones. Walking speed of spiders was decreased by exposure to deltamethrin and their predation by carabid beetles was increased. It was concluded that the effect observed under field conditions is the result of a combination of neurological, physiological, and behavioral disturbance.

Animals↗
PubMed1989

Reduced serum antibodies associated with social defeat in rats.

Many studies have linked various physical stressors with changes in immune function. The present experiment examined the effect of a social stressor, defeat associated with territorial defense, on serum antibodies to a specific protein, keyhole limpet hemocyanin (KLH). Pairs of male rats formed colonies and experimental rats were intruders. Experimental animals were immunized with KLH prior to exposures to territorially defensive colonies. Control animals were placed into colonies but separated from residents by a Plexiglas barrier. Behavioral measures, including number of bites and total time spent in submissive postures, were taken for colony-intruder interactions. Serum antibody levels were determined from blood samples taken one, two, and three weeks following immunization. Experimental animals had significantly less serum antibodies to KLH than did controls. Within the experimental group, total time spent in submissive postures at week one was significantly correlated with serum antibody levels, such that animals spending the most time in submission had lower antibody levels. Total bites correlated only slightly with antibody levels. The correlation between submission and serum antibody levels increased when the bites factor was partialled out. A stressful social encounter may thus affect immune function in a manner independent of the influence of physical (nociceptive) stressors.

Aggression↗
PubMed1988

Suppression of specific antibody production by inescapable shock: stability under varying conditions.

The effect of exposure to uncontrollable shock on the production of antibodies to a novel antigen, keyhole limpet hemocyanin (KLH), was studied in adult male Sprague-Dawley rats. Groups of rats were tested under one of four experimental conditions which included testing during either the light or dark portions of their light cycles and following either one or three daily exposures to tail shock. Control subjects were immunized with KLH in the absence of shock exposure during either the light or dark phases of their light cycle. A tertiary (memory) response was evoked 60 days following the initial immunization sequence in all animals in the absence of a shock exposure. Blood samples were obtained from the tip of the tail at the time of each immunization and at 1-week intervals for 3 weeks following immunizations. Specific IgG antibodies to KLH were determined by an enzyme-linked immunosorbent assay (ELISA). All animals exposed to shock showed reduced levels of IgG antibodies to KLH regardless of the experimental conditions of shock exposure. Antibody levels were highest among animals immunized during the dark phase of their cycle for both control and shocked animals. Antibody production to a novel antigen appears to be a robust and sensitive measure for studies of modulation of immunity by behavioral factors.

Animals↗
PubMed1981

Coronary risk factors in a rural community which includes aborigines: Inverell Heart Disease Prevention Programme.

A coronary risk factor screening and referral service was established in Inverell, New South Wales, in July 1978. In non-Aboriginal subjects, there was an increasing prevalence of coronary risk factors with age (hyperlipidaemia, hypertension and obesity), except for cigarette smoking which showed a reverse trend. Allowing for minor differences in sampling, the average level of plasma cholesterol, blood pressure and cigarette smoking in rural inverell closely resembled that in Sydney. However, Inverell subjects of both sexes were consistently more overweight at all ages. Aboriginal subjects of both sexes showed an increased prevalence of hypertriglyceridaemia and cigarette smoking compared with non-Aboriginal subjects, whilst hypertension and obesity were also more prevalent in the Aboriginal females. High Coronary risk Inverell subjects sustained significant improvements in serum cholesterol, cigarette smoking and body weight levels over one year of follow-up. Community-wide control of hypertension was initially unsatisfactory and this remained so.

Adult↗
PubMedDate not supplied

Hyperlipidemia after heart transplantation.

Because hyperlipidemia may be a factor in the development of late graft atherosclerosis after heart transplantation, we have studied serum lipid levels in patients during the first year after transplantation. Serum cholesterol and triglyceride levels were measured in the preoperative period and at regular intervals up to 12 months after transplantation in 22 consecutive heart transplant recipients. Patients were divided into two groups: group 1 included 10 patients with underlying ischemic heart disease, and group 2 had 12 patients with underlying idiopathic dilated or valvular cardiomyopathy. Mean serum cholesterol concentrations in both groups increased substantially after operation and peaked at 3 months (respective rises of 35% and 30%). By 12 months after transplantation 50% of group 1 and 33% of group 2 manifested a significant degree of hypercholesterolemia (plasma cholesterol greater than 6.5 mmol/L, 250 mg/100 ml). Mean serum triglyceride concentrations increased in both groups during the latter part of the first year (respective increases of 44% and 13%). At 12 months only 10% of group 1 and 8% of group 2 manifested a significant degree of hypertriglyceridemia (plasma triglycerides greater than 3.0 mmol/L, 265 mg/100 ml). Over the first postoperative year there was a progressive increase in body weight, and this correlated highly with the increase in serum lipid levels (r = 0.90 for serum cholesterol and r = 0.84 for serum triglycerides). The role of conventional risk factors including hypercholesterolemia in the development of graft atherosclerosis remains uncertain, but until their role is defined, further strenuous efforts at weight control as a means of preventing or managing hyperlipidemia need to be explored.

Adult↗