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Biomedical subjects

R L Elliott

Publications and source records attributed to R L Elliott.

At least 73 records · Page 4Linked to original sources
PubMed1983

Monocusp aortic valve replacement in dogs: an experimental model.

Aortic valve replacement using human allograft valves is a well established procedure, following which histological evidence of a host-graft interaction is seen. This varies in intensity, depending on the types of sterilizing and storage agents to which the allograft is exposed prior to insertion. A canine experimental model which enables study of these tissue ingrowth patterns in variously treated allografts has been devised. The technique is described in detail.

Animals↗
PubMed1981

Self-poisoning with drugs: a 3 1/2-year study in Newcastle, NSW.

This is a review of 963 cases of self-poisoning with drugs (8.5% of all medical emergencies) treated in the three major Newcastle hospitals over a 3 1/2-year period. The number of patients admitted rose from 243 (July 1976 to June 1977) to 326 (January to December, 1979)-an overall increase of 34%. The most common drugs used were benzodiazepines (34.9% of cases); barbiturates (11.2%); tricyclic depressants (9.2%); paracetamol (8.1%) and phenothiazines (6.2%). In four of 134 cases involving barbiturates, phenobarbitone had been used as part of an anticonvulsant regimen. Six patients died in hospital and 31 who committed suicide with drugs were not admitted to the hospital, but were investigated by the Regional Forensic Pathologist.

Acetaminophen↗
PubMed1981

Comparative studies on the hemodynamic effects of prostaglandin E1 prostacyclin, and tolazoline upon elevated pulmonary vascular resistance in neonatal swine.

Forty-eight hour old anesthetised and ventilated neonatal piglets were cannulated in order to measure pressure, blood gases and cardiac outputs (CO) from which pulmonary (PVR) and systemic (SVR) vascular resistances were calculated. After baseline measurements had been made inspired gases were altered to produce hypoxemia and hypercapnia, to raise PVR. Animals then received Prostaglandin E1 (PGE1), Tolazoline (TOL), and Prostacyclin (PGI2) in varying dosages until PVR was reduced or the dosage no longer tolerated. With "hypoxia" CO, PVR and pulmonary artery (PA) pressures rose; aortic pressure also rose although SVR tended to fall. PGE1 (5microgram/kg/min) and PGI2 (1.0 microgram/kg/min) both produced a significant fall in PVR. The decrease in PVR with TOL (1 mg/kg/10 minutes and 2 mg/kg/1 hour) was less consistent and in surviving animals did not achieve statistical significance by multivariate analysis. SVR fell with all drugs although the change with TOL was again non-significant. With both PGI2 and TOL there was a trend for CO to rise and, although this did not reach significant levels, it restricted the drop in arterial pressure to approximately control levels. The fall in arterial pressure with PGE1 was greater. The death rate with treatment with TOL was much higher than that seen with the other two drugs. Circulatory changes in a group of animals with normal blood gases treated with PGI2 (1 microgram/kg/min) were similar to those seen with the hypoxic group.

Alprostadil↗
PubMed1981

Effect of free fatty acids on protein binding of antimicrobial agents.

The effect of free fatty acids (FFAs) on the binding of antibiotics to human serum proteins was studied by addition of palmitic acid to albumin solutions and normal pooled serum. FFA reduced the binding of dicloxacillin, cefamandole, and sulfamethoxazole at molar ratios of FFA to albumin of greater than 2.0. In contrast, FFA enhanced the binding of benzylpenicillin, cephalothin, and cefoxitin at physiologic molar ratios of FFA to albumin. Elevated levels of FFAs induced in vivo by heparin produced similar results with dicloxacillin and benzylpenicillin. Addition of FFA to serum, but not to albumin, reduced the binding of clindamycin and trimethoprim. That the binding of these drugs was much lower in albumin than in serum suggested the presence in serum of another antibiotic-binding protein and that FFAs can modulate binding to this protein. Binding of chloramphenicol was unaffected by FFAs. The possible clinical significance of the changes in protein binding due to FFAs is discussed.

Anti-Bacterial Agents↗
PubMed1980

Improving intestinal absorption of water-insoluble compounds: a membrane metabolism strategy.

A strategy for improving the intestinal absorption of water-insoluble drugs was developed and tested. The strategy is based on making a soluble derivative of an insoluble compound which, in turn, is a substrate for enzymes in the surface coat of the brush border region of the microvillous membrane. Consequently, just prior to reaching the membrane, the physical properties of the diffusing species are changed from polar to nonpolar. The experimental test used two drug-drug derivative pairs, estrone-lysine estrone ester and p-nitroaniline-lysine p-nitroanilide. Wall permeabilities were determined using an external perfusion technique in the rat intestine and a laminar flow convective diffusion model for transport in the lumen. Analysis of the permeability results indicates that the derivatives have higher wall permeabilities than the parent compounds and that the microvillous surface coat may be a significant contributor to the intestinal wall resistance. Comparison of the absorption rates for estrone and the lysine estrone ester indicates that the absorption rate of the derivatives could be up to five orders of magnitude greater than that for the parent compound.

Aniline Compounds↗
PubMed1980

Analysis of models for determining intestinal wall permeabilities.

In determining intestinal wall permeabilities, several mass transport models may be applied to analyze the results from external perfusion experiments. The appropriateness of any given model depends on the applicability of the model assumptions to the experimental system. This report compares several mass transport models with respect to their assumptions and applicability to a particular experimental design. The models are shown to differ in their assumptions regarding convection and diffusion in the perfusing fluid. However, since the wall permeability is an unknown parameter in each model and is estimated from the data, all of the models fit the mass transfer results reasonably well, despite fundamentally different assumptions. However, the determined permeabilities differ. Residence time distribution analysis of the experimental system is more sensitive to the model assumptions. It is shown that, in a particular experimental system, laminar flow in a cylindrical tube is the most appropriate model. The model also has the advantage of implicitly accounting for the convection-diffusion problem in the perfusing fluid. Hence, the diffusion layer thickness is not estimated from the data. With the hydrodynamics defined, the relative permeabilities resulting from the application of the several models to the data can be interpreted. The wall permeability determined in the suggested manner provides an estimate of the limiting assistance under perfect mixing conditions.

Animals↗
PubMed1979

Plasma levels following single and repeated doses of erythromycin estolate and erythromycin stearate.

The pharmacokinetics of erythromycin and erythromycin 2'-propanoate were studied in healthy male volunteers following single and repeated doses of erythromycin stearate tablets, erythromycin estolate capsules, and a suspension. Estolate dosages gave rise to higher plasma levels of total drug than the stearate. However, the stearate yielded higher plasma levels of erythromycin base. Absorption of all dosage forms, except the suspension, was delayed, and pharmacokinetic interpretation of both single- and multiple-dose data required incorporation of an absorption lag time. The absorption of erythromycin stearate was inhibited by food and also by low fluid volumes in fasted subjects. Absorption of erythromycin estolate was increased in the presence of food and was not greatly affected by fluid volume. Although single-dose data poorly predicted circulating levels of erythromycin following repeated doses, trends observed after single doses were maintained during chronic treatment.

Adult↗
PubMed1979

Control of elevated pulmonary vascular resistance in neonatal swine with prostacyclin (PGI2).

Three groups of neonatal piglets were anesthetised and base-line hemodynamic measurements were made. The piglets were then subjected to hypoxia and hypercapnea to raise pulmonary vascular resistance (PVR) and further hemodynamic measurements were made over a period of at least 100 minutes. During the last 80 minutes of this period the control group received an infusion of 0.05M Tris buffer [the vehicle for prostacyclin (PGI2)], the second group received an infusion of 0.5 microgram/kg/min PGI2, and the third group received an infusion of 1.0 microgram/kg/min PGI2.

Animals↗
PubMed1978

The effects of some methyl prostaglandin derivatives on the ductus arteriosus of swine in vivo.

Three methylated analogues of prostaglandin E1 and E2 were examined for their ability to open the ductus arterious of neonatal piglets in vivo. Fifteen (S) 15 methyl prostaglandin E1 (15-Me PGE1), 15 (S) 1K methyl prostaglandin E2 (15-Me PGE2), and 16' 16' dimethyl prostaglandin E1 (16-diMe PGE1) all opened the ductus when given intravenously, intramuscularly or orally. The effects on ductal patency lasted four hours or more in many instances. Side-effects included apnea with intravenous and intramuscular dosages, and with high oral dosages of 15-Me PGE1. A transient drop in heart rate and blood pressure occurred with each dose. In one animal the ductus was kept open for 19 days with six-hourly intramuscular injections of 3 microgram/kg 15-Me PGE1. Transient sedation occurred with each dose. Death occurred on the 19th day and histological studies showed that the morphology of the ductus wall was similar to that seen in a two day old animal. These studies suggest that maintenance od ductal patency in the infant may be possible with oral administration of methyl prostaglandin derivatives.

Administration, Oral↗
PubMed1976

Studies on the effects of prostaglandins E1, E2, A1, and A2 on the dustus arteriosus of swine in vivo using cineangiography.

Prostaglandins E1, E2, A1, and A2 have been shown by cineaortography to open and dilate the ductus arteriosus in anesthetised piglets 3 to 6 hours of age. The dosage of PGEs required was 1 to 4 mug/kg/min. and of PGAs 20 to 40 mug/kg/min. The effect of PGEs faded within 20 minutes of stopping infusion but the effect of PGAs was still evident up to 45 minutes after stopping the infusion. Little effect was noted from hypoxia or from the addition of indomethacin to prostaglandin infusion. Side effects were not troublesome with the dosage employed but hypotension and apnea sometimes occurred at the onset of PGE infusions.

Animals↗