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Biomedical subjects

D G Smith

Publications and source records attributed to D G Smith.

At least 253 records · Page 14Linked to original sources
PubMed1987

Switching and the definition of modality in end-stage renal disease treatment.

End-stage renal disease treatment expenditures have increased greatly in recent years. Modality of treatment is a very important factor in determining costs as well as outcome and quality of life. Using quarterly observations on treatments received by ESRD patients, this paper presents a definition of modality based on type of treatment received and setting in which treatment is received. This paper also documents the magnitude of switching among defined modalities. Because many patients switch modality, selection of one modality is really a selection of a probable course of treatment by several modalities. The careful definition of modality and recognition that switching occurs are important first steps in conducting cost-effectiveness type analyses of ESRD treatment.

Hemodialysis Units, Hospital↗
PubMed1987

The comparative effects of azathioprine and cyclosporin on some gingival health parameters of renal transplant patients. A longitudinal study.

The periodontal health of 24 adult renal transplant patients was investigated in a longitudinal study. Post-transplant patients were receiving either azathioprine or cyclosporin to prevent graft rejection. No significant difference (P greater than 0.05) was observed for plaque scores on gingival inflammation, either between treatment groups or throughout the investigation period. However, patients on cyclosporin therapy had significantly more gingival hyperplasia and probing sites greater than 3 mm than those on azathioprine (P less than 0.05). In the cyclosporin group, a significant increase in hyperplasia and probing sites greater than 3 mm was observed at 3 and 6 months post-transplant. A significant correlation (rs = 0.55, P less than 0.05) was observed between mean plasma concentrations of cyclosporin throughout the 6-month investigation period and the increase in gingival hyperplasia. The finding from this study would suggest that azathioprine has no unwanted effects on the periodontal health of post-renal transplant patients. Cyclosporin therapy caused an increase in gingival hyperplasia, which may be related to plasma concentrations of the drug.

Adult↗
PubMed1987

Modeling decisions to use tube feeding in seriously ill patients.

Clinical decisions to use life-sustaining technologies, such as tube feeding in seriously ill patients, depend on many important factors. Using case simulations, we analyzed the decisions of students, housestaff, and faculty of Temple University School of Medicine, Philadelphia, to use tube feeding in seriously ill patients. Although patient preference was the most important factor for most respondents, we observed three different patterns of decision strategies. Those in the first group, the autonomists (34% of respondents), considered only patient preference; those in the second group, the mixed strategists (56% of respondents), included patient preference among other important factors; and those in the third group, the paternalists (10% of respondents), used factors other than patient preference. More experienced clinicians and those individuals who believed tube feeding represented an extraordinary level of care were significantly less likely to begin tube feeding in the case simulations. Description of these individual decision strategies and elucidation of the important physician characteristics can help identify the potential ethical dilemmas in these different clinical decisions.

Adult↗
PubMed1986

Fluoxetine-induced attenuation of amphetamine self-administration in rats.

Daily injections of fluoxetine (5.0 mg/kg i.p.) to rats trained to self-administer intravenous d-amphetamine produced marked decreases in drug intake on three successive days of treatment. After fluoxetine injections were stopped, the number of daily amphetamine self-injections was still significantly reduced for an additional 2 days. When trained amphetamine self-administration animals were placed in an apparatus which delivered i.v. saline with each lever press, increased self-injection is observed. Acute fluoxetine injection did not alter this response. However, if fluoxetine is given prior to amphetamine exposure for 1 day and animals are then tested for the saline response, lever pressing activity is significantly reduced. These data might suggest that 5-hydroxytryptaminergic neurons mediate some aversive or negative reinforcing property of amphetamine. If true, this finding could be exploited clinically in cases of human psychomotor stimulant addiction.

Amphetamines↗
PubMed1986

Comparison of two methods of administration of amphetamine on the dynamics of dopaminergic neurons in the rat.

Dopamine (DA) and its metabolite dihydroxyphenylacetic acid (DOPAC) in brain were examined in the striatum and nucleus accumbens septi after the administration of amphetamine by two different methods. A computer-controlled device was constructed to deliver intravenous injections of amphetamine in patterns mimicking those of animals in a self-administration paradigm, i.e. a total of 65 injections of 0.125 mg/kg/injection over 8 hr [total; 8.13 mg/kg (22.05 mumoles/kg)]. The second method was the intraperitoneal injection of 8.13 mg/kg as a single bolus. Control animals were intravenously or intraperitoneally administered saline. The effects of the two injection methods on the concentrations of DA and DOPAC were quite distinct at early times. This may in part be due to differences in the peak concentrations of amphetamine in brain achieved by the two regimens. Differences still persisted 48 hr after injection, particularly in the striatum. Increased levels of DA and DOPAC were observed at this time after the computer-controlled injections, while significantly decreased DA in the striatum is found after intraperitoneal bolus injections. These data strongly suggest that the method of administration of amphetamine can substantially alter the effects and possible toxicity of the drug on dopaminergic systems.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

Tyrosine influence on amphetamine self-administration and brain catecholamines in the rat.

Earlier work had shown that L-tyrosine administration, precursor to both dopamine (DA) and norepinephrine (NE), could increase brain DA metabolite concentrations after amphetamine treatment and restore amphetamine-induced decreases in whole brain NE. Both monoamines have been suggested to participate in some aspects of continued drug abuse. Rats trained to self-administer IV d-amphetamine were treated with IP tyrosine during test sessions to examine the behavioral and neurochemical response. In animals with less than 35 days of amphetamine exposure, L-tyrosine treatments did not alter amphetamine self-administration. Experiments using a computer-controlled injection apparatus which administered IV amphetamine to naive rats in patterns mimicking those of self-administration animals indicated tyrosine could antagonize amphetamine-induced NE depletions. The increases in DA metabolite dihydroxyphenylacetic acid (DOPAC) were found limited to the striatum, an area not involved in the positive reinforcing effects of amphetamine. Concentrations of DOPAC in nucleus accumbens septi were unchanged by the amphetamine or the amphetamine-tyrosine regimen. In rats with 4-6 months of chronic amphetamine exposure, however, L-tyrosine administration significantly reduced daily drug self-injection. While neurochemical responses to tyrosine could not be performed, it is speculated that chronic long-term amphetamine abuse might alter the tyrosine-induced changes in DA and/or NE synthesis and release compared to that in the acute or short-term amphetamine abuse animals. These data suggest that the success or failure of an experimental pharmacologic treatment strategy in psychomotor stimulant abusers might be dependent on the subjects history of drug abuse.

Animals↗
PubMed1986

Dietary tryptophan supplements attenuate amphetamine self-administration in the rat.

Previously, it had been shown that lesions of cerebral 5-hydroxytryptamine (5-HT)-containing neurons and injections of drugs affecting 5-HT synthesis or receptor mediated function would alter amphetamine self-administration in the rat. The present study sought to ascertain whether diets enriched in L-tryptophan (L-TRY), the amino acid precursor to 5-HT, would: elevate cerebral 5-HT concentrations and affect amphetamine self-administration behavior. Diets containing 2.0 and 4.0% L-TRY increased cerebral 5-HT concentrations above those of rats on normal rat chow (0.26% L-TRY). The 4.0% diet elevated brain 5-HT to the same degree in rats exposed to the diet for 1, 2 or 3 days. When normal diets were restored, brain 5-HT concentrations rapidly returned to normal. Animals trained to self-administer d-amphetamine, when given access to the L-TRY enriched diets, significantly reduced their daily amphetamine self-injection during exposure periods. When normal rat chow was restored a delay in recovery to pre-diet amphetamine self-administration was observed: 1 day with the 2.0% L-TRY diet and 2 days with the 4.0% L-TRY diet. The 4.0% L-TRY diet failed to alter saline-frustration responding indicating the diet did not produce decrements in motor performance. When animals were placed on the 4.0% L-TRY diet and allowed access to amphetamine for 1 day then exposed to saline, a profound decrease in saline-frustration responding was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Bilirubin binding by the fractionated alternate allelic components of heterozygous monkey albumin.

Analysis of bilirubin-binding parameters for purified albumin of nine rhesus monkeys heterozygous for albumin MacA and albumin MacB was performed after separating these two albumin forms by fast protein liquid chromatography (FPLC). The binding capacity (n) for MacA-enriched samples was lower than that for the MacB variant in eight of nine fraction pairs analyzed, while the affinity constant (K) was higher in all nine MacA-enriched samples. The values for n X K were higher in MacA-enriched samples in eight of nine pairs tested. These data, together with previous studies, geographic specificity of the MacB variant, and the presence of dietary competitors for the primary bilirubin binding site on the albumin molecule, suggest an evolutionary advantage for the MacB variant only in areas where the dietary competitors are present.

Alleles↗
PubMed1985

A linkage study of protein-coding loci in Macaca mulatta and Macaca fascicularis.

Genealogical and gene marker data from the closely related species Macaca mulatta and Macaca fascicularis have been used to search for linkage between genes coding for the blood proteins albumin, carbonic anhydrase 1 and 2, diaphorase 1 and 2, group-specific component, glucose phosphate isomerase, hemoglobin alpha chains, isocitrate dehydrogenase, prealbumin, and transferrin. The results are consistent with conservation of the linkage between the loci coding for albumin and group-specific component and loci coding for the two carbonic anhydrase isozymes, as observed in other species. Among the 38 possible pairwise comparisons, no new linkage groups were identified. Tight linkage can be excluded for most pairs of loci.

Animals↗
PubMed1985

The effects of phenytoin and sodium valproate on the periodontal health of adult epileptic patients.

The periodontal health of 30 adult epileptic patients treated with either sodium valproate or phenytoin was compared with a control group (n = 15) of otherwise healthy patients. The 3 groups were matched for age and sex. Patients on phenytoin therapy showed significantly higher plaque scores (P less than 0.05), gingival index (P less than 0.05) and pocketing (P less than 0.05) than patients in the control group. The % of gingival hyperplasia was significantly higher (P less than 0.05) in the phenytoin-treated patients than those on sodium valproate or in the control group. However, patients on phenytoin therapy had significantly less bone loss than those on sodium valproate (P less than 0.05) or in the control group (P less than 0.01). No significant differences were observed between the sodium valproate group and the control group on any of the parameters assessed. The results from this study would suggest that sodium valproate has no unwanted effects on periodontal health and may be considered a safe alternative, regarding the periodontal aspects, to phenytoin for the treatment of adult onset epilepsy.

Adolescent↗
PubMed1985

Nervous control of the blood pressure in the Atlantic cod, Gadus morhua.

Dorsal (PDA) and ventral aortic blood pressure (PVA) and heart rate (HR) were measured in conscious resting cod, Gadus morhua L., which has been allowed 24 h recovery from surgery. Plasma adrenalin and nonadrenalin concentrations in these fish were 3.4 and 2.2 nmoll-1 respectively, and thus lower than previously reported values from partially recovered cod. Twenty-four hours after treatment with the adrenergic neurone blocking agent bretylium, PDA was significantly reduced by 17% compared to sham-injected controls, although PVA and heart rate were unaltered. Subsequent alpha-adrenoceptor blockade by phentolamine produced no further fall in PDA and no changes in PVA or HR, provided a 5-h period was allowed to overcome the acute toxic side effects of phentolamine. The effectiveness of the bretylium or phentolamine blockade was confirmed by noting the absence of any vasoconstrictor response during sympathetic nerve stimulation in perfused tails from fish used in the in vivo experiments. Bretylium had no significant effect on the sensitivity of the isolated coeliac artery to adrenalin, but effectively blocked the adrenergic innervation of this artery or the vasculature of the tail. Evidence for a non-selective blockade of non-adrenergic nerves to the heart was also obtained. It is concluded that the adrenergic tonus affecting the dorsal aortic blood pressure in resting cod that have recovered for 24 h following surgery is due solely to an adrenergic nervous tone.

Animals↗