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Biomedical subjects

S Evans

Publications and source records attributed to S Evans.

At least 253 records · Page 14Linked to original sources
PubMed1991

Nursing measures in the prevention and treatment of renal cell damage associated with cisplatin administration.

Renal tubule damage as a result of the nephrotoxic effects of cisplatin is a well-documented effect of cisplatin administration. This damage results in electrolyte imbalances through electrolyte wasting and electrolyte reabsorption failure in the renal tubule. Electrolytes most commonly affected are magnesium, calcium, and potassium. Other indicators of renal cell damage are elevations in blood urea nitrogen and serum creatinine and a decrease in creatinine clearance levels. Individuals with marginal renal function or those who have had multiple doses of cisplatin or other nephrotoxic drugs are at increased risk for developing nephrotoxicity. Early assessment of risk factors and the implementing and evaluating of interventions to facilitate prevention of nephrotoxicity will presumably minimize the incidence and degree of renal damage.

Cisplatin↗
PubMed1990

Early changes in hepatic redox homeostasis following treatment with a single dose of valproic acid.

Changes in reduced glutathione (GSH) and pyridine nucleotide phosphate levels as well as in the activities of the glutathione peroxidase-reductase system and glucose-6-phosphate dehydrogenase have been studied in rats after a single i.p. administration of various doses of valproic acid (VPA). GSH level decreased in a dose-dependent relation. At the end of 180 min GSH levels either returned to control limits (lower doses) or showed a tendency to normalize (higher doses). GSH loss was paralleled by the reduction in glutathione reductase activity. A significant NADPH reduction was also seen after animal exposure to high VPA doses. At the end of 180 min a maximal NADPH decrease was reached. The activities of both glutathione peroxidase and glucose-6-phosphate dehydrogenase were suppressed irrespective of whether animals were given low or high VPA doses.

Animals↗
PubMed1990

Sensitivity of different human lung cancer histologies to photodynamic therapy.

The relative sensitivities of different cancer histologies in a single site to photodynamic therapy (PDT) are unknown and methods to predict PDT sensitivity have not been described. The in vitro response to PDT of six established human lung cancer cell lines and one normal lung fibroblast cell line was studied using the clonogenic assay. Dose-response curves were determined for cells incubated in 25 micrograms/ml of Photofrin II for 2 h, followed by exposure to 630-nm light to total energies of 0-3150 J/m2. None of the cell lines were sensitive to sensitizer alone or light alone. Differences in inherent PDT sensitivities as evaluated by survival curve parameters n, Do, and light dose to yield 1% survival were observed among the cell lines. No clear correlation was found when inherent PDT sensitivity was compared with sensitizer uptake; however, a general association was noted between PDT sensitivity and the plating efficiency of the cell line. These data illustrate that differences in inherent PDT exist for in vitro systems. Such differences may explain some of the failures seen in clinical PDT.

Cell Line↗
PubMed1990

MK-801 reduced cerebral ischemic injury by inducing hypothermia.

The non-competitive N-methyl-D-aspartate (NMDA) antagonist, MK-801, has been reported to prevent or attenuate ischemic brain damage in various animal models. In halothane-anesthetized gerbils it was found that an optimal dose of MK-801 (3.0 mg/kg) for providing cerebral protection also produced hypothermia (31.1 +/- 0.62 degrees C) relative to control animals (34.2 +/- 0.77 degrees C, P less than 0.01). This degree of hypothermia alone was sufficient to provide complete histological and functional protection (spatial memory) against 5 min of carotid artery occlusion. In gerbils made ischemic, but maintained at normal body temperature, a dose of 3.0 mg/kg of MK-801 provided no protection against hippocampal cell loss or spatial memory impairment. These data suggest that the protective actions of MK-801 may be due entirely to drug-induced hypothermia.

Animals↗
PubMed1990

Effect of photodynamic therapy on tumor necrosis factor production by murine macrophages.

Photodynamic therapy (PDT) involves the treatment of tumors in the presence of sensitizer, light, and oxygen, causing energy-dependent cytotoxicity. A vascular effect that causes hemorrhagic tumor necrosis has been described with PDT, but its basis remains undefined. To investigate the possible role of tumor necrosis factor (TNF) production in the generation of such a vascular effect and/or a direct tumor effect, we treated thioglycollate-elicited murine macrophages with PDT, and we measured the possible production of TNF using the L929 assay. An energy-dependent production of TNF by macrophage treated with PDT, stimulated or unstimulated with endotoxin, was demonstrated, and TNF production was inhibited at the highest treatment energy levels. These data represent the first description of cytokine production by PDT-treated macrophages, and may serve as another mechanism of PDT cytotoxicity in vivo, either directly by TNF-mediated tumor necrosis, or indirectly by vascular effects on tumor vessels.

Animals↗
PubMed1990

Neurophysiological and biochemical changes evoked by valproic acid in the central nervous system.

(1) Valproic acid is an anticonvulsant agent widely used in the management of various forms of epilepsy, including absence, myoclonic and tonic-clonic seizures. (2) It also has anticonvulsant potency in a wide variety of animal models of epilepsy. (3) This action is generally thought to be exerted through modulation of the activity of the endogenous inhibitory neurotransmitter, gamma-aminobutyric acid. (4) Evidence that valproic acid interacts with the gamma-aminobutyric acid system is presented. (5) Interactions of valproic acid with other neurotransmitters, i.e. aspartate, glutamate, taurine, serotonin, as well as with cyclic nucleotides and hormones are also considered. (6) Direct effects of valproic acid on excitable membranes and its relationships with analgesia are outlined.

Animals↗
PubMed1990

A behavioral approach to increasing calorie consumption in children with cystic fibrosis.

To increase calorie consumption of 5 mildly malnourished children with cystic fibrosis (CF), intervention was implemented in multiple baseline fashion across snack and three meals. Intervention involved nutritional education establishing gradually increasing calories goals, teaching parents contingency management strategies, and a reward system for achieving calorie goals. Following 6 treatment sessions, the children's calorie intake increased across meals and total calorie intake was 25 to 43% above baseline. The calorie increase was maintained at 9-month follow-up. Significant changes in weight and height were made during treatment and the year following intervention. The results suggest that the long-term oral intake of children with CF can be modified by a short-term behavioral intervention.

Behavior Therapy↗
PubMed1990

The changing prevalence of cervical human papilloma virus infection.

In order to determine the change in frequency of human papillomavirus infection (HPV) over a 10-year period, cervical smears from 1978 were retrieved, cytologically reviewed and compared with cervical smears taken in 1988. In this way, the slides were reviewed using the same diagnostic criteria. The prevalence of HPV infection in the population assessed at Flinders Medical Centre, rose from 0.58% to 5.6% over this period.

Female↗
PubMed1990

Better predictors of successful His-bundle ablation analysis of first shocks.

We have reported here that a longer HV interval in association with a larger His amplitude yields a high rate of success when used to position the ablating catheter for His-bundle ablation. Additionally, we have shown that double discharge shocks are more effective than single discharge shocks, and that negative polarity is more effective than positive polarity. The use of bipolar or tripolar, and not quadripolar catheters, was also associated with a higher success rate. In our institution, using a bipolar catheter, we attempt to record an HV interval greater than 55 msec and a His amplitude greater than 0.35 mV. When both of these criteria are fulfilled, we use 3 to 4 joules per kg, and a single discharge shock. When one or the other of these criteria are not fulfilled, we use the double discharge shock method. Using these techniques, we have achieved successful His-bundle ablation with only one shock in all but one of the most recent 21 consecutive patients.

Bundle of His↗
PubMed1990

Cloning, sequencing, and expression of a xylanase gene from the anaerobic ruminal bacterium Butyrivibrio fibrisolvens.

A gene coding for xylanase activity, xynA, from the anaerobic ruminal bacterium Butyrivibrio fibrisolvens 49 was cloned into Escherichia coli JM83 by using plasmid pUC19. The gene was located on a 2.3-kilobase (kb) DNA insert composed of two adjacent EcoRI fragments of 1.65 and 0.65 kb. Expression of xylanase activity required parts of both EcoRI segments. In E. coli, the cloned xylanase enzyme was not secreted and remained cell associated. The enzyme exhibited no arabinosidase, cellulase, alpha-glucosidase, or xylosidase activity. The isoelectric point of the cloned protein was approximately 9.8, and optimal xylanase activity was obtained at pH 5.4. The nucleotide sequence of the 1,535-base-pair EcoRV-EcoRI segment from the B. fibrisolvens chromosome that included the xynA gene was determined. An open reading frame was found that encoded a 411-amino-acid-residue polypeptide of 46,664 daltons. A putative ribosome-binding site, promoter, and leader sequence were identified. Comparison of the XynA protein sequence with that of the XynA protein from alkalophilic Bacillus sp. strain C-125 revealed considerable homology, with 37% identical residues or conservative changes. The presence of the cloned xylanase gene in other strains of Butyrivibrio was examined by Southern hybridization. The cloned xylanase gene hybridized strongly to chromosomal sequences in only two of five closely related strains.

Amino Acid Sequence↗
PubMed1990

Identification of a high risk subgroup of patients with silent ischaemia after myocardial infarction: a group for early therapeutic revascularisation?

Asymptomatic ("silent") ischaemia has been shown to be of prognostic significance in patients with stable and unstable angina and more recently in patients recovering after myocardial infarction. No therapeutic regimen has yet been shown to improve the prognosis of patients with silent ischaemia after infarction, which can be found in as many as a third of these patients. Attempts to achieve therapeutic revascularisation in all these patients may be undesirable, but early revascularisation could be especially beneficial in some selected high risk patients. Two hundred and fifty consecutive clinically stable survivors of myocardial infarction who had predischarge submaximal exercise tests were followed up for a year. Silent ischaemia was found in 27% of these patients; 15% had symptomatic ischaemia. Patients with a positive exercise test were prescribed a beta blocker before discharge. Mortality in patients with silent (9.4%) and symptomatic (5.4%) ischaemia in the first year after infarction was not significantly different. Patients with symptomatic ischaemia were more likely to have undergone coronary artery bypass grafting in the first year. Patients with silent ischaemia were, however, significantly more likely to die than patients with a negative exercise test (relative odds 12:1). Patients with silent ischaemia and an abnormal blood pressure response or who could not complete a submaximal exercise protocol were at particularly high risk, being 32 times more likely to die than those with a negative test (95% confidence interval from 3.3 to 307 times more likely). First year mortality in this group was 22%. The benefits of therapeutic revascularisation in this high risk group need to be studied.

Coronary Angiography↗
PubMed1990

Occupational asthma in a pharmaceutical worker exposed to hydralazine.

A pharmaceutical worker developed asthma when exposed to hydralazine, an antihypertensive drug. The diagnosis of occupational asthma was supported by specific inhalation challenges, which produced a late asthmatic reaction and an increase in bronchial responsiveness. No evidence of an IgE or an IgG dependent mechanism could be found.

Adult↗
PubMed1989

A child with headache.

A child with recurrent headaches may be a 'heart-sink' patient for some doctors. The mother may fear a brain tumour and the doctor may be reticent so as not to give inappropriate reassurance. Emotional factors may be important and the consultation needs careful handling if the situation is to be resolved.

Child↗