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Biomedical subjects

D Fell

Publications and source records attributed to D Fell.

At least 55 records · Page 3Linked to original sources
PubMed1987

Effects of alfentanil on the pressor and catecholamine responses to tracheal intubation.

The effects of alfentanil (given during induction of anaesthesia) on the haemodynamic and catecholamine responses to tracheal intubation were studied in 44 adult patients who received alfentanil 10 micrograms kg-1 or 40 micrograms kg-1, or saline placebo. Alfentanil 10 micrograms kg-1 and 40 micrograms kg-1 prevented any increase in heart rate and arterial pressure after tracheal intubation. Alfentanil 40 micrograms kg-1 produced profound hypotension and bradycardia. The use of alfentanil in both doses was associated with a decrease in plasma adrenaline concentrations after tracheal intubation.

Aged↗
PubMed1987

Effect of retinol toxicity on hepatic S-adenosylmethionine-dependent transmethylation in rats.

Hepatic metabolism of the labile methyl group donor, S-adenosylmethionine (SAM), was investigated in rats fed toxic levels of retinol (1,000 IU/g of diet) since this treatment is known to decrease hepatic SAM concentration. The turnover rate of the hepatic SAM pool was not affected by the excess retinol, but the use of SAM as a labile methyl donor was restricted. Incorporation of the methyl group into phosphatidylcholine was reduced by 51% and oxidation of the methyl group to CO2 was decreased by 40%. In addition, the concentrations of cysteine and cystine, which are synthesized subsequent to demethylation of SAM, were reduced by 32% and 30%, respectively, in liver of high-retinol-fed rats, while methionine concentration was unchanged. The toxic level of dietary retinol may bring about a shift in the metabolism of SAM from transmethylation toward pathways that regenerate methionine via 5'-methylthioadenosine.

Amino Acids, Sulfur↗
PubMed1986

Modification of hepatic folate metabolism in rats fed excess retinol.

Feeding rats a diet containing 1000 IU of retinol/g diet enhances the folate-dependent oxidation to CO2 of formate and histidine. The activity of hepatic methylenetetrahydrofolate reductase, which plays a critical role in the regulation of liver folate metabolism, is suppressed in these animals, resulting in decreased 5-methyltetrahydrofolate synthesis. This ensures a greater concentration of hepatic tetrahydrofolate, the coenzyme on which formate and histidine oxidation depend, but also compromises the level of S-adenosylmethionine in the liver.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1986

A comparative study of diazepam with sustained-release diazepam as oral premedication in minor gynaecological surgery.

Sixty patients undergoing elective minor gynaecological surgery received oral pre-operative medication with 10 mg diazepam in either conventional tablet form on the morning of operation or as the sustained-release tablet the night before. Subjective and objective assessments of the effectiveness of premedication were made. Patients receiving sustained-release diazepam on the night before surgery experienced fewer periods of wakefulness than those who received placebo. Patients who were given diazepam on the morning of surgery felt more drowsy pre-operatively than those who received sustained-release diazepam the night before.

Adolescent↗
PubMed1986

Sudden sensorineural hearing loss following manipulation of the cervical spine.

Review of the otolaryngologic literature reveals no reports of sudden sensorineural hearing loss resulting from manipulation of the cervical spine. Indeed, in previously reported cases of vertebrobasilar artery injury following spinal manipulation, hearing loss has received little attention. Two patients with sudden sensorineural hearing loss following cervical spine manipulation are presented. The audiologic findings and cerebral arteriograms are reviewed and treatment is discussed. A review of the anatomy and pathophysiology is also included, and a possible mechanism of injury to the vertebral artery is proposed.

Adult↗
PubMed1985

The effects of vitamin A deficiency on hepatic folate metabolism in rats.

The effects of severe vitamin A deficiency (liver retinol less than 2 micrograms/g) on hepatic folate metabolism in rats were studied. The oxidation of a [ring-2-14C] histidine load or a [14C]formate load to 14CO2 was significantly depressed in vitamin A-deficient rats and those given histidine also excreted more urinary formiminoglutamic acid (FiGlu) than pair-fed controls. The increase in FiGlu excretion was not due to augmented production from histidine, implicating an impairment of FiGlu catabolism. FiGlu formiminotransferase activity was unaltered in vitamin A-deficient rats, but hepatic tetrahydrofolic acid (THF) concentration was decreased by 58% in vitamin A-deficient rats given a histidine load while 5-methyl-THF concentration was increased by 39%. Formyl-THF and total folate levels were similar to controls. A redistribution of folate coenzymes was not found in vitamin A-deficient rats not force fed histidine. A 43% decrease in 10-formyl-THF dehydrogenase activity, which generates both THF and the 14CO2 from the labeled substrates, and an 81% increase in 5,10-methylene-THF reductase activity, which generates 5-methyl-THF, were found in vitamin A-deficient rats. It appears that the production of severe vitamin A deficiency results in selective changes in the activities of hepatic folate-dependent enzymes, so that when a load of a one-carbon donor is given, THF concentration decreases and metabolism of the load is impaired.

Animals↗
PubMed1985

Measurement of plasma catecholamine concentrations. An assessment of anxiety.

This study was designed to assess the value of measurement of plasma catecholamine concentrations as an objective index of anxiety. A preliminary study was undertaken on 11 healthy volunteers (medically qualified), to determine if venous cannulation per se produced any change in plasma catecholamine concentrations. There were no changes in plasma catecholamine concentrations in the 2 h following insertion of an i.v. cannula, suggesting that venous cannulation did not induce a measurable stress response. A second study was performed on 48 surgical patients who were asked to rate their perceived anxiety on a linear analogue scale immediately before premedication and immediately before induction of anaesthesia. Venous blood was obtained at the same time as these ratings. There were no significant changes in perceived anxiety or plasma noradrenaline concentrations following premedication. However, compared with values before premedication, there was a mean percentage increase in plasma adrenaline concentration of 40% before induction of anaesthesia. A significant correlation was shown between mean percentage change in Linear Analogue Anxiety Score and mean percentage change in plasma adrenaline concentrations (r = 0.32).

Adolescent↗
PubMed1985

Diazepam premedication in children. Plasma levels and clinical effects.

Oral diazepam 0.25 mg/kg or 0.5 mg/kg was employed as premedication in one hundred and one children undergoing elective surgery. The drug failed to modify the rise in cardiorespiratory indices of preanaesthetic anxiety compared with control values, and there was no difference between the two doses assessed by a sedation scoring system. 0.25 mg/kg diazepam produced less sedation in children under 5 years old, compared with those 5 years and older, whereas 0.5 mg/kg produced no difference between the older and younger age groups. The plasma levels of diazepam were greater postoperatively in the 0.5 mg/kg group. There was no relationship between plasma diazepam and recall at induction, and pre-anaesthetic amnesia was not enhanced with the higher premedication dose.

Anxiety↗
PubMed1985

A comparison of triazolam and diazepam as premedication agents for minor gynaecological surgery.

Triazolam 0.25 mg, diazepam 10 mg and placebo were compared in a randomized double-blind trial of oral premedication in 90 patients undergoing minor gynaecological surgery. Both triazolam and diazepam produced a significant sedative effect as measured by patient self assessment linear analogue scales but only diazepam was more anxiolytic than placebo. Psychomotor performance assessed by the letter-search test at 3 and 6 hours after awakening showed a decrement in performance in patients receiving triazolam at 3 hours compared with the two other groups. Triazolam was shown to have a pronounced amnesic effect and whilst it might be used for premedication, its lack of anxiolysis coupled with a significant impairment of psychomotor performance at 3 hours after awakening, render the drug unsuitable for premedication in the short stay patient.

Adult↗
PubMed1984

Metabolic profiles in patients with acute neurosurgical injuries.

Twenty-seven patients with acute neurosurgical injuries were compared with 23 patients with neurosurgical and multisystem injuries and 10 patients with multi-system injuries without neurosurgical injuries. Patients with isolated acute neurosurgical injuries did not demonstrate a hypermetabolic state with increased loss of nitrogen and decreased circulating levels of albumin, prealbumin, and retinol-binding protein when compared to multisystem-injured patients. Patients with demonstrated hypermetabolism on day 1 were supported with parenteral nutrition which decreased their protein losses and stabilized other metabolic variables such as calcium and phosphorus. It is concluded that patients with neurosurgical and other multisystem injuries require close metabolic monitoring. Early institution of metabolic support in hypercatabolic patients may prevent clinically significant depletion states.

Adult↗
PubMed1983

Plasma catecholamine responses to tracheal intubation.

Plasma adrenaline and noradrenaline concentrations were measured in 24 patients during the induction of anaesthesia and the subsequent tracheal intubation. The patients received either suxamethonium 1 mg kg-1 or pancuronium 0.1 mg kg-1 to facilitate tracheal intubation. Mean arterial pressure (MAP) increased in both groups following laryngoscopy and tracheal intubation and there were concomitant increases in the plasma catecholamine concentrations, the changes being more marked in the suxamethonium group. There was a significant correlation between MAP and plasma catecholamine concentrations in the suxamethonium group. Measurement of plasma catecholamine concentrations in samples obtained simultaneously from central venous, peripheral venous and arterial sites were in broad agreement; the greatest changes occurred in central venous samples.

Aged↗
PubMed1983

Effect of methionine on in vivo histidine metabolism in rats.

Experiments were conducted to examine the effects of methionine supplementation on histidine metabolism in rats. All animals were fed 10% casein diets with a methionine content of either 0.6 or 1.1%. Experiments in which the animals were fed their diets containing an additional 1% histidine ad libitum for at least 10 days revealed that methionine-supplemented animals had a 49% reduction of plasma histidine and an 80% reduction in urinary excretion of formiminoglutamic acid (FIGLU) on day 10. This effect was not observed on day 5. In subsequent experiments rats were fed the control or test diet ad libitum prior to receiving their diets, containing a histidine load, by force-feeding. When a 100-mg histidine load was given on day 5, 24-hour urinary FIGLU excretion was 83% lower in methionine-supplemented animals. When rats were force-fed a 75-mg [ring-2-14C]histidine load on day 10, those receiving supplemental methionine oxidized 21% more of the histidine label to 14CO2 and excreted 61% less of the dose as urinary FIGLU in 24 hours. The activities of histidase and urocanase were unaffected by the methionine supplement. The results suggest that dietary methionine supplementation enhances the in vivo catabolism of histidine by stimulating one-carbon metabolism. Delivery of the methionine supplement by ad libitum feeding requires at least 5 days for this effect to be achieved.

Animals↗