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Biomedical subjects

V Marks

Publications and source records attributed to V Marks.

At least 217 records · Page 12Linked to original sources
PubMed1982

Simultaneous enzyme immunoassay of two thyroid hormones.

We describe an enzyme immunoassay in which the two thyroid hormones, triiodothyronine and thyroxin, are measured simultaneously in a single tube. The method involves labeling the two with separate enzymes (beta-galactosidase and alkaline phosphatase, respectively), whose catalyzed reactions can easily be distinguished from each other by absorption spectrophotometry, with o-nitrophenyl-beta-galactoside and phenolphthalein monophosphate as substrates. Performance of this dual assay method compares well with that of conventional single-hapten enzyme-labeled assays, and results compare well with those by two single-hapten radioimmunoassays. The dual assay has certain advantages over single-hapten methods: smaller sample volume, lower reagent cost, and shorter overall assay time. As presented here, the use of enzyme labels to measure two (or more) haptens simultaneously represents a significant advance in the use of immunoassay techniques.

Humans↗
PubMed1982

Evaluation of a commercially available radioimmunoassay kit for measurement of doxorubicin in plasma.

We evaluated a commercially available (Diagnostic Biochemistry Inc.) doxorubicin 125I radioimmunoassay kit. This kit gave a high apparent doxorubicin concentration (greater than 12 micrograms/L), which was not linearly related to dilution, for two pools of normal human serum and plasma and also for samples collected from patients before they received the drug. In contrast, a doxorubicin 3H radioimmunoassay developed by us gave a low blank (2 micrograms/L), which was linearly related to dilution, for the same pools and patients' samples. Doxorubicin concentrations in the plasma of patients receiving the drug were compared by the two methods; the kit gave results five- to 10-fold those obtained with our assay. High nonspecific interference by serum and plasma as measured by the 125I radioimmunoassay must therefore be borne in mind by users of the kit, and we suggest that results should be corrected for these nonspecific effects.

Doxorubicin↗
PubMed1981

Prednisolone concentrations in plasma, saliva and urine.

Prednisolone was measured in plasma, saliva and urine at various times after a single dose. Peak plasma prednisolone levels were observed about 1 h after the dose. Saliva prednisolone levels were measurable for at least 3 h after dosing but showed no consistent relationship to either total or free plasma prednisolone concentrations. Unchanged prednisolone in amounts up to 14% of the dose administered was found in the 24 h urine and most of it was excreted in the first 5 h.

Adult↗
PubMed1981

Clinical efficacy of testosterone undecanoate in male hypogonadism.

Testosterone undecanoate (Restandol, Organon Laboratories Ltd) dissolved in oleic acid, was administered orally to seventy-six hypogonadal males for three consecutive 3-week periods and the subjective clinical response assessed by a standard interview. Plasma testosterone and testosterone undecanoate levels were determined by radioimmunoassay before the study and after 3, 6 and 9 weeks treatment. The treatment was effective in sixty of the sixty-six patients who completed the trial. Ten patients did not complete the trial; two for reasons unrelated to the drug and eight because of side effects, mainly gastro-intestinal. There was a significant rise in plasma testosterone levels during treatment and a positive correlation between plasma testosterone and testosterone undecanoate levels. Testosterone undecanoate is a potentially valuable drug for the oral treatment of male hypogonadism.

Administration, Oral↗
PubMed1981

Serum methylprednisolone levels following intra-articular injection of methylprednisolone acetate.

Twenty-one patients with rheumatoid arthritis received injections of either 40 mg or 80 mg of methylprednisolone acetate into one or both knee joints. Serum methylprednisolone and cortisol levels were measured at intervals up to 1 week following injection. Peak serum levels of methylprednisolone were reached at between 2 and 12 hours following injection, and increasing the injected dose resulted in correspondingly higher serum levels. Injection of 80 mg of methylprednisolone as 40 mg into each knee produced consistently higher peak serum levels than when given as a single intra-articular injection. Serum cortisol levels were substantially suppressed for up to 1 week, and this effect was seen at all dose levels.

Arthritis, Rheumatoid↗
PubMed1981

Correlation of endogenous somatostatin, gastric inhibitory polypeptide, glucagon and insulin with gastric function in the conscious calf.

Levels of endogenous somatostatin, gastric inhibitory polypeptide (GIP), glucagon and insulin were measured during gastric (abomasal) emptying in the conscious calf. Isotonic NaHCO3 infused into the duodenum increased rates of emptying of a saline test meal and of gastric acid secretion, but had no effect on basal levels of blood glucose, somatostatin, GIP, insulin or glucagon. By contrast, intraduodenal infusion of 60 mM-HCl caused complete inhibition of gastric emptying, reduction of acid secretion, and an immediate increase in plasma somatostatin from 121.3 +/- 9.4 (S.E.M.) to 286.3 +/- 16.3 pg/ml (P less 0.01) but levels of GIP, insulin, glucagon and glucose were unaltered. Intravenous injection of somatostatin (0.5 microgram/kg) suppressed the antral electromyographic recording and gastri efflux so long as plasma somatostatin levels remained above approx. 200pg/ml. This suggest that somatostatin can be released by intraduodenal acidification and that it inhibits gastric function by an endocrine effect. Since somatostatin retards gastric emptying it may therefore have an indirect role in nutrient homeostasis by limiting discharge of gastric chyme to the duodenum.

Animals↗
PubMed1981

Blood glucose and insulin levels in normal subjects following a meal with and without added sugar beet pulp.

The fibrous components of sugar beet pulp were investigated to determine whether they would reduce the post-prandial rise in blood glucose and plasma insulin levels when incorporated into a mixed meal. On two separate occasions six healthy volunteers were given either a control meal (providing 86 g carbohydrate) or an identical meal with the addition of 20 g sugar beet pulp (test meal). Blood glucose and plasma insulin levels were measured post-prandially for 3 hours. There was no significant difference between the mean blood glucose of plasma insulin curves at any time after the two meals. Since viscous types of dietary fibers are known to be effective in reducing post-prandial hyperglycaemia and insulinaemia, it would seem that either the physio-chemical nature of the fibre or the procedure employed to extract the sugar renders the particulate fibre inactive.

Adolescent↗
PubMed1980

Serious renal transplant rejection and adrenal hypofunction after gradual withdrawal of prednisolone two years after transplantation.

Ten patients with stable renal function two years after transplantation had their sole immunosuppressive treatment (oral prednisolone 10 mg daily) withdrawn by reducing the daily dose by 1 mg at monthly intervals. Plasma prednisolone concentration, cortisol concentration, creatinine clearance, and serum creatinine concentration were measured in all patients, and the adrenal response to corticotrophin was determined in five by measuring plasma cortisol concentrations before and after tetracosactrin injection. No episodes of rejection occurred in patients taking over 7 mg prednisolone daily. Although three patients apparently required only minimal immunosuppressive treatment (less than 5 mg daily) the remainder suffered episodes of rejection at daily doses below 7 mg. There was a tenuous association between rejection and low plasma cortisol concentration, but neither the pattern of plasma prednisolone concentrations nor the response to tetracosactrin were related to episodes of rejection. Reducing the daily dose of oral prednisolone to under 7 mg should not be attempted in patients with renal transplants unless there are extenuating circumstances.

Adrenal Insufficiency↗
PubMed1980

Endocrine pancreatic control of the release of gastric inhibitory polypeptide. A possible physiological role for C-peptide.

Intravenous infusion in anaesthetized rats of rat II C-peptide at a dose which produced circulating levels of 22.8 +/- 1.8 nmol/l after 30 min, resulted in a significant reduction (141 +/- 7 to 50 +/- 4 pmol/l, p < 0.001, mean +/- SEM) in the immunoreactive gastric inhibitory polypeptide response to an intestinal perfusion with a fat emulsion. Immunoreactive insulin levels were unchanged from basal in this study. It is suggested that C-peptide must be considered as a candidate for the endocrine pancreatic factor which exerts a negative feedback upon gastric inhibitory polypeptide release.

Animals↗
PubMed1980

A radioimmunoassay for methotrexate adapted to the Centria System 2.

An automated radioimmunoassay for methotrexate using an iodinated tracer has been applied to the centrifugal analyser, Centria System 2. Results obtained for serum samples correlated closely with those using a manual radioimmunoassay method. A major advantage of the assay is its potential for processing large numbers of samples rapidly, making it highly suitable for routine clinical use.

Animals↗
PubMed1980

Pancreatic somatostatinoma presenting with hypoglycaemia.

A 33-year-old woman with a 2 month history of vague ill health was admitted to hospital in hypoglycaemic coma. Preoperative investigation suggested malignant insulinoma as the probable cause of illness, but immunohistological examination of the tumour showed it to consist mainly of somatostatin-containing cells but sparse insulin-secreting cells were also present. Plasma immunoreactive somatostatin levels were from fifty to 200 times the upper limit of normal and rose in response to arginine and fell during diazoxide infusion. The hypoglycaemia was unusually sensitive to the hyperglycaemic effects of diazoxide and chlorothiazide and, with 5-fluorouracil as the only specific anti-tumour agent, there has been clinical, biochemical and radiological evidence of tumour regression.

Adenocarcinoma↗