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Biomedical subjects

V Marks

Publications and source records attributed to V Marks.

At least 163 records · Page 9Linked to original sources
PubMed1985

The role of immunoassay in the analysis of microcontaminants in water samples.

Concentrations of natural and synthetic steroids and an anticancer drug (methotrexate) have been determined in water by adapting established immunoassay procedures. The limits of detection for the assays used were 10 ng/liter for norethisterone, 5 ng/liter for ethinyl estradiol and progesterone, and 6.25 ng/liter for methotrexate. Results below the level of detection were obtained in all the samples examined (8 river samples and 6 potable supply samples) except for 2 river samples (17 ng/liter) for norethisterone, and 1 river sample and 1 potable water sample for progesterone (6 ng/liter). A concentration of 1 microgram/liter of methotrexate was found in a sample of hospital effluent. There appears to be no evidence of adverse effects from reused water resources which may be contaminated from the normal use of such highly active therapeutic agents.

Ethinyl Estradiol↗
PubMed1985

Gut microflora interactions with xylitol in the mouse, rat and man.

The influence of dietary xylitol on the quantity and quality of faecal microflora was studied in Wistar albino rats, CD-1 mice and healthy human volunteers. In animals, the effects of xylitol adaptation and of 4-wk xylitol feeding were examined. No major changes in the numbers of total aerobic or anaerobic bacteria, aerobic streptococci, anaerobic streptococci or yeasts were observed, although there was evidence of a dose-dependent decrease in the numbers of aerobic streptococci in the faeces. However, xylitol feeding caused a clear shift in the rodent faecal microbial population from Gram-negative to Gram-positive bacteria. In human volunteers a similar shift was observed even after a single 30-g oral dose of xylitol. All animals were capable of adapting to 20% dietary xylitol and an accompanying enhancement of the ability of caecal and faecal flora to utilize xylitol was observed.

Adult↗
PubMed1985

How our food affects our hormones.

Food can affect the production and secretion of hormones by direct actions on the gut, by nervous reflexes, through changes in the concentration of various metabolites in the blood, or secondary to changes in circulating gut hormone levels. Not only is the composition of the diet important but also its texture, quantity and duration. GIP and insulin are used as examples of hormones whose production and secretion are diet-dependent. Their possible involvement in the pathogenesis of obesity and non-insulin-dependent (type II) diabetes is discussed.

Diabetes Mellitus↗
PubMed1985

Chronopharmacology.

The time of day that drugs are given can have a profound effect upon both their pharmacodynamics, i.e. their effectiveness and toxicity, and their pharmacokinetics, i.e. the way they themselves behave in the body. The chronopharmacokinetics of relatively few drugs have been investigated and are mostly those used for the treatment of cancer. We have shown that the toxicity and chronopharmacokinetics of drugs can be altered by pretreatment with steroids or melatonin.

Adrenal Cortex Hormones↗
PubMed1985

The effect of guar gum on carbohydrate-, fat- and protein-stimulated gut hormone secretion: modification of postprandial gastric inhibitory polypeptide and gastrin responses.

The effect of incorporating guar gum into predominantly single-component meals of carbohydrate, fat or protein on liquid gastric emptying and on the secretion of gastric inhibitory polypeptide (GIP), gastrin and motilin, was studied in healthy human volunteers. Volunteers were given either 80 ml Hycal (carbohydrate meal), 150 g cooked lean minced beef (protein meal) or 200 ml double cream (fat meal) either with or without 5 or 6 g guar gum. Liquid gastric emptying was monitored in the fat and protein meals by taking 1.5 g paracetamol, consumed in water, with the meals and monitoring its appearance in circulation. Postprandial insulin and GIP levels were both significantly reduced by addition of guar gum to the carbohydrate meal. Postprandial GIP secretion was also reduced by addition of guar gum to the protein meal, but protein-stimulated gastrin secretion was enhanced by guar gum. There was a significant negative correlation between peak circulating gastrin levels and the corresponding GIP levels. Postprandial GIP secretion and plasma motilin levels were unaffected by addition of guar gum to the fat meal. 5 and 10 g guar gum/l solutions in water possessed buffering capacities between pH 2.75 and 5.5. Guar gum at 5 g/l caused no detectable change in liquid gastric-emptying time. The observed augmentation of gastrin secretion by guar gum following a protein meal could be due either to the buffering capacity of guar gum or to the attenuation of GIP secretion. It is possible that the chronic use of guar gum could be associated with changes in gastric acid secretion.

Adult↗
PubMed1985

Measurement of potato steroidal alkaloids in human serum and saliva by radioimmunoassay.

Radioimmunoassay methods are described for measuring potentially toxic potato glycoalkaloids and the aglycone solanidine in human serum and saliva. Solanidine and total alkaloid concentrations in serum and saliva during the summer are given for a group of subjects from the UK and a group from Sweden. Serum concentrations ranged from 3.2 to greater than 125 nmol/l for total alkaloid and 2.5 to 92.5 nmol/l for solanidine and were comparable in the two populations. Salivary total alkaloid concentrations were only about 10% of serum values. Salivary solanidine concentrations did not exceed 20% of the serum levels. Good correlation was found between serum and salivary alkaloid concentrations (r = 0.734, for solanidine; r = 0.892 for total alkaloid). Serum and salivary alkaloid concentrations were significantly raised in a group of Swedish subjects eating potatoes containing unusually high concentrations of alkaloids when compared with those in a group of subjects eating their normal diets.

Adult↗
PubMed1985

Immunoassay of 6-hydroxymelatonin sulfate in human plasma and urine: abolition of the urinary 24-hour rhythm with atenolol.

An assessment of the rhythmic characteristics of melatonin secretion in man and other species requires the determination of 24-h secretion profiles. Measurement of a major excreted metabolite would allow noninvasive study of pineal function, applicable in particular to pediatric and long term circadian rhythm studies. This report describes a simple and rapid RIA for 6-hydroxymelatonin sulfate in human plasma and urine. Physiological studies revealed that both plasma and urinary levels of 6-hydroxymelatonin sulfate were closely related to plasma melatonin, and that the urinary 24-h rhythm was abolished by the beta 1-adrenergic anagonist atenolol.

Animals↗
PubMed1985

Tissue disposition and excretion of gold and 14C in rats treated with sodium aurothio[1,4-14C]malate or thio [1,4-14C] malic acid.

In rats injected intramuscularly with sodium aurothio[1,4-14C]malate, 80% of the 14C was excreted in the urine, mostly in 24 h, 2% in the faeces and 10% as 14CO2 in the expired air during the first six hours with none thereafter. Urinary and faecal gold represented 5% and 2.5% of the dose, respectively. In rats given thio[1,4-14C]malic acid, 50% of the 14C was excreted in the urine, 10% in the expired air as 14CO2 and 2% in the faeces. Radioactivity was found in all tissues with distribution similar for the two compounds, the major sites of accumulation being bone, kidney and liver. Significantly higher amounts of 14C were found in the 14C-aurothiomalate-dosed animals, notably in bone and kidney. Gold was located principally in kidney, liver, lung and spleen with smaller amounts elsewhere. At least seven radioactive metabolites (including sodium aurothiomalate and thiomalic acid) were present in the urine of rats given 14C-aurothiomalate. Urine from 14C-thiomalic acid-treated rats contained at least five radiolabelled compounds, one of which was thiomalic acid. Results show that most of the gold was removed from the thiomalate moiety, however, the 14C distribution and the radioactive metabolites in urine demonstrated that some intact aurothiomalate remains.

Animals↗
PubMed1985

Production and growth of hybridomas secreting monoclonal antibodies to human thyroid stimulating hormone.

Female Balb/c mice were immunized with human thyroid stimulating hormone (hTSH). The spleen cells of responding mice were used in a cell fusion with NS1 mouse myeloma cells to define 27 stable anti-hTSH hybridomas. The antibody-secreting cell lines, designated SY/T8/1-6, were characterized and three were found to be completely specific for h-TSH while the other three showed some cross reactivity with LH and hCG. Six of the monoclonal antibodies have been well characterized and their parent hybridomas isolated and banked at -196 degrees C for future studies. The hybridomas have been raised from liquid nitrogen and recultured in RPMI 1640 medium. Progress is being made in the investigation of the growth characteristics of these hybridoma cell lines.

Animals↗
PubMed1985

The effects of econazole on the growth of murine myeloma cells and its use in hybridoma production.

The effect of econazole, an antifungal agent, on the stability of NS1/Ag4 myeloma cells in culture was investigated with the view to its use in the control of fungal contamination in lymphocyte hybridoma monoclonal antibody production. The recommended dose of 1 microgram/ml was found to reduce cell numbers, viability and survival, and to effect dramatic dose related changes in DNA synthesis in the NS1 myeloma line and hence econazole is not suitable as an added antifungal agent in monoclonal antibody production using NS1 cells and their derived hybridomas.

Animals↗
PubMed1984

The differential effect of intragastric and intravenous tryptophan on plasma glucose, insulin, glucagon, GLI and GIP in the fasted rat.

L-tryptophan was given to fasted rats intragastrically or intravenously at a dose of 500 of 166 mg/kg b.w., respectively. Mean (+/- SEM) plasma insulin levels rose after both stimuli and at 10, 30 and 45 min were 63 +/- 26, 86 +/- 25, 48 +/- 7 mU/l after oral, and 28 +/- 4, 25 +/- 6, 19 +/- 6 mU/l after intravenous administration, respectively; plasma tryptophan levels at the above intervals during the oral study were 27%, 60% and 128%, respectively of those during the intravenous study. Plasma GIP levels rose only after intragastric tryptophan administration, and plasma GLI levels did not change in response to either intragastric or intravenous tryptophan. Intragastric tryptophan consistently raised plasma pancreatic glucagon levels which were significantly higher than those observed in control rats given saline, 5, 10, 30 and 45 min after administration. The rise in plasma glucagon was attributed to the glucagonotropic effect of GIP.

Administration, Oral↗
PubMed1984

Passive inhalation of cannabis smoke.

Six volunteers each smoked simultaneously, in a small unventilated room (volume 27 950 litre), a cannabis cigarette containing 17.1 mg delta 9-tetrahydrocannabinol (THC). A further four subjects - passive inhalers - remained in the room during smoking and afterwards for a total of 3 h. Blood and urine samples were taken from all ten subjects and analysed by radioimmunoassay for THC metabolites. The blood samples from the passive subjects taken up to 3 h after the start of exposure to cannabis smoke showed a complete absence of cannabinoids. In contrast, their urine samples taken up to 6 h after exposure showed significant concentrations of cannabinoid metabolites (less than or equal to 6.8 ng ml-1). These data, taken with the results of other workers, show passive inhalation of cannabis smoke to be possible. These results have important implications for forensic toxicologists who are frequently called upon to interpret cannabinoid levels in body fluids.

Adult↗
PubMed1984

Serum levels and response to amitriptyline in depressed out-patients.

Serum levels of amitriptyline plus nortriptyline were measured by radioimmunoassay at 1 and 6 weeks in depressed out-patients treated with amitriptyline for 6 weeks. Serum concentrations at 6 weeks were higher in older patients. Serum levels showed no relationship to clinical response at 6 weeks, and a week inverse relationship with response at 2 weeks. Routine monitoring of serum levels appears to be of little value in depressed out-patients treated with amitriptyline.

Adult↗