Abnormalities of GIP in spontaneous syndromes of obesity and diabetes in mice

The role of GIP in the pathogenesis of spontaneous syndromes of obesity-diabetes was examined in ob/ob mice of the Aston stock and db/db mice of the C57BL/KsJ background. Compared with lean controls, fed adult ob/ob and db/db mice, respectively, exhibited 1.8-fold and 2.1-fold increases in body weight, 1.8-fold and 2.8-fold elevations of plasma glucose, and 15.4-fold and 5.6-fold elevations of plasma insulin. As indicated by the relative magnitude of the hyperglycemia and hyperinsulinemia, db/db mice displayed a particularly severe form of diabetes. Plasma GIP concentrations of ob/ob and db/db mice were elevated 15.1-fold and 6.2-fold, respectively; the increments closely corresponded with the degrees of hyperinsulinemia. Small intestinal weight was increased 1.4-fold and 1.8-fold in ob/ob and db/db mice, respectively, but the intestinal GIP content expressed as microgram/g intestine or microgram/intestine was raised only in ob/ob mice (1.9-fold and 2.8-fold, respectively). Since glucose stimulation of insulin release is defective in both mutant strains, the results strongly implicate pathologically raised GIP concentrations in the hyperinsulinemia and related metabolic abnormalities of the obesity-diabetes syndromes. It is suggested that hypersecretion of GIP results in part from loss of normal feedback inhibition by endogenous insulin.

Effect of pretreatment with a high fat diet on the gastric inhibitory polypeptide and insulin responses to oral triolein and glucose in rats

Male Wistar rats were pretreated with 3 ml triolein orally for 4 days in addition to their normal diet. A similar control group were allowed free access to normal laboratory food. When given an oral fat load (1 ml triolein) plasma gastric inhibitory polypeptide (GIP) and triglyceride levels were significantly higher in the fat pretreated group. Inhibition of fat-stimulated GIP release by exogenous insulin was demonstrated in the untreated control group (plasma GIP: 663 +/- 49 versus 853 +/- 92 ng/l, mean +/- SEM p less than 0.025), but pretreatment with an oral fat load abolished this effect (plasma GIP: 1008 +/- 95 versus 1116 +/- 100 ng/l, p NS). Plasma glucose levels were significantly higher in fat pretreated rats given oral fat and intraperitoneal insulin compared with untreated controls (plasma glucose nadir 2.6 +/- 0.48 versus 1.6 +/- 0.15 mmol/l, p less than 0.05). Fat-pretreated rats showed significantly higher insulin and glucose levels compared with the untreated rats when given oral glucose (plasma insulin: 6.2 +/- 1.2 versus 2.5 +/- 0.59 micrograms/l, p less than 0.01; plasma glucose: 10.2 +/- 0.39 versus 8.9 +/- 0.41 mmol/l, p less than 0.025). Pretreatment of rats on a high fat diet causes (1) increased GIP secretion in response to an oral fat load, (2) abolition of the feed-back inhibition of exogenous insulin on fat-stimulated GIP release, and (3) some degree of insulin resistance.

Clinical pathology of alcohol

There is good though not conclusive evidence that a small to modest average daily intake of alcohol--that is, 20-30 g/day is associated with increased longevity due mainly to a reduction in death from cardiovascular disease. Larger average daily alcohol intakes--especially those in excess of 60 g/day for men and 40 g/day for women--are associated with gradually increasing morbidity and mortality rates from a variety of diseases. Alcohol may be unrecognised as the cause of somatic disease, which can occur without overt psychosocial evidence of alcohol abuse, unless the index of suspicion is high and a thorough drink history obtained. Laboratory tests for the detection and/or confirmation of alcohol abuse are useful but subject to serious limitations being neither as sensitive nor specific as sometimes believed. The value of random blood and/or breath alcohol measurements, in outpatients, as an aid to diagnosis of alcohol-induced organic disease is probably not sufficiently appreciated and, though relatively insensitive, is highly specific.

Plasma prednisolone studies in rheumatic patients

Prednisolone concentration in plasma after a daily maintenance steroid dose was monitored in 83 patients with rheumatic diseases. Although no restrictions were imposed on the intake of food or drink, plasma drug levels tended to peak at 1 h after the ingestion of the standard tablets, whereas intestinal absorption of the enteric-coated preparation was found to be most unpredictable. A profound individual variation was observed in plasma prednisolone concentrations, and neither total nor unbound drug levels showed any consistent relationship with the size of the prednisolone dose or the control of the disease activity. The basal cortisol production was suppressed in one-third of the patients. There is no support from this study for the concept of an 'optimum therapeutic range' of plasma prednisolone for the treatment of rheumatic disease.

Diurnal variation in prednisolone kinetics

Plasma concentrations of free and total prednisolone were measured after oral doses at four time points to investigate the possibility of a diurnal variation in the drug's kinetics. There were marked differences in plasma prednisolone concentrations, clearance rates, and bioavailability of both free and total fractions at different times of the day. Changes in the protein binding characteristics of prednisolone with clock time resulted in marked differences between the kinetics of free and total prednisolone. It is recommended that for maximum efficacy and minimum toxicity prednisolone therapy be confined to once-daily dosing in the morning.

A bioequivalence study of three preparations of propranolol

The bioequivalence of two different tablets and a solution, each containing 10 mg propranolol hydrochloride was studied in twelve healthy volunteers. Single oral doses of each preparation were administered at intervals of one week. Samples of blood for propranolol radioimmunoassay were taken up to 8 h after dosing. The plasma propranolol concentration at 0.5 h was significantly higher for the solution than for the two tablet formulations which did not differ significantly from each other at any sampling point. The area under the curve was similar for all three preparations. The study demonstrated that the three different preparations of propranolol were bioequivalent.

Plasma prednisolone levels during intravenous therapy in acute colitis

Maximum plasma levels in six acute colitics were about three times greater after an intravenous bolus of 20 mg prednisolone than the mean level achieved during infusion of the same dose (p<0.001) over eight hours; the level during infusion was about twice as great as the maximum recorded previously after a single 40 mg oral dose of prednisolone. These findings favour the use of intravenous administration in severe acute colitis. No difference was found between plasma levels of patients and six normal subjects after the intravenous bolus.

A sensitive radioimmunoassay for budesonide in plasma

Budesonide is a highly potent non-halogenated glucocorticoid with local anti-inflammatory properties. A sensitive radioimmunoassay for the measurement of the drug in unextracted plasma has been developed. Budesonide 21-hemisuccinate and budesonide 3-(O-carboxymethyl)oxime were conjugated to ovalbumin using the mixed anhydride method and antibodies to the haptens produced in sheep. The specificity of the antisera towards cortisol, and possible budesonide metabolites reflected the different sites of the attachment of the haptens to the carrier protein. An antiserum raised against the 3-(O-carboxy methyl)oxime conjugate was more specific (0.001% cross reaction) with respect to cortisol than the antiserum raised against the 21-hemisuccinate conjugate (0.344% cross reaction). Endogenous steroids at concentrations normally encountered in clinical samples, would not interfere with the measurement of budesonide. The radioimmunoassay was developed using the budesonide 3-(O-carboxy methyl)oxime antiserum, [3H]-budesonide and dextran coated charcoal phase separation. The theoretical limit of detection of the assay was 50 pg/ml. Budesonide was quantitatively recovered from normal human drug/free plasma at concentrations above 1 ng/ml (2.32 nmol/l) with a between batch variation of 12-15%. Budesonide was measured in the unextracted plasma of volunteers who had inhaled the drug from a pressurised aerosol spray.

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.

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.

The effects of xylitol on the secretion of insulin and gastric inhibitory polypeptide in man and rats

Xylitol given by gavage to unadapted rats produced profound diarrhoea and no rise in plasma gastric inhibitory polypeptide (GIP) concentration. In xylitol adapted rats it did not cause diarrhoea but still had no effect upon GIP release in contrast to glucose, which did. In healthy human subjects xylitol taken by mouth in solution as a single 30 g dose produced only a minimal rise in blood glucose and no rise in plasma GIP or insulin concentration. Glucose in similar doses, on the other hand, caused a large rise in all three.

Development and application of a radioimmunoassay for pepleomycin

A rapid sensitive radioimmunoassay for pepleomycin (PM) has been developed using an antiserum produced in a sheep in response to a bovine serum albumin-drug conjugate. Radioiodinated PM was prepared using Iodogen. The assay was reproducible with a limit of detection in plasma of 200 ng/liter. The antiserum does not cross-react with bleomycin or with a number of unrelated drugs. Pharmacokinetic studies using the assay were carried out in three patients who received a short iv infusion of 5 mg/m2 of PM. The drug disappeared from the plasma with an elimination half-life of approximately 3 hours.

Human endocrine responses to acceleration stress

Five healthy male volunteers were subjected to accelerations of up to +6 Gz for 1 min in order to investigate the effect of acceleration stress upon the concentration of various hormones in peripheral blood. No significant changes were seen in the levels of GH, PRL, TSH, LH, and FSH compared to control values obtained at +1 Gz (normal gravity). Changes in serum cortisol levels were significant (p less than 0.001) with peak values occurring 20 min after acceleration stress. A significant effect (p less than 0.001) of acceleration was also observed on plasma volume with maximum reductions occurring at the end of acceleration. The unusual specificity of the hormone responses is discussed.

A radioimmunoassay for VP16-213 in plasma

A radioimmunoassay for the semi-synthetic podophyllotoxin VP16-213 has been developed which is suitable for pharmacokinetic studies of the drug. A high titre antiserum was produced in a sheep in response to a VP16-213-BSA conjugate prepared using sodium periodate. Podophyllotoxin does not cross-react with the antiserum and VM26 cross-reacts to only a small extent (less than 0.6%). In the absence of a high specific activity tritium label, a radioiodinated histamine ligand was produced which was only partially displaced from antibody by native drug. VP16-213 can be measured in plasma without prior drug extraction with a theoretical limit of detection of 5-10 micrograms/l. VP16-213 cis (picro) hydroxy acid is recognised by the antiserum to a greater extent than the drug itself. Thus, in order to eliminate any interference from the trans hydroxy acid metabolite chloroform extraction of plasma samples was carried out.

Determination of total bile acids in serum. A comparison of a radioimmunoassay with an enzymatic-fluorimetric method

A solid phase radioimmunoassay kit method for total conjugated bile acids has been compared to an enzymatic fluorimetric method for total serum bile acids. The methods were compared with respect to: precision, cross-reactivity (molar equivalence) of different bile salts, recovery of different bile salts from serum, the reference range for a healthy population, linearity, coefficient of correlation, diagnostic effectiveness, cost and ease of assay. Both assays seemed equally capable of predicting the presence or absence of liver disease. Radioimmunoassay had little advantage over the enzymatic-fluorimetric method. Its relative ease was far outweighed by its greater cost and poorer analytical performance.

The preparation of thyroid microsomal antigen for use in the indirect micro-ELISA method for the detection of anti-thyroid microsomal autoantibody

Thyroid microsomes for use in assay systems for anti-thyroid-microsomal antibodies are normally prepared by ultracentrifugation. By means of gel filtration studies we show that preparations made in this way are invariably contaminated with thyroglobulin. A further purification by gel filtration is described which enables the preparation of thyroid microsomes of sufficient purity for use in a micro-ELISA method for the measurement of anti-thyroid-microsomal antibodies. Microsomes prepared in this way would also be suitable for haemagglutination and radioassays, which are also affected by thyroglobulin contamination.

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.