Effect of glibenclamide on insulin release at moderate and high blood glucose levels in normal man

Insulin release occurs in two phases; sulphonylurea derivatives may have different potencies in stimulating first- and second-phase insulin release. We studied the effect of glibenclamide on insulin secretion at submaximally and maximally stimulating blood glucose levels with a primed hyperglycaemic glucose clamp. Twelve healthy male subjects, age (mean +/- SEM) 22.5 +/- 0.5 years, body mass index (BMI) 21.7 +/- 0.6 kgm-2, were studied in a randomized, double-blind study design. Glibenclamide 10 mg or placebo was taken before a 4-h hyperglycaemic clamp (blood glucose 8 mmol L-1 during the first 2 h and 32 mmol L-1 during the next 2 h). During hyperglycaemic clamp at 8 mmol L-1, the areas under the delta insulin curve (AUC delta insulin, mean +/- SEM) from 0 to 10 min (first phase) were not different: 1007 +/- 235 vs. 1059 +/- 261 pmol L-1 x 10 min (with and without glibenclamide, P = 0.81). However, glibenclamide led to a significantly larger increase in AUC delta insulin from 30 to 120 min (second phase): 16087 +/- 4489 vs. 7107 +/- 1533 pmol L-1 x 90 min (with and without glibenclamide respectively, P < 0.03). The same was true for AUC delta C-peptide no difference from 0 to 10 min but a significantly higher AUC delta C-peptide from 30 to 120 min on the glibenclamide day (P < 0.01). The M/I ratio (mean glucose infusion rate divided by mean plasma insulin concentration) from 60 to 120 min, a measure of insulin sensitivity, did not change: 0.26 +/- 0.05 vs. 0.22 +/- 0.03 mumol kg-1 min-1 pmol L-1 (with and without glibenclamide, P = 0.64). During hyperglycaemic clamp at 32 mmol L-1, the AUC delta insulin from 120 to 130 min (first phase) was not different on both study days: 2411 +/- 640 vs. 3193 +/- 866 pmol L-1 x 10 min (with and without glibenclamide, P = 0.29). AUC delta insulin from 150 to 240 min (second phase) also showed no difference: 59623 +/- 8735 vs. 77389 +/- 15161 pmol L-1 x 90 min (with and without glibenclamide, P = 0.24). AUC delta C-peptide from 120 to 130 min and from 150 to 240 min were slightly lower on the glibenclamide study day (both P < 0.04). The M/I ratio from 180 to 240 min did not change: 0.24 +/- 0.04 vs. 0.30 +/- 0.07 mumol kg-1 min-1 pmol L-1 (with and without glibenclamide, P = 0.25). In conclusion, glibenclamide increases second-phase insulin secretion only at a submaximally stimulating blood glucose level without enhancement of first-phase insulin release and has no additive effect on insulin secretion at maximally stimulating blood glucose levels. Glibenclamide did not change insulin sensitivity in this acute experiment.     

Water balance in elderly people: is there a deficiency of vasopressin?

Since elderly people are prone to develop both hypo- and hyper-natraemia, we have investigated the biochemical and hormonal responses to overnight (9 h) abstinence from fluids and subsequent oral water load (20 ml/kg) in a group of healthy elderly (E) (mean age 68 years) and young (Y) (mean age 28 years) volunteers. The elderly subjects had significantly higher baseline plasma osmolality (E 293.5 +/- 0.5, Y 290.5 +/- 0.8 mOsm/kg, p < 0.05) but lower urinary osmolality (E 508 +/- 47, Y 842 +/- 52 mOsm/kg, p < 0.001) and lower plasma vasopressin (E 0.5 +/- 0.1, Y 2.3 +/- 0.6 pmol/l, p < 0.001) than the young. There was a significant difference in the mode of excretion, particularly maximum free water clearance (E 6.0 +/- 0.6, Y 10.1 +/- 0.8 ml/min) but no difference in the overall ability to excrete the water load (at 4 h E 93 +/- 8%, Y 92 +/- 5%, p > 0.05). The biochemical and hormonal results suggest that the elderly subjects were in a state similar to partial cranial diabetes insipidus which may predispose them to dehydration and hypernatraemia. The reduction in maximum free water clearance may predispose them to hyponatraemia if excess fluid is administered.     

Pharmacological doses of vitamin E and insulin action in elderly subjects

Twenty elderly (77 +/- 0.4 y), nonobese [body mass index (in kg/m2) 26.4 +/- 0.5] subjects with normal glucose tolerance were submitted to a euglycemic hyperinsulinemic (3.5 pmol.min/kg) glucose clamp in a double-blind, crossover, randomized procedure after 4 mo treatment with either vitamin E (900 mg d-alpha-tocopherol/d, Ephynal; Roche, Milan, Italy) or placebo. Body mass index was practically unchanged throughout the study. After the glucose clamp, insulin-mediated stimulation 2 of whole-body glucose disposal (18.4 +/- 0.5 vs 26.1 +/- 0.6 mumol.min/kg lean body mass P < 0.02) was significantly potentiated by vitamin E rather than placebo administration. Furthermore, net changes in plasma vitamin E concentrations correlated with net changes in insulin-stimulated whole-body glucose disposal (r = 0.60 P < 0.003). Plasma vitamin E concentrations seem to play an important role in the modulation of insulin action in elderly people.     

Radioimmunoassay of cholecystokinin in human plasma

A sensitive radioimmunoassay for cholecystokinin (CCK) has been developed. Porcine CCK-33 was labelled by conjugation with 125I-hydroxyphenyl-propionic acid succinimide ester. Antibodies were raised against porcine CCK-33 covalently coupled to egg albumin. Plasma samples were extracted with 96% ethanol prior to assay. Free and bound hormone were separated by dextran-coated charcoal. The antibodies bound CCK-8 and CCK-33 with equimolar potency. The assay detection limit was 1 pmol/l plasma. Within and between assay coefficients of variation were +/- 12.7 and 13.0% at mean plasma CCK concentrations of 13.2 and 13.6 pmol/l. The concentration of CCK in 47 normal fasting subjects ranged from undetectable to 22 pmol/l. Ingestion of a mixed meal in 9 normal subjects increased the plasma concentration from 8.3 +/- 2.5 S.E. to 24.4 +/- 6.5 pmol/l.     

Evaluation of the structures of agreement and disagreement in reliability studies

AIMS: To investigate, in healthy volunteers, the relationships between the plasma concentrations (C, ng ml(-1)) of zabiciprilat, the active metabolite of the angiotensin I-converting enzyme inhibitor (ACEI) zabicipril, and the effects (E) induced on plasma converting enzyme activity (PCEA, nmol ml(-1) min(-1)), brachial and femoral artery flows (BAF, FAF, ml min(-1)), and brachial and femoral vascular resistances (BVR, FVR, mmHg x s ml(-1)) after a single oral administration of two doses (0.5 and 2.5 mg) of zabicipril. METHODS: The study was placebo-controlled, randomized, double-blind and crossover. E was related to C by the Hill model, E = Emax x Cgamma/(CE50gamma + Cgamma), fitted to the data of both doses simultaneously. RESULTS: We obtained (mean +/- s.d.) Emax = -99 +/- 1%, CE50 = 2.2 +/- 1.0 ng ml(-1) and gamma = 1.0 +/- 0.4 for PCEA, Emax = 55 +/- 26 ml min(-1), CE50 = 5.1 +/- 4.0 ng ml(-1) and gamma = 2.4 +/- 1.6 for BAF, and Emax = -45 +/- 10%, CE50 = 2.0 +/- 1.3 ng ml(-1) and gamma = 2.3 +/- 1.4 for BVR. The parameters obtained for FAF and FVR were similar to those obtained for BAF and BVR, respectively. The CE95 (C required to induce 95% of Emax) varies from 7 to 17 ng ml(-1) for haemodynamic effects. CONCLUSIONS: As zabiciprilat peak plasma concentrations average 20 ng ml(-1) after the 2.5 mg dose of zabicipril, this dose of the drug should be sufficient to induce optimal haemodynamic effects.     

The generation of fibrinopeptide A in clinical blood samples: evidence for thrombin activity

Plasma fibrinopeptide A (FPA) concentrations were measured in clinical blood samples incubated in the collecting syringe for different time periods before addition to heparin and Trasylol, and the rate of in vitro generation of FPA was calculated as the mean increment in FPA concentration per minute over the linear portion of the generation curve. 36 normal individuals had a mean plasma FPA level of 0.64 +/- 0.56 pmol/ml and an FPA generation rate of less than 0.5 pmol/ml per min. Clinical samples with elevated plasma FPA levels manifested slow (less than 1 pmol/ml per min) (28 patients) or rapid FPA generation (greater than 1 pmol/ml per min) (33 patients). Slow FPA generation was found in 10/10 patients with venous thrombosis, in 4/4 with aortic aneurysm, and in several patients with acquired hypofibrinogenemia. In one such patient, addition of fibrinogen resulted in rapid FPA generation whereas thrombin addition was without effect. Rapid FPA generation was generally linear, was usually associated with slower fibrinopeptide B generation and was inhibited by parenteral or in vitro heparin. It is thought to reflect increased thrombin activity and was seen in patients with pulmonary embolism, active systemic lupus erythematosus, renal transplant rejection, and after infusion of prothrombin concentrates. The initial rate of FPA cleavage by thrombin at fibrinogen concentrations from 0.05 to 4 mg/ml showed little change between 2 and 4 mg/ml with a Km of 2.99 muM. At a fibrinogen concentration of 2.5 mg/ml the FPA cleavage rate was 49.2 +/- 1.6 nmol/ml per min per U of thrombin. Exogenous thrombin added to normal blood generated 21.7 nmol/ml per U of thrombin FPA in the first minute with a nonlinear pattern reflecting inactivation of thrombin and the presence of alternative substrates. Hence, the thrombin concentration in the blood cannot be calculated from the FPA generation rate. The FPA generation rates in clinical samples with rapid generation (1-28 pmol/ml per min) could be produced by 2 X 10(-5) to 5.6 X 10(-4) thrombin U/ml acting on purified fibrinogen at physiological conditions of pH, ionic strength, and temperature.     

Coordinate activation of the corticotropic axis by insulin-induced hypoglycemia: simultaneous estimates of beta-endorphin, adrenocorticotropin and cortisol secretion and disappearance in normal men

In the present study, we investigated the coordinate kinetic response of the corticotropic axis to the acute metabolic stress of hypoglycemia by applying deconvolution analysis to adrenocorticotropin (ACTH), beta-endorphin and cortisol concentration-time series generated in seven normal men after intravenous administration of insulin. Hypoglycemic stress resulted in a 22-fold increase in the mean plasma concentration of ACTH to a maximum of 77 +/- 15 pmol/l, in conjunction with a 7.5-fold increase in the mean plasma beta-endorphin concentration, the maximal value of which was 96 +/- 11 pmol/l. Plasma cortisol concentrations increased by 2.6-fold with a mean value of 734 +/- 14 nmol/l. Maximal plasma ACTH and beta-endorphin concentrations were preceded by discrete secretory bursts with peak amplitudes of 10.5 +/- 2.7 and 10.6 +/- 2.0 pmol.l-1.min-1 (20-fold and ninefold increases compared to control), respectively. The mass of ACTH released was 114 +/- 20 pmol/l (3.4-fold increase), which corresponds to a total amount of 1.25 micrograms (50% of daily production and 0.5% of reported pituitary stores), assuming a distribution volume of 40 ml/kg. A total amount of 4.4 +/- 0.7 mg of cortisol was released after insulin-induced hypoglycemia, based on a mean cortisol secretory mass of 1088 +/- 137 nmol/l and a presumed 11.3-1 volume of distribution. Deconvolution-based estimates of the endogenous half-lives of ACTH, beta-endorphin and cortisol were 17 +/- 0.6, 22 +/- 1.7 and 65 +/- 5.3 min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Central pathology review in clinical trials for patients with malignant glioma. A Report of Radiation Therapy Oncology Group 83-02

We previously described delayed pressor response (DPR) 3 h after endothelin (ET)-1 injection in normotensive rats. In the current study, we examined effects of the ETA receptor antagonist BQ123 (0.01 mumol/kg/min intravenously, i.v.), phosphoramidon (100 mumol/kg i.v.), the neutral endopeptidase inhibitor SQ28603 (112 mumol/kg + 0.04 mumol/kg/min i.v.), the angiotensin-converting enzyme inhibitor enalaprilat (10 mumol/kg i.v.), and the thromboxane receptor antagonist, SQ29548 (0.5 mumol/kg + 0.5 mumol/kg/h i.v.) on DPR. Vehicle and ET-1 (1.0 nmol/kg i.v.) were administered on day 1; vehicle or drug and ET-1 were administered on day 2. BQ123 inhibited DPR 36% (vehicle 44 +/- 5, BQ123 28 +/- 3 mm Hg); phosphoramidon inhibited DPR 56% (vehicle 45 +/- 4, and phosphoramidon 20 +/- 5 mm Hg). DPR was unchanged after SQ28603 (vehicle 39 +/- 2 and SQ28603 44 +/- 2 mm Hg), enalaprilat (vehicle 39 +/- 2 and enalaprilat 38 +/- 7 mm Hg), or SQ29548 (vehicle 46 +/- 6 and SQ29548 43 +/- 3 mm Hg). The results suggest that DPR 3 h after ET-1 injection in rats is mediated in part through ETA receptors. DPR does not appear to involve thromboxane or synthesis of angiotensin II (AII), but may be related to synthesis of ET-1.     

Vasopressin reduces taurochenodeoxycholate-induced hepatotoxicity by lowering the hepatocyte taurochenodeoxycholate content

BACKGROUND/AIMS: Vasopressin has been reported to reduce bile flow, but its effects on bile acid secretion and bile acid-related hepatotoxicity are still unclear. We therefore investigated the influence of vasopressin on the hepatotoxicity and biliary excretion of taurochenodeoxycholic acid in primary cultured rat hepatocytes and isolated perfused rat liver models. METHODS/RESULTS: 1) Addition of vasopressin to hepatocyte cultures significantly decreased lactate dehydrogenase release as compared to cultures exposed to 1 mM taurochenodeoxycholic acid alone, and also reduced intracellular taurochenodeoxycholic acid content from 19.3 +/- 2.2 to 13.0 +/- 1.6 nmol/mg protein. After 30 min of preincubation with 1 mM taurochenodeoxycholic acid, rinsing and reculture of hepatocytes in bile acid-free medium resulted in gradual decrease in the intracellular level of the bile acid, and addition of vasopressin (10(-9) M) to the reculture medium accelerated this process. 2) Superimposition of vasopressin (330 pmol/l) for 10 min on taurochenodeoxycholic acid infusion (1.0 mumol/min: 25 mumol/l) caused a rapid increase in bile flow and biliary excretion of taurochenodeoxycholic acid (697 +/- 42 vs 584 +/- 27 nmol/10 min per g liver) from perfused rat livers, and significantly reduced lactate dehydrogenase release. 3) Superimposition of the PKC blocker H-7 (5 mumol/l) on taurochenodeoxycholic acid infusion (1.0 mumol/min: 25 mumol/l) caused a gradual increase in bile flow and biliary excretion of taurochenodeoxycholic acid. Furthermore, an additional infusion of vasopressin (100 pmol/l) for 10 min in the presence of H-7 produced a greater increase in bile flow and biliary excretion of taurochenodeoxycholic acid as compared with H-7 alone (754 +/- 71 vs. 657 +/- 26 nmol/g liver). 4) Continuous infusion of vasopressin (330 pmol/l) significantly increased the late peak (10-50 min) of horseradish peroxidase excretion from perfused livers (from 8.48 +/- 1.02 to 21.7 +/- 6.02 ng/g liver). CONCLUSIONS: These findings suggest that vasopressin exerts a protective effect against taurochenodeoxycholic acid-induced hepatotoxicity by stimulating the secretion of this bile acid via intracellular vesicular transport systems.     

Acute effects of estradiol infusion and naloxone on luteinizing hormone secretion in pubertal boys

We have shown previously in pubertal boys that testosterone (T) suppresses the nocturnal augmentation of luteinizing hormone (LH) secretion principally by decreasing LH pulse frequency. As T can be aromatised to estradiol (E2), and E2 effects on LH secretory dynamics may be separate from those of T, we examined the effects of acute E2 infusion on LH secretion in pubertal boys. Opioid receptor blockade has been reported to increase LH secretion after estradiol suppression in adult men, so we also examined whether naloxone might augment LH secretion during E2 treatment in pubertal boys. Starting at 1000 h, eight pubertal boys were given a 33 h saline infusion, followed 1 week later by an E2 infusion at 4.6 nmol/m2/h. During both infusions, four iv boluses of saline were given hourly beginning at 1200 h on the first day, and four naloxone iv boluses, 0.1 mg/kg each, were given hourly beginning at 1200 h on the second day. Blood was obtained every 15 min for LH, and every 60 min for T and E2, from 1200 h until the end of the infusion. Pituitary responsiveness to gonadotropin-releasing hormone (GnRH) was assessed after both infusions by iv administration of 250 ng/kg synthetic GnRH. Estradiol infusion increased the mean plasma E2 concentration from 23 +/- 4 to 46 +/- 6 pmol/L (P < 0.01) and suppressed mean plasma T from 4.9 +/- 1.4 to 3.0 +/- 3.5 nmol/L (saline vs. E2 infusion, P < 0.05). The overall mean LH was suppressed by E2 infusion from 3.7 +/- 0.5 to 2.2 +/- 0.4 IU/L (saline vs. E2 infusion, P < 0.01). LH pulse frequency was suppressed by 50%, whereas mean LH pulse amplitude was not different between saline and E2 infusions. Administration of naloxone did not alter the mean LH, LH pulse frequency, or amplitude during either saline or E2 infusions. Pituitary responsiveness to exogenous GnRH was similar during both infusions. These studies indicate that E2 produces its negative feedback in pubertal boys principally by suppression of LH pulse frequency, and naloxone does not reverse these suppressive effects. Thus E2 suppression of LH secretion is mediated by a decrease of hypothalamic GnRH secretion that is independent of endogenous opioid pathways.     

Enhanced coronary vasoconstriction in the Syrian myopathic hamster supports the microvascular spasm hypothesis

This study examines the relation between blood pressure and insulin resistance in obese, sedentary middle-aged and older men. Eleven hypertensive and 17 normotensive subjects of comparable age (58.6 +/- 1.0 years, mean +/- SEM), percent body fat (27.7 +/- 0.7%), and maximal aerobic capacity (30.2 +/- 0.9 mL.kg-1.min-1) participated in this study. Glucose disposal (M, milligrams per kilogram of fat-free mass per minute) determined during a three-dose hyperinsulinemic euglycemic clamp was lower in the hypertensive than normotensive subjects at the low (M at 120 pmol/m2.min: 2.3 +/- 0.2 versus 3.2 +/- 0.3, P = .06), intermediate (M at 600 pmol/m2.min: 8.0 +/- 0.6 versus 10.4 +/- 0.6, P = .02), and high (M at 3000 pmol/m2.min: 13.5 +/- 0.5 versus 15.5 +/- 0.7, P = .04) insulin infusion rates. The calculated insulin concentration necessary for a half-maximal effect (EC50) was greater in the hypertensive than normotensive subjects (1164 +/- 168 versus 864 +/- 66 pmol/L, P = .03). In this population of normotensive and hypertensive men, systolic, diastolic, and mean arterial blood pressures were related to glucose disposal at these insulin infusion rates (r = -.35 to -.46, P < .05) as well as the EC50 (r = .42 to .44, P < .05). Thus, hypertensive obese, sedentary older men have a reduction in both sensitivity and maximal responsiveness to insulin that is directly related to the severity of hypertension independent of obesity and physical fitness.     

The effectiveness of formaldehyde treatment in protecting dietary protein from rumen microbial degradation

The kinetics of digoxin have been investigated in healthy volunteers using an isotopic tracer technique. A three compartment open kinetic model has been proposed as the simplest model consistent with the plasma, urinary and faecal data obtained. The renal clearance of digoxin (mean +/- s.d.) was found to be 119+/-10 ml/min, which did not differ significantly from the glomerular filtration rate (110+/-14 ml/min). Digoxin extra-renal clearance (mean+/-s.d.) was found to be 47+/-7 ml/min. The model predicts that the tissue concentration attained after four 0.25 mg oral doses spread over 24 h can be achieved within a period of 4 h following a single oral loading dose of 1 mg. Maintenance doses can be derived from a simple formula based on the glomerular filtration rate, extra-renal clearance and bioavailability of the digoxin preparation used.     

Adipose tissue leptin production and plasma leptin kinetics in humans

Abdominal adipose tissue leptin production was determined in vivo by arteriovenous balance in 14 lean and obese men (mean BMI 27.0 +/- 1.9, range 21.4-45.2). Blood samples were taken simultaneously from an abdominal vein that drains subcutaneous adipose tissue and from a radial artery. Adipose tissue blood flow was measured by xenon washout. Abdominal vein leptin concentrations (mean 8.9 +/- 2.4 ng/ml, range 2.1-36.5 ng/ml) were consistently greater than arterial values (mean 6.6 +/- 1.9 ng/ml, range 1.7-28.2 ng/ml) (P < 0.001). The net rate of abdominal adipose tissue leptin production (mean 3.2 +/- 0.5 ng x 100 g(-1) x min(-1)) correlated directly with percentage body fat (rs = 0.59, P = 0.016). Estimated whole-body leptin production rate (797 +/- 283 ng x person(-1) x min(-1)) correlated directly with percent body fat (rs = 0.93, P < 0.0001) and with regional leptin production (rs = 0.81, P < 0.001). In contrast, the rate of leptin clearance from plasma (mean 1.50 +/- 0.23 ml x kg(-1) x min(-1)) and plasma leptin half-life (mean 24.9 +/- 4.4 min) was unrelated to adiposity (rs = 0.06, P = 0.30; rs = 0.16, P = 0.30, respectively). These results provide direct evidence that leptin is produced by adipose tissue in humans and that the rate of production is directly related to adiposity. A combination of greater leptin production per unit of body fat and increased production from expanded total body fat mass, rather than alterations in leptin clearance, account for the increase in plasma leptin concentrations observed in obese humans.     

Determination of norfloxacin in human plasma and urine by high-performance liquid chromatography and fluorescence detection

A method for the determination of norfloxacin in human plasma and urine is described. Plasma samples were deproteinized using acetonitrile. The supernatant was analysed by C18 HPLC. Fluorescence detection at an excitation wavelength of 300 nm and an emission wavelength of 450 nm was utilized. The assay was validated in the concentration range of 31 to 2507 ng/ml when 0.5-ml aliquots of plasma were handled. The intra-day precision of the spiked quality control samples ranged from +/- 0.37 to +/- 4.14% in plasma (concentration range: 70.3-2109.2 ng/ml) and from +/- 0.51 to +/- 1.56% in urine (concentration range: 7.5-299.4 micrograms/ml). The intra-day accuracy obtained for norfloxacin in the quality control samples ranged from -5.18% to -9.47% in plasma and from -10.56% to - 5.91% in urine. The assay has been used to support human pharmacokinetic studies.     

Development of a homologous radioimmunoassay for mouse growth hormone receptor

A RIA for mouse GH receptor (mGHR) was developed. A synthetic peptide corresponding to the carboxyl-terminal 14 amino acids of the mGHR (GHR-2 peptide) was used as the antigen for antiserum production. The synthetic peptide was also used as the standard and radioligand in the RIA. The ability of the antiserum to recognize the mGHR was demonstrated by quantitating receptor concentrations in liver and mammary gland from virgin and 15-day-pregnant mice. Serial dilutions of these samples yielded displacement curves parallel to the synthetic peptide. No significant cross-reactivity was seen with serum from virgin or 15-day-pregnant mice, mGH, recombinant mGH-binding protein (mGHBP), a synthetic peptide identical to the hydrophilic tail of mGHBP, or a 14-amino acid synthetic peptide corresponding to amino acids 338-351 of mGHR (GHR-1 peptide). The concentration range of the mGHR RIA was 0.5-200 nM, and the intra- and interassay coefficients of variation were 6.5% and 6.1%, respectively. The concentration of liver GHR increased significantly during pregnancy compared with that in virgin mice, from 0.246 +/- 0.045 pmol/mg protein (mean +/- SEM; n = 5) in the virgin animals to 1.015 +/- 0.159 pmol/mg protein (n = 5) in pregnant mice. In contrast, the mGHR concentration in the mammary gland decreased significantly during pregnancy from 0.606 +/- 0.201 pmol/mg protein (mean +/- SEM; n = 5) to 0.299 +/- 0.027 pmol/mg protein (n = 5). Comparison of the total number of binding sites in livers from virgin and pregnant mice using the GH RRA and the combined results of the mGHR and mGHBP RIAs showed that the two methods gave almost identical results for livers from virgin animals, or 0.363 +/- 0.063 pmol/mg protein (mean +/- SEM; n = 3) and 0.371 +/- 0.008 pmol/mg protein (n = 3) for the GH RRA and the mGHR plus mGHBP RIAs, respectively. However, in livers from pregnant animals, the combined results from the mGHR and mGHBP RIAs were approximately 1.8 times higher than those obtained by the GH RRA, or 6.732 +/- 0.612 pmol/mg protein (mean +/- SEM; n = 3) and 3.693 +/- 0.67 pmol/mg protein (n = 3) for the mGHR plus the mGHBP RIAs and the GH RRA, respectively. The increase in the total GH binding capacity in livers from pregnant mice compared with those from virgin animals was largely due to an increase in the GHBP content. The increase in GHR was only 2.4-fold, or from 0.153 +/- 0.01 pmol/mg protein (mean +/- SEM; n = 3) in virgin mice to 0.364 +/- 0.03 pmol/mg protein (n = 3) in the 15-day-pregnant mice, whereas GHBP increased almost 30-fold during pregnancy, or from 0.218 +/- 0.003 pmol/mg protein (mean +/- SEM; n = 3) in virgin animals to 6.369 +/- 0.607 pmol/mg protein (n = 3) in pregnant mice.     

Interobserver variability in recognizing arousal in respiratory sleep disorders

BACKGROUND: The study was designed to investigate the influence of haemodialysis on the pharmacokinetics of the non-ionic contrast medium iopentol and the outcome of radiocontrast nephropathy in patients at risk undergoing angiography. METHODS: We prospectively studied 30 patients with reduced renal function (mean serum creatinine concentration (+/- SEM), 2.4 +/- 0.16 mg/dl (212 +/- 14 mumol/l)). Patients were randomly assigned to receive either a haemodialysis procedure for 3 h, started as soon as possible (63 +/- 6 min) after administration of contrast medium, or a conservative treatment. Serum concentrations of iopentol and creatinine were followed for up to 14 days. RESULTS: The extracorporal plasma clearance of contrast medium was 71 +/- 2.5 ml/min. The fraction of the dose eliminated was 32 +/- 3%. The rate of radiocontrast nephropathy (defined as serum creatinine increase of > or = 0.5 mg/dl (44 mumol/l) within 48 h) after administration of contrast medium was similar in both groups (53 and 40% in group 1 (haemodialysis) and group 2 (conservative treatment) respectively). The course of absolute changes in serum creatinine over the whole observation period was not different in both groups. CONCLUSIONS: The data indicate that haemodialysis eliminates contrast medium effectively, but it may not influence the incidence or outcome of contrast induced nephropathy.     

Exogenous insulin reduces proteolysis and protein synthesis in extremely low birth weight infants

OBJECTIVE: To determine the effect of a continuous insulin infusion on protein and glucose metabolism in extremely low birth weight (ELBW) infants. STUDY DESIGN: We measured the rate of appearance (Ra) of the essential amino acids leucine and phenylalanine (reflecting proteolysis), utilization of phenylalanine for protein synthesis, and glucose Ra using stable isotope tracers during a basal infusion of glucose (6 mg/kg/min) and in response to a continuous infusion of insulin (0.05 U/kg/hr) by means of the euglycemic hyperinsulinemic clamp technique. Four clinically stable, euglycemic ELBW infants (26 +/- 0 weeks' gestation, 894 +/- 44 gm birth weight, 2.8 +/- 0.8 days of age) were studied. RESULTS: In response to a greater than tenfold increase in insulin concentration (from 7 +/- 2 to 79 +/- 13 microU/ml), there was a 20% decrease in leucine Ra (Basal: 272 +/- 27 mumol/kg/hr; Insulin: 226 +/- 29 mumol/kg/hr; p < 0.01) and in phenylalanine Ra (Basal: 91 +/- 5 mumol/kg/hr; Insulin: 72 +/- 2 mumol/kg/hr; p < 0.05). Use of phenylalanine for protein synthesis also decreased by a similar magnitude (Basal: 77 +/- 4 mumol/kg/hr; Insulin: 62 +/- 1 mumol/kg/hr; p < 0.05). Glucose utilization doubled (from 8 +/- 0.9 to 15.7 +/- 1.1 mg/kg/min; p = 0.0003) and plasma lactate concentrations tripled (from 2.1 +/- 0.5 to 5.7 +/- 1.0 mmol/L; p < 0.05) during the insulin infusion. CONCLUSIONS: During an infusion of glucose alone, pharmacologic concentrations of insulin in ELBW infants produced no net protein anabolic effect. Furthermore, euglycemic hyperinsulinemia was accompanied by development of significant metabolic acidosis.     

Rapid and sensitive determination of catecholamines and the metabolite 3-methoxy-4-hydroxyphen-ethyleneglycol using HPLC following novel extraction procedures

In the present study assays were improved for the determination of free catecholamines and 3-methoxy-4-hydroxyphenethyleneglycol (MHPG), the major metabolite of peripheral and central noradrenaline. The compounds were extracted by a fluid phase extraction: a diphenyl boric acid method for the purification of catecholamines and an ethyl acetate extraction for MHPG were used, respectively. High-performance liquid chromatography with electrochemical detection was employed for quantitative analysis. In previous studies, significant differences between plasma concentrations of these substances in normal volunteers and hospital patients were demonstrated. Therefore, we established valid reference values for a hospital population. Blood and urine samples of 59 patients without disorders and medication affecting catecholamine synthesis and metabolism or the activity of the sympatho-adrenal system were collected and analyzed for free and total (free plus conjugated) MHPG, noradrenaline (NA), adrenaline (A) and dopamine (DA); total MHPG was assayed after enzymatic hydrolysis of conjugates. Our data clearly demonstrate that these methods are sensitive, specific, rapid, and can easily be standardized. The intra- and inter-assay precision were high (CV 2.6-5.3% and 4.3-6.9% for plasma, CV 3.8-4.9% and 5.1-8.2% for urine, respectively). For plasma, the mean concentrations +/- SD were determined to be 20.82+/-4.70 pmol/ml for free MHPG, 68.43+/-16.21 pmol/ml for total MHPG, 2.11+/-0.24 pmol/ml for NA and 0.31+/-0.08 pmol/ml for A. For 24h-urine the mean concentrations +/-SD were determined to be 0.44+/-0.13 mmol/24h for free MHPG, 8.79+/-2.13 mmol/24h for total MHPG, 169.8+/-58.25 nmol/24h for NA, 62.19+/-21.79 nmol/24h for A and 757.2+/-382.6 nmol/24h for DA. In summary, these novel and rapid methods can clearly be employed in a routine clinical setting.     

Chemoprevention of head and neck cancer

The role of pituitary adenylate cyclase-activating polypeptide (PACAP) in the regulation of exocrine and endocrine pancreas was investigated in conscious sheep. Intravenous infusions of PACAP-27 and PACAP-38 (1, 3, and 10 pmol/kg/min) for 10 min during phase II of the duodenal migrating myoelectric complex accelerated pancreatic protein and amylase outputs dose-dependently. The responses in enzyme secretion to both PACAPs at the highest doses were inhibited significantly by atropine infusion (14.4 nmol/kg/min). Vasoactive intestinal polypeptide (VIP) at 3 pmol/kg/min significantly accelerated protein but not amylase outputs, although the response to the highest dose was not significantly influenced by atropine. PACAP-27 and VIP increased pancreatic juice flow and bicarbonate output dose-dependently; however, the responses to the highest dose were not altered significantly by atropine. On the other hand, intravenous injection of PACAP-38 (100 pmol/kg) did not influence basal plasma concentration of insulin, glucagon, and glucose. Moreover, PACAP-38 (1-100 pmol/kg) altered neither pancreatic endocrine response to intravenous infusion of glucose (20 mumol/kg/min) not that to n-butyric acid (33 mumol/kg/min). These results suggest that PACAP contributes to the regulation of exocrine secretion of the ovine pancreas but not to endocrine secretion. PACAP appears to accelerate pancreatic enzyme secretion mostly via the cholinergic nerves.     

Simultaneous determination of guanine, uric acid, hypoxanthine and xanthine in human plasma by reversed-phase high-performance liquid chromatography with amperometric detection

A reversed-phase high-performance liquid chromatographic method with amperometric detection is described for the separation and quantification of uric acid, guanine, hypoxanthine and xanthine. The isocratic separation of a standard mixture of the compounds was achieved in 5 min on a Spherisorb 5 C18 reversed-phase column, with a mobile phase of NaH2PO4 (300 mmol dm-3, pH 3.0)-methanol-acetonitrile-tetrahydrofuran (97.8 + 0.5 + 1.5 + 0.2). Uric acid, guanine, hypoxanthine and xanthine were completely separated, with detection limits in the range 2-20 pmol per injection. The effect of pH and the composition of the mobile phase on the separation are described. The hydrodynamic voltammograms of these compounds were recorded at a glassy carbon electrode. The linear range of the calibration graph for each compound was: uric acid, 1-5000 mumol dm-3; guanine, 0.5-2000 mumol dm-3; hypoxanthine, 0.1-500 mumol dm-3 and xanthine, 0.5-5000 mumol dm-3. The within- and between-day precision was good. The uric acid and hypoxanthine content in human plasma was measured using the proposed method. Good recoveries of uric acid (97.9-103%), hypoxanthine (98.0-99.2%), guanine (96.0-98.3%) and xanthine (96.0-102%) were obtained from human plasma. The results of electrochemical detection were in good agreement with those of UV detection.