Min In Controls Research Articles

Effect of acid-base balance on the growth hormone response to acute high-intensity cycle exercise

To investigate the effect of acid-base balance on serum human growth hormone (hGH) concentration after an acute high-intensity anaerobic exercise bout, 10 untrained but normally active men [age, 24.6 +/- 1.5 (SE) yr] participated in a randomized double-blind counterbalanced experiment. Each subject reported in a fasted state at the same time of day for two experimental sessions separated by 1 wk. For each session, subjects were administered a decaffeinated tea solution containing either 0.3 g NaHCO3/kg body wt [alkalosis (ALK)] or 0.04 g NaCl/kg body wt [control (CTRL)] over a 45-min ingestion period. Venous blood samples were obtained before [baseline (BL)] and 75 min after the ingestion period, as well as postexercise at 0, 5, 10, 15, 20, and 30 min. The exercise task immediately followed the preexercise blood draw and consisted of 90 s of maximal-effort cycle ergometry against an opposing force of 0.49 N (0.05 kg)/kg body wt. There were no differences between the ALK and CTRL conditions in mean or peak power output or total work during the exercise task. Whole blood pH was significantly (P < or = 0.05) elevated in ALK above CTRL at all time points except BL. Postexercise serum hGH concentration significantly increased above BL at 10, 15, 20, and 30 min in CTRL and at 20 and 30 min in ALK. The hGH concentration was significantly lower in ALK than in CTRL at 15, 20, and 30 min postexercise. These data indicate that an increase in blood hydrogen ion concentration may be partly responsible for the hGH response to acute high-intensity anaerobic exercise.

Pharmacokinetics and Pharmacodynamics of Pipecuronium in Patients with Cirrhosis

To determine the effect of liver cirrhosis on the pharmacokinetics and pharmacodynamics of pipecuronium, the authors administered 100 μg/kg of pipecuronium intravenously to eight patients with liver cirrhosis and eight patients with normal liver and renal function undergoing elective abdominal surgery. All patients were anesthetized with thiopental (5–7 mg/ kg), nitrous oxide (50–70% in oxygen), and fentanyl in repeated doses (2 μg/kg). Plasma concentrations of pipecuronium were determined by high-pressure liquid chromatography. A two-compartment open model was used for pharmacokinetic analysis. Thumb-elicited mechanical response to single-twitch ulnar nerve stimulation was also measured. Total plasma clearance did not differ between controls (2.96 ± 1.05mL·min−1·kg−1, mean ± SD) and cirrhotics (2.61 ± 1.16 mL·min−1·kg−1). Terminal elimination half-life was 111 ± 46 min in controls and 143 ± 25 min in cirrhotics. The total apparent volume of distribution at steady state did not differ between controls (350 ± 81 mL/kg) and cirrhotics (452 ± 222 mL/kg). The volume of the central compartment was not different between the two groups. The onset of neuromuscular blocking effect was longer in cirrhotics (233 ± 112 s) (P < 0.05) than in controls (170 ± 33 s). The clinical duration (injection until single twitch returned to 25%) was similar between the two groups: 167 ± 41 min in controls and 165 ± 48 min in cirrhotics. The authors conclude that hepatic insufficiency due to cirrhosis does not alter the pharmacokinetics and pharmacodynamics of pipecuronium (100 μg/kg).

Loperamide abolishes exercise-induced orocecal liquid transit acceleration

Previous work in our laboratory has found that mild physical activity accelerates mouth-to-large intestinal transit of lactulose in a mixed liquid meal. Because loperamide is commonly used as an antidiarrheal agent, we wondered if it would blunt the orocecal transit acceleration provoked by mild exercise. We investigated this equation in 12 healthy persons by comparing orocolonic liquid transit at rest and in mild exercise. Each subject ingested 8 mg loperamide 1 hr prior to study under both resting and exercise conditions. With loperamide treatment, exercise (walking at 5.6 km/hr) failed to hasten increased H2 excretion (mean transit time 72 +/- 12 min at rest, 90 +/- 15 min in exercise; P = NS). This result contrasts sharply with previously reported controls: loperamide completely abolished exercise-induced orocecal transit acceleration (-23 +/- 5 min in controls; +18 +/- 13 min with loperamide; P < 0.05). Compared with these same controls, resting transit was not significantly slowed by the drug, while transit in exercise was retarded (64 +/- 5 min in controls, 90 +/- 15 min with loperamide; P = 0.06). Loperamide left unchanged the heart rate and oxygen uptake rises associated with exercise. In summary, by showing that loperamide blocks an exercise effect on the upper gut, these results suggest that the drug might prove effective in treating some gut symptoms induced by physical activity.

Determination of 18β-glycyrrhetinic acid in biological fluids from humans and rats by solid-phase extraction and high-performance liquid chromatography

Methods have been developed and characterized allowing rapid isolation and quantification of 18β-glycyrrhetinic acid (GRA) in biological fluids from both humans and rats. Sample preparation includes extraction with urea—methanol for plasma samples, and solid-phase extraction (SPE) for urine and bile samples. Hydrolysis of GRA glucuronides in urine and bile was performed by treatment with β-glucuronidase. MGRA, the 3-O-methyl derivative of GRA was synthesized as an internal standard resistant to hydrolysis. High-performance liquid chromatography (HPLC) was performed with an isocratic system using methanol—water—acetic acid (83:16.8:0.2, v/v/v) as solvent on a Lichrocart RP-18 column at 30°C with ultraviolet detection. The methods allowed base line separation of GRA and MGRA from all biological fluids tested, with a detection limit of 0.15 mg/l. Validation of the methods included determination of recovery, accuracy and precision in plasma, bile and urine from humans and rats. The methods were further evaluated by investigating the pharmacokinetics of GRA in normal rats and in rats with a bile fistula. Following an intravenous dose of 10 mg/kg, the plasma concentration—time curve of GRA could be fitted to a one compartment model both in control and bile fistula rats. The elimination half life averaged 15.0 ± 2.2 versus 16.8 ± 2.4 min in control and bile fistula rats (difference not significant). Within 90 min following administration of GRA, urinary elimination of GRA and GRA glucuronides was less than 1% in both groups whereas biliary elimination averaged 51.3 ± 3.1%. The results show that the methods developed allow pharmacokinetic studies of GRA in humans and rats.

Abnormalities in proximal small bowel motility in patients with cirrhosis

Because altered intestinal motility could be involved in the pathogenesis of small intestine bacterial overgrowth observed in some patients with cirrhosis, we investigated fasting proximal small bowel motility in 16 cirrhotic patients and 8 healthy controls. In addition, the effects of oral tetracycline administration on duodenal motility were investigated in seven cirrhotic patients with evidence of bacterial overgrowth. The mean duration and characteristics of the migrating motor complex were analyzed. Cyclic activity was observed in all healthy controls. It was absent in two cirrhotic patients showing a prolonged phase 2-like pattern. The duration of cycles was significantly longer in the remaining 14 patients with cirrhosis (166 +/- 19 min) compared with controls (81 +/- 14 min; p < 0.02). This difference was caused by a prolonged phase 2 (138 +/- 19 min in patients with cirrhosis vs. 52 +/- 11 min in controls; p < 0.02). Marked changes in the contraction pattern during phase 2 were noted in cirrhotic patients. They were characterized by multiple clusters (frequency, 12 +/- 1/hr; duration, 38 +/- 3 sec) of contractions (frequency, 11 +/- 1 cpm) separated by quiescent periods (duration, 2.4 +/- 0.2 min). This motility profile filled up 58% +/- 8% of the total duration of phase 2, and it was observed in patients with and without bacterial overgrowth. Treatment with tetracycline was followed by only mild modifications, such as a reduction of the fraction of phase 2 occupied by multiple-clustered contractions. In conclusion, an altered proximal small bowel motility has been observed in patients with cirrhosis. These disturbances appear not to be dependent on the presence of bacterial overgrowth.

Pirsidomine, A Novel Nitric Oxide Donor, Suppresses Ischemic Arrhythmias in Anesthetized Pigs

The hemodynamic profile and antiarrhythmic properties of pirsidomine, a nitric oxide donor, were examined in pigs. Intravenous administration of pirsidomine (1 mg/kg) to chloralose-anesthetized open-chest pigs resulted in a decreased afterload, and a reduced myocardial contractility and myocardial oxygen consumption (assessed by rate-pressure product), with no alterations in heart rate. After induction of regional myocardial ischemia by occlusion of the left anterior descending coronary artery, pigs given pirsidomine experienced fewer ventricular ectopic beats (119 +/- 29) than control animals did (217 +/- 53; p < 0.05), seen primarily as a reduction in the number of couplets and triplets. Although the incidence of ventricular fibrillation was unaffected by pirsidomine, the time to onset of this arrhythmia was significantly prolonged by this intervention (21.3 +/- 0.9 min versus 16.1 +/- 2.5 min in controls; p < 0.05). Furthermore, the ST-segment depression seen throughout the 30-min occlusion period in controls was not sustained beyond 5 min postocclusion in pirsidomine-treated pigs. Taken together, and in the absence of an ex vivo antiplatelet effect with this dose of pirsidomine, these results suggest that the antiarrhythmic effect of pirsidomine lies in its hemodynamic effects, resulting in a reduction of ischemia. The ex vivo effect of pirsidomine on free radical generation from isolated leukocytes was also investigated. Luminol-enhanced chemiluminescence produced by leukocytes in response to phorbol myristate acetate was markedly depressed in cells isolated from blood withdrawn after administration of pirsidomine, compared with cells tested before drug administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastroesophageal reflux with drifting onset in infants: a phenomenon unique to sleep.

We have characterized the gastroesophageal reflux (GER) episodes which occurred during sleep in 28 infants with pathologic gastroesophageal reflux and 10 symptomatic age-matched controls without gastroesophageal reflux. We describe three kinds of episodes during the sleeping period-awake episodes which occur completely during electroencephalogram (EEG)-defined wakefulness associated with clinical evidence of the waking state (62 episodes), episodes occurring during EEG-defined sleep which have a rapid drop in pH at their onset (119 episodes), and episodes occurring during EEG-defined sleep in which the esophageal pH drifts down slowly over a period up to 30 min (113 episodes). Only 9 of the 10 control subjects experienced any reflux episodes during monitoring. The total number of episodes of reflux in controls (34) was less than the total number in reflux subjects (260). Controls did, however, experience all three types of reflux episode. Awake episodes all had a rapid drop in pH at their onset and were characterized by a short acid clearance time (2.0 +/- 0.3 min in reflux patients and 1.0 +/- 0.2 min in controls). The sleep episodes with rapid onset had longer mean acid clearance time than the awake episodes, significantly so in GER subjects (20.1 +/- 6.8 min in reflux subjects and 2.6 + 1.3 min in controls). Body movement was noted at the onset of 93.4% of rapid-onset sleep episodes in reflux subjects and 88.9% in controls. Body movement was also common at the termination of rapid-onset sleep episodes (77.8% of rapid-onset episodes in reflux subjects and 80.0% in controls).(ABSTRACT TRUNCATED AT 250 WORDS)

Na pump and plasma membrane structure in L-cell fibroblasts expressing rat liver fatty acid binding protein

Although the intracellular fatty acid binding proteins have been investigated for nearly two decades and purified proteins are now available, little is known regarding the function of these proteins in intact cells. Therefore, L-cell fibroblasts transfected with cDNA encoding for rat liver fatty acid binding protein (L-FABP) were examined as to whether L-FABP expression in intact cells modifies plasma membrane enzyme activities, fluidity, and lipids. Plasma membrane Na K - ATPase activity was 65.9 ± 18.7 and 38.6 ± 22.8 ( P < 0.001) nmol/mg protein × min for control and high-expression transfected cells, respectively. Consistent with this observation, [ 3H] ouabain binding to whole cells was significantly decreased from 3.7 ± 0.3 to 2.0 ± 0.8 pmol ouabain bound/mg cell protein in control and high-expression cells, respectively, whereas the cell's affinity for ouabain was not significantly altered. Unexpectedly, Western blot analysis indicated that transfected cells had higher levels of Na +, K +-ATPase protein; in contrast, the activities of 5′-nucleotidase and Mg-ATPase were unaltered. The effects of L-FABP expression on plasma membrane Na K - ATPase function appeared to be mediated through alterations in plasma membrane lipids and/or structure. The plasma membrane cholesterol/phospholipid ratio decreased and the bulk plasma membrane fluidity increased in the high-expression cells. In conclusion, plasma membrane Na K - ATPase activity in L cells may be regulated in part through expression of cytosolic L-FABP.

β-adrenergic system in myotonic dystrophy

Myotonic dystrophy (DM) is considered an inherited membrane disorder, but the basic defect is unknown. We studies plasma catecholamines as well as lymphocyte and muscle β-adrenergic receptor densities and functioning in 19 DM patients and 15 control subjects. Plasma adrenaline and noradrenaline concentrations were not significantly different between DM patients and controls. In isolated lymphocytes basal cAMP production was 157 ± 26 pmol/mg protein/10 min in DM patients and 91 ± 12 pmol/mg protein/10 min in controls (n.s.), whereas isoproterol-stimulated cAMP production was significantly higher in DM patients with (285 ± 42 pmol/mg protein) compared with control subjects (168 ± 21 pmol/mg protein, P < 0.05). Lymphocyte β-adrenoceptor densities were similar among DM patients (50 ± 3 fmol/mg protein) and controls (47 ± 5 fmol/mg protein). β-Adrenoceptor densities were also similar in muscle biopsy specimens (12.9 ± 1 in DM and 13.1 ± 13.1 ± fmol/mg protein in controls). The correlation between lymphocyte and skeletal muscle recert densities was r = 0.35in DM patients and r = 0.22 in controls. The results do not support the hypothesis of adrenergic dysfunction in DM despite its membrane involvement.

Metabolic responses to lipid infusions in patients with liver cirrhosis

Energy expenditure, whole body substrate oxidation rates and arterial substrate concentrations were measured in 14 patients with liver cirrhosis and 13 control subjects before and during sequential infusions of a long chain (LCT) or a medium chain triglyceride emulsion (MCT) without and with concomitant insulin plus glucose infusions. Resting energy expenditure, basal substrate oxidation rates and the arterial concentrations of glucose, lactate, triglycerides and ketones were normal, whereas plasma free fatty acids and glycerol were both increased in patients with liver cirrhosis. The arterial plasma triglyceride and free fatty acid concentrations as well as whole body lipid oxidation rate rose in response to LCT in both groups and the maximum lipid oxidation rate was 1.1 or 1.3 mg/kg fat free mass × min in controls and in cirrhotics, respectively (n.s.). Concomitantly, glucose oxidation rate fell to 65% of basal values in controls (p < 0.01), but remained nearly unchanged in the cirrhotic group (89% of the basal value; n.s.). The increase in plasma ketones was reduced to 67% of control values in liver cirrhosis (p < 0.01). Only a slight effect on energy expenditure was observed in both groups. When compared to controls, liver cirrhosis impaired insulin-induced increases in glucose disposal (−30%, p < 0.01) and in non oxidative glucose metabolism (−93%, p < 0.01). Concomitantly, normal increases in energy expenditure, glucose oxidation rate and the arterial plasma lactate concentrations and normal decreases in lipolysis, lipid oxidation and ketogenesis were observed in patients with liver cirrhosis. When lipids were given together with glucose, energy expenditure and lipid oxidation increased in controls, but glucose was the preferred fuel oxidised and lipid-induced thermogenesis was reduced in the cirrhotic group. Using a 50% MCT-emulsion, plasma free fatty acid concentrations further increased, but energy expenditure and lipid oxidation remained unchanged in both groups and further increases in plasma ketones were only observed in controls. Infusing glycerol in a subgroup of patients showed no thermogenic effect and a reduced glycerol clearance in liver cirrhosis.

Preservation of continence after ileoanal anastomosis by the coordination of ileal pouch and anal canal motor activity

Nocturnal incontinence may occur after ileoanal anastomosis and may be related to loss of an effective anal canal pressure barrier during sleep; how pressure and contractions in the proximal bowel influence this barrier is unknown. Our aim was to evaluate the relationship between anal canal pressure and contractions and contractile activity of the pouch in continent subjects after ileal pouch-anal anastomosis (IPAA) and of the rectum in normal controls. A fully ambulatory system for 24-hour pressure recording was used. A flexible transducer catheter was introduced endoscopically so that sensors were at 2, 3, 8, 12, 16, and 24 cm from the anal orifice in 12 healthy controls (7 men, 5 women, mean age: 35 years) and 7 fully continent IPAA patients (4 men, 3 women, mean age: 34 years) more than 12 months postoperatively. Twenty-four hour spontaneous motor activity was stored in a 2.5 megabyte (MB) digital portable recorder. Mean anal canal pressure was calculated, and rectal motor complexes and ileal pouch large pressure waves were characterized. During sleep, resting anal canal pressures were similar in the two groups (72 ± 12 mm Hg in controls versus 66 ± 9 mm Hg in IPAA patients [mean ± standard deviation (SD)], p = NS), but anal canal pressure showed cyclic relaxations (periodicity: 95 ± 11 min in controls, 54 ± 18 min in IPAA patients, p < 0.05), during which the mean pressure trough was 15 ± 4 mm Hg in controls and 14 ± 5 mm Hg in IPAA patients (p = NS). In the control patients, during sleep, a mean of six rectal motor complexes were identified (range: 3 to 9). In patients with IPAA, during sleep, a mean of eight large pressure waves per hour were identified (range: 2 to 20). Importantly, in both controls and patients, rectal motor complexes or large pressure waves were always accompanied by rapid return of anal canal pressure from trough to basal values and increased contractile activity. We concluded that, in healthy patients and in continent patients after IPAA, motor activity of the rectum and of the ileal pouch was associated with changes in pressure and contractile activity of the anal canal so that rectal- and neorectal-anal canal pressure gradient, and, in turn, fecal continence were preserved.

Neonatal ovariectomy and pituitary-adrenal responsiveness in the adult rat.

Litters of female rat pups were handled daily from birth to weaning. When 12 days old the pups were ovariectomized or received sham surgery. At 70 days sham and ovariectomized animals were decapitated immediately or placed within a novel environment for 10, 20, or 40 min before decapitation. Basal plasma levels of androstenedione in ovariectomized animals were approximately half that of intact sham controls, and stress caused only a small rise in androstenedione in this group. Androstenedione levels in ovariectomized animals were consistently at or below the lower sensitivity of the radioimmunoassay, indicating that circulating levels of androstenedione in the female rat are primarily of ovarian origin. Basal ACTH and corticosterone levels did not differ significantly between the two groups. However, stress-induced levels of ACTH and corticosterone were significantly depressed in ovariectomized subjects compared to controls following exposure to the novel environment. Furthermore, while ACTH levels started to return to baseline by 40 min in controls, this effect was not observed in ovariectomized animals. These findings demonstrate that prepubertal removal of ovarian humoral factors can have a long-term impact on the responsiveness of the hypothalamic-pituitary-adrenal axis to stress.

Divergent effects of flavone acetic acid on established versus developing tumour blood flow

Flavone Acetic Acid (FAA) exerts much of its effect by reducing tumour blood flow. Previous studies on FAA-induced changes in blood flow have used established tumours with a functional microvasculature. Using radioactive Xenon(133Xe) clearance to monitor local blood flow we show that the effects of FAA are dependent on the presence of this functional microvasculature with no evidence that FAA inhibits the actual development of tumour microcirculation. Thus, administration of multiple doses of FAA around the time of tumour cell injection failed to diminish t1/2 values of 133Xe (e.g. t1/2 16 min for FAA vs 14 min for saline controls at 10 days) or to affect tumour volumes (5.55 +/- 0.06 cm3 in FAA-treated animals vs 5.7 +/- 1.3 cm3 in controls at 25 days). In marked contrast a single dose of FAA (200 mg kg-1 body weight) 2 weeks after tumour cell injection dramatically extended t1/2 times (47 min for FAA vs 7 min for controls; P less than 0.001) and significantly reduced tumour burden. This effect is specific for tumour microvasculature and is not directed simply at new vessels since a similar treatment of animals with implanted-sponge-induced granulation tissue had no effect on t1/2 times (6.8 +/- 1.1 min for FAA at 200 mg kg-1 vs 7.2 +/- 1.0 min for saline-treated controls.

Chronic Undernutrition Accentuates Insulin Deficiency in Rats With Mild Streptozocin-Induced Diabetes

The effect of chronic undernutrition on coexisting diabetes mellitus was studied in pair-fed littermate rats with mild streptozocin-induced diabetes. They were either fed ad libitum or 50% food restricted for 9 wk. Undernourished diabetic rats, in which weight gain was reduced by 40%, had significantly higher glucose intolerance (mean +/- SE, fractional rate of glucose disappearance during glucose tolerance test [Kgtt] 1.77 +/- 0.16) than diabetic littermates fed ad libitum (2.33 +/- 0.21, P less than 0.05) or nondiabetic controls (3.8 +/- 0.7, P less than 0.01). The total area under the insulin response curve was significantly reduced in both groups of diabetic rats, but the undernourished group showed a 45% greater reduction in overall secretion than normally nourished diabetic littermates (21.3 +/- 2.7 vs. 39.4 +/- 6.3 nM.min in the diabetic group, P less than 0.01, and 65.7 +/- 6.1 nM.min in controls). There was also a marked reduction in first-phase insulin secretion in the undernourished rats (4.75 +/- 0.24 vs. 9.84 +/- 1.36 nM, P less than 0.05, and 14.3 +/- 1.8 nM, P less than 0.01, respectively, in normally nourished diabetic littermates and controls). After refeeding, a significant improvement occurred in Kgtt (to 2.67 +/- 0.24, P less than 0.01) and first-phase insulin secretion (to 9.69 +/- 1.65 nM, P less than 0.05). The postrefeeding values were not different from those in the normally nourished diabetic littermates, indicating that the effect was fully reversible and solely attributable to undernutrition rather than to enhanced beta-cell cytotoxicity from streptozocin.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding of serum osteocalcin to hydroxyapatite in Paget's disease of bone

Serum osteocalcin (serum bone Gla protein, sBGP) is elevated in diseases characterized by an enhanced bone turnover. However, in Paget's disease of bone there is a discrepancy between the low increase of sBGP and the high increase of bone remodelling assessed by serum alkaline phosphatase and urinary hydroxyproline. It is possible that the relatively low levels of sBGP reflect an abnormal binding of the molecule to the bone due to an alteration of the BGP molecule and/or of the pagetic mineral phase of bone. Another possibility would be a disregulation of BGP synthesis. In the present work we studied the binding of pagetic sBGP to an experimental model of mineral phase of bone (HPLC hydroxyapatite column). Serum of 14 patients with Paget's disease of bone (sBGP = 7.8 ± 3.5 ng/ml) and of 14 control subjects (sBGP = 3.3 ± 0.9 ng/ml) was purified through a Sephadex G-50 medium column (2.6 × 100 cm, 5 mM NH 4CO 3H). The BGP peak was lyophilized and resuspended in 1 mM KH 2PO 4, 1 mM CaCl 2, 0.02% NaN 3, pH 8.4, and then injected into an HPLC gradient system (Waters 660), from 1 to 300 mM KH 2PO 4 through a hydroxyapatite column (BioGel HPHT, Bio-Rad, 0.78 × 10 cm). A single peak of sBGP was obtained with a retention time of 12 min in control and pagetic patients. From these results we conclude that BGP binding to hydroxyapatite is similar in pagetic patients and in control subjects, suggesting that an alteration in BGP molecule is not responsible for an abnormal binding to the bone. In order to validate our system, the binding of serum BGP from warfarin-treated rats to the hydroxyapatite HPLC column was also studied and compared to binding of serum BGP from normal rats.

Effects of pancreastatin and chromogranin A on insulin release stimulated by various insulinotropic agents

The effects of porcine pancreastatin on insulin release stimulated by insulinotropic agents, glucagon, cholecystokinin-octapeptide (CCK-8), gastric inhibitory polypeptide (GIP) and l-arginine, were compared to those of bovine chromogranin A (CGA) using the isolated perfused rat pancreas. Pancreastatin significantly potentiated glucagon-stimulated insulin release (first phase: 12.5 ± 0.9 ng/8 min ; second phase: 34.5 ± 1.6 ng/25 min in controls; 16.5 ± 1.1 ng/8 min and 44.0 ± 2.2 ng/25 min in pancreastatin group), whereas CGA was ineffective. The first phase of l-arginine-stimulated insulin release was also potentiated by pancreastatin ( 6.9 ± 0.5 ng/5 min in controls, 8.4 ± 0.6 ng/5 min in pancreastatin group), but not by CGA. Pancreastatin did not affect CCK-8 or GIP-stimulated insulin release. Similarly, CGA did not affect insulin release stimulated by CCK-8 or GIP. These findings suggest that pancreastatin stimulates insulin release in the presence of glucagon. Because pancreastatin can have multiple effects on insulin release, which are dependent upon the local concentration of insulin effectors, pancreastatin may participate in the fine tuning of insulin release from B cells.

Insulin Resistance: An Early Metabolic Defect of Turner's Syndrome*

To evaluate whether insulin resistance contributes to the increased risk of diabetes in patients with Turner's syndrome, we measured insulin sensitivity (using the euglycemic insulin clamp technique, 40 mU/m2.min) and whole body glucose and lipid oxidation (assessed by indirect calorimetry) in two groups of nondiabetic patients with Turner's syndrome and age-matched normal controls. Group 1 consisted of eight young patients (mean age, 10 +/- 0.8 yr) who had never received hormone therapy, and group 2 consisted of five patients (mean age, 17.6 +/- 1.4 yr) who had been or were on estrogen therapy. In group 2, [3-3H]glucose was also infused during the euglycemic clamp to assess hepatic sensitivity to insulin. During the euglycemic clamp, insulin-stimulated glucose metabolism was decreased in both groups of patients [group 1, 8.4 +/- 1.0 vs. 14.7 +/- 2 mM/m2.min in controls (P less than 0.05); group 2, 9 +/- 0.7 vs. 11.7 +/- 0.9 mM/m2.min in controls (P less than 0.05)]. The impairment of insulin-stimulated glucose metabolism in patients with Turner's syndrome was accounted for by reduced nonoxidative glucose disposal; glucose oxidation rose to a similar extent in Turner patients and normal controls. Insulin-induced suppression of hepatic glucose production (group 2) and plasma FFA and branched chain amino acid levels in Turner patients was also indistinguishable from that in normal controls. Our data suggest that in patients with Turner's syndrome, insulin resistance is a very early metabolic defect that may be restricted to nonoxidative pathways of intracellular glucose metabolism.

Radionuclide imaging clinical study

A quantitative test, corporeal 133Xe washout, was developed to detect venogenic impotence. Data were acquired in frame mode after intracorporeal injection of 0.1 ml (1-2 mCi or 37-74 MBq) of 133Xe in saline on one side of the midline just behind the glans in the flaccid state for 20 min. A time-activity curve (TAC) was generated from the region of interest (ROI) at the site of injection and a computer routine was then used to calculate clearance half-time (T1/2) in minutes and flow rate (Q) in ml/100 g tissue/min from corporeal 133Xe clearance. The data from 12 controls and 21 patients with venous leakage were analysed. In patients with venogenic impotence, T1/2 (mean +/- S.D.) was greatly increased (24.4 +/- 10.7 min vs 10.7 +/- 4.6 min in controls, P less than 0.005) whereas Q markedly decreased (2.4 +/- 1.3 ml/100 g tissue/min vs 5.4 +/- 2.3 ml/100 g tissue/min in controls, P less than 0.005). The sensitivity and specificity for detecting venous leakage at the optimal threshold of T1/2 equal to 13 min and Q equal to 3.7 ml/100 g tissue/min were 95 and 75%, respectively. The corporeal 133Xe clearance half-time and flow rate are two simple and clinically useful indices for detecting venous leakage.

Impaired uptake of glutathione by hepatic mitochondria from chronic ethanol-fed rats. Tracer kinetic studies in vitro and in vivo and susceptibility to oxidant stress.

Isolated hepatocytes incubated with [35S]-methionine were examined for the time-dependent accumulation of [35S]-glutathione (GSH) in cytosol and mitochondria, the latter confirmed by density gradient purification. In GSH-depleted and -repleted hepatocytes, the increase of specific activity of mitochondrial GSH lagged behind cytosol, reaching nearly the same specific activity by 1-2 h. However, in hepatocytes from ethanol-fed rats, the rate of increase of total GSH specific radioactivity in mitochondria was markedly suppressed. In in vivo steady-state experiments, the mass transport of GSH from cytosol to mitochondria and vice versa was 18 nmol/min per g liver, indicating that the half-life of mitochondrial GSH was approximately 18 min in controls. The fractional transport rate of GSH from cytosol to mitochondria, but not mitochondria to cytosol, was significantly reduced in the livers of ethanol-fed rats. Thus, ethanol-fed rats exhibit a decreased mitochondrial GSH pool size due to an impaired entry of cytosol GSH into mitochondria. Hepatocytes from ethanol-fed rats exhibited a greater susceptibility to the oxidant stress-induced cell death from tert-butylhydroperoxide. Incubation with glutathione monoethyl ester normalized the mitochondrial GSH and protected against the increased susceptibility to t-butylhydroperoxide, which was directly related to the lowered mitochondrial GSH pool size in ethanol-fed cells.

Leukocyte intracellular pH and Na/H antiporter activity in uraemia and type I diabetes mellitus.

The leukocyte Na/H antiporter has been studied in patients with end-stage renal failure on maintenance haemodialysis. Thirteen non-diabetic haemodialysis patients (CRF group) and eight haemodialysis patients with diabetic nephropathy (CRF-DM group) were investigated. Measurements were made using the pH-sensitive fluorescent dye bis (carboxyethyl) carboxyfluorescein (BCECF). The initial intracellular pH (pHi), intracellular buffering capacity, and Na/H antiporter Vmax (at pHi = 6.0) have been recorded in bicarbonate-free solutions. The mean initial intracellular pH in the CRF group was 7.34 (SD 0.05, P less than 0.004) and this was significantly less than the CRF-DM group (7.42, SD 0.07) and normal controls (7.43, SD 0.09, n = 25). The mean intracellular buffering capacity was normal in the CRF and CRF-DM groups. The mean Na/H antiporter Vmax was also normal in the CRF and CRF-DM groups (56.5, SD 9.9; and 56.8, SD 12.8, mmol/l per min respectively compared to 55.2, SD 8.8, mmol/l per min in controls). These data are discussed with reference to the reported high values of Na/H antiporter Vmax in diabetic patients with early nephropathy. This abnormality does not appear to be present in end-stage diabetic nephropathy.