Extracellular volume estimation from ratios of bromide to chloride in urine or saliva.

Use of either urine or saliva samples to estimate extracellular water volume was investigated in 10 men using nonradioactive bromide (Br) and in seven newborn piglets using radioactive Br (82Br) and chloride (36Cl). The relation to Br to Cl concentrations in urine enabled an estimation of Br dilution volume from human urine (267 +/- 42 ml/kg, mean +/- SD) that was not significantly different (P = 1.0) from the Br dilution volume calculated from plasma Br concentration (268 +/- 20 ml/kg). Although the Br dilution volume estimated from saliva was not different from that of plasma, the error in the estimates of Br dilution volume from saliva was too large (mean difference, -36 +/- 64 ml/kg) to make its use practical. The data from piglets showed good agreement between 82Br and 36Cl dilution volumes calculated from 4-hr plasma samples (356 +/- 14 ml/kg and 347 +2- 12 ml/kg; P greater than 0.1) and between 82Br dilution volumes calculated from urine 82Br:36Cl and plasma 82Br (360 +/- 31 ml/kg and 356 +/- 14 ml/kg; P greater than 0.1). Extracellular water volume can be estimated in both adult and young animals using the Br dilution volume calculated from urine samples. It requires (i) two urine collections: one before and one 4 to 8 hr after administration of Br; (ii) a measurement or estimate of plasma Cl concentration; and (iii) a correction factor that describes the relationship of the ratio of Br to Cl in urine to that ratio in plasma.     

Fluid volumes in rainbow trout, Salmo gairdneri: application of compartmental analysis

1. The measurement of fluid volumes by the indicator dilution technique and compartmental analysis was re-evaluated in free-swimming, undisturbed rainbow trout. 2. Plasma (33.5 ml/kg body wt) and blood (41.3 ml/kg body wt) volumes estimated by compartmental analysis from blood samples taken early (less than 5 min) after dye injection were 40% lower than volumes calculated by sampling late (greater than or equal to 80 min). 3. The rate of exchange of dye between plasma and interstitial fluid was high (48%/hr) compared to mammals (5%/hr) which supports the hypothesis that teleost capillaries have high protein permeability. 4. Total extracellular volume estimated using a single pool model (210.5 ml/kg body wt) of inulin kinetics was 20% higher than that calculated by a three pool model (172.8 ml/kg body wt).     

Comparison of cold storage and perfusion of dog livers on function of tissue slices

We compared how two methods of hypothermic preservation affect physiological functions of tissue slices of dog liver. Livers were preserved by either (i) cold storage (CS) in Collins' solution or (ii) continuous perfusion (P) with a perfusate, containing hydroxyethyl starch, sodium gluconate, adenosine, and potassium phosphate, recently developed in our laboratory. Livers were cold stored for 6 to 8, 24, or 48 hr, and perfused for 24 or 72 hr. Tissue slices of preserved livers were incubated at 30 degrees C and analyzed for volume control, electrolyte-pump activity (K and Na), and adenine nucleotide concentration. Also, mitochondria were isolated after preservation to quantify respiratory activity. Slice functions of livers preserved for short periods (6 to 8 hr by CS and 24 hr by P) were similar to those for control livers. After normothermic incubation, the mean (+/- SD) water content of tissue (expressed per unit dry mass of tissue) was 2.3 +/- 0.3 kg/kg for control, 2.6 +/- 0.4 kg/kg for 6- to 8-hr CS, and 2.5 +/- 0.5 kg/kg for 24-hr P. Longer periods of preservation resulted in cell swelling, and water content was 3.3 +/- 0.4 kg/kg for 24- to 48-hr CS and 2.8 +/- 0.3 kg/kg for 72-hr P. The mean (+/- SD) K/Na ratio was nearly normal for livers preserved for short periods: 3.7 +/- 0.5 for control, 4.1 +/- 0.2 for 6- to 8-hr CS, and 3.3 +/- 0.4 for 24-hr P.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth hormone response of bull calves to growth hormone-releasing factor

Three experiments were conducted to determine serum growth hormone (GH) response of bull calves (N = 4; 83 kg body wt) to iv injections and infusions of human pancreatic GH-releasing factor 1-40-OH (hpGRF). Peak GH responses to 0, 2.5, 10, and 40 micrograms hpGRF/100 kg body wt were 7 +/- 3, 8 +/- 3, 18 +/- 7, and 107 +/- 55 (mean peak height +/- SEM) ng/ml serum, respectively. Only the response to the 40-microgram dose was greater (P less than 0.05) than the 0-microgram dose. Concentrations of prolactin in serum were not affected by hpGRF treatment. In calves injected with hpGRF (20 micrograms/100 kg body wt) at 6-hr intervals for 48 hr, GH increased from a mean preinjection value of 3.1 ng/ml serum to a mean peak response value of 70 ng/ml serum. Differences in peak GH response between times of injection existed within individual calves (e.g., 10.5 ng/ml vs 184.5 ng/ml serum). Concentrations of GH in calves infused continuously with either 0 or 200 micrograms hpGRF/hr for 6 hr averaged 7.4 +/- 3 and 36.5 +/- 11 ng/ml serum, respectively (P less than 0.05). Concentrations of GH oscillated markedly in hpGRF-infused calves, but oscillations were asynchronous among calves. We conclude that GH response of bull calves to hpGRF is dose dependent and that repeated injections or continuous infusions of hpGRF elicit GH release, although magnitude of response varies considerably. We hypothesize that differences in GH response to hpGRF within and among calves, and pulsatile secretion in the face of hpGRF infusion may be related to the degree of synchrony among exogenous hpGRF and endogenous GRF and somatostatin.     

Reduced natriuresis after oral sodium load in cholestatic rats: role of compartment volumes and ANP

The purpose of this study was to assess the participation of the atrial natriuretic peptide (ANP)-cGMP system in electrolyte and volume handling of cholestatic rats submitted to an acute oral sodium load. Cholestasis was induced by ligation and section of the common bile duct (n = 51). Control rats were sham operated (n = 56). Three weeks after surgery, 24-hr urinary volume, sodium, potassium, cGMP and creatinine excretion were measured. Three days later, animals received 10 mmol/kg NaCl (1 M) by gavage, and urinary excretion was measured for 6 hr. In parallel groups of rats, plasma volume, electrolytes and ANP concentration, extracellular fluid volume (ECFV), and renal medullary ANP-induced cGMP production were determined in basal conditions or 1 hr after oral sodium overload. As compared with controls, cholestatic rats had a larger ECFV and higher plasma ANP (67.2 +/- 5.2 vs 39.7 +/- 3.5 pg/ml), but lower hematocrit and blood volume, and were hyponatremic. Cholestatic rats showed higher basal excretion of sodium, potassium, and volume than controls, but equal urinary cGMP. After the NaCl overload, cholestatic rats showed a reduced sodium excretion but equal urinary cGMP. One hr after sodium overload, both groups showed hypernatremia, but whereas in control rats ECFV and ANP increased (50.7 +/- 4.1 pg/ml), in cholestatic rats ECFV was unchanged, and plasma volume and ANP were reduced (37.5 +/- 5.8 pg/ml). ANP-induced cGMP production in renal medulla was similar in cholestatic and control nonloaded rats (14.2 +/- 5.2 vs 13.4 +/- 2.6 fmol/min/mg). One hr after the load, medullary cGMP production rose significantly in both groups, without difference between them (20.6 +/- 3.1 vs 22.7 +/- 1. 7 fmol/min/mg). We conclude that the blunted excretion of an acute oral sodium load in cholestatic rats is associated with lower plasma ANP due to differences in body fluid distribution and cannot be explained by renal refractoriness to ANP.     

Effect of leg exercise training on vascular volumes during 30 days of 6 degrees head-down bed rest.

Plasma and red cell volumes, body density, and water balance were measured in 19 men (32-42 yr) confined to bed rest (BR). One group (n = 5) had no exercise training (NOE), another near-maximal variable-intensity isotonic exercise for 60 min/day (ITE; n = 7), and the third near-maximal intermittent isokinetic exercise for 60 min/day (IKE; n = 7). Caloric intake was 2,678-2,840 kcal/day; mean body weight (n = 19) decreased by 0.58 +/- 0.35 (SE) kg during BR due to a negative fluid balance (diuresis) on day 1. Mean energy costs for the NOE, and IKE, and ITE regimens were 83 (3.6 +/- 0.2 ml O2.min-1.kg-1), 214 (8.9 +/- 0.5 ml.min-1.kg-1), and 446 kcal/h (18.8 +/- 1.6 ml.min-1.kg-1), respectively. Body densities within groups and mean urine volumes (1,752-1,846 ml/day) between groups were unchanged during BR. Resting changes in plasma volume (ml/kg) after BR were -1.5 +/- 2.3% (NS) in ITE, -14.7 +/- 2.8% (P less than 0.05) in NOE, and -16.8 +/- 2.9% (P less than 0.05) in IKE, and mean water balances during BR were +295, -106, and +169 ml/24 h, respectively. Changes in red cell volume followed changes in plasma volume. The significant chronic decreases in plasma volume in the IKE and NOE groups and its maintenance in the ITE group could not be accounted for by water balance or by responses of the plasma osmotic, protein, vasopressin, or aldosterone concentrations or plasma renin activity. There was close coupling between resting plasma volume and plasma protein and osmotic content.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasmodium berghei: lactic acidosis and hypoglycaemia in a rodent model of severe malaria; effects of glucose, quinine, and dichloroacetate

Fulminant malaria infections are characterised by hypoglycaemia and potentially lethal lactic acidosis. In young adult Wistar rats (n = 26) infected with Plasmodium berghei (ANKA strain), hyperparasitaemia (greater than 50%), anaemia (PCV 19.6 +/- 5.3%; mean +/- SD) hypoglycaemia (1.04 +/- 0.74 mmol/litre), hyperlactataemia (13.2 +/- 2.20 mmol/litre), hyperpyruvicaemia (0.51 +/- 0.12 mmol/litre) and metabolic acidosis (arterial pH 6.96 +/- 0.11) developed after approximately 14 days of infection. Hypoglycaemia was associated with appropriate suppression of plasma insulin concentrations. In a second series of experiments the metabolic effects of treatment with glucose (500 mg/kg/hr), quinine (5 mg/kg bolus followed by 10 mg/kg over 1 hr) and a potent activator of pyruvate dehydrogenase, dichloroacetate (300 mg/kg) were studied over a 1-hr period. In control animals quinine had no measurable effects, but dichloroacetate significantly reduced arterial blood lactate (74%) and pyruvate (80%). In infected animals, glucose infusion attenuated the rise in lactate (38% compared with 82%; P less than 0.01) but quinine had no additional metabolic effects. Dichloroacetate further attenuated the rise in lactate (14%; P less than 0.01).     

Cellular and biochemical characteristics of semen obtained from pubertal chimpanzees by masturbation

Semen characteristics were studied in 6 wild-born chimpanzees with dental ages ranging approximately from 6 to 12 years. The animals formed 2 groups, early pubertal (EP, N = 3, 6-9 years) and late pubertal (LP, N = 3, 11-12 years). Mean body weight, testicular volume and serum androgen concentration were significantly lower in Group EP (32.2 +/- 1.6 kg, 34.0 +/- 7.7 cm3, 2.1 +/- 0.1 ng/ml) than in Group LP (55.7 +/- 5.7 kg, P less than 0.01; 100.5 +/- 11.9 cm3, P less than 0.01; 3.6 +/- 0.7 ng/ml, P less than 0.05). Ejaculates were obtained by masturbation in all subjects. The mean ejaculate volume was lower in Group EP (0.56 +/- 0.20 ml) than in Group LP (3.77 +/- 0.73 ml, P less than 0.01). In Group EP, 2 animals were azoospermic while the third produced semen with means of 57.1 x 10(6) spermatozoa per ml, 20% motility and 40% vitality. These values were low when compared with the mean values of Group LP (376 x 10(6) spermatozoa per ml, 67% motility and 78% vitality). Mean total sperm count was correlated with testicular volume (r = 0.84) and serum androgen concentration (r = 0.96). The mean concentrations of L-carnitine, fructose, citrate and acid phosphatase for the two groups were not significantly different; but, related to the differences in ejaculate volumes, their total amounts in total ejaculate were lower in Group EP than in Group LP. These results suggest that, in chimpanzees, mechanisms of seminal plasma production and ejaculation are functional early in the reproductive life and that the emission of spermatozoa occurs later.     

Age-related characteristics of ceftazidime pharmacokinetics in children]

To reveal possible age-dependent variations in the ceftazidime pharmacokinetics, the drug plasma concentrations were determined by HPLC in 10 children aged 2 to 13 years with peritonitis. The blood specimens were collected 0.25, 0.5, 1, 3, 6 and 8 hours after intravenous bolus administration of ceftazidime (Kefadym, Eli Lilly) in a single dose of 20 mg/kg. The mean values of the model-independent parameters were: total clearance (Cl), 3.3 +/- 0.8 ml/min.kg; steady-state distribution volume, 0.32 +/- 0.06 ml/kg; mean residence time, 1.7 +/- 0.4 hours. The C-coordinate of the gravity center was equal to 26 +/- 7 mg/l. A noticeable age-dependent decrease in Cl was detected by comparing the Cl estimates in our study for the children aged 7.0 +/- 3.0 years with earlier findings in children aged 12 years as well as in adults (18 and 26 years) and elderly patients (77 years): 2.5, 2.2, 2.0 and 1.1 ml/min.kg, respectively. A similar trend was observed for the ceftazidime volume of distribution (Varea). Due to the described reduction in Cl and Varea the age-induced changes in the half-life of ceftazidime were negligible. The age-dependent differences in ceftazidime pharmacokinetics should be taken into account in designing rational dosage regimens for the drug administration.     

Oxygen uptake capacity of gills and skin in relation to body weight of the air-breathing siluroid fish, Clarias batrachus (Linn.).

Oxygen consumption through gills and skin in relation to body weight was estimated in the air-breathing catfish, Clarias batrachus, under two experimental conditions, viz., (i) when access to air was allowed and (ii) when air-breathing was prevented. There was a positive correlation between VO2 (ml/hr) and body weight in both experimental conditions. Oxygen consumption (ml/hr) increased by a power of 0.869 when access to air was allowed whereas the power was slightly less (b = 0.841) when air-breathing was prevented. As the values for exponent (b) were less than 1.0, the weight specific VO2 (ml/kg/hr) decreased with increasing body weight. The decrease was more marked (b = - 0.180) in fishes which were not allowed air than in those where access to air was allowed (b = - 0.148). Under normal conditions of water and air-breathing the rate of VO2 (ml/kg/hr) via gills and skin from water ranged from 39.7 +/- 3.21 to 76.7 +/- 9.01 and this increased to 42.17 +/- 6.2 to 105.9 +/- 8.33 when air-breathing was prevented. The increase in the rate of VO2 was perhaps associated with the increase in the volume of water irrigating the gills per unit time.     

Plasma volume expansion in humans after a single intense exercise protocol.

We used intense intermittent exercise to produce a 10% expansion of plasma volume (PV) within 24 h and tested the hypothesis that PV expansion is associated with an increase in plasma albumin content. The protocol consisted of eight 4-min bouts of exercise at 85% maximal O2 uptake with 5-min recovery periods between bouts. PV, plasma concentrations of albumin and total protein (TP), and plasma osmolality were measured before and during exercise and at 1, 2, and 24 h of recovery from exercise. During exercise, PV decreased by 15%, while plasma TP and albumin content remained at control levels. At 1 h of recovery, plasma albumin content was elevated by 0.17 +/- 0.04 g/kg body wt, accounting for the entire increase in plasma TP content. PV returned to control level at 1 h of recovery without fluid intake by the subjects, despite a 820 +/- 120-g reduction in body weight. At 2 h of recovery, plasma TP content remained significantly elevated, and plasma TP and albumin concentration were significantly elevated. At 24 h of recovery, PV was expanded by 4.5 +/- 0.7 ml/kg body wt (10 +/- 1%), estimated from hematocrit and hemoglobin changes, and by 3.8 +/- 1.3 ml/kg body wt (8 +/- 3%), measured by Evans blue dye dilution. Plasma albumin content was increased by 0.19 +/- 0.05 g/kg body wt at 24 h of recovery. If 1 g of albumin holds 18 ml of water, this increase in plasma albumin content can account for a 3.4-ml/kg body wt expansion of the PV. No significant changes in plasma osmolality occurred during recovery, but total plasma osmotic content increased in proportion to PV.(ABSTRACT TRUNCATED AT 250 WORDS)     

Splanchnic vascular capacitance and positive end-expiratory pressure in dogs

We have investigated the effect of positive end-expiratory pressure ventilation (PEEP) on regional splanchnic vascular capacitance. In 12 anesthetized dogs hepatic and splenic blood volumes were assessed by sonomicrometry. Vascular pressure-diameter curves were defined by obstructing hepatic outflow. With 10 and 15 cmH2O PEEP portal venous pressure increased 3.1 +/- 0.3 and 5.1 +/- 0.4 mmHg (P less than 0.001) while hepatic venous pressure increased 4.9 +/- 0.4 and 7.3 +/- 0.4 mmHg (P less than 0.001), respectively. Hepatic blood volume increased (P less than 0.01) 3.8 +/- 0.9 and 6.3 +/- 1.4 ml/kg body wt while splenic volume decreased (P less than 0.01) 0.8 +/- 0.2 and 1.3 +/- 0.2 ml/kg body wt. The changes were similar with closed abdomen. The slope of the hepatic vascular pressure-diameter curves decreased with PEEP (P less than 0.01), possibly reflecting reduced vascular compliance. There was an increase (P less than 0.01) in unstressed hepatic vascular volume. The slope of the splenic pressure-diameter curves was unchanged, but there was a significant (P less than 0.05) decrease in unstressed diameter during PEEP. In conclusion, hepatic blood volume increased during PEEP. This was mainly a reflection of passive distension due to elevated venous pressures. The spleen expelled blood and thus prevented a further reduction in central blood volume.     

Insulin-mediated H+ and NH+4 excretion in the urinary bladder of Bufo marinus

This study was done to determine if insulin mediates H+ and NH+4 excretion in the urinary bladder of Bufo marinus. Acidosis was induced by gavaging with 10 ml of 120 mM NH4Cl 3X daily for 2 days. Hemibladders were mounted between Lucite chambers. Insulin (porcine) was added to the serosal solution of the experimental bladder (10(2) mU/ml). After a 15-min equilibration the flux was measured for 2 hr. H+ excretion was measured from change in pH of the mucosal fluid and the NH+4 measured colorimetrically. The excretion was normalized for weight of bladder and reported in units of nanomoles (100 mg bladder)-1(min)-1. Plasma insulin was determined by radioimmunoassay and glucose by the glucose oxidase method. In 14 control bladders H+ excretion was 8.75 +/- 1.28 and experimental was 16.35 +/- 2.50 (P less than 0.025), while NH+4 excretion in control bladder was 3.29 +/- 0.95 and experimental was 6.58 +/- 1.89 (P less than 0.01). This response was absent when the insulin was heat inactivated (P greater than 0.2 and P greater than 0.3 respectively). Plasma insulin-like levels in 10 normal toads was 0.57 +/- 0.16 ngm/ml and in acidotic toads 1.25 +/- 0.16 ng/ml (P less than 0.025). Plasma glucose levels in 10 normal toads were 22.0 +/- 3.5 mg/dl and in 12 acidotic toads 17.8 +/- 0.75 mg/dl (P less than 0.025). We conclude that plasma insulin is increased in acidosis and that insulin stimulates excretion of H+ and NH+4 in the toad urinary bladder.     

Role of vasopressin in rats with bilateral ureteral obstruction

After unilateral release of bilateral ureteral obstruction (BUO), there is a significant increase in renal vasoconstriction that accounts for the marked decrease in glomerular filtration rate and effective renal plasma flow seen in this setting. We examined the potential role of antidiuretic hormone (ADH), a vasoconstrictor of the renal circulation, on renal hemodynamics in female Sprague-Dawley rats with BUO of 24-hr duration. Rats with BUO had significantly higher plasma values of ADH 65.1 +/- 12.2 vs. 12.1 +/- 4.1 pg/ml), sodium (145.4 +/- 0.91 vs 138.6 +/- 1.06 mEq/liter), and osmolality (375.6 +/- 2.0 vs 310.1 +/- 3.6 mOsm/kg) than sham-operated rats. Rats with BUO pretreated with enalapril, an angiotensin-converting enzyme inhibitor, before obstruction had somewhat higher, but not significantly different, plasma values for ADH (84.6 +/- 20.8 pg/ml) than rats with BUO not given enalapril. Rats with unilateral ureteral obstruction of 24-hr duration had plasma levels of ADH (8.2 +/- 1.3) not different from those in sham-operated rats. Rats with BUO pretreated with a specific antagonist of the V1-type receptor for ADH had significantly greater values for the glomerular filtration rate (2.31 +/- 0.24 vs 1.44 +/- 0.08 ml/min/kg body wt) and the effective renal plasma flow (8.95 +/- 0.71 vs 3.81 +/- 0.44 ml/min/kg body wt) and significantly lower values for mean arterial pressure (140.3 +/- 2.0 vs 159.1 +/- 5.5 mm Hg) than did BUO rats not given the antagonist. The results indicate that high levels of ADH play an important role in the decrease in the glomerular filtration rate and effective renal plasma flow observed in rats with BUO of 24 hr. The significant increase in ADH levels after BUO of 24-hr duration may be due to an increase in osmotic stimulation as a consequence of hypernatremia. Activation of the renin-angiotensin axis, known to occur after BUO or unilateral ureteral obstruction of 24-hr duration, does not appear to have a role in the increased circulating levels of ADH.     

Cardiovascular responses to lower body negative pressure in trained and untrained older men.

To determine whether aerobic conditioning alters the orthostatic responses of older subjects, cardiovascular performance was monitored during graded lower body negative pressure in nine highly trained male senior athletes (A) aged 59-73 yr [maximum O2 uptake (VO2 max) = 52.4 +/- 1.7 ml.kg-1 x min-1] and nine age-matched control subjects (C) (VO2 max = 31.0 +/- 2.9 ml.kg-1 x min-1). Cardiac volumes were determined from gated blood pool scintigrams by use of 99mTc-labeled erythrocytes. During lower body negative pressure (0 to -50 mmHg), left ventricular end-diastolic and end-systolic volume indexes and stroke volume index decreased in both groups while heart rate increased. The decreases in cardiac volumes and mean arterial pressure and the increase in heart rate between 0 and -50 mmHg were significantly less in A than in C. For example, end-diastolic volume index decreased by 32 +/- 4 ml in C vs. 14 +/- 2 ml in A (P < 0.01), mean arterial pressure declined 7 +/- 5 mmHg in C and increased by 5 +/- 3 mmHg in A (P < 0.05), and heart rate increased 13 +/- 3 beats/min in C and 7 +/- 1 beats/min in A (P < 0.05). These data suggest that increased VO2 max among older men is associated with improved orthostatic responses.     

Pulmonary function of the green sea turtle, Chelonia mydas

Lung volumes, oxygen uptake (VO2), end-tidal PO2, and PCO2, diffusing capacity of the lungs for CO (DLCO), pulmonary blood flow (QL) and respiratory frequency were measured in the green sea turtle (Chelonia mydas) (49-127 kg body wt). Mean lung volume (VL) determined from helium dilution was 57 ml/kg and physiological dead space volume (VD) was about 3.6 ml/kg. QL, determined from acetylene uptake during rebreathing, increased in proportion to VO2 with temperature. Therefore, constant O2 content difference was maintained between pulmonary arterial and venous blood. DLCO, measured using a rebreathing technique, was 0.04 ml X kg-1 X min-1 X Torr-1 at 25 degrees C. Several cardiopulmonary characteristics in C. mydas are advantageous to diving: large tidal volume relative to functional residual capacity promotes fast exchange of the alveolar gas when the turtle surfaces for breathing: and the concomitant rise of pulmonary blood flow and O2 uptake with temperature assures efficient O2 transport regardless of wide temperature variations encountered during migrations.     

Nitrergic contribution to gastric relaxation induced by glucagon-like peptide-1 (GLP-1) in healthy adults

The incretin glucagon-like peptide-1 (GLP-1), which is used to treat diabetes mellitus, delays gastric emptying by inhibiting vagal activity. GLP-1 also increases fasting and postprandial gastric volume in humans. On the basis of animal studies, we hypothesized that nitric oxide mediates the effects of GLP-1 on gastric volumes. To assess the effects of nitrergic blockade on GLP-1-induced gastric accommodation in humans, in this double-blind study, 31 healthy volunteers were randomized to placebo (i.e., saline), GLP-1, or the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine acetate (L-NMMA; 4 mg.kg(-1) x h(-1)) alone or with GLP-1. Thereafter, 16 additional subjects were randomized to GLP-1 alone or together with a higher dose of L-NMMA (10 mg/kg bolus plus 8 mg.kg(-1).h(-1) infusion). Gastric volumes (fasting pre- and postdrug, postprandial postdrug) were measured by (99m)Tc-single-photon-emission computed tomography imaging. GLP-1 increased (P = 0.04) fasting gastric volume by 83 +/- 16 ml (vs. 17 +/- 11 ml for placebo) and augmented (P < or = 0.01) postprandial accommodation by 688 +/- 165 ml (vs. 542 +/- 29 ml for placebo). L-NMMA (low dose) alone did not affect fasting or postprandial gastric volume. L-NMMA (low dose) did not attenuate the effect of GLP-1 on gastric volumes. In contrast, L-NMMA (high dose) did not affect fasting volume but blunted GLP-1-mediated postprandial accommodation (postprandial change = 494 +/- 37 ml, P < or = 0.01 vs. GLP-1 alone). These data are consistent with the hypothesis that nitric oxide partly mediates the effects of GLP-1 on postprandial but not fasting gastric volumes in humans.     

Ultradian, circadian and seasonal variations of plasma progesterone and LH concentrations during the luteal phase

The circadian variations in plasma progesterone (P) and LH concentrations were investigated in six women, aged 23-40 years. All were studied in the mid-luteal phase (7 +/- 2 days after LH mid-cycle surge). Experiments were conducted in autumn and in spring. Blood samples were obtained every 15 min for 24 hr. Plasma P and LH concentrations were measured by RIA. Each subject's time-series was analysed using three methods; visual inspection (chronogram), spectral analysis to estimate component periods of rhythms (tau) and cosinor analysis to quantify the rhythms parameters. Marked temporal variations in plasma P concentration were observed in each subject. The maximal variations over a 24-hr period, ranged between 13-58.5 mmol/l. Differences related to sampling time were statistically validated by ANOVA (p less than 0.00001). Significant harmonic periods were detected by spectral analysis but differed among subjects. In all subjects but one, a circadian rhythm was detected. The acrophase location was similar (about 0700 hr) in the four subjects studied in autumn, but ranged from 1940 to 0320 hr in those studied in spring. An ultradian rhythm with tau = 8 hr was also validated in six time-series with similar acrophases (about 0200, 1000, and 1800 hr). Cosinor analysis of pooled data revealed that the 24-hr, 12-hr, and 8-hr rhythms were statistically significant (p = 0.001) in autumn. algebraic sum of these three cosine functions yielded a circadian waveform with peak-times occurring near 0300 and 1130 hr and a trough-time about 2200 hr. In spring, the circadian pattern appeared quite different, and peak-times were found near 0700 and 2000 hr, and trough-times near 0300 and 1500 hr. Furthermore, the 24-hr mean of P was higher in autumn (28.9 +/- 0.4 nmol/l) than in spring (17.2 +/- 0.4 nmol/l), p from ANOVA less than 0.00001. The evidence for a similar circadian LH pattern is not as strong. Seasonal, circadian and ultradian rhythms characterize the physiologic time structure of plasma P concentration in mid-luteal phase.     

Blood volume in inbred strain BALB/c, CBA/J and C57BL/10 mice determined by means of 59Fe-labelled red cells and 59Fe bound to transferrin.

Circulating red blood cell (RBC) and plasma volume was determined in male inbred strain BALB/c, CBA/J and C57BL/10 mice by parallel use of the 59Fe-labelled RBC dilution and the dilution of 59Fe bound to transferrin. The whole blood volumes values derived from the venous haematocrit and plasma volume were about double the values calculated from the venous haematocrit and circulating RBC volume. Comparison of the two methods thus explains the marked differences in different studies of blood volume in mice and shows that correct values can be obtained only by parallel measurements of RBC and plasma volume by separate methods, or by correcting the venous haematocrit to whole body haematocrit. Combination of the labelled RBC method and the 59Fe-transferrin method showed the blood volume values in the above strains of mice to be 10.35 +/- 0.16, 7.32 +/- 0.10 and 7.94 +/- 0.15 ml/g b.w. respectively. The ratio of whole body to venous haematocrit in these strains was was 57.3 +/- 1.6%, 68.0 +/- 1.8% and 69.5 +/- 2.2%. Significant interstrain differences were demonstrated in RBC, plasma and blood volume and in the venous and whole body haematocrit and their ratio.     

Inhibition of dipeptidyl-peptidase IV does not increase circulating IGF-1 concentrations in growing pigs

The enzyme dipeptidyl peptidase-IV (DPP-IV) inactivates a variety of bioactive peptides, including glucagon-like peptide-1 (GLP-1) and growth hormone releasing hormone (GHRH). Inhibiting DPP-IV in order to increase circulating GLP-1 is of interest as a treatment for Type II diabetes. Inactivation of DPP-IV may also increase circulating GHRH, potentially enhancing growth in domestic animals. To test the hypothesis that inhibition of DPP-IV activity will influence the growth hormone/ IGF-1 axis, growing pigs (Sus scrofa domesticus, 78 kg) were treated with a DPP-IV inhibitor (Compound 1, the 2,5-difluor-ophenyl analog of the triazolopiperazine MK0431, sitagliptin), and plasma concentrations of IGF-1 were monitored. Pigs were administered either sterile saline (0.11 ml/kg followed by a continuous infusion at 2 ml/hr for 72 hrs, controls, n = 2), Compound 1 (2.78 mg/kg followed by a continuous infusion at 0.327 mg/kg x hr for 72 hrs, n = 4) or GHRH (0.11 ml/kg sterile saline, followed by a continuous infusion of GHRH at 2.5 microg/ kg x hr for 48 hrs, n = 4). Plasma concentrations of Compound 1 were maintained at 1 microM, which resulted in a 90% inhibition of circulating DPP-IV activity. Relative to the predose 24-hr period, area under the IGF-1 concentration curve (AUC) tended to be lower (P = 0.062) with Compound 1 (.79 +/- 130 ng/ml x hr) than controls (543 +/- 330 ng/ml x hr). GHRH treatment increased the IGF-1 AUC (1210 +/- 160 ng/ml x hr, P = 0.049 vs. controls and P = 0.001 vs. Compound 1). We conclude that inhibition of DPP-IV does not alter the circulating levels of IGF-1 in the growing pig.