A PAF receptor antagonist, BN 52021, attenuates thromboxane release and improves survival in lethal canine endotoxemia

Platelet-activating (PAF) is a putative mediator in endotoxemia and sepsis. Administration of a PAF receptor antagonist prior to endotoxin improves survival in rats and attenuates the hypotension of endotoxemia. Both PAF and endotoxin stimulate eicosanoid production. We hypothesized that a PAF receptor antagonist, BN 52021, would alter the hemodynamic events, improve the survival and attenuate the eicosanoid release associated with endotoxemia in a resuscitated, but lethal, canine model. Male dogs were randomzied to two groups (n = 10 each). Group I received only E. coli endotoxin, 1 mg/kg IV, at time 0, while group II received BN 52021, 5 mg/kg IV, 30 min before and again 240 min after endotoxin treatment. During the 4-h study period, hemodynamics were measured and blood samples were taken at 0, 2, 60, 120, and 240 min. Survival was determined at 24, 48, and 72 h. All group I animals died before 24 h; all group II lived longer than 72 h (P less than 0.05). In group I, plasma TXB2 values increased from a baseline value of 0.26 +/- .04 ng/ml to 4.38 +/- 1.56 ng/ml at 120 min and then decreased to 2.64 +/- .96 ng/ml by 240 min. For group II, respective plasma TXB2 values were 0.35 +/- 0.13 ng/ml at baseline, 0.58 +/- 0.14 ng/ml at 120 min, and 0.39 +/- .09 ng/ml at 240 min. At the 120-min and 240-min time points, the groups differed at P less than 0.05. Heart rate tended to be less in group II, but MAP was unaffected. In group I, pH values were more acidotic than those observed in group II.

The amino acid-induced alteration in renal hemodynamics is glucagon independent

The amino acid-induced alteration in renal hemodynamics is glucagon independent. An oral protein load or i.v. administration of an amino acid solution results in an increase in glomerular filtration rate and renal plasma flow in both humans and animals. The change in renal hemodynamics has been attributed to the simultaneous induced rise in glucagon. Whether glucagon is necessary for the change in renal hemodynamics after an amino acid infusion was investigated. Two groups of dogs were used, and the experimental protocol was divided into four different periods (P1 through P4). Group I animals received an amino acid solution, and group II dogs received an equiosmolar solution of mannitol. In P1, the animals in both groups were hydrated with normal saline, whereas, in P2, the pancreatic clamp technique was used to fix the plasma glucagon levels. P2 served as a basal period in which measurements of glomerular filtration rate, renal plasma flow, and plasma glucagon were obtained. IN P3, group I animals received amino acid solution, and group II received mannitol and served as controls. In this period, an increase of 32 and 27% in glomerular filtration rate and renal plasma flow, respectively, in group I dogs was observed, whereas there were no significant changes in these parameters in group II. During this period, plasma glucagon remained still at basal level in both groups. In P4, an infusion of glucagon at a rate of 5 ng/kg/min was added to both groups. This maneuver resulted in a fourfold increase in plasma glucagon levels in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino acids enhance insulin resistance to exogenous glucose infusion in overnight-fasted humans

The role that amino acids play in regulating exogenous glucose infusion during hyperinsulinemia was examined in overnight-fasted volunteers. Each study consisted of both a 30-minute basal period and a 4-hour experimental period during which insulin was infused at either 0.6, 1.2, 2.5, 5.0, 10, or 20 mU/kg/min with euglycemia maintained. Two protocols were used. In the first (I), subjects were allowed to develop hypoaminoacidemia, and in the second (II), plasma amino acid levels were maintained near basal by frequently monitoring plasma leucine levels in conjunction with exogenous infusion of an L-amino acid solution. The amount of amino acids infused were 0.85 +/- 0.11, 1.53 +/- 0.17, 1.97 +/- 0.13, 2.18 +/- 0.50, 2.78 +/- 0.61, and 2.83 +/- 0.44 mg/kg/min at escalating insulin doses, respectively. When amino acids were infused, the amount of glucose required to maintain euglycemia was lower at each insulin dose used (4.5 +/- 0.3 vs 3.6 +/- 0.4, 7.6 +/- 0.5 vs 6.9 +/- 0.3, 10.4 +/- 1.0 vs 8.7 +/- 0.5, 13.3 +/- 0.8 vs 10.2 +/- 0.4, 14.7 +/- 0.8 vs 11.7 +/- 0.6, and 14.9 +/- 0.6 vs 11.8 +/- 0.8 mg/kg/min at escalating insulin doses, respectively; p less than 0.05). The calculated maximal infusion rates were 15.8 +/- 0.6 vs 12.6 +/- 0.4 mg/kg/min (protocol I vs II, p less than 0.001), while the concentrations required to achieve half-maximal rates were 153 +/- 22 and 134 +/- 22 microU/ml (p = ns), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of gut and liver in nitrogen metabolism during exercise

The role of the gut and liver in nitrogen metabolism was studied during rest, 150 minutes of moderate-intensity treadmill exercise, and 90 minutes of recovery in 18 hour-fasted dogs (n = 6). Dogs underwent surgery 16 days before an experiment for implantation of catheters in a carotid artery and in the portal and hepatic veins, and Doppler flow cuffs on the hepatic artery and portal vein. Arterial glutamine, alanine, and alpha-amino nitrogen (AAN) levels decreased gradually with exercise (P less than .05), while arterial glutamate, NH3, and urea were unchanged. Net gut glutamine uptake was 1.3 +/- 0.5 mumol/kg.min at rest, and increased transiently to 2.5 +/- 0.3 mumol/kg.min at 60 minutes of exercise (P less than .05) as gut extraction increased. Net hepatic glutamine uptake was 0.6 +/- 0.4 mumol/kg.min at rest, and increased to 3.4 +/- 0.6 and 2.6 +/- 0.5 mumol/kg.min after 60 and 150 minutes of exercise (P less than .05) as hepatic extraction increased. Net gut glutamate and NH3 output both increased transiently with exercise (P less than .05). These increases were matched by parallel increments in the net hepatic uptakes of these compounds. Alanine output by the gut and uptake by the liver were unchanged with exercise. Net gut AAN output was -2.1 +/- 1.8 mumol/kg.min at rest (uptake occurred), and increased transiently to 11.2 +/- 3.5 mumol/kg.min after 30 minutes of exercise (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of exercise and insulin action in humans

To assess the interaction of exercise and insulin action, healthy males were studied with saline infusion (n = 5) or with a hyperinsulinemic euglycemic clamp (0.5, 1.0, 2.0, or 15.0 mU.kg-1.min-1; n = 5 at each dose) during rest (40 min), moderate-intensity cycle exercise (100 min), and recovery (100 min). Metabolism was assessed using isotopic methods and indirect calorimetry. During rest, exercise, and recovery with saline infusion, plasma glucose was unchanged, total glucose utilization (Rd) was 2.4 +/- 0.4, 4.9 +/- 0.2, and 2.6 +/- 0.2 mg.kg-1.min-1, and carbohydrate (CHO) oxidation (OX) was 1.4 +/- 0.3, 10.6 +/- 1.1, and 0.5 +/- 0.2 mg.kg-1.min-1. The glucose infusion, insulin-dependent Rd, and CHO OX increased synergistically when exercise and insulin clamps were combined. Exercise decreased (P less than 0.05) the half-maximal doses (ED50) and increased the maximal responses (Vmax) for insulin-dependent Rd and CHO OX. Estimates of insulin-independent Rd were 1.3 +/- 0.7, 4.1 +/- 1.3, and 1.9 +/- 0.7 mg.kg-1.min-1 and insulin-independent CHO OX were 1.2 +/- 0.9, 10.4 +/- 1.3, and 0.6 +/- 0.3 mg.kg-1.min-1 during rest, exercise, and recovery. Estimates during exercise were greater than those at rest (P less than 0.05). The total suppression of free fatty acids (FFA) and fat OX by insulin were elevated by exercise (P less than 0.05). In summary, exercise and insulin interact synergistically in stimulating Rd and CHO OX.(ABSTRACT TRUNCATED AT 250 WORDS)

Octreotide acetate induces fasting small bowel motility in patients with dumping syndrome

The long acting somatostatin analogue octreotide acetate has been effective in the treatment of early dumping syndrome. We hypothesized that this may be related to its effects on inhibiting gastric emptying and delaying intestinal transit. To study the effect of octreotide acetate on intestinal motility in patients we carried out a randomized, double-blinded study using a subcutaneous injection of either octreotide acetate (100 micrograms) or placebo given 20 min prior to ingestion of a high carbohydrate "dumping" meal in six patients with known severe dumping syndrome. Prior to each study a multilumen polyethylene tube was inserted into the efferent limb to study small intestinal contractions using low compliance pneumo-hydraulic water-perfused manometry. Octreotide acetate prevented dumping symptoms in all six patients and induced the appearance of migrating myoelectric complexes (MMC) characteristic of interdigestive motility. After ingestion of the dumping meal the postprandial "fed" motility pattern lasted for 141 +/- 9 min while after octreotide acetate the fed motility lasted for 29 +/- 5 min (P less than 0.03). The vigor of the fed motility pattern as measured by the motility index (MI = loge (sum of amplitudes X No. of contractions + 1] was lower after octreotide acetate than after placebo (15.1 +/- 0.1 vs 13.4 +/- 0.2, P less than 0.03). The induction of fasting MMC motility pattern and reduction in the duration and vigor of fed motility may explain the symptomatic relief these patients obtained with octreotide acetate. It is not known whether the induction of the MMC is a direct effect of octreotide acetate or secondary to the concomitant inhibition of peptide release (neurotensin, insulin, glucagon, pancreatic polypeptide) that has been demonstrated in earlier studies.

Efficacy of octreotide acetate in treatment of severe postgastrectomy dumping syndrome

The present study evaluates the acute and chronic use of a long-acting somatostatin analog, octreotide acetate, in the treatment of patients with severe postgastrectomy dumping syndrome. In the acute phase, 10 patients with severe dumping were studied over 2 consecutive days before and for 3 hours after the ingestion of a 'dumping breakfast' in a randomized double-blind fashion. On one day octreotide (100 micrograms) was given subcutaneously 30 minutes before the test meal and on the other day an equal volume of vehicle was injected. An additional group of six postgastrectomy patients without dumping were studied in a similar fashion and these acted as controls. During placebo treatment the test meal resulted in an immediate increase (p less than 0.01) in the pulse rate and in plasma levels of glucose, glucagon, pancreatic polypeptide, neurotensin, and insulin. Similar changes were seen in the control group with respect to placebo; however glucagon and neurotensin (p less than 0.05) did not show the same magnitude of increase as seen with placebo. Treatment with octreotide acetate prevented the development of both vasomotor and gastrointestinal symptoms and completely ablated all of the above responses in plasma peptides. These changes were associated with complete ablation of diarrhea (p less than 0.001). Pretreatment with octreotide acetate completely suppressed the rise in plasma insulin response to the meal and this ablated the late hypoglycemia of dumping. Treatment with octreotide acetate resulted in delayed gastric emptying and transit time (578 +/- 244 minutes) versus 76 +/- 23 minutes with placebo and 125 +/- 36 minutes in controls (p less than 0.05). Chronic daily treatment with octreotide acetate resulted in minimal side effects. These patients demonstrated a stable fasting plasma glucose, normal liver function tests, and an average weight gain of 11% during a 12-month period. In addition most patients were able to resume employment. The long-acting somatostatin analog, octreotide acetate, is highly effective in preventing the development of symptoms of severe dumping syndrome, both vasomotor and gastrointestinal.

Differential effects of alpha and beta adrenergic blockade on glucose and lactate metabolism during acute stress

In this study we examined the role of alpha and beta blockade on glucose and lactate metabolism during the acute stress of insulin-induced hypoglycemia. Three groups of conscious dogs with chronically fitted catheters in the femoral artery and in the femoral, portal, and hepatic veins were studied after an 18-hr fast. After a 1-hr basal period, hypoglycemia was induced with insulin infusion at 5 mU/kg.min for 3 hr. Group 1 received no other treatment. Groups 2 and 3 received, respectively, phentolamine (8 micrograms/kg.min) and propranolol (4 micrograms/kg.min) beginning 30 minutes before and throughout the experimental period. Despite similar hyperinsulinemia, plasma glucose dropped in Group 1 (from 115 +/- 10 to 40 +/- 3 mg/dl) and in Group 2 (from 110 +/- 4 to 60 +/- 3 mg/dl) but in Group 3 it was maintained at 45 +/- 4 mg/dl by exogenous glucose infusion at a rate of 2.2 +/- 0.4 mg/kg.min. Hepatic glucose production increased 50 +/- 13%, 127 +/- 30%, and 55 +/- 30% in Groups 1, 2, and 3, respectively, within 60 minutes and was 56 +/- 19%, 55 +/- 17%, and -0.04 +/- 12% during the last hour of the experiment. Glucose utilization did not change in Groups 1 and 2 but it increased in Group 3. Plasma lactate increased in Group 1 (from 850 +/- 190 to 1,980 +/- 450 mumol/L) and in Group 2 (985 +/- 180 to 4,785 +/- 500 mumol/L), while in Group 3 there was an early rise (to 695 +/- 120 mumol/L) within 30 minutes that gradually dropped to near basal.(ABSTRACT TRUNCATED AT 250 WORDS)

What getting sick means

The concepts of health, disease and death have intrigued man since the beginning of time and are continually evolving. In the nonwestern societies the models which have been proposed for the etiology of disease have a dichotomous view of disease causation which is derived from either natural or supernatural forces. In the Western societies these concepts are well defined. The numerous advances in the fields of genetics and molecular biology have added a new dimension to the understanding of the various factors involved in the pathogenesis of disease processes. These advances have allowed a greater understanding of numerous disease processes including the inborn errors of metabolism, endocrine disorders and human neoplasia. Several recent advances in the areas of molecular biology and physiology allowing this increased understanding of human disease are presented.

Effect of insulin-induced hypoglycemia on protein metabolism in vivo

The effects of insulin-induced hypoglycemia (IIH) on leucine kinetics (mumol.kg-1.min-1) and interorgan flow of amino acids (AA) were examined in 2 groups of 18-h fasted conscious dogs. Insulin was infused at 5 mU.kg-1.min-1 for 3 h. IIH (40 +/- 5 mg/dl) resulted in a drop in plasma leucine (114 +/- 10 to 64 +/- 9 microM) and leucine rate of appearance (Ra) (3.1 +/- 0.1 to 2.4 +/- 0.2) within 1 h but gradually increased (P less than 0.05) to 145 +/- 30 microM and 3.8 +/- 0.5 by 3 h. Leucine oxidative rate of disposal (Rd) increased from 0.44 +/- 0.08 to 1.02 +/- 0.35 (P less than 0.01), and nonoxidative Rd dropped initially but was near basal levels by 3 h. When euglycemia was maintained, there was sustained drop in plasma leucine from 122 +/- 12 to 42 +/- 6 mumol/l, leucine Ra from 3.1 +/- 0.4 to 1.8 +/- 0.2, oxidative Rd from 0.36 +/- 0.03 to 0.22 +/- 0.04, and nonoxidative Rd from 2.75 +/- 0.4 to 1.6 +/- 0.2 (all P less than 0.01). IIH was associated with a significant net release of leucine (and other AA) across the gut (0.04 +/- 0.05 to 1.86 +/- 0.30 mumol.kg-1.min-1; P less than 0.05). In the group with euglycemia there was no significant change in the gut balance of leucine. We conclude that IIH is associated with a proteolytic response and that the gut is the major contributor to this response.

Role of insulin and branched-chain amino acids in regulating protein metabolism during fasting

This study examines the independent effects of insulin and amino acids on protein metabolism after a 12-h and 4-day fast in healthy volunteers. Leucine (Leu) kinetics were examined during sequential insulin infusions of 0 (group I) or 0.0125 (groups II and III), 1.2, and 10 mU.kg-1.min-1. Plasma Leu was maintained at 12-h fasted levels in groups I and II and at 84-h fasted levels in group III. Four-day fast (vs. 1 day, P less than 0.01) was associated with a 79% drop in plasma insulin and elevations in plasma Leu (122%), Leu rates of appearance (Ra) (21%), and Leu oxidation (56%), and no change in nonoxidative rates of disappearance (Rd). Insulin resulted in a dose-dependent suppression of endogenous Leu Ra with group III = I greater than II. Leu oxidation rose 1.7-fold in group III at the highest insulin dose but remained stable in the two other groups. In conclusion, 4-day fasting is associated with enhanced proteolysis and Leu oxidation with no change in nonoxidative Rd (protein synthesis). Elevated branched-chain (and other) amino acids were required to restore tissue sensitivity and specificity to the effects of insulin on protein metabolism after 4 days of fasting.

Amino acids augment insulin's suppression of whole body proteolysis

Leucine (LEU) kinetics were assessed using a primed-continuous infusion of L-[1-14C]LEU in normal overnight-fasted male volunteers during a basal period and an experimental period where insulin (INS) was infused at either 0.6, 1.2, 2.5, 5.0, 10, or 20 mU.kg-1.min-1 with euglycemia maintained. Two protocols were used: 1) subjects were allowed to develop hypoaminoacidemia or 2) plasma essential amino acids (AA) were maintained near basal levels by frequently monitoring plasma LEU in conjunction with variable infusions of an AA solution (LEU infused = 0.41, 0.72, 0.93, 1.03, 1.31, and 1.35 mumol.kg-1.min-1 at escalating INS doses, respectively). Basal rates of LEU appearance (Ra), nonoxidative disappearance (NORd) and oxidative disappearance (OXRd) were similar in both protocols (means = 1.74, 1.40, and 0.36 mumol.kg-1.min-1, respectively). INS infusions without AA resulted in a progressive decrement in LEU Ra (14 to 45%), NORd (16-41%), and OXRd (3-56%) compared with basal values. The infusion of AA resulted in an additional reduction in endogenous Ra (P less than 0.01; approximately 100% suppression achieved at plasma INS greater than 1,000 microU/ml) and a blunting of NORd reduction (P less than 0.05) at each dose of INS. Observed differences in INS's suppression of LEU Ra between the two protocols suggests the existence of a component of whole body proteolysis that is highly dependent on circulating plasma AA. Therefore, hypoaminoacidemia associated with INS treatment would appear to blunt the responsiveness of INS's suppression of protein breakdown and in the presence of near basal plasma AA, proteolytic suppression by INS is enhanced.

Importance of ammonium ions in regulating hepatic glutamine synthesis during fasting

Four-day fasting in the conscious dog is associated with enhanced ammoniagenesis in both the gut and kidneys and a switch in the hepatic glutamine balance from net uptake to that of net production. In the present study we examined the role that the rise in portal venous ammonium ions plays in regulating nitrogen metabolism in vivo. Three groups of 18- to 24-h fasted conscious dogs with catheters surgically implanted in the femoral artery and in the hepatic, portal, and renal veins for 17-21 days were studied. On the day of the study, one group (n = 6) received intraportal ammonium acetate at 3.0 mumol.kg-1.min-1 intended to result in portal venous ammonium ion levels slightly above those seen in the 4-day fasted dog. Another group (n = 5) received an equimolar infusion of sodium acetate, and a third group (n = 6) received saline (0.9%) and acted as controls. Organ balances across the liver, extrahepatic splanchnic tissues (gut), and kidneys were estimated by the arteriovenous differences multiplied by blood flows. All of the load of ammonium acetate infused intraportally was taken up by the liver. As a result there was an immediate switch in hepatic glutamine balance from that of net uptake to net production similar to that seen in the 4-day fasted dog. Simultaneously, net hepatic production of urea nitrogen doubled. These occurred with no change in acid-base balance or no change in circulating arterial or portal venous levels of insulin and glucagon.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of low- and high-intensity exercise on plasma and cerebrospinal fluid levels of ir-beta-endorphin, ACTH, cortisol, norepinephrine and glucose in the conscious dog

This study was designed to assess effects of exercise on plasma and cerebrospinal fluid (CSF) levels of immunoreactive (ir) beta-endorphin, ACTH, cortisol, norepinephrine, and glucose in the conscious dog. Dogs were exercised on a treadmill at low or high intensity (4.2 miles/h and a 6% or 20% incline) for 90 min, and were allowed to recover for 90 additional min. Neither intensity of exercise changed plasma glucose levels, but dose-related changes in glucose kinetics did occur. CSF glucose declined in both groups. During low intensity exercise, plasma levels of ir-beta-endorphin, ACTH, and cortisol increased with duration of exercise. During high intensity exercise, ACTH, ir-beta-endorphin and cortisol increased faster, and the integrated plasma response of these hormones was greater. Thus, peripheral release of ir-beta-endorphin, ACTH, and cortisol during exercise is dose-related with respect to time and intensity. CSF ir-beta-endorphin and ACTH both increased during low- but not high-intensity exercise. CSF cortisol rose markedly in both exercise groups. During high-intensity exercise there was a 50% increase in CSF norepinephrine, indicating that exercise induces alterations in central noradrenergic turnover. We conclude that exercise is a physiologic regulator of both peripheral and central neuroendocrine systems.

Effects of naloxone on glucose homeostasis during insulin-induced hypoglycemia

The present study was designed to examine the role played by beta-endorphin in the physiological response to the stress of insulin-induced hypoglycemia. Three groups (n = 5, each) of conscious overnight-fasted dogs, chronically fitted with catheters in the femoral artery and in the third ventricle were used for these studies. Each experiment consisted of an 80-min equilibration period (0-80 min), a 40-min basal period (80-120 min), and a 180-min (120-300 min) experimental period. One group received a 220-min intracerebroventricular (icv) infusion of naloxone (0.2 mg/h) beginning at t = 80 min. The second group received a 3-h intravenous infusion of insulin at 5.0 mU.kg-1.min-1 beginning at t = 120 min. The third group received naloxone at t = 80 min and insulin beginning at t = 120 min, and both were continued throughout the experimental period. The studies show that insulin-induced hypoglycemia was associated with a rise in plasma cortisol, beta-endorphin, epinephrine, norepinephrine, and glucagon. Pretreatment with naloxone diminished the rises in plasma beta-endorphin, epinephrine, and norepinephrine without affecting the responses of plasma glucagon and cortisol. Although the levels of hypoglycemia achieved in the two groups were identical, glucose rates of appearance into and disappearance from the plasma compartment were higher in the group pretreated with icv naloxone (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Possible sources of glutamine for parenteral nutrition: impact on glutamine metabolism

Due to its instability, glutamine is not included in solutions for parenteral solution. This problem can be obviated by providing glutamine as acetyl-, glycyl-, or alanylglutamine. Using an organ balance technique in conscious dogs, we investigated metabolism of these three sources of glutamine. Liver, gut, kidney, and muscle participated in clearance of glycyl- and alanylglutamine from plasma, but among these organs only kidney cleared acetylglutamine. Furthermore, there was a large urinary excretion for acetylglutamine (38 +/- 6% of amount infused) but only a trace amount for either dipeptide. The infusion of glutamine-dipeptides resulted in similar increases in blood level of free glutamine. The main source of this increase appeared to be hydrolysis of dipeptides by kidney and release of free glutamine to circulation. During the infusion of both dipeptides, glutamine balance (free and dipeptide forms) was always positive (net uptake) across liver, gut, and kidney but was neutral across muscle. Liver or gut glutamine balances were not significantly different during the infusion of dipeptides, but kidney glutamine balance was twofold greater during the infusion of glycyl- than alanylglutamine. We conclude that among these three sources of glutamine, acetylglutamine is least desirable for use in parenteral nutrition. Glycylglutamine may be preferable over alanylglutamine if the objective is to target glutamine for kidney.

Nonfunctioning adrenal tumors. Dilemmas in management

A retrospective study conducted from 1975-1987 at Vanderbilt University Medical Center and affiliated hospitals identified 28 patients, ranging in age from 22 to 74 years, who were noted to have "nonfunctioning" adrenocortical tumors. Eighteen (64%) were men, and ten (36%) were women. A left adrenal mass was present in 16 (57%) patients, a right in 11 (39%) patients, and one (4%) patient had bilateral adrenal enlargements. Nineteen patients underwent an adrenalectomy. Ten were found to have adrenocortical adenomas, ranging is size from 2.5-4.0 cm in greatest diameter. Three were adrenocortical carcinomas (3.0, 5.5, and 8.0 cm). A necrotic mass (14.0 cm) was found in one patient. Two patients had myelolipoma, one had ganglioneuroma, and one had a suspected primary melanoma. Five patients were not operated upon and were followed by serial computed tomographic scans for variable periods; two died of unrelated cardiac problems, and one was lost to follow-up. Three patients underwent biopsy with benign pathology. The data indicate a high incidence of adenoma and carcinoma in patients with nonfunctioning adrenal tumors that measure more than 3.0 cm in diameter. These tumors have the potential to progress to malignant degeneration without any recognizable clinical or endocrine abnormalities. The authors thus conclude that all patients with "nonfunctioning" adrenal tumors that are larger than 3.0 cm in diameter should undergo surgical exploration and excision.

Thermogenesis in humans during overfeeding with medium-chain triglycerides

To test whether excess dietary energy as medium-chain triglycerides (MCT) affects thermogenesis differently from excess dietary energy as long chain triglycerides (LCT), ten male volunteers (ages 22 to 44) were overfed (150% of estimated energy requirement) liquid formula diets containing 40% of fat as either MCT or LCT. Each patient was studied for one week on each diet in a double-blind, crossover design. Resting metabolic rate (RMR) did not change during either week of overfeeding. The thermic response to food (TEF) was greater on day 1 following a meal (1,000 kcal) containing MCT than following an isocaloric meal containing LCT (8 +/- .8% v 5.8 +/- .8% of ingested energy; P less than .05). Moreover, the TEF observed after a 1,000 kcal meal containing MCT increased significantly to 12% (+/- 1.3%) overfeeding. The TEF of the 1,000 kcal meal containing LCT was unchanged by five days of LCT overfeeding (6.6 +/- 1.0% of ingested energy). Energy expenditure during a 20-hour continuous enteral infusion of the diet on day 7 was also significantly higher with the MCT diet than with the LCT diet (15.7 +/- 1.7% v 7.3 +/- .9% of ingested energy; P less than .05). Our results demonstrate that excess dietary energy as MCT stimulates thermogenesis to a greater degree than does excess energy as LCT. This increased energy expenditure, most likely due to lipogenesis in the liver, provides evidence that excess energy derived from MCT is stored with a lesser efficiency than is excess energy derived from dietary LCT.

Characteristics of glutamine transport in dog jejunal brush-border membrane vesicles

The present study characterizes glutamine transport across brush-border membrane vesicles (BBMV) prepared from dog jejunum. The purity of these vesicles was demonstrated by a 20-fold enrichment of leucine aminopeptidase, a marker for BBM. Glutamine uptake was found to occur into an osmotically active space with no membrane binding and to exhibit temperature and pH dependence (optimal uptake at pH 7-7.5). Glutamine uptake was driven by an inwardly directed Na+ gradient with a distinct overshoot not observed under K+ gradient. Lithium could not substitute for Na+ as a stimulator of glutamine uptake. Na+-dependent glutamine uptake was not inhibited by methylaminoisobutyric acid, a typical substrate for system A, and was found to be electrogenic and saturable with a Km of 0.97 +/- 0.58 mM and a Vmax of 3.93 +/- 0.99 nmol.mg protein-1.10 s-1. A Na+-glutamine coupling ratio of 1:1 could be demonstrated by a plot of Hill transformation. Na+-independent glutamine uptake was found to be electroneutral and saturable with a Km of 3.70 +/- 0.66 mM and a Vmax of 2.70 +/- 1.55 nmol.mg protein-1.10 s-1. Inhibition studies confirmed the presence of a Na+-dependent as well as a Na+-independent carrier for glutamine uptake. We conclude that glutamine uptake across dog BBMV occurs via two transport systems: a Na+-dependent high-affinity system similar to the neutral brush-border system and a Na+-independent lower-affinity system similar to system L.

Physiological bases for the treatment of the physically active individual with diabetes

Substrate utilisation and glucose homoeostasis during exercise is controlled by the effects of precise changes in insulin, glucagon and the catecholamines. The important role these hormones play is clearly seen in people with diabetes, as the normal endocrine response is often lost. In individuals with insulin-dependent diabetes (IDDM), there can be an increased risk of hypoglycaemia during or after exercise or, conversely, there can be a worsening of the diabetic state if insulin deficiency is present. In contrast, it appears that people with non-insulin-dependent diabetes (NIDDM) can generally exercise without fear of a deleterious metabolic response. The exercise response both in healthy subjects and in those with diabetes is dependent on many factors such as age, nutritional status and the duration and intensity of exercise. Since there are so many variables which govern individual response to exercise, an exact exercise prescription for all people with diabetes cannot be made. There are many adjustments to the therapeutic regimen which an individual with IDDM can make in order to avoid hypoglycaemia during or after exercise. In general, a reduction in insulin dosage and the added ingestion and continual availability of carbohydrates are wise precautions. On the other hand, exercise should be postponed if blood glucose is greater than 2500 mg/L and ketones are present in the urine. As more is understood about the regulation of substrate metabolism during exercise, more refined therapeutic strategies can be defined. An understanding of the metabolic response to exercise is critical for generating an effective and safe training programme for all diabetic individuals who wish to be physically active.

Burn injury alters intestinal glutamine transport

Several studies have established that intestinal glutamine (GLN) metabolism is altered during catabolic states. It remains unclear whether these alterations are due to a defect in metabolism or in transport of the amino acid. The present study examines the kinetics of GLN transport across basolateral membrane vesicles (BLMV) of enterocytes obtained from control rats and rats subjected to 20% full-thickness scald burn, 48 hr previously. BLMV were prepared from freshly isolated enterocytes using differential centrifugation with separation on a Percoll density gradient. BLMV were enriched (10- to 12-fold) with Na+-K+-ATPase while markers for brush border membranes were impoverished. Previous studies from our laboratory indicated that, in this preparation, GLN transport is into an osmotically sensitive space, dependent on GLN concentration, linear up to 30 sec, and both temperature and Na+ dependent. Our results indicate that in thermal injury, initial rates of GLN uptake were depressed (y = 3.67 + 0.435X for burned rats vs y = 18.7 + 0.907X for controls, P less than 0.01). Kinetic analysis of GLN uptake showed a marked decrease in transport Vmax (81.8 +/- 15 nmole/mg protein/15 sec for burned rats vs 185 +/- 17 nmole/mg protein/15 sec for controls, P less than 0.001). Transport Km also decreased from 0.25 +/- 0.004 mM for controls to 0.08 +/- 0.03 mM glutamine for burned rats (P less than 0.001). Kinetic studies performed at GLN levels greater than 0.6 mM showed that GLN uptake proceeded by a nonsaturable process in both the control and burned rats. No significant alteration in this nonsaturable component was observed.(ABSTRACT TRUNCATED AT 250 WORDS)