A weight-of-evidence approach to integrate suspended sediment source information.

Sediment monitoring, tracing and modelling are widely used to identify suspended sediment sources. Although each method has inherent limitations and uncertainties, their integration provides opportunities to form collective knowledge and encourages robust management strategies. This paper presents a Weight-of-Evidence approach to integrate multiple Lines-of-Evidence for identifying suspended sediment sources. Three sources of evidence were used: i) stream flow and suspended sediment monitoring at river gauges; ii) geochemical sediment tracing at river junctions; and iii) catchment-scale suspended sediment modelling of hillslope, gully, streambank and unsealed road erosion. We applied this approach on two data-poor catchments in Australia. Some reaches were consistently identified as major sources of sediment from all Lines-of-Evidence. However, inconsistencies between the types of evidence in other areas highlighted the high uncertainty in identifying suspended sediment sources in these areas and the need for further investigation. The integration framework maximised the use of scarce information, enabled explicit consideration of uncertainties for catchment management and identified where future monitoring and research should be targeted.

Thyroid-stimulating hormone and prostaglandin E1 stimulation of cyclic 3',5'-adenosine monophosphate in thyroid slices.

Thyroid-stimulating hormone increased the cyclic 3',5'-adenosine monophosphate concentration in dog thyroid slices during a 1-minute incubation period and produced a maximum effect soon thereafter. The elevation persisted for at least 30 minutes. The concentrations of the cyclic 3',5'-adenosine monophosphate increased as the TSH concentration was increased from 0.125 to 50 milliunits per milliliter. Prostaglandin E(1), which increases glucose oxidation in dog thyroid slices, also increased the concentration of cyclic 3',5'-adenosine monophosphate. Although sodium fluoride stimulates thyroid adenyl cyclase, it did not increase concentration of cyclic 3',5'-adenosine monophosphate. Carbamylcholine and menadiol sodium diphosphate augment glucose oxidation in dog thyroid slices but do not change concentrations of cyclic 3',5'-adenosine monophosphate.

Simvastatin plus nitric oxide synthase inhibition modulates remote organ damage following skeletal muscle ischemia-reperfusion injury.

UNLABELLED: Ischemia-reperfusion injury (IRI) to the lower extremities causes both local damage and serious dysfunction to remote organs, including lungs and kidneys. However, effective therapies are not available. This study aims to determine if simvastatin reduced the severity of remote damage following IRI. METHODS: Rats were given simvastatin before hind limb IRI. Lung and kidney tissues were assessed for neutrophil infiltration using myeloperoxidase assays and basement membrane damage by quantitative immunohistochemical measurement of collagen IV. The effect of nitric oxide synthase (NOS) inhibition on remote damage after IRI and simvastatin was assessed using the NOS inhibitor, L-NIO. RESULTS: Simvastatin (2 mg/kg) protected kidneys against IRI-induced neutrophil infiltration. Simvastatin also inhibited the IRI-induced activation of MMP-9 in the lungs. However, paradoxically, simvastatin exacerbated IRI-induced neutrophil infiltration into the lungs. IRI induced collagen IV degradation in the lungs but not in the kidneys. The degree of collagen breakdown in the lungs was significantly ameliorated by 2 mg/kg simvastatin. NOS inhibition markedly protected both the lungs and the kidneys against IRI-induced neutrophil infiltration but did not alter collagen IV degradation. Administration of simvastatin to L-Nio-treated animals enhanced the degree of protection against IRI-induced neutrophil infiltration in the kidneys but not in the lungs. CONCLUSIONS: Simvastatin protects against remote IRI-induced damage in the lungs and kidneys, suggesting statins may reduce the severity of IRI during major vascular surgery.

Effects of long-acting thyroid stimulator on thyrotropin stimulation of adenyl cyclase activity in thyroid plasma membranes.

Both thyroid-stimulating hormone (TSH) and long-acting thyroid stimulator (LATS) stimulated adenyl cyclase activity in plasma membranes obtained from bovine thyroid glands. The stimulation induced by LATS was much less than that obtained with maximal amounts of TSH. LATS inhibited TSH stimulation of adenyl cyclase activity while an equivalent amount of normal human gamma-globulin did not influence basal or TSH-stimulated activity. The inhibition by LATS appeared to be noncompetitive and was greatest when the plasma membranes were initially exposed to LATS for 30 min at 0 degrees C before being incubated with TSH for 10 min at 37 degrees C. Inhibition could still be demonstrated when the plasma membranes were incubated for 30 min at 0 degrees C with TSH before the addition of LATS. Prolonging the period of incubation of plasma membranes with LATS from 30 to 60 min did not augment the stimulation of adenyl cyclase or increase the inhibition of the effect of TSH. Papain digests of LATS also increased adenyl cyclase activity of thyroid plasma membrane and inhibited the stimulation induced by TSH. The inhibitory effect of LATS was not completely specific for TSH and thyroid plasma membranes since glucagon stimulation of adenyl cyclase in hepatic plasma membranes was also inhibited, but to a lesser extent. In contrast to the results obtained with thyroid plasma membranes, LATS did not influence basal adenyl cyclase activity in hepatic plasma membranes. Furthermore equivalent amounts of normal human gamma-globulin also decreased glucagon stimulation of adenyl cyclase activity in plasma membranes obtained from liver. The present data suggest that LATS stimulation of adenyl cyclase in thyroid plasma membranes might be due to a change in the membrane configuration rather than binding to a specific receptor site. Such modification of the membrane structure could interfere with the binding of TSH to specific receptors or to the subsequent stimulation of adenyl cyclase. However, the results do not exclude the possibility that some component in the preparation other than LATS might be responsible for the inhibition of the stimulation by TSH.

Effect of intraduodenal glucose administration on hepatic extraction of insulin in the anesthetized dog.

Extraction of insulin by the liver after administration of glucose in the duodenum has been studied in fourteen anesthetized dogs. Plasma insulin and glucose were measured in the portal vein hepatic vein and hepatic artery. During the control period 40+/-3% of the approximately 11 mU of insulin presented to the liver/min was removed during a single transhepatic passage. Within 5 min after glucose administration, the amount of insulin reaching the liver increased significantly. In some animals this increase preceded any significant increase in the glucose concentration of the femoral artery. After glucose administration, hepatic extraction of insulin remained unchanged in five animals and rose significantly in nine. In five of the latter animals, the increase may have been more apparent than real due to nonrepresentative sampling of hepatic venous blood. However, for the whole group of animals, comparison of arterial insulin levels with the amount of insulin delivered to the liver suggested a transient increase in insulin extraction between 5 and 50 min after glucose administration. In no animal was there a decrease in the proportion of insulin extracted by the liver after glucose administration. The results indicate that the extraction process is not saturable at physiological insulin levels. Prior to glucose administration, net hepatic glucose output averaged between 30 and 40 mg/min. After glucose administration, the liver began to take up glucose and there was a significant correlation between hepatic glucose uptake and the amount of insulin reaching the liver. However, since the amount of glucose presented to the liver also increased, it is not established that the insulin was responsible for the change in hepatic carbohydrate metabolism. The data demonstrate an increase in the absolute amount of insulin extracted by the liver after glucose administration and an important role for the liver in regulating peripheral insulin concentrations.

The content and metabolism of cyclic adenosine 3', 5'-monophosphate and cyclic guanosine 3', 5'-monophosphate in adenocarcinoma of the human colon.

Data from cultured cells have suggested that cyclic AMP and cyclic GMP may be important determinants of cell growth and transformation. However, few studies have examined cyclic nucleotide content and metabolism in naturally occurring tumors of man. Accordingly, in the present study we compared cAMP and cGMP levels and metabolism in carcinomas of the human colon to those of the adjacent uninvolved mucosa after therapeutic resection of these tissues. The cAMP content of the tumors, determined in samples frozen 30 min after excision, was significantly lower than that of the adjacent mucosa, when expressed on the basis of tissue wet weight, protein, or DNA content. By contrast, the cGMP content of the tumors was higher than that of the surrounding mucosa if calculated on the basis of tissue wet weight, but this difference did not persist when correction was made for the higher protein or DNA content of the tumors. Incubation of slices of mucosa or tumor with or without theophylline in vitro increased tissue cAMP and cGMP content above levels observed in frozen samples of the same tissue. However, after such incubations cAMP levels in the tumors remained clearly below that of the mucosa, while cGMP content of the two tissues did not differ. The failure of theophylline to abolish differences in cAMP content and the comparable activities of high and low Km cAMP-phosphodiesterase in homogenates of the two tissues suggested that the lower cAMP content of the tumors was a consequence of diminished cAMP synthesis rather than enhanced degradation. This possibility was supported by the reduction in basal and maximal prostaglandin E1 (PGE1)-responsive adenylate cyclase activity found in tumor homogenates relative to those of mucosa, and the lower levels of cAMP in tumor slices after incubation of the tissues with a maximal dose of PGE1 and theophylline. Since NaF-responsive adenylate cyclase activity was not significantly reduced in the tumors, the lower basal and PGE1 activities may not be related to a deficiency of the catalytic unit of the cyclase complex in this tissue. The role of reduced activity of the adenylate cyclase-cAMP system and/or reduced tissue cAMP-to-cGMP ratios in the pathogenesis of colonic carcinoma is uncertain, but these changes might favor unregulated cellular proliferation.

In vitro stimulation by long-acting thyroid stimulator of thyroid glucose oxidation and 32P incorporation into phospholipids.

Long-acting thyroid stimulator (LATS) increased glucose oxidation and (32)P incorporation into phospholipids in in vitro experiments with dog thyroid slices. The time course of the response was different from that obtained with thyroid-stimulating hormone (TSH), but was very similar to the delayed effect observed in vivo. During a 45 min incubation, TSH, but not LATS increased glucose oxidation, whereas in longer experiments up to 6 hr, both substances augmented (14)CO(2) production. Amounts of pooled human gamma globulin equivalent to LATS were inactive. Although TSH stimulated (32)P incorporation into phospholipids during a 2 hr incubation, LATS was ineffective. In longer incubations, from 4(1/2) to 8 hr, LATS did increase (32)P incorporation. The stimulatory effect of LATS was not abolished by anti-TSH antibody capable of neutralizing human TSH. Effects of LATS were also obtained with beef and pig thyroid slices. In addition to stimulation of glucose oxidation in dog thyroid slices, LATS occasionally also stimulated glucose oxidation in dog spleen and liver slices. Despite a 54-fold increase in LATS concentration, a satisfactory dose-response curve could not be demonstrated when (14)CO(2) production was measured.

Effects of thyroid-stimulating hormone on adenyl cyclase activity and intermediary metabolism of "cold" thyroid nodules and normal human thyroid tissue.

"Cold" thyroid nodules do not concentrate (131)I before or after thyrotropin (TSH) administration. In an attempt to elucidate the reason for this TSH unresponsiveness, the effect of TSH in vitro on several metabolic parameters was studied in 11 "cold" thyroid adenomas, 2 medullary carcinomas, and in the surrounding normal thyroid tissue. Basal adenyl cyclase activity, glucose-1-(14)C oxidation, and (32)P incorporation into phospholipids were significantly greater in the adenomas than in the adjacent normal thyroid; basal cyclic 3',5'-adenosine monophosphate (cyclic AMP) concentration and adenine-(3)H incorporation into (3)H-labeled cyclic AMP were not different. In adenomas as well as normal thyroid, all parameters responded significantly to in vitro TSH stimulation. The response to TSH of adenyl cyclase activity and (32)P incorporation was enhanced in adenomas compared with that of the adjacent normal thyroid. These differences were not explained by an increased cellularity of the adenomas. Medullary carcinomas did not respond to TSH in any of the above parameters. The studies demonstrate an intact, TSH-responsive adenyl cyclase-cyclic AMP system in the adenomas and, accordingly, imply the presence of receptor sites for TSH on the cells of the adenoma. The failure of such nodules to concentrate (131)I may be owing to a subsequent impairment in the expression of cyclic AMP action on iodine metabolism.

Role of the endocrine pancreas in the kalemic response to acute metabolic acidosis in conscious dogs.

Metabolic acidosis due to organic acids infusion fails to elicit hyperkalemia. Although plasma potassium levels may rise, the increase is smaller than in mineral acid acidosis. The mechanisms responsible for the different effects of organic acid acidosis and mineral acid acidosis remain undefined, although dissimilar hormonal responses by the pancreas may explain dissimilar hormonal responses by the pancreas may explain the phenomena. To test this hypothesis, beta-hydroxybutyric acid (7 meq/kg) or hydrochloric acid (3 meq/kg) was infused over 30 min into conscious dogs (n = 12) with chronically implanted catheters in the portal, hepatic, and systemic circulation, and flow probes were placed around the portal vein and hepatic artery. Acid infusion studies in two groups of anesthetized dogs were also done to assess the urinary excretion of potassium (n = 14), and to evaluate the effects of acute suppression of renal electrolyte excretion on plasma potassium and on the release/uptake of potassium in peripheral tissues of the hindleg (n = 17). Ketoacid infusion caused hypokalemia and a significant increase in portal vein plasma insulin, from the basal level of 27 +/- 4 microU/ml to a maximum of 84 +/- 22 microU/ml at 10 min, without changes in glucagon levels. By contrast, mineral acid acidosis of similar severity resulted in hyperkalemia and did not increase portal insulin levels but enhanced portal glucagon concentration from control values of 132 +/- 25 pg/ml to 251 +/- 39 pg/ml at 40 min. A significant decrease in plasma glucose levels due to suppression of hepatic release was observed during ketoacid infusion, while no changes were observed with mineral acid infusion. Plasma flows in the portal vein and hepatic artery remained unchanged from control values in both acid infusion studies. Differences in renal potassium excretion were ruled out as determinants of the disparate kalemic responses to organic acid infusion compared with HCl acidosis. Evaluation of the arteriovenous potassium difference across the hindleg during ketoacid infusion demonstrates that peripheral uptake of potassium is unlikely to be responsible for the observed hypokalemia. Although the tissue responsible for the different kalemic responses could not be defined with certainty, the data are compatible with an hepatic role in response to alterations in the portal vein insulin and/or glucagon levels in both acid infusion studies. We propose that cellular uptake of potassium is enhanced by hyperinsulinemia in ketoacid infusion, and release of potassium results from increased glucagon levels in HCl acidosis. Whether the changes in plasma potassium that other types od organic acid acidosis produce are accounted for by a similar hormonal mechanism remains to be determined.

Effects of vasopressin and prostaglandin E 1 on the adenyl cyclase-cyclic 3',5'-adenosine monophosphate system of the renal medulla of the rat.

Vasopressin increased adenyl cyclase activity in homogenates of both inner and outer renal medulla of the rat. It also increased the concentration of cyclic 3',5'-adenosine monophosphate (AMP) in slices of both inner and outer medulla but not in renal cortex. In the inner medulla, a concentration of prostaglandin E(1) (PGE(1)), which was ineffective by itself significantly reduced the stimulation of adenyl cyclase activity and cyclic AMP concentration induced by vasopressin. These results are consistent with the hypothesis that PGE(1) can compete with vasopressin for adenyl cyclase-binding sites. However, the findings in the outer medulla suggest the situation is more complex. Although 10(-8) M PGE(1) had no effect by itself and inhibited the vasopressin-induced elevation of cyclic AMP, larger amounts of PGE(1) increased both adenyl cyclase activity and cyclic AMP levels. The maximum effect on the latter parameter was at least 6 times as great as that of maximum amounts of vasopressin.

Demonstration of iodide transport defect but normal iodide organification in nonfunctioning nodules of human thyroid glands.

Benign and malignant nodules in human thyroid glands, which did not concentrate iodide in vivo, were also unable to accumulate iodide in vitro. The mean thyroid-to-medium ratio (T/M) in seven benign nodules was 0.8+/-0.2 compared with 7+/-2 in adjacent normal thyroid tissue. In four malignant thyroid nodules, the mean T/M was 0.5+/-0.1 compared with 11+/-4 in adjacent normal thyroid. Despite the inability of such nodules to concentrate iodide, iodide organification was present but was only one-half to one-third as active as in surrounding normal thyroid. Thyroid-stimulating hormone (TSH) increased iodide organification equally in both benign nodules and normal thyroid although it had no effect in three of the four malignant lesions. The reduction in organification is probably related to the absence of iodide transport, since incubation of normal thyroid slices with perchlorate caused similar diminution in iodide incorporation but no change in the response to TSH. Monoiodotyrosine (MIT) and di-iodotyrosine (DIT) accounted for most of the organic iodide in both the nodules and normal tissue. The MIT/DIT ratio was similar in normal and nodule tissue. The normal tissue contained much more inorganic iodide than the nodules, consistent with the absence of the iodide trap in the latter tissue. The thyroxine content of normal thyroid was 149+/-17 mug/g wet wt and 18+/-4 mug/g wet wt in the nodules. The transport defect in the nodules was not associated with any reduction in total, Na(+)-K(+)- or Mg(++)-activated ATPase activities or the concentration of ATP. Basal adenylate cyclase was higher in nodules than normal tissue. Although there was no difference between benign and malignant nodules, the response of adenylate cyclase to TSH was greater in the benign lesions. These studies demonstrate that nonfunctioning thyroid nodules, both benign and malignant, have a specific defect in iodide transport that accounts for their failure to accumulate radioactive iodide in vivo. In benign nodules, iodide organification was increased by TSH while no such effect was found in three of four malignant lesions, suggesting additional biochemical defects in thyroid carcinomas.

Inhibition of thyroid-stimulating hormone stimulation of protein kinase, glucose oxidation, and phospholipid synthesis in thyroid slices previously exposed to the hormone.

Prior exposure of thyroid slices to thyrotropin (TSH) induced refractoriness to subsequent stimulation of the cyclic AMP system by the hormone. Although the inhibition is incomplete, we examined whether the reduction in cyclic AMP was sufficient to alter other metabolic effects of TSH. Bovine or dog thyroid slices were incubated with or without 5-100 mU/ml TSH for 1-2h, washed, and then incubated without hormone for 1-2h. Half of the slices not exposed to TSH initially were then incubated with buffer and half were exposed to 5-100 mU/ml TSH. Slices initially incubated with TSH were also incubated with or without TSH in the third incubation. During the refractory period, TSH activation of protein kinase was inhibited even though the hormone still caused some increase in cyclic AMP concentrations. However, protein kinase activity was fully responsive to dibutyryl cyclic AMP when slices were incubated with it during the third incubation. Stimulation of glucose oxidation by TSH was significantly decreased in thyroid slices previously incubated with the hormone. During refractoriness, stimulation of glucose oxidation caused by prostaglandin E1 and dibutyryl cyclic AMP was also significantly diminished but that due to acetylcholine was not. Thus even though dibutyryl cyclic AMP could fully activate protein kinase activity during refractoriness, its effect on glucose oxidation was still inhibited, suggesting that the metabolic block responsible for this refractoriness was distal to activation of protein kinase. Stimulation of 32Pi incorporation into phospholipid by TSH and acetylcholine was also inhibited during refractoriness. Despite reduction of the stimulatory effect of TSH, binding of 125ITSH was not modified by prior incubation of thyroid slices with TSH. These results indicate that changes in the TSH receptor are not responsible for the development of refractoriness and other metabolic sites besides activation of adenylate cyclase appear to be involved.

Exposure of thyroid slices to thyroid-stimulating hormone induces refractoriness of the cyclic AMP system to subsequent hormone stimulation.

These studies evaluated the influence of an initial exposure of thyroid slices to thyroid-stimulating hormone (TSH) on the subsequent responsiveness to the hormone. Bovine thyroid slices were incubated with or without 50 mU/ml TSH for varying periods and then incubated in hormone-free medium for varying periods. Subsequently, slices were incubated for 20 min with 10 mM theophylline and with or without TSH. Cylic AMP was measured after the third incubation. Phosphodiesterase and adenylate cylase were assayed in homogenates prepared from slices after the second incubation. In some experiments prostaglandin E1, puromycin, thyroxine, and triiodothyronine and propylthiouracil were included in the media. In other experiments, low does of TSH (1 AND 10 mU/ml) were used instead of 50 mU/ml. Slices previously exposed to TSH have decreased responsiveness of the adenylate cyclase-cylic AMP system. Such refractoriness is hormone specific since initial exposure to prostaglandin E1 decreases the subsequent response to this substance but not to TSH. Refractoriness to TSH develops only when the first incubation is at least 30 min. It is not reversed by 5 h of incubation without hormone. Incubation of thyroid slices with puromycin does not eliminate refractoriness. The decreased response to TSH cannot be explained by release of thyroxine, triiodothyronine, or iodide from the slices. Phosphodiesterase activity is not increased during the refractory period. The decreased cyclic AMP response to TSH is associated with diminished response of adenylate cyclase activity to the hormone. Guanosine triphosphate (1 mM) increased adenylate cyclase activity in both control and TSH treated tissue, but the effect was significantly less in the latter. Although with guanosine triphosphate, TSH increased adenylate cyclase activity in TSH treated tissue, the enzyme activity was still less than that present in control tissue incubated with guanosine triphosphate and TSH. NaF caused an equivalent stimulation of adenylate cyclase in both control and TSH treated tissue. These results suggest that the refractoriness represents an alteration in hormone binding or the coupling of the bound hormone to the adenylate cyclase activity rather than any modification of the catalytic site of the enzyme.

Effects of alpha and beta adrenergic blockade on hepatic glucose balance before and after oral glucose. Role of insulin and glucagon.

In conscious dogs, phentolamine infusion significantly increased fasting portal vein insulin, glucagon, and decreased net hepatic glucose output and plasma glucose. Propranolol significantly decreased portal vein insulin, portal flow, and increased hepatic glucose production and plasma glucose. Phentolamine, propranolol, and combined blockade reduced glucose absorption after oral glucose. alpha, beta, and combined blockade abolished the augmented fractional hepatic insulin extraction after oral glucose. Despite different absolute amounts of glucose absorbed and different amounts of insulin reaching the liver, the percent of the absorbed glucose retained by the liver was similar for control and with alpha- or beta blockade, but markedly decreased with combined blockade. Our conclusions are: (a) phentolamine and propranolol effects on basal hepatic glucose production may predominantly reflect their action on insulin and glucagon secretion; (b) after oral glucose, alpha- and beta-blockers separately or combined decrease glucose release into the portal system; (c) net hepatic glucose uptake is predominantly determined by hyperglycemia but can be modulated by insulin and glucagon; (d) direct correlation does not exist between hepatic delivery and uptake of insulin and net hepatic glucose uptake; (e) alterations in oral glucose tolerance due to adrenergic blockers, beyond their effects on glucose absorption, can be, to a large extent, mediated by their effects on insulin and glucagon secretion reflecting both hepatic and peripheral glucose metabolism.

Effect of dexamethasone on hepatic glucose and insulin metabolism after oral glucose in conscious dogs.

To examine whether hyperinsulinemia associated with glucocorticoid treatment results solely from hypersecretion of insulin or also involves altered fractional hepatic extraction, oral glucose (1 g/kg body wt) was administered to dogs with or without dexamethasone treatment (2 mg/d for 2 d). Dexamethasone significantly increased basal glucose and insulin concentrations in the portal vein, hepatic vein, and femoral artery, reduced basal fractional hepatic extraction of insulin from 43 +/- 4% to 22 +/- 4%, and, after oral glucose, increased retention by the liver of net glucose released into the portal system from 27 +/- 4% to 53 +/- 13%. Intraportal insulin infusion (1 and 2 mU/kg per min) after 7 d of dexamethasone treatment (2 mg/d) caused less suppression of endogenous glucose production, and less exogenous glucose was required to maintain an euglycemic clamp than in control animals. Dexamethasone treatment is associated with: decreased basal fractional hepatic insulin extraction contributing to hyperinsulinemia; and less suppression of endogenous glucose production and increase in peripheral uptake in response to insulin, but no reduction in net hepatic glucose uptake after oral glucose.

Differential effects of oral, peripheral intravenous, and intraportal glucose on hepatic glucose uptake and insulin and glucagon extraction in conscious dogs.

The effect of equal (1.1 +/- 0.1 g/kg body wt) amounts of glucose administered orally, or by peripheral intravenous or intraportal infusion on hepatic glucose uptake and fractional hepatic extraction of insulin and glucagon was studied in conscious dogs with chronically implanted Doppler flow probes on the portal vein and hepatic artery and catheters in the portal vein, hepatic vein, carotid artery, and superior mesenteric vein. Portal vein and hepatic vein plasma flow increased only after oral glucose administration. Arterial plasma glucose increased equally to 150-160 mg/100 ml after all three routes of glucose administration. Portal vein glucose was similar after oral (195 +/- 15 mg/100 ml) and intraportal glucose infusion (215 +/- 11 mg/100 ml) and significantly higher than after peripheral intravenous glucose. Hepatic glucose uptake after oral (68 +/- 4%) and intraportal glucose administration (65 +/- 7%) significantly exceeded that after peripheral intravenous glucose infusion (23 +/- 5%). The amount of insulin above basal presented to the liver during the 180 min after oral glucose was 7.6 +/- 1.3 U, 4.3 +/- 0.6 U after intraportal glucose, and 4.1 +/- 0.6 U after peripheral intravenous glucose. Hepatic extraction of insulin increased significantly after oral glucose (42 +/- 3 to 61 +/- 4%), but was unchanged after intraportal and peripheral intravenous glucose administration. When the portal vein glucose levels achieved during peripheral intravenous glucose infusion for 90 min were maintained by a subsequent 90-min intraportal glucose infusion, hepatic glucose uptake was significantly greater during the intraportal glucose infusion. Glucagon secretion was suppressed equally after oral glucose, intraportal glucose, and peripheral intravenous glucose administration; fractional hepatic extraction of that hormone, which was significantly less than that of insulin, was unchanged. These results indicate that hepatic glucose uptake is significantly greater after oral and intraportal glucose administration than after peripheral intravenous glucose infusion. This difference is not simply related to the amount of glucose or insulin presented to the liver and the increased hepatic glucose uptake did not depend solely upon the augmented fractional hepatic extraction of insulin. Hepatic extraction of insulin and hepatic glucose uptake appear to be regulated independently.

In vitro and in vivo refractoriness to thyrotropin stimulation of iodine organification and thyroid hormone secretion.

Earlier studies indicated that initial exposure of thyroid slices to thyrotropin diminished responsiveness of the adenylate cyclase-cyclic AMP system, glucose oxidation, and (32)P(i) incorporation into phospholipids upon readdition of the hormone. The present studies demonstrate that slices from dog, beef, and human thyroid glands initially incubated with thyrotropin (TSH) were less responsive to subsequent addition of the hormone when organification of iodide was examined. Increasing the amount of TSH did not overcome the refractoriness induced by the initial exposure to the hormone. Furthermore, the stimulatory effects of dibutyryl cyclic AMP and prostagladin E(1) were abolished in slices previously incubated with TSH. Development of such refractoriness did not depend upon new protein synthesis and was not abolished by 1 mM prophylthiouracil in the first incubation. Addition of 0.1 muM thyroxine or triiodothyronine or 1.5 muM iodide during all three incubations did not modify the response to TSH, added for the first time in the third incubation. However, 1 mM iodide in the buffer during all three incubations inhibited the response to TSH during the third incubation. During the refractory period, effects of TSH on colloid droplet formation were also diminished. The in vivo effect of TSH on serum l- triiodothyronine in rats was significantly reduced when the rats had been injected with TSH 8 h earlier. These studies demonstrate that TSH-induced refractoriness also includes effects on organification of iodine and secretion of thyroid hormone. The results cannot be adequately explained by unresponsiveness of adenylate cyclase because effects of dibutyryl cyclic AMP and prostagladin E(1) were also inhibited by prior exposure to TSH.

Effect of prostaglandin E 1 on certain renal actions of parathyroid hormone.

Parathyroid hormone increased basal adenyl cyclase activity and that increase was inhibited by prostaglandin E(1) (PGE(1)). Tissue cyclic 3',5'-adenosine monophosphate (cyclic AMP) concentrations were increased by parathyroid hormone and that increase was likewise inhibited by PGE(1). Both parathyroid hormone and dibutyryl cyclic AMP increased (32)P incorporation into renal cortical phospholipids. PGE(1) diminished the effect of parathyroid hormone but not dibutyryl cyclic AMP to influence that parameter. PGE(1) likewise modulated the effect of parathyroid hormone but not dibutyryl cyclic AMP to decrease fractional phosphate reabsorption by the renal tubule. It is suggested that PGE(1) inhibits the effect of parathyroid hormone by decreasing its effect on adenyl cyclase. Such interaction may be important in modulating the intracellular action of parathyroid hormone on kidney cortex.

Catalase-dependent peroxidative metabolism in the alveolar macrophage during phagocytosis.

EVIDENCE FOR THE PRESENCE OF PEROXIDATIVE METABOLISM IN RABBIT ALVEOLAR MACROPHAGES (AM) HAS BEEN OBTAINED FROM THE FOLLOWING OBSERVATIONS: (a) catalase is present in high concentrations; (b) peroxidase activity could not be detected employing guaiacol as substrate; (c) the irreversible inhibition of AM catalase by aminotriazole served as a detection system for H(2)O(2) and demonstrated increased intracellular H(2)O(2) after phagocytosis; (d) formate oxidation, a marker of catalase-dependent peroxidations, occurs in resting AM and is increased by phagocytosis; (c) measurements of H(2)O(2) accumulation in a dialysate of AM demonstrated twofold increase during phagocytosis; and (f) aminotriazole diminishes O(2) utilization and (14)CO(2) production from labelled glucose and pyruvate. It is concluded that, while catalase-dependent H(2)O(2) metabolism is not essential for particle entry, this pathway represents one of the metabolic pathways stimulated by particle entry in the AM.

"Essential" hypernatremia due to ineffective osmotic and intact volume regulation of vasopressin secretion.

A physiological explanation for sustained hyperosmolality was sought in a patient with histiocytosis. During 23 days of observation with only sodium intake regulated at 100 mEq daily, elevation (mean 310 mOsm/kg of water) and fluctuation (range 298-323) of the fasting plasma osmolality were recorded. The presence of endogenous vasopressin was indicated by the patient's ability to concentrate the urine to as high as 710 mOsm/kg of water with a creatinine clearance of 84 cc/min, and by dilution of the urine in response to alcohol. The failure of increasing fluid intake to as high as 6.2 liters daily to lower the plasma osmolality indicated that deficient fluid intake was not solely responsible for the elevated plasma osmolality. Hypertonic saline infusion during water diuresis resulted in the excretion of an increased volume of dilute urine. The water diuresis continued despite a rise in plasma osmolality from 287 to 339. An isotonic saline infusion initiated during hydropenia resulted in a water diuresis which continued despite a rise in the plasma osmolality from 303 to 320. Stable water diuresis induced during recumbency by either oral ingestion of water or intravenous infusion of normal saline was terminated by orthostasis and resumed with the return to the recumbent position. Antecedent alcohol ingestion blocked the antidiuresis of orthostasis. The data are interpreted as indicating impairment of the osmoreceptor mechanism as the primary cause of the hyperosmolar syndrome. They also indicate that vasopressin secretion was regulated primarily by changes in effective blood volume. Chlorpropamide was found to be an effective treatment for the syndrome.