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Modification of nasal membrane potential difference with inhaled amiloride and loperamide in the cystic fibrosis (CF) mouse.

BACKGROUND: In the airway of subjects with cystic fibrosis (CF) the combination of defective cAMP mediated chloride secretion and enhanced sodium absorption leads to dehydration of mucosal mucus and is reflected in an increased trans-epithelial potential difference (PD). The airway secretions may be less viscid and easier to expectorate if sodium (and water) reabsorption is inhibited. METHODS: To evaluate the response to sodium blocking agents, changes in the nasal PD in 20 transgenic CF mice were compared with 14 control mice (MF1 strain) before and after administration of nebulised amiloride and loperamide (both in a concentration of 1 mmol/l). The duration of action for both drugs was also determined after a single inhaled dose of 1 mmol/l for two minutes. RESULTS: The median basal PD was -24 mV in controls and -28 mV in CF mice (p < 0.01). This fell in CF mice after amiloride and loperamide administration by 15 mV and 14 mV, respectively, compared with a decrease of 7 mV and 5.5 mV in controls (p < 0.01). There was no further change in PD when loperamide was given after amiloride. This suggests that loperamide and amiloride may act on sodium absorption via similar mechanisms. Loperamide had a longer duration of action after a single administration than amiloride. CONCLUSION: The administration of amiloride and loperamide reduces the transepithelial potential and inhibits sodium reabsorption in the CF mouse airway. Further studies are required to determine if the more prolonged action of loperamide could be of therapeutic use.

Amiloride↗

Disturbed release of growth hormone in mature dogs: a comparison with congenital growth hormone deficiency.

An acquired defect in growth hormone secretion in mature dogs has been associated with some forms of generalised alopecia. In an attempt to elucidate the pathogenesis of the disturbance in growth hormone release, the plasma concentrations of growth hormone and insulin-like growth factor I (IGF-I) were measured in two seven-year-old poodles with alopecia and, for comparison, in two young German sheperd dogs with congenital hyposomatotropism (pituitary dwarfism). In the poodles the basal concentrations of growth hormone were low, although often above the detection limit of the assay. The concentrations of IGF-I were in the reference range for healthy poodles. No growth hormone could be detected in the plasma of the German sheperd dogs and the concentrations of IGF-I were very low. Stimulation with clonidine and growth hormone releasing hormone (GHRH) before and after repeated injections of GHRH did not result in significant increases in growth hormone concentrations in plasma. The concentrations of growth hormone in the poodles fluctuated at low levels during the test period. In the German sheperd dogs the levels of growth hormone remained unmeasurable during the stimulation tests. It was concluded that in the two poodles the basal concentrations of growth hormone were sufficient to maintain normal IGF-I concentrations, and thus the release of growth hormone was considered appropriate. Based upon measurements of urinary corticoids and a review of the literature it is suggested that the lack of a growth hormone response to stimulation was due to the enhanced release of somatostatin as a result of mild and fluctuating hyperadrenocorticism.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Hormones↗

Stimulatory effect of PYY-(3-36) on gonadotropin secretion is potentiated in fasted rats.

Development and normal function of the reproductive axis requires a precise degree of body energy stores. Polypeptide YY-(3-36) [PYY-(3-36)] is a gastrointestinal secreted molecule recently shown to be involved in the control of food intake with agonistic activity on neuropeptide Y (NPY) receptor subtypes Y2 and Y5. Notably, PYY-(3-36) has been recently demonstrated as putative regulator of gonadotropin secretion in the rat. However, the "reproductive" facet of this factor remains to be fully elucidated. In this context, we report herein our analyses of the influence of the nutritional status on the effects of PYY-(3-36) upon GnRH and gonadotropin secretion. The major findings of our study are 1) the stimulatory effect of central administration of PYY-(3-36) on LH secretion was significantly enhanced after fasting and blocked by a GnRH antagonist; 2) besides central effects, PYY-(3-36) elicited LH and FSH secretion directly at the pituitary level, a response that is also augmented by fasting; 3) PYY-(3-36) inhibited GnRH secretion by hypothalamic fragments from male rats fed ad libitum, whereas a significant stimulatory effect was observed after fasting; and 4) the increase in the gonadotropin responsiveness to PYY-(3-36) in fasting was not associated with changes in the expression of Y2 and Y5 receptor genes at hypothalamus and/or pituitary. In conclusion, our study extends our previous observations suggesting a relevant, mostly stimulatory, role of PYY-(3-36) in the control of gonadotropin secretion. Strikingly, such an effect was significantly enhanced by fasting. Considering the proposed decrease in PYY-(3-36) levels after fasting, the possibility that reduced PYY-(3-36) secretion might contribute to defective function of the gonadotropic axis after food deprivation merits further investigation.

Animals↗

Selective decontamination of the digestive tract attenuated the myocardial inflammation and dysfunction that occur with burn injury.

This study examined the effects of oral antibiotics to selectively decontaminate the digestive tract (SDD) on postburn myocardial signaling, inflammation, and function. We hypothesized that antibiotic therapy to eliminate pathogens from the gastrointestinal (GI) tract would reduce myocardial inflammatory responses and improve postburn myocardial performance. Sprague-Dawley rats received polymyxin E (15 mg), tobramycin (6 mg), and 5-flucytosin (100 mg) by oral gavage twice daily for 3 days preburn and 24 h postburn. Experimental groups included 1) sham burn given vehicle (3 ml water), 2) sham plus SDD, 3) burn over 40% total body surface area (TBSA) plus SDD, and 4) burn over 40% TBSA given vehicle. All burns received lactated Ringer solution (4 mg.kg(-1).%burn(-1)); myocardial signaling (PKCepsilon/p38 MAPK/NF-kappaB) was studied 2, 4, and 24 h postburn; and cytokine secretion (systemic and myocyte secreted cytokines, ELISA) and cardiac function were examined 24 h postburn. Vehicle-treated burn injury increased myocardial PKCepsilon/p38 MAPK expression, promoted NF-kappaB nuclear translocation, promoted TNF-alpha, IL-1beta, IL-6, and IL-10 secretion, and impaired myocardial function. SDD attenuated burn-related proinflammatory myocardial signaling, cytokine secretion, and myocardial contractile defects. Our data suggest that burn-related loss of GI barrier function and translocation of microbial products serve as upstream mediators of postburn myocardial inflammatory signaling and dysfunction.

Animals↗

Liquid secretion inhibitors reduce mucociliary transport in glandular airways.

Because of its possible importance in cystic fibrosis (CF) pulmonary pathogenesis, the effect of anion and liquid secretion inhibitors on airway mucociliary transport was examined. When excised porcine tracheas were treated with ACh to induce gland liquid secretion, the rate of mucociliary transport was increased nearly threefold from 2.5 +/- 0.5 to 6.8 +/- 0.8 mm/min. Pretreatment with both bumetanide and dimethylamiloride (DMA), to respectively inhibit Cl(-) and HCO secretion, significantly reduced mucociliary transport in the presence of ACh by 92%. Pretreatment with the anion channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid similarly reduced mucociliary transport in ACh-treated airways by 97%. These agents did not, however, reduce ciliary beat frequency. Luminal application of benzamil to block liquid absorption significantly attenuated the inhibitory effects of bumetanide and DMA on mucociliary transport. We conclude that anion and liquid secretion is essential for normal mucociliary transport in glandular airways. Because the CF transmembrane conductance regulator protein likely mediates Cl(-), HCO, and liquid secretion in normal glands, we speculate that impairment of gland liquid secretion significantly contributes to defective mucociliary transport in CF.

Acetylcholine↗

Energy restriction with protein restriction increases basal metabolism and meal-induced thermogenesis in rats.

We previously observed an increased sympathetic nervous system (SNS) activity that was partly responsible for a defect in the insulin secretion response to glucose after postweaning protein-energy restriction (PER) in female rats. These results, together with other data on low-protein feeding, suggested that a low protein-to-energy ratio (P/E) in the diet could stimulate energy expenditure (EE), but direct measurements of EE have never been reported under conditions of PER. The goal of the present study was thus to quantify the changes induced by PER to body composition, the various parameters of EE, and plasma triiodothyronine levels. PER induced severe growth retardation, but the subcutaneous white and interscapular brown adipose tissue masses were preserved. Basal metabolism, meal-induced thermogenesis, and triiodothyronine levels were increased, but substrate utilization by the working muscles was unaffected. Meal-induced thermogenesis was increased by spontaneous activity in PER rats only. These results suggest that rats adapt to a low P/E in the diet by burning part of their excess nonprotein energy and storing the remaining excess in subcutaneous adipose tissue.

Animals↗

Cisplatinum-induced lesion of proximal tubule acidification in the rat.

Rats were given a 4- to 6-mg/kg body weight intraperitoneal injection of the antitumor drug, Cisplatin, 5-7 days prior to experiments to study tubule acidification by clearance and stationary microperfusion techniques. Cisplatin reduced the glomerular filtration rate markedly and caused a moderate degree of metabolic acidosis, but urine acidification (pH) was well maintained. Proximal tubule stationary pH and bicarbonate concentrations, as measured by pH microelectrodes, were significantly increased. The defect of proximal H+ secretion is reflected by increased acidification half-times (from 4.44 to 10.2 s) and reduced bicarbonate reabsorption to 37% of control values. H-ion back flux, measured during tubule and capillary perfusions with Ringer's bicarbonate- and CO2-free phosphate solutions, was reduced to 68% of control values. The apparent H-ion permeability was lowered from 0.79 to 0.54 cm/s. These results indicate that proximal acidification is reduced by impairment of H+ transport and not by increased transepithelial H+ shunting. Blunted acidification is compatible with a reduction in the number of Na/H exchangers in the proximal brush border and/or a decrease in the apical sodium gradient, the driving force for proximal H-ion secretion. Cortical distal tubule acidification, measured by double-barreled ion-exchange resin/PD microelectrodes, was not significantly affected by Cisplatin. This accounts for the observation that, in spite of the impaired proximal acidification, urine pH is kept within the normal range.

Acid-Base Equilibrium↗

Serum levels of androstenedione, testosterone and dehydroepiandrosterone sulfate in patients with premature ovarian failure to age-matched menstruating controls.

Serum concentrations of androstenedione, testosterone and dehydroepiandrosterone sulfate (DHEAS) were measured in 29 patients with premature ovarian failure (POF) and an identical number of age-matched normal control subjects. The study was aimed at determining possible differences in androgen concentrations of ovarian and adrenal origin in POF patients and age-matched normal menstruating controls. Serum testosterone and DHEAS concentrations in the 2 populations were not significantly different. The serum androstenedione concentration in the POF patient group (3,077.50 +/- 1,122.33 pmol/l) was significantly lower than in age-matched normal control subjects (4,167.70 +/- 1,381.09 pmol/l, p < 0.005), possibly reflecting the loss of ovarian androstenedione secretion and/or a subtle defect in adrenal steroidogenic capacity.

Adult↗

Lung overexpression of angiostatin aggravates pulmonary hypertension in chronically hypoxic mice.

Exposure to hypoxia leads to the development of pulmonary hypertension (PH) as a consequence of pulmonary smooth muscle hyperplasia. Hypoxia concomitantly stimulates lung expression of angiogenic factors. To investigate the role of angiogenesis processes in development of hypoxic PH, we examined the effects of lung overexpression of angiostatin, an angiogenesis inhibitor, on development of hypoxic PH and lung endothelial cell (EC) density. Angiostatin delivery was achieved by a defective adenovirus expressing a secretable angiostatin K3 molcule driven by the cytomegalovirus promoter (Ad.K3). Comparison was made with a control vector containing no gene in the expression cassette (Ad.CO1). Treatment with Ad.K3 (300 plaque-forming units [pfu]/cell) inhibited cultured human pulmonary artery EC migration by 100% and proliferation by 50%, but was without effects on human pulmonary artery smooth muscle cells. After intratracheal administration of Ad.K3 (109 pfu) to mice, angiostatin protein became detectable in bronchoalveolar lavage fluid. Mice pretreated with Ad.K3 1 d before a 2-wk exposure to hypoxia (10% O2) showed more severe pulmonary hypertension than Ad.CO1-pretreated controls, as assessed by higher right ventricular systolic pressure (36.5 +/- 2.4 versus 30.2 +/- 1.4, respectively), aggravation of right ventricular hypertrophy (P < 0.05), and muscularization of distal vessels (P < 0.01). Lung factor VIII, CD31 immunostaining, as well as eNOS expression were significantly increased after exposure to hypoxia in Ad.CO1-pretreated controls, but decreased in both normoxic and hypoxic animals after treatment with Ad.K3. The results show that inhibition of hypoxia-induced stimulation of lung angiogenic processes aggravates development of hypoxic PH. This suggests that endogenous lung angiogenesis counteracts development of hypoxic PH.

Angiostatins↗

Efcts of chronic ethanol feeding on serum lipoprotein metabolism in the rat.

In rats, chronic ethanol feeding was found to enhance the postprandial hyperlipemia and to increase the incorporation of dietary palmitic acid-(3)H and intravenously injected L-lysine-(14)C into serum lipoproteins. The main increases of total amount, labeling, and specific activity of lipid and protein occurred in the d < 1.019 lipoprotein fraction. Fat absorption and the clearance of injected chylomicrons were not affected by ethanol feeding. Blocking of lipoprotein and chylomicron removal with Triton did not prevent the action of ethanol on serum lipids, indicating that the ethanol effect is not likely due to defective removal of lipids from the circulation. Ethanol enhanced the incorporation of chylomicron fatty acids into newly synthetized very low density lipoproteins, as shown by an increased reappearance of the fatty acid label into the lipids of this fraction after injection of palmitate-(14)C/glycerol-(3)H doubly labeled chylomicrons. These results indicate that alcoholic hyperlipemia is due, at least in part, to an increase in newly synthetized lipoproteins. The hyperlipemia produced by ethanol was accompanied by hepatic steatosis. The simultaneous production of fatty liver and hyperlipemia makes it unlikely that defective lipoprotein synthesis or secretion is a primary mechanism for the pathogenesis of the alcoholic fatty liver.

Animals↗

Effects of 3-nitro-L-tyrosine on thyroid function in the rat: an experimental model for the dehalogenase defect.

The effects on thyroid function of an inhibitor of tyrosine dehalogenase, 3-nitro-L-tyrosine (MNT) have been investigated in rats. In preliminary studies, marked inhibition of iodotyrosine deiodination was demonstrated in rats drinking 8 mM MNT. A series of experiments was then performed in which rats received Remington low iodine diet and 8 mM MNT as drinking fluid. This regimen had the following effects, compared to the effects of a low iodine diet alone: (a) a decrease in serum protein-bound iodine, elevation of serum thyrotropin level, goiter, and growth inhibition all prevented or reversed by iodine supplements: (b) on initiation of MNT, a 2- to 3-fold increase in the rate of release of radioiodine from the thyroid and concomitant urinary excretion of large amounts of organic iodine: and (c) after 2 wk of MNT, a greatly increased rate of thyroidal uptake and release of (131)I, an increase in the ratio of monoiodotyrosine-(131)I to diiodotyrosine-(131)I in thyroid proteolysates and the appearance of labeled iodotyrosines in serum. Acute administration of MNT intraperitoneally to rats on either an iodine-deficient or iodine-sufficient diet did not inhibit thyroidal uptake of (131)I or alter the distribution of (131)I among thyroidal iodoamino acids. It is concluded that MNT is an effective inhibitor of iodotyrosine deiodination in vivo, without other important actions on thyroid function. Thus, MNT treatment affords a model for the human dehalogenase defect. By provoking iodotyrosine secretion and consequent urinary loss of iodine, MNT can exaggerate the effects of a low iodine intake, producing goitrous hypothyroidism despite a rapid rate of iodine turnover in the thyroid.

Administration, Oral↗

Pathogenesis of hypocalcemia in magnesium depletion. Normal end-organ responsiveness to parathyroid hormone.

Hypocalcemia in the hypomagnesemic state in man is usually attributed to refractoriness of end-organs to the calcemic action of parathyroid hormone. We studied the responsiveness of end-organs to bovine parathyroid extract (PTE) in magnesium-depleted and control dogs by the following three methods after thyroparathyroidectomy: (a) assessment of the calcemic response to a set dose of PTE (0.3 U/kg per hr); (b) assessment of PTE dose required to attain normocalcemia; (c) evaluation of regression lines of plasma calcium concentration on PTE dose. The calcemic response of magnesium-depleted thyroparathyroidectomized puppies to a set dose of PTE was similar to that of control puppies. There was no significant difference in the dose of PTE required to attain normocalcemia nor in the dose-response relations between the plasma calcium concentration and the PTE dose. In a group of magnesium-depleted puppies with intact thyroid and parathyroid glands, the dose of PTE required to attain normocalcemia was similar to that required in thyroparathyroidectomized animals, indicating calcitonin was not a factor contributing to hypocalcemia. We conclude that hypocalcemia in magnesium-depleted puppies is not due to refractoriness of end-organs to the calcium-mobilizing action of parathyroid hormone. Defective synthesis or diminished secretion of parathyroid hormone is suggested as an explanation.

Alkaline Phosphatase↗

Amino acid substitution (Ile194----Thr) in exon 5 of the lipoprotein lipase gene causes lipoprotein lipase deficiency in three unrelated probands. Support for a multicentric origin.

Studies on the molecular biology of lipoprotein lipase (LPL) deficiency have been facilitated by the availability of LPL gene probes and the recent characterization of gene mutations underlying human LPL deficiency. Typically, missense mutations have predominated and show a preferential localization to exons 4 and 5. This distribution supports earlier studies attributing functional significance to residues encoded by these exons. We now report a further missense mutation within exon 5 of the LPL gene in three unrelated patients. Amplification of individual exons by the polymerase chain reaction and direct sequencing revealed a T----C transition at codon 194 of the LPL cDNA which results in a substitution of threonine for isoleucine at this residue. The catalytic abnormality induced by this mutation was confirmed through in vitro mutagenesis studies in COS-1 cells. Transfection with a LPL cDNA containing the codon 194 transition resulted in the synthesis and secretion of a catalytically defective protein. The Thr194 substitution was associated with two different DNA haplotypes, consistent with a multicentric origin for this mutation.

Alleles↗

Treatment with the oral antidiabetic agent troglitazone improves beta cell responses to glucose in subjects with impaired glucose tolerance.

Impaired glucose tolerance (IGT) is associated with defects in both insulin secretion and action and carries a high risk for conversion to non-insulin-dependent diabetes mellitus (NIDDM). Troglitazone, an insulin sensitizing agent, reduces glucose concentrations in subjects with NIDDM and IGT but is not known to affect insulin secretion. We sought to determine the role of beta cell function in mediating improved glucose tolerance. Obese subjects with IGT received 12 wk of either 400 mg daily of troglitazone (n = 14) or placebo (n = 7) in a randomized, double-blind design. Study measures at baseline and after treatment were glucose and insulin responses to a 75-g oral glucose tolerance test, insulin sensitivity index (SI) assessed by a frequently sampled intravenous glucose tolerance test, insulin secretion rates during a graded glucose infusion, and beta cell glucose-sensing ability during an oscillatory glucose infusion. Troglitazone reduced integrated glucose and insulin responses to oral glucose by 10% (P = 0.03) and 39% (P = 0.003), respectively. SI increased from 1.3+/-0.3 to 2.6+/-0.4 x 10(-)5min-1pM-1 (P = 0.005). Average insulin secretion rates adjusted for SI over the glucose interval 5-11 mmol/liter were increased by 52% (P = 0.02), and the ability of the beta cell to entrain to an exogenous oscillatory glucose infusion, as evaluated by analysis of spectral power, was improved by 49% (P = 0.04). No significant changes in these parameters were demonstrated in the placebo group. In addition to increasing insulin sensitivity, we demonstrate that troglitazone improves the reduced beta cell response to glucose characteristic of subjects with IGT. This appears to be an important factor in the observed improvement in glucose tolerance.

Administration, Oral↗

Reserpinization: effects on parotid gland function.

Chronic reserpinization of mice and rabbits affected parotid gland function; cholinergic and beta-adrenergic-stimulated amylase release were significantly reduced, and cyclic-AMP and cyclic-GMP levels were significantly elevated above control-stimulated levels. Amylase released by dibutyryl-c-AMP was also reduced, suggesting a defect in stimulus-secretion coupling subsequent to c-AMP formation.

Amylases↗

Protein characterization of fluorosed human enamel.

Despite extensive investigation, the development mechanism or mechanisms resulting in dental fluorosis are unknown. Several hypotheses suggest abnormal matrix synthesis, secretion, and delayed and/or defective matrix degradation with retention of enamel protein. The purpose of this study was to characterize the protein composition of fluorosed human enamel. Nine permanent moderately fluorosed (developed in a 3.2 ppm H2O area) and ten permanent normal control teeth (from individuals with < 0.2 ppm F in their drinking water) were evaluated. The enamel fluoride concentration, protein content, and amino acid composition were determined for each tooth. The enamel proteins were further characterized by gel electrophoresis and by Western blot analysis by means of polyclonal antibodies raised against recombinant amelogenin protein. Fluorotic enamel had significantly elevated (p = 0.0001) F levels compared with normal enamel (mean [F-] fluorosed = 431 ppm; mean [F-] control = 62 ppm). While there was a significantly greater protein content by weight in fluorosed enamel compared with normal enamel (mean fluorosed = 0.27%; mean control = 0.11%), the amino acid profiles were similar for fluorosed and normal enamel. Gel electrophoresis showed fluorosed enamel to have a greater diversity of primarily low-molecular-weight proteins compared with normal enamel. Western blot analysis did not indicate retention of amelogenin in either fluorosed or normal enamel. This investigation showed that the protein content of fluorosed enamel was greater than that of normal enamel; however, the amino acid compositions were similar for fluorosed and normal enamel. Furthermore, there does not appear to be retention of significant amounts of amelogenin in fully mature, moderately fluorosed human enamel. Although delayed removal of the enamel matrix proteins may play a role in the hypomineralization defects seen in fluorosed enamel, the majority of these proteins are absent in the mature tissue of these moderately fluorosed teeth.

Amelogenesis↗

Transient partial hGH deficiency in prepubertal children with delay of growth.

UNLABELLED: The hGH response to an ornithin or an insulin test was measured in 105 children from 11-18 yr old with delay of growth more than 2 SD. Besides 74 subjects with normal values and 7 with complete lack of response, 24 subjects exhibited a partial rise of GH. Most of the latter had decreasing growth rate and no sign of puberty. Out of 15 assessed for GH function after onset of puberty, 14 showed a normal response accompanying a markedly increased growth velocity. Four other subjects with partial response who were receiving sexual hormones for 48 hr before the second test showed a normal response also. An exogenous hGH treatment administered in two of these patients resulted in a marked and sustained growth increase far before entering puberty. SPECULATION: The findings that plasma GH responses to stimulation tests is reduced in some children with decreasing growth rate before puberty and return to normal after onset of sexual development, would suggest a transient and functional defect in growth hormone secretion and the physiologic role of sexual hormones on GH release mechanism at that period of life.

Adolescent↗

Defective cytokine expression but adult-type T-cell receptor, CD8, and p56lck modulation in CD3- or CD2-activated T cells from neonates.

Expression of IL-2, interferon-gamma, and IL-3 mRNA and proteins was investigated in peripheral blood mononuclear cells from cord blood after activation with phytohemagglutinin, CD2, or CD3 MAb. The results showed that interferon-gamma and IL-3 expression was decreased in cord peripheral blood mononuclear cells when compared with expression observed in adult peripheral blood mononuclear cells, irrespective of the stimulation used. In addition, in newborn cells a defect in IL-2 secretion and mRNA expression was observed in response to CD2 or CD3 MAb but not in response to phytohemagglutinin-mediated activation. We further analyzed the modulation of nonlymphokine genes under the same protocol of stimulations. The results indicate that in newborn cells, despite a reduced lymphokine expression observed after CD2 or CD3 MAb activation, the up-regulation of the T-cell receptor, CD8, and p56lck was similar to that found in adult cells, as was also found after phytohemagglutinin activation of both types of cells. These data are in favor of a deficient T-cell responsiveness to CD2 or CD3 MAb in newborn cells. This impairment of the T-cell response appears to selectively affect lymphokine gene expression because the modulation of other genes also implicated in T cell activation is not altered.

Adult↗