Is urea pulsing in toadfish related to environmental O2 or CO2 levels?

The neurochemical, serotonin (5-hydroxytryptamine; 5-HT) is involved in the regulation of toadfish pulsatile urea excretion as well as the teleost hypoxia response. Thus, the goal of this study was to determine whether environmental conditions that activate branchial chemoreceptors also trigger pulsatile urea excretion in toadfish, since environmental dissolved oxygen levels in a typical toadfish habitat show significant diel fluctuations, often reaching hypoxic conditions at dawn. Toadfish were fitted with arterial, venous and/or buccal catheters and were exposed to various environmental conditions, and/or injected with the O(2) chemoreceptor agonist NaCN or the 5-HT(2) receptor agonist alpha-methyl-5HT. Arterial PO(2), as well as ammonia and urea excretion were monitored. Natural fluctuations in arterial PO(2) levels in toadfish did not correlate with the occurrence of a urea pulse. Chronic exposure (24 h) of toadfish to hyperoxia was without effect on nitrogen excretion, however, exposure to hypoxia caused a significant reduction in the frequency of urea pulses, and exposure to hypercapnia resulted in a reduction in the percentage of nitrogen waste excreted as urea. Of toadfish exposed acutely to hypoxia, 20% pulsed within 1 h, whereas none pulsed after normoxic or hypercapnic treatments. Furthermore, 20% of fish injected intravenously with NaCN pulsed within 1 h of injection, but no fish pulsed after injection of NaCN into the buccal cavity. To test whether environmental conditions affected 5-HT(2) receptors, toadfish were injected with alpha-methyl-5HT, which elicits urea pulses in toadfish. No significant differences in pulse size occurred among the various environmental treatments. Our findings suggest that neither the environmental conditions of hypoxia, hyperoxia or hypercapnia, nor direct branchial chemoreceptor activation by NaCN play a major role in the regulation of pulsatile urea excretion in toadfish.     

Branchial and renal handling of urea in the gulf toadfish,Opsanus beta: the effect of exogenous urea loading

The objective of this study was to determine whether the pulsatile facilitated diffusion transport mechanism (tUT) found in the gills of the gulf toadfish (Opsanus beta) and the active secretion transporter thought to be present in its kidney could be saturated when faced with elevated plasma urea concentrations. Toadfish were infused with four consecutive exogenous urea loads at a rate of 0, 150, 300 and 600 micromol kg(-1) h(-1). Initial plasma and urine urea concentrations were 8.1+/-0.9 and 12.4+/-1.5 mmol l(-1), respectively, and steadily increased with increasing infused loads of urea to a maximum of 36.8+/-2.8 mmol l(-1) in the plasma and 39.8+/-6.5 mmol l(-1) in the urine. There was only a very weak relationship (r=0.17) between pulse size (measured as branchial excretion during pulsatile excretion of urea) and plasma urea concentration (slope=9.79 micromol-N kg(-1) per mmol-N l(-1); P<0.05) suggesting that the branchial excretion mechanism was already saturated at normal plasma urea concentrations. Urine flow rate (0.15+/-0.03 ml kg(-1) h(-1)) and glomerular filtration rate (0.025+/-0.004 ml kg(-1) h(-1)) remained constant throughout the experiment despite the increased volume load. Renal urea secretion rate maintained a strong linear relationship (r=0.84) to plasma urea levels (slope=0.391 micromol-N kg(-1) h(-1) per mmol-N l(-1); P<0.001) with no observable transport maximum, suggesting that the renal secretory transport mechanism was not saturated even at plasma urea levels well above normal, in contrast to the branchial excretion mechanism.     

Protein synthesis, RNA concentrations, nitrogen excretion, and metabolism vary seasonally in the Antarctic holothurian Heterocucumis steineni (Ludwig 1898)

Seasonal changes in protein and nitrogen metabolism have not previously been reported in any Antarctic suspension-feeding species that ceases feeding for extended periods in winter. To provide comparison with data reported on Nacella concinna, a species that continues to feed in winter, we have measured feeding activity; oxygen consumption; ammonia, urea, and fluorescamine-positive substance (FPS) excretion; O : N ratios; body wall protein synthesis; RNA to protein ratios; and RNA activity at three times during the year in an Antarctic suspension-feeding holothurian. Feeding activity ceased for 4 mo during winter, and oxygen consumption rates decreased from 8.79+/-0.43 micro mol h(-1) to 4.48+/-0.34 micro mol h(-1). Ammonia excretion also decreased during winter from 2,600+/-177 nmol N h(-1) to 974+/-70 nmol N h(-1), but urea excretion rates increased from 178+/-36 nmol N h(-1) to 281+/-110 nmol N h(-1), while FPS excretion rates remained unchanged throughout the year with a seasonal mean of 88+/-13 nmol N h(-1). Oxygen to nitrogen ratios ranged between 6 and 10, suggesting that proteins were used as the primary metabolic substrate. Body wall protein synthesis rates decreased from 0.35%+/-0.03% d(-1) in summer to 0.23% d(-1) in winter, while RNA to protein ratios decreased from 33.10+/-1.0 microg RNA mg(-1) protein in summer to 27.88+/-1.3 microg RNA mg(-1) protein in winter, and RNA activity was very low, ranging between 0.11+/-0.01 mg protein mg(-1) RNA d(-1) in summer and 0.06+/-0.01 mg protein mg(-1) RNA d(-1) in winter. Heterocucumis steineni shows a larger seasonal decrease in oxygen consumption and ammonia excretion between February (summer) and July (winter) than N. concinna, while the proportional decrease in protein synthesis rates is similar in both species.     

The toadfish serotonin 2A (5-HT(2A)) receptor: molecular characterization and its potential role in urea excretion

Based on early pharmacological work, the serotonin 2A (5-HT(2A)) receptor subtype is believed to be involved in the regulation of toadfish pulsatile urea excretion. The goal of the following study was to characterize the toadfish 5-HT(2A) receptor at a molecular level, to determine the tissues in which this receptor is predominantly expressed and to further investigate the pharmacological specificity of toadfish pulsatile urea excretion by examining the effect of ketanserin, a 5-HT(2A) receptor antagonist, on resting rates of pulsatile urea excretion. The full-length toadfish 5-HT(2A) receptor encodes a 496 amino acid sequence and shares 57-80% sequence identity to 5-HT(2A) receptors of other organisms, with 100% conservation among important ligand-binding residues. Toadfish 5-HT(2A) receptor mRNA expression was highest in the swim bladder and gonad, followed by the whole brain. All other tissues tested (esophagus, stomach, anterior intestine, posterior intestine, rectum, liver, kidney, heart, muscle and gill) had mRNA expression levels that were significantly less than whole brain. Toadfish 5-HT(2A) receptor mRNA expression within the brain was highest in the hindbrain, telencephalon and midbrain/diencephalon regions. Treatment with the 5-HT(2A) receptor antagonist, ketanserin, resulted in a significant decrease in the pulsatile component of spontaneous urea excretion due to a reduction in urea pulse size with no significant change in pulse frequency. These results lend further support for the 5-HT(2A) receptor in the regulation of pulsatile urea excretion in toadfish.     

Ammonia excretion increased and urea excretion decreased in urine of a new world nectarivorous bat with decreased nitrogen intake

We determined the effect of water and nitrogen intake on nitrogenous waste composition in the nectarivorous Pallas's long-tongued bat Glossophaga soricina (Phyllostomidae) to test the hypothesis that bats reduce excretion of urea nitrogen and increase the excretion of ammonia nitrogen as nitrogen intake decreases and water intake decreases. Because changes in urine nitrogen composition are expected only in animals whose natural diets are low in nitrogen and high in water content, we also measured maintenance nitrogen requirements (MNR). We hypothesized that, similar to other plant-eating vertebrates, nectarivorous bats have low MNR. Our nitrogen excretion hypothesis was partly proved correct. There was an increase in the proportion of N excreted as ammonia and a decrease in the proportion excreted as urea in low-nitrogen diets. The proportion of N excreted as ammonia and urea was independent of water intake. Most individuals were ureotelic (n = 28), and only a few were ureo-ammonotelic (n = 3) or ammonotelic (n = 2). According to our nitrogen requirement hypothesis, apparent MNR (60 mg kg(-0.75) d(-1)) and truly digestible MNR (54 mg N kg(-0.75) d(-1)) were low. A decrease in urea excretion in low-nitrogen diets may result from urea recycling from liver to the gut functioning as a nitrogen salvage system in nectarivorous bats. This mechanism probably contributes to the low MNR found in Pallas's long-tongued bats.     

不同剂量阿霉素致大鼠局灶节段硬化肾病模型的建立比较

目的探讨不同剂量阿霉素对大鼠局灶节段硬化肾病模型的影响。方法左侧肾切除加尾静脉注射不同剂量阿霉素致大鼠肾脏局灶节段性硬化,观察不同剂量阿霉素对模型大鼠成活率、24 h尿蛋白定量、血清肌酐、尿素氮、肾脏病理的影响。结果不同阿霉素注射剂量组大鼠4周、8周成活率随着注射剂量的升高呈逐渐下降趋势,且4周、8周时阿霉素注射剂量4.5～6 mg/kg组模型大鼠成活率均低于50%;8周时成活率与注射剂量呈高度显著性负相关（r=0.9045,P〈0.01）。各阿霉素注射剂量组于1周出现尿蛋白明显升高（P〈0.01）、2周出现血清肌酐明显升高（P〈0.01）、4周出现血清尿素氮明显升高（P〈0.01）,并均呈进行性增高,2周时除3 mg/kg组外,其余各组血清尿素氮较正常组高（P〈0.01,P〈0.05）;8周时各注射剂量组大鼠24 h尿蛋白定量、血清肌酐、血清尿素氮与阿霉素注射剂量呈高度显著性正相关（r=0.942 9,P〈0.01;r=0.938 4,P〈0.01;r=0.956 8,P〈0.01）。各组大鼠肾脏病理均提示肾小球出现局灶节段硬化表现,且硬化程度随注射剂量的增加而呈加重趋势。结论阿霉素尾静脉注射剂量3 mg/kg模型组大鼠死亡率低,同时大鼠肾脏病理又能表现出符合人类肾小球局灶节段硬化的改变,是较为理想的造模剂量。     

Glucocorticoid receptors are involved in the regulation of pulsatile urea excretion in toadfish

The objectives of this study were to characterize the pattern of pulsatile urea excretion in the gulf toadfish in the wake of exogenous cortisol loading and to determine the receptors involved in the regulation of this mechanism. Toadfish were fitted with indwelling arterial catheters and were infused with isosmotic NaCl for 48 h after which fish were treated with cortisol alone, cortisol+peanut oil, cortisol+RU486 (a glucocorticoid receptor antagonist) or cortisol+spironolactone (a mineralocorticoid receptor antagonist). Upon cortisol loading, fish treated with cortisol alone, cortisol+oil or cortisol+spironolactone experienced a two- to threefold reduction in pulsatile urea excretion. This reduction was due to a decrease in urea pulse size with no effect on pulse frequency compared to values measured during the control NaCl infusion period. In addition, these fish showed an increase in plasma urea concentrations upon treatment. These apparent effects of cortisol treatment were abolished in fish treated with cortisol+RU486. In contrast, these fish showed an increase in pulsatile urea excretion mediated by a twofold increase in pulse size with no change in frequency. Likewise, fish treated with cortisol+RU486 showed a significant decrease in plasma urea concentrations over the course of the experiment. The findings of this study indicate that high levels of cortisol reduce pulsatile urea excretion by decreasing pulse size. In addition, it appears that glucocorticoid receptors and not mineralocorticoid receptors are involved in the regulation of the toadfish pulsatile urea excretion mechanism.Communicated by G. Heldmaier     

虫草素对慢性肾脏病大鼠血管内皮损伤的保护作用及其机制

摘要 目的：探讨虫草素对慢性肾脏病(chronic kidney disease,CKD)大鼠血管内皮损伤的保护作用及其机制。方法：慢性肾脏病大鼠(n=48)随机平分为四组-模型组、虫草素高剂量组、虫草素中剂量组、虫草素低剂量组,虫草素高剂量组、虫草素中剂量组、虫草素低剂量组,分别给予虫草素160 mg/kg、80 mg/kg、40 mg/kg,模型组灌胃给予等量生理盐水,每天1次,连续给药治疗2周。结果：虫草素高剂量组、虫草素中剂量组、虫草素低剂量组治疗1周、治疗2周的24 h尿量、血清尿素氮(blood urea nitrogen,BUN)与肌酐(serum creatinine,Scr)水平都低于模型组(P<0.05),体重都高于模型组(P<0.05),不同剂量组别之间对比差异也有统计学意义(P<0.05)。虫草素高剂量组、虫草素中剂量组、虫草素低剂量组治疗2周的结缔组织生长因子(Connective tissue growth factor,CTGF)、血管内皮生长因子(Vascular endothelial growth factor,VEGF)蛋白相对表达水平高于模型组(P<0.05),肾小球硬化指数、肾小管损伤评分都低于模型组(P<0.05),不同剂量组别之间对比差异也有统计学意义(P<0.05)。结论：虫草素在慢性肾脏病大鼠的应用能发挥血管内皮损伤保护作用,促进改善大鼠的肾功能,提高大鼠的体重,且具有剂量依赖性。     

The effects of arginine vasotocin and catecholamines on nitrogen excretion and the cardio-respiratory physiology of the gulf toadfish, Opsanus beta

Simultaneous measurements of cardio-respiratory variables, oxygen uptake and whole body urea/ammonia/tritiated water effluxes were performed on cannulated gulf toadfish, Opsanus beta, before and after intra-arterial injection of the vasoactive agents, adrenaline, isoproterenol and arginine vasotocin. These experiments were conducted to test the hypothesis that the phenomenon of pulsatile urea excretion might reflect sudden changes in the general diffusive properties of the gill for solute transfer. Injection of isoproterenol (final nominal circulating level = 10⁻⁶ mol l⁻¹), was used as a tool to maximise the diffusive and perfusive conditions for branchial solute transfer. This protocol caused a pronounced reduction in arterial blood pressure, an elevation of cardiac frequency and associated increases in whole body urea and tritiated water effluxes; ammonia excretion and oxygen uptake were unaffected. Injection of adrenaline (final nominal circulating level=10⁻⁶ mol l⁻¹), caused a significant increase in arterial blood pressure and a tachycardia, yet nitrogen excretion and oxygen uptake were unaffected. Injection of arginine vasotocin, caused a dose-dependent (final nominal circulating levels = 10⁻¹¹–10⁻⁹ mol l⁻¹) increase in arterial blood pressure without affecting cardiac or ventilation frequency. At the two higher concentrations, arginine vasotocin caused large and transient increases in urea excretion without significantly affecting ammonia, water or oxygen fluxes. These results suggest that increased gill diffusive or perfusive conductance, while capable of augmenting urea efflux, cannot fully explain the sudden and massive increases in urea transfer associated with pulsatile urea excretion in toadfish. It is suggested that pulsatile urea excretion in this species may reflect a specific enhancement of urea excretion under the control of the neurohypophyseal hormone, arginine vasotocin. Accepted: 21 April 1998     

Field studies on the ureogenic gulf toadfish, in a subtropical bay. II. Nitrogen excretion physiology

In order to examine the in situ nitrogen excretion physiology of gulf toadfish ( Opsanus beta ) (Fam. Batrachoididae), several biochemical and physiological measurements relating to urea synthesis and excretion were measured in samples taken from freshly collected gulf toadfish from a subtidal population in Biscayne Bay, Florida, U.S.A. This indirect appoach was used, instead of direct measurements of nitrogen excretion, because nitrogen excretion patterns of gulf toadfish are altered markedly during the first 24 h of capture disturbance or laboratory confinement. The values obtained for plasma cortisol levels, and the activities of hepatic ornithine-urea cycle enzymes, including glutamine synthetase (and its partitioning between cytosolic and mitochondrial compartments), suggest that gulf toadfish in Biscayne Bay may excrete a substantial portion of their waste nitrogen as urea. Also conducted were correlation analyses of several biotic variables (plasma [cortisol], enzyme activities, plasma [urea], hepatosomatic index, and plasma [Ca⁺⁺]) with several abiotic variables (temperature, salinity, depth and dissolved oxygen), and with collection site and season. Results of these analyses are discussed in the context of hypotheses to explain ureotely in this teleost fish.     

Does pulsatile urea excretion serve as a social signal in the gulf toadfish Opsanus beta?

This study evaluated the hypothesis that the pulsatile excretion of urea by toadfish could serve as a social signal. In the first experiment, physiological parameters were measured in pairs of dominant and subordinate toadfish. Subordinate toadfish had elevated concentrations of circulating plasma cortisol, an effect maintained even after cannulation. In the second experiment, one fish of a pair was injected with 14C-urea, and the occurrence of urea pulses during social encounters was documented. Social status did not influence the order of pulsing, that is, whether a dominant or subordinate fish pulsed first during a social encounter. However, in seven out of eight pairs, both toadfish pulsed within 2 h of each other, indicating some form of communication between fish. In the third and final experiment, the response of toadfish to urea (natural or synthetic) was observed. There was a tendency for toadfish to avoid synthetic urea but there was no apparent behavioural response to water containing toadfish urea. Pulsing events do not appear to play an integral role during social encounters as previously hypothesised, but the close timing of pulses in toadfish pairs suggests some transfer of information.     

Diel patterns of nitrogen excretion, plasma constituents, and behavior in the gulf toadfish (Opsanus beta) in laboratory versus outdoor mesocosm settings

Nitrogen excretion by the gulf toadfish (Opsanus beta) is of interest because of its high proportion of urea excretion compared with that of other teleosts. To better understand the factors influencing the timing of nitrogen excretion, the ratio of excreted urea∶ammonia, and the effector molecules regulating these processes, gulf toadfish were subjected to a series of experiments that moved them progressively from internal laboratory to outdoor mesocosm settings while assessing their behavior, nitrogen excretion patterns, levels of plasma hormones/effectors, and other parameters. In confined flux chambers in both laboratory and outdoor settings, toadfish nitrogen excretion was largely observed as urea pulses, with no apparent diel patterns to the pulses. Unrestrained toadfish in mesocosms exhibited distinctly nocturnal behavior, remaining exclusively in shelters during the day but taking several forays out into the mesocosm at night. In contrast to nitrogen excretion patterns in chambers, urea and ammonia were coexcreted in mesocosms and ratios for urea∶ammonia were very close to 1∶1 for both fed and fasted toadfish. The majority of measured excretion (and corresponding declines in plasma urea levels) occurred during two distinct periods of pulsing during daylight hours (0600-1000 and 1600-1800 hours). The declines in plasma urea associated with excretion were preceded by/coincided with declines in plasma cortisol. No day/night or hourly patterns in plasma serotonin (5-hydroxytryptamine [5-HT]) were observed, but there was a strong positive correlation among all samples between plasma urea and 5-HT. There was also a negative correlation between plasma cortisol and 5-HT. As expected for a nocturnally active species, plasma melatonin was significantly lower in daylight hours. A variety of enzyme activities (glutamine synthetase, glutaminase) and mRNA levels (glutamine synthetase, urea transporter, and Rhesus proteins) showed no significant variation over a diel cycle. Unlike prior laboratory studies, our results show that gulf toadfish in a natural setting have a distinctly diurnal pattern of nitrogen excretion and that ammonia and urea are coexcreted. The decline in plasma cortisol associated with urea pulses noted in prior laboratory studies was not as evident in the natural setting.     

Induction of sister-chromatid exchanges and chromosomal aberrations in hematopoietic tissue of a marine fish following in vivo exposure to genotoxic carcinogens

The development of procedures to assess genetic damage in fish exposed in situ to point sources of aquatic pollution can be expected to contribute to the evaluation of the role of genotoxic contaminants in epizootic neoplasia in fish populations. To this end methods have been developed for assessing the in vivo induction of chromosomal aberrations (CAs) and sister-chromatid exchanges (SCEs) in tissues of a marine teleost, the oyster toadfish, which may be applicable to other species. An alternative to the solid tissue and squash techniques for metaphase preparation permits the resolution of more than 100 SCEs/metaphase in toadfish kidney cells, which have moderately large chromosomes (0.122 pg DNA/chromosome). The bleeding of toadfish which have been injected with 5-bromodeoxyuridine (BrdUrd) and the subsequent use of hematopoietic tissue (kidney) for cytogenetic analysis was shown to increase the metaphase yield and provide a more predictable production of second-division metaphases required for SCE analysis. With these methods linear dose-dependent increases in chromatid-type exchange CAs and SCEs were obtained with i.p. exposure to ethyl methanesulfonate (EMS) and cyclophosphamide (CP). The doses required to double the observed control SCE frequencies (least effective doses) were 170 mg/kg for EMS and 7.4 mg/kg for CP. which are comparable to those reported for rodent bone marrow assays. A BrdUrd-sensitive site for chromatid breakage was observed on a pair of apparently homologous acrocentric chromosomes for the toadfish.     

Fluoxetine: A Randomized Clinical Trial in the Maintenance of Weight Loss

Because current weight-reduction treatments have considerable recidivism, a therapy that could help patients maintain weight loss would be of benefit. A six-center, randomized, double-blind trial compared the effects of the specific serotonin uptake inhibitor, fluoxetine hydrochloride, and placebo on maintenance of weight loss. Obese outpatients who had lost ≤3.6 kg after 8 weeks of single-blind fluoxetine 60 mg/day in the qualification phase (N=317 [70.4% of patients entered]; mean ± standard deviation [SD] weight loss, 6.8 ± 2.8 kg) were randomly assigned to fluoxetine 20 mg/day (N=104), fluoxetine 60 mg/day (N=106), or placebo (N=107) for 40 weeks (maintenance phase). Patients received minimal nutrition/dietary counseling. Qualification phase clinic visits were biweekly; maintenance phase visits were monthly for 4 months, then bimonthly for 6 months. Patients treated with fluoxetine 60 mg/day continued to lose weight for 8 additional weeks (16 weeks total; maximum mean ± SD weight loss, 7.2 ± 4.6 kg); those treated with fluoxetine 20 mg/day or placebo began to regain weight. Mean weights remained below baseline values at week 48 (all groups); treatment differences were not statistically significant. Study completion rates were comparable (fluoxetine 20 mg/day, 67.3%; fluoxetine 60 mg/day, 56.6%; placebo, 67.3%; p = 0.175). Among commonly reported adverse events (>10% incidence), only asthenia was reported statistically significantly (p< 0.050) more frequently with fluoxetine than with placebo. Few patients discontinued for any single adverse event. Fluoxetine 60 mg/day was effective for a longer period than fluoxetine 20 mg/day or placebo in maintaining weight loss. Overall, fluoxetine was safe and well tolerated.     

A comparative analysis of parvalbumin expression in pinfish (Lagodon rhomboides) and toadfish (Opsanus sp.)

This study examines the role of a myoplasmic protein, parvalbumin, in enhancing muscle relaxation by fishes. Parvalbumin is thought to bind free Ca²⁺ during muscle contraction, thereby reducing intracellular [Ca²⁺] in muscle and speeding muscle relaxation by reducing Ca²⁺ availability to the troponin complex. We hypothesized that parvalbumin expression is ubiquitously expressed in fish muscle and that its expression levels and role in muscle relaxation would depend on the activity level and the thermal environment of a given fish species. Muscle contractile properties and patterns of parvalbumin expression were examined in pinfish (Lagodon rhomboides) and two species of toadfish (gulf toadfish, Opsanus beta, and oyster toadfish, Opsanus tau). Unlike another sparid (sheepshead), the active swimming pinfish does not express parvalbumin in its slow-twitch red muscle. However, both sheepshead and pinfish have relatively high levels of parvalbumin in their myotomal white muscle. Gulf toadfish from the Gulf of Mexico expressed higher levels of parvalbumin and had faster muscle relaxation rates than oyster toadfish from more northern latitudes. The faster muscle of gulf toadfish also expressed relatively more of one parvalbumin isoform, suggesting differences in the binding properties of the two isoforms observed in toadfish swimming muscle. Parvalbumin expression and its role in muscle relaxation appear to vary widely in fishes. There are many control points involved in the calcium transient of contracting muscle, leading to a variety of species-specific solutions to the modulation of muscle relaxation.     

Rank order of success favors longer duration of imidazole-based therapy for Helicobacter pylori in duodenal ulcer disease: a randomized pilot study

Background. Studies on eradication therapy in developing countries have shown a success rate of 70–85%, which is suboptimal. Duration of therapy may be an important factor dictating eradication success in such regions. Aim. The study was undertaken to evaluate the effect of increasing the treatment period on eradication of Helicobacter pylori in duodenal ulcer disease. Methods. A randomized trial was carried out in which 64 consecutive H. pylori‐infected patients with duodenal ulcer disease were enrolled. The patients were randomized to one of the three trial arms. Therapy consisted of lansoprazole 30 mg twice a day (b.i.d.), amoxycillin 1 g b.i.d. and tinidazole 500 mg b.i.d. The treatment period was 1 week in group I, 2 weeks in group II and 3 weeks in group III. At inclusion, patients underwent endoscopy and the presence of H. pylori was documented by a positive urease test and C14 urea breath test. Four weeks after completion of eradication therapy, the patients were subjected to repeat endoscopy to assess ulcer healing and tests for H. pylori infection. Results. Sixty‐four patients (55 male and nine female; mean age 35.5 years) were enrolled in each group. The H. pylori eradication rate for group I (1 week of therapy) was 47.6%, that for group II (2 weeks of therapy) was 80%, and that for group III (3 weeks of therapy) was 91.3% (p = .003). The ulcer healing rates were 71.4, 80 and 95.6% in groups I, II and III, respectively (p = .09). Conclusion. The 3‐week regimen significantly improved the eradication rate as compared with the 1‐week regime. Increasing the duration of therapy significantly improved the chances of eradication of H. pylori in duodenal ulcer disease.     

Dietary arginine degradation is a major pathway in ureagenesis in juvenile turbot (Psetta maxima)

Recent studies indicate that urea excretion is responsive to protein intake and that turbot, Psetta maxima, appear to differ from other species by their urea excretion pattern and levels. This study was undertaken to evaluate the influence of dietary nitrogen and arginine on ureagenesis and excretion in turbot. Juvenile turbot (29 g) were fed semi-purified diets containing graded levels of nitrogen (0-8% dry matter) and arginine (0-3% dry matter) for 6 weeks. Growth data showed that turbot have high dietary nitrogen (123 mg/kg metabolic body weight/day) and very low dietary arginine (9.3 mg/kg metabolic body weight/day) requirements for maintenance. Requirements for unit body protein accretion were 0.31 g and 0.15 g for nitrogen and arginine respectively. Post-prandial plasma urea levels and urea excretion rates showed that urea production was significantly (P<0.05) influenced by dietary arginine levels. While hepatic arginase (EC 3.5.3.1) activity increased significantly (P<0.05) with increasing dietary arginine levels, activities of other enzymes of the ornithine urea cycle were very low. Our data strongly suggest that the ornithine urea cycle is not active in the turbot liver and that dietary arginine degradation is a major pathway of ureagenesis in turbot.     

Attenuation of diabetic nephropathy by tocotrienol: Involvement of NFkB signaling pathway

AimDiabetic nephropathy is a serious complication for patients with diabetes mellitus. Approximately 30–40% of patients with type I and 15% with type II diabetes mellitus develop end stage renal disease. The study was designed to evaluate the impact of tocotrienol on renal function and reno-inflammatory cascade in streptozotocin-induced diabetes.Main methodsStreptozotocin (STZ)-induced diabetic rats were treated with tocotrienol (25, 50 and 100 mg/kg), α-tocopherol (100 mg/kg) or with vehicle form 5th to 8th weeks. After 8 weeks, urine albumin excretion, urine output, serum creatinine, blood urea nitrogen, creatinine and urea clearance were measured. Cytoplasmic and nuclear fractions of kidney was prepared for the quantification of oxidative–nitrosative stress (lipid peroxidation, superoxide dismutase, catalase, non protein thiols, total nitric oxide), tumor necrosis factor-alpha (TNF-α), tissue growth factor-1beta (TGF-β1), p65 subunit of NFκβ and caspase-3.Key findingsAfter 8 weeks of STZ injection, the rats produced significant alteration in renal function, increased oxidative–nitrosative stress, TNF-α, TGF-β1, caspase-3 activity in cytoplasmic lysate and active p65 subunit of NFκβ in nuclear lysate of kidney of diabetic rats. Interestingly, co-administration of tocotrienol significantly and dose-dependently prevented biochemical and molecular changes associated with diabetes. Tocotrienol (100 mg/kg) was demonstrated to be more effective than α-tocopherol (100 mg/kg). Moreover, diabetic rats treated with insulin-tocotrienol combination produced more pronounced effect on molecular parameters as compared to their respective groups.SignificanceTaken together, the data reveal that tocotrienol modulates the release of profibrotic cytokines, oxidative stress, ongoing chronic inflammation and apoptosis and thus exerts a marked renoprotective effect.     

Nitrogen metabolism and excretion in Allenbatrachus grunniens(L): effects of variable salinity, confinement, high pH and ammonia loading

The nitrogen metabolism and excretion patterns of the grunting toadfish Allenbatrachus grunniens and the effects of salinity on these processes were examined. Individuals of A. grunniens were subjected to several experimental treatments, including variable salinity (2 to 30), high pH (8·5 compared to 7·0 for controls), high environmental ammonia (10 mM) and confinement to small water volumes, and measurements were made of activities of selected enzymes of nitrogen metabolism, ammonia and urea excretion rates, and tissue and plasma contents of ammonia, urea and amino acids. Activities of key ornithine‐urea cycle enzymes were rather low ( e.g . liver carbamoyl phosphate synthetase III activity was 0·001 μmols min⁻¹ g⁻¹), and A. grunniens consistently demonstrated a low capacity for urea excretion despite significant elevations of plasma and tissue ammonia contents by the high pH and high ammonia treatments. This species could thus be categorized as ammoniotelic. Total free amino acid contents in plasma and tissues were increased by the high pH and high ammonia treatments, but no patterns were discerned in individual amino acids that would indicate any preferential accumulation ( e.g . alanine and glutamine) as has been noted previously in several semi‐terrestrial fish species. Thus, it appeared that A. grunniens was not unusual in its patterns of nitrogen metabolism and excretion in comparison to other 'typical' teleosts. Furthermore, manipulation of salinity had no major effects on nitrogen excretion in either this species or in comparative studies with the ureotelic gulf toadfish Opsanus beta . The results are discussed in the context of the broader pattern of nitrogen metabolism and excretion in the Batrachoididae.