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Nitrogen acquisition is a major challenge for herbivorous animals, and the repeated origins of herbivory across the ants have raised expectations that nutritional symbionts have shaped their diversification. Direct evidence for N provisioning by internally housed symbionts is rare in animals; among the ants, it has been documented for just one lineage. In this study we dissect functional contributions by bacteria from a conserved, multi-partite gut symbiosis in herbivorous Cephalotes ants through in vivo experiments, metagenomics, and in vitro assays. Gut bacteria recycle urea, and likely uric acid, using recycled N to synthesize essential amino acids that are acquired by hosts in substantial quantities. Specialized core symbionts of 17 studied Cephalotes species encode the pathways directing these activities, and several recycle N in vitro. These findings point to a highly efficient N economy, and a nutritional mutualism preserved for millions of years through the derived behaviors and gut anatomy of Cephalotes ants., Gut bacteria are prevalent across insects including ants, but their precise roles are often unclear. Here, Hu et al. show that microbes aid ants by recycling nitrogen into bio-available amino acids. This function is conserved across the turtle ants, suggesting an ancient nutritional mutualism.

Aim: MicroRNAs (miR) are important diagnostic and treatment targets due to their different tissue expressions and their central position in the regulation of gene expressions. miR studies might pioneer emerging of new diagnostic tools and treatment goals in kidney diseases. Captopril (CAP) and telmisartan (TEL) were shown to be effective in ischemia reperfusion (IR) injury. There is not any study about the effect of TEL and CAP over miR-21-320-146a. Our aim was to study the effects of CAP and TEL over miR on renal IR model. Methods: We used 12–16 weeks-old Wistar-Albino rats that weigh 300–350 g. Rats (n, 6) were randomized into four groups (Control, IR, IR + CAP, IR + TEL). Urea, creatinine, total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), super oxide dismutase (SOD), and miRs were analyzed. Results: Urea, creatinine, TOS, OSI levels of IR + CAP, and IR + TEL groups were lower comparing to IR group. TAS and SOD levels were higher in IR group than IR + TEL group. miR-21-320-146a showed increase in renal IR injury. miR-320, 146a showed significant decrease in IR + CAP and IR + TEL groups comparing to IR group. We showed histopathological recovery and decreased apoptosis in IR + CAP and IR + T groups than IR group. Conclusion: We, for the first time in the literature, showed that miR-320 is increased in IR injury. miR-320 might be a novel diagnosis and treatment target in renal ischemic reperfusion injury. Also, for the first time, we showed that CAP and TEL cause functional and histopathological recovery and lower miR-146a and miR-320. © 2016 Informa UK Limited, trading as Taylor & Francis Group.

BACKGROUND & AIMS: Urea is a major nitrogen source for commensal bacteria that inhabit the large intestine. UT-A urea transporters mediate urea movement across plasma membranes. The aim of this study was to determine whether UT-A proteins are expressed in the mouse colon and, if so, whether they have a functional role in transcellular urea transport.METHODS: Mouse colonic UT-A transporters were investigated with Northern blot analysis, immunoblotting, immunolocalization, and refractive light flux experiments.RESULTS: Northern blot analysis showed that 4 UT-A transcripts were present in mouse colon. Two peptide-targeted polyclonal antibodies showed the presence of UT-A immunoreactive proteins in mouse colon. Antiserum ML446 targeted to the N-terminus of mouse UT-A1 detected proteins of 34 and 48 kilodaltons. Antiserum ML194 targeted to the C-terminus of mouse UT-A1 detected proteins of 48, 75, and 100 kilodaltons. Immunolocalization studies using ML446 showed the presence of UT-A proteins in cells throughout the colonic crypts. ML194 specifically stained cells located in the proliferative and stem regions of the lower portion of colonic crypts. Differential centrifugation and immunoblotting of colonic epithelia showed that UT-A proteins were present in plasma membrane-enriched fractions. Refractive light flux experiments using colonic plasma membrane vesicles showed a significant urea flux, which was completely inhibited by the UT-A inhibitor phloretin.CONCLUSIONS: Functional UT-A transporters are expressed in the plasma membranes of mouse colon, indicating that these proteins may play a key role in host/bacterial interaction.

One of the mechanisms of healthy hepatocytes to detoxify ammonia in the liver consists of converting it into urea. When liver function is impaired, this detoxification capacity decreases and may cause severe pathologies, such as hepatic encephalopathy. Consequently, urea synthesis is a parameter that can be used to monitor liver functionality. In this chapter, a protocol for the measurement of urea synthesis in the culture medium of cultured rat hepatocytes is described. The procedure relies on a chromogenic reagent that specifically forms a colored complex with urea. The latter can be measured colorimetrically and is directly proportional to the urea concentration in the sample.

To determine whether hepatic urea production is limited at low hepatic O2 delivery (DO2) by O2 itself or by the availability of substrate for urea synthesis, we isolated livers from normal rats and perfused them with Krebs-Henseleit bicarbonate (KHB) buffer, KHB + 5 mM NH4Cl, or KHB + 5 mM glutamine (Gln) as an NH3 donor. The pump flow was lowered in stages, and we determined at each flow rate inflow and outflow O2 content and urea levels in the outflow perfusate. Urea production in Gln-perfused livers remained constant at high DO2 and declined in direct proportion to DO2 below a critical oxygen delivery (DO2crit, the point below which the hepatic O2 consumption [VO2] becomes limited by the hepatic DO2). The DO2crit calculated from the urea release-DO2 relationship (147 +/- 32 microl/min/dry g) was similar to the DO2crit calculated from the VO2-DO2 relationship (158 +/- 26 microl/min/dry g). When Gln concentration and flow rate were maintained constant while decreasing PO2 in the inflow perfusate (as well as hepatic DO2), urea production declined below the DO2crit. Furthermore, when Gln concentration in the perfusate was gradually reduced while keeping hepatic DO2 constant, urea production decreased proportionally with Gln concentrations in the perfusate. Consequently, urea production is dependent on Gln and O2 availability and becomes limited at the same DO2crit determined by the VO2-DO2 relationship.

Hepatocytes can be stimulated to express high levels of inducible nitric oxide synthase (iNOS), which utilizes arginine for nitric oxide (NO) synthesis. Hepatocytes also synthesize and catabolize arginine, an intermediate in the urea cycle, raising the possibility that the urea pathway may provide substrate for hepatic NO synthesis. To identify the sources of arginine for iNOS, we measured the release of NO-2 + NO-3 and urea in isolated rat livers perfused in a recirculation model with a Krebs-Henseleit-bicarbonate buffer containing either no added amino acid, arginine, or precursors for urea synthesis. To induce iNOS expression, rats were injected with killed Corynebacterium parvum (C. parvum) or with endotoxin. In livers from C. parvum- and endotoxin-treated rats, we found that 1) an intracellular source of arginine exists that provides substrate to iNOS; 2) additional exogenous arginine increase NO synthesis, demonstrating that endogenous arginine is insufficient for maximal NO synthesis; and 3) an increase in the rate of endogenous arginine synthesis within the urea cycle is inefficient in increasing NO synthesis, demonstrating the independence of the two pathways in the liver.

AIM: To evaluate the relationship between gallbladder (GB) motor function and H pylori infection in the stomach. METHODS: All cases (86) underwent the 14C urea breath test (UBT). 14C-UBT was found as positive in 58 and negative in 28 dyspeptic patients. 14C-UBT was accepted as a gold standard test. Clo test and histopathologic examination were compared with the results of 14C-UBT in cases who tolerated upper gastrointestinal endoscopy procedure. Cholescintigraphy with 99mTc-mebrofenin was used to determine the parameters of GB motor function (GB filling and emptying time, half of the emptying time, ejection fraction at 30th and 60th min) in all patients. RESULTS: We found the sensitivity and specificity as 88% and 86% for Clo test and as 89% and 80% for histologic evaluation, respectively. The parameters of GB function were not significantly different in H pylori positive and negative patients. The GB emptying was normal in both groups. Minimum GB filling time was 30 min in 34 of 86 cases (39.5%), filling was not observed in 2 cases. The GB ultrasonography (USG) results were normal for all cases and bile composition abnormality was not determined. CONCLUSION: Our study showed that 14C-UBT is highly reliable method to detect the presence of H pylori. The presence of H pylori infection does ot directly affect the GB function.

With regard to the principles established for neonatal population screening, the question arises whether for patients with urea cycle disorders there is an accepted treatment which really affects the disease course and prognosis as compared to the natural history of these diseases. A retrospective study of 88 patients was performed. Based on questionnaires, the survival rate and neurodevelopmental outcome of patients treated with protein restriction alone was compared to the new therapy introduced in the 1980s with added citrulline/arginine, essential amino acids for improving the amino acid composition of the restricted natural protein and benzoate. Survival of patients with neonatal presentation was improved by the extensive therapy but this mostly at the cost of an increasing number of retarded patients. Long-term outcome did not differ significantly between the two treatments. Of all patients, 56% were symptomatic within 4 days of age and 67% within the 1st week. Thus a prevention of irreversible damage by neonatal screening on blood obtained at 3–4 days of life is questionable. Whether the benefit of obtaining a rapid diagnosis, e.g. for allowing proper counselling and prospective treatment, is acceptable for the parents of prospective patients remains open. The organisation of a dense network of specialised metabolic centres with sufficient staff and resources is a prior condition for any screening programme in order to ensure the rapid diagnosis, follow-up of treatment and counselling of a cumulative number of affected chronic patients needing this support. A commitment on a long-term basis by the institutions is needed in view of the health budget restrictions. Conclusion: in the short term, the goal is to detect hyperammonaemic patients as early as possible with special emphasis on sick neonates. In practice, quantitative plasma ammonia determination without delay is recommended in any newborn for whom a sepsis work-up is considered and in children who refuse feeding or vomit and show alterations of consciousness and/or neurological symptoms.

The blood-seminiferous tubule barrier is responsible for maintaining the unique microenvironment conducive to spermatogenesis. A key feature of the blood-testis barrier is selective permeability to solutes and water transport, conferred by the Sertoli cells of the seminiferous tubules (SMTs). Movement of fluid into the lumen of the seminiferous tubule is crucial to spermatogenesis. By Northern analysis, we have shown that 4.0-, 3.3-, 2.8-, and ∼1.7-kb UT-A mRNA transcripts and a 3.8-kb UT-B mRNA transcript are detected within rat testis. Western analysis revealed the expression of both characterized and novel UT-A and UT-B proteins within the testis. Immunolocalization studies determined that UT-A and UT-B protein expression are coordinated with the developmental stage of the SMT. UT-A proteins were detected in Sertoli cell nuclei at all stages of tubule development and in residual bodies of stage VIII tubules. UT-B protein was expressed on Sertoli cell membranes of stage II–III tubules. Using in vitro perfusion, we determined that a phloretin-inhibitable urea pathway exists across the SMTs of rat testis and conclude that UT-B is likely to participate in this pathway.

BACKGROUND: Statistical associations between urea removal and survival have been described in a number of publications. Urea removal during treatment may be quantified by the delivered dose of dialysis. Methods in clinical use to measure delivered dose are retrospective and reliant on accurate blood sampling. The new generation of single patient proportionating systems incorporate the facility to automatically measure ionic dialysance throughout dialysis. METHODS: In a prospective study on 9 anuric patients with a stable dialysis prescription, we have compared the agreement of the dose of dialysis determined from ionic dialysance (Dt/V) with that derived from equilibriated Kt/V (eKt/V) and Kt/V measured by direct dialysis quantification (Kt/V(DDQ)) using 2 types of hemodialysis membrane (hemophan and low-flux polysulfone). The variability of the delivered dose over a 1-month period was also determined. RESULTS: Ionic dialysance was independent of membrane type. It was comparable to that established for plasma urea water clearance for hemophan but lower for polysulfone (p < 0.001). The mean (+/- SD) delivered dose of dialysis (Dt/V) was similar for both membranes (1.18 +/- 0.15 (hemophan) and 1.18 +/- 0.11 (low-flux polysulfone)). Bland Altman comparisons showed the limits of agreement between Dt/V and Kt/V(DDQ) were +/- 0.17 and for Dt/V compared with eKt/V +/- 0.15. A 1-month measurement of Dt/V demonstrated considerable treatment to treatment variability indicating that delivered dose cannot be considered stable. CONCLUSION: The availability of online measurement of ionic dialysance provides a step towards monitoring dialysis more closely at the time of delivery, and its clinical application will ensure that a more constant dialysis dose is delivered. Clin Nephrol

Background : Few data exist concerning the consequences of acidosis on intrahepatic vascular resistances and hepatic functions. Methods : The consequences of pH and PCO 2 changes on the intrahepatic vascular reactivity to norepinephrine (NE, 10 −9 to 3×10 −5 M) have been investigated in isolated rat livers perfused with solutions bubbled with 5, 10, or 15% CO 2 and in solutions in which pH was decreased by replacing HCO 3 − with NaCl while maintaining a normal PCO 2 . Hepatic O 2 consumption (VO 2 ) and urea release were also measured during these experiments. Results : The NE-induced increase of portal pressure did not change during hypercarbic and normocarbic acidosis. In contrast, the NE-induced increase of urea release was higher when the solution of perfusion was bubbled with 10 and 15% CO 2 , while during normocarbic acidosis the NE-induced increase of urea release did not change with pH. In the absence of NE, acidosis decreased hepatic VO 2 and urea release but portal pressure was not modified by changing % CO 2 or pH in the Krebs–Henseleit–bicarbonate solution. Conclusions : This study clearly shows that, in the liver, the consequences of acidosis are far more important on the metabolism (VO 2 and urea release) than on the intrahepatic vascular resistance.

BACKGROUND/AIMS: Hypoglycemia has well-described effects on glucose metabolism, whereas the possible effects on hepatic amino nitrogen conversion in relation to muscle amino nitrogen flux are more uncertain.METHODS: We studied six healthy young male subjects three times, i.e. for 6 h in the basal state, during a 6-h euglycemic hyperinsulinemic (1.5 mU/kg/min) clamp and during a 6-h hypoglycemic (plasma glucose below 2.8 mmol/l) clamp. Alanine (2 mmol/kg body weight/h) was infused for 3 h to describe the relationship between blood amino nitrogen concentrations and hepatic ureagenesis estimated from urea urine excretion and accumulation in body water. The slope of this relationship is denoted functional hepatic nitrogen clearance (FHNC) and quantifies substrate-independent alterations in hepatic amino nitrogen degradation. In parallel, amino nitrogen balances across muscles were estimated by the forearm flux method.RESULTS: Euglycemia decreased circulating glucagon values (100+/-25 ng/l vs. 160+/-30 ng/l), whereas hypoglycemia doubled glucagon (350+/-45 ng/l, pCONCLUSION: Hypoglycemia in man induces a marked increase in hepatic amino- to urea-N clearance. This catabolic response to hypoglycemia in the liver may be of primary importance for muscle amino acid release. Our data are compatible with the notion that liver and muscle together are responsible for catabolism during hypoglycemia, and that glucagon may be the primary mediator via its effect on liver metabolism.

BACKGROUND/AIMS: The role of thyroid hormones in the regulation of hepatic conversions of amino nitrogen to urea is unresolved. The present study was designed to assess ureagenesis in rats with experimentally well-established hypo- and hyperthyroidism. The possible role of propylthiuracil (PTU), used for induction of hypothyroidism, was ascertained during thyroxine replacement of PTU treated hypothyroid rats.METHODS: Basal blood amino nitrogen concentrations (AAN), the urea nitrogen synthesis rate (UNSR) and the maximal hepatic capacity for urea nitrogen synthesis (CUNS) obtained during alanine infusion were determined together with N-contents in the soleus muscle and kidneys in experimentally hypothyroid rats (n = 19), upon thyroxine replacement (n = 14) and in experimentally hyperthyroid rats (n = 19). Hypothyroidism was induced by adding propylthiouracil (0.05%) to the drinking water for 5 weeks. Hyperthyroidism was induced by thyroxine 100 micrograms/100 g body weight.RESULTS: During hyperthyroidism, T3 fell to less than 10%, food intake was halved, and body weight fell by 13%. Basal blood AAN fell by 25% (p < 0.01), UNSR more than doubled (p < 0.01), and CUNS rose by 45% (p < 0.05). N-contents of the soleus muscle fell by 13% and by 20% in kidneys, respectively (p < 0.05). Thyroxine replacement normalized AAN, UNSR, CUNS and reduced N-loss to 7% in the soleus muscle (NS) and kidneys (p < 0.05), respectively. During hyperthyroidism, T3 rose five-fold, food intake rose by two thirds, and body weight fell by 10%. Basal AAN rose by 20% (p < 0.05), UNSR doubled (p < 0.01), and CUNS rose by 25% (p < 0.05). N-contents of the soleus muscle decreased by 19%, whereas kidney N-contents increased by 25% (p < 0.05). Overall liver function assessed by galactose elimination capacity did not differ among groups. Both conditions increased the rate of urea synthesis; in the hypothyroid state the hepatic waste of amino-N was limited by low blood concentration of amino-N, probably due to lower proteolysis. In the hyperthyroid state hepatic amino-N loss was aggravated by higher blood concentration of amino-N, probably due to higher proteolysis. This difference may explain the markedly different dietary nitrogen economy between the two groups.CONCLUSIONS: The findings suggest that distinct hepatic acceleration of urea synthesis may contribute to the protein loss seen in both myxedema and in thyrotoxicosis in humans.

OBJECTIVE: Surgery results in a catabolic state of postoperative stress, where the efficiency of the liver to convert amino acids to urea is increased. This study measured the metabolic consequences of the less traumatic laparoscopic surgery in elective cholecystectomy compared with traditional open surgery technique.SUMMARY BACKGROUND DATA: The authors previously have shown that open cholecystectomy doubles the urea synthesis measured by the means of the functional hepatic nitrogen clearance. Glucagon and cortisol increased by 50% (p < 0.05) and 75% (p < 0.05), respectively, after open cholecystectomy.METHODS: Patients undergoing uncomplicated elective laparoscopic cholecystectomies were included. Preoperatively and on the first postoperative day, blood and urine samples were drawn every hour under basal conditions and during amino acid infusion. The urea synthesis rate was calculated from the urea excreted in urine and accumulated in total body water. Functional hepatic nitrogen clearance was quantified as the slope of the linear relation between blood amino-N concentration and the urea synthesis rate. The results were compared with an historic matched group of patients who underwent open cholecystectomies and were studied by the same protocol.RESULTS: The laparoscopic cholecystectomy increased the functional hepatic nitrogen clearance by only 25% (from 8.7 +/- 0.9 to 11.1 +/- 1.5 mL/sec [mean +/- SEM; p < 0.05]), compared with a doubling after open cholecystectomy (from 9.4 +/- 0.9 to 17.6 +/- 3.3 mL/sec [p < 0.05]). The difference between the groups was significant (p < 0.05). Neither glucagon nor cortisol increased significantly after laparoscopic cholecystectomy.CONCLUSIONS: The laparoscopic technique results in a much smaller postoperative hepatic catabolic stress response and probably reduced tissue loss of amino-N. This may be important for the more rapid convalescence and reduced postoperative fatigue.

BACKGROUND/AIMS: A decline in urea excretion is seen following long-term growth hormone administration, reflecting overall protein anabolism. Conversely, hyperthyroidism is characterized by increased urea synthesis and negative nitrogen metabolism. These seemingly opposite effects are presumed to reflect different actions on peripheral protein metabolism. The extent to which these hormonal systems have different direct effects on hepatic urea genesis has not been fully characterized.METHODS: We measured urea nitrogen synthesis rates and blood alanine levels concomitantly before, during, and after a 4-h constant intravenous infusion of alanine (2 mmol.kg bw-1.h-1). Urea nitrogen synthesis rate was estimated hourly as urinary excretion corrected for gut hydrolysis and accumulation in body water. The slope of the linear relationship between urea nitrogen synthesis rate and alanine concentration represents the liver function as to conversion of amino-N, and is denoted the functional hepatic nitrogen clearance. Eight normal male subjects (age 21-27 years; body mass index 22.4-27.0 kg/m2) were randomly studied four times: 1) after 10 days of subcutaneous saline injections, 2) after 10 days of subcutaneous growth hormone injections (0.1 IU/kg per day), 3) after 10 days of triiodothyronine administration (40 micrograms on even dates, 20 micrograms on uneven dates) and 4) after 10 days given 2)+3). All injections were given at 20 00 h.RESULTS: Growth hormone decreased functional hepatic nitrogen clearance (l/h) by 30% (from 33.8 +/- 3.2 l/h (control) to 23.8 +/- 1.5 l/h (10 days growth hormone) (mean +/- SE) (ANOVA; p < 0.01)). Triiodothyronine did not change functional hepatic nitrogen clearance (36.7 +/- 3.2 l/h), but triiodothyronine given together with growth hormone abolished the effect of growth hormone functional hepatic nitrogen clearance (38.8 +/- 4.8 l/h).CONCLUSIONS: The results show that long-term growth hormone administration acts on liver by decreasing functional hepatic nitrogen clearance, thereby retaining amino-N in the body. Triiodothyronine has no effect on functional hepatic nitrogen clearance, but given together with growth hormone, it abolishes the effect of growth hormone on functional hepatic nitrogen clearance. A possible mechanism is the known effect of thyroid hormones in reducing the bioavailability of insulin-like growth factor-I. Thus, the effects of growth hormone and triiodothyronine on amino-N homeostasis are interdependent and to some extent exerted via interplay in their regulation of liver function as to amino-N conversion.