Effects of dissolved carbon dioxide on the integrity of the rumen epithelium: An agent in the development of ruminal acidosis.

The carbon dioxide released and dissolved in rumen fluid may easily permeate across the epithelial cell membrane. Thus, we hypothesized that CO2 may act as proton carrier and induce epithelial damage under acidotic conditions. Ovine ruminal epithelia were mounted in Ussing chambers under short-circuit conditions. The serosal buffer solution had a constant pH of 7.4 and was gassed either with 100% oxygen or with carbogen (95% O2 /5% CO2 ). The mucosal solution was gassed with either 100% oxygen or 100% carbon dioxide. The mucosal pH was lowered stepwise from 6.6 to 5.0 in the presence or absence of short-chain fatty acids (SCFA). The transepithelial conductance (Gt ) as an indicator of epithelial integrity and the short-circuit current (Isc ) as an indicator of active electrogenic ion transfer were continuously monitored. At an initial mucosal pH of 6.6, there was no significant difference in Gt between the treatment groups. In the absence of both SCFA and CO2 , Gt remained constant when the mucosal solution was acidified to pH 5.0. In the presence of SCFA, mucosal acidification induced a significant rise in Gt when the solutions were gassed with oxygen. A small increase in Gt was observed in the mucosal presence of CO2 . However, no difference in final Gt was observed between SCFA-containing and SCFA-free conditions under carbon dioxide gassing during stepwise mucosal acidification. The SCFA+proton-induced increase in Gt could also be minimized by serosal gassing with carbogen. Because of the SCFA+proton-induced changes in Gt and their attenuation by CO2 , a protective role for mucosally available carbon dioxide may be assumed. We suggest that this effect may be due to the intraepithelial conversion of carbon dioxide to bicarbonate. However, the serosal presence of CO2 at a physiological concentration may be sufficient to protect the epithelia from SCFA+proton-induced damage for a certain period of time.

Gamma-aminobutyric acid (GABA) permeates ovine ruminal and jejunal epithelia, mainly by passive diffusion.

Gamma-aminobutyric acid (GABA) represents the most abundant inhibitory neurotransmitter in the mammalian brain. GABA is also produced in plants and/or by the microbial conversion of amino acids. Thus, ruminants may be forced to take up significant amounts of GABA from their diet. However, it is not known whether exogenously acquired GABA might permeate the gastrointestinal barrier in such quantities as to induce systemic alterations. Thus, this study pursues the question of where within the ruminant's GI tract and by which pathways GABA may be taken up from the ingesta. The jejunal and ruminal epithelia of sheep were mounted in Ussing chambers under short-circuit conditions. The flux rates of radiolabelled GABA from the mucosal to the serosal side (Jms ) and vice versa (Jsm ) were measured. GABA was applied in various concentrations with adjustment of the mucosal pH to 6.1 or 7.4. Furthermore, beta-alanine or glycine was used as a competitive inhibitor for GABA transport. In both the jejunal and ruminal epithelium, the Jms of GABA was linearly correlated to the mucosal GABA concentration. However, Jms across the jejunal epithelium was approximately 10-fold higher than Jms across the ruminal epithelium. When 0.5 mmol/l GABA was applied on both sides of the epithelium, no net flux could be observed in the jejunal epithelia. Additionally, there was no effect of decreased mucosal pH or the application of glycine or beta-alanine under these conditions. The Jms and Jsm of GABA were linearly correlated to the transepithelial conductance. Our results suggest that GABA is taken up from the small intestine rather than from the rumen. Due to the lack of influence of pH and competitive inhibitors, this uptake seems to occur primarily via passive diffusion.

Both butyrate incubation and hypoxia upregulate genes involved in the ruminal transport of SCFA and their metabolites.

Butyrate modulates the differentiation, proliferation and gene expression profiles of various cell types. Ruminal epithelium is exposed to a high intraluminal concentration and inflow of n-butyrate. We aimed to investigate the influence of n-butyrate on the mRNA expression of proteins involved in the transmembranal transfer of n-butyrate metabolites and short-chain fatty acids in ruminal epithelium. N-butyrate-induced changes were compared with the effects of hypoxia because metabolite accumulation after O2 depletion is at least partly comparable to the accumulation of metabolites after n-butyrate exposure. Furthermore, in various tissues, O2 depletion modulates the expression of transport proteins that are also involved in the extrusion of metabolites derived from n-butyrate breakdown in ruminal epithelium. Sheep ruminal epithelia mounted in Ussing chambers were exposed to 50 mM n-butyrate or incubated under hypoxic conditions for 6 h. Electrophysiological measurements showed hypoxia-induced damage in the epithelia. The mRNA expression levels of monocarboxylate transporters (MCT) 1 and 4, anion exchanger (AE) 2, downregulated in adenoma (DRA), putative anion transporter (PAT) 1 and glucose transporter (GLUT) 1 were assessed by RT-qPCR. We also examined the mRNA expression of nuclear factor (NF) κB, cyclooxygenase (COX) 2, hypoxia-inducible factor (HIF) 1α and acyl-CoA oxidase (ACO) to elucidate the possible signalling pathways involved in the modulation of gene expression. The mRNA expression levels of MCT 1, MCT 4, GLUT 1, HIF 1α and COX 2 were upregulated after both n-butyrate exposure and hypoxia. ACO and PAT 1 were upregulated only after n-butyrate incubation. Upregulation of both MCT isoforms and NFκB after n-butyrate incubation could be detected on protein level as well. Our study suggests key roles for MCT 1 and 4 in the adaptation to an increased intracellular load of metabolites, whereas an involvement of PAT 1 in the transport of n-butyrate also seems possible.

Bicarbonate-dependent transport of acetate and butyrate across the basolateral membrane of sheep rumen epithelium.

AIM: This study aimed to assess the role of HCO3⁻ in the transport of acetate and butyrate across the basolateral membrane of rumen epithelium and to identify transport proteins involved. METHODS: The effects of basolateral variation in HCO3⁻ concentrations on acetate and butyrate efflux out of the epithelium and the transepithelial flux of these short-chain fatty acids were tested in Ussing chamber experiments using (14)C-labelled substrates. HCO3⁻-dependent transport mechanisms were characterized by adding specific inhibitors of candidate proteins to the serosal side. RESULTS: Effluxes of acetate and butyrate out of the epithelium were higher to the serosal side than to the mucosal side. Acetate and butyrate effluxes to both sides of rumen epithelium consisted of HCO3⁻-independent and -dependent parts. HCO3⁻-dependent transport across the basolateral membrane was confirmed in studies of transepithelial fluxes. Mucosal to serosal fluxes of acetate and butyrate decreased with lowering serosal HCO3⁻ concentrations. In the presence of 25 mm HCO3⁻, transepithelial flux of acetate was inhibited effectively by p-hydroxymercuribenzoic acid or α-cyano-4-hydroxycinnamic acid, while butyrate flux was unaffected by the blockers. Fluxes of both acetate and butyrate from the serosal to the mucosal side were diminished largely by the addition of NO3⁻ to the serosal side, with this effect being more pronounced for acetate. CONCLUSION: Our results indicate the existence of a basolateral short-chain fatty acid/HCO3⁻ exchanger, with monocarboxylate transporter 1 as a primary candidate for acetate transfer.

Case report and study of collagen metabolism in Marfan's syndrome.

The case report on a 33 year old woman with prominent features of Marfan's syndrome is presented. Characteristic signs were seen in the bones, the eyes, the cardiovascular system, and the lungs. Due to regurgitation of both the aortic and mitral valves and an aneurysm of the ascending aorta a double valve replacement was made, including a prosthesis of the aorta. The problems of early diagnosis and therapy of the life-threatening cardiovascular complications are discussed. Tissue specimens from the aorta were analysed histochemically and biochemically. Histology showed a typical necrosis of the media with cyst formation. Biochemical analysis by in vitro labeling of collagen in tissue explants and by electron microscopical evaluation showed proportions of type I and type III collagen which were significantly different from controls. In both the media and the adventitia the amount of type I collagen was drastically reduced as shown by quantitation of collagen and procollagen. Fibroblasts derived from the skin of the patient showed a normal content of type I and type III collagen. It is conceivable that the reduced content of type I collagen in the aortic wall is responsible for the weakness of the vessel wall causing formation of aneurysm and its sequelae.

[Radiological evidence and removal of tablet conglomerates in intoxication with bromide-containing hypnotics (author's transl)]. / Röntgennachweis und Entfernung von Tablettenkonglomeraten bei Intoxikation mit bromhaltigen Hypnotika.

If large amounts of bromide-containing hypnotics are taken together, the tablets may conglomerate in the stomach. Because of the bromide, this is radiologically demonstrable. Conventional gastric lavage does not remove such conglomerates. In order to prevent long-term late absorption with serious complications such as hypothermia, shock-lung and renal failure, previously only gastrotomy had been an effective treatment. But using gastroscopy with lavage and aspiration, such conglomerates can be removed within one to three hours. Fifteen patients in whom this technique was used were rousable within 24 hours, significantly shortening the period of intoxication. At the same time, complications may be avoided. This is also true in instances where the tablet dosage would otherwise have been fetal.

[A prognostic index in acute myocardial infarction: discrimination analysis of clinical parameters on admission to hospital (author's transl)]. / Ein prognostischer Index bei akutem Myokardinfarkt. Diskriminanzanalyse klinischer Parameter bei Klinikaufnahme

In 301 patients admitted to an intensive-care unit because of acute myocardial infarction a prognostic analysis was undertaken, based on 21 parameters (history, condition on admission, laboratory results) and related to ultimate outcome. Although some parameters were singly of prognostic value, discrimination analysis markedly improved predictive value. A prognostic index was constructed from seven easily available parameters: age, pulmonary congestion, leucocytosis, peripheral vasoconstriction, systolic blood pressure, site of infarct and hypertension. For those in a low-risk class (index less than 60, death-rate up to 5%), duration of stay in the intensive-care unit may be shortened and rehabilitation measures accelerated. Those at moderate risk (index 60-90, death-rate up to 25%) require careful monitoring. The highest risk classes (index 90-120, death-rate up to 90%; and index more than 120, death-rate more than 90%) require specially intensive and long-term monitoring, and various procedures for assisted circulation and possible cardiacsurgical intervention should be considered from the outset.

Myocardial high energy phosphates in experimental thyrotoxicosis in guinea pigs.

Experimental thyrotoxicosis was produced in guinea pigs by daily intraperitoneal injection of 0.7 mg/kg thyroxine (T4) or 0.15 mg/kg triiodothyronine (T3), as shown by an increase of PBI over 50 gamma percent, weight reduction of 20--30 percent, and increase in heart rate of 30--50 percent. Control animals received solvent only. Metabolites were determined in heart muscle on the 1st, 3rd, and 7th day using freeze-stop technique and enzymatic methods: creatine phosphate (CP), ATP, ADP, AMP, glucose 6-phosphate (G-6-P), fructose diphosphate (FDP), pyruvate, lactate, and inorganic phosphate (Pi). In thyrotoxic animals there was a decrease in CP which became significant after 3 days and more pronounced after 7 days. The ratio of CP to Pi decreased. G-6-P and FDP levels increased. The results were identical after administration of T4 and T3. ATP decreased slightly and ADP increased slightly after T4. Propranolol up to a dose of 3 mg/kg or practolol up to 10 mg/kg given daily i.p. on the 4th to 7th day did not prevent either the T4-induced decrease in high energy phosphates or the increase in G-6-P.

Dose-relation of thyroxine-induced changes in myocardial energy stores.

Experimental hyperthyroidism was produced in guinea pigs by daily intraperitoneal injection of l-thyroxine (T4) in various doses (0.7, 0.35, 0.175, and 0.07 mg/kg/day) for 7 days. Controls received solvent only. The following metabolites were determined in heart muscle (freeze-stop technique, enzymatic tests): Pi, adenosine tri-, di-, and monophosphates (ATP, ADP, AMP), creatine phosphate (CP), glucose 6-phosphate (G-6-P), fructose diphosphate (FDP), pyruvate, and lactate. Thyroxine induced a dose-related decrease of CP and a corresponding increase of Pi even in the lowest dose used in this study (0.07 mg/kg) and became more pronounced with increased doses. No remarkable changes of adeninenucleotides (ATP, ADP, AMP) were observed. G-6-P and FDP levels were markedly elevated in all dosages. Besides other possible effects (thyroxine-induced activation and induction of enzymes) the dose-related decrease of CP and increase of Pi may be due to the increasing contractility. In the physiological and pathophysiological range of thyroxine doses (T4 less than 20 mug%) high energy phosphates stores are dose-related decreased but not to a critical level. In the toxic range heart failure as a consequence of a deficit of CP may occur.