Plasma atrial/A-type natriuretic peptide (ANP) concentration in horses with various heart diseases.

Objective: Plasma atrial/A-type natriuretic peptide concentration (CpANP) was measured in horses presenting with various heart diseases to assess its potential diagnostic value.

Animals: Fifteen healthy horses (Group 1) and 60 horses with various heart diseases associated with normal chamber size and function (Group 2, n = 24), associated with abnormal left atrial (LA) size and/or function but normal left ventricle (LV) (Group 3, n = 19), or associated with both abnormal LA and LV size and/or function (Group 4, n = 17).

Methods: CpANP was measured by a commercially available radioimmunoassay.

Analytic validation and comparison of three commercial immunoassays for measurement of plasma atrial/A-type natriuretic peptide concentration in horses.

Measurement of atrial/A-type natriuretic peptide (ANP) concentrations may be of use for assessment of cardiac disease, and reliable data on the analytic performance of available assays are needed. To assess the suitability for clinical use of commercially available ANP assays, intra-assay and inter-assay coefficient of variation and dilution parallelism were calculated for three immunoassays (RIAPen, RIAPhoen, and an ELISAPen) using blood samples from healthy and diseased horses to cover a wide range of ANP concentrations. Further, agreement between assays was assessed using linear regression and Bland-Altman analyses.

Atrial natriuretic peptide and cardiac troponin I concentrations in healthy Warmblood horses and in Warmblood horses with mitral regurgitation at rest and after exercise.

Objective: Atrial natriuretic peptide (ANP) and cardiac troponin I (cTnI) serve as biomarkers for increased cardiac pressure/volume loading and for myocardial stress or damage. The objective was to describe the time course of plasma ANP concentrations (CpANP) and plasma cTnI concentrations (CpcTnI) in horses with mitral regurgitation (MR) compared to healthy horses at rest and after exercise, and to describe the relationship of CpANP with cardiac dimensions and intracardiac pressures.

Animals: 15 healthy Warmblood horses and 7 Warmblood horses with MR.

Acute and chronic elevation of erythropoietin in the brain improves exercise performance in mice without inducing erythropoiesis.

Application of recombinant human erythropoietin (rhEpo) improves exercise capacity by stimulating red blood cell production that, in turn, enhances oxygen delivery and utilization. Apart from this, when applied at high doses, rhEpo crosses the blood-brain barrier, triggering protective neuronal effects. Here we show a fundamental new role by which the presence of Epo in the brain augments exercise performance without altering red blood cell production.

Enhanced erythropoietin expression in the brainstem of newborn rats at high altitude.

In addition to its role in elevating red blood cell number, erythropoietin (Epo) exerts protective functions against acute and delayed degenerative diseases of the brain. Moreover, we have recently demonstrated that endogenously synthesized Epo and soluble Epo receptor (a negative regulator of Epo binding to the Epo receptor) in the central nervous system play a crucial role in facilitating the ventilatory response and acclimatization to hypoxia. Here we hypothesized that cerebral Epo in the brainstem is implicated in the process that allows cardiorespiratory acclimatization to high altitude hypoxia during the postnatal period.

Plasma atrial natriuretic peptide concentrations in horses with heart disease: a pilot study.

Atrial natriuretic peptide (ANP) is a cardiovascular biomarker that might be useful in assessing the severity of cardiac disease in horses. Plasma ANP concentrations (Cp(ANP)) were compared between horses with heart disease but normal chamber size and function (Group A; n=6), horses with heart disease associated with left atrial (LA) enlargement, LA dysfunction, and/or left ventricular (LV) enlargement (Group B; n=5), and horses with no clinically apparent cardiovascular disease (Group C; n=13). The median (min-max) for Cp(ANP) was significantly higher in Group B (53.

Quantifying Western blots: pitfalls of densitometry.

Although Western blots are frequently quantified, densitometry is not documented and appears to be based merely on traditions and guesswork. Confirming previous experience, none of 100 randomly selected and systematically scanned most recent papers provided sufficient information on how Western blot results were translated into statistical values. The importance of such information, however, becomes evident from our correlations of plasma erythropoietin values of various mammals determined using RIA and Western blot densitometry.

Inhibition of 4E-BP1 sensitizes U87 glioblastoma xenograft tumors to irradiation by decreasing hypoxia tolerance.

Purpose: Eukaryotic initiation factor 4E (eIF4E) is an essential rate-limiting factor for cap-dependent translation in eukaryotic cells. Elevated eIF4E activity is common in many human tumors and is associated with disease progression. The growth-promoting effects of eIF4E are in turn negatively regulated by 4E-BP1.

Erythropoietin protects from reperfusion-induced myocardial injury by enhancing coronary endothelial nitric oxide production.

Objective: Cardioprotective properties of recombinant human Erythropoietin (rhEpo) have been shown in in vivo regional or ex vivo global models of ischemia-reperfusion (I/R) injury. The aim of this study was to characterize the cardioprotective potential of rhEPO in an in vivo experimental model of global I/R approximating the clinical cardiac surgical setting and to gain insights into the myocardial binding sites of rhEpo and the mechanism involved in its cardioprotective effect.

Methods: Hearts of donor Lewis rats were arrested with cold crystalloid cardioplegia and after 45 min of cold global ischemia grafted heterotopically into the abdomen of recipient Lewis rats.

Fecal shedding of infectious feline leukemia virus and its nucleic acids: a transmission potential.

Although it is assumed that fecal shedding of feline leukemia virus (FeLV) constitutes a transmission potential, no study has been performed showing that feces of infected cats can be a source of infection. In this study, we investigated fecal viral shedding of FeLV and its role in viral pathogenesis with the goal to improve infection control. FeLV RNA and DNA levels were determined in rectal swabs of experimentally infected cats by real-time PCR, and the results were correlated with proviral and viral loads in whole blood and plasma, respectively, and plasma p27 levels.

Placental HIFs as markers of cerebral hypoxic distress in fetal mice.

Reduced oxygen supply during the pre- and perinatal period often leads to acquired neonatal brain damage. So far, there are no reliable markers available to assess the hypoxic cerebral damage and the resulting prognosis during the immediate postnatal period. Thus we aimed to determine whether the hypoxia-inducible transcription factors (HIF-1 and HIF-2) and/or their target genes in the placenta represent reliable indicators of hypoxic distress of the developing brain during systemic hypoxia at the end of gestation.

Abortion in mice with excessive erythrocytosis is due to impaired arteriogenesis of the uterine arcade.

We postulate that repeated pregnancy loss, intrauterine growth restriction, and preeclampsia are caused by impaired elevation of uterine blood flow due to disturbed arteriogenesis of the uterine arcade. This hypothesis is based on the observation that pregnant human erythropoietin-overexpressing (plasma levels elevated 12-fold) mice (termed tg6 mice) suffering from excessive erythrocytosis generally abort at midgestation unless their hematocrit of 0.85 is drastically lowered.

Constitutively overexpressed erythropoietin reduces infarct size in a mouse model of permanent coronary artery ligation.

In view of the emerging role of recombinant human erythropoietin (rhEPO) as a novel therapeutical approach in myocardial ischemia, we performed the first two-way parallel comparison to test the effects of rhEPO pretreatment (1000 U/kg, 12h before surgery) versus EPO transgenic overexpression in a mouse model of myocardial infarction. Unlike EPO transgenic mice who doubled their hematocrit, rhEPO pretreated mice maintained an unaltered hematocrit, thereby offering the possibility to discern erythropoietic-dependent from erythropoietic-independent protective effects of EPO. Animals pretreated with rhEPO as well as EPO transgenic mice underwent permanent left anterior descending (LAD) coronary artery ligation.

Analytical validation of commercial immunoassays for the measurement of cardiovascular peptides in the dog.

Immunoassays for the measurement of concentrations of the cardiovascular peptides pro-atrial natriuretic peptide (proANP), brain natriuretic peptide (BNPPen and BNPPhoe), endothelin-1 (ET-1Bio, ET-1IBL and ET-1Phoe) and big endothelin-1 (Big-ETBio and Big-ETIBL) were validated in canine serum by determination of intra-assay variability and dilutional parallelism. Commercial kits that showed good results were further validated by determination of intra- and inter-assay variability, dilutional parallelism and spiking recovery. Assays for proANP, BNPPhoe, ET-1IBL and Big-ETIBL showed acceptable results in the preliminary validation and were fully validated.

Interrelation of directly measured oxygenation levels, erythropoietin and erythropoietin receptor expression in spontaneous canine tumours.

The expression of the hypoxia-inducible protein erythropoietin in tumour cells correlates with levels of tumour hypoxia. Our aim was to look for an interrelation of directly measured oxygenation levels, the presence of tissue erythropoietin and its receptor. Data of tumour oxygenation status, plasma and tissue erythropoietin and its receptor in a group of spontaneously occurring tumours in 15 dogs were collected.

[High intestinal transport activity for nucleosides in cattle: a synopsis].

In ruminants large amounts of nucleic acids associated with the microbial cell mass leaving the fore-stomach system via the abomasum enter the small intestine. In dairy cows this amounts to 100-200 g microbial nucleic acids per day. These nucleic acids are very efficiently digested in the small intestine whereby nucleosides were found to be the main degradation products.

Na-K-ATPase in rat cerebellar granule cells is redox sensitive.

Redox-induced regulation of the Na-K-ATPase was studied in dispersed rat cerebellar granule cells. Intracellular thiol redox state was modulated using glutathione (GSH)-conjugating agents and membrane-permeable ethyl ester of GSH (et-GSH) and Na-K-ATPase transport and hydrolytic activity monitored as a function of intracellular reduced thiol concentration. Depletion of cytosolic and mitochondrial GSH pools caused an increase in free radical production in mitochondria and rapid ATP deprivation with a subsequent decrease in transport but not hydrolytic activity of the Na-K-ATPase.

Hypoxic responses of Na+/K+ ATPase in trout hepatocytes.

Reduction in oxygenation induces inhibition of Na+/K+ ATPase in a number of cells and tissues, including hepatocytes. When not reversed, decrease in Na+/K+ pump activity leads to a gradual Na+ accumulation, cell swelling and death. However, when accompanied by suppression of dissipative cation pathways, it has also been shown to be a beneficial adaptive strategy used by some hypoxia-tolerant species to reduce ATP consumption during prolonged periods of anoxia.

High altitude training of dogs results in elevated erythropoietin and endothelin-1 serum levels.

Living at 2300-m altitude combined with intermittent training at 3500 m leads to cardiovascular alterations in dogs, including increase in systemic and pulmonary artery pressure. Despite moderate to marked hypoxemia at these altitudes, erythrocytosis does not develop. To study humoral mechanisms of acclimatisation to high altitude, erythropoietin (EPO), endothelin-1 (ET-1), big endothelin (Big-ET) and vascular endothelial growth factor (VEGF) were measured in dogs living at 2300 m and intermittently ascending to 3500 m, and compared to the values obtained in control dogs living at 700-900 m.

Na+ gradient-dependent transport of hypoxanthine by calf intestinal brush border membrane vesicles.

The properties of hypoxanthine transport were investigated in purified brush border membrane vesicles isolated from calf proximal and distal jejunum. Hypoxanthine uptake in the vesicles was stimulated by a transmembrane Na(+) gradient and an inside negative potential resulting in a transient accumulation of intravesicular hypoxanthine, especially in the proximal jejunum. Na(+)-dependent hypoxanthine uptake at this site seemed to occur by two saturable transport systems, a high affinity (K(m)=0.

Nucleosides are efficiently absorbed by Na(+)-dependent transport across the intestinal brush border membrane in veal calves.

In previous work, a comparatively high capacity for Na(+)-dependent transport of nucleosides across the intestinal brush border membrane (BBM) was observed in dairy cows, which might be related to digestion of the large amount of nucleic acids present in ruminal microorganisms in the ruminant small intestine. If this were the case, the capacity for Na(+)-dependent intestinal nucleoside transport should be much lower in veal calves, in which only small amounts of nucleic acids, nucleotides, and nucleosides reach the small intestine via the milk replacer. To test this hypothesis, we investigated Na(+)-dependent transport of 3H-labeled thymidine and guanosine across the BBM using BBM vesicles (BBMV) isolated from the small intestine of veal calves.

Characteristics of Na(+)-dependent intestinal nucleoside transport in the pig.

Since the capacity of nucleic acid digestion and absorption appears to be comparatively high in the pig, we investigated the properties of transport of (3)H-labelled nucleosides across the porcine intestinal brush border membrane (BBM) using BBM vesicles isolated from the small intestine of slaughter pigs. In the presence of a transmembrane Na(+) gradient, uridine, thymidine and guanosine transiently accumulated in the vesicular lumen beyond the equilibrium (60 min) value suggesting the presence of Na(+)/nucleoside cotransporters in the BBM. The findings of inhibitory studies are consistent with the presence of two Na(+)-dependent nucleoside transporters with overlapping substrate specificity, one for pyrimidine nucleosides (N2) and one for purine nucleosides (N1).

Properties of Na(+)-dependent nucleoside transport in the proximal and distal small intestine of cows.

Large amounts of nucleic acids associated with rumen microorganisms are digested in the proximal part of the small intestine of ruminants. We studied how the proximal-distal gradient in nucleic acid digestion is related to activity of Na(+)-nucleoside transporters in brush border membrane vesicles isolated from the proximal and distal small intestine of cows. Two Na(+)-dependent nucleoside transporters with overlapping substrate specificity were shown to be present at the two intestinal sites, one for pyrimidine nucleosides and one for purine nucleosides.

Active intestinal absorption of nucleosides by Na+-dependent transport across the brush border membrane in cows.

Transport of 3H-labeled nucleosides across the bovine intestinal brush border membrane (BBM) was characterized with BBM vesicles (BBMV) isolated from mid-jejunum of cows because large amounts of nucleic acids are digested in the small intestine of ruminants. Two Na+-dependent electrogenic nucleoside transporters with overlapping substrate specificity were shown to be present in the jejunal BBM, one for pyrimidine nucleosides and one for purine nucleosides. As indicated by inhibitory studies, thymidine seemed to be a specific substrate for the pyrimidine nucleoside transporter, while this applied to guanosine and deoxyguanosine for the purine nucleoside transporter.

Na(+)-dependent transport of D-xylose by bovine intestinal brush border membrane vesicles (BBMV) is inhibited by various pentoses and hexoses.

To detect whether pentoses and hexoses occurring in rumen bacteria or in hemicellulose ingested with feed and partly released in the small intestine have an affinity for the Na(+)-dependent glucose transporter of the bovine intestinal brush border membrane (BBM), we investigated whether these monosaccharides inhibit Na(+)-dependent transport of 14C-labelled D-xylose across the BBM using brush border membrane vesicles (BBMV) isolated from the mid-jejunum of cows. We used D-xylose as the transport substrate, because it has a low affinity for the Na(+)-dependent glucose transporter and thus its uptake into BBMV is more efficiently competitively inhibited by other sugars than that of D-glucose. D-Ribose, D-mannose and L-rhamnose occurring in rumen bacteria significantly inhibited Na(+)-dependent uptake of D-xylose into BBMV, but their inhibitory effect was less than that of D-glucose, D-xylose and phlorizin.