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Biomedical subjects

H Höller

Publications and source records attributed to H Höller.

At least 19 recordsLinked to original sources
PubMed1992

Influence of short-chain fatty acids on ammonia absorption across the rumen wall in sheep.

The effects of short-chain fatty acids (SCFA) on ammonia net absorption from the sheep rumen in vivo and on ammonia transport across rumen wall mucosa in vitro were studied. Ammonia net absorption was directly, though in a non-linear manner, correlated with the SCFA concentration in the artificial rumen fluid. Almost 70% of total ammonia absorption was dependent upon the presence of SCFA when 12 mmol l-1 ammonia and 67.5 mmol l-1 SCFA were present. Lactic acid was ineffective. Incubation experiments showed that mucosal disappearance and serosal appearance of ammonia were reduced by 38% and 32%, respectively, when SCFA (63 mmol l-1) were replaced by lactic acid. The SCFA effect was independent of the type of SCFA used. In part of the experiments up to 54% of the ammonia taken up by the tissue was not recovered in the serosal incubation solution and must have been metabolized in the mucosa.

Absorption↗
PubMed1992

Involvement of carbonic anhydrase in ammonia flux across rumen mucosa in vitro.

Carbonic anhydrase activity in mucosa of the sheep rumen wall was completely inhibited by acetazolamide and ethoxyzolamide. This inhibition significantly reduced ammonia flux across mucosal discs in vitro but was ineffective if short-chain fatty acids were present in the bathing solution. The findings are discussed in relation to the mechanism of ruminal ammonia absorption.

Acetazolamide↗
PubMed1992

Toothpastes.

It is well known that plaque is the main cause of caries and parodontopathies, which puts the role of toothpastes as an important means of prevention of odontopathies to the foreground. Toothpastes can be more or less oriented towards having a particular effect, such as cleaning, anticaries effect, antimicrobial effect or inhibition of the formation of tartar. Toothpastes contain substances which promote dental health, such as abrasives (silicium dioxide, brushite, calcite, calcite and aragonite, gibbsite etc.), active components (fluorides, triclosan, metal ions, sanguinarine and surface-active substances), substances which motivate the use of toothpaste (sweetening agents, aromatic oil, colours) and components which are necessary for technical reasons, such as moisturizing agents, binders and opacifiers.

Alkaloids↗
PubMed1990

Failure of 1,25-(OH)2-vitamin D3 to affect calcium flux across sheep rumen wall mucosa in vitro.

Isolated pieces of mucosa from the sheep rumen wall mounted between half-chambers were used in conventional incubation studies (1 h, 39 degrees C) with buffer solutions resembling rumen fluid (= mucosal fluid) and extracellular fluid (= serosal fluid), respectively. The mucosal-to-serosal (ms) flux of calcium was studied by use of 45CaCl2 with and without 1,25-(OH)2-vitamin D3 in the serosal incubation fluid. Different concentrations of the vitamin had no effect on Ca ms-flux.

Animals↗
PubMed1990

Ammonia absorption from the isolated reticulo-rumen of sheep.

In fistulated sheep (50-60 kg live weight) the absorption of ammonia from the reticulo-rumen in vivo was studied applying the technique of the temporarily isolated and washed reticulo-rumen. It was found that, at ammonia concentrations between 3 and 18 mM, ammonia efflux and ammonia net absorption were linearly related to the ammonia concentration in the artificial rumen fluid, whereas influx of ammonia nitrogen from endogenous sources remained almost constant. When the concentration of unionized NH3 was changed at the ratio 1:10:76 by varying the pH from 5.8 to 6.8 and 7.7, ammonia net absorption did not reflect the concentration ratio of unionized NH3, indicating either flux of NH4+ ions or titration of NH4+ to NH3 at the absorptive surface. In the experiments with buffer solutions without ammonium salts and extended over 2 h, ammonia concentrations in the artificial rumen fluid increased due to endogenous nitrogen influx and reached levels far beyond the expected plateau concentration of about 2 mM. Labelling of the N pool in the isolated organ by 15N showed that ammonia efflux had almost ceased in these experiments. It is argued that as yet unidentified changes have taken place in the artificial rumen fluid during the experiment, but there is some reason to believe that volatile fatty acid (VFA) absorption was affecting ammonia absorption.

Absorption↗
PubMed1989

Concentrations of volatile fatty acids and acetate production rates in the forestomachs of grazing camels.

1. Concentration profiles of volatile fatty acids (VFA), fluid volumes and turnover rates, and acetate production rates were measured in two different seasons in the forestomachs of four fistulated dromedary camels grazing in the Kenyan thornbush savannah. 2. VFA profiles and average concentrations were similar under both feeding conditions but, due to a smaller fluid turnover, VFA outflow to lower gastric sections in the dry season was reduced by almost 50%. 3. The mean acetate production rate fell from 2234 mmol/hr in the green season to 816 mmol/hr in the dry season, i.e. by approximately 64%.

Acetates↗
PubMed1988

Flux of inorganic phosphate across the sheep rumen wall in vivo and in vitro.

Experiments were done in vivo and in vitro to study the flux of inorganic phosphate (P1) across the rumen wall in sheep. The technique of the temporarily isolated and washed reticulo-rumen was applied to measure P1 net flux at nine different P1 concentrations in the buffer solutions introduced into the reticulo-rumen for 1 h. Six sheep were either P replete (4.25 g P d-1) or in a P-depleted state (1.05 g P d-1). Under both dietary treatments P1 net secretion into the reticulorumen was found at P1 concentrations between 0.1 and 2.2 mmol l-1 whereas P1 net absorption was observed at P1 concentrations between 4.1 and 15.8 mmol l-1. There were positive linear relationships between P1 concentration and P1 net flux for the whole concentration range studied in repleted and in depleted sheep. There were no indications of active transport components or saturation phenomena. Unidirectional P1 fluxes were then measured in Ussing chambers with 32P using a total of 100 rumen wall epithelia obtained from eighteen sheep of different ages. No P1 net flux was found under short-circuit conditions. Experiments with changed potential differences (+25 or -25 mV at serosal side) showed that P1 flux was influenced by the electrical gradient indicating electrogenic phosphate ion diffusion without involvement of active transport processes. Critical evaluation of the obtained unidirectional flux ratios suggests that part of the P1 flux was electroneutral, e.g. by ion exchange or cotransport. The results from these studies show that the reticulo-rumen substantially contributes to phosphate absorption from the sheep gastrointestinal tract.

Aging↗
PubMed1988

Flux of calcium across the sheep rumen wall in vivo and in vitro.

Experiments were carried out in vivo and in vitro to study the flux of Ca2+ across the sheep rumen wall. Buffer solutions with five different Ca2+ concentrations in the range 0.2-3.6 mmol l-1 were introduced into the isolated, emptied and washed reticulo-rumen for 1 h to determine Ca2+ net flux. Phosphate concentrations were either kept constant at 8 mmol l-1, or varied so as to maintain a constant phosphate/Ca2+ ratio of 2:1. Under both conditions there was a Ca2+ net secretion into the rumen at Ca2+ concentrations below approximately 1 mmol l-1 whereas Ca2+ net absorption occurred at higher Ca2+ concentrations and linearly increased with increasing Ca2+ concentrations. When phosphate concentrations were reduced to 4.3 and 0.6 mmol l-1 (Ca2+, 3 mmol l-1) Ca2+ net absorption was reduced by about 50% and completely abolished, respectively. The unidirectional (mucosal-to-serosal or serosal-to-mucosal) Ca fluxes in vitro, JCams and JCasm, were measured in Ussing chambers with computer-controlled voltage clamp. Under short-circuit current conditions (Ca2+ and phosphate, 2 mmol l-1) there was a significant net flux of Ca2+ from the mucosal to the serosal side. This net flux of Ca2+ was abolished when ouabain was added to the serosal solution, indicating that the unidirectional Ca2+ flux JCams and, hence, the net flux of Ca2+ was dependent upon active Na+ transport accomplished by the Na, K-ATPase system. Under voltage clamp conditions, the net flux of Ca2+ was greatly increased at a potential difference PD = -25 mV (serosa negative) but disappeared at PD = +25 mV (serosa positive). Analysis of the unidirectional Ca2+ fluxes JCams and JCasm under varying potential differences indicated that both Ca2+ fluxes consisted of a PD-dependent and a PD-independent component. The results show that the reticulo-rumen participates in Ca2+ absorption in sheep.

Animals↗
PubMed1982

Thiamin compartment models in healthy sheep.

Adult sheep received a single intravenous injection of 35S-thiamin. Blood and urine samples were taken at short intervals for the following 180 minutes and analyzed for 35S-radioactivity. Tracer disappearance from blood followed three-exponential functions. It was shown by computer simulation of different compartment models that a serial as well as a parallel three-compartment model would adequately describe 35S-thiamin disappearance from blood whereas a cyclic arrangement of the three compartments can be excluded. Total tracer excretion rates exceeding experimentally determined urinary excretion suggest the existence of a fourth compartment with nor or extremely small tracer return during the experimental period.

Animals↗
PubMed1981

Effects of increased blood ammonia concentrations on the concentrations of some metabolites in rat tissues.

Rats were given ammonium chloride intravenously (5 and 10 mg per 100 g body weight) and sacrificed 30 sec, 5 min and 30 min after injection. Ammonia concentrations were determined in brain, liver, skeletal muscle and epididymial fat, and glycogen, glucose, pyruvate, lactate, ATP and cyclic AMP were assayed in brain, liver and muscle. In control animals, muscle and fat showed a high capacity for ammonia accumulation. After injection of NH4Cl the ammonia concentration increased in all tissues analysed, particularly in muscle and fat, where ammonia concentrations remained elevated for 30 min. In brain, glycogen was reduced whereas glucose, pyruvate, lactate and cyclic AMP levels were raised. In liver, glycogen was lower and glucose higher than in controls. ATP concentrations were unchanged in both tissues. In muscle samples taken 30 sec and 5 min after dosing, glycogen concentrations were not affected but glucose, pyruvate and lactate concentrations were reduced and ATP concentrations were increased. In muscle samples taken after 30 min metabolite concentrations were normal again but glycogen concentrations had dropped.

Adenosine Triphosphate↗
PubMed1979

The effect of ammonium ion concentration on the activity of adenylate cyclase in various rat tissues in vitro.

The effects of three different ammonium ion concentrations (0.143; 1.43; 14.3 mmol .1(-1)) on adenylate cyclase activities in liver, muscle, fat and brain tissue in vitro were studied in the rat. At physiological levels, ammonium ions reduced adenylate cyclase activity in liver and fat by about 30%, did not affect enzyme activity in muscle tissue but increased adenylate cyclase activity in brain by 40%. Similar effects were observed at higher ammonium ion concentrations though there were no statistically significant correlations between ammonium ion concentration and the degree of change of enzyme activity.

Adenylyl Cyclases↗