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Biomedical subjects

D Giesecke

Publications and source records attributed to D Giesecke.

At least 37 records · Page 2Linked to original sources
PubMed1985

Ketogenic regulation by certain metabolites in rumen epithelium.

In experiments with rumen epithelium incubated in vitro in the presence of butyrate, the ketogenic effect of glucose was shared by epimeric monosaccharides but not by non-metabolizable analogues. 14C from glucose was not incorporated into ketone bodies. Malate increased ketogenesis from butyrate and decreased its oxidation, pyruvate and NH4+ had the opposite effect, and malonate inhibited both processes. The ketogenic effect of glucose was also effective with isovalerate maintaining the high proportion of acetoacetate which is characteristic of this substrate. Rumen epithelium transformed added acetoacetate into 3-hydroxybutyrate. It is concluded that reducing equivalents produced from glucose and other metabolizable substrates are responsible regulators of ketogenesis from butyrate. The results are discussed in view of the functional role of ruminal ketogenesis.

3-Hydroxybutyric Acid↗
PubMed1985

Metabolism of D(-)lactic acid in rats given high intragastral doses.

In rats given D[u-14C]-labelled DL-lactate with 3.8-13.4 mmol D-lactate per kg 0.75 by stomach tube, the exhalation of CO2 produced from and the renal excretion of D-lactate and metabolites were measured. Exhalation of D-lactate-C accounted for 45-30% of the dosage given with a decreasing proportion at higher doses. The renal excretion of D-lactate averaged 0.9% and that of metabolites from D-lactate 2.4% of the doses given. The fraction of unrecovered D-lactate accounted for about 54-68% of the doses given and increased with doses. The time course of D-lactate oxidation indicated a maximum rate of about 1.5 mmol C per kg 0.75 in 1 hr which was reached at 1 hr after infusion at the earliest and extended up to 8 hr if high doses were given.

Animals↗
PubMed1985

[Why Dalmatians excrete uric acid. Causes and consequences of a classical metabolic disorder].

After introducing into developmental aspects of "Dalmatian dog research" uric acid excretion is explained on the basis of new results by the loss of a specific transport system in liver cell membranes. Therefore, uricase which is present in normal activities is supplied only to a limited extent with uric acid for the transformation into the easily soluble allantoin. As indicated by feeding experiments, the plasma urate level is increased from about 32 mumol/l (no purine intake) up to 150-200 mumol/l at very high levels of purine intake. Thus, the influence of nutrition on plasma urate level is extraordinary. The diseases urate-urolithiasis and "bronze syndrome" associated with dalmatian urate metabolism are characterized in view of the typical pattern of the diseases and of the therapeutical and prophylactical measures to be taken.

Allantoin↗
PubMed1984

Defect of uric acid uptake in Dalmatian dog liver.

The uptake rate of uric acid into liver slices of the Dalmatian dog was found to be significantly lower compared with that in the beagle. Since there was no difference in the hepatic uricase activity between the two breeds, the abnormality of uric acid metabolism in the Dalmatian dog is considered to result from a defective hepatic transport system for uric acid.

Animals↗
PubMed1984

The ketogenic effect of glucose in rumen epithelium of ovine (Ovis aries) and bovine (Bos taurus) origin.

In experiments with rumen epithelium incubated in vitro the ratio of 3-hydroxybutyrate: acetoacetate produced was similar to the ratio reported for portal blood, and the ratio ketogenesis: oxidized to CO2 of butyrate was also close to values reported in vivo. Ovine and bovine epithelium incubated with butyrate differed significantly by the values of about 12-17 and 4-7 obtained for the ratio of 3-hydroxybutyrate: acetoacetate. Increasing levels of butyrate in the incubation medium resulted in a decreasing proportion of butyrate oxidized to CO2 and an increasing proportion of ketogenesis. The addition of glucose to butyrate in the incubation medium significantly increased the rate of ketogenesis from butyrate by ovine and bovine tissues. The addition of glucose to butyrate in the incubation medium significantly decreased the rate of butyrate oxidation to CO2 by ovine and bovine tissues. The ketogenic effect of glucose was also apparent in perfused rumen epithelium with butyrate at the mucosal side and glucose at the serosal side.

3-Hydroxybutyric Acid↗
PubMed1984

Metabolites of nucleic acids in bovine milk.

To investigate metabolites of nucleic acids in milk as by-products of protein biosynthesis, a method for determination of pyrimidine and purine compounds by reversed-phase high-pressure liquid chromatography was developed. Reproducibility of the measured compounds was 2%. Recovery of the main constituents averaged about 99%. In addition to orotic acid, allantoin, and uric acid, the free bases hypoxanthine, xanthine, and guanine, the ribonucleosides uridine, cytidine, and pseudouridine, and the ribonucleotides, guanosine 5'-monophosphate and cytidine 5'-monophosphate, were quantified in milk samples of Holstein-Friesian cows. Milk production from days 45 to 65 of lactation influenced concentrations of individual metabolites differently. Concentrations of orotic acid, allantoin, and uric acid decreased with increasing milk production, whereas concentrations of uridine, cytidine, pseudouridine, hypoxanthine, xanthine, and guanine remained unchanged. The results allowed conclusions on rate limiting steps of catabolic pathways of pyrimidines and purines and indicated relationships with protein biosynthesis. A possible role of metabolites of nucleic acids as taste factors and as substrates for milk microbes is suggested.

Allantoin↗
PubMed1982

Purine availability and metabolism in dogs fed single-cell protein or RNA.

For the evaluation of single-cell protein (SCP) the proportion of dietary purines made available by digestion and absorption was estimated with dogs (Dalmatian) in total urine collection experiments. The animals received a low purine control diet with 25% casein, diets with 25-100% replacement of casein by a bacterial SCP grown on methanol, and the control diet plus yeast RNA purine equivalent to SCP diet. Nucleic acids, bases, and purine metabolites were determined by reversed-phase high-pressure liquid chromatography. The quantitative influence of dietary purines (x) on renal purine excretion (y) was described by the equation (millimoles per day) y = 0.57x + 3.52 (r = 0.955) indicating the endogenous excretion rate of 3.5 mmol/day and the metabolic availability of 57% of ingested purines. As the ratio of urate to allantoin increased with purine intake, individual equations were established for both metabolites. On the control diet + RNA and SCP diet (100% replacement for casein), purine intakes of 20.0 and 18.2 mmol/day resulted in purine excretion values of 7.3 and 11.4 mmol/day (P less than 0.05). The proportion of free bases in the latter diet appeared as the main reason for this differences. Other influences are discussed.

Allantoin↗
PubMed1982

Caecotrophy-dependent changes in the metabolic fate of D(-) lactic acid in rabbits.

In rabbits the influence of the reingestion of special faeces on gastric as well as on intermediary metabolism of [U-14C]-D(-) lactic acid has been studied. In unrestrained animals there was no naturally occurring D(-) lactic acic concentration measurable either in stomach contents or in blood. Orally loaded D(-) lactate was almost completely decomposed in the stomach and absorbed within 15 min. Thereby intermediary oxidation was equally affected. Thus, in rabbits prevented from caecotrophy the exhalation rate of 14CO2 derived from [14C]-D(-) lactic acid at 2 h after oral application was reduced to about 65% of the rate of unrestrained animals. Similar low oxidation rates have been obtained only if [14C]-D(-) lactate was injected intraperitoneally. One can conclude from these experiments that caecotrophy in rabbits prevents the accumulation of D(-) lactic acid in the stomach by rapid bacterial transformation but increases the rate of its intermediary oxidation by absorption of these transformation products.

Animals↗
PubMed1980

D(-)Lactic acid--a physiological isomer in the rat.

D(-)Lactate is produced in significant amounts together with L(+)lactate in the stomach of normal experimental rats. It is absorbed into the blood and constitutes a physiological isomer in this animal species.

Animals↗
PubMed1979

The effect of rumen epithelial development on metabolic activities and ketogenesis by the tissue in vitro.

1. An investigation was made on oxygen consumption, glucose and lactate uptake and ketogenesis from butyrate by rumen epithelium in vitro from lambs at various stages of development. 2. Oxygen uptake was decreased by about 35% and glucose uptake by about 90% between 2 weeks and 1/2 year of age. 3. The uptake of L-lactate and the utilization of butyrate as a substrate for respiration were increased during epithelial development. 4. The production of D(-)-3-hydroxybutyrate and acetoacetate from butyrate by the epithelium was largely increased between 4 to 10 weeks of age, independently of rumen fermentation. 5. A synergistic effect of glucose on the production of D(-)-3-hydroxybutyrate and on total ketone bodies from butyrate by the epithelium was observed. It accounted to 40-80% over butyrate depending on the stage of epithelial development.

3-Hydroxybutyric Acid↗
PubMed1979

Specific methods for the determination of radioactivity in D-(-)-3-hydroxybutyrate in blood plasma.

Two simple, high-yield rapid methods with good reproducibility are described, which permit the determination of radioactivity in plasma D-(-)-3-hydroxybutyrate. The compound is converted to acetoacetate, using a modified enzymatic method. In procedure 1, acetoacetate is reacted with 2,4-dinitrophenylhydrazine; the resulting hydrazone is oxidised by means of a sample oxidiser, and the product 14CO2 is collected in scintillation liquid and counted. In procedure 2, a Conway microdiffusion unit is applied. The acetoacetate is decarboxylated to acetone in the presence of o-phenylenediamine, and the acetone is then diffused into semicarbazide solution. This solution, containing the semicarbazone derivative of labelled acetone, is transferred to liquid scintillation and counted. In both procedures the radioactivity is measured simultaneously in a separate sample which was not subjected to the enzymatic conversion of D-(-)-3-hydroxybutyrate. The difference in radioactivity between the two samples is attributed to labelled (D-(-)-3-hydroxybutyrate.

Carbon Radioisotopes↗
PubMed1979

Quantitative measurement of gluconeogenesis from isobutyrate in sheep.

Experiments with continuous infusion of [14C] isobutyrate and single injection of [3H] glucose were performed in two sheep under fed and fasted conditions in order to investigate the contribution of isobutyrate to glucose synthesis. The pool size, total entry and irreversible loss of glucose in the fed sheep were 2.8 mmol/kg0.75, 1.70 and 1.43 mmol/h per kg0.75. After 72-h fasting these parameters decreased about 40% but recycling of glucose carbon increased from 16 to 38% of the total entry rate. Isobutyrate infused intravenously at a rate of 3.5 mmol/h contributed to a minimum of 3-5% of glucose entry indicating that at least 40-60% of the infused isobutyrate was used for net glucose synthesis. The efficiency of the glucogenic and energetic use of isobutyrate as compared to propionate is discussed.

Animals↗