Search PubMed⌕ Search

Biomedical subjects

W Henke

Publications and source records attributed to W Henke.

At least 55 records · Page 3Linked to original sources
PubMed1991

Ischemia decreases the content of the adenine nucleotide translocator in mitochondria of rat kidney.

The activity of the adenine nucleotide translocator is decreased at ischemia. Studies were undertaken to elucidate changes in the adenine nucleotide translocator by determining its content in mitochondria of ischemic rat kidney. After 60 min of ischemia, the content of the adenine nucleotide translocator amounted only to about 55%, of that measured in control mitochondria. At the same time, the flux control coefficient was increased. These changes paralled the well-known effects of ischemia: the decrease in oxidative phosphorylation and in adenine nucleotides. It is supposed that the decrease in the adenine nucleotide translocatar content accounts, at least partially, for the ischemia-induced impairment of mitochondria.

Animals↗
PubMed1991

Methods compared for determining activity of N-acetyl-beta-D-glucosaminidase in urine without pretreatment of sample: different sensitivity and species effect.

N-Acetyl-beta-D-glucosaminidase (NAG) activities in the urine of men and rats were measured with methods recommended as procedures without pretreatment of the urine sample. Four different derivatives of NAG were compared for determination: 4-nitrophenyl; 3,3-dichlorophenylsulfonphthaleinyl; 3-cresolsulfonphthaleinyl, and 2-methoxy-4-(2-nitro-vinyl)phenyl. The conventional test using the 4-nitrophenyl derivative showed the highest activities and correlated very well with the other tests. There are method-dependent differences between NAG activities measured in men and rats due to the different Km values and inhibitory effects by urea.

Acetylglucosamine↗
PubMed1991

Evaluation of methods for determining N-acetyl-beta-D-glucosaminidase in urine of rats without purification of urine samples.

N-Acetyl-beta-D-glucosaminidase (NAG) activities in urine of rats were measured with methods recommended as procedures without the pretreatment of urine sample. Four different derivatives [4-nitrophenyl; 3-cresolsulfonephthaleinyl; 3,3'-dichlorophenylsulfonephthaleinyl; 2-methoxy-4-(2-nitrovinyl)phenyl] of N-acetyl-beta-D-glucosaminide were compared for determination. The conventional test using the 4-nitrophenyl derivative showed the highest activities and was very well correlated with the other tests. The test using the 3,3'-dichlorophenylsulfonephthaleinyl substrate is most convenient and practical to determine NAG in small animals because it is, in contrast to the other three discontinuous (endpoint) tests, a continuous (kinetic) assay which can be easily adapted to clinical chemistry analyzers.

Acetylglucosaminidase↗
PubMed1991

Kinetic evidence that the sodium-dependent high-affinity and the sodium-independent low-affinity dopamine uptake are mediated by one carrier.

In synaptosomes of the rat striatum the dopamine uptake was measured in a concentration range of 0.03 microM to 100 microM. In the presence of sodium the uptake exhibited a non-Michaelis-Menten kinetics and in a sodium-free medium the uptake kinetics was sigmoid. According to these findings a novel model for the dopamine uptake is proposed. Its main assumption is one carrier with two dopamine binding sites.

Animals↗
PubMed1991

Characterization of a hexammineruthenium-stimulated external NADH oxidase from rat liver mitochondria.

The existence of an external hexammineruthenium-stimulated NADH oxidase in rat liver mitochondria is postulated. This enzyme is localized on the outer surface of the inner mitochondrial membrane, is specific for NADH and requires oxygen. The apparent affinity of the enzyme for NADH amounts to about 4 microM. Furthermore, the enzyme is characterized by an alkaline pH optimum and a linear Arrhenius plot (14 kJ/mol). The electron transfer from NADH to oxygen is not linked with the respiratory chain but is connected with the formation of superoxide radicals.

Animals↗
PubMed1990

The catabolism of endogenous adenine nucleotides in rat liver mitochondria.

The degradation of intramitochondrial adenine nucleotides to nucleosides and bases was investigated by incubating isolated rat liver mitochondria at 37 degrees C under non-phosphorylating conditions in the presence of oligomycin and carboxyatractyloside. Within 30 min the adenine nucleotides were degraded by about 25 per cent. The main products formed were adenosine and inosine the contents of which increased five- to sevenfold. Compartmentation studies revealed that about 50 to 60 per cent of the adenosine formed remained inside the organelles whereas inosine was almost completely released into the surrounding medium. Outside the mitochondria only very small amounts of adenine nucleotides were detected. Similar incubations in the presence of [14C]-adenosine yielded no [14C]-inosine ruling out extramitochondrial adenosine deamination. It is concluded that endogenous adenine nucleotides can be degraded in mitochondria via AMP dephosphorylation and subsequent adenosine deamination. A purine nucleoside transport system mediating at least the efflux of inosine from the mitochondria is suggested.

Adenine Nucleotides↗
PubMed1990

Measurement of carvedilol enantiomers in human plasma and urine using S-naproxen chloride for chiral derivatization.

The enantiospecific procedure for assaying carvedilol includes the extraction of the drug from plasma or urine with diisopropylether after alkalization of the sample with pH 9.8 buffer. After evaporation of the org. solvent a chiral derivatization is performed using S-(+)-naproxen chloride. The HPLC separation of the diastereomeric amides is possible on a silica gel stationary phase with a mixture of n-hexane, dichloromethane, and ethanol as mobile phase. Detection of the products is performed by fluorescence measurement at 285/355 nm. Preliminary pharmacokinetic studies after i.v. infusion of racemic compound to healthy volunteers showed that the concentrations of the R-(+)-enantiomer exceeded those of the S-(-)-enantiomer. Overall, both carvedilol enantiomers exhibited a high clearance with preference for the S-enantiomer. The difference was even more expressed after p.o. dosage indicating a stereoselective first-pass effect with higher extraction of the levorotatory enantiomer, which is more potent with respect to beta-adrenoceptor antagonistic activity.

Adrenergic beta-Antagonists↗
PubMed1989

Adenosine formation by isolated rat kidney mitochondria.

Isolated rat kidney mitochondria are able to generate extraordinary amounts of adenosine. About one-third of the adenosine formed only results from the degradation of adenine nucleotides. Pyridine nucleotides may contribute to adenosine formation. Nevertheless, there must be an additional, as yet unidentified, acid-insoluble compound in mitochondria which is able to form a significant portion of adenosine.

Adenine Nucleotides↗
PubMed1989

Mitochondrial metabolism of guanine nucleotides. Possible role of guanosine.

The catabolism of intramitochondrial guanine nucleotides was examined. During 30 min incubation of rat liver mitochondria at 37 degrees C in the presence of oligomycin and carboxyatractyloside, guanine and xanthine were formed and appeared in the medium. Under these conditions, the direct conversion of GMP to guanine by hypoxanthine-guanine phosphoribosyltransferase is suggested to be the main catabolic route within the organelles. Only very small amounts of guanosine were produced and detected both inside and outside the organelles. [14C]Guanosine and [14C]inosine were taken up by the mitochondria. Therefore, guanosine is suggested to be a precursor of intramitochondrial guanine nucleotides.

Animals↗
PubMed1989

Identification and characteristics of a novel mitochondrial 5'-nucleotidase in rat liver.

In rat liver mitochondria there exists an AMP-dephosphorylating activity which converts external 5'-AMP to adenosine. It exhibits a pH optimum of 7.5 and a Km(AMP) of 0.085 mM. Furthermore, this activity is stimulated by magnesium (Km = 0.5 mM) and seems to be not affected by low concentrations of ATP or ADP. From the characteristics of the enzyme the existence of a 5'-nucleotidase in rat liver mitochondria which is localized on the outer surface of the inner mitochondrial membrane was concluded. The enzyme may be important for the production of cellular adenosine.

5'-Nucleotidase↗
PubMed1989

[Biochemical research in kidney transplantation].

Function and importance of biochemical research in kidney transplantation are presented. By selected examples of the own research work it is shown that fundamental and clinical-related research should be combined to a comprehensive scientific conception. A close cooperation with the clinician of the transplant center and other medical, scientific and technical disciplines are necessary to allow an effective biochemical research.

Animals↗
PubMed1989

The adenine nucleotide catabolism in nonphosphorylating mitochondria of different tissues.

The degradation of endogenous adenine nucleotides was compared in mitochondria isolated from mouse and rat liver, rat renal cortex and solid hepatoma. Mitochondria were incubated for 30 min at 37 degrees C in the presence of carboxyatractyloside and oligomycin. In rat liver mitochondria ATP, ADP and AMP were degraded by about 25% each, whereas in kidney and hepatoma mitochondria a rapid decline of ATP and ADP but no change in the AMP contents were observed. Main products formed were adenosine, inosine and hypoxanthine in all mitochondria examined. Compartment studies revealed that the main route of intramitochondrial adenine nucleotide catabolism seems to proceed via AMP dephosphorylation and subsequent adenosine deamination.

Adenine Nucleotides↗