Search PubMed⌕ Search

Biomedical subjects

W Henke

Publications and source records attributed to W Henke.

At least 73 records · Page 4Linked to original sources
PubMed1989

A computer assisted method to control the steady state of an ATP-regenerating assay.

A mathematical procedure is presented which permits to calculate the steady-state concentrations of AMP, ADP and ATP in an ATP-regenerating assay containing pyruvate kinase and lactate dehydrogenase as auxiliary enzymes. The accuracy of this procedure is demonstrated by the agreement of the calculated concentrations with the experimental data obtained in measurements of mitochondrial ATPase activities. The computer-assisted procedure can be employed (a) to determine extremely low adenine nucleotide concentrations which are difficult to obtain by direct measurements and (b) to adjust and to optimize the assay conditions according to the specific requirements of the experiment, including high concentrations of ATP and prescribed ATP/ADP ratios.

Adenosine Diphosphate↗
PubMed1989

Purine compounds in mitochondria: a quantitative evaluation.

Applying a recently developed reverse-phase ion-pair HPLC technique we determined purine compounds in acid extracts of mitochondria isolated from rat and mouse liver, rat renal cortex, and hepatoma. Intramitochondrial purine nucleosides and bases were evaluated quantitatively for the first time. All mitochondria examined contain significant amounts of adenosine, guanosine, inosine, guanine, and hypoxanthine. Moreover, IMP was identified in all extracts. Adenine was detected in traces only. These results are in accordance with the concept of mitochondrial metabolism of purine compounds.

Animals↗
PubMed1988

Penbutolol: pharmacokinetics, effect on exercise tachycardia, and in vitro inhibition of radioligand binding.

The pharmacokinetics of penbutolol 40 mg, its reduction in exercise-induced tachycardia, and the in vitro inhibition of radioligand binding to beta-adrenoceptors by plasma have been investigated in 7 healthy volunteers. The peak penbutolol concentration of 285 ng/ml was observed 1.2 h after administration, and the maximum of 4'-OH-penbutolol of 4.76 ng/ml was found after 1.64 h. Penbutolol was detected for up to 48 h, and 4'-OH-penbutolol dropped below the limit of detection after about 10 h. The terminal plasma concentration of penbutolol declined with an average half-life of 19 h. The maximum reduction in exercise-induced tachycardia was 33 beats/min 2.6 h after taking penbutolol. There was still a significant reduction of about 7 beats/min after 48 h. This effect could be adequately explained by the concentration-time course of penbutolol in combination with Clark's model of the concentration-effect relationship. Antagonist activity in plasma caused 91% inhibition of radioligand binding in vitro to beta 2-adrenoceptors on rat reticulocyte membranes 1.6 h after intake of penbutolol. By 48 h after intake, radioligand binding was still significantly inhibited (23%). The in vitro inhibition of radioligand binding by plasma showed a linear correlation with the reduction in exercise-induced tachycardia for all phases of the workload. The time course of the reduction in heart rate was completely explained by the in vitro inhibition of radioligand binding. However, it was not possible to explain the in vitro inhibition of radioligand binding by the concentration-time course of penbutolol using a simple competition model, although both variables were based on the same sampling site. When the in vitro inhibition of radioligand binding was plotted against the penbutolol concentration at the same sampling times (with both variables transformed to multiples of the apparent inhibition constant) the discrepancy became even more apparent as time-related counterclockwise hysteresis. None of the known metabolites of penbutolol can explain the discrepancy between the penbutolol concentration and the inhibition of radioligand binding in vitro. It appears that an other active metabolite is formed, which contributes to the effect in vitro and in vivo and so can explain the observed discrepancy.

Adrenergic beta-Antagonists↗
PubMed1988

Effects of tracheal intubation on laryngeal acoustic waveforms.

To assess the feasibility of noninvasive detection of laryngeal injury after tracheal intubation through acoustic waveform measurements, we studied the effects of intubation on "time-expanded" acoustic waveforms of the larynx in 16 patients given general anesthesia, 9 with and 7 without tracheal intubation. Recordings of several utterances were obtained by means of a microphone and an accelerometer attached to the skin at the midpoint of the suprasternal notch. Recordings were taken the day before induction of general anesthesia, 20 minutes after extubation, and 2 and 4 days after extubation. Waveforms of the recordings were subsequently assessed visually for features different from those of normal phonation as determined in preliminary studies. Waveforms in several of the recordings taken soon after extubation showed marked intraperiod and interperiod irregularities. These abnormalities improved and disappeared over the following 4 days. No changes were observed in the acoustic waveforms of seven patients given general anesthesia without tracheal intubation. The analysis of time-expanded acoustic waveforms of the larynx indicates that this technique has considerable potential as a sensitive, noninvasive technique that helps to evaluate the effects of tracheal intubation on laryngeal function, a technique that warrants further study and evaluation.

Adult↗
PubMed1987

Identification and characteristics of a novel mitochondrial ATPase in rat liver.

A novel ATPase is postulated for isolated mitochondria and mitoblasts of rat liver. The enzyme is active in the presence of oligomycin and carboxyatractyloside. It can be distinguished from other well-known mitochondrial and non-mitochondrial ATPases by its insensitivity to common ATPase inhibitors and effectors and by digitonin treatment. The ATPase is localized on the outer side of the inner mitochondrial membrane. It is activated by Mg2+ in the alkaline pH range and exhibits a biphasic kinetics. The novel external ATPase of rat liver mitochondria possesses similar properties with respect to ATP-dependent protease.

Adenosine Triphosphatases↗
PubMed1986

Localization of CEA, HCG, lysozyme, alpha-1-antitrypsin, and alpha-1-antichymotrypsin in gastric cancer and prognosis.

Carcinoembryonic antigen (CEA), beta-human chorionic gonadotropin (HCG), alpha-1-antichymotrypsin (ACT), alpha-1-antitrypsin (AAT) and Lysozyme (LYS) were traced by immunoperoxidase staining in gastric carcinomas. The immunohistological results were evaluated in relation to histological types (WHO and Laurén), stage of disease, grade and survival time. CEA was demonstrated in 96% of the tumours, HCG in 34%, ACT in 78%, AAT in 42%, and LYS in 71%. Comparing the staining patterns of the antigens and the intensity of staining some differences were notable. Except for signet-ring cell carcinomas, all of which were intensively positive, CEA expression decreased significantly with loss of differentiation. This observation was not seen with the other marker substances. None of the tested markers was characteristic for one particular histological type, nor could they be correlated with the tumour stage or grade. The marker positivity of CEA, ACT and LYS was not related to survival time. For HCG only, a correlation between tissue expression and a restricted survival time was established. Patients with AAT positive carcinomas had a significantly better survival probability.

Carcinoembryonic Antigen↗
PubMed1986

H2O2 formation during nucleotide degradation in the hypoxic rat liver: a quantitative approach.

In the hypoxic liver an increased rate of cytosolic and peroxisomal H2O2 generation is due to the accelerated purine nucleotide degradation. The relative contribution of the oxidase type of xanthine oxidoreductase activity increases in hypoxia by less than 10%, the dehydrogenase type of this enzyme is hardly inhibited by the increased concentration of free NADH. Nevertheless, due to the high hypoxanthine supply the xanthine oxidase related H2O2 formation is increased six-fold and together with the peroxisomal uricase-mediated share it accounts for half of the oxygen consumption.

Animals↗
PubMed1985

A mathematical model to study short-term regulation of mitochondrial energy transduction.

A mathematical model is presented which includes the following elementary process of mitochondrial energy transduction: hydrogen supply, proton translocation by the respiratory chain, proton-driven ATP synthesis by the F0F1-ATPase, passive back-flow of protons (leak) and carrier-mediated exchange of adenine nucleotides and phosphate. For these processes empirical rate laws are used. The model is applied to calculate time-dependent states of energy transduction in isolated rat liver mitochondria. From the general agreement of the computational results with experimental data (Ogawa, S. and Lee, T.M. (1984) J. Biol. Chem. 259, 10004-10011) the following conclusions can be drawn. (1) The length of the time interval during which mitochondria are able to maintain a relatively high and constant delta pH in the absence of oxygen (anaerobiosis) is limited by the availability of intramitochondrial ATP. (2) The overshoot kinetics of delta pH which appear when reoxigenating mitochondria after a preceeding anaerobiosis might be due to a lag phase kinetics of the F0F1-ATPase. (3) In phosphorylating mitochondria the homeostasis of delta pH is brought about by a high sensitivity of the respiration rate and the rate of the F0F1-ATPase as to changes of delta pH. (4) Analysis of the mean transient times shows that the rate of ATP synthesis in State 3 is controlled to almost the same extent by the hydrogen supply, the respiratory chain, the adenine nucleotide translocator and the proton leak.

Adenine Nucleotides↗
PubMed1985

[Echinococcus cysticus of the liver--sonographically a solid tumor].

In a patient with Hodgkin's disease, an intrahepatic echodense mass was diagnosed incidentally by ultrasonography. The sonographic pattern suggested a solid tumor. Despite negative or border-line serology, computed tomography established the diagnosis of Echinococcus cysticus by documentation of one "daughter" cyst; this diagnosis was confirmed by surgery. The criteria of Echinococcus cysticus in modern imaging methods like sonography and computed tomography are summarized and the diagnostic value of various procedures including diagnostic procedure in seronegative cases are discussed.

Adult↗
PubMed1984

A new method of parameter estimation from progress curves.

A mathematical procedure is presented which permits kinetic parameters to be determined from progress curve data. The method is applicable to any kind of enzymatic reaction which can be described by a single rate equation. A general criterion is derived to check the accuracy of the method. An application to a simulated 2-substrate reaction is given.

Half-Life↗
PubMed1978

[The Paderborn calvaria--a diluvial Homo sapiens].

In the following work a morphognostic and morphometric analysis of a diluvial calvaria from Sande/Paderborn in Westfalia is presented. Besides the above, absolute dating by two methods (Radiocarbon- and Amino-acid-dating) was applied. The morphological comparison shows strong affinities to comparative material from the Upper Pleistocene like Cro-Magnon. The absolute dates support this morphological analysis. Both findings--morphological analysis and absolute dating--were done in separate analyses and will be documented separately in the following article.

Cephalometry↗