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Biomedical subjects

H Hoppe

Publications and source records attributed to H Hoppe.

At least 19 recordsLinked to original sources
PubMed1992

Growth factors produced by human embryonic kidney cells that influence megakaryopoiesis include erythropoietin, interleukin 6, and transforming growth factor-beta.

Partially purified protein preparations containing megakaryocyte growth factor activity were prepared from human embryonic kidney (HEK) cell conditioned medium using ammonium sulfate precipitation, Cibicron blue affinity chromatography, and wheatgerm lectin affinity chromatography. Treatment of these preparations with neutralizing antibodies directed against erythropoietin (EPO) and interleukin 6 (IL6) resulted in a dramatic reduction in their capacity to stimulate megakaryocyte maturation in vitro. The presence of EPO in these preparations was confirmed by both immunoblotting and use of a mouse spleen erythroid progenitor cell proliferation assay routinely used to quantitate EPO activity in vitro. Northern blot analysis of HEK cell-derived mRNA with IL6 DNA probes revealed the presence of an IL6 transcript with a molecular size of 1.3 kb. Analysis of the HEK cell-derived preparation by ELISA confirmed the presence of immunologically reactive IL6. In addition, it was shown that purified recombinant human EPO and IL6 stimulated megakaryocyte maturation in the in vitro assay used in this study. These data indicate that the activity in HEK cell conditioned medium that stimulates megakaryocyte maturation in vitro is predominantly due to the presence of IL6 and EPO. Immunoneutralization studies of another HEK cell-derived preparation, which was inhibitory in the megakaryocyte maturation assay, demonstrated that it contained transforming growth factor beta (TGF beta), a potent inhibitor of megakaryocyte maturation. Taken together, these studies indicate that HEK cell conditioned medium, which has previously been reported to contain megakaryocyte growth factor activity, is comprised of a complex mixture of growth and differentiation factors, some of which promote and others that inhibit the process of megakaryopoiesis.

Biological Assay↗
PubMed1987

Ultramicro-ELISA for calmodulin and anticalmodulin.

A non-competitive ELISA-technique for the determination of anticalmodulin as well as a sensitive competitive ELISA for calmodulin in 10 microliters samples has been developed. The assay for calmodulin has an inter-assay and intra-assay variability of 18% and 17%, respectively; the limit of detection is 20 pg per assay. The corresponding values for the assay of anticalmodulin are less than 6%, less than 6% and 35 pg, respectively. The methods for the purification of calmodulin and the production of anticalmodulin are also described.

Animals↗
PubMed1986

Turnover of phosphomonoester groups and compartmentation of polyphosphoinositides in human erythrocytes.

The turnover of phosphomonoester groups of phosphatidylinositol 4-phosphate (PtdIns4P) and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] was investigated in human erythrocytes by short-term labelling with [32P]Pi. The procedure applied ensured a quantitative extraction of erythrocyte polyphosphoinositides as well as their reliable separation for the determinations of pool sizes and specific radioactivities. The pool sizes of phosphatidylinositol (PtdIns), PtdIns4P and PtdIns(4,5)P2 are 25, 11 and 44 nmol/ml of cells respectively. Under steady-state conditions, the phosphorylation fluxes from [gamma-32P]ATP into PtdIns4P and PtdIns(4,5)P2 are in the ranges 14-22 and 46-94 nmol X h-1 X ml of cells-1 respectively. Only 25-60% of total PtdIns4P and 6-10% of total PtdIns(4,5)P2 take part in the rapid tracer exchange, i.e. are compartmentalized. In isolated erythrocyte ghosts, the turnover of PtdIns4P approximately corresponds to that in intact erythrocytes, although any compartmentation can be excluded in this preparation. Under the conditions of incubation employed, the turnover of PtdIns(4,5)P2 is more than one order of magnitude smaller in isolated ghosts than that obtained for intact erythrocytes.

Adenosine Triphosphate↗
PubMed1986

Hepatic elimination kinetics of organic anions in rats: developmental aspects and influence of phenobarbital.

Maturation and phenobarbital inducibility of hepatic uptake of the organic anions indocyanine green (ICG) and eosine were studied in rats of different ages. Bile duct ligation reduced the ICG and eosine liver concentration in young rats. Therefore, bile duct ligation cannot be recommended for uptake investigations in rats of different ages. The longest elimination half life time (12.4 min) was found in 10-day-old rats within the first 15 min after i.v. administration of 38 mumol ICG/kg. In 20-day-old rats the ICG half life was significantly shorter than in adult 110-day-old rats (5.8 versus 9.6 min). Phenobarbital pretreatment did not alter the ICG elimination half lives in 10-, 20- and 110-day-old rats. The shortest elimination half life time of eosine was found in 60-day-old rats (33.0 min versus 80.3 min in 10-day-old rats and 62.4 min in 240-day-old ones). Phenobarbital pretreatment did not influence eosine serum concentrations. Our results indicate for ICG that uptake comes to maturity earlier than biliary excretion. Differences between ICG and eosine in maturation of the two transport steps support the assumption of more than one carrier for exogenous organic anions. Dye uptake was not altered after phenobarbital and, consequently, cannot be responsible for enhanced biliary dye excretion in differently aged rats.

Aging↗
PubMed1986

Two-stage median-based methods for characterizing enzyme inhibition.

Non-parametric linear regression is used for inhibition diagnostics and parameter estimation based on the velocity equation v = sKsV/(1 + sKS + iKI + isKIS) = sV(i)/(K(i) + s) = W(s)/(L(s) + i). From velocities measured as a function of inhibitor level i at different constant substrate levels s, median-based estimates of 1/W(s) and L(s)/W(s) are derived. Different diagnostic secondary plots are introduced, which take special shapes at limiting inhibition types. Two-stage median-based methods are presented for fitting the four-parameter equation to the observed velocities. These methods cause only little computational effort in contrast to one-stage median-based estimation which requires medians to be taken of solutions of impracticably large numbers of linear equation systems. Performance of the new methods is compared with that of the least-squares fit by application to simulated velocity data. For velocity data containing outliers, the median-based estimates are superior to the least-squares ones, whereas for normally distributed data the reverse is true.

Enzyme Inhibitors↗
PubMed1979

The effect of changes in cardiac frequency on left and right ventricular dP/dt max at different contractile states of the myocardium.

In 17 canine heart-lung preparations the dependence of frequency potentiation of the right and left ventricular myocardium on the basic inotropic state of the heart was investigated. The effect of unipolar stimulation of the right atrium on dP/dt max in both ventricles was measured. The aortic pressure was maintained constant. Shortly after isolation of the heart, a stepwise increase of rate from 140 to 200 beats/min only had a very weak influence on left ventricular dP/dt max. With deterioration of the myocardium the frequency potentiation of dP/dt max increased considerably. End-diastolic pressure regularly decreased with rising cardiac frequency. Since the real positive inotropic effect is masked by the concomitant fall in diastolic loading, the end-diastolic pressure was maintained constant in a second group of 8 hearts during rate variation. The most pronounced inotropic effect was now found shortly after isolation of the heart. A rate increase of 30 beats/min resulted in a 20% rise of dP/dt max. The frequency potentiation decreased with deterioration of the heart resulting in a 12% dP/dt max increase at an estimated inotropic state of 50% of control. When the contractile state of the heart was improved above the control state by calcium application the frequency potentiation of the myocardium decreased. In the right ventricle similar results were obtained except for the fact that no significant correlation between the steepness of the frequency characteristics and the contractile state of the heart could be found when the end-diastolic pressure was kept constant.

Animals↗
PubMed1979

Direct effects of dopamine, orciprenaline and norepinephrine on the right and left ventricle of isolated canine hearts.

In 31 canine heart-lung preparations the direct cardiac effects of dopamine were compared to those of norepinephrine and orciprenaline. All three agents increased heart rate by 50-60% to a maximum of 240-250 beats/min. The inotropic effects of the three drugs were not significantly different. Even with the highest doses cardiac arrhythmias were rarely observed. To achieve maximal chronotropic and inotropic effects, dopamine required four times higher doses than norepinephrine and orciprenaline. All three drugs increased right ventricular dP/dt max by about twice as much as left ventricular dP/dt max. Peak systolic pressure (P max) in the right ventricle was increased 4-5 times more than P max in the left ventricle while mean aortic pressure was elevated by 12-16 mm Hg and mean pulmonary pressure by 6-14 mm Hg. The positive inotropic effect of all three sympathomimetics and of CaCl2 was substantially more pronounced on the right than on the left ventricle.

Animals↗
PubMed1979

Concentration-dependent mutation by alkylating agents in human lymphoblasts and Salmonella typhimurium: N-methyl-N-nitrosourethane and beta-propiolactone.

The toxic and mutagenic effects of the alkylating agents N-methyl-N-nitrosourethane (MNUT) and beta-propiolactone (BPL) were quantitatively measured in human lymphoblasts and Salmonella typhimurium. Forward mutation to 6-thioguanine resistance was measured in the human lymphoblasts, and forward mutation to 8-azaguanine resistance was measured in the bacterial cells after equigenerational (1.5 doubling times) exposures. In both systems, the induced mutant fraction rose linearly as a function of concentration for BPL and was biphasic for MNUT. The responses of the two assay systems to eight alkylating agents were compared. The exposure of the cells to each alkylating agent was calculated as exposure concentration multiplied by the time of exposure, and allowance was made for the decomposition of the alkylating agents during exposure (integral exposure). Human cells were 2.5--13 times more sensitive than was S. typhimurium to the alkylating agents methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, N-methyl-N'-nitro-N-nitrosoguanidine, methylnitrosourea, and MNUT. S. typhimurium cells were three times more sensitive to butyl methanesulfonate and 25 times more sensitive to BPL than were human cells.

Alkylating Agents↗
PubMed1978

Phenotypic lag and mutation to 6-thioguanine resistance in diploid human lymphoblasts.

Mutants of a diploid human lymphoblast line resistant to 6-thioguanine (6TG) appear 6--16 generations after treatment with any of a diverse group of mutagents: methylnitrosourea (MNU), methylnitrosoguanidine (MNNG), ICR-191, 5-bromodeoxyuridine (BUdR). A hypothesis is advanced that expression of the 6-thioguanine-resistant state may require the removal of essentially all pre-existing hypoxanthine--guanine phosphoribosyl transferase (HGPRT) molecules via division, dilution, and protein turnover. Design of protocols for quantitative mutation assays requires attention to this phenomenon.

Bromodeoxyuridine↗
PubMed1978

Influence of the contractile state of the heart of the preload dependence of the maximal rate of intraventricular pressure rise dP/dt max.

In canine heart-lung preparations the relation between dP/Dt max and end-diastolic pressure exhibits the steepest slope shortly after isolation of the heart. When the heart is deteriorating, the slopes of the preload dependence of right and left ventricular dP/dt max are progressively reduced, but increase again after application of calcium. The preload dependence of dP/dt max is influenced by the contractile state of the myocardium. In the right and left ventricle the change in preload dependence of dp/dt max show a linear correlation. In the individual heart the slopes of the preload dependence of dP/dt max and of aortic flow (representing ventricular function curves) change in a very similar manner with varying contractility. In 33 different isolated hearts the slopes of the preload dependence of the two parameters show a good correlation shortly after isolation of the hearts. The preload dependence of dP/dt max can not only be used for assessment of acute variations in in myocardial contractility, but appears also to be at least as reliable as the ventricular function curves for the evaluation of the basic contractile state of different hearts. This study further shows that if dP/dt max is used for evaluation of relative changes in contractility, the quantitative results are influenced by the end-diastolic pressure level chosen.

Animals↗
PubMed1978

Alkyl methane sulfonate mutation of diploid human lymphoblasts and Salmonella typhimurium.

Concentration dependence of mutation in equigenerational exposures to methyl, ethyl, propyl, and butyl methanesulfonates has been determined in diploid human lymphoblasts and Salmonella typhimurium. Forward mutation was measured at the hypoxanthine guanine phosphoribosyltransferase locus in human lymphoblasts and at the putative guanine phosphoribosyltransferase locus in S. typhimurium. Reverse mutation at the his G46 locus was also measured in S. typhimurium. This analysis and previous reports support the conclusion that S. typhimurium and mammalian cells are essentially equisensitive to the mutagenic effects of ethyl methanesulfonate when concentration and exposure time are taken into account. Comparison of forward and reverse mutation assays in S. typhimurium reveals no important differences in sensitivities for the four compounds studied.

Animals↗
PubMed1978

[Comparison of procedures for determining Michaelis-Menten parameters together with their standard deviations using simulated measurement series].

The direct non-linear fit of Cleland and different methods applying linear regression analysis to linearized forms of the Michaelis-Menten equation have been compared. Comparison was made with respect to bias and standard deviation of the estimated values of Km, Vm, deltak and deltav. The Lineweaver-Burk method, weighted by approximately v3, turned out to produce estimates nearly as reliable as the direct fit of Cleland if one does not know whether the velocities are subject to constant absolute or relative errors. The comparison was based on ca. 10000 simulated series of velocity measurements. Runs with fewer simulated measurement series showed that for comparing different evaluation methods, at least 1000 measurement series should be simulated in order to get reliable results.

Enzymes↗
PubMed1977

[An ion exchange method to determine free metal concentrations, adapted for use in biological fluids: methods and determination of (Mg2+)].

An ion exchange method for measuring concentrations of free (ionized) metal ions and its application to the determination of [Mg2+] is described. A surface sulfonated polystyrene material is used as the "twodimensional" cation exchanger. The sample-volume is 1 ml. About 50 determinations can be performed within 1 hr having a standard error of +/- (2-4)% in the optimal range of measurement. Advantages and disadvantages of the method compared with other ones are demonstrated and discussed. Free Mg2+ ion concentrations were measured in solutions containing pyrophosphate as well as haemoglobin and compared with those which were determined by equilibrium calculation or ultrafiltration.

Cation Exchange Resins↗
PubMed1977

[Long-term effect of hormonal contraceptives on the behavior of serum lipids].

In order to check the long-term effects of oral contraceptives used in the GDR on certain serum-lipid-fractions, triglycerides, phospholipids, total and free cholesterol, and beta-lipoproteins were determined in four groups of 15 women each, taking the contraceptive preparations Ovosiston, Nonovlon, Gravistat, and Deposiston. Determinations were carried out before and following 3, 6, 12, and 18 month of drug administration. Statistically significant increases of triglycerides occurred under the combined preparations, of phospholipids under Ovosiston and Deposiston and of the beta-lipoproteins under Ovosiston and Gravistat. Total cholesterol showed a slight decrease under all preparations tested. At present the prognostic significance of these slight alterations of serum-lipid-concentrations cannot be estimated completely.

Adult↗
PubMed1976

[Clinical ergometry in cardio-pulmonary functional disorders--a comparison of the usual ergometric technics].

It is reported on the results of a comparative examination of 18 patients with two usual ergometric methods (team pathophysiology of respiration and research group diseases of heart and circulation of the GDR). Referred to the intake of oxygen as a measure for the stress of the cardiorespiratory system by means of the ergometric methods recommended by the research group diseases of heart and circulation significantly higher minute volumes of the heart rate were established. Principal differences in the evidence of the two methods did not appear.

Adolescent↗