Search PubMed⌕ Search

Biomedical subjects

G Sager

Publications and source records attributed to G Sager.

153 records · Page 9Linked to original sources
PubMed1979

[A generalization of the Gompertz-function of organic growth (author's transl)].

The traditional Gompertz function of organic growth with a fixed ordinate of its turning point and 3 basic parameters is generalized by introducing an exponent m into the increase function as dW/dt = k Wm e-rt. By this addition integration to the growth function implies one more parameter as W0 (initial amount of a growth unit) or E (final value of W) respectively. The resulting growth function allows variability for the turning point and more flexibility for the function proper. Examples are given for comparing the generalized from with other growth functions.

Growth↗
PubMed1979

[An example of gaining a growth function by its increase values (author's transl)].

In continuation of recent investigations of the author into mathematical presentations of organic growth an analytical expression for an increase function is postulated. Based on observations of growth processes by many authors as accumulated by HOEPPE (1959) a 2 term product of higher degree parabolas has a chance as being representative of a more frequent increase behaviour allowing direct integration to the growth function proper. An example is added for means of comparison with formerly developed growth functions.

Growth↗
PubMed1978

[Integrations of increase functions according to the L. v. Bertalanffy conception of organic growth (author's transl)].

The Bertalanffy (1941, 1949) conception of the change of organic mass M with time t as given by the difference dM/dt = aMm-bMn is transferred to the shap dW/dt = kWm(En-Wn) with W being an element of growth, i.e. length, weight or population and E its final value after reaching adultness. The integration of this expression, resulting in the growth function W, can be performed globally only for m=1. In other cases the integrals become individual with quite different solutions, some of them being presented here for means of comparison. The results show that many growth functions exclude W = 0, and all reach the final value W = E after infinite time although with quite different degrees of approximation. Moreover the graphs allow a survey as to which results this type of growth function can yield. Finally the mathematical deficiencies give rise to investigate modified types of increase functions.

Growth↗
PubMed1978

[Increase functions of the type dW/dt = k Wm (E--W)n and their integrals (author's transl)].

In a preceding paper increase functions have been treated following the Bertalanffy conception of organic growth given in the transformed shape as dW/dt = k Wm (En--Wn). As the growth functions gained by integration reach the final value E only for t leads to infinity, the increase function is changed to dW/dt = k Wm (E--W)n. Now integrations yield growth functions with asymptotic behaviour W leads to E as well as such reaching W = E in finite time, and are so better corresponding with natural development. The mathematical treatment shows a broad variety of resulting integrals given as graphs, some of them having chances as possible growth functions. Future investigations into increase functions should be focussed to the aim of choosing an ansatz allowing allround integrations leading to a variation of the parameters (m and n) in the growth function proper. This would mean avoiding a series of structurally different integrals without continuous transition between them and could be an aggravating mathematical simplification.

Growth↗
PubMed1978

[Increase functions of the type dW/dt=ktp(E-W)n and their integrals (author's transl)].

In 2 previous papers increase functions of the v. Bertalanffy (1941) type dW/dt = kWm (En--Wn) and a modified form dW/dt = kWm (E--W)n were treated, both yielding a variety of integrals resp. growth functions, most of them reaching the final value W = E after infinite time. Now an ansatz with better integration conditions dW/dt = ktp (E--W)n is presented implying t also on the right side of the basic equation and giving only two types of growth functions determined by n = 1 or 0 less than n less than 1. In the first case there appears a slightly generalized Janoschek (1957) growth function with W leads to E for t leads to infinity but a rather good position of the turning point, i.e. the abscissa of maximum increase. In the second case the result is a growth function with a definite time to reach adultness, thus being better suited to natural conditions. Graphs show the flexibility of the 2 solutions and their increase functions, including an example for practical application.

Growth↗
PubMedDate not supplied

The effect of Mg2+, nucleotides and ATPase inhibitors on the uptake of [3H]-cGMP to inside-out vesicles from human erythrocytes.

An ATP-dependent transport system is responsible for the cellular extrusion of cGMP. The objective of the present study was to determine the effect of Mg2+, ATP and other nucleotides (2'-dATP, GTP and ADP), exogenous ATPase modulators (such as metavanadate, ouabain, EGTA, NEM, bafilomycin A1 and oligomycin A) on the cGMP transport. The uptake of [3H]-cGMP (1 microM) at 37 degrees C was studied in inside-out vesicles from human erythrocytes. Magnesium caused a maximal activation between 5 and 10 mM and the optimal ATP concentration was 1.25 mM with K50-values of 0.3-0.5 mM. Among other nucleotides tested, 2'-dATP (K50 of 0.7 mM) was nearly as effective as ATP, whereas cGMP accumulated slowly in the presence of GTP. ADP and metavanadate (P-type ATPase inhibitor) showed to be competitive inhibitors with Ki values of 0.15 mM and 10 microns, respectively. NEM (a sulphydryl agent) reduced the ATP-dependent uptake in a concentration-dependent manner with a Ki value of 10 microM. Ouabain (Na+/K(+)-ATPase inhibitor) had no effect. Bafilomycin A1 (V-type ATPase inhibitor) and oligomycin (F-type ATPase inhibitor) were the most potent inhibitors with Ki values of 0.7 and 1.8 microM, respectively. The present study suggests that the cellular cGMP extrusion is energized by an ATPase with a unique inhibitor profile, which clearly differentiates it from the other major classes of membrane-bound ATPases.

Adenosine Diphosphate↗
PubMedDate not supplied

Progesterone and beta-estradiol influence the cell density-dependent distribution of cyclic nucleotides across the cell membrane of human C4-I cells (squamous carcinoma of the uterine cervix) by a non-genomic mechanism.

The ratio between extracellular levels of cGMP and cAMP (cGMPex/cAMPex) has been proposed as diagnostic tool in many forms of malignancies. In vitro and in vivo studies have shown that sex steroids effect extracellular levels of cyclic nucleotides. Cyclic changes of these hormones in premenopausal women may disturb the interpretation of the diagnostic marker. C4-I cells grew in the presence of beta-estradiol and progesterone in a chemically defined medium. Cells were sampled during the logarithmic growth phase. Cyclic nucleotide levels were determined by RIA. Receptor status was evaluated by immunocytochemistry. Progesterone increased the cGMPex/cAMPex at all cell densities tested. This effect resulted from increased cGMP and reduced cAMP extrusion. Estradiol had no clear effect on cGMPex/cAMPex even when inhibition of cAMP extrusion was observed at low cell density. Receptors for steroids were not detectable. Sex steroids interact with cyclic nucleotides in C4-I cells in a non-genomic manner.

Carcinoma, Squamous Cell↗