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B Kaufmann

Publications and source records attributed to B Kaufmann.

5 recordsLinked to original sources
PubMed2025

One mother for two species via obligate cross-species cloning in ants.

Living organisms are assumed to produce same-species offspring1,2. Here, we report a shift from this norm in Messor ibericus, an ant that lays individuals from two distinct species. In this life cycle, females must clone males of another species because they require their sperm to produce the worker caste. As a result, males from the same mother exhibit distinct genomes and morphologies, as they belong to species that diverged over 5 million years ago. The evolutionary history of this system appears as sexual parasitism3 that evolved into a natural case of cross-species cloning4,5, resulting in the maintenance of a male-only lineage cloned through distinct species' ova. We term females exhibiting this reproductive mode as xenoparous, meaning they give birth to other species as part of their life cycle.

Animals↗
PubMed1992

Contribution of both alpha- and beta-adrenoceptors to the inotropic effects of catecholamines in the rabbit heart.

The functional role of alpha-adrenoceptors was investigated in different parts of the rabbit heart. Phenylephrine (PE) caused a marked increase in force of contraction (Fc) and a prolongation of the action potential (AP) in preparations from the left atrium and the right ventricle. The response was less pronounced in the right atrium and in the left ventricle, whereas APs of spontaneously beating sinoatrial preparations remained completely unchanged. Phentolamine as well as the diesters phorbol 12,13 dibutyrate (PDBu) or 12-O-tetradecanoyl-phorbol-13-acetate (TPA) eliminated the effects of PE. The contribution of alpha-adrenoceptors to the effects of adrenaline (Adr) and noradrenaline (NA) on Fc was determined in preparations from the right ventricle. Phentolamine and the phorbol diesters reduced the effects of Adr and NA by about 30 to 60%; the remaining response was abolished by propranolol. It can be derived from our experiments that, in some parts of the rabbit heart, a considerable amount of the effects of Adr and NA is due to the stimulation of alpha-adrenoceptors. The present findings therefore support the view that, in the rabbit heart, the maximally effective drive of the heart requires the stimulation of both alpha- and beta-adrenoceptors. The inhibitory effects of phorbol diesters on the alpha-adrenoceptor-mediated response indicate that the activation of protein kinase C (PKC) specifically uncouples alpha-adrenoceptors from the effector system, whereas the response to beta-adrenoceptor stimulation remains unchanged.

Action Potentials↗
PubMed1992

Receptor kinetics and concentration-effect relation of cardiac glycosides.

Therapeutic and toxic actions of cardiac glycosides are attributed to an inhibition of Na, K-ATPase. The therapeutically relevant range is between 25% and 50% inhibition. There is a good correlation between the average steady state serum concentration of glycosides and their therapeutic action. However, therapeutic and toxic effects set in with a latency and therefore do not follow the daily variations in glycoside concentration. Although the effect follows the average serum concentrations, only the minimal concentration is measured. In principle this is only adequate if the ratio of average/minimal concentration is constant. A model calculation showed that with a constant average steady state concentration an increase in the distribution volume or a decrease in total body clearance with corresponding reduction of the daily dose lead to an increase of the minimal concentrations of 5-7%. This means a corresponding underestimation of the average concentration from the minimum concentration. However, the deviations are too small to be of clinical relevance.

Cardiac Glycosides↗
PubMed1978

Clinical and pharmacological investigations of the new saluretic azosemid.

Ple 1053 (Azosemid) is a diuretic which resembles furosemide chemically and in its mode of action. When administered intravenously, Ple 1053 was approximately 5 times more potent on a weight basis than furosemide, its dose-response relationship was closer and the slope was steeper. After oral administration Ple 1053 and furosemide were approximately equal in potency. However, the effect of Azosemid in healthy subjects was relatively prolonged and abrupt peaks did not occur.

Administration, Oral↗