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Biomedical subjects

H Rasmussen

Publications and source records attributed to H Rasmussen.

At least 325 records · Page 18Linked to original sources
PubMed1971

A rapidly acting metabolite of vitamin D3.

A vitamin D(3) metabolite in intestine more polar than 25-hydroxy-vitamin D(3)(25-OH D(3)) has been detected by countercurrent distribution. The intestinal metabolite is found also after administration of labeled hydroxy D(3), indicating that it arises from vitamin D(3) via the intermediate 25-hydroxy derivative. The more polar metabolite is localized in the nuclear-chromatin fraction and appears in the gut before the physiological response to vitamin D(3).3.5 mug of the intestinal metabolite was isolated from 1250 chickens; the resulting purified material proved to be a potent mediator of calcium absorption. On a weight basis, it was at least 5 times as effective as vitamin D(3), and acted 3 times faster than either hydroxy D(3) or D(3) in stimulating intestinal calcium transport in the rachitic chick. It is proposed that this as yet uncharacterized steroid represents the active form of vitamin D(3) in the intestine.

Animals↗
PubMed1970

Cell communication, calcium ion, and cyclic adenosine monophosphate.

The hypothesis advanced in this article requires further validation. Undoubtedly it will require modification as our knowledge of biochemical control increases. Nevertheless, it should prove useful in focusing attention on the apparent similarity in the response of a large number of specific cell types to particular stimuli. Emphasis has been placed on a few common and apparently key elements in these responses. It is recognized that other factors are undoubtedly involved. Specifically, the changes in membrane potentials indicate the likelihood of widespread changes in the properties of the cell membrane, for example, changes in Na(+) and K(+) transport and distribution. These aspects of cellular responses may eventually prove to be of equal or greater importance than those common aspects of the system already identified.

Action Potentials↗
PubMed1970

Calcitonin.

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Animals↗
PubMed1970

Parathyroid hormone, 3'5' AMP, Ca++, and renal gluconeogenesis.

Isolated segments of renal tubules prepared from rat kidney cortex were capable of sustained rates of gluconeogenesis when lactate served as substrate. An increase in external Ca(++), or the addition of parathyroid hormone at a fixed Ca(++) concentration led to enhanced rate of gluconeogenesis. However, parathyroid did not increase gluconeogenesis in the absence of external Ca(++) even though it caused a rise in 3'5' AMP whether Ca(++) was present or absent. Metabolite profiles showed that either an increase in external Ca(++), or the addition of hormone in the presence of calcium led to qualitatively very similar changes. However, the addition of hormone had little effect upon metabolite levels in the absence of extracellular calcium even though an increase in extracellular H(+) enhanced gluconeogenesis under similar conditions. These results are discussed in relationship to the close association of 3'5' AMP and Ca(++) in a variety of cellular systems.

Adenine Nucleotides↗
PubMed1970

Cyclic adenosine 3':5'-monophosphate-stimulated phosphorylation of isolated neurotubule subunits.

The possible relationship between cyclic adenosine 3':5'-monophosphate (cAMP) and neurotubules in synaptic transmission has been explored. The neurotubular subunit protein from bovine cerebral cortex has been prepared. The addition of cAMP to this preparation in the presence of ATP stimulates the phosphorylation of serine residue(s) in the principal component of the preparation. The neurotubule subunit thus serves as a substrate for an intrinsic, cyclic nucleotide-dependent protein kinase closely associated with the neurotubule subunit. The significance of this finding is discussed in terms of a general model for cellular secretion involving microtubules, cyclic AMP, protein kinase, and calcium ion.

Adenosine Triphosphate↗
PubMed1969

On the mechanism of action of aldosterone.

Studies to elucidate the mode of action of aldosterone have been carried out in the amphibian urinary bladder. The following previously reported hypotheses were evaluated: (1) aldosterone stimulates sodium transport by increasing the amount of sodium available to the sodium pump; (2) aldosterone enhances energy production for the sodium pump; and (3) aldosterone-stimulated sodium transport is obligatorily coupled to aerobic metabolism. In the present experiments, aldosterone potentiated the effect of vasopressin on sodium transport in the absence of aerobic metabolism or oxidative phosphorylation. This effect was not due to enhanced energy supply. Thus both hypotheses 2 and 3 appear not to be valid. In addition, aldosterone-stimulated sodium transport exhibited increased sensitivity to the specific inhibitor, ouabain, and this inhibition was readily reversed by K(+). These findings, as well as previously reported work, have led us to propose that aldosterone stimulates sodium transport by inducing a change either in the sodium pump itself, i.e., synthesis or activation, or in its environment in the serosal plasma membrane of the responsive cells.

Adenosine Triphosphatases↗