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W Stöcker

Publications and source records attributed to W Stöcker.

40 records · Page 3Linked to original sources
PubMed1981

On the role of dimeric subunits in the quaternary structure of arthropod hemocyanins.

Partial alkaline dissociation of 24 S (12-meric), 35 S (24-meric) and 60 S (48-meric) hemocyanin from various arthropods was studied by polyacrylamide gradient gel electrophoresis and, in some cases, by electron microscopy. If there are no stable dimers among the subunits, dissociation starts by cleavage of interhexamer bonds, leading to intermediates which are hexamers or multiples of hexamers. Whenever a hemocyanin contained stable dimers, inter-hexamer bonds were also very stable as indicated by the formation of 30 S (19-meric) or 18 S (7-eric) intermediates as primary products. In such cases, inter-hexamer bonds could be cleaved by treatment with reducing agents or with 4M urea; correspondingly, these agents also cleaved the respective dimers into the constituent polypeptide chains. It is concluded that in all cases the dimeric subunits function as bridges between hexamers.

Animals↗
PubMed1977

Monitoring of the specific radioactivity of S-adenosylmethionine in kidney in vivo.

The specific radioactivity of S-adenosylmethionine was followed in the cat kidney during the infusion of L-[Me-3H]methionine into the corresponding renal artery. For this purpose 14C-labelled 4-(2-aminoethyl)pyrocatechol([14C]dopamine) as methyl acceptor was injected locally every 15 min and the 3H and 14C activity of the methylation product homovanillic acid, isolated from urine, was measured. Approximately 5% of the 14C label is excreted during the first renal passage as [14C]homovanillic acid. The specific activity of S-adenosy[Me-3H]methionine in the kidney was calculated from the known specific radioactivity of [14C]dopamine injected and the measured radioactivity ratio, 3H: 14C, of homovanillic acid isolated from urine. The specific activity of S-adenosyl[Me-3H]methionine reaches a constant value in kidney about 30-60 min after the beginning of the L-[Me-3H]methionine infusion. This plateau value was 28% +/- 14% (n = 5) lower than the specific activity of L-[Me-3H]methionine in the venous blood from the corresponding kidney. The difference between the specific radioactivity of S-adenosyl[Me-3H]methionine in kidney and of free methionine in plasma is explained by the existence of a methionine source of minor specific activity in the kidney. The average life span of S-adenosylmethionine in the kidney is 19.5 +/- 8.7 min (n = 5).

Animals↗
PubMed1976

Inactivation and excretion of dopamine by the cat kidney in vivo.

14C-Dopamine at a dose between 0.16 and 400 nmol per kg body weight was injected locally into the renal artery and urinary excretion of the label was followed for a period of up to 75 min. During the first renal passage the injected kidney excreted 28.2+/-8.3% (n = 8) of the activity applied. As shown by column chromatography the 14C-activity in urine was mainly present as 3,4-dihydroxyphenyl acetic acid (40%), homovanillic acid (15%) and dopamine (app. 20%). Excretion rate and the pattern of dopamine metabolites in urine was independent of the administered dose. Thus, the excretion of dopamine by the cat kidney is linked to an inactivation by the kidney enzymes MAO and COMT. From the literature it is known that in dog and chicken kidney catecholamines are not metabolized to such a large extent during renal excretion.

Animals↗