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Biomedical subjects

H Senger

Publications and source records attributed to H Senger.

69 records · Page 4Linked to original sources
PubMed1978

Diminished insulin response in highly trained athletes.

Insulin secretion and glucose tolerance were examined in 6 highly conditioned athletes in comparison with a control group of 115 normal healthy persons. During glucose infusion the athletes showed low insulin secretion although there was no difference in the levels of blood glucose compared to the control group. It is concluded that under physiologic conditions the extent of insulin secretion is not dependent only upon the blood glucose levels. The results show that a lack of insulin response can occur as a consequence of adaption to physical training. A reduced insulin response, therefore, does not necessarily indicate a diabetic or prediabetic state.

Adult↗
PubMed1978

Two Biosynthetic Pathways to delta-Aminolevulinic Acid in a Pigment Mutant of the Green Alga, Scenedesmus obliquus.

Pigment mutant C-2A' of the unicellular green alga Scenedesmus obliquus develops only traces of chlorophyll and has no detectable amount of delta-aminolevulinic acid (ALA) when grown in the dark. In light it develops ALA and in the presence of levulinic acid (LA), a competitive inhibitor of ALA dehydratase, it accumulates 0.18 mmoles of ALA per 10 microliters of packed cell volume per 12 hours. This amount could be increased up to 15 times by feeding precursors and cofactors.Incubation with [U-(14)C]glutamate, [1-(14)C]glutamate, and [2-(14)C]glycine yielded significantly labeled ALA, whereas [1-(14)C]glycine did not label the ALA specifically. Thus, two pathways using either glycine/succinyl-coenzyme A or incorporating the whole C-5-skeleton of glutamate into ALA are present in this alga. The efficiency of the glycine/succinyl-coenzyme A pathway seems to be three times higher than that of the glutamate pathway. Incubation with [5-(14)C]2-ketoglutarate, which can serve both pathways as a precursor, resulted in radioactivity of ALA as high as the sum of both labeling with [1-(14)C]glutamate and [2-(14)C]glycine.Since the newly synthesized chlorophyll was radioactive regardless of labeled substrate employed, both pathways culminate in chlorophyll formation.

Journal Article↗
PubMed1976

The 520 nm absorbance changes in Scenedesmus obliquus and its relation to photosystem I.

The kinetics (region of seconds) of the light-induced 520 nm absorbance changes and its dark reversal have been studied in detail in the wild type and in some pigment and photosynthetic mutants of Scenedesmus obliquus. The following 5 lines of evidence led us to conclude that the signal is entirely due to the photosystem I reaction modified by electron flow from Photosystem II. Gradual blocking of the electron transport with 3(3,4-dichlorophenyl)-1,1-dimethylurea resulted in diminution and ultimate elimination of the biphasic nature of the signal without reducing the extent of the absorbance change or of the dark kinetics. On the contrary, blocking electron flow at the oxidizing side of plastoquinone with 2,5-dibromo-3-methyl-6-isoprophyl-p-benzoquinone or inactivating the plastocyanin with KCN, prolonged the dark reversal of the absorbance change apart from abolishing the biphasic nature of the signal. Action spectra clearly indicate that the main signal (I) is due to electron flow in Photosystem I and that its modification (Signal II) is due to the action of Photosystem II. Signal I is pH independent, whereas Signal II demonstrates a strong pH dependence, parallel to the O2-evolving capacity of the cells. Chloroplast particles isolated from the wild type Scenedesmus cells demonstrated in the absence of any added artificial electron donor or acceptor and also under non-phosphorylation conditions the 520 nm absorbance change with approximately the same magnitude as whole cells. The dark kinetics of the particles were comparatively slower. Removal of plastocyanin and other electron carriers by washing with Triton X-100 slowed down the kinetics of the dark reversal reaction to a greater extent. A similar positive absorbance change at 520 nm and slow dark reversal was also observed in the Photosystem I particles prepared by the Triton method. Mutant C-6E, which contains neither carotenoids nor chlorophyll b and lacks Photosystem II activity, demonstrates a normal signal I of the 520 nm absorbance change. This latter result contradicts the postulate that carotenoids are the possible cause of the 520 nm absorbance change.

Chlorophyll↗
PubMed1975

Changes of the oxidative phosphorylation in mitchondria of rat skeletal muscle following strenous exercise.

The rate of oxygen consumption of mitochondria from rat muscles at pH 7.4 is elevated by 1-lactate. The respiratory control ratio and the ADP/O-ratio are decreased under these conditions. Acidification to pH 6.5 in the absence of 1-lactate does not change the interpreted mitochondrial functions. The experimental data are discussed as a partial uncoupling effect of 1-lactate on the oxidative phosphorylation. Similar changes in those mitochondrial functions are found after short-time intensive swimming exercise of rats. These variations might be a reason for the sometimes described reduced aerobic performance after intensive work.

Adenosine Diphosphate↗
PubMedDate not supplied

Protein supplementation of human milk for the nutrition of VLBW-infants: human milk protein vs. meat protein hydrolysate.

In 25 very low birth weight infants appropriate for gestational age the influences of different human milk (HM) preparations on weight gain, gross indices of nitrogen metabolism and energy balance were studied during the second month of postnatal life. HM was fortified either by HM-protein (HMP) or by an enzymatic meat protein hydrolysate (PH) to protein concentrations between 1.5 and 1.7 g/100 ml. The caloric densities of both HM preparations were similar between 62 and 68 kcal/100 ml. There were no differences in weight gain (MM + HMP: 18.6 +/- 3.4 g/kg/day; HM + PH: 16.5 +/- 4.1 g/kg/day), nitrogen retention (HM + HMP: 31.5 +/- 3.1 mmol/kg/day; HM + PH: 30.0 +/- 3.2 mmol/kg/day), and the preprandial estimated essential amino acid profiles between the both feeding groups. In contrast the serum concentrations of alpha-amino-nitrogen 60 minutes postprandially were elevated in the infants fed HM + PH in comparison to the infants fed HM + HMP. This high postprandial amino acid concentrations in serum in the group fed HM + PH were accompanied by increased bile acids concentrations in serum, higher renal amino acid excretion and increased fecal fat losses. The results suggest that due to the more rapid intestinal absorption of amino acids from PH than from HMP the concentrations of amino acids increase postprandially which results in a detectable increase of the newborn cholestasis in these infants. Nevertheless, the scale of these metabolic responses to feeding protein hydrolysates is small and without detectable influences on nitrogen retention or weight gain.

Amino Acids, Essential↗
PubMedDate not supplied

Evidence for nickel in the soluble hydrogenase from the unicellular green alga Scenedesmus obliquus.

Cultures of the green alga Scenedesmus obliquus were grown in the presence of either the chelating reagent EDTA or NiCl2 in various concentrations and assayed for hydrogenase catalyzed photohydrogen evolution after an anaerobic dark adaptation period. Cultivation of algae in the presence of 100 microM EDTA inhibited the formation of hydrogenase activity by 37%. After a cultivation of the cells in the presence of 5-20 microM NiCl2 photohydrogen evolution was increased by 20-40%. Addition of EDTA up to a final concentration of 1.5 mM had no effect on the activity of hydrogenase in cell-free hydrogenase preparations. Cultures grown in the presence of radioactive 63NiCl2 incorporated 63Ni in a parallel fashion to the cell growth. In radioactive labeled hydrogenase preparations a co-elution of radioactivity and hydrogenase activity could be observed using gel filtration chromatography.

Anaerobiosis↗
PubMedDate not supplied

Free, conjugated and bound polyamines during the cell cycle in synchronized cultures of Scenedesmus obliquus.

The levels of free, conjugated and bound polyamines (PA) were analyzed during the cell cycle of the synchronized unicellular green alga Scenedesmus obliquus. The polyamines putrescine (PUT) and spermidine (SPD) in their free and conjugated forms accumulated per cell to a maximum in the cell cycle at about the 16th hour after onset of illumination. The polyamines bound to macromolecules and membrane systems showed an additional peak around the 8-10th hour of the cell cycle. The possible role of the different forms of polyamines in DNA replication, mitosis, cell division and development of the photosynthetic apparatus is discussed.

Cell Cycle↗