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Die Bedeutung der Toleranztests für die Diagnostik der diabetischen Vorstadien wird aus den pathophysiologischen Voraussetzungen abgeleitet. Die Methode der Wahl ist der einzeitige orale Glucosetoleranztest mit 100g Glucose (oder Glucoseoligosacchariden). Dieses Verfahren erfaßt die wesentlichen physiologisch wichtigen Funktionen, was für den intravenösen Glucosetoleranztest und für den Tolbutamidtest nicht gilt. Gleichzeitig ist der orale Toleranztest am einfachsten durchzuführen. Lediglich bei Störungen im Gastrointestinalbereich kann der intravenöse Glucosetoleranztest angezeigt sein. Es gibt keine wichtige Indikation für den Tolbutamidtest.
Die verschiedenen Störmöglichkeiten sowie Fehlermöglichkeiten bei der Durchführung des Glucosetoleranztests werden besprochen.
The isolation of transcribed DNA sequences of P815 cells and the partial characterization with respect to their sequence composition and relative rates of enzymatic DNA methylation are reported in this paper. Transcribed regions were purified by affinity chromatography using immobilized heterogenous nuclear RNA of P815 cells. About 10% of total genome was found in this fraction. Reassociation analyses showed differences in sequence composition of transcribed versus non-transcribed DNA fractions. The relative proportion of inverted repeats was doubled in the transcribed fraction whereas ordinary highly repetitive sequences comprising mainly of satellite DNA were found almost exclusively in the non-transcribed regions of the P815 genome. About 70% of transcribed portions corresponds to unique and intermediary DNA sequences. After labelling of cells with L-[Methyl-3H]methionine and [14C]deoxycytidine relative rates of enzymatic DNA methylation were computed for different kinetic components of transcribed and non- transcribed portions of P815 genome. No difference was found except in inverted repeats. In transcribed DNA the relative rate of enzymatic DNA methylation was only about 40% of that of the non-transcribed ones. We have quantitated this hypomethylation and found that there is, in average, about one 5-methylcytosine residue in 100 nucleotides of transcribed inverted repeats, compared to about 2.5 5-methylcytosines in non-transcribed fractions. In view of these data we propose that the enzymatic methylation of inverted DNA repeats negatively controls the transcriptional process in a given genomic region.
Methods are described for an enzymatic preparation of 14C-labeled terpenoids. With a cell-free system of a white mutant of Phycomyces blakesleeanus (Mucoraceae) [14C]squalene and [14C- cis]phytoene can be synthesized from [2-14C]mevalonate. The application of norflurazon, a phenyl- pyridazinone herbicide, helps to increase the yield of squalene. Furthermore, the liquid endosperm of Echinocystis lobata (Cucurbitaceae) was used for the formation of either [14C(-)]kaurene from [14C]mevalonic acid or [14C-/ra/w]geranylgeranyl pyrophosphate in the presence of Amo 1618.
The hydrocarbons formed were purified by alumina-column chromatography and preparative thin-layer chromatography (TLC). Geranylgeranyl pyrophosphate was separated by DE-column chromatography followed by TLC.
The effect of NH4Cl on the kinetics of the back reaction of photosystem II as derived from luminescence measurements was investigated in dark adapted Chlorella in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) at different temperatures. The kinetics of the back reaction which, under these conditions, leads to the reduction of the S2 state by the primary electron acceptor Q- of photosystem II was observed to be considerably slowed down in the presence of NH4Cl.
Analysis of the kinetic results in the light of the theory of the back reaction developed by Mar and Roy (J. Theor. Biol. 48, 257-281 (1974)) revealed two opposite effects of NH4Cl to be present simultaneously:
1) The enthalpy of activation of the back reaction was lowered (catalyzing effect of NH4Cl)
2) The frequenca factor which indicates the number of collisions of the reacting molecules in the membrane per second is largely decreased (inhibitory effect of NH4Cl).
This reduction of the mobility of the recombining species of the back reaction is the predominant effect of NH4Cl. It is suggested that this effect is due to a change of the conformational state of the membrane induced by dissolution of relative large amounts of NH? within the lipid phase of the thylakoid membrane. This hypothesis is supported by the observation that the value of the exciton yield of the back reaction changes upon addition of NH4Cl.
Photosystem II
It is shown that the kinetics of the back reaction of photosystem II in the seconds time range as derived from the luminescence decay curve in the presence of DCMU is controlled by the internal pH of the thylakoids. Modifications of the conformational state of the photosynthetic membrane while leaving the internal pH unchanged, however, reaction.
The cyanobacterium Synechococcus (Anacystis nidulans strain L 1402-1) was grown at + 37 °C in 3.0 vol.% CO2. The effect of preillumination with white light on the subsequent dark 14CO2 fixation was studied under aerobic conditions at + 30 °C. The radioactive carbon first incoiporated into 3-phosphoglyceric acid was transferred during the later periods of dark 14CO2 fixation to phosphoenolpyruvate and aspartate. No labelling or a very low label in sugar monophosphates could be observed. During the dark/light transients the initial fixation product was mainly aspartate. The pattern of 14C-incorporation into photosynthetic products under steady state conditions (10 min photosynthesis) varied with the temperature during the experiments. The radioactive carbon was firstly incorporated into 3-phosphoglyceric acid. During the later periods of photosynthetic 14CO2 fixation an increased 14C-incorporation into aspartate and glutamate could be observed. Our findings were interpreted with operating of a phosphoenolpyruvate carboxylation besides the Calvin cycle.
Eight-membered rings of the composition [SO2(NR)2PR′]2 3a-d with R = CH3, C2H5, and R′ = CH3, C6H5, were prepared from substituted sulfamides and dichlorophosphanes in the presence of a tertiary amine. These molecules were characterized on the basis of 1H and 31P NMR investigations and of mass spectra. 3 a reacts with phosphorus pentachloride to yield the spirocyclic derivative 4 with the phosphorus atom in the center of two four-membered rings. Methyliodide reacts with 3 a and 3 b under opening of the eight- membered ring and formation of phosphonium salts. The structure of 3 b is discussed in detail. 8b crystallizes in the orthorhombic space group Pna 21 with a = 12.60(0), b = 13.27(1), c = 12.62(4) Å.
Potential energy and dipole moment functions have been calculated for the ground states of the NeH+ (1.0 ≦ R ≦ 15 a. u.) and the KrH+ (1.6 ≦ R ≦ 20 a. u.) ion from highly correlated SCEP/VAR and SCEP/CEPA electronic wave functions. The following spectroscopic constants have been derived: Ne20H+ re = 0.996 ± 0.003 Å, ωe = 2896 ± 20cm-1 , D0(Ne + H+) = 2.10 ± 0.05 eV; Kr84H+ re = 1.419 ± 0.003 Å, ωe = 2561 ±20 cm-1 , D0(Kr + H+) = 4.65 ±0.05 eV. The Einstein transition probability coefficients of spontaneous emission have been calculated for all transitions v ≦ 5 of Ne20H+, Ne20D+, Kr84H+ and Kr84D+, respectively.
We present a unified formulation of the interaction of electrons with the electromagnetic field in heavy ion collisions, based on quantized interacting fields. This reduces the effort in treating many-electron systems substantially, as compared with the usual S-matrix theory. Both formalisms are shown to be equivalent. The simplification achieved by our new approach is demonstrated in detail for the example of quasi-molecular radiation.