Der mikrochemische Nachweis der Alkaloide in der Pflanze

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Properties of a rat liver smooth microsomal subfraction not aggregated by Mg2+

A smooth microsomal fraction (smooth II microsomes) was earlier isolated and characterized in a number of investigations. Using a three-layer discontinuous sucrose gradient containing Mg²⁺ this fraction was divided into two subfractions (IIa and IIb) by a single centrifugation. The smooth IIa fraction proved to be a purified smooth microsomal fraction of specific composition. It contains high amounts of cytochromes $\text{b}{}_5$ and P-450, low activities of other electron transport enzymes and glucose-6-phosphatase, and no UDP-glucuronic acid transferase. No membrane or enzyme synthesis is induced in this subfraction by treatment with phenobarbital or methylcholanthrene. It appears that the membranes of smooth IIa microsomes derive from the smooth endoplasmic reticulum and are devoted to specific functions.     

Distribution and transport of apo- and holocytochrome b5 in the endoplasmic reticulum of rat liver

The transport and distribution of apo- and holocytochrome $\text{b}{}_5$ was investigated with the aid of specific antibodies. The holoenzyme was found to be localized mainly in the rough and smooth endoplasmic reticulum and in the Golgi system but some precipitation could also be obtained in the outer mitochondrial membranes and in the peroxisomes. The apoenzyme, however, could only be detected in the endoplasmic reticulum-Golgi system, which also was shown to be the sole site for incorporation of the prosthetic heme moiety. Time-course studies revealed that the labeled enzyme appeared both as apoenzyme and as holoenzyme in the rough endoplasmic reticulum 10 min after in vivo injection of radioactive leucine and that further transport to the smooth endoplasmic reticulum occurred within 10 min. The subsequent transport to other organelles, however, required a somewhat longer time and peak radioactivity in outer mitochondrial membranes was not attained until after 40 min.     

Über Hyperdaktylie,Regeneration und Vererbung mit Experimenten

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Fine structural localization of acid phosphomonoesterase in the brush border region of osteoclasts

Summary The fine structural localization of acid phosphomonoesterase was studied in osteoclasts of fracture callus in the rat. In addition to being present in the Golgi apparatus and the lysosomes, reaction product was precipitated over tubular elements, vesicles, and vacuoles located subjacent to the brush border. The findings are compatible with the idea that the calcified matrix can be destroyed by the combined effects of absorption with subsequent intracellular digestions in osteoclasts, and actual secretion of lysosomal enzyme to the extracellular space.This study was supported by grants from the Swedish Medical Research Council (Project no. B72-12X-1006-07A) and Konung Gustav V:s åttioårsfond". The assistance of Miss Silwa Mengarelli and Mrs. Britt-Marie Åkerman is gratefully acknowledged.     

HETEROGENEITY OF ROUGH-SURFACED LIVER MICROSOMAL MEMBRANES OF ADULT,PHENOBARBITAL-TREATED,AND NEWBORN RATS

Rough microsomes from the livers of adult, phenobarbital-treated, and newborn rats were subfractionated on a continuous sucrose gradient. Among the subfractions a marked heterogeneity in the distribution patterns of some enzyme activities appears. The isopycnic density of the various fractions in aqueous sucrose ranges from 1.17 to 1.25. The sedimentation coefficients (s₀) in 0.25 M sucrose lie between 0.4 x 10³ S and 1.2 x 10³ S. In adult animals, the NADH- and NADPH-cytochrome c reductase as well as the G6Pase activities are much higher in the slower sedimenting fractions than in the pellet. The increase in the level of G6Pase induced by fasting as well as the phenobarbital-induced changes are most prominent in the slowly sedimenting fractions. Three injections of phenobarbital have no effect on the specific NADPH-cytochrome c reductase activity in the pellet, but cause a significant increase of this enzyme activity in the light fractions. In the newborn animal, the NADH-ferricyanide reductase and NADPH-cytochrome c reductase activities are highest in the light fractions. On the other hand, the amount of cytochrome b ₅ is evenly distributed in all cases. Short-term incorporation of leucine-¹⁴C and glycerol-³H in vivo after phenobarbital treatment shows contrasting results, as the former is increased and the latter is decreased in the slowly sedimenting fractions. Leucine-¹⁴C incorporation into isolated, total membrane proteins is greater in both phenobarbital-treated and newborn animals than in untreated adults. The data support a multistep model for membrane biogenesis and indicate dynamic and individual behavior of the different parts of the rough-surfaced endoplasmic reticulum.     

PERMEABILITY OF MICROSOMAL MEMBRANES ISOLATED FROM RAT LIVER

Water compartments, permeability, and the possible active translocation of various substances in rat liver microsomes were studied by using radioactive compounds and ultracentrifugation. The total water of the microsomal pellet, 3.4 µl/mg dry weight, is the sum of water in the extramicrosomal and intramicrosomal spaces, or 56 and 44%, respectively. Sucrose space accounts for 77% of the intramicrosomal water and the hydration water ~ 14%, leaving almost no sucrose-impermeable space when using the ultracentrifugation approach. With increasing sucrose concentration, microsomes do not show an osmotic response. The intramicrosomal water decreases greatly in the presence of Cs⁺ and Mg⁺⁺ in rough but not in smooth microsomes. Uncharged substances of molecular weight of up to at least 600 freely penetrate microsomal membranes, which already become impermeable to charged substances at a molecular weight of 90. These substances also induce an osmotic response. The vesicles can be made permeable to charged substances after water treatment and cooling, which, however, does not increase glucose-6-phosphatase and inosine diphosphatase (IDPase) activities, and these enzymes can still be activated by deoxycholate. IDPase, reduced nicotinamide adenine dinucleotide-cytochrome c reductase, and reduced nicotinamide adenine dinucleotide phosphate-dependent hydroxylation reactions, performed in vitro, also disproved the hypothesis of an accumulation of charged substances inside of vesicles of being a major pathway. The products of the enzymic reactions as well as the glucuronidated form of a hydroxylated product can be recovered on the cytoplasmic side of membranes, and little accumulation occurs in the intravesicular compartment.     

Ein Ausflug in die Gegend des Neusiedlersees

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Eine neue Flora von Kärnten

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