Elektronenmikroskopische Untersuchungen an spezifischen Organellen von Endothelzellen des Frosches (Rana temporaria)

Zusammenfassung Endothelzellen der Wirbeltiere enthalten spezifische Organellen, deren Funktion unbekannt ist. Diese Organellen werden beim Frosch (Rana temporaria) nach unterschiedlichen Fixierungen elektronenmikroskopisch untersucht. Die Organellen sind walzenförmig mit mannigfachen Abweichungen, bis zu 2 lang und 0,1 bis 0,5 dick. Ihre oft unterbrochene Außenmembran ist dicker als zytoplasmatische Membranen. Das Innere der Organellen besteht aus Tubuli, die in eine elektronendichte Matrix eingebettet sind. Die Dichte dieser Matrix zeigt deutliche Abstufungen. Die Tubuli sind möglicherweise aus einer spiralförmigen Molekülkette aufgebaut. Das Verteilungsmuster der Organellen wird mit stereologischen Methoden untersucht. Die größte Volumendichte weisen die Aortae thoracicae mit 8% auf. Die Volumendichte der Organellen im Zytoplasma der Endothelzellen scheint mehr von der Entfernung der betreffenden Gefäßstrecke zum Herzen abzuhängen als von der Gefäßgröße. Es werden Verbindungen der Organellen zu zytoplasmatischen Membransystemen aufgezeigt. Auf Besonderheiten des Endothels, darunter Aggregationen von Ribosomen, wird hingewiesen.

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Electron microscopic studies on specific organelles of endothelial cells in the frog (Rana temporaria)

Summary Endothelial cells of vertebrates contain specific organelles of unknown function. These organelles are studied by electron microscopy with different fixations. The organelles are rod-shaped with many variations, up to 2 in length and 0.1 to 0.5 in thickness. Their outer membrane, which is often discontinuous, is thicker than cytoplasmic membranes. The density of the matrix shows distinct gradations. The organelles contain tubules, possibly built up by a spiral molecular chain. The distribution of the organelles is investigated with stereological methods. Their volume density in endothelial cell cytoplasm appears to depend more on the distance from the heart than on vessel size, the thoracic aortae showing the highest organellae content of 8%. Connections between organelles and cytoplasmic membranes are demonstrated. Particularities of endothelium, among them aggregations of ribosomes, are pointed out.

Herrn Prof. Dr. med. F. Hammersen und Fräulein Dr. med. M. Lewerenz danke ich herzlich für Anregungen, Unterstützung und Kritik. Die Arbeit entstand während eines vom Deutschen Akademischen Austauschdienst dankenswerterweise gewährten Stipendiums; sie wurde unterstützt vom Schweizerischen Nationalfonds zur Förderung der wissenschaftlichen Forschung, Kredit-Nr. 3952.     

Transfer of amino acids and nitrate from the roots into the xylem of Ricinus communis seedlings

The loading of amino acids and nitrate into the xylem was investigated by collection and analysis of root-pressure exudate from the cut hypocotyl stumps of seedlings of Ricinus communis L. Glutamine was found to be the dominant amino acid in the exudate and also to be the amino acid which is transferred to the xylem most rapidly and accumulated to the greatest extent. The comparison between uptake and xylem loading showed significant differences in specificity between these two transport reactions, indicating a different set of transport systems. Nitrate is transferred to the xylem at a higher relative rate than any amino acid despite the great nitrate-storage capacity of the root system. Thus the supply of nitrate to Ricinus plants leads to enhanced nitrogen allocation to the shoots.     

Review of Colombian Conchostraca (Crustacea) — ecological aspects and life cycles — families Lynceidae,Limnadiidae, Leptestheriidae and Metalimnadiidae

This study gives an overview of our current knowledge of the ecology and distribution patterns of Colombian conchostracans. Colombian euphyllopods are generally restricted to the warm tropical lowlands. OnlyCyclestheria hislopi can be found year-round in larger semipermanent waters and living sympatrically with abundant predators, such as planktivorous fish. The other conchostracans are restricted to the typical habitat of temporary waters.Eulimnadia magadalenensis is especially adapted to very short-term temporary ponds in relatively arid zones andE. colombiensis prefers somewhat cooler ponds of a longer duration. The two species can be found sympatrically in intermediate climatic conditions. A third form,Eulimnadia cf. geayi cohabits with the two other species in the lower Magdalena Valley, its ecological role is not clear.Limnadia orinoquiensis is the selvatic substitute of the open savannah conchostracan fauna (mainlyEulimnadia forms) living in pools in forest clearings in the vicinity of the Upper Orinoco.Four species of Lynceidae were found, twoLynceus and twoParalimnetis. Their distribution patterns are not yet clear, they prefer smaller temporary ponds of moderated temperatures. Two undescribed species ofLeptestheria were found, one restricted to the banks of the Orinoco and the other to one locality in the upper Magdalena Valley, living in ponds with a muddy bottom.Metalimnadia serratura was found in special rock pools of the Guiana Shield in the vicinity of the Orinoco, cohabiting with several other conchostracan species, with differential adaptations to very high water temperatures.     

A characterization of the nucleotide uptake by chromaffin granules of bovine adrenal medulla

Chromaffin granules isolated from bovine adrenal gland were incubated with (3)H-labelled nucleotides and [(14)C]noradrenaline to study the uptake of these substances. [(3)H]ATP, [(3)H]ADP and [(3)H]AMP are taken up by these organelles by the same temperature-dependent mechanism. The apparent K(m) for ATP and ADP is 1.4mm, and for AMP it is 2.9mm. The uptake of ATP has a flat pH optimum, whereas the catecholamine uptake increases with more alkaline pH. Atractyloside and carboxyatractyloside are competitive and specific inhibitors of nucleotide uptake, whereas reserpine inhibits only that for catecholamines. Mg(2+) ions activate uptake of both catecholamine and nucleotides, whereas EDTA and N-ethylmaleimide inhibit these processes. Nucleotide and catecholamine uptakes are inhibited by uncouplers of oxidative phosphorylation and by two ATP analogues. NH(4) (+) ions and nigericin in the presence of KCl inhibit only catecholamine uptake. It is concluded that nucleotide uptake, as proposed previously for catecholamine uptake, depends on an electrochemical proton gradient produced by a proton-translocating adenosine triphosphatase localized in the membrane of chromaffin granules. Furthermore, as suggested by the effect of NH(4) (+) and nigericin, catecholamine uptake apparently depends on the chemical part of this gradient, whereas the results for nucleotide uptake are consistent with its dependence on the electrical component.     

Anencephaly in trisomy 18 associated with elevated alpha-1-fetoprotein in amniotic fluid

Summary Elevated levels of alpha-1-fetoprotein (AFP) were found in the amniotic fluid of a 36-year-old woman in the 15th week of gestation. Because of this and the results of repeated ultrasonography, abortion was induced. An anencephalic fetus with trisomy 18 was delivered. The possible correlation among neural-tube defects, chromosomal abnormalities, and level of AFP is discussed.     

Recovery,structure, and function of dog granulocytes after freeze-preservation with dimethylsulfoxide

The recovery, structure and function of dog granulocytes were determined before and after freeze-preservation. Leucocytes were isolated from defibrinated or anti-coagulated whole blood and subsequent erythrocyte sedimentation on a column of 2:1 dextran (6%)-isopaque (33.9%). Granulocytes isolated by these procedures were examined for changes in O₂ consumption associated with phagocytosis, in vitro directed migration (chemotaxis), bactericidal activity, and ultrastructure before and after freezing. Granulocytes were frozen in DMSO (7.5%) and autologous serum or HBSS-minus and 20% autologous serum at the rate of ?1 °C/min to ?80 °C and stored in liquid N₂ vapor.After freeze-preservation, O₂ consumption associated with phagocytosis was decreased by 54 and 64% for granulocytes isolated from defibrinated or from ACD-anticoagulated blood, respectively. Bactericidal activity is only slightly depressed in samples from either isolation method after freeze-preservation when compared to the prefreeze controls, but granulocytes isolated from defibrinated blood are significantly less effective in killing bacteria than those from ACD-anticoagulated blood. Chemotactic response after freeze-preservation was completely inhibited in granulocytes isolated from defibrinated blood. Exposure of granulocytes to ACD inhibited chemotaxis prior to freezing, but the granulocytes responded chemotactically after freeze-thaw and additional washing. The ultrastructure of granulocytes observed before and after freeze-thaw was similar for cells isolated by both methods. However, nuclear, cytoplasmic, and granular changes observed were slightly greater in granulocytes isolated from defibrinated blood. Dog granulocytes isolated by either method withstood freeze-preservation in DMSO to a degree not previously reported.It is concluded that dog granulocytes freeze-preserved by these methods are functional in vitro, but that phagocytic, directed migration, and bactericidal functions and ultrastructure are impaired to different degrees, according to the method of isolation and preparation for storage. These results indicate the need for continued investigation on the effects of storage variables on the preservation of granulocytes.     

Effect of cold environment on skeletal muscle mitochondria in growing rats

Summary Growing rats (4 weeks old) were kept for 3 weeks at 11° C and 24° C respectively. The cold-adapted animals showed a significantly higher oxygen consumption (64%). Volume density of subsarcolemmal and interfibrillar mitochondria as well as volume density of fat droplets were estimated in M. soleus and the diaphragm of both groups. In cold-adapted animals, the total volume of mitochondria was significantly increased by 24% in diaphragm and 37% in M. soleus. The volume of subsarcolemmal mitochondria was almost doubled in each muscle, but the volume of interfibrillar mitochondria did not change significantly. The surface of the inner mitochondrial membranes per unit volume of mitochondrion in M. soleus was significantly increased both in interfibrillar and subsarcolemmal mitochondria, whereas the surface of the outer mitochondrial membranes per unit volume of mitochondrion was increased only in the subsarcolemmal mitochondria. The volume of fat droplets in the diaphragm and M. soleus of cold adapted animals increased significantly by 62% and 150% respectively.     

Vacuoles from Sugarcane Suspension Cultures : I. ISOLATION AND PARTIAL CHARACTERIZATION

Vacuoles were isolated from suspension cultures of sugarcane (Saccharum sp.) cells by centrifugation of protoplasts at high g force against a 12% (w/v) Ficoll solution. Distribution of marker enzymes and Concanavalin A binding showed an 11% contamination of the vacuole preparation by cytoplasmic components, mitochondria, and endoplasmic reticulum, and 18% contamination by plasma membrane. Acid phosphatase, carboxypeptidase, protease, peroxidase, and ribonuclease activities were enriched in isolated vacuoles. Carboxypeptidase was tonoplast-bound, whereas the other enzymes were soluble. Sucrose, reducing sugars, and free amino acids were measured in protoplasts and vacuoles during growth of cells in suspension culture. Sucrose and reducing sugar content of vacuoles increased as the culture aged, while free amino acids decreased sharply.