Microcalorimetric investigations on human leukemia cells--Molt 4

Heat production by leukemia cells Molt 4, growing in suspensions with 1 and 3 x 10(5) cells/ml for 4 days, was studied by microcalorimetry. Heat production rates were related to cell growth, glucose consumption, lactate production and cellular ATP-content. The results show that the time course of heat dissipation is dependent on initial cell number. However, observed thermal power maxima were fairly identical in all experiments. Heat production rates per cell were similar during the initial phase of the study independently of initial cell number, while higher cell densities resulted in significantly lower rate of heat production. Glycolytic conversion of glucose into lactate is nearly stoichiometric. Our results indicate a relationship between heat production and amounts of glucose and lactate in the medium. ATP concentration in cells decreased after 24 hours of culture.     

A ground-based model to study the effects of weightlessness on lymphocytes

The mitogenic response of human lymphocytes was found to be markedly reduced in weightlessness conditions as compared to normal gravity. One possible explanation is that due to the non-existent sedimentation in space the lymphocytes could not adhere and spread on a substratum. Thus, we investigated the effect of substratum adhesiveness on lymphocyte responsiveness by reducing and blocking cell adhesion with poly-HEMA in a simple on-ground system. Lymphocyte adhesiveness was assessed by measuring the proportion of non-adhesive, slightly, and strongly adhesive 51Cr-radiolabelled cells on uncoated and poly-HEMA coated plastic. The amount of cell spreading on surfaces with varying adhesiveness was determined by measuring the area of cells. Cells grown on medium and thick poly-HEMA films were rounded in shape. By contrast, on tissue culture plastic, they showed clear signs of spreading. The mitogenic response of lymphocytes grown on thick poly-HEMA films was reduced by up to 68% of the control (tissue culture plastic). Interferon-gamma production was virtually nil when the cells were grown on the least adhesive substratum. These results show that activated lymphocytes need to anchor and spread prior to achieving an optimal proliferation response. We conclude that decreased lymphocyte adhesion could contribute to the depressed in vitro lymphocyte responsiveness found in the microgravity conditions of space flight.     

Induction and activity of NO synthase in bone-marrow-derived macrophages are independent of Ca2+.

The aim of the present study was to analyse whether an increase in the intracellular free Ca2+ concentration ([Ca2+]i) plays a role as a signal mediating synthesis of nitric oxide (NO) in bone-marrow-derived macrophages, either by stimulating induction of NO synthase or by regulating the activity of the enzyme. Therefore we compared the effects of various synthetic analogues of bacterial lipopeptide and of lipopolysaccharide (LPS) on NO production (assessed as nitrite formation during an incubation for 24 h) and on [Ca2+]i [measured with the fluorescent probe indo-1 (1-[2-amino-5-(6-carboxyindol-2-yl)phenoxy]-2- 2-(2'-amino-5'-methylphenoxy)ethane-NNN'N'-tetra-acetic acid)]. Strongly dissociating effects were evoked on nitrite formation and on [Ca2+]i by the stimuli. LPS was preferentially effective on nitrite formation, whereas the Ca2+ ionophore ionomycin and AlF3 induced increases only in [Ca2+]i. The lipopeptides N-palmitoyl-(S)-[2,3-bis(palmitoyloxy)-(2RS)- propyl]-(R)-cysteinylalanylglycine, N-palmitoyl-(S)-[2,3-bis(palmitoyloxy)- (2RS)-propyl]-(R)-cysteinylseryl-lysyl-lysyl-lysine and (S)-(1,2- dicarboxyhexadecyl)ethyl-N-palmitoylcysteinylseryl-lysyl-lys yl-lysine stimulated both parameters, but the maximal effects on nitrite formation and the shape of the dose-response curves did not parallel the effects on [Ca2+]i. Reduction of extracellular Ca2+ with EGTA significantly inhibited increases in [Ca2+]i, but did not change nitrite formation. Furthermore, NO synthesis in the cytosolic fraction of stimulated macrophages was not affected by Ca2+ over the concentration range 10 nM-2 microM. We conclude that increases in [Ca2+]i are not required for NO production in bone-marrow-derived macrophages. Thus the cellular regulation of NO production strikingly differs from that in the vascular endothelium, brain and adrenal gland.     

Rapid isolation of triosephosphate isomerase utilizing high-performance liquid chromatography

A new method for the isolation of homogeneous triosephosphate isomerase (TPI, EC 5.3.1.1) has been developed. The method utilizes high-performance liquid chromatography on DEAE 5PW and Hydrophase-polyethyleneimine columns, which results in the rapid isolation and essentially quantitative recovery of the enzyme. The procedure is superior to previous methods with respect to specificity, recovery, and time. In addition, this rapid process minimizes the potential for postsynthetic modifications of the protein. Milligram quantities of TPI can be isolated from 100 g of tissue.     

Fusion of enveloped viruses with cells and liposomes

The fusion of viruses with cells and liposomes is reviewed with focus on the analysis of the final extents and kinetics of fusion.Influenza virus andSendai virus exhibit 100% of fusion capacity with cells at pH 5 and pH 7.5, respectively. On the other hand, there may be in certain cases, a limit on the number of virions that can fuse with a single cell, that is significantly below the limit on binding. It still remains to be resolved whether this limit reflects a limited number of possible fusion sites, or a saturation limit on the amount of viral glycoproteins that can be incorporated in the cellular membrane, like the case of virus fusion with pure phospholipid vesicles, in which the fusion products were shown to consist of a single virus and several liposomes. Both viruses demonstrate incomplete fusion activity towards liposomes of a variety of compositions. In the case ofSendai virus, fusion inactive virions bind essentially irreversibly to liposomes. Yet, preliminary results revealed that such bound, unfused virions can be released by sucrose gradient centrifugation. The separated unfused virions subsequently fuse when incubated with a “fresh” batch of liposomes. We conclude, therefore, that the fraction of initially bound unfused virions does not consist of dective particles, but rather of particles bound to liposomes via “inactive” sites. Details of the low pH inactivation of fusion capacity ofinfluenza virus towards cells and liposomes are presented. This inactivation is caused by protonation and exposure of the hydrophobic segment of HA₂, and affects primarily the fusion rate constants. Some degree of inactivation also occurs when virions are bound to cellular membranes.     

A simple method for mapping aquatic macrophytes

Aerial photography with a balloon-suspended camera is a suitable tool for surveying aquatic vegetation and for measuring water movements. Examples from the lake Lunzer Untersee (Austria) are given.     

Influence de la nature et de l'abondance des proies sur l'augmentation des effectifs de deux coccinelles prédatrices de la cochenille du manioc au Congo

Résumé Les variations d'abondance des 2 cochenillesPhenacoccus manihoti Matile-Ferrero etFerrisia virgata Cockerell et des 2 prédateurs CoccinellidaeHyperaspis senegalensis hottentotta Mulsant etExochomus flaviventris Mader sont étudiées dans une parcelle de manioc. La colonisation de cette dernière parE. flaviventris est précoce, en présence de faibles niveaux numériques des 2 proies, mais avec une dominance deF. virgata; celle d'H. s. hottentotta intervient un mois plus tard en relation semble-t-il avec la présence d'une population deP. manihoti abondante et jeune. Nos observations font ressortir une dynamique des populations propre à chaque espèce de coccinelle, conditionnée par l'abondance de l'une ou l'autre des proies, la structure des colonies de chaque cochenille et les conditions climatiques (température) qui interviennent en synergie. Ainsi, la réponse numérique deH. s. hottentotta, plus forte que celle d'E. flaviventris, semble en relation plus étroite avecP. manihoti. PourE. flaviventris il appara?t difficile de séparer ce qui revient à chaque espèce de cochenille:F. virgata joue sans doute un r?le important pour son implantation dans les champs, puis sa raréfaction, mais c'est probablementP. manihoti qui permet l'augmentation de ses effectifs.      

Mangroves found in Dominica (West Indies)

Mangroves has been described for the whole Caribbean are in their different habitats. The island of Dominica (West Indies) has always been excluded from the distribution area due to supposed inadequated conditions for mangrove growth. However, there are small areas with proper edaphic conditions for mangal in which black mangrove (Avicennia germinans L.) and white mangrove (Laguncularia racemosa L.) has been found. Even the occurrence of an additional Avicennia species is under discussion.     

Spermatogenesis and sperm ultrastructure in the polychaete genusOphryotrocha (Dorvilleidae)

The details of spermatogenesis and spermiogenesis are described forOphryotrocha puerilis. The ultrastructure of mature sperm is shown forO. puerilis, O. hartmanni, O. gracilis, O. diadema, O. labronica, andO. notoglandulata. Clusters of sixteen cells each are proliferated by two stem cells in each setigerous segment ofO. puerilis representing the very early stages of both oogenesis and spermatogenesis. In each spermatocyte-I cluster, the cells are interconnected by cytoplasmic bridges. Early, clusters are enveloped by peritoneal sheath cells. These transient gonad walls break down prior to meiosis. The meiotic processes may start in the clusters with the cells still interconnected, or during breakdown of the original cluster, giving rise to smaller subclusters of both spermatocytes I and spermatocytes II with various numbers of cells. Finally, spermatid tetrads are present. As spermiogenesis progresses, the tetrads disintegrate. Golgi vesicles in both spermatocytes and spermatids contain electron-dense material, presumably preacrosomal. The acrosome is formed by such vesicles. In the six species studied here, the acrosomes appear to be of a similar overall structure but are of different shape. Centrioles are usually located beneath the acrosome. The distal centriole forms the basal body of a flagellum-like cytoplasmic process. The microtubules of these flagellar equivalents do not show a normal ciliar arrangement. The flagellar equivalent appears to be non-motile. InO. hartmanni and inO. notoglandulata, a flagellar equivalent is missing. Microtubules originating from the proximal end of the distal centriole stretch to the nuclear envelope. This feature appears to be especially conspicuous inO. puerilis and inO. labronica. InO. labronica and inO. notoglandulata, bundles of microtubules paralleling the cell perimeter appear to stabilise the sperm. Various numbers of mitochondria are either randomly distributed around the nucleus or accumulate on one side, often directly under the acrosome. Parts of the present paper were presented at the 2^nd International Polychaete Conference, Copenhagen 1986 and at the 3^rd International Polychaete Conference, Long Beach, Ca. 1989.     

The macrofauna and macroflora associated withLaminaria digitata andL. hyperborea at the island of Helgoland (German Bight,North Sea)

This paper describes the macroflora and macrofauna associated with two bull kelp species,Laminaria hyperborea andL. digitata, at the island of Helgoland, North Sea. During a study period of seven months (March–September 1987), 29 macroflora species and 125 macrofauna species were found. The dominant taxonomic groups were Polychaeta (25 species), Bryozoa (17), Amphipoda (14), Hydrozoa (10) and Ascidiae (8). The species maximum was in July. In general,L. hyperborea was preferred as a substrate for settlement toL. digitata. Composition of the communities associated with kelp changed during the season according to exposure to wave action, and according to location on the kelp thallus. The rhizoid community of both kelps bore more species at exposed locations. Wave-exposedL. digitata lacked obvious faunal settlement on both phylloid and cauloid. Phylloid and cauloid ofL. hyperborea were chosen as an attractive substrate at both sheltered and wave-exposed locations, showing an association of encrusting bryozoan and hydrozoan colonies.