Detection and partial purification of two lipases fromCandida rugosa

Summary Two distinct lipases produced byCanadida rugosa were identified and separated by a high resolution anion-exchange column (Mono Q) after an ethanol extraction of the crude lipase. From this Mono Q column, lipase I eluted at 0.05 M NaCl whereas lipase II eluted at 0.15 M NaCl. The less anionic nature of lipase I was also confirmed by native polyacrylamide gel electrophoresis as well as isoelectrophoresis. Both proteins have an apparent molecular weight of 58,000 by SDS-PAGE. The isoelectric points of lipase I and II are 5.6 and 5.8 respectively.     

Single-stranded circular DNA generated from broad host range plasmid R1162 and its derivatives

Extraction of R1162 plasmid DNA with the alkaline lysis method yields considerable amounts of single-stranded circular plasmid DNA. Destabilization of plasmid DNA is stimulated by the R1162 mob region in cis. The formation of single-stranded circular DNA is initiated at a specific site on the plasmid, presumably the origin of transfer (oriT).     

Chemotaxis in Methanospirillum hungatei

Methanospirillum hungatei gave a positive chemotactic response to acetate.     

Nematode parasites of birds of the fauna in Tunisia

330 birds of Tunisia were necropsied; they belong to 73 species among 29 families and 13 orders. We so collect 36 species of nematodes from 9 families. The relative importance of these is variable. The best represented are: Capillariidae (6 species), Spiruridae (6 species), Acuariidae (9 species) and Filariidae (6 species). The parasitism by nematodes is not uniform. Among the 330 birds autopsied only 51 were parasited by nematodes (15.45%) among 25 of the examined birds species (34.2%). Among these 25, sixteen (64%) presented only one species of parasitic nematode, six (24%) arboured two, (8%) three and only one, (partridges) presents six species of nematodes.     

Oligosaccharide synthesis by enzymatic transglycosylation

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Reconstituted skin in culture:a simple method with optimal differentiation

Human skin is a unique organ, which can be reconstituted in vitro and represents an interesting system for studying cell proliferation and differentiation. A simple technique for producing reconstituted skin with optimal epidermal differentiation is described and characterized. A 4-mm punch biopsy of normal human skin is deposited on the epidermal side of mortified de-epidermized human dermis maintained at the air-liquid interface with a metallic support. The culture medium contains insulin, epidermal growth factor (EGF), cholera toxin, hydrocortisone, penicillin/streptomycin and fungizone. A well-differentiated epidermis develops within 15 days. Morphological and ultrastructural studies show a neoepidermis resembling normal skin. Differentiation markers such as involucrin, filaggrin, and various cytokeratins detected with pancytokeratin antibody are present and confirm this resemblance. The keratin profile is comparable to that observed in other skin culture models. A basement-membrane-like structure is reconstituted with hemidesmosomes and anchoring-filament formation. Bullous pemphigoid (BP) antigen is observed at the dermo-epidermal junction after 21 days of culture. Moreover, both dermal substrates and punch biopsies can be kept frozen for long-term storage, with little or no loss of epidermal growth kinetics and morphology. This skin culture technique is rapid, simple, economical and reproducible. Characterization has here shown high-quality epidermal differentiation. Scientists interested in epidermal in vitro studies should take interest in all these advantages.     

Control of respiratory motor pattern by sensory neurons in spinal cord of lamprey

Summary Extracellular stimulation over the dorsal funiculus in the spinal cord of lampreys was found to selectively activate prolonged episodes of fictive arousal respiration (Figs. 1, 3). The induced episodes showed comparable increases in cycle frequency and motoneuron burst duration to the spontaneous arousal pattern observed in isolated brain preparations (Fig. 2). Intracellular stimulation of primary sensory neurons with axons in the dorsal funiculus, called dorsal cells, also elicited the arousal pattern (Fig. 4). Mechanoreceptive dorsal cells respond to cutaneous stimulation. When mechanical stimuli were applied to the skin of intact lampreys (Fig. 6) or to lampreys with ipsilateral vagotomy, arousal respiration was induced (Figs. 7, 8). Bilateral, but not unilateral, trigeminal lesion blocked dorsal cell induction of the arousal response (Fig. 5). Spontaneous arousal respiration was recorded from intact, unrestrained lampreys (Fig. 9). These results suggest that fictive arousal respiration is the in vitro correlate of natural arousal respiration in lampreys, and that one mechanism leading to arousal respiration may be the activity of sensory dorsal cells. A model for respiratory motor pattern switching in lamprey is proposed. The model suggests that the normal and arousal patterns are produced by separately engaging rostral or caudal pattern generators in the medulla, rather than by modifying one pattern generator (Fig. 10).     

Plant regeneration by organogenesis in Vitis rootstock species

A procedure for the regeneration of Vitis rootstocks plantlets by organogenesis from foliar tissues is described. Leaves from mature plants grown in growth chambers or from plantlets grown in tubes were wounded with a scalpel and cultured on a modified Murashige and Skoog liquid medium containing different concentrations of benzyl-aminopurine. The presence of benzyl-aminopurine is required for shoot formation. The age of the source explant, the composition of the culture medium and the culture temperature are important parameters of the regeneration process.Abbreviations BA 6-benzyl-aminopurine - MS Murashige and Skoog medium - MM modified Murashige and Skoog medium