The antigen-binding capacity of mouse lymphocytes. II. Changes during the early immune response

The interaction of antigen with specific receptor sites of primed murine spleen lymphocytes has been estimated quantitatively. The antigen-specific receptors are restricted to a small segment of the entire spleen cell population, one which may be enriched by centrifugation of the cells in a discontinuous density gradient. The specificity of the receptors, their variable affinities for the specific ligand, their quantitative fluctuations following immunization, have been investigated. Attempts have also been initiated for their isolation. The possibility that these receptors may represent passively adherent cytophilic immunoglobulins was excluded. The results of these experiments suggest that the union of antigen with a portion of cell membrane receptors initiates a sequence of reaction steps involving DNA production and multiplication, leading to a small net synthesis of immunoglobulins. The continued presence of antigen during this period leads to complex formation with these immunoglobulins. The resulting immune complexes bind to both adherent and nonadherent cells, thereby amplifying the immune response.     

Genetic transformation and regeneration of transgenic plants in grapevine (Vitis rupestris S.)

Isolated somatic embryos from petiole-derived callus cultures ofVitis rupestris Scheele have been employed in experiments on genetic transformation. Co-cultivation of somatic embryos during embryogenesis induction withAgrobacterium tumefaciens strain LBA4404, which contains the plasmid pBI121 carrying the neomycin phosphotranspherase and the-glucuronidase genes, produced transformed cellular lines capable of recurrent somatic embryogenesis. Precocious selection for high levels of kanamycin (100 mgl^-1) was an important part of our transformation protocol. Transformed lines still have strong-glucuronidase expression as well as stable insertion of the marker genes after 3 years of in-vitro culture, during which they have maintained their capacity to organize secondary embryos and to regenerate transgenic plants with an agreeable efficiency (13%).     

Biogeneration of 2-phenylethanol and 2-phenylethylacetate important aroma components

Summary 2-Phenylethanol and 2-phenylethylacetate important aroma components are obtained in substantial amounts whenHansenula anomala CBS 110 andKloeckera saturnus CBS 5761 are grown with L-phenylalanine as sole nitrogen source. Up to 2 g/L of mixtures of alcohol and ester are obtained. While in the first microorganism the alcohol predominates, in the second the acetate is formed almost exclusively. Experiments with 1-¹³C-d-Glucose show complete incorporation of the label into the methyl group of the acetate.     

The nitrite reductase gene of Pseudomonas aeruginosa: Effect of growth conditions on the expression and construction of a mutant by gene disruption

Abstract The expression of nitrite reductase has been tested in a wild-type strain of Pseudomonas aeruginosa (Pao1) as a function of nitrate concentration under anaerobic and aerobic conditions. Very low levels of basal expression are shown under non-denitrifying conditions (i.e. absence of nitrate, in both aerobic and anaerobic conditions); anaerobiosis is not required for high levels of enzyme production in the presence of nitrate. A Pseudomonas aeruginosa strain, mutated in the nitrite reductase gene, has been obtained by gene replacement. This mutant, the first of this species described up to now, is unable to grow under anaerobic conditions in the presence of nitrate. The anaerobic growth can be restored by complementation with the wild-type gene.     

Flora Palinologica Italiana,Sezione Aeropalinologica — Specie esotiche — S 231:Sequoia sempervirens (Lamb.) Endl. (Taxodiaceae)

Riassunto La scheda morfopalinologica diSequoia sempervirens (Lamb.) Endl. continua lo studio sulle Pinohyta ornamentali più frequenti in Torino. È esaminato polline fresco ed acetolizzato proveniente da due stazioni e la provenienza non determina variazioni significative dei parametri morfometrici.

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Summary The morphopalynological card ofSequoia sempervirens (Lamb.) Endl. is a new contribution to the comprehensive study on pollen of ornamental Pinophyta in Turin. Fresh and acetolysed grains from two stations are examined, and for all parameters no significative differences were observed in relation to the collection site.

Parole chiave: Sequoia sempervirens(Lamb.) Endl., Flora Palinologica Italina, Sezione Aeropalinologica.