Double helical arrangement of spread dinoflagellate chromosomes

Dinoflagellate chromosomes observed in thin section show regular patterns which have been shown to correspond to a liquid crystalline helicoidal arrangement of DNA. Peripheral DNA filaments form a system of loops in the surrounding nucleoplasm. When such chromosomes (studied in Prorocentrum micans) are in presence of water, they extend considerably and form a double helical bundle. At the periphery of these bundles, one observes numerous filaments, which are smooth and devoid of nucleosomes; their diameter is constant.This study, in phase contrast and in electron microscopy, allows statistical measurements. A geometrical model is proposed and shows the simplest way to pass from the intact to the extended form. The liquid crystalline character of the chromosome is probably involved in the extension mechanisms.     

Conformational analysis of somatostatin and selected analogs in oriented polyoxyethylene by infrared dichroism

Infrared dichroic studies and deuterium exchange measurements of somatostatin and some of its analogs incorporated in uniaxially oriented polyoxyethylene are described. Band positions and dichroic ratios in the N-H stretching and amide I and II regions are similar to those of flexible and nonordered peptides like valinomycin and poly[Glu(ONa)]. This information, together with fast deuterium exchange rates, suggests that somatostatin exists in a flexible nonordered conformation in polyoxyethylene. One analog, di-S^3,14-acetamidomethyl dihydrosomatostatin, was found to exist in both nonordered and β-like conformations.     

Occurrence of subcutaneous zygomycosis (Entomophthoromycosis Basidiobolae) caused by Basidiobolus haptosporus with pulmonary involvement

A case of a two-year-old boy with multiple subcutaneous lesions caused by Basidiobolus haptosporus is presented.The child had also a non-toxic familial goiter and clinical and radiological features of a pulmonary illness. The pulmonary manifestations only disappeared with the treatment with potassium iodide. The authors think that the pulmonary lesions must have arisen by direct spread of the fungus from the subcutaneous lesions of the chest.     

Mitochondrial DNA evolution in lagomorphs: Origin of systematic heteroplasmy and organization of diversity in European rabbits

Summary A characterization was conducted on mitochondrial DNA (mtDNA) molecules extracted separately from 107 European rabbits (Oryctolagus cuniculus) both wild and domestic, 13 European hares (Lepus capensis), and 1 eastern cottontail (Sylvilagus floridanus). Experimentally this study took into account restriction site polymorphism, overall length variation of the noncoding region, and numbers of repeated sequences. Nucleotide divergences indicate that the mtDNAs from the three species derived from a common ancestor some 6–8 million years (Myr) ago. Every animal appeared heteroplasmic for a set of molecules with various lengths of the noncoding region and variable numbers of repeated sequences that contribute to them. This systematic heteroplasmy, most probably generated by a rate of localized mtDNA rearrangements high enough to counterbalance the cellular segregation of rearranged molecules, is a shared derived character of leporids.The geographic distribution of mtDNA polymorphism among wild rabbit populations over the western European basin shows that two molecular lineages are represented, one in southern Spain, the second over northern Spain, France, and Tunisia. These two lineages derived from a common ancestor some 2 Myr ago. Their present geographical distribution may be correlated to the separation of rabbits into two stocks at the time of Mindel glaciation.Finally the distribution of mtDNA diversity exhibits a mosaic pattern both at inter- and intrapopulation levels.     

Nano- and picoplankton growth and production in the Bay of Villefranche sur Mer (N.W. Mediterranean)

Plankton production in the Bay of Villefranche was relatively constant during March and April 1986 but the particle size at which the production occurred was more variable. At the beginning of the study, production was dominated by the larger (ca. 6 m) flagellates but towards the end it was more or less equally divided between the nano- and picoplankton. There were considerable differences in the estimates of population growth rates, depending on the methods used, but on average the population doubling times were close to 12 hours for autotrophs and 24 hours for heterotrophs. As autotrophs do not grow during the night, each population was therefore doubling once per day. It seemed that each of the nanoor picoplankton populations could adversely affect the growth of the others. This could be either by simple predation or by some form of inhibition. Although nutrient levels in the bay were uniformly low, the addition of nutrients did not always stimulate algal growth. The plankton populations seemed to be both in a state of equilibrium and intense ecological competition.     

Ovulation and embryo recovery rates following immunization of mares against an inhibin alpha-subunit fragment

Six normally cycling mares were immunized 5 times at 3-week intervals with a synthetic porcine inhibin alpha-subunit fragment which had been conjugated to bovine serum albumin and emulsified in Freund's incomplete adjuvant. Immunized mares ovulated a significantly larger (P < 0.01) number of follicles per estrous cycle (2.8 +/- 1.1; range 1 to 8 ovulations) than 14 nonimmunized control mares (1.1 +/- 0.1; range 1 to 2 ovulations). Day-7 embryo recovery rates tended to be higher (P < 0.1) in immunized mares (1.6 +/- 0.5 embryos per flush) than in control mares (0.7 +/- 0.2 embryos per flush). No differences in interovulatory intervals were found between the 2 groups. These results indicate that immunization against inhibin may be useful in inducing development and ovulation of multiple follicles for embryo transfer in the mare.     

Interactions of surfactin,a biosurfactant fromBacillus subtilis,with inorganic cations

Summary The properties of surfactin, a biosurfactant lipopeptide, were highly modified in the presence of inorganic cations. The micellization of surfactin was favoured by monovalent and, especially by divalent cations with a modification of the molecular area at the air-water interface. Haemolysis of erythrocytes by surfactin was enhanced by low concentrations of divalent cations with an increase of the binding of the lipopeptide to membrane. Inorganic ions induced conformational rearrangements probably due to ion-surfactin associations which modify the surface-active properties.     

The xylanase introns from Cryptococcus albidus are accurately spliced in transgenic tobacco plants

The xylanase gene from Cryptococcus albidus contains seven introns. Genomic and cDNA clones under the control of the CaMV 35S promoter were transferred into tobacco plants using Agrobacterium-mediated cell transformation. The genes were transcribed and the mRNAs were amplified by the polymerase chain reaction using primers on each side of the intron region. About 90% of the amplification products from plants transformed with the genomic clone corresponded to the size of the pre-mRNA (1.2 kb) and 10% represented the spliced product (0.85 kb). The 0.85 kb fragment was cloned and sequenced and the result indicated that the introns from the xylanase gene were accurately spliced by the plant cells.