Nuclear genome characterization of the carrageenophyteAgardhiella subulata (Rhodophyta)

DNA reassociation kinetics were used to determine nuclear genome organization and complexity inAgardhiella subulata (Gigartinales, Rhodophyta). Results indicate the presence of three second-order components corresponding to fast (22%), intermediate (68%) and slow (10%) fractions. Thus, the genome consists of 90% repetitive sequences. Microspectrophotoometry with the DNA-localizing fluorochrome DAPI was used to confirm ploidy level differences in the gametophytic and tetrasporophytic phases. Results indicate that meiosis occurs during tetrasporogenesis. Comparison of mean nuclear DNA (I_f) values to chicken erythrocytes (RBC) resulted in an estimate of 0.9 pg/2C genome forAgardhiella. Karyological studies using aceto-orcein revealed a chromosome complement of 2N = 44 in carposporangia and the presence of 22 bivalents during diakinesis of tetraspore mother cells.     

Nucleosomal organization of chromatin in sperm nuclei of the bivalve mollusc Aulacomya ater

The sperm nuclei of Aulacomya ater, family Mitylidae, contain three proteins (X, Aa5 and Aa6) which are specific to this cell type coexisting with a set of five somatic-type histones. Information about the chromatin structure resulting from this kind of association is scarce. Therefore, we have probed the structure of this sperm chromatin through digestion with micrococcal nuclease in combination with salt fractionation. The data obtained have allowed us to propose a nucleosomal arrangement for this chromatin. However, two types of nucleosomes would be present in agreement with their protein components.     

Pigment patterns in mutants affecting the biosynthesis of pteridines and xanthommatin in Drosophila melanogaster

Eye-color mutants of Drosophila melanogaster have been analyzed for their pigment content and related metabolites. Xanthommatin and dihydroxanthommatin (pigments causing brown eye color) were measured after selective extraction in acidified butanol. Pteridines (pigments causing red eye color) were quantitated after separation of 28 spots by thin-layer chromatography, most of which are pteridines and a few of which are fluorescent metabolites from the xanthommatin pathway. Pigment patterns have been studied in 45 loci. The pteridine pathway ramifies into two double branches giving rise to isoxanthopterin, drosopterins, and biopterin as final products. The regulatory relationship among the branches and the metabolic blockage of the mutants are discussed. The Hn locus is proposed to regulate pteridine synthesis in a step between pyruvoyltetrahydropterin and dihydropterin. The results also indicate that the synthesis and accumulation of xanthommatin in the eyes might be related to the synthesis of pteridines.Support for this work was provided to J.F. in part by a grant from the Ministerio de Universidades e Investigación (Spain) and to F.J.S. by a grant from the Ministerio de Educación y Ciencia (Spain).     

Glucocorticoids Potentiate the Prostaglandin E1-Mediated Cyclic AMP Formation by a Cultured Murine Neuroblastoma Clone

The effect of steroid hormones on the prostaglandin E1 (PGE1)-mediated cyclic AMP formation by murine neuroblastoma clone N1E-115 was studied. Dexamethasone at submicromolar concentrations and corticosterone at micromolar concentrations (steroids with glucocorticoid activity) were able to modify the PGE1-mediated response whereas testosterone, progesterone, and estradiol each at 10 microM had no effect. Glucocorticoids added to the culture medium of N1E-115 cells produced an increase in the maximal response to PGE1 only after long-term (greater than or equal to 4 h) incubation with the hormone. Inhibitors of protein and RNA synthesis blocked this effect of glucocorticoids. Basal activity of adenylate cyclase in treated cells was twofold higher than that in control cells, and this enzyme seemed to be the primary target for the hormone action, since the activity of 3':5'-cyclic AMP phosphodiesterase and the binding of [3H]PGE1 to its receptors were not altered by glucocorticoid treatment. Our results indicate that glucocorticoids modulate receptor-mediated responses in cells of neural origin through a mechanism that involves induction of protein synthesis.     

Zur Mauser spanischer Weiden- und Haussperlinge (Passer hispaniolensis unddomesticus)

Zusammenfassung Die Mauserperiode westspanischer Weidensperlinge(Passer hispaniolensis) und Haussperlinge(P. domesticus) reicht von Ende Juli bis Ende September/Anfang Oktober. Beim Weidensperling endet der Federwechsel im Durchschnitt etwa fünf Tage früher als beim Haussperling. Es gibt keine Geschlechtsunterschiede in der Chronologie der Mauser beim Weidensperling. Ad. beider Arten mausern schneller und synchronisierter als juv., die ihr Gefieder um so rascher erneuern, je später sie mit der Mauser begonnen haben. Die Handschwingenmauser dauert etwa 66 Tage beim Weidensperling und 69 Tage beim Haussperling. Beide Arten brauchen ca. 3 weitere Tage für die Verhornung der 5. und 6. Armschwingen. Die ad. beider Arten und die juv. Weidensperlinge beginnen die Mauser im Durchschnitt am selben Tag (24. Juli), die juv. Haussperlinge später (29. Juli). Der Mauserverlauf und die Beziehungen zwischen den verschiedenen Federreihen sind bei beiden Arten identisch. Die Synchronisation der Mauser ist beim Weidensperling höher. Brut und Mauserperiode überschneiden sich beim Haussperling; beim Weidensperling, bei dem noch kurze Wanderungen gleich nach der Fortpflanzungsperiode und vor der Mauser erfolgen, nicht. Das frühere und höher synchronisierte Mauserende beim Weidensperling scheint eine Anpassung an die stärkere Zugtendenz zu sein.

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On the moult of Spanish Sparrows(Passer hispaniolensis) and House Sparrows(Passer domesticus) in Iberia

Summary The moulting period of Spanish sparrows(Passer hispaniolensis) and House Sparrows(Passer domesticus) in Western Spain extends from late July to late September/early October. House Sparrows finish moulting on average some five days later than Spanish Sparrows. There are no sexual differences in the moulting chronology of adult Spanish Sparrows. Ad. of both species moult faster and better synchronized. The speed of moulting is also higher in later moulting juveniles. The estimated durations of wing feather replacement were 66 days for the Spanish Sparrow and 69 days for the House Sparrow. Some three more days are needed to complete the growth of the 5th and 6th secondary remiges in both species. Adults of both species and juvenile Spanish Sparrows start moulting on average on the same date: 24th July; juvenile House Sparrows start moulting on 29th July. The sequence of moult and the relations between different feather tracts are identical in both species. The synchronization of the moult is higher in the Spanish Sparrow. Breeding and moulting seasons slightly overlap in the House Sparrow, but not in the Spanish Sparrow. In this species the time lapse between both periods allows the birds to wander to suitable areas, where they moult. The earlier ending and higher synchronization of the moult in the Spanish Sparrow is related to its higher migratory tendency.

     

Population growth in random environments

This paper reviews some recent advances in single population stochastic differential equation growth models. They are a natural way to model population growth in a randomly varying environment. The question of which calculus, Itô or Stratonovich, is preferable is addressed. The two calculi coincide when the noise term is linear, if we take into account the differences in the interpretation of the parameters. This clarifies, among other things, the controversy on the theory of niche limiting similarity proposed by May and MacArthur. The effects of correlations in the environmental fluctuations and statistical methods for estimating parameters and for prediction based on a single population trajectory are mentioned. Applications to fisheries, wildlife management and particularly to environmental impact assessment are now becoming possible and are proposed in this paper.     

Inactivation of 1,6-Diphosphatase by Glucose in Yeast

Fructose-1,6-diphosphatase was derepressed in Saccharomyces cerevisiae by incubation in media containing non-sugar carbon sources. Addition of glucose to a derepressed culture led to a rapid loss of the measurable activity of the enzyme. Fructose and mannose also produced inactivation, but 2-deoxyglucose was ineffective. Experiments with cycloheximide indicated that the inactivation does not require protein synthesis. It was also shown that the process is not energy-dependent. The reappearance of the enzyme was dependent on an energy source and was prevented by cycloheximide. These results suggest that fructose diphosphatase inactivation is irreversible and that reappearance of enzyme activity implies de novo synthesis. Screening of different genera of yeasts has shown that the inactivation of fructose diphosphatase is a relatively widespread phenomenon.     

Biosynthesis of Riboflavine in Corynebacterium Species: the Purine Precursor

Corynebacterium species lacks the ability to convert either xanthine or guanine to adenine. This defect and the use of the purine nucleoside antibiotic decoyinine, which blocks the conversion of xanthosine monophosphate --> guanosine monophosphate, permit an experimental design in which the interconversion of purines is largely prevented. Cultures of this organism were grown in the presence of decoyinine and various purine supplements. Data obtained by comparing the radioactivity incorporated from guanine-2-(14)C or xanthine-2-(14)C into bacterial guanine, xanthine, and riboflavine indicate that guanine or a close derivative of guanine is the purine precursor of riboflavine.