Evolution of dispersal in density regulated populations: A haploid model

The evolution of dispersal is explored in a density-dependent framework. Attention is restricted to haploid populations in which the genotypic fitnesses at a single diallelic locus are decreasing functions of the changing number of individuals in the population. It is shown that migration between two populations in which the genotypic response to density is reversed can maintain both alleles when the intermigration rates are constant or nondecreasing functions of the population densities. There is always a unique symmetric interior equilibrium with equal numbers but opposite gene frequencies in the two populations, provided the system is not degenerate. Numerical examples with exponential and hyperbolic fitnesses suggest that this is the only stable equilibrium state under constant positive migration rates (m) less than . Practically speaking, however, there is only convergence after a reasonable number of generations for relatively small migration rates ( ). A migration-modifying mutant at a second, neutral locus, can successfully enter two populations at a stable migration-selection balance if and only if it reduces the intermigration rates of its carriers at the original equilibrium population size. Moreover, migration modification will always result in a higher equilibrium population size, provided the system approaches another symmetric interior equilibrium. The new equilibrium migration rate will be lower than that at the original equilibrium, even when the modified migration rate is a nondecreasing function of the population sizes. Therefore, as in constant viability models, evolution will lead to reduced dispersal.     

Restriction map of Tn7

Tn7, a transposon of 14 kb, encodes resistance to trimethoprim (Tp) and streptomycin (Sm). A cleavage site map of this transposon for twenty-two different restriction enzymes as determined by comparison of restriction enzyme cleavage patterns of the plasmids ColE1 and ColE1::Tn7 is presented. The precise localization of these sites was facilitated by the use of two deletion derivatives of ColE1::Tn7: pGB2 and ColE1::Tn7Δ6, and by the use of pOB14 and pOB15 which contain a part of Tn7 cloned into the plasmid pBR322. This map should aid in the study of the structural and genetic organization of this transposon.     

High Dosage Metolazone in Chronic Renal Failure

Metolazone is a modified quinazolinesulphonamide and in a dose of between 4 and 7·5 mg is an effective diuretic in man with normal renal function. Fourteen patients with non-oedematous stable chronic renal failure (creatinine clearance ranging from 1·2 to 12 ml/min) were given metolazone in doses ranging from 20-150 mg. A noticeable increase in urine flow and sodium excretion occurred, free water clearance increased, and there was a small but significant increase in potassium excretion. No side effects were noted.     

Recherches sur la conservation du virus de la densonucléose

Résumé Le virus de la densonucléose (VDN) conserve une partie de sa virulence en solution aqueuse entre 0°C et 30°C pendant deux mois. Son pouvoir infectieux se maintient à—10°C pendant deux mois mais est supprimé après dix jours de dessication. On peut done considérer ceParvovirus d’Insectes comme un virus relativement résistant aux températures que l’on rencontre ordinairement dans la nature et au laboratoire.

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Summary The persistence of DNV is described. This virus retains a part of its infectivity in aqueous solution between 0°C and 30°C. The log LD₅₀ initially 7,15 drops to 2 after two months. The virus keeps its infectivity at 10°C but it loses all its pathogenicity after 10 days in dry conditions.

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Ce travail a été réalisé en partie dans le cadre d’une convention I.N.R.A.-D.R.M.E.     

Sporulation of Saccharomyces cerevisiae in the Absence of a Functional Mitochondrial Genome

The role of the mitochondrial system during sporulation of Saccharomyces cerevisiae was studied. Addition of ethidium bromide (EthBr) to cells growing in acetate medium resulted in the quantitative (>98%) conversion of the culture to the petite genotype in one generation. The cells were respiratory active (derepressed) but contained no mitochondrial deoxyribonucleic acid (mtDNA) as demonstrated by analytical ultracentrifugation in CsCl. When transferred to acetate sporulation medium, the culture sporulated. Ascus production was only slightly below that of the control culture. Synthesis of mtDNA occurred during sporulation in the control but not in the EthBr-treated culture. Mitochondrial protein synthesis was virtually eliminated in the EthBr-treated culture. Therefore, completely derepressed cells can sporulate without a functional mitochondrial genetic system. When partially repressed cells were treated with EthBr, no ascus formation was observed after transfer to sporulation medium. Control cultures underwent respiratory adaptation in sporulation medium and then sporulated. Extensive derepression of the respiratory system is thus required for sporulation, and this adaptation is dependent on a functional mitochondrial system. Our results suggest that once the cells are fully derepressed no mitochondrial genetic information has to be expressed during meiosis and ascus formation.     

Some Acridine-Resistant Mutations of Bacteriophage T4d

Three new 9-aminoacridine (9AA) resistant mutations of bacteriophage T4D have been isolated and characterized. Two of the mutations, rs and rc, have identical patterns of acridine resistance, but they map on opposite sides of the rII region. In addition, rs has an effect on the plaque morphology of r mutations, whereas rc does not. The third mutation, ama, maps very close to rs but exhibits a different pattern of resistance to 9AA. None of the three is resistant to acridines by virtue of reduced permeability. Taken together with other mutations that have been previously characterized, these new mutations permit us to set the minimum number of acridine-sensitive processes in T4 development at four.     

Struktur und quantitatives Verhalten des perimitochondrialen granulären endoplasmatischen Retikulums der Mäuseleber

Zusammenfassung In normalen Leberzellen der Maus wurde das quantitative Verhalten des perimitochondrialen granulären endoplasmatischen Retikulums untersucht. 74% der Mitochondrien zeigen Beziehungen zum granulären endoplasmatischen Retikulum. Die einzelnen Mitochondrien werden zu 52%19,5 von den Membranen des granulären endoplasmatischen Retikulums bedeckt. Je Mikrometer Membranstrecke sind auf der mitochondriennahen Seite des granulären endoplasmatischen Retikulums 21 und auf der mitochondrienfernen Seite 20 Ribosomen zu finden, was der Zahl im übrigen granulären endoplasmatischen Retikulum entspricht. Die Befunde stellen die Grundlage für Untersuchungen des perimitochondrialen granulären endoplasmatischen Retikulums unter pathologischen Bedingungen dar.

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Structure and quantitative behaviour of the perimitochondrial granular endoplasmic reticulum in the liver cells of the mouse

Summary The perimitochondrial granular endoplasmic reticulum in normal mouse liver cells has been investigated quantitatively. 74% of the mitochondria are in association with the granular endoplasmic reticulum. The individual mitochondrion is covered by the membranes of the granulated E. R. in 52%19.5. The outer surface of the endoplasmic membrane, facing the mitochondrion, is occupied by 21 ribosomes per m; the corresponding surface of the membrane facing the free cytoplasm is occupied by 20 ribosomes per m. These data are in agreement with those of that fraction of the E. R., which is not in association with mitochondria. These findings represent a basis for investigations of the perimitochondrial endoplasmic reticulum under pathological conditions.

     

Secondary and Tertiary Responses of the Induced Bactericidin from the West Indian Spiny Lobster, Panulirus argus

West Indian spiny lobsters, Panulirus argus, synthesized a hemolymph bactericidin after being injected with killed suspensions of gram-negative bacillus EMB-1 isolated from the normal gut of this lobster. To study differences between the primary response and secondary response, animals were given a primary antigen injection of EMB-1 followed by a second injection of the same antigen 22 to 51 days later. As a rule, secondary bactericidal responses were enhanced over the primary in a manner reminiscent of specific anamnesis in mammalian immunoglobulin synthesis. Immunological memory was also suggested when tertiary responses were compared to secondary and by the persistence of residual titers for many days or weeks without additional antigenic stimulation.     

Retting of Flax by Aspergillus niger

In this study, retting was carried out by Aspergillus niger. The pH, galacturonic acid (GA), and total reducing sugar were determined; the end point was identified by the classic empirical processes and by the maximal GA content of the retting water. The process gave clear and resistent fibers, and the retting time was similar to that of current industrial processes with bacterial enzymes. Control of total acidity was not required, since the pH remained close to neutrality throughout the entire process.     

Population structure of some pond Microcrustacea

Summary The aestival species composition of microcrustacea of eight ponds in southwestern Kansas is described. Two benthic Ostracoda and three planktonic Copepoda and eight planktonic Cladocera were collected.On the whole, the Copepoda were more abundant than the Cladocera. Patterns of relative abundance varied from week to week and were more varied than the patterns described for the limnetic zone of lakes. There were two or three copepods in each pond. Except for one pond which had no Cladocera, there were two to five species of Cladocera per pond.There were fourteen significant affinities among the plankters. Two species showed no affinity. The relationships among four recurrent groups were established. Group I contained one cyclopoid, one calanoid and two cladocerans, a pattern not unlike the typical limnetic community.The population structure of each species that occurred in more that one pond was analyzed by analysis of variance. Significant differences between the ponds occurred from various species in per cent copepodids in the population, per cent females with eggs, and the number of eggs per egg sac. There was no significant difference among the ponds regarding the mean number of eggs per ovigerous female for any cladoceran.Interactions among the species and faunal characteristics of the ponds are discussed in relation to the environmental characteristics of the ponds.

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Zusammenfassung Die Zusammensetzung der estivalen Arten von Mikrocrustacean von acht Teichen im Südwesten von Kansas wird beschrieben. Zwei benthische Ostracoden, drei planktonische Copepoden und acht planktonische Cladoceren wurden gefunden.Die Copepoden waren im allgemeinen häufiger als die Cladoceren. Die Schemen der relativen Anzahl wechselten von Woche zu Woche und waren unterschiedlicher als die Schemen für die limnische Seezone. Zwei oder drei Copepoden, sowie zwei bis fünf Arten von Cladoceren kamen in jedem Teich vor, ausser in einem Teich, in dem keine Cladoceren gefunden wurden.Vierzehn wichtige Übereinstimmungen wurden unter den Planktonern gefunden. Zwei Arten zeigten keine Affinität. Der Zusammenhang zwischen vier wiederkehrenden Gruppen wurden nachgewiesen. Gruppe I enthielt einen Cyclopoiden, einen Calanoiden und zwei Cladoceren, ein für typisch limnische Gemeinschaften übliches Schema.Die Bevölkerungsstruktur jeder Art, die in mehr als einem Teich vorkam, wurde durch Streuungsanalyse untersucht. Es wurden signifikante Unterschiede im Prozentsatz der Copepoden: Bevölkerung, der Weibchen mit Eiern, der Anzahl Eier im Brutraum für die verschiedenen Arten zwischen den Teichen gefunden. Keine signifikanten Unterschiede wurden in der Anzahl Eier pro eitragendem Weibchen der Cladoceren zwischen den Teichen gefunden.Auch der Einfluss der Umweltfaktoren der Teiche auf die Arten und auf die Fauna des Teiches wurde untersucht.