Change in the effect of constant photoperiods on the rate of sexual maturation in modern genotypes of domestic pullet

1. Data for modern egg-type hybrids reared on constant daylengths show that, as expected, they mature more quickly than earlier genotypes. However, the constant photoperiod which gives earliest sexual maturity has not changed as a result of selection and is 10 h for both early and modern genotypes. 2. Further analysis showed that the rate of delay in sexual maturity for constant photoperiods above 10 h is similar for modern and for early hybrids ( +0.29 d for each incremental one hour of photoperiod), the response of modern hybrids below 10 h ( +4.22 d for each one-hour reduction in photoperiod) is more than double that of early hybrids ( +1.71 d/h).

Seed development, maturation and storage behaviour of Mimusops elengi L

Mass maturity (end of the seed-filling phase) occurred at about 72 days after flowering (DAF) in developing seeds of Mimusops elengi, at which time seed moisture content had declined to about 55%. The onset of ability to germinate was detected at 56 DAF and seeds showed 98% germination by 84 DAF. Tolerance of desiccation to 10% moisture content was first detected at 70 DAF and was maximal by 84 DAF. Delaying collection by a further 14 days to 98 DAF, when fruits began to be shed, reduced seed viability, particularly for seeds first dried to 10% moisture content. Hence the best time for seed collection appears to be about 14 days before fruits shed. In a separate investigation with six different seed lots, desiccation below about 8-12% moisture content reduced viability (considerably in some lots). The viability of dry seeds (below about 10% moisture content) stored hermetically was reduced at cool temperatures (5 degrees C and below), and none survived storage at sub-zero temperatures. The results suggest that Mimusops elengi shows intermediate seed storage behaviour and that the optimal hermetic seed storage environment is about 10% moisture content at 10 degrees C, while short-term, moist, aerated storage at high (40%) moisture content is also feasible.

Evidence for complex multigenic inheritance of radiation AML susceptibility in mice revealed using a surrogate phenotypic assay

The mapping of genes which affect individual cancer risk is an important but complex challenge. A surrogate assay of susceptibility to radiation-induced acute myeloid leukaemia (AML) in the mouse based on chromosomal radiosensitivity has been developed and validated. This assay was applied to the mapping of radiation-induced AML risk modifier loci by association with microsatellite markers. A region on chromosome (chr) 18 with strong association is identified and confirmed by backcross analysis. Additional loci on chrs 8 and 13 show significant association. A key candidate gene Rbbp8 on chr18 is identified. Rbbp8 is shown to be upregulated in response to X-irradiation in the AML sensitive CBA strain but not AML resistant C57BL/6 strain. This study demonstrates the strength of utilizing surrogate endpoints of cancer susceptibility in the mapping of mouse loci and identifies additional loci that may affect radiation cancer risk.

Genotypic and phenotypic diversity of a baculovirus population within an individual insect host

It is becoming increasingly apparent that many pathogen populations, including those of insects, show high levels of genotypic variation. Baculoviruses are known to be highly variable, with isolates collected from the same species in different geographical locations frequently showing genetic variation and differences in their biology. More recent Studies at smaller scales have also shown that virus DNA profiles from individual larvae can show polymorphisms within and between populations of the same species. Here, we investigate the genotypic and phenotypic variation of an insect baculovirus infection within a single insect host. Twenty four genotypically distinct nucleopolyhedrovirus (NPV) variants were isolated from an individual pine beauty moth, Panolis flammea, caterpillar by in vivo cloning techniques. No variant appeared to be dominant in the population. The Pafl NPV variants have been mapped using three restriction endonucleases and shown to contain three hypervariable regions containing insertions of 70-750 bp. Comparison of seven of these variants in an alternative host, Mamestra brassicae, demonstrated that the variants differed significantly in both pathogenicity and speed of kill. The generation and maintenance of pathogen heterogeneity are discussed. (c) 2005 Elsevier Inc. All rights reserved.

A block in virus-like particle maturation following assembly of murine leukaemia virus in insect cells

Expression of the murine leukaemia virus (MLV) major Gag antigen p65(Gag) using the baculovirus expression system leads to efficient assembly and release of virus-like particles (VLP) representative of immature MLV. Expression of P180(Gag-Pol), facilitated normally in mammalian cells by readthrough of the p65(Gag) termination codon, also occurs efficiently in insect cells to provide a source of the MLV protease and a pattern of p65(Gag) processing similar to that observed in mammalian cells. VLP release from P180(Gag-Pol) expressing cells however remains essentially immature with disproportionate levels of the uncleaved p65(Gag) precursor when compared to the intracellular Gag profile. Changing the p65(Gag) termination codon altered the level of p65(Gag) and p180(Gag-Pol) within expressing cells but did not alter the pattern of released VLP, which remained immature. Coexpression of p65(Gag) with a fixed readthrough p180(Gag-Pol) also led to only immature VLP release despite high intracellular protease levels. Our data suggest a mechanism that preferentially selects uncleaved p65(Gag) for the assembly of MLV in this heterologous expression system and implies that, in addition to their relative levels, active sorting of the correct p65(Gag) and p180(Gag-Pol) ratios may occur in producer cells. (C) 2003 Elsevier Inc. All rights reserved.

Immunohistochemical localization of inhibin/activin alpha, beta(A) and beta(B) subunits and follistatin in bovine oocytes during in vitro maturation and fertilization

The aim of this study was to evaluate the distribution of inhibin/activin alpha, beta(A) and beta(B) subunits and follistatin in immature oocytes and in matured oocytes before and after IVF. Denuded oocytes were submitted to a whole-mount immunofluorescence procedure. Specimens were imaged and fluorescent intensities quantified by scanning laser confocal microscopy. Immunoreactivity for inhibin alpha subunit (both alpha(C) and pro-alpha. regions), abundant in the ooplasm of immature oocytes, decreased after maturation (a 68% and 88% decrease, respectively; P < 0.001), but increased after IVF by 2- and 5.7-fold, respectively (P < 0.01). Intense staining for PA was detected in immature oocytes (predominantly in the outer ooplasm and zona pellucida) but after maturation and fertilization it was localized mainly in the zona pellucida, perivitelline space and oolemma. Immunoreactivity for RA in the ooplasm decreased by 58% after maturation (P < 0.001) but increased again by 75% after fertilization (P < 0.01). Immunoreactivity for beta(B) was localized mainly in the zona pellucida and did not change after maturation. However, immurloreactivity for beta(B) was not detected in the zona pellucida after fertilization, but remained unchanged in unfertilized oocytes. Immunoreactivity for follistatin was detected in the ooplasm and zona pellucida of immature oocytes but decreased progressively in the ooplasm after maturation (a 63% decrease; P < 0.001) and did not change after IVF. Examination of partially denuded cumulus-oocyte complexes confirmed abundant expression of alpha(C), pro-alpha, beta(A) and follistatin immunoreactivity in cumulus cells, whereas beta(B) subunit staining was weak or absent in cumulus cells, but intense in the zona pellucida. In conclusion, the present study shows that qualitative and quantitative changes in the distribution of inhibin/activin subunits and follistatin accompany oocyte maturation and fertilization. The possibility, indicated by these observations, that activin A and activin B may play distinct roles in bovine oocyte maturation and fertilization warrants further study.

Effect of temperature and salt on the maturation of white-salted cheese

White-salted cheeses were prepared from ultrafiltered (UF) cows' milk and salted to give final salt-in-moisture (SM) levels of 2.5, 3.2 and 4.0%. The cheeses were stored at 5degreesC and 10degreesC for up to 15 weeks. The microflora was dominated by lactic acid bacteria (LAB) but some mould growth was evident within 15 weeks at all SM levels and both temperatures. Levels of water-soluble nitrogen (WSN), attributed to chymosin activity, increased significantly with time, the rate being inversely proportional to the SM level and increasing with storage temperature. Similar effects were noted for trichloroacetic acid-soluble nitrogen (TCA-SN) and free amino acid (FAA) levels, both of which would also be affected by bacterial protease activity. The proteolytic activity was reflected by changes in the hardness and fracturability of the cheeses.

Maturation of limbic corticostriatal activation and connectivity associated with developmental changes in temporal discounting

Temporal discounting (TD) matures with age, alongside other markers of increased impulse control, and coherent, self-regulated behaviour. Discounting paradigms quantify the ability to refrain from preference of immediate rewards, in favour of delayed, larger rewards. As such, they measure temporal foresight and the ability to delay gratification, functions that develop slowly into adulthood. We investigated the neural maturation that accompanies the previously observed age-related behavioural changes in discounting, from early adolescence into mid-adulthood. We used functional magnetic resonance imaging of a hypothetical discounting task with monetary rewards delayed in the week to year range. We show that age-related reductions in choice impulsivity were associated with changes in activation in ventromedial prefrontal cortex (vmPFC), anterior cingulate cortex (ACC), ventral striatum (VS), insula, inferior temporal gyrus, and posterior parietal cortex. Limbic frontostriatal activation changes were specifically associated with age-dependent reductions in impulsive choice, as part of a more extensive network of brain areas showing age-related changes in activation, including dorsolateral PFC, inferior parietal cortex, and subcortical areas. The maturational pattern of functional connectivity included strengthening in activation coupling between ventromedial and dorsolateral PFC, parietal and insular cortices during selection of delayed alternatives, and between vmPFC and VS during selection of immediate alternatives. We conclude that maturational mechanisms within limbic frontostriatal circuitry underlie the observed post-pubertal reductions in impulsive choice with increasing age, and that this effect is dependent on increased activation coherence within a network of areas associated with discounting behaviour and inter-temporal decision-making.

Phenotypic and phylogenetic characterization of a new Corynebacterium species from dogs: description of Corynebacterium auriscanis sp. nov.

Six strains of a previously undescribed catalase-positive coryneform bacterium isolated from clinical specimens from dogs were characterized by phenotypic and molecular genetic methods. Biochemical and chemotaxonomic studies revealed that the unknown bacterium belonged to the genus Corynebacterium sensu stricto. Comparative 16S rRNA gene sequencing showed that the six strains were genealogically highly related and constitute a new subline within the genus Corynebacterium; this subline is close to but distinct from C. falsenii, C. jeikeium, and C. urealyticum. The unknown bacterium from dogs was distinguished from all currently validated Corynebacterium species by phenotypic tests including electrophoretic analysis of whole-cell proteins. On the basis of phylogenetic and phenotypic evidence, it is proposed that the unknown bacterium be classified as a new species, Corynebacterium auriscanis. The type strain of C. auriscanis is CCUG 39938T.

Rice seed quality development and temperature during late development and maturation

The potential longevity of japonica rice (Oryza sativa L. subsp. japonica) seed is particularly sensitive to high temperature – and thus climate change – during development and maturation. Cultivar Taipei 309 was grown at 28/208C (12 h/12 h) and then from 19 DAA (days after 50% anthesis), when seeds were just over half filled, at 28/208C, 30/228C, 32/248C or 34/268C (12 h/12 h). Whereas ability to germinate ex planta had been achieved in almost all seeds by 24 DAA, only half the population were desiccation tolerant. Desiccation tolerance continued to increase over the subsequent 28 d, similarly at all four temperatures. Subsequent longevity, assessed by p50 (period in days to reduce viability to 50% in hermetic storage at 408C with c. 15% moisture content), increased progressively at 28/208C until 38 DAA, and remained constant until the final harvest (52 DAA). The three warmer temperature regimes provided similar longevity to 28/208C at any one harvest, except at 38 DAA where the warmest (34/268C) was poorer. That temperature regime also provided greater seed-to-seed variability within each survival curve. The results confirm that appreciable improvement in seed quality occurs during seed development and also subsequent maturation in japonica rice, but that increase in temperature from 28/208C to 34/268C during late seed filling onwards has comparatively little effect thereon. Comparison with previous investigations suggests that seed quality development may be less sensitive to high temperatures during late development and maturation than during the early seed development that precedes it.

Differential phenotypic and genotypic characteristics of qnrS1-harboring plasmids carried by hospital and community commensal enterobacteria

The qnrS1 gene induces reduced susceptibility to fluoroquinolones in enterobacteria. We investigated the structure, antimicrobial susceptibility phenotype, and antimicrobial resistance gene characteristics of qnrS1 plasmids from hospitalized patients and community controls in southern Vietnam. We found that the antimicrobial susceptibilities, resistance gene characteristics, and plasmid structures of qnrS1 plasmids from the hospital differed from those from the community. Our data imply that the characteristics of the two plasmid groups are indicative of distinct selective pressures in the differing environments.