Heritability of male outcrossing ability in the simultaneous hermaphrodite, Bulinus truncatus (Gastropoda: Planorbidae)

The heritability of phally, a dichotomous trait defined by the functional state of the male reproductive tract, was measured in a laboratory population of the simultaneous hermaphrodite snail Bulinus truncatus by means of a breeding experiment and a selection experiment. Euphallic individuals develop a fully functional male and female tract and are capable of receiving and donating sperm. In aphallic individuals the male tract does not develop fully, preventing sperm donation. There was no evidence of a heritable component to phally in the breeding experiment, but the selection experiment demonstrated a slight heritable effect. In both experiments there was more variation in the observed proportion of euphallics than expected by chance alone and no evidence of line or family effects, implicating environmental determination of male outcrossing ability even under controlled laboratory conditions. Previous studies of populations of B. truncatus reported that the proportion of euphallics was under strong genetic control. We suggest that there may be population differences in the extent of environmental control over phally, analogous to that reported for sex determination.     

Purification of polyclonal anti-conformational antibodies for use in affinity selection from random peptide phage display libraries: A study using the hydatid vaccine EG95

The use of polyclonal antibodies to screen random peptide phage display libraries often results in the recognition of a large number of peptides that mimic linear epitopes on various proteins. There appears to be a bias in the use of this technology toward the selection of peptides that mimic linear epitopes. In many circumstances the correct folding of a protein immunogen is required for conferring protection. The use of random peptide phage display libraries to identify peptide mimics of conformational epitopes in these cases requires a strategy for overcoming this bias. Conformational epitopes on the hydatid vaccine EG95 have been shown to result in protective immunity in sheep, whereas linear epitopes are not protective. In this paper we describe a strategy that results in the purification of polyclonal antibodies directed against conformational epitopes while eliminating antibodies directed against linear epitopes. These affinity purified antibodies were then used to select a peptide from a random peptide phage display library that has the capacity to mimic conformational epitopes on EG95. This peptide was subsequently used to affinity purify monospecific antibodies against EG95.     

基于钙黄绿素的荧光分光光度法测定谷胱甘肽

目的:基于钙黄绿素的荧光分光光度法建立一种测定谷胱甘肽的新方法。方法:在pH=8.0介质中,铜(Ⅱ)与钙黄绿素配位引起荧光猝灭,由于谷胱甘肽与铜(Ⅱ)的亲和力很强,可从钙黄绿素-铜离子的络合物中夺取铜离子而使钙黄绿素游离出来使荧光强度得以恢复,荧光恢复的程度与加入谷胱甘肽的浓度在一定浓度范围内成线性。结果:据此建立了一种测定谷胱甘肽的新方法,该方法的线性范围为2.0×10-6～1.4×10-5mol.L-1,F=8.1964C+196.43,检测限为1.0×10-6mol/L。结论:用此法测定谷胱甘肽简便快速,灵敏度高。     

Biomass of primary and secondary vegetation in Rondônia, Western Brazilian Amazon

Biomass estimates of primary and different ages of secondary vegetation are reported for a tropical forest region in Rondônia, Western Brazilian Amazon. The estimates are based on published allometric equations, and on vegetation composition and allometric data collected in areas of primary forest and secondary vegetation of ages 2, 3, 5, 9, 11, 16 and 18 years. Primary forest biomass estimates varied from 290 to 495 t ha^–1. Secondary vegetation biomass estimates accounted for 40–60% of the primary forest biomass after 18 years of abandonment. Secondary growth rates in lightly used areas are estimated to have varied from 6.6 to 8.7 t ha^–1 y^–1 between the third and the eighteenth years after abandonment. CO₂ sequestration by regrowing vegetation is discussed for two scenarios of land abandonment.     

The genome sequence of Bacillus cereus ATCC 10987 reveals metabolic adaptations and a large plasmid related to Bacillus anthracis pXO1

We sequenced the complete genome of Bacillus cereus ATCC 10987, a non-lethal dairy isolate in the same genetic subgroup as Bacillus anthracis. Comparison of the chromosomes demonstrated that B.cereus ATCC 10987 was more similar to B.anthracis Ames than B.cereus ATCC 14579, while containing a number of unique metabolic capabilities such as urease and xylose utilization and lacking the ability to utilize nitrate and nitrite. Additionally, genetic mechanisms for variation of capsule carbohydrate and flagella surface structures were identified. Bacillus cereus ATCC 10987 contains a single large plasmid (pBc10987), of ~208 kb, that is similar in gene content and organization to B.anthracis pXO1 but is lacking the pathogenicity-associated island containing the anthrax lethal and edema toxin complex genes. The chromosomal similarity of B.cereus ATCC 10987 to B.anthracis Ames, as well as the fact that it contains a large pXO1-like plasmid, may make it a possible model for studying B.anthracis plasmid biology and regulatory cross-talk.     

Gene repeat expansion and contraction by spontaneous intrachromosomal homologous recombination in mammalian cells

Homologous recombination (HR) is important in repairing errors of replication and other forms of DNA damage. In mammalian cells, potential templates include the homologous chromosome, and after DNA replication, the sister chromatid. Previous work has shown that the mammalian recombination machinery is organized to suppress interchromosomal recombination while preserving intrachromosomal HR. In the present study, we investigated spontaneous intrachromosomal HR in mouse hybridoma cell lines in which variously numbered tandem repeats of the µ heavy chain constant (Cµ) region reside at the haploid, chromosomal immunoglobulin µ heavy chain locus. This organization provides the opportunity to investigate recombination between homologous gene repeats in a well-defined chromosomal locus under conditions in which recombinants are conveniently recovered. This system revealed several features about the mammalian intrachromosomal HR process: (i) the frequency of HR was high (recombinants represented as much as several percent of the total of recombinants and non-recombinants); (ii) the recombination process appeared to be predominantly non-reciprocal, consistent with the possibility of gene conversion; (iii) putative gene conversion tracts were long (up to 13.4 kb); (iv) the recombination process occurred with precision, initiating and terminating within regions of shared homology. The results are discussed with respect to mammalian intrachromosomal HR involving interactions both within and between sister chromatids.     

Indigestibility of plant cell wall by the Australian plague locust, Chortoicetes terminifera

The plant cell wall may play an important role in defence against herbivores since it can be both a barrier to, and nutrient diluter of, the easily digested cell contents. The aim of this study was to investigate the digestibility of the cell wall of three grasses, Triticum aestivum L., Dactyloctenium radulans (R. Br.) Beauv., and Astrebla lappacea (Lindl.) Domin, by the Australian plague locust, Chortoicetes terminifera Walker (Orthoptera: Acrididae, Acridinae) as determined by the Van Soest method [ Van Soest PJ, Robertson JB & Lewis BA (1991) Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74: 3583–3597]. Determination of plant cell wall digestion by locusts required a precise methodological procedure to determine both the exact intake and the concentration of cell wall in the diet and the faeces. Plant cell wall determination is affected by the particle size distribution of the dried plant material. All three grasses differed in the percentage of cell wall per gram dry matter and the proportions of hemicellulose, cellulose, and acid‐detergent sulphuric lignin within the cell wall. The locust was unable to digest the cell wall of any of the grasses. Thus, plant cell walls are a mechanical barrier hindering locusts assimilating nutrients. That is, access, rather than nutrient concentration per se, may be limiting nutrient factor.