花尾榛鸡的非对称性比和成体存活率

1999至2002年,在法国东南部的阿尔卑斯山,通过无线电追踪方法研究了花尾榛鸡的性比问题。首先,我们通过直接观测无线电标记雄性的配对比例,在消除可能的捕捉误差后,发现繁殖种群性比为1．26（即未配对的雄性占21％）。然后,我们估计了标记个体的存活率和繁殖成功率。在假设窝扩散时幼体的性比平衡的前提下,通过两性和两个年龄组（幼体,〈10月龄的个体;成体〉10月龄的个体）的确定性统计模型,得到的理论性比为1．22（即未配对的雄性占18％）,这一结果与实际观测的性比十分接近。我们认为,雌性死亡率高导致的两性存活率差异可以解释雄性性比偏高现象。我们进而讨论了花尾榛鸡整个分布区内居间强度的非对称性比的适应意义,以及在衰退的花尾榛鸡种群中雌性数量极端不足的后果[动物学报52（4）：655—662,2006]。     

Properties of the Invertases of Cultured Sycamore Cells and Changes in Their Activity during Culture Growth

When cultured sycamore cells are homogenised in a phosphate-citrate buffer at pH 7.0 and the homogenate centrifuged two fractions are obtained both of which show the presence of an acid (opt. pH 4.0–4.5) and a neutral (opt. pH 7.0–7.4) invertase. The activity of the insoluble pellet appears to be located in its cell wall fragments. The acid and neutral invertases of the soluble fraction can be separated by fractional precipitation with (NH₄SO₄. The activities of these enzymes are low in stationary phase cells but they increase following subculture to reach peaks of activity towards the end of the period of most active cell growth and division and then decline again as the cells begin to enter stationary phase. The activities of both enzymes are higher in the cell wall than in the soluble fraction and the acid invertase reaches higher levels of activity than the neutral enzyme in both fractions. When cells are subcultured there occurs within a few hours an increase in the acid invertase and a decline in the neutral invertase activity in the cell wall fraction and a decline in the acid invertase of the soluble fraction prior to the large net increases in the activities of both enzymes in both locations which occurs as the cells embark upon cell division. The pattern of changes in the invertase activities through the growth cycle of batch propagated cultures is similar whether the cells are grown in sucrose, or glucose, or sucrose plus glucose; the highest levels of activities were recorded in the glucose-grown cells. The total yield of invertase activities and the distribution of activities between the soluble and cell wall fractions of the homogenates are affected by the pH of the extraction medium (within the range pH 4.0–8.0). It has not proved possible to completely remove the invertases from the cell wall fraction; upwards of 50 % of the acid invertase was recovered from this fraction by treatment with Triton-X followed by urea, but these treatments inactivated a high proportion of the neutral enzyme. These findings are compared with other studies on the activity and intra-cellular distribution of plant invertases and the possible roles of these enzymes discussed.     

Factors affecting egg maturation in the bean weevil Callosobruchus maculatus

Abstract. This paper concerns the effects of mate and seed availability on the rate of egg maturation in the bean weevil Callosobruchus maculatus (F.). Egg maturation starts before emergence from the seed and, provided that both oviposition sites and mates are available, eggs are laid at a rate determined by the number of oviposition sites, and mature at a similar rate. If seeds or mates are absent then a small number of eggs are laid, but oocytes continue to mature until the oviduct-capacity is approached. The number of eggs that a female can store is dependent on her body weight and does not correlate with the number of ovarioles. If, after a period in which oocyte development has been halted, conditions for egg-laying become suitable, then egg maturation can be re-started, but only after the oviducts have been emptied of eggs. The rate of egg maturation is then similar to that for females of the same age which have been maturing eggs since emergence.     

Cytological Studies in the Laminariales

A cytological investigation of British members of the orderLaminariales has revealed the presence of a very large X-chromosomein dividing nuclei of female gametophytes and young sporophytesof Saccorhiza polyschides. This chromosome pairs with a smallY-chromosome at meiosis. A chromosome which is conspicuouslylarger than the others has also been detected in the femalegametophytes (and young sporophytes) of Laminaria spp., Chordafilum, and Alaria esculenta. There is some evidence that thisalso pairs with a smaller chromosome. Chromosome numbers determinedduring the work are as follows: Laminaria digitata, L. saccharina,L. hyperborea, L. ochroleuca, Saccorhiza polyschides, hap-loid31 and diploid 62; Alaria esculenta, haploid 28 and diploid56; Chorda filum, haploid c. 28 and diploid c. 56     

Conservation genetics of the endangered Pampas deer (Ozotoceros bezoarticus)

The Pampas deer ( Ozotoceros bezoarticus L. 1758) is the most endangered neotropical cervid, and in the past occupied a wide range of open habitats including grassland, pampas, savanna, and cerrado (Brazil) from 5° to 41° S. To better understand the effect of habitat fragmentation on gene flow and genetic variation, and to uncover genetic units for conservation, we examined DNA sequences from the mitochondrial control region of 54 individuals from six localities distributed throughout the present geographical range of the Pampas deer. Our results suggest that the control region of the Pampas deer is one of the most polymorphic of any mammal. This remarkably high variability probably reflects large historic population sizes of millions of individuals in contrast to numbers of fewer than 80 000 today. Gene flow between populations is generally close to one migrant per generation and, with the exception of two populations from Argentina, all populations are significantly differentiated. The degree of gene flow was correlated with geographical distance between populations, a result consistent with limited dispersal being the primary determinant of genetic differentiation between populations. The molecular genetic results provide a mandate for habitat restoration and reintroduction of Pampas deer so that levels of genetic variation can be preserved and historic patterns of abundance can be reconstructed. However, the source of individuals for reintroduction generally should be from populations geographically closest to those now in danger of extinction.     

Similarities between l-Phenylalanine and m-Fluorophenylalanine as Substrates for l-Phenylalanine Ammonia-Lyase

The ability of l -phenylalanine ammonia-lyase (E.C. 4.3.1.5) to metabolize dl -m-, dl -o- and dl -p-fluorophenylalanine in Avena sativa has been examined. Although all three amino acid analogues served as substrates for this enzyme, there was a marked difference in the behavior of the meta isomer from that of the para and ortho species. The Michaelis constant for the meta analogue was similar to that obtained for the natural substrate, l -phenylalanine, but distinct from the kinetic data for the para and ortho isomers. In addition, in vivo analyses demonstrated that both l -phenylalanine and the meta-fluoro-derivative served to protect against chlorogenic acid loss, whereas previous studies have shown that the para and ortho species depressed levels of this phenolic derivative. Finally, treatment of coleoptile apices with either the meta isomer or l -phenylalanine reversed dl -p-fluorophenylalanine stimulated growth and attendant reduction in chlorogenic acid content. These findings provide further clarification of the effects of fluorophenylalanines upon l -phenylalanine ammonia-lyase mediated biosynthesis of low molecular weight phenols in Avena.     

Mechanism of Host Cell Restriction in African Green Monkey Kidney Cells Abortively Infected with Human Adenovirus Type 2

Host cell restriction by GMK cells in abortive infections of adenovirus type 2 can be partially relieved by co-infection with SV40.