Origin of male-biased sex allocation in orphaned colonies of the termite, <Emphasis Type="Italic">Coptotermes lacteus</Emphasis>

In eusocial insects, sex allocation often constitutes a ground for intracolonial conflicts. This occurrence provides ideal opportunities to test kin-selection theory. A vast literature on this topic is available for social Hymenoptera, but the same field remains almost untouched in termites. A preeminent case is that of some species of Coptotermes, where the sex-allocation ratio in nymphs shifts from near equity to all-male when the primary reproductives are replaced by neotenics. To shed light on the developmental origin of this shift, we compared the sex ratio of the various castes and instars in primary- and neotenic-headed mature colonies of Coptotermes lacteus. The male-biased sex allocation in the latter type of colony results from two concurrent events: first, the sex ratio of the youngest instars (larvae) is male-biased by a 3:1 ratio; and second, all female larvae become workers, while a large fraction of the male larvae proceed to the nymphal and alate stages. Colony-founding experiments showed that inbreeding by itself cannot account for the male bias at hatching. We suggest that both genetic factors, due to the reproductive behaviour of neotenics, and environmental factors (colony condition and resource availability) may influence this process. Their exact nature and respective impact have not yet been clarified.     

Effects of temperature and water content on degradation of isoproturon in three soil profiles

The phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), is widely used to control pre- and post-emergence of grass and broad-leaved weeds in cereal crops. Its degradation in soils is a key process for assessing its leaching risk to groundwater resources. The degradation properties of various samples from surface and subsurface soil (down to 1m depth) of a heterogeneous agricultural field were studied using (14)C-IPU. Laboratory incubations were carried out at 22 and 10 degrees C and at water contents 90% and 50% of the estimated water holding capacity (eWHC) corresponding to water potentials between -56 kPa and -660 MPa. Degradation was found to be more sensitive to water content variations than to temperature variations in the ranges that we used. For surface layers, at 10 and 22 degrees C, the degradation half-life increased by a factor 10 and 15, respectively, when water content decreased from 90% to 50% eWHC. Under optimal degradation conditions (i.e. 22 degrees C and 90% eWHC), 3-(4-isopropylphenyl)-1-methylurea (MDIPU) was the main metabolite in surface samples. At subsurface depths, IPU half-lives were larger than 100 d, IPU was the main compound after 92 d of incubation and the main metabolite was an unidentified polar metabolite. These results suggest a metabolic pathway involving hydroxylations for subsurface materials. IPU degradation was largely affected by water availability in both surface and subsurface horizons. Clay content seemed to play a major role in degradation processes in subsurface soil by determining through sorption IPU availability in soil solution and/or by limiting water availability for microorganisms.     

Effects of phosphorus fertilization on the availability and uptake of uranium and nutrients by plants grown on soil derived from uranium mining debris

Subterranean clover and barley were grown on a soil derived from uranium mining debris and fertilized with phosphate as a U immobilizing additive for in situ remediation. We investigated the beneficial effect of P fertilization in the range 0-500 mg P kg(-1) soil in terms of U extractability, plant biomass production and U uptake. Increasing P in the mining debris caused a significant decrease of the water-soluble U and NH(4)-Ac extractable U at pH 7 and 5. For both plant species, P fertilization considerably increased root and shoot dry matter up to a maximum observed for soil receiving 100 mg P kg(-1) while the soil-to-plant transfer of U was regularly decreased by increasing P content in soil. These observations show that P fertilization represents an in situ practical option to facilitate the revegetation of U-mining heaps and to reduce the risks of biota exposure to U contamination.     

Larval salivary glands are a source of primer and releaser pheromone in honey bee (Apis mellifera L.)

A brood pheromone identified in honeybee larvae has primer and releaser pheromone effects on adult bees. Using gas chromatography–mass spectrometry (GC–MS) to evaluate fatty acid esters—the pheromonal compounds—in different parts of the larvae, we have localized the source of the esters as the larval salivary glands. A histochemical study describes the glands and confirms the presence of lipids in the glands. Epithelial cells of the gland likely secrete the fatty acids into the lumen of the gland. These results demonstrate the salivary glands to be a reservoir of esters, components of brood pheromone, in honeybee larvae.     

Sonography in prenatal diagnosis of congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder with an incidence of 1/15 000. More than 90% of CAH cases result from mutations of CYP21, leading to 21-hydroxylase deficiency. In its classical form, CAH is severe and consists of the virilizing (increase of androgens) and salt-wasting (lack of aldosterone) phenotype. When a proband exists, early prenatal diagnosis for CAH can be performed by direct molecular analysis in the first trimester. We describe herein two cases suggesting that the prenatal diagnosis of CAH can be initiated by the sonographic appearance of the adrenal gland at the second-trimester scan in the absence of a family history. Copyright © 2004 John Wiley & Sons, Ltd.     

兰州市西固区蔬菜重金属污染现状及健康风险评价研究

针对西北地区典型的工业区-兰州市西固工业区内种植的蔬菜进行重金属含量状况调查分析,对购自当地市场的8种蔬菜中Cu、Cd、Pb、Zn 4种重金属元素的含量进行分析,通过污染指数法和经蔬菜途径重金属暴露接触对人体的健康风险进行了系统评价.结果表明,蔬菜中均不含有Pb元素或Pb元素在蔬菜中的含量比较少,低于分析方法检测限;Cu元素含量最高的是茄子为0.067 mg/kg,含量最低的是菜花为0.015 mg/kg;Cd元素含量最高的是芹菜为0.067 mg/kg,含量最低的是白菜为0.023 mg/kg;Zn元素含量最高的是菠菜为1.001 mg/kg,含量最低的是辣椒为0.274 mg/kg.美国环境健康风险评估方法评价所得THQ值均小于1,表明实验所采集的大多数蔬菜样品的重金属含量符合农产品安全质量要求.