Possible implications of CpG avoidance in the flatworm Schistosoma mansoni

We report the analysis of the biases of CpG, TpG, and CpA of all the DNA sequences data from the Trematode Schistosoma mansoni. Our results show CpG avoidance whereas TpG and CpA frequencies are over the expected values. These characteristics are similar to the biases displayed by methylated genomes, but in platyhelminths 5mC has not been detected by biochemical methods. The possible implications of this CpG shortage are discussed.     

Ecology of Biomphalaria (Gastropoda: Planorbidae) in Lake Albert, Western Uganda: snail distributions, infection with schistosomes and temporal associations with environmental dynamics

In Lake Albert, an ecological study was conducted, between June 2000 and May 2003, which assessed snail population dynamics, parasite infection patterns and interplay of environmental factors upon Biomphalaria. Monthly sampling surveys were conducted at 29 sites monitoring populations of Biomphalaria stanleyi and Biomphalaria sudanica. Altogether, a total of 21,715 B. stanleyi and 8452 B. sudanica were collected during the period. Both species could be found infected with Schistosoma mansoni although infection prevalence was significantly higher (p < 0.01**) in B. stanleyi (4.4%) than in B. sudanica (3.5%). Each species occupied slightly different aquatic niches with B. stanleyi preferring deeper water habitats whilst B. sudanica was found along the shoreline in shallower water. B. stanleyi was more widely distributed among the sampling locations (19 sites) than B. sudanica (10 sites). Of the four villages included in the study area, snails from sites near Piida and Bugoigo villages had the highest schistosome infection rates, presumably attributable to the closer proximity of people with intestinal schistosomiasis. After inspection of cross-correlation plots which identified most suitable time lags, snail density dynamics could be associated with seasonal variations inclusive of: air temperature, rainfall, lake level, water temperature, water conductivity and water pH. These temporal observations better reveal the relationship between snail populations and environmental factors, providing important information concerning the relative roles of B. stanleyi and B. sudanica in transmission of S. mansoni and development of integrated strategies for disease control around Lake Albert.     

Physiologic studies of snail-schistosome interactions and potential for improvement of in vitro culture of schistosomes

Summary Despite extensive efforts to develop suitable media for rearing the intramolluscan stages of schistosomes, successful in vitro culture of these parasites remains elusive. Recent³¹P NMR studies demonstrated that the levels of free phospholipids, particularly phosphatidylcholine, in the digestive gland of the snail,Biomphalaria glabrata, were dramatically reduced when the host was infected withSchistosoma mansoni. It was speculated that absorption of host phosphatides may be an important source of membrane phospholipid precursors and fatty acids for developing sporocysts and cercariae. During the present investigations,B. glabrata was maintained on a high fat diet of egg yolk, and the lipid composition of control uninfected and infected snails examined by³¹P and¹³C NMR. In addition, the levels of host hemolymph metabolites, including glucose and urea, considered as indicators of parasite nutrient uptake, were monitored. The lipid level of snails fed egg yolk was greatly increased, and hosts developed patent infections in approximately half the time of infected snails maintained on lettuce. The composition of the free phospholipids accumulated in the tissues ofB. glabrata fed egg yolk were the same as those previously reported in the cercarial stage ofS. mansoni. Moreover, the fatty acids ofS. mansoni and those reported here in the neutral lipids and free phosphatides in the host tissues were similar. Uninfected snails maintained on lettuce had higher hemolymph levels of glucose than those reared on egg yolk, and infected hosts on egg yolk had significantly lower levels of hemolymph urea. β-hydroxybutyrate was the principal hemolymph metabolite in snails fed egg yolk, but was not detected in snails maintained on lettuce. The level of β-hydroxybutyrate in the hemolymph of snails on egg yolk was significantly reduced by infection. The results indicated that the pattern of host hemolymph nutrient utilization by larval schistosomes may be markedly altered by host diet, and it was concluded that host lipids may directly and indirectly be important nutrients for developing schistosomes. Future studies on in vitro culture of the intramolluscan stages of schistosomes should emphasize the potential role of lipids and attempt to define the nutritive value of those medium components that presently supply lipids in culture media, most notably serum.     

日本血吸虫胞蚴期超微结构的初步观察

本文用扫描与透射电镜观察了我国大陆品系37日和45日龄日本血吸虫母胞蚴及其体内未成熟子胞蚴体被的结构。同时观察了取自螺肝组织的62日龄成熟子胞蚴。初次揭示日本血吸虫胞蚴期体被的超微结构,基本上与曼氏血吸虫胞蚴期相似。日本血吸虫母胞蚴和成熟子胞蚴除体被无体棘外,其他很相似。比较未成熟的子胞蚴与未成熟的尾蚴,揭示外质膜由两层结构构成;随后,外层结构溶化消失,而同时出现微绒毛。构成这样母子二代胞蚴及其体内胚胎既相同又有差别,认为与幼虫寄生部位及生殖生理状态有关。     

伸筋草类药用植物资源的初步研究

本文报道6种商品伸筋草类药用植物的本草考证、理化分析及药理试验。豚鼠离体肠平滑肌实验结果表明:玉柏石松(Lycopodium obscurum L.)和华中石松(L.centro-chinese Ching)的总提取物有较强兴奋作用,其次是扁枝石松(Diphasiastrum complanatum (L.) Holub),再次是垂穗石松(Palhimhaea cernua (L.) Franco et Vase)、石松(Lycopodium japonicum Thunb.)及藤石松(Lycopodiastrum casuarinodes (Spring) Holub)。这与各自的总生物碱含量相吻合。从抗血小板凝聚试验来看。玉柏石松总提取物作用最强,其次是扁枝石松。     

Increase of Bradyrhizobium japonicum numbers in soils and enhanced nodulation of soybean (Glycine max (L) merr.) using granular inoculants amended with nutrients

Abstract: Mineral microgranules, amended with nutrients and inoculated with either peat or liquid Bradyrhizobium japonicum inoculants, increased the growth and recovery of the bacterium during laboratory incubation in unsterilized soil. Increases in the range of 1 log unit per g or ml inoculant used were observed in different soil types. B. japonicum showed better survival with nutrient-amended granules than in unamended ones, in soil undergoing desiccation. In a growth chamber experiment, the number of nodules per plant were significantly increased by nutrient-amendment of the granules, but only under suboptimal conditions for nodulation. Nutrient-amended granules significantly enhanced early nodulation of soybean and increased N content of the grain at harvest in four field trials. All these effects were obtained using an average of 10 kg granules amended with 1.14 kg glycerol and 0.16 kg sodium glutamate per hectare. The possible use of nutrient-amended granules to improve efficacy and reliability of microbial inoculation is discussed.     

活血莲的核型分析

对活血莲的染色体数目及核型进行了研究,结果表明;活血莲的染色体数目为2n=60,其核型公式为2n=2x=60=46sm+12st+2m,没有观察到带随体的染色体。     

Age/size- and time-specific effects of Schistosoma mansoni on energy allocation patterns of its snail host Biomphalaria glabrata

Snail hosts of different ages constitute different resource environments for larval trematodes because each individual has a particular energy budget and energy allocation pattern at the time of infection. Effects of monomiracidial trematode infections on shell growth, body dry weight and reproductive effort of the snail host were compared between controls and infected juvenile and adult snails during the prepatent and patent periods. The results demonstrate phenotypic plasticity in the host response. There is an age/size-specific effect characterized by limitation of growth rate when snails are infected as juveniles and reduction of reproductive effort when snails are infected as adults, and a time-specific effect with early enhancement of growth rate and reproductive effort for infected juvenile and adult snails respectively during prepatency, before reduction and cessation during patency. The parasite is considered as a generalist in its energy exploitation strategy of the snail host, but taking into account the differential host responses observed relative to the host age, the possibility of a host preference for juvenile or adult snails is discussed. Received: 4 February 1997 / Accepted: 14 July 1997     

From discovery to eradication of schistosomiasis in Japan: 1847–1996

Among the areas in Japan where schistesome infections have occurred for many years, three major areas were Katayama District, Kofu Basin and Chikugo River Basin and three minor areas were Numazu District, Tone River Basin and Obitsu River Bank. The presence of the disease had long been recognised in the Katayama Memoir written by Fujii (1847, in the Chinese Classics). The cause of this endemic disease had been studied by many researchers, and finalty a new treamatode, Schistosoma japonicum, was discovered by Katsurada in 1904 [Tokyo Iji Shinski, Vol. 1371, pp. 13–32]. The route of percutaneous infection was proven by Fujinami & Nakamura (1909) [Kyoto Medical Journal, Vol. 6, pp. 224–252] using 17 calves. Miyairi & Suzuki (1913) [Tokyo Iji Shinshi, Vol. 1836, pp. 1961–1965] determined a small snail, Oncomelania nosophora, as being the intermediate best, and clarified the development of the schistosome in the snail. To kill schistosome eggs, human faecal matter (‘night soil’) was stored for 2 weeks or more before using as fertiliser. Control of the parasite used canstic lime and calcium cyanamide to kill eggs, cercariae and Oncomelania snails. Susceptible cows were replaced with horses, which were more resistant to infection as the animal of burden for agriculture. Ditches around the rice fields were comented for destruction of snail habitats. For snail control, sodium pentachlorophenate (NaPCP) was sprayed extensively. Some wetlands were drained and reclaimed and in selected localities, the river bottom was dredged. Such projects were undertaken with government support and aided by community participation. Epidemiological surveys began in 1910, first at Kofu, and infected people were treated with sodium tartar emetic (Stibnal) after 1921. The total number of cases detected in Japan in 1920 was about 8000. This figure was reduced annually down to 438 by 1970. The last human case of new infection found in Japan was at Kofu in 1977. Although snails were cradicated in most areas by 1983, a limited number of uninfected snails remain at Kofu and Obitsu.