Genetic Structure of a Local Population of the Anopheles gambiae Complex in Burkina Faso

Members of the Anopheles gambiae species complex are primary vectors of human malaria in Africa. Population heterogeneities for ecological and behavioral attributes expand and stabilize malaria transmission over space and time, and populations may change in response to vector control, urbanization and other factors. There is a need for approaches to comprehensively describe the structure and characteristics of a sympatric local mosquito population, because incomplete knowledge of vector population composition may hinder control efforts. To this end, we used a genome-wide custom SNP typing array to analyze a population collection from a single geographic region in West Africa. The combination of sample depth (n = 456) and marker density (n = 1536) unambiguously resolved population subgroups, which were also compared for their relative susceptibility to natural genotypes of Plasmodium falciparum malaria. The population subgroups display fluctuating patterns of differentiation or sharing across the genome. Analysis of linkage disequilibrium identified 19 new candidate genes for association with underlying population divergence between sister taxa, A. coluzzii (M-form) and A. gambiae (S-form).     

Implications of the Hiroshima-Nagasaki genetic studies for the estimation of the human "doubling dose" of radiation

Since 1946 a continuous effort to evaluate the potential genetic effects of the atomic bombs has been sustained. Observations on children born in Hiroshima and Nagasaki include sex ratio, congenital malformations, stillbirths, survival of liveborn infants, chromosomal abnormalities (sex chromosomal abnormalities and balanced chromosomal rearrangements), mutations altering protein structure or activity, and physical growth and development. There are no statistically significant differences between the children of parents who received increased amounts of radiation at the time of the bombings and those whose parents did not. However, the difference between the two sets of children is consistent with the hypothesis of a genetic effect of the exposure, but its magnitude suggests humans are not as sensitive to the genetic effects of radiation as projected from the mouse paradigm.     

A chromosome study of 6-thioguanine-resistant mutants in T lymphocytes of Hiroshima atomic bomb survivors

Cytogenetic characterizations were made of lymphocyte colonies established from somatic mutation assays for 6-thioguanine (TG) resistance in Hiroshima atomic bomb survivors. G-banded chromosomes were analyzed in both TG-resistant (TGr) and wild-type colonies. Included were 45 TGr and 19 wild-type colonies derived from proximally exposed A-bomb survivors, as well as colonies from distally exposed control individuals who did not receive a significant amount of A-bomb radiation (18 TGr and 9-wild type colonies). Various structural and numerical chromosome abnormalities were observed in both TGr and wild-type colonies. Aberrations of the X chromosome, on which the hypoxanthine guanine phosphoribosyl transferase (HPRT) locus is present, were found in 6 colonies: 2 resistant colonies from controls (45,X/46,XX; 46,X,ins(X)), 3 resistant colonies (45,X/46,XX/46,X, + mar; 46,X,t(Xq +;14q-); 46,Y,t(Xq-;5q +)), and 1 wild-type colony (45,X/47,XXX) from proximally exposed persons. In cases with exchange aberrations, each of the break points on the X chromosome was situated proximally to band q26 where the HPRT locus is known to be assigned. DNA-replicating patterns were also studied, and it was found that abnormal X chromosomes showed early replicating patterns, while normal X chromosomes showed late replicating patterns.     

A new type of inversion of a human Y chromosome

Summary Using chromosome banding techniques, a phenotypically normal male was found to have an abnormal banding pattern of the Y chromosome. By the constitutive heterochromatin staining method, a darkly stained band was located on the short arm and the proximal region of the long arm. The quinacrine staining method also showed a similar abnormal banding pattern: a brightly fluorescing band was seen on the short arm and the proximal region of the long arm. By the conventional Giemsa staining method, however, no specific morphological abnormality was detected in the aberrant Y. On detailed karyotype analyses no recognizable abnormality of banding patterns of any other chromosome was found aside from the abnormal Y. The abnormality was determined to be a complex inversion of the Y chromosome, which is described as 46,X,inv(Y)(pterp11::q11q12::cen::q12qter).     

Soft trapping and manipulation of cells using a disposable nanoliter biochamber

Low-power continuous-wave laser radiation is used to form a very stable microbubble at the end of a specially etched and metalized optical fiber probe. We demonstrate that the microbubble, which is firmly attached to the fiber probe, can be used to benignly trap and manipulate living swine sperm cells as well as human embryonic kidney cells. The lifetime of the microbubble has been prolonged and the gaseous environment inside the bubble controlled using micropipette gas injection. The controlled fusion of two microbubbles is demonstrated as a means of transferring microparticles from one bubble to another. These experiments lay the foundation for the use of the microbubble as a mobile, nanoliter-volume disposable biochamber for cellular studies.     

Multiplex 16S rRNA haplotype-specific PCR, a rapid and convenient method for fish species identification: an application to West African Clupeiform larvae

A multiplex haplotype-specific polymerase chain reaction (MHS-PCR) method was developed, which identified seven Clupeiform species living in the tropical Eastern Atlantic region: Sardinella aurita, Sardinella maderensis, Ethmalosa fimbriata, Sardina pilchardus, Engraulis encrasicholus, Pellonula leonensis and Ilisha africana. 16S rRNA fragments were amplified using a species-specific set of primers, yielding species-specific size fragments, and then separated using agarose gel electrophoresis, enabling direct visual identification of targeted species. This method provides an accurate, easy and rapid tool for identifying species within large Clupeiform samples. It is suitable for investigations on early Clupeiform stages, species and identification in fishery management in the tropical Eastern Atlantic area.     

Role of Anopheles melas Theobald (1903) on malaria transmission in a mangrove swamp in Saloum (Senegal)

From June 1995 to January 1998, entomological studies carried out in five villages located in the Delta's Saloum have allowed to better understand the contribution of An. melas Theobald (1903) to malaria transmission in mangrove swamp. Among the five villages studied, three of them (Simal, Djilor and Marlothie) located along the Saloum river, are colonised by An. arabiensis; the two others (Djifere and Diakhanor) located between the sea and the river, are colonised by An. melas. During the rainy season and at the beginning of the dry season, An. melas and An. arabiensis are sympatric. The ratio of An. melas/An. arabiensis increases when we go closer the coast where An. melas becomes quite exclusive. When An. melas is predominant, endophagy, endophily and anthropophily are very marked. The parturity rates are lower in An. melas than in An. arabiensis. In the predominance area of each species, transmission is on the same level. During the period of sympatry, An. arabiensis is responsible for the transmission and when it is absent, An. melas carries on. Transmission occurs from July to March with a maximum at the beginning of the dry season. In the villages of the mangrove swamp, its prolongation until the middle of the dry season is due to An. melas.     

The children of parents exposed to atomic bombs: estimates of the genetic doubling dose of radiation for humans.

The data collected in Hiroshima and Nagasaki during the past 40 years on the children of survivors of the atomic bombings and on the children of a suitable control population are analyzed on the basis of the newly revised estimates of radiation doses. No statistically significant effects emerge with respect to eight different indicators. Since, however, it may confidently be assumed some mutations were induced, we have taken the data at face value and calculated the minimal gametic doubling doses of acute radiation for the individual indicators at various probability levels. An effort has also been made to calculate the most probable doubling dose for the indicators combined. The latter value is between 1.7 and 2.2 Sv. It is suggested the appropriate figure for chronic radiation would be between 3.4 and 4.5 Sv. These estimates suggest humans are less sensitive to the genetic effects of radiation than has been assumed on the basis of past extrapolations from experiments with mice.     

Travel stress alters the intestinal migrating myoelectric complex in rats: antagonist effect of trimebutine.

A novel stress model was developed that may closely resemble a real-life situation. Intestinal motility was monitored in rats before and after a 12 hour train voyage (travel stress). Travel stress reduced the duration of phase III of the intestinal MMC by 30% (3.2 +/- 0.3 vs 4.7 +/- 0.6 min; p less than 0.001) while the durations of phase I and II were unaffected. This effect persisted for two days. Phase III duration returned to basal values after 3 days indicating a reversible alteration on intestinal migrating myoelectric complex (MMC). The infusion of trimebutine at a flow rate of 166 micrograms/kg/h during the stress exposure abolished the changes observed in the duration of phase III of the MMC; the infusion of diazepam (16.6 micrograms/kg/h) had no effect. These results indicate that the travel stress model may be similar to common life events that induce alterations of intestinal motility. Furthermore, trimebutine prevented the reduction of phase III duration induced by travel stress suggesting its possible action on mechanisms involved in the mediation of the stress-induced intestinal motility changes.