Risk factors for infection with human immmunodeficiency virus among European expatriates in Africa.

The pattern of cases of AIDS in Belgium suggests that Europeans infected with human immunodeficiency virus (HIV) acquired the infection in Africa. The prevalence of infection was assessed in Belgian advisers and European expatriates and risk factors for infection defined in a case-control study of expatriate men. Fifteen (1.1%) of 1401 Belgian advisers working in Africa and 41 (0.9%) of 4564 European expatriates living in Africa, were positive for antibody to HIV in a voluntary screening programme in Belgium. Among subjects with antibody to HIV the ratio of men to women was 3:1. These subjects did not have a history of intravenous drug abuse or blood transfusion and only one was homosexual. In a case-control study of 33 expatriate men who had antibody to HIV and 119 controls the men with antibody reported significantly more female sexual partners, who were more commonly local; and significantly more sexual contact with prostitutes in Africa. They had a significantly higher prevalence of history of sexually transmitted disease and had received significantly more injections by unqualified staff in Africa during the previous five years. No specific sexual practices were associated with having antibody to HIV. After multivariate analysis sexual contact with local women (adjusted odds ratio 14.7; 95% confidence interval 2.81 to 76.9), sexual contact with prostitutes (adjusted odds ratio 10.8 (1.6 to 71.9), and injections by unqualified staff (adjusted odds ratio 13.5 (3.7 to 49.8) remained independent risk factors for infection. European expatriates in Africa were at increased risk from infection with HIV and were a means of introducing HIV into the heterosexual population in Europe. Transmission from women to men by vaginal intercourse seemed to be the most probable route of infection.     

Mitochondrial DNA differentiation during the speciation process in Peromyscus

We address the problem of the possible significance of biological speciation to the magnitude and pattern of divergence of asexually transmitted characters in bisexual species. The empirical data for this report consist of restriction endonuclease site variability in maternally transmitted mitochondrial DNA (mtDNA) isolated from 82 samples of Peromyscus polionotus and P. leucopus collected from major portions of the respective species' ranges. Data are analyzed together with previously published information on P. maniculatus, a sibling species to polionotus. Maps of restriction sites indicate that all of the variation observed can be reasonably attributed to base substitutions leading to loss or gain of particular recognition sites. Magnitude of mtDNA sequence divergence within polionotus (maximum approximately equal to 2%) is roughly comparable to that observed within any of five previously identified mtDNA assemblages in maniculatus. Sequence divergence within leucopus (maximum approximately equal to 4%) is somewhat greater than that within polionotus. Consideration of probable evolutionary links among mtDNA restriction site maps allowed estimation of matriarchal phylogenies within polionotus and leucopus. Clustering algorithms and qualitative Wagner procedures were used to generate phenograms and parsimony networks, respectively, for the between-species comparisons. Three simple graphical models are presented to illustrate some conceivable relationships of mtDNA differentiation to speciation. In theoretical case I, each of two reproductively defined species (A and B) is monophyletic in matriarchal genealogy; the common female ancestor of either species can either predate or postdate the speciation. In case II, neither species is monophyletic in matriarchal genotype. In case III, species B is monophyletic but forms a subclade within A which is thus paraphyletic with respect to B. The empirical results for mtDNA in maniculatus and polionotus appear to conform closely to case III. These theoretical and empirical considerations raise a number of questions about the general relationship of the speciation process to the evolution of uniparentally transmitted traits. Some of these considerations are presented, and it is suggested that the distribution patterns of mtDNA sequence variation within and among extant species should be of considerable relevance to the particular demographies of speciation.      

Obtaining cell proliferation for chromosome preparation in gill tissue culture of the oyster Crassostrea gigas

The present results were obtained in the course of theadjustment to the oyster Crassostrea gigas of atissue culture technique recently developed for themussel Mytilus edulis. With respect to theprotocol originally described, the effects of twomodifications are reported: (1) replacement of chickembryo extract by chicken serum for medium enrichment,and (2) achievement of cultures in rotating tubes(roller drum) in place of stationary condition.Paradoxical results were obtained: whereas takenseparately, each modification exerted a negativeeffect which is statistically significant, combinated,they exerted a high positive effect representing athree-fold increase of the mean metaphase spreadnumber per slide (i.e. 71.5). Hypotheses are proposedto explain the mechanisms involved. It is suggestedthat the two additives work differently and thatcultures with chick embryo extract enriched mediumcould not withstand the condition generated by theroller drum. Conversely, cultures performed withchicken serum enriched medium would be in a betterphysiological state and the roller allow to obtain acell proliferation after only six days of incubation.     

Dynamics of long-term continuous culture of Limnospira indica in an air-lift photobioreactor

MELiSSA (Microecological Life Support System Alternative) is a developing technology for regenerative life support to enable long-term human missions in Space and has developed a demonstration Pilot Plant. One of the components of the MELiSSA Pilot Plant system is an 83L external loop air-lift photobioreactor (PBR) where Limnospira indica (previously named Arthrospira sp. PC8005) is axenically cultivated in a continuous operation mode for long-periods. Its mission is to provide O₂ and consume CO₂ while producing edible material. Biological and process characterization of this PBR is performed by analysing the effect of two main variables, dilution rate (D) and PFD (Photon Flux Density) illumination. A maximum oxygen productivity () of 1.35 mmol l⁻¹ h⁻¹ is obtained at a D of 0.025 h⁻¹ and PFD of 930 µmol m⁻² s⁻¹. Photoinhibition can occur when a 1 g l⁻¹ cell density culture is exposed to PFD higher than 1700 µmol m⁻² s⁻¹. This process is reversible if the illumination is returned to dim light (150 µmol m⁻² s⁻¹), proving the cell adaptability and capacity to respond at different illumination conditions. Influence of light intensity in cell composition is also described. Specific photon flux density (qPFD) has a direct effect on phycobiliproteins and chlorophyll content causing a decrease of 62.5% and 47.8%, respectively, when qPFD increases from 6.1 to 19.2 µmol g⁻¹ s⁻¹. The same trend is observed for proteins and the opposite for carbohydrate content. Morphological and spiral structural features of L. indica are studied by confocal microscopy, and size distribution parameters are quantified. A direct effect between trichome width and CDW/OD ratio is observed. Changes in size distribution are not correlated with environmental factors, further confirms the adaptation capacity of the cells. The systematic analysis performed provides valuable insights to understand the key performance criteria of continuous culture in air-lift PBRs.     

Growth monitoring of a photosynthetic micro-organism (Spirulina platensis) by pressure measurement

An on-line measurement technique for estimating biomass production rate in a photosynthetic micro-organism culture was developed and tested experimentally. The technique is based on monitoring O₂ production from the increase in pressure inside a closed photobioreactor. The data obtained by this method correlated with the direct measurement of the biomass concentration. A material balance on the components in the system allows the validity domain of the method to be defined. The method was applied to batch cultures of the cyanobacterium, Spirulina platensis, in a cylindrical photobioreactor validating existing physiological and light energy models.