Attempt to obtain in vitro pre-erythrocyte forms of Plasmodium vivax in human liver cell cultures inoculated with sporozoites]

Using sporozoites of a strain of Plasmodium vivax of North Korean origin maintained in human subjects and in Anopheles atroparvus, the authors inoculated human liver cell cultures (primary cultures and Ist subcultures). The appearance of some rare intracytoplasmic forms is described, which are thought to be very likely connected with the pre-erythrocytic cycle of P. vivax. Further attempts are nevertheless necessary to confirm, or invalidate, the obtained results.     

Interspecific competition between Drosophila melanogaster and Drosophila simulans: Effects of adult density on adult viability

Survival (viability) of newly eclosed adults of D. simulans st and D. melanogaster Or R-C, which had excess quantities of dead yeast available throughout life, was measured daily for 7 days in an experiment where adult density (6 levels), species frequency (6 levels) and ³²P tissue content (2 levels) were varied factorially. A separate experiment comparing viability in different types of experimental unit also was done. Similar experiments were done for D. simulans st competing against D. melanogaster y w. The entire data were subjected to a least-squares (unbalanced, missing-plot) analysis of variance. D. melanogaster Or R-C had a higher average viability than D. melanogaster y w or D. simulans st, which were equal. The competing strain of D. melanogaster influenced D. simulans st viability — viability being higher when y w was the competitor. Viability decreased over the seven day period but at different rates for the three strains. Increasing density reduced viability for all three strains, but species frequency effects, although significant, were generally not consistent. Females had higher viability than males in both D. melanogaster strains, but the reverse was true in D. simulans st. ³²P lowered viability and experimental unit type altered viability. Numerous interactions were significant.Adult density was shown to have a delayed effect on viability — the delay before the appearance of the effect (an increase in death rate) being decreased as density rose. The term variably delayed density dependent has been adopted to describe the fitness component, adult viability. Some high density populations showed a readjustment (a decrease) in their death rate as a reaction to the effect of reduced density caused by high early mortality.     

Estimating the Abundance of Endospores of Sulfate-Reducing Bacteria in Environmental Samples by Inducing Germination and Exponential Growth

It is a challenge to quantitatively distinguish active from dormant microbial populations in environmental samples. Here we present an approach for estimating the abundance of dormant sulfate-reducing bacteria (SRB), present as viable endospores in environmental samples. This is achieved by inducing endospores to germinate and grow exponentially. We demonstrate this approach for thermophilic SRB in temperate sediment from Aarhus Bay, Denmark. The approach is based on measuring bulk sulfate reduction rates (SRRs) in pasteurized sediment and calculating associated cell-specific SRRs based on average values for SRB growth yield and cell size known from exponentially growing pure cultures. The method presented is a faster bioassay than most probable number enumerations and has the potential to distinguish between slow- and fast-growing SRB populations in the same sample. This bioassay is attractive given the challenges posed by endospores with respect to cell permeabilization and lysis, which are prerequisite in quantitative microscopy- and nucleic acid extraction-based strategies. These molecular approaches additionally rely on designing target-appropriate oligonucleotide probes, whereas the method presented here considers the trait of interest more broadly. This strategy thus presents a useful complement to other methods in ecological investigations of microbial biogeography and for specific industrial applications such as reservoir souring and corrosion risk assessments in the oil and gas sector.     

Size at birth and resilience to effects of poor living conditions in adult life: longitudinal study

ObjectiveTo determine whether men who grew slowly in utero or during infancy are more vulnerable to the later effects of poor living conditions on coronary heart disease.DesignFollow up study of men for whom there were data on body size at birth and growth and social class during childhood, educational level, and social class and income in adult life.SettingHelsinki, Finland.Participants3676 men who were born during 1934-44, attended child welfare clinics in Helsinki, were still resident in Finland in 1971, and for whom data from the 1980 census were available.ResultsMen who had low social class or low household income in adult life had increased rates of coronary heart disease. The hazard ratio among men with the lowest annual income (<£8400) was 1.71 (95% confidence interval 1.18 to 2.48) compared with 1.00 in men with incomes above £15 700. These effects were stronger in men who were thin at birth (ponderal index <26 kg/m³): hazard ratio 2.58 (1.45 to 4.60) for men with lowest annual income. Among the men who were thin at birth the effects of low social class were greater in those who had accelerated weight gain between ages 1 and 12 years. Low social class in childhood further increased risk of disease, partly because it was associated with poor growth during infancy. Low educational attainment was associated with increased risk, and low income had no effect once this was taken into account.ConclusionMen who grow slowly in utero remain biologically different to other men. They are more vulnerable to the effects of low socioeconomic status and low income on coronary heart disease.

What is already known on this topic

People who grow slowly in utero and during infancy remain biologically different through their livesSuch people are at increased risk of coronary heart disease

What this study adds

Among men who were thin at birth the risk of coronary heart disease is further increased if they have poor living standards in adult lifeOther men tend to be resilient to the adverse effects of poor living standards     

Epilithic algal communities and their relationship to environmental variables in lakes of the English Lake District

1. The relationship between epilithic algal communities and 17 environmental variables from 17 oligo- to eutrophic lakes in the English Lake District was explored using canonical correspondence analysis (CCA). Total phosphorus (TP) and calcium (Ca) concentration were the most important variables accounting for species distribution.
2. Weighted-averaging regression and calibration models with tolerance downweighting and classical deshrinking were developed to infer TP, Ca, dissolved inorganic carbon (DIC) and conductivity from the relative abundance of 138 epilithic algal taxa.
3. The ranges of the environmental variables covered by the models are 0.8-49.2 μg L−1 for TP, 2.2–13.0 mg L−1 for Ca, 0.5–8.6 mg L−1 for DIC and 38–124 μS cm−1 for conductivity. Within these limits the models can be used to infer chemical properties of lakes from epilithic communities in the English Lake District.
4. The major advantages of using transfer functions based on epilithic communities are the low logistic requirements and the integrative character of algal samples compared to direct point measurements of chemical parameters of the lakes.