Staining of sulphatides in metachromatic leukodystrophy with Alcian blue at high salt concentrations.

Alcian blue combines with purified sulphatide in 1.OM magnesium chloride. In tissue sections from patients with metachromatic leukodystrophy, sulphatide is stained by Alcian blue in 0.8 M magnesium chloride, and the staining can be abolished by prior treatment with chloroform and methanol. The simplicity of the technique, its specificity and ease of interpretation recommend Alcian blue staining at high salt concentrations as a routine method in the diagnosis of metachromatic leukodystrophy.     

No adverse prognostic influence of hepatitis B virus infection in acute childhood lymphoblastic leukemia

In the years 1980-1985 72 children with acute lymphoblastic leukemia were diagnosed and treated by intensive combination chemotherapy (BFM protocols 79, 81, 83). Of these children 33 acquired a Hepatitis B-virus-carrier state with 1983 as the peak year of incidence. Both groups of patients, the infected and the uninfected ones, were comparable as to prognostic factors. All except 8 patients are off chemotherapy after a total duration of treatment of 1 1/2 or 2 years. Probability for event-free survival (life table analysis, maximum observation time 82 months, minimum 12 months) is equal (0.77 vs. 0.75) in both groups. With 3 exceptions, all HBV-infected patients still carry the HBs-antigen in the serum; 22 of the 30 living patients in the infected group developed anti-HBc.     

Herbicide effects on planktonic systems of different complexity

Bioassays of different complexity were compared with respect to their capability to predict the environmental impact of the herbicide atrazine in aquatic systems. Acute toxicity tests with Daphnia did not yield meaningful results. Sublethal tests with Daphnia (feeding inhibition, reduction of growth and reproduction) were more sensitive, but effective concentrations of atrazine were still rather high (2 mg/L). A relatively complicated artificial food chain system that incorporated direct and indirect effects on Daphnia yielded significant reduction of daphnid population growth at 0.1 mg/L. Enclosure experiments with natural communities were by far the most sensitive tools. Community responses could be measured at concentrations as low as 1 µg/L and 0.1 µg atrazine/L. At the lowest concentration, however, communities recovered after three weeks. We conclude that in complex systems indirect effects can be more important than direct effects, so that, contrary to the conditions in simple tests, non-target organisms may be the better indicators of herbicide stress to natural communities.     

Trade-offs inDaphnia vertical migration strategies

Summary Planktonic animals performing diel vertical migration (DVM) experience a tradeoff between reduced mortality and reduced reproductive output due to lower food availability in their refuge. Models of DVM as an evolutionarily stable strategy predict that, under certain conditions, strategies of both migration and non-migration can coexist. Vertical profiles of animal abundances during day and night, however, do not allow any discrimination between the behaviour of individuals or subpopulations. We used length-body protein regressions as a measure of the nutritional state ofDaphnia to distinguish possible sub-populations differing in their migration strategy. An overwhelming part of the population migrated downwards during the day. However, the few daphnids in the epilimnion during the day had significantly higher protein content than the animals in the deep water, indicating that these daphnids did not migrate randomly but remained in the surface food-rich water all day. This shows that migrating animals gain no metabolic advantage over non-migrating ones.Supported by a F.P.U. grant (Spanish Goverment)     

Site-specific alteration of murine hepatitis virus type 4 peplomer glycoprotein E2 results in reduced neurovirulence.

Strains of the murine coronavirus mouse hepatitis virus type 4 (MHV-4) which contained a mutation in the E2 peplomer glycoprotein were obtained by selection for resistance to neutralization by monoclonal antibodies. Characterization of six variants representing two independent epitopes on E2, E2B and E2C, by in vitro neutralization and antibody-binding assays demonstrated that selection for an alteration in epitope E2B also resulted in changes in epitope E2C and vice versa. We observed a mutation frequency of approximately 10(-4.3) to 10(-4.6), which is consistent with the expected occurrence of single point mutations. The variant virus strains were attenuated with respect to neurovirulence when compared with wild-type MHV-4. Mice normally develop encephalomyelitis and die after wild-type MHV-4 infection. Mice receiving 2- to 3-log-higher doses of the variant strains survived and developed demyelinating disease. As the disease progressed, evidence of remyelination and ongoing demyelination was observed up to 65 days after infection. Virus reisolated 15 days after infection retained the variant phenotype. The data indicate that the E2 glycoprotein plays a central role in determining the cellular tropism and virulence of MHV-4 in the mouse.     

Coexistence of similar genotypes of Daphnia magna in intermittent populations: response to thermal stress

We investigated the diversity and thermal response of a fitness related trait, juvenile growth rate, in seasonal population samples of Daphnia magna from two temperate ponds. Both populations were intermittent, i.e. they disappeared from the water body and recolonized seasonally by hatching from resting eggs in the sediment.
Temporally isolated clones of Daphnia magna showed the typical asymmetric response for growth rate with temperature and a sharp decline after the maximum response at 26°C (TMR). There was no evidence for genetically adapted seasonal groups. Despite significant genetic variation among clones and for phenotypic plasticity (G×E interactions without genetic correlations), seasonal groups of clones showed no shift in TMR and mean temperature reaction norms were similar among groups and both populations. Heritabilities remained similar among temperatures despite a large increase in genetic variance at stressfully high temperatures of 29°C and 32°C, due to simultaneous increase in environmental variance. Further, heritabilities remained high among sample periods and were not eroded during several months of asexual reproduction.
Regular diapause, an intrinsic feature of intermittent Daphnia populations, may replace the need for physiological temperature adaptation and promote maintenance of diversity through phenotypic similarity by reducing the time over which competitive interactions occur. Such populations are unlikely to be directly affected by elevated temperatures. They have a large potential for phenotypic plasticity as their TMR is higher than the temperature normally encountered.     

Activation of immobilized acetyl-Coenzyme A carboxylase.

Partially purified acetyl-CoA carboxylase was covalently bound to a Sepharose 4B matrix. Although aggregation was thus prevented, the enzymic activity was stimulated by citrate and isocitrate.     

A field study on the dependence of the fecundity of Daphnia spec. on food concentration

Summary The dependency of the fecundity of Daphnia spec. on the food concentration was studied in Lake Constance. To eliminate the influence of temperature the number of eggs per adult female was plotted against the concentration of particulate carbon (<50 m) at the estimated time of the production of the eggs. The curve obtained is similar to the results of laboratory investigations. The minimum food concentration for egg production is slightly above 0.2 mg C/1; at 0.7 mg C/1 the curve reaches a plateau. The absolute values of the threshold concentration and the incipient limiting level are compared to laboratory results. It appears that the shift of the field curve to higher concentrations is caused by the imcomplete availability of the 50 m particulate carbon fraction to the daphnids. Daphnia in Lake Constance seem to be food limited during most of the year.