Effects of pre-treatment with aflatoxin on a second aflatoxin treatment in guinea pigs

Two-hundred guinea pigs, weighing approximately 500 grams each, were placed in 8 groups, 4 of which received 20 g/kg/day of partially purified aflatoxin for 7 days, followed by a 7 day recovery period. Paired groups then received 0,20,35 or 50 g/kg/day of partially purified aflatoxin for 21 days. Animals were sacrificed periodically from all groups and blood was drawn for chemical and immunologic analysis. Weight gains were recorded and histopathologic studies were done on all animals. Pretreatment did not protect guinea pigs from a second exposure, and in fact enhanced mortality and liver toxicity as determined by histopathology. Serum chemistries and immunologic parameters of guinea pigs dosed twice were less conclusive, as neither high nor low doses differed from guinea pigs treated once. Glycocholic acid concentrations were more sensitive than traditional enzymes (aspartate and alanine amino transferase, alkaline phosphatase) for indicating hepatotoxicity.     

Mortality among male anaesthetists in the United Kingdom, 1957-83.

A cohort of 3769 male anaesthetists resident in the United Kingdom between 1957 and 1983 was followed up for a total of 51,431 person years of observation. All subjects were fellows of the Faculty of Anaesthetists and held full registration with the General Medical Council. With all men in social class I being taken as the standard, the standardised mortality ratio among anaesthetists for all causes of death was 68 (95% confidence interval 59 to 77) and the standardised mortality ratio for all cancers was 50 (95% confidence interval 36 to 67). There was no significant excess mortality from lymphomas or leukaemias, but 16 of the 221 deaths in anaesthetists were due to suicide, giving a standardised mortality ratio of 202 (95% confidence interval 115 to 328). When anaesthetists were compared with all doctors the standardised mortality ratio for suicide was only 114, a nonsignificant excess. These findings confirm that the risk of suicide among anaesthetists is twice as high as among other men in social class I but suggest that the risk does not differ significantly from that among doctors as a whole. There was no evidence of a significant excess risk of cancer, and, in particular, the small excess of cancer of the pancreas reported previously could not be confirmed.     

Blocking of human immunodeficiency virus infection depends on cell density and viral stock age.

Quantitative infectivity assays were used to study how the blocking activity of soluble CD4 (sCD4) is affected by sCD4 concentration, target cell density, and viral stock age. During incubation with 20 nM sCD4, human immunodeficiency virus type 1 (HIV-1) stocks underwent irreversible inactivation. In contrast, inactivation with 2 nM sCD4 was almost entirely reversible. At lower sCD4 concentrations (less than or equal to 2 nM) and target cell densities of 6.25 x 10(4) ml-1, sCD4 blocking activity for HIV-1 gave a gp120-sCD4 association constant (Kassoc) of 1.7 x 10(9) M-1, which agrees with chemical measurements. At the higher density of 1.6 x 10(7) cells ml-1, however, the blocking activity was 20-fold less. During incubation of HIV-1 stock optimized for infectivity by rapid harvest, sCD4 blocking activity increased 20-fold during a 3-h window. These results show that competitive blocking activity depends strongly on target cell density and virion age. Thus, unappreciated variations in HIV stocks and assay conditions may hinder comparisons of blockers from laboratory to laboratory, and the age of HIV challenge stocks may influence studies of drug and vaccine efficacy. The results also suggest that blocking of viral particles in lymphoid compartments will require very high competitive blocker concentrations, which may explain the refractory outcomes from sCD4-based drug trials in humans.     

Pastoral dairy marketing and household wealth interactions and their implications for calves and humans in Ethiopia

Surveys of pastoral households in a semi-nomadic Borana community during 1987–1988 were used to test the hypothesis that poorer families living closest to a market town would be most affected by the enhanced opportunity to sell dairy products, which would intensify competition between people and calves for milk and have negative implications for calf management. These poorer families indeed reported the highest rates of milk offtake per cow, and the milk increment was probably sold to purchase more grain for human consumption at the expense of milk intake for the calf. Consequently, this strategy may increase the susceptibility of malnourished calves to disease, especially those from lower-producing dams. Benefits of improved human energy intake from grain and retention of livestock capital must be weighed against risks of calf death and possible malnutrition of people from milk restriction when assessing dairy marketing trade-offs that are most acute for the poor. Opportunity to sell dairy products at favorable terms of trade helps the poorest people survive, and their risks could be mitigated by policies that facilitate grain marketing in the rangelands and interventions that improve calf feeding management, diversify human diets, and create alternative opportunities for women to generate income. The households postulated to be most at risk were identified from a complex, but logical, interaction among factors of distance to market, household wealth, and the quality of milking cows held. This indicates that targeting such needy groups for development assistance may require a more detailed and interdisciplinary analysis of production systems than is commonly practiced.     

Turkey acrosin. I. Isolation, purification, and partial characterization

Acrosin was extracted from turkey spermatozoa by use of urea together with sonication and freezing, and purified approximately 18-fold by sequential use of chromatofocusing and affinity chromatography. The use of chromatofocusing for the initial purification step proved to be superior to preparative isoelectric focusing. Similar to acrosin from many mammalian species, turkey acrosin was found to be a glycoprotein possessing characteristics of serine proteases. Polyacrylamide gel electrophoresis (PAGE) of the enzyme indicated the presence of two isozymes. Sodium-dodecyl sulfate PAGE under reducing conditions revealed three subunits with approximate molecular weights of 11,700, 13,900, and 15,900.     

The sucrose fuel cell: Efficient biomass conversion using a microbial catalyst

Sucrose was used as a fuel in a thionine-mediated microbial fuel cell containingProteus vulgaris serving as the biocatalyst in the anode compartment. The measured yields show that under suitable conditions the substrate may be oxidised quantitatively to electricity and carbon dioxide.     

The disappearance of isocitrate lyase from the green alga Chlorella fusca studied by immunoprecipitation

When acetate-adapted cultures of Chlorella fusca were transferred to nitrogen-free medium containing glucose, isocitrate lyase activity was lost over a period of about 25 h. Using a combination of in vivo isotope labelling and immunoprecipitation with anti-isocitrate lyase IgG it was shown that: 1. The onset of loss of enzyme activity preceeded the complete cessation of enzyme synthesis. 2. Disappearance of isocitrate lyase activity was accompanied by loss of enzyme protein, without accumulation of antigenic protein distinguishable from the normal subunit polypeptide of the enzyme, as judged by SDS gel electrophoresis of immunoprecipitated samples from supernatant cell-free extracts. 3. SDS gel electrophoresis of immunoprecipitated isocitrate lyase revealed the presence of antigenic protein bands of M_r about twice that of the normal subunit polypeptide, but the appearance of these apparent dimer forms did not obviously correlate with enzyme degradation. 4. Isoelectric focusing of immunoprecipitated isocitrate lyase showed that the enzyme became progressively more oxidised during the period of its degradation in vivo. 5. By titrating crude broken cell suspensions with anti-isocitrate lyase antibody, preliminary evidence was obtained for transfer of the enzyme from the soluble fraction to an insoluble form as part of the process of disappearance.     

INCREASE OF GLUCOSE AND HIGH ENERGY PHOSPHATE RESERVE IN THE BRAIN AFTER HYDROCORTISONE1

Abstract— Young mice treated with hydrocortisone (50 mg/kg) subcutaneously for 10 days showed a doubling of brain glucose. Brain phospho-creatine, glucose-6-phosphate, and ATP increased slightly. Brain glycogen and lactate were unchanged. Total energy reserve of the brain was 23 per cent higher than the control value. Liver glycogen was increased 47 per cent; liver and blood glucose levels were 11 per cent lower than in control animals. Since the animals showed no evidence of sedation, these findings suggest a facilitated transport of glucose from blood into the brain under the influence of hydrocortisone. Other possible explanations include an inhibition of the hexose monophosphate shunt and a proportionate decrease in both the oxidative and glycolytic pathways of the brain, but it was concluded that these explanations are less likely.