Characterization of presumptive histone messenger RNA from a cell line of Aedes aegypti.

Four presumptive histone messenger RNAs were characterized from a cell line of Aedes aegypti, and their molecular weights were determined by electrophoresis. They were shown to be associated with polysomes during the peak of DNA synthesis, but not when DNA synthesis was inhibited by cytosine arabinoside or when DNA was not being synthesized. These mRNAs are associated with polysomes containing less than 8 ribosomes and having a high ratio of incorporation of lysine to tryptophan into their nascent peptides. The mRNAs released from these polysomes were translated in vitro and histone products were synthesized. Histones were not synthesized when the mRNAs were obtained from large polysomes or from small polysomes during the non-DNA synthetic period.     

The new anti-actin agent dihydrohalichondramide reveals fenestrae-forming centers in hepatic endothelial cells

Background  

Liver sinusoidal endothelial cells (LSECs) react to different anti-actin agents by increasing their number of fenestrae. A new structure related to fenestrae formation could be observed when LSECs were treated with misakinolide. In this study, we investigated the effects of two new actin-binding agents on fenestrae dynamics. High-resolution microscopy, including immunocytochemistry and a combination of fluorescence- and scanning electron microscopy was applied.     

Interference of o,p'DDD with interrenal function and cortisol metabolism in Sarotherodon aureus (Steindachner)

The purpose of this study was to investigate possible effects of organochlorine residues on cortisol balance in a freshwater fish. The combined stress of netting, handling and blood sampling in Sarotherodon aureus normally results in a twofold increase of circulating cortisol, within 30–60 min. Fish treated with o,p'DDD (50 mg kg⁻¹) had higher resting level of cortisol than before treatment (155.8±12.7 v. 86.9± 11.2 ngmh⁻¹; n=16). No further increase in cortisol level occurred in these fish after exposure to stress; this inability to respond was maintained for more than 120 days. A recovery of the response to ACTH by superfused interrenal tissue from the treated fish was observed 255 days after treatment. Successive blood sampling of o,p'DDD-treated fish, injected intracardially with labelled cortisol, have shown that the half-life of the steroid in the circulation is prolonged by 370% compared with controls. The hepatic metabolism of cortisol was studied by incubating liver slices with the labelled hormone. Hepatic tissue from o,p'DDD-treated fish metabolized cortisol slower than livers from controls. The high resting level of cortisol in plasma of fish treated with o,p'DDD may be attributed to the retarded metabolism of the steroid by the liver. The lack of augmented cortisol levels in response to stress is attributed to the interference of the organochlorine with the response of the interrenal tissue to the stress-induced surge of endogenous ACTH.     

Desulphation of heparin by mice and guinea pig leukocytes

Leukocytes from mice and guinea pigs were tested for their sulphate-splitting activity on heparin. Mouse macrophages showed the highest degrading activity while mouse neutrophils and lymphocytes were less active. In comparison, guinea pig spleen cells and leukocytes showed only a weak degrading activity. Mouse macrophages maintained in tissue culture were also found to degrade heparin, the amount of sulphate released increasing with time up to 96 h. Spleen extracts were found to neutralize the anticoagulatory activity of heparin.