Negative modulation of Epstein-Barr virus episomes by a human B-cell growth factor.

To study the effect of T-cell-derived BCGF-12kD on human B-cell autocrine growth-associated functions, we cultured Epstein Barr virus (EBV)-transformed normal B cells (LCL 72285) and Burkitt's lymphoma cells (Raji) in the presence or absence of BCGF-12kD. When cultured in media supplemented only with fetal calf serum, the LCL and Raji cell lines maintained relatively high levels of episomes. Although a similar level of proliferation could be maintained under defined culture conditions in media supplemented with BCGF-12kD, these conditions resulted in a time-dependent reduction of EBV sequences, as detected with EBV nuclear antigen (EBNA-1 and EBNA-2) gene probes. These results suggest that stimulation with T-cell-derived BCGF-12kD can alter a regulatory step which may be involved in the EBV transformation of B cells.     

An interactive technique for the display of nucleic acid secondary structure.

The ability to visualize nucleic acid secondary structure has become quite important since the advent of computer prediction and biochemical techniques that depict such structures. Manually drawing the conformations can be quite time consuming and tedious. Thus, the ability to draw with the aid of a computer the secondary structure of nucleic acid molecules is quite advantageous. This paper describes an interactive algorithm that permits one to generate such drawings which may then be used for further analysis and/or publications.     

T-lymphocyte/monocyte interaction in response to phytohemagglutinin.

Macrophage cooperation has been shown to be necessary for the thymus-derived lymphocyte to express many of its differentiated functions. The importance of macrophage-lymphocyte interaction has been extended to the study of nonimmunogenic mitogenesis. Utilizing human macrophages and T-cells prepared separately to greater than 98% purity, we have demonstrated a marked degree of dependence of the T-cell upon the macrophage for mitogenesis in response to phytohemagglutinin. The degree of dependence observed is greater than that seen with other human systems and on the order of that seen in the highly purified nonhuman systems. The nature of the physical interaction between the macrophage and the T-cell was visualized using conventional light microscopy and scanning electron microscopy. Lymphocytes were observed to form a semirosetting pattern around the macrophage very early following mitogenic stimulation. The lymphocytes were observed to proceed through early blastogenesis while in direct contact with the macrophage.     

Inhibition of Cleavage of Large Poliovirus-Specific Precursor Proteins in Infected HeLa Cells by Inhibitors of Proteolytic Enzymes

Inhibitors of chymotrypsin interfere with the post-translational cleavage of large poliovirus-specific polypeptides in the molecular weight range of 100,000 to 250,000 in infected HeLa cells.     

Effects of citronella oil (Cymbopogon winterianus Jowitt ex Bor) on Spodoptera frugiperda (J. E. Smith) midgut and fat body

The armyworm, Spodoptera frugiperda, is the principal pest of corn in Brazil. Control is achieved primarily by synthetic insecticides, which cause problems for the agro-ecosystem. Alternative methods of control are under investigation and citronella (Cymbopogon winterianus) essential oil appears to be a promising agent. We investigated the effects of citronella oil using histological, histochemical and immunohistochemical methods. The midgut of larvae treated with citronella exhibited altered epithelium including cytoplasmic protrusions, columnar cell extrusion, pyknotic nuclei, and increased periodic acid-Schiff positive granules. Regenerative cells in the epithelium of the midgut increased in number, which facilitated subsequent regeneration of this tissue. After exposure to citronella, trophocytes, the principal cell type of the fat body, possessed enlarged vacuoles and mitotic bodies, and contained reduced amounts of glycogen, lipid, and protein. Citronella oil caused morphological changes of the midgut and reduction of stored resources in the fat body, which may adversely affect insect reproduction and survival.