The influence of ecdysterone on gene amplification,DNA synthesis,and puff formation in the salivary gland chromosomes of Rhynchosciara hollaenderi

Many of the DNA and RNA puffing changes observed in Rhynchosciara during the prepupal period have been induced in younger larvae by injection of ecdysterone. However, the dose of hormone necessary for this induction is high, especially in the large cells of the proximal region of the gland. There are differences in the amplification and puffing response from that observed during normal development. Particular similarities and differences with possible explanations for the differences are discussed. Preceding and during the amplification which occurs at certain chromosomal regions, ecdysterone induces DNA synthesis along the entire chromosome. This induction of general DNA synthesis can occur independently of the amplification process. It appears to be similar in pattern to that occurring normally toward the end of larval life. — The normal prepupal behavior of Rhynchosciara was not induced by injection of ecdysterone into larvae of any age thus far examined.     

SEC determination of cross-link efficiency in hyaluronan fillers

The cross-link efficiency in hyaluronan fillers was determined by means of triple detector (RI, LALS-RALS and a Differential Viscometer) GPC/SEC in aqueous buffer. The low water solubility of HA cross-linked with BDDE (HBC) was overcome with an alkaline hydrolysis step. The kinetics of linear HA hydrolysis was investigated at different NaOH concentrations (0.25–0.5–1 M), initial polymer Mws (200–700–1000–1200–1600 kDa) and polymer concentrations (0.1–0.3–0.5 mg/ml). As expected for first-order kinetics, the apparent hydrolysis constant (k_h) was independent of polymer concentration and initial Mws. The k_h was found to be linearly dependent on the NaOH concentration, suggesting a random polymer degradation. A similar behavior was observed for HBC polymers, synthesized with 5–7.5–10–14–18% mol/mol of BDDE for HA repeat unit. The degree of crosslinking was obtained using the Zimm–Stockmayer equation for random, tri-functional polydisperse polymers. The contraction factor (g) was determined after an accurate experimental measurement of the structure factor (?). Comparative studies were performed by ¹H NMR spectroscopy and rheological measurements. Interestingly, the number of effective cross-links found is very low compared to the total BDDE linked; i.e. in a HBC sample only 0.04% of total BDDE linked (equal to 4.6% by ¹H NMR analysis) gives an effective cross-link.     

Regional distribution of Sindbis virus glycoproteins on the plasma membrane of infected baby hamster kidney cells

Sindbis virus-infected baby hamster kidney (BHK) cells were analysed in surface replicas or conventional thin sections after specific immunolabelling with antiviral glycoprotein antibodies in conjunction with colloidal gold-conjugated protein A. Newly synthesized viral glycoproteins were detected, beginning 1 1/2 h after infection, while the virus maturation started 3 h after infection. The glycoproteins appeared to be inserted on the plasma membrane in large spots located mainly in the central area of the cells: no clustering of the labelling was detected. Later, the glycoproteins appeared to arrange linearly in regions in the medial portion of the cells. No labelling was found in the peripheral area or on the cell edges. A drastic change in the surface labelling was detected following the commencement of virus maturation: gold particles were organized mostly in small clusters, each labelling a budding virus. Very few glycoproteins appeared not to be involved in budding figures. The maturation of the virus was clearly regionalized, but during this time it also involved the peripheral area and the cell edges; preferential budding in narrow cellular processes was often observed. It appeared thus that either isolated glycoproteins soon after infection, or clustered glycoproteins at later times, are strictly regionalized on the plasma membrane: however, the early post-infection distribution is clearly different from that seen later during virus maturation. Our experiments support the concept of discrete plasma membrane domains even in cells that do not display distinct specialization of their surface.     

The elimination of herpes simplex plaques by antibody and the emergence of resistant strains.

Established type 1 HSV plaques were eliminated by antibody. Antibody had to remain in contact with infected cells for several days to have a maxi;mum effect. It did not prevent the production of viral induced antigens in a cell when applied after the cell was infected but did prevent the transmission of infection to contiguous cells. Strains which were resistant to elimination by antibody formed syncytia, did not grow to significantly higher titers than nonresistant strains, and were as easily neutralized by antiserum as nonresistant strains.     

Inhibition of TOR signalling in lea1 mutant induces apoptosis in Saccharomyces cerevisiae

The target of rapamycin, TOR, maintains cell growth and proliferation under vivid environmental conditions by orchestrating wide array of growth-related process. In addition to environmental conditions, e.g., nutrient and stress, TOR also governs cellular response to varied intracellular cues including perturbed intracellular mRNA levels which may arise due to altered regulation of mRNA processing at splicing or turnover levels. The purpose of this study is to explore the role of TOR signalling in growth of cells with accumulated unprocessed RNA. Growth analysis of lea1∆ (splicing deficient) was carried out under varied conditions leading to nitrogen starvation. The expression of TORC1 and TORC2 marker genes was examined in this delete strain. Sensitivity of the lea1∆ towards oxidative agents was observed. Apoptosis was analyzed in caffeine-treated lea1∆ cells. The hypersensitivity of lea1∆ cells towards caffeine is outcome of highly perturbed TOR signalling. The growth defect is independent of PKC pathway. Cells with accumulated unprocessed RNA experience high oxidative stress that induces apoptosis. An inadequate TOR signalling in lea1∆ cells substantiates the effect of oxidative stress induced by accumulated RNA to the extent of inducing cell death via apoptosis.