The influence of higher temperature on dengue-2 virus infected C6/36 mosquito cell line

Dengue-2 virus infection of C6/36 cells was studied at 28 and 37 degrees C. In infected cells maintained at 28 degrees C, syncytial development was seen on day 4 postinfection, whereas at 37 degrees C, extensive syncytial development was seen by 32 h. Extracellular virus titre was found to correlate with the cytopathic changes. Nine Dengue-2 virus specified proteins were observed in polyacrylamide analyses of cytoplasmic extracts of C6/36 infected cells. All the proteins were observed, although in varied intensities by 32 h postinoculation at 37 degrees C and only on day 4 postinoculation at 28 degrees C. The GP60 glycoprotein appeared at 32 h postinfection when the cells were maintained at 37 degrees C and became prominent only on day 5 at 28 degrees C. The results revealed that a higher temperature accelerated the onset of cytopathic effects, hastened the development of virus specified proteins, and also enhanced the titre of extracellular infectious virus. The importance of the accumulation of the envelope protein GP60 for the development of CPE was indicated.     

Evidence that epidermal growth factor is present in swiftlet's (Collocalia) nest

1. An epidermal growth factor (EGF)-like activity was detected and partially purified from swiftlet's nest extract. 2. The partially purified EGF-like activity was able to (a) generate competitive binding curves parallel to the standard curves in radioreceptor assay and (b) stimulate thymidine incorporation in quiescent culture of 3T3 fibroblasts and the latter activity can be suppressed by mouse EGF antibody. 3. Partial characterization of the EGF-like activity in terms of pI, molecular weight and its behavior on gel filtration column suggest that it bears similar physical properties to the EGFs isolated from the mouse and the shrew.     

An electrophoretic karyotype for Schizosaccharomyces pombe by pulsed field gel electrophoresis.

The three chromosomal DNAs of S. pombe have been fractionated by pulsed field gel electrophoresis. The resulting molecular karyotype will greatly speed gene mapping in this organism, and it indicates that the separation range of the technique extends to DNA molecules as large as 9,000,000 base pairs.     

Aluminium bone disease in patients receiving plasma exchange with contaminated albumin.

Aluminium balance studies were carried out on eight patients with various immunological disorders who were receiving plasma exchange with albumin solutions known to be contaminated with aluminium. Four patients with impaired renal function (creatinine clearance less than 50 ml/min) retained between 60% and 74% of the aluminium infused during a single plasma exchange. Transiliac bone biopsy specimens from three patients in this group had a high content of aluminium and showed histological evidence of current or previous bone disease related to aluminium. Two of these patients suffered intermittent bone pain. The main route of excretion of injected aluminium was in urine, only a small proportion of the total input being removed in the "plasma bag" during plasma exchange. The extent of aluminium retention and bone deposition was not reflected by the plasma aluminium concentration before or after plasma exchange. Treatment of five patients with intravenous desferrioxamine increased the plasma aluminium concentration and urinary output of aluminium in those with evidence of aluminium retention. These studies show that patients with poor renal function receiving treatment with albumin contaminated with aluminium retain the metal and deposit it in bone, where it may eventually cause aluminium bone disease. Plasma exchange should be used with caution in patients with renal impairment.     

记辽宁东部新鳞齿鱼属一新种

本文记述了产自辽宁东部红庙子盆地下桦皮甸子组的新鳞齿鱼属—新种——Neolepidotes liaodongensis sp. nov..根据新材料,将 Neolepidotes 与 Lepidotes 等属作了补充比较,增订了新鳞齿鱼属的特征.     

Characterization of two proteolytically derived soluble polypeptides from the neurofilament triplet components NFM and NFH.

We have purified to homogeneity the regions derived by chymotryptic digestion of the ox neurofilament polypeptides NFH and NFM; the regions, called M1 and M2, are thought to form part of the projecting sidearms of mammalian neurofilaments [Chin, Eagles & Maggs (1983) Biochem. J. 215, 239-252]. They were isolated and purified under non-denaturing conditions and showed no tendency to interact with each other in solution. The Mr values obtained by sedimentation are approx. 61,000 for M1 and 42,000 for M2, considerably lower than the values obtained by SDS/polyacrylamide-gel electrophoresis. These Mr values were unchanged in the presence of 6 M-guanidine hydrochloride, suggesting that the regions exist as monomers in solution. Both M1 and M2 are highly phosphorylated, and there is only a slight change in the sedimentation value upon dephosphorylation. Dephosphorylation of M1 with alkaline phosphatase was more than 90% efficient but was never absolute. Dephosphorylation of M2 was complete. Both M1 and M2 bind Ca2+; in the case of M1, this binding is phosphorylation-dependent. M1 also binds cytochrome c, and dephosphorylation affects binding. In similar conditions, neurofilaments bind at least twice their own mass of cytochrome c, owing to their opposite net charges. No interactions were observed between native or dephosphorylated M1 and M2, and intact neurofilaments under a wide variety of conditions. These results are discussed in terms of the possible roles that neurofilament sidearms might play and throw doubt upon their supposed function of rigidly cross-linking neurofilaments together within the axoplasm of neurons.     

Expression of a human multidrug resistance cDNA (MDR1) in the bone marrow of transgenic mice: resistance to daunomycin-induced leukopenia.

The human multidrug resistance gene (MDR1) encodes a drug efflux pump glycoprotein (P-glycoprotein) responsible for resistance to multiple cytotoxic drugs. A plasmid carrying a human MDR1 cDNA under the control of a chicken beta-actin promoter was used to generate transgenic mice in which the transgene was mainly expressed in bone marrow and spleen. Immunofluorescence localization studies showed that P-glycoprotein was present on bone marrow cells. Furthermore, leukocyte counts of the transgenic mice treated with daunomycin did not fall, indicating that their bone marrow was resistant to the cytotoxic effect of the drug. Since bone marrow suppression is a major limitation to chemotherapy, these transgenic mice should serve as a model to determine whether higher doses of drugs can cure previously unresponsive cancers.     

Influence of muskmelon cell wall polysaccharides on roridin E production by a pathogenic strain of Myrothecium roridum

Addition of fruit cell wall extracts from two muskmelon cultivars into liquid media affected mycotoxin production by a strain of Myrothecium roridum pathogenic to muskmelon. Cell wall extracts from a susceptible cultivar (Iroquois) significantly increased toxin production while cell wall extracts from a resistant cultivar (Hales Best) significantly inhibited toxin production. Media containing 0.1 or 1.0 mg ml^–1 stimulated toxin production more than media containing 10 or 100 mg ml^–1 of cell wall extracts. Previous studies in our laboratory suggest that roridin E may be involved in virulence or pathogenicity of M. roridum; the present study indicates that cell wall polysaccharides as well as other materials present in cell wall preparations from susceptible host tissue provide a better substrate for toxin production than cell wall preparation from resistant host tissue.     

A C-terminal domain of GAP is sufficient to stimulate ras p21 GTPase activity.

The cDNA for bovine ras p21 GTPase activating protein (GAP) has been cloned and the 1044 amino acid polypeptide encoded by the clone has been shown to bind the GTP complexes of both normal and oncogenic Harvey (Ha) ras p21. To identify the regions of GAP critical for the catalytic stimulation of ras p21 GTPase activity, a series of truncated forms of GAP protein were expressed in Escherichia coli. The C-terminal 343 amino acids of GAP (residues 702-1044) were observed to bind Ha ras p21-GTP and stimulate Ha ras p21 GTPase activity with the same efficiency (kcat/KM congruent to 1 x 10(6) M-1 s-1 at 24 degrees C) as GAP purified from bovine brain or full-length GAP expressed in E. coli. Deletion of the final 61 amino acid residues of GAP (residues 986-1044) rendered the protein insoluble upon expression in E. coli. These results define a distinct catalytic domain at the C terminus of GAP. In addition, GAP contains amino acid similarity with the B and C box domains conserved among phospholipase C-II, the crk oncogene product, and the non-receptor tyrosine kinase oncogene products. This homologous region is located in the N-terminal half of GAP outside of the catalytic domain that stimulates ras p21 GTPase activity and may constitute a distinct structural or functional domain within the GAP protein.