Potentiation of harringtonine cytotoxicity by calcium antagonist diltiazem and biscoclaurine alkaloid cepharanthine in adriamycin-resistant P388 murine leukemia and K562 human leukemia cells

Harringtonine showed cross resistance in adriamycin-resistant murine leukemia P388 (P388/ADM) and human leukemia K562 (K562/ADM) cells. The relative resistance of the P388/ADM and K562/ADM cells to harringtonine was about 7 and 40, respectively. Calcium influx blockers, diltiazem and the biscoclaurine alkaloid cepharanthine enhanced the cytotoxicity of harringtonine in P388/ADM and K562/ADM cells. The extent of enhancement was different for the two drugs, and up to a 9- to 10-fold increase in harringtonine cytotoxicity occurred in P388/ADM cells, and 14- to 22-fold enhancement in K562/ADM cells with diltiazem or cepharanthine. Harringtonine resistance of P388/ADM was circumvented completely, and the resistance of K562/ADM was circumvented partially, by diltiazem or cepharanthine. The mechanism of enhanced cytotoxicity by diltiazem and cepharanthine is probably inhibition of active efflux of harringtonine in P388/ADM and K562/ADM cells.     

Metabolism of d-xylose in Schizosaccharomyces pombe cloned with a xylose isomerase gene

Summary The Escherichia coli xylose isomerase gene was transformed into Schizosaccharomyces pombe for direct d-xylose utilization. In order to understand d-xylose metabolism and determine the limiting factors on d-xylose utilization by the transformed yeast, d-xylose transport, xylose isomerization, and xylulose phosphorylation were investigated. The results indicated that low activity of xylose isomerization in the cloned yeast was the limiting step for d-xylose fermentation. An in vitro study showed that yeast proteases decreased xylose isomerase activity. Xylitol, a by-product of d-xylose fermentation, had no effect on the activity of xylose isomerase.     

Discrimination of benign versus malignant mixed tumors of the salivary gland using digital image analysis

Seven benign and four malignant mixed tumors of the salivary gland, biopsied using fine-needle aspiration, were analyzed using digital image analysis. Mean nuclear form factor, perimeter, and area were significantly increased in malignant cases. Better separation between diagnostic categories, however, was achieved by utilizing the coefficient of variation (CV) within a case rather than mean value. Form factor CV alone divided cases into nonoverlapping diagnostic categories. This quantitative analog of "pleomorphism" provided a useful marker for malignancy in mixed tumors.     

延胡索分类的化学证据

东阳产延胡索与大连产齿瓣延胡索经成分分离和TLC、HPLC对比,发现延胡索以啊扑啡类生物碱如glaucine为主,而齿瓣延胡索则含corynoline类生物碱。根据生物碱的类型及含量比较,二者有明显差异,结合延胡索的植物形态和植化分类特征判断,将延胡索作为与齿瓣延胡索近缘的独立种处理较为合理,即为Corydalis yanhusuo W. T. Wang ex Z.Y. Su et C. Y. Wu     

Modelling basic features of specificity in the binding of a dicationic steroid diamine to double-stranded oligonucleotides.

An investigation of the intrinsically preferred binding modes of a steroid diamine, dipyrandium, to the double-stranded hexanucleotides d(TATATA)2, d(ATATAT)2, and d(CGCGCG)2 is carried out by the energy minimization procedure JUMNA. Several alternative binding modes are compared: groove binding in which the conformation of the oligonucleotide remains close to that of B-DNA, intercalation between base-pairs and interaction with variously kinked structures in which base pairs of dinucleoside steps open towards the groove in which the binding occurs. The favored binding configuration occurs at the d(TpA) step of the AT kinked nucleotides in which the kink opens the base pairs towards the minor groove. Thus, for the d(T1A2T3A4T5A6)2 sequences the preferred complexation involves the kink at the T3A4 step facing the cyclohexane rings A, B, and C of the ligand. For the d(A1T2A3T4A5T6)2 sequence, the kink occurs at the T2A3 step facing the cationic pyrrolidine ring linked to ring A. The binding of dipyrandium to d(CGCGCG)2 is found to be considerably less favourable than for either of the two (AT) sequences.     

Phosphorylation of avian retrovirus matrix protein by Ca2+/phospholipid-dependent protein kinase

The matrix protein from avian myeloblastosis virus and the Rous sarcoma virus, Prague C strain, is a phosphoprotein. A comparison of the amino acid sequences shows these phosphoproteins are very similar. The sites of phosphorylation of the matrix protein purified from virions are identified as serine residues 68 and 106. Treatment with purified rabbit skeletal-muscle protein phosphatase 1 or 2A, selectively releases phosphate from serine 68, while alkali treatment releases phosphate from both sites. When analyzed as a substrate for six different protein kinases, only the Ca2+/phospholipid-dependent protein kinase modifies the matrix protein. The serine residues phosphorylated in vivo are identical to those phosphorylated in vitro by this protein kinase. The role of these phosphorylation events in viral production is discussed.     

Effects of vasoactive intestinal contractor (VIC) and endothelin on intracellular calcium level in neuroblastoma NG108-15 cells

Effects on [Ca2+]i levels of endothelin-l (ET) and vasoactive intestinal contractor peptide (VIC), which is a novel member of the endothelin family, were examined in fura 2-loaded neuroblastoma NG108-15 cells. VIC was found to be a very effective stimulus for intracellular Ca2+ mobilization and to be more potent than ET. Intracellular calcium response to sequential addition of two stimulants exhibited the homologous desensitization of either ET or VIC, but no heterologous desensitization between ET and VIC. This indicates evidence suggesting that these two peptides act through distinct receptors.     

nit-2, the major nitrogen regulatory gene of Neurospora crassa, encodes a protein with a putative zinc finger DNA-binding domain.

The nitrogen regulatory circuit of Neurospora crassa consists of a set of unlinked structural genes which specify various nitrogen catabolic enzymes plus control genes and metabolic effectors which regulate their expression. The positive-acting nit-2 regulatory gene is required to turn on the expression of the nitrogen catabolic enzymes during conditions of nitrogen limitation. The complete nucleotide sequence of the nit-2 gene was determined. The nit-2 mRNA is 4.3 kilobases long and has a long nontranslated sequence at both its 5' and 3' ends. The nit-2 gene nucleotide sequence can be translated to yield a protein containing 1,036 amino acid residues with a molecular weight of approximately 110,000. Deletion analyses demonstrated that approximately 21% of the NIT2 protein at its carboxy terminus can be removed without loss of function. The nit-2 protein contains a single putative Cys2/Cys2 zinc finger domain which appears to function in DNA binding and which has striking homology to a mammalian trans-acting factor, GF-1.