Search PubMed⌕ Search

Biomedical subjects

H Cai

Publications and source records attributed to H Cai.

At least 199 records · Page 11Linked to original sources
PubMed1992

Studies on the immunogenicities of intertypic chimeric polioviruses.

To study the relationship between structure and antigenicity, two hybrid viruses, XF414 and XF3, were constructed. In XF414, N-Agl of PV1 was replaced by N-Agl of PV2; while in XF3, N-Ag1 of PV1 was replaced by N-Ag1 of PV3. In this study, XF414 and XF3 were cultured on a large scale in primary monkey kidney cells. The viruses were concentrated with PEG, purified with chloroform and Sepharose 2B and inactivated with formaldehyde. Their bivalent antigenicity was confirmed by neutralization inhibition test, immunoelectron microscopy, and rabbit immunization. It was also shown that both XF414 and XF3 can elicit bivalent neutralizing antibodies and that the bivalent antigenicities are not destroyed by formaldehyde inactivation. Such a study can provide a basis for the development of multivalent picornavirus vaccines.

Animals↗
PubMed1992

Ras controls coupling of growth factor receptors and protein kinase C in the membrane to Raf-1 and B-Raf protein serine kinases in the cytosol.

A dominant negative mutant of Ras, M17 Ras, was used to study the role of Ras in receptor coupling of Raf-1 and B-Raf protein serine/threonine kinases (PSKs). We found that mutant Ras blocks serum- and 12-O-tetradecanoyl phorbol 13-acetate-induced activation of Raf-1 kinase in NIH3T3 cells and Raf-1 as well as B-Raf PSK stimulation by nerve growth factor (NGF) in PC12 pheochromocytoma cells. Mitogen stimulation of Raf kinase was measured by determination of Raf hyperphosphorylation and activity towards exogenous substrates and both of these events were inhibited in cells expressing M17 Ras. In contrast, tyrosine phosphorylation of a direct substrate of activated tyrosine kinase receptors, phospholipase C-gamma 1 (PLC-gamma 1), was unaffected. These data indicate that tyrosine phosphorylation of PLC-gamma 1 is not sufficient for growth induction in NIH3T3 cells and that Ras mediates signal transfer from activated membrane receptors to Raf kinases in the cytosol. As activated Raf induced differentiation in PC12 cells expressing M17 Ras we conclude that Raf kinase activation may be sufficient to account for this aspect of NGF function.

3T3 Cells↗
PubMed1992

[Pharmacokinetics of sinomenine by HPLC].

Pharmacokinetics of sinomenine in rabbit was studied by reverse-phase HPLC method. After i.v. injection of 20 mg/kg of sinomenine to rabbits, the pharmacokinetic characteristics were found to fit a two-compartment open model.

Animals↗
PubMed1992

Phosphorylation occurs in the amino terminus of the Raf-1 protein.

The ability of the Raf-1 protein to morphologically transform murine fibroblasts can be activated by amino-terminal deletions or substitutions. We have compared the phosphorylation states of full-length and representative transforming and non-transforming amino-terminal deletion mutants of the Raf-1 protein using phosphoamino acid analysis and tryptic phosphopeptide mapping. Several [32P]orthophosphate-labeled tryptic phosphopeptides that were present in the full-length Raf-1 protein were absent from the highly transforming 22W Raf-1 mutant (lacking 305 amino-terminal residues). Peptide-specific antisera localized Raf-1 phosphorylation sites to several amino-terminal cyanogen bromide and tryptic peptides that are deleted from the 22W protein. A major phosphorylated tryptic peptide of the Raf-1 protein was immunoprecipitated by antiserum directed against amino acid residues 257-275, a highly conserved region of the raf family. This tryptic peptide is entirely deleted from the highly transforming 22W protein. Subtractive Edman degradation and electrophoretic analysis of the immunoprecipitated tryptic peptide indicated that phosphorylation of the Raf-1 protein occurs at serine 259. Multiple phosphorylated tryptic peptide forms were immunoprecipitated by antiserum directed against Raf-1 residues 283-309. The majority of this tryptic peptide is also deleted from the highly transforming Raf-1 mutant 22W.

3T3 Cells↗
PubMed1991

[Alkaloids of plumula Nelumbinis].

Six alkaloids were isolated from the green seed embryo of Nelumbo nucifera growing in Ruichang, Jiangxi province. On the basis of physiochemical properties and spectroscopic methods (UV, IR, NMR, MS) they were identified as: lotusine, nuciferine, pronuciferine, liensinine, isoliensinine and neferine.

Alkaloids↗
PubMed1991

[The structure of trijuganone C from Salvia trijuga].

From Salvia trijuga Diels 9 compounds were isolated and eight of them identified as ferruginol, sugiol, triacontanoic acid, tetratriacontanoic acid, octacosanoic acid, hexactecanoic acid, dl-homoserine and parahydroxybenzoic acid. Compound I a red needle crystal C20H20O5, mp 113-114 degrees C is a new diterpenoid related to methyltanshinonate named trijuganone C. Its structure has been proved to be 15, 16-dihydromethyltanshinoate by spectroscopic and chemical means.

Drugs, Chinese Herbal↗
PubMed1990

Effect of a dominant inhibitory Ha-ras mutation on mitogenic signal transduction in NIH 3T3 cells.

We used a dominant inhibitory mutation of c-Ha-ras which changes Ser-17 to Asn-17 in the gene product p21 [p21(Asn-17)Ha-ras] to investigate ras function in mitogenic signal transduction. An NIH 3T3 cell line [NIH(M17)] was isolated that displayed inducible expression of the mutant Ha-ras gene (Ha-ras Asn-17) via the mouse mammary tumor virus long terminal repeat and was growth inhibited by dexamethasone. The effect of dexamethasone induction on response of quiescent NIH(M17) cells to mitogens was then analyzed. Stimulation of DNA synthesis by epidermal growth factor (EGF) and 12-O-tetradecanoylphorbol-13-acetate (TPA) was completely blocked by p21(Asn-17) expression, and stimulation by serum, fibroblast growth factor, and platelet-derived growth factor was partially inhibited. However, the induction of fos, jun, and myc by EGF and TPA was not significantly inhibited in this cell line. An effect of p21(Asn-17) on fos induction was, however, demonstrated in transient expression assays in which quiescent NIH 3T3 cells were cotransfected with a fos-cat receptor plasmid plus a Ha-ras Asn-17 expression vector. In this assay, p21(Asn-17) inhibited chloramphenicol acetyltransferase expression induced by EGF and other growth factors. In contrast to its effect on DNA synthesis, however, Ha-ras Asn-17 expression did not inhibit fos-cat expression induced by TPA. Conversely, downregulation of protein kinase C did not inhibit fos-cat induction by activated ras or other oncogenes. These results suggest that ras proteins are involved in at least two parallel mitogenic signal transduction pathways, one of which is independent of protein kinase C. Although either pathway alone appears to be sufficient to induce fos, both appear to be necessary to induce the full mitogenic response.

Animals↗
PubMed1990

Effect of a dominant inhibitory Ha-ras mutation on neuronal differentiation of PC12 cells.

A dominant inhibitory mutation of Ha-ras which changes Ser-17 to Asn-17 in the gene product p21 [p21 (Asn-17)Ha-ras] has been used to investigate the role of ras in neuronal differentiation of PC12 cells. The growth of PC12 cells, in contrast to NIH 3T3 cells, was not inhibited by p21(Asn-17)Ha-ras expression. However, PC12 cells expressing the mutant Ha-ras protein showed a marked inhibition of morphological differentiation induced by nerve growth factor (NGF) or fibroblast growth factor (FGF). These cells, however, were still able to respond with neurite outgrowth to dibutyryl cyclic AMP and 12-O-tetradecanoylphorbol-13-acetate (TPA). Induction of early-response genes (fos, jun, and zif268) by NGF and FGF but not by TPA was also inhibited by high levels of p21(Asn-17)Ha-ras. However, lower levels of p21(Asn-17) expression were sufficient to block neuronal differentiation without inhibiting induction of these early-response genes. Induction of the secondary-response genes SCG10 and transin by NGF, like morphological differentiation, was inhibited by low levels of p21(Asn-17) whether or not induction of early-response genes was blocked. Therefore, although inhibition of ras function can inhibit early-response gene induction, this is not required to block morphological differentiation or secondary-response gene expression. These results suggest that ras proteins are involved in at least two different pathways of signal transduction from the NGF receptor, which can be distinguished by differential sensitivity to p21(Asn-17)Ha-ras. In addition, ras and protein kinase C can apparently induce early-response gene expression by independent pathways in PC12 cells.

Adrenal Gland Neoplasms↗
PubMed1990

Role of endothelin in the pathogenesis of hypertension in spontaneously hypertensive and 2 kidneys 1 clip rats.

The plasma endothelin (ET) level in spontaneously hypertensive rats (SHR) and 2K1C hypertension animal models and its vasoconstrictive effect on renal and tail arteries were studied. The results demonstrated that there was no difference in plasma ET level between the hypertensive groups SHR, 2K1C, normotensive control groups Wistar Kyot (WKY) and Sprague Dawley (SD), while the vasoconstrictive effect of ET in SHR was more dominant than in WKY. The EC50 of the renal and tail arteries in SHR (0.8912 +/- 0.1662 x 10(-8) M, 0.6103 +/- 0.0878 x 10(-8) M) was apparently lower than that in WKY (1.77 +/- 0.2991 x 10(-8) M, 1.2267 +/- 0.2502 x 10(-8) M, P less than 0.05), but no difference was found in 2K1C and SD rats. The four groups of animals exhibited no difference of such effects as response to norepine-phrine (NA). The findings suggested that the increased arteriole sensitivity to ET be an important factor in the pathogenesis of hypertension in SHR.

Animals↗
PubMed1990

[Role of endothelin in the pathogenesis of experimental hypertension in rats].

The plasma endothelin (ET) level in SHR and 2K1C hypertension animal models and its vasoconstrictive effect in their renal and tail arteries were studied. The results demonstrated that there was no difference of plasma ET level between the hypertensive groups SHR, 2K1C and the normotensive control groups WKY and SD, while the vasoconstrictive effect of ET in SHR was were more predominant than that in WKY. The EC50 of the renal and tail arteries in SHR (0.8912 +/- 0.4398 x 10(-8) M, 0.6103 +/- 0.2633 x 10(-8) M) were apparently lower than those in WKY (1.711 +/- 0.7327 x 10(-8) M, 1.2667 +/- 0.6129 x 10(-8) M, (P less than 0.05); but there was no difference between 2K1C and SD rats. The four groups of animals mentioned above exhibited no differences of such effects in response to norepinephrine (NA). The results suggested that the increased arteriole sensitivity to ET was an important factor in the pathogenesis of hypertension in SHR.

Animals↗
PubMed1989

Effects of endothelin on porcine coronary arterial strips.

Endothelin, a novel endothelium derived 21-residue vasoconstrictor peptide synthesized by Peninsula Laboratories, provoked a concentration-dependent contraction of porcine coronary arterial strips. EC50 value for endothelin was 14 +/- SD 4 nmol/L (n = 6), and significantly lower than the values for 5-hydroxytryptamine (5-HT, 0.28 +/- 0.07 mumol/L, n = 6) and 15-methyl-prostaglandin F2 alpha (15-methyl-PGF2 alpha, 4 +/- 3 mumol/L, n = 7). The maximal increase in tension caused by endothelin was 5.4 +/- 1.1 g, being much greater than that induced by 5-HT (3.7 +/- 0.8 g, P less than 0.05) and 15-methyl-PGF2 alpha (3.7 +/- 0.6 g, P less than 0.01). The changes in tension provoked by endothelin (2-20 nmol/L) were attenuated significantly after pretreated with tetrodotoxin (TTX, 30 mumol/L, P less than 0.05 or 0.01). The results suggest that endothelin is one of the most potent vasoconstrictive agents, and its action is partially related to voltage-sensitive Na+ channel in the cell membrane.

Amino Acid Sequence↗
PubMed1987

Activated c-Ha-ras oncogene with a guanine to thymine transversion at the twelfth codon in a human stomach cancer cell line.

The rat fibroblast cell line Rat 1 was transfected with total DNA of a gastrocarcinoma cell line, BGC-823. The transforming gene was cloned from the genomic library of the secondary transformants using in situ hybridization with a probe of the human Alu repeat sequence. This cloned gene is homologous to the protooncogene c-Ha-ras. The activation lesion of the transforming gene was identified by sequence analysis as a single nucleotide substitution of thymine for guanine in the 12th codon. This results in the substitution of valine for glycine at the 12th amino acid of the Mr 21,000 protein.

Adenocarcinoma↗
PubMed1987

Transcription initiation by RNA polymerase II in vitro. At least two nucleotides must be added to form a stable ternary complex.

We have prepared RNA polymerase II preinitiation complexes by incubating templates containing the adenovirus 2 major late promoter with HeLa cell nuclear extracts in the absence of nucleoside triphosphates. These preinitiation complexes are partially purified by gel filtration and are then provided with the appropriate substrates to allow either one or two phosphodiester bonds to be formed. When substrates that allow only one bond to form are used, no stable ternary complex is obtained and no RNA is made that can be incorporated into longer RNA chains. A stable complex is obtained, however, if the RNA polymerase can make two bonds. The production of a stable ternary complex requires ATP or dATP and is inhibited by alpha-amanitin. In the course of exploring the energy requirement for initiation we found that dATP may be incorporated, in the absence of ATP, as the initial base of the RNA. However, deoxyribonucleotides are not appreciably incorporated into the body of the transcript after the first two bases have been added to the growing chain.

Adenosine Triphosphate↗
PubMed1987

Transcription initiation by RNA polymerase II in vitro. Properties of preinitiation, initiation, and elongation complexes.

We have prepared three types of RNA polymerase II transcription complexes: a preinitiation complex (complex 0), a complex which has synthesized two phosphodiester bonds (complex 2), and a complex which has synthesized 10-13 bonds (complex 10). We have studied the differential response of these complexes to a variety of disruptions: detergent (Sarkosyl), high levels of KCl, extended incubation at 25 degrees C, proteolysis, and digestion with DNase I. Complex 0 is extremely stable at 25 degrees C in the absence of ATP, but it is sensitive to the other treatments including 25 degrees C incubation in the presence of ATP. Once the complex has made two phosphodiester bonds, the properties almost reverse from those of complex 0; complex 2 remains unstable at 25 degrees C in the presence of ATP but is resistant to high levels of Sarkosyl and KCl, to extensive DNase I digestion, and to brief proteolysis. Addition of 10 or more bases to the growing RNA chain results in a complex completely resistant to all of the treatments used. When DNase I-trimmed complex 0 is allowed to initiate RNA synthesis, chains of about 33 bases are obtained. In contrast, DNase-trimmed complex 2 gives only about 23 base transcripts; DNase-treated complex 10 will elongate its nascent chains by about 21 bases as well (to give, on average, 34 base transcripts).

Adenosine Triphosphate↗
PubMed1987

Variations in template protection by the RNA polymerase II transcription complex during the initiation process.

Preinitiation complexes (complex 0) or complexes which either made 2 or an average of 10 phosphodiester bonds (complexes 2 and 10, respectively) were assembled in vitro on the adenovirus 2 major late promoter. Each of the complexes was digested extensively with DNase I; the protected DNAs were purified and hybridized in a series of end-labeled oligonucleotides homologous to sequences on the coding or noncoding strands near the initiation site. The hybrids were then extended with reverse transcriptase to map the extent of template protection conferred by proteins in the complex. The downstream protection edge revealed by this approach was approximately +30, +25, and +35 for complexes 0, 2, and 10, respectively. We subsequently found that the apparent inward movement of the downstream protection boundary on initiation could be produced by satisfying the energy requirement for transcription initiation (i.e., by treating with ATP or dATP). The downstream boundary change occurred as rapidly as we could perform the test (less than 60 s) and was not blocked by alpha-amanitin. DNAs from trimmed complexes 0, 2, or 10 all supported extension to a single upstream edge at about position -42. Upstream protection was stable in the preinitiation complex, but when postinitiation complexes were incubated for extended periods, protection of the entire upstream region was lost. This decay of upstream protection, like the movement of the downstream boundary, was found to result from exposure to ATP or dATP. Unlike the downstream boundary movement, however, the upstream change was relatively slow; about 15 min was required to lose one-half of the protection.

Adenosine Triphosphate↗
PubMed1987

Molecular cloning and nucleotide sequence analysis of a transforming gene from human gastrocarcinoma cell line.

Mouse and rat fibroblasts were transfected with total DNA from human gastrocarcinoma cell line BGC-823. It was shown by hybridization assay that the genome of one of the rat secondary foci contains transforming genes from the human gastrocarcinoma cell line, which are homologous to the protooncogene c-Ha-ras in the normal cells. The genomic library of the rat secondary foci was constructed, using lambda phage EMBL3 as the vector. The transforming gene Ha-ras of the human gastrocarcinoma cell was thus cloned by screening the library with the probes of human Alu repeat sequence and c-Ha-ras. The nucleotide sequences of the first and second exons were analysed by M13-dideoxy method. The result shows that the nucleotide sequence of the transforming gene is the same as that of the normal protooncogene except one nucleotide difference in the first exon.

Amino Acid Sequence↗