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C Lin

Publications and source records attributed to C Lin.

At least 271 records · Page 15Linked to original sources
PubMed1994

[Studies of long-term cryopreservation of hepatocytes and their transplantation treating acute hepatic failure in Wistar rats].

The experiment aimed at studying long-term cryopreservation of hepatocytes and therapeutic effect of their transplantation for acute hepatic failure. Hepatocytes of wistar rats were cryopreserved in liquid nitrogen for 30, 60, 90, and 180 days. Their viabilities were respectively 71.2%, 75.7%, 69.7%, and 73.5% of fresh cells', however, there were no significant differences among all cryopreserved groups. Differences of viably intra-hepatocellular enzyme contents among all groups, such as glutamic oxaloacetic transaminase and so on, were not significant. Morphologically intact hepatocytes were observed under light microscopy and transmission electron microscopy. Survival rate of Sprague-Dawley rats with acute hepatic failure were increased from 1/8 to 5/7 because of the transplantation of syngeneic frozen hepatocytes (P = 0.035). The results showed that after 30 days of cryopreservation in liquid nitrogen, the viability of hepatocytes decreased significantly, but no longer decreased in subsequent freeze up to 180 days. The viable intact cells and their normal enzyme contents were kept. The acute hepatic failure could be treated by them.

Animals↗
PubMed1994

12(S)-hydroxyeicosatetraenoic acid regulates DNA synthesis and protooncogene expression induced by epidermal growth factor and insulin in rat lens epithelium.

Neonatal rat lens epithelium has a high 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] synthetic capacity, which decreases as epithelial cell proliferation decreases with age. To determine whether products of the 12-lipoxygenase pathway are involved in lens cell proliferation, we measured the effect of 12-lipoxygenase inhibitors on endogenous 12-HETE production, epidermal growth factor/insulin-stimulated DNA synthesis and protooncogene expression in cultured neonatal rat lens epithelial cells. Incubation of neonatal rat lenses in epidermal growth factor plus insulin, which stimulated endogenous 12-HETE production 8- to 10-fold, also produced a transient induction of c-fos and c-myc mRNAs after 2 to 3 h, followed by a round of DNA synthesis approximately 20 h later. The lipoxygenase inhibitor, cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate, strongly inhibited both the endogenous 12-HETE synthesis and growth factor-stimulated DNA synthesis with a half-maximal inhibition between 10 and 20 microM. Cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate (10 microM) also inhibited the expression of c-fos and c-myc mRNA and, to a lesser extent, c-jun mRNA. The inhibitory effects of cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate on protooncogene expression and DNA synthesis were prevented by 0.3 microM 12(S)-HETE but not by equivalent concentrations of either 5(S)-HETE or 15(S)-HETE. These findings suggest that endogenously synthesized 12(S)-HETE may mediate epidermal growth factor/insulin-stimulated DNA synthesis in neonatal rat lens epithelial cells by regulating protooncogene expression.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1993

Mutagenesis of conserved residues at the yellow fever virus 3/4A and 4B/5 dibasic cleavage sites: effects on cleavage efficiency and polyprotein processing.

Flavivirus proteins are produced by co- and post-translational proteolytic processing of a large polyprotein using both host- and virus-encoded enzymes. The flavivirus serine proteinase, which consists of NS2B and NS3, is responsible for cleavages of at least four dibasic sites in the nonstructural region. In this study, a number of substitutions for the conserved amino acids flanking the 3/4A and 4B/5 dibasic cleavage sites [Arg(P2)-Arg(P1) decreases Gly(P1')] were examined for their effects on yellow fever virus (YF) polyprotein processing. The substrate for these studies was a truncated YF polyprotein, called sig2A-5(356), which consists of a signal sequence fused to NS2A and extending through the first 356 amino acids of NS5. At the P1' position (Gly) of the 4B/5 site, only Ser and Ala were allowed while six other substitutions abolished cleavage. Substitutions of the 4B/5 P1 Arg residue with Lys, Gln, Asn, or His were tolerated while replacement with Glu eliminated cleavage. The 4B/5 P2 position (Arg) was found to be tolerant of substitutions with polar or hydrophobic residues which allowed varying degrees of partial cleavage. Previous studies have shown that cleavage at the 3/4A site is incomplete in YF-infected cells and that the cleavage efficiency at this site is significantly less for the sig2A-5(356) polyprotein. Replacement of the 3/4A P1 Arg residue with noncharged polar or hydrophobic residues reduced the cleavage efficiency, whereas substitutions with Glu or Pro abolished cleavage. Studies with polyproteins containing one or both of the 3/4A and 4B/5 cleavage sites blocked indicate that there is not an obligatory processing order for cleavages generating the N termini of YF NS4A, NS4B, and NS5.

Amino Acid Sequence↗
PubMed1993

A cosmid contig and high resolution restriction map of the 2 megabase region containing the Huntington's disease gene.

The quest for the mutation responsible for Huntington's disease (HD) has required an exceptionally detailed analysis of a large part of 4p16.3 by molecular genetic techniques, making this stretch of 2.2 megabases one of the best characterized regions of the human genome. Here we describe the construction of a cosmid and P1 clone contig spanning the region containing the HD gene, and the establishment of a detailed, high resolution restriction map. This ordered clone library has allowed the identification of several genes from the region, and has played a vital role in the recent identification of the Huntington's disease gene. The restriction map provides the framework for the detailed analysis of a region extremely rich in coding sequences. This study also exemplifies many of the strategies to be used in the analysis of larger regions of the human genome.

Base Sequence↗
PubMed1993

A gene from chromosome 4p16.3 with similarity to a superfamily of transporter proteins.

We have previously used exon amplification to identify the ADD1 gene in cosmid Y24 from the Huntington's disease (HD) region of 4p16.3. The same technique has now yielded a second gene from this cosmid. This gene appears to encode a novel member of a superfamily of transporter proteins that includes active and passive transporters in a number of species. The predicted protein of 455 amino acids displays sequence similarity with the E. coli tetracycline resistance efflux protein encoded by cloning vector pBR322, and with a number of related transporters. This gene should open a route to isolating additional mammalian members of this growing superfamily.

Amino Acid Sequence↗
PubMed1993

Eccrine adenocarcinoma of the eyelid in a young patient.

Malignant eccrine adenocarcinoma of the lower eyelids is described in a 16-year-old girl. This rare tumor has previously been reported only in males, whose average age was 64 years. Our patient remains tumor free 7 years after wide resection of the eyelid and reconstruction.

Adenocarcinoma↗
PubMed1993

Expression and identification of hepatitis C virus polyprotein cleavage products.

Hepatitis C virus (HCV) is the major cause of transfusion-acquired non-A, non-B hepatitis. HCV is an enveloped positive-sense RNA virus which has been classified as a new genus in the flavivirus family. Like the other two genera in this family, the flaviviruses and the pestiviruses, HCV polypeptides appear to be produced by translation of a long open reading frame and subsequent proteolytic processing of this polyprotein. In this study, a cDNA clone encompassing the long open reading frame of the HCV H strain (3,011 amino acid residues) has been assembled and sequenced. This clone and various truncated derivatives were used in vaccinia virus transient-expression assays to map HCV-encoded polypeptides and to study HCV polyprotein processing. HCV polyproteins and cleavage products were identified by using convalescent human sera and a panel of region-specific polyclonal rabbit antisera. Similar results were obtained for several mammalian cell lines examined, including the human HepG2 hepatoma line. The data indicate that at least nine polypeptides are produced by cleavage of the HCV H strain polyprotein. Putative structural proteins, located in the N-terminal one-fourth of the polyprotein, include the capsid protein C (21 kDa) followed by two possible virion envelope proteins, E1 (31 kDa) and E2 (70 kDa), which are heavily modified by N-linked glycosylation. The remainder of the polyprotein probably encodes nonstructural proteins including NS2 (23 kDa), NS3 (70 kDa), NS4A (8 kDa), NS4B (27 kDa), NS5A (58 kDa), and NS5B (68 kDa). An 82- to 88-kDa glycoprotein which reacted with both E2 and NS2-specific HCV antisera was also identified (called E2-NS2). Preliminary results suggest that a fraction of E1 is associated with E2 and E2-NS2 via disulfide linkages.

Antigens, Viral↗
PubMed1993

Cleavage at a novel site in the NS4A region by the yellow fever virus NS2B-3 proteinase is a prerequisite for processing at the downstream 4A/4B signalase site.

Flavivirus proteins are produced by co- and posttranslational proteolytic processing of a large polyprotein by both host- and virus-encoded proteinases. The viral serine proteinase, which consists of NS2B and NS3, is responsible for cleavage of at least four dibasic sites (2A/2B, 2B/3, 3/4A, and 4B/5) in the nonstructural region. Since the amino acid sequence preceding NS4B shares characteristics with signal peptides used for translocation of nascent polypeptides into the lumen of the endoplasmic reticulum, it has been proposed that cleavage at the 4A/4B site is mediated by a cellular signal peptidase. In this report, cell-free translation and in vivo transient expression assays were used to study processing in the NS4 region of the yellow fever virus polyprotein. With a construct which contained NS4B preceded by 17 residues constituting the putative signal peptide (sig4B), membrane-dependent cleavage at the 4A/4B site was demonstrated in vitro. Surprisingly, processing of NS4A-4B was not observed in cell-free translation studies, and in vivo expression of several yellow fever virus polyproteins revealed that the 4A/4B cleavage occurred only during coexpression of NS2B and the proteinase domain of NS3. Examination of mutant derivatives of the NS3 proteinase domain demonstrated that cleavage at the 4A/4B site correlated with expression of an active NS2B-3 proteinase. From these results, we propose a model in which the signalase cleavage generating the N terminus of NS4B requires a prior NS2B-3 proteinase-mediated cleavage at a novel site (called the 4A/2K site) which is conserved among flaviviruses and located 23 residues upstream of the signalase site. In support of this model, mutations at the 4A/4B signalase site did not eliminate processing in the NS4 region. In contrast, substitutions at the 4A/2K site, which were engineered to block NS2B-3 proteinase-mediated cleavage, eliminated signalase cleavage at the 4A/4B site. In addition, the size of the 3(502)-4A product generated by trans processing of a truncated polyprotein, 3(502)-5(356), was consistent with cleavage at the 4A/2K site rather than at the downstream 4A/4B signalase site.

Amino Acid Sequence↗
PubMed1993

Fetal lung epithelial cells contain two populations of amiloride-sensitive Na+ channels.

Active Na+ transport by the alveolar epithelium plays a major role in reabsorption of the fetal lung fluid after birth. We characterized the biochemical and physiological characteristics of Na+ conductive pathways in distal fetal lung epithelial (FLE) cells isolated from 20-day-old rat fetuses. We demonstrated that a polyclonal antibody to Na+ channel protein (NaAb) binds to the plasma membranes of FLE cells. In Western blot studies, this NaAb and an anti-idiotypic monoclonal antibody to the amiloride-binding subunit of the Na+ channel protein recognized 150- and 90-kDa polypeptides in plasma membrane vesicles of FLE. 22Na+ flux measurements across plasma membrane vesicles of FLE revealed the existence of electrogenic Na+ transport, which was twice as high as the corresponding adult value. One hundred micromolars of amiloride, benzamil, and 5-(N-ethyl-N-isopropyl)-2'-4'-amiloride inhibited 30, 40, and 70% of the electrogenic Na+ transport across plasma membrane vesicles of FLE cells, respectively. The half-maximum inhibition of electrogenic Na+ transport by these substances occurred between 0.3 and 1 microM. [3H]benzamil equilibrium binding studies in membrane vesicles of FLE cells revealed the existence of two binding sites that had dissociation constant values of 19 and 1,525 nM, respectively. These data indicate the presence of both high- and low-amiloride affinity Na+ conductive pathways (channels) in FLE cells.

Amiloride↗
PubMed1993

[Relation between pigment gallstone formation and the ability of bile to scavenge superoxide radicals].

Operative stenosis of common bile duct (CBD) (S group) induced pigment gallstones in 14 of 16 guinea pigs one week after operation. If Vit E and Vit C were given intraperitoneally 10 mg/kg daily from 3 days before to one week after the operation (S+V group), the gallstone incidence decreased to 5/14 (P < 0.01). In comparison with control group (C), unconjugated bilirubin (UCB) and Ca2+ concentration in gallbladder bile of S group increased significantly (P < 0.05 and P < 0.01 respectively), while the scavenge rate (SR) of superoxide radical (O2-.) in bile decreased significantly (P < 0.05). Comparing S+V group with S group showed that the differences of UCB and Ca2+ concentration were not significant (P < 0.05 both); only the SR rose significantly (P < 0.05) and reached the level of C group. It is suggested that besides the increase of UCB and Ca2+ concentration, the participation of oxygen radicals may be needed in formation of pigment gallstones induced by bile duct obstruction.

Animals↗
PubMed1992

A cold-regulated Arabidopsis gene encodes a polypeptide having potent cryoprotective activity.

We previously showed that cor15, a cold-regulated gene from Arabidopsis thaliana, encodes a 15 kDa polypeptide designated COR15. Here we report that COR15 has potent cryoprotective activity in an in vitro cryoprotection assay. Specifically, COR15 was very effective in protecting the cold-labile enzyme lactate dehydrogenase against freeze-inactivation; on a concentration basis, it was about 10(6) times more effective than sucrose and 10(2)-10(3) times more effective than other proteins including bovine serum albumin. The possible role of cor15 in cold acclimation is discussed.

Cloning, Molecular↗
PubMed1992

Effect of human mammary MX-1 tumor on plasma free fatty acids in fasted and fasted-refed nude mice.

We hypothesized that tumor-bearing (TB) nude mice, because they are reported to have no detectable, circulating tumor necrosis factor (TNF)/cachectin, would regulate their plasma free fatty acid (FFA) levels normally when fasted and refed. We compared levels of individual plasma FFA in response to fasting (24 hr) and to refeeding (for 20 hr after fasting) a fat-free, 65% sucrose diet in control, nude mice and in mice bearing 1.3 +/- 0.4 g MX-1 tumors. Total plasma FFA levels were typically high in 24-hr fasted mice [mean concentrations in microM +/- SE (n); controls 515 +/- 63 (6); TB, 625 +/- 63 (6)]. FFA levels were reduced by 65% in each group in response to refeeding. Each major plasma FFA species fell in response to refeeding, except arachidonate, which did not change significantly (fasted vs. fasted-refed concentrations) in either controls or TB mice. In refed mice, the molar FFA ratio of oleate to linoleate rose; however, that of oleate to arachidonate fell markedly. TB nude mice had normal appetites. We conclude that all species of FFA were mobilized from adipose tissue in a normal manner in TB nude mice; therefore, regulation of adipose triacylglycerol fatty acid mobilization (as plasma FFA) by dietary sugar is probably not affected by MX-1 tumor growth in these mice. Our findings are consistent with the hypothesis that nude mice may be unable to secrete TNF/cachectin in response to tumor growth, but they do not establish whether or not endogenous, circulating TNF/cachectin increases FFA mobilization in any TB animal.

Adipose Tissue↗
PubMed1992

Temporal and regional production of 12(S)hydroxyeicosatetraenoic acid [12(S)-HETE] in rat lens.

Enzymatic production of 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] from exogenous arachidonic acid (AA) was studied in the 9000 g supernatant fraction of either whole rat lens or the capsule-epithelium and cortex-nucleus regions with age (4-180 days). Whole rat lens 12(S)-HETE synthetic capacity measured either by RIA or HPLC was significantly decreased with lens growth. 12(S)-HETE production was highest in the 4-day-old rat lens, the earliest time point measured, and declined to background levels by 6 months of age. Regional studies demonstrated that the capsule-epithelium possessed a higher specific activity in comparison to the cortex-nucleus. However, lipoxygenase activity decreased significantly faster in the capsule-epithelium compared to the cortex-nucleus. The bulk of the 12-lipoxygenase activity was located in the cortex-nucleus due to the higher amount of tissue in the region. The elevated lipoxygenase activity in the neonate and its rapid decline with growth suggests that the enzyme may contribute in transforming the epithelial cells to fiber cells.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1992

The Huntington's disease candidate region exhibits many different haplotypes.

Analysis of 78 Huntington's disease (HD) chromosomes with multi-allele markers revealed 26 different haplotypes, suggesting a variety of independent HD mutations. The most frequent haplotype, accounting for about one third of disease chromosomes, suggests that the disease gene is between D4S182 and D4S180. However, the paucity of an expected class of chromosomes that can be related to this major haplotype by assuming single crossovers may reflect the operation of other mechanisms in creating haplotype diversity. Some of these mechanisms sustain alternative scenarios that do not require a multiple mutational origin for HD and/or its positioning between D4S182 and D4S180.

Alleles↗
PubMed1992

A novel G protein-coupled receptor kinase gene cloned from 4p16.3.

Within the Huntington's disease (HD) candidate region of 4p16.3, the D4S127 locus displays strong linkage disequilibrium with the defect and anchors a conserved haplotype found on many HD chromosomes. To isolate genes from this region we have applied the exon amplification technique to overlapping cosmids spanning D4S127. Here, we report the discovery of a new gene encoding a novel member of a family of protein kinases that specifically phosphorylate the activated forms of G protein-coupled receptors. Such kinases are thought to participate in desensitization of specific receptors, thereby blocking further signal transduction. This gene must now be carefully scrutinized to determine whether it might be involved in HD.

Amino Acid Sequence↗
PubMed1992

DNA Sequence Analysis of a Complementary DNA for Cold-Regulated Arabidopsis Gene cor15 and Characterization of the COR 15 Polypeptide.

Previous studies have indicated that changes in gene expression occur in Arabidopsis thaliana L. (Heyn) during cold acclimation and that certain of the cor (cold-regulated) genes encode polypeptides that share the unusual property of remaining soluble upon boiling in aqueous solution. Here, we identify a cDNA clone for a cold-regulated gene encoding one of the "boiling-stable" polypeptides, COR15. DNA sequence analysis indicated that the gene, designated cor15, encodes a 14.7-kilodalton hydrophilic polypeptide having an N-terminal amino acid sequence that closely resembles transit peptides that target proteins to the stromal compartment of chloroplasts. Immunological studies indicated that COR15 is processed in vivo and that the mature polypeptide, COR 15m, is present in the soluble fraction of chloroplasts. Possible functions of COR 15m are discussed.

Journal Article↗
PubMed1992

Ultrasonic attenuation estimation in-vivo using the difference ratio correction method.

In recent years, B scanners have been widely used clinically. Obviously, it is of particular importance to use the commercial B scanners to characterize tissue by estimating its ultrasonic attenuation in vivo. However, there are a lot of difficulties in doing so because the output of a B scanner is affected by many unknown factors. In this paper, a time domain method named the difference ratio correction (DRC) method is proposed to estimate the ultrasonic attenuation of tissue in vivo. In this method, three tissue-mimicking phantoms with known acoustical properties were employed to eliminate the instrumentation errors of the B scanner and the measuring system and to correct beam diffraction for correct attenuation estimation. Other advantages of this method are that it is very convenient to apply this method clinically and there is no need to change the inner construction of the B scanner because this method only utilizes the video output. Experimental and clinical results have proved the validity of this method.

Biophysical Phenomena↗