Biomedical subjects

Y J Lin

Publications and source records attributed to Y J Lin.

At least 109 records · Page 6Linked to original sources

PubMed1992

Direct stimulation of immediate-early genes by intranuclear insulin in trypsin-treated H35 hepatoma cells.

H35 hepatoma cells were treated with trypsin to abolish insulin binding and insulin-stimulated receptor kinase activity. Insulin was, however, internalized by fluid-phase endocytosis in trypsin-treated cells. Furthermore, nuclear accumulation of insulin was similar in control and trypsin-treated hepatoma cells. Northern blot analysis revealed insulin increased g33 and c-fos mRNA concentrations identically in control and trypsin-treated cells but had no effect on beta 2-microglobulin mRNA. Actinomycin D treatment prior to or after insulin addition demonstrated that insulin increased gene transcription and had no effect on mRNA degradation. These studies suggest that the accumulation of intact insulin in cell nuclei may be directly involved in the increased transcription of immediate-early genes.

Cell Cycle↗

PubMed1992

Disulfide-linked and noncovalent dimers of p185HER-2 in human breast carcinoma cells.

Enhanced levels of disulfide-linked dimers of the neu oncogene product have been suggested to be associated with the transformed state [Weiner DB, Liu J, Cohen JA, Williams WV, Greene MI: Nature 338:230-231, (1989)]. We, therefore, investigated the properties of the dimeric forms of p185HER-2/neu from the human breast carcinoma cell line, SK-BR-3. We found disulfide-linked dimers as well as noncovalently associated dimers that were detected by cross-linking with bis(sulfosuccinimidyl) suberate (BS3). However, the disulfide-linked dimers did not exist in intact cells, since they were eliminated when the cells were lysed in the presence of the alkylating agent, sodium iodoacetate. Moreover, the disulfide-linked dimeric molecules were not the activated form of p185HER-2 since they incorporated about the same level of phosphate in an in vitro kinase reaction as the monomeric molecules. In contrast, the noncovalent dimers appeared to be present on the surface of intact cells and were phosphorylated at levels at least tenfold higher than monomers in an in vitro kinase reaction.

Alkylating Agents↗

PubMed1992

Presence of Na+/Ca2+ exchange activity and its role in regulation of intracellular calcium concentration in bovine adrenal chromaffin cells.

The presence of a Na+/Ca2+ exchanger in bovine adrenal chromaffin cells was demonstrated by measuring the efflux of 45Ca2+ which had been preloaded into cells by a brief depolarization. The efflux of 45Ca2+ was dependent on extracellular Na+ (Na+o); 45Ca2+ efflux was significantly decreased by replacing Na+o with N-methylglucamine (NMG), or Li+. Replacement of Na+o by NMG increased the resting intracellular Ca2+ concentration ([Ca2+]i) of freshly isolated chromaffin cells. This could be reversed by adding Na+, suggesting that Na+/Ca2+ exchanger activity was involved in maintaining [Ca2+]i at its resting level. The initial rate of Na(+)-dependent [Ca2+]i recovery after Ca2+ loading by depolarization was dependent on the level of [Ca2+]i. There was an apparent linear relationship between the activity of the Na+/Ca2+ exchanger and [Ca2+]i both in the presence and absence of Na+o. When cells were treated with other stimuli, including 10 microM DMPP or 40 mM caffeine, the ability of the stimulated cells to decrease [Ca2+]i was significantly reduced upon replacing Na+o with NMG. Our data show that the Na+/Ca2+ exchanger is one of the major pathways for regulating [Ca2+]i in chromaffin cells in both resting and stimulated states.

Adrenal Medulla↗

PubMed1992

The adenosine analogue N6-L-phenylisopropyladenosine inhibits catecholamine secretion from bovine adrenal medulla cells by inhibiting calcium influx.

We reported earlier that adenine nucleotides and adenosine inhibit acetylcholine-induced catecholamine secretion from bovine adrenal medulla chromaffin cells. In this article, we used an adenosine analogue, N6-L-phenylisopropyladenosine (PIA), to study the mechanism underlying inhibition of catecholamine secretion by adenosine. PIA inhibits secretion induced by a nicotinic agonist, 1,1-dimethyl-4-phenylpiperazinium, or by elevated external K+. The half-maximal effect on 1,1-dimethyl-4-phenylpiperazinium-induced secretion occurred at approximately 5 x 10(-5) M. The inhibition is immediate and reversible. Fura-2 measurements of cytosolic free Ca2+ indicate that PIA inhibits Ca2+ elevation caused by stimulation; measurements of 45Ca2+ influx show that PIA inhibits uptake of Ca2+. PIA does not inhibit calcium-evoked secretion from digitonin-permeabilized cells, nor does PIA cause any significant change in the dependence of catecholamine secretion on calcium concentration. These data suggest that inhibition by PIA occurs at the level of the voltage-sensitive calcium channel.

Adrenal Medulla↗

PubMed1992

Crystallographic refinement of trichosanthin at 2.6A resolution.

The molecule model of trichosanthin has been rebuilt by using the electron density map improved by the solvent flatten and in accordance with the primary structure put forward by Collins. The crystallographic refinement of two trichosanthin molecules (3828 nonhydrogen atoms) in an asymmetric unit has been carried out by means of the restrain least-square procedure and diffraction data to a resolution of 2.6 A. The results are: an R factor 0.223 and the r.m.s. deviation of the bond length = 0.023 A. The new molecular model is in good agreement with the electron density map calculated with the coefficient 2Fo-Fc.

Crystallography↗

PubMed1991

Cytogenetic analysis of head and neck carcinomas.

Ten primary squamous cell carcinomas (SCC) of the head and neck were evaluated cytogenetically after 10-14 days of in vitro culture. Addition of 3% L-glutamine was essential for consistent epithelial growth of these carcinomas. Outgrowth of cells from tissue explants contained a mixture of chromosomally normal and abnormal cells; the abnormal cells had extensive changes including translocations, marker chromosomes, inversions, deletions, and duplications. In addition, all carcinomas contained cells with pulverization and double minute chromosomes (dmin). Chromosomes 11, 13, and 14 had "hotspots" of rearrangements.

Adult↗

PubMed1991

Physical and biological properties of fluorescent dansylated bile salt derivatives: the role of steroid ring hydroxylation.

The hydroxyl groups of bile salts play a major role in determining their physical properties and physiologic behavior. To date, no fluorescent bile salt derivatives have been prepared which permit evaluation of the functional role of the steroid ring. We have prepared five fluorescent cholanoyl derivatives using a dansyl-ethylene diamine precursor linked to the sulfonyl group of taurine; N-(5-dimethylamino-1-naphthalenesulfonyl)-N'-(2-aminoethanesulf onyl)- ethylenediamine. The fluorescent dansyl-taurine was conjugated to the carboxyl group of free bile acids, enabling the labeling of the series: dehydrocholate, ursodeoxycholate, cholate, chenodeoxycholate and deoxycholate. Despite a systematic hydrophobic shift compared with the native bile salts (aqueous solubility and water:octanol partitioning), the influence of steroid ring hydroxylation was retained, with the dehydrocholate and cholate derivatives more water soluble than the dihydroxy derivatives. Similarly, the sequence of HPLC mobilities, reflecting relative hydrophilicity, was identical in the dansyl-taurine derivatives and the native taurine-conjugated bile salts. Cellular uptake of all five steroid derivatives was rapid, and partial inhibition of [3H]taurocholate uptake was observed in isolated hepatocytes. Rates of biliary excretion of the dansylated derivatives by the isolated perfused rat liver correlated closely with hydrophilicity. Collectively, these findings indicate that the influence of the hydroxyl groups is retained in this series of dansylated steroids, and that hydroxylation is a key determinant of their hepatocellular transport and biliary excretion. These fluorescent bile salt derivatives may thus serve as unique probes for investigating structure-function relationships in hepatic processing of steroid-based compounds.

Animals↗

PubMed1991

Effects of deoxycholate on the transepithelial transport of sucrose and horseradish peroxidase in filter-grown Madin-Darby canine kidney (MDCK) cells.

Madin-Darby canine kidney (MDCK) epithelial cells grown on microporous polycarbonate filters were used as a model system to investigate the mechanisms of enhancement by deoxycholate in the transepithelial transport of horseradish peroxidase (HRP) and 14C-sucrose. Deoxycholate at 0.025% had no effect on the transepithelial electrical resistance (TEER); a fivefold enhancement on the transepithelial transport of HRP, but not on that of 14C-sucrose, was observed. Deoxycholate at 0.05% induced a reversible decrease of TEER; a 2- and 50-fold enhancement on the transepithelial transport of 14C-sucrose and HRP, respectively, was observed. At 0.1%, deoxycholate induced an irreversible decrease in TEER and the epithelial barrier in the cell monolayer was completely eliminated. A 3.3-fold increase in cellular uptake in HRP, but not in 14C-sucrose, was also observed in the presence of 0.025% deoxycholate. The increase in cellular uptake was abolished when HRP was conjugated to polylysine. These results suggest that deoxycholate can increase the transepithelial transport by at least two different mechanisms, i.e., a transcellular pathway, possibly due to the enhancement of cellular uptake of selective molecules, and a nonselective paracellular pathway, due to the loosening of tight junctions by deoxycholate at higher concentrations.

Animals↗

PubMed1991

Caffeine-sensitive calcium stores in bovine adrenal chromaffin cells.

Caffeine was used to study the intracellular Ca2+ pools of bovine chromaffin cells. Its effects on cytosolic Ca2+ concentration ([Ca2+]i) were examined using fura-2. Caffeine caused a transient increase in [Ca2+]i in the presence or absence of extracellular Ca2+. In the former case, the caffeine-induced [Ca2+]i increase was higher and stayed above the basal value for several minutes. In the latter case, the [Ca2+]i rise was lower and fell to the basal level within 1 min. These results suggest that caffeine increases [Ca2+]i by causing both Ca2+ influx and Ca2+ release from intracellular pools. In the absence of extracellular Ca2+, ionomycin but not caffeine caused a further increase in [Ca2+]i in cells that had been treated with caffeine. Apparently there are at least two intracellular Ca2+ pools, only one of which is sensitive to caffeine. The caffeine-induced [Ca2+]i rise became smaller when the cells were pretreated with the inositol trisphosphate-generating agonists, methacholine and bradykinin. In addition, methacholine was unable to initiate a [Ca2+]i transient after the cells had been treated with caffeine. The results indicate that the caffeine-sensitive Ca2+ pools overlap with the inositol trisphosphate-sensitive pool and that the size of the latter pool is smaller than that of the former. The caffeine-sensitive Ca2+ pools were refilled after high K+ treatment, which suggests that the caffeine-sensitive Ca2+ pools may be important in buffering the cytosolic Ca2+. The effect of caffeine on [Ca2+]i is not due to inhibition of phosphodiesterase. Our results support a Ca2+ entry model in which depletion of intracellular Ca2+ pools controls the rate of Ca2+ entry across the plasma membrane.

Adrenal Glands↗

PubMed1991

[Electron microscopic observation of synaptonemal complexes in spermatocytes of six species of fishes].

The synaptonemal complexes (SCs) in spermatocytes of six species of fishes were detected with a combination of surface spreading and silver staining technique and observed under both light and electron microscopes. These fishes are Tilapia nilotica, T. mossambica and Mastacembelus sinensis of Perciformes. Sarcocheilichthys nigripinnis, Pseudorasbora parva and Hemibarbus maculatus of Gobioninae in Cypriniformes. The formation of SCs started in Zygotene and completed at Pachytene. During the pachytene, each SC was morphologically intact, preferentially stained and attached to the nuclear envelope by a dense terminal plaque. Interlock in SCs frequently occurred in Zygotene. In several cases breakage and disentangling of interlocked lateral elements were observed. SCs disappeared in diplotene. The pairing of the SCs started at telomeres and stretched towards kinetochore. The sex determination of Mastacembelus sinensis was xx/xy. The X and Y chromosomal SCs' axes had a distinctive morphology at pachytene and were clearly distinguishable from autosomal SCs. The X and Y chromosomes begain to pair at early pachytene. The X and Y chromosome axes paired to form a length of SC that is somewhat longer than the unpaired portion at the mid-pachytene. There was a dense substance at unpaired portion. Quantitatine evaluation demonstrated that relative length and arm ratio were distinctive characteristics for each autosomal SC. The consistency of relative length and arm ratio indicates the stability of the techniques. The idiograms of SC karyotypes of three species (Tilapia niloticus, T. mossambicus and Mastacembelus sinensis) have been constructed.

Animals↗

PubMed1991

The epidemiology of diarrhoeal diseases in southeastern China.

In a community survey of 19,410 people for 12 months in southeastern China (Fujian Province), the overall annual incidence rate of diarrhoea was 729.9 episodes/1,000 population. The incidence varied with different age groups; children aged under five years had the highest rate, 2.25 episodes per child per year. A bacterial pathogen was isolated from 883 cases (44.03%), and 147 (14.76%) strains from 996 healthy controls. Enterotoxigenic Escherichia coli, enteropathogenic E. coli, and Shigella species were the most frequently isolated bacterial pathogens. Isolation was highest during the hot summer months. The investigation showed that the diarrhoea incidence was related to the status of economy, education, healthy, hygiene, food, and water.

Adolescent↗

PubMed1991

Protease-like sequence in hepatitis B virus core antigen is not involved in the cleavage processes of core protein in Escherichia coli.

A DNA fragment, coding for hepatitis core antigen (HBcAg), was amplified by polymerase chain reaction and inserted into a lambda PL promoter-derived expression vector. The recombinant plasmid was transformed into Escherichia coli and proteins produced after heat induction were analyzed. In addition to the 21 kDa HBcAg protein, several smaller related polypeptides, particularly one of 17 kDa in size, were also detected with rabbit anti-HBcAg antiserum. Whether the protease-like sequence of core protein involved in the self-cleavage process to form the 17 kDa polypeptide was investigated by a deletion experiment. Our results with a mutant in which 7 amino acids of the conserved protease-like region in the core protein have been deleted suggest that the cleavage does not depend on the presence of these protease-like sequence. In addition, the core protein synthesized from in vitro translation reaction was not cleaved. Core particles from E. coli lysate were purified by sucrose and cesium chloride density gradient centrifugations and subsequently treated with 0.2% of SDS and 0.2% of beta-mecaptoethanol. Immunoblotting analysis, however, did not reveal any conversion of the 21 kDa protein to smaller ones. In conclusion, our results suggest that the protease-like domain at the N-terminus of the core protein does not contain intrinsic autocleavage activity, nor could the HBcAg be converted to smaller antigens by detergent treatment.

Aspartic Acid Endopeptidases↗

PubMed1990

New crystalline forms of neuraminidase of type B human influenza virus.

New crystalline forms of tetrameric neuraminidase heads from two strains (B/Lee/40 and B/mem/89) of type B human influenza virus were obtained and the crystals diffracted using X-rays to 2.5 A resolution without lattice disorder. The new B/Lee/40 crystalline form is tetragonal, space group P42(1)2, with unit cell dimensions a = 123.8 A, c = 71.8 A. The B/mem/89 crystalline form is also tetragonal, space group I422, with unit cell dimensions a = 122.9 A, c = 164.4 A. There is one neuraminidase monomer per asymmetric unit in both forms.

Crystallization↗

PubMed1989

Human hepatitis delta virus RNA subfragments contain an autocleavage activity.

Hepatitis delta virus (HDV) contains a single-stranded circular RNA genome of 1.7 kilobases. In this report we demonstrate that subfragments of HDV RNA can undergo autocatalytic cleavage. This cleavage requires at least 500 microM of Mg2+ or Ca2+, is not affected by varying the pH from 5.0 to 9.1, and occurs with RNA fragments as small as 133 nucleotides. The larger RNA fragments containing additional HDV sequences have a lower efficiency of cleavage. Deletion analysis at both ends of RNA subfragments suggested that the catalytic ability of HDV RNA resides in a stretch of no more than 117 nucleotides around the cleavage site. The cleavage occurs at the phosphodiester bond between nucleotides 688 and 689 on the HDV genomic map, generating a 5' fragment with a terminal uridyl 2',3'-cyclic monophosphate residue and a 3' fragment with a guanosyl residue with a 5'-hydroxyl group. The smallest autocleaving RNA does not contain the "hammerhead" sequence required for the autocleavage of other known self-cleaving RNA. The cleavage of HDV RNA occurs at a much faster rate, even at a very low Mg2+ concentration, than that of other "ribozymes." Thus, HDV RNA represents a distinct class of ribozyme.

Base Sequence↗

PubMed1989

Sister chromatid exchange in the Mongolian gerbil, Meriones unguiculatus.

Sister chromatid exchange (SCE) studies have been performed in a variety of animals, both in vitro and in vivo, as well as in plants. To date, no such studies have been performed in any member of the gerbil sub-family (Gerbillinae). A new sister chromatid differential staining method was used with mice in vivo and has now been applied to the Mongolian gerbil, Meriones unguiculatus. With some modifications, this in vivo method was found to be highly reproducible in gerbils, and had consistently produced many metaphase cells with clear sister chromatid differentiation. The method involves subcutaneous implantation of a 50 mg slow-release BrdU pellet, the fluorochrome Hoechst 33258, phosphate buffering at pH 6.8, and incandescent light exposure.

Animals↗

PubMed1989

Triclosan: a safety profile.

Triclosan (2, 4, 4'-trichloro-2'-hydroxydiphenyl ether), an antimicrobial agent, has been used extensively for 20 years in consumer products, principally in deodorants, soaps and other dermatological preparations. Recently, the use of triclosan has been extended to oral health care products such as dentifrices. This paper reviews safety information, both pre-clinical and clinical studies, from the literature, data submitted to the Antimicrobial I OTC Review Panel and unpublished work from the Pharmacology and Toxicology Department of the Colgate-Palmolive Company. The data spans acute, subacute, subchronic and chronic toxicity; mutagenicity, carcinogenicity, reproduction/teratology and pharmacokinetics. Results of these studies show that triclosan is well tolerated by a variety of species including man. In clinical studies with triclosan in solutions and dentifrices, a steady state was reached by day 7 with blood levels in the parts per billion (ppb) range and urine as the main route of excretion. Based on these studies, triclosan can be considered safe for use in dentifrice and mouthrinse products.

Animals↗

PubMed1988

Chromosomal analysis of recurrent laryngeal papillomas.

Recurrent laryngeal papillomas are tumors believed to be induced by human papillomaviruses. Severity of this disease varies due to the unpredictability of clinical remissions and recurrences. However, the severity of the disease does not affect the classification of these tumors as benign, and the rate of spontaneous conversion of recurrent laryngeal papillomas to carcinomas is very low. Laryngeal papillomas from six patients were evaluated cytogenetically after short-term culture. All six specimens were chromosomally normal, consistent with their classification as benign tumors with a low rate of malignant conversion. The presence of human papillomaviruses has no detectable effect on the chromosomes of these tumors.

Adult↗

PubMed1988

Simplified C-banding of mouse chromosomes.

Mouse bone marrow chromosomes incorporated with bromodeoxyuridine (BrdU) were differentially Giemsa stained after exposure to incandescent light in order to study sister chromatid exchange. Over-exposure of the chromosomes to incandescent light often resulted in the complete loss of sister chromatid differentiation, and it frequently resulted in the C-band formation. C-banding was also prominent with chromosomes which were not labelled with BrdU. The method utilized a 300 W, 130 V, inside-frosted incandescent bulb coupled with phosphate buffering at pH 6.8 and an exposure period of 2 h.

Animals↗