Search PubMed⌕ Search

Biomedical subjects

P Lin

Publications and source records attributed to P Lin.

At least 109 records · Page 6Linked to original sources
PubMed1996

GABAA receptors modulate early spontaneous excitatory activity in differentiating P19 neurons.

P19 embryonic carcinoma (EC) stem cells are pluripotent and are efficiently induced to differentiate into neurons and glia with retinoic acid (RA) treatment. Within 5 days, a substantial number of differentiating P19 cells express gene products that are characteristic of a neuronal phenotype. P19 neurons were used as a model to explore the relationship between neuronal "differentiation" in vitro and the acquisition of gamma-aminobutyric acid (GABAA) receptors and functional GABA responses. Pulse-labeling experiments using bromodeoxyuridine indicated that all neurons had become postmitotic within 3-4 days after treatment with RA. This was confirmed by a reduction in the immunocytochemical detection of the undifferentiated stem cell antigen SSEA-1. Subsequently, a transient expression of nestin was observed during the first 5 days in vitro (DIV) after exposure to RA. By 5-10 DIV after RA, a significant number of neurons (approximately 80-90%) expressed immunocytochemically detectable glutamate decarboxylase and GABA coincident with the acquisition of membrane binding sites for tetanus toxin. These phenotypic markers were maintained for > 30 DIV after RA. Under current-clamp conditions, random, low-amplitude, spontaneous electrical activity appeared in neurons within the first few days after RA treatment and this was blocked by the specific GABAA receptor antagonist bicuculline. Thereafter, the appearance and progressive increases in the frequency of spontaneous action potentials in P19 neurons were observed that were similarly attenuated by bicuculline. In neurons > 5 DIV after RA, exogenous application of GABA elicited similar action potentials. The onset of excitatory responses to GABA or muscimol in voltage-clamped neurons appeared immediately after the cessation of neuronal mitosis and before the previously reported acquisition of responses to glutamate. In fura-2 imaging studies, the exogenous application of GABA resulted in neuron-specific increases in intracellular Ca2+. Thus, P19 neurons provide an in vitro model for the study of the early acquisition and properties of electrical excitability to GABA and the expression of functional GABAA receptors.

Action Potentials↗
PubMed1996

[The influence on prognosis of intraoperative chemotherapy for adenocarcinoma of gastric cardia].

Four hundred and four patients underwent surgical treatment for adenocarcinoma of the gastric cardia in our hospital between January 1980 to June 1990. Of 342 resected cases, 231 cases were treated with surgery alone, their 1-, 3-, and 5-year survival rates were 83.8%, 38.5% and 20.8%, respectively. Since January 1987, postoperative chemotherapy was given in 47 patients, their 1-, 3-, and 5-year survival rates were 89.4%, 46.8%, 29.8%, respectively, while intraoperative chemotherapy in 54 cases, had 1-, 3-, and 5-year survival rates of 87.1%, 63.0% and 38.9%, respectively. The result showed that the 3- and 5-year survival rates were higher in postoperative chemotherapy cases than in cases with operation alone, but there was no statistical significance between the two groups. However, intraoperative chemotherapy group had much higher 3- and 5-year survival rates than operation alone (P < 0.01). Intra-operative chemotherapy is recommended especially in patients beyond stage I with lymph node metastasis.

Adenocarcinoma↗
PubMed1996

[Clinical study of the pattern of lymphnode metastasis in carcinoma of esophagus: an analysis of 200 cases].

To study the pattern of lymphnode metastasis in carcinoma of the esophagus, 200 cases of resected esophageal cancer specimens were carefully examined pathologically. Lymphnode metastasis, its pathway and extent in relation to pathological changes were analyzed. Lymphnode metastasis was mainly regional and extended vertically in both directions. Leaping-over metastasis was another feature. The deeper invasion by the tumor, the higher frequencies of metastasis development, and vice versa. However, leaping-over metastasis was more likely to occur where tumor invasion was less severe. Owing to the high frequency of lymphnode metastasis in the superior mediastinum and the widely spanned leaping-over metastases, an operative approach by three incisions through right thoracotomy with excision of the whole segment of esophagus and anastomosis at cervical region was recommended, in order to dissect lymphnodes in the cervical, thoracic and abdominal regions and to leave less or no metastatic lymphnodes behind.

Adult↗
PubMed1995

The complete sequence of human lens gamma s-crystallin.

The complete sequence of human gamma s-crystallin has been determined and confirmed using a combination of MS methods, peptide sequencing and cDNA sequencing. Regions 21-35 and 102-107, which were previously assumed to be the same as the bovine sequence, differ from the bovine sequence at residues 22, 28, 31 and 104. An additional six residues were also found to be different from the original sequence determined for Pakastani lenses. Whether these differences represent errors in the original sequence or two different sequences among human lens crystallins is not yet known.

Amino Acid Sequence↗
PubMed1995

Human IL-12 p40 homodimer binds to the IL-12 receptor but does not mediate biologic activity.

IL-12, a heterodimeric cytokine, consists of two disulfide-linked subunits, p40 and p35. We investigated the role of p40 in ligand binding and signal transduction by expressing this subunit alone in COS cells. Culture media of the transfected COS cells exhibited specific dose-dependent binding to KIT225/K6 cells, a human T cell line that expresses IL-12R. Analysis of the culture media by SDS-PAGE and Western blotting demonstrated the presence of 40-kDa monomers and 80-kDa disulfide-linked homodimers. The two p40 species were purified and identified by N-terminal sequencing and proteolytic peptide mapping. Characterization of the p40 proteins for binding and bioactivity showed that both the p40 monomer and dimer inhibited 125I-labeled IL-12 binding to IL-12R, but the 80-kDa species, having a 50% inhibitory concentration (IC50) of 20 to 70 ng/ml, was at least 20-fold more effective than the monomer. Although neither the monomer nor the dimer stimulated human PHA-blast proliferation, the 80-kDa dimer inhibited IL-12-induced proliferation in a dose-dependent manner with an IC50 of 65 ng/ml. The results suggest that the IL-12 p40 subunit contains the essential epitopes for receptor binding. However, a proper conformation required for high affinity binding is achieved only when p40 is associated with a p35 subunit or another p40 subunit. When p40 is associated with a p35 subunit, the heterodimer acts as an agonist mediating biologic activity. However, when p40 associates with another p40, the homodimer behaves as an antagonist in vitro.

Animals↗
PubMed1995

Excision of ovarian dermoid cyst by laparoscopy and by laparotomy.

OBJECTIVES: Our purpose was to evaluate the efficacy of laparoscopic ovarian dermoid cystectomy and to compare the operative course, postoperative course, and complications between the laparoscopy and the laparotomy techniques. STUDY DESIGN: The safety and efficacy of laparoscopic ovarian dermoid cystectomy were evaluated in 40 women. Twenty-nine of 40 patients underwent laparoscopic excision of a solitary dermoid cyst without any additional procedure. The operative course, the postoperative course, and complications among these 29 women were compared with those of 26 other women who underwent a similar procedure by laparotomy. RESULTS: Spillage of the cyst's content did not lead to any complication. The operating time in the laparoscopy group was 73.5 +/- 4.7 minutes and in the laparotomy group it was 41.4 +/- 2.9 minutes. The duration of hospitalization was significantly shorter in the laparoscopy group (0.7 +/- 0.2 days) than in the laparotomy group (3.8 +/- 0.1 days). CONCLUSIONS: Although ovarian dermoid cystectomy by laparoscopy is associated with a longer operating time than by laparotomy, the duration of hospitalization is shorter and recovery is faster. Spillage of the contents of the dermoid cyst does not lead to any complication; perhaps this is due to the liberal irrigation of the peritoneal cavity.

Adult↗
PubMed1994

Tcp20, a subunit of the eukaryotic TRiC chaperonin from humans and yeast.

Members of the Hsp60 chaperonin family, such as Escherichia coli GroEL/S and the eukaryotic cytosolic chaperonin complex, TRiC (TCP ring complex), are double toroid complexes capable of assisting the folding of proteins in vitro in an ATP-dependent fashion. TRiC differs from the GroEL chaperonin in that it has a hetero rather than homo-oligomeric subunit composition and lacks a GroES-like regulatory cofactor. We have established greater than 57% identity between a protein encoded by the TCP20 gene from a human cDNA library and the newly identified protein encoded by the TCP20 gene located on the right arm of chromosome IV of the yeast Saccharomyces cerevisiae. These Tcp20 proteins showed approximately 30% identity to Tcp1, a known subunit of TRiC. Gel filtration, followed by Western analysis of purified bovine testis TRiC with a Tcp20-specific antibody, indicated that Tcp20 is a subunit of the hetero-oligomeric TRiC. Gene disruption experiments showed that TCP20, like TCP1, is an essential gene in yeast, consistent with the view that TRiC is required for folding of key proteins. The amino acid sequence similarities and the derived evolutionary relationships established that the human and yeast Tcp20 proteins represent members of a new family of subunits of TRiC chaperonins.

Amino Acid Sequence↗
PubMed1994

Temporal regulation of the IgE-dependent 1,2-diacylglycerol production by tyrosine kinase activation in a rat (RBL 2H3) mast-cell line.

We explored the possible role of tyrosine kinases in the IgE-dependent regulation of 1,2-diacylglycerol (DAG) production in RBL 2H3 cells. When triggered via their high-affinity IgE receptors (Fc epsilon RI), there was a rapid phosphorylation of tyrosine residues on a number of proteins. The phosphorylation of these proteins and ultimately histamine release were inhibited in a concentration-dependent manner by the tyrosine kinase inhibitor, tyrphostin. In cells labelled with [3H]myristic acid, we observed a characteristic biphasic increase in [3H]DAG production. In the presence of tyrosine kinase inhibitor, the initial increase in DAG was still observed, but the secondary increase, which was dependent on phosphatidylcholine-specific phospholipase D (PC-PLD) activation, was completely abolished. Tyrphostin significantly inhibited IgE-dependent activation of PC-PLD, suggesting that PC-PLD activation was regulated by tyrosine phosphorylation. Furthermore, when proteins from RBL 2H3 cells were immunoprecipitated with an anti-phosphotyrosine antibody, PC-PLD activity was recovered from the immunoprecipitated fraction. These results demonstrate that the secondary, but not the initial, phase of 1,2-DAG production in response to Fc epsilon RI aggregation is regulated by the initial activation of tyrosine kinases and that PC-PLD may be regulated directly by this mechanism.

Animals↗
PubMed1994

Failure to observe a relationship between bis-(beta-chloroethyl)sulfide-induced NAD depletion and cytotoxicity in the rat keratinocyte culture.

It has been proposed that the activation of poly(ADP-ribose) polymerase (Papirmeister et al., 1985), which results from the presence of strand breaks in bis-(beta-chloroethyl)sulfide (BCES) damaged DNA, causes depletion in the level of nicotinamide adenine dinucleotide (NAD) leading to cell death. This hypothesis has now been evaluated in the primary submerged culture of rat keratinocytes. The DNA content, the viable cell number, and the proliferative capability (measured by thymidine incorporation) of the culture were all reduced 48 h after exposure to 10 microM BCES. However, the total NAD level, that is, NAD+ plus NADH, was not changed at a dose of BCES lower than 50 microM. This observation was the same in both proliferating and early differentiating cultures. To further test this hypothesis, the modifying effect of inhibiting poly(ADP-ribose) polymerase on cytotoxicity in BCES-exposed cells was investigated. After exposure to 250 microM BCES, the NAD level was reduced to approximately 26 pmol/micrograms DNA. This value was increased to 34-49 pmol/micrograms DNA at both 24 and 48 h postexposure when the cultures were incubated in medium supplemented with 1-10 mM nicotinamide. Nevertheless, the decrease in the DNA content of the culture was not reversed. These results suggest that in the rat keratinocyte culture exposed to BCES, depletion of NAD is not a prerequisite for cell death.

Animals↗
PubMed1994

[Immunohistochemical observation of anti-human hepatocellular carcinoma monoclonal antibody HL2 in cancers].

Molecular weight of human hepatocellular carcinoma (HCC)-associated antigen-HL2 antigen was detected to be about 50,000 dalton by SDS-PAGE and Western blot. One hundred and twenty-seven paraffin sections of cancers and pathological liver tissue were tests by ABC immunohistochemical staining. MAb HL2 reacted with 62.7% HCC and also with 8 of the 10 stomach carcinomas but only with a few other digestive system carcinomas (pancreas carcinoma, rectum carcinoma and duodenum carcinoma) and hepatitis. MAb HL2 was negative in hepatocirrhosis and other tumors (vesica carcinoma, skin carcinoma, breast carcinoma, neurogliocytoma and carcinoma of the lung). The results suggest that MAb HL2 has values in diagnosis of HCC and differential diagnosis between HCC and other tumours. HL2 antigen might be a new tumor-associated antigen (TAA). Further study of HL2 antigen will significantly show the actions of TAA in the occurrence and development of tumor.

Antibodies, Monoclonal↗
PubMed1993

Humanized Mik beta 1, a humanized antibody to the IL-2 receptor beta-chain that acts synergistically with humanized anti-TAC.

Mik beta 1 is a mouse mAb directed at the beta-subunit of the human IL-2R (Tac) that inhibits IL-2 binding and inhibits IL-2 induction of large granular lymphocytes (LGL). Mik beta 1 alone does not inhibit IL-2-induced T-cell proliferation, but acts synergistically with anti-Tac to inhibit IL-2-induced proliferation of activated T cells. To evaluate these effects for possible therapy in humans, we constructed two humanized Mik beta 1 antibodies by combining the complementarity-determining regions of the murine antibody with human framework and constant regions. Compared with murine Mik beta 1, the two humanized Mik beta 1 antibodies, which differ in their degree of humanization, had similar affinities for IL-2R beta. The murine Mik beta 1 and one of the humanized Mik beta 1 antibodies were equivalent in competing for IL-2 binding to IL-2R beta and inhibiting IL-2 induction of LGL cytotoxicity. The activity of the second humanized antibody was significantly reduced. The three Mik beta 1 antibodies act synergistically to varying degrees with humanized anti-Tac to prevent IL-2-induced proliferation of activated T cells. This capacity to synergize paralleled their abilities to inhibit IL-2 binding. In addition, both humanized antibodies directed antibody-dependent cell-mediated cytotoxicity. We hope that humanized Mik beta 1 in combination with humanized anti-Tac will provide a new immunosuppressive therapy for the treatment of autoimmune diseases, graft-versus-host disease, and prevention of allograft rejection.

Amino Acid Sequence↗
PubMed1993

Purification and characterization of human recombinant IgE-Fc fragments that bind to the human high affinity IgE receptor.

The Fc-region of immunoglobulin E (IgE) comprising C epsilon 2, C epsilon 3, and C epsilon 4 domains is sufficient for binding to the alpha chain of the high affinity IgE-Fc receptor (Fc epsilon RI alpha). In order to identify the smallest Fc fragment capable of binding to the Fc epsilon RI alpha with high affinity, various regions of the IgE-Fc molecule were expressed in COS cells and investigated for their ability to bind Fc epsilon RI alpha. The smallest fragment that showed Fc epsilon RI alpha binding activity spans amino acids 329-547 and lacks the entire C epsilon 2 domain. Two active fragments, viz. Fc epsilon(315-547) (containing Cys328 which is responsible for interchain S-S bonding) and Fc epsilon(329-547), have been overexpressed in CHO cells and purified to homogeneity. The purified proteins bind to the Fc epsilon RI alpha with high affinity, similar to native IgE. SDS-polyacrylamide gel electrophoresis analyses indicate that Fc epsilon(315-547) is an S-S-linked dimer of apparent molecular mass of 68 kDa. Fc epsilon(329-547) appears on SDS-gel as three distinct bands at approximately 32 kDa, both under reducing and nonreducing conditions. However, size exclusion chromatography and analytical ultracentrifugation studies suggest that Fc epsilon(329-547) also remains associated as a dimer. The presence of N-linked glycosylation was detected in both proteins. The deglycosylated form of Fc epsilon(315-547) was isolated after Endo F/N-glycosidase F digestion and demonstrated to have binding activity comparable to that of the mock-digested protein. These results suggest that the presence of N-linked sugars is not necessary for Fc epsilon RI alpha binding. Both proteins blocked the release of histamine from RBL cells expressing human Fc epsilon RI alpha in a dose-dependent manner. The availability of these recombinant IgE-Fc proteins will be helpful in elucidating the key epitopes essential for the binding of IgE to its high affinity receptor.

Animals↗
PubMed1993

A comparison of flow cytometric and absorption cytometric DNA values as prognostic indicators for pancreatic carcinoma.

BACKGROUND: The DNA content of 30 adenocarcinomas of the head of the pancreas was measured by flow and absorption cytometric analysis. METHODS: Each of the patients in this study had curative pancreatoduodenectomy. The absorption cytometric measurements were done in a research laboratory, and the flow cytometric measurements were performed in a commercial laboratory. The DNA measurements were done on nuclei disaggregated from pancreatic cancer tissue blocks without the examiner knowing whether the patient had survived. RESULTS: Twenty-one of the 30 cancers were found to be aneuploid by absorption cytometric analysis, whereas only 1 of the 30 cancers was aneuploid by flow cytometric analysis. This difference was statistically significant (P < 0.001). CONCLUSIONS: Univariate and multivariate analyses showed that the absorption cytometric DNA measurements were stronger prognostic determinants for patient survival than were the flow cytometric DNA measurements, indicating that some caution may be warranted in the interpretation of commercially obtained DNA distributions of pancreatic carcinomas.

Analysis of Variance↗
PubMed1993

Disposition of SK&F L-190144 in rats and monkeys after oral, intravenous or ocular administration.

The objective of the study was to investigate the systemic disposition of 14C-SK&F L-190144 after single intravenous (10 mg kg-1) and oral (200 mg kg-1) doses to rats and after single intravenous and ocular doses (0.33 mg kg-1) to monkeys. After the intravenous dose, the blood concentration-time profile of 14C-SK&F L-190144 followed a rapid triexponential decline with half-lives of 2.5, 15, and 246 min in rats and 3, 19, and 2520 min in monkeys. The 14C-label in blood was mainly the parent compound. The terminal elimination half-life detected in rats using the urinary excretion rate-time data was 700 min. The total body clearance values were 17.6 +/- 2.1 (mean +/- SD, n = 6) and 1.11 +/- 0.41 (n = 4) ml min-1 kg-1 for rats and monkeys, respectively. Both species had similar values of volume of distribution at the terminal phase, 4 to 6 l kg-1, and similar excretion patterns, approximately 60 per cent and 30 per cent of the dose were excreted in the urine and feces, respectively. 14C-SK&F L-190144 was not absorbed orally in rats with the majority of the dose recovered in the feces. Following ocular administration to monkeys, the plasma drug concentrations peaked at 8 h post-dosing but did not reach a biexponential elimination phase until 18 h post-dosing, suggesting slow systemic absorption of drug from the ocular site. The monkeys excreted 42 per cent of the dose in urine and 50 per cent in feces after ocular administration. This increase in fecal excretion compared to the intravenous route of administration may have been due to the slow absorption by the ocular and nasal tissues altering the relative proportions of drug elimination via the renal and hepatic routes, or to a proportion of the dose passing into the gastrointestinal tract and exiting unabsorbed. Study results demonstrate similar excretion patterns and volume of distribution after intravenous administration in both species. The slow terminal elimination phase in monkeys was attributed to the low body clearance. The low oral bioavailability was possibly due to the poor partitioning behavior of the drug (logarithm of partition coefficient -2.6). A significant fraction of the dose was absorbed in the body via the ocular route.

Administration, Oral↗
PubMed1993

Evidence for altered cell-cycle traverse of the non-modal cells of the heteroploid MCa-11 line.

Classic stem cell theory states that the growth of heteroploid cell populations is due to the proliferation of 'main stemline' cells with modal DNA content and chromosome number. Cells with non-modal DNA content and chromosome number are thought to be blocked and/or destroyed at mitosis. To test this, we studied two chromosomally stable cell populations (mouse bone marrow and WCHE-5 cells) and one heteroploid, chromosomally diverse cell line (MCa-11). The heteroploid MCa-11 cells showed significant [3H]dT labelling for cells with DNA contents below the modal G0/G1 peak and above the modal G2 peaks (P < 0.001). This was consistent with the presence of cells with the non-modal DNA content that were engaged in replicative DNA synthesis. A percentage labelled mitosis analysis showed that MCa-11 cells with non-modal DNA content and chromosome number were able to complete mitosis, although with prolonged pre-karyokinetic time. These results suggest that many non-modal cells present in heteroploid cell populations are capable of continued proliferation.

Aneuploidy↗
PubMed1993

Measurement of DNA content and of tritiated thymidine and bromodeoxyuridine incorporation by the same cells.

We tested a method of measuring DNA content (Feulgen) and tritiated thymidine ([3H]-T) and bromodeoxyuridine (BrdU) incorporation by the same cell. Initial experiments showed that Feulgen hydrolysis denatured the DNA of fixed cells sufficiently to allow detection of incorporated BrdU with monoclonal antibodies. MCa-11 cells were then double-labeled with [3H]-T and BrdU, placed on slides, and Feulgen stained. Next, absorption cytometry was performed to measure the DNA content of randomly selected cells. Feulgen staining and the development and removal of either the [3H]-T or the BrdU grains after DNA measurements did not interfere with subsequent detection of the grains from the other label, and BrdU and [3H]-T can be used reliably in combination for identification of S-phase cells. This method may eventually allow the use of microscope-based image analysis to selectively measure the DNA contents and the BrdU/[3H]-T labeling of non-transformed stromal and cancer cells in solid tumors, thereby providing new insights into the growth kinetics of these heterogeneous cell populations.

Animals↗
PubMed1992

Phosphatidylcholine-specific phospholipase D-derived 1,2-diacylglycerol does not initiate protein kinase C activation in the RBL 2H3 mast-cell line.

We examined the role of phosphatidylcholine-specific phospholipase D (PC-PLD) in the IgE-dependent activation of protein kinase C (PKC) in RBL 2H3 cells (a model for mast-cell function). Cells were sensitized with mouse monoclonal anti-trinitrophenol (TNP) IgE (0.5 micrograms/ml) and were then triggered with an optimal concentration (10 ng/ml) of TNP-ovalbumin conjugate (TNP-OVA). This resulted in an immediate biphasic increase in the production of 1,2-diacylglycerol (DAG) and activation of PKC. The initial increase in DAG production reached a peak within 30 s, and the second phase reached a plateau within 5 min after stimulation. TNP-OVA-induced PC-PLD activation followed the initial increase in DAG formation in response to IgE-receptor cross-bridging, but coincided with the second peak. Phosphatidic acid (PA), derived from the PC-PLD pathway, is metabolized to DAG by the action of PA phosphohydrolase (PAPase). Propranolol (0.3 mM), which inhibits PAPase, blocked the IgE-dependent increase in DAG, activation of PKC, and subsequently degranulation. The PKC inhibitor staurosporine (0.1 microM) inhibited the second, but not first, peak of DAG accumulation, reversed PKC translocation after 10 min and inhibited subsequent mediator release. Taken together, these results demonstrate that PC-PLD does not initiate, but may play a latent role in, IgE-dependent DAG production, PKC activation and mediator release from RBL 2H3 cells.

Alkaloids↗