Search PubMed⌕ Search

Biomedical subjects

H Lin

Publications and source records attributed to H Lin.

At least 397 records · Page 22Linked to original sources
PubMed1994

Lactate transport in freshly isolated human fetal retinal pigment epithelium.

PURPOSE: To study transport mechanisms for small monocarboxylic acids in the apical and basolateral membranes of freshly isolated, human fetal retinal pigment epithelium. METHODS: The epithelium was mounted in a small Ussing chamber that allowed separate perfusion of both the apical and basal compartments and simultaneous measurements of intracellular pH, transepithelial potential, and tissue resistance. Intracellular pH was measured using a pH-sensitive dye, 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein. RESULTS: When 10-100 mM lactate or pyruvate was added to the apical bath the cells acidified by 0.10-0.25 pH units. There were no differences between the initial rates of intracellular acidification produced by L-lactate and D-lactate. These rates could be described as Michaelis-Menten functions of the concentrations of lactate and pyruvate. The Km values were 42 +/- 12 mM for L-lactate and 34 +/- 8 mM for pyruvate. The rates of acidification caused by 50 mM L-lactate were reversibly reduced by 44% or 35% after apical administration of probenecid (2 mM) or alpha-cyano-4-hydroxycinnamate (2 mM), and irreversibly reduced by 78% after apical administration of the sulfhydryl-reagent mersalyl acid (2 mM). The intracellular acidifications caused by apical pyruvate (50 mM) were completely and reversibly inhibited by 50 mM apical L-lactate. Addition of 50 to 100 mM lactate to the basal bath caused intracellular alkalinizations, which could be inhibited by Na+ removal in the basal bath or by 2 mM alpha-cyano-4-hydroxycinnamate in the apical bath.

Basement Membrane↗
PubMed1993

Long-term acceptance of major histocompatibility complex mismatched cardiac allografts induced by CTLA4Ig plus donor-specific transfusion.

Allograft rejection is a T cell-dependent process. Productive T cell activation by antigen requires antigen engagement of the T cell receptor as well as costimulatory signals delivered through other T cell surface molecules such as CD28. Engagement of CD28 by its natural ligand B7 can be blocked using a soluble recombinant fusion protein, CTLA4Ig. Administration of CTLA4Ig blocks antigen-specific immune responses in vitro and in vivo, and we have shown that treatment of rats with a 7-d course of CTLA4Ig at the time of transplantation leads to prolonged survival of cardiac allografts (median 30 d), although most grafts are eventually rejected. Here, we have explored additional strategies employing CTLA4Ig in order to achieve long-term allograft survival. Our data indicate that donor-specific transfusion (DST) plus CTLA4Ig can provide effective antigen-specific immunosuppression. When DST is administered at the time of transplantation followed by a single dose of CTLA4Ig 2 d later, all animals had long-term graft survival (> 60 d). These animals had delayed responses to donor-type skin transplants, compared with normal rejection responses to third-party skin transplants. Furthermore, donor-matched second cardiac allografts were well tolerated with minimal histologic evidence of rejection. These data indicate that peritransplant use of DST followed by subsequent treatment with CTLA4Ig can induce prolonged, often indefinite, cardiac allograft acceptance. These results may be clinically applicable for cadaveric organ and tissue transplantation in humans.

Abatacept↗
PubMed1993

Synthesis of T helper 2-type cytokines at the maternal-fetal interface.

Clinical and experimental evidence has indicated that the maternal immune response is biased toward antibody production and away from cell-mediated immunity during pregnancy, especially in the vicinity of the fetoplacental unit. Because antibody responses are often associated with the Th2 cytokine pattern, this suggests that Th2-type cytokines might predominate locally in the regulation of the maternal immune response. In order to test this hypothesis, we examined the local and distal release of cytokines during murine pregnancy using ELISA assays. We report here that the Th2-specific cytokines IL-4, IL-5, and IL-10 were readily detectable in cell supernatants derived from fetal-placental units in all three trimesters of gestation. IL-3 was also present. These cytokines were detected in lysates of freshly isolated, day 12 decidual and placental cells, and in supernatants as early as 15 min after the beginning of culture. The presence of functional IL-10 was confirmed by specific bioassay. IL-10 mRNA was localized to the decidua at day 6 of gestation by in situ hybridization. IFN-gamma was also found in the supernatants from the first trimester of pregnancy, but was barely detectable in the second, and undetectable in the third trimester. Cytokine expression was consistently detected in samples from individual mice. None of these cytokines was produced by unstimulated spleen or mesenteric lymph nodes from pregnant mice. IL-4, IL-10, and IFN-gamma were produced by Con A-stimulated spleen cells from virgin mice, but in ratios opposite to those found in the placenta. These observations indicate that Th2-specific cytokines are normally produced at the maternal-fetal interface. The continuous presence of IL-4, IL-5, and IL-10, with early and transient expression of IFN-gamma, can provide a molecular basis for the antibody/Th2-like bias of the maternal immune response during pregnancy.

Animals↗
PubMed1993

Hepatitis B and hepatitis C among institutionalized psychiatric patients in Taiwan.

To investigate the seroprevalence of hepatitis B surface antigen (HBsAg) and antibodies to hepatitis C virus (anti-HCV) in a psychiatric institution in Taiwan, where hepatitis B virus (HBV) is hyperendemic, a total of 780 patients with psychiatric disorders were studied. Enzyme-linked immunosorbent assays (ELISA) were used for testing HBsAg and anti-HCV. The prevalence of HBsAg was higher than that of anti-HCV among these patients (18.1% vs. 6.8%, P < 0.0001). The HBsAg carrier rate in these patients was consistent with that of the general population, with a trend for HBsAg carrier rate to be lower in the aged and in females. In contrast, the prevalence of anti-HCV was higher in these patients than in general population. Anti-HCV positivity was found more frequently in patients who had received blood transfusion previously (24% vs. 6.4%, P < 0.05). The majority (92%) of patients with positive anti-HCV did not have a history of apparent parenteral exposure. The prevalence of anti-HCV increased significantly with duration of the psychiatric disorder. The prevalence of anti-HCV also tended to increase with duration of hospitalization but without reaching statistical significance. These findings suggest that these institutionalized psychiatric patients contract hepatitis B, as does the general population in Taiwan, and they should be considered as a specific risk group for hepatitis C infection.

Adult↗
PubMed1993

Germline stem cell division and egg chamber development in transplanted Drosophila germaria.

Germline and somatic stem cells reside within the anterior region (or "germarium") of each ovariole in the Drosophila ovary. When individual germaria were dissected free of developing eggs and sheath tissue and transplanted into the abdominal cavity of a host fly, they regenerated ovariole-like structures and continuously supported the entire process of oogenesis, indicating that the stem cells remained functional. This system allowed us to measure the duration of several stages in oogenesis and to analyze the role of specific germarial cells in providing stem cell function. Laser ablation of presumptive germline stem cells near the apical tip prior to transplantation blocked the production of new germline cysts, but allowed previously initiated cysts to complete development. This confirmed the location of germline stem cells and showed that subsequent development of preexisting cysts did not require continued cyst production. Ablation of a distinct group of somatic cells lying close to the germline stem cells ("the terminal filament") increased the rate of oogenesis by approximately 40%, suggesting that the terminal filament may negatively regulate stem cell division.

Animal Nutritional Physiological Phenomena↗
PubMed1993

Lipopolysaccharide pretreatment of cyclosporine-treated rats enhances cardiac allograft survival.

Lipopolysaccharide (LPS), the endotoxin in gram-negative bacterial cell walls, is a major factor in septic shock. Tumor necrosis factor (TNF) appears immediately after LPS release or LPS injection in rats, but when these animals have LPS reinjected for up to 7 days, TNF production is inhibited. Because inhibiting TNF with anti-TNF antibodies prolongs cardiac allograft survival and is synergistic with cyclosporine (CsA), enhanced graft survival could result from inhibiting TNF via LPS pretreatment. Accordingly, heterotopic rat heart transplants were performed in: I, untreated controls: II, LPS pretransplant treatment: III, LPS post-transplant treatment; IV, low-dose CsA post-transplant treatment; V, CsA post-transplant treatment and PBS (LPS vehicle); or VI, LPS pretransplant treatment and low-dose CsA post-transplant treatment, using Brown Norway (BN) donors and Lewis (LEW) recipients. Rejection was defined by a lack of contractions. Results showed that while LPS pre- or post-treatment alone had little allograft survival effect, LPS pretreatment combined with CsA significantly prolonged survival vs control or CsA alone (22.0 +/- 1.6 days vs 6.8 +/- 0.6 days or 13.4 +/- 1.1 days; P < 0.001). Primary MLRs of LPS-pretreated LEW splenocytes cocultured with irradiated BN splenocytes had significantly less [3H]thymidine incorporation than untreated LEW splenocytes (3671 +/- 349 vs 7828 +/- 14 cpm). TNF assays of untreated and PBS-treated LEW spleen cells cocultured with irradiated BN spleen cells had 1.3 and 1.1 pg of TNF/10(6) cells, respectively, in 2 hr, but no TNF from LPS-pretreated LEW cells was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Characterization of pro-opiomelanocortin processing in heterologous neuronal cells that express PC2 mRNA.

We have investigated processing of monkey pro-opiomelanocortin (POMC) following transfection into heterologous neuronal Neuro 2A (N2A) cells. In several separately transfected stable cell lines (termed N2A/POMC2-like; n = 4), POMC was processed to beta E only, by direct cleavage from the precursor. Thus, these cell lines did not produce beta E in the orderly manner observed in the pituitary, that is, via the intermediate peptide beta LPH. Analysis of one representative N2A/POMC2 cell line revealed that the extent of processing to beta E appeared to be negatively correlated with precursor expression level, suggesting that the processing enzyme(s) in these cells was present in limiting amounts. Northern analysis of PC1 and PC2, two recently cloned processing enzymes, showed that N2A/POMC2 cells expressed low levels of PC2 mRNA, but no detectable PC1 mRNA. These data suggest that (1) the order of processing observed in the pituitary is not exclusively determined by tertiary folding of the precursor, but rather by the complement of processing enzymes in a particular cell, and (2) if PC2 is responsible for POMC processing in N2A/POMC2 cells, this enzyme, expressed in limiting amounts, appeared to show selectivity for the beta E amino terminal processing site.

Animals↗
PubMed1993

Characterization of antacid compounds containing both aluminum and magnesium. I. Crystalline powders.

The composition and antacid properties of 10 samples of crystalline antacids containing both aluminum and magnesium were determined. The composition was found to vary significantly, even within the same type of antacid. For example, three of four hydrotalcite samples exhibit evidence of the presence of a minor phase of amorphous aluminum hydroxide. Almagate and almagcit, which are claimed to be unique compounds, were found to be composed of hydrotalcite, magnesium hydroxycarbonate, and/or magnesium carbonate and amorphous aluminum hydroxide. All three magaldrate samples examined contained a minor phase of amorphous aluminum hydroxide. All 10 samples passed the preliminary antacid test and had high acid neutralizing capacities. However, the rate of acid neutralization varied between samples. In some cases the rate of acid neutralization at a dose of 400 mg was too slow to raise the pH to 3.0 as required by the Rossett-Rice test.

Aluminum↗
PubMed1993

Effect of endothelin-1 on glomerular hydraulic pressure and renin release in dogs.

The present study was designed to analyze quantitatively the effects of a wide range of endothelin-1 levels on renal hemodynamics and renin release in the canine nonfiltering kidney, including their effects on glomerular hydraulic pressure. Intrarenal infusion of endothelin-1 produced dose-dependent reductions in renal blood flow, but it did not affect glomerular hydraulic pressure until the infused dose reached high rates. At the rate of 1.0 ng/kg per minute, endothelin-1 reduced renal blood flow by 23% (p < 0.01), whereas glomerular hydraulic pressure was not significantly changed from 68.1 +/- 1.3 to 67.4 +/- 1.2 mm Hg. However, with a higher rate of endothelin-1 infusion (5.0 and 10.0 ng/kg per minute), glomerular hydraulic pressure fell to 59.5 +/- 1.3 and 51.5 +/- 1.8 mm Hg (p < 0.01), whereas renal blood flow was reduced from 154.5 +/- 15 to 83.0 +/- 9.5 and 53.5 +/- 9.9 mL/min, respectively. Endothelin-1 infusion also produced an inhibitory effect on renin release. With infusion at 1.0 ng/kg per minute, renin release fell from the control level of 47.9 +/- 5.6 to 26.6 +/- 4.9 units/min per gram kidney weight (p < 0.01), and it fell further to 16.1 +/- 4.3 units/min per gram kidney weight with infusion at 10.0 ng/kg per minute. In summary, endothelin-1 infusion did not affect glomerular hydraulic pressure despite a fall in renal blood flow at low doses, but at high doses it reduced both, suggesting that endothelin-1 exerts separate, dose-dependent effects on preglomerular and postglomerular resistances.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Repair of peripheral nerve defects by controlled distraction: a preliminary study.

Five cats underwent a 3.0-cm removal of their ulnar nerves followed by delayed repair. One limb received a standard cable grafting procedure, and the other side had the proximal nerve stump lengthened by controlled distraction and a subsequent direct anastomosis. Histological examination of the lengthened nerves revealed better quality than the grafted nerves in all cats. Nerve conduction velocity of the lengthened side was greater than the graft side in three cats. It appears that this technique of nerve lengthening and direct repair might have clinical applicability.

Anastomosis, Surgical↗
PubMed1992

T-cell activation by the CD28 ligand B7 is required for cardiac allograft rejection in vivo.

Organ graft rejection is a T-cell-dependent process. The activation of alloreactive T cells requires stimulation of the T-cell receptor/CD3 complex by foreign major histocompatibility complex (MHC)-encoded gene products. However, accumulating evidence suggests that, in addition to T-cell receptor occupancy, other costimulatory signals are required to induce T-cell activation. Previously, the CD28 receptor expressed on T cells has been shown to serve as a surface component of a signal transduction pathway that can provide costimulation. In vitro, interaction of CD28 with its natural ligand B7 expressed on the surface of activated B cells or macrophages can act as a costimulus to induce proliferation and lymphokine production in antigen receptor-activated T cells. We now report evidence that stimulation of T cells by the CD28 ligand B7 is a required costimulatory event for the rejection of a MHC-incompatible cardiac allograft in vivo. These results demonstrate that the B7/CD28 activation pathway plays an important role in regulating in vivo T-cell responses.

Animals↗