Biomedical subjects

H Lin

Publications and source records attributed to H Lin.

At least 289 records · Page 16Linked to original sources

PubMed1997

Electron microscopic localization of lacZ expression in the proximal convoluted tubular cells of the kidney in transgenic mice carrying chimeric erythropoietin/lacZ gene constructs.

Regulated expression of the erythropoietin (EPO) gene in the adult kidney plays a key role in the regulation of erythropoiesis. However, uncertainty exists regarding the type of kidney cells involved in EPO gene expression. We previously showed by light microscopy that the lacZ reporter gene is expressed and inducible by hypoxia/anemia in the proximal convoluted tubular (PCT) cells of the kidneys of transgenic mice carrying the 5'-lacZ construct, in which the lacZ gene was placed downstream of a 7.0-kb mouse EPO gene segment containing 6.5 kb of the 5'-flanking sequence. We, report here the light and transmission electron microscopic examination of lacZ expression in the kidneys of transgenic mice carrying the 5'-lacZ construct and two additional constructs carrying the 6.5-kb 5'-flanking sequence with the body of the gene alone, or along with the 1.2-kb 3'-flanking sequence. The electron microscopic analyses unequivocally demonstrated that lacZ under the regulatory control of the 6.5-kb 5'-flanking sequence with or without the body of the gene and the 1.2-kb 3'-flanking sequence was expressed predominantly in the proximal convoluted tubular cells of the kidney following hypoxia induction.

Anemia↗

PubMed1997

Phase-directed therapy and cardiac xenograft survival.

Xenotransplant rejection is facilitated not only by T cell upregulation but also by endothelial activation and B cell/antibody mechanisms, which standard immunosuppression is unable to overcome and xenorejection ensues. However, therapy directed specifically at each phase of xenorejection may improve xenograft survival. To study this we used a heterotopic cardiac xenotransplant mode (Syrian hamster to Lewis rat). Controls had no immunotherapy. Xenorecipients received cyclosporine to restrict T cellular response/development or cyclophosphamide, an antiproliferative, to reduce xenoreactive clones and antibody/complement injury, or anti-TNF antibody to alter cytokine cascades and endothelial activation/inflammation. Further xenorecipients received combinations. While single modalities alone did not enhance survival, combinations appeared to be at least additive in vivo, suggesting that therapy directed at specific phases of xenorejection may prove useful.

Animals↗

PubMed1997

CD28 blockade alters cytokine mRNA profiles in cardiac transplantation.

BACKGROUND: T-cell response to alloantigen is dependent on T-cell receptor activation and costimulation through the CD28 receptor, because T-cell receptor activation alone is insufficient for optimal immune response. The CD28 receptor on helper T cells interacts with its ligand B7 on activated B cells-macrophages as costimulus to support T-cell activity. CTLA4Ig is a recombinant inhibitor of CD28 receptor activation. In vivo studies with a rat major histocompatibility complex mismatch heterotopic cardiac transplant model demonstrate that CTLA4Ig prolongs cardiac allograft survival. This CTLA4Ig survival benefit is enhanced with prior donor-specific antigen exposure. METHODS: To investigate CTLA4Ig mechanisms, we examined the differential expression of B7 and cytokine mRNAs for interferon-gamma (IFN-gamma), interleukin-2 (IL-2), IL-4, and IL-10 (Th1 or Th2 activation) in cardiac allografts after treatment with CTLA4Ig and donor-specific antigen exposure versus conventional immunotherapy (cyclosporine, cyclophosphamide, or antilymphocyte serum). In the above major histocompatibility complex mismatch model, hearts (on day 5 after transplantation at peak rejection) had cytokine mRNA expression determined by semiquantitative reverse transcriptase-polymerase chain reaction. RESULTS: Inhibition of B7 expression was observed in CTLA4Ig animals. Expression of IL-2 and IFN-gamma was near undetectable in CTLA4Ig and cyclophosphamide rats but was only moderately reduced by cyclosporine and antilymphocyte serum. IL-4 mRNA expression was reduced equally in all animals. Finally, IL-10 levels were unchanged by CTLA4Ig but were decreased by other therapies. CONCLUSIONS: The beneficial effect of CTLA4Ig, inhibiting expression of B7, alters Th1 cytokines IL-2 and IFN-gamma, with a resultant predominant IL-10 driven, Th2 tolerogenic response.

Abatacept↗

PubMed1997

Physiological basis for long life span.

A collection of clinical data is reported on nonagenarians in comparison to an 'average' population of younger age. The results of these clinical data indicated that a vital physiological basis for long life span probably existed. The basis include a better micro-blood-flow state, a better cardiac, immune (nature killer cell activity), adrenocortical, hepatic and renal function, and a higher level of high density lipoprotein cholesterol. It is suggested that the method, including Chinese traditional medicine, to improve the micro-blood-flow, nature killer cell activity, high density lipoprotein cholesterol and vital organ function may be beneficial for life preservation and aging retarding.

Aged↗

PubMed1997

Neuroblasts: a model for the asymmetric division of stem cells.

The ability of stem cells to self-renew has hung been attributed to an asymmetry in division that generates one daughter cell identical to the mother and another cell committed to differentiation. Recent studies on neuroblasts, a group of neural stem cells responsible for generating various neurons and glial cells in the central nervous system, have revealed exciting mechanisms that underlie self-renewing asymmetric division. Several important localized cell fate determinants have been characterized, and their segregation mechanism has been explored in the context of cytoskeletal organization, cell-cycle type progression, cytokinesis and mitotic orientation. These findings are illuminating in understanding the general mechanism of stem cell division.

Animals↗

PubMed1997

Differential expression of NADPH-diaphorase between electrophysiologically-defined classes of pyramidal neurons in rat ventral subiculum, in vitro.

The subiculum is the major output region of the hippocampal formation. We have studied pyramidal neurons in slices of rat ventral subiculum to determine if there is a correlation between nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) activity and electrophysiological phenotype. The majority of NADPH-d-positive pyramidal neurons were found in the superficial cell layer (i.e. nearest to the hippocampal fissure) of the subiculum and appreciable NADPH-d activity was absent from pyramidal neurons in area CA1. This distribution of NADPH-d activity was mimicked by that of immunoreactivity for the neuronal isoform of nitric oxide synthase. Subicular pyramidal neurons were classified, electrophysiologically, as intrinsically burst-firing or regular spiking. After electrophysiological characterization, neurons were filled with Neurobiotin and revealed using fluorescence immunocytochemistry. The slices containing these neurons were also processed for NADPH-d. NADPH-d activity was found in six out of eight regular spiking neurons but was not found in any of 13 intrinsically burst-firing neurons (P=0.0008, Fisher's Exact Test). We conclude that in rat ventral subiculum, NADPH-d activity is present in a proportion of pyramidal neurons and indicates the presence of the neuronal isoform of nitric oxide synthase. Furthermore, amongst pyramidal neurons, NADPH-d activity is distributed preferentially to those with the regular spiking phenotype. The distribution of regular spiking neurons suggests that they may not be present to the same extent in all subicular output pathways. Thus, the actions of nitric oxide may be relatively specific to particular hippocampal connections.

Animals↗

PubMed1997

Identification of a candidate tumour suppressor gene, MMAC1, at chromosome 10q23.3 that is mutated in multiple advanced cancers.

Deletions involving regions of chromosome 10 occur in the vast majority (> 90%) of human glioblastoma multiformes. A region at chromosome 10q23-24 was implicated to contain a tumour suppressor gene and the identification of homozygous deletions in four glioma cell lines further refined the location. We have identified a gene, designated MMAC1, that spans these deletions and encodes a widely expressed 5.5-kb mRNA. The predicted MMAC1 protein contains sequence motifs with significant homology to the catalytic domain of protein phosphatases and to the cytoskeletal proteins, tensin and auxilin. MMAC1 coding-region mutations were observed in a number of glioma, prostate, kidney and breast carcinoma cell lines or tumour specimens. Our results identify a strong candidate tumour suppressor gene at chromosome 10q23.3, whose loss of function appears to be associated with the oncogenesis of multiple human cancers.

Amino Acid Sequence↗

PubMed1997

The role of cyclic AMP production, calcium channel activation and enzyme activities in the inhibition of testosterone secretion by amphetamine.

1. The aim of this study was to investigate the mechanism by which amphetamine exerts its inhibitory effect on testicular interstitial cells of male rats. 2. Administration of amphetamine (10(-12)-10(-6) M) in vitro resulted in a dose-dependent inhibition of both basal and human chorionic gonadotropin (hCG, 0.05 iu ml(-1))-stimulated release of testosterone. 3. Amphetamine (10(-9) M) enhanced the basal and hCG-increased levels of adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation in vitro (P<0.05) in rat testicular interstitial cells. 4. Administration of SQ22536, an adenylyl cyclase inhibitor, decreased the basal release (P<0.05) of testosterone in vitro and abolished the inhibitory effect of amphetamine. 5. Nifedipine (10(-6) M) alone decreased the secretion of testosterone (P<0.01) but it failed to modify the inhibitory action of amphetamine (10(-10)-10(-6) M). 6. Amphetamine (10(-10)-10(-6) M) significantly (P<0.05 or P<0.01) decreased the activities of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), P450c17, and 17-ketosteroid reductase (17-KSR) as indicated by thin-layer chromatography. (t.l.c.). 7. These results suggest that increased cyclic AMP production, decreased Ca2+ channel activity and decreased activities of 3beta-HSD, P450c17, and 17-KSR are involved in the inhibition of testosterone production induced by the administration of amphetamine.

17-Hydroxysteroid Dehydrogenases↗

PubMed1997

Primary structure and functional expression of heavy- and light-chain variable region genes of a monoclonal antibody specific for human fibrin.

The immunoglobulin heavy- and light-chain variable region (VH and VK) genes were isolated from 8E5 hybridoma cells, which secreted monoclonal antibody against human fibrin by RT-PCR. An expression vector pOPE51-8E5 was constructed for the recombinant VH-VK scFv expression. The primary sequence of the variable regions was determined. Expression product was found in the periplasmic space and inclusion bodies by SDS-PAGE and immunoblotting. It was a 30 KDa single chain fragment (scFv) with the antigen-binding specificity of the parental monoclonal antibody. A light chain shuffling with an unspecific VL did not result in a loss of fibrin binding specificity.

Amino Acid Sequence↗

PubMed1997

Construction and characterization of retroviral vectors for interleukin-2 gene therapy.

Several investigators have employed interleukin-2 (IL-2) gene transfer to enhance the immunogenicity of tumor cell vaccines. We describe in this report the construction and characterization of retroviral vectors for IL-2 gene therapy. Human IL-2 cDNA with a chimeric rat preproinsulin/IL-2 DNA leader sequence was subcloned into the pLXSN (long terminal repeat promoter) and pLNCX (cytomegalovirus [CMV] promoter) vectors to generate the plasmids pLXSN-iIL2 and pLNCX-iIL2, respectively. Human IL-2 cDNA with a chimeric human tissue factor/IL-2 DNA leader sequence was utilized to construct the vector pLXSN-tIL2. The levels of IL-2 secreted by transduced tumor cells and fibroblasts were evaluated by enzyme-linked immunosorbent assay (ELISA) of culture supernatants and compared with those of normal peripheral blood mononuclear cells (PBMC) activated in vitro with calcium ionophore and phorbol 12-myristate 13-acetate. The highest levels of IL-2 secreted by transduced tumor cells (760 units/10(6) cells/24 h), adult fibroblasts (625 units/10(6) cells/24 h), and embryonic fibroblasts (3,975 units/10(6) cells/24 h) were 150- to 1,000-fold higher than than secreted by the activated PBMC (4 units/10(6) cells/24 h). Similar levels of IL-2 were expressed by human fibroblasts transduced with pLXSN vectors employing the preproinsulin (pLXSN-iIL2) or tissue factor (pLXSN-tIL2) leader sequences (range in IL-2 units/10(6) cells/24 h pLXSN-iIL2 = 375-625 vs. pLXSN-tIL2 = 90-440). Because IL-2-transduced cells for clinical applications are generally irradiated to prevent cellular proliferation, we evaluated the effects of radiation on IL-2 production. Radiation doses between 1,500 and 10,000 cGy resulted in gradual decreases in IL-2 secretion by transduced cells. The range of the decrease in IL-2 secretion was 7-11% by day 7, 0-29% by day 14, and 25-50% by day 35. For clinical applications, stable production of the vector in high concentrations is an important consideration. The retroviral vector pLXSN-tIL2 produced the highest viral titer and was chosen for further characterization. Southern blot analysis of SacI-digested genomic DNA from the LXSN-tIL2 producer cell line and SacI-digested pLXSN-tIL2 plasmid DNA revealed the expected 3.2-kbp fragment, suggesting the absence of transgene rearrangement and the suitability of this vector as a candidate for clinical applications.

3T3 Cells↗

PubMed1997

The tao of stem cells in the germline.

Germline stem cells (GSCs) are the self-renewing population of germ cells that serve as the source for gametogenesis. GSCs exist in diverse forms, from those that undergo strict self-renewing asymmetric divisions in Drosophila to those that maintain their population by balancing between mitosis and differentiation in Caenorhabditis elegans. Most vertebrate spermatogonial GSCs appear to adopt an intermediate strategy. In most animals, GSCs are established during preadult gonadogenesis following the proliferation and migration of embryonic primordial germ cells. GSCs produce numerous gametes throughout the sexually active period of adult life. The establishment and self-renewing division of GSCs are controlled by extracellular signals such as hormones from the hypothalamic-pituitary axis and local interactions between GSCs and their neighboring cells. These extracellular signals may then influence differential gene expression, cell cycle machinery, and cytoskeletal organization of GSCs for their formation and/or divisional asymmetry. In addition, the GSC mechanism is related to that for germline and sex determination. Current knowledge has provided a solid framework for further study of GSCs and stem cells in general.

Animals↗

PubMed1997

Reduction in renin release and renal vascular resistance by H(+)-K(+)-ATPase inhibition.

Results from previous experiments in our laboratory suggested that a H(+)-K(+)-adenosinetriphosphatase (H(+)-K(+)-ATPase) was present in vascular smooth muscle. Here we analyzed the effects on regulation of renal vascular function in anesthetized dogs of inhibition of the H(+)-K(+)-ATPase by a highly specific inhibitor, NC-1300-B. The compound was injected intravenously, 15 mg/kg (5.8 x 10(-5) mol wt/kg), into one group of six dogs, whereas saline was given to a control group of eight. Renal function was measured at controlled levels of renal perfusion pressure ranging from 110 to 60 mmHg. Renal blood flow (RBF) was higher in the treated group at all levels of perfusion pressure; at 70 mmHg, the treated group RBF was 5.85 +/- 1.00 ml.min-1.g kidney wt-1, 71% greater than that of the control group. Glomerular filtration rate (GFR) mean values of the two groups were not significantly different at any perfusion pressure level. Renin release was inhibited (P < 0.01) by H(+)-K(+)-ATPase inhibition; at 90 mmHg, the control group mean was 14.3 +/- 4.3 units, 4.47 times greater than the treated group mean of 3.2 +/- 1.6 units. H(+)-K(+)-ATPase inhibition with NC-1300-B causes profound renal vasodilation and inhibition of renin release without affecting regulation of GFR.

Animals↗

PubMed1997

A novel group of pumilio mutations affects the asymmetric division of germline stem cells in the Drosophila ovary.

Germline stem cells play a pivotal role in gametogenesis; yet little is known about how they are formed, how they divide to self-renew, and how these processes are genetically controlled. Here we describe the self-renewing asymmetric division of germline stem cells in the Drosophila ovarian germline, as marked by the spectrosome, a cytoplasmic structure rich in membrane skeletal proteins. The ontogeny of the spectrosome marks the lineage of germline stem cells. We identified two new groups of mutations in which the divisional asymmetry is disrupted. The first, which we refer to as ovarette (ovt) mutations, was shown to correspond to a novel class of mutations in the pumilio locus. Since pumilio is known to posttranscriptionally repress the expression of target genes at earlier stages of germ cell development, our results suggest that a similar activity is needed to maintain germ line stem cells. We have also identified a second and novel gene, piwi, whose mutations abolish germline stem cell division.

Animals↗

PubMed1997

[The significance of detecting Epstein-Barr virus BNLF1 fragment and its expression in Hodgkin's disease in the Guangdong area].

OBJECTIVE: To study the association between Epstein-Barr virus (EBV) and lymphoma. METHODS: PCR, in situ hybridization and immunohistochemistry were used to detect the presence of EBV in 51 cases of Hodgkin's disease in the Guang dong area. RESULTS: The detection rate of EBV-BNLF1 fragment by PCR was 80.4%, significantly higher than that of reactive hyperplasia of lymph nodes (RHLN). Cloning and sequence analysis revealed the PCR product to be BNLF1 fragment, but no mutation was found. In situ hybridization (ISH) demonstrated EBV in the nuclei of malignant and non-malignant cells in 15 of the 41 PCR-positive cases. The expression product of BNLF1 gene-latent membrane protein (LMP1) was detected in 25 of the 51 cases of HD (49%) and the staining was restricted to the tumor cells. The detection rates of BNLF1 fragment and its expression in the 15 cases of HD under 20 years of age were much higher that those in HD over 20 years of age and RHLN of the same age group (P < 0.01). CONCLUSION: There was EBV infection and expression of its latent membrane protein in the tumor cells in half of the HD cases and may play a role in the genesis and development of HD. The results also suggest that HD in children and adolescence being more closely correlated with EBV latent infection.

Adolescent↗

PubMed1997

[The relationship between prognosis, metastasis and microvessel quantity in invasive breast carcinoma].

OBJECTIVE: To determine the prognostic value and relationship of microvessel quantity (MVQ) with PCNA, c-erbB-2, nm23-H1 and Cathepsin D in invasive breast carcinoma. METHODS: Immunohistochemical techniques (LSAB) were used to detect the expression of PCNA, c-erbB-2, nm23-H1, Cathepsin D and MVQ in 76 cases of invasive breast carcinoma. RESULTS: The mean of MVQ was 57.82 +/- 22.22 in 76 cases of invasive breast carcinoma. The expression of Cathepsin D (cancer cells), c-erbB-2 and node positive were not related to MVQ. MVQ was positively correlated to expression of Cathepsin D (stroma cells), PCNA and distant metastasis (10 years), but negatively correlated to 5 year survival. CONCLUSION: MVQ was significantly correlated to distant metastasis and survival period in invasive breast carcinoma. MVQ may be an independant prognostic indicator.

Adult↗

PubMed1997

[The significance of detecting EB virus and its products in benign and malignant lymphoepithelial lesions of the salivary glands].

OBJECTIVE: To study the relationship between EB virus and benign malignant lymphoepithelial Lesions (ELEL) and malignant lymphoepithelial lesions (MLEL). METHODS: In situ hybridization, polymeras Chain reaction (PCR) and immunohistochemical methods were used to detect EBV DNA, EBER1 and latent membrane protein 1 (LMP1) on paraffin embedded tissues of 18 MLEL cases and 14 BLEL cases. RESULTS: (1) Positive rates for Bam H1 W fragmet by PCR and EBER1 by in situ hybridization in 18 cases of MLEL were both 100%. Positive rates of EBV DNA by PCR and EBER1 by in situ hybridization in 14 cases of BLEL were both zero percent. (2) LMP1 expression was detected in 77.8% (14/18) of MLEL, EBNA2 was examined in 9 cases of MLEL and no expression was found. (3) Among the infiltrating lymphocytes studied by immunohistochemistry, T cells predominated over B cells in MLEL, B cells predominated over T cells in BLEL. (4) Of the 216 cases of salivary gland cancer, 37 cases could satisfy the criteria for MLEL. The incidence of MLEL in this group was 17.13% (37/216). CONCLUSION: Our results suggest that EBV infection may have some relationship with the genesis of MLEL.

Capsid↗

PubMed1997

[Role of endothelial-derived nitric oxide and its synthase in the development of hypoxic pulmonary hypertension in rat].

To clarify the role of endothelial-derived nitric oxide (EDNO) and its synthase (NOS) in the normal and hypertensive pulmonary vasculature, activity of endothelial NOS in the lungs, ENDO-dependent vasodilating response induced by bradykinin (BK), and cGMP content of lung tissue in normoxic and hypoxic rats were investigated. We also studied the effects of NOS inhibitor-L-NAME on the activity of NOS, cGMP content, mean pulmonary arterial pressure (mPAP) and carotid systolic arterial pressure (CAPs) in both rats. The results were as follows (1) In normoxic rats there was no NOS activity in the endothelium of small vessels (phi < or = 80 microns) and no relaxing response to BK. Long-term administration of L-NAME obviously inhibited the activity of ecNOS and cGMP content in the lungs of normoxic rats, therefore it led to the increment of CAPs but failed to elevate mPAP. (2) After hypoxic exposure for 10 days, NADPH-diaphorase (NADPH-d and ecNOS immunoreactivity turned to be positive in the endothelium of small vessels with diameter less than 80 microns. BK-induced EDNO-dependent vasodilation, the enzyme activity of cNOS and cGMP content in the lungs of hypoxic rats were significantly enhanced as compared with normoxic rats. Long-term administration of L-NAME in hypoxic rats markedly inhibited the enhancement of cNOS enzyme activity, the production of EDNO and cGMP content in rat lungs, consequently it significantly decreased mPAP but elevated CAPs obviously. These results suggest that the role of EDNO in maintaining the low basal tone of normal adult pulmonary circulation remain to be studied more precisely. The increased activity of ecNOS and the enhancement of EDNO synthesis might act to moderate the hypertension. The excess synthesis of EDNO might be toxic to the endothelium of pulmonary vessels, therefore potentiating the development of pulmonary hypertension.

Animals↗

PubMed1997

[Study on the relationship between PS2 protein expression and prognosis in invasive breast carcinoma].

OBJECTIVE: To study the relationship between the expression of PS2 protein and prognosis in the invasive breast cancer (IBC). METHOD: Using LSAB immunohistochemical method, PS2 protein expression in 86 cases of IBC was detected. RESULTS: The positive rate of PS2 protein was 66.27% (57/86) in 86 cases of IBC. Under the following 3 conditions, PS2 protein expression levels in the more-than-5-year-survival group (A) were higher than those in the less-than-5-year-survival group (B). (1) In 86 cases of IBC, the expression level was 80.55% (29/36) for Group A, Significantly different from the 56.00% (28/50) of Group B (P < 0.025). (2) In 62 cases of premenopausal patients, the corresponding data were 86.20% (25/29) and 54.54% (18/33) respectively, P < 0.005; whereas in 24 cases of postmenopausal patients, 4/7 and 58.82% (10/17) respectively, P > 0.5. (3) In 62 cases of axillary node positive patients, the expression levels for Groups A and B were 82.35% (14/17) and 55.55% (25/45) respectively, P < 0.05; while in 24 cases of axillary node negative patients, 78.94% (15/19) and (3/5) respectively, P > 0.5. CONCLUSIONS: These results suggest that the expression of PS2 protein was positively correlated with 5-year-survival in IBC, and could be considered as a prognostic predictor for breast cancer, PS2 protein expression was a useful indicator for endocrine therapy in premenopausal patients. In axillary node positive patients, the expression of PS2 protein was associated with a better prognosis.

Adult↗