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Biomedical subjects

H Shen

Publications and source records attributed to H Shen.

At least 271 records · Page 15Linked to original sources
PubMed1996

Molecular cloning of prohormone convertase 1 from the atrial gland of Aplysia.

We have screened an Aplysia atrial gland cDNA library using a prohormone convertase (PC)1 probe prepared by polymerase chain reaction (PCR) and have isolated an Aplysia PC1-related full-length 3.6-kb cDNA clone. The cDNA sequence (3,565 bp) encoded a putative preproendoprotease (APC1) of 703 amino acid residues that showed considerable sequence identity with other eukaryotic PC1s, and indicated a high degree of sequence identity with an Aplysia nervous system PC sequence (aPC1B). Northern blot analysis of atrial gland RNA identified two APC1 transcripts of 3.9 kb and 5.0 kb. APC1 is a candidate PC that may play an important role in the processing of egg-laying hormone (ELH)-related precursors in atrial gland secretory cells and represents one of the first examples of PC1 expression in an exocrine tissue.

Animals↗
PubMed1996

Alpha-2 adrenoceptor agonists decrease cyclic guanosine 3',5'-monophosphate in the mouse brain.

BACKGROUND: In the central nervous system neurotransmitters, drugs or conditions that excite increase cyclic guanosine 3',5'-monophosphate (cGMP), an effect mediated by the neuromodulator nitric oxide, whereas those that sedate decrease cGMP. Volatile anesthetics were shown to decrease cerebellar cGMP, an effect that correlates with their anesthetic and anticonvulsant effect. Because alpha-2 adrenoceptor agonists have anesthetic properties, the role of the nitric oxide-cGMP pathway in the action of the alpha-2 adrenoceptor agonists clonidine and dexmedetomidine was investigated. METHODS: Groups of mice were given, intraperitoneally, one dose of either 30-600 micrograms/kg clonidine, or 3-300 micrograms/kg D-medetomidine (dexmedetomidine) or L-medetomidine. The alpha-2 adrenoceptor antagonists, 0.3-5 mg/kg yohimbine or 1 mg/kg atipamezole, 1 mg/kg of the alpha-1 antagonist prazosin, and 10-300 mg/kg of the nitric oxide synthase inhibitors, N omega-nitro-1-arginine methylester and N omega-nitro-1-arginine, were given 10-20 min before the agonist. The mice were killed by microwave radiation focused to the head. Cyclic GMP was measured by radioimmunoassay in deproteinized extracts from different brain areas. RESULTS: Clonidine and dexmedetomidine, at sedative doses, dose-dependently decreased cerebellar cGMP (ED50: 100 and 50 micrograms/kg for clonidine and dexmedetomidine, respectively). This effect was inhibited by yohimbine and atipamezole, but not by prazosin, confirming the alpha-2 nature of the response to the agonists. L-medetomidine, which has no sedative/hypnotic effect, did not decrease cGMP. Pretreatment of the mice with a maximum dose of 100 mg/kg of a nitric oxide synthase antagonist abolished the cGMP response to the agonists. Similar results were obtained in the cerebral cortex, hippocampus and caudate nucleus. CONCLUSIONS: The results suggest that the nitric oxide-cGMP pathway is an effector system coupled to the alpha-2 adrenoceptor mediating sedation.

Adrenergic alpha-2 Receptor Agonists↗
PubMed1996

Antiviral cytotoxic T-cell memory by vaccination with recombinant Listeria monocytogenes.

Listeria monocytogenes is a facultative intracellular bacterium that is able to escape phagocytic vesicles and replicate in the cytoplasm of infected cells. As with viral vectors, this intracytoplasmic life cycle provides a means for introducing foreign proteins into the major histocompatibility complex class I pathway of antigen presentation. Using recombinant L. monocytogenes (rLM) strains expressing the full-length nucleoprotein (NP) or a single cytotoxic T-lymphocyte (CTL) epitope from lymphocytic choriomeningitis virus (LCMV), we analyzed antiviral CTL responses induced by rLM vaccination. After vaccination, rLM was cleared from the host within 7 days while inducing an LCMV-specific ex vivo CD8+ effector CTL response. Virus-specific CTL memory was maintained for 6 months postvaccination, as demonstrated by vigorous secondary CTL responses after in vitro stimulation. A single immunization with rLM that expressed either the full-length NP gene or the CTL epitope alone resulted in LCMV NP-specific CTL precursor frequencies of approximately 1/10(4) CD8+ T cells. A second rLM vaccination resulted in enhanced virus-specific CTL activity and in vitro proliferation. rLM-vaccinated mice were protected against chronic viral infection by an accelerated virus-specific memory CTL response. These mice cleared infectious virus as well as viral antigen, suggesting that sterilizing immunity was achieved. In contrast to mice that received wild-type LM, rLM-vaccinated mice were protected from virally induced immunosuppression and splenic atrophy associated with chronic LCMV infection. The ability to elicit long-term cell-mediated immunity is fundamental in designing vaccines against intracellular pathogens, and these results demonstrate the efficacy of recombinant LM vaccination for inducing protective antiviral CTL memory.

Animals↗
PubMed1996

Violence and injury in marital arguments: risk patterns and gender differences.

OBJECTIVES: Community-based research on violence against women typically focuses on marital arguments rather than on resulting injuries. This study investigated patterns of victimization, violence perpetration, and injury in marital arguments. METHODS: Data from the National Survey on Families and Households and binomial and multinomial logit models were used to analyze characteristics of those who experienced physical violence, as well as to determine who was the perpetrator and who was the victim. RESULTS: Men and women reported similar behaviors during verbal arguments. Young persons, urban dwellers, the less educated, those with low incomes, and Blacks were more likely to report that there had been physical violence in their marriages in the past year. Ethnicity, income, education, and number and age of children at home were not associated consistently with injury of the wife, the husband, or both. CONCLUSIONS: Persons who report physical violence in their marriage are very similar to those who are at increased risk of interpersonal violence in general. The co-occurrence of street and other nonfamily violence with spousal violence may be a fruitful area for future research.

Adolescent↗
PubMed1996

Homicide risk among immigrants in California, 1970 through 1992.

According to the death certificates of the 65,510. California residents who died of homicide from 1970 through 1992, foreign-born persons are overrepresented in the homicides of California residents. Analysis of homicide data for 15- to 34-year-olds (n = 38,774), who account for a majority of all homicide victims indicated that immigrant-to-nonimmigrant risk patterns differed by ethnicity and across time. During the 23-year study period, foreign-born Whites, Hispanics, and Asians and others were at significantly higher risk and foreign-born Blacks were at a statistically similar risk of homicide compared with their US-born counterparts (risk ratio = 2.12, 1.24, 1.72, and 0.60, respectively).

Adolescent↗
PubMed1996

Youth suicide trends in California: an examination of immigrant and ethnic group risk.

Although immigrants are in better health than the U.S.-born population according to a variety of indicators, little research has investigated current foreign-born/U.S.-born differentials in suicide. A review of 32,928 California death certificates from 1970 to 1992 indicates that although foreign-born persons are consistently underrepresented in the suicide deaths of 15- to 34-year-olds (risk ratio = 0.60), any foreign-versus U.S.-born difference by ethnicity appears to be decreasing. Specifically, although Hispanics born outside the United States consistently are at significantly lower risk of suicide than U.S.-born Hispanics, the discrepancy between the two groups has diminished over time. And, in a comparable trend, non-Hispanic white persons born outside the United States were at higher risk of suicide than their U.S.-born counterparts until 1990, when their risk became similar. Black and Asian/other foreign- and U.S.-born persons have been at statistically similar risk since 1970. A man using a firearm at home was the typical pattern for both the foreign- and U.S.-born.

Adolescent↗
PubMed1996

[Expression of cDNA of human chorionic gonadotropin beta-subunit (beta-hCG) cDNA in insect cells and effect of expressed product on mouse lymphocytes in vitro].

Expression vector pVL 1393-hCG beta containing beta-hCG cDNA has been constructed using an unfused protein nuclear polyhedrosis virus (AcNPV) expression vector. The insect cells (Sf 9) were cotransfected by the expression vector and nuclear polyhedrosis virus genomic DNA, and recombinant virus AcNPV-hCG beta was screened out, beta-hCG cDNA was expressed in insect cells infected by recombinant virus and recombinant beta-hCG (r beta-hCG) was secreted into medium. The purity of r beta-hCG, purified by immuno-affinity chromatography, was about 90% and the molecular weight of r beta-hCG was 22,500 Da. Like hCG, r beta-hCG suppressed significantly proliferation of induced lymphocytes, as well as production of IL-2 to some extent, on a parallel with suppression of lymphoproliferation.

Animals↗
PubMed1996

[Comparison of local antigen-specific IgA responses with serum IgA response after intrapulmonary antigen immunization in healthy subjects].

OBJECTIVE: To observe local lung and serum antigen-specific IgA response after local lung antigen immunization (LLI). METHODS: 11 healthy subjects were immunized with keyhole limpet hemocyanine (KLH) through bronchoscopy. 10-14 days after immunization, IgA responses were obversed in bronchoalveolar lavage fluids (BALF) and serum. RESULTS: LLI induced anti-KLH IgA response in immunized BALF and serum, and both were polymeric IgA. Anti-KLH IgA2/IgA1 ratios were greater in immunized BALF than in serum. Anti-KLH IgA activity in immunized BALF was associated with secretory component (SC), but in serum was not correlated with SC. CONCLUSIONS: LLI could induce local antigen-specific IgA production. There were markedly differences between the structure and subclass distribution of antigen-specific IgA in immunized BALF and serum.

Adjuvants, Immunologic↗
PubMed1996

[Cloning and identification of recombinant cDNA to a rabbit oviductin "DPF-1"].

A recombinant cDNA library to polyA + RNA isolated from rabbit oviduct epithelial cells was constructed, and screened with a polyclonal antibody against DPF-1 (64 kDa). 4 immunopositive plaques (DPF-1.1, DPF-1.2, DPF-1.3 and DPF-1.4) were purified. The polyclonal antibodies were epitope-selected respectively against the fused proteins produced by these positive recombinant plaques. Identification of recombinant clones by epitope selection revealed that the epitope-selected antibodies from DPF-1.1, DPF-1.2 and DPF-1.3 could recognise not only DPF-1, but 44 kDa protein also (Fig. 2). By using EcoRI-Not1 digestion method, the insert cDNA fragment size of these three recombinants was revealed to be 0.8 kb, 1.2 kb and 1.2 kb respectively (Fig. 3). These cDNA fragments were then isolated and subcloned into pBluescriptKS, and recombinant plasmids (pDPF-1.1, pDPF-1.2 and pDPF-1.3) were constructed (Fig. 4). Dot blot hybridization with a 32p-labeled 1.2 Kb-insert of cDNA from pDPF-1.3 indicated that these recombinant plasmids could cross-hybridized (Fig. 5), further indicating that they all possessed a common nucleic acid sequence. Dot and Northern blotting analysis of total RNA prepared from eight different tissues (skeleton muscle, heart, kidney, oviduct, liver, spleen, lung and small intestine) showed that the gene encoding DPF-1 was expressed specifically in the oviduct tissue (Fig. 6, Fig. 7).

Animals↗
PubMed1996

[Preliminary studies on the rabbit oviductin "DPF-1"].

Anti-rabbit 64 kDa oviductin (named Development Promoting Factor-1, DPF-1) antibody could inhibit totally the early development of mouse fertilised eggs cultured in the conditioned medium derived from the rabbit oviduct mucosa epithelial cells, revealed that DPF-1 synthesized and secreted from rabbit oviduct mucosa has a function to overcome the developmental block of early mouse embryos. It seems that DPF-1 consists of a group of polypeptide isoforms, since its isoelectric points are ranging from 7.2 to 8.1 (Fig. 3). The synthesis and secretion of DPF-1 was not dependent on either 17 beta-estradiol or progesterone (Fig. 7), it can pass through zona pellucida easily and associate tightly with the early embryonic cell membrane (Fig. 6). By using Western blotting method, we found that DPF-1 was not appeared in the tissues of liver, heart, lung, spleen, uterus, ovary, small intestine, skeleton muscle and brain, but in that of oviduct (Fig. 4): some DPF-1 homologous molecules were also revealed in the oviduct tissues of mouse and golden hamster, their apparent molecular weights were 32 kDa, 72 kDa in mouse, and 49 kDa, 68 kDa in golden hamster (Fig. 5). Results obtained from the in vivo anti-fertility experiment, namely to analyse the anti-fertility effect in adult female mice after active immunization with DPF-1, showed that the fertility decreased significantly as compared to those of controls (p < 0.01) (Table 1). DPF-1 and its in vivo "loss of function" evidence we obtained will encourage us to study the mechanism of DPF-1 in overcoming the developmental block of early embryos, and its role in transition from maternal to embryonic control of early development.

Animals↗
PubMed1995

Influence of ethacrynic acid on glutathione S-transferase pi transcript and protein half-lives in human colon cancer cells.

Ethacrynic acid (EA) is a plant phenolic acid that is both an inhibitor and an inducer of glutathione S-transferase (GST) activity. To determine contributory factors in the increased GST activity caused by EA treatment, human colon carcinoma HT29 cells were compared with a cloned EA-resistant population (HT6-8) maintained in medium containing 72 microM EA. Several factors are involved in the increased expression of GST pi in HT6-8. For example, nuclear run-on experiments showed an approximately 2-fold increase in the rate of transcription of GST pi. In addition, the half-life of GST pi transcript was increased from 4.1 (wild type, HT29, HT4-1) to 8.4 hr. The half-life of GST pi protein was 1-2 hr in HT4-1 cells versus 8-9 hr in HT6-8 cells. When either human ovarian carcinoma cells (SKOV3) or human prostatic carcinoma cells (DU145) were treated with EA, the half-life of the GST pi transcript was also increased. The transcript half-lives of another thiol-metabolism enzyme, gamma-glutamylcysteine synthetase (gamma-GCS), and a phase II detoxification enzyme, dihydrodiol dehydrogenase (DDH), were also increased in HT6-8, SKOV3 and DU145 cells treated with EA. However, the half-lives of transcripts from "housekeeping genes," such as glyceraldehyde 3-phosphate dehydrogenase (G3PDH), beta-actin and beta-tubulin, were not changed in these cell lines following EA. Apparently, a number of coordinated factors are involved in EA-enhanced expression of GST pi and other detoxification enzymes.

Colonic Neoplasms↗
PubMed1995

Detection of exocytosis at individual pancreatic beta cells by amperometry at a chemically modified microelectrode.

Amperometry at a carbon fiber microelectrode modified with a composite of ruthenium oxide and cyanoruthenate was used to monitor chemical secretions of single pancreatic beta cells from rats and humans. When the insulin secretagogues glucose, tolbutamide, and K+ were applied to the cell, a series of randomly occurring current spikes was observed. The current spikes were shown to be due to the detection of chemical substances secreted from the cell. Chromatography showed that the primary secreted substance detected by the electrode was insulin. The current spikes were strongly dependent on external Ca2+, had an average area that was independent of the stimulation method, and had an area distribution which corresponded to the distribution of vesicle sizes in beta cells. It was concluded that the spikes were due to the detection of concentration pulses of insulin secreted by exocytosis.

Animals↗
PubMed1995

Cellobiohydrolase B, a second exo-cellobiohydrolase from the cellulolytic bacterium Cellulomonas fimi.

The gene cbhB from the cellulolytic bacterium Cellulomonas fimi encodes a polypeptide of 1090 amino acids. Cellobiohydrolase B (CbhB) is 1037 amino acids long, with a calculated molecular mass of 109765 Da. The enzyme comprises five domains: an N-terminal catalytic domain of 643 amino acids, three fibronectin type III repeats of 97 amino acids each, and a C-terminal cellulose-binding domain of 104 amino acids. The catalytic domain belongs to family 48 of glycosyl hydrolases. CbhB has a very low activity on CM-cellulose. Viscometric analysis of CM-cellulose hydrolysis indicates that the enzyme is an exoglucanase. Cellobiose is the major product of hydrolysis of cellulose. In common with two other exoglycanases from C. fimi, CbhB has low but detectable endoglucanase activity. CbhB is the second exo-cellobiohydrolase found in C. fimi. Therefore, the cellulase system of C. fimi resembles those of fungi in comprising multiple endoglucanases and cellobiohydrolases.

Actinomycetales↗
PubMed1995

Recombinant Listeria monocytogenes as a live vaccine vehicle for the induction of protective anti-viral cell-mediated immunity.

Listeria monocytogenes (LM) is a Gram-positive bacterium that is able to enter host cells, escape from the endocytic vesicle, multiply within the cytoplasm, and spread directly from cell to cell without encountering the extracellular milieu. The ability of LM to gain access to the host cell cytosol allows proteins secreted by the bacterium to efficiently enter the pathway for major histocompatibility complex class I antigen processing and presentation. We have established a genetic system for expression and secretion of foreign antigens by recombinant strains, based on stable site-specific integration of expression cassettes into the LM genome. The ability of LM recombinants to induce protective immunity against a heterologous pathogen was demonstrated with lymphocytic choriomeningitis virus (LCMV). LM strains expressing the entire LCMV nucleoprotein or an H-2Ld-restricted nucleoprotein epitope (aa 118-126) were constructed. Immunization of mice with LM vaccine strains conferred protection against challenge with virulent strains of LCMV that otherwise establish chronic infection in naive adult mice. In vivo depletion of CD8+ T cells from vaccinated mice abrogated their ability to clear viral infection, showing that protective anti-viral immunity was due to CD8+ T cells.

Amino Acid Sequence↗
PubMed1995

Transient acidosis induces delayed neurotoxicity in cultured hippocampal slices.

It remains unknown if tissue acidosis contributes to neuronal loss during cerebral ischemia. We report that brief intracellular acidification (pH 6.62) results in delayed neuronal loss in cultured hippocampal slices. Cell loss was located primarily in stratum pyramidale and the hilus suggesting that neurons were preferentially damaged. Removal of molecular oxygen greatly attenuated cell loss suggesting that generation of reactive oxygen species may underlie acidosis-induced toxicity. These data suggest that acidosis and incomplete anoxia contributes to the delayed neuronal loss in the ischemic penumbra.

Acidosis↗