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Biomedical subjects

D Chen

Publications and source records attributed to D Chen.

At least 127 records · Page 7Linked to original sources
PubMed2001

Effects of exposure to organic solvents on menstrual cycle length.

To investigate the association between organic solvent exposure and menstrual disturbance, we conducted a cross-sectional study among 1408 petrochemical workers in China. Based on an industrial hygiene evaluation, we classified the workshops according to the presence or absence of organic solvents (benzene, styrene, toluene, or xylene). We used logistic regression to estimate odds ratios and 95% confidence intervals for prolonged menstrual cycle length (oligomenorrhea: average cycle length > 35 days during the previous year) associated with the exposure. After adjustment for confounders, each additional year of work in an exposed workshop was associated with a 7% increase in oligomenorrhea (odds ratio, 1.07; 95% confidence interval, 1.00 to 1.14). Compared with no exposure, 3 or more years of exposure was associated with a 53% increase in oligomenorrhea (odds ratio, 1.53; 95% confidence interval, 1.00 to 2.34). We concluded that exposure to organic solvents is associated with a trend toward increased frequency of oligomenorrhea.

Adult↗
PubMed2001

Computer-aided virtual surgery for congenital aural atresia.

HYPOTHESIS: Computer-enhanced three-dimensional (3D) computed tomography (CT) provides accurate spatial representation of the complex surgical anatomy of congenitally atretic ears, and is superior to conventional CT for surgical planning. BACKGROUND: The surgical repair of congenital aural atresia is challenging. Conventional CT, routinely used for surgical planning, is limited in its ability to represent spatial relationships between important structures. Because of the lack of density differences between bony structures in the ear, 3D CT has thus far been useful for representing surface contour but not internal anatomy. METHODS: A two-level segmentation scheme was developed to distinguish structures in the temporal bone. 3D CT reconstructions of congenital ears were produced with a high-resolution helical scanner. An interactive tool was used to mark the ossicles and facial nerve. The segmentation scheme was used to color-enhance the ossicles and otic capsule, and render the surrounding bone translucent. "Virtual surgery" was then performed by subtracting a cylindrical volume of bone lateral to the atresia plate. The enhanced 3D CT reconstructions were correlated with intraoperative video recordings. RESULTS: In four congenital ears, computer-enhanced 3D CT was highly predictive of the actual anatomy. Surgery was avoided in two anatomically unfavorable cases. CONCLUSION: Computer-enhanced 3D CT is a major advance over conventional CT for demonstrating the complex spatial relationships in congenitally atretic ears.

Adolescent↗
PubMed2001

Automated construction of high-density comparative maps between rat, human, and mouse.

Animal models have been used primarily as surrogates for humans, having similar disease-based phenotypes. Genomic organization also tends to be conserved between species, leading to the generation of comparative genome maps. The emergence of radiation hybrid (RH) maps, coupled with the large numbers of available Expressed Sequence Tags (ESTs), has revolutionized the way comparative maps can be built. We used publicly available rat, mouse, and human data to identify genes and ESTs with interspecies sequence identity (homology), identified their UniGene relationships, and incorporated their RH map positions to build integrated comparative maps with >2100 homologous UniGenes mapped in more than one species (approximately 6% of all mammalian genes). The generation of these maps is iterative and labor intensive; therefore, we developed a series of computer tools (not described here) based on our algorithm that identifies anchors between species and produces printable and on-line clickable comparative maps that link to a wide variety of useful tools and databases. The maps were constructed using sequence-based comparisons, thus creating "hooks" for further sequence-based annotation of human, mouse, and rat sequences. Currently, this map enables investigators to link the physiology of the rat with the genetics of the mouse and the clinical significance of the human.

Algorithms↗
PubMed2001

Effects of CCK2 receptor blockade on growth parameters in gastrointestinal tract and pancreas in rats.

Gastrin has a growth-promoting effect on the oxyntic mucosa of the stomach but has been claimed also to affect other parts of the gastrointestinal tract and pancreas. This report describes the effects of the cholecystokinin, (CCK2) receptor antagonists YM022 and YF476 on various growth parameters in the gastrointestinal tract and pancreas of the rat. YM022 and YF476 were given subcutaneously in doses known to produce maximum and sustained CCK2 receptor blockade. The body weight was not affected. However, the oxyntic mucosal weight, thickness and protein and DNA contents were reduced by 15-20% already within 1-2 days and by about 30% after 4-8 weeks of CCK2 receptor blockade. Hence, the response of the oxyntic mucosa to CCK2 receptor blockade was in the form of hypotrophy (reduced protein content) and hypoplasia (reduced DNA content). There were no obvious effects of CCK2 receptor blockade on the intestine or pancreas (nor on liver, kidney or thyroid). The proton pump inhibitor omeprazole was used to induce hypergastrinaemia and was given with or without YM022. Omeprazole treatment for 4 weeks increased the oxyntic mucosal weight and thickness by 15-20%. YM022 prevented these effects. We conclude that while elevated circulating gastrin levels, acting on CCK2 receptors, exert a growth-promoting effect on the oxyntic mucosa (but not elsewhere), normal serum gastrin levels exert a mucosa-preserving effect.

Animals↗
PubMed2001

Genetic diversity of Pierce's disease strains and other pathotypes of Xylella fastidiosa.

Strains of Xylella fastidiosa isolated from grape, almond, maple, and oleander were characterized by enterobacterial repetitive intergenic consensus sequence-, repetitive extragenic palindromic element (REP)-, and random amplified polymorphic DNA (RAPD)-PCR; contour-clamped homogeneous electric field (CHEF) gel electrophoresis; plasmid content; and sequencing of the 16S-23S rRNA spacer region. Combining methods gave greater resolution of strain groupings than any single method. Strains isolated from grape with Pierce's disease (PD) from California, Florida, and Georgia showed greater than previously reported genetic variability, including plasmid contents, but formed a cluster based on analysis of RAPD-PCR products, NotI and SpeI genomic DNA fingerprints, and 16S-23S rRNA spacer region sequence. Two groupings of almond leaf scorch (ALS) strains were distinguished by RAPD-PCR and CHEF gel electrophoresis, but some ALS isolates were clustered within the PD group. RAPD-PCR, CHEF gel electrophoresis, and 16S-23S rRNA sequence analysis produced the same groupings of strains, with RAPD-PCR resolving the greatest genetic differences. Oleander strains, phony peach disease (PP), and oak leaf scorch (OLS) strains were distinct from other strains. DNA profiles constructed by REP-PCR analysis were the same or very similar among all grape strains and most almond strains but different among some almond strains and all other strains tested. Eight of 12 ALS strains and 4 of 14 PD strains of X. fastidiosa isolated in California contained plasmids. All oleander strains carried the same-sized plasmid; all OLS strains carried the same-sized plasmid. A plum leaf scald strain contained three plasmids, two of which were the same sizes as those found in PP strains. These findings support a division of X. fastidiosa at the subspecies or pathovar level.

Bacterial Typing Techniques↗
PubMed2001

Serum and mucosal immune responses to an inactivated influenza virus vaccine induced by epidermal powder immunization.

Both circulating and mucosal antibodies are considered important for protection against infection by influenza virus in humans and animals. However, current inactivated vaccines administered by intramuscular injection using a syringe and needle elicit primarily circulating antibodies. In this study, we report that epidermal powder immunization (EPI) via a unique powder delivery system elicits both serum and mucosal antibodies to an inactivated influenza virus vaccine. Serum antibody responses to influenza vaccine following EPI were enhanced by codelivery of cholera toxin (CT), a synthetic oligodeoxynucleotide containing immunostimulatory CpG motifs (CpG DNA), or the combination of these two adjuvants. In addition, secretory immunoglobulin A (sIgA) antibodies were detected in the saliva and mucosal lavages of the small intestine, trachea, and vaginal tract, although the titers were much lower than the IgG titers. The local origin of the sIgA antibodies was further shown by measuring antibodies released from cultured tracheal and small intestinal fragments and by detecting antigen-specific IgA-secreting cells in the lamina propria using ELISPOT assays. EPI with a single dose of influenza vaccine containing CT or CT and CpG DNA conferred complete protection against lethal challenges with an influenza virus isolated 30 years ago, whereas a prime and boost immunizations were required for protection in the absence of an adjuvant. The ability to elicit augmented circulating antibody and mucosal antibody responses makes EPI a promising alternative to needle injection for administering vaccines against influenza and other diseases.

Adjuvants, Immunologic↗
PubMed2001

Epidermal powder immunization induces both cytotoxic T-lymphocyte and antibody responses to protein antigens of influenza and hepatitis B viruses.

Cytotoxic T lymphocytes (CTL) play a vital role in host defense against viral and intracellular bacterial infections. However, nonreplicating vaccines administered by intramuscular injection using a syringe and needle elicit predominantly humoral responses and not CTL responses. Here we report that epidermal powder immunization (EPI), a technology that delivers antigens on 1.5- to 2.5-microm gold particles to the epidermis using a needle-free powder delivery system, elicits CTL responses to nonreplicating antigens. Following EPI, a majority of the antigen-coated gold particles were found in the viable epidermis in the histological sections of the target skin. Further studies using transmission electron microscopy revealed the intracellular localization of the gold particles. Many Langerhans cells (LCs) at the vaccination site contained antigen-coated particles, as revealed by two-color immunofluorescence microscopy, and these cells were found in the draining lymph nodes 20 h later. Immune responses to several viral protein antigens after EPI were studied in mice. EPI with hepatitis B surface antigen (HBsAg) and a synthetic peptide of influenza virus nucleoprotein (NP peptide) elicited antigen-specific CTL responses as well as antibody responses. In an in vitro cell depletion experiment, we demonstrated that the CTL activity against HBsAg elicited by EPI was attributed to CD8(+), not CD4(+), T cells. As controls, needle injections of HBsAg or the NP peptide into deeper tissues elicited solely antibody, not CTL, responses. We further demonstrated that EPI with inactivated A/Aichi/68 (H3N2) or A/Sydney/97 (H3N2) influenza virus elicited complete protection against a mouse-adapted A/Aichi/68 virus. In summary, EPI directly delivers protein antigens to the cytosol of the LCs in the skin and elicits both cellular and antibody responses.

Animals↗
PubMed2001

Effect of intragenic rearrangement and changes in the 3' consensus sequence on NSP1 expression and rotavirus replication.

The nonpolyadenylated mRNAs of rotavirus are templates for the synthesis of protein and the segmented double-stranded RNA (dsRNA) genome. During serial passage of simian SA11 rotaviruses in cell culture, two variants emerged with gene 5 dsRNAs containing large (1.1 and 0.5 kb) sequence duplications within the open reading frame (ORF) for NSP1. Due to the sequence rearrangements, both variants encoded only C-truncated forms of NSP1. Comparison of these and other variants encoding defective NSP1 with their corresponding wild-type viruses indicated that the inability to encode authentic NSP1 results in a small-plaque phenotype. Thus, although nonessential, NSP1 probably plays an active role in rotavirus replication in cell culture. In determining the sequences of the gene 5 dsRNAs of the SA11 variants and wild-type viruses, it was unexpectedly found that their 3' termini ended with 5'-UGAACC-3' instead of the 3' consensus sequence 5'-UGACC-3', which is present on the mRNAs of nearly all other group A rotaviruses. Cell-free assays indicated that the A insertion into the 3' consensus sequence interfered with its ability to promote dsRNA synthesis and to function as a translation enhancer. The results provide evidence that the 3' consensus sequence of the gene 5 dsRNAs of SA11 rotaviruses has undergone a mutation causing it to operate suboptimally in RNA replication and in the expression of NSP1 during the virus life cycle. Indeed, just as rotavirus variants which encode defective NSP1 appear to have a selective advantage over those encoding wild-type NSP1 in cell culture, it may be that the atypical 3' end of SA11 gene 5 has been selected for because it promotes the expression of lower levels of NSP1 than the 3' consensus sequence.

Amino Acid Sequence↗
PubMed2001

Are current textbooks good enough for physiology education? For example, the ECL cells are missing.

Current textbooks are believed to provide an updated knowledge. Medical students usually read the textbooks but not the literature that contain the original research articles and reviews. Here, we examined the gap between the current textbooks and literature with the enterochromaffin-like (ECL) cells as an example. A total of 70 textbooks that were published for medical education during the last 10 yr was examined. The literature has been searched mainly from the Internet. We found that most textbooks (59 of 70) fail to mention the ECL cells. Due to the lack of information on the ECL cells, the mechanisms behind gastric acid secretion are described variously from book to book. However, up to the year 2000, 574 research articles and reviews have been published on the various aspects of the ECL cells. The role of the ECL cells in the regulation of the acid secretion has been well demonstrated for more than 20 years. The fact that the textbooks are out of date cannot be explained by the time required to write and publish them. Therefore, we question whether or not the current textbooks are good enough for physiology education and suggest both teachers and students read not only the textbooks, but also utilize the other sources such as the Internet to find and fill the gaps between the textbooks and literature. This is one of the approaches of problem-based learning.

Enterochromaffin-like Cells↗
PubMed2001

Spinal interneurons that receive input from muscle afferents are differentially modulated by dorsolateral descending systems.

The possibility that descending systems have differential actions on the spinal interneurons that receive input from muscle afferents was investigated. Prolonged, physiological inputs were generated by stretch of the triceps surae muscles. The resulting firing patterns of 25 lumbosacral interneurons were recorded before and during a reversible cold block of the dorsolateral white matter at the thoracic level in nonparalyzed, decerebrate preparations. The strength of group I muscle afferent input was assessed from the response to sinusoidal tendon vibration, which activated muscle spindle Ia afferents directly and tendon organ Ib afferents via the resulting reflex force. The stretch-evoked responses of interneurons with strong responses to vibration were markedly suppressed by dorsal cold block, whereas the stretch-evoked responses of interneurons with weak vibration input were enhanced. The cells most strongly activated by vibration received their primary input from Ia afferents and all of these cells were inhibited by the cold block. These results suggest that a disruption of the descending system, such as occurs in spinal cord injury, will lead to a suppression of the interneuronal pathways with group Ia input while enhancing excitability within interneuronal pathways transmitting actions from higher threshold afferents. One possible consequence of this suppression would be a decreased activity among the Ia inhibitory interneurons that mediate reciprocal inhibition, resulting in abnormal reciprocal relations between antagonists and promoting anomalous muscle cocontraction.

Animals↗
PubMed2001

Role of Sp1 in the induction of p27 gene expression in vascular smooth muscle cells in vitro and after balloon angioplasty.

-The abnormal proliferation of vascular smooth muscle cells (VSMCs) plays an important role in atherosclerosis and restenosis. Although several studies have implicated the growth inhibitory protein p27(Kip1) (p27) in the control of myocyte growth and hypertrophy, little is known about the molecular mechanisms that regulate p27 expression in the cardiovascular system. In the present study, we demonstrate the interaction of the transcription factor Sp1 with 2 GC-rich sequences within the p27 promoter in cultured VSMCs. Importantly, point mutations that disrupted Sp1 binding markedly reduced p27 promoter activity, demonstrating that Sp1 is required for efficient p27 gene transcription in cultured VSMCs. Because p27 expression is upregulated after balloon angioplasty, we investigated Sp1 expression and activity in control and balloon-injured rat carotid arteries to assess the role of Sp1 as a physiological regulator of p27 expression. Although immunohistochemical analysis disclosed Sp1 protein expression in both control and balloon-injured arteries, a high level of Sp1 DNA-binding activity was found only in response to balloon angioplasty. Collectively, these results demonstrate that Sp1 is essential for maximum p27 promoter activity in VSMCs and suggest that posttranslational induction of Sp1 DNA-binding activity contributes to the induction of p27 expression and VSMC growth arrest at late time points after balloon angioplasty.

Angioplasty, Balloon↗
PubMed2001

Induction of c-fos and c-jun messenger ribonucleic acid expression by prostaglandin F2alpha is mediated by a protein kinase C-dependent extracellular signal-regulated kinase mitogen-activated protein kinase pathway in bovine luteal cells.

PGF2alpha triggers the demise of the corpus luteum whereby progesterone synthesis is inhibited, the luteal structure regresses, and the estrus cycle resumes. Upon binding to its heterotrimeric G-protein-coupled receptors, PGF2alpha initiates the phospholipase C/diacylglycerol and inositol-1,4,5-trisphosphate/Ca(2+)-protein kinase C (PKC) signaling pathway. More recently, we have demonstrated that PGF2alpha activates extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase signaling through a Raf-dependent mechanism in bovine luteal cells. However, the relationship between PKC and ERK activation in PGF2alpha signaling has not been clearly defined. Moreover, the signaling pathway that PGF2alpha uses to regulate gene expression is unknown. In this report, primary cultures of bovine luteal cells were used to address the role of PKC in ERK activation and the signaling pathway for induction of c-fos and c-jun messenger RNA (mRNA) expression in response to PGF2alpha. By using a PKC inhibitor and a PKC-deficient luteal cell model, we observed that phorbol ester-responsive isoforms of PKC were required for ERK phosphorylation and activation by PGF2alpha (1 microM) or phorbol 12-myristate 13-acetate (PMA) (20 nM). In PGF2alpha- and PMA-treated cells, active ERK MAP kinase was localized in the nucleus. PGF2alpha-induced ERK phosphorylation was dose-dependently inhibited by the MEK1 inhibitor PD098059 (1-50 microM). The expression of c-fos and c-jun mRNA in luteal cells was markedly increased by treatment with PGF2alpha (1 microM) or PMA (20 nM) for 30 min. We also observed that activation of ERK MAP kinase was required for the expression of c-fos and c-jun mRNA in response to PGF2alpha and PMA because it was abrogated by blocking the ERK pathway with PD098059. In addition, PGF2alpha and PMA-induced c-fos and c-jun mRNA expression was abolished in the PKC-deficient cells. Taken together, our data demonstrate that a PKC-dependent ERK MAP kinase pathway mediates the expression of c-fos and c-jun mRNA in PGF2alpha-treated bovine luteal cells.

Animals↗
PubMed2001

Identification and implantation stage-specific expression of an interferon-alpha-regulated gene in human and rat endometrium.

Implantation of the developing blastocyst is regulated by multiple effectors, such as steroid hormones, growth factors, and cytokines. To understand how these diverse signaling pathways interact to modulate uterine gene expression, we employed a gene expression screen technique to identify the molecules that are induced in the periimplantation rat uterus. Here we report the isolation of a complementary DNA representing a novel gene, interferon-regulated gene 1 (IRG1). This gene exhibits significant homology to interferon (IFN)-alpha/beta-inducible human genes p27 and 6-16, indicating that these genes may belong to the same family. Consistent with this finding, expression of IRG1 messenger RNA (mRNA) in rat uterus increased about 20-fold in response to IFNalpha. Uterine expression of IRG1 was also stimulated by estrogen and was partially inhibited by an antiestrogen, ICI 182,780. In pregnant rats, IRG1 expression was high on day 1, but declined on days 2 and 3. The level of IRG1 mRNA again rose transiently on day 4 immediately preceding implantation. In situ hybridization analysis localized the IRG1 mRNA expression in the endometrial epithelium and the surrounding stroma. Interestingly, the expression of p27, which shows high homology to IRG1, was strongly enhanced in human endometrium during the midsecretory phase of the menstrual cycle, overlapping the putative window of implantation. Both IRG1 and p27 mRNAs are therefore induced in the endometrium in an implantation stage-specific manner. We also observed a synergistic interaction between IFNalpha and estrogen receptor signaling pathways that led to maximal induction of p27 mRNA in Ishikawa cells. Although the functional roles of IRG1 and p27 remain unclear, we describe for the first time, identification of a gene family regulated by IFNalpha in both rodent and human uteri. More importantly, our studies reveal that a complex interplay between the steroid hormone and IFN pathways regulates the expression of these genes in the endometrium at the time of implantation.

Adult↗
PubMed2001

Mucosal T cell response to reovirus.

During the last three decades, immunologists and gastroenterologists have witnessed the formation of mucosal immunology as a discipline in biomedical science, and studies of reovirus infection have substantially contributed to this evolution. We have focused on mucosal T cell responses induced by reovirus in conventional, germfree, nude, and NF-kappaB deficient mice. Several major facets of T cell function in the immune responses to this mucosal pathogen have been examined, including viral selection of oligoclonal-T cells, extrathymic T cell development, and distinct signaling pathways used by CD8 sublineages. In addition, our findings with virus-specific T cells selected in the mucosa have suggested novel mechanisms for the rearrangement, selection, and expansion of TCR genes. With the increasing application of molecular tools, reovirus will continue to be a useful model pathogen to study mucosal immunology and will further our understanding of mucosal immunity in health and disease.

Adult↗
PubMed2001

Reverse transcriptase adds nontemplated nucleotides to cDNAs during 5'-RACE and primer extension.

In determining the terminal sequences of the genomic dsRNAs of rotavirus by 5'-rapid amplification of cDNA ends (5'-RACE), it was found that most of the viral cDNAs contained extra nucleotides at their 5' termini that had not been reported before on any rotavirus sequence. Although the extra nucleotides could be dA, dC, dG, or dT residues, the extra nucleotides on the cDNAs usually consisted of a single dT residue. Experiments performed with DNA/RNA duplexes indicated that reverse transcriptase has an associated terminal nucleotidyl transferase (TdT)-like activity, which can add nontemplated nucleotides to the 3' ends of DNA, and that reverse transcriptase was responsible for the presence of the extra nucleotides detected on the 5'-RACE cDNAs. The TdT-like activity of reverse transcription was specific for double-stranded substrates (i.e., DNA/DNA or DNA/RNA duplexes) and was active over a wide range of temperatures and enzyme concentrations. Both commercially available Moloney murine leukemia virus and avian myeloblastosis virus reverse transcriptases contained the TdT-like activity. This work implies that 5'-RACE and primer extension assays must be used carefully in determining the terminal sequences of nucleic acids because, under standard reaction conditions, reverse transcriptase can add nontemplated nucleotides to the 3' ends of cDNAs following template-directed synthesis.

Base Sequence↗
PubMed2001

[Analysis on associations of cytochrome P450 1A1-Hinc II and glutathion S-transferase-theta with primary dysmenorrhea].

OBJECTIVE: To investigate the genetic susceptibility to primary dysmenorrhea. METHODS: Data of 499 female workers in a textile mill were collected. The associations of cytochrome P450 1A1-Hinc II(CYP 1A1-Hinc II) and glutathion S-transferase-theta(GSTT1) polymorphisms with heavy primary dysmenorrhea were evaluated by Logistic regression, with adjustment for potential confounders. RESULTS: The result showed variant of CYP1A1- Hinc II genotypes slightly reduced the risk of primary dysmenorrhea, but its OR value was not statistically significant (CYP1A1-Hinc II:OR=0.64, 95% CI 0.35-1.17). The GSTT1 genotype variant increased the risk of primary dysmenorrhea (GSTT1:OR=1.83, 95% CI 1.04-3.21). After potential confounders were adjusted, the data showed that CYP1A1-Hinc II variant had the trend of decreasing the risk of dysmenorrhea (CYP1A1-Hinc II:OR=0.58, 95% CI 0.31-1.08), but its decreasing scope was still not statistically significant. The GSTT1 variant genotypes showed a significantly increased risk of dysmenorrhea (GSTT1:OR=2.01, 95% CI 1.12-3.62). CONCLUSION: The results suggested that GSTT1 polymorphism be associated with heavy primary dysmenorrhea.

Adult↗