Biomedical subjects
Publications and source records attributed to J Xu.
Three sesquiterpene lactones isolated from the aerial parts of Ambrosia artemisiifolia were identified as psilostachyin, psilostachyin B and psilostachyin C. All of them have some molluscicidal activity against Oncomelania hupensis.
The drug (2-amino-4,5-dimethyl-3-thienyl)-[3(trifluoromethyl)-phenyl]methanone (PD 81,723) has been shown to enhance allosterically A1 adenosine receptor binding in brain membranes. The objective of this study was to determine the specificity and selectivity (A1 versus A2) of PD 81,723 as an enhancer of the negative dromotropic effect of exogenous adenosine in guinea pig isolated and in situ hearts. In isolated hearts, PD 81,723 alone produced only a small stimulus to His bundle (S-H) interval prolongation of 1.5 to 4 msec, which was completely reversed by the A1 adenosine receptor antagonist 8-cyclopentyltheophylline and adenosine deaminase. PD 81,723 (5 microM) significantly decreased the EC50 value of adenosine for prolongation of the S-H interval from 6.7 +/- 0.6 to 4.4 +/- 0.5 microM. The potentiation of the negative dromotropic effect of adenosine by PD 81,723 was dose dependent, i.e., 5 and 10 microM PD 81,723 enhanced the maximal S-H interval prolongation caused by 3 microM adenosine by 207% and 609%, respectively. In contrast, the same concentration of PD 81,723 had no effect on either the S-H interval prolongation caused by carbachol or MgCl2 or the coronary vasodilatory effect of adenosine. In in situ hearts, PD (2 mumol/kg i.v.) alone caused only a small but not significant negative dromotropic effect, increasing the atrium to His interval from 58 +/- 2 to 61 +/- 1 msec. However, the same dose of PD 81,723 caused a significant leftward and upward shift of the adenosine dose-response curve for inducing atrium to His bundle interval prolongation and increased the degree of atrioventricular block caused by adenosine.(ABSTRACT TRUNCATED AT 250 WORDS)
Intranasal vaccination of newborn pigs with pseudorabies virus (PRV) strain Iowa S62/26 tk- gX- Bgal+ was evaluated to determine whether protective immunity could be stimulated in pigs given colostrum from immune sows. Three litters were vaccinated (2 litters from PRV-immune sows and 1 born to a PRV-free sow), and 2 were left as nonvaccinated controls (1 passively immune and 1 PRV-nonimmune). Pigs were then challenge-exposed at 15 weeks of age with virulent PRV strain 4892. Vaccinated pigs that suckled nonimmune sows developed serum PRV-neutralizing antibody by 15 weeks of age and did not die or have reduction in weight gain or febrile response after challenge exposure. Vaccinated pigs that suckled PRV-immune sows were seronegative for PRV at the time of challenge exposure and had less weight loss and fever than did challenge-exposed control pigs. Intranasal vaccination at birth did not stimulate adequate immunity to reduce virus shedding after challenge exposure in any of the vaccinated pigs.
Previous studies have demonstrated linkage between early-onset breast cancer and ovarian cancer and genetic markers on chromosome 17q21. These markers define the location of a gene (BRCA1) which appears to be inherited as an autosomal dominant susceptibility allele. We analyzed five families with multiple affected individuals for evidence of linkage to the BRCA1 region. Two of the five families appear to be linked to BRCA1. One apparently linked family contains critical recombinants, suggesting that the gene is proximal to the marker D17S579 (Mfd188). These findings are consistent with the maximum-likelihood position estimated by the Breast Cancer Linkage Consortium and with recombination events detected in other linked families. Linkage analysis was greatly aided by PCR-based analysis of paraffin-embedded normal breast tissue from deceased family members, demonstrating the feasibility and importance of this approach. One of the two families with evidence of linkage between breast cancer and genetic markers flanking BRCA1 represents the first such family of African-American descent to be reported in detail.
Cerebellar granule cell cultures of rat express only muscarinic m2 and m3 receptor subtypes and exhibit the pharmacological profile of muscarinic m2 receptors that couple to guanine nucleotide binding proteins to inhibit adenylyl cyclase. In vivo pretreatment with muscarinic agonists desensitizes the muscarinic m2 receptor with 50% complete desensitization within 15 to 20 min. After a 1-hr pretreatment with a maximal concentration of carbachol (short-term desensitization), m2 receptor responsiveness reappeared after a 1-hr treatment of cultures with atropine. However, after a 6-hr pretreatment with carbachol (long-term desensitization), m2 receptor responsiveness did not reappear after 1-hr treatment with atropine. Short-term desensitization was homologous for the m2 receptor because treatment of cultures with carbachol did not alter gamma-aminobutyric acidB receptor-mediated inhibition of adenylyl cyclase. Muscarinic m2 receptor desensitization was not mimicked by the addition of analogs of cyclic AMP, cyclic GMP or diacylglycerol to the cultures. The agonist-induced desensitization was not blocked by a cyclic AMP analog, 8-(4-chlorophenylthio)-cyclic AMP. Pretreatment with antisense oligodeoxynucleotides against the mRNA-encoding beta adrenergic receptor kinase attenuated the desensitization by carbachol (100 microM, 1 hr) of m2 receptors. Irreversible labeling of muscarinic m2 and m3 receptors with [3H]propylbenzilycholine mustard followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis produced a loss of the muscarinic m2 receptor (66-kDa protein), but not the muscarinic m3 receptor (92-kDa protein). We suspect that the short-term desensitization results from the phosphorylation of the muscarinic m2 receptor followed by loss of receptor from the plasma membrane.
Amoeboid microglial cells (AMC) in the corpus callosum were selectively labelled following a single intraperitoneal (i.p.) injection of the fluorescent dye, rhodamine isothiocyanate (RhIc) into postnatal rats. The frequency of RhIc-labelled cells varied with age, with the largest number occurring in 7-d-old animals. Thereafter, the labelled cells declined drastically in number and fluorescence and were barely detectable in 12-d-old injected rats. Labelled cells were absent in 13-d or older rats given an RhIc injection. When the injected RhIc was followed over a time course sequence, it was first detected in the cerebral blood vessels and their lining endothelia within 5 min after the injection. A variable number of AMC emitting a weaker fluorescence were closely adherent to the outer walls of the blood vessels. With time, the fluorescence in the AMC was progressively enhanced, but that in the blood vessels showed a concomitant reduction. In the rats that received an intravenous (i.v.) injection of RhIc, the labelling pattern of AMC, both in terms of its variation with age and in temporal sequence, paralleled that in rats given i.p. injections. In 12-d-old rats subjected to a stab wound coupled with an i.p. injection of RhIc, a considerable number of AMC not normally labelled at this age were activated. The cells exhibited an intense fluorescence and expressed MHC surface antigen immunoreactivity. It is concluded from this study that when injected i.p. or i.v., RhIc is readily circulated to the cerebral vessels, where it enters brain tissue by transendothelial transport.(ABSTRACT TRUNCATED AT 250 WORDS)
The Tradescantia-micronucleus (Trad-MCN) bioassay is an efficient short-term test for genotoxicity of pollutants. In order to increase the efficiency and to standardize the micronucleus (MCN) scoring process, an automated scoring system was developed using the principle of image analysis in computer science. This assemblage is called the Tradescantia-micronucleus image analysis (Trad-MCNIA) system. The MCN frequencies scored by this system were compared with those scored by human observation for its proficiency. A set of low MCN frequency (around 5 MCN/100 tetrads) slides prepared from a control group, a set of medium MCN frequency (around 20 MCN/100 tetrads) slides prepared from sodium azide treated plant cuttings and a set of high MCN frequency (around 50 MCN/100 tetrads) slides prepared from X-ray treated materials were used for this study. In the low MCN frequency slides, the Trad-MCNIA system scored about the same value as human observation. In the medium and high frequency slides, MCN frequencies scored by the system were lower than those scored by human observers. This discrepancy was corrected by increasing the power of the objective of the microscope in the system. The MCN frequencies scored by the system attained 90% congruity with those scored by human observers after the correction. The scoring speed of the system was about 3.5 times as fast as that by human observers, and the data could be statistically analyzed immediately after the data scores were recorded. Further improvements can be made by upgrading the video camera and the computer speed.
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Potentially 96 splice variants among four genes that code for the human heparin-binding fibroblast growth factor receptor family complicate study of structure, metabolism, and function of single isoforms in mammalian cells. As an alternative, we expressed structural subdomains and isoforms of the flg receptor gene in bacteria and baculoviral-infected insect cells. We developed and characterized a panel of 16 isoform and domain-specific polyclonal and monoclonal antibodies. The panel of antibodies was used to distinguish mature glycosylated ligand-binding and kinase-active and -inactive recombinant isoforms in baculoviral insect cells and transfected mammalian cells and natural isoforms in rat prostate and human liver cells. The results revealed a cell type-specific expression of the flg gene and isoforms that result from combinations of splice variations. Reactive epitopes of monoclonal antibodies against both the three (alpha) and two (beta) immunoglobulin-like disulfide loop extracellular domain isoforms were mapped by cross-reactivity with synthetic polypeptide sequences and deletion mutants expressed in bacteria. The native alpha and beta receptor isoforms differed in display of shared epitopes and suggested that the NH2-terminal Loop I and COOH-terminal Loops II and III of the alpha isoform are interactive. Although the common Loops II and III appear qualitatively sufficient for ligand binding, the results suggest that tertiary relationships among loops in the three and two loop isoforms are distinct and, therefore, the two isoforms may have distinct activities. Spatial models for arrangement of immunoglobulin-like loops in the extracellular domain of the two isoforms are presented.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Assessment of the in vivo aneuploidy/micronucleus Assay in bone marrow cells with 16 chemicals is described. This assay is based on the detection of kinetochores (KC) in micronuclei (MN) by antikinetochore-specific (CREST) antibodies. Among sixteen chemicals tested, six were known clastogens, three were known aneuploidy-inducers, and the other seven were suspected spindle poisons. These chemicals were tested for their ability to induce micronuclei with kinetochore(s) in bone marrow cells of CD-1 mice. The majority of MN formed in bone marrow cells treated with aneuploidy-inducing agents contained kinetochore(s) which are considered to be formed from whole chromosomes or centric fragments, while in clastogen treated bone marrow cells, majority of them contained no kinetochore(s) which are considered to be formed from acentric chromosomal fragments. Classification of chemicals into either aneuploidy inducing agents or clastogens is based on the relative frequency of MN with and without KC, respectively. These results suggest that the in vivo aneuploidy/micronucleus assay has a great potential to identify aneuploidy-inducing agents.
Precore defective HBV mutants may gradually prevail because of immune selection and explain spontaneous seroconversion from HBeAg to anti-HBe in HBV carriers. We have analyzed whether the presence of precore HBV mutants is a determinant of responsiveness to interferon-alpha therapy. Fifteen carriers (nine responders and six nonresponders) who were treated with interferon-alpha were examined. Serum samples were collected before and after therapy. After extraction of DNA, the precore region was amplified by the polymerase chain reaction, and the product was identified by gel electrophoresis and ethidium bromide staining and then Southern blotting and molecular hybridization. The amplified products in all patients were asymmetrically amplified by a modified polymerase chain reaction, and the precore region was directly sequenced. All patients were HBV DNA positive initially. Circulating HBeAg-negative mutants were not identified before treatment in either responders or nonresponders. All nine responders were negative for HBV DNA in serum by dot blot during or after treatment, but seven remained positive by polymerase chain amplification and Southern-blot hybridization. All of the nonresponders remained positive for HBV DNA by dot blot. A silent mutation involving the substitution of an A for G at position 1888 was found in seven carriers; however, no HBeAg-negative mutants were detected in the follow-up of either responders or nonresponders to interferon-alpha.(ABSTRACT TRUNCATED AT 250 WORDS)
Hexavalent chromium compounds are carcinogenic to humans, are potent inducers of tumors in experimental animals, and can neoplastically transform cells in culture. In this study, the effects of sodium chromate on the expression of the 78-kDa glucose-regulated protein (GRP78) gene and on general transcription were investigated with respect to the DNA damage induced by this agent. DNA single-strand breaks, DNA-protein cross-links, and chromium-DNA adducts were present in CHO cells immediately after 2 h of treatment with sodium chromate. Subsequently, these types of damage were repaired at different rates. Single-strand breaks were essentially repaired after 8 h. By 24 h posttreatment, no cross-links remained in cells exposed to 30 or 150 microM chromate, although cells treated with the 300-microM concentration still contained cross-links at that time. DNA-chromium adducts remained unrepaired for at least 32 h. The moderate constitutive level of GRP78 mRNA was not affected by chromate. Chromate did, however, suppress induction of this gene by tunicamycin in a concentration-and time-dependent manner. Thirty micromolar sodium chromate (96% survival), which caused the least DNA damage, had no effect on GRP78 induction, general RNA synthesis, or mRNA synthesis. Induction of GRP78 was suppressed immediately and 12 h after treatment with 150 microM chromate (54% survival), although there was a partial recovery of induction at 24 h after treatment, which correlated with the repair of DNA-protein cross-links. In contrast, both total cytoplasmic RNA and mRNA synthesis were suppressed by approximately 60-75% for at least 32 h by 150 microM chromate. At the 300-microM concentration (8% survival), where DNA-protein cross-links persisted beyond 24 h, GRP78 induction was totally suppressed for at least 24 h, while total RNA and mRNA synthesis were suppressed by 80-90% for at least 32 h. Overall, the effects of chromate on GRP78 induction correlated most closely with the presence of DNA-protein cross-links, but suppression of total RNA and mRNA synthesis correlated with the presence of DNA-chromium adducts. These results indicate that chromate exerts differential effects on the induction of the GRP78 gene and on general transcription.
Particulate lead chromate is a highly water-insoluble cytotoxic and carcinogenic agent, but its mechanism of action remains obscure. We investigated its effects on DNA damage in CHO cells after a 24-h exposure using alkaline or neutral filter elution and cytogenetic studies. Concentrations (0.08, 0.4 and 0.8 micrograms/cm2), which reduced the colony-forming efficiency of CHO cells to 94, 50 and 10%, respectively, produced dose-dependent DNA single-strand breaks and DNA-protein crosslinks, but no DNA double-strand breaks or DNA-DNA crosslinks were observed. The single-strand breaks were absent from cells given a 24-h recovery period after removal of the treatment medium, even though most of the particles remained adhered to cells and to the culture dish. In contrast, both the DNA-protein crosslinks and chromosomal aberrations persisted even after the 24-h recovery period. These results suggest that the mechanism of the particle-induced early DNA single-strand breaks may be different from DNA-protein crosslinks and the lesions leading to chromosomal aberrations, or alternatively, that the repair of single-strand breaks is more efficient than the repair of DNA-protein crosslinks in the unavoidable continuing presence of carcinogen. These results also suggest that the chromosome damage may be related to the persistent DNA-protein crosslinks, and further confirm the genotoxic activity of carcinogenic lead chromate particles.
High-dose methylprednisolone (MP) given to patients within 8 h of traumatic spinal cord improved neural function at 6 and 12 months, suggesting a probable secondary injury process that may be amenable to therapeutic intervention. Vascular injury plays an important role in the secondary injury process of CNS trauma. We have examined the effect of MP on vascular changes, including tissue edema, vascular permeability, and polymorphonuclear (PMN) cell infiltration in a rat model of spinal cord impact injury. MP significantly reduced extravasation of fluorescein isothiocyanate dextran (FITC-D), a macromolecular tracer, by 64.3% and 50.7% with trauma forces of 20 and 40 g-cm, respectively, when MP was administered IV immediately after trauma at a bolus of 165 mg/kg, with a subsequent continuous MP infusion at 31.5 mg/kg/h for 23 h. MP reduced the water content in the 40 g-cm traumatic cord lesion to 73.0% compared to the traumatic control (74.3%, p < 0.001) at the same schedule of large dose 24-h infusion. The same doses of MP showed a trend to decrease the extent of neutrophil infiltration as determined by myeloperoxidase (MPO) activity, but the change was not significant. MP had little effect in decreasing FITC-D extravasation and cord edema when given at a lower dose (bolus of 30 mg/kg with continued infusion of 1.3 mg/kg/h for 23 h). MP did not reduce extravasation of FITC-D and edema when administered IV as one bolus injection at high (165 mg/kg) or low (30 mg/kg) doses.(ABSTRACT TRUNCATED AT 250 WORDS)
Partial sequencing of the HindIII C fragment of murine cytomegalovirus (MCMV) revealed an open reading frame of 2172 nucleotides in length encoding a 724 amino acid protein with a predicted Mr of 80.4K. Analysis of the predicted amino acid sequence revealed homology with glycoprotein H (gH) from a number of other herpesviruses. MCMV gH showed strongest amino acid identity with human (H) CMV and human herpesvirus 6 gH, and less identity with the gH protein sequences of Epstein-Barr virus, varicella-zoster virus and herpes simplex virus type 1. The greatest identity between MCMV and HCMV gH occurs in the C-terminal region. The MCMV gH is characterized by having a 14 amino acid signal sequence, a 23 amino acid transmembrane region, a seven amino acid positively charged cytoplasmic anchor sequence and eight putative N-linked glycosylation sites. Comparison of MCMV gH with that of HCMV indicates that there are 12 conserved cysteine residues and three conserved potential N-linked glycosylation sites.