Biomedical subjects

L Zhao

Publications and source records attributed to L Zhao.

At least 325 records · Page 18Linked to original sources

PubMed1996

Translocations and deletions of 5q13.1 in myelodysplasia and acute myelogenous leukemia: evidence for a novel critical locus.

Acquired partial and complete deletions of chromosome 5 (5q-, -5) are common cytogenetic anomalies associated with myelodysplasia (MDS) and acute myeloid leukemia (AML). A critical region of consistent loss at 5q31.1 (in > 90% of cases) has led us and others to postulate the presence of a key negative regulator(s) of leukemogenesis. Although the interstitial deletion limits vary among patients, del(5) (q13q33) and del(5)(q13q35) constitute major subsets. Furthermore, it is not rare to encounter deletions, translocations, or paracentric inversions involving 5q11 to 5q13, which indicates inactivation or disruption of important gene(s) at that locus. In this report, we have localized a novel locus at 5q13.1 to a 2.0-Mb interval between the anonymous markers D5S672 and GATA-P1804. This locus resided within the region of loss in 12 of 27 patients with anomalies of chromosome 5; one of these cases had apparent retention of both alleles of all the telomeric loci. Fluorescence in situ hybridization (FISH) studies demonstrate that the AML cell line ML3 is disrupted at 5q13.1 by a translocation involving chromosome 3, with apparent retention of the entire chromosome 5 sequence. Our results suggest that this novel proximal locus encodes a critical gene that may be deleted or disrupted in a subset of MDS/AML patients with chromosome 5 anomalies.

Adult↗

PubMed1996

RAGE and amyloid-beta peptide neurotoxicity in Alzheimer's disease.

Amyloid-beta peptide is central to the pathology of Alzheimer's disease, because it is neurotoxic--directly by inducing oxidant stress, and indirectly by activating microglia. A specific cell-surface acceptor site that could focus its effects on target cells has been postulated but not identified. Here we present evidence that the 'receptor for advanced glycation end products' (RAGE) is such a receptor, and that it mediates effects of the peptide on neurons and microglia. Increased expressing of RAGE in Alzheimer's disease brain indicates that it is relevant to the pathogenesis of neuronal dysfunction and death.

Alzheimer Disease↗

PubMed1996

Orientation of paramagnetic probes attached to gizzard regulatory light chain bound to myosin heads in rabbit skeletal muscle.

The orientation of the myosin neck was monitored using electron paramagnetic resonance (EPR) spectroscopy. Gizzard regulatory light chain was labeled with a nitroxide spin probe and exchanged for the native subunit, located in the myosin neck, in rabbit psoas muscle fibers. The EPR spectra of rigor fibers indicated a substantial degree of probe immobilization and showed a strong dependence on the orientation of the fiber axis relative to the magnetic field, indicating that the neck was ordered in this state. Spectra of relaxed fibers at 24 degrees C showed that the neck was disordered, but the spectra of relaxed fibers at 4 degrees C indicated that the neck was partially ordered. Active fibers at the two temperatures produced spectra identical to relaxed fibers, indicating that no novel angles could be seen in the neck during the powerstroke. Proteolytic fragments of myosin, S1 and HMM, were exchanged with labeled light chains and bound to thin filaments in unlabeled fibers. The distribution of probe orientations for HMM was identical to that of labeled rigor fibers, while S1 showed a slightly different distribution, suggesting that the neck is distorted (by a few degrees) by the interactions of the two heads of myosin when bound to actin.

Animals↗

PubMed1996

The human serotonin 5-HT2C receptor: complete cDNA, genomic structure, and alternatively spliced variant.

The complete 4775-nt cDNA encoding the human serotonin 5-HT2c receptor (5-HT2cR), a G-protein-coupled receptor, has been isolated. It contains a 1377-nt coding region flanked by a 728-nt 5'-untranslated region and a 2670-nt 3'-untranslated region. By using the cloned 5-HT2cR cDNA probe, the complete human gene for this receptor has been isolated and shown to contain six exons and five introns spanning at least 230 kb of DNA. The coding region of the human 5-HT2CR gene is interrupted by three introns, and the positions of the intron/exon junctions are conserved between the human and the rodent genes. In addition, an alternatively spliced 5-HT2CR RNA that contains a 95-nt deletion in the region coding for the second intracellular loop and the fourth transmembrane domain of the receptor has been identified. This deletion leads to a frameshift and premature termination so that the short isoform RNA encodes a putative protein of 248 amino acids. The ratio for the short isoform over the 5-HT2CR RNA was found to be higher in choroid plexus tumor than in normal brain tissue, suggesting the possibility of differential regulation of the 5-HT2CR gene in different neural tissues or during tumorigenesis. Transcription of the human 5-HT2CR gene was found to be initiated at multiple sites. No classical TATA-box sequence was found at the appropriate location, and the 5'-flanking sequence contains many potential transcription factor-binding sites. A 7.3-kb 5'-flanking 5-HT2CR DNA directed the efficient expression of a luciferase reporter gene in SK-N-SH and IMR32 neuro-blastoma cells, indicating that it contains a functional promoter.

Alternative Splicing↗

PubMed1996

Regulation of cytokine mRNA expression in activated lymphocytes by human choriocarcinoma JAR cells.

Because the fetus is semiallogenic to the mother, considerable modulation of the maternal immune response must occur in order for pregnancy to be successfully carried to term. Some authors have hypothesized that the immunomodulation of pregnancy includes an adjustment of cytokine responses away from the Th1 paradigm and toward the Th2 pattern. In vivo data from murine pregnancy support this hypothesis. However, in humans, the Th1/Th2 model appears to be more complex than that in mice, and cytokine expression of mRNA in human decidual tissue does not reflect a clear-cut Th2 bias. The experiments described here were undertaken to determine whether and how trophoblastic cells modulate cytokine expression in activated lymphocytes, and whether there is a trend toward the use of the Th2 pattern in an experimental model of the maternal-fetal interface. We used reverse transcriptase polymerase chain reaction (rtPCR) to detect cytokine mRNA expression in human peripheral blood mononuclear cells cocultivated with human choriocarcinoma JAR cells. We found that although IL-2 (a paradigmatic Th1 cytokine) was significantly down-regulated by JAR cells at the mRNA level, similar decreases were also seen in IL-10, which participates in the Th2 paradigm. We were unable to detect changes in either interferon-gamma (IFN-gamma, a Th1 cytokine) or IL-4 (a Th2 cytokine) mRNA's or in IL-2R expression by fluorescence-activated cell sorting. These studies indicate that human choriocarcinoma JAR cells are capable of modifying cytokines in activated lymphocytes other than those involved in the Th1 paradigm. While it may be useful to view human responses against the background of these patterns established from murine systems, it is reasonable to conclude that human pregnancy may not involve regulation of Th1 immune responses exclusively.

Base Sequence↗

PubMed1996

Lysis of adult ventricular myocytes by cells infiltrating rejecting murine cardiac allografts.

BACKGROUND: Immunologic mechanisms that mediate myocardial cell injury during rejection are not fully understood. We therefore investigated whether cells that infiltrate rejecting cardiac allografts are capable of directly injuring myocytes and whether this injury resembles that produced by cytotoxic T lymphocytes (CTLs) that are generated in a mixed lymphocyte reaction (MLR). METHODS AND RESULTS: Heart-infiltrating cells (HICs) were isolated from murine heterotopic BALB/c cardiac allografts undergoing rejection 6 to 8 days after transplantation into C57BL/6 mice. An in vitro model system of cultured adult murine ventricular myocytes was developed to facilitate investigation of cell-mediated myocyte injury. Isolated adult myocytes were incubated with either HICs or MLR effector cells, and myocyte death was quantified by counting the number of rod-shaped myocytes excluding trypan blue. The frequency of donor-reactive CTLs was similar in the HIC and MLR populations, as assessed by limiting dilution analysis. However, HICs were less efficient at killing donor-strain myocytes than were MLR cells. CTL-mediated cell lysis occurred by 6 hours, whereas myocyte injury produced by HICs was more gradual, with considerable cytotoxicity occurring between 12 and 24 hours. Furthermore, whereas MLR cells lysed only donor-strain myocytes, HIC lysed donor, third-party, and syngeneic myocytes. Treatment of MLR cells and HICs with anti-CD8 antibody plus complement produced a much greater inhibition of MLR cytotoxicity than of HIC cytotoxicity. CONCLUSIONS: These data demonstrate that only a small component of myocyte injury mediated by allograft-infiltrating cells can be ascribed to CTLs within the infiltrating cell population. These findings suggest that cell types associated with a delayed-type hypersensitivity response, as well as CTLs, cause myocyte injury during cardiac rejection.

Animals↗

PubMed1996

Preservation of global cardiac function in the rabbit following protracted ischemia/reperfusion using monophosphoryl lipid A (MLA).

Monophosphoryl lipid A (MLA), a derivative of the minimal substructure of lipopolysaccharide (lipid A) possesses immunomodulatory activity of the parent lipid A yet enjoys reduced toxicity. It has previously been reported that pretreatment with MLA reduces myocardial infarct size and stunning in dogs following ischemia and reperfusion. The aim of this study was to evaluate the ability of monophosphoryl lipid A (MLA) to preserve global cardiac function and peripheral hemodynamics in a rabbit model of prolonged regional ischemia (90 min), and reperfusion (6 h). An evaluation of potential mechanisms by which MLA may preserve cardiac function was also undertaken. Single dose pretreatment with MLA (35 micrograms/kg i.v.) 24 h prior to ischemia resulted in significant improvement in left ventricular developed pressure, dP/dt, rate-pressure product and mean arterial pressure during reperfusion (P < 0.05 v control). Although in this model of prolonged ischemia MLA pretreatment did not reduce infarct size (54.5 +/- 11.4% in control v 63.3 +/- 8.3% in MLA, P = N.S.), evaluation of myocardial adenylate and adenosine catabolite pools at the end of ischemia indicated a preservation of ATP and ADP and a decreased production of downstream adenosine catabolites including inosine, xanthine and uric acid. Adenosine kinase, but not 5'-nucleotidase (5'-NTase) or adenosine deaminase activity determined following reperfusion was 76% and 60% higher (P < 0.05) in non-risk and post-ischemic myocardium of MLA pretreated rabbits compared with controls. Although there was a trend toward lower tissue myeloperoxidase activity in post-ischemic myocardium from treated rabbits, the results were not significantly different from control animals. These results suggest that a 24-h pretreatment with MLA, without further treatment during ischemia or reperfusion was associated with: (1) preservation of global myocardial function during reperfusion; (2) preservation of myocardial high energy adenylates and reduced formation of adenosine catabolites during ischemia; (3) elevated myocardial adenosine kinase activity. Increased recycling of adenosine to phosphorylated nucleotides may result from MLA's affect on adenosine kinase, which could explain the drugs effect on adenylate and adenosine metabolite pools.

5'-Nucleotidase↗

PubMed1996

A study on the nutritive value of pollen from the Chinese Masson Pine (Pinus massoniana) and its effect on fecal characteristics in rats.

A digestion experiment with growing rats was conducted to study the effect of native and broken pollen of Chinese Masson Pine (Pinus massoniana) on fecal composition and digestibilities of dry matter, crude protein and crude ash. For that issue each 10 of 30 animals were fed a semisynthetic diet containing either no pollen or and addition of 6% native or broken pollen for 17 days at restricted amounts. In a second experiment each 6 of 12 growing rats received a semisynthetic diet containing either no or 5% broken pollen. At day 4, 11 and 18 samples of the feces were collected and analyzed for mesophilic aerobic bacteria. The pollen contained large amounts of cell wall constituents (26-30% lignin and 10-15% cellulose, 2-13% hemicellulose) with higher values found in native pollen. The contents of crude protein, crude fat, total lipids, available carbohydrates (starch and sugars), crude ash, gross energy and metabolizable energy were 13%, 2-10%, 8-10%, 17-18%, 3.1-3.5%, 21-22 kJ/g and 5.7-9.0 kJ/g. The addition of native pollen to the diet increased the total amount of feces by 71% as compared to the control level. The fecal contents of dry matter and of crude protein and crude ash in fecal dry matter changed by -5, +4 and -5 percentage units. The apparent digestibilites of dry matter and crude protein decreased by 3 and 5 percentage units, respectively, while the apparent digestibility of crude ash remained unchanged. Broken pollen acted in the same direction, however the effects were about 20% less pronounced as compared to native pollen. The pollen feeding reduced the fecal germ contents of Proteus mirabilis and Escherichia coli, while the amounts of alpha-hemolysing streptococci was increased. In total, the observed effects of an addition of native broken or pollen to the diet seemed to be based mainly on the increased intake of cell wall constituents.

Animals↗

PubMed1996

Effects of epidermal growth factor (EGF) and colony-stimulating factor-1 (CSF-1) on expression of c-fos in rat mandibular molars: implications for tooth eruption.

The c-fos gene is expressed in the dental follicle of the first mandibular molar of rats. Molecules that accelerate tooth eruption, epidermal growth factor (EGF) and colony-stimulating factor-1 (CSF-1), enhance the expression of the c-fos gene in vitro in both a time- and concentration-dependent manner. In vivo, EGF enhances c-fos expression in the follicle from day 0-7 postnatally, but by day 9 the follicle is refractory to this stimulus. Immunostaining reveals that the c-fos gene is translated in the cultured dental follicle cells, with staining seen in the nucleus and the perinuclear region of the cytoplasm. In vivo, immunostaining for c-fos is prominent in the dental follicle early postnatally, with little or no staining seen in the stellate reticulum and dental pulp. By day 10 postnatally, staining for c-fos is greatly reduced in the dental follicle. Thus, the presence of c-fos early postnatally in the tissue required for eruption, the dental follicle, as well as the enhancement of c-fos gene expression in the follicle by EGF or CSF-1, suggests that c-fos plays a role in tooth eruption. That role may be either to promote differentiation of mononuclear cells into osteoclasts needed for eruption or to recruit the mononuclear cells into the follicle.

Animals↗

PubMed1996

In vivo and in vitro effects of epidermal growth factor on its receptor gene expression in rat dental follicle cells.

Epidermal growth factor receptor (EGFR) is known to be localized early postnatally in the follicle of rat mandibular molars and to decline later. Here, EGFR mRNA present early postnatally in the follicle was revealed by in situ hybridization and reverse transcription-polymerase chain reaction. Injections of epidermal growth factor (EGF) enhanced the expression of EGFR mRNA but not EGF mRNA through day 5 postnatally in the follicle. By day 7 postnatally, the amount of EGFR mRNA was dramatically reduced and EGF injection at that time or later did not enhance its expression. Cultured dental follicle cells were also shown to contain both EGFR mRNA and EGF mRNA, but only EGFR mRNA expression was enhanced after incubation of the cells with EGF. The EGFR mRNA was apparently translated, because the cultured cells could be immunostained for EGFR. This enhancement of EGFR mRNA in the dental follicle cells by EGF may be a necessary prelude to the mitogenic effect of EGF on the cultured cells because incubating the dental follicle cells in EGF over 6 days resulted in almost a doubling in their number as compared to controls. These results indicate that the tissue necessary for eruption to occur, the dental follicle, contains EGFR mRNA in the early postnatal days. In turn, this mRNA is enhanced by EGF, a molecule known to accelerate eruption if injected early postnatally. Whether or not the mitogenic effect of the EGF on the cultured dental follicle cells is a mechanistic factor that contributes to the subsequent tooth eruption is unknown.

Animals↗

PubMed1996

Myocardial ischemia/reperfusion protection using monophosphoryl lipid A is abrogated by the ATP-sensitive potassium channel blocker, glibenclamide.

OBJECTIVES: Monophosphoryl lipid A (MLA), a detoxified derivative of the lipid A portion of the endotoxin molecule, given as a pretreatment 24 h prior to cardiac ischemia/reperfusion reduces myocardial stunning and infarction in dogs. This study was undertaken to evaluate the ability of MLA pretreatment to reduce infarct size in a rabbit model of in situ regional myocardial ischemia and reperfusion. Secondly, the potential role of modulation of ATP-sensitive potassium (KATP) channel in MLA's cardioprotection was evaluated using in vivo pharmacologic antagonism with a KATP channel blocker, as was the role of tumor necrosis factor using an enzyme-linked immunosorbent assay method of serum cytokine analysis. METHODS: Rabbits were pretreated intravenously with MLA or vehicle injection 24 h prior to initiation of 30 min in situ left anterior descending coronary artery occlusion followed by 3 h reperfusion. In animals receiving glibenclamide, the potassium channel antagonist was administered 30 min prior to inducing ischemia. Animals receiving glibenclamide, which possesses hypoglycemic effects, underwent serial blood glucose evaluation prior to drug and throughout the ischemia and reperfusion periods. Hemodynamics were monitored; infarct size and area at risk were assessed by contrast dye staining (triphenyltetrazolium chloride). Serum tumor necrosis factor was measured by enzyme-linked immunosorbent method in animals administered cardioprotective doses of MLA as well as pyrogenic doses of MLA and endotoxin (positive control) to determine if elaboration of this cytokine could be associated with the cardioprotective effect of MLA. RESULTS: MLA administered as a single intravenous dose 24 h prior to ischemia reduced infarct size, expressed as a percent of the area at risk, 64 and 71% at doses of 35 and 10 micrograms/kg, respectively. Lower doses of MLA (2.5 and 5 micrograms/kg) did not significantly reduce infarct size. Administration of glibenclamide (300 micrograms/kg) 30 min prior to ischemia completely blocked the ability of MLA pretreatment to limit infarct size, while MLA vehicle-glibenclamide-treated control rabbits displayed infarcts not significantly different from MLA-vehicle-treated control rabbits. A cardioprotective dose of MLA (35 micrograms/kg) did not induce the elaboration of tumor necrosis factor into rabbit serum (within the limits of assay sensitivity). CONCLUSIONS: Single-dose pretreatment with MLA administered intravenously to rabbits substantially reduces infarct size when administered 24 h prior to ischemia. Pharmacologic preconditioning with MLA appears to be mediated through KATP channels as the channel blocker, glibenclamide, reversed the cardioprotective activity of MLA when administered 1 day following MLA pretreatment, yet 30 min prior to ischemia. In this model the cardioprotective does not appear to be associated with increases in serum tumor necrosis factor.

Adenosine Triphosphate↗

PubMed1996

The regulation of pulmonary vascular tone.

1. The ability to manipulate pharmacologically pulmonary vascular tone independent of effects on systemic blood vessels is a desirable objective. Elucidation of the biochemical mechanisms underlying hypoxia-induced pulmonary vasoconstriction (HPV) may permit preferential targeting of the pulmonary circulation. 2. Here we review our studies of the role of locally synthesized candidate vasoactive factors in HPV. In addition, we present data demonstrating an attenuated pressor response to hypoxia in the pulmonary circulation of Fischer 344 rats compared with the Wistar-Kyoto (WKY) rat strain. 3. We propose that a systematic genome-wide search using the HPV phenotype and a panel of highly informative microsatellite markers will elucidate the genetic loci underlying the difference in susceptibility to HPV in these two rat strains and provide a valuable and novel insight into the factors that determine the HPV response.

Animals↗

PubMed1996

Demonstration of a heat-stable 120-kilodalton protein of Rickettsia japonica as a spotted fever group-common antigen.

Genomic libraries of Rickettsia japonica were cloned into an expression vector lambda gt11. A clone expressing a protein reactive with antiserum against 120-kilodalton (kDa) proteins, a mixture of heat-modifiable and heat-stable polypeptides, was selected and designated as lambda Rj120-1. The expressed protein has a molecular mass of 180 kDa. Western immunoblotting demonstrated that the expressed protein was a fusion protein with beta-galactosidase. The antiserum against 120-kDa proteins was absorbed by the induced lysogen, resulting in the removal of reactivity to the heat-stable 120-kDa polypeptide. The antiserum against the expressed protein reacted with heat-stable 120- to 130-kDa polypeptides of spotted fever group (SFG) rickettsiae in addition to R. japonica. The findings indicated that the protein expressed from the cloned gene of R. japonica possessed the antigenicity group-common to SFG rickettsiae. Primers designed from the gene coding for R. conorii heat-stable 120-kDa protein (Schuenke, K.W., and Walker, D.H., Infect. Immun. 62: 904-909, 1994) and lambda gt11 lacZ gene amplified the lambda Rj120-1 DNA by the polymerase chain reaction (PCR). Analysis of restriction fragment length polymorphism (RFLP) of the PCR-amplified products revealed that the cloned DNA corresponds to a portion of the gene coding for the heat-stable 120-kDa protein of R. conorii with 2,519 nucleotides beginning at nucleotide 190 of the open reading frame. RFLP demonstrated that the cloned gene was highly homologous to the corresponding gene of R. conorii.

Animals↗

PubMed1996

Angiotensin II receptor expression and inhibition in the chronically hypoxic rat lung.

1. Angiotensin II (AII) binding density and the effect of chronic AII receptor blockade were examined in the rat model of hypoxia-induced pulmonary hypertension. 2. [125I]-[Sar1,Ile2]AII binding capacity was increased in lung membranes from rats exposed to hypoxia (10% fractional inspired O2) for 7 days compared to normal rats (Bmax 108 +/- 12 vs 77 +/- 3 fmol mg-1 protein; P < 0.05), with no significant change in dissociation constant. Competition with specific AII receptor subtype antagonists demonstrated that AT1 is the predominant subtype in both normal and hypoxic lung. 3. Rats treated intravenously with the AT1 antagonist, GR138950C, 1 mg kg-1 day-1 rather than saline alone during 7 days of exposure to hypoxia developed less pulmonary hypertension (pulmonary arterial pressure: 21.3 +/- 1.7 vs 28.3 +/- 1.1 mmHg; P < 0.05), right ventricular hypertrophy (right/left ventricle weight ratio: 0.35 +/- 0.01 vs 0.45 +/- 0.01; P < 0.05) and pulmonary artery remodelling (abundance of thick-walled pulmonary vessels: 9.6 +/- 1.4% vs 20.1 +/- 0.9%; P < 0.05). 4. The reduction in cardiac hypertrophy and pulmonary remodelling with the AT1 antagonist was greater than that achieved by a dose of sodium nitroprusside (SNP) that produced a comparable attenuation of the rise in pulmonary arterial pressure during hypoxia. 5. The data suggest that AII, via the AT1 receptor, has a role in the early pathogenesis of hypoxia-induced pulmonary hypertension in the rat.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1996

Systemic uptake and clearance of chloroform by hairless rats following dermal exposure. I. Brief exposure to aqueous solutions.

The systemic uptake of chloroform from dilute aqueous solutions into live hairless rats under conditions simulating dermal environmental exposure was studied. Whole blood was sampled during a 30-min immersion of an animal within water containing a known concentration of chloroform and then for 5.5 h following its removal from the bath. The amount of chloroform systemically absorbed was determined by comparing the AUCs of the blood concentration vs. time plots from dermal exposure to that obtained after i.v. infusion (for a period of 30 min) of an aqueous solution containing a known amount of chloroform (positive control). Although dermal data implied two-compartment disposition characteristics, i.v. infusion data fit best to a three-compartment disposition. Linear pharmacokinetics was observed both by i.v. administration and percutaneous absorption at the dose levels studied. Chloroform was detected in the rat blood as early as 4 min following exposure. Our findings suggest that about 10.2 mg of chloroform was systemically absorbed after dermal exposure of a rat to an aqueous solution of 0.44 mg/ml. This amount is substantially higher than the predictions of mathematical risk-models put forth by some investigators. However, when expressed as the "effective" permeability coefficient (Kpeff), close agreement was noticed between our value and those estimated by others using physiologically based pharmacokinetic (PBPK) models. Also, in terms of Kpeff, reasonable agreement existed between our and another investigator's past estimates of uptake based on depletion of bath level of chloroform and the actual uptake measured in our current experiments. The estimated onset of systemic entry seen here is entirely consistent with our estimate of how long it takes to establish the diffusion gradient across the stratum corneum based on tape stripping.

Animals↗

PubMed1996

Initial characterization of viral sequences from a SHIV-inoculated pig-tailed macaque that developed AIDS.

In this study, we report on the derivation of a pathogenic SIV-HIV chimeric virus (SHIV) and the initial characterization of the viral sequences from the first (macaque PPc) of a series of pig-tailed macaques that developed CD4+ T cell loss and AIDS. Viral genes were amplified by PCR from the brain, lymphoid, and kidney tissues and their sequences compared to the original SHIV used to initiate passages in macaques. Our results show that the vpu gene, which was nonfunctional in the original SHIV, now coded for functional protein in macaque PPc. The tat and rev genes had no consensus changes but the nef gene had 4-5 consensus changes, depending on the tissue examined. The gp 120 gene had the highest number of nucleotide and amino acid substitution rates that varied from 0.64% to 1.44% and 1.17% to 3.71%, respectively, again depending on the tissue examined. These results suggest that a constellation of changes accumulated at the genomic level during the derivation of a SHIV that was pathogenic for pig-tailed macaques.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Erwinia amylovora secretes harpin via a type III pathway and contains a homolog of yopN of Yersinia spp.

Type III secretion functions in flagellar biosynthesis and in export of virulence factors from several animal pathogens, and for plant pathogens, it has been shown to be involved in the export of elicitors of the hypersensitive reaction. Typified by the Yop delivery system of Yersinia spp., type III secretion is sec independent and requires multiple components. Sequence analysis of an 11.5-kb region of the hrp gene cluster of Erwinia amylovora containing hrpI, a previously characterized type III gene, revealed a group of eight or more type III genes corresponding to the virB or lcrB (yscN-to-yscU) locus of Yersinia spp. A homolog of another Yop secretion gene, yscD, was found between hrpI and this group downstream. Immediately upstream of hrpI, a homolog of yopN was discovered. yopN is a putative sensor involved in host-cell-contact-triggered expression and transfer of protein, e.g., YopE, to the host cytoplasm. In-frame deletion mutagenesis of one of the type III genes, designated hrcT, was nonpolar and resulted in a Hrp- strain that produced but did not secrete harpin, an elicitor of the hypersensitive reaction that is also required for pathogenesis. Cladistic analysis of the HrpI (herein renamed HrcV) or LcrD protein family revealed two distinct groups for plant pathogens. The Yersinia protein grouped more closely with the plant pathogen homologs than with homologs from other animal pathogens; flagellar biosynthesis proteins grouped distinctly. A possible evolutionary history of type III secretion is presented, and the potential significance of the similarity between the harpin and Yop export systems is discussed, particularly with respect to a potential role for the YopN homolog in pathogenesis of plants.

Amino Acid Sequence↗

PubMed1996

Adrenomedullin activity in chronically hypoxic rat lungs.

Adrenomedullin (AM) is a novel vasodilator with structural similarities to calcitonin gene-related peptide (CGRP). This study investigated AM activity in the rat lung during hypoxia-induced pulmonary hypertension. Both rat AM (0.2-10 nmol) and alpha-CGRP (0.2-2 nmol) produced dose-related reductions in pulmonary artery pressure in the isolated perfused lung ventilated with 2% O2. Pretreatment with alpha-CGRP, which demonstrated tachyphylaxis, or its antagonist, CGRP-(8-37), reduced the hypotensive response to AM, suggesting that part of the response to AM is mediated by CGRP receptors. 125I-labeled AM and 125I-labeled CGRP binding was significantly increased in lung membranes from 7-day hypoxic animals (AM from 1.94 +/- 0.3 to 3.36 +/- 0.4 and CGRP from 0.06 +/- 0.01 to 0.12 +/- 0.02 pmol/mg protein), with no change in dissociation constant. Moreover, the hypotensive response to both peptides was increased in the lungs of 7-day hypoxic rats. There was no significant change in lung immunoreactive AM concentrations (hypoxic 5.04 +/- 0.48 vs. control 6.28 +/- 0.76 pmol/g wet wt of tissue) or steady-state AM mRNA levels in 7-day hypoxic rats. Nonetheless, AM may be useful for the acute pharmacological manipulation of pulmonary artery pressure in hypoxia-induced pulmonary hypertension.

Adrenomedullin↗