Biomedical subjects

Z Jiang

Publications and source records attributed to Z Jiang.

At least 19 recordsLinked to original sources

PubMed1999

Evolution of the HOXB6 intergenic region: motif conservation at the lateral plate mesoderm (LPM) enhancer element.

This study reports the results of a comparative sequencing study in higher primates, focusing on the intergenic region located between HOXB6 and HOXB7. We have examined an 832 bp. region, encompassing a putative Lateral Plate Mesoderm (LPM) enhancer element in a variety of anthropoid apes. The interspecific comparisons reveal extensive substitutions occurring within this region, with a marked bias in favor of C-->T transitions within the enhancer element. The pattern of these substitutions suggests that the LPM enhancer region is subject to specific sequence and compositional constraints that are only revealed through comparative sequencing. These constraints produce an enhancer signature, the CpG microisland, which may be useful in identifying additional regulatory elements located within the HOX complexes. J. Exp. Zool. (Mol. Dev. Evol.) 285:170-176, 1999.

Animals↗

PubMed1999

Directional guidance of neuronal migration in the olfactory system by the protein Slit.

Although cell migration is crucial for neural development, molecular mechanisms guiding neuronal migration have remained unclear. Here we report that the secreted protein Slit repels neuronal precursors migrating from the anterior subventricular zone in the telencephalon to the olfactory bulb. Our results provide a direct demonstration of a molecular cue whose concentration gradient guides the direction of migrating neurons. They also support a common guidance mechanism for axon projection and neuronal migration and suggest that Slit may provide a molecular tool with potential therapeutic applications in controlling and directing cell migration.

Animals↗

PubMed1999

Bacterial photoreceptor with similarity to photoactive yellow protein and plant phytochromes.

A phytochrome-like protein called Ppr was discovered in the purple photosynthetic bacterium Rhodospirillum centenum. Ppr has a photoactive yellow protein (PYP) amino-terminal domain, a central domain with similarity to phytochrome, and a carboxyl-terminal histidine kinase domain. Reconstitution experiments demonstrate that Ppr covalently attaches the blue light-absorbing chromophore p-hydroxycinnamic acid and that it has a photocycle that is spectrally similar to, but kinetically slower than, that of PYP. Ppr also regulates chalcone synthase gene expression in response to blue light with autophosphorylation inhibited in vitro by blue light. Phylogenetic analysis demonstrates that R. centenum Ppr may be ancestral to cyanobacterial and plant phytochromes.

Acyltransferases↗

PubMed1999

Effect of NO donors on LV diastolic function in patients with severe pressure-overload hypertrophy.

BACKGROUND: Previous experimental studies have shown that nitric oxide (NO) modulates cardiac function by an abbreviation of systolic contraction and an enhancement of diastolic relaxation. However, the response to NO donors of patients with severe pressure-overload hypertrophy and diastolic dysfunction is unknown. METHODS AND RESULTS: Intracoronary NO donors were given to 17 patients with severe aortic stenosis. A dose-response curve was obtained with nitroglycerin (30, 90, and 150 microg) in 11 patients and sodium nitroprusside (1, 2, and 4 microg/min) in 6. Left ventricular (LV) high-fidelity pressure measurements with simultaneous LV angiograms were performed at baseline and after the maximal dose of NO. The dose-response curve for intracoronary NO donors showed a marked fall in LV end-diastolic pressure, from 23 to 14 mm Hg (-39%; P<0.0001), whereas LV peak systolic pressure fell only slightly, from 206 to 196 mm Hg (-4%; P<0.01). End-diastolic chamber stiffness decreased from 0.12 to 0.07 mm Hg/mL (P<0.0001) and end-systolic stiffness from 1.6 to 1.3 mm Hg/mL (P<0.01). Heart rate, right atrial pressure, LV ejection fraction, the time constant of isovolumic pressure decay (tau), and LV filling rates remained unchanged. CONCLUSIONS: In patients with severe pressure-overload hypertrophy, intracoronary NO donors exert a marked decrease in LV end-diastolic pressure without affecting LV systolic pump function. Thus, the hypertrophied myocardium appears to be particularly susceptible to NO donors, with a marked improvement in diastolic function.

Adult↗

PubMed1999

Characterization of a dCTP transport activity reconstituted from human mitochondria.

A protein fraction of mitochondria from human acute lymphocytic leukemia cells, which could be reconstituted into proteoliposomes to have dCTP transport activity, has been partially purified by hydroxyapatite and blue Sepharose chromatography. The dCTP transport activity in proteoliposomes was time-dependent and could be activated by Ca2+ and to a lesser extent by Mg2+. None of the other divalent cations tested could activate the transport activity. The Km value of dCTP in the presence of Ca2+ was shown to be 3 microM. dCDP but not dCMP or dCyd could inhibit the transport activity. Other deoxynucleoside triphosphates could also inhibit the uptake of dCTP with the potency dGTP = dATP > TTP. Although ATP could competitively inhibit dCTP uptake with a Ki value of 8 microM, the reconstituted dCTP uptake activity was not sensitive to the ATP/ADP carrier inhibitor atractyloside or the sulfhydryl reagent N-ethylmaleimide. This suggests that the dCTP transport system studied is not the same as the ATP/ADP carrier. In conclusion, these studies describe the first functionally reconstituted mitochondrial carrier that displays an efficient transport activity for dCTP.

Biological Transport↗

PubMed1999

An in vitro functionally mature mouse spinal cord preparation for the study of spinal motor networks.

An in vitro isolated whole spinal cord preparation has been developed in 'motor functionally mature' mice; that is mice of developmental maturity sufficient to weight-bear and walk. In balb/c mice this stage occurs at around postnatal day 10 (P10). Administration of strychnine elicited synchronous activity bilaterally in lumbar ventral roots. Rhythmic alternating locomotor-like activity could be produced by application of a combination of serotonin (5-HT), N-methyl-d-aspartate (NMDA), and dopamine in animals up to P12. Using a live cell-dead cell assay, it is demonstrated that there are primarily viable cells throughout the lumbar spinal cord. The viability of descending pathways was demonstrated with stimulation of the mid-thoracic white matter tracts. In addition, polysynaptic segmental reflexes could be elicited. Although usually absent in whole cord preparations, monosynaptic reflexes could invariably be elicited following longitudinal midline hemisection, leading to the possible explanation that there might be an active crossed pathway producing presynaptic inhibition of primary afferent terminals. The data demonstrate that this functionally mature spinal cord preparation can be used for the study of spinal cord physiology including locomotion.

Animals↗

PubMed1999

Human and rodent MaxiK channel beta-subunit genes: cloning and characterization.

Voltage- and Ca2+-sensitive K+ (MaxiK) channels play key roles in controlling neuronal excitability and vascular tone. We cloned and analyzed human and rodent genes for the modulatory beta subunit, KCNMB1. The human and mouse beta-subunit genes are approximately 11 and approximately 9 kb in length, respectively, and have a four exon-three intron structure. Primer extension assay localized the transcription initiation site at 442 (human) or 440 (mouse) bp upstream of the translation initiation codon, agreeing with the transcript size in Northern blots. Both genes have a TATA-less putative promoter region, with a transcription initiator-like region, and motifs characteristic of regulated promoters, including muscle-specific enhancing factors-1 and -2. Consistent with a tissue-specific expression of KCNMB1, regulated at the transcriptional level, beta-subunit transcripts are abundant in smooth muscle and heart, but scarce in lymphatic tissues, brain, and liver. Expressed rat and mouse beta subunits increase the apparent Ca2+ sensitivity of the human MaxiK channel alpha subunit.

Amino Acid Sequence↗

PubMed1999

Neuronal and glial DNA fragmentation in Pick's disease.

Pick's disease (PD) is characterized by severe neuronal loss and gliosis in a frontotemporal lobar distribution, often associated with Pick bodies and ballooned neurons. Abnormal tau metabolism has been implicated in the pathogenesis of PD; however, the underlying mechanism of neuronal degeneration remains poorly understood. Evidence from other neurodegenerative diseases has suggested that DNA damage and apoptosis may play a major role in cellular degeneration and death. In the present study, an in situ nucleotidyl transferase assay (ISNTA) was used to identify DNA fragmentation in three cases of classical PD with Pick bodies and ballooned neurons, and two PD "variants", one with ballooned neurons only and the other without Pick bodies or ballooned neurons. In all cases large numbers of ISNTA-positive neurons were present in anatomic regions having obvious degenerative changes (neuronal atrophy and loss, gliosis, cytoplasmic inclusions) by conventional histology. There was no clear association between neuronal DNA fragmentation and the presence of structural abnormalities such as Pick bodies or ballooned cytoplasm. ISNTA-positive glia were present in both cortex and subcortical white matter. Morphologic evidence of apoptosis was not detected in either neurons or glial cells. We suggest that DNA fragmentation in PD and probably other neurodegenerative disorders most likely specifies a population of potentially vulnerable cells in which both cell death and repair mechanisms have been activated. It is likely that only a very small number of these vulnerable cells at a given time will proceed to cell death; however, it is uncertain whether this occurs by apoptosis or some other mechanism.

Adolescent↗

PubMed1999

Invariant chain expression in colon neoplasms.

Invariant chain (Ii) is a chaperone molecule that inhibits binding of endogenous antigens to class II molecules. High levels of Ii in cancer cells may prevent tumour antigen expression with class II and render the tumour less immunogenic. To correlate the expression of Ii and class II molecules in colon carcinomas with the density of tumour infiltrating lymphocytes (TILs), surgical specimens from a total of 48 patients with well-(WDAC), moderately (MDAC) and poorly differentiated adenocarcinomas (PDAC), adenoma with high-grade dysplasia (AdHGD) and adenomas were immunostained for Ii and class II antigen (HLA-DR). Aggregates of TILs were graded in H&E-stained sections. Normal colon epithelium was negative for Ii and HLA-DR. Invasive carcinomas showed a linear increase in the expression of Ii in the progression from low- to high-grade tumours, while there was no significant difference in HLA-DR expression across the groups. Invasive carcinomas showed a disproportionate increase in Ii over HLA-DR. Frequency of TILs showed inverse correlation with expression of Ii and tumour grade. This is the first demonstration that expression of Ii increases in the progression from low- to high-grade colon neoplasms and is most marked in the poorly differentiated carcinomas. Ii expression by carcinomas is inversely related to the frequency of TILs. The findings suggest that increased Ii renders the tumour less immunogenic and less likely to stimulate a host immune response.

Adenocarcinoma↗

PubMed1999

Influence of additives on the protoplasts electrofusion.

Various neutral or charged surface active substances were used for testing the influence of additives on the electrofusion of barley protoplasts. It was found that neutral surface active agents DX, TAGB, Span-80 and AEO-9 could promote the electrofusion. The positively charged surface active agents Bardac 2080, Bardac 2280 and amphoteric surface active agents dodecyl-propyl betaine and CAB betaine also promote the electrofusion, but at high concentration the electrofusion efficiency will reduce. The negatively charged polymer agents Cibacron blue DX, Fluoresceinylthiocarbamoyl DX, and active surface substances K12 and Carsonol TLS- presented negative effect. These phenomena were discussed from the view of adsorption of additives on the membrane and the interactions between protoplasts.

Cell Fusion↗

PubMed1999

Six triterpenoid saponins from Mmaesa laxiflora.

Six new triterpenoid saponins, maelaxins A-F (1-6), were isolated from a n-BuOH extract of the leaves of Maesa laxiflora. They possess 22-O-angeloyl-camelliagenin A, 16-O-acetyl, 22-O-angeloyl-camelliagenin A, or 22-O-(2Z)-hexenoyl-camelliagenin A as the aglycon. The pentasaccharide moiety linked to C-3 of the aglycon consists of D-glucuronic acid, L-rhamnose, D-glucose, and/or D-galactose. Their structures were elucidated by extensive NMR experiments including 1H-1H (COSY, 2D HOHAHA, NOESY) and 1H-13C (HMQC and HMBC) spectroscopy and chemical evidence.

Antineoplastic Agents, Phytogenic↗

PubMed1999

Fimbria-mediated enhanced attachment of nontypeable Haemophilus influenzae to respiratory syncytial virus-infected respiratory epithelial cells.

Respiratory syncytial virus (RSV) infection is known to predispose children to otitis media and sinusitis due to bacteria such as nontypeable Haemophilus influenzae (NTHI). In this study, we investigated the role of NTHI surface outer membrane protein P5-homologous fimbriae (P5-fimbriae) in attachment to RSV-exposed A549 epithelial cells. Analysis by fluorescence flow cytometry showed that a live P5-fimbriated NTHI strain (NTHIF+) attached to a higher proportion of RSV-exposed A549 cells than to control cells (mean, 68% for RSV versus 29% for control; P = 0.008), while attachment of the P5-fimbriae-deficient isogenic mutant strain (NTHIF-) was significantly lower than in control cells and rose only slightly following RSV exposure (mean, 17% for RSV versus 10% for control, P = 0.229). Attachment of NTHIF+ did not correlate with the amount of RSV antigen expressed by A549 cells. Furthermore, paraformaldehyde-fixed NTHIF+ also demonstrated an enhanced binding to RSV-exposed cells. Observations by transmission electronic microscopy showed that the mean number of bacteria attached per 100 RSV-exposed A549 cells was higher for NTHIF+ than NTHIF- (99 versus 18; P < 0.001). No intracellular bacteria were identified. UV-irradiated conditioned supernatants collected from RSV-infected A549 cultures (UV-cRSV) also enhanced the attachment of NTHIF+ to A549, suggesting the presence of a preformed soluble mediator(s) in UV-cRSV that enhances the expression of receptors for P5-fimbriae on A549 cells. In summary, RSV infection significantly enhances NTHI attachment to respiratory epithelial cells. P5-fimbria is the critical appendage of NTHI that participates in this attachment. In clinical settings, blocking of the P5-fimbria-mediated attachment of NTHIF+ by passive or active immunity may reduce the morbidity due to NTHI during RSV infection.

Antigens, Viral↗

PubMed1998

A whole-genome radiation hybrid map of the dog genome.

A whole genome radiation hybrid (RH) map of the canine genome was constructed by typing 400 markers, including 218 genes and 182 microsatellites, on a panel of 126 radiation hybrid cell lines. Fifty-seven RH groups have been determined with lod scores greater than 6, and 180 framework landmarks were ordered with odds greater than 1000:1. Average spacing between adjacent markers is 23 cR5000, an estimated physical distance of 3.8 Mb. Fourteen groups have been assigned to 9 of the canine chromosomes, and a comparison of RH and genetic groups allowed the successful bridging of both types of data on one map composed of 31 RH and 13 syntenic RH groups. Comparison of canine, human, mouse, and pig maps underlined regions of conserved synteny. This integrated map, covering an estimated 80% of the dog genome, should prove a powerful tool for localizing and identifiying genes implicated in pathological and phenotypical traits.

Animals↗

PubMed1998

Structure, organization, and chromosomal mapping of the gene encoding macrosialin, a macrophage-restricted protein.

Murine macrosialin and its human homologue CD68 are heavily glycosylated transmembrane proteins expressed specifically in macrophages and macrophage-related cells. Macrosialin is predominantly a late endosomal protein but is also found on the cell surface where it binds oxidized LDL, an important factor in atherogenesis. We have cloned and sequenced the murine macrosialin gene (Cd68) and localized it by linkage analysis to chromosome 11. The gene is 1908 nucleotides long from the start site of transcription to the end of the 3'UTR. It has six exons, which range in size from 79 to 434 nucleotides. The promoter lacks a classical TATA box but contains other protein binding sites consistent with preferential monocyte/macrophage gene expression. Although the function of macrosialin is unknown, it might play a role in lipoprotein regulation given its binding of oxidized LDL in vitro and its colocalization to a region on chromosome 11 involved in the control of HDL levels.

Animals↗

PubMed1998

Donnaienin, a New Acetogenin Bearing a Hydroxylated Tetrahydrofuran Ring

A novel Annonaceous acetogenin, donnaienin (1), was isolated from the roots of Goniothalamus donnaiensis. Its structure and stereochemistry were elucidated on the basis of spectral data and chemical evidence. This compound represents an unusual type of Annonaceous acetogenin, bearing a hydroxylated tetrahydrofuran ring.

Journal Article↗

PubMed1998

In vivo investigation of blood compatibility of titanium oxide films.

Titanium oxide films were synthesized by ionbeam-enhanced deposition. The films were prepared by depositing titanium atoms and simultaneously bombarding them with Xe+ ions at an energy of 40 keV in an O2 environment. An in vivo investigation, which entailed implanting low-temperature isotropic pyrolytic carbon (LTI carbon) cylinders, widely used to fabricate artificial heart valves, and titanium-oxide-coated LTI carbon cylinders with diameters of 5 mm and thicknesses of 0.5 mm into the ventral aorta of dogs for 14 days, showed that the amount of thrombus on the titanium-oxide-coated LTI carbon was much less than that formed on the surface of LTI carbon alone. Scanning electron microscopy (SEM) was used to observe the morphology of thrombus. On the titanium oxide films no platelet aggregation was found, almost no red blood cells were damaged, and almost no fibrin was found on the surface. However, all three characteristics were found on the surface of LTI carbon alone, proving that the blood compatibility of titanium oxide films is better than that of LTI carbon and titanium-oxide-coated LTI carbon.

Animals↗

PubMed1998

Human magnetic resonance imaging at 8 T.

In this work, we present the first human magnetic resonance image (MRI) obtained at ultrahigh field strengths (8 T). We demonstrate that clinical imaging will be possible at 8 T and that reasonable quality head images can be obtained at this field strength. Most importantly, we emphasize that the power required to excite the spins at 8 T is much lower than had previously been predicted by the nuclear magnetic resonance theory. A 90 degree pulse in the head at 8 T requires only approximately 0.085 J of energy (90 W for a 2-lobe 4 ms sinc pulse). Based on measurements at 4 T, 1-2 J of energy should have been utilized to achieve a 90 degree excitation at 8 T. The fact that the energy required for spin excitation at 8 T is much lower than predicted by the NMR theory, will be extremely important to the viability of ultrahigh field imaging, since concerns related to power absorption and specific absorption rate (SAR) violations at ultrahigh field are alleviated. As such, it will be possible to utilize RF intensive pulse sequences and adiabatic spin excitation at 8 T without significant risk to the subject.

Brain↗

PubMed1998

Cytokine modulation of human corneal epithelial cell ICAM-1 (CD54) expression.

To determine whether pro-inflammatory cytokines modulate intercellular adhesion molecule-1 (ICAM-1; CD54) expression on cultured primary human corneal epithelial cells (HCEs), confluent HCEs were treated with various concentrations of interferon-gamma(IFN-gamma), interleukin-1alpha(IL-1alpha), IL-1beta, IL-4, tumor necrosis factor-alpha (TNF-alpha), or combinations over time. ICAM-1 expression was measured by flow cytometry and/or a cell-based ELISA using a monoclonal mouse anti-human CD54 antibody. The apparent MW of ICAM-1 protein was determined by immunoprecipitation of biotinylated HCEs. RT-PCR was used to detect ICAM-1 RNA. The mature cell surface form of HCE ICAM-1 was approximately 110 kDa as determined by immunoprecipitation. IFN-gammaand TNF-alpha induced both dose- and time-dependent increases in ICAM-1 expression. An approximately 20-fold increase in ICAM-1 was seen at 50-100 U IFN-gamma ml-1. ICAM-1 specific mRNA accumulated approximately 4.5-fold after IFN-gammatreatment. TNF-alpha(100 U ml-1) induced a consistent approximately 6.0-fold increase in ICAM-1 expression. When IFN-gammaand TNF-alpha were mixed, at sub-optimal concentrations of each, a synergistic effect on ICAM-1 expression was not detected. Neither IL-4, IL-1alpha nor IL-1beta affected ICAM-1 expression in a consistent fashion. In summary, ICAM-1 was modulated on primary human corneal epithelial cells by the cytokines IFN-gamma and TNF-alpha in a dose- and time-dependent fashion. Cytokine modulation of corneal epithelial cell ICAM-1 during inflammation may contribute to corneal epithelial cell injury by aiding the attachment of inflammatory cells such as eosinophils which express the receptor for ICAM-1, the beta2 integrins (CD11a,b,c/CD18).

Cell Culture Techniques↗