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Biomedical subjects

Q Zhong

Publications and source records attributed to Q Zhong.

70 records · Page 4Linked to original sources
PubMed1995

Demonstration of human Borna disease virus RNA in human peripheral blood mononuclear cells.

BDV naturally infects horses and sheep, and causes sporadic neurological disease. Serological evidence suggests an association of BDV, or a related virus, with specific psychiatric diseases in humans. Here, by using a nested RT-PCR technique, we demonstrate that human BDV RNA is present in the PBMC of psychiatric patients. In an examination of a total of 60 patients from 5 wards of a hospital in Japan, the detection rate differed within each ward, ranging from 8% to > 50% (37% on the average). Of particular note was the finding that the human derived BDV sequences, which included deleted forms in about 23% of the positive samples, were slightly different from those derived from horse BDV. These results suggest urgent consideration of the measures to be taken to cope with the effects of blood transfusion. In addition, the detection of a high level of BDV in the PBMC of patients will help our understanding of the pathogenesis in the disease.

Antibodies, Viral↗
PubMed1995

Maintenance of high virus load even after seroconversion in newborn cats acutely infected with feline immunodeficiency virus.

The viral loads in adult and newborn cats have been compared following injection with feline CD4+ FeL-039 line cells acutely infected with feline immunodeficiency virus (FIV). The level of virus genome in peripheral blood mononuclear cells (PBMC) increased progressively despite seroconversion in the newborn cats, whereas the virus genome was apparently cleared after seroconversion in the adult cats. Immunohistochemical staining of thymus of the FIV-infected newborn cats showed clusters of viral antigen-positive cells. These results indicate that FIV infection of the newborn cat results in higher virus loads than infection of the adult cat. We discuss these findings in relation to FIV as a model system for studies of the infection of neonates with an immunosuppressive retrovirus.

Acute Disease↗
PubMed1995

Release of EDRF and NO in ex vivo perfused aorta: inhibition by in vivo E. coli endotoxemia.

Previous studies have yielded contradictory results about interrelations between endotoxin and endothelium-derived relaxing factor (EDRF). We tested the hypothesis that in vivo endotoxemia inhibits basal and/or agonist-mediated release of EDRF and nitric oxide (NO). EDRF bioactivity, NO production, and NO synthase (NOS) activity were measured in aorta from guinea pigs following 16 h of Escherichia coli endotoxemia (4 mg/kg endotoxin i.p.). Endothelium-dependent relaxation of aortic rings was studied under standard isometric conditions. Endotoxemia resulted in an 89% reduction in basal EDRF bioactivity and a 62% reduction in basal NO production in perfused aorta. EDRF bioactivity and NO production in response to the receptor-dependent agonists acetylcholine and ADP were significantly reduced in perfused aorta from endotoxemic animals. In contrast, endotoxin did not significantly inhibit EDRF bioactivity and NO production by the receptor-independent agonist A-23187. Aortic rings from endotoxemic animals likewise showed decreased vasodilator responses to acetylcholine and ADP but not to A-23187. Inducible (Ca2+ independent) NOS activity was not significantly different in control and endotoxin-treated animals. These findings indicate that prolonged endotoxemia resulted in diminution of release of EDRF, consistent with the interpretation that endotoxemia decreases basal and agonist-stimulated EDRF bioactivity and NO production with loss of endothelium-dependent vasodilator reserves during gram-negative sepsis.

Acetylcholine↗
PubMed1994

The carboxyl-terminal region of HIV-1 Nef protein is a cell surface domain that can interact with CD4+ T cells.

Our previous studies have shown that the HIV-1 Nef Ag is expressed, at least in part, on the surface of infected cells. We demonstrated this by using membrane immunofluorescence and flow cytometry with Nef murine mAbs. To identify the domain of Nef exposed on the cell surface, epitope mapping of these and a new mAb was performed by ELISAs by using several recombinant truncated Nef fusion proteins and synthetic peptides. The results showed that mAbs F1, E7, E9, and 4H4 recognized Nef epitopes located at amino acid residues 148-157, 192-206, 158-206, and 1-33, respectively. The intensity of cell surface Nef staining was stronger with mAbs E7 and E9 than with F1, and there was no staining by 4H4, which indicates that the carboxyl-terminal region of Nef is predominantly exposed on the surface of HIV-1-infected T cell lines and PBMC. This surface Nef domain displayed high affinity for the surface of uninfected CD4+ T cells, because the binding of a soluble form of recombinant Nef protein to the cell surface was specifically blocked by the E7 and E9 mAbs or by synthetic peptides that contained the carboxyl-terminal region of Nef. In addition, syncytium formation between infected and uninfected cells also was specifically reduced by the same mAbs or peptides. Thus, the cell surface domain of Nef seems to play an important role in the interaction between HIV-1-infected and CD4+ uninfected T cells.

Antibodies, Monoclonal↗
PubMed1994

Conversion of alpha 1-antichymotrypsin into a human neutrophil elastase inhibitor: demonstration of variants with different association rate constants, stoichiometries of inhibition, and complex stabilities.

Despite the homology with alpha 1-protease inhibitor (alpha 1PI), wild-type antichymotrypsin (ACT) is a substrate for HNE rather than an inhibitor of the enzyme. In order to investigate the nature of the specificity between serpins and serine proteases, the reactions of human neutrophil elastase (HNE) with wild-type recombinant ACT and recombinant variants of ACT were studied. ACT variants were generated where (1) the primary interaction site, the P1 position, was replaced with the P1 residue of alpha 1PI, (2) the residues corresponding to P3-P3' were replaced with those of alpha 1PI, and (3) the residues corresponding to the canonical recognition sequence as well as flanking residues encompassing the exposed reactive loop of the inhibitor were replaced with the corresponding residues of alpha 1PI. Each variant was analyzed to determine the effect of the replacements on reactions with human neutrophil elastase and chymotrypsin with regard to (1) the second-order rate constant for enzyme-serpin complex formation, (2) the number of moles of serpin required to completely inhibit 1 mol of enzyme (the stoichiometry of inhibition, SI), and (3) the stability of the enzyme-serpin complex. Replacing Leu with Met in the P1 position (rACT-L358M) was sufficient to convert rACT into an inhibitor of HNE with an apparent second-order rate constant (k'/[I]) of 4 x 10(4) M-1 s-1 and an SI of 5. The high SI was due to a concurrent hydrolytic reaction at sites in the reactive loop.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Analysis of FAS3/ACC regulatory region of Saccharomyces cerevisiae: identification of a functional UASINO and sequences responsible for fatty acid mediated repression.

We have determined the sequence of the FAS3/ACC regulatory region and mapped the transcription initiation site. In this sequence, there are two putative UASINO sequences. Deletion and mutation analyses revealed that the UASINO sequence at nucleotides -719 to -710 is functional. The expression of FAS3-lacZ reporter genes and the measurement of mRNA levels in regulatory mutants of phospholipid biosynthesis clearly indicated that FAS3 is regulated by inositol and choline. Previous studies have shown that the genes coding for fatty acid synthase, FAS1 and FAS2, are regulated by inositol (Chirala, S.S. [1992] Proc. Natl. Acad. Sci. USA 89, 10232-10236). Thus all three genes involved in saturated fatty acid biosynthesis are coordinately regulated with phospholipid biosynthesis. Comparison of the UASINO sequences present in FAS1, FAS2, and FAS3 suggested that the functional sequence of this UAS element is YTTCACATG. However, even when the functional UASINO was mutated, substantial expression of the FAS3-lacZ reporter gene was observed. Deletion analysis, electrophoretic mobility shift assays, and expression using a heterologous reporter gene showed that the region between nucleotides -840 and -736 has two UAS elements. The same sequence seems to be responsible for fatty acid-mediated repression of FAS3. The presence of these additional UAS sequences explains why yeast does not require fatty acids even when repressing amounts of inositol and choline are present in the medium.

Amino Acid Sequence↗
PubMed1994

In vivo induction of human immunodeficiency virus type 1-specific cytotoxic T lymphocytes and delayed-type hypersensitivity by a 23-amino acid peptide from the highly conserved region in major core protein p24.

Cell-mediated immune responses are a major immune defence mechanism against the spread of human immunodeficiency virus type 1 (HIV-1) which may lead to acquired immune deficiency syndrome (AIDS). Therefore, the best candidate for a peptide vaccine preventive from the onset of the disease might be a chain section containing both B- and T-cell epitopes in regions of conserved sequences between the different HIV-1 isolates. We previously identified the highly conserved linear B-cell epitope (23 amino acids in the major core protein p24). Since the epitopes of cytotoxic T lymphocytes (CTLs) can be defined by short synthetic peptides, we examined whether this highly conserved region can elicit viral-specific, cell-mediated immune responses. The results showed specific induction of CD8+ CTLs in mice by immunization with the Gag 13-mer peptide. Lysis of targets is specific since unpulsed cells with the same MHC haplotype or cells with a different MHC haplotype pulsed with the peptide were resistant to lysis. This in vivo response induced by the Gag 23-mer peptide was almost the same as that induced by the 15-amino acid peptide from the HIV-1 Env gp120 which is an immunodominant domain in the V3 loop. Lymphocyte proliferation of T-cell fraction from immune spleen cells was observed after in vitro stimulation with the Gag 23-mer peptide, whereas there was no apparent lymphocyte proliferation with the Env 15-mer peptide. In addition, specific antibodies were raised against Gag p24 in mice immunized with the Gag 23-mer peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Inhibition of endothelium-dependent vasodilation by Escherichia coli endotoxemia.

To test the hypothesis that release of endothelium-derived relaxing factor/nitric oxide is inhibited by Gram-negative lipopolysaccharide (LPS; endotoxin), we examined endothelium-independent and endothelium-dependent vasodilator agents in aortic vascular smooth muscle isolated from guinea pigs 4 h after injection of saline (controls) or induction of Escherichia coli endotoxemia. LPS significantly inhibited vasodilator responses to the endothelium-dependent agonists acetylcholine (ACh; 10(-10)-10(-5) M) and ADP (10(-8)-10(-5) M). However, LPS did not affect vasodilator responses to the endothelium-independent agonist nitroprusside (10(-10)-10(-4) M). The nitric oxide synthase (NOS) inhibitor N gamma-nitro-L-arginine methyl ester (L-NAME) inhibited the vasodilator response to ACh; whereas, the cyclooxygenase inhibitor indomethacin (INDO) did not reduce vasodilator effects of ACh. Neither L-NAME nor INDO affected the vasodilator effects of nitroprusside in LPS or control vessels. In contrast, L-NAME converted the vasodilator action of ADP to a vasoconstrictor response that was blocked individually by INDO and the thromboxane synthase inhibitor dazoxiben, suggesting that ADP releases NO and also the vasoconstrictor and platelet aggregating eicosanoid thromboxane A2. These findings suggest that acute (4 h) endotoxemia inhibits function of the constitutive isoform of NOS in vascular endothelial cells. Since L-NAME unmasked a vasoconstrictor action of the endogenous purinoceptor agonist ADP, pharmacologic agents that inhibit NOS may exacerbate LPS-induced inhibition of endothelial NOS; this series of events could lead to diminution of vasodilator reserves and perhaps to augmentation of platelet aggregation during Gram-negative sepsis.

Acetylcholine↗
PubMed1993

Crystallization and atomic resolution X-ray diffraction analysis of antichymotrypsin variants.

Crystals of two recombinant antichymotrypsin (rACT) variants have been prepared: variant rACT-T345R crystallizes in space group P2(1) (a = 109.2 A, b = 79.4 A, c = 111.9 A, beta = 116.3 degrees, with 2 molecules in the asymmetric unit), and variant ACT' crystallizes in space group P2(1)22(1) (a = 69.7 A, b = 77.2 A, c = 83.8 A, with one molecule in the asymmetric unit). The latter variant is an engineered dimer having the P3-P3' hexapeptide sequence of the related serpin, alpha 1-proteinase inhibitor, substituted for the corresponding wild-type sequence. Crystals of each variant diffract to a limiting resolution of 2.5 A, which represents the best diffraction yet achieved for a crystalline, inhibitory serpin. The exceptional quality of ACT' crystals probably arises from favorable protein-protein interactions as well as a stabilizing disulfide crosslink engineered between the monomers.

Chymotrypsin↗
PubMed1990

Inhibitory effects of transforming growth factor beta 1 on mitogenic response, transforming growth factor alpha, and c-myc in quiescent, well-differentiated colon carcinoma cells.

Previously, we reported that exponentially proliferating cultures of well-differentiated human colon carcinoma cells responded to transforming growth factor beta 1 (TGF-beta) with growth inhibition, alterations in morphology, and increased secretion of the differentiation marker, carcinoembryonic antigen. Poorly differentiated cultures were unresponsive. Here we show that TGF-beta was ineffective in repressing nutrient-stimulated mitogenesis in quiescent, poorly differentiated cells. However, in quiescent, well-differentiated cells, TGF-beta repressed the mitogenic responses to both nutrients alone (by 90%) and to nutrients plus the exogenous stimulatory factors epidermal growth factor (E), insulin (I), and transferrin (T) (by 55-65%). Thymidine incorporation experiments indicated that TGF-beta reduced both the onset and peak mitogenic response to growth factors and/or nutrients in the well-differentiated cells. Additionally, TGF-beta repressed the growth factor (E + I + T)-stimulated upregulation of expression of both c-myc and of transforming growth factor alpha (TGF-alpha) mRNAs in quiescent, well-differentiated cells. TGF-beta also elicited a rapid (t1/2 approximately 1h) down-regulation of c-myc expression in the absence of prior growth factor (E + I + T) stimulation. In contrast, TGF-beta had no effect on c-myc or TGF-alpha mRNA expression in the poorly differentiated cells. The results suggest that TGF-beta exerts rapid inhibitory effects on proliferation-associated genes in quiescent and restimulated, well-differentiated cells. Expression of these genes (c-myc and TGF-alpha) may otherwise (in the absence of TGF-beta) play roles in the cellular signaling of mitogenic responses by growth stimulatory factors in well-differentiated colon carcinoma cells.

Blotting, Northern↗
PubMed1989

Ca2+ channels in chick neural retina cells characterized by 1,4-dihydropyridine antagonists and activators.

The voltage-sensitive calcium channel in cultured chick neural retina cells was characterized by the actions of the enantiomers of Bay K 8644 and 202-791 and other 1,4-dihydropyridines. These cells showed time- and voltage-dependent Ca2+ uptake that was stimulated by K+ depolarization and blocked by the inorganic calcium channel blockers Cd2+ and Co2+. A small fraction only (15% maximum) of the uptake was inactivated by predepolarization of the cells with 80 mM K+. Ca2+ uptake was sensitive to the 1,4-dihydropyridine calcium channel antagonists and activators. (S)-Bay K 8644 and (S)-202-791 stimulated the Ca2+ uptake, and (R)-Bay K 8644 and (R)-202-791 as well as nitrendipine and PN 200-110 inhibited Ca2+ uptake stimulated by K+ depolarization or channel activators. The K+ depolarization-stimulated uptake was inhibited by 90%, but the activator-stimulated uptake was completely blocked by the 1,4-dihydropyridine antagonists. The potencies of these agents as inhibitors of Ca2+ uptake were significantly lower than the binding affinities in membrane preparations from the same cells or their binding and pharmacologic affinities in vascular smooth muscle. K+ depolarization or (S)-Bay K 8644 induced 45Ca2+ uptake was not observed in a glial cell culture. [3H]Nitrendipine and [3H]PN 200-110 bound to membrane preparations of the cells consistent with the presence of a single type of high affinity binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

The interactions of 1,4-dihydropyridines bearing a 2-(2-aminoethylthio)methyl substituent at voltage-dependent Ca2+ channels of smooth muscle, cardiac muscle and neuronal tissues.

The Ca2+ channel antagonistic potencies of tiamdipine [2-(2-aminoethylthio)methyl-3-carboethoxy-5-carbomethoxy-6-m ethyl-4-(3- nitrophenyl)-1,4-dihydropyridine] and nifedipine [2,6-dimethyl-3,5-dicarbomethoxy-4-(2-nitrophenyl)-1,4-dihydrop yri dine] analogs bearing phenyl ring substituents were studied using pharmacologic and radioligand binding techniques. Additionally, analogs of tiamdipine possessing (2-aminoethylthio)methyl-, (2-acetamidoethylthio)methyl- and (2-pyrrolidinylmethylthio)methyl- groups at the C2 position of the 1,4-dihydropyridine ring have been studied. Tiamdipine and nifedipine analogs inhibited K(+)-induced contractile responses in rat tail artery. IC50 values of 4-phenyl ring substituted 2-(2-aminoethylthio)methyl tiamdipine analogs ranged from 10(-7) mol/l to 10(-8) mol/l. However, the corresponding 4-phenyl ring substituted nifedipine analogs covered a wider range of potency from 10(-6) mol/l to 10(-9) mol/l. KI values of the corresponding tiamdipine analogs for the inhibition of specific [3H]PN 200-110 [(+)-[3H]isopropyl-4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-5- methoxycarbonyl-2,6-dimethyl-3-pyridinecarboxylate] binding ranged from 10(-7) mol/l to 10(-9) mol/l in guinea pig ileal and rat heart membranes and rat brain synaptosomes. The two stereoisomers of tiamdipine and its analog 2-(2-acetamidoethylthio)methyl-3-carboethoxy-5-carbomethoxy- 6-methyl-4-(3- nitrophenyl)-1,4-dihydropyridine, and the four stereoisomers of 2-(2-pyrrolidinylmethylthio)methyl-3-carboethoxy-5-carbom eth oxy-6-methyl-4-(3- nitrophenyl)-1,4-dihydropyridine showed high stereoselectivity ratios of approximately (-)/(+) = 100 and 1000 in pharmacologic and binding experiments, respectively. The inhibitory actions of 2-(2-aminoethylthio)methyltiamdipine analogs against K(+)-induced contractile responses in rat tail artery developed very slowly requiring at least 2 h for maximum effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Secondary structures of lipid-associating peptides: a Fourier transform infrared study.

Four peptides from 20 to 28 residues in length were studied by Fourier transform infrared (FTIR) spectroscopy in solution and in complexes with dimyristoylphosphatidylcholine (DMPC). The four peptides included the 20-residue lipid-associating peptide, LAP-20, which was predicted to form an amphipathic helical structure in the presence of lipids, and three other peptides whose sequences had less amphipathic helix-forming properties. The complexes were shown by electron microscopy to be discoidal in shape with mean diameters of 21-27 nm. At the concentrations used for IR, the peptides appeared to form oligomers consisting of intermolecular beta-sheets. In the presence of lipids, the amount of beta-structure decreased; however, amounts of beta-structure were still approximately equal to amounts of alpha-helix. The IR results for LAP-20 contradicted previous circular dichroism results that predicted 50%-90% alpha-helix in DMPC complexes. Convex constraint analysis (CCA) deconvolution of the circular dicroism (CD) spectrum to estimate secondary structures predicted amounts of helix similar to those predicted by IR, but there was still substantial disagreement between IR and CD estimates of other secondary structures. For LAP-20 in complexes, CD predicted random structure. Possible physiological consequences of partial disordering of peptide structures are discussed.

Amino Acid Sequence↗
PubMedDate not supplied

Sequence-specific 1H NMR assignments and secondary structure of a lipid-associating peptide from human ApoC-I: an NMR study of an amphipathic helix motif.

The conformation of a synthetic peptide corresponding to residues 35-53 (SAKM-REWFSETFQKVKEKL) of human apolipoprotein C-I (57 amino acids) was studied by nuclear magnetic resonance and circular dichroism spectroscopy in water and in perdeuterated dodecylphosphocholine solution at 37 degrees C and pH 4.8. The proton resonances of the peptide in both solutions were assigned from TOCSY, NOESY and DQF-COSY experiments. In water solution, the peptide is predominantly "random", although nuclear Overhauser connectivity patterns and H alpha secondary shifts show a threshold population of nascent helical conformers. Upon the addition of 40-fold molar excess dodecylphosphocholine to the water solution, the peptide adopts a helical structure that extends throughout the sequence.

Amino Acid Sequence↗