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Biomedical subjects

J X Jiang

Publications and source records attributed to J X Jiang.

At least 37 records · Page 2Linked to original sources
PubMed1997

Plasma cytokines and endotoxin levels in patients with severe injury and their relationship with organ damage.

In 17 patients plasma TNF-alpha and IL-8 were assayed with enzyme-linked immunosorbent assay. IL-6 activity in plasma was determined by bioassay with IL-6-dependent cell line 7TD1. The limulus amoebocyte lysate chromogenic test was used for plasma endotoxin assay. Plasma cytokine levels in injured patients were significantly increased. Plasma TNF-alpha was shown to be increased earlier, while an increase in plasma IL-6 and IL-8 levels occurred late, all of which were shown to be significantly positively correlated with ISS, cardiac and hepatic enzyme activities, and index of renal function. In addition, obvious endotoxaemia occurred at an early stage of injuries, which was respectively significantly correlated with ISS and plasma TNF-alpha, IL-6 and IL-8 levels. Severe injuries could induce increased successive release of TNF-alpha, IL-6 and IL-8, and obvious endotoxaemia. The post injury release of cytokines might be related to endotoxaemia, and may play an important role in the development of organ damage after injury.

Adolescent↗
PubMed1997

Effect of hemorrhagic shock on endotoxin-inducing TNF production and intra-tissue lipopolysaccharide-binding protein mRNA expression and their relationship.

In order to further elucidate effect of hemorrhagic shock on endotoxin-inducing cytokine production, the present study was designed to investigate the production of tumor necrosis factor alpha (TNF alpha) induced by low-dose (1 microgram/kg) of lipopolysaccharide (LPS) and its cellular sources after hemorrhagic shock (HS) in rats. With combination of expression of lipopolysaccharide-binding protein (LBP) mRNA in the liver, lungs, and kidneys, we further analyzed a possible mechanism for increasing sensitivity to LPS by shock. We found in vivo that plasma TNF alpha levels in the HS + LPS group were 20-fold higher than those in the HS group (p < .01) and 2.7-fold higher than those in the LPS group (p < .05). It was shown in vitro that the capacity of the peripheral white blood cells to produce TNF alpha in response to LPS stimulation was significantly decreased by 126% (p < .01) and 57% (p < .05) compared with the pre-shock levels and sham group, respectively, at the end of resuscitation following shock, and still markedly inhibited 3 h after resuscitation, while the capacity of hepatic Kupffer's cells to produce TNF alpha was significantly increased by 110% compared with the sham group (p < .01) after shock and resuscitation. Results from RT-PCR showed that expression of LBP mRNA in the liver, lungs, and kidneys was increased after shock and resuscitation. It is suggested that hemorrhagic shock could significantly strengthen endotoxin to induce TNF alpha production, which might be due to up-regulation of LBP expression in tissues after shock, and the tissue macrophage population may be the main source for cytokine production in shock.

Acute-Phase Proteins↗
PubMed1996

Heteromeric connexons in lens gap junction channels.

Gap junction channels are formed by paired oligomeric membrane hemichannels called connexons, which are composed of proteins of the connexin family. Experiments with transfected cell lines and paired Xenopus oocytes have demonstrated that heterotypic intercellular channels which are formed by two connexons, each composed of a different connexin, can selectively occur. Studies by Stauffer [Stauffer, K. A. (1995) J. Biol. Chem. 270, 6768-6772] have shown that recombinant Cx26 and Cx32 coinfected into insect cells may form heteromeric connexons. By solubilizing and subfractionating individual connexons from ovine lenses, we show by immunoprecipitation that connexons can contain two different connexins forming heteromeric assemblies in vivo.

Animals↗
PubMed1995

Characterization of four novel CAG repeat-containing cDNAs.

Stretches of CAG nucleotides coding for the amino acid glutamine are an important feature of many transcription factors and genes that are involved in neurodegenerative disorders. In an attempt to isolate CAG repeat-containing cDNAs expressed in nervous tissue, we screened a human fetal brain cDNA library with a probe containing a CAG repeat. Five different clones were characterized and found to contain CAG repeats. Sequence data revealed that four of these cDNAs were derived from novel genes. These cDNAs were designated CAG6, CAG12, CAG24, and CAG40 and were found to correspond to transcripts of 5.0, 7.5, 4.4, and 15 kb, respectively. The genes encoding CAG6, CAG12, CAG24, and CAG40 were assigned to chromosomes 12, 16, X, and 12, respectively. For the 5th gene, CAG26/pRHpA, a localization on two different chromosomes was established: 16 and X. None of the repeats showed any length polymorphisms in human DNA.

Base Sequence↗
PubMed1995

Changes in connexin expression and distribution during chick lens development.

Gap junctions are composed of the connexins, a family of proteins which have been shown to be the structural and functional building blocks of gap junctional intercellular channels. In the chick lens, three members of the connexin (Cx) family have been characterized: Cx 43 has been shown to be a component of interepithelial cell gap junctions, and Cx 45.6 and Cx 56 have been shown to be part of fiber-to-fiber junctions. Early in chick development, gap junctional communication between differentiating lens fibers in the chick loses its sensitivity to blockade by elevated carbon dioxide (CO2). The lens epithelial cells, however, remain CO2-sensitive throughout development. A possible explanation for the change in CO2 sensitivity is that the lens fibers express differentiation-specific connexins with different physiological properties. Using specific antibodies for each of the three lens connexins, we show here that the lens fibers began to express Cx 45.6, and Cx 56 at the developmental stage when lens fibers acquired CO2-insensitivity. However, electron microscopic immunocytochemistry revealed that both Cx 45.6 and Cx 56 were found in interepithelial cell gap junctions, in addition to Cx 43. Conductances between paired Xenopus oocytes injected with Cx 43, Cx 45.6 and Cx 56 mRNAs revealed that all three connexins were CO2-sensitive in this expression system. Taken together, these data ruled out the possibility that the change in CO2 sensitivity observed in vivo could be explained on the basis of the distribution of connexins alone; other parameters of cellular context, such as post-translational processing, must be involved in the observed developmental changes in physiology.

Animals↗
PubMed1994

Molecular cloning and functional characterization of chick lens fiber connexin 45.6.

The avian lens is an ideal system to study gap junctional intercellular communication in development and homeostasis. The lens is experimentally more accessible in the developing chick embryo than in other organisms, and chick lens cells differentiate well in primary cultures. However, only two members of the connexin gene family have been identified in the avian lens, whereas three are known in the mammalian system. We report here the molecular cloning and characterization of the third lens connexin, chick connexin45.6 (ChCx45.6), a protein with a predicted molecular mass of 45.6 kDa. ChCx45.6 was encoded by a single copy gene and was expressed specifically in the lens. There were two mRNA species of 6.4 kilobase (kb) and 9.4 kb in length. ChCx45.6 was a functional connexin protein, because expression in Xenopus oocyte pairs resulted in the development of high levels of conductance with a characteristic voltage sensitivity. Antisera were raised against ChCx45.6 and chick connexin56 (ChCx56), another avian lens-specific connexin, permitting the examination of the distribution of both proteins. Immunofluorescence localization showed that both ChCx45.6 and ChCx56 were abundant in lens fibers. Treatment of lens membranes with alkaline phosphatase resulted in electrophoretic mobility shifts, demonstrating that both ChCx45.6 and ChCx56 were phosphoproteins in vivo.

Amino Acid Sequence↗
PubMed1993

Efficacy of a recombinant Norwalk virus protein enzyme immunoassay for the diagnosis of infections with Norwalk virus and other human "candidate" caliciviruses.

A recombinant Norwalk virus antigen enzyme immunoassay (rNV EIA) for the detection fo Norwalk virus (NV) antibodies was evaluated using sera from volunteers and patients infected with Norwalk, Hawaii, Snow Mountain Agent, small round structured viruses (SRSV), and human calicivirus (HuCV) strains. The results for NV antibodies correlated well with previous results obtained using a NV radioimmunoassay. The test rNV EIA was found to be highly specific for NV. The results of tests on sera obtained from patients involved in confirmed outbreaks of SRSV in the UK showed that only 1/12 was due to Norwalk virus. Further evidence is presented that SRSV strain UK2 is antigenically related to NV.

Adult↗
PubMed1993

[Scanning electron microscopic observation on the encysted and excysted metacercariae of Paragonimus heterotremus].

The surface ultrastructure of metacercariae of Paragonimus heterotremus was studied by scanning electron microscope. Encysted metacercaria was egg-shaped with a button-like structure on its end. The oral sucker of the newly excysted metacercaria was larger than the ventral sucker. Single-pointed spines were covered densely on all of the tegumental surface. There were two and three rings sensory papillae on the oral and ventral suckers, respectively. Six papillae of the most inner ring were distributed on the ventral sucker inner-pore symmetrically. A few sensory papillae were dispersed on each side of the anterior part of the worms. These papillae of some excysted metacercariae were arranged irregularly in two rows with 5 to 6 papillae in each row (Figs. 1-8).

Animals↗
PubMed1993

Posttranslational phosphorylation of lens fiber connexin46: a slow occurrence.

PURPOSE: To study in both in situ and primary cultures the posttranslational phosphorylation of connexin46 (Cx46), one of two members of the connexin family of gap junction proteins expressed by lens fibers. METHODS: Phosphatase digestion, gel electrophoresis, cell culture, organ culture, immunoprecipitation, metabolic labeling, and phosphoamino acid analysis were the methods used in this study. RESULTS: Cx46 immunoprecipitated from either rat or bovine lenses resulted in a shift to a more rapidly migrating species. During rat embryonic development, the more rapidly migrating, nonphosphorylated form of Cx46 was prevalent at 15 days gestation; as development progressed, there was a loss of the nonphosphorylated form with a concomitant increase in the phosphorylated form, such that by 28 days after birth only the phosphorylated form was detectable. The rate of posttranslational phosphorylation was very slow compared to previously measured rates for connexin43. Primary cultures of rat embryonic lens epithelial cells, which contained differentiating lentoids, were labeled with 35S-methionine and chased for 8 days. Very low levels of Cx46 were detectable, and none of this labeled material shifted to the slower mobility during the 8-day chase period. Similarly, in organ culture of bovine lenses, Cx46 could be labeled with 35S-methionine, but the immunoprecipitated material remained in the rapidly migrating form for 1 week, the longest time measured. This immunoprecipitated material was shown to be serine-phosphorylated, which was insufficient to cause the electrophoretic mobility shift. CONCLUSIONS: There are low levels of Cx46 synthesis and phosphorylation in rat embryo lens primary cultures and a slow rate of phosphorylation of Cx46 in bovine organ cultures.

Animals↗
PubMed1992

[Effects of Salvia miltiorrhiza Bunge on isolated perfused liver and portal vein of rats].

The experiment results showed that Salvia miltiorrhiza (SMB) had a protective effect on the isolated perfused liver injured by CCl4 of rats, made the activity of GPT in perfusate of SMB group lower than that of intoxicated groups and relieved the hepato-pathohistologic lesions of SMB group as compared to the intoxicated group. SMB had no significant effects on both the activities of SGPT in vitro and the portal vein of rats.

Alanine Transaminase↗
PubMed1991

Self-translocation of diphtheria toxin across model membranes.

To understand the mechanism of diphtheria toxin membrane translocation, the toxin was entrapped within lipid vesicles, and its low pH-induced translocation across the lipid bilayer was measured. Proteolysis and resistance to guanidinium chloride denaturation were used to demonstrate that the toxin molecules were entrapped. Low pH-induced movement of entrapped toxin to the outer (trans) face of the bilayer was assayed by the binding of external streptavidin to biotin-labeled entrapped toxin. Complete translocation was quantified by the amount of protein released into the external medium. Using whole toxin, it was found that the A fragment was efficiently translocated, but the B fragment was not. This was true both in the low temperature (A domain folded) and high temperature (A domain unfolded) toxin conformations previously identified [Jiang J. X., Abrams, F. S., and London, E. (1991) Biochemistry 30, 3857-3864]. Remarkably, even isolated fragment A appeared to self-translocate under some conditions. Toxin-induced translocation may partly result from formation of a nonspecific toxin-induced pore. This idea is supported by the toxin-induced release of fluorescent dextrans coentrapped within the vesicles. However, low pH-induced exposure of entrapped toxin on the outside of the membrane was conformation dependent. Exposure was greatest for the high temperature conformation. This suggests the existence of a more specific translocation process. The nature and relationship of these processes, and their relative roles in translocation in vivo are discussed.

Binding Sites↗
PubMed1991

Folding changes in membrane-inserted diphtheria toxin that may play important roles in its translocation.

Diphtheria toxin membrane penetration is triggered by the low pH within the endosome lumen. Subsequent exposure to the neutral pH of the cytoplasm is believed to aid in translocation of the catalytic A domain of the toxin into the cytoplasm. To understand the effects of low pH and subsequent exposure to neutral pH on translocation, we studied toxin conformation in solution and in toxin inserted in model membranes. Two conformations were found at low pH. One form, L', predominates below 25-30 degrees C, and the other, L", predominates above 25-30 degrees C and is formed from the L' state by an unfolding event. Both forms are hydrophobic and penetrate deeply into membranes. After pH neutralization, the L' and L'' conformations give rise to two new conformations, R' and R'', respectively. The R' and R" conformations differ from each other in that in the R' state the A domain remains folded, whereas in the R" state the A domain is unfolded. This is confirmed by the finding that only the R' state possesses the capacity to bind and hydrolyze NAD+. It is also supported by the finding that the R'' state can also be formed by thermal unfolding of the R' state. The R conformations differ from the low-pH L conformations in that although they remain largely membrane-inserted, it appears that a large portion of the toxin is no longer in contact with the hydrophobic core of the bilayer.(ABSTRACT TRUNCATED AT 250 WORDS)

Diphtheria Toxin↗
PubMed1991

[Relaxant effects of protopine on smooth muscles].

The relaxant effects of protopine (Pro) on smooth muscles were studied by recording isotonic contraction and radioimmunoassay. Pro relaxed the contraction of rabbit thoracic aorta, mesenteric artery, portal vein and guinea pig ileum and taenia colon induced by high K+ (70 mmol.L-1). Pro also inhibited the contraction of rabbit thoracic aorta, mesenteric artery, portal vein induced by NE (0.3 mumol.L-1) and guinea pig taenia colon induced by BaCl2 (1 mmol.L-1). Pro inhibited the intracellular Ca2+ release, but did not inhibit Ca2+ influx induced by NE. These results suggested that the smooth muscle relaxant mechanism of action of Pro may be the inhibition of intracellular Ca2+ release.

Alkaloids↗
PubMed1991

[Hypoglycemic effect of sanchinoside C1 in alloxan-diabetic mice].

Sanchinoside C1 (ginsenoside Rg1), one of the major effective components of Panax notoginseng, was reported to be effective in lowering glucose-induced hyperglycemia and synergizing the action of insulin in normal animals. The present study was aimed at investigating its effects on diabetic animals and comparing them with that of insulin. The results showed that sanchinoside C1 was able to lower plasma glucose level in alloxan-diabetic mice. The action was strengthened with repeated administration and tended to be dose-dependent; its effect lasted for more than four hours and no synergism or antagonism between sanchinoside C1 and insulin was observed. A single dose of sanchinoside C1 neither elevated plasma insulin level nor lowered hepatic cAMP level in alloxan-diabetic mice; while the uptake of [3H] glucose by isolated rat hepatocytes, oxidation of glucose and sodium succinate in liver homogenate and synthesis of liver glycogen in normal mice were increased.

Animals↗
PubMed1990

Involvement of denaturation-like changes in Pseudomonas exotoxin a hydrophobicity and membrane penetration determined by characterization of pH and thermal transitions. Roles of two distinct conformationally altered states.

Previous investigators have shown that exotoxin A undergoes a conformational switch to a hydrophobic state at low pH. This change appears to play a role in exotoxin A entry into cells by facilitating its penetration of the membranes of acidic organelles. We have examined the effects of pH, temperature, and denaturants in order to define the role of conformational changes in membrane penetration by the exotoxin. We find that two distinct low pH conformations exist. An intermediate low pH state (LI) dominates at pH 3.7-5.4 and is distinguished by blue-shifted fluorescence and weak or no hydrophobicity. The second low pH state (LII) is dominant below pH 3.7 and is characterized by red shifted fluorescence and strong hydrophobicity. LI is a folded state as judged by its spectroscopic properties and the observation that it undergoes distinct and cooperative thermal and denaturant induced unfolding transitions. LII appears to be more like a denatured state, as it shows no cooperative thermal or denaturant induced transitions and has spectroscopic properties very similar to exotoxin A that has been thermally denatured at pH 7. Exotoxin A in the LII state strongly binds detergent micelles and binds and inserts into model membranes. Therefore, denaturation-like conformational changes appear to play an important role in membrane insertion. The pH of the transition to a membrane-inserting state is influenced by the composition of the model membranes and is close to pH 5 in the presence of vesicles containing a phosphatidylglycerol/phosphatidylcholine mixture. These vesicles probably promote formation of the LII state via mass action effects. The implication of these results for membrane penetration and translocation of proteins without apparent hydrophobic regions, such as exotoxin A, is discussed.

ADP Ribose Transferases↗
PubMed1989

[Protective effects of the pollen of Codonopsis pilosula (Franch.) Nannf. on liver lesions at the ultrastructural level].

The experimental hepatic lesion of C57 mice was induced by carbon tetrachloride (CCI4), and the feeds containing pollen of Codonopsis pilosula were given to the animals. It was found by electronic microscopy that these pollens evidently reduced the hepatic steatosis, improved liver necrosis, suppressed the formation of the collagen fibrils in Disse's spaces and around central veinules. It was shown that the pollens of Codonopsis pilosula could counteract efficiently the liver lesion of mice induced by CCI4.

Animals↗