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Biomedical subjects

J Yuan

Publications and source records attributed to J Yuan.

At least 307 records · Page 17Linked to original sources
PubMed1994

Plastocyanin and the 33-kDa subunit of the oxygen-evolving complex are transported into thylakoids with similar requirements as predicted from pathway specificity.

Plastocyanin and the 33-kDa subunit of the oxygen-evolving complex (OE33) are two of several thylakoid lumen-located proteins that are made in the cytosol, imported into chloroplasts, and subsequently transported into thylakoids. Recently, competition studies showed that there are two pathways for protein transport into the thylakoid lumen and that plastocyanin and OE33 are on the same pathway (Cline, K., Henry, R., Li, C., and Yuan, J. (1993) EMBO J. 12, 4105-4114). Our expectation is that transport requirements reflect the steps of the process and that proteins on the same pathway share similar requirements. Unfortunately, the transport requirements for plastocyanin and OE33 are not well established. Here, we investigated transport in a reconstituted system with isolated thylakoids. Efficient transport of OE33 and plastocyanin was only obtained when stromal extract was included in the assay. Heat or protease treatment of stromal extract eliminated its ability to stimulate transport. Transport was abolished by treatments designed to deplete ATP or to prevent its formation and was greatly reduced in the presence of ionophores that dissipate the trans-thylakoidal proton gradient. These results show that transport of OE33 and plastocyanin requires ATP and is stimulated by stromal protein(s) and the trans-thylakoidal proton gradient. Taken together, these and previous results suggest that there are two mechanistically distinct pathways for protein transport into the thylakoid lumen.

Adenosine Triphosphate↗
PubMed1994

Substitutions for Glu-537 of beta-galactosidase from Escherichia coli cause large decreases in catalytic activity.

Glu-537 of beta-galactosidase (EC 3.2.1.23) was replaced by Asp, Gln and Val using synthetic oligonucleotides. The kcat values of the purified enzyme mixtures were reduced by about 100-fold for the Asp mutant, 30,000-60,000-fold for the Val mutant and 160,000-300,000-fold for the Gln mutant. The greatest differences in properties from the wild-type enzyme were found for the Asp-substituted enzyme: the Km values increased (from 0.12 to 0.42 mM for o-nitrophenyl beta-D-galactopyranoside), and from 0.04 to 0.37 mM for p-nitrophenyl beta-D-galactopyranoside), the Ki value for isopropyl beta-D-galactopyranoside increased (from 0.11 to 0.30 mM), the stability to heat decreased and methanol did not act as an acceptor. The enzymes with the other two substitutions had properties similar to those of the wild-type. For all three substituted enzymes, the inhibitory effects of the transition-state analogues (2-deoxy-2-amino-D-galactose and L-ribose) and the Mg2+ effects were similar to those of the normal enzyme. As all of the properties (except the kcat values) of the Gln- and Val-substituted enzyme preparations were similar to those of the wild-type enzyme, the activities in those preparations were probably due to the presence of a few wild-type enzyme molecules (formed from misreads) among the substituted enzymes. The enzymes with Gln and Val substitutions appear to be totally inactive. The results obtained support a recent suggestion that Glu-537 is an important catalytic residue of beta-galactosidase.

Amino Acid Sequence↗
PubMed1994

Multi-target PCR analysis by capillary electrophoresis and laser-induced fluorescence.

Quantitative analysis of polymerase chain reaction (PCR) amplified HIV-1 DNA or cDNA fragments is attained using an automated system that combines capillary-gel electrophoresis (CGE) for high-efficiency separation and laser-induced fluorescence (LIF) for high-sensitivity detection. This system enables the detection of PCR-amplified multiple target DNA or cDNA in the same tube by a single injection with high precision.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Prevention of vertebrate neuronal death by the crmA gene.

Interleukin-1 beta converting enzyme (ICE) is a mammalian homolog of CED-3, a protein required for programmed cell death in the nematode Caenorhabditis elegans. The activity of ICE can be specifically inhibited by the product of crmA, a cytokine response modifier gene encoded by cowpox virus. Microinjection of the crmA gene into chicken dorsal root ganglion neurons was found to prevent cell death induced by deprivation of nerve growth factor. Thus, ICE is likely to participate in neuronal death in vertebrates.

Animals↗
PubMed1994

Association of transcription factor APRF and protein kinase Jak1 with the interleukin-6 signal transducer gp130.

Interleukin-6 (IL-6), leukemia inhibitory factor, oncostatin M, interleukin-11, and ciliary neurotrophic factor bind to receptor complexes that share the signal transducer gp130. Upon binding, the ligands rapidly activate DNA binding of acute-phase response factor (APRF), a protein antigenically related to the p91 subunit of the interferon-stimulated gene factor-3 alpha (ISGF-3 alpha). These cytokines caused tyrosine phosphorylation of APRF and ISGF-3 alpha p91. Protein kinases of the Jak family were also rapidly tyrosine phosphorylated, and both APRF and Jak1 associated with gp130. These data indicate that Jak family protein kinases may participate in IL-6 signaling and that APRF may be activated in a complex with gp130.

Antigens, CD↗
PubMed1994

Toxicokinetics of oxazepam in rats and mice.

The comparative toxicokinetics of oxazepam were studied in F344 rats, B6C3F1 mice, and Swiss-Webster mice of both sexes after an i.v. dose of 20 mg/kg and oral gavage doses of 50, 200, and 400 mg/kg. In addition, the toxicokinetics of oxazepam in a 3-week dosed-feed study of male B6C3F1 mice at 125 and 2500 ppm were also investigated. Results indicated that the elimination of oxazepam from plasma after i.v. injection in both rats and mice were first-order and could be best described by a two-compartment model with a terminal elimination half-life of 4-5 h for rats and 5-7 h for mice. After oral gavage dosing the peak oxazepam plasma concentrations in most rodents were reached within 2-3.5 h. At all doses studied, female rodents had significantly higher plasma concentrations than males. Absorption of oxazepam was significantly extended at higher oral doses of 200 and 400 mg/kg. At 50 mg/kg, the bioavailability of oxazepam in rats (< 50%) was lower than in Swiss-Webster mice (> 80%). The bioavailability of oxazepam in both B6C3F1 and Swiss-Webster mice decreased with increasing dose. A dose proportionality of Cmax was not observed in rats and mice after gavage doses of 50, 200, and 400 mg/kg. Plasma concentrations of oxazepam in the dosed-feed study increased with the concentration of oxazepam in the feed, a quasi-steady-state of plasma concentrations of oxazepam was reached after approximately 4 days ad libitum exposure. In B6C3F1 mice, the estimated relative bioavailability of oxazepam from dosed feed (relative to gavage study at 50 mg/kg) was about 43%.

Animals↗
PubMed1994

Purification and properties of a glycerophosphocholine phosphodiesterase from bovine brain myelin.

An enzyme releasing phosphocholine from glycerophosphocholine was purified to apparent homogeneity based upon SDS-PAGE. The enzyme was liberated from lyophilized bovine myelin by differential detergent extraction and final purification was accomplished with Q-Sepharose Fast Flow chromatography yielding an apparently homogeneous protein. The molecular mass based upon PAGE was approximately 14 kDa. The enzyme was also capable of releasing p-nitrophenol from p-nitrophenyl-phosphocholine. Maximal activity was obtained with 0.2 mM ZnCl2 or 1 mM CoCl2. p-Nitrophenylphosphocholine and phosphocholine were competitive inhibitors of glycerophosphocholine hydrolysis with Ki's of 0.028 mM and 0.03 mM respectively. Glycerophosphocholine and phosphocholine were competitive inhibitors of p-nitrophenylphosphocholine hydrolysis with Ki's of 0.5 mM and 1.75 mM respectively.

Animals↗
PubMed1994

Comparison of the toxicity of cinnamaldehyde when administered by microencapsulation in feed or by corn oil gavage.

The toxicity of cinnamaldehyde (CNMA) was compared after administration by gavage and in dosed feed. Rats and mice of both sexes received CNMA by daily corn oil gavage (for 2 wk), or in microencapsulated form in feed (2 wk for rats, 3 wk for mice). Feed formulations contained 0-10% CNMA microcapsules, equivalent to approximate daily doses of 0-3000 mg CNMA/kg body weight for rats and 0-10,000 mg CNMA/kg body weight for mice. Concentrations were chosen to deliver CNMA doses approximately equal to doses in the gavage study. Gavage doses of 2620 mg/kg/day and above in mice and 940 mg/kg/day and above in rats produced nearly 100% mortality; there were no deaths in animals receiving microencapsulated CNMA. Rats and mice receiving CNMA in feed showed a dose-related decrease in body weight gain, which was accompanied in rats by hypoplastic changes in reproductive organs and accessory sex glands. CNMA administration by either route caused hyperplasia of the forestomach mucosa. These results demonstrate that microencapsulation in feed can present a useful alternative to gavage dosing for repeated-dose or prolonged-exposure studies, in that (1) the toxic effects of CNMA were similar after gavage dosing and after administration in microencapsulated form in feed, (2) ingestion of chemical in the feed more closely approximates human exposures, and (3) microencapsulation allows the delivery of higher net doses of chemical, while avoiding the acutely toxic effects of a bolus dose.

Acrolein↗
PubMed1994

Analysis of collagens solubilized from cartilage of normal and spontaneously osteoarthritic rhesus monkeys.

Osteoarthritis (OA) is a disorder which results in the destruction of the articular cartilage and the remodeling of the subchondral bone in synovial joints. We have analyzed the cartilage collagen from normal and osteoarthritic free-ranging rhesus monkeys from the Cayo Santiago colony. The cartilage samples were assigned a severity score based on histological staging system and were divided into four groups (normals, mild OA, moderate OA and severe OA). After a 4.0 M guanidinium chloride (GuCl) extraction, the remainder of the cartilage was digested with pepsin and the collagen was salt precipitated at 2.5 M and 4.3 M NaCl. The GuCl solubility of the osteoarthritic cartilage increased compared to normals. Collagen extractability by GuCl also increased with the severity of disease. Pepsin digestion followed by salt precipitation shows that collagen from rhesus osteoarthritis cartilage is more easily extracted than from normal cartilage. With an anti-type I collagen antibody we have detected the presence of type I collagen in the severe OA cartilage samples but not in the milder OA groups or in normal cartilage. Total collagen content decreases with severity of OA, which is not due to changes in propyl hydroxylation because examination of collagen hydroxylation, based on hydroxyproline analysis, shows no difference between OA and normal cartilage.

Animals↗
PubMed1994

An efficient method for large-scale isolation of plasmid DNAs by heat-alkali co-denaturation.

A method is presented for efficient and large-scale isolation of plasmid DNAs from bacterial cells. Based on the cooperativity of heat and alkali actions, the method provides DNA preparations with high quality and yield (about 2 micrograms of DNA/ml culture), which are completely digestable by restriction enzymes and have a high transformation efficiency. Furthermore, the DNA preparations are extremely stable, and even through 4-year storage at -20 degrees C, the electrophorogram and transformation efficiency remain as high as before. The factors affecting the stability of various DNA samples are discussed.

1-Propanol↗
PubMed1994

The signalling pathways of interleukin-6 and gamma interferon converge by the activation of different transcription factors which bind to common responsive DNA elements.

Interleukin-6 (IL-6) and gamma interferon (IFN-gamma) induce a partially overlapping set of genes, including the genes for interferon regulatory factor 1 (IRF-1), intercellular adhesion molecule 1 (ICAM-1), and the acute-phase protein alpha 2-macroglobulin. We report here that the rat alpha 2-macroglobulin promoter is activated by IFN-gamma in human hepatoma (HepG2) cells and that the IFN-gamma response element maps to the same site previously defined as the acute-phase response element (APRE), which binds the IL-6-activated transcription factor APRF (acute-phase response factor). As was reported for fibroblasts, the IFN-gamma-regulated transcription factor GAF is phosphorylated at tyrosine after IFN-gamma treatment of HepG2 cells. IFN-gamma posttranslationally activates a protein which specifically binds to the alpha 2-macroglobulin APRE. This protein is shown to be identical or closely related to GAF. Although APRF and GAF are shown to represent different proteins, their binding sequence specificities are very similar. APRF and GAF bind equally well to the APRE sequences of various acute-phase protein genes as well as to the IFN-gamma response elements of the IRF-1, ICAM-1, and other IFN-gamma-inducible genes. Transient transfection analysis revealed that the IFN-gamma response elements of the IRF-1 and ICAM-1 promoters are able to confer responsiveness to both IFN-gamma and IL-6 onto a heterologous promoter. Therefore, APRF and GAF are likely to be involved in the transcriptional induction of these immediate-early genes by IL-6 and IFN-gamma, respectively. Taken together, these results demonstrate that two functionally distinct hormones, IL-6 and IFN-gamma, act through common regulatory elements to which different transcription factors sharing almost the same sequence specificity bind.

Alkaloids↗
PubMed1994

The interleukin-6-activated acute-phase response factor is antigenically and functionally related to members of the signal transducer and activator of transcription (STAT) family.

Interleukin-6 (IL-6), leukemia inhibitory factor, oncostatin M, IL-11, and ciliary neurotropic factor are a family of cytokines and neuronal differentiation factors which bind to composite plasma membrane receptors sharing the signal transducing subunit gp130. We have shown recently that IL-6 and leukemia inhibitory factor rapidly activate a latent cytoplasmic transcription factor, acute-phase response factor (APRF), by tyrosine phosphorylation, which then binds to IL-6 response elements of various IL-6 target genes. Here we demonstrate that APRF is activated by all cytokines acting through gp130 and is detected in a wide variety of cell types, indicating a central role of this transcription factor in gp130-mediated signaling. APRF activation is also observed in vitro upon addition of IL-6 to cell homogenates. Protein tyrosine kinase inhibitors block both the tyrosine phosphorylation and DNA binding of APRF. The factor was purified to homogeneity from rat liver and shown to consist of a single 87-kDa polypeptide, while two forms (89 and 87 kDa) are isolated from human hepatoma cells. As reported earlier, the binding sequence specificity of APRF is shared by gamma interferon (IFN-gamma) activation factor, which is formed by the Stat91 protein. Partial amino acid sequence obtained from purified rat APRF demonstrated that it is likely to be related to Stat91. In fact, an antiserum raised against the amino-terminal portion of Stat91 cross-reacted with APRF, suggesting the relatedness of APRF and Stat91. Altogether, these data indicate that APRF belongs to a growing family of Stat-related proteins and that IFN-gamma and IL-6 use similar signaling pathways to activate IFN-gamma activation factor and APRF, respectively.

3T3 Cells↗
PubMed1994

Anti-apogens and anti-engulfens: monoclonal antibodies reveal specific antigens on apoptotic and engulfment cells during chicken embryonic development.

We have isolated a group of monoclonal antibodies that specifically recognize either apoptotic or engulfment cells in the interdigit areas of chicken hind limb foot plates, and throughout the embryo. Ten of these antibodies (anti-apogens) detect epitopes on dying cells that colocalize to areas of programmed cell death, characterized by the presence of apoptotic cells and bodies with typical cellular and nuclear morphology. Our results indicate that cells destined to die, or that are in the process of dying, express specific antigens that are not detectable in or on the surface of living cells. The detection of these apoptotic cell antigens in other areas of programmed cell death throughout the chick embryo indicates that different cell types, which form specific tissues and organs, may utilize similar cell death mechanisms. Six of the monoclonal antibodies (antiengulfens) define a class of engulfment cells which contain various numbers of apoptotic cells and/or apoptotic bodies in areas of programmed cell death. The immunostaining pattern of the anti-engulfen R15F is similar to that of an antibody against a common leukocyte antigen, suggesting the participation of cells from the immune system in the removal of apoptotic cell debris. These novel monoclonal antibody markers for apoptotic and engulfment cells will provide new tools to assist the further understanding of developmental programmed cell death in vertebrates.

Animals↗
PubMed1994

Impact of annual screening and chemotherapy with praziquantel on schistosomiasis japonica on Jishan Island, People's Republic of China.

The impact of annual screening and treatment with praziquantel on schistosomiasis japonica was examined on Jishan Island in Po Yang Lake, Jiangxi Province. China. Prevalence of infection in the community decreased from 39% in year 1 to 33% in year 3 with a corresponding decrease in the geometric mean egg count from 51 eggs per gram of stool (epg) to 31 epg. The most dramatic changes in infection status and intensity of infection were observed in younger individuals (0-19 years of age). The prevalence of hepatosplenomegaly also significantly decreased, again primarily in younger individuals. No change in the community prevalence of schistosome-induced hepatic fibrosis was observed as determined by ultrasonography. Longitudinal cohort analysis, however, demonstrated significant improvement in treated individuals with advanced hepatic fibrosis. These data indicate that annual screening and treatment had a significant impact on infection status and morbidity and suggest that community therapy may be an effective approach to control schistosomiasis japonica in lake regions and marshlands in China. Further studies are necessary to determine the optimal and most cost-effective approach for drug delivery.

Adolescent↗
PubMed1994

Dexfenfluramine and serotonin neurotoxicity: further preclinical evidence that clinical caution is indicated.

Dexfenfluramine, a drug used as an appetite suppressant in Europe, is currently under evaluation for approval in the United States. Studies in animals indicate that dexfenfluramine damages brain serotonin neurons, but have been challenged by some because of questions regarding their relevance to humans. The present studies were designed to address the three most salient questions regarding the applicability of preclinical dexfenfluramine neurotoxicity data to humans. Specifically, the present studies sought to determine: 1) whether dexfenfluramine's effects on brain serotonin neurons are transient and related to its therapeutic actions; 2) whether the p.o. route of administration affords protection against dexfenfluramine neurotoxicity; and 3) whether the mouse, an animal thought to best approximate the human with regard to dexfenfluramine metabolism, is sensitive to dexfenfluramine's neurotoxic action. Results from the present study indicate that monkeys continue to show large serotonergic deficits as long as 12 to 17 months after dexfenfluramine treatment, suggesting that dexfenfluramine's effects in nonhuman primates are persistent and unlikely to be related to its therapeutic actions. Furthermore, the present results indicate that the p.o. route of administration affords little or no protection against dexfenfluramine neurotoxicity. Finally, mice, like all other animals tested to date, were found to be susceptible to dexfenfluramine neurotoxicity. Taken together, these findings indicate that concern over possible dexfenfluramine neurotoxicity in humans is warranted, and that physicians and patients alike need to be aware of dexfenfluramine's toxic potential toward brain serotonin neurons.

Animals↗
PubMed1994

[Effect of berberine on transit time of human small intestine].

Sorbitol was used as a test sugar for the determination of small intestinal transit time (SITT) by means of breath hydrogen test (BHT). After oral administration of 15g sorbitol, breath hydrogen increased markedly (delta H2 > 5 mumol/L) in 26 of 30 subjects. Following ingestion of a mixture of meglucamine diatrizoate and sorbitol by 18 subjects, SITT measured by BHT correlated closely with the simultaneously determined time for the meglucamine diatrizoate in reaching ileo-cecum. The BHT was used to investigate the effect of berberine on SITT in human. SITT in 20 healthy subjects was 71.10 +/- 22.04 min, SITT was significantly delayed to 98.25 +/- 29.03 min after oral administration of the 1.2g of berberine (P < 0.01). This result suggested that the antidiarrheal property of berberine might be mediated, at least in part, by its ability to delay the small intestinal transit.

Adult↗
PubMed1994

[The experimental study of prevention and treatment of the side-effects of chemotherapy with acupuncture (comparison among the effect of acupuncture at different acupoint)].

After an intraperitoneal injection of cyclophosphamide in rats, there was pathologic changes in hemopoietic, immune and visceral function. Acupuncture respectively at Zusanli, Dazhui and Shenshu points could decrease the above mentioned harms in the rats, the effect of acupuncture on hemopoietic function: Dazhui more than or equal to Zusanli, Zusanli more than Shenshu; the effect of acupuncture on immune function: Zusanli more than Dazhui, Dazhui more than or equal to Shenshu; the effect of acupuncture on the function of the liver and the kidney: Shenshu more than or equal to Zusanli, Zusanli more than Dazhui. The effect of acupuncture at all three points, i.e. Zusanli. Dazhui and Shenshu was more than that at any single point due to their coordination. There was no obvious effect when acupuncture at non-acupoints on tail.

Acupuncture Points↗