PubMed Health⌕ Search

Biomedical subjects

G Shen

Publications and source records attributed to G Shen.

At least 109 records · Page 6Linked to original sources
PubMed1995

The NSY mouse: a new animal model of spontaneous NIDDM with moderate obesity.

The NSY (Nagoya-Shibata-Yasuda) mouse was established as an inbred strain of mouse with spontaneous development of diabetes mellitus, by selective breeding for glucose intolerance from outbred Jcl:ICR mice. NSY mice spontaneously develop diabetes mellitus in an age-dependent manner. The cumulative incidence of diabetes is 98% in males and 31% in females at 48 weeks of age. Neither severe obesity nor extreme hyperinsulinaemia is observed at any age in these mice. Glucose-stimulated insulin secretion was markedly impaired in NSY mice after 24 weeks of age. In contrast, fasting plasma insulin level was higher in male NSY mice than that in male C3H/He mice (545 +/- 73 vs 350 +/- 40 pmol/l, p < 0.05, at 36 weeks of age). Pancreatic insulin content was higher in male NSY mice than that in male C3H/He mice (76 +/- 8 vs 52 +/- 5 ng/mg wet weight, p < 0.05, at 36 weeks of age). Morphologically, no abnormal findings, such as hypertrophy or inflammatory changes in the pancreatic islets, were observed in NSY mice at any age. These data suggest that functional changes of insulin secretion in response to glucose from pancreatic beta cells may contribute to the development of non-insulin-dependent diabetes mellitus (NIDDM) in the NSY mouse. Although insulin sensitivity was not measured, fasting hyperinsulinaemia in NSY mice suggests that insulin resistance may also contribute to the pathogenesis of NIDDM. Since these findings are similar to the pathophysiologic features of human NIDDM patients, the NSY mouse is considered to be useful for investigating the pathogenesis and genetic predisposition to NIDDM.

Aging↗
PubMed1995

Autoantibody profile of primary sclerosing cholangitis.

Primary sclerosing cholangitis (PSC) is a chronic progressive liver disease of unknown etiology. It has been suggested that genetic and immunological factors are important in its pathogenesis. The present study examined the prevalence of 23 different autoantibodies in 25 PSC sera, by ELISA, in order to better define the autoimmune profile of PSC. The results indicate that 88% of PSC patients produced at least 1 autoantibody, and 36% had reactivity to multiple autoantibodies. Moreover, 35% of the PSC patients produced anti-endothelial-cell antibodies (AECA) and 75% of the sera contained perinuclear antineutrophil cytoplasmic antibodies (pANCA), detected by indirect immunofluorescence. The prominent ANCA autoantibody was anti-cathepsin-G, demonstrated in 35% of the patients. The multiplicity of the autoantibody profile, revealed in the present study, points to the autoimmune characteristics of PSC. In addition, the association of ANCA and of AECA in PSC may suggest a pathogenic role for these antibodies in PSC.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed1995

Analysis of amelogenin proteins using monospecific antibodies to defined sequences.

Amelogenins are the predominant proteins found in the developing enamel matrix and are believed to play a crucial role in normal mineralization. Although the amelogenin gene is found as a single copy in all species in which it has been examined, multiple amelogenin polypeptides ranging in size from 5 to 25 kDa are obtained upon extraction of developing enamel matrix, making identification and characterization of individual components difficult. This heterogeneity may be ascribed to transcription of divergent genes located on the X and Y chromosomes, alternative splicing of the primary transcripts, physiologic degradative processing, and artefactual degradation. In order to characterize individual components, antibodies were produced to the following peptides: (1) QPLQPMQPMQPLQPLQPL (corresponding to the repeat sequence encoded only in the bovine X chromosome gene), (2) IRHPPLPP (corresponding to a unique sequence generated by alternative splicing found in leucine-rich amelogenin peptide (LRAP), (3) LPDLPLEAWPATDKTKREEVD corresponding to the amelogenin carboxy-terminus. Amelogenin proteins obtained from fetal bovine molars were subjected to SDS PAGE and Western electrotransfer, and immuno-ultrastructural analysis. These analyses demonstrated that: (1) the distribution of amelogenin polypeptides isolated from male fetuses differed appreciably from that of females, (2) the LRAP junctional peptide sequence can be specifically identified, and (3) the LRAP peptide can be immunolocalized in the enamel matrix of both males and females.

Alternative Splicing↗
PubMed1995

[A study on growth and development of maxillofacial region with vector analysis]

In order to observe the maxillofacial growth and development quantitatively, the vector analysis was applied in this study to divide Y axis,which is advocated in Downs method,into horizontal section and vertical one,from which the ratio of the facial growth separately in anterior and inferior direction was obtained.75 pieces of x ray films for various dental stages of Shanghaiese with normal occlusion were selected and their angle of Y axis together with their cotangents were measured. The results showed that the cotangent of those with mixed,early permanent and permanent dentition were separately 0.47,0.48 and 0.45 indication that there was a certain relationship between anterior direction and inferior one for the maxillofacial region growth and development.

Journal Article↗
PubMed1995

[Bioavailability study on xiaohuoluo pills].

According to the relationship between dosage and effect, the time course of analgesic was determined after oral administration of Xiaohuoluo Pills to mice. Based on this experiment, contrasting the commercial pills with the reference preparation, the bioavailability of Xiaohuoluo Pills was studied. It was shown that the bioavailability of different batches of product from the same factory was different. This method was good for the study of compound preparations of Chinese materia medica.

Analgesics↗
PubMed1994

Mutation of chlorophyll ligands in the chlorophyll-binding CP47 protein as studied in a Synechocystis sp. PCC 6803 photosystem I-less background.

Site-directed mutations have been introduced to replace conserved histidine residues in the chlorophyll-binding protein CP47 of photosystem II (PS II) in a PS I-less/apcE-background strain of the cyanobacterium Synechocystis sp. PCC 6803. In thylakoids isolated from such a system, the degree of loss of the 695-nm fluorescence emission maximum at 77 K compared to that at 685 nm generally was consistent with the decrease in oxygen evolution rates measured at saturating light intensity. Taking into account that in the absence of CP47 and PS I some chlorophyll remains detectable in cells, the relative 695-nm fluorescence emission and the rate of oxygen evolution also correlate with the relative amount of chlorophyll per cell and with the number of PS II reaction centers on a chlorophyll basis. Interestingly, the 77 K fluorescence excitation spectra monitoring 695-nm emission of thylakoids from the CP47 His-to-Tyr mutants in a photosystem I-less/apcE-background showed increases in the 413- and 531-nm absorption regions, compared to spectra of thylakoids from the background strain. These wavelengths coincide with absorption maxima of pheophytin. No increase in the 531-nm excitation band was observed in thylakoids from mutants lacking PS II or with a His-to-Asn mutation. These results are interpreted to indicate that replacement of conserved histidine residues by tyrosine in CP47 leads to the loss of Mg2+ from chlorophyll, resulting in the formation of pheophytin, or to the binding of pheophytin (rather than chlorophyll) at a particular pigment-binding site of CP47 during biogenesis and assembly of the protein. It was observed that the light-harvesting efficiency of CP47 His mutants was lower judging from the light intensity dependence of electron transport and analysis of fluorescence decay kinetics. This suggests that the presence of pheophytin in the antenna decreases antenna efficiency.

Chlorophyll↗
PubMed1994

Chlorophyll in a Synechocystis sp. PCC 6803 mutant without photosystem I and photosystem II core complexes. Evidence for peripheral antenna chlorophylls in cyanobacteria.

The chlorophyll protein organization has been investigated in thylakoid membranes from mutants of the cyanobacterium Synechocystis sp. PCC 6803, in which the photosystem II (PS II) genes psbB and/or psbC (coding for CP47 and CP43, respectively) were inactivated together with the psaAB operon (coding for the photosystem I (PS I) core complex) and the apcE gene (coding for the phycobilisome anchor protein). Lack of the CP43 protein led to a significant decrease of the D1, D2, and CP47 proteins and a decrease in the 77 K fluorescence emission peak at 685 nm. In the absence of the CP47 protein, no PS II reaction center assembly was detected and the 77 K fluorescence emission peak at 695 nm was lost. The psbB-/psbC-/PS I-less/apcE- mutant had no assembly of the D1, D2, CP47, and CP43 proteins, had lost the 77 K fluorescence emission peaks at 685 and 695 nm, but retained about 15% of the chlorophyll present in the PS I-less/apcE- background strain. A broad 77 K fluorescence emission band with a maximum at 678 nm was displayed in the PS II-less, PS I-less mutant upon excitation of the remaining chlorophyll. A 678 nm shoulder was observed in the 77 K fluorescence emission spectrum of thylakoids from the psbB-/PS I-less/apcE- mutant, which still contains CP43 but no PS II reaction center. This shoulder was absent in thylakoids from the psbC-/PS I-less/apcE- mutant, which contain some PS II reaction center complexes. These results are consistent with the chlorophyll associated with the 678 nm emission to serve as peripheral antenna to PS II. The fluorescence emission characteristics of this chlorophyll are different from those of an accessory chlorophyll-binding protein expressed under iron-stress conditions in cyanobacteria. The chlorophyll remaining in the absence of PS II and PS I is indicative of a new chlorophyll-binding protein in cyanobacterial thylakoids.

Chlorophyll↗
PubMed1994

Electrons generated by photosystem II are utilized by an oxidase in the absence of photosystem I in the cyanobacterium Synechocystis sp. PCC 6803.

The reduction and reoxidation kinetics of the first quinone-type electron acceptor in photosystem II, QA-, were measured by fluorescence in a light-tolerant, photosystem I-less strain of the cyanobacterium Synechocystis sp. PCC 6803. In this strain, which shows excellent amplitudes of variable fluorescence, the rate of QA- oxidation after photoreduction of the plastoquinone pool was about half of that in the presence of photosystem I. However, upon addition of 5 mM KCN, QA- decay was very slow, and the rate was comparable to that seen in the presence of diuron, which blocks electron transport between QA and QB. The KCN-imposed block of QA- oxidation was removed efficiently by addition of exogenous quinones that can oxidize the plastoquinone pool. These results indicate that, in the absence of photosystem I, photosystem II-generated electrons are used very effectively by an oxidase located in the thylakoid; this oxidase may be a component of the respiratory chain.

Cyanobacteria↗
PubMed1994

On the field inhomogeneity of a birdcage coil.

A mathematical model is developed for the numerical analysis of birdcage coils constructed using capacitors having different capacitance. With the aid of this model, it is shown that the deviation of some capacitance introduced by tune, balance, and drive mechanisms can cause inhomogeneity in the B1 field produced by the coil. Useful curves and formulae are developed to provide a guideline for the design of birdcage coils.

Algorithms↗
PubMed1994

[Propagation of the HTV in primary human embryonic kidney and lung cell culture].

2 strains of Hantaan virus (HTV, 76-118, Hubei-114) have been propagated successfully in cultured primary human embryonic kidney (HEK) and lung (HEL) cells. Cytopathic effect (CPE) was observed in the two kind of cells on day 5 to 7 postinoculation which showed the cell became round and clustered, then detached. The replicating peak of the Hubei-114 in two kinds of cell cultures appeared on the 11th day and another strain on the 14th or 17th day after infection. The ultrastructure changes were observed with EM and IEM, which stained by ICGT before embedding. It was discovered that the mitochondia atrophied and decreased, and inclusion bodies in the cytoplasma of HEK and KEL cells. A large amount of gold granulae were found in the inclusion bodies and the virions were seen occasionally. Contamination with other agents have been ruled out. Our data suggest that the replicating characters of HTV in these cell systems might be possible for the pathogenicity of HFRS for human.

Cells, Cultured↗
PubMed1994

A study of c-myc oncogene expression and amplification in colorectal cancer.

Expression of c-myc oncogene transcripts in colorectal neoplasia was studied in paraffin embedded tissue sections from 25 patients undergoing surgery and from the rectal carcinoma cell line HR-8348 by using in situ hybridization, and its amplification was investigated in tumor and normal mucosa tissue from 25 coloproctomy samples by slot blot hybridization. Overexpression of this gene was seen in 78% (7/9) of the benign adenomas and 91% (20/22) of the malignancies sampled. There was no significant correlation between overexpression and the histologic type or grade, and no significant relationship between the level of expression and clinical stage was found, although overexpression was apparently more common in tumors with metastasis. Amplification of the gene was found in 0 of 4 benign adenomas and 7 of 22 malignancies. No obvious correlation was found between amplification and histological type or grade, though amplification was more frequent in tumors with metastasis. Amplification was also found in 2 adenomas with malignant change. The results suggest that multiple factors are involved in the progression of colorectal cancer, and in situ hybridization with a nonradiolabeled probe is useful in the detection of gene expression.

Adenocarcinoma↗
PubMed1993

Mutation of histidine residues in CP47 leads to destabilization of the photosystem II complex and to impairment of light energy transfer.

Site-directed mutagenesis has been used to change conserved histidine residues in hydrophobic regions of the photosystem II chlorophyll-binding protein CP47 in the cyanobacterium Synechocystis sp. PCC 6803. Nine mutants with one, four mutants with two, and four mutants with three His mutations in CP47 have been generated and characterized. Mutation of any one of seven different His residues to Tyr leads to slower photoautotrophic growth and apparent destabilization of the PS II complex. Mutations introduced into multiple His residues in one mutant exhibited a cumulative effect. Replacing His by Asn leads to a much smaller effect than observed upon mutation to Tyr. This is consistent with the hypothesis that the mutated His residues are chlorophyll ligands: Asn can substitute as chlorophyll ligand, whereas Tyr cannot. Further evidence supporting a role of the mutated His residues in chlorophyll binding comes from measurements of the light intensity needed to half-saturate oxygen evolution. All His mutants with impaired PS II function needed higher light intensities for half-saturation than wild type. A possible explanation for this decrease in antenna efficiency in the mutants is a loss of the Mg in the chlorophyll due to a loss of the fifth ligand, and thus the formation of a pheophytin molecule in the antenna. We conclude that conserved His residues in hydrophobic regions of CP47 indeed are chlorophyll ligands and that these ligands are important for PS II stability as well as efficient antenna function.

Binding Sites↗
PubMed1993

Synechocystis sp PCC 6803 strains lacking photosystem I and phycobilisome function.

To design an in vivo system allowing detailed analysis of photosystem II (PSII) complexes without significant interference from other pigment complexes, part of the psaAB operon coding for the core proteins of photosystem I (PSI) and part of the apcE gene coding for the anchor protein linking the phycobilisome to the thylakoid membrane were deleted from the genome of the cyanobacterium Synechocystis sp strain PCC 6803. Upon transformation and segregation at low light intensity (5 microE m-2 sec-1), a PSI deletion strain was obtained that is light tolerant and grows reasonably well under photoheterotrophic conditions at 5 microE m-2 sec-1 (doubling time approximately 28 hr). Subsequent inactivation of apcE by an erythromycin resistance marker led to reduction of the phycobilin-to-chlorophyll ratio and to a further decrease in light sensitivity. The resulting PSI-less/apcE- strain grew photoheterotrophically at normal light intensity (50 microE m-2 sec-1) with a doubling time of 18 hr. Deletion of apcE in the wild type resulted in slow photoautotrophic growth. The remaining phycobilins in apcE- strains were inactive in transferring light energy to PSII. Cells of both the PSI-less and PSI-less/apcE- strains had an approximately sixfold enrichment of PSII on a chlorophyll basis and were as active in oxygen evolution (on a per PSII basis) as the wild type at saturating light intensity. Both PSI-less strains described here are highly appropriate both for detailed PSII studies and as background strains to analyze site- and region-directed PSII mutants in vivo.

Base Sequence↗
PubMed1993

[The effect of iontophoresis on accelerating orthodontic tooth movement]

This paper reported that acceleration of tooth movement can be gained by submucosal injection of some kind of medicine.To avoid the pain caused by the injection,conventional drug administration was ameliorated in this study by adopting the method of ionophoresis rabibits were divided into 2 groups and the standard otthodontic appliances were placed in the lower incisors of all animals.The 2 groups were separately recieved submucosal iontophoresis and injection of 0.9% NaCl which served as control.The result showed that animals with iontophoresis,in whose periodontal pression side more osteoclasts were observed histologically,had gained rapider tooth movement than those with injections.

Journal Article↗
PubMed1992

Bovine amelogenin message heterogeneity: alternative splicing and Y-chromosomal gene transcription.

The amelogenins are the most abundant proteins in developing tooth enamel. Previous analyses have demonstrated that transcriptionally active genes encoding the proteins are located on both the bovine X and the bovine Y chromosomes. We report here the cloning and sequence analysis of the Y-chromosomal gene and corresponding cDNA. The Y-specific mRNA encodes a translation product in which a 21 amino acid domain has been deleted, relative to the X-specific amelogenin, resulting in loss of a structure tentatively described as a beta-spiral. There are also 13 single amino acid differences compared to the X-specific amelogenin. In addition, we have cloned and sequenced an X-chromosomal alternatively spliced amelogenin cDNA that encodes a 43 amino acid amelogenin primary translation product. Hydrophobicity analysis indicates that all analyzed amelogenin proteins have a mean hydrophilic character and the two peptides translated from alternatively spliced messages have significant increases in percentage of hydrophobic amino acids.

Amelogenin↗
PubMed1992

[Pathogenetic and clinical significance of peripheral activated T-lymphocyte subsets in Basedow's disease].

The peripheral activated T-cell subsets which express concurrently DR and CD antigens were determined in 22 patients with Graves' disease using the fluorescence-rosette double labelling technique. In the active phase of the disease a decrease in the percentage of CD8+ cells, an increase in the CD4+/CD8+ ratio and an elevation of various DR+CD+T-lymphocytes was found. A concurrent marked increase in DR+CD4+ cells accounts for an abnormality in the equilibrium of activated T-lymphocyte subsets and an increase in DR+CD4+/DR+CD8+ ratios. In comparison with the active phase the DR+CD3+ and DR+CD4+ cells decreased in remission, but DR+CD8+ cells remained unchanged. The decrease in the ratio of CD4+/CD8+ cells was less marked than that of the DR+CD4+/DR+CD8+ cells, which fell into the normal range. Our results suggest an excessive activation of T-helper cells as well as a deficiency in T-suppressor cells which may play an important role in the pathogenesis of Graves' disease.

Adult↗