Biomedical subjects

S Jiang

Publications and source records attributed to S Jiang.

At least 181 records · Page 10Linked to original sources

PubMed1999

[The postoperative complications and management of excimer laser in situ keratomilleusis].

OBJECTIVE: To evaluate the safety of excimer laser in situ keratomilleusis (LASLK) METHODS: The postoperative complications in 699 eyes of LASIK were observed and statistically analyzed. RESULTS: The haze, halo, growth of corneal epithelium under valve, the foreign body under valve, the fold of corneal valve, infection, decentralization, irregular astigmatism, valvular damage, low contrast sensibility, undercorrection and over correction, the psychological dysopia, glaucoma, fluctuating visual acuity and the loss of the best corrected visual acuity were found. CONCLUSION: LASIK has it's advantages of accurate manipulation, extensive range of correction and rapid recovery, but some of the complications resulting from this operation are so difficult to treat that careful consideration should be given before using this technique.

Adolescent↗

PubMed1999

[Intracellular calcium mobilization and effects of ATP on ampullate crista hair cells of the guinea pig].

OBJECTIVE: To further understand the intracellular calcium mobilization features of the isolated ampullate crista vestibular hair cells(VHCs) and ATP effects on intracellular free calcium concentration([Ca2+]i) in VHCs of the guinea pig. METHODS: Vestibular hair cells were isolated from the guinea pig crista ampullaris by enzymatic and mechanical methods. The influence of high K+ solution and ATP on [Ca2+]i was investigated. The [Ca2+]i of VHC was examined using laser scanning confocal microscopy(LSCM) and the Ca2+ sensitive dye Fluo-3. RESULTS: (1) 75 mmol/L K+ Hank's solution resulted in an increase of [Ca2+]i in both the cytoplasm and the cuticular plate of 5 type I VHCs. In the Ca(2+)-free medium, however, 75 mmol/L K+ solution could not induce [Ca2+]i an increase in observed 5 type I VHCs. (2) In the presence of 1.0 mmol/L or 0.1 mmol/L of ATP, there was a rapid reversible rise of the [Ca2+]i in 18/19 type I VHCs. A small response of ATP-induced [Ca2+]i was found only in 1/10 of type I VHC in Ca(2+)-free medium. There was no significant increase in [Ca2+]i when the same volume of Hank's solution was applied to the chamber containing VHCs. CONCLUSIONS: The result suggests that high K+ solution led to Ca2+ influx via voltage-dependent calcium channels. Extracellular Ca2+ influx is a major source of the ATP-induced [Ca2+]i increase.

Adenosine Triphosphate↗

PubMed1999

[The Raman spectra of monohydrate citric acid].

The Raman Spectra of monohydratecitric acid in different geometric arrangements have been reported in this paper. From the shift of some spectra, the anisotropic Raman scattering and depoearization effects, we can conclude that there exist hydrogen bonds in the crystal. Because of the effect of hydrogen bonds, electrical coupling between molecules causes the C-C, C-O bonds to possess some double bond character. On the other hand, the C=O bond possesses some single bond character.

Citric Acid↗

PubMed1998

Synthesis and transporter binding properties of (R)-2 beta, 3 beta- and (R)-2 alpha, 3 alpha-diaryltropanes.

(R)-2-Aryl-2-tropinone (9) was synthesized from (R)-2-carbomethoxy-3-tropinone (5) and was used as the key intermediate for the synthesis of (R)-2 beta, 3 beta- and (R)-2 alpha, 3 alpha-diaryltropanes. Inhibition of radioligand binding studies at the dopamine, serotonin, and norepinephrine transporters showed that the (R)-3 beta-(4-methylphenyl)-2 beta-phenyltropane (3b, RTI-422) possessed an IC50 value of 1.96 nM at the dopamine transporter and was highly selective for this transporter relative to the serotonin and norepinephrine transporters.

Carrier Proteins↗

PubMed1998

Strain-dependent developmental relaxation of imprinting of an endogenous mouse gene, Kvlqt1.

Genomic imprinting is an epigenetic modification of the gamete or zygote leading to parental origin-specific differential expression of the two alleles of a gene in somatic cells of the offspring. We previously reported that the human KVLQT1 gene is imprinted and disrupted in patients with germline balanced chromosomal rearrangements and Beckwith-Wiedemann syndrome. In human, the gene is imprinted in most fetal tissues except the heart, and KVLQT1 is part of a 1-Mb cluster of imprinted genes on human chromosome 11p15. 5. We sought to determine whether the mouse Kvlqt1 gene is imprinted, by performing interspecific crosses of 129/SvEv mice with CAST/Ei (Mus musculus castaneus). We identified a transcribed polymorphism that distinguishes the two parental alleles in F1 offspring. Examination of embryonic, neonatal, and postnatal tissues revealed that Kvlqt1 is imprinted in mouse early embryos, in both female 129 x male CS and female CS x male 129 offspring, with preferential expression of the maternal allele, like the human homologue. Surprisingly, imprinting was developmentally relaxed, and the developmental stage and tissue specificity of relaxation of imprinting was strain-dependent. To our knowledge, this is the first example of an endogenous gene that shows strain-dependent developmental relaxation of imprinting.

Alleles↗

PubMed1998

Expression of beta1,4-galactosyltransferase in the development of mouse brain.

Beta1,4-galactosyltransferase (GalTase, EC 2.4.1.38) transfers galactose to the terminal N-acetylglucosamine of complex-type N-glycans, which have great importance for cell-cell interactions during fertilization and early embryogenesis. In this study, the activity of beta1,4-galactosyltransferase in mouse brain during development was measured with the method of reverse HPLC using a fluorescence-labeled biantenary sugar chain, GlcNAcbeta1-2Manalpha1-6(GlcNAcbeta1-2Manalpha1- 3) Manbeta1-4GlcNAcbeta1-4GlcNAc-PA. The level of messenger RNA of this enzyme during the development of mouse brain was also investigated with Northern blot analysis. The results showed that: (1)beta1,4-galactosyltransferase showed similar branch specificity and kinetics for the biantenary substrate during development; (2) GalTase activity in fetal mouse brain was four times higher than that in adult mouse brain and decreased gradually in the course of development; (3) messenger RNA level was highest in fetal mouse and decreased dramatically after birth. However, the contents of mRNA were not parallel to the enzyme activity.

Animals↗

PubMed1998

Characterization and chromosomal localization of PTP-NP-2, a new isoform of protein tyrosine phosphatase-like receptor, expressed on synaptic boutons.

Recently, there have been several reports describing the cloning and characterization of the novel family of protein tyrosine phosphatase-like receptor molecules (known as IA-2 and PTP-NP/PTP-IAR/IA-2beta/phogrin), which may act as autoantigens in diabetes. Here, we report the molecular characterization and chromosomal localization of a new isoform of this family in brain termed PTP-NP-2 (for PTP-NP tyrosine phosphatase isoform), and its function in rat primary hippocampal neurons. PTP-NP-2 has 48% identity to IA-2. The principal difference between PTP-NP-2 and PTP-NP is a 17-amino-acid insert near the N-terminus of PTP-NP that is absent in PTP-NP-2. Genomic DNA analysis indicates that the 17-amino-acid insert is coded by a separate exon, suggesting that both IA-2beta and PTP-NP-2 are isoforms arising by alternate splicing of the same gene. Reverse transcriptase-PCR revealed that both isoforms are present in human SH-SY5Y neuroblastoma cells. PTP-NP-2 mRNA expression is highly restricted, with a 5.5-kb specific transcript in human fetal and adult brain and 5.5 and 3. 8 kb in human adult pancreas. SH-SY5Y neuroblastoma and U87-MG glioblastoma cells showed specific transcripts of 5.5 and 3.8 kb, respectively, indicating the existence of several isoforms of this molecule in the nervous system. The human gene encoding PTP-NP-2 was assigned to human chromosome 7q22-qter using Southern blot analysis of genomic DNAs from rodent/human somatic hybrid cell lines. Confocal microscopy analyses of rat primary hippocampal neurons revealed that PTP-NP-2 is abundantly expressed on synaptic boutons in primary neurons. Wild-type PTP-NP-2 showed no measurable tyrosine phosphatase activity using an in-vitro pNPP assay. Examination of the PTP-NP-2 catalytic consensus sequence revealed that this sequence differed from the typical tyrosine phosphatase-domain consensus sequence by an alanine to aspartate change (amino acid 930). Mutation of aspartate 930 to alanine produced a catalytically active enzyme, suggesting that native PTP-NP and its isoform PTP-NP-2 are catalytically inactive receptor protein tyrosine phosphatase homologues. Taken together, these results indicate that the tyrosine phosphatase PTP-NP-2 is a new isoform of PTP-NP tyrosine phosphatase, is expressed on synaptic boutons and may participate in the regulation of synaptic bouton endocytosis.

Adult↗

PubMed1998

Organization of the dorsocaudal neostriatal complex: a retrograde and anterograde tracing study in the domestic chick with special emphasis on pathways relevant to imprinting.

In the forebrain of domestic chicks, a network of distinct regions is crucially involved in auditory and visual filial imprinting. Among these areas, a distinct part of the dorsocaudal neostriatal complex (dNC complex), termed neostriatum dorsocaudale (Ndc), was recently discovered by its enhanced metabolic activity during the presentation of auditory and visual imprinting stimuli. Since there is evidence that the dNC complex consists of several distinct functional subareas, we investigated the neural connections of different parts of the dNC complex by retro- and anterograde pathway tracing. Special emphasis was put on the connections of the dNC complex with other imprinting relevant regions in the rostral telencephalon, such as the mediorostral neostriatum/hyperstriatum ventrale (MNH) and the intermediate and medial part of the hyperstriatum ventrale (IMHV). By anterograde and multiple retrograde pathway tracing, we found that the dNC complex may at least be subdivided into three major constituents. The most medial part of the dNC complex, termed neostriatum dorsale (Nd), is characterized by strong reciprocal connections with the neostriatal part of the MNH and by its auditory related inputs, including those from the output layers L1 and L3 of field L, and the shell region of the thalamic n. ovoidalis. The Ndc, which occupies the central aspects of the dNC complex, is mainly characterized by reciprocal connections with the ectostriatal belt (Ep) and the adjacent neostriatum (N). Furthermore, Nd and Ndc receive strong thalamic input from the n. dorsolateralis posterior (DLP), both project to the IMHV, and both are reciprocally connected with the archistriatum intermedium (AI). The most lateral aspect of the dNC complex, termed Ndl, is characterized by afferents from the neostriatum frontale, pars trigeminalis (NFT), and by the lack of a thalamic input. Results indicate that the dNC complex comprises distinct subregions, which are characterized by their specific afferents from parasensory areas of different sensory modalities. These different subregions may be integral components of a general pattern of sensory processing in the avian telencephalon. The strong interconnections between Nd, Ndc, and MNH as well as IMHV may constitute essential parts of auditory and visual imprinting circuits.

Animals↗

PubMed1998

Protein splicing in trans by purified N- and C-terminal fragments of the Mycobacterium tuberculosis RecA intein.

Protein splicing involves the self-catalyzed excision of protein splicing elements, or inteins, from flanking polypeptide sequences, or exteins, leading to the formation of new proteins in which the exteins are linked directly by a peptide bond. To study the enzymology of this interesting process we have expressed and purified N- and C-terminal segments of the Mycobacterium tuberculosis RecA intein, each approximately 100 amino acids long, fused to appropriate exteins. These fragments were reconstituted into a functional protein splicing element by renaturation from 6 M urea. When renaturation was carried out in the absence of thiols, the reconstituted splicing element accumulated as an inactive disulfide-linked complex of the two intein fragments, which could be induced to undergo protein splicing by reduction of the disulfide bond. This provided a useful tool for separately investigating the requirements for the reconstitution of the intein fragments to yield a functional protein splicing element and for the protein splicing process per se. For example, the pH dependence of these processes was quite different, with reconstitution being most efficient at pH 8.5 and splicing most rapid at pH 7.0. The availability of such an in vitro protein splicing system opens the way for the exploration of intein structure and the unusual enzymology of protein splicing. In addition, this trans-splicing system is a potential protein ligase that can link any two polypeptides fused to the N- and C-terminal intein segments.

Bacterial Proteins↗

PubMed1998

BCL-2 expression correlates with lower proliferative activity in the intermediate- and high-grade non-Hodgkin's lymphomas: an Eastern Cooperative Oncology Group and Southwest Oncology Group cooperative laboratory study.

An inverse relationship between BCL-2 expression and cell cycle transition has been suggested by recent studies in murine models. To investigate the clinical relevance of these laboratory studies, a group of 116 paraffin-embedded non-Hodgkin's lymphoma (NHL) biopsy specimens (Working Formulation Groups D-H, and J) from a cooperative group study of cellular DNA content were analyzed for the 14;18 translocation using polymerase chain reaction (PCR)-based methods and, if sufficient tissue remained, for BCL-2 and BAX expression by immunohistochemistry. The results of these studies were then compared with the results of the previously performed flow cytometric analysis of ploidy and proliferative activity (S-phase-fraction). BCL-2 expression was inversely associated with proliferative activity (P = .001; n = 41), but there was no association between staining for Bax and %S-phase. Ploidy was not associated with either BCL-2 or BAX expression. The t(14;18) was detected in 21 of the 54 cases in which PCR-amplifiable DNA was recovered; 20 of these occurred at the major breakpoint region and 1 at the minor breakpoint region. High levels of BCL-2 or BAX expression occurred independently of t(14;18). There was no association between t(14;18) and either ploidy or proliferative activity. The inverse relationship between BCL-2 expression and proliferative activity in the intermediate- and high-grade NHLs is consistent with recent studies suggesting that Bcl-2 both retards entry into the cell cycle and inhibits apoptosis.

Cell Division↗

PubMed1998

Effect of procaine hydrochloride on cyanide intoxication and its effect on neuronal calcium in mice.

Cyanide intoxication in mice can be antagonized by the local anesthetic, procaine HCI, either alone or in combination with sodium nitrite and/or sodium thiosulfate. Antitoxic potency, derived from LD50 values, was compared in groups of mice pretreated with sodium nitrite (43.9 mg/kg i.p.), sodium thiosulfate (1 g/kg i.p.), and procaine HCI (37.0 mg/kg i.p.) either alone or in various combinations. The results of present study indicated that procaine HCI provides a significant protection against the lethal effects of potassium cyanide. Dose-response studies revealed procaine hydrochloride pretreated 3 min before KCN, at doses of 18.48-73.9 mg/kg, produced significant elevation of KCN LD50, moreover it has a good dose-effect relationship, but its antidotal effect was weaker than sodium nitrite or sodium thiosulfate when they were administered alone. The protective effect of sodium nitrite and sodium thiosulfate was enhanced with procaine HCI. When procaine was administered in combination both with sodium nitrite and sodium thiosulfate, its protective effects were further enhanced. Its antitoxic potency is 6.22. The effects of procaine on antagonizing the cyanide-induced whole-brain total calcium increase were also studied. KCN (7 mg/kg i.p.) significantly increased whole-brain total calcium level from 28.37 +/- 0.75 to 48.05 +/- 1.06 mg/g dry wt within 30 min, which can be prevented by procaine pretreated 15 min before KCN. One of the possible mechanism of procaine on antagonizing cyanide toxicity seems, at least, related to its effect on inhibiting the cyanide-induced neuronal calcium increase and maintaining the homeostasis of neuronal calcium.

Anesthetics, Local↗

PubMed1998

The morphologic changes in lamellar bodies and intercorneocyte lipids after tape stripping and occlusion with a water vapor-impermeable membrane.

It has been reported that artificial restoration of barrier function by a water vapor-impermeable membrane after tape stripping induces barrier abrogation in hairless mice, impeding rather than enhancing barrier recovery. To address this issue, we examined the morphologic changes in the epidermis after tape stripping and occlusion with a water vapor-impermeable membrane in murine skin. Male hairless mice were used for all studies of barrier perturbation and occlusion. Barrier disruption was achieved by repeated application of cellophane tape. Immediately after tape stripping the animals were wrapped in a tightly fitting water vapor-impermeable membrane. Transepidermal water loss (TEWL) was measured 20 min after tape stripping and 14, 24, 36, 48 and 60 h after occlusion. For electron microscopy the samples were treated with osmium tetroxide (OsO4) or ruthenium tetroxide (RuO4). When tape-stripped animals were wrapped in a water vapor-impermeable membrane, thereby preventing water flux, barrier function did not recover normally. These results demonstrate that an artificial block to TEWL with an impermeable membrane did not enhance barrier recovery. By electron microscopy many transitional cells and lacunae of various sizes were seen within the intercellular spaces of the stratum corneum after occlusion following tape stripping. Occlusion also caused alterations in both lipid lamellar membrane structures in the stratum corneum interstices and the lamellar bodies in the cytosol of granulocytes and transitional cells. Secreted lamellar body contents also appeared to be abnormal in the stratum corneum-stratum granulosum junction.

Animals↗

PubMed1998

Further characterization of cyclophosphamide resistance: expression of CD95 and of bcl-2 in a CML cell line.

Drug resistance is a common cause of treatment failure in oncology. In addition to the resistance caused by over-expression of p-glycoprotein and similar molecules other mechanisms are involved in the selection or induction of drug resistant tumor cells. In this study, we characterized a CML cell line made resistant to cyclophosphamide (KBM7-B5-1803) further for the expression of apoptosis promoting and inhibiting molecules. We found that KBM7-B5-1803 has a 3 4-fold over-expression of the receptor CD95 (Fas/Apo-1) compared with the parent line. The regulation of CD95 by cytokines was comparable to other types of cells. Despite the inducibility and over-expression of CD95, CD95 failed to trigger apoptosis in both the parent and the drug resistant line. The drug resistant line has a particular pattern of the expression of bcl-2 family members: bcl-2 protein and message were expressed to a similar extent, however, compared with the parent line, the message for bclx short was decreased. P-glycoprotein was not expressed in either cell line. Taken together we show here in a leukemia cell line that the phenotype of cyclophosphamide resistance is associated with a particular pattern of apoptosis-related molecules.

Apoptosis↗

PubMed1998

Induction of MHC-class I restricted human suppressor T cells by peptide priming in vitro.

The induction of regulatory T cells may offer an effective means for specific immunosuppression of autoimmune disease and allograft rejection. The existence of suppressor T cells has been previously documented, yet their mechanism of action remains poorly characterized. Our studies demonstrate that T suppressor (Ts) cell lines can be generated by in vitro immunization of human PBMCs, with synthetic peptides or soluble proteins coupled to beads. Such Ts cells express the CD8+CD28- phenotype and show the following characteristics: (a) antigen specificity and restriction by self MHC Class I molecules; (b) limited TCR V beta gene usage; (c) ability to inhibit antigen-specific, MHC Class II restricted, Th proliferative responses; and (d) capacity to downregulate and/or inhibit the upregulation by Th of CD40, CD80, and CD86 molecules on APCs. The inhibitory activity of Ts on Th proliferation requires the tripartite interaction between Th, Ts, and APCs and results from inefficient costimulation of Th.

Amino Acid Sequence↗

PubMed1998

Age-related changes in the absolute number of CD95 positive cells in T cell subsets in the blood.

Comparison of the absolute number of cells in distinct T cells subsets expressing CD95 (Fas) was carried out in two populations of healthy female volunteers. In one population, the average age was 30 +/- 5 years, and in the second population the average age was 73 +/- 13 years. No significant difference was noted in the total number of lymphocytes, CD3+, CD4+, or CD8+ cells per microL of blood between the two age groups, but major differences were noted in the number of cells expressing CD95. A significant reduction was seen in the number of cells per microL of blood in both the CD4+ CD45RA+ CD95+ and CD8+ CD45RA+ CD95+ populations in the older group compared with the younger group. Within the memory pool significantly fewer CD8+ CD45RO+ CD95+ cells were found in the older population compared with the younger group. No such difference were found in the number of CD4+ CD45RO+ CD95+ cells between groups. Such a significant decline in the number of CD95+ cells, whose expression is known to be linked with activation, may be implicated as a mechanism by which cells that have reached a stage of replicative senescence remain in the peripheral T cell pool. Anti-CD3-mediated activation of cells from both groups revealed much lower proliferative responses from the older group, supporting the idea that there is an age-associated increase in the number of cells that have reached their replicative limit. These cells may not be lost from the peripheral pool because they fail to express CD95.

Adult↗

PubMed1998

Effect of process conditions on recovery of protein activity after freezing and freeze-drying.

The objective of this research was to gain a better understanding of the degree to which recovery of activity of model proteins after freeze-drying can be maximized by manipulation of freeze-dry process conditions in the absence of protective solutes. Catalase, beta-galactosidase and lactate dehydrogenase (LDH) were used as model proteins. All of the three proteins exhibited a concentration-dependent loss of activity after freezing, with significantly higher recovery at higher concentration. The freezing method and the type of buffer were also important, with sodium phosphate buffer and freezing by immersion of vials in liquid nitrogen associated with the lowest recovery of activity. Differential scanning calorimetry was predictive of the onset of collapse during freeze-drying only for beta-galactosidase. For the other proteins, either no Tg' transition was observed, or the apparent glass transition did not correlate with the microscopically-observed collapse temperature. The time course of activity loss for beta-galactosidase and LDH was compared during freeze-drying under conditions which produced collapse of the dried matrix and conditions which produced retention of microstructure in the dried solid. Recovery of activity decreased continuously during primary drying, with no sharp drop in recovery of activity associated with the onset of collapse. The most important drying process variable affecting recovery of activity was residual moisture level, with a dramatic drop in activity recovery associated with residual moisture levels less than about 10%.

Animals↗

PubMed1998

An anti-CD19 antibody coupled to a tetanus toxin peptide induces efficient Fas ligand (FasL)-mediated cytotoxicity of a transformed human B cell line by specific CD4+ T cells.

Treatment of B cell lymphoma patients with MoAbs specific for the common B cell marker (CD20) has shown a good overall response rate, but the number of complete remissions is still very low. The use of MoAbs coupled to radioisotopes can improve the results, but induces undesirable myelodepression. As an alternative, we proposed to combine the specificity of MoAbs with the immunogenicity of T cell epitopes. We have previously shown that an anti-Ig lambda MoAb coupled to an MHC class II-restricted universal T cell epitope peptide P2 derived from tetanus toxin induces efficient lysis of a human B cell lymphoma by a specific CD4+ T cell line. Here we demonstrate that the antigen presentation properties of the MoAb peptide conjugate are maintained using a MoAb directed against a common B cell marker, CD19, which is known to be co-internalized with the B cell immunoglobulin receptor. In addition, we provide evidence that B cell lysis is mediated by the Fas apoptosis pathway, since Fas (CD95), but not tumour necrosis factor receptor (TNFr) or TNF-related receptors, is expressed by the target B cells, and FasL, but not perforin, is expressed by the effector T cells. These results show that B cell lymphomas can be 'foreignized' by MoAb-peptide P2 conjugates directed against the common B cell marker CD19 and eliminated by peptide P2-specific CD4+ T cells, via the ubiquitous Fas receptor. This approach, which bridges the specificity of passive antibody therapy with an active T cell immune response, may be complementary to and more efficient than the present therapy results with unconjugated chimeric anti-CD20 MoAbs.

Antibodies, Monoclonal↗

PubMed1998

Injection of T-cell receptor peptide reduces immunosenescence in aged C57BL/6 mice.

Previous studies established that retrovirally infected young mice produced large amounts of autoantibodies to certain T-cell receptor (TCR) peptides whose administration diminished retrovirus-induced immune abnormalities. C57BL/6 young (4 weeks) and old (16 months) female mice were injected with these same synthetic human TCR V beta 8.1 or 5.2 peptides. Administration of these autoantigenic peptides to old mice prevent immunosenescence, such as age-related reduction in splenocyte proliferation and interleukin-2 (IL-2) secretion. TCR V beta peptide injection into young mice had no effect on T- or B-cell mitogenesis and IL-4 production while modifying tumour necrosis factor-alpha (TNF-alpha), IL-6, and interferon-gamma (IFN-gamma) secreted by mitogen-stimulated spleen cells. TCR V beta injection also retarded the excessive production of IL-4, IL-6 and TNF-alpha induced by ageing. These data suggest that immune dysfunction and abnormal cytokine production, induced by the ageing process, were largely prevented by injection of selected TCR V beta CDR1 peptides.

Aging↗