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Biomedical subjects

S Jiang

Publications and source records attributed to S Jiang.

At least 217 records · Page 12Linked to original sources
PubMed1998

[Thermal influence on intracellular calcium concentration of isolated vestibular hair cells in guinea pig].

OBJECTIVE: To further understand the mechanism of caloric test. METHODS: Vestibular hair cells(VHC) were isolated from guinea pig crista ampullaris by enzymatic and mechanical methods and the variations of intracellular free calcium ion concentration ([Ca2+]i) with changes of the extracellular medium temperature were observed. The [Ca2+]i of VHC was examined using laser scanning confocal microscopy (LSCM) and the Ca2+ sensitive dye Fluo-3. RESULTS: Were as follows: 1. There was an increase in [Ca2+]i of 81.8% (18/22) type I VHC and 7/12 type II VHC with the heat stimulation and a decrease in [Ca2+]i with temperature decrease. The magnitude of variation in [Ca2+] i in type I VHC was larger than that in type II VHC. 2. There was no significant change in [Ca2+]i of outer hair cells (OHC) with the heat stimulation. CONCLUSION: There is a direct thermal influence on vestibular sensory cells and this influence accompany with the variation of [Ca2+]i in VHC.

Animals↗
PubMed1998

[Study on the methodology of potassium channel expression in Xenopus oocytes by messenger RNA from rat cochlear nucleus].

OBJECTIVE: To study the properties of voltage-dependent ion channels expressed in Xenopus oocytes by mRNA from rat cochlear nucleus and to lay a methodological foundation for studying the changes of ion channels in auditory centre with sensorineural hearing loss. METHODS: Poly (A)+ mRNAs isolated from the rat cochlear nucleus by acid guanidinum thiocyanate-phenol-chloroform (AGPC) method and Promega's new magnesphere technique were microinjected into Xenopus laevis oocytes to express functional ion channels. Voltage clamp technique was used to record the current of voltage-dependent ion channels. RESULTS: A voltage-dependent ion channel was detected from oocytes injected with rat cochlear nucleus mRNA. The maximum amplitude of the outward current was 364 +/- 42 nA (n = 16). It was identified as transient outward potassium channel. CONCLUSION: The model set up by the test may play an important role in studying the physiology, pathology and pharmacology of auditory centre.

Animals↗
PubMed1998

[Effects of extremity cuffs against physiological changes induced by head-down bedrest].

-6 degrees head down bedrest (HDBR) 10d was used to simulate weightlessness. 12 volunteers were randomed into control group and cuffs group, with 6 in each group. Inflated cuffs on the upper part of thighs and arms were performed 12 h/d in cuffs group during bedrest. No countermeasures were applied in the control group. During head up tilt (HUT) +75 degrees 20 min orthostatic tolerance test after HDBR, 5 in control group became presyncopal, while only one in cuffs group. The study indicates that the use of inflated cuffs provides a protective effect against the cardiovascular deconditioning after bedrest.

Adolescent↗
PubMed1998

[Effect of repeated cerebral ischemia induced by lower body negative pressure on neuronal morphology and ions contents, ATPase activity of brain tissue in rats].

To investigate the effect of repeated + Gz-induced loss of consciousness on the brain and its mechanism, we observed the changes of ions contents, ATPase activity of brain tissues and neuronal morphology after repeated cerebral ischemia induced by lower body negative pressure(LBNP) in rats. Thirty male Sprague-Dawley rats were divided into 3 groups randomly. Rats were anesthetized and exposed to LBNP of -4 kPa at a rate of 0.67 kPa/s. The pressure rapidly returned to control level 2 min after EEG becomes isoelectric. Cortical Na(+)-K(+)-ATPase activity decreased significantly lh after one LBNP exposure (P < 0.05), While Na+, K+ and water contents of brain tissues showed a tendency to increase (P > 0.05). Na(+)-K(+)-ATPase activity decreased significantly while Na+, K+ and water contents increased significantly 1 h after three LBNP exposures, and ischemic changes were found in a few neurons. It suggested that three cerebral ischemia exposure induced by LBNP can result in disturbance of ion homeostasis and neuronal damage.

Animals↗
PubMed1998

[Diterpenoid alkaloids from Aconitum bulleyanum Diels].

OBJECTIVE: To investigate the diterpenoid alkaloids from Aconitum bulleyanum. METHOD: Diterpenoid alkaloids were separated by solvent extraction and chromatography on silical gel, and their structures were determined by spectral analysis and chemical evidence. RESULT: Five diterpenoid alkaloids were elucidated as yunaconitine, crassicauline A, vilmorrianine C, lycoctonine and lappaconitine. CONCLUSION: All the compounds were isolated from this plant for the first time.

Aconitine↗
PubMed1998

[Heat shock response in experimental acute middle ear bacterial infection].

OBJECTIVE: To investigate the association between bacteria antigen and inner ear antigen and effects of stress on the expression spectrum and level of the antigen bearing hsp70 related epitope. METHODS: Use monoclonal antibody against mammiferous hsp70 to recognize the related antigens of Bacillus pyocyaneus, Bacillus proteus, Bacillus coli, Staphylococcus aureus and Klebsiella pneumoniae with modified western blotting. The expression level of hsp70 in unstressed guinea pig inner ear was tested. An animal model of middle ear acute infection by Klebsiella pneumoniae was established. The dynamic changes of mammiferous hsp70 epitope related proteins were tested with modified western blotting. RESULTS: All the bacteria antigens recognized by anti-mammiferous hsp70 antibody were not of the hsp70 family and the expression level of hsp70 in normal guinea pig was extraordinarily low. Klebsiella pneumoniae expressed 70,000 dalton and 17,000 dalton hsp after its invasion into guinea pig middle ear. 70,000 dalton antigen expressed most intensely at 3rd day of invasion and then fell. 17,000 dalton antigen was expressed most intensely at 5th day of invasion and then fell. The expression of 70,000 dalton hsp was much weaker than 31,000 dalton hsp at acute periods of middle ear infection. CONCLUSIONS: The elevated expression of hsp both in bacteria and inner ear during middle ear acute infection provides material base for immune impairment on inner ear induced by bacterial infection. The low molecular weight hsp may be involved in the inner ear autoimmune impairment.

Animals↗
PubMed1998

[A specific property of microvasomotion in the guinea pig cochlea].

OBJECTIVE: To investigate specific property of vasomotion in cochlear microvessels and its response to the endothelium-derived relaxation factor (EDRF). METHODS: The dynamic changes of cochlea microvessels were observed using intravital microscopy and measured by the microcirculatory image processing system. The frequency and amplitude of vasomotion were analyzed with fast Fourier transform (FFT) according to the diameter changes. RESULTS: The vasomotion of cochlear arteriole with a small amplitude existed in normal condition. The diameter changed from (10.41 +/- 3.03) microns to (12.29 +/- 1.9) microns with a mean value of (11.2 +/- 2.7) microns. The specific property of vasomotion was characterized by a frequency (0.021 +/- 0.002) Hz and amplitude of (0.37 +/- 0.11) micron. The contraction index was determined as 0.42 +/- 0.17. The vasomotion was significantly enhanced after the administration of EDRF. CONCLUSION: The vasomotion existed in the cochlea and EDRF can increase the cochlear blood flow by improving the vasomotion.

Animals↗
PubMed1998

[The relationship between loudness recruitment phenomenon and distortim product otoacoustic emission and their clinical significance].

OBJECTIVE: To study the relationship between loudness recruitment and abnormal cochlear mechanism. METHODS: The basic properties of input/output (I/O) of distortion product otoacoustic emission (DPOAE) in 20 normal subjects(40 ears) and 50 cases with cochlear deafness (63 ears) with positive recruitment were studied and analyzed. RESULTS: Average slope of I/O at different frequencies in all deaf ears with recruitment was greater than those in the normal subjects with a statistical significance (P < 0.01). Moreover, thresholds of DPOAE in the recruitment positive ears were higher than those in normal subjects. CONCLUSION: Loudness recruitment and abnormal cochlear active mechanism are specially related. I/O functions of DPOAE are more perceptive and precise to appraise cochlear active mechanism. It probably may become a valuable test for early diagnosis of cochlear deafness.

Adolescent↗
PubMed1998

[Extraction, amplification, recombination and sequencing of the mitochondrial DNA from celloidin embedded human temporal bone sections].

OBJECTIVE: To establish an analytical method of DNA extracted from human celloidin-embedded temporal bone sections by molecular biologic technique. METHODS: Polymerase chain reaction (PCR) with different primers, special amplification methods or coorperated with enzyme restricted reactions was adapted to detect several types of genetic mutations from 9 human celloidin-embedded temporal bone sections. The pGEM-T vector was used for the recombination and cloning of the amplified DNA fragment. RESULTS: The 135 bp fragments of normal mtDNA were detected from all of the 9 cases. The 316bp fragment related to mtDNA 4977bp deletion was also detected in two cases who suffered from presbycusis before death by the nested PCR. The result of sequencing confirmed the accuracy of PCR. CONCLUSION: The application of molecular biologic techniques in temporal bone research is important in improving the quality and value of retrospective study of ear diseases and has resulted in findings of the relevant mutant or pathogenetic genes in the ear diseases such as presbycusis, ototoxic deafness, otosclerosis and viral infections of the ear.

Adolescent↗
PubMed1998

[Isolation of and intracellular calcium mobilization in vestibular hair cells of the patients with acoustic neuroma].

OBJECTIVE: To further understand the biological features of the human vestibular organ. METHODS: Vestibular hair cells were isolated from patients with acoustic neuroma during the surgery and intracellular free calcium concentration of the cells was monitored with calcium-sensitive dye Fura-2 and digital imaging microscopy. RESULTS: Isolated vestibular hair cells were mainly of type I and could survive about 2.5 hours in vitro. Perfusion with 150 mmol/L KCl, induced a depolarization, resulting in a temporary increase of 340 nm/380 nm ratio from 0.52 to 1.16 within 1 min. In Ca2+ free environment, 150 mmol/L KCl failed to induce intracellular calcium increase. In the presence of 2.5 mumol/L ionomycin, there was an irreversible increase in 340 nm/380 nm ratio. CONCLUSION: Human vestibular hair cell apparently possess voltage sensitive calcium channels. The method and observation aid in elucidating human vestibular biological features.

Aged↗
PubMed1997

Characterization and chromosomal localization of PTPRO, a novel receptor protein tyrosine phosphatase, expressed in hematopoietic stem cells.

Hematopoietic stem cells (HSCs) support blood cells throughout life by utilizing their self-renewing and multilineage differentiating capabilities. Hematopoietic growth factors mediate their effects on stem cells by the tyrosine phosphorylation of proteins. Regulation of tyrosine phosphorylation is partially mediated by protein tyrosine phosphatases (PTPases). A possible mechanism by which hematopoietic stem cells maintain their self-renewing capacity and undifferentiated state is by controlling the balanced and opposing actions of protein tyrosine kinases (PTKs), receptors for growth factors, and PTPases. We have characterized the expression of PTPases in 5-fluorouracil (5-FU)-treated murine bone marrow cells, which represent a very primitive population of progenitors enriched for reconstituting stem cells, by using a consensus polymerase chain reaction (PCR) method. Several PTPases were expressed abundantly in the 5-FU-treated bone marrow stem cells. A novel PTP, termed protein tyrosine phosphatase receptor omicron (PTPRO), which is related to the homotypically adhering kappa, mu and PCP-2 receptor-type tyrosine phosphatases, was identified and characterized. We have cloned the murine and full-length human PTPRO cDNAs which share 89% homology, indicating that PTPRO is highly conserved between these species. The human PTPRO cDNA clone encodes a polypeptide of 1439 amino acids (aa) and has a calculated molecular mass of approximately 162 kDa. PTPRO consists of an extracellular segment containing a MAM domain, an immunoglobulin (Ig) domain, four fibronectin-type III (FN-III) repeats, a transmembrane segment, and two tandem intracellular PTP domains. The human PTPRO gene was assigned to human chromosome 1p35-pter using Southern blot analyses of genomic DNAs from rodent/human somatic hybrid cell lines containing human chromosome 1 or the p35-pter region of the chromosome. The mouse Ptpro gene was mapped to chromosome 4, closely linked to D4Mit16 and Elp1 (elliptocytosis-1), by using genomic DNAs from a (C57BL/6J x Mus spretus)F1 x Mus spretus backcross. In fetal tissues, PTPRO expression was observed in the brain and lung, whereas lower levels were observed in the kidney. In adult tissues, PTPRO was less restricted and was observed in the lung, heart, skeletal muscle, prostate, testis, and in various areas of the brain, indicating that PTPRO expression is developmentally regulated. Expression of PTPRO was also observed in human CD34+ bone marrow cells and 5-FU-treated murine primitive stem cells. These results suggest a potential role for PTPRO in stem cell adhesion and in mediating homophilic cell-cell interactions in other cell types.

Amino Acid Sequence↗
PubMed1997

Localization of dopamine D1 receptors and dopaminoceptive neurons in the chick forebrain.

The distributions of dopamine D1 receptors, dopaminoceptive neurons, and catecholaminergic fibers were investigated in the forebrain of the domestic chick by using D1 receptor autoradiography and immunohistochemical detection of D1 receptor protein (D1rp), the dopamine- and cAMP-regulated phosphoprotein DARPP-32, and tyrosine hydroxylase (TH). Particular attention was paid to two forebrain regions, the mediorostral neostriatum/ hyperstriatum ventrale (MNH) and neostriatum dorsocaudale (Ndc), which have been shown to be crucially involved in filial imprinting. In general, there was a good, but not complete, correlation between the immunohistochemical pattern of DARPP-32 positive perikarya and the distribution of D1 receptors. Both, DARPP-32 positive neurons as well as D1 receptors were highly enriched in the striatal part of the basal ganglia including the lobus parolfactorius (LPO) and paleostriatum augmentatum. High to moderate densities were observed in the outer rind of the pallium. Low to moderate densities were found in the belt regions of primary sensory areas, whereas densities in the respective core regions were generally low. Labeling in the MNH and Ndc was heterogeneous. Whereas the neostriatal part of MNH displayed both, moderate DARPP-32 immunostaining and moderate D1 receptor densities, the hyperstriatal part showed also moderate D1 receptor densities but was only weakly labeled by DARPP-32. The rostral part of the Ndc was among the most intensely DARPP-32 labeled areas of the pallium, its caudal part revealed only moderate DARPP-32 immunostaining. By using D1 receptor autoradiography, a homogeneous labeling throughout the rostrocaudal extension of the Ndc was found. Double-labeling experiments with antibodies to DARPP-32 and TH revealed that TH positive fibers in the MNH, Ndc, and LPO were often closely related to DARPP-32 positive perikarya. At the ultrastructural level, both immunoreaction for D1rp and DARPP-32 in the MNH and Ndc were primarily found to be associated with postsynaptic elements. Whereas D1rp immunoreactivity was enriched at postsynaptic densities or in their vicinity, reaction product for DARPP-32 was present throughout the perikaryal cytoplasm, dendrites, and dendritic spines. These results indicate that DARPP-32 as well as D1 receptors in the avian forebrain reveal a distribution that is substantially similar to that of mammals.

Animals↗
PubMed1997

Vasoactive intestinal peptide (VIP) stimulates in vitro growth of VIP-1 receptor-bearing human pancreatic adenocarcinoma-derived cells.

Vasoactive intestinal peptide (VIP) appears to be responsible for atropine-resistant, neurally mediated pancreatic ductal bicarbonate secretion and plays a role in both stimulation and inhibition of neoplastic growth in other organs. cDNAs encoding high affinity VIP-1 and VIP-2 receptors have been cloned, and these receptors may be differentiated based on the ability of VIP-1, but not VIP-2, receptors to couple to adenylyl cyclase in response to stimulation with micromolar concentrations of secretin. Recent data from our laboratory suggest expression of a low affinity secretin receptor in seven cell lines derived from human ductal pancreatic adenocarcinomas. In combination with the recent use of (123)I-labeled VIP to successfully image pancreatic adenocarcinomas in humans and the high affinity binding of both VIP and pituitary adenylate cyclase-activating peptides to sections from human pancreatic tumors, these findings suggest that VIP-1 receptors may be expressed on the majority of neoplastic pancreatic duct epithelial cells in vivo. To initially test the hypothesis that expression of VIP-1 receptors plays an important role in the pathophysiology of human ductal pancreatic adenocarcinomas, we used reverse transcription-PCR with Southern blot hybridization to confirm expression of VIP-1 and VIP-2 receptor mRNA in the vast majority of 28 human ductal pancreatic adenocarcinomas. Based on the cellular heterogeneity of these tumors, we also assessed VIP receptor subtype expression in seven well-characterized, secretin-responsive cell lines derived from human ductal pancreatic adenocarcinomas. Only VIP-1 receptor mRNA was detected in all seven secretin-responsive cell lines. A half-maximal increase in intracellular cyclic AMP was obtained with 0.5-5 nM VIP in each of these cell lines, consistent with expression of high affinity VIP receptors. The ability of 1 microM, but not 1 nM, secretin to stimulate intracellular cyclic AMP generation in these cells was consistent with VIP-1 receptor expression. Interestingly, 100 pM, but not 1 microM, VIP stimulated significant growth of VIP-1 receptor-bearing Capan-2 cells both in the absence and presence of serum. Because VIP-1 receptors appear to be expressed in the majority of neoplastic pancreatic duct cell lines and VIP stimulates growth of VIP-1 receptor-bearing Capan-2 cells in vitro, this peptide may well play an important role in the pathophysiology of tumors expressing these receptors in vivo.

Adenocarcinoma↗
PubMed1997

Direct association of Csk homologous kinase (CHK) with the diphosphorylated site Tyr568/570 of the activated c-KIT in megakaryocytes.

The Csk homologous kinase (CHK), formerly MATK, has previously been shown to bind to activated c-KIT. In this report, we characterize the binding of SH2(CHK) to specific phosphotyrosine sites on the c-KIT protein sequence. Phosphopeptide inhibition of the in vitro interaction of SH2(CHK)-glutathione S-transferase fusion protein/c-KIT from SCF/KL-treated Mo7e megakaryocytic cells indicated that two sites on c-KIT were able to bind SH2(CHK). These sites were the Tyr568/570 diphosphorylated sequence and the monophosphorylated Tyr721 sequence. To confirm this, we precipitated native CHK from cellular extracts using phosphorylated peptides linked to Affi-Gel 15. In addition, purified SH2(CHK)-glutathione S-transferase fusion protein was precipitated with the same peptide beads. All of the peptide bead-binding studies were consistent with the direct binding of SH2(CHK) to phosphorylated Tyr568/570 and Tyr721 sites. Binding of FYN and SHC to the diphosphorylated Tyr568/570 site was observed, while binding of Csk to this site was not observed. The SH2(CHK) binding to the two sites is direct and not through phosphorylated intermediates such as FYN or SHC. Site-directed mutagenesis of the full-length c-KIT cDNA followed by transient transfection indicated that only the Tyr568/570, and not the Tyr721, is able to bind SH2(CHK). This indicates that CHK binds to the same site on c-KIT to which FYN binds, possibly bringing the two into proximity on associated c-KIT subunits and leading to the down-regulation of FYN by CHK.

Animals↗
PubMed1997

Expression of CD95(FAS) by gene transfer does not sensitize K562 to Fas-killing.

CD95(FAS/Apo-1) belongs to the family of TNF receptor related molecules and is expressed on many benign and malignant types of cells. CD95 triggering is involved in the apoptotic death of lymphoid cells and may also be important in myelopoiesis. Myeloid leukemia cells are in most cases resistant to CD95 triggering despite expressing the antigen. We reasoned that myeloid leukemic cells can become sensitized to the Fas pathway of cell death if CD95 expression is restored by gene transfer. As a model, we utilized the cell line K562 which does not express CD95 on their cell surface. The gene for CD95 was introduced into K562 cells (by electroporation). As a control, the gene coding for beta-galactosidase was used. The CD95 transfected K562 cells stably expressed CD95, and had a growth pattern comparable to untransfected cells, but still remained resistant to Fas-triggering (tested using recombinant Fas-ligand). Our experiment shows that antigen expression is not a critical determinant of Fas-mediated apoptosis, but further down-stream mechanisms determine the fate of the cells. The transfected cells also had a comparable susceptibility to NK-mediated lysis which shows that the expression of CD95 does not interfere with NK-mediated lysis of target cells.

Annexin A5↗
PubMed1997

The role of proteolysis in T cell apoptosis triggered by chelation of intracellular Zn2+.

Our previous work showed that chelation of intracellular Zn2+ with N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN) induces apoptosis in rat thymocytes. The molecular mechanism involved in TPEN-triggered apoptosis remains unknown, except that it is a Ca2+-independent process. In the present study, we show that TPEN is unable to induce DNA fragmentation when added to isolated thymocyte nuclei, indicating that activation of a cytoplasmic component is essential for TPEN-induced apoptosis. Since cytosolic proteases related to interleukin-1beta-converting enzyme (ICE) are implicated as key activators of apoptosis in many different systems, we investigated the possible involvement of such proteases in TPEN-induced apoptosis. We found that treatment of thymocytes with TPEN caused an early degradation of nuclear poly(ADP-ribose) polymerase (PARP) and lamin prior to DNA cleavage. This could be inhibited by Z-Val-Ala-Asp-chloromethylketone (VADcmk), an inhibitor of ICE-like proteases, but not by an inhibitor of Ca2+-regulated serine protease. Jurkat T cells also underwent extensive DNA fragmentation when incubated with TPEN. A cytosolic fraction, prepared from TPEN-treated Jurkat cells, produced extensive DNA fragmentation when applied to isolated thymocyte nuclei, whereas the cytoplasmic extract from untreated cells was ineffective either alone or together with TPEN. The apoptosis-inducing activity in cytosolic fraction from TPEN-treated Jurkat cells was blocked by incubating cells in the presence of VADcmk or another inhibitor of ICE-like proteases, Ac - Asp - Glu - Val - Asp-aldehyde (DEVD-CHO), which has been found to competitively inhibit CPP32/apopain. An increase in enzyme activity that cleaves Ac-Asp-Glu-Val-Asp-7-amino-4-methylcoumarin (DEVD-AMC), a fluorogenic substrate of CPP32/apopain and Mch3alpha, was detected in TPEN-treated thymocytes and Jurkat cells. In addition, the proteolytic cleavage of CPP32 resulting in the formation of two active fragments (p17 and p12) was observed in cytosolic extracts from TPEN-treated Jurkat cells, but not in extracts which were prepared from cells treated with TPEN in the presence of VADcmk or DEVD-CHO. Our results suggest that activation of cytosolic ICE-like proteases is an essential step in TPEN-induced apoptosis, and that CPP32/apopain is critically involved in this process.

Journal Article↗