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Biomedical subjects

W Jin

Publications and source records attributed to W Jin.

At least 19 recordsLinked to original sources
PubMed1997

Determination of cysteine by capillary zone electrophoresis with end-column amperometric detection at a gold/mercury amalgam microelectrode without deoxygenation.

Capillary zone electrophoresis was employed for the determination of cysteine using an end-column amperometric detection with a gold/mercury amalgam microelectrode, at a constant potential of 0.02-0.06 V vs. saturated calomel electrode. In this procedure deoxygenation is not necessary. The electrochemical characteristics at the microelectrode, the effect of the concentration of the buffer and the separation voltage across the capillary on the migration time and separation efficiency, and the dependence of the injection voltage and time on the detection signal, the separation efficiency and coulometric efficiency has been investigated. The calibration plot was found to be linear over four orders of magnitude and the limit of detection was 5.8 x 10(-8) mol/l (or 14.5 amol). The method was applied to the determination of cysteine in human plasma, blood and urine.

Buffers↗
PubMed1997

Sequence requirements for regulated RNA splicing of the human fibroblast growth factor receptor-1 alpha exon.

Progression of astrocytes from a benign to a malignant phenotype is accompanied by a change in the RNA processing of the fibroblast growth factor receptor 1 (FGFR-1) gene. The level of a high affinity form of the FGFR-1 is dramatically elevated as a result of alpha-exon skipping during RNA splicing. In this paper we have been able to duplicate this tumor-specific RNA processing pathway by transfection of a chimeric minigene containing a 4-kilobase fragment of the human FGFR-1 gene (including the alpha-exon) into a variety of cell lines. In a transfected human astrocytoma cell line, alpha-exon skipping was consistently observed for RNA transcripts derived from both the chimeric minigene and endogenous gene expression. This exon skipping phenotype was dependent on the size of the flanking intron as deletions which reduced the introns to less than approximately 350 base pairs resulted in enhanced alpha-exon inclusion. Increased exon inclusion was not sequence-specific as exon skipping could be restored with insertion of nonspecific sequence. Cell-specific exon recognition was maintained with a 375-nucleotide sequence inclusive and flanking the alpha-exon, provided that intron size was maintained. These results identify the minimal cis-regulatory sequence requirements for exclusion of FGFR-1 alpha-exon in astrocytomas.

Base Sequence↗
PubMed1997

Glycine68 to histidine73 has an important role in the function of human tumor necrosis factor alpha.

Mutant human tumor necrosis factor alpha(hTNF alpha) genes have been constructed by in vitro mutagenesis and expressed in Escherichia coli. A deletion involving Gly68 to His73 in hTNF alpha remarkably decreased the solubility and biological activity of hTNF alpha. From the above and results of a molecular dynamics simulation it is proposed that the region of Gly68 to His73 in hTNF alpha has an important role in the maintenance of the 3-D structure and modulation of the biological activity of hTNF alpha.

Amino Acid Sequence↗
PubMed1997

Extracellular Ca2+ directly regulates tight junctional permeability in the human cervical cell line CaSki.

Lowering extracellular calcium concentration ([Ca2+]o) increases acutely and reversibly the transepithelial electrical conductance (G(TE)) and the epithelial permeability to pyranine (Ppyr) across CaSki cultures. Effects were already observed after lowering calcium from 1.2 to 1.0 mM and were maximal at 0.1 mM. The dose-response curves were sigmoidal (calcium concentration that produces half-maximal effect = 0.3 mM), and the time courses indicated simple exponential trends (time constants of 4-5 min). The effect of calcium was not mediated by mobilization of cytosolic calcium or altering calcium influx, and manganese was found to be a partial agonist to [Ca2+]o. The effects of [Ca2+]o, on permeability were additive to those of hypertonic conditions, indicating that calcium modulates junctional permeability. The experimental data were fitted to theoretical models that relate changes in G(TE) to the probability of assembled/disassembled tight junctions. The results suggest that calcium interacts directly and cooperatively at extracellular sites with junctional elements that are arranged in parallel, and it shifts the probability state of the junctions from "open" to "closed" state. Changes in extracellular calcium may affect the permeability of tight junctions of the cervical epithelium and may play a role in regulating production of cervical mucus.

Calcium↗
PubMed1997

Purinergic-mediated inhibition of Na+-K+-ATPase in proximal tubule cells: elevated cytosolic Ca2+ is not required.

The involvement of cytosolic Ca2+ concentration ([Ca2+]i) as messenger for the regulation of Na+-K+-ATPase activity was investigated in a renal cell line recently developed by immortalization of early proximal tubule primary cultures from the Wistar-Kyoto rat strain. Na+-K+-ATPase was measured as short-circuit current (Isc) in intact monolayers after permeabilization of the apical plasma membrane with amphotericin B. With symmetrical solutions, Isc quantitatively reflects Na+-K+-ATPase activity as judged by ouabain inhibition and dependence on Na+ and K+. Extracellular ATP (50% effective concentration = 0.32 mM) on the apical side produced acute inhibition of Na+-K+-ATPase-generated Isc of up to 50%. The inhibition peaked within 1 min and lasted approximately 5 min. The potency order was ATP > ADP >> beta,gamma-methyleneadenosine 5'-triphosphate = UTP, consistent with a P2y receptor. Extracellular ATP also stimulated a transient increase in [Ca2+]i. This increase had a similar time course as the inhibition of ATPase and reached a peak change of approximately 120 nM. However, the elevation of [Ca2+]i is not required in the purinergic inhibition of the Na+-K+-ATPase, since, first, increases in [Ca2+]i produced with a Ca2+ ionophore (ionomycin) failed to mimic the purinergic inhibition and, second, 1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid, which abolished the [Ca2+]i elevation, failed to block the purinergic inhibition.

Adenosine Triphosphate↗
PubMed1997

Anatomic dissociation between HIV-1 and its endogenous inhibitor in mucosal tissues.

The rarity of oral transmission of human immunodeficiency virus (HIV)-1 by saliva suggests the absence of HIV-1 in the oral cavity and/or the presence of viral inhibitory molecules. We analyzed salivary gland tissues from 55 individuals with acquired immune deficiency syndrome (AIDS) for the presence of HIV-1 by in situ hybridization and detected the virus in more than 30% of these salivary glands. These data, together with previous demonstrations of HIV-1 in oral secretions, implicate a key role for an anti-viral molecule(s) in suppressing transmission. Thus, we focused on the characterization and localization of the endogenous antiviral molecule secretory leukocyte protease inhibitor (SLPI), which inhibits HIV-1 infection in vitro. Expression of SLPI transcripts was evident in submandibular, parotid, and minor salivary glands from both HIV-1-infected and seronegative subjects. Gene expression was reflected by similar levels of SLPI protein by immunohistochemical analysis in the tissues and by enzyme-linked immunosorbent assay in the saliva. However, although SLPI accumulated in acinar cells or ductal epithelium, HIV-1 transcripts did not, and these viral transcripts were identified only in mononuclear cells within the salivary gland stroma. By in situ hybridization, we found no evidence of productive HIV-1 infection of salivary gland epithelium. Thus, HIV-1 was frequently identified in salivary gland tissue, but the virus was found in interstitial mononuclear cells only and did not co-localize with SLPI. Once within the oral cavity, HIV-1 exposure to antiviral levels of SLPI may impede infection of additional target cells, contributing to the virtual absence of oral transmission of HIV-1 by saliva. These studies emphasize the importance of innate, endogenous inhibitors of HIV-1, particularly SLPI, as effective inhibitors of HIV-1 transmission.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Kappa opioid receptor tolerance in the guinea pig hippocampus.

We investigated whether chronic, in vivo administration of U50,488H, a kappa-1 opioid agonist, caused the development of tolerance to both the electrophysiological effects of applied kappa opioids and endogenously released dynorphins. In hippocampal slices from drug-naive guinea pigs, application of U69,593, a kappa-1 agonist, produced a concentration-dependent inhibition (EC50 = 20 nM) of the amplitude of the granule cell population response in the dentate gyrus. In slices from chronically U50,488H-treated animals, the concentration-response curve for U69,593 was shifted 3-fold to the right (EC50 = 59 nM), with a significant decrease in the maximal effect of U69,593. We also found that the effects of endogenously released dynorphins were significantly attenuated by chronic U50,488H treatment. There was no cross-tolerance between kappa and mu opioid receptor agonists as measured with the in vitro electrophysiological assay, and the noncompetitive N-methyl-D-aspartate receptor antagonist MK801 did not prevent the development of tolerance to either the electrophysiological effects or the hypothermic effects of kappa opioids. Our study demonstrates that receptor-selective tolerance to the kappa opioid actions in the guinea pig hippocampus does develop after chronic U50,488H treatment; but, unlike the mechanisms reported to underlie tolerance to kappa opioid analgesia, the inhibitory effects in the hippocampus did not depend on activation of N-methyl-D-aspartate receptors.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1996

Ceramide selectively inhibits early events in the response of human neutrophils to tumor necrosis factor.

Cell spreading and the respiratory burst of neutrophils responding to soluble, physiological agents and adherent to model biological surfaces are typically delayed in onset by 15 min or more. The lag period may be a physiologically important feature of the action of such agents on neutrophils in that it may allow for migration before secretion. However, the mechanism that interposes such a long delay between stimulus and response is unknown. Tumor necrosis factor alpha (TNF-alpha) mediates some of its actions by triggering sphingomyelinase to generate ceramide. In adherent human neutrophils, however, exogenous ceramide did not mimic TNF-alpha's ability to stimulate cell spreading, paxillin tyrosine phosphorylation, or the respiratory burst. On the contrary, ceramide suppressed each such response. Ceramide did so by extending the lag period in the cells' response to TNF-alpha. Ceramide extended the lag period whether it was added exogenously or generated endogenously by sphingomyelinase, and the effect was reversible. Remarkably, however, ceramide inhibited cell spreading or the respiratory burst only if added together with TNF-alpha or within the next few minutes. Neutrophils ignored ceramide if it was added later, even if the TNF-alpha-triggered respiratory burst had not yet commenced. These features suggest that an early, brief elevation of ceramide in response to TNF-alpha could mediate the lag period. By temporarily inhibiting tyrosine phosphorylation, cell spreading, and the respiratory burst, ceramide or a functionally similar mediator could serve as a phase coordinator of the neutrophil's response to soluble agonists.

Adult↗
PubMed1996

Immortalization and characterization of proximal tubule cells derived from kidneys of spontaneously hypertensive and normotensive rats.

Epithelial cell lines from the proximal tubule of SHR and WKY rats were generated by microdissection, cell growth on 3T3 cell feeder layers, and transduction of the SV40 large T-antigen gene. The cell lines that formed confluent, electrically-resistive monolayers (basal conductance 1 to 20 mS/cm2) were selected for further study. Of these, cell lines generated from one rat did not show evidence of T-antigen expression or integration, and apparently immortalized spontaneously. Cell lines from three other rats expressed high levels of T-antigen, and showed evidence of integration of one or more copies of T-antigen. All cell lines formed polarized monolayers with apical microvilli, tight junctional complexes, and convolutions of the basolateral plasma membrane. Most cell lines grew in the absence of extracellular glucose indicating a capacity for gluconeogenesis. Sodium succinate cotransport and P2-purinergic receptor mediated signaling were demonstrated in all lines tested. The cell lines also showed that Na/H exchanger activity is regulated by angiotensin II. The results indicate that these cell lines express a proximal tubular phenotype, and are morphologically and functionally similar to primary cultures. These rat cell lines represent a new, potentially useful cell model for elucidating the cellular and molecular mechanisms of genetic differences in proximal tubule Na+ reabsorption.

3T3 Cells↗
PubMed1996

[Clinical trial of an anti-fertility method with testosterone enanthate in normal men].

OBJECTIVE: To establish the feasibility of anti-fertility by ultraphysiological-dosage testosterone in male. METHODS: Ten healthy, fertile men received 200 mg testosterone enanthate weekly by intramuscular injection based on international standard protocol. RESULTS: After 3-month injection, severe oligospermia was achieved. After 6-month injection, azoospermia was achieved. The total consecutive administration lasted for 12 months. During the period of severe oligospermia and azoospermia no partner was pregnant. After stopping injection, the sperm output returned to normal (20 x 10(8)/ml) in 2-3 months up to individual's own level before administration in 6 months. CONCLUSION: Severe oligospermia and azoospermia can be induced by ultra-pathological-dosage tesosterone through inhibiting FSH, LH to cause spermatogenesis inhibition. The sperm output would recover to its previous level in 6 months after stopping injection. It is suggested that there is a strong possibility that high-dosage testosterone may act as a male contraceptive.

Adult↗
PubMed1995

Biosensor based on an enzyme modified electrode for highly-sensitive measurement of polyphenols.

The use of glucose dehydrogenase from Acinetobacter calcoaceticus for highly sensitive measurement of polyphenols, based on bioelectrocatalytic analyte recycling, has been demonstrated. A polyphenol (analyte) is oxidized on the surface of a glassy carbon electrode at an anodic potential and is regenerated by immobilized glucose dehydrogenase (GDH) in the presence of glucose, resulting in an amplified response. The dynamic properties of the enzyme-modified glassy carbon electrode allow the convenient monitoring of subnanomolar analyte concentration. The detection limits for p-aminophenol and norepinephrine are 0.2 nM and 0.5 nM, respectively.

Acinetobacter↗
PubMed1995

Influence of the compliance of the pump housing and cannulas of a paracorporeal pneumatic ventricular assist device on transient pressure characteristics.

The dependence of transient pressure characteristics of a ventricular assist device (VAD) on the compliance of its housing and cannulas was investigated in a mock circulation. The peak rate of change of pressure (dP/dtmax) values was greater in the cannulas than other compartments and was associated with valve closure-induced pressure oscillations. When cannula compliance was increased from 0.0057 to 0.0129 cm3/mm Hg, these values decreased by approximately 20%, and outflow cannula pressure oscillation frequency decreased from 17.5 Hz by 35%. This trend was also apparent in the inflow. A VAD housing compliance increase from 0.0162 to 0.0483 cm3/mm Hg caused a dP/dtmax decrease of 30% in both the blood chamber and the outflow cannula. The effect of this change on the inflow was weaker implying that housing absorbs the energy associated with outflow deceleration more effectively than the inflow. These findings suggest that increasing VAD housing and cannulas compliance can improve hydrodynamic performance.

Biocompatible Materials↗
PubMed1995

[Anti-lipid peroxidation effects of sini decoction and its components on ischemic myocardium and the dose- and time-effects].

The complete Sini Decoction can significantly reduce the content of MDA in ischemic myocardium. Single ingredients of the decoction, such as Radix Aconoti Praeparata or Radix Glycyrrhizae, except Rhizoma Zingiberis, also have similar effect but inferior to that of the complete decoction. Under the present conditions of experiment, anti-lipid peroxidation of Sini Decoction is significant at doses ranging from 0.05 to 0.2ml/20g administered for 2-7 days at 0.1ml/(20g.d).

Animals↗
PubMed1994

U73122 inhibits phospholipase C-dependent calcium mobilization in neuronal cells.

The aminosteroid U73122 inhibited phospholipase C (PLC)-mediated intracellular Ca2+ release in differentiated and undifferentiated NG108-15 cells, as well as rat dorsal root ganglion (DRG) neurons grown in primary culture. 1 microM U73122 blocked bradykinin (BK)-induced increases in the intracellular free Ca2+ concentration ([Ca2+]i) measured in single cells with indo-1-based dual emission microfluorimetry. A close structural analog, U73343, was without effect. The effects of U73122 were time and concentration-dependent. 1 microM drug produced half maximal inhibition in approximately 3 min. The IC50 for a 20-min exposure was approximately 200 nM. The effects of the compound were irreversible for the duration of experiments as long as 1 h. Treatment with 1 microM U73122, but not U73343 produced a small but significant increase in [Ca2+]i which resulted from Ca2+ release from an intracellular store. It is not clear whether this [Ca2+]i increase resulted from inhibition of PLC or an action on the store directly. In differentiated NG108-15 cells U73122 blocked completely depolarization-induced Ca2+ influx. In contrast, in DRG neurons U73122 inhibited only slightly voltage-sensitive Ca2+ channels. Thus, we caution that U73122 may not be selective at concentrations required for maximal block of PLC and that the selectivity of U73122 is dependent on cell type. Overall, our results are consistent with U73122 inhibiting PLC in neuronal cells and indicate that under the appropriate conditions, this compound is a useful tool for studying inositol 1,4,5-trisphosphate (IP3)-mediated Ca2+ mobilization.

Animals↗
PubMed1994

Experimental investigation of the motions of the pumping diaphragm within a sac-type pneumatically driven ventricular assist device.

The motions of the pumping diaphragm within a sac-type pneumatically driven ventricular assist device (VAD) were monitored non-intrusively using a laser Doppler anemometer (LDA) working in the back-scattering mode. The interaction between the diaphragm and the flow, and the causative factors of the motions were investigated. The motions of a number of points on the diaphragm were determined by analysing the timing of interruption of the Doppler signals due to intrusion of the diaphragm on the LDA sampling volume. The position-time relationships for the identified diaphragm points were then interpolated into two-dimensional surfaces to reconstruct the moving patterns of the diaphragm at selected instants. The motion is strongly affected by the orientation of the device with respect to gravity due to hydrostatic pressure gradients on the liquid side, which are generally large compared with those associated with the fluid accelerations. Hence, during ejection, the part of the diaphragm experiencing the lowest hydrostatic pressure is always set in motion first, while during filling, the part with the highest hydrostatic pressure moves first. Consequences of these non-symmetrical motions on local flow behaviour are discussed, and methods of controlling diaphragm shape during pumping are outlined.

Acceleration↗
PubMed1994

Pressure development within a sac-type pneumatically driven ventricular assist device.

Intrinsic features of the pumping process of a pneumatically driven ventricular assist device (VAD) and the effects of different types of pneumatic drivers upon its performance were investigated in vitro by analysing the pressure distributions within the device and the motions of the prosthetic valves. It was found that the stretching of the flexible, elastic diaphragm in both late systole and diastole initiates a pressure oscillation which directly affects the timing of the pumping process. The timing was also found to be dependent on the length and stiffness of the cannulae which link the VAD to the model circulation system. During the stretch-induced oscillation in late systole, the VAD housing experiences partial collapse due to fluid momentum effects, which tends to increase the effective stroke volume of the device, and reduce the amplitude of the pressure oscillation. Reducing the rising (falling) rate of driving pressures (dpd/dt) may not necessarily reduce the maximum rate of change of the blood chamber pressure (dpch/dtmax) but may upset the stability of the pumping process. This is because a minimum dpch/dtmax exists, which is determined by the stretch-induced oscillation. In order to minimize dpch/dtmax and to provide the device with a stable working condition, dpd/dt should match the dpch/dtmax.

Algorithms↗