Biomedical subjects

Y Fang

Publications and source records attributed to Y Fang.

At least 145 records · Page 8Linked to original sources

PubMed1998

Contact-dependent regulation of N-type calcium channel subunits during synaptogenesis.

The developmental regulation of the N-type calcium channel during synaptogenesis was studied using cultured rat hippocampal neurons to elucidate the roles of extrinsic versus intrinsic cues in the expression and distribution of this channel. Prior to synapse formation, alpha1B and beta3 subunits of the N-type calcium channel were distributed diffusely throughout neurites, growth cones, and somata. As synaptogenesis proceeded, the subunit distributions became punctate and colocalized with the synaptic vesicle protein synaptotagmin. Isolated neurons were also examined to test for the requirement of extrinsic cues that control N-type calcium channel expression and distribution. These neurons expressed N-type calcium channel subunits, but their distributions remained diffuse. Functional omega-conotoxin GVIA-sensitive channels were expressed in isolated neurons, although the distribution of alpha1B subunits was diffuse. The distribution of the alpha1B subunit and synaptotagmin only became punctate when neuron-neuron contact was allowed. Thus, the expression of functional N-type calcium channels is the result of an intrinsic program while extrinsic regulatory cues mediated by neuron-neuron contact are required to control their distribution during synaptogenesis.

Animals↗

PubMed1998

The effects of electroendosmosis in agarose electrophoresis.

The effects of agarose gel strips without and with 0.03 m(r) electroendosmosis (EEO) on isoelectric focusing (IEF) were studied. It is shown that only agarose without EEO can be used for IEF. The effects of electrode buffer strips using agarose with different EEO of 0, 0.03, 0.08, 0.20 m(r) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and native PAGE were also studied. It apparently did not affect SDS-PAGE, but affected native PAGE to a certain extent. The higher the EEO value was, the more water was present on the agarose gel strip during a separation. Agarose gel strips with an EEO of 0.2 m(r) are not suitable as electrode buffer strips for native PAGE.

Electrochemistry↗

PubMed1998

Automated sizing of DNA fragments in atomic force microscope images.

Current techniques used to measure lengths of DNA fragments in atomic force microscope (AFM) images require a user to operate interactive software and execute tedious error-prone cursor selections. An algorithm is proposed which provides an automated method for determining DNA fragment lengths from AFM images without interaction from the computer operator (e.g. cursor selections or mouse clicks). The approach utilises image processing techniques tailored to characteristics of AFM images of DNA fragments. The automated measurements have a mean absolute deviation of less than 1 pixel when compared to manual image-based measurements. The DNA length determined from the histogram of calculated lengths is accurate to within 3% of the actual DNA length in solution. For fragments that are 250 base-pairs long, the precision is estimated to be within 17 nm, which is about 20% of the total length. This precision was confirmed when the algorithm easily resolved fragments in one image that differed by only 17 nm. Fragment sizes up to 2000 base-pairs have been tested and successfully sized. This algorithm is being developed as part of a new solid-state DNA sizing technique for applications such as genotyping and construction of physical genome maps.

Algorithms↗

PubMed1998

Mode-actions of the Na(+)-Ca2+ exchanger: from genes to mechanisms to a new strategy in brain disorders.

Mode-actions of the Na(+)-Ca2+ exchanger from genes to mechanisms to a new strategy for brain disorders were comparatively studied in oxidative stress. In transfected Chinese hamster ovary (CHO) cells steadily expressing the Na(+)-Ca2+ exchanger's gene, Ca(2+)-efflux via an active mode of the Na(+)-Ca2+ exchanger was elicited by hydrogen peroxide (H2O2) after preincubation of the cell with a Ca(2+)-free medium, whereas Ca(2+)-influx via a reverse mode of the Na(+)-Ca2+ exchanger was dramatically evoked by H2O2 after preincubation of the cell with a Ca2+ medium, as a prelude to neuronal death. According to [45Ca2+] uptake of transfected CHO cells at given time intervals or extracellular Na+[Na+]o gradients, hyperbola, logarithmic and sigmoid curve equations of the Na(+)-Ca2+ exchanger's mode-actions were respectively defined in the absence and the presence of H2O2. The Na(+)-Ca2+ exchanger's conformational transition in oxidative stress was dominated by adenosine triphosphate (ATP)-dependent cytoskeletal redox modification, cation-pi interactions and secondary Ca2+ activation. These mechanisms were used to generate an intracellulary distributed tetra-cluster (named VISA931) for rescuing G-protein agonist-sensitive signal transduction and cortico-cerebral somatosensory evoke potential (SEP) from oxidation via activating forward operation of the Na(+)-Ca2+ exchanger, the beta-adrenergic and the P2-purinergic receptors, blocking Ca2+ influx and catalyzing the dismutation of superoxide anions (O2-.) to H2O2. In conclusion, knowledge-based drug design is a new strategy for developing promising candidates of neuroprotective agents.

Aluminum Compounds↗

PubMed1998

Interaction of the Na(+)-Ca2+ exchanger with small molecules on cell Ca2+ signaling.

Interactions of the Na(+)-Ca2+ exchanger with small molecules on cell Ca2+ signaling were elucidated in Chinese hamster ovary (CHO) C1 cells, which transfected a control vector without any expression of the Na(+)-Ca2+ exchanger's gene while CHO CK1.4 cells transfected an expression vector encoding the bovine cardiac Na(+)-Ca2+ exchanger's cDNA, treated with lithium- or sodium-buffer medium respectively, by using L16(2)15 multifactorial orthogonal statistics and fura-2 fluorescence real-time imaging. In contrast to controls of Li(+)-treated C1 cells, the store-dependent Ca(2+)-influx (SDCI) was enhanced by either the Na(+)-Ca2+ exchanger, Na(+), 1-¿(beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl¿-1H-imidazole HCl (SK&F96365) or ouabain, and by interactions of the Na(+)-Ca2+ exchanger with either Na+, SK&F96365 or both SK&F96365 and ouabain; and ATP-induced Ca2+ release (AICR) was activated by SK&F96365 or Na+ alone, interactions of the Na(+)-Ca2+ exchanger with SK&F96365 or Na+, and an interaction between SK&F96365 and ouabain. The dramatic interaction of the Na(+)-Ca2+ exchanger with small molecules indicates that cell Ca2+ signaling is generated by inositol triphosphate (InsP3)-dependent pathways, allosteric effects of the G-protein coupled P2y&2u purinoceptor and multi-site recognition. Our findings provide meaningful clues for designing new strategies of cardiocerebral vascular oxidative diseases.

Adenosine Triphosphate↗

PubMed1998

Induction of axon-like and dendrite-like processes in neuroblastoma cells.

Neuroblastoma cells are widely utilized models for the study of the neuritic outgrowth phase of neuronal differentiation, but relatively few such studies have attempted to identify the nature of the process outgrowths. This identification will be necessary in developing strategies for utilizing these models to distinguish the underlying mechanisms involved in axonogenesis vs dendritogenesis. In an effort to identify procedures for inducing specific types of neurite outgrowth, and for distinguishing axon- from dendrite-like processes, we have subjected two neuroblastoma cell lines to a variety of stimuli previously shown to induce neurite outgrowth in these cells. These include neuraminidase, ionomycin, KCl+dibutyryl cAMP, cholera toxin B subunit, retinoic acid, dibutyryl cAMP (alone), GM1 ganglioside, and low serum. The first four of these (group 1) gave rise to neurites with axon-like characteristics, including immunostaining that was positive for phosphorylated high molecular weight neurofilament protein (NF-H) and synaptic vesicle protein-2 (SV2), but negative for microtubule-associated protein-2 (MAP2). The next three treatments (group 2) resulted in dendrite-like processes, as evidenced in immunostaining that was positive for MAP2 and negative for NF-H and SV2. Neurites produced by low serum had mixed properties. These cytoskeletal differences were supported by immunoblot analysis with antisera to the above cytoskeletal proteins. Striking morphological differences were also noted, group 2-induced neurites being significantly shorter with more branch points than those generated by group 1 stimulants. Time of exposure to stimulatory agent was crucial in determining expression of the neuritic phenotype. Correlation with previous studies suggests that axon-like neurites result from stimulants which elevate intracellular Ca2+, a dependence not previously reported to our knowledge. Dendrite-like process outgrowth, on the other hand, does not appear to depend on altered intracellular Ca2+.

Animals↗

PubMed1998

Endogenous orphanin FQ: evidence for a role in the modulation of electroacupuncture analgesia and the development of tolerance to analgesia produced by morphine and electroacupuncture.

1. Our previous work has demonstrated that exogenously administered orphanin FQ (OFQ) antagonizes morphine analgesia and electroacupuncture analgesia (EAA) in the brain and potentiates morphine analgesia and EAA in the spinal cord of the rat. In the present study we evaluated the role of endogenously released OFQ in the development of tolerance to morphine and electroacupuncture (EA) and the analgesia produced by electroacupuncture, by use of the IgG fraction of an anti-OFQ antibody (OFQ-Ab) microinjected into the rat central nervous system (CNS). 2. EAA was produced by stimulating rats at a frequency of 100 Hz. Rats were classified as either high responders (HR) or low responders (LR) based on the analgesic effects of EA. LRs could be converted into HRs by the intracerebroventricular (i.c.v.) microinjection of OFQ-Ab at both 1:1 and 1:10 dilutions but not 1:100. HRs could be changed into LRs by the intrathecal (i.t.) injection of OFQ-Ab at both 1:1 and 1:10 dilutions, but not 1:100. 3. Acute morphine tolerance was induced in rats by repeated subcutaneous (s.c.) injections of morphine (5 mg kg, every 2 h) for 16 h. When injected i.c.v. the OFQ-Ab (1:1 dilution) had no effect on the development of acute morphine tolerance. 4. Chronic morphine tolerance was produced in rats by repeated injection of morphine (5-60 mg kg, s.c., 3 x a day) for 6 days. I.c.v. injection of OFQ-Ab (1:1 dilution) reversed this type of morphine tolerance in rats by 50% (P < 0.01). 5. Acute tolerance to the analgesia produced by EA developed after 6 h of continuous (100 Hz, 3 mA) stimulation. This tolerance was almost completely reversed by the i.c.v. injection of OFQ-Ab (1:1 dilution) (P < 0.05). 6. Chronic tolerance to the analgesic effect of EA was produced by repeatedly administering increasing current (1, 2 and 3 mA, each lasting for 10 min, for a total of 30 min) at a frequency of 100 Hz once a day for 6 days. I.c.v. injection of OFQ-Ab (1:1 dilution) reversed this kind of tolerance by 50% (P < 0.01). 7. Together these results suggest that 100 Hz EA may enhance the release of endogenous OFQ in the CNS of the rat, which in turn may act to antagonize EA-produced analgesia in the brain but potentiate EA produced analgesia in the spinal cord. Therefore, OFQ appears to play an important role in the development of tolerance to the analgesic effects produced by EA. 8. The mechanisms underlying the development of acute morphine tolerance and chronic morphine tolerance appear to be different. Central OFQ may play an important role in the development of tolerance after chronic morphine administration.

Adaptation, Physiological↗

PubMed1998

Studying early nodulin gene ENOD40 expression and induction by nodulation factor and cytokinin in transgenic alfalfa.

ENOD40, an early nodulin gene, is expressed following inoculation with Rhizobium meliloti or by adding R. meliloti-produced nodulation (Nod) factors or the plant hormone cytokinin to uninoculated roots. We isolated two MsENOD40 clones, designated MsENOD40-1 and MsENOD40-2, with distinct promoters from an alfalfa (Medicago sativa cv Chief) genomic library. The promoters were fused to the reporter gene uidA (gus), and the constructs were introduced into alfalfa. We observed that the MsENOD40-1 construct was expressed almost exclusively under symbiotic conditions. The MsENOD40-2 construct was transcribed under both symbiotic and nonsymbiotic conditions and in nonnodular and nodular tissues. Both MsENOD40 promoter-gus constructs were similarly expressed as nodules developed, and both were expressed in roots treated with 6-benzylaminopurine or purified Nod factor. However, no blue color was detected in nodule-like structures induced by the auxin transport inhibitor N-1-(naphthyl)phthalamic acid on roots of plants containing the MsENOD40-1 promoter construct, whereas pseudonodules from plants containing the MsENOD40-2 promoter construct stained blue. A 616-bp region at the distal 5' end of the promoter is important for proper spatial expression of MsENOD40 in nodules and also for Nod-factor and cytokinin-induced expression.

Bacterial Proteins↗

PubMed1998

SBA1 encodes a yeast hsp90 cochaperone that is homologous to vertebrate p23 proteins.

The Saccharomyces cerevisiae SBA1 gene was cloned by PCR amplification from yeast genomic DNA following its identification as encoding an ortholog of human p23, an Hsp90 cochaperone. The SBA1 gene product is constitutively expressed and nonessential, although a disruption mutant grew more slowly than the wild type at both 18 and 37 degreesC. A double deletion of SBA1 and STI1, encoding an Hsp90 cochaperone, displayed synthetic growth defects. Affinity isolation of histidine-tagged Sba1p (Sba1(His6)) after expression in yeast led to coisolation of Hsp90 and the cyclophilin homolog Cpr6. Using an in vitro assembly assay, purified Sba1(His6) bound to Hsp90 only in the presence of adenosine 5'-O-(3-thiotriphosphate) or adenyl-imidodiphosphate. Furthermore, interaction between purified Sba1(His6) and Hsp90 in yeast extracts was inhibited by the benzoquinoid ansamycins geldanamycin and macbecin. The in vitro assay was also used to identify residues in Hsp90 that are important for complex formation with Sba1(His6), and residues in both the N-terminal nucleotide binding domain and C-terminal half were characterized. In vivo analysis of known Hsp90 substrate proteins revealed that Sba1 loss of function had only a mild effect on the activity of the tyrosine kinase v-Src and steroid hormone receptors.

Amino Acid Sequence↗

PubMed1998

Regulation of Na+/Ca2+ exchange activity by cytosolic Ca2+ in transfected Chinese hamster ovary cells.

Transfected Chinese hamster ovary cells stably expressing the bovine cardiac Na+/Ca2+ exchanger (CK1.4 cells) were used to determine the range of cytosolic Ca2+ concentrations ([Ca2+]i) that activate Na+/Ca2+ exchange activity. Ba2+ influx was measured in fura 2-loaded, ionomycin-treated cells under conditions in which the intracellular Na+ concentration was clamped with gramicidin at approximately 20 mM. [Ca2+]i was varied by preincubating ionomycin-treated cells with either the acetoxymethyl ester of EGTA or medium containing 0-1 mM added CaCl2. The rate of Ba2+ influx increased in a saturable manner with [Ca2+]i, with the half-maximal activation value of 44 nM and a Hill coefficient of 1.6. When identical experiments were carried out with cells expressing a Ca2+-insensitive mutant of the exchanger, Ba2+ influx did not vary with [Ca2+]i. The concentration for activation of exchange activity was similar to that reported for whole cardiac myocytes but approximately an order of magnitude lower than that reported for excised, giant patches. The reason for the difference in Ca2+ regulation between whole cells and membrane patches is unknown.

Animals↗

PubMed1998

Regulation of epidermal growth factor expression in mammary epithelial cells by a Yin-Yang-1-like element.

The hormone combination of insulin, dexamethasone and prolactin induced accumulation of preproepidermal growth factor (EGF) mRNA in HC11 mouse mammary epithelial cells 16-24 h after the hormones were added to the cultures. Individual hormones or combinations of two of the hormones had no effect on EGF mRNA concentrations. The same hormone combination was capable of inducing expression of a reporter gene construct containing -888 to +25 bp of the EGF gene fused with luciferase. Deletions of the promoter between -888 and -271 bp had no detectable effect on basal or hormone-induced reporter gene expression. However, further deletion from -270 to -74 bp increased baseline to approximately equal hormone-induced reporter gene expression. This deletion also abolished the hormone-induced increase in reporter gene expression. Sequence analysis suggested that this region contained a binding site for Yin-Yang-1 (YY1), which was confirmed by gelshift analysis. Mutation of the YY1 binding site increased baseline reporter gene expression to the same level as induced by insulin, dexamethasone and prolactin in the wild-type promoter. These results indicate that expression of the EGF gene in mammary epithelium is repressed by the YY1 site, and that removal of repression may play a part in regulating EGF gene expression in lactating mammary tissue.

Animals↗

PubMed1998

[Changes of GABA immunoreactivity in aged rat cochlear nucleus].

OBJECTIVES: To detect the changes of gama-aminobutyric acid (GABA) immunoreactivity in the aged rat cochlear nucleus and to investigate its relationship with the initiation of presbycusis. METHODS: The cochlear nucleuses of adult (2-3 months) and aged (20-36 months) Wistar rats were stained with streptavidin/peroxidase (S-P) technique. GABA-positive neurons were counted with a computer-aid image analysis system. RESULTS: Most of the GABA-immunoreactive cell bodies were found in the superficial layers of the dorsal cochlear nucleus (DCN). The number of GABA-positive neurons decreased significantly in the DCN of the aged rat cochlear nucleus (P < 0.001). CONCLUSION: The reduction of GABA positive neurons in the aged rat cochlear nucleus may be related to presbycusis.

Aging↗

PubMed1998

[The effect of PMN adhesion mediated by CD11b/CD18 on the increasing permeability of microvascular endothelial monolayer after severe burn injury].

OBJECTIVE: To detect the effect of burn-activated PMN adhesion and its adhesion molecule CD11b/CD18 on microvascular endothelial permeability using an experimental model of endothelial monolayer on polycarbonate microporous filters. METHODS: An experimental model for in vitro study of endothelal monolayer for permeability analysis was established. Seven groups were divided into according to the treatment of microvascular endothelial monolayer. Fluid filtration coeffecient(Kf) and albumin reflection coeffecient(delta) were measured after endothelial monolayer was perfused with albumin labelled by FITC. RESULTS: Burn-activated PMN could increase the level of fluid filtration coeffecient(Kf) and decrease the albumin reflection coeffecient(delta). Monoclonal antibody sealing off CD11b/CD18 on PMN provented the change of delta induced by burn-activated PMN. Another microporous filter interposed between PMNs and endothelial monolayer corrected the changes of Kf and delta. CONCLUSION: The permeability enhancing effect of PMNs may be attributed mainly to the PMN-EC adhesion mediated by CD11b/CD18. Blocking the PMN-EC over-adhesion in moderation may be helpful in reducing the lung injury due to severe burn injury.

Animals↗

PubMed1998

[Effect of hyperbaric oxygen on cerebral microcirculation and tissue cells in animals with cerebral ischemic injury].

Changes of cerebral microcirculation and tissue cells after Hyperbaric Oxygen (HBO) exposure were observed in 136 gerbils with cerebral ischemia by observation of meningeal microcirculation pathological study in cerebral tissues and determination of Na, K-ATPase. It is indicated that HBO may be helpful in improving microcirculatory dynamics and other microcirculatory functions, and enhancing cerebral tissue cell activity and cell function, as well as increasing oxygen content. It is suggested that HBO (250 approximately 300kPa) may play a role in protecting vessel endothelial cells and nerve cells.

Adenosine Triphosphatases↗

PubMed1998

[Anatomical study and clinical observation of thoracic outlet syndrome].

OBJECTIVE: To investigate the etiology of thoracic outlet syndrome (TOS) from the point of anatomical and clinical view. METHOD: Anatomical study was made on both sides of 30 cadavers. The minimus scalene muscle and the insertions of anterior and middle scalene muscle were dissected and observed. Clinically, 45 cases of thoracic outlet syndrome (TOS) were treated and followed up. RESULT: The minimus scalene muscle was found in 88.3% of the cadavers. T(1) nerve root or the lower trunk of brachial plexus crossed the first rib just over the proximal tendinous part of minimus scalene muscle. Of 45 cases of TOS 34 presented neck-shoulder-pain 17 had. Unchanged symptoms postoperatively, and 7 had aggravated symptoms. Of the recent 8 cases of TOS, 7 presented neck-shoulder-pain. However, the symptom remained in only case after the resection of the tendinous tissue around 5, 6 nerve root from anterior and middle scalene muscle. CONCLUSION: The tendinous tissue of minimus muscle is the cause of the compression of T(1) nerve root or the lower trunk of the brachial plexus. The crossed tendinous origins from the anterior and posterior tubercle of C(4,5) transverse process is the cause of the compression of C(5,6) nerve root or the upper trunk of brachial plexus.

Adolescent↗

PubMed1998

[Effect of CD11b/CD18 on burn-activated PMN-mediated permeability of pulmonary microvascular in isolated perfused lung].

OBJECTIVE: To determine the effect of intercellular adhesion molecule (ICAM-1) CD11b/CD18 in burn-activated PMN-mediated permeability of microvascular in isolated perfused lung. METHOD: Isolated lungs were distributed into 7 groups according to the different contents of perfused fluid: normal perfused fluid, normal rat serum, burn rat serum, normal rat PMN, burn rat PMN, normal rat PMN blocked by monoclonal antibody to adhesion molecule CD11b/CD18 and burn rat PMN blocked by antibody. The extent of isolated lung edema, vascular permeability to small molecules (fluid) and vascular permeability to large molecules (albumin) were expressed by lung weight gain (LWG), fluid filtration coefficient (Kf) and pulmonary albumin permeability-surface area product (PS) respectively. RESULT: Burn serum could increase LWG, Kf PS, so did burn-activated PMN. The latter could make PS increase more obviously. Monoclonal antibody to CD11b/CD18 on PMN could obviously decrease PMN sequestration in isolated perfused lung. The protective effect of antibody on increasing LWG and Kf, and particularly PS was demonstrated. CONCLUSION: (1) The effect of mediators from burn-activated PMN to EC was mediated by PMN adhesion to EC. (2) Some mediators from burn-activated PMN increase mainly the pulmonary vascular permeability to small molecules, and PMN adhesion to EC mediated by CD11b/CD18 may increase directly the permeability to large molecules. (3) Adhesion molecule CD11b/CD18 perhaps have an ability to regulate directly EC by combining its receptor ICAM-1 on EC.

Animals↗

PubMed1998

[Effect of ischemia-reperfusion on membrane structure and function in rat retina].

OBJECTIVE: To study the effect of ischemia-reperfusion on membrane structure and function in rat retina. METHODS: Thirty-two SD rats were randomly grouped into 4 groups. Group 1 served as the control group, group 2, 3 and 4 served as reperfusion 3 hours, 30 hours and 5 days respectively. The intraocular pressure (IOP) was raised to occlude retinal and choroidal blood vessels to form retinal ischemia; afterwards the IOP was lowered to normal to allow reperfusion. The animal was sacrificed after reperfusion. The colorimetric determination of phosphorus was used to investigate Na(+)-K(+)-ATPase activity of rat retina; the cellular membrane was labelled by fluorescence probe DPH to detect its fluidity which was measured by means of fluorescence spectrophotometer. RESULTS: Na(+)-K(+)-ATPase and membrane influidity were damaged at early stage. The longer the ischemia, the more serious was the reperfusion injury. CONCLUSIONS: The mechanism of the decrease of Na(+)-K(+)-ATPase activity is due to the production of substances involved in peroxidation and excitatory amino acid (EAA) which are produced during reperfusion. They can damage the Na(+)-K(+)-ATPase directly. Lipid peroxidation disrupts membrane integrity and causes decrease of membrane influidity. For these reasons, membrane stability is reduced and Na(+)-K(+)-ATPase protein function is changed.

Animals↗

PubMed1998

[Chitosan pin fixation of rabbit proximal tibia osteotomy].

Degradatable chitosan pin, 4 millimeters in diameter and 30 to 40 millimeters in length, was studied radiographically and histologically (oxytetracycline-labeling) at 3, 6, 12, 24 and 48 weeks after the implantation for fixation of a transverse proximal tibia osteotomy in fourty rabbits. The results showed that new bone formation and oxytetracycline uptake were increased 3-6 weeks after operation and the fracture was completely healed 12 weeks after operation, but in two rabbits the chitosan pin broke, in 3 weeks. Histologically, there was a massive inflammation (non-specific foreign body reaction) 3-12 weeks after implantation, which gradually subsided 24 weeks aften operation. Chitosan pin was slowly degradated in bone and was not replaced by normal tissue 48 weeks after operation. The questions to be addressed in future include how to increase the mechanical strength of chitosan pin and how to improve the characteristics of its surface.

Animals↗