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Biomedical subjects

Z Guan

Publications and source records attributed to Z Guan.

At least 73 records · Page 4Linked to original sources
PubMed1998

Brain-derived neurotrophic factor stimulates hindlimb stepping and sprouting of cholinergic fibers after spinal cord injury.

Neurotrophic factors have been proposed as a therapeutic treatment for traumatic brain and spinal cord injury. The present study determined whether exogenous administration of one such factor, brain-derived neurotrophic factor (BDNF), could effect behavioral recovery and/or histopathological changes after spinal cord injury. Adult rats received a mild or moderate contusion injury or complete transection of the mid-thoracic spinal cord. Immediately thereafter, they were infused intrathecally with vehicle or BDNF for 28 days. Behavioral recovery was evaluated for 6 weeks after injury, at which time the rats were sacrificed and the spinal cord tissue was examined histologically. The infusion of BDNF resulted in acute stimulation of hindlimb activity. These effects included activation of alternating airstepping in injured rats when the hindlimbs were unloaded as well as slight improvements in the rate of recovery in open field locomotion score. BDNF infusion was also associated with enhanced growth of cholinergic fibers at the injury epicenter, but did not affect white matter sparing or density of serotonergic axons at or below the injury site. Based on immunohistochemical detection of BDNF protein distribution, these described effects are likely to be mediated by the activation of cells and axons within the central injury region and the along the peripheral rim of the spinal cord. Together, these findings demonstrate that the exogenous infusion of BDNF after spinal trauma can influence postinjury outcome through mechanisms that include acute stimulation of hindlimb activity and neuritogenesis at the injury site.

Animals↗
PubMed1998

Growth factor-like phospholipids generated after corneal injury.

The present study provides evidence that growth factor-like glycerophosphate mediators of the lysophosphatidic acid (LPA) family are present in the aqueous humor and the lacrimal gland fluid of the rabbit eye. By use of a combination of HPLC, two-dimensional TLC, mass spectrometry, and the Xenopus oocyte bioassay, the LPA-like phospholipids LPA, cyclic PA, alkenyl-glycerophosphate (GP), lysophosphatidylserine, and phosphatidic acid were detected as physiological constituents of the fluids bathing the cornea. Corneal injury resulted in an increased production of some of these mediators. Alkenyl-GP, a novel member of the LPA family, has been identified in postinjury aqueous humor, establishing that it is generated endogenously. LPA and its homologues were found to be mitogenic in freshly dissociated keratocytes from uninjured corneas. There appears to be a link between the occurrence of LPA responsiveness in keratocytes activated by injury and the increase in LPA-like activity in aqueous humor. These data suggest that LPA and its homologues are involved in maintaining the integrity of the normal cornea and in promoting cellular regeneration of the injured cornea.

Animals↗
PubMed1998

IGF-I and insulin amplify IL-1 beta-induced nitric oxide and prostaglandin biosynthesis.

The inflammatory cytokine interleukin-1 beta (IL-1 beta) induces both cyclooxygenase-2 (Cox-2) and the inducible nitric oxide synthase (iNOS) with concomitant release of PGs and nitric oxide (NO) by glomerular mesangial cells. In our current studies, we determine whether insulin and IGF-I are involved in the signal transduction mechanisms resulting in IL-1 beta-induced NO and PGE2 biosynthesis in renal mesangial cells. We demonstrate that both insulin and IGF-I increase IL-1 beta-induced Cox-2 and iNOS protein expression, which in turn enhance PGE2 and NO production. Our data also indicate that both insulin and IGF-I enhance IL-1 beta-induced p38 mitogen-activated protein kinase (MAPK) phosphorylation and SAPK activation. These findings implicate the possible role of the MAPK pathway in mediating the effects of insulin and IGF-I on the upregulation of cytokine-stimulated NO and PG biosynthesis. Together, our results indicate that IGF-I and insulin may function to modulate the renal inflammatory process.

Animals↗
PubMed1998

Assessment of the mechanism by which prolactin stimulates progesterone production by early corpora lutea of pigs.

Previously, we reported that administration of prolactin (PRL) during the early luteal phase in sows increases plasma progesterone concentrations. In the current study, we searched for the mechanisms by which PRL exerts this luteotrophic effect. The objectives of the study were (1) to examine the effect of PRL and/or low-density lipoproteins (LDL) on progesterone production by porcine luteal cells derived from early corpora lutea, and (2) to assess the ability of PRL to activate phosphoinositide-specific phospholipase C (PI-PLC) and protein kinase C (PKC) in these luteal cells. Ovaries with early corpora lutea (day 1-2 of the oestrous cycle) were obtained from the slaughterhouse. Progesterone production by dispersed luteal cells was measured after treatment with PRL, phorbol 12-myristate 13-acetate or inhibitors of PKC in the presence or absence of LDL. LDL increased progesterone concentration in the incubation medium (304.5 vs 178.6 ng/ml in control, P<0.05). PRL augmented LDL-stimulated progesterone secretion by luteal cells (to 416 ng/ml, P<0.05), but PRL alone did not affect progesterone production (209.6 ng/ml, P>0.05). Staurosporine, a PKC inhibitor, inhibited progesterone secretion stimulated by the combined action of LDL and PRL; however, such inhibition was not demonstrated when cells were treated with the PKC inhibitor, H-7. PKC activation was assessed by measuring the specific association of [H]phorbol dibutyrate (H-PDBu) with luteal cells after treatment with PRL or ionomycin (a positive control). PRL and ionomycin increased H-PDBu-specific binding in early luteal cells by 28+/-5.5% (within 5 min) and 70.2+/-19.3% (within 2 min) over control binding respectively (P<0.05). In addition, PRL did not augment the LDL-stimulated progesterone production in PKC-deficient cells. In contrast with PKC, total inositol phosphate accumulation, as well as intracellular free calcium concentrations, were not affected by PRL in the current study. We conclude that PRL, in the presence of LDL, stimulates progesterone production by early corpora lutea in vitro. Moreover, PRL appears to activate PKC, but not PI-PLC, in these cells. Thus intracellular transduction of the PRL signal may involve activation of PKC that is not dependent on PI-PLC.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1998

[Comparative study on biological characteristics and ultrastructure of the fibroblasts derived from normal skin, hypertrophic scar and keloidin in vitro culture].

OBJECTIVE: This study was to investigate the in vitro cultivation, biological characteristics and ultrastructure of the fibroblasts derived from normal skin, hypertrophic scar and keloid, to elucidate the value of their application. METHOD: A comparative study was performed on cell proliferation, cell morphology, cytogenetic feature and cell ultrastructure of fibroblasts from normal skin, hypertrophic scar and keloid by means of the technique of in vitro culture. RESULT: The results indicated that the fibroblasts isolated from normal skin, hypertrophic scar and keloid exhibited similar morphology and growth rates. The cytogenetic feature and cell ultrastructure were also alike. CONCLUSION: According to our study and that of others, we conclude that it is entirely feasible to establish an in vitro culture model of fibroblasts from normal skin for investigation, prevention and treatment of scars.

Adolescent↗
PubMed1998

[A phase II clinical study of China-made paclitaxel in the treatment of cancer patients].

OBJECTIVE: To evaluate the efficacy and toxicity of China-made paclitaxel in patients with a variety of advanced malignancies. METHODS: Paclitaxel was administered by i.v. infusion at a dose of 175 mg/m2 in 3-hour every three weeks. All patients received premedication(dexamethasone, diphenhydramine and cimetidine) to prevent allergic reactions. RESULTS: Of 116 patients, 114 patients received 2 to 3 courses of therapy and were evaluable for response. The overall response rate for ovarian cancer was 46.7%, for breast cancer 56.4%, for non-small-cell lung cancer 25.0%, for small-cell lung cancer 66.7%, and for nasopharyngeal cancer 41.7%. Responses were also achieved in patients who had failed to respond to prior chemotherapy, with the overall response rate of 42.9% for ovarian cancer, 57.6% for breast cancer, 33.3% for non-small-cell lung cancer, 25.0% for small-cell lung cancer, and 40.0% for nasopharyngeal cancer. Paclitaxel did not show cross-resistance with doxorubicin and cisplatin. The major toxicity associated with paclitaxel included neutropenia, arthralgia, myalgia, numbness of hands and feet and alopecia. No severe hypersensitivity reactions were observed. CONCLUSION: At the above-mentioned dose and schedule, paclitaxel is effective with tolerable side effects.

Adolescent↗
PubMed1998

Minipig model for the study of voiding parameters in the conscious state and natural posture: normal urodynamic profiles.

OBJECTIVE: To provide baseline data on an animal model in which collecting and voiding can be accurately characterized urodynamically in the conscious state and natural posture. METHODS: Thirty-one female Yucatan microswines (age 4-8 months, weight 11-43 kg) were used. Portcatheters were placed in the bladder and peritoneal cavity, and reservoirs were implanted under the back skin for easy access. For urodynamic study, conscious pigs were restrained in specially designed adjustable cages. The portcatheter reservoirs were connected by 20-gauge needles and tubings to a UDS-120 digital computer polygraph to measure the total bladder pressure (pves) and abdominal pressure (pabd). A flow meter was placed behind and underneath the animal to measure the uroflow. Diuresis was induced with furosemide, and 2-4 voiding cycles were monitored. Isovolumetric detrusor pressure (pdet, isv) was obtained in the last cycle by manual interruption of flow per vagina. Urodynamic investigations were performed satisfactorily in all animals. RESULTS: The voided volume was 102-340 ml (mean 181.7 +/- 11.9 ml). Seven pigs had residual urine (4-39 ml, mean 14.3 +/- 4.7 ml). The initial opening pressure at the start of voiding was 19.9 +/- 1.5 cmH2O; detrusor pressure at maximum flow rate was 15.7 +/- 1.3 cmH2O; average flow was 12.6 +/- 0.7 ml/s; maximum flow rate was 20.7 +/- 1.1 ml/s; pdet, isv was 51.6 +/- 2.4 cmH2O; flow time was 15.9 +/- 1.2 seconds; mean resistance factor (R) was 0.06 +/- 0.01 cmH2O ml-2s2; mean urethral resistance factor (URA) was 7.10 +/- 0.51 cmH2O; and mean strength of voiding detrusor contraction was 3.91 +/- 0.20 W/m2. CONCLUSION: The above model allows reliable measurement of pressure-flow parameters in the conscious state and natural posture, permitting in-vivo urodynamic characterization of obstructive voiding dysfunction and correlation with detrusor structure.

Animals↗
PubMed1998

[Measurement for optical nonlinearity and optical bistability in II - VI semiconductor by optical waveguide method].

The untransparent substrates on the epitaxial layer need not be etched out from chemistry etching to prepare the "window" through light. The optical absorption, optical nonlinearities and optical bistabilities of the semiconductor thin films with the nanostructure grown on the untransparent substrates can be directly measured by the end face coupling method of optical waveguide. Meanwhile, the several experiment examples of II - VI single crystal thin films and superlattices grown on GaAs substrate are demonstrated in this paper.

English Abstract↗
PubMed1997

p38 mitogen-activated protein kinase down-regulates nitric oxide and up-regulates prostaglandin E2 biosynthesis stimulated by interleukin-1beta.

The inflammatory cytokine interleukin 1beta (IL-1beta) induces both cyclooxygenase-2 (Cox-2) and the inducible nitric-oxide synthase (iNOS) with increases in the release of prostaglandins (PGs) and nitric oxide (NO) from glomerular mesangial cells. However, the intracellular signaling mechanisms by which IL-1beta induces iNOS and Cox-2 expression is obscure. Our current studies demonstrate that IL-1beta produces a rapid increase in p38 mitogen-activated protein kinase (MAPK) phosphorylation and activation. Serum starvation and SC68376, a drug which selectively inhibits p38 MAPK in mesangial cells, were used to investigate whether p38 MAPK contributes to the signaling mechanism of IL-1beta induction of NO and PG synthesis. Serum starvation and SC68376 selectively inhibited IL-1beta-induced activation of p38 MAPK. Both SC68376 and serum starvation enhanced NO biosynthesis by increasing iNOS mRNA expression, protein expression, and nitrite production. In contrast, both SC68376 and serum starvation suppressed PG release by inhibiting Cox-2 mRNA, protein expression, and PGE2 synthesis. These data demonstrate that IL-1beta phosphorylates and activates p38 MAPK in mesangial cells. The activation of p38 MAPK may provide a crucial signaling mechanism, which mediates the up-regulation of PG synthesis and the down-regulation of NO biosynthesis induced by IL-1beta.

Animals↗
PubMed1997

A glucose-sensing polymer.

We have prepared a robust polymer that can be used to measure glucose concentrations in complex biological media. At alkaline pH, the metal-complexing polymer binds glucose and instantly releases protons in proportion to the glucose concentration over a clinically relevant range (0 to 25 mM). The inexpensive polymer is sufficiently selective to provide an easily measurable response to glucose in porcine plasma. The polymer's ability to function at nonphysiological pH (at which the buffer capacity of biological samples is small) makes it possible to design simple and inexpensive sensing devices based on measurement of changes in proton concentration.

Animals↗
PubMed1997

Purinergic Ca2+ signaling in myenteric neurons via P2 purinoceptors.

Fura 2 microfluorimetry was used to test the hypothesis that ATP acts at P1 and P2 purinoceptors to elevate cytosolic free Ca2+ concentrations [Ca2+]i) in calbindin-immunoreactive cultured myenteric neurons from adult guinea pig small intestine. Local "micro-puff" application of ATP or ATP(gamma)S caused an increase in [Ca2+]i in 99% of 200 multipolar neurons. The potency profile of agonists for the rise in [Ca2+]i was ATP(gamma)S = ATP >> ADP >> AMP, adenosine, 5'-(N-ethylcarboxamido)adenosine, and 2-chloro-N(6)-cyclopentyladenosine. Tetrodotoxin-sensitive synaptic transmission could contribute as much as 25% to the ATP response. The P1 antagonist 8-cyclopentyl-1,3-dipropylxanthine blocked 50% of the peakATP Ca2+ response. P2 antagonists blocked the ATP response: pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid > reactive blue 2 > suramin. Suramin enhanced the ATP response in 27.5% of neurons. Some neurons (<15%) displayed distinct multiphasic Ca2+ signatures. About 54% of ATP-responsive neurons expressed calbindin. The data support the following hypotheses: 1) two distinct P2 purinoceptors are linked to the rise in [Ca2+]i in myenteric neurons; 2) purinergic Ca2+ signaling is not restricted to one neuronal phenotype; and 3) intraneuronal Ca2+ is not involved in adenosinergic hyperpolarization in AH/type 2 neurons.

Adenosine↗
PubMed1997

[Brain dialysis--a new technique for determining the release of neurotransmitters and neuropeptides].

Brain dialysis, also called microdialysis, is a new technique based on the push-pull cannula. It can be used for continuously perfusing and collecting perfusate of certain brain areas in freely moving animals. Coupled with high performance liquid chromatography (HPLC) and radioimmunoassay (RIA), brain dialysis is allowed to determine the extracellular changes of many neurotransmitters in the brain, such as acetylcholine, noradrenaline, dopamine, 5-HT and their metabolites, free amino acids, small peptides, phosphoethanolamine, vitamins, various ions and so on.

Acetylcholine↗
PubMed1997

[Laser transnasal dacryocystorhinostomy under head mirror].

Laser transnasal dacryocystorhinostomy under head mirror is a new approach for surgical treatment of chronic lacrimal obstruction. This technique has several advantages, such as less damage, less operative complications and so on. This paper presented the results of 37 cases who had undergone transnasal dacryocystorhinostomy for chronic dacryocystitis under head mirror. The postoperative follow-up time was 3-24 months. The effective rate was 95.6%. The operative technique was also discussed in this paper.

Adolescent↗
PubMed1997

Phorbol ester modulation of rabbit corneal endothelial permeability.

PURPOSE: Phorbol esters have been shown to have a profound influence on cellular activity in many cell types. The purpose of this study was to examine the influence of phorbol esters on the function and structure of corneal endothelial cells. METHODS: Corneas were placed under a specular microscope, and the endothelium was superfused with glutathione bicarbonate Ringer's solution (GBR); with GBR and 10 nM, 100 nM, or 1 microM 4 beta-phorbol 12-myristate 13-acetate (PMA); or with 100 nM 4-alpha-PMA. Corneal swelling curves were generated, and endothelial permeability was determined. Corneal endothelial structure was examined with a scanning electron microscope. RESULTS: Significant increases in swelling and endothelial permeability were found in corneas perfused with 100 nM PMA versus that observed in controls (swelling rate = 26 microns/hr versus 6.9 microns/hr; permeability = 6 x 10(-4) cm/min versus 3.4 x 10(-4) cm/min) and in corneas receiving 1 microM PMA versus that in controls (swelling rate = 26.3 microns/hr versus 0.12 micron/hr; permeability = 6.9 x 10(-4) cm/min versus 4.9 x 10(-4) cm/min). Application of 10 nM PMA did not significantly alter either parameter. Study with transmission electron microscope demonstrated significant morphologic changes in cells perfused with all concentrations of PMA. Corneas perfused with 100 nM 4-alpha-PMA versus 100 nM PMA had significantly lower slope and permeability values (swelling rate = 5.9 microns/hr versus 25.1 microns/hr; permeability = 3 x 10(-4) cm/min versus 6.7 x 10(-4) cm/min). CONCLUSIONS: Phorbol esters are detrimental for corneal endothelial function, creating significant corneal swelling, increases in endothelial permeability, and changes in endothelial cell structure. This effect appears to be mediated through a protein kinase C pathway.

Animals↗
PubMed1997

[Influence of experimental fluorosis on phospholipid content and fatty acid composition in rat brain].

OBJECTIVE: To investigate the pathogenesis of brain damage by fluoride intoxication, phospholipid content, and fatty acid composition in rat brain with fluorosis were annlysed. METHODS: Wistar rats were fed with NaF in various amounts and time periods to produce the animal model with chronic fluorosis. Phospholipid content and fatty acids composition were analysed using high performance liquid chromatography and gas chromatography, respectively. RESULTS: All animals fed with high amount of fluoride suffered from chronic fluorosis. The total brain phospholipid content was lower in the rat treated with fluoride, which mainly influenced phosphatidylethanolamine, phosphatidylcholin, and phosphatidylserine. No modifications were detected in fatty acid and aldehyde compositions of individual phospholipid classes. CONCLUSION: The metabolism of brain phospholipid might be interfered by fluoride accumulated in brain tissue, which is related with the degeneration of neuron. The changes of brain phospholipid could be involved in the pathogenesis of chronic fluorosis.

Animals↗
PubMed1997

[Changes of coenzyme Q content in brain tissues of rats with fluorosis].

Animal models with pathological damage caused by chronic fluorosis to a different extent were duplicated in Wistar rats by feeding them with 66.3 mg/L and 221 mg/L fluorine-containing water for three, five and seven months, respectively. Cholesterol, dolichol and coenzyme Q in animal brain tissues were determined by high performance liquid chromatography. Results showed that no significant difference of cholesterol and dolichol contents in brian tissues between rats with fluorosis and normal controls were detected. Coenzyme Q content of brain tissue in rats fed with fluorine-containing water decreased at early stage of fluorosis, but increased significantly at late stage. It is speculated that changes in content of coenzyme Q could correlate with changes in free radical levels induced by fluorine.

Animals↗
PubMed1996

Responsiveness to ATP with an increase in intracellular free Ca2+ is not a distinctive feature of calbindin-D28 immunoreactive neurons in myenteric ganglia.

The aim of this study was to test the hypothesis that ATP elevates cytosolic free Ca2+ levels ([Ca2+]i) in myenteric neurons expressing the Ca2+ binding protein, calbindin-D28. A laser microbeam marked the location of cultured neurons on coverslips and provided unequivocal relocation of ATP-responsive neurons after immunocytochemistry. All myenteric multipolar neurons displayed ATP Ca2+ transients, and 42% also expressed calbindin-D28 reactivity. Statistical analysis of the kinetics and shape of ATP Ca2+ transients revealed no differences between calbindin and non-calbindin neurons. The identity of other responsive neurons is unknown. Less than 8% of ganglion cells with ATP Ca2+ transients were immunopositive for the glial protein S-100. We conclude that one of the actions of ATP in myenteric ganglia is to increase [Ca2+]i which may activate gKCa leading to membrane hyperpolarization in AH, Dogiel Type II neurons expressing calbindin-D28. An efficient buffering mechanism for handling large purinergic Ca2+ loads is a common feature of all types of myenteric ganglion cells.

Adenosine Triphosphate↗