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Biomedical subjects

G Yang

Publications and source records attributed to G Yang.

At least 343 records · Page 19Linked to original sources
PubMed1996

Glutamate microinjections in cerebellar cortex reproduce cerebrovascular effects of parallel fiber stimulation.

Electrical stimulation of cerebellar parallel fibers releases glutamate and increases local blood flow (BFcrb), an effect in part mediated by glutamate-induced nitric oxide (NO) production. We studied whether local microinjection of glutamate into the cerebellar cortex would produce increases in BFcrb comparable to those elicited by parallel fiber stimulation. In halothane-anesthetized rats equipped with a cranial window, glutamate was microinjected into the cerebellar molecular layer, and BFcrb was monitored by laser-Doppler flowmetry. Glutamate microinjections increased BFcrb dose dependently (2-200 pmol in 200 nl) (n = 9) and by 55 +/- 6% at 200 pmol (mean +/- SE). The magnitude and temporal profile of the increases in BFcrb compared favorably with the increase in flow produced by parallel fiber stimulation. The glutamate-induced BFcrb increase was attenuated by superfusion with the Na2+ channel blocker tetrodotoxin (10 microM; -50 +/- 10%; n = 5; P < 0.05; t-test) or by blocking synaptic activity by treatment of the cerebellar cortex with Ringer containing 20 mM Mg2+ and 0 mM Ca2+ (-80 +/- 4%; n = 6; P < 0.05). The glutamate-receptor antagonist kynurenate (10 mM) attenuated the increase in BFcrb by 59 +/- 6% (P < 0.05; n = 5). The relatively selective inhibitor of neuronal NO synthase 7-nitroindazole (100 mg/kg ip) reduced the flow response evoked by microinjection of glutamate (-46 +/- 7%; n = 5; P < 0.05) but not acetylcholine (10 microM; P > 0.05; n = 6). We conclude that glutamate microinjections increase local BFcrb via activation of glutamate receptors. The glutamate-induced vasodilation is mediated, in part, by neurally derived NO. The striking similarities between the vascular responses evoked by parallel fiber stimulation and that produced by microinjection of glutamate support the hypothesis that the increase in BFcrb produced by parallel fiber stimulation is mediated by glutamate release and activation of glutamate receptors. The data also strengthen the hypothesis that glutamate and NO are important mediators in the mechanisms linking synaptic activity to BFcrb in cerebellar cortex.

Acetylcholine↗
PubMed1996

Neural mechanisms of blood flow regulation during synaptic activity in cerebellar cortex.

1. We investigated the neural mechanisms of the increases in blood flow produced by synaptic activity using the parallel fiber (PF) system of the cerebellum as a model. The midline cerebellum was exposed in anesthetized rats and the PFs were stimulated with tungsten microelectrodes. Cerebellar blood flow (BFcrb) was recorded using a laser-Doppler probe, whereas field potentials were recorded using glass micropipettes. PF stimulation produced increases in BFcrb that were related to the frequency and intensity of stimulation (+60 +/- 9%, mean +/- SE, at 100 microA and 30 Hz; n = 6). The greatest increases were confined to a band stretching along the major axis of the stimulated folium and corresponding to the beam of activated PFs. The increase in evoked by PF stimulation was associated with a corresponding increase in glucose utilization, assessed by the 2-deoxyglucose method. The increases in BFcrb and the field potentials evoked by PF stimulation were abolished by tetrodotoxin (1 microM; n = 6). Ringer solution containing 12 mM Mg2+ and 0 mM Ca2+ blocked synaptic activity in the PFs and abolished the increases in flow (P > 0.05 from baseline; n = 5). The broad-spectrum glutamate receptor antagonist kynurenate (5 mM) prevented depolarization of Purkinje cells and interneurons and abolished the increase in BFcrb evoked by PF stimulation (P > 0.05; n = 6). Treatment with tetrodotoxin, Mg2+, or kynurenate did not affect the increase in BFcrb elicited by systemic hypercapnia or by topical application of the nitric oxide donor 3-morpholino sydnonimine (P > 0.05 from Ringer solution). We conclude that the increases in flow produced by synaptic activity are linked to glutamate-induced depolarization of Purkinje cells and interneurons. These findings provide evidence that activation of glutamate receptors participates in the mechanisms of functional hyperemia, and they support the validity of the PF system as a model for study of the relationship between synaptic activity and blood flow in the CNS.

Animals↗
PubMed1996

Morphological studies on avian spinal cord chimeras.

Spinal cord chimeras were constructed by orthotopic grafting of quail embryonal neutral folds, neural crest and neural tube into chicken embryos. The spinal cord xenografts were accepted for varying lengths of time, but most chimeras eventually rejected the quail transplant. This was associated with perivenular cuffing and demyelination with preservation of most neurons, as well as clinical neurological symptoms. Twenty-four chimeras were studied to delineate the time of first appearance of glial deposits of immunoglobulin and to identify the subpopulations of T cells in spinal cord infiltrates. The results suggested that deposits of immunoglobulins on glial elements preceded inflammatory cell infiltration. The perivenular cuffs consisted predominantly of T cells and showed a preponderance of CD8- over CD4-positive cells (CD4/CD8 ratios around 0.6). Further, CD4+ cells were found almost exclusively in the central portions of the infiltrate, with the periphery consisting almost only of CD8+ cells. The diffuse cellular infiltrate of the parenchyme contained T and plasma cells. The T cells were almost exclusively CD8+. Plasma cells were seen only at the outer borders of the cuffs and dispersed throughout the quail-derived spinal cord tissue. It seemed that rejection of quail-derived melanocytes in feathers ('quail-like feathers'), described by us earlier, often preceded neurological symptoms and showed a histopathological pattern comparable to spinal cord lesions, i.e., predominantly perivascular cuffing. In preliminary studies, enhancement of disease by immunization with quail organ suspension and decreased intensity of disease by combined immunosuppressive treatment with FK 506 and cycylophosphamide were suggested. The data presented here are compatible with the hypothesis that rejection of CNS quail tissue by chimeras is preceded in the periphery by rejection of melanocytes in segments of skin and in feathers, and that the spinal cord rejection relies on xenoantibodies and on cytotoxic as well as delayed hypersensitivity-type T cells. Finally, these data strengthen the analogy between the histopathologic presentation and immune effector composition of the xenograft rejection lesions in the chimeras and the plaques seen in patients with multiple sclerosis.

Animals↗
PubMed1996

Antibodies to quail erythrocytes in quail-chicken spinal cord chimeras.

Quail-chicken spinal cord chimeras are a model for temporary acceptance followed by rejection of xenografts and also for demyelinating lesions of the central nervous system. The antiglobulin test with quail erythrocytes was employed to detect antibodies in sera of quail-chicken spinal cord chimeras. Sera of all 46 chimeras tested gave positive results. In virtually all instances, antibodies were detected within 10 weeks after hatching and they persisted for all the observation time up to 8 months. The antibodies detected in these tests were directed against species antigens of the quail. They were apparently identical with xenoantibodies described in a previous study, which were detected by indirect immunofluorescence with quail tissue sections; on the other hand, mixed agglutination tests with quail embryonal cell monolayers employed previously had detected a broader spectrum of antibodies that did the antiglobulin tests with quail erythrocytes. The antiglobulin test with quail erythrocytes seems the most cost-efficient and convenient test to monitor xenoantibody formation in this animal model.

Agglutination Tests↗
PubMed1996

Dioxinlike properties of a trichloroethylene combustion-generated aerosol.

Conventional chemical analyses of incineration by-products identify compounds of known toxicity but often fail to indicate the presence of other chemicals that may pose health risks. In a previous report, extracts from soot aerosols formed during incomplete combustion of trichloroethylene (TCE) and pyrolysis of plastics exhibited a dioxinlike response when subjected to a keratinocyte assay. To verify this dioxinlike effect, the complete extract, its polar and nonpolar fractions, some containing primarily halogenated aromatic hydrocarbons, were evaluated for toxicity using an embryo assay, for antiestrogenicity using primary liver cell cultures, and for the ability to transform the aryl hydrocarbon receptor into its DNA binding form using liver cytosol in a gel retardation assay. Each of these assays detect dioxinlike effects. Medaka (Oryzias latipes) embryos and primary liver cell cultures of rainbow trout (Oncorhynchus mykiss) were exposed to concentrations of extract ranging from 0.05 to 45 micrograms/l. Cardiotoxicity with pericardial, yolk sac, and adjacent peritoneal edema occurred after exposure of embryos to concentrations of 7 micrograms/l or greater. These same exposure levels were associated with abnormal embryo development and, at the higher concentrations, death. Some of the fractions were toxic but none was as toxic as the whole extract. In liver cells, total cellular protein and cellular lactate dehydrogenase activity were not altered by in vitro exposure to whole extract (0.05-25 micrograms/l). However, induction of cytochrome P4501A1 protein and ethoxyresorufin O-deethylase activity occurred. In the presence of whole extract, estradiol-dependent vitellogenin synthesis was reduced. Of the fractions, only fraction 1 (nonpolar) showed a similar trend, although vitellogenin synthesis inhibition was not significant. The soot extract and fractions bound to the Ah receptor and showed a significantly positive result in the gel retardation/DNA binding test. Chemical analyses using GC-MS with detection limits for 2,3,7,8-tetrachlorodibenzo-p-dioxin and dibenzofuran in the picomole range did not show presence of these compounds. Our results indicate that other chemicals associated with TCE combustion and not originally targeted for analysis may also pose health risks through dioxinlike mechanisms.

Aerosols↗
PubMed1996

Use of a retroviral vector with an internal opsin promoter to direct gene expression to retinal photoreceptor cells.

PURPOSE: Viral-mediated gene transfer to retina, as well as to other tissues, is evolving rapidly. We have evaluated the potential of a retroviral vector with an internal opsin promoter fragment to direct gene expression to retinal photoreceptor cells. METHODS: Two recombinant retroviral vectors were prepared; in each Vector, a 1.4 kb fragment of the mouse opsin promoter was placed downstream from the neoR gene in the Moloney murine leukemia virus-based vector G1Na. The opsin promoter fragment was linked either to the cDNA for mouse rod photoreceptor phosphodiesterase (PDE) beta-subunit or to the bacterial lacZ reporter gene. These vectors were tested for their ability to direct gene expression after transduction of 3T3 and Y79 cells, or of dissociated retinal cell cultures or retinal explants from neonatal mice. RESULTS: As expected, PDE beta-subunit and beta-galactosidase mRNAs were expressed only at low levels in 3T3 fibroblasts and Y79 retinoblastoma cells. Northern blot analysis indicated that expression was derived from the viral long terminal repeat (LTR) promoter. Infection of primary retinal cell cultures or explants from neonatal mice with BAG retrovirus, in which beta-galactosidase is driven by the viral LTR, resulted in expression in many cell types, while the opsin-lacZ vector mediated the expression of the lacZ reporter gene specifically in photoreceptor cells. CONCLUSIONS: The internal opsin promoter fragment appears capable of selectively directing gene expression to photoreceptor cells after retroviral-mediated gene transfer. These findings serve as a basis for future studies using the opsin promoter-beta PDE retroviral vector to rescue photoreceptor cells in the rd mutant mouse, in which the beta-PDE gene is mutated resulting in degeneration of photoreceptor cells during the early postnatal period.

3T3 Cells↗
PubMed1996

Retroviral transduction of transforming growth factor-beta1 induces pleiotropic benign prostatic growth abnormalities in mouse prostate reconstitutions.

Transforming growth factor-beta1 (TGF-beta1) plays an important role in the normal growth and differentiation of the mouse prostate with accumulations of extracellular TGF-beta1 in fetal and neonatal prostate tissues particularly at epithelial-mesenchymal interfaces. We have demonstrated increased accumulation of TGF-beta1 in areas of human prostates with benign prostatic hyperplasia and adenocarcinoma by immunohistochemistry. To study the role of TGF-beta1 in pathologic processes, we constructed retroviruses that express the cDNA for murine TGF-beta1 along with either a dominant selectable geneticin (G418) resistance (Neo) gene, BabeTGF-beta1Neo, or a histochemically detectable beta-galactosidase gene, BabeTGF-beta1Gal. The biologic activity of these retroviruses was evaluated in vitro in NIH3T3 fibroblasts and in vivo using the mouse prostate reconstitution (MPR) model. Expression of the retrovirus in MPR was confirmed by beta-galactosidase staining and by reverse transcription followed by PCR for the virus-encoded RNA. Pathologic evaluation of hematoxylin and eosin-stained sections was complemented by immunohistochemical analysis of cytokeratin and neuronal markers. TGF-beta1 transducing retrovirus infection did not have an effect on total growth of the MPR; however, changes in the growth and distribution of specific cell types were observed. A phenotype of benign hyperplasia that involved increased numbers of cytokeratin 14-positive cells characteristic of basal epithelial cells was observed. Immunohistochemical studies colocalized an increased accumulation of extracellular TGF-beta1 with these cytokeratin 14 expressing hyperplastic lesions, An increase in stromal abnormalities was also observed and included a significant increase in the density of neuronal cells. The TGF-beta1-induced hyperplastic response involving basal epithelial cells may be the result of paracrine stimulation of growth of specific cell types in the prostate and may represent a divergence of normal growth processes. Benign growth abnormalities of basal epithelial cells in the human prostate have also been reported. An increased density of neuronal cells and other stromal abnormalities in response to TGF-beta1 retroviral transduction is also consistent with benign growth abnormalities in the human prostate.

3T3 Cells↗
PubMed1996

[Detection of point mutation of p53 gene by silver staining PCR-SSCP in paraffin-embedded malignant fibrous histiocytoma].

Silver staining PCR-SSCP method was used to detect point mutation of p53 gene in paraffin-embedded malignant fibrous histiocytoma (MFH) tissues. The abnormal shifting of the single-stranded DNA (ssDNA) was identified in 9 out of 16 cases. The positive figure of SSCP was 1,4,4, 3 in exon 5, 6, 7, 8, respectively. The mutant p53 protein was detected by microwave oven treatment and ABC immunohistochemistry. Positive nuclear staining was observed in 10 cases. The positive coincidence rate was 90.0% between SSCP and p53 protein expression. The mutation of p53 gene was not correlated with the subtypes of MFH. Our results indicate that detection of point mutations with silver staining PCR-SSCP is convenient, rapid and reliable in the screening of point mutation of genes.

Genes, p53↗
PubMed1996

[Clinical study of scopolamine detoxification for the treatment of heroin addicts].

OBJECTIVE: To evaluate the efficacy of treatment of heroin addicts (n = 100) by scopolamine detoxification (10 days program). METHODS: Methadone detoxification (10 days program) group (n = 50) and clonidine treated group (n = 50) served as controls. RESULTS: The scores of abstinence syndrome in scopolamine detoxification group were lower that those in clonidine treated group in the first three days of protocol, but this difference disappeared in the late stage of treatment. While scopolamine detoxification was effective as methadone detoxification in the control of abstinence syndrome during the first five days of treatment but the difference in the scores of abstinence syndrome between scopolamine and methadone group was observed during the late five days of protocol. The side-effects produced by scopolamine in general were dry mouth, somnolence, tachycardia, blurred vision and so on, which relieved gradually or disappeared with decreasing of its doses. CONCLUSION: Scopolamine does not result in potential dependence and has definite curative effect in the treatment of heroin addiction.

Adult↗
PubMed1996

[A study of P53 protein expression in fibrous neoplasms].

An immunohistochemical method utilizing microwave oven treated avidin-biotin complex (ABC) technique was used in this study to detect P53 protein expression in 87 parafin-embedded fibrous neoplasm tissues. The results showed that the total positive staining rate was 20.7%. The positive staining rate in fibroma (FA), dermatofibrosarcoma protuberans (DFSP) fibrosarcoma (FS) and malignant fibrous histiocytoma (MFH) were 0%, 4.0%, 37.5% and 62.5% respectively. The positive staining rate of P53 protein was increased with the increase in malignancy of the neoplasma. The expression of P53 protein was not correlated with the subtypes of DFSP and MFH, but correlated with cell differentiation. Therefore, detection of P53 protein expression may have significant value in the evaluation of malignancy, metastatic potential and the prognosis of fibrous neoplasma.

Dermatofibrosarcoma↗
PubMed1996

[Immunohistochemical study of lactate dehydrogenase isoenzymes in gastric cancer: light and electron microscopic observations].

In order to study the metabolic features of gastric cancer, the relationship between intestinal metaplasia or dysplasia and gastric cancer, and the relationship between LDH isoenzymes and biological behavior of gastric cancer, the content and distribution of lactate dehydrogenase (LDH) isoenzymes in 60 cases of gastric cancer were observed with immunohistochemical and immunoelectron microscopic techniques. The results showed that the content of LDH5 in gastric cancer cells was higher than that in any cells of normal gastric epithelium except parietal cells (P < 0.001). LDH-H (LDH1-LDH4) in cancer cells was lower than in parietal cells, but was not significantly different from that in chief cells and surface epithelium. Under electron microscope, LDH5 in cancer cells was mainly distributed in the matrix of cytoplasm, while LDH-H was scarce. LDH5 in the epithelium of intestinal metaplasia (IM) or dysplasia was higher than in pyloric glandular epithelium (P < 0.05), but was not significantly different from that in cancer cells (P > 0.2). LDH-H in the epithelium of IM or dysplasia was higher than that in pyloric glandular epithelium and gastric cancer cells (P < 0.05). The results suggest that increased LDH in gastric cancer cells is resulted mainly from increased LDH5, which makes the gastric cancer cells produce more lactate, with decrease in local pH. Invasion and spread of cancer cells could be indirectly promoted through an elevated activity of acid hydrolases. IM and dysplasia may be considered as borderline lesions from normal gastric mucosa to gastric cancer.

Gastric Mucosa↗
PubMed1996

[An X-ray study of the density and orientation of the cutaneous arteries in the lower leg].

Angiography was performed on 10 legs of fresh cadavers to investigate the density and orientation of small arteries of the lower leg. It was revealed that there were more vertically arranged arteries than the horizontally arranged ones in the skin and superficial fascia. The entire surface of the lower leg was divided into 9 regions. The density of arteries of different orientations in the skin and fascia was measured regionally. Though the density of different regions had a significant difference, no statistical significant difference was found in vessel anastomosis rate between different regions. Where the density was high, the anastomoses were rich. According to these findings, suggestions for the design of random flaps in the lower leg were discussed.

Adult↗
PubMed1996

[Effects of injectio reduqing on plasma IL-8 and nitric oxide levels in rabbits with endotoxin induced disseminated intravascular coagulation].

Experiments were performed for investigating the effects of Injectio Reduqing (RDQ) on plasma interleukin-8 (IL-8), NO2-/NO3-, complement 5a(C5a) and polymorphonuclear neutrophilic leukocyte (PMN) Chemotaxis Index (CI) in rabbits with endotoxin-induced disseminated intravascular coagulation (DIC). The results showed that plasma IL-8, NO2-/NO3-, C5a and CI levels of PMN increased markedly in model group, which were confirmed pathologically with obvious damage of tissues or organs. While in RDQ group the abov-mentioned parameters and damage of tissues or organs were reduced significantly (P < 0.01). The results suggested that the IL-8 and NO might be involved in pathogenesis of endotoxin-induced DIC, and RDQ could be used in preventing or treating DIC through mechanism of regulation of cytokines network.

Animals↗
PubMed1996

[Effect of angiotensin II on the adrenal glucocorticoids secretion].

The effect of angiotensin II on adrenal cortisol secretion was studied using incubated adrenal tissues of cells preparation of guinea pig and dog. The results showed that: the cortisol secretion in guinea pigs was increased by the addition of angiotensin II in both dose-dependent and time-dependent manner at concentration > or = 10(-9) mol/L (P < 0.01). When ACTH was further added to the angiotensin primed preparation, the output of cortisol was further increased. Deprivation of free calcium largely suppressed the production of cortisol induced by angiotensin II (P < 0.05). These results suggested that angiotensin II exerts a direct effect on the secretion of adrenal cortisol, which required the presence of Ca2+ and is promoted by ACTH.

Adrenal Glands↗
PubMed1996

[On diagnostics of malignant meningioma and invasive meningioma].

We have made a clinicopathological study of 90 cases of malignant meningiomas and 18 cases of invasive meningiomas. The results show that the diagnostic features of malignant meningioma include increased cellularity, nuclear pleomorphism, tumorous giant cells, numerous mitotic figures, focal necrosis, cystic change and hemorrhage. The diagnosis of malignant meningioma can be more positively made when invasive growth, recurrence and metastasis are present. In making the diagnosis of invasive meningioma, both changes of benign meningioma and invasive growth should be present.

Adolescent↗