PubMed Health⌕ Search

Biomedical subjects

C G Ma

Publications and source records attributed to C G Ma.

16 recordsLinked to original sources
PubMed2000

Protective effects of Ginkgo biloba extract on gastric mucosa.

AIM: To study the protective effects of Ginkgo biloba extract (GbE) on gastric mucosa. METHODS: By means of restaint-cold stress (RCS) in rats and 100% ethanol gavage in mice, the index of gastric mucosal injury was evaluated. The gastric juice was collected using pyloric ligation, and the volume and acidity of juice, and activity of pepsin were determined. The content of malondialdehyde (MDA) was measured by thiobarbituric acid (TBA) method. RESULTS: GbE (25, 50, and 100 mg/kg, bid x 5 d, ig) inhibited dose-dependently the gastric mucosal injury induced by RCS and 100% ethanol gavage. The index of gastric mucosal injury after RCS in groups pretreated with GbE was 58%, 43%, and 31% of control group respectively. The index of gastric mucosal injury induced by ethanol in groups pretreated with GbE was 62%, 36%, and 26% of the control group, respectively. And GbE enhanced the protective effects of cimetidine (Cim) on gastric mucosa. But it did not obviously influence the volume and acidity of gastric juice as well as the activity of pepsin. One hour after the administration of ig 100% ethanol, the contents of MDA in gastric mucosa and serum in mice increased (P < 0.01) vs the control group. But pretreatment with GbE (25, 50, and 100 mg/kg, ig) could inhibit this increase of MDA both in gastric mucosa and in serum. CONCLUSION: GbE had protective effects on gastric mucosa and GbE plus Cim possessed the synergism in the treatment of acute gastric mucosal lesions.

Animals↗
PubMed1999

Effects of hyperin on free intracellular calcium in dissociated neonatal rat brain cells.

AIM: To study the effects of hyperin (Hyp) on free intracellular calcium concentration ([Ca2+]i) of brain cells. METHODS: The neonatal rat brain cells were dissociated. [Ca2+]i in presence and absence of extracellular high K+, L-glutamic acid (Glu), 5-hydroxytryptamine (5-HT), and norepinephrine (NE) were assayed with Fura 2-AM. RESULTS: The resting [Ca2+]i in Hanks' solution (CaCl2 1.3 mmol.L-1) was (208 +/- 12) nmol.L-1 (n = 17). Hyp had no significant effects on the resting [Ca2+]i. Hyp 1.0, 4.0, and 16.0 mumol.L-1 markedly inhibited the increase of [Ca2+]i evoked by K+ 50 mmol.L-1 in a concentration-dependent manner. Hyp 16.0 mumol.L-1 inhibited the increases of [Ca2+]i induced by NE 1, 2, 4, and 8 mumol.L-1. Hyp (16.0 mumol.L-1) also markedly attenuated 5-HT and Glu-induced increase of [Ca2+]i. CONCLUSION: Hyp possessed inhibitory effects on influx of Ca2+ in the neonatal rat brain cells.

Animals↗
PubMed1998

Decrease of LFA-1 is associated with upregulation of TGF-beta in CD4(+) T cell clones derived from rats nasally tolerized against experimental autoimmune myasthenia gravis.

Tolerance to experimental autoimmune myasthenia gravis by nasal administration of microgram amounts of acetylcholine receptor (AChR) has been reported. To elucidate the mechanisms behind tolerance induction via the respiratory tract and the involvement of CD4(+) T cells, we established AChR-specific CD4(+)CD8(-) T cell clones from nasally tolerized rats. Nasal tolerance decreased leukocyte function-associated antigen-1 (LFA-1) expression in CD4(+) T cells from tolerized rats. There was no difference between nasally tolerized and control rats in expression of intercellular adhesion molecule-1. The levels of transforming growth factor-beta (TGF-beta) mRNA-expressing cells were upregulated in CD4(+) T cell clones after tolerance induction. These findings suggest that decreased LFA-1 expression in CD4(+) T cells contributes to reduction of the infiltration of inflammatory CD4(+) T cells, while upregulated TGF-beta may inhibit lymphocyte functions.

Administration, Intranasal↗
PubMed1996

Mucosal tolerance to experimental autoimmune myasthenia gravis is associated with down-regulation of AChR-specific IFN-gamma-expressing Th1-like cells and up-regulation of TGF-beta mRNA in mononuclear cells.

Oral and nasal administration of nicotinic acetylcholine receptor (AChR) to Lewis rats prior to myasthenogenic immunization with AChR and complete Freund's adjuvant (CFA) resulted in prevention or marked decrease of the severity of experimental autoimmune myasthenia gravis (EAMG) and suppression of AChR-specific B-cell responses and of AChR-reactive T-cell function. To examine the involvement of immunoregulatory cytokines and the underlying mechanisms involved in tolerance induction, in situ hybridization with radiolabeled cDNA oligonucleotide proves was adopted to enumerate mononuclear cells (MNC) expressing mRNA for the proinflammatory cytokine interferon-gamma (IFN-gamma), the B cell-stimulating interleukin-4 (IL-4), and the immunosuppressive transforming growth factor-beta (TGF-beta). Popliteal and inguinal lymph nodes from EAMG rats contained elevated numbers of AChR-reactive IFN-gamma, IL-4, and TGF-beta mRNA-expressing cells, compared to control rats receiving PBS orally or nasally and injected with CFA only. Oral and nasal tolerance was accompanied by decreased numbers of AChR-reactive IFN-gamma and IL-4 mRNA-expressing cells and strong up-regulation of TGF-beta mRNA-positive cells in lymphoid organs when compared to nontolerized EAMG control rats. The results suggest that IFN-gamma and IL-4 are central effector molecules in the development of EAMG and that TGF-beta plays an important role in tolerance induction to EAMG.

Administration, Intranasal↗
PubMed1996

Autoreactive T cell responses and cytokine patterns reflect resistance to experimental autoimmune myasthenia gravis in Wistar Furth rats.

Various mouse and rat strains show different susceptibilities to experimental autoimmune myasthenia gravis (EAMG) that can be induced by immunization with acetylcholine receptor (AChR) and Freund's complete adjuvant, and represents a model for the antibody-mediated myasthenia gravis in humans. We examined AChR-induced B and T cell responses and cytokine mRNA expression to study the mechanisms behind susceptibility to EAMG in Lewis rats and resistance in Wistar Furth (WF) rats. Both strains had similarly elevated concentrations and affinities of serum anti-AChR antibodies, and no difference between the two strains for frequencies of cells in lymphoid organs expressing mRNA of the B cell stimulating cytokine interleukin-4 was found. In contrast, T cell responses to AChR measured by proliferation and by enumeration of interferon-gamma-expressing cells at both mRNA and protein level were lower in the resistant WF rats. This strain showed, instead, an up-regulation of the anti-inflammatory transforming growth factor-beta. Strain-related differences in the susceptibility to actively induced EAMG are thus related to quantitative differences in distribution between pro-inflammatory and anti-inflammatory cytokines.

Animals↗
PubMed1996

The cerebrospinal fluid from patients with multiple sclerosis promotes neuronal and oligodendrocyte damage by delayed production of nitric oxide in vitro.

Nitric oxide (NO) may be involved in myelin and oligodendrocyte injury associated with multiple sclerosis (MS), a demyelinating disease of unknown etiology. The cerebrospinal fluid (CSF) from MS patients may provide an important signal inducing a pathologic process within the central nervous system (CNS). To investigate this question, CSF-induced NO production by glial cells was studied in 38 patients with multiple sclerosis (MS), 30 patients with other CNS inflammatory diseases (ID) and 20 with tension headache (TH) as control. Neuron damage was estimated by release of lactate dehydrogenase (LDH), whereas oligodendrocyte damage was estimated by a percentage of viable cells in primary oligodendrocyte cultures. Here we show that CSFs from 13/38 (34%) patients with MS stimulate glial cells to produce NO, compared to 2/20 (10%) of patients with ID and 1/30 (3%) with tension headache. The levels of NO production correlated positively with the amounts of LDH released and negatively with percentage of viable oligodendrocytes, suggesting that NO may represent a mechanism for oligodendrocyte losses in affected tissues and play a role in lesion formation in MS and its animal model experimental allergic encephalomyelitis (EAE).

Animals↗
PubMed1996

Cellular mRNA expression of interferon-gamma (IFN-gamma), IL-4 and transforming growth factor-beta (TGF-beta) in rats nasally tolerized against experimental autoimmune myasthenia gravis (EAMG).

Nasal administration of nicotinic acetylcholine receptor (AChR) to Lewis rats prior to myasthenogenic immunization with AChR plus Freund's complete adjuvant (FCA) resulted in prevention or marked decrease of the severity of EAMG, suppression of AChR-specific B cell responses and of AChR-reactive T cell functions. To examine the involvement of immunoregulatory cytokines and the underlying mechanisms involved in tolerance induction, in situ hybridization with radio-labelled synthetic oligonucleotide probes was adopted to enumerate mononuclear cells (MNC) expressing mRNA for the proinflammatory cytokine IFN-gamma, the B cell stimulating IL-4 and the immune response-down-regulating TGF-beta. Popliteal and inguinal lymph nodes from EAMG rats contained elevated numbers of AChR-reactive IFN-gamma, IL-4 and TGF-beta mRNA-expressing cells compared with control rats receiving PBS nasally and injected with FCA only. Nasal tolerance to EAMG was accompanied by decreased numbers of AChR-reactive IFN-gamma and IL-4 mRNA-expressing cells, and strong up-regulation of TGF-beta mRNA-positive cells in lymphoid organs compared with non-tolerized EAMG control rats. The relative affinity of anti-AChR antibodies was lower, but muscle AChR amounts were higher in nasally tolerized rats compared with non-tolerized EAMG control rats. The results suggest that IFN-gamma and IL-4 are central effector molecules in the development of EAMG, and that TGF-beta plays an important role in tolerance induction to EAMG.

Administration, Intranasal↗
PubMed1996

Transforming growth factor-beta 1 (TGF-beta1)-mediated inhibition of glial cell proliferation and down-regulation of intercellular adhesion molecule-1 (ICAM-1) are interrupted by interferon-gamma (IFN-gamma).

We utilized a model of myelin basic protein (MBP) activation in vivo and MBP-stimulated cultures in vitro to study the influence of TGF-beta1 on glial cell proliferation and ICAM-1/leucocyte function-associated antigen-1 (LFA-1) expression, and to observe the antagonistic effects of TGF-beta1 and IFN-gamma. TGF-beta1 inhibited MBP-stimulated and MBP-activated glial cell proliferation, especially in MBP-stimulated separated microglia and astrocytes, and down-regulated the expression of ICAM-1 on MBP-stimulated glial cells and separated microglia. ICAM-1 expression on MBP-activated glial cells was intensely suppressed, whereas its expression on MBP-stimulated astrocytes was not influenced. TGF-beta1 had no effect on LFA-1 expression. In contrast, IFN-gamma up-regulated ICAM-1 expression, but inhibited proliferative response on MBP-stimulated glial cells when cultured without TGF-beta1. Examination of TGF-beta1 and IFN-gamma interactions revealed that TGF-beta1-mediated inhibition of proliferation and down-regulation of ICAM-1 on glial cells were prevented by IFN-gamma. The suppressive effect was re-established with high doses of TGF-beta1 in cultures, indicating that biological effects of TGF-beta1 vary depending on nitric oxide (NO) production, its concentration in the microenvironment and regulation of the cytokine network.

Animals↗
PubMed1996

Protective effect of hyperin against myocardial ischemia and reperfusion injury.

AIM: To study the protective and antiperoxidative effects of hyperin (hyperoside; quercetin-3-O-galactoside; Hyp) on myocardial ischemia/reperfusion. METHODS: The rabbit anterior descenging branch of left coronary artery was occluded for 60 min and then released to allow reperfusion for 20 min. Hemodynamics (LVP, LV +/- dp/dt) and electrocardiogram (ECG, lead II) were monitored continuously with polygraph. After reperfusion, the blood sample and myocardium were taken to assay plasma creatine phosphokinase (CPK), lactate dehydrogenase (LDH), and cations in myocardium. Using a Langendorff system, the isolated heart of rat was initiated by ischemia for 40 min followed by 30 min of reperfusion. Malondialdehyde (MDA) contents of cardiac effluent and myocardium were measured with fluorescence spectrophotometer. RESULTS: Hyp 10 mg.kg-1 i.v. depressed changes in LVP, LV +/- dp/dtmax, ECG, plasma CPK, LDH, and cations (Ca2+, Mg2+, Na+) in myocardium induced by ischemia/reperfusion in rabbits. Hyp 10 and 100 mumol.L-1 markedly reduced the increase in MDA production in isolated rat hearts after ischemia/reperfusion. CONCLUSION: Hyp possesses a protective effect against myocardial ischemia/reperfusion injury via attenuating lipid peroxidation.

Animals↗
PubMed1995

Depletion of CD8+ T cells suppresses the development of experimental autoimmune myasthenia gravis in Lewis rats.

To understand the role of CD8+ T cells in experimental autoimmune myasthenia gravis (EAMG), CD8+ T cells were depleted by injecting a monoclonal anti-rat CD8 antibody (OX8) into Lewis rats immunized with Torpedo acetylcholine receptor (AChR) in complete Freund's adjuvant (CFA). CD8-depleted EAMG rats showed strikingly less muscle weakness and lower anti-AChR IgG antibody levels compared to Hy2-15-injected control EAMG rats. Moreover, the numbers of AChR-specific IgG antibody-secreting cells, AChR-reactive interferon-gamma-secreting T helper type 1-like cells and lymphocyte proliferation to AChR were lower in the CD8-depleted group than in control EAMG rats. These differences were significant among mononuclear cells from inguinal and popliteal lymph nodes, mesenteric lymph nodes and spleen, but not from thymus when examined 3, 5 and 7 weeks post-immunization. We suggest that CD8+ T cells are involved in the induction and persistance of EAMG by directly or indirectly affecting AChR-reactive T cells and anti-AChR IgG antibody-secreting cells.

Animals↗
PubMed1995

Suppression of experimental autoimmune myasthenia gravis by nasal administration of acetylcholine receptor.

Experimental autoimmune myasthenia gravis (EAMG) is a well established animal model, which can be induced in various animal species and strains with acetylcholine receptor (AChR) and represents an experimental counterpart of human myasthenia gravis (MG). Current immunotherapies of both EAMG and MG are non-specific and limited by their toxicity. Tolerance to EAMG has been achieved by oral administration of milligram quantities of Torpedo AChR. In the present report we demonstrate that nasal administration of microgram doses of Torpedo AChR to female Lewis rats prior to immunization with Torpedo AChR and complete Freund's adjuvant resulted in the prevention of subsequently induced EAMG, the suppression of serum anti-AChR antibody levels, the decrease of delayed-type hypersensitivity responses to AChR, as well as the suppression of AChR-specific immunoglobulin G-secreting cells, AChR-reactive interferon-gamma-secreting cells and T cell proliferation in peripheral lymphoid organs, particularly in popliteal and inguinal lymph nodes regional to immunization. We conclude that clinical signs of EAMG can be efficiently prevented by nasal administration of AChR in parallel with the downregulation of both B and T cell responses specific to AChR.

Administration, Intranasal↗
PubMed1995

Suppression of experimental autoimmune myasthenia gravis after CD8 depletion is associated with decreased IFN-gamma and IL-4.

CD8+ T cells can perform both Th1- and Th2-like functions by producing cytokines such as interferon-gamma (IFN-gamma) and interleukin-4 (IL-4), as well as the immune response down-regulating transforming growth factor-beta (TGF-beta), which are all involved in the development of experimental autoimmune myasthenia gravis (EAMG), a model for human MG. We have reported that depletion of CD8+ T cells results in the suppression of EAMG accompanied by the down-regulation of AChR-specific B cell responses and AChR-reactive IFN-gamma secreting Th1-like cells. To identify the involvement of IFN-gamma, IL-4 and TGF-beta in the development of EAMG after CD8+ T cell depletion, the expression of mRNA for these cytokines was studied in mononuclear cells from popliteal, inguinal and mesenteric lymph nodes, spleen and thymus by adopting in situ hybridization with complementary DNA oligonucleotide probes. Depletion of CD8+ T cells resulted in decreased levels of IFN-gamma and IL-4 mRNA expressing cells in different lymphoid organs except thymus, but no change in the numbers of TGF-beta mRNA expressing cells. The results imply that the suppression of EAMG after depletion of CD8+ T cells is caused by decreasing the effector factors but not by increasing the suppressor factor(s).

Animals↗
PubMed1994

[The blocking effect of hyperin on the inward flow of calcium ion].

Hyperin(Hyp) was shown to inhibit the positive inotropic action of calcium ion on the isolated papillary muscles and shift the dose response curve of calcium ion to the right. As a plot lg(x-1) vs -lg(B) resulted in straight lines with slopes of -0.625. On the action potentials of guinea pig myocardial cells, Hyp markedly decreased the duration of plateau of action potentials (APD20%) but did not influence the APD100%, RP, APA, OS and Vmax. In the atrium preparations of mice, Hyp significantly inhibited influx of 45Ca induced by high K+. All findings indicate that Hyp can inhibit the inward flow of calcium ion.

Action Potentials↗
PubMed1989

[Mechanism of analgesic action of hyperin].

In previous works, we reported that Hyp (hyperin) showed strong analgesic effect, and inhibited discharges induced by multianalgesics, but without anesthetic action. In this study, the analgesic mechanism of Hyp was further investigated. In the tail-flick test in mice, EGTA was shown to markedly enhance the analgesic effect of Hyp and shift the dose-effect curve to the upper-left. CaCl2 significantly antagonized the effect of Hyp and shifted the dose-effect curve to the lower-right. In the afferent discharges induced by analgesics, EGTA markly elevated while cacl2 lowered the effect of Hyp. It was also found that A23187, which promote influx of Ca2+, could antagonize the effect of Hyp. In the frog sciatic nerves, we found that Hyp could significantly inhibit influx of Ca2+. This finding suggests that the analgesic effect of Hyp may have close relationship with the reduction of calcium in afferent nerve endings.

Analgesics↗