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Biomedical subjects

G Niu

Publications and source records attributed to G Niu.

17 recordsLinked to original sources
PubMed2001

Microwave-assisted extraction of tanshinones from Salvia miltiorrhiza bunge with analysis by high-performance liquid chromatography.

A novel microwave-assisted extraction (MAE) method has been developed for the extraction and determination of tanshinones (tanshinone IIA, cryptotanshinone and tanshinone I) from the root of Salvia miltiorrhiza bunge with analysis by HPLC. Various experimental conditions were investigated to optimize the percentage extraction. Under appropriate MAE conditions, such as ethanol concentrations of 95% (v/v), MAE for 2 min, liquid/solid ratio of 10:1 (ml/g), the percentage extraction can reach high in a short time. The percentage extraction (tanshinone IIA: 0.29%; cryptotanshinone: 0.23%; tanshinone I: 0.11%) by MAE was the same or even higher than conventional extraction methods. MAE only needs 2 min, but extraction at room temperature, heat reflux extraction, ultrasonic extraction and Soxhlet extraction need 24 h, 45 min, 75 min and 90 min, respectively. MAE was also available in pilot plant form for larger scale extraction.

Abietanes↗
PubMed2001

Microwave-enhanced dehydration and solvent washing purification of penicillin G sulfoxide.

In the present study, a new microwave-enhanced dehydration and solvent washing purification of penicillin G sulfoxide technique has been developed. The results show that microwave irradiation can dehydrate penicillin G sulfoxide from a water content of 14-26 to below 0.5% in 40-60 min in N2 or air. After washing with ethyl acetate to remove impurities and residual water, the penicillin G sulfoxide can be used to synthesize cephalosporanic acid. The recovery of cephalosporanic acid was equal to and the purity of cephalosporanic acid was higher by 2% than that of the current dehydration technique. FTIR spectroscopy was used to study the process of microwave-enhanced dehydration and solvent washing purification of penicillin G sulfoxide.

Chemistry, Pharmaceutical↗
PubMed2001

Constitutive activation of Stat3 by the Src and JAK tyrosine kinases participates in growth regulation of human breast carcinoma cells.

Constitutive activation of signal transducer and activator of transcription (STAT) proteins has been detected in a wide variety of human primary tumor specimens and tumor cell lines including blood malignancies, head and neck cancer, and breast cancer. We have previously demonstrated a high frequency of Stat3 DNA-binding activity that is constitutively-induced by an unknown mechanism in human breast cancer cell lines possessing elevated EGF receptor (EGF-R) and c-Src kinase activities. Using tyrosine kinase selective inhibitors, we show here that Src and JAK family tyrosine kinases cooperate to mediate constitutive Stat3 activation in the absence of EGF stimulation in model human breast cancer cell lines. Inhibition of Src or JAKs results in dose-dependent suppression of Stat3 DNA-binding activity, which is accompanied by growth inhibition and induction of programmed cell death. In addition, transfection of a dominant-negative form of Stat3 leads to growth inhibition involving apoptosis of breast cancer cells. These results indicate that the biological effects of the Src and JAK tyrosine kinase inhibitors are at least partially mediated by blocking Stat3 signaling. While EGF-R kinase activity is not required for constitutive Stat3 activation in breast cancer cells, EGF stimulation further increases STAT DNA-binding activity, consistent with an important role for EGF-R in STAT signaling and malignant progression. Analysis of primary breast tumor specimens from patients with advanced disease revealed that the majority exhibit elevated STAT DNA-binding activity compared to adjacent non-tumor tissues. Our findings, taken together, suggest that tyrosine kinases transduce signals through Stat3 protein that contribute to the growth and survival of human breast cancer cells in culture and potentially in vivo.

Animals↗
PubMed2001

Overexpression of a dominant-negative signal transducer and activator of transcription 3 variant in tumor cells leads to production of soluble factors that induce apoptosis and cell cycle arrest.

Gene therapy of B16 tumors with a dominant-negative signal transducer and activator of transcription (Stat3) variant, designated Stat3beta, results in inhibition of tumor growth and tumor regression. Although only 10-15% of the tumor cells are transfected in vivo, the Stat3beta-induced antitumor effect is associated with massive apoptosis of B16 tumor cells, indicative of a potent bystander effect. Here, we provide evidence that blocking Stat3 signaling in B16 cells results in release of soluble factors that are capable of inducing apoptosis and cell cycle arrest of nontransfected B16 cells. RNase protection assays using multi-template probes specific for key physiological regulators of apoptosis reveal that overexpression of Stat3beta in B16 tumor cells induces the expression of the apoptotic effector, tumor necrosis factor-related apoptosis-inducing ligand. These in vitro results suggest that the observed in vivo bystander effect leading to tumor cell growth inhibition is mediated, at least in part, by soluble factors produced as a result of overexpression of Stat3beta in tumor cells.

3T3 Cells↗
PubMed2001

[The black diaphragm intraocular lens implantation].

OBJECTIVE: To evaluate the clinical effect of the black diaphragm intraocular lens (IOL) implantation. METHODS: The black diaphragm IOL implantation performed on 23 cases (23 eyes) of traumatic aniridia (21 eyes) and congenital aniridia (2 eyes) was studied retrospectively. RESULTS: Photophobia was reduced obviously and the naked visual acuity was improved in all 23 cases after the black diaphragm IOL implantation, VA > or = 0.1 in 16 cases (70%). The complications included vitreous hemorrhage (2 eyes) in the operation, and there were exudates on the surface of IOL (13 eyes), IOP elevation (3 eyes), macular hole (1 eye), recurrent retinal detachment (1 eye) and corneal decompensation (5 eyes) after the operation. CONCLUSION: The black diaphragm IOL implantation provides an effective means of treating traumatic or congenital aniridia, but the indication should be strictly controlled.

Adolescent↗
PubMed2000

Bing de ling, a Chinese herbal formula, stimulates multifaceted immunologic responses in mice.

Bing de ling is a Chinese herbal formula most commonly used in complementary medical settings against viral disorders. We have found that bing de ling potentiates upregulation of immune activity when administered to mice in dosages proportional to those used clinically. These mice demonstrated significant elevation of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) production in splenocytes and enhancement of macrophage, natural killer cell, and lymphokine-activated killer cell cytotoxicity. These data are consistent with bing de ling's clinically observed efficacy against viruses and identify the formula as a promising candidate for clinical trials against diverse diseases that may respond to increased immunologic activity.

Adjuvants, Immunologic↗
PubMed1999

Gene therapy with dominant-negative Stat3 suppresses growth of the murine melanoma B16 tumor in vivo.

Whereas signal transducers and activators of transcription were originally discovered as mediators of normal cytokine signaling, constitutive activation of certain signal transducer and activator of transcription proteins, including Stat3, has been found in increasing numbers of human cancers. Recently, a causal role for Stat3 activation in oncogenesis has been demonstrated, suggesting that Stat3 represents a novel target for cancer therapy. We report here that in vitro expression of a Stat3 variant with dominant-negative properties, Stat3beta, induced cell death in murine B16 melanoma cells that harbored activated Stat3. By contrast, expression of Stat3beta had no effect on normal fibroblasts or the Stat3-negative murine tumor MethA, suggesting that only tumor cells with activated Stat3 have become dependent on this pathway for survival. Significantly, gene therapy by electroinjection of the Stat3beta expression vector into preexisting B16 tumors caused inhibition of tumor growth as well as tumor regression. This Stat3beta-induced antitumor effect is associated with apoptosis of the B16 tumor cells in vivo. These findings demonstrate for the first time that interfering with Stat3 signaling induces potent antitumor activity in vivo and thus identify Stat3 as a potential molecular target for therapy of human cancers harboring activated Stat3.

Animals↗
PubMed1998

[The suppressing effect of TIMP-3 gene transfection on the invasion and metastasis of human lung carcinoma cells line].

OBJECTIVE: The purpose of this study is to determine if increasing levels of tissue inhibitor of metalloproteinase 3 (TIMP-3) expression could suppress the malignant phenotype of human cancer cells. METHODS: The recombinant expression vector, which contains full length cDNA of human TIMP-3, was constructed and transfected into BE1 cell line by lipofectin technique. The invasive and spontaneous metastatic potential was examined. RESULTS: TIMP-3 mRNA expression in TIMP-3 gene transfected BE1 cells was upregulated as detected by Northern blot. The invasion of TIMP-3 gene-transfected cells across matrigel-coated filters was significantly decreased when compared with controls. Following subcutaneous injection into nude mice, the TIMP-3 transfected cells suppressed primary tumor growth, as characterized by reduced tumor incidence (9/12 vs 6/6), longer latency and reduced metastatic potential to the lungs (1/12 vs 5/6) and lymph nodes (5/12 vs 6/6). CONCLUSION: The results suggest that upregulation of TIMP-3 expression in BE1 cells resulted in suppression of the invasive potential of BE1 cells in vitro as well as tumorigenic and metastatic potential in nude mice.

Animals↗
PubMed1997

Unscheduled apoptosis during acute inflammatory lung injury.

Apoptosis is a mode of cell death currently thought to occur in the absence of inflammation. In contrast, inflammation follows unscheduled events such as acute tissue injury which results in necrosis, not apoptosis. We examined the relevance of this paradigm in three distinct models of acute lung injury; hyperoxia, oleic acid, and bacterial pneumonia. In every case, it was found that apoptosis is actually a prominent component of the acute and inflammatory phase of injury. Moreover, using strains of mice that are differentially sensitive to hyperoxic lung injury we observed that the percent of apoptotic cells was well correlated with the severity of lung injury. These observations suggest that apoptosis may be one of the biological consequences during acute injury and the failure to remove these apoptotic cells may also contribute to the inflammatory response.

Journal Article↗
PubMed1997

[Effect of B16 cells transfected with IL-2 gene on mouse immunity].

IL-2 was introduced into mice B16 melanoma cell line by using retrovirus infection method. Both B16 and B16-IL-2 cells were treated with Mit C beforehand and were then inoculated intraperitoneally as vaccines in mice respectively. Hanks solution was used instead of the vaccine in the control group. The data showed that the tumor incidence rate was zero in the group receiving B16-IL-2 vaccine followed by B16 inoculation. However, incidence rate was 100% in both the B16 vaccine immunization group and in the control groups. Experiments also indicated that the proliferation of splenic lymphocytes induced by MLTR, the specific cytotoxicity of CTL against B16 cells, the activities of splenic NK, LAK, and the level of IL-2 secretion in mice immunized by B16-IL-2 were much higher than those in the mice immunized only with B16 cells as well as the controls. These data indicated that secretion of IL-2 in mice promoted specific and nonspecific anti-tumor immunity of mice. The theoretic basis was provided for IL-2-secreting tumor vaccine.

Animals↗
PubMed1997

[Miniplate osteosynthesis for multiple mandibular fractures].

This retrospective study involved 34 patients with multiple mandibular fractures. Monocortical miniplates were used for fixation of fractures followed by a short term intermaxillary fixation. All the patients were evaluated radiographically and clinically. The results indicated that all fractures healed uneventfully. No malocclusion, delayed union, injury of the nerves or teeth due to the procedure were found. We concluded that monocortical miniplate osteosynthesis is effective and reliable for multiple mandibular fractures, and a short term intermaxillary fixation is helpful for the healing of fracture.

Adolescent↗
PubMed1996

Effects of tetramethylpyrazine phosphate and sodium ferulate alone or in combination on hemodynamics in anesthetized dog.

Hemodynamic actions of intravenous (iv) administration of tetramethylpyrazine phosphate (TMPP) and sodium ferulate (SF) alone or in combination were studied in anesthetized dogs. When given alone, TMPP increased left ventricular systolic pressure (LVSP), peak positive first derivative of left ventricular pressure (+LVdp/dt), coronary blood flow (CBF) and heart rate (HR) while decreasing mean aortic pressure (mAoP). SF alone did not produce any significant hemodynamic changes. When the two were administered in combination, SF antagonized dose-dependently the hemodynamic actions of TMPP. Results of this study did not support the efficacy of combined treatment of Ligusticum wallichi and Angelica root, which contain TMPP and SF respectively.

Analysis of Variance↗
PubMed1996

[The effect of IL2 gene transfection on the growth and metastatic characteristics of muous B16 melanoma cells].

In order to investigate the antitumor effect of IL2 gene transfected tumor vaccine, gene transfected tumor cells which secrete IL2 in a comparatively sustained manner must be obtained. Their growth and metastatic characteristics must be identified. This study used the retrovirus infection method to introduce human IL2 cDNA into mouse B16 melanoma cells. Southern blot analysis confirmed the establishment of IL2-integrated B16 cells (B16-IL2). Northern blot also showed the expression of IL2 gene in mRNA level. IL2 secretion of B16-IL2 was comparatively stable for a period of 6 months with the highest production rate of 53u/ml. No obvious influence was observed on the morphology and growth of the tumor cells in vitro after the transfection of IL2-cDNA. But, their oncogenicity in vivo was reduced and the tumor growth induced by B16-IL2 cells was inhibited. Lung metastasis rate and extent was also reduced. This study laid the foundation for the preparation of an IL2-secreting tumor vaccine.

3T3 Cells↗
PubMed1993

[Experimental histopathological studies of renal lesions induced by high- or low-osmolality contrast media].

To elucidate the morphological basis of renal lesions due to intravenous administration of radiocontrast media, a comparative study was performed by injecting contrast media with different properties, such as high-osmolar ionic diatrizoate (60% Urografin), low-osmolar ionic ioxaglate (Hexabix 320) and low-osmolar non-ionic iopamidol (lopamiron 300), via the tail vein of male Wistar rats. Physiologic saline was injected in controls. Each contrast media was administered singly as a low dose (1 g I/kg), a moderate dose (3 g I/kg) or a high dose (9 g I/kg) to three separate groups of rats. In additional groups of rats, a high dose of each contrast media (9 mg I/kg) was administered repeatedly two or four times. The animals were sacrificed chronologically from 5 minutes to 30 days after the last administration and their renal tissues were examined by light and electron microscopy. The results indicated that the low osmolar contrast media is beneficial in decreasing general symptoms, but there are no definite differences between high and low osmolar contrast media in the data of blood and urine examination after administration. The iodinated contrast media with a low or moderate dose does not induce definite histopathological changes of the renal tissue, however, with a high dose it causes vacuolization of proximal tubular epithelia, although this change recovers within three days. The repeated administration of contrast media with a high dose induces severe damage of proximal tubular epithelia with prominent vacuolization, appearance of intracytoplasmic granular structure and occasional cell necroses. The vacuolization appears even in distal and collective tubules and glomerular epithelia. Recovery is retarded under this condition. There are no qualitative histological differences of renal lesions induced by the three different contrast media. In conclusion, either high or low osmolar contrast media induces almost the same histological alteration in renal tissues under the same experimental conditions. The more the quantitative increase in administered iodinated contrast media, the more prominent is the histological impairment of the kidney. The degree of renal lesion and its recovery might depend on the dose of iodine rather than the osmolality of the contrast media.

Animals↗
PubMed1992

[Extracellular calcium in the rat brains and the effects of nifedipine in experimental cerebral infarction using calcium ion selective microelectrodes in vivo].

Extracellular Ca2+ (Ca2+ e) changes in the cerebral infarction areas of the rats with the double-tubulus calcium ion-selective microelectrodes made of calcium active material, di-2-isooctylphenyl calcium phosphate to observe the effects of two concentrations of nifedipine given before the middle cerebral artery (MCA) occlusion. Twenty-four rats were divided into three groups: group A: with just the left MCA occlusion, Group B: with intramuscular injection of nifedipine 1mg/kg one hour before the MCA occlusion, and Group C with intramuscular injection of nifedipine 5mg/kg one hour before the MCA occlusion. The results indicated that the mean concentration of Ca2+ e in the normal brain Group A was 1.119 mM. The Ca2+ e concentrations became 0.4613 mM, 0.191 mM and 0.0654 mM, 2, 5 and 30 minutes after the MCA occlusion respectively. The other groups, Group B and Group C, receiving two kinds of dosages of nifedipine respectively showed the Ca2+ e concentrations to be 0.5262 mM and 0.5588 mM, 0.3456 mM and 0.3058 mM, 0.2156 mM and 0.1989 mM, 2, 5 and 30 minutes after the MCA occlusion respectively. There is no statistic significance between group B and group c (P greater than 0.25) By comparing Group A with Group B or C, it was found that the Ca2+ e level of Group B or C is about 3 times greater than that of Group A (P less than 0.0025) and (P less than 0.005) 30 minutes after the MCA occlusion.

Animals↗