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Biomedical subjects

G Ma

Publications and source records attributed to G Ma.

At least 55 records · Page 3Linked to original sources
PubMed2000

[Discussions on some problems related to fluid inclusion analysis by SXRF].

X-ray fluorescence experiments were carried out at Beijing Synchrotron Radiation Facilities (BSRF) using synchrotron radiation as excitation source. The samples were made by mixing national reference standard GBW07106 and certain amount of reagent NaCl and KCl, and pressed into pellets. The purpose of the experiment is to verify the detection ability of the XRF setup at BSRF for elements in geological samples, especially for light elements. The beam size was 20 x 20 microns2, and the current in the storage ring was about 40 mA. The gap between the sample and the Si(Li) detector was 2 cm. With measuring time of 200 sec., The relative and absolute detection limits for 10 elements have been calculated. The sampling depth and sampling weight, which are critical in individual fluid inclusion analysis, have also been estimated. Some problems concerning the individual fluid inclusion analysis by SXRF, such as inclusion depth determination, effect of the inclusion depth on XRF intensity etc., are discussed based on the experiment results.

English Abstract↗
PubMed1999

[Effect of energy intake at breakfast on school performance].

In order to examine the effect of energy intake at breakfast on school performance, 151 grade three school children from four classes of two schools were sampled for this study. Children were randomly assigned to breakfast A or B on any given day. They were provided with breakfast with either high or low energy content at school over a period of 5 successive days. The remained foods were collected and weighed. Performance tests including addition, multiplication, number checking, logic, creativity, physical endurance, visual-analogue scales were applied at the third or fourth period of courses in the morning on Tuesday through Friday during the experimental week. The teachers involved in the study were blind to the kind of treatment. No significant effect of energy intake at breakfast on these performance indicators was found in this study.

Child↗
PubMed1999

Bcr: a negative regulator of the Bcr-Abl oncoprotein.

Chronic myelogenous leukemia is typically characterized by the presence of the Philadelphia chromosome (Ph) in which 5' portions of the BCR gene are fused to a large portion of the ABL gene. Our studies and those of others indicate that Bcr sequences within the Bcr-Abl oncoprotein are critically involved in activating the Abl tyrosine kinase and actively participate in the oncogenic response, which is generated by the Bcr-Abl oncoprotein. We investigated the role of the Bcr protein in the oncogenic effects of Bcr-Abl. Reduction of the level of the Bcr protein by incubating cells with a 3' BCR anti-sense oligodeoxynucleotide increased the growth rate and survival of hematopoietic cell lines expressing Bcr-Abl. Also, enforced expression of Bcr in Bcr-Abl cell lines strongly reduced transformation efficiency. Induction of Bcr expression drastically reduced the phosphotyrosine content of Bcr-Abl in Rat-1 fibroblasts transformed by P185 BCR-ABL and in hematopoietic cells expressing P210 Bcr-Abl within days following induction of Bcr. Rat-1/P185 cells maintained for three weeks after Bcr induction had dramatically reduced amounts of phosphotyrosine proteins compared to cells in which Bcr expression was repressed by the addition of Tet. In contrast Bcr expression did not decrease the phosphotyrosine content of either v-Src or activated Neu tyrosine kinase. Importantly, the phosphotyrosine content of total P160 BCR (induced plus endogenous) was strongly reduced by inducing expression of Bcr, indicating that the induced Bcr protein was not a target of the tyrosine kinase activity of Bcr-Abl but instead functioned as an inhibitor of Bcr-Abl. These results show that the Bcr protein can function as a negative regulator of Bcr-Abl, but that the inhibitory effects of Bcr are dependent on achieving an elevated level of Bcr expression relative to Bcr-Abl.

Animals↗
PubMed1999

Structure-activity relationships: analogues of the dicaffeoylquinic and dicaffeoyltartaric acids as potent inhibitors of human immunodeficiency virus type 1 integrase and replication.

The dicaffeoylquinic acids (DCQAs) and dicaffeoyltartaric acids (DCTAs) are potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) integrase. They also inhibit HIV-1 replication at nontoxic concentrations. Since integrase is an excellent target for anti-HIV therapy, structure-activity relationships were employed to synthesize compounds with: (1) improved potency against HIV-1 integrase, (2) improved anti-HIV effect in tissue culture, and (3) increased selectivity as indicated by low cellular toxicity. Thirty-four analogues of the DCTAs and DCQAs were synthesized and tested for cell toxicity, anti-HIV activity, and inhibition of HIV-1 integrase. Seventeen of the 34 analogues had potent activity against HIV-1 integrase ranging from 0. 07 to >10 microM. Seventeen analogues that were synthesized or purchased had no inhibitory activity against integrase at concentrations of 25 microM. Of the biologically active analogues, 7 of the 17 inhibited HIV replication at nontoxic concentrations. The most potent compounds were D-chicoric acid, meso-chicoric acid, bis(3,4-dihydroxydihydrocinnamoyl)-L-tartaric acid, digalloyl-L-tartaric acid, bis(3,4-dihydroxybenzoyl)-L-tartaric acid, dicaffeoylglyceric acid, and bis(3, 4-dihydroxyphenylacetyl)-L-tartaric acid. Anti-HIV activity of the active compounds in tissue culture ranged from 35 to 0.66 microM. Structure-activity relationships demonstrated that biscatechol moieties were absolutely required for inhibition of integrase, while at least one free carboxyl group was required for anti-HIV activity. These data demonstrate that analogues of the DCTAs and the DCQAs can be synthesized which have improved activity against HIV integrase.

Anti-HIV Agents↗
PubMed1999

Promotional effects of CO(2) laser and scalpel incision on 4-NQO-induced premalignant lesions of mouse tongue.

BACKGROUND AND OBJECTIVES: CO(2) laser and scalpel incision have been demonstrated to have promotional effects on oral neoplastic lesions. However, a precise understanding has not been achieved as to which modality has a more significant effect on cancer promotion. The purpose of this study was to determine the histological and biological changes after CO(2) laser surgery and scalpel incision in oral premalignant lesions. STUDY DESIGN/MATERIALS AND METHODS: Premalignant lesions of mouse tongue induced by 4-nitroquinoline-1-oxide (4NQO) in drinking water for 4 months were used in this study. A 2-mm incision was made on the right margin of each mouse tongue, using either a CO(2) laser (group A) or a scalpel (group B). Mice without incisional treatment were used as controls (group C). Seven months after laser and scalpel treatments, hematoxylin-eosin staining and proliferating cell nuclear antigen (PCNA), epidermal growth factor receptor (EGFR), and p53 immunostaining were performed for tongue specimens. RESULTS: The epithelia of right tongue margins showed more severe dysplasia than those of left tongue margins in both group A and group B. The PCNA labeling indices (LIs) and EGFR expression for right tongue margins were also higher than for left margins in both group A and group B. There was no obvious difference between these two groups. Almost no p53-positive staining was found in either group. CONCLUSION: CO(2) laser surgery and scalpel incision seem to have similar promotional effects on oral premalignant lesions.

4-Nitroquinoline-1-oxide↗
PubMed1999

Inverse relationship between potassium intake and coronary artery disease in the cholesterol-fed rabbit.

We tested the hypothesis that a low level of dietary potassium intake would exacerbate the severity of vascular lesion formation in rabbit coronary arteries during high cholesterol intake. Two groups of nine rabbits were studied for 6 weeks while eating a diet containing 2% cholesterol and 0.9% sodium. The normal potassium group consumed a diet containing 1.5% potassium and the low potassium group consumed a diet containing 0.4% potassium. After 6 weeks the animals were killed, the hearts were removed, and blood samples were withdrawn from the abdominal aorta immediately before removing the heart. The hearts were sectioned and slides were prepared and fixed with hematoxylin and eosin. The numbers of normal and abnormal vessels, and those with foam cells in the subintima, were counted in selected sections. Plasma potassium concentration in the normal and low potassium intake groups averaged 4.27 +/- 0.27 mmol/L and 3.90 +/- 0.11 mmol/L, respectively. No differences between the groups were observed in plasma cholesterol or body weight gain. The percentages of abnormal arteries in the groups were 4.20 +/- 0.35 in the normal intake group and 6.36 +/- 0.50 in the low intake group, 51% greater in the normal intake group (P < .001). These results support the hypothesis that low potassium intake exacerbates the severity of subintimal lesion development in the coronary arteries.

Animals↗
PubMed1999

Effect of photodynamic therapy using 5-aminolevulinic acid on 4-nitroquinoline-1-oxide-induced premalignant and malignant lesions of mouse tongue.

A new photosensitizing agent 5-aminolevulinic acid (ALA)-based photodynamic therapy (PDT) has been demonstrated as a useful method for treatment of superficial neoplastic lesions. The aim of this study was to determine the effects of topically and systemically ALA-based PDT in neoplastic lesions of the oral cavity. Premalignant and malignant lesions of mouse tongue induced by 4-nitroquinoline-l-oxide (4NQO) were used in this study. At 1, 2 and 3 h after topical application of ALA or 3 h after systemic administration of ALA (250 or 1000 mg/kg), the lesions were irradiated with Nd: YAG dye laser at 630 nm (200 J/cm2). Both premalignant and early malignant lesions showed complete response to systemically ALA-based PDT. In an invasive nodular malignant lesion, however, only the superficial portion was affected. There was no apparent difference in the PDT effect between 250 and 1000 mg/kg doses of ALA. In contrast, topically ALA-based PDT had virtually no effect on most lesions. It was concluded that systemically ALA-based PDT is a useful method for treating premalignant and early malignant lesions in the oral cavity, while topically ALA-based PDT using this preparation may be unsuitable for treatment of oral lesions.

4-Nitroquinoline-1-oxide↗
PubMed1999

Vascular protective effects of potassium.

Potential mechanisms responsible for the cardiovascular protection associated with high levels of dietary potassium were investigated in in vitro and in vivo studies. Elevation of extracellular potassium concentration within the physiological range inhibited free radical formation from macrophages and endothelial cells, inhibited proliferation and thymidine incorporation of vascular smooth muscle cells, and reduced platelet sensitivity to thrombin and other agonists. The effects of potassium on several well-characterized animal models of vascular pathology were also studied. Acute elevation of plasma potassium concentration inhibited thrombus formation in the coronary artery of the dog and the carotid artery of the rabbit. In cholesterol-fed rabbits, 6 weeks of diet containing low potassium content increased by approximately 50% (compared with control rabbits) the number of arteries in the myocardium showing signs of arteriosclerotic lesion formation. And in rats and pigs, 4 weeks of eating high potassium-content diet reduced the severity compared with control animals of neointimal proliferation associated with balloon angioplasty. We propose that high levels of dietary potassium provide cardiovascular protection by inhibiting the function of the cells that are responsible for vascular lesion formation.

Animals↗
PubMed1999

Changes in serum cardiac troponin I levels after percutaneous transluminal coronary angioplasty.

OBJECTIVE: To evaluate the possible effect of percutaneous transluminal coronary (PTCA) on myocardium. METHODS: Serum cTnl and CK-MB were measured in 60 patients with coronary artery disease (CAD) who underwent PTCA before and at the 6th, 12th, 24th, 48th and 72nd hour after the interventional procedure respectively. RESULTS: The serum cTnl levels began to increase at 6 hours (9.65 +/- 6.27 micrograms/L) in 18 patients, reached the peak levels during 12-24 hours (20.43 +/- 11.28 micrograms/L, 18.52 +/- 9.52 micrograms/L), and returned to normal range till 48-72 hours (7.35 +/- 7.62 micrograms/L, 5.51 +/- 3.13 micrograms/L) after PTCA. The serum cTnl and CK-MB levels were kept normal range pre- and post-PTCA in 30 cases. The levels of cTnl in 12 cases were over baseline either before or after the procedure, while for CK-MB, only in 3 cases were over normal range after PTCA. Compared with normal cTnl group, elevated cTnl levels were related to total inflation times and dilated times (P < 0.05). CONCLUSIONS: PTCA may cause some minor damage in myocardium, serum cTnl level was more sensitive and specific for monitoring myocardial injury.

Adult↗
PubMed1999

[Immunohistochemical study of safe resection margin in the surgical treatment of laryngeal carcinoma].

OBJECTIVE: To study safe resection margin of laryngectomy according to the level of protein of gene expression. METHOD: Using citric-LSAB-immunochemical technique, the expressions of ras, c-myc and P53 were studied in different regions of larynx including 30 cases laryngeal carcinoma, border area, adjacent mucosa which was 0.5, 1.0, 1.5, 2.0 cm away from cancer and four normal laryngeal mucosa. RESULT: The results showed that both single expression and co-expression of p21, p62 and p53 increased as tissue progressed in sequence from normal mucosa, 2.0, 1.5, 1.0, 0.5 cm distant mucosa adjacent to carcinoma, border area and carcinoma. A significant different expression in most of them can be seen at regions of 0.5 cm and 1.0 cm distant from the tumor (P < 0.05). CONCLUSION: The tissue 0.5 cm adjacent to the tumor should be regarded as precancerous lesion. It is appropriate to regard 0.5 cm away from tumors as resection margins for surgical treatment of laryngeal carcinoma.

Adult↗
PubMed1999

[The development of model DYC-I multi-purpose device for lumbar vertebra puncture].

A multi-purpose device for lumbar Vertebra puncture, which is ablete obtain cerebrospinal fluid (csf) and to determine the intracranial pressure, is presented here. This device has the functions of avoiding blindness of puncture, measuring pressure hermetically, liquid crystal display and controlling the flow of CSF.

Equipment Design↗
PubMed1999

[FTIR and FT-Raman studies on interactions between water and surfactants in water/KDEHP (75%)-HDEHP (25%)/n-HEPTANE microemulsion systems].

The conformation of the hydrocarbon chains in water/KDEHP(75%)-HDEHP(25%)/n-HEPTANE microemulsion systems was studied by FT-Raman spectroscopy. The increase in the intensity ratio Ir (I2937/I2875) showed trans to gauche transformation. The hydration of the polar heads in microemulsions was investigated by FT-IR spectroscopy. Some probable structures of KDEHP and HDEHP in microemulsions were proposed.

Emulsions↗
PubMed1999

[Water structure in water/KDEHP-HDEHP/n-Heptane microemulsion by FTIR spectroscopy].

The structure of water in microemulsion is one of the basic subjects in the field of surface science. FTIR spectroscopy is considered as a powerful tool in the study on water structure. In this paper, we investigated water structure in the water/KDEHP (potassium bis (2-ethylhexyl) phosphate) -HDEHP/n-Heptane system. By using the Fourier self-deconvolution and curve-fitting method, the OH stretching band of water in the KDEHP-HDEHP microemulsion was resolved into four subpeaks which were tentatively assigned to absorbances of four different components of water. In order to explain the variations of peak positions of subpeaks with water content some probable hydration models of surfactants were proposed.

English Abstract↗
PubMed1999

[Continuous determination of Zn, Cu and Mn in tea by flame atomic absorption spectrophotometry].

This paper reports the determination of trace metals Zn, Cu and Mn in tea by flame atomic absorption spectrophotometry. The method is simple and rapid with good precision and accuracy. The characteristic concentration is 0.009 microg/mL/1% for Zn, 0.031 microg/mL/1% for Cu and 0.017 microg/mL/1% for Mn, respectively. The relative standard deviation is between 0.9% and 5.0%. The recovery rate is between 92.0% and 106.0%.

Camellia sinensis↗
PubMed1999

[Neural cluster structure with single component prediction in multiple variable systems for X-ray fluorescence spectrometry].

A neural cluster structure with single component prediction (NCSCP) was proposed for X-ray fluorescence spectrometry in a multivariable system. The neural cluster structure is built by the collection of a group of neurons which have close relationships among one another. In X-ray fluorescence analysis, the structure is constructed by choosing the elements in which there exist serious matrix effects, and deleting the components containing large noise. The predictability of the neural cluster structure was compared with that of the classical backward error propagation algorithm with single component prediction. The results show that the neural cluster structure is significantly superior to the classical algorithm in prediction accuracy, antidisturbance and the predictabilty to outliers.

English Abstract↗
PubMed1998

Association of petrochemical exposure with spontaneous abortion.

OBJECTIVES: To assess the association between petrochemical exposure and spontaneous abortion, a retrospective epidemiological study in a large petrochemical complex in Beijing, China was conducted. METHODS: Plant employment records identified 3105 women who were married, were 20-44 years of age, and had never smoked. Of those, 3070 women (98.8%) reported at least one pregnancy. From this group, 2853 (93%) of the women participated in the study. According to their plant employment record, about 57% of these women workers reported occupational exposure to petrochemicals during the first trimester of their pregnancy. Trained interviewers administered a standardised questionnaire to this group of women and their husbands, collecting information on reproductive history, pregnancy outcomes, employment history, occupational exposure, smoking habits, alcohol consumption, indoor air pollution, and demographic variables. The results from the womens' first pregnancies were analysed. RESULTS: There was a significantly increased risk of spontaneous abortion for women working in all of the production plants with frequent exposure to petrochemicals (8.8%; range of 5.8%-9.8%) compared with those working in nonchemical plants (2.2%; range of 0.0%-7.1%). Also, when a comparison was made between exposed and non-exposed groups within each plant, exposure to petrochemicals was consistently associated with an increased risk of spontaneous abortion. The overall odds ratio (OR) was 2.7 (95% confidence interval (95% CI) 1.8 to 3.9) after adjusting for potential confounders. When the analysis was performed with the exposure information obtained from the women' interview responses for (self reported) exposures, the estimated OR for spontaneous abortions was 2.9 (95% CI 2.0 to 4.0). The analysis was repeated by excluding those 452 women who provided inconsistent reports between recalled exposure and work history, and a comparable risk of spontaneous abortion (OR 2.9; 95% CI 2.0 to 4.4) was found. In analyses for exposure to specific chemicals, an increased risk of spontaneous abortion was found with exposure to most chemicals, and the results for benzene (OR 2.5; 95% CI 1.7 to 3.7), gasoline (OR 1.8; 95% CI 1.1 to 2.9), and hydrogen sulphide (OR 2.3; 95% CI 1.2 to 4.4) were significant. CONCLUSION: An increased risk of spontaneous abortion was found associated with the exposure to petrochemicals, including benzene, gasoline, and hydrogen sulphide.

Abortion, Spontaneous↗
PubMed1998

Comparison of bromodeoxyuridine labeling indices of smears and sections from mouse NR-S1 tumor.

Bromodeoxyuridine (BrdU) labeling indices (LIs) of smears and sections from mouse NR-S1 tumor were labeled in vivo or in vitro and compared to confirm the reliability of smears labeled in vitro. In vivo labeling was carried out by administering 40 mg/kg 5-bromo-2'-deoxyuridine while in vitro labeling was performed by incubating the tumor specimens in RPMI 1640 culture medium containing 200 microM 5-bromo-2'-deoxyuridine under 3 atmospheres. BrdU LIs of sections labeled in vitro (9.49 +/- 0.16) showed lower values than those labeled in vivo (14.95 +/- 0.36). BrdU LIs of smears labeled in vitro (9.87 +/- 0.23) also showed lower values than those labeled in vivo (14.83 +/- 0.49). However, the BrdU LIs of smears were similar to those of sections labeled in vivo and in vitro. In vitro BrdU immunochemistry in smears seems useful for evaluating the biological properties of tumor tissues.

Animals↗