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Biomedical subjects

M Gu

Publications and source records attributed to M Gu.

120 records · Page 7Linked to original sources
PubMed1991

Possible role of leukotrienes in hypoxic contraction of canine isolated basilar artery.

1. Hypoxia reversibly increased isometric tension in unstimulated canine isolated basilar artery rings. 2. Nordihydroguaiaretic acid (NDGA; 5 x 10(-6) M), an inhibitor of lipoxygenase and quinacrine (10(-5) M), which blocks the release of arachidonic acid from phospholipids by inhibiting the enzyme phospholipase A2, blocked hypoxia-induced contractions. 3. The preferential leukotriene D4 (LTD4) antagonist, L-660,711, also inhibited the hypoxia-induced contractions in concentrations ranging from 10(-8) M to 10(-5) M. The effects seen were statistically significant (P less than 0.05). Two components of inhibition were seen. 4. Arachidonic acid (5 micrograms ml-1) caused contraction of the isolated basilar artery rings. This response was inhibited by NDGA (5 x 10(-6) M) and L-660,711 (10(-5) M). 5. The LTD4 (10(-8) M-10(-7) M)-induced contraction was relaxed by L-660,711 in a dose-dependent manner. Both the contraction caused by LTD4 as well as that caused by hypoxia were relaxed by 5 x 10(-6) M adenosine. 6. Leukotriene(s) may be involved in hypoxia-induced contraction of canine isolated basilar artery. However, they may not be the sole mediator(s).

Animals↗
PubMed1991

Inhibition of the acetylcholine-induced relaxation of canine isolated basilar artery by potassium-conductance blockers.

Canine basilar artery rings precontracted with 5-hydroxytryptamine (0.1-0.5 microM) relaxed in the presence of acetylcholine (25-100 microM), sodium nitroprusside (0.1 microM), or stimulation of the electrogenic sodium pump by restoration of extracellular K+ (4.5 mM) after K(+)-deprivation. Acetylcholine-induced relaxation is believed to be caused by the release of endothelium-derived relaxing factor (EDRF) and is prevented by mechanical removal of the endothelium, while relaxations induced by sodium nitroprusside or restarting of the sodium pump are endothelium-independent. Acetylcholine-induced relaxation was selectively blocked by pretreatment of the tissue with the nonselective K+ conductance inhibitors, 4-aminopyridine (4-AP, 3 mM), Ba2+ (1 mM), and tetraethylammonium (20 mM), 4-AP also blocked ACh-mediated relaxation in muscles contracted with elevated external K+. Relaxation of 5-hydroxytryptamine-induced contraction by sodium nitroprusside, or by addition of K+ to K(+)-deprived muscle, was not affected by 4-AP. Relaxation of basilar artery with acidified sodium nitrite solution (containing nitric oxide) was reduced by 4-AP. These results suggest that 4-AP and possibly Ba2+ inhibit acetylcholine-induced endothelium-dependent relaxation by inhibition of the action of EDRF on the smooth muscle rather than through inhibition of release of EDRF. The increase in K+ conductance involved in acetylcholine-induced relaxation is not due to ATP-inhibited K+ channels, as it is not blocked by glyburide (10(-6) M). Endothelium-derived relaxant factor(s) may relax smooth muscle by mode(s) of action different from that of sodium nitroprusside or by hyperpolarization due to the electrogenic sodium pumping.(ABSTRACT TRUNCATED AT 250 WORDS)

4-Aminopyridine↗
PubMed1991

[Effects of cyclosporine A on insulin content and insulin release in neonatal rat islet cell monolayer cultures].

We investigated the effects of cyclosporine A (CsA) on insulin content and insulin release in neonatal rat islet cell monolayer cultures. Insulin content in 5.5-day-old monolayers was not affected after 12-hour incubation in the medium containing 16.7 mmol/L glucose plus 0.1 or 100 micrograms/ml CsA and 5.6 mmol/L glucose plus 10 micrograms/ml CsA. Insulin release in 7.5-day-old monolayers was inhibited after 12-hour incubation in the medium containing 5.6 or 16.7 mmol/L glucose plus 0.01-100 micrograms/ml CsA in a dose-responsive manner. At 16.7 mmol/L glucose, CsA less than or equal to 0.1 microgram/ml did not affect insulin release, while CsA greater than or equal to 1.0 microgram/ml significantly inhibited insulin release and the inhibitory effect did not return to normal after a 16-hour incubation in CsA-free medium. At 5.6 mmol/L glucose, CsA 1.0 microgram/ml did not affect insulin release. CsA 100 micrograms/ml inhibited insulin release less than it did at 16.7 mmol/L glucose. These experimental data demonstrated that high doses of CsA have inhibitory effects on insulin release in islet monolayer cultures.

Animals↗
PubMed1990

[Genotoxic effect of cigarette smoke condensate on human diploid cell 2BS strain].

A higher sister chromatid exchange (SCE) frequency (17.0/cell) was observed in 2BS cells treated with cigarette smoke condensate (CSC) at 100 micrograms/ml, as compared with 6.9/cell of the background (P less than 0.01). Chromosomal aberration was significantly increased from 4% to 36% in cells treated with 10 micrograms/ml CSC (P less than 0.001). Micronuclei rate varied with CSC from 4 to 26%. There was a dose-effect response between SCE frequency, chromosomal aberration, micronuclei rate and the dose of CSC. The cell-cycle of 2BS cells was markedly delayed by CSC.

Cell Cycle↗
PubMed1989

Protease/inhibitor mechanisms involved in ATP-dependent proteolysis.

ATP-dependent proteolytic activities constitute a family of distinct enzymes and enzyme complexes which function in the selective degradation of proteins in the cytosol and possibly other non-lysosomal cellular compartments. In reticulocytes as well as other eukaryotic cells, conjugation of the polypeptide ubiquitin to proteins, an ATP-requiring process, is important for proteolysis. However, the popular view that ubiquitin functions by tagging substrates for recognition by conjugate-specific proteases should be viewed with caution. Evidence is reviewed implicating an ATP-independent high molecular weight protease (HMP) which can degrade non-ubiquitinated proteins in the ATP-dependent pathway. This protease consists of several related subunits based upon monoclonal antibody studies. HMP by itself, can account for effects of substrate amino group blockage on ATP-dependent proteolysis. Endogenous inhibitors (40 kDa and 50 kDa) have been isolated and shown to block HMP non-competitively. Unlike the soluble system in reticulocytes, the major ATP-dependent activity in mouse erythroleukemia cells is particulate in aqueous media but soluble in the presence of sucrose. Despite such differences, evidence suggests analogous inhibitory components in this system. The possibility that protease/inhibitor interaction is regulated by ATP and ubiquitin in different systems is discussed.

Adenosine Triphosphate↗
PubMed1989

[Effect of cigarette smoke condensate on unscheduled DNA synthesis (UDS) in human lung fibroblast cells].

The effect of cigarette smoke condensate (CSC) on UDS in human lung fibroblast cells (2BS) was studied. The results showed that CSC induced a marked increase in UDS of 2BS cells in a dose-dependent manner. 3H/14C ratio was 1.77 +/- 0.34 at a dose of 125 micrograms/ml of CSC as compared with 1.33 +/- 0.04 of the control. Catalase, at doses of 40, 60 units/ml, could significantly inhibit UDS induced by CSC (75 micrograms/ml), but after inactivation catalase had no effect. It is suggested that the increase in UDS is due to free radicals generated from CSC.

Catalase↗
PubMed1987

[Sister chromatid exchanges (SCE), chromosomal aberrations and micronuclei of cultured peripheral lymphocytes in patients with lung cancer, miners and non-mining workers of the tin mine in Yunnan].

Determination of SCE frequency, chromosomal aberration and micronucleus rate of cultured peripheral lymphocytes in 32 patients with lung cancer, 33 miners and 40 non-mining workers in Yunnan Tin Mine was carried out. The results showed that the cancer patients had higher SCE incidence, chromosomal aberration and micronucleus rate, the non-mining workers had the least and miners on an intermediate level. There was a significant difference of SCE, chromosomal aberrations and micronucleus rate between patients and non-mining workers (P less than 0.05-0.01). We also found that miners had a significant higher SCE and chromosomal aberration rate but not micronucleus rate as compared with the non-mining workers. We proposed that some carcinogens present in the Yunnan Tin Mine be responsible for the genetic damages in the miners. Chemical drugs may be considered to contribute to the genetic damage in cancer patients who had a tendency toward an increased SCE, chromosomal aberration and micronucleus rate as compared to the miners, though without reaching a statistical significance. We suggested that combination assay of SCE with chromosomal aberration or micronucleus be an useful index for screening of the high risk population and monitoring the chemical drug prevention of lung cancers in Yunnan Tin Mine.

Cells, Cultured↗
PubMedDate not supplied

Three-dimensional localisation of fluorescence resonance energy transfer in living cells under two-photon excitation.

Three-dimensional (3-D) imaging of fluorescence resonance energy transfer (FRET) in human cells under two-photon excitation was demonstrated in this study. A sample was prepared by expressing a donor and an acceptor in living cells and using an antibody to secure the proximity of contact between the donor and the acceptor. The quenching of fluorescence emission of a donor in the double-labelled cells indicates the presence of FRET that occurred in these living cells. Because of the quadratic relation of the excitation power, 3-D localisation of FRET becomes possible.

Animals↗
PubMedDate not supplied

Pap smears in women with endometrial carcinoma.

OBJECTIVE: To correlate Pap smear findings with the histology of endometrial carcinoma and stage of the disease. STUDY DESIGN: Between 1995 and 1998, 76 women with endometrial carcinoma, having had Pap smears done within two to three months of hysterectomy at Memorial Sloan-Kettering Cancer Center, formed the basis for this study. All Pap smears and histologic sections were reviewed. RESULTS: Thirty-four patients had normal Pap smears (45%), and 42 had abnormal ones (55%). The mean age of the two groups was 65.1 and 65.2 years, respectively. Histologic subtypes included 44 International Federation of Gynecology and Obstetrics (FIGO) grade 1 endometrioid adenocarcinoma (low grade) and 32 high grade carcinomas, including 19 FIGO grade 2 or 3 endometrioid adenocarcinomas, 5 papillary serous carcinomas (PSC), 2 clear cell carcinomas (CC), 1 adenosquamous carcinoma, 3 endometrioid adenocarcinomas mixed with PSC and 2 endometrioid adenocarcinomas mixed with CC. The proportions of patients with low and high grade tumors with abnormal Pap smears were 43% (19/44) and 72% (23/32), respectively (P=.01). The proportions of patients with abnormal Pap smears and no myometrial invasion, invasion of <50% and >50% myometrial thickness were 40% (8/20), 62% (26/42) and 57% (8/14), respectively (P =.27). Vascular invasion was identified in 56% (9/16) of patients with abnormal Pap smears and in 55% (33/60) of patients with normal ones (P = .93). The proportions of patients having abnormal Pap smears with stage I and stages II, III or IV disease were 48% (30/62) and 86% (12/14), respectively (P =.01). CONCLUSION: Although the Pap smear is not a sensitive screening test for endometrial cancer and a negative Pap smear does not rule it out, this study revealed that abnormal Pap smears are significantly associated with high grade of tumor and stage II-IV endometrial carcinoma. However, they are not associated with patient age, depth of myometrial invasion or vascular invasion.

Adenocarcinoma↗
PubMedDate not supplied

Peritoneal washings in endometrial carcinoma. A study of 298 patients with histopathologic correlation.

OBJECTIVE: To correlate findings of peritoneal washings in patients with endometrial carcinoma with histologic parameters. STUDY DESIGN: Between 1995 and 1998, 298 women with endometrial carcinoma were treated by hysterectomy with intraoperative peritoneal washings (PW) at Memorial Sloan-Kettering Cancer Center. All cytology and pathology slides were available for review. Pathologic parameters of hysterectomy specimens were evaluated and correlated with the findings of PW. RESULTS: Thirty-two patients (10.7%) had abnormal PW. Two hundred sixty-two had endometrioid adenocarcinoma; 26 of them had abnormal PW (10.0%). Thirty-six patients had other histologic subtypes (papillary serous carcinoma, clear cell carcinoma and adenosquamous carcinoma), and six of them had abnormal PW (16.7%). The incidence of abnormal PW in the two groups was not significantly different (P = .78). Among 26 patients with endometrioid adenocarcinoma and abnormal PW, there were 17 cases (9.9%) of International Federation of Gynecology and Obstetrics (FIGO) grade 1, 7 (12.7%) of grade 2 and 2 (5.7%) of grade 3 (P = .56). Ten cases (14.9%) had no myometrial invasion, 10 (7.0%) had myometrial invasion of < or = 50% of myometrial thickness, and 6 (11.5%) had invasion of > 50% of myometrial thickness (P = .18). Vascular invasion was present in 8 cases (14.8%) and absent from 17 (8.2%) (P = .14). Eighteen patients (7.6%) had stage I/II disease, and eight patients (30.8%) had stage III/IV disease (P = .001). Among 298 patients, cervicovaginal smears performed before surgery were available for review in 76. Five of the 7 patients (71.4%) with abnormal PW and 37 of the 69 patients (53.6%) with normal PW had abnormal Pap smears (P = .45). CONCLUSION: Abnormal PW did not correlate with histologic subtypes, FIGO grade, depth of myometrial invasion, vascular invasion or abnormal Pap smears. A significantly higher incidence of abnormal PW was associated with stage III/IV disease.

Adult↗