Gene therapy for human hepatocellular carcinoma with cytosine deaminase gene and prodrug flucytosine

AIM

To investigate the antitumor effects of cytosine deaminase (CD) gene in combination with prodrug flucytosine (Flu, 5-fluorocytosine) on human hepatocellular carcinoma.

METHODS

CD gene was transduced into human hepatocellular carcinoma cell line SMMC7721 with retroviral method and the cytotoxicity of Flu on the tumor cells was assayed in vitro with clonogenic techniques. The xenograft tumor model in nude mice was used to study in vivo therapeutic effects of CD gene/Flu system against human hepatocellular carcinoma.

RESULTS

CD gene/Flu system had significant antitumor activities on human hepatocellular carcinoma cells in vitro and in nude mice. The antitumor activities of Flu 500 mg.kg-1 on hepatocellular carcinoma xenografts in nude mice were more potent than those of 5-fluouracil 10 mg.kg-1. CD gene/Flu system possessed bystander killing effects on hepatocellular carcinoma xenografts in nude mice.

CONCLUSION

The experiment demonstrates the potential value of the CD gene/Flu system in the treatment of human hepatocellular carcinoma.

Quercetin decreased heart rate and cardiomyocyte Ca2+ oscillation frequency in rats and prevented cardiac hypertrophy in mice

AIM

To study the effects of quercetin (Que) on myocardial excitation-contraction coupling and cardiac remodeling.

METHODS

Left ventricles and femoral arteries of rats were cannulated for hemodynamic recording. Mouse cardiac hypertrophy was induced by abdominal aortic coarctation (AAC). Cultured myocardial cells in neonatal rats were loaded with Fura 2-AM. The intracellular calcium ([Ca2+]i) and spontaneous [Ca2+]i oscillations ([Ca2+]i-SO) were tested by AR-CM-MIC cation measurement system.

RESULTS

Que 3 or 25 mg.kg-1 i.v. in rats decreased heart rate from (420 +/- 19) to (390 +/- 15) and (314 +/- 18) beat.min-1, respectively, companied with very modest changes in both left ventricular pressures (LVP) and its differential dpLV/dtmax. Que 10, 50, 250 mumol.L-1 concentration-dependently slowed the frequency of [Ca2+]i-SO in cultured myocardial cells from (26 +/- 4) to (25 +/- 3), (18 +/- 4), and (12 +/- 3) time.min-1, respectively, but did not change their resting [Ca2+]i or amplitudes of [Ca2+]i-SO. Similarly, the increases in frequency of [Ca2+]i-SO caused by either isoproterenol (Iso) or ouabain (Oua) were prevented by Que 100 mumol.L-1, while the simultaneous increases in amplitude of [Ca2+]i-SO remained. Besides, [Ca2+]i rises excited by angiotensin II (Ang II) but not high [K+]o were prevented by Que 100 mumol.L-1. Daily administration of Que 120 mg.kg-1 i.g. for 5 d markedly prevented the cardiac hypertrophy in AAC mice, without effects on the ventricular mass to body weight ratio (VM/BW) in sham-operated mice.

CONCLUSION

Que decreased myocardial [Ca2+]i-oscillation frequency and prevented cardiac remodeling, but had no direct effect on cardiac excitation-contraction coupling.

Antianginal effects of ranolazine in various experimental models of angina

The effects of ranolazine (CAS 95635-55-5, KEG-1295), a novel antianginal drug, on the ST-segment changes induced by coronary ligation, epinephrine, and vasopressin were examined following oral or intraduodenal administration. In anesthetized dogs, intraduodenal administration of KEG-1295 (10, 30, or 50 mg/kg) or atenolol (10 mg/kg) significantly attenuated the ST-T wave elevation induced by 2-min coronary ligation imposed during electrical heart pacing (200 beats/min). This antianginal effect of KEG-1295 persisted for 3 h without any changes in hemodynamic parameters, while that of atenolol was accompanied by more or less maintained decreases in diastolic blood pressure, heart rate, and the maximum first derivative of left ventricular pressure. In anesthetized rats, oral administration of KEG-1295 (10, 30, or 50 mg/kg) attenuated the ST-T wave elevation induced by epinephrine (0.3 microgram/kg i.v.) in a dose-dependent manner, although KEG-1295 (10 or 30 mg/kg p.o.) failed to attenuate the ST-segment depression induced by vasopressin (0.2 IU/kg i.v.). These findings suggest that, taken orally, KEG-1295 may exert potent protective effects against angina pectoris, except that caused by vasospasm. Further, KEG-1295 may be categorized as a new type of antianginal agent, without any primary hemodynamic effects.

Effects of dexamethasone on intracellular Ca2+ in its sensitive cells from neonatal mouse hippocampus and cultured cortical neurogliocytes

AIM

To investigate the effects of dexamethasone (Dex) on intracellular free calcium ([Ca2+]i) in the single neuron or neurogliocyte.

METHODS

Neonatal mouse hippocampal cells (NMHC) and cultured cortical neurogliocytes (CCN) were loaded with Fura 2-AM. The [Ca2+]i was measured with AR-CM-MIC-cation measurement system.

RESULTS

Most of freshly isolated NMHC exhibited a rapid and concentration-dependent [Ca2+]i increase after administration of Dex 40-200 mumol.L-1. Only 10% of NMHC showed their [Ca2+]i decreases in total 96 tested cells. Dex-triggered [Ca2+]i rise was prevented by incubating the cells with Mg(2+)-free solution and reduced by adding LaCl3. Suspended NMHC in Ca(2+)-free solution or pretreated cells with mifepristone or tetrodotoxin prevented the initial [Ca2+]i increases caused by Dex 40-90 mumol.L-1, but only diminished the later [Ca2+]i rises by Dex 200 mumol.L-1. About 50% of tested single CCN showed a rapid and concentration-related [Ca2+]i increase due to Dex 90-270 mumol.L-1 exposure. This effect was partially inhibited under extracellular Ca(2+)- or Mg(2+)-free and mifepristone pretreatment conditions.

CONCLUSION

Dex produces the rapid [Ca2+]i changes in both neurons and glia cells. Reactions among most cells include a Mg(2+)-dependent and glucocorticoid receptor-related extracellular Ca2+ influx and a high concentration of Dex-mediated intracellular Ca2+ release.

High-throughput screening for ligand-induced c-fos mRNA expression by branched DNA assay in Chinese hamster ovary cells

We have developed a generally useful screening assay for receptor agonists and antagonists in Chinese Hamster Ovary (CHO) cells. Three key features of the assay make it applicable to a broad range of receptors: (1) the use of CHO cells as host cells to overexpress receptors, (2) measurement of endogenous c-fos mRNA, which responds to a wide spectrum of stimuli, and (3) the use of branched chain DNA assay which is highly sensitive, quantifiable, amenable to high-throughput analysis, and easy to execute. The combination of these features provides a powerful means to screen rapidly for peptide and small molecule ligands for a variety of receptors. CHO cells overexpressing insulin receptor were used as a test system to compare conventional signaling assays with the high-throughput c-fos branched DNA assay.

Thioredoxin fusion/HIV-1 protease coexpression system for production of soluble human IL6 in E. coli cytoplasm

In this paper, thioredoxin (TRX) fusion expression system has been modified to produce soluble human IL6 (hIL6) without TRX moiety in E. coli cytoplasm. A novel TRX gene fusion vector was developed that contained at the 3'-end of TRX gene a short DNA sequences encoding a linker peptide '-GSGSGVSQNYPIVQHHHHHH-', serving not only as a specific HIV-1 protease site but also providing six contiguous histidine (His) residues to foreign proteins. The cDNA for hIL6 was cloned into this vector resulting in plasmid pTRX@HISIL6. The cDNA for the HIV-1 protease has been cloned into another compatible plasmid pHMM2, resulting in plasmid pHMM2-PR. Both plasmids were transformed into E. coli strain GI724, and when induced for expression of both proteins, the correct processing of TRX@HISIL6 was obtained, producing hIL6 with His6-tag at the N terminus named HISIL6. A fraction of HISIL6 was found in soluble form and could be purified to homogeneity by Ni-NTA Superflow and ion-exchange chromatography. The biological activity of purified HISIL6 was measured by MTT method in an IL-6-dependent cell line 7TD1 to be 2.1 x 10(8) unit/mg.

Effect of Coriaria lactone on cytosolic free calcium of cultured neurons from rat cerebral cortex

AIM

To study the effect of Coriaria lactone (CL) on cytosolic free calcium ([Ca2+]i) of cultured neurons from cerebral cortex.

METHODS

Primary neuron culture (14d) and AR-CM-MIC cation measurement system were used, the [Ca2+]i were measured. CL effect was observed by loading egtazic acid.

RESULTS

The [Ca2+]i of cultured neurons (99.4-103.4) nmol.L-1 was elevated concentration-dependently by CL (25-500) mumol.L-1 (P < 0.01). This effect disappeared after loading egtazic acid 5 mmol.L-1, but reappeared after adding CaCl2 to 1 mmol.L-1.

CONCLUSION

The [Ca2+]i of cultured neurons was elevated by CL, depending on extracellular Ca2+.

Electrochemical immunoassay based on catalytic conversion of substrate by labeled metal ion and polarographic detection of the product generated

In a new electrochemical immunoassay based on the conversion of a substrate catalyzed by a labeled metal ion and the polarographic detection of the product generated, metal copper ion was used to label model antigen human serum albumin through the bifunctional chelating agent diethylenetriaminepentaacetic acid. After heterogeneous competitive immunoreaction, the labeled copper ion was released or activated by acidification and chemically catalyzed the conversion of the substrate o-phenylenediamine to the electroactive product 2,3-diaminophenazine (DAP). The DAP was quantified using linear-potential scan polarography. The sensitivity of the proposed assay was 100 times higher than that of the previous methods based on direct detection of the metal ion labels. This immunoassay can be used to detect any protein of interest.

Naltrexone suppresses the rejection of cardiac tissue transplantation

The present study demonstrates the following: 1. Transplantation of cardiac tissue induces an inflammatory response that ultimately leads to the rejection of the tissue by the host within 9 days; 2. Treatment with the opiate antagonist, naltrexone, significantly increased the survival of the transplanted cardiac tissue to 13 days, suggesting the involvement of opioid signaling molecules in tissue rejection; 3. In further experiments it was demonstrated that in mixed lymphocyte populations from different mice, the DNA synthesis inhibitor, mitomycin C, reduced the lymphocyte proliferative response as did naltrexone; 4. Mice injected with naltrexone for 10 days and given concanavalin A exhibited a suppressed spleen lymphocyte proliferative response compared to controls. Taken together, these data suggest that endogenous opioid signals not only activate immunocytes, but also stimulate DNA synthesis.

[8-(N,N-diethylamino)-n-octyl-3,4,5-trimethoxybenzoate(TMB-8) reduced the elevation of [Ca2+]i induced by BHQ, NE and KCl in cultured single smooth muscle cells of the calf basilar artery]

The effect of 8-(N, N-diethylamino)-n-octyl-3,4,5-trimethoxybenzoate (TMB-8) on the elevation of [Ca2+]i induced by 2, 5-di (tert-butyl)-1, 4-benzohydroquinone (BHQ), norepinephrine (NE), KCl in cultured single smooth muscle cells of the calf basilar artery was studied by a system of measurement of AR-CM-MIC, using Fura-2/AM as a fluoresent indicator. In the presence of extracellular Ca2+ 1.3 mmol.L-1, the resting [Ca2+]i was not changed by TMB-8 (10, 30 and 100 mumol.L-1), but the elevation of [Ca2+]i induced by BHQ, NE and KCl were reduced by TMB-8 (30 mumol.L-1) significantly. In Ca2+ free Hank's solution containing EGTA 0.1 mmol.L-1, the resting [Ca2+]i was markedly reduced by TMB-8 (10, 30 and 100 mumol.L-1), and the increase of [Ca2+]i evoked by BHQ and NE was blocked completely by TMB-8 (30 mumol.L-1). The result suggested that TMB-8 inhibited the Ca2+ release from intracellular stores or increased the up-take of Ca2+ into sarcoplasmic reticulum and the inhibition of Ca(2+)-influx from extracellular site may be an indirect machanism.

3-Phosphohistidine cannot replace phosphotyrosine in high-affinity binding to phosphotyrosine binding or Src homology 2 domains

Posttranslational phosphorylation of proteins is an important event in many cellular processes. Phosphorylated tyrosine residues can serve as association sites for other proteins in signal transduction cascades of tyrosine kinase receptors. Formation of phosphohistidine residues in proteins has been found in eukaryotic and prokaryotic organisms. Furthermore, it has been suggested that phosphohistidine might substitute for phosphotyrosine in conferring high-affinity binding to proteins involved in signal transduction. We have analyzed the ability of 3-phosphohistidine to associate with the known phosphotyrosine-specific phosphotyrosine binding and src homology 2 protein domains. From our binding studies using synthetic peptides, we conclude that 3-phosphohistidine cannot replace phosphotyrosine in conferring high-affinity binding to the phosphotyrosine binding domain of shc or the src homology 2 domain of phospholipase C-gamma1.

Effects of praeruptorine C on the intracellular free calcium in normal and hypertrophied rat ventricular myocytes

AIM

To study the intracellular free calcium ([Ca2+]i) in normal and hypertrophic left ventricular myocytes isolated from adult rat hearts and the effects of praeruptorine C (Pra-C) on them.

METHODS

[Ca2+]i of single myocyte was measured with Fura 2-AM.

RESULTS

The resting [Ca2+]i was 87 +/- 4 nmol.L-1 in normal left ventricular myocytes, 123 +/- 7 nmol.L-1 in hypertrophied myocytes. After exposure to KCl (20, 40, and 60 mmol.L-1), the [Ca2+]i were increased by 66%, 141%, and 268% in normal myocytes, and 77%, 185%, and 243% in hypertrophic myocytes, respectively. Pra-C (1, 10, and 100 mumol.L-1) concentration-dependently inhibited the [Ca2+]i elevation caused by KCl (35 mmol.L-1) or norepinephrine (20 mumol.L-1) in both normal and hypertrophied myocytes. All of the effects of Pra-C were similar to that of nifedipine.

CONCLUSION

[Ca2+]i of hypertrophied myocytes was higher than that of normal ones and Pra-C decrease the [Ca2+]i elevation in left ventricular myocytes resulted from its calcium channel blockade.

5-Hydroxytryptamine-induced endothelium-dependent and -independent relaxations in isolated dog anterior spinal small arteries

The mode of action of 5-hydroxytryptamine (5HT) was investigated in isolated dog anterior spinal small arteries. Lower concentrations of 5HT (10(-9)-10(-7) M) caused a dose-dependent contraction and higher concentrations (10(-6)-10(-3) M) produced a dose-dependent relaxation of the arteries precontracted by 10(-7) M U 46619. The 5HT-induced relaxation was significantly antagonized by methiothepin (10(-9)-10(-6) M). Ketanserin (10(-6) M) and ICS 205-930 (3 x 10(-6) M) did not affect the 5HT-induced relaxation of the arteries. The relaxant response to 5HT was reduced significantly by mechanical rubbing of the endothelial cells. The 5HT-induced endothelium-independent relaxation was also antagonized significantly by methiothepin (10(-6) M). Aspirin (5 x 10(-5) M) or N omega-nitro-L-arginine methyl ester (L-NAME) (10(-6) M) significantly suppressed the 5HT-induced endothelium-dependent relaxation. L-Arginine (10(-3) M) also significantly reversed the L-NAME induced reduction of the 5HT-induced endothelium-dependent relaxation. Treatment with L-NAME in the presence of aspirin also produced much greater reduction of the 5HT-induced endothelium-dependent relaxation. Isocarbacyclin (10(-9)-10(-5) M) induced a concentration-dependent relaxation of the isolated spinal small arteries precontracted by 10(-7) M U 46619. These results suggest that 5HT induces endothelium-dependent and -independent relaxations of the isolated anterior spinal small arteries mainly via activation of 5HT1-like receptor and that endogenous nitric oxide and vasodilative prostaglandins may contribute to the 5HT-induced endothelium-dependent relaxation of the arteries.

Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance. The Da Qing IGT and Diabetes Study

OBJECTIVE

Individuals with impaired glucose tolerance (IGT) have a high risk of developing NIDDM. The purpose of this study was to determine whether diet and exercise interventions in those with IGT may delay the development of NIDDM, i.e., reduce the incidence of NIDDM, and thereby reduce the overall incidence of diabetic complications, such as cardiovascular, renal, and retinal disease, and the excess mortality attributable to these complications.

RESEARCH DESIGN AND METHODS

In 1986, 110,660 men and women from 33 health care clinics in the city of Da Qing, China, were screened for IGT and NIDDM. Of these individuals, 577 were classified (using World Health Organization criteria) as having IGT. Subjects were randomized by clinic into a clinical trial, either to a control group or to one of three active treatment groups: diet only, exercise only, or diet plus exercise. Follow-up evaluation examinations were conducted at 2-year intervals over a 6-year period to identify subjects who developed NIDDM. Cox's proportional hazard analysis was used to determine if the incidence of NIDDM varied by treatment assignment.

RESULTS

The cumulative incidence of diabetes at 6 years was 67.7% (95% CI, 59.8-75.2) in the control group compared with 43.8% (95% CI, 35.5-52.3) in the diet group, 41.1% (95% CI, 33.4-49.4) in the exercise group, and 46.0% (95% CI, 37.3-54.7) in the diet-plus-exercise group (P < 0.05). When analyzed by clinic, each of the active intervention groups differed significantly from the control clinics (P < 0.05). The relative decrease in rate of development of diabetes in the active treatment groups was similar when subjects were stratified as lean or overweight (BMI < or > or = 25 kg/m2). In a proportional hazards analysis adjusted for differences in baseline BMI and fasting glucose, the diet, exercise, and diet-plus-exercise interventions were associated with 31% (P < 0.03), 46% (P < 0.0005), and 42% (P < 0.005) reductions in risk of developing diabetes, respectively.

CONCLUSIONS

Diet and/or exercise interventions led to a significant decrease in the incidence of diabetes over a 6-year period among those with IGT.

Effect of praeruptorin C on spontaneous [Ca2+]i transients in cultured myocardial cells of neonatal rats

AIMS

To study the effects of praeruptorin C (Pra-C) on [Ca2+]i transients in cultured neonatal myocardiocytes.

METHOD

Using Ca(2+)-sensitive fluorescent indicator, Fura 2-AM, spontaneous cytosolic Ca2+ transients were measured in cultured myocardial cells of neonatal rats.

RESULTS

Pra-C 10, 30 mumol.L-1 caused a decrease in the peak of Ca2+ transients. Pra-C 30 mumol.L-1 and 10-30 mumol.L-1 inhibited partly the stimulatory effects of CaCl2 4.8 mmol.L-1 and Bay k 8644 100 nmol.L-1 on peak Ca2+ transients, respectively. Pra-C did not cause any marked change in the basal [Ca2+]i level between beats. Pra-C inhibited the reduced [Ca2+]i transients after inhibition of sarcoplasmic reticulum Ca2+ release in ryanodine pretreated cells.

CONCLUSIONS

Pra-C inferred with the Ca2+ influx responsible for excitation-contraction coupling in myocardiocytes.

[Risk and influential factors of female breast cancer among medical diagnostic X-ray workers in China]

To study whether prolonged or repeated low-dose ionizing radiation could induce female breast cancer, we analyzed the incidence and risk factors of breast cancer among female medical diagnostic X-ray workers in China by cohort study and case-control study nested in the cohort. The risk of breast cancer enhanced significantly than the control group. It occurred in those who engaged in X-ray work before 1960, those who have been worked more than 25 years and those who are exposed before age 30, however, the age of onset cancer did not advance. The significant risk factors are accumulative radiation dose of the breast, obesity and family history of breast cancer. In addition, interaction could exists between obesity, non-lactation history and occupational X-ray exposure.

Nerve growth factors prevent glutamate toxicity in cortical neuronal cultures

AIM

To determine if nerve growth factors (NGF) can protect against glutamate-induced cortical neuron damage.

METHODS

Neuron viability and lactate dehydrogenase (LDH) efflux in the bathing medium in primary cultures from 17-d-old mouse fetal cortex were measured to assay NGF effect. Imaging of the calcium indicator dye Fura-2 was used to measure the [Ca2+]i.

RESULTS

The LD50 for NGF-free glutamate was 0.2 mmol.L-1 (95% confidence limits 0-1.6 mmol.L-1). In the presence of NGF 60 micrograms.L-1, 59% of the neurons survived in glutamate 1.6 mmol.L-1. The protective effect afforded by NGF was maximal at 60 micrograms.L-1, at which it prevented the elevation in [Ca2+]i.

CONCLUSION

NGF protect cortical neurons against glutamate-induced toxicity via "stabilizing" [Ca2+]i level or suppression of the rise in [Ca2+]i.

[Correlation between ability of learning-memory and synaptosomal free [Ca2+]i in mice of different age]

In the present investigation, the behavior of learning and memory of 1-month and 6-month-old mice was studied by using Y-maze and one-trial passive avoidance response device. The synaptosomal free [Ca2+]i of four main brain regions (Hippocampus, Cerebral cortex, Cerebellum, Tectum of midbrain) of these mice were measured by fluorescent probe Ca2+ indicator Fura-2 and an AR-CM-MIC cation measurement system. The results showed that, in comparison with 1-month-old mice, the ability of discrimination learning and memory of 6-month-old ones were attenuated, and the synaptosomal free [Ca2+]i of hippocampus was increased.

[Building up of an animal model of conditioned immunosuppression and analysis of its possible mechanism]

In the present study, camphor odor and intraperitoneal (ip) injection of cyclophosphamide (CY) were used as conditional and unconditional stimulus, respectively, in mice. Mice were exposed to camphor odor for 1 h in their cage in a closed area followed by an ip injection of CY (75 mg.kg-1). This association trial session was repeated once on the next day. Delayed type hypersensitivity response (DTH) was induced as follows: six days after the second association trial session the mice were sensitized by smearing dinitrochlorobenezene (DNCB) on their abdominal skin. The mice were challenged by smearing DNCB on the left ear 5 days after the antigen sensitization. The left and right ears were removed 24 h after the challenge and weighed, the weight ratio of left/right ears was calculated for identification of the response. The ratio was 1.30 +/- 0.113 (+/- s, P < 0.001), indicating that the challenged ear was heavier than the other and DTH was induced. In the unconditioned response (UCR) group, CY (75 mg.kg-1) was given 24 h prior to the challenge and the ratio was 1.09 +/- 0.024 (P < 0.001) indicating that DTH was suppressed by unconditional stimulus (CY). In the conditioned response (CR) group mice were reexposed to camphor odor 24 h prior to the challenge and normal saline was injected instead of CY. The ratio was 1.13 +/- 0.074 (P < 0.001), indicating that DTH was also suppressed by conditional stimulus (camphor odor). These results show that a conditioned immunosuppressive response was induced. In the experiment, many other groups, including unconditioned response group, CYE group and camphor control group, were described in more details in the text. In order to further analyse the mechanisms of the conditioned response, the blood from the mice in CR group was obtained 6 h after reexposure to camphor odor and the serum was injected to normal mice 6 h prior to the challenge. DTH was found to be suppressed significantly when compared with the mice injected with normal serum. The conditioned serum was dialyzed against a membrane with a 10,000 molecular weight cut off. The suppressive activity of the conditioned serum disappeared, suggesting that the molecular weight of the suppressive element in the serum was probably less than 10,000 kDa.

Effects of tetrandrine on cytosolic free calcium in cultured rat myocardial cells

AIM

To study the effects of tetrandrine (Tet) on myocardium.

METHODS

Using Fura 2-AM and AR-CM-MIC cation measurement system, cytosolic free calcium ([Ca2+]i) was examined in cultured rat single myocardial cells.

RESULTS

The resting [Ca2+]i was 90 +/- 12 nmol.L-1 in the presence of Ca2+ 1.3 mmol.L-1 in Hanks' solution. Tet 1-100 mumol.L-1 had no effect on the resting [Ca2+]i, but 10-100 mumol.L-1 depressed the [Ca2+]i elevation when extracellular Ca2+ was 5 mmol.L-1. Tet 1-100 mumol.L-1 inhibited KC1 (30 and 60 mmol.L-1) induced [Ca2+]i elevation in a concentration-dependent manner, the IC50 value was 8.8 mumol.L-1 (95% confidence limits: 3.3-23.7 mumol.L-1) and 6.9 mumol.L-1 (95% confidence limits: 2.8-17.4 mumol.L-1), respectively. Norepinephrine (NE) 10 mumol.L-1 caused a rapid increase in [Ca2+]i in the presence or absence of extracellular Ca2+, Tet 30-100 mumol.L-1 only decreased the former. Tet 10-100 mumol.L-1 also decreased ouabain (Oua)-induced elevation in [Ca2+]i.

CONCLUSION

Tet had inhibitory effects on Ca2+ transmembrane movement, but it is not a selective calcium channel blocker in rat myocardial cells.

[The study on the mechanism of EGF inducing the in vitro meiotic maturation resumption of mouse oocytes]

The effect and mechanism of EGF and progesterone on the meiotic maturation resumption were studied. The results showed that progesterone regulated the action of EGF. The inhibitor of 3 beta-HSD, the key enzyme of progesterone synthesis, Epostane could not only prevent the effect of EGF, but inhibit the progesterone production promoted by EGF in cultured ovary granulosa cells as well. On the other hand, heparin could lessen the function of EGF and progesterone, which implies that calcium participated the effect of EGF and progesterone. Fura-2 was used to indicate the changes of intracellular calcium level in single cumulus cell. It is found that a calcium wave appeared in cumulus cell when EGF or progesterone acted. But Ca2+ level returned to normal immediately after progesterone was added, and Ca2+ in the cumulus cell still remained higher level after EGF acted. This results indicated that calcium in cumulus cell adjusted the action of EGF and progesterone.