[Intervention effects of drugs on GSH and SOD enzyme activity of rats kidney acutely poisoned by nickel carbonyl].

Objective: To evaluate the intervention effect of various drugs on glutathione (GSH) and superoxide dismutase (SOD) enzyme activity of rats kidney with acute nickel carbonyl poisoning. Methods: In January 2019, The 250 SPF male SD rats were randomly divided into normal control group (n=10) , poisoned group (n=40) and treatment groups (n=200) according to the random number table method. And the treatment groups were divided into methylprednisolone group (20 mg/kg) , DDC group (100 mg/kg) , sodium selenite group (10 µmol/kg) , Shenfu huiyang decoction group (0.25 ml) and methylprednisolone combined with DDC group (100 mg/kg) , with 40 mice in each group. Except for the normal control group, rats in the other groups were exposed to nickel carbonyl for 30 min, at 4 h and 30 h after exposure, the rats in each treatment group were intraperitoneally injected with corresponding drugs, and kidney tissues were collected 3 d and 7 d after administration, with 10 mice in each group. The activities of GSH and SOD in kidney were measured by enzyme-linked immunosorbent assay, and using electron microscopy observe ultrastructure changes. Results: Compared to the control group, the activities of GSH and SOD enzyme of poisoned group were significantly decreased at 3 d or 7 d after 4 h or 30 h exposure, and the difference was statistically significant (P=0.000, 0.031, 0.001, 0.033) , the epithelial nuclei of proximal convoluted tubules were pyknosis and lysosome hyperplasia in the cytoplasm. And compared to poisoned group, the activities of GSH and SOD enzyme of methylprednisolone+DDC group were significantly increased at treatment with 7 d after 4 h exposure, the difference was statistically significant (P=0.022, 0.000) , and the activities of GSH and SOD enzyme of methylprednisolone and enzyme of methylprednisolone+DDC group were significantly higher at 7 days than at 3 days, the difference was statistically significant (P=0.020, 0.017, 0.018, 0.033) . The results of electron microscopy showed that the cell nuclei and cytoplasmic organelles of proximal convolute tubule were almost restored to normal tissue level of both methylprednisolone group and methylprednisolone+DDC group. Conclusion: The methylprednisolone and methylprednisolone+DDC have obvious repair effect on renal enzyme activity level of rats with acute nickel carbonyl poisoning, and the treatment effect is better for a long time of medication.

[Clinical significance of combined sST2 and NT-proBNP detection for the short-term prognosis of acute organophosphorus pesticide poisoning].

Objective: To explore the value of soluble growth stimulation expression gene 2 protein (soluble suppression of tumorigenicity 2; sST2) and N terminal B type brain natriuretic peptide (N-terminal probrainnatriuretic peptide, NT-proBNP) in evaluating the short-term prognosis of acute organophosphorus pesticide poisoning. Methods: select 228 patients with acute organophosphorus pesticide poisoning in our hospital from October 2017 to March 2020. According to the grade of poisoning degree, it was divided into 82 cases in mild and moderate group and 146 cases in severe group. hs-cTnI、CK-MB、sST2、NT-proBNP、APACHE Ⅱ score and cholinesterase activity were detected 4 h、12 h、24 h after admission. ROC curve was used to evaluate sST2 and NT-proBNP to predict the prognosis of AOPP. Results: 4 hours after admission, there was no significant difference in the scores of hs-cTnI, APACHE Ⅱ, cholinesterase and CK-MB between the Severe Group and the mild and moderate Group (P<0.05) . At 12 and 24 hours after admission, the scores of hs-cTnI, CK-MB and APACHE Ⅱ in severe group were higher than those in mild and moderate group, and the changes of Cholinesterase were more significant than those in 12 hours after Admission (P<0.05) . 4 hours after admission, SST2 and NT-proBNP levels were significantly higher in severe group than those in mild and moderate Group (P<0.05) . The level of SST2 and NT-proBNP in the severe group was significantly higher than that in the mild and moderate group 12 and 24 hours after Admission (P<0.01) , and the level of SST2 and NT-proBNP was significantly higher than that in the mild group 12 hours after Admission (P<0.05) . Correlation analysis showed that 24 hours after admission, sST2, NT-proBNP were positively correlated with APACHE-Ⅱ scores (R=0.634, 0.723, P<0.01) . The area under sST2 combined with NT-proBNP was 0.891, higher than that under sST2 and NT-proBNP at 12 h after admission. The 24 h APACHE Ⅱ score after admission area under the curve was 0.838. Conclusion: sST2 and NT-proBNP combined detection can early predict the occurrence of recent complications in AOPP patients.

[Predictive value of early detection of hs-cTnI and sST2 for secondary cardiac damage in severe acute organophosphorus pesticide poisoning].

Objective: To investigate the value of high-sensitivity cardiac troponin I (hs-cTnI) and soluble suppression of tumorigenicity 2 (sST2) in predicting cardiac complications of severe acute organophosphorus pesticide poisoning (SAOPP) . Methods: All 274 SAOPP patients from September 2014 to February 2019 were selected. According to the results of hs-cTnI detection, the patients were divided into non-elevated troponin group (78 cases) and troponin elevation group (196 cases) at 1 hour after admission. 3 days after admission, there were 109 cases of complication and 165 cases of non-complication according to the presence or absence of cardiac complications. The changes of hs-cTnI, sST2, N-terminal B-type brain natriuretic peptide (NT proBNP) , acute physiology and chronic health (APACHE-Ⅱ) , cholinesterase activity, left ventricular ejection fraction (LVEF) , short axis shortening rate (FS) were observed and analyzed. The predictive value of hs-cTnI and sST2 were evaluated by receiver operating characteristic curve (ROC) analysis. Results: The sST2 level in patients with troponin elevation group was significantly higher than that in non-elevated troponin group (P<0.05) . Compared with the non-complication and non-elevated troponin group, the patients with non-complication and troponin elevation group had elevated hs-cTnI, sST2 and decreased cholinesterase (P<0.05) . Compared with other groups, the hs-cTnI, sST2, NT-proBNP, and APACHE-Ⅱ scores in the complication and troponin elevation group were significantly increased, and cholinesterase was significantly reduced (P<0.05) . In the non-complication group, LVEF and FS were in the normal range, and there was no significant difference between the groups (P>0.05) . Compared with other groups, the LVEF and FS of patients with elevated troponin in the complications group were significantly decreased (P<0.05) . Correlation analysis showed that hs-cTnI and sST2 were positively correlated in patients with SAOPP complications (r=0.725, P<0.01) . hs-cTnI, sST2 and APACHE-Ⅱ scores were positively correlated in the complications group (r=0.846, 0.885, P<0.01) . ROC results showed that the areas under the curve for predicting SAOPP secondary heart damage of hs-cTnI (1 hour after admission) and sST2 (3 days after admission) were 0.945 and 0.833, respectively. Conclusion: hs-cTnI and sST2 may have important clinical value in the early diagnosis and prognosis evaluation of patients with SAOPP secondary cardiac damage.

[Effects of Ginaton on nitric oxide and nitric oxide synthase in patients with delayed encephalopathy after carbon monoxide poisoning].

Objective: To observe the effects of Ginaton on blood nitric oxide (NO) and nitric oxide synthase (NOS) in patients with delayed encephalopathy after acute carbon monoxide poisoning (DEACMP). Methods: A total of 116 patients with DEACMP who were treated in Emergency Department of Harrison International Peace Hospital Affiliated to Hebei Medical University from January 2012 to April 2016 were enrolled and ran-domly divided into control group and treatment group using a random number table, with 58 patients in each group. The patients in the control group were given conventional treatment including hyperbaric oxygen, preven-tion and treatment of cerebral edema, and promotion of brain cell metabolism, and those in the treatment group were given Ginaton in addition to the conventional treatment. The course of treatment was 2 weeks for both groups. The levels of neuron-specific enolase (NSE) , NO, NOS, and inducible nitric oxide synthase (iNOS) were measured before treatment and at 2 weeks after treatment, and the change in Mini-Mental State Examina-tion (MMSE) score and clinical outcome were observed in both groups. The correlation between the blood NO level on admission and the MMSE score was analyzed. Results: There was a significant difference in the overall response rate between the treatment group and the control group (81.03% vs 62.07%, χ(2) = 5.124, P=0.024). Be-fore treatment, there were no significant differences in the levels of NO and NSE, the activity of NOS and iN-OS, and MMSE score between the two groups (P>0.05). After treatment, both groups showed reductions in the levels of NO and NSE and the activity of NOS and iNOS, but the treatment group had significantly greater reduc-tions compared with the control group (P<0.05). Both groups showed a significant increase in the MMSE score after treatment, while the treatment group had a significantly greater increase compared with the control group (P<0.05). In the patients with DEACMP, the blood NO level on admission was negatively correlated with the MMSE score (r=-0.268, P=0.004). Conclusion: In the treatment of patients with DEACMP, Ginaton can effectively reduce the levels of NO and NSE and the activity of NOS and iNOS, increase the MMSE score, and promote the recovery of neurological function.

[Effects of extract of Ginkgo biloba on magnetic resonance imaging and electroencephalography in patients with delayed encephalopathy after acute carbon monoxide poisoning].

Objective: To observe the effects of extract of Ginkgo biloba (Ginaton) on magnetic resonance imaging (MRI) and electroencephalography (EEG) in patients with delayed encephalopathy after acute carbon monoxide poisoning. Methods: The 84 patients with delayed encephalopathy after acute carbon monoxide poisoning treated in our hospital from Jan. 2011 to Apr. 2016 were randomly divied into therapy group and observation group. The therapy group received routine treatments of hyperbaric oxygen, cure cerebral edema and promote brain cell metabolism, and observation group was given intravenous injection (intravenous drip) Ginaton 70 mg (adding 0.9% sodium chloride injection 250 ml) , once a day, 2 weeks for one therapeutic course. The changes of MRI and EEG before and after treatment between therapy group and observation group were observed. Results: In the observation group, the white matter and globus pallidus lesions of 14 d after treatment were smaller than those in the treatment group, and the abnormal signal intensity was decreased. At 14 days after treatment the improvement of EEG in observation group were better than therapy group (P<0.05) . Conclusion: Early treatment of extract of Ginkgo biloba (Ginaton) in delayed encephalopathy after acute carbon monoxide poisoning can effectively improve lesion and signal on MRI and abnormal rate on EEG. It has a certain therapeutic effect in clinical.

Correlations among copeptin, ischemia-modified albumin, and the extent of myocardial injury in patients with acute carbon monoxide poisoning.

This study evaluated the relationships among copeptin, ischemia-modified albumin (IMA), and extent of myocardial injury in patients with acute carbon monoxide poisoning (ACOP). A total of 110 patients with different degrees of ACOP were selected as the poisoning group, and 30 healthy individuals as the control group. The levels of troponin I (cTnI), IMA, and copeptin were detected. Based on the presence of complications, the patients were assigned to the complication (26 patients) or non-complication (84 patients) group. Levels of cTnI, IMA, and copeptin were compared among the control, complication, and non-complication groups. Compared with the control group, in the 2 h after admission, the IMA levels decreased and copeptin levels increased in the poisoning group; these changes were more significant in patients with severe ACOP than in those with mild ACOP, and the difference was statistically significant (P < 0.05). There were no differences in the IMA and copeptin levels between the groups 7 days after admission; the cTnI levels increased more significantly in patients with severe ACOP than in patients with mild and moderate ACOP, and the differences were statistically significant (P < 0.05). In the complication group, at 7 days after admission, the IMA levels decreased whereas the copeptin and cTnI levels were significantly higher than in the non-complication group, with a statistically significant difference (P < 0.05). IMA was negatively correlated with copeptin. IMA and copeptin detection is clinically useful in the early diagnosis and prognosis of ACOP-related myocardial injury and in guiding early clinical drug application.

Evaluation of the overall impact of antibiotics growth promoters on broiler health and productivity during the medication and withdrawal period.

The effectiveness of some common combination of antibiotic growth promoters (AGP) on growth performance, gut health, and meat quality was evaluated during the medication and withdrawal period in broilers. A total of 540 male Arbor Acre broilers at 0 D of age were randomly assigned to 5 treatments, with 6 replicates of 18 chicks. Broilers received diets during the medication period (0 to 42 D) as follows: NC (control diet without AGP), EN (NC + enduracidin 8 ppm + colistin sulfate 8 ppm), BZ (NC + bacitracin zinc 40 ppm + colistin sulfate 8 ppm), CT (NC + chlortetracycline 50 ppm + colistin sulfate 8 ppm), and VG (NC + virginiamycin 20 ppm + colistin sulfate 8 ppm). Broilers were switched to the same finisher diet without AGP during the withdrawal period (43 to 49 D). The feed:gain ratio in EN, BZ, CT, and VG groups were significantly decreased by 0.07, 0.10, 0.06, and 0.05 during 0 to 42 D (P < 0.05), but increased by 0.19 (P > 0.05), 0.33 (P > 0.05), 0.49 (P < 0.05), and 0.69 (P < 0.05) during the withdrawal period, respectively. The jejunum villus height (VH) increased in EN group (P < 0.05) and crypt depth (CD) reduced in BZ, CT, and VG groups (P < 0.05) at 42 D, while jejunum VH increased in EN and BZ groups (P < 0.05) at 49 D compared to NC group (P < 0.05). Meat quality detection at 49 D found all AGP groups with the higher cook loss of the breast muscle, while CT group with the higher cook loss of thigh muscle. Consequently, the overall effects of 4 AGP combinations in the whole period were not significant on growth performance. Their poor growth performance during the withdrawal period should be partly attributed to the falling off a cliff of most digestive enzyme activities from 42 to 49 D. Attention should be paid to the adverse effects of AGP supplementation on meat quality, especially cook loss.

Influence of acidified drinking water on growth performance and gastrointestinal function of broilers.

The ban on the use of antibiotic feed additives as growth promoters compelled the researchers for exploring the future utility of other alternatives. This experiment was designed to evaluate the effect of acidified drinking water on growth performance, gastrointestinal pH, digestive enzymes, intestinal histomorphology, and cecum microbial counting of the broiler chicken. A total of 540 one-day-old male broilers (Arbor Acre) were randomly assigned to 5 treatments, with 6 replicates of 18 chicks per replicate. Broilers received diets and water as follows: NC (negative control, basal diet, normal water), PC (positive control, basal diet + 8 ppm colistin sulfate + 8 ppm enduracidin, normal water), A1 (basal diet, continuous supply of acidified water during whole experiment period), A2 (basal diet, intermittent acidification of water during 0 to 14 d, 22 to 28 d, and 36 to 42 d), and A3 [basal diet, intermittent acidification of water (24 h/d from 0 to 14 d and from 10:00 am to 4:00 pm on d 15 to 42)]. During the entire period, the acidified groups (A1, A2, and A3) and PC group showed improve on weight gain, average daily gain and feed conversion ratio compared to NC group (P < 0.05). The pH in crop, proventriculus and ileum at 43 d declined by 0.04, 1.03, 1.23; 0.55, 0.69, 0.70; and 0.63, 0.74, 1.21 in A1, A2, and A3 group, respectively. There was a significant decline of lipase activity in the PC and acidified groups compared to NC group. The A2 group had higher villus height in jejunum than NC group. The PC and acidified groups reduced (P < 0.05) the total aerobic bacteria count of cecum when contrasted to NC group. Therefore, we conclude that acidified drinking water can improve growth performance, compensate for gastric acidity, and control pathogenic bacteria in broilers and may be considered as a potential alternative to improve production parameters. Discontinuous supply of acidified water had the same or even better influence on broilers compared to continuous supply.

Efficacy assessment of phenobarbital in epilepsy: a large community-based intervention trial in rural China.

BACKGROUND: Many people with epilepsy need not experience further seizures if the diagnosis and treatment are correct. Most epilepsy patients have convulsions, which are usually fairly easy to diagnose. This study tested a model for treatment of people with convulsive forms of epilepsy at primary health-care level in rural areas of China. METHODS: Patients with convulsive epilepsy were identified at primary care level and provided with phenobarbital monotherapy. Local physicians, who were provided with special training, carried out screening, treatment, and follow-up. A local neurologist confirmed the diagnoses. Efficacy was assessed from the percentage reduction in seizure frequency from baseline and the retention of patients on treatment. FINDINGS: The study enrolled 2455 patients. In 68% of patients who completed 12 months' treatment, seizure frequency was decreased by at least 50%, and a third of patients were seizure free. 72% of patients who completed 24 months' treatment had reduction of seizure frequency of at least 50% and a quarter of patients remained seizure free. Probability of retention was 0.84 at 1 year, and 0.76 at 2 years. Medication was well tolerated and reported adverse events were mild; only 32 patients (1%) discontinued medication because of side-effects. INTERPRETATION: This pragmatic study confirmed that this simple protocol was suitable for the treatment of convulsive forms of epilepsy in rural areas of China. Physicians with basic training could treat epilepsy patients with phenobarbital, with beneficial effects for most patients with convulsive seizures. Few cognitive or behavioural adverse events were noted, but formal psychometric testing was not done.

Ribosomal RNA turnover and the level of ribonuclease activity in the liver of the pregnant rat.

Studies were undertaken on the turnover of ribosomal RNA and on ribonuclease activity in the liver of the pregnant rat in an attempt to explain the accumulation of liver RNA which occurs during the latter half of pregnancy. Between the 15th and 20th day of gestation the rate constant of degradation, biological half-life and daily rate of synthesis of ribosomal RNA were calculated to be 0.0887, 7.81 days and 6.21 mg per liver per 100g body weight respectively. Corresponding values in non-pregnant rats were 0.123, 5.68 days and 3.47 mg per liver per 100g body weight. The increase in RNA was therefore associated with an increase in its rate of synthesis and a decrease in its rate of breakdown. From the 14th day of pregnancy there was a decrease in alkaline ribonuclease activity and a marked increase in the level of alkaline ribonuclease inhibitor. The activity of acid ribonuclease was found to increase and that of acid phosphatase to decrease during this period.

Progesterone-induced phospholipid N-methylation and sphingomyelin synthesis in the amphibian oocyte plasma membrane: a second source of the 1,2-diacylglycerol second messenger associated with the G2/M transition.

The effects of progesterone and GTP gamma S on phospholipid N-methylation and sphingomyelin synthesis were studied in plasma-vitelline membranes isolated from amphibian (Rana pipiens) oocytes. Plasma-vitelline membranes were preincubated with S-adenosyl-L-[methyl-3H]methionine for 2 min at 20 degrees C and total phospholipids extracted at 0, 15, 30 and 60 s after addition of progesterone and/or GTP gamma S. Progesterone levels (3 microM) that induce meiosis in the intact oocyte stimulated [3H-methyl]incorporation into phosphatidylmonomethylethanolamine (PME) 9-10-fold over the first 60 s, with smaller increases in phosphatidyldimethylethanolamine (PDE) and phosphatidylcholine (PC). [methyl-3H] labeling of sphingomyelin (SM) rises after 30 s, approaching that of [methyl-3H]PME by 60 s. 17 beta-Estradiol, a noninducer of meiosis, was inactive. When oocytes were prelabeled with [3H]palmitic acid, it was found that a fall in [3H]ceramide coincides with the transient increase in [3H]SM, indicating that the end product of N-methylation (PC) undergoes a transfer reaction with ceramide to form SM and 1,2-DG. GTP gamma S levels previously reported to stimulate PC-specific phospholipase C activity in oocyte plasma membranes (5 microM) also stimulated both [methyl-3H]PME and [methyl-3H]SM formation. An inhibitor of phospholipid N-methylation, 2-(methyl-amino)ethanol, blocked stimulation of [methyl-3H]SM synthesis by both progesterone and GTP gamma S as well as induction of meiosis by progesterone. Progesterone thus acts at the oocyte plasma membrane to stimulate PE N-methyltransferase and SM synthase. The finding that GTP gamma S mimics progesterone suggests that N-methyltransferase is mediated by G-protein(s). The transient increase in 1,2-DG which we had previously reported to occur within 1-2 min following progesterone stimulation of the Rana oocyte appears to arise from PC by two different pathways: SM synthesis and hydrolysis of PC by phospholipase C.

Progesterone triggers the rapid activation of phospholipase D in the amphibian oocyte plasma membrane when initiating the G2/M transition.

Previous reports indicate that, in the Rana pipiens oocyte, progesterone triggers a rapid rise in 1,2-diacylglycerol (DAG) derived from phosphatidylcholine (PC) in the plasma membranes. This DAG transient, which appears and is terminated within 60-90 s, is derived both from a phospholipase which we assumed to be phospholipase C and from sphingomyelin (SM) synthase. We now find that progesterone stimulates PC and DAG turnover primarily via the phospholipase D (PLD) and phosphatidic acid phosphohydrolase (PAP) pathways as well as via the SM-ceramide pathway. Rana oocytes were prelabeled with [3H]choline chloride under conditions in which about 70% is incorporated into PC of the plasma membrane of the intact oocyte or with [3H]lysoplatelet activating factor (1-O-octadecyl-sn-glycero-3-phosphocholine, lysoPAF) which is selectively incorporated into plasma membrane PC. Progesterone induced the release of [3H]choline from intact oocytes into the medium within 60-90 s. This choline release was dose-dependent and was not inhibited by a putative PC-specific phospholipase C inhibitor, D609. Progesterone also induced a transient rise in [3H]lysoPAF-derived [3H]DAG within 1-2 min followed by a rise in [3H]PA. In the presence of 20 mM ethanol, progesterone stimulated formation of [3H]lysoPAF-derived phosphatidylethanol, indicating progesterone activation of PC-specific PLD and concomitant formation of PA. A DGK inhibitor (D102) reduced the level of [3H]PA, produced a sustained rise in [3H]DAG and was a weak inducer of meiosis in oocytes not exposed to progesterone. A PA phosphohydrolase inhibitor (propranolol) elevated [3H]PA and completely inhibited the progesterone-induced rise in DAG. Progesterone thus acts at oocyte plasma membrane receptors to release PC-derived DAG via both SM synthase and PC-PLD. The duration of the DAG signal is regulated by the coordinate action of DGK and PAP.

Metabolic actions of vasopressin, glucagon and adrenalin in the intact rat.

Metabolic effects of vasopressin, glucagan and adrenalin were compared, in intact rats, especially in regard to time courses of effects. Hyperglycaemia was transient in response to vasopressin, prolonged following adrenalin, and, suprisingly, was not discernible after glucagon, except in response to a very large dose. Vasopressin decreased and adrenalin increased, the plasma free fatty acid concentration; both hormones decreased the triacylglycerol level. Muscle glycogen concentrations, measured in heart, diaphragm and skeletal muscle, exhibited small changes, with complex time courses, following hormone administration. Vasopressin brought about a rapid but transient activation of heaptic glycogen phosphorylase which resembled that due to adrenalin. The activation by glucagon of phosphorylase was greater and more prolonged, despite the absence of hyperglycaemia. In response to vasopressin, there was in increase in plasma insulin. Incorporation of 14C from [14C]glucose into glycogen or fatty acids was not influenced by vasopressin. Taken together, these results may be explained by rapid metabolic action of vasopressin on hepatic glycogenolysis, whereas adrenalin has multiple prolonged actions.

Mg2+ modulates membrane lipids in vascular smooth muscle: a link to atherogenesis.

Epidemiological studies associate low dietary magnesium intake with an increased incidence of ischemic heart disease and sudden cardiac death. We have used proton-magnetic resonance (1H-NMR) techniques and Mg2+-selective electrodes to monitor changes in lipid extracts of aortic and cerebrovascular smooth muscle as extracellular ionized magnesium ion concentration ([Mg2+]o) is lowered. We have found that, within the pathophysiological range of Mg2+ concentrations, fatty acid chain length and double bond content are progressively reduced as [Mg2+]o is lowered. In contrast, the plasmalogen content is progressively increased. A concomitant decrease in fatty acid chain length and double bonds indicates oxidation of double bonds resulting in truncation of the fatty acids. A decrease in lipid oxidation in the presence of elevated Mg2+ could contribute to the apparent protective role of increased Mg2+ intake on vascular function in humans.

Mg2+ modulates membrane sphingolipid and lipid second messenger levels in vascular smooth muscle cells.

In vitro studies with smooth muscle cells from rat aorta and dog cerebral blood vessels indicate that variation in free Mg2+, within the pathophysiological range of Mg2+ concentrations, found in human serum, causes sustained changes in membrane phospholipids and lipid second messengers. Incorporation of [3H]palmitic acid into phosphatidylcholine (PC) and sphingomyelin (SM) was altered within 15-30 min after modifying the extracellular Mg2+ ion level ([Mg2+]o). Decreased Mg2+ produced a fall in both [3H]SM and [3H]PC over the first 2 h. After an 18-h incubation, the [3H]PC/[3H]SM ratio changed from about 20:1 to about 50:1. Increased [Mg2+]o resulted in a 2- to 3-fold increase in [3H]SM compared to only a small increase in [3H]PC over the same period. There was a reciprocal relationship between [3H]ceramide and [3H]1,2-DAG levels with highest [3H]ceramide and lowest [3H]-1,2-DAG levels seen at lowest [Mg2+]o. The results indicate that a fall in extracellular ionized Mg2+ concentration produces a rapid and sustained decrease in membrane sphingomyelin and a moderate rise in intracellular ceramide. A major effect of lowering [Mg2+]o appears to be a down-regulation of SM synthase. The increased membrane SM content and a concomitant decrease in cell ceramide, in the presence of elevated [Mg2+]o, may be relevant to the apparent protective role of adequate Mg intake on vascular function in humans.

Steroid action at the plasma membrane: progesterone stimulation of phosphatidylcholine-specific phospholipase C following release of the prophase block in amphibian oocytes.

Progesterone, acting at the amphibian oocyte plasma membrane, triggers the progression of the prophase oocyte nucleus through the first meiotic metaphase. We previously reported a transient increase in 1,2-diacylglycerol (1,2-DG) within the first 1-2 min after exposure of Rana pipiens oocytes to progesterone. We have now investigated the source of the 1,2-DG, using this highly synchronous oocyte population. Phospholipid pools of intact prophase-arrested oocytes were labeled with [3H]glycerol, [methyl-3H]choline chloride or 1-O-[3H]octadecyl-sn-glycero-3-phosphocholine (lyso platelet activating factor, lysoPAF). [3H]LysoPAF is selectively taken up into the plasma membrane of the intact oocyte and esterified to form the [3H]alkyl-analogue of phosphatidylcholine (PC). Intact oocytes and/or isolated plasma membranes were then stimulated with progesterone and the changes in [3H]DG, [methyl-3H]phosphocholine and [3H]phospholipids were monitored as a function of time. Progesterone induced a transient increase in [3H]glycerol-derived DG, [methyl-3H]phosphocholine and [3H]alkyl-2-acylglycerol from [3H]alkyl-PC within the first 2 min, indicating activation of a PC-specific phospholipase C. Different pulse-labeling conditions indicate a biphasic rise in [3H]DG from [3H]glycerol-labeled oocytes; the first rise (1-2 min) when phospholipid labeling in the plasma membrane is enriched followed by an approximately 3-fold larger rise at 5-15 min when phospholipids of intracellular membranes are preferentially labeled. An early transient increase in [3H]DG or [3H]alkyl-2-acylglycerol was also seen when progesterone and/or guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S) were added to isolated plasma-vitelline membranes prepared from oocytes prelabeled with either [3H]glycerol or [3H]lysoPAF. Progesterone thus appears to activate a G-protein-linked PC-specific phospholipase C in the oocyte plasma membrane which is followed by much larger DG release from intracellular membranes. The transient character of the hydrolysis suggests that this may represent a mechanism for transducing a membrane event into a meiotic signal.

The first product of phospholipid N-methylation, phosphatidylmonomethylethanolamine, is a lipid mediator for progesterone action at the amphibian oocyte plasma membrane.

Progesterone has been shown to act at plasma membrane receptors on the amphibian oocyte to trigger a cascade of changes in membrane phospholipids and to initiate the G(2)/M transition of the first meiotic division. The earliest event (0-1 min) is the transient N-methylation of phosphatidylethanolamine (PE) to form phosphatidylmonomethylethanolamine (PME), demonstrated using [(3)H]glycerol to prelabel oocyte plasma membrane PE. [(3)H]Glycerol-labeled PME rises 10-fold within the 1-2 min after exposure to progesterone and accounts for conversion of about 50% of the [3H]Glycerol-labeled PE. [(3)H]PME levels slowly decline over the following 10-30 min. [(3)H] or [(14)C] labeled fatty acid experiments showed that newly formed PME is enriched in linoleic or palmitic, but not in arachidonic acid, indicating that specific PE pools undergo progesterone-induced N-methylation. Two plasma membrane changes: activation of serine protease, and Ca(2+) release from the oocyte surface coincide with PME formation; both are prevented by pretreatment of oocytes with the N-methylation inhibitor, 2-methylaminoethane. Media containing PME micelles release both protease and Ca(2+) from intact oocytes within the first 1-2 min. The immediate downstream metabolites of PME, PDE and PC, do not induce serine protease activity or Ca(2+) release. We conclude that progesterone initially activates N-methyltransferase in the oocyte plasma membrane, and that the first product, PME, is responsible for activation of serine protease in the plasma membrane and the release of Ca(2+) from the oocyte surface.