Hypothermia decreases ethanol MAC in rats

Despite the known capacity of hypothermia to increase anesthetic potency (decrease the partial pressure required to produce anesthesia), many in vitro studies examine the effects of ethanol and other anesthetics in oocytes or isolated neurons at room temperature. We tested whether, as predicted for potent inhaled anesthetics, a proportionate increase in solubility with hypothermia matched a decrease in ethanol minimum alveolar concentration (MAC), and thereby made the use of a single anesthetic concentration appropriate regardless of temperature. We determined ethanol MAC in normothermic (37.3°C) and hypothermic (28.5°C) rats, and, at the two temperatures, also determined ethanol solubilities in olive oil and saline. Ethanol MAC decreased, while olive oil/gas and saline/gas partition coefficients increased. However, the increase in the saline/gas partition coefficient did not match the decrease in MAC, and thus the aqueous-phase partial pressure producing absence of movement in 50% of rats (EC₅₀) values for ethanol decreased by 17%. Although this decrease is not large, it may be important for comparative estimates of the in vitro effects of ethanol at different temperatures.     

Temporal evaluation of methionine synthase and related metabolites in the MAC15A mouse adenocarcinoma animal model

Methionine dependence is unique to cancer cells and defined as the inability to grow in a methionine-deprived environment even if supplemented with the metabolic precursor homocysteine. Cobalamin-dependent methionine synthase (MS) catalyses the formation of methionine and tetrahydrofolate from homocysteine and methyltetrahydrofolate, thus linking the methionine and folate pathways. The apparent altered methionine metabolism in methionine-dependent cancer cells suggests a role for MS, although results to date are conflicting. We have analysed key metabolites of the MS-associated transmethylation, transsulphuration and folate pathways of the methionine-dependent MAC15A tumour model as a function of tumour progression over a 10-day period. MS activity increased 2-fold from day 1 to day 10. Cysteine, homocysteine, S-adenosylmethionine and S-adenosylhomocysteine levels in tumour cytosolic fractions decreased as a function of tumour progression. Plasma cysteine levels also decreased, whilst the distribution of folates in erythrocytes was altered, with a maximum increase in methyltetrahydrofolate observed by day 5. The increasing MS activity and decreasing cysteine levels suggest an increasing methionine requirement by the tumour, whilst the induction of enzyme activity indicates that MS is not defective in the methionine-dependent MAC15A tumour. The decrease in tumour S-adenosylmethionine and S-adenosylhomocysteine levels suggests that methionine is required for some function other than cellular methylation, e.g., incorporation into protein. Overall, the results support a theory of methionine conservation in response to tumour growth, where the methionine-dependent MAC15A tumour has a higher than normal methionine requirement.     

Nomogram to estimate age-related MAC

Background. In clinical practice it is difficult to estimaterapidly two important values: (i) the total age-corrected MACmultiple from measured end-expired concentrations of volatileagent and nitrous oxide; (ii) the end-expired concentrationof volatile agent needed to obtain a given total MAC multiple.We have developed a nomogram to do this. Methods. We used standard nomogram methods to construct onesingle nomogram covering wide ranges of age (1–100 yr)and MAC (0.1–1.8 MAC) for halothane, enflurane, isoflurane,sevoflurane, and desflurane, alone or in combination with variousconcentrations of nitrous oxide. The user only has to draw twostraight lines to obtain the desired result. Results. The nomogram is simple to use. End-expired concentrationsof halothane 0.48%, enflurane 1.05%, isoflurane 0.75%, sevoflurane1.18%, or desflurane 4.3% in the presence of nitrous oxide 50%will give 1.4 MAC in a patient of 75 yr vs 0.9 MAC in a 1-yr-old.A reverse example is: a total MAC of 1.3 when using sevofluraneand nitrous oxide 67% in oxygen, requires an end-expired sevofluraneconcentration of 1.8% in a 3-yr-old whereas 0.55% is neededin a patient of 90 yr. Conclusions. The nomogram gives accurate results if it coversa whole A4 sheet in landscape format and could be extended toapply to other agents, for example xenon.     

环磷腺苷葡胺预处理对大鼠局灶性脑缺血海马iNOS含量的影响

目的 研究诱导型一氧化氮合酶（iNOS）在大鼠局灶性脑缺血再灌注损伤海马中的表达，观测环磷酸腺苷葡甲胺（MAC）在对其含量的影响，探讨MAC在脑缺血病理过程中的作用。方法 线栓法建立大鼠局灶性脑缺血再灌注损伤模型，化学比色法检测脑组织诱导型一氧化氮合酶的活性。TTC染色观察再灌注48h缺血损伤面积。结果 iNOS活性在正常组及假手术组脑组织内板低，在缺血再灌注组和治疗组活性显著升高（P〈0．01），于再灌注48h达到高峰，在MAC预处理组显著低于缺血再灌注组（P〈0．01），MAC预处理组TTC染色缺血损伤面积也显著低于缺血再灌注组（P〈0．05）。结论 iNOS在大鼠局灶性脑缺血再灌注中活性显著增高，MAC预处理能有效抑制iNOS激活，减轻缺血性损伤范围，在大鼠局灶性脑缺血再灌注中脑损伤中起到保护作用。     

Treatment and developmental therapeutics of Mycobacterium avium complex (MAC) infections

Opportunistic infections associated with AIDS pose very serious problems because of their exceedingly high morbidity and mortality. For their part, Mycobacterium avium and M. intracellulare, two organisms belonging to M. avium complex (MAC), are the most often isolated bacteria from AIDS patients. Although in recent years, some progress has been made, by and large, there is no viable drug and /or combinations of drugs effective against MAC, especially in AIDS patients. Conventional therapies with multiple drug combinations involving isoniazid, rifampin, ethambutol, streptomycin, ethionamide, and cycloserine are still widely used, as well as prophylactic treatment with rifabutin. The use of clofazimine and ciprofloxacin has also been reported. Studies on new quinolones (sparfloxacin, difloxacin, WIN 57273), macrolides, folate antagonists and antimcobacterial anitbiotics are being actively pursued along with novel strategies involving drugs inhibiting mycobacterial cell wall biosynthesis. The role of various cytokines in enhancing host immune defenses against MAC infections is also discussed.     

Effect of oestrogen on Mycobacterium avium complex pulmonary infection in mice

The purpose of the present study was to elucidate the role of oestrogen in the pathogenesis of Mycobacterium avium complex (MAC) pulmonary disease, which occurs most frequently in postmenopausal women. The study was carried out in a murine infectious model using ovariectomized DBA/2 female mice. Infection with MAC was established by intratracheal administration of bacilli. In some experiments, ovariectomized mice were treated with exogenous 17 beta-estradiol (E2). The number of bacilli in the lungs of infected mice which received ovariectomy was significantly larger than that in the lungs of sham-operated control mice, and treatment of ovariectomized mice with exogenous E2 restored the burden of bacilli to the same level as that in the sham-operated control mice. We next examined the effect of E2 in vitro using bone marrow-derived macrophages obtained from DBA/2 female mice. The macrophages showed bacteriostatic activity against MAC after treatment with interferon-gamma (IFN-gamma) and this activity was further enhanced by the exogenous addition of E2 to the culture medium. In parallel with these findings, E2 augmented the production of reactive nitrogen intermediates (RNI) by macrophages pretreated with IFN-gamma and stimulated with MAC, as shown by evaluating nitrite production and inducible nitric oxide synthase mRNA expression. These findings taken together suggest that absence of endogenous oestrogen appears to be responsible for the development of MAC pulmonary disease in this mouse model and that the enhancement by E2 of anti-MAC activity of murine macrophages induced through increased RNI production may play some role in resistance to MAC infection.     

急性失血所致的麻醉深度变异性及机制探讨

目的：为探讨急性失血患者对麻醉深度耐受性的影响及与血浆β－啡肽改变的关系,本文通过动物实验对失血状态下麻醉最低肺泡有效浓度（ＭＡＣ）和β－内啡肽浓度变化进行研究。方法：（１）新西兰兔２０只随机分成对照组和失血组。连续监测ＭＡＰ,ＣＶＰ,ＰＥＴＣＯ２和ＥＣＧ;（２）测定对照组七氟醚ＭＡＣ;失血组经动脉放血将ＭＡＰ降至基础值的２／３,测定失血状态下七氟醚ＭＡＣ;（３）两组动物分别于下列时间点测定血浆β     

右美托咪定复合瑞芬太尼MAC在无痛肠镜中的应用

目的探讨右美托咪定复合盐酸瑞芬太尼MAC用于无痛肠镜中的可行性与安全性。方法将60例自愿行无痛肠镜检查患者随机分为DR组(右美托咪定复合瑞芬太尼组)和DP组(右美托咪定复合丙泊酚组),每组30例。两组患者均先缓慢注入右美托咪定0.6μg/kg,时间大于10 min。DR组注射完毕后给予盐酸瑞芬太尼1.0μg/kg,时间大于1 min,然后以0.1μg·kg-1·min-1持续静脉泵注。DP组注射完毕后给予丙泊酚1.5~2.0μg/kg。记录基础值(T0)、检查开始(T1)、手术结束(T2)、术毕10 min(T3)各个时间点的血压、心率、脉搏血氧饱和度(Sp O2)、Ramsay镇静评分;苏醒时间(术毕至呼之睁眼);并发症包括恶心、呕吐、呼吸抑制、头晕等。结果两组患者均顺利完成手术,DR组Ramsay镇静评分明显低于DP组(P0.05),血流动力学更平稳(P0.05),副作用小。结论右美托咪定复合盐酸瑞芬太尼MAC可安全用于无痛肠镜,血流动力学稳定,副作用小。     

Predictors of Left Ventricular Outflow Tract Obstruction After Transcatheter Mitral Valve Replacement

Objectives

The aim of this study was to evaluate the predictors of left ventricular outflow tract (LVOT) obstruction after transcatheter mitral valve replacement (TMVR).