Pharmacokinetics of tablet huperzine A in six volunteers

AIM: To study pharmacokinetics of tablet huperzine A (Hup-A) in Chinese volunteers to help establishing its drug administration schedule. METHODS: For 6 volunteers after a single oral dose of 0.99 mg, drug concentrations in plasma were assayed by reverse phase high pressure liquid chromatography (HPLC) at 0.5, 0.75, 1.0, 1.25, 1.5, 2, 4, 6, 8, and 10 h. The pharmacokinetic parameters were calculated with a 3P87 program by computer. RESULTS: The time course of plasma concentrations conformed to a one-compartment open model with a first order absorption. The pharmacokinetic parameters were as follows: T 1/2ka = 12.6 min, T 1/2ke = 288.5 min, Tmax = 79.6 min, Cmax = 8.4 micrograms L-1, AUC = 4.1 mg L-1 min. CONCLUSION: Hup-A was absorbed rapidly, distributed widely in the body, and eliminated at a moderate rate.     

Specific features of the effect of pressure on the heat-transfer rate in the boiling of water on a porous surface

The data on the combined effect of pressure, structure thickness, and heat-flux density on heat transfer during the boiling of water on a porous surface are given, and a relation for the calculation of the heat-transfer coefficient is grouped.Kiev Polytechnic Institute. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 6, pp. 779–782, June, 1992.     

"产生效益的电力驱动"-客车和重型车辆的动力电子设备

商用车辆传动系统的电气化是ZF公司的基本策略之一.ZF Electronics的动力电子设备不仅经久耐用,而且处于不断创新之中.低运行成本意味着混合动力将能够为重型车辆和公共汽车带来效益.     

楼梯间及前室加压送风系统余压动态控制方法

通过对加压送风系统开关门状态等引起风量差异原因的分析,说明对消防前室加压和10层以下的楼梯间加压系统设置余压控制措施是必要的。提出对目前设计手册中泄压阀选用计算公式的修正。已完成的工程实例参考了香港地区加压系统余压控制的做法。结论是使用压差探测开关＋电动旁通阀应用于消防前室加压系统及使用泄压阀应用于10层以下的楼梯间加...     

Antagonism of l-stepholidine against bromocriptine-inhibition on prolactin level in lactational rats

AIM: To study the antagonism of l-stepholidine (SPD) against bromocriptine (Bro)-inhibition on prolactin (PRL) level. METHODS: Bro (0.5 mg.kg-1.d-1, s.c.) reduced the PRL and caused a dysplasia of mammary gland in lactational rats. The weight growing of newborn rats was retarded. The PRL of the lactational rats was assessed by immunoradiometric assay (IRMA); the weight of newborn rats and development of mammary glands in lactational rats were also examined. Antagonism of SPD was evaluated. RESULTS: SPD (30 & 100 mg.kg-1.d-1, i.p.) obviously antagonized the Bro that induced lowering the PRL level in lactational rats, the PRL was 11 +/- 4 & 23 +/- 6 micrograms.L-1 (NS 7 +/- 2) respectively on d 15 of postpartum and the development of mammary gland in lactational rats was normal. The newborn rats grew rapidly in 11-15 d. CONCLUSION: SPD possessed an antagonism with Bro inhibition on D2 receptors located in the pituitary gland, and was an antagonist of dopamine D2 receptors.     

Genetic susceptibility to head and neck cancer: interaction between nutrition and mutagen sensitivity

The development of head and neck cancer may depend not only on exposure to environmental carcinogens but also on a genetically based susceptibility to carcinogen-induced damage. This thesis presents a case-control study that demonstrates the significance of mutagen sensitivity, a measure of an individual's intrinsic DNA repair capacity against free radical damage, as a risk factor for the disease. As part of the case-control analysis, 167 previously untreated patients and 177 age- and sex-matched healthy controls were assessed for various lifestyle factors including tobacco and alcohol habits, occupational exposures, and diet. Mutagen sensitivity expressed by each individual was determined by quantifying bleomycin-induced chromosomal breaks within peripheral blood lymphocytes in vitro. Consistent with our initial observations and those of others, mutagen hypersensitivity was strongly associated with increased risk of head and neck cancer (odds ratio, 4.95; 95% confidence interval, 2.67 to 9.17) after adjusting for age, sex, and race. Low intake of vitamins C and E was also associated with an increased risk of disease and was interactive with mutagen sensitivity in risk estimates. Individuals with both a low intake of various antioxidants and increased chromosomal sensitivity to oxidant-induced DNA damage were at greatest risk. This study supports the concept that the risk of head and neck cancer is determined by a balance of factors that either enhance or protect against free radical oxygen damage, including innate capacities for DNA repair.     

Regulatory mechanisms of replication growth limits in cellular senescence

Normal human diploid fibroblasts cannot divide indefinitely in culture. At the end of their lifespan they withdraw from the cell cycle permanently by a process termed cellular senescence. Recent molecular studies indicate that upregulation of two inhibitors of cyclin-dependent kinases, p16 and p21, is responsible for blocking the G1/S transition in senescent cells. Although the state of senescence resembles terminal differentiation in that both exhibit irreversible growth arrest and resistance to apoptosis, other molecular changes are seen only in senescent cells. This suggests that the signal pathway specific for senescence is present in normal cells. Changes in chromosomes, such as progressive shortening of the telomeres and erosive damage by detrimental by-products in metabolism, may be the signals that trigger senescence, leading to the inactivation of cell cycle progression. On the other hand, it seems that a dominant genetic program is intrinsically preset to ensure a growth limit in the normal cell. This notion is supported by cell fusion and microcell transfer experiments which show that escaping from senescence requires recessive mutations in senescence-specific genes. Identification of these participating genes and clarification of their mode of action will provide the basis for understanding the mechanisms governing the differences between mortality in normal cells and immortality in cancer cells.