Heat shock mRNA in mouse epidermis after UV irradiation

Total RNA from murine epidermis was extracted at different times after irradiation with erythemogenic doses of ultraviolet light (UVB or UVB/UVA) and hybridized to a DNA probe from the gene of a heat shock protein (hsp 70). An intense and transitory enrichment in RNA molecules hybridizing to the DNA probe was found between 15 and 120 min after irradiation, followed by a return to control levels over the next 70 h. Dose-response analysis indicates that 30 min after the irradiation, the relative amount of RNA hybridizing to the hsp 70 DNA probe increases with the dose (within the range explored: 0-180 mJ/cm2) up to values greater than 5 times the control.     

Histidine modulates the clastogenic effect of oxidative stress

The kinetics of the formation of single-strand breaks induced by H2O2 in DNA is more rapid in Eagle's Modified Minimal Essential Medium (MEM) than in phosphate-buffered saline (PBS). Among the components of MEM, we found that histidine increases the rate of degradation of DNA by H2O2 in PBS dose-dependently. In hamster lung fibroblasts histidine increases the cytotoxicity of H2O2, as well as the number of sister-chromatid exchanges and the frequency of micronuclei induced by hydrogen peroxide.     

Liposome-delivered phosphatidylcholine enhances the acetylcholine sensitivity of dystrophic mouse myotubes

Myotubes were obtained in vitro from satellite cells of normal and dystrophic C57BL/6J/dydy mice. The acetylcholine sensitivity (mV/nC) of dystrophic myotubes determined with conventional electrophysiological techniques, was lower than that of normal myotubes. Incubation of dystrophic myotubes with liposomes containing phosphatidylcholine (a lipid present in higher amounts in normal adult muscle) significantly increased their acetylcholine sensitivity.     

猫脑干上涎核节前神经元电活动的观察

在麻醉的32只猫记录了电刺激颌下腺神经支引起的上涎核平均场电位和单位放电。逆行电刺激颌下腺神经支引起的上涎核平均场电位分布在同侧脑干背面闩部头端5.5—8mm处,与过去的组织学结果大致符合。用微电极在上涎核记录了68个对刺激颌下腺神经支有反应的单位,其中33个单位作了碰撞试验。有9个单位符合逆向反应标准,它们是真正的颌下腺节前神经元,逆行反应的潜伏期为14.4±2.5ms,其轴突传导速度为2.9±0.1m/s。其他不符合逆向反应标准的单位,对刺激颌下腺神经支仍能发生反应,估计多为中间神经元。在一部分单位观察了电刺激舌神经或味觉刺激舌引起的反应。根据这些观察对上涎核内存在复杂神经元回路的可能性作了讨论。     

Protein . nucleic-acid reaction kinetics. Theoretical analysis of the binding reaction between DNA and RNA polymerase.

This paper presents methods developed in order to analyze experimental results concerning the binding of Escherichia coli DNA-dependent RNA polymerase to DNA at high and at low DNA concentrations, using the filter retention assay. The basis hypotheses, under which the mathematical expressions for describing the kinetics of binding are derived, are as follows. (a) At low DNA concentration: equivalence and independence of the specific binding sites; first-order dependence of the binding reaction on both DNA and protein concentration. (b) At high DNA concentration: equivalence and independence of the non-specific binding sites; no direct transfer or one-dimensional sliding of the protein along the DNA. Comparison between theoretical predictions and experimental results at high DNA concentration will allow one to determine the relative value of the rates of binding of RNA polymerase to different promoters (between 1 and 2 in T5 DNA). Binding experiments performed at low DNA concentration are reported in this paper: these results and the analysis which is reported allow one to determine the value of the rate constant of formation of non-filterable complexes for the system fd DNA (replicative form) . RNA-polymerase (kappa a = 3.3 X 10(8) M-1 s-1 in 0.1 M NaCl, 0.01 M MgCl2).     

Disorders of the Menstrual Cycle in Elite Female Ice Hockey Players and Figure Skaters

The purpose of this study was to assess and compare the incidence of delayed menarche and menstrual dysfunction among elite ice hockey players and figure skaters. Forty-three ice hockey players (23.5 ± 4.8 years, 68.2 ± 1.2 kg, 1.68 ± 0.01 m) and 39 figure skaters (17.5 ± 3.4 years, 53.7 ± 5.8 kg, 1.64 ± 0.05 m) completed a self-administered questionnaire on their menstrual status and history, training regimens and lifestyle. Age at menarche did not differ significantly between ice hockey players (13.3 ± 1.3 years) and figure skaters (13.7 ± 1.4 years). Menarche was unrelated to nationality, vigorous training premenarche or age at which the athlete began her sport, but was correlated with the age at menarche of the athletes’ mothers (r = 0.39, p < 0.05). Hormonal contraceptives were used by 35% of ice hockey players and 15% of the figure skaters. Amenorrhea and oligomenorrhea were experienced by 7.1% and 38.7% of postmenarcheal, ice hockey players and figure skaters respectively not using hormonal contraceptives. Menstrual dysfunction was associated with both age and age at menarche in the ice hockey players only. Training factors, and psychological pressure were perceived by the athletes to contribute to menstrual dysfunction. A greater training volume, younger age at commencing sport, lower body mass, greater subjective body image pressure and younger biological and gynaecological age were reported among the figure skaters, and were proposed to explain the higher incidence of menstrual dysfunction among the figure skaters compared with the ice hockey players. Figure skaters appear at increased risk of amenorrhea and oligomenorrhea compared with ice hockey players, which may be linked to training and physical characteristics of the sports.