Altered impedance during pigment aggregation in<Emphasis Type="Italic">Xenopus laevis</Emphasis> melanophores

Melanophores are dark-brown pigment cells located in the skin of amphibia, fish and many invertebrates. The skin colour of these organisms is regulated by the translocation of pigment organelles, and the pigment distribution can be altered by external stimuli. The ability to change colour in response to stimuli makes these cells of interest for biosensing applications. It was investigated whether pigment aggregation in Xenopus laevis melanophores can be detected by impedance measurements performed in transparent microvials. The results show that cell attachment, cell spreading and pigment aggregation all resulted in impedance changes, seen particularly at the highest frequency tested (10 kHz). The mechanisms behind the impedance changes were investigated by the addition of latrunculin or melatonin, both of which cause pigment aggregation. The latrunculin-induced aggregation was associated with cell area decrease and filamentous actin (F-actin) breakdown, processes that can influence the impedance. Lack of F-actin breakdown and an increase in cell area during melatonin-induced aggregation suggest that some other intracellular process also contributes to the impedance decrease seen for melatonin. It was shown that impedance measurements reflect not only cell attachment and cell spreading, but also intracellular events.     

Morphological, physiological and biochemical observations on skate electric organ

Summary The electric organs of two species of skate have been examined morphologically, physiologically and biochemically. They can be easily dissociated into innervated or denervated component electrocytes by a Torpedo Ringer's solution containing 1% collagenase. Collagenase treatment did not, however, separate the Schwann cell cover capping the synaptosomes. Isolated electrocytes generate normal MEPP frequencies and show evoked responses for two days in Torpedo Ringer's. The nerve terminals retain excitability and transmitter release properties up to the time of separation. Since isolated terminals and denervated electrocytes show normal ultrastructural characteristics for up to 12 h, the skate electric organ provides several preparations which are not attainable with Torpedo tissue. Acetylcholine (ACh) content of supernatant fractions containing the synaptosomes was comparable to that found in Torpedo (sps.). Collagenase specifically eliminates the basal lamina associated with the synaptic junctional region. Neuronal cell death and synaptic terminal degeneration were also noted in the adult organs of both species. The skate electric organ is ideally suited for the study of cholinergic development and transmission.     

成人高分级脑胶质瘤术后放疗设野的探讨

目的：探讨用局部扩大野的设野方法照射成人高分级脑胶质瘤的可行性。方法：经术后病理证实为Ⅲ～Ⅳ级星形细胞瘤５３例,分为实验组（Ａ组,２５例）和对照组（Ｂ组,２８例）,放疗采用常规分割,总剂量ＤＴ５０～６５Ｇｙ,设野方法：Ａ组用局部扩大野,Ｂ组用全脑加局部照射野。随访其放疗后生存期及１、３年生存率,复发率。并行统计学处理。结果：Ａ、Ｂ组的中位生存期分别是１４个月,１５．５个月,１,３年生存率分别是８０     

A dose-response study of the effects of alcohol on the perceptions of pain and discomfort due to electric shock in men at high familial-genetic risk for alcoholism

Alcoholics have previously been found to be more sensitive to painful stimulation than controls, and more sensitive to the pain-reducing effects of alcohol. The present study was designed to examine these effects in men at high familial-genetic risk for alcoholism and controls. Subjects were assigned to one of four alcohol doses [0.135 (active placebo), 0.50, 0.75, or 1.00 ml 95% USP alcohol/kg body weight]. Ratings of the amount of discomfort and pain experienced during an aversive shock procedure were taken immediately post-shock, both while subjects were sober and after they had consumed one of the four alcohol doses. High risk men were found to rate the experience of the shock as more uncomfortable and painful overall than the low risk controls. Pharmacologically significant levels of alcohol were found to reduce or eliminate these group differences, suggesting that alcohol has a normalizing effect on pain and discomfort perceptions in high risk men. Only the higher doses of alcohol were found significantly to dampen subjects' shock rating scores. High risk males' increased sensitivity to pain and discomfort, combined with the negatively reinforcing effects of reducing these perceptions at moderate to high alcohol doses, may play a role in predisposing high risk males for the development of alcoholism.     

Preliminary evaluation of pelvic vascular bed isolation chemotherapy in the treatment of advanced cervical carcinoma

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Mechanism for polarisation of cardiac tissue at a sealed boundary

If current is flowing in cardiac tissue, and if the myocardial fibres approach a sealed boundary at an angle, then the tissue within a few length constants of the boundary is polarised. This polarisation occurs when the cardiac tissue has different anisotropy ratios in the intracellular and extracellular spaces. This new mechanism of tissue polarisation is demonstrated using a simple, analytical model, and it is shown quantitatively that this polarisation can be nearly as large as that occurring near an electrode.     

高压下滴流床反应器动持液量的测定

在常压－２．０ＭＰａ的系统压力下测定了滴流床中气－液两相并流下流动的动持液量,了气－液流率,液相粘度,填料大小,压力以及床层高度对动持液量的影响。实验结果表明增中液体流率动持流量增加,气体流率增加时,结果相反粘度的增加对动持液量的影响不大,动持液量随填料空隙率的增大而变小。     

中药复方对卧床模拟失重引起"血淤"的对抗效果

目的观察中药对卧床模拟失重引起血淤证改善的效果。方法１０名被试者随机分为中药组和对照组。两组均头低位－６°卧床７ｄ,中药组卧床中服中药复方,对照组服安慰剂。结果中药组的血淤证较对照组有明显减轻,某些生理指标维持卧床前状态,即血压平稳;心功能（每搏量、心肌收缩力、每搏功指数等）、尿量,与卧床前比较基本保持不变,而对照组比中药组血淤证较重。结论提示中医药可能成为防治短期航天失重时对机体影响的的一种选择措施     

Electric and magnetic fields (EMF): What do we know about the health effects?

Because we use electric power throughout our homes and workplaces, we are all subject to electric and magnetic fields (EMF) that are created by the voltages and currents present in electrical conductors and electrical equipment. Interest in the health effects of electric-power EMF has been motivated by several epidemiologic studies showing weak associations between surrogate measures of low-level EMF exposure and both childhood cancers and adult cancers. Due to the ubiquitous presence of electric power, the public health implications of this association are potentially very significant; however, good evidence for a causal relationship between exposure to EMF and any health effect has not been found. Yet, uncertainty, plus the suggestive epidemiologic findings, have fueled public anxiety and media attention. To put this potential health threat into perspective, it is important to consider the strength of the epidemiology, the availability of supporting animal studies, and mechanistic or biophysical information about the interaction of EMF with matter. Any discussion of steps that might be taken to avoid potential EMF health-effects needs to incorporate a perspective on how hypothetical EMF risks relate to other hazards to life and health.Work presented at the 23rd Congress on Occupational and Environmental Health in the Chemical Industry (Medichem 1995) The Chemical Industry as a Global Citizen - Balancing Risks and Benefits, 19-22 September 1995, Massachusetts Institute of Technology, Cambridge, Massachusetts     

The effect of electric fields on osteoporosis of disuse

Summary An experiment originally done by McElhaney et al. was repeated to obtain additional information about the effects of electrical fields on osteoporosis of disuse. The right femurs of 35 male rats were immobilized in plaster casts. Sixteen rats were treated with transcutaneous electrical fields of 30 Hz and 100 V/cm for periods of 2 or 8 h a day. While the right femurs of the untreated rats were found to be atrophic with respect to the opposite limb, in the treated rats the immobilized femur was made larger than the opposite bone. Longer daily treatments exaggerated this effect. The tumors found in the previous study were not seen in our experiments. Other similarities and differences in the 2 studies are discussed.