人眼微光下夜近视机制的研究

本文利用激光散斑屈光测试系统详细探讨了夜近视(night myopia)的产生机制。夜近视在环境亮度降低到产生暗视觉时出现,并随亮度继续降低而增大,平均值为1.35D。实验证明眼睛球差和色差不是造成夜近视的主要因素。夜近视数值在暗适应过程中呈增大的趋势。在暗视觉时,由于视野中缺少适宜的刺激,眼睛处于暗焦(dark focus)休止状态,这是造成夜近视的主要原因。     

Biochemical and genetic characterization of three hamster cell mutants resistant to diphtheria toxin

We describe here three different hamster cell mutants which are resistant to diphtheria toxin and which provide models for investigating some of the functions required by the toxin inactivates elongation factor 2 (EF-2). Cell-free extracts from mutants Dtx(r)-3 was codominant. The evidence suggests that the codominant phenotype is the result of a mutation in a gene coding for EF-2. The recessive phenotype might arise by alteration of an enzyme which modifies the structure of EF-2 so that it becomes a substrate for reaction with the toxin. Another mutant, Dtx(r)-2, contained EF-2 that was sensitive to the toxin and this phenotype was recessive. Pseudomonas aeruginosa exotoxin is known to inactivate EF-2 as does diphtheria toxin and we tested the mutants for cross-resistance to pseudomonas exotoxin. Dtx(r)-1 and Dtx(r)-3 were cross-resistant while Dtx(r)-2 was not. It is known that diphtheria toxin does not penetrate to the cytoplasm of mouse cells and that these cell have a naturally occurring phenotype of diphtheria toxin resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance of the hybrid cells to diphtheria toxin. Intraspecies hybrids containing the genome of mutants Dtx(r)-1 and Dtx(r)-3 had some resistance while those formed with Dtx(r)-2 were as sensitive as hybrids derived from fusions between wild-type hamster cells and mouse 3T3 cells.     

Endosymbiotic bacteria and their relationship with chlorella in the ciliate Climacostomum virens

Structure of cytoplasmic bacterial symbionts of chlorella-free ciliate Climacostomum virens has been investigated. It is shown that ciliates are not able to support simultaneously growth and duplication of two different symbionts--bacteria and chlorella. Cells of C. virens lost bacterial symbionts after an artificial infection with chlorella by microinjection. Competitive relationships between two endopionts are discussed.     

Monitoring the orientation of myosin bridges on two-dimensional maps of birefringence in a single muscle fiber

Two-dimensional maps of birefringence in sarcomers of a single fiber of rabbit m.psoas were obtained by an automated interference microscope developed at our laboratory. The changes in birefringence of muscle fibers reflect the movement of myosin cross-bridges. The orientation of cross-bridges was modified by varying the pH (pH 7.0, 6.0, 8.0) and ionic strength (mu = 0.115, 0.085, 0.235) of the bathing rigor solution. The maximum value of total birefringence in the rigor state was observed at neutral pH. Total birefringence markedly decreased (by 40%) as pH was changed from 7.0 to both 8.0 and 6.0. No significant changes in light phase shifts were found at a 1.5 reduction of ionic strength in the rigor solution. The calculated birefringence values were 45% higher in rigor solutions of a high (mu = 0.235) ionic strength. The results observed are discussed in terms of changes in the orientation of cross-bridges due to the movement of the alpha-helical subfragment-2 away from the filament shaft (pH 8) or coming closer to it (mu = 0.235). The available data do not allow one to explain the results obtained at pH 6.0.     

Digital volume tomography in the diagnosis of the surgical anatomy of the frontal recess area

Frontal recess anatomy can be very complex, with accessory cells, such as frontal bulla, agger nasi, suprabulla, and frontal ethmoidal (Kuhn) cells, which may lead to obstruction of the frontal sinus. Digital volume tomography of paranasal sinuses used in this investigation revealed the rate of types of development of various anatomic structures and their correlation with frontal sinusitis in patients with (a study) and without the latter (a control group).     

Coherent oscillations of the molecular state of protein in live cells

The paper describes results of experimental studies of changes in the refractive index of the live cell (human erythrocyte) substance. The measurements were carried out using automated interference microscope. Oscillations of the refractive index were detected with the amplitude 5-10% and period 1 x 10(3)-3 x 10(3). In other words, oscillations with a near one hour period is equal to 10-45 min. It is supposed that these oscillations may result from coherent changes in the state of protein molecules.     

ANTIPYRETIC ACTION OF DEXAMETHASONE ON EGTAZIC ACIDINDUCED FEVER IN RABBITS

本文用脑室灌注和Ｆｕｒａ２测定细胞内游离钙技术观察了地塞米松（ｄｅｘａｍｅｔｈａｓｏｎｅ,ＤＥＸ）对家兔乙二醇双（２氨基乙醚）四乙酸性发热效应和下丘脑细胞内游离钙浓度（［Ｃａ２＋］ｉ）的影响,借此深入探讨地塞米松解热作用的中枢机制。结果发现：脑室灌注乙二醇双（２氨基乙醚）四乙酸（０６ｎｍｏｌ）引起家兔结肠温度明显升高,静脉注射地塞米松（５ｍｇ／ｋｇ）显著抑制家兔乙二醇双（２氨基乙醚）四乙酸性发热,地塞米松（６０～１２０μｍｏｌ／Ｌ）并不影响下丘脑细胞内［Ｃａ２＋］ｉ,而事先脑室灌注抑制基因转录的放线菌素Ｄ（３ｎｍｏｌ）则完全取消了地塞米松对乙二醇双（２氨基乙醚）四乙酸性发热的解热作用。这些结果提示：地塞米松显著抑制家兔乙二醇双（２氨基乙醚）四乙酸性发热,其机制与地塞米松激活脑内某些基因的表达有关,而与下丘脑神经细胞跨膜钙离子流无关。     

Instant success for Instant Pharmacology

Instant Pharmacology (1999). Saeb-Parsy K, Assomull RG, Kahn FZ, Saeb-Parsy K, and Kelly E. John Wiley and Sons 349 pp. £19.99 pbk; ISBN 0471976393 © 1999 John Wiley & Sons, Inc.     

瓜类枯萎病研究进展(综述)

瓜类枯萎病是由尖孢镰刀菌Fusarium oxysporum侵染引起,在全球大部分瓜类产区均有发生。该病已成为影响我国瓜类品质和产量的重要病害。本文从瓜类作物枯萎病的防治方法、致病机理和分子生物学研究等方面综述其研究现状,并对今后的研究方向进行展望。