DNA序列数值映射方法的研究

DNA序列的数值映射是用数学方法、物理方法和数字信号处理方法分析生物分子序列首先要解决的问题。本文分析了现有8种DNA序列数值映射方法的特点和适应性。在此基础上,提出了一种基于DNA序列中碱基出现概率的数值映射方法。大多数蛋白编码序列具有3-碱基周期特性(周期-3性质)。借助于具有周期-3性质的DNA序列的频谱分析,比较了8种数值映射方法的优劣,并证实了新方法的有效性。计算机仿真结果表明,基于复域的映射方法无论从携带原有生物分子序列的信息量,还是数值映射后所得功率谱的效果均优于其它7种映射方法,而DNA序列新数值映射方法能够获得与复域法几乎相同的识别率。     

Circadian rhythmicity and sleep: Effects of aging in laboratory animals

—This literature review of research on age-related differences in sleep and rhythmic phenomena in laboratory animals covers three general areas: (1) age-related differences in biorhythms in general; (2) age-related differences in sleep patterns as assessed by psychophysiological measures; and (3) neurobiological correlates of biorhythms and sleep, including consideration of possible morphological, chemical, and endocrine bases of age-related defects in animal models. It is concluded that systematic research bridging these areas is lacking although several promising areas have been explored.     

Interhemispheric connections of the visual cortex in the grey squirrel (Sciurus carolinensis)

The total pattern of visual callosal connections was studied in the grey squirrel by using the Fink-Heimer technique for axonal and terminal degeneration and the autoradiographic and horseradish peroxidase techniques for axonal transport. The pattern of terminations was correlated with architectonic landmarks. The results show that callosal terminations are distributed in a complex fashion within the visual cortical areas. The major terminations form a band in area 17 along its border with area 18. This band is contiguous rostrally with the callosal terminations in area L that extend caudomedially onto the medial wall of the hemisphere. Caudally the band in area 17 wraps around the ventral aspect of the occipital pole and ends medially at the level of the hippocampus. This band exhibits a distinct periodicity in the density of terminations. The callosal terminations in area 18 are usually found along the lateral and medial borders and are concentrated in discrete patches. The pattern in area 19 exhibits two or three primary patches and only loosely corresponds to the borders of the area. Few callosal terminations are found in area 19p and the posterior temporal area, Tp, while the intermediate temporal area, Ti, receives an extensive input. The laminar distribution of callosal terminations is different in each area studied. Characteristically, area 18 has dense terminations in layers III, II, and the inner one-half of layer I, with less dense terminations in layers V and VI, and sparse terminations in layer IV. Area 17 has a similar pattern in the supragranular and infragranular layers but also has dense terminations in layer IV. The patterns in area 19 are intermediate between these extremes but are more similar to those in area 17. The cells that give rise to the callosal projections were found primarily in layers III and V and occasionally in layers II, IV, and VI. The distribution of the callosal efferent neurons is more extensive than the areas of terminations. The distribution of callosal terminations suggests that the organization of visual cortical areas in the grey squirrel is more complex than had been previously recognized. This finding is discussed with reference to the general organization of the mammalian visual cortical areas, and a need for more extensive analyses of visual cortical areas in the grey squirrel, particularly with respect to extrastriate visual areas, is indicated.     

石杉碱及氯硝西泮治疗慢性失眠症的临床观察

目的 :评价石杉碱、氯硝西泮治疗慢性失眠症的临床疗效。方法 :5 3例长期服用各类催眠药物无效的慢性失眠症患者在停用原药物三天后 ,进入连续二周的夜间睡前 30分钟服用氯硝西泮 2mg (A阶段 ) ;然后连续四周的石杉碱 ,上午、中午各服用 10 0ug ;氯硝西泮夜间睡前 30分钟服用 2mg (B阶段 ) ;最后连续四周 ,自选氯硝西泮夜间用量 (C阶段 )。A、B、C三阶段分别登记日间觉醒及夜间睡眠时间及其每日二者的平均比值 ,每日氯硝西泮用量及每阶段前后匹兹堡睡眠质量指数。结果 :昼夜交替服用石杉碱、氯硝西泮B、C阶段治疗与单一夜间口服氯硝西泮的A阶段比较显示 ,通过延长夜间睡眠时间 ,使睡眠一觉醒时间比值降至 1:4 7± 2 1,较A阶段的 1:6 3± 3 5有明显下降 (P <0 0 2 ) ,同时提高了睡眠质量 ,匹兹堡睡眠质量指数评分值由A阶段的 14 2± 4 5降至C阶段的 8 3± 3 7(P <0 0 1)。并且在C阶段中 ,平均每例患者的用量为 0 8mg± 0 2 2mg ,与A、B阶段的 2mg降低约 6 0 % ,其中有 16例患者在C阶段末期停用氯硝西泮。结论 :石杉碱、氯硝西泮昼夜服用治疗慢性失眠症通过延长睡眠时间而改善睡眠觉醒周期节律的同时亦提高睡眠质量。并逐步减少了氯硝西泮用量 ,其疗效较原夜间服用氯硝西泮方案更有效     

Theoretical Evaluation of the Rosenblueth Hypothesis

Rosenblueth's hypothesis states that atrioventricular (AV) nodal conduction delay and Wenckebach periodicity of AV transmission are not due to overall decremental conduction within the AV node but are due to a single step delay which is caused by a special element or layer of the AV nodal tissue. This paper discusses some theoretical considerations which allow detailed evaluation of the original hypothesis. Two artificial conduction structures which incorporate the Rosenblueth phenomenon are presented and tested by theoretical experiments that consider the potential of these structures to produce (a) basic pattern of Wenckebach periods, (b) decremental shortening of RR intervals during Wenckebach periods. These experiments are also employed to test whether or not the Rosenblueth concept can be used to explain (c) appropriate dependence of AV conduction changes on the prematurity of atrial depolarizations, and of (d) alternating cycle lengths such as may be seen with atrioventricular reentrant tachycardia. The results of the theoretical considerations show that the original concept of the Rosenblueth hypothesis is sufficient to explain (a) but it cannot be used for realization of (b), (c) and (d). A modification of the original concept complying with both (a) and (b) is proposed. This modified structure can also reproduce (c), but not simultaneously with (b). The experiments show that anisotropy of intra AV nodal conduction may create an electrophysiological mechanism of single-step delay. Different anisotropic conduction structures have to be considered to reproduce phenomenon (d).     

Complexity of AV Nodal Function: Complex Nodal Structure or Complex Behavior of Nodal Elements?

This paper discusses the hypothesis that the complex behavior of the atrioventricular (AV) node, with particular reference to Wenckebach periods, may be explained by the complexity of nodal structure and that complicated function of individual AV nodal fibers need not necessarily be considered. To prove this hypothesis, a computer model of cardiac excitation has been employed to simulate AV nodal function for two different anisotropic AV nodal model images. The experimental computer results show that the pattern of Wenckebach periods, and decremental and concealed AV nodal conduction can be explained without considering decremental conduction properties of individual AV nodal cells.     

Effect of acclimation and fixation temperatures on the number of lamellae and periodicity of myelin in fibres of the optic nerve of goldfish

Summary Previous findings from our laboratory have shown that the optic nerves of goldfish acclimated to different temperatures differ considerably in their glycerophospholipid composition. This paper describes changes in the morphology of the nerve with different acclimation and fixation temperatures. Optic nerves of 5 and 25° C acclimated fish were excised and fixed at the temperature of acclimation, or at the reverse temperature, and the morphology observed by electron microscopy. Under all temperature conditions considered there is a statistically significant linear relationship between the radius of the axon and the number of myelin lamellae. However, the temperature of acclimation and fixation both influence the regression coefficients for this relationship, the higher the acclimation temperature the lower the coefficient and the higher the fixation temperature the higher the coefficient. The periodicity of the myelin also alters with these temperatures, being greater in the 25° C fish than in the 5° C ones. Myelin sheath thickness is also significantly greater in the 25° C fish. These results are discussed in relation to observed changes in glycerophospholipid composition and conduction velocities.This work was supported by the Natural Sciences and Engineering Research Council of Canada grant no. A6052 to B.I. Roots     

Enamel apposition rate and the prism periodicity in human teeth

Abstract – A method is presented which allows the average daily rate of enamel apposition to be estimated based on measurements of the length of prisms in longitudinal ground sections, and on available data for the time of formation of the tooth crown. The method was applied on 21 sections of human maxillary premolars. The reproducibility of the method was satisfactory, the error of measurement being in the order of 3.8%. After corrections having been made for the deviation of prisms from a radial direction, the average daily rate of enamel apposition along the prisms for any maxillary premolar was estimated to be within a range of from 2.0 to 6.1 μm, while a more probable rate would be 2.7–4.6 μm. These results are in agreement with experimental data, and are also compatible with the observed cross-striation prism periodicity. The present study supports the theory that there exists a relationship between the prism periodicity and a 24-h rhythm in enamel apposition in human teeth.     

Click train encoding in primary and non-primary auditory cortex of anesthetized macaque monkeys

We studied encoding of temporally modulated sounds in 28 multiunits in the primary auditory cortical field (AI) and in 35 multiunits in the secondary auditory cortical field (caudomedial auditory cortical field, CM) by presenting periodic click trains with click rates between 1 and 300 Hz lasting for 2-4 s. We found that all multiunits increased or decreased their firing rate during the steady state portion of the click train and that all except two multiunits synchronized their firing to individual clicks in the train. Rate increases and synchronized responses were most prevalent and strongest at low click rates, as expressed by best modulation frequency, limiting frequency, percentage of responsive multiunits, and average rate response and vector strength. Synchronized responses occurred up to 100 Hz; rate response occurred up to 300 Hz. Both auditory fields responded similarly to low click rates but differed at click rates above approximately 12 Hz at which more multiunits in AI than in CM exhibited synchronized responses and increased rate responses and more multiunits in CM exhibited decreased rate responses. These findings suggest that the auditory cortex of macaque monkeys encodes temporally modulated sounds similar to the auditory cortex of other mammals. Together with other observations presented in this and other reports, our findings also suggest that AI and CM have largely overlapping sensitivities for acoustic stimulus features but encode these features differently.     

The occurrence and significance of myelin with unusually large periodicity

Summary The occurrence of myelin with an unusually large periodicity has been noted in a variety of human and animal diseases by many authors. It has also proved possible to create regular alterations in periodicity by various treatments of fresh unfixed nerve. We have quantified the changes found in material from a variety of sources and conclude that they are compatible with the occurrence of physicochemical changes in the myelin membranes, leading to overhydration.A preliminary account of these findings was presented at a meeting of the Peripheral Nerve Study Group in Fontevraud, France, in July 1983Financially supported by the Medical Research Council and the National Fund for Research into Crippling Diseases