毛白杨插条苗的年生育过程和成活阶段某些生理特点的研究

根据物候观察,生长速度测定和某些生理指标的材料,在我们的试验中把毛白杨的年生育过程分为六个时期:1、萌动期;2、展叶拔节期,即生根初期;3、新梢生长停滞期,即生根临界期;4、二次生长期;5、封顶充实期;6、越冬休眠期。 在插条苗的发育过程中观测了下列主要生理特点: 1、插穗中贮藏的营养物质在扦插后不断消耗。直到二次生长开始前(6月中旬)插穗中没有积累新的营养物质。 2、从四月中旬到五月初,尚未生根的插条苗中发生水分亏缺。到五月末水分亏缺变得十分严重,其水分饱和差达25—29％。 3、处在生根临界期的插条苗其光合作用由于水分亏缺而中断或受到抑制。     

初烤烟叶评吸质量主成分分析

[目的]探索初烤烟叶评吸质量的主体指标,为初烤烟叶评吸质量综合评价提供参考。[方法]选择云南玉溪烟区的适熟烟叶,经中温中湿方法调制处理后,对烤后烟叶评吸鉴定;应用主成分分析法对初烤烟叶评吸鉴定指标:香气质、香气量、刺激性、杂气、浓度、劲头、余味、燃烧性、灰色、使用价值进行分析。[结果]烤后烟叶评吸质量指标中,香气因子是影响烟叶评吸质量的主体指标,直接关系到烟叶评吸质量的总体评价。根据累计贡献率达到85%以上,确定了反映评吸质量主要的4个主成分及其主成分的函数方程;并对评价结果进行了验证,发现综合分析计算值与烟叶使用价值高度正相关。[结论]主成分分析法是一种可行、客观的评价初烤烟叶评吸质量的方法。     

LONG-TERM STABILITY OF VISUALLY EVOKED POTENTIALS IN MAN

Although the variability of averaged evoked potentials as recorded from cortex in man has been a constant source of concern among investigators, the degree of variability has not received systematic treatment. The authors have accordingly undertaken an exploratory study of reliable differences that may occur in the first 300 msec of the averaged evoked response over long periods of time. Computer analysis of visually evoked responses in seven subjects over several weeks indicated stability of the response of each individual, with reliable intra-individual correlations. Inter-individual differences, however, were large. The evoked responses of different individuals were found to be unique.     

Evoked potential correlates of signal recognition between and within modalities

Electrical responses evoked by clicks, flashes, changes in noise level, and changes in light level were recorded from the scalps of human subjects set to detect one of the stimuli. An early negative component of the evoked responses reflects selection between sensory modalities, whereas the later positive component reflects a more complex intramodal discrimination.     

Damage to the insula disrupts addiction to cigarette smoking

A number of brain systems have been implicated in addictive behavior, but none have yet been shown to be necessary for maintaining the addiction to cigarette smoking. We found that smokers with brain damage involving the insula, a region implicated in conscious urges, were more likely than smokers with brain damage not involving the insula to undergo a disruption of smoking addiction, characterized by the ability to quit smoking easily, immediately, without relapse, and without persistence of the urge to smoke. This result suggests that the insula is a critical neural substrate in the addiction to smoking.     

Effects of rectilinear acceleration and optokinetic and caloric stimulations in space

During the flight of Spacelab 1 the crew performed a number of experiments to explore changes in vestibular function and visual-vestibular interactions on exposure to microgravity. Measurements were made on the threshold for detection of linear oscillation, vestibulo-ocular reflexes elicited by angular and linear movements, oculomotor and posture responses to optokinetic stimulations, and responses to caloric stimulation. Tests were also conducted on the ground, during the 4 months before and on days 1 to 6 after flight. The most significant result was that caloric mystagmus of the same direction as on the earth could also be evoked in the weightless environment.     

Venom of the Scorpion Vejovis spinigerus

The chemical composition of lyophilized venom from Vejovis spinigerus is reported. At least 13 distinct bands were obtained on disc electrophoresis; on Sephadex G-50, four major peaks were found. The lethal activity was associated with the second peak. The intravenous lethal dose, median (lethal for 50 percent of inoculated group), of the crude venom was 4.87 milligrams per kilogram of body weight. Neither the crude venom nor its fractions had a deleterious effect on neuromuscular transmission, reflex discharge, or antidromic inhibition. Crude venom evoked simultaneous changes in systemic arterial, venous, and cisternal pressures.     

苹果汁对吸烟小鼠肝、肾、肺SOD和MDA的影响

研究苹果汁对吸烟小鼠肝、肾、肺组织超氧化物歧化酶(SOD)和丙二醛(MDA)的影响。选用昆明种小鼠,随机分成3组,对照组正常饲喂、吸烟模型组吸烟、预防组吸烟后进行苹果汁预防,7 d后检测小鼠肝、肾、肺组织匀浆中SOD活性及MDA含量。结果显示,预防组与正常组相比,肺、肾SOD活性显著升高,肝、肺、肾MDA含量降低达极显著水平;预防组与吸烟模型组相比,肝、肺、肾SOD活性升高达极显著水平,MDA含量则显著下降。     

Metacontrast and evoked potentials: a reappraisal

Stimulation of the parafoveal retina may give rise to visual evoked responses generated in large part by stray light impinging upon the fovea. This effect appears to account for the absence of changes in the visual evoked response to parafoveal stimulation during metacontrast suppression. When the central retina is directly stimulated, the spatiotemporal interactions associated with brightness suppression during metacontrast may be readily demonstrated in a late component of the visual evoked response.     

Oxygen tension changes evoked in the brain by visual stimulation

Localized changes in oxygen tension were recorded with platinum cathodes placed in the lateral geniculate nucleus in both anesthetized and awake cats. The amplitude of the responses increased with increasing stimulus intensity, but decreased with increasing flash rate. Both increases and decreases in cathode current were produced by steady illumination. The characteristics of the responses suggest that the responses reflect localized variations in blood flow, produced in turn by changes evoked in the tonic neural activity of the lateral geniculate nucleus.     

A specificity-enhancing factor for the ClpXP degradation machine

Events that stall bacterial protein synthesis activate the ssrA-tagging machinery, resulting in resumption of translation and addition of an 11-residue peptide to the carboxyl terminus of the nascent chain. This ssrA-encoded peptide tag marks the incomplete protein for degradation by the energy-dependent ClpXP protease. Here, a ribosome-associated protein, SspB, was found to bind specifically to ssrA-tagged proteins and to enhance recognition of these proteins by ClpXP. Cells with an sspB mutation are defective in degrading ssrA-tagged proteins, demonstrating that SspB is a specificity-enhancing factor for ClpXP that controls substrate choice.     

Quantitative electroencephalogram in smoking and smoking deprivation

After being deprived of cigarettes for 24 hours, eight young males who were heavy smokers showed significant changes in the electroencephalogram analyzed electronically and by digital computer. Compared to their records before smoking deprivation, there was a significant increase in slow frequencies. Resumed smoking reversed these trends.     

Pharmacological modulation of perceptual learning and associated cortical reorganization

The pharmacological basis of perceptual learning and associated cortical reorganizations remains elusive. We induced perceptual learning by Hebbian coactivation of the skin of the tip of the right index finger in humans. Under placebo, tactile two-point discrimination was improved on the coactivated but not on the left index finger. This augmentation was blocked by an N-methyl-D-aspartate-receptor blocker, but doubled by amphetamine. No drug effects were found on the left index finger. The individual amount of cortical reorganization as assessed by mapping of somatosensory evoked potentials was linearly correlated with the pharmacological modulation of discrimination thresholds, implying that perceptual learning and associated cortical changes are controlled by basic mechanisms known to mediate and modulate synaptic plasticity.     

Learning induces long-term potentiation in the hippocampus

Years of intensive investigation have yielded a sophisticated understanding of long-term potentiation (LTP) induced in hippocampal area CA1 by high-frequency stimulation (HFS). These efforts have been motivated by the belief that similar synaptic modifications occur during memory formation, but it has never been shown that learning actually induces LTP in CA1. We found that one-trial inhibitory avoidance learning in rats produced the same changes in hippocampal glutamate receptors as induction of LTP with HFS and caused a spatially restricted increase in the amplitude of evoked synaptic transmission in CA1 in vivo. Because the learning-induced synaptic potentiation occluded HFS-induced LTP, we conclude that inhibitory avoidance training induces LTP in CA1.     

Iodine-131 in the thyroids of North American deer and caribou: comparison after nuclear tests

Concentrations of I(131) in the thyroids of deer from Washington, Colorado, and Maryland, and of caribou from Alaska were measured after the resumption of nuclear weapon tests by the U.S.S.R. on 1 September 161. Maximum concentrations occurred nearly 2 months after the first nuclear test and then decreased at an effective half-time of about 15 days. Thyroids from Washington and Colorado deer showed the highest concentrations, thyroids from Alaskan caribou the lowest.     

Hormonal inhibition of feeding and death in octopus: control by optic gland secretion

Female Octopus hummelincki lays eggs, broods them, reduces its food intake, and dies after the young hatch. Removal of both optic glands after spawning results in cessation of broodiness, resumption of feeding, increased growth, and greatly extended life-span. Optic gland secretions may cause death of most cephalopods and may function to control population size.     

Toward the primary prevention of cancer

This is the threshold of an era when many of the most prevalent human cancers can, to a significant extent, be prevented through life-style changes or medical interventions. For lung cancer, the leading cause of cancer deaths in the United States, the major cause, cigarette smoking, is known and strategies for reducing smoking are slowly succeeding. Dietary changes can reduce the risk of developing large bowel cancer, the second most common cancer overall. The etiology of the major cancer in women, cancer of the breast, is sufficiently well understood that large-scale medical intervention trials are imminent. Recent changes in the incidence and mortality of these and the other major human cancers are reviewed with a brief explanation as to why these changes have occurred, followed by a summary of the state of knowledge regarding the major causes of cancer.     

A sperm cytoskeletal protein that signals oocyte meiotic maturation and ovulation

Caenorhabditis elegans oocytes, like those of most animals, arrest during meiotic prophase. Sperm promote the resumption of meiosis (maturation) and contraction of smooth muscle-like gonadal sheath cells, which are required for ovulation. We show that the major sperm cytoskeletal protein (MSP) is a bipartite signal for oocyte maturation and sheath contraction. MSP also functions in sperm locomotion, playing a role analogous to actin. Thus, during evolution, MSP has acquired extracellular signaling and intracellular cytoskeletal functions for reproduction. Proteins with MSP-like domains are found in plants, fungi, and other animals, suggesting that related signaling functions may exist in other phyla.     

冬凤兰非共生萌发和低温离体保存

[目的]利用组培技术建立冬凤兰(Cymbidium dayanum)非共生萌发和低温离体保存技术,以达到快速繁殖和长期离体保存该植物的目的。[方法]以冬凤兰种子为外植体,选择不同培养基建立冬凤兰非共生萌发技术;同时利用原球茎为材料,选择低温离体保存,恢复增殖及植株再生条件,初步建立冬凤兰低温离体保存技术体系。[结果]冬凤兰种子在花宝1号,MS培养基上培养90 d萌发率98%以上;原球茎在花宝1号培养基上于5℃、黑暗中能连续保存18个月以上,成活率达90%,并能在1/2 MS、花宝1号培养基中进行恢复增殖;壮苗生根培养基为1/2 MS培养基。[结论]该研究为冬凤兰种质的离体保存和快速繁殖提供了实践基础。