L-tryptophan: a common denominator of biochemical and neurological events of acute hepatic porphyria?

Hepatic porphyrias are disorders of heme synthesis characterized by genetically determined lesions of one of the key enzymes of heme synthesis. In carriers of such lesions, several factors (drugs, environmental chemicals, or diet) precipitate acute and often fatal attacks of neurologic dysfunction, which are promptly relieved by intravenous infusion of heme. However, the mechanism of such heme-induced amelioration remains elusive. To probe this mechanism, the biochemical events triggered by acute hepatic heme deficiency were examined in an animal model of chemically induced porphyria. Acute hepatic heme depletion in porphyric rats was found to impair hepatic tryptophan pyrrolase activity which, in turn, elevated tryptophan and 5-hydroxytryptamine turnover in the brain. These alterations in porphyric rats were dramatically reversed by parenteral heme administration. These findings suggest that increased tryptophan and 5-hydroxytryptamine in the nervous system may be responsible for the neurologic dysfunctions observed in humans with acute attacks of hepatic porphyria.     

The use of animals in research

A law professor, who was a member of the National Academy of Sciences/National Research Council committee which authored The Use of Laboratory Animals in Biomedical and Behavioral Research, argues that political attacks by animal rights organizations constitute the most important practical aspect of this issue because they lead to restrictions that severely inhibit the ability of researchers to afford the use of animals. Researchers and "patient groups" must be mobilized to struggle against these organizations in order to prevent a disaster from overtaking biomedical research in the United States.     

结合奇异值分解和DCT变换的零水印算法

提出了一种结合奇异值分解(SVD)和DCT变换的零水印算法。其核心思想是合理选取阈值，根据该阈值对图像块进行相应的奇异值分解或DCT变换，然后利用几个重要系数构造原始图像的提取水印信息，同时又从外部加载水印信息，既满足图像认证的需要，又能用来进行数据隐藏。同时针对现有水印技术大都难以抵抗几何攻击的现象，利用一个或多个几何矩对经过几何变换的水印图像进行参数估计并校正。实验表明此算法在压缩、滤波、几何变换等方面都具有很强的鲁棒性。     

Conflicting objectives in regulating the automobile

Federal regulation of automobile safety, emissions, and fuel economy is contradictory. Safety equipment and emissions control reduce fuel economy; reducing the size of automobiles is estimated to increase fatalities by 1400 a year and significantly increase serious injuries. These secondary impacts of regulation roughly double the estimated costs of achieving the individual goals. In formulating regulations, these contradictions must be taken into account, along with the effects on the price of the vehicle and its attractiveness to buyers.     

Pharmacological differentiation of allergic and classically conditioned asthma in the guinea pig

A whole-body plethysmographic technique was developed and then used to detect experimentally induced asthma in guinea pigs and to assess pharmacological treatments of allergic and classically conditioned attacks. Inhalation of a beta adrenergic compound (isoproterenol) controlled both forms of attack. Atropine and methscopolamine, parasympathetic blocking agents, prevented conditional but not allergic attacks; diphenhydramine, an antihistamine, prevented allergic attacks; and methysergide, which blocks serotonin (which is believed to trigger human asthma), prevented neither. The guinea pig's allergic reaction is probably the result of a bronchospasm induced by histamine released in tissue of the airway by a local combination of allergen and antibody. The conditional attack is believed to be a constriction of the airway mediated by parasympathetic fibers of central origin.     

Injuries from the wichita falls tornado: implications for prevention

We examined the circumstances of death and injury among victims of the tornado that struck Wichita Falls, Texas, on 10 April 1979. We also assessed the protective measures taken by a representative sample of community residents who suffered no major injury in order to estimate the relative risk of injury to people directly in the tornado's path. Twenty-six (60 percent) of the 43 traumatic deaths and 30 (51 percent) of the 59 serious injuries occurred in people who, despite ample warning, went to their cars to drive out of the storm's path. These people had a risk of serious or fatal injury of 23 per 1000. People who remained indoors and in stationary homes were at relatively low risk (3 per 1000) if they took simple precautions; people in mobile homes were at greatest risk (85 per 1000). Current safety recommendations and housing codes for single family homes and mobile homes need to be amended to decrease the impact of future tornadoes on human health.     

Sleep disorders: disorders of arousal? Enuresis, somnambulism, and nightmares occur in confusional states of arousal, not in "dreaming sleep"

In summary, the classical sleep disorders of nocturnal enuresis, somnambulism, the nightmare, and the sleep terror occur preferentially during arousal from slow-wave sleep and are virtually never associated with the rapid-eye-movement dreaming state. Original data are reported here which indicate that physiological differences from normal subjects, of a type predisposing the individual to a particular attack pattern, are present throughout the night. The episode, at least in the case of enuresis, appears to be simply a reinforcement of these differences to a clinically overt level. A number of features are common to all four sleep disorders. These had been shown previously to be attributable to the arousal itself. New data obtained by means of evoked potential techniques suggest that these common symptoms of the confusional period that follows non-REM sleep are related to alterations of cerebral reactivity, at least of the visual system. The symptoms which distinguish the individual attack types (that is, micturition, prolonged confusional fugues, overt terror) appear to be based upon physiological changes present throughout sleep which are markedly accentuated during arousal from slow-wave sleep. These changes may in some way be related to diurnal psychic conflicts. But, to date, it has proved impossible to demonstrate potentially causal psychological activity, dreaming or other forms of mental activity, or even a psychological void in sleep just preceding the attacks. The presence of all-night or even daytime predisposing physiological changes and the difficulty in obtaining any solid evidence of a preceding psychological cause explain, no doubt, why the results of efforts to cure the disorders at the moment of their occurrence (for example, by conditioning procedures in nocturnal enuresis) have been far from satisfactory. I stress the points that the attacks are best considered disorders of arousal and that the slow-wave sleep arousal episode which sets the stage for these attacks is a normal cyclic event. Indeed it is the most intense recurrent arousal that an individual regularly experiences. The most fruitful possibilities for future research would appear to be more detailed studies of those physiological changes that predispose individuals to certain types of attacks when they undergo intense arousal or stress; the reversal of these changes by psychological or pharmacological means; and more refined investigations of the physiological and psychological characteristics of the process of cyclic arousal from non-REM sleep.     

Penetration of Lead by the Wood Piddock Martesia striata

An attack by Martesia striata Linnaeus on the lead sheathing of a power cable is described. This is the third such attack recorded and all have occurred in Florida waters. A guide for describing future attacks is recommended with the hope that the specific conditions under which attacks occur can be learned.     

克氏原螯虾与中华绒螯蟹混养条件下的行为观察

[目的]对克氏原螯虾与中华绒螯蟹混养条件下的行为进行观察和研究。[方法]在相对狭小空间进行等重量级的虾蟹混养试验,观察记录两者相遇初期的格斗行为及混养后期的胜负结局;在相对宽敞空间——"Y"型迷宫内,观察记录克氏原螯虾对较高重量级中华绒螯蟹的趋避行为。[结果]混养试验中虾蟹相遇初期,螯虾首次攻击及靠近的次数、累计主动靠近次数均极显著大于蟹(P<0.01),累计主动攻击次数显著多于蟹(P<0.05);混养30 d后,虾死蟹存组占30%,蟹死虾存组占10%,共存组占60%。在每只受试虾对较高重量级蟹趋避行为试验中,随着试验次数的增多,螯虾对蟹与空白的选择次数和时间由差异性不显著(P>0.05)变为显著偏向选择空白(P<0.05),即螯虾对蟹的识别能力显著提高了,同时试验螯虾的选择行为受到明显抑制。[结论]可以推测,若提供适合的生境条件,虾蟹混养理论上可获得较好效益。     

Secondary evolutionary escalation between brachiopods and enemies of other prey

The fossil record of predation indicates that attacks on Paleozoic brachiopods were very rare, especially compared to those on post-Paleozoic mollusks, yet stratigraphically and geographically widespread. Drilling frequencies were very low in the early Paleozoic (<1%) and went up slightly in the mid-to-late Paleozoic. Present-day brachiopods revealed frequencies only slightly higher. The persistent rarity of drilling suggests that brachiopods were the secondary casualties of mistaken or opportunistic attacks by the enemies of other taxa. Such sporadic attacks became slightly more frequent as trophic systems escalated and predators diversified. Some evolutionarily persistent biotic interactions may be incidental rather than coevolutionary or escalatory in nature.     

Ribonuclease P catalysis differs from ribosomal RNA self-splicing

Two RNA-catalyzed reactions have been described, the Tetrahymena self-splicing ribosomal RNA and ribonuclease P. The Tetrahymena self-splicing reaction proceeds through a transesterification cascade that is dependent upon nucleophilic attacks by ribose 3'-OH groups. Periodate oxidation of the catalytic (or substrate) RNA, which destroys the nucleophilicity of RNA 3' termini, did not inhibit ribonuclease P activity. Thus, catalysis by ribonuclease P differs from the self-splicing reaction.     

Curative potencies against -amanitin poisoning by cytochrome c

The fatalities occurring after ingestion of the poisonous mushroom Amanita phalloides are thought to be due to alpha-amanitin. Cytochrome c provided antidotal effects against a lethal dose of this toxin in mice. Significant survival was obtained even when the treatment was withheld for 8 hours. The enzyme was superior to a previously explored therapeutic regimen consisting of penicillin and its combination with chloramphenicol and sulfamethoxazole.     

对Scholz-Kraft局部效应模型中X线存活曲线模型的不合理性分析

介绍了M. Scholz和G. Kraft等人在计算重离子照射细胞存活率的局部效应模型中使用的X线存活曲线的数学模型,指出此曲线中存在一个毫无依据的自由参数Dt。依据Scholz等人的局部效应模型利用Fortran语言编程计算,证明了此参数取值的不同对局部效应模型的计算结果产生极大影响,由于X线存活曲线是局部效应模型的实验基础,因此此影响对局部效应模型来说是致命的。     

Molecular cloning of a feline leukemia virus that induces fatal immunodeficiency disease in cats

A replication-defective variant of feline leukemia virus was molecularly cloned directly from infected tissue and found to induce a rapid and fatal immunodeficiency syndrome in cats. Studies with cloned viruses also showed that subtle mutational changes would convert a minimally pathogenic virus into one that would induce an acute form of immunodeficiency. The data suggest that acutely pathogenic viruses may be selected against by current methods for isolation of the human and simian immunodeficiency viruses.     

河南省猪链球菌病病原分群鉴定

从河南省郑州、漯河、许昌、南阳等30个市、县的261份送检材料中，检出链球菌阳性者197例，占75．65。对分离的20个典型链球菌菌株进行了系统的生化分群。结果表明，河南省发生的猪链球菌病主要由E群（7／20）、C群兽疫链球菌（6／20）、D群（猪链球菌）（3／20）和L群（3／20）链球菌引起，从而为猪链球菌病的防制提供了重要依据。     

粘质沙雷氏菌对棉铃虫、菜青虫致病力及田间控制的研究初报

从棉田中自然死亡的棉铃虫体上分离到1株粘质沙雷氏菌，经实验研究，该菌对棉铃虫、菜青虫、甜菜液蛾具有致病力和田间控制作用。     

SAFETI在LPG储罐事故后果评价中的应用

分析了LPG危险特性及LPG储罐潜在的火灾爆炸危险性,运用SAFETI软件对某LPG储罐区的各类重大事故后果进行了定量评价,建立了针对性强的事故后果模型.该模型能客观准确地模拟与预测重大事故后果,获得事故危害程度的计算机模拟图表和报告等结果,可提供预测、预防事故发生的措施.     

草莓红蜘蛛的生物学特性及其药剂防治研究

在室内测定3种杀虫剂对草莓红蜘蛛的毒力,并通过试验来了解草莓红蜘蛛的生物学特性。结果表明,1.8%齐螨素的LC50为0.07 mg·L-1;48%毒死蜱乳油的LC50为0.082 mg·L-1;40%漩螨可湿性粉剂的LC50为0.102 mg·L-1。药剂中防治草莓红蜘蛛效果最好的是1.8%齐螨素,40%漩螨可湿性粉剂最差,草莓红蜘蛛的死亡率由高到低依次为使用1 000倍液齐螨素的死亡率96.4%;使用500倍液毒死蜱的死亡率84.6%;使用1 250倍液漩螨的死亡率88.9%,因此,防治草莓红蜘蛛的药剂按效果依次是1.8%齐螨素、48%毒死蜱乳油以及40%漩螨可湿性粉剂。     

图书馆局域网防ARP病毒攻击方法探讨

ARP病毒攻击在图书馆局域网中经常出现,这种病毒清理和防范比较困难,不少网络管理员对此感到困扰.在图书馆以电子阅览室受害最为明显,影响也较大,给读者和工作人员带来诸多不便.为避免或尽量减少因ARP病毒攻击造成的影响.笔者对ARP病毒的症状、攻击原理及处理办法等几个方面作了粗浅的探讨.     

小蠹蛀梢危害对云南松生长及抗性的影响

采用人工接种、林间调查等方法，研究纵坑切梢小蠹蛀梢危害对云南松生长和抗性的影响。结果表明，受害梢率在20．0％以下时，蛀梢危害对云南松的生长和抗性无明显影响。但当受害梢率高于20．1％后，云南松的高、径生长随受害梢率的增加而降低，蛀干成功率则随受害梢率的增加而增高。