朊蛋白(PrPc)生理功能的研究进展

朊蛋白是主要分布在神经系统的一种糖蛋白,对其生理功能的研究已逐渐成为Prion病研究领域内的另一个热点.朊蛋白可以作为受体与配体结合,传递胞内或胞外信号,它还可能具有抗氧化活性和抗细胞凋亡的特性.     

细胞型朊蛋白对睡眠和认知功能的影响及其调节机制

细胞型朊蛋白(cellular prion protein,PrPC)是一种细胞膜糖蛋白,广泛存在于人和动物的正常组织与细胞中,在神经元中的表达量最高.它是正常细胞基因编码的产物,约含40％的α螺旋结构,而仅含少量β折叠结构,对蛋白酶敏感,通常不致病.PrPC的生理功能尚未阐明,但已有研究提示其与信号转导、金属离子转运、睡眠、学习和记忆、突触可塑性、神经保护、细胞增殖和分化等均有关联.我们就PrPc对于睡眠和认知功能的影响及其调节机制研究现状进行综述.     

1例朊蛋白病患者的护理

朊蛋白病是具有传染性的朊蛋白所致的散发性CNS变性疾病,具有传染性又缺乏核酸的致病因子引起.分人类朊蛋白病和动物朊蛋白病.人类软蛋白病分:CJD、Kuru病、GSS综合征、致死性家族性失眠症.动物朊蛋白病分:羊瘙痒病、传染性水貂脑病、麋鹿&骡鹿慢性消耗病、牛海绵状脑病.     

朊蛋白在神经系统作用机制研究进展

细胞型朊蛋白(PrP~C)作为一种跨膜糖蛋白在哺乳动物中广泛存在。基因敲除的研究显示PrP~C在神经系统的活动中的关键作用包括周围神经髓鞘的形成以及对神经毒素刺激的保护。PrP~C在不同的细胞类型中也有不同的生物学作用。如PrP~C模块化结构、多种结合伴侣以及与脂质筏的密切关联的特性,使其具有组装多组分复合物的能力,从而触发不同的信号通路,调节细胞分化。PrP~C在大脑中参与的病理性作用仍然没有一致的定论,其错误折叠产生的异构体PrP~(SC)是朊病毒疾病的主要致病因素。但有证据指出PrP~C在朊病毒疾病中发挥的致病作用独立于羊瘙痒病朊蛋白亚型(PrP~(SC)),在朊病毒感染过程中,朊病毒疾病的临床和神经病理症状与大脑中PrP~C而不是PrP~(SC)的表达水平成正比。另外,PrP~C可能还是一种与神经退行性病变相关的蛋白,参与β淀粉样蛋白(Aβ)等聚集性蛋白的神经毒素信号转导,还充当α-突触核蛋白的细胞受体,促进其在细胞吸收以及大脑中传播。虽然朊病毒的研究已经取得很大的进展,但PrP~C在大脑中的作用仍然没有明确,因此探索PrP~C在细胞中作用具有十分重要的意义。     

神经变性疾病的朊蛋白样作用机制研究进展

神经变性疾病是一类病因未明、起病隐匿,慢性进行性发展的神经系统疾病,其病理学改变包括异常折叠蛋白沉积、神经元变性及脱髓鞘改变。越来越多文献报道,这类异常折叠蛋白与朊蛋白在分子结构与生物学行为上具有相似性,朊蛋白可能是影响神经变性疾病发生和发展的原因。本文就神经变性疾病的朊蛋白样作用机制作出探讨。     

Creutzfeldt-Jakob病神经影像学研究进展

正Creutzfeldt-Jakob病(CJD)又称皮质-纹状体-脊髓变性,是由变异的朊蛋白(PrP)引起的一种罕见的可传染的、慢性、进展性、致死性神经退行性病变。其发病率为1/100万,CJD病因可分为外源性朊蛋白感染和内源性朊蛋白基因突变。健康人体内存在正常的朊蛋白,即PrPc当外来致病的朊蛋白或遗传性突变导致PrPc变为PrPsc时,PrPsc又会促进PrPc转化为越来越多的PrPsc,致使神经细胞逐渐失去功能,     

星形胶质细胞的生理病理研究进展

星形胶质细胞是中枢神经系统的重要组成细胞。在人类大脑的全部细胞中,星形胶质细胞所占比例可达20%～30%。数量众多的星形胶质细胞具有与其所占比例相对应的重要生理功能,例如为神经元供能、调控神经系统的离子和代谢平衡,以及维持大脑与血脑屏障结构等。除此之外,越来越多的研究表明,星形胶质细胞非常主动地参与到神经系统的发育、成熟和病理过程中。本文对星形胶质细胞的起源、生理功能及其在神经系统疾病研究中的进展进行综述。     

突触蛋白与神经系统疾病

突触蛋白是一组与突触相关的具有神经元特异性的磷酸蛋白,突触蛋白在调节神经递质的释放和神经元的早期发育、再生等方面起着重要的作用。脑缺血缺氧、Alzheimer病、朊蛋白病和癫痫等神经系统疾病均存在突触蛋白表达的改变,研究突触蛋白表达的改变是研究这些神经系统疾病的发病机制、病理及生理改变的重要手段。     

1例朊蛋白病患者的护理

朊蛋白病是具有传染性的朊蛋白所致的散发性CNS变性疾病,具有传染性又缺乏核酸的致病因子引起。分人类朊蛋白病和动物朊蛋白病。人类软蛋白病分：CJD、Kuru病、GSS综合征、致死性家族性失眠症。动物朊蛋白病分：羊瘙痒病、传染性水貂脑病、麋聘＆骡鹿慢性消耗病、牛海绵状脑病。1995年英国发现疯牛病至今已在许多国家传播,人类海绵状脑病新变异型的发现再次引起国际医学界重视,约15％的人类朊蛋白病患者为遗传性（常染色体显性）,特征性病理改变是脑海绵状变性．CJD又称皮质纹状体脊髓变性是可传播的致命性CNS疾病,也是最常见的人类朊蛋白病,临床特征以快速进展性痴呆及大脑皮质基底节＆脊髓局灶性病变为主,成全球性分布,年发病率1／100万．多为老年,平均发病年龄60岁。现将护理报告如下。     

朊蛋白病百年历史回顾

人们首次认识并报道朊蛋白病可追溯至1922年克雅氏病的提出。一百年来, 从对临床症状的困惑到典型组织病理学改变的描述, 从提出"朊蛋白假说"到发现朊蛋白病相关基因, 人们对朊蛋白病的认识在不断加深, 朊蛋白病也逐渐成为一组少见的传染性致死性退行性脑病的总称, 主要包括克雅氏病及其变异型、Kuru病、Gerstmann-Straussler-Scheinker综合征、家族性致死性失眠等。本文现从克雅氏病的发现入手, 详述朊蛋白病特征性病理改变的发现、传染性的验证、朊蛋白及PRNP基因的发现, 以及朊蛋白病多种亚型的临床表现、病理改变、基因突变类型等, 拟通过回顾朊蛋白病的研究历史, 帮助临床同道更深入地了解该病诊断治疗的进展及困境。     

Epilepsy and anomalies of neuronal migration: MRI and clinical aspects

Neuronal migration disorders are the result of disturbed brain development. In such disorders, neurons are abnormally located. In diagnosing these conditions, magnetic resonance imaging is superior to any other imaging technique. This enables us to improve our knowledge of the clinical correlates of neuronal migration. With reference to migrational disorder, a retrospective study of all 303 patients with epileptic seizures referred for magnetic resonance imaging during a 3-year period was performed, 13 patients (aged 12-41, mean age 27) were identified. They represent 4.3% of the entire study group. Of the patients with known epilepsy, 6.7% and of the mentally retarded, 13.7% had migrational disorders. Four patients had schizencephaly as the dominant finding, one was classified as hemimegalencephaly, 2 had isolated heterotopias, and 6 had localized pachy- and/or poly-microgyria. The clinical pictures are complex. Ectopias of grey matter are recognised foci of epilepsy, but from an epileptological and a clinical viewpoint little attention has been given to these disorders. The present study shows that malmigration is not rare in epilepsy patients, especially not in the mentally retarded.     

Classification of methods in transcranial Electrical Stimulation (tES) and evolving strategy from historical approaches to contemporary innovations

Transcranial Electrical Stimulation (tES) encompasses all methods of non-invasive current application to the brain used in research and clinical practice. We present the first comprehensive and technical review, explaining the evolution of tES in both terminology and dosage over the past 100 years of research to present day. Current transcranial Pulsed Current Stimulation (tPCS) approaches such as Cranial Electrotherapy Stimulation (CES) descended from Electrosleep (ES) through Cranial Electro-stimulation Therapy (CET), Transcerebral Electrotherapy (TCET), and NeuroElectric Therapy (NET) while others like Transcutaneous Cranial Electrical Stimulation (TCES) descended from Electroanesthesia (EA) through Limoge, and Interferential Stimulation. Prior to a contemporary resurgence in interest, variations of transcranial Direct Current Stimulation were explored intermittently, including Polarizing current, Galvanic Vestibular Stimulation (GVS), and Transcranial Micropolarization. The development of these approaches alongside Electroconvulsive Therapy (ECT) and pharmacological developments are considered. Both the roots and unique features of contemporary approaches such as transcranial Alternating Current Stimulation (tACS) and transcranial Random Noise Stimulation (tRNS) are discussed. Trends and incremental developments in electrode montage and waveform spanning decades are presented leading to the present day. Commercial devices, seminal conferences, and regulatory decisions are noted. We conclude with six rules on how increasing medical and technological sophistication may now be leveraged for broader success and adoption of tES.     

Hepatic Considerations in the Use of Antiepileptic Drugs

Summary: Virtually all of the major antiepileptic drugs (AEDs) can cause hepatotoxicity, although fatal hepatic reactions are rare. The mechanisms, incidences, and risk profiles for such reactions differ from drug to drug. With carbamazepine and phenytoin, hepatotoxicity may be due to drug hypersensitivity. Although the profiles of patients at risk have not been well-defined for these two antiepileptic drugs, it would appear from reports in the literature that older adolescents and adults are at higher risk than children of developing serious or fatal hepatotoxicity. Once hepatotoxicity develops, mortality rates are 10–38% with phenytoin and 25% for carbamazepine. The risk profile for valproate fatal hepatotoxicity has been more clearly defined. Those at primary risk of fatal hepatic dysfunction are children under the age of 2 years who are receiving multiple anticonvulsants and also have significant medical problems in addition to severe epilepsy. The risk is considerably lower for patients over the age of 2 years on valproate monotherapy. In contrast to the risk profile with other AEDs, adults receiving valproate as monotherapy have the lowest risk of hepatotoxicity. Fatal hepatic dysfunction coincident with valproate may be the result of aberrant drug metabolism. Concomitant use of AEDs that induce microsomal P450 enzymes (e.g., phenytoin and phenobarbital) may enhance the production of a toxic metabolite, and hence the greater risk of hepatotoxicity with polypharmacy.     

Vascular Malformations and Epilepsy: Clinical Considerations and Basic Mechanisms

Summary: Vascular malformations (VMs) are associated with epilepsy. The natural history of the various VMs, clinical presentation, and tendency to provoke epilepsy determine treatment strategies. Investigations have probed the mechanisms of epileptogenesis associated with these lesions. Electrophysiologic changes are associated with epileptogenic cortex adjacent to VMs. Putative pathophysiologic mechanisms of epileptogenesis include neuronal cell loss, glial proliferation and abnormal glial physiology, altered neurotransmitter levels, free radical formation, and aberrant second messenger physiology.     

Neonatal Seizures: Problems in Diagnosis and Classification

Summary: The clinical identification of neonatal seizures is critical for the recognition of brain dysfunction; however, diagnosis is often difficult because of the poorly organized and varied nature of these behaviors. Current classification systems are limited in their ability to communicate motor, autonomic, and electroencephalo-graphic features of seizures precisely and to provide a basis for uniform effective diagnosis, therapy, and determination of prognosis. Recent investigations of neonates, utilizing bedside electroencephalographic/polygraphic/ video monitoring techniques, have provided the basis for improved diagnosis and classification of seizures in the newborn. These studies have demonstrated that not all clinical phenomena currently considered to be seizures require electrocortical epileptiform activity for their initiation or elaboration. In addition, the specific clinical character of the phenomena considered to be seizures, the clinical state of the infant, and the character of the EEG indicate the probable pathophysiological mechanisms involved and suggest probable etiologies, prognosis, and therapy. Similarities between animal models that demonstrate reflex physiology and neonates with motor automatisms and tonic posturing suggest that these clinical behaviors may not be epileptic in origin but, rather, primitive movements of progression and posture mediated by brainstem mechanisms. Although not all clinical behaviors currently considered to be neonatal seizures may have similar pathophysiological mechanisms, they are clinically significant because they all indicate brain dysfunction.     

Valproate Monotherapy in the Management of Generalized and Partial Seizures

Summary: For decades, therapeutic tradition has promoted the concept of polypharmacy in the management of epilepsy. In recent years, however, studies have shown that, for most patients, monotherapy can provide comparable or better seizure control than administration of multiple anticonvulsants, while diminishing the potential for adverse reactions, drug interactions, and poor compliance. Valproate is an important monotherapeutic agent that is highly effective in the control of idiopathic primary and secondarily generalized epilepsies, and partial seizures that do not generalize. Comparative studies have found that valproate is at least as effective as phenytoin and carbamazepine in the treatment of generalized and partial seizures. Given the similar efficacy, other factors such as pharmacokinetics and side effects may therefore determine anticonvulsant selection for monotherapy.     

Un nouveau cadre conceptuel de travail pour la psychiatrie

In an attempt to place psychiatric thinking and the training of future psychiatrists more centrally into the context of modern biology, the author outlines the beginnings of a new intellectual framework for psychiatry that derives from current biological thinking about the relationship of mind to brain. The purpose of this framework is twofold. First, it is designed to emphasize that the professional requirements for future psychiatrists will demand a greater knowledge of the structure and functioning of the brain than is currently available in most training programs. Second, it is designed to illustrate that the unique domain which psychiatry occupies within academic medicine, the analysis of the interaction between social and biological determinants of behavior, can best be studied by also having a full understanding of the biological components of behavior.     

Carbamazepine Efficacy and Utilization in Children

Summary: Carbamazepine is effective for preventing partial and generalized tonic-clonic seizures in children. Although absence epilepsies are more common in children than adults, an estimated 80% of children with epilepsy have seizure types or epilepsies that are potentially responsive to carbamazepine. The differential diagnosis of ictal staring is an especially important issue in children because absence and atypical absence seizures are more prevalent in children than adults. Age-related pharmacokinetic differences and drug interactions are major considerations in children. On average, children have higher clearance rates of carbamazepine, shorter half-lives, and higher ratios of carbamazepine-10, 11-epoxide to carbamazepine than adults. In addition, children with severe epilepsy are more likely to require multiple-drug therapy, which can lead to complex drug interactions. When carbamazepine is administered along with valproate, drug protein binding interactions can cause intermittent side effects.     

Special Pharmacokinetic Considerations in Children

Summary: Pediatric patients have greater degrees of pharmacokinetic variability and unpredictability than adults. This variability results from the effects of pharmacogenetics, age and growth, prior and current comedication, and disease. Newborns with seizures have the least predictable dosage requirements, and their needs change as drug-eliminating mechanisms mature in the neonatal period. Infants have the highest relative capacities to eliminate antiepileptics of any age group and require the largest relative doses. In addition to age-related trends, children demonstrate the same drug-specific, pharmacokinetic phenomena that adults do, including nonlinear phenytoin elimination, nonlinear valproate binding, and autoinduction of carbamazepine. Intercurrent illness and drug interactions further modify the age-related pharmacokinetic patterns in children and make dosage requirements even more unpredictable. Recent studies have shown that febrile illness can affect drug elimination, sometimes decreasing drug levels by 50% or more. Intermittent treatment with benzodiazepines administered either orally or rectally can be an important adjunct and help minimize this type of problem for children with marginally controlled epilepsy. Intermittent benzodiazepines are also helpful for children who have febrile seizures and who need only occasional antiepileptic protection.