The hypocretins/orexins: novel hypothalamic neuropeptides involved in different physiological systems

The hypothalamus regulates diverse physiological functions, including the control of energy metabolism, circadian rhythms, stress and anxiety, sexual and reproductive behaviors. An overview of the most prevalent hypothalamus-enriched mRNAs revealed that this area of the brain specializes in producing intercellular signaling molecules. Two new secreted peptides derived from a single neuropeptide precursor, named hypocretins and orexins by two different groups, are synthesized in a small set of neurons in the perifornical area of the hypothalamus. Intracerebroventricular injection of the hypocretins/orexins increases food consumption in rats. Here we review recent progress in identifying the role of the hypocretins/orexins in the control of energy balance and in other physiological systems.     

浅谈英语教学中的激情

对于职中学生来说，英语是门枯燥的学科；而作为职中老师，面对学生无精打采的课堂反应，也颇为头疼。大部分职高生认为他们将来不参加高考，毕业后当工人，英语对他们用处也不大，再加上学生初中英语基础不扎实，有的甚至从未考过及格，自然到高中就更没兴趣去学，学英语就一直处于很被动的状态；他们对英语课缺乏兴趣，喜欢上英语课的只占少数，把自己对上英语课的不感兴趣归咎于任课教师讲课枯燥。针对职中教育的特殊性，我们一方面要对职中学生反复强调学习英语的重要性，另一方面我们老师则要对自己的英语教学方法积极思索，从而提高学生的课堂积极性。教学方法是教学活动的一个主要部分，直接感染影响学巾。青少年学生对任何事物都存在着求新好奇的特点，新奇多变的事物往往使学生产生浓厚的兴趣。反之，教无趣，必不乐学。而一成不变的方法上课只会使教学方法单调呆板。如念电词、读课文、讲语法、做练习，教师讲、学生听，教师写、学生抄这类固定的模式，学生看不到新鲜的东西，使大脑皮层受到抑制，好奇心内驰力逐渐消失，兴趣也就会慢慢低落下去。     

基于信息技术环境的民族高师教育地理学课程研究性学习的实证研究

提出通过研究性学习帮助高师民族师范学生形成对地理知识主动、积极学习的模式.文章重点论述了研究性学习的教学特点与民族师范学生学习的适应性,研究性学习实证研究的内涵及其特征意义,信息技术环境下民族师范生地理学课程的研究性学习实证研究的方案、实施过程与研究结论.     

Why large-scale climate indices seem to predict ecological processes better than local weather

Large-scale climatic indices such as the North Atlantic Oscillation are associated with population dynamics, variation in demographic rates and values of phenotypic traits in many species. Paradoxically, these large-scale indices can seem to be better predictors of ecological processes than local climate. Using detailed data from a population of Soay sheep, we show that high rainfall, high winds or low temperatures at any time during a 3-month period can cause mortality either immediately or lagged by a few days. Most measures of local climate used by ecologists fail to capture such complex associations between weather and ecological process, and this may help to explain why large-scale, seasonal indices of climate spanning several months can outperform local climatic factors. Furthermore, we show why an understanding of the mechanism by which climate influences population ecology is important. Through simulation we demonstrate that the timing of bad weather within a period of mortality can have an important modifying influence on intraspecific competition for food, revealing an interaction between climate and density dependence that the use of large-scale climatic indices or inappropriate local weather variables might obscure.     

Epigenetic inactivation of SFRP genes allows constitutive WNT signaling in colorectal cancer

Aberrant WNT pathway signaling is an early progression event in 90% of colorectal cancers. It occurs through mutations mainly of APC and less often of CTNNB1 (encoding beta-catenin) or AXIN2 (encoding axin-2, also known as conductin). These mutations allow ligand-independent WNT signaling that culminates in abnormal accumulation of free beta-catenin in the nucleus. We previously identified frequent promoter hypermethylation and gene silencing of the genes encoding secreted frizzled-related proteins (SFRPs) in colorectal cancer. SFRPs possess a domain similar to one in the WNT-receptor frizzled proteins and can inhibit WNT receptor binding to downregulate pathway signaling during development. Here we show that restoration of SFRP function in colorectal cancer cells attenuates WNT signaling even in the presence of downstream mutations. We also show that the epigenetic loss of SFRP function occurs early in colorectal cancer progression and may thus provide constitutive WNT signaling that is required to complement downstream mutations in the evolution of colorectal cancer.     

Generalized solutions to the Benjamin-Ono equations in sense of Colombeau

This paper discusses the existence and uniqueness of the generalized solution in the sense of Colombeau to the Benjamin-Ono (B-O) equation and the relationship between the new generalized solution and the classical solution.     

Mathematical modeling of salt-gradient ion-exchange simulated moving bed chromatography for protein separations

The salt-gradient operation mode used in ion-exchange simulated moving bed chromatography (SMBC) can improve the efficiency of protein separations. A detailed model that takes into account any kind of adsorption/ion-exchange equilibrium, salt gradient, size exclusion, mass transfer resistance, and port periodic switching mechanism, was developed to simulate the complex dynamics. The model predictions were verified by the experimental data on upward and downward gradients for protein separations reported in the literature. All design and operating parameters (number, configuration, length and diameter of columns, particle size, switching period, flow rates of feed, raffinate, desorbent and extract, protein concentrations in feed, different salt concentrations in desorbent and feed) can be chosen correctly by numerical simulation. This model can facilitate the design, operation, optimization, control and scale-up of salt-gradient ion-exchange SMBC for protein separations.     

Pathogenesis of Plasmodium falciparum malaria: the roles of parasite adhesion and antigenic variation

Malaria results in up to 2.5 million deaths annually, with young children and pregnant women at greatest risk. The great majority of severe disease is caused by Plasmodium falciparum. A characteristic feature of infection with P. falciparum is the accumulation or sequestration of parasite-infected red blood cells (RBCs) in various organs, such as the brain, lung and placenta, and together with other factors is important in the pathogenesis of severe forms of malaria. Sequestration results from adhesive interactions between parasite-derived proteins expressed on the surface of infected RBCs and a number of host molecules on the surface of endothelial cells, placental cells and uninfected RBCs. Some receptors for parasite adhesion have been implicated in particular malaria syndromes, such as intercellular adhesion molecule 1 in cerebral malaria and chondroitin sulfate A and hyaluronic acid in placental infection. The principal parasite ligand and antigen on the RBC surface, P. falciparum erythrocyte membrane protein 1 encoded by a multigene family termed var, is clonally variant, enabling evasion of specific immune responses. An understanding of these host-parasite interactions in the context of clinical disease and immunity may reveal potential targets to prevent or treat severe forms of malaria. Received 25 June 2001; received after revision 22 August 2001; accepted 24 August 2001