Structure and function of alpha-fetoprotein: a biophysical overview

alpha-Fetoprotein (AFP) is a large serum glycoprotein belonging to the intriguing class of onco-developmental proteins. AFP has attracted considerable attention since it was shown that the change in its serum level during pregnancy is a hallmark of the development of numerous embryonic disorders, while the increase in its content in the plasma of adults correlates with the appearance of several pathological conditions. Over the past 30 years, some 11000 papers have been published concerning AFP, an average rate of over a publication a day since 1969. The majority of publications are about the application of the protein in diagnostics, or about other uses of AFP in biomedicine; though some of them describe the biochemical and functional properties of AFP, two aspects have been extensively reviewed. However, surprisingly little is currently known about structural properties of this protein as well as about the molecular mechanism of its function. The present review pursues the aim to describe the current state of the art in studies of structural properties and conformational stability of AFP. An attempt to establish the relationship between conformational transformations in AFP and its function is also made.     

A possible energy-saving role for the major fascia of the thigh in running quadrupedal mammals

Experiments were performed to determine the mechanical importance of the fascia lata in stopping the hind limb during its rearward extension and reversing the direction of leg swing. Samples of fascia lata from a number of different mammals were subjected to tensile tests. Tangent Young's moduli reached about 0.5 GPa and stresses at failure about 50 MPa for fascia from each of the species examined. Energy losses incurred in a loading-unloading cycle were generally about 20%. The moment arms of the fascia lata, in combination with its muscle, about the hip and knee joints were determined and the extension of the fascia lata while its muscle is active was estimated. Calculations suggest that the fascia lata could help to reverse the backward swing of the hind limb by recoiling elastically shortly after the foot leaves the ground. Substantial savings of internal kilnetic energy could be made.     

New insights about host response to smallpox using microarray data

Background  

Smallpox is a lethal disease that was endemic in many parts of the world until eradicated by massive immunization. Due to its lethality, there are serious concerns about its use as a bioweapon. Here we analyze publicly available microarray data to further understand survival of smallpox infected macaques, using systems biology approaches. Our goal is to improve the knowledge about the progression of this disease.     

激光在医学中的应用

本文叙述了几种激光器的优点及其在医学中的应用。它们在治疗过程中的应用方法有很多种,并且还存在有更多种类的激光器,这里选择叙述的是医生和专家常应用的。随着科技的发展,激光技术在医学中的应用将会越来越成熟,旧的激光器也将会被淘汰,越来越先进的激光器一定会问世。本文还将叙述激光的基本理论,以及不同手术中所采用的激光应用技术。     

γH2AX as a Checkpoint Maintenance Signal

A key function of the conserved signaling cascade triggered by DNA damage is to promote the arrest or pause of cell cycle progression, a phenomenon commonly termed a “checkpoint”. This response allows time for DNA repair to proceed before entering a new phase of the cell cycle. Although much is known about the initiation and propagation of this signaling pathway, much less is understood about the mechanisms that lead to its extinction. Recent work highlights a role for H2AX phosphorylation as a checkpoint maintenance factor and of its dephosphorylation as a signal for resumption of the cell cycle.     

A Slow Rotary Shaker for Embedding in Viscous Media

Embedding vessels are carried by a metal tray which has a tilt of about 20° to the horizontal plane. The tray is supported by a shaft attached perpendicular to its bottom. The shaft passes loosely through a hole in a rigid plate and is attached by a ball joint to a crank, which is driven at about 20 rev/min by a geared-down electric motor. Thus a combined tilting and rotary motion is imparted to the tray to produce a continuous flow of the embedding medium about the specimens.     

Purification and properties of theDrosophila zen protein

Summary The zen protein is encoded by the zerknullt gene required for normal early development inDrosophila. Like many regulatory proteins of this type, zen contains a 60 amino acid homeobox sequence. We have purified the zen protein and studied its solution behavior and its interaction with DNA. The zen protein exists as a monomer in solution with a molecular weight of about 40000. It binds specifically to a site about 900 bases upstream from thezen gene. Within this binding site DNase protection experiments indicate that binding is confined to two regions approximately 11 and 14 bases in length that are separated by about 30 base pairs. The protein concentration dependence of the binding curve suggests that protein binding is non cooperative.     

Population biology: wild origins of a model yeast

Yeast is a superb laboratory model organism, but little is known about its natural lifestyle. Recent studies of wild yeast are beginning to reveal details of Saccharomyces population structure and evolution that challenge assumptions about speciation and dispersal in microbes.     

Racialization: a defense of the concept

This paper defends the concept of racialization against its critics. As the concept has become increasingly popular, questions about its meaning and value have been raised, and a backlash against its use has occurred. I argue that when “racialization” is properly understood, criticisms of the concept are unsuccessful. I defend a definition of racialization and identify its companion concept, “racialized group.” Racialization is often used as a synonym for “racial formation.” I argue that this is a mistake. Racial formation theory is committed to racial ontology, but racialization is best understood as the process through which racialized – rather than racial – groups are formed. “Racialization” plays a unique role in the conceptual landscape, and it is a key concept for race eliminativists and anti-realists about race.     

三峡河谷地区柑橘大实蝇羽化、交配及产卵习性

对柑橘大实蝇Bactrocera(Tetracus) minax(Enderlein)的羽化、交配与产卵习性进行初步观察。结果表明,柑橘大实蝇的出土始期为每年的5月8日~5月14日,高峰为5月12日~5月18日,末期为5月30日~6月4日,近几年出土时间有所提前。在早熟蜜柑上主要产卵于果腰部,深度约为4.5mm;在中晚熟蜜柑上主要产卵于果蒂部,深度约为4.1mm;在脐橙上主要产卵于果脐部,深度约为9.7mm;在柚上主要产卵于果蒂和果腰部,深度约为13.0mm。观察结果也与以往记载有所不同。     

A quantitative approach to understand the ultramicro-structure responsible for input mechanism in excitation-contraction (E-C) coupling, on the basis of physio-morphological observations]

Our morphophysiological studies using concanavalin A-ferritin (Con A-F) have indicated that: (1) an out- and up-ward movement of a movable structure at the luminal surface-portion of the T-tubular membrane opposite the feet initiates contraction; (2) the grade of the movement depends on that of depolarization; (3) the movable structure is essentially a 'moving arm', which is fixed in wall of T-tubules at its fixed end and is able to be bound to the Con A-moiety of Con A-F particle about at its free end. Calculation based on molecular morphology and behaviour of Con A-F particle revealed following points: If (a) the origin of coordinate be the intersection of longitudinal center line of foot and the surface of T-tubular membrane in the transverse section of the tubules, (b) the fixed point of the arm is exactly on the surface of T-tubular membrane, and (c) the movement takes place in the transverse direction to the longitudinal axis of T-tubules, (1) the location of the center point of the movement of the moving arm is at 5.4 nm in the outside direction from the origin, (2) the arm is about 4 nm in length and moves by about 2.4 nm up- and out-ward at its free end upon about complete depolarization.     

Passive and active components of the internal moment developed about the ankle joint during human ambulation

The internal moment developed about a joint during a functional activity is the result of contraction of muscles and the visco-elastic properties of the joint and its surrounding soft tissues. In this study, the contribution of each one of these mechanisms to the total internal moment developed about the ankle joint during human level walking was assessed. The results indicate that during normal level walking the internal moment about the ankle is mainly due to contraction of muscles surrounding the joint. The contribution of the passive component was found to be negligible. These results, however, were found to be different for the pathological case tested. The results indicated that in a subject with a mild equinus ankle deformity, a substantial portion (21%) of the total internal moment was contributed by the passive resistance of the joint and its surrounding structures.     

Water? What's so special about it?

What is so special about water? Why does it have the properties it has, and how might these reasons be relevant to its apparent biological importance? By exploring the structure and dynamics of water, from the isolated molecule and its interactions, through its many crystalline phases and to its so-called anomalous liquid phase, some of its apparently unusual behaviour is rationalized. The way in which it interacts with some relatively simple interfaces is also discussed. As a result of this exploration, a checklist of possible molecular-level reasons for its biological importance is devised.     

紫茎泽兰的光合作用特征及其生态学意义

本文研究了紫茎泽兰(Eupatorium adenophorum Spreng)光合作用强度的变化规律及其与环境主要生态因子的关系,比较了它与某些农作物叶片净光合速率的差异,得到如下结果: 1.紫茎泽兰是一种阳性偏阴的C_3类草本植物,其光合作用的光饱和点约为40000 lx,光补偿点约为700 lx,且具有80 ppm左右的CO_2补偿点。 2.紫茎泽兰的最大净光合速率能达到23毫克CO_2/平方分米·时左右,叶片净光合速率的日变化规律呈双峰曲线型(主峰在10时左右,次峰在16时左右)。在一年中有较长的时间,它的光合速率保持着较高的水平。 3.生长在一般菜园土上的紫茎泽兰,当土壤含水量降至17％左右时,叶片光合速率接近0:而且,受过干旱处理的紫茎泽兰植株,在恢复供水后的第三天,其光合速率只达到原来的53％。 根据以上结果,结合受紫茎泽兰危害地区干湿季分明的特点,提出干季是防除紫茎泽兰的最佳季节。     

Is the dynein motor a winch?

Dyneins are the largest and most complex of the three classes of linear motor proteins in eukaryotic cells. The mass of the dynein motor domain is about ten times that of the other microtubule motor, kinesin. Dynein's homology with the AAA+ superfamily of mechanoenzymes distinguishes it from both kinesin and myosin, which share a common fold and ancestry as members of the G-protein superfamily. In contrast to the other motor proteins, little is known about the mechanism of dynein; its three-dimensional structure is unknown even at low resolution. Recent two-dimensional images from electron microscopy have revealed new details of its structure and how this changes to produce movement. These and the recently solved crystal structure of another AAA+ protein, ClpB, offer tantalising hints about dynein's mechanism, suggesting it may act like a molecular winch.     

Medical professionalism and the social contract

Conceptions of professionalism in medicine draw on social contract theory; its strengths and weaknesses play out in how we reason about professionalism. The social contract metaphor may be a heuristic device prompting reflection on social responsibility, and as such is appealing: it encourages reasoning about privilege and responsibility, the broader context and consequences of action, and diverse perspectives on medical practice. However, when this metaphor is elevated to the status of a theory, it has well-known limits: the assumed subject position of contractors engenders blind spots about privilege, not critical reflection; its tendency to dress up the status quo in the trappings of a theoretical agreement may limit social negotiation; its attempted reconciliation of social obligation and self-interest fosters the view that ethics and self-interest should coincide; it sets up false expectations by identifying appearance and reality in morality; and its construal of prima facie duties as conditional misdirects ethical attention in particular situations from current needs to supposed past agreements or reciprocities. Using philosophical ideas as heuristic devices in medical ethics is inevitable, but we should be conscious of their limitations. When they limit the ethical scope of debate, we should seek new metaphors.     

Campylobacter jejuni: molecular biology and pathogenesis

Campylobacter jejuni is a foodborne bacterial pathogen that is common in the developed world. However, we know less about its biology and pathogenicity than we do about other less prevalent pathogens. Interest in C. jejuni has increased in recent years as a result of the growing appreciation of its importance as a pathogen and the availability of new model systems and genetic and genomic technologies. C. jejuni establishes persistent, benign infections in chickens and is rapidly cleared by many strains of laboratory mouse, but causes significant inflammation and enteritis in humans. Comparing the different host responses to C. jejuni colonization should increase our understanding of this organism.