Etude cytochimique des protides myéliniques

Résumé Ce travail nous a permis de mettre en évidence une fluorescence bleuâtre de la myéline et de certaines inclusions péricaryales après fixation par le glutaraldehyde. L'observation de l'extinction de cette fluorescence par le noir Soudan B et de son renforcement par l'addition au fixateur de chlorure de calcium, nous a amené à penser que ce phénomène pourrait être imputé aux édifices lipoprotidiques complexes rencontrés dans les inclusions soudanophiles et PAS-positives, et dans la gaine de myéline.En vue de vérifier si ce phénomène s'observait après traitement, in vitro, de diverses molécules lipidiques, nous avons fractionné chimiquement l'ensemble des constituants du cerveau du rat, puis isolé la myéline par ultracentrifugation et séparé ses composants par Chromatographie sur couche mince. Les résultats obtenus par ces deux types de méthodes ont été ensuite vérifiés par une analyse des gangliosides, des protéolipides et des protéines myéliniques après extraction selon des méthodes appropriées.On observe un très net renforcement de l'autofluorescence naturelle des composés lipidiques grâce à l'action du glutaraldehyde. Cette différence est marquée au niveau des cérébrosides, des phosphatides et des protéolipides.La technique d'électrophorèse et de filtration sur gel préalable ou après dialyse des extraits de la myéline contre des solvants organiques permet d'imputer ce phénomène aux protides myéliniques.

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Cytochemical study of myelin proteids

Summary In the present study, it is shown that myelin and some perikaryal inclusions show a bluish fluorescence after glutaraldehyde fixation. This fluorescence can be extinguished by Sudan Black B and reinforced when calcium chloride is added to the fixation fluid; so, we think that this reaction must be due to the complex lipoproteidic patterns found in sudanophil, PAS-positive inclusions, and in the myelin sheath.In order to find out if similar results could be obtained, in vitro, after an identical treatment of different lipidic structures, at first, a chemical fractionation of the components of the rat brain was performed; then, after the isolation of a myelin fraction by ultracentrifugation, we identified its components by thin-layer chromatography. Controls were made directly on gangliosides, proteolipids and myelin proteins after extraction with suitable techniques.We observe a marked reinforcement of the natural autofluorescence of lipidic components after glutaraldehyde treatment. This difference is clearly shown at the level of cerebrosides, phosphatides and proteolipids.Electrophoresis and gel filtration before and after dialysis of the myelin extracts against organic solvents allow us to attribute the reaction mainly to the myelin proteids.

     

Does my mouse have Alzheimer's disease?

Small animal models that manifest many of the characteristic neuropathological and behavioral features of Alzheimer's disease (AD) have been developed and have proven of great value for studying the pathogenesis of this disorder at the molecular, cellular and behavioral levels. The great progress made in our understanding of the genetic factors that either cause or contribute to the risk of developing AD has prompted many laboratories to create transgenic (tg) mice that overexpress specific genes which cause familial forms of the disease. Several of these tg mice display neuropathological and behavioral features of AD including amyloid β-peptide (Aβ) and amyloid deposits, neuritic plaques, gliosis, synaptic alterations and signs of neurodegeneration as well as memory impairment. Despite these similarities, important differences in neuropathology and behavior between these tg mouse models and AD have also been observed, and to date no perfect animal model has emerged. Moreover, ascertaining which elements of the neuropathological and behavioral phenotype of these various strains of tg mice are relevant to that observed in AD continues to be a challenge. Here we provide a critical review of the AD-like neuropathology and behavioral phenotypes of several well-known and utilized tg mice that express human APP transgenes.     

Is my hand connected to my body? The impact of body continuity and arm alignment on the virtual hand illusion

When a rubber hand is placed on a table top in a plausible position as if part of a person’s body, and is stroked synchronously with the person’s corresponding hidden real hand, an illusion of ownership over the rubber hand can occur (Botvinick and Cohen 1998). A similar result has been found with respect to a virtual hand portrayed in a virtual environment, a virtual hand illusion (Slater et al. 2008). The conditions under which these illusions occur have been the subject of considerable study. Here we exploited the flexibility of virtual reality to examine four contributory factors: visuo-tactile synchrony while stroking the virtual and the real arms, body continuity, alignment between the real and virtual arms, and the distance between them. We carried out three experiments on a total of 32 participants where these factors were varied. The results show that the subjective illusion of ownership over the virtual arm and the time to evoke this illusion are highly dependent on synchronous visuo-tactile stimulation and on connectivity of the virtual arm with the rest of the virtual body. The alignment between the real and virtual arms and the distance between these were less important. It was found that proprioceptive drift was not a sensitive measure of the illusion, but was only related to the distance between the real and virtual arms.

Electronic supplementary material

The online version of this article (doi:10.1007/s11571-011-9178-5) contains supplementary material, which is available to authorized users.     

‘They’re my Contacts,not my Friends’: Reconfiguring Affect and Aspirations Through Mobile Communication in Nigeria

ABSTRACT

In Calabar, Nigeria, young women envisage their futures to be full of possibilities. By contrast, their present realities often see them stuck in the house enduring long periods of waiting. Restricted by failing institutions, family and church pressures, and the fear of others’ jealousy, young women find that there is no clear route to realising their aspirations. As they wait alone in the house, they constantly communicate with others on mobile phones and BlackBerries. This paper examines how young women in Calabar use mobile phones as a way of reconceptualising issues of trust, affect and intimacy. It argues that where they employ methods of concealment to chat with others – revealing neither their true identity nor personal details – mobile communication enables distance, becoming an invaluable means for creating new forms of sociality and future opportunities. Illuminating ‘feminine cultures of waiting’, this paper furthers recent analyses of youth, time and productivity.     

Will cardiac surgery improve my quality of life?

Background. The intention of this study is to analyse the correlation between a visual analogue scale (VAS) and the most common preoperative comorbidity and cardiac variables in patients undergoing elective cardiac surgery. This VAS is simple, easy to register and can be used as a global measurement of quality of life (QOL). Methods. Preoperative assessment of QOL in 1351 patients, 979 men and 372 women, with a mean age of 64.5±10.5 (18-88), undergoing elective cardiac surgery between January 2003 and December 2005. QOL was measured by the EuroQol questionnaire. Results. The mean VAS was 58.7±20.9, range 3 to 100. Univariate analysis showed a difference for sex (p=0.000), and NYHA (p=0.009) between patients with an isolated CABG and those with a combined revascularisation (p=0.05). Stepwise logistic regression analysis identified female gender (p=0.00), NYHA (p=0.00) and valve disease (p=0.03) as independent variables for a low QOL. The correlation between NYHA and QOL was low (r=-0.09, p=0.003). Conclusion. The clinical consequence is that using this simple VAS we can identify patients with a good QOL. If these patients present for high-risk surgery, with a better quality of life as primary indication, more extended counselling regarding their QOL is recommended. (Neth Heart J 2007; 15:51-4.)     

Where, oh where has my protein gone?

A recent publication by R. Chikwamba and colleagues highlights interesting issues in recombinant protein expression in transgenic plants. In the study they expressed a bacterial antigen in maize seed and obtained aberrant localization data. This work is of great importance to the biotechnology industry and raises fascinating questions in plant cell biology that require creative thinking.     

Won't you be my neighbor? Local induction of arteriogenesis

Two recent papers in Cell and Developmental Cell provide evidence that VEGF directs arterial differentiation. Evidence that sensory nerves direct arteriogenesis and that the membrane-spanning Notch signaling system is downstream of VEGF emphasize the paracrine regulation of vessel formation.     

Will my protein crystallize? A sequence‐based predictor

We propose a machine-learning approach to sequence-based prediction of protein crystallizability in which we exploit subtle differences between proteins whose structures were solved by X-ray analysis [or by both X-ray and nuclear magnetic resonance (NMR) spectroscopy] and those proteins whose structures were solved by NMR spectroscopy alone. Because the NMR technique is usually applied on relatively small proteins, sequence length distributions of the X-ray and NMR datasets were adjusted to avoid predictions biased by protein size. As feature space for classification, we used frequencies of mono-, di-, and tripeptides represented by the original 20-letter amino acid alphabet as well as by several reduced alphabets in which amino acids were grouped by their physicochemical and structural properties. The classification algorithm was constructed as a two-layered structure in which the output of primary support vector machine classifiers operating on peptide frequencies was combined by a second-level Naive Bayes classifier. Due to the application of metamethods for cost sensitivity, our method is able to handle real datasets with unbalanced class representation. An overall prediction accuracy of 67% [65% on the positive (crystallizable) and 69% on the negative (noncrystallizable) class] was achieved in a 10-fold cross-validation experiment, indicating that the proposed algorithm may be a valuable tool for more efficient target selection in structural genomics. A Web server for protein crystallizability prediction called SECRET is available at http://webclu.bio.wzw.tum.de:8080/secret.     

What cardiovascular defect does my prenatal mouse mutant have,and why?

Since the advent of mouse targeted mutations, gene traps, an escalating use of a variety of complex transgenic manipulations, and large-scale chemical mutagenesis projects yielding many mutants with cardiovascular defects, it has become increasingly evident that defects within the heart and vascular system are largely responsible for the observed in utero lethality of the embryo and early fetus. If a transgenically altered embryo survives implantation but fails to be born, it usually indicates that there is some form of lethal cardiovascular defect present. A number of embryonic organ and body systems, including the central nervous system, gut, lungs, urogenital system, and musculoskeletal system appear to have little or no survival value in utero (Copp, 1995). Cardiovascular abnormalities include the failure to establish an adequate yolk-sac vascular circulation, which results in early lethality (E8.5-10.5); poor cardiac function (E9.0-birth); failure to undergo correct looping and chamber formation of the primitive heart tube (E9.0-11.0); improper septation, including division of the common ventricle and atria and the establishment of a divided outflow tract (E11.0-13.0); inadequate establishment of the cardiac conduction system (E12.0-birth); and the failure of the in utero cardiovascular system to adapt to adult life (birth) and close the interatrial and aorta-pulmonary trunk shunts that are required for normal fetal life. Importantly, the developmental timing of lethality is usually a good indicator of both the type of the cardiovascular defect present and may also suggest the possible underlying cause/s. The purpose of this review is both to review the literature and to provide a beginner's guide for analysing cardiovascular defects in mouse mutants.     

Strangers no more’s several contributions (and my few regrets)

ABSTRACT

The main strengths of the book include, I argue, the authors’ sophisticated conceptualization of immigrants’ and their offspring’s integration into the host society as complex, multi-dimensional processes which can contain contradictory tendencies; a well-executed and informative comparative analysis of these developments in several countries with – rare among the social scientists – a firm anchoring of the present situations in the past from which they emerge; and useful practical suggestions for policy-making derived by the authors from their findings. Rather than outright criticisms, I then present a few regrets regarding, on the one hand, the book’s presentation style or what I felt were some too forcefully stated claims, and, on the other hand, some un(der)explored issues which, in my opinion, merited more analytic attention.     

Review: “Doctor,will that x-ray harm my unborn child?”

Abstract: Exposure to ionizing radiation can be a source of anxiety for many pregnant women and their health care providers. An awareness of the radiation doses delivered by different techniques and the acceptable exposure thresholds can help both patients and practitioners. We describe exposure to radiodiagnostic procedures during pregnancy and suggest an approach to assess the potential risk.Case 1: A 29-year-old patient underwent an upper gastrointestinal series as part of the diagnosis of prolonged heartburn. She comes to see you 1 week later and is very upset because her period is 1 week late and she was about 4 weeks pregnant at the time of the procedure. The patient asks you to schedule the termination of her pregnancy on the advice of several family members.Case 2: A 40-year-old woman arrives at the emergency department with acute pleuritic chest pain and shortness of breath. The patient is 15 weeks'' pregnant. To rule out a pulmonary embolus, should you perform a ventilation-perfusion scan or computed tomography (CT) angiography?Case 3: A 37-year-old woman who is 20-weeks pregnant reports persistent pain in her right upper thigh that is exacerbated after jogging. The pain is localized and has no radicular properties. A physical examination shows localized tenderness on the right hip joint without any abnormal neurological findings. You suspect hip bursitis but want to order a radiograph to rule out osteoarthritis with degenerative changes. The patient is nervous about the possible effects of the radiation on her baby; how would you counsel her?Many women are exposed to radiation from diagnostic imaging procedures before they know they are pregnant or because it is necessary during a known pregnancy. These patients often question the potential effects of the radiation on the developing fetus, and they may perceive radiation as being very harmful.^1–4 A realistic and informed approach to counselling these patients can minimize the anxiety felt by both patients and health care providers.Humans are exposed to both background and man-made sources of radiation. For the purpose of this review, “radiation” refers to ionizing radiation (e.g., x-rays, γ-rays, radionuclides) and not to other forms of radiation (e.g., long-wavelength electromagnetic waves such as radar, microwaves, diathermy and FM radio waves).Ionizing radiation in the form of x-rays and γ-rays are short-wavelength electromagnetic rays. Low-energy photons in x-rays and high-energy photons in γ-rays can alter the normal structure of a living cell both directly and indirectly. The direct mechanism involves disruption of the atom''s structure to produce an ionized compound and a free electron. The indirect mechanism involves radiolysis of water and generation of free radicals.⁵Ionizing radiation can cause two types of effects.⁵ First, loss of tissue function (deterministic effect) can occur. This type of injury has tissue-specific thresholds and may involve various repair and compensatory mechanisms. If the radiation dose is fractionated, there is greater repair and proliferation, hence there is greater tolerance of the tissue to the radiation. Second, damage can occur from a single random modification in a cell component (e.g., DNA) (stochastic effect). There is no dose threshold for stochastic effects.Since invention of the x-ray in 1895, ionizing radiation has been harnessed for diagnostic and therapeutic purposes. With the atomic bombings in World War II, the world became aware of the serious potential carcinogenic, teratogenic and mutagenic effects of ionizing radiation. Despite the increase in concern about the health effects of ionizing radiation, the medical use of x-rays has continued to grow. In 1980, the number of radiographs performed in the United States was 225 million, including about 80 million fertile men and women.⁵ In 2006, the estimated total number of radiographs in the US was about 330 million.⁶ The fetus is exposed to unavoidable (background) radiation from cosmic rays, terrestrial radiation from ground and building and naturally occurring radioisotopes that are inhaled or ingested. The total fetal dose from background radiation sources is 0.1 rad or less during the entire pregnancy.⁵     

Is my study system good enough? A case study for identifying maternal effects

In this paper, we demonstrate how simulation studies can be used to answer questions about identifiability and consequences of omitting effects from a model. The methodology is presented through a case study where identifiability of genetic and/or individual (environmental) maternal effects is explored. Our study system is a wild house sparrow (Passer domesticus) population with known pedigree. We fit pedigree‐based (generalized) linear mixed models (animal models), with and without additive genetic and individual maternal effects, and use deviance information criterion (DIC) for choosing between these models. Pedigree and R‐code for simulations are available. For this study system, the simulation studies show that only large maternal effects can be identified. The genetic maternal effect (and similar for individual maternal effect) has to be at least half of the total genetic variance to be identified. The consequences of omitting a maternal effect when it is present are explored. Our results indicate that the total (genetic and individual) variance are accounted for. When an individual (environmental) maternal effect is omitted from the model, this only influences the estimated (direct) individual (environmental) variance. When a genetic maternal effect is omitted from the model, both (direct) genetic and (direct) individual variance estimates are overestimated.