Participation of the endothelium in the development of the atherosclerotic plaque

In the past decade, initiated by the response-to-injury hypothesis of Ross and Glomset, the endothelium has been implicated in atherogenesis but as a passive participant--more involved through its absence than its presence. The hypothesis stated that endothelial desquamation due to an undefined injury led to platelet adhesion to the exposed basement membrane, and infiltration of serum lipoproteins. The subsequent release from the platelet alpha-granule of a potent smooth muscle cell mitogen and chemoattractant--the platelet-derived growth factor (PDGF)--was postulated to cause the intimal proliferative response that is known to be important in atherosclerotic plaque development. Recent evidence from several laboratories indicates that the endothelium has the potential to play a more active role in plaque development than simply contributing to pathological sequelae resulting from the loss of the nonthrombogenic surface provided by the endothelium. First, the endothelial cell (EC) is the site of attachment, and possibly activation, of blood-borne monocytes which enter the vessel wall as an early event in experimental atherogenesis. We have obtained in vitro evidence that the expression of monocyte binding sites on the surface of EC is a regulatable process and that increased EC turnover and certain exogenous agents acting on EC cause increased monocyte adhesion. Similar events may be responsible for focal adhesion of monocytes to the endothelium in vivo following hypercholesterolemia. Secondly, EC in culture are capable of chemically modifying low density lipoprotein (LDL) by a free radical oxidation process that renders the LDL toxic to proliferating cells and recognizable to the scavenger receptor of monocyte-derived macrophages. Thus, by oxidation of LDL, the EC have the potential to play an active role both in the formation of lipid-laden foam cells and in the accumulation of necrotic tissue which are hallmarks of the atherosclerotic lesion. Thirdly, cultured EC have been recently shown to secrete multiple mitogens for cultured smooth muscle cells. One of these mitogens appears to be closely related, if not identical, to PDGF using the criteria of receptor binding and biochemical and immunological similarity. Production of growth factors by EC is a regulatable process that is stimulated by exogenous agents such as endotoxin and phorbol esters which cause severe injury to cultured EC. Such a regulatory mechanism may participate in the in vivo proliferation of vascular SMC during the atherosclerotic process.(ABSTRACT TRUNCATED AT 400 WORDS)     

On the existence of a gradient of sensitivity to the lack of sodium in the spinal roots of the bullfrog

The Et class of fibers includes fibers of Gasser's d.r. C group. The fibers of the dorsal root are more sensitive to the effect of lack of sodium than are the fibers of the ventral root. In the two roots there is a gradient of sensitivity to the lack of sodium, which is such that in all the root fibers the sensitivity decreases with increasing distance from the spinal cord. The gradient continues in the trunk up to about 10 to 12 mm. peripheral to the trunk-roots margin. No comparable gradient of sensitivity to the lack of sodium has been observed in the rest of the nerve trunk. The gradient of sensitivity to the lack of sodium has no relationship to the anatomical distribution of the epineurium. As a working hypothesis it is suggested that the gradient of sensitivity to the lack of sodium is one aspect of a transitional gradient that serves to establish a gradual change between the properties that the axons have inside the spinal cord and the properties that they have inside the nerve trunks. Details are given of the temporal course of the loss of excitability by root fibers deprived of sodium. It is suggested that sodium is present in the nerve fibers, in 2 forms, loosely and tightly bound sodium and that loss of loosely bound sodium is sufficient to render the nerve fibers unable to conduct impulses. If the rate of loss of loosely bound sodium is decreased, conversion of tightly bound into loosely bound sodium may temporarily restore the excitability of the nerve fibers.     

Characterization of the structure and the amyloidogenic properties of the Josephin domain of the polyglutamine-containing protein ataxin-3

Expansion of the polyglutamine (polyQ) region in the protein ataxin-3 is associated with spinocerebellar ataxia type 3, an inherited neurodegenerative disorder that belongs to the family of polyQ diseases. Increasing evidence indicates that protein aggregation and fibre formation play an important role in these pathologies. In a previous study, we determined the domain architecture of ataxin-3, suggesting that it comprises a globular domain, named Josephin, and a more flexible C-terminal region, that includes the polyQ tract. Here, we have characterised for the first time the biophysical properties of the isolated Josephin motif, showing that it is an autonomously folded unit and that it has no significant interactions with the C-terminal region. Study of its thermodynamic stability indicates that Josephin has an intrinsic tendency to aggregate and forms temperature-induced fibrils similar to those described for expanded ataxin-3. We show that, under destabilising conditions, the behaviours of the isolated Josephin domain and ataxin-3 are extremely similar. Our data therefore strongly suggest that the stability and aggregation properties of non-expanded ataxin-3 are determined by those of the Josephin domain, which is sufficient to reproduce the behaviour of the full-length protein. Our data support a mechanism in which the thermodynamic stability of ataxin-3 is governed by the properties of the Josephin domain, but the presence of an expanded polyQ tract increases dramatically the protein's tendency to aggregate.     

The functions of the proprioceptors of the eye muscles

This article sets out to present a fairly comprehensive review of our knowledge about the functions of the receptors that have been found in the extraocular muscles--the six muscles that move each eye of vertebrates in its orbit--of all the animals in which they have been sought, including Man. Since their discovery at the beginning of the 20th century these receptors have, at various times, been credited with important roles in the control of eye movement and the construction of extrapersonal space and have also been denied any function whatsoever. Experiments intended to study the actions of eye muscle receptors and, even more so, opinions (and indeed polemic) derived from these observations have been influenced by the changing fashions and beliefs about the more general question of how limb position and movement is detected by the brain and which signals contribute to those aspects of this that are perceived (kinaesthesis). But the conclusions drawn from studies on the eye have also influenced beliefs about the mechanisms of kinaesthesis and, arguably, this influence has been even larger than that in the converse direction. Experimental evidence accumulated over rather more than a century is set out and discussed. It supports the view that, at the beginning of the 21st century, there are excellent grounds for believing that the receptors in the extraocular muscles are indeed proprioceptors, that is to say that the signals that they send into the brain are used to provide information about the position and movement of the eye in the orbit. It seems that this information is important in the control of eye movements of at least some types, and in the determination by the brain of the direction of gaze and the relationship of the organism to its environment. In addition, signals from these receptors in the eye muscles are seen to be necessary for the development of normal mechanisms of visual analysis in the mammalian visual cortex and for both the development and maintenance of normal visuomotor behaviour. Man is among those vertebrates to whose brains eye muscle proprioceptive signals provide information apparently used in normal sensorimotor functions; these include various aspects of perception, and of the control of eye movement. It is possible that abnormalities of the eye muscle proprioceptors and their signals may play a part in the genesis of some types of human squint (strabismus); conversely studies of patients with squint in the course of their surgical or pharmacological treatment have yielded much interesting evidence about the central actions of the proprioceptive signals from the extraocular muscles. The results of experiments on the eye have played a large part in the historical controversy, now in at least its third century, about the origin of signals that inform the brain about movement of parts of the body. Some of these results, and more of the interpretations of them, now need to be critically re-examined. The re-examination in the light of recent experiments that is presented here does not support many of the conclusions confidently drawn in the past and leads to both new insights and fresh questions about the roles of information from motor signals flowing out of the brain and that from signals from the peripheral receptors flowing into it. There remain many lacunae in our knowledge and filling some of these will, it is contended, be essential to advance our understanding further. It is argued that such understanding of eye muscle proprioception is a necessary part of the understanding of the physiology and pathophysiology of eye movement control and that it is also essential to an account of how organisms, including Man, build and maintain knowledge of their relationship to the external visual world. The eye would seem to provide a uniquely favourable system in which to study the way in which information derived within the brain about motor actions may interact with signals flowing in from peripheral receptors. The review is constructed in relatively independent sections that deal with particular topics. It ends with a fairly brief piece in which the author sets out some personal views about what has been achieved recently and what most immediately needs to be done. It also suggests some lines of study that appear to the author to be important for the future.     

On the nature of the tumor-initiating cell

Certain aspects of tumors that may influence areas of basic biology and medicine are reviewed. The hypothesis that malignant stem cells evolve from normal stem cells, is considered. Information is being accumulated on the possibility that certain cell populations that can be propagated as cell lines in vitro can produce cells with features of differentiated cells in addition to others that maintain the line and, in some cases may also initiate tumor formation in vivo. Up to the present time, there is evidence to show that cancer stem cells persist in many cell lines. Tyrosine kinase inhibition produces combinations of autophagy and apoptosis in the human erythroleukemia cell line TF-1 hinting at a heterotypic aggregation of cells containing cancer stem cells. Finally, the mechanisms of cancer development, invasion and metastasis are operatively defined. The purpose of this paper is to review some of the salient features of cancer stem cells in support of the proposal that research in neoplasia be increased. Rather than presenting details of various studies, we have attempted to indicate general areas in which work has been done or is in progress. It is hoped that this survey of the subject will demonstrate a variety of opportunities for additional research in human neoplasia.     

Digitoxose and the existence of a glucoreceptor in the beta cells of the islets of langerhans of the rat

On the basis that digitoxin is the only drug reported up to now that stimulating insulin release per se, partially inhibits glucose stimulated insulin release, in this work the idea that the competition glucose-digitoxin may be at the level of a hypothetical glucoreceptor in the beta cells (binding of the glycoside sugar molecule) has been investigated. Our findings indicate that the integrity of the chemical structure of digitoxin is needed to exert its pharmacological action on insulin release. We also demonstrate that digitoxose inhibits glucose stimulated insulin release without inhibiting the glucose oxidation rates of the islets. The discovery of a sugar (digitoxose) that inhibitis the insulin secretory response to glucose without inhibiting glucose metabolism is a strong evidence that the action of glucose itself is blocked at the level of glucoreceptors located in the cell membrane, which appear to be the regulator sites of insulin release.     

An Analysis of the Metabolic Theory of the Origin of the Genetic Code

A computer program was used to test Wong's coevolution theory of the genetic code. The codon correlations between the codons of biosynthetically related amino acids in the universal genetic code and in randomly generated genetic codes were compared. It was determined that many codon correlations are also present within random genetic codes and that among the random codes there are always several which have many more correlations than that found in the universal code. Although the number of correlations depends on the choice of biosynthetically related amino acids, the probability of choosing a random genetic code with the same or greater number of codon correlations as the universal genetic code was found to vary from 0.1% to 34% (with respect to a fairly complete listing of related amino acids). Thus, Wong's theory that the genetic code arose by coevolution with the biosynthetic pathways of amino acids, based on codon correlations between biosynthetically related amino acids, is statistical in nature. Received: 8 August 1996 / Accepted: 26 December 1996     

Analysis of the association of syncollin with the membrane of the pancreatic zymogen granule

Syncollin is a pancreatic zymogen granule protein that was isolated through its ability to bind to syntaxin. Here we show that syncollin has a cleavable signal sequence and can be removed from granule membranes by washing with sodium carbonate. When membranes were subjected to Triton X-114 partitioning, syncollin was found predominantly in the aqueous phase, indicating that it is not sufficiently hydrophobic to be embedded in the membrane. Syncollin has intramolecular disulfide bonds and was accessible to water-soluble cross-linking and biotinylating reagents only when granules were lysed by sonication. These results indicate that syncollin is tightly bound to the luminal surface of the granule membrane. In situ, syncollin was resistant to proteases such as trypsin. When granule membranes were solubilized in ionic detergents such as deoxycholate, this trypsin resistance was maintained, and syncollin migrated on sucrose density gradients as a large (150 kDa) protein. In contrast, in non-ionic detergents such as Triton X-100, syncollin became partially sensitive to trypsin and behaved as a monomer. Syncollin in alkaline extracts of granule membranes was also monomeric. However, reduction of the pH regenerated the oligomeric form, which was insoluble. We conclude that syncollin exists as a homo-oligomer and that its ability to self-associate can be reversibly modulated via changes in pH. In light of our findings, we reassess the likely role of syncollin in the pancreatic acinar cell.     

Development of the catecholaminergic innervation of the song system of the male zebra finch

Catecholamines (CA) have been proposed to have neuromodulatory actions, particularly on attention and learning, in a number of neural systems. Because several of the interconnected brain nuclei that mediate song learning and production in the adult male zebra finch (Taeniopygia guttata) contain these neurotransmitters, we investigated the appearance of the catecholaminergic innervation of the song nuclei of male zebra finches during posthatch development, specifically during the period in which song learning occurs. We studied the development of immunoreactivity for tyrosine hydroxylase (TH) in the song nuclei HVc, RA, NIf, LMAN, and Area X in young males aged 20, 35, and 60 days as well as in adults (>90 days). We also visualized catecholamines directly in Area X using CA histofluorescence. Both TH immunoreactivity and CA histofluorescence were initially low in Area X relative to their levels in the surrounding parolfactory lobe (LPO), and then increased during development to become more intense than in LPO by days 60–90. Similarly, TH immunoreactivity in HVc was initially low relative to that in the surrounding neostriatum, then increased during development to become more intense than that in the surround by day 60. TH immunostaining also increased markedly in NIf, RA, and LMAN over the same period. These results show that the levels of catecholamines and their major synthetic enzyme increase in song nuclei during development and thus raise the possibility that these transmitters contribute to the development of the song system or to song learning. © 1996 John Wiley & Sons, Inc.     

On the analysis of competition at the level of the individual plant

Summary The extent to which some measure of local crowding can account for the performance of individual plants is examined with reference to populations of two species of annual plant. Only a relatively small proportion of the variation in individual plant yield could be accounted for by measures of local crowding. These included the number of close neighbours, an estimate of the area available to each plant and competitive pressure. A multiple regression that took account of both emergence time and local crowding increased the proportion of variance that could be accounted for up to 50%. Computer simulations of the growth of indivudual plants in monoculture were then caried out in order to determine whether the unexplained variation resulted from fundamental flaws in the models or from unaccounted for sources of variation in the field. The results from the simulations again indicated that only a relatively low proportion of the variation in individual plant yield could be accounted for by emergence time and local density, even though these were known to be the only variables present. These findings are discussed in relation to the relative importance of one-sided and two-sided competition, and the complex cross-correlations that occur between individuals in plant populations. These two factors will make it very difficult for field workers to determine accurately what factors determine individual plant yield and in particular to predict the effects of local crowding on the performance of individual plants.     

The development of the bladder trigone, the center of the anti-reflux mechanism

The urinary tract is an outflow system that conducts urine from the kidneys to the bladder via the ureters that propel urine to the bladder via peristalsis. Once in the bladder, the ureteral valve, a mechanism that is not well understood, prevents backflow of urine to the kidney that can cause severe damage and induce end-stage renal disease. The upper and lower urinary tract compartments form independently, connecting at mid-gestation when the ureters move from their primary insertion site in the Wolffian ducts to the trigone, a muscular structure comprising the bladder floor just above the urethra. Precise connections between the ureters and the trigone are crucial for proper function of the ureteral valve mechanism; however, the developmental events underlying these connections and trigone formation are not well understood. According to established models, the trigone develops independently of the bladder, from the ureters, Wolffian ducts or a combination of both; however, these models have not been tested experimentally. Using the Cre-lox recombination system in lineage studies in mice, we find, unexpectedly, that the trigone is formed mostly from bladder smooth muscle with a more minor contribution from the ureter, and that trigone formation depends at least in part on intercalation of ureteral and bladder muscle. These studies suggest that urinary tract development occurs differently than previously thought, providing new insights into the mechanisms underlying normal and abnormal development.     

Evolution of the turtle bauplan: the topological relationship of the scapula relative to the ribcage

The turtle shell and the relationship of the shoulder girdle inside or ‘deep’ to the ribcage have puzzled neontologists and developmental biologists for more than a century. Recent developmental and fossil data indicate that the shoulder girdle indeed lies inside the shell, but anterior to the ribcage. Developmental biologists compare this orientation to that found in the model organisms mice and chickens, whose scapula lies laterally on top of the ribcage. We analyse the topological relationship of the shoulder girdle relative to the ribcage within a broader phylogenetic context and determine that the condition found in turtles is also found in amphibians, monotreme mammals and lepidosaurs. A vertical scapula anterior to the thoracic ribcage is therefore inferred to be the basal amniote condition and indicates that the condition found in therian mammals and archosaurs (which includes both developmental model organisms: chickens and mice) is derived and not appropriate for studying the developmental origin of the turtle shell. Instead, among amniotes, either monotreme mammals or lepidosaurs should be used.     

Contribution of the Belgian school of embryology to the concept of neural induction by the organizer

Albert BRACHET, founder of the Brussels School of embryology, conducted delicate experiments in which he selectively destroyed zones of the grey crescent with heated needles. This allowed him to observe, in 1923, that the median region of the grey crescent of the blastula is a area of spontaneous differentiation and that this "primary self-differentiation centre" organizes the axial organs in anurans. It is thus fair to say that A. BRACHET contributed significantly to the emergence of the organizer concept. Albert DALCQ and Jean PASTEELS, successors of A. BRACHET, trying to solve the problem of the organizer's determination, proposed their famous quantitative theory of embryonic development resulting in the concept of morphogenetic potential, which increases with the CV concentration, a combination of a cortical constituent C and a vegetal substance V. Jean BRACHET, the younger son of A. BRACHET and one of the founding father of molecular biology and embryology, was soon convinced that the organizer owes its inducing power to a chemical substance. Being the first to suggest the role of RNA in protein synthesis, he first imagined that RNA could be the active substance in induction but became convinced afterwards that the inducer must have a proteic nature. His interest in the molecular aspects of induction stimulated research that was to make chemical embryology molecular.     

Simulation of the diffusion of acetylcholine in the neuroeffector junctions of the sinus node

Traditionally, the diffusion of acetylcholine (ACh) from a neuron to cardiac muscle in a neuroeffector junction has been modeled as radial diffusion from a nerve ending into a spherical homogeneous medium. Various microscopic structures in the heart may or may not influence the spatial distribution of ACh within neuroeffector junctions. To determine the effect of microscopic anatomy on the diffusion of ACh in neuroeffector junctions, we simulated the diffusion of ACh in a two-dimensional inhomogeneous geometry that was based on micrographs of neuroeffector junctions in the sinus node. ACh was released at sites adjacent to a neuron. Simulations showed that the times of peak concentration after release and the peak concentrations per se were distributed symmetrically above and below and to the right and left of the neuron, but not radially about the neuron. We conclude that the diffusion of ACh in the neuroeffector junctions of the sinus node cannot be predicted well by a mathematical model that assumes radial diffusion in a spherical and homogeneous medium.     

Forms of the Word and the Mystery of the Objectified Nature of the Word

The time has come to proceed from forms of givenness of the word to forms of the word as such. They can, if you like, be called external and inner structures. Humboldt, however, preferred to speak of the external and inner forms of the language. Shpet adopted precisely this distinction. Why did this problem interest Shpet? Already in [Appearance and sense], he had set the task of returning to the source of pretheoretical, living science. Shpet wrote that the outer cover of words and logical expressions obscure the objectified meaning and that it was necessary to remove another cover from the objectified sign so as to grasp a certain genuine intimacy, and in it the fullness of being (Shpet, 1914. Pp. 5-6). We shall keep in mind this major undertaking posed by this scientist. The existence of the inner form of words should not come as a surprise. That same year (1914) Ortega y Gasset wrote that material objects have a third dimension. However, we cannot see or touch it: "For just as depth needs a surface beneath which to be concealed, the surface, or outer cover, in order to be so, needs something over which to spread, covering it" (Ortega y Gasset, 2000. Pp. 62-63).     

Analysis of the spatial-temporal EEG organization as the way to the knowledge of neurophysiological mechanisms of the integrative brain activity

Short results' review of investigations of Laboratory of Neurophysiology of Child of Sechenov Institute is presented in the article. Investigations are based on concept of academic M.N. Livanov about special role of spatial-temporal relations of brain potentials oscillations of various brain areas in providing of functional connection between them. It is shown, that in rest condition the structure of interregional relations of cortex biopotentials in all healthy people is characterized by high spatial orderliness that obviously assists to optimal realization of informational processes during various functional conditions from rest to complex cognitive functions. Special attention is given for the problem of functional signigicance of phase shifts of EEG waves. Data, that allows concluding that brainstem and thalamocartical integrative systems are characterized with relatively small inherited and phenotypic variability whereas fiber systems of both hemispheres that provide processes of intercortical integration are characterized by more expressed inter-individual variability, is presented. Intensive development of long associative and commissural tracks of telencephalon that joined even the most distanced cortical regions of hemispheres in united formation apparently results in formation of morpho-functional "skeleton" of neocortex, that occurred to be the basis for origin of qualitatively new (in comparison to animals) principals of formation of system organization of integral activity of the brain. Existence of long mono- and oligo-synaptic connections provides conditions for correlative develoment in ontogenesis of new function that is not conditioned by phylogenetic development.     

Elaborations of the basal surface of the cells of the Malpighian tubules of an insect

Electrical measurements of membrane potential and resistance using intracellular microelectrodes showed that the fluid-secreting parts of the Malpighian tubules of Rhodnius have superficial regions different in electrical properties from the main body of the cell. The membrane potential in these superficial regions was smaller by 30-40 mV, but showed a standard depolarization on changing the potassium concentration of the bathing medium. The response to changes in the external chloride concentration also differed in the two regions, a finding that was reinforced by different responses to the drug, furosemide. Electron microscopy of the basal regions of the cells revealed many long cellular projections that run parallel to the cell surface and interdigitate with similar projections from neighbouring cells. The degree of interdigitation was examined by marking individual cells with alcian blue or by horseradish peroxidase injection. A survey of the published micrographs of insect Malpighian tubules shows that most have similar projections on their basal surfaces and not the simple basal infoldings previously supposed.     

An investigation of the specificity of cholinesterase in the developing brain of the chick

Summary 1. The specificity of chick brain cholinesterase has been investigated by a thiocholine technique.2. From preliminary experiments it appears that this enzyme differs markedly from that of rat brain, so that the histochemical technique had to be modified in several ways.3. Comparative photometric measurements of the intensity of staining obtained with acetyl and propionyl substrates were made and the results subjected to statistical analysis.4. The difference in intensity of staining obtained with the two substrates showed that the enzyme has a definite preference for the propionyl substrate, under the histochemical conditions used.With 1 Figure in the Text