The theory of diazymes and functional coupling of pyruvate kinase and creatine kinase

The physical-chemical principles governing the interactions of enzymes having common metabolic products are presented. Methods for comparing the dissociation rates of the metabolic product and the rates of enzyme-enzyme interaction are given. Using muscle pyruvate kinase (PK) and creatine kinase (CK) as an example, it is shown that the probability of forming an enzyme-product-enzyme complex is much greater than the rate of ATP dissociation from either enzyme. Experimental evidence using 31P-NMR demonstrates that in the presence of both pyruvate kinase and creatine kinase, there is exchange of phosphate between phosphocreatine and phosphoenolpyruvate without a change in the intermediate, ATP. This confirms the formation of a PK.ATP.CK complex in an aqueous solution without enzyme attachment to a substructure. Enzymes capable of forming these mobile clusters are defined as diazymes, and the criteria for their formation are given. The metabolic implications of diazymes are discussed.     

Interval graphs and maps of DNA

A special class of interval graphs is defined and characterized, and an algorithm is given for their construction. These graphs are motivated by an important representation of DNA called restriction maps by molecular biologists. Circular restriction maps are easily included. Supported by a grant from the System Development Foundation. Supported by an NSF grant and through a grant from the System Development Foundation.     

Ultrastructural and biochemical studies of the swelling of developing chick telencephalic slices

Summary An ultrastructural and biochemical study of the importance and localization of tissue swelling was performed on telencephalic slices of 1- and 30-day-old chicks incubated in an oxygenated or a non-oxygenated physiological medium. The swelling of slices is greater for 30-day-old chick material than for that from 1-day-old chicks. It also reaches higher values in the non-oxygenated than in the oxygenated medium. When the 30-day-old chick telencephalic slices are incubated in an oxygenated medium, swelling mainly affects astrocytes, and especially the astrocytic endfeet. When they are incubated in a non-oxygenated medium, the astrocytes and astrocytic endfeet are very swollen and in addition the swelling also affects the neurons and their organelles. Extracellular space is increased. When 1-day-old chick telencephalic slices are incubated in a non-oxygenated medium, the tissue structures are well preserved. Swelling predominantly affects astrocytes and astrocytic endfeet. Neurons are not affected and the extracellular space is reduced. However, when they are incubated in an oxygenated medium, tissue structures are greatly affected showing a high degree of disorganization. Extracellular space is greatly increased. This study thus indicates that the best incubation conditions are an oxygenated medium for 30-day-old chick telencephalic slices which are characterized by an aerobic metabolism, and a non-oxygenated medium for 1-day-old chick telencephalic slices which have a predominantly anaerobic metabolism.     

Mechanisms of integrin activation and trafficking

Integrin adhesion receptors are essential for the normal function of most multicellular organisms, and defective integrin activation or integrin signaling is associated with an array of pathological conditions. Integrins are regulated by conformational changes, clustering, and trafficking, and regulatory mechanisms differ strongly between individual integrins and between cell types. Whereas integrins in circulating blood cells are activated by an inside-out-induced conformational change that favors high-affinity ligand binding, β1-integrins in adherent cells can be activated by force or clustering. In addition, endocytosis and recycling play an important role in the regulation of integrin turnover and integrin redistribution in adherent cells, especially during dynamic processes such as cell migration and invasion. Integrin trafficking is strongly regulated by their cytoplasmic tails, and the mechanisms are now being identified.     

Self-Reproduction of Micelles and Liposomes and the Transition to Life

Abstract

Micelles and vesicles (liposomes) are examples of geometrically bounded molecular structures. Conditions have been found under which micelles can be brought to self-reproduction by a simple chemical reaction which takes place at the boundary of the micellar system, at the interface between the micelles' interior and the exterior bulk solvent. During this reaction, the molecules of the boundary are produced which leads to the formation of more micelles as time progresses. The examples are micelles and reverse micelles build by octanoate molecules, and the reactions which lead to self-reproduction are ester hydrolysis or alcohol oxidations.

In another approach, the reproducing micelles are first created chemically by a simple hydrolysis reaction in a two-phase system made of an alkaline aqueous phase and an organic fatty acid ester phase. In an extension of this concept, as upper organic phase octanoic anhydride was used. The initial conditions of the alkaline aqueous phase were so that the pH drop during the reaction led to the formation of vesicles which were able to take up anhydride molecules and to act as a catalyst for the hydrolysis of the remaining anhydride molecules.

The investigation of fatty acid micelles and vesicles is related to the possible role of bounded molecular structures during the early prebiotic evolution on Earth. Because self-reproducing micelles and vesicles can be considered as examples for the chemical version of an autopoietic unit, the requirements of the minimal and universal definition of the living are fulfilled. (According to the definition by Maturana and Varela, an autopoietic unit is a structure which is self-generating and self-perpetuating as a consequence of its own activities within a boundary of its own making).     

Structure and histochemistry of the epithelia of lips and associated structures of a catfishRita rita

InRita rita the upper lip is associated with the rostral cap and the lower lip with a skin fold. The epithelia of the lips, which are modified with respect to the peculiar feeding behaviour of the fish, are mucogenic. The superficial layer of epithelial cells, in addition to the mucous cells, are involved in active secretion of mucopolysaccharides. Mucus, apart from its diverse functions, as in fish epidermis, lubricates the epithelia giving protection against possible mechanical injury during the searching and catching of prey from bottom debris. Furthermore, the epithelia are thick, an adaptation to their mucogenic nature, so as to provide additional protection. The contents of the club cells are proteinaceous, which correlates with the helical filaments reported in similar cells in fish epidermis. Characteristic ridges on the surface of the lips are considered to be an adaptation to assist in manipulation during the procuring of food. Mucus secreted in the grooves between them reduces friction and prevents the deposition of foreign matter. The skin fold facilitates an increase in gape. The taste buds and ampullary organs, which on the lips and the rostral cap are associated with the localization of prey and triggering of a pick-up reflex, are not located on the skin fold, as the latter often remains concealed between the lower lip and the ventral head skin. The importance of histochemical analysis as a supplement to histological studies is emphasised.     

Explained variation and degrees of necessity and of sufficiency for competing risks survival data

In this contribution, the Schemper–Henderson measure of explained variation for survival outcomes is extended to accommodate competing events (CEs) in addition to events of interest. The extension is achieved by moving from the unconditional and conditional survival functions of the original measure to unconditional and conditional cumulative incidence functions, the latter obtained, for example, from Fine and Gray models. In the absence of CEs, the original measure is obtained as a special case. We define explained variation on the population level and provide two different types of estimates. Recently, the authors have achieved a multiplicative decomposition of explained variation into degrees of necessity and degrees of sufficiency. These measures are also extended to the case of competing risks survival data. A SAS macro and an R function are provided to facilitate application. Interesting empirical properties of the measures are explored on the population level and by an extensive simulation study. Advantages of the approach are exemplified by an Austrian study of breast cancer with a high proportion of CEs.     

Nonequilibrium thermodynamics and different axioms of evolution

Proponents of two axioms of biological evolutionary theory have attempted to find justification by reference to nonequilibrium thermodynamics. One states that biological systems and their evolutionary diversification are physically improbable states and transitions, resulting from a selective process; the other asserts that there is an historically constrained inherent directionality in evolutionary dynamics, independent of natural selection, which exerts a self-organizing influence. The first, the Axiom of Improbability, is shown to be nonhistorical and thus, for a theory of change through time, acausal. Its perception of the improbability of living states is at least partially an artifact of closed system thinking. The second, the Axiom of Historically Determined Inherent Directionality, is supported evidentially and has an explicit historical component. Historically constrained dynamic populations are inherently nonequilibrium systems. It is argued that living, evolving systems, when considered to be historically constrained nonequilibrium systems, do not appear improbable at all. Thus, the two axioms are not compatible. Instead, the Axiom of Improbability is considered to result from an unjustified attempt to extend the contingent proximal actions of natural selection into the area of historical, causal explanations. It is thus denied axiomatic status, and the effects of natural selection are subsumed as an additional level of constraint in an evolutionary theory derived from the Axiom of Historically Determined Inherent Directionality.     

The actions and side effects of Anabolic Steroids in sport and social abuse

Anabolic steroids (AS) derived from testosterone have both anabolic (muscle and strength enhancing) and androgenic (primary and secondary sexual) effects. Efforts to limit the androgenic while enhancing the anabolic effects have not been successful. Alterations to the structure of testosterone, so as to improve the pharmacokinetics of AS, have resulted in drugs, which are orally active, have a longer plasma half life and may be administered as depot injections. Therapeutic doses of AS produce statistically significant effects on strength and athletic performance in well-controlled scientific and clinical trials. At low, therapeutic doses, diet and an intensive training regime are equally important in producing a statistically significant increase in strength. Higher doses 6–7000mg per week are regularly administered in sport and produce the greatest increases in muscle strength erythropoiesis and lean body mass. Patterns of steroid abuse can be complex, reflecting a desire to minimise side effects, and avoid detection. AS side effects are of many types. AS increase salt and water retention leading to an expansion of the blood volume, but effects of steroids on blood pressure are equivocal and most cardiovascular side effects appear to be reversible. Abuse of AS causes an increase in blood triglyceride and cholesterol levels and this is associated with a decline in High Density Lipoproteins (HDLs) and an increase in the Low Density (LDL) type. Though these effects are reversible they are associated with an increased risk of both acute and chronic cardiovascular pathology. The most serious irreversible anabolic steroid side effects are associated with carcinomas-mainly of the liver, prostate and kidney. Hepatic carcinomas are strongly associated with abuse of the orally active 17alpha methyl substituted steroids, which also produce a reversible jaundice. In males, anabolic steroid abuse causes suppression of LH and FSH release leading to inhibition of testosterone production often accompanied by testicular atrophy, and azoospermia. High, chronic doses of the drugs may also cause moderate to severe feminising effects in the form of gynaecomastia. Male secondary sexual characteristics are a side effect of AS abuse in women. Increased insulin resistance and elevated fasting blood glucose levels are the commonest non-gonadal endocrine side effects of AS.     

Sensory and secretory potencies and differentiations of the central nervous system

Secretory neurons capable of elaborating neuropeptides and biogenic amines are an integral component of nervous systems. This apparatus is more extended than assumed during an earlier period of investigations. It is involved in short- and long-range communication by means of paracrine, transmitter-like, modulatory and neurohormonal types of messages. This finely adjusted activity of secretory neurons serves the control of a variety of important biological functions. Secretory pinealocytes are derivatives of pineal photoreceptors, primary sensory cells of neuronal character. In contrast to these neuron-like or paraneuronal elements, the secretory cells of the subcommissural organ are of ependymal origin.     

Floral structure and development of Ceratiosicyos laevis (Achariaceae) and its systematic position

The morphology and development of the flowers of Ceratiosicyos laevis (Achariaceae) were investigated. Plants are monoecious and the inflorescence is a thyrse composed of a single female flower and two male cymose partial inflorescences. The sympetalous flowers of both sexes have an unusual urceolate shape. In young buds the free parts of the petals are postgenitally united. Before anthesis the fusion is ruptured but the petals remain coherent due to marginal cilia. Nectary-like bodies situated at the floral base seem to stabilize the shape of the flower additionally. The anthers are coherent by interlocking epidermal cells and form a narrow tube. They lack an endothecium. In anthesis only the style and the anther tube respectively protrude out of the flower. The synorganization of the anthers, the powdery pollen and the lack of an endothecium are suggestive of a buzz pollination syndrome. Some characters point to an affinity of Achariaceae with Cucurbitaceae. However, the family seems to be more closely related to Passifloraceae.     

Frequency and viability of diploid and haploid male offspring of mated females of solitary endoparasitoid Diadromus pulchellus

Sex determination in the order Hymenoptera is based on arrhenotoky, hymenopteran males are usually haploid and females diploid. Males of the Ichneumonidae Diadromus pulchellus, solitary endoparasitoid of A Acrolepiopsis assectella pupae, are normally haploid, but diploid males are present in a natural population and can be obtained in an experimental population. The future of an ovocyte laid by mated females of the solitary endoparasitoid D. pulchellus was characterised by six probabilities related to the sex and development of the ovocyte. The probabilities of fertilisation of female ovocyte (k1) or non-fertilisation (k3) showed that an inseminated female functioned as a unmated female for half of the time (since k1 = 0.492 and k3 = 0.455) with the probability of fertilisation of male ovocyte, k2, equal to 0.053. The survival probabilities of each type of ovocyte showed that an ovocyte had a high probability of developing up to the adult stage, although the difference between the calculated sex ratios at laying (males/females = 1.032) and at emergence (0.90) revealed a slight reduction in the number of haploid sons. The probabilities of fertilisation and of viability of all the ovocytes laid by each of the 33 mated females were analysed by an ascending hierarchical classification of Euclidean distances and by an analysis of their principal components. The 33 mothers were distributed into four distinct sub-groups characterised by a sex ratio varying from an exclusive presence of females to an exclusive presence of males. Our hypothesis was that this distribution in four sub-sets could not simply result from the random nature of the sample.     

Distribution and vegetation dynamics of humid savannas in Africa and Asia

Abstract. A review is presented on the literature about the distribution of savannas in humid climates in Africa and Asia and their vegetation dynamics. Sections are devoted to African lowland and montane savannas (the latter divided into southern, eastern, western and northern African), Madagascar, Indian subcontinent, SE Asia and New Guinea. It is concluded that the extension of savannas under humid climatic conditions and the relation to the distribution of forests is a function of cultivation, grazing by domestic and wild animals, present and previous climate, geomorphology and soil characteristics. Once established, savannas are often maintained by fires, both natural and man-made. Montane savannas are generally brought about by man's clearing, cultivation and burning. Fire is a stochastic variable; it creates an ecotone sensu stricto (an environmentally stochastic stress zone) at the forest/savanna border. On the other hand, if geomorphology and soil are the determinants, the transition between forest and savanna would have the character of an ecocline (a gradient zone) with fundamentally different conditions. In humid African lowland climates forests expand into savannas if the latter are not maintained by man. Whether forests also expand in less humid climates is disputed. In montane areas forest expansion may be delayed on degraded soils and when diaspores are lacking.     

Fine Structure of Protoplasts and L-Forms of Clostridium botulinum Types A and E

Spherical bodies, that are obtained by adding penicillin and lysozyme to Clostridium botulinum types E and A cultures which are growing in an osmotically stabilized medium, are shown to be protoplasts by electron microscopy. The L-forms of these two culture types have morphologically different inclusion bodies.     

Synthesis of magnetic resonance-, X-ray- and ultrasound-visible alginate microcapsules for immunoisolation and noninvasive imaging of cellular therapeutics

Cell therapy has the potential to treat or cure a wide variety of diseases. Non-invasive cell tracking techniques are, however, necessary to translate this approach to the clinical setting. This protocol details methods to create microcapsules that are visible by X-ray, ultrasound (US) or magnetic resonance (MR) for the encapsulation and immunoisolation of cellular therapeutics. Three steps are generally used to encapsulate cellular therapeutics in an alginate matrix: (i) droplets of cell-containing liquid alginate are extruded, using an electrostatic generator, through a needle tip into a solution containing a dissolved divalent cation salt to form a solid gel; (ii) the resulting gelled spheres are coated with polycations as a cross-linker; and (iii) these complexes are then incubated in a second solution of alginate to form a semipermeable membrane composed of an inner and an outer layer of alginate. The microcapsules can be rendered visible during the first step by adding contrast agents to the primary alginate layer. Such contrast agents include superparamagnetic iron oxide for detection by (1)H MR imaging (MRI); the radiopaque agents barium or bismuth sulfate for detection by X-ray modalities; or perfluorocarbon emulsions for multimodal detection by (19)F MRI, X-ray and US imaging. The entire synthesis can be completed within 2 h.     

Learning and coding of concepts in neural networks

Our environment consists of virtually an infinite number of scenarios in which we have to function. In order to respond properly to an incoming stimulus, the brain has first to analyze it, and to find out the basic familiar elements that are part of it. In other words, by using a library which contains a relatively small number of basic concepts, the brain analyzes the multitude of incoming events. Some of those basic concepts are innate, but many of them must be learned, in order to accommodate for the arbitrary environment around us. A classifying box is defined as the neural network that finds out the familiar concepts that are present in an incoming stimulus. Models for classifying boxes are introduced, and possible mechanisms by which they may establish their libraries of concepts are suggested, and then compared and evaluated by computer simulations.     

Synthesis and characterization of carnitine nitro-derivatives

Nitric oxide (NO) acts as an autacoid molecule that diffuses from its endothelial production site to the neighboring muscular cells. NO-donors are often used to mimic the physiological effects of NO in biological systems. Organic nitrates are commonly used as NO-donors; the most popular, glycerol trinitrate (GTN), has been used in therapy for more than a century. Carnitine nitrates have been synthesized using an endogenous non-toxic molecule: (L)-carnitine. The biotransformation of carnitine nitro-derivatives in biological fluids (saliva and blood plasma) and in red blood cells (RBC) has been monitored by an electrochemical assay and the interaction of carnitine nitrates with the plasma membrane carnitine transporter has been investigated. Differences in the way carnitine nitro-derivatives are metabolized in biological fluids and cells and transported by OCTN2 transporter are modulated by the chemical structures and by the length of the acyl template which carries the nitro-group.     

Photography: conservation and restoration problems of archives

Summary The more and more numerous photographs witnessing the past are often kept, or better, forgotten and confined to the attics and cellars and are thus running the risk of an irreparable deterioration or worse, of an impending and probable destruction. The study of photograph production systems, the analysis of components and thus the chemico-physical investigations are of extreme importance. Nonetheless the aerobiological research is essential for the daily management of archives.