Current Treatment for Venom-Induced Consumption Coagulopathy Resulting from Snakebite

Venomous snakebite is considered the single most important cause of human injury from venomous animals worldwide. Coagulopathy is one of the commonest important systemic clinical syndromes and can be complicated by serious and life-threatening haemorrhage. Venom-induced consumption coagulopathy (VICC) is the commonest coagulopathy resulting from snakebite and occurs in envenoming by Viperid snakes, certain elapids, including Australian elapids, and a few Colubrid (rear fang) snakes. Procoagulant toxins activate the clotting pathway, causing a broad range of factor deficiencies depending on the particular procoagulant toxin in the snake venom. Diagnosis and monitoring of coagulopathy is problematic, particularly in resource-poor countries where further research is required to develop more reliable, cheap clotting tests. MEDLINE and EMBASE up to September 2013 were searched to identify clinical studies of snake envenoming with VICC. The UniPort database was searched for coagulant snake toxins. Despite preclinical studies demonstrating antivenom binding toxins (efficacy), there was less evidence to support clinical effectiveness of antivenom for VICC. There were no placebo-controlled trials of antivenom for VICC. There were 25 randomised comparative trials of antivenom for VICC, which compared two different antivenoms (ten studies), three different antivenoms (four), two or three different doses or repeat doses of antivenom (five), heparin treatment and antivenom (five), and intravenous immunoglobulin treatment and antivenom (one). There were 13 studies that compared two groups in which there was no randomisation, including studies with historical controls. There have been numerous observational studies of antivenom in VICC but with no comparison group. Most of the controlled trials were small, did not use the same method for assessing coagulopathy, varied the dose of antivenom, and did not provide complete details of the study design (primary outcomes, randomisation, and allocation concealment). Non-randomised trials including comparison groups without antivenom showed that antivenom was effective for some snakes (e.g., Echis), but not others (e.g., Australasian elapids). Antivenom is the major treatment for VICC, but there is currently little high-quality evidence to support effectiveness. Antivenom is not risk free, and adverse reactions can be quite common and potentially severe. Studies of heparin did not demonstrate it improved outcomes in VICC. Fresh frozen plasma appeared to speed the recovery of coagulopathy and should be considered in bleeding patients.     

Dynamic interaction of membrane transport of cations and biosynthesis in the regulation of animal cell growth. A theoretical model

Possibility of direct participation of the cell volume stabilization system in biosynthesis and growth control in animal cells is postulated and theoretically treated in terms of general membraneous cell model. The states of proliferative quiescence or proliferative activity were attributed, respectively, to the states of stability or non-stability of dynamical interactions between ion-dependent volume regulating system and biosynthetic apparatus which controls metabolic renewal and current number of ion transporters. The results showed that in the case of fixed Na+/K+ pumping ratio the cellular steady-state is quite stable. Necessary conditions are described when labialization of Na+/K+ exchange stoichiometry must initiate metabolic instability and cellular growth. The loss of the cell membrane ability to link together different fluxes may thus be accounted for the uncontrolled cellular and tissue growth. Quantitative criteria for the cell growth capacity are obtained depending on the high enough requiring level of transmembrane ion asymmetry and low enough value of intracellular electric potential.     

Clinical Effects and Antivenom Dosing in Brown Snake (Pseudonaja spp.) Envenoming — Australian Snakebite Project (ASP-14)

Background

Snakebite is a global health issue and treatment with antivenom continues to be problematic. Brown snakes (genus Pseudonaja) are the most medically important group of Australian snakes and there is controversy over the dose of brown snake antivenom. We aimed to investigate the clinical and laboratory features of definite brown snake (Pseudonaja spp.) envenoming, and determine the dose of antivenom required.

Methods and Finding

This was a prospective observational study of definite brown snake envenoming from the Australian Snakebite Project (ASP) based on snake identification or specific enzyme immunoassay for Pseudonaja venom. From January 2004 to January 2012 there were 149 definite brown snake bites [median age 42y (2–81y); 100 males]. Systemic envenoming occurred in 136 (88%) cases. All envenomed patients developed venom induced consumption coagulopathy (VICC), with complete VICC in 109 (80%) and partial VICC in 27 (20%). Systemic symptoms occurred in 61 (45%) and mild neurotoxicity in 2 (1%). Myotoxicity did not occur. Severe envenoming occurred in 51 patients (38%) and was characterised by collapse or hypotension (37), thrombotic microangiopathy (15), major haemorrhage (5), cardiac arrest (7) and death (6). The median peak venom concentration in 118 envenomed patients was 1.6 ng/mL (Range: 0.15–210 ng/mL). The median initial antivenom dose was 2 vials (Range: 1–40) in 128 patients receiving antivenom. There was no difference in INR recovery or clinical outcome between patients receiving one or more than one vial of antivenom. Free venom was not detected in 112/115 patients post-antivenom with only low concentrations (0.4 to 0.9 ng/ml) in three patients.

Conclusions

Envenoming by brown snakes causes VICC and over a third of patients had serious complications including major haemorrhage, collapse and microangiopathy. The results of this study support accumulating evidence that giving more than one vial of antivenom is unnecessary in brown snake envenoming.     

Rat mesentery exteriorization: a model for investigating the cellular dynamics involved in angiogenesis

Microvacular network growth and remodeling are critical aspects of wound healing, inflammation, diabetic retinopathy, tumor growth and other disease conditions. Network growth is commonly attributed to angiogenesis, defined as the growth of new vessels from pre-existing vessels. The angiogenic process is also directly linked to arteriogenesis, defined as the capillary acquisition of a perivascular cell coating and vessel enlargement. Needless to say, angiogenesis is complex and involves multiple players at the cellular and molecular level. Understanding how a microvascular network grows requires identifying the spatial and temporal dynamics along the hierarchy of a network over the time course of angiogenesis. This information is critical for the development of therapies aimed at manipulating vessel growth. The exteriorization model described in this article represents a simple, reproducible model for stimulating angiogenesis in the rat mesentery. It was adapted from wound-healing models in the rat mesentery, and is an alternative to stimulate angiogenesis in the mesentery via i.p. injections of pro-angiogenic agents. The exteriorization model is attractive because it requires minimal surgical intervention and produces dramatic, reproducible increases in capillary sprouts, vascular area and vascular density over a relatively short time course in a tissue that allows for the two-dimensional visualization of entire microvascular networks down to single cell level. The stimulated growth reflects natural angiogenic responses in a physiological environment without interference of foreign angiogenic molecules. Using immunohistochemical labeling methods, this model has been proven extremely useful in identifying novel cellular events involved in angiogenesis. Investigators can readily correlate the angiogenic metrics during the time course of remodeling with time specific dynamics, such as cellular phenotypic changes or cellular interactions.     

Membrane potential perturbations induced in tissue cells by pulsed electric fields

Pulsed electric fields directly influence the electrophysiology of tissue cells by transiently perturbing their transmembrane potential. To determine the magnitude and time course of this interaction, electrotonic cable theory was used to calculate the membrane potential perturbations induced in tissue cells by a spatially uniform, pulsed electric field. Analytic solutions were obtained that predict shifts in membrane potential along the length of cells as a function of time in response to an electrical pulse. For elongated tissue cells, or groups of tissue cells that are coupled electrotonically by gap junctions, significant hyperpolarizations and depolarizations can result from millisecond applications of electric fields with strengths on the order of 10–100 mV/cm. The results illustrate the importance of considering cellular cable parameters in assessing the effects of transient electric fields on biological systems, as well as in predicting the efficacy of pulsed electric fields in medical treatments. © 1995 Wiley-Liss, Inc.     

Electrical signals for chondrocytes in cartilage

An important step toward understanding signal transduction mechanisms modulating cellular activities is the accurate predictions of the mechanical and electro-chemical environment of the cells in well-defined experimental configurations. Although electro-kinetic phenomena in cartilage are well known, few studies have focused on the electric field inside the tissue. In this paper, we present some of our recent calculations of the electric field inside a layer of cartilage (with and without cells) in an open circuit one-dimensional (1D) stress relaxation experiment. The electric field inside the tissue derives from the streaming effects (streaming potential) and the diffusion effect (diffusion potential). Our results show that, for realistic cartilage material parameters, due to deformation-induced inhomogeneity of the fixed charge density, the two potentials compete against each other. For softer tissue, the diffusion potential may dominate over the streaming potential and vice versa for stiffer tissue. These results demonstrate that for proper interpretation of the mechano-electrochemical signal transduction mechanisms, one must not ignore the diffusion potential.     

METABOLISME DU CALCIUM ET LIBERATION DE L''ACETYLCHOLINE DANS L''ORGANE ELECTRIQUE DE LA TORPILLE

Abstract— Calcium metabolism was studied in the electric organ of Torpedo , at rest and after electrical stimulation, in vivo and in vitro , by measuring total calcium and using ⁴⁵Ca. Seasonal variations in the calcium metabolism were observed, summer animals being richer in the ion than winter ones. When the tissue was incubated in high calcium concentrations, complete exchange was obtained between cellular calcium and that of the external medium. In the presence of low concentrations, the tissue retained its calcium which, in this case, was poorly exchanged. Stimulation was accompanied by a net increase of cellular calcium and by acceleration of its exchange with that of extracellular space. This entry of calcium seems to involve mainly the presynaptic nerve endings, since it is also observed when transmission was blocked by curare which acts at the level of the postsynaptic electroplaques. Calcium may also influence the intracellular repartition of the transmitter. As a matter of fact, the presynaptic entry of calcium is accompanied by diminution of 'bound' ACh (vesicular ACh). When the tissue was incubated in a solution devoid of calcium, especially if EDTA was added, the electrical response disappeared; then 'free' ACh which is the immediately available compartment, decreased but its turnover rose. 'Bound' and 'free' ACh were also measured under various conditions of homogenization and the results discussed. It is concluded that extracellular calcium is required for the maintenance of the immediately available compartment of ACh.     

生物体发育过程中细胞膜电位变化与衰老

维持一定的跨质膜电势,关乎到细胞内外物质交换的基本代谢能否顺利进行,因此是所有细胞生存的前提。这是生物的单细胞祖先发展出的有效生存手段,当进化到多细胞生物体后却遇到麻烦。多细胞生物为细胞营群居生活,在物理导体的静电荷分布规律的支配下,个体细胞所携外正内负的净电荷有向细胞集团边缘汇集的趋势,导致多数细胞失去本身所携净电荷,不能维持正常跨膜电势,从而逐渐失去活力。这可能就是多细胞生物衰老的根本原因。衰老是生物体在发育中随细胞数量增多不可避免的自然发生的效应。有证据显示以上描述的电荷分布变化过程的假说是真实存在。植物体中细胞所携电荷的汇集,以及随之发生的带电离子从高浓度区向低浓度区的扩散流失,可导致产生有趣的植物生电的现象,例如大树发电。对植物电压、电的极性、高密度电荷位点分布的测结果与此假说理论完全吻合。     

Black spot gill syndrome of the northern shrimp Pandalus borealis

Northern shrimp, Pandalus borealis, taken in the Gulf of Maine show tissue destruction of gill lamellae. Vacuolated chitin growth over damaged tissue produces macroscopic black spots on the gills. First noticed in 1966, semiquantitative records were kept for four consecutive years. Incidence of infestation for this period is described.     

Characteristics of synaptic and intracellular neuron activation

Stimulation of the leech abdominal neural chain with electric pulses of 1 imp/sec frequency results in alterations in the activity of the Retzius cells in addition to an increased protein metabolism in the postactivation period. The direct stimulation produces a decrease in the cellular protein metabolism.     

Hard labour: bacterial infection of the skeleton

The skeleton is the largest mammalian organ system, containing a myriad of blood vessels, tissue surfaces and bone cells for bacterial colonization. Although rock-like, the skeleton is a dynamic structure that is undergoing constant remodelling. This is the result of the opposing actions of two key cells: the osteoblast, which produces bone, and the osteoclast, a multinucleate cell that ‘eats’ bone. It is not generally realized that the most prevalent chronic bacterial diseases of Homo sapiens afflict the skeleton. Several pathogens, and members of the normal microbiota, have evolved specific cellular and molecular mechanisms for invading bone, including its cellular constituents. The host cellular pathways that are activated and lead to destruction or loss of the bone matrix will be described.     

Electrophorus electricus as a model system for the study of membrane excitability

The stunning sensations produced by electric fish, particularly the electric eel, Electrophorus electricus, have fascinated scientists for centuries. Within the last 50 years, however, electric cells of Electrophorus have provided a unique model system that is both specialized and appropriate for the study of excitable cell membrane electrophysiology and biochemistry. Electric tissue generates whole animal electrical discharges by means of membrane potentials that are remarkably similar to those of mammalian neurons, myocytes and secretory cells. Electrocytes express ion channels, ATPases and signal transduction proteins common to these other excitable cells. Action potentials of electrocytes represent the specialized end function of electric tissue whereas other excitable cells use membrane potential changes to trigger sophisticated cellular processes, such as myofilament cross-bridging for contraction, or exocytosis for secretion. Because electric tissue lacks these functions and the proteins associated with them, it provides a highly specialized membrane model system. This review examines the basic mechanisms involved in the generation of the electrical discharge of the electric eel and the membrane proteins involved. The valuable contributions that electric tissue continues to make toward the understanding of excitable cell physiology and biochemistry are summarized, particularly those studies using electrocytes as a model system for the study of the regulation of membrane excitability by second messengers and signal transduction pathways.     

Intertissue Differences for the Role of Glutamate Dehydrogenase in Metabolism

The enzyme glutamate dehydrogenase (GDH) plays an important role in integrating mitochondrial metabolism of amino acids and ammonia. Glutamate may function as a respiratory substrate in the oxidative deamination direction of GDH, which also yields α-ketoglutarate. In the reductive amination direction GDH produces glutamate, which can then be used for other cellular needs such as amino acid synthesis via transamination. The production or removal of ammonia by GDH is also an important consequence of flux through this enzyme. However, the abundance and role of GDH in cellular metabolism varies by tissue. Here we discuss the different roles the house-keeping form of GDH has in major organs of the body and how GDH may be important to regulating aspects of intermediary metabolism. The near-equilibrium poise of GDH in liver and controversy over cofactor specificity and regulation is discussed, as well as, the role of GDH in regulation of renal ammoniagenesis, and the possible importance of GDH activity in the release of nitrogen carriers by the small intestine.     

Current Estimates for HIV-1 Production Imply Rapid Viral Clearance in Lymphoid Tissues

It has recently been estimated that a single HIV-1 infected cell produces between and more than viral particles over its life span. Since body-wide estimates of the ratio of free virus to productively infected cells are smaller than and much smaller than , individual virions must be cleared rapidly. This seems difficult to reconcile with the fact that most of the total body virus is trapped on follicular dendritic cells where it can survive for many months. It has also been difficult to reconcile the vast difference in the rates at which the virus is cleared from the blood in rhesus macaques and in chronically infected patients. Here we attempt to reconcile these seemingly contradictory observations by considering the virion clearance rate in various organs and the virion exchange rates between them. The main results are that the per capita clearance rate of free virus in lymphoid tissue should be fast, the virion exchange rate between lymphoid tissue and the blood should be slow, and the comparatively slow previous estimates for the virion clearance rate from the blood correspond to the rate of virion efflux from the blood to other organs where the virus is ultimately cleared.     

Structural aspects of gas exchange

The lung is composed of several million small air spaces, lined by a delicate tissue membrane separating air from capillary blood. The design features of the gas exchange region in the lung are optimal for gaseous diffusion, by having a very extensive contact surface but with a minimal tissue barrier composed of an epithelial and endothelial layer separating an interstitial layer. The extent of the gas exchange surface in adult lungs is determined by general maturation which in turn is influenced by metabolic requirements of the organism. Environmental factors can modulate the pattern of ultimate lung development. Lung inflation causes air spaces to expand mainly by a process of tissue unfolding beneath an extremely thin layer of alveolar surfactant. This ensures cellular integrity during extreme deformations while at the same time providing a reserve of gas exchange surface so that functional diffusion capacity at all lung volumes is less than the structural maximum.     

A parallel path model forNecturus proximal tubule

Summary A parallel path model based on the principles of nonequilibrium thermodynamics was developed for theNecturus proximal tubule. The cellular path was represented as a luminal membrane followed by an irreversible active NaCl transport system in the peritubular barrier. The shunt pathway was described as three coarse barriers in series: tight junction, lateral intercellular spaces, and basement membrane with connective tissue. Volume and solute flows were predicted by the model equations as a function of applied electric current. Variations of the model parameters revealed the quantitative importance of the shunt path properties and the relative insensitivity of epithelial transport to changes in most cell parameters. Circulation of electric current and solute within the epithelium were shown to significantly influence the bahavior of the tubule in the presence of an electric field. Values for all transport parameters of the shunt path and epithelium were calculated and compared with available experimental evidence. Volume flow and electric currents predicted by the model compared favorably with experimental observations.     

Charges, currents, and potentials in ionic channels of one conformation.

Flux through an open ionic channel is analyzed with Poisson-Nernst-Planck (PNP) theory. The channel protein is described as an unchanging but nonuniform distribution of permanent charge, the charge distribution observed (in principle) in x-ray diffraction. Appropriate boundary conditions are derived and presented in some generality. Three kinds of charge are present: (a) permanent charge on the atoms of the protein, the charge independent of the electric field; (b) free or mobile charge, carried by ions in the pore as they flux through the channel; and (c) induced (sometimes called polarization) charge, in the pore and protein, created by the electric field, zero when the electric field is zero. The permanent charge produces an offset in potential, a built-in Donnan potential at both ends of the channel pore. The system is completely solved for bathing solutions of two ions. Graphs describe the distribution of potential, concentration, free (i.e., mobile) and induced charge, and the potential energy associated with the concentration of charge, as well as the unidirectional flux as a function of concentration of ions in the bath, for a distribution of permanent charge that is uniform. The model shows surprising complexity, exhibiting some (but not all) of the properties usually attributed to single filing and exchange diffusion. The complexity arises because the arrangement of free and induced charge, and thus of potential and potential energy, varies, sometimes substantially, as conditions change, even though the channel structure and conformation (of permanent charge) is strictly constant. Energy barriers and wells, and the concomitant binding sites and binding phenomena, are outputs of the PNP theory: they are computed, not assumed. They vary in size and location as experimental conditions change, while the conformation of permanent charge remains constant, thus giving the model much of its interesting behavior.     

Exchange of unsaturated fatty acids between adipose tissue and atherosclerotic plaque studied with artificial neural networks

The linoleic C18:2 (n-6) and linolenic C18:3 (n-3) are recognized as essential components of the diet. Free radical peroxidation of essential fatty acids (EFAs) present in lipoproteins produces oxidized low-density lipoproteins which play a critical role in the development of atherosclerosis. The accumulation of EFAs in the vascular wall and correlations between their content in the adipose tissue and atherosclerotic plaque have been confirmed. The present study was undertaken to determine the usefulness of a neural network for studying the exchange between tissues of linoleic, alpha-linolenic, and arachidonic acids-three fatty acids with a well-understood metabolism. Atheromatous plaques, adipose tissue, and serum were obtained from 31 patients who underwent surgery due to atherosclerotic stenosis of the abdominal aorta, iliac or femoral arteries. Fatty acids were extracted and separated as methyl esters using gas chromatography. Statistical analysis was done with STATISTICA neural networks package. Several correlations reported previously were corroborated and factors modifying the content of individual EFAs in adipose tissue and atherosclerotic plaque were revealed. Artificial neural networks (ANNs) were used to determine factors modifying the content of linoleic, alpha-linolenic, and arachidonic acids in human atheromatous plaques. The mechanism of exchange of some fatty acids between the adipose tissue, atheromatous plaque, and plasma is discussed. The results provide evidence for an effective mechanism of tissue uptake and turnover of linoleic acid. Reduced plasma levels of this acid are compensated by release from adipose tissue and atheromatous plaque. While alpha-linolenic acid is continuously taken up by the plaque, adipose tissue absorbs this acid to a certain level only. The dynamics of exchange of arachidonic acid between adipose tissue and atheromatous plaque reflects a minor role for adipose tissue in determining plaque content of this acid, suggesting that "de novo" synthesis is the chief source of arachidonic acid in plaques.     

The galvanotaxis response mechanism of keratinocytes can be modeled as a proportional controller

Human keratinocytes actively crawl in vitro when plated onto a collagen-coated glass substrate, and their direction of migration is totally random. In response to an imposed dc electric field, they migrate asymmetrically, moving mostly toward the negative pole of the field. The authors have analyzed experimental data reported by others to determine the basic characteristics of the cellular response machinery in these keratinocytes. This movement can be completely described mathematically using two independent variables: the speed, V, and the angle of migration, ϕ. The authors propose a model in which a steerer (controller without feedback) is responsible for determining the speed, and an automatic controller (controller with feedback) is responsible for determining the angle of migration. The torque to rotate is induced by a deterministic cellular signal and a stochastic cellular signal. The cellular machine characteristics are determined as follows: The angular dependence of the detection unit is sin ϕ; the detection unit detects the guiding field in a linear fashion; the cellular reaction unit can be described by a constant; the chemical amplifier, as well as the cellular motor work, is linear; the cellular characteristic time, which quantifies the cellular stochastic signal, is 50 min.     

Hepatocytes volume regulation

Cell volume regulation has been studied during isolated dog liver perfusion. In presence of ouabain (10(-4) M) rapid but quantitatively matched exchange of K for Na occurs and the cellular volume is maintained until (90 min later) intracellular K concentration falls below 80 mEq/litre. Additional mechanism of protection of cell volume as loss of intracellular anions should also play a r?le since ouabain produces rapidly a membrane depolarization and chloride gain. A similar sequence of events is obtained when inhibition of the sodium pump is produced by anoxia but in this case the chloride gain in excess of cation gain is particularly marked. Submitted to an hypotonic shock the hepatocytes swell but tend to partially recover their volume by loosing K, indeed when osmolarity is corrected the cells maintain a sub-normal volume. Ouabain inhibits (or masks?) this iso-osmotic regulation. When submitted to an hypertonic medium a reduced cell volume is obtained and maintained for hours even in presence of ouabain, which produces a Na/K exchange at the same rate as in normal conditions.