The protein phosphatase 2C (PP2C) superfamily: detection of bacterial homologues

A thorough sequence analysis of the various members of the eukaryotic protein serine/threonine phosphatase 2C (PP2C) family revealed the conservation of 11 motifs. These motifs could be identified in numerous other sequences, including fungal adenylate cyclases that are predicted to contain a functionally active PP2C domain, and a family of prokaryotic serine/threonine phosphatases including SpoIIE. Phylogenetic analysis of all the proteins indicates a widespread sequence family for which a considerable number of isoenzymes can be inferred.

Spatial heterogeneity of blood flow in the dog heart. I. Glucose uptake, free adenosine and oxidative/glycolytic enzyme activity

The spatial heterogeneity of myocardial perfusion and metabolism was studied in 11 anaesthetized dogs under resting conditions. In each heart local myocardial blood flow was assessed using the tracer microsphere technique in 256 samples (mean mass: 83.1 mg) taken from the left anterior ventricular wall. In the same samples, the following biochemical parameters were determined: accumulation of [3H]-deoxyglucose (a measure of glucose uptake), free cytosolic adenosine (S-adenosylhomocysteine accumulation technique, a measure of tissue oxygenation and a possible mediator of blood flow regulation), and the specific activities of oxidative (citrate synthase, cytochrome-c-oxidase) and glycolytic (hexokinase, phosphoglycerate kinase) enzymes. Capillary density and mitochondrial and myofibril volume densities were determined by morphometry. Myocardial perfusion in each sample (average 0.77 ml min-1 g-1) varied between 0.1 and 2.5 times the mean (coefficient of variation 0.30+/-0.02). [3H]-deoxyglucose was deposited locally in proportion to perfusion. Samples showing low flow (<0.2 ml min-1 g-1) did not exhibit increased levels of cytosolic adenosine. The specific activities of the oxidative and glycolytic enzymes, however, were uniformly distributed between low and high flow areas. Furthermore, capillary density and mitochondrial and myofibril densities were similar in high and low flow regions. The results show firstly that local glucose metabolism in the heart occurs in proportion to local blood flow, suggesting that high flow regions have a higher than average metabolic rate. Secondly, regions of low flow are not compromized by critical oxygenation and most likely have a lower than average oxygen demand and finally, the homogeneous distribution of oxidative and glycolytic enzymes, as well as the homogeneous myocardial ultrastructure, suggest that areas with high and low blood flow under resting conditions may increase their metabolic rate to similar levels when required.

Interactions of spermidine and methylspermidine with DNA studied by nuclear magnetic resonance self-diffusion measurements

The NMR pulsed field gradient self-diffusion method has been used to study the self-diffusion of the polyamine spermidine and the polyamine analog methylspermidine (completely N-methylated spermidine). The self-diffusion coefficient, D, was measured in solutions of calf thymus DNA prepared from nucleosome core particles (with an average length of 120 base pairs) as a function of the concentration ratio of polyamine to DNA phosphate. A study of the self-diffusion quotient, D/Do (where Do is the diffusion coefficient for free polyamine, not associated with DNA), in additions of spermidine and methyl-spermidine to solutions of NaDNA/NaCl, gave almost identical results with complete association of polyamine to DNA in the initial part of the titrations, indicating similar affinities for DNA. A large influence on the measured self-diffusion coefficients was detected for methylspermidine in NaDNA solutions with different concentrations of NaCl, which shows a considerable salt effect on the polyamine-DNA association. No notable differences in D/Do for methylspermidine were observed in competitive titrations of solutions of Li- and NaDNA, indicating that sodium and lithium ions behave similarly in their interactions with DNA. In titration experiments of methylspermidine into MgDNA solution, the results showed that the polyamine association is less effective than in the case of NaDNA, because of competition from magnesium binding to DNA. Comparisons with calculations based on the electrostatic Poisson-Boltzmann cell model were performed. It is suggested that the interaction is primarily of electrostatic nature, with no binding to specific sites on the DNA molecule.

Reduction of rat myocardial ischemia and reperfusion injury by sialyl Lewis x oligosaccharide and anti-rat P-selectin antibodies

Polymorphonuclear leukocytes (PMN) are directly involved in development of ischemic myocardial injury. Adhesion of PMN to endothelial cells is an initial step that triggers a sequential process leading to acute inflammatory responses. Interaction between P-selectin and its oligosaccharide ligand, sialyl Lewis x (sLex), plays an important role in the early stage of the adhesion. To examine the role of P-selectin in various animal disease models especially in rats, we have cloned rat E- and P-selectin cDNAs and established monoclonal antibodies against these rat selectins. In this report, we describe the generation and characterization of anti-rat P-selectin antibodies (ARPs). These antibodies detect cell surface P-selectin on thrombin-stimulated rat platelets. More importantly, intravenous administration of ARP2-4 reduced infarction developed after 30 min of ischemia followed by 24 h of reperfusion in a rat myocardial injury model. In addition, similar protective effect was also observed by administration of a sLex-oligosaccharide. These results indicate that cell adhesion mediated via P-selectin is involved in the development of ischemia and reperfusion injury in rat heart.

Expression of the protooncogene bcl-2 in Alzheimer's disease brain

To investigate the role of the apopotosis-related protooncogene bcl-2 in Alzheimer's disease (AD), we compared levels of its protein product, designated Bcl-2, in AD and nondemented (ND) age-matched control neocortical samples. The 26 kD Bcl-2 protein is increased in expression by more than three-fold in AD compared to ND samples as detected by immunoblots. Immunohistochemical analyses give similar results. In AD patients Bcl-2 immunoreactivity is dense and profuse and appears to occur on reactive astrocytes, whereas Bcl-2 immunoreactivity of astrocytes in ND patients is light and sparse. Staining of both gray and white matter is observed but is most prominent in the latter. Increased expression of Bcl-2 by astrocytes may partially underlie their resistance to loss in AD. By contrast, neuronal Bcl-2 immunoreactivity is more sparse and equivocal, perhaps reflecting the vulnerability of this cell type to apoptotic mechanisms in AD. High levels of Bcl-2 in glial cells may aid in cell survival of reactive astrocytes resulting in either beneficial or deleterious effects on neuronal viability.

A New Theoretical Approach to Cavitation in Rubber

In order to analyse the stability and bifurcation phenomena occurring during expansion of a small void in a rubbery material, the behavior of spherical shells submitted to a combined far-field pressure and uniaxial tension has been investigated, considering a general nonlinear isotropic elastic compressible behavior of the material and without any restrictions on the shell thickness. A radial solution for the deformation gradient with a spherical symmetry has been exhibited, which is valid for any behavior law and consists of a homogeneous deformation. The three-dimensional problem is then linearized around this trivial solution, and we show the existence of a pressure interval containing the zero value, in which the solution is reduced to the trivial solution, which is therefore infenitesimally stable. When the applied pressure lies outside the stability interval, we determine the bifurcation points of the shell around the trivial solution, first when only a pressure is applied and secondly when there is an additional far-field tension, much smaller than the applied pressure. The form of the stress distribution on the boundary of the cavity suggests a possible bifurcation of the spherical solution towards a family of axisymmetric solutions. Within this hypothesis, we get a relation between the geometrical parameter of the shell (its radius and thickness), the mechanical properties of the material and the critical load.

Signal transduction and growth control in yeast

An understanding of how an extracellular stimulus causes changes in cell growth is emerging from the study of four signal transduction pathways in Saccharomyces cerevisiae: the pheromone-response, pseudohyphal differentiation, osmolarity-response, and protein kinase C activated pathways. Each of these pathways contains at its core a distinct mitogen-activated protein kinase cascade. Biochemical and molecular studies have determined the functional order of the kinases in the pheromone-response pathway and have suggested that they are organized into a complex by a protein scaffold. The cell surface sensor system for the osmolarity-response pathway has been identified. It shows striking similarity to bacterial two-component sensor-responder systems. Finally, components that integrate information from these pathways and communicate it to cell growth regulators have been revealed.

Enhanced cytotoxicity of amyloid beta-peptide by a complement dependent mechanism

Amyloid beta-peptide (A beta) has been shown to activate the classical complement pathway in vitro. Here, we demonstrate that this interaction is fully capable of killing cells and damaging cellular processes in mixed hippocampal cultures from embryonic day 18 rat fetuses. Lactic acid dehydrogenase (LDH) release and morphologic changes were used to evaluate toxicity.

A mechanochemical study of MgDNA fibers in ethanol-water solutions

Highly oriented calf-thymus MgDNA fibers, prepared by a wet spinning method, were studied with a simple mechanochemical set-up. The relative fiber length, L/Lo, was measured with the fibers submerged in ethanol-water solutions. In one type of experiment L/Lo was measured as a function of ethanol concentration at room temperature. No substantial decrease in L/Lo with increasing ethanol concentration was observed, indicating that MgDNA fibers stay in the B form even when the water activity is very low. For low ethanol concentrations the fiber structure is stable and does not dissolve even at very high water activities. In a second type of experiment, the heat-induced helix-coil transition was manifested by a marked contraction of the fibers. The transition temperature decreases linearly with increasing ethanol concentration between 52 and 68% ethanol. At higher ethanol concentrations the helix-coil transition temperature increases due to strong aggregation within the DNA fibers, and above 77% ethanol the fibers do not contract at all, not even at the upper temperature limit of the experiments, approximately 80 degrees C. This behavior is discussed with reference to dried DNA and the P form of DNA. The helix-coil transition temperature of the MgDNA fibers in 70% ethanol does not show any dependence on the MgCl2 concentration. It is shown that the Poisson-Boltzmann cylindrical cell model can account qualitatively for this lack of salt dependence.

Efficient enzymatic synthesis of the sialyl-Lewisx tetrasaccharide. A ligand for selectin-type adhesion molecules

Sialyl-Lewisx (NeuAc alpha 2-->3Gal beta 1-->4[Fuc alpha 1-->3]GlcNAc] has been identified as a ligand for E-selectin, P-selectin and recently also for L-selectin. We have synthesized the sialyl-Lewisx tetrasaccharide by total enzymatic synthesis from N-acetyllactosamine using a placental alpha 2-->3-sialyltransferase specific for type-2 chain acceptors, followed by a cloned human alpha 1-->3-fucosyltransferase (FucTV, the 'plasma-type' enzyme). This procedure resulted in the tetrasaccharide in a 61% overall yield.

[Coronary artery fistula--surgical or percutaneous embolization treatment?]

Three children aged 4 months, 2.7 and 7 years with the unusual fistula of the left coronary artery to the right atrium were observed over a 2-year period. The two younger children underwent emergency surgery although they showed no clinical symptoms. The reasons for surgical intervention were an aneurysm in the right atrium with obstruction of the vena cava superior and a considerably enlarged fistula, respectively. In the older child, we percutaneously embolized a terminate fistula of the ramus circumflexus with two platinum microcoils without complications. Two-dimensional-echocardiography and color flow mapping were used to confirm the diagnosis. After such diagnosis we recommend a coronary angiography in every case. The transcatheter-coil-embolization is an alternative method to surgical closure in selected cases. We recommend an early onset intervention in case of congenital coronary artery fistula.

Association cortex, cerebellum, and serum concentrations of C1q and factor B in Alzheimer's disease

Concentrations of C1q, the first subcomponent of the classical complement pathway, were assayed by Western blot analysis of sera and brain homogenates from Alzheimer's disease (AD) and nondemented (ND) control patients. Immunoreactive serum C1q concentrations did not differ in the two groups, whereas AD superior frontal gyrus exhibited nearly 4-fold more immunoreactive C1q than ND superior frontal gyrus. Cerebellar C1q concentrations were significantly lower than those in superior frontal gyrus, and ND cerebellar C1q was lowest of all. Parallel immunohistochemical experiments showed a linkage between the extent of beta-amyloid immunoreactivity or AD pathology in a structure and the extent of C1q immunoreactivity. These data support and extend the hypothesis that complement mediated processes are related to beta-amyloid deposition and may be involved in the pathogenesis of AD.

Localized interaction of the polyamine methylspermidine with double-helical DNA as monitored by 1H NMR self-diffusion measurements

The 1H NMR pulsed field gradient self-diffusion method has been used to measure the diffusion coefficient of the polyamine analogue methylspermidine (completely N-methylated spermidine) in DNA solution, as a function of the concentration ratio of methylspermidine to DNA phosphate. Three different DNA's have been investigated: d(GC)4 (8 base pairs), core length calf thymus DNA (approximately 120 base pairs), and sonicated high molecular weight calf thymus DNA (average 7500 base pairs). For a constant ratio of methylspermidine to DNA phosphate, the diffusion coefficient decreases with increasing DNA length. Moreover, at low concentration ratios the diffusion coefficient of methylspermidine approaches a limiting value that is close to that of the DNA molecule. The experimental data are well reproduced by a two-state diffusion model. In this model the diffusion coefficient of the polyamine is a population-weighted average of polyamine associated with DNA (with a diffusion coefficient given by that of the DNA molecule) and polyamine free in solution.