Tissue regeneration in dentistry: Can salamanders provide insight?

The ability to regenerate damaged tissues would be of tremendous benefit for medicine and dentistry. Unfortunately, humans are unable to regenerate tissues such as teeth and fingers or to repair injured spinal cord. With an aging population, health problems are more prominent and dentistry is no exception as loss of bone tissue in the orofacial sphere from periodontal disease is on the rise. Humans can repair oral soft tissues exceptionally well; however, hard tissues, such as bone and teeth, are devoid of the ability to repair well or at all. Fortunately, Mother Nature has solved nearly every problem that we would like to solve for our own benefit and tissue regeneration is no exception. By studying animals that can regenerate, like Axolotls (Mexican salamander), we hope to find ways to stimulate regeneration in humans. We will discuss the role of the transforming growth factor beta cytokines as they are central to wound healing in humans and regeneration in Axolotls. We will also compare wound healing in humans (skin and oral mucosa) to Axolotl skin wound healing and limb regeneration. Finally, we will address the problem of bone regeneration and present results in salamanders which indicate that in order to regenerate bone you need to recruit non-bone cells. Fundamental research, such as the work being performed in animals that can regenerate, offers insight to help understand why some treatments are successful while others fail when it comes to specific tissues such as bones.

Status of the SPIRAL2 injector commissioning.

The SPIRAL2 injector, installed in its tunnel, is currently under commissioning at GANIL, Caen, France. The injector is composed of two low energy beam transport lines: one is dedicated to the light ion beam production, the other to the heavy ions. The first light ion beam, created by a 2.45 GHz electron cyclotron resonance ion source, has been successfully produced in December 2014. The first beam of the PHOENIX V2 18 GHz heavy ion source was analyzed on 10 July 2015. A status of the SPIRAL2 injector commissioning is given. An upgrade of the heavy ion source, named PHOENIX V3 aimed to replace the V2, is presented. The new version features a doubled plasma chamber volume and the high charge state beam intensity is expected to increase by a factor of 1.5 to 2 up to the mass ∼50. A status of its assembly is proposed.

Functional role of a polymorphism in the Pannexin1 gene in collagen-induced platelet aggregation.

Pannexin1 (Panx1) forms ATP channels that play a critical role in the immune response by reinforcing purinergic signal amplification in the immune synapse. Platelets express Panx1 and given the importance of ATP release in platelets, we investigated Panx1 function in platelet aggregation and the potential impact of genetic polymorphisms on Panx1 channels. We show here that Panx1 forms ATP release channels in human platelets and that inhibiting Panx1 channel function with probenecid, mefloquine or specific (10)Panx1 peptides reduces collagen-induced platelet aggregation but not the response induced by arachidonic acid or ADP. These results were confirmed using Panx1-/- platelets. Natural variations have been described in the human Panx1 gene, which are predicted to induce non-conservative amino acid substitutions in its coding sequence. Healthy subjects homozygous for Panx1-400C, display enhanced platelet reactivity in response to collagen compared with those bearing the Panx1-400A allele. Conversely, the frequency of Panx1-400C homozygotes was increased among cardiovascular patients with hyper-reactive platelets compared with patients with hypo-reactive platelets. Exogenous expression of polymorphic Panx1 channels in a Panx-deficient cell line revealed increased basal and stimulated ATP release from cells transfected with Panx1-400C channels compared with Panx1-400A expressing transfectants. In conclusion, we demonstrate a specific role for Panx1 channels in the signalling pathway leading to collagen-induced platelet aggregation. Our study further identifies for the first time an association between a Panx1-400A>C genetic polymorphism and collagen-induced platelet reactivity. The Panx1-400C variant encodes for a gain-of-function channel that may adversely affect atherothrombosis by specifically enhancing collagen-induced ATP release and platelet aggregation.

Light ion source for proton∕deuteron production at CEA Saclay for the Spiral2 project.

The production of rare radioactive ion beam (RIB) far from the valley of stability is one of the final purposes of the Spiral2 facility in Caen. The RIB will be produced by impinging a deuteron beam onto a carbon sample to produce a high neutron flux, which will interact with a uranium target. The primary deuteron beam is produced by an ion source based on ECR plasma generation. The deuteron source and the low energy beam transport (LEBT) has been assembled and tested at CEA Saclay. Diagnostics from other laboratories were implemented on the LEBT in order to characterize the deuteron beam produced and compare it to the initial simulations. The ion source has been based on a SILHI-type source, which has demonstrated good performances in pulsed and continuous mode, and also a very good reliability on long term operation. The 5 mA of deuteron beam required at the RFQ entrance is extracted from the plasma source at the energy of 40 kV. After a brief description of the experimental set-up, this article reports on the first beam characterization experiments.

The treatment of negative symptoms: a clinical and methodological study.

The primary objective of this study was to evaluate the efficacy, safety and tolerability of remoxipride (controlled release) versus haloperidol in patients with negative symptoms. The study comprised a multicentre, randomised, double-blind, parallel-group clinical trial. Two hundred and five patients were randomised to either remoxipride or haloperidol. Patients eligible for this study were aged 18-65 years, met the DSM-III-R diagnosis for chronic schizophrenia and the Positive and Negative Symptoms Scale (PANSS) criteria for predominant negative symptoms. There was a statistically significant reduction in the PANSS scores of at least 20% from baseline to last rating for 39 remoxipride (49.4%) and 45 haloperidol (47.6%) treated patients. There were no statistical differences found between the two treatment groups with respect to improvement of negative symptoms and adverse events. The PANSS data suggest that both remoxipride and haloperidol improve the cluster of negative symptoms concerned with social functioning. In addition, the design of the study provides a methodology that is appropriate to the study of primary negative symptoms in schizophrenia.

SNAP-23 participates in SNARE complex assembly in rat adipose cells.

SNARE proteins are required for vesicle docking and fusion in eukaryotic cells in processes as diverse as homotypic membrane fusion and synaptic vesicle exocytosis [SNARE stands for SNAP receptor, where SNAP is soluble NSF attachment protein]. The SNARE proteins syntaxin 4 and vesicle-associated membrane protein (VAMP) 2/3 also participate in the insulin-stimulated translocation of GLUT4 from intracellular vesicles to the plasma membrane in adipose cells. We now report the molecular cloning and characterization of rat SNAP-23, a ubiquitously expressed homologue of the essential neuronal SNARE protein SNAP-25 (synaptosomal-associated protein of 25 kDa). Rat SNAP-23 is 86% and 98% identical respectively to human and mouse SNAP-23. Southern blot analysis reveals that the rat, mouse and human SNAP-23 genes encode species-specific isoforms of the same protein. Co-immunoprecipitation of syntaxin 4 and SNAP-23 shows association of these two proteins in rat adipose cell plasma membranes, and insulin stimulation does not alter the SNAP-23/syntaxin 4 complex. In addition, we demonstrate for the first time the participation of SNAP-23, along with syntaxin 4 and VAMP2/3, in the formation of 20S SNARE complexes prepared using rat adipose cell membranes and recombinant alpha-SNAP and NSF proteins. The stoichiometry of the SNARE complexes formed is essentially identical using membranes from either unstimulated or insulin-stimulated adipose cells. These data demonstrate that rat SNAP-23 associates with syntaxin 4 before insulin stimulation and is present in the SNARE complexes known to mediate the translocation of GLUT4 from intracellular vesicles to the plasma membrane of rat adipose cells.

Role of SNARE's in the GLUT4 translocation response to insulin in adipose cells and muscle.

Insulin stimulates glucose transport in skeletal muscle, heart, and adipose tissue by promoting the appearance of GLUT4, the major glucose transporter isoform present in these tissues, on the cell surface. This is achieved by differentially modulating GLUT4 exocytosis and endocytosis, between a specialized intracellular compartment and the plasma membrane. Ligands which activate the heterotrimeric GTP-binding proteins Gs and Gi appear to modulate insulin-stimulated glucose transport through effects on the fusion of docked GLUT4-containing vesicles with the plasma membrane. In insulin resistance states, reduced cellular GLUT4 levels in adipose cells fully account for the decreased glucose transport response to insulin in these cells. In contrast, although insulin-stimulated GLUT4 translocation is also impaired in muscle, total cellular levels of GLUT4 are not altered. The defect in muscle has been attributed to a GLUT4 trafficking problem and thus studies of this mechanism could provide clues as to the nature of the impairment. The movement of GLUT4-containing vesicles from an intracellular storage site to the plasma membrane and the fusion of docked GLUT4-containing vesicles with the plasma membrane are conceptually similar to some secretory processes. A general hypothesis called the SNARE hypothesis (soluble NSF attachment protein receptors where NSF stands for N-ethylmaleimide-sensitive fusion protein) postulates that the specificity of secretory vesicle targeting is generated by complexes that form between membrane proteins on the transport vesicle (v-SNARE's) and membrane proteins located on the target membrane (t-SNARE's). Several v- and t-SNARE's have been identified in adipose cells and muscle. VAMP2 and VAMP3/cellubrevin (v-SNARE's) have been shown to interact with the t-SNARE's syntaxin 4 and SNAP-23. The cytosolic protein NSF has the characteristic of binding to the v-/t-SNARE complex through its interaction with alpha-SNAP, another soluble factor. Furthermore, recent studies have demonstrated that VAMP2/3, syntaxin 4, SNAP-23, and NSF are functionally involved in insulin-stimulated GLUT4 translocation in adipose cells and thus are likely to be involved in the Gs- and Gi-mediated modulation of the glucose transport response to insulin as well. This review summarizes recent advances on the normal mechanism of GLUT4 translocation and discusses how this process could be affected in insulin resistant states such as type II diabetes.

Vp165 and GLUT4 share similar vesicle pools along their trafficking pathways in rat adipose cells.

vp165 (or gp160) is an aminopeptidase that has been identified as one of the major proteins of the GLUT4-containing vesicles. In the present study we have determined the degree of co-localization between vp165 and GLUT4 in rat adipose cells and used perturbation by wortmannin to assess the exocytic and endocytic steps along the translocation and recycling pathways of GLUT4 in the absence and presence of insulin. Western blots of subcellular membrane fractions demonstrate very similar distributions of vp165 and GLUT4. Confocal microscopy of whole cells provides direct evidence that these proteins share the same vesicle populations moving both towards and from the plasma membrane. These data are consistent with the presence of a distinct insulin-sensitive compartment that sequesters both GLUT4 and vp165 and suggest similar trafficking routes through the recycling compartments.

Glucose transport and glucose 6-phosphate hydrolysis in intact rat liver microsomes.

Glucose transport was investigated in rat liver microsomes in relation to glucose 6-phosphatase (Glu-6-Pase) activity using a fast sampling, rapid filtration apparatus. 1) The rapid phase in tracer uptake and the burst phase in glucose 6-phosphate (Glu-6-P) hydrolysis appear synchronous, while the slow phase of glucose accumulation occurs during the steady-state phase of glucose production. 2) [14C]Glucose efflux from preloaded microsomes can be observed upon addition of either cold Glu-6-P or Glu-6-Pase inhibitors, but not cold glucose. 3) Similar steady-state levels of intramicrosomal glucose are observed under symmetrical conditions of Glu-6-P or vanadate concentrations during influx and efflux experiments, and those levels are directly proportional to Glu-6-Pase activity. 4) The rates of both glucose influx and efflux are characterized by t1/2 values that are independent of Glu-6-P concentrations. 5) Glucose efflux in the presence of saturating concentrations of vanadate was not blocked by 1 mM phloretin, and the initial rates of efflux appear directly proportional to intravesicular glucose concentrations. 6) It is concluded that glucose influx into microsomes is tightly linked to Glu-6-Pase activity, while glucose efflux may occur independent of hydrolysis, so that microsomal glucose transport appears unidirectional even though it can be accounted for by diffusion only over the accessible range of sugar concentrations.

Evidence for a membrane exchangeable glucose pool in the functioning of rat liver glucose-6-phosphatase.

We have investigated the kinetics of tracer uptake into rat liver microsomes in relation to [14C]glucose 6-phosphate (Glu-6-P) hydrolysis by glucose 6-phosphatase (Glu-6-Pase). 1) The steady-state levels of intravesicular tracer accumulated during the rapid (AMP1) and slow (AMP2) phases of uptake both demonstrate Michaelis-Menten kinetics relative to outside Glu-6-P concentrations with Km values similar to those observed for the initial burst (Vi) and steady-state (VSS) rates of Glu-6-P hydrolysis. 2) The AMP1/AMP2 ratio is constant (mean value = 0.105 +/- 0.018) over the whole range of outside Glu-6-P concentrations and is equal to the AMP1max/AMP2max ratio (0.109 +/- 0.032). 3) Linear relationships are observed between the initial rates of glucose transport during the slow uptake phase (V alpha 2) and [AMP1], and between [VSS] and [AMP2]. 4) The value of Vss max exceeds by more than 10-fold that of V alpha 2 max. 5) It is concluded that the substrate transport model is incompatible with those results and that AMP1 represents a membrane exchangeable glucose pool. 6) We propose a new version of the conformational model in which the catalytic site lies deep within a hydrophilic pocket of an intrinsic membrane protein and communicates with the extra- and intravesicular spaces through channels with different glucose permeabilities.

Histone II-A stimulates glucose-6-phosphatase and reveals mannose-6-phosphatase activities without permeabilization of liver microsomes.

The effect of histone II-A on glucose-6-phosphatase and mannose-6-phosphatase activities was investigated in relation to microsomal membrane permeability. It was found that glucose-6-phosphatase activity in histone II-A-pretreated liver microsomes was stimulated to the same extent as in detergent-permeabilized microsomes, and that the substrate specificity of the enzyme for glucose 6-phosphate was lost in histone II-A-pretreated microsomes, as [U-14C]glucose-6-phosphate hydrolysis was inhibited by mannose 6-phosphate and [U-14C]mannose 6-phosphate hydrolysis was increased. The accumulation of [U-14C]glucose from [U-14C]glucose 6-phosphate into untreated microsomes was completely abolished in detergent-treated vesicles, but was increased in histone II-A-treated microsomes, accounting for the increased glucose-6-phosphatase activity, and demonstrating that the microsomal membrane was still intact. The stimulation of glucose-6-phosphatase and mannose-6-phosphatase activities by histone II-A was found to be reversed by EGTA. It is concluded that the effects of histone II-A on glucose-6-phosphatase and mannose-6-phosphatase are not caused by the permeabilization of the microsomal membrane. The measurement of mannose-6-phosphatase latency to evaluate the intactness of the vesicles is therefore inappropriate.

A conformational model for the human liver microsomal glucose-6-phosphatase system: evidence from rapid kinetics and defects in glycogen storage disease type 1.

Rapid kinetics of glucose-6-phosphate (G6P) uptake and hydrolysis as well as of orthophosphate uptake were investigated in microsomes prepared from normal and glycogen storage disease type 1a (GSD 1a) human livers using a fast sampling, rapid filtration apparatus and were compared to those of rat liver microsomes. As shown before with rat microsomes, the production of [U-14C]glucose from 0.2 mmol/L [U-14C]G6P by untreated normal human microsomes was characterized by a burst in activity during the first seconds of incubation, followed by a slower linear rate. The initial velocity of the burst was equal to the rate of glucose production in detergent-treated microsomes. In untreated and detergent-treated GSD 1a microsomes, no glucose-6-phosphatase activity was observed. When untreated normal human or rat microsomes were incubated in the presence of 0.2 mmol/L [U-14C]G6P, an accumulation of [U-14C]glucose was observed, whereas no radioactive compound (G6P and/or glucose) was taken up by GSD 1a microsomes. Orthophosphate uptake was, however, detectable in both GSD 1a and normal untreated vesicles. These results do not support a rate-limiting transport of G6P in untreated normal human microsomes and further show that in this case of GSD 1a, no distinct G6P transport activity is present.

Absence of glucose uptake by liver microsomes: an explanation for the complete latency of glucose dehydrogenase.

The permeability of rat liver microsomes to glucose was investigated in relation to the hexose-6-phosphate dehydrogenase system (EC 1.1.1.47). It was found that glucose-6-phosphate dehydrogenase activity could be assayed with NADP as coenzyme in both untreated and detergent-treated microsomes. However, when glucose was used as substrate, activity was only measurable in detergent-treated microsomes. Moreover, radioactive glucose added to microsomes in a variety of experimental conditions was never taken up by the vesicles. Our results indicate that NADP (or NAD) availability is probably not the reason for the absence of glucose dehydrogenase activity in untreated microsomes but rather membrane impermeability to glucose would account for the complete latency observed. This finding calls for a reevaluation of glucose transport in relation to other enzymes of the endoplasmic reticulum, such as glucose-6-phosphatase.

Interaction of mannose-6-phosphate with the hysteretic transition in glucose-6-phosphate hydrolysis in intact liver microsomes.

We showed previously that glucose-6-phosphatase activity was characterised in intact liver microsomes by a hysteretic transition between a rapid and a slower catalytic form of the enzyme. We have now further investigated the substrate specificity of these two kinetic forms. It was found that the pre-incubation of intact microsomes with mannose-6-phosphate or glucose-6-phosphate (50 microM for 30 s) suppressed the burst in glucose-6-phosphatase activity, that the hysteretic transition was reversible and that mannose-6-phosphate inhibited glucose-6-phosphate hydrolysis during the first seconds of incubation, but not anymore after the burst. Our results indicate (i) that mannose-6-phosphate is recognised by the enzyme and can promote the hysteretic transition and (ii) that the transient phase is part of the catalytic mechanism itself.

A test to evaluate the effect of individual components of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid buffers on enzymatic activity.

A simple dilution test for evaluating the individual effect on enzymatic activity of [Ca2+], [EGTA], or [Ca.EGTA] variations in Ca-EGTA buffers is presented. We verified that a 50-fold dilution of the buffer (25-0.5 mM) at constant pH did not affect [Ca2+] (measured with fura-2), whereas [EGTA] and [Ca.EGTA] varied. Therefore the test can be applied to evaluate the proper effect of Ca2+ in a Ca-EGTA buffer on enzyme activity because such an effect is expected to remain unchanged upon dilution of the buffer. Applications of the test are shown for three enzymes apparently sensitive to Ca2+ but found to be effectively influenced only by Ca.EGTA (liver glucose-6-phosphatase), EGTA (intestinal mucosa phosphatase), or indeed Ca2+ (brain cyclic nucleotide phosphodiesterase).

[Personality disorders in psychiatry]. / Le problème des troubles de la personnalité en psychiatrie.

Psychiatric patients with personality disorders are among the most difficult because of the counter-transferential strain they put on clinicians and the paucity of specific treatment. The author develops the point that personality disorders are not diseases as implied in Axis I disorders, but social illness syndromes which depict systemic problems in which clinicians can be engulfed and entrapped. The difficult patient does not exist in isolation, a victim of his own drives and psyche, but rather is a specific socio-cultural actor living and emerging from a particular environmental context. Personality disorders are considered to be interpersonal patterns in which a person's debilitating behaviour elicits complementary behaviour that reinforces the original behaviour. Within a systems perspective, there is not a disordered personality so much as a disordering system of relationships. As with families and society, healers too become involved in the vicious cycle of personality disorders if they fail to see the manipulative interpersonal devices used by these patients. If clinicians accept too naively the lay person's simplistic belief that personality disorders are diseases to be treated by psychiatrists, they run the risk of fostering inappropriate passivity in patients in the face of life demands. Overindulgence and angry rejection are the two major pitfalls often seen in clinical practice. The approach proposed here may seem conterintuitive in laying stress on the need to actively resist the temptation to take over responsibility for a patient's life. There is a difference between a behaviour that a patient's illness (Axis I disorder) prevents him from controlling and an impulsive deliberate behaviour stemming from character pathology. It is a logical error to deal with personality disorders in the same manner and with the same conceptual terminology as for depressive and psychotic disorders. Principles of management are detailed and can be summarized as a kind firmness to bring back patients to take on their own responsibilities.

[Antipsychotics in psychiatry.]. / Les antipsychotiques en psychiatrie.

In this article we have tried to situate the anti-psychotic drugs within modern psychiatry in relation to the various therapies for schizophrenia. Without entering into detail, we have touched upon the main advantages and disadvantages of neuroleptics. We conclude that the advantages outweight the disadvantages. However, we have also stressed the necessity of selecting patients carefully and of taking certain precautions in regard to the neurological effects of anti-psychotic drugs currently available in clinics.