Noncontact Atomic Force Microscope Dissipation Reveals a Central Peak of SrTiO_{3} Structural Phase Transition.

The critical fluctuations at second order structural transitions in a bulk crystal may affect the dissipation of mechanical probes even if completely external to the crystal surface. Here, we show that noncontact force microscope dissipation bears clear evidence of the antiferrodistortive phase transition of SrTiO_{3}, known for a long time to exhibit a unique, extremely narrow neutron scattering "central peak." The noncontact geometry suggests a central peak linear response coupling connected with strain. The detailed temperature dependence reveals for the first time the intrinsic central peak width of order 80 kHz, 2 orders of magnitude below the established neutron upper bound.

The prevalence of cobalamin deficiency among vegetarians assessed by serum vitamin B12: a review of literature.

Individuals following vegetarian diets are at risk for developing vitamin B12 deficiency owing to suboptimal intake. As vitamin B12 is essential for the synthesis of nucleic acids, erythrocytes and in the maintenance of myelin, deficiency may result in a variety of symptoms. Some of these symptoms may be severe while others may be irreversible. The objective of this review was to assess vitamin B12 deficiency, based on reported serum vitamin B12, among individuals adhering to different types of vegetarian diets. A systematic literature search was carried out using multiple search engines including PubMed, Medline, CINAHL plus, ERIC, Nursing and Allied Health Collection and Nursing/Academic Edition. The inclusion criteria consisted of original studies that assessed serum vitamin B12, studies written in English, non-case studies and studies that reported actual percentages of vitamin B12 deficiency. Forty research studies were included. The deficiency prevalence among infants reached 45%. The deficiency among the children and adolescents ranged from 0 to 33.3%. Deficiency among pregnant women ranged from 17 to 39%, dependent on the trimester. Adults and elderly individuals had a deficiency range of 0-86.5%. Higher deficiency prevalence was reported in vegans than in other vegetarians. Thus, with few exceptions, the reviewed studies documented relatively high deficiency prevalence among vegetarians. Vegans who do not ingest vitamin B12 supplements were found to be at especially high risk. Vegetarians, especially vegans, should give strong consideration to the use of vitamin B12 supplements to ensure adequate vitamin B12 intake. Vegetarians, regardless of the type of vegetarian diet they adhere to, should be screened for vitamin B12 deficiency.

A single gene defect causing claustrophobia.

Claustrophobia, the well-known fear of being trapped in narrow/closed spaces, is often considered a conditioned response to traumatic experience. Surprisingly, we found that mutations affecting a single gene, encoding a stress-regulated neuronal protein, can cause claustrophobia. Gpm6a-deficient mice develop normally and lack obvious behavioral abnormalities. However, when mildly stressed by single-housing, these mice develop a striking claustrophobia-like phenotype, which is not inducible in wild-type controls, even by severe stress. The human GPM6A gene is located on chromosome 4q32-q34, a region linked to panic disorder. Sequence analysis of 115 claustrophobic and non-claustrophobic subjects identified nine variants in the noncoding region of the gene that are more frequent in affected individuals (P=0.028). One variant in the 3'untranslated region was linked to claustrophobia in two small pedigrees. This mutant mRNA is functional but cannot be silenced by neuronal miR124 derived itself from a stress-regulated transcript. We suggest that loosing dynamic regulation of neuronal GPM6A expression poses a genetic risk for claustrophobia.

Regulation of neuronal plasticity and fear by a dynamic change in PAR1-G protein coupling in the amygdala.

Fear memories are acquired through neuronal plasticity, an orchestrated sequence of events regulated at circuit and cellular levels. The conventional model of fear acquisition assumes unimodal (for example, excitatory or inhibitory) roles of modulatory receptors in controlling neuronal activity and learning. Contrary to this view, we show that protease-activated receptor-1 (PAR1) promotes contrasting neuronal responses depending on the emotional status of an animal by a dynamic shift between distinct G protein-coupling partners. In the basolateral amygdala of fear-naive mice PAR1 couples to Gαq/11 and Gαo proteins, while after fear conditioning coupling to Gαo increases. Concurrently, stimulation of PAR1 before conditioning enhanced, but afterwards it inhibited firing of basal amygdala neurons. An initial impairment of the long-term potentiation (LTP) in PAR1-deficient mice was transformed into an increase in LTP and enhancement of fear after conditioning. These effects correlated with more frequent 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl)propanoic acid (AMPA) receptor-mediated miniature post synaptic events and increased neuronal excitability. Our findings point to experience-specific shifts in PAR1-G protein coupling in the amygdala as a novel mechanism regulating neuronal excitability and fear.

Inhomogeneous relaxation of a molecular layer on an insulator due to compressive stress.

We discuss the inhomogeneous stress relaxation of a monolayer of hexahydroxytriphenylene (HHTP) which adopts the rare line-on-line (LOL) coincidence on KCl(001) and forms moiré patterns. The fact that the hexagonal HHTP layer is uniaxially compressed along the LOL makes this system an ideal candidate to discuss the influence of inhomogeneous stress relaxation. Our work is a combination of noncontact atomic force microscopy experiments, density functional theory and potential energy calculations, and a thorough interpretation by means of the Frenkel-Kontorova model. We show that the assumption of a homogeneous molecular layer is not valid for this organic-inorganic heteroepitaxial system since the best calculated energy configuration correlates with the experimental data only if inhomogeneous relaxations of the layer are taken into account.

ß3 integrin is dispensable for conditioned fear and hebbian forms of plasticity in the hippocampus.

Integrins play key roles in the developing and mature nervous system, from promoting neuronal process outgrowth to facilitating synaptic plasticity. Recently, in hippocampal pyramidal neurons, ß3 integrin (ITGß3) was shown to stabilise synaptic AMPA receptors (AMPARs) and to be required for homeostatic scaling of AMPARs elicited by chronic activity suppression. To probe the physiological function for ITGß3-dependent processes in the brain, we examined whether the loss of ITGß3 affected fear-related behaviours in mice. ITGß3-knockout (KO) mice showed normal conditioned fear responses that were similar to those of control wild-type mice. However, anxiety-like behaviour appeared substantially compromised and could be reversed to control levels by lentivirus-mediated re-expression of ITGß3 bilaterally in the ventral hippocampus. In hippocampal slices, the loss of ITGß3 activity did not compromise hebbian forms of plasticity--neither acute pharmacological disruption of ITGß3 ligand interactions nor genetic deletion of ITGß3 altered long-term potentiation (LTP) or long-term depression (LTD). Moreover, we did not detect any changes in short-term synaptic plasticity upon loss of ITGß3 activity. In contrast, acutely disrupting ITGß1-ligand interactions or genetic deletion of ITGß1 selectively interfered with LTP stabilisation whereas LTD remained unaltered. These findings indicate a lack of requirement for ITGß3 in the two robust forms of hippocampal long-term synaptic plasticity, LTP and LTD, and suggest differential roles for ITGß1 and ITGß3 in supporting hippocampal circuit functions.

High-resolution imaging of C60 molecules using tuning-fork-based non-contact atomic force microscopy.

Recent advances in non-contact atomic force microscopy (nc-AFM) have led to the possibility of achieving unprecedented resolution within molecular structures, accomplished by probing short-range repulsive interaction forces. Here we investigate C(60) molecules adsorbed on KBr(111) and Cu(111) by tuning-fork-based nc-AFM. First, measurements of C(60) deposited on KBr(001) were conducted in cryogenic conditions revealing highly resolved nc-AFM images of the self-assembly. Using constant-frequency shift mode as well as three-dimensional spectroscopic measurements, we observe that the relatively weak molecule-substrate interaction generally leads to the disruption of molecular assembled structures when the tip is probing the short-range force regime. This particular issue hindered us in resolving the chemical structure of this molecule on the KBr surface. To obtain a better anchoring of C(60) molecules, nc-AFM measurements were performed on Cu(111). Sub-molecular resolutions within the molecules was achieved which allowed a direct and unambiguous visualization of their orientations on the supporting substrate. Furthermore, three-dimensional spectroscopic measurements of simultaneous force and current have been performed above the single molecules giving information of the C(60) molecular orientation as well as its local conductivity. We further discuss the different imaging modes in nc-AFM such as constant-frequency shift nc-AFM, constant-height nc-AFM and constant-current nc-AFM as well as three-dimensional spectroscopic measurement (3D-DFS) employed to achieve such resolution at the sub-molecular scale.

Three-dimensional dynamic force spectroscopy measurements on KBr(001): atomic deformations at small tip-sample separations.

Three-dimensional dynamic force spectroscopy measurements were carried out above KBr(001) at low temperature in order to investigate the distance dependence of the tip-sample interactions. In particular, the recorded 3D frequency shift data as well as the extracted interaction force and potential energy fields were analysed with respect to influences of tip and/or sample deformations. We found that a postprocessing correction of the observed deformations significantly modifies the magnitude of the extracted interaction forces and also the image contrast.

Socio-demographic predictors and reasons for vitamin and/or mineral food supplement use in a group of outpatients in Skopje.

BACKGROUND: Vitamins and/or mineral food supplements (VMS) are mono- or multi-component products prepared in different pharmaceutical forms and categorized as food supplements. Numerous researchers have investigated the epidemiological predictors of use of VMS in population. Data of this kind in our setting are limited. AIMS: This survey aimed to gain information on the prevalence of use, certain sociodemographic predictors and reasons for VMS use in a group of 256 outpatients in Skopje. MATERIALS AND METHODS: This study was designed as an open-ended, cross-sectional survey. Data on VMS use were collected by survey method with a specially designed questionnaire as an instrument for this research. Appropriate statistical tests were used to analyse the data. RESULTS: Data from 256 outpatients from Skopje were analysed. Of them, one hundred and five (41.02%) reported using VMS. Female outpatients (p<0.01) and participants of Macedonian ethnicity (p<0.01), with a higher educational level (p<0.01) and those having their own income (p<0.05) reported significantly higher consumption of VMS. We found a statistically significant difference between the group of users and non-users of VMS regarding smoking status (p<0.05), alcohol consumption (p<0.05) and presence of a chronic disease (p<0.01). Physicians, magazines and friends were the most common source of information on VMS while maintaining good health and prevention of disease was the most common reasons for the use of these products. Only 63% of the users had disclosed the information on taking VMS to their physicians. CONCLUSION: This research provided an insight into VMS in our setting. Predictors on the use of VMS are of interest since these products contribute to total intake of vitamins and minerals in the population and they represent a source of valuable information when planning public health activities.

Tissue plasminogen activator in the amygdala: a new role for an old protease.

Evidence has accumulated that point to the tissue plasminogen activator (tPA), a serine protease historically associated with blood physiology, as an important regulator of the central nervous system functioning. tPA is highly expressed in the limbic system where it regulates neuronal viability and experience-induced plasticity. In the amygdala tPA is a critical mediator of stress-induced structural and functional rearrangements that ultimately shape up behavioral responses to stressful stimuli. The importance of tPA in the limbic system was confirmed using tPA-deficient mice; these animals do not show biochemical, structural and behavioral signatures normally associated with stress. tPA-mediated facilitation of experience-induced plasticity in the limbic system is mediated by a complex mechanism that may involve direct or indirect interactions of tPA with NMDA receptor, its binding to the LRP receptor or activation of brain-derived growth factor.

Stress-induced spine loss in the medial amygdala is mediated by tissue-plasminogen activator.

The amygdala, which exerts a regulatory influence on the stress response, is itself affected by stress. It has been reported that the serine protease tissue-plasminogen activator (tPA), a key mediator of spine plasticity, is required for stress-induced facilitation of anxiety-like behavior. Importantly, tPA is also involved in stress-induced activation of molecular signals that have the potential to contribute to neuronal remodeling in the medial amygdala (MeA). However, little is known about the precise nature of, and specific role played by tPA in, stress-induced structural plasticity in the MeA. Hence, we compared the impact of chronic restraint stress on spine density of medium spiny stellate neurons in MeA in wild-type mice with mice in which the tPA gene is disrupted (tPA-/-). In wild-type mice, chronic stress caused significant reduction in MeA spine density, which was in contrast to enhanced spine density in the neighboring basolateral amygdala (BLA). Strikingly, tPA-/- mice exhibited significant attenuation of stress-induced spine retraction in the MeA, but BLA spinogenesis was not affected. Therefore, tPA-dependence of stress-induced modulation in spine density was restricted to the MeA. Further, MeA neurons in tPA-/- mice, even when challenged with repeated stress, were able to maintain levels of spine density that were comparable to that of wild-type mice without stress. Our findings provide novel evidence for a permissive role for tPA in amygdalar spine plasticity elicited by behavioral stress.

Tissue plasminogen activator in the bed nucleus of stria terminalis regulates acoustic startle.

The bed nucleus of stria terminalis is a basal forebrain region involved in regulation of hormonal and behavioral responses to stress. In this report we demonstrate that bed nucleus of stria terminalis has a high and localized expression of tissue plasminogen activator, a serine protease with neuromodulatory properties and implicated in neuronal plasticity. Tissue plasminogen activator activity in the bed nucleus of stria terminalis is transiently increased in response to acute restraint stress or i.c.v. administration of a major stress mediator, corticotropin-releasing factor. We show that tissue plasminogen activator is important in bed nucleus of stria terminalis function using two criteria: 1, Neuronal activation in this region as measured by c-fos induction is reduced in tissue plasminogen activator-deficient mice; and 2, a bed nucleus of stria terminalis-dependent behavior, potentiation of acoustic startle by corticotropin-releasing factor, is attenuated in tissue plasminogen activator-deficient mice. These studies identify a novel site of tissue plasminogen activator expression in the mouse brain and demonstrate a functional role for this protease in the bed nucleus of stria terminalis.

Changes in remnant-like particle cholesterol level during treatment of hypertension with amlodipine and cilnidipine

This study was designed to determine the effect of antihypertensive agents (calcium channel blockers) on the levels of remnant-like particle (RLP) cholesterol; a major risk factor for coronary heart disease, during treatment of hypertension. Thirty six hypertensive patients of both sexes were selected into this study. Twenty-five of them were treated with amlodipine while eleven patients were treated with cilnidipine all for 3 months. At the beginning and after 3 months of treatment, serum RLP-cholesterol levels were measured in the two treatment groups. RLP-cholesterol level was significantly reduced after clinidipine treatment while the reduction in RLP-cholesterol level after amlodipine treatment was not statistically significant. Our findings show that calcium channel blockers may lower the risk of myocardial infarction, coronary atherosclerosis and/or coronary thrombus formation through reduction in RLP-cholesterol levels during antihypertensive pharmacotherapy

Rapid, specific and active site-catalyzed effect of tissue-plasminogen activator on hippocampus-dependent learning in mice.

In the present study we trained tissue-plasminogen activator (tPA)-knockout (tPA -/-) and wild-type (tPA +/+) male mice in step-down inhibitory avoidance learning, a hippocampus-dependent task. tPA -/- displayed significantly shorter latencies to step down at 90 min, one, two and seven days after training indicating the learning deficit in these animals (P < 0.05 vs tPA +/+). The locomotor activity, the level of anxiety in an elevated-plus maze, as well as the pain threshold did not differ between the two strains of mice. The learning disability of tPA -/- was overcome by more intense training. The learning deficit was also partially restored by limited intrahippocampal delivery of tPA (infused for 2 h before training; P < 0.05 vs control), but not by the delivery of urokinase plasminogen activator, indicating the acute need for tPA in learning. The beneficial effect of tPA was abolished by co-infusion of its inhibitor tPA-STOP, indicating that the facilitatory effect of tPA on learning requires a proteolytic step. However, tPA activity in the hippocampus was not indispensable for effective memory retrieval in tPA-infused tPA -/- mice. Thus, rapid, specific and proteolytic action of tPA facilitates hippocampus-dependent learning, but not retrieval of previously acquired information.

Propranolol modifies platelet serotonergic mechanisms in rats.

Though the mechanisms for the vascular actions of vasodilatory beta-blockers are mostly determined, some of their interactions with monoaminergic systems are not elucidated. Because there are evidences supporting a possible involvement of serotonin (5-HT) in the actions of beta-blockers, we studied the effect of propranolol on peripheral serotonergic mechanisms in normotensive and Goldblatt two-kidney - one clip (2K1C) hypertensive rats. In both groups of animals propranolol decreased systolic blood pressure, significantly increased whole blood serotonin concentration and at the same time it decreased platelet serotonin level. The uptake of the amine by platelets from hypertensive animals was lower than that of normotensive animals and it was decreased by propranolol only in the latter. In both groups propranolol inhibited potentiation of ADP-induced platelet aggregation by serotonin. In conclusion, this study provides evidence that propranolol modifies platelet serotonergic mechanisms in normotensive and renal hypertensive rats.

Angiotensin-(1-7): an active member of the renin-angiotensin system.

Angiotensin-(1-7) [Ang-(1-7)] is an active member of renin-angiotensin system (RAS). It counterbalances vasoconstriction, mitogenic, arrhythmogenic and prothrombotic actions of Ang II. Inducing natiuresis and diuresis opposes also the water and sodium retention produced by Ang II. Till now the specific receptor side for Ang-(1-7) has been not cloned, but the current data strongly suggest that an interaction (cross-talk) between angiotensin receptors may play a role in the effects of Ang-(1-7).

Studies on the antithrombotic action of AT1 receptor antagonists.

BACKGROUND: In our previous experiments we showed that the prototype member of the AT1 receptor antagonists (AT1-As) family, losartan, prevented the development of arterial and venous thrombosis in rats. Recent studies have demonstrated that apart from blocking AT1 receptor, losartan is also a competitive antagonist to thromboxane A2/prostaglandin H2 receptor (TP receptor). Thus, we decided to assess if this feature could contribute to the antithrombotic action of losartan. MATERIAL AND METHODS: We compared the influence losartan, its active metabolite EXP3174 and valsartan on rat platelet adhesion to fibrillar collagen and platelet aggregation in response to thromboxane A2 analogue, U46619. We also assessed the efficacy of these drugs in platelet-dependent pulmonary thrombosis in mice as well as preventive and therapeutic models of venous thrombosis in rats. RESULTS: All the three compounds, given in a single dose, inhibited rat platelet adhesion to fibrillar collagen and platelet aggregation induced with U46619 in vitro and ex vivo, with the action of losartan being much more pronounced than that of EXP3174 or valsartan. Losartan also more effectively protected mice from death in response to the intravenous injection of collagen / epinephrine and it was the only compound which reduced mice mortality after the intravenous injection of U46619. In contrast, all the three AT1 receptor antagonists exerted a similar thrombolytic action and comparably decreased the thrombus weight in the therapeutic and preventive model of venous thrombosis, although in the latter case a high dose of losartan was slightly more effective than a corresponding dose of EXP3174 and valsartan. CONCLUSIONS: Since losartan is endowed with a relatively low affinity towards the AT1 receptor, we conclude that its superiority over EXP 3174 and valsartan in inhibiting thrombocyte function and platelet-dependent thrombosis could result from its stronger action on the TP receptor. This feature seems to be less important in the thrombolytic effect of AT1-As and in the inhibition of the venous thrombosis development, in which platelets play only a minor role.

The differential effect of angiotensin II and angiotensin 1-7 on norepinephrine, epinephrine, and dopamine concentrations in rat hypothalamus: the involvement of angiotensin receptors.

Angiotensin 1-7 has been recently claimed the active member of the angiotensins' family. In the present study we compared the effect of angiotensin II and angiotensin 1-7 on the concentration of dopamine, serotonin, epinephrine, and norepinephrine and some of their metabolites in the rat hypothalamus, where the levels of angiotensins are particularly high. Intracerebroventricular injection of angiotensin II, but not angiotensin 1-7, time-dependently elevated the levels of both epinephrine (p < 0.05) and norepinephrine (p < 0.05) in the hypothalamus and both effects could be prevented by intracerebroventricular injection of either AT(1) (candesartan), AT(2) (PD123319) or AT(1-7) (A-779) receptor antagonist. Neither angiotensin II nor angiotensin 1-7 produced any changes in the level of dopamine, dihydroxyphenylacetic acid, homovanilic acid, serotonin, 5-hydroxyindoleacetic acid, or tryptophan at any time point in comparison with the control groups. However, AT(1) but not AT(2) receptor blockade, unmasked the stimulatory effect of angiotensin 1-7 on dopamine concentration in the hypothalamus. Thus, angiotensin II and its active metabolite angiotensin 1-7 regulate selectively, albeit differentially, adrenergic, noradrenergic and dopaminergic systems in the hypothalamus, the effects that involve AT(1), AT(2) and AT(1-7) angiotensin receptors.