Protective Effect of ACE Inhibitors on Ischemia-Reperfusion-induced Arrhythmias in Rats: Is this Effect Related to the Free Radical Scavenging Action of these Drugs?

The antiarrhythmic effects of captopril, a sulphydrylcontaining angiotensin converting enzyme (ACE) inhibitor, were compared with those of the non-sulphydryl-containing ACE inhibitor lisinopril and the sulphydryl-containing agent glutathione in an in vivo rat model of coronary artery ligation. To produce arrhythmia, the left main coronary artery was occluded for 7 min, followed by 7 min of reperfusion. Captopril (3 mg kg^-1) and lisinopril (0.1, 0.3 or 1 mg kg^-1) caused marked decreases in mean arterial blood pressure (BP) and heart rate, whereas glutathione (5 mg kg^-) had no effect on them. The incidence of ventricular tachycardia (VT) on ischemia and reperfusion was significantly reduced by captopril and lisinopril. Captopril and 1 mg kg^-1 lisinopril also significantly decreased the number of VEB during occlusion and the duration of VT on reperfusion, respectively. These drugs also attenuated the incidence of reversible ventricular fibrillation (VF) and the number of ventricular ectopic beats (VEB) during reperfusion. However, glutathione only reduced the incidence of VT on reperfusion, significantly. These results suggest that, in this experimental model, ACE inhibitors limit the arrhythmias following ischemia-reperfusion and free radical scavenging action of these drugs does not have a major contributory role in their protective effect.     

Is the LDL Receptor Involved in Cortical Amyloid Protein Clearance?

This article puts forward the hypothesis that the Low Density Lipid Receptor (LDLR) is one of the molecules that is involved in the clearance of amyloid proteins in the brain and that it may play a role in Alzheimer’s Disease (AD) via its up-regulation by statins. The hypothesis is built on the following observations: a-statins (which have been shown to increase LDLR in astrocytes, see below) have a beneficial role in AD, b-defects in the LDL receptor gene are found in AD, c-molecules with similar structure to the LDLR have been shown to clear amyloid protein from the brain.     

Is Calmodulin Involved in Electrophysiology of Chara corallina?

The role of calmodulin in Chara was investigated using the antipsychoticdrug trifluoperazine (TFP), which is known to bind to the calmodulin/Ca⁺⁺complex preventing it from carrying out its normal functions. At low concentration (4.0 µM), TFP had profound and irreversibleeffects on the electrophysiology of Chara plasmalemma. The restingp.d. depolarized and the membrane conductance decreased suggestingan inhibition of the proton pump. After several hours of exposurethe membrane became leaky, as cells deteriorated. The excitation was also affected by TFP. Spontaneous repetitivefiring was observed. The excitation increased in duration andthe action potential peak depolarized to + 20 mV. The cytoplasmic streaming was unaffected by TFP; the streamingrate at the resting potential remained unchanged when TFP wasadded to the medium, stoppage occurred at the time of excitationand the streaming slowly resumed. Key words: Calmodulin, Chara corallina, Proton pump, Cytoplasmic streaming, Current, voltage characteristics     

Is Hypothalamic GABA Involved in Immune Function in Relation to Dietary Protein During Aging?

Hypothalamic GABAergic activity and immune response in spleen were not significantly changed with the increase of age from 3 to 6 months in adult male albino rats. Further increase of age from 6 to 9 months increased the GABAergic activity and decreased the cell viability in spleen without any change in its T-lymphocyte cytotoxicity. Consumption of low protein diet (LPD) for a short-term period (STP; 7 consecutive days) increased the hypothalamie GABAergic activity without changing the immune response in 3 months old rats. When supplemented for a long-term period (LTP; 30 consecutive days) to 3 months old rats, a reduction of hypothalamie GABAergic activity and the immune response was observed. Intake of high protein diet (HPD) for both STP and LTP increased the GABAergic activity and immune response, but the increase of GABAergic activity in hypothalamus under STP was greater than that observed under LTP. In 6 months old rats consumption of LPD for STP reduced the GABAergic activity without any alteration of its immune response. Long-term supplementation of this LPD to the same age group increased GABAergic activity and the mitotic activity of spleen cells without any alteration of the functional activity of the T-cells in spleen. Consumption of HPD for STP failed to produce any change in hypothalamic GABAergic activity and the immune response of 6 months old rats. Supplementation of HPD for LTP reduced the hypothalamic GABAergic activity and the immune response of the same age group. The reduction in hypothalamic GABAergic activity without any change in the immune response was observed following the supplementation of low protein diet to 9 months old rat for STP. Intake of the LPD for LTP also reduced the hypothalamie GABAergic activity and the mitotic activity of the spleen cells without any alteration of the functional activity of the T-cells in spleen of 9 months old rats. Supplementation of HPD for STP to this aged rat, on the other hand, failed to produced any change in hypothalamic GABAergic activity and the immune response. Intake of HPD for LTP by this aged rats increased the hypothalamie GABAergic activity along with the immune response. The results of this study, thus, suggest that hypothalamic GABAergic activity during aging is an index of immune response and it is modulated following the short- and long-term consumption of protein poor and protein rich diet.     

Is GABA Involved in the Development of Caffeine Tolerance?

Caffeine (10 or 20 mg/kg per day, po)-induced stimulation of locomotor activity (LA) reached its peak following 4 consecutive days of caffeine administration. Caffeine-induced stimulation of LA was restored to the control values following caffeine tolerance after 16 or 12 consecutive days of caffeine treatment at a dose of 10 or 20 mg/kg per day, po. Biochemical studies showed that caffeine in the nontolerant condition reduced GABAergic activity in cerebral cortex, corpus striaturn, cerebellum, hypothalamus and pons-medulla; but tolerance to caffeine (10 or 20 mg/kg per day, po) pushed up the GABAergic activity to the control value in all these regions of brain. Further, it was found that muscimol reduced the LA while bicuculline stimulated LA in the caffeine tolerant condition. Thus, from the present study it may be concluded that: (a) caffeine-induced stimulation of LA is dependent on dose and duration of caffeine treatment, (b) development of tolerance to caffeine is dependent on the dosage of caffeine, and (c) the reduction of central GABAergic activity in the caffeine-nontolerant condition pushed up and restored the LA to the control level on the development of tolerance to caffeine.     

Effect of Day and Night Temperature on Internode and Stem Length in Chrysanthemum: Is Everything Explained by DIF?

In many plant species, including chrysanthemum, a strong positive correlation between internode length and DIF [difference between day (DT) and night (NT) temperature] has been observed. However, Langton and Cockshull (1997. Scientia Horticulturae 69: 229-237) reported no such relationship and showed that absolute DT and NT explained internode length rather than DIF. To investigate these conflicting results and to clarify the validity of the DIF concept, cut chrysanthemums (Chrysanthemum 'Reagan Improved') were grown in growth chambers at all 16 combinations of four DT and four NT (16, 20, 24 and 28 degrees C) with a 12 h day length. Length of internode 10, number of internodes and stem length were measured on days 5, 10, 17, 22 and 27 after starting the temperature treatments. Internode length on day 10 showed a positive linear relationship with DIF (R2 = 0.64). However, when internodes had reached their final length in all treatments (day 27), a much stronger positive linear relation was observed (R2 = 0.81). A model to predict final internode length was developed based on the absolute DT and NT responses: both responses were optimum curves and no significant interaction between DT and NT occurred [final internode length (mm) = -32.23 + 3.56DT + 1.08NT - 0.0687DT2 - 0.0371NT2; R2 = 0.91, where TD is day temperature and TN is night temperature]. It is shown that DIF can predict final internode length only within a temperature range where effects of DT and NT are equal in magnitude and opposite in sign (18-24 degrees C). Internode appearance rate, as well as stem length formed during the experiment, showed an optimum response to DT.     

How Long and Low Can You Go? Effect of Conformation on the Risk of Thoracolumbar Intervertebral Disc Extrusion in Domestic Dogs

Intervertebral disc extrusion (IVDE) is a common neurological disorder in certain dog breeds, resulting in spinal cord compression and injury that can cause pain and neurological deficits. Most disc extrusions are reported in chondrodystrophic breeds (e.g. Dachshunds, Basset Hounds, Pekingese), where selection for ‘long and low’ morphologies is linked with intervertebral discs abnormalities that predispose dogs to IVDE. The aim of this study was to quantify the relationship between relative thoracolumbar vertebral column length and IVDE risk in diverse breeds. A 14 month cross-sectional study of dogs entering a UK small animal referral hospital for diverse disorders including IVDE was carried out. Dogs were measured on breed-defining morphometrics, including back length (BL) and height at the withers (HW). Of 700 dogs recruited from this referral population, measured and clinically examined, 79 were diagnosed with thoracolumbar IVDE following diagnostic imaging ± surgery. The BL:HW ratio was positively associated with IVDE risk, indicating that relatively longer dogs were at increased risk, e.g. the probability of IVDE was 0.30 for Miniature Dachshunds when BL:HW ratio equalled 1.1, compared to 0.68 when BL:HW ratio equalled 1.5. Additionally, both being overweight and skeletally smaller significantly increased IVDE risk. Therefore, selection for longer backs and miniaturisation should be discouraged in high-risk breeds to reduce IVDE risk. In higher risk individuals, maintaining a lean body shape is particularly important to reduce the risk of IVDE. Results are reported as probabilities to aid decision-making regarding breed standards and screening programmes reflecting the degree of risk acceptable to stakeholders.     

Mammalian Homologue of the Caenorhabditis elegans UNC-76 Protein Involved in Axonal Outgrowth Is a Protein Kinase C ζ–interacting Protein

By the yeast two-hybrid screening of a rat brain cDNA library with the regulatory domain of protein kinase C ζ (PKCζ) as a bait, we have cloned a gene coding for a novel PKCζ-interacting protein homologous to the Caenorhabditis elegans UNC-76 protein involved in axonal outgrowth and fasciculation. The protein designated FEZ1 (fasciculation and elongation protein zeta-1) consisting of 393 amino acid residues shows a high Asp/Glu content and contains several regions predicted to form amphipathic helices. Northern blot analysis has revealed that FEZ1 mRNA is abundantly expressed in adult rat brain and throughout the developmental stages of mouse embryo. By the yeast two-hybrid assay with various deletion mutants of PKC, FEZ1 was shown to interact with the NH₂-terminal variable region (V1) of PKCζ and weakly with that of PKCε. In the COS-7 cells coexpressing FEZ1 and PKCζ, FEZ1 was present mainly in the plasma membrane, associating with PKCζ and being phosphorylated. These results indicate that FEZ1 is a novel substrate of PKCζ. When the constitutively active mutant of PKCζ was used, FEZ1 was found in the cytoplasm of COS-7 cells. Upon treatment of the cells with a PKC inhibitor, staurosporin, FEZ1 was translocated from the cytoplasm to the plasma membrane, suggesting that the cytoplasmic translocation of FEZ1 is directly regulated by the PKCζ activity. Although expression of FEZ1 alone had no effect on PC12 cells, coexpression of FEZ1 and constitutively active PKCζ stimulated the neuronal differentiation of PC12 cells. Combined with the recent finding that a human FEZ1 protein is able to complement the function of UNC-76 necessary for normal axonal bundling and elongation within axon bundles in the nematode, these results suggest that FEZ1 plays a crucial role in the axon guidance machinery in mammals by interacting with PKCζ.     

Is the Effect of Aerobic Exercise on Cognition a Placebo Effect?

A number of studies and meta-analyses conclude that aerobic fitness (walking) interventions improve cognition. Such interventions typically compare improvements from these interventions to an active control group in which participants engage in non-aerobic activities (typically stretching and toning) for an equivalent amount of time. However, in the absence of a double-blind design, the presence of an active control group does not necessarily control for placebo effects; participants might expect different amounts of improvement for the treatment and control interventions [1]. We conducted a large survey to explore whether people expect greater cognitive benefits from an aerobic exercise intervention compared to a control intervention. If participants expect greater improvement following aerobic exercise, then the benefits of such interventions might be due in part to a placebo effect. In general, expectations did not differ between aerobic and non-aerobic interventions. If anything, some of the results suggest the opposite (e.g., respondents expected the control, non-aerobic intervention to yield bigger memory gains). These results provide the first evidence that cognitive improvements following aerobic fitness training are not due to differential expectations.     

Are Cellulosome Scaffolding Protein CipC and CBM3-Containing Protein HycP,Involved in Adherence of Clostridium cellulolyticum to Cellulose?

Clostridium cellulolyticum, a mesophilic anaerobic bacterium, produces highly active enzymatic complexes called cellulosomes. This strain was already shown to bind to cellulose, however the molecular mechanism(s) involved is not known. In this context we focused on the gene named hycP, encoding a 250-kDa protein of unknown function, containing a Family-3 Carbohydrate Binding Module (CBM3) along with 23 hyaline repeat modules (HYR modules). In the microbial kingdom the gene hycP is only found in C. cellulolyticum and the very close strain recently sequenced Clostridium sp BNL1100. Its presence in C. cellulolyticum guided us to analyze its function and its putative role in adhesion of the cells to cellulose. The CBM3 of HycP was shown to bind to crystalline cellulose and was assigned to the CBM3b subfamily. No hydrolytic activity on cellulose was found with a mini-protein displaying representative domains of HycP. A C. cellulolyticum inactivated hycP mutant strain was constructed, and we found that HycP is neither involved in binding of the cells to cellulose nor that the protein has an obvious role in cell growth on cellulose. We also characterized the role of the cellulosome scaffolding protein CipC in adhesion of C. cellulolyticum to cellulose, since cellulosome scaffolding protein has been proposed to mediate binding of other cellulolytic bacteria to cellulose. A second mutant was constructed, where cipC was inactivated. We unexpectedly found that CipC is only partly involved in binding of C. cellulolyticum to cellulose. Other mechanisms for cellulose adhesion may therefore exist in C. cellulolyticum. In addition, no cellulosomal protuberances were observed at the cellular surface of C. cellulolyticum, what is in contrast to reports from several other cellulosomes producing strains. These findings may suggest that C. cellulolyticum has no dedicated molecular mechanism to aggregate the cellulosomes at the cellular surface.     

Is Sonic Hedgehog Involved in Human Fracture Healing? - A Prospective Study on Local and Systemic Concentrations of SHH

Introduction

Sonic Hedgehog (SHH) is a new signalling pathway in bone repair. Evidence exist that SHH pathway plays a significant role in vasculogenesis and limb development during embryogenesis. Some in vitro and animal studies has already proven its potential for bone regeneration. However, no data on the role of SHH in the human fracture healing have been published so far.

Methods

Seventy-five patients with long bone fractures were included into the study and divided in 2 groups. First group contained 69 patients with normal fracture healing. Four patients with impaired fracture healing formed the second group. 34 volunteers donated blood samples as control. Serum samples were collected over a period of 1 year following a standardized time schedule. In addition, SHH levels were measured in fracture haematoma and serum of 16 patients with bone fractures.

Results

Fracture haematoma and patients serum both contained lower SHH concentrations compared to control serum. The comparison between the patients'' serum SHH level and the control serum revealed lower levels for the patients at all measurement time points. Significantly lower concentrations were observed at weeks 1 and 2 after fracture. SHH levels were slightly decreased in patients with impaired fracture healing without statistical significance.

Conclusion

This is the first study to report local and systemic concentration of SHH in human fracture healing and SHH serum levels in healthy adults. A significant reduction of the SHH levels during the inflammatory phase of fracture healing was found. SHH concentrations in fracture haematoma and serum were lower than the concentration in control serum for the rest of the healing period. Our findings indicate that there is no relevant involvement of SHH in human fracture healing. Fracture repair process seem to reduce the SHH level in human. Further studies are definitely needed to clarify the underlying mechanisms.     

Protein S-nitrosylation: What's going on in plants?

Nitric oxide (NO) is now recognized as a key regulator of plant physiological processes. Understanding the mechanisms by which NO exerts its biological functions has been the subject of extensive research. Several components of the signaling pathways relaying NO effects in plants, including second messengers, protein kinases, phytohormones, and target genes, have been characterized. In addition, there is now compelling experimental evidence that NO partly operates through posttranslational modification of proteins, notably via S-nitrosylation and tyrosine nitration. Recently, proteome-wide scale analyses led to the identification of numerous protein candidates for S-nitrosylation in plants. Subsequent biochemical and in silico structural studies revealed certain mechanisms through which S-nitrosylation impacts their functions. Furthermore, first insights into the physiological relevance of S-nitrosylation, particularly in controlling plant immune responses, have been recently reported. Collectively, these discoveries greatly extend our knowledge of NO functions and of the molecular processes inherent to signal transduction in plants.     

Effect of 1-Methyladenine on Localization of Gαi Protein in Starfish Oocytes

Localization and quantitative dynamics of _i subunit of G protein was studied by electron immunocytochemistry and immunoenzyme assay after hormonal induction of oocyte maturation in starfish Asterias amurensis. G_i protein was chiefly localized in the plasma membrane of immature oocytes; 1-methyladenine induced redistribution of the _i protein from the plasma membrane to intracellular structure up to the breakdown of the germinal vesicle.     

Resveratrol: Is There Any Effect on Healthy Subject?

This preliminary study was planned to investigate the effects of resveratrol on oxidative–nitrosative stress markers and on trace element concentrations in blood and on circulatory system parameters in rats. Twenty-five Sprague–Dawley male rats, 10–12 weeks old, with mean body weight of 295 g were used in the study. Administration of resveratrol (0.5 ml/day) was performed in experimental group in 10 days. In control (n = 10) and in experimental groups (n = 15), after 1 week training period, systolic arterial blood pressures and heart rates were recorded daily. At the end of the tenth day, blood samples of control and experimental groups were drawn. Total nitrite, nitrite, nitrate, malondialdehyde, copper, zinc concentrations in plasma, superoxide dismutase, and catalase activities and copper, zinc concentrations in red cell were determined both in control and experimental groups. Alterations in oxidative and nitrosative stress markers, trace element concentrations, and circulatory system parameters in experimental group compared to controls were observed. The results of this study were discussed according to the effect of resveratrol. This study was presented at “The 5th International Congress of Pathophysiology (ISP2006)” June 28–July 1, 2006 Beijing, China.     

Steroid Hormone Actions on the Brain: When Is the Genome Involved?

It has become customary to distinguish between so-called "genomic" actions of steroid hormones involving intracellular receptors and "non-genomic" effects of steroids that involve putative cell surface receptors. Whereas there is no doubt that this distinction has considerable validity, it does not go far enough in addressing the variety of mechanisms that steroid hormones use to produce their effects on cells. This is because cell surface receptors may signal changes in gene expression, while genomic actions sometimes affect neuronal excitability, often doing so quite rapidly. Moreover, steroid hormones and neurotransmitters may operate together to produce effects, and sometimes these effects involve collaborations between groups of neurons. As illustrations. evidence is reviewed in this article that a number of steroid actions in the hippocampus involves the co-participation of excitatory amino acids. These interactions are evident for the regulation of synaptogenesis by estradiol in the CA1 pyramidal neurons or hippocampus and for the induction of dendritic atrophy of CA3 neurons by repeated stress as well as by glucocorticoid injections. In addition, neurogenesis in the adult and developing dentate gyrus is "contained" by adrenal steroids as well as by excitatory amino acids. In each of these three examples, NMDA receptors are involved. These results not only point to a high degree of interdependency between certain neurotransmitters and the actions of steroid hormones but also emphasize the degree to which structural plasticity is an important aspect of steroid hormone action in the adult as well as developing nervous system.     

Is Performance Time a Prerequisite for the Onset and Intensity of the Occlusion-Reperfusion Arrhythmias in Anaesthetised Rats?

The aim of the present study is to investigate the onset and the intensity of arrhythmias in anaesthetized rats as a function of time under a standardized experimental condition, which is composed of 30 min occlusion and 60 min reperfusion. Local bred rats (250-350 g) housed in a 12-h light-dark cycle (lights on at 09.00 h, lights off at 21.00 h) were anaesthetized by sodium thiopentone (60 mg kg^-1 i.p.) and left anterior descending coronary artery ligation method using 6/0 braided silk ligature was used to induce 30 min occlusion and 60-min reperfusion. Animals were randomly allocated into three groups to exposure to 30-min occlusion at 9.00 h and 60 min reperfusion at 9:30 h (Group I, n = 6); to 30 min occlusion at 15.00 h and 60 min reperfusion at 15:30 h (Group II, n = 6); and to 30 min occlusion at 21.00 h and 60 min reperfusion at 21.30 h (Group III, n = 6). ECG and haemodynamic parameters were recorded throughout the experiments. The onset of ventricular ectopic beats (VEBs), number of VEBs, incidences of ventricular tachycardia (VT) and ventricular fibrillation (VF) during the periods of occlusion-reperfusion were analysed. Total VF incidence during occlusion were lower than the VT incidence in all groups. Either VT or VF incidences during reperfusion showed same profiles in all groups but VT incidence was 2-fold higher than VF. Time-dependent application of occlusion-reperfusion induced by coronary artery ligation method in the anaesthetized rats did not result in a variation in the onset and the intensity of arrhythmias. The duration of the experimental ischaemia was the principal factor, which determines the time of onset and intensity of the occlusion-reperfusion arrhythmias.     

Sequential Activation of Classic PKC and Estrogen Receptor α Is Involved in Estradiol 17?-D-Glucuronide-Induced Cholestasis

Estradiol 17ß-d-glucuronide (E17G) induces acute cholestasis in rat with endocytic internalization of the canalicular transporters bile salt export pump (Abcb11) and multidrug resistance-associated protein 2 (Abcc2). Classical protein kinase C (cPKC) and PI3K pathways play complementary roles in E17G cholestasis. Since non-conjugated estradiol is capable of activating these pathways via estrogen receptor alpha (ERα), we assessed the participation of this receptor in the cholestatic manifestations of estradiol glucuronidated-metabolite E17G in perfused rat liver (PRL) and in isolated rat hepatocyte couplets (IRHC). In both models, E17G activated ERα. In PRL, E17G maximally decreased bile flow, and the excretions of dinitrophenyl-glutathione, and taurocholate (Abcc2 and Abcb11 substrates, respectively) by 60% approximately; preadministration of ICI 182,780 (ICI, ERα inhibitor) almost totally prevented these decreases. In IRHC, E17G decreased the canalicular vacuolar accumulation of cholyl-glycylamido-fluorescein (Abcb11 substrate) with an IC50 of 91±1 µM. ICI increased the IC50 to 184±1 µM, and similarly prevented the decrease in the canalicular vacuolar accumulation of the Abcc2 substrate, glutathione-methylfluorescein. ICI also completely prevented E17G-induced delocalization of Abcb11 and Abcc2 from the canalicular membrane, both in PRL and IRHC. The role of ERα in canalicular transporter internalization induced by E17G was confirmed in ERα-knocked-down hepatocytes cultured in collagen sandwich. In IRHC, the protection of ICI was additive to that produced by PI3K inhibitor wortmannin but not with that produced by cPKC inhibitor Gö6976, suggesting that ERα shared the signaling pathway of cPKC but not that of PI3K. Further analysis of ERα and cPKC activations induced by E17G, demonstrated that ICI did not affect cPKC activation whereas Gö6976 prevented that of ERα, indicating that cPKC activation precedes that of ERα. Conclusion: ERα is involved in the biliary secretory failure induced by E17G and its activation follows that of cPKC.