Measurement of steroids in rats after exposure to an endocrine disruptor: mass spectrometry and radioimmunoassay demonstrate similar results

INTRODUCTION

Commercially available radioimmunoassays (RIAs) are frequently used to evaluate the effects of endocrine disrupting chemicals (EDCs) on steroidogenesis in rats. Currently there are limited data comparing steroid concentrations in rats as measured by RIAs to those obtained using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). This study evaluates the concordance of serum and urine steroid concentrations as quantified by select RIA kits and LC-MS/MS following exposure to an EDC, atrazine (ATR).

METHODS

Adult male rats were orally dosed with ATR (200 mg/kg/day) or methylcellulose (1%, vehicle control) for 5 days. Serum was collected and separated into aliquots for analysis. Serum was assayed by RIA for androstenedione (ANDRO), corticosterone (CORT), estradiol (E2), estrone (E1), progesterone (P4), and testosterone (T). Serum was extracted prior to LC-MS/MS analysis with positive electrospray ionization in multiple-reaction monitoring mode for ANDRO, CORT, P4, and T. E1 and E2 concentrations were quantified similarly by LC-MS/MS, following derivatization with dansyl chloride. To compare CORT values from urine, pregnant adult rats were orally dosed with either ATR (100 mg/kg/day) or methylcellulose for 5 days (i.e., gestational days 14-18). Urine samples were collected daily and assayed for CORT by RIA and LC-MS/MS as described above.

RESULTS

Data analyses demonstrated significant agreement between the two detection methods as assessed by Pearson product-moment correlation coefficient, Bland-Altman analysis, and the interclass correlation coefficient. No statistically significant differences were observed between RIA and LC-MS/MS means for any of the steroids assayed.

DISCUSSION

These findings indicate a significant correlation between the measurement of steroids within rat serum and urine using RIA kits and LC-MS/MS. Differences in the absolute measurements existed, but these were not statistically significant. These findings indicate that steroids may be reliably measured in rat biological media using RIAs or LC-MS/MS.

Omega-3 fatty acids can reverse the long-term deficits in hippocampal synaptic plasticity caused by prenatal ethanol exposure

Fetal alcohol spectrum disorders result in long-lasting neurological deficits including decreases in synaptic plasticity and deficits in learning and memory. In this study we examined the effects of prenatal ethanol exposure on hippocampal synaptic plasticity in male and female Sprague-Dawley rats. Furthermore, we looked at the capacity for postnatal dietary intervention to rescue deficits in synaptic plasticity. Animals were fed an omega-3 enriched diet from birth until adulthood (PND55-70) and in vivo electrophysiology was performed by stimulating the medial perforant path input to the dentate gyrus and recording field excitatory post-synaptic potentials. LTP was induced by administering bursts of five 400 Hz pulses as a theta-patterned train of stimuli (200 ms inter-burst interval). Ethanol-exposed adult males, but not females, exhibited a significant reduction in LTP. This deficit in male animals was completely reversed with an omega-3 enriched diet. These results demonstrate that omega-3 fatty acids can have benefits following prenatal neuropathological insults and may be a viable option for alleviating some of the neurological deficits associated with FASD.

Heterogeneity and function of K(ATP) channels in canine hearts

BACKGROUND

The concept that pore-forming Kir6.2 and regulatory SUR2A subunits form cardiac ATP-sensitive potassium (K(ATP)) channels is challenged by recent reports that SUR1 is predominant in mouse atrial K(ATP) channels.

OBJECTIVE

To assess SUR subunit composition of K(ATP) channels and consequence of K(ATP) activation for action potential duration (APD) in dog hearts.

METHODS

Patch-clamp techniques were used on isolated dog cardiomyocytes to investigate K(ATP) channel properties. Dynamic current clamp, by injection of a linear K(+) conductance to simulate activation of the native current, was used to study the consequences of K(ATP) activation on APD.

RESULTS

Metabolic inhibitor (MI)-activated current was not significantly different from pinacidil (SUR2A-specific)-activated current, and both currents were larger than diazoxide (SUR1-specific)-activated current in both the atrium and the ventricle. Mean K(ATP) conductance (activated by MI) did not differ significantly between chambers, although, within the ventricle, both MI-induced and pinacidil-induced currents tended to decrease from the epicardium to the endocardium. Dynamic current-clamp results indicate that myocytes with longer baseline APDs are more susceptible to injected K(ATP) current, a result reproduced in silico by using a canine action potential model (Hund-Rudy) to simulate epicardial and endocardial myocytes.

CONCLUSIONS

Even a small fraction of K(ATP) activation significantly shortens APD in a manner that depends on existing heterogeneity in K(ATP) current and APD.

Proline-induced changes in acetylcholinesterase activity and gene expression in zebrafish brain: reversal by antipsychotic drugs

Hyperprolinemia is an inherited disorder of proline metabolism and hyperprolinemic patients can present neurological manifestations, such as seizures, cognitive dysfunctions, and schizoaffective disorders. However, the mechanisms related to these symptoms are still unclear. In the present study, we evaluated the in vivo and in vitro effects of proline on acetylcholinesterase (AChE) activity and gene expression in the zebrafish brain. For the in vivo studies, animals were exposed at two proline concentrations (1.5 and 3.0mM) during 1h or 7 days (short- or long-term treatments, respectively). For the in vitro assays, different proline concentrations (ranging from 3.0 to 1000 μM) were tested. Long-term proline exposures significantly increased AChE activity for both treated groups when compared to the control (34% and 39%). Moreover, the proline-induced increase on AChE activity was completely reverted by acute administration of antipsychotic drugs (haloperidol and sulpiride), as well as the changes induced in ache expression. When assessed in vitro, proline did not promote significant changes in AChE activity. Altogether, these data indicate that the enzyme responsible for the control of acetylcholine levels might be altered after proline exposure in the adult zebrafish. These findings contribute for better understanding of the pathophysiology of hyperprolinemia and might reinforce the use of the zebrafish as a complementary vertebrate model for studying inborn errors of amino acid metabolism.

Stepping in persons poststroke: comparison of voluntary and perturbation-induced responses

OBJECTIVES

To examine the stepping performance during voluntary and waist-pull perturbation-induced step initiation in people with chronic stroke.

DESIGN

Repeated-measures single-case design.

SETTING

University-based research laboratory.

PARTICIPANTS

Community-dwelling stroke survivors (N=10).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Ground reaction forces and kinematic data were recorded to assess anticipatory postural adjustments (APAs) and step characteristics for both voluntary and induced stepping conditions.

RESULTS

Induced stepping was performed with both the paretic (35% trials) and nonparetic legs (65% trials). Induced first steps occurred earlier and were executed faster than rapid voluntary steps. Compared with voluntary stepping, induced first step APAs were shorter in duration. Step height was higher with the nonparetic leg for both stepping conditions. Use of the paretic leg increased (52%) during the diagonal perturbations that passively unloaded the stepping limb compared with the use of the paretic leg (33%) for forward perturbations.

CONCLUSIONS

The results indicated differences in executing voluntary and induced stepping, and between the paretic and nonparetic limbs in individuals with chronic stroke. The findings suggested guidelines for using stepping as a component of neurorehabilitation programs for enhancing balance and mobility. Additional larger-scale studies remain to be undertaken to further investigate these issues.

Reversal of novelty-induced hyperlocomotion and hippocampal c-Fos expression in GluA1 knockout male mice by the mGluR2/3 agonist LY354740

Dysfunctional glutamatergic neurotransmission has been implicated in schizophrenia and mood disorders. As a putative model for these disorders, a mouse line lacking the GluA1 subunit (GluA1-KO) of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptor displays a robust novelty-induced hyperlocomotion associated with excessive neuronal activation in the hippocampus. Agonists of metabotropic glutamate 2/3 receptors (mGluR2/3) inhibit glutamate release in various brain regions and they have been shown to inhibit neuronal activation in the hippocampus. Here, we tested a hypothesis that novelty-induced hyperlocomotion in the GluA1-KO mice is mediated via excessive hippocampal neuronal activation by analyzing whether an mGluR2/3 agonist inhibits this phenotypic feature. GluA1-KO mice and littermate wildtype (WT) controls were administered with (1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740) (15 mg/kg, i.p.) 30 min before a 2-h exposure to novel arenas after which c-Fos immunopositive cells were analyzed in the hippocampus. LY354740 (15 mg/kg) decreased hyperactivity in male GluA1-KO mice, with only a minimal effect in WT controls. This was observed in two cohorts of animals, one naïve to handling and injections, another pre-handled and accustomed to injections. LY354740 (15 mg/kg) also reduced the excessive c-Fos expression in the dorsal hippocampal CA1 pyramidal cell layer in maleGluA1-KO mice, while not affecting c-Fos levels in WT mice. In female mice, no significant effect for LY354740 (15 mg/kg) on hyperactive behavior or hippocampal c-Fos was observed in either genotype or treatment cohort. A higher dose of LY354740 (30 mg/kg) alleviated hyperlocomotion of GluA1-KO males, but not that of GluA1-KO females. In conclusion, the excessive behavioral hyperactivity of GluA1-KO mice can be partly prevented by reducing neuronal excitability in the hippocampus with the mGluR2/3 agonist suggesting that the hippocampal reactivity is strongly involved in the behavioral phenotype of GluA1-KO mice.

The effect of Parkinson's disease and levodopa on adaptation of anticipatory postural adjustments

Postural support alters anticipatory postural adjustments (APAs). Efficient adaptation to changes in postural support in reactive and centrally initiated postural synergies is impaired in Parkinson's disease (PD). This study examined whether APAs are affected differently by familiar and novel supports in people with PD, ON and OFF levodopa. The effect of PD and levodopa on the ability to immediately adapt APAs to changes in support and refine with practice was also investigated. Fourteen people with PD and 14 healthy control participants performed 20 single rapid leg lift tasks in four support conditions: unsupported, bilateral handgrip (familiar), bite plate (novel) and a combined handgrip+bite plate condition. APAs, identified from force plate data, were characterized by an increase in the vertical ground reaction force under the lifted leg as a result of a shift of weight toward the stance limb. Results showed the ability to incorporate familiar and novel external supports into the postural strategy was preserved in PD. Controls and PD patients in the OFF state further refined the postural strategy with practice as evidenced by changes in amplitude of vertical ground reaction forces and forces applied to support apparatus within conditions between the initial and final trials. In the ON state, people with PD failed to refine the use of postural supports in any condition. The results suggest that immediate postural adaptation is intact in people with PD and unaffected by levodopa administration but the ability to refine postural adaptations with task experience is compromised by dopamine therapy.

Scratching inhibits serotonin-evoked responses of rat dorsal horn neurons in a site- and state-dependent manner

Scratching inhibits pruritogen-evoked responses of neurons in the superficial dorsal horn, implicating a spinal site for scratch inhibition of itch. We investigated if scratching differentially affects neurons depending on whether they are activated by itchy vs. painful stimuli, and if the degree of inhibition depends on the relative location of scratching. We recorded from rat lumbar dorsal horn neurons responsive to intradermal (id) microinjection of serotonin (5-hydroxytryptamine, 5-HT). During the response to 5-HT, scratch stimuli (3mm, 300 mN, 2 Hz, 20s) were delivered at the injection site within the mechanosensitive receptive field (on-site), or 4-30 mm away, outside of the receptive field (off-site). During off-site scratching, 5-HT-evoked firing was significantly attenuated followed by recovery. On-site scratching excited neurons, followed by a significant post-scratch decrease in 5-HT-evoked firing. Most neurons additionally responded to mustard oil (allyl isothiocyanate). Off-site scratching had no effect, while on-site scratching excited the neurons. These results indicate that scratching exerts a state-dependent inhibitory effect on responses of spinal neurons to pruritic but not algesic stimuli. Moreover, on-site scratching first excited neurons followed by inhibition, while off-site scratching immediately evoked the inhibition of pruritogen-evoked activity. This accounts for the suppression of itch by scratching at a distance from the site of the itchy stimulus.

Impact of telemedicine on hospital transport, length of stay, and medical outcomes in infants with suspected heart disease: a multicenter study

BACKGROUND

Previous single-center studies have shown that telemedicine improves care in newborns with suspected heart disease. The aim of this study was to test the hypothesis that telemedicine would shorten time to diagnosis, prevent unnecessary transports, reduce length of stay, and decrease exposure to invasive treatments.

METHODS

Nine pediatric cardiology centers entered data prospectively on patients aged <6 weeks, matched by gestational age, weight, and diagnosis. Subjects born at hospitals with and without access to telemedicine constituted the study group and control groups, respectively. Data from patients with mild or no heart disease were analyzed.

RESULTS

Data were obtained for 337 matched pairs with mild or no heart disease. Transport to a tertiary care center (4% [n = 15] vs 10% [n = 32], P = .01), mean time to diagnosis (100 vs 147 min, P < .001), mean length of stay (1.0 vs 26 days, P = .005) and length of intensive care unit stay (0.96 vs 2.5 days, P = .024) were significantly less in the telemedicine group. Telemedicine patients were significantly farther from tertiary care hospitals than control subjects. The use of inotropic support and indomethacin was significantly less in the telemedicine group. By multivariate analysis, telemedicine patients were less likely to be transported (odds ratio, 0.44; 95% confidence interval, 0.23-0.83) and less likely to be placed on inotropic support (odds ratio, 0.16; 95% confidence interval, 0.10-0.28).

CONCLUSIONS

Telemedicine shortened the time to diagnosis and significantly decreased the need for transport of infants with mild or no heart disease. The length of hospitalization and intensive care stay and use of indomethacin and inotropic support were less in telemedicine patients.

Increased anesthesia time using 2,2,2-tribromoethanol-chloral hydrate with low impact on mouse psychoacoustics

BACKGROUND

To examine psychoacoustics in mice, we have used 2,2,2-tribromoethanol anesthesia in multiple studies. We find this drug is fast-acting and yields consistent results, providing 25-30 min of anesthesia. Our recent studies in binaural hearing prompted development of a regimen to anesthesia time to 1h. We tested a novel cocktail using 2,2,2-tribromoethanol coupled with low dose chloral hydrate to extend the effective anesthesia time.

NEW METHOD

We have established an intraperitoneal dosing regimen for 2,2,2-tribromoethanol-chloral hydrate anesthesia. To measure efficacy of the drug cocktail, we measured auditory brainstem responses (ABRs) at 10 min intervals to determine the effects on hearing thresholds and wave amplitudes and latencies.

RESULTS

This novel drug combination increases effective anesthesia to 1h. ABR Wave I amplitudes, but not latencies, are marginally suppressed. Additionally, amplitudes of the centrally derived Waves III and V show significant inter-animal variability that is independent of stimulus intensity. These data argue against the systematic suppression of ABRs by the drug cocktail.

COMPARISON WITH EXISTING METHODS

Using 2,2,2-tribromoethanol-chloral hydrate combination in psychoacoustic studies has several advantages over other drug cocktails, the most important being preservation of latencies from centrally- and peripherally-derived ABR waves. In addition, hearing thresholds are unchanged and wave amplitudes are not systematically suppressed, although they exhibit greater variability.

CONCLUSIONS

We demonstrate that 375 mg/kg 2,2,2-tribromoethanol followed after 5 min by 200mg/kg chloral hydrate provides an anesthesia time of 60 min, has negligible effects on ABR wave latencies and thresholds and non-systematic effects on amplitudes.

Spinal 5-HT7 receptors and protein kinase A constrain intermittent hypoxia-induced phrenic long-term facilitation

Phrenic long-term facilitation (pLTF) is a form of serotonin-dependent respiratory plasticity induced by acute intermittent hypoxia (AIH). pLTF requires spinal Gq protein-coupled serotonin-2 receptor (5-HT2) activation, new synthesis of brain-derived neurotrophic factor (BDNF) and activation of its high-affinity receptor, TrkB. Intrathecal injections of selective agonists for Gs protein-coupled receptors (adenosine 2A and serotonin-7; 5-HT7) also induce long-lasting phrenic motor facilitation via TrkB "trans-activation." Since serotonin released near phrenic motor neurons may activate multiple serotonin receptor subtypes, we tested the hypothesis that 5-HT7 receptor activation contributes to AIH-induced pLTF. A selective 5-HT7 receptor antagonist (SB-269970, 5mM, 12 μl) was administered intrathecally at C4 to anesthetized, vagotomized and ventilated rats prior to AIH (3, 5-min episodes, 11% O2). Contrary to predictions, pLTF was greater in SB-269970 treated versus control rats (80 ± 11% versus 45 ± 6% 60 min post-AIH; p<0.05). Hypoglossal LTF was unaffected by spinal 5-HT7 receptor inhibition, suggesting that drug effects were localized to the spinal cord. Since 5-HT7 receptors are coupled to protein kinase A (PKA), we tested the hypothesis that PKA inhibits AIH-induced pLTF. Similar to 5-HT7 receptor inhibition, spinal PKA inhibition (KT-5720, 100 μM, 15 μl) enhanced pLTF (99 ± 15% 60 min post-AIH; p<0.05). Conversely, PKA activation (8-br-cAMP, 100 μM, 15 μl) blunted pLTF versus control rats (16 ± 5% versus 45 ± 6% 60 min post-AIH; p<0.05). These findings suggest a novel mechanism whereby spinal Gs protein-coupled 5-HT7 receptors constrain AIH-induced pLTF via PKA activity.

An acute rat in vivo screening model to predict compounds that alter blood glucose and/or insulin regulation

INTRODUCTION

Drug-induced glucose dysregulation and insulin resistance have been associated with weight gain and potential induction and/or exacerbation of diabetes mellitus in the clinic suggesting they may be safety biomarkers when developing antipsychotics. Glucose and insulin have also been suggested as potential efficacy biomarkers for some oncology compounds. The objective of this study was to qualify a medium throughput rat in vivo acute Intravenous Glucose Tolerance Test (IVGTT) for predicting compounds that will induce altered blood glucose and/or insulin levels.

METHODS

Acute and sub-chronic studies were performed to qualify an acute IVGTT model. Double cannulated male rats (Han-Wistar and Sprague-Dawley) were administered vehicle, olanzapine, aripiprazole or other compounds at t=-44min for acute studies and at time=-44min on the last day of dosing for sub-chronic studies, treated with dextrose (time=0min; i.v.) and blood collected using an automated Culex® system for glucose and insulin analysis (time=-45, -1, 2, 10, 15, 30, 45, 60, 75, 90, 120, 150 and 180min).

RESULTS

Olanzapine significantly increased glucose and insulin area under the curve (AUC) values while aripiprazole AUC values were similar to control, in both acute and sub-chronic studies. All atypical antipsychotics evaluated were consistent with literature references of clinical weight gain. As efficacy biomarkers, insulin AUC but not glucose AUC values were increased with a compound known to have insulin growth factor-1 (IGF-1) activity, compared to control treatment.

DISCUSSION

These studies qualified the medium throughput acute IVGTT model to more quickly screen compounds for 1) safety - the potential to elicit glucose dysregulation and/or insulin resistance and 2) efficacy - as a surrogate for compounds affecting the glucose and/or insulin regulatory pathways. These data demonstrate that the same in vivo rat model and assays can be used to predict both clinical safety and efficacy of compounds.

Statistical approaches to assessing single and multiple outcome measures in dry eye therapy and diagnosis

Dry eye is a multifactorial disease which would require a broad spectrum of test measures in the monitoring of its treatment and diagnosis. However, studies have typically reported improvements in individual measures with treatment. Alternative approaches involve multiple, combined outcomes being assessed by different statistical analyses. In order to assess the effect of various statistical approaches to the use of single and combined test measures in dry eye, this review reanalyzed measures from two previous studies (osmolarity, evaporation, tear turnover rate, and lipid film quality). These analyses assessed the measures as single variables within groups, pre- and post-intervention with a lubricant supplement, by creating combinations of these variables and by validating these combinations with the combined sample of data from all groups of dry eye subjects. The effectiveness of single measures and combinations in diagnosis of dry eye was also considered.

Cyclopropane-based conformational restriction of GABA by a stereochemical diversity-oriented strategy: identification of an efficient lead for potent inhibitors of GABA transports

A series of cyclopropane-based conformationally restricted γ-aminobutyric acid (GABA) analogs with stereochemical diversity, that is, the trans- and cis-2,3-methano analogs Ia and Ib and their enantiomers ent-Ia and ent-Ib, and also the trans- and cis-3,4-methano analogs IIa and IIb and their enantiomers ent-IIa and ent-Iib, were synthesized from the chiral cyclopropane units Type-a and Type-b that we developed. These analogs were systematically evaluated with four GABA transporter (GAT) subtypes. The trans-3,4-methano analog IIa had inhibitory effects on GAT3 (IC50=23.9μM) and betaine-GABA transporter1 (5.48μM), indicating its potential as an effective lead compound for the development of potent GAT inhibitors due to its hydrophilic and low molecular weight properties and excellent ligand efficiency.

Ca(2+) spiking activity caused by the activation of store-operated Ca(2+) channels mediates TNF-α release from microglial cells under chronic purinergic stimulation

Cytokines released from microglia mediate defensive responses in the brain, but the underlying mechanisms are obscure. One proposed process is that nucleotide leakage or release from surrounding cells is sensed by metabotropic (P2Y) and ionotropic (P2X) purinergic receptors, which may trigger long-term intracellular Ca(2+) flux and tumor necrosis factor α (TNF-α) release. Indeed, 3h of exposure to ATP was required to evoke TNF-α release from a murine microglial cell line (MG5). A Ca(2+) chelator, ethylene glycol tetraacetic acid (EGTA), reduced ATP-induced TNF-α release, suggesting that intracellular Ca(2+) is important in this response. Therefore, Ca(2+) sensor genes (YC3.6) were transfected into MG5 cells to investigate the Ca(2+) dynamics underlying ATP-induced TNF-α release. The results demonstrated ATP-induced biphasic Ca(2+) mobilization mediated by P2Y (~5min) and P2X7 receptors (5-30min). Moreover, Ca(2+) spiking activity in cell processes progressively increased with a reduction in P2X7 receptor-mediated Ca(2+) elevation during 3-h ATP stimulation. Increased Ca(2+) spiking activity paralleled the reduction in thapsigargin-sensitive internal Ca(2+) stores, dendrite extension, and expression of macrophage scavenger receptors with collagenous structure. The Ca(2+) spiking activity was enhanced by a P2X7 receptor antagonist (A438079), but inhibited by a store-operated channel antagonist (SKF96365) or by co-transfection of small interference ribonucleic acid (siRNA) targeted on the channel component (Orai1). Furthermore, ATP-induced TNF-α release was enhanced by A438079 but was inhibited by SKF96365. Because store-operated channels (Stim1/Orai1) were expressed both in MG5 and primary microglial cultures, we suggest that P2X7 receptor signaling inhibits store-operated channels during ATP stimulation, and disinhibition of this process gates TNF-α release from microglial cells.

Neuroprotective effects of NGF, BDNF, NT-3 and GDNF on axotomized extraocular motoneurons in neonatal rats

Neurotrophic factors delivered from target muscles are essential for motoneuronal survival, mainly during development and early postnatal maturation. It has been shown that the disconnection between motoneurons and their innervated muscle by means of axotomy produces a vast neuronal death in neonatal animals. In the present work, we have evaluated the effects of different neurotrophic factors on motoneuronal survival after neonatal axotomy, using as a model the motoneurons innervating the extraocular eye muscles. With this purpose, neonatal rats were monocularly enucleated at the day of birth (postnatal day 0) and different neurotrophic treatments (NGF, BDNF, NT-3, GDNF and the mixture of BDNF+GDNF) were applied intraorbitally by means of a Gelfoam implant (a single dose of 5 μg of each factor). We first demonstrated that extraocular eye muscles of neonatal rats expressed these neurotrophic factors and therefore constituted a natural source of retrograde delivery for their innervating motoneurons. By histological and immunocytochemical methods we determined that all treatments significantly rescued extraocular motoneurons from axotomy-induced cell death. For the dose used, NGF and GDNF were the most potent survival factors for these motoneurons, followed by BDNF and lastly by NT-3. The simultaneous administration of BDNF and GDNF did not increase the survival-promoting effects above those obtained by GDNF alone. Interestingly, the rescue effects of all neurotrophic treatments persisted even 30 days after lesion. The administration of these neurotrophic factors, with the exception of NT-3, also prevented the loss of the cholinergic phenotype observed by 10 days after axotomy. At the dosage applied, NGF and GDNF were revealed again as the most effective neuroprotective agents against the axotomy-induced decrease in ChAT. Two remarkable findings highlighted in the present work that contrasted with other motoneuronal types after neonatal axotomy: first, the extremely high efficacy of NGF as a neuroprotective agent and, second, the long-lasting effects of neurotrophic administration on cell survival and ChAT expression in extraocular motoneurons.

An examination of cardiovascular collapse induced by eastern brown snake (Pseudonaja textilis) venom

The Pseudonaja genus (Brown snakes) is widely distributed across Australia and bites account for significant mortality. Venom-induced consumption coagulopathy (VICC) and, less often, early cardiovascular collapse occur following envenoming by these snakes. We have previously examined possible mechanism(s) behind the early cardiovascular collapse following Papuan taipan (Oxyuranus scutellatus) envenoming. In the present study, we investigate early cardiovascular collapse in anaesthetized rats following administration of eastern brown snake (Pseudonaja textilis) venom, and prevention of this effect with prior administration of 'priming' doses (i.e. doses of venom which caused a transient hypotensive response) of venom. P. textilis venom (5-10 μg/kg, i.v.) induced cardiovascular collapse in anaesthetized rats, characterized by a rapid decrease in systolic blood pressure until non recordable. Prior administration of 'priming' doses of P. textilis venom (2 and 3 μg/kg) or, at least, 4-5 doses of O. scutellatus (2 μg/kg, i.v.) or Daboia russelii limitis (20 μg/kg, i.v.) venoms prevented cardiovascular collapse induced by P. textilis venom. Moreover, early collapse was also inhibited by prior administration of 2 discrete doses of Acanthophis rugosus venom. Prior administration of commercial polyvalent snake antivenom (500-3000 units/kg, i.v.) or heparin (300 units/kg, i.v.) also inhibited P. textilis venom-induced cardiovascular collapse. Our results indicate that P. textilis venom-induced cardiovascular collapse can be prevented by prior administration of sub-lethal doses of venom from P. textilis, O. scutellatus, A. rugosus and D. russelii limitis. This suggests that sudden cardiovascular collapse following envenoming is likely to involve a common mechanism/pathway activated by different snake venoms.

Role of hydrogen sulfide in the pain processing of non-diabetic and diabetic rats

Hydrogen sulfide (H2S) is a gasotransmitter endogenously generated from the metabolism of L-cysteine by action of two main enzymes called cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). This gas has been involved in the pain processing and insulin resistance produced during diabetes development. However, there is no evidence about its participation in the peripheral neuropathy induced by this metabolic disorder. Experimental diabetes was induced by streptozotocin (50mg/kg, i.p.) in female Wistar rats. Streptozotocin injection increased formalin-evoked flinching in diabetic rats as compared to non-diabetic rats after 2 weeks. Peripheral administration of NaHS (an exogenous donor of H2S) and L-cysteine (an endogenous donor of H2S) dose-dependently increased flinching behavior in diabetic and non-diabetic rats. Contrariwise, hydroxylamine (HA, a CBS inhibitor) and DL-propargylglycine (PPG, a CSE inhibitor) decreased formalin-induced nociceptive behavior in both experimental groups. In addition, an ineffective dose of HA and PPG partially prevented the L-cysteine-induced hyperalgesia in diabetic and non-diabetic rats. Interestingly, HA and PPG were three order of magnitude more potent in diabetic rats respect to non-diabetic rats, whereas NaHS was ten times more potent in the streptozotocin-diabetic group. Nine to 11 weeks after diabetes induction, tactile allodynia was observed in the streptozotocin-injected rats. On this condition, subcutaneous administration of PPG or HA reduced tactile allodynia in diabetic rats. Paradoxically, H2S levels were decreased in nerve sciatic, dorsal root ganglion and spinal cord, but not paw nor blood plasma, during diabetes-associated peripheral neuropathy development. Collectively, results suggest that H2S synthesized by CBS and CSE participate in formalin-induced nociception in diabetic and non-diabetic rats, as well as; in tactile allodynia in streptozotocin-injected rats. In addition, data seems to indicate that diabetic rats are more sensible to H2S-induced hyperalgesia than normoglycemic rats.

Long-term impact of strength training on muscle strength characteristics in older adults

OBJECTIVE

To evaluate the long-term preventive impact of strength training on muscle performance in older adults.

DESIGN

A 7-year follow-up on a 1-year randomized controlled trial comparing the effects of combined resistance training and aerobic training and whole-body vibration training on muscle performance.

SETTING

University training center.

PARTICIPANTS

Men and women (N=83; control [CON] group, n=27; strength-training intervention [INT] group, n=56) between 60 and 80 years of age.

INTERVENTIONS

The INT group exercised 3 times weekly during 1 year, performing a combined resistance training and aerobic training program or a whole-body vibration training program. The former training program was designed according to American College of Sports Medicine guidelines. The whole-body vibration training program included unloaded static and dynamic leg exercises on a vibration platform. The CON group did not participate in any training program.

MAIN OUTCOME MEASURES

Static strength (STAT), dynamic strength at 60°/s (DYN60) and at 240°/s (DYN240), speed of movement at 20% (S20).

RESULTS

From baseline to postintervention, muscle performance did not change in the CON group, except for S20 (+6.55%±2.88%, P<.001). One year of strength training increased (P≤.001) STAT (+11.46%±1.86%), DYN60 (+6.96%±1.65%), DYN240 (+9.25%±1.68%), and S20 (+7.73%±2.19%) in the INT group. Between baseline and follow-up, muscle performance decreased (P<.001) in both groups. However, STAT and DYN60 showed a significantly lower loss in the INT group (-8.65%±2.35% and -7.10%±2.38%, respectively) compared with the CON group (-16.47%±2.69% and -15.08%±2.27%, respectively). This positive impact might be due to the preservation of the training-induced gains, given the similar annual decline rates in both groups from postintervention to follow-up. Additionally, in trained participants, aging seems to impact velocity-dependent strength and power more compared with basic strength, as the total losses in DYN240 (CON, -15.93%±2.64%; INT, -11.39%±1.95%) and S20 (CON, -14.39%±2.10%; INT, -13.16%±1.72%) did not differ significantly between the groups.

CONCLUSIONS

A 1-year strength-training intervention results in an improved muscle performance in older adults 7 years after their enrollment in the intervention. However, an extensive exercise program cannot attenuate the age-related decline once the intervention stops.

P2X7R/cryopyrin inflammasome axis inhibition reduces neuroinflammation after SAH

Neuroinflammation contributes to the pathogenesis of early brain injury (EBI) after subarachnoid hemorrhage (SAH). Cytotoxic events following SAH, such as extracellular accumulation of adenosine triphosphate (ATP), may activate the P2X purinoceptor 7 (P2X7R)/cryopyrin inflammasome axis, thus inducing the proinflammatory cytokine IL-1β/IL-18 secretion. We therefore hypothesized that inhibition of P2X7R/cryopyrin inflammasome axis would ameliorate neuroinflammation after SAH. In the present study, SAH was induced by the endovascular perforation in rats. Small interfering RNAs (siRNAs) of P2X7R or cryopyrin were administered intracerebroventricularly 24h before SAH. Brilliant blue G (BBG), a non-competitive antagonist of P2X7R, was administered intraperitoneally 30min following SAH. Post-assessments including SAH severity score, neurobehavioral test, brain water content, Western blot and immunofluorescence, were performed. Administration of P2X7R and cryopyrin siRNA as well as pharmacologic blockade of P2X7R by BBG ameliorated neurological deficits and brain edema at 24h following SAH. Inhibition of P2X7R/cryopyrin inflammasome axis suppressed caspase-1 activation, which subsequently decreased maturation of IL-1β/IL-18. To investigate the link between P2X7R and cryopyrin inflammasome in vivo, Benzoylbenzoyl-ATP (BzATP), a P2X7R agonist, was given to lipopolysaccharide (LPS) primed naive rats with scramble or cryopyrin siRNAs. In LPS-primed naive rats, BzATP induced caspase-1 activation and mature IL-1β release were neutralized by cryopyrin siRNA. Thus, the P2X7R/cryopyrin inflammasome axis may contribute to neuroinflammation via activation of caspase-1 and thereafter mature IL-1β/IL-18 production following SAH. Therapeutic interventions targeting P2X7R/cryopyrin pathway may be a novel approach to ameliorate EBI following SAH.

Exercise facilitates the action of dietary DHA on functional recovery after brain trauma

The abilities of docosahexaenoic acid (DHA) and exercise to counteract cognitive decay after traumatic brain injury (TBI) is getting increasing recognition; however, the possibility that these actions can be complementary remains just as an intriguing possibility. Here we have examined the likelihood that the combination of diet and exercise has the added potential to facilitate functional recovery following TBI. Rats received mild fluid percussion injury (mFPI) or sham injury and then were maintained on a diet high in DHA (1.2% DHA) with or without voluntary exercise for 12days. We found that FPI reduced DHA content in the brain, which was accompanied by increased levels of lipid peroxidation assessed using 4-hydroxy-2-hexenal (4-HHE). FPI reduced the enzymes acyl-CoA oxidase 1 (Acox1) and 17β-hydroxysteroid dehydrogenase type 4 (17β-HSD4), and the calcium-independent phospholipases A2 (iPLA2), which are involved in metabolism of membrane phospholipids. FPI reduced levels of syntaxin-3 (STX-3), involved in the action of membrane DHA on synaptic membrane expansion, and also reduced brain-derived neurotrophic factor (BDNF) signaling through its tyrosine kinase B (TrkB) receptor. These effects of FPI were optimally counteracted by the combination of DHA and exercise. Our results support the possibility that the complementary action of exercise is exerted on restoring membrane homeostasis after TBI, which is necessary for supporting synaptic plasticity and cognition. It is our contention that strategies that take advantage of the combined applications of diet and exercise may have additional effects to the injured brain.

Honokiol: a non-adipogenic PPARγ agonist from nature

Background

Peroxisome proliferator-activated receptor gamma (PPARγ) agonists are clinically used to counteract hyperglycemia. However, so far experienced unwanted side effects, such as weight gain, promote the search for new PPARγ activators.

Methods

We used a combination of in silico, in vitro, cell-based and in vivo models to identify and validate natural products as promising leads for partial novel PPARγ agonists.

Results

The natural product honokiol from the traditional Chinese herbal drug Magnolia bark was in silico predicted to bind into the PPARγ ligand binding pocket as dimer. Honokiol indeed directly bound to purified PPARγ ligand-binding domain (LBD) and acted as partial agonist in a PPARγ-mediated luciferase reporter assay. Honokiol was then directly compared to the clinically used full agonist pioglitazone with regard to stimulation of glucose uptake in adipocytes as well as adipogenic differentiation in 3T3-L1 pre-adipocytes and mouse embryonic fibroblasts. While honokiol stimulated basal glucose uptake to a similar extent as pioglitazone, it did not induce adipogenesis in contrast to pioglitazone. In diabetic KKAy mice oral application of honokiol prevented hyperglycemia and suppressed weight gain.

Conclusion

We identified honokiol as a partial non-adipogenic PPARγ agonist in vitro which prevented hyperglycemia and weight gain in vivo.

General significance

This observed activity profile suggests honokiol as promising new pharmaceutical lead or dietary supplement to combat metabolic disease, and provides a molecular explanation for the use of Magnolia in traditional medicine.

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Honokiol is identified and characterized as novel partial PPARγ agonist from nature.

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In cell models honokiol increases glucose uptake but is not adipogenic.

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In KKAy diabetic mice it decreases blood glucose and suppresses weight gain.

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PPARγ agonism of honokiol may explain the use of Magnolia bark in traditional medicine.

A neuregulin 1 transmembrane domain mutation causes imbalanced glutamatergic and dopaminergic receptor expression in mice

The neuregulin 1 gene has repeatedly been identified as a susceptibility gene for schizophrenia, thus mice with genetic mutations in this gene offer a valuable tool for studying the role of neuregulin 1 in schizophrenia-related neurotransmission. In this study, slide-based receptor autoradiography was used to quantify glutamatergic N-methyl-d-aspartate (NMDA), dopaminergic D2, cannabinoid CB1 and acetylcholine M1/4 receptor levels in the brains of male heterozygous transmembrane domain neuregulin 1 mutant (Nrg1(+/-)) mice at two ages. Mutant mice expressed small but significant increases in NMDA receptor levels in the cingulate cortex (7%, p=0.044), sensory cortex (8%, p=0.024), and motor cortex (8%, p=0.047), effects that were independent of age. In the nucleus accumbens and thalamus Nrg1(+/-) mice exhibited age-dependent alterations in NMDA receptors. Nrg1(+/-) mice showed a statistically significant increase in NMDA receptor levels in the nucleus accumbens of 14-week-old Nrg1(+/-) mice compared to control littermates of the same age (12%, p=0.026), an effect that was not seen in 20-week-old mice. In contrast, NMDA receptor levels in the thalamus, while initially unchanged in 14-week-old mice, were then decreased in the 20-week-old Nrg1(+/-) mice compared to control littermates of the same age (14%, p=0.011). Nrg1(+/-) mutant mice expressed a significant reduction in D2 receptor levels (13-16%) in the striatum compared to controls, independent of age. While there was a borderline significant increase (6%, p=0.058) in cannabinoid CB1 receptor levels in the substantia nigra of Nrg1(+/-) mice compared to controls, CB1 as well as acetylcholine M1/4 receptors showed no change in Nrg1(+/-) mice in any other brain region examined. These data indicate that a Nrg1 transmembrane mutation produces selective imbalances in glutamatergic and dopaminergic neurotransmission, which are two key systems believed to contribute to schizophrenia pathogenesis. While the effects on these systems are subtle, they may underlie the susceptibility of these mutants to further impacts.

Phasic synaptic incorporation of GluR2-lacking AMPA receptors at gonadotropin-releasing hormone neurons is involved in the generation of the luteinizing hormone surge in female rats

Reproductive success depends on a robust and appropriately timed preovulatory luteinizing hormone (LH) surge, which is induced by the activation of gonadotropin-releasing hormone (GnRH) neurons in response to positive feedback from increasing estrogen levels. Here we document an increase in postsynaptic GluR2-lacking Ca2+ -permeable AMPA-type glutamate receptors (CP-AMPARs) at synapses on GnRH neurons on the day of proestrus in rats, coincident with the increase in estrogen levels. Functional blockade of CP-AMPARs depressed the synaptic responses only on the day of proestrus and concomitantly attenuated the LH surge. Thus, the phasic synaptic incorporation of postsynaptic CP-AMPARs on GnRH neurons is involved in the generation of the LH surge.

Treating chronic arsenic toxicity with high selenium lentil diets

Arsenic (As) toxicity causes serious health problems in humans, especially in the Indo-Gangetic plains and mountainous areas of China. Selenium (Se), an essential micronutrient is a potential mitigator of As toxicity due to its antioxidant and antagonistic properties. Selenium is seriously deficient in soils world-wide but is present at high, yet non-toxic levels in the great plains of North America. We evaluate the potential of dietary Se in counteracting chronic As toxicity in rats through serum biochemistry, blood glutathione levels, immunotoxicity (antibody response), liver peroxidative stress, thyroid response and As levels in tissues and excreta. To achieve this, we compare diets based on high-Se Saskatchewan (SK) lentils versus low-Se lentils from United States. Rats drank control (0ppm As) or As (40ppm As) water while consuming SK lentils (0.3ppm Se) or northwestern USA lentils (<0.01ppm Se) diets for 14weeks. Rats on high Se diets had higher glutathione levels regardless of As exposure, recovered antibody responses in As-exposed group, higher fecal and urinary As excretion and lower renal As residues. Selenium deficiency caused greater hepatic peroxidative damage in the As exposed animals. Thyroid hormones, triiodothyronine (T3) and thyroxine (T4), were not different. After 14weeks of As exposure, health indicators in rats improved in response to the high Se lentil diets. Our results indicate that high Se lentils have a potential to mitigate As toxicity in laboratory mammals, which we hope will translate into benefits for As exposed humans.