A Single Dose of Ginkgo biloba Extract Induces Gene Expression of Hypothalamic Anorexigenic Effectors in Male Rats

Previous studies have shown that Ginkgo biloba extract (GbE) reduces food intake and body mass gain and regulates proteins related to lipid metabolism in obese rats. In ovariectomized rats, GbE restored the hippocampal and hypothalamic serotonergic system activity, favoring the spontaneous feeding decrement. Considering the promising hypophagic effect of GbE, this study aimed to investigate the effect of a single acute dose on hypothalamic pathways that regulate feeding behavior in male rats. Four-month-old Wistar male rats received either a single acute oral GbE dose (500 mg/kg) or vehicle. Food intake and body mass were measured after 1, 4, 12, and 24 h. Rats were euthanized, and hypothalami were removed for mRNA quantification of anorexigenic (POMC/CART) and orexigenic (AgRP/NPY) neuropeptides, leptin/serotonin receptors (5HT1A, 5HT1B, 5HT2C), and serotonin transporters. We also investigated POMC, 5-HT1B, and 5-HT2C protein levels. A single acute GbE dose induced the hypothalamic POMC, CART, and 5-HT2C gene expression but failed to modify orexigenic effectors. No alterations in food intake, body mass, and hypothalamic protein levels were observed. In summary, the present findings demonstrate the rapid stimulation of pivotal hypothalamic anorexigenic pathways in response to a single GbE administration, reinforcing the GbE hypophagic activity. However, more studies are necessary to evaluate its potential as an appetite modulator.

Activation of GPER limits adverse changes to Ca2+ signalling and arrhythmogenic activity in cardiomyocytes of ovariectomised guinea pigs

Background Post-menopausal women have an enhanced risk of developing cardiovascular disease and disturbances of cardiac rhythm, generally attributed to declining oestrogen levels during menopause. In an animal model that mimics menopause, the long-term withdrawal of oestrogen dysregulated Ca2+ signalling and increased the formation of a pro-arrhythmic substrate. Selective targeting of the membrane bound G-protein coupled oestrogen receptor 1 (GPER) eliminated such arrhythmogenic activity associated with the loss of oestrogen. Purpose We aim to assess the “cardioprotective” role of GPER in response to oestrogen withdrawal. Methods Ovariectomy (OVx) or sham surgeries were conducted on female guinea pigs. Left ventricular cardiomyocytes were isolated 150-days post-operatively for experimental use. GPER expression was quantified by western blot. Myocytes were incubated in solutions containing GPER agonist G-1 for >2h before recording some electrophysiological and Ca2+ regulatory parameters. Results GPER expression was 32% higher in OVx. OVx cardiomyocytes had prolonged action potential duration (APD) compared with sham and in the presence of G-1, APD90 shortened by 12% and 22% in sham and OVx, respectively. G-1 reduced early after depolarisation (EAD) formation by >99% in OVx. OVx cells had larger sarcoplasmic reticulum (SR) Ca2+ content (by 13%), compared with sham. While G-1 had little effect on SR content, it reduced Ca2+ transient amplitude (by 40%), SR fractional release (by 11%) and sarcomere shortening (by 29%) in OVx cells. The frequency of occurrence of spontaneous Ca2+ waves evoked by periods of rapid stimulation reduced by 40% and wave-free survival time prolonged in OVx cells incubated with G-1. Conclusions In the hearts of an animal species whose electrophysiology and intracellular Ca2+ regulation is akin to humans, we show that following oestrogen deficiency, GPER expression increased and its activation induces negative inotropic responses in cardiomyocytes. It limits the adverse changes to Ca2+ signalling and induces anti-arrhythmogenic behaviours in OVx. FUNDunding Acknowledgement Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): British Heart Foundation

The effect of oestrogen withdrawal on cardiac Ca2+ regulation and the influence of GPER1

Background Post-menopausal women have an enhanced risk of developing heart failure, attributed to declining oestrogen levels during menopause. However, the signalling mechanisms remain undetermined. Purpose We aim to determine the role of G-protein coupled oestrogenic receptor 1 (GPER1) in intracellular Ca2+ regulation and the consequences of hormonal changes that may exacerbate the pathophysiology of heart failure. Methods Ovariectomy (OVx) (mimics menopausal hormone changes) or sham surgeries were conducted on female guinea pigs. Left ventricular cardiomyocytes were isolated 150-days post-operatively for experimental use. Cellular t-tubule network and structural integrity was measured using fluorescent di-8-ANEPPs staining and scanning ion conductance microscopy. GPER1 expression and localisation was measured by Western blot and immunostaining. The role of GPER1 activation was measured using selective agonist G-1 in electrophysiological and Ca2+-sensitive dye fluorescence experiments. Results Following oestrogen withdrawal, the t-tubule network density decreased by 13% and z-groove index reduced by 15%. GPER1 predominantly localised to the peri-nuclear endoplasmic reticulum and its expression increased by 32% in OVx. Action potential duration (APD) prolonged in OVx and following GPER1 activation, APD90 shortened by 11% and 25% in sham and OVx respectively. OVx cells had larger peak inward Ca2+ current (ICaL) (by 22%) and sarcoplasmic reticulum (SR) Ca2+ content (by 13%), compared with sham. While GPER1 activation had little effect on peak ICaL or SR content, it reduced Ca2+ transient amplitude (by 20%), SR fractional release (by 11%) in OVx cells. The frequency of occurrence of spontaneous Ca2+ waves evoked by periods of rapid stimulation reduced by 40% and wave-free survival time prolonged in OVx cells following GPER1 activation. Conclusions In the hearts of an animal species whose electrophysiology and intracellular Ca2+ regulation is akin to humans, we show that following oestrogen deficiency, the t-tubule network is down-regulated and becomes disorganised, GPER1 expression is increased and its activation induces negative inotropic responses in cardiomyocytes. This may limit the adverse changes to Ca2+ signalling reported in OVx that could be pro-arrhythmic and exacerbate the progression to heart failure. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): British Heart Foundation

Rapid stimulation of cellular Pi uptake by the inositol pyrophosphate InsP8 induced by its photothermal release from lipid nanocarriers using a near infra-red light-emitting diode

Thermosensitive liposomes were used to deliver inositol pyrophosphates (highly polar, cell-impermeant signaling molecules) into cultured cells; cargo release was induced within 5 min irradiation by a high power, near infra-red, light emitting diode.

P99 Rapid ventricular stimulation induces augmented conduction delay in Brugada syndrome patients

Background The exact mechanism for Brugada Syndrome (BrS) is still not clear. There are two main physiologic hypotheses that have been suggested: the repolarization and the depolarization disorder models. Right ventricular (RV) activation delay was verified by echocardiography, conduction time in an explanted heart or in computer simulation. Verification of prolonged longitudinal activation time in human RV of only 5 patients of type-1 BrS and 5 controls was reported in 2008. Methods Bidirectional longitudinal activation times were assessed between RV outflow tract (RVot) and RV-apex (RVa) by stimulating and mapping RV endocardium in BrS patients. Conduction velocity was calculated considering ventricle size and distance between catheters. Results The studies were performed in controls (n = 18) and BrS patients (n = 6). There was no statistical difference in RP interval and QRS duration (PR 146 ± 21.7 vs 167 ± 45.2 ms, p = 0.325; QRS 102 ± 28.2 vs 122 ± 32.2 ms, p = 0.163). There was no difference of longitudinal activation time on stimulation at 500 ms (RVa to RVot: 63 ± 14.3 versus 80 ± 34.2 ms, p = 0.290; RVot to RVa: 50 ± 12.2 versus 76 ± 35.1 ms, p = 0.122). The BrS patients had longer longitudinal activation time on stimulation at 400 ms (RVa to RVot: 61 ± 15.2 versus 87 ± 28.7 ms, p = 0.009; RVot to RVa: 52 ± 11.1 versus 76 ± 35.3 ms, p = 0.029). The difference was not significant when isoproterenol was infused. Conclusions BrS patients display bidirectional longitudinal conduction delay when rapid stimulation. These findings support that BrS might be partly attributable to depolarization abnormality.

Conclusion

The Conclusion links the emergence of boredom to the modernist construction of the individual as the producer of meaning in his or her own life. It explains how imperial boredom differed from domestic forms of boredom, and not only reflected changes in the empire, but was also the product of unmet expectations about personal happiness, professional fulfillment, and financial security. It asserts that expressions of boredom were veiled confessions of discontent with the empire. And, it locates imperial boredom in the ongoing debate about whether the British Empire—and by extension empire more broadly—should be regarded as a force for good in the world, suggesting, as Hannah Arendt did, that the imperial experience was fundamentally banal. It calls into question key assumptions about the British Empire, not least that it was glamorous, glorious, and filled with adventure, excitement, and opportunity. It also hints at the broader applicability of the notion of imperial boredom to empire building in the twenty-first century, as well as to the challenges of finding meaning and engagement in a world increasingly orientated around rapid stimulation.

Insights into the roles of CMK-1 and OGT-1 in interstimulus interval-dependent habituation in Caenorhabditis elegans

Habituation is a ubiquitous form of non-associative learning observed as a decrement in responding to repeated stimulation that cannot be explained by sensory adaptation or motor fatigue. One of the defining characteristics of habituation is its sensitivity to the rate at which training stimuli are presented—animals habituate faster in response to more rapid stimulation. The molecular mechanisms underlying this interstimulus interval (ISI)-dependent characteristic of habituation remain unknown. In this article, we use behavioural neurogenetic and bioinformatic analyses in the nematode Caenorhabiditis elegans to identify the first molecules that modulate habituation in an ISI-dependent manner. We show that the Caenorhabditis elegans orthologues of Ca 2+ /calmodulin-dependent kinases CaMK1/4, CMK-1 and O-linked N-acetylglucosamine (O-GlcNAc) transferase, OGT-1, both function in primary sensory neurons to inhibit habituation at short ISIs and promote it at long ISIs. In addition, both cmk-1 and ogt-1 mutants display a rare mechanosensory hyper-responsive phenotype (i.e. larger mechanosensory responses than wild-type). Overall, our work identifies two conserved genes that function in sensory neurons to modulate habituation in an ISI-dependent manner, providing the first insights into the molecular mechanisms underlying the universally observed phenomenon that habituation has different properties when stimuli are delivered at different rates.