TSH Pulses Finely Tune Thyroid Hormone Release and TSH Receptor Transduction

Detection of circulating TSH is a first-line test of thyroid dysfunction, a major health problem (affecting about 5% of the population) that, if untreated, can lead to a significant deterioration of quality of life and adverse effects on multiple organ systems. Human TSH levels display both pulsatile and (nonpulsatile) basal TSH secretion patterns; however, the importance of these in regulating thyroid function and their decoding by the thyroid is unknown. Here, we developed a novel ultra-sensitive ELISA that allows precise detection of TSH secretion patterns with minute resolution in mouse models of health and disease. We characterized the patterns of ultradian TSH pulses in healthy, freely behaving mice over the day-night cycle. Challenge of the thyroid axis with primary hypothyroidism because of iodine deficiency, a major cause of thyroid dysfunction worldwide, results in alterations of TSH pulsatility. Induction in mouse models of sequential TSH pulses that mimic ultradian TSH profiles in periods of minutes were more efficient than sustained rises in basal TSH levels at increasing both thyroid follicle cAMP levels, as monitored with a genetically encoded cAMP sensor, and circulating thyroid hormone. Hence, this mouse TSH assay provides a powerful tool to decipher how ultradian TSH pulses encode thyroid outcomes and to uncover hidden parameters in the TSH-thyroid hormone set-point in health and disease.

Median eminence blood flow influences food intake by regulating ghrelin access to the metabolic brain

Central integration of peripheral appetite-regulating signals ensures maintenance of energy homeostasis. Thus, plasticity of circulating molecule access to neuronal circuits involved in feeding behavior plays a key role in the adaptive response to metabolic changes. However, the mechanisms involved remain poorly understood despite their relevance for therapeutic development. Here, we investigated the role of median eminence mural cells, including smooth muscle cells and pericytes, in modulating gut hormone effects on orexigenic/anorexigenic circuits. We found that conditional activation of median eminence vascular cells impinged on local blood flow velocity and altered ghrelin-stimulated food intake by delaying ghrelin access to target neurons. Thus, activation of median eminence vascular cells modulates food intake in response to peripheral ghrelin by reducing local blood flow velocity and access to the metabolic brain.

Atrial fibrillation diagnosis by a systematic 14-day continuous ECG-Holter in patients with high cardiovascular risk and clinical palpitation: the prospective AFTER study

Background

Atrial Fibrillation (AF) is asymptomatic in 20–30% of cases. New technologic tools for continuous ECG monitoring have been developed to detect and potentially treat AF in specific population with high cardiovascular risk.

Purpose

We aimed to evaluate the prevalence and the management of AF diagnosed in patients with no previous documented AF but with a high cardiovascular risk and clinical palpitation undergoing systematic 14-day continuous ECG-Holter monitoring and associated characteristics.

Methods

Patients were prospectively enrolled from December 2019 to December 2021 in this multicentered study, sponsored by the French National College of Cardiology. Patients needed to meet the following criteria: CHA2DS2VASc score ≥3 in women >2 in men associated with clinical palpitation without previous documented arrhythmia, particularly AF. Exclusion criteria were: previous documented AF, participation to another study that could interfere with the current study, pregnancy, previous skin intolerance to ECG-Holter electrodes. Included patients underwent a 14-day monitoring Holter-ECG to detect cardiac arrhythmia, particularly AF. Patients' characteristics, type of arrythmias and management of detected AF were described.

Results

Among the 336 included patients, 39% were men, median age was 73 [64.5–78] years, 71.5% had hypertension and 46.5% had a previous history of stroke. AF was detected in 14% of patients, among which 23.4% in the first 24 hours monitoring. In univariate analyses, older age (p=0.045) was significantly associated with AF, and a trend was observed regarding male gender (p=0.067) and less antiplatelet therapy (p=0.058). Patients with diagnosed AF had a prescription of anticoagulation therapy in 90% of cases consisting in apixaban and rivaroxaban for 72% and 28% respectively. Antiarrhythmic drugs were administered in 90% of AF patients and 13% underwent AF ablation.

Conclusions

The systematic AF screening of selected patients based on CHA2DS2VASc score ≥3 in women >2 in men associated with palpitations allows to diagnose AF in 14% of the population with a 14-day continuous ECG-Holter. This strategy seems efficient as it induced the prescription of anticoagulation and antiarrhythmic therapy in 90% of individuals.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): NATIONAL COLLEGE OF FRENCH CARDIOLOGISTS

Atrial fibrillation detection with long-term continuous Holter ECG recording in patients with high cardiovascular risk and clinical palpitations: the prospective after study

AIM

New technologic tools for continuous ECG monitoring have been developed to detect and treat atrial fibrillation (AF) in specific populations with high cardiovascular risk. We evaluated the prevalence and the management of AF diagnosed in patients with high cardiovascular risk and non-documented clinical palpitation undergoing systematic 14-day continuous ECG-Holter monitoring.

METHODS

Patients were prospectively enrolled from December 2019 to December 2021 in this multicentre study, sponsored by the French National College of Cardiology. Patients met the following criteria: CHA₂DS₂VASc score ≥ 2 in males and ≥ 3 in females and clinical palpitations without previously documented arrhythmia. Enrolled patients underwent a continuous 14-day Holter-ECG monitoring for arrhythmia detection.

RESULTS

Among the 336 included patients, 39% were male, 75% were greater than 65 years of age and 46.5% had suffered a prior stroke. AF was detected in 14% of patients, among which 23.4% were detected in the first 24 h of monitoring. Finally, age ≥ 65 years (p = 0.037) was significantly associated with AF, as well as male gender (p = 0.023) and a lower rate of antiplatelet therapy (p = 0.018). Patients with diagnosed AF had a prescription of anticoagulation therapy in 90%. Antiarrhythmic drugs were administered in 90% of AF patients and 13% underwent AF ablation.

CONCLUSIONS

The systematic AF screening of patients with palpitations and high cardiovascular risk resulted in a diagnostic yield of AF in 14% of the population with a 14-day continuous ECG-Holter monitor. This strategy resulted in the prescription of anticoagulation and antiarrhythmic therapy in 90% of the AF detected population.

Metabolic Stress Impairs Pericyte Response to Optogenetic Stimulation in Pancreatic Islets

Pancreatic islets are highly vascularized micro-organs ensuring whole body glucose homeostasis. Islet vascular cells play an integral part in sustaining adequate insulin release by beta cells. In particular, recent studies have demonstrated that islet pericytes regulate local blood flow velocity and are required for maintenance of beta cell maturity and function. In addition, increased metabolic demand accompanying obesity alters islet pericyte morphology. Here, we sought to explore the effects of metabolic stress on islet pericyte functional response to stimulation in a mouse model of type 2 diabetes, directly in the pancreas in vivo . We found that high fat diet induced islet pericyte hypertrophy without alterations in basal local blood flow. However, optogenetic stimulation of pericyte activity revealed impaired islet vascular responses, despite increased expression of genes encoding proteins directly or indirectly involved in cell contraction. These findings suggest that metabolic stress impinges upon islet pericyte function, which may contribute to beta cell failure during T2D.

Older adults’ daily activities during lockdown in France, spring 2020: a cross sectional survey

Background

The 2020 COVID-19 pandemic prompted many countries to go into lockdown for varying periods. The French population was limited to 1km around their house, with the need to have a travel declaration when going out. According to the World Federation of Occupational Therapists (2020), “populations around the world have been required to adjust and make compensations to usual routines in order to participate in ongoing or newly acquired activities that are necessary for daily life.” AIMS. In this context, we aimed to describe changes in daily activities, social contacts, and mental health and wellbeing of older adults (i.e. aged 60 or more) living in France.

Methods

We performed an online cross-sectional survey, based on the Canadian Occupational Performance Measure (COPM) for restriction of and satisfaction with daily activities, and the Cantril's ladder for mental health and wellbeing. RESULTS. Of the 512 respondents, 9% did not feel restricted at all in their daily activities, and 13% reported no change. About one third (31%) reported to have less diverse activities than usual but to be satisfied with it. Regarding social contacts, 72% of the respondents reported to have a lot more contacts than usual with their relatives. Concerning the type of activities, 2477 restricted activities could be identified, but also 2190 that were done more often during the lockdown. Most restricted ones concerned leisure (83%), especially active leisure, the most mentioned being walking. The more engaged activities also concerned leisure (73%), especially quiet recreation, the most mentioned reading. The median value of Cantril's ladder was 5 [4;7].

Conclusions

Lockdown measures led to some activity restrictions for older adults, but also offered opportunities for new engagements. Remarkably was the increase in social contacts with relatives, probably related to the use of new technologies.

Framework Implementation of the INSPIRE ICOPE-CARE program in collaboration with the World Health Organization (WHO) in the Occitania region

Introduction: Limiting the number of dependent older people in coming years will be a major economic and human challenge. In response, the World Health Organization (WHO) has developed the «Integrated Care for Older People (ICOPE)» approach. The aim of the ICOPE program is to enable as many people as possible to age in good health. To reach this objective, the WHO proposes to follow the trajectory of an individual’s intrinsic capacity, which is the composite of all their physical and mental capacities and comprised of multiple domains including mobility, cognition, vitality / nutrition, psychological state, vision, hearing. Objective: The main objective of the INSPIRE ICOPE-CARE program is to implement, in clinical practice at a large scale, the WHO ICOPE program in the Occitania region, in France, to promote healthy aging and maintain the autonomy of seniors using digital medicine. Method: The target population is independent seniors aged 60 years and over. To follow this population, the 6 domains of intrinsic capacity are systematically monitored with pre-established tools proposed by WHO especially STEP 1 which has been adapted in digital form to make remote and large-scale monitoring possible. Two tools were developed: the ICOPE MONITOR, an application, and the BOTFRAIL, a conversational robot. Both are connected to the Gerontopole frailty database. STEP 1 is performed every 4-6 months by professionals or seniors themselves. If a deterioration in one or more domains of intrinsic capacity is identified, an alert is generated by an algorithm which allows health professionals to quickly intervene. The operational implementation of the INSPIRE ICOPE-CARE program in Occitania is done by the network of Territorial Teams of Aging and Prevention of Dependency (ETVPD) which have more than 2,200 members composed of professionals in the medical, medico-social and social sectors. Targeted actions have started to deploy the use of STEP 1 by healthcare professionals (physicians, nurses, pharmacists,…) or different institutions like French National old age insurance fund (CNAV), complementary pension funds (CEDIP), Departmental Council of Haute Garonne, etc. Perspective: The INSPIRE ICOPE-CARE program draws significantly on numeric tools, e-health and digital medicine to facilitate communication and coordination between professionals and seniors. It seeks to screen and monitor 200,000 older people in Occitania region within 3 to 5 years and promote preventive actions. The French Presidential Plan Grand Age aims to largely implement the WHO ICOPE program in France following the experience of the INSPIRE ICOPE-CARE program in Occitania.

Size and affinity kinetics of nanobodies influence targeting and penetration of solid tumours

A compound's intratumoural distribution is an important determinant for the effectiveness of molecular therapy or imaging. Antibodies (Abs), though often used in the design of targeted compounds, struggle to achieve a homogenous distribution due to their large size and bivalent binding mechanism. In contrast, smaller compounds like nanobodies (Nbs) are expected to distribute more homogenously, though this has yet to be demonstrated in vivo at the microscopic level. We propose an intravital approach to evaluate the intratumoural distribution of different fluorescently labeled monomeric and dimeric Nb tracers and compare this with a monoclonal antibody (mAb). Monomeric and dimeric formats of the anti-HER2 (2Rb17c and 2Rb17c-2Rb17c) and control (R3B23 and R3B23-R3B23) Nb, as well as the dimeric monovalent Nb 2Rb17c-R3B23 were generated and fluorescently labeled with a Cy5 fluorophore. The mAb trastuzumab-Cy5 was also prepared. Whole-body biodistribution of all constructs was investigated in mice bearing subcutaneous xenografts (HER2+ SKOV3) using in vivo epi-fluorescence imaging. Next, for intravital experiments, GFP-expressing SKOV3 cells were grown under dorsal window chambers on athymic nude mice (n = 3/group), and imaged under a fluorescence stereo microscope immediately after intravenous injection of the tracers. Consecutive fluorescence images within the tumour were acquired over the initial 20 min after injection and later, single images were taken at 1, 3 and 24 h post-injection. Additionally, two-photon microscopy was used to investigate the colocalization of GFP (tumour cells) and Cy5 fluorescence (tracers) at higher resolution. Whole-body images showed rapid renal clearance of all Nbs, and fast tumour targeting for the specific Nbs. Specific tumour uptake of the mAb could only be clearly distinguished from background after several hours. Intravital imaging revealed that monomeric Nb tracers accumulated rapidly and distributed homogenously in the tumour mere minutes after intravenous injection. The dimeric compounds initially achieved lower fluorescence intensities than the monomeric. Furthermore, whereas the HER2-specific dimeric bivalent compound remained closely associated to the blood vessels over 24 h, the HER2-specific dimeric monovalent tracer achieved a more homogenous tumour distribution from 1 h post-injection onwards. Non-specific tracers were not retained in the tumour. Trastuzumab had the most heterogenous intratumoural distribution of all evaluated compounds, while -due to the long blood retention- achieving the highest overall tumour uptake at 24 h post-injection. In conclusion, monomeric Nbs very quickly and homogenously distribute through tumour tissue, at a rate significantly greater than dimeric Nbs and mAbs. This underlines the potential of monomeric Nb tracers and therapeutics in molecular imaging and targeted therapies.

Topographic Reorganization of Cerebrovascular Mural Cells under Seizure Conditions

Reorganization of the neurovascular unit has been suggested in the epileptic brain, although the dynamics and functional significance remain unclear. Here, we tracked the in vivo dynamics of perivascular mural cells as a function of electroencephalogram (EEG) activity following status epilepticus. We segmented the cortical vascular bed to provide a size- and type-specific analysis of mural cell plasticity topologically. We find that mural cells are added and removed from veins, arterioles, and capillaries after seizure induction. Loss of mural cells is proportional to seizure severity and vascular pathology (e.g., rigidity, perfusion, and permeability). Treatment with platelet-derived growth factor subunits BB (PDGF-BB) reduced mural cell loss, vascular pathology, and epileptiform EEG activity. We propose that perivascular mural cells play a pivotal role in seizures and are potential targets for reducing pathophysiology.

Imaging and Manipulating Pituitary Function in the Awake Mouse

Extensive efforts have been made to explore how the activities of multiple brain cells combine to alter physiology through imaging and cell-specific manipulation in different animal models. However, the temporal regulation of peripheral organs by the neuroendocrine factors released by the brain is poorly understood. We have established a suite of adaptable methodologies to interrogate in vivo the relationship of hypothalamic regulation with the secretory output of the pituitary gland, which has complex functional networks of multiple cell types intermingled with the vasculature. These allow imaging and optogenetic manipulation of cell activities in the pituitary gland in awake mouse models, in which both neuronal regulatory activity and hormonal output are preserved. These methodologies are now readily applicable for longitudinal studies of short-lived events (e.g., calcium signals controlling hormone exocytosis) and slowly evolving processes such as tissue remodeling in health and disease over a period of days to weeks.

How to Manage Frail Older Adults in the Community? Proposal of a Health Promotion Program Experienced in a City of 16,638 Inhabitants in France

BACKGROUND

Health promotion programs could prevent and delay frailty and functional decline. However, in practice, the planning and establishment of such a program is a challenge for health care providers. We report an experimental model of screening and management for frail elderly conducted in Cugnaux, city of 16,638 inhabitants in France, by the Toulouse Gerontopole and the social care service of the Cugnaux City Hall.

METHODS

A frailty screening self-administered questionnaire (FiND questionnaire) was sent to community-dwelling residents of 70 years old and over of Cugnaux. The completed questionnaires were analyzed and the subjects were classed into three groups: robust, frail, mobility disability, based on their score. Frail subjects and those with mobility disability invited to undergo a frailty assessment in the premises of the town hall realized by a nurse in order to identify the causes of their frailty and propose them a personalized intervention plan (PIP).

RESULTS

The FiND questionnaire was sent to the residents of Cugnaux of 70 years old and over (n=2,003). After two mailings, 860 (42.9%) completed questionnaires were received. Mean age of the responders was 79.0 ± 6.2 years and 59.6% women (n= 511). According to the questionnaires analysis, 393 (45.7%) were robust, 212 (24.6%) frail, 240 (27.9%) had a mobility disability and 15 (1.7%) could not be classified due to missing data. 589 (68.5%) subjects accepted to be contacted by the Gerontopole nurse. The assessment by the nurse was proposed to frail subjects and those with mobility disability (n=313). Until 31 December 2016, 136 patients have been evaluated. The mean age was 80.1±5.4 and most patients were women (69.9%). The mean ADL score was 5.8±0.5 and the IADL showed a mean score of 6.9±1.7. According to Fried definition of frailty, 76 patients (55.9%) were pre-frail, and 35 (25.7%) frail. Concerning the frailty domains identified, 75 patients (55.1%) showed the alteration of physical performance, 70 (51.5%) thymic disorders and 46 (33.8%) sensory disorders. Preventive interventions proposed in the PIP were mostly physical interventions (86.8%, n=118) followed by cognitive (61.8%, n=84) and nutritional (39.7%, n=54) interventions.

DISCUSSION

This project shows the feasibility to implement a care model in the community. It permitted a large identification of frail elderly people in the city population, insuring their assessment and clinical follow up to maintain their capacities and referring them to social services.

SAT-547 Pituitary Thyrotrophs: A Generator of Repetitive Calcium Waves in Freely-Moving Animal Models

Hypothyroidism refers to the pathological state of thyroid hormone (TH) deficiency. It affects between 0.3% and 3.7% of the general population in the USA and between 0.2% and 5.3% in Europe. Hypothyroid patients suffer from extreme fatigue, altered heart rate, depression, weight gain, and difficulty in conceiving. Also, maternal hypothyroidism, which affects 0.5% of all pregnant women, is the leading preventable cause of mental retardation in offspring. Importantly, diagnosis of hypothyroidism is based on a single thyroid-stimulating-hormone (TSH) measurement. TSH secretion by pituitary thyrotrophs is under the positive control of hypothalamic thyrotropin-releasing-hormone (TRH) and negative feedback exerted by THs. Despite the undeniable implication of thyrotrophs in the hypothalamus-pituitary-thyroid (HPT) axis regulation, little is known about the mechanisms underlying adaptive TSH secretion. Being the smallest endocrine cell population of the pituitary (2-4%), thyrotrophs display high plasticity in cell shape, number and network topology throughout development and in disease. Moreover, enzymatically-dispersed thyrotrophs lose their ability to express and secrete TSH in both basal and TRH-stimulated conditions. Altogether, these findings led us to the hypothesis that thyrotrophs form a very finely regulated and highly plastic functionally-organized cell population capable of adapting to physiological (i.e. pregnancy) and pathological (i.e. hypothyroidism) demand. The aim of this study was to investigate how thyrotrophs function in their native environment. Using gradient-index (GRIN) lenses implanted at the pituitary level and a 2g head-mounted miniscope, multicellular calcium activities of the thyrotroph population were monitored in freely-moving TSHβ-crexR26fl-flGCaMP6f mice. Strikingly, thyrotrophs displayed both short-lived calcium spikes of high amplitude, and slowly-evolving calcium waves propagating among the thyrotroph population (n=3). Such calcium waves recurred every 80min during episodes lasting 3min and were interspaced by short-lived activity/silent periods. As TSH displays a 2.722min half-life (n=6), repetitive bouts of calcium-dependent TSH exocytosis would lead to cumulative increase in circulating TSH levels. Hence, the thyrotroph population functions in vivo as a robust generator of repetitive calcium waves which would orchestrate the generation of ultradian TSH fluctuations. Such signaling events could be monitored during longitudinal studies (weeks to months) in which individual animals could be their own controls.

An updated view of hypothalamic-vascular-pituitary unit function and plasticity

The discoveries of novel functional adaptations of the hypothalamus and anterior pituitary gland for physiological regulation have transformed our understanding of their interaction. The activity of a small proportion of hypothalamic neurons can control complex hormonal signalling, which is disconnected from a simple stimulus and the subsequent hormone secretion relationship and is dependent on physiological status. The interrelationship of the terminals of hypothalamic neurons and pituitary cells with the vasculature has an important role in determining the pattern of neurohormone exposure. Cells in the pituitary gland form networks with distinct organizational motifs that are related to the duration and pattern of output, and modifications of these networks occur in different physiological states, can persist after cessation of demand and result in enhanced function. Consequently, the hypothalamus and pituitary can no longer be considered as having a simple stratified relationship: with the vasculature they form a tripartite system, which must function in concert for appropriate hypothalamic regulation of physiological processes, such as reproduction. An improved understanding of the mechanisms underlying these regulatory features has implications for current and future therapies that correct defects in hypothalamic-pituitary axes. In addition, recapitulating proper network organization will be an important challenge for regenerative stem cell treatment.

Complementary actions of dopamine D2 receptor agonist and anti-vegf therapy on tumoral vessel normalization in a transgenic mouse model

Angiogenesis contributes in multiple ways to disease progression in tumors and reduces treatment efficiency. Molecular therapies targeting Vegf signaling combined with chemotherapy or other drugs exhibit promising results to improve efficacy of treatment. Dopamine has been recently proposed to be a novel safe anti-angiogenic drug that stabilizes abnormal blood vessels and increases therapeutic efficacy. Here, we aimed to identify a treatment to normalize tumoral vessels and restore normal blood perfusion in tumor tissue with a Vegf receptor inhibitor and/or a ligand of dopamine G protein-coupled receptor D2 (D2R). Dopamine, via its action on D2R, is an endogenous effector of the pituitary gland, and we took advantage of this system to address this question. We have used a previously described Hmga2/T mouse model developing haemorrhagic prolactin-secreting adenomas. In mutant mice, blood vessels are profoundly altered in tumors, and an aberrant arterial vascularization develops leading to the loss of dopamine supply. D2R agonist treatment blocks tumor growth, induces regression of the aberrant blood supply and normalizes blood vessels. A chronic treatment is able to restore the altered balance between pro- and anti-angiogenic factors. Remarkably, an acute treatment induces an upregulation of the stabilizing factor Angiopoietin 1. An anti-Vegf therapy is also effective to restrain tumor growth and improves vascular remodeling. Importantly, only the combination treatment suppresses intratumoral hemorrhage and restores blood vessel perfusion, suggesting that it might represent an attractive therapy targeting tumor vasculature. Similar strategies targeting other ligands of GPCRs involved in angiogenesis may identify novel therapeutic opportunities for cancer.

Control of ventricular ciliary beating by the melanin concentrating hormone-expressing neurons of the lateral hypothalamus: a functional imaging survey

The cyclic peptide Melanin Concentrating Hormone (MCH) is known to control a large number of brain functions in mammals such as food intake and metabolism, stress response, anxiety, sleep/wake cycle, memory, and reward. Based on neuro-anatomical and electrophysiological studies these functions were attributed to neuronal circuits expressing MCHR1, the single MCH receptor in rodents. In complement to our recently published work (1) we provided here new data regarding the action of MCH on ependymocytes in the mouse brain. First, we establish that MCHR1 mRNA is expressed in the ependymal cells of the third ventricle epithelium. Second, we demonstrated a tonic control of MCH-expressing neurons on ependymal cilia beat frequency using in vitro optogenics. Finally, we performed in vivo measurements of CSF flow using fluorescent micro-beads in wild-type and MCHR1-knockout mice. Collectively, our results demonstrated that MCH-expressing neurons modulate ciliary beating of ependymal cells at the third ventricle and could contribute to maintain cerebro-spinal fluid homeostasis.

Anterior pituitary cell networks

Both endocrine and non-endocrine cells of the pituitary gland are organized into structural and functional networks which are formed during embryonic development but which may be modified throughout life. Structural mapping of the various endocrine cell types has highlighted the existence of distinct network motifs and relationships with the vasculature which may relate to temporal differences in their output. Functional characterization of the network activity of growth hormone and prolactin cells has revealed a role for cell organization in gene regulation, the plasticity of pituitary hormone output and remarkably the ability to memorize altered demand. As such, the description of these endocrine cell networks alters the concept of the pituitary from a gland which simply responds to external regulation to that of an oscillator which may memorize information and constantly adapt its coordinated networks' responses to the flow of hypothalamic inputs.

A tridimensional view of pituitary development and function

Recent advances in tridimensional (3D) tissue imaging have considerably enriched our view of the pituitary gland and its development. Whereas traditional histology of the pituitary anterior lobe portrayed this tissue as a patchwork of cells, 3D imaging revealed that cells of each lineage form extensive and structured homotypic networks. In the adult gland these networks contribute to the robustness and coordination of the cell response to secretagogs. In addition, the network organization adapts to changes in endocrine environment, as revealed by the sexually dimorphic growth hormone (GH) cell network. Further work is required to establish better the molecular basis for homotypic and heterotypic interactions in the pituitary as well as the implications of these interactions for pituitary function and dysfunction in humans.

Existence of long-lasting experience-dependent plasticity in endocrine cell networks

Experience-dependent plasticity of cell and tissue function is critical for survival by allowing organisms to dynamically adjust physiological processes in response to changing or harsh environmental conditions. Despite the conferred evolutionary advantage, it remains unknown whether emergent experience-dependent properties are present in cell populations organized as networks within endocrine tissues involved in regulating body-wide homeostasis. Here we show, using lactation to repeatedly activate a specific endocrine cell network in situ in the mammalian pituitary, that templates of prior demand are permanently stored through stimulus-evoked alterations to the extent and strength of cell–cell connectivity. Strikingly, following repeat stimulation, evolved population behaviour leads to improved tissue output. As such, long-lasting experience-dependent plasticity is an important feature of endocrine cell networks and underlies functional adaptation of hormone release.

Experience-dependent plasticity and functional adaptation are thought to be restricted to the central nervous and immune systems. This study shows that long-lasting experience-dependent plasticity is a key feature of endocrine cell networks, allowing improved tissue function and hormone output following repeat demand.

Coordination of calcium signals by pituitary endocrine cells in situ

The pulsatile secretion of hormones from the mammalian pituitary gland drives a wide range of homeostatic responses by dynamically altering the functional set-point of effector tissues. To accomplish this, endocrine cell populations residing within the intact pituitary display large-scale changes in coordinated calcium-spiking activity in response to various hypothalamic and peripheral inputs. Although the pituitary gland is structurally compartmentalized into specific and intermingled endocrine cell networks, providing a clear morphological basis for such coordinated activity, the mechanisms which facilitate the timely propagation of information between cells in situ remain largely unexplored. Therefore, the aim of the current review is to highlight the range of signalling modalities known to be employed by endocrine cells to coordinate intracellular calcium rises, and discuss how these mechanisms are integrated at the population level to orchestrate cell function and tissue output.

Influence of estrogens on GH-cell network dynamics in females: a live in situ imaging approach

The secretion of endocrine hormones from pituitary cells finely regulates a multitude of homeostatic processes. To dynamically adapt to changing physiological status and environmental stimuli, the pituitary gland must undergo marked structural and functional plasticity. Endocrine cell plasticity is thought to primarily rely on variations in cell proliferation and size. However, cell motility, a process commonly observed in a variety of tissues during development, may represent an additional mechanism to promote plasticity within the adult pituitary gland. To investigate this, we used multiphoton time-lapse imaging methods, GH-enhanced green fluorescent protein transgenic mice and sexual dimorphism of the GH axis as a model of divergent tissue demand. Using these methods to acutely (12 h) track cell dynamics, we report that ovariectomy induces a dramatic and dynamic increase in cell motility, which is associated with gross GH-cell network remodeling. These changes can be prevented by estradiol supplementation and are associated with enhanced network connectivity as evidenced by increased coordinated GH-cell activity during multicellular calcium recordings. Furthermore, cell motility appears to be sex-specific, because reciprocal alterations are not detected in males after castration. Therefore, GH-cell motility appears to play an important role in the structural and functional pituitary plasticity, which is evoked in response to changing estradiol concentrations in the female.

Endocrine cells and blood vessels work in tandem to generate hormone pulses

Hormones are dynamically collected by fenestrated capillaries to generate pulses, which are then decoded by target tissues to mount a biological response. To generate hormone pulses, endocrine systems have evolved mechanisms to tightly regulate blood perfusion and oxygenation, coordinate endocrine cell responses to secretory stimuli, and regulate hormone uptake from the perivascular space into the bloodstream. Based on recent findings, we review here the mechanisms that exist in endocrine systems to regulate blood flow, and facilitate coordinated cell activity and output under both normal physiological and pathological conditions in the pituitary gland and pancreas.

Delayed postconditioning in the mouse heart in vivo

BACKGROUND

Reperfusion during acute myocardial infarction remains the best treatment for reducing infarct size. Postconditioning, applied at the onset of reperfusion, reduces myocardial infarction both in animals and humans. The objective of this study was to identify the time delay to apply postconditioning at reperfusion, allowing preservation of cardioprotection in the mouse myocardium. This is a major issue in the management of acute myocardial infarction patients.

METHODS AND RESULTS

Mice were subjected to 40 minutes of ischemia and 60 minutes of reperfusion (IR(60')). Postconditioning protocols corresponding to repetitive ischemia (3 cycles of 1 minute of ischemia and 1 minute of reperfusion) were applied during early reperfusion at various time durations (Δt) after reopening of the coronary artery (Δt=10 seconds, 1, 5, 10, 15, 20, 30, and 45 minutes; PostC(Δt)). Infarct size/area at risk was reduced by 71% in PostC(Δ1) compared with IR(60') mice (P=5×10(-6)). There was a linear correlation (r(2)=0.91) between infarct size and Δt, indicating that the cardioprotective effect of delayed postconditioning was progressively attenuated when Δt time increased. The protective effect of PostC(Δ1) and PostC(Δ15) was still effective when the duration of reperfusion was prolonged to 24 hours (IR(24 hours); PostC(Δ1) and PostC(Δ15) versus IR(24 hours), P=0.001). Similar results were obtained for internucleosomal DNA fragmentation and lactate dehydrogenase release.

CONCLUSIONS

This study in our in vivo mouse model of myocardial IR shows for the first time that delaying the intervention of postconditioning to 30 minutes does not abrogate the cardioprotective effect of postconditioning. This finding provides evidence that the time window of protection afforded by postconditioning may be larger than initially reported.

Reducing "iatrogenic disability" in the hospitalized frail elderly

BACKGROUND

Hospitalization is the first cause of functional decline in the elderly: 30 to 60% of elderly patients lose some independence in basic activities of daily living (ADL) during a stay in hospital. This loss of independence results from the acute condition that led to admission, but is also related to the mode of management.

OBJECTIVE

This paper is a review of the literature on functional decline in elderly hospitalized patients. It is the first stage in a project aiming to prevent dependence that is induced during the course of care.

METHODS

During a 2-day workshop in Monaco, a task force of 20 international experts discussed and defined the concept of "iatrogenic disability".

RESULTS

1- "Iatrogenic disability" was defined by the task force as the avoidable dependence which often occurs during the course of care. It involves three components that interact and have a cumulative effect: a) the patient's pre-existing frailty, b) the severity of the disorder that led to the patient's admission, and lastly c) the hospital structure and the process of care. 2- The prevention of "iatrogenic disability" involves successive stages. - becoming aware that hospitalization may induce dependence. Epidemiological studies have identified at-risk populations by the use of composite scores (HARP, ISAR, SHERPA, COMPRI, etc). - considering that functional decline is not a fatality. Quality references have already been defined. Interventions to prevent dependence in targeted populations have been set up: simple geriatric consultation teams, single-factor interventions (aimed for example at mobility, delirium, iatrogenic disorders) or multidomain interventions (such as GEM and ACE units, HELP, Fast Track, NICHE). These interventions are essentially centered on the patient's frailty and have limited results, as they take little account of the way the institution functions, which is not aimed at prevention of functional decline. The process of care reveals shortcomings: lack of geriatric knowledge, inadequate evaluation and management of functional status. The group suggests that interventions must not only identify at-risk patients so that they may benefit from specialized management, but they must also target the hospital structure and the process of care. This requires a graded "quality approach" and rethinking of the organization of the hospital around the elderly person.

Functional importance of blood flow dynamics and partial oxygen pressure in the anterior pituitary

The pulsatile release of hormone is obligatory for the control of a range of important body homeostatic functions. To generate these pulses, endocrine organs have developed finely regulated mechanisms to modulate blood flow both to meet the metabolic demand associated with intense endocrine cell activity and to ensure the temporally precise uptake of secreted hormone into the bloodstream. With a particular focus on the pituitary gland as a model system, we review here the importance of the interplay between blood flow regulation and oxygen tensions in the functioning of endocrine systems, and the known regulatory signals involved in the modification of flow patterns under both normal physiological and pathological conditions.

Different degrees of somatotroph ablation compromise pituitary growth hormone cell network structure and other pituitary endocrine cell types

We have generated transgenic mice with somatotroph-specific expression of a modified influenza virus ion channel, (H37A)M2, leading to ablation of GH cells with three levels of severity, dependent on transgene copy number. GH-M2(low) mice grow normally and have normal-size pituitaries but 40-50% reduction in pituitary GH content in adult animals. GH-M2(med) mice have male-specific transient growth retardation and a reduction in pituitary GH content by 75% at 42 d and 97% by 100 d. GH-M2(high) mice are severely dwarfed with undetectable pituitary GH. The GH secretory response of GH-M2(low) and GH-M2(med) mice to GH-releasing peptide-6 and GHRH was markedly attenuated. The content of other pituitary hormones was affected depending on transgene copy number: no effect in GH-M2(low) mice, prolactin and TSH reduced in GH-M2(med) mice, and all hormones reduced in GH-M2(high) mice. The effect on non-GH hormone content was associated with increased macrophage invasion of the pituitary. Somatotroph ablation affected GH cell network organization with limited disruption in GH-M2(low) mice but more severe disruption in GH-M2(med) mice. The remaining somatotrophs formed tight clusters after puberty, which contrasts with GHRH-M2 mice with a secondary reduction in somatotrophs that do not form clusters. A reduction in pituitary beta-catenin staining was correlated with GH-M2 transgene copy number, suggesting M2 expression has an effect on cell-cell communication in somatotrophs and other pituitary cell types. GH-M2 transgenic mice demonstrate that differing degrees of somatotroph ablation lead to correlated secondary effects on cell populations and cellular network organization.

Characterization of adherens junction protein expression and localization in pituitary cell networks

Our view of anterior pituitary organization has been altered with the recognition that folliculo-stellate (FS) and somatotroph cell populations form large-scale three-dimensional homotypic networks. This morphological cellular organization may optimize communication within the pituitary gland promoting coordinated pulsatile secretion adapted to physiological needs. The aim of this study was to identify the molecules involved in the formation and potential functional organization and/or signaling within these cell-cell networks. Here, we have focused on one class of cell adhesion molecules, the cadherins, since beta-catenin has been detected in the GH cell network. We have characterized, by qPCR and immunohistochemistry, their cellular expression and distribution. We have also examined whether their expression could be modulated during pituitary tissue remodeling. The mouse anterior pituitary has a restricted and cell-type specific repertoire of cadherin expression: cadherin-11 is exclusively expressed in TSH cells; N-cadherin displays a ubiquitous expression pattern but with different levels of expression between endocrine cell types; E-cadherin is restricted to homotypic contacts between FS cells; while cadherin-18 is expressed both in somatotrophs and FS cells. Thus, each cell type presents a defined combinatorial expression of different subsets of cadherins. This cell-type specific cadherin expression profile emerges early during development and undergoes major changes during postnatal development. These results suggest the existence within the anterior pituitary of cell-cell contact signaling based on a defined pattern of cadherin expression, which may play a crucial role in cellular recognition during the formation and fate of pituitary cell homotypic networks.

Stress-induced intercellular communication remodeling in the rat adrenal medulla

To understand the mechanisms by which a prolonged exposure to stress enhances catecholamine secretion, we examined the effects of 5-day cold exposure on cell-cell communication pathways in the rat adrenal medulla. Upon stress, the neurosecretory tissue undergoes dramatic morphofunctional changes resulting in increased chromaffin cell excitability, upregulation of both chemical transmission at the splanchnic nerve terminal-chromaffin cell synapses and spreading of gap junction-permeant Lucifer yellow between cells. All these changes converge to improve the stimulus-secretion coupling efficiency within the adrenal medulla and subsequently to adapt catecholamine release to a sustained organism demand.

Intrahypothalamic angiogenesis induced by osmotic stimuli correlates with local hypoxia: a potential role of confined vasoconstriction induced by dendritic secretion of vasopressin

We have previously shown that hyperosmotic stimulation of adult Wistar rats induces local angiogenesis within hypothalamic magnocellular nuclei, in relation to the secretion of vascular endothelial growth factor (VEGF) by the magnocellular neurons. The present study aimed at understanding how osmotic stimulus relates to increased VEGF secretion. We first demonstrate a correlation between increased VEGF secretion and local hypoxia. Osmotic stimulation is known to stimulate the metabolic activity of hypothalamic magnocellular neurons producing arginine vasopressin (AVP) and to increase the secretion of AVP, both by axon terminals into the circulation and by dendrites into the extracellular space. In AVP-deficient Brattleboro rats, the dramatic activation of magnocellular hypothalamic neurons failed to induce hypoxia, VEGF expression, or angiogenesis, suggesting a major role of hypothalamic AVP. A possible involvement of dendritic AVP release is supported by the findings that 1) hypoxia and angiogenesis were not observed in non osmotically stimulated Wistar rats in which circulating AVP was increased by the prolonged infusion of exogenous AVP, 2) contractile arterioles afferent to the magnocellular nuclei were strongly constricted by the perivascular application of AVP via V1a receptors (V1a-R) stimulation, and 3) after the intracerebral or ip administrations of selective V1a-R antagonists to osmotically stimulated rats, hypothalamic hypoxia and angiogenesis were or were not inhibited, respectively. Together, these data strongly suggest that the angiogenesis induced by osmotic stimulation relates to tissue hypoxia resulting from the constriction of local arterioles, via the stimulation of perivascular V1a-R by AVP locally released from dendrites.

Ligamentoplasty of the forearm interosseous membrane using the semitendinosus tendon: anatomical study and surgical procedure

Total longitudinal disruptions of the interosseous membrane can allow proximal radius migration and are seen in Essex-Lopresti lesions. We propose an original technique of ligamentoplasty using the semitendinosus tendon. The graft corresponds to the forearm rotation axis for an optimized isometry and longitudinal stabilization. Our ligamentoplasty technique was performed on ten fresh frozen right forearms. We successively assessed the innocuousness, efficiency and resistance of the ligamentoplasty. The ligamentoplasty induced neither passive limitation of pronation-supination nor neurovascular lesions. It prevented from radius proximal migration. The mean load to failure was 28 kg at both ulnar and radial sides of the graft. Our technique is original for the type and position of the graft. It seems safe, efficient and resistant enough for in vivo procedures. This technique decreases longitudinal loads on the radius. It should be indicated in patients with Essex-Lopresti syndrome, in association with radial head internal fixation or arthroplasty.

Comparison of the efficacy of a synthetic dog-appeasing pheromone with clomipramine for the treatment of separation-related disorders in dogs

Sixty-seven dogs that showed signs of distress when separated from their owners (destructiveness, excessive vocalisation and house soiling) and hyperattachment were used in a randomised, blind trial to assess the potential value of a dog-appeasing pheromone in reducing the unacceptable behaviours. For ethical reasons, there was no placebo group and the effects of the pheromone were compared with the effects of clomipramine which is regularly used to treat this type of problem. The undesirable behaviours decreased in both groups, but the overall assessment by the owners indicated that there was no significant difference between the two treatments, although there were fewer undesirable events in the dogs treated with the pheromone, and the administration of the pheromone appeared to be more convenient.

Conformational changes in actin-myosin isoforms probed by Ni(II).Gly-Gly-His reactivity

Crucial information concerning conformational changes that occur during the mechanochemical cycle of actin-myosin complexes is lacking due to the difficulties encountered in obtaining their three-dimensional structures. To obtain such information, we employed a solution-based approach through the reaction of Ni(II).tripeptide chelates which are able to induce protein cleavage and cross-linking reactions. Three different myosin motor domain isoforms in the presence of actin and nucleotides were treated with a library of Ni(II).tripeptide chelates and two reactivities were observed: (1) muscle motor domains were cross-linked to actin, as also observed for the skeletal muscle isoform, while (2) the Dictyostelium discoideum motor domain was cleaved at a single locus. All Ni(II).tripeptide chelates tested generated identical reaction products, with Ni(II).Gly-Gly-His, containing a C-terminal carboxylate, exhibiting the highest reactivity. Mass spectrometric analysis showed that protein cleavage occurred within segment 242-265 of the Dictyostelium discoideum myosin heavy chain sequence, while the skeletal myosin cross-linking site was as localized previously within segment 506-561. Using a fusion protein consisting of the yellow and cyan variants of green fluorescent protein linked by Dictyostelium discoideum myosin segment 242-265, we demonstrated that the primary sequence of this segment alone is not a sufficient substrate for Ni(II).Gly-Gly-His-induced cleavage. Importantly, the cross-linking and cleavage reactions both exhibited specific structural sensitivities to the nature of the nucleotide bound to the active site, validating the conformational changes suggested from crystallographic data of the actin-free myosin motor domain.

L’électrostimulation surimposée à la contraction musculaire volontaire présente-t-elle un intérêt physiologique chez les sujets âgés ?

OBJECTIVE

To analyze the physiological effects of electrical stimulation with voluntary muscle contraction exercise in postmenopausal women.

MATERIALS AND METHODS

Thirty-two females aged 62 to 75 years were randomly assigned to three groups to perform four activity sessions for six weeks: group ME (N =11) climbed up and down stairs, group ES (N =11) practised electrostimulation, and group ME + ES (N = 10) undertook both activities. Physiological adaptations of body composition (lean and fat masses and bone mineral density), muscular strength (isometric and dynamic), vertical jump and posturokinetic activities (balance and gait) were analysed.

RESULTS

For the three groups, the isometric strength at angle 100 degrees (average increase right and left legs, ME: 19 N.m; ES: 4.5 N.m; ME + ES: 11.5 N.m), the dynamic strength at speed 60 degrees.s(-1) (average increase right and left leg, ME: 15 N.m; ES: 14 N.m; ME+ES: 18.5 N.m) and the vertical jump (ME: 23 mm; ES: 16 mm; ME + ES: 34 mm) increased contrary in the body composition and posturokinetic activities. Nevertheless, the group ME + ES adapted differently on some parameters of bone mineral density (P < 0.05) and dynamic strength (P < 0.01) in relation to the groups ES and ME.

CONCLUSION

Electrostimulation with voluntary muscle contraction exercise could induce different physiologic adaptations compared with electrostimulation or voluntary muscle contraction exercise alone.

Effects of brisk walking on static and dynamic balance, locomotion, body composition, and aerobic capacity in ageing healthy active men

This work analyses the short-term physiological and neurophysiological effects of a brisk walking programme in ageing, healthy, active men. Twenty-one men 63 to 72 years of age were recruited and separated into 2 groups. One group performed a walking programme (WP) (n = 11) and another served as control (C) group (n = 10). The walking programme lasted for twelve weeks and included five sessions per week. Several parameters were assessed before and after the programme for the WP group. The same tests were performed (separated by twelve weeks) in group C. During each assessment, the subjects were put through static and dynamic balance tests, spatio-temporal gait analysis, body composition measurements and determination of aerobic capacity and bone mineral density. The statistic analysis showed a significant improvement in dynamic balance performance, especially in lateral sway when the subjects kept their eyes open, an increase of VO(2) max and loss of fat mass in the WP group. However, no alterations appeared in spatiotemporal gait characteristics, static balance performance, lean mass or bone mineral density (total body and hip). According to these results, this walking programme may have positive effects on preventing ageing subjects from falling.

Neuromuscular effects of three training methods in ageing women

AIM

The present study aimed to compare the effects of 3 strength development methods on muscular mass and muscular strength in healthy ageing women.

METHODS

Thirty-two healthy women, 62 to 75 years old were randomised into 3 groups. The 3 groups performed 4 sessions a week of strength development for 6 weeks. The 1(st) group (SC) climbed up and down 300 stairs per session. The 2(nd) group (ES) followed an electrostimulation programme on the quadriceps muscles. The 3(rd) group (SC+ES) combined stair climbing with electrostimulation. Before and after the 3 programmes, the muscular mass of the leg was assessed using a biphotonic absorptiometry machine. Isometric (angle 20 degrees and 100 degrees ) and isokinetic (60 degrees /s and 240 degrees /s) knee extension torque was measured using an isokinetic dynamometer.

RESULTS

None of the programmes changed the muscular mass. All 3 groups increased isometric (angle 20 degrees, p<0.001; angle 100 degrees, p<0.003) and isokinetic (60 degrees /s, p<0.0001; 240 degrees /s, p<0.0001) knee extension torque. None of the programmes appeared more efficient than the others for muscular mass or muscular strength.

CONCLUSION

Six weeks of activity (SC, ES or SC+ES) improved the isometric and dynamic muscular strength in ageing healthy women. However, this period was too short to change the muscular mass. None of the activities presented a real advantage over the others in ageing women.

Comparison between three strength development methods on body composition in healthy elderly women

The effects of three strength development methods (during 6 weeks) were assessed on the body composition in 32 women, 62 to 75 years old and randomised in 3 groups. The first group (SC) has climbed and come down 300 stairs per session. The second group (ES) followed an electrostimulation programme on quadriceps muscles. The third group (SC+ES) has combined the stairs climbing with electrostimulation. Body composition and bone mineral density (BMD) was assessed using Absorptiometry machine before and after the programmes. None of the programmes has increased significantly BMD. Nevertheless, the SC+ES group BMD enhanced more on the trochanter (p<0,05) and the two legs (p<0,05) than the SC and ES groups BMD (interaction group/time). The combined activity (SC+ES) would deserve to be tested on a longer period.

Cholesterol reduction and increased cardiovascular fitness following a 12 weeks brisk walking

The effects of a walking training programme were assesed on 10 healthy, active men aged 63-69 years. Serum lipids, pulse and blood pressure, maximum oxygen consumption (VO2 max) and anthropometric parameters, were measured before and after this programme. There was a significant fall in LDL (p<0.02) and mean diastolic BP (p<0.005). In spite of the subjects's initial good level of fitness there was still an 8% rise in the mean VO2 max of the group. There was also a significant loss of body fat (P<0.01). These positive physiological effects suggest that brisk walking can be considered as a a useful activity for improving the fitness and general health in this age-range.

Are there differences in postural regulation according to the level of competition in judoists?

The aim of this work was to study the posturokinetic capacities and use of visual information by judoists according to their level of competition. Twenty male judoists aged between 16 and 19 took part. They were separated into two groups: those that competed at regional level and those that competed at national and international level. Static balance was measured on a force platform. No difference was seen between the two groups. However, it seems that visual information is more important to the higher level judoists. Perhaps the level of competition influences the sensory canals involved in balance.