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Papers by eaton lambert

This study aimed to investigate the cardiac response to sympathetic stimulation and norepinephrin... more This study aimed to investigate the cardiac response to sympathetic stimulation and norepinephrine exposure following subarachnoid hemorrhage (SAH). Cardiac functional response was assessed 3 days following an injection of 300 Al of homologous blood in the cisterna magna using an in situ perfused, innervated rat heart model. Sympathetic nervous activity was indirectly assessed from measurements of arterial plasma and tissue norepinephrine concentration and cardiac h-receptor density. In in situ perfused hearts, sympathetic nerve stimulation (2, 4 and 8 Hz, 1 min duration) induced a frequency-dependent increase in left ventricular pressure (VP), with the response being more pronounced in the SAH group of animals at the higher frequency (P < 0.05). However, the concomitant release of norepinephrine was identical in the two groups of animals. Increasing doses of norepinephrine (10 À 9 to 10 À 5 M) added to the perfusate induced a dosedependent increase in VP and its first derivative (dP/dt). Both responses were greater in the SAH animals compared to the sham rats (P < 0.01). ECG recordings from SAH animals presented a higher incidence of different types of arrhythmias, both at rest and when submitted to electrical stimulation or norepinephrine exposure. No difference was found between groups in left ventricle norepinephrine content, plasma norepinephrine nor left ventricle h-receptor density. In conclusion, hearts from animals following acute experimental SAH exhibit enhanced sensitivity to norepinephrine infusion and sympathetic nerve stimulation, and are more prone to develop arrhythmias. However, hypersensitivity of the heart may not be explained by changes in norepinephrine release or by h-receptor density.

Background-Clinical observations in patients with postural tachycardia syndrome (POTS) suggest ab... more Background-Clinical observations in patients with postural tachycardia syndrome (POTS) suggest abnormal sympathetic nervous system activity and a dysfunction of the norepinephrine (NE) transporter (NET). Methods and Results-We examined sympathetic nervous system responses to head-up tilt by combining NE plasma kinetics measurements and muscle sympathetic nerve activity recordings and by quantifying NET protein content in peripheral sympathetic nerves in patients with POTS compared with that in controls. POTS patients had an elevated heart rate during supine rest (81Ϯ2 bpm versus 66Ϯ2 bpm in healthy subjects [HS], PϽ0.01). Head-up tilt to 40°i nduced a greater rise in heart rate in patients with POTS (ϩ24Ϯ4 bpm versus ϩ13Ϯ2 bpm in HS, PϽ0.001). During rest in the supine position, muscle sympathetic nerve activity, arterial NE concentration, and whole-body NE spillover to plasma were similar in both groups. Muscle sympathetic nerve activity response to head-up tilt was greater in the POTS group (ϩ29Ϯ3 bursts/min in patients with POTS and ϩ13Ϯ2 bursts/min in HS, PϽ0.001), but the NE spillover rise was similar in both groups (51% in the POTS subjects and 50% in the HS). Western blot analysis of NET protein extracted from forearm vein biopsies in patients with POTS and HS demonstrated a decrease in the expression of NET protein in patients with POTS. Conclusion-Patients with POTS exhibit a decrease in NET protein in their peripheral sympathetic nerves. Paradoxically, whole-body NE spillover to plasma during rest in the supine position and in response to head-up tilt is not altered despite excessive nerve firing rate in response to the head-up tilt.

The demonstration of the effectiveness of endothelin antagonists and nitric oxide donors in manag... more The demonstration of the effectiveness of endothelin antagonists and nitric oxide donors in managing vasospasm following subarachnoid hemorrhage is encouraging. Whether such drugs can modify the sympathoexcitation that accompanies this condition remains unknown and was the basis for the present report. Subarachnoid hemorrhage was induced in conscious rats by injecting blood via a catheter placed along the surface of the brain and directed towards the circle of Willis. We combined measurements of arterial plasma catecholamines with the spectral analysis of blood pressure variability in order to examine sympathetic nervous activation following subarachnoid hemorrhage. Experiments were performed in untreated animals and in rats following pretreatment with either bosentan or sodium nitroprusside. Indicative of a pronounced sympathoexcitation, the 0.2-0.6 Hz frequency components of blood pressure were markedly elevated following subarachnoid hemorrhage (2.5 +/- 0.5 vs. 8.9 +/- 2.6 mmHg2, P < 0.01). Parallel changes in plasma norepinephrine concentration were observed (1.0 +/- 0.2 vs. 2.4 +/- 0.4 nmol/l, P < 0.01). The subarachnoid injection of saline did not modify blood pressure variability or plasma norepinephrine concentrations. Pretreatment with either bosentan or sodium nitroprusside completely prevented the subarachnoid hemorrhage induced sympathoexcitation. Experimental subarachnoid hemorrhage is associated with a pronounced activation of the sympathetic nervous system. It would appear that this sympathoexcitation has its roots ensconced in either the release of endothelin or an impairment in nitric oxide mediated vasodilation.

Background: The aim of this study was to examine the influences of genetic predisposition to hype... more Background: The aim of this study was to examine the influences of genetic predisposition to hypertension and of age on the sympathetic nervous system response to the cold pressor test (CPT). Methods: A total of 32 young subjects (aged 27 Ϯ 2 years) were studied: 11 normotensive subjects without a family history of hypertension (FH), 14 normotensive subjects with a strong family history of hypertension (FHϩ), and eight hypertensive subjects. In addition, 21 older subjects (aged 53 Ϯ 2 years) were studied: 13 hypertensive and eight normotensive subjects. Blood pressure (BP), heart rate (HR), and muscle sympathetic nerve activity (MSNA) were recorded at rest and during a 2-min period of a CPT. Results: Both young and older hypertensive subjects had higher resting MSNA than did the normotensive ones (47 Ϯ 7 v 29 Ϯ 4 bursts per 100 heartbeats (P Ͻ .05) and 66 Ϯ 4 v 40 Ϯ 7 bursts per 100 heartbeats (P Ͻ .01), respectively). The CPT resulted in HR increases of similar magnitude in all groups of patients. The FHϩ group displayed slightly less increase in systolic BP than that of the FH-group (P Ͻ .05). The MSNA increased to a far greater degree in FH-(103%) than in FHϩ (32%) and in young hypertensive patients (12%) (P Ͻ .05). Similarly, MSNA change with the CPT was greater in older normotensive subjects than in older hypertensive patients (61% v 12%, P Ͻ .05). Conclusions: Our results show that a CPT induces sympathetic responses that are subnormal in hypertensive patients and those with a family history of hypertension, highlighting the importance of genetic factors in determining the sympathetic nervous reactivity to CPT.

Archives of Ophthalmology, 2008

Objectives: To present the results for subgroups defined by center point (CP) measurement and to ... more Objectives: To present the results for subgroups defined by center point (CP) measurement and to assess the repeatability of the Fast Retinal Thickness Map analysis results from the Stratus OCT3 machine. Methods: Two hundred eighty-one replicate OCT3 scans from 134 operators' certification submissions to a reading center were analyzed, including scans from eyes that were reported to be normal and eyes with exudative agerelated macular degeneration and with macular edema due to diabetic retinopathy or retinal vascular occlusion. Results: The mean (SD) of the CP was 284 (150) µm and the center subfield (CC) was 301 (130) µm. The CP coefficient of repeatability (CR) was 49 µm and the CC CR was 27 µm. The CR increased by increasing retinal thickness for the CP and the CC within arbitrarily defined subgroups. For the 87 eyes with a session 1 CP of 175 µm or less, the CP CR was 17 µm and the CC CR was 10 µm. Conclusions: Among experienced operators, given the same operator, machine, and eye at the same sitting, OCT3 retinal thickness maps appear to have a CR that is likely to be less than the clinically important difference.

… of Objects in …, 1988

© European Space Agency Provided by the NASA Astrophysics Data System IMAGD4G SPE APPLIED TO TH... more © European Space Agency Provided by the NASA Astrophysics Data System IMAGD4G SPE APPLIED TO THE REMOTE SENSTh OF SUBMERGED SEAWEED NT O'Neill*, Y Gauthier E Lambert**, L Hubert*, JMM Dubois* & H Edel *Ca Université de Sherbrooke, Sherbrooke, ...

L'année psychologique, 2001

Annals of Physics, 1973

The two coupled channel formalism for high energy elastic scattering [l] is extended to include s... more The two coupled channel formalism for high energy elastic scattering [l] is extended to include spin and isospin effects. For a spin and isospin zero nucleus these manifest themselves by additional spin-orbit terms in the potentials. Explicit formulas for these potentials are obtained in terms of the fully spin and isospin dependent nucleon-nucleon scattering amplitude, the ground state nuclear form factor and the state dependent correlation functions. The coupling potential except for a small term arising from double spin and isospin flip process involving nuclear excitation depends only upon the pair correlations. Numerical calculations are performed for the elastic scattering of 1 GeV protons incident on 4He. Various phenomenological dynamical two-body correlations as well as correlations generated from the Reid soft-core and Tabakin potentials in an approximate Brueckner-Hartree-Fock calculation are considered. The angular distribution beyond its first diffraction minimum as well as the polarization in the same angular range are shown to be sensitive to these correlations. However, the present accuracy of the experimental data and the lack of knowledge of the nucleon-nucleon scattering amplitude prevent any definitive conclusion about their nature.

Annales Françaises d'Anesthésie et de Réanimation, 1996

…, 2006

... (Hypertension. 2006;48:787.) © 2006 American Heart Association, Inc. Brief Reviews. Mechanism... more ... (Hypertension. 2006;48:787.) © 2006 American Heart Association, Inc. Brief Reviews. Mechanisms of Sympathetic Activation in Obesity-Related Hypertension. Murray Esler; Nora Straznicky; Nina Eikelis; Kazuko Masuo; Gavin Lambert; Elisabeth Lambert ...

We investigated the relation between lifetime physical activity and bone mineral density (BMD) in... more We investigated the relation between lifetime physical activity and bone mineral density (BMD) in South African women using data collected in a case-control study of breast cancer in relation to BMD. Subjects (n = 144) were of black African or mixed ancestral origin, and <60 years of age (mean age 42.6 +/- 8.9 years). Cases had newly diagnosed breast cancer (n = 62) and controls were referred for conditions unrelated to BMD or breast cancer (n = 82). Physical activity data consisting of household, occupational and leisure-time activity, and activity for transport, were collected via questionnaire at 4 life stages (epochs), viz. 14-21, 22-34, 35-50, and 50+ years of age. Total energy (MET hrs) and peak strain scores were calculated. Lumbar spine and total proximal femur BMD were measured using dual-energy x-ray absorptiometry. BMD measures were similar between groups, therefore data were combined. BMD measures were unrelated to total lifetime physical activity. However, the major determinants of total proximal femur BMD included age, transport activity including walking and bicycling between the ages of 14 and 21 years, and current weight (adjusted r2 = 0.33, P < 0.0001). The major determinants of lumbar spine BMD included age, household energy expenditure between the ages of 14 and 21 years, and current weight (adjusted r2 = 0.23, P < 0.0001). Total peak bone strain score for activities between 14-21 years of age was also significantly correlated with lumbar spine BMD ( r = 0.18, P < 0.05). Intraclass correlation coefficients to assess tracking of activity through epochs 1, 2, and 3 were high for total energy expenditure (0.96; 95%CI: 0.94-0.97), household (0.98; 95%CI: 0.97-0.99) and occupational activity (0.78; 95%CI: 0.71-0.84) and activity for transport (0.92; 95%CI: 0.89-0.94). These data suggest that walking or activities resulting in impact loading at a young age are associated with higher BMD in later years. In addition, our findings suggest tracking of physical activity over time.

We demonstrated an ultra small 12 channels 400GHz AWG on SOI with flattened spectral response usi... more We demonstrated an ultra small 12 channels 400GHz AWG on SOI with flattened spectral response using a MMI mode shaper. Insertion loss and crosstalk are −3.29db and 17.0db, respectively. The device size is only 560×350µm 2 .

Frontiers in Psychology,, 2013

Plant Cell Tissue and Organ Culture, 2009

To study the production of secondary metabolites of Maesa lanceolata and Medicago truncatula, hai... more To study the production of secondary metabolites of Maesa lanceolata and Medicago truncatula, hairy root cultures of both plant species were established. Because maintenance of large numbers of cultures is laborious and costly, we developed a cryopreservation protocol and stored different isolated lines over time. Using encapsulation-dehydration, high survival rates were observed for both Maesa and Medicago hairy roots. Root tips were isolated and encapsulated in calcium-alginate beads, containing 0.1 M sucrose. The encapsulated hairy roots were precultured for 3 days using basal medium containing high sucrose concentrations. Medicago root tip growth during the preculturing time lead to unwanted outgrowth which could be tempered by addition of plant growth inhibitors. After preculturing, the beads were dehydrated in the air flow of a laminar flow until 35–40% of the initial bead weight was reached. Dehydrated beads were plunged into liquid nitrogen and after different storage times ...