Pierre-Hugues Fortier

Non-nutritive swallowing and respiration coordination in full-term newborn lambs.

Swallowing is a powerful inhibitor of respiratory rhythm in infants. The present study was aimed at investigating the influence of states of alertness on non-nutritive swallowing (NNS) frequency, on NNS and respiration coordination, and on bursts of NNS frequency in newborn lambs. Six full term newborn lambs were instrumented for electroencephalogram, eye movement, diaphragm and thyroarytenoid muscle electromyogram, nasal flow and electrocardiogram. Polysomnographic recordings were performed in non-sedated lambs, using radiotelemetry. NNS frequency was significantly higher during quiet wakefulness (W) and active sleep (AS) than during quiet sleep (QS). NNS mainly interrupted inspiration and the transition phases between expiration and inspiration, especially in W and AS. Bursts of NNS occurred significantly more often during AS. This study highlights the relevance of the ovine model to study ontogeny of NNS during sleep, and documents the influence of sleep on NNS and respiration coordination.

Effects of simulated reflux laryngitis on laryngeal chemoreflexes in newborn lambs

It has been suggested that reflux laryngitis (RL) is involved in apneas-bradycardias of the newborn. The aim of the present study was to develop a unique RL model in newborn lambs to test the hypothesis that RL enhances the cardiorespiratory components of the laryngeal chemoreflexes (LCR) in the neonatal period. Gastric juice surrogate (2 ml of normal saline solution with HCl pH 2 + pepsin 300 U/ml) (RL group, n = 6) or normal saline (control group, n = 6) was repeatedly injected onto the posterior aspect of the larynx, 3 times a day for 6 consecutive days, via a retrograde catheter introduced into the cervical esophagus. Lambs instilled with gastric juice surrogate presented clinical signs of RL, as well as moderate laryngitis on histological observation. Laryngeal chemoreflexes were thereafter induced during sleep by injection of 0.5 ml of HCl (pH 2), ewes milk, distilled water or saline into the laryngeal vestibule via a chronic, transcutaneous supraglottal catheter. Overall, RL led to a significantly greater respiratory inhibition compared with the control group during LCR, including longer apnea duration (P = 0.01), lower minimal respiratory rate (P = 0.002), and a more prominent decrease in arterial hemoglobin saturation (SpO(2)) (P = 0.03). No effects were observed on cardiac variables. In conclusion, 1) our unique neonatal ovine model presents clinical and histological characteristics of RL; and 2) the presence of RL in newborn lambs increases the respiratory inhibition observed with LCR, at times leading to severe apneas and desaturations.

Evaluation of PACE4 isoforms as biomarkers in thyroid cancer

BackgroundTo date, no single molecular marker has been demonstrated as clinically useful in differentiating malignant from benign thyroid nodules when a fine needle aspiration falls in the “unknown significance” categories of the Bethesda Classification. PACE4, a member of the proprotein convertase family of enzymes, has been shown to play a major role in the pathogenesis of prostate cancer, through the formation of an oncogenic isoform named PACE4-altCT. PACE4 isoforms have also been suggested to play a role in other cancers, including thyroid cancer, but have never been investigated in a detailed manner. Our objective is to compare the histochemical distribution of the two major PACE4 isoforms in benign and malignant thyroid nodules, in order to determine their potential usefulness as discriminatory biomarkers.MethodsThyroid tissues of patients who underwent thyroidectomy were classified according to final pathology. Corresponding tissue sections were immunostained, using two previously validated antibodies raised against the C-terminal end of the two PACE4 isoforms, namely the full-length PACE4 protein (PACE4-FL) and its alternative isoform (PACE4-altCT). Nodules were compared with adjacent normal parenchyma and immunostaining was rated as “low” or “high” by a head and neck pathologist.ResultsNon-lesional thyroid parenchyma did not express PACE4-FL (p = 0.002). As a group, malignant (n = 17) nodules expressed PACE4-FL significantly more than benign (n = 24) nodules (percentage of high immunostaining: 52.9% vs 4.2%; p = 0.001). Reciprocally, there was a statistically lower expression of PACE4-altCT in malignant nodules than in adjacent non-lesional parenchyma (p = 0.014). The specificity of a high PACE4-FL immunostaining in determining malignancy was 95.8% (95% CI, 78.9% to 99.9%).ConclusionThis study supports the previously described relationship between PACE4-FL and PACE4-altCT through alternative splicing. It also suggests that PACE4-FL is a promising biomarker for thyroid malignancy. Its high specific expression for malignancy could make it an interesting “rule in” test for thyroid cancer. Further prospective, quantitative studies are currently being designed to address how measurements of PACE4 isoforms could be used in a clinical setting.Trial registrationThis study does not report the results of a health care intervention on human participants. It was nonetheless registered on ClinicalTrials.gov under reference number NCT03160482.

Effects of reflux laryngitis on non-nutritive swallowing in newborn lambs

Reflux laryngitis in infants may be involved not only in laryngeal disorders, but also in disorders of cardiorespiratory control through its impact on laryngeal function. Our objective was to study the effect of reflux laryngitis on non-nutritive swallowing (NNS) and NNS-breathing coordination. Two groups of six newborn lambs, randomized into laryngitis and control groups, were surgically instrumented for recording states of alertness, swallowing and cardiorespiratory variables without sedation. A mild to moderate reflux laryngitis was induced in lambs from the experimental group. A significant decrease in the number of NNS bursts and apneas was observed in the laryngitis group in active sleep (p=0.03). In addition, lower heart and respiratory rates, as well as prolonged apnea duration (p<0.0001) were observed. No physiologically significant alterations in NNS-breathing coordination were observed in the laryngitis group. We conclude that a mild to moderate reflux laryngitis alters NNS burst frequency and autonomous control of cardiac activity and respiration in lambs.