Browsing by Autor "Max Gassmann"

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Altered thermal and metabolic control in newborn rats at high altitude
(Wiley, 2008) Vincent Joseph; Jorge Soliz; Max Gassmann; Marcelino Gonzales Isidro; Enrique Vargas; Rudy Soria
In acute hypoxia, newborn reduce oxygen consumption (VO2) and rectal temperature (Tr), but it remains unclear if these responses are maintained in chronic hypoxia. We used rats living at high altitude (3600 m, La Paz Bolivia) at postnatal days 7–8 (P7, n=5, body weight 13±1 g) and 15–16 (P15, n=6, 21±1 g). Tr and VO2 were measured in 21%O2 (room air), 35%O2 (sea level PO2), and 10%O2 (hypoxia), during 20 minutes each. Ambient temperature (Ta) was 34°C at P7 and 30°C at P15. Tr‐Ta was used as an index of thermoregulatory control. At P7, Tr‐Ta was −0.1±0.2°C, suggesting that thermoregulatory control is not established. In 35%O2, Tr was 34.8±0.2°C, and 32.0±0.6°C in 10%O2. At P15, Tr‐Ta was 5.2±0.2°C in room air, Tr did not increased in 35%O2, and was 31.8±0.4°C in 10%O2. VO2 was high (P7=8.6±0.8; P15=9.4±0.4 ml/min/100g) compared to sea level rats (5 ml/min/100g in 20g P10 rats). In P7 and P15 rats, VO2 increased in 35%O2 and dropped in 10%O2. Our results suggest that chronic hypoxia delays the establishment of thermoregulation and increases metabolic rate in newborn rats. The drop of Tr and VO2 in 10%O2 were however well maintained. Founded by NSERC
Hypercapnic ventilatory response is decreased in a mouse model of excessive erythrocytosis
(American Physiological Society, 2016) Sofien Laouafa; Elizabeth Elliot‐Portal; Susana Revollo; Edith M. Schneider Gasser; Vincent Joseph; Nicolas Voituron; Max Gassmann; Jorge Soliz
The impact of cerebral erythropoietin (Epo) in the regulation of the hypercapnic ventilatory response (HcVR) is controversial. While we reported that cerebral Epo does not affect the central chemosensitivity in C57Bl6 mice receiving an intracisternal injection of sEpoR (the endogenous antagonist of Epo), a recent study in transgenic mice with constitutive high levels of human Epo in brain and circulation (Tg6) and in brain only (Tg21), showed that Epo blunts the HcVR, maybe by interacting with central and peripheral chemoreceptors. High Epo serum levels in Tg6 mice lead to excessive erythrocytosis (hematocrit ~80-90%), the main symptom of chronic mountain sickness (CMS). These latter results support the hypothesis that reduced central chemosensitivity accounts for the hypoventilation observed in CMS patients. To solve this intriguing divergence, we reevaluate HcVR in Tg6 and Tg21 mouse lines, by assessing the metabolic rate [O consumption (V̇) and CO production (V̇)], a key factor modulating ventilation, the effect of which was not considered in the previous study. Our results showed that the decreased HcVR observed in Tg6 mice (~70% reduction; < 0.01) was due to a significant decrease in the metabolism (~40%; < 0.0001) rather than Epo's effect on CO chemosensitivity. Additional analysis in Tg21 mice did not reveal differences of HcVR or metabolism. We concluded that cerebral Epo does not modulate the central chemosensitivity system, and that a metabolic effect upon CO inhalation is responsible for decreased HcVR observed in Tg6 animals. As CMS patients also show decreased HcVR, our findings might help to better understand respiratory disorders at high altitude.
Nocturnal Sleep Breathing Patterns in Healthy Adolescents Residing at Very High Altitudes in Bolivia
(Wiley, 2026) Keaton Patterson; Santiago Ucrós Rodríguez; E. Nicolás Arancibia‐Levit; Fernanda Aliaga Raduan; José Antonio Viruez Soto; Max Gassmann; Silvia Ulrich; Michael Furian; Edith M. Schneider Gasser
Data on sleep and respiratory patterns among adolescents residing at very high altitude (> 3500 m) remain scarce, and altitude-related physiological differences may influence these parameters. Studying adolescents at different very high altitudes is crucial, as subtle environmental variations could affect sleep-related oxygenation and respiratory function. This study aimed to characterise sleep-related oxygenation and respiratory parameters in healthy adolescents native to two distinct very high-altitude environments. Overnight sleep polygraphy was performed in 163 healthy adolescents aged 13.5 to < 18 years living in La Paz (3620 m) and El Alto (4060 m), Bolivia. Mean nocturnal oxygen saturation, oxygen desaturation index, and apnea-hypopnea index were assessed alongside subjective sleep quality, morning blood pressure, heart rate, haemoglobin concentration, and Epworth Sleepiness Scale scores. Adolescents at 4060 m had significantly lower mean nocturnal oxygen saturation (84.8% ± 2.2%) compared with those at 3620 m (87.8% ± 1.8%), and a higher oxygen desaturation index (21.2 ± 8.5/h vs. 17.1 ± 9.0/h). The apnea-hypopnea index did not differ significantly between altitudes (6.2 ± 4.8/h vs. 5.6 ± 4.6/h). At 3620 m, females showed lower oxygen desaturation and apnea-hypopnea indices compared with males. Despite the more pronounced nocturnal hypoxemia at 4060 m, haemoglobin concentration did not increase, suggesting limited haematological compensation. Subjective sleep quality, blood pressure, and heart rate were similar between both altitude groups. Healthy adolescents living chronically at very high altitude exhibit altitude-dependent reductions in nocturnal oxygenation and increased desaturation frequency, without evidence of sleep-disordered breathing. These findings underscore the need for altitude-specific normative values to support accurate interpretation of sleep studies in high-altitude populations.