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Biomedical subjects

G Vannier

Publications and source records attributed to G Vannier.

5 recordsLinked to original sources
PubMed1998

Thermoregulatory responses to variations of photoperiod and ambient temperature in the male lesser mouse lemur: a primitive or an advanced adaptive character?

The lesser mouse lemur, a small Malagasy primate, is exposed to strong seasonal variations in ambient temperature and food availability in its natural habitat. To face these environmental constraints, this nocturnal primate exhibits biological seasonal rhythms that are photoperiodically driven. To determine the role of daylength on thermoregulatory responses to changes in ambient temperature, evaporative water loss (EWL), body temperature (Tb) and oxygen consumption, measured as resting metabolic rate (RMR), were measured in response to ambient temperatures ranging from 5 degrees C to 35 degrees C, in eight males exposed to either short (10L:14D) or long (14L:10D) daylengths in controlled captive conditions. In both photoperiods, EWL, Tb and RMR were significantly modified by ambient temperatures. Exposure to ambient temperatures below 25 degrees C was associated with a decrease in Tb and an increase in RMR, whereas EWL remained constant. Heat exposure caused an increase in Tb and heat loss through evaporative pathways. Thermoregulatory responses to changes in ambient temperature significantly differed according to daylength. Daily variations in Tb and EWL were characterized by high values during the night. During the diurnal rest, lower values were found and a phase of heterothermia occurred in the early morning followed by a spontaneous rewarming. The amplitude of Tb decrease with or without the occurrence of torpor (Tb < 33 degrees C) was dependent on both ambient temperature and photoperiod. This would support the hypothesis of advanced thermoregulatory processes in mouse lemurs in response to selective environmental pressure, the major external cue being photoperiodic variations.

Adaptation, Physiological↗
PubMed1998

Influence of daylength on metabolic rate and daily water loss in the male prosimian primate Microcebus murinus.

In its natural habitat, Microcebus murinus, a small malagasy prosimian primate, is exposed to seasonal shortage of water and resources. During the winter dry season, animals enter a pronounced fattening period with concurrent decrease in behavioural/physiological activities, whereas the breeding season is restricted to the rainy summer months. To determine the role of daylength on metabolic rate and water loss in this nocturnal primate, we measured body mass, oxygen consumption at 25 degrees C (RMR), circadian water loss through urine output (UO) and evaporation (EWL) in eight males exposed to either short days (8L:16D SD) or long days (14L:10D LD), under controlled captive conditions. Exposure to SD led to a ponderal increase (maximal body mass: 125 +/- 4 g, N = 8), and to significant changes in RMR and water loss, both reaching lowest values after 3 months under SD (0.84 +/- 0.04 ml O2 h-1 g-1 and 38 +/- 0.3 mg H2O g-1 day-1, respectively). Following exposure to LD, body mass decreased to 77 +/- 3 g (N = 8), whereas both RMR and water loss, mainly through EWL, significantly increased (P < 0.001), the highest value occurring after 2 months (1.51 +/- 0.08 ml O2 h-1 g-1 and 87 +/- 7 mgH2O g-1 day-1, respectively). Moreover, independent of daylength, circadian changes in EWL were characterized by significantly reduced values during the diurnal rest. The results demonstrate that daylength variations affect the physiology of this tropical primate, allowing anticipatory adaptation to seasonal environmental constraints.

Animals↗
PubMed1997

[Decrease of supercooling capacity during embryogenesis and larval growth in Coleoptera].

Potential cold resistance of non-diapause eggs and first instar larvae of Osmoderma eremita (Coleoptera, Cetoniidae, Trichiinae) during embryogenesis and post-embryonic growth was assessed by measuring individual supercooling points (SCP): sterile eggs had a mean SCP of -24.3 +/- 2.0 degrees C; fertilized newly laid eggs a mean SCP of -23.4 +/- 3.2 degrees C and eggs about to hatch a mean SCP of -9.2 +/- 2.9 degrees C. Water absorption by fertilized eggs is a necessary requirement for the development of the embryo and results in an increase in weight and water content: fertilized newly laid eggs had a mean fresh weight of 10.687 +/- 1.072 mg and a mean water content (expressed as a percentage of the dry weight) of 79.5 +/- 10.83%; eggs about to hatch had a mean fresh weight of 19.127 +/- 3.183 mg and a mean water content of 250.10 +/- 74.15%. The ex-ovo larvae, hatched 30 days after oviposition, had a mean SCP of -10.1 +/- 3.6 degrees C (no significant difference with eggs about to hatch) and had gained in weight (24.845 +/- 3.911 mg) and in water content (499.72 +/- 55.49%). Feeding 1st instar larvae had a decreased supercooling ability (mean SCP = -5.7 +/- 0.4 degrees C) whereas their mean fresh weight (99.858 +/- 53.091 mg) and mean water content (665.83 +/- 82.74%) increased. The eggs and larvae of O. eremita are freezing intolerant. Before overwintering, all larvae switch to being freezing tolerant and can survive ice formation in their tissues and body fluids, whereas their mean SCP stays at around -5 degrees C. However, recent experiments in the winter of 1996 have shown that frozen larva mortality does occur at temperatures lower than about -12 degrees C.

Animals↗
PubMed1986

[Fracture-separation of the atlas. A case].

A case of fracture-separation of the atlas is presented. The diagnosis, suspected on the antero-posterior open-mouth film and the frontal tomograms, was confirmed by computed tomography which showed the double fracture of the anterior and posterior arches of the atlas and demonstrated that the transverse ligament, factor of stability of this fracture, was intact.

Adult↗