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Biomedical subjects

G Vannier

Publications and source records attributed to G Vannier.

10 recordsLinked to original sources
PubMed2000

A sexually dimorphic response in supercooling temperature, enhanced by starvation, in the lesser mealworm Alphitobius diaperinus (Coleoptera: Tenebrionidae).

The effect of starvation on supercooling temperature (SCP) distribution was investigated in adults and larvae of Alphitobius diaperinus (Coleoptera: Tenebrionidae).The mean values for SCPs of adults fed at 20 degrees C were -14.5+/-2.4 degrees C (31 males) and -10.3+/-1.3 degrees C (29 females). The distribution of the SCPs of these control adults was unimodal. No significant differences were observed in either mean wet weight or mean dry weight between males and females.The mean values for SCPs of adults starved for 1 month at 20 degrees C were found to be bimodal due to sexual dimorphism. The mean SCPs for males was lower (-17+/-2.6 degrees C; 28) than that for females (-11.2+/-1.8 degrees C; 26). No significant differences were observed in either mean dry weight or wet weight between males and females.The SCPs of both fed and starved larvae, kept for 1 month at 20 degrees C were -12.3+/-2.4 degrees C (fed) and -18.0+/-2.6 degrees C (starved).

Journal Article↗
PubMed1999

Supercooling capacity of seeds and seedlings in Arabidopsis thaliana.

The influence of the water content of seeds and seedlings of Arabidopsis thaliana (Ecotype Columbia:2) on their supercooling capacity was investigated. Equilibration of the seeds to various air relative humidities resulted in final moisture contents ranging from 8 to 82% (dry weight basis). No supercooling point could be detected when the water content remained below 32.5%, and in seeds at just above this moisture level ice crystals started to form at -26 degrees C. However, cooling partly affected the germination of seeds down to a water content of 26.5%. Upon imbibition, the supercooling point of the seeds remained around -21.6 degrees C and rose sharply to -14.7 degrees C when visible germination started. It remained around -13 degrees C during the following 96 h while the water content of the seedlings increased from 155 to 870%. Hydrated seeds (above 32.5% water content), germinated seeds, and seedlings of Arabidopsis cannot survive being frozen.

Arabidopsis↗
PubMed1999

Effects of temperature and humidity on transpiration in adults of the lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae).

Measurements of water loss were made on adults of the lesser mealworm, Alphitobius diaperinus, using a recording micro-electrobalance and a programmable heat circulator bath. This species originates in tropical regions and infests poultry houses in temperate countries. Two routes of water loss were examined: the general cuticle and via the spiracles. Temperature and relative humidity of the ambient air substantially affect the cuticular transpiration in adults (fresh body weights from 12 mg to 22 mg). At near 0% R.H., between 20 and 40 degrees C the rate of body water loss gradually increased; on the other hand, the insects gained weight in an atmosphere close to saturation. Above 40 degrees C transpiration flow abruptly increased coinciding with the start of vigorous locomotor activity. This critical point corresponds to the opening of the spiracles from which the water is expelled from the tracheal system.In dead specimens, killed by cyanide or solvent, the water vapour slowly diffused out of the spiracles and, as in atracheate insects, the transpiration curves did not show a peak as the air temperature was increased.The thermostupor point (TSP) occurred as the insects became motionless; the corresponding temperature is significantly affected by atmospheric relative humidity (TSP=47.4+/-0.6 degrees C at c. 0% R.H.; TSP=46.6+/-0.7 degrees C at c. 100% R.H.).The transpiration flow was about four times as fast in specimens treated with solvent as in the individuals (live or cyanide-killed) that had undamaged water-proof cuticle. This species has to cope with a double challenge: (i) to adapt its physiology and ecology to poultry-house conditions which constitutes an extension of its primary habitats, and (ii) to survive over winter; high drought resistance and heat tolerance may constitute a pre-adaptation to conquer anthropogenic air-conditioned sites.

Journal Article↗
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↗
PubMedDate not supplied

Survival at low temperatures in insects: what is the ecological significance of the supercooling point?

Many freezing-intolerant insects may die during long or even brief exposures to temperatures above their supercooling point (SCP). Consequently, the real ecological value of the SCP remains ambiguous, particularly for tropical species that never experienced cold exposures. The bimodal distribution of SCP is discussed in the light of sexual dimorphism. The importance of sex in insect cold hardiness has been regularly neglected and although we admit that in some species sex may be uneasy to determine, it should be taken into account in further studies. We suggest that supercooling ability may be, at least partially, a result of adaptations to other functions unrelated to cold, including the desiccation resistance. The potential causes of insect death at low temperatures during survival experiments have also been examined. Prolonged exposures at lethal low temperatures can produce deleterious effects (including death) even if the insect does not freeze; during long-term exposure to low temperatures the organisms may finally die from the exhaustion of energy reserves.

Animals↗
PubMedDate not supplied

Cold resistance in the lesser mealworm Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae).

We have investigated cold resistance, measured by the supercooling point (SCP) temperature, in life stages of the lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae), collected in Brittany poultry houses. Mean SCP values drastically increased during the insect ontogeny: egg (-26.1 C), first instar larvae (-21.6 C), last instar larvae (-15.5 C), pupae (-11.6 C), teneral adults (-12.0 C) and mature adults (-13.1 C). Nymphal metamorphosis and adult maturation did not promote substantial decrease of freezing resistance. The SCP values reflect the physiological states of the developmental stages especially the absence of ice nucleating agents: (i) lower SCP values in egg and unfed newly-emerged larvae I (i.e. -25.1 C), (ii) higher SCP values in fed larvae (i.e. -14.7 C), pupae and adults most likely due to the presence of ice nucleation sites in the gut. A tropical species, A. diaperinus, seems not to use its potential cold hardiness even in winter to remain in this warm habitat in temperate regions.

Acclimatization↗