Ultradian and circadian CO2 emission variations in nocturnal and diurnal animals exposed to a light stimulus.

1. Carbon dioxide emission (VCO2) has been continuously recorded in three laboratory animal species (Sprague-Dawley rats, Japanese quail, Hartley guinea-pigs) which differ by their nocturnal and diurnal activities. A 100 lux stimulus has been delivered at various time intervals. 2. A regular alternation of 12, 3 or 1.5 hr light (L) and darkness (D) gives VCO2 circadian and ultradian rhythms of 24, 6 or 3 hr periods, respectively, in quail and rats. 3. Such circadian and ultradian LD rhythms are not induced in all guinea-pigs. 4. The amplitudes of the VCO2 responses are greatest at D----L when the animals have a maximum diurnal activity and at L----D when their maximum activity is nocturnal. 5. Interactions between circadian and ultradian rhythms are seen in all LD experiments, as well as in continuous light (LL) or continuous dark (DD). 6. No more well-marked or even inverted VCO2 responses to the light stimuli may occur after several days of exposure to these LD alternations.

Age and survival of an acute carbon monoxide intoxication: an animal model.

Pathogen-free OF1 male and female mice of six different ages (between 31 and 387 days), grouped by 10, sex-separated and synchronized by a light (100 lux)-dark 12:12 alternation, were submitted to an acute LD50 carbon monoxide intoxication during the light period during which respiratory and motor activities are at a minimum. For this range of ages carbon monoxide survival is not significantly influenced by age and is significantly (P less than 0.001) less so in males than in females. Resistance to the acute carbon monoxide challenge seems more related to factors influencing the longevity of this mouse strain where grouped males are particularly aggressive than to respiratory exchanges (VCO2), heart frequencies or body temperature.

Sex-related factors in acute carbon monoxide intoxication in one strain of mice.

In the OF1 mouse strain, males are less resistant than females to acute carbon monoxide intoxication. Castration of males increases their resistance to carbon monoxide. For Neonates injected with four different doses of testosterone (20-500 mg per kg) or oestradiol (2-50 mg per kg), more effect on resistance to carbon monoxide in the (adult) mice was found for oestradiol than for testosterone. Pregnancy decreases resistance to carbon monoxide intoxication. Experiments performed with males and females of different ages, in various societal conditions, show the effects of sex-related dimorphism and aggressiveness. The sex-related difference in carbon monoxide resistance is not modified by a previous hypoxic stress (nitrogen hypoxia, carbon monoxide intoxication, sodium cyanide injection) but is suppressed when the CO intoxication is carried out at a low ambient temperature (13 degrees C).

Sex-related factors in acute hypoxia survival in one strain of mice.

In mice of different ages from the OF1 mouse strain, males are less resistant than females to a normobaric hypoxia obtained in a few hours by a progressive lowering of normoxic PO2 with nitrogen flushing. Injection of estradiol to castrated males and spayed females increases hypoxic survival. Neonates which have been injected with a high dose of estradiol show, when adult, a high hypoxic resistance. In adult females, hypoxic survival is lower during diestrus than during estrus. Pregnancy decreases resistance to hypoxia. Experiments, performed with males and females of different ages, show the effects of sex-related dimorphism and aggressiveness. Hypoxias at various ambient temperatures demonstrate that the sex difference in hypoxic survival persists in spite of variations in rectal temperatures.

Environmental parameters in the experimental evaluation of a respiratory aggression.

Acute nitrogen normobaric hypoxic challenges, resulting in an approximately 50% overall survival, were performed in young adult male and female heterozygous OF1 mice under various environmental conditions. The time required to obtain 50% survival was 20 min for a constant pO2 of 42 Torr, and 151 min when pO2 was progressively lowered by nitrogen flushing from 159 to 16.5 Torr. In LD12:12 synchronized animals, survival was significantly (P less than 0.001) less when hypoxia was performed during the light (L) than during the dark (D) phase. Lowering the ambient temperature from 33.8 to 13.2 degrees C increased the length of the progressive hypoxia necessary to obtain a 50% survival of the mice by 1.7 times, and diminished the final pO2 from 35 to 12 Torr. Grouping and crowding both decreased hypoxic survival. A previous stress (starvation) diminished hypoxic resistance of mice, while a preceding hypoxia, carbon monoxide inhalation, or sodium cyanide injection had the opposite effect. In all instances, OF1 females were more resistant than males. Most of these variations can be related to differences in respiratory exchanges, locomotor activity and aggressiveness, which are dependent upon the various experimental environmental parameters.

Harmonic analysis of ultradian respiratory rhythms in four small laboratory vertebrates lit in LD12:12.

Fourier harmonic analysis has been applied to 20-min samples of VCO2, recorded every 12 sec over several (7-12) days, in one mouse, one rat, one guinea-pig, or one quail, maintained in controlled conditions of temperature, humidity and ventilation, and lit in LD12:12 (100 lux). The harmonic computations, during L and D of ultradian periods (1.2 hr less than tau less than 12 hr) evidence statistically significant differences in amplitude and phase between these four small laboratory species. These periodic respiratory differences correspond to discrepancies in their diurnal and nocturnal activities, and in their responses to light and dark.

Aging and intraspecific interactions in acute hypoxic survival of specific pathogen free OF1 mice of both sexes.

In light-synchronized pathogen-free OF1 mice, and LD50 acute hypoxic challenge was performed during the light period in which respiratory and motor activities are minimal. In males and females acute hypoxic resistance decreases with age. Grouping by ten significantly decreases hypoxic survival in young, adult, and senescent males, and in young females. In young mice, hypoxic survival is significantly less in males than in females, whether or not they have interindividual contacts. This sex-related difference disappears with aging in separated individuals, but remains in 230- and 420-day-old mice when there are interindividual contacts.

[Ultradian (between 5 and 70 minutes) respiratory (VO2, VCO2) rhythms of 4 small vertebrates used in biomedical research]. / Rhythmes ultradiens (5 less than tau less than 70 mn) respiratoires (VO2, VCO2) de quatre petits Vertébrés utilisés pour la recherche biomédicale.

Four laboratory Vertebrate species with a predominant activity, either diurnal (Coturnix coturnix japonica), nocturnal (Rattus norvegicus, Mus musculus), or equivocal (Cavia porcellus), present, in usual housing conditions (temperature 20 degrees C, hygrometry 60-70%, acoustical background 70 dB, LD12:12 lighting L = 150 lx), food and water ad libitum, ultradian respiratory (VO2, VCO2) rhythms of short periods. The frequencies of these rhythms are independent of food intake and activity variations correlated to the lighting phase and regimen (LD, LL). The period (tau) of these ultradian respiratory rhythms is in isolated animals, between 5 and 70 min., according to the species studied. Grouping of several individuals of a same species, in a ventilated chamber, modifies the statistical distribution of the periods of the ultradian rhythms, but does not change the interspecies differences.