Search PubMed⌕ Search

Biomedical subjects

M Perret

Publications and source records attributed to M Perret.

At least 37 records · Page 2Linked to original sources
PubMed1998

Age-related effects on reproductive function and sexual competition in the male prosimian primate, Microcebus murinus.

In the male lesser mouse lemur (Microcebus murinus), a polygamous long-day breeder of which the life span may reach 12-14 years, the effects of aging on socio-sexual relationships were studied on 44 captive animals of various ages. In this primate, new dominance relationships must be established at the beginning of each breeding season. During the breeding season induced by exposure to artificial long days, preoestrous females were introduced into cages of paired males to elicit sexual competition. Sexual behaviors, social interactions through chemical signals, and dominance relationships were recorded in paired males either of similar age (young or aged pairs), or of mixed ages. In all pairs, competition for priority access to females always occurred and dominance relationships were established unrelated to body weight. Although aged animals exhibited significantly less number of sexual and aggressive behaviors, they outranked younger males excepted when reaching oldest age. Independent of male's age, the typical pattern of seasonal rhythm of testosterone was observed, but aged males demonstrated a significant reduction in mean hormonal levels (25.5 +/- 2.8 ng/mL, n = 8) compared to young animals (50 +/- 2.7 ng/mL, n = 8). Moreover, their hormonal response to photoperiod was phase-shifted leading to reduced testosterone values when females entered oestrus. Despite the fact that testosterone levels and sexual behaviors decreased with aging in this primate, older males reached a dominant position, increasing thus their reproductive success.

Aging↗
PubMed1998

Cloning of the presenilin 2 cDNA and its distribution in brain of the primate, Microcebus murinus: coexpression with betaAPP and Tau proteins.

A 1340-bp cDNA fragment encoding the lemurian presenilin 2 protein (PS2) was isolated from a Microcebus murinus brain cDNA library by PCR using oligonucleotide primers based on the nucleotide sequence of the human gene. Analysis of five isolated clones showed that the sequence encoded a 448-amino-acid open reading frame, 95.5% identical to the human and 93.5% identical to the mouse presenilin 2 sequences. However, neither the localization of the 2 positions in PS2 nor that of the 43 positions in PS1 associated with early onset Alzheimer's disease were changed. Expression of the presenilin 2 was detected by RT-PCR and compared with that of presenilin 1 and betaAPP in the brain and in peripheral tissues (liver, kidney, and spleen). Immunohistochemistry with a specific polyclonal antiserum raised against a synthetic peptide from the N-terminal part of the human PS2 showed that the protein is distributed throughout the microcebe brain, in vascular and nerve structures. In cortical and in subcortical areas, PS2 labeling was weak and granular in appearance and was scattered throughout the cytoplasm of many neurones, extending into neurites. The gene expression of PS2 increased with age but was not affected by the presence of numerous amyloid plaques. Double labeling immunocytochemistry detected very few neurones with combined immunoreactivity PS2 and APP, or PS2 and Tau.

Amino Acid Sequence↗
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

Age dependence of the T2-weighted MRI signal in brain structures of a prosimian primate (Microcebus murinus).

Mouse lemurs (Microcebus murinus) are prosimian primates described to be convenient models of brain aging. We observed very high correlations between the T2-weighted magnetic resonance imaging (MRI) signal decrease and the natural logarithm of age in the basal ganglia. The correlation coefficient was higher for the pallidum (r = 0.95, P < 0.0001) than for other structures. We suggest that the ratio of the pallidum intensity divided by the amygdala and temporal lobe intensity should be a valuable non-invasive marker of age and of cerebral aging. It should be particularly useful for the non-invasive assessment of interventions and drugs that affect the aging process.

Aging↗
PubMed1997

[Endobronchial brachytherapy: the Saint-Louis Hospital experience].

PURPOSE: During the evolution of lung cancer, bronchial obstruction is often noticed and is sometimes responsible for serious symptoms. Several methods of desobstruction can be proposed, including brachytherapy. MATERIALS AND METHODS: One hundred forty-nine patients presenting with endobronchial brachytherapy were included into the study. Seventy-three were treated with curative intent, 47 with palliative intent and 29 with a combination of external irradiation and brachytherapy. We usually delivered a series of two 7-Gy fractions (1 cm from the catheter), the treatment being repeated one, two or three times. RESULTS: When all symptoms were taken into account, respiratory function improvement was present in 79% of the patients. Among the 132 tumors that could be evaluated via a new endoscopy 2 months after treatment, 64 (48.5%) were in complete histological remission. The median survival was 14.4 months for the patients treated with curative intent. Eleven massive hemoptysies and 13 radiation bronchitis were observed. CONCLUSION: These results confirm the feasibility and good results related to endobronchial brachytherapy, though controlled studies are needed to better define its place in the therapeutic strategy of bronchial carcinomas.

Aged↗
PubMed1997

Change in photoperiodic cycle affects life span in a prosimian primate (Microcebus murinus).

The lesser mouse lemur, a small prosimian primate, exhibits seasonal rhythms strictly controlled by photoperiodic variations. Exposure to day lengths shorter than 12 h results in complete sexual rest, fattening, lethargy, and reduced behavioral activities; whereas exposure to day lengths greater than 12 h induces sexual activity, an increase in behavioral activities, and high hormonal levels. The objective of this study was to test whether long-term acceleration of seasonal rhythms may affect survival and longevity of this primate. In captivity, acceleration of seasonal rhythms was obtained by exposing the animals to an accelerated photoperiodic regimen consisting of 5 months of long photoperiod followed by 3 months of short photoperiod. The age-specific survival rate in animals exposed from birth to accelerated photoperiodic conditions (n = 89) was compared to the age-specific survival rate of animals maintained under a natural photoperiod (n = 68). Independent of sexes, the mean life span (45.5 +/- 2.1 months) and maximal survival (79.3 +/- 3.3 months) were significantly (p < .01) shortened in mouse lemurs exposed to the accelerated photoperiodic cycle compared to those in animals living under annual photoperiod (63.2 +/- 2.5 and 98 +/- 3.9 months for mean life span and maximal survival, respectively). This reduction of about 30% of life span was not accompanied by a desynchronization of biological rhythms under photoperiodic control and was not related to an increase in reproduction or in duration of time spent in active conditions. However, when the number of seasonal cycles experienced by 1 individual is considered rather than chronological age, the mean life span was 5 seasonal cycles and maximum survival reached 9-10 cycles, independent of sex or of photoperiodic regimen. These results suggest that in mouse lemurs, as in other seasonal mammals, longevity may depend on the expression of a fixed number of seasonal cycles rather than on a fixed biological age.

Aging↗
PubMed1997

[Intrabronchial curietherapy. Experiences at Hôpital Saint-Louis after the treatment of 149 patients].

Endobronchial tumour obstruction threatens to occur in cases of carcinoma of the bronchus throughout the course of the disease. Such patients can benefit from relief of the bronchial obstruction by several techniques which are currently available. We have treated 149 patients with endobronchial radiotherapy. Seventy three patients were treated with a view to cure, 47 with a palliative dose and 29 received endobronchial radiation in complement with external irradiation. The treatment was carried out in series repeated every 15 days until a maximum of three treatments, consisting of two sessions at 24 hour intervals delivering at each session and irradiating of 7 Gy with a 1 cm catheter. All the clinical signs were relieved and in 79% of patients there was a symptomatic benefit. One hundred and thirty two patients were evaluated by control endoscopy two months after the treatment and 64 had a complete histological remission. The median survival was 14.4 months for patients treated with intent to cure. Obtaining a histological remission was a gauge for prolonged survival (median survival 26.5 months), 11 (7.4%) had massive hemoptysis and 13 (8%) irradiation pneumonitis, all of which occurred some time after the therapeutic procedure. The results confirm the feasibility and the good results of endobronchial irradiation in this field and encourage the idea of controlled multi-centre trials in order to assess a placed of endobronchial radiotherapy in the therapeutic strategy of bronchial cancer.

Adenocarcinoma↗
PubMed1995

Sexual responses to urinary chemosignals depend on photoperiod in a male primate.

In male lesser mouse lemurs, testicular size and plasma testosterone levels are controlled by photoperiodic variations but can be modified by urinary cues from conspecifics. To test whether urinary cues may have differential effects on testicular size and testosterone levels depending on the photoperiodic state of the receiver, isolated males were exposed for 4 wk to urinary cues from oestrous females or dominant males:--at the beginning of the breeding season induced by long photoperiod (LD),--during refractoriness to LD leading to spontaneous sexual regression and during sexual quiescence exhibited by males kept in short photoperiod (SD). Urinary chemosignals from females were always stimulatory producing significant increases in testosterone levels. By contrast, urinary cues from dominant males produced significant differential effects on reproductive function. They depressed sexual function only at the beginning of the breeding season. During SD or during refractoriness to LD, chemosignals were stimulatory leading to increases in testosterone levels and full development of testes. These results demonstrate that the same chemosignal may have opposite effect on sexual function of the receiver depending on endocrine mechanisms set up by photoperiod.

Animals↗
PubMed1993

The effect of adrenomedullin on the isolated heart.

A novel peptide found in human blood, adrenomedullin (ADM), has been shown to have systemic vasodepressor activity in the rat. However, the direct effects of ADM on cardiac function are unknown. Results of the present study demonstrate that ADM13-52 possesses marked systemic vasodepressor activity in the anesthetized rat. Although ADM13-52 modestly decreased peak systolic pressure (PSP) indicating mild negative inotropic activity, the present data suggest that bolus administration of ADM decreases systemic arterial pressure by dilating the systemic vasculature. The present data also suggest that only a portion of the ADM molecule is necessary to produce systemic vasodilation.

Adrenomedullin↗
PubMed1993

Removal of the olfactory bulbs modifies the gonadal responses to photoperiod in the lesser mouse lemur (Microcebus murinus).

The sexual activity of the lesser mouse lemur, unlike that of most living primates, is clearly dependent on photoperiod. Males responded to long daylengths (> 12 h light/day) by rapid testicular development and an increase in testosterone levels reaching 65.8 +/- 1.5 ng/ml (n = 12) after 3 wk of inductive photoperiod. Levels were maintained unchanged until 14 wk of exposure to long photoperiod, when spontaneous gonadal regression was observed. Under short daylengths, intact males exhibited regressed gonadal function with low plasma concentrations of testosterone: 5.4 +/- 1 ng/ml. To investigate the effect of olfactory bulb deprivation on gonadal responses to photoperiod, 12 males were bulbectomized (BX) during exposure to either long (n = 8, BX1) or short (n = 4, BX2) daylengths. In both groups of BX males, responses to long or short daylengths were maintained. However, the timing and the amplitude of gonadal responses to photoperiod were modified; BX males underwent a significant delay in testis development and also had reduced testosterone levels (53.3 +/- 2.3 ng/ml and 37.3 +/- 0.9 ng/ml for BX1 and BX2 groups, respectively). Moreover, BX males did not exhibit spontaneous gonadal regression after 14 wk of exposure to long daylengths, indicating that the photorefractory state did not appear, at least under our experimental conditions. In this primate, olfactory bulbs exert an important effect on the neuroendocrinological control of reproductive responsiveness to photoperiod.

Animals↗
PubMed1993

Response to short photoperiod and spontaneous sexual recrudescence in the lesser mouse lemur: role of olfactory bulb removal.

The body weight and sexual activity of the male lesser mouse lemur, a prosimian primate, undergo cyclic changes that are photoperiod-dependent. Exposure to long daylength (LD; 14 h light/day) led to sustained sexual activity, fully developed testes and high plasma testosterone concentrations (228 +/- 25 nmol/l, n = 10). After 14 weeks under LD, a marked decrease in testosterone levels occurred. Gonadal regression was completed within 20 weeks under LD without concomitant changes in body weight. Exposure to short daylength (SD; 8 h light/day) reinforced the sexual quiescence and was associated with a high ponderal gain (from 60 to 110 g). However, independent of the date of gonadal arrest, the sexual activity of males spontaneously resumed at a fixed time after exposure to SD. The testes developed, testosterone concentrations increased to 155 nmol/l and the body weight decreased (from 110 to 80 g) within 20 weeks under SD exposure. The timing for refractoriness appeared very similar under inhibitory and stimulatory photoperiods. This is consistent with the hypothesis that the perception of a critical daylength is used to regulate the timing of the following sexual phase through a mechanism involving photorefractoriness. Contrary to cricetid rodents, a direct response to photoperiodic signals for both body weight and sexual activity were not prevented by olfactory bulb removal in male mouse lemurs. In bulbectomized males (n = 12), sexual activity was stimulated by LD and inhibited by SD. Their plasma testosterone levels, however, significantly differed from those of controls in both photoperiods. Likewise, ponderal cycles remained intact but the fattening phase was delayed and reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Antipyretic effect of tiaprofenic acid in children. Comparative study with paracetamol].

The authors report the results of a randomised, multi-centric study comparing the antipyretic activity of tiaprofenic acid to that of acetaminophen. Seventy nine children of both sexes, aged 8 months to 9 years, having an average temperature at inclusion of 38.5 degrees C (+/- 0.5 degree C), received as a single dose 50 mg of tiaprofenic acid (3.7 +/- 0.9 mg/kg) (40 children) or 100 mg of acetaminophen (7.7 +/- 1.7 mg/kg) (39 children) for upper respiratory tract infection. The rectal temperature was taken regularly over a 6-hour period. Whatever the criteria considered (gradient between the initial temperature and the lowest temperature observed, difference of temperature at the different time points between the two groups), tiaprofenic acid appeared as effective an antipyretic as acetaminophen. Tolerance was good in both groups. Tiaprofenic acid appears as an interesting alternative to acetaminophen in the treatment of fever in upper respiratory tract infections in children.

Acetaminophen↗
PubMed1992

Environmental and social determinants of sexual function in the male lesser mouse lemur (Microcebus murinus).

Environmental factors that regulate the sexual activity of male lesser mouse lemurs have been studied experimentally with more than 60 captive animals over an 8-year period. In this nocturnal Malagasy prosimian, variation in day length is the primary factor controlling seasonal sexual activity. Plasma testosterone concentrations were low (= 9 ng/ml) during short days and reached 60 ng/ml during long days (> 12-hour day). This cyclic pattern persists unchanged when artificial photoperiodic rhythms are applied and is not altered by ageing. The timing of puberty is also regulated by photoperiodic changes. Nevertheless, the sexual activity of the male lesser mouse lemur can be dramatically modified by the social environment. In heterosexual groups, behavioural and physiological components of sexual activity are depressed in all males except the dominant one, whose aggressive interactions are always successful. Intermale sexual inhibition was shown to be mediated by chemical cues present in the urine of dominant or isolated males but not in urine of subordinate individuals. The inhibitory signals possess lipophilic properties and are not contingent on the gonadal activity of the urine donor but are linked to adrenocortical activity. By contrast, chemical signals stimulating the reproductive function of all males are found in the urine of females, the presence of which is required for the establishment of clear dominance among grouped males. Endocrine mechanisms underlying intermale sexual inhibition by chemical cues were analysed. Variations in prolactin strongly suggest that olfaction interacts with the photoperiodic regulation of reproductive function, leading to changes in the sensitivity of the negative feedback effect of testosterone on gonadotrophin secretion. Inhibitory or stimulatory effects of chemical signals are discussed in the context of their functional significance for wild populations.

Aggression↗
PubMed1991

Male influence on oestrous cycles in female woolly opossum (Caluromys philander).

Plasma progesterone concentrations and the occurrence of oestrous cycles were studied in isolated woolly opossums subsequently subjected to male influences during a 40-day period. Pairing (N = 48) or exposure to male urine (N = 15) resulted in all females exhibiting oestrous during the stimulation phase, providing evidence that the activation of ovarian activity in the woolly opossum involves pheromonal cues from males. The latency of occurrence of oestrous in stimulated females depended upon their sexual state before male stimulation. In anoestrous females, the mean latency was 20.7 +/- 0.9 days (N = 35), a value which agrees with the duration of the follicular phase. In females which first entered oestrous before male stimulation, the latency of induced oestrous was inversely correlated to the date of occurrence of the previous oestrous. The inter-oestrous interval was normal (38.1 +/- 1 days, N = 5) when females were in oestrous at the beginning of male stimulation. In contrast, the inter-oestrous interval was significantly shortened (28.7 +/- 2 days, N = 7) or lengthened (51.1 +/- 1.7 days, N = 16) depending on whether females were in the luteal or follicular phases at the beginning of male stimulation. During pairing several females became pregnant and gave birth 24 +/- 0.9 days (N = 13) after copulation. In the woolly opossum, the response to male influences involves mechanisms similar to those observed in eutherians and results in enhancement and synchronization of oestrous cycles in females. Pheromonal interactions could play an important role in synchronizing oestrous cycles in wild females during the dry season, a period when animals regroup to feed on spatially localized food resources.

Animals↗
PubMed1990

Vomeronasal activation by urine in the primate Microcebus murinus: a 2 DG study.

The vomeronasal system (VNS) seems to be functional in some primates and involved in the detection of urinary signals. Anterograde tracing (WGA-HRP) and evoked metabolic activity (2-DG method) were used in order to clarify the conditions under which the VNS is activated in the prosimian mouse lemur. After WGA-HRP deposition at one of the oral entries of the nasopalatine duct, reaction product was observed within the accessory bulb (AOB). 2-DG experiments show that urine in the volatile phase stimulates the main but not the accessory bulb (AOB). Liquid urine produced bilateral or unilateral activation of AOB depending on whether the stimulation was exclusively unilateral or not; under the same conditions distilled water could not produce 2-DG labelling. It is concluded that VNS is activated by urine in the liquid but not the volatile phase. The biological implications of these results are discussed.

Animals↗
PubMed1989

Plasma concentrations of progesterone and testosterone in captive woolly opossums (Caluromys philander).

Plasma testosterone and progesterone concentrations were measured in captive woolly opossums, a didelphid marsupial originating from neotropical forests in French Guyana. Although not exposed to cyclic environmental conditions as in the field, both sexes exhibited spontaneous circannual changes in sexual hormones. Males showed synchronous variations in plasma testosterone characterized by significant elevated concentrations during April and September (8.6 +/- 1 ng/ml, N = 5) and lower levels from May to July (3.6 +/- 0.4 ng/ml). In females, synchronous periods of 2-3 successive oestrous cycles occurred. Between these periods, females remained acyclic. The oestrous cycle, determined by urogenital smears, lasted 28-45 days (n = 14) and included a 20-day spontaneous luteal phase in which progesterone concentrations reached 30-40 ng/ml plasma. Even though testosterone concentrations in paired males increased significantly in response to oestrous periods of the paired females, spontaneous circannual rhythms of sexual activity were not well synchronized between the sexes in captivity. When compared to field data, sexual activity of captive animals followed a pattern similar to that in wild animals, without any changes in males but with a delay of 3 months in females.

Animals↗