Search PubMed⌕ Search

Biomedical subjects

M Perret

Publications and source records attributed to M Perret.

At least 55 records · Page 3Linked to original sources
PubMed1987

Role of prolactin in a pheromone-like sexual inhibition in the male lesser mouse lemur.

Sexual activity of the male lesser mouse lemur can be induced by a long photoperiod, and plasma testosterone concentrations increase from 20 to 220 nmol/l within 3 weeks of photoperiodic stimulation. When isolated males were exposed to the volatile compounds from the urine of an active dominant male for 4 weeks at the beginning of the long daylight period, they demonstrated a significant decrease in testosterone concentrations (134 +/- 11 nmol/l) compared with controls (210 +/- 26 nmol/l) within 2 weeks. Lowering concentrations of prolactin by daily injections of bromocriptine prevented the decrease in testosterone in males simultaneously exposed to the odorant stimulation. Increasing concentrations of prolactin by daily injections of sulpiride mimicked the effect of the odorant stimulation in males receiving only fresh non-odorized air. The decrease in testosterone was strengthened when sulpiride was administered concurrently with exposure to urine. These results support the conclusion that variations in the concentration of prolactin are involved in the neuroendocrinological process mediating the pheromone-like sexual inhibition in the male lesser mouse lemur. However, daily injections of bromocriptine in males which were photoperiodically stimulated but not exposed to dominant male urine odour, also induced a significant decrease in testosterone concentrations. This finding suggests that two different systems involving prolactin and leading to opposite effects might be implicated in the regulation by environmental factors of sexual activity in the male lesser mouse lemur.

Animals↗
PubMed1986

Social influences on oestrous cycle length and plasma progesterone concentrations in the female lesser mouse lemur (Microcebus murinus).

Plasma progesterone concentrations were recorded during one breeding season in 19 lesser mouse lemur females living in different social conditions. The oestrous cycle length and the progesterone profile mainly depended on the social environment of the female. For totally isolated females, the oestrous cycle lasted 38 +/- 5.7 days and included a 25-30-days spontaneous luteal phase with a progesterone peak about 100 ng/ml between the 20th and 25th days after oestrus, and a prolonged preovulatory period of 10-15 days which could be considered equivalent to the follicular phase of a menstrual cycle. When females were able to communicate through olfactory, visual and auditory signals, the oestrous cycle was significantly lengthened (53.7 +/- 5.9 days). When females had tactile contacts, the oestrous cycle was further lengthened (62.7 +/- 0.8 days). This lengthening of the oestrous cycle was related to an extension of the luteal phase associated with a decrease in progesterone concentrations during this period. In females maintained with one male (paired) or with males and females (heterosexually grouped), large individual variations were shown in cycle lengths or in progesterone concentrations. In these females, cycle lengths and progesterone concentrations were inversely correlated to plasma cortisol concentrations.

Animals↗
PubMed1986

Plasma testosterone-binding globulin-binding capacity in the male lesser mouse lemur (Microcebus murinus): relationship to seasonal and social factors.

Plasma testosterone-binding globulin (TeBG)-binding capacity was determined by equilibrium dialysis in the lesser mouse lemur (Microcebus murinus), a prosimian which exhibits a clear photoperiod-dependent sexual cycle. Plasma TeBG-binding capacity showed significant seasonal changes which were inversely correlated to those of plasma testosterone concentrations. The capacity of TeBG was at its maximum (1.72 +/- 0.4 mumol/l) during the sexual rest period and decreased to 0.98 +/- 0.24 mumol/l during the breeding season when testosterone concentrations were about 200-280 nmol/l. In addition, when males developed a social hierarchy in groups, the decreased sexual function in non-dominant animals was associated with a higher TeBG-binding capacity. However, although TeBG-binding capacity increased when testosterone concentrations decreased either during sexual rest or under social dominance, a positive correlation was found between TeBG-binding capacity and testosterone levels during the breeding season in males with a normal reproductive cycle, i.e. in both isolated and dominant males. This suggests that factors other than sex steroids are involved in the changes in TeBG-binding capacity occurring under seasonal and social influences.

Animals↗
PubMed1985

Diurnal variations in plasma testosterone concentrations in the male lesser mouse lemur (Microcebus murinus).

In 6 isolated adult male lesser mouse lemurs, concentrations of testosterone in plasma were determinated at 6-h intervals over a 24-h period. Blood samples were collected at monthly intervals and for a period of 12 months under natural photoperiod. In this nocturnal prosimian, there were no apparent diurnal changes in testosterone concentrations during the non-breeding season (autumn). During seasonal sexual activity (January-August), diurnal changes in testosterone concentrations were characterized by a significant rise during the light phase. The daily testosterone peak occurred about 8.5 h after sunrise from February to July, but at the beginning (January) or at the end (August) of the breeding season, the daily testosterone peak was displaced to the morning. A circannual testosterone rhythm occurred with the highest testosterone values in May/June and the lowest values 6 months later. The dramatic fall in testosterone concentrations after the summer solstice may be associated with a change in the peripheral metabolism of testosterone.

Animals↗
PubMed1985

[Hemangioma of the pancreas].

A 62 year old woman lacking any alteration in her general condition and without digestive disorders was found fortuitously to have a large mass in the epigastric region. Complementary investigations localized the lesion to the peritoneal cavity, either in the gastrocolic omentum or the mesentery, close to the pancreas. Imaging showed a multicystic heterogeneous structure. A large hemangioma of pancreatic origin was removed at operation.

Angiography↗
PubMed1984

Effects of long-term grouping on serum cortisol levels in Microcebus murinus (Prosimii).

The influence of social interactions on plasma cortisol was studied in captive Microcebus murinus, a prosimian primate. Regardless the group composition, there is an annual variation in cortisol levels characterized by an autumn peak that coincides with the fattening and sexual resting period. The beginning of activity, early in January, is accompanied by a fall in cortisol levels. Cortisol levels are higher in females than in males both in pairs and in heterosexual groups. In paired animals, mean cortisol levels vary around 140 ng/ml in males and 230 ng/ml in females. In all grouped animals, a persistent adrenocortical activation was found and represents a 75 to 120% increase compared to paired animals. Due to the fact that M. murinus, the mouse lemur, is a solitary species with a primitive social structure, the high concentrations of cortisol found in grouped mouse lemurs could be a reaction to persistent social stress. Such high concentrations of cortisol may be related to poor reproductive success of grouped females and could play a major part in the pathological lesions found in males that die while maintained in social groups.

Animals↗
PubMed1984

Sexual inhibition in a prosimian primate: a pheromone-like effect.

The effect of dominant urine odour on plasma levels of testosterone and cortisol was studied in the prosimian primate Microcebus murinus. This species shows a photoperiod-dependent cycle of sexual activity. In particular, mean testosterone levels vary from 15 nmol/l during the annual rest period to 245 nmol/l during the breeding season. When males of this solitary and territorial species are artificially grouped in captivity, they develop a social hierarchy which in turn results in physiological disorders, especially of reproductive function, in non-dominant individuals. Since olfactory behaviours appear to be important in the establishment and maintenance of the social structure, we have tested the effects of dominant odorant signals upon the sexual inhibition observed in male conspecifics. A preliminary experiment showed that a decrease in plasma testosterone concentrations could be induced by dominant scent marks. Furthermore, dominant urine odour alone was found to be sufficient to induce this modification. Plasma cortisol levels also increased in these animals. Conversely, when sexually inhibited males were olfactorily isolated from dominant urine odour, testosterone and cortisol concentrations returned to a normal seasonal level. These effects were observed even in males which had had no previous contact with the dominant urine donor. It is inferred from these results that a pheromone-like process could lead to sexual inhibition in male Microcebus murinus exposed to an odorant urinary signal produced by a dominant individual. Nevertheless, the endocrine response seems to vary according to the seasonal period of the sexual activity cycle which suggests that the social effect described is modulated by other external (e.g. photoperiodic) or internal (e.g. reproductive physiology) factors.

Animals↗
PubMed1982

Stress-effects in Microcebus murinus.

Histological investigations were made over a 10-year period on 164 lesser mouse lemurs that died spontaneously in captivity. The principal lesions found were chronic nephrosis with nephritis which affects 90% of the animals, myocardial necrosis, respiratory insufficiency induced by interstitial pneumonia, fatty changes in the liver, and splenic and gastric lesions. The following are associated with these pathologies: progressive hypothyroidism, stable hypercorticism, slight medulloadrenal hyperactivity, and sexual disorders such as testicular atrophy in males and estrous cycle disturbance or uterine tumor in females. All these data were treated by correspondence analysis; this showed that, except for some rare cases of death which can be attributed to massive parasitic infestation or generalized cancer, the whole captive population of lesser mouse lemurs is suffering from a syndrome that leads to renal insufficiency and death. Most of the observed pathologies are considered as being associated with aging in mammals. But captive Microcebus murinus died between 3 and 4 years of age, whereas their potential life survival is 13 years. Our hypothesis is that these pathologies arise due to an overload of cortico- and medulloadrenal secretions. The above-mentioned hormonal imbalance could be induced by stress factors occurring in captivity, the most important of which would be social stress.

Adrenal Glands↗