Urinary Chemosignal Research Articles

Monte-Carlo methods for determining optimal number of significant variables. Application to mouse urinary profiles

Three methods for variable selection are described, namely the t-statistic, Partial Least Squares Discriminant Analysis (PLS-DA) weights and regression coefficients, with the aim of determining which variables are the most significant markers for discriminating between two groups: a variable’s level of significance is related to its magnitude. Monte-Carlo methods are employed to determine empirical significance of variables, by permuting randomly the class membership 5000 times to obtain null distributions, and comparing the observed statistic for each variable with the null distribution. Seven simulations consisting of 200 samples, divided equally between two classes, and 300 variables, are constructed; in one dataset there are no induced correlations between variables, in two datasets correlations are induced but there is no induced separation between the classes, and in four datasets, separation is induced by selecting 20 of the variables to be discriminators. In addition two metabolomic datasets were analysed consisting of the GCMS of urinary extracts from mice both to determine the effect of stress and to determine the effect of diet on the urinary chemosignal. It is shown that the t-statistic combined with Monte-Carlo permutations provides similar results to PLS weights. PLS regression coefficients find the least number of markers but, for the simulations, the lowest False Positives rates.

Pregnancy in female house mice exposed to urinary chemosignals from other females.

Seven experiments were performed to investigate pregnancy termination, urinary chemosignals, and litter sex ratio variation in female house mice. Experiments tested the effects of urine from adult and prepubertal females, housed individually or in groups, on successful insemination and litter production by females treated at different times and for different periods during the 3 weeks before mating and during gestation. Treatment of females with urine from adult females housed eight per cage or with urine pooled from eight adult females housed individually for 2 or 3 weeks before mating resulted in fewer successful pregnancies and significantly more female-biased litters. Treatment with urine from adult or prepubertal females housed eight per cage or with urine pooled from eight mice housed individually for the first 6 days of gestation or throughout pregnancy resulted in a significant increase in the rate of pregnancy termination. These treatments resulted in lower body weights at birth and slower growth rates in all males and in some females. Puberty was delayed in female progeny from urine-treated dams in five of seven experiments, and these young females attained first oestrus at greater mean body weights than mice in other treatments. These findings indicate that, in mice, at high population density, communication via a urinary chemosignal can alter reproduction in recipient females. Availability of, and competition for, resources such as food would be greater at higher densities, possibly lowering the probability of reproductive success. Pregnancy termination and delays in reproduction and attainment of sexual maturity might lead to greater successful reproduction at a later time.

Sexual maturation in male prairie voles: Effects of the social environment

The effects of various social contexts on sexual maturation in captive male prairie voles were investigated. Sexual maturity was assessed as the ability of a young male to produce urine capable of activating a diestrous adult female into estrus, as females remain anestrus until they ingest a male urinary chemosignal. In five experiments the postweaning social environments of developing males were manipulated (e.g., presence or absence of dam, sire, or junior litter, exposure to unfamiliar adult voles, social isolation) to determine if the age at which males begin to produce potent urine was sensitive to social effects. In general, there was no difference in the age of potent urine production as a function of social environment. Findings are discussed in the context of dispersal, inbreeding avoidance, and mate acquisition.

Long-term effect of a urinary chemosignal on reproductive fitness in female mice.

The effect of synthetic 2,5-dimethylpyrazine (a compound naturally produced by grouped females) on the overall reproductive success of female mice was investigated. The exposure of tested females to control or experimental stimuli began on the day of birth and lasted throughout maturation, mating, pregnancy, and the lactating of their first litters. Females exposed to this urinary compound attained their first estrus significantly later than the animals exposed to water only. On average, the prepubertal, exposed females reached puberty 3.7 to 3.9 days later than the unexposed animals. The females in which puberty was delayed by this synthetic chemosignal did not show a single fully completed estrous cycle before the age of 35 days. Only 52-64% of exposed females successfully bred and reared their litters as compared to 86-96% of the unexposed, control females (p < 0.05). A significantly higher mortality of pups associated with 2,5-dimethylpyrazine exposure during lactation was observed. The reproductive deficit displayed by females born into a 2,5-dimethylpyrazine environment is qualitatively similar to the effect observed in dense populations, in both laboratory and free-living conditions.

Parental influences on female puberty in the monogamous California mouse, Peromyscus californicus

Sexual maturation of juvenille Peromyscus californicus females was delayed if females were housed with both parents. This delay was attributed to contact with the mother rather than the father. Sexual maturation was not affected by contact with a strange male, but puberty was delayed by contact with a strange female. In subsequent studies, the role of maternal urinary chemosignals and physical contact in delaying puberty was examined. Exposure to maternal urine or soiled bedding had no effect on sexual maturation in juvenile females. Puberty was delayed in juvenile females that had direct physical contact with their mother compared with females not exposed to their mother. Females exposed to their mother, but prevented physical contact by a double wire-mesh barrier, showed an intermediate delay in sexual maturation which did not differ significantly from either the contact or unexposed females. Thus physical contact with the mother and not a urinary chemosignal per se is necessary to delay sexual maturation in P. californicus.

Mechanisms mediating the operation of puberty-influencing chemosignals in wild mice, Mus musculus domesticus

Acceleration of puberty in juvenile females ceased to occur when they were denied direct contact with adult males. On the other hand, the delay in pubertal onset in juveniles in the presence of adult stimulus females persisted in the absence of physical contact. These results suggest that the male urinary chemosignal is nonvolatile and acts through contact. In contrast, the female factor, seems to be a volatile chemosignal that does not require contact for operation.

Urinary chemosignals, reproduction, and population size for house mice (Mus domesticus) living in field enclosures

The effects of urinary chemosignals influencing reproduction and puberty were studied in free-living house mice maintained in six 0.1-ha outdoor enclosures. Two enclosures were provided with urine and soiled bedding from male mice, two with urine and soiled bedding from group-caged female mice, and two with water and clean bedding as a control. Reproduction, puberty, recruitment, and population size all were affected by the urine treatments. Overall, populations reached significantly greater numbers in the enclosures treated with male urine and soiled bedding, intermediate levels with the water and clean bedding treatment, and were lowest for enclosures treated with urine and soiled bedding from grouped females. The population differences resulted from urinary chemosignal effects on adult female reproduction and female puberty; in general, females were in higher states of reproductive condition, more pregnancies occurred, and young females attained puberty earlier in male-treated enclosures and later in female-treated enclosures than in control enclosures. Urinary chemosignals that affect endocrine physiology and related reproductive processes may be one mechanism by which various factors influence population size in house mice.

A maternal chemosignal maintains paternal behaviour in the biparental california mouse, Peromyscus californicus

Relatively little is known about the proximate mechanisms underlying paternal behaviour in mammals. Paternal behaviour in the biparental California mouse, Peromyscus californicus, is maintained during the first 3 days postpartum by the male's mate and by maternal excreta. Here, it is reported that (1) maintenance of paternal responsiveness is specific to the male's mate. Fathers exposed to excreta from their mates were significantly more likely to exhibit parental behaviour than fathers exposed to virgin or lactating female excreta, or no excreta. (2) Mere familiarity with a female was not sufficient to maintain paternal behaviour. (3) Maternal urine was sufficient to maintain paternal solicitude. Fathers given 100 μl of maternal urine on their nares twice a day were parental compared to fathers similarly exposed to distilled water. (4) The maternal urinary chemosignal(s) was contained in the volatile fraction of maternal urine.

Intermittent stimulation and delay of puberty by urinary chemosignals and social contact in wild stock female house mice (Mus Domesticus)

A sequence of six experiments using wild stock house mouse ( Mus domesticus) tested the effects of intermittent stimulation with either the urinary chemosignal released by grouped female mice or social contact from grouped females on the age of first vaginal oestrus in young females. Weanling female mice were exposed to bedding soiled by grouped females or cages containing grouped females for 15 min periods, then removed for a prescribed period, and placed again in a cage with soiled bedding or grouped females. The nature of the exposure to the puberty delaying effect, the number of total exposures each day, the total length of exposure to the stimulus, and the total time period over which the exposures occurred were varied. None of the treatment regimes employed here with soiled bedding from grouped females resulted in delays in the onset of first oestrus in test females. Young females exposed to grouped females for 6 or 8 exposures in a 4 h period, 6 or 8 exposures in an 8 h period, or 8 exposures in a 12 h period were significantly delayed in attaining puberty relative to control females that were exposed to cages containing clean bedding. These results are in contrast to earlier findings involving chemosignals that accelerate first oestrus wherein young females exhibited the capacity to accumulate the exposures to the urinary chemosignals from males, females in oestrus and pregnant or lactating females. Direct exposure to the grouped females on an intermittent basis can provide stimulation that is cummulative and results in delays in the onset of first oestrus.

Multiple exposures to adult males and reproductive activation of virgin female [formula omitted

Virgin female Microtus ochrogaster living in family groups were reproductively activated by twelve 1-hr exposures over a 3-day period to unrelated sexually experienced males. Reproductive activation among virgin females receiving six or eight exposures over a 2- or 3-day period did not differ significantly from that of unexposed control females. Thus, frequent multiple exposures to unfamiliar males (and repeated stimulation by a male urinary chemosignal) can override the reproductive suppression typically experienced by virgin females remaining in family groups.

T-locus effects on the male urinary chemosignal that accelerates puberty in female mice

T-locus effects on the male urinary chemosignal that accelerates puberty in female mice

Intermittent stimulation and acceleration of puberty by urinary chemosignals in female mice (Mus musculus domesticus).

A sequence of 17 experiments was used to test the effects of intermittent stimulation with urinary chemosignals on the age of puberty in young female mice. The three chemosignals tested all accelerate the age of sexual maturation: urine from adult males, urine from females in estrus, and urine from females that are pregnant or lactating. The basic technique involved presenting the prepubertal females with 'Nestlets' on which the urine was placed. The 'Nestlets' were placed in the cages of the test females for a 15-min period, removed for a variable period, and then replaced in the cage for 15 min. In this manner it was possible to vary the number of exposures, the total length of exposure, and the total time period over which the exposures occurred. Control procedures, involving exposures of young females to cotton squares with water rather than urine placed upon them, resulted in no alterations in puberty relative to untreated females. For mice exposed to the urine-treated cotton squares, acceleration of puberty occurred with less total stimulus-exposure time when the stimulus was presented in short exposures over a number of hours than in previous investigations when the exposure to the urinary chemosignal occurred in a single block of time of one or two hours. For each of the three acceleratory chemosignals, there was a diminution of acceleratory effect when the ratio of total stimulus-exposure time to total exposure time grew smaller. This diminution was more pronounced for urine from pregnant or lactating females than for urine from males or from females in estrus.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of a Puberty-Regulating Chemosignal in Wild Mouse Populations

The density of females in wild house mouse populations confined to highway cloverleafs was experimentally altered by adding foreign females. Urine collected from resident females before and after the additions was tested for its ability to delay puberty in juvenile female mice. Only urine collected after density was increased caused a significant delay of puberty. These results suggest that a urinary chemosignal produced in response to increased density may reduce population growth rate by increasing generation time. In a separate study, the fate of female mice introduced to a highway cloverleaf population was examined. Intensive mark-recapture trapping during 3 weeks following introduction of foreign females revealed high mortality and/or emigration rates for this group. However, the interlopers remained on the cloverleaf long enough to transiently increase the female interaction rate, which presumably mediates production of the puberty-delay pheromone.

Effects of urine from females in oestrus on puberty in female mice.

A series of 9 experiments was conducted to examine various characteristics of the urinary chemosignal found in the urine of oestrous female mice that accelerates the sexual development of conspecific females. This urinary chemosignal was effective in doses as small as 0.001 ml/day, was present in excreted and bladder urine, required 3 days of treatment starting before Day 29 of age to effect an acceleration of puberty, required a minimum daily exposure of 2 h, and was relatively nonvolatile. In addition the chemosignal from oestrous females was effective in summer but not in winter months, was significantly more effective when collected at the middle or end of the dark portion of the daily cycle than at the beginning of the dark phase or middle of the light phase, and was not affected by food deprivation or shortened photoperiod. Simultaneous treatment of test subjects with urine from oestrous females and grouped females resulted in delays in puberty and simultaneous treatment with urine from oestrous females and urine from males or pregnant or lactating females did not result in any enhanced acceleration of puberty.

Hormonal regulation of chemosignals of female mice that elicit ultrasonic vocalizations from males

Two experiments examined the properties of vaginal, facial, salivary, and urinary odors from female house mice to elicit ultrasonic vocalizations from male mice. Experiment 1 demonstrated that facial and salivary secretions from hypophysectomized females were significantly less effective in eliciting ultrasonic vocalizations from male mice than were these same secretions from either intact or ovariectomized females. Thus the hormonal control of chemosignals from these two sources paralleled earlier findings of pituitary rather than ovarian regulation of the urinary chemosignal that elicits ultrasounds. In contrast, ovariectomy and hypophysectomy seemed to have similar depressive effects upon the vaginal cue that elicits ultrasounds. Experiment 2 demonstrated that long-term ovariectomy (8 or 9 months) diminished the effectiveness of female saliva, but not urine, to elicit vocalizations. The apparent dissociation of the hormonal regulation of salivary, vaginal, and urinary chemosignals suggests that multiple chemosignals may possess the property of eliciting male vocalizations.

An accessory sex gland aggression-promoting chemosignal in male mice.

The present study investigated male murine accessory sex glands as potential sources of a urinary aggression-promoting chemosignal. Experiments 1-4 were designed to determine whether the removal of the following glands would eliminate voided urine chemosignal activity: vesicular and coagulating glands, Cowper's gland, prostate gland, or preputial gland. The findings indicate that only preputialectomy eliminated the aggression-promoting properties of voided urine, which provides evidence that this gland is a necessary condition for chemo-activity. The efficacy of the preputial gland as sufficient for chemosignal production was examined in Experiment 5. Urine from males that had an intact preputial but removed vesicular, coagulating, Cowper's, and prostate glands was assessed and shown to possess the chemocue. It was concluded that the presence of a functional preputial gland is a necessary and sufficient condition for providing an accessory sex gland aggression-promoting chemosignal.

Mouse vomeronasal organ: Effects on chemosignal production and maternal behavior

Adult male mice excrete a urinary chemosignal that accelerates puberty in females, whereas group-housed female mice excrete a urinary chemosignal that delays puberty in young females. We found that: (1) the excretion of the puberty-acceleration chemosignal by males persisted in the absence of the vomeronasal organs and (2) the puberty-delay chemosignal was not present in the urine of group-housed females whose vomeronasal organs had been surgically removed (VNX), but was present in the urine of group-housed females subjected to sham surgery (SHAM). These results suggest that in males, vomeronasal chemoreception does not affect the excretion of the puberty-acceleration chemosignal, but that in females, the vomeronasal organ receives chemosignals that influence the excretion of the puberty-delay chemosignal. Additionally, we found no difference between SHAM and VNX females in rates of conception, litter size, pup growth, pup recognition, or maternal behavior, indicating that normal maternal processes are expressed in the absence of an intact accessory olfactory system.

Acceleration of Puberty by a Urinary Chemosignal from Pregnant and Lactating Mus musculus

Acceleration of Puberty by a Urinary Chemosignal from Pregnant and Lactating Mus musculus

Acceleration of puberty in female mice by a urinary chemosignal from pregnant or lactating females: Timing and duration of stimulation

Six experiments were designed to test the acceleration of puberty in young female mice treated with urine from pregnant or lactating females. Manipulations involved varying the age of onset for and duration of treatment with urine. For both urine sources the findings were similar: 1 day of treatment was insufficient to accelerate puberty, but a minimum of about 3 consecutive days of urine exposure begun before the mice were 30 days of age did hasten the onset of first vaginal estrus.

Effect of period of grouping of donors and duration of stimulus exposure on delay of puberty in female mice by a urinary chemosignal from grouped females.

Females housed at a density of 8 mice/cage had to be grouped for a minimum of about 10 days before their urine was capable of producing delays for first vaginal oestrus in test females comparable to the delays occasioned by treatment with urine from females grouped for 30 days or longer. Young test females had to receive a minimum daily exposure of 1-2 h to the chemosignal to produce the complete delay of puberty.