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Biomedical subjects

C T Snowdon

Publications and source records attributed to C T Snowdon.

At least 19 recordsLinked to original sources
PubMed2000

Gonadal source of testosterone metabolites in urine of male cotton-top tamarin monkeys (Saguinus oedipus).

Examining gonadal function in the small excitable cotton-top tamarin monkey (Saguinus oedipus) requires noninvasive sampling techniques. Two studies were performed to identify the quantifiable urinary metabolites of testosterone in cotton-top tamarins and which of the measurable metabolites would best reflect a gonadal source of testosterone secretion. In the first study, we injected unlabeled testosterone i.m. in males at either 500-ng or 1-microg levels. Urine samples were analyzed for androgens and estrogens. Testosterone and dihydrotestosterone (DHT) increased significantly following the injections in test males but not in control males. No significant increases in androstenedione occurred. Mean levels of estradiol and estrone did not consistently increase during the 5 days following injection. In the second study, a gonadotropin-releasing hormone antagonist, Antide, was used to block LH stimulation of gonadal steroidogenesis. Males given Antide at either a 6 mg/kg dose or an 18 mg/kg dose showed significantly lower levels of urinary LH than controls. At the higher Antide dose, testosterone levels were significantly reduced during weeks 1 and 2 posttreatment, whereas DHT levels significantly declined during the 2nd week posttreatment. Estradiol levels were highly variable prior to treatment but decreased significantly following treatment, whereas estrone levels remained variable throughout. These results indicate that measurement of urinary testosterone and possibly DHT reflect gonadal function in male cotton-top tamarins. Other sources of urinary estrogens may occur for the male cotton-top tamarin, but these data suggest that a substantial part of urinary estradiol is from gonadal sources, whereas urinary estrone appears to be mainly from extragonadal sources.

Androstenedione↗
PubMed1998

Chemical communication of reproductive status in female cotton-top tamarins (Saguinus oedipus oedipus).

Among Callitrichids, scent secretions have been identified as carrying information regarding species, subspecies, gender, social status, individuality, hormonal status, and timing of ovulation. We propose that information regarding familiarity and reproductive status is also communicated. Seven male-female pairs of cotton-top tamarins (Saguinus oedipus oedipus) were presented with several drops of distilled water, a scent secretion from the female of that pair, scent secretions from unfamiliar, reproductively mature but noncycling females, and scent secretions from unfamiliar, reproductively cycling females. Behavioral responses from both males and females were recorded over a 10 min period. Differences in behavioral response for both males and females were significant across all four conditions. This indicates that cotton-top tamarins are capable of discriminating a familiar scent from an unfamiliar scent as well as the reproductive status of an unfamiliar female. The communication of this information may play an important role in regulating mate selection, reducing reproductive competition, and stabilizing transfers in and out of groups in the wild.

Animal Communication↗
PubMed1997

Affiliative processes and vocal development.

Affiliative behavior is often expressed through communication, and the nature of affiliative interactions affects the ontogeny of communication. I presented three phenomena that demonstrate the importance of affiliation in vocal development in marmosets and tamarins, but the results have parallels in many other species including birds, dolphins, and humans. Pygmy marmosets use trill-like vocalizations to maintain contact with other group members. Individuals change subtle aspects of call structure when they encounter new social groups or acquire a new mate. This process of vocal accommodation is common in many other species. Infant pygmy marmosets go through a stage of "babbling." producing long sequences of vocalizations that have several similarities to the babbling of human infants. Babbling infants receive more social attention than nonbabbling infants, and these social interactions may shape vocalizations towards more adult forms. In adult cotton-top tamarins, food-associated vocalizations communicate the presence and quality of food. However, reproductively inhibited juveniles and subadults use many other types of calls in feeding situations and display a high proportion of imperfect forms of adult food-associated calls. When subadult monkeys are paired with new mates and change their reproductive status, they rapidly (within 3-6 weeks) display both adult structure and adult usage of food-associated calls, suggesting that affiliative processes can both facilitate and inhibit vocal ontogeny. Three mechanisms of how social interactions affect communication (multimodal stimulation, attentional focus, and reinforcement) were proposed and illustrated through examples of parrots learning English labels for objects and attributes and infant cotton-top tamarins acquiring food-associated vocalizations.

Animals↗
PubMed1997

Reproductive events of wild cotton-top tamarins (Saguinus oedipus) in Colombia.

Reproductive patterns of wild cotton-top tamarin (Saguinus oedipus) females located in La Reserva Forestal Protectora Serranía de Coraza-Montes de María in Colosó, Colombia, were examined using long-term behavioral observations and fecal steroid analysis. Using an enzyme immunoassay, we analyzed fecal samples for E1C and PdG. Comparisons of reproductive cycles of a reproductively active female and her daughters were made. An inhibition of ovarian cycles has been observed in daughters living in their families. However, daughters also exhibited normal ovarian cycling that subsequently resulted in pregnancy. Factors influencing the fertility are discussed as they relate to the reproductive strategies of wild cotton-top tamarin females.

Animals↗
PubMed1997

Ovarian function of pygmy marmoset daughters (Cebuella pygmaea) in intact and motherless families.

Reproductive inhibition of subordinate Callitrichid group members has been shown to vary with genus; whereas female Leontopithecus subordinates have normal ovarian cycles and occasionally breed within groups, subordinate Saguinus females almost never do so, with Callithrix species showing intermediate levels of reproductive inhibition. No information has been available on patterns of reproduction or inhibition in subordinate females in the genus Cebuella. We assessed fertility in Cebuella pygmaea daughters to allow comparison with the remaining Callitrichid genera. Specifically, the project had two goals: 1) to determine if there was evidence of reproductive inhibition of daughters living in family groups, and 2) to compare the ovarian function of daughters living in intact family groups with that of daughters residing in motherless families (i.e., without the breeding female). We collected daily urine samples for 6-8 weeks from eight pygmy marmoset daughters living in intact family groups or motherless families. Determination of ovulatory cycling or reproductive quiescence depended on the hormonal profiles generated from urinary luteinizing hormone and pregnanediol-3-glucuronide concentrations. All females in the motherless condition (aged 13-30 months) (n = 4) ovulated during the study. In contrast, only one of four daughters (aged 13-20 months) residing in intact families was found to be cycling. Data from motherless groups indicate ovarian cycling may begin between 15 and 17 months of age. Reproductive inhibition occurs in pygmy marmosets, although in a pattern more similar to Callithrix than to other Callitrichid genera.

Age Factors↗
PubMed1996

Hormonal responses to parental and nonparental conditions in male cotton-top tamarins, Saguinus oedipus, a New World primate.

The socially monogamous cotton-top tamarin (Saguinus oedipus) monkey is a cooperative breeder with the breeding male providing extensive parental care shortly after birth. We examined the relationship of urinary prolactin and cortisol excretion both to male parental care and as a stress response in the cotton-top tamarin monkey. First-morning urine samples were collected to determine hormonal concentrations. Hormonal and behavioral data were collected on 8 male cotton-top tamarins during the 2 weeks before and the 2 weeks following birth of infants to their mate, 11 nonparental males with exposure to females, and three eldest sons from large family groups. Prolactin levels were significantly higher in experienced fathers during the postpartum period than in the other males, while cortisol levels were significantly lower in experienced fathers and eldest sons. Prolactin levels in experienced fathers were consistently elevated before birth, following birth, and after infants were weaned; prolactin levels during times of infant independence were still significantly higher than those in nonfather males. First-time fathers exhibited prolactin levels that were significantly higher after the births of infants than these same males did when they were paired with nonpregnant females. Elevated prolactin concentrations also occurred prior to the first birth, suggesting that males may be receiving cues from their pregnant females. The elevated prolactin levels in parental males may be associated with the experience of the fathers. Correlation between prolactin levels and number of successful births, number of previous births, and age were high. The care of newborn infants did not appear to be a stressful event since cortisol levels were not elevated postpartum. Both cortisol and prolactin were elevated following capture and injection of saline or a dopaminergic receptor antagonist, indicating that prolactin does respond to acute stress. Cortisol levels did not coincide with prolactin levels except under acute stress conditions, suggesting that different neural pathways are probably involved in prolactin release during parental care versus acute stress. These studies provide evidence that male urinary prolactin levels may be elevated due to cues from pregnant females and the constant exposure of males to the family environment.

Animals↗
PubMed1996

Metabolism of reproductive steroids during the ovarian cycle in two species of callitrichids, Saguinus oedipus and Callithrix jacchus, and estimation of the ovulatory period from fecal steroids.

Gonadal steroids were measured in daily fecal samples providing comparative data on steroid metabolism in two genera of New World primates. Circulating bioactive LH and progesterone concentrations and fecal progesterone, pregnanediol, estradiol, and estrone concentrations were measured by collecting blood and daily fecal samples from four captive common marmoset females and four cotton-top tamarin females for 30 days. High recoveries (> 80%) of labeled steroids that were added directly to the feces before extraction were recovered from feces of both species. Because of the presence of complex steroid conjugates, only one fifth the amount of estradiol was measured without solvolysis as compared to the amount measured with solvolysis. In tamarins, steroids were metabolized rapidly, with all postovulatory increases occurring within two days after the circulating LH peak (an increase of 2 SD higher than mean follicular levels). In marmosets, steroid excretion was slower; increased steroid levels occurred 2-4 days after the LH peak except in the case of estrone, which did not consistently increase after the LH peak. Circulating estrone and estradiol both contributed to the high excretion of estradiol in the feces from both species. The timing in the delay in excretion of fecal steroids was used to accurately determine the ovulatory period to within a 2-day window. This degree of accuracy is possible when the duration of the delay to the LH peak is known for a given species. Additionally, steroid concentrations were highly correlated between frozen and lyophilized fecal samples (0.81 +/- 0.07 SEM), indicating that fluid removal from the feces did not effectively alter steroid profiles.

Animals↗
PubMed1995

The relationship of cortisol levels to social environment and reproductive functioning in female cotton-top tamarins, Saguinus oedipus.

Cortisol levels were examined in 17 cotton-top tamarin monkeys (Saguinus oedipus) to determine: (1) if first-morning void urine sampling could be used as a noninvasive method for monitoring cortisol excretion, (2) if capture and bleeding were associated with changes in urinary cortisol levels, (3) the relative cortisol levels in reproductively active and reproductively suppressed females, and (4) the relationship between cortisol levels and changes in social condition in cotton-top tamarins. Mean urinary cortisol levels during ovarian cycling did not differ between captured and bled females and undisturbed females. Mean cortisol levels were significantly lower in females who were housed in their natal groups and reproductively suppressed than in the same females when they were removed and placed adjacent to a novel male and ovarian cycling began. For all females, mean cortisol levels were higher during the periovulatory period than during the nonperiovulatory period of the ovulatory cycle, with mean cortisol levels higher in newly cycling females than in long-term cycling females. No differences were found in mean cortisol levels between long-term cycling females and prepubertal females and postpubertal natal females. Cortisol levels from long-term cycling females were much lower than during the first two to three ovarian cycles occurring in newly cycling female tamarins, during the last part of pregnancy, and during the first 6 weeks postpartum. These data provide evidence that (1) suppression of ovarian cycling in postpubertal females remaining in their natal family is not associated with stress-induced changes in cortisol levels, (2) cortisol levels are not strictly tied to reproductive condition, and (3) social change may be reflected in cortisol elevation.

Animals↗
PubMed1992

Affiliative vocalizations in infant rhesus macaques (Macaca mulatta).

In Experiment 1, infant rhesus monkeys (Macaca mulatta) were separated and then reunited with mothers, united with a male, or placed in an empty cage. Infants girned more when with mothers or the male than when alone. Girns declined over time when infants were united with the male. Coo rates were high when the infant was alone or with the male. Shrieks, barks, and fear-related behavior were higher with the male. In Experiment 2 the vocalizations of infants were examined during separation when alone or when mothers or a male were in the same room. Infants cooed more when mothers or a male were present. Cooing increased over time, with a greater increase in the mothers' presence. Girns were given to both mothers and males, but more were given to mothers. Coos and girns are both affiliative vocalizations but are differentially modulated as infants cease cooing when they receive contact comfort.

Animal Communication↗
PubMed1990

Urinary excretion of oestrone conjugates and gonadotrophins during pregnancy in the Goeldi's monkey (Callimico goeldii).

Oestrone conjugate and LH/CG were measured in the urine of 4 Goeldi's monkeys during 6 pregnancies. The gestational length was a mean of 148.8 days from the post-partum LH/CG peak to parturition. CG was first detected a mean of 18.8 days after the LH/CG peak and values remained elevated for a mean of 44.8 days. Three different gonadotrophin assays were used to detect LH/CG: the mouse in-vitro interstitial cell bioassay, a mixed heterologous LH RIA, and a monkey CG RIA. The mouse in-vitro interstitial cell bioassay was useful for measuring both the LH peak which occurred post partum and the CG concentrations during pregnancy. However, both immunoassays were inconsistent in measuring LH due to poor cross-reactivity or lack of specificity; CG concentrations were measurable. Oestrone conjugates became elevated at the time of the LH/CG peak and concentrations continued to increase throughout pregnancy, reaching peak levels before parturition. The postpartum interval, pregnancy and parturition can therefore be monitored in the Goeldi's monkey by the use of urinary assays: those for bioactive LH and immunoreactive oestrone conjugates to determine the post-partum LH peak and those for immunoreactive LH/CG and immunoreactive oestrone conjugates to follow pregnancy and parturition.

Animals↗
PubMed1990

Nursing does affect the duration of the post-partum to ovulation interval in cotton-top tamarins (Saguinus oedipus).

Reports on callitrichid monkeys have not revealed a significant effect of nursing on interbirth intervals or on post-partum to ovulation intervals. We examined 25 post-partum intervals in cotton-top tamarin females to determine whether nursing infants would affect the length of the post-partum to ovulation interval. Urinary LH/CG and oestrone conjugates were measured in urine samples collected in the 6 weeks after birth. The post-partum to ovulation interval is the number of days between parturition and the rise of urinary LH and oestrone conjugates associated with ovulation. There was an 84% conception rate post partum. Neither mother's parity nor sex of the infants influenced the length of the post-partum to ovulation interval. The post-partum to ovulation interval for females nursing 2 infants was twice as long as for those not nursing or nursing 1 infant (P less than 0.05). The range of post-partum to ovulation interval lengths was more variable in nursing than in non-nursing females (P less than 0.01). Females spent less than 50% of observed time in contact and less than 20% of observed time nursing their infants. Neither the number of tamarins within the family nor the amount of time the mother was in contact with infants correlated with the length of the post-partum to ovulation interval. However, there was a positive correlation between the percentage time that mothers nursed 1 infant at a time and the length of the post-partum to ovulation interval (r = 0.75, P less than 0.02). The underlying mechanisms of suckling-induced delay of ovulation are present in the cotton-top tamarin as in other primate species. However, these nursing effects do not cause the substantial delay in fertility post partum that is associated with non-callitrichid primates.

Animals↗
PubMed1987

The endocrinology of puberty and reproductive functioning in female cotton-top tamarins (Saguinus oedipus) under varying social conditions.

Sexual maturation and fertility were assessed in fourteen cotton-top tamarin (Saguinus oedipus) females under various social conditions. Six tamarin females (20-28 mo of age) showed a suppression of fertility while living with their families. Hormonal profiles demonstrated low, acyclic levels of urinary luteinizing hormone (LH) and estrone-conjugates (E1C). A rapid onset of ovarian and pituitary cyclicity occurred when four of the six females were removed from their families and paired with an unrelated male. In one female, an ovulatory LH peak occurred as early as eight days after pairing and resulted in conception and full-term pregnancy. Two of the six females were housed in total isolation for 30 days following their removal from the family and prior to pairing. Gradual increases in hormone concentrations occurred during isolation; however, there was no ovarian cyclicity until each female was paired with an unrelated male. In all six females, conception occurred before or as a result of the third ovulatory cycle. Partial isolation of a 36-mo-old female resulted in elevated LH and E1C levels, but cyclicity was not observed until the female was paired with an unrelated male. These findings indicate that removal of a female from the family alone does not initiate ovarian cycling. Sexual maturation, or puberty, occurs in female tamarins living with their families between 15 and 17 mo of age when mean LH and E1C levels began to increase. However, when a female is removed and paired at 9 mo of age with an unrelated male, elevated levels of LH and E1C may be seen by 10 and 11 mo of age. Our findings indicate that a suppression of fertility occurs in cotton-top tamarins living with their families, but that reproductive suppression does not affect the process of sexual maturation. Both removal from the family environment and stimulation by an unrelated male tamarin were necessary to induce normal reproductive activity. An acceleration of puberty occurred when a female tamarin was removed from her family early in development and paired with a male.

Animals↗
PubMed1987

Color discrimination by the cotton-top tamarin (Saguinus oedipus oedipus) and its relation to fruit coloration.

Old World monkeys and apes have been reported to differ from New World monkeys in their abilities to discriminate colors across the visible spectrum. Old World monkeys and apes (Macaca, Pan, Pongo) discriminate colors quite accurately, while some New World monkeys studied (Saimiri, Cebus) have shown lower sensitivity to and poorer discrimination of long wavelength light. This study examined the color discrimination ability of another New World primate, the cotton-top tamarin, Saguinus oedipus oedipus (family Callitrichidae). The tamarins were trained to discriminate a set of Munsell color chips, both within the same hue category and from the 2 hue categories on either side of the training hue. Results indicated that the cotton-top tamarin can make accurate discriminations across the visible spectrum. Human subjects were tested under similar conditions in order to compare their color discrimination abilities to those of the tamarins. The tamarins and human subjects had the most difficulty discriminating the same hues. The discrimination abilities of the monkeys were assessed in relation to the coloration of fruits eaten in a natural environment. A list of the species of fruits commonly eaten by various species of New World monkeys was compiled and the coloration of fruits at maturity was noted. It was found that most New World primate species eat fruits whose mature coloration ranges across most of the spectrum.

Adolescent↗