Treating heifers with GnRH from 4 to 8 weeks of age advanced growth and the age at puberty

In heifer calves, an early transient increase in circulating concentrations of LH is associated with early follicular development and is thought to regulate the timing of puberty. In an attempt to hasten the onset of sexual maturity, the early rise in LH concentration was advanced by injecting heifer calves with 120 ng/kg of GnRH (n=6) twice daily from 4 to 8 weeks of age; control calves received saline (n=6). Blood samples were collected every 15 min for 10h at 4, 8, 14, 20, 26, 32, 38, 44 and 50 weeks of age. Treatment with GnRH increased mean circulating concentrations of LH at 8 weeks of age (P<0.05), LH pulse frequency at 4 and 8 weeks of age (P<0.05), and reduced the mean age at puberty by 6 weeks (56.8+/-1.7 versus 62.8+/-2.4 weeks of age, for GnRH treated and control calves, respectively; P=0.04). Body weight gain was greater in GnRH-treated calves than control calves (P<0.05), and the rate of weight gain was shown to be a significant covariate within age at puberty. In conclusion, we suggest that the timing of the early rise in LH concentrations is a critical signal involved in the timing of puberty in heifers.     

Effect of in-utero exposure to diethylstilbestrol on age at onset of puberty and on postpubertal hormone levels in boys.

A group of boys exposed to diethylstilbestrol (DES) in utero who had earlier been found to have urogenital abnormalities were studied for evidence of later effects of DES on their health, physical development and hormonal status. They showed no difference in age at onset of puberty, development of sexual characteristics or hormone levels from boys of the same age who had not been exposed to DES. However, the exposed group tended to have smaller testes.     

Variation in maxillary sinus anatomy among platyrrhine monkeys

Variations in the maxillary sinus anatomy of extant and fossil catarrhine primates have been extensively examined using computed tomography (CT), and have potential utility for phylogenetic analyses. This approach has also been used to demonstrate its anatomical variation in eight of the 16 extant genera of platyrrhines and the absence of the sinus in Saimiri and Cacajao. We used this approach to evaluate the three-dimensional anatomy of the maxillary sinus in all extant platyrrhine genera, and here argue the phylogenic implications of this variation. This study confirms, for the most part, previous CT studies and augments them with the six genera not studied previously: Ateles, Lagothrix, Callithrix, Cebuella, Pithecia and Chiropotes. The entire maxilla is pneumatized by the sinus in the atelines, Cebus, and Callicebus, whereas the sinus pneumatizes only the medial part of the maxilla in the callitrichines and Aotus. Pithecia has a unique conformation in which the maxillary sinus and the expanded inferior meatus pneumatize the posteromedial and anterolateral parts of the entire maxilla, respectively. Chiropotes has no sinus, and the inferior meatus possibly expands into the area between the middle meatus and medial surface of the maxilla to disturb sinus formation, as in the case of its close relative Cacajao. Finally, we argue that the sinus that pneumatizes the entire maxilla is a primitive feature in extant platyrrhines and was probably shared by the last common ancestor of the anthropoids.     

Variation in gaze-following between two Asian colobine monkeys

Gaze-following is a basic cognitive ability found in numerous primate and nonprimate species. However, little is known about this ability and its variation in colobine monkeys. We compared gaze-following of two Asian colobines—François’ langurs (Trachypithecus francoisi) and golden snub-nosed monkeys (Rhinopithecus roxellana). Although both species live in small polygynous family units, units of the latter form multilevel societies with up to hundreds of individuals. François’ langurs (N = 15) were less sensitive to the gaze of a human experimenter than were golden snub-nosed monkeys (N = 12). We then tested the two species using two classic inhibitory control tasks—the cylinder test and the A-not-B test. We found no difference between species in inhibitory control, which called into question the nonsocial explanation for François’ langur’s weaker sensitivity to human gaze. These findings are consistent with the social intelligence hypothesis, which predicted that golden snub-nosed monkeys would outperform François’ langurs in gaze-following because of the greater size and complexity of their social groups. Furthermore, our results underscore the need for more comparative studies of cognition in colobines, which should provide valuable opportunities to test hypotheses of cognitive evolution.     

Spatial cognition in rhesus monkeys: male superiority declines with age.

Twelve young (4-7 years of age) and 14 old (20-27 years of age) male and female rhesus monkeys were tested on seven cognitive tasks. Males and females performed similarly on tasks of object memory and executive function, but young males outperformed young females on a spatial memory task (Delayed Recognition Span Test) that requires the identification of a new stimulus among an increasing array of serially presented stimuli. This superior level of spatial ability in young males declined sharply with age, so that old males did not perform significantly better than old females. These findings in the nonhuman primate suggest that biological rather than sociocultural factors underlie the sex differences in cognition and their diminution with age.     

Hand preference in capuchin monkeys varies with age

The purpose of this research was to examine the influence of age on hand preference in capuchin monkeys (Cebus apella). Twenty-two capuchins, aged 6 months to 30 years, were presented with a task that involved reaching for food and a task that involved using sponging tools to absorb juice. Adults exhibited a greater percentage of right-handed actions in each task than did immature subjects. Adults also exhibited a stronger lateral bias than did immature subjects in the sponging task. These results are consistent with hypotheses: a) adult capuchin monkeys are biased toward use of their right hand for reaching; b) adult capuchins exhibit a greater incidence of right-hand preference than do immature capuchins; and c) primates exhibit age-related differences in the strength and direction of hand preference in tasks that involve the use of tools.     

Establishment of spermatogenesis in guinea-pigs at puberty

The establishment of spermatogenesis in the guinea-pig was studied by a microscopic method. The spermatogenesis starts before day 16 and the first spermatozoa appear on day 55. Spermatozoa are seen in the tail of the epididymis on day 60 and in the ductus deferens between day 70 and day 80. Relations exist between increase of testicular testosterone and setting of spermatogenesis in the guinea-pig.     

Variation in length and age at sexual maturity of Atlantic groundfish: a reply

Synopsis The assertion has been made by Halliday (1987) that trends in size and age at maturity of Atlantic groundfish published by Beacham (1983a, b, c, d, e, f) are artifacts induced by errors in determining the sex of an individual, distinguishing between immature and mature fish, sampling fish outside of the regular spawning season, and by nonrandom sampling of the population. In particular, Halliday asserts that for the Atlantic argentine,Argentina silus analysis, the conclusions of Beacham (1983a) that: (1) median length at sexual maturity declined over time; and (2) males matured at older ages than did females are invalid owing to biases in both sampling and analysis. In fact, if some of the biases indicated by Halliday were significant, then the decline in median length at sexual maturity is enhanced and the conclusions of Beacham (1983a) reinforced. Size and age at sexual maturity are dynamic characters in many vertebrate populations, and the fact that they should change for Atlantic groundfish should not be surprising given variable exploitation patterns in the fisheries since 1960.     

Genetic variability of the length of postpartum anoestrus in Charolais cows and its relationship with age at puberty

Fertility records (n = 1 802) were collected from 615 Charolais primiparous and multiparous cows managed in an experimental herd over an 11-year period. The objectives of the study were to describe the genetic variability of the re-establishment of postpartum reproductive activity and the relationship with body weight (BW) and body condition score (BCS) at calving and age at puberty. The length of postpartum anoestrus was estimated based on weekly blood progesterone assays and on twice daily detection of oestrus behaviour. The first oestrus behaviour was observed 69 days (± 25 days s.d.) post-calving and the first positive progesterone measurement (≥ 1 ng mL^-1) was observed at 66 days (± 22 days s.d.) for the group of easy-calving multiparous suckling cows. Estimates of heritability and repeatability were h² = 0.12 and r = 0.38 respectively, for the interval from calving to first oestrus (ICO). Corresponding values were h² = 0.35 and r = 0.60 for the interval from calving to the first positive progesterone test (ICP). The genetic correlation between both criteria was high (r_g = 0.98). The genetic relationships between postpartum intervals and BW and BCS of the female at calving were negative: the genetic aptitude to be heavier at calving and to have high body reserves was related to shorter postpartum intervals. A favourable genetic correlation between age at puberty and postpartum intervals was found (r_g between 0.45 and 0.70). The heifers which were genetically younger at puberty also had shorter postpartum intervals.     

Plasma melatonin rhythm in disorders of puberty: interactions of age and pubertal stages.

A concurrent effect of age and puberty has hampered assessment of the influence of melatonin on human puberty. This study examined the pineal-puberty interaction in 41 subjects (ages 5-17 years) whose puberty was asynchronous from age (constitutional delay, hypopituitarism and idiopathic precocious puberty). Melatonin nocturnal profile was determined using blood samples drawn hourly by constant withdrawal. There was no significant trend for melatonin peak or time peak in pubertal or age groups. The linear correlation between age and melatonin peak was not significant. Thus, neither age nor puberty alone can account for the decline in nocturnal melatonin concentration observed across human development.     

Rise in age of sexual maturation in male Japanese monkeys at Takasakiyama in relation to nutritional conditions

A few reports have suggested the possibility that feeding conditions might affect the sexual maturation of free-ranging Japanese monkeys in provisionized troops. In the present study, the sexual maturation of male monkeys at Takasakiyama in 1984, nine years after the start of restriction of artificial feeding, was examined externally and histologically and the results were compared with data obtained in 1971, when artificial foods were abundantly given. Spermatogenesis was not observed in any of the males under 4.5 years old in the present study, whereas it was noted in some premature 3.5-year-old males and in all males over 4.5 years old in the 1971 study. The age of sexual maturation thus rose by one or more years over the 13-year period from 1971 to 1984. The lag in sexual maturation of the males at Takasakiyama in 1984 could have been induced by the restriction of artificial feeding.     

生长发育期上颌牙列严重拥挤患者30例未拔牙治疗机制探讨

目的:探讨生长发育期牙弓宽度宽变化的可塑性的限度及规律,尽可能减少正畸治疗中拥挤患者的拔牙比率.方法:通过回顾性分析选出我科十年来治疗完成的、采用未拔牙手段治疗成功的病例100例.从中选出30例严重拥挤病例,其中男18例,女12例,平均年龄11.2岁,对其治疗前后牙弓宽度长度及拥挤部位进行比较分析.结果:尖牙唇侧错位造成间隙不足的患者,通过牙弓前段和中段宽度的增加来解除拥挤排齐牙列,治疗前后比较,有显著性差异;牙齿腭侧错位造成拥挤的患者,通过拥挤对应区段长度的增加来解除拥挤,治疗前后比较,差异有显著性.结论:生长发育期严重拥挤惠者可通过牙弓长度或宽度的生长适应性改建而非绝对拔牙手段采解除拥挤.     

Effects of season of birth on the prepubertal pattern of gonadotropin secretion and age at puberty in beef heifers

There is an early transient rise in gonadotropin secretion in spring-born prepubertal heifers and there is an indication that this pattern is different in autumn-born heifers. The effect of season of birth on age and weight at puberty is equivocal. This study was designed to compare the temporal patterns of LH and FSH secretion between spring- and autumn-born heifers and to determine the effects of season of birth on age and weight at puberty. Blood samples from 2 groups of heifer calves born in spring (last week of March, n = 5) or autumn (last week of October, n = 5) were collected every other week from birth to puberty and every 15 min for 10 h at 6, 12, 18, 24 and 32 wk of age. Timing of puberty was determined by measuring progesterone in plasma samples collected every 2 to 3 d starting at 42 wk of age. Age and weight at onset of puberty did not differ between the 2 groups of heifers (P > 0.05); however, the autumn-born heifers tended to mature in a wider range of ages and weights. Based on the 10-h sampling periods, mean serum concentrations of LH and LH pulse frequency and amplitude were higher in spring-born heifers at 18 wk of age than in autumn-born heifers (P < 0.05). In spring-born heifers, LH pulse frequency increased over time to 32 wk of age, and LH pulse amplitude was higher at 12 and 18 wk than at 32 wk of age (P < 0.05). Autumn-born heifers had higher LH pulse frequency at 6 wk and showed a decrease in mean concentrations of LH at 12 and 18 wk of age (P < 0.05). The FSH pulse frequency of spring-born heifers was higher at 12 wk of age than in autumn-born heifers (P < 0.05), FSH pulse amplitude in autumn-born heifers decreased from 6 to 32 wk of age. It was concluded that although the mean age and weight at puberty did not differ between spring- and autumn-born heifers, the range in age and weight at puberty was wider in the autumn-born heifers. The patterns of LH secretion differed between spring- and autumn-born prepubertal heifers, with spring-born calves exhibiting an early rise in LH secretion, while mean serum concentrations of LH decreased during this period in autumn-born heifers.     

Short-day melatonin pattern advances puberty in seasonally breeding rhesus monkeys (Macaca mulatta)

Prepubertal, spring-born females (Group H: N = 5) living outdoors were given a daily injection of melatonin (0.70 microgram/kg, s.c.) late in the afternoon to produce a short-day melatonin pattern equivalent to a night of approximately 14 h. The dose of melatonin produced serum concentrations of melatonin which simply extended, within the 24 h day, the normal endogenous nighttime elevation (80-100 pg/ml). The study was started in March when the females were 23 months of age and continued through January. Parameters of sexual maturation for this group were compared to those of untreated, age-matched females (Group C: N = 5) which also lived outdoors under changing environmental conditions. Melatonin treatment significantly advanced age at first perineal swelling (23.9 +/- 0.5 vs 30.5 +/- 0.2 months) and menarche (26.2 +/- 0.9 vs 31.2 +/- 2.4 months). Since all of the females were spring-born, these events occurred earlier in the year in Group H females (swelling: April vs October; menarche: June vs November). Furthermore, 4/5 Group H females exhibited first ovulation in December at 31.8 +/- 0.3 months. None of the Group C females ovulated during their 2nd year, but all did so the next breeding season at 43.5 +/- 0.3 months. All first ovulations in females had luteal-phase progesterone concentrations elevated for at least 12 days with peaks greater than 3.0 ng/ml. Body weights were similar between groups until the post-menarchial interval when weight gain was greater in the melatonin-treated females. A similar pattern of group differences also was observed for serum concentrations of growth hormone and somatomedin-C. In addition, prolactin concentrations were seasonally elevated during the summer months in both groups, but concentrations fell to nadir values by August in Group H females and remained elevated until October in Group C animals. These results suggest that, in adolescent females housed outdoors, exposure to a short-day melatonin pattern permits sexual maturation to be initiated at an earlier age, allowing first ovulation to occur in the months immediately after menarche. A long-day melatonin pattern, typically experienced by females at this developmental age, may actually delay the initiation of maturational events until the subsequent fall months.