Life Sciences Commons^™

Pubertal And Adult Leydig Cell Function In Mullerian Inhibiting Substance-Deficient Mice, Xiufeng Wu, Ramamani Arumugam, Stephen Baker, Mary Lee

Mary M. Lee

Mullerian inhibiting substance (MIS) causes Mullerian duct regression during sexual differentiation and regulates postnatal Leydig cell development. MIS knockout (MIS-KO) mice with targeted deletions of MIS develop Leydig cell hyperplasia, but their circulating androgen concentrations are reportedly unaltered. We compared reproductive hormone profiles, androgen biosynthesis, and the expression of key steroidogenic and metabolic enzymes in MIS-KO and wild-type (WT) mice at puberty (36 d) and sexual maturity (60 d). In pubertal animals, basal testosterone and LH concentrations in plasma were lower in MIS-KO than WT mice, whereas human chorionic gonadotropin-stimulated testosterone concentrations were similar. In adults, basal LH, and both …

Dioxin Exposure And Age Of Pubertal Onset Among Russian Boys, Susan A. Korrick, Mary M. Lee, Paige L. Williams, Oleg Sergeyev, Jane S. Burns, Donald G. Patterson, Wayman E. Turner, Larry L. Needham, Larisa Altshul, Boris Revich, Russ Hauser

Mary M. Lee

Background: Animal data demonstrate associations of dioxin, furan, and PCB exposures with altered male gonadal maturation. It is unclear whether these associations apply to human populations. Objectives: We investigated the association of dioxins, furans, PCBs and corresponding toxic equivalent (TEQ) concentrations with pubertal onset among boys in a dioxin-contaminated region. Methods: Between 2003-2005, 489 boys were enrolled at ages 8-9 years in a longitudinal study in Chapaevsk, Russia. Pubertal onset - stages 2 or higher for genitalia (G2+) or testicular volume (TV) > 3 ml - was assessed annually between ages 8-12 years. Serum levels at enrollment were analyzed by the …

Male Pubertal Development: Are Endocrine-Disrupting Compounds Shifting The Norms, William Zawatski, Mary Lee

Mary M. Lee

Endocrine-disrupting compounds (EDCs) are synthetic or natural compounds that interfere with endogenous endocrine action. The frequent use of chemicals with endocrine active properties in household products and contamination of soil, water, and food sources by persistent chemical pollutants result in ubiquitous exposures. Wildlife observations and animal toxicological studies reveal adverse effects of EDCs on reproductive health. In humans, a growing number of epidemiological studies report an association with altered pubertal timing and progression. While these data are primarily reported in females, this review will focus on the small number of studies performed in males that report an association of polychlorinated …

Androgen Profiles During Pubertal Leydig Cell Development In Mice, Xiufeng Wu, Ramamani Arumugam, Ningning Zhang, Mary Lee

Mary M. Lee

Postnatal Leydig cell (LC) development in mice has been assumed empirically to resemble that of rats, which have characteristic hormonal profiles at well-defined maturational stages. To characterize the changes in LC function and gene expression in mice, we examined reproductive hormone expression from birth to 180 days, and quantified in vivo and in vitro production of androgens during sexual maturation. Although the overall plasma androgen and LH profiles from birth through puberty were comparable to that of rats, the timing of developmental changes in androgen production and steroidogenic capacity of isolated LCs differed. In mice, onset of androgen biosynthetic capacity, …

Blood Lead Levels And Delayed Onset Of Puberty In A Longitudinal Study Of Russian Boys, Paige Williams, Oleg Sergeyev, Mary Lee, Susan Korrick, Jane Burns, Olivier Humblet, Julie Del Prato, Boris Revich, Russ Hauser

Mary M. Lee

OBJECTIVE: We evaluated the association of blood lead levels (BLLs) with pubertal onset in a longitudinal cohort of Russian boys.

METHODS: A total of 489 Russian boys were enrolled in 2003-2005, at 8 to 9 years of age, and were monitored annually through May 2008. Cox proportional-hazards models were used to evaluate the association of BLLs at enrollment with time to pubertal onset during follow-up monitoring.

RESULTS: A total of 481 boys had BLLs, with a median of 3 microg/dL and 28% with values of > or =5 microg/dL. The proportion of pubertal boys increased with age, from 12% at age …

Physical Growth And Sexual Maturation Of Boys In Chapaevsk, Russia, Mary Lee, Oleg Sergeyev, Paige Williams, Susan Korrick, Vladimir Zeilert, Boris Revich, Russ Hauser

Mary M. Lee

We characterized physical growth and sexual maturation in 2,579 boys, ages 10 through 16.99 years, residing in Chapaevsk, Russia in order to establish region-specific reference data. Age-specific norms were established for height, weight, and BMI, and compared to US reference data by z-score analysis, while mean heights and weights by age were compared to published national Russian data. Compared to US boys, height was slightly lower (overall z-score -0.18) at all ages except the oldest (16-16.99 yr), while weight and BMI were moderately lower (overall z-score -0.52 and -0.61, respectively). Chapaevsk boys were significantly taller (1.15 cm) and thinner (-1.28 …

Short Communication: Relationship Between Body Growth And Mammary Development In Dairy Heifers, L F. Silva, M J. Vandehaar, Brian K. Whitlock, R P. Radcliff, H A. Tucker

Brian K Whitlock, PhD, DVM, DACT

Our objective was to determine if prepubertal rate of body weight (BW) gain, independent of diet, was related to mammary development of dairy heifers. Data from two studies recently conducted at Michigan State University were used to identify factors, within a dietary treatment group, that would account for variation in first lactation milk production or amount of mammary parenchymal DNA at the time of puberty. Factors analyzed for variation in milk production during first lactation were: postpartum BW, prepubertal BW gain, gestational BW gain, postpartum BW gain, body condition score (BCS) at breeding, and BCS at calving. Factors analyzed for …

Effect Of Dietary Protein On Prepubertal Mammary Development In Rapidly Growing Dairy Heifers, Brian K. Whitlock, M J. Vandehaar, L F. Silva, H A. Tucker

Brian K Whitlock, PhD, DVM, DACT

The objective was to determine whether increased dietary protein would enhance mammary development in prepubertal heifers fed for rapid body growth (1.2 kg/d). Fifty-four Holstein heifers (weighing approximately 134 kg) were assigned to one of three treatments. Heifers were fed a total mixed ration with metabolizable energy at 2.85 Mcal/kg and metabolizable protein at low, standard, or high concentrations (37, 41, or 44 g/Mcal of metabolizable energy, respectively) from 3.5 mo of age until slaughter at approximately 46 d after puberty. Heifers fed low, standard, and high protein gained 1130, 1170, and 1180 g/d, respectively. Dietary protein did not affect …