Amplitudes of visually evoked potentials to patterned stimuli: Age and sex comparisons

Electrophysiological age and sex differences in visual pattern responsivity were investigated. Pattern reversal evoked potentials (PREPs) and visual evoked potentials (VEPs) to patterned and unpatterned flashes were recorded from 20 normal subjects in each of 4 groups: young females and males aged 25–35 years and older females and males aged 55–70 years. PREP waves N70-P100 and P100-N150 from the older women were significantly larger than those from subjects in the other groups; mean amplitudes for the young females, young males and older males were not different. A similar effect, unusually large potentials for the older women, was obtained for VEPs, but only for VEPs elicited by patterned flashes and recorded from occipital scalp, i.e., an area overlying visual cortex which is sensitive to lines and edges. Our findings suggest that the visual system of older females is unusually responsive to patterned stimuli.     

Life history in male mandrills (Mandrillus sphinx): physical development, dominance rank, and group association

We assess life history from birth to death in male mandrills (Mandrillus sphinx) living in a semifree-ranging colony in Gabon, using data collected for 82 males that attained at least the age of puberty, including 33 that reached adulthood and 25 that died, yielding data for their entire lifespan. We describe patterns of mortality and injuries, dominance rank, group association, growth and stature, and secondary sexual character expression across the male lifespan. We examine relationships among these variables and investigate potential influences on male life history, including differences in the social environment (maternal rank and group demography) and early development, with the aim of identifying characteristics of successful males. Sons of higher-ranking females were more likely to survive to adulthood than sons of low-ranking females. Adolescent males varied consistently in the rate at which they developed, and this variation was related to a male's own dominance rank. Males with fewer peers and sons of higher-ranking and heavier mothers also matured faster. However, maternal variables were not significantly related to dominance rank during adolescence, the age at which males attained adult dominance rank, or whether a male became alpha male. Among adult males, behavior and morphological development were related to a male's own dominance rank, and sons of high-ranking females were larger than sons of low-ranking females. Alpha males were always the most social, and the most brightly colored males, but were not necessarily the largest males present. Finally, alpha male tenure was related to group demography, with larger numbers of rival adult males and maturing adolescent males reducing the time a male spent as alpha male. Tenure did not appear to be related to characteristics of the alpha male himself.     

The interaction between sex and click polarity in brain-stem auditory potentials evoked from control subjects of Oriental and Caucasian origin

Brain-stem auditory evoked potentials (BAEPs) were performed on 30 male and 30 female young normal Oriental subjects, using both condensation and rarefaction stimulation. The effects of sex and click polarity on the BAEP latencies and amplitudes were studied. Females had shorter absolute and interpeak latencies and higher absolute amplitudes than the males. These sex-related BAEP differences were independent of the click polarity. Rarefaction clicks produced shorter wave I latency and longer I–III interpeak latency, but the differences were significant in the female only. The polarity-related BAEP amplitude differences were essentially independent of the sex. BAEPs performed on 60 sex- and age-matched young Caucasian subjects produced similar results. The importance of establishing control BAEP values according to the sex and click polarity is emphasised.     

Characterization of Obese Phenotypes in a Small Nonhuman Primate,the Common Marmoset (Callithrix jacchus)

This report explores aspects of developing obesity in two captive populations of common marmosets (Callithrix jacchus), a small primate with a short lifespan that may be of value in modeling chronic aspects of obesity acquisition and its lifetime effects. Two populations were examined. In study 1, body composition, lipid parameters, and glucose metabolic parameters were measured in a population of 64 adult animals. Animals classified as obese (>80th percentile relative fat based on sex) displayed both dyslipidemia (higher triglyceride and very low–density lipoprotein (VLDL)) and altered glucose metabolism (higher fasting glucose and HbA_1c). Using operational definitions of atypical values for factors associated with metabolic syndrome in humans, five subjects (7.8%) had at least three atypical factors and five others had two atypical factors. A previously unreported finding in these normally sexually monomorphic primates was higher body weight, fat weights, and percent fat in females compared to males. In a second study, longitudinal weight data for a larger population (n = 210) were analyzed to evaluate the development of high weight animals. Differences in weights for animals that would exceed the 90th percentile in early adulthood were evident from infancy, with a 15% difference in weight between future‐large weight vs. their future‐normal weight litter mates as early as 4–6 months of age. The marmoset, therefore, demonstrates similar suites of obesity‐related alterations to those seen in other primates, including humans, suggesting that this species is worthy of consideration for obesity studies in which its fast maturity, high fertility, relatively short lifespan, and small size may be of advantage.     

Umbilical Cord Blood Testosterone and Childhood Internalizing and Externalizing Behavior: A Prospective Study

Antenatal testosterone exposure influences fetal neurodevelopment and gender-role behavior in postnatal life and may contribute to differences in developmental psychopathology during childhood. We prospectively measured the associations between umbilical cord blood testosterone levels at birth and childhood behavioral development in both males and females from a large population based sample. The study comprised 430 females and 429 males from the Western Australian Pregnancy Cohort (Raine) Study where umbilical cord blood had been collected. Total testosterone concentrations were determined by mass spectrometry and bioavailable testosterone (BioT) levels were calculated. At two, five, eight and ten years of age, the participants completed the Child Behavior Checklist (CBCL). Linear regression models were used to analyse the relationship between BioT concentrations (in quartiles) and CBCL scores (total, internalizing, externalizing and selected syndrome). Boys had higher mean CBCL T-scores than girls across all ages of follow-up. There was no significant relationship between cord blood BioT quartiles and CBCL total, internalizing and externalizing T-scores at age two or five to ten combined. In the syndrome score analyses, higher BioT quartiles were associated with significantly lower scores for attention problems for boys at age five, eight and ten, and greater withdrawal symptoms in pre-school girls (age five). We did not identify a consistent relationship between antenatal testosterone exposure and total, internalizing or externalizing behavioral difficulties in childhood. Higher umbilical cord BioT levels were associated with lower scores for attention problems in boys up to 10 years and more withdrawn behavior in 5-year-old girls; however, these findings were not consistent across ages and require further investigation in a larger sample.     

Ontogeny of epididymal sperm reserves during the reproductive lifespan of rats after previous sexual experiences

Epididymal sperm quantity and quality were examined throughout the reproductive lifespan of sexually experienced and inexperienced rats. Males were housed with gonadally intact or ovariectomized females for 2 weeks to 1 year, and epididymides were analysed 1 week to 9 months after the females were removed. Results for the virgin males suggest a peak in sperm numbers at 6 months of age followed by a gradual decline and then notable decrements in sperm numbers and motility by 24 months of age. The same general pattern emerged for sexually experienced males, with two exceptions. There was a chronic increase of sperm numbers relative to those of virgin males at every age examined, and the decline in spermatozoa with ageing was slowed by previous sexual contact. The implications of these data for the ontogeny of fertility are not readily apparent because the epididymis remained reproductively functional throughout the lifespan. We do, however, suggest that epididymides are sensitive to experiential and hormonal changes during adulthood and, most important, the effects of these changes are maintained chronically and into old age.     

Spinal and cortical potentials evoked by tibial nerve stimulation in humans: effects of sex, age and height.

Somatosensory evoked potentials by posterior tibial nerve stimulation at the ankle were performed in 74 healthy volunteers (36 females and 38 males) aged 14-76 years. Cortical potentials were obtained in all subjects and spinal potentials (N22) in 71 subjects. All parameters were related to subject's age, height and sex. Sex influenced only P40-N50 amplitude, which was greater in females. All latencies of spinal and cortical components increased in a similar manner with subject's height (about 0.16-0.18 ms per cm), whereas the N22-P40 interpeak latency was independent from height, but related to T12-Cz distance. Absolute latencies of the spinal and of most cortical components, but not interpeak latencies, increased with subject's age (about 0.06-0.09 ms per year). The parameters to compute normative data (according to univariate or bivariate regression models) are furnished. Limits of right-left differences are reported.     

Auditory event-related potentials in well-characterized groups of children

Sixty-eight subjects ranging in age from 6 to 23 years were studied in an ‘auditory oddball’ event-related potential (ERP) paradigm. Our results replicate other studies, finding P3 as the most consistent component of ERPs since childhood, although great variability of this component was found in the 6-year-old group. Separate age/ERP component latency and amplitude linear regressions were computed for subjects 6–14 and 6–23 years old. Our data show in both groups a significant negative and positive correlation between age and P3 latency and N1-P2 amplitude respectively. The age/P3 latency slope for the subjects under 15 years old was −19.00 msec/year versus 8.15 msec/year for all subjects (6–23 years old). Our results indicate that P3 latency during childhood decreases with age, reaching an asymptote after or during the second decade of life. No curvilinear relationship between age and P3 latency was found over the child groups, although a significant curvilinear relationship was found over the entire age range.This study showed no significant gender differences in latency at any age group. However, in the adult group females showed significantly larger amplitudes than males.     

Craniometric allometry in the thicktailed bushbabyOtolemur Crassicaudatus

Static adult craniometric allometry was evaluated in a sample of 66Otolemur crassicaudatus skulls (34 males, 32 females). Although cranial measures were equally well correlated to skull length in males and females, there were noteworthy differences in the exponential values between the sexes. These results underlined the need for caution when allometric analyses are based on pooled data. From the cranial allometric analyses it is concluded that the longer the skull, the shorter and the narrower the maxilla, and the broader the bizygomatic distance. Although cranial length increased proportionately to the increase in skull length, the cranial width in females was positively allometric whilst in males it was negatively allometric. Allometric analyses of mandibular dimensions suggest that larger animals will have proportionately longer mandibulae, which will, in turn, be relatively wider across the gonia, yet shallower behind the first molars. It is postulated that the disproportionate widening of the zygomata might be related to the widening across the gonia.     

P300 in young and elderly subjects: Auditory frequency and intensity effects

Auditory event-related potentials (ERPs) were assessed in young and elderly subjects when stimulus intensity (40 vs. 60 dB SL) and standard/target tone frequency (250/500 Hz and 1000/2000 Hz) were manipulated to study the effects of these variables on the P3(00) and N1, P2 and N2 components. Auditory thresholds for each stimulus type were obtained, and the stimulus intensity was adjusted to effect perceptually equal intensities across conditions for each subject. Younger subjects demonstrated larger P3 amplitudes and shorter latencies than elderly subjects. The low frequency stimuli produced larger P3 amplitude and shorter latencies than the high frequency stimuli. Low intensity stimuli yielded somewhat smaller P3 amplitudes and longer peak latencies than high intensity stimulus tones. Although additional stimulus intensity and frequency effects were obtained for the N1, P2 and N2 components, these generally differed relatively little with subject age. The findings suggest that auditory stimulus parameters contribute to P3 measures, which are different for young compared to elderly subjects.     

Brain-stem auditory evoked potentials in the rat: Effects of gender,stimulus characteristics and ethanol sedation

Rat BAEPs varied significantly as a function of gender and ethanol sedation as well as stimulus intensity and repetition rate. All BAEP wave latencies decreased and amplitudes increased with increasing stimulus intensity. Contrary to the prevailing view, the I–IV interpeak latency changed significantly as a function of stimulus intensity. In terms of repetition rate, all BAEP wave latencies increased and amplitudes decreased with increasing repetition rate. Male rats, compared to females, had significantly longer latencies for several BAEP components and interpeak latencies as well as smaller wave II amplitudes across a broad range of stimulus intensities. Males, compared to females, also had longer BAEP wave IV latencies and I–IV interpeak latencies at a slow stimulus repetition rate (8 clicks/sec) but shorter wave IV and I–IV latencies at a fast repetition rate (120 clicks/sec). These gender-dependent differences indicate that male and female rat BAEP data should not be combined indiscriminantly. Ethanol sedation had a statistically significant effect on the I–IV interpeak latency that was judged to be largely independent of core temperature changes. This finding suggests that while sedatives and anesthetics used to immobolize animals may have apparently minor temperature-independent effects on BAEP latencies, these effects can be statistically significant.     

Growth charts of head length and breadth for regional areas? A study in Sardinia (Italy)

There exist few standards of head length and breadth from childhood to adulthood in Europoid populations. Moreover, such standards are based on samples that cannot be used as references for all populations since they were taken from different ethnic groups and from different periods. The aims of this study were: (1) to test whether standards derived from North Americans of European extraction can be used to assess the Sardinian population; and (2) to produce growth charts for head length and breadth for Sardinian males and females from 3 to 22 years of age.The cross sectional sample consisted of 9,721 subjects of Sardinian origin (4,884 males and 4,837 females), aged 3–22 years, measured from 1998 to 2008. Growth percentiles were produced with the LMS method. The mean values for each sex in each age class (3–18 years) are almost always significantly lower for both head length and breadth than the corresponding North American values. The exceptions are the head length of boys of 14 years and girls of 16–18 years where values for Sardinians are lower, but not significantly so. The results show that the North American standards are not appropriate for the assessment of Sardinian children. For the Sardinian population, specific regional growth charts should be used to correctly evaluate the normal range and the cut-off points of the extreme percentiles.     

Plasma BDNF levels vary in relation to body weight in females

Brain derived neurotrophic factor (BDNF) has been implicated in the pathophysiology of depression as well as neuropsychiatric and neurodegenerative disorders. Recent studies show a role of BDNF in energy metabolism and body weight regulation. We examined BDNF levels in plasma and cerebrospinal fluid (CSF) samples from age matched elderly depressed and control subjects. Also, the association of BDNF levels with age, gender, body weight, body mass index (BMI), and cognitive performance was evaluated. We did not find any significant differences in plasma and CSF BDNF levels between depressed and control subjects. Plasma BDNF levels were negatively correlated with age (but not with BMI and body weight), when analyses were performed including both depressed and control subjects. A significant reduction in plasma BDNF levels was observed in females as compared to male subjects, and the change in BDNF levels were significantly and positively related to body weight in females. Furthermore, significant increases in Total Recall and Delayed Recall values were found in females as compared to males. In conclusion, the lower BDNF levels observed in females suggest that changes in peripheral BDNF levels are likely secondary to an altered energy balance. However, further studies using larger sample size are warranted.     

Potential contribution of progesterone receptors to the development of sexual behavior in male and female mice

We previously showed that estradiol can have both defeminizing and feminizing effects on the developing mouse brain. Pre- and early postnatal estradiol defeminized the ability to show lordosis in adulthood, whereas prepubertal estradiol feminized this ability. Furthermore, we found that estradiol upregulates progesterone receptors (PR) during development, inducing both a male-and female-typical pattern of PR expression in the mouse hypothalamus. In the present study, we took advantage of a newly developed PR antagonist (ZK 137316) to determine whether PR contributes to either male- or female-typical sexual differentiation. Thus groups of male and female C57Bl/6j mice were treated with ZK 137316 or OIL as control: males were treated neonatally (P0–P10), during the critical period for male sexual differentiation, and females were treated prepubertally (P15–P25), during the critical period for female sexual differentiation. In adulthood, mice were tested for sexual behavior. In males, some minor effects of neonatal ZK treatment on sexual behavior were observed: latencies to the first mount, intromission and ejaculation were decreased in neonatally ZK treated males; however, this effect disappeared by the second mating test. By contrast, female mice treated with ZK during the prepubertal period showed significantly less lordosis than OIL-treated females. Mate preferences were not affected in either males or females treated with ZK during development. Taken together, these results suggest a role for PR and thus perhaps progesterone in the development of lordosis behavior in female mice. By contrast, no obvious role for PR can be discerned in the development of male sexual behavior.     

Sexual dimorphism in neuromuscular junction size on a muscle used in courtship by green anole lizards

The green anole lizard exhibits seasonal courtship behavior that is sexually dimorphic. This courtship consists of the extension of a bright red throat fan (dewlap) associated with head‐bobbing display behavior. While males extend their dewlaps in aggressive encounters as well as in courtship, females use their considerably smaller dewlaps much less frequently and mainly in agonistic encounters. In parallel, a number of components of the neuromuscular system controlling dewlap extension are greater in males than in females during the breeding season, including dewlap motoneuron soma size and muscle fiber size and number. These features do not seem to change substantially in adulthood, despite a dramatic decline in dewlap use during the nonbreeding season. We explored the morphology of this neuromuscular system in more detail in the present experiment in males and females during both the breeding and nonbreeding seasons. Fiber and whole muscle length (approximately perpendicular to the fibers) were measured. Acetylcholinesterase histochemistry was used to visualize neuromuscular junctions (NMJs), and the surface area and density of NMJs were assessed for each animal. During the breeding season, NMJ size was larger in males than in females, but NMJ density along each fiber was equivalent between the sexes. In addition, whole muscle length and that of individual muscle fibers, was larger in males than in females. However, when corrected for body size, the sex difference in muscle fiber length disappeared. In the nonbreeding season, the sexual dimorphisms were maintained, suggesting that these features do not change substantially due to differences in circulating testosterone or a difference in use across seasons. Overall, these results are consistent with the idea that enhanced NMJ size is a relatively stable feature of the dewlap muscle in adulthood that either facilitates or is a consequence of using a larger muscle to extend a bigger dewlap in males compared to females. © 2002 Wiley Periodicals, Inc. J Neurobiol 50: 24–30, 2002     

Hematologic and blood biochemical variables of captive chimpanzees: cross-sectional and longitudinal analyses

Hematologic and blood biochemical variables are of great importance in medical and veterinary practice. In addition, these analytes may have significance as potential biomarkers of aging. Previous reports on normative values of these variables in the chimpanzees are based on cross-sectional studies that did not include individuals of advanced age. To address this omission, we performed cross-sectional and longitudinal analyses of hematologic and blood biochemical data collected from chimpanzees over a 9-year period. One-hundred forty-six females and 106 males of ages representing the entire life span of the species were studied. We derived normative cross-sectional values of 14 commonly measured hematologic and 20 blood biochemical variables, which should provide a useful reference for clinical blood studies in chimpanzees. In addition, we found in a cross-sectional regression analysis of our data that most analytes varied significantly between males and females, and that they varied markedly with age. Most variables had year-to-year consistency within the same individuals, as indicated by statistically significant intra-year correlation coefficients. Finally, we performed a longitudinal analysis of the analytes in chimpanzees by calculating the slopes and intercepts of the best-fitting trend line for each individual. The resulting slopes were analyzed by sex and by decade of age of subjects to determine whether trends were consistent. Consistent trends detected in the longitudinal analysis were usually restricted to the first decade of life, and thus represented maturational processes. The overall lack of within-animal trends covering all or most of the period from early adulthood through old age in this 9-year study suggests that a longer period of follow-up than used here may be required to document senescence-related changes.     

Logistic growth curve of chickens: a comparison of techniques to estimate parameters

Parameters of a mathematical function of growth, fit to the body weight curve of two randombred control populations of each sex of chickens from hatching through 45 weeks of age, were estimated. The logistic function was chosen from among growth formulae that express rate of gain as a function of weight at a given time and gain to be made. Two logistic parameters, growth-rate constant and age at the point of inflection, were estimated by the methods of sample quantiles and nonlinear regression from weekly mean body weights of 225 males and 281 females of the Rhode Island Red (RIR) line, and 164 males and 239 females of the White Leghorn (WL) line. Males had a larger growth-rate constant than females of the same line. The RIR line had a larger rate constant than the WL line, for each sex. Age at the point of inflection was similar for males and females in the RIR line, but smaller for males than females in the WL line. Sample quantiles yielded larger, less precise estimates of the growth-rate constant than nonlinear regression. Estimates of age at the point of inflection were usually smaller using sample quantiles.     

Spatio-temporal variation of natural and sexual selection in breeding populations of the coreid bug,Colpula lativentris (Heteroptera: Coreidae)

Spatio-temporal variations of lifetime reproductive succes (LRS) of both male and female individuals of a coreid bugColpula lativentris were measured and analyzed using the multiple regression method of Arnold and Wade (1984a, b). The standardized variance of LRS was larger in males than that in females as males often to secure mates for a long period whereas females could easily find mates and oviposit simply dependent on ovarial maturation. LRS was partitioned into 4 consecutive fitness components: (1) reproductive lifespan, (2) copulating efficiency, (3) guarding efficiency (for males) or oviposition efficiency (for females), and (4) number of eggs per clutch. In males copulating efficiency was the largest determining factor of LRS, whereas in females reproductive lifespan was the most important factor. Such tendencies were stable on both a yearly and local basis. Patterns of relative contribution of natural selection (reproductive lifespan and number of eggs per clutch) and sexual selection (copulating efficiency and guarding or oviposition efficiency) to LRS were clearly different between males and females. This sexual difference is, at least to some extent, thought to be brought about by sexual selection among males for mating opportunity, though no physical fight was observed among males. Directional selection on body length was found only in relation to the clutch size of females because large females tended to lay larger clutches. No significant directional selection was found in other fitness components.     

Aging process of leg muscle endurance in males and females

In order to estimate muscle endurance during knee extension (KME) and plantar flexion (PME) using a simple method, holding times for the half-squatting posture for KME and for the calf-raising posture for PME were measured in 3,792 males and 3,620 females aged between 6 and 79 years. The regression lines of the aging process for KME and PME in both sexes were determined. Peak values were found at 13 years in males and 12 years in females for KME, and at 15 years in males and 16 years in females for PME. The mean values increased sharply with age up to each peak and then decreased abruptly to a low level at around 20 years, thereafter declining gradually. The values of KME as a percentage of the peak value were 71, 75 and 34 at the ages of 6, 20 and 70-79 years respectively in males, while the corresponding values were 80, 77 and 36 for females. The values of PME at these ages were 34, 93 and 69 in males and 54, 91 and 73 in females. The mean values for males were generally higher than those for females. These results suggest that endurance of the leg muscles differs according to age, sex and the region of the leg muscle. These data will be useful as standard values for evaluating endurance and for prescribing suitable exercise for the promotion of physical fitness.     

Distinctive stress effects on learning during puberty

Puberty is a time of significant change in preparation for adulthood. Here, we examined how stressful experience affects cognitive and related hormonal responses in male and female rats prior to, during and after puberty. Groups were exposed to an acute stressor of brief periodic tailshocks and tested 24 h later in an associative memory task of trace eyeblink conditioning. Exposure to the stressor did not alter conditioning in males or females prior to puberty but enhanced conditioning in both males and females during puberty. The enhancement occurred in pubescent females irrespective of the estrous cycle. In adulthood, sex differences in trace conditioning and the response to stress emerged: females outperformed males under unstressed conditions, but after stressor exposure, trace conditioning in females was impaired whereas that in males was enhanced. These differences were not related to changes in gross motor activity or other nonspecific measures of performance. The effects of acute stress on corticosterone, estradiol, progesterone, and testosterone were also measured. Stressor exposure increased the concentration of corticosterone in all age groups, although sex differences were only evident in adults. All reproductive hormones except estradiol increased with age in a predictable and sex dependent fashion and none were affected by stressor exposure. Estradiol decreased in male rats across age, and remained stable for female rats. Together, these data indicate that males and female respond similarly to learning opportunities and stressful experience before and during puberty; it is in adulthood that sex differences and the opposite responses to stress arise.