Androgen-induced yawning in rhesus monkey females is reversed with a nonsteroidal anti-androgen

In the adult rhesus monkey, yawning is an androgen-dependent sexually dimorphic behavior with males yawning more frequently than do females reflecting sex differences in circulating androgens. Studies in a variety of species indicate that yawning is mediated by various neurochemicals including dopamine, serotonin, and oxytocin. In rhesus monkeys, exogenous androgen reliably induces yawning in females to male-like levels. This study investigated whether flutamide, a nonsteroidal anti-androgen, reverses yawning induced by exogenous androgen administration in adult female rhesus monkeys. Six adult female rhesus monkeys were given chronic DHT alone and in combination with daily injections of flutamide and observed for yawning behavior. Treatment with DHT alone significantly increased yawning from 0.3 yawns per 30 min at the pretreatment baseline to 4.7 yawns per 30 min. Concurrent administration of flutamide significantly reduced the rate of yawning to 1.9 yawns per 30 min. These data indicate that flutamide is an effective tool for blocking the central effects of androgens in rhesus monkey females and that androgens regulate yawning similarly in both males and females.     

Transmission electron microscopic studies of the organization of the ependymocytes in the central canal of the spinal cord of Cercopithecus nigroviridis (Pocock 1907), (Platyrrhina, Cercopithecoidea)

The ependyma of the central canal of the spinal cord of the monkey Cercopithecus nigroviridis was examined by transmission electron microscopy. In the lumbar region and in the filum terminale, many cytoplasmatic protrusions are visible. They are irregular in size and shape and display many microvilli. They are extending into the lumen of the central canal. The basal parts of the ependymocytes occasionally have a very close association with the ependymal blood vessels. The pericapillary space, the pericapillary structures like pericytes and collagen fibrils, and the basal lamina are absent. Opposite branches of the ependymocytes growing together could be observed in the central canal, eventually forming a cytoplasmic unit. Cytoplasmatic extensions of the ependymocytes bridge the lumen of the central canal and melt into each another. Lacunae, such as described by LEONHARDT (1980) in the apical cytoplasm of the ependyma in the rabbit, do also exist in the ependyma coating the central canal of the spinal cord of the monkey Cercopithecus nigroviridis. Some of these lacunae have direct contact to the luminar surface of the central canal, others are separated. Cilia and short microvilli are coating the lacunae. Adjacent ependymal cells form complex interdigitations with each other. Close to their surface on the central canal, there are numerous zonulae adhaerentes. Profiles of the granular and agranular endoplasmatic reticulum are in very close contact to the fine filaments of the zonulae.     

Electron microscopic studies on the pars intermedia of the ferret

Summary The structure of the pars intermedia of the ferret has been studied with the electron microscope, with particular reference to the morphology of the glandular cells and their innervation. Two types of cell were found. The predominant cell is ovoid in shape and contains membrane-bound vesicles of varying size (1,000–5,000 Å) and density, the most electron-dense of which are associated with the Golgi region. The nucleus is indented and the cytoplasm contains rough endoplasmic reticulum. The second cell type is often associated with the colloid material and is elongated or stellate-shaped with long processes which extend between the predominant cells. It is devoid of cytoplasmic vesicles and has a poorly defined Golgi apparatus. Certain other structural features of this cell such as microvilli, cilia or cytoplasmic microfilaments are reminiscent of ependymal cells.Numerous nerve endings are observed throughout the pars intermedia, making synaptic contact with the predominant cell type. The majority contain vesicles with an electron-dense core measuring 750 Å; less frequently terminals contain dense granules measuring 1,000 A or more. Both also contain small electron-lucent vesicles (200–400 Å); occasionally terminals containing only the latter type are found. The pattern of innervation in the ferret is thus comparable to that previously observed in the cat, rather than that seen in rodents or monkeys, and the implications of this finding are discussed.We are indebted to Prof. Sir Solly Zuckerman, O. M., K. C. B., F. R. S., for his help and guidance and to Mr. J. Wallington for his unfailing technical assistance.     

Comparative scanning and transmission electron microscopy studies of the ependyma of the central canal in the spinal cord of primates. I. Electron optical image of the ependyma in the central canal of the spinal cord of the callithrix monkey (Callithrix jacchus, Linné 1758)

The ependyma lining the central canal of the spinal cord of adult males and females monkey, Callithrix jacchus, was examined by scanning and transmission electron microscopy. The cross section of the lumen of the central canal are round, oval, or triangular. Light and dark ependymal cells, depending on the density of the cytoplasm, were found. The light ependymal cells are fewer than the dark cells. The ependyma cytoplasm contained numerous mitochondria, filamentous structures, one or more well-developed Golgi-complexes, vesicles of the smooth endoplasmic reticulum, ribosomes, lysosomes, multivesicular bodies, profiles of the rough endoplasmic reticulum, large osmophilic bodies, and microtubules. The nuclei of the ependyma cells usually have a simple, regular round or oval shape. They occupy a relatively large portion of the cell volume and lie in the central or mediobasal position. Some of the nuclei show deep invaginations into the karyoplasm. Most of the mitochondria occupy mainly the supranuclear portion of the apical cytoplasm. There are of the crista-typ. Ribosomes occur free in the cytoplasm, but some attached to the profiles of the rough endoplasmic reticulum or being arranged as polysomes. The filamentous structures are generally prominent cytoplasmic components and are distributed at the apical, lateral, or basal region of the ependymocytes. They are grouped into bundles and arranged in parallel arrays. Some of these bundles reach the plasmamembrane at the free lumina of the central canal, others take contact to the filamentous structures of the zonulae adherentes of the junctional complex below the free surface. The granular endoplasmic reticulum shows specializations. There profiles surrounding granular substances and widely distributed granulations in connection with the nuclear envelope. The functional significance of the deposition of these granulations is still unknown. The luminal surface of the ependymocytes bears many microvilli and cilia. The cilia are regularly arranged in cranio-caudal direction. Each cilium has the typical (9 + 2)-subfibres. The intercellular space at the surface of the ependymal layer shows a single zonula adherens or zonulae adherentes in the row. Tight junctions and gap junctions were not found in the material examined. Cell processes of liquor contacting neurons between adjacent ependyma cells, protruding into the lumen of the central canal, could be observed. The termination of these neurons contains accumulations of mitochondria in the central part, large amounts of vesicles, and small dense bodies. They have short microvilli and some stereocilia at the free surface.(ABSTRACT TRUNCATED AT 400 WORDS)     

Timing of prenatal androgen exposure: anatomical and endocrine effects on juvenile male and female rhesus monkeys

Prenatal androgen shapes genital differentiation. In humans, genital anatomy determines sex of rearing and subsequent behavioral development. Rhesus monkey genital anatomy and neuroendocrine function are sexually differentiated, and behavioral development occurs in a complex social environment. We investigated prenatal hormonal influences on sexual differentiation by suppressing or increasing androgens in male and female rhesus monkeys. Pregnant multiparous female rhesus monkeys received 35-40 days of testosterone enanthate (TE) treatment, androgen antagonist (flutamide, FL) treatment, or vehicle starting on gestation day (GD) 35 or 40 (early) or GD 110 or 115 (late). Exogenous androgen increased neonatal LH secretion in females when given early and altered female genital differentiation when administered either early or late. TE treatment, early or late in gestation, had no measurable effects on male genital differentiation or neuroendocrine function. Early FL treatment, however, radically altered male genital differentiation, producing in two cases males with a urethral opening separate from the glans. In females, early FL treatment produced detectable alterations in genitalia consistent with a reduced exposure to prenatal androgen, suggesting that female rhesus monkeys are naturally exposed prenatally to meaningful levels of T. Late FL treatment reduced male penis size and increased neonatal T secretion, but had no effect in females. This is the first study to block endogenous prenatal testosterone in rhesus monkeys, thereby altering sexual differentiation. These findings illustrate the complexity of prenatal influences on anatomical and neuroendocrine development. The relationship between the anatomical changes reported here and sex differences in behavior is currently under investigation.     

A Golgi study of third ventricle tanycytes in the adult rodent brain

Summary Tanycytes along the third ventricle have been studied in adult rat and mouse brains with the rapid Golgi method. A tanycyte can be divided into three portions: somatic, neck, tail. The somatic portion is in the ependymal layer and frequently has thin cytoplasmic extensions. The neck portion originates from the soma and sticks into the periventricular layer. It, too, has numerous fine lamellar processes radiating from it. The neck contacts a blood vessel. Distal to this contact, the neck becomes thin and devoid of its cytoplasmic processes. This is the tail portion, which courses through hypothalamic nuclei to terminate as small bulbous swellings either on a vessel or at the pial surface.Although tanycytes occur throughout the dorsoventral extent of the ventricle, they are especially numerous ventrally. Midway down the ventricular wall, the neck processes interdigitate and form a moderately loose fabric beneath the ependyma. Proceeding ventrally, this becomes denser and thicker.Because the tails have no apparent associations with cells in the hypothalamic nuclei, the functional interactions of tanycytes with hypothalamic neuropil are probably confined to the periventricular layer.Supported by: NINDS Grants 5 RO1 NS 09001-02 NEUA, 5 TO1 NB 5309, and GM 00958, and by the Eleanor Roosevelt Cancer Foundation Research Institute.It is a pleasure to acknowledge the expert photographic assistance of Mr. Keith Johnson.     

Nature Needs Nurture: The Interaction of Hormonal and Social Influences on the Development of Behavioral Sex Differences in Rhesus Monkeys

Thirty years of research on early social and hormonal environments and their relationship to the expression of behavioral sex differences in rhesus monkeys are reviewed. These studies demonstrate that whether aggressive and submissive behaviors are sexually dimorphic depends primarily on the social and not the hormonal environment. Early rearing environments without mothers or allowing brief periods of peer interaction produced higher levels of male aggression and female submission. Presenting behavior was expressed more by females than males in environments with high male aggressivity and female submissiveness. No sex differences in presenting occurred in low aggressivity environments, unless monkeys were reared isosexually, when males presented more than females. Rough and tumble play and foot-clasp mounting were consistently exhibited more by males than females across all rearing environments studied, but rearing environment affected the degree of the sex difference. When reared isosexually males displayed less, and females more, foot-clasp mounting than when heterosexually reared. No social environment increased the low frequency of female rough and tumble play. Suppressing neonatal androgen in males did not effect any sexually dimorphic behavior. Prenatal androgen administration to genetic females masculinized many aspects of their juvenile behavior, consistently increasing rough and tumble play and foot-clasp mounting across different social environments. Thus the sexually dimorphic behaviors which showed the smallest variability across social contexts were the most profoundly affected by the prenatal hormonal environment. These studies demonstrate that the expression of consistent juvenile behavioral sex differences results from hormonally induced predispositions to engage in specific patterns of juvenile behavior whose expression is shaped by the specific social environment experienced by the developing monkey.     

Mitotic Figures in the Median Eminence of the Hypothalamus

The median eminence of the hypothalamus is part of the avenue by which neurosecreted hormones from the hypothalamic nuclei reach the pars nervosa (neural lobe) of the pituitary and eventually the bloodstream. Lithium treatment and osmotic stress increases the transport of neurosecretory hormones to the pituitary in the adult rat. Specialized astrocytes termed pituicytes in the pars nervosa of the pituitary participate in the secretory process and also develop considerable mitotic activity. The present work reveals similar mitotic figures in cells within the median eminence following 3 days of lithium treatment. The location and appearance of these mitoses add to the evidence that pituicytes are present in the median eminence. Moreover, mitoses occur within the ependymal (tanycyte) layer of the median eminence. Thus, the present results suggest that the tanycyte layer may contain pituicytes, indicating that the hypothalamus possesses specialized cells for modulating neurosecretion in response to osmotic challenges.     

Cognitive performance in rhesus monkeys varies by sex and prenatal androgen exposure

Men and women differ on performance and strategy on several spatial tasks. Rodents display similar sex differences, and manipulations of early hormone exposure alter the direction of these differences. However, most cognitive testing of nonhuman primates has utilized sample sizes too small to investigate sexually differentiated behaviors. This study presents an investigation of sex differences and the effects of prenatal androgen on spatial memory and strategy use in rhesus monkeys. Monkeys prenatally exposed to vehicle, testosterone, or the androgen receptor blocker flutamide performed a search task in which 5 of 12 goal boxes contained food rewards. Spatial consistency and the presence of local landmarks were varied. Performance when both spatial and marker cues were available did not differ by sex or prenatal treatment. Contrary to predictions, females easily solved the task when local markers were removed, and their performance outscored males. Although eliminating spatial consistency and requiring subjects to use local markers impaired performance by all monkeys, females continued to locate correct goal boxes at higher than chance levels and scored better than males. Blocking prenatal androgen exposure in males improved use of local markers. These findings suggest that the tendency to attend to landmarks and to use them in solving spatial problems is typical of females across many species, including rodents, humans, and rhesus monkeys. In rhesus monkeys and rodents, developmental androgen eliminates this specialization. However, these results are the only known example of better performance of females than males when salient markers are removed.     

A review of sexual initiating behavior by male and female cynomolgus monkeys and some species comparisons

The sexual initiating behavior of male and female cynomolgus monkeys (Macaca fascicularis) observed during standard laboratory tests is reviewed and compared with that of rhesus monkeys (M. mulatta) observed under identical conditions. Species differences in sexual behavior are related here to differences in habitat, sexual dimorphism, and the dominance gradient between the sexes. Compared with rhesus monkeys, cynomolgus monkeys appear to be more arboreal, less sexually dimorphic, and have a smaller dominance gradient between the sexes. They exhibit a facultative single-mount copulatory pattern rather than the serial mount pattern of the rhesus monkey. Female cynomolgus monkeys are less dominated than rhesus females by their male partners. Direct aggression between mates is more frequent and redirected aggression occurs less often than in rhesus monkeys. These behavioral differences affect the interpretation of changes in initiation rates that occur (1) during the menstrual cycle, (2) when females are ovariectomized and given hormone replacement treatments, and (3) when males are castrated and treated with androgens. We conclude that estradiol in the female and testosterone in the male increase the sexual motivation of both the treated and the untreated partner. Valid interpretations of changes in initiation rates depend on accurate and exclusive definitions of behavior and on a consideration of the behavioral context in which they are made.     

Localization of Angiopoietin-1 and Tie2 Immunoreactivity in Rodent Ependyma and Adjacent Blood Vessels Suggests Functional Relationships

Angiopoietin-1 (Angpt1; previously Ang-1) participates in vascular maintenance and remodeling. In the current study, we investigated the distribution of Angpt1 protein in rat brain. We detected Angpt1 immunoreactivity (IR) in cerebral blood vessels, cuboidal ependyma, and tanycytes, which are specialized hypothalamic bipolar ependymal cells. We also evaluated patterns of IR of endothelium-specific receptor tyrosine kinase 2 (Tie2, the receptor for Angpt1). Tie2 IR was present in Angpt1-immunoreactive cuboidal ependyma in a membranous pattern, suggesting an autocrine or paracrine role for Angpt1–Tie2. Tie2 IR was also associated with peri-ependymal blood vessels, some of which were contacted by tips of Angpt1-immunoreactive tanycyte processes, implying a potential functional ligand−receptor interaction mediating communication between the cerebrospinal fluid and vascular compartments. Because we previously found that cerebral Angpt1 expression was modulated by 17β-estradiol (E2), and because some tanycyte functions are modulated by E2, we tested the hypothesis that E2 affects ependymal and tanycyte Angpt1 expression in vivo. No gross E2 effect on the ependymal pattern of Angpt1 IR or cerebral Angpt1 protein content was observed. (J Histochem Cytochem 58:53–60, 2010)     

Species discrimination and concept formation by rhesus monkeys (Macaca mulatta)

There are 19 species in genusMacaca and some of them are living in sympatry (Fooden, 1980). Although inter-specific hybrids are relatively easy to produce under artificial conditions, hybridization does not occur naturally. What is preventing that among the species of genusMacaca? Three rhesus monkeys acquired a discrimination between pictures with rhesus monkeys and without rhesus monkeys. All subjects showed positive transfer of this discrimination to new pictures with rhesus monkeys and without rhesus monkeys. A further test showed that these monkeys could discriminate between pictures of rhesus monkeys and pictures of Japanese monkeys. The results suggest that rhesus monkeys recognize rhesus monkeys as a class, independent of the actual stimuli such as a picture or an individual monkey. The ability to recognize members of their own species and the opportunities for such learning may be an important factor preventing hybridization among the species of genusMacaca.     

A radioimmunoassay for dehydroepiandrosterone sulfate in the circulation of rhesus monkeys

A radioimmunoassay for dehydroepiandrosterone sulfate (DHAS) was established and validated for use in the rhesus monkey. The validation demonstrated the co-migration of immunoreactive material with tritiated dehydroepiandrosterone after hydrolysis and indicated the absence of other interfering steroids in the measurement. The application of this assay to perinatal samples verified that there are microgram quantities of DHAS present in the circulation. The measurement of circulating concentrations of DHAS in male and female rhesus monkeys at different stages of development demonstrated the absence of increases associated with puberty in this macaque species. Concentrations of DHAS were similar in adult males and females, but were elevated in pregnant females (p less than 0.05). Adult males had increased DHAS concentrations after GnRH administration (p less than 0.05), but no change was detected in infant male monkeys. Cortisol and DHAS responses of both infant and adult males occurred at a similar dose of ACTH (0.05 mU per kg versus 0.015 mU per kg, infant and adult, respectively). These data demonstrate the validity of the DHAS measurement in the rhesus monkey and suggest that the secretion of DHAS from infant and adult adrenals is generated by a similar stimulus. Since there was no evidence of gonadal secretion of DHAS in the infant, changes in either adrenal secretion and/or metabolic clearance of DHAS probably account for the microgram concentrations found during the perinatal period.     

Variation in age at puberty in monkeys.

5 female and 3 male patas monkeys and 6 female and 3 male talapoin monkeys matured in a captive breeding colony. Age at puberty is given, and some variation discussed. The talapoin, a very small monkey, becomes adult at 4 1/2 years for females, 1 or 2 years later for males. The patas, a rather large monkey, becomes adult at 2 1/2 years, for females, and 1 or 2 years later for males. Both these ages for puberty differ from data for the rhesus monkey which has been accepted as generalizable to all Old World monkeys. Possible causes of differences between species in average age at puberty are discussed, including nutrition, environmental inconstancy, and relative size of infant and mother. It is suggested that age at first conception, a biologically more relevant index than menarche, should be considered as a potentially important adaptive variable when describing primate species.     

Fine structure of the ependyma and intercellular junctions in the area postrema of the rat

Summary Ependymal cells and their junctional complexes in the area postrema of the rat were studied in detail by tracer experiments using horseradish peroxidase (HRP) and colloidal lanthanum and by freeze-etch techniques, in addition to routine electron microscopy. The ependyma of the area postrema is characterized as flattened cells possessing very few cilia, a moderate amount of microvilli, a well-developed Golgi apparatus and rough endoplasmic reticulum. Numerous vesicles or tubular formations with internal dense content were found to accumulate in the basal processes of ependymal cells; the basal process makes contact with the perivascular basal lamina. It is suggested that the dense material in the tubulovesicular formations is synthesized within the ependymal cell and discharged into the perivascular space. The apical junctions between adjacent ependymal cells display very close apposition, with a gap of 2–3 nm, but no fusion of adjacent plasma membranes; they thus represent a transitional form between the zonulae adhaerentes present in the ordinary mural ependyma and the zonulae occludentes in the choroidal epithelium. A direct intercommunication between the ventricular cerebrospinal fluid (CSF) and the blood vascular system indicates that a region exists lacking a blood-ventricular CSF barrier.     

Changes in the activity of the ependyma in the infundibular recess of the brain of Rana esculenta L. in the annual cycle.

Volume of the cell nuclei of the ependyma of the infundibular recess was measured in 30 female and 30 male water frogs (Rana esculenta L.) obtained from their natural environment, taking into account the phase of the annual cycle. Karyometry of the ependymal cell nuclei in the infundibular recess in males and females showed statistically significant differences of volume (activity) in the annual cycle. The largest volume of nuclei of the ependymal cells in females and males was observed in the first decade of April (end of hibernation), and the smallest in the first decade of September (end of the period of active life). Activity of nuclei of cells from the infundibular recess clearly correlated with gonadal development.     

Ependymoneuronal specializations between LHRH fibers and cells of the cerebroventricular system

Summary Light-and electron-microscopic immunocytochemistry (LM-ICC and EM-ICC) were used to visualize luteinizing hormone-releasing hormone (LHRH) in fibres associated with ventricular ependyma and tanycytes of the median eminence. LM-ICC suggests that LHRH fibers appear to enter the third ventricle. However, with EM-ICC, LHRH fibers are in fact found within ependymal canaliculi formed by adjacent ependymal cells. The canaliculi contain other myelinated and unmyelinated axons in addition to immunoreactive LHRH fibers. Thin slips of ependymal and tanycyte processes project into the canaliculi and enclose axons to varying degrees. At the median eminence many LHRH fibers bend sharply downwards from their ventricular course and travel with tanycytic processes towards their common destination — the perivascular space of the hypophysial-portal vascular system. Here, EM-ICC reveals that LHRH fibers closely contact basal processes of tanycytes. Lateral processes from tanycytes form glioplasmic sheaths which surround some individual LHRH fibers. A few LHRH terminals contact the perivascular space directly but more often are separated from the perivascular space by intervening glia. It is hypothesized that: (1) glia of this region responds to the physiological state of the animal and may determine the degree of LHRH secretion by varying the extent of glial investment of LHRH terminals; and (2) may play a role during development by providing direction and support for LHRH fibers similar to that described for radial and other glial cells.     

Ependyma and ependymal protrusions of the lateral ventricles of the rabbit brain

Summary The ependymal lining of the lateral ventricles of the rabbit brain was studied by means of scanning (SEM) and transmission electron microscopy (TEM). There exist cells devoid of cilia in the anterior horn over the region of the caudate nucleus, in the inferior horn over the hippocampus and on the opposite side over cortical regions. On the surface of some of these ependymal cells, accumulations of cytoplasmic folds and globules can be found. They bulge at different height over the ependymal cells. Clots of these cell particles are tied off from the cell, coming to lie as globules either on or between the cilia of the ependyma. TEM reveals that these tissue protrusions are cell debris consisting of different sized vesicles, cell organelles, tubuli and filaments. They originate from the ependymal layer but may reach down to subependymal cells. Multivesicular protrusions into the ventricular lumen are also observed. Possible causes of these protrusions are discussed; they are likely to be related to the age of the animals.On the ependyma of the caudate nucleus cilia, microvilli, microblebs and supraependymal neuronal cell processes are distributed unevenly over the surface. Within regions where cilia predominate there are cells which are tightly covered with microvilli. A certain direction of the course of the supraependymal neuronal fibers could not be found.The author is pleased to acknowledge useful discussions with Prof. Dr. med. E. van der Zypen. This study was partly supported by the Stanley Thomas Johnson Foundation     

Seasonal breeding in rhesus monkeys: Influence of the behavioral environment

The accepted model of breeding seasonality in rhesus monkeys states that females become reproductively active in response to an environmental cue and that males become sexually active in response to ovulating females. This model must be modified to include direct responses of the male to the physical environment, endocrine responses of males to sexual activity, and responses of the female to the sexual activation of fellow group members. The complex set of social stimuli that influences the breeding readiness of both sexes may serve to delimit more precisely the annual periods of conception and birth than would be the case if each individual responded only to the changing physical environment.     

Aging in the musculoskeletal system of rhesus monkeys: I. Passive joint excursion

In order to describe ontogenetic change in the musculoskeletal system of rhesus monkeys, 126 Macaca mulatta from Cayo Santiago, ranging in age from 7 months to 21 years, were examined under anesthesia. Passive joint excursions were measured at the wrist, elbow, shoulder, hip, and knee. Mean ranges of excursion at these joints differed significantly between age groups and by sex. The potential for most movements appeared to decrease approximately 25 degrees over the first two decades of the macaque life span, and males generally showed less potential for movement than females in all age groups. These results are similar to those obtained for humans and are consistent with patterns of positional behavior, trauma, and osteoarthritis observed in this rhesus monkey population. Thus, to fully describe the locomotor strategy of rhesus monkeys, age- and sex-related variation in locomotor anatomy and functional capacity must be considered.