Kristin H. Lopez

Distribution of arginine vasotocin in the brain of the lizard Anolis carolinensis.

SummaryThe distribution of immunoreactive arginine vasotocin (AVT-ir) was determined in the brain of the lizard Anolis carolinensis. Cells and fibers containing AVT-ir were found in the medial septal region, lamina terminalis, lateral forebrain bundle, preoptic area, supraoptic nucleus, anterior hypothalamus, paraventricular nucleus, periventricular nucleus, arcuate nucleus, and ventromedial nucleus of the thalamus. Occasional AVT-ir cells were found in the interpeduncular nucleus. Fibers containing AVT-ir were found in the cortex, around the olfactory ventricle, in the diagonal band of Broca, amygdala area, dorsal ventricular ridge, striatum, nucleus accumbens, septum, ventromedial hypothalamus, lateral hypothalamus, medial forebrain bundle, median eminence, pars nervosa, nucleus of the solitary tract, locus coeruleus, cerebellar cortex (granular layer), dorsal part of the nucleus of the lateral lemniscus, substantia nigra, and myelencephalon. The intensity of AVT-ir staining was, in general, greater in males than in females. Comparison of AVT-ir distribution in A. carolinensis with those previously published for other reptilian species revealed species-specific differences in distribution of AVT.

Differential Mechanisms for the N-Acetylation of Alpha-Melanocyte-Stimulating Hormone and Beta-Endorphin in the Intermediate Pituitary of the Frog, Xenopus laevis

Immunohistochemical analysis of the pituitary of Xenopus laevis revealed the colocalization of alpha-melanocyte-stimulating-hormone (MSH)-related immunoreactivity and N-acetyl-beta-endorphin-related immunoreactivity in the cells of the intermediate pituitary. In order to determine whether the immunoreactive N-acetylated beta-endorphin is released in parallel with the immunoreactive alpha-MSH, intermediate pituitaries were incubated in L-15 medium for 24 h. The medium and an acid extract of the intermediate pituitaries from each incubation were separately fractioned by a combination of gel filtration chromatography, reverse-phase high-performance liquid chromatography, and cation exchange chromatography. In the intermediate pituitary extract, the major form of alpha-MSH had chromatographic properties which corresponded to nonacetylated alpha-MSH (ACTH)(1-13)amide; whereas the major form of beta-endorphin had an apparent molecular weight of 1.2 kDa and was N-acetylated. The 1.2-kDa form of beta-endorphin and ACTH(1-13)amide were present in equimolar amounts. Analysis of the medium indicated that both end products were released in parallel. However, as reported in the literature, there was a significant increase in the N-acetylation of ACTH(1-13)amide during secretion. There was no further processing of beta-endorphin during secretion. Collectively, these observations indicate that in the intermediate pituitary of X. laevis there are separate mechanisms for the N-acetylation of alpha-MSH and beta-endorphin.

Catecholaminergic cells and fibers in the brain of the lizard Anolis carolinensis identified by traditional as well as whole-mount immunohistochemistry.

SummaryUsing traditional as well as whole-mount immunohistochemistry, we described the location of tyrosine hydroxylase-and dopamine beta hydroxylase-positive cells and fibers in the brain of the lizard Anolis carolinensis. Major catecholaminergic cell groups were in the ependyma in certain ventricular regions, alous coeruleus, anterior hypothalamic and lateral hypothalamic areas, and in the mesencephalic tegmental region, locus coeruleus, nucleus of the solitary tract, vagal motor nucleus, and rhombencephalic reticular formation. Major catecholaminergic fibers, tracts and varicosities included tuberohypophysial, mesolimbic, nigrostriatal, isthmocortical, medullohypothalamic, and coeruleospinal systems. Although the catecholaminergic systems in A. carolinensis are similar to those in the brains of other lizards studied, there are a few species differences. Our information about A. carolinensis will be used to help localize the hypothalamic asymmetry in catecholamine metabolism previously described in this lizard.

Adrenergic inhibition of uterine contractions and oviposition in the lizard Anolis carolinensis

Injection of arginine vasotocin (AVT), which induces oviposition in several lizard species, fails to do so in Anolis carolinensis. We tested the hypothesis that epinephrine-induced activation of beta-adrenoreceptors in the uterus inhibits AVT action on uterine smooth muscle. Pretreatment of gravid females with the beta-adrenoreceptor antagonist dichloroisoproterenol 15 min before an AVT injection resulted in uterine sensitivity to AVT and subsequent oviposition. Furthermore, in vitro tests indicated that epinephrine as well as a beta-adrenoreceptor agonist (isoproterenol) inhibit uterine tonic and rhythmic contractions that normally follow exposure to AVT. These results suggest that stress-induced secretion of epinephrine can act as a short-term inhibitor of oviposition in this species.

The Human Sexual Response

This chapter discusses the response cycle in men and women, and shows how malfunction of the cycle occurs. It also discusses how hormones, pheromones, therapeutic, and nontherapeutic drugs influence the sex drive and the sexual response cycle. It also discusses how present day human females may feel more sexually receptive around ovulation. The genetic sex determines the biological maleness and femaleness. Gender identity is the psychological awareness of ones biological sex. Sex role is the outward expression of ones gender identity. The human sexual response cycle is a sequence of physiological changes divided into four phases: excitement, plateau, orgasmic, and resolution. Hormones can influence sexual behavior by acting centrally or on peripheral tissues. A substance that increases sexual desire is an aphrodisiac, whereas one that decreases sexual desire is an anaphrodisiac. In both the sexes, orgasm involves the release of neuromuscular tension and is experienced as a highly pleasurable event. During the resolution phase in both the sexes, the sexual systems return to an unexcited state. Sexual dysfunction is present when a persons ability to receive sexual gratification is consistently compromised such as sexual dysfunctions in women are vaginismus and orgasmic dysfunction, whereas men can develop ejaculatory incompetence, premature ejaculation, and erectile dysfunction.

Asymmetry in diencephalic monoamine metabolism is related to side of ovulation in a reptile

The green anole lizard (Anolis carolinensis), like humans and other higher primates, alternates ovulation between left and right ovaries. To test the possible role of hypothalamic function in ovarian asymmetry, we measured levels of 3 major monoamine neurotransmitters (norepinephrine; dopamine; serotonin) and their metabolites in microdissected left and right diencephalon from lizards during the first cycle of ovulation in the spring. All of the metabolite/parent neurotransmitter ratios were significantly higher on the side of the diencephalon ipsilateral to the quiescent ovary than on the side of the maturing ovary. Simultaneous ovarian and brain asymmetry suggests direct communication between the ovary and brain, presumably through the ovarian innervation.

Sex differentiation and early gonadal development in Bombina orientalis (anura: Discoglossidae)

Gonadal differentiation in premetamorphic Bombina orientalis is described and staged. The pattern of events during differentiation in Bombina differs in several respects from that previously described in other anurans. The Bombina gonad initially develops on the ventral surface of the vena cava, where there is no pre‐existent somatic genital ridge prior to the arrival of the germ cells. The sexually undifferentiated gonad does not have a distinct cortex and medulla; instead, medullary cells ingress from the mesonephric blastema during sexual differentiation. Formation of a testis or an ovary appears to depend on the ability (or lack of ability) of the medulla to invade the germ cell‐containing cortex. In the germ line, sexual differetiation can be recognized by a premeiotic increase in oogonial cell volume.

The Female Reproductive System

This chapter discusses the anatomy, endocrinology, and disorders of the adult female reproductive system. The female reproductive system consists of the ovaries, oviducts, uterus, vagina, external genitalia, and mammary glands. All of these structures have evolved for the primary functions of the ovulation, the fertilization of an ovum by a sperm, and the birth and care of a newborn. The components of this system are integrated structurally and physiologically. The female primary sexual characteristics are the internal structures of the reproductive system, including the ovaries, the female sex accessory ducts, and the external genitalia. The female secondary sexual characteristics include all the external features that distinguish an adult female from an adult male. These include enlarged breasts and characteristic distribution of fat in the torso. The anatomical features that distinguish females from males are the female sexual characteristics. The growth and function of the glandular tissues are controlled by the hormones. Breast cancer is a relatively common disease that might be influenced by lifetime exposure to natural and environmental estrogens as well as inherited genes.

Gonadotropin-induced ovulation in a reptile (Anolis carolinensis): Histological observations

Although much is known about morphological changes in the apex of the mammalian ovarian follicle prior to its rupture (ovulation), information about this process in nonmammalian vertebrates is limited to only a few species. We describe here the histological changes in the stigma of the lizard (Anolis carolinensis) ovarian follicle preceding FSH-induced ovulation. Females with a large vitellogenic follicle received two injections, separated by 7 hr, of either porcine FSH (25 micrograms) or saline, and then were sampled at 6, 9, 12, 15, 18, and 24 hr after the first injection. Thus, all but the 6-hr group received two injections. By 12 hr, about half of the FSH-treated females had ovulated, and most had ovulated by 15 hr. In contrast, only 1 of 40 control females ovulated. Large unovulated follicles were fixed and bisected through the circular stigma; one hemisphere was embedded in paraffin and stained with Mallorys trichrome, and the other was embedded in plastic and stained with toluidine blue. FSH treatment produced marked histological changes in the stigma region, as well as alterations in nonstigmal areas of the follicle. The membrana granulosa of control follicles consisted of a single layer of squamous, darkly staining granulosa cells. After FSH treatment, nonstigmal granulosa cells separated slightly, and their nuclei became more clear and assumed an oval shape; in the stigma, these cells became widely separated, with round, light-staining nuclei containing one or two prominent nucleoli. The nonstigmal theca of FSH-treated follicles was similar to that of control follicles except that collagen fibers were more dissociated. In the stigma, collagen fibers were widely dissociated, and the theca swelled, presumably due to accumulation of extracellular fluid. Abundant fluid accumulated in the stigma, especially between the granulosa cells and their basement membrane and between the tunica albuginea and the theca externa. These changes in the lizard stigma are similar to those reported in mammals except that no marked inflammatory response occurs in the lizard stigma. We hypothesize that the Anolis follicle undergoes preovulatory luteinization, and that the stigma exhibits ischemic necrosis before rupture.

Number and state of rat ovarian mast cells after exogenous administration of luteinizing hormone

Diestrous rats were treated with an injection of luteinizing hormone (LH), and their ovaries were examined for mast cell number and stage of degranulation at 2 and 4 hr post-injection. LH tripled the number of medullary mast cells at 2 hr. The source or origin of the additional mast cells is unknown. Comparison of the present results with other studies of rat ovarian mast cell dynamics suggests the occurrence of a reduction in mast cell number in early to mid-proestrus followed by an LH-induced increase in late proestrus.