Occupational status and reproductive behavior in nineteenth-century Sweden: Locknevi Parish.
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In gynandromorphs of Drosophila, a detailed examination was made of the association between male courtship behavior and the chromosomal genotype of various parts of the central nervous system. Mosaic flies that behave as males repeatedly show a shorter courtship than normal males. If there is to be male behavior, the posterior dorsal brain must be haplo-X on at least one side for occurrence of the early courtship events. Tapping, following of females and wing extension. Licking (proboscis extension) has nearly the same focus but is submissive; that is, male tissue must be present in both left and right dorsal brain. The next courtship step, attempted copulation, has a focus (especially for actual genital contact) located in the thoracic ganglia, though apparently not in a discrete region. Attempted copulation, which can occur even in mosaics with a gravid abdomen, may be correlated with the presence of sex combs. The role of courtship foci are interpreted in terms of known sensory inputs to and functions of the major insect ganglia.
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The necessity of brain aromatization for sexual differentiation was investigated by treating pregnant guinea pigs with an aromatase inhibitor, 1,4,6-androstatriene-3,17-dione (ATD), from Day 30 to Day 55 of gestation. In postnatal Week 16, subjects were gonadectomized, and blood samples were collected after treatment with 10 micrograms estradiol benzoate (EB), used to elicit an LH surge; subjects were subsequently treated with GnRH to test pituitary responsiveness. Plasma samples were assayed for LH by RIA. Prenatal ATD treatment did not affect the organization of the LH surge mechanism in either male or female subjects. All animals, regardless of sex or treatment, released LH after GnRH treatment, but the responsiveness of the gonadotroph to GnRH was attenuated in both males and females treated with ATD in utero. In addition, a significant sex difference in the pattern of LH released in response to a GnRH challenge was found. ATD-treated animals did not respond to the negative feedback actions of EB on LH secretion (p < 0.05), and the percentage of males displaying lordosis behavior was greater in this group than in controls (p < 0.05). Mounting behavior and lordosis behavior of females were not significantly affected by treatment. These data demonstrate a need for estrogen in the organization of brain areas that mediate negative feedback control of LH in both sexes and lordosis behavior in the male guinea pig. The organization of positive feedback mechanisms for controlling LH seems to be under androgenic control. Our data also suggest that the responsiveness of the gonadotroph to GnRH action is developmentally coordinated by prenatal estrogen and is sexually differentiated.
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In many regions of Asia and Africa, consanguineous marriages currently account for approximately 20 to 50% of all unions, and preliminary observations indicate that migrants from these areas continue to contract marriages with close relatives when resident in North America and Western Europe. Consanguinity is associated with increased gross fertility, due at least in part to younger maternal age at first livebirth. Morbidity and mortality also may be elevated, resulting in comparable numbers of surviving offspring in consanguineous and nonconsanguineous families. With advances in medicine and public health, genetic disorders will account for an increased proportion of disease worldwide. Predictably, this burden will fall more heavily on countries and communities in which consanguinity is strongly favored, as the result of the expression of deleterious recessive genes. However, studies conducted in such populations indicate that the adverse effects associated with inbreeding are experienced by a minority of families.
Electrical stimulation in the mesencephalic central gray (CG) and adjacent subtectum through chronically implanted electrodes in free-moving estrogen-primed ovariectomized female rats elicited a rapid and large facilitation of the lordosis reflex in response to either male mounts or manula cutaneous stimuli. Unilateral stimulation was sufficient for this effect. The facilitation increased in a graded manner to increased stimulus intensity, and was optimally evoked by stimuli delivered at 50--150 Hz. Facilitation disappeared rapidly following the end ot electrical stimulation, and within 15 min, reflex performance returned to the prestimulation level. Lordosis facilitation appeared when no aversive responses occurred; stimulation with comparable parameters at the lateral edge of CG or in the mesencephalic reticular formation often resulted in postural changes or aversive responses but was not able to facilitate lordosis. Lordosis refelx facilitation was probably mediated by projections descending from neurons in and around the CG, and represents stimulation of a functional link between ascending somatosensory and descending motor systems for the control of lordosis behavior.
Placement of bilateral electrolytic lesions in the mesencephalic central gray (CG) of estrogen-primed ovariectomized female rats produced an immediate decline in performance of the lordosis reflex. Lesions that destroyed the dorsal half of the CG and the adjacent subtectal region were effective. The decrease in individual animals in terms of the lordosis reflex score ranged from 20 to 100% of the prelesion performance. Such lesions abolished the facilitation of lordosis by electrical stimulation of the ventromedial nucleus of the hypothalamus. Similar abrupt losses of lordosis followed bilateral lesions of either a) the area between CG and the cuneiform nucleus of the mesencephalic reticular formation (NCf); or b) the ventrolateral quadrant of the NCf. The difference between these two lesions was that the effect of the latter could be overridden by electrical stimulation of the CG, whereas that of the former could not. We conclude that the CG is an important supraspinal component of the circuit for lordosis behavior, constituting a link between ascending somatosensory and descending motor systems for lordosis. It probably facilitates lordosis when activated by behaviorally relevant peripheral somatosensory and/or ventromedial hypothalamic inputs.
Recent studies of experimentally elicited egg-care behaviors in three species of small, hole-nesting parrots, and of their evolutionary implications are reviewed. A suite of primarily nonthermal egg-care responses are adaptive for nesting in shallow terrestrial scrapes, rather than in cavities. These responses appear to be relics from times before hole-nesting began; as such, they may provide 'windows' into certain nonthermal aspects of terrestrial-nesting practices during ancestral stages. A suite of primarily thermal egg-care behaviors, elicited when nests are exposed to light and view, progress from mere initial curiosity, inspection, and manipulation of fostered eggs by nonbreeding parents, to more extensive manipulation and episodic concealment of a pair's own eggs by crouching over them, to crouching lengthily over eggs with some incubation but nighttime abandonment, to continuous 24-hour incubation. This progression may retrace certain aspects of major ancestral stages of thermal egg care. Stages of primary oocytes and follicles during ovarian development, and of maturing follicles during breeding cycles of some species, may retrace the phylogenetic progression of sizes of ancestral clutches and ripe follicles. These phenomena and the retention of many of the experimentally elicited egg-care responses are attributed largely to the highly conservative evolution of the central nervous system.
The present study demonstrates that an intracerebroventricular injection of luteinizing hormone-releasing hormone (LHRH) activates sexual behaviors and elevates the plasma androgen concentrations in rough-skinned newts (Taricha granulosa). The stimulatory effect of LHRH on male behavior may be a seasonal phenomenon, because LHRH stimulation of sexual behavior was only observed during the early part of the breeding season (November and December). When an active LHRH antagonist was injected into male newts, sexual behavior was suppressed. These studies indicate that endogenous LHRH is involved in regulating sexual behavior in this amphibian.
In a group of 150 working-class Jamaican women, lack of information from their mothers about sex coupled with chronic resentment was associated with having had more sexual partners, impregnators, and children. In contrast to age at first coitus, age at first pregnancy did not seem related to the early availability of information about sex, and it was less significantly correlated with overall education.
The androgen aromatization hypothesis was examined in the male lizard, Anolis carolinensis. After castration, sc silastic implants of testosterone (T) restored both challenge and courtship behavior, while dihydrotestosterone (DHT) or 17beta-estradiol (E) had no effect on male behaviors. Both T and DHT, but not E, stimulated hypertrophy and colloid production by the renal sex segment, a secondary sexual characteristic of male lizards. In two separate studies, castrates received DHT in combination with E. In each replicate, half of the castrates responded with increases in courtship behavior after hormone treatment. Epithelial cell height of the sex segment of all DHT and E-treated castrates was comparable to T- or DHT-treated castrates, but colloid production was not stimulated. These experiments indicate that in this species, treatment with T stimulates both sexual behavior and secondary sex character development, whereas treatment with E alone is without effect centrally or peripherally.
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