RESUMO

A copper-bearing intrauterine device (IUD), designed to cause a slight distention of the uterus, was inserted through the cervix into each uterine horn of 230 heifers; an additional 230 heifers served as the control group. Blood was drawn at 0, 1, 2, 20 and 120 d for progesterone and testosterone assays. The heifers were checked twice daily for estrus and examined at 0, 60 and 120 d for weight gain. Thereafter they were bred over a 120-d period. The IUD caused anestrus in 98% of the heifers, with a daily weight gain 25.5 % higher than in the control heifers. Moreover, the device was 100% effective in preventing pregnancy. At 20 and 120 d after IUD insertion progesterone levels averaged 0.7 ng/ml, which was 4 to 5 times lower than in the control animals, suggesting a failure in ovulation or in corpus luteum (CL) formation due to the IUD. Simultaneously, testosterone values were increased up to 8 times in IUD-treated heifers, reaching a mean concentration of 163 pg/ml. Associated histological evaluations of the ovaries from UD-treated heifers revealed the presence of 2 or more cysts per ovary, with marked hyperthecosis in many antral follicles in which the granulosa cell layers were either thinned or lacking. The results suggest that the action of the copper-releasing IUD used in this study resulted in high contraceptive efficiency but also in disturbance of ovarian function. Our findings further raise the possibility of a cause and effect relationship between hyperandrogenism and the higher body weight gain observed in heifers treated with the IUD.

RESUMO

The purpose of this study was to evaluate the developmental changes of the Leydig cells and their precursors during postnatal development in the monkey Cebus apella. Four groups of monkeys were studied: neonatal, infantile, early pubertal and late pubertal. Light microscopy, immunocytochemistry, electron microscopy and stereological studies were performed to determine cytologic and cytochemical characteristics, volume density, absolute volume and cell counts of Leydig cells. In the interstitial tissue two components were recognized: specific interstitium comprising mature and immature Leydig cells and differentiating Leydig cell precursors, and non-specific interstitium including connective tissue and blood vessels. Mature Leydig cells were polygonal with a round, euchromatic nucleus and abundant cytoplasm. Immature Leydig cells were more elongated and the nucleus showed more heterochromatin. Mature and immature Leydig cells showed either a pale- or a dark-stained cytoplasm. Pale Leydig cells showed abundant smooth endoplasmic reticulum (SER), mitochondria with tubular cristae and glycogen granules. The SER of dark Leydig cells consisted of abundant flat cisternae, only few glycogen inclusions and abundant lipid droplets. All Leydig cells were intensely reactive for 3beta-hydrohysteroid dehydrogenase (3beta-HSD). Some peritubular cells acquired nuclear and cytoplasmic characteristics that indicated that they were differentiating to Leydig cells, as evidenced by the strong 3beta-HSD positivity found in scattered elongated cells of the peritubular tissue. Absolute interstitial volume increased from birth to the end of puberty due to an increment in Leydig cells numbers and size. The mature and immature Leydig cell populations showed a different evolution during postnatal development. While immature Leydig cells increased 7-fold from the neonatal to the early pubertal period and increased at a lower rate during puberty, mature Leydig cells remained stable until early puberty and increased significantly during late pubertal development.

Assuntos

RESUMO

We have investigated the role of the utero-ovarian ligament (UOL) in the alternating ovulatory performance of the ovaries in the capuchin monkey. In intact animals, the ovulation rate was near 90%, with 67.5% of ovulations occurring in the left ovary. Sectioning the UOL in any phase of the cycle decreased the ovulation rate by 40%, and restricted ovulations to the ovary still connected to the uterus by the UOL. Estradiol and progesterone levels were significantly reduced throughout the following cycles in treated monkeys. Removal of the ovary that had been disconnected 18-20 months previous, restored both the ovulation rate and normal steroid levels. Histological study of the UOL revealed the presence of arteries, veins, lymph vessels, and nerves. Electrical stimulation of the UOL was followed by an abrupt discharge of estradiol by the ovary bearing the follicle, advancing ovulation which was followed by a normal luteal development. Conversely, stimulation of the ovary bearing a corpus luteum did not modify either the ovarian or the peripheral levels of ovarian steroids. The UOL ligament appeared to be functional for products arising from the uterus. The distribution and effects of hCG injected intrauterinely depended upon the day of the luteal phase. In the early luteal phase, hCG was distributed symmetrically between both ovaries, and increased the progesterone secretion by the ovulatory ovary only. In the late luteal phase, hCG was preferentially distributed to the ovulatory ovary, and increased the progesterone secretion by both ovaries. The present findings provide evidence for a local mechanism, throughout the UOL, controlling both the alternation of ovulation and the transfer of substances originating in the uterus that regulate the ovarian function in primates. © 1994 Wiley-Liss, Inc.

RESUMO

The objective of this study was to describe the maturational changes observed in the seminiferous tubules of the monkey Cebus apella, a New World primate species, from birth to the end of puberty. Nineteen animals were subdivided into four groups: neonatal (1-40 days), infantile (4 months to 1 yr), early pubertal (1 yr, 8 months to 2 yr, 9 months), and late pubertal (4-8 yr). Volumetric determinations of different testicular components were made, tubule diameter and length were calculated, and spermatogenic cells, Sertoli cells, and androgen-binding protein secretion were quantified. Testicular and seminiferous tubule volumes increased significantly in the first 5 months of life and during puberty due to the combined increment in seminiferous tubule diameter and length. The total number of spermatogonia increased until late puberty to stabilize subsequently. Spermatocytes and spermatids appeared during puberty and increased dramatically until the end of this period. The germ cell ratios, indicative of spermatogenic efficiency, improved continuously in late puberty coincidentally with a reduction of spermatocyte degeneration. Sertoli cells proliferated in the neonatal and infantile periods, determining a longitudinal growth of the seminiferous tubules, but remained stable during puberty, when androgen-binding protein secretion increased significantly. The multiplication of germ cells is the main factor responsible for the increment in tubule diameter during puberty and determines the most noticeable postnatal modification of testicular volume. During late puberty, the reduction of spermatocyte degeneration leads to an increment in germ cell ratios and a progressive, but slow, improvement of spermatogenic efficiency, explaining why pubertal development of the testis occurs over such a prolonged period in this primate. This is in contrast to what happens in most laboratory animals and suggests that the Cebus is a useful model for studies of human male puberty.

Assuntos

RESUMO

In basal conditions, progesterone concentrations were similar in the ovarian veins of the ovary +CL (3211 +/- 526 ng/ml) and the ovary -CL (3165 +/- 554 ng/ml), but after blocking the blood flow between the ovary +CL and the uterus, the progesterone values in the vein draining the ovary -CL decreased to 1218 +/- 394 ng/ml (P less than 0.01). When [3H]progesterone was injected in the ovary +CL, the radioactivity appeared earlier and more concentrated in the vein draining the ovary -CL (30 sec, 0.53% of injected dose) than in the femoral vein (150 sec, 0.08% of injected dose). Removal of the ovary +CL was followed by a brief maintenance of peripheral progesterone within luteal-phase levels. The in-vitro progesterone production by a suspension of cells isolated from the corpus luteum was 47.5 +/- 12.8 ng/ml/2 h, whereas luteal-like cells isolated from the ovary -CL secreted 14.3 +/- 6.0 ng/ml/2 h (P less than 0.01) into the medium. We therefore suggest that the symmetrical and high secretion rate of progesterone by the ovaries of the capuchin monkey indicates a between-ovary communication system, and that the luteal-like tissue of the ovary -CL can produce relatively large amounts of progesterone.

Assuntos

RESUMO

The pineal has undergone marked changes as vertebrates have evolved from amphibians to mammals. The amphibian pineal is a photoreceptive organ which sends nervous information to the brain via pineal nerves: the mammalian and avian pineal have no direct connections to the CNS and their metabolism is controlled by an indirect pathway involving their peripheral sympathetic nerves. In addition, the pinealocytes of some birds also function as photoendocrine transducers, i.e., they convert a photic input reaching them directly through the skull into a hormone output. Through the secretion of melatonin and of some as yet undefined low molecular weight peptides, the pineal participates in the control of other neuroendocrine rhythms such as seasonal cycles in gonadal function.

Assuntos

Assuntos

RESUMO

The pineal has undergone marked changes as vertebrates have evolved from amphibians to mammals. The amphibian pineal is a photoreceptive organ which sends nervous information to the brain via pineal nerves: the mammalian and avian pineal have no direct connections to the CNS and their metabolism is controlled by an indirect pathway involving their peripheral sympathetic nerves. In addition, the pinealocytes of some birds also function as photoendocrine transducers, i.e., they convert a photic input reaching them directly through the skull into a hormone output. Through the secretion of melatonin and of some as yet undefined low molecular weight peptides, the pineal participates in the control of other neuroendocrine rhythms such as seasonal cycles in gonadal function.

RESUMO

The pineal has undergone marked changes as vertebrates have evolved from amphibians to mammals. The amphibian pineal is a photoreceptive organ which sends nervous information to the brain via pineal nerves: the mammalian and avian pineal have no direct connections to the CNS and their metabolism is controlled by an indirect pathway involving their peripheral sympathetic nerves. In addition, the pinealocytes of some birds also function as photoendocrine transducers, i.e., they convert a photic input reaching them directly through the skull into a hormone output. Through the secretion of melatonin and of some as yet undefined low molecular weight peptides, the pineal participates in the control of other neuroendocrine rhythms such as seasonal cycles in gonadal function.

Assuntos