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M L Bacci

Publications and source records attributed to M L Bacci.

12 recordsLinked to original sources
PubMed2000

Vascular endothelial growth factor production in growing pig antral follicles.

Angiogenesis is the process that drives blood vessel development in growing tissues in response to the local production of angiogenic factors. With the present research the authors have studied vascular endothelial growth factor (VEGF) production in ovarian follicles as a potential mechanism of ovarian activity regulation. Prepubertal gilts were treated with 1250 IU equine chorionic gonadotropin (eCG) followed 60 h later by 750 IU of human chorionic gonadotropin (hCG) in order to induce follicle growth and ovulation. Ovaries were collected at different times of the treatment and single follicles were isolated and classified according to their diameter as small (<4 mm), medium (4-5 mm), or large (>5 mm). VEGF levels were measured in follicular fluid by enzyme immunoassay, and VEGF mRNA content was evaluated in isolated theca and granulosa compartments. Equine chorionic gonadotropin stimulated a prompt follicular growth and induced a parallel evident rise in VEGF levels in follicular fluid of medium and large follicles. Analysis of VEGF mRNA levels confirmed the stimulatory effect of eCG, showing that it is confined to granulosa cells, whereas theca cells maintained their VEGF steady state mRNA. Administration of hCG 60 h after eCG caused a dramatic drop in follicular fluid VEGF that reached undetectable levels in 36 h. A parallel reduction in VEGF mRNA expression was recorded in granulosa cells. The stimulating effect of eCG was also confirmed by in vitro experiments, provided that follicles in toto were used, whereas isolated follicle cells did not respond to this hormonal stimulation. Consistent with the observation in vivo, granulosa cells in culture reacted to hCG with a clear block of VEGF production. These results demonstrate that while follicles of untreated animals produce stable and low levels of the angiogenic factor, VEGF markedly rose in medium and large follicles after eCG administration. The increasing levels, essentially attributable to granulosa cells, are likely to be involved in blood vessel development in the wall of growing follicles, and may play a local key role in gonadotropin-induced follicle development. When ovulation approaches, under the effect of hCG, the production of VEGF is switched off, probably creating the safest conditions for the rupture of the follicle wall while theca cells maintained unaltered angiogenic activity, which is probably required for corpus luteum development.

Animals↗
PubMed1996

In situ detection of apoptosis in regressing corpus luteum of pregnant sow: evidence of an early presence of DNA fragmentation.

Luteolysis has been shown to be correlated with apoptosis in rats, sheep, and cows. In pigs, apoptosis has already been demonstrated as regards atretic follicles. The present study has been conducted to evaluate whether apoptosis occurs during corpora lutea regression in the pregnant pig and to investigate the temporal relationship between apoptosis and functional luteolysis. The apoptotic process has been studied through the research of oligonucleosome fragmentation by means of classical electrophoresis methods and by in situ detection on histological luteal sections. The latter method allows the identification of apoptosis and the localization of apoptotic cells. Pregnant sows were cloprostenol (PGF2 alpha analog) treated and ovariectomized 0, 6, 12, 24, 48, and 72 hr after treatment. Corpora lutea were utilized for progesterone and DNA extraction and in situ evaluation of apoptosis. Clear evidence of apoptosis was seen earlier with the in situ technique (6 hr for stromal tissue, 12 hr for luteal cells) than with the classical method (24 hr). Apoptosis was, however, apparent after plasma and tissue progesterone had reached basal levels. In conclusion, these results are consistent with the hypothesis that apoptosis occurs during luteolysis in pigs. Moreover, the data obtained with the in situ technique made it possible to identify signs of structural regression in stromal tissue first than in parenchymal cells. A two-stage activation of apoptosis has been discussed to explain structural changes that occur during luteolysis after cloprostenol treatment in swine corpora lutea.

Animals↗
PubMed1991

Changes in maturation-promoting activity in the cytoplasm of pig oocytes throughout maturation.

Maturation-promoting factor (MPF) was examined in maturing pig oocytes by electrofusing them with germinal vesicle (GV) oocytes. Oocytes containing high levels of MPF (MI or MII stages) induced the breakdown of the GV introduced by fusion and the formation of the metaphase plate in 1 hr. A similar effect was seen when two or three GV oocytes were fused with a MII oocyte and then incubated for 1 hr in the presence of cycloheximide (a specific protein synthesis inhibitor), indicating that high levels of preformed MPF are present at the metaphase stage. During the maturation in vitro of cumulus-enclosed oocytes, a first sharp rise in MPF was seen between 26 and 29 hr of culture (MI stage); MPF declined after 2 hr (AI-TI stages) and again reached high levels at 35 hr, where it remained for the rest of maturation. Denuded oocytes showed a similar behavior, but MPF appeared 9 hr earlier and the rise, due to the asynchronous maturation of these oocytes, was not as sharp as in cumulus enclosed oocytes. Cycloheximide was used to study protein synthesis requirements for oocyte maturation. Intact GV were observed after 44 hr of culture when cycloheximide was added at 26 hr or earlier, and chromosome decondensation and pronuclear formation were observed when the drug was added at 32 hr. Transcriptional requirements were investigated by treating the oocytes with alpha-amanitin, an RNA polymerase inhibitor. This drug could completely inhibit the maturation of cumulus-enclosed oocytes, but this was a somatic cell-mediated effect since denuded oocytes were insensitive to this treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Maturation of pig oocytes: observations on membrane potential.

The membrane-potential changes of pig oocytes during maturation are described. Cumulus-enclosed oocytes have a resting potential of -41.81 +/- 0.60 mV; the removal of cumulus cells caused this potential to drop to -30.95 +/- 0.43 mV. Adding LH to the culture medium did not influence the potential of denuded oocytes but depolarized the potential of cumulus-enclosed oocytes to -32.90 +/- 0.43 mV. FSH did not affect the membrane potential of denuded or cumulus-enclosed oocytes, but significantly reduced the amplitude of the depolarization induced by LH. The effect of gonadotropins on cultured granulosa cells was also investigated. Plated granulosa cells have a resting potential of -45.21 +/- 0.72 mV, similar to that of cumulus-enclosed oocytes. As recorded in cumulus-enclosed oocytes, LH depolarized granulosa cell membrane potential (-30.33 +/- 0.69 mV) and FSH reduced this effect. To evaluate if oocyte maturation in vivo is accompanied by membrane-potential depolarization, follicular growth and oocyte maturation were induced in 6 prepubertal gilts by using an eCG-hCG treatment. Twenty hours after the beginning of oocyte maturation in vivo (induced by hCG), the membrane potential of the oocyte was depolarized to -28.84 +/- 1.01 mV, a value similar to that observed in vitro. These data indicate that both LH and FSH can influence the membrane potential of follicular somatic cells and, consequently, that of the oocyte. The electrical coupling between somatic cell and oocyte may represent a means by which the gonadotropin message is passed to the germinal cell by the somatic compartment.

Animals↗
PubMed1988

Follicular factors influence oocyte fertilizability by modulating the intercellular cooperation between cumulus cells and oocyte.

In order to investigate whether the follicular tissue influences cumulus-oocyte interaction and, consequently, the fertilizability of the egg, four experiments were carried out. In the first, cumulus-enclosed pig oocytes were cultured for 44 h in control medium (modified TCM-199) or in follicle-conditioned medium, and the intercellular coupling was studied by measuring 3H-uridine uptake. In control medium the intercellular cooperation started to decline immediately, and at 24-32 h the uncoupling was almost complete. By contrast, in follicle, conditioned medium, it remained at high levels until 24-32 h. In the second experiment protein synthesis patterns of oocytes were studied. Oocytes cultured in conditioned medium were characterized by a 45-kD protein band, while those maturing in control medium were identifiable by a marked 56-kD band. In the third experiment mature oocytes were fertilized in vitro. The percentage of penetrated egg was higher in oocytes matured in conditioned medium than in control medium. In addition, only oocytes matured in conditioned medium could consistently decondense spermatozoa and form male pronuclei. Metabolic cooperation, protein synthesis patterns, and fertilizability were also studied in oocytes matured in control medium supplemented with either 17 beta-estradiol or progesterone or testosterone or dihydrotestosterone or androstenedione or ether extract of conditioned medium. Only ether extract and progesterone stimulated cumulus oocyte interaction and sperm decondensation. In the last experiment oocytes denuded at different stage of their maturation in conditioned medium were fertilized in vitro. The longer the eggs were cultured with the cumulus, the higher was their penetrability. Moreover, only oocytes denuded after 40 h of culture could, once fertilized, promote the formation of male pronuclei. These data demonstrate that follicular secretions are fundamental for the maintenance in vitro of a functional intercellular coupling between cumulus and oocyte, which is necessary for the egg to become penetrable by spermatozoa and to acquire the conditions required for the formation of male pronuclei.

Animals↗
PubMed1983

[Not Available].

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