Search PubMed⌕ Search

Biomedical subjects

A Makris

Publications and source records attributed to A Makris.

At least 73 records · Page 4Linked to original sources
PubMed1989

Outer membrane alterations in multiresistant mutants of Pseudomonas aeruginosa selected by ciprofloxacin.

Spontaneous mutants of Pseudomonas aeruginosa selected by ciprofloxacin were studied for outer membrane alterations. Acquisition of ciprofloxacin resistance was at least partially related to defects in lipopolysaccharide synthesis. When ciprofloxacin resistance was combined with resistance to beta-lactams and aminoglycosides, several alterations in outer membrane proteins were noted.

Bacterial Outer Membrane Proteins↗
PubMed1988

Immunoreactive substance P in the human ovary.

Although substance P has been demonstrated in the nonhuman ovary, it has not previously been identified in normal human ovarian tissue. We examined ovarian surgical specimens from 30 women for the presence of immunoreactive substance P. With the use of a specific radioimmunoassay, immunoreactive substance P was identified in these ovarian extracts. The geometric mean of the immunoreactive substance P concentration was 0.55 pg/mg wet weight (95% confidence limits 0.04 and 6.15). Thecal and stromal concentrations of immunoreactive substance P were greater than those in the corpora lutea and tunica albuginea. Large follicles had a lower concentration of immunoreactive substance P than did small follicles. We conclude that the neuropeptide substance P is present in some normal human ovaries and may be a modulator of ovarian function.

Adult↗
PubMed1986

Insulin stimulates androgen accumulation in incubations of ovarian stroma obtained from women with hyperandrogenism.

The effects of insulin and insulin-like growth factors (IGFs) on ovarian androgen production were examined in ovarian stroma obtained from four women with hyperandrogenism and three women without hyperandrogenism. In incubations of stroma obtained from all four hyperandrogenic patients, insulin alone (500 ng/ml) significantly stimulated androstenedione and testosterone release. LH alone (25 ng/ml) significantly stimulated androstenedione release in incubations of stroma obtained from three of the four hyperandrogenic patients and testosterone release in incubations of stroma obtained from one of the four hyperandrogenic patients. In stromal incubations from three of the four hyperandrogenic patients, insulin alone (500 ng/ml) resulted in a significantly greater release of androstenedione and testosterone than did LH alone (25 ng/ml). Dihydrotestosterone was released in measurable quantities in incubations of stromal tissue obtained from three of the four hyperandrogenic women. In all three instances in which dihydrotestosterone was detectable, insulin alone (500 ng/ml), but not LH alone (25 ng/ml), significantly stimulated dihydrostestosterone release. Incubations of stroma obtained from three nonhyperandrogenic, normally cycling women demonstrated low levels of androstenedione release and negligible testosterone and dihydrotestosterone release. Insulin alone (500 ng/ml) and LH alone (25 ng/ml) produced no significant increase in androstenedione release. Insulin (500 ng/ml) plus LH (25 ng/ml) significantly stimulated androstenedione accumulation in stroma obtained from two of the nonhyperandrogenic women. One insulin dose-response experiment was performed using stromal tissue obtained from a hyperandrogenic woman. In this experiment, insulin, at a dose of 50 ng/ml, was as effective as insulin at a dose of 500 ng/ml in stimulating androstenedione and testosterone release. In addition to insulin, IGF-I/somatomedin C (50 ng/ml) stimulated androstenedione and testosterone release. Relaxin (1 microgram/ml) and multiplication-stimulating activity (50 ng/ml) did not stimulate androstenedione and testosterone release. These studies suggest that human ovarian stroma may be a target tissue for insulin and IGF-I, and that hyperinsulinemia may be an important factor contributing to ovarian hyperandrogenism.

Adult↗
PubMed1985

Biphasic progesterone synthesis by the hamster preovulatory follicle in vitro.

In vitro time course studies of progesterone and protein synthesis by hamster preovulatory follicles (harvested prior to the proestrous gonadotropin surge) were done. LH appears to stimulate progesterone synthesis in 2 phases. The first phase lasts 0 to 4 or 5 hr and is not inhibited by either puromycin or cycloheximide. The second phase (apparent by 4-5 hr) is distinguished from the first phase by its inhibition by puromycin and cycloheximide, and by the differential dose response of dibutyryl cyclic AMP on the respective 2 phases. Incorporation of a H-labelled mixture of amino acids into protein is not seen in LH-stimulated follicles in 2 hr incubations but is apparent by 4 hr. The LH-stimulated protein synthesis is inhibited by puromycin. The results indicate that although LH stimulates both phases of progesterone synthesis, the mechanisms may be different for each phase.

1-Methyl-3-isobutylxanthine↗
PubMed1984

Insulin stimulates androgen accumulation in incubations of human ovarian stroma and theca.

The effects of insulin on ovarian steroidogenesis were examined in four-day incubations of minced stroma and theca obtained from a woman with hyperandrogenism, insulin resistance, and acanthosis nigricans, and from a normally cycling woman. In incubations of theca obtained from the patient with hyperandrogenism, insulin resistance, and acanthosis nigricans, lutenizing hormone (LH) (25 ng/mL) alone stimulated androstenedione, testosterone, progesterone, and estradiol accumulation. Insulin (500 ng/mL) alone stimulated androstenedione and testosterone accumulation, but not progesterone or estradiol accumulation. In incubations of stroma obtained from the hyperandrogenism, insulin resistance, and acanthosis nigricans patient, LH (25 ng/mL) alone stimulated androstenedione and testosterone accumulation, but not dihydrotestosterone accumulation. Insulin (500 ng/mL) alone stimulated androstenedione, testosterone, and dihydrotestosterone accumulation. In incubations of stroma from the normally cycling woman, LH plus insulin acted synergistically to stimulate androstenedione accumulation. These results suggest that insulin may be a regulator of steroid biosynthesis in the thecal and stromal compartments of the human ovary.

Acanthosis Nigricans↗
PubMed1984

The nonluteal porcine ovary as a source of angiogenic activity.

Nonluteal ovarian tissue extracts were tested for their ability to stimulate migration and proliferation of cultured bovine capillary endothelial cells. Stimulation of migratory and proliferative activity was found in the 105,000 X g supernatant of homogenates of either whole nonluteal porcine ovaries or isolated theca (follicular walls). Maximal proliferative and migratory activity was obtained with 1-10 micrograms homogenate protein. Neither follicular fluid nor extracts of granulosa cells showed significant activity when tested over a broad concentration range. The proliferative and migratory activities were associated with a heat-labile, nondialyzable, protease-sensitive fraction that was soluble in 40%, but not 60% (NH4)2SO4. The tissue extracts that effectively stimulated growth and migration of capillary endothelial cells in vitro also stimulated the formation of new capillary blood vessels in an angiogenesis assay performed on chick chorioallantoic membranes.

Allantois↗
PubMed1983

Significance of the delta 5 and delta 4 steroidogenic pathways in the hamster preovulatory follicle.

Isolated hamster granulosa cells and theca from preovulatory follicles were incubated in vitro for 2 and 6 h in the absence/or presence of LH and steroid substrates. The purpose of the experiments was to determine, in theca, the relative activities of the delta 5 and delta 4 pathways under controlled conditions, and to compare the ability of granulosa cells and theca to form progesterone from exogenous pregnenolone. The results of the experiments show that the delta 5 pathway in theca predominates before and up to 2 h after LH stimulation. The delayed effect of LH after 2 h is a switch from delta 5 to delta 4 as the major metabolic pathway. Progesterone formation from exogenous pregnenolone is 7 to 10 times greater in unstimulated granulosa cells than in theca. Acute effects of LH lead to increased conversion of exogenous pregnenolone to progesterone in granulosa cells but not theca. LH does, however, acutely stimulate the thecal conversion of DHEA to androstenedione. The longer term effect of LH in both cell types is to increase pregnenolone conversion to progesterone.

Androstenedione↗
PubMed1983

An endogenous ovarian growth factor which stimulates BALB/3T3 and granulosa cell proliferation.

Extracts of whole porcine ovary stimulate BALB/3T3 [3H] DNA synthesis in BALB/3T3 cells. Biochemical characterization indicates the growth factor is associated with a soluble cationic protein that is labile to heat, stable to dithiothreitol treatment and elutes from Sephadex G-100 between chymotrypsin (25,000 Mr) and cytochrome C (12,700 Mr). Extracts of thecal tissue have growth-promoting activity in both granulosa and 3T3 cells. Conditioned medium from thecal but not granulosa cell cultures stimulates [3H] DNA synthesis in quiescent 3T3 and granulosa cells. The results indicate the presence of an endogenous protein ovarian growth factor found in the theca that stimulates granulosa cell proliferation in vitro.

Animals↗
PubMed1983

Effects of insulin on steroidogenesis in cultured porcine ovarian theca.

The effects of insulin on porcine thecal steroidogenesis were examined in long-term cultures of hyaluronidase-collagenase dispersed thecal cells. The thecal cultures made significant amounts of progesterone (P) and androstenedione (delta 4 A). Testosterone, dihydrotestosterone, estrone, and estradiol could not be detected in the media. Luteinizing hormone (LH) alone significantly increased P and delta 4 A accumulation. Insulin alone increased P accumulation on days 2 to 4 of culture. Insulin alone did not stimulate delta 4 A accumulation. Insulin plus LH resulted in a significantly greater accumulation of P and delta 4 A than LH alone. These results suggest that insulin may be a regulator of ovarian thecal steroidogenesis.

Androstenedione↗
PubMed1980

Effects of luteinizing hormone on steroidogenesis by thecal tissue from human ovarian follicles in vitro.

The steroidogenic responsiveness of human thecal tissue to different doses of LH was investigated in vitro in relation to the health of the follicle and to the responsiveness of stromal tissue. The results show that small incremental increases in LH, over a low range of concentrations (1 to 10 ng/ml), markedly increased the thecal output of androstenedione from healthy and/or atretic follicles. Theca from healthy follicles were also stimulated to increase their output of progesterone and estradiol in response to small increases in LH whereas theca from atretic follicles produced more variable amounts of progesterone and were unable to generate estradiol. In contrast, relatively high concentrations of LH (50 ng/ml) reduced the total steroid output from the theca of both healthy and atretic follicles while 'switching on' a low level of steroidogenesis in stromal tissue. These data suggest that the steroidogenic response of thecal tissue is related to the mass of tissue (i.e., the size of the follicle), the health of the follicle and the amount of LH to which it is exposed.

Adult↗
PubMed1980

Steroidogenesis by the human oocyte-cumulus cell complex in vitro.

The ability of the human oocyte-cumulus cell complex to synthesize progesterone, androgens and estrogens and to modify its endocrine environment in vitro was investigated. Germinal-vesicle stage oocytes with adhering layers of cumulus cells were recovered from human ovaries and maintained for 40--50 h in vitro in a culture medium with or without antral fluid. The results show that oocyte-cumulus (O-C) cell complexes were capable of synthesizing progesterone, androgens and estrogens. Oocytes with the capacity of resuming meiosis in vitro were part of an O-C complex producing significantly more progesterone than those O-C complexes containing oocytes incapable of resuming meiosis. Irrespective of the stage of oocyte maturation at the end of culture, testosterone and estrone were respectively the major androgen and estrogen produced. It is concluded that the oocyte-cumulus compartment of the antral follicle is a steroidogenically competent unit and that it has the capacity to modify the endocrine microenvironment of the follicle.

Adult↗
PubMed1980

The source of follicular androgens in the hamster follicle.

The comparative ability of granulosa cells and theca of the hamster preovulatory follicle to produce androgens in vitro from endogenous and exogenous substrates was assessed. The results indicate that theca are the major source of follicular androstenedione, but that the granulosa cells may be the major source of follicular testosterone. Theca and granulosa cells accumulate comparable amounts of dihydrotestosterone from exogenous androstenedione and testosterone and both may be a significant source of follicular DHT. LH stimulates the conversion of progesterone and 17 alpha-OH progesterone to androstenedione, testosterone and DHT in theca. LH does not stimulate the conversion of androstenedione to testosterone or DHT, and that of testosterone to DHT in either granulosa cells or theca. FSH, in granulosa cells but not in theca, stimulates the conversion of adrostenedione to testosterone but it has no effect in DHT accumulation from exogenous testosterone.

Androgens↗
PubMed1980

The intraovarian sites of androgen and estrogen formation in women with normal and hyperandrogenic ovaries as judged by in vitro experiments.

The status of oocytes, the follicular fluid concentrations of steroids, and the in vitro steroidogenic capacities of stromal tissue, thecal tissue, and granulosa cells from a 15-yr-old girl with primary amenorrhea, ovarian hyperandrogenism, insulin-resistant diabetes mellitus, and acanthosis nigricans were compared to those from normal adult human ovaries. Most oocytes (95%) in the antral follicles recovered from the hyperandrogenic ovaries were degenerative, and the antral fluid levels of testosterone were 30- to 200-fold higher than those in normal ovaries. Granulosa cells from the hyperandrogenic ovaries produced mainly estradiol as did those from normal healthy follicles. The thecal tissues produced 2- to 6-fold more androgen than similar tissues from normal ovaries. However, the stroma from the hyperandrogenic ovaries produced 49- to 250-fold more testosterone than that generated by normal tissues. These data suggest that the removal of stromal tissue as well as follicular tissue from patients with certain types of hyperandrogenism may sometimes contribute to a reduction in androgen secretion.

Adolescent↗
PubMed1979

Metabolism of androstenedione by human ovarian tissues in vitro with particular reference to reductase and aromatase activity.

The ability of granulosa and theca cells of the human ovarian follicle at different stages of development, as well as stromal and luteal tissues from human ovaries to metabolize androstenedione (delta 4) to testosterone (T), dihydrotestosterone (DHT), estrone (E1) and estradiol (E2) with or without exposure to additional amounts of folicle-stimulating hormone was investigated by in vitro experiments. The results show that all the aforementioned ovarian tissues metabolized delta 4 to DHT. Indeed, with the exception of estrogen-secreting granulosa cells from large antral follicle (greater than 10 mm diameter) and possibly also luteal tissue from mid-luteal phase ovaries, the various ovarian tissues preferentially metabolized delta 4 to DHT instead of E (E1 + E2). Although thecal tissue is a major source of delta 4 in human ovaries it is concluded that the granulosa cells do not interact with the theca for the synthesis of E as the follicle enlarges from 1 to 10 mm in diameter. Indeed, excessive thecal delta 4 during this growth phase probably inhibits normal follicular development. However, as the follicle enlarges beyond 10 mm in diameter, and as the granulosa cells begin to preferentially metabolize delta 4 to E, the two cell-types of the follicle may increasingly interact to enhance the follicular output of E.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1979

Testicular aromatization in immature rats: localization and stimulation after gonadotropin administration in vivo.

Aromatization was measured in testicular microsomal preparations obtained from rats treated 3--4 days with FSH, hCG, or vehicle, hCG, but not FSH, was found consistently to stimulate testicular aromatase activity at least 10-fold. As a marker for FSH action, epididymal androgen-binding protein was assayed and found to be 3 times higher in FSH-treated rats than in either hCG or control rats. hCG, but not FSH or vehicle, stimulated serum testosterone levels more than 100-fold. In all groups, aromatase activity in the microsomal fraction was at least 6 times higher than that found in the mitochondrial fraction. In experiments in which testicular compartments were separated, microsomal preparations from interstitial tissue of hCG-treated rats had 5--7 times more aromatase activity than microsomes from seminiferous tubules and 2--3 times more activity than microsomes from whole testes. It is concluded the hCG administered in vivo can stimulate testicular aromatase activity in immature rats, and the increase in activity is localized in the interstitial tissue.

Animals↗