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Biomedical subjects

M Lacey

Publications and source records attributed to M Lacey.

At least 19 recordsLinked to original sources
PubMed2003

Phytoestrogens inhibit aromatase but not 17beta-hydroxysteroid dehydrogenase (HSD) type 1 in human granulosa-luteal cells: evidence for FSH induction of 17beta-HSD.

BACKGROUND: Studies using purified enzyme preparations, placental microsomes or cell lines have shown that certain phytoestrogens can inhibit the enzymes that convert androgens to estrogens, namely aromatase and 17beta-hydroxysteroid dehydrogenase (HSD) type 1 and type 5. The study aim was to investigate the effects of selected phytoestrogens on aromatase and 17beta-HSD type 1 activity in primary cultures of human granulosa-luteal (GL) cells. METHODS AND RESULTS: GL cells, cultured for 48 h in medium containing 5% fetal calf serum and for a further 24 h in serum-free medium with or without hFSH or hCG, were exposed to steroid substrates during the last 1-4 h of the experiment. The production of progesterone in the presence of pregnenolone or estradiol synthesis from androstenedione, estrone or testosterone showed dose- and time-dependent increases. Whilst hCG priming had no effect on progesterone production, FSH priming induced mean 68 and 56% increases in the production of estradiol from androstenedione (A-dione) and estrone respectively, but had no significant effect on the metabolism of testosterone to estradiol. None of the phytoestrogens investigated had any acute effects on enzyme activity. In contrast, when GL cells were exposed to the compounds for 24 h prior to exposure to steroid substrates for 4 h, 10 micro mol/l apigenin and zearalenone significantly inhibited aromatase activity, whilst biochanin A and quercetin had no effect. None of the phytoestrogens inhibited FSH-induced 17beta-HSD type 1 activity, and only quercetin significantly inhibited progesterone production. CONCLUSIONS: The inability of phytoestrogens to acutely inhibit steroidogenic enzymes in human GL cells (as has been shown in cell-free models) suggests that they are either rapidly metabolized to relatively inactive compounds or that the high enzyme activity in human GL cells masks any inhibitory effects of the compounds at the concentration tested.

17-Hydroxysteroid Dehydrogenases↗
PubMed2003

Hepatic gene expression patterns in thyroid hormone-treated hypothyroid rats.

Thyroid hormone (T3) is essential for normal development, differentiation and metabolic balance. We have performed DNA microarray experiments using hepatic RNA from hypothyroid and T3-treated hypothyroid rats in order to characterize T3-induced gene expression patterns after various time points (6, 24 and 48 h after the administration of the hormone). Sixty-two of 4608 different genes displayed a reproducible T3-response, and cluster analysis divided these differentially regulated genes into six expression patterns. Thirty-six genes were not significantly regulated within the first 24 h. Transient transfection experiments of eight late-induced gene promoters failed to detect a thyroid hormone response element within their regulatory elements, suggesting an indirect activation mechanism(s). In search for an intermediate factor of T3 action, we examined whether various rather ubiquitous transcription factors, peroxisome proliferator-activated receptors (PPARs) and coactivators of the PPARgamma coactivator 1 family (PGC-1) are regulated by T3. Only PPARgamma and PERC/PGC-1beta exhibit a significant T3-response within the first 6 h after treatment, identifying these factors as candidate components for mediating the late-induced expression pattern. Regulation of early-induced genes within the first 6 h after administration of T3 on transcript levels correlates with altered protein levels after 24 and 48 h in vivo.

Animals↗
PubMed2001

Differing effects of endocrine-disrupting chemicals on basal and FSH-stimulated progesterone production in rat granulosa-luteal cells.

Previous studies have shown that the phytoestrogen, genistein, inhibits basal and forskolin-stimulated progesterone synthesis in rat granulosa-luteal cells. Genistein, however, not only binds and activates the estrogen receptor (ER), but is also a potent inhibitor of tyrosine kinase. In these studies we have compared the effects of estradiol, two other phytoestrogens, apigenin and coumarin, the pesticide, [2-(chlorphenyl)-2-(4-chlorphenyl)-1,1,1-trichlorethan] (2,4'DDT), and the industrial chemical, 4-octyl-phenol, on basal and follicle stimulating hormone (FSH)-stimulated progesterone production in the same experimental system. Only a supraphysiological dose of estradiol (10(-5) M) significantly inhibited basal and forskolin-stimulated progesterone production in granulosa-luteal cells, but had no effect on FSH-stimulated production. In contrast, apigenin, DDT, and octyl-phenol stimulated basal progesterone production at doses around 10(-8) to 10(-7) M, but this effect was reversed at higher doses. Coumarin was without effect. Like basal production, the two phytoestrogens had opposing effects on FSH-stimulated progesterone production. Genistein at 10(-5) M was inhibitory, while apigenin significantly potentiated the response at 19(-7) M. In contrast, DDT had no effect on the FSH-induced response, though 10(-7) M octyl-phenol nearly doubled the response. While all these chemicals are known to interact with the estrogen receptor to a greater or lesser extent, these studies suggest that like genistein, these different endocrine-disrupting chemicals may have other actions apart from those on the estrogen receptor.

Animals↗
PubMed2000

Protein tyrosine kinase activity of lavendustin A and the phytoestrogen genistein on progesterone synthesis in cultured rat ovarian cells.

OBJECTIVE: To compare the effects of two protein tyrosine kinase inhibitors, lavendustin A and the phytoestrogen genistein, on progesterone synthesis in cultured rat ovarian cells. DESIGN: Experimental animal study. SETTING: Medical school laboratory. ANIMAL(S): Porton Wistar rats. INTERVENTION(S): Ovaries from estrous rats were used to establish cell cultures of granulosa-luteal cells from freshly ruptured follicles, granulosa-luteal cells cocultured with peritoneal macrophages, and whole ovarian dispersates. MAIN OUTCOME MEASURE(S): Progesterone and nitrite concentrations in the culture medium. RESULT(S): The protein tyrosine kinase inhibitors suppressed steroid synthesis in a dose-dependent manner and completely inhibited the steroidogenic response to both FSH and the adenyl cyclase stimulator forskolin. The inhibitory action of cocultured macrophages on basal and forskolin-stimulated progesterone production in granulosa-luteal cells was not reversed by genistein, nor was the inhibitory effect of interleukin-1beta in cultures of ovarian dispersates. CONCLUSION(S): Genistein and the nonestrogenic protein tyrosine kinase inhibitor lavendustin A exert potent inhibitory effects on steroidogenesis that are independent of cytokines. The toxic effects of genistein on sexual development and reproduction may be attributed not only to its estrogenic action but also to its action as a protein tyrosine kinase inhibitor.

Animals↗
PubMed1997

L(p) estimates for the bilinear Hilbert transform.

For the bilinear Hilbert transform given by: H fg(x) = p.v.integral f(x - y)g(x + y) dyy, we announce the inequality parallel H fg parallel (p(3) ) </= K(p(1) ) (,p(2) ) parallel f parallel (p(1) ) parallel g parallel (p(2) ), provided 2 < p(1), p(2) < infinity, 1/p(3) = 1/p(1) + 1/p(2) and 1 < p(3) < 2.

Journal Article↗
PubMed1997

Interactions between interleukin-1 beta, nitric oxide and prostaglandin E2 in the rat ovary: effects on steroidogenesis.

It has been reported that interleukin (IL)-1 beta induces the synthesis of both nitric oxide (NO) and prostaglandin (PG)E2 in cultures of dispersed ovarian cells and exerts cytotoxic effects on these cells. Since PGE2, NO and IL-1 beta have been implicated as modulators of steroidogenesis, experiments have been undertaken to determine how IL-1 beta-induced NO and PGE2 production may affect steroidogenesis in cultures of ovarian dispersates obtained from untreated adult oestrous rats and to compare the action of IL-1 beta in cultures of granulosa/luteal (GL) cell-only cultures and GL cells co-cultured with peritoneal macrophages. IL-1 beta significantly increased the production of NO (assessed by nitrite measured in the culture medium) and PGE2 in cultures of ovarian dispersates but had no effect on cultures of GL cells in which NO production was typically very low and PGE2 production was undetectable. In contrast both NO and PGE2 were high in co-cultures and were not significantly altered by the addition of IL-1 beta. The NO donor sodium nitroprusside inhibited steroidogenesis in cultures of ovarian cells in a dose-dependent manner while PGE2 had a stimulatory effect. Concomitant inhibition of NO production with aminoguanidine and PG production with indomethacin resulted in a significant enhancement of basal progesterone production in these cultures. Finally, IL-1 beta inhibited progesterone responses to forskolin and PGE2 in ovarian dispersates: an effect not observed in GL cell-only cultures nor in co-cultures in which forskolin-induced progesterone production is always inhibited. No cytotoxic effects of IL-1 beta during the 48 h period of culture were observed. A comparison of the steroidogenic NO and PGE2 responses to IL-1 beta in the three culture models suggests that (i) the response to IL-1 beta observed in ovarian dispersates could be due to cytokine activation of resident and infiltrating macrophages or that the action of IL-1 beta requires some other heterologous cell-cell contact, and (ii) IL-1 beta acts indirectly on signal transduction pathways which stimulate steroidogenesis.

Animals↗
PubMed1996

Inhibitory effect of peritoneal macrophages on progesterone release from cocultured rat granulosa cells is reversed by dexamethasone: evidence for an action independent of nitric oxide and distal to cyclic adenosine 3',5'-monophosphate generation.

We investigated the effects of cocultured macrophages on progesterone release from granulosa cells obtained at different stages of the rat estrous cycle and determined whether the immunosuppressive actions of the synthetic glucocorticoid can modulate the effects of cocultured macrophages. Basal and hCG-stimulated progesterone release from granulosa cell-only cultures varied according to the stage of the estrous cycle at which granulosa cells were obtained, but macrophages exerted profound inhibitory effects on both basal and hCG-stimulated steroidogenesis at all stages. These inhibitory effects were partially reversed by the addition of dexamethasone (5 x 10(-7) to 5 x 10(-5) M) to the culture medium. Measurement of nitrite accumulation in the media, as an index of nitric oxide production, showed that granulosa cells produce very low levels of this metabolite compared with macrophages, although granulosa/luteal cells from freshly ruptured follicles of estrous rats produced significantly higher concentrations of nitrite compared with granulosa cells obtained from diestrous and proestrous rats. Dexamethasone had only limited effects in suppressing the accumulation of nitrite, showing that the macrophages were synthesizing nitric oxide synthase and suggesting that the action of dexamethasone was independent of nitric oxide. Macrophages also inhibited the steroidogenic response of granulosa cells to forskolin (5 x 10(-6) M to 10(-4) M) and dibutyryl cAMP (1mM and 0.5 mM) and the potentiation of the response by the addition of hCG. However, this inhibition was reversed by the presence of 5 x 10(-6) M dexamethasone, and responses were comparable with those measured from granulosa cell-only cultures. Overall, the results suggest that macrophage inhibition of progesterone synthesis acts at a site distal to the generation of cAMP and that dexamethasone reverses this inhibition.

Animals↗
PubMed1994

Isolation and characterization of a mouse amelogenin expressed in Escherichia coli.

A mouse cDNA encoding a 180 amino acid amelogenin was subcloned into the pET expression plasmid (Novagen, Madison, WI) for production in Escherichia coli. A simple growth and purification protocol yields 20-50 mg of 95-99% pure recombinant amelogenin from a 4.5-liter culture. This is the first heterologous expression of an enamel protein. The expressed protein was characterized by partial Edman sequencing, amino acid composition analysis, SDS-PAGE, Western blotting, laser desorption mass spectrometry, and hydroxyapatite binding. The recombinant amelogenin is 179 amino acids in length, has a molecular weight of 20,162 daltons, and hydroxyapatite binding properties similar to the porcine 173 residue amelogenin. Solubility analyses showed that the bacterially expressed protein is only sparingly soluble in the pH range of 6.4-8.0 or in solutions 20% saturated with ammonium sulfate. The purified protein was used to generate rabbit polyclonal anti-amelogenin antibodies which show specific reaction to amelogenins in both Western blot analyses of enamel extracts and in immunostaining of developing mouse molars.

Amelogenin↗
PubMed1994

Temporal contour deformity after coronal flap elevation: an anatomical study.

Temporal contour deformity is defined as a concavity or depression in the temporal region located superior to the zygomatic arch and immediately posterior to the lateral orbital rim. The deformity can present as a consequence of extended coronal flap elevation for exposure of the lateral craniofacial skeleton. This study describes the anatomical and pathological features of the deformity and identifies causative factors. The series consists of unilateral temporal contour deformities after coronal flap elevation in 6 patients. A standardized data sheet was used in documenting details of the initial temporal dissection, clinical findings, and radiological features. Elevation of the temporal soft tissues was based on a qualitative analysis of coronal magnetic resonance imaging (MRI) scans comparing the affected and the unaffected temporal regions. The MRI studies demonstrated normal volume of the temporalis muscle in all cases, with no evidence of atrophy or disinsertion of the muscle. Diminution in the volume of the superficial temporal fat pad was identified in 4 patients, whereas inferior displacement or prolapse of the superficial temporal fat pad was noted in 2 patients.

Adipose Tissue↗
PubMed1993

Use of porous high-density polyethylene implants in temporal contour reconstruction.

A temporal contour deformity is characterized by a concavity or depression in the soft-tissue contour of the temporal region and is associated with exaggerated relief of the lateral orbital rim and the zygomatic arch. The etiology of the deformity is varied, comprising any condition that results in displacement, atrophy, or absence of the temporalis muscle or the superficial temporal fat pad. We describe reconstruction of this deformity with porous high-density polyethylene implants in 16 consecutive patients, treated between July 1988 and September 1990. The etiology of the deformity and the surgical treatment are described. The results of treatment are assessed on long-term follow-up, ranging from 2 to 4 years postoperatively.

Adult↗
PubMed1990

Demonstration of a nonsteroidal factor in human follicular fluid that attenuates the self-priming action of gonadotropin-releasing hormone on pituitary gonadotropes.

The self-priming effect of gonadotropin-releasing hormone (GnRH) on luteinizing hormone (LH) release can be demonstrated in vitro by perfusing pituitary tissue with a continuous GnRH stimulus. A characteristic biphasic response is produced. We have used this system to investigate whether or not human follicular fluid (hFF) contains a nonsteroidal substance that can attenuate the GnRH-induced LH secretion in perfused rat pituitary glands. Steroid-extracted hFF, added to the perfusing medium, attenuated the self-priming action of GnRH in a dose-dependent manner. This was not abolished by selectively depleting the inhibin content of hFF by 97% on an immunoaffinity column. Furthermore, the biological activity of the substance was resistant to heating and was removed by dialysis. It is concluded that hFF contains a nonsteroidal factor, distinct from inhibin, that can attenuate the self-priming action of GnRH on pituitary gonadotropes.

Animals↗
PubMed1988

Actions of cocaine on central monoamine neurons: intracellular recordings in vitro.

Intracellular recordings from monoaminergic neurons in brain slice preparations have been used to study the action of cocaine. The firing rate of noradrenergic neurons in the locus coeruleus, serotonergic neurons of dorsal raphe and dopaminergic neurons from substantia nigra zona compacta is reduced or inhibited by the transmitter substance that they produce. This process, which can be brought about by release of the transmitter from either dendrites or axon collaterals in the vicinity of the cell bodies, has been referred to as 'autoinhibition'. In each case, the inhibition results from a membrane hyperpolarization caused by an increased conductance to potassium ions. In each of the nuclei, cocaine caused a decrease in spontaneous firing through a membrane hyperpolarization. This action of cocaine was blocked by the respective 'autoreceptor' antagonist. In the locus coeruleus and dorsal raphe cocaine prolonged an inhibitory postsynaptic potential caused by the release of noradrenaline and 5-HT respectively. The concentration-response curve for the exogenously applied agonist in each of the three nuclei was shifted to the left in the presence of cocaine. These observations indicate that the activity of these aminergic neurons was affected by cocaine through an inhibition of the reuptake of endogenously release transmitter. The blockade of reuptake increased the extracellular level of noradrenaline, 5-HT and dopamine in the respective nuclei to concentrations which caused electrophysiologically detectable effects. This suggests that the reuptake process is a primary mechanism for termination of the response. In addition, this action of cocaine occurs at behaviorally relevant concentrations. The fact that all monoaminergic transmission can be affected by cocaine may contribute to the complexity of its behavioral actions.

Action Potentials↗