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N J MacLusky

Publications and source records attributed to N J MacLusky.

At least 91 records · Page 5Linked to original sources
PubMed1987

Regional sex differences in progestin receptor induction in the rat hypothalamus: effects of various doses of estradiol benzoate.

In the rat, sex differences in behavioral responsiveness to progesterone have been correlated with a sex difference in estrogen-induced progestin receptor induction in the ventromedial nucleus (VMN). It has recently been suggested that this sex difference in progestin receptor induction may only be present after treatment with large doses of estrogen. We have evaluated the sex difference in hypothalamic cytosol progestin receptor induction in gonadectomized/adrenalectomized rats treated with moderate doses of estradiol benzoate (EB; 20 micrograms/kg body weight). No sex differences were detected in cytosol progestin binding in mediobasal hypothalamus or preoptic area of animals treated with this dose 48 hr before they were killed. However, a higher level of progestin binding in the VMN of females than of males was found when these brain regions were examined using a microdissection technique. Saturation binding analysis of progestin binding in the VMN indicated that this sex difference in binding reflects a difference in the number of progestin binding sites, and not a difference in binding affinity. A dose-response study of progestin receptor induction in the medial preoptic nucleus (mPON), arcuate-median eminence region (ARC-ME), and VMN of male and female rats indicated a sex difference in cytosol progestin binding in the VMN at all EB doses tested (2, 8, 40, or 200 micrograms/kg body weight). No sex differences in cytosol progestin binding in the mPON or ARC-ME were observed at any of the tested doses. These results support the idea that the differences in behavioral sensitivity to progesterone may result in part from sex differences in the estrogen induction of progestin receptors in the VMN.

Animals↗
PubMed1986

Preservation of steroid receptors in frozen brain and pituitary tissue: use of the cryoprotective agent, dimethylsulfoxide.

This paper examines the effects of freezing and thawing on steroid receptor concentrations in the brain and pituitary of the rat. Storage at -70 degrees C for 1-2 weeks had no detectable effect on levels of cytoplasmic estrogen receptors. However, freezing and thawing resulted in measurable losses of cytoplasmic androgen, progestin and glucocorticoid receptors. Cell nuclear receptors were measured by exchange assay after in vivo administration of non-radioactive steroids. Nuclear estrogen, androgen and progestin receptor concentrations were all reduced by freezing compared to the levels in fresh tissue. In all cases except that of cytoplasmic glucocorticoid receptors, these losses could be prevented by freezing the tissue in 10% aqueous dimethylsulfoxide.

Animals↗
PubMed1986

Monoamine oxidase activity in the term human placenta.

Using a radioenzymatic assay, placental monoamine oxidase (MAO) activity was measured at term after delivery in normal and high-risk pregnancies where decreases in placental blood flow previously were shown. MAO activity in placentas of healthy controls after spontaneous labor was similar to that after elective cesarean section not in labor (mean +/- SE, 133 +/- 18 versus 100 +/- 15 nmol/min/mg protein, respectively). Compared to controls, there was a significant reduction in placental MAO activity in high-risk pregnancies (chronic hypertension, toxemia, and diabetes mellitus), 71 +/- 14, 69 +/- 22, and 69 +/- 7, respectively (P less than 0.05). These differences also were maintained when data were expressed per total placental weight. Effects of antihypertensive drugs on MAO activity in healthy placental tissue were assessed. In homogenates, both hydralazine and magnesium sulfate reduced enzyme activity, while in explants this was not observed. The effects of certain metabolites (which are elevated in plasma of diabetic patients) on healthy homogenates also were studied. Only butyrate reduced enzyme activity. In conclusion, placental MAO activity in vitro is low in term high-risk pregnancies. This may reduce local metabolic inactivation of catecholamines and serotonin and consequently lead to a decrease in blood flow. Such a direct relationship must be confirmed in further studies.

Antihypertensive Agents↗
PubMed1986

Estrogen formation and binding in the cerebral cortex of the developing rhesus monkey.

These studies were undertaken to determine whether estrogen receptors and the microsomal enzyme system called the aromatase complex, which is responsible for conversion of androgen to estrogen, are present in the brain of the rhesus monkey during perinatal life. Four monkeys (three females--one fetus removed on day 153 of gestation and two infants, 5 and 6 days postnatal--and 1 male, 2 days postnatal) were studied. Cytosol estrogen receptors were detected in all brain regions examined. The apparent equilibrium dissociations constants for reaction of these sites with [3H]moxestrol were similar to those for uterine and pituitary cytosol estrogen receptors (0.3-1.1 nM). Within the brain, highest levels of binding were observed in the hypothalamus-preoptic area, with fairly even, lower concentrations throughout the cortical structures. Aromatase complex activity was detected in the majority of the tissue specimens. The highest levels of estrogen formation were observed in the hypothalamus. However, the amygdala, the hippocampus, and several of the cortex samples also contained measurable aromatase complex activity. Among the cortical samples, the highest levels of aromatase complex activity were found in regions of the association cortex (the dorsolateral-prefrontal, orbital-prefrontal, anterior cingulate, and parietal cortices). The lowest levels of aromatase activity were found in the somatosensory and motor cortices of the postnatal animals. These results suggest that locally-formed estrogen may be involved in the effects of circulating androgens on the developing primate neocortex.

Animals↗
PubMed1986

Reproductive failure due to experimentally induced constant estrus does not alter the LH-RH fiber density in the median eminence of the rat.

The effects of anterior hypothalamic deafferentation on luteinizing hormone releasing hormone (LH-RH) fiber density in the mediobasal hypothalamus (MBH) were compared to those of a number of nonsurgical treatments which give rise to anovulatory sterility (injections of estradiol valerate, exposure to constant light, or neonatal androgen administration) in the female rat. All of the treatments used (surgical and nonsurgical) disrupted the normal 4-day pattern of estrous cyclicity. Bilateral anterior hypothalamic deafferentation markedly reduced the packing density of LH-RH fibers in the MBH. Unilateral deafferentation reduced the number of fibers on the ipsilateral side of the MBH by 31-64% and on the contralateral side by 15-40%. In contrast, none of the three nonsurgical treatments had any significant effect on the LH-RH fiber density. Electron microscopic examination revealed no morphologic, or distribution differences in MBH LH-RH fibers between control females and animals rendered anovulatory by the nonsurgical experimental procedures. These results demonstrate that estrogen, androgen, and constant light induced anovulatory sterility are not associated with any overt change in the number or morphology of LH-RH immunoreactive fibers in the MBH, suggesting that the primary lesion responsible for the failure of normal estrous cyclicity in such animals resides in the systems responsible for regulating the activity of the LH-RH neurons rather than in the LH-RH neurons themselves.

Afferent Pathways↗
PubMed1986

The use of gold-substituted silver-intensified diaminobenzidine (DAB) and non-intensified DAB for simultaneous electron microscopic immunoperoxidase labeling of tyrosine hydroxylase and glutamic acid decarboxylase immunoreactivity in the rat medial preoptic area.

An improved gold-substituted silver intensification procedure for the peroxidase-diaminobenzidine (DAB) reaction product was developed. The method was applied in the rat medial preoptic area to label tyrosine hydroxylase (TH)-immunoreactive profiles. Following the gold toning, the same sections were immunostained for glutamic acid decarboxylase (GAD) immunoreactivity with non-intensified peroxidase-DAB. Single DAB-labeled GAD axons were found in symmetric synaptic connection with unlabeled dendrites as well as with gold-toned immunoperoxidase-containing TH neurons.

3,3'-Diaminobenzidine↗
PubMed1986

Are catechol oestrogens obligatory mediators of oestrogen action in the central nervous system? I. Characterization of pharmacological probes with different receptor binding affinities and catechol oestrogen formation rates.

In an attempt to define pharmacological probes with which to test the role of catechol oestrogen formation in the central nervous system, five oestrogens (oestradiol-17 beta, oestradiol-17 alpha, 4-fluoro-oestradiol, 2-fluoro-oestradiol and moxestrol (11 beta-methoxy-17 alpha-ethynyloestradiol) were studied for binding to oestrogen receptors and conversion to catechol metabolites. Binding to cytosol oestrogen receptors was measured in the hypothalamus-preoptic area-amygdala (HPA), pituitary gland and uterus of ovariectomized rats. Conversion to catechol oestrogens was tested in microsomes from the HPA, pituitary gland and liver, using a catechol-O-methyltransferase-coupled radioenzymatic assay. Oestradiol-17 alpha was the only weak oestrogen receptor ligand. Binding affinities of the other compounds tested were much higher and comparable to those of oestradiol-17 beta. In contrast, oestradiol-17 alpha was rapidly converted to catechol metabolites, while moxestrol was a relatively poor substrate for catechol oestrogen formation. 4-Fluoro-oestradiol could be 2-hydroxylated but not 4-hydroxylated. 2-Fluoro-oestradiol exhibited impaired 2-hydroxylation but normal 4-hydroxylation.

Animals↗
PubMed1986

Are catechol oestrogens obligatory mediators of oestrogen action in the central nervous system? II. Potencies of natural and synthetic oestrogens for induction of gonadotrophin release and female sexual behaviour in the rat.

The role of catechol oestrogen formation in the mechanism by which circulating oestrogens facilitate gonadotrophin release and female sexual behaviour was explored in adult female rats. The effects of oestradiol-17 beta were compared with those of a group of oestrogens with either a reduced affinity for oestrogen receptors (oestradiol-17 alpha) or a reduced ability to act as substrates for catechol oestrogen formation (2-fluoro-oestradiol, 4-fluoro-oestradiol and moxestrol (11 beta-methoxy-17 alpha-ethynyloestradiol]. Rats were ovariectomized on the evening of dioestrus day 1 of the 4-day oestrous cycle and implanted s.c. 12 h later with infusion pumps containing either one of the test oestrogens or vehicle alone. Infusion rates for oestradiol-17 beta, moxestrol, 2-fluoro-oestradiol and 4-fluoro-oestradiol were adjusted to give concentrations of nuclear oestrogen receptors in the brain and pituitary gland within the range of those found in intact female rats during pro-oestrus. Oestradiol-17 alpha was infused at the same and at a tenfold higher rate than that of oestradiol-17 beta; neither of these treatments with oestradiol-17 alpha significantly increased brain or pituitary gland nuclear oestrogen receptor levels. On the day after the pump was implanted, samples of tail vein blood were withdrawn at 12.00, 14.00, 16.00 and 18.00 h for LH assay. All animals were then injected s.c. with 1 mg progesterone in propylene glycol, and tested for feminine sexual behaviour 5 h later. Oestradiol-17 beta, moxestrol, 2-fluoro-oestradiol and 4-fluoro-oestradiol all elicited pronounced LH surges and facilitated progesterone-triggered proceptive and lordosis behaviours.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Intrinsic tyrosine hydroxylase (TH) immunoreactive axons synapse with TH immunopositive neurons in the rat arcuate nucleus.

Synaptic connections were demonstrated between tyrosine hydroxylase (TH) immunoreactive axons and dendrites in the arcuate nucleus of the rat, by electron microscopic immunocytochemistry. These connections were primarily found in the lateral part of the nucleus. The results of two types of medial-dorsal-lateral surgical de-afferentation suggest that the TH-TH contacts represent intrinsic connections.

Animals↗
PubMed1985

Estrogen responsive cells in the arcuate nucleus of the rat contain glutamic acid decarboxylase (GAD): an electron microscopic immunocytochemical study.

Twenty-one days after ovariectomy (OVX) an increased frequency of lamellar cytoplasmic organelles, termed 'whorl' bodies (WB), was observed in neurons of the rat arcuate nucleus (AN). When estradiol valerate (2 mg s.c.) was injected either at the time of OVX or one week later, the frequency of WB at 21 days was reduced. The estrogen treatment resulted in a concomitant rise in the frequency of 'nematosomes' (NS), filamentous electron-dense cytoplasmic structures. In the medial part of the AN glutamic acid decarboxylase (GAD) immunopositive symmetric (Gray II) synapses were observed in contact with WB- and NS-containing cells. After colchicine treatment, GAD immunoreactivity was observed in the WB- and NS-containing perikarya in the medial AN. Some of the NS-containing cells in the lateral AN of the colchicine-pretreated animals remained immunonegative for GAD.

Animals↗
PubMed1985

Gap junctions and myometrial steroid hormone receptors in pregnant and postpartum rats: a possible cellular basis for the progesterone withdrawal hypothesis.

Myometrial gap junctions, levels of cytosol and nuclear estradiol and progesterone receptors, and serum estradiol and progesterone levels were determined simultaneously in pregnant and postpartum rats. Between days 15 to 20 after conception, levels of progesterone nuclear receptors decreased (776.8 +/- 88.5 versus 241.1 +/- 56.5 fmol/mg of DNA, p less than 0.05). The mean serum progesterone also fell by about 50% during this period, but variation in individual levels between days 15 to 20 did not allow for this group to achieve statistical significance until day 21. As the progesterone nuclear receptors decreased, estradiol remained stable, but estradiol nuclear receptors increased (day 21 versus 22: 1710.6 +/- 61.1 versus 3254.8 +/- 203.8 fmol/mg of DNA, p less than 0.05), preceding the increase in gap junctions observed at parturition (day 21 versus 22: 2.0 +/- 0.2 versus 8.0 +/- 3.2 [per 1000 micron plasma membrane], p less than 0.05). Gap junctions fell to prepartum levels by 12 hours, when progesterone nuclear receptors were markedly increasing (6 versus 12 hours post partum: 637.7 +/- 324.8 versus 1509.6 +/- 283.2 fmol/mg of DNA, p less than 0.05). Relationships between gap junctions and cellular estradiol and progesterone nuclear receptors are clearer than could be forecast by circulating hormone measurements alone, and may offer a cellular basis for the role of progesterone in controlling labor.

Animals↗
PubMed1985

Application of avidin-ferritin and peroxidase as contrasting electron-dense markers for simultaneous electron microscopic immunocytochemical labelling of glutamic acid decarboxylase and tyrosine hydroxylase in the rat arcuate nucleus.

A pre-embedding immunostaining procedure was developed using ferritin and peroxidase to enable simultaneous electron microscopic localization of two antigens in the same tissue section. This method was used to study the anatomic relationship between glutamic acid decarboxylase (GAD) immunoreactive axons and tyrosine hydroxylase (TH) - containing neurons of the rat arcuate nucleus. The findings provide ultrastructural evidence that GAD-immunoreactive terminals establish symmetric (Gray II) synapses on TH-reactive neurons.

Animals↗
PubMed1985

The naturally occurring C-17 fatty acid esters of estradiol are long-acting estrogens.

C-17 fatty acid esters of estradiol are naturally occurring biosynthetic metabolites of estradiol. A representative component of this family of esters, estradiol-17-stearate, was studied in order to determine the estrogenic properties of these unusual hydrophobic steroids. Following the classical estrogen bioassay, a solution of this ester in oil was injected subcutaneously into immature rats once a day for 3 days. There was little effect on the uterus on the first day after the third injection. However, on subsequent days a large stimulation of uterine growth occurred. The course of this estrogenic effect was exactly opposite to that obtained with estradiol. In order to eliminate the possibility that this effect on the time course of estrogenic stimulation was caused by increased solubility of the hydrophobic esters in the carrier oil, the steroids were administered to adult ovariectomized animals in aqueous medium via a single intravenous injection. The uterotrophic response to estradiol was maximal at 12 h and was completely dissipated in 48-60 h. Estradiol-17-stearate produced a uterotrophic effect of twice the duration of estradiol. In the immature rat, aqueous intravenous injections of estradiol-17-stearate produced a greater uterotrophic effect than estradiol and this effect was still maximal 96 h later. In addition, this single injection of estradiol-17-stearate advanced the time of vaginal opening, a marker for puberty in the female rat. The mechanism of the prolonged estrogenic stimulation was investigated by studying the steroidal content of the uterus after injecting [3H]estradiol and [3H]estradiol-17 -stearate i.v. into immature rats. At 1 and 4 h there was significantly more radioactivity in the uteri of the [3H]estradiol treated animals. At later times (8 h and onwards) the total radioactivity in the uterus did not differ appreciably between the two groups. However at these later times, the amount of [3H]estradiol was far greater in the uteri of animals receiving [3H]estradiol-17-stearate. Consequently, the prolonged estrogenic effects of the endogenous C-17 fatty acid esters of estradiol are caused by the increased duration of the estrogenic signal. It is hypothesized that one of the roles of the fatty acid is to protect the steroid nucleus from metabolism and thereby prolong the life of the parent C18 steroid. Thus, the results of these experiments are consistent with the family of endogenous alkyl esters of estradiol having a physiological role as long-acting estrogens.

Animals↗
PubMed1985

Estrogen replacement and tardive dyskinesia.

A double-blind randomized clinical trial was conducted among 10 post-menopausal women with tardive dyskinesia (TD) to test the effect of estrogen replacement of the severity of abnormal movements and other outcome variables. After 3 weeks of treatment, the mean Abnormal Involuntary Movement Scale (AIMS) score decreased by 38% in the estrogen group and by 9% in the placebo group; the difference between groups was marginally significant (p less than 0.10). However, the small sample size and the imbalance between groups in baseline AIMS scores do not allow us to rule out the confounding effects of other prognostic factors. There were no significant differences between treatment groups for parkinsonian and psychological symptoms at any visit or for changes in these variables between visits. The findings of this preliminary trial are consistent with the results of other human and animal investigations, and they support the need for future research to understand the role of estrogens in the neuropathology and treatment of TD.

Aged↗
PubMed1985

Estrogen formation in the developing rat brain: sex differences in aromatase activity during early post-natal life.

Aromatase activity in the brain of the rat was measured during perinatal development and in adulthood. In pooled hypothalamus, preoptic area, septum and amygdala (HPAS), estrogen formation per gram protein increased between embryonic days 15 and 19 and then declined. Results for males and females were indistinguishable, except for post-natal days 1 and 2 and 3 and 4 when estrogen formation was significantly higher in the male. Aromatization was not convincingly demonstrated in cerebral cortical tissue at any time studied. Regional dissection of the HPAS in 2-3 day post-natal animals revealed significant sex differences in aromatase activity in the corticomedial amygdala and the hypothalamus, but not in the preoptic-septal region or the remainder of the amygdala. These results are consistent with the idea that perinatal androgen secretion in the male rat may stimulate estrogen formation in the brain.

Age Factors↗
PubMed1985

Effect of 5 alpha-dihydrotestosterone on sexual receptivity and neural progestin receptors in ovariectomized rats given pulsed estradiol.

Experiments were carried out to examine the mechanism whereby 5 alpha-dihydrotestosterone (DHT) antagonizes the stimulatory effects of estrogen plus progesterone (P) on sexual receptivity (lordosis) in the ovariectomized rat. Estradiol (E2; 1 microgram s.c. in 10% ethanol) was administered in a discontinuous (pulsed) treatment regimen thought to mimic phase requirements of estrogen action; two injections of E2 were given either 6 or 12 h apart (first injection, Hour 0). Progesterone (0.5 mg in oil) was injected at Hour 20, and behavioral testing occurred at Hour 24. Dihydrotestosterone (2.5 mg s.c. in 10% ethanol/propylene glycol) inhibited lordosis when it was given before (-12 or -3 h), between (+3, or -3 and +3 h), or after (+8 h) the two E2 injections, but was not effective when given at +20 h. Significant inhibition of E2 + P-induced lordosis was achieved by 2.5 but not 1.0 or 0.2 mg DHT at -3 h, while uterine weights in the same animals were reduced significantly by 2.5 and 1.0 mg DHT. Serum E2 and DHT concentrations peaked rapidly after injection, declining to near baseline by 3 and 12 h, respectively. Induction of cytosolic progestin receptors (cPR) in the preoptic area and medial basal hypothalamus by estrogen was not prevented by DHT when animals were given the two pulsed E2 injections or daily injections of estradiol benzoate, although P was able to override the inhibitory behavioral effects of DHT in the latter but not the former group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗