Recent insights into the varying activity of estrogens

Recent advances have added substantially to our understanding of the biology of estrogens. Estrogens are no longer considered to differ only in potency. Two estrogens can have similar effects in one tissue and very different effects in another. Additionally, an estrogen can have different effects in different tissues. It is now recognized that there are at least two estrogen receptors, ER-alpha and ER-beta, and that it is quite likely that estrogens also work through non-genomic mechanisms. The development of new methods of chromatographic separation has aided substantially in our ability to characterize the composition of Premarin, including the identification of estradiene, the fourth-most abundant estrogen in Premarin. Recent studies have contributed to our understanding of the unique profile of Delta(8,9) dehydroestrone sulfate, another of the Premarin estrogens. It was found that Delta(8,9) dehydroestrone sulfate is an active estrogen with a distinct pharmacological profile that results in significant clinical activity in vasomotor, neuroendocrine and bone preservation parameters. However, it displayed little or no efficacy, at the dose studied, on other peripheral parameters normally affected by classical estrogens. Increasing knowledge of the unique profiles of the Premarin components, as well as their complex interaction, will help to increase our understanding of the clinical profile of Premarin.

On the Nature of the Compact Star in 4U 1728-34

The discovery of kilohertz quasi-periodic oscillations (kHz QPOs) in low-mass X-ray binaries (LMXBs) with the Rossi X-Ray Timing Explorer has stimulated extensive studies of these sources. Recently, Osherovich & Titarchuk suggested a new model for kHz QPOs and the related correlations between kHz QPOs and low-frequency features in LMXBs. Here we use their results to study the mass-radius relation for the atoll source 4U 1728-34. We find that, if this model is correct, 4U 1728-34 is possibly a strange star rather than a neutron star.

Estrogen activity and novel tissue selectivity of delta8,9-dehydroestrone sulfate in postmenopausal women

Recent basic and clinical advances have consolidated the concept of tissue-selective estrogens, i.e. molecules that express different degrees of partial agonist, full agonist or antagonist activity in different tissues or cells. Delta8,9-Dehydroestrone sulfate (delta8,9-DHES) is a conjugated estrogen and a component of conjugated equine estrogens (CEE). It is metabolized in the human in at least a 1:1 ratio to its 17beta form, 17beta-delta8,9-DHES. To evaluate its activity in different clinical and biochemical parameters, a clinical research study was conducted with delta8,9-DHES and estrone sulfate as a comparator in postmenopausal women. Delta8,9-DHES was given orally at a daily dose of 0.125 mg for 12 weeks in a group of 10 women. Two additional groups of women received either estrone sulfate alone (1.25 mg/day) or the combination of delta8,9-DHES and estrone sulfate at the previously specified doses. A significant and consistent suppression of hot flushes (number, severity, and total score) was observed with delta8,9-DHES, reaching more than 95% suppression in all parameters of vasomotor symptoms. This level of activity was equal to that obtained with the much higher dose of estrone sulfate, and it was sustained for the duration of the treatment period (12 weeks). Measurements of a bone resorption marker, i.e. urinary excretion of N-telopeptide, demonstrated that delta8,9-DHES at 8 weeks produced a degree of suppression (40%) similar to that observed with the higher dose of estrone sulfate. Gonadotropin secretion (FSH and LH) was significantly suppressed in women receiving delta8,9-DHES, similar to that observed with estrone sulfate alone or with the combination of the two. Other parameters, such as total cholesterol, low density lipoprotein cholesterol and high density lipoprotein cholesterol were not modified significantly, whereas serum globulins (sex hormone-binding globulin and corticosteroid-binding globulin) showed only marginal increases after delta8,9-DHES administration. Taken together with preclinical data, it is found that delta8,9-DHES is an active estrogen with a distinct pharmacological profile that results in significant clinical activity in vasomotor, neuroendocrine (gonadotropin and PRL) and bone preservation parameters, whereas displaying little or no efficacy, at the dose tested, on other peripheral parameters normally affected by estrogens. Collectively, this information supports the concept that delta8,9-DHES is an integral component of CEE, with distinct tissue selectivity contributing to the CEE's overall clinical activity, and places this estrogen as a distinct member of a novel class of centrally active molecules with unique peripheral tissue selectivity.

Effects of equine oestrogens on markers of vasoactive function in human coronary artery endothelial cells

A large proportion of the beneficial effects that oestrogens demonstrate on the vasculature are believed to be mediated via direct effects on the vascular wall. In this study we compared a number of oestrogenic compounds isolated from pregnant mare's urine including 17beta-oestradiol and oestrone, in terms of their abilities to inhibit stimulated endothelin-1 release from normal human coronary artery endothelial cells (CAEC). We also examined their ability to stimulate expression of constitutive endothelial nitric oxide synthase (eNOS) and explored their effects on cellular angiotensin converting enzyme (ACE). All the oestrogens tested were able to inhibit serum-stimulated ET-1 release. Oestrone and 17alpha-dihydroequilenin failed to significantly affect cellular eNOS levels. 17Beta-oestradiol and oestrone significantly increased cellular ACE levels while 17beta,delta(8,9)-dehydroestradiol decreased cellular ACE. We discuss these observations in terms of their potential clinical relevance and use as a means of screening novel oestrogen-like compounds.

The neuropeptides, VIP and NPY, that are present in the thyroid nerves are not released into the thyroid vein

In the present study, we tested the hypothesis that the neuropeptides, vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY), which are present in the thyroid nerves, act as physiological neurotransmitters involved in the regulation of thyroid hormone secretion and thyroid blood flow. Specifically, we examined whether these neuropeptides can be released into thyroid blood vessels by electrical stimulation of the major thyroid nerves or whether their expression is altered by changes in iodine intake. Sprague-Dawley rats were used in this study. The cervical sympathetic trunk or the superior laryngeal nerve was stimulated by bipolar electrodes in anesthetized rats. During nerve stimulation, blood samples were withdrawn from the thyroid vein. Thyroid blood flow was monitored by laser Doppler blood flowmetry. Sympathetic stimulation caused a marked decrease in thyroid blood flow, which was associated with a significant increase in release of norepinephrine. However, these effects were not accompanied by any change in NPY release into the thyroid vein. Stimulation of the superior laryngeal nerve was not associated with changes in thyroid blood flow or VIP release into the thyroid vein. In a separate experiment, rats were fed a diet containing low-, high-, or normal iodine concentrations. Triiodothyronine (T3) and thyroxine (T4) levels in thyroid venous plasma were significantly reduced in rats fed a low-iodine diet but not in a separate group of rats fed a high iodine diet. However, these treatments had no effect on VIP or NPY concentrations in thyroid venous plasma or in thyroid ganglia. Thus, our results indicate that VIP and NPY, which are present in the thyroid nerves, may not be directly involved in the regulation of thyroid function.

Immunostimulation of murine spleen cells by materials associated with bovine milk protein fractions

Purified bovine milk proteins that were added to cultures of murine spleen cells significantly increased cell proliferation and production of immunoglobulin M. Casein and a whey mixture consisting of alpha-lactalbumin, bovine serum albumin, bovine gamma globulin, and beta-lactoglobulin (beta-LG) were stimulatory. Of the three beta-LG preparations that are commercially available (beta-LG containing variants A and B, purified variant A, and purified variant B), the unseparated mixture containing both the A and B variants showed the most immunomodulatory activity. Both alkaline treatment and trypsin digestion of the beta-LG preparation markedly reduced its effectiveness. Polymyxin B, while greatly diminishing the stimulatory effect of lipopolysaccharide, had no significant effect on either the enhancement of cell proliferation or the enhancement of immunoglobulin production by beta-LG. In the presence of S-(n-butyl)-homocysteine sulfoxamine, the stimulatory effect of beta-LG on cell proliferation and IgM production in vitro was markedly reduced.

Diurnal sensitivity of the testes to exogenous testosterone propionate in sexually regressed whitethroated munia Lonchura malabarica

The testes in different groups of whitethroated munia (Lonchura malabarica) were studied following exogenous treatment of testosterone propionate (1 mg/100 g body wt./day) at 06.00 h or 14.00 h or 22.00 h for 15 consecutive days during the quiescent phase of the annual testicular cycle. The testicular conditions in each group of testosterone treated and appropriate control (administered only with the vehicle of hormone at corresponding time-points) group of birds were analyzed by the studies of paired testicular weight, seminiferous tubular diameter, spermatogenetic index, and cytology of the testicular germ cells. The results of the study revealed that exogenous testosterone was stimulatory to the testicular functions irrespective of the time of treatment. The gametokinetic response of the testes to exogenous testosterone also did not show any statistical difference among the birds treated at different hours of the day. The present study demonstrates for the first time that the responses of the testes to exogenous testosterone during the post-breeding phase in an annual testicular cycle of a wild bird does not vary with the time of administration.

Analysis of high-mass biomolecules using electrostatic fields and matrix-assisted laser desorption/ionization in a Fourier transform mass spectrometer

A new decelerating technique that places dc potentials on the orthogonal excitation and receiver plates as well as the rear trapping plate (conductance limit) of the source cell of a dual cubic cell has been applied to the standard matrix-assisted laser desorption/ionization Fourier transform mass spectrometry technique. When this five-plate trapping method is applied, high-mass ions with large translational kinetic energies can be trapped efficiently and detected. Using this approach, low-resolution spectra of carbonic anhydrase (MW = 29,000), egg albumin (MW = 45,000), and bovine albumin (MW = 66,000) have been obtained. Because the new decelerating method requires no modification to the existing cell, it is also possible to obtain high-resolution spectra for compounds with masses of ca. 14,000 Da and lower. Utilizing the five-plate trapping method, a bovine insulin spectrum with a resolving power of 20,000 was obtained. It is not yet possible to obtain higher resolution for the higher mass proteins. The reasons for this difficulty are currently being investigated.

Activations of mitogen-activated protein kinases and phospholipase D in A7r5 vascular smooth muscle cells

Activation of mitogen-activated protein kinases (MAPKs) was examined in the A7r5 rat vascular smooth muscle cell line. Treatment of A7r5 cells with vasopressin, phorbol ester (PMA), or serum resulted in activation of two MAPKs, Erk-1 and Erk-2. Phosphatidylinositol-specific phospholipase C was activated in response to vasopressin but not to PMA. Vasopressin and PMA both caused maximal activation of PLD within 5 minutes. Application of bacterial phospholipase D (PLD) to A7r5 cells increased phosphatidic acid to levels similar to those seen with vasopressin or PMA. Acute exposure of the cells to vasopressin, PMA, or PLD increased phosphorylation of many of the same cytosolic and membrane proteins. However, bacterial PLD did not promote significant activation of Erk-1 and Erk-2. Phosphatidic acid and lysophosphatidic acid (LPA) likewise did not stimulate MAPK activity in A7r5 cells. Serum and vasopressin stimulated DNA synthesis when present for more than 30 min, while PLD, PMA, phosphatidic acid, and LPA were not mitogenic. These data suggest that activations of MAPKs and PLD are concurrent but independent responses to vasopressin in A7r5 cells. Acute activation of these enzymes is not sufficient to simulate DNA synthesis.

Castration and testosterone induced changes in the pinealocytes of roseringed parakeet, Psittacula krameri, during different phases of the annual testicular cycle

The pinealocytes in male roseringed parakeets (Psittacula krameri) were studied following bilateral castration and/or therapeutic administration of testosterone during the preparatory (June-July), progressive (Nov.-Dec.), pre-breeding (Jan.-Feb.) and breeding (March-April) phases of the annual testicular cycle. The responses of the pineal to either treatment were found to be almost identical throughout the investigation. In each reproductive phase, the pineal appeared to be hypertrophied following castration and the effect was reversed by therapeutic administration of testosterone, while hormonal treatment to the intact parakeets induced regressive changes in the pinealocytes. Collectively, the results of the current study support the hypothesis that the testis through its hormone testosterone exerts inhibitory influences on the activity of pineal, and may thus be considered as being involved in the determination of an inverse relationship between the pineal and the testis during the annual cycle of free-living parakeets.

Immunization against vasoactive intestinal peptide does not affect thyroid hormone secretion or thyroid blood flow

Vasoactive intestinal peptide (VIP) is present in thyroid parasympathetic nerves. To assess the involvement of endogenous VIP in the regulation of thyroid function, blood levels of thyroid hormones and thyroid blood flows (TBF) were measured after systemic immunization against VIP or after transection of the superior laryngeal nerves in male rats, which reduced the thyroid content of VIP but did not affect blood levels of thyroid hormones or TBF. Anti-VIP monoclonal antibody or anti-VIP serum was used for immunization against VIP in normal rats. In addition, VIP antibody was given to rats fed an iodine-deficient diet for 5 days to examine the involvement of this peptide in iodine deficiency-induced increases in TBF. Effects were measured at different times (90 s, 30 min, 1 h, and 5 days) after immunoneutralization, but none of these treatments changed blood levels of thyroid hormones or TBF in normal or iodine-deficient rats. However, passive immunization against VIP was associated with a high binding capacity of rat plasma to VIP, and this treatment reduced blood levels of prolactin as well as blood flows to the duodenum, stomach, and lung. These findings suggest that the VIP present in thyroid nerves is not involved in maintaining basal thyroid hormone secretion or TBF and that this neuropeptide does not mediate thyroid vascular adjustments to dietary iodine deficiency.

Sympathetic thyroidal vasoconstriction is not blocked by a neuropeptide Y antagonist or antiserum

Sympathetic nerve fibers to thyroid blood vessels contain both norepinephrine (NE) and neuropeptide Y (NPY). To assess the involvement of endogenous NPY in the sympathetic neural control of thyroid blood flow, appropriate doses of a selective NPY antagonist, alpha-trinositol, and an NPY antiserum (NPY-AS) were used during cervical sympathetic trunk stimulation in anesthetized rats. During all experiments, thyroid blood flow was continuously monitored by laser Doppler blood flowmetry. Neither alpha-trinositol nor NPY-AS blocked the thyroidal vasoconstriction evoked by either the first or second stimulation of the cervical sympathetic trunks. Our results suggest that NPY is not involved either directly or indirectly during acute sympathetic vasoconstriction in the rat thyroid gland.

The dissolution and bioavailability of etodolac from capsules exposed to conditions of high relative humidity and temperatures

The dissolution and bioavailability of etodolac from capsules exposed to high relative humidity and temperature were compared to those from capsules stored at room temperature (RT). Dissolution of stressed and control capsules was evaluated using a USP basket apparatus at 100 rpm with 900 mL pH 7.5 phosphate buffer (0.05 M) at 37 degrees C. The dissolution of etodolac from capsules exposed to stressed conditions was also evaluated with enzymes (pancreatin, 1%, w/v) added to the dissolution medium. The bioavailability of etodolac from capsules exposed to stressed conditions was compared in both dogs and humans to capsules stored at RT conditions. Capsules, 200 and 300 mg, exposed to stressed conditions failed the dissolution (without enzymes) specification [not less than 85% released (80% Q) in 30 min]. However, upon enzyme addition, all capsules met the specification. The rate and extent of absorption from these 200 and 300 mg etodolac capsules in dogs were equivalent to those from capsules stored at RT conditions that passed the dissolution specification. Similarly, the bioavailability of etodolac from 300 mg capsules that failed the dissolution specification upon exposure to stressed conditions was equivalent to that of control capsules in 24 adult male volunteers. Thus, an in vitro dissolution test with enzymes provides a better indication of stressed capsule performance in vivo.

NPY is not a primary mediator of the acute thyroid blood flow response to sympathetic nerve stimulation

It has been suggested that thyroid blood flow is regulated by both sympathetic and parasympathetic nerves. The purpose of our experiments was to study the role of neuropeptide Y (NPY) in the sympathetic neural control of thyroid blood flow. Sympathetic nerve fibers to the thyroid contain both norepinephrine (NE) and NPY. Therefore, NE (15 nmol iv bolus) and NPY (12 or 1.7 nmol/kg body wt iv infusion; 4 min) were administered to anesthetized male rats (250-300 g) either alone or together, with or without an alpha-adrenergic receptor blocker (phentolamine; 10 mg/kg body wt iv bolus). Experiments were also performed in which the cervical sympathetic trunks were stimulated (30 Hz, 10 V; 0.5 ms; 2 min) with or without phentolamine. Thyroid blood flow was monitored continuously by laser-Doppler blood flowmetry. Results are expressed as thyroid vascular conductance (TVC). NE or NPY at both doses decreased TVC relative to that in control saline-infused rats (P < 0.05). No potentiation of the NE effect by NPY was observed when the first dose of NE was injected 2 min after a high or low dose of NPY. However, the effect of a second dose of NE, injected 15 min after the end of the low dose of NPY, was prolonged compared with the effect of a second dose of NE in saline-infused rats. Phentolamine blocked the effect of NE but not that of NPY. Stimulation of the cervical sympathetic trunks decreased TVC (P < 0.01 vs. sham), and this effect was completely blocked by phentolamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics and bioavailability of medroxyprogesterone acetate in the dog and the rat

Medroxyprogesterone acetate (MPA) has been administered to rats and dogs. Dogs received single oral doses of 2.5, 5, and 10 mg MPA and a single intravenous dose of 1 mg MPA. Rats received single oral doses of 0.2, 1, 5, and 20 mg kg-1 MPA and multiple oral doses (14 daily doses) of 0.2, 5, and 20 mg kg-1 MPA. Dog plasma MPA levels from the intravenous dose were characterized by a triexponential decay with disposition half-lives of 0.3, 1.8, and 21.6 h. A Loo-Riegelman analysis of the dog plasma MPA levels from oral doses indicated absorption was not a simple first-order process. The Weibull Function was used to characterize the absorption kinetics of MPA. The oral absorption of MPA in dogs appears to be dose-linear over the dosage range studied, and the absolute bioavailability was estimated at 27 per cent. Rat plasma MPA levels from single and multiple oral doses were analyzed by a non-compartmental approach. AUC and Cmax values were not dose-linear over the dosage range studied; indicative of the self-induced metabolism of MPA. Exposure of similar dosages of MPA to both the rat and the dog resulted in similar plasma profiles and pharmacokinetics.

Endogenous neuropeptide Y regulates thyroid blood flow

Neuropeptide Y (NPY) is present in thyroid sympathetic nerve fibers. To assess the involvement of endogenous NPY in the regulation of thyroid function, a NPY antiserum was produced in a rabbit, characterized, and used for immunization of normal and hyperthyroid rats. Plasma thyroxine, thyroid-stimulating hormone (TSH), thyroidal, and other organ blood flows (BF) were measured in anesthetized (ketamine and pentobarbital sodium) male Sprague-Dawley rats at 1 h after intravenous administration of 1 ml of the antiserum, normal rabbit serum, or saline. Immunization against NPY had no effect on the plasma levels of thyroxine, TSH, or arterial blood pressure, but it significantly increased thyroidal BF in normal rats. In the hyperthyroid rats (treated with 5 micrograms.100 g body wt-.day-1 thyroxine for 6 days), the NPY antiserum reversed the hyperthyroidism-induced decrease in thyroid BF and significantly increased duodenal and testicular BF values, but it did not alter BF values in four other organs. These results indicate that endogenous NPY regulates thyroid BF in normal rats. They also provide an example of NPY involvement in the pathophysiological adjustment of some organs to hyperthyroidism.

Thyroidal vascular responsiveness to parasympathetic stimulation is increased in hyperthyroidism

It has been suggested that thyroid blood flow (TBF) is regulated by both parasympathetic and sympathetic nerves. Because thyroxine (T4) pretreatment increases the sensitivity of the thyroid to the effects of thyrotropin, the present study was conducted to determine whether T4 pretreatment can also sensitize the thyroid to the effect of parasympathetic stimulation on TBF. Untreated or T4-pretreated rats were anesthetized, and both superior laryngeal nerves (SLN) were transected. TBF was continuously monitored by laser Doppler flowmetry (LDF), and thyroid vascular conductance (TVC) was also determined by the microsphere technique. Stimulation of the SLN had no effect on TBF or TVC in untreated rats when measured by LDF or microspheres. In contrast, stimulation of the SLN after T4 pretreatment increased TBF by 65 +/- 21% over prestimulus levels as measured by LDF. TVC was also increased significantly (P < 0.05) in these rats compared with TVC in a nonstimulated T4-pretreated group. To examine the role of muscarinic receptor activation in the mediation of these increases in TVC, T4 pretreated rats were given saline or atropine prior to SLN transection. Stimulation of the SLN in T4-pretreated rats given saline increased TVC significantly (P < 0.05) compared with TVC in the nonstimulated saline-treated or atropine-treated group. In contrast, TVC in the stimulated group given saline was not significantly different from the group that was stimulated after atropine injection. Our results suggest that the thyroidal vascular responsiveness to parasympathetic stimulation is increased in the hyperthyroid condition.

Importance of photoperiods in determining temporal pattern of annual testicular events in rose-ringed parakeet (Psittacula krameri)

Male rose-ringed parakeets (Psittacula krameri) were transferred to a long photoperiod (LP; LD 16:8) or a short photoperiod (SP; LD 8:16) for 45 or 90 days on four dates corresponding to the beginnings of different reproductive phases in an annual testicular cycle, and testicular responsiveness was evaluated by comparison with the testicular volume, weight, seminiferous tubular diameter, and germ cell profiles of birds in a natural photoperiod (NP). Exposure of birds to LP during the progressive phase (November) led to precocious maturation of testes after 45 days, but induced regression at 90 days. After showing retarded gametogenic functions at 45 days, parallel (November) SP birds exhibited an accelerated rate of germ cell formation at day 90. During the prebreeding phase (January), there were no remarkable differences in any features of testes among NP. LP, and SP birds at 45 days, but gonadal involution in LP parakeets and active spermatogenesis in SP birds occurred after 90 days. The testes did not show any response to LP or SP for 45 and 90 days when the birds were transferred to altered photoperiods during the breeding (March) and preparatory (June) phases, indicating that the parakeets were photorefractory for at least 6 months (March through September). The results also suggest that initiation and termination of seasonal gametogenic activity in parakeets are possibly functions of endogenous rhythmicity or extraphotoperiodic environmental factors. Duration of light may have certain influences on the attainment of annual peak in spermatogenesis, but in all probability the species has a low photoperiod threshold for induction of testicular growth.