Cellular and molecular mechanisms of 17β-estradiol postconditioning protection against gastric mucosal injury induced by ischemia/reperfusion in rats

AimsTo investigate the protective effects of 17β-estradiol postconditioning against ischemia/reperfusion (I–R)-induced gastric mucosal injury in rats.Main methodsThe animal model of gastric ischemia/reperfusion was established by clamping of the celiac artery for 30 min and reperfusion for 30 min, 1 h, 3 h, 6 h, 12 h or 24 h. 17β-estradiol at doses of 5, 50 or 100 μg/kg (rat) was administered via peripheral veins 2 min before reperfusion. In a subgroup of rats, the estrogen receptor antagonist fulvestrant (Ful, 2 mg/kg) was intravenously injected prior to 17β-estradiol administration. Histological and immunohistochemical methods were employed to assess the gastric mucosal injury index and gastric mucosal cell apoptosis and proliferation. The malondialdehyde (MDA) concentration, superoxide dismutase (SOD) activity, xanthine oxidase (XOD) activity and hydroxyl free radical (–OH) inhibitory ability were determined by colorimetric assays. Subsequently, the expression of Bcl-2 and Bax in rat gastric mucosa was examined by western blotting.Key findings17β-estradiol dose-dependently inhibited gastric I–R (GI–R) injury, and 17β-estradiol (50 μg/kg) markedly attenuated GI–R injury 1 h after reperfusion. 17β-estradiol inhibited gastric mucosal cell apoptosis and promoted gastric mucosal cell proliferation in addition to increasing SOD activity and –OH inhibitory ability and decreasing the MDA content and XOD activity. The Bax protein level increased 1 h after GI–R and was markedly reduced by intravenous administration of 17β-estradiol. In contrast, the level of Bcl-2 protein decreased 1 h after GI–R and was restored to normal levels by intravenous administration of 17β-estradiol. These effects of 17β-estradiol were inhibited by pretreatment with fulvestrant.Significance17β-estradiol postconditioning should be investigated further as a possible strategy against gastric mucosal injury.     

The effect of 17β-estradiol treatment on the mass and the turnover of bone in ovariectomized rats taking a mild dose of thyroxin

We performed the dosing experiment to establish whether estrogen administration has any beneficial effects on the mass and the turnover of bone in ovariectomized rats taking a mild dose of thyroxin. Thirty-five Wistar rats, 28 weeks of age, received ovariectomies (OVX) or sham operations and were divided into five groups. Group I was the sham group, Groups 2–5 were ovariectomized. Group 2 was the OVX-control, Group 3 treated with thyroxin 30 μg/kg/day (T4), Group 4, 17β-estradiol 0.3 mg/kg/week (E2), and Group 5, the combination of T4 and E2. The duration of the experiment was 12 weeks. At the end of the experiment, serum chemistries were measured. Bone minerals in the femur were determined with single photon absorptiometry and bone turnover was assessed histomorphometrically. Alkaline-phosphatase increased in Group 3 (OVX-T4), but it reduced in Groups 4 (OVX-E2) and 5 (OVX-T4 + E2). Bone minerals decreased in Groups 2 (OVX) and 3. In Group 4, it was preserved at the same level as in Group 1. Group 5 showed a significant increase of bone mass compared with Group 1. Eroded surface and osteoid surface increased in Groups 2 and 3 and they were reduced in Groups 4 and 5. Bone volume and mineral apposition rate were at a maximum in Group 5. This study demonstrated that 17β-estradiol was capable of preventing the bone mass decrease by regulating the turnover in ovariectomized rats taking a mild dose of thyroxin. Osteoblast function appeared to be stimulated in combination with 17β-estradiol and thyroxin.     

Estrogen alleviates neuropathic pain induced after spinal cord injury by inhibiting microglia and astrocyte activation

Neuropathic pain after spinal cord injury (SCI) is developed in about 80% of SCI patients and there is no efficient therapeutic drug to alleviate SCI-induced neuropathic pain. Here we examined the effect of estrogen on SCI-induced neuropathic pain at below-level and its effect on neuroinflammation as underlying mechanisms. Neuropathic pain is developed at late phase after SCI and a single dose of 17β-estradiol (100, 300?μg/kg) were administered to rats with neuropathic pain after SCI through intravenous injection. As results, both mechanical allodynia and thermal hyperalgesia were significantly reduced by 17β-estradiol compared to vehicle control. Both microglia and astrocyte activation in the lamina I and II of L4-5 dorsal horn was also inhibited by 17β-estradiol. In addition, the levels of p-p38MAPK and p-ERK known to be activated in microglia and p-JNK known to be activated in astrocyte were significantly decreased by 17β-estradiol. Furthermore, the mRNA expression of inflammatory mediators such as Il-1β, Il-6, iNos, and Cox-2 was more attenuated in 17β-estradiol-treated group than in vehicle-treated group. Particularly, we found that the analgesic effect by 17β-estradiol was mediated via estrogen receptors, which are expressed in dorsal horn neurons. These results suggest that 17β-estradiol may attenuate SCI-induced neuropathic pain by inhibiting microglia and astrocyte activation followed inflammation.     

Pharmacological characterization of the mechanisms involved in the vasorelaxation induced by progesterone and 17β-estradiol on isolated canine basilar and internal carotid arteries

Progesterone and 17β-estradiol induce vasorelaxation through non-genomic mechanisms in several isolated blood vessels; however, no study has systematically evaluated the mechanisms involved in the relaxation induced by 17β-estradiol and progesterone in the canine basilar and internal carotid arteries that play a key role in cerebral circulation. Thus, relaxant effects of progesterone and 17β-estradiol on KCl- and/or PGF_2α-pre-contracted arterial rings were investigated in absence or presence of several antagonists/inhibitors/blockers; the effect on the contractile responses to CaCl₂ was also determined. In both arteries progesterone (5.6–180 μM) and 17β-estradiol (1.8–180 μM): (1) produced concentration-dependent relaxations of KCl- or PGF_2α-pre-contracted arterial rings; (2) the relaxations were unaffected by actinomycin D (10 μM), cycloheximide (10 μM), SQ 22,536 (100 μM) or ODQ (30 μM), potassium channel blockers and ICI 182,780 (only for 17β-estradiol). In the basilar artery the vasorelaxation induced by 17β-estradiol was slightly blocked by tetraethylammonium (10 mM) and glibenclamide (K_ATP; 10 μM). In both arteries, progesterone (10–100 μM), 17β-estradiol (3.1–31 μM) and nifedipine (0.01–1 μM) produced a concentration-dependent blockade of the contraction to CaCl₂ (10 μM–10 mM). These results suggest that progesterone and 17β-estradiol produced relaxation in the basilar and internal carotid arteries by blockade of L-type voltage dependent Ca²⁺ channel but not by genomic mechanisms or production of cAMP/cGMP. Potassium channels did not play a role in the relaxation to progesterone in both arteries or in the effect of 17β-estradiol in the internal carotid artery; meanwhile K_ATP channels play a minor role on the effect of 17β-estradiol in the basilar artery.     

Coordination of epithelial branching and salivary gland lumen formation by Wnt and FGF signals

Branching morphogenesis is a molecularly conserved mechanism that is adopted by several organs, such as the lung, kidney, mammary gland and salivary gland, to maximize the surface area of a tissue within a small volume. Branching occurs through repetitive clefting and elongation of spherical epithelial structures, called endbuds, which invade the surrounding mesenchyme. In the salivary gland, lumen formation takes place alongside branching morphogenesis, but in a controlled manner, so that branching is active at the distal ends of epithelial branches while lumen formation initiates at the proximal ends, and spreads distally. We present here data showing that interaction between FGF signaling and the canonical (β-catenin dependent) and non-canonical branches of Wnt signaling coordinates these two processes. Using the Axin2^lacZ reporter mice, we find Wnt/β-catenin signaling activity first in the mesenchyme and later, at the time of lumen formation, in the ductal epithelium. Gain and loss of function experiments reveal that this pathway exerts an inhibitory effect on salivary gland branching morphogenesis. We have found that endbuds remain devoid of Wnt/β-catenin signaling activity, a hallmark of ductal structures, through FGF-mediated inhibition of this pathway. Our data also show that FGF signaling has a major role in the control of lumen formation by preventing premature hollowing of epithelial endbuds and slowing down the canalization of presumptive ducts. Concomitantly, FGF signaling strongly represses the ductal marker Cp2l1, most likely via repression of Wnt5b and non-canonical Wnt signaling. Inhibition of canonical and non-canonical Wnt signaling in endbuds by FGF signaling occurs at least in part through sFRP1, a secreted inhibitor of Wnt signaling and downstream target of FGF signaling. Altogether, these findings point to a key function of FGF signaling in the maintenance of an undifferentiated state in endbud cells by inhibition of a ductal fate.     

Changes in the Mutagenic and Estrogenic Activities of 17β-Estradiol after Treatment with Nitrite

We determined the changes in the mutagenic and estrogenic activities of 17β-estradiol after a nitrite treatment. Nitrite-treated 17β-estradiol showed mutagenic activities toward Salmonella typhimurium strains TA 100 and TA 98. We confirmed that nitrite-treated 17β-estradiol generated radicals from the results of an analysis of electron spin resonance. By applying an instrumental analysis, we identified 2-nitro-17β-estradiol to have been formed in the reaction mixture. 2-Nitro-17β-estradiol did not exhibit mutagenic activities toward Salmonella typhimurium strains, suggesting that other mutagens might have been formed in the reaction mixture. The clastogenic properties of nitrite-treated 17β-estradiol and 2-nitro-17β-estradiol were analyzed by a micronucleus test with male ICR mice. Nitrite-treated 17β-estradiol and 2-nitro-17β-estradiol induced a significantly higher frequency of micronucleated reticulocytes in mice. The estrogenic activity of 2-nitro-17β-estradiol was found to be lower than that of 17β-estradiol. These data suggest that a daily oral intake of 17β-estradiol and nitrite might induce the formation of mutagenic compounds in our body.     

Effects of 17-α-estradiol on a free-living marine nematode community: a microcosm experiment

A microcosm experiment was used to examine the effects of 17-α-estradiol on a nematode community. Four 17-α-estradiol concentrations (0.15, 0.31, 0.62 and 1.24 ppm) were tested, and effects were examined after 30 days. Significant differences were noted between nematode assemblages from the control and those from 17-α-estradiol treatments. Total nematode abundance, Shannon–Wiener index and evenness were affected by 17-α-estradiol contamination, but species richness was unaffected. Chromadorina metulata and Ascolaimus elongatus were eliminated at all doses tested and seemed to be intolerant to estradiol. Kraspedonema octogoniata decreased at all doses and could be categorised as sensitive to estradiol contamination. Spirinia gerlachi increased at all doses tested and seemed to be an opportunistic species at the doses tested.     

Modulation of human β-defensin-2 expression by 17β-estradiol and progesterone in vaginal epithelial cells

We investigated the expression of HBD-1 and -2 in vaginal epithelial cells treated with lipopolysaccharide (LPS) and the effects on HBD-2 expressions by 17β-estradiol and progesterone. Primary vaginal epithelial cells were isolated from a segment of normal anterior vaginal wall obtained during vaginoplasty and were cultured in keratinocyte growth medium and were allowed to undergo their 3rd passage. Expression of HBD-1 and -2 by different stimuli using LPS 0.5 μg/ml, 17β-estradiol 2 nM and progesterone 1 μM was measured by RT-PCR, ELISA and real-time RT-PCR, respectively. HBD-1 was produced constitutively in vaginal epithelial cells and the production of HBD-1 was not influenced by LPS, 17β-estradiol and progesterone, but the production of HBD-2 was increased inducibly by LPS. 17β-Estradiol and progesterone did not change the production of HBD-2 in normal state, but 17β-estradiol increased the production of HBD-2 and progesterone suppressed the production of HBD-2 under the circumstances with infection. The HBD-2 plays an important role at innate host defense on genitourinary tract. The lacks of estrogen during menopause or uses of a progesterone-based oral contraceptive in sexually active women may influence production of HBD-2 in vaginal epithelium and may increase susceptibility to bacterial vaginitis or recurrent UTI.     

The mitogenic effect of testosterone and 17β-estradiol on airway smooth muscle cells

Airway disease distribution and/or severity exhibit sex differences suggesting that sex hormones are involved in the respiratory system physiology and pathophysiology. The implication of airway smooth muscle cells (ASMCs) in the physiology of the airways and the pathogenetic mechanism of airway remodeling is of great interest. Therefore, we studied the effect of testosterone and 17β-estradiol on ASMC proliferation and the mechanisms involved.Cell proliferation was estimated using the methyl-[³H]thymidine incorporation and Cell Titer 96^® AQueous One Solution Assay methods. ASMC isolated from adult male or female rabbit trachea were incubated with testosterone (1 pM-1 μM) or 17β-estradiol (1 pM-1 μM), in the presence or absence of the androgen receptor antagonist flutamide (10 nM) or estrogen receptor antagonist ICI182780 (10 nM), as well as of the PI3K inhibitors LY294002 (20 μM) or wortmannin (1 μM), or the MAPK inhibitors PD98059 (100 μM) or U0126 (1 μM).After 24 h of incubation, testosterone and 17β-estradiol increased methyl-[³H]thymidine incorporation and cell number, in ASMC isolated from male or female animals. The induction of ASMC proliferation by testosterone or 17β-estradiol was inhibited by flutamide or ICI182780 respectively, as well as by LY294002, wortmannin, PD98059 or U0126.In conclusion, testosterone and 17β-estradiol have a mitogenic effect on ASMC, which is receptor-mediated and involves the MAPK and PI3K signaling pathways. Moreover, their effect is the same for ASMC from male and female animals. It is possible that gender-related differences in ASMC remodeling, may be influenced by the different patterns of sex steroid hormone secretion in males and females.     

Evaluation of the Preventive Effect of Isoflavone Extract on Bone Loss in Ovariectomized Rats

To examine a potential role for soybean phytoestrogens in postmenopausal bone loss, twenty-four 12-week-old Sprague-Dawley rats were divided randomly into 4 groups and given controlled diets for 16 weeks. The treatment groups were as followed: sham operated, ovariectomized (OVX) control, OVX + isoflavone extract (6.25 g/kg), and OVX + 17β-estradiol (4 mg/kg). OVX treatments reduced femoral and fourth lumbar vertebral bone density and mineral content (p<0.01), decreased uterine weight (p<0.01), accelerated body weight increases (p<0.05), and increased the activities (p<0.01) of both serum alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP). Supplementation with isoflavone prevented the losses of bone density and mineral content caused by OVX (p<0.01). Although both isoflavone and 17β-estradiol exhibited similar bone-sparing ability on the OVX-induced bone loss, the effect of isoflavone was not the same as that of 17β-estradiol on the serum ALP and TRAP, body weight increase, and uterine weight change. We concluded that dietary supplementation with soybean isoflavone can prevent postmenopausal bone loss via a different mechanism of estrogen in OVX rats.     

Reconstituted human normal breast in nude mice using collagen gel or Matrigel.

Human breast epithelial cells dissociated from reduction mammoplasty specimens were embedded in two commonly used extracellular matrices, type I collagen gel or Matrigel, and subsequently transplanted subcutaneously into athymic nude mice. Histological sections from both types of recovered gels showed epithelial structures arranged as short tubules with some branching as well as preservation of epithelial cell polarity. Proliferation was studied in vivo by 5-bromo-2′-deoxy-uridine labeling followed by immunostaining of sections from recovered gels. Human breast epithelia embedded in collagen gel or Matrigel had similar proliferative activity. Cholera toxin, 17β-estradiol, and epidermal growth factor, when tested singly, were growth promoting, and in combination 17,β-estradiol and cholera toxin had an additive effect but 17,β-estradiol and epidermal growth factor were not additive. Our model system provides a means to study the endocrine control of normal human breast development.     

Estradiol lowers intracranial self-stimulation thresholds and enhances cocaine facilitation of intracranial self-stimulation in rats

Women initiate cocaine use at a younger age and have more complications (e.g., higher rates of major or minor depression) related to cocaine use than men. It has been proposed that estrogens play an important role in these sex differences. The addictive potential of psychoactive drugs can be measured in rats via a rewarding intracranial self-stimulation (ICSS) procedure. The rate-independent method of ICSS allows researchers to assess the “pure” rewarding effect of cocaine without influence of nonspecific motor reactions. The present study aimed to estimate effects of estradiol and a combination of estradiol and cocaine on ICSS in ovariectomized female rats. 17-β-estradiol (5 μg/animal/day, 2 days) produced a long-lasting gradual lowering of the thresholds for ICSS. The ability of estradiol to decrease thresholds for ICSS has never been shown previously. Combination of 17-β-estradiol and cocaine (5.0 mg/kg, 5 days) produced a greater effect on ICSS thresholds than the effect of either compound alone. No tolerance or sensitization to cocaine developed during the study. Present findings suggest estradiol increases sensitivity of the brain reward system in rats, which may have an important implication in understanding sex differences in cocaine effects.     

Effects of long-term cortisol treatments on gonadal development, sex steroids levels and ovarian cortisol content in cultured great sturgeon Huso huso

The objective of this study was to examine the effect of cortisol implantations on gonadal development, sex steroid levels, and ovarian cortisol content in cultured great sturgeon Huso huso. Three groups of 5 fish for each treatment were considered. The experimental groups included: control (capsules containing cocoa butter alone), low cortisol (C(5); 5mg cortisol/kg body mass+cocoa butter) and, high cortisol (C(50); 50mg cortisol/kg body mass+cocoa butter). The capsules containing hormones and cocoa butter were intraperitoneally implanted into 3-year-old female fish at pre-vitellogenic stage (mean initial body mass 6809.7 ± 73 g) every 6 weeks over a 6-month period from January to June. The serum levels of cortisol, glucose, cholesterol and sex steroids (testosterone and 17β-estradiol) were determined at the initial time and three weeks after each implantation. Oocyte histological characteristics (the diameter and area of the oocyte, the diameter and area of the nucleus and the ratio of the nucleus area to the oocyte area) were measured at the end of the experiment and compared to those at the initial time. Ovarian cortisol content was measured at the end of the experiment. The results showed that serum cortisol levels varied in a dose-independent manner, so that the highest cortisol concentrations were observed in C(5)-treated fish throughout the experiment. Serum glucose levels were significantly higher in cortisol-treated groups than those in the control group. The high dose of cortisol elicited a significant constant increase in serum cholesterol concentrations. Fish implanted with the high cortisol dose showed significant declines in serum testosterone and 17β-estradiol concentrations throughout the experiment. No significant differences were found in oocyte histological characteristics among experimental groups. The cortisol implants elicited a dose-dependent increase in ovarian cortisol content. At the end of trial, body-growth indices were the lowest in C(50)-implanted fish, while the low cortisol dose had no effect on growth relative to the controls. These results indicated that chronic stress induced by cortisol implantation in great sturgeon suppressed gonadal steroidogenesis and somatic growth but had no effect on ovarian growth and development.     

Paradoxical effects of 17β-estradiol on glucose transport in primary cell cultures of a rat mammary tumor

Primary cell cultures of rat mammary carcinoma R3230AC exhibited a rapid, reversible and dose-related inhibition of carrier-mediated 3-0-methyl-D-glucose transport when estrone, 17β-estradiol, estriol, diethylstilbestrol or phloretin was present during the transport assay. With 17β-estradiol, maximal transport inhibition (66%) was observed at 40μM, a concentration also effective in preventing cell growth when present in the media. Cultures preincubated in growth media containing 5mM glucose plus 40μM 17β-estradiol for one day displayed enhanced rates of carrier mediated 3-0-methyl-D-glucose transport. This increase was prevented by 50mM glucose and can be explained as an adaptive response to a condition simulating glucose starvation.     

Microbial hydroxylation of 17β-estradiol by Penicillium brevicompactum

Microbial hydroxylation of 17β-estradiol (1) with Penicillium brevicompactum, a fungal species not used in biotransformation so far, yielded four metabolites: 1, 3, 5-estratriene-3, 15α-diol-17-one (2); 1, 3, 5-estratriene-3, 6α, 17β-triol (3); 1, 3, 5-estratriene-3, 15α, 17β-triol (4); and 1, 3, 5-estratriene-3, 6α, 15α-triol-17-one (5). All the products were determined by ¹H NMR, ¹³C NMR, two-dimensional NMR, and HRMS techniques. Compounds 3, 4, and 5 are reported for the first time via microbial transformation, and 5 is a new compound as far as we know. Possible metabolic pathway of 17β-estradiol via Penicillium brevicompactum was also proposed.     

Age-related changes in the epithelial and stromal compartments of the mammary gland in normocalcemic mice lacking the vitamin D3 receptor

The vitamin D(3) receptor (VDR) serves as a negative growth regulator during mammary gland development via suppression of branching morphogenesis during puberty and modulation of differentiation and apoptosis during pregnancy, lactation and involution. To assess the role of the VDR in the aging mammary gland, we utilized 12, 14, and 16 month old VDR knockout (KO) and wild type (WT) mice for assessment of integrity of the epithelial and stromal compartments, steroid hormone levels and signaling pathways. Our data indicate that VDR ablation is associated with ductal ectasia of the primary mammary ducts, loss of secondary and tertiary ductal branches and atrophy of the mammary fat pad. In association with loss of the white adipose tissue compartment, smooth muscle actin staining is increased in glands from VDR KO mice, suggesting a change in the stromal microenviroment. Activation of caspase-3 and increased Bax expression in mammary tissue of VDR KO mice suggests that enhanced apoptosis may contribute to loss of ductal branching. These morphological changes in the glands of VDR KO mice are associated with ovarian failure and reduced serum 17β-estradiol. VDR KO mice also exhibit progressive loss of adipose tissue stores, hypoleptinemia and increased metabolic rate with age. These developmental studies indicate that, under normocalcemic conditions, loss of VDR signaling is associated with age-related estrogen deficiency, disruption of epithelial ductal branching, abnormal energy expenditure and atrophy of the mammary adipose compartment.     

Hepatic and plasma sex differences in saturated and monounsaturated fatty acids are associated with differences in expression of elongase 6, but not stearoyl-CoA desaturase in Sprague–Dawley rats

Monounsaturated fatty acids (MUFA) have been viewed as either beneficial or neutral with respect to health; however, recent evidence suggests that MUFA may be associated with obesity and cardiovascular disease. Sex differences in MUFA composition have been reported in both rats and humans, but the basis for this sexual dimorphism is unknown. In the current study, enzymes involved in MUFA biosynthesis are examined in rat and cell culture models. Male and female rats were maintained on an AIN-93G diet prior to killing at 14 weeks of age after an overnight fast. Concentrations of 16:0 (2,757 ± 616 vs. 3,515 ± 196 μg fatty acid/g liver in males), 18:1n-7 (293 ± 66 vs. 527 ± 49 μg/g) and 18:1n-9 (390 ± 80 vs. 546 ± 47 μg/g) were lower, and concentrations of 18:0 (5,943 ± 1,429 vs. 3,987 ± 325 μg/g) were higher in phospholipids in livers from female rats compared with males. Hepatic elongase 6 mRNA and protein were 5.9- and 2.0-fold higher, respectively, in females compared with males. Stearoyl-CoA desaturase expression did not differ. Specific hormonal effects were examined in HepG2 cells cultured with varying concentrations of 17β-estradiol, progesterone and testosterone (0, 10, 30 and 100 nM) for 72 h. Progesterone and 17β-estradiol treatments increased, while testosterone decreased, elongase 6 protein. Sex differences in MUFA composition were associated with increased expression of hepatic elongase 6 in females relative to male rats, which appears to be mediated by sex hormones based on observations of hormonal treatments of HepG2 cells.     

Response of primary rabbit kidney proximal tubule cells to estrogens

The effects of estrogens on the growth and function of primary rabbit kidney proximal tubule (RPT) cells have been examined in hormonally defined phenol red–free medium. 17β-estradiol was observed to stimulate growth at dosages as low as 10⁻¹⁰ M. The growth stimulatory effects of 17β-estradiol were mitigated in the presence of hydrocortisone, suggesting that these two steroid hormones acted at least in part by common mechanisms. The effects of other steroids known to interact with the estrogen receptor were examined. Alpha estradiol was found to be growth stimulatory over a concentration range of 10⁻⁹ to 10⁻⁸ M, albeit to a lower extent than beta estradiol. In addition, the anti-estrogen tamoxifen was also growth stimulatory (unlike the case with the human mammary tumor cell line MCF-7). The effects of several metabolic precursors of 17β-estradiol were examined, including testosterone, which was growth stimulatory, and progesterone, which was growth inhibitory. The growth stimulatory effects of 17β-estradiol, alpha estradiol, and tamoxifen could possibly be explained by their interaction with an estrogen receptor. Indeed, metabolic labelling and immunoprecipitation studies indicated the presence of such an estrogen receptor in the primary cultures. The rate of biosynthesis of the estrogen receptor was found to be affected by the presence of exogenously added 17β-estradiol. 17β-estradiol was also observed to increase the activity of two brush border enzymes, alkaline phosphatase and gamma glutamyl transpeptidase, during the growth phase of the primary cultures. J Cell Physiol 178:35–43, 1999. © 1999 Wiley-Liss, Inc.     

BRANCH GEOMETRY AND EFFECTIVE LEAF AREA: A STUDY OF TERMINAUA-BRANCHING PATTERN. 1. THEORETICAL TREES

Single lateral branches and branch tiers of Terminalia catappa L. are simulated and drawn by computer. Leaf clusters on the branches are approximated by discs, and the effective leaf areas are determined by use of Dirichlet domains. Theoretical optimal branching angles which produce the maximum effective leaf area are obtained from simulations. Symmetrical and asymmetrical branching angles are contrasted; the latter characterize real trees. Varying leaf disc radius and ratio of branch-unit lengths affects optimal branching angles, as does the symmetry of a tier of five branches. Leaf area indices for individual branches and branch tiers are given for all simulations. The number of branches in a tier has a major effect on leaf area index and effective leaf area. The theoretical optimal branching angles of many simulations are very close to the values observed in real trees of T. catappa. We conclude that the observed branching angles and number of branches in a tier of this species optimize light interception within constraints of a fixed pattern of branching, one that is widespread among tropical trees.     

Acute estrogen treatment facilitates recognition memory consolidation and alters monoamine levels in memory-related brain areas

Acute effects of estrogens on mnemonic processes were examined at the behavioral and neurochemical levels. 17β-estradiol and 17α-estradiol influences on memory consolidation were assessed using object placement (OP) and object recognition (OR) tasks. Subjects received treatment immediately after a sample trial (exploring two novel objects), and memory of objects (OR memory) or location of objects (OP memory) was tested 4 h later. Both isomers of estradiol enhanced memory. For spatial memory, 15 and 20 µg/kg of 17β-estradiol facilitated OP, while lower and higher doses were ineffective. 17α-estradiol had a similar pattern, but a lower dose was effective. When treatment was delayed until 45 min after a sample trial, memory was not enhanced. For non-spatial memory, OR was facilitated at 5 µg/kg of 17β-estradiol and at 1 and 2 µg/kg of 17α-estradiol and, similar to OP, lower and higher doses were ineffective. These data demonstrate that beneficial effects of estrogens are dose, time and task dependent, and the dose-response pattern is an inverted U. Because monoamines are known to have contributions to memory, brains were removed 30 min after treatment for measurements of dopamine (DA), norepinephrine (NE), serotonin (5-HT), and metabolites. Estrogen elevated 5HT, NE metabolite MHPG, turnover ratio of NE to MHPG, and DA metabolite DOPAC levels in the prefrontal cortex, while NE and MHPG were decreased in the hippocampus. Thus, acute estrogens exert rapid effects on memory consolidation and neural function, which suggests that its mnemonic effects may involve activation of membrane associated estrogen receptors and subsequent signaling cascades, and that monoamines may contribute to this process.