Endocrine disrupting chemicals: exposure, effects on human health, mechanism of action, models for testing and strategies for prevention

Endocrine Disrupting Chemicals (EDCs) are a global problem for environmental and human health. They are defined as "an exogenous chemical, or mixture of chemicals, that can interfere with any aspect of hormone action". It is estimated that there are about 1000 chemicals with endocrine-acting properties. EDCs comprise pesticides, fungicides, industrial chemicals, plasticizers, nonylphenols, metals, pharmaceutical agents and phytoestrogens. Human exposure to EDCs mainly occurs by ingestion and to some extent by inhalation and dermal uptake. Most EDCs are lipophilic and bioaccumulate in the adipose tissue, thus they have a very long half-life in the body. It is difficult to assess the full impact of human exposure to EDCs because adverse effects develop latently and manifest at later ages, and in some people do not present. Timing of exposure is of importance. Developing fetus and neonates are the most vulnerable to endocrine disruption. EDCs may interfere with synthesis, action and metabolism of sex steroid hormones that in turn cause developmental and fertility problems, infertility and hormone-sensitive cancers in women and men. Some EDCs exert obesogenic effects that result in disturbance in energy homeostasis. Interference with hypothalamo-pituitary-thyroid and adrenal axes has also been reported. In this review, potential EDCs, their effects and mechanisms of action, epidemiological studies to analyze their effects on human health, bio-detection and chemical identification methods, difficulties in extrapolating experimental findings and studying endocrine disruptors in humans and recommendations for endocrinologists, individuals and policy makers will be discussed in view of the relevant literature.

NTS Catecholamine Neurons Mediate Hypoglycemic Hunger via Medial Hypothalamic Feeding Pathways

Glucose is the essential energy source for the brain, whose deficit, triggered by energy deprivation or therapeutic agents, can be fatal. Increased appetite is the key behavioral defense against hypoglycemia; however, the central pathways involved are not well understood. Here, we describe a glucoprivic feeding pathway by tyrosine hydroxylase (TH)-expressing neurons from nucleus of solitary tract (NTS), which project densely to the hypothalamus and elicit feeding through bidirectional adrenergic modulation of agouti-related peptide (AgRP)- and proopiomelanocortin (POMC)-expressing neurons. Acute chemogenetic inhibition of arcuate nucleus (ARC)-projecting NTS^TH neurons or their target, AgRP neurons, impaired glucoprivic feeding induced by 2-Deoxy-D-glucose (2DG) injection. Neuroanatomical tracing results suggested that ARC-projecting orexigenic NTS^TH neurons are largely distinct from neighboring catecholamine neurons projecting to parabrachial nucleus (PBN) that promotes satiety. Collectively, we describe a circuit organization in which an ascending pathway from brainstem stimulates appetite through key hunger neurons in the hypothalamus in response to hypoglycemia.

Evidence that membrane-bound G protein-coupled melatonin receptors MT1 and MT2 are not involved in the neuroprotective effects of melatonin in focal cerebral ischemia

Melatonin is synthesized and released by the pineal gland in a circadian rhythm, and many of its peripheral actions are mediated via membrane MT1 and MT2 receptors. Apart from its metabolic functions, melatonin is a potent neuroprotective molecule owing to its antioxidative actions. The roles of MT1 and MT2 in the neuroprotective effects of melatonin and cell signaling after cerebral ischemia remain unknown. With the use of MT1 and MT2 knockout (mt1/2(-/-) ) mice treated with melatonin, we evaluated brain injury, edema formation, inducible nitric oxide synthase (iNOS) activity, and signaling pathways, including CREB, ATF-1, p21, Jun kinase (JNK)1/2, p38 phosphorylation, resulting from ischemia/reperfusion injury. We show that the infarct volume and brain edema do not differ between mt1/2(-/-) and wild-type (WT) animals, but melatonin treatment decreases infarct volume in both groups and brain edema in WT animals after middle cerebral artery occlusion. Notably, melatonin's neuroprotective effect was even more pronounced in mt1/2(-/-) animals compared to that in WT animals. We also demonstrate that melatonin treatment decreased CREB, ATF-1, and p38 phosphorylation in both mt1/2(-/-) and WT mice, while p21 and JNK1/2 were reduced only in melatonin-treated WT animals in the ischemic hemisphere. Furthermore, melatonin treatment lowered iNOS activity only in WT animals. We provide evidence that the absence of MT1 and MT2 has no unfavorable effect on ischemic brain injury. In addition, the neuroprotective effects of melatonin appear to be mediated through a mechanism independent of its membrane receptors. The underlying mechanism(s) should be further studied using selective melatonin receptor agonists and antagonists.

Immune effects of surgical menopause and estrogen replacement therapy in peri-menopausal women

The complex relationship between sex hormones and immune function suggests that sex hormone deficiency and estrogen replacement therapy (ERT) in post-menopausal women may have pleiotropic effects on immune function. For this reason, we aimed to investigate short-term effects of surgical menopause and ERT on immunity profile in peri-menopausal women. Seventeen healthy peri-menopausal women who were to undergo total abdominal hysterectomy and bilateral salpingo-oopherectomy (TAH + BSO) for uterine myoma were enrolled into this study. Three blood samples were collected from each patient: 1-day prior to surgery, 30 days after the operation (before ERT) and 30 days after transdermal ERT. The percentages of peripheral blood lymphocyte subpopulations, serum interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) concentrations were determined by flow-cytometry and ELISA, respectively. Following TAH + BSO, the percentage of CD8+ cells was increased ( P < 0.001 ) while the percentage of CD19+ cells, serum IL-4, and IFN-gamma concentration and the ratio of CD4+ to CD8+ cells were decreased ( P < 0.001, P < 0.001, P < 0.002, and P < 0.05 respectively). After ERT, this trend reversed and a decrease in the CD8+ cells ( P < 0.001 ), increase in the CD19+ cells percentages ( P < 0.02 ) and increase in serum IFN-gamma concentration ( P < 0.002 ) were observed. Although an increasing trend in the CD4+ to CD8+ ratio occurred by ERT, this was not significant. However, the decrease in the serum IL-4 concentration after TAH + BSO was not reversed by ERT. Hormone deficiency in post-menopausal women may cause an impaired immune response, and ERT can restore this phenomenon. Estrogen seems to have an important role in the regulation of immune function.

Effects of pinealectomy and exogenous melatonin on serum leptin levels in male rat

The effects of pinealectomy and exogenous melatonin (N-acetyl-5-methoxytryptamine) on serum leptin levels were investigated in rats. Exogenous administration of melatonin to intact rats resulted in significant decreases in serum leptin levels (P < 0.05) compared to those of the intact control group. Serum leptin levels were significantly elevated in the pinealectomised rats in comparison to the sham-pinealectomised animals (P < 0.001) and were significantly suppressed by exogenous administration of melatonin compared to those of non-treated pinealectomised rats (P < 0.001). Hormone concentrations in the melatonin-treated pinealectomised group were found to be similar to those seen in the sham-pinealectomised group. These results suggest that pineal gland has an effect on leptin release.

The effects of intracerebroventricular infusion of apelin-13 on reproductive function in male rats

Apelin is a novel bioactive peptide as the endogenous ligand for APJ. Apelin and APJ have also been identified in the testis, hypothalamic nuclei such as arcuate, supraoptic and paraventricular nuclei, implicating roles in the control of reproduction. Therefore, the present study was designed to investigate the effects of chronic central infusion of apelin-13 on LH, FSH and testosterone levels and testis morphology. 21 Wistar-Albino male rats received continuous intracerebroventricular infusion via Alzet osmotic mini pumps filled artificial cerebrospinal fluid (vehicle) or apelin-13 at concentrations of 1 or 10 nmol (10 μl/h) for seven days. At the last 90 min of the infusion period, the blood samples were collected at 15 min intervals (0-90 min) for LH and FSH analyses. At the last sampling point, the blood samples were analyzed for testosterone levels. Infusion of high dose apelin-13 significantly suppressed LH release compared with the vehicle values at 30, 60 and 75 min (p<0.05). However, FSH levels did not significantly differ among the groups. Serum testosterone levels in high dose apelin-13 group were statistically lower than the control group (p<0.05). In addition, histological examination showed that infusion of high dose apelin-13 significantly decreased the number of Leydig cells compared with the control and lower dose apelin-13 groups (p<0.05, p<0.01). Our results suggest that apelin-13 may play a role in the central regulation and decreases testosterone release by suppressing LH secretion. Thus, antagonists of the apelin receptor may, therefore, be useful for pharmaceuticals in the treatment of infertility.

The efficacy of ProTaper Universal rotary retreatment instrumentation to remove single gutta-percha cones cemented with several endodontic sealers

AIM

To evaluate residual root filling material following removal of three newly developed root canal sealers used with a matched-taper single-cone root filling technique and to compare the efficacy of ProTaper Universal rotary retreatment instruments with that of a conventional manual technique.

METHODOLOGY

The canals of 120 palatal roots in maxillary molar teeth were instrumented with EndoWave nickel-titanium rotary instruments and filled using Hybrid Root SEAL, EndoSequence BC Sealer, Activ GP system or AH Plus with matched-taper single gutta-percha cones. The root fillings were then removed with ProTaper Universal retreatment rotary instruments or a manual technique. Buccolingual and proximal digital radiographs of the roots were exposed to determine the area of remaining filling material in the coronal, middle and apical thirds. The area percentages of remaining filling material in each third and total canal area were calculated. Data were analysed statistically with Kruskal-Wallis and Mann-Whitney U-tests. The level of significance was set at P<0.05.

RESULTS

Irrespective of the sealer type and retreatment technique, filling material could not be removed completely from the root canals. Significantly, more remaining filling material was observed in the apical third (P<0.05). When comparing the sealers, the only significant difference was detected between AH Plus/manual and Activ GP/manual groups with respect to residual material in the total canal area (P<0.05). There were no significant differences between manual and ProTaper groups.

CONCLUSIONS

When using gross radiographic criteria, the Activ GP was more effectively removed from root canals than AH Plus with hand instrumentation. Hybrid Root SEAL, EndoSequence BC Sealer and AH Plus were removed to a similar extent. ProTaper Universal retreatment instruments were as safe and effective as hand instruments in reaching the working length.

Anticonvulsant activity of resveratrol-loaded liposomes in vivo

Resveratrol (3,5,4'-stilbenetriol), a natural polyphenol produced by various plants, has attracted attention over the past decade because of its multiple beneficial properties, including anti-inflammatory, anti-oxidant and chemopreventive, yet, there is limited information about its antiepileptic effects. Moreover, its poor solubility in water and low bioavailability are the challenging issues. In the present study, we aimed to investigate effects of free resveratrol and resveratrol delivered in amphipathic liposomal delivery system, which has a high blood-brain barrier crossing potential, on penicillin-induced epileptic seizure model. For this purpose, adult male Sprague-Dawley rats were divided into four groups as saline (Control), liposome (LIP), free resveratrol (RES) and resveratrol+liposome (RES+LIP). Penicillin-induced epileptic activity was recorded for 120 min by electrocorticography. Glutathione S-transferase (GST), Glutathione (GSH), Superoxide dismutase (SOD) and Malondialdehyde (MDA) assays were performed in brain tissues collected. Our results showed that RES+LIP was the most effective anticonvulsant treatment on penicillin-induced epileptic seizures when compared to control, as RES+LIP immediately decreased the number of spikes per minute. GST and SOD activity, as well as the GSH levels, were significantly increased in the RES+LIP group as compared with the control group. Also, the MDA levels were significantly higher in the RES+LIP compared to RES and control groups. In conclusion, RES+LIP treatment was more effective on the decrease in spike frequency and spike amplitudes than other treatments. Our results suggest that the RES+LIP is more effective than RES on penicillin-induced epileptiform activity.

Influence of chronic morphine exposure on serum LH, FSH, testosterone levels, and body and testicular weights in the developing male rat

Opiate abuse has been a matter of serious concern in male adolescents. This study investigates the effects of chronic morphine administration on serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone levels, testicular histology, and body and testes weight in developing male rats. Animals were subcutaneously injected with morphine (5 mg/kg) or saline (1 mL/kg) twice daily for 30 days. Body weight determinations and injections were carried out under light ether anesthesia. At the end of the experiments, the rats were decapitated and blood samples were collected. Serum levels of LH and FSH were measured. Chronic morphine administration significantly decreased decreased serum testosterone (p < .02) and LH (p < .01) levels, but not FSH release compared to controls. Morphine exposure reduced body weight (p < .01), but had no significant effect on the testicular weight. When the testicular tissue was histologically examined, structural features of the seminiferous tubules and Leydig cells were similar in both saline and morphine-treated animals. The results suggest that opiates affect testosterone release through the hypothalamo-hypophyseal-gonadal axis rather than by a local testicular mechanism. Chronic morphine exposure during sexual maturation may have long-term endocrine disturbances in male rats.

Influence of Cement Shade and Water Storage on the Final Color of Leucite-reinforced Ceramics

Luting cement under 0.8 mm thick leucite-reinforced ceramic changed the final color of the ceramic and could be seen by the human eye. Therefore, clinicians may prefer to use try-in pastes or polymerized luting composite shade guides to compensate for the change in color of definitive restorations, such as laminate veneers. The final color differences between ceramics luted with cements in A1 and A3 shades were not clinically perceivable at each measurement. Within the limitations of this study, changing the color of an IPS Empress laminate veneer restoration via the shade of the cement seems not to be a preferred method.

Effects of heart position on the body-surface electrocardiogram

Previous studies have examined the influence of body position, respiration, and habitus on body surface potentials. However, the authors could only estimate the sources of the effects they documented. Among the proposed origin of changes in body surface potentials from those studies were the position of the heart, alterations in autonomic tone, differences in ventricular blood volume, and variations in torso resistivity. The goal of this study was to investigate specifically the role of geometric factors in altering body surface potentials and the electrocardiogram. For this, we used experiments with an isolated, perfused dog heart suspended in a realistically shaped electrolytic torso tank. The experimental preparation allowed us to measure epicardial and tank surface potentials simultaneously, and then reconstruct the geometry of both surfaces. Our results mimicked some of the features described by previous investigators. However, our results also showed differences that included considerably larger changes in the peak QRS and T-wave amplitudes with heart movement than those reported in human studies. We detected smaller values of root-mean-squared variability from heart movements than those reported in a human study comparing body surface potentials during change in inspiration and body position. There was better agreement with relative variability, which in these studies ranged from 0.11 to 0.42, agreeing well with an estimate from human studies of 0.40. Our results suggest that the isolated heart/torso tank preparation is a valuable tool for investigating the effects of geometric variation. Furthermore, the geometric position of the heart appears to be a large source of variation in body surface potentials. The size of these variations easily exceeded thresholds used to distinguish pathologic conditions and thus such variations could have important implications on the interpretation of the standard electrocardiogram.

Effects of PCB 52 and PCB 77 on cell viability, [Ca2+]i levels and membrane fluidity in mouse thymocytes

Exposure to polychlorinated biphenyls (PCBs) is known to suppress immune system function and this action is usually ascribed to dioxin-like PCBs that act via the Ah receptor. We have studied the effects of one ortho-substituted, non-dioxin-like PCB (PCB 52) and one coplanar, dioxin-like congener (PCB 77) on properties of thymocytes acutely isolated from mice. Viability of thymocytes was dose- and time-dependently reduced by PCB 52 with a threshold concentration of about 1 microM, while there was no effect of PCB 77 on viability at concentrations less than 10 microM. Cell death was detectible within 5 min of exposure. Both congeners caused a dose-dependent increase in [Ca(2+)](i), but the threshold concentration was 1 microM for PCB 52 and 5 microM for PCB 77. However, the cell death was not due to the elevation of [Ca(2+)](i), since it was not reduced by incubation in Ca-free Tyrode's Solution. PCB 52, but not PCB 77, caused an increase in membrane fluidity at a concentration of 5 microM. These observations are consistent with previous results that suggest that ortho-substituted PCB congeners dissolve in cell membrane and cause greater disruption of function than do dioxin-like PCB congeners.

Genotoxic effects of PCB 52 and PCB 77 on cultured human peripheral lymphocytes

Polychlorinated biphenyls (PCBs) are known to be carcinogenic, but the mechanisms of this action are uncertain. Most, but not all, studies have concluded that PCBs are not directly mutagenic, and that much if not all of the carcinogenic activity resides in the fraction of the PCB mixture that contains congeners with dioxin-like activity. The present study was designed to determine genotoxic effects of an ortho-substituted, non-coplanar congener, 2,2',5,5'-tetrachlorobiphenyl (PCB 52), and a non-ortho-substituted coplanar congener with dioxin-like activity, 3,3',4,4'-tetrachlorobiphenyl (PCB 77) on cultured human peripheral lymphocytes. DNA damage was assessed by use of the comet assay (alkaline single-cell gel electrophoresis). After cell cultures were prepared, test groups were treated with different concentrations of PCB 52 (0.2 and 1 microM) and PCB 77 (1 and 10 microM) for 1h at 37 degrees C in a humidified carbon dioxide incubator, and compared to a DMSO vehicle control group. The cells were visually classified into four categories on the basis of extent of migration such as undamaged (UD), low damage (LD), moderate damage (MD) and high damage (HD). The highest concentration of PCBs 52 and 77 significantly increased DNA breakage in human lymphocytes (p<0.001). Our results indicate that both the non-coplanar PCB 52 and coplanar PCB 77 cause DNA damage, and that the ortho-substituted congener was significantly more potent than the dioxin-like coplanar congener.

A retrospective comparison of allogeneic peripheral blood stem cell and bone marrow transplantation results from a single center: a focus on the incidence of graft-vs.-host disease and relapse

To detect the effect of the stem cell source, allogeneic peripheral blood stem cell transplantations (alloPBSCTs) performed between 1995 and 1997 from human leukocyte antigen (HLA)-identical siblings in 40 patients with acute and chronic hematological disorders were compared with a historical group of 40 patients with similar variables who had received allogeneic bone marrow transplants (alloBMTs) between 1993 and 1995. Patients in both groups were identical except that both the recipient and the donor ages were, on average, higher in the alloPBSCT group (26 vs. 36 [p = 0.005] and 27 vs. 32 [p = 0.024], respectively). Patients received similar therapy excluding posttransplant granulocyte colony-stimulating factor administration (97% in alloBMT vs. 12.5% in alloPBSCT). The median time to reach neutrophil counts >0.5 x 10(9)/L and platelet counts >20 x 10(9)/L was 13 and 14 days, respectively, in patients receiving alloPBSCTs compared with 19 and 27 days in patients receiving alloBMTs (p = 0.0014 and p = 0.0002). The alloPBSCT group required similar transfusions of red blood cells or platelets. The incidence of grade II-IV acute graft-vs.-host disease (aGVHD) was similar in both groups. However, chronic GVHD (cGVHD) of all grades developed in 78.1% of patients in the alloPBSCT group after a median follow-up period of 12.5 (range 0.5-34) months. In alloBMT recipients, cGVHD of all grades developed in 21.4% after a median follow-up period of 38 (range 0.5-62) months (p = 0.00001). Day 100 transplant-related mortality was also similar: 20% (8 of 40) in the alloBMT patients and 17.5% (7 of 40) in the alloPBSCT group. Although not statistically significant, a relatively higher relapse rate occurred in the alloBMT group (21.4 vs. 10.7%). The estimated disease-free survival in month 24 was 51.3% for alloBMT and 54.6% for alloPBSCT, and the estimated overall survival in month 24 was 56.1% for alloBMT and 64.6% for alloPBSCT. In conclusion, this retrospective comparison suggests that alloPBSCT from HLA-identical donors is associated with faster engraftment, fewer transfusions, and no greater incidence of aGVHD, but a high incidence of cGVHD.

Effects of melatonin on synaptic transmission and long-term potentiation in two areas of mouse hippocampus

We have examined the effects of melatonin on synaptic transmission and long-term potentiation (LTP) in the Schaffer Collateral-CA1 and the mossy fiber-CA3 pathways in mouse hippocampus brain slices. Melatonin (0.1-1 mM) application had different actions on both the field excitatory postsynaptic potentials (fEPSPS) and LTP in the CA1 as compared to the CA3. In CA1, 0.1 mM melatonin blocked LTP, while 1 mM melatonin also depressed the fEPSP. In CA3, neither 0.1 nor 1 mM melatonin altered the fEPSP, whereas both concentrations only slightly reduced LTP. These results demonstrate that melatonin significantly alters synaptic transmission and LTP in the CA1 but has only modest actions in CA3.

Inactivation of Magel2 suppresses oxytocin neurons through synaptic excitation-inhibition imbalance

Prader-Willi and the related Schaaf-Yang Syndromes (PWS/SYS) are rare neurodevelopmental disorders characterized by overlapping phenotypes of high incidence of autism spectrum disorders (ASD) and neonatal feeding difficulties. Based on clinical and basic studies, oxytocin pathway defects are suggested to contribute disease pathogenesis but the mechanism has been poorly understood. Specifically, whether the impairment in oxytocin system is limited to neuropeptide levels and how the functional properties of broader oxytocin neuron circuits affected in PWS/SYS have not been addressed. Using cell type specific electrophysiology, we investigated basic synaptic and cell autonomous properties of oxytocin neurons in the absence of MAGEL2; a hypothalamus enriched ubiquitin ligase regulator that is inactivated in both syndromes. We observed significant suppression of overall ex vivo oxytocin neuron activity, which was largely contributed by altered synaptic input profile; with reduced excitatory and increased inhibitory currents. Our results suggest that dysregulation of oxytocin system goes beyond altered neuropeptide expression and synaptic excitation inhibition imbalance impairs overall oxytocin pathway function.

MCH Neuron Activity Is Sufficient for Reward and Reinforces Feeding

BACKGROUND

Melanin-concentrating hormone (MCH)-expressing neurons have been implicated in regulation of energy homeostasis and reward, yet the role of their electrical activity in short-term appetite and reward modulation has not been fully understood.

OBJECTIVES

We investigated short-term behavioral and physiological effects of MCH neuron activity manipulations.

METHODS

We used optogenetic and chemogenetic approaches in Pmch-cre transgenic mice to acutely stimulate/inhibit MCH neuronal activity while probing feeding, locomotor activity, anxiety-like behaviors, glucose homeostasis, and reward.

RESULTS

MCH neuron activity is neither required nor sufficient for short-term appetite unless stimulation is temporally paired with consumption. MCH neuronal activation does not affect short-term locomotor activity, but inhibition improves glucose tolerance and is mildly anxiolytic. Finally, using two different operant tasks, we showed that activation of MCH neurons alone is sufficient to induce reward.

CONCLUSIONS

Our results confirm diverse behavioral/physiological functions of MCH neurons and suggest a direct role in reward function.

Effects of paint thinner exposure on serum LH, FSH and testosterone levels and hypothalamic catecholamine contents in the male rat

We have investigated the effects of thinner inhalation on serum LH, FSH and testosterone levels together with changes in hypothalamic catecholaminergic system in the male rat. A control group inhaled normal air ventilation. The remaining animals were divided into two groups and exposed to paint thinner in a glassy cage for 15 or 30 d. Toluene concentration (the largest constituent in thinner, 66%) was set at 3000 ppm in the inhalation air. At the end, all animals were decapitated and blood samples obtained. Serum LH and FSH levels were measured by RIA and testosterone by enzyme immunoassay. Following removal of brains on dry ice, medial preoptic area, suprachiasmatic nucleus, median eminence and arcuate nucleus were isolated by micropunch technique. Noradrenaline, 3,4-dihydroxyphenylglycol (DHPG) and dopamine concentrations of these hypothalamic areas were determined by HPLC-ECD. Fifteen-day thinner inhalation significantly suppressed serum LH and testosterone levels in parallel (p<0.001) compared to control group values (LH: 0.77+/-0.07; testosterone: 2.67+/-0.39). Thirty-day exposure markedly decreased LH levels (p<0.001), but surprisingly had no significant effect on testosterone. Serum FSH levels were not significantly altered in either group. Thinner inhalation for 15 or 30 d did not cause any significant change in noradrenaline, DHPG or dopamine concentrations in the hypothalamic regions examined (except in the arcuate nucleus). These results suggest that paint thinner has an anti-gonadotropic effect and may cause long-term endocrine disturbances in the male. It is thought that the hypothalamic catecholaminergic system is not involved in thinner inhibition of LH and testosterone secretion.

Salmon calcitonin ameliorates migraine pain through modulation of CGRP release and dural mast cell degranulation in rats

The exact mechanism of migraine pathophysiology still remains unclear due to the complex nature of migraine pain. Salmon calcitonin (SC) exhibits antinociceptive effects in the treatment of various pain conditions. In this study, we explored the mechanisms underlying the analgesic effect of salmon calcitonin on migrane pain using glyceryltrinitrate (GTN)-induced model of migraine and ex vivo meningeal preparations in rats. Rats were intraperitoneally administered saline, GTN (10 mg/kg), vehicle, saline + GTN, SC (50 μg/kg) + GTN, and SC alone. Also, ex vivo meningeal preparations were applied topically 100 μmol/L GTN, 50 μmol/L SC, and SC + GTN. Calcitonin gene-related peptide (CGRP) contents of plasma, trigeminal neurons and superfusates were measured using enzyme-immunoassays. Dural mast cells were stained with toluidine blue. c-fos neuronal activity in trigeminal nucleus caudalis (TNC) sections were determined by immunohistochemical staining. The results showed that GTN triggered the increase in CGRP levels in plasma, trigeminal ganglion neurons and ex vivo meningeal preparations. Likewise, GTN-induced c-fos expression in TNC. In in vivo experiments, GTN caused dural mast cell degranulation, but similar effects were not seen in ex vivo experiments. Salmon calcitonin administration ameliorated GTN-induced migraine pain by reversing the increases induced by GTN. Our findings suggested that salmon calcitonin could alleviate the migraine-like pain by modulating CGRP release at different levels including the generation and conduction sites of migraine pain and mast cell behaviour in the dura mater. Therefore salmon calcitonin may be a new therapeutic choice in migraine pain relief.

Hippocampal long-term potentiation (LTP) is reduced by a coplanar PCB congener

Neurotoxicity of polychlorinated biphenyls (PCBs) is usually ascribed to the ortho-substituted congeners. We have examined the effects of acute perfusion of 3,3',4,4'-tetrachlorobiphenyl (PCB 77), a coplanar, dioxin-like congener, on long-term potentiation (LTP) in the Schaffer collateral-CA1 and the mossy fiber-CA3 pathways in mouse hippocampus. LTP in both pathways was blocked by PCB 77, with a threshold effect at a concentration of 1 microM. LTP is a useful model of learning and memory function in which a patterned stimulation of an afferent pathway produces a persistent increase in the efficacy of synaptic transmission. LTP is reduced by PCB mixtures and ortho-substituted congeners at concentrations comparable to those studied here. These observations provide evidence in support of the hypothesis that dioxin-like and non-dioxin-like PCB congeners are equally potent in causing the cognitive decrements seen in children exposed prenatally to PCBs.

The comparison of intraocular pressure reductions after isometric and isokinetic exercises in normal individuals

The lowering effect of physical exercise on intraocular pressure (IOP) has been reported both in healthy people and those with glaucoma, but a comparison of the lowering effect of isometric and isokinetic exercises on IOP has not been conducted in any study. Our aims were to investigate the relationship between intensity of exercise and IOP, and whether a significant difference in IOP lowering effect existed between isometric and isokinetic exercises. Sixty-seven patients with an age range of 23-40 who had no ocular disease were randomly divided into two groups. While 31 patients in the first group, group A, performed isokinetic exercise with the Cybex 6000 dynamometer, 32 patients in the second group, group B, had isometric exercises with the same machine. IOP was measured in the right eye of patients with Shiotz tonometer just before and 10 min following exercise. Exercise intensity and total energy consumption were determined by the machine for each patient. While IOP values measured before exercise, the degree of exercise applied, and total energy consumption did not differ significantly between groups, both isometric and isotonic exercises lowered IOP significantly. As a result, isometric and isokinetic exercises lowered IOP in ophthalmologically normal subjects with direct relationship to exercise intensity and total energy consumption. Since the pressure lowering effect of isokinetic exercise was more significant, it might prove useful to glaucomatous patients.

Effects of apelin on reproductive functions: relationship with feeding behavior and energy metabolism

Apelin is an adipose tissue derived peptidergic hormone. In this study, 40 male Sprague-Dawley rats were used (four groups; n = 10). Apelin-13 at three different dosages (1, 5 and 50 μg/kg) was given intraperitoneally while the control group received vehicle the same route for a period of 14 days. In results, apelin-13 caused significant decreases in serum testosterone, luteinizing hormone and follicle-stimulating hormone levels (p < 0.05). Administration of apelin-13 significantly increased body weights, food intake, serum low-density lipoprotein and total cholesterol levels (p < 0.05), but caused significant decreases in high-density lipoprotein levels (p < 0.05). Serum glucose and triglyceride levels were not significantly altered by apelin-13 administration. Significant decreases in both uncoupling protein (UCP)-1 levels in the white and brown adipose tissues and UCP-3 levels in the biceps muscle (p < 0.05) were noted. The findings of the study suggest that apelin-13 may not only lead to obesity by increasing body weight but also cause infertility by suppressing reproductive hormones.

Mu opioid modulation of oxytocin secretion in late pregnant and parturient rats. Involvement of noradrenergic neurotransmission

We have investigated effects of micro- and kappa-opioid agonists and antagonists on plasma oxytocin levels and noradrenaline content in the supraoptic nucleus (SON) and paraventricular nucleus (PVN) of 20-day pregnant rats. beta-Endorphin, oxytocin, estrogen and progesterone profiles in late pregnant and parturient rats were also sought. Stage of estrous cycle was monitored by vaginal smear, and pro-estrous animals were left overnight with male. In the first set of experiments, pregnant rats were monitored and decapitated on days 20 and 21 and after the delivery of second pup. In the second set, 20-day pregnant rats were intracerebroventricularly infused with morphine (50 microg/10 microl), U50,488H (kappa-agonist; 50 microg/10 microl), clocinnamox (micro-antagonist; 50 microg/10 microl) and norbinaltorphimine (kappa-antagonist; 50 microg/10 microl). Controls received saline alone. Serum estrogen and progesterone levels were measured by enzyme immunoassay, and plasma oxytocin and beta-endorphin by radioimmunoassay. Noradrenaline and its metabolite (3,4-dihydroxyphenylglycol) were determined in micropunched hypothalamic nuclei by HPLC-ECD. In parturient rats, oxytocin levels were increased (p < 0.05) and beta-endorphin decreased (p < 0.01) compared to 20-day pregnant animals. Serum progesterone concentrations progressively declined towards parturition (p < 0.001). Clocinnamox raised oxytocin levels (p < 0.01) while U50,488H caused decreases (p < 0.05). Noradrenaline content was elevated by clocinnamox in the SON (p < 0.01) and PVN (p < 0.05) compared to control values. Other agonists and antagonists had no significant effect on the noradrenergic neurotransmission or oxytocin secretion. We suggest that noradrenaline may mediate the inhibitory effects of micro-opioids on oxytocin release. Our findings have also shown that kappa-opioid receptors are not involved in modulation of oxytocin neurons in late pregnant rats.