Oxytocin action on components of endoplasmic reticulum in hippocampal neuronal cells

Despite the known importance of the endoplasmic reticulum (ER) in protein synthesis and vesicular transport, it is not clear whether neuropeptide and neuromodulator oxytocin can directly affect components of the ER in neuronal cells. Therefore, in the present study, we hypothesize that incubation of hippocampal neuronal cells in a presence of oxytocin 1) plays a role in the regulation of the expression of selected ER chaperone components and molecules involved in unfolded protein response pathway 2) affects distribution of the intracellular fluorescence signal highly selective for the ER. We found that oxytocin (1 μM) after 60 min significantly decreased the gene expression of oxidoreductase Ero1β, chaperone glucose-regulated proteins (Grp) 78 and Grp94. A significant decrease in GRP78 protein levels in response to oxytocin treatment occurred after 30, 60 and 120 min. We also observed a time-dependent increase in calreticulin protein levels with a statistically significant increase observed after 360 min. We found that the dynamics of the ER network changes significantly within 2 h of incubation under the influence of oxytocin. In conclusion we have shown that ER chaperones, oxidoreductases and trafficking molecules in neuronal cells are changing in response to oxytocin treatment in a short-term scenario potentially relevant for growth of dendrites and axons.

Intracellular distribution of 3,6-bis(3-alkylguanidino)acridines determines their cytotoxicity

Cytotoxicity of two derivatives of 3,6-bis(3-alkylguanidino)acridines (GNDAs; pentyl- and hexyl-GNDA) was determined against three cell lines: a murine immortalized fibroblast cell line NIH-3T3, a human ovarian carcinoma cell line A2780, and a human neuroblastoma cell line SH-SY5Y. We found out that these GNDAs were cytotoxic against A2780 and NIH-3T3 cells but they showed only a marginal cytotoxicity against neuroblastoma cells SH-SY5Y. To explain differences in cytotoxicity, intracellular distribution of GNDAs was monitored. GNDAs were accumulated in A2780 and NIH-3T3 cells in the nuclei (fluorescence microscopy). In contrast to these cell lines, in SH-SY5Y cells, GNDAs were localized outside of the nuclei, at the plasma membrane and surroundings, extending also to the cytosol. This distribution of GNDAs was confirmed by an ImageStream Flow Cytometer. Acetylcholinesterase (AChE) activity in the SH-SY5Y cells decreased upon incubation with GNDAs. Kinetic studies showed that GNDAs were able to inhibit AChE by the same mode as tacrine (9-amino-1,2,3,4-tetrahydroacridine), a known inhibitor of AChE. A low cytotocity of GNDAs against SH-SY5Y cells could be caused by their affinity to AChE (the enzyme is localized mainly at the plasma membrane). The interaction of GNDAs with AChE may affect their intracellular distribution and consequently the cytotoxicity.

KEYWORDS

acetylcholinesterase, acridine, neuroblastoma cell line SH-SY5Y.

Stereoselective coordination: a six-membered P,N-chelate tailored for asymmetric allylic alkylation

Six-membered chelate complexes [Pd(1a–b)Cl₂], (2a–b) and [Pd(1a–b)(η³-PhCHCHCHPh)]BF₄, (3a–b) of P,N-type ligands 1a, ((2S,4S)-2-diphenyl-phosphino-4-isopropylamino-pentane) and 1b, ((2S,4S)-2-diphenyl-phosphino-4-methylamino-pentane) have been prepared.

[Mechanisms of growth of neuronal axons and dendrites]

Brain development is determined by neuronal differentiation including changes of cell polarity and asymetric growth of neuronal processes. Although, there are many unkown factors contributing to changes of lenght of neuronal cones, mounting experimental and review papers focus on changes of growth conus and role of axonal transport. In particular, mechanisms of actin/microtubule polymerisation and depolymerisation are important. Role of intracellular calcium is also significant. Normal and properly timed changes of lenght of axons and dendrites are dependent on interaction of neurons and glia. Moreover, regeneration of injured axons is dependent on growth factors secreted from glial cells. The aim of the present study is characterisation of the most important mechanisms underlying changes of lenght of neurites.

Cell proliferation in the hippocampus and in the heart is modified by exposure to repeated stress and treatment with memantine

The present studies were aimed to verify the hypothesis that treatment with memantine, a low affinity NMDA glutamate receptor antagonist, can reduce possible stress-induced alterations in cell proliferation in the hippocampus and in the heart and has consequences on stress hormone release. Adult male Wistar rats were exposed to repeated hypokinesis (movement restraint, 2 h daily) or remained undisturbed and they were treated with memantine (5 mg/kg/day, s.c.) or vehicle for 8 days. On the day 7, all animals were injected with 5-bromo-2'-deoxyuridine (BrdU), a marker of cell proliferation. The mild form of chronic stress used resulted only in moderate decrease in BrdU incorporation into DNA in the hippocampus, while the same stimulus caused a pronounced reduction of the new cells formed in left heart ventricle. In both tissues, stress-induced reduction in cell proliferation was more evident in memantine-treated rats. Memantine failed to modify hormones of the hypothalamic-pituitary-adrenocortical axis, while the treatment increased plasma renin activity. The present study demonstrates that treatment with memantine potentiated rather than prevented stress-induced reduction of cell proliferation. We have shown that stress exposure may induce a reduction in cell proliferation in the heart, even in a higher extent than that in the hippocampus. Effects of memantine under stress conditions might be relevant with respect to clinical use of memantine, which is being used in the treatment of neurodegenerative diseases.

Neuroendocrine and cardiovascular parameters during simulation of stress-induced rise in circulating oxytocin in the rat

Physiological functions of oxytocin released during stress are not well understood. We have (1) investigated the release of oxytocin during chronic stress using two long-term stress models and (2) simulated stress-induced oxytocin secretion by chronic treatment with oxytocin via osmotic minipumps. Plasma oxytocin levels were significantly elevated in rats subjected to acute immobilization stress for 120 min, to repeated immobilization for 7 days and to combined chronic cold stress exposure for 28 days with 7 days immobilization. To simulate elevation of oxytocin during chronic stress, rats were implanted with osmotic minipumps subcutaneously and treated with oxytocin (3.6 microg/100 g body weight/day) or vehicle for 2 weeks. Chronic subcutaneous oxytocin infusion led to an increase in plasma oxytocin, adrenocorticotropic hormone, corticosterone, adrenal weights and heart/body weight ratio. Oxytocin treatment had no effect on the incorporation of 5-bromo-2-deoxyuridine into DNA in the heart ventricle. Mean arterial pressure response to intravenous phenylephrine was reduced in oxytocin-treated animals. Decrease in adrenal tyrosin hydroxylase mRNA following oxytocin treatment was not statistically significant. Oxytocin treatment failed to modify food intake and slightly increased water consumption. These data provide evidence on increased concentrations of oxytocin during chronic stress. It is possible that the role of oxytocin released during stress is in modulating hypothalamic-pituitary-adrenocortical axis and selected sympathetic functions.

Oxytocin levels in the posterior pituitary and in the heart are modified by voluntary wheel running

We hypothesized that voluntary wheel running results in increased secretion of oxytocin, a peptide involved in the stress response. An additional hypothesis was that prolonged exercise affects oxytocin levels in the heart, which is in line with the potential role of oxytocin in cardiovascular functions. Voluntary wheel running lasted 3 weeks and daily running distances increased progressively reaching maximum levels about 8 km (Sprague-Dawley rats) and 4 km (Lewis strain). The exercise resulted in significant reduction of epididymal fat, slight increase in glucose transporter GLUT4 mRNA levels and significant enhancement of plasma density. Voluntary exercise failed to influence plasma oxytocin levels either in Lewis or Sprague-Dawley rats, but it resulted in a significant decrease of oxytocin concentrations in the posterior pituitary. Plasma oxytocin concentrations were not modified even if the measurements were made in the dark phase of the day. In voluntary wheel running Sprague-Dawley rats, the content of oxytocin in the right heart atrium was lower than in controls. Thus, the present findings demonstrate that prolonged voluntary wheel running results in a decrease in pituitary oxytocin content without evident changes in hormone concentrations in peripheral blood. However, prolonged exercise used has a significant impact on oxytocin levels in the heart.

Synthesis of sulfated mono- and ditertiary phosphines, complex chemistry and catalysis

Cyclic and bicyclic sulfates have been prepared from commonly available alcohols. Nucleophilic cleavage of the cyclic sulfates affords a new type of water-soluble mono- and ditertiary phophines bearing -OSO3Li groups in distinguished positions in the molecular framework. Both phosphines have amphiphilic character. Reactions of the chiral 2 and the dppp analogue 5 with [Rh(COD)Cl]2 and Pt(PhCN)2Cl2 provide novel zwitterionic complexes. Rhodium complexes of 2 and 5 have been successfully applied in liquid biphasic hydroformylation of styrene and octene-1. When the rhodium complex of 5 was used as catalyst in hydroformylation of styrene, less then 4 ppm rhodium could be detected in the organic phase.Key words: cyclic sulfates, water soluble phosphines, amphiphilic character, Rh complexes, Pt complexes, hydroformylation.

Asymmetric hydroformylation of styrene catalyzed by platinum complexes of chiral diphosphites with atropisomeric terminal moieties

To study the nature of steric and electronic effects of diphosphites, a novel diphosphite was synthesized and tested with regard of its catalytic performance in the hydroformylation of styrene catalyzed by platinum complexes. The novel ligand 3 was prepared by the reaction of enantiomerically pure pentane-2,4-diol with (S)-2-chloro-5,5',6,6',7,7',8,8'-octahydro-dinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepine based on H8-BINOL (H8-BINOL = 5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol). For a comparative study, the BINOL (1,1'-bi-2-naphthol) based analogue 4 of 3 has also been synthesized. The highest chemoselectivity to aldehyde (71%) and regioselectivity to branched aldehyde (85%) with an enantiomer excess (ee) of 86% was obtained with the platinum(II)-SnCl2 catalytic system associated with (2S,4S)-bis(S)-3.Key words: asymmetric hydroformylation, chirality, homogeneous catalysis, P ligands, platinum.

Urinary 6-sulphatoxymelatonin excretion is increased in rats after 24 hours of exposure to vertical 50 Hz, 100 microT magnetic field

The effect of exposure to a 50 Hz, vertical magnetic field on the excretion of urinary 6-sulphatoxymelatonin (aMT6s) of rats was studied in a self-controlled experiment. Ten male Wistar rats were kept under 9:15 h light: dark conditions in metabolic cages. The rats were exposed to 1.0 or 100 microT flux density for 24 h. The excretion of aMT6s, which is the primary metabolite of melatonin in the urine, did not show a statistically significant decrease, as measured by 125I radioimmunoassay, during or after magnetic field exposure of rats to either flux density. At 100 microT flux density, the increase of aMT6s excretion on the day after exposure was statistically significant (P < .02), compared with the value under exposure, but was not significant compared with the baseline values before exposure.

Effect of continuous-wave and amplitude-modulated 2.45 GHz microwave radiation on the liver and brain aminoacyl-transfer RNA synthetases of in utero exposed mice

Investigations have been carried out concerning the effects of microwave (MW) exposure on the aminoacyl-transfer ribonucleic acid (tRNA) synthetase of the progeny of females that were exposed during their entire period of gestation (19 days). The changes caused by continuous-wave (CW) and amplitude-modulated (AM) MW radiation have been compared. CFLP mice were exposed to MW radiation for 100 min each day in an anechoic room. The MW frequency was 2.45 GHz, and the amplitude modulation had a 50 Hz rectangular waveform (on/off ratio, 50/50%). The average power density exposure was 3 mW/cm2, and the whole body specific absorption rate (SAR) was 4.23 +/- 0.63 W/kg. The weight and mortality of the progeny were followed until postnatal day 24. Aminoacyl-tRNA synthetase enzymes and tRNA from the brains and livers of the offspring (461 exposed, 487 control) were isolated. The aminoacyl-tRNA synthetase activities were determined. The postnatal increase of body weight and organ weight was not influenced by the prenatal MW radiation. The activity of enzyme isolated from the brain showed a significant decrease after CW MW exposure, but the changes were not significant after 50 Hz AM MW exposure. The activity of the enzyme isolated from liver increased under CW and 50 Hz modulated MW.

Sinusoidal 50 Hz, 500 microT magnetic field has no acute effect on urinary 6-sulphatoxymelatonin in Wistar rats

The effect of a 50 Hz, vertical magnetic field on the excretion of urinary 6-sulphatoxymelatonin (aMT6s) of male and female Wistar rats was studied in a self-controlled experiment. Twenty rats were kept in metabolic cages under 9:15 h light:dark conditions. The urine of the animals was collected twice per day for 5 consecutive days. The concentration of aMT6s in the rat urine was measured by 125I radioimmunoassay. The rats were exposed to 5 and 500 microT flux density for 24 h. The excretion of urinary aMT6s did not show significant changes during or after magnetic field exposure.

Simultaneous response of brain electrical activity (EEG) and cerebral circulation (REG) to microwave exposure in rats

The correlations between physiological modalities in microwave field-activated systemic or localized regulatory mechanisms with changes in the central nervous system (CNS) seem not to be identical. These problems are important because of the increased number of radiating appliances, e.g. portable radios and mobile telephones. In two series of experiments on anaesthetized rats (N = 40) (i) before and after 10 min, whole body exposures to 2.45 GHz CW microwaves, and (ii) during 30 min exposures to 4 GHz amplitude modulated (AM, 16 Hz) microwaves, the effects on the CNS were observed simultaneously with those on the cardiovascular system by quantitative polygraphic measurement. In acute experiments on rats, electroencephalograms (EEG), rheoencephalograms (REG) as an index of cerebral blood flow (CBF), brain tissue DC impedance and temperature and ECG were recorded simultaneously. The total power of EEG spectra increased after whole body 30 mW/cm2 2.45 GHz CW exposure for 10 min. No changes occurred at 10 mW/cm2. The CBF increased after 10 mW/cm2 exposure. The power of EEG delta (0.5-4 Hz) waves was increased by thermal level of brain localized 4 GHz CW exposure at 42 mW/g specific absorption rate (SAR) simultaneously with the REG amplitude as an index of cerebral blood flow. Amplitude modulation at 16 Hz and 8.4 mW/g SAR was associated with increased power of EEG beta (14.5-30 Hz) waves but changes in the CBF were not observed. CW radiation at 8.4 mW/g increased the cerebral blood flow, but did not change EEG spectra.

Solid-state 31P CP/MAS NMR vs. solution study of bis(tertiary phosphines)

Solid-state 31C CP/MAS results of several diphosphines are compared with solution phase data. Non-equivalence of the P atoms are observed in the solid state for the less flexible derivatives (including all chiral diphosphines studied), whereas the more flexible compounds with a linear alkyl chain such as the 1,2-ethane and the 1,4-butane derivatives give only rise to a single resonance. For the more strained bis(diphenylphosphino)methane contradictory data have been reported. Our experiments confirm the existence of an AB spin system, i.e., two different P atoms in solid state. Substantial chemical shift difference between P atoms have been observed in the solid state but not in solution of the chiral compounds. A possible explanation is suggested in terms of the concerted anisotropic effect of the phenyl rings attached to the phosphorus atom.

Ocular hypothermia: anterior chamber perfusion

The anterior chambers of 27 rabbit eyes were perfused at constant pressure with room temperature (25 degrees C) or cooled (11 degrees C) balanced salt solution at constant flow rates of 4.8 ml/min or 8.5 ml/min. Intraocular temperature changes in the anterior chamber, anterior vitreous, mid vitreous, and posterior vitreous and on the retina surface were monitored with an intraocular thermocouple probe. Perfusion of the anterior chamber of the pigmented rabbit eye with cooled fluid significantly reduced the temperature of the anterior chamber and anterior vitreous and even that of the retina. Both an increase in the rate of perfusion and a lowering of the perfusion temperature enhanced the cooling effect. The observed decrease in temperatures returned to approximately normal 4 minutes following the cessation of perfusion.