The immunomodulatory effects of Ipomoea cornea in rats vary depending on life stage

Ipomoea cameo Jacq. ssp. fistulosa (Mart. Ex Choisy; Convolvulaceae; I. cameo) possesses a toxic component: an indolizidine alkaloid swainsonine (SW) that has immunomodulatory effects due to its inhibition of glycoprotein metabolism. It is also known that SW is excreted into both the amniotic fluid and milk of female rats exposed to I. cameo. Thus, the aim of this study was to determine whether SW exposure, either in utero or from the milk of dams treated with I. cornea, modulates offspring immune function into adulthood. In addition, adult (70 days old) and juvenile rats (21 days old) were exposed to I. cameo in order to evaluate several other immune parameters: lymphoid organs relative weight and cellularity, humoral and cellular immune responses. Offspring exposed to I. cornea during lactation developed rheumatoid arthritis (RA) in adulthood after an immunogenic challenge. In addition, both adult and juvenile rats exposed to I. cameo showed discrepancies in several immune parameters, but did not exhibit any decrease in humoral immune response, which was enhanced at both ages. These findings indicate that SW modulates immune function in adult rats exposed to SW during lactation and in juvenile and adult rats exposed to SW as juveniles and adults, respectively.

Effect of diode laser on enzymatic activity of parotid glands of diabetic rats

The aim of this study was to evaluate the effect of laser irradiation (LI) on enzymatic activities of amylase, catalase and peroxidase in the parotid glands (PG) of diabetic and non-diabetic rats. Ninety-six female rats were divided into eight groups: D0; D5; D10; D20 and C0; C5; C10; C20, respectively. Diabetes was induced by administration of streptozotocin and confirmed later by the glycemia results. Twenty-nine (29) days after the induction, the PGs of groups D5 and C5; D10 and C10; D20 and C20, were irradiated with 5 J/cm(2), 10 J/cm(2) and 20 J/cm(2) of laser diode (660 nm/100 mW) respectively. On the following day, the rats were euthanized and the enzymatic activity in the PGs was measured. Diabetic rats that had not been irradiated (group D0) showed higher catalase activity (P < 0.05) than those in group C0 (0.14 +/- 0.02 U/mg protein and 0.10 +/- 0.03 U/mg protein, respectively). However, laser irradiation of 5 J/cm(2) and 20 J/cm(2) decreased the catalase activity of the diabetic groups (D5 and D20) to non-diabetic values (P > 0.05). Based on the results of this study, LI decreased catalase activity in the PGs of diabetic rats.

Influence of nicotine on healing process of autogenous bone block grafts in the mandible: A histomorphometric study in rats

Purpose: The aim of this study was to perform qualitative and quantitative analyses of the effect of nicotine on autogenous bone block grafts and to describe events in the initial healing phase and the differences in the repair processes between animals exposed to nicotine and controls. Materials and Methods: Forty-eight female Wistar rats were randomly divided into 2 groups, the nicotine group and the saline group. All animals received either nicotine (3 mg/kg) or saline 4 weeks before the surgical procedure and continued to receive nicotine from surgery to sacrifice at 7, 14, or 28 days. The autogenous bone block graft was harvested from the calvaria and stabilized on the external cortical area near the angle of the mandible. Results: The histologic analyses of the nicotine group depicted a delay in osteogenic activity at the bed-graft interface, as well as impairment of the organization of the granulation tissue that developed instead of blood clot. Nicotine-group specimens exhibited less bone neoformation, and the newly formed bone was poorly cellularized and vascularized. The histometric analysis revealed significantly less bone formation in the nicotine group at both 14 days (23.75% +/- 6.18% versus 51.31% +/- 8.31%) and 28 days (42.44% +/- 8.70% versus 73.00% +/- 4.99%). Conclusion: Nicotine did jeopardize the early healing process of autogenous bone block grafts in rats but did not prevent it.

Prolactin differentially modulates the macrophage activity of lactating rats: possible role of reproductive experience

Reproductive experience (i.e., pregnancy and lactation) induces physiological changes in mammals. We recently showed that a previous reproductive experience can modulate the activity of dopaminergic hypothalamic systems while decreasing serum prolactin (PRL) levels and oxidative burst activity in peritoneal macrophages. Dopamine receptor antagonists increase serum PRL levels, and both PRL and dopamine receptors might be involved in the modulation of macrophage activity, providing a means of communication between the nervous and immune systems. The present study evaluated the in vitro effects of PRL and the dopamine receptor 02 antagonist domperidone (DOMP) on the peritoneal activity of macrophages from primiparous and multiparous female rats during lactation. Oxidative bursts and phagocytosis in peritoneal macrophages were evaluated by flow cytometry. Primiparous and multiparous Wistar rats, during the period of lactation (i.e., days 5-7 after parturition) were used. Samples of peritoneal fluid from these rats were first incubated with PRL (10 and 100 nM) for different periods of time. The same procedure was repeated to evaluate the effects of DOMP (10 and 100 nM). Our results showed that macrophages from multiparous rats respond more effectively to in vitro incubation with PRL, especially with regard to oxidative bursts and the percentage of phagocytosis. Additionally, these effects were more pronounced after 30 min of incubation. These data suggest that reproductive experience is associated with a reduction in serum PRL levels, and cells in experienced female animals, including their macrophages, become more sensitive to the effects of PRL (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Locus coeruleus mediates cold stress-induced polycystic ovary in rats

Previous reports about the rat ovary have shown that cold stress promotes ovarian morphological alterations related to a polycystic ovary (PCO) condition through activation of the ovarian sympathetic nerves. Because the noradrenergic nucleus locus coeruleus (LC) is activated by cold stress and synaptically connected to the preganglionic cell bodies of the ovarian sympathetic pathway, this study aimed to evaluate the LC`s role in cold stress-induced PCO in rats. Ovarian morphology and endocrine and sympathetic functions were evaluated after 8 wk of chronic intermittent cold stress (4 C, 3 h/d) in rats with or without LC lesion. The effect of acute and chronic cold stress upon the LC neuron activity was confirmed by Fos protein expression in tyrosine hydroxylase-immunoreactive neurons. Cold stress induced the formation of follicular cysts, type III follicles, and follicles with hyperthecosis alongside increased plasma estradiol and testosterone levels, irregular estrous cyclicity, and reduced ovulation. Considering estradiol release in vitro, cold stress potentiated the ovarian response to human chorionic gonadotropin. Ovarian norepinephrine (NE) was not altered after 8 wk of stress. However, LC lesion reduced NE activity in the ovary of cold-stressed rats, but not in controls, and prevented all the cold stress effects evaluated. Cold stress increased the number of Fos/tyrosine hydroxylase-immunoreactive neurons in the LC, but this effect was more pronounced for acute stress as compared with chronic stress. These results show that cold stress promotes PCO in rats, which apparently depends on ovarian NE activity that, under this condition, is regulated by the noradrenergic nucleus LC.

Determination of permethrin and its metabolites in hearts and urines of rats by GC-ECD and GC-MS

Pyrethroids are pesticides very used in agriculture, which tend to replace organophosfate and carbamate insecticides. These pesticides have shown to exhibit cardiotoxicity. The aim of this study was to assess if cardiotoxicity is due to direct or indirect effects (metabolites) of permethrin on hearts. There were studies 8 rats; three of them were sacrificed after 24 of the end of treatment with permethrin and the other four were sacrificed after 14 days of the end of treatment. Afterwards hearts and urines were collected. The amounts of permethrin and its main metabolite (3-PBA) were evaluated on hearts and urines of female rats which were treated with permethrin and sacrificed the day after and 14 days after the treatment. Moreover has been highlighted the difference of amount of permethrin and its metabolite between rats sacrificed immediately at the end of treatment and those sacrificed after 14 days. The study of permethrin was accomplished by liquid-liquid extraction and GC-ECD. The evaluation of 3-PBA was performed by SPE procedure with 2-PBA as internal standard and gas-chromatography GC-MS. The concentration of permethrin in hearts is basically the same in 24h and 14 days. The 3-PBA concentration in urines decreased 50 times from 24h to 14 days. In hearts the 3-PBA level also decrease but only 2.24 times and a high variation of results were achieved in rats after 14 days.

Determination of permethrin and its metabolite in brains and urines of rats by GC-ECD and GC-MS

Synthetic pyrethroids are pesticides derived from naturally occurring pyrethrins, taken from pyrethrum of dried Chrysanthemum flowers. Pyrethroid insecticides are one of the most commonly used residential and agricultural insecticides. Many pyrethroids can significantly harm the nervous system. Permethrin could be one of the factors involved in the onset of neurodegenerative diseases. The present study aims to evaluate in brain, the effect that can induce the exposure to permethrin, during early life of female rats (from 6 to 21 days of life). Therefore, have been examined the concentrations of permethrin and its main metabolite (3-PBA) in the brain and urine in female rats sacrificed the day after and 14 days after treating. The different concentrations of permethrin and 3-PBA (after 24h and after 14 days in the end of treatment) were obtained using two different methods. The evaluation of permethrin by liquid-liquid extraction and GC-ECD was performed. The levels of the 3-PBA (in urine and brains) were obtained by SPE procedure and GC-MS using the 2- PBA as internal standard.

Induction of experimental mammary carcinogenesis in rats with 7,12-dimethylbenz(a)anthracene

PURPOSE: To test an experimental model of chemical mammary carcinogenesis induction in rats. METHODS: Twenty young virgin Sprague-Dawley female rats, aged 47 days, received 20 mg of 7,12-dimethylbenz(a)anthracene (DMBA) intragastrically by gavage. Afterwards, at 8 and 13 weeks, their mammary glands were examined. At the end of the experiment, the animals were sacrificed, and the mammary tumors were measured and weighed. Tumor fragments were analyzed using light microscopy. RESULTS: Eight weeks after DMBA injection, 16 rats presented at least 1 breast tumor (80%). After 13 weeks, all of them (100%) developed breast carcinomas that were confirmed by histopathological analysis. CONCLUSION: This experimental animal model of chemical mammary induced carcinogenesis is feasible and can be used in further experiments on the role of tumorigenic biomodulator substances.

Effects of neuropeptide Y on intrarenal hemodynamics, plasma renin activity and urinary sodium excretion in rats.

Neuropeptide Y (NPY) is a vasoconstrictor peptide possibly involved in the regulation of renal sodium handling and renin release. This investigation was undertaken to assess in conscious normotensive rats the acute effects of a non-pressor dose of NPY on renal plasma flow, glomerular filtration rate, sodium excretion and plasma renin activity. Experiments were also performed during concomitant beta-adrenoceptor stimulation with isoproterenol. NPY per se had no effect on the studied parameters. Renal plasma flow was increased by isoproterenol and was significantly higher when the beta-adrenoceptor stimulant was infused alone (13.4 +/- 2.1 ml/min, p < 0.05, mean +/- SEM) that when administered together with NPY (7.2 +/- 2.0 ml/min). This was also true for glomerular filtration rate (3.3 +/- 0.3 vs. 1.8 +/- 0.3 ml/min, p < 0.01) and plasma renin activity (6.3 +/- 1.7 vs. 2.1 +/- 0.4 ng Ang I/ml/h, p < 0.05). Our data however do not allow to deduce whether the inhibitory effect of NPY on isoproterenol-induced renin release is mediated by changes in intrarenal hemodynamics or a direct effect on juxtaglomerular cells.

Detection of neuronal activity and metabolism in a model of dehydration-induced anorexia in rats at 14.1 T using manganese-enhanced MRI and 1H MRS.

In this study, hypothalamic activation was performed by dehydration-induced anorexia (DIA) and overnight food suppression (OFS) in female rats. The assessment of the hypothalamic response to these challenges by manganese-enhanced MRI showed increased neuronal activity in the paraventricular nuclei (PVN) and lateral hypothalamus (LH), both known to be areas involved in the regulation of food intake. The effects of DIA and OFS were compared by generating T-score maps. Increased neuronal activation was detected in the PVN and LH of DIA rats relative to OFS rats. In addition, the neurochemical profile of the PVN and LH were measured by (1) H MRS at 14.1T. Significant increases in metabolite levels were measured in DIA and OFS relative to control rats. Statistically significant increases in γ-aminobutyric acid were found in DIA (p=0.0007) and OFS (p<0.001) relative to control rats. Lactate increased significantly in DIA (p=0.03), but not in OFS, rats. This work shows that manganese-enhanced MRI coupled to (1) H MRS at high field is a promising noninvasive method for the investigation of the neural pathways and mechanisms involved in the control of food intake, in the autonomic and endocrine control of energy metabolism and in the regulation of body weight.

Neuropeptide Y infusion decreases plasma renin activity in postmyocardial infarction rats.

We wished to determine if chronic neuropeptide Y (NPY) infusion (1 ng/min for 1 week by Alzet minipump) could decrease plasma renin activity (PRA) and norepinephrine (NE) in a rat myocardial infarction (MI) model of moderate compensated congestive heart failure (CHF). CHF was produced by prior (6-8 weeks) ligation of the left coronary artery; control rats were sham-operated. Carotid arterial blood was drawn for PRA and NE in conscious unrestrained rats that had been instrumented 24 h earlier. MI rats had increased PRA as compared with sham-operated rats [8.73 +/- 1.27 vs. 5.10 +/- 0.91 ng angiotensin (AI) I/ml.h, mean +/- SE]. During chronic NPY infusion, PRA was reduced to normal in the MI group (4.78 +/- 0.91) but was not affected in the sham group (5.65 +/- 0.51). Plasma NE was altered similarly, but the changes did not reach statistical significance. These data suggest that NPY has the capacity to restrain renin release in moderate compensated CHF.

Endotoxin-induced hypotension in rats is not mediated by prekallikrein activation.

To test whether endotoxin decreases blood pressure acutely in rats by activating the plasma kinin-forming system, plasma kallikrein activity was determined in different experimental settings of endotoxemia. Conscious normotensive rats were infused for 45 min with endotoxin (LPS E. coli 0111:B4) at a dose (0.01 mg/min) which had no effect on blood pressure. Additional rats were infused with the vehicle of endotoxin. Plasma prekallikrein activity was measured at the end of the 45 min infusions. In other rats, a bolus intravenous injection of endotoxin (2 mg) was administered following the 45 min infusion of endotoxin or its vehicle. In these two latter groups of rats, plasma prekallikrein activity was determined 15 min after administration of the bolus dose of endotoxin. In rats pretreated with the endotoxin infusion, the bolus dose of endotoxin had no significant effect on blood pressure, whereas rats infused with the vehicle became and remained hypotensive up to the end of the experiment. There was however no significant difference in plasma prekallikrein activity within the different groups of rats. In another group of rats, dextran sulfate (0.25 mg i.v.), which activates factor XII and thereby the conversion of prekallikrein to kallikrein, induced a short-lasting fall in blood pressure. 15 min after administration of dextran sulfate, plasma prekallikrein activity was almost completely suppressed. These results obtained in unanesthetized rats strongly suggest that the blood pressure fall induced by E. coli endotoxin is not due to activation of prekallikrein and consequently of the kinin-forming system.

Markedly reduced blood pressure responsiveness in endotoxemic rats; reversal by neuropeptide Y.

This study in conscious normotensive rats was performed to assess the effect of the vasoconstrictor peptide, neuropeptide Y (NPY), on blood pressure responsiveness to exogenous norepinephrine in endotoxaemia. NPY and endotoxin were infused at doses which had no effect on blood pressure, whether given alone or in combination. Endotoxin markedly reduced the pressor responses to bolus injections of norepinephrine. However, blood pressure responsiveness could be enhanced by infusing NPY simultaneously with the endotoxin. It is suggested that low dose NPY infusions may be clinically useful in reversing the reduced vascular responsiveness to pressor amines in shock.

Beta-adrenoceptor stimulation increases neuropeptide Y release from sympathetic nerves in intact rats.

This study was undertaken to assess in conscious normotensive rats the effects of beta-adrenoceptor stimulation on plasma neuropeptide Y (NPY) levels. Wistar rats were subjected to adrenal demedullation on the right side and were either adrenalectomized or sham-operated on the left side. Eleven days later, the conscious rats were infused i.v. for 30 min with either isoproterenol (10 ng/min) or its vehicle. Plasma NPY levels were significantly lower (23.8 +/- 2.6 pM, means +/- S.E.M., n = 12, P < 0.01) in vehicle-treated medullectomized rats than in corresponding sham-operated controls (36.7 +/- 4.1 pM, n = 12). The medullectomized rats infused with isoproterenol showed plasma NPY levels (36.7 +/- 3.3 pM, n = 11) comparable to those of sham-operated rats having received the vehicle. These data therefore demonstrate that plasma NPY levels are lower in rats without adrenal medulla and that in these animals isoproterenol increases NPY release, most likely by activating pre-synaptic beta-adrenoceptors.

Corticosterone inhibits the lipid-mobilizing effects of oleoyl-estrone in adrenalectomized rats

Oleoyl-estrone (OE) is an adipose-derived signal that decreases energy intake and body lipid, maintaining energy expenditure and glycemic homeostasis. Glucocorticoids protect body lipid and the metabolic status quo. We studied the combined effects of OE and corticosterone in adrenalectomized female rats: daily OE gavages (0 or 10 nmol/g) and slow-release corticosterone pellets at four doses (0, 0.5, 1.7, and 4.8 mg/d). Intact and sham-operated controls were also included. After 8 d, body composition and plasma metabolites and hormones were measured. OE induced a massive lipid mobilization (in parallel with decreased food intake and maintained energy expenditure). Corticosterone increased fat deposition and inhibited the OE-elicited mobilization of body energy, even at the lowest dose. OE enhanced the corticosterone-induced rise in plasma triacylglycerols, and corticosterone blocked the OE-induced decrease in leptin. High corticosterone and OE increased insulin resistance beyond the effects of corticosterone alone. The presence of corticosterone dramatically affected OE effects, reversing its decrease of body energy (lipid) content, with little or no change on food intake or energy expenditure. The maintenance of glycemia and increasing insulin in parallel to the dose of corticosterone indicate a decrease in insulin sensitivity, which is enhanced by OE. The reversal of OE effects on lipid handling, insulin resistance, can be the consequence of a corticosterone-induced OE resistance. Nevertheless, OE effects on cholesterol were largely unaffected. In conclusion, corticosterone administration effectively blocked OE effects on body lipid and energy balance as well as insulin sensitivity and glycemia.