Phase transition in poly(vinylidene fluoride) investigated with micro-Raman spectroscopy

The phase transition from the non-polar a-phase to the polar beta-phase of poly(vinylidene fluoride) (PVDF) has been investigated using micro-Raman spectroscopy, which is advantageous because it is a nondestructive technique. Films of alpha-PVDF were subjected to stretching under controlled rates at 80 degrees C, while the transition to P-PVDF was monitored by the decrease in the Raman band at 794 cm(-1) characteristic of the a-phase, along with the concomitant increase in the 839 cm-1 band characteristic of the P-phase. The alpha ->beta transition in our PVDF samples could be achieved even for the sample stretched to twice (2 X -stretched) the initial length and it did not depend on the stretching rate in the range between 2.0 and 7.0 mm/min. These conclusions were corroborated by differential scanning calorimetry (DSC) and X-ray diffraction experiments for PVDF samples processed under the same conditions as in the Raman scattering measurements. Poling with negative corona discharge was found to affect the a-PVDF morphology, improving the Raman bands related to this crystalline phase. This effect is minimized for films stretched to higher ratios. Significantly, corona-induced effects could not be observed with the other experimental techniques, i.e., X-ray diffraction and infrared spectroscopy.

Paraventricular nucleus administration of DuP753 or PD123319 inhibits the effects of angiotensin on water and sodium intake

We determined the effects of DuP753 and PD123319 (both nonpeptides and selective antagonists of the AT(1) and AT(2) angiotensin receptors, respectively), and [Sar(1), Ala(8)]ANG II (a non-selective peptide antagonist of angiotensin receptors) on water and 3%NaCl intake induced by administration of angiotensin II (ANG II) into the paraventricular nucleus (PVN) of sodium-depleted Holtzman rats weighing 250-300 g. Twenty hours before the experiments, the rats were depleted of sodium using furosemide (10 ng/rat, sc). The volume of drug solution injected was 0.5 mu l over a period of 10-15 sec. Water and sodium intake were measured at 0.25, 0.5, 1.0 and 2.0 h. Pre-treatment with DuP753 (14 rats) at a dose of 60 ng completely abolished the water intake induced by injection of 12 ng of ANG II (15 rats) (6.4 +/- 0.6 vs 1.4 +/- 0.3 ml/2 h), where [Sar(1), Ala(8)]ANG II (12 rats) and PD123319 (10 rats) at the doses of 60 ng partially blocked water intake (6.4 +/- 0.6 vs 2.9 +/- 0.5 and 2.7 +/- 0.2 ml/2 h, respectively). In the same animals, [Sar(1), Ala(8)]ANG II, DuP753, and PD123319 blocked the sodium intake induced by ANG II (9.2 +/- 1.6 vs 3.3 +/- 0.6, 1.8 +/- 0.3, and 1.4 +/- 0.2 ml/2 h, respectively). These results indicate that both DuP753 and PD123319, administered into the PVN, blocked the water and sodium intake induced by administration of ANG II into the same site.

Antagonism of clonidine injected intracerebroventricularly in different models of salt intake

Clonidine, an alpha 2-adrenergic agonist, injected into the brain inhibits salt intake of animals treated by the diuretic model of sodium depletion. In the present study, we address the question of whether central injection of clonidine also inhibits salt intake in animals deprived of water or in the need-free state. Saline or clonidine (30 nmol) was injected into the anterior third ventricle of 24-h sodium-depleted (furosemide + removal of ambient sodium), of 24-h water-deprived and of normovolemic (need-free state) adult male rats, Clonidine injected intracerebroventricularly (icv) inhibited the 1.5% NaCl intake for 120 min by 50 to 90% in every model tested. Therefore, different models of salt intake are inhibited by icv injection of clonidine, Idazoxan, an alpha 2-adrenergic antagonist, injected icy at a dose of 160 nmol, inhibited the effect of clonidine only in the furosemide + removal of ambient sodium model of salt intake. This indicates that the antagonism of this effect by idazoxan is dependent on the body fluid/sodium status of the animal.

Toxic effects of alcohol intake on prostate of rats

BACKGROUND. The present report was carried out to determine whether alcohol intake could induce prostate lesions.METHODS. We tested male rats for 300 days. Animals were divided into three groups: controls received only tap water as liquid diet; the chronic alcohol intake group received only ethanol solution in semivoluntary research; and the withdrawal group received the same treatment as chronic alcohol intake until 240 days, after which they reverted to drinking water.RESULTS. Chronic alcohol intake increased lipoperoxide concentrations and acid phosphatase activities. Cu-Zn superoxide dismutase (SOD) was decreased at 60 days, but approached controls values at 300 days following treatment. The serum increased alkaline phosphatase, and alanine transaminase activities reflected the chronic toxic effect of ethanol.CONCLUSIONS. Since SOD activity was unable to scavenge superoxide radical and lipoperoxide formation, we can conclude that superoxide is an important intermediate in prostate damage of chronic alcohol intake. (C) 1997 Wiley-Liss, Inc.

Effects of digitonin on hyperglycaemia and dyslipidemia induced by high-sucrose intake

This study examined whether high-sucrose intake effects on lipid profile and oral glucose tolerance may be inhibited by a single administration of digitonin, a saponin from the seeds of Digitalis purpurea Male Wistar 24 rats were initially divided into two groups (n = 12): (C) was given standard chow and water; (S) received standard chow and 30% sucrose in its drinking water. After 30 days of treatments, C rats were divided into two groups (n = 6): (CC) given an intra-gastric dose 0.5 mL saline, (CD) given a single intragastric dose of 15 mg/kg digitonin. S rats were also divided into two groups (n = 6): (SC) given intra-gastric saline and (SD) given digitonin. Rats were sacrificed after the oral glucose tolerance test (OGTT) at 2 h after the digitonin administration. S rats had higher total energy intake and final body weight than C. SC rats had fasting hyperglycaemia and impaired OGTT. Digitonin in SD group improved the glucose tolerance. Triacylglycerol (TG), very-low-density lipoprotein (VLDL-C) and free fatty acid (FFA) serum concentrations were increased in SD rats from CC. Digitonin in SD rats decreased FFA and led TG and VLDL-C concentrations at the levels observed in the CC group. Despite the enhanced cholesterol in CD group from CC., the high-density lipoprotein (HDL-C) was increased in these animals. HDL-C/TG ratio was higher in CD and SD than in CC and SC, respectively. No significant differences were observed in lipid hydroperoxide(LH) between the groups. VLDL-C/LH ratio and gamma-glutamyl transferase (GGT) activity were increased in SC group and were decreased in SD rats from the SC. In conclusion digitonin enhanced glucose tolerance and had beneficial effects on serum lipids by improve antioxidant activity. (c) 2005 Elsevier Ltd. All rights reserved.

Sedation and need-free salt intake in rats treated with clonidine

The effect of intraperitoneal injection of clonidine (9-72 mu g/kg) on need-free 1.5% NaCl intake and on performance (defined as percent of a complete trial) in the rotarod test, was studied in normovolemic adult male rats. Clonidine (18 and 36 mu g/kg) inhibited the 1.5% NaCl intake in a 2-h test at doses that did not alter the performance in the rotarod test. The dose of 36 mu g/kg did not inhibit 10% sucrose intake. Only the highest dose (72 mu g/kg) of clonidine inhibited the 1.5% NaCl intake and the performance in the rotarod test, and produced signs of sedation. Sedation was determined either by change in posture (immobility or lack of postural tonus) of the animals during the ingestive test or by their performance in the rotarod test. The results suggest that sedation is not a determinant effect on the inhibition of 1.5% NaCl intake induced by clonidine. (C) 1999 Elsevier B.V.

PROGESTERONE ADMINISTRATION TO OVARIECTOMIZED RATS REDUCES WATER AND SALT INTAKE INDUCED BY CENTRAL ADMINISTRATION OF ANGIOTENSIN-II

We tested the effects of estradiol, progesterone and testosterone on water and salt intake induced by angiotensin II (ANG II) injected into the third ventricle of female Holtzman rats weighing 250-300 g. The water and salt ingestion observed after 120 min in the control experiments (injection of 0.5 mu l of 0.15 M NaCl into the third ventricle) was 1.6 +/- 0.3 ml (N = 10) and 0.3 +/- 0.1 ml (N = 8) in intact rats, respectively, and 1.4 +/- 0.3 ml (N = 10) and 0.2 +/- 0.1 (N = 8) in ovariectomized rats, respectively. ANG II injected in intact rats (4, 6, 12, 25, and 50 ng, icv, in 0.5 mu l saline) induced an increase in water intake (4.3 +/- 0.6, 5.4 +/- 0.7. 7.8 +/- 0.8, 10.4 +/- 1.2, 11.2 +/- 1.4 ml/120 min, respectively) (N = 43). The same doses of icv ANG II in intact rats increased the 3% NaCl intake (0.9 +/- 0.2; 1.4 +/- 0.3, 2.3 +/- 0.4, 2.2 +/- 0.3. and 2.5 +/- 0.4 ml/120 min, respectively) (N = 42). When administered to ovariectomized rats ANG II induced comparable amounts of water intake (4.0 +/- 0.5, 4.8 +/- 0.6, 6.9 +/- 0.7. 9.6 +/- 0.8, and 10.9 +/- 1.2 ml/120 min, respectively) (N = 43) but there was a significant decrease of 3% NaCl solution ingestion (0.3 +/- 0.1, 0.4 +/- 0.1, 0.8 +/- 0.2, 0.7 +/- 0.2, and 0.6 +/- 0.2 ml/120 min, respectively) (N = 44). Estrogen (50 mu g), progesterone (25 ng), and testosterone (300 mu g) were injected daily into ovariectomized rats for 21 days. Treatment with estrogen decreased the water intake and abolished the saline ingestion induced by icy injection of ANG II (12 ng (2.8 +/- 1.2 and 0.3 +/- 0.1 ml/120 min, respectively) (N = 8). Treatment with progesterone also reduced the water intake (3.3 +/- 0.6 ml/120 min) (N = 8) and abolished the ANG II-induced saline ingestion (0.4 +/- 0.1 ml/120 min) (N = 8), but these effects were not observed with testosterone (6.4 +/- 0.8 and 2.2 +/- 0.3 ml/120 min, respectively) (N = 8). These results indicate that ANG II induces a greater increase in sodium intake in intact female rats than in ovariectomized rats and that estrogen and progesterone impair water and sodium intake in ovariectomized rats.

Ibotenate lesion of the medial hypothalamus alters the salt intake and pressor responses to activation of the median preoptic nucleus in rats

We investigated the influence of ibotenic acid lesions of the medial hypothalamus (MH) on salt appetite and arterial blood pressure responses induced by angiotensinergic and adrenergic stimulation of the median preoptic nucleus (MnPO) of rats. Previous injection of the adrenergic agonists norepinephrine, clonidine, phenylephrine, and isoproterenol into the MnPO of sham MH-lesioned rats caused no change in the sodium intake induced by ANG II. ANG II injected into the MnPO of MH-lesioned rats increased sodium intake compared with sham-lesioned rats. Previous injection of clonidine and isoproterenol increased, whereas phenylephrine abolished the salt intake induced by ANG II into the MnPO of MH-lesioned rats. Previous injection of norepinephrine and clonidine into the MnPO of sham MH-lesioned rats caused no change in the mean arterial pressure (MAP) induced by ANG II. Under the same conditions, previous injection of phenylephrine increased, whereas isoproterenol reversed the increase in MAP induced by angiotensin II (ANG II). ANG II injected into the MnPO of MH-lesioned rats induce a decrease in MAP compared with sham-lesioned rats. Previous injection of phenylephrine or norepinephrine into the MnPO of MH-lesioned rats induced a negative MAP, whereas pretreatment with clonidine or isoproterenol increased the MAP produced by ANG II injected into the MnPO of sham- or MH-lesioned rats. These data show that ibotenic acid lesion of the MH increases the sodium intake and presser responses induced by the concomitant angiotensinergic, alpha(2) and beta adrenergic activation of the MnPO, whereas alpha(1) activation may have opposite effects. MH involvement in excitatory and inhibitory mechanisms related to sodium intake and MAP control is suggested.

Effect of ibotenate lesions of the ventromedial hypothalamus on the water and salt intake induced by activation of the median preoptic nucleus in sodium-depleted rats

In this study we investigated the influence of a ventromedial hypothalamus (VMH) lesion with ibotenic acid on water and sodium intake and presser responses induced by combined treatment of the median preoptic nucleus (MnPO) with angiotensin Il (ANG II) and adrenergic agonists (phenylephrine, norepinephrine, isoproterenol and clonidine). Male Holtzman rats with a stainless steel cannula implanted into the MnPO and bilateral sham (vehicle) or VMH lesions with ibotenic acid were used. The ingestion of water and sodium and mean arterial pressure (MAP) were determined in separate groups submitted to sodium depletion with the diuretic furosemide (20 mg/rat). ANG II (10 pmol) injection into the MnPO of sham-lesioned rats induced water and sodium intake and presser responses. VMH-lesion reduced ANG II-induced water intake and increased saline intake, In sham rats phenylephrine (80 nmol) into MnPO increased, whereas norepinephrine (80 nmol) and clonidine (40 nmol) reduced ANG II-induced water intake while sodium intake was reduced only by clonidine into MnPO. In VMH-lesioned rats, phenylephrine reduced, noradrenaline increased and clonidine produced no effect on ANG II-induced water intake. In lesioned rats ANG II-induced sodium intake was reduced by phenylephrine and noradrenaline, whereas clonidine produced no change. ANG II-induced presser response was reduced in VMH-lesioned rats, but the presser response combining ANG II and phenylephrine or noradrenaline in VMH-lesioned rats was bigger than sham rats. These results show that the VMH is important for the changes in water and sodium intake and cardiovascular responses induced by angiotensinergic and adrenergic activation of the MnPO. (C) 1997 Elsevier B.V. B.V.

Influence of fluoride-containing solutions on the translucency of flowable composite resins

The aim of this study was to evaluate the influence of fluoride-containing solutions on the translucency of flowable composite resins, with respect the immersion time. Flow-It! (FI) and Natural Flow (NF) composite resins and three commercial brands of fluoride-containing solutions (Fluordent, Fluorgard and Oral B) were used. Specimens were prepared and stored in the solutions at 37degreesC, until the measurements were made after the following treatments: T1 - after 1 hour in relative humidity; T2 - after 1 h in solution; T3 - 24 h; T4 - 48 h; T5 - after a week; from T9, the measurements were accomplished weekly, up to 30-day immersion. To obtain translucency values an electrophoresis equipment was employed. Data were submitted to ANOVA and Tukey tests. The results disclosed that NF showed highest values of translucency and was statistically different from FI (p < 0.001). As regards the solutions, Fluordent and Oral B presented similar values and were statistically superior to Fluorgard (p < 0.05). Concerning the immersion time, similar results were observed for the different evaluation periods. It may be concluded that the fluoride-containing solutions affected the translucency of the composite resins, independently of the materials used. Among the tested resins, NF presented the best performance. (C) 2003 Kluwer Academic Publishers.

The investigation of alpha -> beta phase transition in poly(vinylidene fluoride) (PVDF)

The phase transition from the non-polar a-phase to the polar beta-phase of poly(vinylidene fluoride) (PVDF) has been investigated using micro-Raman spectroscopy, which is advantageous for being a non-destructive technique. Films of alpha-PVDF were subjected to stretching under controlled rates and at 80 degrees C, the transition to beta-PVDF being monitored by the decrease in the Raman band at 794 cm(-1) characteristic of the a-phase, with the concomitant increase in the 839 cm(-1) band characteristic of the beta-phase. Poling with negative corona discharge was found to affect the alpha-PVDF morphology improving the Raman bands related to this crystalline phase. This effect is minimized for films stretched to higher ratios. Significantly, corona-induced effects could not be observed with the other experimental techniques, viz. X-ray diffraction and infrared spectroscopy.