Differential lasting inhibitory effects of oxytocin and food-deprivation on mediobasal hypothalamic polydipsia.

This study analyzed the effects of systemic oxytocin (OT) administration and 48-h food deprivation on the polydipsia, hyperphagia, and polyuria produced by electrolytic lesions of the mediobasal hypothalamus (MBH). In a first experiment, food deprivation transiently decreased the polydipsic response, whereas food deprivation plus OT administration reduced the water intake and urine excretion of polydipsic animals but not their subsequent food intake. These results were replicated in a second experiment (20 days), which also showed that OT potentiates sodium excretion, reducing the estimated plasma sodium levels in food-deprived MBH-lesioned animals. Administration of OT on day 21 to food-deprived (from day 20 to 22) animals (second period of the experiment 2) blocked the differences in water intake and urine excretion volumes between MBH and control animals on days 21 and 22. Subsequently, this 48-h food deprivation induced an additional and lasting (days 23-40) reduction in the intake of water and food of MBH animals. According to these findings, OT administration and/or food deprivation may potentially exert enduring reducing effects on the polydipsia, polyuria, and hyperphagia of MBH syndrome.

Oxytocin polyuria and polydipsia is blocked by NaCl administration in food-deprived male rats.

We examined the effects of NaCl injections on the polydipsia and polyuria induced by subcutaneous oxytocin (OT) administration in food-deprived male rats. During the first 12 h of the treatment day, both food deprivation and OT administration increased urine excretion but reduced water intake, water balance (fluid intake minus urine volume) and body weight. OT treatment enhanced urine excretion and the reduction in water balance and body weight without reducing the water intake of food-deprived animals. Analysis of the physiological effects of OT administration showed increases in urinary sodium concentration, sodium excretion and a reduced plasma sodium concentration. During the second 12 h, OT increased both urine excretion and water intake in food-deprived but not in ad lib.-fed rats. However, hypertonic NaCl administration at the start of this second 12-h period blocked the polyuric and polydipsic responses observed in the OT/deprived group but increased the water intake of the ad lib. groups. After the whole 24-h period, animals treated with OT showed a water balance and body weight change matching those observed in Control animals. Although the recording time period is a critical factor to demonstrate the effect of peripheral OT administration on water intake, the results obtained suggest that the polyuric and polydipsic responses observed in food-deprived animals depend on the negative sodium and water balance induced by the natriuretic effect of OT and the unavailability of sodium. These OT-induced deficits can be counteracted by the administration of hypertonic NaCl solutions or simply by the intake of standard food.

Extractable atrazine and its metabolites in agricultural soils from the temperate humid zone.

Extractable atrazine and its metabolites (hydroxyatrazine, deethylatrazine and deisopropylatrazine) were evaluated in agricultural soils from the temperate humid zone (Galicia, NW Spain) under laboratory conditions. The experiment was performed with five soils with different properties (organic C, soil texture and atrazine application history), both unamended and treated with atrazine at field application rate. Measurements of the atrazine compounds were made at different time intervals (1, 3, 6, 9 and 12 weeks) during a 3-month incubation period. Results showed that only hydroxyatrazine was detected in the extractable fraction of the unamended soils, with values remaining relatively constant throughout the incubation period. Atrazine addition notably increased the concentration of the parent compound and its degradation products; deisopropylatrazine and hydroxyatrazine were the main metabolites detected in the extractable fraction of the treated soils, whereas deethylatrazine was not detected. After 7 days incubation, values of total extractable residues, expressed as percentage of initially added atrazine, ranged from 75 to 86% (25-68% of atrazine, 7-11% of hydroxyatrazine and 9-57% of deisopropylatrazine). The values decreased rapidly during the first 3 weeks of incubation, showing values of 2-8% in soils with higher atrazine application and from 28 to 30% in soils with lower application history. At the end of the incubation, 2-8% of total extractable residues were still detected (0-4% of atrazine, 2-3% of hydroxyatrazine and 0-2% of deisopropylatrazine), indicating a residual effect of atrazine addition. These variations in the extractable fraction indicated that most added atrazine was rapidly degraded, especially in soils with higher application history.

Dipsogenic potentiation by sodium chloride but not by sucrose or polyethylene glycol in tuberomammillary-mediated polydipsia.

The aim of this study was to examine the dipsogenic mechanisms involved in the recently discovered tuberomammillary (TM)-mediated polydipsia. Rats with bilateral electrolytic lesions of each TM subnucleus underwent several dipsogenic treatments, both osmotic and volemic. Animals with ventral (E2) or medial TM lesions (E3 or E4) showed a potentiated hyperdipsic response to hypertonic sodium chloride administration but not to sucrose or polyethylene glycol treatments. The increase in response to sodium chloride was significantly greater in groups E3/E4 and E2 than in the non-lesioned group and in animals with polydipsia induced by lesion of the median eminence. As previously reported, hyperphagia was induced by lesion to ventral TM nuclei (E1 or E2), confirming a possible role for the TM complex in food intake. However, lesions in medial nuclei (E3 or E4) did not produce this increase in food intake. These results are interpreted in relation to the hypothalamic systems involved in food and water intake.

Oxytocin, water intake, and food sodium availability in male rats.

This study examined the effect of subcutaneous administration of the neurohormone oxytocin on water intake of ad lib-fed (with or without sodium availability in the diet) and food-deprived animals. Results of the first experiment showed that oxytocin increased water intake and urine excretion in food-deprived but not in ad lib-fed animals. However, oxytocin treatment did not modify the reduced water "balance" (fluid intake minus urine volume) resulting from food deprivation or the daily food intake (Experiment 1). The dose-dependent polydipsic effect of oxytocin on food-deprived rats was always preceded by an increase in sodium and fluid urine excretion (Experiment 2). Oxytocin also increased the water intake of animals fed ad lib with a low sodium diet (Experiment 3). These results suggest that the effect of oxytocin on water intake is dependent on the presence or absence of sodium in the diet and that the excretion of sodium is the main mechanism of oxytocinergic polydipsia in food-deprived male rats.

Hyperphagia and increased body weight induced by lesions of the ventral tuberomammillary system.

Individual lesions of the caudal (E1) or rostral (E2) ventral tuberomammillary nuclei induced hyperphagia in Wistar rats. The aim of the present study was to examine the additive or united effects of combined lesions of E1+E2 in food intake. E1+E2 lesions produced an immediate, potent and permanent hyperphagic response that was greater than that observed in groups with individual lesions (E1 or E2) during the 22-day observation period. Furthermore, at the end of this period (Days 17/22), the combined lesions induced a greater increase in body weight compared with groups with individual lesions. As previously reported, polydipsia is also induced by lesions of the ventral tuberomammillary subnuclei. However, in this case, responses of the individual polydipsic groups did not differ from those found in the E1+E2 ventral tuberomammillary group. These results are interpreted in terms of the hypothalamic systems involved in food and water intake.

Atrazine degradation and residues distribution in two acid soils from temperate humid zone.

Mineralization of atrazine and formation of extractable and non-extractable "bound" residues were followed under laboratory conditions in two contrasting soils (organic C, texture, and atrazine application history) from northern Spain. The soils, a Humic Cambisol (MP) and a Gleyic Cambisol (G) were incubated with labeled atrazine (ring-13C atrazine) at field application dose and measurements were made at different time intervals during 3 mo. Fate and behavior of atrazine along the incubation showed different patterns between the two soils, the time taken for degradation of 50% (DT50) being 9 and 44 d for MP and G soils, respectively. In MP soil, with 40 yr of atrazine application and lower organic C and clay content, more than 89% of U-13C-atrazine added was mineralized after 12 wk, with most mineralization occurring within the first 2 wk. G soil, with 10 yr of atrazine application, exhibited a more progressive U-13C-atrazine mineralization, reaching 54% of initially added atrazine at 12 wk. Hydroxyatrazine and deisopropylatrazine were the metabolites founded in the extractable fraction, demonstrating that both chemical and biological processes are involved in atrazine degradation. Soil G showed during all the incubation times an extractable residues fraction greater than that in MP soil, indicating a high potential risk of soil and water contamination. Rapid microbial degradation through s-triazine ring cleavage was proposed to be the main decomposition pathway of atrazine for the two soils studied. Bound residues pool also differed notably between soils accounting for 9 and 41% of initially added atrazine, the higher values shown by soil with higher organic matter and clay content (G soil).

Lesions of tuberomammillary nuclei induce differential polydipsic and hyperphagic effects.

This study aimed to examine the function of the tuberomammillary complex in water and food intake of Wistar rats. The results show that lesions restricted to tuberomammillary subnuclei: caudal ventral tuberomammillary nucleus (E1), rostral ventral tuberomammillary nucleus (E2), medial ventral tuberomammillary nucleus (E3) or medial dorsal tuberomammillary nucleus (E4), induce a strong and persistent polydipsia with specific characteristics for each nucleus. Interestingly, the distribution of tuberomammillary hyperdipsia throughout the day was similar to that in non-lesioned animals, in contrast to the lack of rhythmicity observed in rats with anodic lesion to median eminence. This polydipsia appears to be independent of food intake, as food deprivation for 22 h did not significantly reduce the water intake. Finally, lesions in ventral tuberomammillary nuclei E1 and E2 induce hyperphagia, confirming a possible role for the tuberomammillary complex in food intake. This increase in food intake is not observed after lesions in medial subnuclei E3 and E4. These results are interpreted in terms of the hypothalamic systems involved in the consumption of both food and water.

Synthesis, characterization, and magnetic properties of self-assembled compounds based on discrete homotrinuclear complexes of Cu(II).

Three new supramolecular entities of Cu(II) were synthesized and characterized: [(Cu(H(2)O)(tmen))(2)(mu-Cu(H(2)O)(opba))](2)[(ClO(4))(2)](2).2H(2)O (1), [(Cu(H(2)O)(tmen))(2) (mu-Cu(H(2)O) (Me(2)pba))](2)[(ClO(4))(2)](2) (2), and [(Cu(H(2)O)(tmen))(Cu(tmen))(mu-Cu(OHpba))](n)() ((ClO(4))(2))(n)().nH(2)O (3), where opba = o-phenylenbis(oxamato), Me(2)pba = 2,2-dimethyl-1,3-propylenbis(oxamato), OHpba = 2-hydroxy-1,3-propylenbis(oxamato), and tmen = N,N,N'N'-tetramethylethylenediamine. The crystal structures of 1, 2, and 3 were solved. Complex 1 crystallizes in the monoclinic system, space group C2/c with a = 20.572(4) A, b = 17.279(6) A, c = 22.023(19) A, beta = 103.13(4) degrees, and Z = 8. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 16.7555(7) A, b = 13.5173(5) A, c = 17.1240(7) A, beta = 104.9840(10) degrees, and Z = 4. Complex 3 crystallizes in the orthorhombic system, space group Pca2(1) with a = 21.2859(4) A, b = 12.8286(10) A, c = 12.6456(2) A, and Z = 4. The three complexes are very similar in structure: a trinuclear Cu(II) complex with the two terminal Cu(II) ions blocked by N,N,N',N'-tetramethylethylenediamine, but with a different environment in the Cu(II) central ion. In the case of complex 1, two of these trinuclear entities are packed with a short distance between the central Cu(II) ions of two separate entities forming a hexanuclear-type compound. In the case of 2, two of these trinuclear entities are linked by a hydrogen bond between a water molecule of one terminal Cu(II) and one oxygen atom of the oxamato ligand of the neighboring entity, also forming a hexanuclear complex. In the case of complex 3, the intermolecular linkages give a one-dimensional system where the OH groups of the OHpba entities are linked to the terminal Cu(II) of the neighboring entities. The magnetic properties of the three complexes were studied by susceptibility measurements vs temperature. For complex 1, an intramolecular J value of -312.1 cm(-)(1) and a contact dipolar interaction of -0.44K were found. For complex 2 and 3 the fit was made by the irreducible tensor operator formalism (ITO). The values obtained were as follows: J(1) = -333.9 cm(-)(1) and J(2) = 0.67 cm(-)(1) for 2 and J(1) = -335.9 cm(-)(1) and J(2) = 3.5 cm(-)(1) for 3.

Regiocontrolled one-step synthesis of 3,3'-disubstituted 2,2'-bipyridine ligands by cobalt(I)-catalyzed cyclotrimerization.

A one-step, regioselective synthesis of annelated symmetric and asymmetric 3,3'-disubstituted 2,2'-bipyridines by cobalt(I)-catalyzed [2+2+2] cycloadditions between 5-hexynenitrile and 1,3-diynes is described. In the symmetric case, the total regioselectivity of the first cycloaddition is ensured electronically by the conjugation of the triple bonds, and for aminomethylated diynes that of the second is ensured by the cobalt coordinating to the aminomethyl rather than to the hexynenitrile nitrogen. In the asymmetric case, the first cycloaddition took place chemoselectively, which in the case of bis(trimethylsilyl)-1,3,5-hexatriyne (viewed as a 1,3-diyne) is explained by semiempirical calculation of LUMO coefficients. The copper(I) complex of 6b, constituting the first reported complex of the form ML2 (L is a symmetric 3,3'-disubstituted 2,2'-bipyridine), has been prepared. It had UV/Vis and NMR spectra reflecting the 3-substituent-induced mutual torsion of the bipyridine rings in the cis conformation, as was confirmed by x-ray diffractometric determination. The bipyridine 6c forms the dinuclear complex [Cu2(6c)2(CH3CN)2]2+ in the solid state.