Age and sex influence the response in lipid metabolism of dehydrated Wistar rats.

Aging is associated a decrease in thirst sensation, which makes old people more susceptible to dehydration. Dehydration produces energy metabolism alterations. Our objective was to determinate the effect of water deprivation (WD) in the lipid metabolism of old male and female rats. Here we show that in the state of WD, aging and sex alters retroperitoneal white adipose tissue (R-WAT) weight of rats, WD old female rats had more lipolysis products than old male rats, a sexual dimorphism in the hormonal response related with metabolism of the adipose tissue of old rats during WD, the expression of P-para mRNA in R-WAT did not present any alteration in animals submitted to WD, the expression of Aqp7 mRNA in R-WAT is altered by WD, age, and sex. Also, WD stimulated an increase in the plasma concentration of oxytocin and the expression of mRNA of the oxytocin receptors in R-WAT.

Effects of Supplements with Different Protein Contents on Nutritional Performance of Grazing Cattle During the Rainy Season.

The objective of this study was to evaluate the effects of supplements with different crude protein (CP) contents on grazing cattle intake, digestibility, ruminal fermentation pattern, and nitrogen (N) metabolism characteristics during the rainy season. Five ruminal and abomasal cannulated Holstein×Zebu steers (296 kg body weight, BW) were used in a 5×5 Latin square design. The animals grazed five signal grass paddocks (0.34 ha). The five treatments evaluated were: Control (no supplement) and 1.0 g of supplement/kg BW with 0, 330, 660, and 1,000 g of CP/kg as-fed. The supplement was composed of starch, soybean meal, urea, and ammonium sulphate. There was a positive linear effect (p≤0.033) of the CP content in the supplements on the organic matter (OM), CP, and digested OM intakes. The provision of supplements did not increase (p≥0.158), on average, total and ruminal digestibilities of OM and CP. However, the increase in CP content in the supplements caused a positive linear effect (p≤0.018) on ruminal digestibilities of OM and CP. Additionally, a quadratic effect of the CP contents of the supplements were observed (p = 0.041) for the ruminal digestibility of neutral detergent fiber corrected for ash and protein, with the highest estimate obtained with the CP content of 670 g/kg. The supply of supplements increased (p<0.001) the ruminal ammonia N concentration, which also changed linearly and positively (p<0.001) according to increase in CP content in the supplements. The apparent N balance and relative N balance (g/g N intake) were not, on average, changed (p≥0.164) by the supplements supply. However, both showed a tendency of a linear increase (p≤0.099) with increasing supplement CP content. The supplements increased (p = 0.007) microbial N production in the rumen, which also changed linearly and positively (p = 0.016) with increasing supplement CP content. In conclusion, protein supplementation in grazing cattle during the rainy season, while stimulating voluntary forage intake, results in higher efficiency of N utilization when compared to energy supplementation. This is a possible response to increased microbial protein synthesis in the rumen and improved N status in the animal body.

Carbon monoxide and nitric oxide interactions in magnocellular neurosecretory neurones during water deprivation.

Nitric oxide (NO) and carbon monoxide (CO) are diffusible gas messengers in the brain. Previously, we have shown their independent involvement in central fluid/electrolyte homeostasis control. In the present study, we investigated a possible functional interaction between NO/CO in the regulation of vasopressin (VP) and oxytocin (OT) magnocellular neurosecretory cells (MNCs) activity in euhydrated (EU) and dehydrated [48-h water-deprived (48WD)] rats. Using brain slices from EU and 48WD rats, we measured, by immunohistochemistry, the expression of neuronal NO synthase (nNOS, which synthesises NO) and haeme-oxygenase (HO-1, which synthesises CO) in the hypothalamic supraoptic nucleus (SON). In addition, we used patch-clamp electrophysiology to investigate whether regulation of SON MNC firing activity by endogenous CO was dependent on NO bioavailability and GABAergic inhibitory synaptic function. We found a proportion of OT and VP SON MNCs in EU rats to co-express both of HO-1 and nNOS (33.2 ± 2.9% and 15.3 ± 1.4%, respectively), which was increased in 48WD rats (55.5 ± 0.9% and 21.0 ± 1.7%, respectively, P < 0.05 for both). Inhibition of endogenous HO activity [chromium mesoporphyrin IX chloride (CrMP) 20 µm] induced MNC membrane hyperpolarisation and decreased firing activity, and these effects were blunted by previous blockade of endogenous NOS activity (l-NAME, 2 mm) or blockade of inhibitory GABA function [Picrotoxin (Sigma-Aldrich, St Louis, MO, USA), 50 µm]. No significant changes in SON NO bioavailability (4,5 diaminofluorescein diacetate fluorescence) were observed after CrMP treatment. Taken together, our results support a state-dependent functional inter-relationship between NO and CO in MNCs, in which CO acts as an excitatory gas molecule, whose effects are largely dependent on interactions with the inhibitory SON signals NO and GABA.

Mapping and signaling of neural pathways involved in the regulation of hydromineral homeostasis.

Several forebrain and brainstem neurochemical circuitries interact with peripheral neural and humoral signals to collaboratively maintain both the volume and osmolality of extracellular fluids. Although much progress has been made over the past decades in the understanding of complex mechanisms underlying neuroendocrine control of hydromineral homeostasis, several issues still remain to be clarified. The use of techniques such as molecular biology, neuronal tracing, electrophysiology, immunohistochemistry, and microinfusions has significantly improved our ability to identify neuronal phenotypes and their signals, including those related to neuron-glia interactions. Accordingly, neurons have been shown to produce and release a large number of chemical mediators (neurotransmitters, neurohormones and neuromodulators) into the interstitial space, which include not only classic neurotransmitters, such as acetylcholine, amines (noradrenaline, serotonin) and amino acids (glutamate, GABA), but also gaseous (nitric oxide, carbon monoxide and hydrogen sulfide) and lipid-derived (endocannabinoids) mediators. This efferent response, initiated within the neuronal environment, recruits several peripheral effectors, such as hormones (glucocorticoids, angiotensin II, estrogen), which in turn modulate central nervous system responsiveness to systemic challenges. Therefore, in this review, we shall evaluate in an integrated manner the physiological control of body fluid homeostasis from the molecular aspects to the systemic and integrated responses.

Mapping and signaling of neural pathways involved in the regulation of hydromineral homeostasis

Several forebrain and brainstem neurochemical circuitries interact with peripheral neural and humoral signals to collaboratively maintain both the volume and osmolality of extracellular fluids. Although much progress has been made over the past decades in the understanding of complex mechanisms underlying neuroendocrine control of hydromineral homeostasis, several issues still remain to be clarified. The use of techniques such as molecular biology, neuronal tracing, electrophysiology, immunohistochemistry, and microinfusions has significantly improved our ability to identify neuronal phenotypes and their signals, including those related to neuron-glia interactions. Accordingly, neurons have been shown to produce and release a large number of chemical mediators (neurotransmitters, neurohormones and neuromodulators) into the interstitial space, which include not only classic neurotransmitters, such as acetylcholine, amines (noradrenaline, serotonin) and amino acids (glutamate, GABA), but also gaseous (nitric oxide, carbon monoxide and hydrogen sulfide) and lipid-derived (endocannabinoids) mediators. This efferent response, initiated within the neuronal environment, recruits several peripheral effectors, such as hormones (glucocorticoids, angiotensin II, estrogen), which in turn modulate central nervous system responsiveness to systemic challenges. Therefore, in this review, we shall evaluate in an integrated manner the physiological control of body fluid homeostasis from the molecular aspects to the systemic and integrated responses.

Enhanced expression of heme oxygenase-1 and carbon monoxide excitatory effects in oxytocin and vasopressin neurones during water deprivation.

A growing body of evidence indiates that carbon monoxide (CO) acts as a gas neurotransmitter within the central nervous system. Although CO has been shown to affect neurohypophyseal hormone release in response to osmotic stimuli, the precise sources, targets and mechanisms underlying the actions of CO within the magnocellular neurosecretory system remain largely unknown. In the present study, we combined immunohistochemistry and patch-clamp electrophysiology to study the cellular distribution of the CO-synthase enzyme heme oxygenase type 1 (HO-1), as well as the actions of CO on oxytocin (OT) and vasopressin (VP) magnocellular neurosecretory cells (MNCs), in euhydrated (EU) and 48-h water-deprived rats (48WD). Our results show the expression of HO-1 immunoreactivity both in OT and VP neurones, as well as in a small proportion of astrocytes, both in supraoptic (SON) and paraventricular (PVN) nuclei. HO-1 expression, and its colocalisation with OT and VP neurones within the SON and PVN, was significantly enhanced in 48WD rats. Inhibition of HO activity with chromium mesoporphyrin IX chloride (CrMP; 20 µm) resulted in a slight membrane hyperpolarisation in SON neurones from EU rats, without significantly affecting their firing activity. In 48WD rats, on the other hand, CrMP resulted in a more robust membrane hyperpolarisation, significantly decreasing neuronal firing discharge. Taken together, our results indicate that magnocellular SON and PVN neurones express HO-1, and that CO acts as an excitatory gas neurotransmitter in this system. Moreover, we found that the expression and actions of CO were enhanced in water-deprived rats, suggesting that the state-dependent up-regulation of the HO-1/CO signalling pathway contributes to enhance MNCs firing activity during an osmotic challenge.

Glucocorticoid modulation of atrial natriuretic peptide, oxytocin, vasopressin and Fos expression in response to osmotic, angiotensinergic and cholinergic stimulation.

The regulation of fluid and electrolyte homeostasis involves the participation of several neuropeptides and hormones that utilize hypothalamic cholinergic, alpha-adrenergic and angiotensinergic neurotransmitters and pathways. Additionally, it has been suggested that hypothalamus-pituitary-adrenal axis activity modulates hormonal responses to blood volume expansion. In the present study, we evaluated the effect of dexamethasone on atrial natriuretic peptide (ANP), oxytocin (OT) and vasopressin (AVP) responses to i.c.v. microinjections of 0.15 M and 0.30 M NaCl, angiotensin-II (ANG-II) and carbachol. We also evaluated the Fos protein immunoreactivity in the median preoptic (MnPO), paraventricular (PVN) and supraoptic (SON) nuclei. Male Wistar rats received an i.p. injection of dexamethasone (1 mg/kg) or vehicle (0.15 M NaCl) 2 h before the i.c.v. microinjections. Blood samples for plasma ANP, OT, AVP and corticosterone determinations were collected at 5 and 20 min after stimulus. Another set of rats was perfused 120 min after stimulation. A significant increase in plasma ANP, OT, AVP and corticosterone levels was observed at 5 and 20 min after each central stimulation compared with isotonic saline-injected group. Pre-treatment with dexamethasone decreased plasma corticosterone and OT levels, with no changes in the AVP secretion. On the other hand, dexamethasone induced a significant increase in plasma ANP levels. A significant increase in the number of Fos immunoreactive neurons was observed in the MnPO, PVN and SON after i.c.v. stimulations. Pre-treatment with dexamethasone induced a significant decrease in Fos immunoreactivity in these nuclei compared with the vehicle. These results indicate that central osmotic, cholinergic, and angiotensinergic stimuli activate MnPO, PVN and SON, with a subsequent OT, AVP, and ANP release. The present data also suggest that these responses are modulated by glucocorticoids.

Nitrergic modulation of vasopressin, oxytocin and atrial natriuretic peptide secretion in response to sodium intake and hypertonic blood volume expansion.

The central nervous system plays an important role in the control of renal sodium excretion. We present here a brief review of physiologic regulation of hydromineral balance and discuss recent results from our laboratory that focus on the participation of nitrergic, vasopressinergic, and oxytocinergic systems in the regulation of water and sodium excretion under different salt intake and hypertonic blood volume expansion (BVE) conditions. High sodium intake induced a significant increase in nitric oxide synthase (NOS) activity in the medial basal hypothalamus and neural lobe, while a low sodium diet decreased NOS activity in the neural lobe, suggesting that central NOS is involved in the control of sodium balance. An increase in plasma concentrations in vasopressin (AVP), oxytocin (OT), atrial natriuretic peptide (ANP), and nitrate after hypertonic BVE was also demonstrated. The central inhibition of NOS by L-NAME caused a decrease in plasma AVP and no change in plasma OT or ANP levels after BVE. These data indicate that the increase in AVP release after hypertonic BVE depends on nitric oxide production. In contrast, the pattern of OT secretion was similar to that of ANP secretion, supporting the view that OT is a neuromodulator of ANP secretion during hypertonic BVE. Thus, neurohypophyseal hormones and ANP are secreted under hypertonic BVE in order to correct the changes induced in blood volume and osmolality, and the secretion of AVP in this particular situation depends on NOS activity.

Nitrergic modulation of vasopressin, oxytocin and atrial natriuretic peptide secretion in response to sodium intake and hypertonic blood volume expansion

The central nervous system plays an important role in the control of renal sodium excretion. We present here a brief review of physiologic regulation of hydromineral balance and discuss recent results from our laboratory that focus on the participation of nitrergic, vasopressinergic, and oxytocinergic systems in the regulation of water and sodium excretion under different salt intake and hypertonic blood volume expansion (BVE) conditions. High sodium intake induced a significant increase in nitric oxide synthase (NOS) activity in the medial basal hypothalamus and neural lobe, while a low sodium diet decreased NOS activity in the neural lobe, suggesting that central NOS is involved in the control of sodium balance. An increase in plasma concentrations in vasopressin (AVP), oxytocin (OT), atrial natriuretic peptide (ANP), and nitrate after hypertonic BVE was also demonstrated. The central inhibition of NOS by L-NAME caused a decrease in plasma AVP and no change in plasma OT or ANP levels after BVE. These data indicate that the increase in AVP release after hypertonic BVE depends on nitric oxide production. In contrast, the pattern of OT secretion was similar to that of ANP secretion, supporting the view that OT is a neuromodulator of ANP secretion during hypertonic BVE. Thus, neurohypophyseal hormones and ANP are secreted under hypertonic BVE in order to correct the changes induced in blood volume and osmolality, and the secretion of AVP in this particular situation depends on NOS activity

Intramedullary nailing versus plate fixation for unstable forearm fractures in children.

The purpose of this study was to compare the clinical and radiographic results of plate and screw fixation with intramedullary nailing for unstable fractures of the radius and ulna in children. We proposed that there was a statistically significant difference in the functional outcome and rate of complications between the two groups of patients. A retrospective analysis of 23 patients who were treated with plate-and-screw fixation and 18 who were treated with intramedullary nailing was performed. The average age was 10 years (range, 5-15). Indications for operative treatment included open fractures, irreducible fractures, and unstable fractures. Excellent results were obtained in 78% of patients in both groups at an average of 12 months after surgery. The functional results, rate of union, and rate of complications were statistically similar for the two groups. Intramedullary fixation allows short operative time, excellent cosmesis, minimal soft-tissue dissection, ease of hardware removal, and early motion after nail removal. Intramedullary fixation may provide a useful alternative for treatment of unstable fractures of the radius and ulna.