Development of a green and low-cost method to determine mercury content in sediments affected by oil spill on the Brazilian coast.

Tons of crude oil were found on the Brazilian coast in 2019, and studies assessing its chemical composition are still scarce. This study aimed to develop a new and simple technique of cold vapor generation using infrared irradiation coupled with atomic absorption spectrometry to determine mercury content in sediments contaminated by crude oil. Experimental conditions were evaluated, including formic acid concentration, reactor temperature, and carrier gas flow rate. The accuracy of the method was validated by comparison with mercury contents in a certified reference material (PACS-2). The detection limit was found to be 0.44 µg kg-1. The developed method was applied to determine the total mercury content in marine sediment samples collected from beaches in Ceará State. Mercury concentrations ranged from 0.41 to 0.95 mg kg-1. The proposed method is efficient, simple, low-cost, and adequate for its purpose.

Effects of the insecticide imidacloprid on the post-embryonic development of the honey bee Apis mellifera (Hymenoptera: Apidae).

The widespread use of pesticides in agriculture has been linked to declines in bee populations worldwide. Imidacloprid is a widely used systemic insecticide that can be found in the pollen and nectar of plants and has the potential to negatively impact the development of bee larvae. We investigated the effects of oral exposure to a realistic field concentration (20.5 ng g-1) of imidacloprid on the midgut and fat body of Apis mellifera worker larvae. Our results showed that larvae exposed to imidacloprid exhibited changes in the midgut epithelium, including disorganization of the brush border, nuclear chromatin condensation, cytoplasm vacuolization, and release of cell fragments indication cell death. Additionally, histochemical analysis revealed that the midgut brush border glycocalyx was disorganized in exposed larvae. The fat body cells of imidacloprid-exposed larvae had a decrease in the size of lipid droplets from 50 to 8 µm and increase of 100 % of protein content, suggesting possible responses to the stress caused by the insecticide. However, the expression of de cdc20 gene, which plays a role in cell proliferation, was not affected in the midgut and fat body of treated larvae. These results suggest that imidacloprid negatively affects non-target organs during the larval development of A. mellifera potentially impacting this important pollinator species.

Insights about levels and source appointment of petroleum hydrocarbons in Brazilian semi-arid coastal: baseline status assessment for ocean decade targets.

The Ocean decade (2021-2030) for sustainable development proclaimed in 2017 by the UN, seeks to promote and conserve the sustainable use of oceans, seas, and marine resources. For this, the distribution of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and biomarkers, in sediments from the Fortaleza coastal zone (Mucuripe harbor (MH) and Inner Continental shelf (ICS)) were used to assess the impacts of anthropogenic activities in the area. The concentrations of total n-alkanes (Σ16 n-alkanes) in MH and ICS sediments varied from 35.9 to 94.9 and 17.9 to 197.3 µg g-1, respectively, while the isoprenoids phytane and pristane in MH and ICS sediments ranged from 0.1 to 1.69 ug g-1 and from 0.14 and 1.20 µg g-1, respectively. Most of the sediment samples presented carbon preference index (CPI) values close to unity, indicating that the area is submitted to petroleum-related sources. The concentrations of Σ16 PAHs in MH and ICS sediments varied from 87.0 to 562.0 and 98 to 288.0 ng g-1. This work presents the first investigation of the petroleum biomarkers hopanes and steranes in the Fortaleza coastal zone, in which ΣBiomarkers varied from 0.10 to 1.79 and 0.02 to 0.24 ug g-1 in MH and ICS sediments, respectively. The presence at stations of biomarkers also indicates petrogenic input. The diagnosis of the distribution of pollutants in the investigated zones of the Fortaleza coast suggests contamination from urban areas and oil spills and vessel traffic.

Water vulnerability to pesticide contamination in a Brazilian semiarid watershed.

This study aimed to prepare an inventory of the main active ingredients of pesticides and estimate the risk of pollution of groundwater and surface water resources in a Brazilian semiarid basin. The inventory was prepared using data from government agency databases. The contamination risk estimate was obtained using the GOSS index, Groundwater Ubiquity Score (GUS), Groundwater Screening Index (GSI), Leachability Index (LIX), US Environmental Protection Agency (USEPA) criteria, Leaching Index (LEACH), and Relative Leaching Potential Index (RLPI). The inventory identified 57 active ingredients commercialized under a well-defined chemical class. Most of these (51.5%) belong to the very dangerous class, while 43.6% belong to the moderately toxic class. The GOSS model showed that 23.7% of the active ingredients have a low potential, 50.85% have a moderate potential, and 13.56% have a high potential for surface water contamination, with its transport being associated with the sediment. The GUS index indicates a low potential for groundwater contamination. However, the GSI points to a high potential for water contamination, the USEPA criteria for a possible contamination of groundwater, and, according to the LIX, most of the pollutants do so by leaching. The information provided contributes to the management of xenobiotic compounds in arid and semiarid basins, adding to the water security effort by providing tools for the assessment of potential pesticide pollution. Integr Environ Assess Manag 2023;19:804-816. © 2022 SETAC.

Zinc-dithiocarbimates for the control of Hemileia vastatrix: a versatile alternative.

BACKGROUND: The purpose of this work was to investigate the potential use of zinc-dithiocarbimate salts to control Hemileia vastatrix, the causal agent of the coffee leaf rust disease, and to evaluate their toxicity towards Apis mellifera, one of the most important coffee plant pollinators. RESULTS: Zinc-dithiocarbimate salts were prepared and fully characterized by infrared, proton (1 H) and carbon-13 (13 C) nuclear magnetic resonance and elemental analyses of carbon (C), hydrogen (H), nitrogen (N) and zinc (Zn). X-ray diffraction technique studies confirmed the proposed structures. The salts inhibited the germination of H. vastatrix spores in vitro, with a 50% inhibitory concentration (IC50 ) from 12 to 18 µmol.L-1 and a 90% inhibitory concentration (IC90 ) from 23 to 26 µmol.L-1 . Zinc-dithiocarbimate salts with the best in vitro results were selected for in vivo experiments with Coffea arabica var Caturra and with the pollinator A. mellifera. The results were similar to those of Mancozeb, a broad-spectrum contact fungicide, with a good control of the disease and low toxicity to the honeybee. CONCLUSION: The zinc-dithiocarbimate complex salts have potential to control coffee leaf rust, with low toxicity to the pollinator insect. © 2022 Society of Chemical Industry.

Acute oral exposure to imidacloprid induces apoptosis and autophagy in the midgut of honey bee Apis mellifera workers.

The honey bee Apis mellifera is an important pollinator that increases the yield and quality of crops. In recent years, honey bee populations have declined in some parts of the world, which has been associated with several causes, including pesticides used in agriculture. Neonicotinoids are neurotoxic insecticides widely used in the world with systemic action mode contaminating nectar and pollen that may be consumed by bees. This study evaluated the side effects of imidacloprid in the midgut of A. mellifera after acute oral exposure. Toxicity, histopathology, cytotoxicity, and expression of autophagy-related gene atg1 were evaluated in honey bee workers orally exposed to imidacloprid. The estimated imidacloprid LC50 was 1.44 mg L-1. The midgut epithelium of bees fed on imidacloprid LC50 has the occurrence of cytoplasm vacuoles, enlarged intercellular spaces, disorganization of the striated border, and nuclear pyknosis, with an organ injury index that increases with time exposure. The midgut digestive cells of treated bees have apical protrusions, damaged mitochondria, and autophagosomes that were characterized for content with organelle debris and high expression of atg1. These features indicate the occurrence of high cell death in the midgut of workers exposed to imidacloprid, which may affect the digestibility the physiology of the insect.

Exposure to copper sulfate impairs survival, post-embryonic midgut development and reproduction in Aedes aegypti.

Aedes aegypti is a vector of several global human viruses responsible for high human morbidity and mortality. The method to prevent the transmission of vector-borne viruses is mainly based on the control of the insect vector using insecticides. Among these chemicals, copper sulfate is a compound widely used in agriculture with the potential to be used as an alternative to control these insects. This study evaluated the effects of the exposure of A. aegypti larvae to copper sulfate on survival, midgut morphology, blood-feeding and fecundity. The exposure to CuSO4 decreased the survival of A. aegypti during the immature phase. Adults obtained from exposed larvae had their lifespan decreased at all tested concentrations. The exposure to CuSO4 impaired the development in the transition from larvae to pupae and from pupae to adult. The number of eggs laid by females developed from larvae treated with CuSO4 was significantly lower than in control. In addition, the egg hatching rates were also negatively affected. The midguts of treated larvae and pupae showed epithelial disorganization. The number of cleaved caspase-3 cells increased in the midgut of exposed pupae compared to control. Moreover, there was a reduction in proliferating cells in treated larvae and pupae compared to the control. In conclusion, the results reveal that CuSO4 exposure has insecticidal activity against A. aegypti, which may be related to the impairment of the midgut metamorphosis and reduced proliferation of stem cells, with the consequent impairment of female mosquito fertility and fecundity.

Medullary Noradrenergic Neurons Mediate Hemodynamic Responses to Osmotic and Volume Challenges.

Despite being involved in homeostatic control and hydro-electrolyte balance, the contribution of medullary (A1 and A2) noradrenergic neurons to the hypertonic saline infusion (HSI)-induced cardiovascular response after hypotensive hemorrhage (HH) remains to be clarified. Hence, the present study sought to determine the role of noradrenergic neurons in HSI-induced hemodynamic recovery in male Wistar rats (290-320 g) with HH. Medullary catecholaminergic neurons were lesioned by nanoinjection of antidopamine-ß-hydroxylase-saporin (0.105 ng·nl-1) into A1, A2, or both (LES A1; LES A2; or LES A1+A2, respectively). Sham rats received nanoinjections of free saporin in the same regions (SHAM A1; SHAM A2; or SHAM A1+A2, respectively). After 15 days, rats were anesthetized and instrumented for cardiovascular recordings. Following 10 min of stabilization, HH was performed by withdrawing arterial blood until mean arterial pressure (MAP) reaches 60 mmHg. Subsequently, HSI was performed (NaCl 3 M; 1.8 ml·kg-1, i.v.). The HH procedure caused hypotension and bradycardia and reduced renal, aortic, and hind limb blood flows (RBF, ABF, and HBF). The HSI restored MAP, heart rate (HR), and RBF to baseline values in the SHAM, LES A1, and LES A2 groups. However, concomitant A1 and A2 lesions impaired this recovery, as demonstrated by the abolishment of MAP, RBF, and ABF responses. Although lesioning of only a group of neurons (A1 or A2) was unable to prevent HSI-induced recovery of cardiovascular parameters after hemorrhage, lesions of both A1 and A2 made this response unfeasible. These findings show that together the A1 and A2 neurons are essential to HSI-induced cardiovascular recovery in hypovolemia. By implication, simultaneous A1 and A2 dysfunctions could impair the efficacy of HSI-induced recovery during hemorrhage.

Spiromesifen induces histopathological and cytotoxic changes in the midgut of the honeybee Apis mellifera (Hymenoptera: Apidae).

The honeybee Apis mellifera is an important pollinator that, similarly to other bees, undergoes colony losses due to several problems, including the use of pesticides in the agriculture. In addition to direct mortality, pesticides cause side-effects in some non-target organs, such as the midgut, which is the main organ for digestion and absorption. Spiromesifen is a pesticide used to control mites and whiteflies, which can be ingested by bees feeding on contaminated floral resources. This study evaluated the histopathological and cytological effects of the ingestion of spiromesifen on the midgut of A. mellifera workers. The bees were exposed per os to the field recommended dose of spiromesifen, and the midgut was analyzed after 24h and 48h of exposure to the pesticide. The midgut has a single layer of digestive cells, with spherical nucleus, nests of regenerative cells and layers of peritrophic matrix in the lumen. Bees treated with spiromesifen presented histological and cytological changes in the midgut, including disorganization of the epithelial architecture, release of cell fragments to the lumen, accumulation of mitochondria in the apical cytoplasm, alteration of the basal labyrinth, changes in the rough endoplasmic reticulum and cell degeneration. The occurrence of damage in the digestive cells of the A. mellifera midgut indicates that spiromesifen does not cause mortality in honeybees, but its side-effects can damage the midgut, which may affect the longevity and behavior of this pollinator.

A peritrophin mediates the peritrophic matrix permeability in the workers of the bees Melipona quadrifasciata and Apis mellifera.

The permeability of the peritrophic matrix, essential for its function, depends on its chemical composition. The objective was to determine if the permeability of the peritrophic matrix varies along the midgut and in the presence of anti-peritrophin-55 antibody in Melipona quadrifasciata and Apis mellifera bees. The thickness of the peritrophic matrix in both species varies between the anterior and posterior midgut regions in workers. In A. mellifera dextran molecules with 40 kDa cross the peritrophic matrix, whereas those ≥70 kDa are retained in the endoperitrophic space. In M. quadrifasciata the peritrophic matrix permeability was for molecules <40 kDa. Bees fed on anti-peritrophin-55 antibody showed an increase in peritrophic matrix permeability, but survival was not affected. In the bees studied, the peritrophic matrices have morphological differences between midgut regions, but there is no difference in their permeability along the midgut, which is affected by peritrophin 55.

Forced internal desynchrony induces cardiometabolic alterations in adult rats.

Disruptions in circadian rhythms have been associated with several diseases, including cardiovascular and metabolic disorders. Forced internal desynchronization induced by a period of T-cycles of 22 h (T22 protocol) reaches the lower limit of entrainment and dissociates the circadian rhythmicity of the locomotor activity into two components, driven by different outputs from the suprachiasmatic nucleus (SCN). The main goal of this study was to evaluate the cardiovascular and metabolic response in rats submitted to internal desynchronization by T22 protocol. Male Wistar rats were assigned to either a control group subjected to a usual T-cycles of 24 h (12 h-12 h) or an experimental group subjected to the T22 protocol involving a 22-h symmetric light-dark cycle (11 h-11 h). After 8 weeks, rats subjected to the T22 exhibited desynchrony in their locomotor activity. Although plasma glucose and insulin levels were similar in both groups, desynchronized rats demonstrated dyslipidemia, significant hypertrophy of the fasciculate zone of the adrenal gland, low IRB, IRS2, PI3K, AKT, SOD and CAT protein expression and an increased expression of phosphoenolpyruvate carboxykinase in the liver. Furthermore, though they maintained normal baseline heart rates and mean arterial pressure levels, they also presented reduced baroreflex sensitivity. The findings indicate that circadian timing desynchrony following the T22 protocol can induce cardiometabolic disruptions. Early hepatic metabolism dysfunction can trigger other disorders, though additional studies are needed to clarify the causes.

Role of the Carotid Bodies in the Hypertensive and Natriuretic Responses to NaCl Load in Conscious Rats.

Hyperosmotic challenges trigger a hypertensive response and natriuresis mediated by central and peripheral sensors. Here, we evaluated the importance of the carotid bodies for the hypertensive and natriuretic responses to acute and sub-chronic NaCl load in conscious rats. Male Wistar rats (250-330 g) submitted to bilateral carotid body removal (CBX) or sham surgery were used. One day after the surgery, the changes in arterial blood pressure (n = 6-7/group) and renal sodium excretion (n = 10/group) to intravenous infusion of 3 M NaCl (1.8 mL/kg b.w. during 1 min) were evaluated in non-anesthetized rats. Another cohort of sham (n = 8) and CBX rats (n = 6) had access to 0.3 M NaCl as the only source of fluid to drink for 7 days while ingestion and renal excretion were monitored daily. The sodium balance was calculated as the difference between sodium infused/ingested and excreted. CBX reduced the hypertensive (8 ± 2 mmHg, vs. sham rats: 19 ± 2 mmHg; p < 0.05) and natriuretic responses (1.33 ± 0.13 mmol/90 min, vs. sham: 1.81 ± 0.11 mmol/90 min; p < 0.05) to acute intravenous infusion of 3 M NaCl, leading to an increase of sodium balance (0.38 ± 0.11 mmol/90 min, vs. sham: -0.06 ± 0.10 mmol/90 min; p < 0.05). In CBX rats, sub-chronic NaCl load with 0.3 M NaCl to drink for 7 days increased sodium balance (18.13 ± 4.45 mmol, vs. sham: 5.58 ± 1.71 mmol; p < 0.05) and plasma sodium concentration (164 ± 5 mmol/L, vs. sham: 140 ± 7 mmol/L; p < 0.05), without changing arterial pressure (121 ± 9 mmHg, vs. sham: 116 ± 2 mmHg). These results suggest that carotid bodies are important for the maintenance of the hypertensive response to acute hypertonic challenges and for sodium excretion to both acute and chronic NaCl load.

Clinical data and risk factors for diabetic nephropathy in Brazilian central population.

This article describes data set of the profile of patients diagnosed with Diabetic Nephropathy (DN) undergoing hemodialysis and followed-up by Hemodialysis Service in medical centers in Goiânia, Go, Brazil. These data describe specifically the demographic, clinical, and lifestyle variables of 101 patients. In addition, these data provide detailed clinical associations about the profile of patients diagnosed with DN and which are made publicly available to enable critical or extended analyzes. For further interpretation of the data presented in this article, see the research article: Do GST polymorphisms influence in the pathogenesis of diabetic nephropathy? (Lima et al., 2018).

Median preoptic nucleus mediates the cardiovascular recovery induced by hypertonic saline in hemorrhagic shock.

Changes in plasma osmolarity, through central and peripheral osmoreceptors, activate the median preoptic nucleus (MnPO) that modulates autonomic and neuroendocrine adjustments. The present study sought to determine the participation of MnPO in the cardiovascular recovery induced by hypertonic saline infusion (HSI) in rats submitted to hemorrhagic shock. The recordings of mean arterial pressure (MAP) and renal vascular conductance (RVC) were carried out on male Wistar rats (250-300 g). Hemorrhagic shock was induced by blood withdrawal over 20 min until the MAP values of approximately 60 mmHg were attained. The nanoinjection (100 nL) of GABAA agonist (Muscimol 4 mM; experimental group (EXP)) or isotonic saline (NaCl 150 mM; control (CONT)) into MnPO was performed 2 min prior to intravenous overload of sodium through HSI (3 M NaCl, 1.8 mL/kg, b.wt.). Hemorrhagic shock reduced the MAP in control (62 ± 1.1 mmHg) and EXP (61 ± 0.4 mmHg) equipotently. The inhibition of MnPO impaired MAP (CONT: 104 ± 4.2 versus EXP: 60 ± 6.2 mmHg) and RVC (CONT: 6.4 ± 11.4 versus EXP: -53.5 ± 10.0) recovery 10 min after HSI. The overall results in this study demonstrated, for the first time, that the MnPO plays an essential role in the HSI induced resuscitation during hypovolemic hemorrhagic shock.

Increased expression of angiotensin II type 2 receptors in the solitary-vagal complex blunts renovascular hypertension.

Angiotensin II increases and decreases arterial pressure by acting at angiotensin type 1 and type 2 receptors, respectively. Renovascular hypertensive rats exhibit a high level of activity of the peripheral and central renin-angiotensin system. Therefore, in the present study, we evaluated the effect of increasing the expression of angiotensin type 2 receptors in the solitary-vagal complex (nucleus of the solitary tract/dorsal motor nucleus of the vagus), a key brain stem region for cardiovascular regulation, on the development of renovascular hypertension. Holtzman normotensive rats were implanted with a silver clip around the left renal artery to induce 2-kidney 1-clip renovascular hypertension. Three weeks later, rats were microinjected in the solitary-vagal complex with either an adenoassociated virus to increase the expression of angiotensin type 2 receptors or with a control vector. We observed that increasing angiotensin type 2 receptor expression in the solitary-vagal complex attenuated the development of renovascular hypertension and also reversed the impairment of the baroreflex and the increase in the low-frequency component of systolic blood pressure observed in renovascular hypertensive rats. Furthermore, an observed decrease in mRNA levels of angiotensin-converting enzyme 2 in the solitary-vagal complex of renovascular hypertensive rats was restored to control levels after viral-mediated increases in angiotensin type 2 receptors at this site. Collectively, these data demonstrate specific and beneficial effects of angiotensin type 2 receptors via the brain of hypertensive rats and suggest that central angiotensin type 2 receptors may be a potential target for therapeutics in renovascular hypertension.

Involvement of the median preoptic nucleus in blood pressure control.

Studies have demonstrated that median preoptic nucleus (MnPO) neurons play a role in organizing the cardiovascular responses induced by changes in the circulating blood volume. The present study examined whether the MnPO controls cardiovascular function. Male Wistar normotensive (NT) rats and spontaneously hypertensive rats (SHRs; 250-300 g) were anesthetized with urethane (1.2 g kg(-1), i.v.) and instrumented for recordings of mean arterial blood pressure (MAP) and renal blood flow (RBF). The renal vascular conductance (RVC) was calculated as the RBF:MAP ratio and was expressed as a percentage of the baseline value. In the NT rats (n=6), MnPO inhibition produced a MAP reduction (-8.1±1.1 mmHg, p<0.05). In the SHRs (n=6), the MAP response to MnPO inhibition was significantly greater (-22.3±4 mmHg, p<0.05) than in the NT rats. Furthermore, the increase in the RVC was higher in the SHRs (10.9±3.3%, p<0.05). Histological analyses confirmed that the injection sites were confined to the MnPO. We conclude that the MnPO is involved in the tonic regulation of blood pressure in NT rats. Moreover, the greater cardiovascular response to MnPO inhibition observed in the SHRs strongly suggests that the MnPO may contribute to the pathophysiology of essential hypertension.

A1 noradrenergic neurons lesions reduce natriuresis and hypertensive responses to hypernatremia in rats.

Noradrenergic neurons in the caudal ventrolateral medulla (CVLM; A1 group) contribute to cardiovascular regulation. The present study assessed whether specific lesions in the A1 group altered the cardiovascular responses that were evoked by hypertonic saline (HS) infusion in non-anesthetized rats. Male Wistar rats (280-340 g) received nanoinjections of antidopamine-ß-hydroxylase-saporin (A1 lesion, 0.105 ng.nL(-1)) or free saporin (sham, 0.021 ng.nL(-1)) into their CVLMs. Two weeks later, the rats were anesthetized (2% halothane in O2) and their femoral artery and vein were catheterized and led to exit subcutaneously between the scapulae. On the following day, the animals were submitted to HS infusion (3 M NaCl, 1.8 ml • kg(-1), b.wt., for longer than 1 min). In the sham-group (n = 8), HS induced a sustained pressor response (ΔMAP: 35±3.6 and 11±1.8 mmHg, for 10 and 90 min after HS infusion, respectively; P<0.05 vs. baseline). Ten min after HS infusion, the pressor responses of the anti-DßH-saporin-treated rats (n = 11)were significantly smaller(ΔMAP: 18±1.4 mmHg; P<0.05 vs. baseline and vs. sham group), and at 90 min, their blood pressures reached baseline values (2±1.6 mmHg). Compared to the sham group, the natriuresis that was induced by HS was reduced in the lesioned group 60 min after the challenge (196±5.5 mM vs. 262±7.6 mM, respectively; P<0.05). In addition, A1-lesioned rats excreted only 47% of their sodium 90 min after HS infusion, while sham animals excreted 80% of their sodium. Immunohistochemical analysis confirmed a substantial destruction of the A1 cell group in the CVLM of rats that had been nanoinjected withanti-DßH-saporin. These results suggest that medullary noradrenergic A1 neurons are involved in the excitatory neural pathway that regulates hypertensive and natriuretic responses to acute changes in the composition of body fluid.

Macrophage migration inhibitory factor in the nucleus of solitary tract decreases blood pressure in SHRs.

AIMS: The macrophage migration inhibitory factor (MIF) is an intracellular inhibitor of the central nervous system actions of angiotensin II on blood pressure. Considering that angiotensin II actions at the nucleus of the solitary tract are important for the maintenance of hypertension in spontaneously hypertensive rats (SHRs), we tested if increased MIF expression in the nucleus of the solitary tract of SHR alters the baseline high blood pressure in these rats. METHODS AND RESULTS: Eight-week-old SHRs or normotensive rats were microinjected with the vector AAV2-CBA-MIF into the nucleus of the solitary tract, resulting in MIF expression predominantly in neurons. Rats also underwent recordings of the mean arterial blood pressure (MAP) and heart rate (via telemetry devices implanted in the abdominal aorta), cardiac- and baroreflex function. Injections of AAV2-CBA-MIF into the nucleus of the solitary tract of SHRs produced significant decreases in the MAP, ranging from 10 to 20 mmHg, compared with age-matched SHRs that had received identical microinjections of the control vector AAV2-CBA-eGFP. This lowered MAP in SHRs was maintained through the end of the experiment at 31 days, and was associated with an improvement in baroreflex function to values observed in normotensive rats. In contrast to SHRs, similar increased MIF expression in the nucleus of the solitary tract of normotensive rats produced no changes in baseline MAP and baroreflex function. CONCLUSION: These results indicate that an increased expression of MIF within the nucleus of the solitary tract neurons of SHRs lowers blood pressure and restores baroreflex function.

A2 noradrenergic lesions prevent renal sympathoinhibition induced by hypernatremia in rats.

Renal vasodilation and sympathoinhibition are recognized responses induced by hypernatremia, but the central neural pathways underlying such responses are not yet entirely understood. Several findings suggest that A2 noradrenergic neurons, which are found in the nucleus of the solitary tract (NTS), play a role in the pathways that contribute to body fluid homeostasis and cardiovascular regulation. The purpose of this study was to determine the effects of selective lesions of A2 neurons on the renal vasodilation and sympathoinhibition induced by hypertonic saline (HS) infusion. Male Wistar rats (280-350 g) received an injection into the NTS of anti-dopamine-beta-hydroxylase-saporin (A2 lesion; 6.3 ng in 60 nl; n = 6) or free saporin (sham; 1.3 ng in 60 nl; n = 7). Two weeks later, the rats were anesthetized (urethane 1.2 g⋅kg(-1) b.wt., i.v.) and the blood pressure, renal blood flow (RBF), renal vascular conductance (RVC) and renal sympathetic nerve activity (RSNA) were recorded. In sham rats, the HS infusion (3 M NaCl, 1.8 ml⋅kg(-1) b.wt., i.v.) induced transient hypertension (peak at 10 min after HS; 9±2.7 mmHg) and increases in the RBF and RVC (141±7.9% and 140±7.9% of baseline at 60 min after HS, respectively). HS infusion also decreased the RSNA (-45±5.0% at 10 min after HS) throughout the experimental period. In the A2-lesioned rats, the HS infusion induced transient hypertension (6±1.4 mmHg at 10 min after HS), as well as increased RBF and RVC (133±5.2% and 134±6.9% of baseline at 60 min after HS, respectively). However, in these rats, the HS failed to reduce the RSNA (115±3.1% at 10 min after HS). The extent of the catecholaminergic lesions was confirmed by immunocytochemistry. These results suggest that A2 noradrenergic neurons are components of the neural pathways regulating the composition of the extracellular fluid compartment and are selectively involved in hypernatremia-induced sympathoinhibition.

Participação do grupamento catecolaminérgico A2 do núcleo do trato solitário comissural nos ajustes cardiovasculares e do equilíbrio hidroeletrolitíco induzidos por alterações da osmolaridade ou volume plasmático / Participation of A2 catecholaminergic neurons of nucleus of tract solitary on cardiovascular and hydroelectrolytic balance adjustments induced by plasmatic osmolality or volume changes

É de extrema importância para o funcionamento do organismo a manutenção da osmolaridade e volume dos líquidos corporais. O sistema nervoso central (SNC) tem um papel fundamental para esta manuntenção. O núcleo do trato solitário (NTS) é o sítio primário das aferências cardiovasculares e de osmorreceptores periféricos e se projeta à areas prosencefálicas envolvidas com a regulação cardiovascular e do equilíbrio hidroeletrolítico. Desta forma, o NTS pode fazer a ligação entre as aferências viscerais e o SNC e participar dos ajustes necessários a regulação da osmolaridade e da volemia. A maior porção dos neurônios do grupamento catelocaminérgicos A2 do bulbo está localizada na porção comissural no NTS (NTScom). Assim, os objetivos deste estudo foram: a) estudar os efeitos na pressão arterial, na ingestão de água e na excreção renal subsequentes a administração de NaCl 2 M, estímulo osmótico agudo, em ratos com lesão seletiva dos neurônios A2 do NTScom; b) estudar os efeitos na expressão da proteína c-FOS subsequente a administração de NaCl 2 M, em ratos com lesão seletiva dos neurônios A2 do NTScom, c) estudar alterações na expressão de RNAm no NTS após a administração de NaCl 2 M, d) estudar os efeitos na pressão arterial subsequentes a hemorragia hipotensiva, em ratos com lesão seletiva dos neurônios A2 do NTScom. Ratos Holtzman (280-320 g) ou ratos Sprague-Dawley (230-280 g) foram utilizados neste estudo. Para a lesão seletiva dos neurônios A2 do NTScom ou lesão fictícia (LF), os animais foram submetidos a uma craniotomia parcial e a superfície dorsal do bulbo foi exposta. A lesão seletiva dos neurônios noradredérgicos foi realizada por meio da injeção no NTScom da toxina anti-dopamina-ß-hidroxilase-saporina. Nos ratos LF foi injetado anti-IgGsaporina. Em ratos com lesão do grupamento A2 do commNTS observamos que as respostas reflexas do barorreflexo bem como as respostas pressora e bradicárdica do quimiorreflexo estavam intactas, assim como o reflexo cardiopulmonar, ativado com fenilbiguanida. Nos ratos com lesão A2 mas não nos ratos LF, a sobrecarga de NaCl 2 M ig, que promove aumento da osmolaridade sem alterar o volume plasmático, promoveu aumento da pressão arterial, que foi dependente de vasopressina, e perdurou por pelo menos 60 min. Observamos também nos ratos com lesão A2 um incremento na resposta dipsogênica, enquanto que a excreção renal foi semelhante entre os ratos com lesão A2 e ratos LF. Após a gavagem com NaCl 2 M observamos que a expressão de c-Fos na região magnocelular do núcleo paraventricular do hipotálamo (PVNm) foi significantemente maior nos ratos com lesão A2 comparados com os ratos com lesão fictícia, sendo que parte desses neurônios eram vasopressinérgicos ou ocitocinérgicos. Em ratos intactos, observamos que a gavagem de NaCl 2 M foi capaz de aumentar a expressão do RNAm no NTS para o fator inibitório da migração de macrófagos, DßH e vesícula transportadora de glutamato indicando que a gavagem hipertônica é capaz de promover alterações na expressão gênica em determinadas áreas do SNC, visando um controle da osmolaridade a longo prazo. Observamos também que ratos com lesão A2 ou LF submetidos ao protocolo de hemorragia hipotensiva, (4 retiradas de sangue consecutivas com intervalos de 10 minutos entre elas) que a hipotensão causada pela hemorragia foi semelhante em ambos os grupos. Entretanto, os animais com lesão A2 apresentaram uma melhor recuperação da hemorragia, retornando os valores de pressão arterial média (PAM) aos níveis pré-hemorragia, enquanto animais LF não recuperam os valores de PAM até o final do experimento (60 min). Observamos também que nos animais com lesão A2 a melhor recuperação da resposta hipotensiva da hemorragia é devida a mecanismos angiotensinérgicos periféricos e centrais. Nossos resultados sugerem que os neurônios do grupamento A2 do NTScom fazem parte de uma circuitaria neural inibitória que controla a pressão arterial, secreção de vasopressina e ingestão de água induzida pelo aumento da osmolaridade plasmática, bem como possuem um papel inibitório sobre as vias angiotensinérgicas ativadas pela hemorragia

The central nervous system has an important role controlling the mechanisms involved in the regulation of body fluid osmolality. The nucleus of the solitary tract (NTS) is the primary site of cardiovascular and peripheral osmoreceptors afferents and projects to prosencephalic areas involved in hydroelectrolytic balance and cardiovascular regulation. The great part of the catecholaminergic neurons of the A2 group is located in the commissural part of the NTS (NTScom). Thus, the aims of this study were: a) to verify the effects in the arterial pressure, water intake and renal excretion observed after intragastric (ig) 2 M NaCl in rats with lesion of the A2 neurons of the NTScom, b) to verify the effects in the c-Fos expression after ig 2 M NaCl in rats with lesion of the A2 neurons of the NTScom, c) to study changes in gene expression on NTS after ig 2 M NaCl, d) to study the effects in arterial pressure after hypotensive hemorrhage in rats with lesion of the A2 neurons of the NTScom.Male Holtzman rats (280-320 g) or Sprague-Dawley (250-280 g) were used. For the A2 lesion of the NTScom, a partial craniotomy of the occipital bone was performed, and the dorsal surface of the brainstem was exposed. The lesion was performed by the injection of the toxine antidopamine-ß-hydroxylase-saporin into the NTScom to destroy A2 neurons in this region. Sham lesioned rats anti-IgG-saporin was injected into the NTScom. We observed that in A2 lesioned rats, ig 2 M NaCl induced a vasopressin dependent-pressor response, for at least 60 min. The water intake induced by sodium overload was also incremented in A2 lesioned rats, however the natriuresis and dieresis after 2 M NaCl were similar in both groups. After 2 M NaCl, we observed that the number of the c-FOS expressing cells in the magnocelular paraventricular nucleus (mPVN) was greater in the NTScom lesioned rats, and part of these neurons was either vasopressinergic or oxytocinergic. In intact animals, the intragastric 2 M NaCl load promoted an increase in the RNAm expression levels for macrophage inhibitory factor, DßH and vesicular glutamate transporter that indicate a possible chronic mechanism to control changes in osmolality. We observed that hemorrhage (4 consecutive blood withdraw) promoted a similar hypotension in both groups, but A2-lesioned rats showed a greater recovery in blood pressure levels than sham rats. Sham animals did not recover from hypotension until the end of the recording (60 min). The greater recovery of the hypotensin in A2 lesioned rats were due to an increase in central and peripheral angiotensinergic mechanism, and not vasopressin mechanisms. The present data suggest that the A2 neurons of the NTScom are part of an inhibitory neural circuitry controlling arterial pressure, vasopressin secretion and water intake induced by increasing plasma osmolality. In addition, A2 noradrenergic neurons of the NTScom have an inhibitory role upon angiotensinergic pathways activated by hemorrhage