Effects of oxygen in lungs of rats

PURPOSE: To analyze microscopically the effects of different concentrations of oxygen in the lungs of rats. METHODS: There were 20 rats distributed in three experimental groups (concentration of oxygen to 40%, 70% and 100%) and a control group. The animals were exposed to the oxygen in a chamber of acrylic during three days and after exposition, the animals were submitted to median thoracotomia to remove the lungs. The lung tissue of all of the animals was analyzed as regards presence of acute and chronic inflammation, capillary congestion, alveolar walls thick, interstitial and alveolar edema, alveolar hemorrhage, denudation capillary and alveolar endothelium areas and atelectasis. RESULTS: The analysis histopathologic revealed significant statistics difference for acute and chronic inflammation, capillary congestion, alveolar walls thick, interstitial and alveolar edema, alveolar hemorrhage, denudation capillary and alveolar epithelium areas. CONCLUSIONS: Exposition to the oxygen during 72 hours in the concentration of 40% does not produce significant histopathologic alterations in the lung tissue; in the concentration of 70%, can promotes the alveolar walls thick and capillary congestion and in the concentration of 100% can cause death and originate diffuse pulmonary lesion. .

Alterações da histoarquitetura pulmonar de camundongos neonatos expostos à hiperóxia / Alterations in the pulmonary histoarchitecture of neonatal mice exposed to hyperoxia

OBJETIVOS: Analisar os efeitos da exposição à hiperóxia (100% de oxigênio) sobre a histoarquitetura pulmonar de camundongos neonatos. MÉTODOS: Camundongos neonatos da linhagem Balb/c foram expostos à hiperóxia (GH) (100% de oxigênio) (n = 10) em uma câmara (15 x 20 x 30 cm) por 24 horas, com fluxo de 2 L/min. O grupo controle (GC) (n = 10) foi exposto a normóxia em um mesmo tipo de câmara e pelo mesmo tempo. Após a exposição, os animais foram sacrificados por decapitação, os pulmões foram removidos para análise histológica e processados de acordo com a rotina do laboratório. Cortes de 3 µm de espessura foram corados com hematoxilina e eosina (H&E). A análise morfométrica foi realizada com o objetivo de analisar macrófagos presentes na luz alveolar, densidade de superfície (Sv) de trocas gasosas, densidade de volume (Vv) de parênquima pulmonar e áreas de atelectasias. RESULTADOS: Foi verificada diminuição do número de macrófagos alveolares (MØ) no GH (GH = 0,08±0,01 MØ/mm²; GC = 0,18±0,03 MØ/mm²; p = 0,0475), Sv de troca gasosa no GH (GH = 8,08 ± 0,12 mm² /mm³; GC = 8,65 ± 0,20 mm² /mm³; p = 0,0233), Vv de parênquima pulmonar no GH (GH = 54,7/33,5/83,5 %/mm²; GC = 75/56,7/107,9 %/mm²; p < 0.0001) quando comparado com o GC. Entretanto, houve aumento de áreas de atelectasias no GH (GH = 17,5/11,3/38,4 atelectasia/mm²; GC = 14/6,1/24,4 atelectasia/mm²; p = 0,0166) quando comparado com o GC. CONCLUSÃO: Nossos resultados indicam que a hiperóxia promoveu alterações na histoarquitetura pulmonar, aumentando áreas de atelectasia e hemorragia alveolar difusa.

OBJECTIVES: To analyze the effects of exposure to hyperoxia (100% oxygen) on the lung histoarchitecture of neonatal mice. METHODS: Neonatal Balb/c mice were exposed to hyperoxia (HG) (100% oxygen) (n = 10) in a chamber (15 x 20 x 30 cm) for 24 horas ours with a flow of 2 L/min. The control group (CG) (n = 10) was exposed to normoxia in the same type of chamber and for the same time. After exposure, the animals were euthanized by decapitation; the lungs were removed and processed for histological examination according to the laboratory routine. Three-mm thick sections were stained with hematoxylin and eosin (H&E). The morphometric analysis was performed with in order to analyze the macrophages present in the alveolar lumen, surface density (Sv) of gas exchange, volume density (Vv) of lung parenchyma, and areas of atelectasis. RESULTS: A decrease in the number of alveolar macrophages (MØ) was observed in the HG (HG = 0.08±0.01 MØ/mm², CG = 0.18±0.03 MØ/mm², p = 0.0475), Sv of gas exchange in HG (HG = 8.08±0.12 mm² /mm³, CG = 8.65±0.20 mm² /mm³, p = 0.0233), Vv of lung parenchyma in HG (HG = 54.7/33.5/83.5%/ mm²; CG = 75/56.7/107.9%/mm², p < 0.0001) when compared with the CG. However, there was an increase in areas of atelectasis in HG (HG = 17.5/11.3/38.4 atelectasis/mm², CG = 14/6.1/24.4 atelectasis/mm², p = 0.0166) when compared with the CG. CONCLUSION: The present results indicate that hyperoxia caused alterations in lung histoarchitecture, increasing areas of atelectasis and diffuse alveolar hemorrhage.

Triamcinolone Acetonide Prevents Enhancement of Hypoxia-induced Neuronal and Inducible Nitric Oxide Synthases in the Retinas of Rats with Oxygen-induced Retinopathy

PURPOSE: We investigated whether oxygen-induced retinopathy (OIR) results in changes in the protein expression of neuronal and inducible nitric oxide synthases (nNOS and iNOS, respectively) in rat model of OIR. In addition, we evaluated whether treatment of rats with triamcinolone acetonide (TA) prevents this response. METHODS: To promote OIR, Sprague-Dawley rats were exposed to hyperoxia from postnatal day 2 (P2) to P14. They were then returned to normoxia after P15. TA was injected into the right vitreous of P15 rats, while saline was injected into the left vitreous. At P18 the expression of nNOS and iNOS was determined using Western blotting and immunostaining techniques in retinas obtained from control rats. RESULTS: In P18 OIR rats, the abundance of nNOS and iNOS protein was significantly increased compared with controls. These increases were not observed in the retinas of rats treated with TA. The change in expression of nNOS and iNOS were specific to parvalbumin and glial fibrillary acidic protein-positive cells. Treatment with TA prevented the increased expression of nNOS and iNOS in all samples. CONCLUSIONS: Hypoxia upregulates expression of nNOS and iNOS in OIR rat retinas, which is can be prevented by treatment with TA.

Retinal Protective Effects of Resveratrol via Modulation of Nitric Oxide Synthase on Oxygen-induced Retinopathy

PURPOSE: Retinopathy of prematurity (ROP) is one of the leading causes of blindness, with retinal detachment occurring due to oxygen toxicity in preterm infants. Recently, advances in neonatal care have led to improved survival rates for preterm infants, and ROP has increased in incidence. In the present study, we aimed to determine whether or not resveratrol exhibits protective effects in an animal model of ROP and in primary retinal cell cultures of neonatal rat via nitric oxide (NO)-modulating actions using western blotting and real-time PCR with inducible nitric oxide synthase (iNOS), endothelial NOS (eNOS) and neuronal NOS (nNOS) antibodies and mRNAs. METHODS: In an in vivo oxygen-induced retinopathy (OIR) model, cyclic hyperoxia was induced with 80% O2 for one day and 21% O2 for one day from P1 to P14 in newborn Sprague-Dawley (SD) rats. Resveratrol was injected intravitreally for seven days and rats were sacrificed at P21. In vitro OIR primary retinal cell culture was performed using P0-2 SD rats. Hyperoxia injuries were induced through 100% O2 exposure for six hours. Western blotting and real-time PCR using iNOS, eNOS, nNOS antibodies and primers were performed in the rat model of ROP and the dispersed retinal cell culture. RESULTS: In both in vivo and in vitro OIR, the expression of iNOS antibody and mRNA was increased and of eNOS and nNOS were reduced in the resveratrol-treated group. CONCLUSIONS: In conclusion, resveratrol appeared to exert retinal protective effects via modulation of NO-mediated mechanism in in vivo and in vitro OIR models.

Lung morphometry, collagen and elastin content: changes after hyperoxic exposure in preterm rabbits

INTRODUCTION: Elastic and collagen fiber deposition increases throughout normal lung development, and this fiber network significantly changes when development of the lung is disturbed. In preterm rats and lambs, prolonged hyperoxic exposure is associated with impaired alveolization and causes significant changes in the deposition and structure of elastic fibers. OBJECTIVES: To evaluate the effects of hyperoxic exposure on elastic and collagen fiber deposition in the lung interstitial matrix and in alveolarization in preterm rabbits. METHODS: After c-section, 28-day preterm New-Zealand-White rabbits were randomized into 2 study groups, according to the oxygen exposure, namely: Room air (oxygen = 21 percent) or Oxygen (oxygen > 95 percent). The animals were killed on day 11 and their lungs were analyzed for the alveolar size (Lm), the internal surface area (ISA), the alveoli number, and the density and distribution of collagen and elastic fibers. RESULTS: An increase in the Lm and a decrease in the alveoli number were observed among rabbits that were exposed to hyperoxia with no differences regarding the ISA. No difference in the density of elastic fibers was observed after oxygen exposure, however there were fewer collagen fibers and an evident disorganization of fiber deposition. DISCUSSION: This model reproduces anatomo-pathological injuries representing the arrest of normal alveolar development and lung architecture disorganization by just a prolonged exposition to oxygen. CONCLUSIONS: In the preterm rabbit, prolonged oxygen exposure impaired alveolization and also lowered the proportion of collagen fibers, with an evident fiber network disorganization.

Ultraestructura de la retinopatía causada por la hiperoxia en ratas en desarrollo / Ultra structure of retinopathy induced by hyperoxia in developing rats

In order to evaluate the effect of postnatal hyperoxia on retinal structure, newborn rats were exposed to different oxygenation intervals (80 ± 1%) with three interruptions of 21% (30 min each). Four groups of rats were exposed from birth to the 6th, 9th, 12th and 14th postnatal day, respectively and another group was placed under normoxia. After this period all oxygenated groups and the controls remained under normoxia until they were 30 days old for the structural analysis of retina. Retinal histology was carried out using conventional techniques for transmission electron microscopy (TEM). In the ganglion cell layer of the retina from rats exposed for 9 days to hyperoxia, capillaries with large projections toward the lumen, were observed as a possible consequence of cellular edema of endothelium. The most severe damage was observed in rats exposed to hyperoxia during 12 and 14 days, showing mitochondrias swollen up and without crests in the areas surrounding the capillaries, necrosis and apoptosis processes, dense bodies, cells with swollen cytoplasms and rupture of the plasmatic membrane. The results suggest that postnatal hyperoxia causes severe damages to the retina in developing rats with a direct relationship between the time exposed to oxygen and ultra structural damages.

Con el propósito de evaluar el efecto de la hiperoxia posnatal sobre la estructura retiniana se analizaron retinas de ratas recién nacidas expuestas a diferentes periodos de oxigenación (80 ±1%), con tres interrupciones de 21% (30 min c/u). Cuatro grupos de ratas fueron expuestas desde su nacimiento hasta el 6to, 9no, 12mo y 14to días de vida y otro grupo fue mantenido en normoxia. Después de este periodo tanto los grupos expuestos a la hiperoxia como los controles permanecieron en normoxia hasta una edad de 30 días para el análisis estructural de la retina. La histología se hizo usando técnicas convencionales para microscopía electrónica de transmisión (MET). En la capa de células ganglionares de la retina de ratas expuestas a nueve días de hiperoxia, se observaron capilares con notables proyecciones hacia la luz, posiblemente como consecuencia de edema celular del endotelio. El daño más intenso fue observado en las ratas expuestas a hiperoxia durante 12 y 14 días, mostrando mitocondrias hinchadas y sin crestas en las áreas circundantes a los capilares, procesos de necrosis y apoptosis, cuerpos densos, células con citoplasmas hinchados y con ruptura de la membrana plasmática. Los resultados sugieren que la hiperoxia posnatal causa graves daños a la retina en las ratas en desarrollo, con una relación directa entre el tiempo de exposición al oxígeno y los daños ultraestructurales.

Oxygen toxicity and antioxidants: state of the art.

Although the use of oxygen as metabolic fuel allows an attractive harvest of energy rich phosphates per molecule of glucose, a significant fraction of oxygen utilized by the body incompletely reduced and is known to be toxic. Such partially reduced forms of oxygen and some of their derivatives are highly reactive pro-oxidants that are collectively referred to as reactive oxygen species (ROS). A multitude of factors are known to modulate the amount of ROS formation in the body. To escape ROS dependent toxicity biological structures have their protective machinery in the form of physiological antioxidants. It appears that the physiological antioxidants are not independently capable of completely detoxifying the ROS constantly produced by the body. The supply of exogenous antioxidants is thus crucial. Endo- and exogenous antioxidants act in concert to minimize ROS dependent damage. ROS are involved in the pathogenesis of a large number of clinical disorders. The sensitive balance between the pro- and anti- oxidant forces in the body appears to be very crucial in determining the state of health, well being and longevity. This article presents an introductory overview covering the current concepts related to oxidants and antioxidants with special reference to human health.

Oxígeno toxicidad evidenciada por ciitología de lavado bronquial / Oxigen-toxicity identify by citology of bronchial lavage

Los objetivos del trabajo son: Identificar la presencia de alteraciones celulares en la vías aéreas producidas por oxigenoterapia e intentar determinar en los casos de oxigenotoxicidad la relación con FiO2, presión en las vías aéreas, PEEP y tiempo de exposición. El análisis reporta 14 pacientes con signos de oxigenotoxicidad (78 por ciento) siendo el hallazgo más significativo a nivel microscópico: hipoplasia de células alveolares tipo I, metaplasia escamosa y células reactivas. 43 por ciento de los pacientes evidenciaron signos de oxigenotoxicidad en las primeras 48 horas de oxigenoterapia, no lográndose establecer relación con Fio2, PEEP y PIM. En todos los pacientes en etapa neonatal (22 por ciento) se evidenció toxicidad por oxígeno, llamándose a la reflexión en relación al uso indiscriminado de oxigenoterapia

Açäo de íons Fe+++ no sistema de óxido-reduçäo do glutation e na lipoperoxidaçäo de membrana em eritrócitos humanos / Lipid peroxidation, antioxidant enzymes and glutathione levels in human erythrocytes exposed to ion Fe+++

Várias säo as doenças que estäo relacionadas ao desequilíbrio entre a açäo de agentes oxidantes e o sistema de defesa do órgäo acometido. Dentre elas destaca-se a hemocromatose transfusional, na qual a funçäo de vários órgäos está comprometida pelo excesso de ferro. Nesta condiçäo, pouco é conhecido sobre o papel e as consequências da sobrecarga deste metal no eritrócito. A presença de ácidos graxos polinsaturados na membrana, do ferro ligado à hemoglobina, e de altas tensöes de oxigênio em seu interior permite supor que o eritrócito é, intrinsicamente, uma célula vulnerável ao estresse oxidativo. Alguns autores, que utilizam a sobrecarga de ferro com o intuito de provocar estresse oxidativo eritrocitário, verificaram diminuiçäo dos níveis de GSH e aumento de lipoperoxidaçäo mensurada pelo MDA. Com a finalidade de estudar a ocorrência da lipoperoxidaçäo e as possíveis alteraçöes do sistema anti-oxidante do glóbulo vermelho em funçäo da exposiçäo ao Fe+++, o presente trabalho analisou as variáveis glutation reduzido (GSH total), glutation oxidado (GSSG), índice de estresse oxidativo (R=GSSG/GSHtotal-GSSG), CATALASE, glutation redutase (GSH-Rd), glutation peroxidase (GSH-Px), superóxido dismutase (SOD) e malonaldeído (MDA) de eritrócitos normais submetidos a diferentes concentaçöes de ferro. O estudo foi realizado em duas fases, sendo que na primeira foram estudadas todas as variáveis eritrocitárias citadas acima, em funçäo de seis concentraçöes de ferro (0, 1, 5, 10, 50 e 100 uM Fe+++). Na segunda fase, foi analisado o GSH total de hemolisados e sobrenadanantes em 50, 100, 150, 200, 250 e 300 segundos de leitura espectrofotométrica. Nesta fase, foi também avaliada a interferência do tampäo EDTA no nível de GSH total de hemácias submetidas a quatro concentraçös de Fe+++ (0, 5, 10 e 100 uM Fe+++). Os resultados da Fase I näo mostraram diferenças significativas quando as variáveis foram analisadas em funçäo do aumento da concentraçäo de Fe+++. Entretanto, em relaçäo aos outros grupos, os resultados sugerem que eritrócitos incubados com 5 e 10 uM Fe+++ estäo sob estresse oxidativo máximo, documentado pelo alto índice R de 0,07 M/M, e a incubaçäo com 5, 10 e 50 uM Fe+++ provoca lipoperoxidaçäo de membrana, mensurada pelo MDA, maior que nos outros grupos. Apesar de näo termos observado alteraçöes enzimáticas eritrocitárias (GSH-Rd, GSH-Px, CATALASE e SOD), pode ser inferido que com as incubaçöes de 5 e 10 uM Fe+++ ocorre entrada de ferro no eritrócito...

Biochemical and pathological changes in response to hyperoxia and protection by antioxidants in rats.

A significant decrease in blood haemoglobin, reduced glutathione and protein in lung and liver, without any change in blood reduced glutathione, was observed in rats exposed to 80% oxygen. Hydrogen peroxide induced erythrocyte haemolysis was significantly increased following exposure to hyperoxia. The lungs of rats exposed to hyperoxia showed perivascular edema. Simultaneous treatment with antioxidants, vitamin A, C, or E, protected the animals against oxygen toxicity.

Toxicidade do oxigênio: implicaçöes clínicas / Toxicity of oxygen: clinical implications

O uso de altas concentraçöes de oxigênio tem aumentado na medicina moderna. Säo discutidas as alteraçöes bioquímicas, anatomopatológicas bem como os efeitos fisiológicos, os principais sinais clínicos e sintomas da exposiçäo a altas fraçöes inspiradas de oxigênio. O tratamento profilático e o limite de segurança do uso de oxigênio säo apresentados