Endoneural vessels vascular pattern on the vagus nerve of Wistar-Kyoto rats: A longitudinal study.

Os nervos são abundantemente vascularizados em toda sua extensão, por intermédio de uma sucessão de vasos que, por suas consecutivas divisões e anastomoses no interior do nervo, formam uma rede vascular intraneural ininterrupta. Já está bem definido que o número de vasos nutrientes para um nervo em particular varia amplamente, não apenas de indivíduo para indivíduo, como também entre os dois lados do corpo. Nervos maiores não necessariamente recebem mais vasos que nervos menores. Os nervos podem percorrer distâncias consideráveis sem receber um vaso nutriente e o calibre desses vasos varia em amplos intervalos. Desse modo, o número e o tamanho dos vasos, juntamente com a sua distribuição no interior dos nervos estão sujeitos a uma grande variabilidade, não apenas em vários segmentos do mesmo nervo como também no mesmo nervo em diferentes sujeitos. Nosso objetivo, com o presente estudo foi o de realizar uma descrição do padrão longitudinal de vascularização do endoneuro e de avaliar a existência de uma possível correlação entre a área fascicular e a área endoneural ocupada pelos vasos capilares, no nervo vago de ratas da linhagem Wistar-Kyoto, em três diferentes fases da vida: 30, 180 e 360 dias de idade. Para tanto, três animais de cada grupo foram mortos e tiveram seus nervos vagos direitos preparados com técnicas histológicas de rotina para inclusão em resina epóxi. Secções transversais semifinas (0,4 µm) seriadas, obtidas a cada 100 µm de extensão longitudinal do nervo, até o esgotamento completo dos blocos, foram analisadas em nível de microscopia de luz. A morfometria dos fascículos e dos vasos capilares endoneurais, foi realizada com o auxílio de um sistema analisador de imagens computacional. A área fascicular média e a área média ocupada pelos capilares foram calculadas para cada segmento estudado (proximal, médio e distal) e comparadas entre segmentos (estudo longitudinal) e entre os grupos. A correlação entre a área fascicular total e a área endoneural ocupada pelos capilares foi estudada através de uma análise de regressão linear e do cálculo dos coeficientes de correlação. A porcentagem da área fascicular total ocupada pelos capilares endoneurais também foi calculada para cada segmento estudado e comparada entre segmentos e entre os grupos. Nossos resultados mostram que a área fascicular média de todos os segmentos estudados foi significativamente maior nos animais com 180 e 360 dias, comparados aos com 30 dias, em todos os segmentos estudados, acompanhando o ganho ponderal dos animais. Interessantemente, nos animais jovens (30 dias), houve uma tendência ao aumento dos valores dessa área no sentido longitudinal dos nervos, o que não foi observado nos animais mais velhos (180 e 360 dias). A área média dos capilares endoneurais aumentou no sentido longitudinal em todos os grupos estudados. Na comparação entre os grupos, houve uma estabilização da área fascicular média nos animais mais velhos enquanto que houve uma diminuição da área média dos capilares endoneurais com o avançar da idade. A porcentagem da área fascicular total ocupada pelos capilares aumentou, no sentido longitudinal, nos animais jovens (30 dias) e tendeu à estabilidade nos animais mais velhos (180 e 360 dias), havendo nítida diminuição progressiva dessa porcentagem com o avançar da idade. O estudo dos diâmetros dos capilares endoneurais mostrou que esses diâmetros variam amplamente, sem nenhum padrão específico entre segmentos de um mesmo grupo os entre os diferentes grupos. Nossos resultados também mostraram a existência de uma correlação positiva fraca (coeficientes de correlação com valores muito baixos) entre a área fascicular total e a área endoneural ocupada pelos capilares. Esses dados sugerem que a entrada dos capilares no nervo não é acompanhada de um aumento proporcional na área do fascículo. Os dados de diminuição da porcentagem da área fascicular total ocupada pelos capilares com o avançar da idade podem sugerir que os nervos de animais mais velhos possam ser mais susceptíveis aos processos isquêmicos.Peripheral nerves are abundantly vascularised throughout their length by a succession of vessels which, by their repeated division and anastomosis within the nerve, for an unbroken intraneural vascular network. It is well defined that the number of nutrient vessels to any particular nerve varies greatly not only from subject to subject but also on the two sides of the body. Larger nerves do not necessarily receive more vessels than do smaller nerves. Nerves may run considerable distances without receiving a nutrient vessel and the caliber of the nutrient vessels fluctuates over wide limits. Thus, the number and size of these vessels, together with their distribution within the nerve, are subject to a wide range of variation, not only between various segments of a nerve but also in the same nerve in different specimens. In this way, our objectives were to study the longitudinal pattern of the endoneural vascularisation and, to determine the existence of a correlation between the fascicular total area and the endoneural area occupied by the capillary vessels on the vagus nerve of Wistar-Kyoto female rats, in three different ages. Three animas aged 30, 180 or 360 days were killed and their right vagus nerves were prepared for epoxy resin embedding and light microscopy study, by conventional techniques. Serial semihtin sections (0.4 µm), obtained every 100 µm of the vagus nerve longitudinal extension were measured with the aid of a computer software. The average fascicular area and the average area occupied by the endoneural capillary were obtained for each segment (proximal, medium and distal) and compared between segments (longitudinal study) and between ages. The correlation between the fascicular area and the area occupied by the endoneural capillary was accessed by linear regression analysis and correlation coefficient calculations. The percentage of the total fascicular area occupied by the capillaries was also calculated for each segment and compared between segments and between ages. Our results show that the average fascicular area, in all segments studied, was significantly larger in the older animals (180 and 360 days), compared to the younger (30 days). This was compatible with the weight gain of the animals. Interestingly, in the younger animals, there was a tendency of an increase in the average fascicular area from proximal to distal, and this was not observed in the older animals (180 and 360 days). The average area of the endoneural capillaries increased from proximal to distal in all groups studied. The analysis between groups showed a stabilization of the fascicular area in the older animals while the average capillary area got smaller with ageing. The percentage of the fascicular area occupied by the endoneural capillary vessels increased from proximal to distal in the younger animals (30 days) and got stable in the older (180 and 360 days). There was an obvious decrease in this percentage with ageing. The capillary vessels diameter study showed that this parameter varied considerably, without a established pattern between segments or groups. Our results also show the existence of a weak but positive correlation between the fascicular area and the area occupied by the endoneural capillary. This data suggests that the entrance of blood vessels to the endoneural space is not followed by an increase on the fascicular area. The result of a smaller percentage of the fascicular area occupied by the capillary vessels with ageing suggests that older animals may be more susceptible to nerve ischemia

Endoneural vessels vascular pattern on the vagus nerve of Wistar-Kyoto rats: A longitudinal study.

Os nervos são abundantemente vascularizados em toda sua extensão, por intermédio de uma sucessão de vasos que, por suas consecutivas divisões e anastomoses no interior do nervo, formam uma rede vascular intraneural ininterrupta. Já está bem definido que o número de vasos nutrientes para um nervo em particular varia amplamente, não apenas de indivíduo para indivíduo, como também entre os dois lados do corpo. Nervos maiores não necessariamente recebem mais vasos que nervos menores. Os nervos podem percorrer distâncias consideráveis sem receber um vaso nutriente e o calibre desses vasos varia em amplos intervalos. Desse modo, o número e o tamanho dos vasos, juntamente com a sua distribuição no interior dos nervos estão sujeitos a uma grande variabilidade, não apenas em vários segmentos do mesmo nervo como também no mesmo nervo em diferentes sujeitos. Nosso objetivo, com o presente estudo foi o de realizar uma descrição do padrão longitudinal de vascularização do endoneuro e de avaliar a existência de uma possível correlação entre a área fascicular e a área endoneural ocupada pelos vasos capilares, no nervo vago de ratas da linhagem Wistar-Kyoto, em três diferentes fases da vida: 30, 180 e 360 dias de idade. Para tanto, três animais de cada grupo foram mortos e tiveram seus nervos vagos direitos preparados com técnicas histológicas de rotina para inclusão em resina epóxi. Secções transversais semifinas (0,4 µm) seriadas, obtidas a cada 100 µm de extensão longitudinal do nervo, até o esgotamento completo dos blocos, foram analisadas em nível de microscopia de luz. A morfometria dos fascículos e dos vasos capilares endoneurais, foi realizada com o auxílio de um sistema analisador de imagens computacional. A área fascicular média e a área média ocupada pelos capilares foram calculadas para cada segmento estudado (proximal, médio e distal) e comparadas entre segmentos (estudo longitudinal) e entre os grupos. A correlação entre a área fascicular total e a área endoneural ocupada pelos capilares foi estudada através de uma análise de regressão linear e do cálculo dos coeficientes de correlação. A porcentagem da área fascicular total ocupada pelos capilares endoneurais também foi calculada para cada segmento estudado e comparada entre segmentos e entre os grupos. Nossos resultados mostram que a área fascicular média de todos os segmentos estudados foi significativamente maior nos animais com 180 e 360 dias, comparados aos com 30 dias, em todos os segmentos estudados, acompanhando o ganho ponderal dos animais. Interessantemente, nos animais jovens (30 dias), houve uma tendência ao aumento dos valores dessa área no sentido longitudinal dos nervos, o que não foi observado nos animais mais velhos (180 e 360 dias). A área média dos capilares endoneurais aumentou no sentido longitudinal em todos os grupos estudados. Na comparação entre os grupos, houve uma estabilização da área fascicular média nos animais mais velhos enquanto que houve uma diminuição da área média dos capilares endoneurais com o avançar da idade. A porcentagem da área fascicular total ocupada pelos capilares aumentou, no sentido longitudinal, nos animais jovens (30 dias) e tendeu à estabilidade nos animais mais velhos (180 e 360 dias), havendo nítida diminuição progressiva dessa porcentagem com o avançar da idade. O estudo dos diâmetros dos capilares endoneurais mostrou que esses diâmetros variam amplamente, sem nenhum padrão específico entre segmentos de um mesmo grupo os entre os diferentes grupos. Nossos resultados também mostraram a existência de uma correlação positiva fraca (coeficientes de correlação com valores muito baixos) entre a área fascicular total e a área endoneural ocupada pelos capilares. Esses dados sugerem que a entrada dos capilares no nervo não é acompanhada de um aumento proporcional na área do fascículo. Os dados de diminuição da porcentagem da área fascicular total ocupada pelos capilares com o avançar da idade podem sugerir que os nervos de animais mais velhos possam ser mais susceptíveis aos processos isquêmicos.Peripheral nerves are abundantly vascularised throughout their length by a succession of vessels which, by their repeated division and anastomosis within the nerve, for an unbroken intraneural vascular network. It is well defined that the number of nutrient vessels to any particular nerve varies greatly not only from subject to subject but also on the two sides of the body. Larger nerves do not necessarily receive more vessels than do smaller nerves. Nerves may run considerable distances without receiving a nutrient vessel and the caliber of the nutrient vessels fluctuates over wide limits. Thus, the number and size of these vessels, together with their distribution within the nerve, are subject to a wide range of variation, not only between various segments of a nerve but also in the same nerve in different specimens. In this way, our objectives were to study the longitudinal pattern of the endoneural vascularisation and, to determine the existence of a correlation between the fascicular total area and the endoneural area occupied by the capillary vessels on the vagus nerve of Wistar-Kyoto female rats, in three different ages. Three animas aged 30, 180 or 360 days were killed and their right vagus nerves were prepared for epoxy resin embedding and light microscopy study, by conventional techniques. Serial semihtin sections (0.4 µm), obtained every 100 µm of the vagus nerve longitudinal extension were measured with the aid of a computer software. The average fascicular area and the average area occupied by the endoneural capillary were obtained for each segment (proximal, medium and distal) and compared between segments (longitudinal study) and between ages. The correlation between the fascicular area and the area occupied by the endoneural capillary was accessed by linear regression analysis and correlation coefficient calculations. The percentage of the total fascicular area occupied by the capillaries was also calculated for each segment and compared between segments and between ages. Our results show that the average fascicular area, in all segments studied, was significantly larger in the older animals (180 and 360 days), compared to the younger (30 days). This was compatible with the weight gain of the animals. Interestingly, in the younger animals, there was a tendency of an increase in the average fascicular area from proximal to distal, and this was not observed in the older animals (180 and 360 days). The average area of the endoneural capillaries increased from proximal to distal in all groups studied. The analysis between groups showed a stabilization of the fascicular area in the older animals while the average capillary area got smaller with ageing. The percentage of the fascicular area occupied by the endoneural capillary vessels increased from proximal to distal in the younger animals (30 days) and got stable in the older (180 and 360 days). There was an obvious decrease in this percentage with ageing. The capillary vessels diameter study showed that this parameter varied considerably, without a established pattern between segments or groups. Our results also show the existence of a weak but positive correlation between the fascicular area and the area occupied by the endoneural capillary. This data suggests that the entrance of blood vessels to the endoneural space is not followed by an increase on the fascicular area. The result of a smaller percentage of the fascicular area occupied by the capillary vessels with ageing suggests that older animals may be more susceptible to nerve ischemia

A histomorphometric study of unmyelinated fibers of the fibular nerve in Wistar rats

ABSTRACT There are few histomorphometric studies on the unmyelinated fibers of the fibular nerve in rats, and the number of experimental studies using this nerve has been increasing in the last years. Sixty-two percent of the endoneurial area from 10 fibular nerves of adult Wistar rats was scanned by electron microscopy, and digitized. The total number of unmyelinated axons (1.882 ± 271) was significantly lesser, and their axon diameters (0.2 µm to 2.8 µm) significantly higher than that determined in previous studies. The histogram peaked at 1 µm. The differences could be due to the nerve sampled area, the number and the age of the animals evaluated, and the laboratory techniques used. This study brings new and referential data to be used in experimental investigations involving histomorphometric evaluation of the rat fibular nerve

Identification of adequate vehicles to carry nerve regeneration inducers using tubulisation

Abstract Background Axonal regeneration depends on many factors, such as the type of injury and repair, age, distance from the cell body and distance of the denervated muscle, loss of surrounding tissue and the type of injured nerve. Experimental models use tubulisation with a silicone tube to research regenerative factors and substances to induce regeneration. Agarose, collagen and DMEM (Dulbecco’s modified Eagle’s medium) can be used as vehicles. In this study, we compared the ability of these vehicles to induce rat sciatic nerve regeneration with the intent of finding the least active or inert substance. The experiment used 47 female Wistar rats, which were divided into four experimental groups (agarose 4%, agarose 0.4%, collagen, DMEM) and one normal control group. The right sciatic nerve was exposed, and an incision was made that created a 10 mm gap between the distal and proximal stumps. A silicone tube was grafted onto each stump, and the tubes were filled with the respective media. After 70 days, the sciatic nerve was removed. We evaluated the formation of a regeneration cable, nerve fibre growth, and the functional viability of the regenerated fibres. Results Comparison among the three vehicles showed that 0.4% agarose gels had almost no effect on provoking the regeneration of peripheral nerves and that 4% agarose gels completely prevented fibre growth. The others substances were associated with profuse nerve fibre growth. Conclusions In the appropriate concentration, agarose gel may be an important vehicle for testing factors that induce regeneration without interfering with nerve growth.</p

Geoeconomic variations in epidemiology, ventilation management, and outcomes in invasively ventilated intensive care unit patients without acute respiratory distress syndrome: a pooled analysis of four observational studies

Background: Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. Methods: In this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middle-income countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality. Findings: Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42·4% vs 44·2%; absolute difference -1·69 [-9·58 to 6·11] p=0·67; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5-8] vs 6 [5-8] cm H2O; p=0·0011). ICU mortality was higher in MICs than in HICs (30·5% vs 19·9%; p=0·0004; adjusted effect 16·41% [95% CI 9·52-23·52]; p&lt;0·0001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0·80 [95% CI 0·75-0·86]; p&lt;0·0001). Interpretation: Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status