Diagnóstico del estrés en peces / Stress diagnosis in fish

Se presenta una revisión de estrés y sus diferente tipos, observados en los peces; por ejemplo, el estrés social debido a las altas densidades de población que se manejan en acuicultura intensiva; estrés físico, causado por cambios en la temperatura, oxígeno y pH del agua; estrés químico, debido a contaminantes endógenos y exógenos; estrés físico, debido a traumatismos; y estrés nutricional, por deficiencias o excesos de algún nutrimento en la dieta. También se describen los métodos actuales para diagnosticarlos, entre ellos: indicadores moleculares y bioquímicos como la medición de aductores estables de ADN; medición de receptores de hormonas esteroides, medición de metalothioneínas y medición de la peroxidación lipídica. La metodología bioquímica hormonal mide las respuestas endocrinas secundarias al estrés, como la hipersecreción de catecolaminas o niveles de cortisol plasmático, propiomelanocortina y concentración de glucosa plasmática. Para el estrés por calor se cuenta con métodos de medición de las proteínas del choque de calor. Algunos parámetros reproductivos se utilizan para medir también el estrés. Se describe un método computarizado no invasivo, así como la metodología histopatológica que se basa en la observación de células de rodlet y las modificaciones en tamaño y forma de algunas células

Cambios inducidos por el estres en la actividad dopaminérgica de la corteza prefrontal / Stress induced changes in the activates dopaminergic in the prefrontal cortex

Estudiamos los efectos del estrés por inmovilización durante 1,2,3,10 ó 22 días en el metabolismo de la dopamina en la corteza prefrontal de la rata. Determinamos las concentraciones de dopamina (DA), ácido dihidroxifenilacético (DOPAC) y ácido homovanílico (HVA) usando HPLC con detección electroquímica y calculamos las razones DOPAC/DA, HVA/DA y HVA/DOPAC. Encontramos un aumento de las razones DOPAC/DA y HVA/DA al 2§ y 5§ días, que indican un incremento en el metabolismo de DA por el estrés. Además encontramos una segunda fase de activación al día 22 el cual se caracterizó por un incremento significativo de la razón HVA/DA sin cambios en la razón DOPAC/DA. El aumento de la razón HVA/DOPAC los días 2 y 22 sugiere una activación predominante de las vías metabólicas que conducen a la formación de HVA

Biochemical changes in brain catecholamines and serotonin during gastric ulcer induced by cold restraint stress in male albino rats

The present study was undertaken to investigate the chronological effect of cold restraint stress on the profile of biogenic amines [epinephrine, norepinephrine, dopamine and serotonin] in different areas of the brain, which are known to affect gastric function and are critically involved in the stress response [frontal cortex, hypothalamus and hippocampus]. Cold restraint stress was applied to pylorically ligated male albino rats in half hourly increasing duration [5-3 hr]. In the three selected brain areas, cold restraint stress produced a significant decrease in both norepinephrine and epinephrine concentrations and a significant increase in dopamine and serotonin levels. These changes in brain amines were significantly correlated with the increased duration of stress. The relevance of these findings was discussed

Efectos del estrés por inmovilización sobre la corteza motora en la rata / The effects of immobilization-Stress on rat motor cortex

El presente estudio analiza el efecto del estrés por inmovilización aplicado a ratas gestantes sobre las neuronas piramidales de la V capa de la corteza motora de sus descendientes. Se usaron ratas hembra de la cepa Wistar que se distribuyeron al azar en dos grupos: control y experimental (con cinco ratas cada uno). El grupo experimental fue sometido a estrés por inmovilización en períodos que variaron de 2 a 6 horas diarias durante la gestación, el grupo control se mantuvo en condiciones normales de bioterio. Las crías de cada grupo fueron sacrificadas a los 14 y 21 días de edad. Se extrajo el cerebro y se colectaron bloques de la corteza motora que se procesaron con la técnica de Golgi Rápido. Se analizaron las neuronas piramidales de esta área cuantificando el número de intersecciones de las ramificaciones dendríticas con ocho círculos concéntricos. Los resultados mostraron en ambas edades reducción significativa del número de ramificaciones dendríticas en todos los círculos concéntricos en el grupo experimental en comparación con el grupo control. Estos hallazgos indican reducción de la complejidad neuronal que puede ser responsable de deficiencias en la capacidad de aprendizaje, comportamiento adaptativo y de alteraciones de la actividad locomotora reportadas en animales descendientes de madres sometidas a estrés durante la gestación.

effect of some stress conditions on reproduction in tilapia nilotica

Nineteen mature male and female Tilapia nilotica were kept under natural environmental conditions in November 1991. They were classified into three groups. The first group was maintained in aquaria with one liter of water for each cm. of fish length under natural conditions of temperature and photo-period and fed once daily at a ratio of 1% of the body weight. The second group was fasted for 6 days. The third groups was kept with average of one liter of water/2.5 cm of fish length. Plasma samples as well as samples from the testes and ovaries for histological examination were taken after 3 and 6 days. The obtained results indicated a high significant decrease in plasma testosterone in the fasted group after 3 days which returned to the control levels after 6 days, while in the overcrowded group, testosterone showed no significant change from the control values. The histological studie of the testes showed no noticeable changes of both seminferous tubules or interstitial cells neither in the fasted nor in the overcrowded group. Estradiol -17 beta in the plasma of the fasted female Tilapia nilotica showed a significant decrease after 3 and 6 days, while its levels in the overcrowded females showed a significant increase after 3 days then declined after 6 days. Plasma progesterone revealed no detectable changes from the control group both in fasted and overcrowded group. The histological findings revealed that, in the ovaries of 3 days fasted females, the oocytes of early and late-perinucleous [stages 1 and II] were more than the vitellogenic stage [stage IV, V, VI]. While, in the ovaries of 6 days fasted females, the vitellogenic stages were predominated. In ovaries of both 3 and 6 days fasted females there were few atretic or empty follicles to be seen. The ovary of the 3 days overcrowded females was nearly similar to that of the control, but the number of the atretic follicles was more than that of control. After 6 days overcrowding, there was increase in vitellogenic stages. In addition there was a few number of empty or atretic follicles

Changes in hemostatic mechanism of broiler chickens in response to overcrowdness

The present investigation was done to study the effect of overcrowdness as a stress factor on the hemostatic mechanism in broiler chickens. Birds were allocated into 2 groups. The first group acted as control [100 baby chicks/m 2] and the second was crowded group [200 baby chicks/m 2]. Blood samples were collected by cardiac puncture from birds of both groups every week for 7 successive weeks. Some blood coagulation parameters were determined including prothrombin time [PT], activated partial thromboplastin time [APTT], activities of clotting factor 8 and 9, fibrinogen concentration and platelet count. The results revealed that no changes in the tested blood coagulation parameters were recorded during the first three weeks of experiment except a significant increase in the platelet count that occurred between the 2nd and 5th weeks of the experimental period. No changes were recorded in PT all over the experimental period. Activated partial thromboplastin time and fibrinogen concentration were significantly decreased from the 4th and 5th weeks till the end of the experimental period, respectively. Activities of clotting factors 8 and 9 were significantly increased from the 4th week till the end of the experiment. So, it is clear that overcrowdness may affect the hemostatic mechanism of broilers in the form of enhanced intrinsic blood coagulation pathway that detected after the first three weeks of life. This may lead to intravascular coagulation that considered as a possible cause of increased mortality in stressed chickens