Effects of soy milk as a dietary complement during the natural aging process.

INTRODUCTION: Oxidative stress is one mechanism that could contribute to the acceleration of aging and age-related diseases. On the other hand, because of their antioxidative qualities soybean derived foods could have beneficial effects on the aging process. OBJECTIVES: The aim of our work was to study the effects of a diet supplemented with soy milk on certain biological features of aging in rats. METHODS: Male Wistar rats of 3 to 18 months of age, were assigned to one of two diets: 1) Experimental Group, commercial rat formula and soy milk; 2) Control Group, commercial rat formula and water. Every three months both lipid profile and lipid peroxidation were determined and neuronal cells of hippocampus were counted in control and experimental rats. RESULTS: The soy milk diet significantly improved the plasmatic lipid profile, decreasing serum cholesterol (total as well as LDL) and serum triglycerides, HDL-cholesterol was significatively higher in experimental animals. The LDL/HDL ratio was thus significantly lowered. The soy diet also produced decreased values of lipid peroxidation in brain, liver and kidney. These effects were significant after 6 to 9 months. The experimental animals lost fewer hippocampal neurons than the controls. Finally at 18 months of age, a greater number of surviving animals in experimental group with respect to the control one was observed. CONCLUSIONS: 1) soy intake could have beneficial effects as a complement of normal diet, but not as a replacement for animal proteins and 2) these effects are the result of a very long period (almost lifelong) of consumption of this diet.

Recovery from experimental malnutrition with soymilk: immunological and genetic aspects.

Experimental malnutrition models have been useful to study the effects of malnutrition at early ages. Substantial evidence exists that malnutrition in critical stages of development could result in chromosomal damages. The effect of nutritional rehabilitation with soymilk as a complement of a restricted diet, on plasma and muscle proteins, chromosomal integrity, and unspecific and mucosa immune responses, was studied. Adult male and female Wistar rats (5 weeks old) were assigned to different nutritional conditions: (a) 14 days on protein restricted diet (corn flour and water), followed by 14 days in which water was replaced by soymilk, as nutritional rehabilitation; (b) the same conditions above but periods of 28 days of a protein restricted diet, and 28 days of nutritional rehabilitation and (c) age-matched malnourished (protein restricted diet without nutritional rehabilitation) and normally nourished controls. After both nutritional rehabilitation periods, the weights reached were significantly higher (p < 0.001) than the malnourished control values, but lower than the normal control ones. Plasma protein concentrations were similar in all groups. Muscle proteins that were diminished during the restricted diet, reached normal control values after both rehabilitation periods. The protein restricted diet, produced numeric and structural chromosomal abnormalities. Nutritional rehabilitation was only partially able to revert these abnormalities. The phagocytic activity and gut mucosa IgA-secreting cells were significantly reduced (p < 0.001) during the restricted diet; both nutritional rehabilitation periods induced a significant increase of both, phagocytic activity and IgA secreting cells. These values were similar to controls. Our results show that the supplementation of a protein-restricted diet with soymilk improved tissue protein content, as well as unspecific and gut mucosa immune responses, even though it was not able to reinstate fully normal body weight and a normal chromosome karyotype.

Effects of psychological stress on cold pressor test results.

The authors evaluated the incidence of a psychological stressor in the modification of blood pressure induced by the cold pressor test in normotensive and medicated hypertensive subjects. The study was carried out in two stages: In the first, 28 (14 normotensive and 14 hypertensive) subjects were administered a cold pressor test. Fifteen days later, 14 subjects repeated the same experiment. The remaining 14 subjects (7 hypertensive and 7 normotensive) also repeated the cold pressor test, with the difference that, to add a stressful psychological situation, the physician "abandoned" them at the beginning. The addition of the psychological stress significantly increased only systolic blood pressure in both the hypertensive and the normotensive subjects. Furthermore, the hypertensive subjects did not recover their basal blood pressure values following the cold pressor test when the psychologically stressful situation had been added. These results show the importance of considering psychological aspects when applying physical pressor tests.

Environmental effects on cardiovascular reactivity.

The hypothesis on which this paper is based states that the environment where subjects live has a modifying effect on their psychophysic reactivity when faced with unknown stressing stimuli. To prove such hypothesis, subjects of an isolated country village were studied. An urban sample was used as control. Vascular reactivity was used to determine psychophysics reactivity. Both groups were submitted in their respective environments to a standardized conflicting stimulus which was produced by a device developed in our laboratory. The variables of cardiovascular reactivity were systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). Paired samples by age and basal SBP were used (N = 24 pairs). The results of this experience showed that city dwellers had significantly higher SBP increments than country dwellers. After discussing different variables that may have accounted for these results, it was concluded that city life increases the psychophysics reactivity of city dwellers when faced with stressing stimuli as compared to country dwellers.

Blockage of vibrissal afferents: III. Electrocorticographic effects.

We have shown signs of behavioral depression after vibrissal deafferentation. Locomotor slowing, motor impairments and footshock thresholds increment were demonstrated after vibrissal afferent blockages. Here, we study the electrocortical (ECoG) effects of vibrissal pad anaesthesia, also replicated by bilateral brachial plexus blockage. We found in both cases, that this acute and massive deafferentation produces synchronization over the entire neocortex accompanied by an important loss of muscular electrical activity. Slow waves observed in this condition were similar to those recorded in the sleeping rat without any treatment, but in our case, there were no behavioral signs of sleep. Thus a clear behavioral electroencephalographic dissociation was obtained by acute deafferentation. These results would seem to support the sleep deafferentation hypothesis.

Blockage of vibrissae afferents: II. Footshock threshold increments.

Because of their dense innervation rat vibrissae have been regarded as a very important sensory system. Many behavioral deficits have been reported by other authors after rat vibrissal afferent blockades. In the present work we found significant threshold increments to footshock following either reversible nerve block (procaine or nerve pressure) or section of the vibrissal afferent nerves, but not following vibrissae trimming. These results are discussed in reference to the tonic or level-setting function of afferent systems.

Blockage of vibrissae afferents: I. Motor effects.

In the past, it has been proposed that the rat vibrissae play an important role in other hand, postural abnormalities, muscle tone decreases and hypomotility after sensory organ destructions were proposed as evidence supporting the "level setting" or "tonic" hypothesis. This hypothesis postulates that afferent activity, besides its well know transductive functions, sets the excitability state of the central nervous system. We thought the vibrissal system to be a good model to dissect these two postulated roles because vibrissae trimming would annul the transductive function without affecting the integrity of nerve activity. Thus we compare the effects of trimming the whiskers with blocking the vibrissal afferent nerves on two types of motor behavior: activity in an open field and walking over a rope connecting two elevated platforms. We found that only vibrissal afferent blockage (both nerve section and local anaesthesia) produced severe failures in the motor performances studied. These effects could not be fully explained by the abolition of the vibrissae as a sensory modality because cutting the whiskers did not significantly affect the motor performance. These data are discussed in reference to a tonic or general excitatory function of sensory inputs upon the central nervous system.

Efectos de la suplementacion dietaria con soja en un modelo experimental de cáncer de colon / Effects of dietary supplementation with soya on a colon cancer experimental model

Objetivos: Estudiar la acción de la leche de soja en la aparición de focos de criptas displásicas (FCD) en un modelo experimental de cáncer de colon y su relación con el estrés oxidativo, la actividad apoptótica y la inestabilidad genómica. Metodología: La inducción de la carcinogénesis se produjo en ratas Wistar machos adultas por inoculación subcutánea de 1,2-dimetilhidrazina (DMH) (20 mg/kg) 2 dosis semanales de DMH durante 8 semanas. Se trabajó con 3 grupos (N=12 c/u): A) Control normal con dieta estándar B) Control de carcinogénesis, inoculados con DMH y dieta estándar C) Experimental: inoculados con DMH, con dieta con leche de soja. Los animales se estudiaron a los 4, 5 y 6 meses después de la última inoculación. El colon fue procesado con técnicas histológicas convencionales, se determinó proteína P53 (inmunohistoquímica) y actividad apoptó- tica (Test de Tunel). En suero se determinó (NO) Óxido Nítrico. En homogenatos de hígado se dosó malonildialdehído (MDA). Resultados: En el período estudiado los animales experimentales no desarrollaron cáncer, en tanto que en los controles de carcinogénesis, se detectaron tumores a partir del 5º mes. La detección de indicadores displásicos (FCD) se relacionó con la sobreexpresión de la proteína P53, el aumento de la actividad apoptótica y la disminución de NO y MDA. Conclusiones: La administración de leche de soja, como suplemento dietario por un tiempo prolongado podría retardar la aparición de FCD. La función anticancerígena se debería a la acción antioxidante de la soja que dismunuiría los daños acumulativos sobre el ADN (AU)

Objectives: to study the effects of soy milk consumption in the occurrence of dysplastic crypt foci (DCF) in an experimental model of colon cancer. To relate oxidative stress with apoptotic activity and genomic unsteadiness. Methods: experimental model of colon cancer was achieved by subcutaneous injections of 1,2-dimetilhidrazina (DMH, 20 mg/Kg) twice a week during eight weeks in adult male Wistar rats. Three groups were studied: A) Normal control: saline injections and standard diet (commercial formula and water ad libitum); B) Carcinogenesis control: DMH inoculation and standard diet; C) Experimental: DMH inoculation, soy diet (commercial formula and soy milk). Four rats of each group were study 4, 5 and 6 months after last inoculation: colon tissue was processed with conventional histological techniques; protein P53 was determined by inmunhistochemistry. Apoptotic activity was measured by Tunel test, Nitric Oxide in serum and malondialdehyde in liver homogenates were also determined. Results: Experimental rats did not develop cancer in the studied period, while we found tumors in carcinogenesis control groups in the 5th month. Dysplastic indicators (DCF) were related with P53 over expression, augmented apoptotic activity and decreases of nitric oxide and malondialdehyde. Conclusions: Soy milk intake as diet supplement for prolonged time could delay de DCF emergence. These anticancers effects may be due to the soy antioxidative action, that could decrease the accumulative ADN damage (AU)

Recovery from experimental malnutrition with soymilk: immunological and genetic aspects / Recuperación de la malnutrición experimental con leche de soja: aspectos inmunológicos y genéticos

Experimental malnutrition models have been useful to study the effects of malnutrition at early ages. Substantial evidence exists that malnutrition in critical stages of development could result in chromosomal damages. The effect of nutritional rehabilitation with soymilk as a complement of a restricted diet, on plasma and muscle proteins, chromosomal integrity, and unspecific and mucosa immune responses, was studied. Adult male and female Wistar rats (5 weeks old) were assigned to different nutritional conditions: a) 14 days on protein restricted diet (corn flour and water), followed by 14 days in which water was replaced by soymilk, as nutritional rehabilitation; b) the same conditions above but periods of 28 days of a protein restricted diet, and 28 days of nutritional rehabilitation and c) age-matched malnourished (protein restricted diet without nutritional rehabilitation) and normally nourished controls. After both nutritional rehabilitation periods, the weights reached were significantly higher (p < 0.001) than the malnourished control values, but lower than the normal control ones. Plasma protein concentrations were similar in all groups. Muscle proteins that were diminished during the restricted diet, reached normal control values after both rehabilitation periods. The protein restricted diet, produced numeric and structural chromosomal abnormalities. Nutritional rehabilitation was only partially able to revert these abnormalities. The phagocytic activity and gut mucosa IgA-secreting cells were significantly reduced (p < 0.001) during the restricted diet; both nutritional rehabilitation periods induced a significant increase of both, phagocytic activity and IgA secreting cells. These values were similar to controls. Our results show that the supplementation of a protein- restricted diet with soymilk improved tissue protein content, as well as unspecific and gut mucosa immune responses, even though it was not able to reinstate fully normal body weight and a normal chromosome karyotype

Los modelos de malnutrición experimental han sido útiles para estudiar los efectos de la misma en edades tempranas. Hay evidencia sustancial de que la malnutrición en etapas críticas del desarrollo podría producir daños cromosómicos. Se estudió el efecto de la rehabilitación nutricional con leche de soja como complemento de una dieta restringida sobre las proteínas plasmáticas y musculares, la integridad cromosómica y las respuestas inmunitarias inespecíficas de las mucosas. Se asignaron ratas Wistar adultas macho y hembra (5 semanas de edad) a distintas condiciones nutritivas: a) 14 días con una dieta de restricción de proteínas (harina de maíz y agua), seguida de 14 días en los que se reemplazó el agua por leche de soja, como rehabilitación nutricional; b) las mismas condiciones anteriores pero con períodos de 28 días de dieta con restricción de proteínas y 28 días de rehabilitación nutricional; c) controles desnutridos (dieta de restricción proteica sin rehabilitación nutricional) y adecuadamente nutridos, emparejados por edad. Tras ambos períodos de rehabilitación, los pesos alcanzados fueron significativamente superiores (p <0,001) que las cifras en los controles desnutridos, pero inferiores a las de los controles normales. La concentración plasmática de proteínas fue similar en todos los grupos. Las proteínas plasmáticas, que estaban disminuidas durante la restricción dietética, alcanzaron los valores de los controles normales tras ambos períodos de rehabilitación. La dieta con restricción proteíca produjo anomalías en el número y estructura de los cromosomas. La rehabilitación nutricional sólo pudo revertir parcialmente estas anomalías. La actividad fagocítica de las células intestinales productoras de IgA estaba significativamente disminuida (p < 0,001) durante la dieta restringida; ambos períodos de rehabilitación nutricional produjeron aumentos significativos de ambos parámetros. Estos valores eran similares a los controles. Nuestros resultados muestran que la complementación con leche de soja de una dieta restringida en proteínas mejoró el contenido tisular de proteínas así como las respuestas inmunitarias inespecíficas y de la mucosa intestinal, aunque no fue capaz de restablecer por completo a la normalidad el peso corporal y el cariotipo cromosómico

Environmental effects on cardiovascular reactivity.

The hypothesis on which this paper is based states that the environment where subjects live has a modifying effect on their psychophysic reactivity when faced with unknown stressing stimuli. To prove such hypothesis, subjects of an isolated country village were studied. An urban sample was used as control. Vascular reactivity was used to determine psychophysics reactivity. Both groups were submitted in their respective environments to a standardized conflicting stimulus which was produced by a device developed in our laboratory. The variables of cardiovascular reactivity were systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). Paired samples by age and basal SBP were used (N = 24 pairs). The results of this experience showed that city dwellers had significantly higher SBP increments than country dwellers. After discussing different variables that may have accounted for these results, it was concluded that city life increases the psychophysics reactivity of city dwellers when faced with stressing stimuli as compared to country dwellers.