ABSTRACT The birth of fraternal twins is a characteristic frequently observed in callitrichids. Cytogenetic studies have demonstrated hematopoietic chimerism in marmosets with the occurrence of two cell lines 2n=46,XX/46,XY in females and males co-twins, without phenotypic changes. Amplification by PCR have also been used to verify the presence of the SRY gene in female chimaeras. Our aim was to verify the occurrence of chimerism in Callithrix sp. individuals considered as hybrids according to their intermediate phenotypes between C. jacchus and C. penicillata. Blood samples from 37 Callithrix sp. individuals were collected. Hematopoietic chimerism 2n=46,XX/46,XY was detected by cytogenetic analysis in five individuals, three males and two females. A fragment of approximately 200bp of the SRY gene was amplified in seven females with normal external genitalia. The percentage of 32% of chimeric individuals detected in the present study is similar to that observed for pure specimens of Callithrix. These data suggests that hybridization probably does not interfere with the occurrence of twin gestation, nor of chimerism. Although cytogenetics is the main tool to identify the two cell lineages present in cases of chimerism, the amplification of the SRY gene by PCR has proved to be more efficient to identify the Y chromosome in cases of chimeric female marmoset.

Introduction: aging and obesity cause changes in water exchange rate, which could affect the equilibrium time of deuterium oxide (²H2O). Objective: to assess the effect of overweight and obesity on the equilibrium time of the stable isotope deuterium in saliva samples of older adults. Methods: a sample of 18 women over 63 years with a body mass index (BMI) of 20.8 to 40.5 kg/m² were included. A basal saliva sample was took and immediately a dose of 30 g of ²H2O was administered orally. Saliva samples at 2, 2.5, 3, 3.5 and 4 hours post-dose were taken. Deuterium in saliva samples were analyzed by Fourier Transform Infrared spectroscopy technique. Results: the average in equilibrium time (plateau) in women of normal BMI (18.5-24.9 kg/m²) was 3.6 ± 0.2 hours, which was statistically different to those obtained in the group with overweight (25-29.9 kg/m²) and obese (>30 kg/m²) of 2.9 ± 0.4 hours and 2.8 ± 0.4 hours, respectively (p<0.05). The values of total body water and fat free mass calculated with the values of isotopic enrichment at 3.6 (plateau reached in the group with normal BMI) did not differ statistically from the values calculated to plateau at 2.9 and 2.8 hours in the overweight and obesity group, respectively (p>0.05). Conclusion: obesity had an effect on the equilibrium times; however, did not affect the calculation of total body water and body composition in this older women adult group.

Introducción: el envejecimiento y la obesidad producen cambios en la tasa de recambio de agua, lo que podría afectar al tiempo de equilibrio del óxido de deuterio (²H2O). Objetivo: se evaluó el efecto del sobrepeso y la obesidad sobre el tiempo de equilibrio del isótopo estable de deuterio en muestras de saliva de adultos mayores. Métodos: se incluyeron 18 mujeres entre 63 y 80 años con un índice de masa corporal (IMC) de 20,8 a 40,5 kg/m². Después de la toma de una muestra de saliva basal se administró una dosis vía oral de 30 g de ²H2O. Se tomaron muestras de saliva a las 2, 2,5, 3, 3,5 y 4 horas post-dosis, las cuales fueron analizadas mediante espectrometría infrarroja con transformada de Fourier. Resultados: el tiempo de equilibrio (plateau) promedio en las mujeres con un IMC normal (18,5-24,9 kg/m²) fue de 3,6 ± 0,2 horas, el cual fue diferente estadísticamente al obtenido en el grupo con sobrepeso (25-29,9 kg/m²) y obesidad (>30 kg/m²) de 2,9 ± 0,4 horas y 2,8 ± 0,4 horas, respectivamente (p<0,05). Los valores de agua corporal total y la masa corporal libre de grasa calculados con los valores de enriquecimiento isotópico a las 3,6 (plateau alcanzado en el grupo con IMC normal) no fueron diferentes estadísticamente a los valores calculados al plateau a las 2,9 y 2,8 horas en el grupo con sobrepeso y obesidad, respectivamente (p>0,05). Conclusión: se encontró un efecto de la obesidad sobre el tiempo de equilibrio; sin embargo, no afectó al cálculo del agua corporal total y a la composición corporal en este grupo etario.