ABSTRACT
The effect of breeder age on long bone development was studied in chicken embryos from 12 days of incubation until hatching. Fertile eggs were incubated and randomly assigned in a 2 x 6 factorial arrangement (two breeder ages - 38 and 60 weeks and six incubation days - 12, 14, 16, 18, 20, and 21). Enzymatic activity of acid and alkaline phosphatases in tibial epiphyses and weights as well as length and width in tibias and femurs of the embryos were determined. Tartrate-resistant acid and alkaline phosphatases activity in epiphyses was not affected by breeder age. Absolute weight and width of femur and tibia were larger in 60-week-old embryos compared to 38-week-old. Enzymatic activity and morphometric measurements increased with incubation day, independently of breeder age. The results showed that the process of endochondral ossification during the last two thirds of embryo development was not influenced by the age of the breeders. Although, in terms of absolute weight, the long bones of embryos from older breeders were heavier, which was associated with the larger width of the bones, but and not with their length.
O efeito da idade da matriz sobre o desenvolvimento dos ossos longos foi estudado em embriões de frango de 12 dias de incubação até o nascimento. Ovos férteis foram incubados e distribuídos em delineamento inteiramente casualizado em arranjo fatorial 2 x 6 (duas idades de matriz - 38 e 60 semanas e seis dias de incubação - 12, 14, 16, 18, 20 e 21 dias). Determinou-se a atividade enzimática das fosfatase alcalina e ácida-resistente ao tartrato no peso e nas epífises da tíbia, no comprimento e na largura da tíbia e do fêmur. A atividade das fosfatases não foi afetada pela idade da matriz. O peso absoluto e a largura de fêmur e tíbia foram maiores nos embriões das matrizes com 60 semanas de idade. Atividade enzimática e medidas morfométricas aumentaram com o dia de incubação independentemente da idade da matriz. Concluiu-se que o processo de ossificação endocondral durante os dois últimos terços de desenvolvimento embrionário não foi influenciado pela idade das matrizes. No entanto, em termos de peso absoluto, os ossos longos de embriões provenientes de matrizes velhas foram mais pesados o que foi associado à maior largura e não ao maior comprimento dos ossos.
Subject(s)
Animals , Age Factors , Alkaline Phosphatase , Bone Development , Embryonic Development , PoultryABSTRACT
The nucleus isthmi (NI) is a mesencephalic structure of the amphibian brain. It has been reported that NI plays an important role in integration of CO2 chemoreceptor information and glutamate is probably involved in this function. However, very little is known about the mechanisms involved. Recently, it has been shown that nitric oxide synthase (NOS) is expressed in the brain of the frog. Thus the gas nitric oxide (NO) may be involved in different functions in the brain of amphibians and may act as a neurotransmitter or neuromodulator. We tested the hypothesis that NO plays a role in CO2-drive to breathing, specifically in the NI comparing pulmonary ventilation, breathing frequency and tidal volume, after microinjecting 100 nmol/0.5 µl of L-NAME (a nonselective NO synthase inhibitor) into the NI of toads (Bufo paracnemis) exposed to normocapnia and hypercapnia. Control animals received microinjections of vehicle of the same volume. Under normocapnia no significant changes were observed between control and L-NAME-treated toads. Hypercapnia caused a significant (P<0.01) increase in ventilation only after intracerebral microinjection of L-NAME. Exposure to hypercapnia caused a significant increase in breathing frequency both in control and L-NAME-treated toads (P<0.01 for the control group and P<0.001 for the L-NAME group). The tidal volume of the L-NAME group tended to be higher than in the control group under hypercapnia, but the increase was not statistically significant. The data indicate that NO in the NI has an inhibitory effect only when the respiratory drive is high (hypercapnia), probably acting on tidal volume. The observations reported in the present investigation, together with other studies on the presence of NOS in amphibians, indicate a considerable degree of phylogenetic conservation of the NO pathway amongst vertebrates.