A light and electron microscopic study of the limb long bones perichondral ossification in the quail embryo (Coturnix coturnix japonica).

The perichondral ossification of the limb long bones in the quail embryo is investigated, in this study, by means of light and electron microscopy. Longitudinal sections of the humerus, radius, ulna, femur, tibia and fibula stained with haematoxylin-eosin were examined by the light microscope. Ultrathin cross sections were selected for the electron microscope as well. Light microscopic analysis showed that the ossification began at the same time in the long bones of the wing and leg. At the embryonic day 6, all the cartilaginous rudiments consisted of three zones. The central zone composed of hypertrophic chondrocytes, a second zone on either side of the central zone, which consisted of flattened cells and a third zone, which represented the epiphyseal region. A thin sheath of osteoid and a bi-layered perichondrium-periosteum surrounded the central zone of the cartilaginous rudiments of the long bones. The perichondrium consisted of a layer of osteoblasts, in contact with the cartilage, and a layer of fibroblasts. At the embryonic day 7, the thickness of the calcified osteoid ring increased and a vasculature appeared between the layer of osteoblasts and the layer of fibroblasts. At the embryonic day 8, a second sheath of periosteal bone began to be formed. Concurrently, vascular and perivascular elements began to invade the cartilage. The ossification spread towards the distal ends of both the diaphysis. At the electron microscopic level, the osteoblasts of the perichondium showed cytoplasmatic characteristics of cells involved in protein synthesis. The perichondral ossification is the first hallmark of the osteogenesis in the long bones. The observations reported above, are in accordance with previous studies in the chick embryo.

Bone morphogenetic protein expression in newborn rat kidneys after prenatal exposure to radiofrequency radiation.

Effects of nonthermal radiofrequency radiation (RFR) of the global system of mobile communication (GSM) cellular phones have been as yet mostly studied at the molecular level in the context of cellular stress and proliferation, as well as neurotransmitter production and localization. In this study, a simulation model was designed for the exposure of pregnant rats to pulsed GSM-like RFR (9.4 GHz), based on the different resonant frequencies of man and rat. The power density applied was 5 microW/cm2, in order to avoid thermal electromagnetic effects as much as possible. Pregnant rats were exposed to RFR during days 1-3 postcoitum (p.c.) (embryogenesis, pre-implantation) and days 4-7 p.c. (early organogenesis, peri-implantation). Relative expression and localization of bone morphogenetic proteins (BMP) and their receptors (BMPR), members of a molecular family currently considered as major endocrine and autocrine morphogens and known to be involved in renal development, were investigated in newborn kidneys from RFR exposed and sham irradiated (control) rats. Semi-quantitative duplex RT-PCR for BMP-4, -7, BMPR-IA, -IB, and -II showed increased BMP-4 and BMPR-IA, and decreased BMPR-II relative expression in newborn kidneys. These changes were statistically significant for BMP-4, BMPR-IA, and -II after exposure on days 1-3 p.c. (P <.001 each), and for BMP-4 and BMPR-IA after exposure on days 4-7 p.c. (P <.001 and P =.005, respectively). Immunohistochemistry and in situ hybridization (ISH) showed aberrant expression and localization of these molecules at the histological level. Our findings suggest that GSM-like RFR interferes with gene expression during early gestation and results in aberrations of BMP expression in the newborn. These molecular changes do not appear to affect renal organogenesis and may reflect a delay in the development of this organ. The differences of relative BMP expression after different time periods of exposure indicate the importance of timing for GSM-like RFR effects on embryonic development.