Rat hyaline and fibrous cartilages whose glycosaminoglycans had been removed by hyaluronidase digestion were studied by comparing the ultrastructural features with the observation of sections stained by selective methods for elastic system fibers under the light microscope. Except for the fibrous layer in the perichondrium of tracheal hyaline cartilage, where elastic fibers were found, no elastic fibers could be detected in the cartilages studied. However, cartilaginous tissues contained oxytalan and elaunin fibers. A distinct pattern of distribution of the above-mentioned elastic-related fibers could be observed in both kinds of cartilages. Hyaline cartilages possess oxytalan fibers in the extracellular matrix that surrounds the chondrocytes, whereas elastic fibers were localized in the fibrous layer of the perichondrium that encloses the cartilage. Elaunin fibers could be detected in the transition (chondrogenic) layer adjacent to the perichondrium. The methods used disclosed the presence of oxytalan and elaunin fibers running along the periphery of the collagen bundles in fibrocartilage.

The uterine cervix is a dynamic structure with a high capacity to adapt to different, even opposing, roles during the sequence of physiological events of gestation (for example, acting as a barrier to retain the fetus during pregnancy and dilating to allow delivery at term). Histoarchitectural changes of the uterine cervix allow its successful adaptation. The aim of this study was to investigate whether fibroblastic cell plasticity, described in the lamina propria of the rat uterine cervix at term, could be observed in women too. Biopsy specimens of non-pregnant and intrapartum human cervices were studied under the transmission electron microscope, and cytoskeletal differentiation markers were identified by immunohistochemistry under the light microscope. Desmin-positive cells were present in the mucous layer of the cervix during labour. These cells displayed cytoplasmic processes (typical of myofibroblasts) that also stained positively for vimentin. The main ultrastructural features for defining the myofibroblast under the electron microscope were also observed in these cells. However, cervices of non-pregnant women contained resident fibroblasts at the same location. Examination of the differentiation repertoire of fibroblastic cells in the mucous layer of the uterine cervix resulted in the characterization of myofibroblasts at term. The implications of the plasticity of fibroblastic-myofibroblastic cells in the physiological changes displayed in the uterine cervix during pregnancy, labour and postpartum involution require further investigation.