Histology and histopathology Vol.11, nº 1 (1996)
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- PublicationOpen AccessFine structure of the retinal pigment epithelium of the barred owl (Strix varia)(F. Hernández y Juan F. Madrid. Universidad de Murcia: Departamento de Biología Celular e Histología, 1996) Braekevelt, Charlie, R.; Smith, S. A.; Smith, B. J.The retinal pigment epithelium (RPE) as well as the choriocapillaris and Bruch's membrane (complexus basalis) have been studied by light and electron microscopy in the barred owl (Strix varia). The RPE consists of a single layer of cuboidal cells joined laterally by a series of tight junctions that forms part of the blood-ocular barrier. Basally (sclerally) the retinal epithelial cells display numerous deep infoldings while apically (vitreally) microvillar processes interdigitate with the photoreceptor outer segments. Internally the RPE cells show a large vesicular nucleus, plentiful smooth endoplasmic reticulum (SER) and polysomes but very little rough endoplasmic reticulum (RER). Numerous pleomorphic (including ring-shaped) mitochondria are basally located. In the light-adapted state the small melanosomes are almost exclusively located within the apical process indicating that retinomotor movements probably occur. Phagosomes and lysosome-like bodies are present as are myeloid bodies which may show ribosomes on their outer surface. Bruch's membrane is typical of avian species in that it is pentalaminate and the central lamina densa is displaced towards the choroid. The choriocapillaris endothelium is thin but only minimally fenestrated facing Bruch's membrane. Most fenestrations present show a single-layered diaphragm while others display a double-layered diaphragm as noted in other avian species.
- PublicationOpen AccessFine structure of the pecten oculi of the barred owl (Strix varia)(F. Hernández y Juan F. Madrid. Universidad de Murcia: Departamento de Biología Celular e Histología, 1996) Smith, B. J.; Smith, S. A.; Braekevelt, C. R.The pecten oculi of the barred owl (Strix varia) has been examined by light and transmission electron microscopy. The pecten in this species is of the pleated type and is small in comparison to the size of the ocular globe. The pecten consists of 8-10 accordion-like folds that are linked apically by a pigmented tissue bridge. Each fold contains numerous capillaries, larger supply and drainage vessels, and abundant pleomorphic melanocytes. Most of these capillaries are extremely specialized vessels that possess plentiful microfolds on both the luminal and abluminal surfaces. Some capillaries however display only a few microfolds. The endothelial cell bodies are extremely attenuated, with most organelles located near the nucleus. All capillaries are surrounded by a very thick fibrillar basal lamina, which is thought to provide structural support to these small vessels. Pericytes are commonly found within these thickened basal laminae. Numerous melanocytes are also present, with processes that form an incomplete sheath around the capillaries. These processes are also presumed to provide structural support for the capillaries. As in other avian species, the morphology of the barred owl pecten is indicative of extensive involvement in substance transport. When compared to the pecten of more visually-oriented species, this pecten is smaller, has fewer folds, and displays a reduced number of microfolds within the capillaries. In these and other features, the barred owl pecten is similar to the pecten of the great horned owl (Bubo virginianus).
- PublicationOpen AccessArgyrophilic nucleolar organizer region (AgNOR) counting in astrocytic gliomas: prognostic value(Murcia : F. Hernández, 1996) Cardesa, Antonio; Ferreres, Joan-Carles; Figols, J.; Val-Bernal, José Fernando; Cruz Sánchez, F.F.In 87 astrocytic gliomas the number of AgNORs/nucleus was retrospectively studied and data correlated with the histological type of the tumors and survival. Al1 patients were treated by the same surgical team and with uniform criteria. Statistically significant differences (p<0.01) were found in relation with the AgNOR averages among the histological types of tumors. A statistically significant linear correlation (p<0.05) between the AgNOR values and survival of the patients was also found. Patients with mean AgNOR values higher than 2.23 and lower than 2.9 survived an average of 11.5I9.1 months vs. a sumival in average of 24.4I34.1 months with mean AgNOR values under 2.23 (p<0.05). Patients with AgNOR values higher than 2.9 survived, on average, 7.7I3.9 months. AgNOR counting in astrocytic gliomas is a reproducible, easy, quick method with prognostic value. AgNORs may be successfully applied in routine material to assess the growth potential of astrocytic gliomas.
- PublicationOpen AccessCell rounding with «Rip off» detachment(Murcia : F. Hernández, 1996) Sit, K.H.The «rounding up» characteristic of mitotic, apoptotic, transformed and non-transformed cells appears to be initiated by various causative factors. Cytoskeletal and adhesion modulations have been implicated. Endocytic intemalization via large channels seen in the rounding of arnoeba and human cells alike, implicate a third mechanism, viz. membrane flow and fusion, where «rip off» detachment sheds parts of the cell to achieve freedom. Mutilation as a means for detachment is also used by moving fibroblasts, linking shape change with movement via a distinct mechanism. While rounding may follow detachment and detachment may follow rounding, «rip off» mutilation, whether selfinflicted or imposed, and modulation of stickiness are fundamentally different processes
- PublicationOpen AccessFine structure of the retina and pigment epithelium in the creek chub, Semotilus atromaculatus (Cyprinidae, Teleostei)(Murcia : F. Hernández, 1996) Collin, S.P.; Collin, H.B.; Ali, M.A.The structure of the light- and dark-adapted retina, the pigment epithelium and the choroid of the creek chub, Semotilus atromaculatus (Cyprinidae, Teleostei) is examined by light and electron microscopy. An extensive network of vitreal blood vessels emanating from the hyaloid artery enters the eye with the optic nerve and overlies the inner limiting membrane. This membrane closely apposes the fine protrusions of the Müller cell processes which traverse the entire retina, dividing the inner retina into alternating fascicles of ganglion cells and optic axons. The inner nuclear layer consists of bipolar, amacrine, Müller cell soma and two layers of horizontal cells. The outer plexiform layer possesses both rod spherules and cone pedicles. Each rod spherule consists of a single synaptic ribbon in either a triad or quadrad junctional arrangement within the invaginating terminal endings of the bipolar and horizontal cell processes. In contrast, cone pedicles possess multiple synaptic ribbons within their junctional complexes and, in the light-adapted state, the horizontal cell processes show spinule formation. Four photoreceptor types are identified on morphological criteria; unequal double cones, large single cones, small single cones and rods. Al1 but the small single cones are capable of retinomotor responses. The rod to cone ratio is approximately 5:l and the rods form two ill-defined rows in the light-adapted condition. The retinal pigment epithelium possesses two types of osmiophilic granules. These are bound within slender microvilli and migrate vitread to surround the photoreceptors in response to light. Bruch's membrane is trilaminar and the vascularised choroid consists of up to three layers of melanocytes. The endothelial borders of the choroidal blood vessels abutting the outer lamina of Bruch's membrane are fenestrated.