On the pathogenesis and therapy of dementia of the Alzheimer type: some neuropathological, biochemical, genetic and pharmacotherapeutic considerations.

The extensive literature on dementia of Alzheimer type (DAT) testifies to the enormous progress achieved in the clinical and biochemical delineation of this disease. Newly developed laboratory and imaging techniques are also being applied to the diagnosis of DAT. Nevertheless, unequivoval diagnosis still relies primarily on morphological data from biopsy or autopsy. An overview is presented of major morphological changes occurring at different levels of organization in the central nervous system (CNS) in DAT. Currently formulated etiopathogenic hypotheses of DAT are reviewed and discussed in the context of morphological alterations. Some of the recombinant DNA methods, that are currently available for gene analysis, are described. Some approaches for studying Alzheimer specific genes using the above methods have been suggested. Finally, a critical overview of the current pharmacotherapeutic armamentarium used in DAT and senile dementia is presented. The efficacy, side effects, and the main mechanisms of action of the two categories of drug therapy -supposed etiopathogenic and symptomatic- are presented.

Leptomeningeal cysts after spot freezing: transmission and scanning electron microscopic observations.

The sequential development of the early phases of leptomeningeal cyst formation was studied in an experimental model. Light, transmission and scanning electron microscopic data were compared with those from human arachnoid cysts. Common features observed were: the participation of leptomeningeal cells in the structure of the cysts with exclusion of dural components; the absence of internal traversing trabeculae; the hyperplasia of leptomeningeal cells, particularly in the dome of the cysts. Other features of the experimental cysts were: the splitting of the pio-arachnoid membrane; the scarcity of collagen at the early stages; the presence of areas of mineralization at more advanced stages; the presence of remodeling parenchymal changes at the underlying nervous tissue.

Solitary abscess in rat brain: light and electron microscopy observations.

The authors describe the histological and ultrastructural features of a well demarcated single abscess. Histopathological features are consistent with those observed in experimental models and human material. In addition this study allowed the ultrastructural definition of some of the capsule components as meningothelial-like structures and myofibroblasts. Their possible role in the evolution of the lesion is discussed.

The fate of human umbilical vein grafts as an infrarenal aortic substitute in monkeys.

The literature contains conflicting reports about the potential value of the processed human umbilical vein graft as an arterial substitute. With a view to a better understanding of the ultimate fate of this device, a series of long-term implantation was undertaken with a nonhuman primate model. Dardik Biografts were implanted as an infrarenal aortic substitute in 13 monkeys. Nine were put to death following complications after post-operative periods ranging from 3 months to 3 years, while four animals remain alive. No calcification or lipid infiltration was found, presumably because the animals were healthy. The patency rate was poor because of complications associated with thrombotic deposits and thinning of the graft wall after implantation, which led to stenosis and fibrous hyperplasia along the anastomoses. The external polyester mesh was found to encourage external tissue proliferation, which could not prevent the graft from dilating since it contained neither elastin nor smooth muscle cells. Because the places where the graft had been damaged before or during processing were the sites of thrombotic accumulation and initial collagen degeneration, it is essential to use only defect-free material. As a consequence the long-term durability of this graft continues to be questioned.

[Pathology of cerebral edema. I. Concept, etiopathogenesis and classification]. / Patología del edema cerebral. I. Concepto, etiopatogenia y clasificación.

Taking into account its complex pathogenesis, we stress the inadequacy of considering brain edema as a single clinical or pathological entity. Vasogenic, cytotoxic and hydrocephalic varieties are considered. Some clinical conditions underlied by the common morphologic feature of "status spongiosus" are discussed. The methods of investigation of brain edema are presented as well as problems concerning its diffusion and resolution.

[Pathology of cerebral edema. II. Experimental models and modifying agents]. / Patología del edema cerebral. II. Modelos experimentales y agentes modificadores.

Current experimental models of brain edema are described and evaluated for their contribution to the knowledge of basic processes involved in its production as well their contribution to the understanding of different clinical forms. The participation of each main pathogenic mechanism in a given experimental model is analyzed and proves to vary with each particular model and site studied. The importance of various experimental models in the evaluation of different therapeutic procedures directed to control the genesis and evolution of brain edema is stressed.

[Brain aging. Ultrastructural study of changes in man and laboratory animals]. / Envejecimiento cerebral. Estudio ultraestructural de algunas alteraciones en el hombre y en el animal de laboratorio.

The authors present a study on ultrastructural changes observed in aged human and animal brain. These changes are analyzed and compared with those described in classic optic microscopy and with those observed in experimental models of the same lesions.

[Ultrastructural semiology of lesions of striated muscle]. / Semiologia ultraestructural de las lesiones del músculo estriado.

Basic changes of the striated muscle fiber are described after the electron microscopy study of 200 surgical muscle biopsies from the Montevideo Neurological Institute. The inventory of these changes--true ultrastructural "signs" of muscle derangement--is presented according to the involved organelle. The value of these data is considerably enhanced by a systematic approach to the study of a muscle biopsy that should begin with the in situ examination of the muscle territory before the excision of the tissue. A throroughful histopathological study and a careful screening of semithin sections previous to the selection of areas for E.M. are also of paramount importance. The description of individual fiber lesions and that of the topography of the lesions should be accompanied by the study of vessels. nerves and muscle spindles. We stress that most of the ultrastructural findings are nonspecific. They will however acquire diagnostic value and greater interest when grouped and related to the clinical data and to the results of other diagnostic methods, besides morphology.

Metallic deposition in specimens presenting cavities using the sputter coater.

Local charging effects in small biological cavities during SEM observation are apparent, even after sputter coating. Using an experimental model, the thickness of metallic coating at the bottom of cylindrical cavities has been measured and found to be less than 50% the thickness on the surface, depending on the relation of diameter to depth of the cylinder.