Smooth endoplasmic reticulum and other agranular reticulum in frog retinal photoreceptors.

Frog retinal photoreceptors are favourable material for studying a number of unresolved issues concerning the interconnections, three-dimensional organization and functions of intracellular membrane systems in neurons. At least two distinct regions of smooth endoplasmic reticulum (SER) are present in these cells. One region, the subellipsoid SER, is located in rod cells at the base of the mitochondria-rich ellipsoid region, and is comprised of arrays of stacked tubules which exhibit frequent continuities with the rough endoplasmic reticulum (RER).

Ultrastructural localization of glycerolipid synthesis in rod cells of the isolated frog retina.

The incorporation of two glycerolipid precursors, 3H-glycerol and 3H-choline, into rod cells of the isolated frog retina has been studied using quantitative electron microscope autoradiography. The results indicate that the endoplasmic reticulum (ER) is the major site of early incorporation of these precursors suggesting that the ER is the primary site of lipid synthesis. Of the different types of ER present in rod cells, the rough ER (RER) and nuclear envelope predominate in this activity.

[Gastric lesions in closed abdominal injuries (considerations on 8 cases)].

The Authors present 8 cases of traumatic lesions of the stomach, during the course of closed abdominal trauma, observed in the First Aid and Emergency Surgery Division of the Niguarda Ca' Granda Hospital, Milan, in the years 1970-1979. They take this as the starting point for a re-examination of the etiopathogenetic and anatomopathological data, and for diagnostic, prognostic and therapeutic considerations.

[Considerations on two cases of spigelian hernia (author's transl)].

The Authors describe two cases of abdominal hernia through the linea semilunaris (spigelian hernia) of their own observation; they outline the anatomic substrate and clinical picture of this condition and conclude by advocating surgical correction as a constant indication.

An electron microscopic study on the type I pneumocyte in the cat: pre-natal morphogenesis.

This investigation describes the pre-natal morphogenesis of the type I pneumocyte subsequent to its differentiation from pulmonary epithelium. Cells lining subpleural alveolar septa were photographed from serial sections with the electron microscope, and a three-dimensional representation of each cell was obtained by transferring the contours of the cell membranes from montages to transparent plastic sheets which were then spaced to scale and stacked. The results of this study indicate that: The nascent blood-air barrier of a 50-day reconstructed cell was twice as thick as the average definitive barrier; definitive barrier thickness was observed in some areas in a 63-day reconstructed cell; the amorphous component of elastic tissue which appears peripherally in septal connective tissue during pre-natal morphogenesis may be directly juxtaposed to the basal lamina of the alveolar epithelium; the orientation of the cell junction between a pneumocyte and its neighboring cells, as observed in sections of alveolar septa, changes as the contour of the pneumocyte changes from simple abutment to overlapping patterns.

An electron microscopic study on the type I pneumocyte in the cat: differentiation.

This investigation describes the differentiation of the type I pneumocyte from undifferentiated pulmonary epithelium. Cells lining subpleural alveolar septa were photographed from serial sections with the electron microscope and a three dimensional representation of each cell was obtained by transferring the contours of the cell membranes from micrographs to transparent plastic sheets which were then spaced to scale and stacked. The results of this study indicate that: (1) the only reliable criterion for differentiating between type I and type II cells is the commencement of attenuation of the type I cell; (2) differentiation of the type I cell occurs via the formation of one or more cytoplasmic attenuations that eventually fuse peripherally, thereby surrounding the unattenuated cell soma; (3) with respect to individual cells, blood-air barriers tend to form in distal areas of the attenuating cytoplasm before proximal areas; (4) both type I and type II pneumocytes retain certain characteristics that reveal their common origin.