Subcellular Responses Research Articles

Subcellular responses in frog pituitary gonadotrophic cells to constant environmental conditions: a morphometric study

An ultrastructural study of the pars distalis of the pituitary in Rana ridibunda specimens subjected to constant environmental conditions revealed significant structural differences which indicate a short-time increase in the activity of gonadotrophic cells. Planimetry was used for morphometric and stereological analysis of the rough endoplasmic reticulum, Golgi complex, secretory granules and lysosomes. The presence of a vesicular endoplasmic reticulum throughout the cytoplasm of gonadotrophic cells was observed in the pituitary gland of the intact frog. After 7 days of constant environmental conditions, there was an increase in the volume density of the endoplasmic reticulum vesicles, while on the 11th day there was a slight reversal in the vesicle content that was complete the 15th day. In the hypertrophy of the endoplasmic reticulum, the larger vesicles (bigger than 0,52 micron2) play a more important role than the smaller ones (similar to the endoplasmic reticulum observed in control cells). However, the small vacuoles were also hypertrophied in relation to the control. Degranulation was also observed after 7 days of constant environmental conditions. On the 15th days, there was an increase in the numerical density of secretory granules and lysosomes compared to the control while their volume density was similar to the control.

Cellular responses to free grafting of the extensor digitorum longus muscle of the rat

The cellular and subcellular responses related to the survival or destruction and subsequent regeneration of muscle fibers within the freely grafted extensor digitorum longus muscle of the rat were examined by light and electron microscopy. A small number of fibers at the periphery of the grafts survived the initial ischemia but underwent denervation changes and accumulated lipid deposits. The majority of fibers in the grafts, however, became ischemic and underwent an intrinsic degeneration within 4 hours. Cell-mediated destruction of the degenerating fibers occurred as the grafts became revascularized. The basal laminae and some of the satellite cells were the only elements of the original fibers that persisted. Regeneration began at the periphery of the graft within three days after grafting and reached the center about three days later. After phagocytosis of the original fibers, presumptive myoblasts within the grafts differentiated into myoblasts and myotubes. The formation of myotubes followed a biphasic pattern of development comparable to that of normal fetal muscle. Although most of the myotubes were formed within the basal lamina remaining from the original fiber, there was also evidence for regeneration outside the basal lamina. Myotubes matured into muscle fibers which were essentially normal in appearance when examined up to 180 days after grafting. Some fibers, however, were atrophic, presumably due to a failure to become innervated, and some fibers were joined by myo-myous junctions. Pre-denervated grafts and Marcaine-treated grafts were also examined. There were more surviving fibers in pre-denervated grafts, and cell-mediated destruction of degenerating fibers proceeded more rapidly than in normal grafts. No surviving fibers were found in Marcaine-treated grafts. The changes in these grafts were otherwise similar to normal grafts. A schematic model of the spatial and temporal sequence of degeneration and regeneration within a free muscle graft is presented.

An Ultrastructural Study of Inclusions and Disease Development in Plant Cells Infected by Cowpea Chlorotic Mottle Virus

SUMMARY Subcellular responses of leaf cells to infection by bean yellow stipple virus, a strain of cowpea chlorotic mottle virus (CCMV), in two varieties of bean, Phaseolus vulgaris L., and three varieties of cowpea, Vigna sinensis (Torner) Savi, were investigated by electron microscopy. Amorphous inclusions (AI), filamentous inclusions (FI), which appeared to be characteristic of CCMV infection, and membranous vesicles (30 to 100 nm in diam.), containing fibrils and virus particles, were consistently found in cells in all infected hosts. The AI occurred in cytoplasm as granular masses sandwiched between the rough endoplasmic reticulum (RER) and the nuclear envelope (NE) at an early stage of infection. In later samples AI were scattered randomly in masses of various sizes, numbers and shapes. Electron lucent areas containing virus particles were present in large masses of AI. The FI were long, unbranched, flexuous, rod-like structures of 17 nm in diam. They appeared after AI were formed in the cytoplasm and also occurred in the nucleus. Cytoplasmic FI were usually associated with AI, and nuclear FI with the nucleolus. Intranuclear virus particles were observed only when FI were located in the nuclei. Both FI and AI were similarly degraded by treatment with subtilisin or pronase, but virus particles were not. Fibril-containing vesicles arising from the membranes of NE and RER were concurrently present in the perinuclear space and the lumen of ER associated with AI and FI.

Autoradiographic study of the rejection phenomenon in tissue culture

1. 1. A model system to study cellular and subcellular responses of skin allografts after transplantation has been established. 2. 2. The techniques of tissue culture and autoradiography with tritiated thymidine have been utilized to document sites of DNA synthesis and, therefore, mitotic activity after transplantation. 3. 3. DNA synthesis within the basal layer of epithelium decreases as rejection progresses, while mitotic activity in the round cell infiltrate beomes more evident. 4. 4. The possibility of selective irradiation of DNA and control of antibody production at this level is discussed.

Subcellular responses of mesophyll cells to wild cucumber mosaic virus

Particles of wild cucumber mosaic virus (WCMV) were found in various concentrations in mesophyll cells of Marah oreganus. When low in concentration, virus particles were scattered in the ground cytoplasm. When particles were highly concentrated, crystalline aggregates occurred. Cells in an advanced stage of breakdown had lost their plasma membranes and virus particles occurred within chloroplasts, but were not in crystalline arrays. Chloroplasts contained numerous double membrane-bound vesicles, and single membrane-bound vesicles were present in the ground cytoplasm surrounding the chloroplasts. Similar vesicles have been reported in turnip yellow mosaic virus (TYMV)-infected cells. WCMV and TYMV are serologically related and similar in size and external morphology. They show a similar chloroplast pathology, although not in a common host, The diagnostic value of chloroplast vesicle formation is discussed.

An in vitro study of flow response by cells

Living cells grown as an attached, confluent monolayer are subjected to a steady, uniform laminar flow. The cells are grown in a specially designed cell culture chamber in which the flow conditions over the cells may be precisely defined and are experimentally verified. The flow conditions at the cell proximity are described, and the cellular and subcellular responses to the observed flow conditions are presented. The observed responses of the cells in the attached geometry are described for shear stresses ranging from 10 −3 to 10 1 dyn/cm 2. The relative importance of the rheological properties of the cellular components is seen to vary with the magnitude of the shear stress applied. The significance of such flow studies is presented in relation to their possible use in evaulating mechanical site predilection in atherosclerosis.

Subcellular responses to localized infection of Chenopodium quinoa by pokeweed mosaic virus

Subcellular responses to localized infection of Chenopodium quinoa by pokeweed mosaic virus