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J Beaulaton

Publications and source records attributed to J Beaulaton.

18 recordsLinked to original sources
PubMed1989

Ultrastructural localization of calcium in post-mortem bovine muscle: a cytochemical and X-ray microanalytical study.

Calcium localization was demonstrated in bovine longissimus muscle using the antimonate precipitation technique in combination with electron probe X-ray microanalysis. Samples were taken each hour during the first 24 h post-mortem, and then after a storage period of 8 and 15 days. For all sampling times analysed, heavy precipitates were seen in dense parts of nuclei and on N-lines of myofibrils. Up to 18-20 h post-mortem, deposits were observed in sarcoplasmic reticulum at the level of triads. In comparison with the earlier post-mortem samples, myoplasmic precipitates were strongly increased at 4 h post-mortem, and just before rigor onset, at 19 h where intermyofibrillar spaces were completely blackened and triads were no more visible. These localizations of precipitates were still observed up to 15 days post-mortem. At these storage times, myofibril disruptions were seen at the level of N-lines. Wavelength-dispersive and energy-dispersive spectrometric analyses indicated that significant amounts of calcium occurred in the dense precipitates observed.

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PubMed1988

Programmed cell death: cytochemical and X-ray microanalytical characterization of calcium compartments in neuromuscular junctions during the normal breakdown of the intersegmental muscles in the giant silkmoth Antheraea polyphemus.

Calcium stores were cytochemically demonstrated using a combined oxalate-pyroantimonate method in the neuromuscular junctions of the degenerating intersegmental muscles in the giant silkmoth Antheraea polyphemus. The elemental composition of punctate precipitates of the reaction product was determined by electron probe X-ray microanalysis of unstained thin sections by energy-dispersive spectrometry and wavelength-dispersive spectrometry. The wavelength-dispersive spectra collected over terminal axons demonstrate a significant calcium signal and a trace of antimony. During the rapid lytic phase of spontaneous muscle degeneration, the calcium punctate deposits were detected in presynaptic terminals in the following sites: the synaptic vesicles and the mitochondria. Calcium precipitates were also found in the dense bodies and the mitochondria encountered in the glial convolutions. No calcium deposit was seen in the synaptic clefts and intercellular spaces of the subsynaptic reticulum of type I and type II. A comparison of calcium to antimony ratios between the terminal axons and the sarcoplasmic lysosomes revealed highly significant differences (P less than 0.001). Such a variability of the calcium to antimony ratio may be related to different conditions of precipitation or antimony diffusion in the different cell compartments. It was concluded that such synaptic terminals do not appear damaged in spite of the muscle degeneration and presumably continue to perform vital functions while the muscles are no longer contractile 20 h after adult ecdysis.

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PubMed1986

Programmed cell death. Cytochemical evidence for accumulation of calcium in mitochondria and its translocation into lysosomes: X-ray microanalysis in metamorphosing insect muscles.

The intersegmental muscles in the metamorphosing silkmoth Antheraea polyphemus were examined by two electron cytochemical procedures for demonstration of calcium compartmentation during the two-day period of degeneration after emergence. Muscle fibres were treated with either oxalate-pyroantimonate, or phosphate-pyroantimonate procedures. The elemental composition of the reaction product arising from the oxalate procedure was determined with electron probe X-ray microanalysis of unstained thin sections by energy dispersive spectrometry and wavelength dispersive spectrometry. The wavelength dispersive data revealed high peaks of calcium and antimony in the electron-dense precipitates. No reaction was obtained in muscles after treatment with the phosphate-pyroantimonate method. Shortly after the emergence of the moth, very few calcium deposits were found in the mitochondria, which also contained amorphous matrix densities. During the rapid lytic phase (17 and 30 h after ecdysis), the mitochondria, autophagic vacuoles sequestering mitochondria, and lysosomal dense bodies issuing from the latter were highly reactive in each muscle fibre. These results demonstrate that the collapse of tracheae (hypoxic conditions) is correlated with the calcium overload of mitochondria when the cell calcium homeostasis is apparently lost. Such calcium overload of the mitochondria appears to cause irreversible damage to these organelles which are then sequestered in autophagic vacuoles. This mitochondrial autophagic process leads to calcium translocation into a lysosomal compartment. We suggest that the calcium lysosomal stores may have a transient function of cell detoxification and stimulation of calcium-dependent degradative processes prior to the final muscle collapse.

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PubMed1979

Programmed cell death. electrophysiological and ultrastructural correlations in metamorphosing muscles of lepidopteran insects.

Individual spontaneously degenerating fibers of moths have been examined successively by electrophysiological and ultrastructural techniques. The correlations observed by this method have revealed two phases of lysis. The first lytic phase begins at or before the ecdysis of the moth. It is characterized by a probable but occult respiratory lesion, normal movement of the ions across the plasma membrane, and limited degradation of myofilaments and autophagy of mitochondria. There are nevertheless early degenerative changes in the Z-band and a slight swelling of the T system. The second lytic phase is introduced, at approximately 15 hr after ecdysis, by collapse of the tracheal airways. The collapse of the tracheae is followed within 2 or 3 hr by a drastic reduction of input resistance, depolarization of the fiber, and loss of contractility. The rate of proteolysis increases, and the remaining myofilaments lose all structural identity by the twentieth hour. During this period of rapid change, the electron density of the reticular portion of the dyads decreases before a compactive process increases their opacity. Neural elements degenerate secondarily. The early lytic phases are apparently non-lysosomal for the myofilaments, although organelles such as mitochondria, ribosomes, and glycogen are destroyed in autophagic vacuoles. Elimination of oxygen and collapse of the resting potential, with the presumed equilibration of intracellular ionic content, provokes a rapid dissolution of the myofilament, with continued autophagic elimination of the organelles.

Animals↗
PubMed1979

Hemocytes and hemocytopoiesis in Silkworms.

A brief review is presented of the current state of ultrastructure, cytochemistry, and physiology of the hemocytes and meso- and metathoracic peri-imaginal-wing organs in silkworms. According to the accepted morphological classification, five circulating types of hemocytes are recognized in Bombyx mori as well as in Antheraea pernyi. They are prophemocytes or stem cells, plasmatocytes or pre-differentiated cells and three specialized cells, granulocytes, spherule cells and oenocytoids. During post-embryonic development the last four types are the most common in the circulating hemolymph. Plasmatocytes are considered to be pluripotent cells from which granulocytes, spherule cells and oenocytoids are derived. Contrary to the situation in most insects the plasmatocytes are not phagocytic in Antheraea. The granulocytes are efficient phagocytes. Both plasmatocytes and granulocytes are involved in pinocytosis. Another possible function of the granulocytes is hemolymph coagulation. The function of the spherule cells which contain a paracrystalline material (muco- or glycoproteins) is by no means clear. The phenoloxidase activity found within the cytosol of oenocytoids appears effective against the natural monophenol and diphenol substrates. The involvement of oenocytoids in the complex metabolism of phenols and particularly in the production of plasma phenolases has been reported. The mitotic division of five circulating hemocyte types is well known and was long regarded as the only mechanism of postembryonic hemocyte production. We present for silkworms, experimental evidence of the hemocytopoietic function of the meso- and metathoracic organs surrounding the imaginal wing discs. Ablation experiments demonstrate that the mitotic activity of free hemocytes is unable to maintain the normal hemocytogram in the absence of the two paris of organs. These organs are typically divided into cell islets ensheathed by a connective tissue membrane. Two types of islets may be classified by the disposition of the cells : the compact islets or aggregations of stem cells and the reticulate islets which are mainly composed of hemocytes at different steps of differentiation. The relative number of prohemocytes in the total hemocyte population ranges from 84 to 97 p. cent in organs of Antheraea pernyi. This well-defined cell type appears to be the major hemocyte type in hemocytopoietic organs. In Antheraea, the mitotic index (the relative number of mitotic hemocytes in the total cell population) varies from 0.5 to about 3 p. cent. Finally, our data direct attention to cyclic functional changes such as mitotic divisions and hemocyte differentiation which run parallel to the molting cycle.

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PubMed1976

[Glycoproteins in the microtubular granules of the paragonial secretory cells in Drosophila melanogaster Meig (author's transl)].

Cytochemical observations of the paragonial microtubular granules during the first 2 weeks after emergence have shown the ultrastructural localization of glycoprotein in peripheral or central matrices by periodic acid-thio-carbohydrazide-silver proteinate method (PATAg). The microtubules do not appear to contain glycoprotein moiety. The functional significance of the components of paragonial secretion is discussed.

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