Electron microscopic and cytochemical studies of the thrombocytes of the tortoise (Geoclemys reevesii)

The thrombocytes of the tortoise (Geoclemys reevesii) were studied at the electron microscopic level. The presence of a surface connected canalicular system, composed of numerous anastomosing canaliculi, has been demonstrated by the ruthenium red technique. However, monoamine storage organelles have not been found in tortoise thrombocytes. Peroxidase activity is localised to the nuclear envelope and the rough surfaced endoplasmic reticulum, but is not present in the Golgi apparatus or granules. Acid phosphatase is localised to the large inclusions with myelin bodies, but is not found in the electron-lucent small granules. These results are discussed in relation to those from comparable studies of mammalian and submammalian thrombocytes.

Uptake of 3H-dopamine in megakaryocytes and blood platelets measured by quantitative electron-microscope autoradiography

We studied the uptake of dopamine by mature megakaryocytes and blood platelets in mouse spleen after a single intraperitoneal injection of 3H-dopamine. In order to compare the uptake of 3H-dopamine in mature megakaryocytes and blood platelets, we used quantitative autoradiography at the electron-microscope level. Dense accumulations of silver grains were observed on both mature megakaryocytes and blood platelets; all other tissue elements of the spleen exhibited considerably less dense labeling. No significant differences with regard to dopamine uptake were observed in megakaryocytes and blood platelets. This is in contrast to the previous finding of very different patterns of 3H-5-hydroxytryptamine labeling in mature megakaryocytes and blood platelets (Daimon and Uchida 1985). The results of the present study provide new evidence in favor of the hypothesis that the active uptake mechanism of dopamine through the plasma membrane is different from the uptake mechanism of 5-hydroxytryptamine.

Ultrastructural evidence of the existence of the surface connected canalicular system in the thrombocyte of the shark (Triakis scyllia)

The existence of the surface-connected canalicular system has been demonstrated ultrastructurally in shark [Triakis scyllia) thrombocytes using the ruthenium red method to fix and stain the glycocalyx. In ultrathin sections fixed routinely in glutaraldehyde followed by osmium tetroxide, numbers of electron-lucent vesicles are distributed throughout the cytoplasm. Since ruthenium red-positive reaction product is deposited on the inner surface of these vesicles, they are defined as the surface-connected canalicular system. Moreover, the semithin sectioned thrombocytes fixed by the ruthenium red method provide evidence that the surface-connected system is not composed of vesicles but also of numerous canaliculi. These results suggest that the surface-connected canalicular system is one of the most basic organelles of the thrombocyte system, common to submammalian species and to mammals.

Ultrastructural distribution of peroxidase in thrombocytes of mammals and submammals

The localization and distribution of peroxidase (PPO) activity were studied ultracytochemically in thrombocytes from lampreys, carps, frogs, snakes, tortoises, rabbits, sheep, dogs, and monkeys. PPO activity was not detectable in the thrombocytes of lampreys, carps, frogs, and snakes. However, this enzyme activity was demonstrated in the nuclear envelope and endoplasmic reticulum of tortoise thrombocytes. Dog and monkey thrombocytes (blood platelets) exhibited PPO activity in the dense tubular system, but this enzyme activity was not detectable in rabbit and sheep thrombocytes. Our observations are interpreted to suggest that thrombocytes from animals lower than amphibia are peroxidase negative. Furthermore, it can be said that thrombocytes from animals higher than reptiles are generally positive, although there are exceptions. PPO activity was localized in the endoplasmic-reticulum system, but not in the cytoplasmic granules of thrombocytes common to submammals and mammals. In this study, we also compared the distribution of peroxidase activity in thrombocytes, neutrophils, and eosinophils and conclude that these are significant differences in the distribution of PPO and myeloperoxidase.

Morphometric study on the absolute volume of differentiating hepatocytes in rats

Quantitative changes in the mean absolute volume of rat hepatocytes during prenatal development were studied by light microscopic stereological methods. Combining these light microscopic measurements with electron microscopic relative volume (volume density) data (Daimon et al. 1982) enabled the evaluation of the mean absolute volumes of cytoplasmic organelles of fetuses and newborns. On the 15th day of gestation the mean absolute volume of hepatocytes was 1,523 +/- 10.7 microns3. After 3 days hepatocytes were enlarged 66.2% (2,531.5 +/- 108.2) and at birth 157.1% (3,915.6 +/- 190.8). The comparison of the absolute volume and the volume density of each cell organelle made possible the interpretation of much functional and morphometric data of the development of hepatocytes.

Precursors of monoamine-storage organelles in developing megakaryocytes of the rat

Identification and distribution of the precursors of amine-storage organelles in rat megakaryocytes during cell maturation were studied, using the uranaffin reaction for adenine nucleotide. The precursors of the amine-storage organelles appeared as 200-300 nm vesicles having an uranaffin electron dense granule, whereas they appeared as empty vesicles by conventional glutaraldehyde-OsO4 fixation. X-ray probe microanalysis confirmed the existence of U and P in the uranaffin reaction positive vesicles. The precursors appeared in the immature megakaryocytes, especially at the trans(mature) face of the Golgi apparatus, and rapidly increased in number in the maturing cells. The size of the uranaffin granules in the precursor organelles increased gradually during cell maturation and became almost equivalent to the dense body of blood platelets in the final stage of cell maturation.

Elemental composition of the dense bodies of rat platelets determined by electron probe x-ray microanalysis of freeze-substituted sections

A semiquantitative x-ray microanalytical study was made of dense bodies in rat and human blood platelets prepared by freeze substitution. After the freeze substitution, electron dense bodies containing 5-hydroxytryptamine(5-HT) were well preserved. Electron probe x-ray microanalyses clearly defined species differences in the cations of dense bodies of rat and man. Direct calculation of elemental concentration ratios demonstrated a high level of Mg, with lesser amounts of K and Ca in rat, while there was a negligible level of Mg in man but a high amount of Ca. These results indicate that freeze-substitution is a suitable preparation for the study of diffusible electrolytes which may open the way to quantitative analysis using appropriate standards for analytical electron microscopy of resin sections.

Cytochemical demonstration of amine-storing vacuoles and lysosomes in the chicken thrombocytes

A combined electron microscopic and cytochemical study of the thrombocytes of the chicken has clearly identified the amine-storing organelles and lysosomes. A chromaffin positive-reaction product was observed on the inner surface and the granules of the large electron-lucent vacuoles. No acid phosphatase activity was localized in these amine-storing vacuoles. However, the acid phosphatase activity was observed in the small vesicles, the primary lysosomes, and in the large electron dense inclusions with myelin which may be secondary lysosomes. The results of this study suggest that the large empty vacuoles, with one or two very dense osmiophilic peripherally-situated granules, in the chicken thrombocytes are comparable to the vesicles with electron dense materials called "dense bodies" in mammalian thrombocytes.

Intracellular calcium translocation during contraction in vertebrate and invertebrate smooth muscles as studied by the pyroantimonate method

The intracellular localization of activator Ca and its translocation during the mechanical activity were studied on vertebrate and invertebrate smooth muscles by fixing muscle fibers with a 1% OsO4 solution containing 2% potassium pyroantimonate for electron microscopic examination. When guniea-pig taenia coli, Mytilus anterior byssal retractor muscle, and Dorabella longitudinal body wall muscle were fixed during the relaxed state, electron-opaque pyroantimonate precipitate containing Ca was localized along the inner surface of the plasma membrane and at other membranous structures in close apposition to the plasma membrane, in accordance with physiological evidence that these muscles contain intracellularly stored activator Ca. When they were fixed during the contracted state, the precipitate was distributed diffusely in the myoplasm in the form of small particles, indicating the release of activator Ca from the peripheral structures. The contraction in dog coronary artery smooth muscle appears to be associated with the inward movement of extracellular Ca. In accordance with this, the resting coronary artery muscle fibers exhibited the precipitate in the lumen of the caveolae, i.e., the bottle-shaped plasma membrane investigations, but not at the peripheral intracellular structures, though the contracted fibers showed the diffuse distribution of the precipitate in the myoplasm. These results indicate that the pyroantimonate method is very effective in studying the translocation of activator Ca in various types of smooth muscles.

Correlated ultrastructural and morphometric studies on the liver during prenatal development of rats

Quantitative and qualitative changes in liver tissues during prenatal development were studied by electron microscopy and morphometry. On the 15th day, 30% of fetal liver volume consisted of hepatocytes, and the extrahepatocytic spaces amounted to 63%. The hemopoietic cells occupied 93% of the extrahepatocytic spaces. Immature bile canaliculi were observed and amounted only to 0.14% of extrahepatocytic spaces. The hepatocytes were irregular in shape and possessed several large lipid droplets which amounted to 19% of the cytoplasm. Although the rough surfaced endoplasmic reticulum (RER) was well developed, the smooth surfaced endoplasmic reticulum (SER) was not yet differentiated. The typical peroxisomes with nucleoid and glycogen were not observed in the cytoplasm. On the 18th day the volumetric densities of hepatocytes and bile canaliculi were increased. The typical peroxisomes with nucleoid appeared in the cytoplasm. The accumulation of glycogen which amounted to 12% of the cytoplasmic volume had taken place, while the volume of lipid droplets decreased significantly. In glycogen areas the differentiation of SER began. At birth the histogenesis of the liver was well established. The hemopoietic cells decreased in number and were confined to perisinusoidal spaces. The volumes of biliary capillaries and sinusoids were comparable with these of young rats now. The volumetric density of hepatocytes increased and occupied about 74% of the liver. The volumetric densities of mitochondria, SER, peroxisomes, secondary lysosomes, and lipid droplets increased significantly in comparison with those of the 18 days old fetus, while RER, Golgi area, and primary lysosomes were rather constant. The volumetric density of glycogen decreased rapidly at birth.

The surface connected canalicular system of carp (Cyprinus carpio) thrombocytes: its fine structure and three-dimensional architecture

The presence and the three dimensional distribution of the surface connected canalicular system (SCCS) in thrombocytes of a teleost, Cyprinus carpio, were studied using a transmission electron microscope, a high voltage electron microscope and a scanning electron microscope. When the specimens were fixed routinely in glutaraldehyde followed by osmium tetroxide, numerous electron lucent vesicles and canaliculi were distributed throughout the cytoplasm. As ruthenium red-positive reaction product was observed on the inner surface of the vesicles and canaliculi, these are defined as the SCCS of carp thrombocytes. In the stereo-pair of the photographs of thick sectioned specimens and the plastic reconstruction of serially sectioned thrombocytes, we succeeded in finding the whole structure of the SCCS which is composed of numerous anastomosing canaliculi. Scanning electron micrographs revealed many crater-like depressions throughout the cell surface which seem to be the openings of the SCCS.

Fine structural distribution of the surface-connected canalicular system in frog thrombocytes

The existence of the surface-connected canalicular system (SCCS) has been demonstrated in semithick sections of the frog thrombocytes by the use of a high voltage electron microscope. The SCCS of the thrombocytes in Rana catesbeiana and Rana nigromaculata consists of numerous canaliculi and vesicles with a diameter of 250 nm, which join with one another to make a complex network throughout the cytoplasm. Although the SCCS of Xenopus laevis fits well into the pattern described in Rana catebeiana, the diameter of the canaliculi of the SCCS is about 500 nm. The results of this study suggest that the SCCS is a specific organelle of the thrombocyte system common to submammals and mammals.

Electron Microscopic Analysis of Subcellular Distribution and Translocation of Ca ION in Human Platelet

For the analysis of the subcellular distribution of Ca ion in human platelet, the washed platelet suspension was fixed in the potassium antimonate-OsO4 method or in the potassium oxalate-glutaraldehyde method without post-fixation with OSO4. The STEM-images were observed with scanning image system fitted with the transmission electron microscope without electron staining.

The dense deposition of antimonate or oxalate was found in plasmalemma, the membrane of open canalicular system, mitochondria, α-granules and dense bodies. It was revealed with the energy dispersive type electron probe x-ray microanalyzer system that the deposition of oxalate was exclusively composed of Ca.

In the process of platelet aggregation with various agents, α-granules and dense bodies were expelled out together with Ca, which suggested the least role of these ion depositions in the aggregation and clot retraction. The translocation of antimonate deposits was not observed in the Verapamil-treated platelets even after the addition of aggregation agents. This phenomenon indicated that this drug inhibited the release of Ca from the Ca-storing organelles. The distribution of Ca was identical in the platelets of a case of thrombasthenia and the translocation of Ca was not observed with the addition of various aggregating agents.

Ultrastructural localization of calcium around the membrane of the surface connected system in the human platelet

The localization of calcium in the membrane system of human platelets was determined by ultrahistochemical methods equipped with an electron probe x-ray microanalyzer. After potassium oxalate-glutaraldehyde treatment large amounts of electron opaque precipitates were observed around the membrane of the surface connected system. Electron probe x-ray microanalysis clearly defined that the precipitates were composed of calcium oxalate. The localization of calcium on the membrane of the surface connected system was also confirmed even after treatment of the platelets with potassium antimonate-OsO4. These results support a model which depicts the surface connected membrane system taking part in the store and the transport of calcium.

Electron microscopic and cytochemical observations on the membrane systems of the chicken thrombocyte

A combined electron microscopic and cytochemical study of the thrombocytes of the mature chicken has demonstrated the existence of two membrane systems, the surface connected system (SCS) and the dense tubular system (DTS). The SCS consists of light tubules and vacuoles which are in continuity with the plasmalemma. A ruthenium red-positive reaction product was observed on the inner surface of this membrane system. Ferritin particles were present in the tubules and the vacuoles of the SCS after the thrombocytes had been incubated in vitro with ferritin. The DTS consisted of the nuclear envelope, the rough-surfaced endoplasmic reticulum, dense tubules and concentric double membrane structures, all of which give a peroxidase-positive reaction. Although actual continuity between the DTS and the SCS of thrombocytes was not observed in this study, close approximation between the two systems was observed at many points. These results are discussed in relation to those from comparable studies of human platelets.

Electron microscopic and enzyme cytochemical studies on granules of mature chicken granular leucocytes

Detailed morphologic and enzyme cytochemical analysis was carried out by electron microscopy on granules of mature granulocytes obtained from the circulating chicken blood. Heterophils possessed three types of granules: large, rod-shaped, dense (Type I); medium sized, oval, light (Type II); and small-core (Type III). Acid phosphatase activity was present in Type I granules, but peroxidase and alkaline phosphatase were not demonstrable. The cytochemical nature of Types II and III granules remains unknown. Eosinophils contained only one type of granule, which was circular and had electron-opague contents. Both peroxidase and acid phosphatase, but not alkaline phosphatase, were present, indicating that the granules are lysosomes like the granules of mammalian eosinophils. Basophils possessed two types of granules, the characteristic large basophilic granules (Type I) and small dense granules (Type II). Acid phosphatase activity was found in only a small proportion of Type I granules: peroxidase and alkaline phosphatase were not demonstrable.

The presence and distribution of glycogen particles in chondrogenic cells of the tibiotarsal anlage of developing chick embryos

The distribution and localization of glycogen particles in mesenchymal cells, chondroblasts and in young, hypertrophic and degenerating chondrocytes of the tibiotarsal anlage of developing chick embryos were examined ultrastructurally using the periodic acid--thiocarbohydrazide--silver proteinate. The distribution of glycogen particles increased with the degree of differentiation and maturation of the chondrogenic cells. Mesenchymal cells showed minimal content of glycogen particles which gradually increased in the chondroblasts. The young chondrocytes further showed increased glycogen particle content compared to chondroblasts. This content reached a maximum level in hypertrophic chondrocytes. This level subsided in degenerating chondrocytes which showed a much reduced distribution of glycogen particles compared to hypertrophic chondrocytes. The morphological nature of glycogen particles depended on the degree of cellular differentiation. Both mesenchymal cells and chondroblasts contained single particles, while the glycogen particles of chondrocytes aggregated and formed a series of interconnected particles.

Ultrastructural localization of acid protein polysaccharides and calcium in the vacuoles of the chicken thrombocyte

The coexistence of acid protein polysaccharides and calcium in the vacuoles of chicken thrombocytes were studied by means of ultrahistochemical methods and electron probe X-ray microanalysis. The thrombocytes possessed large vacuoles of a surface connected membrane system. After both ruthenium red staining and tannic acid fixation the innersurface coat of vacuoles was always strongly and continously visualized. Electron microscopic X-ray microprobe analysis of antimonate precipitates in thrombocytes fixed in K-antimonate-OsO4 revealed calcium localization on the innersurface of vacuoles. From these facts it seems likely that the vacuoles of the surface connected membrane system may take part in the pool or the transport of calcium.

The passage of thiamine across the rat placenta and its uptake by the fetal organs. II. The uptake of thiamine by fetal organs

Having injected 3H-thiamine into the maternal bloodstream of rats in their 15th day of pregnancy, the uptake by the fetal organs (liver and cardiac muscle) of the 3H-thiamine which had been transported across the placenta was studied by electron microscope autoradiography and by measuring the radio-activity of the tissues, using the same methods reported in the first paper of this series. In the fetal liver both developed silver grains and radioactivity were found in greates amounts in specimens collected 5 hrs after injection. Developed silver grains were abundant in the mitochrondria, Golgi apparatus, rough-surfaced endoplasmic reticulum, glycogen area, and nucleus, indicating that these cell organelles take up thiamine and utilize it for the cell metabolism. In the fetal cardiac muscle, the developed silver grains and radioactivity were found in greatest amounts 2 hrs after injection. The silver grains were abundant in the glycogen area, Golgi apparatus, and myofibrils, but they were especially abundant in the mitochondria. This indicates that thiamine is taken up by these organelles and employed in the cell metabolism.

The passage of thiamine across the rat placenta and its uptake by the fetal organs. I. The transport of thiamine across the placenta

It is well known that thiamine is highly soluble in water. However, if chloroplatinic acid (H2PtCl6) is used during fixation, an insoluble, electron-dense thiamine-PtCl6 precipitate is formed. Using this method we performed electron microscope autoradiography of the placental labyrinth of rats in their 15th day of pregnancy after injection into the maternal bloodstream of 3H-thiamine, and we also measured the radioactivity of the tissues, in order to study the transport of the thiamine across the placenta. Both developed silver grains and radioactivity were found in the largest amounts 30 min after injection; the amounts of both declined after 2 hrs and declined further after 5 hrs. The majority of the developed silver grains were localized in the smooth-surfaced endoplasmic reticulum, which is generally thought to be the vehicle for the transport of materials in the cell, while in the mitochondria, Golgi apparatus, etc. the grains were few. Considering the substantial depletion of the amounts of both sivler grains and radioactivity after the relatively short time of 5 hrs, we conclude that the greater portion of the thiamine passes quickly across the placenta to the fetus, where it is used in the metabolism of the fetal organs, and that only a small part of the thiamine is retained in the placenta for its own metabolism.