[Morphology of glycogen. Electron microscopic study of the negative stains of particulate glycogen]

1H NMR spectroscopy study of the dynamic properties of glycogen in solution by steady-state magnetisation measurement with off-resonance irradiation

The dynamics of size-selected fractions of glycogen in solution have been investigated by proton NMR spectroscopy, using a recently described relaxation study method which relies on strong offresonance irradiation. The dependence of the steady-state magnetisation on angle and intensity of the effective radio-frequency field was measured and compared to theoretical curves derived from different models of motion. Absence or presence of contributions to relaxation from molecular motions on the microsecond time scale can be tested with this method, without having to resort to models. We found that glycogen dipolar relaxation did not result from isotropic Brownian rotation, and despite some contribution from slow motion (> 1 microsecond) to relaxation in glycogen alpha-particles extracted from rat liver, bulk movement of the molecules did not appear to participate in averaging the dipolar term to zero. Whereas hepatic glycogen rat beta-particles and commercial oyster glycogen displayed very similar relaxation properties, alpha-particles showed significantly different behaviour. However, all results were compatible with a diversity of movements within the molecule, ranging from freely rotating pyranoside rings through collective chain motion and possibly to bulk movement of the beta sub-units within the alpha-particle.

Glycogen biogenesis in rat 1 fibroblasts expressing rabbit muscle glycogenin

Glycogenin, a self-glucosylating protein involved in the initiation of glycogen biosynthesis, varies in intracellular concentration from barely detectable in liver to a high level in muscle. The effect of increasing the glycogenin level on glycogen synthesis was studied in rat 1 fibroblasts stably overexpressing rabbit muscle glycogenin. In the presence of glucose, all of the expressed glycogenin was attached to polysaccharide and the free protein could only be detected by western blot analysis after incubation of cells in a glucose-depleted medium or treatment of the cell extract with alpha-amylase. In control cells, increased extracellular glucose concentrations promoted translocation of glycogen synthase from the soluble to the pellet fraction with an increase in the associated glycogen. Overexpression of glycogenin did not affect total intracellular glycogen and glycogen synthase levels at any concentration of glucose but significantly reduced glucose-induced accumulation of insoluble glycogen and translocation of glycogen synthase. Immunofluorescence analysis revealed a diffuse cytoplasmic distribution of glycogenin expressed in rat 1 cells. In rat 1 cells incubated with glucose, discrete deposits of glycogen were detected by staining with HIO4/Schiff but this was eliminated by overexpressing glycogenin. Analysis of [14C]glucose- or [35S]methionine-labeled extracts from glycogenin-expressing cells by continuous polyacrylamide gel electrophoresis and by two-dimensional gel electrophoresis revealed a continuum of glycogenin-containing species from low molecular mass to sizes significantly greater than 400 kDa. We conclude that (a) overexpression of glycogenin does not enhance glycogen synthesis but causes production of more, smaller, glycogen molecules with a concomitant change in their intracellular localization; (b) glycogenin and elevated glucose have opposing effects on the distribution of glycogenin and glycogen synthase in rat 1 cells; and (c) the biogenesis of glycogen in rat 1 cells occurs without the accumulation of any major intermediate form.

Glycosomes--the organelles of glycogen metabolism

This article reviews the data concerning the electron microscopical interpretation of glycogen. It demonstrates that glycogen in the cell is associated with the enzymes involved in its metabolism and that the glycogen-protein complex forms morphologically distinct cell organelles called glycosomes. Glycogen can be visualized in the electron microscope (EM) by histochemical procedures, or by negative staining, but it does not react with heavy metals such as uranium and lead. The protein component of glycosomes, stainable by heavy metals, appears in EM as 20-30 nm granules. While biochemical findings have long indicated the association of glycogen and protein in the cell, morphological interpretation traditionally defined the protein component of glycosomes as particles of glycogen. Accordingly, the term alpha or beta particles, introduced to define particles of glycogen, became subsequently applied to the protein component visible in sections stained by heavy metals. The history of microscopic research reveals the conditions which led to such interpretation. Morphological analysis of the reaction of glycosomes to the acids shows that glycosomes deposited free in the cytosol (lyoglycosomes) are acid labile, whereas the others (desmoglycosomes), intimately associated with different cellular structures, are acid-resistant. These 2 groups correspond to lyo- and desmoglycogen distinguished in early biochemical studies on the basis of their different resistance to the cold trichloroacetic acid. The theory of glycosomes provides a new paradigm which clarifies numerous unexplained data in the microscopic literature on glycogen, and opens a vast field for the research on the cellular metabolism of glycogen, with the use of modern molecular and cellular biology techniques.

Retention of glycogen in cryosubstituted mouse liver

A periodic acid-Schiff (PAS)-type reaction in which osmium-ammine was used as the reagent was carried out on ultrathin sections of mouse liver in order to study the extent to which glycogen is preserved. Comparisons were made between tissues that were, on the one hand, conventionally fixed and dehydrated and, on the other, those that were high-pressure frozen and cryosubstituted in acetone. A control was carried out for both groups using a routine uranyl acetate-lead citrate staining procedure. In the latter case, glycogen could be identified as electron-clear patches in the cytoplasm whereas after a PAS-type reaction, glycogen became darkly contrasted. In the case of conventionally fixed samples, glycogen appeared to display a certain amount of clumping separated by gaps whereas in cryosubstituted specimens it was denser and often showed elongated interconnecting structures. These results suggest that cryofixation and cryosubstitution provide better preservation of glycogen in mouse liver tissue compared with chemically fixed specimens. In addition, the fine structure of glycogen appears more homogeneous, showing less aggregation in cryo-treated liver samples.

Reliability of histological criteria in glycogen storage disease of the liver

The histological criteria for the diagnosis of the hepatic glycogen storage diseases (GSDs) are well recognized. However, some biopsies do not have the characteristic features peculiar to their type and not all biopsies with GSD changes are confirmed by enzyme analysis. We reviewed the liver biopsies of 59 patients with clinically suspected GSD. The enzyme defects in 31 of 40 patients with GSD morphology were demonstrated by enzyme analysis. We describe the history and histology of the 9 patients with GSD morphology not confirmed by enzyme analysis, present the diagnoses of the 19 patients shown not to have a GSD, and evaluate the reliability of the morphological criteria used to distinguish the types of hepatic GSD. In this study the predictive value of a biopsy with GSD changes was 90%. Mosaicism, the most sensitive criterion in the diagnosis of GSD, is not type-specific. Fibrosis does not reliably distinguish between the GSD types and although nuclear hyperglycogenation and lipid are characteristic of type I GSD, these features are not diagnostic of any particular enzyme deficiency. The lack of morphological specificity implies that a complete enzyme analysis be performed on each biopsy. A normal enzyme analysis does not exclude a GSD and careful long-term follow-up may be necessary.

Some aspects of carbohydrate metabolism in the brain

A convenient physiology of the nervous system closely depends on the availability of glucose, the lack of which quickly results in syncope and death. Carbohydrate metabolism in the brain was long thought of as being specific and different from liver carbohydrate metabolism. The present report tries to summarize current data and advances in our knowledge about carbohydrate metabolism. Glucose is brought to the brain by blood flowing through a special network of arteries and is quickly catabolized by the glycolytic and tricarboxylic acid cycle pathways to synthesize energy. It is also used in the synthesis of numerous amino acids, nucleotides and NADPH. Glucose can be polymerized into glycogen in the brain. The nerve tissue is capable of synthesizing glucose-6-phosphate in the gluconeogenic pathway since the fructose-1,6-bisphosphatase, the key enzyme believed to be absent, is actually active and has been purified up to electrophoretic homogeneity. Moreover, the possibility of free glucose synthesis by astrocytes exists. Although the exact role of glycogen in the brain is not totally clear, it is known that the polysaccharide content generally decreases when the functioning of the brain is stimulated and increases in sedative state. This carbohydrate can therefore serve as an indicator for the level of brain activity. Through the administration of methionine sulfoximine, it is possible to increase the amount of glycogen in the brain massively and obtain particles similar to those found in the liver. These in vivo findings have been confirmed by studies based on cultured astrocytes. It has been shown with cultured astrocytes that glutamate increases glycogen synthesis in a pathway which still remains to be elucidated. Brain carbohydrate metabolism is thus in many ways similar to liver carbohydrate metabolism. The astrocyte constitutes the main cell implicated in this metabolism. Improvement in our knowledge about brain carbohydrate metabolism should spread the use of brain glucose metabolism in the diagnosis of certain diseases.

Alterations of inner ear morphology in experimental hypercholesterolemia

Previous clinical and experimental studies have indicated that auditory function may be compromised by hypercholesterolemia. In this investigation, inner ear tissue from chinchillas maintained on a cholesterol-supplemented diet for 3 months was examined for morphological alterations which might underlie the physiological changes observed with this condition in earlier studies. Ultrastructural analysis of cochleas from 16 hypercholesterolemic chinchillas revealed alterations in both the stria vascularis and outer hair cells. Strial marginal cells throughout the cochlea and outer hair cells of the apical turn, contained electron-lucent patches of an amorphous material. These patches had the morphological characteristics and histochemical properties of glycogen. Mild extracellular edema and increased numbers of lysosomes were also noted in the stria vascularis of experimental animals. These alterations suggest that chronic hypercholesterolemia metabolically stresses inner ear tissue. It is hypothesized that such changes could increase susceptibility of the cochlea to ototraumatic agents.

Biochemical and ultrastructural study of glycogen in cultured astrocytes submitted to the convulsant methionine sulfoximine

The convulsant methionine sulfoximine is a potent glycogenic agent in the central nervous system of rodents in vivo. This investigation was undertaken to look for the basic mechanism underlying this property. Astrocytes were cultivated from newborn rat neopallium and glycogen was studied by both biochemical and ultrastructural methods. When the astrocytes were incubated in a medium containing 5.55 mM glucose, methionine sulfoximine (0.55 mM) induced a significant increase in their glycogen content. Glucose content did not change in astrocytes, but it diminished in the medium in all cases. When the decrease in glucose level in the medium was limited, the same glycogenic effects of methionine sulfoximine were observed, but the glycogen contents were higher. The augmentation of the concentration of the convulsant enhanced its glycogenic effect, but this was not directly dose dependent. When the flat and polygonal astrocytes were transformed into process-bearing astrocytes by dibutyryl cyclic AMP methionine sulfoximine always induced an increase in glycogen content. In this case, the values of glycogen contents were lower. In electron microscopy, no glycogen particles were present in the astrocytes even after methionine sulfoximine treatment, contrary to the case in vivo. These results show that the convulsant does not need the presence of neuronal cells to induce glycogen accumulation and that astrocytes may be the direct cell targets. The apparent discrepancy between the biochemical and ultrastructural data is probably due to the relatively low concentration of glycogen in cultured astrocytes.

13C NMR relaxation times of hepatic glycogen in vitro and in vivo

The field dependence of relaxation times of the C-1 carbon of glycogen was studied in vitro by natural-abundance 13C NMR. T1 is strongly field dependent, while T2 does not change significantly with magnetic field. T1 and T2 were also measured for rat hepatic glycogen enriched with [1-13C]glucose in vivo at 4.7 T, and similar relaxation times were observed as those obtained in vitro at the same field. The in vitro values of T1 were 65 +/- 5 ms at 2.1 T, 142 +/- 10 ms at 4.7 T, and 300 +/- 10 ms at 8.4 T, while T2 values were 6.7 +/- 1 ms at 2.1 T, 9.4 +/- 1 ms at 4.7 T, and 9.5 +/- 1 ms at 8.4 T. Calculations based on the rigid-rotor nearest-neighbor model give qualitatively good agreement with the T1 field dependence with a best-fit correlation time of 6.4 X 10(-9) s, which is significantly smaller than tau M, the estimated overall correlation time for the glycogen molecule (ca. 10(-5) s). A more accurate fit of T1 data using a modified Lipari and Szabo approach indicates that internal fast motions dominate the T1 relaxation in glycogen. On the other hand, the T2 relaxation is dominated by the overall correlation time tau M while the internal motions are almost but not completely unrestricted.

Cerebral glycogenosis, alpha particle type: morphologic and biochemical observations in an infant

A 3-month-old infant with congenital hypotonia suffering from an unusual form of glycogenosis is reported. The most striking neuropathologic findings were vacuolation of neuropile and glycogen accumulation, especially in the cerebral cortex and cerebellar molecular layer. Ultrastructurally, glycogen accumulation was present mainly in neurites and astrocytic processes, and mostly appeared as rosettes (alpha glycogen particles). Biochemical analysis of glycogen in various regions of the central nervous system showed an increase of up to 100-fold. The cerebral cortex, deep nuclei, and cerebellar cortex had the highest glycogen elevations, while the cerebral white matter glycogen level was normal. Among other tissues, the heart showed a several-fold increase in glycogen content. Muscle, liver, and kidney glycogen levels were not elevated. Findings in this case and in three other reported patients with cerebral glycogenosis of alpha particle type are discussed.

Electron microscopy of Microsporum cookei after 'in vitro' treatment with protoanemonin: a combined SEM and TEM study

The ranunculaceous derivative protoanemonin (PrA) was studied as an antifungal agent on the dermatophyte Microsporum cookei. The ultrastructural changes that PrA brought about in this fungus were observed with both the transmission and scanning electron microscopes. The main anomalies noted were abnormally shaped hyphae and within the cytoplasm, multimembranous bodies which were irregular in shape and size, and tubules of 25 and 60 nm in diameters. Mitochondria, nuclei and vacuoles were also variously affected by PrA. Although multifarious, the observed cellular alterations in M. cookei can be considered the result of a PrA interaction with cytoplasmic microtubules. Since these cell structures contain a great number of ASH groups, our previous hypothesis, that sulphydryl groups are the primary targets of this molecule, appears to be supported.

Comparative study of nuclear and cytoplasmic glycogen isolated from mutant HD33 ascites cells

Mutant cells of the HD33 subline of the Ehrlich-Lettré ascites tumor synthesize and store glycogen mainly intranuclearly, when growing in vivo, and exclusively in the cytoplasm, when permanently cultivated as a suspension cell strain. To investigate whether there exist differences between glycogen of nuclear and cytoplasmic origin, the ultrastructure and the biophysical and biochemical properties of glycogen from in vivo and in vitro grown HD33 ascites cells were compared. Pronounced heterogeneity and differences in glycogen particle ultrastructure were evident in situ and after isolation of the native, high-molecular polysaccharide. Nuclear glycogen contains a fraction of heavier molecules (up to 2 X 10(9)) and larger particles (up to 340 nm) which could not be found in the cytoplasmic preparations, which contained only particles smaller than 140 nm. The subparticles of beta-type are similar in both nuclear and cytoplasmic glycogen. The absorption spectra and glucose analysis after degradation with phosphorylase and debranching enzyme indicate that nuclear glycogen has a higher degree of branching, associated with a decrease in the average chain length between the branching points, and shorter external polyglucosidic chains than cytoplasmic glycogen. This is the first report about the analysis and properties of isolated nuclear glycogen.

Compartmentation of glycogen metabolism in the liver

The incorporation of radioactivity into liver glycogen has been shown not only to be a metabolically inhomogeneous process but also to depend critically on the nature of the precursor. D-Galactose is incorporated into glycogen by a mechanism which is separate from that associated with the incorporation of D-glucose. D-Galactose is favoured for incorporation into high-molecular-weight glycogen and consequently is affected more by treatment of the animal with the antibiotic tunicamycin, since high-molecular-weight glycogen is preferentially found in the lysosomal compartment.

Glycogen particles in methionine sulfoximine epileptogenic rodent brain and liver after the administration of methionine and actinomycin D

Rats and mice were submitted either to the convulsant methionine sulfoximine (MSO) alone or to MSO combined with actinomycin D or methionine respectively. Twenty-four hours after the intraperitoneal administration of these compounds, the animals were killed and tissue samples were prepared for electron microscopy. Methionine sulfoximine induced 'grand mal' type seizures which were abolished by methionine. In saline controls, glycogen was as beta particles located in the cytoplasm of astrocytes, i.e. in perikarya and processes. Liver glycogen was as perinuclear masses of alpha and beta particles or as alpha particles scattered in all the cytoplasm. When the rodents were treated with MSO, glycogen was as alpha and beta particles which invaded all areas of the astrocyte cytoplasm, this increase being tremendous in perivascular end feet. Actinomycin D slowed down the accumulation of glycogen particles while methionine completely abolished it. In any case, glycogen particles were confined to the astrocytes and were never seen in other types of cells. In liver, MSO induced an important decrease or a complete disappearance of glycogen particles. When the convulsant was combined with actinomycin D or with methionine, the figures looked like those of controls. These results have been discussed in relation to the mechanism of glycogenesis in central nervous system of rodents submitted to MSO.

Glycogen of high molecular weight from mammalian muscle

Glycogen of high molecular weight has been isolated from mammalian muscle, in contrast to the material of low molecular weight commonly described. The large polysaccharide is similar to liver glycogen in the structure of its individual beta-particles and also, partially, in the mode of assembly into the gross alpha-particles. The large particles may be disrupted by 2-mercaptoethanol, but not to the same extent as their liver counterparts.

Ordered synthesis and degradation of liver glycogen involving 2-amino-2-deoxy-D-glucose

The incorporation of 2-amino-2-deoxy-D-glucose from precursor 2-amino-2-deoxy-D-galactose into liver glycogen has been shown to be a metabolically inhomogeneous process after starvation. The protein-to-polysaccharide ratio is also heterogeneous with respect to molecular size, and enhanced overall as compared to normal glycogen. The results are discussed from the viewpoint of a molecular order in the synthesis and degradation of liver glycogen.

The alpha particulate liver glycogen. A morphometric approach to the kinetics of its synthesis and degradation

Electron micrographs of rat hepatocytes with a glycogen content between 0.36 and 2.55% (w/w) were submitted to morphometrical analysis. From the number and size of glycogen profiles, the distribution of radius and volume of glycogen alpha particles were computed. The 7-fold difference in glycogen content was accompanied by an only 1.8-fold increase in the mean volume of the particles while their number increased by a factor of 4. On the basis of these observations, it is proposed that the population of glycogen particles can be divided in two groups. The first one is made of growing particles, still associated with glycogen synthase; they are the only particles present at low glycogen concentration and their number is limited. Application of a simple mathematical model allows to estimate their number in hepatocytes as 49 X 10(12) particles . ml-1. The second group is made of glycogen particles which have reached their maximal size and the number of which is in principle unlimited. The maximal particle size is estimated to be 0.36 X 10(-15) ml, corresponding to an average molecular weight of 178 X 10(6). The average molecular weight of glycogen, as measured from the actual size of the particles, varied from 89 X 10(6) to 161 X 10(6).

Ultrastructure and cytochemistry of glycogen-containing vacuoles in gastrodermal cells in developing hydranths of a hydromedusan coelenterate

Hydranth buds from the colonial hydroid Sertularia pumila (Hydromedusae) were observed by electron microscopy during their development. Before hydranth expansion, the gastrodermal columnar digestive cells had large numbers of vacuoles. These vacuoles contained many membranous components as well as alpha-glycogen and dense ring- and crescent-shaped bodies. The rings and crescents were not osmiophilic, but did react to periodic acid oxidation in the PA-TSC-SP test for carbohydrate. These structures were digestible by alpha-amylase and pullulanase. The chemical analyses and the close association of the rings and crescents to alpha-glycogen particles showed that they may be a highly condensed form of glycogen. Golgi bodies in association with the gastrodermal vacuoles had acid phosphatase activity. This enzyme was only slightly active in the vacuoles. It is suggested that the vacuoles are primarily storage organelles with a potential for digestion.

Ultrastructure of the branchial epithelium of an amphibious brackish-water crab

The ultrastructure of the branchial epithelium of the amphibious brackish-water crab Uca mordax (Smith) was investigated in relation to adaptation to the salinity of the medium. No distinct differences were observed in the epithelial structure of animals adapted to either 100% sea water or to 1% sea water. Thus any interpretation of the significance of particular structures in relation to specific transport processes should be regarded with caution. Apart from strict epithelial cells, pillar cells and glycogen (presumed) storage cells were found. The epithelial cells showed very well-developed apical microvilli or lamellae and basal interdigitations with adjacent cells. Well-developed junctional complexes were seen (band desmosomes, septate desmosomes, gap junctions). The cells are extremely rich in mitochondria. Microtubules, peroxisome-like bodies, multivesicular bodies and near-nuclear Golgi complexes were present.

Hepatic ultrastructure in leprechaunism. Hepatic ultrastructural evidence suggesting a syndrome with defective hepatic glucose release

Leprechaunism is a congenital syndrome with characteristic habitus and facies, with fasting hypoglycemia and hyperinsulinism. In response to a glucose challenge there is prolonged severe hyperglycemia with an increased hyperinsulinemia. Our studies on such a patient showed a normal response of the serum glucose to glucagon stimulation in the fed state but no response in the postabsorptive state. Ultrastructural studies on the hepatocytes demonstrated that a lack of hepatic glycogen was not responsible for the biochemical features, since there was abundant normal beta-glycogen in both the fed and fasting state, the granules being smaller in the fasted state. We speculate that carbohydrate intolerance in leprechaunism may be due to a relative insulin resistance of cell receptors in the fed state. Reactive hyperinsulinemia persisting into the postabsorptive phase appears to antagonize the usual glycogenolytic response to glucagon during fasting, resulting in hypoglycemia despite the presence of large hepatic glycogen stores.

Random, presumably hydrolytic, and lysosomal glycogenolysis in the livers of rats treated with phlorizin and of newborn rats

1. The glycogen formed in the livers of adult rats was labelled by injection of [1-14C] galactose soon after initiation of re-feeding after starvation. The rats were anaesthetized 4h later and glycogenolysis was induced by giving them a mixture of glucagon and insulin. In confirmation of previous work [Devos & Hers (1979) Eur J. Biochem. 99, 161-167],, there was a delay in degradation of the labelled glycogen by comparison with total glycogen. This pattern is considered as characteristic of an ordered glycogenolysis. Treatment of rats with phlorizin abolished the difference between the fate of labelled and total glycogen, causing, therefore, a random glycogenolysis. 2. Foetal liver glycogen was made radioactive by injecting [14C] glucose into the mother at the 19.5 day of gestation, i.e. at the time when this glycogen starts to be synthesized. During the postnatal degradation of this glycogen, radioactive and total glycogen were degraded at approximately the same rate, indicating that glycogenolysis occurred at random. In contrast, when puromycin was injected into the newborn rats, there was a delay in he degradation of the labelled glycogen as compared with that of total glycogen, as currently observed in the normal adult liver. 3. These data are discussed in relation with the fact that glycogen-filled vacuoles are currently seen in the livers of adult rats treated with phlorizin, and also in the neonatal livers, and that puromycin is known to cause the disappearance of these autophagic pictures in the liver of newborn rats. It is suggested that random glycogenolysis occurs through hydrolysis by the lysosomal acid alpha-glucosidase, in the course of autophagy.

Histochemical observations of polyglucose synthesized by enzyme activities in human gastric carcinoma

Polyglucose particles histochemically synthesized from glucose 1-phosphate by phosphorylase and branching glycosyltransferase were observed in the gastric carcinoma cells, in intestinal metaplastic epithelium of the gastric mucosa and in fetal epithelium of the fetal gastric mucosa by light and electron microscopical studies. Light microscopical observations resembled those in previous reports. As for the electron microscopical observations, in gastric carcinoma cells, the polyglucaose synthesizing area were expansively widened by a deposition of synthesized polyglucose particles. Three patterns of their intracellular distribution, (Focal type, scattered type and singly deposited type) were observed. Besides, two types of polyglucose particle were synthesized. One type appeared as monoparticles which were relatively similar in size and the other type appeared as rosette-like structures which varied in size. Larger polyglucose particles which resembled the polyglucose particle synthesized in the fetal epithelium were observed among them. In the intestinal metaplastic epithelium, polyglucose particles which were similar in size were synthesized in narrow focal areas of the cytoplasmic matrix. The distribution, shape and size of polyglucose particles synthesized in the carcinoma cells were irregular as compared with those in the intestinal metaplastic elpithelium. It seems that these irregularities were due to the influence of enzymne deviation caused by carcinoma.

An electron microscopic study of the salivary gland of Rhynchosciara angelae

The structure of the salivary gland of the dipteran insect Rhynchosciara angelae in a defined stage of the larval development, characterized by the synthesis and storage of secretion product, is described. Observations were made with both Nomarski optics and electron microscopy. Filiform projections extending into the lumen of the gland were observed in the apical portion of the cells. At the basal region junctions, characterized as hemidesmosomes, were observed between the membrane of the cell and the basal lamina. The plasma membrane presents numerous infoldings into the cell increasing considerably the surface area at this region. Throughout the cytoplasm of the gland cells numerous mitochondria, Golgi complexes, microtubules, profiles of endoplasmic reticulum, secretion granules and glycogen granules were observed. Carbohydrates were detected on ultrathin sections by using the periodic acid-silver methenamine and the periodic acid-thiosemicarbazide-silver proteinate techniques.

Fine structure and secretion of the capsule enclosing the embryo in a crab (Carcinus maenas (L.))

Carcinus maenas oocyte is encased, at the end of vitellogenesis phase, by two superposed vitelline envelopes. If the outermost (envelope 1a) is relatively thin, the innermost (envelope 1b) is however five times much thicker. The envelope 1b, secreted mostly by the oocyte, contains proteinaceous material and a substance which strongly binds WGA. The 1b material deposition is completed when the oocyte nuclear apparatus still has the characteristics of a germinal vesicle. After the secretion phase and always at the ovarian level, envelope 1b material undergoes remarkable structural modifications. These last events occur while the oocyte nuclear apparatus is in the first meiotic metaphase stage. Later, after egg-laying, a new material appears below the two superimposed vitelline envelopes 1a and 1b. This new innermost material (envelope 2), observed as a very thick and homogeneous secretion, is secreted by the newly laid egg probably after fecondation. Envelope 2 material is wholly deposited in few hours and arises from vesicles of an oocytic origin. These three superimposed envelopes make up the embryo capsule of which the main part is constituted by envelope 2. This tripartite capsule will stay, surrounding the developmental stages, superimposed to newly secreted successive embryonic envelopes, up to the end of embryogenesis.

Glycosomes (protein-glycogen complex) in the canine heart. Ultrastructure, histochemistry and changes induced by acidic treatment

Cardiac conducting fibers were selected from two dogs defined as A and B. The specimens differed in the reaction of their electron dense granules, commonly referred to as glycogen, to the treatment en bloc with uranyl acetate. Material was fixed in glutaraldehyde and OsO4. Blocks were processed either conventionally or immersed in uranyl acetate before dehydration. Sections were examined unsatined, stained with U and/or Pb or with a histochemical technique (PA-TSC-SP) specific for glycogen. Electron dense granules have affinity to Os, U and Pb which suggests ionic reactions specific for protein but improbable for glycogen. Large granules in A turned into pale ghosts and small granules in B disappeared after treatment en bloc with uranyl acetate. PA-TSC-SP in conventional samples showed glycogen particles arranged into aggregates corresponding in size to the electron dense granules. Treatment en bloc slightly affected glycogen aggregates in A and resulted in a formation of large clumps of glycogen particles in B. It was concluded that the electron dense granules represented protein bound to glycogen in the organelles called glycosomes. Acidic action of uranyl acetate removed protein from glycosomes. The degree of this removal depended on the amount of protein present in glycosomes in the moment of fixation.

Ultrastructure and cytochemistry study of the yolk syncytial layer in the alevin of trout (Salmo fario trutta L.) after hatching. I. The vitellolysis zone

After hatching, the yolk syncytial layer of Salmo fario trutta may be subdivided into two zones, namely, the vitellolysis zone (containing numerous yolk platelets), and the cytoplasmic zone (where yolk platelets are rare). In the vitellolysis zone, two stages in the utilization of the yolk are observed: 1) The first stage, comprises the formation of yolk platelets from coalescent yolk by spherical cutting out and basal scission. This process seems to be achieved by the invagination of fibrillar elements into the coalescent yolk to form individual yolk platelets surrounded by a limiting membrane. 2) The second stage essentially consists of the extrusion or budding of yolk matter from a yolk platelet. Again, where the yolk matter leaves a platelet, fibrillar elements are evident and show an alkaline phosphatase activity. The platelets of the vitellolysis zone have a homogeneous content and variable diameter; they never acquire a heterogeneous and polymorphic aspect which could be interpreted as an intermediate stage in their degradation.

Transvascular endomyocardial biopsy in infants and small children. Myocardial findings in 10 cases of cardiomyopathy

Transvascular endomyocardial biopsy specimens from nine children with congestive cardiomyopathy and one with hypertrophic cardiomyopathy were studied by light microscopy using sections 1 mu thick cut from Epon embedded tissue and by electron microscopy. There was a disparity between the severity of the physiologic impairment and the morphologic abnormalities. Interstitial fibrosis was present only in the one case in which significant viral antibody titers were obtained. The sizes of the cardiac muscle cells varied abnormally in all specimens. Cardiac muscle cells in two patients contained abnormal mitochondria, and a leptomeric fibril was found in one patient. Virologic cultures of the tissues were negative and no viral particles were identified by electron microscopy. An attempt was made to correlate the clinical and pathologic findings.

Quantitative analysis of RNA, glycogen and nucleotides from different developmental stages of Ascaris lumbricoides (var. suum)

Cold acid phenol extractions (Kirby, K.S. (1968) in Methods in Enzymology, Vol. XII B, pp. 87--99, Academic Press, New York) of homogenates from oocytes, zygotes and larval stages of Ascaris lumbricoides yield predominantly glycogen, some glycogen . phosphate complexes and guanine nucleotides, but only small amounts of RNA. Oocytes contain 10.0 pg of extractable 19 S and 26 S rRNA and 1.1 pg 4 S and 5 S RNA per cell. During the maturation of the oocyte to the zygote stage, the amount of 19 S and 26 S rRNA increases by 57%, and that of 4 S and 5 S RNA by 130%. Larval stages contain 62% more 19 S and 26 S rRNA, and 47% more 4 S and 5 S RNA than zygotes. The amount of the extractable glycogen decreases by about 80% and nucleotides by about 70% from oogenesis to the larval stage. The Kirby extract from homogenates of spermatids contains only traces of glycogen, glycogen . phosphate complexes and nucleotides, and 115 times less RNA per spermatid than oocytes. The nucleotide pool sizes of oocytes, zygotes and larval stages were determined; the pools consist of 71--88% guanine nucleotides. Spermatids contain only adenine nucleotides and an unidentified, nucleotide-like compound.

Effect of castration and testosterone administration on the neuromuscular junction in the levator ani muscle of the rat

The ultrastructure of the neuromuscular junction (n.m.j.) of the androgen-sensitive levator ani muscle was studied in normal adult male rats, in 8-month-old rats castrated at the age of one month and in castrated rats treated with testosterone propionate (TP). Castration does not result in significant changes of the n.m.j. The density of synaptic vesicles and the postsynaptic junctional folds remain practically normal inspite of marked atrophy of the muscle. TP administration for 7 days results in marked changes in pre- and postsynaptic structures. There is slow progressive depletion of synaptic vesicles, appearance of cisternae and coated vesicles in axon terminals, and coalescence of coated vesicles with the plasma membrane. Coated vesicles are also found inside Schwann cells and among junctional folds. Dense core vesicles appear both in the axon terminals and in the postsynaptic area. Collateral sprouting of terminal axons with the formation of new immature junctions is observed. After 35 days of TP administration depletion of synaptic vesicles continues. Glycogen beta-particles, mostly freely dispersed, occasionally seen in axon terminals 7 days after TP administration, subsequently increase in number. In the endplate zone of the muscle fibre increased protein synthesis is indicated by a rapid increase in ribosomes and irregularly located myofilaments and myofibrils. The appearance of n.m.j. after testosterone administration resembles that described after nerve stimulation; the degree of change is however less pronounced.

Resurgence of glycogen synthesis and storage capacity in cultured hepatoma cells

This paper describes a new cultured hepatoma cell line referred as ZHC cells, derived from the ascitic Zajdela rat hepatoma. Since 1963, the dedifferenciated in vivo transplanted ascitic cells were characterized by the absence of glycogen as in generally the case in all fast growing hepatic tumors. In 1974, we succeeded in adapting these tumor cell to in vitro defined growth conditions, where we observed the progressive recovery of the ability to synthesize and to store large amounts of glycogen, as shown by histochemical, ultrastructural and biochemical studies. It can now be considered as an established cell line in which the reverted phenotype has been stable for 3 years.

Anatomical and ultrastructural study of the pharyngeal bulb in Protodrilus (Polychaeta, Archiannelida). I. Muscles and myo-epithelial junctions

The pharyngeal bulb of Protodrilus is both a muscular and an epithelial organ whose function is the drawing up of food particles. The muscular system of the bulb is formed of tightly connected antagonistic muscles: the bulbus muscle and the sagittal and "grating plate" muscles. All of them are composed of obliquely striated fibers whose ultrastructural characteristics are similar to those of Hirudina and even more to those of epitokous forms of Nereidae and Syllinadae. Myo-epithelial cells do not exist in the pharyngeal bulb of Protodrilus contrary to what was previously thought; the muscles and the stomodeal epithelium are united by junction areas on both sides of the basal lamina. These myo-epithelial junctions may be compared of the myoepidermic junctions known in several Arthropods. A comparison of the ultrastructural features of the bulbus muscle fibers of Protodrillus (Protodrilidae) and Trilobodrilus (Dinophilidae) shows that the Protodrilus fiber clearly belongs to the obliquely striated type classically found in Polychaeta, while the Trilobodrilus fiber is a very peculiar type of obliquely striated fiber. These differences do not agree with Jägerstens hypothesis on the unity of the Archiannelida established on the basis of a structural similarity of the bulbus muscles.

Hydrodynamic properties of 2-mercaptoethanol-modified glycogen

Treatment of glycogen with 2-mercaptoethanol and iodoacetamide gives rise to a modified glycogen which resembles the original glycogen in its hydrodynamic behaviour but has a pronounced tendency to aggregate. The modified glycogen can be distinguished easily, by its diffusion coefficient, from glycogen degraded by more traditional methods of extraction. The 'fundamental' glycogen particle appears to be composed of two or three glycogen beta-particles linked by a single protein chain.