EVALUATION OF THE GLYCOGENOLYTIC EFFECT OF α-AMYLASE USING RADIOAUTOGRAPHY AND ELECTRON MICROSCOPY

Optimization of PAS stain and similar Schiff's based methods for glycogen demonstration in liver tissue

Demonstration of glycogen in tissue holds considerable diagnostic relevance across various pathological conditions, particularly in certain tumors. The histochemical staining of glycogen using methods utilizing Schiff's reagents is subject to influences arising from the type of fixative, fixation temperature, and oxidizing agents employed. This study aimed to assess diverse fixatives, fixation temperatures, and oxidizing agents, each with variable treatment durations, in conjunction with Schiff's reagent for optimal glycogen demonstration. Paraffin blocks derived from a rabbit's liver served as the experimental substrate, encompassing 340 paraffin sections subjected to different procedures. For tissues fixed at 4 °C, good staining outcomes, as determined by the periodic acid-Schiff (PAS) stain, were observed with 10% neutral buffered formalin (NBF), 80% alcohol, and Bouin's solution. Tissues fixed at room temperature (RT) demonstrated good PAS staining results with both 10% NBF and 80% alcohol. Notably, other oxidizing agents exhibited poor outcomes across all fixatives and fixation temperature, with two exceptions, as satisfactory staining results were obtained when using 5% chromic acid. Consequently, Both 10% NBF and 80% emerge as preferred fixatives of choice for glycogen demonstration when coupled with PAS stain. It is noteworthy that Bouin's solution could also provide good outcomes when fixation occurred at 4 °C.

Differential gene expression during compensatory sprouting of dendrites in the auditory system of the cricket Gryllus bimaculatus

Neurones that lose their presynaptic partners because of injury usually retract or die. However, when the auditory interneurones of the cricket Gryllus bimaculatus are denervated, dendrites respond by growing across the midline and forming novel synapses with the opposite auditory afferents. Suppression subtractive hybridization was used to detect transcriptional changes 3 days after denervation. This is a stage at which we demonstrate robust compensatory dendritic sprouting. Whereas 49 unique candidates were down-regulated, no sufficiently up-regulated candidates were identified at this time point. Several candidates identified in this study are known to influence the translation and degradation of proteins in other systems. The potential role of these factors in the compensatory sprouting of cricket auditory interneurones in response to denervation is discussed.

Cytochemical studies of a glycogen-sarcoplasmic reticulum complex

Enzymatically active cardiac sarcoplasmic reticulum (SR) fractions contain glycogen. Previous biochemical and morphological studies indicate that the glycogen particles are membrane associated. In the present study, further evidence for membrane-associated glycogen particles in these cardiac SR fractions is presented: (1) morphological parameters, (2) enzymatic digestion by glucoamylase and alpha-amylase and (3) cytochemical staining by two different methods. Dense granules comparable in size (20-30 nm diameter), electron density and substructure to glycogen particles observed in intact cardiac muscle and in glycogen preparations isolated from skeletal muscle were seen. Most of these glycogen particles were removed by amylase digestion except for glycogen particles closely adhering to vesicle membranes. Two different cytochemical techniques (bismuth subnitrate and silver proteinate) revealed a positive reaction product over the glycogen particles. These findings provide further support for the biochemical finding of a structured enzyme complex involving the SR, glycogenolytic enzymes and glycogen.

Electron microscopic evidence of glycogen storage in the dark pinealocytes of the rabbit pineal gland

Electron microscopic evidence is given that the small dark granules in the rabbit dark pinealocytes represent glycogen. The conception is put forward that this glycogen, synthesized at the membranes of the rough endoplasmic reticulum, is taken up by lysosomes to participate then in the conversion of the lysosomes into pigment bodies.

Degenerative changes in the mitochondria of flight muscle from aging blowflies

Mitochondria from flight muscle of aging blowflies, Phormia regina, were examined morphologically and biochemically with the electron microscope. An age-dependent degeneration of the mitochondria that is characterized, in part, by the reorganization of the inner membrane into myelin-like whorls has been found. The concentric rings increase in size and number, eventually replacing the normal cristal conformation. Glycogen rosettes are frequently seen in the center of the whorl and may represent the intrusion into the mitochondria of the glycogen in the cytoplasmic matrix of the muscle. The degenerating mitochondria are not associated with lysosomal activity, as indicated by the absence of acid phosphatase. An intense acid phosphatase activity is noted, however, in the dyad, comprising elements of the T system and sarcoplasmic reticulurn. Cytochrome oxidase is active in the ultrastructurally intact portion of the mitochondrion but activity is not evident in that part of the mitochondrion that has undergone morphological change. Thus, the ultrastructural degradation of the mitochondria is correlated with a decrease in biochemical function. This suggests a correspondence between a decrease in the bioenergetic capacity of the flight muscle and a decline in the ability of the aged insect to fly.

Electron microscope radioautographic study of glycogen synthesis in the rabbit retina

Glycogen is present in the rabbit retina in monoparticulate form. Beta particles ( approximately 229 A) are abundant in Müller cell cytoplasm, particularly in its inner portion, decreasing in number outwards along the cell. They are slightly larger ( approximately 250 A) and much scarcer in neurons, though regularly present in the juxtanuclear Golgi region of ganglion cells. When the retina was incubated in a glucose-free medium, it was rapidly depleted of native glycogen. On further incubation in medium containing glucose-(3)H plus unlabeled glucose, glycogen reappeared in the form of beta particles of the same size and distribution as native ones, while radioautography revealed the appearance of amylase-labile radioactivity in the same locations. This newly formed glycogen was not associated with any particular organelle. The rate of synthesis, as judged from the amount of radioactivity, was high in the inner portion of Müller cells and declined uniformly toward the cell outer end, following a logarithmic gradient. The rate of synthesis was low in ganglion cells, at best approaching values in the outer portion of Müller cells. The concentration of glycogen in the inner portion of Müller cells is consistent with the view that it may be the source of glucose for the anaerobic glycolysis prevailing in the inner retina.

Isolation, ultrastructure, and biochemal characterization of glycogen in insect flight muscle

Glycogen from flight muscle of the blowfly, Phormia regina, has been characterized ultrastructurally and biochemically. In situ, glycogen is in the form of rosettes, which vary in size with diameters of up to 0.1 micro. Sedimentation analysis of pure glycogen, isolated by mild buffer extraction, reveals a polydisperse molecular weight spectrum, with larger particles having molecular weights of 100 million. Treatment of native glycogen with alkali, under conditions usual for the extraction of the polysaccharide from tissues, results in a 5- to 10-fold reduction in molecular weight, as well as a chemical alteration of the molecule. Flight muscle phosphorylase has a lower affinity for native than for alkali-treated glycogen. The maximum velocity of the enzyme is also lower with native substrate. The apparent K(m) for inorganic phosphate is higher with native glycogen as cosubstrate. These kinetic differences with native and partially degraded glycogen demonstrate the importance of using the natural substrate in studies of biochemical control mechanisms.