STUDIES ON GLYCOGEN NEPHROSIS IN ALLOXAN-TREATED DIABETIC RATS

Two hundred and seven albino rats were injected subcutaneously with alloxan in doses varying from 140 to 200 mg. per cent per kilo of body weight. Fifty-nine animals which developed hyperglycemia (blood sugar levels above 150 mg. per cent) were observed for periods from 5 days to 32 weeks. Postmortem examination of the kidneys of these diabetic animals revealed glycogen deposition in the loops of Henle and convoluted tubules in 26 rats or 44 per cent. Glycogen could not be demonstrated in the glomeruli. Within the time limits of this experiment (32 weeks) no intercapillary glomerulosclerosis was observed. The following facts were revealed regarding glycogen nephrosis in alloxan diabetes: (a) Its appearance in the kidneys of the diabetic rats depended solely upon the terminal blood sugar levels of these animals. A value of 350 mg. per cent was the critical level, above which glycogen nephrosis was almost invariably demonstrable. With terminal levels below 300 mg. per cent no glycogen nephrosis was found. (b) No relationship existed between the postmortem finding of glycogen nephrosis and the initial blood sugar level, or the maximum height of the hyperglycemia attained by individual rats. (c) The results suggest that glycogen nephrosis is a reversible lesion.

Biosynthesis and biosynthetic pathways of pentoses in Escherichia coli

Sable, Henry Z. (Western Reserve University, Cleveland, Ohio) and Elayne E. Cassisi. Biosynthesis and biosynthetic pathways of pentoses in Escherichia coli. J. Bacteriol. 84:1169-1172. 1962.-Resting glucose-adapted Escherichia coli supplied with glucose continues to synthesize pentose by the oxidative pathway characteristic of logarithmically growing glucose-adapted cells. This behavior is unlike that of acetate-adapted resting E. coli supplied with glucose, which continues to synthesize most of its pentose by the nonoxidative pathway characteristic of acetate-adapted cells. When infected with bacteriophage T2H, E. coli continues to use the oxidative pathway predominantly. This finding is in contrast to reports that infection with T6r+ bacteriophage increases the participation of a nonoxidative pathway. Resting glucose-adapted E. coli supplied with acetate-1-C(14) as sole carbon source synthesizes pentose by a pathway or pathways which cannot be assessed completely by methods previously developed (which are based on the relative labeling of C-1, C-2, and C-3 of the pentose) but which is most probably predominantly nonoxidative.

Control of glycogen utilization and glucose uptake in the anaerobic turtle heart

Glucose uptake and lactate production of isolated, perfused turtle ( Pseudemys scripta) hearts were measured under anaerobic conditions. At low pressure-volume workloads the hearts used glycogen stores rather than exogenous glucose to provide hexose substrate for glycolysis. Glycogenolysis increased in proportion to increased workload up to a critical maximum value for each heart. Increase of workload beyond this critical point was associated with utilization of exogenous glucose or, in the absence of glucose, with mechanical failure of the heart. Glucose-U-C14 was quantitatively (98%) converted into lactate, and neither dilution of exogenous glucose specific activity nor incorporation of label into glycogen or fatty acids occurred. The maximal rate of glycogenolysis was found to be a linear function of initial glycogen concentration. It is concluded that the input of hexose units into glycolysis is regulated jointly by hexokinase and phosphorylase; however, the known properties of these two enzymes will not fully account for all the features of this regulation.

Pancreatectomy in rats: onset of metabolic changes in liver, adipose, and diaphragm

The time of onset of metabolic alterations in utilization of C14-labeled glucose and acetate by liver and adipose tissue, and in uptake of glucose by diaphragm was studied in "totally" depancreatized rats, a preparation in which severe manifestations of diabetes develop rapidly. The earliest changes were observed in glucose utilization by liver and adipose tissue. Two hours after pancreatectomy, conversion of glucose carbon to a) fatty acids, glycogen, and CO2 by liver slices and b) fatty acids and CO2 by adipose tissue was depressed. Defective utilization of acetate appeared earlier in adipose tissue than in liver. A decrease in the liver's capacity to convert acetate carbon to fatty acids developed some time between 4 and 14 hr after pancreatectomy. In adipose tissue this occurred between 2 and 4 hr. Defective uptake of glucose by diaphragm was observed later after pancreatectomy, some time between 4 and 14 hr. The results are discussed from the standpoint of the nature of metabolic lesions in the diabetic liver and of whether insulin has a direct or indirect action on hepatic tissue.

CO-2 FORMED FROM ENDOGENOUS AND EXOGENOUS SUBSTRATES IN PERFUSED RAT HEART

Measurements of total CO2 and C14O2 production by the isolated, perfused rat heart showed the extent of respiration dependent on endogenous and exogenous substrates. Glucose, acetate, and palmitate, but not glutamic acid or leucine, contributed appreciably to respiration. With optimal glucose and palmitate oxidation endogenous substrates accounted for over half of CO2. Endogenous substrates were adequate to maintain respiration for 30 but not for 60 min. Dependence of respiration on lipids was suggested by the similarity of metabolic CO2 in glycogen-depleted hearts perfused with no added substrate, with palmitate-1-C14, and with glucose-U-C14 plus palmitate. A reduction in C14O2 and in total CO2 formation with glucose-U-C14 in the presence of palmitate provided further support for the preferential oxidation of fatty acids. The Vo2, estimated from the total and C14O2, and an assumed respiratory quotient, indicated adequate oxygenation of the heart in the closed recirculated system. The necessity of maintaining an adequate coronary artery flow rate was indicated by an altered pattern of cell metabolism in hearts with reduced coronary perfusion.

CYTOCHEMISTRY OF PARACOCCIDIOIDES BRASILIENSIS. I. CYTOCHEMISTRY OF CYTOPLASMIC POLYSACCHARIDES IN YEAST FORM CULTURES WITH LIGHT MICROSCOPE

1. The histochemical distribution and localization of cytoplasmic polysaccharides are studied in the yeast form of P. brasiliensis. Glycogen and an acid mucopolysaccharide probably containing sulfate groups are demonstrated. These polysaccharides disappear after the sixth day of culture. The glycogen and the acid mucopolysaccharide are bound to protein.

2. Stains and enzyme treatments applied in sequence help demonstrate the site of different polysaccharides.

CARP MYOGENS OF WHITE AND RED MUSCLES. GROSS ISOLATION ON SEPHADEX COLUMNS OF THE LOW-MOLECULAR-WEIGHT COMPONENTS AND EXAMINATION OF THEIR PARTICIPATION IN ANAEROBIC GLYCOGENOLYSIS

1. The combined low-molecular-weight protein components of the myogens from carp white and red muscles [about 30% (w/w) of the myogen proteins] have been isolated by gel filtration on Sephadex G-75 columns. 2. The presence in this fraction from myogen of white muscle of the three main electrophoretic components previously isolated has been confirmed, and the low molecular weight of the fourth component has been definitely established. 3. The exclusive presence of this fourth component in the myogen of red muscle, apart from myoglobin, has also been demonstrated. 4. Glycogenolysis experiments in vitro have shown that the low-molecular-weight protein fraction from carp myogen does not contain enzymes from the Embden-Meyerhof chain.

AN ELECTRON MICROSCOPE STUDY OF CULTURED RAT SPINAL CORD

Explants prepared from 17- to 18-day fetal rat spinal cord were allowed to mature in culture; such preparations have been shown to differentiate and myelinate in vitro (61) and to be capable of complex bioelectric activity (14–16). At 23, 35, or 76 days, the cultures were fixed (without removal from the coverslip) in buffered OsO₄, embedded in Epon, sectioned, and stained for light and electron microscopy. These mature explants generally are composed of several strata of neurons with an overlying zone of neuropil. The remarkable cytological similarity between in vivo and in vitro nervous tissues is established by the following observations. Cells and processes in the central culture mass are generally closely packed together with little intervening space. Neurons exhibit well developed Nissl bodies, elaborate Golgi regions, and subsurface cisternae. Axosomatic and axodendritic synapses, including synaptic junctions between axons and dendritic spines, are present. Typical synaptic vesicles and increased membrane densities are seen at the terminals. Variations in synaptic fine structure (Type 1 and Type 2 synapses of Gray) are visible. Some characteristics of the cultured spinal cord resemble infrequently observed specializations of in vivo central nervous tissue. Neuronal somas may display minute synapse-bearing projections. Occasionally, synaptic vesicles are grouped in a crystal-like array. A variety of glial cells, many apparently at intermediate stages of differentiation, are found throughout the otherwise mature explant. There is ultrastructural evidence of extensive glycogen deposits in some glial processes and scattered glycogen particles in neuronal terminals. This is the first description of the ultrastructure of cultured spinal cord. Where possible, correlation is made between the ultrastructural data and the known physiological properties of these cultures.

FINE STRUCTURAL CHANGES IN RESPONSE TO HORMONAL STIMULATION OF THE PERFUSED CANINE PANCREAS

The dog pancreas isolated in situ was perfused with oxygenated dog blood and stimulated with pancreozymin, secretin, or both. There were no significant changes in the fine structure of the acinar, centroacinar, or duct cells attributable to the perfusion. Combined glutaraldehyde and osmium fixation gave good preservation of the secretory products of the acinar cell. Before stimulation, the lumen of the acini is filled with material similar in texture to the content of the zymogen granules, but of somewhat lower density. Release of secretion commonly takes place by coalescence of the limiting membrane of zymogen granules with the plasmalemma, but one granule opening at the surface may frequently be joined by others coalescing with its membrane and forming an interconnected series all with contents having the same texture as the released zymogen. Such a mechanism seems to permit a more rapid release of secretory product than discharge of individual granules. Pancreozymin stimulation caused marked depletion of zymogen granules, but no obvious changes in the Golgi apparatus. It is clear, therefore, that this hormone exerts its effect upon release of granules rather than upon their formation. Secretin stimulation of water and bicarbonate secretion caused a marked washing out of the luminal contents, but had little detectable effect on cellular structure.

SOME BIOCHEMICAL CHANGES IN THE GUINEA PIG DURING INFECTION WITH COXIELLA BURNETII

Paretsky, D. (University of Kansas, Lawrence), C. M. Downs, and C. W. Salmon. Some biochemical changes in the guinea pig during infection with Coxiella burnetii. J. Bacteriol. 88:137-142. 1964.-Guinea pigs infected with Coxiella burnetii, the rickettsial agent of Q fever, were studied for 11 days postinfection. Maximal changes in liver lipids, liver phosphorylase, and uridine diphosphate glucose (UDPG)-glycogen glucosyl-transferase activities occurred 3 to 4 days post-infection. In this period, total liver lipids increased from 1.26 to 5.46 mg/mg of N, with the largest increment in the glyceride fraction. Liver glycogen virtually disappeared by the second day, with no chemically detectable restoration until the eleventh day. A pattern of altered phosphorylase and UDPG-glycogen transglucosylase activities was observed, with maximal phosphorylase and minimal glucosyltransferase activities at the third and fourth days. Histochemical observations confirmed chemical analyses for lipids and glycogen.