Cytochemical Study on the Pancreas of the Guinea Pig

Abstract

Pancreatic ribosomes (guinea pig) aggregate and lose upon treatment with polyamincs, particularly spcrmine, their bound secretory enzymcs. Spcrmine, at 0.5 mM, for example, causes the releasc of about 85 per cent of the chymotrypsinogcn and RNasc, and from 85 to 100 pcr cent of the ribosomal amylase. At the same time, the particles lose about 10 per cent of their RNA, 7 to 24 per cent of thcir total protein, and from 75 to 100 per cent of their Mg ++. Obscrvations with the electron microscope confirm the heavy agglutinating of the ribosomes but otherwise show little change in the structure of the particles. Using radioactive spcrminc it was found that, concomitant with thc loss of bound cnzymcs and Mg ++ from the ribosomes, spermine became bound to the particle. The extent of binding ranged from 0.29 to 1.49 #moles per I0/zmoles RNA-P. The bound radioactivc spcrmine can bc rcmovcd by subsequent treatment of the ribosomes with GTP, ATP, or P-P, which treatment also removes most of the RNA of the particles, leaving behind ribosomes with a much lower RNA/protein ratio. From this evidence it was inferred that spcrminc, in releasing the Mg ++ of the particle, bccomes salt-linked to the free phosphate hydroxyl groups of the RNA. Frcshly isolatcd pancreatic and hcpatic ribosomes contain very littlc spcrminc, about 0.1 to 0.2 pmolcs polyaminc/10/zmoles RNA-P. The results are discussed in terms of the linkages between the structural protein, the bound sccretory enzymes, and the RNA of the ribosomes.

The Synthesis and Turnover of Rat Liver Peroxisomes

“…This theory, in addition to borrowing some concepts from findings made on very different systems (5,17,18,34,38), has rested mainly on morphological observations of widespread connections between peroxisomes and the ER (11,16,28,31,35,40,41,43) and on the biochemical results of Higashi and Peters (15), as they were interpreted by de Duve and Baudhuin (8) to fit newly acquired knowledge on the structural and functional properties of peroxisomes .…”

Fine Structural Changes in Response to Hormonal Stimulation of the Perfused Canine Pancreas

“…2he exocrine pancreas of the guinea pig has been intensively studied by correlated biochemical and electron microscopic methods in different phases of its normal functional activity (16,(23)(24)(25)(26)(27). These investigations have established the respective functions of the various cell organelles in the synthesis, concentration, storage, and release of the zymogens.…”

Protein Synthesis, Storage, and Discharge in the Pancreatic Exocrine Cell

“…This system has been the object of a number of recent studies involving the biochemical analysis of cell fractions separated by differential centrifugation (1)(2)(3)(4)(5)(6)(7)(8). Such studies have provided a sizable amount of data on the secretory cycle but have left several points in doubt and could not provide any information on important steps of the process.…”