Corpora amylacea (CA) accumulation in the central nervous system (CNS) is associated with both normal aging and neurodegenerative conditions such as Alzheimer's disease (AD). CA is reported to be primarily composed of glucose polymers, but approximately 4% of the total weight of CA is consistently composed of protein. CA protein resolved on sodium dodecylsulfate-polyacrylamide gel electrophoresis showed a broad range of polypeptides ranging from 24 to 133 kDa, with four abundant bands. Immunoblots of the profile of polypeptides solubilized from purified CA, showed positive ubiquitin (Ub) immunoreactivity for all the bands. Antisera to heat-shock proteins (hsp) 28 and 70 reacted selectively with bands of 30 and 67 kDa. These results show that Ub is associated with the primary protein components of CA and that the polypeptides are likely to be Ub conjugates. Immunostaining experiments were performed to specifically characterize the protein components of CA in brain tissue sections as well as those of CA purified from both AD and normal aged brains. In all cases CA showed positive reactions with antibodies to Ub, with antibodies raised against either paired helical filaments or hsp 28 or 70, the most prominent staining being with antibodies to Ub, hsp 28 or hsp 70. The presence of Ub and hsp 28 and 70, which are actively induced after stress, suggests that accumulation of altered proteins, possibly attributed to an increased frequency of unusual post-translational modifications or to a sustained physiological stress (related to both normal aging and neurodegenerative process), may be involved in the pathogenesis of CA.

The distribution of the large and small subunits of ribulose-1,5-bisphosphate carboxyhse in the chloroplast of Chiamydomomus reinhardtii was studied by immunoelectron microscopy by labeling Lowicrylembedded sections with antibody to each subunit followed by protein Agold. In light-harvested synchronously dividing cells, antibodies to each subunit heavily labeled the pyrenoid, whereas the thylakoid region of the plastid was lightly labeled. By estimating the volume of each chloroplast compartment, it was determined that approximately 40% of the total small subunit in the plastid and 30% of the large subunit are localized in the thylakoid region, presumably in the stroma. In synchronously dividing cells exposed to an extended dark period, the amount of labeling of the pyrenoid region by antibody to the small subunit stayed constant, but the labeling of the thylakoid region decreased. In stationary phase cells, the proportion of the label over the pyrenoid is higher than in synchronously dividing cells suggesting that the pyrenoid may be a storage organele.Pyrenoids are distinctive structures found in the chloroplasts of many species of algae from all algal classes and also in the plastid of the bryophyte Anthoceros. They are recognized as dense, homogeneous, occasionally crystalline, regions ofthe chloroplast stroma from which plastid ribosomes and DNA are excluded. Thylakoids are either absent in the pyrenoid region or reduced to varying degrees. The pyrenoids of green algae and Anthoceros are especially conspicuous for they are demarcated from the rest of the chloroplast by a shell of starch grains. In the groups of algae which store starch or a related polysaccharide outside the chloroplast, this photosynthate frequently caps the pyrenoid region of the chloroplast.Although it was realized early that pyrenoids were proteinaceous bodies, it was not until 1971 that Holdsworth (13)

No abstract

Antibody raised against the small subunit of ribulose-1,5-bisphosphate carboxylase [3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39] of Chlamydomonas reinhardtii labeled the mitochondria as well as the chloroplast of the chrysophyte alga Ochromonas danica in sections prepared for immunoelectron microscopy by the protein A-gold technique. The same antibody labeled the chloroplast but not the mitochondria of C. reinhardti. A quantitative study of labeling in dark-grown, greening (32 hr light), and mature green cells of 0. danica revealed that anti-small-subunit staining in the mitochondria increased progressively in the light as it does in the plastid. Antibody to the large subunit of the enzyme did not label the mitochondria of either 0. danica or C. reinhardWi. In view of the recent demonstrations of homologous DNA sequences in the mitochondrial and chloroplast genomes of higher plants, we suggest that the DNA sequence coding for the small subunit has migrated to the mitochondria from nucleus or chloroplast and is expressed within the organelle.Since many chloroplast and mitochondrial proteins are encoded by nuclear genes, it is implicit in the endosymbiont theory for the evolution of thsse organelles that DNA was able to migrate from the genome of the endosymbiont to that of the host cell. The recent discovery of chloroplast (1) 1456The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.