During apoptotic execution, chromatin undergoes a phase change from a heterogeneous, genetically active network to an inert highly condensed form that is fragmented and packaged into apoptotic bodies. We have previously used a cell-free system to examine the roles of caspases or other proteases in apoptotic chromatin condensation and nuclear disassembly. But so far, the role of DNase activity or ATP hydrolysis in this system has not yet been elucidated. Here, in order to better define the stages of nuclear disassembly in apoptosis, we have characterized the apoptotic condensation using a cellfree system and time-lapse imaging. We demonstrated that the population of nuclei undergoing apoptosis in vitro appears to follow a reproducible program of nuclear condensation, suggesting the existence of an ordered biochemical pathway. This enabled us to define three stages of apoptotic chromatin condensation: Stage 1 ring condensation; Stage 2 necklace condensation; and Stage 3 nuclear collapse/disassembly. Electron microscopy revealed that neither chromatin nor detectible subnuclear structures were present inside the stage 1 ring-condensed structures. DNase activity was not essential for stage 1 ring condensation, which could occur in apoptotic extracts depleted of all detectible DNase activity. However, DNase(s) were required for stage 2 necklace condensation. Finally, we demonstrated that hydrolysable ATP is required for stage 3 nuclear collapse/disassembly. This requirement for ATP hydrolysis further distinguished stage 2 from stage 3. Together, these experiments provide the first steps towards a systematic biochemical characterization of chromatin condensation during apoptosis.

Elevated plasma homocysteine is a risk factor for atherosclerotic disease. In the present study, we have examined whether the oxidative stress due to a low level of vitamin B 6 accelerates the development of homocysteine-induced atherosclerosis in rats. First, the effect of homocysteine thiolactone intake (50 mg/kg per d) on vascular integrity, lipid peroxide concentration, endothelial NO synthase (eNOS) expression and biochemical profiles was examined at day 1, day 21 and day 42 (five rats per group). The histochemical staining of the rat aorta showed no change at day 1 and day 21, but the subendothelial space was observed to be enlarged in rat aorta at day 42 with exposure to homocysteine thiolactone. Expression of eNOS was observed in rat aorta at day 42, but not at day 1 and day 21. Serum lipid peroxide concentration and biochemical profiles including glucose cholesterol and triacylglycerol showed no change at any day. Second, the effect of homocysteine thiolactone intake in the presence and absence of vitamin B 6 on vascular integrity was examined at day 1 and day 14 (five rats per group). Aortic lesions were observed in vitamin B 6 -deficient rat aorta at day 14 but not in vitamin B 6 -supplemented rats. The expression of eNOS was also observed in vitamin B 6 -deficient rat aorta at day 14. Serum lipid concentrations of the vitamin B 6 -deficient group significantly increased compared with concentrations of the vitamin B 6 -supplemented group, though serum concentration of homocysteine did not change between both groups. These results suggest that the oxidative stress caused by a low level of vitamin B 6 accelerates the development of homocysteine-induced atherosclerosis in rats.

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A keratinolytic alkaline proteae (NAPase) from Nocardiopsis sp. TOA-1 degraded a scrapie prion without any chemical or physical treatment. Optimal temperature and pH were 60 degrees C and above pH 10.0. The scrapie prion was completely degraded within 3 min under optimal conditions.

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Perchloric acid-soluble protein (PSP) may play an important role in the regulation of cellular physiological functions because it has been highly conserved throughout evolution; however, this role has not been well elucidated. In previous reports, we suggested that PSP regulates cell proliferation. In this study, we examined the effect of PSP expression on proliferation of the normal rat kidney cell line NRK-52E, the rat hepatocyte cell line RLN-10, and the rat hepatoma cell line dRLh-84. Cells transfected with pcDNA-sense-PSP (pcDNA-S-PSP) over-expressed PSP mRNA and protein, and cell proliferation of the transfected cells was suppressed compared with that of cells transfected with pcDNA-empty (pcDNA-E). Cell viability of pcDNA-S-PSP-transfected cells was similar to that of pcDNA-E-transfected cells. Thus, over-expression of PSP suppresses cell proliferation without any influence on cell viability. These findings are the first to report an inhibitory activity of PSP on cell proliferation.

To clarify the biological role of kidney perchloric acid-soluble protein 1 (K-PSP1), its expression and intracellular distribution were examined in normal rat kidney epithelial NRK-52E cells. K-PSP1 expression was low during the proliferating phase and high in the stationary phase, and shown to have a negative relationship with the protein-synthesizing activity of the cells. Immunocytochemical studies revealed that K-PSP1 is predominantly located in the cytosol, especially in endoplasmic reticulum and Golgi apparatus of proliferating cells. In the stationary phase, K-PSP1 was not detected immunologically even though protein and mRNA expression were high. This disappearance of reactivity with anti-serum seems to be due to a conformational change in K-PSP1 induced by unknown factors. These results suggest that the role of K-PSP1 is to regulate cell proliferation, and this may be related to a previously reported ability to inhibit protein synthesis.