Overexpression of the protein disulfide isomerase AtCYO1 in chloroplasts slows dark-induced senescence in Arabidopsis.

BACKGROUND: Chlorophyll breakdown is the most obvious sign of leaf senescence. The chlorophyll catabolism pathway and the associated proteins/genes have been identified in considerable detail by genetic approaches combined with stay-green phenotyping. Arabidopsis CYO1 (AtCYO1), a protein disulfide reductase/isomerase localized in the thylakoid membrane, is hypothesized to assemble the photosystem by interacting with cysteine residues of the subunits. RESULTS: In this study, we report that ectopic overexpression of AtCYO1 in leaves induces a stay-green phenotype during darkness, where oxidative conditions favor catabolism. In AtCYO1ox leaves, Fv/Fm and both chlorophyll a and chlorophyll b content remained high during dark-induced senescence. The thylakoid ultrastructure was preserved for a longer time in AtCYO1ox leaves than in wild type leaves. AtCYO1ox leaves maintained thylakoid chlorophyll-binding proteins associated with both PSII (D1, D2, CP43, CP47, LHCB2, and Cyt f) and PSI (PSA-A/B), as well as stromal proteins (Rubisco and ferredoxin-NADP+ reductase). AtCYO1ox did not affect senescence-inducible gene expression for chlorophyll catabolism or accumulation of chlorophyll catabolites. CONCLUSIONS: Our results suggest that ectopic overexpression of AtCYO1 had a negative impact on the initiation of chlorophyll degradation and proteolysis within chloroplasts. Our findings cast new light on the redox regulation of protein disulfide bonds for the maintenance of functional chloroplasts.

Changes in the microhemodynamics of nerve root retraction in patients with lumbar spinal canal stenosis.

STUDY DESIGN: Assessment of qualitative and quantitative changes in the microcirculation of nerve roots, such as the diameter of blood vessels and the low rate of erythrocytes, was observed during lumbar interbody fusion. OBJECTIVE: To ascertain changes in the microcirculation of nerve roots before and after retraction during lumbar interbody fusion surgery. SUMMARY OF BACKGROUND DATA: The changes in microhemodynamics caused by nerve root retraction have not yet been elucidated. METHODS: Subjects were patients with lumbar spinal canal stenosis who underwent lumbar interbody fusion. Changes in the microcirculation of nerve roots were examined in the L5 nerve root in 26 patients and the S1 nerve root in 3 patients. Through the use of video images captured by contact endoscope and stored in a computer, erythrocytes were automatically followed to measure flow rate and the diameter of blood vessels. RESULTS: Plasma skimming, where blood cells and plasma flow separately, was seen in 3 of the 29 patients (10.3%) before retraction of the nerve root and in 8 of the 29 patients (27.6%) following retraction. Intravascular erythrocyte agglutination, when erythrocytes flow in clumps due to changes in the charge state of erythrocytes, was seen in blood vessels larger than 100 microm in 3 patients (10.3%) after retraction. Following nerve root retraction, the flow rate of erythrocytes through blood vessels decreased an average of 23.9% (P< 0.005). CONCLUSIONS: A contact endoscope was used to observe the microhemodynamics of nerve roots before and after retraction of the nerve root during lumbar interbody fusion surgery, and a decrease in the flow rate of erythrocytes was observed.

Parachordoma with multiple metastases.

We present a very rare case of parachordoma with local aggressiveness and widespread metastases. A 68-year-old male presented with a mass in his left calf. The lesion was depicted as a poorly marginated mass with inhomogeneous signal intensity on magnetic resonance imaging. The tumor invaded surrounding muscles, neurovascular bundles, and bones. Widespread metastasis to lung, bone, and skin developed after amputation surgery. The histologic features of primary and metastatic lesions were the same and consistent with parachordoma.