Mainly using the protein immunoblot technique, we observed the decrease in amounts of the large subunit (LSU) and the small subunit (SSU) of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) in detached primary leaves of French bean plants during senescence under the light or in darkness, but detected no significant degradation products of these subunits. Treatment of the detached leaves with 0.6 % (masshol.) dimethyl sulfoxide, 0.05 % (masshol.) Tween 80 considerably promoted the senescence, as estimated by the reduction in content of the soluble protein, and also in the amounts of LSU and SSU, but no degradation product of either subunit was found. When extracts prepared from the primary leaves were incubated at pH 5.4 or pH 7.4, the amount of LSU of 53 kDa decreased and concurrently 50-kDa and 42-kDa polypeptides were formed. Since the results suggested that Rubisco may be degraded by vacuolar enzymes, we incubated Rubisco with vacuolar lysates prepared from the senescing primary leaves and found that the LSU, but not SSU, was degraded to a 41-kDa polypeptide through three intermediates of 50 kDa, 48 kDa and 42 kDa. Determination of amino-terminal amino acid sequences of these fragments indicated that each of the proteolysis steps occurred by removal of a small amino-terminal peptide. Experiments with various inhibitors of proteases as well as with a purified Vigna mungo vacuolar protease, termed SH-EP [Mitsuhashi, W. & Minamikawa, T. (1989) Plant Physiol. 89, 274-2791 suggested the involvement of two types of proteases in these steps: a cysteine protease that is the same type of enzyme as SH-EP catalyzes the steps from the LSU to the 48-kDa polypeptide through the 50-kDa polypeptide, and a serine protease catalyzes the steps from the 48-kDa polypeptide to the 41-kDa polypeptide through the 42-kDa polypeptide.
Low-density lipoprotein (LDL) is an important risk factor for coronary artery disease, but its localization within the human coronary arterial wall is poorly understood. Imaging of LDL in 30 coronary arteries excised from 15 subjects who underwent autopsy was performed using near-infrared fluorescent angioscopy system and using indocyanine green dye as a biomarker of LDL. The percentage incidence of LDL in 28 normal segments, 24 white plaques (early stage of plaque growth), and 21 yellow plaques (mature stage of plaque) classified by conventional angioscopy, was 14.2, 79.1 (p <0.01 vs normal segments and p <0.05 vs yellow plaques), and 28.5, respectively. Coronary near-infrared fluorescent angioscopy showed similar results in 7 patients in vivo. Our results suggested that LDL begins to deposit in the human coronary arterial wall in the early stage of atherosclerosis, increasingly deposits with plaque growth and decreases in the mature stage; and therefore, molecular therapy targeting LDL should be started before plaque maturation.
A 70-year-old woman developed paraneoplastic cerebellar degeneration (PCD) due to P/Q-type and N-type voltage-gated calcium channel antibodies and small cell lung cancer, the main clinical manifestations of which were severe positioning vertigo and vomiting. Loss of the visual suppression of caloric nystagmus, spontaneous downbeat nystagmus, periodic alternating nystagmus, and positioning vertigo in our patient most probably corresponds to the cerebellar flocculus/paraflocculus lesion caused by PCD.
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