Reduction of a disulphide in relation to the metabolic states of mitochondria

The role of -SH groups in mitochondrial energy transfer reaction was studied by observing the reduction of a disulphide, 5, 5'-dithiobis (2-nitrobenzoic acid), DTNB, a specific analytical agent for the estimation of -SH groups in biological materials, by addition of it to the isolated rat liver mitochondria in various respiratory states, as defined by CHANCE and WILLIAMS. 1. In the various respiratory states, states 1 to 5, the reduction of DTNB proceeds most rapidly at state 5, and most slowly at state 3. DTNB reduction at state 5 is suppressed by the partial oxidation of respiratory carriers with oxygen (state 4) and the addition of respiratory substrate does not affect the DTNB reduction. 2. The retardation in the reduction rate at state 3 is relieved partially by a respiratory inhibitor, KCN, and is intensified markedly by oligomycin, an inhibitor of oxidative phosphorylation. An uncoupler for oxidative phosphorylation, DNP, does not affect the reduction rate at state 3. At state 4 the reduction is stimulated by DNP and KCN, but is unaffected by oligomycin. The results suggest that the alteration in the functions of the energy transfer reaction in mitochondria is accompanied by changes in the occurrence and the functioning of -SH groups which can be detected by the reactivity with DTNB. The data suggest also that there are at least two kinds of -SH groups reacting with DTNB: the one is the -SH group which reacts DTNB actively when the respiratory carriers are kept reduced, and the other is the one which reacts actively when the respiratory carriers are kept oxidized, participating in the phosphorylating system and its reactivity with DTNB diminishes in the actively phosphorylating states (states 2 and 3).</p

Conformational studies of mitochondrial DNA

Ring DNA from rat liver mitochondria has been examined by circular dichroism (CD) in the region of the 225 to 320 m/~ and the followings have been clarified. The ring DNA gives a CD spectral curve somewhat different from linear DNA from nuclei, showing a big positive peak at 266 m/~ and a small negative band at 243 m!~. That is, the positive CD band of ring DNA shifted by about 7 m/~ to the shorter wavelength side from the band of the ordinary nuclear DNA, 273 m!~. Negative band appeared at the same region as that of linear DNA but reduced in depth. Heat denaturation of the ring DNA induced a red shift of the positive band, by about 4 mp., but no change in negative band. From these experimental results it has been concluded that the ring DNA has highly twisted conformation and high in G.C contents, both of which are responsible for the blue shift of the CD spectrum.</p

Energy metabolism during the maturation of reticulocyte in vitro

1. For the purpose to clarify the mechanism of the revolutional changes in energy metabolism during the reticulocyte maturation the metabolisms of glucose and of the pentose moieties of acid soluble nucleotides have been observed on rabbit reticulocytes incubated in vitro under various conditions. 2. The maturation of reticulocyte proceeds by using the energy produced by aerobic glycolysis and is arrested in the glucose deficient medium, but the pentose moieties of purine nucleotide and nucleoside added exogenously serve as the energy source for reticulocyte maturation even in the absence of glucose. 3. The test on the utility efficiency of glucose and inosine as the energy source for reticulocyte maturation revealed that glucose is used more effectively than the pentose moiety of inosine under aerobic condition, which is advantageous for reticulocyte maturation, and vice versa under anaerobic condition, which is comparable to the metabolism of mature red cell. 4. From these results it has been suggested that the maturation of reticulocyte is the process of degradation of RNA and acid soluble nucleotides supported by the aerobic glycolysis, where the degradation products of RNA and acid soluble purine nucleotides provide the purine derivatives as the material for ATP synthesis (36) and the pentose moieties as energy source. 5. A possible mechanism for the superior utility of glucose to nucleoside pentose during reticulocyte maturation and vice versa in mature red cell has been discussed.</p

Does reticulocyte synthesize RNA ?

As has been well established, reticulocytes (RC) synthesize the species specific protein, globin, actively for about 24 hours or more till the time of their complete maturation1,2,3. This will be possible only in the presence of messenger RNA (m-RNA)4,5. Since the splendid hypothesis of m-RNA proposed by JACOB and MONOD6 for explaining the mechanism of the transfer of genetic information from nucleus to cytoplasm, it has largely been accepted through the numerous observations that followed7,8,9,10. However, the m-RNA hypothesis, which has been deduced by observing the protein synthesis in E. Coli, includes the meaning of labile RNA which is incessantly decomposed and newly synthesized to compensate the rapid degradation. As m-RNA cannot be synthesized in RC which have no detectable DNA, it has been supposed that the m-RNA of RC should be considerably stablell,12,13. Even in the denucleated cells, however, the RNA synthesis might be possible because Borsook reported the positive RNA synthesis of RC14, and this result has recently been reconfirmed by BURNY15.</p

A Feasibility Study of Postoperative Adjuvant Therapy of Carboplatin and Weekly Paclitaxel for Completely Resected Non-small Cell Lung Cancer

IntroductionRecent clinical trials have shown significant survival benefits from postoperative adjuvant therapy for respectable nonsmall cell lung cancer (NSCLC). However, evaluation of adjuvant chemotherapy with carboplatin combination is still uncertain. The purpose of the study was to test the feasibility of adjuvant chemotherapy with carboplatin and separate weekly paclitaxel after complete resection of pStage IB, II, IIIA NSCLC in a multicenter study.MethodsThe study was conducted from 2001 to 2006 in the outpatient setting. A total of 61 patients were enrolled. Patients received adjuvant chemotherapy with 4 cycles of carboplatin (AUC 5) on day 1 and paclitaxel (70 mg/m2) on day 1, 8, and 15 every 4 weeks. Primary endpoints were toxicity and chemotherapy compliance. Secondary endpoints were disease-free survival and overall survival.ResultsMore than 65% of eligible patients had pStage IIIA. The median number of chemotherapy cycles was 4 (range 1–4). Grade 3 or 4 toxicities of neutropenia were 34% (grade 4: 2%). Other hematologic adverse effects were extremely less frequent. Regarding the nonhematologic adverse effect, hair loss was frequent; however, peripheral neuralgia was less frequent. Treatment-related death was not registered. During median follow-up of 21 months, 24 patients developed recurrent disease. Estimated disease-free survival and overall survival at 2 years was 51.2% and 84.6%, respectively.ConclusionsPostoperative carboplatin and weekly paclitaxel showed favorable feasibility and acceptable toxicity in comparison with the cisplatin-containing regimen. Consequently, it is desirable that this regimen would be validated in a phase III clinical trial for NSCLC after curative resection

Inhibition of Phospholipase A2 and Platelet Aggregation by Grycyrrhizin, an Anti-inframmation Drug

We studied the effect of glycyrrhizin, a compound known as an anti-inflammatory and antiallergic drug, on the membrane permeability change induced by phospholipase A2 (PLA2) and on platelet aggregation. Glycyrrhizin was found to inhibit the PLA2-induced carboxyfluorescein (CF) release from D,L-dipalmitoyl phosphatidylcholine (DPPC) liposomes. Part of this inhibitory effect of glycyrrhizin on PLA2 is accounted for by the physical state of the substrate, the DPPC liposome membrane. Glycyrrhizin also inhibited collagen-induced platelet aggregation in a concentration dependent manner, which may in part account for its inhibitory effect on PLA2.</p