pH-dependent characteristics of Y(Z) radical in Ca(2+)-depleted photosystem II studied by CW-EPR and pulsed ENDOR

The Y(Z)-tyrosine radical was trapped by freezing immediately after illumination in Ca(2+)-depleted Photosystem II (PS II) membranes and the pH-dependent characteristics of the radical were investigated using CW-EPR and pulsed ENDOR. The spectrum of the Y*(Z) radical trapped in the Y*(Z)S(1) state at pH 5.5 was cation-like as reported in Mn-depleted PS II (H. Mino et al., Spectrochim. Acta A 53 (1997) 1465-1483). By illuminating the PS II-retaining S(2) state, the Y*(Z) radical and a broad doublet signal formed in the g approximately 2 region were trapped concomitantly. The spectrum of the trapped Y*(Z) radical in the Y*(Z)S(2) state was cation-like at pH 5.5 but the pulsed ENDOR measurements reveals the involvement of the neutral Y*(Z) radical in the doublet signal. At pH 7.0, the resulting Y*(Z) signal was the mixture of the cation-like and neutral radical spectra, and considerably different from the neutral radical found in Mn-depleted PS II. pH-Dependent changes in the properties of the Y*(Z) radical are discussed in relation to the redox events occurring in Ca(2+)-depleted PS II.     

Pulsed EPR studies of doublet signal and singlet-like signal in oriented Ca2+-depleted PS II membranes: location of the doublet signal center in PS II

Doublet signal and singlet-like signal induced in Ca(2+)-depleted PS II were investigated by pulsed EPR in one-dimensionally oriented photosystem (PS) II membranes. The doublet signal showed marked angular dependent change in its spectrum in term of the applied magnetic field, indicating that the magnetic dipole-dipole interaction is mainly responsible for the doublet signal. The singlet-like signal also showed angular dependence, which was less pronounced than that of the doublet signal. The parameters of dipole and exchange interactions used to simulate the doublet signal indicate that the signal arises from a magnetically coupled organic radical pair. Angular dependence of the doublet signal indicates that the radius vector of the radical pair (r) and the normal of the thylakoid membrane is at an angle of 65 degrees. Pulsed ELDOR studies in the oriented membranes indicate that the vector (R) connecting the doublet-signal center with the Y(D)(*) radical and the plane of the thylakoid membrane are at an angle of 8 degrees. Furthermore, the angle between the projections of the R and r vectors on the plane of the thylakoid membrane was determined to be 64 degrees. The location of the doublet-signal species in PS II is discussed.     

Liver-Derived Systemic Factors Drive β Cell Hyperplasia in Insulin-Resistant States

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Highlights? Circulating nonneuronal factors drive β cell replication in LIRKO mice ? LIRKO serum increases mouse and human islet β cell replication in vitro ? LIRKO serum induces selective β cell replication in vivo ? Hepatocyte-derived factors stimulate mouse and human β cell replication in vitro     

Insulin and nateglinide reduce monocyte adhesion to endothelial cells in Goto-Kakizaki rats exhibiting repetitive blood glucose fluctuation

Epidemiological studies demonstrated the importance of postprandial hyperglycemia on the progression of atherosclerosis. However, whether treatment of postprandial hyperglycemia by insulin or insulin secretagogues has a beneficial effect on atherosclerosis has not been elucidated. To elucidate the effects of reduction of postprandial rise of blood glucose by insulin and nateglinide on monocyte adhesion to endothelial cells, we used non-obese type 2 diabetic Goto-Kakizaki (GK) rats fed twice daily, as a model of repetitive postprandial hyperglycemia. We investigated the effects of insulin injection and nateglinide administration just before each meal for 12 weeks on monocyte adhesion to endothelial cells. By setting the doses of insulin and nateglinide, both treatment significantly reduced postprandial hyperglycemia without significant reduction of HbA1c. Nateglinide also reduced serum insulin level just after 1 h meal. Both nateglinide and insulin therapy reduced the number of monocytes adherent to the aortic endothelial layer. Nateglinide, but not insulin, reduced intimal thickness of the thoracic aorta. While increased serum insulin level might be regarded as a factor responsible for the progression of atherosclerosis, our data showed that treatment with pre-meal insulin or nateglinide, which reduces postprandial hyperglycemia, reduced monocyte adhesion to endothelial cells.     

A model for evaluation of the peroral insulin therapy: short-term treatment of alloxan diabetic rats with oral water-in-oil-in-water insulin emulsions.

Alloxan diabetic rats with fasting blood glucose levels above 300 mg/100 ml were treated with oral administration of water-in-oil-in-water (W/O/W) insulin emulsions at a dose of 50 U/100 g body weight, three times daily for 10 to 14 days. The course of diabetes was followed by determinations of glucose levels in blood and urine. During treatment with oral W/O/W insulin emulsions, daily excretion of urinary glucose decreased by about 30 to 40% (2 to 3 g/day) in all of the five rats studied, and returned to the pre-treatment levels after the treatment being discontinued. During treatment, a significant reduction in fasting blood glucose levels was observed in 4 out of 5 rats, giving the decrease by 18 to 44%. Quantitative estimates suggested that the effectiveness of 50 U/100 g of oral W/O/W insulin emulsions was comparable to that after intramuscular regular insulin at a dose of 0.5 U/100 g. Although oral W/O/W insulin emulsions are still of low efficiency, these results would indicate that diabetes can be controlled by effective oral insulin preparations.     

Immunological Properties of Borrelia burgdorferi Isolated from the Ixodes ovatus in Shizuoka,Japan

Three strains of spirochetes (IKA1 to 3) were isolated from the midgut of Ixodes ovatus collected in the Ikawa region of the northern part of Shizuoka, Japan. These isolates had eight flagella, and their size and other morphological features were similar to Borrelia burgdorferi. They showed similar motility and reacted with monoclonal antibody (MAb) H9724 against borrelial flagella and with MAb H5332 against the outer surface protein A. These strains showed similar SDS-PAGE profiles to that of B. burgdorferi strain B31 and P/Bi isolated in the U.S.A. and Europe, respectively. Immunoblot with Lyme disease patient serum showed positive reactions with the flagella (41 Kilodalton, kDa), protein C (20 to 22 kDa), and outer surface protein A (29 kDa) of the isolates. Immunological properties, morphological characteristics, and epidemiological features revealed that these isolates were B. burgdorferi.     

Reconstitution of photosynthetic charge accumulation and oxygen evolution in CaCl2-treated PS II particles: II: EPR evidence for reactivation of the S1 → S2 transition in CaCl2-treated PS II particles with the 17-, 23-, and 34-kDa proteins

Extraction of PS II particles with 1 M CaCl₂ caused complete disappearance of the light-induced signal of the possible Kok S₂ state of the water-splitting complex and total loss of the O₂, evolving activity, concomitant with perfect removal of the 17-, 23- and 34-kDa proteins from the particles. The recovery of the multiline signal in the CaCl₂-treated PS II was performed by reinserting the 34-kDa protein, when CI^? was present in the solution for the EPR measurement. However, in the absence of Cl^?, besides the 34-kDa protein, the 17- and 23-kDa proteins were required for the recovery of the signal. These results are compared with the results on the recovery of the O₂, evolution in the reconstituted PS II to examine the role of these three proteins on the water splitting.