Glyceraldehyde-derived advanced glycation end-products having pyrrolopyridinium-based crosslinks

Reducing sugars and reactive aldehydes, such as glyceraldehyde, non-enzymatically react with amino or guanidino groups of proteins to form advanced glycation end-products (AGEs) by the Maillard reaction that involves Schiff base formation followed by Amadori rearrangement. AGEs are found relatively in abundance in the human eye and to accumulate at a higher rate in diseases that impair vision such as cataract, diabetic retinopathy or age-related macular degeneration. We identified two novel AGEs of pyrrolopyridinium lysine dimer derived from glyceraldehyde, PPG1 and PPG2, in the Maillard reaction of N^α-acetyl-l-lysine with glyceraldehyde under physiological conditions. Having fluorophores similar to that of vesperlysine A, which was isolated from the human lens, PPGs were found to act as photosensitizers producing singlet oxygen in response to blue light irradiation. Moreover, PPG2 interacts with receptor for AGE (RAGE) in vitro with a higher binding affinity than GLAP, a well-known ligand of the receptor. We also proposed a pathway to form PPGs and discussed how they would be formed in vitro. As glyceraldehyde-derived AGEs have been studied extensively in connection with various hyperglycemia-related diseases, further studies will be required to find PPGs in vivo such as in the lens or other tissues.     

Secretion of TNF-α from macrophages following induction with a lignin derivative.

Macrophages derived from rat bone marrow were treated with macrophage colony stimulating factor (M-CSF) to obtain a sufficient number of cells for the tumor necrosis factor (TNF-α) assay. The present study has been designed to investigate whether the production of TNF-α, which induces multinucleated giant cell formation, is regulated by polyanions such as lignin derivatives. ELISA for TNF-α showed that the polyanion induced TNF-α production by macrophages. The secretion of TNF-α from the cells reached a maximum at 3-6 h, and then showed a slight decline. Northern blotting of TNF-α mRNA showed that the amount of TNF-α reached a maximum within 1 h of macrophage culture in the presence of a lignin derivative. On the other hand, TNF-α mRNA was undetectable in the control cells. It was concluded that stimuli such as that provided by lignin derivatives increases the amount of TNF-α mRNA, which is then followed by translation of TNF-α.     

An Approach to Prebiotic Synthesis of α-Oligoribonucleotides and Description of Their Properties: Selective Advantage of β-RNA over α-RNA

Oligomerization of α-adenosine 5′-phosphorimidazolide (α-ImpA) has been done in an aqueous solution using a uranyl-ion catalyst or a poly(U) template as a model process of prebiotic synthesis of RNA with α-glycosidic linkage. α-Oligoriboadenylates up to hexamer were formed from α-ImpA by the uranyl-ion catalyst. 3′-5′ Linkage was mainly formed in the oligomerization. The poly(U) template mediated the oligomerization of α-ImpA, but to a very low extent. The yield and chain length of the resulting α-oligomers were far lower than those of the corresponding β-oligomer formation under the same conditions. Physico-chemical properties of α-oligoriboadenylates are presented along with those of the corresponding β-oligoriboadenylates. The results indicate that β-RNA is more advantageous than α-RNA from the points of their synthesis and properties. Received: 10 February 1997 / Accepted: 31 March 1997     

Examination of the food processes on mixed inferior host plants in a polyphagous grasshopper

The mass gain of polyphagous grasshoppers fed a mixture of intrinsically inferior plants is often greater than that of grasshoppers fed each inferior plant alone. We examined the cause of this greater mass gain by assessing the food processes of a polyphagous grasshopper in detail. Food processes were divided into five stages: consumption, fecal mass, assimilated food, approximate digestibility, and efficiency of conversion of digested food (ECD). Using final-stadium female nymphs of the polyphagous grasshopper Parapodisma subastris, we compared the mass gain of nymphs fed the inferior plants Polygonum cuspidatum and Weigela hortensis or the superior plant Artemisia princeps. The mass gain of nymphs fed a single inferior plant was less than that of nymphs fed the superior plant because of reduced ECD. However, the mass gain of nymphs fed a mixture of the two inferior plants was not only greater than that of nymphs fed a single inferior plant, but also did not differ from that of nymphs fed the superior plant. Since consumption by nymphs fed the mixture was greater than that by nymphs fed P. cuspidatum and smaller than that by nymphs fed W. hortensis, and since the ECD of nymphs fed the mixture was greater than that of nymphs fed W. hortensis and was not different from that of nymphs fed P. cuspidatum, consumption and ECD appeared to cause the greater mass gain in nymphs fed the mixture.     

Effect of probucol on recovery from streptozotocin diabetes in rats.

The present study was conducted to see the effect of probucol on streptozotocin diabetes in rats. After 2 weeks of a 1% probucol diet, 35 or 50 mg/kg of streptozotocin were intravenously injected into male Wistar rats. All the rats became diabetic 2 days after treatment. Thereafter, in order to see the effect of probucol on spontaneous recovery from streptozotocin diabetes, 25 mg/kg of streptozotocin was injected into rats after two weeks of probucol diet and the diet was continued for additional two weeks. All the rats with a standard diet (group CS, n = 13) and 12 of 13 rats with probucol diet (group PS) became diabetic 2 days after streptozotocin injection. One rate from group PS did not develop diabetes. Two weeks after injection, only 4 of 13 rats in groups CS showed recovery, while 11 of 12 rats in group PS showed recovery from streptozotocin diabetes (p less than 0.05). The average blood glucose levels in group PS were significantly lower than group CS (10.5 +/- 4.6 vs 18.5 +/- 0.6 mM, p less than 0.05). In addition, the pancreatic insulin content of group PS was 8 times greater than that of group CS (0.75 +/- 0.24 vs 0.09 +/- 0.03 mmol/pancreas, p less than 0.01). Thus, the in vivo diabetogenic action of streptozotocin could not be reduced by pretreatment with probucol. However, recovery from streptozotocin diabetes was induced by subsequent treatment with probucol. The precise mechanisms for this phenomenon were not known; but the present findings suggest the protective effect of probucol on beta-cell damage induced by small dose of streptozotocin.     

Granilin and ivasperin from Ambrosia polystachya. 13C-NMR spectra of hydroxylated isoalantones

The eudesmanolides granilin and ivasperin were isolated from Ambrosia polystachya DC. ¹³C-NMR spectra are reported for these and other naturally-occurring ring A-hydroxylated isoalantolactones.