Trehalose Increases Freeze-Thaw Damage in Liposomes Containing Chloroplast Glycolipids

Chloroplast thylakoids contain three classes of glycolipids, monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol (SQDG). We have investigated the stability of large unilamellar vesicles made from egg phosphatidylcholine (EPC) and different chloroplast glycolipids during freezing to -18 degreesC, as a function of the presence of three sugars: glucose, sucrose, or trehalose. Contrary to the situation in thylakoids, where cryoprotection increases from glucose < sucrose < trehalose, liposomes containing 50% DGDG showed the opposite behavior. In fact, carboxyfluorescein leakage increased over the control values (freezing in the absence of sugar) in the presence of trehalose. This effect was not seen in vesicles made from pure EPC, or a mixture of EPC and MGDG, or EPC and SQDG. Liposomes made from mixtures of all three glycolipids, however, showed even more leakage in the presence of trehalose than liposomes containing only DGDG and EPC. Copyright 1998 Academic Press.     

Plasma concentrations of 13,14-dihydro-15-keto-prostaglandin E2 in rabbits bearing the VX2 carcinoma: Effects of hydrocortisone and indomethacin

In rabbits bearing the prostaglandin-producing VX₂ carcinoma, the plasma concentration of 13,14-dihydro-15-keto-PGE₂ (PGE₂-M) was elevated within one week after tumor implantation and preceded the development of hypercalcemia. Both the rate of rise and magnitude of the increase were greater for the metabolite than for PGE₂; at the time of peak hypercalcemia (about 4 to 5 weeks after tumor implantation), the increase over basal in plasma PGE₂-M was about 75 fold whereas it was previously shown that the increase in PGE₂ was less than 2 fold. Indomethacin, which inhibits PGE₂ synthesis in VX₂ cells in culture, lowered in parallel plasma calcium and PGE₂-M in tumor-bearing rabbits. Administration of hydrocortisone to rabbits bearing the VX₂ tumor prevented the development of hypercalcemia when given at the time of tumor implantation and reversed the elevated plasma calcium in previously untreated animals; the steroid hormone also lowered plasma concentrations of PGE₂-M. These findings are consistent with our hypothesis that the hypercalcemic syndrome in VX₂ tumor-bearing rabbits is due to the secretion of PGE₂ by the tumor.     

Creatine kinase isoenzyme activity during and after an ultra-distance (200 km) run

It is commonly assumed that creatine kinase (CK) activity in plasma is related to the state of an inflammatory response at 24-48 h, and also it has shown biphasic patterns after a marathon run. No information is available on CK isoenzymes after an ultra-marathon run. The purpose of the present study is to examine the CK isoenzymes after a 200 km ultra-marathon run and during the subsequent recovery. Blood samples were obtained during registration 1 2 h before the 200-km race and during the race at 100 km, 150 km and at the end of 200 km, as well as after a 24 h period of recovery. Thirty-two male ultra-distance runners participated in the study. Serum CPK showed a marked increase throughout the race and 24 h recovery period (p < 0.001). Serum CK during the race occurs mostly in the CK-MM isoform and only minutely in the CK-MB isoform and is unchanged in the CK-BB isoform. High-sensitivity C-reactive protein (hs-CRP), oestradiol, AST and ALT increased significantly from the pre-race value at 100 km and a further increase took place by the end of the 200 km run. The results of our study demonstrate a different release pattern of creatine kinase after an ultra-distance (200 km) run compared to the studies of marathon running and intense eccentric exercise, and changes in several biomarkers, indicative of muscle damage during the race, were much more pronounced during the latter half (100–200 km) of the race. However, the increases in plasma concentration of muscle enzymes may reflect not only structural damage, but also their rate of clearance.     

Lack of geographic variation in anonymous nuclear polymorphisms in the American oyster, Crassostrea virginica

Comparing geographic variation of noncoding nuclear DNA polymorphisms, which presumably are neutral to natural selection, with geographic variation of allozymes is potentially a good way to detect the effects of selection on allozyme polymorphisms. A previous study of four anonymous nuclear markers in the American oyster, Crassostrea virginica, found dramatic differences in allele frequency between the Gulf of Mexico and the Atlantic Ocean. In contrast, 14 allozyme polymorphisms were fairly uniform in frequency between the two areas. This led to the conclusion that all of the allozyme polymorphisms were kept uniform in frequency by balancing selection. To test the robustness of this pattern, six additional anonymous nuclear DNA polymorphisms were surveyed in oysters from Panacea, Fla, and Charleston, S.C. on the Gulf and Atlantic coasts, respectively. Unlike the previously studied DNA markers, the six DNA polymorphisms examined here show geographic variation that is not significantly greater than that of allozymes. The reason for the discrepancy between the two sets of DNA polymorphisms is unclear.      

Quenching of intrinsic tryptophan fluorescence in membranes of rat pituitary cells

The GH₄C₁ strain of hormone-producing rat pituitary cells has specific receptors for the tripeptide thyrotropin-releasing hormone (TRH). Membranes prepared from GH₄C₁ cells show intrinsic tryptophan fluorescence which was quenched by low concentrations (10–100 nM) of TRH and N^τ-methyl TRH but not by biologically inactive analogs of TRH. Membranes from GH₄C₁ cells were subjected to thermal denaturation. A conformational transition was noted above 40°C and an irreversible denaturation was observed at 52°C. TRH-induced quenching of intrinsic fluorescence was lost completely in membranes previously incubated for 10 min at 30°C while loss of [³H]-TRH binding was only about 20% at this temperature. Collisional quenching by iodide revealed that about 38% of the tryptophanyl residues in GH₄C₁ membranes were exposed to solvent. Quenching by TRH occurred with a shift in wavelength maximum from 336 to 342 nm suggesting that few of the tryptophanyl residues quenched by the tripeptide are totally exposed. Membranes prepared from cells preincubated with 20 nM TRH for 48 h, in which TRH receptors were decreased to 30% of control values, showed no quenching of tryptophan fluorescence in response to freshly added TRH. We conclude that the TRH-receptor interaction in GH₄C₁ cells is associated with a change in membrane conformation that can be measured by differential spectrofluorometry of intrinsic tryptophan fluorescence.     

Molecular docking analysis of bioactive compounds from Plectranthus amboinicus with glucokinase

Natural remedies from medicinal plants are known to be effective and reliable appropriate medicine for illnesses. The current research examined Plectranthus amboinicus'' anti diabetic property by docking the bioactive compounds of certain target proteins. We document the molecular docking analysis of bioactive compounds from Plectranthus amboinicus with protein Glucokinase. Molecular docking experiments were carried out in PyRx software. Results of these docking experiments showed that most of the compounds showed very strong interaction with the target protein Glucokinase. Based on the scoring parameters we have selected best four compounds (Rutin, Salvianolic acid, Luteolin and Salvigenin) which showed very good docking score and hydrogen bond interaction for diabetics.