Sequential cytotoxicity: a theory examined using a series of 3,5-bis(benzylidene)-1-diethylphosphono-4-oxopiperidines and related phosphonic acids

The concept of sequential cytotoxicity, which states that successive chemical attacks on cellular constituents can be more deleterious to neoplasms than normal cells, was evaluated using a series of 3,5-bis(benzylidene)-1-diethylphosphono-4-oxopiperidines 1 and related phosphonic acids 2, which were screened against a panel of malignant and normal cell lines. The compounds proved to be not only potent cytotoxins (71% of the CC(50) figures are submicromolar) but to display greater cytotoxicity to the neoplastic cells. QSAR revealed that both cytotoxic potencies and selective toxicity were increased by a rise in the electron-withdrawing properties and a decrease in the hydrophobicity of the aryl substituents. Utilisation of the PL10 concept and evaluation of druglike properties revealed 1c as the lead tumour-specific cytotoxin. This molecule activated caspase-3 in HL-60 cells but not in the HSC-2 cell line. While 1c caused internucleosomal DNA fragmentation in HL-60 cells, it did not elicit this effect in either HSC-2 and HSC-4 cells. Clearly 1c exerts its cytotoxic potencies by different mechanisms and such pleiotropy is likely the principal reason for the remarkable display of preferential toxicity towards malignant cells of the compounds in series 1 and 2.     

Long-range negative correlation of glucose dynamics in humans and its breakdown in diabetes mellitus

Diurnal fluctuations in glucose levels continuously monitored during normal daily life are investigated using an extended random walk analysis, referred to as detrended fluctuation analysis (DFA), in 12 nondiabetic subjects and 15 diabetic patients. The DFA exponent alpha = 1.25 +/- 0.29 for healthy individuals in the "long-range" (>2 h) regime is shown to be significantly (P < 0.01) smaller than the reference "uncorrelated" value of alpha = 1.5, suggesting that the instantaneous net effects of the dynamical balance of glucose flux and reflux, causing temporal changes in glucose concentration, are long-range negatively correlated. By contrast, in diabetic patients, the DFA exponent alpha = 1.65 +/- 0.30 is significantly (P < 0.05) higher than that in nondiabetic subjects, evidencing a breakdown of the long-range negative correlation. It is suggested that the emergence of such positive long-range glucose correlations in diabetic patients-indicating that the net effects of the flux and reflux persist for many hours-likely reflects pathogenic mechanisms of diabetes, i.e., the lack of long-term stability of blood glucose and that the long-range negatively correlated glucose dynamics are functional in maintaining normal glucose homeostasis.     

Solid phase synthesis of peptides containing novel amino acids, substituted 3-benzimidazolealanines

A direct solid-phase synthesis of a series of substituted benzimidazole-containing peptides is described. The method involves on-resin formation of new amino acids containing benzimidazole derivatives in the side chain. The heterocycle conjugates were obtained by reaction between aldehydes and peptides containing β-(3,4-diaminophenyl)alanine residue, immobilized on a polymeric solid support.     

Investigation of interaction of human platelet membrane components with anticoagulant drugs Abciximab and Eptifibatide

Abciximab (Abci) and eptifibatide (Epti) are antiaggregate drugs which may reduce thrombotic complications in acute coronary syndromes. The aim of this work was the investigation of the interaction between the phospholipid-GPIIb/IIIa glycoprotein complex and Abci or Epti, and the influence of these drugs on the phospholipid ratio in the platelet membrane. The interaction between the phospholipid-GPIIb/IIIa glycoprotein complex and antiaggregate drugs were investigated using the Surface Plasmon Resonance Imaging technique (SPRI). Phospholipids phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM) were first immobilized onto the gold chip surface. The phospholipid ratio in the platelet membrane was determined by the HPLC. Only PI, PS, PE and PC were determined. Human platelets treated 'in vitro' with Abci or Epti exhibit changes in the phospholipid ratio in the platelet membrane. The ratio of PS decreases and PC rises. The SPRI distinctly shows interactions between phospholipids and glycoprotein GPIIb/IIIa, and between the phospholipid-glycoprotein GPIIb/IIIa complex and Abci or Epti. The interaction between phospholipids and glycoprotein GPIIb/IIIa is growing in the sequence: PI相似文献   

Hydrogen Cycling by the Unicellular Marine Diazotroph Crocosphaera watsonii Strain WH8501

The hydrogen (H₂) cycle associated with the dinitrogen (N₂) fixation process was studied in laboratory cultures of the marine cyanobacterium Crocosphaera watsonii. The rates of H₂ production and acetylene (C₂H₂) reduction were continuously measured over the diel cycle with simultaneous measurements of fast repetition rate fluorometry and dissolved oxygen. The maximum rate of H₂ production was coincident with the maximum rates of C₂H₂ reduction. Theoretical stoichiometry for N₂ fixation predicts an equimolar ratio of H₂ produced to N₂ fixed. However, the maximum rate of net H₂ production observed was 0.09 nmol H₂ μg chlorophyll a (chl a)⁻¹ h⁻¹ compared to the N₂ fixation rate of 5.5 nmol N₂ μg chl a⁻¹ h⁻¹, with an H₂ production/N₂ fixation ratio of 0.02. The 50-fold discrepancy between expected and observed rates of H₂ production was hypothesized to be a result of H₂ reassimilation by uptake hydrogenase. This was confirmed by the addition of carbon monoxide (CO), a potent inhibitor of hydrogenase, which increased net H₂ production rates ∼40-fold to a maximum rate of 3.5 nmol H₂ μg chl a⁻¹ h⁻¹. We conclude that the reassimilation of H₂ by C. watsonii is highly efficient (>98%) and hypothesize that the tight coupling between H₂ production and consumption is a consequence of fixing N₂ at nighttime using a finite pool of respiratory carbon and electrons acquired from daytime solar energy capture. The H₂ cycle provides unique insight into N₂ fixation and associated metabolic processes in C. watsonii.The biological production of hydrogen (H₂) can occur as a by-product of photosynthesis, fermentation, and N₂ fixation (22). Of these three metabolic pathways, N₂ fixation remains a particularly enigmatic process, and to date there is no clear explanation for why H₂ evolves during the reduction of N₂ (11). The unfavorable energy cost of N₂ fixation can be mitigated by reassimilating the released H₂ via uptake hydrogenase enzyme activity (30). The coupled production and consumption of H₂ during cellular nitrogenase activity creates a H₂ cycle that can be hidden from measurements of ambient environmental H₂ concentrations and fluxes, depending upon the overall efficiency of H₂ assimilation (Fig. ​(Fig.11).Open in a separate windowFIG. 1.H₂ is formed during N₂ fixation by the binding of a N₂ molecule to the molybdenum-iron protein of the nitrogenase enzyme complex, prior to the reduction of N₂ to ammonia (11, 15). The most energetically favorable theoretical in vivo stoichiometry predicts that one mole of H₂ is produced for every mole of N₂ reduced: N₂ + 8H⁺ + 8e⁻ + 16ATP → 2NH₃ + H₂ + 16ADP + 16P_i. The production of H₂ consumes 25% of the electron flux through nitrogenase and diazotrophs mitigate this loss of potential energy by reassimilating the H₂ via uptake hydrogenase (21, 30). The electrons produced by uptake hydrogenase either generate reductant or ATP with simultaneous consumption of O₂ (3). (Adapted from reference 32a.)For most cultures of phototrophic marine diazotrophs grown under optimal conditions, complete reassimilation of H₂ is not achieved, and the excess H₂ is lost to the surrounding environment. This excess H₂ equates to the net production of H₂ and is expressed as the ratio of H₂ formed to N₂ fixed or the H₂/N₂ ratio. To date, H₂/N₂ ratios have mainly been measured on filamentous, colony-forming diazotrophs such as Anabaena spp. and Trichodesmium spp. with H₂ production rates of up to 20 nmol H₂ μg chlorophyll a (chl a)⁻¹ h⁻¹ and H₂/N₂ ratios ranging from 0.01 to 0.48 (3, 20, 24). H₂ production has also been quantified in unicellular diazotrophs (12, 16, 17, 32), although the H₂ measurements have rarely been performed in conjunction with rates of N₂ fixation. However, recent H₂ measurements of two N₂-fixing unicellular cyanobacteria species reached a maximum of 1.38 nmol H₂ μg chl a⁻¹ h⁻¹, with H₂/N₂ ratios ranging from 0.003 to 0.05, indicating an effective reassimilation of H₂ can occur under certain conditions (34).H₂ cycling in marine diazotrophs has important ecological implications both for the cell and for the marine H₂ cycle. Surface waters of low-latitude oceans are typically 200 to 300% supersaturated in dissolved H₂ with respect to atmospheric concentrations (25), implying a sustained localized production of H₂. The source of the dissolved H₂ is thought to be biological N₂ fixation (7); however, the relative contributions of diverse diazotrophic communities and in situ controls on H₂/N₂ ratios are not well constrained. N₂ fixation is performed by a suite of diazotrophs typically identified by their nitrogenase gene (nifH) sequences amplified directly from oceanic water samples (35). The importance of unicellular diazotrophs, including Crocosphaera spp., in marine N₂ fixation has recently become widely recognized (36). Size-fractionated rates of N₂ fixation indicate that in the oligotrophic ocean, <10-μm microorganisms, which include the unicellular cyanobacteria, make a substantial contribution to the daily N₂ fixation (9, 18). Correlating the species-specific production of H₂ with the activity and biomass of diazotrophs will help elucidate dissolved H₂ cycling in the upper ocean.We examined the cycling of H₂ in cultures of Crocosphaera watsonii strain WH8501, a marine unicellular diazotroph, and correlated it with other metabolic parameters, including N₂ fixation measured via acetylene (C₂H₂) reduction, O₂ production and consumption, and photosynthetic efficiency. Carbon monoxide (CO) was used as an inhibitor of intracellular H₂ reassimilation to reveal the H₂ cycling that can occur in conjunction with nitrogenase activity. H₂ reassimilation by C. watsonii was shown to be very efficient in our laboratory experiments, which is considered to be a consequence of the temporal separation between daytime photosynthetic activity and nighttime N₂ fixation. Therefore, the present study not only reveals the cell''s H₂ cycle but also provides insight into the metabolism of nitrogenase in C. watsonii.     

Genetic predisposition to papillary thyroid cancer

Approximately 5% of differentiated thyroid cancers are hereditary. Hereditary non-medullary thyroid cancer may occur as a minor component of familial cancer syndromes (e.g. familial adenomatous polyposis) or as a primary feature (familial non-medullary thyroid cancer [FNMTC]). Among FNMTC, PTC is the most common. Although a hereditary predisposition to non-medullary thyroid cancer is well established, the susceptibility genes are poorly known. Up to now, by linkage analysis using microsatellite markers, several putative loci have been described - 1q21, 6q22, 8p23.1-p22, and 8q24; however, validation studies have been unsuccessful. In the present review we discuss the results of linkage analysis and the most recent results of genome wide association studies (GWAS) with high resolution SNP (single nucleotide polymorphism) arrays.     

On the photosynthetic properties of marine bacterium COL2P belonging to Roseobacter clade

Aerobic anoxygenic phototrophs (AAPs) are prokaryotic microorganisms capable of harvesting light using bacteriochlorophyll-based reaction centres. Marine AAP communities are generally dominated by species belonging to the Roseobacter clade. For this reason, we used marine Roseobacter-related strain COL2P as a model organism to characterize its photosynthetic apparatus, level of pigmentation and expression of photosynthetic complexes. This strain contained functional photosynthetic reaction centres with bacteriochlorophyll a and spheroidenone as the main light-harvesting pigments, but the expression of the photosynthetic apparatus was significantly reduced when compared to truly photoautotrophic species. Moreover, the absence of peripheral light-harvesting complexes largely reduced its light-harvesting capacity. The size of the photosynthetic unit was limited to 35.4 ± 1.0 BChl a molecules supplemented by the same number of spheroidenone molecules. The contribution of oxidative phosphorylation and photophosphorylation was analysed by respiration and fluorometric measurements. Our results indicate that even with a such reduced photosynthetic apparatus, photophosphorylation provides up to three times higher electron fluxes than aerobic respiration. These results suggest that light-derived energy can provide a substantial fraction of COL2P metabolic needs.