Assessment of DNA binding of platinum-radiosensitizer complexes by inhibition of restriction enzymes

A simple and rapid method has been used to compare the binding of platinum complexes to DNA, in a relatively qualitative manner. A compound bound at or near the restriction site inhibits enzymatic cleavage of DNA; inhibition of BamHI and EcoRI activity by complexes was assessed in this study using linearized pSV2-gpt plasmid. Our particular interest was in DNA binding by complexes of platinum (Pt) with known organic radiosensitizers (RS), to determine whether the Pt was able to target the RS to the DNA. Although the Pt-RS complexes investigated themselves have moderate radiosensitizing ability (like the inorganic complexes, cis- or trans-diamminedichloroplatinum(II), c- or t-DDP) none of the Pt-RS inhibit to the same extent as c- or t-DDP. However, there appears to be some correlation between enhanced radiosensitization by Pt-RS over Pt(RS)2, with the degree of Pt binding (as assessed by our assay). Our results using isolated DNA suggest that not all complexes bind well (e.g. Pt with two RS ligands), but that in certain cases (e.g. Pt with only one RS), it is possible to target the drug to the DNA. An ammine or amine ligand may be required in order to target a radiosensitizer to DNA using platinum.     

El carcinoma diferenciado incidental de tiroides es menos prevalente en la enfermedad de Graves que en el bocio multinodular

ObjectiveRisk factors for differentiated thyroid carcinoma (DTC) are poorly understood, but serum TSH levels, thyroid nodularity, and presence of autoimmunity are well-recognized factors that modulate DTC prevalence. TSH stimulates proliferation of both normal and neoplastic follicular cells. Consequently, thyroid-stimulating immunoglobulins (TSI), because of its TSH-like action, should induce DTC progression in patients with Graves’ disease (GD). The study objective was to compare the prevalence of incidental DTC in patients undergoing thyroidectomy for benign thyroid disease.MethodsThe pathology reports of 372 patients with preoperative diagnosis of euthyroid multinodular goiter (EMG) or hyperthyroidism were reviewed. Scintigraphy results and serum TSI levels were used to diagnosed either GD or hyperactive MG (HMG) to hyperthyroid subjects. Prevalence of DTC in each category was calculated using a Chi-square test.ResultsEMG, GD, and HMG were diagnosed in 221, 125, and 26 patients. There were 58 DTCs, distributed as follows [n (%)]: EMG, 49 (22.2%); GD, 8 (6.4%), and HMG, 1 (3.8%). Difference in prevalence of incidental DTC between the groups was statistically significant (p < 0.001). After adjustment for age, patients with EMG had a greater DTC prevalence than GD patients, with an OR of 4.17 (p < 0.001). Tumor size (mm, mean ± SD) was 6.92 ± 11.26, 1.97 ± 1.85, and 9.0 for EMG, GD and HMG respectively (p = 0.017).ConclusionsIncidental DTC was less prevalent in GD as compared to EMG irrespective of age. This finding may suggest a predisposition to develop DTC in patients with thyroid nodular disease and/or a potential effect of autoimmunity to protect against development of neoplastic disease.     

Comparison of Zinc Reduction with Platinum Reduction for Analysis of Deuterium‐Enriched Water Samples for the Doubly Labeled Water Technique

Objective: Isotope ratio mass spectrometry of hydrogen and oxygen is frequently used to determine total energy expenditure (TEE) using doubly labeled water. Conventionally, hydrogen isotope ratio is determined in hydrogen gas generated from water samples using zinc reduction. We compare this with a new automated platinum method to determine the ratios of hydrogen isotopes in deuterium‐enriched water samples. Research Methods and Procedures: The platinum method of sample preparation was compared with the zinc method in three ways: analytical variation in deuterium enrichment (within sample; n = 51), analytical variation in TEE estimates (within sample set; n = 10), and level of agreement of TEE estimates between both methods (n = 14). Results: For the zinc method, the standard deviation for multiple sets of triplicate ²H₂O sample analysis was ±4.36‰ and ±2.07‰ for platinum. The correlation between TEE estimates when sample sets were analyzed in duplicate was r = 0.89 for zinc and r = 0.83 for platinum. The intercept and slope of the regression line were significantly different from the line of identity for duplicate TEE estimates by zinc but were not different from the line of identity for platinum. After correction for the intra‐assay variation of each method, the correlation between zinc and platinum for TEE was 0.77, and the intercept, but not the slope, of the regression was significantly different from the line of identity. The mean difference between the zinc method and the platinum method was 56 kcal/day, and the 95% confidence interval was ?438 to 550 kcal/day. Discussion: These data suggest that the platinum method is at least as reliable as the zinc method as a sample preparation technique for isotope ratio mass spectrometry of deuterium‐enriched water samples. The platinum method is also less costly and less labor‐intensive than the zinc method.     

Nutrients and disturbance history in two Plantago species: maternal effects as a clue for observed dichotomy between resprouting and seeding strategies

We assessed the role of nutrients and disturbance experienced by mothers (maternal effects) in the growth of progeny in a pot experiment using two Plantago species. Photosynthetic capacity, biomass allocation and fecundity were measured. Offspring of plants grown in nutrient poor conditions produced more leaves, spikes and longer leaves and in case of P. lanceolata , they had also higher photosynthetic capacity. The progeny of P. media mothers that had resprouted after disturbance was favored in nutrient poor conditions whereas the progeny of undisturbed plants was favored in nutrient rich conditions.
This study demonstrates that maternal effects may play a role in the success of either a seeding or a resprouting strategy in environments with different nutrient availability. Moreover, we showed that alteration of photosynthetic capacity, even during adult stages, is a mechanism through which maternal plants may impact their progeny.     

Deglutarylation of glutaryl-CoA dehydrogenase by deacylating enzyme SIRT5 promotes lysine oxidation in mice

A wide range of protein acyl modifications has been identified on enzymes across various metabolic processes; however, the impact of these modifications remains poorly understood. Protein glutarylation is a recently identified modification that can be nonenzymatically driven by glutaryl-CoA. In mammalian systems, this unique metabolite is only produced in the lysine and tryptophan oxidative pathways. To better understand the biology of protein glutarylation, we studied the relationship between enzymes within the lysine/tryptophan catabolic pathways, protein glutarylation, and regulation by the deglutarylating enzyme sirtuin 5 (SIRT5). Here, we identify glutarylation on the lysine oxidation pathway enzyme glutaryl-CoA dehydrogenase (GCDH) and show increased GCDH glutarylation when glutaryl-CoA production is stimulated by lysine catabolism. Our data reveal that glutarylation of GCDH impacts its function, ultimately decreasing lysine oxidation. We also demonstrate the ability of SIRT5 to deglutarylate GCDH, restoring its enzymatic activity. Finally, metabolomic and bioinformatic analyses indicate an expanded role for SIRT5 in regulating amino acid metabolism. Together, these data support a feedback loop model within the lysine/tryptophan oxidation pathway in which glutaryl-CoA is produced, in turn inhibiting GCDH function via glutaryl modification of GCDH lysine residues and can be relieved by SIRT5 deacylation activity.