Higher temporal variability of forest breeding bird communities in fragmented landscapes

Understanding the relationship between animal community dynamics and landscape structure has become a priority for biodiversity conservation. In particular, predicting the effects of habitat destruction that confine species to networks of small patches is an important prerequisite to conservation plan development. Theoretical models that predict the occurrence of species in fragmented landscapes, and relationships between stability and diversity do exist. However, reliable empirical investigations of the dynamics of biodiversity have been prevented by differences in species detection probabilities among landscapes. Using long-term data sampled at a large spatial scale in conjunction with a capture-recapture approach, we developed estimates of parameters of community changes over a 22-year period for forest breeding birds in selected areas of the eastern United States. We show that forest fragmentation was associated not only with a reduced number of forest bird species, but also with increased temporal variability in the number of species. This higher temporal variability was associated with higher local extinction and turnover rates. These results have major conservation implications. Moreover, the approach used provides a practical tool for the study of the dynamics of biodiversity.     

A validated prediction model for all forms of acute coronary syndrome: estimating the risk of 6-month postdischarge death in an international registry

Context  Accurate estimation of risk for untoward outcomes after patients have been hospitalized for an acute coronary syndrome (ACS) may help clinicians guide the type and intensity of therapy. Objective  To develop a simple decision tool for bedside risk estimation of 6-month mortality in patients surviving admission for an ACS. Design, Setting, and Patients  A multinational registry, involving 94 hospitals in 14 countries, that used data from the Global Registry of Acute Coronary Events (GRACE) to develop and validate a multivariable stepwise regression model for death during 6 months postdischarge. From 17 142 patients presenting with an ACS from April 1, 1999, to March 31, 2002, and discharged alive, 15 007 (87.5%) had complete 6-month follow-up and represented the development cohort for a model that was subsequently tested on a validation cohort of 7638 patients admitted from April 1, 2002, to December 31, 2003. Main Outcome Measure  All-cause mortality during 6 months postdischarge after admission for an ACS. Results  The 6-month mortality rates were similar in the development (n = 717; 4.8%) and validation cohorts (n = 331; 4.7%). The risk-prediction tool for all forms of ACS identified 9 variables predictive of 6-month mortality: older age, history of myocardial infarction, history of heart failure, increased pulse rate at presentation, lower systolic blood pressure at presentation, elevated initial serum creatinine level, elevated initial serum cardiac biomarker levels, ST-segment depression on presenting electrocardiogram, and not having a percutaneous coronary intervention performed in hospital. The c statistics for the development and validation cohorts were 0.81 and 0.75, respectively. Conclusions  The GRACE 6-month postdischarge prediction model is a simple, robust tool for predicting mortality in patients with ACS. Clinicians may find it simple to use and applicable to clinical practice.      

Overexpression of mutated MRP4 in cisplatin resistant small cell lung cancer cell line: collateral sensitivity to azidothymidine

Cisplatin (CDDP) resistance is one of the major impediments in cancer chemotherapy. In an attempt to define this complex mechanism(s) of resistance, we have identified 7 cDNA fragments which are overexpressed in CDDP resistant small cell lung cancer cell line (SR-2) using PCR selected cDNA subtraction. One of these fragments was identical with nucleotide 3657-4042 of MRP4. The other fragments share sequence homology with elongation factor alpha, human placenta villi cDNA, heat shock protein (Hsp70), ribosomal RNA, BNP1 brain specific Na-dependent inorganic phosphate cotransporter and telomeric catalytic subunit. Examination of other MRP members (MRP1, 2, 3, 5, 6) did not show discernable differences in their expression between the parental (SCLC1) and the CDDP-resistant variant (SR-2). Full length MRP4 cDNA was obtained from SCLC1 and SR-2. Both cell lines carry a point mutation at nucleotide 3532 while SR-2 carries two additional mutations at 3228 and 3246. Since MRP4 is known to transport azidiothymidine (AZT) and overexpression of MRP4 confers AZT resistance, we have studied growth inhibitory effects of AZT and [3H]-AZT accumulation. Interestingly, SR-2 is more sensitive to AZT while accumulating lesser amounts of [3H]-AZT. The thymidine kinase activity is similar in both cell lines. Thus, the increased sensitivity to AZT in SR-2 could not be solely due to mutation of MRP4. These findings are most likely due to the inhibitory effects of telomere catalytic subunit by AZT. Thus, certain biochemical changes induced by CDDP can be explored for future treatment to overcome this form of resistance.