Limited repair of 8-hydroxy-7,8-dihydroguanine residues in human testicular cells

Oxidative damage in testicular DNA is associated with poor semen quality, reduced fertility and increased risk of stillbirths and birth defects. These DNA lesions are predominantly removed by base excision repair. Cellular extracts from human and rat testicular cells and three enriched populations of rat male germ cells (primary spermatocytes, round spermatids and elongating/elongated spermatids) all showed proficient excision/incision of 5-hydroxycytosine, thymine glycol and 2,6-diamino-4-hydroxy-5-formamidopyrimidine. DNA containing 8-oxo-7,8-dihydroguanine was excised poorly by human testicular cell extracts, although 8-oxoguanine-DNA glycosylase-1 (hOGG1) was present in human testicular cells, at levels that varied markedly between 13 individuals. This excision was as low as with human mononuclear blood cell extracts. The level of endonuclease III homologue-1 (NTH1), which excises oxidised pyrimidines, was higher in testicular than in somatic cells of both species. Cellular repair studies of lesions recognised by formamidopyrimidine-DNA glycosylase (Fpg) or endonuclease III (Nth) were assayed with alkaline elution and the Comet assay. Consistent with the enzymatic activities, human testicular cells showed poor removal of Fpg-sensitive lesions but efficient repair of Nth-sensitive lesions. Rat testicular cells efficiently repaired both Fpg- and Nth-sensitive lesions. In conclusion, human testicular cells have limited capacity to repair important oxidative DNA lesions, which could lead to impaired reproduction and de novo mutations.     

Identification of the capsular polysaccharides of Type D and F Pasteurella multocida as unmodified heparin and chondroitin,respectively

Pasteurella multocida is a pathogenic Gram-negative bacterial species that infects a wide variety of animals and humans. A notable morphological feature of many isolates is the extracellular capsule. The ability to remove the capsule by treatment with certain glycosidases has been utilized to discern various capsular types called A, D and F. Based on this preliminary evidence, these microbes have capsules made of glycosaminoglycans, linear polysaccharides composed of repeating disaccharide units containing an amino sugar. Glycosaminoglycans are also abundant components of the vertebrate extracellular matrix. It has been shown previously that the major Type A capsular material was hyaluronan (hyaluronic acid). We report that the Type D polymer is an unmodified heparin (N-acetylheparosan) with a -->4)-beta-D-Glcp-UA-(1-->4)-alpha-D-Glcp-NAc-(1--> repeating unit and the Type F polymer is an unmodified chondroitin with a -->4)-beta-D-Glcp-UA-(1-->3)-beta-D-Galp-NAc-(1--> repeating unit. The monosaccharide compositions, disaccharide profiles, and 1H NMR analyses are consistent with these identifications. The molecular size of the Pasteurella polymers is approximately 100-300 kDa as determined by gel electrophoresis and multi-angle laser light scattering; this size is much greater than the 10-30 kDa size of the analogous polymers isolated from animal tissues. The glycosaminoglycan capsular polymers are relatively non-immunogenic virulence factors that enhance microbial pathogenicity.     

Assessment of DNA strand breakage by the alkaline COMET assay in dialysis patients and the role of Vitamin E supplementation

Although the role of reactive oxygen species (ROS) in chronic renal failure (CRF) is not definitely demonstrated, a consistent number of observations has provided evidence for the presence of oxidative stress in uremic patients undergoing maintenance dialysis. In order to investigate this hypothesis further and to understand the role of antioxidant supplementation, peripheral blood lymphocytes were taken from 36 dialysis patients before and after Vitamin E supplementation in a dosage of 600 mg per day (2x300 mg) for 14 weeks and examined in the alkaline Comet assay for DNA strand breakage. The results were also compared with those of 36 controls with comparable age, sex, and smoking habits, and with no history of renal disease. The DNA breakage observed in the lymphocytes of patients before Vitamin E supplementation was significantly higher than in the controls (P<0.001) but a clear protective effect of Vitamin E supplementation were observed after 14 weeks of therapy.     

High-Throughput Mutation Profiling Changes before and 3 Weeks after Chemotherapy in Newly Diagnosed Breast Cancer Patients

Background

Changes in tumor DNA mutation status during chemotherapy can provide insights into tumor biology and drug resistance. The purpose of this study is to analyse the presence or absence of mutations in cancer-related genes using baseline breast tumor samples and those obtained after exposure to one cycle of chemotherapy to determine if any differences exist, and to correlate these differences with clinical and pathological features.

Methods

Paired breast tumor core biopsies obtained pre- and post-first cycle doxorubicin (n = 18) or docetaxel (n = 22) in treatment-naïve breast cancer patients were analysed for 238 mutations in 19 cancer-related genes by the Sequenom Oncocarta assay.

Results

Median age of patients was 48 years (range 32–64); 55% had estrogen receptor-positive tumors, and 60% had tumor reduction ≥25% after cycle 1. Mutations were detected in 10/40 (25%) pre-treatment and 11/40 (28%) post-treatment samples. Four mutation pattern categories were identified based on tumor mutation status pre- → post-treatment: wildtype (WT)→WT, n = 24; mutant (MT)→MT, n = 5; MT→WT, n = 5; WT→MT, n = 6. Overall, the majority of tumors were WT at baseline (30/40, 75%), of which 6/30 (20%) acquired new mutations after chemotherapy. Pre-treatment mutations were predominantly in PIK3CA (8/10, 80%), while post-treatment mutations were distributed in PIK3CA, EGFR, PDGFRA, ABL1 and MET. All 6 WT→MT cases were treated with docetaxel. Higher mutant allele frequency in baseline MT tumors (n = 10; PIK3CA mutations n = 8) correlated with less tumor reduction after cycle 1 chemotherapy (R = -0.667, p = 0.035). No other associations were observed between mutation pattern category with treatment, clinicopathological features, and tumor response or survival.

Conclusion

Tumor mutational profiles can change as quickly as after one cycle of chemotherapy in breast cancer. Understanding of these changes can provide insights on potential therapeutic options in residual resistant tumors.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00212082","term_id":"NCT00212082"}}NCT00212082     

Climate and demography of the planktivorous Cassin's auklet Ptychoramphus aleuticus off northern California: implications for population change

1. We performed demographic analyses on Cassin's auklet Ptychoramphus aleuticus, a zooplanktivorous seabird inhabiting the variable California Current System, to understand how temporal environmental variability influences population dynamics. 2. We used capture-recapture data from 1986 to 2002 to rank models of interannual variation in survival, breeding propensity, breeding success, and recruitment. 3. All demographic parameters exhibited temporal variability. Interannual variation in survival was best modelled as a nonlinear function of the winter Southern Oscillation Index (SOI). Breeding propensity was best modelled as a threshold function of local sea surface temperature. Breeding success and recruitment were best modelled with year-dependent annual variation. 4. Changes in the SOI force El Ni?o/La Ni?a events, which in turn alter prey availability to seabirds in this system. Demographic responses varied during El Ni?os/La Ni?as. Survival diminished substantially during the 1997-98 El Ni?o event, while breeding propensity was affected during both the 1992 and 1998 El Ni?os. Breeding success was reduced during the 1992, 1993, and 1998 El Ni?os, but was unusually high in 2002. Recruitment was higher at the beginning and end of this time-series. 5. While demographic responses varied interannually, parameter values covaried in a positive fashion, a situation conducive to rapid population change. During the 11 years study period, the Farallon auklet breeding population declined at 6.05 +/- 0.80% (SE) per year, a cumulative decline of 49.7%. This study demonstrates how climate variability has influenced key demographic processes for this diminished marine bird population.     

Mode of infection of Hokkaido virus (Genus Hantavirus) among grey red-backed voles, Myodes rufocanus, in Hokkaido, Japan

Hokkaido virus (HOKV) is a member of the genus Hantavirus, in the family Bunyaviridae. To investigate HOKV infection in the host Myodes rufocanus, the grey red-backed vole, 199 animals were captured at Tobetsu (October 2004 and July 2005) and Nakagawa (October 2004) in Hokkaido, Japan, for detection of antibody, antigen, and viral RNA. In the surveys in Tobetsu (2004) and Nakagawa (2004), seropositive animals were detected at a frequency of 6.0% (5/84) and 10.4% (5/48), respectively. No seropositive animals were detected in Tobetsu in 2005. Seroprevalence in males in Tobetsu and Nakagawa in 2004 was 25% (1/4) and 45.5% (5/11), respectively, which was higher than in females, at 5.0% (4/80) and 0% (0/37), respectively (P<0.01). These results suggest that male animals play an important role in the maintenance of HOKV in M. rufocanus. Two females were seronegative but viral RNA-positive, indicating that these animals had acute infections before antibody was produced. Another five infected animals in Nakagawa were all male and had high levels of antibodies and viral RNA, suggesting that they had persistent infections. Viral RNA copies in organs of infected animals in Nakagawa were quantified by real-time polymerase chain reaction. Two acutely infected animals had > or = 10 times the number of RNA copies in their lungs compared to those of persistently infected animals. In most cases, lungs or spleen had the highest RNA copy number, regardless of infection status.     

Decelerating growth in tropical forest trees

The impacts of global change on tropical forests remain poorly understood. We examined changes in tree growth rates over the past two decades for all species occurring in large (50-ha) forest dynamics plots in Panama and Malaysia. Stem growth rates declined significantly at both forests regardless of initial size or organizational level (species, community or stand). Decreasing growth rates were widespread, occurring in 24–71% of species at Barro Colorado Island, Panama (BCI) and in 58–95% of species at Pasoh, Malaysia (depending on the sizes of stems included). Changes in growth were not consistently associated with initial growth rate, adult stature, or wood density. Changes in growth were significantly associated with regional climate changes: at both sites growth was negatively correlated with annual mean daily minimum temperatures, and at BCI growth was positively correlated with annual precipitation and number of rainfree days (a measure of relative insolation). While the underlying cause(s) of decelerating growth is still unresolved, these patterns strongly contradict the hypothesized pantropical increase in tree growth rates caused by carbon fertilization. Decelerating tree growth will have important economic and environmental implications.