Geochemical compositional controls on DNA strand breaks induced in in vitro cell-free assays by crushed rock powders from the Panasqueira mine area, Portugal

DNA strand breaks are a common form of DNA damage that can contribute to chromosomal instability or gene mutations. Such strand breaks may be caused by exposure to heavy metals. The aim of this study was to assess the level of DNA strand breaks caused by µm-scale solid particles of known chemical composition with elevated heavy metals/metalloids, notably arsenic, using an in vitro cell-free DNA plasmid scission assay. These samples were incubated with and without H2O2 to see whether damage occurs directly or indirectly through the Fenton reaction. Levels of DNA damage in the absence of H2O2 were < 10%, but in the presence of H2O2, all samples showed higher levels of damage ranging from 10 to 100% suggesting that damage was being incurred through the Fenton reaction. Using bivariate correlation analysis and multiple linear regression, manganese oxide (MnO), sulphur (S), copper (Cu), and zinc (Zn) concentrations in the particulates were found to be the most significant predictors of DNA damage. The mechanism of this DNA damage formation has yet to be thoroughly investigated but is hypothesised to be due to reactive oxygen species formation. Further work is required to assess the extent of contribution of reactive oxygen species to this DNA damage, but this study highlights the potential role of chemistry and/or mineralogy to the extent and/or nature of DNA damage caused by particulates.

Optimization of radiation dosing schedules for proneural glioblastoma

Glioblastomas are the most aggressive primary brain tumor. Despite treatment with surgery, radiation and chemotherapy, these tumors remain uncurable and few significant increases in survival have been observed over the last half-century. We recently employed a combined theoretical and experimental approach to predict the effectiveness of radiation administration schedules, identifying two schedules that led to superior survival in a mouse model of the disease (Leder et al., Cell 156(3):603-616, 2014). Here we extended this approach to consider fractionated schedules to best minimize toxicity arising in early- and late-responding tissues. To this end, we decomposed the problem into two separate solvable optimization tasks: (i) optimization of the amount of radiation per dose, and (ii) optimization of the amount of time that passes between radiation doses. To ensure clinical applicability, we then considered the impact of clinical operating hours by incorporating time constraints consistent with operational schedules of the radiology clinic. We found that there was no significant loss incurred by restricting dosage to an 8:00 a.m. to 5:00 p.m. window. Our flexible approach is also applicable to other tumor types treated with radiotherapy.

Total knee arthroplasty in patients with peripheral vascular disease

Vascular complications following total knee arthroplasty (TKA) are rare in the general population; however, the consequence could be devastating and limb threatening. Many of the patients who develop these complications, if not all, have pre-existing peripheral vascular disease (PVD). Following guidelines in the pre-operative assessment, intra-operative procedure and post-operative management in this group of patients can help orthopaedic surgeons to assess candidates for TKA and trim down the arterial complications afterwards.

OBJECTIVE

To propose a strategy to assess TKA candidates with underlying PVD, in order to address the increasing concerns of the orthopaedic surgeons with regard to the likelihood of vascular complications in these patients.

METHODS

Review of the literature looking for relevant studies and case reports using different medical search engines (PubMed, EMbase and Cochrane Library).

RESULTS

Our search produced very few studies relevant to our topic. Most of these are case reports dealing with various vascular complications following TKA and are therefore not helpful in making conclusive recommendations. However, there are a handful of studies that have specifically addressed this issue and have been included in our review.

CONCLUSION

Vascular complications following TKA are rare (<0.5%). There are conflicting views in the literature with regard to the optimum management of these patients. However, patients with risk factors of PVD should be referred to the local vascular surgeons for assessment prior to TKA. The use of tourniquet in these patients is generally not recommended and should be based on the advice obtained from vascular surgeons. Individual orthopaedic surgeons or units, together with their vascular colleagues, should have agreed protocols for pre- and post-operative vascular assessments of patients undergoing TKA.

Endovascular Treatment of a Ruptured Splenic Artery Aneurysm using Amplatzer(®) Vascular Plug

Splenic Artery Aneurysms are commonly detected incidentally and can present acutely as a source of intra-abdominal catastrophe. Management options include both surgical and endovascular repair. The role of endovascular repair in an haemodynamically stable acute rupture is undefined and the use of Amplatzer(®) Vascular Plug has not to our knowledge been reported.

Homology-driven assembly of a sequence-ready mouse BAC contig map spanning regions related to the 46-Mb gene-rich euchromatic segments of human chromosome 19

Draft sequence derived from the 46-Mb gene-rich euchromatic portion of human chromosome 19 (HSA19) was utilized to generate a sequence-ready physical map spanning homologous regions of mouse chromosomes. Sequence similarity searches with the human sequence identified more than 1000 individual orthologous mouse genes from which 382 overgo probes were developed for hybridization. Using human gene order and spacing as a model, these probes were used to isolate and assemble bacterial artificial chromosome (BAC) clone contigs spanning homologous mouse regions. Each contig was verified, extended, and joined to neighboring contigs by restriction enzyme fingerprinting analysis. Approximately 3000 mouse BACs were analyzed and assembled into 44 contigs with a combined length of 41.4 Mb. These BAC contigs, covering 90% of HSA19-related mouse DNA, are distributed throughout 15 homology segments derived from different regions of mouse chromosomes 7, 8, 9, 10, and 17. The alignment of the HSA19 map with the ordered mouse BAC contigs revealed a number of structural differences in several overtly conserved homologous regions and more precisely defined the borders of the known regions of HSA19-syntenic homology. Our results demonstrate that given a human draft sequence, BAC contig maps can be constructed quickly for comparative sequencing without the need for preestablished mouse-specific genetic or physical markers and indicate that similar strategies can be applied with equal success to genomes of other vertebrate species.

Nucleic acid hybridization assays employing dA-tailed capture probes. II. Advanced multiple capture methods

A fourth capture is added to the reversible target capture procedure of the preceding paper. This results in an improved radioisotopic detection limit of 7.3 x 10(-21) mol of target. In addition, the standard triple capture method is converted into a nonradioactive format with a detection limit of under 1 amol of target. The principal advantage of nonradioactive detection is that the entire assay can be performed in about 1 h. Nucleic acids are released from cells in the presence of the ('capture probe') which contains a 3'-poly(dA) sequence and the ('labeled probe') which contains a detectable nonradioactive moiety such as biotin. After a brief hybridization in solution, the target is captured on oligo(dT) magnetic particles. The target is further purified from sample impurities and excess labeled probe by recapture either once or twice more on fresh magnetic particles. The highly purified target is then concentrated to 200 nl by recapture onto a poly(dT) nitrocellulose filter and rapidly detected with streptavidin-alkaline phosphatase using bromochloroindolyl phosphate and nitroblue tetrazolium. Using this procedure, as little as 0.25 amol of a target plasmid has been detected nonradioactively in crude samples in just 1 h without prior purification of the DNA and RNA. Finally, a new procedure called background capture is introduced to complement the background-reducing power of RTC.