Hyperthermia adds to trabectedin effectiveness and thermal enhancement is associated with BRCA2 degradation and impairment of DNA homologous recombination repair

The tetrahydroisoquinoline trabectedin is a marine compound with approved activity against human soft‐tissue sarcoma. It exerts antiproliferative activity mainly by specific binding to the DNA and inducing DNA double‐strand breaks (DSB). As homologous recombination repair (HRR)‐deficient tumors are more susceptible to trabectedin, hyperthermia‐mediated on‐demand induction of HRR deficiency represents a novel and promising strategy to boost trabectedin treatment. For the first time, we demonstrate enhancement of trabectedin effectiveness in human sarcoma cell lines by heat and characterize cellular events and molecular mechanisms related to heat‐induced effects. Hyperthermic temperatures (41.8 or 43°C) enhanced significantly trabectedin‐related clonogenic cell death and G2/M cell cycle arrest followed by cell type‐dependent induction of apoptosis or senescence. Heat combination increased accumulation of γH2AX foci as key marker of DSBs. Expression of BRCA2 protein, an integral protein of the HRR machinery, was significantly decreased by heat. Consequently, recruitment of downstream RAD51 to γH2AX‐positive repair foci was almost abolished indicating relevant impairment of HRR by heat. Accordingly, enhancement of trabectedin effectiveness was significantly augmented in BRCA2‐proficient cells by hyperthermia and alleviated in BRCA2 knockout or siRNA‐transfected BRCA2 knockdown cells. In peripheral blood mononuclear cells isolated from sarcoma patients, increased numbers of nuclear γH2AX foci were detected after systemic treatment with trabectedin and hyperthermia of the tumor region. The findings establish BRCA2 degradation by heat as a key factor for a novel treatment strategy that allows targeted chemosensitization to trabectedin and other DNA damaging antitumor drugs by on‐demand induction of HRR deficiency.     

Prevention strategies for blood‐borne viruses—in the Era of vaccines,direct acting antivirals and antiretroviral therapy

Blood‐borne viruses, such as hepatitis B virus, hepatitis C virus, human immunodeficiency virus, and the facultative blood‐borne hepatitis E virus, are considered a major public health problem given that they are accountable for millions of deaths each year. Treatment options, including effective vaccine design, development of antiviral strategies and the implementation of antiretroviral therapy have improved substantially over the last couple of years and contribute to successful treatment and prevention of these infectious diseases. In this review, we summarise the current knowledge and concepts in prevention of transmission of these blood‐borne viruses.     

Clinical effects after subgingival polishing with a non-aggressive ultrasonic device in initial therapy

OBJECTIVES: The Vector ultrasonic system provides root debridement supported by different abrasive irrigation fluids. The aim of this study was to investigate the clinical outcome of initial therapy with subgingival low-abrasive debridement. MATERIAL AND METHODS: Twenty patients, who had at least two teeth with pocket depths >5 mm in each quadrant, took part in this prospective randomized clinical study. Patients were treated in a split-mouth design as one test quadrant (1) subgingivally with Vector fluid polish (VU-H) and as three control quadrants, (2) with only supragingival polishing (PO-H), (3) with hand instruments (HI-H) performed by a hygienist and (4) with hand instruments (HI-D) performed by a dentist. At baseline, 3 and 6 months after treatment, pocket depths and attachment levels (ALs) were measured and bleeding on probing (BOP) was recorded. RESULTS: At 6-month evaluation, all groups showed an improvement in clinical parameters. No statistically significant differences in any of the investigated parameters could be observed between the Vector group and the hand scaling groups, or when comparing the results of the two different operators. CONCLUSION: This study demonstrates that Vector treatment with polishing fluid was able to reduce pocket depths and the prevalence of BOP and improve clinical AL in a similar way as scaling with curettes.     

Desflurane Induces Only Minor Ca2+ Release from the Sarcoplasmic Reticulum of Mammalian Skeletal Muscle

Background: Desflurane is a weaker trigger of malignant hyperthermia than is halothane. There are very few data of the pathophysiologic background of this observation. Therefore, the authors' aim was to investigate the direct effect of desflurane on calcium release in skinned skeletal muscle fibers.

Methods: For the measurements, single saponin-skinned muscle fiber preparations of BALB/c mice were used. For Ca2+ release experiments, liquid desflurane at 0.6 and 3.5 mm was applied to weakly calcium-buffered solutions with no added Ca2+. Desflurane was diluted in strongly Ca2+-buffered solutions, with [Ca2+] between 3.0 and 24.9 [mu]m for [Ca2+]-force relations. Force transients were transformed into Ca2+ transients based on the individual [Ca2+]-force relations. As controls, 30 mm caffeine and equimolar sevoflurane were investigated in the same muscle fibers.

Results: At 3.5 mm, desflurane induced peak force transients of 8 +/- 4% (mean +/- SD) of maximal Ca2+-activated force (Tmax). These peak values were significantly smaller than those in the presence of 3.5 mm sevoflurane (24 +/- 10% of Tmax, P < 0.05), and 4 or 5 times smaller than previously reported Ca2+-release-induced force transients by equimolar halothane. Calculated peak Ca2+ transients derived from force transients and induced by 3.5 and 0.6 mm desflurane were significantly smaller than those induced by 30 mm caffeine. The [Ca2+]-force relation was shifted by desflurane, resulting in a Ca2+-sensitizing effect. The maximal Ca2+-activated force was significantly increased by 0.6 mm desflurane in comparison with the control, with no added substance (P <= 0.05).     

Permanent cerebral hypoperfusion: ‘preconditioning-like' effects on rat energy metabolism towards acute systemic hypotension

Chronic cerebrovascular disorders are often complicated by additional temporary ischaemic insults, resulting in substantial deterioration of brain energy metabolism. In the present study, chronic limitations of oxygen supply were induced in Wistar rats by 2 weeks of permanent bilateral common carotid artery occlusion (2-vo) to initiate a ‘preconditioning-like' effect that protects rat brain energy metabolism against further acute systemic hypotension (15 min). Haemodynamic parameters, arterial blood gases and body temperature were monitored. Energy metabolites were determined in rat parietotemporal cerebral cortex: adenosine 5′-triphosphate (ATP), adenosine 5′-diphosphate (ADP), adenosine 5′-monophosphate (AMP), phosphocreatine (PCr), and adenosine by the high-pressure liquid chromatography (HPLC) technique and lactate spectrophotometrically. After 2 weeks, permanent 2-vo led to a significant decrease in the concentrations of cortical tissue ATP and PCr, from 3.06±0.48 to 2.09±0.28 and from 4.27±0.63 to 3.35±0.41 μmol/g, respectively. These changes were associated with a two-fold increase in AMP and adenosine. Acute systemic hypotension alone (non-preconditioning) reduced ATP and PCr drastically, to 0.97±0.51 and 1.76±1.23 μmol/g. Tissue concentrations of lactate, AMP, and adenosine were markedly increased, three- to five-fold, in ‘non-preconditioned' brain tissue. In contrast, after 2 weeks of 2-vo acute hypotension did not significantly alter the cortical energy state any further. The effects of preconditioning on tissue ATP and PCr were most pronounced at 5 min and 48 h after reperfusion. In conclusion, permanent 2-vo seems to activate compensatory mechanisms, which effectively protect the rat's cortical energy metabolism against an additional ischaemic attack (‘preconditioning-like' effect).     

Assessment of acute myocardial infarction: current status and recommendations from the North American society for cardiovascular imaging and the European society of cardiac radiology

There are a number of imaging tests that are used in the setting of acute myocardial infarction and acute coronary syndrome. Each has their strengths and limitations. Experts from the European Society of Cardiac Radiology and the North American Society for Cardiovascular Imaging together with other prominent imagers reviewed the literature. It is clear that there is a definite role for imaging in these patients. While comparative accuracy, convenience and cost have largely guided test decisions in the past, the introduction of newer tests is being held to a higher standard which compares patient outcomes. Multicenter randomized comparative effectiveness trials with outcome measures are required.     

Long‐lasting post‐mortem activity of spinal microglia in situ in mice

As CNS macrophages, microglia show a high spontaneous motility of their processes, continuously surveying their microenvironment. Upon CNS injury, microglia react by immediate cellular polarization and process extension toward the lesion site as well as by subsequent amoeboid lesion‐directed migration and phagocytosis. To determine the ability of microglia to fulfill their role within distinctively lesioned tissue in the absence of life support, we investigated microglial activity and responsiveness to laser‐induced axonal injuries in the spinal dorsal columns in situ after cardiac and respiratory arrest, i.e., post‐mortem, in the progressively degrading nervous tissue. For this purpose, we used time‐lapse two‐photon laser scanning microscopy in double transgenic mice expressing enhanced green fluorescent protein in microglia and enhanced yellow fluorescent protein in projection neurons. Depending on the premortal condition of the animal, microglial activity and responsiveness remain for up to5–10 hr post‐mortem. Thereby, the continuously decreasing glial reaction is independent of oxygen and glucose supply but requires residual ATP, suggesting a parasitic form of energy, such as a transmembrane uptake of ATP released from injured nervous tissue. Even though initially microglia are able to detect axonal injury after disruption of the blood supply, the later aspects of glial reaction, for example amoeboid conversion and migration, are absent post‐ mortem, corresponding to the failure of microglia to prevent secondary damage after injury of nervous tissue. © 2010 Wiley‐Liss, Inc.