On the source of Ca(2+) activating the tonic component of contraction of myocytes of guinea pig heart

OBJECTIVE: Contractions of isolated, single myocytes of guinea pig heart stimulated at 37 degrees C consist of a phasic component and a voltage dependent tonic component. In this study we investigated the source of Ca(2+) activating the tonic component. METHODS: Experiments were performed at 37 degrees C in ventricular myocytes of guinea pig heart. Voltage-clamped cells were stimulated by the pulses from the holding potential of -40 to +5 mV. [Ca(2+)](i) was monitored as fluorescence of Indo 1-AM and contractions were recorded with the TV edge-tracking system. RESULTS: Superfusion of 5 mmol/l Ni(2+) during 30 s pause did not inhibit subsequent biphasic Ca(2+) transients and contractions despite inhibition of Ca(2+) current and Na(+)/Ca(2+) exchange. KB-R7943 (5 micromol/l) or intracellular dialysis with 0 Na(+) solution, both of which inhibit reversed Na(+)/Ca(2+) exchange, decreased amplitude of Ca(2+) transients and contractions by approximately 40%. The ratio of amplitudes of tonic to phasic component was increased by Ni(2+) and was not changed by KB-R7943 or 0 Na(+)(i). Ryanodine (200 micromol/l) inhibited both components of contractions in cells superfused with Ni(2+). The phasic component but not the tonic component was inhibited by 20 micromol/l nifedipine in cells superfused with Ni(2+). CONCLUSIONS: Tonic component of contraction of single myocytes of guinea pig heart is not activated by Ca(2+) current or by the reverse mode Na(+)/Ca(2+) exchange as currently proposed in literature. Rather, it is activated by Ca(2+) released from the sarcoplasmic reticulum. However, kinetics and mechanism of release seem to be quite different from those of Ca(2+) fraction activating the phasic component of contraction.     

Ultrasensitive Amplification Refractory Mutation System Real-Time PCR (ARMS RT-PCR) Assay for Detection of Minority Hepatitis B Virus-Resistant Strains in the Era of Personalized Medicine

Resistance to antiviral treatment for chronic hepatitis B virus (HBV) has been associated with mutations in the HBV polymerase region. This study aimed at developing an ultrasensitive method for quantifying viral populations with all major HBV resistance-associated mutations, combining the amplification refractory mutation system real-time PCR (ARMS RT-PCR) with a molecular beacon using a LightCycler. The discriminatory ability of this method, the ARMS RT-PCR with molecular beacon assay, was 0.01 to 0.25% for the different HBV resistance-associated mutations, as determined by laboratory-synthesized wild-type (WT) and mutant (Mut) target sequences. The assay showed 100% sensitivity for the detection of mutant variants A181V, T184A, and N236T in samples from 41 chronically HBV-infected patients under antiviral therapy who had developed resistance-associated mutations detected by direct PCR Sanger sequencing. The ratio of mutant to wild-type viral populations (the Mut/WT ratio) was >1% in 38 (63.3%) of 60 samples from chronically HBV-infected nucleos(t)ide analogue-naive patients; combinations of mutations were also detected in half of these samples. The ARMS RT-PCR with molecular beacon assay achieved high sensitivity and discriminatory ability compared to the gold standard of direct PCR Sanger sequencing in identifying resistant viral populations in chronically HBV-infected patients receiving antiviral therapy. Apart from the dominant clones, other quasispecies were also quantified. In samples from chronically HBV-infected nucleos(t)ide analogue-naive patients, the assay proved to be a useful tool in detecting minor variant populations before the initiation of the treatment. These observations need further evaluation with prospective studies before they can be implemented in daily practice.     

EGFR-Targeted Therapy for Non-Small Cell Lung Cancer: Focus on EGFR Oncogenic Mutation

The two essential requirements for pathologic specimens in the era of personalized therapies for non-small cell lung carcinoma (NSCLC) are accurate subtyping as adenocarcinoma (ADC) versus squamous cell carcinoma (SqCC) and suitability for EGFR molecular testing, as well as for testing of other oncogenes such as EML4-ALK and KRAS. Actually, the value of EGFR expressed in patients with NSCLC in predicting a benefit in terms of survival from treatment with an epidermal growth factor receptor targeted therapy is still in debate, while there is a convincing evidence on the predictive role of the EGFR mutational status with regard to the response to tyrosine kinase inhibitors (TKIs).This is a literature overview on the state-of-the-art of EGFR oncogenic mutation in NSCLC. It is designed to highlight the preclinical rationale driving the molecular footprint assessment, the progressive development of a specific pharmacological treatment and the best method to identify those NSCLC who would most likely benefit from treatment with EGFR-targeted therapy. This is supported by the belief that a rationale for the prioritization of specific regimens based on patient-tailored therapy could be closer than commonly expected.     

Numerical and In Vitro Investigation of a Novel Mechanical Circulatory Support Device Installed in the Descending Aorta

Traditional implantation techniques of assist devices from the apex of left ventricle to the ascending or descending aorta are highly invasive and carry substantial complications for end‐stage heart failure patients. This study has shown that the descending aorta can be a promising location to install an implantable mechanical circulatory support with minimally invasive surgery. Herein, the hemodynamic effect of an in‐house prototyped pump implanted in the descending aorta was investigated numerically as well as experimentally. The objective of the experimental study is met by using the in‐house simulator of the cardiovascular loop replicating congestive heart failure conditions. The objective of the numerical study was met by using the modified version of the concentrated lumped parameter model developed by the same team. The results show that the pump placement in the descending aorta can lead to an improvement in pulsatility. The pressure drop, generated at the upstream of the pump, facilitates the cardiac output as a result of after‐load reduction, but at the same time, it induces a slight drop in the carotid as well as the coronary perfusion. The pressure rise, generated at the downstream of the pump, improves the blood perfusion in the renal circulation.     

Amplified C lambda and c-abl genes are on the same marker chromosome in K562 leukemia cells.

The human leukemia cell line K562, derived from a patient with Philadelphia chromosome-positive chronic myelogenous leukemia, contains amplified c-abl oncogenes and unrearranged C lambda genes. Using in situ hybridization techniques, we have determined that the amplified c-abl and C lambda DNA sequences of K562 cells are both located on the same abnormal acrocentric marker chromosome, which may represent an altered Philadelphia chromosome.