The effect of alterations to action potential duration on beta-adrenoceptor-mediated aftercontractions in human and guinea-pig ventricular myocytes

Aftercontractions induced by beta-adrenoceptor stimulation in human and guinea-pig cardiomyocytes may be related to changes in action potential duration (APD). We investigated the effects of altering APD during the occurrence of isoproterenol-induced aftercontractions, using the KATP channel openers cromakalim and lemakalim or the action potential voltage clamp technique, in guinea-pig and human ventricular cardiomyocytes. Contractile responses were measured at 32 degrees C using a video-based edge-detection system. In guinea-pig myocytes, action potentials, Indo-1 fluorescence and contraction were measured at 22 degrees C. Isoproterenol (< or = 12 nM) had variable effects on APD but induced aftercontractions, the majority (14/19 cells) of which occurred during the action potential. Short action potentials were produced using K+ channel openers. These compounds reduced or completely abolished the isoproterenol-induced aftercontractions. Increasing isoproterenol in the presence of K+ channel opener restored the main contraction to a level similar to or above those with isoproterenol alone, but without the reappearance of aftercontractions. When cells were stimulated to contract under action potential voltage clamp, isoproterenol-induced aftercontractions were abolished by voltage clamping with action potentials of short duration. It was possible to induce aftercontractions in some cells without application of isoproterenol if voltage clamp-imposed action potentials of very long duration were used. These aftercontractions were also abolished by shortening action potential duration. We conclude that K+ channel openers or the imposition of action potentials of short duration can dissociate positively inotropic beta-adrenoceptor stimulation from aftercontraction formation and that action potentials of long duration can be pro-arrhythmic.     

Measurements of Ca2+ entry and sarcoplasmic reticulum Ca2+ content during the cardiac cycle in guinea pig and rat ventricular myocytes

This study investigates the contribution of Ca2+ entry via sarcolemmal (SL) Ca2+ channels to the Ca2+ transient and its relationship with sarcoplasmic reticulum (SR) Ca2+ content during steady-state contraction in guinea pig and rat ventricular myocytes. The action potential clamp technique was used to obtain physiologically relevant changes in membrane potential. A method is shown that allows calculation of Ca2+ entry through the SL Ca2+ channels by measuring Cd(2+)-sensitive current during the whole cardiac cycle. SR Ca2+ content was calculated from caffeine-induced transient inward current. In guinea pig cardiac myocytes stimulated at 0.5 Hz and 0.2 Hz, Ca2+ entry through SL Ca2+ channels during a cardiac cycle was approximately 30% and approximately 50%, respectively, of the SR Ca2+ content. In rat myocytes Ca2+ entry via SL Ca2+ channels at 0.5 Hz was approximately 3.5% of the SR Ca2+ content. In the presence of 500 nM thapsigargin Ca2+ entry via SL Ca2+ channels in guinea pig cardiac cells was 39% greater than in controls, suggesting a larger contribution of this mechanism to the Ca2+ transient when the SR is depleted of Ca2+. These results provide quantitative support to the understanding of the relationship between Ca2+ entry and the SR Ca2+ content and may help to explain differences in the Ca2+ handling observed in different species.     

"Expressed emotion", marital quality and risk of recurrence in depressed patients

BACKGROUND: This study investigated the assignment of preference values to health states which may follow head and neck cancer (HNC) treatment. Preference values for these health states were provided by HNC patients, HNC health-care providers, and a group of college students representing individuals with little knowledge of HNC. METHODS: A time trade-off technique was used by participants to assign preference values to four health states in the domains of appearance, eating, speech, breathing, pain, and work/social functioning. RESULTS: Patients' and health-care professionals' rank-ordered preference value scores for health states in appearance, breathing, eating, and speech were not significantly different (p < .05). These two groups differed significantly in ranking four of the eight pain and work/social functioning health states. Patients and students differed significantly in ranking 21 of the 24 health states (p < .05). CONCLUSIONS: Health-care professionals and patients had very similar perspectives regarding health states in the HNC-specific domains, indicating that these professionals appear to be a legitimate proxy for patients' attitudes in these domains. Healthcare professionals placed a significantly greater value on avoiding both pain and social confinement than did patients. Students, representing individuals naive regarding HNC, differed from patients and health-care professionals in their rankings of these health-state outcomes.     

Proteases and their inhibitors are indicative in gestational disease

OBJECTIVE: To assess whether various proteolytic factors which are involved in trophoblast invasion show different concentrations in plasma and placenta of patients with HELLP syndrome, pre-/eclampsia and highly pathological Doppler flow measurements but without additional complications (hpD). DESIGN: Case control and observational study; 18 women with HELLP syndrome, 21 with pre-/eclampsia, 13 with hpD, as well as healthy pregnant women (matched pairs); statistical analysis: sign test and Wilcoxon test. RESULTS: Urokinase-type plasminogen activator (uPA), uPA receptor, tissue-type plasminogen activator (tPA), plasminogen activator inhibitor 1 (PAI-1), matrix metalloproteinases MMP-8, MMP-9 and tissue inhibitor of metalloproteinases TIMP-1 were measured by ELISA. PAI-1 plasma levels are significantly elevated in all three groups studied. In HELLP syndrome, tPA and TIMP-1 are also elevated, and in patients with hpD, MMP-8 is increased, whereas MMP-9, and TIMP-1 are lower. In placenta extract, only pre-/eclampsia shows reduced MMP-9 concentrations. CONCLUSIONS: The increased frequency of small-for-gestational-age infants observed in all three study groups is an expression of impaired placental implantation and remodelling processes. These disturbances manifest themselves in the form of changes in some of the factors in plasma and placenta extract that are involved in these processes.     

Dendritic cell-based vaccines in the setting of peripheral blood stem cell transplantation: CD34+ cell-depleted mobilized peripheral blood can serve as a source of potent dendritic cells

We are investigating the use of tumor-pulsed dendritic cell (DC)-based vaccines in the treatment of patients with advanced cancer. In the current study, we evaluated the feasibility of obtaining both CD34+ hematopoietic stem/ progenitor cells (HSCs) and functional DCs from the same leukapheresis collection in adequate numbers for both peripheral blood stem cell transplantation (PBSCT) and immunization purposes, respectively. Leukapheresis collections of mobilized peripheral blood mononuclear cells (PBMCs) were obtained from normal donors receiving granulocyte colony-stimulating factor (G-CSF) (for allogeneic PBSCT) and from intermediate grade non-Hodgkin's lymphoma or multiple myeloma patients receiving cyclophosphamide plus G-CSF (for autologous PBSCT). High enrichment of CD34+ HSCs was obtained using an immunomagnetic bead cell separation device. After separation, the negative fraction of mobilized PBMCs from normal donors and cancer patients contained undetectable levels of CD34+ HSCs by flow cytometry. This fraction of cells was then subjected to plastic adherence, and the adherent cells were cultured for 7 days in GM-CSF (100 ng/ml) and interleukin 4 (50 ng/ml) followed by an additional 7 days in GM-CSF, interleukin 4, and tumor necrosis factor alpha (10 ng/ml) to generate DCs. Harvested DCs represented yields of 4.1+/-1.4 and 5.8+/-5.4% of the initial cells plated from the CD34+ cell-depleted mobilized PBMCs of normal donors and cancer patients, respectively, and displayed a high level expression of CD80, CD86, HLA-DR, and CD11c but not CD14. This phenotypic profile was similar to that of DCs derived from non-CD34+ cell-depleted mobilized PBMCs. DCs generated from CD34+ cell-depleted mobilized PBMCs elicited potent antitetanus as well as primary allogeneic T-cell proliferative responses in vitro, which were equivalent to DCs derived from non-CD34+ cell-depleted mobilized PBMCs. Collectively, these results demonstrate the feasibility of obtaining both DCs and CD34+ HSCs from the same leukapheresis collection from G-CSF-primed normal donors and cancer patients in sufficient numbers for the purpose of combined PBSCT and immunization strategies.     

A prospective study of N-acetyltransferase genotype, red meat intake, and risk of colorectal cancer

Carcinogenic heterocyclic amines are activated by N-acetyltransferase (NAT) enzymes, encoded by NAT1 and NAT2, to genotoxic compounds that can form DNA adducts in the colon epithelium. We have examined the relation of polymorphisms in the genes coding for both enzymes to risk of colorectal cancer and the gene-environment interaction with red meat intake among participants in the prospective Physicians' Health Study. Baseline blood samples from 212 men subsequently diagnosed with colorectal cancer during 13 years of follow-up were genotyped, along with 221 controls. NAT genotypes were analyzed by a PCR-restriction fragment length polymorphism method. Effect modification of the relation of red meat intake and risk of colorectal cancer by NAT genotype was assessed using conditional logistic regression. There was no overall independent association of NAT acetylation genotypes and colorectal cancer risk. The relative risks for the rapid acetylation genotype were 0.93 [95% confidence interval (CI), 0.61-1.42] for NAT1, 0.80 (95% CI, 0.53-1.19) for NAT2, and 0.81 (95% CI, 0.52-1.27) for NAT1/NAT2 combined. We observed a stronger association of red meat intake with cancer risk among NAT rapid acetylators, especially among men 60 years old or older. Among those men who were rapid acetylators for both NAT1 and NAT2, consumption of >1 serving of red meat per day was associated with a relative risk of 5.82 (95% CI, 1.11-30.6) compared with consumption of < or = 0.5 serving per day (P, trend = 0.02). These prospective data, which need to be confirmed in other studies, suggest that polymorphisms in the NAT genes confer differential susceptibility to the effect of red meat consumption on colorectal cancer risk.