On the mechanism of barium induced diastolic depolarisation in isolated ventricular myocytes

Barium can induce spontaneous activity in cardiac non-pacemaker cells. The mechanism of barium induced diastolic depolarisation was studied in isolated ventricular myocytes, using a microelectrode technique. Barium (0.05-0.2 mmol.litre-1) decreased resting potential and caused the membrane potential at the end of the action potential to undershoot the diminished resting value temporarily, thereby inducing diastolic depolarisation. Resting membrane resistance was increased by Ba but at the end of phase 3 repolarisation the resistance temporarily decreased below its steady state diastolic value. In presence of Ba, hyperpolarisation abolished or reversed diastolic depolarisation. At the end of phase 3 repolarisation, membrane resistance was decreased, whether diastolic depolarisation was present, absent or reversed. A high [K]o (15.4 mmol.litre-1) decreased Ba effects on action potential, membrane resistance and diastolic depolarisation. Caesium decreased the Ba induced diastolic depolarisation and the associated increase in membrane resistance, but had little effect on spontaneous activity at depolarised levels. Barium induced an oscillatory potential, with increased membrane resistance. Noradrenaline plus low [Ba]o, and high [Ba]o alone (1-5 mmol.litre-1), can induce spontaneous activity. Thus, in myocardial cells barium induces diastolic depolarisation at polarised levels by a voltage and time dependent block of potassium conductance, which is modulated by action potential voltage changes. However, as [Ba]o is increased, spontaneous activity at a depolarised level may be related to the decay of potassium currents and to oscillatory potentials.     

Breast-saving operations in breast cancer

Breast preserving surgery or conservative surgery consists at present of a combination of a reduced operation--tumorectomy or wedge resection or subcutaneous mastectomy--with adequate radiotherapy whereby a doses of 40-50 Gy is used with or without an additional booster dose of 10 Gy. Recent studies of 5-year- and 10-year-survival rates after conservative management have been shown to be identical with radical operations (Rotter-Halsted, Patey-Auchincloss). In the Departments of Gynecology and Obstetrics of the Universities of Münster and Rostock the partial bilateral subcutaneous mastectomy with lymphadenectomy and irradiation is the preferred method of conservative management for breast cancer. Indications and technique are discussed.     

Interaction of a plasminogen activator proteinase, LV-PA with human alpha2-macroglobulin.

Lachesis venom plasminogen activator (LV-PA) is a 33-kDa serine proteinase isolated from bushmaster (Lachesis muta muta) snake venom, which activates the fibrinolytic system in vitro. This study has examined the effect of the plasma proteinase inhibitor alpha2-macroglobulin (alpha2-M) towards LV-PA and compares it with the effect on tissue type plasminogen activator (t-PA). The proteolytic activity of LV-PA alone or previously incubated with human plasminogen (Plg) on the large molecular mass protein substrates, dimethylcasein (DMC) and fibrinogen (Fg) was completely inhibited by human alpha2-M. However, the synthetic peptides Tos-Gly-Pro-Lys-pNA and H-D-Pro-Phe-Arg-pNA (S-2302) were hydrolyzed with almost no reduction in rate. At pH 7.4 and 37 degrees C the proteinase (0.15 microM over 15 min) interacted with alpha2-M, and each mole of alpha2-M bound 2 mol of enzyme. Sodium dodecyl sulfate gel electrophoresis of reduced samples showed that the interaction of alpha2-M with either LV-PA or t-PA preincubated with Plg resulted in the formation of approximately 90 kDa fragments and high molecular mass complexes (Mr 180 kDa), generated by the incubation mixture (LV-PA or t-PA) and Plg. The data suggest that LV-PA is a direct-type PA and its fibrinolytic effect can be reduced by alpha2-M in vivo.     

Correlating digit span performance and event-related potentials to assess working memory.

Event-related brain potentials (ERPs) were recorded during a computerized and modified version of the Digit Span Backwards (DB) task from the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III). The modified DB version (ERP-DB task) was divided into two sections of 2, 4, 6 and 8 digits in length (Group 1) and 3, 5 and 7 digits in length (Group 2). Each trial had a study phase and a test phase. For the study phase, a series of digits was presented sequentially and aurally to 20 participants (10 for each group). For the test phase, a second series of digits was also presented sequentially and aurally that either corresponded to the reverse order of the digits in the study phase (correct condition) or had one digit in the sequence replaced by an incorrect digit (incorrect condition). The traditional DB task of the WAIS-III was also administered for comparison purposes. A prolonged positive slow wave (PSW) peaking between 450 and 750 ms was elicited to incorrect condition trials. For each participant, a derived measure was calculated from the ERP differentiation between correct and incorrect conditions. The derived measure was defined as the mean of the t-values obtained from the correct and incorrect waveform comparison, within the temporal interval that encompassed this component. The strongest statistical correlations between the derived measure and the traditional DB test scores were found at the Pz site (Group 1: r=0.79; Group 2: r=0.59). This statistical approach shows that it is possible to adequately relate an individual's performance on a traditional measure of working memory and ERP patterns. Overall, we believe that this kind of ERP approach holds promise as a technique for assessing quantitatively non-communicative patients.     

Preconception Care for Improving Perinatal Outcomes: The Time to Act

Maternal and Child Health Journal -     

MRI evaluation of bulky tumor masses in the mesentery and bladder involvement in peritoneal carcinomatosis

AIM: Peritonectomy procedures with intraperitoneal chemohyperthermia are an effective but costly treatment for peritoneal carcinomatosis (PC). Consequently a proper selection of patients is necessary. We evaluated the benefit of MRI prior to surgery, in the detection of two of the main surgery contraindications: bulky mesenteric tumors and bladder implants. METHODS: Three experts retrospectively reviewed abdominal and pelvic MRI from 19 cases of surgically proved PC (ovary: 7; colorectal: 7; gastric: 2; pseudomyxoma peritonei: 2; appendix: 1). RESULTS: Mesenteric tumors were always identified as hypersignal masses on axial and coronal fat suppression gadolinium-enhanced T1 images (n=3). Three out of five bladder implants were detected. The two cases of bladder implants that were not detected on MRI were missed because the bladder was not filled. The best sequence for the detection of bladder involvement was axial T2-weighted images with bladder filling. CONCLUSIONS: Evaluating the preoperative resectability of PC is crucial for patient management. MRI seems to reliably detect bulky mesenteric tumors and bladder implants on condition the bladder is filled and appropriate sequences are used.