Yoshihiko Yamamoto

Changes in cardiac rhythm in man during underwater submersion and swimming studied by ECG telemetry.

SummaryA previously reported method for electrocardiographic (ECG) telemetry in water using frequency-modulated current was improved to obtain more stable ECGs. The ECGs of seven healthy men were monitored using the improved method during and after whole-body submersion or underwater swimming. Bradycardia and arrhythmias were observed during the submersion, and transient tachycardia was detected after the start of underwater swimming, followed by bradycardia with arrhythmias. Three different types of arrhythmias were observed: sinus arrhythmia (SA), supraventricular extra-systole (SE) and ventricular extrasystole (VE). SA and SE tended to develop during the latter half of the period of submersion or underwater swimming, and especially after the restart of breathing. VEs were detected in only one subject during submersion, whereas they occurred in most subjects during and after underwater swimming. Individual variations were found in development of arrhythmias, one subject showing no arrhythmia. Bradycardia, SA and SE could depend on vagal suppression in underwater conditions, and VE may be related to the effect of muscular movement on cardiac function in addition to vagal inhibiton.

Functional Analysis of vif Genes Derived from Various Primate Immunodeficiency Viruses

Replication property in cells of human and simian immunodeficiency viruses (HIVs and SIVs) lacking intact vif gene was evaluated. Of 10 vif mutants constructed in vitro of the major four HIV/SIV groups, only those derived from HIV-1 and HIV-2/SIVmac displayed replication defect. The cell lines non-permissive for the vif mutants of HIV-1 and SIVmac were found to be different. To determine whether Vif is exchangeable between HIV-1 and SIVmac, chimeric virus clones with respect to the vif gene were constructed and virus replication in the cells non-permissive for the vif mutant viruses was monitored. Productive infection in these cells of chimeric viruses clearly indicated that Vif is functionally exchangeable, and that Vifs of different virus origin act through a similar mechanism.

Stem-cell factor regulates the expression of cyclin A and retinoblastoma gene product in the growth and differentiation pathway of human megakaryocytic cells

The biological effects of c-kit ligand (stem-cell factor: SCF) on an immortalized human megakaryocytic cell line (CMK) was evaluated using methods including the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, surface marker analysis, DNA cell-cycle analysis and immunoblotting. SCF stimulated the growth of CMK cells. Incubation with SCF resulted in increased expression of IIb/IIIa platelet-related glycoprotein (gpIIb/IIIa), indicating enhanced differentiation of CMK cells. Treatment of CMK cells with SCF resulted in a decrease in the subpopulation in the G1 phase, with a reciprocal increase in those in the S phase and the G2+M phase. Moreover, SCF significantly increased cellular expression of cyclin A, a regulatory subunit of cyclin-dependent protein kinase (CDK), and the ratio of phosphorylated/dephosphorylated retinoblastoma gene product (RB protein). These results suggest that SCF stimulates the growth and differentiation of megakaryocytic cells possibly through mechanisms related to the activation of cell-cycle-dependent serine/threonine kinase and inactivation of the nuclear tumor-suppressor gene product.

Estimating CD4+ cell counts of an individual using population historical data.

+ cell count; Total lymphocyte count; Sample-based prediction method; Individual-based prediction method; Sensitivity; Predictive-positive rate Abstract Background and objective: WHO guidelines in 2010 no longer recommend the total lymphocyte count (TLC), instead of the CD4 + cell (CD4) count, in deciding on the initiation of anti-retroviral treatment. This is very problematic because of the cost and resources involved in getting CD4 counts. To solve this problem, we developed an efficient and reliable method for predicting CD4 counts based on a previous CD4 count. Subjects and methods: To surmount the degrading of the precision due to the individual variability in CD4 counts, we developed an individual-based prediction method. Results: The sensitivity and the predictive-positive rate of CD4 counts below 350 cells/mm 3 were 89% and 88%, respectively, at a one-month interval and 76% and 84%, respectively, at a six-month interval. Conclusion: The individual-based prediction method of the CD4 count will be useful and critical in resource-poor regions where CD4 counts are not repeatedly available.