Postextrasystolic Changes in the Complexity of the QRS Complex and T Wave

We tested the hypothesis that ventricular repolarization of the first sinus beat following a ventricular premature beat (VPB) can be modulated in the absence of clearly discernible T‐wave changes. We applied principal component analysis (PCA) to assess QRS and T‐wave complexity of sinus beats preceding and following VPBs in multiple 10‐second resting 12‐lead electrocardiograms of two subjects with frequent VPBs and no apparent heart disease. In both subjects, T‐wave complexity of the first post‐VPB beat was significantly increased compared to the beats preceding the VPB.     

The impact of menstrual cycle phase on cardiac autonomic regulation

This study investigated menstrual cycle phase differences in heart rate (HR) and RR interval variability (RRV) in 49 healthy, premenopausal, eumenorrheic women (age 30.2±6.2 years). HR and RRV were computed from ambulatory 24-h electrocardiogram, collected for up to 6 days, with at least 1 day each during early to midfollicular and midluteal menstrual phases. Phase effects on HR and RRV were assessed using linear mixed effects models with a random intercept to account for the correlation of observations within each subject as well as intrasubject variation. During follicular phase monitoring, women had significantly lower average HR (−2.33 bpm), and higher standard deviation, the root mean squared successive difference, and high frequency (0.04–0.15 Hz) and low frequency (0.15–0.40 Hz) RRV than during the luteal phase. These results provide strong support for the influence of menstrual phase on cardiac autonomic regulation in premenopausal women.     

Independent initiation of primary electron transfer in the two branches of the photosystem I reaction center

Photosystem I (PSI) is a large pigment-protein complex that unites a reaction center (RC) at the core with ∼100 core antenna chlorophylls surrounding it. The RC is composed of two cofactor branches related by a pseudo-C2 symmetry axis. The ultimate electron donor, P₇₀₀ (a pair of chlorophylls), and the tertiary acceptor, F_X (a Fe₄S₄ cluster), are both located on this axis, while each of the two branches is made up of a pair of chlorophylls (ec2 and ec3) and a phylloquinone (PhQ). Based on the observed biphasic reduction of F_X, it has been suggested that both branches in PSI are competent for electron transfer (ET), but the nature and rate of the initial electron transfer steps have not been established. We report an ultrafast transient absorption study of Chlamydomonas reinhardtii mutants in which specific amino acids donating H-bonds to the 13¹-keto oxygen of either ec3_A (PsaA-Tyr696) or ec3_B (PsaB-Tyr676) are converted to Phe, thus breaking the H-bond to a specific ec3 cofactor. We find that the rate of primary charge separation (CS) is lowered in both mutants, providing direct evidence that the primary ET event can be initiated independently in each branch. Furthermore, the data provide further support for the previously published model in which the initial CS event occurs within an ec2/ec3 pair, generating a primary ec2⁺ec3^- radical pair, followed by rapid reduction by P₇₀₀ in the second ET step. A unique kinetic modeling approach allows estimation of the individual ET rates within the two cofactor branches.     

Metabolic cycling in single yeast cells from unsynchronized steady-state populations limited on glucose or phosphate

Oscillations in patterns of expression of a large fraction of yeast genes are associated with the “metabolic cycle,” usually seen only in prestarved, continuous cultures of yeast. We used FISH of mRNA in individual cells to test the hypothesis that these oscillations happen in single cells drawn from unsynchronized cultures growing exponentially in chemostats. Gene-expression data from synchronized cultures were used to predict coincident appearance of mRNAs from pairs of genes in the unsynchronized cells. Quantitative analysis of the FISH results shows that individual unsynchronized cells growing slowly because of glucose limitation or phosphate limitation show the predicted oscillations. We conclude that the yeast metabolic cycle is an intrinsic property of yeast metabolism and does not depend on either synchronization or external limitation of growth by the carbon source.     

Systolic blood pressure, not BIS, is associated with movement during laryngoscopy and intubation

OBJECTIVE: To compare bispectral index (BIS) values to hemodynamic variations, in order to evaluate adequacy of anesthesia during orotracheal intubation with muscle relaxants. METHODS: Forty-one patients ASA I-II, scheduled for elective peripheral surgery under general anesthesia with tracheal intubation were enrolled in the study. Fentanyl/thiopental followed by vecuronium were used for induction. Onset of relaxation was monitored at the orbicularis occuli (OO) muscle using train-of-four stimulation. Intubation was performed when no response at the OO was detected visually. Intubating conditions were noted. The "isolated forearm" technique was used to detect movement during laryngoscopy/intubation. BIS values, pulse rate (PR), and systolic pressure were recorded before induction, during laryngoscopy/intubation and 60 sec after intubation. RESULTS: Although intubating conditions were clinically adequate for all patients, ten out of 41 had movement of the isolated arm during laryngoscopy/intubation. BIS values were not significantly different for these patients: 67 (55-83) compared to those who had no movement: 60 (35-80), P = 0.6. During laryngoscopy, PR increased for all patients while systolic pressure increased significantly only in patients who moved: 125 (100-136) mmHg vs those who did not: 108 (67-140), P < 0.05. CONCLUSION: Systolic pressure elevations were associated with inadequate anesthesia as evaluated by the "isolated forearm" technique, during laryngoscopy/intubation. BIS values were not different between groups, suggesting that systolic blood pressure may be a better predictor of inadequate anesthesia under the circumstances described.     

The age-related changes in the incidence of 'natural' anti-sperm antibodies suggest they are not auto-/isoantibodies

PROBLEM: Establishing the age-dependent patterns of sperm antibody levels among normal humans. METHODS OF STUDY: Sera samples from 498 healthy subjects aged 0-97 years - 246 males and 252 females - were tested by the gelatin agglutination test of Kibrick, tray agglutination test of Friberg, sperm immobilization test of Isojima and enzyme-linked immunosorbent assay (ELISA). RESULTS: We found a significant increase in the level of sperm agglutinins after 40 years, which decreased after 88 years. The antibodies detected by ELISA were the highest among prepubertal subjects and also declined with aging. No age-dependent changes were established for the sperm immobilizins. With few exceptions, there were no significant differences between male and female sera, as well as between sera of newborn and their mothers. CONCLUSIONS: These data are similar to those established for the age-dependent changes of antibodies towards exogenous antigens, suggesting that the 'naturally occurring' antibodies against human spermatozoa are not auto-/isoantibodies.     

Effect of amiodarone on the descending limb of the T wave

Comparing patients treated after myocardial infarction with amiodarone or with placebo, we found a significant rate-dependent prolongation of TpTe interval in patients who received amiodarone. Patients who had arrhythmic death had significantly longer TpTe intervals than others on placebo but not on amiodarone. Assuming that TpTe reflects transmural repolarization heterogeneity, our findings suggest that heterogeneity and arrhythmic risk are increased by amiodarone. This contradicts the finding of decreased transmural repolarization heterogeneity by amiodarone and the appreciated antiarrhythmic efficacy of this drug.     

Pharmacokinetics and pharmacodynamics of rapacuronium in patients with cirrhosis.

BACKGROUND: Delayed elimination kinetics of steroidal neuromuscular blocking agents have been observed in patients with cirrhosis. Like other steroidal muscle relaxants, rapacuronium may, in part, be eliminated by the liver. To determine the influence of liver disease on its neuromuscular blocking effect, we studied the pharmacokinetics and pharmacodynamics of rapacuronium in patients with cirrhosis. METHODS: Sixteen patients undergoing elective surgery or endoscopy with general anesthesia, eight with cirrhosis and eight with normal liver function, were studied. Anesthesia was induced with fentanyl 2 microg/kg and thiopental 5-7 mg/kg and maintained with 60% nitrous oxide and 0.6-0.8% isoflurane in oxygen and repeated doses of fentanyl 1 microg/kg. Rapacuronium 1.5 mg/kg was administered intravenously before tracheal intubation. Thumb adduction force evoked by supramaximal ulnar nerve stimulation was recorded in 16 patients. Venous blood was sampled at frequent intervals for 8 h. Rapacuronium and its breakdown product Org 9488 were measured in plasma by high-pressure liquid chromatography. Values are reported as median (range). RESULTS: The central volume of distribution was increased to 131 (104-141) ml/kg in patients with cirrhosis (P < 0.01), compared with 75 (47-146) ml/kg in controls. The total apparent volume of distribution was also increased (P < 0.05) to 331 (284-488) ml/kg in patients with cirrhosis, compared with 221 (124-285) ml/kg in controls. The elimination half-life was 88 (77-102) min in controls and 90 (76-117) min in patients with cirrhosis. Plasma clearance was increased (P < 0.05) to 6.9 (6.1-8.9) ml x min(-1) x kg(-1) in patients with cirrhosis, compared with 5.3 (4.2-8.4) ml x min(-1) x kg(-1) in controls. Rapacuronium neuromuscular blocking effect was similar between the two groups. Onset time was 65 (40-110) s in controls and of 60 (52-240) s in patients with cirrhosis. Time to return to 90% of thumb adduction force control value was of 49 (28-80) min in controls and 47 (28-71) min in patients with cirrhosis. CONCLUSION: The neuromuscular blocking effect of a single bolus dose of rapacuronium in patients with cirrhosis is not different from that of patients with normal hepatic function. No decrease in plasma clearance of rapacuronium was observed in patients with cirrhosis.     

The combined IGG, IGM and IGA peroxidase conjugate can facilitate determination of immune complexes by CIF-ELISA and anti-C3 ELISA.

To determine the levels of circulating immune complexes (CIC) in normal and patients sera, CIF-ELISA and anti-C3 ELISA were performed. Immune complexes containing different antibody isotypes were detected simultaneously by the combined anti human IgG, IgM and IgA peroxidase conjugate as detecting antibody. The results obtained confirm the higher CIF-ELISA sensitivity, specificity and reproductivity compared to anti-C3 ELISA and provide good evidence to justify the use of CIF-ELISA as a screening test for CIC assessment.