Identification of Atrial Fibrillation Episodes in Ambulatory Electrocardiographic Recordings: Validation of a Method for Obtaining Labeled R-R Interval Files

MURGATROYD, F.D., et.al .: Identification of Atrial Fibrillation Episodes in Ambulatory Electrocardiographic Recordings: Validation of a Method for Obtaining Labeled R-R Interval Files . Current systems for analyzing ambulatory electrocardiograms (ECGs) are unable to distinguish precisely between sinus rhythm and atrial fibrillation (AF) episodes, and are unable to produce RR interval listings that distinguish AF from sinus rhythm on a beat-to-beat basis. We describe a method for obtaining such a computerized listing ("Composite Rhythm" file) from ambulatory recordings containing episodes of AF. The file lists the rhythm of each beat, its real time, and the QRS complex morphology. A visual inspection is made of a full printout of the recording to identify the precise time of onset and termination of each episode of AF. These times are entered into a computer and identified with the corresponding beats on a conventional RR interval file generated by Holter analysis. The method was validated using 1-hour segments from 20 ambulatory ECGs containing 145 episodes of AF. These were visually identified by four independent observers with a mean sensitivity of 99.1%. The first beat of AF was identified concordantly in 96% of episodes, with a discrepancy of ≤ 3 beats in the other episodes. The times of 200 selected QRS complexes were then entered into the computer by each observer; 91.1 % of these complexes were identified exactly and 100% were identified to within one beat. The Composite Rhythm files have several potential applications for testing AF detection algorithms and studying the mode of onset of AF.     

Qualitative and Quantitative Analysis of T Lymphocytes During Normal Human Pregnancy

PROBLEM : Human reproduction involves contact between cells which are allogeneic to one another, however the fetus not only survives but thrives. METHODS : Aspects of T-cell-mediated immunity during normal human pregnancy were studied. PBMNCs of pregnant and nonpregnant women were stimulated with PHA and cytomegalovirus antigens (CMV). The capacity of stimulated cells to proliferate, to produce IL-2 and IFN-γ, to express IL-2 receptor (IL2R1) and the effect of rIL2 on the proliferation rate of lymphocytes were examined. FACS was utilized for T-cell subset comparisons. RESULTS : The proliferation rate, IL-2, and IFN-γ synthesis were all significantly impaired at suboptimal concentration of PHA throughout pregnancy. Exogenous rIL-2 corrected this depression of cell-mediated immunity (CMI). At optimal concentration of PHA, proliferation rate and production of IFN-γ and IL-2 were all decreased. Exogenous rIL-2 corrected these deficits only in the third trimester. Third trimester pregnant women demonstrated a significant depression of proliferation as well as IL-2 and IFN-γ production after CMV stimulation, which was partially corrected by exogenous rIL-2. FACS analysis suggested that after stimulation by CMV and optimal concentration of PHA, T cells were activated and both CD4+ and CD8+ lymphoblasts expressed normal density of IL-2R1. With suboptimal PHA, the number of activated CD4+ and CD4+IL2R1+ cells were diminished and CD4+ and CD8+ T lymphoblasts expressed lower number of IL2R1. CONCLUSIONS : CD4 T helper (Thl) cell function is down regulated progressively during the three trimesters of pregnancy without changes in the quantity of T cell subsets.     

The attitudes of medical students to the objective structured practical examination

Summary. The objective structured practical examination (OSPE) together with the classical practical examination (CPE) form the basis for evaluation of laboratory teaching at the All India Institute of Medical Sciences, New Delhi. Students' attitudes to OSPE and CPE were assessed by preparing a questionnaire containing 32 item statements on Likert's 5-point scale (LS) and 11 bipolar adjectives on Osgood's 7-point Semantic Differential Scale (OSDS). The questionnaire was administered to 50 medical undergraduates before their final examination. Forty-two (84%) students responded to the questionnaire. The LS showed high internal consistency and validity. Attitude scoring on LS and OSDS revealed a high degree of correlation. The majority of students showed a positive attitude to OSPE, and high-rank students had a greater intensity of positive attitude. OSPE was rated as a reliable, effective, useful, interesting and challenging examination, although considered taxing, mentally and physically. The students preferred a combination of OSPE and CPE as in the present system to a complete change-over to the OSPE. The item analysis of the questionnaire is discussed.     

A High Proportion of Double-Headed and Double-Tailed Sperm in Semen of a Human Male. A Case Report

We present the case of a patient whose semen contained 30% of sperm with double heads and double tails at various stages of attachment due to abnormal meiosis. The genital system, sperm density, endocrinological profile and karyotype were normal. It is postulated that abundance of the above-noted type of sperm pathology in the human semen might not necessarily be associated with oligozoospermia or fertility impairment.     

Effect of tertiary amines and amine salts on racemization in peptide synthesis

An effect of different tertiary amines, anions and cations on yield, product purity and reaction rate in DCC-mediated Ac-Phe-Leu-OMe synthesis was studied. Degree of racemization and side-product yields down to 0.05% were readily determined by HPLC. The increasing effect of tertiary amino salts on degree of racemization was determined more precisely than previously and, more interestingly, their suppression of N-acylurea formation was discovered. Unexpectedly, we found that the suppressing effect of the racemization of l-hydroxybenztriazole was completely blocked by tribenzylamine. Furthermore, kinetic investigation showed that degree of racemization was not directly linked with 5(4H)-oxazolone formation and aminolysis. The much greater racemization observed than calculated from the rate of formation and aminolysis of 5(4H)-oxazolone led us to the conclusion that an activated form of Ac-Phe other than 5(4H)-oxazolone could be co-responsible for racemization in the investigated reaction. An efficient method for preparation of N-(acetyl-DL-phenylalanyl)-dicyclohexylurea is described.