Assessment of baroreceptor-cardiac reflex sensitivity using time domain analysis in patients with IDDM and the relation to left ventricular mass index

Autonomic dysfunction in insulin-dependent diabetic (IDDM) patients has been associated with abnormalities of left ventricular function and an increased risk of sudden death. A group of 30 patients with IDDM and 30 age, sex and blood pressure matched control subjects underwent traditional tests of autonomic function. In addition, baroreceptor-cardiac reflex sensitivity (BRS) was assessed using time domain (sequence) analysis of systolic blood pressure and pulse interval data recorded non-invasively using the Finapres beat-to-beat blood pressure recording system. 'Up BRS' sequences-increases in systolic blood pressure associated with lengthening of R-R interval, and 'down BRS' sequences-decreases in systolic blood pressure associated with shortening of R-R interval were identified and BRS calculated from the regression of systolic blood pressure on R-R interval for all sequences. We also assessed heart rate variability using power spectral analysis and, after expressing components of the spectrum in normalised units, assessed sympathovagal balance from the ratio of low to high frequency powers. IDDM subjects underwent 2-D echocardiography to assess left ventricular mass index. Standard tests of autonomic function revealed no differences between IDDM patients and control subjects, but dramatic reductions in baroreceptor-cardiac reflex sensitivity were detected in IDDM patients. 'Up BRS' when supine was 11.2 +/- 1.5 ms/mmHg (mean +/- SEM) compared with 20.4 +/- 1.95 in control subjects (p < 0.003) and when standing was 4.1 +/- 1.9 vs 7.6 +/- 2.7 ms/mmHg (p < 0.001). Down BRS when supine was 11.5 +/- 1.2 vs 22 +/- 2.6 (p < 0.001) and standing was 4.4 +/- 1.9 vs 7.3 +/- 2.5 ms/mmHg (p < 0.003). There were significant relations between impairment of the baroreflex and duration of diabetes (p < 0.001) and poor glycaemic control (p < 0.001). From a fast Fourier transformation of supine heart rate data and using a band width of 0.05-0.15 Hz as low-frequency and 0.2-0.35 Hz as high frequency total spectral power of R-R interval variability was significantly reduced in the IDDM group for both low-frequency (473 +/- 62.8 vs 746.6 +/- 77.6 ms2 p = 0.002) and high frequency bands 125.2 +/- 12.9 vs 459.3 +/- 89.8 ms2 p < 0.0001. When the absolute powers were expressed in normalised units the ratio of low frequency to high frequency power (a measure of sympathovagal balance) was significantly increased in the IDDM group (2.9 +/- 0.53 vs 4.6 +/- 0.55, p < 0.002 supine: 3.8 +/- 0.49 vs 6.6 +/- 0.55, p < 0.001 standing). Thus, time domain analysis of baroreceptor-cardiac reflex sensitivity detects autonomic dysfunction more frequently in IDDM patients than conventional tests. Impaired BRS is associated with an increased left ventricular mass index and this abnormality may have a role in the increased incidence of sudden death seen in young IDDM patients.     

Nqr experiments on Sc-Y alloys at very low temperatures

We have performed Nuclear Quadrupole Resonance (NQR) experiments on an alloy of scandium and yttrium. We find that the characteristic resonance frequencies in zero external field are 50 percent larger than in pure scandium. This increase in frequency makes the Sc-Y alloy a better candidate for absolute thermometry below 500 µK. However, the spin-lattice relaxation time of this alloy is more than an order of magnitude longer than in the pure scandium. In addition, we have observed an abrupt increase in the Korringa constant for temperatures below 5mK.     

Efficient computation of the steady-state response of periodicnonlinear microwave circuits using a convolution-based sample-balancetechnique

The authors describe an efficient and robust approach to the computation of the steady-state response of periodic nonlinear microwave circuits. The problem of solving a set of differential equations is converted into that of solving a system of nonlinear algebraic equations using a technique called convolution-based sample balance. Although exact in all cases for which harmonic-balance techniques are exact, this technique does not require the use of discrete Fourier transforms, and calculating the Jacobian is straightforward. For the solution of the resulting system of nonlinear equations, an efficient and yet robust algorithm has been developed. In the examples given, savings in computational effort of over 85% are reported when this algorithm is compared with Newton's method     

Time-dependent modelling and asymptotic analysis of electrochemical cells

A (time-dependent) model for an electrochemical cell, comprising a dilute binary electrolytic solution between two flat electrodes, is formulated. The method of matched asymptotic expansions (taking the ratio of the Debye length to the cell width as the small asymptotic parameter) is used to derive simplified models of the cell in two distinguished limits and to systematically derive the Butler–Volmer boundary conditions. The first limit corresponds to a diffusion-limited reaction and the second to a capacitance-limited reaction. Additionally, for sufficiently small current flow/large diffusion, a simplified (lumped-parameter) model is derived which describes the long-time behaviour of the cell as the electrolyte is depleted. The limitations of the dilute model are identified, namely that for sufficiently large half-electrode potentials it predicts unfeasibly large concentrations of the ion species in the immediate vicinity of the electrodes. This motivates the formulation of a second model, for a concentrated electrolyte. Matched asymptotic analyses of this new model are conducted, in distinguished limits corresponding to a diffusion-limited reaction and a capacitance-limited reaction. These lead to simplified models in both of which a system of PDEs, in the outer region (the bulk of the electrolyte), matches to systems of ODEs, in inner regions about the electrodes. Example (steady-state) numerical solutions of the inner equations are presented.     

Serotonin-4 receptor antagonists reverse cocaine-induced cardiac arrhythmia

CONTEXT: Adolescent smoking prevalence is tracked annually and has increased since 1991. In contrast, little is known about trends in smoking among college students, a group that has previously been more resistant to tobacco use than other young adults. OBJECTIVE: To examine changes in cigarette smoking among college students between 1993 and 1997 and among different types of students and colleges. DESIGN: Self-administered survey (Harvard School of Public Health College Alcohol Study). SETTING: One hundred sixteen nationally representative 4-year colleges. SUBJECTS: A total of 15103 randomly selected students in 1993 (70% response rate) and 14251 students in 1997 (60% response rate). MAIN OUTCOME MEASURES: Self-reports of cigarette smoking in the past 30 days and in the past year, age at smoking first cigarette, and number of attempts to quit. RESULTS: Over 4 years, the prevalence of current (30-day) cigarette smoking rose by 27.8%, from 22.3% to 28.5% (P<.001). The increase was observed in 99 of 116 colleges and was statistically significant (P<.05) in 27 (23%) of them. Current smoking increased across all student subgroups (defined by sex, race/ethnicity, and year in school) and in all types of colleges. Smoking is rising faster in public schools (from 22.0% to 29.3%) than in private schools (from 22.9% to 26.8%). Eleven percent of college smokers had their first cigarette and 28% began to smoke regularly at or after age 19 years, by which time most were already in college. Half of current smokers tried to quit in the previous year; 18% had made 5 or more attempts to quit. CONCLUSIONS: Cigarette use is increasing on campuses nationwide in all subgroups and types of colleges. Substantial numbers of college students are both starting to smoke regularly and trying to stop. National efforts to reduce smoking should be extended to college students.     

Recommendations for the prevention of coronary artery disease in Asians: a scientific statement of the International College of Nutrition

PURPOSE: Two types of glass wool were used to remove leukocytes in semen for evaluation of reactive oxygen species production by spermatozoa in oligozoospermic patients with leukocytospermia. METHODS: Semen samples were prepared using fine-structure glass wool (SpermFertil) and coarse-structure glass wool. In each treatment group, native semen was evaluated for sperm concentration, percentage motility, viability, leukocyte concentration, and production of reactive oxygen species. RESULTS: Electron microscopically, SpermFertil showed a higher number of leukocytes attached to the fibers compared to coarse-structure glass wool. Leukocytes in native semen and after glass wool filtration as determined by peroxidase cytochemistry confirmed this observation. Reactive oxygen species decreased from 45.303 counts/10(7) viable cells in native semen to 15.806 counts/10(7) cells in coarse structure wool and 7.465 counts/10(7) cells in Spermfertil, respectively. CONCLUSIONS: Removal of leukocytes from semen of oligozoospermic patients by means of glass wool filtration is a useful method to distinguish production of reactive oxygen species by leukocytes versus sperm cells.     

Intermediate filament expression in prostate cancer

The human prostate is composed of a series of tubular-alveolar glands and their ducts surrounded by a fibro-muscular stroma. The parenchymal glands secrete the seminal fluid and are anatomically arranged into the central, peripheral, and transitional zones. In this chapter the pattern of intermediate filament expression by the various epithelial components of the ducts, tubuloalveolar glands, and stroma are described. The changes which occur during malignant transformation from normal glands to prostatic intraepithelial neoplasia and subsequent invasive carcinoma are presented. The usefulness of cytokeratin markers in the diagnosis of prostate carcinoma is also discussed.