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D Lewinsohn

Publications and source records attributed to D Lewinsohn.

7 recordsLinked to original sources
PubMed1995

[Circadian rhythms in the spectrum of heart rate variability].

Heart rate shows a circadian rhythm. This has not yet been sufficiently investigated for its variability till now, which challenges the analysis of rhythms of the variability and their validity in long time records. For this purpose, time series of heart period duration (HPD) and sinus arrhythmia (SA) were measured in 30 children in a boarding-school (14 male, 16 female, 12 to 14 years of age) from the ECG for 5 min/h during 24 h. Fast Fourier transform provided the spectra and the power density. HPD, SA, power maxima and their frequencies were analyzed for circadian rhythms according to Halberg. Times of meals and sleep were uniform. Power and frequencies of the spectra showed individual patterns, stable throughout the day in 2 diverse groups. SA, high- (HF) and middle frequent (MF) spectral parts show circadian oscillations in frequency or power with acrophases during day or night, often in contrast to HF and MF. This proves the existence of circadian rhythms of heart rate variability for SA, HF and MF. In some cases, the individual 24-h patterns are superimposed by effects of external zeitgeber, e.g. meals.

Adolescent↗
PubMed1995

[Correlation between respiration and heart rate in 12- to 14-year-old children during sleep and wakefulness].

The coupling of respiratory and cardiac rhythm is determined by interactions of oscillating brain stem centers and external physical and psychical influences. Not well known are effects of sleep and wakefulness which will be investigated over the day. From the ECG and respirogram of 42 healthy children (11 female, 31 male, 12 to 14 years) during 24 h the time series of instantaneous heart rate (HR) and respiratory rhythm and from this by FFT the density spectra of power, the maximal power and related frequency in the respiratory range were ascertained. Differences between nonREM sleep and wakefulness and the strength of coupling were determined by coherence analysis. In all probands the maximal power of HR and of the coherence were higher during nonREM sleep than in wakefulness. Both values were stable during each state. The maximum related frequencies of HR and respiration shifted parallel between sleep and wakefulness. The results mean augmentation in nonREM sleep following to improved transfer of respiratory activity to the control of HR. The increased coherence hints at a stronger linear coupling which is stable during each state. The changes of cardiorespiratory coupling may be effected by stronger non-linear parts in the interactions during wakefulness.

Adolescent↗
PubMed1995

[Development of heart rate in newborn infants during quiet sleep].

The small number of investigations of the development of heart rhythm during the first half year of life provide only rough ideas regarding the maturation of heart rate control. In the present study, in 10 newborns, ECG and respiratory effort were recorded in 13 sessions from birth up to the sixth month. The total power (TP), power in the low (LF) and high frequency range (HF), and the ratio LF/HF were used from the heart rate power spectra. All parameters reveal no linear developmental patterns: TP, LF, and HF increase during the first days to a maximum, then decrease subsequently and remain low until the second month. TP and HF increase between the second and sixth month. LF/HF increases up to the second month followed by a decrease down to the sixth month. The developmental courses of TP, HF and LF/HF correlate with the course of breathing rate (BR), whereby high BR is associated with low HF and TP. The results hint at a maturated cardiorespiratory system.

Child Development↗
PubMed1986

Interactions between endothelial cells and leukocytes.

We present evidence that specific receptors are utilized by neutrophils to control their interaction with endothelial cells at sites of acute inflammation and that these receptors are related if not identical to lymphocyte "homing receptors" for lymphoid tissue high endothelium. We speculate that such receptors play a fundamental but not exclusive role in controlling the extravasation and tissue localization of all bone marrow-derived nucleated cells. In addition, we emphasize the active role of endothelial cells in the process of lymphocyte migration and leukocyte extravasation. By the expression of as yet unidentified organ-specific determinants for lymphocyte recognition, endothelial cells control the exit of particular lymphocyte subsets into mucosal versus nonmucosal sites, thus helping to determine the unique features of mucosal versus nonmucosal immune responses. Furthermore, we argue that endothelial cells are exquisitely responsive to local immune reactivity and present evidence that specific lymphokines, including gamma-interferon, play an important role in inducing postcapillary venules to express differentiated features required for the support of lymphocyte traffic into lymphoid organs and into sites of chronic inflammation. Leukocytes, endothelial cells, and probably other tissue cell classes appear to interact at multiple levels by a variety of mechanisms to regulate the local extravasation of immune effector cells.

Animals↗