Bright Light Therapy Increases Blood Pressure and Changes the Structure of Circadian Rhythm of Melatonin Secretion in Spontaneously Hypertensive Rats.

Phototherapy (therapy with bright light) is widely used to treat seasonal affective disorders, different types of depression, sleep disorders, and other diseases; it has no significant contraindications, but its effects on functional state and biological rhythms of the cardiovascular system in hypertension are poorly studied. In experiments on Wistar-Kyoto and SHR (spontaneously hypertensive rats) rats, the effect of bright light therapy on the daily profile of BP, HR, and production of epiphyseal melatonin was investigated. Phototherapy was simulated by exposure to 9000-lux cold light at the level animal eyes over 1 h (from 10.00 to 11.00 h) with LED lamps. In freely moving rats (free access to food), daily profiles of BP and HR were studied by 24-h continuous telemetry monitoring. The production of epiphyseal melatonin was assessed by measuring urinary concentration of its stable metabolite 6-sulfatoxymelatonin (aMT6s) during the day and night. During phototherapy, systolic BP significantly increased in in animals of both lines and diastolic BP increased in SHR rats. This effect persisted after the end of phototherapy session. Bright light had no effect on HR. In Wistar-Kyoto rats, phototherapy induced a significant decrease in daily concentration of aMT6s, but its nocturnal level did not change. In SHR rats, bright light therapy significantly decreased nighttime concentration of aMT6s in the urine and had no effect on daytime concentration of this metabolite. As a result, the difference between the night and day levels of aMT6s in the urine was leveled. Phototherapy produced more pronounced and less favorable effect on animals with primary arterial hypertension.

Influence of lighting color temperature on effort-related cardiac response.

Higher color temperature refers to a higher proportion of blue spectral components of light, that are known to be associated with higher alertness state in humans. Based on motivational intensity theory (Brehm & Self, 1989), here we predicted that this lighting-induced alertness state should inform about the readiness to perform and this way influence subjective task demand and thus mental effort. To test this, study participants spent 15min under one of four lighting color temperature conditions and then performed a cognitive task. As predicted, effort-related cardiac response, indexed by a shortened cardiac pre-ejection period, decreased with increasing color temperature of light, as indicated by a significant single planned linear contrast. These results demonstrate that spectral properties of light can influence mental effort mobilization.

Identification of a Group's Physiological Synchronization with Earth's Magnetic Field.

A new analysis technique for the evaluation of the degree of synchronization between the physiological state of a group of people and changes in the Earth's magnetic field based on their cardiac inter-beat intervals was developed and validated. The new analysis method was then used to identify clusters of similar synchronization patterns in a group of 20 individuals over a two-week period. The algorithm for the identification of slow wave dynamics for every person was constructed in order to determine meaningful interrelationships between the participants and the local magnetic field data. The results support the hypothesis that the slow wave rhythms in heart rate variability can synchronize with changes in local magnetic field data, and that the degree of synchronization is affected by the quality of interpersonal relationships.

Effect of Oxidative Stress on Cardiovascular System in Response to Gravity.

Long-term habitation in space leads to physiological alterations such as bone loss, muscle atrophy, and cardiovascular deconditioning. Two predominant factors-namely space radiation and microgravity-have a crucial impact on oxidative stress in living organisms. Oxidative stress is also involved in the aging process, and plays important roles in the development of cardiovascular diseases including hypertension, left ventricular hypertrophy, and myocardial infarction. Here, we discuss the effects of space radiation, microgravity, and a combination of these two factors on oxidative stress. Future research may facilitate safer living in space by reducing the adverse effects of oxidative stress.

Simulated sudden increase in geomagnetic activity and its effect on heart rate variability: Experimental verification of correlation studies.

Previous research investigating the potential influence of geomagnetic factors on human cardiovascular state has tended to converge upon similar inferences although the results remain relatively controversial. Furthermore, previous findings have remained essentially correlational without accompanying experimental verification. An exception to this was noted for human brain activity in a previous study employing experimental simulation of sudden geomagnetic impulses in order to assess correlational results that had demonstrated a relationship between geomagnetic perturbations and neuroelectrical parameters. The present study employed the same equipment in a similar procedure in order to validate previous findings of a geomagnetic-cardiovascular dynamic with electrocardiography and heart rate variability measures. Results indicated that potential magnetic field effects on frequency components of heart rate variability tended to overlap with previous correlational studies where low frequency power and the ratio between low and high frequency components of heart rate variability appeared affected. In the present study, a significant increase in these particular parameters was noted during geomagnetic simulation compared to baseline recordings.

The influence of adjuvant therapy on cardiorespiratory fitness in early-stage breast cancer seven years after diagnosis: the Cooper Center Longitudinal Study.

We examined cardiorespiratory fitness (CRF) levels in early stage breast cancer patients and determined whether CRF differs as a function of adjuvant therapy regimen. A total of 180 early breast cancer patients representing three treatment groups (surgery only, single-, and multi-modality adjuvant therapy) in the Cooper Center Longitudinal Study (CCLS) were studied. A non-cancer control group (n = 180) matched by sex, age, and date of the CCLS visit was included. All subjects underwent an incremental exercise tolerance test to symptom limitation to assess CRF (i.e., peak metabolic equivalents [METs] and time to exhaustion). The mean time from breast cancer diagnosis to exercise tolerance testing was 7.4 ± 6.2 years. In adjusted analyses, time to exhaustion and peak METs were incrementally impaired with the addition of surgery, single-, and multi-modality adjuvant therapy compared to those of matched controls (p = 0.006 and 0.028, respectively). CRF was lowest in the multi-modality group compared to all other groups (all p's < 0.05). Despite being 7 years post-diagnosis, asymptomatic early breast cancer survivors have marked reductions in CRF. Patients treated with multi-modal adjuvant therapy have the greatest impairment in CRF.

Long-term effects of neck irradiation on cardiovascular autonomic function: a study in nasopharyngeal carcinoma patients after radiotherapy.

INTRODUCTION: Baroreflex failure has been reported as a late sequalum of neck radiotherapy. In this study we investigated cardiovascular autonomic function in patients after neck radiotherapy to determine predictive factors associated with outcome. METHODS: Eighty-nine patients with nasopharyngeal carcinoma were evaluated ≥6 months after radiotherapy for cardiovascular autonomic function and compared with 48 control subjects. Inflammatory markers and carotid intima-media thickness were also assessed. RESULTS: Autonomic parameters of heart rate response to deep breathing and Valsalva ratio were significantly lower in the patient group. Cardiovascular autonomic impairment was generally mild with relative sparing of the efferent cardiovagal pathway. By univariate and multivariate analyses, the time after radiotherapy and C-reactive protein level were significantly associated with the degree of cardiovascular autonomic dysfunction. CONCLUSIONS: Radiation-induced cardiovascular autonomic impairment is a dynamic and progressive process that occurs long after radiotherapy. Chronic inflammation plays a major role in this process.

Respuesta cardiovascular y respiratoria aguda derivada de la aplicación de estímulos vibratorios de diferente magnitud / Cardiovascular and respiratory response resulting from the application of vibratory stimuli with different magnitudes

IntroducciónEl objetivo del presente estudio es conocer la respuesta de los sistemas cardiovascular y respiratorio tras la aplicación de estímulos vibratorios de diferente magnitud, analizando la frecuencia cardíaca (FC), la tensión arterial (TA) y el consumo de oxígeno (VO2).Material y métodosLos sujetos participantes en el estudio, los cuales presentaban en el momento de la realización de éste una edad media de 22±3,89 años, una altura de 1,76±0,61m, una masa corporal de 75,56±8,83kg y un índice de masa corporal de 24,49±2,30kg/m2, fueron distribuidos en tres grupos de forma aleatoria. Cada uno fue sometido a una sesión con estímulos vibratorios de diferente magnitud: grupo experimental 1 (GEA: 30Hz y 4mm), grupo experimental 2 (GEB: 26Hz y 4mm) y grupo experimental 3 (GEC: 20Hz y 4mm).ResultadosLos resultados mostraron una respuesta semejante en los diferentes grupos conformados, no existiendo una relación directa entre la magnitud del estímulo vibratorio y la respuesta fisiológica. Por otro lado, las modificaciones experimentadas en los tres grupos fueron estadísticamente significativas en el caso del VO2 y la FC; fue más variable la respuesta en el caso de la TA.ConclusionesA la vista de los datos obtenidos, se podría afirmar que la aplicación de estímulos vibratorios, utilizando parámetros habituales de entrenamiento, no es suficiente para provocar adaptaciones fisiológicas relacionadas con las variables analizadas(AU)

IntroductionThe aim of the current study is to determine the cardiovascular and respiratory systems response after different vibratory stimuli. Heart rate (HR), blood pressure (BP) and oxygen uptake (VO2) were analyzed during the training. Subjects (22±3,89 yr, height:1,76±0,61m; weight:75,56±8,83kg; IMC: 24,49±2,30 kg/m2) were randomly allocated to one of three groups.Material and methodsEach group performed a vibratory training session with different magnitude: GEA (30Hz and 4mm), GEB (26Hz and 4mm) and GEC (20Hz and 4mm).ResultsA similar response in all groups and a direct relationship between vibratory magnitude and physiological response wasn’t established. In other hand, significant differences in VO2 and HR were found in the three groups, being the response regarding BP more variable.ConclusionsIt may be concluded that the use of vibratory stimuli with in standard training parameters is not enough to induce physiological adaptations in relation to the variables analyzed(AU)

Effect of deep brain stimulation of the posterior hypothalamic area on the cardiovascular system in chronic cluster headache patients.

The objective of this study was to determine the cardiovascular effects of chronic stimulation of the posterior hypothalamic area (PHA) in cluster headache (CH) patients. Systolic and diastolic blood pressure (SBP, DBP), cardiac output, total peripheral resistance (TPR), heart rate (HR) and breathing were monitored at supine rest and during head-up tilt test (HUTT), Valsalva manoeuvre, deep breathing, cold face test and isometric handgrip in eight drug-resistant chronic CH patients who underwent monolateral electrode implantation in the PHA for therapeutic purposes. Autoregressive power spectral analysis (PSA) of HR variability (HRV) was calculated at rest and during HUTT. Each subject was studied before surgery (condition A) and after chronic deep brain stimulation (DBS) of PHA (condition B). Baseline SBP, DBP, HR and cardiovascular reflexes were normal and similar in both conditions. With respect to condition A, DBP, TPR and the LF/HF obtained from the PSA of HRV were significantly (P < 0.05) increased during HUTT in condition B. In conclusion, chronic DBS of the PHA in chronic CH patients is associated with an enhanced sympathoexcitatory drive on the cardiovascular system during HUTT.

The effect of colored illumination on heart rate variability.

BACKGROUND: We investigated the effects of illumination with colored fluorescent light on heart rate variability (HRV) and autonomic regulation. Previous examinations have only focused on full-spectrum fluorescent bright light as it is used for the therapy of seasonal affective disorder and disturbances of circadian rhythms. MATERIALS AND METHODS: In 3 experiments, 12 healthy volunteers were exposed for 10 min to red, green and blue fluorescent light of 700 lux, respectively. These illumination periods were followed and preceded by 15 min of darkness. HRV series were recorded within the last minutes of each illumination and darkness period. HRV analysis encompassed time domain variables, frequency domain variables and detrended fluctuation analysis (DFA). RESULTS: DFA yielded a highly significant increase of the self-similarity parameter aDFA under red and green illumination, while blue light was accompanied by a decrease. A spectral analysis revealed parallel behavior of very low frequency components in the range of 0.003-0.04 Hz. Green light also seemed to induce a reduction in high frequency components. CONCLUSIONS: Results show that colored light can influence HRV within minutes and that the effects of individual colors can be distinguished by HRV analysis.

Role of unmyelinated fibers in electroacupuncture cardiovascular responses.

The afferent fiber type responsible for the transmission of sensory neural traffic to the central nervous system during acupoint stimulation is uncertain. Several early studies evaluating compound action potentials have suggested that myelinated fibers contribute to the afferent input of the autonomic reflex adjustments during electroacupuncture (EA). Our more recent data, employing single unit recordings of somatic afferents, show that both myelinated and unmyelinated fibers are stimulated by EA, although more finely myelinated than unmyelinated fibers are activated by low frequency, low current stimulation. We hypothesized in this study that unmyelinated group VI fibers also contribute significantly to the inhibitory influence of EA on cardiovascular pressor responses. We found that neonatal capsaicin-treated rats depleted of substance P from primary afferents were insensitive to the inhibitory EA effect during gastric distention. Thus, EA at P5-P6 reduced gastric distention-induced pressor responses from 19+/-3 to 11+/-2 mmHg in eight untreated rats while capsaicin-treated rats (n=9) were unresponsive to EA. Substance P containing neurons in dorsal root ganglion cells at Ti-T5 were significantly decreased in the capsaicin-treated rats from 47+/-4 to 22+/-4 cells. Treated compared to untreated rats also demonstrated a significantly (P<0.03) reduced number of group IV fibers identified with single unit recording techniques. This study demonstrates that the inhibitory effect of EA at P5-P6 on cardiovascular autonomic excitatory reflexes involves unmyelinated group IV fibers of the median nerves.

Comparative effect of positive and negative static magnetic fields on heart rate and blood pressure in healthy adults.

OBJECTIVE: To compare changes in heart rate (HR) and blood pressure (BP) associated with short-term exposure to static magnetic fields (SMFs) of positive versus negative polarity. DESIGN: A double-blind, randomized controlled trial using a time series design. SETTING: Physical therapy laboratory in a university setting. SUBJECTS: Seventy-five adults with a mean age of 30.6 years were assigned to one of three treatment groups. No subjects had any symptoms of cardiovascular disease or cardiac irregularity. INTERVENTIONS: Fifteen-minute exposure to an SMF by lying on a mattress pad containing magnets of positive polarity, negative polarity, or none (placebo). MAIN OUTCOME MEASURES: HR and BP were monitored prior to exposure, at 1-minute, 5-minute, 10-minute and 15-minute intervals following exposure, and again 5 minutes after exposure. RESULTS: Subjects in all groups demonstrated slight decreases in HR and BP, but none of these changes were associated with the intervention (p = 0.170). CONCLUSIONS: Short-term exposure to an SMF of either positive or negative polarity does not appear to cause any clinically meaningful changes in HR or BP among asymptomatic subjects. This finding supports the safe use of unipolar SMFs that contain low-intensity magnets (< 1000 gauss) relative to the cardiovascular system.

Alternating light-darkness-influenced human electrocardiographic magnetoreception in association with geomagnetic pulsations.

Geomagnetic variations of partly interplanetary origin, with cyclic signatures in human affairs and pathology include the incidence of various diseases, regarding which this study of healthy subjects attempted to determine an underlying mechanism by worldwide archival and physiological monitoring, notably of heart rate variability (HRV). In the past half-century, the possible health and other hazards of natural, solar variability-driven temporal variations in the earth's magnetic field have become a controversial subject in view of the inconsistent results. Some well-documented claims of associations between geomagnetic storms and myocardial infarction or stroke have been rejected by a study based on more comprehensive data analyzed by rigorous methods - covering, however, only part of a solar cycle in only part of a hemisphere. It seems possible that inter-solar cycle and geographic variability, if not geographic differences, may account for discrepancies. Herein, we examine the start of a planetary study on any influence of geomagnetic disturbances that are most pronounced in the auroral oval, on human HRV. The magnetic field variations exhibit complex spectra and include the frequency band between 0.001-10 Hz, which is regarded as ultra-low frequency by physicists. Since the 'ultra-low-frequency' range, like other endpoints used in cardiology, refers to much higher frequencies than the about-yearly changes that are here shown to play a role in environmental-organismic interactions revealed by HRV, the current designations used in cardiology are all placed in quotation marks to indicate the need for possible revision. Whether or not this suggestion has an immediate response, we have pointed to a need for the development of instrumentation and software that renders the assessment of circadian, infradian and even infra-annual (truly low frequency) modulations routinely feasible. HRV was examined on the basis of nearly continuous 7-day records by ECG between December 10, 1998, and November 2, 2000, on 19 clinically healthy subjects, 21 to 54 years of age, in Alta, Norway. A geomagnetic record was obtained from the Auroral Observatory of the University of Tromsø. First, frequency-domain measures of HRV were compared for each person in 24-hour spans of high geomagnetic disturbance versus quiet conditions. Second, cross-spectra between geomagnetic activity and HRV measures were quantified via the squared coherence spectrum using 7-day time series. A 7.5% increase in the 24-hour average of heart rate, HR (P = 0.00020) and a decrease in HRV were documented on days of high geomagnetic disturbance. The decrease in HRV was validated statistically for the 'total frequency', 'TF' endpoint (18.6% decrease, P= 0.00009). The decrease in spectral power was found primarily in the 'circaminutan frequency', 'VLF' (21.9% decrease, P< 0.000001) in conjunction with the 'minutes-to-hours' component, ultra-low-frequency, 'ULF' (15.5% decrease, P= 0.00865) and circadecasecundan 'low frequency', 'LF' (14.2% decrease, P = 0.00187) regions of the spectrum. Power-law scaling of the power spectra did not show any statistically significant difference. It is noteworthy that most of the decrease in HRV, except for the circaminutan (VLF) component, was observed only in the season in which sunshine alternated with darkness (D/L), a finding suggesting a mechanism influenced by the alternation of light and darkness. The hypothesis of a light-dark-influenced magnetoreception was also supported by cross-spectral analysis. Group-averaged coherence at frequencies coincident with the geomagnetic Pc 6 pulsations (with periods ranging from 10 minutes to 5 hours) differed with a statistical significance (P < 0.000001) among the three natural lighting conditions, the association being weaker during UL or D/D than during D/L. By contrast, no statistically significant differences were found in terms of the circadian and circasemidian frequencies in relation to the alternation of sunshine with darkness or rather circannual rhythm stage. In conclusion, evidence is provided herein that an alteration of HRV is most apparent in the circaminutan ('VLF') region, which is clinically important, because a reduction in its power is a predictor of morbidity and mortality from cardiovascular disease. The circadecasecundan ('LF') component of HRV also decreased in association with geomagnetic disturbance, which may reflect an episodic alteration of arterial pressure related to changes in geomagnetic activity. Lastly, our study suggests the existence of a light-dark-influenced magnetoreception mechanism in humans involving mainly the Pc 6 band of the magnetic field.

Associations by signatures and coherences between the human circulation and helio- and geomagnetic activity.

Helio-geomagnetic influences on the human circulation are investigated on the basis of an 11-year-long record from a clinically healthy cardiologist, 35 years of age at the start of monitoring. He measured his blood pressure and heart rate around the clock with an ambulatory monitor programmed to inflate an arm cuff, mostly at intervals of 15-30 minutes, with only few interruptions, starting in August 1987. While monitoring is continuing, data collected up to July 1998 are analyzed herein by cosinor rhythmometry and cross-spectral coherence with matching records of solar activity, gauged by Wolf numbers (WN) and of the geomagnetic disturbance index, Kp. A direct association between heart rate (HR) and WN is found to be solar cycle stage-dependent, whereas an inverse relationship between heart rate variability (HRV) and WN is found consistently. An inverse relation is also observed between WN and the variability in systolic blood pressure (SBP), and to a lesser extent, diastolic blood pressure (DBP). Moreover, HR is cross-spectrally coherent with WN at a frequency of one cycle in about 7.33 months. The results support previously reported associations on morbidity and mortality statistics, extending their scope to human physiology monitored longitudinally.

[Experimental assessment of the cardiovascular system functional state in rats after chronic gamma-irradiation in various absorbed doses]. / Eksperimental'naia otsenka funktsional'nogo sostoianiia serdechno-sosudistoi sistemy u krys posle khronicheskogo gamma-oblucheniia v raznykh pogloshchennykh dozakh.

Prolonged anthenatal gamma-irradiation of rats with total doses of 1.25; 1.9 and 2.5 Gy resulted in discoordination of cardiovascular system function. This study confirm our previous data on negative effect of chronic gamma-irradiation on forming and development of the functional systems in the anthenatally irradiated organism.