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T Ritz

Publications and source records attributed to T Ritz.

18 recordsLinked to original sources
PubMed2006

On the use of magnets to disrupt the physiological compass of birds.

Behavioral researchers have attached magnets to birds during orientation experiments, assuming that such magnets will disrupt their ability to obtain magnetic information. Here, we investigate the effect of an attached magnet on the ability to derive directional information from a radical-pair based compass mechanism. We outline in some detail the geometrical symmetries that would allow a bird to identify magnetic directions in a radical-pair based compass. We show that the artificial field through an attached magnet will quickly disrupt the birds' ability to distinguish pole-ward from equator-ward headings, but that much stronger fields are necessary to disrupt their ability to detect the magnetic axis. Together with estimates of the functional limits of a radical-pair based compass, our calculations suggest that artificial fields of comparable size to the geomagnetic field are not generally sufficient to render a radical-pair based compass non-functional.

Animal Migration↗
PubMed2001

The structure of symptom report in asthma: a reevaluation.

OBJECTIVES: We studied the structure of symptom report in a sample of British asthma patients using the Asthma Symptom Checklist (ASC). METHODS: The ASC was administered to 193 patients, together with a questionnaire on demographics and asthma-related information and the Perceived Control of Asthma Questionnaire. RESULTS: Principal Component Analysis yielded evidence for a six-dimensional structure of the ASC, with positively correlated subscales for panic-fear, irritation, obstruction-dyspnea, obstruction-congestion, fatigue, and hyperventilation symptoms. Individual subscales showed good to excellent item characteristics and internal consistencies in individual subscales. Panic-fear and obstruction-congestion were related to self-reported duration of oral corticosteroid intake. Other ASC subscales were positively related to aspects of health care utilization, limitations in daily activity, and lower perceived control of asthma mainly in women. The dyspnea subscale of the ASC showed only little relationship with either of these variables. CONCLUSION: The ASC can reliably assess the multidimensional structure of asthma symptom report. Its subscales are associated with important aspects of asthma management behavior.

Administration, Oral↗
PubMed2001

Relaxation therapy in adult asthma. Is there new evidence for its effectiveness?

Studies of relaxation training for adult asthma patients were reviewed for the period between 1980 and 2000. Six controlled and three uncontrolled studies were identified, employing a variety of methods, such as progressive relaxation, functional relaxation, autogenic training, or yoga. Most studies had low sample sizes and suffered from one or more methodological deficiencies, such as suboptimal data analysis, high dropout rates, problematic measurement procedures, or insufficient descriptions of methodology and results. Overall effects on parameters of lung function, symptoms, medication consumption, and health care use were generally negligible. Problems with the underlying rationale of relaxation therapy in asthma are discussed from a psychophysiological viewpoint. Examples are given of potential beneficial and detrimental effects of these techniques on lung function with respect to emotional processes, the musculoskeletal system, and ventilation as targets of a relaxation intervention. It remains to be demonstrated that relaxation training can significantly contribute to the standard treatment of asthma in adult patients.

Adult↗
PubMed2001

Experimentally induced emotions, facial muscle activity, and respiratory resistance in asthmatic and non-asthmatic individuals.

We studied the effects of emotion induction on total respiratory resistance, and their relationship with cardiac vagal activity and facial muscle activity in asthma. Groups of 20 asthmatic and 20 non-asthmatic participants were exposed to series of happy and depressing pictures or self-referent Velten statements. Facial electromyographic activity over corrugator supercilii, orbicularis oculi, and zygomaticus major regions was recorded during periods of presentation and imagery of each stimulus. Following each stimulus series, mood, respiratory resistance, ventilation, and cardiac activity including respiratory sinus arrhythmia (RSA) were recorded. Significant increases of respiratory resistance were observed in asthmatic patients following depressing stimulation. Resistance increases were positively correlated with RSA and heart period. No substantial group differences were found in facial response to emotional stimuli. Changes in facial target muscle sites during positive stimulation were inversely correlated with RSA following stimulation. We conclude that respiratory resistance increases in asthmatics following depressing stimulation are dependent on vagal activity. Greater facial muscle activation during emotional stimulation can reduce vagal activation, which is consistent with claims in the clinical literature of the benefits of emotional expression in asthma.

Adult↗
PubMed2001

Modulation of respiratory sinus arrhythmia by respiration rate and volume: stability across posture and volume variations.

We tested the assumption that the slope of the within-individual regression equation of respiratory sinus arrhythmia (RSA) normalized by tidal volume (V(T)) upon respiratory cycle length (T(TOT)) can characterize ventilatory RSA modulation independent of cardiac vagal tone, whereas the intercept is varying as a function of vagal tone. We also explored whether a variation of V(T) is necessary to estimate slopes reliably. Four 3-min sequences paced at 8-18 cycles/min were performed supine and standing. Participants also breathed the same sequences in supine posture with voluntarily varying V(T). The mean slope of RSA/V(T) upon T(TOT) was identical, and the mean intercept was lower for standing than supine (spontaneous V(T)) conditions. Stability of slopes was low between body postures, and was higher between spontaneous V(T) versus varying V(T) at the same body posture. The regression of RSA/V(T) upon T(TOT) allows for a valid estimation of ventilatory influences on RSA.

Adult↗
PubMed2000

Excitation transfer in the peridinin-chlorophyll-protein of Amphidinium carterae.

Peridinin-chlorophyll-protein (PCP) is a unique light-harvesting protein that uses carotenoids as its primary light-absorbers. This paper theoretically investigates excitation transfer between carotenoids and chlorophylls in PCP of the dinoflagellate Amphidinium carterae. Calculations based on a description of the electronic states of the participating chromophores and on the atomic level structure of PCP seek to identify the mechanism and pathways of singlet excitation flow. After light absorption the optically allowed states of peridinins share their electronic excitation in excitonic fashion, but are not coupled strongly to chlorophyll residues in PCP. Instead, a gateway to chlorophyll Q(y) excitations is furnished through a low-lying optically forbidden excited state, populated through internal conversion. Carbonyl group and non-hydrogen side groups of peridinin are instrumental in achieving the respective coupling to chlorophyll. Triplet excitation transfer to peridinins, mediated by electron exchange, is found to efficiently protect chlorophylls against photo-oxidation.

Animals↗
PubMed2000

A model for photoreceptor-based magnetoreception in birds.

A large variety of animals has the ability to sense the geomagnetic field and utilize it as a source of directional (compass) information. It is not known by which biophysical mechanism this magnetoreception is achieved. We investigate the possibility that magnetoreception involves radical-pair processes that are governed by anisotropic hyperfine coupling between (unpaired) electron and nuclear spins. We will show theoretically that fields of geomagnetic field strength and weaker can produce significantly different reaction yields for different alignments of the radical pairs with the magnetic field. As a model for a magnetic sensory organ we propose a system of radical pairs being 1) orientationally ordered in a molecular substrate and 2) exhibiting changes in the reaction yields that affect the visual transduction pathway. We evaluate three-dimensional visual modulation patterns that can arise from the influence of the geomagnetic field on radical-pair systems. The variations of these patterns with orientation and field strength can furnish the magnetic compass ability of birds with the same characteristics as observed in behavioral experiments. We propose that the recently discovered photoreceptor cryptochrome is part of the magnetoreception system and suggest further studies to prove or disprove this hypothesis.

Animals↗
PubMed2000

Increases in total respiratory resistance during forehead temperature stimulation.

We investigated the effects of forehead temperature stimulation on total respiratory resistance in healthy individuals. In two experiments involving a total of 38 participants we studied the time course and stability of the response at moderate temperature (20-23 degrees C). Small plastic bags filled with water were positioned on the forehead for a duration of 60 s. Oscillatory resistance (R(os)), heart period (HP), respiratory sinus arrhythmia (RSA), and ventilatory parameters were measured continuously. Experiment 1 showed similar phasic increases in R(os) during the first 20 s of stimulation with moderate (20-23 degrees C) as compared to cold (8-11 degrees C) temperature. Phasic increases by moderate temperature were replicated in Experiment 2 over five successive stimulation trials. Within-session stability of individual differences in response was only modest. Ventilatory adjustments did not facilitate the phasic R(os) increases. As increases were mainly due to the inspiratory component of R(os), a substantial contribution of upper airway artifacts was less likely. Increases in HP were the most pronounced responses to all stimulation conditions, while RSA did not increase significantly.

Adult↗
PubMed2000

Respiratory resistance during emotional stimulation: evidence for a nonspecific effect of experienced arousal?

We investigated the effects of phasic emotional stimuli on total respiratory resistance (TRR) in 16 nonasthmatic students. Six series of happy, neutral, and depressing affective pictures and self-referent Velten statements were presented. Each stimulus was presented for 12 s and subsequently imagined for 12 s. TRR was measured by forced oscillations throughout the stimulus series, together with ventilation, cardiac activity (including respiratory sinus arrhythmia), and facial EMGs (corrugator supercilii, orbicularis oculi, and masseter). In addition, self-reports of mood, pleasure and arousal were obtained. TRR was increased during happy and depressing stimuli compared to neutral stimuli, with stronger effects for the inspiratory component of TRR. Ventilatory parameters did not explain the changes observed in TRR. Discrimination of affective categories by facial EMG was weak. Although EMG masseter activity did not account for this result, an influence of the respiration measurement procedure on facial EMG cannot be ruled out. The TRR results are in accordance with clinical reports of asthmatic symptom aggravation due to positive or negative emotional arousal.

Adult↗
PubMed2000

Efficient light harvesting through carotenoids.

We review the factors that control the efficiency of carotenoid-chlorophyll excitation transfer in photosynthetic light harvesting. For this we summarize first the recently developed theory that describes electronic couplings between carotenoids and chlorophylls and we outline in particular the influence of length of conjugated system and of symmetry breaking on the couplings. We focus hereby on the structurally solved lycopene-BChl system of LH 2 from Rhodospirillum molischianum and the peridinin-Chl a system of PCP from Amphidinium carterae. In addition, we review recent spectroscopic data for neurosporene, spheroidene and lycopene, three carotenoids with different lengths of conjugated systems. On the basis of the measured energies, emission lineshapes, solution and protein environment lifetimes for their 2A ( g ) (-) and 1B ( u ) (+) states as well as of the theoretically determined couplings, we conclude that the transfer efficiencies from the 2A ( g ) (-) state are controlled by the Car(2A ( g ) (-) )-BChl(Q(g)) electronic couplings and the 2A ( g ) (-) --> 1A ( g ) (-) internal conversion rates. We suggest that symmetry breaking and geometry rather than length of conjugated system dominate couplings involving the 2A ( g ) (-) state. Differences in transfer efficiencies from the 1B ( u ) (+) state in LH 2 and PCP are found to be dominated by the differences in spectral overlap. The role of the 1B ( u ) (+) state is likely to be influenced by a lower-lying (in longer polyenes), optically forbidden 1B ( u ) (-) state.

Journal Article↗
PubMed1998

Architecture and mechanism of the light-harvesting apparatus of purple bacteria.

Photosynthetic organisms fuel their metabolism with light energy and have developed for this purpose an efficient apparatus for harvesting sunlight. The atomic structure of the apparatus, as it evolved in purple bacteria, has been constructed through a combination of x-ray crystallography, electron microscopy, and modeling. The detailed structure and overall architecture reveals a hierarchical aggregate of pigments that utilizes, as shown through femtosecond spectroscopy and quantum physics, elegant and efficient mechanisms for primary light absorption and transfer of electronic excitation toward the photosynthetic reaction center.

Crystallography, X-Ray↗
PubMed1998

Stability of total respiratory resistance under multiple baseline conditions, isometric arm exercise and voluntary deep breathing.

Little is known about total respiratory resistance (TRR) as a psychophysiological parameter in normal subjects. Therefore, we investigated TRR in 45 healthy students under multiple baseline conditions, isometric arm muscle tension and voluntary deep breathing (VDB). TRR was measured by the forced oscillation technique. In addition, heart rate (HR) as well as volume and time components of the respiratory cycle, respiratory timing and respiratory drive were monitored. Subjects repeated the protocol 14 days later. Coefficients of stability and dependability were calculated for 20 s measurement epochs within and between both sessions. Increases of HR and shortening of time components of the respiratory cycle were found during muscle tension, prolongation of time components and increases in volume were found for deep breathing. During both experimental tasks TRR increased significantly. Short-term as well as long-term stability of absolute TRR scores proved to be comparable or even better than reliability of other physiological parameters, however, difference scores from baseline revealed only low coefficients.

Adult↗
PubMed1998

Effects of static forehead and forearm muscle tension on total respiratory resistance in healthy and asthmatic participants.

The impact of static muscle tension on total respiratory resistance (TRR) was examined. Participants (24 healthy, 24 asthmatic) performed biofeedback-assisted sequences of tensing (15 s) and relaxing (20 s) forehead and forearm muscles. Muscle tension levels were 40% or 80% of the maximum individual force. Oscillatory TRR, electromyograms, ventilation, heart period, and respiratory sinus arrhythmia were recorded. Baseline TRR did not change over the session as a whole. Decreases in TRR during forehead tension in both groups were accompanied by increases in end-expiratory volume, which could have mediated TRR changes. During forearm tension, decreases in TRR with minimal ventilation changes were only observed in healthy participants, whereas asthmatic patients revealed marked increases in respiratory volume and flow. These results indicate that static muscle activity and TRR are negatively related. Ventilatory changes can exaggerate or diminish evidence for this relationship.

Adult↗
PubMed1997

Psychophysiological reactivity of borderline hypertensives and their recovery after mental stress.

UNLABELLED: The question of psychophysiological reactivity of borderline hypertensives is still controversial. METHODS: Young males with borderline blood pressure levels and normotensive controls were recruited during a routine examination. Samples of study I comprised 19 subjects, samples of study II 18 subjects. Two stressors were presented (distressing movie, mental arithmetic), each followed by a recovery phase. Systolic and diastolic blood pressure, heart rate, and electrodermal parameters were assessed repeatedly. RESULTS: Borderline hypertensives showed greater reactions to stressors in systolic blood pressure only. Changes in percentage of baseline levels were essentially the same. Recovery after stress did not differ between groups. CONCLUSION: Only moderate support is given to the hypothesis that borderline hypertensives show increased and slowly recovering psychophysiological responses.

Adaptation, Physiological↗
PubMed1995

Psychophysiological responses of borderline hypertensives in two experimental situations.

Given the contradictory reports concerning psychophysiological reactivity of hypertensives this issue was reexamined. In contrast to the large majority of studies, the hypertensive sample should not be made up of patients in medical care and the control group should be comparable in all relevant aspects other than blood pressure. Twelve male subjects with blood pressure values in the borderline range and 12 normotensive controls were recruited from a blood donation program. Experiments consisted of two parts with baseline, stress and follow-up. Stressors were a short distressing movie and mental arithmetic. Systolic and diastolic blood pressure (SBP and DBP), heart rate (HR), skin conductance level (SCL) and number of spontaneous electrodermal fluctuations (SF) were assessed in 2-min intervals, plasma adrenaline and noradrenaline once during baselines, stress 2 and follow-up 2. Hypertensives exhibited significantly higher SPB levels, and partially elevated values for DBP, HR and SCL. Response reactions to stressors, however, did not differ between groups. There was no evidence that psychophysiological adaptation during stress and recovery thereafter was impaired in hypertensives. Our results do not support the reactivity hypothesis of hypertension. Possible reasons for our failure to replicate findings from other studies are discussed.

Adult↗
PubMedDate not supplied

Emotions and stress increase respiratory resistance in asthma.

OBJECTIVES: Clinical reports suggest that various emotions and types of stress can precipitate asthmatic symptoms, but there is little experimental evidence to substantiate this claim. We studied the impact of different emotional states and stress on respiratory resistance in asthmatic and nonasthmatic individuals. METHODS: Participants (24 asthmatic and 24 nonasthmatic patients) viewed short film sequences selected to induce anxiety, anger, depression, elation, happiness, contentment, or a neutral affective state and completed two stressful tasks, mental arithmetic to induce active coping efforts and viewing of medical slides to induce passive coping efforts. Oscillatory resistance, heart rate, blood pressure, baroreflex sensitivity, skin conductance level, respiration rate and volume, and self-reported affective state were measured throughout the session. RESULTS: Uniform increases in oscillatory resistance were found in all emotional states compared with the neutral state and during mental arithmetic in both groups. Asthmatic patients showed stronger reactions to the medical slides than healthy control subjects, with significant increases in oscillatory resistance, blood pressure, skin conductance level, and minute volume, as well as higher levels of self-reported depression, arousal, and shortness of breath. Changes in oscillatory resistance were inconsistently correlated with other physiological indices. CONCLUSIONS: Various emotional states and stress increase oscillatory resistance largely independently of concurrent increases in autonomic or ventilatory activity. The particular sensitivity of asthmatics to passive coping demand requires additional research.

Adult↗
PubMedDate not supplied

Emotion and pulmonary function in asthma: reactivity in the field and relationship with laboratory induction of emotion.

OBJECTIVE: We investigated the modulation of pulmonary function by mood states in the daily life of asthmatic patients and nonasthmatic control subjects and its relationship to the airway effects of laboratory induction of emotion using films. METHODS: Twenty asthmatic patients and 20 nonasthmatic control subjects participated in a laboratory session in which various emotions (ie, anxiety, anger, depression, happiness, elation, contentment, and neutrality) were induced by films. Respiratory resistance (Ros) was measured by forced oscillation. After this session, participants kept mood diaries, including regular spirometric self-assessments, for at least 3 weeks. Episodes of strong negative or positive mood were selected from these diaries and compared with conditions of relative affective neutrality. RESULTS: In asthmatic patients, negative mood states, and to a lesser degree positive mood states, were associated with a reduction in forced expiratory volume in the first second (FEV1) compared with neutral states. These effects were not observed in nonasthmatic control subjects. Self-reports of arousal varied in a reciprocal manner with FEV1, whereas physical activity did not vary systematically between mood episodes. A moderate negative relationship between changes in FEV1 during negative mood episodes and changes in Ros during viewing of the depressing film was also observed in asthmatic patients. CONCLUSION: Pulmonary function of asthmatic patients is negatively affected by strong mood states in daily life. Airway effects of negative emotion induction, particularly depression, can predict changes in pulmonary function in response to negative mood in the field.

Adult↗