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Biomedical subjects

A Lindqvist

Publications and source records attributed to A Lindqvist.

At least 55 records · Page 3Linked to original sources
PubMed1995

Skin blood flow oscillations respond more effectively to rhythmic thermal stimulation than to continuous or periodic breathing in newborn infants.

Effect of continuous (n = 30) and periodic (n = 5) breathing on forehead skin blood flow (SBF) oscillations was studied in healthy 3-day-old preterm and term infants. Femoral SBF was measured in 10 of the term infants during continuous breathing. Respiratory and SBF signals were analysed by power spectrum during the control period. The signal analysis was repeated during rhythmic thermal stimulation which was applied to the skin of each infant in order to synchronise spontaneous SBF oscillations. During the control period, the forehead and femoral SBF of all the studied infants oscillated at frequencies corresponding to the frequency of regular continuous breathing. External thermal stimulation decreased these high-frequency oscillations of forehead SBF in both preterm and term infants. Oscillations in femoral SBF of term infants remained unchanged. During periodic breathing, the spontaneous forehead SBF oscillation was synchronised to the frequency of respiratory amplitude variation. Despite periodic breathing, thermal stimulation was able to resynchronise the SBF oscillation to the stimulation frequency in 4/5 infants. Forehead SBF oscillates at the frequency of both continuous and periodic breathing in preterm as well as in term infants on postnatal day 3. Rhythmic thermal stimulation synchronises SBF and affects SBF more effectively than continuous or periodic breathing. These results suggest functional neural control of cutaneous vasculature at birth.

Blood Flow Velocity↗
PubMed1995

Cardiovascular functional disorder and distress among patients with thoracic outlet syndrome.

Cardiovascular functional stability of 11 women with thoracic outlet syndrome (TOS; mean age 34.5) and nine female controls (mean age 35.1) was studied using an orthostatic test, a deep breathing test, Valsalva manoeuvre and hand-grip test. The heart rate at rest was significantly higher in TOS patients. The TOS group showed significant accentuation in T wave vacillation in the orthostatic test. The rise in diastolic blood pressure of the TOS group during a hand-grip test was significantly less than that of the control group. TOS patients experienced significantly more distress according to the modified somatic perception questionnaire (MSPQ) than the control group. Pain was correlated with the score of MSPQ, the resting heart rate and increase in diastolic blood pressure in a hand-grip test. The results suggest that TOS patients' symptoms often reflect a wider disturbance than merely anatomical compression in the thoracic outlet. It seems possible that sympathetic tone is higher in TOS patients than in controls. In addition to possible operative treatment, it may be necessary to provide psychological help, relaxation and endurance training.

Adult↗
PubMed1995

Beat-to-beat agreement of non-invasive finger artery and invasive radial artery blood pressure in hypertensive patients taking cardiovascular medication.

The aim of this study was to investigate and quantify the agreement between simultaneous and ipsilateral non-invasive finger artery blood pressure (Finapres) and intra-arterial radial blood pressure among 13 volunteer hypertensive patients, aged 36-71 years and taking cardiovascular medication, during steady-state fluctuation of arterial blood pressure and during an increase in blood pressure induced by static exercise. Eight patients were being treated with beta-blocking agents, eight with calcium antagonists, four with angiotensin-converting enzyme inhibitors, four with diuretics and one with prazosin in combination therapy. Their auscultatory brachial artery blood pressures ranged in systole from 142 to 206 mmHg and in diastole from 88 to 120 mmHg during the treatment. The mean systolic finger artery blood pressure deviated by -14 +/- 5 mmHg (P = 0.02, mean value +/- SEM) and the diastolic finger artery blood pressure deviated by 0.6 +/- 3 mmHg (P = 0.70) from the corresponding radial artery pressure. The maximal beat-to-beat difference between systolic and diastolic finger and radial artery pressure, respectively, showed that a range of less than 10 mmHg in the steady state after individual adjustment for bias. In general, neither systolic nor diastolic differences between the methods exceeded the limits of +/- 10 mmHg, and the bias did not significantly increase (P > or = 0.12) during a 10-mmHg increase in arterial blood pressure caused by static exercise. Among three subjects, an increase in bias and poorer agreement was associated with atrial fibrillation and steplike changes in the Finapres output after autocalibration. The results support usage of the Finapres technique to measure beat-to-beat changes of peripheral arterial blood pressure in hypertensive patients taking cardiovascular medication, with a feasible agreement with beat-to-beat radial artery blood pressure.

Adult↗
PubMed1994

Post-prandial effects in reactivity of forehead and mid-femoral skin blood flow and heart rate in neonates.

The effect of post-prandial period on the cutaneous vascular reactivity was studied in twelve full-term infants on their 3rd postnatal day. The differences in vasomotor reactions between the forehead and femoral skin were also investigated. Two 10-min control registrations about 30 and 90 min after feeding were followed by a registration of equal duration during thermal stimulation of the skin. The lower extremity of each infant was stimulated by warm and cool air currents (5 cycles/min) to induce periodic vasomotor changes. The fast Fourier transform was used to compute variability spectra for the recorded skin blood flow, heart rate and respiratory wave form signals. The skin blood flow became synchronised to the thermal stimulation in both skin regions. Neither the spontaneous nor synchronised oscillations of the skin blood flow differed significantly between femoral skin and forehead. The post-prandial time did not have any influence on this synchronisation. Heart rate variability was synchronised to the periodicity of thermal stimulation more 1.5 h after feeding than 0.5 h after feeding. Respiration was not affected. The results show that increasing post-prandial time has no influence on the synchronised oscillations of skin blood flow. However, it potentiates reactivity of heart rate to perturbations in the peripheral vasculature.

Body Temperature↗
PubMed1994

Interaction between streptococcal protein Arp and different molecular forms of human immunoglobulin A.

Protein Arp, the IgA-binding protein of the group A Streptococcus, has affinity for the Fc-part of IgA. The binding between protein Arp and several different molecular forms of human IgA was characterized. It was found that protein Arp bound with higher affinity to uncomplexed forms of IgA than to complexed forms (secretory IgA, alpha 1-antitrypsin-IgA and alpha 1-microglobulin-IgA). Thus, the affinity constant was 2.0-5.9 x 10(8) M-1 for the binding to monomeric, dimeric, trimeric, and quadrimeric IgA, and 4.5-5.0 x 10(7) M-1 for binding to the complexed forms. Among the uncomplexed IgA-molecules, the affinity constant was in the same range for J chain-containing forms (dimeric, trimeric and quadrimeric IgA) as for forms without J chain (monomeric and a particular quadrimeric IgA devoid of J chain). Western blotting demonstrated that protein Arp bound exclusively to the alpha-chain of all IgA-forms. Several lines of evidence pointed to a localization of the binding site to the C alpha 3-domain. First, protein Arp did not bind to three N-terminal alpha-chain fragments which lacked a region corresponding to the C alpha 3-domain, including that form a four-chain myeloma IgA, naturally occurring in plasma. Second, the binding to dimeric and tri/quadrimeric IgA was partially blocked by an added secretory component, which has been suggested to bind to the C alpha 2- and C alpha 3-domains of the alpha-chain. Finally, alpha 1-antitrypsin and alpha 1-microglobulin, in the weakly binding IgA-complexes, have been shown to be linked to the C alpha 3-domain via the penultimate amino acid residue of the alpha-chain peptide, supporting the hypothesis of a localization of the binding site of protein Arp to the C alpha 3-domain.

Bacterial Proteins↗
PubMed1994

Heart rate and cardiac arrhythmia during high-Gz flight.

Twenty-four pilots (age 20-32 years) were monitored with a Holter monitor during 26 hours including a high-Gz flight in order to evaluate heart rate (HR) and cardiac rhythm. Flight experience did not predict the mean in-flight HR (range 69-121 beats/minute), which decreased with increasing age and correlated to the maximum HR during sleep. We recorded maximally 27 ventricular and 97 supraventricular ectopic beats, 10 junctional rhythms, 5 gray-out, 1 vestibular symptom, and 1 instance of numbness of the feet during the flight. No causal relationship between HR, cardiac arrhythmia, or symptoms was found. Adaptation to in-flight +Gz stress takes place without significant arrhythmia and at a submaximal age-related HR.

Adaptation, Physiological↗
PubMed1993

Circadian variation in peripheral blood flow in relation to core temperature at rest.

The aim of the present study was to examine the circadian variation in skin blood flow and its relationship to the rhythm of rectal temperature. Eight young men were confined to continuous bed rest for 24 h in a thermoneutral environment. Rectal temperature, oxygen consumption, and peripheral blood flow (laser-Doppler flowmetry and plethysmography) were measured at intervals of 2 h, except at 2400 hours and 0600 hours. According to the cosinor-method, the mean rectal temperature displayed a statistically significant circadian variation with a minimum at 0400 hours. A significant circadian rhythm was also observed in total finger blood flow, finger laser-Doppler flow, and forearm laser-Doppler flow, but not in total forearm blood flow and forehead laser-Doppler flow. The rhythms of rectal temperature and extremity skin blood flow were phased differently, i.e. the decrease in rectal temperature was preceded by an increase in extremity skin blood flow with an average of 4-h time difference. The results would support the idea that circadian rhythm of core temperature is, at least in part, regulated by variation in extremity skin blood flow.

Adult↗
PubMed1992

Protein Arp and protein H from group A streptococci. Ig binding and dimerization are regulated by temperature.

Cell surface proteins that bind to the Fc part of Ig are expressed by many strains of group A streptococci, an important human pathogen. Two such bacterial strains, AP4 and AP1, were shown to bind IgA and IgG, respectively, in a temperature-dependent manner. The binding of radiolabeled Ig to the bacterial cells was lower at 37 degrees C than at 22 and 4 degrees C. Similarly, protein Arp, the IgA-binding protein isolated from strain AP4, and protein H, the IgG-binding protein isolated from strain AP1, displayed a strong Ig-binding at 22 degrees C and lower temperatures, and virtually no binding at all at 37 degrees C. The effect was reversible: lowering of the temperature restored the binding and vice versa. A gradual shift between binding and nonbinding took place between 27 and 37 degrees C. Gel chromatography and velocity sedimentation centrifugation showed that protein Arp and protein H appeared as noncovalently associated dimers at 10 and 22 degrees C, and as monomers at 37 degrees C. These results strongly suggest that the dimerization of protein Arp and protein H, rather than the low temperature itself, yielded the strong Ig-binding of the proteins at 10 and 22 degrees C. Indeed, after covalent cross-linking of the dimers at 10 degrees C by incubation with low concentrations of glutaraldehyde, full Ig-binding was achieved even at 37 degrees C. A carboxyl-terminal proteolytic fragment of protein Arp, which completely lacked the IgA-binding capacity at any temperature, showed the same temperature-dependent dimerization as intact protein Arp, suggesting that the Ig-binding part of the protein is not required for dimerization. The implications of these results for the function of Ig-binding group A streptococcal proteins, and their role in the host-parasite relationship are discussed.

Bacterial Proteins↗
PubMed1992

Rat alpha 1-microglobulin: co-expression in liver with the light chain of inter-alpha-trypsin inhibitor.

A 1162 bp rat liver cDNA clone encoding the immunoregulatory plasma protein alpha 1-microglobulin was isolated and sequenced. The open reading frame encoded a 349 amino acid polyprotein, including alpha 1-microglobulin, 182 amino acids, and bikunin, the light chain of the plasma protein inter-alpha-trypsin inhibitor, 145 amino acids. The alpha 1-microglobulin/bikunin mRNA was found only in the liver when different tissues were examined. Free alpha 1-microglobulin and a polyprotein, containing both alpha 1-microglobulin and inter-alpha-trypsin inhibitor epitopes, were found in the microsomal fraction from rat liver homogenates.

Alpha-Globulins↗
PubMed1992

Cardiovascular functional disorder in primary fibromyalgia: a noninvasive study in 17 young men.

Cardiovascular functional stability was studied in 17 young men (20-year-old conscripts) with the symptoms of primary fibromyalgia (PF). They were compared to 20 medical students of the same age. The subjects underwent an orthostatic test, deep breathing test, Valsalva maneuver, and a handgrip test. They were evaluated by an autoanamnestic questionnaire on vegetative symptoms and laboratory tests on blood chemistry. The heart rate of the PF group after 8 min of active standing was 32 +/- 15 beats/min greater than at supine rest. The corresponding figure for the controls was 23 +/- 7 beats/min (p = 0.001). Twelve conscripts with PF (71%) presented sympathicotonic cardiovascular reaction on the orthostatic test (p < 0.001). Four of these sympathicotonic conscripts and two other conscripts (total 35%) had an abnormal high index of dystonic symptoms (p = 0.01). The results suggest that young men with symptoms of PF have not only cardiovascular dystonic symptoms but also increased sympathetic nervous reactivity of the cardiovascular system.

Adolescent↗
PubMed1992

Exercise alters the pharmacokinetics of midazolam.

Six healthy volunteers received 15 mg midazolam, 50 mg ephedrine, or placebo orally before a 50-minute aerobic treadmill exercise and in a control session. Plasma drug concentrations for pharmacokinetic calculations were estimated from samples drawn up to 24 hours after drug intake. Heart rate, blood pressure, critical flicker fusion test, Maddox wing test, and visual analog scales relating to mood and feelings of tiredness were included in the sessions as pharmacodynamic measures. These tests were made at 35, 55, and 75 minutes and at 2, 2 1/2, 3 1/2, and 5 hours after drug intake. Exercise impaired the absorption of midazolam and counteracted the midazolam-induced decrement in flicker fusion threshold. Whether the effect on flicker fusion was caused mainly by the pharmacokinetic changes or by a general alerting effect of exercise cannot be verified by this experiment. The kinetics of ephedrine was not affected by exercise, but exercise enhanced the tachycardic response to ephedrine and abolished its pressor effect.

Adult↗
PubMed1991

Clinical testing of thermally stimulated cardiovascular oscillations in man.

STUDY OBJECTIVE: The study assessed the physiological validity of an automatic thermal stimulation method to induce synchronised oscillations in the neural cardiovascular control system. DESIGN: Automatic alternating rhythmic warm and cool immersion of different skin areas of 18 males was done at different frequencies and water temperatures. The neurally mediated responses to the periodic thermal stimulation were measured from skin blood flow and heart rate and compared to those of a sham stimulation. Respiration was monitored for control purposes. The reproducibility of the stimulation and responses was examined. SUBJECTS: 18 young males volunteered for the study. MEASUREMENTS AND MAIN RESULTS: The water bath method produced reproducible thermal stimulation and responses of skin blood flow and heart rate. Rhythmic thermal stimulation at 0.013-0.096 Hz synchronised the oscillations of the forearm skin blood flow when the thermal stimulus amplitude exceeded 10 degrees C. The increase in the stimulus amplitude or enlargement of the stimulus area did not further increase the oscillatory response of skin blood flow. Sham stimulation or mean temperature of the periodic thermal stimulation in the range 23-33 degrees C did not influence the oscillations of skin blood flow. Local cooling of the stimulated lower legs attenuated the response of skin blood flow. Both thermal stimulation and sham stimulation affected heart rate, but no stable synchronisation of the periodic heart rate variability was found at supine rest. Thermal stimulation of the sitting subjects' forearm instead of legs increased the synchronisation of the periodic heart rate variability. CONCLUSIONS: The response of skin blood flow agreed with the theory of the thermal entrainment. In a supine man, both thermal stimulation and non-specific central nervous influences induced significant and reproducible interactions with periodic heart rate variability and respiration.

Adult↗
PubMed1990

Effect of posture on spontaneous and thermally stimulated cardiovascular oscillations.

STUDY OBJECTIVE: The aim of the study was to investigate the effect of posture on thermally stimulated cardiovascular oscillations. DESIGN: The effect of increased gravitational stress (rising from sitting to standing position) on the thermally stimulated cardiovascular oscillations was measured in young male volunteers. Extensive cardiovascular function data were obtained using a cardiovascular investigation protocol. SUBJECTS: The volunteers were five fit young men, aged 20-21 years. EXPERIMENTS AND MAIN RESULTS: Cardiovascular changes from sitting to standing indicated increased sympathetic and decreased parasympathetic influence on heart and skin blood vessels; mean heart rate increased, beat to beat heart rate variability diminished, high frequency periodic heart rate variability decreased, low frequency heart rate oscillations and ratio of low frequency to high frequency heart rate variability increased, mean skin blood flow and oscillations of skin blood flow decreased (all p less than 0.05). Thermal skin stimulation at 0.01-0.10 Hz frequency increased both sitting and standing 0.10 Hz periodic heart rate variability (p less than 0.05), and 0.10 Hz thermal stimulation entrained the heart rate oscillations in sitting and standing subjects (p less than 0.05). In contrast, skin blood flow oscillations in sitting subjects decreased, while in standing subjects it increased during 0.10 Hz thermal stimulation compared to the corresponding prestimulus values (p less than 0.04). CONCLUSIONS: On the basis of previous physiological experiments, these results suggest coupling between thermoregulatory and 0.10 Hz reflex activities.

Adult↗
PubMed1990

Noninvasive methods to study autonomic nervous control of circulation.

The major findings and conclusions of this study are the following: 1. Indirect evidence suggested that nervous afferentation from the cutaneous thermoreceptors and nervous efferentation to the skin blood vessels mediated the 0.01-0.10 Hz thermally entrained response of the oscillations of the forearm skin blood flow in supine and upright subjects. 2. Postural stimulation decreased skin blood flow and oscillations of skin blood flow. The 0.10 Hz thermal stimulation interacted with the postural stimulation by increasing the oscillations of skin blood flow from sitting to standing position on the contrary to the expected postural effect. 3. The thermal entrainment of periodic heart rate variability was not constant. Both 0.01-0.10 Hz thermal and postural and sensory stimulations affected the periodic heart rate variability selectively at the frequency of the periodic stimulus or the less than 0.12 Hz frequencies. 4. The periodic thermal stimulation had a frequency-selective effect on the oscillations of the neonatal heart rate. The thermally stimulated reactivity increased with an increased maturity of a neonate. 5. Intermittent tilting had a frequency-selective influence on the oscillations of heart rate. Continuous deep breathing entrained the periodic heart rate variability. The estimation of the power spectral density function of heart rate quantified the chronotropic respiratory effects more accurately than the statistical indices of heart rate variability. 6. Response of periodic heart rate variability to intermittent tilting and deep breathing stimulation suggested normal vagal control of heart rate in children with juvenile diabetes and juvenile rheumatoid arthritis. 7. Normal vagal bradycardic response was found during the phase IV of the Valsalva manoeuvre in functionally abnormal nervous control of circulation. The simulated diving test was not found clinically useful. 8. The ratio of electrical to electromechanical systole of the heart was greater than 1.00 both at rest and during the orthostatic, Valsalva and diving reflex tests. This finding suggested constantly exaggerated sympathetic cardiac inotropic control during vagal and sympathetic stimulation of heart rate. 9. The decreased thermally stimulated heart rate variability was interpreted as an indication of inhibited vagal modulation of the sinoatrial node of the heart in subjects with dystonic symptoms and orthostatic intolerance. The exaggerated sympathetic reactivity of these subjects explained the abnormally high gain of periodic heart rate variability to 0.01-0.03 Hz periodic thermal stimulation.

Autonomic Nervous System↗
PubMed1989

A non-invasive method for testing neural circulatory control in man.

Exaggerated cardiovascular responsiveness is common in young men and may cause non-specific symptoms and poor performance. Conventional autonomic function tests are not clinically useful. We have therefore designed a thermal entrainment method to evaluate sympathetic and parasympathetic cardiovascular function in subjects with dystonic symptoms and orthostatic intolerance. Oscillations of thermal gradient in the skin were produced by standardised periodic stimulation of the lower part of the arm with warm and cool water. Vasomotor activity of the skin induced oscillations of arterial blood pressure which were thought to be regulated by sympathetic and parasympathetic heart rate control and by oscillation of the sympathetically controlled peripheral vascular resistance. We tested the method in subjects with cardiovascular symptoms (n = 7) and controls (n = 7). At supine rest, the frequency response of the heart rate variability to the thermal stimulation at frequencies of 0.01, 0.02, 0.03 and 0.1 Hz was significantly different (p = 0.008) between symptomatic subjects and controls. The gain of the heart rate control was increased to 0.03 Hz [-1.3(SEM 0.5) dB v -3.8(0.8) dB, p = 0.068] and decreased at 0.1 Hz [-3.9(1.1) dB v -1.5(0.6) dB, p = 0.076] in the test group compared to the control group. At stimulus frequencies of less than 0.03 Hz the individual overall heart rate variability of the subjects with symptoms stayed below the mean control value, at 60(6) ms v 79(15) ms, p = 0.16. The cutaneous temperature oscillations at the site of stimulation, frequency response of the oscillations of the skin blood flow and respiration to the thermal stimulation, and mean heart rate were similar in the both groups. The results show that this thermal entrainment method quantifies the increased sympathetic and decreased parasympathetic cardiac control of subjects with dystonic symptoms.

Adult↗
PubMed1989

Seasonal variability of exercise-induced asthma especially outdoors. Effect of birch pollen allergy.

A study was made to determine whether natural allergenic exposure modulates exercise-induced asthma. Eighteen asthmatic men, ten non-allergic and eight allergic to birch pollen, underwent heart rate-monitored outdoor exercise tests during both the cold winter season and in the spring, the birch pollen season. The mean fall in FEV1 after the outdoor exercise test increased in the allergic group from 17 +/- 3% in the winter to 27 +/- 6% in the spring, while it decreased in the non-allergic group from 31 +/- 6% to 22 +/- 4%, respectively (P less than 0.01). Initial FEV1 and FCV values remained unchanged in both groups. The non-specific airway responsiveness to histamine did not change significantly in birch pollen allergic or non-allergic subjects during the spring, when compared with the winter values. We conclude that the exercise-induced asthma is aggravated in the birch pollen allergic asthmatics during the pollen season, when compared to the non-birch pollen allergic asthmatics, in whom the exercise-induced bronchoconstriction is attenuated as expected, because of the warmer and more humid weather in the spring.

Adult↗