Biomedical subjects

K Baum

Publications and source records attributed to K Baum.

At least 55 records · Page 3Linked to original sources

PubMed1992

Influence of body position and pre-exercise activity on cardiac output and oxygen uptake following step changes in exercise intensity.

Parallel measurements of breath-by-breath oxygen uptake, cardiac output (Doppler technique), blood pressure (Finapres technique) and heart rate were performed in nine subjects during cycle ergometer exercise in the upright and supine positions. Transients were monitored during power steps starting from and leading to either rest or lower levels of exercise intensity. Oxygen uptake (VO2) and cardiac output kinetics were markedly faster than in all other conditions when exercise was started from rest. In contrast to exercise-exercise on steps, the computed arteriovenous difference in O2 content increased almost immediately in this situation, indicating that not only the additional energy expenditure due to the acceleration of the flywheel but also an increased venous admixture from non-exercising parts of the body contributed to the early kinetics. The off kinetics generally showed a more uniform pattern and did not simply mirror the on transients. The present findings indicate that transitions from rest should be avoided when muscle VO2 kinetics are to be assessed on the basis of VO2 measurements at the mouth.

Adult↗

PubMed1992

Blood pressure and heart rate during rest-exercise and exercise-rest transitions.

The transients of mean arterial blood pressure (BPa) and heart rate (fc) during rest-exercise and exercise-rest transitions have been studied in six healthy sport students. After 5 min of rest in an upright position on a cycle ergometer they exercised for 15 min and remained seated for a further 5 min. The subjects exercised at four different constant intensities (40 W, 80 W, 120 W, 160 W) in random order separated by at least 24 h. The BPa was determined by a noninvasive and continuous method. During the first minute of exercise, three phases of response could be distinguished, with the first two showing no clear relationship to intensity. Phase 1 consisted of simultaneous increases in both fc and BP during the first 6 s. In phase 2, BPa decreased while fc continued to increase. During phase 3, BPa and fc approximated constant values or a linear increase. Both parameters showed no comparable intensity-independent reactions during the off-transients. In conclusion, during the first 15 s of rest-exercise transitions there seems to be a fast and uniform cardiovascular drive which overrode other influences on fc.

Adult↗

PubMed1992

Influence of calf muscle contractions on blood flow parameters measured in the arteria femoralis.

Ten healthy male subjects performed single (< 1 s), sustained and intermittent plantarflexions (up to 40 s) of one foot in sitting exercise position. Two different absolute forces were applied, which, in terms of maximal voluntary contraction, ranged between 5%-10% and 25%-30%. Blood velocity was continuously recorded in the proximal arteria femoralis by means of the Doppler technique. Heart rate (HR) and mean blood pressure (BP) were simultaneously determined using standard ECG and the FINAPRES method. Despite the distance between the proximal arteria femoralis and the exercising muscle the Doppler data showed: effects of single contractions on the individual Doppler data, the influence of consecutive contractions, variation with exercise intensity and differences between sustained and intermittent contractions. In all exercise tests there was an immediate significant increase in blood velocity at the onset of exercise. The major part (range 52%-73%) of the response to the 40 s tests was seen during the first 6 s. It was followed by a second phase of adjustment which depended on the type of exercise and exercise intensity. The single plantarflexion provoked increases in blood velocity for about 20 s. A comparison of HR and BP tracings with the Doppler data demonstrated the importance of local mechanical factors for the perfusion of the exercising muscle. The early adjustment of muscle perfusion were not correlated to the systemic blood pressure and, therefore, appeared to be related to muscle pump effects. The subsequent flow values were influenced by passive vessel compression and changes in local vasomotor tone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Periventricular plaques in multiple sclerosis: irreversible? An MRI follow-up study.

Follow-up MRIs over a period of 2-3 years in 50 patients with multiple sclerosis demonstrate that, in contrast to the circumscribed nonperiventricular lesions of the cerebral white matter, the periventricular plaques only show a remission in exceptional cases as ovoid lesions adjacent to the pars centralis of the lateral ventricles. 90% of the patients exhibited at least one new or enlarged nonperiventricular lesion. 72% had more pronounced periventricular lesions in the second scan. With the help of serial MRIs, inferences can be drawn about the histopathological stage of individual demyelination plaques.

Adolescent↗

PubMed1991

Changes in extracellular muscle volume affect heart rate and blood pressure responses to static exercise.

To investigate the effect of microgravity-induced peripheral extracellular fluid reductions on heart rate and blood pressure during isometric exercise, six healthy male subjects performed three calf ergometer tests with different extracellular volumes of working muscles. In all tests, body positions during exercise were identical (supine with the knee joint flexed to 90 degrees). After a pre-exercise period of 25 min, during which calf volumes were manipulated, subjects had to counteract an external force of 180 N for 5 min. During the pre-exercise period three different protocols were applied. Test A: Subjects rested in the exercise position; test B: Body position was the same as in A but calf volume was increased by venous congestion (cuffs inflated to 80 mm Hg); test C: Calf volumes were decreased by a negative hydrostatic pressure (calves about 40 cm above heart level with the subjects supine). To clamp the changed calf volumes in tests B and C, cuffs were inflated to 300 mm Hg 5 min before the onset on exercise. This occlusion was maintained until termination of exercise. Compared to tests A and B, the reduced volume of test C led to significant increases in heart rate and blood pressure during exercise. Oxygen uptake did not exceed resting levels in B and C until cuffs were deflated, indicating that exclusively calf muscles contributed to the neurogenic peripheral drive. It is concluded that changes in extracellular muscle volume have to be taken into account when comparing heart rate and blood pressure during 1g- and microgravity-exercise.

Adult↗

PubMed1991

Test of exercise experiments proposed for the MIR '92 mission.

During exercise, heart rate and blood pressure drives can be elicited by receptors situated in the interstitial space of the muscle. It was recently shown that these receptors are sensitive to the local state of hydration: Increased reflex responses during dehydration were shown in rat preparates as well as in humans during dynamic and static exercise. Weightlessness could affect these receptor mechanisms through the redistribution of body fluids and through secondary changes in the interstitial structure. To investigate such effects we suggested to determine heart rate and blood pressure responses to light isometric calf exercise at different calf volumes during the MIR '92 mission (experiment ISX). The First North Sea Parabolic Flight campaign provided an opportunity to test the setup and some operational aspects of this experiment. The experience of this campaign led to some modifications of the original setup.

Blood Pressure↗

PubMed1990

Pneumococcal vaccine. Efficacy and associated cost savings.

We evaluated the efficacy and cost savings of the pneumococcal pneumonia vaccine in a retrospective cohort study of 762 vaccinated and 1161 randomly selected unvaccinated age-sex matched persons in Blue Cross/Blue Shield of Minnesota using medical and pharmaceutical claims. The pneumonia incidence and the ratio of incidence in the postvaccination to prevaccination periods (rate ratio) were examined in the vaccine group by sex and risk factors. Vaccination significantly reduced pneumonia incidence, with overall efficacy of 69% and higher efficacy in women (86%) than in men (33%). We assigned persons to risk categories based on disease conditions as recorded in the claims by the ICD-9-CM (International Classification of Diseases, Ninth Revision, Clinical Modification) diagnostic codes. In the risk categories, efficacy varied from 50% to 75% and was confounded by sex. Immunocompromised and immunocompetent women had high efficacy (83% to 88%), while immunocompetent and immunocompromised men had lower efficacy (33%). Persons with a precondition of pneumonia exhibited similar vaccine efficacy to the overall cohort relative to the comparison group. Projected costs of pneumonia cases are 3.6 times the observed costs of vaccination and postvaccination pneumonia costs. We conclude that the pneumococcal pneumonia vaccine is efficacious in persons having had pneumonia, persons "at risk" of developing pneumonia, or persons over 50 years of age, and it corresponds to overall savings of $141 per person.

Aged↗

PubMed1990

Reduction in extracellular muscle volume increases heart rate and blood pressure response to isometric exercise.

To investigate the effect of local dehydration on heart rate and blood pressure during static exercise, six healthy male subjects performed exercise of the calf muscles with different extracellular volumes of the working muscles. Exercise consisted of 5 min of static calf muscle contractions at about 10% of maximal voluntary contraction. The body position during exercise was identical in all tests, i.e. supine with the knee joint 90 degrees flexed. During a 25-min pre-exercise period three different protocols were employed to manipulate the calf volume. In test A the subjects rested in the exercise position; in test B the body position was the same as in A but calf volumes were increased by venous congestion [cuffs inflated to 10.67 kPa (80 mmHg)]; in test C the calf volumes were decreased by lifting the calves about 40 cm above heart level with the subjects supine. To clamp the changed calf volumes in tests B and C, cuffs were inflated to 300 mmHg 5 min before the onset of exercise. This occlusion was maintained for 1 min after the termination of exercise. Compared to tests A and B, the reduced volume of test C led to significant increases in heart rate and blood pressure during exercise. Oxygen uptake did not exceed resting levels in tests B and C until the cuffs were deflated, indicating that only calf muscles contributed to the neurogenic peripheral drive. It is concluded that extracellular muscle volume plays a significant role in adjusting heart rate and blood pressure during static exercise.

Blood Pressure↗

PubMed1990

Multiple sclerosis: relations between MRI and CT findings, cerebrospinal fluid parameters and clinical features.

Cerebral MRI and CT findings were compared with various cerebrospinal fluid (CSF) parameters and clinical features in 75 patients with multiple sclerosis (MS). There were positive correlations between CSF albumin as a parameter of blood-brain barrier function and morphological parameters, namely the number of nonperiventricular foci and periventricular involvement demonstrated by MRI and ventricular enlargement as shown by CT. Apart from positive correlations between the number of nonperiventricular foci and CSF levels of IgA and IgG, including the IgG synthetic rate, no other correlations were found between CSF parameters (leucocyte count and immunoglobulin concentrations) and morphological findings. The unremitting-progressive type of MS was distinguished from the relapsing-remitting form by a lower CSF leucocyte count and a higher degree of disability, but there was no difference between the morphological findings in the two forms. Positive correlations were found between degree of disability and both periventricular involvement in the MRI and CT evidence of ventricular enlargement. In terms of correlations with the duration of disease, cerebral MRI proved to be far superior to CSF evaluations.

Adolescent↗

PubMed1990

Long-term follow-up of MS: disease activity detected clinically and by MRI.

Prospective clinical and magnetic resonance imaging (MRI) studies were performed over a period of 2-3 years on 51 MS patients. Comparing cerebral MRI and neurological evaluation for sensitivity in detecting disease activity, follow-up MRI turned out to be superior to standardized clinical assessment. In particular, an interval during which the clinical findings remain stable may not necessarily indicate that there is no florid inflammatory activity during this time. The morphological progression demonstrated a preference towards periventricular localization around the posterior horns of the lateral ventricles, and non-periventricularly in the frontal white matter. Longitudinal MRI studies of the disease activity can be an aid in obtaining a more definite diagnosis. Patients having had the disease for a longer period showed a more rapid clinical and morphological progression. Clinical progression and an increase in periventricular involvement were observed more often in the primary unremitting-progressive form of MS than in the relapsing-remitting form.

Adolescent↗

PubMed1989

[Quantifying functional deficits in patients with multiple sclerosis using a computer-assisted visuomotor tracking procedure].

23 Patients with multiple sclerosis were subjected to a visuomotor tracking test, consisting of subtests of different task difficulty, while being in a state of acute exacerbation and four weeks later, while exhibiting a more or less pronounced clinical remission (Kurtzke DSS 3.9 (+/- 1.4) vs. 3.3 (+/- 1.5); p less than 0.001). Corresponding to this the tracking test performances improved, the difference being significant only with the easiest test run. The tracking performances correlated with the Kurtzke scores, both for the acute state and for the remitted state, the highest correlation showing up for the easiest test run. Hence, the visuomotor tracking test seems to be suited to measure functional deficits and to evaluate the efficiency of therapeutic procedures.

Adrenocorticotropic Hormone↗

PubMed1988

Cerebral magnetic resonance imaging findings in multiple sclerosis. Relation to disturbance of affect, drive, and cognition.

Forty-six patients with multiple sclerosis were rated with respect to their psychologic symptoms, and magnetic resonance imaging was performed. A significant correlation between the cerebral multiple sclerosis manifestations and the psychologic scores was found. The periventricular and frontal lesions seem to be the most important lesions for the psychologic symptoms of patients with multiple sclerosis.

Affect↗

PubMed1988

The influence of muscle interstitial volume on K+-induced heart rate drive in rats.

During exercise heart rate is influenced by reflexogenic drives which are elicited by receptors situated in the interstitial space. Since the structure of interstitial tissue is complex (e.g. fixed negative charges of glycosaminoglycans), the situation in the immediate surrounding of the receptors might differ from the free fluid phases of blood or lymph in which the concentrations of stimulating substances are usually determined. Physiological variations of the interstitial structure may be due to changes in interstitial volume induced by exercise or the hydrostatic effects on body fluids. The objective of the present study was to investigate the effect of the interstitial volume on the relationship between heart rate and K+ stimuli applied through the muscle blood vessels. The calves of 12 male Wistar rats were artificially perfused and separated from the rest of the body with the sciatic nerve remaining intact. In these preparations the heart rate (HR) responses to low (4 mM) and high (8 mM) potassium concentrations were determined at different interstitial volumes. Expansion of the interstitial volume was obtained by reducing the colloid-osmotic pressure of the perfusate. The combination of intracellular oedema and mechanical limitation of total volume expansion (tapeing) was utilized to decrease the interstitial volume. When switching between the low and high potassium concentrations, significant heart rate responses could be observed only with reduced interstitial volume. It is suggested that the interstitial structure surrounding the muscular receptors modifies the relationship between heart rate response and the K+ stimuli determined in blood or lymph.

Animals↗

PubMed1988

[Early detection of multiple sclerosis: MR findings in the initial manifestations of multiple sclerosis].

The MR results in 21 patients showing the initial manifestations of multiple sclerosis (MS) were compared with those in 45 patients with a long history of MS. As in the old cases, MR proved a very sensitive technique during the early manifestations, with abnormal findings in 20 out of the 21 patients. The relatively characteristic MR findings in long-standing MS (predominant peri-ventricular involvement with a relatively typical pattern) was seen in the early stages is only rare cases. The value of MR during the initial manifestations of MS is in cases where the clinical findings are not conclusive and laboratory diagnosis (evoked potentials, CSF findings) are indefinite. In these patients the findings of multiple lesions in the brain can confirm the suspected diagnosis of MS.

Adult↗

PubMed1988

Detection of brainstem lesions in multiple sclerosis: comparison of brainstem auditory evoked potentials with nuclear magnetic resonance imaging.

Topographical information provided by brainstem auditory evoked potentials (BAEPs) was investigated in 43 patients by comparison with cerebral nuclear magnetic resonance imaging (NMR). Lesions in the region of the brainstem auditory pathways were demonstrated by BAEPs in 44.2%, and in 39.5% by NMR. As regards brainstem levels, in 15/21 (71.4%) with abnormal findings at least one lesion was verified by NMR-matched BAEP results. The study confirms the topographical information provided by the BAEPs on the different levels of the brainstem, but not the assumption that generation of the BAEPs is predominantly ipsilateral. BAEPs retain their importance for the detection of disseminated lesions in the diagnosis of multiple sclerosis (MS) in the era of expensive imaging methods.

Adolescent↗

PubMed1988

Local fluid losses enhance heart rate drives in light to moderate exercise.

UNLABELLED: Dynamic calf muscle exercise of different intensities was performed at 90 degrees knee-joint flexion. To obtain different hydrostatic pressures and calf volumes, all exercise tests were conducted both in prone and supine position after 10 min of rest in the respective positions. Severe prone exercise was associated with increased anaerobic metabolism, reduced exercise tolerance time, and pain sensation. Despite these differences, maximal heart rates were nearly identical in both positions. During light to moderate exercise, heart rate was significantly increased in the prone position. In a steady-state exercise test this difference developed gradually during the first 10 min of exercise. Neither changes in muscle metabolism nor baroreceptor influence or pain sensation could account for this effect. DISCUSSION: 1) At high exercise intensities in the prone position, the decreased hydrostatic pressure reduces maximal exercise duration by virtue of reduced maximal muscle perfusion. 2) In steady-state prone exercise, the local fluid loss appears to increase peripheral heart rate drives.

Adult↗

PubMed1987

Response of chemosensitive nerve fibers of group III and IV to metabolic changes in rat muscles.

Spike recordings were obtained with preparations of group III and IV fibers from the nervus peroneus of the rat. During the recordings the muscle was stimulated by chemical substances simulating metabolic effects of static exercise: increase of [K+], enhancement of osmolality and increase of concentrations of lactic acid and inorganic phosphates. Two experimental setups were used: in series I application was performed by a perfusion of the circulatorily isolated hindleg, and in series II a single muscle of the hindleg (musculus extensor digitorum longus) was superfused by control or test solutions. Only those fiber preparations were further investigated which did not respond to pressure, tension or squeezing of the muscle. Only few fibers that were exposed to all of our stimuli responded to none of them; from the rest, about the half were selective or only preferential for one stimulus. The majority of the fibers adapted their response after 8 min while the applications still endured. A comparison of all fibers (in series II) proved that all the four stimuli elicited significant increases of activity. The greatest significant effects were found for lactic acid and potassium (in series I and II). Since the concentrations used in the test applications were characteristic for medium and heavy exercise these results support the hypothesis that metabolic muscle receptors participate in the peripheral control of circulatory and respiratory drives during static exercise.

Action Potentials↗

PubMed1987

[Cortical somatosensory evoked potentials following median and tibial nerve stimulation in multiple sclerosis; relation to sensory disorders and duration of the disease].

In 40 patients with multiple sclerosis, 11 of whom presented with their first disease manifestation, cortical somatosensory evoked potentials following median and tibial nerve stimulation were examined. 45 percent of the patients with first manifestation had at least one pathological SEP, while 79 percent of the patients with longer course of the illness showed pathological SEPs. The group of patients with first manifestation differs significantly in this aspect from the group of those patients with longer duration of the illness. The occurrence of pathological SEPs was associated significantly more often with impairment of joint position and vibration sense, than with nonspecific sensory disturbances. Not only in some patients with first manifestation, but also in some patients with long, but mild courses, there were nonspecific sensory disturbances in association with normal SEPs. One should not underestimate the complaints in such cases.

Adult↗