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Biomedical subjects

P Buser

Publications and source records attributed to P Buser.

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

Effect of residential cardiac rehabilitation following bypass surgery. Observations in Switzerland.

BACKGROUND: Cardiac rehabilitation in central Europe traditionally involves isolating patients in a residential idyllic setting where exercise is performed frequently but in a relatively unstructured fashion. Few studies have been performed on the effects of these programs among patients who have undergone bypass surgery. Recent data suggest that postbypass patients may enter these programs too soon after surgery or that exercise is not structured enough to distinguish the benefits of rehabilitation from those experienced by a control group. METHODS: Forty-two male patients (mean age, 58 +/- 7 years) were divided into exercise and control groups approximately 1 month after undergoing bypass surgery. Exercise training consisted of 1 h of group walking twice daily, with the intensity stratified into four levels based on initial exercise capacity. Using a crossover design, patients in the exercise group participated in rehabilitation for 1 month, followed by 1 month of usual care, while control patients underwent the opposite sequence. At 1, 2, and 3 months, patients in both groups underwent pulmonary function testing and maximal ramp exercise testing using lactate and gas exchange analysis. RESULTS: A main effect for maximal oxygen uptake was observed; significant improvements within each group occurred across each testing period (range, 5 to 13%; p < 0.05). However, there was no significant interaction between groups. Mean lactate levels throughout exercise were reduced within both groups (p < 0.01). A reduction in oxygen uptake for test 2 at the lactate threshold in the exercise group resulted in differences between groups in lactate, heart rate, and other gas exchange variables at this point. CONCLUSION: Similar changes occur in the functional status of postbypass surgery patients regardless of their participation in the short but concentrated programs common in central Europe. This suggests that a significant spontaneous effect of healing occurs in the recovery phase after surgery. These programs may have greater efficacy if they began later after surgery, lasted longer, or were more structured, and studies are needed to determine their effect on psychosocial factors and return to work.

Aged↗
PubMed1994

Pattern of development of the callosal transfer of visual information to cortical areas 17 and 18 in the cat.

The aim of this study was to investigate the development of visual callosal transfer in the normally reared cat. Two- to nine-week-old kittens and adults (used as controls) underwent section of the optic chiasm. Three days later, the animals were placed under anesthesia and paralysed; unit activities were recorded from visual cortical areas 17 and 18 and from the white matter in one hemisphere. The units were tested for their responses to visual stimulation of each eye successively. Out of 1036 recorded neurons, 185 could be activated through the eye contralateral to the explored cortex via callosal transfer. Most of them could also be driven through the ipsilateral eye via the 'direct' geniculo-cortical pathway. For animals aged > or = 2 weeks, virtually all of these units were located at the 17/18 border zone, with a majority in the supragranular layers. When activated through the corpus callosum, they displayed receptive fields located either on the central vertical meridian of the visual field or in the hemifield ipsilateral to the explored cortex. Such extension into the ipsilateral hemifield as well as receptive field disparities of binocular units decreased with age, while spontaneous activity, strength of response, orientation selectivity and ability to respond to slits moving at middle-range velocity increased. The main conclusion is that the transient callosal projections described by anatomists, which are present until 3 months of age, do not achieve supraliminar synaptic contacts with parts of areas 17 and 18 other than the 17/18 border zone, at least from 12 days after birth. However the visual callosal transfer in young animals displays some characteristics which disappear with age.

Aging↗
PubMed1994

Intracerebral recording of movement related readiness potentials: an exploration in epileptic patients.

Readiness potentials (RPs) preceding voluntary self-paced limb movements were recorded intracerebrally in 13 patients suffering drug resistant, intractable epilepsy. Multilead depth electrodes were positioned using the Talairach's coordinate system; they allowed simultaneous recording from the external and mesial cortices and from the interposed white matter during self-paced unilateral hand or plantar flexions. Our intracerebral explorations have shown RPs in the primary motor cortex (MC) contralateral to the movement and in both supplementary motor areas (SMAs), indicating that at least 3 cortical sites become active before the movement. At variance with the scalp RPs recorded in the same patients, the intracerebral potentials were either negative, or positive, depending on the recording site. No consistent differences in duration and time of onset could be established between the MC and the SMA RPs, at least with the used time resolution. RPs were only occasionally observed in the parietal cortex and hippocampus and none were recorded from the amygdala, the temporal, temporo-occipital, prefrontal, frontal and cingular cortices. The wide topographical distribution of the scalp RPs may not be fully explained by the above intracortical findings, leaving the possibility that other generators exist, whose locations remain to be determined.

Adolescent↗
PubMed1994

Relationship between posterior thalamic nucleus unit activity and parietal cortical rhythms (beta) in the waking cat.

Cat behavioural states of attentive fixation on a target are associated with episodes of electrocortical rhythms at 40 Hz ("beta rhythms") in the parietal cortex. Previous field potential studies indicate that the nucleus posterior pars medialis of the thalamus displays this particular rhythmic activity. We investigated single units of the nucleus posterior pars medialis and its surrounding nuclei to assess their participation in the cortical beta rhythms. Only a small proportion of thalamic cells underwent changes in their firing pattern during beta episodes. "Beta-related cells" were localized in the nucleus posterior pars medialis or its immediate vicinity; no such beta-related cells were found in other regions of the lateral thalamus. Some beta-related cells showed a one-spike to one-wave relationship ("homorhythmicity"), while others displayed a prolonged decrease or a suppression of their firing throughout each beta episode ("pause cells"). For comparison, neurons in the same thalamic area were also recorded during sleep episodes with slow waves and spindles: there was no correlation between spindles and cell firing. Thus, the nucleus posterior pars medialis thalamic nucleus contains cells whose firing is correlated with the beta rhythms. No such correlation was found with sleep spindles.

Animals↗
PubMed1994

Preservation of pointing accuracy toward moving targets after extensive visual cortical ablations in cats.

Impairments in reaching toward stationary and moving targets were studied in cats after restricted or extensive removal of visual cortical areas (areas 17, 18 and 19 and lateral suprasylvian visual areas). Regardless of the extent of the cortical lesion, cats were at first unable to localise and reach for a stationary target whereas they were soon able to detect and accurately point toward a mobile one. Moreover, the onset latency of such movements was dramatically increased. During post-operative re-training, the cats were unable to improve their accuracy scores when reaching towards stationary targets. In contrast, full compensation was observed for the accuracy of reaching movements directed toward moving targets. A partial recovery was observed for movement latency values that progressively decreased but left a permanent 30-40 ms impairment following extensive lesions. The role of extrageniculate messages and alternative routes involving other cortical areas in taking in charge the visuomotor activity is discussed.

Animals↗
PubMed1993

Effects of locus coeruleus lesions on vigilance and attentive behaviour in cat.

Previous data have suggested that in the cat, expectancy behaviour (waiting for a target to appear) and associated electrocortical, focal, synchronized activity ('mu' rhythms) are modulated by a noradrenergic system possibly originating from the locus coeruleus (LC). To test the latter hypothesis, we have examined the behavioural and ECoG changes induced after bilateral LC lesions. Our results demonstrated that destruction of the anterior 3/4th of the LC (A6 noradrenergic cell group) resulted in a considerable increase of mu rhythms and expectancy behaviour, without episodes of drowsiness that normally occur. Destruction of the posterior fourth of LC (A4 noradrenergic group) only increased the duration of slow sleep. Extending the A6 lesion to include the dorsal ascending noradrenergic bundle also increased the expectancy behaviour and mu rhythms. Finally, when the nucleus subcoeruleus was also involved, the duration of slow sleep and the frequency of paradoxical sleep episodes increased. These findings indicate that the LC exerts an inhibitory effect on structures involved in the induction and persistence of expectancy behaviour with accompanying mu rhythms.

Animals↗
PubMed1993

A new yeast translation initiation factor suppresses a mutation in the eIF-4A RNA helicase.

We have isolated a gene, STM1, which encodes a new translation initiation factor from Saccharomyces cerevisiae. The gene acts, if present on a multicopy plasmid, as a suppressor of a temperature-sensitive mutation in eIF-4A. The single copy STM1 gene is not essential, but disruption causes a slow growth phenotype. Analysis of polysomes from a strain carrying a disrupted stm1 allele shows a clear defect in translation initiation as shown by a strong reduction in polysomes and an increase in the monosomes. Sequence analysis revealed interesting features of the putative Stm1 protein. Comparison of the entire protein sequence with databanks showed some similarity with the human eIF-4B protein. The Stm1 protein has potential RNP1 and RNP2 motifs characteristic for RNA-binding proteins. The protein also contains six highly conserved direct repeats of 21-26 amino acids and one partial repeat.

Amino Acid Sequence↗
PubMed1993

Cardiac rehabilitation in Switzerland. Efficacy of the residential approach following bypass surgery.

BACKGROUND: The traditional central European approach to cardiac rehabilitation involves sending patients to an idyllic setting, where they reside for a specified period following a cardiac event. Favorable results have been demonstrated using this approach in Germany, but to our knowledge no data have been reported from Switzerland, where these programs tend to be short (4 weeks) and exercise training is concentrated (2 h daily, 6 days per week). METHODS AND RESULTS: Seventeen patients (aged 58 +/- 6 years) who resided in a rehabilitation center for 4 weeks were compared with 11 patients (aged 54 +/- 7 years) given usual community care beginning approximately 6 weeks after coronary artery bypass surgery (CABS). Exercise training consisted of 1 h of group walking twice daily, with the intensity stratified into 4 levels based on clinical status and initial exercise capacity. All patients underwent pulmonary function testing and maximal ramp exercise testing on a cycle ergometer with continuous ventilatory gas exchange and lactate analysis before and after the study period. Patients receiving beta-blockers and those with cardiomyopathy or valvular heart disease were excluded. Medication status was not changed during the study period. Although maximal oxygen uptake increased by approximately 12 percent within both groups, the change was not significant between groups. Analysis of variance demonstrated that mean lactate levels were reduced throughout exercise within both groups (p < 0.001); however, there were no differences between groups. Oxygen uptake at the lactate threshold was not different in either group after the study period. CONCLUSIONS: Similar changes occur in the functional status of post-CABS patients regardless of their participation in the short but concentrated rehabilitation programs common in Switzerland, suggesting that these programs either begin too soon after CABS or are too short to achieve training benefits.

Coronary Artery Bypass↗
PubMed1993

Alpha rhythm in the cat thalamus.

In cats, electrocortical rhythms at about 10 Hz displaying common characteristics with the human alpha rhythm [1] were recorded from the part of the visual cortex that includes the anterior half of areas 17 (on the cortical convexity), of area 18 and of their common limit, representing the projection of the lower contralateral visual quadrant and that of the lower vertical meridian. It is shown here that activities highly correlated with these rhythms and at the same frequency, were recorded from the anterior half of the laminar dorsal lateral geniculate body (mediodorsal part of layer A), and also from a limited area medial to this nucleus. The cat thalamocortical alpha system thus appears to concern only the projection of the lower quadrants, probably excluding the area centralis itself.

Alpha Rhythm↗
PubMed1992

Effects of mediodorsalis thalamic nucleus lesions on vigilance and attentive behaviour in cats.

In this study performed on 10 cats we analysed the effects of limited lesions of nucleus medialis dorsalis of the thalamus (MD) on behaviour and on some specific electrocorticographic (ECoG) patterns, known from previous works to accompany various states of waking attentiveness. The animals were tested during 90 min in three distinct behavioural situations; a neutral one (NS) where they simply explored their environment and then usually went to sleep; a second one (FA) where they could watch a mouse (but not catch it), which favoured 'focussed' attentiveness accompanied by the development of rhythmic ECoG activities in the anterior frontoparietal cortex ('beta rhythms' at 40 Hz); a third one (EX) with a hidden mouse whose appearance the cat was waiting for ('expectancy') which rather than favouring the development of beta rhythms elicited the appearance of another rhythmic activity dominating in somatic area SI, 'mu rhythms' at 14 Hz. The duration of each waking behaviour and its ECoG concomitant as well as that of slow wave and of paradoxical sleep were compared in each cat before and after lesion. Our results showed that MD lesions situated in the posterior part of the nucleus tended to increase the time occupied by focussed attentive behaviour and the accompanying beta rhythms. On the other hand, anteriorly located MD lesions elicited a concomitant reduction of both manifestations, behavioural and electrocortical. No such contrasting effects could be systematically noticed for the durations of expectancy, of slow sleep and of paradoxical sleep. These findings were discussed considering previous data showing that at least two systems project upon MD, that play distinct--in a way even antagonistic--roles in focussed attention upon a target. Both originate from the ventral tegmental mesencephalic area; one reaches MD through the ventral striatum (nucleus accumbens), the other one through the amygdala. The MD nucleus thus receiving contrasting information may participate in a final adjustment of the attentive state of the animal to its environment.

Animals↗
PubMed1992

ATP hydrolysis by initiation factor 4A is required for translation initiation in Saccharomyces cerevisiae.

Saccharomyces cerevisiae translation initiation factor eIF-4A, an RNA helicase of the Asp-Glu-Ala-Asp (DEAD) box protein family, was mutated in the putative ATP binding site and expressed in Escherichia coli. Mutant proteins with alanine at position 66 replaced by glycine [eIF-4A(A66G)] or valine [eIF-4A(A66V)] were purified from Escherichia coli extracts and analyzed in vitro for activity in ATP crosslinking, ATP hydrolysis, RNA helicase, and translation assays. The results show that in vitro ATP hydrolysis activity, RNA helicase activity, and translation activity of eIF-4A correlate with in vivo activity of the factor. Whereas eIF-4A(A66G) showed wild-type activity in all assays, eIF-4A(A66V) was active in ATP crosslinking but inactive in ATP hydrolysis and RNA helicase assays. In vitro translation was supported by wild-type eIF-4A and eIF-4A(A66G) but not by eIF-4A(A66V). The results show that, for their translation, the majority of mRNAs from Saccharomyces cerevisiae including an mRNA with the initiator AUG positioned 8 nucleotides downstream of the cap structure require eIF-4A that is able to hydrolyze ATP.

Adenosine Triphosphate↗
PubMed1992

A 10 Hz "alpha-like" rhythm in the visual cortex of the waking cat.

Rhythms at about 10 Hz were recorded from the primary visual cortex of the cat (anterior part of area 18), with characteristics close to those of the alpha rhythm in man: frequency band (7-14 Hz), localization and reactivity to visual stimulation. Coherence analysis of this activity with the "mu" rhythms on the somatosensory cortex showed that although both types develop in the same overall behavioural situations (quiet waking and/or expectancy of an event to occur), they are independent.

Alpha Rhythm↗
PubMed1992

Activation of glycolysis with isoproterenol but not digoxin reverses chronic alcohol depression in hamster hearts.

The purpose of this study was to confirm that an agent, which increases diastolic [Ca2+]i, namely digoxin, depresses cardiac performance, mitochondrial activity, and glycolysis in chronic alcohol-treated and myopathic hearts, and that an agent, which lowers diastolic [Ca2+]i, namely isoproterenol, activates cardiac performance, mitochondrial activity, and glycolysis in these animals. Energy levels, glycolysis, mitochondrial activity, hemodynamics, and cAMP were studied in isolated hearts from three groups of animals, i.e., 9-month control hamsters, hamsters given 50% alcohol until 9 months of age, and 6-month-old cardiomyopathic hamsters in heart failure. Isolated hearts were perfused with either a control medium, a medium containing isoproterenol, digoxin, or digoxin + isoproterenol. Measurement of phosphomonoester sugars, and glucose-6-phosphate, were used to assess glycolytic activity. Oxygen consumption was used to analyze mitochondrial activity. All hearts perfused with either isoproterenol or isoproterenol + digoxin showed an increase in developed pressure, rate-pressure-product, and a decrease in end-diastolic pressure. Isoproterenol activated mitochondrial activity and glycolysis in hearts from myopathic and chronic alcohol hamsters. Based on 31P-NMR studies, isoproterenol or isoproterenol + digoxin improved the over-all energy state of hearts from cardiomyopathic hamsters, but not hearts from control and chronic alcohol hamsters. Digoxin alone augmented the rate-pressure-product and oxygen consumption in control hearts but not hearts from myopathic and chronic alcohol hamsters. Digoxin caused an increase in end-diastolic pressure in myopathic and chronic alcohol hearts but not control hearts. Digoxin depressed glycolysis and worsened the energy state in hearts from cardiomyopathic and chronic alcohol hamsters, but not hearts from control hamsters. In conclusion digoxin, but not isoproterenol nor isoproterenol + digoxin, depressed cardiac performance and glycolysis as well as high energy phosphates in cardiomyopathic and chronic alcohol hearts. Isoproterenol added to digoxin negated the adverse effects of digoxin in cardiomyopathic and chronic alcohol hearts.

Animals↗
PubMed1991

Functional description of the left ventricle in patients with volume overload, pressure overload, and myocardial disease using cine magnetic resonance imaging.

Cine magnetic resonance imaging (MRI) is a three-dimensional imaging technique with sufficient temporal resolution to provide quantitation of left ventricular (LV) dimensions and function. It can be used to describe the three-dimensional geometrical and functional characteristics of various cardiac disease states. Accordingly, the purpose of the study was to noninvasively characterize LV function with cine MRI using LV mass, systolic wall stress, ejection fraction, and fractional wall thickening, and to compare these functional determinants among three major cardiac disease states. Patients were selected from echocardiographic criteria and specific history of disease and divided into the following groups: compensated moderate to severe aortic regurgitation; compensated LV hypertrophy caused by systemic hypertension; and dilated congestive cardiomyopathy. Normal subjects without evidence of heart disease were studied for comparison. Cine MRI was performed at 1.5 Tesla in the short-axis plane. Wall stress was calculated from MRI, along with blood pressure recordings and carotid pulse tracings, according to the Laplacian expression. The end-diastolic volume to LV mass ratio distinguished between concentric and eccentric LV hypertrophy. Peak-systolic wall stress was increased in volume overload lesions and myocardial disease and significantly different (P less than .01) compared with pressure overload lesions and normal subjects. Ejection fraction was significantly decreased (P less than .01) in myocardial disease compared with volume and pressure overload lesions and normal subjects. Among these disease states, LV mass was not different but was significantly higher in all (P less than .01) compared with normal subjects. Fractional wall thickening was increased in pressure overload lesions. Thus, the increase in LV mass in volume overload lesions and primary myocardial disease is not adequate to prevent an increase in wall stress, whereas LV mass increased sufficiently in pressure overload lesions to normalize systolic wall stress. Cine MRI can be used to noninvasively describe the three-dimensional geometry and functional state of the heart in various pathological conditions and might be used to monitor therapeutic effects.

Adult↗