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Biomedical subjects

M Lang

Publications and source records attributed to M Lang.

At least 163 records · Page 9Linked to original sources
PubMed1988

[Left ventricular hypertrophy in arterial hypertension].

Arterial hypertension is frequently and at an early stage complicated by left ventricular hypertrophy, i.e. an increase in muscular mass due to the proliferation of myofibrillae. This in fact is a physiological mechanism aimed at maintaining systolic function and systemic blood flow rate. Left ventricular hypertrophy may be associated with myocardial alterations, such as increase of collagen, abnormalities of diastolic function, reduced contractility, increased cell excitability and disorders of coronary perfusion. It is responsible for a higher risk of cardiovascular mortality. Antihypertensive treatments, therefore, must not only bring blood pressure down to normal values, but also reduce the myocardial mass. In order to avoid a detrimental effect on coronary reserve, it is highly desirable that arterial hypertension and left ventricular hypertrophy regress simultaneously. Regression of the myocardial hypertrophy associated with arterial hypertension is observed with most antihypertensive drugs, except vasodilators that act directly on the vascular smooth muscle, probably due to stimulation of the sympathetic system. Diuretics also have an inconstant beneficial effect on left ventricular hypertrophy. When a choice has to be made between two drugs that have the same antihypertensive activity, it is the one that also brings about an early and lasting regression of myocardial hypertrophy which must be prescribed.

Cardiomegaly↗
PubMed1988

DC-potential shifts and regional cerebral blood flow reveal frontal cortex involvement in human visuomotor learning.

In the present study, two different physiological parameters were measured to describe brain activity related to visuomotor learning: performance-related DC-potential shifts and regional cerebral blood flow (rCBF) by Tc-99m HMPAO brain SPECT (Single Photon Emission Computerized Tomography). Visuomotor learning was required in a conflicting situation: a visual target moved on a screen and had to be tracked by moving the right hand in an inverted fashion (IT), e.g. movements of the target to the right side required hand movement to the left and vice versa. Compared to a normal, non-inverted control task (T), IT required the development of a novel motor program and the prevention of returning to routine direct pursuit. These additional demands in IT caused a relative hyperperfusion in regions including the middle frontal gyri, frontomedial cortex (including the supplementary motor area, SMA), right basal ganglia (caudate-putamen) and left cerebellum. Correlations of rCBF values between the middle frontal gyrus and basal ganglia may indicate a functional relation between these two brain structures. Visuomotor performance was accompanied by slow negative DC-potential shifts. In frontal and to a lesser degree in central recordings, amplitudes of DC-negativity were larger in IT than they were in T. This additional frontal negativity covaried with the success of learning. Results substantiate, now using a dual approach, previous suggestions that the frontal lobe plays an important role in visuomotor learning.

Adolescent↗
PubMed1988

Negative cortical DC shifts preceding and accompanying simultaneous and sequential finger movements.

Cortical DC shifts preceding and accompanying the execution of five different bimanual motor tasks were analysed in 20 subjects. All tasks required repetitive flexions and extensions of the two forefingers for a period of at least six seconds. The temporal and spatial structures organization varied in the different tasks: (1) Simultaneous agonistic performance (forefinger flexion on both sides), (2) simultaneous antagonistic performance (e.g. flexion of the right, extension of the left forefinger), (3) sequential agonistic performance, (4) sequential antagonistic performance, (5) uncoordinated flexions and extensions of the two forefingers. Compared to (1) and (2), conditions (3) and (4) included a temporal delay between the performance of the two forefingers; compared to (1) and (3), conditions (2) and (4) required the subjects to perform movements of opposite directions with their two forefingers. Effects of the temporal factor (T; simultaneous vs. sequential) and the spatial factor (S; agonistic vs. antagonistic) on cortical DC shifts were investigated. The voluntary initiation of each motor task was preceded by a Bereitschaftspotential (BP). The performance of the complex tasks (1-4) was accompanied by a slow negative DC potential shift (N-P). In general, the BP did not differ depending on the temporal or spatial structures of the tasks (1-4). However, amplitudes of N-P (i.e. during tasks) were influenced by the temporal factor with significantly larger amplitudes in sequential than in simultaneous tasks. This difference was not a global phenomenon in all recordings but was selectively found in the recordings over the fronto-central midline.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Left frontal lobe in verbal associative learning: a slow potential study.

In the present experiment pairs of words had to be memorized. The words were either meaningful or meaningless. The experimental design compares conditions of preestablished learning (L-) with active learning (L+). The effects of these two factors, "semantic content (S)" and "learning (L)", on the slow potential shifts accompanying presentation and processing of the verbal material were tested. In the memorizing tasks, the two words were given in a fixed temporal sequence. A slow negative potential shift having a maximum in parietal leads emerged within the inter-stimulus-interval. Its amplitudes were larger in the learning tasks (L+) than in conditions of pre-established learning (L-). This difference of amplitudes may reflect different levels of attention: In L-, the second word could be anticipated, but not in the L+ tasks. After the presentation of the second item, learning tasks (L+) were characterized by a slow negative potential shift in the recordings of the left dorso-lateral frontal lobe. It is assumed that this potential shift may indicate an importance of the left frontal lobe in the elaborative encoding of verbal material.

Adult↗
PubMed1988

Cortical slow potentials in verbal and spatial tasks--the effect of material, visual hemifield and performing hand.

Fifteen right-handed students voluntarily initiated the tachistoscopic presentation of visual stimuli containing either verbal (abstract words) or spatial (stereogeometric figures) material. Subjects had to reproduce stimulus material which had been presented either in their right or their left hemifield of vision by writing or drawing, either with their right or their left hand. Material-specific effects were found during the reproduction period: amplitudes of the performance-related negative potential shifts were larger in parietal and occipital recordings (P4, O1, and O2) when drawing as compared to writing. The opposite was true in frontal and left central leads (F3, F4, and C3) where writing was associated with larger negative amplitudes than drawing. Although subjects were informed about the nature of the forthcoming stimulus before voluntarily initiating the task, material-specific effects were missing in the preparation period. The performing hand had an influence on potentials in central leads, whereas hemifield of vision had no effect on preparation- and performance-related slow potential shifts.

Adolescent↗
PubMed1988

Suppressive effects of transdermal clonidine administration on contact hypersensitivity reactions in guinea pigs.

In the present study, immunopharmacological effects of clonidine-TTS on allergic contact dermatitis (ACD) to non-related, established contact sensitizers were investigated in guinea pigs. First, to evaluate the hypotensive effect of clonidine-TTS in guinea pigs, intra-arterial blood pressure was recorded. After 4 days of treatment with one (or two) TTS per animal, a reduction of arterial blood pressure from 71 +/- 1 to 51 +/- 2 mm Hg was observed. We subsequently assessed the effects of clonidine-TTS on contact hypersensitivity reactions to 2,4-dinitrochlorobenzene (DNCB) and 4-ethoxymethylene-2-phenyl-oxazolone (Ox). This study indicates that clonidine-TTS suppressed the elicitation of contact hypersensitivity reactions. The observed immunosuppressive effect of clonidine may account for the relatively weak hypersensitivity reactions to this drug in experimental animal studies. Further studies are needed to determine whether such findings are of relevance to the clinical use of clonidine in patient populations.

Administration, Cutaneous↗
PubMed1988

Molecular biology of the HLA-B27 locus.

The molecular biology of the HLA-B27 locus is reviewed. The HLA-B27 gene itself does not differ between healthy individuals and ankylosing spondylitis patients. Several unique features of the HLA-B27 molecule have been identified and one epitope was proposed to cross-react with bacterial proteins.

Amino Acid Sequence↗
PubMed1988

Effect of systemic nicotine on mucus secretion from tracheal submucosal glands and on cardiovascular, pulmonary, and hematologic variables.

To investigate effects of systemic nicotine on mucus secretion from tracheal submucosal glands we anesthetized 13 ferrets (5 male, 8 female; average weight 1138 +/- 469 g, mean +/- SD) with pentobarbital (initial dose, 62 +/- 26, total dose, 90 +/- 26 mg/kg), cannulated the jugular vein for i.v. application of infusions and drugs and cannulated the femoral artery for determination of blood pressure, heart rate, blood cells, and blood gases. We opened the thorax, cannulated the trachea 1 cm above the carina and ventilated the lungs through the lower airways with a Harvard respirator. We placed an electromagnetic flow probe around the ascending aorta for measurement of cardiac output. We measured transpulmonary pressure as tracheal pressure with a strain gauge transducer. We created an isolated segment of trachea between the larynx and the tracheal cannula. We perfused the segment with medium M-199 containing 30 microCi/ml Na(2)35SO4 (35S) and we injected 100 microCi 35S intravenously. After 90 min we drained the radioactive solution from the luminal side and replaced it with nonradioactive medium which we collected at 5-min intervals for determination of nondialyzable radioactivity. At 25 min we injected nicotine sulfate (5 x 10(-7)-10(-5) M/kg) and continued to collect the perfusate every 5 min. Systemic nicotine had profound effects on circulatory and ventilatory variables and on gland secretion. Initial hypertension was followed by bradycardia and a fall in blood pressure and cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Event-related EEG-spectra in a concept formation task.

Event-related spectra of short EEG epochs were investigated in a concept formation paradigm. In this task, subjects had to learn to transform letters into Morse codes. Related to a resting state, cognitive performance in this learning task was characterized (i) by an increased mean power density (MPD) within the Theta frequency band (theta) in recordings over the frontal lobes and (ii) by a reduced Alpha (alpha) MPD in all recording sites. The performance-related increase of the theta-MPD, as obtained in left frontolateral and frontomedial recordings, separated (i) the learning task from an appropriate control and (ii) a group of successful learners from a group which performed less efficiently. MPDs of the alpha- and the delta-(Delta) frequency band did not differ between tasks and groups. A consistent finding in the learning tasks was a temporal dissociation of performance-related alpha-attenuation between parietal and frontal recordings: in the period preceding the presentation of the informative stimuli, the alpha-rhythm is attenuated especially at parietal recordings, whereas in frontal recordings, alpha-attenuation accompanied information processing and response selection.

Adult↗
PubMed1987

Monitoring of heparin therapy with the activated partial thromboplastin time and chromogenic substrate assays.

Heparin therapy was monitored with the activated partial thromboplastin time (APTT) and with chromogenic substrate assays (factor Xa and factor IIa inhibition) in 100 plasma samples from 47 patients. Heparin concentrations were classified as being below, within or above a defined therapeutic range (TR; 0.2-0.55 units heparin/ml). In a first group of patients (A), all three assays allocated the plasma heparin levels to the same concentration interval with respect to the TR. The most frequent diagnoses in group A were uncomplicated arterial or venous thromboembolism, myocardial infarction with limited tissue necrosis, cardiac surgery without major complications and successfully treated infectious disease. In a second group of patients (B), the results of APTT suggested higher heparin concentrations with respect to the TR than the chromogenic assays. Predominant diagnoses were severe infectious diseases, severe liver disorders, extensive myocardial infarction and postoperative complications after cardiac surgery. The discrepancy between heparin concentrations determined by either APTT or the chromogenic substrate assays is most likely due to a non-heparin related prolongation of APTT caused by the underlying disease.

Chromogenic Compounds↗
PubMed1987

Sequential calcium and phosphorus balance studies in preterm infants.

Forty-six infant boys less than 1500 g at birth and less than 32 weeks gestation were fed enterally from birth until day 47. Cohorts were given milk formula varying in calcium and phosphorus content: group A, calcium 45 mg/dL, phosphorus 33 mg/dL; group B, calcium 85 mg/dL, phosphorus 33 mg/dL; group C, calcium 125 mg/dL, phosphorus 33 mg/dL; group D, calcium 125 mg/dL, phosphorus 50 mg/dL; and group E, calcium 125 mg/dL, phosphorus 64 mg/dL. Three-day balance studies were begun at days 10, 20, 30, and 40. Calcium net absorption and retention were influenced by postnatal age and calcium intake. Calcium retention best approached intrauterine accretion rates in group C. Phosphorus was well absorbed irrespective of the calcium content of the milk. Phosphorus retention increased with increments in the calcium content of the milk. Increasing the phosphorus content of the milk (groups D and E) resulted in no overall change in calcium absorption and retention but some increments in phosphorus retention.

Birth Weight↗
PubMed1987

[Comparative study of the effects of verapamil and propranolol therapy in 16 cases of obstructive hypertrophic myocardiopathy].

In a randomized, double-blind, cross-over study with plasma drug assays, 16 patients (11 men, 5 women; mean age 48.56 +/- 3.61 years) presenting with hypertrophic obstructive cardiomyopathy confirmed by echocardiography, left ventriculography and left intraventricular gradient measurement were treated with verapamil 480 mg/day or propranolol 320 mg/day. Both treatments produced functional improvement (p less than 0.01) which was more distinct with verapamil (NS). No changes in cardiothoracic index, echocardiographic parameters and Sokolow's index were observed. Mean total heart work during exercise, which was 1,197.27 +/- 135.89 watts before treatment, increased to 1,260.91 +/- 146.60 watts under propranolol (NS) and to 1,344.09 +/- 171.06 watts under verapamil (NS). Maximum heart rate during exercise, which was 162.3 +/- 3.46 beats/min before treatment, was reduced to a greater extent by propranolol (122.1 +/- 6.6 beats/min; p less than 0.001) than by verapamil (147.7 less than 5.08 beats/min; p +/- 0.01). The two treatments did not significantly modify ventricular arrhythmia, arterial and capillary pulmonary pressures, mean aortic pressure and left ventricular end-systolic pressure. Cardiac index, unchanged under verapamil, fell from 2.98 +/- 0.16 1 X min-1 X m-2 to 2.60 +/- 0.11 1 X min-1 X m-2 under propranolol (p less than 0.05). The left intraventricular gradient present in 5 patients at rest and during exercise, was reduced by both drugs. The gradient under isoprenaline (n = 16), which was 162.07 +/- 18.77 mmHg before treatment, fell to 93.86 +/- 24.48 mmHg with propranolol (p less than 0.05) and to 128.86 +/- 18.22 mmHg with verapamil (p less than 0.05). Left ventricular ejection fraction, mean circumferential fibre shortening speed and compliance coefficient remained unchanged under both drugs (NS). Left ventricular diastolic function, evaluated by radioisotope angiography in the last 9 patients, was most often improved by verapamil (NS). Verapamil was better tolerated generally and by the heart than propranolol. No correlation was observed between plasma verapamil levels and clinical results. Low plasma propranolol levels were often noted in non-responders, suggesting a need for treatment with high doses. It is concluded that at the dosage level used in this study propranolol and verapamil were equally effective, but there were individual variations in best response to one or the other of these two drugs.

Cardiomyopathy, Hypertrophic↗
PubMed1987

[Primary leiomyosarcoma of the pulmonary artery. Apropos of a case].

A case of leiomyosarcoma of the pulmonary artery in a 64-year old man without previous cardiovascular disease is reported. The clinical picture, which comprised episodes of paroxysmal dyspnoea associated with acute cor pulmonale, suggested pulmonary embolism. Radioisotope perfusion study and pulmonary angiography seemed to confirm this diagnosis, but no improvement was obtained with a prolonged thrombolytic treatment. The presence of a median mass at CT led to exploratory thoracotomy and to the finding of a tumour in the pulmonary artery, which turned out to be a leiomyosarcoma. The disease rapidly took an unfavourable course. Comparison of this case with data from the literature showed that primary tumours of the pulmonary artery are extremely rare, that they are diagnosed with difficulty and often at a late stage and that their prognosis is usually very sombre.

Humans↗