Search PubMed⌕ Search

Biomedical subjects

B Conrad

Publications and source records attributed to B Conrad.

At least 181 records · Page 10Linked to original sources
PubMed1986

Delayed visual evoked potentials in chronic alcoholism.

Pattern reversal visual evoked potentials (VEPs) were studied in 80 chronic alcoholics and in 43 normal subjects. In the patient group, P2 latencies and inter-eye differences were found above the 98% confidence limit in 30%, and above the 99.9% confidence limit in 10%. An abnormal waveform was observed in 12.5% and 7.5% of the patients. VEP abnormalities showed some statistical correlation with the gamma-type of alcoholism of Jellinek, but almost no correlation was observed with a variety of clinical and laboratory data. This suggest that VEP abnormalities are unrelated to other toxic effects of alcohol on the peripheral and central nervous systems or on metabolism.

Adult↗
PubMed1985

Hesitation vowels: a motor speech respiration hypothesis.

In spontaneous speech the relation of hesitation vowels 'ah' and 'mh' (filled pauses) and respiration was studied in 16 healthy native speakers of German. Hesitation vowels did not occur randomly in expiration during speech. When expiratory duration was divided into four segments of equal length, the highest incidence of hesitation vowels was to be found at early loci during expiration. As speech respiration is reset to vegetative breathing as soon as speech production stops, hesitation vowels act as phonomotoric subroutines during halting speech production to prevent the respiratory system from uneconomic air loss and to keep it in the speech respiration mode.

Adult↗
PubMed1985

Rapid goal-directed elbow flexion movements: limitations of the speed control system due to neural constraints.

In rapid goal-directed elbow flexion movements the influence of both movement amplitude and inertial load on the three-burst pattern and the consequences on movement time were studied. Subjects performed visually guided, self-paced movements as rapidly and as accurately as possible. An increase of both the movement amplitude and the inertial load were found to be interacting factors for the modulation of the three-burst-pattern and movement time. The first biceps burst progressively increased in duration and amplitude for larger movements, resulting in prolonged movement times. Surplus inertial loads further prolonged the agonist burst for large, but not for small movement amplitudes. The activity of the antagonist burst, in contrast, was largest in small movements and successively decreased at increasing movement amplitudes. Its duration, however, remained fairly constant. As was similarly observed for the agonist burst, surplus inertial loads lead to a prolongation of antagonist burst duration and an small movement amplitudes. It is suggested that in elbow flexion movements the programming of fastest goal-directed movements must take into account neural constraints and biomechanical characteristics of the agonist muscle and the antagonist muscle. Due to neural constraints of the biceps muscle, in contrast to finger movements, the concept of movement time invariance does not hold for elbow movements. Furthermore, neural constraints of the antagonist muscle lead to a limited force production of the agonist muscle at small movement amplitudes in order to avoid an overload of the braking process.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

The flexor reflex--influence of stimulus parameters on the reflex response.

The flexor reflex evoked in the tibialis anterior muscle by stimulation of the medial plantar nerve was investigated in 54 normal subjects. Three main reflex components were identified (excitation--inhibition-- excitation), the early excitation being composed of two subcomponents. Occasionally, a fourth (excitatory) reflex component was seen breaking through EMG inhibition. The individual reflex components were differentially susceptible to facilitatory influences which suggested transmission via a central multichannel system. Methodological experiments showed that the amplitudes and to some degree also the latencies of the individual reflex components were modified by both the parameters of the stimulus as well as by the degree of pre-innervation. However, the patterning of the reflex response was basically independent from methodological permutations.

Adult↗
PubMed1985

[Lesion of the intercostobrachial nerve].

After surgery in the area of the armpit, and particularly after axillary lymphonodectomy during mastectomy, severe pain and paraesthesia can occur in the region of the medial and posterior side of the proximal upper arm. It is shown by means of four case reports that this discomfort can be caused by a lesion in the intercostobrachial nerve. The differential diagnosis must consider injury to the brachial plexus or a local metastasis.

Arm↗
PubMed1984

Changes of somatosensory evoked potentials in man as correlates of transcortical reflex mediation?

Somatosensory evoked potentials (SSEP) from the scalp of the sensori-motor cortex were recorded together with long latency reflexes in the EMG of the contralateral biceps muscle in 17 human subjects, who were instructed to compensate a sudden biceps stretch. In this 'compensate' condition the earliest deviation from the shape of the SSEP obtained in a 'let go' situation (exhibiting only short latency reflexes) occurred as early as 35-40 ms. The results indicate that SSEP changes associated with the occurrence of long latency reflexes might be compatible with a transcortically mediated reflex activity.

Adult↗
PubMed1984

Microcomputer programs for graphic analysis of nucleic acid and protein sequences.

Four computer programs are described which allow two amino acid or DNA sequences to be compared for homology, the results being displayed in a 2-dimensional array on a printer page. The programs also may be used to visualize repeated sequences or dyad symmetry within a DNA sequence. Two of the four programs may be used with any printer, the other two require a printer with graphics capability. Many options are available including using only a portion of a sequence, specifying a window to demonstrate more significant structures and special restrictions on matching such as excluding the third base in a codon. Written in the C programming language, the programs run under the CP/M 80 operating system, and may be copied in binary format through a modem. They are also available for the IBM/PC.

Amino Acid Sequence↗
PubMed1984

Microcomputer programs for back translation of protein to DNA sequences and analysis of ambiguous DNA sequences.

Three computer programs are described which may be used to translate a DNA sequence into a protein sequence, back translate the protein sequence into an ambiguous DNA sequence, and then do pattern searching in the ambiguous sequence. The programs are written in the C programming language, have been compiled to run on a microcomputer under the CP/M 80 operating system, and may be copied in binary format through a modem. They are also to become available for the IBM/PC.

Amino Acid Sequence↗
PubMed1984

Human ballistic finger flexion: uncoupling of the three-burst pattern.

In isotonic and isometric goal-directed index finger movements made as fast as possible, the "braking hypothesis" ascribed to the antagonist burst was tested. Under isotonic conditions, the extensor burst often failed to occur in small angle movements with low inertial load. It regularly occurred, however, in small angle movements with high inertial load and in wide angle movements with both low and high inertial loads. Such features suggest, indeed, the antagonist burst as being part of braking strategies. Under isometric conditions, the antagonist burst - if it occurred - exhibited characteristics which suggested a rapidly alternating movement rather than a braking strategy.

Electromyography↗
PubMed1984

Eye movements during reading in aphasics.

In 40 normal subjects and in 21 patients with anomic, Wernicke's, and Broca's aphasia, eye movements were registered with DC-EOG during reading of two standardized texts and analysed with respect to the number of fixations and regressions and reading time. Patients with these aphasic syndromes developed different internal strategies of their saccadic construction: Patients with Wernicke's aphasia showed increasing difficulty in overcoming the text with a tendency to make smaller leaps over the line, with almost a complete disintegration of the saccadic structure ("strategy of small and smallest steps"). The saccadic pattern in Broca's aphasics was clearly better preserved. During oral reading there was a characteristic increase in fixation times and number of regressions ("motor waiting and searching behaviour"). Patients with anomic aphasia showed alterations most similar to the reading behaviour of unskilled normal readers.

Anomia↗
PubMed1984

The stiff-man syndrome: new pathophysiological aspects from abnormal exteroceptive reflexes and the response to clomipramine, clonidine, and tizanidine.

Neurophysiological investigations of a patient suffering from the stiff-man syndrome revealed that exteroceptive reflexes, in particular those elicited from the skin, were excessively enhanced. In contrast, no abnormalities were found within the monosynaptic reflex arc. Clomipramine injection severely aggravated the clinical symptoms whereas diazepam, clonidine, and tizanidine decreased both muscular stiffness and abnormal exteroceptive reflexes. The hypothesis is put forward that the stiff-man syndrome is a disorder of descending brain-stem systems which exert a net inhibitory control on axial and limb girdle muscle tone as well as on exteroceptive reflex transmission. Detection of abnormal exteroceptive reflex activity in conjunction with neuropharmacological testing might help in the diagnosis of this rare disease.

Adult↗
PubMed1983

Premovement silent period in fast movement initiation.

Premovement inhibitory processes were studied in human subjects performing ballistic elbow movements in a self-paced or reaction time situation. The experiments were designed to test the hypothesis that there is an interdependence between a preparatory disfacilitatory process at the motoneurone level and an impending phasic motoneurone activation. The results indicate that in ballistic movements there is a positive relation between extent of premovement depression of tonic activity and subsequent phasic innervation. The results suggest that in high speed movements where a maximal number of motor units have to be recruited, those motoneurones which are already tonically active have to be released from tonic activity for optimal synchrony.

Acoustic Stimulation↗
PubMed1983

Denervation activity in the EMG of patients with upper motor neuron lesions: time course, local distribution and pathogenetic aspects.

EMG denervation activity was studied in patients without peripheral neuron disorder but with upper motor neuron lesions. The time course of such central denervation activity, the local distribution and the quantitative relationship between denervation activity and the degree of paresis and spasticity were also studied. A total of 101 patients, who had developed hemiplegia or hemiparesis as a result of a cerebral vascular accident, underwent needle electromyographic examination at regular intervals in proximal and distal muscle groups. The maximum observation time was 1 year. Denervation activity in cases of central paresis first occurred 2-3 weeks after stroke. This could be observed most frequently in the distal arm and hand muscles. In the course of weeks and months the frequency of the denervation activity decreased in parallel with the development of spasticity and the increasing voluntary innervation. The occurrence and the dynamic properties of the denervation activity in cases of central paresis support the assumption of a trans-synaptic degeneration of alpha-motoneurons and of a compensating segmental "sprouting" of afferents.

Cerebral Infarction↗
PubMed1983

[Standardization of the electromyographic tetany test in the diagnosis of normocalcemic tetany: the 10-minute Trousseau test in patients and healthy humans].

Eighteen adult patients with typical history and signs of normocalcemic tetany (hyperventilation syndrome) and 18 age- and sex-matched controls were submitted to a provocation test for tetany. This consisted of 10-min ischemia of the right arm produced by suprasystolic cuff compression at the upper arm (Trousseau test) and a postischemic electromyographic recording from the right interosseous I muscle. Postischemic repetitive discharges were found in all patients and predominantly consisted of multiples of 5 times and more. These discharges lasted 8 min on the average. Of the normal controls, as many as 16 subjects (88.8%) also exhibited tetanic discharges. However, these preferred a lower number of repetitions, such as doublets or triplets. Both number of repetition and duration of postischemic tetanic activity were significant parameters discriminating between patients and controls (2P less than 0.001), as was the cumulative total number of spontaneous potentials, amounting, on the average, to 10,266 in the group of patients and to only 320 in the controls (2P less than 0.001). The investigation has shown that the occurrence of postischemic tetanic spontaneous activity per se does not help to discriminate between cases of latent tetany and healthy controls. However, a normocalcemic tetanic condition may be assumed if multiples occur with a complexity of quadruplets or more, if these multiples last at least 2 min, and if they appear in a rhythmic order and in groups.

Adult↗
PubMed1983

Visual evoked potentials in neurosyphilis.

The visual evoked potential (VEP) to pattern reversal was recorded in 79 patients with neurosyphilis. Sixteen patients (20%) had abnormal VEP latencies with a predominance of pathological VEP values in the group of tabes dorsalis (50%) as compared to general paresis (18%) or meningovascular forms (13%). A comparison of the frequency of abnormal VEPs with that of other ophthalmological tests (visual acuity, visual field, central campimetry, pupillary reactions, dark adaptation, optic fundus) yielded no diagnostic superiority of VEP.

Adult↗