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Biomedical subjects

H B Brinkhus

Publications and source records attributed to H B Brinkhus.

8 recordsLinked to original sources
PubMed1986

Activities of single neurons in midbrain and thalamus of cats during conditioned nocifensive behavior.

Extracellular recordings of neuronal activity were performed in 3 conscious cats in the rostral mesencephalic reticular formation (MRF) and in the nucleus posterior (PO) of the thalamus. The animals were trained by operant conditioning to operate a panel switch with a forepaw to escape a noxious cutaneous heat stimulus. We recorded 12 neurons in the MRF, which responded in association with this nocifensive behavior. Some of the neurons increased their firing rate before the noxious stimulus was terminated, whereas other neurons responded immediately afterwards. The activity of these neurons, however, could be related to the animal's behavior, which was independent of the noxious stimuli. It was found that the neurons showed changes in firing patterns when the animal reacted to a discriminative light stimulus in order to obtain a milk reward. In the PO of the thalamus we did not find any neurons, which could be activated by noxious heating or any nocifensive-related behavior. Modification of the discharge patterns, however, occurred in relation to sensory events and behavioral acts.

Animals↗
PubMed1983

Characteristics of spinal dorsal horn neurons after partial chronic deafferentation by dorsal root transection.

Unilateral transections of 1-3 lumbar dorsal roots were performed in 13 adult cats to investigate the effect of partial deafferentation on dorsal horn neurons. Eleven to 45 days after deafferentation various parameters of spontaneous and evoked activity of 169 neurons were measured and compared to the data of 168 neurons from previous experiments recorded under identical experimental conditions except that these animals had not been deafferented. Eighty-six of the units encountered were located in the segment of transected dorsal root(s) and 82 in the caudally adjacent segment. No significant differences could be observed in the functional properties of these two samples of units. Most parameters measured indicate that either no change at all in responsiveness or signs of decreased excitability occurred in the partially deafferented neurons compared to units recorded in control animals. Discharges evoked by noxious skin heating indicate a linear relationship between discharge frequency and skin temperature. This kind of encoding curve could also be measured during a reversible cold block of the spinal cord at segment L1. The mean encoding curves before and during spinal blockade were not different in deafferented compared to corresponding curves measured in control animals. The only finding that could be interpreted as an indication for increased excitability of partially deafferented neurons was that the mean frequency of spontaneous discharges of a subsample of heat-sensitive neurons was higher in deafferented compared to control animals. Possible mechanisms are discussed.

Action Potentials↗
PubMed1979

Encoding of graded noxious skin heating by neurons in posterior thalamus and adjacent areas in the cat.

Impulse discharges were recorded from 62 single units in the posterior thalamic and adjacent nuclei of the cat which received input from hindlimb cutaneous nerves. Noxious radiant heating (e.g., 50 degrees C for 10 sec) of the hindpaw excited 32% of the units. The magnitude of heat-evoked unit discharges was graded with the intensity of noxious heating. Such units had large cutaneous receptive fields spanning 2 or more limbs, and responded to strong mechanical stimuli (pressure, pinch). About half of the units responded also to light stimuli such as hair bending or touch.

Animals↗
PubMed1977

[Heart diagnosis using M-mode-echocardiography. Continuous registration of the left ventricular transversal internal diameter. III. Measurements on highly trained athletes (author's transl)].

"Relative Cross-sectional area Differences" (RCD) and "Relative Velocities of Contraction" (RVC) permit a differentiation between normal subjects and patients with different degrees of myocardial failure, as previously described. Important determinants of the parameters RCD and RVC are changed, if ventricular volume and stroke volume increase and heart rate decreases, as is commonly observed in athletes. Examinations were performed at rest and after exercise on 31 athletes and 33 untrained normal subjects. Ventricular volumes were clearly increased in athletes. RCD, however, which is an equivalent to the ejection fraction, showed only slight alterations with physical training. RVC was obviously not changed by athletic training. After exercise athletes showed a significant increase in RCD. In untrained subjects only small changes in RCD were observed. In conclusion, the results show that RCD and RVC can quantitatively assess the degree of myocardial failure in cases of left ventricular dilatation without having to take into account the patients' degree of physical training.

Adolescent↗
PubMed1975

[Heart diagnosis using M-mode echocardiography. Continuing registration of transverse left ventricular inner diameters. I. Measurement in healthy persons].

Transversal internal diameters of the left ventricle can be determined simply, quickly, precisely and continuously by external application of impulse reflected ultrasound. These measurements permit the calculation of "relative cross-sectional area differences" between end-diastole and end-systole (RCD); peak and mean velocity of circumferential fiber contraction can be equally determined. The present report gives an analysis of 133 measurements on 81 healthy individuals. All persons were examined at rest, a part of them during exercise. All measurements were taken while supine position. The transversal internal diameters averaged 4.9 cm with considerable standard deviations. There was only a trend showing diminution of diameters during exercise. The "relative cross-sectional area differences" (RCD) between end-diastole and end-systole have only small standard deviations compared with the diameters. The average 58.3% and show a slight increase during exercise. The RCD were only slightly influenced by heart rate at rest. In contrast, peak and mean velocity of circumferential fiber contraction are obviously dependent on the heart rate. The results indicate a linear correlation between mean velocity and heart rate. The "relative mean velocities of contraction" (RVC), defined by normalization of the values to a rate of 60/min, average 1.0 and have small standard deviations like the RCD. The small physiological variety and the excellent reproducibility of data offer RCD and RVC determined by echocardiography as sensitive dynamic heart parameters applicable in clinical cardial diagnosis without any stress for the patient.

Anthropometry↗
PubMedDate not supplied

Controlling behavioral experiments with a new programming language (SORCA) for microcomputer systems.

A new programming language SORCA has been defined and a compiler has been written for Z80-based microcomputer systems with CP/M operating system. The language was developed to control behavioral experiments by external stimuli and by time schedule in real-time. Eight binary hardware input lines are sampled cyclically by the computer and can be used to sense switches, level detectors and other binary information, while 8 binary hardware output lines, that are cyclically updated, can be used to control relays, lamps, generate tones or for other purposes. The typical reaction time (cycle time) of a SORCA-program is 500 microseconds to 1 ms. All functions can be programmed as often as necessary. Included are the basic logic functions, counters, timers, majority gates and other complex functions. Parameters can be given as constants or as a result of a step function or of a random process (with Gaussian or equal distribution). Several tasks can be performed simultaneously. In addition, results of an experiment (e.g., number of reactions or latencies) can be measured and printed out on request or automatically. The language is easy to learn and can also be used for many other control purposes.

Animals↗