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Biomedical subjects

F Behrens

Publications and source records attributed to F Behrens.

50 records · Page 3Linked to original sources
PubMed1980

The enzyme-linked immunosorbent assay (ELISA) for determination of IgG and IgM antibodies after infection with mumps virus.

Under routine laboratory conditions ELISA was tested for suitability for serological demonstration of specific antibodies of the immunoglobulin classes G and M against mumps virus. Sera from patients with known clinical and virological data were used. The results of ELISA were compared with those of CFT. 45 paired sera were tested in ELISA IgG, 87 first sera in ELISA IgM. Both tests were highly sensitive, antibodies were detected earlier and with higher titers than with the CFT. The ELISA IgM is particularly suitable for early diagnosis of mumps infection with the first serum. In addition 23 paired sera from patients with acute parainfluenza virus infection were examined for cross-reacting antibodies. Low anti-mumps IgG antibody titers were found in some sera. These findings reduced the mumps specificity of the IgG test. In five serum samples from one patient--obtained before, during, and after an infection with mumps--the course of IgG and IgM antibodies could be demonstrated. Advantages and limitations of ELISA IgG and IgM are summarized.

Antibody Formation↗
PubMed1979

Smooth pursuit eye movements and optokinetic nystagmus elicited by intermittently illuminated stationary patterns.

Stationary periodic visual patterns (row of equally spaced dots or black-white stripes) of the period Ps illuminated stroboscopically with a flash frequency fs induce an apparent movement perception (sigma-movement) when slow eye movements are performed across the periodic pattern. The movement appears in the direction of the eye movements when the angular speed VE of the eyes corresponds to the following condition: Ve = k . Ps . fs [deg . s-1] (1) k is a constant and equals 1 (or exceptionally 2 or 3). The sigma-movement induces a sigma-OKN with an average angular speed of its slow phases corresponding to Eq.(1). sigma-OKN can be elicited when identical foveal or identical extrafoveal stimulus patterns are applied from flash to flash. A considerable random variability of the flash sequence does not interrupt the sigma-movement and the sigma-OKN. Both phenomena can also be elicited by a stimulus pattern with its periodicity hidden in spatial noise and this periodic pattern only becomes visible during the eye movements. It is argued that the sigma-phenomena are caused by efference copy signals of the gaze control system, which interact with the afferent signals (displacement of visual stimuli on the retina) at different levels of the afferent visual system. One interaction is supposed at a cortical level where the extrapersonal visual space is represented.

Adult↗
PubMed1978

Diarrhea in newborn cynomologus monkeys infected with human rotavirus.

Of six newborn cynomolgus monkeys (Macaca fascicularis) naturally delivered and normally nursed five developed diarrhea after oral administration of human rotavirus. Virus excretion was observed in the stool of four animals. This virus was transmitted to four out of six other monkeys causing diarrhea in only one animal.

Animals↗
PubMed1977

[Seroepidemiological Investigations on the epidemiology of human rotavirus infections (author's transl)].

263 sera of infants and children up to 10 years of age were tested for antibodies (CF-test) against Nebraska calf diarrhoea virus (NCDV) which is antigenically related to the rotavirus of man; in addition the mean antibody titers in different age groups were investigated. Antibodies of maternal origin were eliminated during the first year of life. Most of the infections occurred during the second year of life and at the end of this year 40-50% of the investigated children demonstrated antibodies against NCDV; this frequency persists during the rest of the investigated life period.

Antibodies, Viral↗
PubMed1976

Metabolic recovery of articular cartilage after intra-articular injections of glucocorticoid.

The recovery of adult rabbit articular cartilage after nine weekly intra-articular injections of hydrocortisone acetate was investigated using biochemical, autoradiographic, and tracer methods. After the cessation of steroid injections, the rates of synthesis of proteoglycans and collagen increased by up to 900 per cent. The increase occurred because of accelerated metabolism of existing cells and an increase (caused by mitosis) in the number of functioning chondrocytes. The proteoglycan concentration only returned to normal values after six months.

Animals↗
PubMed1975

Alterations of rabbit articular cartilage by intra-articular injections of glucocorticoids.

The destruction of rabbit articular cartilage after intra-articular injections of hydrocortisone acetate was investigated using histological, biochemical, and tracer methods. Fissures and cysts increased in number as increasing amounts of hydrocortisone were given. A linear decrease of hexosamine to less than 50 per cent after twelve injections was accompanied by insigificant changes in deoxyribonucleic acid and hydroxyproline content. The synthesis of proteoglycans and proteins was reduced to one-third, while the production of collagen dropped to less than one-fifth. The changes in thymidine incorporation were not significant. Based on these data, a model indicating the sequence of events which leads to joint destruction after intra-articular injections of glucocorticoid is proposed.

Animals↗
PubMedDate not supplied

Investigation of the horizontal, vertical, and oblique optokinetic nystagmus and afternystagmus in squirrel monkeys.

A moving random dot pattern was projected onto a tangent screen in front of awake untrained monkeys that were always placed in upright position. Eye movements were recorded in two dimensions to study the oblique optokinetic nystagmus (OKN) and compare it to the horizontal and vertical OKN. Any direction of pattern movement across the screen could be achieved. The angular velocity of pattern movement was varied between 6 and 180 degrees/s. To display off-horizontal and off-vertical eye movements, the instantaneous direction and velocity of the eye movements were computed from the horizontal and vertical search coil voltages. At pattern velocities below 90 degrees/s, stimulus-direction and direction of the OKN slow phase matched very precisely. Above 90 degrees/s the slow-phase eye movement direction was systematically shifted toward the horizontal except for pure vertical stimulation. The slow-phase eye velocity at off-horizontal stimulation was inconstant, however; stable periods occurred repeatedly that were used to define the gain of OKN. Up to stimulus speeds of about 90 degrees/s the OKN gain did not depend on the direction of stimulation and of OKN. At higher velocities the gain decreased with the increasing angle between stimulus direction and horizontal. Practically no vertical optokinetic afternystagmus (OKAN) could be observed, in either the up or down direction. At the onset of afternystagmus after oblique stimulation the direction of the OKAN slow phase immediately shifted over to the horizontal. The data indicate that the slow-phase direction and gain of oblique OKN with the monkey's head upright can be described by the sum of a horizontal and a vertical velocity vector obtained during stimulation in these cardinal directions.

Afterimage↗
PubMedDate not supplied

On the optokinetic response during step-wise changes in stimulus velocity in squirrel monkeys.

In two awake untrained squirrel monkeys the horizontal optokinetic nystagmus (OKN) was studied. The goal was to quantify the buildup of the slow-phase eye movement velocity during the first two seconds and the eye movements after OKN interruption by a stationary surround. We intended to uncover possible effects of a "charged' velocity storage on eye movements at a stationary surround. Using an optokinetic drum, a paradigm was designed to create sudden changes of the pattern (within 5 ms) between appearing to be stationary or rotating. Velocity steps from zero to 14 to 73 degrees/s and back to zero could be achieved. OKN onset: 201 velocity trajectories were analyzed. The mean latency between the onset of pattern movement and the onset of slow-phase eye movements was 82.8 +/- 16.5 ms. Over a limited period the initial increase in slow-phase velocity could be approximated by a straight line. The slope was on average 103 +/- 67 degrees/s2 and did not show a significant dependency on pattern movement velocity. Eye movement velocity at the end of the linear part increased linearly with drum velocity; the slope was 0.59. After the linear range, the slow-phase velocity increased further but at slower accelerations and usually reached the final gain within the two seconds. The initial linear acceleration component is an open-loop reflex response and we conclude that closing the loop happens when about 60% of the stimulus velocity is reached. OKN-offset: The influence of a fully charged OKN velocity storage mechanism on eye movements after a sudden exposure of a stationary surround was studied in 23 trials. After OKN interruption the velocity decay commenced after an interval of 83.5 +/- 16.6 ms. On average the slope of the consecutive linear velocity decay was -195.4 +/- 83.6 degrees/s2. During 5.8 +/- 0.98 s the OKN still had some impact on the fixating eye movements. We conclude that this time represents the time for velocity storage discharging. An active process seems to control the impact of velocity storage on eye movements.

Animals↗
PubMedDate not supplied

The velocity storage mechanism of the optokinetic nystagmus under apparent stimulus movements in squirrel monkeys.

Experiments in two awake untrained squirrel monkeys were performed to study the velocity storage mechanism during fast rise of OKN slow phase velocity. This was done by testing the monkey's capability to perform OKN in response to a stationary-appearing stroboscopically illuminated stripe pattern of a horizontally rotating drum. Nystagmus was initially elicited during constant illumination lasting between 0.6 and 25 s. The periodicity of the stripe pattern was 2.37 degrees. When after the constant light the flash illumination was switched on again, two types of behavior could occur, depending on the length of the constant light interval (CLI): 1) when the CLI was shorter than a threshold value of 6.2 seconds, the OKN ceased under the flash stimulation. Then a "post-OKN" occurred that increased with the length of the CLIs, indicating that the intermittently illuminated pattern did not provoke fixation suppression of OKN aftereffects. 2) when the CLI was above threshold, the OKN continued under the flash light; it will be called "apparent movement OKN." The threshold CLI between the type 1 and the type 2 response did not depend on drum velocities between 21.5 degrees/s and 71.3 degrees/s. The average gain of the apparent movement OKN was 0.83 +/- 0.04; gain and stability of slow phase eye movement velocity did not deviate systematically from the usually elicited OKN. OKAN after apparent movement OKN did not deviate from OKAN after constantly illuminated moving patterns. In response to the OKN initiation by a constantly illuminated pattern up to pattern velocities of 100 degrees/s, the OKN steady state gain was reached within the first 2 or 3 nystagmus beats. We ascribe the increase of the post-OKN with CLI and the existence of a threshold constant light interval to activity-accumulation in the common velocity-to-position integrator (velocity storage) of the brain stem. Loading of the velocity storage takes place after the OKN gain has already reached the steady-state value. Apparent movement OKN could also be elicited in guinea pigs that lack an effective smooth pursuit system. We suggest that apparent movement OKN is produced by mechanisms located in the brain stem.

Animals↗