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Biomedical subjects

H P Schmidt

Publications and source records attributed to H P Schmidt.

11 recordsLinked to original sources
PubMed1993

The retinal irradiance and spectral properties of the multiport illumination system for vitreous surgery.

The multiport illumination system was developed as a fiberoptically illuminated pars plana cannula system for vitreous surgery. The retinal irradiance of the multiport illumination system and several other commonly used endoilluminators (light pipes) measured at 5 mm are comparable, ranging from 94 to 256 mW/cm2. In the actual surgical setting, however, the retinal irradiance of the multiport illumination system is far less (56 mW/cm2) because the end of the fiberoptic cables are fixated in the pars plana 16.5 mm away from the retinal surface. A reduction in the maximal intensity (100%) to 50% reduces the retinal irradiance by approximately two thirds to 3.7 mW/cm2. The light emitted by the multiport illumination system used in conjunction with a long-wave pass filter with a cutoff wavelength of 420 nm reduces the amount of short-wavelength light by one third to about 4% of the overall irradiance.

Eye Diseases↗
PubMed1989

Stability of WISC-R scores for a sample of learning disabled children.

The study was designed to assess the stability of WISC-R profiles of 36 learning disabled children given the WISC-R two times. The mean time between tests was 2.5 yr. The pattern reported for learning disabled children on Bannatyne's categories was evident for the group at both times, however, this pattern was not found for the majority of subjects. Analysis indicated a decrease over time in Verbal IQs, Full Scale IQs, and Bannatyne's Conceptual category, confirming previous findings. Possible reasons for the changes in scores are discussed.

Child↗
PubMed1984

Variations in WISC-R patterns of learning disabled children.

The WISC-R was administered to 19 learning disabled students at the time of diagnosis and following a period of time in special program placements. Group analyses indicated fluctuations between testing times in the Verbal and Full-Scale IQs and the V-P IQ discrepancies. Small but significant differences in Verbal, Performance and V-P scatter indices were observed at one or both testings in comparison to the normal standardization sample. Although the suggested group pattern for learning disabled children based on the Bannatyne categories was confirmed on both occasions, there was considerable variation for individual subjects.

Child↗
PubMed1979

Horseradish peroxidase as a label of injured cells.

The present study is concerned with artifacts likely to occur in a horseradish peroxidase exclusion test. Incubation of murine peritoneal macrophages and lymphocytes with the peroxidase showed a close relationship between the number of living cells and the percentage of cells excluding the tracer. The penetration of the cytoplasm by horseradish peroxidase is attributed to an increase in the permeability of the cell membrane during the incubation (ranging from 10 to 120 min). It was not increased by the presence of tracer throughout the incubation period. However, concomitant fixation of the cell in the presence of horseradish peroxidase caused an increase in the influx of the tracer. The horseradish peroxidase exclusing test applied to the guinea-pig organ of Corti has proved to be valid provided that: (a) mechanical lesions prior to the tracer incubation are avoided; (b) incubation is terminated by removal of the extracellular tracer; (c) fixation is carried out as soon as possible; (d) a low concentration of horseradish peroxidase is used; and (e) specimens are incubated in diaminobenzidine-H2O2 medium for the shortest possible period. Although fixation-induced cytoplasmic infiltration by horseradish peroxidase was not detected in cochlear specimens, the findings call attention to possible sources of error and define the level of significance of the test. Horseradish peroxidase does not appear to be a cytotoxic agent under the conditions used.

Animals↗
PubMed1979

[Cardiac effect of fenoterol alone or combined with Verapamil (author's transl)].

Two groups each consisting of twelve healthy students received Fenoterol (0,03 microgram/kg/min) alone or in combination with Verapamil (1,2 micrograms/kg/min) intravenously. In both groups, heart rate, arterial blood pressure amplitude and echocardiographically determined left ventricular contractility parameters increased significantly and equally. These results suggest that Verapamil does not counteract the positive chronotropic and inotropic effect of Fenoterol.

Adult↗
PubMed1978

Endolymphatic leakage in case of acute loss of cochlear microphonics.

Rapid loss of cochlear microphonics in guinea-pigs previously exposed to high-energy impulse noise was shown to be related to the breakdown of the endolymphatic boundary. The cochlear duct was rendered leaky by deterioration of the reticular membrane, and damage of sensory and supporting cells.

Animals↗
PubMed1978

[Peroxidase distribution pattern and cochlear microphonics in the impulse-noise exposed cochlea of the guinea pig (author's transl)].

Morphological findings evidenced the impulse noise trauma primarily a mechanical lesion of cells. The loss of mechanically damaged sensory cells results in the initial decline of cochlear microphonics. Due to mechanical lesions many sites of leakage in the wall of the cochlear duct give way to the diffusion of components of either lymph, which will produce a general functional disturbance associated with additional decline of microphonics. The functional restoration of the inner ear requires the previous repair of the endo/perilymphatic barrier.

Animals↗
PubMed1978

[Distribution pattern in the guinea pig cochlea of intravitally injected peroxidase].

Following perilymphatic perfusion and injection into the cisterna cerebello-medullaris, respectively, the distribution pattern of horseradish peroxidase in the cochlea of the guinea pig was studied light and electron microscopically. The findings prove effective tight junctions (zonulae occludentes) between the cells of the epithelial lining of the endolymphatic compartment. At the level of the reticular membrane the tight junctions are far more extended than elsewhere at the cochlear duct epithelium. From the findings a fairly rapid exchange is suggestive between the lymphatic space of the organ of Corti and the tympanic scale. Various types of cells of the cochlear duct actively take up considerable amounts of peroxidase. However, endocytosis of peroxidase by hair cells and particularly by the outer ones is rather scanty. Passive permeation of the tracer through the membran of undamaged hair cells was disproven.

Animals↗