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Biomedical subjects

H A Kues

Publications and source records attributed to H A Kues.

9 recordsLinked to original sources
PubMed1999

Absence of ocular effects after either single or repeated exposure to 10 mW/cm(2) from a 60 GHz CW source.

This study was designed to examine ocular effects associated with exposure to millimeter waves (60 GHz). Rabbits served as the primary experimental subjects. To confirm the results of the rabbit experiments in a higher species, the second phase of the study used nonhuman primates (Macaca mulatta). First, this study used time-resolved infrared radiometry to assess the field distribution patterns produced by different antennas operating at 60 GHz. These results allowed us to select an antenna that produced a uniform energy distribution and the best distance at which to expose our experimental subjects. The study then examined ocular changes after exposure at an incident power density of 10 mW/cm(2). Acute exposure of both rabbits and nonhuman primates consisted of a single 8 h exposure, and the repeated exposure protocol consisted of five separate 4 h exposures on consecutive days. One eye in each animal was exposed and the contralateral eye served as the sham-exposed control. After postexposure diagnostic examinations, animals were euthanized and the eyes were removed. Ocular tissue was examined by both light and transmission electron microscopy. Neither microscopic examinations nor the diagnostic procedures performed on the eyes of acute and repeatedly exposed rabbits found any ocular changes that could be attributed to millimeter-wave exposure at 10 mW/cm(2). Examination of the primates after comparable exposures also failed to detect any ocular changes due to exposure. On the basis of our results, we conclude that single or repeated exposure to 60 GHz CW radiation at 10 mW/cm(2) does not result in any detectable ocular damage.

Animals↗
PubMed1993

Visual abnormalities associated with high-energy microwave exposure.

A 44-year-old man was accidentally exposed to high-energy microwave irradiation. After resolution of facial erythema and iritis, he noted a foreign body sensation and blurring of vision. Ophthalmoscopic examination showed bilateral, small hard drusen. Ancillary tests were consistent with abnormal cone function. Electroretinogram testing revealed a marked decrease in the flicker electroretinogram. Results of D15 and Farnsworth Munsel Hue 100 color tests were abnormal. Two years later, the patient's visual acuity was stable at 20/25 in both eyes; however, results of flicker electroretinogram test remain markedly decreased.

Adult↗
PubMed1992

Modification of membrane fluidity in melanin-containing cells by low-level microwave radiation.

The treatment of a B16 melanoma cell line with 2.45-GHz pulsed microwaves (10 mW/cm2, 10-microseconds pulses at 100 pps, 1-h exposure; SAR, 0.2 W/kg) resulted in changes of membrane ordering as measured by EPR (electron paramagnetic resonance) reporter techniques. The changes reflected a shift from a more fluid-like phase to a more solid (ordered) state of the cell membrane. Exposure of artificially prepared liposomes that were reconstituted with melanin produced similar results. In contrast, neither B16 melanoma cells treated with 5-Bromo-2-Deoxyuridine (3 micrograms/day x 7 days) to render them amelanotic, nor liposomes prepared without melanin, exhibited the microwave-facilitated increase of ordering. Inhibition of the ordering was achieved by the use of superoxide dismutase (SOD), which strongly implicates oxygen radicals as a cause of the membrane changes. The data indicate that a significant, specific alteration of cell-membrane ordering followed microwave exposure. This alteration was unique to melanotic membranes and was due, at least in part, to the generation of oxygen radicals.

Animals↗
PubMed1992

Increased sensitivity of the non-human primate eye to microwave radiation following ophthalmic drug pretreatment.

Previous studies in our laboratory have established that pulsed microwaves at 2.45 GHz and 10 mW/cm2 are associated with production of corneal endothelial lesions and with disruption of the blood-aqueous barrier in the non-human primate eye. In the study reported here we examined ocular damage in monkeys (M. mulatta and M. fascicularis) following topical treatment with one of two ophthalmic drugs (timolol maleate and pilocarpine) that preceded exposure to pulsed microwaves. Anesthetized monkeys were sham exposed or exposed to pulsed, 2.45 GHz microwaves (10 microseconds, 100 pps) at average power densities of 0.2, 1, 5, 10, or 15 mW/cm2 4 h a day for 3 consecutive days (respective SARs were 0.052, 0.26, 1.3, 2.6, and 3.9 W/kg). Immediately before microwave exposure, one or both eyes were treated topically with one drop of 0.5% timolol maleate or of 2% pilocarpine. Following administration of a drug, we observed a significant reduction in the power-density threshold (from 10 to 1 mW/cm2) for induction of corneal endothelial lesions and for increased vascular permeability of the iris. Diagnostic procedures (in vivo specular microscopy and fluorescein iris angiography) were performed following each exposure protocol. In addition, increased vascular permeability was confirmed with horseradish peroxidase tracer techniques. Although we did not measure intraocular temperatures in experimental animals, the results suggest that a mechanism other than significant heating of the eye is involved. Our data indicate that pulsed microwaves at an average SAR of 0.26 W/kg, if administered after pretreatment with ophthalmic drugs, can produce significant ocular effects in the anesthetized primate.

Administration, Topical↗
PubMed1985

Effects of 2.45-GHz microwaves on primate corneal endothelium.

Both eyes of anesthetized cynomolgus monkeys (Macaca fascicularis) were irradiated with 2.45-GHz microwaves, either pulsed or continuous wave. In vivo corneal endothelial abnormalities were observed by specular microscopy and confirmed through histologic techniques after a 16- to 48-hour postexposure period. Pulsed microwaves with an average power density of 10 mW/cm2 (equivalent to a specific absorption rate (SAR) = 2.6 W/kg) produced these effects, while levels of 20-30 mW/cm2 (equivalent to a SAR = 5.3 to 7.8 W/kg) with continuous wave irradiation were required to produce similar changes.

Animals↗
PubMed1984

Cross-polarization photography of the nerve fiber layer.

Cross-polarized photography was used to enhance the visibility of the arcuate bundles of the retinal nerve fiber layer ( NFL ). A fundus camera (Zeiss) was modified to accept a linear polarizing filter in front of the flash and another polarizing filter in front of the film plane. The azimuths of the two filters were kept at right angles to one another. Cross-polarized photographs were taken of the NFL of seven normal eyes and 18 eyes with ocular hypertension. The polarizers were rotated together to obtain four different orientations, equally spaced through 90 degrees. The manner in which visibility of the arcuate fibers was enhanced varied consistently with the orientation of the polarizing filters. Cross-polarization accentuated apparent defects in the NFL when compared with standard red-free illumination.

Adult↗
PubMed1983

High-resolution photography of the retinal nerve fiber layer.

Abnormalities in the appearance of the retinal nerve fiber layer can indicate the presence of optic nerve atrophy, but a major problem has been the difficulty of visualizing the nerve fiber layer in some individuals. By selectively illuminating the white nerve fiber layer in comparison with the red retinal pigment epithelium and choroidal background, red-free light increases the visibility of the nerve fiber layer. Compared with the standard red-free photographic technique, a 560-nm short-pass cut-off filter, used with extended-range, high-resolution, extremely fine-grain film (Kodak No. 2415 Technical Pan film), considerably enhanced the ability to resolve nerve fiber bundles.

Adolescent↗
PubMed1983

Posterior corneal rings in monkeys.

Contact wide-field specular microscopy was performed on 27 monkeys of known ages. The induction of posterior corneal rings as a result of applanation pressure to be age-dependent. There was a total absence of these folds in animals under two years of age, and they usually occurred only in animals older than four years of age.

Animals↗