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Biomedical subjects

D McCulloch

Publications and source records attributed to D McCulloch.

11 recordsLinked to original sources
PubMed1995

Clinical assessment, optic disk measurements, and visual-evoked potential in optic nerve hypoplasia.

PURPOSE: Because there is a broad spectrum of visual dysfunction in eyes with optic nerve hypoplasia, we determined whether any clinical observations, including optic disk measurements, could predict visual outcome in eyes with hypoplastic optic nerves. METHODS: We prospectively studied the eyes of 19 children (eight consecutive and 11 randomly selected), ages 7 to 92 months, in whom a diagnosis of optic nerve hypoplasia was made by an ophthalmologist. Clinical assessment included visual acuity, pupillary responses, and nystagmus. The ratio of the horizontal disk diameter to the disk-macula distance was calculated from fundus photographs. The amplitude and latency of the flash visual-evoked potential as well as the threshold response to pattern reversal checks were recorded. RESULTS: Visual acuity was associated with pupil reactivity, nystagmus, the ratio of the horizontal disk diameter to the disk-macula distance, pattern visual-evoked potential threshold, and flash visual-evoked potential amplitude (P < .001 for all parameters). All eyes with a ratio of the horizontal disk diameter to the disk-macula distance greater than .30 had good visual acuity, and all eyes with a ratio of the horizontal disk diameter to the disk-macula distance less than .30 had poor visual acuity. No eye with a ratio of the horizontal disk diameter to the disk-macula distance less than or equal to .15 had visual acuity better than light perception. CONCLUSIONS: Visual-evoked potential and photogrammetric measurement of relative disk size can be used to approximate visual acuity in eyes with optic nerve hypoplasia. This finding could lead to a diagnostic criterion or a severity classification for optic nerve hypoplasia.

Child↗
PubMed1986

Effect of low-level, 60-Hz electromagnetic fields on human lymphoid cells: I. Mitotic rate and chromosome breakage in human peripheral lymphocytes.

Dividing human peripheral lymphocytes from 10 normal adults (5 males and 5 females) were exposed in vitro to low level 60-Hz electromagnetic fields for 69 hours. The current density of the electrical field was 30 microA/cm2, while the magnetic field was either 1 or 2 gauss. The cytological endpoints measured were mitotic rate and chromosome breakage. No statistically significant differences, indicative of a field effect, were observed between treated and control cells whether exposed to an electric field, a magnetic field, or to various combinations of the two.

Adult↗
PubMed1986

The effect of low-level 60-Hz electromagnetic fields on human lymphoid cells. II. Sister-chromatid exchanges in peripheral lymphocytes and lymphoblastoid cell lines.

Dividing human peripheral lymphocytes from 10 normal adults (5 males and 5 females) as well as lymphoid cell lines from patients with the chromosomal instability syndromes were exposed to low-level 60-Hz sinusoidal electromagnetic fields (EMF). The current density of the electrical field was 30 microA/cm2 while the strength of the magnetic field was either 1 or 2 gauss. The cytological endpoints measured included the frequency of sister-chromatid exchanges per chromosome; the distribution of first-, second-, and third-division cells and chromosome breakage (lymphoblastoid cells only). No statistically significant differences, indicative of EMF effects were observed between the treated and control cells regarding SCE frequency, cell cycle progression or chromosome breakage.

Cell Line↗
PubMed1985

Far-field 2.45 GHz irradiation system for cellular monolayers in vitro.

A 2.45-GHz microwave exposure facility was developed for long-term TEM irradiation of cellular monolayers. Culture flasks with cells attached to the inside bottom surface were filled with medium, submerged in a 60 X 60 X 12-cm water bath on the field central axis, and exposed in the far-field 2 m below the ceiling-mounted antenna. A quarter-wave transformer plate increased the power transmitted into the water bath, and treatment temperatures were maintained by closed circulation with an external temperature control reservoir. Power density mapped below the quarter-wave plate indicated uniform TEM fields in the 25 X 25-cm region where flasks were located. With 1 kW of forward power to the antenna, the SAR [W/kg] = 45 exp(-0.607d) where d [cm] is the depth in water at any point within this area.

Animals↗
PubMed1984

Pseudoretinitis pigmentosa.

A 52-year-old black male with Duane's retraction syndrome and fundus pigmentation was examined. The patient had high hyperopia and reported ocular problems in other family members. A battery of tests indicated that the pigmentary anomalies were not due to retinitis pigmentosa.

Duane Retraction Syndrome↗
PubMed1982

Thin-layer liquid crystal thermometry of cells in vitro during hyperthermal microwave irradiation.

A nonperturbing technique of thin-layer liquid crystal thermometry was developed to quantitate heating of Chinese hamster ovary cells and the bacterium Serratia marcescens when exposed to 2450-MHz microwave fields at 0.2-0.5 W/cm2. Cells suspended in culture medium were injected into 5-cm glass microcapillary tubes coated on the inside with a thin layer of liquid crystal. The tubes were sealed and placed parallel to the electric field in a watertight waveguide exposure chamber where they were heated by circulating temperature-controlled water. Even at high circulation rates, liquid crystal color changes indicated local microwave capillary tube heating of 0.1-0.25 degrees C. Precision of measurement was 0.02 degrees C. Observations during microwave heating were significantly different from observations without microwaves at the 1% level, and heating increased as circulating water flow was reduced from 300 ml/s to 100 ml/s. The results of a cell survival assay following hyperthermal treatment were in good agreement with expectations based on the observations of microwave heating using liquid crystals.

Animals↗
PubMed1976

Microwave heating of malignant mouse tumors and tissue equivalent phantom systems.

Studies were conducted on the free-field heating of mammary tumors on the flank of mice and of tissue equivalent phantoms. A 200 watt, P.M., 2450 MHZ source was marginal in heating 1 cm tumors from room ambient to 38 degrees C. A technique was developed using warm air to raise the thermal baseline of the tumors to body core temperature and microwaves to produce significant hyperthermal levels. This allowed the production tumor temperatures of 45 degrees with greatly reduced microwave power and with significantly more uniform temperatures. However, the non-uniformity in temperature achieved with monodirectional microwave heating is still considered to be excessive: +/- 1 degrees C.

Animals↗