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Biomedical subjects

J H Merritt

Publications and source records attributed to J H Merritt.

At least 37 records · Page 2Linked to original sources
PubMed1989

Thermal and physiological responses of rats exposed to 2.45-GHz radiofrequency radiation: a comparison of E and H orientation.

Ketamine-anesthetized Sprague-Dawley rats were exposed in both E and H orientations to far-field 2.45-GHz continuous-wave radiofrequency radiation (RFR) at a power density of 60 mW/cm2 (whole-body average specific absorption rate of approximately 14 W/kg). Intermittent exposures were performed in both orientations in the same animal to repeatedly increase colonic temperature from 38.5 to 39.5 degrees C. Tympanic, subcutaneous (sides toward and away from RFR source), and colonic temperature, ECG, arterial blood pressure, and respiratory rate were continuously recorded. The pattern of heat distribution within the animal and the physiological responses were significantly different between E- and H-orientation exposure. Irradiation in E orientation resulted in greater peripheral and tympanic heating, while irradiation in H orientation resulted in greater core heating. Heart rate and blood pressure increased significantly during irradiation and returned to baseline levels when exposure was discontinued; the increases were significantly greater in E than in H orientation. Respiratory rate increased significantly during irradiation in H, but not in E orientation. The physiological responses could have been influenced by the different levels or rates of subcutaneous and tympanic heating, or the differential between core and peripheral heating during E- and H-orientation irradiation. These results suggest that, when interpreting results of RFR exposure, animal orientation during irradiation must be considered.

Animals↗
PubMed1988

Orbital decompression for optic neuropathy secondary to thyroid eye disease.

To improve our management of optic neuropathy from thyroid eye disease, we have refined the external ethmoidectomy approach, which permits the removal of the medial orbital wall and adjacent floor. We now report our experience with six patients (11 eyes) selected for this surgical technique. These patients are part of a larger population of patients with thyroid eye disease who have been surgically managed by us over the last 6 years.

Adult↗
PubMed1985

Effects of 20-MHz radiofrequency radiation on rat hematology, splenic function, and serum chemistry.

In this study, Sprague-Dawley rats were exposed in a TEM chamber to 20-MHz (HF-band) continuous-wave radiofrequency radiation (RFR) for 6 hr/day, 5 days/week up to 6 weeks. The average E-field intensity was 2686 +/- 164 V/m (mean +/- SD) and the calculated specific absorption rate was 0.3 W/kg. Randomly sampled rats killed on Days 8, 22, 39, and 42 after initiation of exposure showed no statistically significant differences from controls for body mass, spleen cell density, erythrocyte and leukocyte counts, hematocrit, hemoglobin, methemoglobin, erythrocyte fragility, bilirubin, creatinine, SGPT, alkaline phosphatase, calcium, sodium, potassium, and spleen cell chemiluminescence. Splenic mass differences were statistically significant (p less than 0.05) only on Day 22. Spleen to body mass ratios differed significantly between exposed and control groups on Days 22 and 39 (P less than 0.05 and P less than 0.025, respectively). Histologic examination of the rats revealed the successive accumulation of phagocytic cells, lymphoid proliferation, development of lesions, and tissue necrosis characteristic of respiratory mycoplasmosis. In a followup experiment, a separate set of rats was exposed for 6 weeks to identical levels of RFR. No significant differences were found in splenic parameters and spleen cell peroxidative activity. Histologic examination of these animals revealed no evidence of mycoplasma infection. The observed differences between exposed and control animals of the first experiment appear to have resulted from subclinical respiratory mycoplasmosis rather than exposure to RFR.

Alanine Transaminase↗
PubMed1984

In utero exposure to microwave radiation and rat brain development.

Timed-pregnancy rats were exposed in a circular waveguide system starting on day 2 of gestation. The system operated at 2,450 MHz (pulsed waves; 8 microseconds PW; 830 pps). Specific absorption rate (SAR) was maintained at 0.4 W/kg by increasing the input power as the animals grew in size. On day 18 of gestation the dams were removed from the waveguide cages and euthanized; the fetuses were removed and weighed. Fetal brains were excised and weighed, and brain RNA, DNA and protein were determined. Values for measured parameters of the radiated fetuses did not differ significantly from those of sham-exposed fetuses. A regression of brain weight on body weight showed no micrencephalous fetuses in the radiation group when using as a criterion a regression line based on two standard errors of the estimate of the sham-exposed group. In addition, metrics derived from brain DNA (ie, cell number and cell size) showed no significant differences when radiation was compared to sham exposure. We conclude that 2,450-MHz microwave radiation, at an SAR of 0.4 W/kg, did not produce significant alterations in brain organogenesis.

Animals↗
PubMed1984

In utero exposure to low-level microwaves does not affect rat foetal development.

Forty pregnant Sprague-Dawley rats were used in a study to determine low-level microwave effects on foetal development. Animals were continuously exposed to 2450 MHz radiation from day 2 to day 18 of gestation, at a specific absorption rate of 0.4 W/kg. Foetuses were removed, weighed and measured. They were then either fixed in Bouin's fluid, sectioned at 6 microns, stained with hematoxylin and eosin and examined by light microscopy, or cleared and stained with alizarin red. No significant difference was noted with respect to foetal weight, length, resorption rate or abnormality rate.

Animals↗
PubMed1981

In vitro study of microwave effects on calcium efflux in rat brain tissue.

In this study we investigated the prospect of microwave-induced alteration of 45Ca2+ efflux from rat neural tissue at low pulse repetition frequencies and low power densities under in vitro conditions. Rat cerebral tissue, preloaded with 45Ca2+, was exposed to pulsed-microwave radiation (1-GHz carrier frequency) according to one of several PRF-power density exposure schemes: 16 Hz at 0.5, 1.0, 2.0, or 15 mW/cm2, or 32 Hz at 1.0 or 2.0 mW/cm2 average power density. Measurements of radioactivity in the efflux medium and in the tissue sample were used to calculate an efflux value for each sample. The results indicate that the radiation conditions used did not alter calcium efflux in rat brain tissue.

Animals↗
PubMed1981

Vitreous fluorophotometry: identification of sources of variability.

Slit-lamp vitreous fluorophotometry (VF) has been used by several investigators to document the early breakdown of the blood-ocular barrier. After an injection of fluorescein, levels of fluorescein in the vitreous humor are reported to be elevated in diabetic patients compared with controls even when there is no retinal pathologic condition discernible by angiography or ophthalmoscopy. We have examined the technique of VF in normal persons and have identified several potential sources of error in the determination of vitreous fluorescein levels. Fluorescein in the choroidal circulation significantly influences VF readings taken at the retinal surface and in the posterior vitreous. This effect is modulated by ocular pigmentation, with heavy pigmentation of dark-eyed normals more effectively screening out choroidal fluorescence than the light pigmentation of blue-eyed subjects. Influence of choroidal fluorescein extends toward the midvitreous, and the range of influence is directly related to the slit width of the exciting light. At narrow slit widths the effect is diminished but can never be completely eliminated. Blood fluorescein levels decrease with time, and since choroidal fluorescein contributes to VF values, the time after injection that VF reading are taken is a critical parameter.

Adult↗
PubMed1978

Studies on blood-brain barrier permeability after microwave-radiation.

Since the reported alterations of permeability of the blood-brain barrier by microwave radiation have implications for safety considerations in man, studies were conducted to replicate some of the initial investigations. No transfer of parenterally-administered fluorescein across the blood-brain barrier of rats after 30 min of 1.2-GHz radiation at power densities from 2--75 mW/cm2 was noted. Increased fluorescein uptake was seen only when the rats were made hyperthermic in a warm-air environment. Similarly, no increase of brain uptake of 14C-mannitol using the Oldendorf dual isotope technique was seen as a result of exposure to pulsed 1.3-GHz radiation at peak power densities up to 20 mW/cm2, or in the continuous wave mode from 0.1--50 mW/cm2. An attempt to alter the permeability of the blood-brain barrier for serotonin with microwave radiation was unsuccessful. From these studies it would appear that the brain must be made hyperthermic for changes in permeability of the barrier induced by microwave radiation to occur.

Animals↗
PubMed1977

Microwave fixation of brain tissue as a neurochemical technique- a review.

Microwave devices have been developed for rapidly inactivating brain enzymes by focusing the power output into the heads of small laboratory animals. The rapid inactivation achieved prevents postmortem changes and permits the measurement of neurochemicals such as acetylcholine at concentrations close to those obtained in vivo. The technique promises the assay of neurochemical parameters not possible before.

5-Hydroxytryptophan↗
PubMed1977

Orientation effects on microwave-induced hyperthermia and neurochemical correlates.

This paper describes the effect of field orientation on the hyperthermia produced by microwave irradiation. Rats exposed in the E-orientation (long-axis of animal parallel to E-field) to 1600 tmhz radiation become significantly hotter than those exposed in the H-field at the same power density. Norepinephrine and dopamine, but not serotonin content of the basal hypothalamus is reduced as a concomitant of microwave-induced brain hyperthermia.

Animals↗
PubMed1976

Radioimmunoassay technology in mass drug screening: an evaluation of an absorbent paper disk transport system.

These studies have demonstrated the feasibility of using urine-saturated paper disks in place of urine in the RIA system for drug abuse detection. Results with the disks are consistent with those using urine. A satisfactory procedure has been devised which provides reproducibility of results with no loss of sensitivity or specificity. Further, the procedure is essentially the same as the current procedure requiring urine except that a paper disk punched from a filter paper strip impregnated with urine is used. Complete flexibility is retained to switch from urine to disk. No new or additional equipment is required. It is envisioned that the urine would remain at the collection site and dried filter paper strips containing urine under test be shipped to toxicology laboratories. Sould the disk assay be positive, the urine specimen identified with that disk could then be shipped to the laboratory for confirmation by gas-liquid chromatography or other acceptable methods. The time and expense incurred in shipping large volumes of urine would thus be eliminated.

Clinical Trials as Topic↗
PubMed1975

A semiautomated radioimmunoassay for mass screening of drugs of abuse.

A rapid, semiautomated radioimmunoassay system for detection of morphine, barbiturates, and amphetamines is described. The assays are applicable to large drug abuse screening programs. The heart of the system is the automatic pipetting station which can accomplish 600 pipetting operations per hour. The method uses 15 to 30 mul or urine for the morphine and barbiturate assay and 100 mul for the amphetamine and combined morphine/barbiturate assays. A number of other drugs were tested for interference with the assays and the results are discussed.

Amphetamine↗