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Biomedical subjects

M W Miller

Publications and source records attributed to M W Miller.

At least 289 records · Page 16Linked to original sources
PubMed1983

On the mechanism of 60-Hz electric field induced effects in Pisum sativum L. roots: vertical field exposures.

Roots of Pisum sativum L. were chronically exposed to 60-Hz vertical electric fields ranging from 150 to 450V/m in an aqueous medium whose conductivity was approximately 0.07 S/m. Control and exposed roots were grown concomitantly in the same tank whose medium was continuously circulated and maintained at 19 degrees C. The experiments were conducted blind. Root growth rates were determined daily and the mitotic index was determined for various intervals over a 24-h period, ranging from 12 h before to 12 h after electrode energization. Root growth rates were affected in a dose dependent relationship by exposures greater than 250 V/m. Mitotic indices were not affected by 150 V/m but were affected at 350 V/m; the former exposure did not alter root growth rates, the latter did. The growth rates of vertically exposed roots were compared to those of horizontally exposed roots; the former are more sensitive at a given field strength. The observations are consistent with the postulate that the electric field acts upon the cell through a perturbation of the transmembrane potential.

Analysis of Variance↗
PubMed1983

Absence of an effect of diagnostic ultrasound on sister-chromatid exchange induction in human lymphocytes in vitro.

The frequency of sister-chromatid exchanges in human lymphocytes cultured in vitro was not changed after a 30-min exposure to a 2 MHz focused, diagnostic ultrasound beam with a pulse repetition rate of 1000 Hz, 1 musec burst duration, 100 W/cm2 temporal peak, spatial peak intensity. These results are consistent with those obtained with a number of other cell types and are contrary to some previously reported effects for human lymphocytes.

Bromodeoxyuridine↗
PubMed1983

Anticoccidial derivatives of 6-azauracil. 5. Potentiation by benzophenone side chains.

Attachment of p-benzophenone side chains at N1 was found to be one of the most effective modifications for enhancing the potency of 6-azauracil against a broad spectrum of coccidia in chickens. Compound 20 was about 1000-fold more potent than 6-azauracil. Structure-activity relationships paralleled those found in a previously reported series of related analogues containing diphenyl sulfide and sulfone side chains. Drug metabolism studies showed the ketones to be reduced rapidly to carbinols, which are the prevalent species in vivo.

Animals↗
PubMed1983

Anticoccidial activity of 1-phenyluracils.

The minimum effective concentration (MEC) of 6-azauracil against Eimeria tenella when incorporated in feed is about 1000 ppm. Attachment of suitably substituted phenyl side chains at the 1-position reduces the MEC to less than 1 ppm. Uracil itself is devoid of anticoccidial activity, but side chains attached at the 1-position potentiate uracil and result in activity against E. tenella. Although effective at levels as low as 60 ppm, the 1-phenyluracils are less active than the corresponding 1-phenyl-6-azauracils. They also are less acidic.

Animals↗
PubMed1983

Response of multicell spheroids to 1-MHz ultrasonic irradiation: cavitation-related damage.

The response of EMT6/Ro single cells and multicell spheroids (150-800 microns diameter) to 1-MHz ultrasonic irradiation was determined for intensities of 0-5 W/cm2 for 1-5 min. Damage was assessed by evaluating both lysis and survival of individual spheroid cells, growth of whole spheroids, and the physical integrity of whole spheroids by histological and scanning electron microscopic techniques. The surviving fraction of spheroid cells was higher than that of single cells, and several of the intensity-duration combinations showed a statistically significant correlation between resistance to ultrasound and increased spheroid size. This resistance with size was also found in spheroid growth experiments. Histological sections showed that both peripheral and internal damage occur. The relationship of spheroid damage to studies of effects on tissues and possible therapeutic use of nonthermal ultrasound are discussed.

Animals↗
PubMed1982

The exposure vessel as a factor in ultrasonically-induced mammalian cell lysis--II. An explanation of the need to rotate exposure tubes.

This paper is an attempt to explain the need to rotate a polystyrene tube containing a cell suspension in order to obtain cell lysis. Calculations, based on known physical laws, were performed in order to determine the important forces on cells and bubbles and the movements and interactions which these forces are likely to cause. These calculations support the following conclusions: (1) in the absence of rotation, cells and bubbles larger than resonance size are trapped at pressure minima while bubbles smaller than resonance size are trapped at pressure maxima, (2) at 1 W/cm2 with rotation, lysis is caused by cells sweeping through arrays of trapped small bubbles, (3) at higher intensities lysis is caused by both trapped and non-trapped small bubbles.

Animals↗
PubMed1982

Ultrasonically induced nuclear aberrations in an in vitro multicellular tumour system.

Chinese hamster V-79 cells, attached to an acoustically transparent membrane and EMT6/Ro mouse mammary sarcoma cells as small multicellular spheroids or in suspension, were exposed to therapeutic intensities of 1 MHz ultrasound (0-10 W/cm2) and examined for the production of atypical nuclear or chromosomal aberrations. In the monolayer configuration no abnormalities occurred. In multicell spheroids or suspension cells 3 classes of abnormalities were found: (1) pyknotic/irregular nuclei; (2) lysed nuclei with extruding nucleoplasm; and (3) agglomerations which have an irregular shape and "fused" morphology similar to that which has been reported for plant tissues (Cataldo et al, 1973).

Animals↗
PubMed1981

Inhibition and recovery of growth processes in roots of Pisum sativum L. exposed to 60-Hz electric fields.

Roots of Pisum sativum L. were chronically exposed in aqueous inorganic nutrient medium to 60-Hz electric fields between 140 and 490 V/m (growth medium conductivity approximately 0.08 S/m). The growth rate, meristematic mitotic index, and growth rate recovery of the roots were determined. At 140 V/m there was no perturbation in growth rate or mitotic index. At 430 V/m the growth rate and the mitotic index were reduced. The mitotic index had a maximum depression (approximately 55% of control), which occurred at 4 h. The depression in growth rate was immediate and constant over time. When roots were exposed to an electric field at 430 V/m for 2 days, the growth rate was depressed by about 40%. When the field was terminated, the growth rate steadily increased and was almost normal after 5 days. At 490 V/m root growth rate was almost completely arrested. According to these results, there is a narrow range of induced membrane potentials that span the range from slightly altered to almost completely arrested growth rates.

Electromagnetic Fields↗
PubMed1981

Some effects of proctolin on the cardiac ganglion of the Maine Lobster, Homarus americanus (Milne Edwards).

The neuropeptide proctolin has excitatory effects on the isolated lobster cardiac ganglion. Selective application to the anterior cell body region produces a dose-dependent (10(-8)--10(-5) M) prolonged depolarization of large anterior cells as well as marked increases in burst frequency and/or duration. In ganglia which have been silenced with tetrodotoxin, proctolin application to anterior cells elicits long-lasting depolarizing responses which are accompanied by a 10-30% increase of the apparent membrane input resistance. Higher proctolin concentrations produce high-frequency trains of driver potentials. It is proposed that a proctolin like peptide may serve a neurohumoral role in the lobster cardiac ganglion and that the anterior motor neurons exhibit endogenous rhythmicity in its presence.

Animals↗
PubMed1981

Relationship of 60-Hz electric-field parameters to the inhibition of growth of Pisum sativum roots.

Roots of Pisum sativum were chronically exposed to 60-Hz electric fields ranging from 215--430 V/m and current densities from 1.5--2.7 mA/cm2. Adjustments of the exposure medium's conductivity (0.035--0.14 mho/m) allowed for distinction between a field or a current induced perturbation in root growth rates. Inhibition of root growth rates was directly related to the magnitude of the applied field and not the current density. The results are consistent with the postulate that the applied field acts upon the cell membrane and perturbs its function.

Cell Division↗
PubMed1981

Anticoccidial derivatives of 6-azauracil. 4. A 1000-fold enhancement of potency by phenyl sulfide and phenyl sulfone side chains.

We report further progress in exploiting our earlier discovery that the anticoccidial activity of 6-azauracil increases markedly when appropriately substituted benzyl or phenyl groups are attached at N-1. With guidance from previous structure-activity relationships and a multiple linear regression analysis, 6-azauracils containing phenyl sulfone or phenyl sulfide side chains were prepared. These prevented a broad spectrum of coccidial infections in chickens at minimum inhibitory concentrations by weight in feed as low as 0.25 ppm, a 4000-fold increase in potency over 6-azauracil, and had shorter plasma half-lives than earlier potent analogues. Sulfides were more potent than sulfones, although they were oxidized rapidly to sulfones in vivo.

Animals↗