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Biomedical subjects

M W Miller

Publications and source records attributed to M W Miller.

At least 271 records · Page 15Linked to original sources
PubMed1985

Diagnostic ultrasound and sister chromatid exchanges: failure to reproduce positive findings.

Human lymphocytes were exposed in vitro to ultrasound from two clinical devices, one of which was previously reported to have increased the frequency of sister chromatid exchanges. The ultrasonic exposures had no significant effect on the frequency of sister chromatid exchanges from three blood donors. Exposure to ultrasound also had no effect on cell cycle progression. A concomitant positive control (mitomycin C) resulted in a significant increase in sister chromatid exchanges.

Cell Cycle↗
PubMed1985

A cytohistological analysis of roots whose growth is affected by a 60-Hz electric field.

Roots of Pisum sativum were exposed for 48 h to 60-Hz electric fields of 430 V/m in an aqueous inorganic growth medium. The growth in length of the exposed roots was 44% of that for control roots. Root tips were analyzed for mitotic index and cell cycle duration. Mature, differentiated root sections from tissue produced after electrode energization were analyzed for cell lengths and number of files. The major reason for the observation that exposed roots are shorter than control roots is that cell elongation in the former is greatly diminished relative to controls.

Cell Cycle↗
PubMed1985

Growth rate and mitotic index analysis of Vicia faba L. roots exposed to 60-Hz electric fields.

Growth, mitotic index, and growth rate recovery were determined for Vicia faba L. roots exposed to 60-Hz electric fields of 200, 290, and 360 V/m in an aqueous inorganic nutrient medium (conductivity 0.07-0.09 S/m). Root growth rate decreased in proportion to the increasing strength; the electric field threshold for a growth rate effect was about 230 V/m. The induced transmembrane potential at the threshold exposure was about 4-7 mV. The mitotic index was not affected by an electric field exposure sufficient to reduce root growth rate to about 35% of control. Root growth rate recovery from 31-96% of control occurred in 4 days after cessation of the 360 V/m exposure. The results support the postulate that the site of action of the applied electric fields is the cell membrane.

Electromagnetic Fields↗
PubMed1985

The relationship between sensitivity to 60-Hz electric fields and induced transmembrane potentials in plants root cells.

Growth rates and cell diameters were determined from 12 species of plant roots exposed to a 60-Hertz (Hz) electric field of 360 Volts per meter (V/m) in an aqueous inorganic nutrient medium [conductivity: 0.07-0.09 Siemens per meter (S/m)]. The degree of growth depression ranged from zero to nearly 100 percent of control. Cell diameters ranged from 13.5 to 31.8 micron as an averaged value for procambial, cortical, and meristem cells. Sensitivity to the electric field as determined by root growth rate reduction increased with increasing cell size. Sensitivity also increased with increase in 60 Hz induced transmembrane potentials; the transmembrane potential threshold for growth reduction was about 6.0 mV and the potential for near-complete cessation of growth was about 10-11 mV. Two different hypothetical mechanisms of action by which applied electric fields induce biological effects at the cellular level were tested. The two mechanisms pertain to different possible modes of action of applied electric fields: one mechanism postulates the involvement of the transmembrane field, the other mechanism postulates the tangential electric field as the important factor for inducing biological effects. The data support the transmembrane and not the tangential field mechanism. It is concluded that the effects observed are consistent with a membrane related mechanism and that there is a narrow range (a few mV) between threshold and debilitating induced membrane potentials.

Electromagnetic Fields↗
PubMed1985

Cogeneration of retrogradely labeled corticocortical projection and GABA-immunoreactive local circuit neurons in cerebral cortex.

The times of origin of cortico-cortical projection neurons and local circuit neurons in rat visual cortex were determined. The birthdates of the projection neurons were assessed using a technique that combined retrograde labeling with lectin-bound horseradish peroxidase and tritiated thymidine autoradiography. The birthdates of some cortical local circuit neurons were determined by combining GABA immunocytochemistry with [3H]thymidine autoradiography. Double-labeled neurons (those with retrograde or immunoreactive label in their perikarya and autoradiographic silver grains over their nuclei) were born during the third week of gestation. Projection and local circuit neurons born on gestational day 14, 15, 17, 19 or 20 were located primarily in layer VIb, VIa, V, III or II, respectively. Thus, both populations of neurons are generated by parallel and concurrent inside-to-outside patterns.

Animals↗
PubMed1985

Dopaminergic modulation of neuromuscular transmission in the prawn.

The action of the putative crustacean neurohormone dopamine was examined in the fast extensor musculature of the prawn with intracellular and extracellular recording techniques. Dopamine produced a concentration-dependent (10(-7)-10(-5) M) decrease in the size of the excitatory junctional potential (e.j.p.). It had no effect on the muscle fibre resting membrane potential or input resistance. High concentrations (10(-5)M) of dopamine had no effect on the amplitude distribution or decay time of quantal unit currents, indicating that the agent does not act by blocking post-synaptic receptors or channels. Bath application of dopamine reduced the quantal content at single release sites with a similar time course and concentration dependence as that observed for the e.j.p. Dopamine had no effect on histograms of synaptic delays determined over a 10 degree C range, indicating that it does not modify the time course of phasic neurosecretion. Twin-impulse facilitation experiments showed a marked decrease in the duration of facilitation in the presence of dopamine. These results are interpreted according to recent theoretical and experimental findings as indicating that the dopamine-induced reduction in transmitter release is produced by a decrease in the entry of Ca during the nerve terminal action potential.

Action Potentials↗
PubMed1985

Failure of bone marrow cells to reconstitute T cell immunity in graft-vs-host mice.

A chronic GVH reaction (detected by T cell immune deficiency) was induced in unirradiated, adult (C57BL/10 X B10.A)F1 mice by injecting them i.v. with 3 X 10(7) B10.A parental spleen cells. Thirty-four days later, attempts were made to reconstitute the GVH immune-deficient mice by whole-body irradiation and repopulation with bone marrow cells from normal syngeneic F1 mice. The reconstituted mice were tested for CTL responses 147 and 272 days after repopulation with normal F1 bone marrow. These GVH/chimera mice remained immunoincompetent for at least 272 days for CTL responses to hapten-self and H-2 allogeneic antigens.

Animals↗
PubMed1984

Direct connections of rat visual cortex with sensory, motor, and association cortices.

Each division of rat visual cortex, areas 17, 18a, and 18b, has connections with sensory, motor, and association cortices. These corticocortical connections were sampled using anterograde autoradiographic and retrograde horseradish peroxidase labeling techniques. Area 17 is connected via reciprocal pathways with each division of visual cortex, the posterior one-third of motor area 8, association area 7, and posteroventral area 36 of temporal cortex. It also receives projections from perirhinal areas 13 and 35. Area 18a has reciprocal connections with areas 17 and 18b, a patch in posterior somatosensory area 3, and dorsal auditory area 41. Like area 17, area 18a receives afferents from and projects to the posterior one-third of motor area 8. The connections of area 18a with association cortices are extensive; these regions include parietal areas 7, 39, 40, and 14, posteroventral and dorsal area 36, and perirhinal cortex. Area 18b is connected with areas 17 and 18a, a patch in medial area 3, and dorsal area 41. There are reciprocal projections between area 18b and posterior area 8. As for association cortex, area 18b projects to frontal area 11, area 7, posteroventral and dorsal area 36, and perirhinal cortex. In addition, area 18b receives input from and projects efferents to the dorsal claustrum. Most of the interconnections among areas 17, 18a, and 18b originate from neurons in layers II, III, and V and end in terminal fields in layers I-III and V. In contrast, projections of other sensory, motor, and association cortices to visual cortex originate mainly from neurons in layer V and to a lesser extent from layer II. The reciprocal pathways from visual cortex terminate predominantly in the supragranular layers. In conclusion, these corticocortical pathways provide the basis for cortical visuosensory and visuomotor integration that may aid the rat in the coordination of visually guided behaviors.

Animals↗
PubMed1984

Heterotopic and homotopic callosal connections in rat visual cortex.

Heterotopic and homotopic callosal projections of rat visual cortex are evaluated. Callosal termination zones in visual cortex are identified with a degeneration technique following complete section of the corpus callosum. The zones which receive callosal afferents are the lateral one-third of area 17, an anteroposterior strip in dorsal and in ventral areas 18a, and 4 patches in area 18b. Following a large injection of lectin-bound horseradish peroxidase (WGA-HRP) into visual cortex, many retrogradely labeled neurons are found in the medial two-thirds of area 17 which does not receive callosal afferents, as well as in the lateral, callosal-recipient zone. These data suggest that heterotopic callosal pathways exist in visual cortex. Injections of tritiated amino acids into restricted parts of visual cortex show the following heterotopic connections: lateral area 17 projects to dorsal area 18a; medial area 17 projects to lateral area 17 and dorsal area 18a; area 18a projects to lateral area 17 and anteromedial area 18b; area 18b projects to lateral area 17, dorsal area 18a, heterotopic sites in area 18b, and to area 29d . Heterotopic connections are generally less dense than homotopic ones. In addition, heterotopic connections are generally less dense than homotopic ones. In addition, heterotopic projections terminate in the supragranular layers. This contrasts with the homotopic afferents of areas 17 and 18a which have additional strong projections to layer V. The distribution of label through the depth of the cortex in some of the callosal recipient zones has been quantified. Injections of WGA-HRP restricted to areas 17, 18a or 18b corroborate the presence of each of the heterotopic connections described above. Heterotopic afferents originate mostly from layer V neurons, whereas homotopic afferents arise from neurons primarily in layers II-V. Like the afferents, the numbers of callosal projection cells in heterotopic regions are substantially less than that in homotopic sites. heterotopic callosal connections may be one factor responsible for binocular vision and also may provide the basis for large, nonoriented receptive fields of units in layer V of rodent visual cortex.

Animals↗
PubMed1984

Dual effects of proctolin on the rhythmic burst activity of the cardiac ganglion.

The neuropeptide proctolin has distinguishable excitatory effects upon premotor cells and motorneurons of Homarus cardiac ganglion. Proctolin's excitation of the small, premotor, posterior cells is rapid in onset (5-10 s) and readily reversible (less than 3 min). Prolonged bursts in small cells often produce a "doublet" ganglionic burst mode via interactions with large motorneuron burst-generating driver potentials. In contrast to small cell response, proctolin's direct excitatory effects upon motorneuron are slow in onset (60-90 s to peak) and long-lasting (10-20 min). The latter include: a concentration-dependent (10(-9)-10(-7)M) depolarization of the somatic membrane potential; increases in burst frequency and enhancement of the rate of depolarization of the interburst pacemaker potential. Experiments on isolated large cells indicate: the slow depolarization is produced by a decrease in the resting GK and proctolin can produce or enhance motorneuron autorhythmicity . A two- tiered non-hierarchical network model is proposed. The differential pharmacodynamics exhibited by the two cell types accounts for the sequential modes of ganglionic burst activity produced by proctolin.

Animals↗
PubMed1984

Diagnostic insonation of extra utero human placentas: no effect of lymphocytic sister chromatid exchange.

Freshly delivered human placentas were exposed to ultrasound for 30 min using a diagnostic linear array unit. Blood was then drawn and cultured in the presence of bromodeoxyuridine, and the frequencies of sister chromatid exchanges (SCE) in the lymphocytes determined. There was no statistically significant difference in SCE frequencies between control and exposed cells; the frequencies of SCEs per cell ranged from 4.50 to 6.02 for control and from 4.66 to 6.10 for exposed cells in five separate experiments. Positive control mitomycin C treated cells were significantly affected, with more than 50 SCEs per cell.

Crossing Over, Genetic↗
PubMed1984

The postnatal growth of the callosal connections of primary and secondary visual cortex in the rat.

The growth of callosal projections is completed earlier in primary than in secondary visual cortex. In area 17, the areal and laminar distributions of callosal projections are mature by days 9 and 12, respectively, whereas in area 18b, these developmental milestones occur by days 12 and 15, respectively. This suggests that the pruning and infiltration of callosal axons follow different schedules in different cortical areas.

Animals↗
PubMed1984

A teleconference course for clinical laboratory personnel: a pilot project.

This article describes a pilot project teleconference course offering made possible through inter-institutional and intra-institutional cooperation. A continuing education program for clinical laboratory personnel was planned and delivered in six locations in northwest Illinois using teleconference equipment and a telelecture delivery mode. The program was evaluated by two techniques, a videotape interview with participants at one site and a mailed post-program form. Both evaluation methods are described. The evaluation results indicated that the majority of participants were receptive to the new instructional mode and would recommend it to their professional peers.

Area Health Education Centers↗
PubMed1984

Lack of effect of weak low frequency electromagnetic fields on chick embryogenesis.

Fertilised chicken eggs were incubated for 48 hours while exposed to pulsed trains of square wave magnetic fields having a duration of 0.5 msec and pulse repetition rates of 100 or 1000 Hz at magnetic field flux densities of 1.2 and 12 mu T. After exposure the embryos were scored blind for eight different gross structural features: primary vesicles, anterior neuropore, optic vesicles, auditory pits, truncal nervous system, heart, somites and blood vessels. There were no differences between exposed, sham-exposed and control eggs.

Animals↗
PubMed1984

Production of thymine base damage in ultrasound-exposed EMT6 mouse mammary sarcoma cells.

Mouse mammary sarcoma cells, line EMT6/Ro, were exposed for 1 min to 1 MHz continuous wave ultrasound over a range of intensities from 0.5 to 30 W/cm2 (spatial peak). The presence of thymine base damage (TBD) products of the 5,6-dihydroxydihydrothymine type was determined by an alkali degradation assay. Production of damage was found to be greatest (approximately 2.7 X 10(-3%) t'/T) at an intensity of 10 W/cm2 and fell off rapidly above and below this intensity. The amount of base damage produced at 10 W/cm2 ultrasound was approximately equivalent to the damage produced by a gamma-ray absorbed dose of 12 krad. Assay of cells immediately after sonication at 10 W/cm2 showed that approximately 14% of the cells had been lysed. Tests showed that it was the DNA of the intact cells, however, which sustained all of the TBD. Survival data demonstrated that of the remaining unlysed cell population approximately 5% were viable, whereas cells exposed to 12 krad showed no survival. Additionally, cells were exposed for up to 5 min at 5 W/cm2. An increase in TBD was demonstrated with increasing time of exposure such that the rate of production at 5 min was approximately three times greater than that of a 1-min exposure. TBD was found to be completely suppressed when cells were sonicated at 10 W/cm2 for 2 min under 4 bar of hydrostatic pressure. Addition of the radical scavengers beta-MEA and cystamine eliminated TBD but had minimal effect on survival. The pressure and scavenger experiments demonstrate that TBD results from cavitation-induced free radicals. Based on the values for both the half-life and diffusion distance of such radicals, our results indicate that at least part of the bubble collapse occurs intracellularly.

Animals↗
PubMed1983

Cortical connections between rat cingulate cortex and visual, motor, and postsubicular cortices.

The connections of rat cingulate cortex with visual, motor, and postsubicular cortices were investigated with retrograde and anterograde tracing techniques. In addition, connections between visual and the postsubicular (area 48) and parasubicular (area 49) cortices were evaluated with the same techniques. The following conclusions were drawn. Area 29 connections: Afferents to area 29 originate mainly from cingulate areas 24 and 25, visual cortex (primarily area 18b), motor cortex area 8, area 11 of frontal cortex, areas 48 and 49, and the subiculum. Efferent connections of area 29 within cingulate cortex and to visual areas differ for each cytoarchitectural subdivision of area 29. Thus, area 29c has limited projections both within cingulate cortex and to areas 48 and 49, while area 29d projects to these areas as well as to area 8, area 18b, and medial area 17. These visual cortex afferents originate mainly from layer V neurons of areas 29b and 29d, while areas 29a and 29c have virtually no projections to visual cortex. Area 24 connections: Afferents to area 24 originate primary from cingulate areas 25 and 29 and visual area 18b and medial area 17. Efferent projections of area 24a are distributed within cingulate cortex, while area 24b has more extensive projections to posterior cingulate and visual cortices. Area 24b is the cingulate subdivision which is both the primary recipient of visual cortex afferents as well as the source of most of the projections of anterior cingulate cortex to visual areas. Visual cortex has reciprocal connections with parts of the postsubicular and parasubicular cortices. Neurons of the internal pyramidal cell layer of both areas 48 and 49 project to areas 17 and 18b, while layers I and III of these parahippocampal areas receive projections from areas 17 and 8b. In conclusion, areas 29d have particularly extensive interconnections with visual cortex, while area 29d also maintains projections to area 8 of motor cortex. This connection scheme supports the view that cingulate cortex may have a role in feature extraction from the sensory environment, as well as in sensorimotor integration. Finally, the postsubiculum may be classified as a limbic association cortex in which extensive visual and cingulate efferents converge.

Animals↗