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Biomedical subjects

M W Miller

Publications and source records attributed to M W Miller.

At least 217 records · Page 12Linked to original sources
PubMed1990

Intracellular recording and injection study of corticospinal neurons in the rat somatosensory cortex: effect of prenatal exposure to ethanol.

The effects of prenatal exposure to ethanol on the structure and function of corticospinal neurons was investigated. The subjects were the 3-4-month-old offspring of hooded rats fed a nutritionally balanced liquid diet containing 6.7% (v/v) ethanol (Et), pair-fed a nutritionally matched isocaloric diet (Ct), or fed chow and water (Ch). Corticospinal neurons in primary somatosensory cortex were examined by intracellularly recording and filling cells that were driven by antidromic stimulation of the pyramidal decussation. In the control rats, corticospinal neurons comprised a homogeneous morphophysiological population. Morphologically, all of the antidromically driven cells examined were pyramidal neurons with cell bodies in layer Vb. The dendrites of these neurons were spinous and branched within layers I, IV, and V. Their axons arborized within layers IV, V, and VI and some collaterals extended laterally for distances up to 2.6 mm from the cell body. The mean conduction latency was 3.6 and 3.4 msec for Ch- and Ct-treated rats, respectively. In Et-treated rats, corticospinal neurons constituted a heterogeneous population. The laminar distribution of the corticospinal neurons in Et-treated rats was broad; the cell bodies of labeled neurons were in layers II, IV, V, and VI. The dendrites of layer Vb neurons were spinous; however, many of the spines appeared dysmorphic and the density of spines was significantly greater (32%) in Et-treated rats than in Ct-treated rats. Although the dendritic branching pattern for layer Vb neurons was similar to that described for the controls, a Sholl analysis showed that the complexity and extent of their dendritic trees were significantly greater in Et-treated rats. The axons of all layer Vb neurons in Et-treated rats had long horizontal processes that arborized in layers IV-VI, and some neurons also had an array of collaterals that ascended to layer I. The mean conduction latency for layer Vb neurons was 3.9 msec. The structure and function of ectopic neurons (those in layers II, IV, Va, Vc, and VI) in Et-treated rats differed markedly from those of the layer Vb neurons. Morphologically, the dendritic and axonal fields of these neurons were narrower than for the layer Vb neurons, and the ectopic neurons had a mean conduction latency of 7.1 msec. The heterogeneity of the population of corticospinal neurons in Et-treated rats may result from the effects of ethanol on early events in neuronal development such as neuronal generation and migration.

Animals↗
PubMed1990

Buccalin is present in the cholinergic motor neuron B16 of Aplysia and it depresses accessory radula closer muscle contractions evoked by stimulation of B16.

The accessory radula closer (ARC) buccal muscle motor neuron B16 is buccalin-immunoreactive and it synthesizes a peptide with chromatographic properties identical to those of buccalin. Terminal varicosities in the ARC muscle are buccalin-immunoreactive, and buccalin reduces muscle contractions evoked by stimulation of neuron B16, probably by a presynaptic action.

Animals↗
PubMed1990

Numbers of neurons and glia in mature rat somatosensory cortex: effects of prenatal exposure to ethanol.

Stereological methods were used to examine the consequences of prenatal exposure to ethanol on the structure of area 3, primary somatosensory cortex, of the mature hooded rat. Pregnant rats were fed a liquid diet containing 6.7% (v/v) ethanol (Et), pair-fed an isocaloric liquid control diet (Ct), or fed a diet of chow and water (Ch). Cresyl violet-stained sections of 3-month-old pups were examined. The corrected mean size of the cell bodies of neurons in layers other than layer V was significantly smaller in the Et-treated rats; conversely, the mean somatic size of glia in each layer was significantly larger in the Et-treated rats. The laminar cell packing density for neurons and glia, however, was similar in rats from both treatment groups. The overall volume of area 3 and the volume of individual layers were about 33% smaller in Et-treated rats than in the pair-fed controls. Thus, the estimated total number of neurons in Et-treated rats (1.79 X 10(6] was significantly fewer than in Ch-treated rats (2.77 X 10(6] and in Ct-treated rats (2.66 X 10(6]. The total number of glia also was about 30% fewer in Et-treated rats than in the controls. Not all layers were affected equivalently. The space occupied by the neuropil was significantly greater in Et-treated rats, but only in layers II/III, IV, and VI; hence, the cell body/neuropil ratio in these layers was less in Et-treated rats than in the controls. Therefore, microcephaly caused by prenatal exposure to ethanol results not only from a miniaturization of the brain, but also from a permanent abnormal organization of cerebral cortex.

Animals↗
PubMed1990

Cholinergic activation of the lobster cardiac ganglion.

The frequency of rhythmic burst activity of the isolated lobster cardiac ganglion is increased by exogenously applied acetylcholine and muscarinic agonists. Responses of individual motor neurons isolated from the ganglion by transection consist of a slow depolarization and repetitive bursting. The pharmacological profile of the receptors mediating this response is similar to that of vertebrate neuronal muscarinic receptors. Isolated ganglia incubated in the presence of [3H]-choline (18-19 h) exhibited radiolabelled acetylcholine accumulation. It is suggested that ganglionic excitation may be accomplished by extrinsic or intrinsic activation of muscarinic receptors on the motor neurons.

Acetylcholine↗
PubMed1990

Enhancement and stabilization of the production of glucoamylase by immobilized cells of Aureobasidium pullulans in a fluidized-bed reactor.

Glucoamylase production by Aureobasidium pullulans A-124 was compared in free-living cells, cells immobilized in calcium alginate gel beads aerated on a rotary shaker (agitation rate 150 rpm), and immobilized cells aerated in an air bubble column reactor. Fermentation conditions in the bioreactor were established for bead concentration, substrate (starch) concentration, calcium chloride addition to the fermentation medium, and rate of aeration. Production of glucoamylase was optimized at approximately 1.5 units of enzyme activity/ml medium in the bioreactor under the following conditions: aeration rate, 2.0 vol air per working volume of the bioreactor (280 ml) per minute; gel bead concentration, 30% of the working volume; substrate (starch) concentration, at 0.3% (w/v); addition of calcium chloride to the medium at a final concentration of 0.01 M. Productivity levels were stabilized through the equivalent of ten batches of medium with the original inoculum of immobilized beads.

Alginates↗
PubMed1990

Proportionality of ELF electric field-induced growth inhibition to induced membrane potential in Zea mays and Vicia faba roots.

The postulate that 60-Hz electric field-induced bioeffect severity is proportional to induced transmembrane potential [Vmi] magnitude was tested and supported using a plant root model cell system. Statistically significant correlations were obtained upon regression of the relative rates of exposed Vicia faba and Zea mays root segment growth on the average Vmi (calculated) arising in those segments under specified 60 Hz field exposure conditions. The Vmi associated with the apparent threshold for growth inhibition was similar in Zea and Vicia roots (2.5 vs 2.4 mV, respectively). At Vmi greater than this threshold, Zea root growth declined by about 9% per mV, and Vicia root growth by about 19% per mV induced potential.

Electricity↗
PubMed1990

Time lapse and microscopic examinations of insonated in vitro cells.

A fibroblast cell line (Balb/c 3T3) was sham/exposed to ultrasound (2.2 MHz resonant frequency, 35.4 W/cm2 SPTP, 3 microseconds pulse duration, 200 Hz prf) for 30 min and subsequently scored for cell motility and alterations in cell morphology. Cell motility was assessed by computerized tracking of cells. Cell morphology ("normal" or "abnormal") was determined blindly by three independent scorers. A positive control (1-4 Gy) yielded statistically significant alterations in cell motility and morphology; no such differences were observed for the ultrasound regimen. The results thus fail to confirm an earlier report by Liebeskind et al. (Brit. J. Cancer 45(Suppl. V):176-186; 1982) of ultrasound-induced alterations in cell motility and morphology.

Animals↗
PubMed1990

Confirmation of an ultrasound-induced mutation in two in-vitro mammalian cell lines.

In-vitro V79 and L5178Y cells were exposed in a rotating test tube to continuous-wave (CW) 1 MHz 35 W/cm2 ultrasound (0-4 or 0-3 min, respectively) and subsequently assayed for mutation as evidenced by resistance to 6-thioguanine (6-TG). There was a modest but statistically significant increase in mutation frequency in both cell types with increase in ultrasound exposure duration. X-ray exposures (3-9 Gy, a "positive control") yielded a large increase in 6-TG resistance. The data support an earlier report by Kaufman (1985) of an ultrasound-induced increase in mutation to 6-TG resistance in in-vitro mammalian cells.

Analysis of Variance↗
PubMed1990

Lysis of cells in Elodea leaves by pulsed and continuous wave ultrasound.

Resonance lysis of the cells in the leaves of the aquatic plant Elodea originally reported by Miller have thresholds at intensities of a few W/cm2. With pulsed ultrasound, the resonance behavior vanishes and the thresholds are at much higher amplitudes. This is similar to the characteristics of the thresholds for killing of Drosophila larvae by pulsed ultrasound. Both organisms contain small gas bodies within the tissues which may serve as nuclei for a cavitation related phenomenon. The results suggest that the response of these bubbles to continuous wave fields and very short pulses is qualitatively different.

Cell Survival↗
PubMed1990

Effects of ingested lead on antibody production in mallards (Anas platyrhynchos).

We examined the effects of lead ingestion on in vitro and in vivo indices of immune function in mallards (Anas platyrhynchos). Twenty-four mallard drakes were randomly divided into three groups (I, II, III), then assigned to treatment or control subgroups (n = 4). On day 0, all treatment birds were dosed orally with one number 4 lead shot (mean = 0.2 g). We challenged all individuals in each group with washed sheep red blood cells (SRBC) injected intraperitoneally on days 0 (Group I), 7 (Group II) or 14 (Group III), and collected blood for analyses 7 and 8 days after SRBC challenge. We measured and compared blood lead concentrations, in vitro lymphocyte transformation responses to phytohemagglutinin A and lipopolysaccharide, and hemagglutination titers to SRBC. Mean blood lead concentrations were elevated (P less than or equal to 0.04) in treatment birds at each sampling period. Large individual variability in lymphocyte stimulation responses precluded further analysis of those data. Hemagglutination titers to SRBC were lower (P less than 0.0001) in lead-poisoned ducks than in controls, suggesting that ingested lead may have immunosuppressive effects on mallards.

Animals↗
PubMed1990

60-Hz electric field exposure inhibits net apparent H(+)-ion excretion from excised roots of Zea mays L.

Plant root model cell systems have provided insight into the biophysical mechanism by which extremely low frequency electric fields (EF; f less than or equal to 100 Hz) affect nonexcitable eukaryotic cells. The evidence indicates that the plasma membrane is the site of interaction with applied extremely low frequency EF, and that cells respond to field exposure via a sensing mechanism involving the induction of extremely low frequency membrane potentials (Vim). We suggest a mechanism by which Vim may be transduced into EF-induced root growth inhibition. Suspensions of excised Zea root tips were used to test the hypothesis that growth-inhibiting extremely low frequency EF exposures inhibit net H+ excretion from protoplasts, a process mediated by a plasma membrane H(+)-ATPase which is intimately involved in cellular extension. Rates of acidification of root tip suspensions were measured as an analog for net H+ efflux. The experimental results support this hypothesis. At the apparent threshold for inhibition of H+ excretion, the associated 60-Hz EF strength was about 220 V.m-1 (root mean square). Estimates of Vim associated with inhibition of net H+ excretion are in agreement with those known to affect Na+/K+ transport in human erythrocytes.

Adenosine Triphosphatases↗
PubMed1990

Repetitive pulsed-train "off" duration mitigates reductions in root growth rates of Pisum sativum L. induced by 60-Hz electric field.

An investigation was undertaken to define a 60-Hz electric field exposure system which would affect a eukaryotic cell system while mitigating a potential thermal rise. The biological effectiveness of pulsed 60-Hz electric fields on a cell system of defined sensitivity to continuous-wave 60-Hz electric fields was sought. Roots of garden pea (Pisum sativum L.) were exposed to pulsed trains of 60-Hz, 430 V/m electric fields. The "on" time was constant at 1 s and the "off" time varied. The repetitive on:off regimens used were 1:20, 1:50, 1:100, 1:130, 1:200, and 1:300. With continuous or 1:20 pulsed fields the growth response was equivalent (representing a 60% depression in root growth rate). The severity of the growth effect diminished as the off time increased; for the 1:100 regimen, the relative growth rate was depressed by about 30%; for the 1:300 regimen, the relative growth rate was equal to that of the controls.

Electromagnetic Fields↗
PubMed1989

Effects of prenatal exposure to ethanol on neocortical development: II. Cell proliferation in the ventricular and subventricular zones of the rat.

Prenatal exposure to ethanol alters the generation of neocortical neurons; ethanol reduces the numbers of neurons generated between gestational day (G) 12 and G19 but paradoxically increases neuronogenesis after G19. The present study used [3H]thymidine autoradiography to examine the effects of ethanol on the proliferation of cells in the two cortical germinal zones, the ventricular and subventricular zones. Pregnant rats were fed one of three diets: a liquid ethanol-containing (6.7% v/v) diet (Et), a nutritionally matched isocaloric liquid diet (Ct), or chow and water (Ch). Fetuses were administered with [3H]thymidine on G13, G17, or G20 and killed 45-60 minutes later. Autoradiographs were prepared to identify radiolabeled and mitotic cells. Additional brains from 13-23-day-old fetuses were processed for cytoarchitectonic analyses. The size of the lateral ventricles in the fetuses was not significantly affected by the prenatal exposure. Both the ventricular and subventricular zones were evident throughout the period from G13 to G23. In all three groups, the ventricular zone was thickest from G13 to G17, but from G15 on, the ventricular zone of Et-treated fetuses was significantly thinner than those of either controls. On G13, G17, and G20, the labeling index (the ratio of radiolabeled cells to the total population) was significantly less in Et-treated fetuses. The mitotic index was similar in Et-, Ch-, and Ct-treated fetuses. The subventricular zone of all fetuses was most prominent during later fetal ages and it was thicker in Et-treated fetuses than in controls. Moreover, the labeling and mitotic indices for the subventricular zone of Et-treated rats were significantly greater than for controls. Thus, ethanol had different effects on the two neocortical germinal zones: the proliferation of ventricular cells was inhibited, whereas the proliferation of subventricular cells was stimulated. These data suggest that ethanol-induced changes in neuronogenesis result from alterations in proliferative activity.

Animals↗
PubMed1989

Functional and phenotypic alterations in T cell subsets during the course of MAIDS, a murine retrovirus-induced immunodeficiency syndrome.

The functional and phenotypic characteristics of Ly-4(CD4)+ and Ly-2(CD8)+ T cells were studied after induction of murine AIDS with LP-BM5 murine leukemia virus. Assays of spleen cells for their ability to generate in vitro CTL responses to TNP-modified autologous cells (self + x CTL) and to alloantigens (allo CTL) showed that self + x CTL responses were greatly impaired at 3 to 4 wk postinfection and were undetectable thereafter. Allo CTL responses were normal at 3 to 4 wk, but were reduced at 8 to 9 wk and absent at 14 wk postinfection. This sequential loss of self + x and allo CTL responses was related to a selective defect in Ly-4(CD4)+ Th cell function associated with impaired production of IL-2 and deficient proliferative responses to Con A or to soluble Ag. Changes in the functional characteristics of Ly-4(CD4)+ T cells were unrelated to changes in their frequency in spleen, but did correlate with marked alterations in their distribution among four subsets defined by mAb SM3C11 and SM6C10. Assays of CTL responses generated by mixtures of spleen cells from normal and infected mice suggested that active suppression of Ly-4(CD4)+ Th function may contribute to this defect. Studies of Ly-2(CD8)+ T cells showed that infection with LP-BM5 murine leukemia virus also induced a major phenotypic shift in subpopulations defined by their reactivity with mAb 6C10. However, this phenotypic change did not appear to correlate with major functional defects.

Animals↗
PubMed1989

Structure and histogenesis of the principal sensory nucleus of the trigeminal nerve: effects of prenatal exposure to ethanol.

Clinical and experimental evidence shows that prenatal exposure to ethanol causes craniofacial malformations, microcephaly, and abnormal development of the central nervous system. This study describes the effects of ethanol on the development of the principal sensory nucleus of the trigeminal nerve (PSN). The offspring of two groups of rats were examined. Pregnant females in one group were fed a liquid diet containing 6.7% (v/v) ethanol (Et) and rats in the other group were fed an isocaloric liquid control diet (Ct). Each pregnant rat was administered [3H]thymidine on one day during the period from gestational day (G) 10 to G22. After pups grew to 30 days of age, they were killed and their brains were processed by an autoradiographic procedure. Qualitatively, the PSN of Ct- and Et-treated rats appeared similar; they were composed chiefly of small neurons and a few scattered large neurons. On the other hand, quantitative analyses revealed significant differences between both groups. Although the volume of the PSN of Et-treated rats was not significantly different (-3.2%) than that for Ct-treated rats, the PSN of Et-treated rats had significantly (P less than 0.01) fewer (30.0%) neurons than did the PSN of Ct-treated rats. The number of the small neurons, but not of the large neurons, was affected most by the ethanol exposure. Prenatal exposure to ethanol also altered the generation of PSN neurons. Most neurons in the PSN of Ct-treated rats were born between G12 and G15, the small neurons being generated before the large neurons. In Et-treated rats, too, small neurons were born before the large neurons; however, the time frame of neuronogenesis was delayed as it occurred between G13 and G16. Thus, prenatal exposure to ethanol produces profound developmental abnormalities that lead to permanent alterations in the structure of the mature central nervous system.

Animals↗
PubMed1989

Transient expression of Alz-50 immunoreactivity in developing rat neocortex: a marker for naturally occurring neuronal death?

Alz-50-immunoreactive neurons were evident in the subplate and cortical plate of the neonatal rat, but immunoreactivity was lost by the beginning of the second postnatal week. Many of these neurons were double-labeled by an injection of [3H]thymidine on gestational day (G) 12. Moreover, subplate neurons that were generated on G12 were eliminated from cortex by the end of the third postnatal week. Thus, Alz-50 immunoreactivity may be an early indicator of naturally occurring neuronal death.

Animals↗