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M W Miller

Publications and source records attributed to M W Miller.

At least 235 records · Page 13Linked to original sources
PubMed1989

Effect of prenatal exposure to ethanol on the ultrastructure of layer V of mature rat somatosensory cortex.

Recent data have shown that the structure and function of layer V pyramidal neurons, e.g. corticospinal neurons, is altered by prenatal exposure to ethanol. We examined the effect of ethanol on the ultrastructure of layer V in somatosensory cortex. Timed pregnant rats were fed a diet containing 6.7% (v/v) ethanol (E) or pair-fed a nutritionally matched control diet (C). Thirty-day-old offspring of these mothers were prepared by standard electron microscopic techniques. The somata of pyramidal and local circuit neurons and the neuropil were analysed. Prenatal exposure to ethanol induced alterations in the somata of both populations of neurons. The parallel stacking of cisternae characteristic of C-treated rats was disorganized in E-treated rats. Moreover, the Golgi complex and lysosomes occupied a larger fraction of the somata of E-treated rats. The number and frequency of symmetric axosomatic synapses, but not asymmetric axosomatic synapses, formed by both types of neurons were significantly greater in E-treated rats. Gestational exposure to ethanol produced a variety of changes in the neuropil. Dendrites, particularly dendritic shafts, occupied less space in E-treated rats. In contrast, axons accounted for significantly more of the neuropil in E-treated rats than in controls. This increase in axonal space was due to a significantly greater coverage by non-myelinated axons and a significantly smaller coverage by myelinated axons in E-treated rats than in C-treated rats. Although the overall frequency of synapses was similar in both treatment groups, there were significantly more asymmetric synapses in E-treated rats, and most of these were axospinous synapses. These differences may contribute to documented physiological changes such as the lower rate of glucose utilization in layer V of somatosensory cortex of E-treated rats and they may underlie the mental retardation which is characteristic of children with foetal alcohol syndrome.

Animals↗
PubMed1989

Bromodeoxyuridine immunohistochemical determination of the lengths of the cell cycle and the DNA-synthetic phase for an anatomically defined population.

A cumulative labelling protocol using 5-bromo-2'-deoxyuridine (BUdR) was followed to determine: (1) the growth fraction (i.e., the proportion of cells that comprise the proliferating population), (2) the length of the cell cycle, and (3) the length of the DNA-synthetic phase (S-phase) for proliferative cells in the dentate gyrus of the mouse. On postnatal day 20 (P20), C57BL/6J mice were injected with BUdR at two hour intervals for a total period of 12 hours. Animals were sacrificed at selected intervals, and the brains were processed for immunohistochemistry using a monoclonal antibody directed against single-stranded DNA containing BUdR. The numbers of BUdR-labelled and unlabelled cells in sections through the hilus of the dentate gyrus were counted. The number of BUdR-labelled cells increased linearly from an initial value of about 12% of the total number of cells to a maximum value of just over 24% of the total. These findings indicate that, at P20, a maximum of 24.2 +/- 1.2% of the cells in the dentate hilus are part of the proliferating population. The calculated length of the cell cycle of the cells comprising the intrahilar proliferative zone was estimated to be 16.1 +/- 0.8 h. The length of the S-phase was estimated at 8.0 +/- 0.4 h. In addition, mathematical analysis, using one and two population models, indicates that over 90% of the proliferating cells in the dentate hilus at this age comprise a single population at least in terms of the lengths of the cell cycle and the S-phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Confirmation of the protective effect of cysteamine in in vitro ultrasound exposures.

Armour and Corry (Radiat. Res. (1982) 89 369-380) reported that ultrasound-induced damage to in vitro Chinese hamster ovary cells was significantly reduced in the presence of cysteamine. The objective of this study was to attempt verification of this result. Four series of experiments were undertaken using in vitro cell suspensions, namely: (1) determination of the effect of cysteamine concentration on cell growth; (2) determination of the temperature dependence of ultrasonically induced cell damage; (3) determination of a dose-response relationship for the cytotoxicity of cysteamine; and (4) assessment of cell integrity and reproductive capacity in the presence or absence of cysteamine during ultrasonic exposure. Ultrasound parameters included a resonance frequency of 1 MHz, a continuous wave exposure duration of 5 min, and intensities from 0 to 21.6 W cm-2. The results indicated a dependence of ultrasound's efficacy on the medium's temperature during insonation and a significant reduction of ultrasound efficacy in compromising cellular integrity in the presence of cysteamine.

Animals↗
PubMed1989

Sister chromatid exchanges in Chinese hamster ovary cells exposed to high intensity pulsed ultrasound: inability to confirm previous positive results.

This study was undertaken in an attempt to determine a physical mechanism of action for a recently published report of a small but statistically significant increase in sister chromatid exchanges (SCEs) in Chinese hamster ovary cells exposed to high-intensity pulsed ultrasound. The "positive" report's protocol involved a sizeable chance of ultrasound beam impingement on the side wall of the cell exposure chamber. Ten experiments per regimen were conducted; the regimens included exposures of (a) chamber center, (b) chamber wall, (c) nine grid sites, 0.5 mm between sites, and (d) nine grid sites, 1.5 mm between sites. The last was an exact replication of the conditions previously reported to induce the small SCE effect. The results did not support the postulate of an increase in SCEs with the ultrasound exposures.

Animals↗
PubMed1989

Biological consequences of hyperthermia.

Because of the potential for certain modalities of clinical ultrasound to cause tissue heating, it was deemed important to survey the literature for reports on temperatures and hyperthermia exposure durations at which biological effects occur in a wide spectrum of organisms. In general the higher the temperature or the longer the hyperthermia exposure, the greater the chance for observing a perturbation to the biological system. Special attention was given to ascertaining temperature exposure conditions below which no biological effects have been reported. The physical mechanism(s) by which heat produces biological effects is(are) not known but substantial quantities of empirically derived data have allowed for the calculation of exposure temperature-duration equivalences. It appears reasonably well established that short exposures to sharply-elevated temperatures result in a protective effect against further thermal insult; the generation of heat shock proteins by cells coincides with the onset of such "thermal protection." The information contained in this review indicates an absence of reported effects in animals below 39 degrees C.

Animals↗
PubMed1989

A test of I2t as a dose parameter for fetal weight reduction from exposure to ultrasound.

It has been suggested that fetal weight reduction by ultrasound exposure is linearly related to the dose parameter I2t, where I is the intensity and t the exposure time. A direct test of the concept was conducted using CF-1 mice. No effect on fetal weight was found at values of the dose parameter large enough to produce measurable heating in the fetal and maternal tissues.

Animals↗
PubMed1989

An explanation for the decrease in cell lysis in a rotating tube with increasing ultrasound intensity.

Previous observations indicate that for in vitro mammalian cells insonated in rotating test tube the amount of cell lysis initially increases to some maximum and then decreases with further increase in ultrasound exposure. The results of the present investigation support the postulate that the reduction in cell lysis with increase in ultrasound intensity is related to the development of an ultrasonically induced "cloud" of bubbles in the fluid between the transducer and test tube; these bubbles mitigate against acoustic transmission thus reducing cell lysis in the insonated test tube.

Animals↗
PubMed1989

Snakebite in captive Rocky Mountain elk (Cervus elaphus nelsoni).

Eight cases of snakebite occurred in seven of 11 captive Rocky Mountain elk (Cervus elaphus nelsoni) during June and July 1987. Severity of reactions to envenomation varied; affected elk presented with combinations of signs that included painful swelling restricted to the face and muzzle, submandibular edema, inspiratory dyspnea, epistaxis, frothy, blood-tinged nasal discharge, epiphora, anorexia and anxiousness or depression. We observed puncture wounds in only two cases. Treatment consisted of dexamethasone (about 0.1 mg/kg subcutaneously, single dose) and procaine penicillin G (about 25,000 IU/kg subcutaneously, once or twice daily, for 5 to 6 days), as well as revaccination using clostridium and tetanus toxoids. Swelling resolved and elk recovered in 3 to 5 days without complications. Using immunodiffusion, we detected serum antibodies to prairie rattlesnake (Crotalus viridis viridis) venom in six of seven affected elk, demonstrating seroconversion in three cases and anamnesis in one elk bitten twice. Venom was undetectable in any serum samples using similar techniques.

Animals↗
PubMed1989

Echocardiography: principles of interpretation.

Doppler echocardiography allows the serial, noninvasive collection of quantitative hemodynamic information. When coupled with the results of physical examination, thoracic radiographs, ECG, and routine cross-sectional and M-mode echocardiogram, DE helps identify the nature as well as the severity of cardiac disease. As more experience is gained with DE, more applications will be discovered and the indications for more invasive diagnostic tests including cardiac catheterization will diminish.

Animals↗
PubMed1989

Emil M. Mrak.

Explore the source record for details and available documents.

California↗
PubMed1989

Proportionality of 60-Hz electric field bioeffect severity to average induced transmembrane potential magnitude in a root model system.

The postulate that electric field-induced bioeffects in the root model system are related to the induction of 60-Hz transmembrane potentials (Vim) was quantitatively tested. Root segment growth rate data and the calculated mean 60-Hz Vim which would arise in the cortical cells of a segment under specified exposure conditions were subjected to regression analysis. Statistically significant correlations between segmental growth rate and segmental-average Vim were obtained using data analyzed (1) within species at a constant applied field strength, (2) within species and pooled across field exposures, and (3) pooled across both species and exposures. In C. sativus roots, segmental growth is inhibited when segmental-average Vim attain a value of 3.4-3.6 mV. In C. maxima roots, growth inhibition occurs when Vim attain or exceed 2.3-2.7 mV. Segmental growth cessation is predicted to occur when segmental-average Vim exceed 7-9 mV.

Cell Physiological Phenomena↗
PubMed1988

Structural and metabolic alterations in rat cerebral cortex induced by prenatal exposure to ethanol.

The effects of prenatal exposure to ethanol on glucose utilization in specific laminae of mature rat cerebral cortex were examined. Pregnant hooded rats were fed a liquid diet containing 35% ethanol-derived calories (E) or pair-fed an isocaloric liquid control diet (C) on gestational days 7-21. The cytoarchitecture of motor areas 4 and 6/8 and of somatosensory areas 3 and 2 of 105 day old, male pups was examined in Cresyl violet-stained sections. The glucose utilization of these cortical regions was assessed using a 2-deoxyglucose autoradiographic technique. Overall, cortex was significantly thinner (5-10%) in E-treated rats than in C-treated rats, but with few exceptions, the thickness of individual laminae was not significantly affected by prenatal treatment. Despite these small structural differences, the overall glucose utilization in areas 4, rostral 6/8 3, and 2 of E-treated rats was significantly less (21-24%) than in C-treated rats. Layer IV was the most affected by the prenatal ethanol exposure (29%) and layers I and VI were the least affected (14-22%). The metabolism of caudal area 6/8 was not significantly affected by gestational exposure to ethanol. These results indicate that thalamic and callosal connections and corticospinal projection neurons are specifically affected by prenatal exposure to ethanol. Such alterations may underlie the learning deficits and motor dysfunction characteristic of fetal alcohol syndrome.

Animals↗
PubMed1988

Maturation of rat visual cortex: IV. The generation, migration, morphogenesis, and connectivity of atypically oriented pyramidal neurons.

The generation, migration, and morphogenesis of atypically oriented pyramidal neurons in the rat visual cortex were examined. In the mature cortex, these neurons were distributed through layers II-VI. Moreover, the atypically oriented pyramidal neurons in a particular layer tended to be oriented in a specific way; atypically oriented pyramidal neurons in layer II, layers III-VIa, and layer VIb were obliquely, radially, and obliquely oriented, respectively. Ultrastructurally, the somata of atypically oriented pyramidal neurons contained large euchromatic ovoid nuclei and cytoplasm that was replete with rough endoplasmic reticulum and Golgi apparatus. These somata formed only symmetric axosomatic synapses. Many atypically oriented pyramidal neurons projected axons into the white matter as demonstrated by a Golgi method and by a retrograde tract-tracing technique; however, some of these pyramidal neurons in layers III-V had axons that ascended to layer I. By using a technique which combined retrograde tract tracing with [3H]thymidine autoradiography, it was determined that most atypically oriented pyramidal neurons in layers V and VIa, layer IV, and layer II were generated on gestational days (GD) 15-17, GD 17-19, and GD 20-21, respectively. Atypically oreinted pyramidal neurons were identified during the period from postnatal day 0 (day of birth) to day 30. On day 0, obliquely oriented pyramidal neurons were distributed in the deep cortical plate, i.e., immature layer VI. On day 3, the youngest atypically oriented pyramidal neurons were radially oriented and were located in layer IV. Some obliquely oriented pyramidal neurons were present in layer II on day 6, but the greatest number and the most severely canted pyramidal neurons in layer II were evident on day 9. The orientations of the cell body and the apical dendrite did not change appreciably after migration was complete, except for those in layers V and VI with obliquely oriented cell bodies and radially oriented apical dendrites. The second and third postnatal weeks were marked by substantial morphological differentiation of all pyramidal neurons as noted by the lengthening and branching of dendrites and by the appearance of dendritic spines. By the fourth postnatal week, atypically oriented pyramidal neurons achieved their mature morphology. The generation, migration, and morphogenesis of atypically oriented pyramidal neurons proceed by an inside-to-outside sequence. This development is similar and concurrent with that of typically oriented pyramidal neurons.

Aging↗
PubMed1988

Use of bromodeoxyuridine-immunohistochemistry to examine the proliferation, migration and time of origin of cells in the central nervous system.

The use of an exogenously administered thymidine analog, 5-bromo-2'-deoxyuridine (BrdU), for studies of the proliferation, migration and time of origin of cells in the cerebral cortex was investigated and compared with [3H]thymidine [( 3H]dT) autoradiography. Pregnant rats or mice were injected with BrdU and/or [3H]dT and processed by standard immunohistochemical techniques using a primary antibody directed against BrdU in single-stranded DNA, autoradiographic methods, or both. In animals that survived only 1 h after the injection, BrdU-positive cells were distributed in the proliferative zones throughout the central nervous system (CNS). In animals killed 1-3 days after the BrdU injection, intensely immunoreactive cells were in the superficial cortical plate and less intensely labeled cells were scattered throughout the deep cortical plate, the intermediate zone, and the germinal zones. In adult animals, 60 days or more after an injection of BrdU on GD 19, BrdU-positive cells were located in layer II/III of neocortex, the hippocampal pyramidal layer, and the granule layer of the dentate gyrus. In the double-labeling studies, the distribution of BrdU-immunoreactive cells was identical to that of autoradiographically labeled cells, and all autoradiographically labeled neurons were BrdU positive. Thus, BrdU immunohistochemistry is suitable for developmental studies of the CNS; moreover, it provides several advantages over [3H]dT autoradiography.

Animals↗
PubMed1988

Lack of inductively-generated 60-Hz, 3 V.m-1 electric field effect on CHO cell plating efficiency.

Chinese hamster ovary (CHO) fibroblasts were exposed or sham-exposed to inductively-generated 60-Hz, 3.1 V.m-1 fields for 24 h. The absolute plating efficiency of the cells was determined immediately following the field exposure/sham-exposure, and after one week of post-exposure incubation. One-way analyses of variance performed on replicate experimental treatment means indicated no treatment effect on cell colony-forming ability.

Analysis of Variance↗
PubMed1988

Lack of effect of continuous wave ultrasound exposure on in vivo Chinese hamster cheek pouch epithelial mitotic index.

Chinese hamster cheek pouches were everted and the epithelia exposed in vivo for 1 min to continuous wave 1.07 MHz ultrasound at intensities ranging from 0.5 to 10.0 W cm-2. Since the mitotic index of the hamster epithelium exhibited a circadian rhythm, the times of sonication and tissue sampling were arranged to allow for detection of a division delay as evidenced by a change in mitotic index in cells insonated in the early S or late S/early G2 phases of the cell cycle. There was no demonstrated effect of the ultrasound exposures on mitotic index.

Animals↗
PubMed1988

Increased sister chromatid exchanges in Chinese hamster ovary cells exposed to high intensity pulsed ultrasound.

This study comprised two repeat experiments in which Chinese hamster ovary (CHO) cells were exposed to nominal peak intensity Im = 2500 W/cm2, 2.5 MHz, pulsed ultrasound. Cells contained in a 0.53 cm diameter chamber in 0.48 cm thick Plexiglas were exposed to 10 microseconds pulses at 200 Hz prf in 9 sites for 3 min per site for a total duration of 27 min. The -3 dB focal beamwidth was 0.115 cm at an axial distance of 4.8 cm. Analysis of the pooled data from each series of experiments showed a statistically significant increase in the mean frequency of sister chromatid exchanges (SCE) in exposed compared to control cells. The results show a high degree of variability in the controls and insonated samples, which suggests that large numbers of insonations may be required in studies with SCE to reduce the high probability of missing an effect. The results of this series of experiments provide the first confirmation of an increase in SCEs following exposure to pulsed ultrasound.

Animals↗