Search PubMed⌕ Search

Biomedical subjects

M W Miller

Publications and source records attributed to M W Miller.

At least 109 records · Page 6Linked to original sources
PubMed1997

Effects of prenatal exposure to ethanol on callosal projection neurons in rat somatosensory cortex.

The distribution and density of callosal projection neurons in the somatosensory cortex of mature rats was altered by prenatal exposure to ethanol. The density of callosal neurons was significantly greater in ethanol-treated rats than in controls. Ethanol exposure also altered the laminar distribution of callosal projection neurons. Whereas in control rats the cell bodies of callosal projection neurons were in layers II/III and V, in ethanol-treated rats most of these neurons were distributed in layers V and VI. Many of the ectopic neurons were generated toward the end of cortical neuronogenesis (i.e., on gestational day 20). This contrasts with controls wherein co-generated cohorts were distributed in layer II/III. Thus, the connectional phenotype of the callosal projection neurons is retained regardless of its laminar residence. These ethanol-induced abnormalities apparently result from defects in neuronal migration and axonal pruning.

Animals↗
PubMed1997

Genetic analysis of experimentally induced lupus in mice.

The DBA/2 and C57BL/6 mouse strains, as well as the BXD RI lines derived from these strains, were used to map the genes controlling experimentally induced systemic lupus erythematosus (SLE). SLE was induced using two immunologic approaches: (1) immunization with the human monoclonal anti-DNA antibody expressing the 16/6Id, to which the DBA/2 strain is susceptible (responder) and the C57BL/6 strain is resistant (nonresponder); and (2) induction of autoimmune GVHD in B6D2F1 hosts by inoculation of parental DBA/2 (induces SLE) or C57BL/6 (does not induce SLE) T cells. By both approaches the BXD RI lines could be divided into distinct DBA/2-like and C57BL/6-like categories. Concordance of SLE induced by both methods was observed for susceptibility and resistance in 13/15 BXD lines (P < 0.005). The results suggest that at least two non-H-2 genes control susceptibility and resistance to experimentally induced SLE, one mapping to chromosome 7 and the other mapping to chromosome 14.

Animals↗
PubMed1997

Acoustic cavitation nuclei survive the apparent ultrasonic destruction of Albunex microspheres.

The hypothesis tested was that gas bodies capable of nucleating violent cavitation activity in vitro would survive the rapid disruption of Albunex microspheres by 1-MHz ultrasound. Human erythrocyte hemolysis was used as a proxy measure of cavitation. Fluid (5% human serum albumin [HSA]) with or without Albunex (ALX) was exposed or sham-exposed to 1-MHz ultrasound (P+ = 1.25 +/- 0.01 MPa, P- = 0.81 +/- 0.01 MPa; ISPTP approximately 35 W/cm2) for 60 s using 10-microseconds pulses and a duty factor of 0.5. An equal volume of whole human blood was then added to the fluid, followed by a second 60-s treatment. Insonation of cell suspensions prepared in previously sham-exposed HSA + ALX fluid produced about 4% hemolysis, a level significantly greater than in the controls. Insonation of cell suspensions prepared in previously insonated HSA + ALX fluid produced about 0.4% hemolysis; this also differed significantly from the controls. The data thus support the hypothesis.

Albumins↗
PubMed1997

Comparative sensitivity of human erythrocytes and lymphocytes to sonolysis by 1-MHz ultrasound.

Many studies of ultrasonic hemolysis have used erythrocytes; other blood cells are less well studied. The hypothesis tested was that human lymphocytes, being large and relatively fragile, are more sensitive to sonolysis than are erythrocytes at equivalent cell concentrations. Human lymphocytes (RPMI 1788) grown in vitro and erythrocytes obtained by venipuncture were used at a nominal cell concentration of 2.5 x 10(6) cells/mL. Cells were contained in rotated (200 rpm) exposure vessels and were exposed/sham-exposed to 1-MHz continuous-wave ultrasound for 60 s. Cell lysis was determined by hemacytometer counts of aliquots taken before/after treatment. The hypothesis was supported; the mean levels of lysis in insonated lymphocyte and erythrocyte preparations were 89.8% +/- 0.6% and 78.9% +/- 3.1%, respectively. This difference was significant at p < 0.005.

Cells, Cultured↗
PubMed1997

Hemolysis of 40% hematocrit, Albunex-supplemented human erythrocytes by pulsed ultrasound: frequency, acoustic pressure and pulse length dependence.

The dependence of hemolysis produced by pulsed ultrasound on ultrasound frequency, acoustic pressure and pulse length was explored. Human erythrocytes (40% hematocrit; in Albunex-supplemented autologous plasma) were exposed (60 s) to 20 or 200 microns pulses of ultrasound at frequencies of 1.02, 2.24 or 3.46 MHz and at peak negative pressures [P-] ranging from 0.0 to approximately 3.0 MPa in 0.5 MPa increments. The duty factor was 0.01. At each frequency, hemolysis increased with increasing acoustic pressure and depended weakly on pulse duration. At relatively high acoustic pressures, hemolysis depended strongly on ultrasound frequency; at lower pressures, the frequency dependence was weaker. The potential clinical significance of ultrasonic hemolysis is discussed.

Albumins↗
PubMed1997

Spongiform encephalopathy in free-ranging mule deer (Odocoileus hemionus), white-tailed deer (Odocoileus virginianus) and Rocky Mountain elk (Cervus elaphus nelsoni) in northcentral Colorado.

Between March 1981 and June 1995, a neurological disease characterized histologically by spongiform encephalopathy was diagnosed in 49 free-ranging cervids from northcentral Colorado (USA). Mule deer (Odocoileus hemionus) were the primary species affected and accounted for 41 (84%) of the 49 cases, but six Rocky Mountain elk (Cervus elaphus nelsoni) and two white-tailed deer (Odocoileus virginianus) were also affected. Clinical signs included emaciation, excessive salivation, behavioral changes, ataxia, and weakness. Emaciation with total loss of subcutaneous and abdominal adipose tissue and serous atrophy of remaining fat depots were the only consistent gross findings. Spongiform encephalopathy characterized by microcavitation of gray matter, intraneuronal vacuolation and neuronal degeneration was observed microscopically in all cases. Scrapie-associated prion protein or an antigenically indistinguishable protein was demonstrated in brains from 26 affected animals, 10 using an immunohistochemical staining procedure, nine using electron microscopy, and seven using Western blot. Clinical signs, gross and microscopic lesions and ancillary test findings in affected deer and elk were indistinguishable from those reported in chronic wasting disease of captive cervids. Prevalence estimates, transmissibility, host range, distribution, origins, and management implications of spongiform encephalopathy in free-ranging deer and elk remain undetermined.

Adipose Tissue↗
PubMed1997

Effect of simulated stress on susceptibility of bighorn sheep neutrophils to Pasteurella haemolytica leukotoxin.

We examined the effects of simulated stress on susceptibility of Rocky Mountain bighorn sheep (Ovis canadensis canadensis) neutrophils to Pasteurella haemolytica leukotoxin in a blocked, crossover experiment. Ten captive-raised bighorn sheep were sampled 10 hr after separate administrations of long-acting adrenocorticotrophic hormone (ACTH) gel and normal saline (control). We then compared in vitro leukotoxin-dependent neutrophil death rates after exposure to culture supernatants from four unique P. haemolytica isolates (one from domestic and three from bighorn sheep). Simulated stress effects were evidenced by elevated (P = 0.002) mean plasma cortisol concentrations, more neutrophils (P = 0.037), and fewer lymphocytes and eosinophils (P < or = 0.043) in ACTH-treated bighorn sheep. Maximum leukotoxin-dependent neutrophil death rates were > or = 61% for three of four P. haemolytica isolates tested. For all three cytotoxic isolates, neutrophil death rates at 150 micrograms/50 microliters supernatant were about 1.13 times higher (P = 0.0001) after bighorns received ACTH; for two of these, overall neutrophil death rates were higher (P < or = 0.001) in ACTH-treated bighorn sheep. Although variable leukotoxin production among P. haemolytica strains appeared principally responsible for differences in leukotoxin-dependent neutrophil death rates, susceptibility of bighorn sheep neutrophils to leukotoxin was increased by prior exposure to elevated plasma cortisol concentrations. It follows that if similar processes occur in neutrophils and alveolar macrophages in vivo, they could contribute to greater susceptibility of stressed bighorn sheep to pneumonic pasteurellosis.

Animals↗
PubMed1997

Evaluation of a multivalent Pasteurella haemolytica vaccine in bighorn sheep: safety and serologic responses.

We examined effects of a multivalent Pasteurella haemolytica vaccine (serotypes A1, A2, T10) on humoral immune responses and P. haemolytica isolation rates in bighorn sheep (Ovis canadensis). Thirty captive bighorns, divided into groups of three on the basis of age, sex, and previous history of pneumonic pasteurellosis, received 0, 1, or 2 vaccine doses. Mild, transient lameness in most bighorns 1 day after initial vaccination was the only adverse effect observed. Oropharyngeal (> or = 75%) and nasal (< or = 50%) isolation rates for P. haemolytica did not differ among treatment groups. Ten of 36 distinguishable biogroup variants accounted for about 87% of the 464 P. haemolytica isolates from bighorns, but prevalences of specific biogroups were not affected by vaccination. Bighorns receiving 1 or 2 vaccine doses showed marked elevations in leukotoxin neutralizing antibody titers beginning 1 wk after vaccination. Agglutinating antibody titers to serotype A1 and A2 surface antigens were also elevated in vaccinated bighorns within 2 wk after vaccination; agglutinating antibody titers to serotype T10 surface antigens were relatively high in all three groups but appeared unaffected by vaccination. Vaccination 7 to 14 wk prior to parturition elevated leukotoxin neutralizing antibody titers in colostrum, but neither leukotoxin neutralizing nor serotype A1 surface antigen agglutinating antibody titers differed through 16 wk of age among lambs born to dams from different vaccine dose groups. Our data demonstrate that this multivalent P. haemolytica vaccine is safe and stimulates marked antibody responses in bighorn sheep. Further evaluation of this vaccine as a tool in preventing and managing pasteurellosis in bighorn sheep appears warranted.

Age Factors↗
PubMed1997

A cellular approach to the study of complex natural behavior patterns in the ragged sea hare (Bursatella leachii), a marine invertebrate indigenous to Puerto Rico.

The ragged sea hare (Bursatella leachii), an aplysiid mollusc indigenous to the tropical waters of Puerto Rico, possesses numerous properties that make it suitable for a neuroethological approach to the study of complex behavior patterns. Field studies spanning three years have established a location and season of Bursatella availability on the north coast of the island. In the natural habitat, the Bursatella exhibit a daily rhythm of behavior patterns in which feeding-related activities predominate during the day and reproductive behaviors predominate at night. Some aspects of this natural pattern persist in animals held in the laboratory. The Bursatella nervous system contains large neurons, some of which appear to be homologous to cells that have been characterized extensively in related species. Following isolation of the nervous system, neural centers associated with feeding movements and locomotion retain extraordinarily robust rhythm generating capabilities. It is proposed that this species offers unique opportunities for deriving general principles governing the regulation and integration of central pattern generator circuits underlying complex natural behavior patterns.

Animals↗
PubMed1997

Differential sensitivity of human neuroblastoma cell lines to ethanol: correlations with their proliferative responses to mitogenic growth factors and expression of growth factor receptors.

Early ethanol exposure depletes neurons in the developing nervous system, however the effects on neuronal precursors are not homogeneous. Some cells are more susceptible to ethanol toxicity than others. Growth factors are important mitogens for neuronal precursors. We tested the hypothesis that the differential sensitivity of neuronal precursors to ethanol is determined by their responses to growth factors using an in vitro model (SH-SY5Y, SK-N-SH, and IMR32 neuroblastoma cells) of neuronal precursors. The three cell lines were raised in a medium containing 10% or 0% fetal calf serum. Cells were exposed to ethanol and/or a growth factor. These factors included basic fibroblast growth factor, epidermal growth factor, insulin-like growth factor-I, nerve growth factor, and platelet-derived growth factors AA and BB. The numbers of cells per culture were counted both before and after 3 days of ethanol and/or growth factor treatment. In addition, the effect of ethanol exposure on the expression of receptors for these growth factors was examined. Neuroblastoma cells displayed differential sensitivity to ethanol. The growth of SH-SY5Y and SK-N-SH cells was inhibited by ethanol in a concentration-dependent manner. Ethanol did not affect cell viability. Thus, this inhibition resulted from a reduction of cell proliferation. In contrast, IMR32 cells were not affected by ethanol (even at concentrations as high as 800 mg/dl). The response to growth factors was also heterogeneous. In serum-supplemented medium, SH-SY5Y and SK-N-SH cells were stimulated by all of the tested growth factors. For cells raised in a serum-free medium, only the nerve growth factor was ineffective. IMR32 cells, however, were unaffected by most of these growth factors, regardless of the medium conditions. Ethanol blocked the action of all growth factors tested. In general, all cells expressed the specific receptors for the six growth factors. Only the expression of the basic fibroblast growth factor, insulin-like growth factor-I, and nerve growth factor receptors were reduced by ethanol exposure. In summary, neuroblastoma cells exhibit differential susceptibility to ethanol, and this correlates with their response to mitogenic growth factors. Some growth factors are a target of ethanol toxicity. These heterogeneous effects seem to parallel ethanol-induced changes of proliferating neuronal precursors in vivo.

Brain↗
PubMed1997

Performance by adult rats in sensory-mediated radial arm maze tasks is not impaired and may be transiently enhanced by chronic exposure to ethanol.

The effect of chronic exposure to ethanol on learning and memory was assessed in rats. Adult rats were fed a liquid diet containing ethanol (Et) ad libitum, pair-fed an isocaloric/isonutritious control diet (Ct), or fed lab chow and water (Ch) ad libitum. These diets were provided for as long as 28 weeks prior to testing and during the period of behavioral testing. Rats were required to learn a radial arm maze task that depended upon extramaze cues (visual and spatial) or intramaze cues (various odors). Each rat was tested twice daily for 26 days. The number of reference and working memory errors and the time required to successfully navigate the maze (latency) were recorded. Et-fed rats consistently performed the same or better than the Ct-fed or Ch-fed rats. The enhanced behavior was task-specific and transient. The enhancement was observed in rats after 14 or 20 weeks of ethanol exposure, but not in rats exposed to ethanol for 28 weeks. Et-fed rats performed significantly better on the reference memory task in the odor condition of the maze task, whereas their performance in the spatial task was similar to that for the two control groups. Thus, after an extended period of exposure (e.g., 28 weeks), ethanol had no effect on learning and memory. On the other hand, under certain conditions (14 or 20 weeks), ethanol transiently enhanced memory.

Animals↗
PubMed1996

A test of the hypothesis that ELF magnetic fields affect calcium uptake in rat thymocytes in vitro.

The experiment's objective was to test the statistical hypothesis that a 60-min exposure of rat thymocytes in vitro to a unique combination of static and a.c. magnetic fields results in suppression of calcium influx triggered by concanavalin A (Con A). Con A (10 micrograms/ml) induced about a 50% increase in 45Ca2+ uptake relative to no Con A (control). Magnetic field exposures had no statistically significant effect on Con A-stimulated calcium uptake. The data did not support the hypothesis.

Animals↗
PubMed1996

L5-67 and LUQ-1 peptide precursors of Aplysia californica: distribution and localization of immunoreactivity in the central nervous system and in peripheral tissues.

Two genes (L5-67 and LUQ-1) that encode neuropeptide precursors have recently been shown to be expressed in a distinct and non-overlapping manner in the five left upper quadrant (LUQ) cells of the abdominal ganglion of Aplysia (Landry et al. [1992]. J. Neurobiol 23:89-101). By using wholemount immunohistochemistry and radioimmunoassay (RIA), the pattern of expression of these two genes was assessed at the protein level throughout the central nervous system (CNS) and in peripheral tissues of Aplysia californica. The distribution of LUQ-1 precursor-like immunoreactivity was fairly limited, occurring in the ventral LUQ cell (L5) and in a total of approximately 20 additional neurons in the abdominal and cerebral ganglia. L5-67 precursor-like immunoreactive material was more prevalent, appearing in a total of approximately 100 neurons distributed among each of the central ganglia. Identified L5-67-immunoreactive neurons included the four dorsal LUQ cells (L2-4 and L6) and two giant neurons (R2 and LPI1). In one group of cells, the H cluster of the cerebral ganglion, L5-67 immunofluorescence was substantially more intense in larger versus smaller animals, suggesting that this peptide precursor is subject to developmental regulation in certain neurons. Immunoelectron microscopic examination of the subcellular localization of L5-67 immunoreactivity in LUQ cell somata and axons revealed its association with dense-core vesicles (approximately 114 nm in diameter). In the periphery, L5-67-immunoreactive fibers were detected in specific regions of the circulatory system (auricle, ventricle, cristae aorta, anterior aorta) and the reproductive system (genital ganglion, large hermaphroditie duct, small hermaphroditie duct, ovotestis). The kidney and the intestine, two tissues in which considerable secretion and absorption occur, contained material immunoreactive to both L5-67 and LUQ-1 antisera. The localization of the two peptide precursors in these tissues differed substantially, with L5-67 occurring in widely ramifying varicose fibers, whereas LUQ-1 was found in restricted foci of fibers and in small spherical cells that appeared to lack processes. These results support previous findings concerning the heterogeneity of neurotransmitter phenotypes in the LUQ cells. Furthermore, they are indicative of a fairly broad role for the L5-67-derived neuropeptides, and a more limited role for the LUQ-1-derived neuropeptides, in the regulation of the visceral organ systems of Aplysia.

Animals↗
PubMed1996

Effect of early exposure to ethanol on the protein and DNA contents of specific brain regions in the rat.

A hallmark of fetal alcohol syndrome is microencephaly. Microencephaly can result from either a reduction in the number of cells, in the amount of neuropil, or both. Inasmuch as CNS structures develop along different time lines, the window of vulnerability to ethanol for each structure may differ. Therefore, the growth of the brain after prenatal exposure to ethanol was compared with that following postnatal ethanol exposure. Rats were exposed to ethanol prenatally (between gestational days 6 and 21 via oral consumption by the pregnant dam) or postnatally (between postnatal days 4 and 12 via intubation). The mean of the daily peak blood ethanol concentration was 146 +/- 16 and 127 +/- 18 mg/dl for the rats exposed to ethanol pre- or postnatally, respectively. Pair-fed control rats were generated for both the pre- and postnatal conditions. Wet weights, DNA content, and protein content were quantified for 6 brain segments (right and left neocortices, right and left hippocampi, the cerebella, and brainstems) of 21-day-old rats. The total weight of the brain was reduced 12% by pre- or postnatal exposure to ethanol. Only the weights of the neocortex and the cerebellum were significantly reduced by pre- or postnatal treatment. Interestingly, postnatal ethanol exposure increased the weight of the hippocampi. The DNA and protein contents of specific brain segments were affected by ethanol exposure, but all structures were not affected similarly. The greatest effect was on the neocortex; both measures decreased following pre- or postnatal ethanol exposure. The DNA and protein contents of the cerebellum were also affected by pre- or postnatal ethanol exposure. In contrast, while DNA content in the hippocampus was unaffected by prenatal exposure, it was significantly increased by postnatal ethanol exposure. Thus, ethanol-induced microcephaly and differences in DNA and protein content result from changes in cell number and in neuropil volume. These effects, however, differ among CNS structures in a time-dependent manner suggesting that the primary, but not sole target of ethanol is the proliferating cell.

Animals↗
PubMed1996

c-neu oncoprotein in developing rostral cerebral cortex: relationship to epidermal growth factor receptor.

The c-neu oncoprotein, p185c-neu, is a transmembrane tyrosine kinase that shares structural similarities with the receptor for epidermal growth factor (EGFr). We used immunoblots, immunoprecipitation, and immunohistochemistry 1) to test the hypothesis that p185c-neu and EGFr are coordinately expressed in central nervous system tissue and 2) to assess the spatiotemporal expression of both the c-neu oncoprotein and EGFr in the rostral cerebral cortex. In nondenaturing gels, anti-c-neu antibody identified high molecular weight proteins (about 300-400 kDa) that were reduced by EDTA to a molecular weight of 180-200 kDa. Sodium dodecylsulfate polyacrylamide gel electrophoresis broke down this protein into an array of smaller peptides, which were expressed prenatally, transiently during the first three postnatal weeks, or in the adult. Perinatally, c-neu immunoreactivity was evident in subplate neurons, ascending processes of neurons in the cortical plate, and ventricular zone cells. During the second postnatal week, cells throughout cortex expressed somatodendritic immunostaining, but, in the adult, c-neu immunoreactivity was expressed only by pyramidal neurons in layer V and by glia in the white matter and ependyma. EGFr-positive proteins behaved in the nondenaturing gels as did c-neu-positive oncoproteins, suggesting that both proteins naturally formed dimers. This contention was supported by the EGFr-or c-neu immunolabeling of tissue that was previously immunoprecipitated with anti-c-neu or anti-EGFr, respectively. The pattern of EGFr immunolabeling in the developing and mature cortex was virtually identical to that described for c-neu immunoreactivity. Cortical neurons express the c-neu oncoprotein and EGFr, probably as heterodimers. The specific immunolabeling of layer V neurons in the adult cortex with anti-c-neu and anti-EGFr suggests that the p185c-neu ligand and EGF regulate the activity of corticofugal systems. The expression of different c-neu- and EGFr-positive peptides is developmentally defined and may be related to specific ontogenetic events.

Age Distribution↗
PubMed1996

Genetic regulation of delta-aminolevulinate dehydratase during erythropoiesis.

In an effort to understand how the heme biosynthetic pathway is uniquely regulated in erythroid cells, we examined the structure of the gene encoding murine delta-aminolevulinate dehydratase (ALAD; EC4.2.1.24), which is the second enzyme of the pathway. The gene contains two first exons, named 1A and 1B, which are alternatively spliced to exon 2, where the coding region begins. Each first exon has its own promoter. The promoter driving exon 1A expression is TATA-less and contains many GC boxes. In contrast, the exon 1B promoter bears regulatory sequences similar to those found for beta-globin and other erythroid-specific genes. Tissue distribution studies reveal that ALAD mRNA containing axon 1A is ubiquitous, whereas mRNA containing axon 1B is found only in erythroid tissues. This finding, together with our further observation that GATA-1 mRNA levels increase 3-fold during maturation of murine erythroid progenitor cells, may help explain simultaneous 3-fold increases in exon 1B expression. The unexpected result that axon 1A expression also increases 3-fold during CFU-E maturation may be attributable to the action of NF-E2, since there is a potential binding site in a position analogous to the NF-E2 site in the locus control region of the beta-globin gene cluster.

Animals↗
PubMed1996

Re-evaluation of the concept that high cell concentrations "protect" cells in vitro from ultrasonically induced lysis.

Diminution of apparent ultrasonic cell lysis in vitro with increasing cell concentration/volume fraction has often been observed. A substantial fraction of the cells may be lysed by ultrasound at low cell concentrations, but only a few percent are lysed when the concentration is a fraction of that of whole blood. This suggests that sonolysis of cells in vitro is suppressed by high cell concentrations, and, therefore, that sonolysis of cells in vivo is unlikely. We present the results of a retrospective analysis of experimental data and a theoretical analysis; these indicate that while relative sonolytic yield declines with increasing cell concentration, the "absolute" extent of ultrasound-induced lysis remains large. We find evidence that in vitro sonolysis of cells is limited at high cell densities by the number of available microbubbles and/or the number of cells each bubble may encounter and lyse prior to bubble "inactivation." Theory indicates the latter arises in consequence to the cell concentration-dependent formation of cell aggregates around pulsating bubbles.

Animals↗