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D R Averill

Publications and source records attributed to D R Averill.

At least 19 recordsLinked to original sources
PubMed1995

Cytochemical localization of the acetone-inducible cytochrome P-450 isoform, CYP2E1, in murine colonic epithelium.

Immunolocalization of a toxicologically important cytochrome P-450 isoform, the alcohol-inducible CYP2E1, was examined in mouse colon. Male CD-1 mice (30-40 g) were exposed to acetone (1% v/v), a potent inducer of hepatic CYP2E1, in drinking water for 14 days. Tissue sections were fixed in 1% paraformaldehyde and incubated with anti-rat CYP2E1 polyclonal antibody. Immunohistochemical staining on tissue sections was performed using the indirect peroxidase-antiperoxidase method. In acetone-exposed mice, immunoreactivity was localized exclusively within the cytoplasm of surface epithelial cells of the proximal colon. Infrequently, only very faint staining was evident in colons of untreated control mice. Using the same monospecific antibody, the presence of CYP2E1 was confirmed by Western blot analysis. A 2-to 3-fold elevation in immunoreactivity corresponding to cytochrome P-4502E1 was found in colon microsomes isolated from acetone-exposed form acetone-exposed mice. Further evidence for colonic CYP2E1 is provided by elevation (up to 2.5-fold) in levels of chlorzoxazone 6-hydroxylase, a CYP2E1 substrate, after acetone treatment. The significance of these finding is discussed in terms of the potential for proximal colonic epithelial cells to participate directly in bioactivation of dietary promutagenic substances.

Acetone↗
PubMed1989

Characterization of encephalitis in adult mice induced by intracerebral inoculation of herpes simplex virus type 1 (KOS) and comparison with mutants showing decreased virulence.

The spread of herpes simplex virus type 1 (HSV-1) strain KOS, and two less neurovirulent mutants of the strain was studied in female DBA/2 mice during the 1- to 5-day postinoculation period after intracerebral inoculation. Immunohistopathology showed that wild-type KOS virus first infected the meninges and ependymal cells but did not infect cells at the inoculation sites. The virus continued to spread to some cells directly adjacent to ventricles; however, the most extensive and severe lesions were found in the pyriform lobes and other structures associated with the limbic system. The pattern of spread suggested that direct cell to cell viral spread is important but that retrograde axonal transport to distant sites probably accounts for the more severe lesions associated with the limbic system. Both less neurovirulent mutant viruses multiplied to a much lesser degree in the brain and spread less extensively than the wild type virus when equivalent doses were given; however, when a large dose of the least neurovirulent mar C10.1 mutant virus was inoculated, infection spread rapidly to the same regions of the brain affected by KOS. Studies of mar C10.1 showed that thymidine kinase deficiency, rather than a mutation in the gene coding for glycoprotein C, probably accounted for the decreased neurovirulence of this mutant. This mouse model of HSV-1 virus-induced encephalitis, in combination with appropriate studies of the molecular biology of the HSV-1 KOS strain, should be useful for the study of neurovirulence factors contributing to the pathogenesis of HSV-1.

Animals↗
PubMed1988

Tissue-specific pharmacodynamics of 5-bromo-2'-deoxyuridine incorporation into DNA in VX2 tumor-bearing rabbits.

The thymidine analog 5-bromo-2'-deoxyuridine (BrdUrd) is felt to exert its cytotoxic effects primarily through incorporation into DNA. We have evaluated the incorporation of BrdUrd into the DNA of relevant normal tissues (bone marrow, gut mucosa, and liver) and tumor in rabbits with the VX2 tumor growing intrahepatically. Using constant i.v. infusions, steady state plasma drug concentrations ranging from 0.4 to 65.4 microM were maintained for 24 h and tissues were harvested and processed so that a sensitive gas chromatography/mass spectrometry (GC/MS) method could be used to analyze the thymine and 5-bromouracil content of hydrolyzed DNA. In all tissues, DNA incorporation showed saturating effects as plasma BrdUrd concentration was increased and, BrdUrd incorporation as a function of plasma concentration could be fitted to a Langmuir-like equation generating tissue-specific pharmacodynamic parameters: Imax for percentage thymine replacement at infinite plasma BrdUrd concentrations, and C50 for the arterial BrdUrd concentration generating incorporation that is Imax/2. At all plasma concentrations of BrdUrd the incorporation into DNA of bone marrow was greater than that observed in VX2 tumor. However, BrdUrd labeling index (with a BrdUrd monoclonal antibody) was greater in tumor than bone marrow. Thus, pharmacodynamic differences in incorporation do not result solely from cytokinetic differences between tissues. This model may prove useful in evaluating the pharmacodynamics of incorporation in studies using hepatic arterial infusion and biochemical modulation to improve selectivity.

Animals↗
PubMed1988

Intra-arterial 5-bromo-2-deoxyuridine (BUdR) radiosensitization with external beam radiation in rhesus monkeys: toxicity study.

A primate toxicity study was performed to test the hypothesis that BUdR does not increase the likelihood of unilateral or bilateral central nervous system damage secondary to radiation therapy. BUdR, a halogenated pyrimidine analog is incorporated into DNA of dividing cells and sensitizes them to radiation. It is best given unilaterally, intra-arterially by continuous infusion because of its regional advantage (Rd) estimated to be between 11 and 16. Six rhesus monkeys were implanted with a Model 400 Infusaid pump perfusing the right internal carotid artery. Three of the six monkeys received intra-arterial (IA) BUdR infusion plus whole brain external beam radiation (6,000 R over 6 weeks) and three received radiation alone. The two BUdR treated animals completing radiation developed symmetric bilateral high signal aberrations on MRI in the frontal, parietal, and occipital centrum semiovale and corona radiata at nine months. At autopsy, confluent microinfarcts were found to correspond topographically to the MRI abnormalities. In the radiation alone group, two animals had normal MRI and autopsy while the third animal had bilateral MRI high signal aberrations develop sequentially with corresponding microinfarcts at autopsy. These changes were greater in severity than those seen in the BUdR treated animals. We support previous evidence that there is differential intraspecies sensitivity to radiation. We find that BUdR produces no unilateral potentiation of radiation toxicity.

Animals↗
PubMed1988

A multiple-well method for immunohistochemical testing of many reagents on a single microscopic slide.

Multiple wells (M-wells) have been made over tissue sections on single microscopic slides to simultaneously localize binding specificity of many antibodies. More than 20 individual 4-microliter wells over tissue have been applied/slide, representing more than a 5-fold improvement in wells/slide and a 25-fold reduction in reagent volume over previous methods. More than 30 wells/slide have been applied over cellular monolayers. To produce the improvement, previous strategies of placing specimens into wells were changed to instead create wells over the specimen. We took advantage of the hydrophobic properties of paint to surround the wells and to segregate the various different primary antibodies. Segregation was complete on wells alternating with and without primary monoclonal antibody. The procedure accommodates both frozen and paraffin sections, yielding slides which last more than a year. After monoclonal antibody detection, standard histologic stains can be applied as counterstains. M-wells are suitable for localizing binding of multiple reagents or sample unknowns (polyclonal or monoclonal antibodies, hybridoma supernatants, body fluids, lectins) to either tissues or cells. Their small sample volume and large number of sample wells/slide could be particularly useful for early screening of hybridoma supernatants and for titration curves in immunohistochemistry (McKeever PE, Shakui P, Letica LH, Averill DR: J Histochem Cytochem 36:931, 1988).

Antibodies, Monoclonal↗
PubMed1988

The identification of Eperythrozoon ovis in anemic sheep.

Eperythrozoon ovis, a rickettsial parasite of erythrocytes, was found in anemic lambs maintained for reproductive endocrinology research. The parasite was identified in the blood films of 13 animals in the flock of 30. The sexes were infected equally (7/16 males versus 6/14 females). The relationship between the severity of the anemia and the presence of organisms in blood was statistically significant. One animal died with severe anemia. Light, scanning electron, and transmission electron microscopy of peripheral erythrocytes revealed an extracellular organism identified as E. ovis. These findings indicate that this parasite can cause disease in sheep and therefore may interfere with biomedical research.

Anaplasmataceae Infections↗
PubMed1987

Quantitative scintigraphy with deconvolutional analysis for the dynamic measurement of hepatic function.

A mathematical technique known as deconvolutional analysis was used to provide a critical and previously missing element in the computations required to quantitate hepatic function scintigraphically. This computer-assisted technique allowed for the determination of the time required, in minutes, of a labeled bilirubin analog (99mTc-disofenin) to enter the liver via blood and exit via bile. This interval was referred to as the mean transit time (MTT). The critical process provided for by deconvolution is the mathematical simulation of a bolus injection of tracer directly into the afferent blood supply of the liver. The raw data required for this simulation are obtained from the intravenous injection of labeled disofenin, a member of the HIDA family of radiopharmaceuticals. In this study, we perform experiments which document that the simulation process itself is accurate. We then calculate the MTT under a variety of experimental conditions involving progressive hepatic ischemia/reperfusion injury and correlate these results with the results of simultaneously performed BSP determinations and hepatic histology. The experimental group with the most pronounced histologic findings (necrosis, vacuolization, disorganization of hepatic cords) also have the most prolonged MTT and BSP half-life. However, both quantitative imaging and BSP testing are able to identify milder degrees of hepatic ischemic injury not reflected in the histologic evaluation. Quantitative imaging with deconvolutional analysis is a technique easily adaptable to the standard nuclear medicine minicomputer. It provides rapid results and appears to be a sensitive monitor of hepatic functional disturbances resulting from ischemia and reperfusion.

Animals↗
PubMed1984

Familial reflex myoclonus in Labrador Retrievers.

Three 6-week-old male purebred yellow Labrador Retrievers were presented with intermittent stimulus-sensitive contractions of the appendicular and axial muscles. Five littermates were normal, although the grandsire of the affected litter had sired 2 previous litters containing similarly affected pup. Although alert and responsive, the affected dogs appeared decerebrate with extensor rigidity and opisthotonus during handling. During severe episodes, respiratory distress was observed. Generalized contractions were initiated by voluntary movements, but at rest the muscles relaxed. Neurologic deficits were not detected, although efforts to elicit segmental reflexes, assess muscle tone, or assist walking resulted in generalized stiffness. Electromyograms from the semitendinous muscles (musculi semitendinosus) had increased motor unit amplitude (up to 5,000 microV) with polyphasic action potentials. There were no myotonic discharges. A reduced interference pattern was seen. A single tactile stimuli of the distal limb resulted in 3 responses, each lasting less than or equal to 10 ms at latencies of 0 to 12 ms, 20 to 30 ms, and 35 to 40 ms, characteristic for reflex myoclonus. The motor nerve conduction velocities were normal for age (32 to 35 ms). Age-matched control dogs had motor unit action potentials of 100 to 200 microV and single compound motor unit discharges to single tactile stimuli. Therapeutic trials with diazepam and clonazepam produced minimal effects on the muscle contractions. Values of urinalyses, complete blood cell counts, and serum chemistries were within normal limits. Frozen muscle section biopsy findings, including enzyme histochemical assessment of muscle fiber types, were normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Peripheral vestibular syndrome in the dog: a review of 83 cases.

Clinical data and follow-up evaluations of 83 cases of peripheral vestibular syndrome in the dog were reviewed. The absence of physical abnormalities of the tympanic membrane and absence of radiographic changes within the tympanic bulla or petrous temporal bone were the criteria used to make the diagnosis of idiopathic benign vestibular disease. When grouped according to the cause of the syndrome, most of the dogs had been diagnosed as having either otitis media/interna (49%) or idiopathic benign vestibular disease (39%). Clinical evidence suggested that most of the cases of otitis media/interna were secondary to otitis externa.

Animals↗
PubMed1981

The neurologic examination.

With practice, an orderly routine, and a basic understanding of neuroanatomy, the clinician should be able to tentatively localize lesions in the nervous system. Once the lesion is localized, ancillary studies are usually necessary to identify the disease process. In difficult cases when referral is impractical, an accurate description of the findings from the neurologic examination will greatly improve the value of consultation.

Animals↗
PubMed1979

Brain carbohydrate metabolism during experimental Haemophilus influenzae meningitis.

Five-day-old infant rats which acquire Haemophilus influenzae b bacteremia and meningitis after intranasal inoculation have a transient depression in weight gain (2 days), but then continue to grow at the same rate as strain U--11 inoculated controls. Brain lactate, glucose, and glycogen concentrations increase during the first 5 days of disease in infected animals. The increase in brain glycogen can be accounted for by an influx of glycogen containing polymorphonuclear leukocytes. The increased concentrations of glucose and lactate were found not to be due to a change in brain weight to dry weight ratio or the volume of entrapped blood. The mean cerebrospinal fluid (CSF) glucose concentration was higher in animals with meningitis (2.7 mM) in comparison to U-11 inoculated controls (1.8 mM). This increase in brain and CSF glucose concentration appeared secondary to an increased brain uptake of hexoses as manifested by an increased [3H]mannitol uptake. Brain lactate accumulation was not explicable from the data available. There was no evidence of cerebral cortical cellular damage because in vitro oxygen uptake and lactate production were equivalent in control and meningitic animals. The ability of the infant rat brain to maintain cerebral adenosine triphosphate (ATP) content in menigitis and the failure of CSF glucose concentration to decrease might be a reflection of the importance of alternative oxidative substrate (e.g., beta-hydroxybutyrate) to the cerebral metabolism of the developing rat brain.

Adenosine Triphosphate↗
PubMed1978

Thiamine deficiency encephalopathy in a specific-pathogen-free cat colony.

Thiamine deficiency encephalopathy occurred in a specific-pathogen-free cat colony where the diet consisted exclusively of commercially canned diet. This product was described by the manufacturer as a complete diet for cats. The clinical diagnosis was confirmed by the demonstration of bilaterally symmetrical hemorrhage and microvascular fibrinoid necrosis in the brain and low erythrocyte transketolase levels. Treatment of clinically ill cats with vitamin B complex was followed by recovery within 24 hours.

Animals↗
PubMed1977

Neonatal endotoxin encephalopathy.

Telencephalic white matter of the neonatal kitten frequently contained diffuse astrogliosis or focal necrosis (sometimes including the thalamus and the caudate) following a single intraperitoneal injection of Escherichia coli lipopolysaccharide. No evidence for a disseminated intravascular coagulopathy was found. Telencephalic lesions in neonatal monkey and rabbit were also hemorrhagic. Enhanced karyorrhexis of glial nuclei was presented in the telencephalic white matter of the neonatal rat. In the kitten, a delay in the generation of macrophages and hypertrophic astrocytes occurs following transient neonatal endotoxemia. Marked weight loss and temperature fluctuation are prominent systemic effects. Large hemispheric cavitary lesions are not accompanied by obvious neurological deficits in the kitten.

Animals↗
PubMed1977

Molecular basis of reovirus virulence: role of the S1 gene.

A genetic approach has been used to define the molecular basis for the different patterns of virulence and central nervous system cell tropism exhibited by reovirus types 1 and 3. Intracerebral inoculation of reovirus type 3 into newborn mice causes a necrotizing encephalitis (without ependymal damage) that is uniformly fatal. Animal inoculated with reovirus type 1 generally survive and may develop epedymal cell damage (without neuronal necrosis) and hydrocephalus. Using recombinant clones derived from crosses between reovirus types 1 and 3, we have been able to determine that the S1 genome segment is responsible for the differing cell tropism of reovirus serotypes and is the major determinant of neurovirulence. The type 1 S1 genome segment is responsible for ependymal damage with subsequent hydrocephalus; the type 3 S1 genome segment is responsible for neuronal necrosis and neurovirulence. We postulate that these differences are due to the specific interaction of the sigma1 outer capsid polypeptide (the protein coded for by the S1 genome segment) with receptors on the surface of either ependymal cells or neuronal cells.

Animals↗