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Biomedical subjects

D Avery

Publications and source records attributed to D Avery.

At least 19 recordsLinked to original sources
PubMed2006

EEG and the variance of motor evoked potential amplitude.

The motor threshold is an important parameter in selecting the treatment intensity of patients undergoing transcranial magnetic stimulation. The large variance in magnitude of motor evoked responses has forced clinicians to perform many trials and average the results to find a repeatable value for motor threshold. Our objective is to investigate the source of the variance in amplitude. Four clinically healthy adult males participated in an EEG and EMG during transcranial magnetic stimulation of the left motor cortex, 100% motor threshold, 0.1 Hz. Per our hypothesis, a significant negative correlation of .22 was found between the amplitude of the motor evoked potential and the power in the high alpha frequency band during the pre-stimulus period (p < .001). In addition, a significant positive correlation of .17 was found between the motor evoked potential (MEP) amplitude and the gamma band (p < .001). The strongest correlation of .27 (p < .001) was found between the MEP amplitude and the ratio of the power in the low gamma to high alpha band. We conclude that the gamma to alpha power ratio may be a useful indicator of cortical excitability.

Adult↗
PubMed2001

A note on hair whorl position and cattle temperament in the auction ring.

The objective of this study was to further describe the relationships between facial hair whorls and temperament in cattle. Cattle (n=1636) from six commercial cattle auctions in Colorado and Texas were observed. Whorl location was classified according to lateral position (left, right, or middle) and height (high: above the top of the eye, middle: at eye level, low: below the bottom of the eye). A 4-point temperament score was used to rate each animal while it was in the auction ring. Cattle with a score of 1 remained calm and stood still or walked around, and those with a score of 4 were highly agitated and hit the ring fence, walls, partitions, or people with its head. The cattle observed were 75% Bos taurus beef breeds, 21% Holstein dairy cattle, 3% Bos indicus beef breeds, and 1% non-Holstein dairy breeds. Ten percent of cattle surveyed had no facial hair whorl, while 86% had a single spiral hair whorl, of which 47% had middle-middle whorl placement. Animals with a high whorl position or no hair whorl had higher temperament scores (P=0.01). Cattle with low whorls were more likely to have greater lateral displacement of whorls off of the centerline than cattle with high or middle whorls (P<0.01). Abnormally shaped whorls were more common on cattle with low whorls (P<0.01) and on cattle with lateral whorls located off of the centerline (P<0.01). Cattle with hair whorls on the centerline had more variable temperament scores (P=0.04). Beef cattle had more abnormal whorls than Holsteins (P<0.01). Temperament scores showed that Holsteins were calmer than beef cattle (P<0.01). Facial hair whorls in cattle may be a useful management tool in assessing which animals may become disturbed in novel environments.

Journal Article↗
PubMed2000

Characterization of the selectivity filter of the epithelial sodium channel.

The epithelial sodium channel (ENaC) is composed of three homologous subunits termed alpha, beta, and gamma. Previous studies suggest that selected residues within a hydrophobic region immediately preceding the second membrane-spanning domain of each subunit contribute to the conducting pore of ENaC. We probed the pore of mouse ENaC by systematically mutating all 24 amino acids within this putative pore region of the alpha-subunit to cysteine and co-expressing these mutants with wild type beta- and gamma-subunits of mouse ENaC in Xenopus laevis oocytes. Functional characteristics of these mutants were examined by two-electrode voltage clamp and single channel recording techniques. Two distinct domains were identified based on the functional changes associated with point mutations. An amino-terminal domain (alpha-Val(569)-alpha-Gly(579)) showed minimal changes in cation selectivity or amiloride sensitivity following cysteine substitution. In contrast, cysteine substitutions within the carboxyl-terminal domain (alpha-Ser(580)-alpha-Ser(592)) resulted in significant changes in cation selectivity and moderately altered amiloride sensitivity. The mutant channels containing alphaG587C or alphaS589C were permeable to K(+), and mutation of a GSS tract (positions alpha587-alpha589) to GYG resulted in a moderately K(+)-selective channel. Our results suggest that the C-terminal portion of the pore region within the alpha-subunit contributes to the selectivity filter of ENaC.

Amiloride↗
PubMed2000

The relationship between reaction to sudden, intermittent movements and sounds and temperament.

Casual observations indicated that some cattle are more sensitive to sudden movement or intermittent sound than other cattle. Six commercial livestock auctions in two states and a total of 1,636 cattle were observed to assess the relationship between breed, sex, and temperament score on the response to sudden, intermittent visual and sound stimuli, such as the ringman swinging his arm for a bid and the sound of him briefly yelling a bid. A 4-point temperament score was used to score each animal while it was in the ring. The scores used were 1) walks and(or) stands still, with slow, smooth body movements; 2) continuously walks or trots, and vigilant; 3) gait is faster than a trot (runs even a couple of steps), with fast, abrupt, jerky movements, and very vigilant; and 4) hits the ring fence, walls, partitions, or people with its head. Animals were observed for flinches, startle responses, or orientation toward sudden, intermittent sounds, motions, and tactile stimulation, such as being touched with a cane or plastic paddle. The cattle observed were mostly Bos taurus beef breeds and Holstein dairy cattle. Holsteins were more sound-sensitive (P = .02) and touch-sensitive (P < .01) than beef cattle. Sensitivity to sudden, intermittent stimuli (e.g., sound, motion, and touch) increased as temperament score (excitability) increased. Cattle with a temperament score of 1 were the least sensitive to sudden, intermittent movement and sound and those with a temperament score of 4 were the most sensitive (P < .01). This same relationship was sometimes observed for touch but was not statistically significant. Motion-sensitive cattle were more likely than nonsensitive cattle to score a temperament rating of 3 or 4 (P < .01). Steers and heifers were more motion-sensitive than the older bulls and cows (P = .03). Beef cattle urinated (P < .01, n = 1,581) and defecated (P < .01, n = 1,582) more often in the ring than did dairy cattle. Cattle that became agitated during handling in an auction ring were the individuals that were most likely to be startled by sudden, intermittent sounds and movements. Reactivity to sudden, intermittent stimuli may be an indicator of an excitable temperament.

Animals↗
PubMed1999

Quantitative analysis of lymphocyte differentiation and proliferation in vitro using carboxyfluorescein diacetate succinimidyl ester.

Mature T and B lymphocytes respond to receptor-delivered signals received during and following activation. These signals regulate the rates of cell death, growth, differentiation and migration that ultimately establish the behaviour patterns collectively referred to as immune regulation. We have been pursuing the philosophy that in vitro systems of lymphocyte stimulation, when analysed quantitatively, help reveal the logical attributes of lymphocyte behaviour. The development of carboxyfluorescein diacetate succinimidyl ester (CFSE) to track division has enabled the variable of division number to be incorporated into these quantitative analyses. Our studies with CFSE have established a fundamental link between differentiation and division number. Isotype switching, expression of T cell cytokines, surface receptor alterations and changes to intracellular signalling components all display independent patterns of change with division number. The stochastic aspects of these changes and the ability of external signals to independently regulate them argue for a probabilistic modelling framework for describing and understanding immune regulation.

Antigens, Differentiation↗
PubMed1999

Simultaneous determination of muscle 31P and O2 uptake kinetics during whole body NMR spectroscopy.

Our understanding of O2 uptake (VO2) control mechanisms during exercise may be improved by the simultaneous determination of the kinetics of intramuscular high-energy phosphate turnover and pulmonary VO2. We therefore developed a technique for remote gas-exchange analysis while subjects exercised in a whole body 1.5-T NMR system. Knee-extension exercise was performed against restraining rubber bands in the prone position. Free induction decays were acquired every 1,875 ms by using a transmit-receive coil, which was placed under the quadriceps. This allowed 31P spectra of intramuscular ATP, Pi, and creatine phosphate dynamics to be determined every 15 s. Airflow was measured with a custom-designed turbine and a 45-ft.-long cable to reach the volume-measuring module. This was located in an adjacent radio-frequency-shielded room, as was the respiratory mass spectrometer, which also used a 45-ft.-long sampling line. The respired gas profiles were not discernibly different from those that used the standard inlet; the increase in the delay was readily incorporated into the breathby-breath algorithm, allowing the VO2 kinetics to be determined in concert with those of intramuscular phosphate metabolism.

Adenosine Triphosphate↗
PubMed1998

A brief medical necessity scale for mental disorders: reliability, validity, and clinical utility.

Managed care organizations (MCOs) use the concept of "medical necessity" to decide whether a prescribed treatment is warranted for a given medical condition. Because mental disorders lack the objective disease criteria common to medical illness, behavioral health administrators need a validated means to identify and quantify the severity of "medically important" aspects of mental disorders. The authors developed and tested a brief medical necessity scale for mental disorders in 205 patients presenting for initial evaluation. The scale had a factor structure with four subscales; good internal consistency, interrater reliability, and concurrent and predictive validity; and modest ability to identify patients requiring hospitalization and, in hospitalized patients, those requiring involuntary hospitalization. The authors propose use of the scale to better clarify decisions about level of care assignments and to better assess patient characteristics predictive of good outcome.

Adult↗
PubMed1998

Guidelines for prescribing melatonin.

Although compelling logic suggests that melatonin may be effective for a variety of disorders, there are few empirical clinical studies. The optimal dose of melatonin is not clear; most studies have used doses that produce supraphysiological blood levels. The timing of melatonin administration is important. Melatonin has few immediate side-effects except drowsiness, but the effects of chronic administration are unclear. Melatonin may be effective in reducing jet lag. In elderly patients with poor sleep and documented low melatonin production, melatonin may be helpful. In several studies, melatonin has been shown to shorten sleep latency. Further studies are needed to clarify the efficacy and safety of melatonin.

Aged↗
PubMed1997

Psychiatric status, quality of life, and level of care as predictors of outcomes of acute inpatient treatment.

OBJECTIVE: The study examined the role of five types of variables--demographic characteristics, psychiatric status, functional quality of life, satisfaction with quality of life, and level of care--in predicting key outcomes of inpatient treatment. METHODS: Multivariate canonical regression and univariate multiple regression models were constructed using data from 1,053 inpatients at a public hospital in Washington State. The models were used to predict length of stay, change in symptom severity during hospitalization, psychiatrists' ratings of patients' insight into their illness at discharge, patients' global satisfaction with life, and rehospitalization within 18 months. Hierarchical stepwise procedures were used to select variables that were significant predictors of outcomes. RESULTS: All five classes of predictors were related to the outcomes. The roles of demographic characteristics and diagnoses were minimal. Previous hospitalization and severity of symptoms at admission were strong predictors of psychiatric status. Indicators of functional quality of life and satisfaction with quality of life explained significant variance in all models after accounting for the other classes of predictors. Frequency of family visits was the strongest functional quality-of-life predictor, relating to positive outcomes. Pretreatment satisfaction with life was a significant predictor of most outcomes, and increased satisfaction was associated with positive outcomes. CONCLUSIONS: Patients' quality of life before psychiatric inpatient treatment predicted treatment outcomes independently of psychiatric status, demographic characteristics, and level-of-care variables. Prospective studies are needed to predict outcomes using multidimensional constructs.

Adolescent↗
PubMed1997

Patient swallows removable partial denture: a clinical report.

The indications for a unilateral partial denture would appear to be when there is a single posterior tooth missing, bound on both sides by usable abutments. Another consideration for a unilateral partial denture is that the patient does not want to restore the space with a fixed partial denture. One drawback to this treatment modality is that the prosthesis needs to be removed after each meal and cleaned. Other more important reasons for not making a 1-tooth removable partial denture is that it provides no cross-arch stabilization and there is the chance that it may be swallowed if it becomes dislodged. This clinical and laboratory report describes how this patient was treated.

Deglutition↗
PubMed1996

Adverse effects of dextromethorphan on the spatial learning of rats in the Morris water maze.

The effects of the non-competitive NMDA receptor antagonist dextromethorphan on spatial learning were assessed using the Morris water maze. Dextromethorphan was administered to 4 groups of rats in 10, 20, 30, and 40 mg/kg doses. An additional group of rats was administered saline to serve as a vehicle control group. Dextromethorphan impaired learning dose dependently in the initial training phase of the experiment. During the probe trial, dose-dependent performance deficits were noted in the first 15 s of the trial only. Search strategy differences between the lowest and highest dose groups were also observed during the probe trial. During the reversal training phase, when the platform was moved to a new location, the dose-dependent impairment was seen again, but the 40 mg/kg group perseverated to the former location longer than the other groups. A cued control trial indicated that in addition to the learning impairment produced, the highest dose of dextromethorphan may also impair sensory-motor coordination.

Animals↗
PubMed1995

Delaney reform.

Explore the source record for details and available documents.

Animals↗
PubMed1994

Codon usage and bias among individual genes of the coccidia and piroplasms.

Codon usage has been analysed in individual gene sequences, derived from a variety of parasitic protozoa in the class Sporozoa of the phylum Apicomplexa using metric multidimensional scaling. The two groups of codon usage patterns detected reflect the two main subgroups of organisms studied (the coccidia and the piroplasms), and it is the pattern of usage of synonymous codons that has the largest influence on overall codon usage in the individual genes, rather than being the pattern of amino acid composition of the gene product. The magnitude of the codon usage bias in the sequences was determined using three commonly used indices-NC, GC3S and B. In general, although relatively low levels of codon usage bias were detected in these gene sequences, codon usage bias does explain at least some of the codon usage patterns observed. Codon usage bias was observed to be dependent on the overall base composition of the genes analysed, which in turn was reflected in the types of codons that were either over- or under-represented in the nucleotide sequences. In keeping with observations on prokaryotic organisms, it is speculated that the codon usage patterns detected in these parasitic protozoa are the result of directional mutation pressure on the base composition of the genomic DNA.

Animals↗
PubMed1994

Lyme disease: a search for a causative agent in ticks in south-eastern Australia.

Attempts were made to identify the causative organism of Lyme disease in Australia from possible tick vectors. Ticks were collected in coastal areas of New South Wales, Australia, from localities associated with putative human infections. The ticks were dissected; a portion of the gut contents was examined for spirochaetes by microscopy, the remaining portion inoculated into culture media. The detection of spirochaetes in culture was performed using microscopy, and immunochemical and molecular (PCR) techniques. Additionally, whole ticks were tested with PCR for spirochaetes. From 1990 to 1992, approximately 12,000 ticks were processed for spirochaetes. No evidence of Borrelia burgdorferi or any other spirochaete was recovered from or detected in likely tick vectors. Some spirochaete-like objects detected in the cultures were shown to be artifacts, probably aggregates of bacterial flagellae. There is no definitive evidence for the existence in Australia of B. burgdorferi the causative agent of true Lyme disease, or for any other tick-borne spirochaete that may be responsible for a local syndrome being reported as Lyme disease.

Animals↗