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Biomedical subjects

T Morris

Publications and source records attributed to T Morris.

At least 19 recordsLinked to original sources
PubMed1997

Direct and indirect corticospinal control of arm and hand motoneurons in the squirrel monkey (Saimiri sciureus).

Anatomic evidence suggests that direct corticomotoneuronal (CM) projections to hand motoneurons in the New World squirrel monkey (Saimiri sciureus) are weak or absent, but electrophysiological evidence is lacking. The nature of the corticospinal linkage to these motoneurons was therefore investigated first with the use of transcranial magnetic stimulation (TMS) of the motor cortex under ketamine sedation in five monkeys. TMS produced early responses in hand muscle electromyogram, but thresholds were high (compared with macaque monkey) and the onset latency was variable. Second, stimulation of the pyramidal tract (PT) was carried out with the use of chronically implanted electrodes in ketamine-sedated monkeys; this produced more robust responses that were markedly facilitated by repetitive stimulation, with little decrease in latency on the third compared with the first shock. Finally, postsynaptic potentials were recorded intracellularly from 93 arm and hand motoneurons in five monkeys under general chloralose anesthesia. After a single PT stimulus, the most common response was a small, slowly rising excitatory postsynaptic potential (EPSP), either alone (35 of 93 motoneurons) or followed by an inhibitory postsynaptic potential (39 of 93). The segmental delay of the early EPSPs was within the monosynaptic range (mean 0.85 ms); however, the rise time of these EPSPs was slow (mean 1.3 ms) and their amplitude was small (mean 0.74 mV). These values are significantly slower and smaller than EPSPs in a comparable sample of Old World macaque monkey motoneurons. The results show that CM connections do exist in the squirrel monkey but that they are weak and possibly located on the remote dendrites of the motoneurons. The findings are consistent with earlier anatomic studies. Repetitive PT stimulation produced large, late EPSPs in some motoneurons, suggesting that, in this species, there are relatively strong nonmonosynaptic pathways linking the corticospinal tract to hand motoneurons.

Animals↗
PubMed1997

Perceived uncertainty of outcome as a contributing factor in competitive state anxiety.

The Martens, Vealey, and Burton (1990) model of competitive anxiety contains perceived uncertainty, perceived importance, and competitive trait anxiety (A-trait) as key determinants affecting a person's perception of threat and competitive state anxiety (A-state). This experiment tested perceived uncertainty of outcome and A-trait influences on A-state. Club level golfers (N = 72) were assigned to either a low uncertainty condition (LU) or a high uncertainty (HU) condition. In this experiment participants were matched and competed for 12 golf balls in a modified chipping competition. Participants also completed the Competitive State Anxiety Inventory -2 and the Match Orientation Questionnaire (a measure of perceived uncertainty) prior to, and during breaks in the competition. Players alternated in taking four rounds of eight shots from a zone marked approximately 30 metres from the hole. A series of tests did not support the manipulation of uncertainty. This was probably due to likely losers and likely winners not experiencing similar levels of A-state, as Martens et al. assume. Recoding the uncertainty data to reflect levels of confidence, and entering confidence and A-trait into multiple regression equations resulted in these two variables accounting for between 15% and 23% of the A-state variance at different stages of the competition. Recommendations for future research, and possible revisions of the model in light of the present findings are discussed.

Adolescent↗
PubMed1997

Psychophysiological stress in elite golfers during practice and competition.

This study examined self-reported state anxiety (cognitive anxiety, somatic anxiety and self-confidence) measured by the Competitive State Anxiety Inventory-2 (CSAI-2; Martens, Vealey, Bump, & Smith, 1990) and physiological responses (salivary cortisol concentration and heart rate) in elite golfers prior to, during and on completion of a tournament and practice round. The relationships between psychophysiological variables were investigated by comparing physiological and psychological responses during competition and practice to each other, and to performance. Performance was determined for each player as the difference between 18 hole score and handicap. Fifteen male Professional Golfing Association (PGA) trainees (aged 21-25 years) competed in a PGA sanctioned tournament and a practice round on the same, or similar golf course. Players completed the CSAI-2 and collected saliva for cortisol analysis on four occasions: prior to tee off, and after completing holes 6, 12 and 18. Cortisol concentration was corrected for circadian variations in cortisol secretion, using baseline cortisol measures. Within-subject analysis revealed elite golfers experienced elevated cortisol, heart rate, cognitive and somatic anxiety, and lower self-confidence during competition compared to practice. For both game conditions, the highest cortisol response was measured prior to the commencement of play, whilst state anxiety measures did not change significantly during the golf rounds. Univariate and multivariate analyses failed to reveal significant correlations between the psychophysiological variables and golf performance. In conclusion, competition and practice were clearly discriminated by the psychophysiological variables, but none of these predicted performance.

Adult↗
PubMed1996

Molecular cloning and disease association of hepatitis G virus: a transfusion-transmissible agent.

An RNA virus, designated hepatitis G virus (HGV), was identified from the plasma of a patient with chronic hepatitis. Extension from an immunoreactive complementary DNA clone yielded the entire genome (9392 nucleotides) encoding a polyprotein of 2873 amino acids. The virus is closely related to GB virus C (GBV-C) and distantly related to hepatitis C virus, GBV-A, and GBV-B. HGV was associated with acute and chronic hepatitis. Persistent viremia was detected for up to 9 years in patients with hepatitis. The virus is transfusion-transmissible. It has a global distribution and is present within the volunteer blood donor population in the United States.

Acute Disease↗
PubMed1996

Rapid reverse transcription-PCR detection of hepatitis C virus RNA in serum by using the TaqMan fluorogenic detection system.

We describe the application of a new fluorogenic probe-based PCR assay (TaqMan; Perkin Elmer Corp./Applied Biosystems, Foster City, Calif.) for the detection of hepatitis C virus RNA in serum and plasma. This assay allows for the direct direction of specific PCR products within minutes of completion of the PCR by monitoring the increase in fluorescence of a dye-labeled oligonucleotide probe. We evaluated this assay by comparing the results obtained by nested PCR with those obtained by TaqMan PCR. Test samples included two separate dilutions series of plasma samples from experimentally infected chimpanzees and a panel of 48 serum specimens from patients with community-acquired hepatitis C virus. The quantity of HCV RNA in each chimpanzee plasma sample was determined by using branched DNA (bDNA) signal amplification assay (Quantiplex HCV RNA assay; Chiron Corp., Emeryville, Calif.). Both PCR assays demonstrated similar levels of detection and could reliably detect 13 bDNA genome equivalents per sample. We found an overall concordance of 88% between results of two PCR assays with the community-acquired panel, which resolved to 100% when discrepant samples were retested by nested PCR. TaqMan compared favorably with nested PCR with key advantages of speed, increased throughput, and decreased opportunity for false-positive results because of elimination of second-round amplification.

Animals↗
PubMed1996

An electronic consumer health library: NetWellness.

NetWellness is a community-based, consumer-defined grant program supporting the delivery of electronic health information to rural residents of southern Ohio and urban and suburban communities in the Greater Cincinnati tri-state region. NetWellness is a collaboratively developed and publicly and privately funded demonstration project. Information is delivered via ISDN, standard dial, dedicated network connections, and the Internet. TriState Online (Greater Cincinnati's Free-Net) and other southern Ohio Free-Nets are key access points in the larger project communities. The other access points are more than forty workstations distributed at public sites throughout the project's primary geographical area. Design strengths and limitations, training initiatives, technical issues, and the project's impact on medical librarianship are examined in this paper. Also discussed are ways of determining community needs and interest, building political alliances, finding and developing funding sources, and overcoming technical obstacles. NetWellness's Internet address is: http:@www.netwellness.org.

Community Participation↗
PubMed1995

A pseudoepidemic due to laboratory contamination deciphered by molecular analysis.

OBJECTIVE: A clinical, microbiological, and molecular analysis to identify the source of a cluster of pseudoinfections. DESIGNS: Retrospective analysis of the cases, prospective epidemiologic survey, and laboratory investigation. Molecular analysis of the isolates was performed using pulsed-field gel electrophoresis (PFGE). SETTING: A tertiary Veterans Affairs medical center. PATIENTS: Three patients admitted over a 2-week period with musculoskeletal complaints had one or more joint fluid specimens submitted for culture. In each case, anaerobic chopped meat-glucose broth (CMGB) tubes yielded one or more organisms not typically associated with septic arthritis (Enterobacter cloacae, Enterococcus faecium, Enterococcus casseliflavus, Enterococcus faecalis, Escherichia hermannii, and Pseudomonas diminuti). The first three organisms were isolated from specimens from multiple patients. Two patients had multiple positive cultures; for two patients, separate cultures yielded additional organisms on solid media. RESULTS: Laboratory investigation yielded an isolate of E faecium from 1 of 30 sham-inoculated CMGB tubes. PFGE analysis demonstrated that a single strain of E cloacae was isolated from four CMGB tubes representing all three patients, and a single strain of E faecium was isolated from CMGB tubes representing two patients and the sham-inoculated tube. CONCLUSIONS: The application of molecular typing clearly demonstrated clonality among the isolates and indicated that a common source of contamination, most likely the CMGB tubes, was responsible for these cases.

Adult↗
PubMed1995

The effect of prosthetic alignment on relative limb loading in persons with trans-tibial amputation: a preliminary report.

The prosthetic sockets of 14 independent persons with unilateral trans-tibial (BK) amputation were mounted on an adjustable alignment pylon. Vertical ground reaction forces were recorded in neutral prosthetic alignment and in 10 degrees of prosthetic socket varus, valgus, flexion, and extension. Stance phase time, peak vertical ground reaction force, and impulse were all found to be increased on the sound limb when compared to the amputated residual limb. Significant differences were found in stance phase time and peak vertical ground reaction force when comparing malaligned with neutrally aligned prosthetic limbs. Significant differences were also seen in impulse between neutrally aligned and malaligned prosthetic limbs. The results suggest that prosthetic malalignment in persons with trans-tibial amputation leads to increased loading of the contralateral limb.

Adult↗
PubMed1994

Incisal overjet as an outcome measure in unilateral cleft lip and palate management.

The Goslon Yardstick is a clinical tool used to rank dental study casts of persons with cleft lip and palate in the late mixed or early permanent dentition into one of five categories. It has been successfully used to investigate the outcomes of the surgical treatment of these anomalies as well as the effects of these deformities on untreated individuals. In this study, 40 study casts ranked by the Goslon Yardstick were digitized using a reflex metrograph. The overjet, overbite, and incisal angulation, and the crossbites of the canines and molars were calculated for each of the sets of casts. Multiple regression analysis was used to determine the predictive value of these variables upon the Goslon scores. The overjet was found to explain 87% of the variance of the Goslon score (p < .0001). No other component had a significant predictive value. The range of overjet associated with the different Goslon scores was calculated from the regression equation. In conclusion, the advantages of using overjet as an indicator of outcome as an alternative to the Goslon Yardstick were discussed.

Child↗
PubMed1993

Formation of large deletions by illegitimate recombination in the HPRT gene of primary human fibroblasts.

HPRT gene mutants were isolated from untreated and x-irradiated cultures of primary human fibroblasts, and mutants carrying large deletions were identified. The breakpoints of the deletions were mapped by methods based on the polymerase chain reaction, and the deletion junctions of four different mutants were sequenced. Alu repeats were associated with one end of three of these junctions, but in each case repeat sequences were not found at the other end. Sequence features found at the deletion breakpoints included in particular short direct and inverted repeats, which may mispair to promote illegitimate recombination. One mutant had additional bases inserted at the deletion junction; these bases formed a direct repeat with a sequence immediately adjacent to the junction, suggesting a mechanism of templated repair of broken DNA in deletion formation.

Base Sequence↗
PubMed1993

Analysis of large deletions in the HPRT gene of primary human fibroblasts using the polymerase chain reaction.

Spontaneous and X-ray-induced mutants of the HPRT gene were isolated from two primary human fibroblast lines. The limited life-span of the mutants restricted the use of methods requiring large quantities of DNA, and the polymerase chain reaction (PCR) was used in particular to check for the presence of multiple genomic sites in mutant analysis. Robust PCR primers were designed to amplify sites of up to 1 kb, mostly with 1-kb spacings between sites, over the entire 56-kb HPRT gene region. Using PCR, large deletions were found in 43% of independent X-ray-induced mutants, and their breakpoints were localized where these fell within the gene. Anonymous DNA sites in the Xq26 chromosomal region containing HPRT (covering > or = 1.5 Mb) were also amplified by PCR to assess codeletion with HPRT; sites up to 1 Mb distal to the gene (DXS86, DXS10) were codeleted in some mutants, but no mutant was found with loss of a proximal site (DXS79).

Base Sequence↗
PubMed1993

Rhinometry and open-mouth posture in young children.

A biracial sample of 348 elementary school children who were in the first grade were assessed for open-mouth posture (OMP) in the natural environment. In addition, rhinometry was performed on 296 of the children. Means were computed for percent OMP and cross-sectional nasal airway. Results indicated that, in general, these children exhibited relatively high rates of OMP. Boys displayed significantly greater OMP than girls, and black children showed significantly larger cross-sectional nasal areas than white children. A significant correlation between OMP and nasal area only was evident for children exhibiting OMP during more than 80% of the observation intervals. The implications of the findings were discussed.

Analysis of Variance↗
PubMed1993

High-resolution cytogenetic analysis of X-ray induced mutations of the HPRT gene of primary human fibroblasts.

We report cytogenetic analysis of X-ray induced mutants of the HPRT gene isolated from a primary human fibroblast line. The mutants were shown previously by molecular analysis to have total or partial HPRT gene deletions. Detailed analysis of the chromosomal region containing HPRT (the cytogenetic band Xq26) identified Xq26 aberrations in five of five total HPRT gene deletions but failed to detect any changes in two of two partial gene deletions. Four microdeletions were verified and quantified by a method termed the band ratio, which compares the distance between bands encompassing Xq26 and an adjacent X-chromosome region in elongated chromosomes. These measurements were supported by the presence or absence of the sub-band Xq26.2. One total HPRT gene deletion was also associated with an X;11 translocation involving band Xq26. The data strengthen earlier findings on the tolerance of the Xq26 region to large genetic changes (> 1 Mb), but also indicate that some mutations are more complex than simple deletion of DNA sequence.

Cells, Cultured↗