PubMed Health⌕ Search

Biomedical subjects

D W Morgan

Publications and source records attributed to D W Morgan.

At least 19 recordsLinked to original sources
PubMed1996

Short-term changes in 10-km race pace aerobic demand and gait mechanics following a bout of high-intensity distance running.

Following treadmill accommodation and a 3-day period of tapered running, ten well-trained male distance runners [x maximum oxygen uptake (VO2max) = 71.3 ml.kg-1.min-1] performed two 10-min level treadmill runs designed to assess running economy at 90% VO2max. Video recordings were obtained during the last minute of each run to quantify selected gait descriptors. Two to 3 days following the second economy run, each subject completed 30 min of high-intensity (HI) running at 90% VO2max. One 2, and 4 days after the HI run, subjects repeated the 10-min economy runs. Compared to pre HI-run values, no significant change (P > 0.05) in running economy was observed during the post-HI runs. Biomechanical analyses also revealed that running style remained unaltered after the HI run. These results support earlier findings obtained on moderately trained subjects featuring measurement of running economy and gait mechanics at less-demanding intensities and suggest that among well-trained athletes, 30 min of HI running does not elicit an increase in VO2 or disrupt gait mechanics over the short term in subsequent distance runs performed at near-maximal speeds.

Aerobiosis↗
PubMed1996

Relationships between running economy and temporal EMG characteristics of bi-articular leg muscles.

Relationships between running economy (RE; submaximal VO(2) for a given running speed) and the temporal EMG characteristics of bi-articular leg muscles were quantified in a group of well-trained runners. Nine subjects completed three test sessions: a determination of maximal aerobic demand (VO(2)max); an accommodation session at the experimental speed of 4.13 m.s(-1) and a session during which EMG and RE data were collected simultaneously at the experimental speed of 4.13 m.s(-1) Measures of muscle onset, on-time durations, and on-time coactivation durations were calculated from the following muscles: rectus femoris, medial hamstrings, lateral hamstrings, and gastrocnemius. Nonparametric correlations between RE and EMG characteristics displayed both positive and negative relationships and exhibited a wide range of values. Two EMG measures were significantly correlated (r > 0.67) with RE. Earlier onset of rectus femoris during swing phase and a shorter duration of hamstring - gastrocnemius coactivation during swing were associated with more economical runners. Although not statistically significant, correlation coefficients calculated for measures of coactivation during stance and RE ranged from -0.42 to -0.65. This trend indicates that individuals who exhibited a greater amount of coactivation between bi-articular muscles during the stance phase of the running cycle tended to be more economical. These relationships suggest different activation patterns in bi-articular muscles between economical and uneconomical runners.

Adult↗
PubMed1996

The association between flexibility and running economy in sub-elite male distance runners.

The purpose of this study was to examine the association between nine measures of limb and trunk flexibility and running economy. Within a week prior to running economy assessment, and after 10 min of jogging at 3.13 m.s-1, 19 well-trained male sub-elite distance runners underwent two complete sets of lower limb and trunk flexibility assessments. Runners then completed two 10-min running economy assessment sessions on consecutive days at 4.13 m.s-1 following two 30-min sessions of treadmill accommodation at 4.13 m.s-1. Intraclass correlation coefficients indicated that the repeated flexibility measurements were highly reliable (X R = 0.92 +/- 0.09), as were the two running economy appraisals (R = 0.99). Correlational analyses revealed that dorsiflexion (r = 0.65) and standing hip rotation (r = 0.53) were significantly (P < or = 0.05) associated with the mean aerobic demand of running, such that runners who were less flexible on these measures were more economical. Although speculative, these results suggest that inflexibility in certain areas of the musculoskeletal system may enhance running economy in sub-elite male runners by increasing storage and return of elastic energy and minimizing the need for muscle-stabilizing activity.

Adult↗
PubMed1996

Are prostaglandins major mediators in perennial allergic rhinitis?

Certain prostaglandins acting as inflammatory mediators have been implicated in the aetiology of perennial allergic rhinitis (PAR). Inhibition of prostaglandin synthesis in the nasal mucosa might therefore influence the symptoms associated with PAR. A randomised, doubleblind, placebo-controlled cross-over trial using 0.1% Diclofenac eye-drops has been conducted to investigate this hypothesis. Diclofenac, a non-steroidal anti-inflammatory drug (NSAID), reduces prostaglandin synthesis through the inhibition of the cyclo-oxygenase pathway. Twenty-five patients with significant PAR and positive skin tests to relevant perennial allergens were recruited and two drops of the given preparation were administered bilaterally q.d.s.. Thirteen patients completed the study. Nasal symptom score (itch, rhinorrhoea, sneezing, and blockage), smell test score, saccharin transit time, total nasal airflow resistance, and nasal inspiratory peak flow measurements were obtained at each of three study visits. No significant treatment effects were found. The daily nasal symptom score over the entire study period showed no significant variation. Adverse effects such as local invitation, dry nose or throat were rare. No untoward changes in haematological, biochemical profiles and urinalysis occurred. In conclusion, topical 0.1% Diclofenac eye-drops applied nasally have no significant effect on PAR. Prostaglandins alone may not play a major role in mediation of symptoms in this condition.

Administration, Intranasal↗
PubMed1995

Attentional strategy use by experienced distance runners: physiological and psychological effects.

The purpose of this investigation was twofold: (a) to compare most and least economical runners on use of attentional strategies and (b) to determine whether the least economical runners within the subject sample could improve running economy (RE) with the use of an active associative (relaxation) attentional strategy. Subjects (N = 36) completed an initial assessment of attentional style and RE; then the 12 least economical runners ran in each of three laboratory sessions using control, passive associative, and active associative attentional strategies. Results showed that the most economical and least economical runners did not differ in associative style use. The most economical runners, however, reported less dissociation use and more use of relaxation than did the least economical runners. No significant physiological or psychological changes were associated with any of the three attentional strategy conditions. The findings are related to possible differences in how most and least economical runners use associative strategies.

Adolescent↗
PubMed1995

Variation in the aerobic demand of running among trained and untrained subjects.

Variation in the aerobic demand (VO2) of submaximal running was quantified among trained and untrained subjects stratified by performance capability. Based on a retrospective analysis of seven published studies, maximal aerobic power (VO2max), and submaximal VO2 values were analyzed in three groups of trained distance runners (Category 1 (C1) (elite runners; N = 22), Category 2 (C2) (sub-elite runners; N = 41), and Category 3 (C3) (good runners; N = 16), and one group (N = 10) of untrained subjects (Category 4; C4). Results indicated that VO2max differed significantly (P < 0.05) across groups, such that C1 > C2 > C3 > C4. Analysis of submaximal VO2 data also revealed that C4 was more uneconomical than C1, C2, and C3 and that C2 and C3 were less economical than C1. Average within-group variability in submaximal VO2 was similar across categories and a marked overlap of minimum, mean and maximal economy values existed across categories. These data suggest that 1) trained subjects are more economical than untrained subjects, 2) elite runners display better economy compared to less-talented counterparts, and 3) economical and uneconomical runners can be found in all performance categories.

Adult↗
PubMed1995

Seroprevalence of human immunodeficiency virus among inpatient pretrial detainees.

Medical records of inpatients discharged from a forensic unit in Columbia, South Carolina, from January 1991 to December 1991 were reviewed to determine the incidence of human immunodeficiency virus (HIV) seropositivity. Results were linked to age, gender, ethnicity, history of intravenous drug use, and Axis I diagnoses. HIV status was obtained for 74 percent of patients 18 to 55 years of age. The incidence of HIV seropositivity among patients tested was 5.5 percent, which is greater than 40 times the incidence for the general population in South Carolina. Intravenous drug use was reported for 33 percent of the seropositive males. We conclude that inpatient pretrial detainees are at increased risk for HIV infection. HIV testing should be mandated at all facilities housing detainees. Further studies are needed to determine any factors about these patients that can be linked to seropositivity.

AIDS Serodiagnosis↗
PubMed1994

Interleukin-1 beta induces cytosolic phospholipase A2 and prostaglandin H synthase in rheumatoid synovial fibroblasts. Evidence for their roles in the production of prostaglandin E2.

OBJECTIVE: In order to investigate potential regulatory mechanisms for the increased production of prostaglandin E2 (PGE2) in interleukin-1 beta (IL-1 beta)-stimulated rheumatoid synovial fibroblasts (RSF), this study examined the induction of phospholipase A2 (PLA2) and prostaglandin H synthase (PGHS) enzymes and the correlation of these events with PGE2 production in IL-1 beta-stimulated RSF. METHODS: Protein and messenger RNA (mRNA) levels of cytosolic PLA2 (cPLA2) and PGHS-2 enzymes in IL-1 beta-stimulated RSF were measured by Western and Northern blotting, respectively, using specific antisera and complementary DNA probes. Enzymatic activity of cPLA2 was determined in cell-free reaction mixtures utilizing mixed micelles of 14C-phosphatidylcholine and Triton X-100 as the substrate. PGE2 levels were quantitated using a commercial enzyme immunoassay kit. RESULTS: Incubation of RSF with IL-1 beta increased the mRNA and protein levels for the high molecular weight cPLA2 as well as for the mitogen/growth factor-responsive PGHS (PGHS-2). The IL-1 receptor antagonist completely abolished the induction of these two enzymes and the stimulation of PGE2 production by IL-1 beta in RSF. In contrast, levels of the other known forms of these enzymes, i.e., the 14-kd secretory group II PLA2 (sPLA2) and the constitutive form of PGHS (PGHS-1), were unaffected by IL-1 beta treatment. CONCLUSION: These are the first data to demonstrate the coordinate induction by IL-1 of cPLA2 and PGHS-2 in RSF. The time-course for the induction of these enzymes suggests that their increase contributes to the increased production of PGE2 in IL-1-treated RSF, and may help explain the capacity of RSF to produce large amounts of PGE2.

Arthritis, Rheumatoid↗
PubMed1994

Daily variability in exercise ventilation.

The purpose of this study was to quantify daily variability in ventilation (VE) during submaximal exercise and establish the number of testing sessions required to produce stable exercise ventilation measures. Following 60 min of treadmill accommodation, four male (M) and four female (F) distance runners completed 5 weeks of daily treadmill testing at the same time of day while engaged in a normal routine of training and racing. During each test session, subjects completed three 6-min level treadmill runs at either 3.13, 3.57, and 4.02 m.sec-1 for F or 3.57, 4.02, and 4.47 m.sec-1 for M. Measures of VE were obtained during the last 2 min of each 6-min run. Results indicated that the mean coefficient of variation (CV) for VE across speeds was 4.33%. Reliability analyses examining all possible combinations of testing days over the 5-week period revealed that 97% of the variation in mean VE was accounted for in either 2 consecutive or non-consecutive days, while 98% of the variation in mean VE was accounted for in 5 consecutive days. These data suggest that when treadmill exposure and circadian variation are controlled, intraindividual differences in exercise VE are relatively small in male and female subjects following an unrestricted program of training and competitive racing. Additionally, acceptably stable VE values in this cohort can be derived by averaging duplicate measures obtained from consecutive or non-consecutive testing sessions.

Adult↗
PubMed1994

Relationship between VO2max and the aerobic demand of running in elite distance runners.

The purpose of this study was to assess the relationship between VO2max and the aerobic demand of running (VO2submax) in elite distance runners. On at least one occasion, VO2max and VO2submax values were obtained on 22 male subjects (mean age = 27 +/- 2 yrs; mean height = 178.6 +/- 6.8 cm; mean body mass = 64.1 +/- 5.6 kg; mean 10 km run time = 28.89 +/- 1.05 min) training for the 1994 Olympic Trials. Subjects performed 6-min, submaximal level-grade treadmill runs at four speeds (ranging from 4.47 to 5.50 m.s-1) to determine VO2submax. VO2 during each run was calculated by analyzing a 2-min gas sample collected during the last 2 min of running. These values were expressed relative to distance traveled and averaged to derive an overall VO2submax value. Shortly following these submaximal runs, VO2max was measured. When more than one set of VO2submax and VO2max data were available for a particular subject, the average of all tests was used. Results indicated that mean VO2max and VO2submax values were 75.8 +/- 3.4 ml.kg-1.min-1 and 184.6 +/- 8.6 ml.kg-1.km-1, respectively. Correlational analyses also revealed a significant relationship (r = 0.59; p < 0.01) between VO2max and VO2submax. These data suggest that among similarly-performing elite distance runners, a positive relationship exists between VO2max and the aerobic demand of running.

Adult↗
PubMed1993

Recombinant human type II phospholipase A2 lacks edema producing activity in rat.

The rat paw edema-inducing, acute inflammatory activity of four snake venom phospholipase A2S (PLA2) (Naja naja, Naja mocambique mocambique, Crotalus atrox and recombinant Naja naja naja) and of recombinant human type II PLA2 (rh-PLA2) found in rheumatoid synovial fluid, were compared after a bolus subplantar injection. The snake venom-derived PLA2s, including the recombinant Naja naja naja, were potent inducers of paw edema. On the other hand, when given in similar amounts (protein and/or enzymatic activity), the rh-PLA2 did not produce paw edema. Furthermore, the addition of Naja naja PLA2, blood plasma from rats with adjuvant arthritis or the E. coli-based enzymatic incubation mixture used to measure PLA2 activity to the injection mixture containing rh-PLA2, did not result in paw edema-inducing activity. These results suggest that the lack of paw edema-inducing activity of rh-PLA2 may be due to significant structural differences between snake venom PLA2s and human PLA2 which allow snake venom PLA2s, but not the human group II PLA2, to express inflammatory activity as measured by paw edema in rat induced by a bolus injection.

Animals↗
PubMed1993

Interleukin-1 beta induces cytosolic PLA2 in parallel with prostaglandin E2 in rheumatoid synovial fibroblasts.

We investigated the temporal relationship between the increase in enzymatic activity and protein of a high molecular weight (100 kDa), cytosolic PLA2 (cPLA2) in interleukin-1 beta (IL-1 beta)-treated rheumatoid synovial fibroblasts (RSF). Both of these responses increased according to a similar time-course which correlates with PGE2 production by these cells. In contrast, 14 kDa, secreted PLA2 (sPLA2), which was also produced by RSF, was not affected by IL-1 beta treatment. These findings support that an augmentation of CPLA2 activity, caused by an induction of cPLA2 protein, rather than sPLA2, is temporally associated with increased PGE2 production in IL-1 beta-treated RSF.

Arthritis, Rheumatoid↗
PubMed1993

Secretory phospholipase A2 inhibitors and calmodulin antagonists as inhibitors of cytosolic phospholipase A2.

Human cytosolic phospholipase A2 (cPLA2, 85 kDa) appears to be pharmacologically distinct from human secretory phospholipase A2 (sPLA2, 14 kDa). Marine natural products and PLA2 substrate and product analogs were potent inhibitors of human recombinant sPLA2 (r-sPLA2), whereas these compounds stimulated, weakly inhibited, or had no effect on cPLA2 activity from the human monocytic cell line U937. In contrast, within a series of seven reported calmodulin (CaM) antagonists tested, significant correlations among the rank order of potencies of these compounds as inhibitors of cPLA2, r-sPLA2, and a CaM-dependent phosphodiesterase were observed. The correlated inhibitory effects of the hydrophobic CaM antagonists on cPLA2 and sPLA2 may reflect a common feature (possibly a hydrophobic domain) shared by these two types of enzymes.

3',5'-Cyclic-AMP Phosphodiesterases↗