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Biomedical subjects

D Morgan

Publications and source records attributed to D Morgan.

At least 217 records · Page 12Linked to original sources
PubMed1991

Use of recovery VO2 to predict running economy.

The purpose of this study was to determine whether running economy (RE) could be predicted accurately using recovery VO2 values. Twelve runners (means VO2max = 61.9, SD 4.9 ml.kg-1.min-1) completed three treadmill RE sessions over a 2-week period. During each session, subjects performed three 6-min runs at 69%, 78%, and 87% VO2max. RE was calculated from a single 2-min gas collection during the last 2 min of running. Immediately following each run, recovery VO2 data obtained during randomly assigned 15-s, 20-s, or 25-s gas collections were used to predict exercise VO2. Correlations and mean absolute percentage variation (% VAR) between actual and predicted VO2 at each relative intensity and recovery period are reported. Although the relationship between actual and predicted VO2 was significant and more pronounced at higher exercise intensities, the overall magnitude of the association was low to moderate (r range = 0.50-0.81). The range of % VAR between actual and predicted aerobic demands also obscured marked underprediction (-6.5% to -12.5%) and overprediction (+10.1% to +17.4%) of actual VO2 in some subjects. These data suggest that 15-, 20-, and 25-s recovery VO2 values do not correlate strongly with steady-state VO2, nor do they adequately account for variation in individual economy profiles.

Adult↗
PubMed1991

Spontaneously productive C-type retrovirus infection of fish cell lines.

The spontaneous production and release of morphologically typical, 85 to 90 nm diameter C-type retrovirus particles from four cell lines derived from three species of warmwater fish have been identified. Virus pellets from cell culture supernatants showed high levels of Mn(2+)-dependent reverse transcriptase activity at 24 degrees C. Peak enzyme activity was associated with a 1 x 16 g/ml sucrose gradient fraction. All four isolates induced a cytolytic infection of a bluegill fry cell line within 6 to 10 days.

Animals↗
PubMed1991

Limitations of the countershock dose response: a study of transthoracic current.

Dose response assessment of countershock efficacy has been widely determined with respect to energy but not current. The purpose of this study was to examine the utility of the dose response method in a current-based model of transthoracic defibrillation (pentobarbital anesthetized dogs, n = 8). Ventricular fibrillation induction lasting 15 seconds was separated by 5-minute intervals. Current defibrillation threshold (DFT; the lowest current that successfully defibrillated) was determined by decreasing current on successive trials. Energy DFT equaled the energy value of the corresponding current DFT. Subsequent data were expressed in normalized terms with each DFT assigned a normalized value of 1.00. Three shocks were delivered in random order at each of seven normalized current nodes (total of 21 shocks): 0.55, 0.70, 0.85, 1.00, 1.15, 1.30, and 2.00 x DFT (early testing). Randomization was repeated, and a second set of 21 trials were performed (late testing). Composite plots were made relating normalized current and energy to the percent successful defibrillation. The dose response expressed in normalized energy demonstrated an overall shift to the left compared to current. The difference was significant at every node value below the estimated DFT. Ninety percent of successful trials with respect to current and energy occurred at or above 0.85 DFT and 0.55 DFT, respectively. Significant changes in impedance occurred between early testing (60 +/- 6 ohms) and late testing (47 +/- 5 ohms), n = 8, mean +/- SD. Current, compared to energy, is a more accurate parameter in the dose response assessment of transthoracic defibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Ciliary beat frequency in newborn infants.

The ciliary beat frequencies of 31 newborns and 14 adults were measured in vitro by a photodiode method at body temperature (37 degrees C). The mean (SD) neonatal ciliary beat frequency (12.7 (0.82) Hz) was faster than that in adults (11.1 (0.84) Hz) (p less than 0.01). Increased ciliary beat frequency may be advantageous during the neonatal period.

Adult↗
PubMed1991

An investigation of involvement in leisure activities after a stroke.

The purpose of this study was to determine the efficacy of occupational therapy intervention related to the leisure activities of stroke survivors. Forty discharged stroke patients were randomly assigned to an experimental group, which received occupational therapy intervention related to leisure activities, or to a control group. An independent evaluator assessed the patients' involvement in activities and satisfaction with that involvement on three separate occasions. The results showed no statistically significant differences between the experimental and control groups in activity involvement or satisfaction with that involvement. There are likely two reasons for these findings. First, the intervention was limited in scope (i.e., only five therapist visits), and second, many environmental factors strongly influence activity participation and satisfaction.

Activities of Daily Living↗
PubMed1991

Evolution of in vitro transformation and tumorigenesis of HPV16 and HPV18 immortalized primary cervical epithelial cells.

Cervical carcinoma develops through a progressive spectrum of premalignant intraepithelial lesions (CIN I-III), the majority of which are associated with human papillomavirus (HPV) types 16 and 18. We established HPV16 and HPV18 immortalized human cervical epithelial cell lines and used them as a model to investigate the genesis and progression of cervical malignancy. The cell lines when cultured in vitro in a system mimicking their in vivo environment exhibit cytologic atypia and a variety of defects in morphologic differentiation at early passage compared to their normal counterparts. With increased passage, these alterations progress to more severe grades, histologically similar to CIN III; however only a limited number of the cell lines are tumorigenic, mimicking the epidemiologic evidence on the rate of conversion from premalignant to invasive carcinoma. The observed changes are not associated with alterations of viral DNA integration or expression and may reflect specific cellular events or changes in virus-host interactions associated with malignant progression.

Cell Transformation, Neoplastic↗
PubMed1990

Prostaglandin E1 bladder instillations to control severe hemorrhagic cystitis.

Severe hemorrhagic cystitis developed in 6 children after marrow transplantation, 3 of whom had a viral etiology. All 6 patients received instillations of prostaglandin E1 directly into the bladder and 5 of the 6 had complete resolution of hematuria. This finding contrasts with our previous experience with severe hemorrhagic cystitis, particularly the type due to a viral infection, persisting in the face of numerous bladder manipulations. We encourage the use of this nontoxic treatment to gain further information regarding its effect on the bladder epithelium. The mechanism of action remains completely unknown.

Administration, Intravesical↗
PubMed1990

Human papillomavirus type 6b DNA required for initiation but not maintenance of transformation of C127 mouse cells.

We describe the transformation of C127 mouse fibroblasts with human papillomavirus type 6b (HPV-6b) DNA, which is associated primarily with benign tumors of the human genital tract. The major transformed phenotype of the HPV-6b-transfected cells lines, which had been G418 selected, pooled, and maintained without subsequent selection, was tumorigenicity in nude mice. We found that, unlike that reported for other HPVs or papovaviruses, the transformed phenotype was expressed after a delay, in which the cells had undergone extensive culture passages (about 20 passages or 100 generations). Interestingly, the HPV-6b DNA had become reduced or nondetectable in copy number in the cells by the time the transformed phenotype was expressed and in most of the tumors induced by the cells in nude mice, indicating that high levels of HPV-6b DNA were not required for maintenance of the transformed phenotype. Clonal cell lines gave similar results. When continued G418 selection was used to maintain high-copy-number HPV-6b DNA, the cells were tumorigenic, indicating that high levels of HPV-6b DNA did not suppress tumorigenesis. These studies suggest that HPV-6b DNA initiates transformation of C127 cells but is dispensable for expression or maintenance of the transformed phenotype. Transformation by HPV-6b DNA in vitro may provide insights into the HPV type-specific association with benign versus malignant lesions in vivo and may elucidate some of the oncogenic processes involved in tumor progression.

Animals↗
PubMed1990

Signature patterns of DNA restriction fragments of Helicobacter pylori before and after treatment.

The genomic DNA of Helicobacter pylori was studied by electrophoretic analysis of restriction endonuclease fragments. Twenty seven isolates from eight patients in the United Kingdom, obtained before and after treatment with nitrofurantoin, and two reference strains from Australia and Peru were investigated. Digestion of DNA with HaeIII, which gave the clearest band pattern of the 20 enzymes tested, showed that each set of isolates from a single patient had a unique band pattern. The DNA signature band patterns of strains from different patients were less than or equal to 62% similar (average 43%); similarities of patterns from the same patient were generally greater than or equal to 86%. Some minor but reproducible polymorphisms (less than or equal to five bands) in the signature region were detected in most consecutive isolates. Plasmid DNA was detected in isolates from five patients, but major pattern differences were attributed to genomic variation. It is concluded that the HaeIII DNA digest signature fingerprints provide a reproducible and sensitive method of discriminating between isolates of H pylori.

Campylobacter↗
PubMed1990

Nature of defibrillation: determinism versus probabilism.

The gradual transitions that are found between unsuccessful and successful shock strengths in percent success or dose-response curves suggest that defibrillation is a probabilistic phenomenon. This concept appears to be reinforced by the fact that a frequency distribution is observed in defibrillation threshold data and that a dose-response relationship is also obtained by integration of the frequency distribution. The purpose of this study was to investigate whether a deterministic threshold model (based on experimental results) could produce 1) gradual transitions in dose-response curves, and 2) a threshold frequency distribution for individual subjects. In the experimental phase of the study, a linear deterministic relationship was found between transthoracic threshold current and defibrillation episode number (other variables held constant) in pentobarbital-anesthetized dogs. The correlation coefficient for each dog was between 0.77 and 0.98 (P less than 0.01), and both positive and negative slopes were found. Based on these results, threshold current was modeled for computer simulation as a linear function of episode number. The model was thus purely deterministic with no random variability. For each simulated experiment, several parameters were varied: order of shocks (increment, decrement, random order), slope of threshold function, and percent error of the initial threshold. Several hundred computer simulations were performed to determine the effect of varying these parameters. In all cases, threshold-frequency distributions and sigmoidal dose-response curves with gradual transitions were produced. The results of this investigation demonstrate that the apparent probabilistic behavior of defibrillation can be produced by a deterministic relationship.

Animals↗
PubMed1990

Induction and autocrine receptor binding of transforming growth factor-beta 2 during terminal differentiation of primary mouse keratinocytes.

Primary cultures of mouse keratinocytes maintain a basal cell phenotype in 0.05 mM Ca2+ medium, while culture in 1.4 mM Ca2+ results in terminal differentiation and inhibition of DNA synthesis. Induction of differentiation by Ca2+ results in a 10- to 20-fold increase in the expression of transforming growth factor-beta 2 (TGF-beta 2) mRNA and peptide, but a decrease in the expression of TGF-beta 1. In contrast, binding and cross-linking analyses show that the number of available surface 80 kilodalton (kDa) and 65 kDa TGF-beta receptor types decrease during differentiation. However, a mild acid wash significantly increases the number of available receptor sites on the differentiated keratinocytes, indicating that the TGF-beta receptors are unavailable for binding due to masking by endogenous ligand. A significant level of TGF-beta 2 secretion and receptor binding occur before the decrease in DNA synthesis, suggesting that the inhibition of DNA synthesis associated with differentiation of keratinocytes is mediated through the production and autocrine action of TGF-beta 2.

Animals↗
PubMed1990

Immunological studies on onchocerciasis in Sierra Leone. 1. Pretreatment baseline data.

Cellular immune responses were tested in vitro using peripheral blood mononuclear cells from 203 individuals resident in an area of Sierra Leone where onchocerciasis is hyperendemic, and 32 individuals (Gambians) with no history of contact with Onchocerca volvulus. Mean reactivity to the mitogen, Concanavalin A, did not differ between these two groups, but responses to PPD were markedly lower in those with onchocerciasis. Proliferative responses to adult female O. volvulus antigen in the latter group were generally low although elevated reactivity was found in certain sub-groups. Higher responses were evident in infected 10-14 year olds, and there was an association between elevated reactivity to O. volvulus antigens and acute reactive dermatological signs, with individuals in the latter group also carrying higher dermal microfilarial loads. A sub-group presenting with lymphadenopathy showed the strongest associations of these three parameters. These results suggested the requirement for a threshold density of dermal microfilariae for induction of acute reactivity. The presence of immunosuppressive factors in soluble O. volvulus antigen was indicated by the ability to suppress, at low concentrations, the cellular responses to PPD of a proportion of individuals.

Adolescent↗
PubMed1990

Digital spot-film fluorography.

Initial assessment of the DSI unit proved the ergonomic advantages of the system compared with a conventional fluoroscopic/fluorographic system. Also, a decrease in radiation dose levels proved encouraging. Savings in respect of hard copy expenditure and higher patient throughout area which the DSI technique can exploit. However, spatial resolution is still not equal to that of conventional film/screen imaging, but the 1024 matrix option and the facility for post-processing of the images in terms of contrast, brightness and edge enhancement have produced diagnostically acceptable images for all examinations undertaken (see figures 4 and 5).

Adult↗