Biomedical subjects
Publications and source records attributed to David L Jones.
Explore the source record for details and available documents.
Accurate estimates of mycelial exudation in time and space are crucial for the assessment of ectomycorrhizal involvement in biogeochemical processes. Knowledge of exudation from mycelia of ectomycorrhizal fungi is still limited, especially for fungi in symbiosis with a host. Pinus sylvestris seedlings colonized by Hebeloma crustuliniforme were grown in aseptic multicompartment dishes. This novel system enabled identification of exudates originating only from extramatrical mycelium. At harvest, hyphal density and numbers were estimated using microscopic imaging. A fractal geometric approach was adopted for calculation of exudation rates. The main compounds identified were oxalate and ferricrocin. The exudation rate for oxalate was 19 +/- 3 fmol per hyphal tip h(-1) (mean +/- standard error of the mean) or 488 +/- 95 fmol hyphal mm(-2) h(-1). Ferricrocin rates were approx. 10 000 times lower. The fractal dimension (D) of the mycelia was 1.4 +/- 0.1, suggesting an explorative growth. Potassium nutrition was a significant regulatory factor for ferricrocin but not oxalate. The results suggest that hyphal exudation may alter the chemical conditions of soil microsites and affect mineral dissolution. Calculations also indicated that oxalate exudation may be a significant carbon sink.
Survival and movement of Escherichia coli O157:H7 in both soil and vermicompost is of concern with regards to human health. Whilst it is accepted that E. coli O157:H7 can persist for considerable periods in soils, it is not expected to survive thermophilic composting processes. However, the natural behavior of earthworms is increasingly utilized for composting (vermicomposting), and the extent to which earthworms promote the survival and dispersal of the bacterium within such systems is unknown. The faecal material produced by earthworms provides a ready supply of labile organic substrates to surrounding microbes within soil and compost, thus promoting microbial activity. Earthworms can also cause significant movement of organisms through the channels they form. Survival and dispersal of E. coli O157:H7 were monitored in contaminated soil and farmyard manure subjected to earthworm digestion over 21 days. Our findings lead to the conclusion that anecic earthworms such as Lumbricus terrestris may significantly aid vertical movement of E. coli O157 in soil, whereas epigeic earthworms such as Dendrobaena veneta significantly aid lateral movement within compost. Although the presence of earthworms in soil and compost may aid proliferation of E. coli O157 in early stages of contamination, long-term persistence of the pathogen appears to be unaffected.
OBJECTIVE: The aero-acoustic aspects of nasalization that distinguish speakers with velopharyngeal adequacy from those with velopharyngeal inadequacy are well known. Differences in aerodynamic aspects of nasalization also have been demonstrated in normal speakers with cleft palate and their noncleft counterparts. The purpose of this study was to compare the amplitude and temporal patterns of oral-nasal balance in speakers with cleft palate and normal speech to those with normal speech without cleft palate. PATIENTS AND METHODS: Using the Nasal Accelerometric Vibrational Index technique, the time course and amplitude of oral-nasal balance were studied in 10 children with cleft palate and velopharyngeal adequacy and 10 noncleft controls. The speech sample included syllable, word, and sentence contexts, most of which were devoid of nasal consonants. RESULTS: The results indicate few differences between the two groups in contexts devoid of nasal consonants. However, significant differences were evident with regard to temporal aspects of oral-nasal balance in a nasal-oral consonant word context. CONCLUSIONS: Subtle structural-motor differences that may exist between normal speakers with and without cleft palate may be more evident when the spatiotemporal requirements for velar movement become more complex and result in a greater possible combination of oral-nasal impedance ratios.
OBJECTIVE: The present investigation was conducted to examine the prevalence of preschoolers with cleft palate who require speech therapy, demonstrate significant nasalization of speech, and produce compensatory articulations. The relationship among these three dependent variables and the independent variables of cleft type and age of primary palatal surgery was also examined. PARTICIPANTS: The participants included 212 preschoolers with repaired cleft palate aged 2 years 10 months to 5 years 6 months. MAIN OUTCOME MEASURES: Chi-square analyses were performed to examine the relationship between two independent variables (cleft type and age of surgery) and three dependent variables (percentage of children requiring speech therapy, percentage demonstrating moderate to severe hypernasality and receiving secondary management for velopharyngeal insufficiency, and percentage producing glottal/pharyngeal substitutions). RESULTS: Sixty-eight percent of the children were enrolled in (or had previously received) speech therapy. Thirty-seven percent of the children demonstrated moderate-severe hypernasality or had received secondary surgical management for velopharyngeal insufficiency. Chi-square analyses revealed a significant relationship between cleft type and the number of children referred for speech therapy as well as the number of children with significant hypernasality. The analyses also revealed a significant relationship between age of palatal surgery and number of children with significant hypernasality. CONCLUSIONS: Despite advances in surgical management and the advantages offered by team care, the majority of preschoolers with cleft palate continue to demonstrate delays in speech sound development that require direct speech therapy. An optimal treatment regimen for these children is one that includes primary palatal surgery no later than 13 months of age.
The temporal dynamics of partitioning and rhizodeposition of recent photosynthate in wheat (Triticum aestivum) roots were quantified in situ in solution culture. After a 30-min pulse of (14)CO(2) to a single intact leaf, (14)C activities of individual carbon fluxes in the root, including exudation, respiration, and root content, were measured continuously over the next 20 h concurrently with (14)C efflux from the leaf. Immediately after the end of the (14)CO(2) pulse, (14)C activity was detected in the root, the hydroponic solution, and in root respiration. The rate of (14)C exudation from the root was maximal after 2 to 3 h, and declined to one-third of maximum after a further 5 h. Completion of the rapid phase of (14)C efflux from the leaf coincided with peak (14)C exudation rate. Thus, exudation flux is much more rapidly and dynamically coupled to current photosynthesis than has been appreciated. Careful cross-calibration of (14)C counting methods allowed a dynamic (14)C budget to be constructed for the root. Cumulative (14)C exudation after 20 h was around 3% of (14)C fixed in photosynthesis. Partitioning of photosynthate between shoot and root was manipulated by partial defoliation before applying the (14)CO(2) pulse to the remaining intact leaf. Although the rate of photosynthesis was largely unaffected by partial defoliation, the proportion of new photosynthate subsequently partitioned to and exuded from the root was substantially reduced. This clearly indicates that exudation depends more on the rate of carbon import into the root than on the rate of photosynthesis.
OBJECTIVE: The purpose of this study was to determine whether amplitude or temporal patterns of oral-nasal balance differentiate speakers with cleft palate who are classified as belonging to the "almost but not quite" (ABNQ) and "sometimes but not always" (SBNA) subgroups of marginal velopharyngeal inadequacy. DESIGN: The nasal accelerometric vibrational index (NAVI) was used to measure amplitude and temporal aspects of oral-nasal balance during the productions of oral and nasal syllables, words, and sentences. NAVI measures obtained include mean amplitude, time integral (area under the curve), duration, rise time, and fall time. SETTING: Tertiary care center for patients with cleft palate-craniofacial anomalies. PARTICIPANTS: Seventeen patients with repaired cleft palate who were assigned by perceptual assessment to the ABNQ subgroup and 17 patients who were assigned to the SBNA subgroup. RESULTS: No differences were found between the ABNQ and SBNA subgroups with regard to patterns of nasalization. Further analysis as a function of level of production and phonetic context revealed no differences between the subgroups. CONCLUSIONS: Although clinicians may report perceived differences in the resonance patterns of speakers who fall within the category of marginal velopharyngeal inadequacy, further division into the ABNQ and SBNA subgroups has yet to be validated.
The purpose of this study was to determine whether 2 speech measures (peak intraoral air pressure [IOP] and IOP duration) obtained during the production of intervocalic stops would be altered as a function of the presence or absence of auditory stimulation provided by a cochlear implant (CI). Five pediatric CI users were required to produce repetitions of the words puppy and baby with their CIs turned on. The CIs were then turned off for 1 hr, at which time the speech sample was repeated with the CI still turned off. Seven children with normal hearing formed a comparison group. They were also tested twice, with a 1-hr intermediate interval. IOP and IOP duration were measured for the medial consonant in both auditory conditions. The results show that auditory condition affected peak IOP more so than IOP duration. Peak IOP was greater for /p/ than /b/ with the CI off, but some participants reduced or reversed this contrast when the CI was on. The findings suggest that different speakers with CIs may use different speech production strategies as they learn to use the auditory signal for speech.
A therapeutic-interchange clinic for statins is described. In 1999, the Department of Defense mandated the use of cerivastatin and simvastatin as the formulary statins in all military health care facilities by April 2000. Cerivastatin was the preferred agent; the goal was to use this agent in 60-65% of all patients. Walter Reed Army Medical Center developed a voluntary therapeutic-interchange clinic for patients receiving statins. Goals included facilitating the rapid switching of patients to the formulary statins, maximizing the use of the preferred agent, maintaining or improving lipid control, monitoring safety, determining costs, educating patients about their treatment, and documenting satisfaction with the clinic. Written educational materials were prepared, an algorithm for statin conversion was created, and laboratory tests were performed, among other measures. Between January and April 2000, 1356 patients were seen by the therapeutic-interchange clinic; of these, 942 agreed to have the efficacy and safety of their therapy monitored by the clinic. Before the formulary change, the most commonly prescribed statins were atorvastatin (44% of patients) and pravastatin (42%). Under the conversion policy, 96% of patients received cerivastatin and 4% simvastatin. The percentage of patients achieving their targeted low-density-lipoprotein cholesterol concentration increased from 65% to 75%. The policy saved an average of $115 per patient in the first year. Most patients were satisfied with the clinic, but only 36% of providers were satisfied. Cerivastatin was withdrawn from the market in August 2001; simvastatin became the only formulary statin. A therapeutic-interchange clinic at a military medical center provided an efficient means of switching a large number of patients to alternative statin therapy, monitoring the outcomes, and individualizing patient care.
OBJECTIVE: To determine whether speech hypernasality in subjects born with cleft palate can be reduced by graded velopharyngeal resistance training against continuous positive airway pressure (CPAP). DESIGN: Pretreatment versus immediate posttreatment comparison study. SETTING: Eight university and hospital speech clinics. PATIENTS: Forty-three subjects born with cleft palate, aged 3 years 10 months to 23 years 8 months, diagnosed with speech hypernasality. INTERVENTION: Eight weeks of 6 days per week in-home speech exercise sessions, increasing from 10 to 24 minutes, speaking against transnasal CPAP increasing from 4 to 8.5 cm H(2)0. MAIN OUTCOME MEASURES Pretreatment to immediate posttherapy change in perceptual nasality score based on blinded comparisons of subjects' speech samples to standard reference samples by six expert clinician-investigators. RESULTS: Participating clinical centers treated from two to nine eligible subjects, and results differed significantly across centers (interaction p =.004). Overall, there was statistically significant reduction in mean nasality score after 8 weeks of CPAP therapy, whether weighted equally across patients (mean reduction = 0.20 units on a scale of 1.0 to 7.0, p =.016) or across clinical centers (mean = 0.19, p =.046). This change was about one-sixth the maximum possible reduction from pretreatment. Nine patients showed reductions of at least half the maximum possible, but hypernasality of eight patients increased at least 30% above pretreatment level. Most improvement was seen during the second month when therapy was more intense (p =.045 for nonlinearity). No interactions with age or sex were detected. CONCLUSION: Patients receiving 8 weeks of velopharyngeal CPAP resistance training showed a net overall reduction in speech hypernasality, although response was quite variable across patients and clinical centers. The net reduction in hypernasality is not readily explainable by random variability, subject maturation, placebo effect, or regression to the mean. CPAP appears capable of substantially reducing speech hypernasality for some subjects with cleft palate.
BACKGROUND: Electron beam computed tomography is promoted as a test that may enhance patient motivation to alter cardiovascular risk behaviors. METHODS: We surveyed a consecutive sample of asymptomatic, active smokers (N = 144) who underwent screening electron beam computed tomography about their current motivation to alter their smoking behavior in the context of their tomography results. RESULTS: Patients with coronary artery calcification (42% of the sample) were more likely to perceive increased cardiovascular risk (42 vs. 13%; p < 0.01). Overall, most patients (59%) rated themselves as more motivated to quit smoking after electron beam computed tomography, but there was no relationship between motivational levels or smoking behavioral change and the presence of coronary artery calcification. CONCLUSIONS: In smokers predominantly self-referred for electron beam computed tomography, the presence of coronary artery calcification does not appear to influence motivation for smoking cessation or smoking behavior.