Search PubMed⌕ Search

Biomedical subjects

B Jones

Publications and source records attributed to B Jones.

At least 109 records · Page 6Linked to original sources
PubMed2000

The role of magnetic resonance imaging in late presentation of isolated injuries of the flexor digitorum profundus tendon in the finger.

Four patients had magnetic resonance imaging (MRI) after a clinical diagnosis of a flexor digitorum profundus tendon rupture of the hand. The delay before presentation ranged from 1 to 5 weeks. Three patients had closed ruptures and one had a minor laceration which had healed. MRI showed proximal retraction of the profundus tendon to the palm in two patients and limited retraction in the other two. MRI provides important preoperative information for surgical decision-making and planning in patients who present late with closed flexor tendon injuries of the hand.

Adult↗
PubMed2000

Peak occurrence of female sexual initiation predicts day of conception in rhesus monkeys (Macaca mulatta).

The present study investigated whether peaks in female sexual initiation could accurately predict conception in group-living female rhesus monkeys. Behavioral observations, 4 or 5 days per week in large, stable, social groups of monkeys, provided frequencies of female initiation of proximity, sexual solicitation, mounts, and ejaculations. Since a preovulatory peak in female sexual initiation is likely linked to the preovulatory oestradiol surge, we used the third day after a peak in behavior as the behavioral estimate of conception date. For each pregnancy, an independent estimate of conception date was derived from ultrasound determination of fetal length. Estimates of conception based on female initiation of proximity with adult males were accurate for more than 90% of pregnancies, whereas observation of ejaculations by males predicted conception in fewer than 60% of pregnancies. Behavioral and ultrasound estimates of conception date were highly correlated and differed by less than I day on average. Accordingly, predictions of delivery date based on behavioral estimates of conception date were as accurate as those based on ultrasound-derived estimates. These data suggest that female-initiated sexual behavior can be used in rhesus monkeys as a practical, non-invasive tool for producing timed matings in social groups of monkeys, providing accurate estimates of conception date, gestational age, and predicted date of birth.

Animals↗
PubMed2000

Modeling pharmacokinetic data using heavy-tailed multivariate distributions.

Pharmacokinetic studies of drug and metabolite concentrations in the blood are usually conducted as crossover trials, especially in Phases I and II. A longitudinal series of measurements is collected on each subject within each period. Dependence among such observations, within and between periods, will generally be fairly complex, requiring two levels of variance components, for the subjects and for the periods within subjects, and an autocorrelation within periods as well as a time-varying variance. Until now, the standard way in which this has been modeled is using a multivariate normal distribution. Here, we introduce procedures for simultaneously handling these various types of dependence in a wider class of distributions called the multivariate power exponential and Student t families. They can have the heavy tails required for handling the extreme observations that may occur in such contexts. We also consider various forms of serial dependence among the observations and find that they provide more improvement to our models than do the variance components. An integrated Ornstein-Uhlenbeck (IOU) stochastic process fits much better to our data set than the conventional continuous first-order autoregression, CAR(1). We apply these models to a Phase I study of the drug, flosequinan, and its metabolite.

Clinical Trials, Phase I as Topic↗
PubMed2000

Estrogen variation and resting left ventricular structure and function in young healthy females.

PURPOSE: A potential confounding factor in the interpretation of left ventricular (LV) structural and functional data in female subjects could be menstrual phase or contraceptive use upon assessment. To date no study has addressed this issue. METHODS: Seventeen eumenorrheic (EU; mean +/- SD age = 21 +/- 3 yr) and 14 combined-oral contraceptive pill-using (COC: mean +/- SD age = 21 +/- 3 yr) females volunteered to participate. The EU had stable menstrual cycles and the COC had all been using the same pill preparation for a minimum of 6 months. Echocardiographic examinations occurred during the mid-follicular phase and mid-luteal phases in the EU and during mid-consumption and mid-end of withdrawal in the COC. LV structure and function were assessed using M-mode and pulsed-wave Doppler echocardiography. Data were compared via Student t-tests and limits of agreement (LoA) were calculated. RESULTS: Structure and function did not significantly differ between phases of the menstrual cycle or between consumption and withdrawal of oral contraception (P > 0.05). However, there was considerable variance in the LoA between variables. Smaller LoA were reported for those variables directly measured from echocardiograms compared with those from derived data. For example, in a measured variable such as LV internal dimension in diastole, the LoA data represented a variation of +/- 0.4 mm (+/- 1%) between phases. Conversely, data for LV mass, a derived variable, reported LoA values of +/- 15 g (10%) between phases. The LoA were consistent between EU and COC. Variation in both measured and derived variables were within, or close to, accepted limits of measurement or biological error. CONCLUSION: It would seem that in studies assessing LV structure and function in women the influence of menstrual phase or oral contraceptive use is of minor significance.

Adult↗
PubMed2000

Generalized nonlinear models for pharmacokinetic data.

Phase I trials to study the pharmacokinetic properties of a new drug generally involve a restricted number of healthy volunteers. Because of the nature of the group involved in such studies, the appropriate distributional assumptions are not always obvious. These model assumptions include the actual distribution but also the ways in which the dispersion of responses is allowed to vary over time and the fact that small concentrations of a substance are not easily detectable and hence are left censored. We propose that a reasonably wide class of generalized nonlinear models allowing for left censoring be considered now that this is feasible with current computer power and sophisticated statistical packages. These modelling strategies are applied to a Phase I study of the drug flosequinan and its metabolite. This drug was developed for the treatment of heart failure. Because the metabolite also exhibits an active pharmacologic effect, study of both the parent drug and the metabolite is of interest.

Adult↗
PubMed2000

Peak expiratory flow profiles delivered by pump systems. Limitations due to wave action.

Pump systems are currently used to test the performance of both spirometers and peak expiratory flow (PEF) meters, but for certain flow profiles the input signal (i.e., requested profile) and the output profile can differ. We developed a mathematical model of wave action within a pump and compared the recorded flow profiles with both the input profiles and the output predicted by the model. Three American Thoracic Society (ATS) flow profiles and four artificial flow-versus-time profiles were delivered by a pump, first to a pneumotachograph (PT) on its own, then to the PT with a 32-cm upstream extension tube (which would favor wave action), and lastly with the PT in series with and immediately downstream to a mini-Wright peak flow meter. With the PT on its own, recorded flow for the seven profiles was 2.4 +/- 1.9% (mean +/- SD) higher than the pump's input flow, and similarly was 2.3 +/- 2.3% higher than the pump's output flow as predicted by the model. With the extension tube in place, the recorded flow was 6.6 +/- 6.4% higher than the input flow (range: 0.1 to 18.4%), but was only 1.2 +/- 2.5% higher than the output flow predicted by the model (range: -0.8 to 5.2%). With the mini-Wright meter in series, the flow recorded by the PT was on average 6.1 +/- 9.1% below the input flow (range: -23.8 to 2. 5%), but was only 0.6 +/- 3.3% above the pump's output flow predicted by the model (range: -5.5 to 3.9%). The mini-Wright meter's reading (corrected for its nonlinearity) was on average 1.3 +/- 3.6% below the model's predicted output flow (range: -9.0 to 1. 5%). The mini-Wright meter would be deemed outside ATS limits for accuracy for three of the seven profiles when compared with the pump's input PEF, but this would be true for only one profile when compared with the pump's output PEF as predicted by the model. Our study shows that the output flow from pump systems can differ from the input waveform depending on the operating configuration. This effect can be predicted with reasonable accuracy using a model based on nonsteady flow analysis that takes account of pressure wave reflections within pump systems.

Calibration↗
PubMed2000

'When more is less'. Reviewing the safety and cost of cardioplegia delivery.

There have been several new cardioplegia delivery systems that have been developed by various manufacturers in the last few years. In this evaluation, the safety and costs associated with the present 4:1 roller pump cardioplegia delivery were compared to the Medtronic Cardioplegia Safety System (CSS). One hundred and five patients participated in a randomized, prospective evaluation. The current cardioplegia delivery system consists of using the 4:1-B MYOtherm XP disposable by Avecor Cardiovascular and a Sarns MDX 7000 roller pump. The Medtronic Cardiotherm disposable cardioplegia unit was used in conjunction with the CSS. The current delivery system will be referred to as group A and the system under evaluation will be referred to as group B. Two varying techniques are employed for cardioplegia delivery and are based on surgeon preference. An equal distribution of techniques was seen in both groups. Results indicated that in group A, a hemoconcentrator was required 60.3% of the time, whereas in group B, a hemoconcentrator was added only 25.0% of the time. The average total cardioplegia delivered in group A was 6,588 cm3 compared to 7,123 cm3 in group B. Although this is insignificant, the greatest difference was seen in the amount of crystalloid given. In group A, the crystalloid portion was 1,317 cm3 compared to only 877 cm3 in group B. There was equal weight gain and hemodilution postop in both groups. Twenty-five incidences of pressurization of the cardioplegia system occurred during the evaluation, with equal distribution in both groups. This evaluation showed that the CSS responded without fail to all pressurization incidences. The Medtronic CSS has incorporated several safety systems for pressurization and air embolism protection, which are programmable and preset by the perfusionist. The Avecor disposable has a pressurization valve that activates at a pressure greater than 600 mmHg in the cardioplegia circuit. The Sarns MDX 7,000 does not incorporate any safety shutoffs. Cost savings were achieved in two areas: hemoconcentrator use and volume of cardioplegia solution required. There was a reduction of 35% in the use of a hemoconcentrator in group B, with more total cardioplegia delivered. The cardioplegia patient cost savings in group B totaled $265.95 per case in the plain cardioplegia group and $315.95 with the amino acid cardioplegia group. The new technology incorporated into the Medtronic CSS demonstrated that it could provide more safety with less cost than the current cardioplegia pump system.

Aged↗
PubMed2000

EEG hemispheric asymmetry as a predictor and correlate of short-term response to clozapine treatment in schizophrenia.

In search of early neuroleptic response predictors in schizophrenia, functional interhemispheric and intrahemispheric asymmetry indices, derived from spectrally analyzed resting electroencephalographic (EEG) activity, were examined in 17 schizophrenic patients prior to open label treatment with the atypical neuroleptic clozapine. Compared to EEG asymmetry indices derived from a normative data bank, patients exhibited significant interhemispheric (left greater than right) and intrahemispheric (anterior greater than posterior) deviations in delta, theta, alpha and beta frequency bands. Intrahemispheric indices were positively correlated with clinical ratings of positive symptoms and global psychopathology. Clozapine-induced improvements in positive and negative symptoms and global psychopathology symptom ratings were related to pretreatment intrahemispheric asymmetry only, with relationships varying with symptom, recording region and frequency band. The results are discussed in relation to the neurobiology of schizophrenia and the utility of EEG as an informative predictor of treatment response.

Adult↗
PubMed2000

Bilateral radical radiotherapy in a patient with uterus didelphys.

We report a case of congenital abnormality of uterus didelyphys in a patient who developed invasive carcinoma of the cervix. She received radical radiotherapy by a combination of external beam pelvic radiotherapy and high dose rate brachytherapy by insertion of afterloading catheters into both uterine canals. A newly defined prescription point was used midway between the two catheters and 2 cm above the mean cervical os position. The classical point A was regarded as inappropriate in this patient with a rare condition. Acute toxicity was minor and the patient is tumour free with no significant normal tissue late effects after follow-up of nearly 3 years.

Brachytherapy↗
PubMed2000

Dose equivalents of tumour repopulation during radiotherapy: the potential for confusion.

When employing linear quadratic equations to calculate compensation for changes in overall treatment time, a potential confusion exists regarding use of the parameter commonly described as the dose equivalent of tumour repopulation. The more correct term for this factor is the biologically effective dose equivalent of tumour repopulation. The distinction between the two concepts is discussed and the potential errors arising from their confusion are illustrated by means of an example.

Dose Fractionation, Radiation↗
PubMed2000

Clinical education in two-year colleges: cost-benefit issues.

Allied health program directors and administrators need to be aware of the costs and benefits of their clinical training programs to assure continued availability of training facilities for students. In a pilot study, program directors and administrators who are members of the National Network of Health Career Programs in Two-year Colleges (NN2) were surveyed concerning items to include in a cost-benefit-analysis tool, intangible and tangible costs and benefits of clinical education programs, and evaluation of a tool to analyze costs and benefits. Surveys were sent to 138 NN2 members, with 58 responding. Clinical sites were primarily in independent hospitals or health care systems. Most programs had preceptor-to-student ratios of 1:1-1:2, with few students being paid for clinical work. The respondents identified costs as staff time, materials and supplies, equipment, and others. Benefits were orientation and recruitment savings; increased professionalism, job satisfaction, and work quality of staff; ability to maintain and upgrade staff skills and knowledge; and student assistance with clinical coverage. Few programs were required to perform cost analysis. Allied health clinical education programs continue to depend on the willingness of health care facilities to accept students for clinical training.

Allied Health Personnel↗
PubMed2000

A comparison of individual and population smoking data from a postal survey and general practice records.

BACKGROUND: Data on smoking held by general practitioners (GPs) may contribute to clinical care and to an assessment of population health. However, these data are prone to several biases and their validity has not been tested. AIM: To examine the accuracy of general practice data as an estimate for population prevalence of smoking and to estimate the accuracy of GP data on individuals' smoking habit compared with self-report. METHODS: A postal questionnaire on smoking habit over the past six years was sent to a random sample of individuals aged 15 to 74 years and registered with five out of seven general practices in one part of Leicester. GP records of those sampled were examined for an entry of smoking status over this period. RESULTS: Response rate to the postal questionnaire was 1906 out of 2490 (76.5%). Reported smoking prevalence was 35.2%. Of those notes sampled, 1784 out of 2432 (73.4%) had an entry about smoking recorded between 1991 and 1996. Patients recorded as smokers were less likely to respond to the postal questionnaire than non-smokers. Using practice data to ascribe smoking status to non-responders produced an estimated prevalence of 38.6%. Using questionnaire data alone as the 'gold standard', the last practice record collected since 1991 overestimated current smoking prevalence by a factor of 1.22; using questionnaire data supplemented by practice data for non-responders as the 'gold standard' meant that the overestimate was by a factor of 1.11. Data from notes and the questionnaire were available for 1398 individuals and 2188 observations. Levels of agreement were high (kappa = 0.83). CONCLUSION: GP-held data are valid for individuals but over-estimate smoking prevalence at a population level.

Adolescent↗
PubMed1999

Frontonasal dysostosis in two successive generations.

Frontonasal dysostosis (also called frontonasal "dysplasia") comprises ocular hypertelorism, median facial cleft affecting nose and/or upper lip, unilateral or bilateral cleft of the alae nasi, anterior cranium bifidum occultum, or a widow's peak. Usually it is a sporadic disorder, although a few familial cases have been reported. We describe a 2-year-old girl with anterior cranium bifidum occultum, lipoma of genu and anterior part of the corpus callosum, and hypertelorism. Her mother had a history of a nasal drip at birth caused by a defect in the cribriform plate and phenotypically, a widow's peak. This observation suggests either autosomal dominant or X-linked dominant inheritance. The family illustrates the importance of identifying mild expression of frontonasal dysostosis before genetic counseling.

Abnormalities, Multiple↗