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Biomedical subjects

C White

Publications and source records attributed to C White.

At least 73 records · Page 4Linked to original sources
PubMed2000

Temporal and small-scale spatial variations of dissolved oxygen in the Rivers Thames, Pang and Kennet, UK.

Small-scale spatial dissolved oxygen concentrations were measured on three rivers by taking a number of transects along a river reach. Temporal (diurnal) variations were measured by use of continuous (15-min) monitors located at the mid-transect of the spatial observations. Spatial variation of dissolved oxygen concentrations were found to be relatively small (approx. +/- 10% dissolved oxygen) and biologically insignificant compared to diurnal changes under conditions of high productivity (approx. +/- 60% dissolved oxygen). The diurnal curves were analysed in order to estimate values of reaeration, photosynthesis and respiration on a daily basis for almost 3 months using process-based analytical techniques (the Delta and Hornberger and Kelly methods). The River Kennet was shown to be the most productive river followed by the River Pang and then the River Thames. The patterns of reaeration, photosynthesis and respiration and the behaviour of the three rivers are discussed.

England↗
PubMed2000

Copper accumulation by sulfate-reducing bacterial biofilms.

Sulfate-reducing bacterial biofilms were grown in continuous culture. When exposed to medium containing 20 or 200 microM Cu, biofilms accumulated Cu. Energy-dispersive X-ray analysis (EDXA) showed that accumulation of Cu occurred in the form of sulfides while EDXA mapping of Cu and S in biofilm sections indicated that they were not uniformly distributed but located in the surface of the biofilm. While the polymer content of biofilm exposed to 20 microM Cu did not appear to increase relative to control Cu-free biofilms, biofilms exposed to 200 microM Cu accumulated carbohydrate and smaller amounts of protein throughout the incubation period. The mechanism of uptake, therefore, appeared to be precipitation of Cu sulfides at the biofilm surface or in the liquid phase followed by entrapment of precipitated Cu sulfide by the exopolymer-enhanced biofilm.

Bacteria↗
PubMed2000

Ca2+ uptake by the sarcoplasmic reticulum decreases the amplitude of depolarization-dependent [Ca2+]i transients in rat gastric myocytes.

Gastric myocytes loaded with fura-2 were voltage-clamped at -60 mV. Depolarizations to 0 mV evoked nifedipine-sensitive (5 microM) inward currents and Ca2+ transients. Cyclopiazonic acid (5 microM) elevated steady-state [Ca2+]i and reduced Ca current (ICa), but when divalent cations were omitted from the extracellular solution, cyclopiazonic acid had no effect on either the amplitude or the current-voltage relationship of the nifedipine-sensitive current. This suggests that the reduction in ICa was caused by the rise in steady-state [Ca2+]i. The relationship between the total Ca2+ influx carried by the Ca2+ current (sigmaI(Ca).dt) and the amplitude of the Ca2+ transient (delta[Ca2+]i) was analysed for experiments using physiological Ca2+ solutions by calculating the ratio delta[Ca2+]i/sigmaI(Ca).dt. Cyclopiazonic acid (5 microM) and ryanodine (10 microM) both increased this ratio, indicating a decrease in the buffering power of the cell. Mimicking the increase in steady-state [Ca2+]i produced by these agents by changing the holding potential to -40 mV, however, did not affect delta[Ca2+]i/sigmaI(Ca).dt. It was concluded that up-take by a ryanodine-sensitive store normally limits Ca2+ distribution to the bulk cytoplasm following entry to the cell through dihydropyridine-sensitive channels.

Animals↗
PubMed2000

The role of personality in the development and perpetuation of chronic fatigue syndrome.

OBJECTIVES: Qualitative evidence suggests that personality may have special relevance to the predisposition, precipitation and perpetuation of chronic fatigue syndrome (CFS). This study compares three dimensions of personality - perfectionism, self-esteem, and emotional control in the personality profiles of CFS patients (N=44) and a control group (N=44) without a history of CFS, matched for age and gender. METHODS: Participants were assessed on the MPS [Frost RO, Marten P, Lahart C, Rosenblate R. The dimensions of perfectionism. Cognit Ther Res 1990;14:449-468.]; the Rosenberg Self-Esteem Scale [Rosenberg M. Society and the Adolescent Self-image. Princeton, NJ: Princeton Univ Press, 1965.]; the Courtauld Emotional Scale [Watson M, Greer S. Development of a questionnaire measure of emotional control. J Psychosom Res 1983;27:299-305.] and the Marlowe-Crowne Social Desirability Scale [Crowne DP, Marlowe D. A new scale of social desirability independent of psychopathology. J Consult Psychol 1960;24:349-354.]. RESULTS: Analyses revealed that the CFS group reported higher levels than the control group on the Total Perfectionism score and Doubts about Actions and the Concern over Mistakes subscales. Furthermore, the CFS group also reported lower self-esteem than the control group. No difference between the two groups was found on the dimensions of emotional control and social desirability response bias. CONCLUSION: A developmental model of CFS, which considers the predisposing, precipitating, and perpetuating factors that may account for the course of the disorder irrespective of etiology, is proposed. In the context of the results, recommendations for practice and future research are discussed.

Adolescent↗
PubMed2000

Copper resistance of Calluna vulgaris originating from the pollution gradient of a Cu-Ni smelter, in southwest Finland.

The copper (Cu) resistance of 1-year-old seedlings of heather (Calluna vulgaris) was tested in a greenhouse experiment. The plant material originated from seeds collected from three peatland sites located 1.2 km to the NW, and 2.5 and 5.5 km to the NE of the Harjavalta Cu-nickel (Ni) smelter, SW Finland. The plants were watered with a nutrient solution containing five different levels of Cu (1, 10, 22, 46 and 100 mg l(-1)). Cu clearly decreased the length growth of shoots, shoot and root biomass of C. vulgaris. More than 50% of the seedlings exposed to the highest Cu treatment died. C. vulgaris accumulated high amounts of Cu, the living old roots containing a maximum of 2200 mg kg(-1) Cu and the living stems 1300 mg kg(-1) Cu. Discolouring leaves contained higher Cu concentrations than green leaves. The results indicate Cu accumulation in roots and root-to-shoot transport. Some differences were found between the responses of the three seed provenances, but none of the populations proved to be more resistant to Cu than the others in all the measured responses.

Journal Article↗
PubMed2000

Percutaneous endoscopic gastrostomy at the time of tumour resection in advanced oral cancer.

The role of percutaneous endoscopic gastrostomy (PEG) in patients undergoing resection of head and neck malignancy is well established. The procedure may be performed pre- or post-operatively with intravenous sedation or alternatively under general anaesthesia at the time of tumour resection. There are concerns as to the safety of PEG, particularly when performed under intravenous sedation. Elderly patients with poor general health and those with airway compromise may be at significant risk. We believe that patients with advanced oral malignancy often fall into such groups and, therefore, we routinely perform PEG at the time of resection. The aim of this study was to determine the potential risk factors for PEG insertion in patients with advanced oral malignancy and present our experience with insertion at the time of resection. A retrospective study was undertaken of the risk factors for PEG insertion in 72 consecutive patients with stage IV oral cancer treated between April 1993 and March 2000. Age, sex, tumour site, past medical history, American Society of Anaesthesiologists (ASA) and laryngoscopy grade, as an assessment of potential airway compromise, were recorded. There were 72 patients, 40 males and 32 females, with a mean age of 63 years (27-90). Eighteen patients (25%) scored 3 or 4 on the ASA scores of physical status. Laryngoscopy grades were recorded in 65 patients; of these, 18 (25%) had reduced visualisation of the larynx and in two patients not even the epiglottis could be seen. It is concluded that patients with advanced oral cancer have significant risk factors for PEG placement. However, PEG can be safely performed at the time of ablative surgery and has the advantage of avoiding an additional operative event for the patient.

Adult↗
PubMed2000

Testicular dysfunction in men with primary hypothyroidism; reversal of hypogonadotrophic hypogonadism with replacement thyroxine.

OBJECTIVE: Primary hypothyroidism can cause disturbances in normal gonadal function. The aim of this study was to investigate the relationship in men between hypogonadism and primary hypothyroidism and the extent to which free and total testosterone levels rose after introduction of replacement thyroxine. DESIGN: Paired study of patients in a hypothyroid and thyroxine treated state. PATIENTS: Ten men with primary hypothyroidism. MEASUREMENTS: Free and total testosterone, gonadotrophin and prolactin levels before and after thyroxine replacement therapy. RESULTS: Low free testosterone levels (161 +/- 62 pmol/l) demonstrated at the time the men were hypothyroid rose significantly with the commencement of thyroxine replacement (315 +/- 141 pmol/l; P < 0.001). Gonadotrophin levels were not elevated consistent with hypogonadotrophic hypogonadism. Hyperprolactinaemia, which can occur in primary hypothyroidism and cause hypogonadotrophic hypogonadism, was not present in the majority of these patients. However a reduction in prolactin level was evident with thyroxine replacement and a rise in free testosterone levels. CONCLUSION: This suggests an effect of hypothyroidism on gonadotrophin secretion at the level of the hypothalamus-pituitary, either directly or through modulation of prolactin secretion. Low free testosterone may also be a contributing factor to some of the symptoms and signs of hypothyroidism in men.

Adult↗
PubMed2000

Medical students' self-assessments and their allocations of learning time.

PURPOSE: To investigate the impact of self-assessed diagnostic strengths and weaknesses on medical students' allocation of learning time (one indicator of self-directed learning) during a third-year internal medicine clerkship. METHOD: In 1997-98, 107 students at the University of Michigan Medical School self-assessed their diagnostic skills in 14 clinical areas before and after the clerkship and reported the relative amounts of time spent learning about these topics during the clerkship. RESULTS: Individual-level analyses indicated that, for the average student, self-assessed strengths and weaknesses did not correlate with allocation of educational time, but that time allocation was positively related to changes in self-assessed skill. Considerable variations in these relationships, however, suggest a need for closer study. CONCLUSION: Although individual students evidenced different levels of self-directed learning, this study suggests overall that students at this level of training are neophytes in applying both information generated through self-assessment and principles of self-directed learning in their clinical education. Attempts to advance students beyond this level depend on many factors, including the extent to which the learning environment encourages or even permits self-directed learning, the progression and time frame through which students become self-directed practitioners, and the impact of educational interventions to promote this development.

Humans↗
PubMed2000

Need for an external proficiency testing program for cytokines, chemokines, and plasma markers of immune activation.

An external evaluation program for measuring the performance of laboratories testing for cytokines and immune activation markers in biological fluids was developed. Cytokines, chemokines, soluble cytokine receptors, and other soluble markers of immune activation (CSM) were measured in plasma from a healthy human immunodeficiency virus (HIV)-seronegative reference population and from HIV-seropositive individuals as well as in supernatant fluids from in vitro-stimulated human immune cells. The 14 components measured were tumor necrosis factor (TNF) alpha, gamma interferon, interleukin-1 (IL-1), IL-2, IL-4, IL-6, IL-10, Rantes, MIP-Ia, MIP-Ibeta, soluble TNF receptor II, soluble IL-2 receptor alpha, beta(2)-microglobulin, and neopterin. Twelve laboratories associated with the Adult and Pediatric AIDS Clinical Trial Groups participated in the study. The performance features that were evaluated included intralaboratory variability, interlaboratory variability, comparison of reagent sources, and ability to detect CSM in the plasma of normal subjects as well as the changes occurring in disease. The principal findings were as follows: (i) on initial testing, i.e., before participating in the program, laboratories frequently differed markedly in their analytic results; (ii) the quality of testing of a CSM in individual participating laboratories could be assessed; (iii) most commercial kits allowed distinction between normal and abnormal plasma CSM levels and between supernatants of stimulated and unstimulated cells; (iv) different sources of reagents and reference standards frequently provided different absolute values; (v) inexperienced laboratories can benefit from participating in the program; (vi) laboratory performance improved during active participation in the program; and (vii) comparability between analyses conducted at different sites can be ensured by an external proficiency testing program.

Adult↗
PubMed2000

Radiotherapy-associated anemia: the scope of the problem.

The impact of anemia on cancer patients undergoing chemotherapy is well established, but only recently has the prevalence of anemia in patients receiving radiotherapy received much attention. Many cancer patients present with anemia prior to radiotherapy, and even more experience anemia or a worsening of anemia at some point during treatment. However, the problem of anemia is often ignored because patients may experience only functional anemia, defined as a hemoglobin level less than 12 g/dl. Unless physiologic anemia (hemoglobin = 8 g/dl) is discovered, efforts to correct anemia are often not made. Because hemoglobin levels <12 g/dl seem to be associated with tumor hypoxia and poorer outcomes of radiotherapy in a number of patient populations, ignoring even modest anemia can result in decreased locoregional control, overall survival, and quality of life (QOL). Because increasing hemoglobin levels 1-2 g/dl is usually easily accomplished, there exists the potential for improving outcomes by paying greater attention to this problem. This article focuses on the prevalence of anemia, particularly functional anemia, and discusses the impact of anemia on locoregional control, overall survival, and QOL.

Anemia↗
PubMed2000

Radiotherapy-Associated Anemia: The Scope of the Problem.

The impact of anemia on cancer patients undergoing chemotherapy is well established, but only recently has the prevalence of anemia in patients receiving radiotherapy received much attention. Many cancer patients present with anemia prior to radiotherapy, and even more experience anemia or a worsening of anemia at some point during treatment. However, the problem of anemia is often ignored because patients may experience only functional anemia, defined as a hemoglobin level less than 12 g/dl. Unless physiologic anemia (hemoglobin = 8 g/dl) is discovered, efforts to correct anemia are often not made. Because hemoglobin levels <12 g/dl seem to be associated with tumor hypoxia and poorer outcomes of radiotherapy in a number of patient populations, ignoring even modest anemia can result in decreased locoregional control, overall survival, and quality of life (QOL). Because increasing hemoglobin levels 1-2 g/dl is usually easily accomplished, there exists the potential for improving outcomes by paying greater attention to this problem. This article focuses on the prevalence of anemia, particularly functional anemia, and discusses the impact of anemia on locoregional control, overall survival, and QOL.

Journal Article↗
PubMed2000

Workforce projections for optometry.

BACKGROUND: A 1995 workforce study conducted by RAND estimated a large current surplus of eye care providers in the United States. Due to data limitations of the RAND study and the outdated optometric workforce information available, the American Optometric Association contracted with Abt Associates to conduct a study to project future workforce requirements for optometry. METHODS: We collected extensive data on both the supply (work hours, retirement rates, new entrants) and demand (patient encounters and associated time requirements) of optometrists. These data were collected from a survey using stratified random sampling of 1,100 practicing optometrists and were used to develop workforce projections for optometry through the year 2030. Projections were calculated using a forecasting tool that can be used to derive workforce and training requirements under a range of future scenarios. RESULTS: Workforce projections suggest an excess supply of optometrists is likely over the next 20 years. Over the next five years, approximately 550 optometrists are expected to retire each year, while more than 1,100 optometrists enter practice annually. Patient encounter volume is projected to increase steadily, but the effects of this increase are largely offset by an anticipated decrease in optometrist time requirements for routine eye examinations. DISCUSSION: To reduce the size of the anticipated excess supply, optometry may want to focus on ways that demand can be increased. One way to increase demand is through greater convergence between the actual demand for eye care services and the underlying public health need for eye care.

Adult↗
PubMed1999

Rural health. Country strife.

Funding mechanisms in the NHS need to take more account of rurality in allocating funds. Rurality is considered in allocating funds to other public services such as the police, education and district council services. Country areas have more, and smaller, hospitals than cities, and this involves extra costs.

Catchment Area, Health↗