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Biomedical subjects

M McGrath

Publications and source records attributed to M McGrath.

At least 19 recordsLinked to original sources
PubMed2006

Chemical phosphorus removal to extremely low levels: experience of two plants in the Washington, DC area.

Chemical phosphorus removal using metal (iron and aluminium) salts is frequently used to control effluent soluble phosphorus levels in wastewater treatment plants. In the Washington DC area effluent phosphorus requirements are extremely stringent to protect the Chesapeake Bay. Full-scale data from two plants in the area were analysed to establish phosphate behaviour in the presence of iron. Titration experiments and mathematical modelling were performed to determine the role of ferric phosphate and hydroxide precipitation and other mechanisms that may potentially be involved in phosphorus removal. Iron addition is described in the model using a chemical equilibrium approach extended with surface charges and adsorption. The model verifies key observations from full-scale data: (a) extremely low orthophosphate levels can be achieved over a wide range of pH values, (b) a mixture of ferric phosphate and ferric hydroxide precipitate is forming with the hydroxide acting as sorbent, (c) molar ratios of Fe/P (iron dosed to phosphate removed) vary widely (1.0-3.9) based on the technology used and residual phosphate levels. The model will be a useful tool for engineers to optimise preliminary, simultaneous and tertiary P removal, both for design and plant operation.

District of Columbia↗
PubMed2005

Hypovitaminosis D among healthy adolescent girls attending an inner city school.

AIMS: To determine the prevalence of hypovitaminosis D among healthy adolescent schoolgirls attending an inner city multiethnic girls' school. METHODS: Fifty one (28%) of 182 girls (14 white, 37 non-white; median age 15.3 years, range 14.7-16.6) took part in the study. Biochemical parameters, dietary vitamin D intake, muscle function parameters, duration of daily sunlight exposure (SE), and percentage of body surface area exposed (%BSA) were measured. RESULTS: Thirty seven (73%) girls were vitamin D deficient (25-hydroxyvitamin D (25OHD) <30 nmol/l) and 9 (17%) were severely deficient (25OHD <12.5 nmol/l). The median (range) 25OHD concentration of white girls (37.3 nmol/l (18.3-73.3)) was higher than that of non-white girls (14.8 nmol/l (5.8-42.8)). The median (range) concentration of parathyroid hormone in white girls (2.8 pmol/l (1.0-3.7)) was lower than that of non-white girls (3.4 pmol/l (1.7-34.2)). Serum Ca, inorganic phosphate, alkaline phosphatase, and 1,25-dihydroxyvitamin D were not different in white and non-white girls. For the whole group, 25OHD concentration was related to the estimated SE and %BSA, but not to estimated intake of vitamin D. In white girls, the estimated SE and %BSA were significantly higher than that of non-white girls. The median times taken to complete the Gower's manoeuvre and grip strength were not different in the two groups; these variables were not related to serum 25OHD. CONCLUSIONS: Hypovitaminosis D is common among healthy adolescent girls; non-white girls are more severely deficient. Reduced sunshine exposure rather than diet explains the difference in vitamin D status of white and non-white girls.

Adolescent↗
PubMed2004

Effects of a vertical magnetic field on particle confinement in a magnetized plasma torus.

The particle confinement in a magnetized plasma torus with superimposed vertical magnetic field is modeled and measured experimentally. The formation of an equilibrium characterized by a parallel plasma current canceling out the grad B and curvature drifts is described using a two-fluid model. Characteristic response frequencies and relaxation rates are calculated. The predictions for the particle confinement time as a function of the vertical magnetic field are verified in a systematic experimental study on the TORPEX device, including the existence of an optimal vertical field and the anticorrelation between confinement time and density.

Journal Article↗
PubMed2004

Effects of lesions of the human posterior thalamus on ocular fixation during voluntary and visually triggered saccades.

OBJECTIVE: To investigate the role of the posterior thalamus in controlling voluntary and visually triggered eye movements and ocular fixation. METHODS: The latency to initiate saccades to peripheral targets (visually triggered) and in response to verbal commands (voluntary) was measured in three patients with unilateral lesions of the posterior thalamus, in normal controls, and in neurological controls with Parkinson's disease. On half the trials a fixation point offset simultaneously with target onset, and on half it remained visible. RESULTS: Offset of the fixation point simultaneous with target onset decreased saccade latency for both voluntary and visually triggered eye movements in controls, but only for voluntary saccades in patients with thalamic lesions. CONCLUSIONS: These findings suggest that separate neural systems control fixation when making voluntary and visually triggered eye movements, and that the thalamus is involved in the control of fixation for visually triggered but not for voluntary saccades.

Aged↗
PubMed2001

Determination of low-molecular-mass carboxylic acids in atmospheric aerosol and vehicle emission samples by capillary electrophoresis.

A method is developed for the determination of a large number of airborne and vehicle-emitted low-molecular-mass mono- and dicarboxylic acids using capillary electrophoresis with indirect UV detection. A background electrolyte (BGE) consisting of 2,6-naphthalenedicarboxylic acid and tetradecylmethylammonium bromide, adjusted to pH 6.2 with 2,2-bis(hydroxymethyl)-2,2',2"-nitrilotriethanol, is employed. Separations are robust using the buffered BGE, proper rinse steps, and constant current mode with migration time variations less than 3% RSD on a day-to-day basis, using different capillaries and performed by different analysts. Detection limits are at the tens of microg/l level using pressure injection. A comparison of the CE method with ion chromatography is also made.

Aerosols↗
PubMed2001

Aortopulmonary size discrepancy is not a contraindication to the pediatric Ross operation.

BACKGROUND: Modification of the aortic annulus or the ascending aorta, or both, may be required in pediatric patients undergoing the Ross operation. The fate of these autografts remains uncertain. METHODS: Retrospective review of 15 patients undergoing Ross operation without aortic annular modification (group 1), 11 patients requiring annular reduction (group 2, n = 11), and 8 patients requiring annular enlargement (group 3, n = 8). Autograft function and dimensions were evaluated by echocardiography. RESULTS: Autograft insufficiency was less than or equal to mild in 33 patients and moderate in 1 patient. The annulus body surface area ratio increased in group 1 from 19.7 +/- 5 to 20.3 +/- 5 mm/M2 (p = 0.8). The average annular reduction in group 2 was 5 +/- 1.5 mm, and 10 of 11 patients required reduction of the ascending aorta (mean 11 +/- 5 mm). The annulus body surface area ratio increased from 18.6 +/- 7 to 20.5 +/- 9 mm/M2 (p = 0.2). The mean augmentation in annulus diameter in group 3 was 6 +/- 4 mm; the annulus body surface area ratio decreased from 23.7 +/- 14 to 20.3 +/- 8 mm/M2 (p = 0.5). CONCLUSIONS: We continue to offer the Ross operation to pediatric patients even when aortic annular or ascending aortic size discrepancies mandate surgical modifications.

Adolescent↗
PubMed2001

Evaluation of the prognosis of in vitro fertilization pregnancies with initially low serum human chorionic gonadotropin levels.

OBJECTIVE: The objective of this study was to investigate the prognostic significance of initially low serum early human chorionic gonadotropin levels in in vitro fertilization pregnancies that progress to an intrauterine gestational sac. STUDY DESIGN: This retrospective cohort study compared 65 in vitro fertilization pregnancies with an initial human chorionic gonadotropin value at 4 weeks of < or =20 mIU/mL with 130 pregnancies with human chorionic gonadotropin values >20 mIU/mL. All pregnancies had a singleton intrauterine sac at 6 weeks' gestational age. Spontaneous abortion rates and pregnancy complications were compared. RESULTS: Women with a low initial serum human chorionic gonadotropin level showed a statistically significant increase in first-trimester pregnancy loss (36.5% vs 9.2%; odds ratio, 5.7; 95%; confidence interval, 2.6, 12.4; P <.0001). Once pregnancies progressed to 13 weeks, there were no significant differences. CONCLUSIONS: In vitro fertilization pregnancies with a low initial human chorionic gonadotropin value, despite progressing to a gestational sac, are at an increased risk of spontaneous abortion.

Abortion, Spontaneous↗
PubMed2001

Review of policies and guidelines on infant feeding in emergencies: common ground and gaps.

Recent crises in regions where exclusive breastfeeding is not the norm have highlighted the importance of effective policies and guidelines on infant feeding in emergencies. In 1993, UNICEF compiled a collection of policy and guideline documents relating to the feeding of infants in emergency situations. In June 2000 Save the Children, UK, UNICEF and the Institute of Child Health undertook a review of those documents, updating the list and identifying the common ground that exists among the different policies. The review also analysed the consistency of the policy framework, and highlighted important areas where guidelines are missing or unclear. This article is an attempt to share more widely the main issues arising from this review. The key conclusions were that, in general, there is consensus on what constitutes best practice in infant feeding, however, the lack of clarity in the respective responsibilities of key UN agencies (in particular UNICEF, UNHCR and WFP) over issues relating to co-ordination of activities which affect infant-feeding interventions constrains the implementation of systems to support best practice. Furthermore, the weak evidence base on effective and appropriate intervention strategies for supporting optimal infant feeding in emergencies means that there is poor understanding of the practical tasks needed to support mothers and minimise infant morbidity and mortality. We, therefore, have two key recommendations: first that the operational UN agencies, primarily UNICEF, examine the options for improving co-ordination on a range of activities to uphold best practice of infant feeding in emergencies; second, that urgent attention be given to developing and supporting operational research on the promotion of optimal infant-feeding interventions.

Guidelines as Topic↗
PubMed2001

From policy to practice: challenges in infant feeding in emergencies during the Balkan crisis.

The preparation and dissemination of policy statements are necessary but insufficient to prevent the inappropriate use of infant-feeding products in emergencies. The widespread failure of humanitarian agencies operating in the Balkan crisis to act in accordance with international policies and recommendations provides a recent example of the failure to translate infant-feeding policies into practice. This article explores the underlying reasons behind the failures which include: (1) the weak institutionalisation of policies; (2) the massive quantities of unsolicited donations of infant-feeding products: (3) the absence of monitoring systems; (4) inadequate co-ordination mechanisms; (5) the high costs of correcting mistakes; and (6) the cumulative effects of poor practice. Efforts to uphold best practice during the crisis are also documented. Finally, the article identifies actions that could be undertaken in advance of and during future emergencies to enhance the application of infant feeding policies in emergencies.

Albania↗
PubMed2000

Phasic and enduring negative symptoms in schizophrenia: biological markers and relationship to outcome.

Negative symptoms have been associated with poor response to neuroleptics, enlarged ventricles, cognitive impairment, and poor outcome in schizophrenia. These associations appear, however, to be dependent on the phase of study, suggesting that acute-phase (phasic) negative symptoms may be pathophysiologically distinct from enduring negative symptoms that persist through the residual phase. To compare correlates of enduring and phasic negative symptoms, we studied 60 drug-free schizophrenic patients (DSM-III-R and SADS/RDC) at baseline, 4 weeks after neuroleptic treatment, and assessed the 1 year outcome. We rated positive and negative symptoms at baseline and 4 weeks after treatment. At baseline, premorbid function, neuropsychological function, ventricle-brain ratio (VBR) and symptom response to an anticholinergic agent were assessed, and a two-night sleep EEG and 1mg dexamethasone suppression test (DST) were conducted. Phasic negative symptoms were defined as the change in negative symptoms (baseline to 4 weeks) and enduring negative symptoms as severity of negative symptoms at 4 weeks. Patients had varying proportions of phasic and enduring symptoms; the two did not define distinct subgroups. Phasic negative symptoms were significantly correlated with global treatment response, positive symptom treatment response, response to anticholinergic agent, baseline post-dexamethasone cortisol, and shortened REM latency. Enduring negative symptoms were significantly correlated with residual positive symptoms and global psychopathology, VBR, poor performance on neuropsychological testing, decreased slow-wave sleep, poor premorbid function, and poor 1 year outcome. These data suggest that phasic negative symptoms and enduring negative symptoms may be caused by different pathophysiological mechanisms.

Adult↗
PubMed2000

Determination of low-molecular-weight carboxylic acids in the ambient air and vehicle emissions: a review.

This review surveys analysis of airborne and vehicle emitted low-molecular-weight carboxylic acids. Attention is paid to providing a comprehensive coverage of collection techniques, sample handling, storage, extraction methods followed by a discussion of recent developments in carboxylic acid analysis using chromatographic (gas and ion chromatography) and electrophoretic (capillary electrophoresis) techniques. The occurrence and sources of carboxylic acids in the ambient air are also summarized.

Air Pollutants↗
PubMed2000

Thromboprophylaxis using a low molecular weight heparin delays fracture repair.

Low molecular weight heparins are significantly superior to unfractionated heparin or warfarin in the prevention of thromboembolic episodes associated with orthopaedic surgery. Therapeutic doses of heparin and warfarin have been shown to delay bone repair in a rabbit model. The current study investigated the effect of prophylactic administration of a low molecular weight heparin, enoxaparin, on the healing of a closed rabbit rib fracture. Fracture healing was assessed using histomorphometric, histologic, and immunohistochemical methods at 3, 7, and 14 days, and biomechanical testing with torsional loading was assessed after 21 days. Bone repair was significantly attenuated at all times in animals receiving subcutaneous enoxaparin compared with that of the control animals. Numerous putative mechanisms for this phenomenon are discussed, and additional studies are proposed to elucidate the effects of this pharmacologically diverse group of compounds on all aspects of bone physiology and repair.

Animals↗
PubMed1999

Sarcoidosis in a patient with AIDS: a manifestation of immune restoration syndrome.

Sarcoidosis has been rarely reported in the presence of HIV infection. Helper T-lymphocyte depletion may attenuate granuloma formation. We present a patient who developed active sarcoidosis after being started on highly active antiretroviral therapy (HAART), which increased his CD4 count and decreased his viral load. There have been reports of exaggerated responses to mycobacteria and viruses with the restoration of T-cell function after HAART in HIV-infected patients. We propose that active sarcoidosis seen in this patient is also a manifestation of this newly observed "immune restoration disease."

Acquired Immunodeficiency Syndrome↗
PubMed1999

Successful PBSC mobilization with high-dose G-CSF for patients failing a first round of mobilization.

PBSC are the preferred source of stem cells for autologous transplantation. However, regardless of the mobilization procedure used, 10%-20% of patients fail to collect an adequate number to ensure prompt engraftment. There is as yet no standard mobilization procedure for patients who fail a first mobilization attempt. Here, we describe a highly efficient strategy to obtain an adequate number of stem cells for patients who failed a first mobilization attempt. Seventy-four patients with various hematologic malignancies underwent initial mobilization with various regimens including hematopoietic growth factors with or without chemotherapy. In 72% of patients, > or =2 x 10(6) CD34+ stem cells/kg were collected in the initial mobilization attempt, and patients engrafted in a median of 10 days for neutrophils and 12 days for platelets. Eighteen patients failed to mobilize adequate numbers of stem cells, defined as the inability to collect 0.2 x 10(6) CD34+ stem cells/kg/day in the first 2-3 days. These patients had their apheresis halted. Patients were immediately given G-CSF (32 microg/kg/day) for 4 days as a second attempt at mobilization. Eighty-eight percent of these patients achieved the target of > or =2 x 10(6) CD34+ cells/kg, with a median duration of apheresis of 5 days (including the first and second mobilizations). The mean CD34+ cells/kg/day increased after administration of high-dose G-CSF from 0.16 after the first mobilization attempt to 0.61 (p = 0.0002) after the second mobilization. All patients engrafted in a median of 11 and 13 days for neutrophils and platelets, respectively. We conclude that patients whose apheresis yield is <0.4 x 10(6) CD34+ cells/kg after the first two apheresis collections can be successfully mobilized if high-dose G-CSF is administered immediately and continued until achieving > or =2 x 10(6) CD34+ stem cells/kg.

Adult↗
PubMed1999

Effect of a curfew law on juvenile trauma.

OBJECTIVE: As a method of crime reduction among teenagers, several cities, counties, and states across the country have enacted, or attempted to enact, curfew laws. A curfew law was successfully implemented in Dade County, Florida, in January of 1996. Although its efficacy for crime reduction has been questioned, its benefit for trauma prevention may be real. METHODS: Trauma registry data was collected retrospectively and prospectively from Dade County's Level I trauma center for all trauma victims 5 to 16 years of age. The time period spanned the 2 years before the institution of the curfew law (January 1, 1996) and the 2 years after. Total adult and pediatric trauma volumes during the 4-year period were used as comparisons, as well as juvenile traumas occurring during noncurfew hours. RESULTS: Total trauma volume did not change significantly across the 4-year period, nor did the volume among the curfew age group during noncurfew hours. The predominant mechanisms of injury during curfew hours were motor vehicle crashes and gunshots. Neither the patterns of mechanisms nor ages changed significantly during the precurfew and postcurfew eras. However, the volume of cases seen at the trauma center among the curfew age group was significantly lower with the curfew law in effect (mean, 7.0/month) than before it was in effect (mean, 9.5/month, p = 0.043). CONCLUSION: Although the overall trauma admissions and juvenile trauma admissions during the noncurfew hours remained relatively stable, juvenile trauma admissions during curfew hours dropped significantly in the 2 years after enforcement of the curfew law compared with the 2 years before the curfew law. This finding suggests that attempts to prevent late-night nonproductive street presence among teens can decrease the incidence of trauma occurrences.

Adolescent↗