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Biomedical subjects

R Clark

Publications and source records attributed to R Clark.

At least 37 records · Page 2Linked to original sources
PubMed2004

Portable lead analyzer to locate source of lead.

OBJECTIVE: To investigate the sources of lead in the environment in children with elevated blood, with the help of a Field Portable X-Ray Fluorescence Analyzer. METHODS: One hundred and seven school children were chosen for this study on a random basis, from Mangalore and Karnataka. Their blood lead was analyzed. Of the cases analyzed, 10 students whose blood lead level was more than 40 microg/dl were investigated using a field portable X-Ray Fluorescence Analyzer. This is the first time such a device has been available for this purpose in India. RESULTS: The 'likely' source of lead exposure could be determined in eight cases which was from the immediate environment of the children like 'lead-based' paint on surfaces in the house, on playground and other exterior equipment; lead storage batteries, contaminated dust and soil and other lead-containing substances. CONCLUSION: The use of an X-Ray Fluorescence Analyser appeared to be useful in determining the source of lead.

Child↗
PubMed2003

Measurement of the proton spin structure function g1(x,Q2) for Q2 from 0.15 to 1.6 GeV2 with CLAS.

Double-polarization asymmetries for inclusive ep scattering were measured at Jefferson Lab using 2.6 and 4.3 GeV longitudinally polarized electrons incident on a longitudinally polarized NH3 target in the CLAS detector. The polarized structure function g(1)(x,Q2) was extracted throughout the nucleon resonance region and into the deep inelastic regime, for Q(2)=0.15-1.64 GeV2. The contributions to the first moment Gamma(1)(Q2)= integral g(1)(x,Q2) dx were determined up to Q(2)=1.2 GeV2. Using a parametrization for g(1) in the unmeasured low x regions, the complete first moment was estimated over this Q2 region. A rapid change in Gamma(1) is observed for Q2<1 GeV2, with a sign change near Q(2)=0.3 GeV2, indicating dominant contributions from the resonance region. At Q(2)=1.2 GeV2 our data are below the perturbative QCD evolved scaling value.

Journal Article↗
PubMed2003

First measurement of transferred polarization in the exclusive ep-->e'K+Lambda--> reaction.

The first measurements of the transferred polarization for the exclusive e-->p-->e(')K+Lambda--> reaction have been performed at Jefferson Laboratory using the CLAS spectrometer. A 2.567 GeV beam was used to measure the hyperon polarization over Q2 from 0.3 to 1.5 (GeV/c)(2), W from 1.6 to 2.15 GeV, and over the full K+ center-of-mass angular range. Comparison with predictions of hadrodynamic models indicates strong sensitivity to the underlying resonance contributions. A nonrelativistic quark-model interpretation of our data suggests that the ssmacr; quark pair is produced with spins predominantly antialigned. Implications for the validity of the most widely used quark-pair creation operator are discussed.

Journal Article↗
PubMed2002

Eta photoproduction on the proton for photon energies from 0.75 to 1.95 GeV.

Differential cross sections for gammap-->etap have been measured with tagged real photons for incident photon energies from 0.75 to 1.95 GeV. Mesons were identified by missing mass reconstruction using kinematical information for protons scattered in the production process. The data provide the first extensive angular distribution measurements for the process above W=1.75 GeV. Comparison with preliminary results from a constituent quark model support the suggestion that a third S11 resonance with mass approximately 1.8 GeV couples to the etaN channel.

Journal Article↗
PubMed2002

Sequence of Plasmodium falciparum chromosomes 1, 3-9 and 13.

Since the sequencing of the first two chromosomes of the malaria parasite, Plasmodium falciparum, there has been a concerted effort to sequence and assemble the entire genome of this organism. Here we report the sequence of chromosomes 1, 3-9 and 13 of P. falciparum clone 3D7--these chromosomes account for approximately 55% of the total genome. We describe the methods used to map, sequence and annotate these chromosomes. By comparing our assemblies with the optical map, we indicate the completeness of the resulting sequence. During annotation, we assign Gene Ontology terms to the predicted gene products, and observe clustering of some malaria-specific terms to specific chromosomes. We identify a highly conserved sequence element found in the intergenic region of internal var genes that is not associated with their telomeric counterparts.

Animals↗
PubMed2002

Direct decay from the superdeformed band to the yrast line in 15266Dy86.

The excitation energy, spin, and parity of the yrast superdeformed band in 152Dy have been firmly established. The evidence comes mainly from the measured properties of a 4011 keV single-step transition connecting the yrast superdeformed level fed by the 693 keV transition to the 27- yrast state. Four additional, weaker, linking gamma rays have been placed as well. The excitation energy of the lowest superdeformed band member is 10 644 keV and its spin and parity are determined to be 24+.

Journal Article↗
PubMed2002

Display of positron emission tomography with Cadplan.

Recent clinical experience at Peter MacCallum Cancer Institute (PMCI) with the use of unregistered Positron Emission Tomography (PET) images for radiotherapy target marking in the lung suggests that co-registered PET images would be invaluable. PMCI has three radiotherapy treatment planning systems but none of them currently is able to display or co-register PET images with Computed Tomography (CT) images. This paper details the approach taken to display co-registered PET images with the CADPLAN treatment planning system. CT Image files are normally transferred to Cadplan by DICOM transfer, but the Cadplan DICOM server will not receive (has no presentation context for) PET images. The fundamental design of the CADPLAN system envisages display of only a single image dataset, which must be a CT scan for planning reasons. The problem of data transfer is crudely solved by File Transfer Protocol (FTP) over the network. Fortunately the multislice format of the PET image files makes individual transfer manageable. A menu based C program running at the same time as Cadplan is invoked to sample the DICOM PET Image and create multiple Cadplan CART image format files that are co-registered with each existing transverse CT slice. With the Cadplan in contour mode, the program allows the co-registered PET images to be swapped in and out of the image section of the CART files promptly, while keeping the contour information. This allows radiotherapy target volumes to be marked using transverse PET emission images, and effectively circumvents the design constraints prohibiting the display of more than one image set. Contours can be over-laid for review on reconstructed sagittal or coronal views of CT or PET images constructed using the standard Cadplan tools. Co-registration is facilitated by identical positioning with the aid of lasers and FDG loaded fiducial markers on the PET scanner and CT couch. A polyurethane cast fixed with EFFILOCK is used to ensure identical patient orientation on the CT and PET couches. Since both imaging modalities are without significant geometric distortion the co-registration is then simply a translation. PET transmission images can be used for co-registration verification. The practical implementation of display of PET images with CADPLAN has enabled us to begin a trial of 10 patients, the results of which will be reported separately.

Data Display↗
PubMed2002

Validity and responsiveness of the euroqol as a measure of health-related quality of life in people enrolled in an AIDS clinical trial.

OBJECTIVE: Brief utility measures are needed in clinical trials in addition to existing descriptive measures of health-related quality of life (HRQOL). We examined the reliability and validity of the EuroQol (EQ-SD) and MOS-HIV and their responsiveness to HIV-related clinical events. METHODS: Subjects with advanced HIV disease (CD4 < 100) were enrolled in a randomized trial for CMV prophylaxis (n = 990). The EQ-5D includes a weighted sum of five domains (EQ-5D Index) and a visual analog scale (EQ-VAS). The MOS-HIV has 10 subscales and physical (PHS) and mental health summary scores (MHS). Construct validity of the EQ-5D was tested based on hypothesized relationships to subscales of the MOS-HIV. Relative precision and responsiveness to adverse experiences and opportunistic infections (Ols) were compared for the two instruments. RESULTS: Mean age of the patients was 38, 94% were male, 80% white, and 7% had injected drugs. Mean baseline scores for EQ-5D Index and EQ-VAS were 0.80 and 76.0, respectively, 28 and 4% reported maximum scores. Mean MOS-HIV subscales score ranged from 55 (role) to 84 (cognitive); mean PHS and MHS were 47.4 and 49.5, respectively. Correlations between MOS-HIV subscales and EQ-5D Index ranged from 0.45 (role) to 0.63 (pain); correlations with EQ-VAS ranged from 0.33 (cognitive) to 0.66 (health perceptions). Correlations between MOS-HIV PHS and MHS with EQ-5D Index were 0.61 and 0.58; and with EQ-VAS, 0.57 and 0.60, respectively. Responsiveness to adverse experiences was highest for MOS-HIV pain and PHS (effect sizes = 0.9 and 0.4); pain had the highest relative precision (2.4) for adverse experiences: EQ-VAS had the greatest relative precision (1.6) for developing an OI. CONCLUSION: In these patients with advanced HIV disease. EQ-5D showed good construct validity, but there may be a ceiling effect for its EQ-5D Index component. EQ-5D was less responsive to adverse events than the MOS-HIV. However, the EQ-VAS was most sensitive to developing an OI and is likely to be a useful measure of HRQOL for generating QALYs in cost-utility studies involving patients with advanced HIV disease.

AIDS-Related Opportunistic Infections↗
PubMed2002

The effects of new topical treatments on management of glaucoma in Scotland: an examination of ophthalmological health care.

BACKGROUND: The management of glaucoma has been changed in the past decade by the introduction of new drugs. The impact of these changes on clinical care of patients was examined by examining operation and prescribing rates for glaucoma in four geographical areas of Scotland for the years 1994 to 1999. METHODS: A retrospective analysis of national health statistics: primary care prescribing data, hospital derived operation rates, consultant numbers, optometrist numbers, and eye test data, expressed by estimated population at risk of glaucoma. The outcome measures were prescribing volume and cost for glaucoma medications, and operation rates, corrected for population estimated to be at risk of glaucoma (PEG), for trabeculectomy, for Scotland as a whole, and for four geographical "regions" (north east, south east, central, and south west Scotland). RESULTS: Prescribed items per 1000 population estimated to have glaucoma (PEG) increased by 24.9% between 1994 and 1999. This was above the general increase in prescribing in Scotland (17.8%). This increase varied in the four health regions evaluated (14.3% to 31.9%). Prescribing of topical beta blockers increased little (6.4%), but there was a large increase in the use of new products (topical prostaglandins, carbonic anhydrase inhibitors, and alpha(2) agonists), at the expense of miotics (47.7% fall), and older sympathomimetics. This change in prescribing pattern was accompanied by a 61.5% increase in cost (range 42.2% to 73.4% in the four regions). New drugs accounted for more than half of total glaucoma expenditure in 1999. Operation rates (corrected for PEG) fell by 45.9% (range 43.1 to 58.6%) between 1994 and 1999. Other indicators suggested increased activity in ophthalmic areas (for example, cataract operations, eye tests, numbers of optometrists and ophthalmic surgeons all increased). Within north east Scotland operation rates decreased and prescribing increased less than in other regions, both from lowest regional baseline in 1994. CONCLUSIONS: The introduction of new drug classes has had dramatic effects on the prescribing of glaucoma treatments. There has been a decline in older treatments and an increase in new agents, which has been associated with a large reduction in operation rates for glaucoma in Scotland over 6 years. Comparison of prescribing and operation data indicates regional differences in healthcare delivery for glaucoma.

Administration, Topical↗
PubMed2001

Medicare reform.

Explore the source record for details and available documents.

Aged↗
PubMed2001

Quantification of optic nerve axon loss associated with a relative afferent pupillary defect in the monkey.

OBJECTIVE: To quantify the amount of optic nerve axonal loss associated with the presence of a mild relative afferent pupillary defect (RAPD) in an experimental monkey model. METHODS: The right macula of 5 rhesus monkeys (Macaca mulatta) was treated with concentrically enlarging diode laser burns until an RAPD was detected using a transilluminator light and measured with neutral density filters. Intervals between treatments were 3 to 7 days over a period of 2 months. Pupillary responses to light stimulation were recorded with a monocular infrared television pupillometer. Two months after detection of an RAPD, 5 treated and 4 control monkeys underwent euthanasia and enucleation. Histopathologic analysis and quantification of optic nerve axon counts using an image analysis system were performed. RESULTS: No RAPD was observed despite an estimated ganglion cell loss of up to 26%. A 0.6 log unit RAPD was present in 5 monkeys when the laser scar incorporated the entire macula within the temporal vascular arcades. One eye had progressive vitreomacular traction with worsening of the RAPD to 1.8 log units without further laser treatment. Histopathologic evaluation disclosed complete loss of the normal retinal architecture within the macula. The average fiber loss for the 4 treated eyes with 0.6 log unit RAPDs compared with fellow eyes was 53.3% (95% confidence interval [CI], 45.0%-61.6%). The average difference in axon counts between untreated pairs of optic nerves was 12.8% (95% CI, 10.0%-15.6%). Optic nerve axon loss between pairs of experimental and control eyes was statistically significant (P<.001). CONCLUSION: In rhesus monkeys, an RAPD develops after an approximate unilateral loss between 25% and 50% of retinal ganglion cells. CLINICAL RELEVANCE: Owing to redundancy in the anterior visual pathways, unilateral retinal ganglion cell loss may occur prior to the observation of an RAPD. The presence of an RAPD measuring 0.6 log units implies that significant retinal ganglion cell injury has occurred.

Animals↗
PubMed2001

Effects of biologic and experiential conditions on the pattern of growth in weight of premature and full-term infants.

In this exploratory study we examined the contribution of biologic and experiential conditions to the pattern of growth in weight for premature and full-term infants. The three components of the pattern were: (a) the infant's weight level; (b) the linear growth rate; and (c) the quadratic growth rate. Biologic conditions were maturity at birth and gender. Experiential conditions included variables in the mother's caregiving and the infant's feeding behavior, nutrient intake, and acuity of illness. At 1, 4, 8, and 12 months, premature infants (n = 61) weighed significantly less than full-term infants (n = 53), but neither linear nor quadratic rates of weight gain were significantly different from the rates for the full-term infants. Multilevel analytic models showed that female gender significantly affected weight level and linear and quadratic growth rates. Negative affect and behavior in both the mother and the infant significantly increased the linear rate of weight gain. The interaction of several experiential conditions with the two biologic conditions, birth maturity and gender, affected growth outcomes. Further exploration of the model with a larger sample is indicated to enable simultaneous testing of biologic and experiential conditions.

Adolescent↗
PubMed2001

Naumoff short-rib polydactyly syndrome compounded with Mohr oral-facial-digital syndrome.

A stillborn baby boy had findings of severe constitutional dwarfism with short limbs, short ribs, and polydactyly that were consistent with Naumoff (type III) short-rib polydactyly syndrome. He also had additional congenital anomalies, including cleft palate, notching of the upper lip, small tongue with accessory sublingual tissue. These oral and pharyngeal anomalies were consistent with Mohr (type II) oral-facial-digital syndrome. We suggest the stillborn infant represented a compound of Naumoff short-rib polydactyly syndrome (SRPS-III) and Mohr oral-facial-digital syndrome (OFDS-II).

Fatal Outcome↗
PubMed2001

Effects of in vivo heregulin beta1 treatment in wild-type and ErbB gene-targeted mice depend on receptor levels and pregnancy.

Mice heterozygous (+/-) for either heregulin (HRG), ErbB2, or ErbB3 were created by gene targeting, resulting in the loss of one functional gene copy and an associated decrease in targeted protein. We examined the in vivo activity of recombinant HRG peptide, rHRG beta1 (amino acids 177 to 241), in the three heterozygous mouse lines and in wild-type (WT) mice, both pregnant and nonpregnant. Nonpregnant WT and HRG(+/-) mice of both sexes were sensitive to rHRG beta1 treatment as evidenced by a high mortality rate associated with abdominal enlargement and parietal cell loss. However, pregnant WT mice and ErbB2 and ErbB3 heterozygous mice treated with rHRG beta1 were less affected, with significantly lower mortality rates and a less severe abdominal phenotype. Histological analysis revealed extensive breast ductal hyperplasia in females of all genotypes after rHRG beta1 treatment. Hyperplasia of other epithelial tissues such as the pancreas and intestine and the growth of cardiac nerve bundles were also observed, independent of sex.

Animals↗
PubMed2001

Acoustic measures of phonatory improvement secondary to treatment by oral corticosteroids in a professional singer: a case report.

Short-term administration of corticosteriods is sometimes indicated for professional voice users experiencing laryngeal edema and/or inflammation. Unfortunately, no data are available to document the effectiveness of these medications to improve phonatory parameters. We present a case report of a 32-year-old male professional singer with vocal fold edema experiencing imminent vocal demands who was prescribed a 6-day course (dose-pack) of oral methyl prednisolone. Endoscopic and stroboscopic evaluations were completed premedication and postmedication, and acoustic measures of phonatory function were obtained premedication, 3 days during the dose cycle, 5 days during the dose cycle, and 1 day postmedication. Postmedication results revealed an increase in fundamental frequency (F0) and large decreases in jitter, shimmer, long-term frequency, and amplitude variability. These corresponded with patient and evaluator perceptual measures of improved voice, and with endoscopic observations of reduced edema. The benefits and risks of corticosteroid therapy are discussed, specific to their use in the professional voice population.

Adult↗