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Biomedical subjects

D R Smith

Publications and source records attributed to D R Smith.

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

Metamaterials and negative refractive index.

Recently, artificially constructed metamaterials have become of considerable interest, because these materials can exhibit electromagnetic characteristics unlike those of any conventional materials. Artificial magnetism and negative refractive index are two specific types of behavior that have been demonstrated over the past few years, illustrating the new physics and new applications possible when we expand our view as to what constitutes a material. In this review, we describe recent advances in metamaterials research and discuss the potential that these materials may hold for realizing new and seemingly exotic electromagnetic phenomena.

Journal Article↗
PubMed2004

Epidemiology of hand dermatitis among rural nursing students in mainland China: results from a preliminary study.

INTRODUCTION: Although hand dermatitis (HD) is known to affect nursing students worldwide, no studies of this disease have yet been conducted in China. Similarly, rural populations are often neglected in international research. METHODS: A preliminary study of female students from both grades of a hospital-based nursing school was conducted in Hebei Province, China, approximately 280 km south of Beijing. There were 27 students from the 2nd year of the course (47.4%) and 30 students from the 3rd year (52.6%). The study protocol involved an anonymous questionnaire distributed to a convenience sample of both grades from the nursing school. Statistical differences in prevalence by year of study were calculated using Fisher's exact test for discrete variables and One-way Analysis of Variance (ANOVA) for continuous variables. Statistical associations between HD and demographic items were investigated using the chi2 test. Where statistical association with HD were identified, simple logistic regression was also performed to establish a basic risk magnitude. Results were compared with similar populations of student nurses from previous studies in Australia, Japan, Denmark, the Netherlands and Germany. RESULTS: HD prevalence fell from 29.6% in the 2nd year to 13.3% in the 3rd year and averaged 21.1% across both grades. Systemic allergic disease among family members was found to be statistically associated with HD (p < 0.05). Overall, our preliminary study showed that HD probably affects Chinese nursing students at rates similar to that of their Japanese counterparts, but at a higher rate than students in other investigations from Germany, Holland and Australia. The identification of familial allergic disease as a possible risk factor for HD was also novel. CONCLUSION: The investigation was conducted as a preliminary investigation, and as such, our results need to be treated with caution. Further research is recommended to more carefully elucidate the prevalence of HD among larger groups of Chinese nursing students.

Journal Article↗
PubMed2004

Terahertz magnetic response from artificial materials.

We show that magnetic response at terahertz frequencies can be achieved in a planar structure composed of nonmagnetic conductive resonant elements. The effect is realized over a large bandwidth and can be tuned throughout the terahertz frequency regime by scaling the dimensions of the structure. We suggest that artificial magnetic structures, or hybrid structures that combine natural and artificial magnetic materials, can play a key role in terahertz devices.

Journal Article↗
PubMed2004

Identification of GRP 78 (BiP) as a liver cell expressed receptor element for dengue virus serotype 2.

This study sought to identify receptor elements for dengue virus serotype 2 on human liver cells (HepG2) using the viral overlay protein binding assay (VOPBA) technique and Mass Spectrometry fingerprinting. A single major and several minor virus binding bands were observed, and mass spectrometry identified a candidate binding protein for the major binding band as GRP 78 (BiP). GRP78 expression on the cell surface was confirmed, and antibodies directed against both the N and C-terminus of GRP 78 (BiP) altered both the binding of the virus to the cell surface as well as the infectivity profile of HepG2 cells in response to dengue serotype 2 infection. GRP 78 (BiP), which has previously been identified as a co-receptor protein for coxsackievirus A9, is the first non-Fc receptor protein identified for the dengue virus, although GRP78 probably functions as part of a receptor complex.

Carrier Proteins↗
PubMed2004

A diagnostic strategy to determine the Shiga toxin-producing Escherichia coli O157 status of pens of feedlot cattle.

Although cattle are reservoirs, no validated method exists to monitor Shiga toxin-producing Escherichia coli O157 (STEC O157) on farms. In 29 Midwestern United States feedlot pens we compared culturing faeces from the individual cattle to: (1) culturing rope devices that cattle rub or chew; and (2) culturing a composite of faecal pats. Eighty-six per cent (68-96%) of pens were classified correctly using rope devices to detect pens with at least 16% of the cattle shedding STEC O157 [sensitivity=82% (57-96%); specificity=92% (62-100%)]. Ninety per cent of pens (73-98%) were classified correctly using composite faeces to detect pens with at least 37% of the cattle shedding STEC O157 [sensitivity=86% (42-100%); specificity=91% (71-99%)]. Ranking pens into three risk levels based on parallel interpretation of the pen-test results correlated (Spearman's r=0.76, P<0.0001) with the pen's prevalence. This strategy could identify pens of cattle posing a higher risk to food safety.

Animals↗
PubMed2004

Effect of aluminum chloride and dietary phytase on relative ammonia losses from swine manure.

Ammonia (NH3) losses from swine manure contribute to odor problems, decrease animal productivity, and increase the risk of acid rain deposition. This study was conducted to determine whether aluminum chloride (AlCl3) or dietary manipulation with phytase could decrease relative NH3 losses from swine manure. Twenty-four pens of nursery pigs were used in two trials, and the pigs were fed normal or phytase-supplemented (500 IU/kg) diets. Aluminum chloride was added to manure pits (1.9 x 1.2 x 0.5 m) under each pen at 0, 0.25, 0.50, or 0.75% (vol:vol) of final manure volume. Manure pH and NH3 losses (measured by relative NH3 flux) were determined twice weekly. The addition of AlCl3 at 0.75% decreased (P < 0.05) manure pH from 7.48 to 6.69. Phytase decreased (P < 0.05) manure pH to 7.07 compared with 7.12 in the normal diet manure. Aluminum chloride administered at 0.75% without phytase reduced (P < 0.05) relative NH3 losses 52% for the entire 6-wk period. Relative NH3 losses were decreased (P < 0.05) from 109 mg of NH3/(m2 x h) in pens containing pigs fed the normal diet without AlCl3 to 81 mg of NH3/(m2 x h) in pens housing pigs administered the phytase diet, a 26% reduction. When the phytase diet and 0.75% AlCl3 additions were used in combination, relative NH3 losses were reduced (P < 0.05) by 60% compared with pens of pigs fed the control diet without AlCl3. Decreases in manure pH were likely responsible for the observed reduction in NH3 losses. Multiple regression was performed with relative rates of NH3 losses as the dependent variable and rate of AlCl3 addition, diet, and manure pH as independent variables. The model was tested using a stepwise regression (P < 0.001), and results indicated that the most important factors determining NH3 losses were manure pH and diet. However, the contribution of AlCl3 cannot be discounted. When manure pH was regressed against AlCl3 and dietary phytase, AlCl3 levels accounted for 64% of the variation in manure pH (P < 0.001). Dietary manipulation with phytase and application of AlCl3 to manure are promising management practices for the reduction of NH3 from swine facilities.

6-Phytase↗
PubMed2003

Musculoskeletal disorders among hospital nurses in rural Japan.

INTRODUCTION: Although musculoskeletal disorders (MSD) represent a significant occupational problem for hospital nurses, few investigations target nurses in rural facilities. This study investigated the prevalence and correlates of MSD among nurses within an affiliated hospital conglomerate of rural Japan. METHODS: A self-reporting survey was used as diagnostic tool; the reliability, validity and cost-effectiveness of this method has been established. RESULTS: An initial group of 329 nurses was recruited from three affiliated, rural locations in Yamanashi prefecture, central Japan; 247 usable replies were obtained (final response rate: 75.1%). The 12-month period-prevalence of self-reported MSD at any body site was 91.9% (95% CI 87.8-94.7). Low back pain (LBP) was the most commonly reported MSD with a prevalence of 82.6% (95% CI 77.4-86.8). Next most reported were shoulder (61.1%, 95% CI 54.9-67.0), neck (36.8%, 95% CI 31.1-43.0), upper back (29.1%, 95% CI 23.8-35.1), knee (23.5%, 95% CI 18.6-29.1) and upper leg MSD (19.4%, 95% CI 15.0-24.8). MSD of the wrist (14.2%, 95% CI 10.4-19.1), upper arm (13.0%, 95% CI 9.3 -17.7) and lower arm (11.7% 95% CI 8.3-16.4) were less common. Logistic regression indicated that nurses who were regularly involved in the manual handling of patients had an increased LBP risk of 16.7 (OR 16.7, 95% CI 1.3-412.7, p = 0.0340) when compared with nurses who were not involved in manual handling of patients. CONCLUSION: Overall, our study indicated that MSD is common among rural Japanese nurses and its prevalence is consistent between related facilities. The excessive amount of LBP, however, suggests that Japanese nurses are at higher risk of this condition compared with their foreign counterparts.

Journal Article↗
PubMed2003

Resonant and antiresonant frequency dependence of the effective parameters of metamaterials.

We present a numerical study of the electromagnetic response of the metamaterial elements that are used to construct materials with negative refractive index. For an array of split ring resonators (SRR) we find that the resonant behavior of the effective magnetic permeability is accompanied by an antiresonant behavior of the effective permittivity. In addition, the imaginary parts of the effective permittivity and permeability are opposite in sign. We also observe an identical resonant versus antiresonant frequency dependence of the effective materials parameters for a periodic array of thin metallic wires with cuts placed periodically along the length of the wire, with roles of the permittivity and permeability reversed from the SRR case. We show in a simple manner that the finite unit cell size is responsible for the antiresonant behavior.

Journal Article↗
PubMed2003

Increased permeability of psoriatic skin to the protein, plasminogen activator inhibitor 2.

The penetration and permeation of the recombinant protein plasminogen activator inhibitor type 2 (PAI-2) in two formulations, one containing a penetration enhancer, into the psoriatic and uninvolved skin of eight patients with plaque-type psoriasis were investigated. Penetration and permeation of PAI-2 were measured by gamma counting and imaging following radiolabelling of a fraction of the applied PAI-2 with (123)I. The feasibility of topical delivery of drug to psoriatic plaques was confirmed by the finding that the permeability of psoriatic plaques to radiolabelled PAI-2 (P=0.007) and free (123)I (P=0.001) was approximately tenfold higher than the permeability of uninvolved skin. The addition of a penetration enhancer improved the permeation of PAI-2 into psoriatic plaques from an average of 35% to 46% (P=0.005). Occlusion decreased the permeation amount of PAI-2 from 46% to 15% due to losses on the occlusive dressing (P=0.001).

Administration, Topical↗
PubMed2003

Electromagnetic wave propagation in media with indefinite permittivity and permeability tensors.

We study the behavior of wave propagation in materials for which not all of the principal elements of the permeability and permittivity tensors have the same sign. We find that a wide variety of effects can be realized in such media, including negative refraction, near-field focusing, and high impedance surface reflection. In particular, a bilayer of these materials can transfer a field distribution from one side to the other, including near fields, without requiring internal exponentially growing waves.

Journal Article↗
PubMed2003

Immune function of cryopreserved avian peripheral white blood cells: potential biomarkers of contaminant effects in wild birds.

Contaminants can cause detrimental effects in wild birds. However, these effects are difficult to measure in all but the most severe cases. Immune function is a sensitive and meaningful biological marker of contaminant-induced effects in captive birds but has more limitations in wild birds due in part to the lack of a proven blood preservation method. We developed methods to assess ex vivo immune function in wild birds using cryopreserved peripheral white blood cells (WBCs). We assessed the effects of cryopreservation on WBC viability and functionality in two immunoassays (concavalin A-induced T lymphocyte proliferation and macrophage phagocytosis) in domestic chickens (Gallus spp.: white Wyandottes and Dominiques) and validated this approach on cryopreserved WBC samples from wild American coots (Fulicia americana). Cryopreservation of chicken WBCs caused a slight but significant decrease in cell viability (99% +/- 0.2 SE for fresh cells versus 84% +/- 2 SE for cryopreserved cells, p = 0.001, Mann-Whitney U, n = 8). No difference was detected in viability between cells that were cryopreserved for less than 10 days (88% +/- 3.7 SE) and more than 50 days (89% +/- 1.3 SE) (n = 6). Overall, there was no statistical difference in the performance of cryopreserved cells compared to fresh cells. Across multiple experiments, cryopreserved T lymphocytes exhibited 200-900% stimulated proliferation above nonstimulated cells, and 40-80% of cryopreserved macrophages ingested yeast. 9,10,Dimethyl-1,2-benz-anthracene (DMBA) reduced proliferation and phagocytosis in cryopreserved cells over an ex vivo exposure range of 0-170 microM DMBA. Tests of immune function on American coot WBCs cryopreserved for up to 10 months (viability of 72% +/- 2.5 SE, n = 24) were similar to the cryopreserved chicken WBCs. This study will facilitate greater use of ex vivo immune function assays as tools to study effects of contaminant exposure in wildlife by demonstrating the viability and functionality of cryopreserved avian cells.

Animals↗
PubMed2003

Total and water-soluble phosphorus in broiler litter over three flocks with alum litter treatment and dietary inclusion of high available phosphorus corn and phytase supplementation.

Three pen trials were conducted to determine the main effect of alum addition to litter on form of poultry litter P using a 2 x 2 factorial structure of the subunit treatments: diets including high available phosphorus/low phytate corn (HAPC) and phytase (PHYT). Male broilers (1,760 per flock) were grown to 42 d having starter diets with 0.45% available P and grower diets with 0.35% available P. In the first trial, total litter P (tP) was greatest for the yellow dent corn (YDC) diet (12 g/kg) and least for the HAPC and PHYT combination (H&P) diet (6.9 g/kg) with the individual PHYT and HAPC diets falling in between at 9.1 g/kg and 9.4 g/kg tP. Also in the first trial, the litter water-soluble P (wP) was highest for PHYT (2.8 g/kg), least for the HAPC and H&P diets (1.5 g/kg) with the YDC diet falling between (2.2 g/kg). Alum was added to the litter after the first experiment. In the second and third experiments, alum inclusion significantly reduced the wP when compared with the treatments with no alum. In the third trial, the least wP was present in the alum-HAPC treatment. Phytase, YDC, and HAPC diets with no alum litter treatment generated the most wP. Since these diets appear to have little or no difference with respect to quantity of wP, this work suggests that form of litter P generated by alternative diets should be considered as criteria when attempting to reduce P in broiler litter applied to land.

6-Phytase↗
PubMed2003

Incidence, duration, and prevalence of Escherichia coli O157:H7 fecal shedding by feedlot cattle during the finishing period.

The objective was to describe variability in prevalence, incidence, and duration of fecal shedding of naturally occurring E. coli O157:H7 by a group of feedlot cattle over time. One hundred steers, randomly assigned to 10 pens, were fed a high-concentrate finishing diet for 136 days (19 weeks). Rectal feces from each animal were tested for E. coli O157:H7 every week for 19 weeks. E. coli O157:H7 was recovered from each animal that completed the study and was detected from at least one animal every week. Average pen prevalence of cattle shedding E. coli O157:H7 varied significantly over time (P < 0.0001) and across pens (P < 0.0001), ranging from 1 to 80%. Pairwise comparisons of mean pen prevalence of E. coli O157:H7 between weeks and estimation of the predicted probability of an incident case of E. coli O157:H7 over time allowed the definition of three distinct phases--namely, the preepidemic, epidemic, and postepidemic periods. Average pen prevalence varied significantly over time (P < 0.01) and across pens (P < 0.001) for all time periods. The odds of an incident case were significantly greater during epidemic and postepidemic periods relative to the preepidemic period (P = 0.0002 and P = 0.03, respectively). Duration of infection was significantly longer for first or second infections that began during epidemic or postepidemic periods relative to the preepidemic period (P < 0.001). Both incidence and duration of shedding peaked during the epidemic period. Pen-level prevalence of cattle shedding E. coli O157:H7 was affected by both incidence and duration of shedding and could be explained by time- or pen-dependent risk factors, or both.

Animal Husbandry↗
PubMed2002

Low cumulative manganese exposure affects striatal GABA but not dopamine.

The introduction of the anti-knock methylcyclopentadienyl manganese (Mn) tricarbonyl (MMT) in gasoline has raised concerns about the potential for manganese neurotoxicity. Because subpopulations such as the elderly in the early stages of neurodegenerative disease may be at increased risk for manganese toxicity, a pre-Parkinsonism rat model was used to evaluate whether sub-chronic manganese exposure can aggravate the neurochemical and behavioral dysfunctions characteristic of Parkinsonism. Sub-threshold levels of dopamine depletion of 3.5, 53 and 68% were generated via intrastriatal unilateral 6-hydroxydopamine (6-OHDA) doses. A sub-chronic dosing regimen of low cumulative manganese exposure (4.8 mg Mn/kg body weight, 3 i.p. injections per week x 5 weeks) was started 4 weeks after 6-OHDA treatments. Neurochemical and neuromotor (functional observational battery (FOB)) measures were evaluated. Manganese produced significant (P < 0.05) reductions of 30-60% in motor function. This effect was exacerbated in the presence of a pre-Parkinsonism condition [Neurotox. Teratol. 22 (2000) 851]. Manganese did not affect striatal dopamine, but resulted in significant increases in striatal y-aminobutyric acid (GABA) of 16 and 22% (P < 0.01) in both striati and a borderline non-significant 4% increase in frontal cortex (P = 0.076). Manganese treatment produced increased aspartate (P < 0.01) in the manganese and 6-OHDA treated striatum. In light of previous studies predominantly showing dopamine depletion with elevated manganese exposures, the significant effects of manganese on striatal GABA but not on striatal dopamine at the low cumulative exposure administered here suggest a progression in manganese toxicity with increasing cumulative dose, whereby GABA levels are adversely affected before striatal dopamine levels. Because these neurochemical disruptions were accompanied by motor dysfunction that was exacerbated in the presence of a pre-Parkinsonism condition, an increased environmental burden of manganese may have deleterious effects on populations with sub-threshold neurodegeneration in the basal ganglia (e.g. pre-Parkinsonism).

Animals↗
PubMed2001

A fatality caused by accidental production of hydrogen sulfide.

A 55-year-old male Caucasian truck driver was dead at the scene after breathing hydrogen sulfide (H(2)S) produced by an accidental transfer of sodium hydrogen sulfide (NaHS) from a tanker truck to a tank containing 4% sulfuric acid (H(2)SO(4)) and iron(II) sulfate (FeSO(4)). Autopsy of the decedent's body revealed pulmonary edema and passive congestion in lungs, spleen, kidneys, and adrenal glands. Postmortem biological samples were analyzed for carbon monoxide, cyanide, ethanol, and drugs. Since a potential exposure to H(2)S was involved, blood was also analyzed for sulfide (S(2-)). The analysis entailed isolating S(2-) from blood as H(2)S using 0.5M H(3)PO(4), trapping the gas in 0.1M NaOH, and determining the electromotive force using a sulfide ion specific electrode. Acetaminophen at a concentration of 14.3 microg/ml was found in blood, and metoprolol was detected in the blood, liver, and kidney samples. The blood S(2-) level was determined to be 1.68 microg/ml. It is concluded that the cause of death was H(2)S poisoning associated with a hazardous material accident in an industrial situation.

Accidents, Occupational↗
PubMed2001

Quantitative imaging and microlocalization of boron-10 in brain tumors and infiltrating tumor cells by SIMS ion microscopy: relevance to neutron capture therapy.

Boron neutron capture therapy (BNCT) is dependent on the selective accumulation of boron-10 in tumor cells relative to the contiguous normal cells. Ion microscopy was used to evaluate the microdistribution of boron-10 from p-boronophenylalanine (BPA) in the 9L rat gliosarcoma and the F98 rat glioma brain tumor models. Four routes of BPA administration were used: i.p. injection, intracarotid (i.c.) injection [with and without blood-brain barrier disruption (BBB-D)], and continuous timed i.v. infusions. i.p. injection of BPA in the 9L gliosarcoma resulted in a tumor-to-brain (T:Br) boron-10 concentration ratio of 3.7:1 when measured at the tumor-normal brain interface. In the F98 glioma, i.c injection of BPA resulted in a T:Br ratio of 2.9:1, and this increased to 5.4:1 when BBB-D was performed. The increased tumor boron uptake would potentially enhance the therapeutic ratio of BNCT by >25%. At present, ion microscopy is the only technique to provide a direct measurement of the T:Br boron-10 concentration ratio for tumor cells infiltrating normal brain. In the 9L gliosarcoma, this ratio was 2.9:1 after i.p. administration. In the F98 glioma, i.c injection resulted in a ratio of 2.2:1, and this increased to 3.0:1 after BBB-D. Ion microscopy revealed a consistent pattern of boron-10 microdistribution for both rat brain tumor models. The boron-10 concentration in the main tumor mass (MTM) was approximately twice that of the infiltrating tumor cells. One hour after a 2-h i.v. infusion of BPA in rats with the 9L gliosarcoma, tumor boron-10 concentrations were 2.7 times higher than that of infiltrating tumor cells [83 +/- 23 microg/g tissue versus 31 +/- 12 microg/g tissue (mean +/- SD)]. Continuous 3- and 6-h i.v. infusions of BPA in the 9L gliosarcoma resulted in similar high boron-10 concentrations in the MTM. The boron-10 concentration in infiltrating tumor cells was two times lower than the MTM after a 3-h infusion. After 6 h, the boron-10 concentration in infiltrating tumor cells had increased nearly 90% relative to the 2- and 3-h infusions. A 24-h i.v. infusion resulted in similar boron-10 levels between the MTM and the infiltrating tumor cells. Boron concentrations in the normal brain were similar for all four infusion times (approximately 20 microg/g tissue). These results are important for BNCT, because clinical protocols using a 2-h infusion have been performed with the assumption that infiltrating tumor cells contain equivalent amounts of boron-10 as the MTM. The results reported here suggest that this is not the case and that a 6-h or longer infusion of BPA may be necessary to raise boron-10 levels in infiltrating tumor cells to that in the MTM.

Animals↗