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Biomedical subjects

J A Grant

Publications and source records attributed to J A Grant.

At least 19 recordsLinked to original sources
PubMed2006

Artificial composite bone as a model of human trabecular bone: the implant-bone interface.

The use of artificial bones in implant testing has become popular due to their low variability and ready availability. However, friction coefficients, which are critical to load transfer in uncemented implants, have rarely been compared between human and artificial bone, particularly for wet and dry conditions. In this study, the static and dynamic friction coefficients for four commercially used titanium surfaces (polished, Al(2)O(3) blasted, plasma sprayed, beaded) acting on the trabecular component of artificial bones (Sawbones) were compared to those for human trabecular bone. Artificial bones were tested in dry and wet conditions and normal interface stress was varied (0.25, 0.5, 1.0MPa). Friction coefficients were mostly lower for artificial bones than real bone. In particular, static friction coefficients for the dry polished surface were 20% of those for real bone and 42-61% for the dry beaded surface, with statistical significance (alpha<0.05). Less marked differences were observed for dynamic friction coefficients. Significant but non-systematic effects of normal stress or wet/dry condition on friction coefficients were observed within each surface type. These results indicate that the use of artificial bone models for pre-clinical implant testing that rely on interface load transfer with trabecular bone for mechanical integrity can be particularly sensitive to surface finish and lubrication conditions.

Biomechanical Phenomena↗
PubMed2005

Assessment of Mars Exploration Rover landing site predictions.

Comprehensive analyses of remote sensing data during the three-year effort to select the Mars Exploration Rover landing sites at Gusev crater and at Meridiani Planum correctly predicted the atmospheric density profile during entry and descent and the safe and trafficable surfaces explored by the two rovers. The Gusev crater site was correctly predicted to be a low-relief surface that was less rocky than the Viking landing sites but comparably dusty. A dark, low-albedo, flat plain composed of basaltic sand and haematite with very few rocks was expected and found at Meridiani Planum. These results argue that future efforts to select safe landing sites based on existing and acquired remote sensing data will be successful. In contrast, geological interpretations of the sites based on remote sensing data were less certain and less successful, which emphasizes the inherent ambiguities in understanding surface geology from remotely sensed data and the uncertainty in predicting exactly what materials will be available for study at a landing site.

Journal Article↗
PubMed2004

The Opportunity Rover's Athena science investigation at Meridiani Planum, Mars.

The Mars Exploration Rover Opportunity has investigated the landing site in Eagle crater and the nearby plains within Meridiani Planum. The soils consist of fine-grained basaltic sand and a surface lag of hematite-rich spherules, spherule fragments, and other granules. Wind ripples are common. Underlying the thin soil layer, and exposed within small impact craters and troughs, are flat-lying sedimentary rocks. These rocks are finely laminated, are rich in sulfur, and contain abundant sulfate salts. Small-scale cross-lamination in some locations provides evidence for deposition in flowing liquid water. We interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water, followed by evaporation, exposure, and desiccation. Hematite-rich spherules are embedded in the rock and eroding from them. We interpret these spherules to be concretions formed by postdepositional diagenesis, again involving liquid water.

Atmosphere↗
PubMed2004

Surficial deposits at Gusev Crater along Spirit Rover traverses.

The Mars Exploration Rover Spirit has traversed a fairly flat, rock-strewn terrain whose surface is shaped primarily by impact events, although some of the landscape has been altered by eolian processes. Impacts ejected basaltic rocks that probably were part of locally formed lava flows from at least 10 meters depth. Some rocks have been textured and/or partially buried by windblown sediments less than 2 millimeters in diameter that concentrate within shallow, partially filled, circular impact depressions referred to as hollows. The terrain traversed during the 90-sol (martian solar day) nominal mission shows no evidence for an ancient lake in Gusev crater.

Extraterrestrial Environment↗
PubMed2004

Localization and physical properties experiments conducted by Spirit at Gusev Crater.

The precise location and relative elevation of Spirit during its traverses from the Columbia Memorial station to Bonneville crater were determined with bundle-adjusted retrievals from rover wheel turns, suspension and tilt angles, and overlapping images. Physical properties experiments show a decrease of 0.2% per Mars solar day in solar cell output resulting from deposition of airborne dust, cohesive soil-like deposits in plains and hollows, bright and dark rock coatings, and relatively weak volcanic rocks of basaltic composition. Volcanic, impact, aeolian, and water-related processes produced the encountered landforms and materials.

Extraterrestrial Environment↗
PubMed2004

Wind-related processes detected by the Spirit Rover at Gusev Crater, Mars.

Wind-abraded rocks, ripples, drifts, and other deposits of windblown sediments are seen at the Columbia Memorial Station where the Spirit rover landed. Orientations of these features suggest formative winds from the north-northwest, consistent with predictions from atmospheric models of afternoon winds in Gusev Crater. Cuttings from the rover Rock Abrasion Tool are asymmetrically distributed toward the south-southeast, suggesting active winds from the north-northwest at the time (midday) of the abrasion operations. Characteristics of some rocks, such as a two-toned appearance, suggest that they were possibly buried and exhumed on the order of 5 to 60 centimeters by wind deflation, depending on location.

Evolution, Planetary↗
PubMed2004

Pancam multispectral imaging results from the Spirit Rover at Gusev Crater.

Panoramic Camera images at Gusev crater reveal a rock-strewn surface interspersed with high- to moderate-albedo fine-grained deposits occurring in part as drifts or in small circular swales or hollows. Optically thick coatings of fine-grained ferric iron-rich dust dominate most bright soil and rock surfaces. Spectra of some darker rock surfaces and rock regions exposed by brushing or grinding show near-infrared spectral signatures consistent with the presence of mafic silicates such as pyroxene or olivine. Atmospheric observations show a steady decline in dust opacity during the mission, and astronomical observations captured solar transits by the martian moons, Phobos and Deimos, as well as a view of Earth from the martian surface.

Atmosphere↗
PubMed2004

The Spirit Rover's Athena science investigation at Gusev Crater, Mars.

The Mars Exploration Rover Spirit and its Athena science payload have been used to investigate a landing site in Gusev crater. Gusev is hypothesized to be the site of a former lake, but no clear evidence for lacustrine sedimentation has been found to date. Instead, the dominant lithology is basalt, and the dominant geologic processes are impact events and eolian transport. Many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration. Any lacustrine sediments that may exist at this location within Gusev apparently have been buried by lavas that have undergone subsequent impact disruption.

Atmosphere↗
PubMed2003

Extracting material parameters from x-ray attenuation: a CT feasibility study using kilovoltage synchrotron x-rays incident upon low atomic number absorbers.

The work reported here is a feasibility study of the extraction of material parameters from measurements of the linear x-ray attenuation coefficient of low atomic number absorbers. Computed tomography (CT) scans of small samples containing several liquids and solids were carried out with synchrotron radiation at the Australian National Beamline Facility (BL 20B) in Japan. Average values of the x-ray linear attenuation coefficient were extracted for each material for x-ray energies ranging from 11 keV to 20.5 keV. The electron density was estimated by applying results derived from a parametrization of the x-ray linear attenuation coefficient first developed by Jackson and Hawkes and extended for this work. Average estimates for the electron density of triethanolamine and acetic acid were made to within +5.3% of the actual value. Other materials examined included furfuraldehyde, perspex and teflon, for which average estimates of the electron density were less than 10% in excess of the calculated value.

Acetic Acid↗
PubMed2001

A report of a rare immediate reaction after ingestion of acetaminophen.

BACKGROUND: Acetaminophen hypersensitivity is rare and, when seen, is usually in association with sensitivity to nonsteroidal anti-inflammatory drugs. METHODS: This is a case report of an immediate reaction to acetaminophen, confirmed by a drug challenge, in a subject who tolerated ibuprofen. RESULTS: After an oral challenge with 50 mg of acetaminophen, the subject had generalized pruritus, urticaria, and dyspnea. CONCLUSIONS: This patient demonstrates a rare but potentially severe reaction to acetaminophen that may occur in patients who are not otherwise sensitive to other nonsteroidal anti-inflammatory drugs.

Acetaminophen↗
PubMed2001

Spina bifida outcome: a 25-year prospective.

BACKGROUND: Open spina bifida is the most complex congenital abnormality compatible with long-term survival. This report outlines the 20- to 25-year outcome for our original cohort of patients with a myelomeningocele treated in a nonselective, prospective manner. METHODS: Of the initial 118 children, 71 patients were available for our most recent review. Nineteen patients have been lost to follow-up and 28 patients have died. Data were collected on: motor level, shunt status, education/employment, seizure history, mobility, bladder/bowel continence, tethered cord, scoliosis, latex allergy, posterior cervical decompression, tracheostomy and/or gastrostomy tube. RESULTS: Mortality (24%) continues to climb into young adulthood. Eighty-six percent of the cohort have cerebrospinal fluid diversion, with 95% having undergone at least one shunt revision. Thirty-two percent have undergone a tethered cord release, with 97% having an improvement or stabilization in their preoperative symptoms. Forty-nine percent have scoliosis, with 43% eventually requiring a spinal fusion. Sixteen patients (23%) have had at least one seizure. Eighty-five percent are attending or have graduated from high school and/or college. More than 80% of young adults have social bladder continence. Approximately 1/3 of patients are allergic to latex, with 6 patients having experienced a life-threatening reaction. CONCLUSION: At least 75% of children born with a myelomeningocele can be expected to reach their early adult years. Late deterioration is common. One of the greatest challenges in medicine today is establishing a network of care for these adults with spina bifida.

Adult↗
PubMed2000

Eotaxin induces degranulation and chemotaxis of eosinophils through the activation of ERK2 and p38 mitogen-activated protein kinases.

Eotaxin and other CC chemokines acting via CC chemokine receptor-3 (CCR3) are believed to play an integral role in the development of eosinophilic inflammation in asthma and allergic inflammatory diseases. However, little is known about the intracellular events following agonist binding to CCR3 and the relationship of these events to the functional response of the cell. The objectives of this study were to investigate CCR3-mediated activation of the mitogen-activated protein (MAP) kinases extracellular signal-regulated kinase-2 (ERK2), p38, and c-jun N-terminal kinase (JNK) in eosinophils and to assess the requirement for MAP kinases in eotaxin-induced eosinophil cationic protein (ECP) release and chemotaxis. MAP kinase activation was studied in eotaxin-stimulated eosinophils (more than 97% purity) by Western blotting and immune-complex kinase assays. ECP release was measured by radioimmunoassay. Chemotaxis was assessed using Boyden microchambers. Eotaxin (10(-11) to 10(-7) mol/L) induced concentration-dependent phosphorylation of ERK2 and p38. Phosphorylation was detectable after 30 seconds, peaked at about 1 minute, and returned to baseline after 2 to 5 minutes. Phosphorylation of JNK above baseline could not be detected. The kinase activity of ERK2 and p38 paralleled phosphorylation. PD980 59, an inhibitor of the ERK2-activating enzyme MEK (MAP ERK kinase), blocked phosphorylation of ERK2 in a concentration-dependent manner. The functional relevance of ERK2 and p38 was studied using PD98 059 and the p38 inhibitor SB202 190. PD98 059 and SB202 190 both caused inhibition of eotaxin-induced ECP release and chemotaxis. We conclude that eotaxin induces a rapid concentration-dependent activation of ERK2 and p38 in eosinophils and that the activation of these MAP kinases is required for eotaxin-stimulated degranulation and directed locomotion. (Blood. 2000;95:1911-1917)

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed2000

Personal accounts of the role of God in health and illness among older rural African American and White residents.

This paper addresses how older rural residents view the relationship between God and both health and illness. We employed semi-structured interviews and qualitative analytical strategies with 15 African Americans residing in predominantly African American communities and 13 Whites living in nearby predominantly White communities, in order to identify similarities and differences in views about a divine other's roles in health and illness. African Americans were more likely than Whites to describe their religious lives in personal terms, in ways suggesting there is a set of religious truths that do not require further investigation or analysis, and in a manner indicating that religious belief permeated their lives. They were also more likely to describe specific role expectations for God in health and illness. The results point to the substantial cultural diversity that exists in small rural areas, and to the need for health care workers to be sensitive to the health-related religious beliefs of patients.

Journal Article↗
PubMed2000

Fetal MRI.

Explore the source record for details and available documents.

Female↗
PubMed1999

Impact of cetirizine on the burden of allergic rhinitis.

OBJECTIVE: The goals of this article include the reporting of the epidemiology, economic and medical impact of allergic rhinitis. In addition, the pharmacology and clinical profile of the therapeutic agent cetirizine are reviewed. DATA SOURCES: A detailed literature search was conducted. References are limited to the English language and human subjects and tissues. Studies considered relevant and important over the past 20 years are highlighted. STUDY SELECTION: Prevalence and morbidity data were chosen from more recent assessments. Because cetirizine is a relatively new compound, studies from the past several years from peer-reviewed journals have been emphasized. RESULTS: Allergic rhinitis affects between 15% and 25% of the US general population. It shares common pathophysiologic mechanisms with conjunctivitis and asthma and predisposes to nasal infections, otitis media, sinusitis, nasal polyposis, and orthodontic malocclusions. Direct medical care costs amount to up to 3 billion dollars every year. In addition, the quality of life of affected individuals is substantially compromised. Cetirizine is a potent H1-receptor antagonist and has anti-inflammatory properties. It does not interact with concomitantly administered medications, has no cardiac adverse effects, and does not appear to be associated with teratogenicity. Impairment of CNS function is comparable to other low-sedating antihistamines at the recommended dose of 10 mg daily for adults. Its clinical efficacy for allergic respiratory diseases has been established in numerous trials. CONCLUSIONS: Allergic rhinitis causes considerable suffering. Cetirizine, with a fine risk-benefit ratio, can be a most valuable therapeutic option.

Anti-Allergic Agents↗
PubMed1999

A double-blind, single-dose, crossover comparison of cetirizine, ebastine, epinastine, fexofenadine, terfenadine, and loratadine versus placebo: suppression of histamine-induced wheal and flare response for 24 h in healthy male subjects.

BACKGROUND: New H1-antagonists have become available, but there has been no comparison of their potency for inhibiting histamine in the skin. METHODS: Cetirizine 10 mg, ebastine 10 mg, epinastine 20 mg, fexofenadine 60 mg, terfenadine 60 mg, loratadine 10 mg, or placebo was given to 14 healthy male volunteers in a double-blind, crossover randomized manner. Inhibition of the wheal and flare response to epicutaneous histamine phosphate (100 mg/ml) challenge was measured at 0, 0.5, 1, 2, 4, 6, 8, 10, 12, and 24 h after doses. RESULTS: Epinastine inhibited the wheal and flare after 30 min. Cetirizine commenced acting at 1 h and was superior to other treatments. Ebastine was no better than placebo until 4 h, but was efficacious thereafter until 24 h. Terfenadine induced potent inhibition after 1 h and was superior to its metabolite fexofenadine. Loratadine was the least potent inhibitor. Inhibition of the flare response paralleled the patterns seen for wheals. The rank order for area under the curve (0-24 h) was cetirizine, epinastine, terfenadine, ebastine, fexofenadine, loratadine, and placebo. CONCLUSIONS: The inhibition of histamine effects in the skin may be useful in predicting the clinical utility of newly introduced antihistamines in treating allergic disorders.

Adult↗
PubMed1999

Admission-related migration by older nursing home residents.

OBJECTIVE: To examine recent admissions of older adults to intermediate care facilities in order to identify the factors associated with whether the individual originated in another county, a non-adjacent county, and another state. METHODS: Employing a conceptual framework based upon migration theory and the long-term care decision process and a data set derived from multiple sources, logistic regression was used to examine whether characteristics of the county of residence prior to admission, the admission facility, and the individual are significant net predictors of the three types of mobility. Separate analyses were conducted for married and unmarried individuals. RESULTS: The analytical models tended to have relatively good fit but only moderate predictive accuracy. In general, persons on Medicaid payment status were more likely to move to another county and to a non-adjacent county, whereas Medicaid payment was associated with a lower likelihood of migrating to Virginia from another state. Individuals originating in counties with higher bed rates had lower rates of migration to another county and non-adjacent county, whereas those from counties with higher occupancy rates were more likely to leave their county of origin. CONCLUSION: Examination of factors associated with the distance and patterns of nursing home mobility improves our understanding of the nursing home selection process and helps to illuminate the impact of public policy, market forces, and nursing home staff on who goes where to be admitted to a nursing home.

Aged↗