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Biomedical subjects

B D Snyder

Publications and source records attributed to B D Snyder.

At least 19 recordsLinked to original sources
PubMed2001

Acid-suppressive therapy use associated with antihypertensive agents.

Nitrates and calcium channel blockers (CCBs) have been shown to decrease lower esophageal sphincter pressure and theoretically may precipitate or aggravate gastroesophageal reflux. Thus, the authors hypothesized that patients who receive these agents would have greater use of acid-suppressive drug use, defined as histamine2 antagonists or proton pump inhibitors. A retrospective cohort design was used to assess the use of acid-suppressive drug use in hypertensive patients with respect to both nitrates and antihypertensive therapy. Of 15,662 treated hypertensive patients, 20% received acid-suppressive therapy. An increased use of acid-suppressive therapy was associated with nitrate (odds ratio [OR] = 1.71), CCB (OR = 1.46), and alpha 1 antagonist (OR = 1.32) treatment, which appeared to be additive when patients received two or more of the agents. Within the class of CCBs, there was no significant difference among the individual agents. As the clinical and economic burden may be substantial, further study is warranted.

Adult↗
PubMed2001

Treatment of hypertension in a managed care setting.

BACKGROUND: Based on recommendations of the Fifth and Sixth Reports of the Joint National Committee (JNC) on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, Health Care Plan (now Univera Healthcare) Buffalo, NY, developed a clinical guideline to improve the management of patients with hypertension. To increase awareness and utilization, the guideline was distributed as hard copy reports and made available through our electronic information system. OBJECTIVE: To determine blood pressure (BP) control rates and adherence to guideline recommendations. STUDY DESIGN: Retrospective chart review. PATIENTS AND METHODS: We randomly sampled hypertensive patients seen during 1998 to evaluate hypertension management. Computerized medical and pharmacy records were reviewed for patient demographics, antihypertensive medications, comorbid conditions, and BP readings. Patient assessment was based on antihypertensive regimen and achievement of target BP according to the recommendations of the guidelines (< 140/90 mm Hg for the general population and < 130/85 mm Hg for special populations). In addition, we assessed control rates using traditional Health Plan Employer Data and Information Set (HEDIS) measures (< 140/90 mm Hg). RESULTS: Overall, 35% of patients achieved target BP and 68% were treated with agents recommended by our JNC-based guideline. In contrast, using traditional HEDIS measures, 41% of patients achieved BP control. Of 39 patients with compelling indications (primarily diabetic patients), 13% achieved BP target and 67% were treated with recommended agents. CONCLUSIONS: The impact of our clinical guideline is reflected through the relatively high utilization of recommended drugs. However, optimal BP control continues to be problematic. In particular, patients with diabetes warrant focused attention.

Aged↗
PubMed2001

A pharmacy-based approach to cholesterol management.

OBJECTIVE: To determine the clinical and economic impact of a pharmacy-based cholesterol management program in patients with cardiovascular disease. STUDY DESIGN: Demonstration project. PATIENTS AND METHODS: From January 1, 1999, through June 30, 1999, 300 patients with a documented history of cardiovascular disease were enrolled in a pharmacy-based cholesterol program. A similar group of 150 randomly selected patients receiving usual care during the same period served as the comparator group. The following were collected for both groups: patient demographics, comorbidities, fasting lipid profiles, cholesterol medication, cost of medication, and cardiovascular events. The McNemar symmetry chi2 test was used to compare appropriate laboratory monitoring, receipt of cholesterol medication, and achievement of target low-density lipoprotein cholesterol levels at baseline and 1 year for both groups. Kruskal-Wallis analysis of variance was used to compare the cost of therapy for both groups at baseline and follow-up. RESULTS: Mean +/- SD age of program and usual care patients was 67 +/- 10 and 69 +/- 11 years, respectively. At 1 year, >95% of program patients were receiving appropriate laboratory monitoring. In 1 year, the percentage of patients reaching target low-density lipoprotein cholesterol levels increased from 45% to 72% (P< .01) and from 33% to 43% (P = .26) in program and usual care patients, respectively. Despite increased medication use among program patients, their cost per patient per month was lower at 1-year follow-up vs baseline. CONCLUSION: Regular patient interaction and close patient monitoring allowed the pharmacy-based lipid management program to improve cholesterol management in patients with cardiovascular disease.

Adult↗
PubMed2000

Magnetic resonance imaging measurements of bone density and cross-sectional geometry.

Magnetic resonance imaging (MRI) is commonly used in the assessment of the musculoskeletal system and associated pathology. The ability of MRI to measure the signals from water and lipid protons enables quantitative measurements of bone porosity. The goal of this investigation was to demonstrate that the density and cross-sectional geometry of whole bones can be noninvasively measured using MRI. Ten trabecular specimens cored from whale vertebrae were used to compare apparent bone density measured directly, and using a quantitative MRI algorithm. Bone density and several cross-sectional geometric properties were also measured using MRI in the distal tibia of 14 volunteers. The MRI measurements were compared with measurements made using quantitative-computed tomography (QCT). A proton density sequence was used for all MRI studies. A porosity phantom was included in the MRI examinations and used to convert the MRI signal intensity to bone volume fraction. Bone density and cross-sectional bone geometry were calculated from the bone volume fractions by assuming constant tissue properties. The apparent density of trabecular bone cores measured directly and using quantitative MRI were linearly related (r(2) = 0.959; P < 0. 01). A strong linear relation also existed between MRI and QCT measurements of ash density (r(2) = 0.923; P < 0.01) and cross-sectional geometric properties (r(2) = 0.976-0.992; P < 0.01). MRI data can be used to measure bone density and cross-sectional geometry of whole bones if a proton density sequence is used to homogenize differences in marrow composition and a porosity phantom is used for slice-specific volume fraction calibration.

Adult↗
PubMed2000

Noninvasive imaging predicts failure load of the spine with simulated osteolytic defects.

BACKGROUND: The clinical management of lytic tumors of the spine is currently based on geometric measurements of the defect. However, the mechanical behavior of a structure depends on both its material and its geometric properties. Quantitative computed tomography and dual-energy x-ray absorptiometry were investigated as noninvasive tools for measuring the material and geometric properties of vertebrae with a simulated lytic defect. From these measures, yield loads were predicted with use of composite beam theory. METHODS: Thirty-four fresh-frozen cadaveric spines were segmented into functional spinal units of three vertebral bodies with two intervertebral discs at the thoracic and lumbar levels. Lytic defects of equal size were created in one of three locations: the anterior, lateral, or posterior region of the vertebra. Each spinal unit was scanned with use of computed tomography and dual-energy x-ray absorptiometry, and axial and bending rigidities were calculated from the image data. Each specimen was brought to failure under combined compression and forward flexion, and the axial load and bending moment at yield were recorded. RESULTS: Although the relative defect size was nearly constant, measured yield loads had a large dispersion, suggesting that defect size alone was a poor predictor of failure. However, image-derived measures of structural rigidity correlated moderately well with measured yield loads. Furthermore, with use of composite beam theory with quantitative computed tomography-derived rigidities, vertebral yield loads were predicted on a one-to-one basis (concordance, r(c) = 0.74). CONCLUSIONS: Although current clinical guidelines for predicting fracture risk are based on geometric measurements of the defect, we have shown that the relative size of the defect alone does not account for the variation in vertebral yield loads. However, composite beam theory analysis with quantitative computed tomography-derived measures of rigidity can be used to prospectively predict the yield loads of vertebrae with lytic defects. CLINICAL RELEVANCE: Image-predicted vertebral yield loads and analytical models that approximate loads applied to the spine during activities of daily living can be used to calculate a factor of fracture risk that can be employed by physicians to plan appropriate treatment or intervention.

Absorptiometry, Photon↗
PubMed1998

Descending neural projections to the spinal cord in the channel catfish, Ictalurus punctatus.

Retrograde transport of horseradish peroxidase was used to determine the descending projections to the spinal cord in an otophysan fish, the channel catfish, Ictalurus punctatus. The majority of cells projecting to the spinal cord are located in the reticular formation, which is organized into rhombomeric segments. Vestibulospinal neurons are located in the descending, magnocellular, and tangential octaval nuclei, as well as in the medial octavolateralis nucleus of the lateral line system. Cells in the facial lobe project to the spinal cord. Additionally, axons of cells of the trigeminal system and the nucleus of the lateral lemniscus project caudally into the spinal cord. In the midbrain, descending spinal projections arise from cells of the medial longitudinal fasciculus and the red nucleus. More rostrally, cells of the ventrolateral thalamus, dorsal periventricular hypothalamus, central pretectal and magnocellular preoptic nuclei also project to the cord. The results of this study indicate that there are a number of homologies in the descending systems of bony fishes and other vertebrate taxa, including tetrapods. We also provide further evidence that a red nucleus is present in the brains of bony fishes and is therefore a primitive vertebrate character antedating the evolution of tetrapods.

Animals↗
PubMed1997

Noninvasive measurement of distal radius instability.

Except for subjective clinical criteria, there is no formal definition of distal radius fracture instability in the literature. The purposes of this ex vivo biomechanical study were (1) to provide an objective mechanical definition of fracture instability and (2) to demonstrate a noninvasive method that allows for direct measurement of instability. The following 3 questions are addressed: (1) Can the stability of distal radius fractures be measured using computed tomography (CT)? (2) Are the stability measurements reproducible? (3) How does external fixation change stability? A CT technique is described that was used to measure displacement of fracture fragments and measure the compliance of ex vivo distal radius fractures before and after external fixation. Validation studies of the CT technique revealed a mean coefficient of variation of 0.38. There was a linear relationship between measured and known displacements for all 3 orthogonal planes (coefficient of determination 0.99; p < .01). There was significant fracture displacement with loads as small as 20 N. The slope of the load-displacement curve (structural compliance) provided a quantitative measure of fracture instability. Fracture compliance decreased up to 69% after application of an external fixator.

Biomechanical Phenomena↗
PubMed1996

Trabecular bone morphology from micro-magnetic resonance imaging.

Micro-magnetic resonance imaging (micro-MRI) is potentially a widely available tool to image and quantify the three-dimensional structure of trabecular bone. However, it has not been demonstrated that the same quantitative measurements can be obtained using micro-MRI as would be obtained from conventional light microscope images. Bovine trabecular bone from several anatomic sites was imaged with both optical and micro-MRI methods. The six faces of approximately cubic trabecular bone specimens were examined with the light microscope, and the volume of bone internal to these faces was then imaged using an 8.6 T 25 mm bore magnet. Three-dimensional measures of bone morphology were calculated from both the optical and micro-MR images using the method of directed secants. Quantitative measures from the two imaging methods were compared by paired t-tests. Volume fractions (BV/TV) measured by micro-MRI were linearly related to (r2 = 0.81) and did not differ statistically from (p = 0.96) similar measurements from optical images. The trabecular plate number (Tb.N) measured by micro-MRI also was linearly related to (r2 = 0.53) and did not differ statistically from (p = 0.17) similar measurements from optical images. The orientation of trabeculae predicted from micro-MRI was within 6 degrees of that calculated from optical images in 10 out of 16 specimens. The micro-MRI morphology measurements are relatively easy to perform, and since several hundred small-bore high-field strength MRI systems are available, this technique could be used widely to quantify the morphology of trabecular bone.

Algorithms↗
PubMed1995

Does bracing affect bone density in adolescent scoliosis?

STUDY DESIGN: This is a case-control, cross-sectional analysis of bone density. OBJECTIVES: To determine if bracing during growth affects bone density in adolescent idiopathic scoliosis and whether the effect is local or systemic. SUMMARY OF BACKGROUND DATA: Data concerning the effect of bracing on bone mass in adolescents with idiopathic scoliosis are nonexistent. We were concerned that bone mass loss resulting from long-term brace use may be permanent and may predispose to problems with osteoporosis. METHODS: Healthy adolescent females (n = 85) with scoliosis measuring 20-45 degrees and treated either by brace or observation were studied. Dietary calcium, activity level, body mass index, and pubertal status were evaluated. Scoliosis was measured by Cobb angle. Bone mineral density at the hip and spine were measured by dual energy x-ray absorptiometry to differentiate local versus systemic effects of bracing. Lateral scans of the L3 vertebral body were used to minimize the influence of the pedicles, the effect of the scoliosis, and the interference of the ilium. RESULTS: Mean age, height, and weight were similar between braced and observed groups. After adjusting for curve, Cobb angle, body mass index, activity, and diet, two-way analysis of covariance showed L3 and femoral bone mineral density was the same for braced and observed patients, and pubertal status affected spinal bone mineral density but had no effect on femoral bone mineral density. Pubertal status and body mass index accounted for 53% of the variation in spine bone mineral density and was not affected by brace use. Cobb angle, curve pattern, activity, and diet were not associated with bone mineral density. CONCLUSION: Brace treatment does not adversely affect bone mass at the spine and hip in children with idiopathic scoliosis.

Absorptiometry, Photon↗
PubMed1995

Predicting the integrity of vertebral bone screw fixation in anterior spinal instrumentation.

STUDY DESIGN: Using 2-week-old calf lumbar vertebrae as a model for the human adolescent spine, the strength and rigidity of different methods of anterior spinal screw fixation and the use of noninvasive techniques for predicting bone screw stability before surgery and screw insertional torque intraoperatively were investigated. OBJECTIVES: The objectives were to determine what factors most affect the strength and rigidity of screw fixation, to determine the strongest and most rigid type of screw fixation for anterior spinal instrumentation, and to determine if noninvasive measurements of bone density before surgery by dual energy x-ray absorptiometry or quantitative computed tomography and if intraoperative measurement of screw insertional torque can be used to predict the in vivo strength and rigidity of vertebral screw fixation. SUMMARY OF BACKGROUND DATA: Anterior spinal instrumentation is an efficient method to correct spinal deformities in the thoracolumbar and lumbar spine. Fewer vertebrae are instrumented and arthrodesed, allowing for greater spine mobility. The forces transmitted to each vertebra are higher, perhaps accounting for the clinical failure rate of 13-30% at the metal bone interface from screw cut out. METHODS: Quantitative computed tomography and dual energy x-ray absorptiometry were used to assess the bone density of 24, 2-week-old calf lumbar vertebrae. Four different methods of vertebral screw fixation were evaluated: unicortical screw, bicortical screw, bicortical screw and washer, and bicortical screws and staple. The maximal screw insertional torque was measured for each specimen. Each vertebral body-screw construct failed in a mode simulating in vivo screw cut out. The applied moment and rotatory displacement were recorded. Ash density was measured for each vertebral body after removing all hardware. RESULTS: Noninvasive measures of bone density varied linearly with ash density (P < 0.01). Screw insertional torque varied linearly with bone mineral content and bone mineral density (r2 = 0.50) and was correlated with the yield moment for all types of fixation except the staple. Density measured by quantitative computed tomography did not affect rigidity or yield moment. Post hoc analysis showed that the screw-staple construct was the strongest and most rigid form of fixation. CONCLUSIONS: Measurement of bone density before surgery using dual energy x-ray absorptiometry and intraoperative measurement of screw insertional torque can be used to assess the stability of anterior spinal instrumentation. A bicortical screw inserted through a Dwyer-type staple provided the strongest and most rigid form of fixation.

Absorptiometry, Photon↗
PubMed1994

Effect of acaricide treatment of cattle on Amblyomma variegatum (Acari: Ixodidae) infestation of mongooses (Carnivora: Viverridae: Herpestes auropunctatus) in Guadeloupe, French West Indies.

The effect of acaricide treatment of cattle on the infestation of the small Indian mongoose (Herpestes auropunctatus Hodgson) by Amblyomma variegatum (F.) was determined during a field evaluation of selected acaricides in Guadeloupe, French West Indies. From April 1990 to April 1991, cattle at one site were treated every 14 d with pour-on formulations of deltamethrin, flumethrin, or permethrin; and cattle at a second site were treated as per a local standard treatment using a spray formulation of coumaphos every 30 d. The protocol was then reversed, and from April to July 1991 cattle at the original standard treatment site were treated using the pour-on treatment. Mongooses were examined for ticks during February-March and July 1990 and 1991. The mean prevalence of infestation of mongooses by A. variegatum larvae was reduced from 41 to 27% during the February-March to July periods at the pour-on treatment sites but increased from 29 to 43% during the same periods at the standard treatment sites. The mean relative density of infestation by larvae decreased from 2.15 to 0.65 at the pour-on treatment sites and increased from 0.7 to 1.95 at the standard treatment sites during the same periods. Data on nymphal infestations were inconclusive, and mongooses were not infested by adult ticks. The infestation of mongooses by A. variegatum may be of importance as a short-term alternative host system for immature stages of this tick during an eradication program.

Acari↗
PubMed1994

Field evaluation of baits and baiting strategies for delivering oral vaccine to mongooses in Antigua, West Indies.

A field study was conducted on Antigua, West Indies, to determine the feasibility of delivering an oral rabies vaccine or population control agent to free-ranging mongooses (Herpestes javanicus). Two biomarkers (tetracycline hydrochloride [THCL] and DuPont Oil Blue A dye) and two bait types (DuPont polymer fish meal and polyurethane foam) were used to bait three study sites. Four hundred polymer baits containing both biomarkers were distributed at 36 central point bait stations (11 baits/station) on an 80 ha study site (5 baits/ha); 69% of the mongoose population consumed one or more baits. Two thousand baits containing THCL and 400 baits containing DuPont dye were distributed on two additional 100 ha study sites (24 baits/ha). Polymer fish meal baits were used on the first site and polyurethane baits on the second site. Based on the presence of biomarkers in bone or soft tissue, 96 to 97% of the mongooses at both sites consumed at least one bait. We conclude that oral baiting of mongooses is a feasible method for delivery of vaccines for the control of rabies in this species.

Adipose Tissue↗
PubMed1993

Role of trabecular morphology in the etiology of age-related vertebral fractures.

Osteoporotic compression fractures of the spine differ from most other age-related fractures in that they usually are associated with minimal trauma and with loads no greater than those encountered during normal activities of daily living. With aging and osteoporosis, there is progressive resorption of bone, resulting in reductions in bone density, thinning of trabeculae, and loss of trabecular contiguity. These changes in trabecular bone structure are associated with losses in bone strength which are disproportionate to the reductions in bone mass alone. To explain this disproportionate loss of bone strength, the prevailing opinion is that density reductions in the vertebral centrum are accompanied by a reduction in the number of trabeculae, by preferential resorption of horizontal trabeculae, and by hypertrophy of the remaining vertical trabeculae. To evaluate this view of vertebral morphology, we performed three-dimensional stereological analysis of trabecular bone extracted from midsagittal sections of first lumbar vertebral bodies from 12 donors spanning an age of 27-81 years. We found that both the number (R2 = 0.63, P < 0.01) and thickness (R2 = 0.91, P < 0.01) of trabeculae decreased linearly with density (as expressed by bone volume fraction) whereas the spacing between the trabeculae (R2 = 0.61, P < 0.01) increased reciprocally. There were more vertical trabeculae with transverse trabeculae at all densities, and the number of vertical trabeculae changed with density at twice the rate of the number of transverse trabeculae (P < 0.001). These data do not support the prevailing view that there is preferential resorption of horizontal trabeculae or hypertrophy of the remaining vertical trabeculae.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Evaluation of baits for oral rabies vaccination of mongooses: pilot field trials in Antigua, West Indies.

A field study was conducted on the island of Antigua, West Indies, to evaluate baits for delivering an oral rabies vaccine to the small Indian mongoose (Herpestes auropunctatus). Tracking tiles were used to determine that mongooses were nonselective and took both egg-flavored polyurethane baits and fish-flavored polymer baits containing several different food materials. A high proportion of baits were taken the day of placement with minimal disturbance by nontarget species. DuPont Oil Blue A dye was an effective short-term biomarker for use in baits; based on its subsequent detection in mongooses, some of the population had consumed and not cached or discarded baits. Central point baiting stations showed promise as an alternative delivery technique.

Administration, Oral↗
PubMed1992

Acute radicular pain as a presenting symptom in multiple sclerosis.

From December 1973 through November 1988, we cared for 11 patients who presented with acute radicular pain and in whom radicular compression was ruled out by imaging techniques. Eventually, multiple sclerosis was diagnosed and judged to be responsible for the acute radiculopathy. The patients (seven women, aged 18 to 40 years; median, 32 years) and four men (aged 23 to 34 years; median, 29 years) were followed up from 6 months to 15 years (mean, 4 years 11 months). They represent 3.9% of 282 newly diagnosed cases of multiple sclerosis during the same 15 years. A retrospective analysis of the characteristics of their illness and its evolution was conducted. Six had lumbosacral radiculopathies; three, cervical and two, thoracic. In six of the 11 patients, symptoms occurred in close relationship to trauma; seven had recurrent radicular pain; four had other pain syndromes; and three others, paroxysmal symptoms. One patient died of complications from multiple sclerosis 3 years after diagnosis. Three others were rated five or greater in the extended Kurtzke disability status scale during follow-up.

Adolescent↗
PubMed1989

Outcome data.

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Health Maintenance Organizations↗
PubMed1988

Posterior cortical atrophy.

Five patients had progressive dementia heralded by disorders of higher visual function. All eventually developed alexia, agraphia, visual agnosia, and components of Balint's, Gerstmann's, and transcortical sensory aphasia syndromes. Memory, insight, and judgment were relatively preserved until late in the course. Predominant parieto-occipital atrophy was demonstrated on both computed tomography and magnetic resonance imaging in two of the patients; posterior circulation was normal by angiography in the three studied. To date, no pathologic specimen is available for study; speculations on the underlying pathologic condition include an atypical clinical variant of Alzheimer's disease, a lobar atrophy analogous to Pick's disease, or some previously unrecognized entity.

Aged↗