Search PubMed⌕ Search

Biomedical subjects

D L Wheeler

Publications and source records attributed to D L Wheeler.

47 records · Page 3Linked to original sources
PubMed1990

Historical estimates of external gamma exposure and collective external gamma exposure from testing at the Nevada Test Site. II. Test series after Hardtack II, 1958, and summary.

The historical data on the cumulative individual external gamma exposures are tabulated for communities around the Nevada Test Site for the time periods of 1961 to the signing of the Limited Test Ban Treaty on 5 August 1963, and from then until 1975. The collective exposures during the two time periods are calculated to be 610 and 320 person-R, respectively. The total collective external gamma exposure from 1951 through 1975 for these communities s calculated to be 86,000 person-R. The area considered includes the countries of Clark, Lincoln, Nye, and White Pine in Nevada and the countries of Iron and Washington in Utah; inclusion of Salt Lake City would have substantially increased the calculated collective exposure because of the large population. The methods of calculation are reviewed. Also, the historical data on the assessment of dose via ingestion are reviewed with emphasis on the dose to the thyroid of infants living in St. George, UT, at the time of fallout from event HARRY on 19 May 1953.

Environmental Exposure↗
PubMed1977

Negotiating and bidding for good results.

When determining a method of procurement, the purchasing manager must remember his goals. Whether it be by bidding, negotiating, or open-ended contracts, the method chosen is a means of obtaining savings for the hospital and, ultimately, for the patient.

Georgia↗
PubMedDate not supplied

Capabilities and potentialities of transverse pore gradient gel electrophoresis.

Transverse pore gradient gel electrophoresis is important as a tool for obtaining nonlinear Ferguson plots [log(mobility) vs. gel concentration], e.g. in application to DNA in polyacrylamide gels or to agarose gels, with the purpose of evaluating molecular properties (size, conformation, malleability) and gel fiber properties (fiber radius and length per unit volume). To date, it is capable of (i) yielding gel patterns ("Ferguson curves") of migration distance vs. predicted % T-range of the pore gradient, assuming its linearity; (ii) yielding information regarding molecular conformation from the intersection of Ferguson curves of unknowns (e.g. bent DNA) with those of standards; (iii) acquisition of Ferguson curves by computer, using prototype instrumentation; (iv) mathematical manipulation of acquired Ferguson curves to yielding Ferguson plots, providing that mobility in free solution has been assessed by capillary zone electrophoresis. The potentialities of the method remain unfulfilled to date due to (i) the unavailability, with a single exception, of an accurate and precise way to produce pore gradients of known shape; (ii) unavailability of a routinely applicable analysis for % T; (iii) unavailability of optimized, user-friendly and foolproof instrumentation for computer acquisition of Ferguson curves, including the present inapplicability of a commercially available electrophoresis apparatus with intermittent optical detection to transverse pore gradient gels; and (iv) unresolved problems in the statistical evaluation of Ferguson curves.

DNA↗
PubMedDate not supplied

Transverse pore gradient gel electrophoresis, using the PhastSystem.

The application of pore gradient gels prefabricated for the PhastSystem (Pharmacia) to transverse pore gradient gel electrophoresis is demonstrated. It has the twofold advantage of (i) horizontal positioning, avoiding gel stretching during the preparation of these gels and resulting pore size irreproducibility experienced with vertically applied pore gradient gels, which necessitate an orthogonal transfer of spacers, and (ii) miniaturized gel dimensions, which allow a small sample load and a short duration of electrophoresis and staining.

Base Composition↗
PubMedDate not supplied

Biomechanical evaluation of the dynamic hip screw with two- and four-hole side plates.

OBJECTIVES: To determine the biomechanical strength and stiffness of a dynamic hip screw (DHS; Synthes USA, Paoli, PA, U.S.A.) with a two-hole side-plate as compared with a four-hole side-plate design for the reconstruction of unstable three-part intertrochanteric fractures. DESIGN: Eight matched pairs of embalmed human femurs were tested in two modes: (a) 2,000 cycles of simulated physiologic loading; (b) test to failure. SETTING: Laboratory. Simulated single leg stance using a simulated pelvic loading mechanism with abductor loading. Strain and displacement sensors were used to measure fragment shear and distraction and surface strain in the proximal side plate. SPECIMENS: Eight pairs of skeletonized embalmed cadaveric specimens were selected on the basis of femoral neck angle and absence of old fracture, anatomic anomaly, or pathology. INTERVENTION: The specimens were divided into two groups: (a) left femurs received the two-hole side-plate design; (b) right femurs received the four-hole side-plate design. All fractures were reconstructed by the same surgeon using the manufacturer's instructions. MAIN OUTCOME MEASUREMENTS: Implant placement was verified by radiographic measurement of tip-to-apex distance. In cyclic testing, the amount of femoral neck fragment migration in both distraction and shear was quantified. Strain magnitude in the side plate was measured in both cyclic and failure testing. The peak load withstood by the reconstruction was quantified in the failure test. RESULTS AND CONCLUSIONS: Peak load in the failure test was not found to be statistically different between the two-hole and four-hole designs. In cyclic testing, the two-hole configuration exhibited statistically smaller fragment migration in both shear and distraction than the four-hole design (p < 0.05). The strain magnitude in the side plate was not statistically different in the cyclic or failure tests. The femurs with a greater neck angle failed by crushing of the bone in the neck. The femurs with a lesser neck angle failed due to bending of the hardware. The results of this investigation revealed that the two-hole DHS is biomechanically as stable as the four-hole DHS in cyclic and failure loads under the conditions tested. These results, in concert with clinical experience, can be used to support the use of the two-hole DHS for the reconstruction of intertrochanteric fractures without a diaphyseal extension.

Adult↗
PubMedDate not supplied

Stress fractures of the sacrum. An atypical cause of low back pain in the female athlete.

Low back pain is a common finding in an athletically active premenopausal female population. We describe an unusual cause of persistent low back/sacroiliac pain: a fatigue-type sacral stress fracture. Plain radiographs, bone scans, computed tomography, and magnetic resonance imaging studies were obtained in the female athletes to determine the nature of the pathologic abnormality. The most significant risk factor for fatigue-type sacral stress fractures was an increase in impact activity due to a more vigorous exercise program. Potential risk factors such as abnormal menstrual history, dietary deficiencies, and low bone mineral density were examined. The clinical course was protracted, with an average 6.6 months of prolonged low back pain before resolution of symptoms. Sacral fatigue-type stress fractures did not preclude the athletes from returning to their previous level of participation once healing had occurred.

Adult↗
PubMedDate not supplied

Stress fractures of the femoral shaft in athletes--more common than expected. A new clinical test.

Athletes from 20 Division I AA collegiate varsity sports and 1 club sport were followed carefully for the development of stress fractures during the 1990 to 1991 and the 1991 to 1992 academic years. During this period, among 914 athletes, 34 stress fractures were sustained. Seven of these, or 20.6%, were of the femoral shaft. This represents a much higher incidence than previously observed in athletes. A new clinical test is described that significantly aids in the early diagnosis and follow-up treatment of femoral shaft stress fractures.

Adolescent↗
PubMedDate not supplied

Protein kinase C epsilon signals ultraviolet light-induced cutaneous damage and development of squamous cell carcinoma possibly through Induction of specific cytokines in a paracrine mechanism.

Protein kinase C (PKC), a family of phospholipid-dependent serine/threonine kinases, is not only the major intracellular receptor for the mouse skin tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) but also is activated by a variety of stress factors including ultraviolet radiation (UVR). PKCepsilon is among six isoforms (alpha, delta, epsilon, eta, mu and zeta) expressed in the mouse skin. To determine the in vivo functional specificity of PKCepsilon in mouse skin carcinogenesis, we generated PKCepsilon transgenic mouse (FVB/N) lines 224 and 215 that overexpress PKCepsilon protein approximately 8- and 18-fold, respectively, over endogenous levels in the basal epidermal cells and cells of the hair follicle. PKCepsilon transgenic mice were observed to be highly sensitive to the development of papilloma-independent metastatic squamous cell carcinoma (mSCC) elicited either by repeated exposure to UVR or by the 7,12-Dimethylbenzanthracene-TPA tumor promotion protocol. The development of squamous cell carcinoma (SCC) appears to be linked to the PKCepsilon-mediated induction of cytokine tumor necrosis factor-alpha(TNFalpha). Immunohistochemical analysis for the expression of PKCepsilon in the SCC of PKCepsilon transgenic mice revealed that PKCepsilon was not expressed in the tumor itself; however, the uninvolved tissue surrounding the SCC exhibited intense PKCepsilon expression. Also, human SCC, similar to mouse SCC, did not express PKCepsilon in the tumor, whereas the surrounding uninvolved epidermis revealed strong PKCepsilon expression. These findings in both the PKCepsilon mouse model and human SCC indicate that overexpression of PKCepsilon in epidermis may lead to a microenvironment, which is suitable for enhancing the development of mSCC by a paracrine mechanism involving specific cytokines including TNFalpha.

Animals↗