PubMed Health⌕ Search

Biomedical subjects

D Wheeler

Publications and source records attributed to D Wheeler.

At least 55 records · Page 3Linked to original sources
PubMed1995

Identity and pathogenesis of stomach tumors in Sprague-Dawley rats associated with the dietary administration of butachlor.

Macroscopic stomach tumors induced in Sprague-Dawley rats during two chronic bioassays with the acetanilide herbicide butachlor at a dietary concentration of 3000 ppm, were evaluated histologically and immunohistochemically in order to determine their identity and pathogenesis. The tumors, which occurred primarily in female rats, were a heterogeneous series, including a few consisting wholly or partly of classic solid or anaplastic epithelium, but with the majority containing diffusely distributed primitive neoplastic cells. The latter had either the general appearance of undifferentiated epithelium or presented a more "mesenchyme-like" pattern where the cells were epithelioid, blastema-like, neuroendocrine-like or sarcoma-like with fascicular disposition. Gastric glandular profiles were also present, usually located near the periphery of the tumors, but in some cases extending into the diffuse tumor tissue. Most of the tumors displayed variable immunohistochemical reactivity for cytokeratin, vimentin and neuron-specific enolase but were negative for muscle-specific actin or desmin except in the stromal tracts. Detailed examination of all available gastric tissue revealed the presence of additional microscopic neoplasms and precursor hyperplastic lesions. All of these were typical gastric neuroendocrine cell lesions (gastric carcinoids) originating in the fundic mucosa but occasionally invading submucosally, and consisting of epithelial cells in organized clusters, rosettes or primitive tubules. The enterochromaffin-like (ECL) nature of these microscopic neoplasms and precursor lesions was substantiated by strong immunohistochemical reactivity for cytokeratin, neuron-specific enolase and chromogranin A, and a negative reaction for vimentin. One microscopic tumor showed a transition from differentiated neuroendocrine type in the fundic mucosa to a dispersed "mesenchyme-like" pattern in the submucosal extension. An additional finding in the butachlor-treated male and female rats was atrophy of the fundic mucosa involving, in particular, reduction in the numbers of parietal cells. This effect was dose-related, being most severe in the high-dose (3000 ppm) females. On the basis of their morphological characteristics, coupled with the continuity evident in the microscopic lesions, it is concluded that the macroscopic stomach tumors associated with the dietary administration of butachlor are poorly differentiated gastric carcinoids, in some cases admixed with a non-neuroendocrine epithelial element. Fundic ECL and stem cells are known to be under the trophic influence of gastrin, which is apparently responsible for the induction of the tumors associated with butachlor administration. Gastric tumor development involving gastrin is recognized as a secondary, hormonal mechanism of carcinogenesis, demonstrating a dose-threshold phenomenon.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetanilides↗
PubMed1995

Reliability of in-bed weighing procedures for critically ill infants.

The purpose of this study was to describe the intra- and interexaminer reliability of weight measurements obtained from critically ill infants on an in-bed electronic scale. Weight measurements were obtained using the in-bed scale (Smart Model 35, Olympic Medical, Seattle, Washington) for 32 infants; 16 were in an incubator, and 16 were under a radiant warmer. Two nurses each obtained two weight measurements for each infant for three consecutive days, for a total of 96 data collection sessions. The nurses were blinded to their own and to the other nurse's weight measurements. The average mean absolute difference for individual nurses' weight measurements (interexaminer reliability) was 12.58 gm for weights obtained in the incubator and 19.19 gm for weights obtained under the radiant warmer. The average mean absolute difference for pairs of nurses' weight measurements (interexaminer reliability) was 14.29 gm for weights obtained in the incubator and 24.42 gm for weights obtained under the radiant warmer. The average mean absolute differences for weights obtained in the two bed types differed significantly for both intra- (Z = -2.46, p = .0141) and interexaminer (Z = -3.11, p = .0019) reliability. The number of pieces of equipment that had to be held during the weight measurement was weakly correlated with both the intra- (rs = .1878, p = .0091) and interexaminer (rs = .1600, p = .0266) mean absolute differences. These findings suggest that weight measurements of critically ill infants obtained using the Smart Model 35 in-bed electronic scale are sufficiently reliable for calculation of medication, parenteral fluid, blood replacement, and nutritional requirements.(ABSTRACT TRUNCATED AT 250 WORDS)

Anthropometry↗
PubMed1994

Intravenous immunoglobulin-induced osmotic nephrosis.

Intravenous immunoglobulin preparations are being used for an increasing number of indications in clinical medicine. To minimize adverse reactions, sugar additives such as sucrose are added to some preparations to serve as stabilizing agents. We describe a patient treated with an immunoglobulin preparation containing sucrose who developed a fully reversible form of acute renal failure with histologic changes characterized by vacuolization and swelling of renal proximal tubular cells. We believe the high concentration of sucrose in the immunoglobulin preparation resulted in osmotic injury to the renal tubules. Such changes, which are identical to those described in humans and experimental animals given intravenous infusions of hypertonic sucrose, have come to be known as osmotic nephrosis. Risk factors for the development of this lesion are renal insufficiency and volume depletion. The risk for such injury can be minimized by further diluting the immunoglobulin preparation and slowing the infusion rate.

Aged↗
PubMed1994

Incidence of ligament lesions and associated degenerative changes in the elderly wrist.

The scapholunate, lunotriquetral, and triangular fibrocartilage of 62 cadaveric wrists were examined to determine the incidence of pathologic changes in asymptomatic elderly wrists. A scapholunate ligament lesion was noted in 18 wrists; the majority of defects were incomplete and involved the central portion of the ligament only. Lunotriquetral ligament defects were noted in 20 wrists; eight were partial defects, most of them were central ligament lesions. Triangular fibrocartilage defects were present in 33 wrists and consisted of two distinct patterns: a central oval pattern with actual tissue loss and a linear defect running in the dorsal anterior direction 2-3 mm ulnar to the radial attachment of the triangular fibrocartilage. X-ray film evaluation showed few significant degenerative changes with no pronounced collapse deformities. Defects involving the scapholunate, lunotriquetral, or triangular fibrocartilage were very common, with the presence of at least one of these ligament defects in wrists. These ligament defects occur as a process of aging and behave in a manner quite different from traumatic lesions of these same structures in the younger population.

Aged↗
PubMed1994

Enhanced ethidium fluorescence of large DNA electrophoresed in gels submersed in an immiscible solvent.

Agarose gel electrophoretic separation of a lambda/HindIII DNA marker containing detectable fragments of 23 to 2 kb was carried out in the conventional submarine apparatus and in the horizontal gel slab apparatus of Wieme, using identical samples, agarose, gel width and procedure for ethidium bromide staining. In the Wieme apparatus, the gel on its microscope slide support is immersed in an immiscible solvent such as petroleum ether or silicone oil. Although band resolution and speed of migration are equivalent between gels run in the two systems, the relative fluorescence intensity of the ethidium bromide-stained bands is substantially more responsive to an increase in DNA length in the Wieme gels than in the submarine gels. The predicted relative fluorescence is by an average factor of 0.5 less than that observed after electrophoresis in the Wieme apparatus but is by an average factor of 3.4 more than that observed on bands derived from the submarine technique.

DNA↗
PubMed1993

A gel-concentration-independent retardation detected in two fragments of the rrnB P1 promoter of E. coli using transverse polyacrylamide pore gradient gel electrophoresis.

Two fragments of the E. coli rrnB ribosomal RNA P1 promoter Upstream Activation Region exhibit a constant gel retardation, over a polyacrylamide gel concentration range of 3% to 10%. Gel retardation is usually seen to increase with polyacrylamide gel concentration as in the case of the 219 base pair Crithidia fasciculata kinetoplast DNA fragment which represents the classic case of sequence directed curvature. Computer modeling of the Upstream Activation Region fragments suggests that their unusual electrophoretic behavior can be accounted for on the basis of a "screw" model proposed by Drak and Crothers (1991, Proc. Natl. Acad. Sci. USA 88,3074-3078).

Animals↗
PubMed1993

Characterization of the electrophoretic properties of nucleosome core particles by transverse polyacrylamide pore gradient gel electrophoresis.

Transverse pore gradient gel electrophoresis, previously applied to bent DNA, has extended the usefulness of the gel retardation assay in two ways: (i) by differentiating between different DNA conformations; (ii) by providing information regarding the physical properties of DNA. In the present study, similarly extended information is obtained with regard to a well-characterized DNA-protein complex, the chicken erythrocyte nucleosome core particle. (i) The winding of DNA around the protein core constrains the DNA which renders its Ferguson curve (migration distance vs. gel concentration) similar to that of kinetoplast DNA, i.e. it intersects sharply with the Ferguson curves of linear DNA standards. By contrast, the deproteinized nucleosome DNA exhibits a Ferguson curve similar to linear standards of the same length. (ii) Interpretation of the Ferguson curve based on a mathematical model shows that the nucleosome exhibits a linear Ferguson plot [log(mobility) vs. gel concentration]. This is similar to and characteristic of spherical proteins, contrasting with the concave plot typical for linear and bent DNA. (iii) The effective size of the nucleosome, evaluated in terms of an "equivalent sphere" (i.e. a hypothetical spherical particle with a radius, Res, having the same electrophoretic mobility as DNA for a particular set of experimental conditions), remains invariant across the gel concentration range of 3-9%T. This is similar to proteins and bacteriophages and contrasts with the progressive decline of Res with increasing gel concentration observed for linear DNA and the deproteinized nucleosomal DNA.

Animals↗
PubMed1993

The fractional volume available to prolate spheroids in a network of randomly oriented fibers obtained by computer modeling: correlation with the Ogston equation.

Computer modeling was used to measure the fractional volumes available to prolate spheroid objects in a random, inert network of fibers. The data fit the Ogston equation exactly when the object was a sphere (axial ratio = 1). When the axial ratio was increased from 1 to 9, the Ogston equation was still obeyed if the fiber concentration is multiplied by a factor, A, which increases linearly in proportion to the axial ratio. The factor A allows one to adjust the retardation coefficient derived from gel electrophoresis, KR, for spherical objects to that of prolate spheroids with axial ratios from 1 to 9. Potentially, the same adjustment of KR is possible for objects of other shapes.

Algorithms↗
PubMed1993

A three-dimensional plot for the display of transverse pore gradient gel electrophoresis data: application to a kinetoplast DNA fragment of planar circular conformation.

A 219 bp fragment of kinetoplast DNA from Crithidia fasciculata has previously been shown to exhibit a gel concentration dependent, anomalously low migration rate in 3-10% polyacrylamide transverse pore gradient gels relative to that of straight standards. The anomaly was interpreted in accordance with previous results of Marini et al. [1] as being due to the planar circular conformation of the fragment. The transverse pore gradient gel pattern is displayed here as a three-dimensional plot of migration distance vs. gel concentration and DNA length for the kinetoplast fragment and straight DNA standards. The plot yields a smooth surface for the standards clearly separated from the curve of the kinetoplast DNA fragment. Thus, transverse gradient gel electrophoresis in conjunction with the three-dimensional plot provides a unique method for the recognition of abnormal conformational features of DNA on the basis of electrophoretic mobility in a pore-size gradient.

Animals↗
PubMed1993

Phylogenetic and structural analyses of MMTV LTR ORF sequences of exogenous and endogenous origins.

The long terminal repeat (LTR) of mouse mammary tumor virus (MMTV) harbors an open reading frame (ORF) that encodes a glycoprotein and is present in all exogenous and endogenous MMTV proviruses. The ORF protein has been reported to interact with the immune system of mice to cause deletion of specific V beta-bearing subsets of T cells. Twenty-two MMTV LTR ORF sequences were analyzed. Although highly conserved, the MMTV ORF sequences are not identical, with approximately 35% of the total variation clustered at the carboxy terminus. Statistical analysis revealed the presence of two conserved regions in the protein, one of which contained a transmembrane-like domain (residues 45-63). Two potential nuclear localization signals were recognized. Many ORF sequences shared polymorphisms. To analyze relationships, phylogenetic trees were constructed on the basis of alignments of LTR ORF sequences. A tree generated from the carboxy-terminal 35 residues clustered the sequences into three divergent families. The topology of the tree based on the amino-terminal 288 residues differed significantly, with some MMTV sequences rearranged relative to their carboxy-terminal families. A continuum of exogenous-like to endogenous-like character was suggested by the amino-terminal tree. The discordance between the topologies of the two trees suggests that some type of genetic exchange has occurred in the MMTV LTR gene. Mechanisms and implications of such genetic exchange are discussed.

Amino Acid Sequence↗
PubMed1993

Identification of two storage hexamers in the ant, Camponotus festinatus: accumulation in adult queenless workers.

Two electrophoretically and immunologically distinct storage hexamers (Hex 1 and Hex 2) have been identified in Camponotus festinatus workers. The molecular weights of the native molecules were estimated to be 460,000 (Hex 1) and 580,000 (Hex 2) by pore limiting gradient electrophoresis. Hex 1 partially dissociates with moderate alkaline pH. Both proteins are composed of a single type of apoprotein of approx. 73 (Hex 1) and 80 kDa (Hex 2). While most of Hex 2 is sequestered by the fat body before pupation, Hex 1 remains largely in the hemolymph during the last larval and pupal stages. Both proteins were detected only in low concentrations in the hemolymph of newly emerged adults, and they gradually disappear from adult workers maintained in the colonies. In queenless workers, however, Hex 1 and Hex 2 accumulate in the hemolymph and fat body, constituting the most abundant proteins together with vitellogenin. Camponotus festinatus storage hexamers bear some homologies in their N-terminal sequence with the arylphorins of Diptera and Lepidoptera, as well as with a crab hemocyanin. However, with respect to their amino acid composition, they can not be classified as arylphorins.

Amino Acid Sequence↗
PubMed1993

Reconstruction of the humerus with an intramedullary fibular graft. A clinical and biomechanical study.

Nine patients with nonunited humeral shaft fractures were treated by open reduction and internal fixation with an intramedullary fibular bone graft and a compression plate. Fixation of the screws was enhanced by passing them through the fibula as well as the two humeral cortices (quadricortical fixation). Eight of the nine fractures united at an average of 3.5 months. Tests on cadaver bones showed that quadricortical fixation was as strong as methylmethacrylate augmentation and significantly better than bicortical fixation.

Adult↗
PubMed1992

Distinction between supercoiled and linear DNA in transverse agarose pore gradient gel electrophoresis.

Four species of linear DNA and the first four members of a linking series, generated by treatment of plasmid DNA (PUC19, 2.7 kb) with mitochondrial topoisomerase I, were differentiated by transverse agarose pore gradient gel electrophoresis. The experimental curves of migration distance vs. agarose concentration (Ferguson curves) of supercoiled DNA exhibit a steeper trajectory than those of linear DNA of the same size range. As a consequence, the four supercoiled species exhibit an increase in apparent size (relative to linear DNA standards) with increasing agarose concentration. Both the crossing of the Ferguson curves with those of linear standards as well as the apparent size increase with agarose concentration can serve to detect supercoiled plasmid-sized DNA in mixtures with linear DNA.

DNA↗
PubMed1992

Computer-aided analysis of DNA curves on transverse gradient gels.

Transverse pore gradient polyacrylamide gel electrophoresis of DNA restriction fragments was used to generate gel patterns describing migration distance as a function of gel concentration (Ferguson curves). These Ferguson curves were digitized, traced and analyzed with the aid of a personal computer. The traced curves were plotted semi-logarithmically and the plots were subjected to least-squares linear regression analysis to yield values of the slope (KR) and the intercept at %T = 0 (YO). These values are highly precise since they are based on approx. 100 measurements per curve. The computerized method reduces the errors due to manual measurements of migration distances and is time and labor saving. The method is still limited to intra-experimental comparison of Ferguson curves, since it does not as yet comprise a determination of gel concentration. At present, curve tracing remains semi-automated, requiring manual intervention when Ferguson curves cross or approach one another. Potentially, the importance of the computerized analysis of transverse pore gradient gels lies in the rapid quantitative interpretation of Ferguson curves for detection of anomalously migrating DNA species. Potentially, that application provides a more sensitive and informative mode of detection than either the mere visual observation of crossing Ferguson curves or of a shift in mobility at a single gel concentration.

Buffers↗