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Biomedical subjects

D S Davis

Publications and source records attributed to D S Davis.

At least 37 records · Page 2Linked to original sources
PubMed1998

Conservation of germ plasm from bison infected with Brucella abortus.

Reproductive procedures for cattle were adapted to American bison (Bison bison) to evaluate the potential preservation of germ plasm from bison infected with Brucella abortus without transmission of the pathogen to the recipient or offspring. Two of four experimentally inoculated bison bulls excreted B. abortus in the semen. Four healthy calves were produced from non-infected, un-vaccinated bison cows by natural breeding with a bison bull excreting B. abortus in the semen. There was no seroconversion of the cows or their calves. Two culture negative bison calves were produced by superovulation of infected bison donor cows followed by artificial insemination and embryo transfer without transmitting B. abortus to recipient cows or calves. These limited data indicate that embryo manipulatory procedures and natural breeding in bison may facilitate preservation of valuable germ plasm from infected bison while reducing the risk of transmission of B. abortus to recipients and progeny.

Animals↗
PubMed1998

Safety of Brucella abortus strain RB51 in Bison.

To determine the safety of Brucella abortus strain RB51 (SRB51) vaccine in American bison (Bison bison), 31 animals from a herd with brucellosis were used. In October 1996, 10 adult bison males and seven calves were vaccinated with the standard calfhood cattle dose of 1.8 x 10(10) colony forming units (CFU) of SRB51 subcutaneously while the adult females received the standard adult cattle dose of 1 x 10(9) CFU. Western immunoblot indicated the presence of SRB51 antibodies following vaccination. To evaluate prolonged bacterial colonization of tissues, the adult males, calves, and three adult females were divided into two groups which were slaughtered at either 13 or 16 wk post-vaccination. At necropsy, tissue samples were obtained for B. abortus culture from the liver, spleen, lymph nodes, and reproductive tract of each animal. While B. abortus field strain was cultured from one adult bull, no SRB51 was isolated from any of the animals. Seven pregnant females were monitored until parturition for signs of abortions and fetal lesions. Six cows delivered healthy calves and one delivered a dead full-term calf that was brucellae negative. Based on these results, administration of SRB51 to bison did not cause prolonged bacterial colonization of tissues in calves, adult males, or adult females. Furthermore, SRB51 did not induce abortions following vaccination in the second month of gestation.

Abortion, Veterinary↗
PubMed1998

[Splicing factors in oocyte nuclei from human antral follicles].

Three groups of oocytes in the human antral follicules were previously distinguished on the basis of nuclear structures arrangement and 3H-uridine incorporation in the oocyte nuclei revealed by ultrastructural and autoradiographic research (Parfenov et al., 1984, 1989). These groups can be regarded as consecutive states of oocyte development, i. e. active, intermediate and inactive ones. The latter is characterized by compactization of nuclear structures arranged within a limited nuclear volume. The present study concerns the distribution of splicing factors (snRNP and SC35) and p80 coilin in the nuclei of oocytes being at either of the three states. Along with transcription decreasing in oocyte nuclei, reduction of snRNP and SC35 amounts in the karyoplasm was detected. Simultaneously, accumulation of these splicing factors occurred in clusters of interchromatin granules (CIG). snRNP and SC35 are spatially segregated in CIG. snRNP are located within the fibrillar zones of CIG, while SC35 corresponds to the granular component of CIG. CIG are the only structures containing splicing factors in the nuclei of oocytes from the human antral follicules. These nuclei lack typical coiled bodies (CB). Considerable amounts of the marker protein of CB--p80 coilin are revealed in the nucleolus-like bodies (NLB) of human oocyte nuclei. Contrary to the data obtained on the oocytes from the antral follicules of other mammals (Kopecny et al., 1996a, 1996b) NLB in human oocytes do not contain snRNPs and SC35. The present study allows to make the following conclusions: a) splicing factors recruted to the sites of transcription in karyoplasm of oocytes are assembled in CIG when inactivation of transcription takes place; b) CIG in preovulated human oocytes play substantial role in the storage and preservation of splicing factors.

Adult↗
PubMed1997

TG-21 versus TG-25: a comparison for electrons.

Since 1984, the Radiological Physics Center (RPC) has used the American Association of Physicists in Medicine Task Group 21 (TG-21) protocol (absorbed dose determination) as the basis of its On-site Dosimetry Review visits to institutions participating in the National Cancer Institute's cooperative clinical trials. Subsequent to the TG-21 protocol, the Task Group 25 (TG-25) report on electron-beam dosimetry was published. The TG-25 report was not intended to supercede the TG-21 protocol, but to supplement it for depths other than dmax. However, both reports included measurement techniques and data regarding the calibration of electron beams. TG-25 was not intended for absolute calibrations made clear by the fact that it does not present all of the data required for plastic phantom calibrations, i.e., unrestricted stopping power ratios. As a result, some confusion has arisen at various institutions as to which protocol should be used for machine calibration. In this study, possible discrepancies that arise when using TG-21, a version of TG-21 modified by the RPC, and TG-25 are compared. The differences in the results are calculated as a function of energy (6 and 20 MeV), chamber type (cylindrical or parallel plate), and the type of phantom material (water, polystyrene, or acrylic). The largest discrepancies noted were between TG-25 and the two TG-21 methods for low-energy electrons in either water or polystyrene. The mean difference for all conditions was 0.8% with a maximum value of 3.3% in polystyrene. The definition of the effective point of measurement; determination of the mean nominal incident energy (E0), mean energy at depth (EZ) and most probable energy at the surface (Ep,0) for each protocol, and subsequent stopping power ratio, chamber replacement factor, and electron fluence correction factor are the major contributors to the calculated differences.

Clinical Protocols↗
PubMed1997

Segond fracture: lateral capsular ligament avulsion.

Recently, there has been an emphasis placed on incorporating fundamental radiology in graduate level physical therapy curricula; however, the majority of practicing physical therapists never received formal radiology instruction. As health care changes, so must the role of the physical therapist. In a managed care environment, it is essential that physical therapists recognize basic radiographic findings and understand their clinical ramifications. The purpose of this article is to review the literature and provide commentary on avulsion fractures of the lateral tibial condyle, known as Segond fractures. Segond fractures typically occur by forced internal tibial rotation with the knee flexed. This mechanism placed tremendous force on the middle portion of the lateral capsule and associated meniscotibial ligament and results in a small bony avulsion. The Segond fracture is an important radiographic sign that is critical to recognize because it is generally associated with anterior cruciate ligament disruption.

Diagnosis, Differential↗
PubMed1996

Nuclear bodies of stage 6 oocytes of Rana temporaria contain nucleolar and coiled body proteins.

The genetically inactive stage 6 oocyte nuclei of Rana temporaria contain certain nuclear bodies that label with nucleolus-specific and coiled body (CB)-specific antibodies. We designate them multicomponent bodies (MCBs) to reflect their mixed composition. Morphologically, each MCB contains five distinct zones: zone I composed of electron-dense fibrils similar to the dense fibrillar component (DFC) of the typical eukaryotic nucleoli; zone II resembled the fibrillar material of the inactive agranular nucleoli of stage 6 oocytes; zone III consisted of fine filamentous material corresponding to the fibrillar center (FC) of lower electron density seen in the typical nucleoli; and zones IV and V contained packed coiled threads typical of CBs. Of these, zone IV was seen in the interior of MCBs and contained tightly packed coiled threads (20 nm thick), while zone V occurred at the periphery and consisted of similar threads but loosely packed and electron dense. The material of both zones IV and V resembled that of CBs. To determine the composition of these zones, we extracted oocytes with a buffer that removes chromatin and most of the soluble proteins and processed them for immunogold labeling with a variety of antibodies. Anti-p80 coilin antibody predominantly labeled zone IV and, to a lesser extent, zone V. Anti-snRNP antibody also showed a similar labeling pattern. Anti-fibrillarin antibody predominantly labeled zone I and to a lesser extent zones IV and V. Anti-B23 antibody labeled all zones. These observations suggest that MCBs contain both nucleolar and CB material. We postulate that MCBs represent storage structures which provide material needed for the early stage of embryogenesis. The demonstration of MCBs further supports the close interrelationship between nucleoli and CBs.

Animals↗
PubMed1996

The pathogenicity of Brucella suis biovar 4 for bison.

The pathogenicity of Brucella suis biovar 4 for bison (Bison bison) was evaluated by inoculation of 2.1 x 10(7) colony forming units (CFU) in 0.1 ml saline into the conjunctival sac of six pregnant cows. Six pregnant bison were inoculated with 1.27 x 10(7) CFU of Brucella abortus strain 2308 as a positive control. Bison were inoculated on 23 January 1992, and observed until calving or abortion after which they were euthanized, and necropsied. Bacteriological and histological examinations were conducted on lymph nodes, reproductive tract, mammary gland, and internal organs. Terminal serum samples from calves and cows were evaluated by card, rivanol precipitation, standard tube agglutination, cold complement fixation tube, indirect bison conjugated enzyme linked immunosorbent assay (ELISA), competitive ELISA, and particle-concentration fluorescence immunoassay. No clinical signs of brucellosis were seen in bison inoculated with B. suis biovar 4, and infection was found only in lymph nodes of two animals. There was no evidence of metastasis of this organism to the mammary gland or the reproductive tract. There were no detectable levels of antibodies to Brucella spp. in terminal blood samples taken from B. suis biovar 4-challenged bison. Brucella abortus was isolated from several tissues in all control bison. All B. abortus-challenged animals developed uterine infection and five developed mammary gland infection. Reproductive disease resulted in abortions in five B. abortus-challenged bison and neonatal death in the remaining calf. Brucella suis biovar 4 does not appear to be pathogenic for bison.

Abortion, Veterinary↗
PubMed1995

Nuclear actin filaments and their topological changes in frog oocytes.

Previous morphological and biochemical studies have suggested that actin and actin-containing filaments (microfilaments) exist in the eukaryotic nucleus and that they perform important nuclear functions. However, the concept is not widely accepted. In this study, we demonstrate actin and bundles of actin in the nuclei of oocytes of Rana temporaria by immunoblotting and immunogold labeling/electron microscopy. The system and methods used here provided nuclei, free from cytoplasmic contamination. Additionally, we have compared the topological distribution of intranuclear actin filaments in two structurally and functionally distinct stages (stages 3 and 6) of oogenesis. The stage 3 nuclei are extremely active in rRNA transcription and contain multiple nucleoli located at the periphery with the central part occupied by the lampbrush chromosomes. The stage 6 nuclei are transcriptionally inert and contain both nucleoli and chromosomes confined to a small area in the central part. The nuclear lysates derived from the manually isolated stage 3 and 6 nuclei and the nuclear contents obtained by manually removing the nuclear envelope of stage 6 nucleus both contained actin as demonstrated by immunoblotting with an actin-specific monoclonal antibody. When examined by immunogold electron microscopy using the anti-actin antibody, the stage 3 oocyte nuclei showed distinct intranuclear tracks composed of bundles of actin that extended from the nucleoli and chromosomes to the nuclear envelope. The stage 6 oocyte nuclei, on the other hand, showed short stretches of actin bundles in the central part mainly in association with the nucleoli; none of these bundles extended to the nuclear envelope. Taken together, the above results suggest that actin is a structural component of the oocyte nucleus and that polymerized actin undergoes dramatic topological changes correlated with changes in the distribution of nuclear components and their function.

Actins↗
PubMed1995

Enzyme-linked immunoelectrotransfer blot analysis of excretory-secretory proteins of Fascioloides magna and Fasciola hepatica.

Fasciola hepatica is a parasite of cattle (Bos taurus), but not of white-tailed deer (Odocoileus virginianus), while Fascioloides magna is a parasite of white-tailed deer which also infects cattle as dead-end host. Adult parasites were collected from naturally infected white-tailed deer or cattle. Excretory-secretory proteins (ESP) were obtained from each parasite. Protein banding patterns were analysed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and probed using sera from experimentally infected deer of cattle using enzyme-linked immunoelectrotransfer blot (EITB, also known as Western blot) analysis. Protein banding patterns of the two species were different. EITB analysis of Fascioloides magna ESP using sera from Fascioloides magna infected deer or cattle identified three bands of approximately 17, 22 and 27 kDa of which the 27 kDa antigen cross-reacted with sera from Fasciola hepatica infected cattle. EITB analysis of Fasciola hepatica ESP probed with sera from Fasciola hepatica infected cattle identified three bands of approximately 15, 26 and 46 kDa. The 46 and 26 kDa ESP cross-reacted with sera from Fascioloides magna infected cattle, but not with sera from Fascioloides magna infected deer. The band at 15 kDa which reacted specifically for Fasciola hepatica infected cattle sera consisted of two protein bands close to each other as seen on the SDS-PAGE gel. The EITB reaction at approximately 17 kDa and 22 kDa of Fascioloides magna ESP, and at approximately 15 kDa of Fasciola hepatica ESP can be used for species specific diagnosis.

Animals↗