Search PubMed⌕ Search

Biomedical subjects

D G Baker

Publications and source records attributed to D G Baker.

At least 55 records · Page 3Linked to original sources
PubMed1996

An unusual coccidian parasite causing pneumonia in a northern cardinal (Cardinalis cardinalis).

In June 1993 an unusual coccidian parasite was identified in lung tissue from a northern cardinal (Cardinalis cardinalis), collected near Tucson, Arizona (USA), which died in respiratory distress. Histologically, there was evidence of severe, generalized interstitial pneumonia, associated with the parasite. Both asexual and sexual stages were seen. Schizonts, gamonts, and sporulated oocysts were seen in lung tissue. The parasite most closely resembled coccidia of the genus Lankesterella. This is the first report of such a coccidian parasite in the alveolar tissue of a cardinal.

Animals↗
PubMed1996

Effect of a nonsteroidal antiinflammatory drug on synovial fluid in osteoarthritis.

OBJECTIVE: The use of nonsteroidal antiinflammatory drug (NSAID) therapy in osteoarthritis (OA) is controversial because of suggestions that pure analgesics can be as effective as NSAID for pain relief. In addition, there is incomplete information whether antiinflammatory effects have any longterm benefit in OA. NSAID have been known to affect synovial fluid (SF) prostaglandins in rheumatoid arthritis. We describe the first examination of the effect of an NSAID, etodolac, on SF prostaglandins, cytokines, and cells in OA. METHODS: Joint fluids were studied before and 2 weeks after initiation of therapy with etodolac 400 mg tid. Leukocyte counts, prostaglandin, interleukin 6, and tumor necrosis factor were measured. RESULTS: Pretreatment features of SF did not predict clinical response. We found no change in the relatively low leukocyte counts. However, SF prostaglandin levels and interleukin 6 levels were significantly decreased and tumor necrosis factor alpha levels were increased after therapy with NSAID. CONCLUSION: This NSAID had potentially important local effects that could be either beneficial or deleterious. Further studies on effects of this and other NSAID on a broader variety of SF and synovial cytokines may help predict longterm effects of NSAID on progression of OA.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1995

A double-blind, randomized, placebo-controlled, multi-center study of brofaromine in the treatment of post-traumatic stress disorder.

A large multi-center, double-blind, parallel trial to assess the efficacy of brofaromine in the treatment of post traumatic stress disorder (PTSD) failed to show a significant difference between the brofaromine and placebo treatment groups. The placebo response rate in this study was higher than that in previously published double-blind, placebo-controlled studies of PTSD.

Adult↗
PubMed1995

Squamous cell carcinoma growth in irradiated tissue: a murine model for quantitative assessment of treatment.

Locoregional recurrent and distant metastases from squamous cell carcinomas, despite multimodality therapy, remain troublesome clinical realities. Discrepancies in success rates of various surgery and radiation treatment regimens dealing with these problems are confusing to the clinician attempting to recommend the most beneficial treatments. There is a need for an experimental model to assess therapeutic effectiveness quantitatively from which guidelines for developing clinical trials may be suggested. In this study, we provide such a model. We injected DBA-2 mice with defined numbers of KLN-205 squamous carcinoma cells to obtain baseline growth characteristics; 216 animals had no previous irradiation. The remaining 131 received 30 Gy irradiation to the right leg 50 days before injection of the tumor cells. Tumor incidence, growth and number, and location of tumor metastasis were determined in both previously irradiated and nonirradiated groups. The data demonstrate a growth-retardant effect on tumor groups by the previous irradiation (tumor bed effect). The data also show that the incidence of hematogenously spread metastases was more frequent in mice in which tumors developed in previously irradiated tissue than in mice with tumors in nonirradiated tissue.

Animals↗
PubMed1995

Experimental oral inoculations in birds to evaluate potential definitive hosts of Neospora caninum.

Experimental oral inoculations to evaluate potential definitive hosts of Neospora caninum were conducted by feeding infected rodent tissues to 9 carnivorous birds of 4 species. Birds included 2 red-tailed hawks (Buteo jamaicensis), 2 turkey vultures (Cathartes aura), 2 barn owls (Tyto alba), and 3 American crows (Corvus brachyrhynchus). The rodents (mice or rats) had been inoculated with 100,000 culture-derived tachyzoites of N. caninum 1-6 mo before feeding to the birds. Fecal samples were collected from each bird daily for 1 mo after feeding rodents and examined for oocysts by fecal flotation. In addition, processed aliquots from all avian fecal samples were fed to BALB/c mice. Five weeks after feeding, mice were bled and sera were tested for antibodies against N. caninum. One to two months later, mice were killed and brain tissue was examined microscopically for protozoal cysts. While occasional oocysts were found in avian fecal samples, these were likely not N. caninum because they were not infective to BALB/c mice. It was concluded that the bird species tested are not likely to be definitive hosts of N. caninum.

Animals↗
PubMed1994

In vivo inflammatory response to polymethylmethacrylate particulate debris: effect of size, morphology, and surface area.

Particulate debris, including that from polymethylmethacrylate (PMMA) cement, is observed commonly in the membrane surrounding loose joint prostheses. Such debris is assumed to cause an inflammatory response and contributes to osteolysis and failure of the implant. A subcutaneous rat air-pouch model was used to assess quantitatively the in vivo effects of the size, morphology, and surface area of PMMA particles on the acute inflammatory response. PMMA particles were divided into three groups. In Group A, mechanical grinding of cured bone cement produced irregularly shaped particles; Group B included spherical particles of PMMA powder (Simplex P); and Group C consisted of commercially prepared spherical latex particles. All three groups had two size distributions: < 20 microns and 50-350 microns. For a given mass or dose, the small, irregularly shaped mechanically produced particles in Group A elicited a significantly greater inflammatory reaction than the large particles in Group A, as expressed by the release of tumor necrosis factor (TNF), neutral metalloprotease (NMP), and prostaglandin E2 (PGE2) and the white blood cell (WBC) count within a 24-hour period. Similar findings were seen in Group B. Particles in Group C were used to compare the effect of absolute numbers of large and small particles and surface area. Large (10-126 microns) spherical PMMA particles at a dose of 1.7 x 10(6) particles/ml caused a significantly higher inflammatory response, as measured by WBC count and production of NMP and PGE2, than small (1-10 microns) spheres at a dose of 4 x 10(6) particles/ml. However, the production of TNF in the rats was significantly increased with small particles (p < 0.05) at a concentration 4-fold less than that with the large particles (4 x 10(5) compared with 1.7 x 10(6) particles/ml). This finding may reflect a different cellular mechanism for the TNF component of the inflammatory response than is measured by WBC counts or by levels of PGE2 and NMP. As the calculated surface area of the PMMA particles increased, a threshold level was reached, at which point the inflammatory response increased dramatically. The size of particles has a role in the prolongation and intensity of the release of specific cytokines. The total surface area of the particles appeared to be an important factor in determining the inflammatory response, as measured by WBC count, PGE2, TNF, and NMP.

Animals↗
PubMed1994

Comparison of the inflammatory response to particulate polymethylmethacrylate debris with and without barium sulfate.

Particulate polymethylmethacrylate debris has been implicated in the inflammatory response observed surrounding loosened cemented implants. The rat subcutaneous pouch model and the Howie implant model (used to study bone resorption) were used to quantify the response to mechanically produced endotoxin-free polymethylmethacrylate debris with and without 10% (wt/vol) BaSO4. In the rat subcutaneous pouch model, the inflammatory response to polymethylmethacrylate particles containing BaSO4 was greater than the response to plain polymethylmethacrylate particles of similar size. Increased inflammation was measured by leukocyte counts and levels of prostaglandin E2, tumor necrosis factor, and neutral metalloprotease. In addition, particulate polymethylmethacrylate with BaSO4 caused significantly greater bone resorption in the Howie model than did particulate plain polymethylmethacrylate. In in vitro studies, particulate polymethylmethacrylate with BaSO4 stimulated more prostaglandin E2, neutral metalloprotease, and tumor necrosis factor from human monocytes in culture and stimulated greater proliferation of synovial cells than did particulate plain polymethylmethacrylate. The presence of BaSO4 appears to significantly intensify the inflammatory response to polymethylmethacrylate debris.

Animals↗
PubMed1994

Swine immunity to selected parasites.

Swine parasitism exerts a significant economic impact worldwide. In the United States, the greatest losses are due directly or indirectly to the costs of zoonotic parasitisms. Three of the six most common foodborne parasitic diseases of humans in the United States are associated with pork consumption. These include toxoplasmosis, taeniasis or cysticercosis (caused by the pork tapeworm Taenia solium), and trichinellosis. Toxoplasmosis is of particular concern because of the fulminating disease that occurs in immunocompromised people. Generalizations and extrapolations of information derived from rodent and human studies, to swine parasitisms, are complicated by immunological differences between the hosts, and by the diverse biological characteristics of internal and external parasites studied. Swine studies thus far reported have demonstrated that protective immunity to helminth infection involves both cellular and humoral mechanisms, with antibodies and antibody-mediated responses playing important roles in preventing establishment of newly acquired larvae. Protection against protozoan parasites is primarily by cell-mediated strategies, whereas protective immunity to arthropod infestation is primarily through humoral mechanisms, principally those associated with type 1 hypersensitivity.

Animals↗
PubMed1994

Alpha-adrenergic and muscarinic cholinergic inhibition of ACh release in guinea pig trachea: role of neuronal K+ channels.

Our goals were to establish that an alpha 2-adrenergic agonist (clonidine) inhibits ACh release from airway nerve endings and to test effects of iberiotoxin (IBTX), an inhibitor of fast-conductance, Ca(2+)-activated K+ channels on alpha 2-adrenergic and muscarinic attenuation of ACh release. Guinea pig tracheas were mounted between electrodes in buffer containing indomethacin and neostigmine, and high-performance liquid chromatography with electrochemical detection was used to measure ACh release during electrical field stimulation. Clonidine inhibited ACh release in a concentration-dependent fashion [maximum reduction: 48 +/- 3%; 50% inhibitory constant (IC50): 0.1 microM], and idazoxan, alpha 2-adrenergic antagonist, reversed the effect. However, IBTX failed to alter clonidine-induced attenuation of ACh release. In contrast, IBTX did cause an increase in tracheal tension. In addition, IBTX failed to reverse any of the potent autoinhibitory effects of endogenous ACh. Our results confirm the presence of inhibitory alpha 2-adrenergic receptors. However, activation of IBTX-sensitive K+ channels does not appear necessary for either alpha 2-adrenergic or muscarinic cholinergic inhibition of ACh release.

Acetylcholine↗
PubMed1994

Persistence of immunity to toxoplasmosis in pigs vaccinated with a nonpersistent strain of Toxoplasma gondii.

Persistence of the vaccine RH strain of Toxoplasma gondii was studied by bioassay and histologically in 14 pigs. Pigs were euthanatized 2, 4, 7, 8, 14, 15, 21, 29, 36, 42, 52, 57, and 76 days after IM inoculation with 100,000 T gondii tachyzoites. Viable T gondii tachyzoites derived from the RH strain were isolated by bioassay in mice inoculated with tissues of pigs euthanatized up to 14 days after vaccination. Except for fever, pigs vaccinated IM with the RH strain remained clinically normal. Two other pigs inoculated IV with 100,000 T gondii tachyzoites of the RH strain became ill, and 1 pig was comatose by 4 days after inoculation. These findings indicate that route of inoculation may influence the response of pigs to T gondii. To evaluate protective immunity in pigs vaccinated with the RH strain, 16 age-matched pigs were allotted to 4 groups (A-D) of 4 pigs each. Eight pigs (groups A and C) were vaccinated IM with 100,000 RH strain tachyzoites and 8 pigs (groups B and D) were nonvaccinated controls. Pigs of groups A and C were challenge-inoculated orally with a lethal dose of T gondii oocysts (100,000 oocysts) 81 days after vaccination, pigs of groups B and D were inoculated similarly 220 days after vaccination. The concentration of T gondii at 3 days after challenge inoculation of pigs vaccinated 81 days earlier was reduced 100,000-fold in mesenteric lymph nodes, compared with that in a nonvaccinated pig euthanatized at 3 days after challenge inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Cellular and chemical mediators of type 1 hypersensitivity in calves infected with Ostertagia ostertagi: mast cells and eosinophils.

Abomasal mucosal mast cell and eosinophil accumulation was morphometrically evaluated in 26 Holstein steers after natural or experimental infection with Ostertagia ostertagi. Results showed that following infection, accumulation of mast cells and eosinophils in abomasal tissue was dependent on infection pattern. Eosinophilia was greater in steers with type 1 ostertagiosis, while mastocytes was more pronounced in steers with type 2 ostertagiosis.

Abomasum↗
PubMed1993

Cellular and chemical mediators of type 1 hypersensitivity in calves infected with Ostertagia ostertagi: histamine, prostaglandin D2, prostaglandin E2 and leukotriene C4.

Plasma histamine, prostaglandin E2 (PG) D2, PGE2, and leukotriene (LT) C4 levels were determined in 26 Holstein steers before and after natural or experimental infection with Ostertagia ostertagi. Post-infection abomasal lymph was also assayed for PGD2, PGE2, and LTC4. Histamine determinations were performed on abomasal tissue from three locations. Results showed that: (1) tissue histamine levels increased in steers with type 2 ostertagiosis, (2) lymphatic PGD2 and PGE2 levels were increased, probably as a result of macrophage activity, (3) lymphatic LTC4 levels increased in steers with type 1 ostertagiosis, and were correlated with tissue eosinophilia, and (4) plasma levels of PGD2, PGE2, LTC4 and histamine were not useful for predicting worm burdens. These findings suggest a functional role for eosinophils and mast cells in the pathophysiology of ostertagiosis, through mediation of a type 1 hypersensitivity reaction.

Animals↗
PubMed1993

Abomasal lymphatic lymphocyte subpopulations in cattle infected with Ostertagia ostertagi and Cooperia sp.

Abomasal lymphatic cannulation was performed on steers naturally or experimentally infected with Ostertagia ostertagi and Cooperia sp.. Abomasal lymphatic lymphocyte subpopulations were evaluated using antibodies specific for bovine mononuclear cell surface antigens, followed by flow cytometric analysis. When compared with the non-infected or experimentally infected steers, naturally infected steers with Type 1 or Type 2 ostertagiosis had increased percentages of B-lymphocytes. The percentages of B-lymphocytes were related to the numbers of O. ostertagi and Cooperia sp.. These findings are compatible with reports of worm-specific antibody synthesis in bovine nematodiases.

Abomasum↗
PubMed1993

SDS-PAGE profiles of somatic proteins from third-stage infective larvae of Ostertagia ostertagi and Cooperia oncophora.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles of somatic proteins from third-stage infective larvae of Ostertagia ostertagi and Cooperia oncophora were evaluated using laser densitometry. Several protein bands were present from both parasite preparations. A few bands from each parasite appeared to be unique. Purification of these proteins for use in serologic monitoring of cattle naturally infected with O. ostertagi and C. oncophora should allow circumvention of cross-reactivity between the two genera, which has been reported by others.

Animals↗
PubMed1993

Immunoglobulin E and type I hypersensitivity in bovine ostertagiosis.

A series of experiments were performed to determine whether immunoglobulin E (IgE) and Type I hypersensitivity reactions might be involved in the immune response of cattle to infection with Ostertagia ostertagi. The following observations were made. (1) When calves were lightly infected, serum IgE levels paralleled worm burdens. However, in heavy infections, both serum and lymph IgE levels were inversely related to burdens of O. ostertagi. (2) Increases in mediators, especially histamine and leukotriene (LT) C4 were detected in tissue or lymph, and were associated with cellular changes indicative of hypersensitivity.

Animals↗