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Biomedical subjects

W D Davenport

Publications and source records attributed to W D Davenport.

17 recordsLinked to original sources
PubMed1999

The effect of guided tissue regeneration on the healing of osseous defects in rat calvaria.

The effect of guided tissue regeneration procedures on the healing of osseous defects was studied in Sprague-Dawley rats. A full thickness flap was reflected and two 5 mm defects were made in the calvaria of 17 rats. A resorbable membrane was placed over one defect in each animal, while the remaining defect served as a control. After 3, 5, or 7 wk, healing of the osseous defects was evaluated histologically. There was no statistical difference in bone regeneration between experimental and control sites at any time period.

Absorbable Implants↗
PubMed1995

Retroviral suicide vector does not inhibit neointimal growth in a porcine coronary model of restenosis.

We attempted to attenuate neointimal formation following vascular injury using a retroviral suicide vector. Epicardial coronary arteries of adult miniature swine were injured by deployment of oversized tantalum stents. One week later, injured segments were exposed to packaged retroviral constructs with or without the herpes simplex virus thymidine kinase gene. Ganciclovir treatments were initiated 48 hours later in both control and experimental swine and continued for two weeks. Four weeks following vascular injury, both control and experimental arteries were harvested and histologically prepared for image analysis. Despite adequate marker gene expression, there was no significant difference in the neointimal area or neointimal/media ratio between control and experimental groups. While the HSVtk ganciclovir system attenuates cell proliferation in other systems, retroviral vector targeting of vascular smooth muscle cells for elimination may be too inefficient to prevent restenosis following angioplasty.

Animals↗
PubMed1995

Dome epithelium and follicle-associated basal lamina pores in the avian bursa of Fabricius.

BACKGROUND: The immunological role played by the avian bursa of Fabricius has been well established. Although numerous studies have also reported on the development and general morphology of this organ, some structure-function relationships still have not been fully explained. METHODS: Bursae from chickens at three developmental stages were removed and examined by scanning electron microscopy. Routine preparation was used as well as sonication (microdissection). Micrographs were used for qualitative morphological study and for quantitative morphometric analyses. RESULTS: Routine SEM observations were similar to those previously reported in the literature. Sonicated specimens allowed topographical study of various levels of surface erosion. Two types of surface cells were observed: typical absorptive epithelium and follicle-associated epithelial (FAE) cells. Erosion of the dome surface epithelium revealed basal lamina pores in the region over the subepithelial lymphoid follicles. These pores were present at hatching. Morphometric analysis of dome and pore areas revealed that the pore area decreases in relation to dome area with aging. CONCLUSIONS: Basal lamina pores may provide a communication route between the lymphoid follicles and the external environment via the FAE cells. Also, the close association between the FAE cells of the epithelial domes, the epithelial pores, the capillary complex of the previously described bursal--blood barrier, and the subepithelial lymphoid follicles could represent a morphological "pore complex" that matures early in posthatching development and may be related to the immunological function of the bursa.

Aging↗
PubMed1989

Induction of macrophage-like differentiation of HL-60 leukemia cells by tumor necrosis factor-alpha: potential role of fos expression.

Tumor necrosis factor-alpha (TNF-alpha) is a macrophage-derived cytokine elicited during cellular responses to various microbial infections. TNF-alpha exerts direct cytotoxicity toward some tumor cells in vitro and produces hemorrhagic tumor necrosis in vivo. In human promyelocytic HL-60 leukemia cells, human recombinant TNF-alpha (rTNF-alpha) exhibits a small early proliferative effect (within 48 h), followed by marked cytostatic activity at 96 h after the addition of rTNF-alpha. Cytostasis is contiguous with an induction of cell differentiation along the monocyte/macrophage lineage. The cell proliferation effects and the induction of the differentiated phenotype are preceded by an approximate 5-fold increase in c-fos mRNA levels within 90 min after rTNF-alpha treatment of log phase HL-60 cells. Nuclear in vitro transcription assays indicate that the effect of rTNF-alpha on c-fos mRNA abundance is controlled at the transcriptional level. We have also used a postembedding immunocolloidal gold electron microscopy technique to localize and semiquantitate pp55c-fos proto-oncoprotein levels in the nucleus of both control and rTNF-alpha-treated HL-60 leukemia cells. In response to rTNF-alpha, we have observed a rapid and transient accumulation of pp55c-fos in discrete nuclear substructures within 2 h after treatment. C-fos staining appears in clusters, which are preferentially localized over semi-condensed chromatin and interchromatin granules. These results suggest that pp55c-fos is involved in the signal transduction system initiated by rTNF-alpha during the induction of HL-60 differentiation.

Cell Line↗
PubMed1988

Responsiveness of isolated adrenocortical cells from lean and obese Zucker rats to ACTH.

Morning plasma corticosterone concentrations have been reported to be elevated in obese Zucker rats compared with lean rats. The aim of this study was to determine if differences in adrenal sensitivity or maximal responsiveness to adrenocorticotropic hormone (ACTH)-(1-24) could account for this disparity. Serum and adrenal glands were collected from lean and obese, male and female Zucker rats (10-13 wk old) between 10:00 and 11:00 A.M. Adrenocortical cells were isolated and challenged with ACTH-(1-24). The serum corticosterone and ACTH concentrations were significantly greater in obese males compared with lean males (45.3 +/- 10.3 vs. 23.2 +/- 1.45 ng/ml and 156.6 +/- 15.3 vs. 113.3 +/- 9.4 pg/ml, respectively). Although serum corticosterone concentrations were similar in female rats, serum ACTH concentrations tended (P = 0.07) to be lower in obese female rats than in lean female rats (67.6 +/- 9.3 vs. 103.5 +/- 15.1 pg/ml, respectively). The median effective concentration (EC50) and the maximal corticosterone response per microgram of DNA of dose-response curves derived from lean and obese rats were not significantly different. Additionally, a morphometric evaluation of adrenal tissue from lean and obese rats suggested that cells of the zona glomerulosa were smaller in obese rats than in lean rats. Our data confirm that morning serum corticosterone concentrations are elevated in 10- to 13-wk-old male Zucker rats. This difference does not appear to be due to differences in the sensitivity or maximal secreting capacity of adrenocortical cells to ACTH.

Adrenal Cortex↗
PubMed1987

A diagnostic and epidemiologic survey of 15,783 oral lesions.

Tissue specimens submitted to an oral pathology biopsy service during a 17 1/2-year period were studied to determine the types of diagnoses rendered, the general types of pathological processes represented, and the epidemiologic distribution of patients. A total of 15,783 cases were studied. Normal structures were observed in 480 cases, mostly dental follicles, and were eliminated from the study. The remaining 15,303 cases had been diagnosed as pathological entities. A majority of the oral biopsies were taken from either infectious or reactive conditions. Fibromas, periapical granulomas, periodontitis, mucoceles, and radicular cysts were the most frequently encountered lesions. Neoplasms constituted nearly 15% of all the specimens, with approximately 18% of these being malignant. An additional 360 lesions (2.4% of the total number of specimens) harbored dysplasia and might be considered premalignant. The peak age groups represented in these patients were the third through sixth decades of life. More oral biopsies were performed on females than males. A majority of the patients were white. The purpose of this study was to determine the relative frequency of oral lesions that were considered to be of sufficient clinical significance to merit a biopsy. Although this data might be used as a guide for forming clinical impressions about oral lesions, the clinician must always be aware of the possible occurrence of more rare lesions.

Adolescent↗
PubMed1986

Postmortem examination of incinerated teeth with the scanning electron microscope.

Fragments recovered from the burned wreckage of a gasoline truck and thought to be parts of teeth were confirmed as such after they were examined with a scanning electron microscope. The appearance of the fragments was compared with previously published descriptions of teeth which had been incinerated under laboratory conditions and also examined by scanning electron microscopy.

Accidents, Traffic↗
PubMed1985

Evidence for a blood-bursa barrier.

By use of horseradish peroxidase (Sigma Type II) as a vascular tracer the competence of the bursal microvasculature was evaluated in 15-day-old chicks. Within 5 min circulation time tracer could be identified only within the vascular tree with no leakage into the perivascular or extracellular spaces. After 10 min circulation time tracer was no longer present in the bursal vessels. Since no tracer was ever identified among the parenchymal elements of the organ these data suggest that a blood-organ (blood-bursa) barrier may exist similar to that found in thymus and brain.

Animals↗
PubMed1985

Oral malignancy: a regional incidence observed over a 13-year period.

In this study slightly more than two out of every 100 biopsy specimens from the set population of 10,414 specimens showed malignant oral lesions. The most common sites for oral malignancy were the floor of the mouth and the alveolar ridge, respectively. Lesions were most common during the fifth decade of life, followed by the sixth. Eighty-eight percent of the malignant lesions occurred in whites and 12% inn blacks. This does not deviate significantly from the percentage in the total biopsies reported. Of the categories of neoplasms, surface ectodermal neoplasms predominated, followed by salivary and mesenchymal lesions, respectively. There did not appear to be a significant difference in sex incidence.

Adult↗
PubMed1981

Diet-induced atrial endothelial damage--a scanning electron-microscopic study.

A semipurified diet containing 28% fat (as lard), but no known atherogenic substances such as cholesterol, was fed to a group of Swiss stock mice. A group of similar mice was fed laboratory chow as controls. Within six weeks of diet feeding, experimental mice developed atrial thrombosis. In scattered areas of atria where thrombi were not present, the scanning electron microscope showed an endothelial response to the high-fat diet in the form of holes and crater-like lesions. In extreme cases, a whole endothelial cell might be almost totally destroyed. Clusters of leucocytes mixed with platelets and fibrin attached to the larger holes, suggesting the initiating mechanism of thrombogenesis, were also observed.

Animals↗
PubMed1980

Effect of indomethacin on desoxycorticosterone acetate-sodium chloride-induced renal lesions in the pregnant rat and her offspring.

To explore the effects of inhibition of prostaglandin synthesis on renal lesions, 37 female rats were made hypertensive and of these, 22 were treated with indomethacin. The blood pressure (207 +/- 5 mm Hg) in the indomethacin group was significantly (p < 0.01) higher than the blood pressure (191 +/- 7 mm Hg) in the control group. Weight changes were not significantly different. Renal lesions of varying severity were noted in mothers and offspring of both groups. The lesions ranged from thickening of the basement membranes to glomerular congestion, some with nearly complete eradication of glomerular architecture. Although the lesions appeared to be more marked in the indomethacin-treated group, no specific pattern of lesion location nor significant differences in the severity of the lesions was demonstrated. These data suggest that the lesions noted were the result of the hypertension. However, exacerbation by indomethacin could not be excluded.

Animals↗
PubMed1979

Observations on the results of specific histochemical techniques and empirical staining methods on several tissue/organ types using a variety of fixing fluids.

Several histotechniques (Harris hematoxylin and alcoholic eosin, Gomori's reticulum method, Verhoeff's elastic stain; Gomori's trichrome, Mallory's aniline blue collagen stain and the Cameron and Steele method) were each used with a number of fixatives (Lavdowsky's chromic acid, Karnovsky's glutaraldehyde/paraformaldehyde, neutral buffered formalin, Lavdowsky's formalinacetic acid-alcohol, Zenker's and Helley's). Lavdowsky's chromic acid fixative provided superior results as compared to the other fixing fluids and its use was critical with respect to the trichrome or connective tissue staining procedures. The Cameron and Steele modification used with Lavdowsky's chromic acid fixative gave the best differentiation of tissue types and was also the most reproducible.

Aging↗