The role of epidermal growth factor as a mediator of hyperplasia in equine laminitis /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Equine chronic laminitis is characterized in part by hyperplasia of the keratinizing hoof wall epidermal laminae. The possibility that epidermal growth factor (EGF) plays a role in the mediation of this inappropriate growth is investigated here. It is demonstrated that EGF-specific plasma membrane receptors were present in hoof wall laminae in concentrations comparable to liver, a highly regenerative issue. Scatchard analysis of the binding data revealed the presence of two affinity classes of receptors on the cell surface of laminar tissue from clinically normal horses. In plasma membrane preparations from laminitis-affected horses there was an apparent absence of the high-affinity receptor class. EGF-specific binding activity was present in the urine of all horses tested (n = 25) in concentrations comparable to those of humans. Concentrations of EGF binding activity in urine from clinically normal horses did not differ significantly from those of horses affected by chronic laminitis. Explant hoof wall laminar tissue was maintained in culture in the presence and in the absence of EGF and tested for the following parameters: cellular proliferation, DNA synthesis, total protein synthesis, and keratin synthesis. No dramatic EGF-mediated effect was evident with respect to cellular proliferation, DNA synthesis, and total protein synthesis. A slight increase in the number of heavily labeled nuclei was observed in explant tissue from laminitis-affected horses following autoradiographic analysis of [3H]thymidine incorporation into DNA. These heavily labeled nuclei were generally not present in explant tissue from normal horses. A difference in methionine incorporation into total cellular protein could not be demonstrated between control and laminitic explants. However, when only the water-insoluble cytoskeletal protein fraction was considered, differences were noted in the keratin region of the SDS-polyacrylamide electrophoretic profiles. In normal horses, keratin synthesis was suppressed, consistent with EGF's reported ability to delay terminal differentiation. In explant tissue from horses affected by chronic laminitis, keratin synthesis was maintained or enhanced. Collectively, these data, suggest a loss of EGF-mediated control of the suppression of terminal differentiation on laminar basal keratinocytes in horses affected by chronic laminitis. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Veterinary physiology." |
| Physical Description: | ix, 100 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |