Search PubMed⌕ Search

Biomedical subjects

W Parker

Publications and source records attributed to W Parker.

85 records · Page 5Linked to original sources
PubMed1969

Hearing and age.

Explore the source record for details and available documents.

Aged↗
PubMedDate not supplied

Molecular modeling of phytochrome using constitutive C-phycocyanin from Fremyella diplosiphon as a putative structural template.

Phytochrome, the ubiquitous photosensor in green plants, is similar to C-phycocyanin in a number of ways. We have produced a model of the phytochrome chromophore binding pocket based on the X-ray crystal structure of C-phycocyanin from Fremyella diplosiphon [Duerring et al. (1991) J. Mol. Biol. 217, 577-592]. Twenty residues around the chromophore binding site of C-phycocyanin were changed to the corresponding residues of Avena phytochrome A for the modeling. In the minimized model, Arg-318, Ala-319, the methylene of Ser-322, Leu-325, Gln-326, and Tyr-327 (using the numbering of the Avena sequence; Cys-323 is chromophore bound) form a pocket on one side of the chromophore. The other side of the chromophore lacks hydrogen-bond donors and is involved only in van der Waals contact with the chromophore. The overall structure of the model may be described as one peptide segment "anchoring" the chromophore hydrophobically, covalently, and electrostatically from several directions, while the other key peptide segment simply provides a hydrophobic surface for the chromophore to rest against. The red light absorbing (Pr) chromophore of the model is buried more deeply in the binding pocket than the far red light absorbing (Pfr) chromophore. This apparently reflects reduced compatibility of the chromophore with the pocket upon photoisomerization, which requires the insertion of hydrophilic parts of ring D into the hydrophobic core of the protein. This concept is consistent with the experimental evidence that photoisomerization of the Pr chromophore is followed by movement of the chromophore from its binding pocket. In the proposed model, increased exposure of hydrophobic portions of the Pfr chromophore compared to the Pr chromophore is consistent with the red shift observed in the first intermediate of the Pr to Pfr photoconversion. The proposed model may be tested by mutation experiments, thus providing a viable model to foster the current rapid progress of molecular biology in this field.

Amino Acid Sequence↗
PubMedDate not supplied

Spontaneous adult-onset hypothyroidism in a cat.

Spontaneous adult-onset hypothyroidism, confirmed by a thyroid-stimulating hormone stimulation test, thyroid biopsy, and response to replacement therapy, is described in a female cat. Clinical signs consisted of profound apathy, hypothermia, poor hair growth, severe seborrhea sicca, and a puffy face. Cutaneous histological changes consisted of epidermal and follicular hyperkeratosis, teloginization of hairs, and dermal mucin deposition. There was no adnexal atrophy. Lymphocytic thyroiditis, equivalent to Hashimoto's thyroiditis, was shown by thyroid biopsy. Clinical signs rapidly responded to thyroxine replacement therapy. Glucose intolerance was coexistent with the hypothyroidism, but was not dramatically influenced by thyroxine therapy and probably was an independently occurring endocrinopathy.

Animals↗
PubMedDate not supplied

Lingual thyroid: review, case reports, and therapeutic guidelines.

The literature on lingual thyroid is reviewed. The incidence is relatively rare and sex incidence is four or five to one in favor of females. The embryology and development of the thyroid gland is discussed and some evidence presented to suggest that the lateral thyroid primordia are not involved in the formation of functional thyroid tissue. The pathologic findings of lingual thyroid tissue are similar to that of cervical thyroid tissue, including goiter formation. Diagnostic measures include mirror examination, I-125 scan, and tomography. Thyroid function studies are helpful in evaluating the level of thyroid function. Treatment includes surgical removal, transplantation, I-131, and thyroid replacement. Since the first three methods usually require supplemental thyroid treatment afterward, it is believed that initial thyroid replacement is the treatment of choice since it is simple, safe, effective, and noninvasive. Four new cases are reported.

Adolescent↗
PubMedDate not supplied

Nonoperative treatment of double lateral ligament tears of the ankle.

In this article the objective evaluation of 39 cases of double lateral ligament tears of the ankle treated by cast immobilization is described. Such treatment resulted in a 79.5% success rate as determined by repeat stress roentgenograms. In addition, a statistical method which may aid the orthopaedist in deciding whether to use nonoperative or operative treatment is presented.

Adolescent↗