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S S Harris

Publications and source records attributed to S S Harris.

42 records · Page 3Linked to original sources
PubMed1980

Vitamin A influence on calcium metabolism and calcification.

Vitamin A deficiency has been shown to affect vision, reproduction, cellular differentiation, and maintenance of epithelial and skeletal tissues. Different vitamin A compounds, i.e., retinol and retinoic acid, vary in their ability to fulfill these biologic functions. Aside from vision, the exact molecular mechanisms of action for retinoids are largely unexplained. High doses of vitamin A are known to increase bone resorption through stimulation of lysosomal proteolytic activity, which also leads to increased secretion of PTH. Deficiency of retinol affects bone morphology by increasing bone thickness. Using a standardized guinea pig model, bone formed entirely during a retinol-deficient (A --) period contained less calcium and took up more 35S into glycosaminoglycan (GAG) fractions in vitro than did control (A+) samples. Using rat calvaria, a pulse-chase experiment indicated that the rate of 35S loss from calvaria cultured with A -- serum was lower than in controls. Thus, retinol deficiency seems to increase the amount of sulfated GAG in bone through a defect in the degradation of GAG.

Animals↗
PubMed1980

Tracheal stenosis: an unusual presenting complication of idiopathic fibrosing mediastinitis.

Idiopathic fibrosing mediastinitis is a rare, obliterative, inflammatory process which is characterized by an abnormally exuberant proliferation of fibrous tissue within the superior mediastinum, resulting in the encroachment and occlusion of its contained structures. Usually, this is one of the low-pressure vascular structures, most often the superior vena cava. Airway obstruction as a primary presenting complication of this condition is rare with past treatment results usually being palliative at best. In this article, a patient with this complication is presented in whom emergent surgical treatment and tracheal decortication afforded permanent relief. The clinial presentation, morphology of the disease, and treatment are reviewed.

Adult↗
PubMed1978

Sulfate metabolism in rat calvaria cultured under vitamin A deficient conditions.

The metabolism of sulfated glycosaminoglycans (GAG) in bone has been found to be altered in vitamin A deficiency. A neonatal rat calvarium model system was used to determine if these changes are related to catabolic defects. Two day old rat pup calvaria were cultured in media containing serum from A- or A+ rats and radiolabeled sulfate or glucosamine. The incorporation of 35S-sulfate into the GAG fraction of calvaria cultured with A- serum for 48 hours was significantly increased compared to the values found in calvaria cultured with A+ serum (A-, 1,970 +/- 300; A+, 940 +/- 177; X +/- SD). The uptake of 35S-sulfate into the GAG fraction of calvaria cultured with A- serum showed continuous increase over 96 hours,whereas, 35S-sulfate uptake leveled off after 24 hours in the A+ group. There was also a significant increase in [14C]glucosamine uptake into the GAG fractions of calvaria cultured with A-serum (A-, 1,966 +/- 537; A+, 1,662 +/- 244; X +/- SD). To determine if the alteration in metabolism of sulfated GAG was in the biosynthetic or degradative pathways, a chase study was performed in which the calvaria were prelabeled with 35SO4. The rate of tissue loss of 35S-sulfate was lower in the total digests and the GAG fractions from calvaria cultured with A- serum than those cultured with A+ serum. Thus, the alteration in the metabolism of the sulfated GAG resulting from A- culture conditions seems to be defect in the degradative process.

Animals↗
PubMed1978

Vitamin A deficiency and new bone growth: histologic changes.

Using a standardized guinea pig model system, the histologic appearance of newly formed bone from vitamin A deficient, vitamin A adequate and retinoic acid treated animals was compared. Microscopic examination of the histologic sections of bone collected from vitamin A deficient guinea pigs indicated the presence of highly cellular and loosely woven bone spicules. This model system is an osteoblastic model, since osteoclasts are essentially absent in tissue formed in 14-day implants. Thus, new bone formation in the vitamin A deficient guinea pig reveals morphologic changes which are principally mediated through the osteoblastic process.

Animals↗
PubMedDate not supplied

Physical activity counseling for healthy adults as a primary preventive intervention in the clinical setting. Report for the US Preventive Services Task Force.

Physical activity has been associated with the prevention and control of several medial conditions that are major causes of death and disability in the United States. The criterion-based approach adopted by the US Preventive Services Task Force is used to objectively evaluate the evidence regarding the effectiveness of physical activity counseling for healthy adults as a primary preventive intervention in the clinical setting. This evaluation addresses: (1) the burden of suffering attributable to physical inactivity; (2) the efficacy of physical activity in disease prevention in regard to six medical conditions; and (3) the characteristics of the intervention in terms of simplicity, cost, safety, acceptability, and patient compliance. Based on consideration of the evidence for each of these issues, specific recommendations are made regarding the role of physical activity counseling in routine clinical practice. In addition, practical guidelines are presented to aid clinicians in physical activity counseling.

Adult↗