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Biomedical subjects

I S Schwartz

Publications and source records attributed to I S Schwartz.

At least 19 recordsLinked to original sources
PubMed1996

Overdentures. Principles and procedures.

Although advances in methods and improved materials have contributed to better treatment results, caries and periodontal problems still remain significant threats to overdenture service life. The prevention of caries and recurrent periodontal disease thus becomes a most important aspect of postinsertion care. Undoubtedly, there are a number of successful overdenture methods. This article outlines two treatment sequences previously described by Brewer and Morrow that continue to be effective (Fig. 23). Common to most overdenture techniques is that an overdenture may be the only treatment that permits retention using the patient's last few retainable teeth. A conservative approach to root preservation still is a valid and practical measure in preventative dentistry.

Dental Abutments↗
PubMed1993

Color stability of selected dual-cure composite resin cements.

PURPOSE: This in vitro study was conducted to determine the color stability of five dual-cure composite resin cements: Kerr Porcelite (Kerr Manufacturing Co, Romulus, NY), Jelenko PVS System (J.F. Jelenko and Co, Armonk, NY), Vivadent Heliolink (Vivadent USA, Amherst, NY), Mirage FLC (Chameleon Dental Products, Inc, Kansas City, KS), and Den-Mat Ultra Bond (Den-Mat Corp, Santa Maria, CA). MATERIALS AND METHODS: Each cement was used to lute two 10 mm circular Vita VMK porcelain disks 0.75 mm in thickness. The surfaces to be luted were sand blasted and a silane coupling agent applied. The natural glaze was unaltered. Manufacturer's directions were followed for manipulation of the cements. A jig was used during the application of the resins to control cement thickness. The samples were stored in distilled water at 37 degrees C. Using a Hunter Tristimulus Colorimeter (Hunter Associates Laboratory, Inc, Reston, VA), values were obtained for each specimen immediately, at 24 hours, and at 1, 2, 3, 4, 8, 12, 16, 20, and 24 weeks. RESULTS: An analysis of variance (ANOVA) showed significant differences for all specimens. Using the Scofield Hunter formula for identifying color differences (delta E), at 24 hours, and 24 weeks, Vivadent Heliolink showed the least color changes (24 hours delta E = 0.82, 24 weeks delta E = 0.98) and Kerr Porcelite the greatest (24 hours delta E = 3.94, 24 weeks delta E = 4.73). CONCLUSIONS: All dual-cure composite resin cements in this study showed short-term and long-term color change. Vivadent Heliolink showed the least color change, while Kerr Porcelite showed the most change.

Analysis of Variance↗
PubMed1992

Human hepatic 3 alpha-hydroxysteroid dehydrogenase: possible identity with human hepatic chlordecone reductase.

3 alpha-Hydroxysteroid dehydrogenase is a cytosolic, monomeric, NADPH-dependent oxidoreductase which reduces 3-keto-5-dihydrosteroids to their tetrahydro products. We present here the first partial amino acid sequence data for the human liver enzyme and show these sequences to be identical to the deduced amino acid sequence for human hepatic chlordecone reductase. In addition, these two enzymes exhibit similar substrate and cofactor specificities and immunological reactivity. The results suggest that the natural substrates for chlordecone reductase are 3-keto-5-dihydrosteroids and that these two proteins may be identical.

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Purification and properties of human hepatic 3 alpha-hydroxysteroid dehydrogenase.

3 alpha-Hydroxysteroid dehydrogenase (3 alpha-HSD) was purified greater than 500-fold from human liver cytosol. The purification was monitored using 5 beta-[3H]dihydrocortisol (5 beta-DHF) as substrate. Electrophoretically homogeneous enzyme was obtained using a procedure that involved ammonium sulfate precipitation and three successive column chromatography steps: DEAE-cellulose, hydroxylapatite and Blue-Sepharose. The enzyme is a monomer since the native molecular weight was found to be 37,000, using a calibrated Sephadex G-75 column, and the denatured subunit molecular weight was determined to be 38,500, by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The enzyme had a pI of 5.6-5.9. The 3-ketosteroids: cortisol, testosterone, progesterone and androstenedione, were not substrates for 3 alpha-HSD indicating that a saturated 4,5 double bond was required for substrate activity. The conformation at the 5 position, however, did not influence substrate activity since 5 alpha- and 5 beta-DHF and 5 alpha-dihydrotestosterone were all reduced at similar rates. The purified enzyme preferred NADPH to NADH as a cofactor and showed a broad peak of activity in the pH range of 6.8-7.4. The apparent Km for 5 beta-DHF was 18 microM. The enzyme was markedly stabilized by 50 mM phosphate buffer containing 10 to 20% glycerol at 4 degrees C. Freezing and thawing of the enzyme resulted in a large loss of activity during early stages of the purification. This is the first report of the purification to homogeneity of 3 alpha-HSD from human tissue.

3-Hydroxysteroid Dehydrogenases↗
PubMed1991

An unusual organoid tumor. Alveolar soft part sarcoma or paraganglioma?

The histogenesis of alveolar soft part sarcoma (ASPS) is a subject of continued debate. Although many recent reports suggest a muscle origin, others advocate a neuroendocrine derivation. A tumor in the chest wall of a 16-year-old woman was diagnosed and treated as ASPS. The light microscopic, electron microscopic, and immunohistochemical findings showed features of both ASPS and paraganglioma. In addition, this lesion was positive for antibody to glucagon, a characteristic of neither ASPS nor paraganglioma, although seen in a few gangliocytic paragangliomas. This case demonstrates the need for continued inquiry into the histogenesis of ASPS.

Adolescent↗
PubMed1991

Sudden asphyxial death due to a prolapsed esophageal fibrolipoma.

Fibrolipomas of the esophagus are extremely uncommon benign tumors. Accurate diagnosis and resection are essential, due to their tendency to become impacted and obstruct the airway. The case is presented of a 56-year-old man who died suddenly of asphyxia because of upper airway obstruction by a prolapsed fibrolipoma of the esophagus.

Asphyxia↗
PubMed1991

Social validity assessments: is current practice state of the art?

The use of evaluative feedback from consumers to guide program planning and evaluation is often referred to as the assessment of social validity. Differing views of its role and value in applied behavior analysis have emerged, and increasingly stereotyped assessments of social validity are becoming commonplace. This paper argues that current applications of social validity assessments are straying from the point originally proposed for them. Thus, several suggestions for improving current social validity assessment are proposed, including (a) expanding the definition of consumers to acknowledge the variety of community members able and likely to affect a program's survival, (b) increasing the psychometric rigor of social validity assessments, (c) extending assessment to heretofore underrepresented populations, (d) implementing widespread application of well-designed social validity assessments, (e) increasing meaningful consumer involvement in the planning and evaluation of behavioral programs, and (f) educating consumers to make better informed programming decisions.

Community Participation↗
PubMed1990

Human hepatic cortisol reductase activities: enzymatic properties and substrate specificities of cytosolic cortisol delta 4-5 beta-reductase and dihydrocortisol-3 alpha-oxidoreductase(s).

The metabolism of cortisol by human liver homogenates has been studied. Cortisol delta 4-reductase and dihydrocortisol-3-oxidoreductase activities were distributed in all subcellular fractions. The products of the soluble enzymes were identified. Cortisol and 5 beta-dihydrocortisol were reduced to 3 alpha,5 beta-tetrahydrocortisol, and 5 alpha-dihydrocortisol was reduced to 3 alpha,5 alpha-tetrahydrocortisol. The soluble enzymes showed a wide range of substrate specificity. The 21 substituted cortisol derivatives were not metabolized. The apparent Km values of cortisol delta 4-5 beta-reductase and dihydrocortisol-3 alpha-oxidoreductase for their substrates (cortisol, 5 alpha-dihydrocortisol, and 5 beta-dihydrocortisol) all ranged from 18 to 27 microM. Dexamethasone inhibited the reduction of all of these substrates and the inhibition was abolished by 21 substitution of the dexamethasone. Testosterone was a competitive inhibitor of the reduction of cortisol, 5 alpha-dihydrocortisol, and 5 beta-dihydrocortisol with a Ki ranging from 11 to 32 microM. NADPH was the preferred cofactor for the cortisol delta 4-5 beta-reductase and dihydrocortisol-3 alpha-oxidoreductase. No end product inhibition was observed.

Chromatography, High Pressure Liquid↗
PubMed1990

Lymphocytic mastopathy. An autoimmune disease of the breast?

Eight cases are reported of an unusual breast lesion consisting of dense intralobular, perilobular, and perivascular lymphocytic infiltrates associated with lobular atrophy and sclerosis. Immunologic studies on paraffin-embedded tissue (seven cases) and frozen tissue (two cases) demonstrated a predominance of B-cells and expression of HLA-DR antigen in involved lobular epithelium. The immunologic features of this lesion are reminiscent of lymphoepithelial lesions of salivary glands and other sites. A possible autoimmune pathogenesis is suggested.

Adult↗
PubMed1990

Gangrenous herpetic whitlow in a human immunodeficiency virus-positive patient.

An unusual case of a gangrenous herpetic whitlow is reported. The patient, a 37-year-old man with a ten-year history of intravenous drug abuse, was antibody positive for human immunodeficiency virus. Progressive, extremely painful paronychia of the left third and fourth fingers gradually developed, which persisted despite a variety of treatment protocols, including antibiotics and radiotherapy, ultimately necessitating amputation of the distal portions of the digits. Characteristic herpes-type intranuclear inclusions within epidermal cells were identified in histologic sections of the specimen. Immunohistochemistry using rabbit antihuman herpes virus antibody confirmed the diagnosis. This apparently represents the first documented case of herpetic gangrene in an immunocompromised patient.

Adult↗
PubMed1990

Nonpalpable breast masses: radiologic predictability of malignancy.

Of 568 nonpalpable breast lesions detected by screening mammography 242 proved to be noncalcified masses; biopsy showed 165 to be benign and 77 malignant. The lesions were evaluated with respect to contour, radiographic density and size. Of the malignant lesions 90% were infiltrating carcinomas, 88% of which had an indistinct contour and were of moderate to high density. Of the benign lesions 40% of those with an indistinct contour demonstrated high radiographic density. Low-density, distinct masses were all benign. There was no correlation between the size of the lesion and whether it was malignant.

Aged↗
PubMed1989

Meningeal nodules with features of extranodal sinus histiocytosis with massive lymphadenopathy.

We present an unusual case of multiple intracranial meningeal nodules in a 30-year-old man. Histologically, the nodules consisted predominantly of plasma cells, histiocytes, and lymphoid cells with Russell bodies and emperipolesis. Emperipolesis may be a clue to understanding the pathogenesis of the process that has features consistent with so-called sinus histiocytosis with massive lymphadenopathy in the extranodal location.

Adult↗