Farhad Moatamed

Health implications of natural fibrous zeolites for the intermountain west

INTRODUCTION Fibrous zeolites have recently been implicated in an endemic outbreak of malignant pleural mesothelioma in several villages in Cappadocia in central Tur- key (Baris et al., 1979; Lilis, 1981). The possible association between fibrous zeolites and mesothelioma and the potential biological activity of fibrous erionite from the United States are under active investigation. The zeolite minerals com- prise a group of over forty hydrated aluminum silicates. More than 300 probable deposits of the various natural zeolites are located in 25 states in the United States. Reserves of perhaps 10 trillion tons are present in the western United States; about 120 million tons are deposited near the surface (Sheppard, 1975). Several zeolites, including erionite and mordenite, may occur with a fibrous habit. Fibrous erionite is found in several well-defined deposits in Arizona, Nevada, Oregon, and Utah, where it occurs as thin, pure beds within sedimentary tuff sequences, or as outcrops in desert valleys of the Intermountain region. MINERALOGY Zeolites were first recognized as a new group of minerals by Baron Cronstedt with the discovery of stilbite in 1756 (Papke, 1972). Because of the unique quality of intumescence, zeolites were aptly named from the Greek zein and lithos mean- ing “boiling stones.” Zeolites are a group of crystalline sedimentary minerals’ that contain alkali or alkaline-earth elements in a hydrated aluminum silicate structure. They have an open, three-dimensional framework composed of silicon and aluminum tetrahedra (Flanigan, 1959). The central silicon or aluminum in each tetrahedron is sur- rounded by four oxygen atoms each of which is shared by two tetrahedra in a honeycombed, crystalline lattice with cavities and apertures characteristic of each

Fiber contamination of vermiculites: a potential occupational and environmental health hazard

Vermiculite ores from Montana, Virginia, and South Africa have been analyzed for the presence of amphibole contamination. Fibrous actinolite was found in unexpanded Montana vermiculite ore at a maximum concentration of 2.0%. The fibers persisted in the expanded ore at a maximum concentration of 0.6%. Actinolite was also found in the Virginia vermiculite ore but at a lower concentration and mostly as cleavage fragments with low length-to-width ratios. South African ore contained rare anthophyllite fibers also with low length-to-width ratios. Vermiculite ores have the potential for amphibole contamination and can represent potential health hazards without proper occupational and environmental control measures.

Acute effects of argon laser on human atherosclerotic plaque

Although the laser has been demonstrated to vaporize coronary artery plaque, there is little information about its ability to resect or vaporize the range of plaques present in peripheral vessels. This study attempts to determine the ability of the argon laser to resect all grades of atherosclerotic plaque, the risk of perforation during plaque resection, the effects on surrounding arteries, and the effect of different transmission media (air, saline solution, and blood) on the delivery of laser energy to the vessel. Seventy-five adult human cadaveric aortic specimens with a range of atherosclerosis from grossly normal artery to extensive calcification with ulceration were exposed to variable energy densities (200 to greater than 20,000 J/cm2) within 48 hours of harvesting. Specimens were examined grossly for the visual effects of laser and microscopically after preparation with hematoxylin-eosin, trichrome, and/or Verhoeffs elastin stains. Our results indicate that normal arteries and noncalcified plaques absorb laser energy and are vaporized. As the atherosclerosis becomes more complex with calcification, calcified regions are not vaporized and cannot be resected. In normal arteries and noncalcified plaque, perforation times were less than 5 seconds. Where palpable calcification was present in atherosclerotic lesions, average perforation time was doubled. In some vessels areas of calcification prevented wall perforation, but areas of subintimal hemorrhage perforated rapidly because of the selective absorption of laser energy by the red color of hemorrhagic tissue. These results remain the same when saline solution is used as a transmission media, although the amount of energy required to achieve the effects is increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of a variety of standard collagen substrates: ultrastructure, uniformity, and capacity to bind and promote growth of neurons

SummaryCollagen substrates were characterized after preparation by the four methods most commonly used for tissue culture (saline precipitation, exposure to ammonium hydroxide vapor, exposure to ultraviolet light, and air drying). Although roughly equivalent percentages of collagen were precipitated by each technique (87 to 97%), marked differences were found in surface uniformity and ultrastructure. Substrates were quite uniform if precipitated by exposure to ammonium hydroxide or ultraviolet light, of intermediate uniformity if saline precipitated, and not at all uniform if air dried. Scanning electron microscopy revealed that (a) ammonium hydroxide and saline precipitation primarily resulted in formation of collagen fibrils, (b) air drying produced a small number of fibrils plus a large amount of amorphous material, and (c) exposure to ultraviolet light only resulted in the formation of globular, nonfibrillar collagen aggregates.The capacity of collagen substrates to bind and grow neurons differed markedly with the method of preparation and the amount of collagen plated per unit area. Quantification of binding and growth of both cerebral and sympathetic neurons revealed that these are separate measures of the biocompatibility of a surface and that growth was uniformly inferior on globular collagen that had been precipitated by ultraviolet light. Long-term (≥2 wk) growth of sympathetic neurons was optimal on thick beds of saline-precipitated collagen, whereas short-term growth was best on thin layers of either saline or ammonium hydroxide-precipitated collagen. Cerebral neurons bound and grew optimally on thick collagen beds after both short- and long-term culture. In addition, cerebral neurons were found to be more dependent on the method of precipitation of the thin collagen substrates than were sympathetic neurons.

Peri-articular reactions to microscopic erosion of silicone-polymer implants. Light- and scanning electron-microscopic studies with energy-dispersive x-ray analysis.

Two patients are described who underwent implantation of silicone-polymer prostheses: one for an arthroplasty of the left great toe after a bunionectomy, and another for replacement of fractured trapezoid bone of the left wrist. Each patient developed unexplained severe pain at the sites of surgery at 3 and 7 months postoperatively. On removal of the implants and adjacent tissues, there was a microscopic foreign-body reaction to amorphous material in the subsynovial connective tissue. Although both prostheses were grossly intact, scanning electron microscopy revealed multiple erosions on their surfaces. Energy-dispersive x-ray analysis of foreign material in the paraffin-embedded sections revealed a peak for silicon. These two cases indicate that clinically significant pathological reaction may occur as early as 3 months after silicone-polymer implantation and that energy-dispersive x-ray analysis of excised tissue is a useful and specific diagnostic procedure.

Effects of argon laser on variable grades of atherosclerosis in the human aorta

Laser vaporization of coronary artery plague and peripheral arterial lesions has been documented in scattered clinical and cadaver studies, but the nature of atherosclerosis present in these studies was not fully documented. This paper reviews work done in cadaver specimens of infrarenal aorta to document the response of atherosclerotic peripheral vascular lesions of variable severity to application of argon laser light. Specimens were obtained, graded for degree of atherosclerotic involvement, and treated within 48 hours of harvesting. Argon laser energy was applied using an air medium with energy densities of 200-> 20,000 J/cm2 to investigate the effects of argon light on normal and atherosclerotic aorta. Specimens were examined grossly to determine degree of atherosclerosis present and to assess effects of the laser. Light microscopy was performed after staining with Hematoxylin and Eosin, Trichrome and Verhoff’s Elastin. The studies reported herein suggest that normal and non-calcified atherosclerotic aortas are comparable and predictable in rate of penetration and perforation by argon laser light (perforation time approximates 4 seconds at 500-600 W/cm2). When calcification is present in atherosclerotic lesions, the response to laser energy is less predictable. Calcium is a general retardent of laser vaporization of tissue and penetration of aortic wall. We find that the nature of an atherosclerotic lesion may affect resectability of atherosclerosis by argon laser. The incidence and severity of potential complications including acute thrombosis or accelerated atherogenesis in treated vessels, aneurysm formation and distal embolization awaits further study in chronic animal models.Laser vaporization of coronary artery plague and peripheral arterial lesions has been documented in scattered clinical and cadaver studies, but the nature of atherosclerosis present in these studies was not fully documented. This paper reviews work done in cadaver specimens of infrarenal aorta to document the response of atherosclerotic peripheral vascular lesions of variable severity to application of argon laser light. Specimens were obtained, graded for degree of atherosclerotic involvement, and treated within 48 hours of harvesting. Argon laser energy was applied using an air medium with energy densities of 200-> 20,000 J/cm2 to investigate the effects of argon light on normal and atherosclerotic aorta. Specimens were examined grossly to determine degree of atherosclerosis present and to assess effects of the laser. Light microscopy was performed after staining with Hematoxylin and Eosin, Trichrome and Verhoff’s Elastin. The studies reported herein suggest that normal and non-calcified atherosclerotic...