THE EFFECT OF INGESTION OF DIATOMACEOUS EARTH IN WHITE RATS: A SUBACUTE TOXICITY TEST.
Abstract The effects of 5% diatomaceous earth in the diet fed to white rats over a 90-day period indicated no mechanical or chemical damage to the tissues. There was no significant increase in the percentage of residual silica in liver, kidneys, and spleens of the test animals. Comparison of weight changes in the 5% group with the control showed a greater weight gain in the 5% test group. Histologic sections of animals fed 3% and 1% diatomaceous earth also showed no damage.
Diatomaceous Earth Silicosis
Diatomaceous earth and tripoli are hydrated amorphous silica minerals of organic origin, which are generally considered to be a variety of opal. The diatomaceous earth or diatomite (German: Kieselgur; Italian: farina fossile), are found in the lake deposits of innumerable diatom shells: it forms a very porous mass, sometimes loose and floury, sometimes compact and claylike, always very light-white, grtey, or yellowish. Tripoli on the other hand is a marine sediment mainly composed of skeletons of radiolarii: it is more compact and generally light, often containing well-preserved fossils of fish and shellfish. After quarrying, drying, and pulverizing, diatomaceous earth is marketed for a great variety of industrial purposes, including dynamite, refractory bricks, and filters for drinking water or wine or syrups; it is also used as an insulating material. Tripoli is less used but is especially valuable for polishing metals, precious stones, and the like. Diatomite is chiefly formed of amorphous hydrated silica (SiO2nH20) and in small part (2 to 6 per cent.) of basic oxides.
Chemical, biological, and immunological characterization of mono- and diiodothyrotropin releasing factor.
Abstract Iodination of thyrotropin releasing factor (TRF) with chloramine-T and NaI at pH 7.5 produces both mono- and diiodo-TRF as well as unreacted TRF and I − . The four compounds can be separated by ion-exchange chromatography on SP-Sephadex C-25, using a stepwise gradient of 0.01 m MH 4 OAc at pH 3.5, 5.2 and 7.2. The monoiodo-TRF was characterized by nuclear magnetic resonance, mass spectra, and elemental analysis as [Im-5-iodo-His 2 ]-TRF while the diiodo-TRF was similarly characterized as [Im-2,5-diiodo-His 2 ]-TRF. Both iodination products showed no thyrotropin releasing activity at doses up to 1 μg in the in vivo mouse bioassay. The specific binding of mono- and diiodo-TRF was measured against three different TRF antisera. In the absence of TRF, antisera A and C bound more diiodo-TRF than monoiodo-TRF while antiserum B seemed to bind both tracers equally. In all cases steeper curves were produced when diiodo-TRF was displaced by synthetic TRF.