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A simple double-antibody enzyme immunoassay that uses a microtechnique was developed for detecting staphylococcal enterotoxin A in food products. Sample preparation can be completed in less than 15 min. Assay sensitivity ranges from 0.4 ng (20-h test time) to 3.2 ng (1to 3-h test time)4Of toxin per ml of prepared sample. Separation and detection of enterotoxin from spiked food products ranged between 72 and 98% of the amount added.

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-Parallel experiments on human tooth enamel with sp.g. > 2.95 and synthetic hydroxyapatite have been carried out to study the substitution of CO~-for OH-, produced at 1000°C in dry C02, with the complementary use of neutron diffraction, x-ray diffraction, infrared spectroscopy and thermochemical techniques.It was verified that the substitution (i) is CO B-++ 2(OH-) and is completely reversible on specimen exposure to H20 vapor at 1000°C, (ii) takes place with the carbon atom on or near the hexad axis, (ii) places one CO~-group per unit cell in an ordered fashion and so changes the space group from P63/m to one without a screw axis, (iii) was consistent, by its incompleteness, with the occurrence of substitution of 02-for 2(OH-) in 25 to 40% of the unit cells, (iv) produced similar marked changes in the neutron powder diffraction patterns of both tooth enamel and hydroxyapatite, and (v) took place at a site where only a minor portion of the CO B -in normal, untreated human tooth enamel occurs.From comparative Rietveld analysis results from x-ray and neutron powder diffraction patterns it is suggested that the carbon atom of this A-site CO B -is near 0,0,0.12 and the CO B -plane makes an angle of zi8 ° with the o direction.On being heated at 400°C in H20 vapor, tooth enamel retained much of its CO B-but its a lattice parameter changed from 9.445(3) ~ to 9.420(i~ ~, essentially that of hydroxyapatite.After once being heated at high temperatures, "tooth enamel" and hydroxyapatite showed similar responses to various treatments, including carbonation. After heating, more 8-Ca3(PO4) 2 was found in the tooth enamel specimen.Comparative weight change, IR, and other data for tooth enamel and hydroxyapatite heated in He, then in CO2, and then in H20 vapor showed a 20% or more deficiency of structural OH-in the untreated tooth enamel.

The rapid, indirect enzyme-labeled antibody (ELA) microplate test has been developed as a diagnostic and surveillance tool to aid in the control of animal disease. The test has been applied to viral (hog cholera), parasitic (trichinosis), and bacterial (brucellosis) diseases of animals. A correlation of greater than 95% was observed between the hog cholera ELA test and the serum neutralization test for hog cholera in greater than 2,000 field samples obtained during the 1976 epizootic in New Jersey. Serum samples from all of 56 swine naturally infected with Trichinella spiralis at a level considered dangerous to humans were ELA-positive, whereas only one of 360 packinghouse sera negative for T. spiralis was ELA-positive. Preliminary experiments with bovine brucellosis (Brucella abortus) indicate that the ELA test is more sensitive than other test methods currently in use. ELA procedures should soon become tests of choice for the detection of antibodies to animal disease agents.