Comparative study of aflatoxins M1 and B1 production in solid-state and shaking liquid cultures

Production of aflatoxins M1 (AFM) and B1 (AFB) by Aspergillus flavus NRRL 3251 in solid-state and shaking liquid cultures using rice as the carbon source was compared. In general, solid-state cultures produced more aflatoxins than shaking liquid cultures on an equal rice weight basis. Solid-state cultures with continuous shaking yielded higher levels of toxins than those with intermittent shaking. However, intermittent shaking is a feasible replacement for the continuous shaking method for AFM production. A typical solid rice culture supplemented with yeast extract produced 30 and 2600 mg per kg rice of AFM and AFB, respectively, in 8 days at 29 degrees C. The optimal culture conditions for toxin production in a shaking liquid culture were also studied. Parameters under consideration included the amount of carbon (rice) and nitrogen source, initial medium pH, and aeration rate. At optimum conditions, a representative shaking liquid culture produced 18 and 1680 mg per kg rice of AFM and AFB, respectively, in 5 days at 29 degrees C. This shaking liquid culture appears feasible for scaling up and routine production of AFM and AFB for toxicological investigations.     

Identity cards for patients infected with HIV?

Dr A C Srivastava has written to us to describe a case that raises the suggestion that people infected with the human immuno-deficiency virus (HIV) should carry identity cards. We asked two physicians, a general practitioner working with patients with the acquired immune deficiency syndrome (AIDS), and a general practitioner with a special interest in medical ethics to respond to the broad issues raised by Dr Srivastava''s letter.     

Immunoelectron microscopic localization of progesterone receptor in the chick oviduct

A peroxidase-anti-peroxidase (PAP) method using polyclonal anti-PR antibodies was used to localize progesterone receptor (PR) electron microscopically in the chick oviduct. The immunoreaction precipitate indicating PR was localized inside the nuclei of epithelial, glandular and stromal cells. In the estrogen withdrawn oviduct cytoplasmic immunoreaction precipitate was not seen. Inside the nucleus unoccupied PR was localized mainly like the heterochromatin. As visualized by the PAP technique, the localization of PR was not systematically changed after progesterone administration. In conclusion, we suggest that progesterone receptor in the chick oviduct is an intranuclear protein.     

An optical method for the determination of the isotopic composition of 1H2O/2H2O mixtures: Eu3+ luminescence lifetimes

A spectroscopic method employing pulsed dye laser instrumentation is described for the determination of the 1H2O/2H2O composition of aqueous solutions by the measurement of reciprocal excited state lifetimes of EuEDTA-. The reciprocal lifetimes, gamma-1, of the 1H2O/2H2O mixtures increase linearly with the mole fraction of 1H2O. For EuEDTA- the relationship between gamma-1 and the mole fraction, chi H, of 1H2O in 1H2O/2H2O mixtures is expressed by the equation chi H = 0.37 gamma-1-0.152, with a sensitivity in chi H of +/- 0.02. The reciprocal lifetimes are independent of pH in the range 5.1 to 10.5, changes in ionic strength, and the type of buffer used in EuEDTA- containing solutions.