The effects of maize-bran phytate and of a polyphenol (tannic acid) on iron absorption from a white-bread meal were tested in 199 subjects. The phytate content was varied by adding different concentrations of phytate-free and ordinary maize bran. Iron absorption decreased progressively when maize bran containing increasing amounts of phytate phosphorous (phytate P) (from 10 to 58 mg) was given. The inhibitory effect was overcome by 30 mg ascorbic acid. The inhibitory effects of tannic acid (from 12 to 55 mg) were also dose dependent. Studies suggested that greater than or equal to 50 mg ascorbic acid would be required to overcome the inhibitory effects on iron absorption of any meal containing greater than 100 mg tannic acid. Our findings indicate that it may be possible to predict the bioavailability of iron in a diet if due account is taken of the relative content in the diet of the major promoters and inhibitors of iron absorption.

Analysis of drug efficacy in animal models of Pneumocystis cainii pneumonia requires an accurate method of quantification of organisms, as well as a means of assessing viability. Lung homogenates were prepared from a colony of athymic nude F344 rats experiencing a spontaneous outbreak of P. carinii pneumonia. With the fluorescent nucleic acid stain propidium iodide, flow cytometric analysis was able to quantify P. carinii cysts and trophozoites reproducibly. As this stain is excluded by living cells, this method was also used to assess the viability of organisms. Application of this technique to analysis of bronchoalveolar lavage specimens was demonstrated.

The degradation of the foreign protein [ 'T]methyl apohaemoglobin ([ T-melglobin) was stimulated by ATP in cell-free extracts from exponential phase and shaken and standing stationary phase Vibrio cells. A marked stimulation by ATP of the degradation of [ lSC-me]globin was observed with exponential phase cell extracts which were preincubated for 30 min at 30 "C.Maximum stimulation was obtained with 3 mhi-ATP and optimum degradation was at pH 8-0-8-5. Preincubation of extracts from both types of stationary phase cells did not affect the degree of ATP stimulation. The amount of ATP stimulation of [I4C-me)globin degradation by exponential phase extracts decreased markedly when the cells were starved in a growth limiting minimal medium before preparation of the cell extracts. In the exponential and both types of stationary phase extracts most of the activity was located in the cytoplasmic fractions. Although the periplasmic preparations contained a minor portion of the total activity, this activity showed a greater percentage stimulation by ATP. In the absence of ATP the specific proteolytic activities of the extracts from exponential and both types of stationary phase cells were similar. The proteolytic activities in all the cell extracts were inhibited to the same extent by phenylmethylsulphonyl fluoride, but the exponential and both types of stationary phase cell extracts were inhibited to different extents by EDTA and p-hydroxymercuribenzoate. The results suggest that the proteolytic systems responsible for the degradation of abnormal proteins are different in exponential and stationary phase Vibrio cells.