The effects of various pharmacological agents on the distribution of antihistamine activity of rat tissue extracts

Extracts of rat tissues (ear and abdominal skin, heart, cerebrum, spleen, kidney, lung, liver, stomach, and jejunum) were tested for their ability to antagonize histamine on the guinea pig ileum preparation. Antihistamine activity varied considerably between tissues; it was found to be highest in the ear skin and lowest in the jejunum and stomach. After pretreatment with semicarbazide (plus a pyridoxine-free diet) or reserpine, or after adrenalectomy, the antihistamine activity was reduced in some tissues but was increased in others. The variation in the behavior of the different tissues with these treatments made it impossible to interpret the distribution of antihistamine activity in terms of known sites of amine formation. After treatment with compound 48/80, however, there was an apparent parallelism between loss of antihistamine activity and depletion of mast cell histamine.

Assay and properties of diaminopimelate epimerase from Bacillus megaterium

1. Diaminopimelate epimerase from a soluble extract of Bacillus megaterium N.C.I.B. 7581 was purified about 25-fold by fractionation with ammonium sulphate and chromatography on calcium phosphate gel-cellulose. The product was impure but was unstable on further purification. 2. Quantitative assay methods for the enzyme were devised in which meso- or ll-diaminopimelic acid may be the substrate. 3. Between 25 degrees and 45 degrees at pH7.0 enzyme action leads to an equilibrium mixture containing 65% meso-isomer and 35% ll-isomer. 4. The initial rate of epimerization was 2-3 times as fast with ll-diaminopimelic acid as substrate as with the meso-isomer; a number of other amino acids were not racemized by the enzyme. The Michaelis constants at 37 degrees were 6.7mm (ll-isomer) and 100mm (meso-isomer); with both substrates enzyme activity was maximal at pH7-8. The relative rates of epimerization of ll-diaminopimelic acid at 25 degrees , 37 degrees and 45 degrees were 0.77:1.00:1.15. 5. A thiol compound (of which 2,3-dimercaptopropan-1-ol was the most effective) was needed as an activator of the purified enzyme. 6. Carbonylbinding reagents and several other compounds did not inhibit diaminopimelate epimerase. 7. Pyridoxal phosphate did not stimulate enzymic activity even in preparations that had been almost completely freed of derivatives of vitamin B(6) (as shown by microbiological assay).

High resolution recombination analysis of the pyridoxine-1 locus of Neurospora

Seven alleles of the pyridoxine locus of Neurospora were mapped by inter-allelic crosses, using pyr-1 and col-4 as outside markers. Excluding a few exceptional crosses, the data give a linear order of the sites of the seven alleles within the gene, and confirm that allele 44204, previously assigned to a separate locus, pdx-2, is in fact an allele of pdx-1.