Isolation and structure of nocobactin NA, a lipid-soluble iron-binding compound from Nocardia asteroides

Nocobactin NA, a lipid-soluble iron-chelating product with an unusual and characteristic u.v.-absorption spectrum, was isolated from Nocardia asteroides grown under conditions of iron deficiency. Its structure was determined by physical methods and by synthesis of one of its degradation products. Nocobactin NA was obtained as a homologous mixture of compounds with side chains of differing length, and resembles mycobactin M in structure except that it has an oxazole ring in place of an oxazoline ring, and the side chains in the cobactin fragment are considerably shorter.     

Preliminary characterization of Thy-1.1 and Ag-B antigens from rat tissues solubilized in detergents

1. A radioactive binding assay for Thy-1.1 alloantigen which functions in the presence of detergents was established by using glutaraldehyde-fixed thymocytes as target cells. Thy-1.1 activity in detergent extracts was then assayed by measuring inhibition of the binding assay. 2. Solubilization of Thy-1.1 from whole thymocytes, and their membranes by a large number of non-ionic detergents and deoxycholate was studied. In the same extracts Ag-B(4) histocompatibility antigenic activities were measured. With the exception of Nonidet P-40, the detergents did not affect the antigenicity of Thy-1.1, but only Lubrol-PX and deoxycholate gave effective solubilization as measured by activity remaining in the supernatant after centrifugation at 200000g for 40min. With Ag-B(4) antigen, Triton X-100, Triton X-67 and Nonidet P-40 gave effective solubilization as well as Lubrol-PX and deoxycholate. Solubilization of Thy-1.1 activity from leukaemia cells and a brain homogenate was also studied, but none of the non-ionic detergents gave satisfactory results with these tissues. 3. Extracts from thymocyte membranes were further examined by gel filtration and sucrose gradient centrifugation. The Thy-1.1 activity behaved as a single component in deoxycholate with a density similar to that of a globular protein, but in Lubrol-PX the antigen was contained in a low-density complex. In Lubrol-PX extracts Ag-B(4) was also found in aggregates not observed in deoxycholate. 4. The s(20,w) values for Thy-1.1 and Ag-B(4) antigens in deoxycholate were 2.4 and 4.4, and v values were 0.70 and 0.75 respectively. The Stokes radius observed for Thy-1.1 was 3.1nm and for Ag-B(4) 5.3nm. By using these values the molecular weights for the antigen-detergent complexes were calculated to be 28000 for Thy-1.1 and 100000 for Ag-B(4).     

EVIDENCE FOR A CRYPTOMONAD SYMBIONT IN THE CILIATE,CYCLOTRICHIUM MEUNIERI1

Extracts of the marine ciliate Cyclotrichium meunieri contained chlorophylls a and c, carotenoids, and a phycoerythrin with a single absorbance maximum at 542 nm. This assemblage of pigments suggests that the numerous photosynthetic symbionts present in each ciliate cell belong to the Cryptophyceae.     

Measurement of Glomerular Filtration Rate by Inulin Clearance without Urine Collection

A continuous infusion method for measuring inulin clearance (and hence glomerular filtration rate) which does not require urine collection has been re-evaluated and found to give satisfactory results. In two non-oedematous and anephric patients the plasma level of inulin became virtually constant four hours after a single intravenous dose, and hence this is the minimum time required for the infusion with this method.     

Area-sampling Technique for Quantitative Pharyngeal Cultures

An area-sampling device for obtaining quantitative samples of the oropharyngeal bacterial flora is described and illustrative data are presented.     

Citrate-cleavage enzyme, `malic'' enzyme and certain dehydrogenases in embryonic and growing chicks

The activities of several enzymes possibly implicated in lipogenesis were measured in the soluble fraction of homogenates of liver and adipose tissue of embryonic and growing chicks. The activities of adipose-tissue enzymes showed little or no change. The activities of hepatic hexose monophosphate-shunt dehydrogenases, malate dehydrogenase, 3-phosphoglyceraldehyde dehydrogenase and NAD-linked α-glycerophosphate dehydrogenase also showed little or no change. Isocitrate dehydrogenase activity in liver rose to a peak on the day of hatching and fell to half the peak value during the next 12 days, where it remained to 26 days after hatching. The activities of `malic' enzyme and citrate-cleavage enzyme showed very low stable values in embryonic liver and remarkable rises during the early part of the post-hatching period. An 85-fold increase in the activity of `malic' enzyme activity was completed in 7 days and a 15-fold increase in that of citrate-cleavage enzyme in 5 days. The activities then attained were maintained up to 26 days after hatching. 2. The increases in the activities of hepatic citrate-cleavage enzyme and `malic' enzyme occurred simultaneously with a marked increase in lipogenesis, suggesting a relationship of these enzymes to lipogenesis in chick liver. By contrast, activity of the hexose monophosphate-shunt dehydrogenases does not appear to be thus associated.     

Distribution of gibberellin-like substances in light-and dark-grown seedlings of Phaseolus multiflorus

Summary Lettuce and barley endosperm bioassays of successive eluates from a phosphate-buffered celite column detected two gibberellin-like compunds, Phaseolus I and Phaseolus II, in extracts of both light-and dark-grown seedlings of Phaseolus multiforus. There were differences in the gibberellin content of light-and dark-grown seedlings, the former containing more Phaseolus I but less Phaseolus II than the latter. An examination of the gibberellin content of leaves and apical buds, stems, cotyledons, and roots of light-and dark-grown seedlings revealed distinct qualitative and quantitative differences in the distribution of Phaseolus I and Phaseolus II.