O2 incorporation into a long-chain fatty acid during bacterial luminescence

The bioluminescence-dependent oxidation of a long-chain fatty aldehyde catalyzed by luciferase from Photobacterium phosphoreum has been studied in ¹⁸O₂ experiments. The results show the incorporation of one atom of molecular oxygen into the product, the corresponding fatty acid. This incorporation is not the result of exchange of ¹⁸O₂ with the aldehyde prior to oxidation to the acid, thereby indicating that the bacterial luciferase catalyzes an aldehyde monooxygenase reaction which is coupled with bioluminescence.     

Cell to cell relationships in the seminiferous epithelium in the mouse embryo

Summary Germ cells and Sertoli cells in embryonic mouse testes (day 14 to 20 of gestation) were examined by sectioning and freeze-fracture. Intercellular cytoplasmic bridges between the germ cells are observed in day 14 and older embryos. Membrane specializations with dense fuzzy material similar to the socalled desmosome-like structures are found between Sertoli cells and germ cells. A cell contact area with dense opposed membranes is also found between adjacent germ cells. Asymmetrical dense fuzzy lining of both Sertoli and germ cell membranes is noted. Pinocytotic pits or caveolae are frequently found in the Sertoli cell membrane. Between adjacent Sertoli cells, gap junctions of various sizes and focal meshworks of the occluding junctions are found. Most of the occluding junctional particles are located in the center of the grooves in the E face, and are similar to those in postnatal and adult Sertoli cell junctions. In addition, on both fractured faces there are ridges and grooves devoid of particles which are continuous with occluding junctions with particles, suggesting an initial stage in the formation of occluding junctions of the Sertoli cells. Particles gathered at the site of desmosome-like structures are present on the P face of the Sertoli cell.This work is supported by the Japanese Ministry of Education     

Reversible inhibition of adenylate cyclase activity of rat brain caudate nucleus by oxidized glutathione

Basal and dopamine-stimulated adenylate cyclase (EC 4.6.1 1.) activities were strongly inhibited by GSSG, but not by GSH. Adenylate cyclase that had been inactivated by GSSG was reactivated by incubation with various sulfhydryl compounds including GSH. Formation of mixed disulfides by reaction between GSSG and protein-SH groups increased on incubation with GSSG and returned to the normal level on subsequent incubation with DTT.     

Morphogenesis of tight junctions in the peritoneal mesothelium of the mouse embryo

The peritoneal mesothelium of mouse embryos (12 to 18 day of gestation) was studied by freeze-fracture and in sections in order to reveal the initial formation of the tight junctions. Freeze-fracture observations showed three types of tight junctions. Type I consists of belt-like meshworks of elevations on the P face and of shallow grooves on the E face. No tight junctional particle can be seen either on the elevations or in the grooves. Type II shows rows of discontinuous particles on the elevations on the P face. Type III consists of strands forming ridges on the P face. On the E face, the grooves of Type II and III appear to be narrower and sharper than those of Type I. Quantitatively, Type I junctions are most numerous during the early stages (day 12-13) of embryonic development, while Type III junctions become more common in the later stages, and are the only type seen by day 18. Observations on sections, however, fail to distinguish between the three types. The results suggest that an initial sign of tight junction formation is close apposition of the two cell membranes in the junctional domain, without tight junctional particles. Later, the particles appear to be incorporated in the tight junctions and the strands form by fusion of the particles.     

Lanthionine as an essential constituent of cell wall peptidoglycan ofFusobacterium nucleatum

Lanthionine, a sulfur-containing diamino acid which had not previously been reported as one of the main amino acids of any bacterial cell wall peptidoglycan, was demonstrated inFusobacterium nucleatum peptidoglycan isolated by sodium dodecyl sulfate extraction and protease digestion. Lysine, diaminopimelic acid, and ornithine were absent. Lanthionine seems to be an essential dibasic amino acid, involved in cross-linkages betwen stem peptide subunits inF. nucleatum.     

Continuous cultures of tomato and citron roots in vitro

Summary Initial trials with tomato-root cultures disclosed the desirability of employing a gently agitated liquid medium containing iron in the chelated form. For the normal cultivars “Ace” and “Tropic”, subcultures were best achieved by utilizing sectors that possessed one or more newly emerged laterals. Continuous cultures of a nonlateral-forming tomato mutant, “Diageotropica”, and of citron were accomplished by subculturing tips of the elongating primary roots. The tomato roots were cultured in White's medium with the Fe₂(SO₄)₃ replaced by 0.03 mM NaFeEDTA. Sustained growth of citron-root tips necessitated the use of a medium containing Murashige and Skoog salts, 7.5% sucrose, 100 mg per I each of citric acid and thiamine HCl, and 5000 mg per li-inositol. The success with citron-root cultures was extendable to all cultivars ofC. medica L., but not to otherCitrus species relatives. Both citron and “Diageotropica” root cultures manifested undiminished elongation through repeated subcultures; but neither produced laterals in response to any cultural treatments. Research was supported in part by National Science Foundation Grant OIP75-10390 and Elvenia J. Slosson Fellowship in Ornamental Horticulture.     

Characterization of an extracellular polysaccharide from a xanthomonas species

An extracellular polysaccharide containing glucose, mannose, D-manno-octulosonic acid (KDO), an unidentified component (X), and acetyl groups in the molar ratio of 1.3:3.8:1.6:1.1:2.9, was obtained from the incubated medium of a Xanthomonas species. The extracellular polysaccharide contained traces of phosphate and nitrogen but no lipid. Mild hydrolysis with 0.025M sulfuric acid released all of the KDO in the polysaccharide and a KDO-free product was obtained, which on hydrolysis with 0.05M sulfuric acid, gave mainly an oligosaccharide containing glucose, mannose, and X in molar ratio of 1:1:1. The reducing end-group of this oligosaccharide was X, and other hexose residues were linked (1 → 4). Compound X seems to be a 6-deoxyhexose that differs from fucose and rhamnose.     

An improved assay method for amylase activity using an amylodextrin fraction as substrate

A rapid and simple method for determination of amylase activity, by using a fraction of an amylo-oligosaccharide (amylodextrin, 1) as substrate, is described. The sample solution is incubated with a solution of 1 and the substrate consumed is estimated by measuring the difference in absorbance at 460 nm. The K_m value of 1 is about half that of starch. The homogeneity of 1 in its chemical structure and molecular weight facilitated the specification of amylase units according to the international definition. This procedure was applied for assay of human-serum amylase with excellent reproducibility. This method did not require a large dilution factor, as the standard curve showed a linear relationship over a wide range of amylase concentrations.