Nodulation ofTrifolium subterraneum byRhizobium leguminosarum

Summary Four cultivars ofTrifolium subterraneum were nodulated by five strains ofRhizobium leguminosarum; all combinations except one gave 100% nodulation. Rates of nodule formation and total nodule numbers were similar to those with an effectiveR. trifolii strain. The nodules were more commonly associated with lateral roots and were ineffective in nitrogen fixation.     

Swelling and contraction of potato mitochondria

Mitochondria isolated from potato tubers fail to undergo passive osmotic swelling when suspended in isotonic Na⁺ acetate or phosphate, in NaCl following addition of tripropyltin, or in Na⁺ nitrate following addition of an uncoupler. Swelling under each of these conditions in mitochondria from other sources has been attributed to the inward movement of Na⁺ on an endogenous Na⁺/H⁺ exchanger. Such a monovalent cation/H⁺ exchanger has also been implicated in respiration-dependent cation extrusion and contraction of swollen mitochondria. Potato mitochondria swollen in chloride and nitrate salts extrude ions and contract when respiration is initiated. The contraction reaction is slower and less efficient than that in beef heart mitochondria, but like the latter, is sensitive to uncouplers and stimulated by nigericin, butacaine, and Mg²⁺. These comparative studies suggest that a cation⁺/H⁺ exchanger is present in potato tuber mitochondria, but that it functions exclusively as a cation-extruding mechanism. They further suggest that cation⁺/H⁺ exchange activity is not identical in mitochondria from different sources and that these exchange components may have a directionality and regulatory features which differ with the metabolic needs of the source tissue.     

Ring chromosome 16

Summary Ring chromosome 16 was found in a 33-year-old woman with mental, motor, and growth defects. Apart from a low percentage of monosomy 16 cell lines, the patient appears to have virtually all of the normal chromosome 16 genetic material at the microscopic level. Her impressive problems highlight the limitation of our ability to detect small deletions and the profound importance of the integrity of chromosome 16 in normal human development.     

Pulmonary maturation in the hypophysectomised ovine fetus. Differential responses to adrenocorticotrophin and cortisol

Pulmonary maturation in six ovine fetuses hypophysectomised by a cryosurgical method at 0.7-0.8 of pregnancy and delivered by hysterotomy at 152.2 +/- 2.9 (SD) days was compared with that in seven control fetuses delivered at 144.5 +/- 3.5 days. Both the wet and the dry weight of the lungs was less in the hypophysectomised fetuses but total DNA did not differ. Lung volumes at 40 cm of H2O and at 5 cm of H2O on deflation in hypophysectomised fetuses were less than one-third that of controls. Saturated phosphatidylcholine, as an estimate of surfactant, was lower in both lung tissue and lavage fluid. A further group of hypophysectomised fetuses was infused intravenously either with cortisol at 1 mg/h for 72 h (n = 6), or with ACTH1-24 at 5 microgram/h for 84 h (n = 6) before delivery at 155.0 +/- 2.1 days and 154.2 +/- 3.9 days respectively. None of the indices of pulmonary maturation in the cortisol-treated fetuses differed from those in untreated hypophysectomised fetuses whereas values for lung volumes at 40 and 5 cm of H2O in ACTH-treated fetuses were more than twice those of untreated hypophysectomised fetuses and did not differ significantly from controls. In addition, the amount of saturated phosphatidylcholine in lavage fluid was greater in ACTH-treated fetuses (0.13 +/- 0.10 mg/g) than in untreated hypophysectomised fetuses (0.04 +/- 0.48 mg/g). Lung volume at 40 cm of H2O in four fetuses that were thyroidectomised at the time of hypophysectomy responded to ACTH as in hypophysectomised fetuses with intact thyroids but other indices were unaffected. We conclude that hypophysectomy retards pulmonary maturation in fetal sheep. Since ACTH restores distensibility and increases alveolar surfactant in the absence of other pituitary hormones it is likely that ACTH has a major role in lung maturation. The lack of response to cortisol suggests that the effect of ACTH is not mediated only by circulating cortisol.     

Interaction of cadmium and zinc during prenatal development in the rat

Cadmium chloride, zinc chloride, or a mixture of the two, labeled with 115m-Cd or 65-Zn was administered intraperitoneally to Wistar rats on day 9 of gestation. On day 20 fetuses of Cd-treated rats exhibited malformations, but those of rats given zinc or zinc plus cadmium did not. No radioactive cadmium was recovered in the fetuses or fetal membranes, although some was found in the placentas. Simultaneous administration of zinc did not alter the distribution of cadmium, but cadmium significantly increased the amount of zinc in the fetus and placenta. In a second experiment, cadmium or cadmium plus zinc was administered on day 9 of gestation and embryonic units were removed on days 10, 11, and 12. On day 10 cadmium was found in the embryonic unit and maternal uterus, and cadmium in both was significantly reduced by simultaneous administration of zinc. The cadmium concentration in uterus and embryonic units decreased sharply on day 11 and 12 and by day 12 did not differ in animals treated with cadmium or with cadmium plus zinc. It is concluded that cadmium reaches the placenta or embryo at an organogenetically sensitive time, and that zinc may protect the embryo by decreasing the exposure to cadmium this time.     

The interaction of methemoglobin and modified poly-(hydroxyethylmethacrylates) studied by spectroscopic methods

The interaction between methemoglobin (MetHb) and macroporous matrices on the basis of polymethacrylates was investigated by means of optical and e.p.r. spectroscopy. The spectroscopic data show that the adsorption of MetHb to imidazole-containing matrices occurs by complex formation between matrix-bound imidazole and the iron of the prosthetic group, with all 4 polypeptide chains of the MetHb molecule being included in the interaction. The adsorption to hydrophobic side chains containing matrices leads, via the protein-matrix interaction, to considerable disturbances of iron protoporphyrin IX in equilibrium or formed from protein-contacts, which are of general importance with respect to the functional variablity and control, respectively, of iron porphyrins in hemoproteins. In case of matrix containing n-hexyl groups deoxyHb is oxidized by O2 to MetHb, instead of being oxygenated to HbO2. Not all prosthetic groups are able to bind N-3. With the increase in hydrophobicity of the matrix a conformational change is enforced leading in the beta-chains to the direct interaction between iron and sulfur of cysteine (beta-cys 92), as it is proved in all cytochrome P-450 and other model compounds.     

Chemotaxonomic significance of the xanthomonadins,novel brominated aryl-polyene pigments produced by bacteria of the genus Xanthomonas

The cell pigments produced by strains of Xanthomonas spp. (including representatives of all five presently recognized taxospecies of these phytopathogenic bacteria) have been isolated as isobutyl esters, purified, and characterized in terms of electronic absorption, chromatographic and co-chromatographic, and mass spectrometric properties. This comparative examination reveals that these bacteria produce brominated aryl-polyene pigments which are given the trivial name xanthomonadins. The several xanthomonadins usually occur as mixtures which have been resolved by chromatography and sorted into several Pigment Groups, thus enabling a more rational approach in our on-going systematic study of their exact chemical structures and biosynthesis. From what is presently known, some of the xanthomonadins might differ from xanthomonadin I, the exact structure of which has previously been determined in material from Xanthomonas juglandis ICPB XJ103, by their being monobrominated (rather than dibrominated, as is xanthomonadin I), by their having the equivalent of one methyl group less than does xanthomonadin I, and/or in other ways. The pigments of Xanthomonas ampelina (a little known and possibly questionable member of this genus) seem somewhat different from the pigments of the other Xanthomonas spp. The ability to form these distinctive xanthomonadin pigments is a useful chemotaxonomic marker for the genus Xanthomonas, since such pigments are not known to be formed by taxonomically or ecologically adjacent bacteria. Sufficient characterization of this assemblage of xanthomonadin pigments is presented so that they can be isolated and identified routinely on the basis of the aforementioned properties.