In vitro pollen germination of species and two interspecific hybrids from the genus Brassica

In vitro pollen germination of five species and two interspecific hybrids from the genus Brassica was tested in four media. Genetically fixed differences in the demands for optimal pollen germination among species were found. The experiments were designed to define optimal content of mineral salts, sugar, and PEG for every investigated species or hybrids. The differences found among species are discussed in relation to the evolutionary trend.     

The complete amino acid sequence of the major alpha subunit of the lectin from the seeds of Dioclea grandiflora (Mart)

The complete amino acid sequence of the major alpha subunit of the lectin from seeds of Dioclea grandiflora was determined. The sequence was deduced from analysis of peptides derived from the native alpha subunit by digestion with trypsin, chymotrypsin, the Staphylococcus aureus V8 protease, and pepsin; and from larger peptides produced by digestion of the citraconylated protein with trypsin. The alpha subunit consists of a single polypeptide chain of 237 amino acids which differs from the sequence of concanavalin in 53 positions. Significant levels of heterogeneity were observed in five positions in the sequence.     

Distribution of the genus Ancylostoma (Dubini, 1843) along the digestive tube of the dog (author's transl)

The A. A. studied the distribution of nematodes of the genus Ancylostoma (Dubini, 1843) along the digestive tube of 45 dogs. For the collection of the worms they used the method developed by Mello and Campos. The distribution found was: 97,5% in the jejunum, 1,2% in the ileon, 0,7% in the duodenum, 0,3% in the colon, 0,2% in the cecum and 0,1% in the stomach.     

Association of Azospirillum with Grass Roots

The association between grass roots and Azospirillum brasilense Sp 7 was investigated by the Fahraeus slide technique, using nitrogen-free medium. Young inoculated roots of pearl millet and guinea grass produced more mucilaginous sheath (mucigel), root hairs, and lateral roots than did uninoculated sterile controls. The bacteria were found within the mucigel that accumulated on the root cap and along the root axes. Adherent bacteria were associated with granular material on root hairs and fibrillar material on undifferentiated epidermal cells. Significantly fewer numbers of azospirilla attached to millet root hairs when the roots were grown in culture medium supplemented with 5 mM potassium nitrate. Under these growth conditions, bacterial attachment to undifferentiated epidermal cells was unaffected. Aseptically collected root exudate from pearl millet contained substances which bound to azospirilla and promoted their adsorption to the root hairs. This activity was associated with nondialyzable and proteasesensitive substances in root exudate. Millet root hairs adsorbed azospirilla in significantly higher numbers than cells of Rhizobium, Pseudomonas, Azotobacter, Klebsiella, or Escherichia. Pectolytic activities, including pectin transeliminase and endopolygalacturonase, were detected in pure cultures of A. brasilense when this species was grown in a medium containing pectin. These studies describe colonization of grass root surfaces by A. brasilense and provide a possible explanation for the limited colonization of intercellular spaces of the outer root cortex.     

Enhancement of α-methylglucoside efflux by respiration in respiratory mutants of Escherichia coli K-12

The rate of α-methylglucoside efflux from wild-type cells of Escherichia coli K-12 is enhanced by different substrates, as long as they are readily respired. A similar enhancement takes place in strains with impaired oxidative phosphorylation (unc mutants), regardless of their being able (strains AN120, N₁₄₄, and AN382) or unable (strain NR70) to energize the membrane through respiratory electron flow. The uncouplers carbonylcyanide-m-chlorophenylhydrazone and tetrachlorosalicylanilide do not diminish the efflux acceleration in wild-type strains or unc mutants. However, the stimulation of α-methylglucoside efflux does not occur in the mutant AN59 which cannot perform a normal respiratory electron transport due to a defective synthesis of ubiquinone. The failure to stimulate the efflux is observed with succinate, which is a typical substrate of respiration, as well as with substrates which can yield ATP both at respiratory and substrate levels such as gluconate or glycerol. Moreover, potassium cyanide nullifies the acceleration of α-methylglucoside efflux caused in any type of strain and by any substrate. These results show that neither ATP nor an energized state of the membrane appears to be needed for respiration to accelerate α-methylglucoside release from E. coli cells, and question the existence of any energy-requiring reaction for αMG exit, previously proposed by other authors.     

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.     

Evolution of the nucleotide sequence of influenza virus RNA segment 7 during drift of the H3N2 subtype

The complete genetic information contained in the influenza virus RNA segment 7 of the A/Bangkok/ $\text{1}\text{79}$ (H3N2) strain has been cloned by in vitro synthesis of the complementary dsDNA and its insertion into plasmid pBR322. The nucleotide sequence of the viral RNA segment has been determined from the cDNA insert. It is 1027 nucleotides long, and contains two open reading frames, as shown for other influenza virus strains. When compared with the previously published sequence for the A/Udorn/72 (H3N2) strain, 15 nucleotide exchanges are observed, most of them silent mutations, and only two causing amino acid changes in each of the M1 and M2 protein sequences.     

Modified oscillation behavior and decreased D-3-hydroxybutyrate dehydrogenase activity in diabetic rat liver mitochondria

One month after induction of diabetes in adult white rats with streptozotocin or 4–10 months after its induction by pancreatectomy (in every case glycemia was over 3 g/liter), the following alterations were observed in liver mitochondria: (a) a decrease of amplitude and an increase of the damping factor of volume oscillations induced by potassium ions and valinomycin; (b) a 50% decrease of d-3-hydroxybutyrate dehydrogenase (HBD) activity in mitochondria disrupted by repeated freeze-thawing; (c) a similar decrease in the rate of d-3-hydroxybutyrate oxidation by intact mitochondria; (d) a significant increase of cytochrome oxidase activity and cytochrome aa₃ content. Measurement of succinate dehydrogenase and NADH dehydrogenase activity, the cytochrome b, c₁, and c content, and the P:O ratio for mitochondria oxidizing d-3-hydroxybutyrate did not reveal significant differences between control and diabetic rat mitochondria. In the streptozotocin-injected rats, the variation of HBD activity and the modification of the mitochondrial oscillation pattern were time-dependent phenomena, both effects reaching their maximal expression about 1 month after the onset of diabetes. The variation of HBD activity followed a biphasic course, since it rose to above the control level during the first 2 weeks of diabetes, then fell progressively to about half the control value after the third week. Treatment of diabetic rats with NPH insulin (5 IU twice daily, for 3 days, reinforced by the same dose 45 min before sacrifice) restored the mitochondrial oscillation pattern, HBD activity, and rate of d-3-hydroxybutyrate oxidation by intact mitochondria to their normal values.     

Multiple phosphorylation of rat liver 3-hydroxy 3-methylglutaryl coenzyme a reductase

Rat liver homogeneous ³²P-labeled hydroxy methylglutaryl coenzyme A reductase, was treated independently with CNBr and trypsin and the resulting [³²P]phosphopeptides were analyzed by disc gel electrophoresis. CNBr treatment produced only one ³²P-fragment of Mr 18,000. The time course of trypsin hydrolysis initially showed the appearance of some phosphopeptides, which were lately converted in two phosphopeptides of low Mr. These results provide direct support for the concept that hydroxy methyl glutaryl coenzyme A reductase kinase solubilized from microsomes phosphorylates only two sites or set of sites in the reductase molecule.