Somatic aberration induction in Tradescantia occidentalis by neutrons, x- and gamma-radiations. II. Biological results, r.b.e. and o.e.r.

Biological results, including statistical features, are described for the irradiation of Tradescantia occidentalis with 250 kVp X-rays, cobalt-60 gamma-radiation and monoenergetic neutrons with energies between 0-08 and 15 MeV. The effect studied was that of the induction of pink sectors in the otherwise blue staminal hairs of the flowers at low doses of radiation. Statistical aspects of the results suggest that a fraction of the asynchronous cell population in the hairs is very sensitive to neutron radiation, but not necessarily to lower LET radiations. All the results were fitted by a least-squares method by polynomials of different degrees. Best fits to X- and gamma-ray data were provided by second-degree polynomials, and to the neutron data by either second- or third-degree polynomials. Limiting r.b.e. and o.e.r. values at low doses are derived. Some computed microdosimetric parameters are presented in comparison with the r.b.e. values. It is concluded that the effect studied is complex and may not provide a critical test of bio-physical theories of radiation effects.     

Species 7. Cisticola Brunnescens. Pl. VII.

This third species of Cloud-scraper was first named by Dr. von Heuglin in 1862 from an adult male in Summer dress obtained by himself in Abyssinia. Later (in 1869), not realizing their specific identity, von Heuglin gave examples of the same species in Winter and juvenile dresses with different specific names, viz. iodopyga and habessinica , but did not have to contend with the difficulty of separating ayresii from brunnescens because the former species does not occur in Abyssinia. Elsewhere, from Kenya Colony to South Africa, that has always been the difficulty, and wherever the two species were subsequently found they were more or less indiscriminately related to one another as forms or allies of ayresii (under that bird's wrong name terrestris) , until, in 1913 *, Roberts showed the differences between them in South Africa, and, in 1922†, van Someren the same for Kenya Colony.     

Two benzaldehyde dehydrogenases in bacterium N.C.I.B. 8250. Distinguishing properties and regulation

Evidence is presented for the existence in bacterium N.C.I.B. 8250 of two inducible NAD⁺-linked benzaldehyde dehydrogenases. They may be distinguished in crude extracts by their different thermal stabilities at high pH values, benzaldehyde dehydrogenase I being much more heat-stable than benzaldehyde dehydrogenase II. Only benzaldehyde dehydrogenase I is activated by K⁺ and certain other univalent cations. Gel-filtration experiments indicate that both enzymes have molecular weights of about 180000. Both enzymes are induced by growth on l-mandelate or phenylglyoxylate; only benzaldehyde dehydrogenase I is gratuitously induced by thiophenoxyacetate and only benzaldehyde dehydrogenase II is induced by benzyl alcohol, by benzaldehyde, and by a number of heterocyclic compounds which do not support growth. Mutants have been isolated that lack either benzaldehyde dehydrogenase II or benzyl alcohol dehydrogenase, or both of the enzymes. Results obtained in induction experiments with the wild-type bacterium N.C.I.B. 8250 and with the mutants show that benzaldehyde dehydrogenase II and benzyl alcohol dehydrogenase are co-ordinately regulated. Overall, the results suggest that benzaldehyde dehydrogenase I is associated with the metabolism of l-mandelate whereas benzaldehyde dehydrogenase II is associated with the metabolism of benzyl alcohol.     

Nitration of angiotensin II by .NO2 radicals and peroxynitrite. .NO protects against .NO2 radical reaction.

To react with peptides, nitric oxide.NO has to be activated by oxidation, or by coupling with superoxide (O.-2) thereby producing peroxynitrite. In the course of.NO oxidation,.NO2 free radicals and N2O3 may be formed. Using gamma-irradiation methods, we characterized the products formed by these nitrogen oxides with angiotensin II. Angiotensin II is specifically nitrated at its tyrosinyl residue by.NO2 or peroxynitrite. Equimolecular amounts of each reagent in K+/Pi solutions at pH 7.4 led to 56% and 5% nitration yields, respectively. Nitrogen oxides produced by autoxidation of.NO, as well as.NO2 under.NO, reacted only with the arginine residue, giving a mixture of peptides containing citrulline, a N-(hydroxylamino-cyanamido-) instead of guanido group, and a conjugated diene derived from an arginine side-chain. However, nitrosation reactions by N2O3 occurred only when the initial concentration of.NO2 was 10 times that able to react with angiotensin II. Thus, in this case.NO appears to protect against.NO2 action.     

Conlarium duplumascospora gen. et. sp. nov. and Jobellisia guangdongensis sp. nov. from freshwater habitats in China

Conlarium duplumascospora gen. et. sp. nov. and Jobellisia guangdongensis sp. nov. are described and illustrated from submerged wood collected from Guangdong Province, China. Conlarium duplumascospora is characterized by gregarious, coriaceous and beaked ascomata; cylindrical, unitunicate asci with a bipartite apical ring; biseriate, fusiform, hyaline, 0-5-septate ascospores with or without appendages; and anamorph with muriform conidia. Jobellisia guangdongensis is characterized by globose to subglobose, gregarious and papillate ascomata; three-layered peridium; cylindrical, unitunicate asci with a refractive apical ring; and one-septate, fusiform, greenish brown ascospores. Sequence analyses of partial nuclear large subunit ribosomal DNA (LSU rDNA) were performed to infer the phylogenetic affinities of these new taxa. A key to species of Jobellisia is provided.     

Magnesium-induced self-association of calf brain tubulin. I. Stoichiometry.

The self-association of calf brain tubulin at pH 7.0 in the presence of magnesium ions has been examined by velocity sedimentation. The schlieren patterns were analyzed by methods described by Gilbert and by Cox. The observed process is best described in terms of a rapidly reversible progressive self-association of the tubulin dimer with identical chain elongation equilibrium constants, k, terminated by a ring-closing step, at degree of polymerization n = 26 +/- 2, with k26 greater than k. The end product of the polymerization reaction has a sedimentation coefficient s20,w0 k2 +/- 2 S. It is hydrodynamically equivalent to a closed ring structure observed in the electron microscope at identical conditions.     

High resolution 13C-n.m.r. spectroscopy of 'mixed linkage' xylans.

Three xylan fractions, obtained by stepwise precipitation with ethanol, were analysed by 75-MHz 13C-n.m.r. spectroscopy. Diad frequencies, determined from the C-2 resonances, show that the (1----3)-linkages are interspersed throughout the chain rather than grouped contiguously. This type of distribution is in agreement with a random coil conformation and with the constancy of the optical rotation in solvents of different ionic strength and chaotropic power. These diad frequencies were compared with the theoretical values calculated for a random distribution from the ratio of (1----4)-:(1----3)-linkages in the 1H-n.m.r. spectra, and from the methylation analysis for one of the fractions.     

A.M.A. Denver Meeting

This summary covers only a few of the many important subjects dealt with by the A.M.A. House of Delegates at its Denver meeting and is not intended as a detailed report on all actions taken.     

RS virus components. II. Antigenicity.

Rabbits were immunized with RS virus components, isolated as described previously. The sera were tested by neutralization, double diffusion and complement-fixation. RS virus components induced low titers of precipitating and complement-fixing antibodies, and failed to stimulate the neutralizing antibodies.     

Cytochrome c from Schizosaccharomyces pombe. 2. Amino-acid sequence.

The amino acid sequence of Schizosaccharomyces pombe cytochrome c has been established by automatic degradation of the protein and by manual degradation of fragments obtained by cyanogen bromide cleavage and chymotryptic digestion. The chymotryptic peptides were aligned by homology with other known cytochrome c sequences. The protein is 108 residues long, with a four-residue amino-terminal tail. It has only one methionine residue and differs from other fungal cytochromes c in lacking the one-residue deletion at the C-terminal end. After a cyanogen bromide step, an unexpected cleavage of the peptide chain before a cysteine residue was observed. This is ascribed to formation of a dehydroalanyl residue during an incomplete S-carboxymethylation of the apoprotein, and subsequent cleavage under acidic conditions. Experimental evidence is presented in favour of the proposed mechanisms.     

E.s.r. of spin-trapped radicals in aqueous solutions of amino acids. Reactions of the hydrated electron.

The reactions of hydrated electrons (eaq-) with amino acids were investigated by the spin-trapping method and by electron spin resonance. Tertiary nitrosobutane was used as a spin-trap to stabilize the short-lived radicals. Hydrated electrons were produced by gamma-radiolysis of de-aerated aqueous solutions of amino acids in the presence of sodium formate or tertiary butanol to scavenge OH. Radicals produced by reductive deamination of 19 amino acids were identified. Radicals formed by scission of the CH3-S- and -S-CH2- bonds of methionine as well as by deamination were observed. In the case of phenylalanine the radical formed by electron addition followed by proton transfer was identified. The reaction of proline and of hydroxyproline with eaq- resulted in the opening of the cyclic structure.     

Iodoglucagon. Preparation and characterization.

Iodinated derivatives of glucagon containing an average of 1 to 5 g-atoms of 127I per mol have been prepared by reacting the hormone with increasing amounts of iodine monochloride. Their iodoamino acid composition has been determined by ion-exchange chromatography and electrophoresis, following hydrolysis by pronase. Iodination of the two tyrosyl residues occurs first and is nearly complete after addition of a 4-fold molar excess of ICl. Iodination of the single histidyl residue is a later event and does not exceed an average of one atom per residue. Hydrolysis of iodoglucagon by trypsin and subsequent separation of the iodotyrosyl peptides shows that iodine is equally distributed between tyrosyl residues 10 and 13. Crude iodoglucagon containing an average of 1 g-atom of iodine per mol has been resolved into several components of differing iodine content and iodoamino acid composition by chromatography on DEAE-cellulose. Monoiodoglucagon isolated by this procedure shows a single band when analyzed by polyacrylamide gel electrophoresis. Iodoglucagons containing an average of 1 to 4 g-atoms of iodine per mol are more potent than native glucagon in their ability to stimulate adenylate cyclase activity and to bind to glucagon receptors of liver cell membranes of the rat. The maximal increase in biological potency occurring upon iodination is about 5-fold with respect to adenylate cyclase activity, and 2-fold with respect to binding to receptors; tetra and triiodinated derivatives show, respectively, the highest potency. Similar effects occur whether inactivation by liver membranes is inhibited or not, indicating an enhancement in the intrinsic affinity of iodoglucagon for the receptors. Iodination beyong 4 g-atoms per mol slightly decreases the affinity of the hormone for adenylate cyclase and for the receptors. Iodination causes a 2-20 fold decrease in the ability of liver plasma membranes and of blood plasma to inactivate glucagon in vitro; these effects correlate with the degree of iodination. With liver microsomal membranes, a decrease in glucagon inactivation occurs only at iodine contents exceeding 4 g-atoms per mol, and lower degrees of iodination result in opposite effects. Monoiodination causes a 4-6-fold increase in the plasma concentration of glucagon within the first 18 min following a single intrvenous injection of the hormone to rats. More extensive iodination results, in addition, in a marked decrease in the rate of dissappearance of glucagon from the blood. The immunological reactivity of glucagon is little affected by monoidination, but strongly depressed by higher degrees of iodination...     

Calreticulin-melatonin. An unexpected relationship.

Increasing evidence suggests that melatonin can exert some effect at nuclear level. Previous experiments using binding techniques clearly showed the existence of specific melatonin binding sites in cell nucleus of rat liver. To further identify these sites, nuclear extracts from rat hepatocytes were treated with different percentages of ammonium sulfate and purified by affinity chromatography. Subsequent ligand blot analysis shows the presence of two polypeptides of approximately 60 and approximately 74 kDa that bind specifically to melatonin. N-Terminal sequence analysis showed that the 60 kDa protein shares a high homology with rat calreticulin, whereas the 74 kDa protein shows no homology with any known protein. The binding of melatonin to calreticulin was further characterized incubating 2-[125I]melatonin with recombinant calreticulin. Binding kinetics show a Kd = 1.08 +/- 0.2 nm and Bmax = 290 +/- 34 fmol.mg protein-1, compatible with other binding sites of melatonin in the cell. The presence of calreticulin was further identified by Western blot analysis, and the lack of endoplasmic reticulum contamination in our material was assessed by Western blot and immunostaining with anti-calnexin Ig. The results suggest that calreticulin may represent a new class of high-affinity melatonin binding sites involved in some functions of the indoleamine including genomic regulation.     

An h.p.l.c. assay for protoporphyrinogen oxidase activity in rat liver.

An h.p.l.c. method is described for the assay of protoporphyrinogen oxidase activity in rat liver. A relatively pure protoporphyrinogen IX substrate was obtained by selectively removing any protoporphyrin IX unreduced by sodium amalgam on a small disposable cartridge packed with a strong anion-exchanger. The protoporphyrin IX formed was extracted with dimethyl sulphoxide/methanol (3:7, v/v) containing mesoporphyrin as the internal standard for separation and quantification by reversed-phase chromatography. The Km for protoporphyrinogen was 9.5 +/- 1.6 microM, and the enzyme activities were 0.59 +/- 0.11 nmol of protoporphyrin IX produced/min per mg of mitochondrial protein and 33.5 +/- 2.7 nmol protoporphyrin IX produced/min per g of liver tissue homogenate. The method is applicable to the determination of enzyme activity in small amounts of human liver biopsy.     

Supergenes in polymorphic land snails. I. Partula taeniata.

The general colour of the shell in Partula taeniata is controlled by at least two loci. One of these (C) has a series of six alleles which determine the yellow (Y) and neutral brown (N) series of colours. Alleles for darker colours are dominant to those for lighter colours, but dominance is not always complete. The pink (P) colours are determined by a second locus (P) which modified the expression of the lighter alleles of the C locus. Orangeshell colour segregates with yellow but its allelic relationship is unknown. Colour of the lip is controlled by a locus (L) with pink lip dominant to white lip. The colour of the spire is determined by a locus (S) with dark (N4) spire dominant to light spire. An intermediate spire colour shows the same pattern of inheritance and may represent the effect of another allele. Banding of the shell is dominant to absence of bands, with two loci (B1 and B2) determining the type of banding. An allele at B1 produces the frenata pattern; an allele at B2 produces zonata; together they produce lyra. All the loci for which linkage data are available are linked so strongly that the whole array may be considered a supergene. Self-fertilisation takes place primarily during early reproductive life. About 20 per cent of the young of the first mating of an individual are produced by selfing, but over the whole reproductive span the frequency is only about 2-5 per cent. There is inconclusive evidence for heterozygote advantage of banded individuals.     

R.M. Cowling,D.M. Richardson & S.M. Pierce (eds.) 1977. Vegetation of Southern Africa.

We determined the role of bird dispersal in seed and seedling dynamics of the tree Kalopanax pictus from 7 years of observing seed rain and seedling emergence in a broad-leaved deciduous forest in central Japan. We also performed an experiment on the influence of seed pulp on germination of seeds of K. pictus. Seeds of this species can lie dormant for several years, and this causes rather constant yearly seedling emergence in spite of irregular seed production. The spatial distribution of the seedlings that emerged each year (maximum distance from nearest conspecific seed-bearing tree of 90 m) was wider than that of gravity-dispersed seeds (max. distance of 37 m), suggesting seed dispersal by birds in winter. Emerged seedling densities at sites over 20 m from the nearest conspecific seed-bearing tree were highest in the spring of 1991, about half a year after the largest seed fall of the observation period. However, emerged seedling densities within 20 m from seed-bearing trees were highest in 1992, 1.5 years after the largest seed fall. These field observations may be explained by the experimental results on the effects of seed pulp on germination. Intact seeds germinate slowly at low germination rates, while seeds without seed pulp germinate quickly at high germination rates. Fallen seeds with seed pulp thus appear to form a seed bank near seed sources (temporal dispersal), while seeds scattered by birds appear to increase the possibility of reaching the present safe sites in distant areas with quick germination (spatial dispersal).     

Saccharopine dehydrogenase. Substrate inhibition studies.

In the direction of reductive condensation of alpha-ketoglutarate and lysine, saccharopine dehydrogenase (N6-(glutar-2-yl)-L-lysine:NAD oxidoreductase (lysine-forming) is inhibited by high concentrations of alpha-ketoglutarate and lysine, but not by NADH. NAD+ and saccharopine show no substrate inhibition in the reverse direction. Substrate inhibition by alpha-ketoglutarate and lysine is linear uncompetitive versus NADH. However, when the inhibition is examined with alpha-ketoglutarate or lysine as the variable substrate, the double reciprocal plots show a family of curved lines concave up. The curvature is more pronounced with increasing concentrations of the inhibitory substrate, suggesting an interaction of variable substrate with the enzyme form carrying the inhibitory substrate. These inhibition patterns, the lack of interaction of structural analogs of lysine such as ornithine and norleucine with the E-NAD+ complex (Fujioka M., and Nakatani, Y. (1972) Eur. J. Biochem. 25, 301-307), the identity of values of inhibition constants of alpha-ketoglutarate and lysine obtained with either one as the substrate inhibitor, and the substrate inhibition data in the presence of a reaction product, NAD+, are consistent with the mechanism that substrate inhibition results from the formation of a dead-end E-NAD+-alpha-ketoglutarate complex followed by the addition of lysine to this abortive complex.     

The glycolipids of Lactobacillus casei A.T.C.C. 7469

1. The lipids were extracted from Lactobacillus casei A.T.C.C. 7469 with chloroform-methanol mixtures. The glycolipids were obtained by chromatography on silicic acid and DEAE-cellulose (acetate form). 2. Hydrolysis of the glycolipids with alkali gave two glycerol glycosides and a mixture of fatty acids. 3. The glycosides were separated and their structures elucidated. The major component was O-alpha-d-galactopyranosyl-(1-->2)-O-alpha-d-glucopyranosyl-(1-->1)-glycerol and the minor component O-alpha-d-glucopyranosyl-(1-->6)-O-alpha-d-galactopyranosyl-(1-->2)-O-alpha-d-glucopyranosyl-(1-->1)-glycerol. 4. Analysis of the fatty acids by gas-liquid chromatography showed that they were predominantly palmitic acid, octadecenoic acid and lactobacillic acid.     

Vitamin E analogue Trolox C. E.s.r. and pulse-radiolysis studies of free-radical reactions.

The reactions between Trolox C, a water-soluble vitamin E analogue, and several oxidizing free radicals including the hydroxyl radical and various peroxy radicals were examined by using the pulse-radiolysis technique. The results demonstrate that Trolox C may undergo rapid one-electron-transfer reactions as well as hydrogen-transfer processes; the resulting phenoxyl radical is shown to be relatively stable, in common with the phenoxyl radical derived from vitamin E. The reactions between the Trolox C phenoxyl radical and a variety of biologically relevant reducing compounds were examined by using both pulse radiolysis and e.s.r. The results demonstrate that the Trolox C phenoxyl radical is readily repaired by ascorbate (k = 8.3 x 10(6) dm3.mol-1.s-1) and certain thiols (k less than 10(5) dm3.mol-1.s-1) but not by urate, NADH or propyl gallate. Evidence from e.s.r. studies indicates that thiol-containing compounds may also enter into similar repair reactions with the alpha-tocopherol phenoxyl radical. Kinetic evidence is presented that suggests that Trolox C may 'repair' proteins that have been oxidized by free radicals.