Photoproduction of amino acids by mutant strains of N2-fixing cyanobacteria

Summary Mutant strains of the N₂-fixing cyanobacterium bacterium Anabaena variabilis resistant to 6-fluorotryptophan or to ethionine were isolated. Many of these strains liberated amino acids into their media in the absence of 6-fluorotryptophan and ethionine. Nitrogenase activity was higher in mutant strains than in the parent strain. Mutant strains were immobilised in calcium alginate and sustained photoproduction of amino acids has been demonstrated.Abbreviations ETH ethionine - FT 6-fluorotryptophan - Hepes 4-(2-hydroxyethyl)-1, piperazine ethanesulphonic acid - PEP phosphoenolpyruvate - DAHP 3-deoxy-d-arabinoheptulosonate 7-phosphate - chl a chlorophyll a     

The effect of lime on phosphorus adsorption and barley growth in three acid soils

For three acid soils from Santa Catarina, Brazil, lime application and time of incubation with lime had little effect on the adsorption of added phosphorus. In two soils with high contents of exchangeable aluminium, solution P and isotopically exchangeable P were decreased by incubating with lime for 1 month: phosphorus was probably adsorbing on freshly precipitated aluminium hydrous oxides. In one soil with less exchangeable aluminium, P in solution was increased by liming. After 23 months lime increased solution and exchangeable P possibly due to crystallization of aluminium hydrous oxides reducing the number of sites for P adsorption. All these changes were however small. In a pot experiment, lime and phosphorus markedly increased barley shoot and root dry matter and P uptake. Although liming reduced P availability measured by solution P, isotopically exchangeable P and resin extractable P, it increased phosphorus uptake by reducing aluminium toxicity and promoting better root growth. The soil aluminium saturation was reduced by liming, but the concentration of aluminium in roots changed only slightly. The roots accumulated aluminium without apparently being damaged.     

Enzymic synthesis,chemical characterisation and Sda activity of GalNAcß1-4[NeuAcα2-3]Galß1-4GlcNAc and GalNAcß1-4[NeuAcα2-3]Galß1-4Glc

The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and¹H-500 MHz NMR spectroscopy. In Sd^a serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity.     

Expression of glutamine synthetase in mutant strains of the cyanobacterium Anabaena variabilis which liberate ammonia

Abstract The nucleoside analogue ganciclovir has clinical efficacy in the treatment of serious infections with human cytomegalovirus (CMV) in AIDS patients. The mechanism of action of the drug against CMV is different from that described for herpes simplex viruses (HSVs) as the crucial formation of the monophosphate derivative appears to be carried out by cellular rather than virus-coded enzymes. Adenovirus infections also induce the expression of cellular genes including kinase activity and a novel DNA polymerase and the results reported here show that these viruses are sensitive to ganciclovir. The 50% effective dose (ED₅₀) range for known serotypes and one clinical isolate was 4.5−33 μM. By comparison with the sensitivity of CMV in vitro and the known clinical response of infections with this virus to ganciclovir, our results suggest that this drug or its analogous may form the basis of chemotherapy for adenovirus infections.     

Complex sex-linked fusion heterozygosity in the Australian huntsman spider Delena cancerides (Araneae: Sparassidae)

In the vast majority of spider species studied to date, the karyotype is homogeneous in morphology and exclusively telocentric. The sex-determining system consists of one to three X chromosomes in the male and, correspondingly, two to six in the female. This is the case in species of huntsman spiders belonging to the genera Heteropoda (2n=40+3X), Isopoda, Olios, and Pediana (2n=40+3X) and some populations of the colonial species Delena cancerides (2n=40+3X). In other populations of D. cancerides, wholesale fusion of the karyotype has occurred, reducing the standard huntsman karyotype of 43 telocentric chromosomes to 21 metacentrics and 1 telocentric. Eight of the centric fusion products, including an X-autosome fusion, are maintained in the heterozygous condition in males and, with the single telocentric, form a chain of nine chromosomes at meiosis. The two complexes comprising the chain behave as neo-X and neo-Y chromosomes, and thus the ancestral X₁X₂X₃X₁X₁X₂X₂X₃X₃ sex-determining system has been converted to a system of six X and four Y chromosomes in the male and twelve X chromosomes in the female. Since sex-linked complex heterozygosity is also found in a number of species of social termites, it is suggested that such heterozygosity may have adaptive significance for a colonial lifestyle. Breakdown products of the chain of nine are present in specimens of D. cancerides from Canberra and these appear to represent hybrid products between the 2n=22 and 2n=43 forms. Hybridisation may also have been involved in the origin of the chain-forming races.     

The uptake and metabolism of methylamine by N2-fixing cyanobacteria

The cyanobacteria Anabaena variabilis and Nostoc CAN showed a biphasic pattern of ¹⁴CH₃NH ₃ ⁺ uptake at external pH values of 7.0 and 9.0. The initial phase of uptake, which was independent of metabolism of ¹⁴CH₃NH ₃ ⁺ , was attributed to uptake via a CH₃NH ₃ ⁺ (NH ₄ ⁺ ) transport system at pH 7.0 and probably to passive diffusion of uncharged CH₃NH₂ and trapping by protonation at pH 9.0. The second slower phase of uptake was attributed to metabolism of CH₃NH ₃ ⁺ via glutamine synthetase to form -methylglutamine which accumulates. Anabaena cylindrica showed an initial rapid uptake at pH 7.0 and pH 9.0 but metabolism of ¹⁴CH₃NH ₃ ⁺ was undetectable at pH 7.0 and was barely detectable at pH 9.0. Pretreatment of A. variabilis with l-methionine-d,l-sulphoximine to inactivate glutamine synthetase, inhibited the second phase of ¹⁴CH₃NH ₃ ⁺ uptake at both pH 7.0 and pH 9.0 and the accumulation of -methylglutamine but had no effect on the first phase of uptake. Following transfer of A. variabilis to darkness the initial phase of ¹⁴CH₃NH ₃ ⁺ uptake at pH 7.0 and 9.0 was unaffected but the subsequent metabolism via glutamine synthetase was inhibited.Abbreviations MSX l-methionine-d,l-sulphoximine - GS glutamine synthetase     

Forest living baboons in Uganda

The climate and vegetation of the study area is described: in many ways it was not typical of baboon habitats in Uganda, but had the advantage and interest of offering a clear choice of a variety of habitats. The structure and composition of the baboon population is described Ndashthis was a rapidly expanding population with no seasonality in breeding. Their use of the     

Hypoxemia raises muscle sympathetic activity but not norepinephrine in resting humans

The experimental objective was to determine whether moderate to severe hypoxemia increases skeletal muscle sympathetic nervous activity (MSNA) in resting humans without increasing venous plasma concentrations of norepinephrine (NE) and epinephrine (E). In nine healthy subjects (20-34 yr), we measured MSNA (peroneal nerve), venous plasma levels of NE and E, arterial blood pressure, heart rate, and end-tidal O2 and CO2 before (control) and during breathing of 1) 12% O2 for 20 min, 2) 10% O2 for 20 min, and 3) 8% O2 for 10 min--in random order. MSNA increased above control in five, six, and all nine subjects during 12, 10, and 8% O2, respectively (P less than 0.01), but only after delays of 12 (12% O2) and 4 min (8 and 10% O2). MSNA (total activity) rose 83 +/- 20, 260 +/- 146, and 298 +/- 109% (SE) above control by the final minute of breathing 12, 10, and 8% O2, respectively. NE did not rise above control at any level of hypoxemia; E rose slightly (P less than 0.05) at one time only with both 10 and 8% O2. Individual changes in MSNA during hypoxemia were unrelated to elevations in heart rate or decrements in blood pressure and end-tidal CO2--neither of which always fell. We conclude that in contrast to some other sympathoexcitatory stimuli such as exercise or cold stress, moderate to severe hypoxemia increases leg MSNA without raising plasma NE in resting humans.     

Evidence for Functional Activity of Up-Regulated Nicotine Binding Sites in Rat Striatal Synaptosomes

A number of studies have found that the chronic administration of nicotine causes an increase in the density of nicotinic binding sites in the brain, but it is not known whether these additional binding sites are functionally active receptors. In this study, the effects of 1-week administration of the potent nicotinic agonist, (+)-anatoxin-a (96 nmol/day via osmotic minipumps), was assessed on [3H]nicotine binding and [3H]dopamine uptake and release in rat striatal synaptosomes. Chronic (+)-anatoxin-a treatment resulted in a 32% increase in the Bmax of [3H]nicotine binding in anatoxin-treated animals compared to control. There was a 43% increase in the activity of 3 microM nicotine to release [3H]dopamine from synaptosomes of anatoxin-treated animals, but the release induced by 20 mM K+ depolarization was unaffected. There was no effect of chronic (+)-anatoxin-a treatment on the uptake of [3H]dopamine. A strong positive correlation (r = 0.64) was found between the density of [3H]nicotine binding sites and the nicotine-induced stimulation of [3H]dopamine release in individual animals. These results indicate that (+)-anatoxin-a, like nicotine, produces an up-regulation of nicotine binding sites following chronic administration, and that these additional sites are functional receptors capable of mediating the release of dopamine from striatal synaptosomes.