The role of protons in a medium in gamma-radiation-induced damage of nucleic acids

The study of the combined effect of gamma-radiation and acid medium (pH 7.0-2.0) on DNA and RNA showed that the radiation-induced injury to nucleic acids increased with increasing concentration of H+-ions in the medium up to pH values below which protons exerted a protective action. Irradiation of native DNA in acid medium, as compared to neutral one, increased not only the number of injured bases but also the average size of the induced local defect in the secondary structure. It was shown that the proton sensitization was determined both by the number of protonated bases and by the degree of ordering the polynucleotide chain.     

Volatile fatty acids as indicators of process imbalance in anaerobic digestors

In continuously stirred tank reactor experiments, with manure as substrate at thermophilic temperatures, the use of volatile fatty acids (VFA) as process indicators was investigated. Changes in VFA level were shown to be a good parameter for indicating process instability. The VFA were evaluated according to their relative changes caused by changes in hydraulic loading, organic loading or temperature. Butyrate and isobutyrate together were found to be particularly good indicators. Butyrate and isobutyrate concentrations increased significantly 1 or 2 days after the imposed perturbation, which makes these acids suitable for process monitoring and important for process control of the anaerobic biological system. In addition it was shown in a batch experiment that VFA at concentrations up to 50 mM did not reduce the overall methane production rate. This showed that VFA accumulation in anaerobic reactors was the result of process imbalance, not the cause of inhibition, thus justifying the use of VFA as process indicators.     

Degradation of commercial detergent products by microbial populations of the Lagos lagoon

The biodegradability potentials of three detergent products with the trade names Omo, Teepol and sodium dodecyl sulfate (SDS) by the native bacteria of the Lagos lagoon was carried out using the lagoon die-away method. Physicochemical parameters of the water samples showed that the lagoon in Apapa was more polluted than at theUniversity of Lagos. In 12 days, approximately 30, 60 and 97% of Omo, Teepol and SDS respectively were degraded. SDS with an alkyl sulfate moiety as surfactant supported the highest growth of the detergent-utilizing organisms, indicating that the components of Omo and Teepol are more resistant to microbial attack. The detergent-utilizing bacteria identified were mainly Gram-negative and of the following genera:Vibrio, Klebsiella, Flavobacterium, Pseudomonas, Escherichia, Enterobacter, Proteus, Shigella andCitrobacter. Vibrio was the most frequently encountered organism whileProteus was the rarest. Results of this investigation had shown that detergents made in Nigeria may still contain components that are recalcitrant to biodegradation.     

Evidence indicating that pig renal phosphate-activated glutaminase has a functionally predominant external localization in the inner mitochondrial membrane

Phosphate-activated glutaminase in intact pig renal mitochondria was inhibited 50-70% by the sulfhydryl reagents mersalyl and N-ethylmaleimide (0.3-1.0 mM), when assayed at pH 7.4 in the presence of no or low phosphate (10 mM) and glutamine (2 mM). However, sulfhydryl reagents added to intact mitochondria did not inhibit the SH-enzyme beta-hydroxybutyrate dehydrogenase (a marker of the inner face of the inner mitochondrial membrane), but did so upon addition to sonicated mitochondria. This indicates that the sulfhydryl reagents are impermeable to the inner membrane and that regulatory sulfhydryl groups for glutaminase have an external localization here. The inhibition observed when sulfhydryl reagents were added to intact mitochondria could not be attributed to an effect on a phosphate carrier, but evidence was obtained that pig renal mitochondria have also a glutamine transporter, which is inhibited only by mersalyl and not by N-ethylmaleimide. Mersalyl and N-ethylmaleimide showed nondistinguishable effects on the kinetics of glutamine hydrolysis, affecting only the apparent Vmax for glutamine and not the apparent Km calculated from linear Hanes-Woolf plots. Furthermore, both calcium (which activates glutamine hydrolysis), as well as alanine (which has no effect on the hydrolytic rate), inhibited glutamine transport into the mitochondria, indicating that transport of glutamine is not rate-limiting for the glutaminase reaction. Desenzitation to inhibition by mersalyl and N-ethylmaleimide occurred when the assay was performed under optimal conditions for phosphate activated glutaminase (i.e. in the presence of 150 mM phosphate, 20 mM glutamine and at pH 8.6). Desenzitation also occurred when the enzyme was incubated with low concentrations of Triton X-100 which did not affect the rate of glutamine hydrolysis. Following incubation with [14C]glutamine and correction for glutamate in contaminating subcellular particles, the specific activity of [14C]glutamate in the mitochondria was much lower than that of the surrounding incubation medium. This indicates that glutamine-derived glutamate is released from the mitochondria without being mixed with the endogenous pool of glutamate. The results suggest that phosphate-activated glutaminase has a functionally predominant external localization in the inner mitochondrial membrane.     

Antibiotic activity of isoxazolylnaphthoquinone imines on mice infected with Staphylococcus aureus

I. ALBESA, P. BOGDANOV, A. ERASO, N.R. SPERANDEO AND M.M. DE BERTORELLO. 1995. The antibiotic activity of new synthetic isoxazolylnaphthoquinone imines was studied. Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922 were resistant to the four compounds studied (MIC > 128 µg ml⁻¹), but Staphylococcus aureus ATCC 25923, ATCC 29213 and 30 clinical isolates of Staph. aureus were inhibited by 2-hydroxy- N -(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinone-4-imine (I). This compound diminished bloodstream infection of mice injected i.m. with Staph. aureus; septicaemia decayed significantly when I was applied at the beginning of the infection while when I was given 3 d after bacterial challenge, a significant protection was afforded. Bactericidal activity in serum increased during the 5 h after I was administered i.p.
The acetyl derivative of I had a high MIC but when inoculated orally in mice decreased the Staph. aureus counts in circulation. This protection occurred only when the schedule of administration started close to the bacterial challenge. Antibiotic activity in vivo may be associated with in vitro effects.     

Active papain renatured and processed from insoluble recombinant propapain expressed in Escherichia coli.

For the first time the pro-form of a recombinant cysteine proteinase has been expressed at a high level in Escherichia coli. This inactive precursor can subsequently be processed to yield active enzyme. Sufficient protein can be produced using this system for X-ray crystallographic structure studies of engineered proteinases. A cDNA clone encoding propapain, a precursor of the papaya proteinase, papain, was expressed in E. coli using a T7 polymerase expression system. Insoluble recombinant protein was solubilized in 6 M guanidine hydrochloride and 10 mM dithiothreitol, at pH 8.6. A protein-glutathione mixed disulphide was formed by dilution into oxidized glutathione and 6 M GuHCl, also at pH 8.6. Final refolding and disulphide bond formation was induced by dilution into 3 mM cysteine at pH 8.6. Renatured propapain was processed to active papain at pH 4.0 in the presence of excess cysteine. Final processing could be inhibited by the specific cysteine proteinase inhibitors E64 and leupeptin, but not by pepstatin, PMSF or EDTA. This indicates that final processing was due to a cysteine proteinase and suggests that an autocatalytic event is required for papain maturation.     

Lipid composition of thylakoid membranes of cadmium treated wheat seedlings.

Cadmium (200 ppm) applied through the rooting medium to 30-day-old wheat plants decreased chlorophyll content, net CO2 exchanges and PSII activity by 34, 54 and 43% respectively. Thylakoid total lipids, total glycolipids, total phospholipids and total neutral lipids decreased by 22, 23, 12 and 25%, respectively, under cadmium treatment. Thylakoid membrane glycolipids had three major constituents, viz. monogalactosyl diacylglycerol, digalactosyl diacylglycerol and sulphoquinovosyl diacylglycerol. Monogalactosyl diacylglycerol and digalactosyl diacylglycerol contents decreased by 32 and 27%, respectively, under cadmium. Cadmium application also decreased the concentration of phosphatidyl glycerol and phosphatidyl choline to the extent of about 57 and 31%, respectively. On the other hand, phosphatidic acid and free fatty acids content showed an increase. These compositional changes in thylakoid membranes might be responsible for reduced PSII activity and rate of photosynthesis as observed under cadmium treatment.     

Biosorption of Cd, Zn and Cu by Sargassum sp. waste biomass

Biosorption is becoming an important component in the integrated approach to the treatment of aqueous effluents. The economics of biomass technical applications are improved by using waste biomass instead of purposely-produced biomass. Biomass derived from an alginate extraction industry - Sargassum sp. - was examined for its ability to function as a biosorbent for metals such as cadmium, zinc and copper. For use in column applications, biomass should be immobilized. To the algae reinforcement, the biomass was embedded in polyethleneimine (PEI), followed by glutaraldehyde crosslinking. Equilibrium Zn and Cu isotherms were analysed using the immobilization ratio that showed the best Cd performance. Either Freundlich or Langmuir models can describe the passive biosorption equilibrium of cadmium, zinc and cooper. The preference for this series of metals by the biomass was found to be Cd > Zn > Cu, with maximum uptake values of 157.8, 118.5 and 77.4 mg/g dry weight biomass for Cd, Zn and Cu. respectively. The metal binding capacity by non-living biomass is an important quality for industrial use.     

The lagena (the third otolith endorgan in vertebrates)

In this review, the structure and functions of the lagena (the third otolith organ) in an evolutionary lineage of the vertebrates are described and discussed. The lagenar macula appears first in the posterior part of the sacculus of elasmobranchs; in these animals, the lagena is considered to be involved in the balance support (orientation with respect to the gravitation force). The lagena as a separate endorgan has been described in teleost fishes; in some species, the lagena is connected with the sacculus, while in other species the interrelations of these structures can be dissimilar. The lagena supplements the functions of the sacculus; in fishes (animals with no special organ of hearing), it is involved in discrimination of sound oscillations, identification of the gravitation vector, and orientation in the course of movements within the vertical plane. In amphibians, the lagena is localized in the posterior part of the sacculus, near the auditory structures; it performs mostly vestibular and (to a much lesser extent) auditory functions. In amniotes, the lagena was first separated from the sacculus; it is localized in the cochlear canal, distally with respect to the hearing organ. Information on the functions of the lagena in amniotes is rather limited and contradictory. Central projections of this organ have been examined practically only in birds. Lagenar afferents project to the vestibular nuclei and cerebellum, while some fibers come to the auditory nuclei of the medulla. The lagena in birds can be related to their navigation abilities (birds are supposed to be capable of orienting within the magnetic field of the Earth due to the magnetic properties of the lagenar otoconia; this structure can also provide detection of movements along the vertical axis. The close proximity between the otolithic and auditory endorgans in the cochlear canal of amniotes can be indicative of the functional significance of these interrelations. This aspect, however, remains at present undiscovered. In mammals (except Monotremata), there is no lagena as an independent endorgan. Neirofiziologiya/Neurophysiology, Vol. 40, No. 2, pp. 160–178, March–April, 2008.