Sulphate reduction in oxic and sub-oxic North-East Atlantic sediments

Abstract Oxic and sub-oxic N.-E. Atlantic sediments were examined for sulphate-reducing activity. Oxygen and/or nitrate reduction are probably the dominant mineralisation processes in the abyssal plain sediment studied. A low rate of sulphate reduction (0.1 nmol SO²⁻₄/ml/day) was recorded in the surface 5 cm of the continental slope sediment, together with the presence of a range of sulphate-reducing bacteria (SRB). A higher activity of sulphate reduction (2.2 nmol SO²⁻₄/ml/day) occurred in the continental shelf sediment which led to a small decrease in pore water sulphate and an increase in titration alkalinity. This sediment contained approx. 10²–10³ acetate, lactate and propionate oxidising SRB/ml. No low- M _r organic acids were detected in these sediments. However, amendment with 75 μM acetate stimulated sulphate-reducing activity in the shelf sediment.     

Molecular cloning and nucleotide sequences of cDNAs specific for rat liver ribosomal proteins S17 and L30

cDNA clones coding for rat liver ribosomal proteins S17 and L30 have been isolated by positive hybridization-translation assay from a cDNA library prepared from 8-9S poly(A)+RNA from free polysomes of regenerating rat liver. The cDNA clone specific for S17 protein (pRS17-2) has a 466-bp insert with the poly(A) tail. The complete amino acid (aa) sequence of S17 protein was deduced from the nucleotide sequence of the cDNA. S17 protein consists of 134 aa residues with an Mr of 15 377. The N-terminal aa sequence of S17 protein determined by automatic Edman degradation is consistent with the sequence data. The aa sequence of S17 shows strong homology (76.9%) to that of yeast ribosomal protein 51 [Teem and Rosbash, Proc. Natl. Acad. Sci. USA 80 (1983) 4403-4407] in the two-thirds N-terminal region. The cDNA clone specific for L30 protein (pRL30) has a 394-bp insert. The aa sequence of L30 protein was deduced from the nucleotide sequence of the cDNA. The protein consists of 114 aa residues with an Mr of 12 652. When compared with the N-terminal aa sequence of rat liver L30 protein [Wool, Annu. Rev. Biochem. 48 (1979) 719-754], pRL30 was found not to contain the initiation codon and 5'-noncoding region. The cDNA showed twelve silent changes in the coding region, one point mutation and one base deletion in the 3'-noncoding region, compared with mouse genomic DNA for L30 protein [Wiedemann and Perry, Mol. Cell Biol. 4 (1984) 2518-2528].     

Biochemical characteristics of adhesion factors isolated from the retina of 8-day-old chick embryos

While isoelectrofocusing the extracts obtained after dissociation of the retina of eight day old chick embryos, two active protein fractions were found: AF I with pI 3 and AF II with pI below 3. The content of these fractions in the extracts depended on the method of dissociation: treatment with EDTA increased the content of AF II, whereas trypsin treatment increased the yield of AF I. After electrophoresis in the denaturating conditions both fractions were divided in two components. The effect of AF I on aggregation of retinal cells, unlike that of AF II, does not depend on the presence of bivalent cations in the medium and is realized within 1 h of interaction with the cells at 4 degrees. It is suggested that the retinal extracts of eight day old chick embryos contain substances providing two types of adhesiveness: Ca2+-independent (AF I) and Ca2+-dependent (AF II).     

Laryngeal influences on breathing pattern and posterior cricoarytenoid muscle activity

Receptors responding to transmural pressure, airflow, and contraction of laryngeal muscles have been previously identified in the larynx. To assess the relative contribution of these three types of receptors to the reflex changes in breathing pattern and upper airway patency, we studied diaphragmatic (DIA) and posterior cricoarytenoid muscle (PCA) activity in anesthetized dogs during spontaneous breathing and occluded efforts with and without bypassing the larynx. Inspiratory duration (TI) was longer, mean inspiratory slope (peak DIA/TI) was lower, and PCA activity was greater with upper airway occlusion than with tracheal occlusion (larynx bypassed). Bilateral section of the superior laryngeal nerves eliminated these differences. When respiratory airflow was diverted from the tracheostomy to the upper airway the only change attributable to laryngeal afferents was an increase in PCA activity. These results confirm the importance of the superior laryngeal nerves in the regulation of breathing pattern and upper airway patency and suggest a prevalent role for laryngeal negative pressure receptors.     

Assessment of pharyngeal airway stability in normal and micrognathic infants

A current hypothesis for obstructive sleep apnea states that 1) negative airway pressure during inspiration can collapse the pharyngeal airway, and 2) neural control of pharyngeal airway-dilating muscles is important in preventing this collapse. To test this hypothesis we performed nasal mask occlusions to increase negative pharyngeal airway pressures during inspiration in eight normal and five micrognathic infants. Both groups developed midinspiratory pharyngeal obstruction, but obstruction was more frequent in micrognathic infants and varied in some infants with sleep state. The airway usually reopened with the subsequent expiration. The occasional failure to reopen was presumably due to pharyngeal wall adhesion. If airway obstruction occurred in sequential breaths during multiple-breath nasal mask occlusions in normal infants, there was a breath-by-breath change in the airway pressure associated with airway closure (airway closing pressure); the airway closing pressure became progressively more negative. Micrognathic infants showed less ability to improve the airway closing pressure, but this ability increased with age. These findings suggest that nasal mask occlusion can test the competence of the neuromuscular mechanisms that maintain pharyngeal airway patency in infants. Micrognathic infants had spontaneous midinspiratory pharyngeal airway obstructions during snoring. Their episodes of obstructive apnea began with midinspiratory pharyngeal obstruction similar to that seen during snoring and nasal mask occlusions. These findings imply a similar pathophysiology for snoring, spontaneous airway obstruction, and obstruction during snoring.     

Deposition of type X collagen in the cartilage extracellular matrix

In cultured chick embryo chondrocytes, type X collagen is preferentially deposited in the extracellular matrix, the ratio between type II and type X collagen being about 5 times higher in the culture medium than in the cell layer. When the newly synthesized collagens deposited in slices from the epiphyseal cartilage of 17-day-old embryo tibiae were isolated, type X collagen was always the major species. In agreement with this result the mRNA for type X collagen was the predominant mRNA species purified from the same tissue. When the total collagen (unlabeled) deposited in the epiphyseal cartilage was analyzed, it was observed that type X collagen represented only 1/15 of the type II collagen recovered in the same preparation. The possible explanations for these differences are discussed.     

DNA single-strand breaks,double-strand breaks,and crosslinks in rat testicular germ cells: Measurements of their formation and repair by alkaline and neutral filter elution

This work describes a neutral and alkaline elution method for measuring DNA single-strand breaks (SSBs), DNA double-strand breaks (DSBs), and DNA-DNA crosslinks in rat testicular germ cells after treatments in vivo or in vitro with both chemical mutagens and gamma-irradiation. The methods depend upon the isolation of testicular germ cells by collagenase and trypsin digestion, followed by filtration and centrifugation. ¹³⁷Cs irradiation induced both DNA SSBs and DSBs in germ cells held on ice in vitro. Irradiation of the whole animal indicated that both types of DNA breaks are induced in vivo and can be repaired. A number of germ cell mutagens induced either DNA SSBs, DSBs, or cross-links after in vivo and in vitro dosing. These chemicals included methyl methane sulfonate, ethyl methane sulfonate, ethyl nitrosurea, dibromochlorpropane, ethylene dibromide, triethylene melamine, and mitomycin C. These results suggest that the blood-testes barrier is relatively ineffective for these mutagens, which may explain in part their in vivo mutagenic potency.This assay should be a useful screen for detecting chemical attack upon male germ-cell DNA and thus, it should help in the assessment of the mutagenic risk of chemicals. In addition, this approach can be used to study the processes of SSB, DSB, and crosslink repair in DNA of male germ cells, either from all stages or specific stages of development.Abbreviations DBCP dibromochlorpropane - DSB(s) DNA double-strand break(s) - EDB ethylene dibromide - EMS ethyl methane sulfonate - ENU ethyl nitrosurea - MC mitomycin C - MMS methyl methane sulfonate - SDS sodium dodecyl sulfate - SSB (s) DNA single-strand break(s) - TEM triethylene melamine - UDS unscheduled DNA synthesis     

Mitochondrial monoamine oxidase activity during preneural developmental stages of Bufo bufo

Monoamine oxidase specific activities against PEA and 5-HT have been measured in mitochondria isolated from early embryos of Bufo bufo. During the early development up to the neural fold stage, MAO activity undergoes a continuous decrease that is more evident when PEA is used as the substrate. The inhibition patterns of deprenyl and clorgyline demonstrate that, at the neural fold stage, both type A and B MAO are present. Both in eggs and embryos MAO type A activity appears slightly more sensitive to the inhibitory effect of various concentrations (0.1-2 M) of the denaturing agent urea.     

Isolation and purification of deoxyribonucleosides from 90% 13C-enriched DNA of algal cells and their characterization by 1H and 13C NMR.

13C-enriched deoxyribonucleosides have been isolated from the DNA of Algal cells grown in an atmosphere of 90% 13C-labelled carbon dioxide. The 13C enriched DNA was quantitatively hydrolysed with DNase I, snake venom phosphodiesterase I and alkaline phosphatase of intestinal mucosa. The resulting deoxyribonucleosides were separated by preparative reversed-phase high pressure liquid chromatography in 60 minutes with detection by ultraviolet absorption at 254 nm. The final products were obtained in milligram quantities in high purity and in high yield. The 1H resonances of the base and sugar protons of these deoxyribonucleosides appear as well resolved multiplets in the 600 MHz NMR spectrum, due to the extensive 1H-13C couplings. Similarly, the 13C resonances of these deoxyribonucleosides appear as multiplets in the 75.5 MHz 13C NMR spectrum, due to 13C-13C couplings. The 1H-13C and 13C-13C coupling constants were also measured and tabulated. The isotopic enrichment of 13C these deoxyribonucleosides was obtained by integration of the 1H and/or 13C NMR spectra. It was found that the enrichment varied from carbon to carbon and species to species in the range of 70-89%, suggesting differential uptake and assimilation of 90% 13CO2 during metabolism pathways. This protocol provides experimentally useful quantities of 13C-enriched deoxyribonucleosides, which may be incorporated into site-specifically labeled oligonucleotides by chemical synthesis.     

Molecular organization of dinoflagellate ribosomal DNA: evolutionary implications of the deduced 5.8 S rRNA secondary structure

The 5.8 S rRNA gene of Prorocentrum micans, a primitive dinoflagellate, has been cloned and its 159 base pairs (bp) have been sequenced along with the two flanking internal transcribed spacers (ITS 1 and 2), respectively, 212 and 195 bp long. Nucleotide sequence homologies between several previously published 5.8 S rRNA gene sequences including those from another dinoflagellate, an ascomycetous yeast, protozoans, a higher plant and a mammal have been determined by sequence alignment. Two prokaryotic 5'-ends of the 23 S rRNA gene have been compared owing to their probable common origin with eucaryotic 5.8 S rRNA genes. Several nucleotides are distinctive for dinoflagellates when compared with either typical eucaryotes or procaryotes. This is consistent with an early divergence of the dinoflagellate lineage from the typical eucaryotes. The secondary structure of dinoflagellate 5.8 S rRNA molecules fits the model of Walker et al. (1983). Conserved nucleotides which distinguish dinoflagellate 5.8 S rRNA from that of other eucaryotes are located in specific loops which are assumed to play a structural role in the ribosome. A 5.8 S rRNA phylogenetic tree which is proposed, based on sequence data, supports our initial assumption of the dinoflagellates.