Sequence of the S-layer gene of Thermus thermophilus HB8 and functionality of its promoter in Escherichia coli.

The nucleotide sequence of the slpA gene, which is responsible for the synthesis of the S-layer protein of Thermus thermophilus HB8, is described. This gene is transcribed as a unit in which the coding region is preceded by a 127-base-long leader mRNA sequence. The promoter region is also recognized by the RNA polymerase of Escherichia coli because of the presence of homologous -35 and -10 boxes. Homologies with other promoters from Thermus spp. are also presented.     

Effects of Feeding and Drinking on Acetylcholine Release in the Nucleus Accumbens, Striatum, and Hippocampus of Freely Behaving Rats

Extracellular levels of acetylcholine (ACh) were measured in the nucleus accumbens (NAC), striatum (STR), and hippocampus (HIPP) using microdialysis in 30-min intervals before, during, and after free-feeding in 20-h food-deprived rats. The effects on ACh in the NAC and STR were also observed in response to water intake in 20-h water-deprived animals. Neostigmine was used in the perfusate to improve ACh recovery. Basal ACh was sensitive to tetrodotoxin and low calcium, and therefore largely neuronal in origin. Feeding caused a 38% increase in extracellular ACh in the NAC and no change in the STR or HIPP. Dopamine was also increased in the NAC (48%) and to a lesser extent in the STR (21%) following feeding. Drinking caused 18-20% increases in ACh release in both the NAC and STR. In a separate experiment, ACh release in the NAC was monitored in 10-min intervals during free-feeding; ACh increased in the interval immediately following maximal food intake. These results suggest a site-specific increase in ACh release following feeding that cannot be solely attributed to the activation associated with this behavior.     

In vivo and in vitro effects of boron on the plasma membrane proton pump of sunflower roots

The effect of boron excess and deficiency on H⁺ efflux from excised roots from sunflower ( Heliarahus annuus L. cv. Enano) seedlings and on plasma membrane H⁺-ATPase (EC 3.6.1.35) in isolated KI-washed microsomes has been investigated. When seedlings were grown in media with toxic levels of H₃BO₃ (5 m M ) or without added boron and exposed to light conditions, an inhibition of the capacity for external acidification by excised roots was observed as compared to roots from seedlings grown with optimal H₃BO₃ concentration (0.25 m M ). Toxic and deficient boron conditions also inhibited the vanadate-sensitive H⁺-ATPase of microsomes isolated from the roots. The mechanism of boron toxicity was investigated in vitro with microsorne vesicles. A strong effect of boron on the vanadate-sensitive, ATP-dependent H⁺ transport was found, but the vanadate-sensitive phospho-bydrolase activity was not affected. These results suggest that boron could exert an effect on the plasma membrane properties, directly or indirectly regulating, proton transport.     

One-step synthesis of Gly-Gly-PheNH2 from N-unprotected amino acid derivatives by papain in one-phase liquid media

Summary Papain was able to catalyze the one-step synthesis of Gly-Gly-PheNH₂, from N-unprotected amino acid derivatives. Maximum synthetic activity was obtained for a pH value of 6.5 and for a ]PheNH₂]/[Gly-GlyOEt] ratio of 6. The presence of an organic cosolvent, such as ethylene glycol, influenced the synthetic activity. Synthetic yield was higher than 65% for a 12.5 M cosolvent concentration.     

Kinetics of aerobic biodegradation of benzene and toluene in sandy aquifer material

Monod's equation adequately described aerobic biodegradation rates of benzene and toluene by the microbial population of a sandy aquifer when these compounds were initially present at concentrations lower than 100 mg/l each. Concentrations higher than 100 mg/l were inhibitory, and no benzene or toluene degradation was observed when these compounds were initially present at 250 mg/l each. The Monod coefficients were calculated as k = 8.3 g-benzene/g-cells/day and Ks = 12.2 mg/l for benzene, and k = 9.9 g-toluene/g-cells/day and Ks = 17.4 mg/l for toluene. Specific first-order coefficients would be 0.68 l/mg.day for benzene and 0.57 l.mg.day for toluene.     

Plasma determination of the novel anticonvulsant d,l-3-hydroxy-3-ethyl-3-phenylpropionamide and preliminary pharmacokinetic studies in the rat

A sensitive gas chromatographic method with flame ionization detection was developed for the analysis in plasma of the novel anticonvulsant d,l-3-hydroxy-3-ethyl-3-phenylpropionamide (HEPP), using d,l-2-hydroxy-2-ethyl-2-phenylacetamide as the internal standard. HEPP was extracted from alkalinized plasma into dichloromethane and quantified after derivatization with bis(trimethylsilyl)-trifluoroacetamide. Standard curves were linear from 0.5 to 50 and from 2 to 100 μg/ml of plasma, using 1.5 and 5 μg of the internal standard, respectively. The lower limit of detection at a signal-to-noise ratio of 3 standard deviations was 0.33 μg/ml of sample. The sensitivity, accuracy and reproducibility of the method were shown to be satisfactory for pharmacokinetic studies of HEPP. After intraperitoneal administration of 50 mg/kg to Wistar rats, the principal kinetic parameters were: absorption half-life = 0.04 h; volume of distribution = 1.32 l/kg; clearance = 4.40 ml/min; peak concentration = 50 μg/ml; peak time = 0.25 h; mean residence time = 4.55 h.     

Effects of eel (Anguilla anguilla L.) removals from selected sites of a stream on its subsequent densities

We assessed the effect of eel (Anguilla anguilla) removal from three sites of a Cantabrian stream upon its subsequent densities. In the first sample (Sept. 1986) numbers and densities were estimated as 43, 45 and 84 ind and 3490, 3030 and 3750 ind ha ⁻¹. Removal of these eels reduced the subsequent numbers and densities which, except on two occasions, were never reached again during the two years (eleven estimates) of study. Highest densities were recorded in the uppermost site in May and July, 1987, coincident with a strong drought and the lowest densities occurred in 1988 during a normal wet year. We hypothesize first that, because of a selective underground homing behaviour of eels, electro-fishing is inefficient and results in underestimates of the population. Second, seasonal variations of water discharge and droughts may not influence the homing behaviour of'eels until a threshold of dryness is reached. If this occurs, eels abandon their refuges and move towards the stream bottom. It seems that in Arroyo Chabatchos this threshold was exceeded in the summer of 1987 when the highest densities were estimated. The re-colonization of these sites experimentally depleted of eels, is a slow procces that lasts for, at least, two years.     

Comparison of the folding of 2-Keto-3-deoxy-6-phosphogluconate aldolase,triosephosphate isomerase and pyruvate kinase: Implications in molecular evolution

The 8-fold α/β barrel conformation of 2-keto-3-deoxy-6-phosphogluconate aldolase has been compared to that of triosephosphate isomerase and the A-domain of pyruvate kinase. There are eight supersecondary structure units (α/β) in each of these proteins, and the comparisons were carried out in orientations corresponding to each of the possible congruences, i.e. first to first, first to second,… of the supersecondary structure units. The comparison of the C_α structure of the main chain folding of the three enzymes indicated about 150 equivalences with rootmean-square differences of about 3.1 Å, with no orientational preference, including the aldolase with itself. In addition, there is no sequence homology between the aldolase and the isomerase, and no indication of gene duplication in the former. The lack of orientational preference among the three enzymes suggests convergence to a fold of exceptional stability. However, all three enzymes activate a CH bond adjacent to a carbonyl, and their active sites correspond to the f strand, F helix region of the α/β barrel, thus contradicting the foregoing and suggesting divergent evolution from a common precursor. Other and similar arguments are also presented for and against convergent evolution of these three strikingly similar enzymes.