Fibroblastlike primary cells from human colon adenocarcinoma explants: Collagen biosynthesis

Summary Fibroblastlike primary cells have been obtained from human colon adenocarcinoma explants. Such cells disappear during cell culture and thus have not been previously studied. These cells have a number of altered phenotypic characteristics: a) morphology; b) growth behavior and adherence to culture substrate (they required 3 h for 90% attachment and only presented a flattened morphology 40 h after platting); and c) collagen metabolism. Increased protein biosynthesis (about double than control colon-derived fibroblasts) and maintained ability for collagen biosynthesis have been observed for the tumor-associated fibroblastlike cells. Thus, the collagen to noncollagenous proteins ratio was decreased for these cells. They exhibited an altered type I:type III collagen (5:1 instead of 3:1 in colon fibroblasts) and procollagen (2:1 against 5:1 in colon fibroblasts) ratios as well as a decreased secretion of collagen with an abnormal deposition of procollagens in the cell layer. These studies show a permanent phenotypic alteration in the tumor-associated fibroblastlike cells.     

In vitro studies on the growth of Shigella sonnei by Lactobacillus casei and Lact. acidophilus.

The inhibitory effect of lactobacilli on growth of Shigella sonnei was studied. The effect was not due to pH alone, as addition of hydrochloric, lactic or acetic acids to culture media did not inhibit the normal growth of the shigellas. The degree of inhibition was measured by disc assay and showed that the inhibitory substance(s) can be extracellular and diffusible, varying the degrees of inhibition depending on the media tested. When broth was inoculated with mixed cultures of Lactobacillus and Shigella strains, the inhibition began at 6 h and the death phase at 9 h. The higher inhibition was produced by the mixture of lactobacilli (35.5 +/- 2.5% at 6 h culture, 57.4 +/- 1.9% at 9 h and 91.2 +/- 1.2% at 14 h). The degree of inhibition was higher when the relationship pathogen : lactobacilli was 1:10(3). The specific growth rate of lactobacilli and shigella was different in pure or mixed cultures. When the lactobacillus alone was grown for 12 h and the shigellas then added, the numbers of shigellas began to decrease immediately at 37 degrees C. This work shows that the Lactobacillus strains employed in fermented milk can be used to inhibit the growth of Sh. sonnei.     

Uridine transport in basolateral plasma membrane vesicles from rat liver

Summary The characteristics of uridine transport were studied in basolateral plasma membrane vesicles isolated from rat liver. Uridine was not metabolized under transport measurement conditions and was taken up into an osmotically active space with no significant binding of uridine to the membrane vesicles. Uridine uptake was sodium dependent, showing no significant stimulation by other monovalent cations. Kinetic analysis of the sodium-dependent component showed a single system with Michaelis-Menten kinetics. Parameter values were K _M 8.9 m and V _max 0.57 pmol/mg prot/sec. Uridine transport proved to be electrogenic, since, firstly, the Hill plot of the kinetic data suggested a 1 uridine: 1 Na⁺ stoichiometry, secondly, valinomycin enhanced basal uridine uptake rates and, thirdly, the permeant nature of the Na⁺ counterions determined uridine transport rates (SCN^– > NO ₃ ^– > Cl^– > SO ₄ ^2– ). Other purines and pyrimidines cis-inhibited and trans-stimulated uridine uptake.This work has been partially supported by grant PM90-0162 from D.G.I.C.Y.T. (Ministerio de Educación y Ciencia, Spain). B.R.-M. is a research fellow supported by the Nestlé Nutrition Research Grant Programme.     

Lung tissue behavior during methacholine challenge in rabbits in vivo.

Previous studies have shown that lung challenge with smooth muscle agonists increases tissue viscance (Vti), which is the pressure drop between the alveolus and the pleura divided by the flow. Passive inflation also increases Vti. The purpose of the present study was to measure the changes in Vti during positive end-expiratory pressure- (PEEP) induced changes in lung volume and with a concentration-response curve to methacholine (MCh) in rabbits and to compare the effects of induced constriction vs. passive lung inflation on tissue mechanics. Measurements were made in 10 anesthetized open-chest mechanically ventilated New Zealand male rabbits exposed first to increasing levels of PEEP (3-12 cmH2O) and then to increasing concentrations of MCh aerosol (0.5-128 mg/ml). Lung elastance (EL), lung resistance (RL), and Vti were determined by adjusting the equation of motion to tracheal and alveolar pressures during tidal ventilation. Our results show that under baseline conditions, Vti accounted for a major proportion of RL; during both passive lung inflation and MCh challenge this proportion increased progressively. For the same level of change in EL, however, the increase in Vti was larger during MCh challenge than during passive inflation; i.e., the relationship between energy storage and energy dissipation or hysteresivity was dramatically altered. These results are consistent with a MCh-induced change in the intrinsic rheological properties of lung tissues unrelated to lung volume change per se. Lung tissue constriction is one possible explanation.     

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.     

Sequence of the Streptococcus pneumoniae bacteriophage HB-3 amidase reveals high homology with the major host autolysin.

We have sequenced a DNA fragment containing the pneumococcal bacteriophage HB-3 hbl gene, which codes for the phage lytic amidase. A remarkable nucleotide similarity (87.1%) between the lytA gene, coding for the pneumococcal amidase, the major autolysin of Streptococcus pneumoniae, and the hbl gene was found. This similarity completely disappeared outside the open reading frames coding for both amidases. The hbl gene transformed amidase-deficient strains of S. pneumoniae to the wild-type phenotype, and Southern blotting experiments provided evidence for recombination between donor and recipient genes. A comprehensive evaluation of these and previous results on the peptidoglycan hydrolases of S. pneumoniae and its bacteriophages suggested that recombination mechanisms participate in the evolution of the genes coding for these enzymes.     

Identification of a region of Escherichia coli ribosomal protein L2 required for the assembly of L16 into the 50 S ribosomal subunit

In vitro mutagenesis of rplB was used to generate changes in a conserved region of Escherichia coli ribosomal protein L2 between Gly221 and His231. Mutants were selected by temperature sensitivity using an inducible expression system. A mutant L2 protein with the deletion of Thr222 to Asp228 was readily distinguishable from wild-type L2 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and ribosomes from the strain overexpressing this mutant protein were characterized by sucrose density gradient centrifugation and protein composition. In addition to 30 S and 50 S ribosomal subunits, cell lysates contained a new component that sedimented at 40 S in 1 mM Mg2+ and at 48 S in 10 mM Mg2+. These particles contained mutant L2 protein exclusively, completely lacked L16, and had reduced amounts of L28, L33, and L34. They did not reassociate with 30 S ribosomal subunits and were inactive in polyphenylalanine synthesis. Other mutants in the same conserved region, including the substitution of His229 by Gln229, produced similar aberrant 50 S particles that sedimented at 40 S and failed to associate with 30 S subunits.     

Usefulness of the stomacher in a microbiological regulatory laboratory.

The relative efficiency of the Waring blender, the Stomacher 400, and the Stomacher 3500 for preparing food samples for microbiological analysis was studied. Comparative aerobic plate count (APC) values were determined on 671 samples, representing 30 categories of foods. Of the 26 categories of nonfatty foods, the blender gave significantly higher geometric mean APC values than those given by the Stomacher 400 and the Stomacher 3500 in 65 and 69 percent of the categories, respectively. In a comparison of the two Stomacher models, the Stomacher 400 gave significantly higher geometric mean APC values than these given by the Stomacher 3500 in 73 percent of the food categories. Addition of Tween 80 to four categories of fatty foods at concentrations of 0.5, 1.0, and 2.0 percent did not raise the APC values given by either model of stomacher to the levels given by the Waring blender. Overall, the efficiency of both models of Stomacher, relative to the blender and to each other, was specific and depended upon the particular food being analyzed.     

Time-dependent regulation of muscle caveolin activation and insulin signalling in response to high-fat diet

We studied the effect of high-fat diet on the expression and activation of the three caveolins in rat skeletal muscle and their association with the insulin signalling cascade. Initial response was characterized by increased signalling through Cav-1 and Cav-3 phosphorylation, suggesting that both participate in an initial acute response to the calorie surplus. Afterwards, Cav-1 signalling was slightly reduced, whereas Cav-3 remained active. Late chronic phase signalling through both proteins was impaired inducing a prediabetic state. Summarizing, caveolins seem to mediate a time-dependent regulation of insulin cascade in response to high-fat diet in muscle.