Characterization and solution properties of a new exopolysaccharide excreted by the bacterium Alteromonas sp. strain 1644.

This paper concerns the study of a new bacterial exopolysaccharide. The ionic properties of the polymer are considered in relation to the first structural results. This polysaccharide is a carboxylic polyelectrolyte with a charge parameter of 1.33, and exhibits usual polyelectrolyte properties with monovalent and Mg2+ ions. In contrast, its affinity for the divalent ions Ca2+, Sr2+ and Ba2+ is greater than predicted from electrostatic theory. In solution, the polysaccharide undergoes a local conformational transition related to the number of divalent ions bound per carboxylic group. This interaction is mainly an intramolecular process. The dimensions of the polymeric chain were also considered using light-scattering and viscometric measurements. The intrinsic persistence length Lp is equal to 80 +/- 5 A and allows this polymer to be classified as a semi-rigid chain.

Solution and gel rheology of a new polysaccharide excreted by the bacterium Alteromonas sp. strain 1644.

A new bacterial polysaccharide '1644' is studied in aqueous solutions and in the gel state. The viscometric measurements for dilute and semi-dilute solutions in presence of monovalent salts are usual; however, in presence of divalent cations like Ca2+ an original behaviour is observed, related to intermolecular bonds. For larger polymer concentrations a clear gel is obtained with divalent counterions. This gel exhibits unusual properties compared to other gelling polysaccharides: it is very elastic and resistant because of low crosslinking. The mechanical properties of this gel depend closely on the fraction of divalent ions linked to the polymer and so on thermodynamic parameters.

Production and Characterization of an Exopolysaccharide Excreted by a Deep-Sea Hydrothermal Vent Bacterium Isolated from the Polychaete Annelid Alvinella pompejana.

The heterotrophic and mesophilic marine bacterium HYD-1545 was isolated on a metal-amended medium from the dorsal integument of the hydrothermal vent polychaete Alvinella pompejana. This strain, which can be assigned to the genus Alteromonas on the basis of its G+C content and phenotypical features, produced large amounts of an acidic polysaccharide in batch cultures. The polysaccharide was excreted during the stationary phase of growth and contained glucose, galactose, glucuronic acid, galacturonic acid, and 4,6-O-(1-carboxyethilidene)-galactose as major components. This polysaccharide was a polyelectrolyte, and the viscosity of its solutions depended on the ionic strength. The decrease in viscosity with increasing NaCl concentrations and the effect of Ca in decreasing the viscosity at low Ca concentrations support a model in which the polysaccharide carries anionic groups. However, an unusual behavior was observed at higher concentrations and could be related to intermolecular interactions involving Ca ions.

Effect of low-level NO2 chronic exposure on elastase-induced emphysema.

The effect of chronic exposure to 2 ppm nitrogen dioxide (NO2) for 8 hr a day, 5 days a week, for 8 weeks was assessed in normal and emphysematous hamsters by measuring (1) lung morphometry (mean linear intercept [Lm] and internal surface area [ISA]), (2) lung mechanics (lung volume, compliance and coefficient of static deflation, pressure-volume curve fitted to an exponential equation), and (3) serum elastolytic activity and protease inhibitor capacity. Emphysema was induced by a single intratracheal injection of 6 IU porcine pancreatic elastase. Four groups of animals were used; Control, NO2-exposed, elastase-treated, and NO2-exposed postelastase. Our results show that NO2 exposure alone induced mild emphysematous lesions whose degree of severity estimated by morphometry increase in Lm and decrease in ISA. P less than 0.01) was of the same order as that of the lesions induced by 6 IU elastase. Exposure to 2 ppm NO2 enhanced elastase-induced emphysema (further increased Lm and further reduced ISA. P less than 0.01). By contrast, study of lung mechanics revealed no difference between the control and NO2-exposed groups or between the elastase-treated animals exposed to NO2 and those not so exposed. This apparent discrepancy between results of morphometry and lung mechanics may be due to the lower sensitivity of lung mechanics parameters and their consequent inability to reflect changes in the emphysematous lesions induced by elastase injection or 2 ppm NO2 inhalation. In vivo, serum elastolytic activity and protease inhibitor capacity were not modified in any group, indicating that either serum does not reflect the degree of protease inhibitor capacity in the alveolar spaces or chronic inhalation of low concentrations of NO2 is not sufficient to cause elastase/antielastase imbalance. Lastly, our results suggest that chronic exposure to 2 ppm NO2 may cause individuals with inherited or acquired emphysematous lesions to develop more severe emphysema.

[Depression of the ST segment in precordial derivations: prognostic value in inferior myocardial infarct]. / Sottoslivellamento del tratto ST nelle derivazioni precordiali: valore prognostico in corso di infarto miocardico a sede inferiore.

We have assessed the prognostic significance of ST segment depression in the anterior precordial leads in patients with an acute inferior infarction. Eighty-four patients with ST segment depression greater than or equal to 1 mm in at least 2 chest leads (Group A) and 82 patients without ST depression (Group B), all admitted to the hospital within 24 hours from the onset of an acute inferior myocardial infarction, were evaluated. Patients with an old infarction, those with intraventricular conduction abnormalities or other causes that could modify the ST segment were excluded from the study. The number of patients affected by complications during the hospital stay was significantly higher in group A (54 patients of group A vs 27 of group B, p less than 0,001). Death, left ventricular failure, ventricular arrhythmias were considerably higher in group A. Moreover we observed that the persistence of the ST segment depression for more than 24 hours identified a subgroup of patients with a very strong risk of complications, particularly death and left ventricular failure. The follow up after 3-6 months, however, did not show any significant difference in both groups. In conclusion, from our study it appears that patients with an inferior infarction precordial ST segment depression have a graver prognosis in the acute phase while their mid-term fate does not seem to be influenced by the presence of this electrocardiographic abnormality.

[4 cases of tricholeukocytic leukemia]. / Osservazioni su 4 casi di leucemia tricoleucocitica.

The clinical, haematological, cytomorphological, cytochemical, ultrastructural, and bone marrow biopsy histological data observed in 4 cases of tricholeukocytic leukaemia are reported, along with some unusual findings. Stress is placed on the varied course of this disease and the difficulties associated with its treatment. Some criteria for the choice of therapy are also proposed.

Depression of contact sensitivity by Pseudomonas aeruginosa-induced suppressor cells which affect the induction phase of immune response.

The cellular basis of depression of contact sensitivity to oxazolone in mice injected with Pseudomonas aeruginosa was studied. Cells from draining lymph nodes of mice sensitized with oxazolone 18 h previously were able to induce contact sensitivity to normal mice when administered in their footpads. In contrast, cells from draining lymph nodes of P. aeruginosa-injected and oxazolone-sensitized donors failed to induce contact sensitivity when injected in the footpad of normal mice and were capable of actively blocking the immunizing process brought about by lymph node cells from sensitized mice when injected together in the footpad of normal recipients. The P. aeruginosa-induced suppressor cells required antigenic stimulation, had precursors sensitive to cyclophosphamide, and did not affect the effector mechanisms of contact sensitivity. Thus, the results suggest that P. aeurginosa depresses contact sensitivity to oxazolone by enhancing the activity of suppressor cells which normally arise during the sensitization process and which affect the afferent limb of the immune response, probably by inhibiting the normal recruitment of T lymphocytes in the draining lymph nodes.

A mechanism for the depression of contact sensitivity with B-cell mitogens.

LPS or DxS impair contact sensitivity to oxazolone in mice, evaluated as ear thickness and DNA synthesis of regional lymph node cells in vitro. Lymphoid cells from LPS- or DxS-injected and sensitized mice were able to transfer specifically the suppression when injected into animals sensitized immediately before cell transfer. This cell suppressor activity was eliminated by nylon wool filtration. These results suggest that B-cell mitogens may enhance suppressor cell activity of regulatory cells which arise during conventional immunization.

Depression of the antibody response in Pseudomonas aeruginosa-injected mice.

Heat-killed Pseudomonas aeruginosa inhibit antibody response in C57BL/6 mice. The depression of this response is dependent on the dose of bacteria injected, on the time interval between microorganism injection and antigen administration, and on the nature of the antigen used. Cell transfer experiments provide evidence that suppressor cells are not operative in this model. Furthermore, the results show that P. aeruginosa induces a marked dose-dependent proliferation of spleen cells in vivo, and the in vitro targets of this proliferative effect are B lymphocytes. It is suggested that whole, heat-killed P. aeruginosa in vivo also behave as cell mitogens on B lymphocytes which, when strongly stimulated to proliferate, temporarily lose their capacity to mount a normal antibody response.