[Influence of the autolytic system on the bactericidal effect induced by beta-lactamic antibiotics (author's transl)]

New experimental conditions showing the phenomena of "antibiotic tolerance" are described. In Streptococcus pneumoniae, a strong protection against the loss of viability induced by penicillin was obtained when TRIS (hydroxymethyl aminomethane), instead of potassium phosphate, was used as buffer of the growth medium. The main pneumococcal autolysin (N-acetyl-muramil amidase) present in S. pneumoniae was found to be, at least partially, responsible for the loss of viability induced by beta-lactamic molecules.

Bacteriophages of Streptococcus pneumoniae. Physicochemical properties of bacteriophage Dp-4 and its transfecting DNA

The properties of Dp-4 phage and its DNA have been studied. The phage has a polyhedral head of 60 nm diameter, a tail 155 nm long and a buoyant density in CsCl of 1.48 g/cm3. Analysis by acrylamide gel electrophoresis indicates the presence of five polypeptides. Dp-4 DNA has a molecular weight of 37 x 10(6), a melting point of 83.5 degrees C (when dissolved in 0.15 M NaCl/0.015 M sodium citrate, pH 7.0) and a G + C content of about 33%. Denaturation of DNA yields two strands of different buoyant density in a neutral CsCl gradient. The interaction of poly(U, G) with the heavy strand strongly enhances its density and allows the preparative separation of both strands. Native Dp-4 DNA has unusual physical properties: abnormally low buoyant densities both in CsCl (1.666 g/cm3) and in Cs2SO4 (1.410 g/cm3) (which do not correspond to the value predictable from the G + C content of the DNA), and a high thermal stability at low ionic strength.

Optimization on the selection of auxotrophic mutants in Candida utilis by snail enzyme treatment

The determination of the best conditions for the application of the snaill enzyme digestion method in the enrichment of auxotrophic mutants in Candida utilis was carried out following Box and Wilson's mathematical method. The selection procedure proposed was tested in the enrichment of auxotrophic mutants from a mutagenized culture of a wild-type strain. Mutant frequency was increased 46-fold by treatment with snail enzyme. The method also proved useful in the selection of additional auxotrophic mutations from single auxotrophs.

A reversed jejunal segment interposition as feeding gastrostomy

Permanent feeding gastrostomies are needed for prolonged alimentation in some patients with foregut obstruction. The usual gastric flap or tube may be limited in patients with previous gastric surgery or with a small stomach. In these patients, interposition of a short, vascularized jejunal segment between the anterior wall of the stomach and the outside may be valuable. Periodic intubation is easy. Tested initially in dogs and then applied to selected patients, we have not seen ulcers, regurgitation, soiling, pain, or other complications.

Competence in continuous cultures of Bacillus subtilis: inhibition by arginine and reversal of the inhibition by Mn2+

Arginine inhibited the competence of Bacillus subtilis growing in a chemostat at a dilution rate of 0-277 h-1. The biosynthesis of competence-stimulating activity was only partially repressed. The inhibitory effect may be due to an alteration in the cell's capacity for being stimulated to competence and/or in its ability to take up DNA irreversibly. MnSO4 at 10(-6) M restored competence immediately.

Changes in plasma membranes during the prereplicative phase of the isoproterenol-stimulated parotid glands of mice

A single intraperitoneal injection of isoproterenol induces resting cells from the acini of the mouse parotid gland to enter the proliferative cycle. Parotid plasma membrane from non-stimulated and isoproterenol-treated mice were prepared by differential centrifugation of the homogenates. Comparing the chemical composition of plasma membranes from non-stimulated and isoproterenol-treated mice, no variation in the phospholipid/protein ratio was observed. However, the levels of neutral sugars, hexosamines and sialic acid fall drastically in the early prereplicative phase. The decrease in neutral sugars and hexosamines in plasma membranes caused by isoproterenol is imitated by pilocarpine, which induces secretion but little or no increase in DNA synthesis. However, pilocarpine does not mobilize sialic acid from the plasma membrane. Moreover, dosis of isoproterenol that elicits secretion but not mitosis in the acinar cells, does not induce the movement of sialic acid from the plasma membrane. The mobilization of sialic acid from plasma membranes caused by isoproterenol was also demonstrated in an in vitro system. Treatment of the plasma membrane with chloroform/methanol shows that around 60% of the sialic acid is present in the less polar phase. We conclude that the separation of sialic acid from the plasma membrane is one of the early steps in the sequence of events leading to DNA synthesis and cell division in the isoproterenol-stimulated parotid gland of mice.

The gamut of paracoccidioidomycosis

Paracoccidioidomycosis is a systemic mycosis of importance in Latin America. Because of its polymorphic manifestations, it is not always suspected and patients are sometimes misdiagnosed. Case histories of patients with paracoccidioidomycosis are presented in order to illustrate its various manifestations, with emphasis on the primary pulmonary localization.

The effect of isoproterenol upon the chemical composition of plasma membranes in the mouse parotid gland

A single intraperitoneal injection of isoproterenol induces resting cells from the acini of the mouse parotid gland to enter the proliferative cycle. Parotid plasma membrane from non-stimulated and isoproterenol-treated mice were prepared by differential centrifugation of the homogenates. Comparing the chemical composition of plasma membranes from non-stimulated and isoproterenol-treated mice, no variation in the phospholipid/protein ratio was observed. However, the levels of neutral sugars, hexosamines and sialic acid falls drastically in the early prereplicative phase. The decrease in neutral sugars and hexosamines in plasma membranes caused by isoproterenol is imitated by pilocarpine, which induces secretion but little or no increase in DNA synthesis. However, pilocarpine does not mobilize sialic acid from the plasma membrane. Moreover, dosis of isoproterenol that elicits secretion but not mitosis in the acinar cells, does not induce the movement of sialic acid from the plasma membrane. The mobilization of sialic acid from plasma membranes caused by isoproterenol was also demonstrated in an in vitro system. Treatment of the plasma membrane with chloroform/methanol shows that around 60% of the sialic acid is present in the less polar phase. We conclude that the separation of sialic acid from the plasma membrane is one of the early steps in the sequence of events leading to DNA synthesis and cell division in the isoproterenol-stimulated parotid gland of mice.

Protective effect of steroids on liver ischemia

Occlusion of the afferent liver circulation for variable periods of time would be advantageous to temporarily control bleeding from profound lacerations or during extensive resections. Because of its low tolerance to ischemia we attempted to protect the liver with steroids during inflow occlusion. Total hepatic ischemia was produced in rabbits by ligating the portal triad and gastrohepatic ligament for 30 minutes. A 10 per cent survival was obtained in untreated controls whereas pre-treatment with methylprednisolone improved survival to 100 per cent. Methylprednisolone injection after occlusion improved survival only to 57 per cent. There were profound pathohistologic and electron microscopic changes in untreated controls. In animals treated with methylprednisolone either before or after occlusion changes were minimal or absent. This treatment was used in four trauma patients in whom occlusion of the liver inflow was carried out for various periods of time. Even though no significant statement can be made from such small group, the early postoperative course was remarkably smooth and stable. Methylprednisoline protects the liver during warm ischemia, especially if given before occlusion, and decreases the mortality from this maneuver in experimental animals.