Anti-Clostridium difficile Potential of Tetramic Acid Derivatives from Pseudomonas aeruginosa Quorum-Sensing Autoinducers

ABSTRACT We have examined the potential bactericidal activities of several tetramic acids derived from Pseudomonas autoinducers against Clostridium difficile, a cause of antibiotic-associated pseudomembranous colitis. Clinical isolates of C. difficile (n = 4) were incubated in broth with a chemically synthesized Pseudomonas autoinducer and its tetramic acid derivatives. The structure-activity relationship and the mechanisms of action were examined by a time-killing assay and by determination of the morphological/staining characteristics. The use of some tetramic acids derived from N-3-oxododecanoyl l-homoserine lactone resulted in more than 3-log reductions in the viability of C. difficile within 30 min at 30 μM. The outer membrane was suggested to be one of the targets for the bactericidal activity of tetramic acid, because disturbance of the bacterial outer surface was demonstrated by alteration of the Gram-staining characteristic and electron microscopy. The data for the tetramic acid derivatives demonstrate that the keto-enol structure and the length of the acyl side chain of tetramic acid may be essential for the antibacterial activity of this molecule. These results suggest the potential for tetramic acid derivatives to be novel agents with activity against C. difficile.

Cellular adaptations of the ventilatory muscles to a chronic increased respiratory load

It is not known whether cellular adaptations of the ventilatory muscles are induced by increased respiratory loads. A chronic respiratory load was produced in rats by tracheal banding. Five weeks after the imposition of this increased load, biochemical and histochemical analyses were performed on the diaphragm and intercostal muscles. The oxidative capacity, as indicated by succinate dehydrogenase (SDH) activity, increased 38% in the diaphragm. The capacity for beta-oxidation fatty acids, as indicated by 3-hydroxy-acyl-CoA dehydrogenase (HADH) activity, increased 29%. The glycolytic capacity, as indicated by phosphofructokinase (PFK) activity, did not change. Similar enzymatic adaptations were observed in the intercostal muscles. The proportion of slow-twitch muscle fibers, as indicated by the myofibrillar adenosine triphosphatase (ATPase) stain, increased in the diaphragm, but not in the intercostal muscles. Thus, these ventilatory muscles responded with an increase in their oxidative capacity, and the diaphragm reponded with an increase in the proportion of muscle fibers having the myofibriller ATPase staining characteristic of slow-twich fibers. We conclude that cellular adaptations are induced in the ventilatory muscles by chronic increased respiratory loads.

Cholinesterase as a Possible Marker for Early Cells of the Megakaryocytic Series

Among marrow cells of rats only megkaryocytes stain appreciably for acetylcholinesterase. An investigation was therefore undertaken to determine whether this staining characteristic might be used to identify precursors of recognizable megakaryocytes. Marrow cells smaller than recognizable megakaryocytes were positive for the enzyme. The number of these cells increased after induction of severe thrombocytopenia by injection of antiplatelet antiserum. Subsequently, the number of recognizable megakaryocytes increased, suggesting their derivation from the small acetylcholinesterase-positive cells. These results suggest that acetylcholinesterase activity can be used as a marker for megakaryocytic cells that cannot be detected with conventional staining methods.

SOME HISTOCHEMICAL CHARACTERISTICS OF TISSUES IN LARVAE OF CTENICERA DESTRUCTOR (BROWN) (COLEOPTERA, ELATERIDAE), WITH SPECIAL REFERENCE TO CUTANEOUS SENSILLA

The sensory axons from the cutaneous sensilla and some of those in the recurrent nerve stain strongly with S-specific stains. The axons of the efferent system and those from the ocelli lack this staining characteristic. This difference among axons possibly is related to the origin of their precursors in the ontogenetic sequence.Some of the metabolites involved in the synthesis of cuticular structures are demonstrated and discussed. The following sequence in the synthesis of the cuticula is suggested: glycogens → more complex, diastase-fast polysaccharides → chitin → a carbohydrate–protein complex containing SS groups → a complex (procuticle) with potential SH groups → a complex (exocuticle) with bound S and a high content of tyrosine and other phenols. The sequence in the synthesis of the cuticular nerve sheaths appears basically similar. The last step was not evident in tonofibrillae, and the last two steps were not evident in the subcuticular sheaths or axoplasm of reactive axons.The mechanisms of the histochemical reactions are discussed, with particular reference to staining with aldehyde-fuchsin after oxidation with potassium permanganate. This method may serve to differentiate histologically certain afferent from efferent axons in insect nervous systems.

OBSERVATIONS ON THE MOVEMENT OF MOISTURE IN LARGE WOODY STEMS

The movement of moisture in large woody stems under normal conditions of uptake is described. Consideration is also given to the aberrant patterns of staining characteristic of woody stems following partial injection of lower boles of standing trees. Staining patterns resulting from very drastic disruption of the normal channels of water conduction are discussed, and the results reviewed in the light of the mechanism of moisture movement in large woody stems.