Evaluation of Nisin F in the Treatment of Subcutaneous Skin Infections, as Monitored by Using a Bioluminescent Strain of Staphylococcus aureus

The potential of nisin F as an antimicrobial agent in treating subcutaneous skin infections was tested in vivo by infecting C57BL/6 mice with a bioluminescent strain of Staphylococcus aureus (Xen 36). Strain Xen 36 has the luxABCDE operon located on a native plasmid. Mice were grouped into four groups: Infected with strain Xen 36 and treated with nisin F, infected with strain Xen 36 and treated with saline (placebo), not infected and treated with nisin (control) and not infected and not treated (control). The immune systems of the mice were suppressed with deksamethasone. Mice were treated with either nisin F or sterile physiological saline 24 and 48 h after infection with subcutaneously injected S. aureus Xen 36 (4 × 10⁶ CFU). Histology and bioluminescent flux measurements revealed no significant difference between infected mice treated with nisin and saline, respectively. However, infected mice treated with nisin F had an increased number of polymorphonuclear cells when compared with infected mice treated with saline. Also, not infected mice treated with nisin F had an influx of polymorphonuclear cells. Nisin F is thus ineffective in combating deep dermal staphylococcal infections. The apparent immune modulation of nisin when subcutaneously injected has to be investigated.     

An improved purification method for cytosolic malate dehydrogenase from several sources

A new purification method for cytosolic malate dehydrogenases from several sources has been developed. The procedure, employing chromatographies on 5'AMP-Sepharose, DEAE-Sephacel and Blue-Sepharose, allows for a rapid isolation of the enzyme (approximately 40 hours), in large quantities, with good yields (45-54%). The specific activity of final preparations were around 1300 I.U./mg and were judged homogeneous by polyacrylamide gradient gel and sodium dodecyl sulfate polyacrylamide gel electrophoresis, high performance size exclusion chromatography and isoelectric focusing.     

Inborn errors of complex II--unusual human mitochondrial diseases.

The succinate dehydrogenase consists of only four subunits, all nuclearly encoded, and is part of both the respiratory chain and the Krebs cycle. Mutations in the four genes encoding the subunits of the mitochondrial respiratory chain succinate dehydrogenase have been recently reported in human and shown to be associated with a wide spectrum of clinical presentations. Although a comparatively rare deficiency in human, molecularly defined succinate dehydrogenase deficiency has already been found to cause encephalomyopathy in childhood, optic atrophy or tumor in adulthood. Because none of the typical housekeeping genes encoding this respiratory chain complex is known to present tissue-specific isoforms, the tissue-specific involvement represents a quite intriguing question, which is mostly addressed in this review. A differential impairment of electron flow through the respiratory chain, handling of oxygen, and/or metabolic blockade possibly associated with defects in the different subunits that can be advocated to account for tissue-specific involvement is discussed.     

Poly(ADP-ribose) polymerase forms loops with DNA

The interaction between highly purified poly(ADP-ribose) polymerase from calf thymus and different topological forms of pBR322 DNA has been studied by gel retardation electrophoresis and electron microscopy. We show that: (i) in the absence of nicks on DNA the enzyme has a marked affinity for supercoiled (form I) DNA, (ii) in the presence of single stranded breaks poly(ADP-ribose) polymerase preferentially binds to form II, (iii) in all cases enzyme molecules are frequently located at DNA intersections, (iv) a cooperative binding of the enzyme on DNA occurs.     

Regulation of ATP synthesis catalyzed by the calcium pump of sarcoplasmic reticulum

The role of pH, KCl, ATP, water activity, and temperature in ATP synthesis from ADP and Pi was investigated in sarcoplasmic reticulum vesicles isolated from rabbit skeletal muscle. In totally aqueous medium, the synthesis of ATP was inhibited by ATP, KCl, and pH values above 6.5. When the water activity of the medium was decreased by the addition of 30% (v/v) dimethyl sulfoxide, the synthesis of ATP was no longer inhibited by ATP; it was activated by KCl and the optimum pH changed from 6.5 to 7.5. In totally aqueous medium, the concentration of MgCl2 needed for half-maximal synthesis of ATP was found to vary with the temperature of the assay medium; at 35 degrees C it was 1 mM and increased to a value higher than 10 mM when the temperature was decreased to 15 degrees C. In the presence of 30% dimethyl sulfoxide, maximal synthesis of ATP was attained in presence of 0.05 mM MgCl2 at both 15 and 35 degrees C. The hypothesis is raised that in the living cell water structure may play a role in regulating the synthesis of ATP observed during the reversal of the Ca2+ pump of the sarcoplasmic reticulum.