Minocycline treatment following hypoxic/ischaemic injury attenuates white matter injury in a rodent model of periventricular leucomalacia.

AIMS: Periventricular white matter injury in premature infants occurs following hypoxia/ischaemia and systemic infection, and results in hypomyelination, as well as neuromotor and cognitive deficits later in life. Inflammatory infiltrates are seen within human cerebral white matter from periventricular leucomalacia (PVL) cases. METHODS: In this study, we examine the time course of CD-68+ microglial cell responses relative to cell death within white matter following hypoxia/ischaemia in a rat model of PVL. We also tested the efficacy of the minocycline, an agent that suppresses microglial activation, in this model when administered as a post-insult treatment. RESULTS: We show that preoligodendrocyte injury in the post-natal day 6 begins within 24 h and continues for 48-96 h after hypoxia/ischaemia, and that microglial responses occur primarily over the first 96 h following hypoxia/ischaemia. Minocycline treatment over this 96 h time window following the insult resulted in significant protection against white matter injury, and this effect was concomitant with a reduction in CD-68+ microglial cell numbers. CONCLUSIONS: These results suggest that anti-inflammatory treatments may represent a useful strategy in the treatment of PVL, where clinical conditions would favour a post-insult treatment strategy.

Intraventricular leptin reduces food intake and body weight of lean rats but not obese Zucker rats.

The protein encoded by the obese (ob) gene, leptin, is secreted from adipose tissue and is proposed to act in the brain as an important regulator of food intake and body weight. To investigate the direct effects of leptin within the CNS, we injected 3.5 microg of either mouse or human leptin into the third ventricle (ICV) of lean Long-Evans rats or obese (fa/fa) Zucker rats, in which obesity results from a mutation in the leptin receptor gene. ICV administration of leptin reduced 4-h food intake in both deprived and non-deprived lean rats. In addition, repeated ICV administration produced a long-lasting reduction in body weight while peripheral administration of the same dose had no effect. ICV administration of the same dose of leptin into the third ventricle of obese Zucker rats did not reduce food intake. These results are consistent with the hypothesis that leptin has direct actions in the CNS as an afferent signal related to the state of energy stores in adipose tissue. Furthermore, insensitivity to these central effects of leptin may be an important determinant of obesity.

Gardnerella vaginalis has a gram-positive cell-wall ultrastructure and lacks classical cell-wall lipopolysaccharide.

Gardnerella vaginalis has a very thin cell wall with a characteristic gram-negative staining pattern and an apparent lamellar structure when viewed at an oblique angle by electronmicroscopy. Examination at right angles to the cell-wall plane and by freeze-etching showed absence of an outer membrane or any other lamellar structure. Cell-wall extracts made by methods specific for lipopolysaccharide (LPS) gave negative reactions by silver staining and for endotoxin in the limulus amoebocyte lysate assay. 2-Keto-3-deoxy-D-manno-2-octonoic acid (KDO), heptose and hydroxy fatty acids specific for LPS were not detected in the extracts. G. vaginalis cell walls are unequivocally gram-positive in their ultrastructural characteristics and chemical composition.

Electron microscopic description of glycocalyx and fimbriae on the surface of Pasteurella haemolytica-A1.

Several electron microscopic techniques were used to examine the surface of cells of Pasteurella haemolytica (biotype A, serotype 1) grown in vitro. All methods showed the presence of a very extensive glycocalyx on logarithmic phase (6 h) cells grown in liquid media. The anionic glycocalyx of these cells stained well with ruthenium red, but collapsed during dehydration for electron microscopy unless stabilized with specific antibodies. When the same techniques were used to examine cells in the stationary phase (18 h) the glycocalyx was much reduced. Large numbers of fimbriae were seen on both 6 h and 18 h cells grown in fluid media without shaking. In summary, logarithmic phase cells of P. haemolytica have both fimbriae and extensive anionic glycocalyx at their surface and we suggest that either or both of these structures may be important in the colonization of the bovine respiratory tract and the subsequent pathogenesis of Pasteurella pneumonia.

A scanning and transmission electron microscopic study of an infected endocardial pacemaker lead.

We studied the pacemaker lead that had been removed from a patient who suffered three sequential episodes of Staphylococcus aureus bacteremia. This organism was recovered from the surface of the lead. Scanning electron microscopy showed differential colonization of the pacemaker lead. The metal tip, the inner surface and the internal wires were covered with a heavy biofilm of bacteria. The outer silastic surface had no biofilm adherent to it; instead, well-spaced bacterial cells were seen. These observations illustrate why infection of implantable devices persists despite intensive antibiotic chemotherapy.