Carbon blacks as EPR sensors for localized measurements of tissue oxygenation.

New electron paramagnetic resonance (EPR) oximetry probes were identified in the class of carbon black materials. These compounds exhibit very high oxygen sensitivity and favorable EPR characteristics for biological applications. At low pO(2), the linewidth is particularly sensitive to changes in oxygen tension (sensitivity of 750 mG/mmHg). The application of the probes for oximetry was demonstrated in vivo: the pO(2) was measured in muscle in which the blood flow was temporarily restricted as well as in tumor-bearing mice during a carbogen breathing challenge. The responsiveness to pO(2) was stable in muscle for at least 3 months. No toxicity was observed using these materials in cellular experiments and in histological studies performed 2, 7, and 28 days after implantation. In view of their EPR characteristics (high sensitivity) as well as the well-characterized production procedure that make them available on a large scale, these probes can be considered as very promising tools for future developments in EPR oximetry.     

Metal ions protect DNA against strand breakage induced by fast neutrons.

Single and double strand breaks (SSB and DSB) are induced by fast neutrons in plasmid (pBR322) DNA in 1 mM potassium phosphate buffer (pH 7.25). Increasing the concentration of monovalent (Na+, Cs+, Li+), divalent (Mg2+, Ca2+) and trivalent (Al3+, Co3+ (NH3)6) metal cations strongly decreases the yield of DSB. The extent of the observed protection depends on the valence of the cation. The production of SSB is only slightly decreased, except for Al3+ and Co3+ (NH3)6, whose effects are particularly large (complete protection at 1 and 0.1 mM respectively). Circular dichroism spectra show that Al3+ induces an important structural change of DNA at the ion concentration where the protection becomes total. This change is probably a condensation (collapse), as in the well-known case of Co3+ (NH3)6. Our results suggest two mechanisms of protection by metal ions: (i) the induction of structural changes of DNA, that render less accessible the critical sites of attack by OH. radicals; and (ii) the stabilization of the double helical regions between two close-set nicks on opposite strands, that hinders the effective double strand breakage of DNA.     

A study of 15 cases of primary mediastinal lymphoma of B-cell type.

Fifteen cases of pure supradiapragmatic lymphoma with initial prominent antero-superior mediastinal involvement displaying a B-cell pattern of reactivity were studied. These cases occurred in six men and nine women with a median age of 33 years at diagnosis (range, 23 to 75 years). Supradiapragmatic peripheral lymphadenopathies were present in three cases, and intrathoracic extension to the lung, pericardium, or pleura was possible. In five cases a thymic origin was obvious. All cases exhibited a B-cell pattern of differentiation, with a great variety of histopathologic aspects associated with a high frequency of fibrosis and/or necrosis. Hodgkin's disease was initially misdiagnosed in four cases. The evolution was purely local, with extrathoracic extension in five cases, at the ultimate phase of the disease. The prognosis appeared to be poor with only five patients still alive at a median survival time of 16 months. A complete chemoresistance and radio-resistance was observed in seven cases; only two complete remissions were achieved with aggressive chemotherapy. Prolonged remission could be achieved after surgical reduction of the mass. Primary B-cell mediastinal lymphoma appears to be a distinct clinical entity with local evolution and resistance to therapy. A new therapeutic regimen, which could include surgery in some cases, should be found for this disease.     

Distribution of nocardia species in clinical samples and their routine rapid identification in the laboratory

Eighty-six Nocardia strains isolated from clinical samples in Belgium were identified by 16S rRNA gene sequencing. Eighty-three (96%) strains belonged to only six Nocardia species: N. farcinica (38 [44%]), N. nova (19 [22%]), N. cyriacigeorgica (13 [15%]), N. brasiliensis (6 [6.9%]), N. abscessus (5 [5.8%]), and N. paucivorans (2 [2.3%]). A gallery of nine conventional and enzymatic tests was developed for the rapid identification of the most common species isolated during this survey. Pyrrolidonyl aminopeptidase, γ-glutamyl aminopeptidase, α-mannosidase, and α-glucosidase were found to be highly discriminating and could be used to develop an identification scheme.     

Inhibition of adhesion of enterotoxigenic Escherichia coli cells expressing F17 fimbriae to small intestinal mucus and brush-border membranes of young calves

Enterotoxigenic Escherichia coli strains expressing F17 fimbriae bind to the intestinal mucosa of young calves. F17 fimbriae recognize receptors present in the mucus layer and the brush-border membranes from duodenum, jejunum and ileum. The adhesion of E. coli F17 can be inhibited by several glycoproteins. Adhesion is also inhibited by pretreatment of mucus and brush-border membranes with sodium metaperiodate. The use of glycoconjugates as potential adhesion-blockers is further discussed.     

An epidemic of fatal hepatic necrosis of viral origin in racing pigeons (Columba livia)

In October 1992, a new disease characterised by acute death in racing pigeons of all ages was noted among the Belgian pigeon population. Clinical symptoms were minimal since affected birds usually died within 24 h. Mortality in pigeon lofts usually amounted to 30%. The most typical necropsy finding was a yellow, pale and swollen liver. Histological and cytological examinations revealed extensive focal or diffuse hepatic necrosis and the presence of eosinophilic or amphophilic nuclear inclusion bodies. This hepatic necrosis of viral origin was diagnosed in 151 (15%) of 988 submissions of pigeons at our Institute in 1993 and 1994. Oral and intramuscular inoculation of pigeons with a bacteria-free homogenate prepared from the liver of pigeons that died from the disease did not result in clinical signs. However, when similar inoculations were done in pigeons previously treated orally with dexamethasone, pigeons died very suddenly within 4-5 days of inoculation. Necropsy findings in experimentally infected pigeons were identical to those observed in naturally occurring cases. Electron microscopic examination of the liver of inoculated pigeons showed the presence of numerous adenovirus-like particles inside nuclei of hepatocytes. The virus could not be cultured in the allantoic cavity or on the chorioallantoic membrane of embryonated chicken eggs. Clinical signs and lesions described here are clearly different from adenovirus enteritis in young pigeons abundantly described since 1976.