Plasmid pGA1 from Corynebacterium glutamicum codes for a gene product that positively influences plasmid copy number

The complete nucleotide sequence (4,826 bp) of the cryptic plasmid pGA1 from Corynebacterium glutamicum was determined. DNA sequence analysis revealed four putative coding regions (open reading frame A [ORFA], ORFA2, ORFB, and ORFC). ORFC was identified as a rep gene coding for an initiator of plasmid replication (Rep) according to the high level of homology of its deduced amino acid sequence with the Rep proteins of plasmids pSR1 (from C. glutamicum) and pNG2 (from Corynebacterium diphtheriae). This function was confirmed by deletion mapping of the minimal replicon of pGA1 (1.7 kb) which contains only ORFC. Deletion derivatives of pGA1 devoid of ORFA exhibited significant decreases in the copy number in C. glutamicum cells and displayed segregational instability. Introduction of ORFA in trans into the cells harboring these deletion plasmids dramatically increased their copy number and segregational stability. The ORFA gene product thus positively influences plasmid copy number. This is the first report on such activity associated with a nonintegrating bacterial plasmid. The related plasmids pGA1, pSR1, and pNG2 lacking significant homology with any other plasmid seem to be representatives of a new group of plasmids replicating in the rolling-circle mode.     

攀钢1450热轧带钢厂精轧机组电动压下机构带钢压下时的动特性计算和探讨

从理论上和实践上对武钢１７００、鞍钢１７００改造前后、本钢１７００改造前后和攀钢１４５０精轧机组的电动压下机构在带钢压下时的动特性进行计算和探讨，得出有说服力的结论。主题词：     

Improvements in the silver-staining technique for nucleolar organizer regions (AgNOR)

The silver-staining technique for nucleolar organizer regions (AgNOR) of Ploton et al., as popularized by Crocker, is being widely used for evaluation of nucleolar function, especially in neoplasia. It suffers from limited reliability, background staining, precipitates, and fading of the sections. Factors were identified that affect these problems. The oxidation-reduction level and gelatin used are particularly important. An improved procedure is presented which incorporates pre-reduction of the sections, selection of an optimal gelatin, and post-treatment of the sections to produce a permanent preparation. It is compatible with many fixatives and with other stains used before or after the silver stain.     

Thoracic electric impedance and fluid balance during aortic surgery

Indices of fluid balance were evaluated during and after aortic surgery in 16 consecutive patients. Thoracic electrical impedance (TI), heart rate (HR), central venous (CVP), pulmonary artery mean (PAMP), pulmonary wedge (PWP) and mean arterial (MAP) pressures as well as fourteen arterial and venous blood gas variables were followed. Consistent with a reduction of TI during the operation, fluid balance was in excess, and it remained elevated on the first postoperative morning. The HR, MAP and PWP remained stable, while CVP and PAMP decreased. Of the determined variables only TI revealed a meaningful correlation to fluid balance (rho = -0.41; p < 0.01). The results indicate that while central venous and pulmonary artery mean pressures gave the impression of a volume deficit, the positive fluid balance was mirrored by thoracic electrical impedance.     

Characterization of allergoids from ovalbumin in vitro and in vivo

Several in vivo and in vitro methods for monitoring immunological properties of two allergoids obtained by formaldehyde treatment of ovalbumin (OA) were developed. The calculated molecular weight of allergoids was 80 kD (OA-F1) and 165 kD (OA-F2), respectively. The allergenic activity in vitro of allergoids in mast-cell histamine release assay was 1000 times lower than of OA. Both allergoids showed reduced ability to induce passive cutaneous anaphylaxis in the Sprague-Dawley rats or systemic anaphylaxis in Dunkin-Harley guinea-pigs. The ability of OA and allergoids to bind to the OA-specific IgE antibodies was measured in vivo by the inhibition of passive cutaneous anaphylaxis (PCA-inhibition). Allergoid binding to IgE was 51-66% lower than the native allergen. Moreover, the avidity of OA-specific IgG antibodies, measured by ELISA-inhibition, for allergoids and allergen was of the same order. Allergoids induced a different pattern of humoral immune response from that, induced by the native allergen. Thus, after immunization of BALB/c mouse, both allergoids induced a higher production of IgG and a lower production of IgE than OA, only OA-F2 induced a lower production of IgG1. The differences in the IgA response to the immunogens was not significant. Delayed hypersensitivity studies in the BALB/c mouse showed that allergoids were 5- to 12-times less effective in inducing a cell-mediated immune response than OA. The present study provides a battery of immunological methods for preclinical testing of modified allergens.     

Surfactant replacement therapy in acute respiratory distress syndrome from viral pneumonia

A modified natural surfactant was administered to a patient with life-threatening adult respiratory distress syndrome caused by viral pneumonia. Subsequently, there was a marked improvement in gas exchange. In order to assess the mechanism for improved oxygenation, computed tomography of the lungs was done. Quantitative analysis of the scans taken before and after surfactant administration indicates that improvement in gas exchange was largely due to the expansion of underinflated and collapsed lung areas. Although this is a single case report, it provides insight into the possible beneficial effect of instilled surfactant in severe respiratory distress from viral pneumonia.