Altered functional responsiveness of thymocyte subsets from CD3delta-deficient mice to TCR-CD3 engagement

CD3delta-deficient (delta degrees) mice are defective in alphabeta T cell development. Here we explore the capacity of TCR-CD3 signaling complexes expressed on delta degrees thymocytes to mediate the following functional outcomes in response to antibody cross-linking: (i) the transition from the CD4-CD8- to CD4+CD8+ stage, (ii) the transition from the CD4+CD8+ to CD4+CD8- or CD4-CD8+ stages and (iii) the induction of apoptosis. We provide evidence that CD3deltaepsilon complexes are dispensable for mediating the anti-CD3-mediated CD4-CD8- to CD4+CD8+ transition. On the other hand, CD3delta is critical at the CD4+CD8+ stage. We demonstrate that CD4+CD8+ thymocytes from delta degrees mice, unlike delta degrees CD4-CD8- thymocytes and wild-type CD4+CD8+ thymocytes, require prolonged or consecutive stimuli to elicit functional responses. Depending on the nature of the secondary stimulus, delta degrees thymocytes can be induced to undergo apoptosis or preferential maturation to the CD4-CD8+ stage. Taken together these results indicate that the signaling capacity of the TCR-CD3 complex is noticeably altered in the absence of CD3delta. The essential role of CD3delta at the CD4+CD8+ stage of development correlates with the onset of TCRalpha rearrangement, consistent with a critical structural and/or functional relationship between CD3delta and TCRalpha.     

Assessment of workload in the microbiology laboratory

Workload measurement is necessary for laboratory management and planning. Adaptation of the College of American Pathologists' scheme to the requirements of a large clinical microbiology laboratory is described. Our method of applying basic work values is simpler and the calculation of workload is easily adapted to take account of alterations in laboratory method. The resulting system of workload measurement can be instituted without undue effort.     

Optimization of collimation system parameters of radioisotope tomograph]

An index of completion of phagocytosis was studied for staphylococcus cultures of various biological activity in experiments with surviving polymorphonuclear leukocytes. Among the coagulase-forming staphylococci virulent strains proved to be nonviable in a lesser percentage of cases than the avirulent ones. Coagulase- and mannite-negative cultures proved to be most unstable. Staphylococcus toxin depressed the migration of polymorphonuclear leukocytes to the focus of irritation, inhibited ingestion of the virulent, and, to a lesser degree, of avirulent coagulase-forming staphylococci, but failed to influence the ingestion of coagulase-negative epidermal staphylococci. The influence of staphylotoxin on the phagocytosis completion index was either the minimal or absent entirely.     

Prevention of balloon damage during initiation of intra-aortic balloon counterpulsation

Damage to an intra-aortic balloon occurred on two occasions in 93 insertion procedures. The complication was recognized before gas embolization occurred, and neither patient suffered ill effects. On both occasions the balloon was holed when pinched by artery forceps applied to the 'dacron' graft.     

Quantitative aspects of the formation of a half chromatid chiasma as an intermediate product of genetic recombination in bacteriophages

Formal genetic consequences of generation and break-up of a half chromatid chiasma have been studied on the basis of a model with the symmetric exchange of two strands between parental DNA molecules. In recombination analysis, generation and break-up of this structure gives rise to a critical frequency R (zeta), which corresponds to recombination between two markers separated by a distance equal to the mean genetic length zeta of the hybrid region at the time of scission of the cross connection. The use of the distance zata as a natural unit of a genetic map is suggested. In the case of bacteriophage T4 under conditions of standard crosses the half chromatid chiasma is characterized by the value R (zata) equal to 3.0-10(-2), the structure acquiring with equal probability either of the two alternative isomeric configurations at the time of scission of the cross connection. About four per cent of the total number of mismatches as a result of break-up to the half chromatid chiasm were repaired.     

Cloning and expression of a plasmid pBS195 gene, determining oxygenase activity, in Escherichia coli cells

Plasmid pBS195, detected in a strain of Lactobacillus sp. isolated from long-living persons, has a broad host range, including Gram-positive and Gram-negative microorganisms [1]. Plasmid-harboring colonies of the strain Escherichia coli HB101 give a color reaction with catechol. This indicates that genes mediating the activity of oxygenase are present in this plasmid. The high activity level of this enzyme, mediated by pBS195, and substrate specificity, which has not bee detected in any known metapyrocatechases, were found in cells of E. coli. Hybridization with a 32P-labeled fragment containing the NahC gene revealed a region of homology with a 1.6-kb EcoR I- BamH I fragment of plasmid pBS195. Deletion variants of this plasmid that lost oxygenase activity confirmed the location of the oxygenase gene in this region. The gene responsible for oxygenase activity in the plasmid was cloned on the pUC19 vector in E. coli cells. The expression of the cloned gene is controlled by the lac promoter of this vector. Physical, hybridization, and deletion analyses as well as analysis of polypeptides, which are synthesized in E. coli mini-cells, showed that this activity requires the participation of a polypeptide with molecular mass of 34 kDa.