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Biomedical subjects

A Gruss

Publications and source records attributed to A Gruss.

63 records · Page 4Linked to original sources
PubMed1989

Evaluation of the T stage of carcinoma of the bladder by transurethral ultrasonography.

In order to evaluate the accuracy of transurethral ultrasonography in predicting the T stage of bladder tumors a prospective study was initiated. Transurethral ultrasonography was performed in 308 consecutive patients prior to cystoscopy, transurethral resection, biopsy or cystectomy. The findings of ultrasonography were compared with the histopathologic results. In 218 out of the 308 patients a carcinoma of the bladder was diagnosed histologically, whereas in 90 patients a tumor could not be detected on histological examination. In 78.2% of those patients, in whom a carcinoma of the bladder was present, it was possible to predict the correct T stage. It was not possible, however, to distinguish tumors of stage TA from those of stage T1. Further analysis of the results revealed an overstaging of the tumor in 12.0%, whereas in 8.0% of the cases the tumor was understaged or had not been recognized at all by ultrasonography.

Humans↗
PubMed1988

Insertion of foreign DNA into plasmids from gram-positive bacteria induces formation of high-molecular-weight plasmid multimers.

Plasmids pUB110, pC194, pE194, and pT181 are commonly used as cloning vectors in both Bacillus subtilis and Staphylococcus aureus. We report that insertion of foreign DNA into any of these plasmids results in the generation of high-molecular-weight plasmid multimers (HMW) of the recombinant, present as tandem head-to-tail copies. HMW was detected in wild-type B. subtilis and S. aureus strains. The production of HMW depended on the nature of the DNA insertion. Inserts of Escherichia coli DNA, e.g., pBR322 or pUC18, resulted in large amounts of HMW, whereas some inserts of S. aureus DNA of the same size had no effect on plasmid profile. The generation of HMW depended on the mode of plasmid replication; plasmids which replicate via a single-stranded DNA intermediate produced HMW upon foreign DNA insertion, whereas plasmid pAM beta 1, which does not generate single-stranded DNA, did not generate HMW. We propose that HMW is a product of imparied termination of rolling-circle replication and that the impairment is due to the nature of the DNA insertion.

Bacillus subtilis↗
PubMed1986

Regulation of exoprotein gene expression in Staphylococcus aureus by agar.

Insertion of the erythromycin-resistance transposon Tn551 into the Staphylococcus aureus chromosome at a site which maps between the purB and ilv loci has a pleiotrophic effect on the production of a number of extracellular proteins. Production of alpha, beta and delta hemolysin, toxic shock syndrome toxin (TSST-1) and staphylokinase was depressed about fifty-fold while protein A production was elevated twenty-fold. Hybridization analysis showed that the defect in expression of TSST-1 and alpha hemolysin was at the transcriptional level. Inability of the mutant strain to express either a cloned TSST-1 gene or the chromosomal gene indicates that the transposon has inactivated a trans-active positive control element. This element has been designated agr for accessory gene regulator.

Bacterial Proteins↗
PubMed1986

Plasmid instability in regenerating protoplasts of Staphylococcus aureus is caused by aberrant cell division.

Elimination of plasmids from regenerating S. aureus protoplasts occurred when the regeneration medium contained sucrose but not when it contained sodium succinate. This difference was caused by the occurrence of cell division prior to regeneration of the cell wall on sucrose but not on succinate. Coexisting compatible plasmids were cured independently; coexisting incompatible plasmids were cured jointly. These results support the hypothesis that plasmid pools exist as physically sequestered units in protoplasts and that curing is a consequence of the segregation of such units during abnormal division of wall-less organisms.

Cell Division↗
PubMed1985

Replication control for pT181, an indirectly regulated plasmid.

PT181 is a fully sequenced Staphylococcus aureus plasmid whose size is 4,437 bp. It specifies tetracycline resistance and has a copy number of about 22 per cell in exponentially growing cultures. The functional organization of the pT181 replicon is centered around the coding sequence for a 35-kd protein, RepC, that is absolutely required for replication of the plasmid. The replication origin is contained within the repC coding sequence and the region immediately 5' to the RepC start is involved in control of the plasmid replication rate. PT181 replication is controlled at the level of RepC synthesis by a negative regulatory system that is functionally similar to that of the Co1E1 and IncFII plasmids of Escherichia coli. The pT181 control circuit involves 2 short transcripts, RNA I and RNA II, that are transcribed from the region specifying the 5' end of the untranslated repC mRNA leader and in the opposite direction. These are referred to as countertranscripts. The countertranscripts regulate RepC synthesis by a mechanism that probably involves interaction with the repC mRNA leader in a manner that interferes with translation. Both of the countertranscripts seem to be necessary for normal replication control; their separate roles remain unclear. Unlike plasmids of the Co1E1 and IncFII groups, plasmids such as Co1E1 are considered to have direct regulation of replication because the inhibitory element of the copy control circuit directly inhibits the initiation of replication. Plasmids such as pT181 are considered to have indirect regulation of replication because the product of the regulated step, RepC, is trans-active. Plasmids of the IncFII type are considered to have direct regulation of replication because the product of the regulated step, RepA is cis-active The analysis of pT181 replication physiology has illustrated 2 important differences between directly and indirectly regulated plasmids: a) for directly regulated plasmids, copy mutants specifying a normal inhibitor substance but an inactive target site exclude the wild-type or recessive mutants by directly interfering with their replication. Analogous mutants of indirectly regulated plasmids coexist readily with the wild-type and all mutants (although they do manifest segregational incompatibility) because the Rep protein is always shared by all plasmids in the cell, regardless of its source. b) Mutations of directly regulated plasmids in the region where target transcript and countertranscript overlap may give rise to totally new incompatibility groups because they engender independently self-correcting copy pools.(ABSTRACT TRUNCATED AT 400 WORDS)

Base Sequence↗
PubMed1984

Control of pT181 replication I. The pT181 copy control function acts by inhibiting the synthesis of a replication protein.

pT181 is a fully sequenced 4.4-kb 20 copy Tcr plasmid from Staphylococcus aureus. Its replication system involves a unique unidirectional origin embedded in the coding sequence for a plasmid-determined protein, RepC, that is required for initiation. When joined to a 55 copy carrier plasmid, pE194, pT181 excludes autonomous isologous replicons by inhibiting their replication. Two types of spontaneous pT181 copy mutants have been isolated, one that eliminates sensitivity to this inhibition and another that does not. A spontaneous 180-bp deletion, delta 144, eliminates both the inhibitory activity and sensitivity to it. This deletion increases copy number by 50-fold and RepC production by at least 10-fold. It is located directly upstream from the repC coding sequence and the deletion-bearing plasmid supports the replication of inhibitor-sensitive plasmids in cells containing active inhibitor. This effect is probably due to the overproduction of RepC by the delta 144 plasmid. On the basis of these results, it is suggested that RepC synthesis is negatively controlled by an inhibitor that is encoded directly upstream from the repC coding sequence and acts as a tareget set in the same region. It is likely, therefore, that pT181 replication rate is determined by the level of RepC.

Bacterial Proteins↗
PubMedDate not supplied

Characteristics of Chi distribution on different bacterial genomes.

The availability of full genome sequences provides the bases for analyzing global properties of the genetic text. For example, oligonucleotide sequences that are over- or underrepresented can be identified by taking into account the overall genome composition and organization. One of the most overrepresented oligonucleotides in Escherichia coli is the Chi site, an octanucleotide that stimulates DNA repair by homologous recombination. Here we analyze the genomic distribution of Chi in E. coli and in the three other bacteria where a Chi sequence has been identified; note that Chi is a different sequence in each organism. For each bacterial genome, Chi sequences are frequent, regularly distributed, and overrepresented. This suggests that selection for Chi may have occurred during evolution to favor efficient repair of a damaged chromosome. Other characteristics of Chi distribution are not conserved and might reflect specific features of DNA repair in each host. The different sequence and characteristics of Chi in each microorganism suggest that selection for Chi occurred independently in different bacteria.

Bacillus subtilis↗