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Biomedical subjects

H E Lane

Publications and source records attributed to H E Lane.

13 recordsLinked to original sources
PubMed1998

Iliosacral screw insertion using computer-assisted CT image guidance: a laboratory study.

Procedures were performed to evaluate the efficacy of using a computer-assisted image-guided system to improve the accuracy of inserting iliosacral screws for posterior pelvic ring injuries. The fluoroscopic method currently in use has shortcomings that do not eliminate the risk to the L5 and sacral nerve roots and iliac vessels. The procedure was performed on embalmed cadaver pelvis specimens with intact soft tissues. Iliosacral screws were inserted across each sacroiliac joint after registering the opposite ilium to simulate a clinical situation. Two trials were performed. The first was necessary to become familiar with the system and test the basic methods of registration. In the second trial, deficiencies were corrected by using spherical-headed fiducial screws for fiducials and a better reference frame clamp, and by better spacing of more fiducials. Results were evaluated by inlet and outlet X-ray views and dissection. All eight S-1 iliosacral 7.0-mm cannulated screws were entirely inside bone. Of the eight S-2 screws, five were inside bone, two infringed upon an S-1 foramen, and one had threads out of the sacral body anteriorly and intruding into an S-1 foramen. This system was felt to be effective and sufficiently safe to warrant clinical trials.

Bone Screws↗
PubMed1986

The miniF plasmid C protein: sequence, purification and DNA binding.

The C (pifC) protein of miniF represses transcription of its own gene by binding to the pif operator (pifO); it is also needed for replication initiated from the miniF primary origin (ori-1). We have determined the nucleotide sequence of the C gene. The gene has been inserted into an expression vector under Ptrp control where it is expressed at high levels. The C protein has been purified from cells carrying the Ptrp-C plasmid, and a preliminary study of C protein-DNA binding properties has been carried out. C protein binds strongly to pifO, and weakly to sequences in the ori-1 region.

Amino Acid Sequence↗
PubMed1982

IncD, a genetic locus in F responsible for incompatibility with several plasmids of the IncFI group.

Cloning of mini-F DNA segments has led to the identification and mapping of a locus, incD, involved in incompatibility reactions with many IncFI plasmids. The cloned incD locus expressed incompatibility with F, R386, and six other IncFI plasmids but not with ColV3-K30 or pHH507 which lack sequence homology with the incD region. A sequence of 360 bp (48.66-49.02 FKB) was found to be sufficient for expression of incD incompatibility. Multicopy vectors containing incD are compatible with each other, but can be displaced by mini-F plasmids deleted for incD. These results indicate that incD-mediated incompatibility reactions require the presence of replication genes to which incD is normally linked. The degree of incompatibility exercised by incD is moderate compared with that of other inc loci in F, suggesting that incD is involved in an aspect of plasmid maintenance, such as partition, different from the functions of the other inc loci.

Bacteriocin Plasmids↗
PubMed1982

Effects of Tn5 insertion in the incD region on mini-F maintenance and polypeptide synthesis.

The gene coding for the 33,000 dalton protein (B protein) of the mini-F plasmid has been mapped by minicell polypeptide analysis to 47.3-48.2 Fkb. Transcription of the gene is initiated near 47.3 Fkb. Gene B mutants overproduce the 42,000 dalton protein (A protein) of mini-F. Insertions of Tn5 in the B gene and in the incD region cause instability of plasmid inheritance. Mini-F plasmids deleted for part of gene B are not maintained in the absence of the incD region. B protein and the incD region appear to interact in promoting mini-F maintenance.

Bacterial Proteins↗
PubMed1982

An Mr 29000 protein is essential for mini-F maintenance in E. coli.

Plasmids consisting of mini-F inserted into multicopy vectors were constructed. Derivatives of these hybrid replicons were isolated which contained the transposon Tn5. The polypeptides encoded by these plasmids were identified by Escherichia coli minicell analysis. We show that a previously unidentified polypeptide of 29000 Mr is encoded by the mini-F gene E between 45.1 and 46.2 F kb on the mini-F plasmid map, and that this coding sequence (E gene) is transcribed rightward. Hybrid plasmids carrying Tn5 inserted into the E gene are unable to replicate in a polA- strain. Hence the E protein is essential for mini-F replication. Mutations in the A and B genes of mini-F affect E gene expression, and the results suggest that E protein synthesis is stimulated by A protein.

Bacterial Proteins↗
PubMed1982

Molecular homology and incompatibility in the IncFI plasmid Group.

The usual grounds for the inclusion of a plasmid in a particular incompatibility group are its mutual incompatibility with a type plasmid of that group, and, in some cases, the demonstration of shared regions of specific homology, presumed to be related to DNA replication. We have found that some plasmids classified as IncFI on genetical grounds share no homology with the previously described incompatibility regions of F on the basis of hybridization of specific radioactive probes to restriction enzyme digests of DNA from these plasmids. Others show homology with some or all of the regions of the F plasmid that can express incompatibility. The incompatibility behaviour of these plasmids has been examined to determine the relationship between the possession of regions of homology and the expression of incompatibility. Three plasmids, ColV3-K30, pHH507 and Entp307, show homology only with the secondary replicon of F and appear to use sequences homologous with the secondary F replicon in their replication. The results are consistent with the propositions that some contemporary IncFI plasmids arose by the integration of several replicons, and, in general, the replicon not being used for replicon expresses its incompatibility, as does the replicon being used for replication. We conclude that incompatibility of two plasmids with F does not necessarily demonstrate relatedness of the plasmids to each other, and that inclusion within the IncFI group can result from the possession of any of several combinations of inc sequences.

Base Sequence↗
PubMed1981

Analysis of mini-F plasmid replication by transposition mutagenesis.

Derivatives of a mini-F plasmid in which Tn3 is inserted in F deoxyribonucleic acid were obtained, and the sites of insertion for 40 of the derivatives were mapped. Tn3 was found to insert at many sites within mini-F, but most insertions were within the 43.0- to 43.7-kilobase (kb), 44.2- to 44.7-kb, and 45.9- to 46.3-kb segments. Hence, these segments are unnecessary for mini-F replication. Most of the Tn3 derivatives were similar to their parent miniplasmid with respect to copy number, stability, and incompatibility. Insertions at 45.15 kb and near 46.0 kb caused a moderate disruption of copy number control, and insertion at 47.6 kb resulted in unstable maintenance. Deletion derivatives lacking deoxyribonucleic acid between 40.3 and 44.76 kb and between 45.92 and 49.4 kb were obtained. This observation suggests either that mini-F contains a third origin, in addition to those already reported to be at 42.6 and 44.4 kb, or that the reported position of the secondary origin, 44.4 kb, is incorrect and that this origin is between 44.76 and 45.92 kb.

Base Sequence↗
PubMed1980

Production of extrachromosomal r-determinant circles from integrated R100.1: involvement of the E. coli recombination system.

The drug resistance plasmid R100.1 can integrate into the E. coli chromosome at several sites on the plasmid. Many of the resulting Hfr strains continuously produce extrachromosomal circular forms of the r-determinant. These r-det 'plasmids' seem incapable of stable autonomous replication. We show that their presence in the cell requires the continuous activity of functional recA and recC genes but does not require the lexA function. The production of r-det circular forms is correlated with an increased copy number of r-det sequences, relative to RTF sequences, This copy number increase is, however, also found in a recA- background where no circular forms of r-det are found. These results show that a specific replication of r-det sequences, not present in the wild-type R100.1 plasmid, occurs in these R-Hfr strains. They suggest that a rec promoted recombination, posterior to the specific replication event, is needed for the production of circular r-det forms.

DNA Replication↗
PubMed1979

Characterization of plasmids from antibiotic-resistant Shigella isolates by agarose gell electrophoresis.

Gel electrophoresis of DNA from 95 clinical isolates of Shigella sonnei and Shigella flexneri resistant to antibiotics revealed a heterogeneous plasmid population. Most of the plasmids were smaller than 6 megadaltons (Mdal). Six S. sonnei isolates with the most common antibiotic resistance pattern were characterized. They had two plasmids in common: one was a self-transmissible Fi+ plasmid of 46 Mdal encoding resistance to streptomycin and sulphafurazole. In addition, several cryptic plasmids ranging in size from 1.0 to 24.5 Mdal were present. Mobilization of the 5.5 Mdal SuSm plasmid and a 1.0 Mdal cryptic plasmid was demonstrated with all six S. sonnei isolates during conjugation. This mobilization was mediated by the 46 Mdal self-transmissible Fi+ R plasmid and also by a 24.5 Mdal Fi- plasmid carrying no known drug resistance determinants.

Anti-Bacterial Agents↗
PubMed1974

The rep mutation. III. Altered structure of the replicating Escherichia coli chromosome.

The rep gene function of Escherichia coli is essential for the replication of P2 and phiX174 double-stranded deoxyribonucleic acid (DNA). Compared with isogenic rep(+) strains, rep mutants show the following characteristics: larger cell size, more DNA per cell, and a slightly lower DNA/mass ratio. The replicating rep chromosomes show a steeper gradient of marker frequencies and contain more replicating forks per chromosome. The nucleoid body of rep mutants sediments faster and contains more DNA. We deduce that the rep function is required for the "normal" replication of the E. coli chromosome and that in its absence the E. coli chromosome replicates in an altered manner, perhaps involving slower-moving replicating forks.

Autoradiography↗