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J Light

Publications and source records attributed to J Light.

51 records · Page 3Linked to original sources
PubMed1983

Further studies on the inviability of Escherichia coli K12 rho mutant strains carrying IncFII plasmids.

Previous results (Baumberg and Lovett 1977) showed that many conjugative plasmids, most notably those of the IncFII group, were only transferable to Escherichia coli K12 rho mutants at very low frequencies, and that this appeared to be due to a lethal interaction between plasmid and rho- allele. Experiments reported here were designed to examine this phenomenon further, and in particular to test the possibility that uncontrolled plasmid replication in the presence of the rho mutant allele occurs. The rifampicin resistance allele rpo203 antagonizes the effect of rho201 on conjugal plasmid transfer; since the former is known to counteract the latter's effect on transcription termination, this result indicates that the plasmid-rho interaction stems directly from the lack of transcription termination caused by a rho mutant allele. Direct estimation of Rldrd19 replication after conjugal transfer to rho+ and rho201 recipients showed no difference according to rho status. Also, cotransduction of rho101 and 201 with ilv::Tn5 into recipients carrying miniplasmid derivatives of R1, which retain a restriction fragment containing all the DNA known to be involved in plasmid replication, was normal and the rho- transductants retained the miniplasmids. It therefore appears that the lethal interaction between the Inc FII plasmids and rho mutant alleles does not involve plasmid replication functions.

Alleles↗
PubMed1983

Application of the kidney to aortic blood flow index to renal transplants.

One hundred forty-nine standardized K/A rations (renal bolus ascending slope: aortic bolus ascending slope) were performed on 33 post-transplant patients with acute or chronic rejection, obstruction, acute tubular necrosis, infection or acute hypertension after rapid intravenous injection of Tc-99m DTPA. The correlation of creatinine clearance versus the K/A ratio for 123 pairs of data performed on the same day was poor (r = 0.37), but the correlation was greatly improved (r = 0.72) when K/A ratio maxima or minima were compared with corresponding creatinine clearances performed during a nonrejection period, or acute rejection episode, respectively. Seventeen acute rejection episodes resulted in a 20% or greater decrease in the K/A ratio 16 times, but were observed as a change in the serial perfusion phase scintiphotos only five times, or in the function phase scintiphotos only six times. Of 27 significant decreases in K/A ratios, 22 were due to acute rejection, two to obstruction, one to infection, one to acute hypertension, and one was unexplained. Thus the K/A ratio is a sensitive but not specific index for following pathological changes in the renal allograft.

Aorta↗
PubMed1982

Convergent transcription interferes with expression of the copy number control gene, copA, from plasmid R1.

The copy number control gene, copA, of plasmid R1 codes for an 80-nucleotide untranslatable RNA. In Escherichia coli minicells, some copA hybrid plasmids and R1 miniplasmids also express a transcript of 200 nucleotides. Only the small RNA mediates the CopA phenotype. The switch between 80- and 200-nucleotide RNA synthesis is shown to be caused by convergent transcription; if transcription proceeds in both directions the inactive larger RNA is synthesised; the active small RNA is formed when copA transcription is not opposed by transcription from the other direction. The data presented indicate that convergent transcription interferes with copA expression by abolishing or reducing normal copA transcription termination.

Journal Article↗
PubMed1982

The sites of action of the two copy number control functions of plasmid R1.

Two negatively acting functions - the CopA-RNA and the CopB protein - are involved in the control of replication of plasmid R1. They both act as inhibitors of expression of a gene, repA, which seems to be positively required for autonomous plasmid replication. Here we show that the two control functions act separately and independently. The CopB protein represses initiation of transcription of the repA gene, and its target site lies within a 60 base pair region containing the repA promoter. The CopA-RNA acts downstream of the repA promoter in the leader sequence containing the copA gene itself, preceding the repA structural gene. Measurements of RepA-beta-galactosidase expression from wild-type and a copA mutant fusion hybrid in the presence of extra copies of the respective copA genes show that a point mutation affecting the activity of the CopA-RNA can also affect CopA target properties. It is therefore concluded that the target site for the CopA-RNA resides within the copA gene in a small region encoding the loop of a stem-loop structure in the CopA-RNA. In addition, the data indicate a direct nucleic acid-nucleic acid interaction as the basis for the CopA inhibitor activity.

Bacterial Proteins↗
PubMed1982

Expression of a copy number control gene (copB) of plasmid R1 is constitutive and growth rate dependent.

The copy number control gene copB from plasmid R1 was fused to the lacZ gene in vitro, resulting in expression of a fused polypeptide consisting of the first 53 amino acids of the CopB polypeptide and the beta-galactosidase polypeptide minus its first 8 amino acids. Based on measurements of specific activities of this fused protein under various conditions, it was concluded that expression of copB is gene dosage dependent, unregulated by plasmid-coded functions, and proportional to growth rate between 0.4 and 2.0 doublings per h. The rate of expression of the copB gene is surprisingly high compared with other known cases of regulatory proteins.

Bacterial Proteins↗
PubMed1981

Isolation and characterization of new copy mutants of plasmid R1, and identification of a polypeptide involved in copy number control.

Site-specific deletions and insertions in the replication region of plasmid R1 have generated a new class of copy mutants that are present in the cell with 10-15-fold increased copy number. All mutations described inactivate a copy number control gene which is distinct from another cop inc gene that was identified previously (Molin and Nordström 1980). Insertion of the lac operon lacking the normal lac promoter has been used to determine the direction of transcription of this cop gene. The mutants may all be complemented by wild-type plasmid derivatives and are thus recessive. In incompatibility tests with wild-type R1 plasmids, these mutants are indistinguishable from the wild-type plasmid. It therefore seems that this cop function does not play an important role for the incompatibility function. A polypeptide, molecular weight 11,000, has been identified as being the product of this cop gene.

Bacterial Proteins↗
PubMed1978

Prosthetic functional therapy. A new method for rehabilitation of the orally handicapped patient.

A new approach to the rehabilitation of individuals who are orally handicapped after surgery offers direct support to dysfunctioning oral musculature, as well as physiologic conditioning to redirect tongue posture. Prosthetic functional therapy can be used to improve problems of speech, swallowing, drooling, and mastication in cases where structural loss of neuromuscular impairment have affected the functional competence of oral tissues. Patients who experience this therapy become highly motivated to succeed in rehabilitation as a result of a positive feedback that is provided by improvement in functional competence. Patients express both satisfaction and comfort and tend to progress favorably in the course of therapy.

Adult↗
PubMed1976

The use of an intraoral training aid in the speech rehabilitation of laryngectomy patients.

This study was undertaken to determine whether the speech of poorly rated esophageal speakers could be improved with the aid of a structured palatal prosthesis. Palatograms testing certain speech sounds critical to the plosive-injection technique for air intake showed that improvement resulted after one week of wearing the training prosthesis. All subjects showed some improvement in speech after wearing the prosthesis for one week. Eight out of 10 subjects showed marked improvement in speech. It is suggested that a physiologically structured palatal prosthesis can assist some esophageal speakers to improve their speech.

Humans↗
PubMed1975

Nephrectomy in selected patients with severe refractory hypertension receiving dialysis.

The effect of bilateral nephrectomy was examined in ten patients with severe hypertension in whom dialysis and multiple drug therapy had not resulted in blood pressure control and was compared with that in 15 patients undergoing nephrectomy solely in preparation for transplantation. A highly significant, P less than 0.0005, and clinically impressive reduction in mean blood pressure occurred in the first group of patients, permitting discontinuation of all drugs. Although impossible to quantitate, these patients also demonstrated a reversal of a failure-to-thrive syndrome which had seriously compromides prenephrectomy management. Nephrectomy resulted in a reduction in mean hematocrit values of greater than 20 per cent and less than or equal to 20 percent showed a significant fall in the former but not in the latter. No increase in transfusion requirements developed in these patients. Until more potent and reliable medical therapy becomes generally availabe, nephrectomy will remain an important treatment modality in those patients requiring dialysis and having severe unremitting hypertension.

Antihypertensive Agents↗