Search PubMed⌕ Search

Biomedical subjects

J M Watson

Publications and source records attributed to J M Watson.

At least 181 records · Page 10Linked to original sources
PubMed1987

Evidence for genetic exchange and recombination of Rhizobium symbiotic plasmids in a soil population.

A soil population of 16 Rhizobium leguminosarum bv. trifolii isolates was characterized by using three Sym (for symbiotic) plasmid-specific DNA hybridization probes: (i) an R. leguminosarum bv. trifolii-specific, repeated-sequence probe; (ii) a nifHDK gene probe, and (iii) a nod gene probe. A predominant Sym plasmid family was identified among the isolates. Three other unrelated Sym plasmid families were also identified. The isolates were also classified either by using a chromosomal DNA hybridization probe or by serological relatedness to 25 different R. leguminosarum bv. trifolii antisera. With either method, it was possible to group the 16 soil isolates into identical or related families. However, the correlation between the two techniques was not high. Irrespective of the means used to classify the bacterial host strain, it was possible to identify the same Sym plasmids in unrelated strains, as well as unrelated Sym plasmids in identical host strains. These data indicate that, within this soil population, there has been genetic exchange of Sym plasmids, and in one instance the hybridization pattern indicates that in vivo recombination of two different Sym plasmids may have occurred. Symbiotic effectiveness tests on red, strawberry, and subterranean clovers clearly differentiated the isolates. In general, the pattern of response was similar within groupings on the basis of Sym plasmid and chromosomal profiles but different between such groups.

Journal Article↗
PubMed1986

DNA sequence of Rhizobium trifolii nodulation genes reveals a reiterated and potentially regulatory sequence preceding nodABC and nodFE.

The Rhizobium trifolii nod genes required for host-specific nodulation of clovers are located on 14 kb of Sym (symbiotic) plasmid DNA. Analysis of the nucleotide sequence of a 3.7 kb portion of this region has revealed open reading frames corresponding to the nodABCDEF genes. A DNA sequencing technique, using primer extension from within Tn5, has been used to determine the precise locations of Tn5 mutations within the nod genes and the phenotypes of the corresponding mutants correlate with their mapped locations. The predicted nodA and nodB genes overlap by four nucleotides and the nod F and nodE genes overlap by a single nucleotide, suggesting that translational coupling may ensure the synthesis of equimolar amounts of these gene products. The nodABC and nodFE genes constitute separate transcriptional units and each is preceded by a conserved 76-bp sequence which may be involved in the regulation of expression of these genes.

Amino Acid Sequence↗
PubMed1986

Expression of biosynthetic genes from Pseudomonas aeruginosa and Escherichia coli in the heterologous host.

We examine the expression of constitutive or repressible, monocistronic genes from Pseudomonas aeruginosa and Escherichia coli after their transfer to the heterologous host. To this end, chromosomal DNA from P. aeruginosa was cloned into the mobilizable broad-host-range vector pKT240; recombinant plasmids carrying the argA, argF, or proC genes were identified by complementation of the corresponding auxotrophic mutations. The isofunctional E. coli genes and the E. coli proB gene were subcloned into pKT240 from existing recombinant plasmids. The enzyme expression specified by the Pseudomonas genes in E. coli, calculated per gene copy, ranged from 0.3%-5% of the levels observed in Pseudomonas. Fusion of the P. aeruginosa proC gene to the E. coli consensus tac promoter resulted in very high proC enzyme production in E. coli, indicating that, at least in this case, the expression barrier is essentially at the level of transcriptional initiation. The E. coli argA and argF enzymes, which are controlled by repression in their native host, were synthesized constitutively in P. aeruginosa at 5% of the levels measured in E. coli under derepressed conditions. The constitutive E. coli proB and proC genes were expressed at high levels (ca. 50%) in the heterologous host. These results support the idea that P. aeruginosa may be a more permissive host than E. coli for the heterologous expression of genes from gram-negative bacteria.

Chromosomes, Bacterial↗
PubMed1985

Conservation of nif- and species-specific domains within repeated promoter sequences from fast-growing Rhizobium species.

In the fast-growing Rhizobium species, repeated DNA sequences, which include the promoter region of the nif HDK operon have been described. These repeated sequences are promoters which specifically activate transcription in the endosymbiotic state. Hybridization analysis of these sequences from R. trifolii has revealed that they may be involved in the species-specific activation of the various genes whose transcription they promote. Comparative analysis of various copies of these repeated sequences, from R. trifolii (the clover symbiont) and R. meliloti (the alfalfa symbiont), reveals the presence of domains of intra- and interspecific conservation within the promoter regions. We suggest that these promoter elements represent sites which are involved in the species-specific and general, nif-specific activation of Rhizobium symbiotic genes.

Klebsiella pneumoniae↗
PubMed1984

Genetic and molecular characterization of the Pseudomonas plasmid pVS1.

A restriction map of the 30-kb nonconjugative Pseudomonas plasmid pVS1 was constructed. Derivatives of pVS1 obtained in vitro by successive deletions were used to localize on the physical map the determinant for resistance to mercuric ions (carried by transposon Tn501), the gene(s) encoding sulfonamide resistance, a 1.6-kb region affecting plasmid stability and establishment in P. fluorescens ATCC 13525, and a segment required for mobilization of pVS1 by plasmid RP1. The sulfonamide resistance determinant of pVS1 appeared to be closely related to that of transposon Tn21. A mini-pVS1 replicon, pME259, consisting of an essential 1.55-kb segment (designated rep and thought to carry the origin of replication) and a mercury resistance determinant was able to replicate P. aeruginosa PAO but selective pressure was needed for plasmid maintenance. The copy number of pVS1 derivatives was estimated to be 6-8 per chromosome equivalent. Plasmids possessing the essential rep segment plus the adjacent stability region could be established in strains of P. aeruginosa, P. putida, P. fluorescens, P. acidovorans, P. cepacia, P. mendocina, P. stutzeri, P. syringae, Agrobacterium tumefaciens, and Rhizobium leguminosarum.

DNA Replication↗
PubMed1983

Construction of recombination-deficient strains of Pseudomonas aeruginosa.

The rec-102 mutation had pleiotropic effects in Pseudomonas aeruginosa: low recombinational proficiency in conjugation and transduction; high UV sensitivity; inability to induce pyocin R2 by mitomycin C; and increased susceptibility to mitomycin C and nalidixic acid. The rec-102 locus was mapped by R68.45-mediated conjugation in the 45 min region of the PAO chromosome, between argF and thr-9001. By selection for a marker in this region, rec-102 can be introduced into a P. aeruginosa strain of interest using an R68.45 rec-102 donor. The recombination-deficient strains constructed in this way were phenotypically similar to Escherichia coli recA mutants.

Chromosome Mapping↗
PubMed1982

Clawfinger correction: results of extensor-flexor many tailed operation.

The patient with paralytic clawfingers is greatly handicapped. This is especially true for the leprosy patient who needs his hands to earn a living. The inability to 'reach out' with the fingers is the most serious functional loss in an ulnar palsy. This study is a follow up of 155 hands whereby the extensor carpi radialis longus was employed to substitute for this lumbrical-interosseus function. The best results were obtained in hands with full assisted extension. Retropulsion of the metacarpal arch occurred in all hands with total loss of ulnar function.

Fingers↗
PubMed1982

Solvent abuse: presentation and clinical diagnosis.

1 Solvent abuse is not a new phenomenon--it has been practised by children and adolescents in America and elsewhere since the 1950s. 2 It was in November 1970 that police in the west of Scotland first identified the problem in a local industrial area. Since then there appears to have been an enormous increase in the size of the problem throughout Britain. 3 This paper deals with a review of 400 cases of solvent abuse referred to the investigator between 1975 and 1981. The substance used, the methods employed and the many and varied clinical effects resulting from solvent misuse in these cases are reviewed and discussed.

Adolescent↗
PubMed1981

Solvent encephalopathy.

Nineteen children aged 8-14 years were admitted over a six-year period with an acute encephalopathy due to toluene intoxication. Seven had a history of euphoria and hallucinations. The remainder presented with coma (4), ataxia (3), convulsions (3), and behaviour disturbance with diplopia (2), A history of glue sniffing was elicited in 14, but in the remainder toluene assay confirmed the diagnosis. Thirteen children recovered completely; five still had psychological impairment and personality change on discharge from hospital but were lost to follow-up, and one has a persistent cerebellar ataxia one year after the acute episode, despite absence of further exposure. Toluene inhalation is an important cause of encephalopathy in children and may lead to permanent neurological damage. Diagnosis is most important if further damage due to continued abuse is to be prevented, and toluene assay is a valuable aid to diagnosis.

Adhesives↗
PubMed1981

Zimelidine: comparison of different dosage regimes in general practice.

Various studies have demonstrated that depressive symptoms are a frequent and important problem in general practice. Zimelidine has been shown to have effective antidepressant activity. A controlled double-blind trial was set up to compare the efficacy and side effects of zimelidine when given as a single daily dose (200 mg night or morning) and when given as a divided dose (100 mg b.d.). These three dosage schedules were studied. The trial was conducted among patients attending their general practitioners and suffering from a depressive disorder. Using one of the three dosage schedules, these patients were treated with zimelidine for a minimum period of 6 weeks. Symptom severity was measured by means of the Hamilton Rating Scale for Depression and the side effects assessed using an adverse event record and a symptom checklist. The findings are discussed.

Adult↗
PubMed1980

Centres of excellence.

The present Government may not be enthusiastic about health centres. But Dr Joyce M. Watson, of Glasgow University Department of General Practice and based at Woodside Health Centre in Glasgow, writes with enthusiasm of their advantages for the practice of medicine and the care of patients.

Community Health Centers↗