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J A Newton

Publications and source records attributed to J A Newton.

At least 19 recordsLinked to original sources
PubMed2004

Potato plants genetically modified to produce N-acylhomoserine lactones increase susceptibility to soft rot erwiniae.

Many gram-negative bacteria employ N-acylhomoserine lactones (AHL) to regulate diverse physiological processes in concert with cell population density (quorum sensing [QS]). In the plant pathogen Erwinia carotovora, the AHL synthesized via the carI/expI genes are responsible for regulating the production of secreted plant cell wall-degrading exoenzymes and the antibiotic carbapen-3-em carboxylic acid. We have previously shown that targeting the product of an AHL synthase gene (yenI) from Yersinia enterocolitica to the chloroplasts of transgenic tobacco plants caused the synthesis in planta of the cognate AHL signaling molecules N-(3-oxohexanoyl)-L-homoserine lactone (3-oxo-C6-HSL) and N-hexanoylhomoserine lactone (C6-HSL), which in turn, were able to complement a carI-QS mutant. In the present study, we demonstrate that transgenic potato plants containing the yenI gene are also able to express AHL and that the presence and level of these AHL in the plant increases susceptibility to infection by E. carotovora. Susceptibility is further affected by both the bacterial level and the plant tissue under investigation.

Carboxylic Ester Hydrolases↗
PubMed2004

Integration of environmental and host-derived signals with quorum sensing during plant-microbe interactions.

Many plant-associated microbes use secreted autoinducer molecules, including N-acylhomoserine lactones (AHLs), to regulate diverse behaviours in association with their population density (quorum sensing). Often, these responses are affected by environmental conditions, including the presence of other AHL-producing bacterial species. In addition, plant-derived metabolites, including products that arise as a direct result of the bacterial infection, may profoundly influence AHL-regulated behaviours. These plant products can interact directly and indirectly with the quorum-sensing network and can profoundly affect the quorum-sensing behaviour. Local conditions on a microscopic scale may affect signal molecule longevity, stability and accumulation, and this could be used to give information in addition to cell density. Furthermore, in many Gram-negative bacteria, AHL signalling is subservient to an additional two-component signalling system dependent upon homologues of GacS and GacA. The signal(s) to which GacS responds are not known, but recent research suggests that a self-produced ligand may be being detected. This review will focus on two well-studied examples of AHL-regulated plant-associated behaviour, Erwinia carotovora and Agrobacterium tumefaciens, to illustrate the complexity of such signalling networks.

Agrobacterium tumefaciens↗
PubMed1994

Malaria in US Marines returning from Somalia.

OBJECTIVE: To identify malaria in US Marines returning from Somalia and to determine their compliance with chemoprophylaxis. DESIGN: Case series. SETTING: The US Navy health care system. PATIENTS: Consecutive sample of 106 US Marines diagnosed with malaria after returning from Somalia in 1993. MAIN OUTCOME MEASURES: Identification of the incidence and clinical features of imported malaria. Determination of compliance with chemoprophylaxis in this cohort. RESULTS: As of December 20, 1993, there were 112 cases of imported malaria in 106 US Marine Corps personnel returning from Somalia. Plasmodium vivax accounted for 97 (87%) of 112 malaria cases, and Plasmodium falciparum accounted for eight (7%) of 112 cases. Mixed infection with P vivax and P falciparum was noted in six (5%) of 112 cases, and a single case of Plasmodium malariae was identified. Patients with P falciparum malaria were diagnosed a mean of 20.9 days (range, 1 to 82 days) after returning to the United States compared with 91.8 days (range, 7 to 228 days) for P vivax infection (P < .0001). The self-reported chemoprophylaxis compliance rate was 56%; however, only 45 (50%) of 90 patients were given an optimal chemoprophylaxis regimen. CONCLUSIONS: Noncompliance with personal protective measures and chemoprophylaxis contributed to the largest outbreak of imported malaria in US military personnel since the Vietnam conflict. Since military personnel frequently go on leave after deployment, health care providers throughout the United States must be aware of the presence of imported malaria from Somalia.

Cohort Studies↗
PubMed1994

Genetics of melanoma.

Melanoma may cluster in families with 'family cancer syndromes' in which there is a predisposition to a variety of different tumours. Other families seem vulnerable to melanoma alone. In the majority of these families, the propensity to melanoma is associated with the presence of abnormal melanocytic naevi, the so-called atypical mole syndrome (AMS) phenotype. However, in a smaller number of families, individuals are susceptible to melanoma but have normal naevi. There appears, therefore, to be clinical (and probably genetic) heterogeneity. Segregation analysis does not support a predisposition by single dominant gene as an explanation for the AMS/melanoma syndrome. To date, a single gene which is clearly important for susceptibility to melanoma has not been identified. Karyotypic studies of melanoma tumours have pointed to chromosomes 1, 6, 7, 9 and 10 as possible sites for melanoma related genes. Loss of heterozygosity studies have suggested that chromosome 9 may carry a tumour suppressor gene important in familial disease, and linkage studies appear to confirm this. It is not yet clear, however, what percentage of familial melanoma is attributable to this gene. A more longstanding suggestion that a gene on chromosome 1 may be important has not been confirmed, but a chromosome/gene may be responsible for susceptibility in a small subset of melanoma families. Even within AMS families, there is a lack of concordance between the AMS phenotype and susceptibility to melanoma. This might be explained either by the effects of modifying genes, or the environment.

Cytogenetics↗
PubMed1994

Muir-Torre syndrome: a variant of the cancer family syndrome.

Muir-Torre syndrome is characterised by the association of sebaceous tumours of the skin with internal malignancy. In many instances there is a strong family history of cancer and the autosomal dominant mode of inheritance, tumour spectrum, and high incidence of synchronous and metachronous tumours show parallels with the cancer family syndrome or Lynch II syndrome. We report a five generation family with at least two persons displaying the Muir-Torre phenotype, while many other family members have had tumours consistent with cancer family syndrome. The majority of tumours are gastrointestinal, gynaecological, and urological, with several persons having multiple primaries. The prognosis appears to be better than would be expected. Sebaceous tumours are a marker for internal malignancy and should prompt a search for occult cancer in the individual person and family members. In documented Muir-Torre families, at risk persons should be entered into screening programmes similar to those used in the Lynch II syndrome.

Adult↗
PubMed1993

How common is the atypical mole syndrome phenotype in apparently sporadic melanoma?

BACKGROUND: Although patients from some families with the atypical mole syndrome (AMS) are predisposed to melanoma, it is not known how frequently this underlies the apparently sporadic presentation of melanoma. OBJECTIVE: This study was designed to estimate the frequency of the AMS (dysplastic nevus or FAMMM syndrome) phenotype in a population-based study of patients with melanoma in the United Kingdom and to determine the prevalence of the phenotype in the relatives of the patients with AMS. METHODS: The nevi of patients with melanoma and controls in a case-control study, and the nevi of some relatives of patients with AMS, were examined. An AMS scoring system was used to define the AMS phenotype. The familiarity of the AMS phenotype was then determined by screening first-degree relatives of persons with the AMS phenotype. RESULTS: Forty of 266 (15%) of patients with melanoma had the AMS phenotype compared with 7 of 305 (2%) of the controls (odds ratio 7.5, 95% confidence interval 3.4-16.8). Screening of relatives of patients with melanoma who had the AMS phenotype identified the same phenotype within the families, providing evidence that the AMS phenotype in patients with melanoma is predictive of the same phenotype in relatives, consistent with so-called type D1 AMS. CONCLUSION: The AMS phenotype is a potent risk factor for cutaneous melanoma and is present in 15% of patients. Melanoma in the United Kingdom is more common in women than in men, but the AMS phenotype was more frequent in men in this study. It is our hypothesis that the effects of the putative AMS gene are diluted by environmental factors in U.K. women. Screening of relatives of patients with melanoma who have the AMS phenotype may identify persons at increased risk of melanoma.

Adolescent↗
PubMed1993

Soft-tissue infection due to Mycobacterium smegmatis: report of two cases.

Mycobacterium smegmatis is an uncommon pathogen in humans. Fourteen cases of skin or soft-tissue infection due to M. smegmatis have been previously reported. We report two cases of posttraumatic M. smegmatis infection of the lower extremity. M. smegmatis infection produces chronic cellulitis with fistula formation that is most commonly a result of direct traumatic inoculation of contaminated material. Extensive surgical debridement followed by skin grafting has been necessary for cure in the majority of cases.

Adult↗
PubMed1993

Three cases of primary acquired melanosis of the conjunctiva as a manifestation of the atypical mole syndrome.

We report three patients with the atypical mole syndrome (AMS) [also known as dysplastic naevus or FAMMM syndrome] who presented with primary acquired melanosis (PAM). PAM is a melanocytic lesion of the conjunctiva which may progress to conjunctival melanoma. The association of this rare condition with the AMS phenotype in three individuals suggests that PAM may be a conjunctival manifestation of the AMS.

Adult↗