Biomedical subjects
Publications and source records attributed to S Cutler.
Live-cell imaging has yielded surprising pictures of subcellular structures and dynamics in living plant cells. Recent studies illustrate the power of live-cell observation for revealing new biological phenomena and for generating new questions about plant cell structure and function.
Although abscisic acid (ABA) is involved in a variety of plant growth and developmental processes, few genes that actually regulate the transduction of the ABA signal into a cellular response have been identified. In an attempt to determine negative regulators of ABA signaling, we identified mutants, designated enhanced response to ABA3 (era3), that increased the sensitivity of the seed to ABA. Biochemical and molecular analyses demonstrated that era3 mutants overaccumulate ABA, suggesting that era3 is a negative regulator of ABA synthesis. Subsequent genetic analysis of era3 alleles, however, showed that these are new alleles at the ETHYLENE INSENSITIVE2 locus. Other mutants defective in their response to ethylene also showed altered ABA sensitivity; from these results, we conclude that ethylene appears to be a negative regulator of ABA action during germination. In contrast, the ethylene response pathway positively regulates some aspects of ABA action that involve root growth in the absence of ethylene. We discuss the response of plants to ethylene and ABA in the context of how these two hormones could influence the same growth responses.
The irregular xylem3 (irx3) mutant of Arabidopsis has a severe deficiency in secondary cell wall cellulose deposition that leads to collapsed xylem cells. The irx3 mutation has been mapped to the top arm of chromosome V near the marker nga106. Expressed sequence tag clone 75G11, which exhibits sequence similarity to cellulose synthase, was found to be tightly linked to irx3, and genomic clones containing the gene corresponding to clone 75G11 complemented the irx3 mutation. Thus, the IRX3 gene encodes a cellulose synthase component that is specifically required for the synthesis of cellulose in the secondary cell wall. The irx3 mutant allele contains a stop codon that truncates the gene product by 168 amino acids, suggesting that this allele is null. Furthermore, in contrast to radial swelling1 (rsw1) plants, irx3 plants show no increase in the accumulation of beta-1,4-linked glucose in the noncrystalline cell wall fraction. IRX3 and RSW1 fall into a distinct subgroup (Csa) of Arabidopsis genes showing homology to bacterial cellulose synthases.
The authors describe the production and characterization of a collection of Arabidopsis lines each carrying a transposed Ac (trAc) element. A total of 507 lines were obtained following germinal transpositions of a single Ac element located on the upper portion of chromosome III. Southern analysis revealed that up to 90% of the lines in this collection harbour distinct insertions of Ac in the Arabidopsis genome. As previous studies on the behaviour of Ac in Arabidopsis have indicated that approximately two out of three transposition events occur to linked loci, the authors hypothesized that this collection could be of great use in isolating insertional mutants for genes located in the vicinity of the donor locus. PCR and phenotypic screens were performed to identify mutations in five loci located within a 40 cm region of chromosome III centered on the donor locus. Molecular analyses confirmed the presence of germinal insertions of Ac in three of the loci (NPTII, ABI3 and EST #210A22). At a fourth locus (AtDMC1), despite the absence of a germinal insertion, one line in which somatic insertions occurred regularly was identified and may be of use in isolating a germinal insertion. This collection of trAc lines constitutes a useful complement to the existing collection of T-DNA insertion lines and will soon be made available through the Arabidopsis Biological Resource Center.
Cellulose is a major component of plant cell walls, but identification of the enzymes that synthesize it has proven difficult. Now, however, several candidate proteins with sequence homology to bacterial cellulose synthases have been identified by partial sequencing of anonymous cDNA clones from cotton fibers.
The hormone abscisic acid (ABA) modulates a variety of developmental processes and responses to environmental stress in higher plants. A collection of mutations, designated era, in Arabidopsis thaliana that confer an enhanced response to exogenous ABA includes mutations in the Era1 gene, which encodes the beta subunit of a protein farnesyl transferase. In yeast and mammalian systems, farnesyl transferases modify several signal transduction proteins for membrane localization. The era1 mutants suggest that a negative regulator of ABA sensitivity must be acted on by a farnesyl transferase to function.
The effect of methylprednisolone on the myocardial beta-adrenergic receptors after long term ( > 72 h) catecholamine infusion was studied. In 56 patients with pulmonary arterial catheter, 10 mg/kg of methylprednisolone was given as an intravenous bolus. Significant increases could be seen in cardiac output and blood pressure in patients who were simultaneously treated with vasopressors like dopamine and/or dobutamine. In patients who were on dopamine infusion higher than 10 micrograms/kg/min methylprednisolone there was an increase in the systemic vascular resistance. Patients who were not on vasopressors but received methylprednisolone, had no similar changes in hemodynamic parameters. In an in vitro analysis of tissue from the myocardium in 12/56 patients who succumbed and in four additional patients who expired after multiple trauma, a beta-adrenergic receptor assay was performed. It was found that the long term infusion of catecholamines decreased the receptor number and the methylprednisolone abolished or caused the decrease to be less pronounced. In this study we could not control the selection of the patients; a randomized study needs to be conducted in the future.
The purpose of this study was to evaluate the use of autogenous gingival grafts as barriers for endosseous implants placed directly into fresh extraction sockets. This study consisted of four patients who presented with hopeless teeth due to endodontic pathology, caries, or root resorption. In all cases, the teeth in question were extracted at the Stage 1 surgery. An endosseous root form implant was immediately placed into the extraction socket in each case. As a consequence of immediate placement, there was a lack of primary closure over the fixture and a large space was present between the fixture and the remaining alveolus. An autogenous gingival graft was sutured in place to cover the fixture and act as a physical barrier to epithelium, food debris, and possibly bacteria. At the Stage 2 surgery, all implants achieved complete osseointegration clinically and radiographically. The results at 16 to 24 months reveal continued success in all four cases. This report demonstrates the potential of autogenous gingival grafts in immediate implant placement. A clinical trial to fully assess the potential of this procedure is recommended.
The data pertaining to Irish specimens sent to the Lyme disease Laboratory at Charing Cross Hospital since 1986 is presented and discussed. In the period up to June 1990, 484 specimens were tested, 14% of these were positive by enzyme linked immunosorbent assay or indirect immunofluorescent assay. Only 13 of these were confirmed as positive by immunoblotting.
OBJECTIVE: To determine effectiveness of advice from general practitioners to heavy drinkers to reduce their excessive alcohol consumption (35 U or more a week for men, 21 U or more for women). DESIGN: Randomised, controlled double blind trial over 12 months with interim assessment at six months. SETTING: Group practices (n = 47; list size averaging 10,000) recruited from Medical Research Council's general practice research framework, mostly in rural or small urban settings. PATIENTS: Patients recruited after questionnaire survey. Of total of 2571 (61.2%) of 4203 patients invited for interview who attended, 909 (35.4%) stated that in past seven days they had drunk above the limits set for study and had not received advice; they were randomised to control and treatment groups. INTERVENTIONS: Patients in treatment group were interviewed by general practitioner (who had had a training session) and received advice and information about how to reduce consumption and also given a drinking diary. END POINT: Study aimed at detecting a reduction in proportion of men with excessive alcohol consumption of 30% in treatment group and 20% in control group (for women 40% and 20%, respectively) with a power of 90% at 5% level of significance. In addition, corroborative measures such as estimation of gamma-glutamyltransferase activity were included. MEASUREMENTS AND MAIN RESULTS: At one year a mean reduction in consumption of alcohol of 18.2 (SE 1.5) U/week had occurred in treated men compared with a reduction of 8.1 (1.6) U/week in controls (p less than 0.001). The proportion of men with excessive consumption at interview had dropped by 43.7% in the treatment group compared with 25.5% in controls (p less than 0.001). A mean reduction in weekly consumption of 11.5 (1.6) U occurred in treated women compared with 6.3 (2.0) U in controls (p less than 0.05), with proportionate reductions of excessive drinkers in treatment and control groups of 47.7% and 29.2% respectively. Reduction in consumption increased significantly with number of general practitioner interventions. At one year the mean value for gamma-glutamyltransferase activity had dropped significantly more in treated men (-2.4 (0.9)IU/l) than in controls (+1.1(1.0)IU/l; t = 2.7, p less than 0.01). Reduction in gamma-glutamyltransferase activity tended to increase with number of intervention sessions in men. Changes in gamma-glutamyltransferase activity in women and changes in other indicators in both sexes did not differ significantly between treatment and control groups. CONCLUSIONS: If the results of this study were applied to the United Kingdom intervention by general practitioners could each year reduce to moderate levels the alcohol consumption of some 250000 men and 67500 women who currently drink to excess. General practitioners and other members of the primary health care team should therefore be encouraged to include counselling about alcohol consumption in their preventive activities.
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BACKGROUND AND OBJECTIVES: The authors previously reported a case in which injection of local anesthetic posterior to the endothoracic fascia at the T11 vertebral level gave rise to extended analgesia in thoracic and lumbar dermatomes. They now report a study in which this type of anesthesia was used in patients undergoing herniorrhaphy. METHODS: A 12-mL dose of 2% mepivacaine was injected at the T11 level posterior to the endothoracic fascia in 15 patients. RESULTS: On average, seven dermatomes could be blocked with this dose and with a single injection. Nine patients experienced adequate analgesia and underwent operation with no additional sedation. In three patients the block resulted in inadequate analgesia, and additional sedative drugs were used. Three patients experienced no analgesia and were given general anesthesia CONCLUSION: Injection of local anesthetic posterior to the endothoracic fascia resulted in extended unilateral anesthesia that was adequate for herniorrhaphy in 9 of the 15 patients (60%) studied.