Biomedical subjects

Christine Martin

Publications and source records attributed to Christine Martin.

5 recordsLinked to original sources

PubMed2003

Leucine-responsive regulatory protein-mediated repression of clp (encoding CS31A) expression by L-leucine and L-alanine in Escherichia coli.

CS31A produced by septicemic and diarrheic Escherichia coli belongs to the Pap-regulatory family of adhesive factors, which are under methylation-dependent transcriptional regulation. Common features of operons encoding members of this family include two conserved GATC sites in the upstream regulatory region, and transcriptional regulators homologue to the PapB and PapI proteins. Methylation protection of GATC sites was previously shown to be dependent on the leucine-responsive regulatory protein (Lrp). Lrp and ClpB, the PapB equivalent, repressed clp basal transcription. A PapI homologue (AfaF) was required together with Lrp to establish the phase variation control, which gave rise to phase-ON cells that expressed CS31A and phase-OFF cells that did not express CS31A. In phase-OFF cells, the GATC(dist) site was methylated and the GATC(prox) site was protected from methylation, whereas in phase-ON cells, the inverse situation was found. Unlike Pap fimbriae, CS31A synthesis was dramatically reduced in media containing L-alanine or L-leucine. L-Alanine prevented the OFF-to-ON switch, locking clp expression in the OFF phase, whereas L-leucine repressed transcription without obvious effect on the switch frequency of phase variation. In phase-variable cells, leucine and alanine promoted methylation of GATC(dist) and methylation protection of GATC(prox), increasing the methylation pattern characteristic of repressed cells. Furthermore, alanine prevented the AfaF-dependent methylation protection of GATC(dist) and thus the appearance of phase-ON cells. In addition, analysis of clp expression in a Lrp-negative background indicated that alanine and leucine also repressed clp transcription by a methylation-independent mechanism.

Adenosine Triphosphatases↗

PubMed2002

Shifting paradigms: from Flexner to competencies.

Realizing medical education is on the brink of a major paradigm shift from structure- and process-based to competency-based education and measurement of outcomes, the authors reviewed the existing medical literature to provide practical insight into how to accomplish full implementation and evaluation of this new paradigm. They searched Medline and the Educational Resource Information Clearinghouse from the 1960s until the present, reviewed the titles and abstracts of the 469 articles the search produced, and chose 68 relevant articles for full review. The authors found that in the 1970s and 1980s much attention was given to the need for and the development of professional competencies for many medical disciplines. Little attention, however, was devoted to defining the benchmarks of specific competencies, how to attain them, or the evaluation of competence. Lack of evaluation strategies was likely one of the forces responsible for the three-decade lag between initiation of the movement and wide-spread adoption. Lessons learned from past experiences include the importance of strategic planning and faculty and learner buy-in for defining competencies. In addition, the benchmarks for defining competency and the thresholds for attaining competence must be clearly delineated. The development of appropriate assessment tools to measure competence remains the challenge of this decade, and educators must be responsible for studying the impact of this paradigm shift to determine whether its ultimate effect is the production of more competent physicians.

Clinical Competence↗

PubMed2001

Ca3Mn2O7.

The tricalcium dimanganese heptaoxide (Ca3Mn2O7) member of the Ruddlesden-Popper series Ca(n+1)Mn(n)O(3n+1), i.e. with n = 2, was previously reported with an I-centred tetragonal lattice [a(t) = 3.68 and c(t) = 19.57 A] by Fawcett, Sunstrom, Greenblatt, Croft & Ramanujachary [Chem. Mater. (1998), 10, 3643-3651]. It is now found to be orthorhombic, with an A-centred lattice [a = 5.2347 (6), b = 5.2421 (2) and c = 19.4177 (19) A]. The structure has been refined in space group A2(1)am using X-ray single-crystal diffraction data and assuming the existence of twin domains related by the (1-10) plane. A comparison with the basic perovskite structure CaMnO3 (n = infinity) is proposed.

Journal Article↗

PubMed2001

Do future general surgery residents have adequate exposure to endocrine surgery during medical school?

During their general surgical rotations, medical students should ideally have exposure to a wide breadth of surgical procedures, especially if they are interested in pursuing surgical careers. To determine their exposure to endocrine surgery during medical school, we surveyed students from more than 20 medical schools who interviewed for general surgery residency positions at our institution over a 2-year period. Questions focused on the total number of index surgical procedures observed during all of their medical school education. Of 211 surveys sent, 146 were returned (66%). The mean age of the students was 26.0 +/- 0.3 years, and 21% were women. The average times spent on general surgery and surgery subspecialty rotations during medical school were 11.1 +/- 0.6 weeks and 7.6 +/- 0.4 weeks, respectively. The mean number of thyroidectomies (2.8 +/- 0.3), parathyroidectomies (1.9 +/- 0.3), and adrenalectomies (0.5 +/- 0.1) observed by the medical students were significantly lower than operations such as mastectomies (9.4 +/- 0.3), coronary bypass surgeries (8.7 +/- 1.4), and laparoscopic cholecystectomies (10.0 +/- 0.7). Furthermore, of these 146 future surgical residents, 34% failed to observe a single thyroid resection, 42% did not see a parathyroidectomy, and 65% failed to see an adrenalectomy. In conclusion, future general surgery residents seem to observe a wide variety of surgical cases, but most have little or no exposure to endocrine surgery. This paucity of exposure may have significant educational and career ramifications.

Adrenalectomy↗

PubMedDate not supplied

Effect of diet on Shiga toxin-producing Escherichia coli (STEC) growth and survival in rumen and abomasum fluids.

The gastrointestinal tract of ruminants is the main reservoir for Shiga toxin-producing Escherichia coli (STEC) strains, potentially pathogenic for humans. We used for the first timerumen fluid in which no exogenous carbon source or other supplement was added to compare acid resistance and growth of STEC in physiological physico-chemical conditions. We showed that acidic conditions resulting from the combination of high volatile fatty acid concentration and moderately acidic pH did not alter the survival of STEC, and that human non-O157:H7 STEC isolates were able to persist in the rumen contents in spite of acid stress, low oxygen availability and nutrient deprivation, in the same manner as bovine STEC isolates do. Furthermore, our results support the hypothesis that a grain-rich diet may induce mechanisms of STEC acid resistance in the rumen that allow STEC survival in the abomasum.

Abomasum↗