Impact of a teaching rotation on residents' attitudes toward teaching: a 5-year study.

BACKGROUND: Residents play a tremendous role in educating medical students and other residents during their training. Many residency programs have thus instituted formal instruction on teaching. This 5-year study was conducted to quantitatively evaluate the impact of a teaching rotation on residents' attitudes towards teaching. METHODS: Residents participated in a 1-month teaching rotation, which included didactic sessions as well as protected time to practice their teaching skills. Before and after the rotation, residents anonymously filled out surveys regarding their attitudes towards teaching. Data were collected from 73 residents from July 2004 to September 2009. The data were analyzed using a 2-tailed t-test with independent variables and a 1-way ANOVA followed by a posttest. RESULTS: Four categories showed significant improvement, including feeling prepared to teach (P < .0001), having confidence in their teaching ability (P < .0001), being aware of their expectations as a teacher (P < .0001), and feeling that their anxiety about teaching was at a healthy level (P = .0037). There was an increase in the level of enthusiasm, but the P value did not reach a significant range (P = .12). The level of enthusiasm started high and was significantly higher on the pretest than every other tested category (P < .0001). Footnote c to Table 2 should read: P value as calculated using the Mann-Whitney U test [corrected]. CONCLUSIONS: Residents are enthusiastic about teaching, and their level of enthusiasm remains high following a teaching rotation. Residents feel more prepared to teach, more confident in their teaching ability, more aware of their expectations as a teacher, and less anxious about teaching following a formal teaching rotation.

Contribution of oligosaccharides to protection of the H,K-ATPase beta-subunit against trypsinolysis.

The proton-pumping H+,K+-adenosinetriphosphatase (H,K-ATPase), responsible for acid secretion by the gastric parietal cell, faces a harshly acidic environment, with some pepsin from neighboring chief cells, at its luminal surface. Its large catalytic alpha-subunit is mostly oriented cytoplasmically. The smaller beta-subunit (HKbeta), is mainly extracellular, with one transmembrane domain and a small cytoplasmic domain. Seven N-linked oligosaccharides in the extracellular domain of HKbeta are thought to contribute to protection of the H,K-ATPase, since previous work has shown that their complete removal, by peptide N-glycosidase F (PNGase F), greatly increased susceptibility of HKbeta to proteolysis. The possibility of graded protection by different numbers of oligosaccharides was investigated here with the use of mutant HKbeta cDNA, having various N-glycosylation sites mutated (Asn to Gln), transfected into HEK-293 cells. Membrane preparations, two days after transfection, were solubilized in 1% Triton X-100 and subjected to trypsinolysis (pH 8, 37 degrees C, trypsin:protein 1:10-1:25). Relative amounts of HKbeta remaining after 20 min trypsin were determined, after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and probing of Western blots with an antibody to the HKbeta extracellular domain, by chemiluminescent development of blots and densitometry of resulting films. Maturely glycosylated HKbeta was made significantly more susceptible to trypsin than wild type when at least five oligosaccharides were deleted, while the high-mannose form (pre-beta), from the endoplasmic reticulum, became significantly more susceptible than wild-type pre-beta with removal of only two or more oligosaccharides. For each mutant, and wild type, pre-beta was consistently more susceptible than the mature form. While the number, and kind, of oligosaccharides seem to affect protection for HKbeta against trypsinolysis, other aspects of protein maturation, including proper folding of peptide domains and possible subtle alterations of conformation during Golgi processing, are also likely to contribute to this protection.

Gastric H-K-ATPase and acid-resistant surface proteins.

Despite the fact that mucus and bicarbonate are important macroscopic components of the gastric mucosal barrier, severe acidic and peptic conditions surely exist at the apical membrane of gastric glandular cells, and these membranes must have highly specialized adaptations to oppose external insults. Parietal cells abundantly express the heterodimeric, acid-pumping H-K-ATPase in their apical membranes. Its beta-subunit (HKbeta), a glycoprotein with >70% of its mass and all its oligosaccharides on the extracellular side, may play a protective role. Here, we show that the extracellular domain of HKbeta is highly resistant to trypsin in the native state (much more than that of the structurally related Na-K-ATPase beta-subunit) and requires denaturation to expose tryptic sites. Native HKbeta also resists other proteases, such as chymotrypsin and V8 protease, which hydrolyze at hydrophobic and anionic amino acids, respectively. Removal of terminal alpha-anomeric-linked galactose does not appreciably alter tryptic sensitivity of HKbeta. However, full deglycosylation makes HKbeta much more susceptible to all proteases tested, including pepsin at pH <2.0. We propose that 1) intrinsic folding of HKbeta, 2) bonding forces between subunits, and 3) oligosaccharides on HKbeta provide a luminal protein domain that resists gastric lytic conditions. Protein folding that protects susceptible charged amino acids and is maintained by disulfide bonding and hydrophilic oligosaccharides would provide a stable structure in the face of large pH changes. The H-K-ATPase is an obvious model, but other gastric luminally exposed proteins are likely to possess analogous protective specializations.