Ronald L. Shew

DIABETIC AND AGE-RELATED ENHANCEMENT OF COLLAGEN-LINKED FLUORESCENCE IN CORTICAL BONES OF RATS

Nonenzymatic collagen cross-linking occurs in a variety of connective tissues as a result of formation of advanced glycosylation end products. Diabetes and aging significantly increase levels of nonenzymatic collagen cross-linking in connective tissues. This study was undertaken to determine whether nonenzymatic collagen cross-linking occurs in rat cortical bone and if these levels are increased in diabetic and aged rats. Collagen-linked fluorescence, a measurement of nonenzymatic collagen cross-linking, was significantly increased in rat cortical bone with diabetes and age. In addition, incubation of bone powder with glucose resulted in a similar increase in collagen-linked fluorescence. These changes in bone collagen may contribute to alterations observed in bone with diabetes and age by influencing bone cell function and the ability of the matrix to be responsive to bone cells.

Hyperoxia-induced airway remodeling and pulmonary neuroendocrine cell hyperplasia in the weanling rat

Infants dying with bronchopulmonary dysplasia (BPD) demonstrate increased numbers of pulmonary neuroendocrine cells (PNEC). These infants also possess altered airway epithelial and smooth muscle dimensions reminiscent of oxygen-exposed animals. Because the pathogenesis of BPD involves oxygen toxicity, we hypothesized that chronic hyperoxia would induce both airway remodeling and PNEC hyperplasia. To test this theory, we compared the small airway morphology of 21-d-old rats subsequently exposed to 2 wk of >95% O2 (Ox; n = 12) with that of normoxic controls (Con;n = 12). In paraffin-embedded sections, airways <1500 μm cut in cross-section were analyzed using light microscopy and image analysis software. The degree of epithelial and smooth muscle hyperplasia was assessed with proliferating cell nuclear antigen (PCNA). PNEC content was assessed via immunohistochemical staining for calcitonin gene-related peptide (CGRP) and the number of solitary PNEC (PNECsol) and PNEC clusters(neuroepithelial bodies, NEB) counted per section. We found that oxygen exposure increased epithelial and smooth muscle wall thickness (epithelium: Con, 12.3 ± 1.4 versus Ox, 14.8 ± 1.4 μm,p < 0.05; smooth muscle: Con, 7.0 ± 1.0 versus Ox, 10.0 ± 1.0 μm, p < 0.05). The changes in wall dimensions were accompanied by a 20% increase in fractional PCNA labeling of the epithelium but not the smooth muscle. Both PNECsol and NEB number increased in the Ox group (PNECsol Con, 3.6 ± 2.6versus Ox, 6.3 ± 3.1/100 mm epithelium, p < 0.05; NEB Con, 7.1 ± 4.0 versus 11.9 ± 3.6/100 mm epithelium, p < 0.05). These findings document an association between hyperoxia, airway remodeling, and PNEC hyperplasia and imply that PNEC products may contribute to the pathogenesis of oxygen-related pulmonary diseases such as BPD.

Is Reflective Ability Associated With Professionalism Lapses During Medical School

Purpose Recently, many have argued that learning to reflect on one’s experiences is a critical component of professional identity formation and of professionalism. However, little empirical evidence exists to support this claim. This study explored the association between reflective ability and professionalism lapses among medical students. Method The authors conducted a retrospective case–control study of all students who matriculated at Indiana University School of Medicine from 2001 to 2009. The case group (n = 70) included those students who had been cited for a professionalism lapse during medical school; the students in the control group (n = 230) were randomly selected from the students who had not been cited for a professionalism lapse. Students’ professionalism journal entries were scored using a validated rubric to assess reflective ability. Mean reflection scores were compared across groups using t tests, and logistic regression analysis was used to assess the relationship between reflective ability and professionalism lapses. Results Reflection scores for students in the case group (2.46 ± 1.05) were significantly lower than those for students in the control group (2.82 ± 0.83) (P = .01). A lower reflection score was associated with an increased likelihood that the student had been cited for a professionalism lapse (odds ratio = 1.56; P < .01). Conclusions This study revealed a significant relationship between reflective ability and professionalism, although further study is needed to draw any conclusions regarding causation. These findings provide quantitative evidence to support current anecdotal claims about the relationship between reflection and professionalism.

Relaxation of porcine tracheal smooth muscle by parathyroid hormone-related protein

Parathyroid hormone-related protein (PTHrp) has been shown to relax uterine and gastrointestinal smooth muscles, but the mechanisms underlying its effects have not been characterized. Furthermore, its effect on pulmonary smooth muscle is unknown. Therefore we designed the present study to determine the PTHrp dose-response; the interaction of PTHrp and PTH; and the role of cyclic nucleotides and potassium channels in the PTHrp response in porcine tracheal smooth muscle (TSM). Our results indicate that, (1-34)PTHrp causes dose-dependent relaxation of TSM; that (1-34)PTHrp and (1-34)PTH demonstrate cross-tachyphylaxis to one another; that phosphodiesterase inhibition augments and phosphodiesterase stimulation attenuates the relaxation response while guanylate cyclase blockade has little effect, and that charybdotoxin and iberiotoxin, inhibitors of large conductance, Ca(2+)-activated, K+ channels, diminish the relaxation response. These findings suggest that (1-34)PTHrp-induced relaxation of TSM is mediated through a common PTHrp/PTH pathway or receptor, stimulation of cAMP and activation of large conductance, Ca(2+)-activated, K+ channels.

Pregnancy and labor increase the capacity of human myometrial cells to secrete parathyroid hormone-related protein

Parathyroid hormone-related protein (PTHrP), a oncofetal gene product possessing smooth muscle relaxant properties, has been found in rat and human uterine smooth muscle cells (USMC) where it is postulated to regulate myometrial tone and/or blood flow. Studies investigating the gestational regulation of PTHrP in human USMC have not been performed. This study was conducted to determine if pregnancy alters the capacity of USMC to secrete or respond to PTHrP. USMC cultures were established from 8 hysterectomy specimens (H) and 7 non-laboring (NP) and 5 laboring term pregnant uterine biopsies (LP). PTHrP secretion was measured at baseline and in response to TGF-beta1 using a immunoradiometric assay. The USMC response to PTHrP was assessed by incubating cultures with human (1-34)PTHrP and measuring cellular cAMP by radioimmunoassay. We found that cultures from the groups did not differ with respect to basal PTHrP secretion. TGF-beta1, on the other hand, produced dose-dependent increases in secreted PTHrP in each group such that LP>NP>H at 12 hrs and LP>NP and H 24 hrs. Maximal responses were found at 24 hrs in cells treated with 10 ng/ml TGF-beta1 (LP: 2034+/-366 vs NP: 1485+/-427; H: 1250+/-202 fmol/mg). Incubation of cultures with PTHrP produced dose-dependent increases in cAMP production, with 10(-7) M increasing levels by 64%. Neither pregnancy nor labor significantly affected the cAMP response. These findings indicate that the human myometrium has the capacity to increase PTHrP secretion during pregnancy and labor through a TGF-beta-dependent pathway. Such findings are consistent with a role of PTHrP in enhancing uterine blood flow.

The Association Between Peer and Self-Assessments and Professionalism Lapses Among Medical Students

Peer and self-assessments are widely used to assess professionalism during medical school as part of a multisource feedback model. The purpose of this study was to examine the associations between peer and self-assessments and professionalism lapses at a large medical school. A retrospective case–control study design was used to compare peer and self-assessment scores from Years 1 to 3 of medical school for students who had been cited for professionalism lapses during medical school (case group; n = 78) with those of a randomly selected control group (n = 230). Students in the case group had significantly lower peer assessment scores than students in the control group during all 3 years. Year 3 peer assessment scores showed the greatest difference (cases = 7.81 ± 0.65, controls = 8.22 ± 0.34, p < .01). Students with lower peer assessment scores were also significantly more likely to have been cited for a professionalism lapse (odds ratio = 6.25, 95% CI [3.13, 11.11], p < .01). This study reinforces the value of peer assessments of professionalism, which may be useful to help identify students who may be at risk for professionalism lapses during medical school.

PARATHYROID HORMONE-RELATED PEPTIDE (PTHrP) AND CALCITONIN GENE-RELATED PEPTIDE (CGRP) DO NOT INHIBIT UTERINE CONTRACTION THROUGH ATP-SENSITIVE K+ CHANNELS IN THE RAT UTERUS. † 423

PTHrP has been localized in the uterine endometrium and myometrium while CGRP has been localized in nerves in the uterus. We have previously reported that both peptides relax uterine contraction in a dose-related manner using tissue from nonpregnant and pregnant rats. We have been interested in the signal transduction of these peptides in the uterus. ATP-sensitive K+ channels are present in various tissues including smooth muscle and have been suggested to play a role in the vasodilatory effect of CGRP in uterine arteries. Thus, we investigated the role of ATP-sensitive K+ channels and PTHrP, CGRP and ritodrine, a β-agonist, on the relaxation of rat uterine tissue. We used an in vitro uterine assay utilizing 3-10 tissue strips for each dose from 38 nonpregnant rats. PTHrP(5×10-7-10-9 M), CGRP (10-6-10-9 M), ritodrine (10-6-10-9 M) and cromakalim (10-4-10-7 M), an ATP-sensitive K+ channel activator, inhibited acetylcholine(Ach)-stimulated (10-6 M) uterine contraction in a dose-related manner. Glyburide (10-4-10-5 M), an ATP-sensitive K+ channel blocker significantly blocked the ability of cromakalim at all doses to inhibit Ach-stimulated uterine contraction. However, using the same paradigm, glyburide at effective doses failed to block PTHrP, CGRP and ritodrine inhibition of Ach-stimulated uterine contraction. These data suggest, that in our assay, cromakalim reactive ATP-sensitive K+ channels do not play a role in PTHrP, CGRP and ritodrine relaxation of Ach-stimulated uterine contraction.

The influence of chronic verapamil treatment on calcium absorption and homeostasis in the geriatric rat

Abstract It has been demonstrated that verapamil produces a significant reduction in calcium transport in rat everted gut sacs in vitro. The purpose of the present study was to determine the effect of oral verapamil treatment on calcium absorption and homeostasis in vivo in the geriatric rat. Verapamil was administered (either oral or parenteral) to groups of 12-month-old female rats at a moderate (5 mg/kg) to large (15 mg/kg) dose over a period of 8 weeks. At the end of the 8-week treatment period, calcium transport was examined in duodenal segments and femoral bone was removed to measure bone density and mechanical strength. Blood levels of verapamil as measured by high pressure liquid chromatography were consistent with the administered dose. The results of this study indicate that chronic verapamil treatment at a dose of 15 mg/kg caused an increase in calcium transport, a reduction in calcium uptake into duodenal tissue, and an increase in serum and urinary calcium. Therefore, these results support the concept that chronic oral and/or parenteral use of calcium channel blocking agents may alter calcium homeostasis in the geriatric patient.