TEP and Lichtenstein anatomy: does simulation accelerate acquisition among interns?

PURPOSE: The anatomy of the inguinal region is notoriously challenging to master. We sought to teach open inguinal hernia (OIH) and totally extraperitoneal (TEP) anatomy with simulation models among general surgery (GS) interns. METHODS: Low-fidelity OIH and TEP models were constructed out of cardboard, plastic bins, fabric, and yarn. GS interns (n = 30) participated in a 3-h hernia session including a pretest, anatomy lecture, simulated OIH and TEP hernia repair, and posttest. Pre- and posttest scores were based on a difficult 30-point exam which included didactic questions (10 points), drawing relevant TEP (10 points), and OIH (10 points) anatomy. Participants were surveyed following the session. RESULTS: Median pretest scores were 13 % (range 0-60 %). Median posttest scores improved to 47 % (range 20-93 %, p < 0.001). Median number of structures drawn in the TEP image improved from 2 (range 0-14) to 11 (range 1-21, p < 0.001). Median number of structures drawn in the OIH image improved from 3 (range 0-15) to 7 (range 1-19, p < 0.001). 67 % (12/18) demonstrated improvement in knowledge of abdominal wall layers. 23 % (7/30) knew the triangles of pain/doom on the pretest vs. 77 % (23/30) on the posttest. Mean Likert scores favored session enjoyability (4.5), not a waste of training time (4.4), and improved understanding of OIH and TEP anatomy (4.4, 4.2). CONCLUSIONS: Low-fidelity simulators can be used to teach and assess knowledge of TEP and OIH anatomy. While enjoyable and useful, one 3-h session does not create master hernia surgeons or expert anatomists out of novice trainees.

Thiazolidinedione toxicity to isolated hepatocytes revealed by coherent multiprobe fluorescence microscopy and correlated with multiparameter flow cytometry of peripheral leukocytes.

Thiazolidinediones (TZDs) are effective for the treatment of adult-onset insulin-resistant diabetes. Unfortunately, TZDs are associated with sporadic hepatic dysfunction that is not predictable from experimental animal studies. We investigated the response of isolated rat and human hepatocytes to various TZDs using biochemical assays, coherent multiprobe fluorescence microscopy and flow cytometric analyses. The results identified direct effects of TZD on mitochondria from live human and rodent hepatocytes. The multiprobe fluorescence assays showed disruption of mitochondrial activity as an initiating event followed by increased membrane permeability, calcium influx and nuclear condensation. Other TZD-related cellular effects were increased hepatic enzyme leakage, decreased reductive metabolism and cytoplasmic adenosine triphosphate depletion. Mitochondrial effects were similar in cryopreserved hepatocytes from diabetic or non-diabetic donors. Peripheral blood mononuclear cells (PBMCs) had baseline mitochondrial energetics and metabolism comparable with isolated hepatocytes. Mitochondrial effects in isolated hepatocytes were found in human PBMCs exposed to the TZDs. The relative potency of TZDs for causing hepatocyte and PBMC effects was troglitazone > pioglitazone > rosiglitazone. These studies clearly demonstrated that hepatic alterations in vitro are characteristic of TZDs, with only quantitative differences in subcellular organelle dysfunction. Monitoring mitochondrial function in isolated PBMCs may be beneficial in diabetics undergoing TZD therapy.

p53 is not inactivated in B6C3F1 mouse vascular tumors arising spontaneously or associated with long-term administration of the thiazolidinedione troglitazone.

Hemangiomas and hemangiosarcomas are uncommon in rodents and humans and, as such, the mechanisms giving rise to these tumors are poorly understood. Inactivating mutations in the p53 gene have been detected in sporadic and chemically induced human and rodent hemangiosarcomas. Additionally, experimental ablation of p53 function in mice by targeted gene disruption increases the incidence of both spontaneous and carcinogen-induced vascular tumors. These findings implicate p53 disruption in vascular tumor development. In this study, we characterized p53 inactivation immunocytochemically and by gene sequencing in a large number of vascular tumors that developed in B6C3F1 mice during a long-term (2-year) study of the thiazolidinedione troglitazone. For comparative purposes, a murine hemangiosarcoma induced by polyoma middle-T antigen, which transforms endothelial cells via a p53-independent mechanism, five spontaneous human hemangiosarcoma specimens, and species-specific positive control tissues were also evaluated by immunocytochemistry for p53 inactivation. While 20% of the human hemangiosarcomas and all positive control tissues expressed significant levels of nuclear p53, indicating functional inactivation of the protein, none of the 161 mouse vascular tumors studied expressed detectable p53 protein. The absence of inactivating mutations was confirmed in eight of the histologically most malignant mouse hemangiosarcomas by sequencing exons 5 to 8 of the p53 gene. These results demonstrate that p53 inactivation did not play a role in development of the vascular tumors seen in the long-term study of troglitazone, and they indicate that loss of p53 function is not essential for vascular tumor development in mice.

Effects of troglitazone and pioglitazone on cytokine-mediated endothelial cell proliferation in vitro.

We examined whether troglitazone and pioglitazone, antidiabetic thiazolidinediones, would directly induce endothelial cell proliferation or influence cytokine-driven proliferation in vitro. Monolayers of Balb/c mouse aortic endothelial cells were treated with troglitazone or pioglitazone in the absence of fetal bovine serum. Endothelial cells also were exposed to varying concentrations of basic fibroblast growth factor (bFGF) or insulin with or without either thiazolidinedione. After 48 h, 3-[4,5-dimethylthiozol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assays were performed to quantitate endothelial cell proliferation by using the various treatment regimens. The data demonstrate that the antidiabetic thiazolidinediones troglitazone and pioglitazone negligibly affect direct endothelial cell proliferation in vitro. Furthermore, troglitazone and pioglitazone significantly inhibit bFGF-induced endothelial cell mitogenesis, whereas only high concentrations of troglitazone affect insulin-mediated proliferation.

Retinoic acid metabolites exhibit biological activity in human keratinocytes, mouse melanoma cells and hairless mouse skin in vivo.

Topical all-trans retinoic acid (RA) modulates growth and differentiation of skin and is used in the treatment of various dermatological disorders. RA is metabolized to 4-hydroxy RA, 4-oxo RA and 5,6-epoxy RA, which are believed to be markedly less active than RA. 3,4-didehydroretinoic acid (ddRA) is a metabolite of 3,4-didehydroretinol which is present in skin. ddRA is biologically active and acts as a morphogen. We have determined the relative biological activity of ddRA, 4-hydroxy RA, 4-oxo RA and 5,6-epoxy RA as assessed by three retinoid responsive systems relevant to skin. RA, ddRA, 4-hydroxy RA, 4-oxo RA and 5,6-epoxy RA (10-100 nM) reduced epidermal transglutaminase activity in human keratinocytes to similar extents, and inhibited alpha-melanocyte-stimulating hormone-isobutylmethylxanthine-inducible tyrosinase activity in Cloudman S-91 mouse melanoma cells by 67, 39, 48, 51 and 19%, respectively, at 100 nM. Daily topical application of the retinoids to hairless mouse skin for 4 days resulted in dose-dependent changes in epidermal thickness and global histological score. The relative potencies of RA, ddRA, 4-hydroxy RA, 4-oxo RA and 5,6-epoxy RA, as calculated by parallel line assay, were 1.0, 0.60, 0.34, 0.29 and 0.18, respectively, for epidermal hyperplasia and 1.0, 0.78, 0.23, 0.14 and 0.08, respectively, for global histological score. Interestingly, the compounds exhibited a similar rank order of potency with respect to induction of cellular retinoic acid binding protein-II mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium influx at the tip of growing root-hair cells of Arabidopsis thaliana.

The role of extracellular Ca(2+) in root-hair tip growth has been investigated in Arabidopsis thaliana (L.) Heynh. Root-hair length was found to be dependent on the concentration of Ca(2+) in the growth medium, with maximum length achieved at [Ca(2+)] of 0.3-3.0 mM. Using a non-intrusive calcium-specific vibrating microelectrode, an extracellular Ca(2+) gradient was detected at the tips of individual growing root-hair cells. The direction of the gradient indicated a net influx of Ca(2+) into root-hair cells. No gradient was detected near the sides of the root hairs or at the tips of non-growing root hairs. When root hairs were exposed to the Ca(2+)-channel blocker nifedipine, tip growth stopped and the extracellular Ca(2+) gradient was abolished. These results indicate that Ca(2+) influx through plasma-membrane Ca(2+) channels is required for normal root-hair tip growth.