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Previous work in our group has demonstrated that mouse salivary gland has the highest concentration of salivary-derived VEGF protein compared with other organs and is essential for normal palatal mucosal wound healing. We hypothesize that salivary VEGF plays an important role in maintaining the integrity of the gastrointestinal mucosa following small bowel resection (SBR). Thirty-five 8- to 10-wk-old C57BL/6 female mice were divided into seven treatment groups: 1) sham (transaction and anastomosis, n = 5); 2) SBR (n = 8); 3) sialoadenectomy and small bowel resection (SAL+SBR, n = 8); 4) sialoadenectomy and small bowel resection with EGF supplementation (SAL+SBR+EGF, n = 9); 5) sialoadenectomy and small bowel resection with VEGF supplementation (SAL+SBR+VEGF, n = 9); 6) sialoadenectomy and small bowel resection supplemented with EGF and VEGF (SAL+ SBR+VEGF+EGF, n = 6); 7) selective inhibition of VEGF in the submandibular gland by Ad-VEGF-Trap following small bowel resection (Ad-VEGF-Trap+SBR, n = 7). Adaptation was after 3 days by ileal villus height and crypt depth. The microvascular response was evaluated by CD31 immunostaining and for villus-vessel area ratio by FITC-labeled von Willebrand factor immunostaining. The adaptive response after SBR was significantly attenuated in the SAL group in terms of villus height (250.4 [+ or -] 8.816 vs. 310 [+ or -] 19.35, P = 0.01) and crypt depth (100.021 [+ or -] 4.025 vs. 120.541 [+ or -] 2.82, P = 0.01). This response was partially corrected by orogastric VEGF or EGF alone. The adaptive response was completely restored when both were administered together, suggesting that salivary VEGF and EGF both contribute to intestinal adaptation. VEGF increases the vascular density (6.4 [+ or -] 0.29 vs. 6.1 [+ or -] 0.29 vs. 5.96 [+ or -] 0.20) and villus-vessel area ratio (0.713 [+ or -] 0.01 vs. 0.73 [+ or -] 0.01) in the adapting bowel. Supplementation of both EGF and VEGF fully rescues adaptation, suggesting that the adaptive response may be dependent on VEGF-driven angiogenesis. These results support a previously unrecognized role for VEGF in the small bowel adaptive response. sialoadenectomy; small bowel resection; VEGF; EGF

Previous studies have demonstrated that the proapoptotic protein Bax plays an important role in the elevated enterocyte apoptosis that occurs during the intestinal adaptation response to massive small bowel resection (SBR). Additionally, epidermal growth factor receptor (EGFR) activation prevents SBR-induced enterocyte apoptosis. The present study aims to delineate the relationship between EGFR activity and intestinal epithelial cell apoptosis. Treatment of model intestinal epithelial cells (RIEC-18) with both a selective EGFR inhibitor (ZD1839) and EGFR small interfering RNA knockdown resulted in a dramatic increase in apoptosis, accompanied by rapid phosphorylation of p38[alpha]. Concurrently, Bax underwent conformational changes consistent with activation and transloeated to mitochondria. In contrast, EGF stimulation enhanced cell survival by attenuating p38[alpha] phosphorylation, Bax conformational change, mitochondrial trafficking, and apoptosis. These results demonstrate that that diminished EGFR activity initiates the intrinsic pathway of apoptosis through p38[alpha]-dependent Bax activation in intestinal epithelial cells. These finding provide mechanistic insight into the role that EGFR signaling plays in the regulation of enterocyte apoptosis following massive intestinal loss. intestinal adaptation; short bowel syndrome

The magnitude of gut adaptation is a decisive factor in determining whether patients are able to live independent of parenteral nutrition after massive small bowel loss. We previously established that the cyclin-dependent kinase inhibitor (CDKI) [p21.sup.waf1/cip1] is necessary for enterocyte proliferation and a normal adaptation response. In the present study, we have further elucidated the role of this CDKI in the context of [p27.sup.kip1], another member of the Cip/Kip CDKI family. Small bowel resections (SBRs) or sham operations were performed in control (C57/BL6), [p21.sup.waf1/cip1]-null, [p27.sup.kip1]-null, and [p21.sup.waf1/cip1]/[psup.27kip1] double-null mice. Morphological (villus height/crypt depth) alterations in the mucosa, the kinetics of enterocyte turnover (rates of enterocyte proliferation and apoptosis), and the protein expression of various cell cycle-regulatory proteins were recorded at various postoperative times. Enterocyte compartment-specific mRNA expression was investigated using laser capture microdissection. Resection-induced adaptation in control mice coincided with increased protein expression of [p21.sup.waf1/cip1] and decreased [p27.sup/kip1] within 3 days postoperatively. Identical changes in mRNA expression were detected in crypt but not in villus enterocytes. Adaptation occurred normally in control and [p27.sup.kip1]-null mice: however, mice deficient in both [p21.sup.waf1]/cip1] and [p27.sup.kip1] failed to increase baseline rates of enterocyte proliferation and adaptation. The expression of [p21.sup.waf1/cip1] protein and mRNA in the proliferative crypt compartment is necessary for resection-induced enterocyte proliferation and adaptation. The finding that deficient expression of [p27sup.kip1] does not affect adaptation suggests that these similar CDKI family members display distinctive cellular functions during the complex process of intestinal adaptation. cyclin-dependent kinase inhibitor: enterocyte proliferation; apoptosis

Prior studies of intestinal adaptation after massive small bowel resection (SBR) have focused on growth factors and their effects on amplification of the gut mucosa. Because adaptive changes have also been described in intestinal smooth muscle, we sought to determine the effect of targeted smooth muscle growth factor overexpression on resection-induced intestinal adaptation. Male transgenic mice with smooth muscle cell overexpression of insulin-like growth factor I (IGF-I) by virtue of an [alpha]-smooth muscle actin promoter were obtained. SMP8 IGF-I transgenic (IGF-I TG) and nontransgenic (NT) littermates underwent 50% proximal SBR or sham operation and were then killed after 3 or 28 days. NT mice showed the expected alterations in mucosal adaptive parameters after SBR, such as increased wet weight and villus height. The IGF-I TG mice had inherently taller villi, which did not increase significantly after SBR. In addition, IGF-I TG mice had a 50% postresection persistent increase in remnant intestinal length, which was associated with an early decline and later increase in relative mucosal surface area. These results indicate that growth factor overexpression within the muscularis layer of the bowel wall induces significant postresection adaptive intestinal lengthening and a unique mucosal response. IGF-I signaling within the muscle wall may play an important role in the pathogenesis of resection-induced adaptation. growth factors; transgenic mice; short bowel syndrome

Intestinal adaptation following small bowel resection (SBR) is associated with greater rates of enterocyte apoptosis by unknown mechanism(s). Because postresection adaptation is associated with increased translocation of luminal bacteria, we sought to characterize the role for the extrinsic, death receptor pathway for the activation of enterocyte apoptosis after massive SBR. We first performed SBR or sham operations in mice, and the temporal expression of caspases 8, 9, and 3, death receptors tumor necrosis factor receptor-1 ([TNFR.sub.1]) and Fas and corresponding ligands (TNF and Fas ligand) was determined in the remnant intestine at various postoperative time points. Ileal [TNFR.sub.1] and Fas expression were then measured after SBR in the setting of increased (waved-2 mice) or decreased (exogenous EGF administration) apoptosis. Finally, intestinal adaptation and apoptosis were recorded in the remnant ileum after SBR in [TNFR.sub.1]-null and Fas-null mice. The expression of death receptor family proteins and caspases demonstrated only modest changes after SBR and did not correlate with the histological appearance of apoptosis. In the setting of accelerated apoptosis, [TNFR.sub.1] and Fas expression were paradoxically decreased. Apoptotic and adaptive responses were preserved in both [TNFR.sub.1]-null and Fas-null mice. These results suggest that the mechanism for increased enterocyte apoptosis following massive SBR does not appear to involve the extrinsic, death receptor-mediated pathway. tumor necrosis factor receptor; Fas; intestinal mucosa; short bowel syndrome; intestinal adaptation

Several growth factors are trophic for the gastrointestinal tract and able to reduce the degree of intestinal damage caused by cytotoxic agents. However, studies of epidermal growth factor (EGF) for chemotherapy-induced intestinal injury are conflicting. The development of a transgenic mouse that specifically overexpresses EGF in the small intestine provided a unique opportunity to assess the contribution of EGF in mucositis. After a course of fluorouracil, transgenic mice fared no better than control mice. Weight recovery was inferior, and mucosal architecture was not preserved. Apoptosis was not decreased and proliferation was not increased in the crypts. To corroborate the findings in transgenic mice, ICR mice were treated with exogenous EGF after receiving fluorouracil. Despite ileal upregulation of native and activated EGF receptor, the mice were not protected from intestinal damage. No benefits were observed with different EGF doses or schedules or routes of EGF administration. Finally, mucositis was induced in mutant mice with specific defects of the EGF signaling axis. Compared with control mice, clinical and histological parameters of intestinal injury after fluorouracil were no different in waved-2 mice, which have functionally diminished EGF receptors, or waved-1 mice, which lack transforming growth factor-[alpha], another major ligand for the EGF receptor. These findings do not support a critical role for EGF or its receptor in chemotherapy-induced intestinal injury. intestinal mucosa; fluorouracil; enteritis; transgenic mouse; transforming growth factor-[alpha]

Neural networks have received a great deal of attention over the last few years. They are being used in the areas of prediction and classification, areas where regression models and other related statistical techniques have traditionally been used. In this paper we discuss neural networks and compare them to regression models. We start by exploring the history of neural networks. This includes a review of relevant literature on the topic of neural networks. Neural network nomenclature is then introduced, and the backpropagation algorithm, the most widely used learning algorithm, is derived and explained in detail. A comparison between regression analysis and neural networks in terms of notation and implementation is conducted to aid the reader in understanding neural networks. We compare the performance of regression analysis with that of neural networks on two simulated examples and one example on a large dataset. We show that neural networks act as a type of nonparametric regression model, enabling us to model complex functional forms. We discuss when it is advantageous to use this type of model in place of a parametric regression model, as well as some of the difficulties in implementation. KEY WORDS: Artificial intelligence; Backpropagation; Generalized linear model; Nonparametric regression., 1. INTRODUCTION Neural networks have recently received a great deal of attention in many fields of study. The excitement stems from the fact that these networks are attempts to model [...]

Stern, Lawrence E., Richard A. Falcone, Jr., Christopher J. Kemp, Margaret C. Braun, Christopher R. Erwin, and Brad W. Warner. Salivary epidermal growth factor and intestinal adaptation in male and female mice. Am J Physiol Gastrointest Liver Physiol 278: G871-G877, 2000. --Salivary epidermal growth factor (sEGF) levels are increased in male mice after small bowel resection (SBR) and may be important during intestinal adaptation. Since males have greater sEGF than females, the influence of sex on postresection adaptation was tested. Females had lower sEGF; however, sEGF substantially increased in both sexes after a massive (50%) SBR. Adaptive increases in DNA and protein content, villus height, and crypt depth, as well as crypt cell proliferation rates in the remnant ileum, were not different between males and females. Although significant postresection increases in sEGF were identified, EGF mRNA and protein did not change within the submandibular gland. Glandular kallikrein-13 and ileal EGF receptor expression were greater after SBR in female mice. Intestinal adaptation is equivalent in female and male mice after SBR. Despite lower sEGF, females demonstrated increased expression of a kallikrein responsible for sEGF precursor cleavage as well as amplified ileal EGF receptor expression. These results endorse an important differential response between sexes regarding sEGF mobilization and intestinal receptor availability during adaptation. small bowel resection; kallikrein; salivary gland

Shin, Cathy E., Richard A. Falcone, Jr., Christopher J. Kemp, Christopher R. Erwin, David A. Litvak, B. Mark Evers, and Brad W. Warner. Intestinal adaptation and enterocyte apoptosis following small bowel resection is p53 independent. Am. J. Physiol. 277 (Gastrointest. Liver Physiol. 40): G717-G724, 1999.--Adaptation following small bowel resection (SBR) signals enterocyte proliferation and apoptosis. Because p53-induced [p21.sup.waf1/cip1] may be important for apoptosis in many cells, we hypothesized that these genes are required for increased enterocyte apoptosis during adaptation. Male C57BL/6 (wild-type) or p53-null mice underwent 50% proximal SBR or sham operation (bowel transection-reanastomosis). Adaptation (DNA-protein content, villus height-crypt depth, enterocyte proliferation), appearance of apoptotic bodies, and p53 and [p21.sup.waf1/cip1] protein expression were measured in the ileum after 5 days. Adaptation was equivalent after SBR in both wild-type and p53-null mice as monitored by significantly increased ileal DNA-protein content, villus height, and enterocyte proliferation. The number of crypt apoptotic bodies increased significantly after SBR evenly in both wild-type and p53-null mice. In the p53-null mice, SBR substantially induced the expression of [p21.sup.waf1/cip1] protein in villus enterocytes. The p53-independent induction of [p21.sup.waf1/cip1] may account for the similar intestinal response to SBR between wild-type and p53-null mice. Intestinal adaptation and increased enterocyte apoptosis following intestinal resection occur via a p53-independent mechanism. enterectomy; mice; intestinal resection; short-gut syndrome; programmed cell death

Erwin, Christopher R., Michael A. Helmrath, Cathy E. Shin, Richard A. Falcone, Jr., Lawrence E. Stern, and Brad W. Warner. Intestinal overexpression of EGF in transgenic mice enhances adaptation after small bowel resection. Am. J. Physiol. 277 (Gastrointest. Liver Physiol. 40): G533-G540, 1999.--The effect of direct intestinal overexpression of epidermal growth factor (EGF) on postresection adaptation has been investigated by the production of transgenic mouse lines. A murine pro-EGF cDNA construct was produced, and expression of the EGF construct was targeted to the small intestine with the use of the rat intestinal fatty acid-binding protein promoter. An approximately twofold increase in intestinal EGF mRNA and protein was detected in heterozygous mice. No changes in serum EGF levels were noted. Except for a slightly shortened small intestine, no other abnormal phenotype was observed. Intestinal adaptation (increases in body weight, DNA, protein content, villus height, and crypt depth) was markedly enhanced after a 50% proximal small bowel resection in transgenic mice compared with nontransgenic littermates. This transgenic mouse model permits the study of intestinal adaptation and other effects of EGF in the small intestine in a more physiological and directed manner than has been previously possible. These results endorse a direct autocrine/paracrine mechanism for EGF on enterocytes as a means to enhance adaptation. intestinal resection; intestine development; short gut; RT-PCR; ribonuclease protection assay; epidermal growth factor