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C J Kemp

Publications and source records attributed to C J Kemp.

At least 19 recordsLinked to original sources
PubMed2001

Epithelial permeability is not increased in rats following small bowel resection.

BACKGROUND: Increased intestinal permeability and translocation of bacteria and/or bacterial products may cause infection and liver dysfunction in patients with the short bowel syndrome. In previous studies, serum from mice undergoing small bowel resection (SBR) enhanced growth of cultured rat intestinal epithelial cells (RIEC-6), implicating a role for a serum factor(s) in the enterocyte response to SBR. These experiments tested the hypothesis that epithelial cell permeability is increased following SBR. MATERIALS AND METHODS: Male Sprague-Dawley rats underwent a 75% SBR or sham operation. Intestinal permeability in the remnant ileum was determined by Ussing chambers on Postoperative Day (POD) 3. Additionally, serum was collected on POD 1, 3, and 7 and mesenteric lymph was harvested on POD 3. Once confluent, RIEC-6 cells were incubated for 3 days in media supplemented with 10% fetal bovine serum (FBS; control), 1% FBS, 1% FBS plus 9% Sham serum, or 1% FBS plus 9% SBR serum or exposed to media with varied concentrations of SBR or Sham lymph. Monolayer permeability was determined by measuring the passage of dextran-rhodamine. RESULTS: Intestinal permeability was reduced in rats undergoing SBR. Sham serum-treated monolayers demonstrated the greatest permeability. Incubation with SBR serum reduced permeability to near control media. There were no permeability differences between SBR and Sham lymph-treated monolayers. CONCLUSION: The early adaptive response of the remnant intestine after SBR is associated with reduced permeability. These results suggest an alternative mechanism for the increased bacterial translocation that has been described following SBR.

Adaptation, Biological↗
PubMed2001

p27(Kip1): regulation and function of a haploinsufficient tumor suppressor and its misregulation in cancer.

A major function of p27, also known as Kip1, is to bind and inhibit cyclin/cyclin-dependent kinase complexes, thereby blocking cell cycle progression. As p27 operates at the heart of the cell cycle, it is perhaps not surprising that it is emerging as a key player in multiple cell fate decisions including proliferation, differentiation, and cell death. The central role of p27 makes it important in a variety of disease processes that involve aberrations in cellular proliferation and other cell fates. Most notable among these processes is neoplasia. A large number of studies have reported that p27 expression is frequently downregulated in human tumors. In most tumor types, reduced p27 expression correlates with poor prognosis, making p27 a novel and powerful prognostic marker. In addition to these practical implications, murine and tissue culture models have shown that p27 is a potent tumor suppressor gene for multiple epithelially derived neoplasias. Loss of p27 cooperates with mutations in several oncogenes and tumor suppressor genes to facilitate tumor growth, indicating that p27 may be a "nodal point" for tumor suppression. In contrast to most tumor suppressor genes studied to date, which are recessive at the cellular level, p27 is haploinsufficient for tumor suppression. The fact that tumor suppression by p27 is critically dependent on the absolute level of p27 expression indicates that p27 acts as a rheostat rather than as an on/off switch to control growth and neoplasia.

Animals↗
PubMed2001

Synthetic lethality between mutation in Atm and DNA-PK(cs) during murine embryogenesis.

The gene product mutated in ataxia telangiectasia, ATM, is a ubiquitously expressed 370 kDa protein kinase that is a key mediator of the cellular response to DNA damage [1]. ATM-deficient cells are radiosensitive and show impaired cell cycle arrest and increased chromosome breaks in response to ionizing radiation. ATM is a member of the phosphatidylinositol-3-kinase (PI3K)-related protein kinase superfamily, which includes the catalytic subunit of DNA-dependent protein kinase (DNA-PK(cs)) and ATR [2]. DNA-PK is a 470 kDa protein kinase that is required for proper end-to-end rejoining of DNA double-strand breaks [3]. Prkdc(scid/scid) mice have a homozygous mutation in the gene encoding DNA-PK(cs) and, like Atm(-/-) mice, are viable and radiosensitive [4-8]. To determine if Atm and DNA-PK(cs) show genetic interaction, we attempted to generate mice deficient in both gene products. However, no scid/scid Atm(-/-) pups were recovered from scid/scid Atm(+/-) intercrosses. Developmental arrest of scid/scid Atm(-/-) embryos occurred around E7.5, a developmental stage when embryonic cells are hypersensitive to DNA damage [9]. This reveals synthetic lethality between mutations in Atm and DNA-PK and suggests that Atm and DNA-PK have complementary functions that are essential for development.

Animals↗
PubMed2001

p53 induction and apoptosis in response to radio- and chemotherapy in vivo is tumor-type-dependent.

The p53 protein rapidly accumulates in cells in response to DNA damage, which can trigger apoptosis. This pathway is hypothesized to be important for tumor suppression by p53, as well as for the response of tumors to chemo- or radiotherapy. Implicit in these ideas is that the p53 induction-apoptosis pathway is active in tumor cells in vivo. Because tumor suppression by p53 in mice is markedly tissue-type-dependent, we tested the activity of the pathway in tumors in vivo by inducing tumors in six different tissues and treating tumor-bearing mice with DNA damaging cancer therapeutic agents. In response to treatment, cells from T-cell lymphomas, intestinal adenomas, and mammary tumors rapidly induced p53 and underwent apoptosis. In squamous cell papillomas, p53 was constitutively expressed and was further induced by the treatments, but apoptotic cells were only rarely observed. In treated mice bearing lung or liver adenomas, minimal or no p53 accumulation or apoptosis was observed in the tumor cells. Thus, there is marked variation in the intrinsic ability of autochthonous tumor cells to accumulate p53 and undergo apoptosis. This variation provides one explanation for the tissue specificity of tumor suppression by p53. It also indicates that the role of apoptosis in the response of tumors to therapy varies significantly among tumor types.

Animals↗
PubMed2001

cDNA microarray analysis of adapting bowel after intestinal resection.

BACKGROUND/PURPOSE: Studies of the genetic regulation of various physiologic processes have been hampered by methodologies that are limited to the analysis of individual genes. The advent of cDNA microarray technology has permitted the simultaneous screening of numerous genes for alterations in expression. In this study, cDNA microarrays were used to evaluate gene expression changes during the intestinal adaptive response to massive small bowel resection (SBR). METHODS: Male ICR mice (n = 20) underwent either a 50% SBR or sham operation and then were given either orogastric epidermal growth factor (EGF, 50 microg/kg/d) or saline. After 3 days, cDNA microarray analysis was performed on mRNA extracted from the remnant ileum. RESULTS: From over 8,700 different genes, the array identified 27 genes that were altered 2-fold or greater after SBR. Small proline-rich protein 2 (sprr2), the gene with the greatest expression change (4.9-fold), was further upregulated by EGF. This gene has never been characterized in the intestine or described in intestinal adaptation. CONCLUSIONS: cDNA microarray analysis showed enhanced expression of sprr2, a gene not previously known to be involved in the physiology of adaptation after SBR. This technology provides a more rapid and efficient means of dissecting the complex genetic regulation of gut adaptation.

Adaptation, Biological↗
PubMed2000

Epidermal growth factor alters the bax:bcl-w ratio following massive small bowel resection.

BACKGROUND: Following massive small bowel resection (SBR), the expression of bax and bcl-w is associated with increased enterocyte apoptosis. Epidermal growth factor (EGF) has been shown to enhance enterocyte proliferation and retard apoptosis in the adapting bowel. This study examined the effect of EGF on the expression of these bcl-2 family members during adaptation. MATERIALS AND METHODS: Mice (C57Bl/6; n = 38) underwent a 50% SBR or sham operation and then were randomized to receive twice-daily orogastric saline or EGF (50 microg/kg/day). After 3 days, the remnant ileum was removed, apoptotic index (No. apoptotic bodies/crypt) calculated, and expression of mRNA and protein for bax and bcl-w quantified. RESULTS: EGF prevented the expected increase in the apoptotic index after SBR and altered the ratio of bax to bcl-w in favor of cell survival. CONCLUSION: Following massive small bowel resection, EGF retards rates of enterocyte apoptosis and modifies the expression of bcl-2 family members. By decreasing bax and increasing bcl-w expression, the balance between pro- and anti-apoptotic genes is shifted in favor of cell survival. Alteration of bcl-2 family member expression may be an important mechanism by which EGF reduces the increased enterocyte apoptosis that occurs after massive small bowel resection.

Adaptation, Physiological↗
PubMed2000

p21 (WAF1/CIP1) is required for the mitogenic response to intestinal resection.

BACKGROUND: Increased enterocyte proliferation and apoptosis characterize the intestinal adaptive response to massive small bowel resection (SBR). Since p21 (WAF1/CIP1) has been implicated to play a role in cellular differentiation and apoptosis, this study tested the hypothesis that p21 is obligatory for adaptation to occur. MATERIALS AND METHODS: p21-null (n = 36) and wild-type (C57B1/6, n = 19) mice underwent a 50% SBR or sham operation. After 3 days, parameters of adaptation (ileal wet weight, villus/crypt morphology, and ileal protein content), an enterocyte proliferation index (PI), and an apoptotic index (AI) were determined in the residual ileum. In a separate set of experiments, p21-null (n = 11) and control (n = 20) mice underwent the aforementioned operative procedures and the remnant intestine was subjected to a reverse transcription polymerase chain reaction for p27 (KIP1). RESULTS: Both AI and PI increased after SBR in the wild-type mice. In the p21-null mice, SBR increased AI, but did not affect the PI. After SBR, adaptive parameters increased in the wild-type mice, but failed to increase in the p21-null mice. The absence of p21 caused a baseline increase in p27 mRNA, which did not change after SBR. CONCLUSION: p21 appears to be required to increase enterocyte proliferation and to augment the other parameters of intestinal adaptation. In the absence of p21, the proliferative and apoptotic responses to SBR are uncoupled. These results suggest a differential mechanism for the regulation of enterocyte proliferation and apoptosis in the adapting intestine.

Adaptation, Physiological↗
PubMed2000

Intestinal adaptation occurs independent of transforming growth factor-alpha.

BACKGROUND/PURPOSE: Signal transduction via the epidermal growth factor receptor (EGFR) is critical for intestinal adaptation after massive small bowel resection (SBR). Although it has been assumed that the major ligand for the EGFR during adaptation is EGF, the role for transforming growth factor-alpha (TGF-alpha), another major ligand for the EGFR is unknown. The purpose of this study was to test the hypothesis that TGF-alpha is an important ligand for the EGFR during intestinal adaptation. METHODS: Wild-type mice (C57BI/6) underwent a 50% proximal SBR or sham operation (bowel transection or reanastomosis) and were then assigned randomly to receive either intraperitoneal TGF-alpha or placebo. In a separate experiment, SBR or sham operations were performed in mice lacking TGF-alpha (Waved-1). After 3 days, adaptation was measured in the ileum. RESULTS: Exogenous TGF-alpha enhanced intestinal adaptation in the wild-type mice after SBR as shown by increased ileal wet weight and DNA content. Normal adaptation occurred in the mice lacking TGF-alpha as shown by increased ileal wet weight, protein and DNA content, proliferation, villus height, and crypt depth. CONCLUSIONS: Although exogenous TGF-alpha enhanced adaptation after massive SBR, adaptation was preserved in TGF-alpha-absent mice. These results refute TGF-alpha as an essential ligand for EGFR signaling during intestinal adaptation.

Adaptation, Physiological↗
PubMed2000

Bax is required for increased enterocyte apoptosis after massive small bowel resection.

BACKGROUND: Massive small bowel resection (SBR) increases rates of both enterocyte proliferation and apoptosis. Previous studies have demonstrated increased intestinal expression of proapoptotic bax mRNA and protein, as well as the appearance of an 18-kd bax cleavage product within 12 hours of SBR. This study tested the hypothesis that bax is required for postresection increases in enterocyte apoptosis. METHODS: Male bax-null and C57Bl/6 (control) mice underwent either a 50% proximal SBR or sham operation. After 3 days, the remnant ileum was harvested and weighed. Apoptotic indexes, proliferation indexes, villus heights, and crypt depths were determined. RESULTS: The usual adaptive increases in ileal wet weight, crypt depth, and rate of proliferation occurred in both the control and bax-null mice. Resection significantly increased the rate of apoptosis in the control mice; however, it failed to alter the apoptotic index in the bax-null mice. CONCLUSIONS: Bax is necessary for the increase in apoptosis that occurs after SBR, but its absence has no significant effect on short-term adaptation. These findings suggest that enterocyte proliferation and apoptosis are differentially regulated during intestinal adaptation.

Animals↗
PubMed2000

Salivary epidermal growth factor and intestinal adaptation in male and female mice.

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.

Adaptation, Physiological↗
PubMed1999

Tumor suppression by p27Kip1 and p21Cip1 during chemically induced skin carcinogenesis.

p27Kip1 and p21Cip1 are cyclin dependent kinase inhibitors which can arrest cell proliferation and p27 is a tumor suppressor gene. To address the mechanism of tumor suppression by p27 and to determine if p21 has a tumor suppressor phenotype, we utilized the two stage skin carcinogenesis model on p27 and p21 knockout mice. In this model, initiation, which involves mutation of H-ras induced by DMBA, can be distinguished from promotion induced by TPA, and progression to carcinoma. The mean number of papillomas did not differ between p27-/- and control littermates, but papilloma growth rate was increased and carcinomas developed earlier. Thus, p27 deficiency did not enhance initiation, but resulted in more rapid clonal expansion of initiated cells during promotion. TPA treatment reduced p27 expression in keratinocytes also supporting a role for p27 during promotion. Tumors from p27-/- mice contained mutant H-ras indicating that p27 deficiency did not substitute for mutant ras and further, that during ras driven tumor growth, p27 is partially antagonistic since its removal led to faster growth. The treated p27-/- mice also developed intestinal adenomas. p21-/- mice did not display a significant increase in tumor numbers, growth rate or progression to carcinomas and these tumors also had mutated H-ras. Carcinomas from p21-/- mice were more poorly differentiated with a high frequency of anaplastic spindle cell carcinomas. Thus p21 deficiency mainly resulted in higher grade undifferentiated tumors.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1999

Apoptosis and the pattern of DNase I expression following massive small bowel resection.

INTRODUCTION: Following massive small bowel resection (SBR), histologic evidence of increased enterocyte apoptosis has been demonstrated in several animal models. Deoxyribonuclease I (DNase I) is requisite for intranuclear cleavage of DNA during apoptosis; we therefore hypothesized that the expression of this gene would be increased following SBR. METHODS: Male ICR mice underwent either 50% proximal SBR or sham surgery (bowel transection/reanastomosis). After 12 h and 1, 3, and 7 days, rates of enterocyte proliferation and apoptosis were recorded as well as DNase I mRNA expression and activity. RESULTS: Adaptation after SBR was confirmed at each time point by increased proliferation. Enterocyte proliferation was increased by 12 h and apoptosis was increased by 24 h and remained elevated through Day 7. When compared with sham-operated mice, SBR resulted in a twofold increase in both DNase I expression and activity at 24 h postoperatively, which returned to baseline by Postoperative Day 3. CONCLUSIONS: DNase I expression and activity are increased early following massive SBR but return to baseline despite persistent increased rates of enterocyte apoptosis and proliferation. This enzyme may be important in the early induction of apoptosis following massive SBR, but not once a new set point has been established in the balance between the rate of enterocyte production and enterocyte loss.

Adaptation, Physiological↗
PubMed1999

Resistance to skin tumorigenesis in DNAPK-deficient SCID mice is not due to immunodeficiency but results from hypersensitivity to TPA-induced apoptosis.

Scid/scid mice have a mutation in the gene encoding the catalytic subunit of DNA-dependent protein kinase (DNAPK(cs)) and are defective in end joining of DNA double-strand breaks. As a consequence, they are radiosensitive, lack mature T and B lymphocytes and are predisposed to lymphomagenesis. To determine if this DNA repair defect also increased predisposition to skin tumor formation, we treated the dorsal skin of scid/scid mice with the carcinogen 7,12-dimethylbenz[a]anthracene followed by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Contrary to expectations, we observed a 5-fold reduction in skin tumor multiplicity in scid/scid mice. We addressed whether this was related to their immunodeficiency by similarly treating Rag1(-/-) and Rag2(-/-) knockout mice which also lack mature T and B lymphocytes. We observed no difference in skin tumor multiplicity for either strain compared with control littermates. This indicates a lack of a significant role for T or B lymphocyte mediated immunity on either papilloma or carcinoma formation. We observed a significant increase in apoptotic and necrotic cell death in follicular and interfollicular epithelial cells of scid/scid mice following TPA treatment. This hypersensitivity of SCID (severe combined immunodeficient) cells to TPA indicates that the resistance to skin tumor formation in scid/scid mice is due to loss of initiated cells through TPA-induced cell killing.

Animals↗
PubMed1999

Intestinal adaptation and enterocyte apoptosis following small bowel resection is p53 independent.

Adaptation following small bowel resection (SBR) signals enterocyte proliferation and apoptosis. Because p53-induced p21(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(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(waf1/cip1) protein in villus enterocytes. The p53-independent induction of p21(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.

Adaptation, Physiological↗
PubMed1998

The murine gene p27Kip1 is haplo-insufficient for tumour suppression.

p27Kip is a candidate human tumour-suppressor protein, because it is able to inhibit cyclin-dependent kinases and block cell proliferation. Abnormally low levels of the p27 protein are frequently found in human carcinomas, and these low levels correlate directly with both histological aggressiveness and patient mortality. However, it has not been possible to establish a causal link between p27 and tumour suppression, because only rare instances of homozygous inactivating mutations of the p27 gene have been found in human tumours. Thus, p27Kip1 does not fulfil Knudson's 'two-mutation' criterion for a tumour-suppressor gene. Here we show that both p27 nullizygous and p27 heterozygous mice are predisposed to tumours in multiple tissues when challenged with gamma-irradiation or a chemical carcinogen. Therefore p27 is a multiple-tissue tumour suppressor in mice. Molecular analyses of tumours in p27 heterozygous mice show that the remaining wild-type allele is neither mutated nor silenced. Hence, p27 is haplo-insufficient for tumour suppression. The assumption that null mutations in tumour-suppressor genes are recessive excludes those genes that exhibit haplo-insufficiency.

Animals↗