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C L Bevins

Publications and source records attributed to C L Bevins.

At least 19 recordsLinked to original sources
PubMed2002

The multifaceted Paneth cell.

Paneth cells (PCs) were described over a century ago as granulated cells located at the base of small intestinal crypts, the 'crypts of Lieberkühn.' Various histochemical staining procedures were developed that identified PCs based on their distinctive granule-staining pattern. Early on, PCs were proposed to perform a specialized function other than absorption of digested nutrients, the predominant task of the small intestinal epithelium. Since then, many constituents of the PC granules have been biochemically characterized. The presence of various granule-associated antimicrobial substances and their release upon microbial challenge suggest that PCs function as specialized defense cells in the small intestine. Altered resistance to microbial infection in animal models with disrupted or augmented PC function provides further support for the host defense role of PCs. Other PC components suggest that PCs may also participate in the regulation of lumenal ionic composition, crypt development, digestion, and intestinal inflammation.

Animals↗
PubMed2001

Endoscopic and histologic evaluation together with symptom assessment are required to diagnose pouchitis.

BACKGROUND & AIMS: Pouchitis often is diagnosed based on symptoms alone. In this study, we evaluate whether symptoms correlate with endoscopic and histologic findings in patients with ulcerative colitis and an ileal pouch-anal anastomosis. METHODS: Symptoms, endoscopy, and histology were assessed in 46 patients using Pouchitis Disease Activity Index (PDAI). Patients were classified as either having pouchitis (PDAI score > or =7; N = 22) or as not having pouchitis (PDAI score <7; N = 24). RESULTS: Patients with pouchitis had significantly higher mean total PDAI scores, symptom scores, endoscopy scores, and histology scores. There was a similar magnitude of contribution of each component score to the total PDAI for the pouchitis group. Of note, 25% of patients with symptoms suggestive of pouchitis did not meet the PDAI diagnostic criteria for pouchitis. In both groups, the correlation coefficients between symptom, endoscopy, and histology scores were near zero (range, -0.26 to 0.20; P > 0.05). CONCLUSIONS: The symptom, endoscopy, and histology scores each contribute to the PDAI and appear to be independent of each other. Symptoms alone do not reliably diagnose pouchitis.

Adult↗
PubMed2001

A randomized clinical trial of ciprofloxacin and metronidazole to treat acute pouchitis.

Metronidazole is effective for the treatment of acute pouchitis after ileal pouch-anal anastomosis, but it has not been directly compared with other antibiotics. This randomized clinical trial was designed to compare the effectiveness and side effects of ciprofloxacin and metronidazole for treating acute pouchitis. Acute pouchitis was defined as a score of 7 or higher on the 18-point Pouchitis Disease Activity Index (PDAI) and symptom duration of 4 weeks or less. Sixteen patients were randomized to a 2-week course of ciprofloxacin 1,000 mg/d (n = 7) or metronidazole 20 mg/kg/d (n = 9). Clinical symptoms, endoscopic findings, and histologic features were assessed before and after therapy. Both ciprofloxacin and metronidazole produced a significant reduction in the total PDAI score as well as in the symptom, endoscopy, and histology subscores. Ciprofloxacin lowered the PDAI score from 10.1+/-2.3 to 3.3+/-1.7 (p = 0.0001), whereas metronidazole reduced the PDAI score from 9.7+/-2.3 to 5.8+/-1.7 (p = 0.0002). There was a significantly greater reduction in the ciprofloxacin group than in the metronidazole group in terms of the total PDAI (6.9+/-1.2 versus 3.8+/-1.7; p = 0.002), symptom score (2.4+/-0.9 versus 1.3+/-0.9; p = 0.03), and endoscopic score (3.6+/-1.3 versus 1.9+/-1.5; p = 0.03). None of patients in the ciprofloxacin group experienced adverse effects, whereas three patients in the metronidazole group (33%) developed vomiting, dysgeusia, or transient peripheral neuropathy. Both ciprofloxacin and metronidazole are effective in treating acute pouchitis with significant reduction of the PDAI scores. Ciprofloxacin produces a greater reduction in the PDAI and a greater improvement in symptom and endoscopy scores, and is better tolerated than metronidazole. Ciprofloxacin should be considered as one of the first-line therapies for acute pouchitis.

Acute Disease↗
PubMed2000

A novel murine beta -defensin expressed in tongue, esophagus, and trachea.

beta-Defensins are broad spectrum antimicrobial peptides expressed at epithelial surfaces. Two human beta-defensins, HBD-1 and HBD-2, have been identified. In the lung, HBD-2 is an inducible product of airway epithelia and may play a role in innate mucosal defenses. We recently characterized rat homologs (RBD-1, RBD-2) of the human genes and used these sequences to identify novel mouse genes. Mouse beta-defensin-4 (MBD-4) was amplified from lung cDNA using polymerase chain reaction primers designed from conserved sequences of RBD-2 and HBD-2. A full-length cDNA was cloned which encodes a putative peptide with the sequence MRIHYLLFTFLLVLLSPLAAFTQIINNPITCMTNGAICWGPCPTAFRQIGNCGHFKVRCCKIR. The peptide shares approximately 40% identity with HBD-2. MBD-4 mRNA was expressed in the esophagus, tongue, and trachea but not in any of 20 other tissues surveyed. Cloning of the genomic sequence of MBD-4 revealed two nearly (>99%) identical sequences encoding MBD-4 and the presence of numerous additional highly similar genomic sequences. Radiation hybrid mapping localized this gene to a region of chromosome 8 near several other defensins, MBD-2, MBD-3, and alpha-defensins (cryptdins)-3 and -17, consistent with a gene cluster. Our genomic cloning and mapping data suggest that there is a large beta-defensin gene family in mice. Identification of murine beta-defensins provides an opportunity to understand further the role of these peptides in host defense through animal model studies and the generation of beta-defensin-deficient animals by gene targeting.

Amino Acid Sequence↗
PubMed2000

Transcriptional regulation of beta-defensin gene expression in tracheal epithelial cells.

Innate immunity provides an ever-present or rapidly inducible initial defense against microbial infection. Among the effector molecules of this defense in many species are broad-spectrum antimicrobial peptides. Tracheal antimicrobial peptide (TAP) was the first discovered member of the beta-defensin family of mammalian antimicrobial peptides. TAP is expressed in the ciliated epithelium of the bovine trachea, and its mRNA levels are dramatically increased upon stimulation with bacteria or bacterial lipopolysaccharide (LPS). We report here that this induction by LPS is regulated at the level of transcription. Furthermore, the transfection of reporter gene constructs into tracheal epithelial cells indicates that DNA sequences in the 5' flanking region of the TAP gene, within 324 nucleotides of the transcription start site, are responsible in part for mediating gene induction. This region includes consensus binding sites for NF-kappaB and nuclear factor interleukin-6 (NF IL-6) transcription factors. Gel mobility shift assays indicate that LPS induces NF-kappaB binding activity in the nuclei of these cells, while NF IL-6 binding activity is constitutively present. The gene encoding human beta-defensin 2, a human homologue of TAP with similar inducible expression patterns in the airway, was cloned and found to have conserved NF-kappaB and NF IL-6 consensus binding sites in its 5' flanking region. Previous studies of antimicrobial peptides from insects indicated that their induction by infectious microbes and microbial products also occurs via activation of NF-kappaB-like and NF IL-6-like transcription factors. Together, these observations indicate that a strategy for the induction of peptide-based antimicrobial innate immunity is conserved among evolutionarily diverse organisms.

Animals↗
PubMed1999

Cloning and expression of bovine neutrophil beta-defensins. Biosynthetic profile during neutrophilic maturation and localization of mature peptide to novel cytoplasmic dense granules.

beta-Defensins are microbicidal peptides implicated in host defense functions of phagocytic leukocytes and certain surface epithelial cells. Here we investigated the genetic structures and cellular expression of BNBD-4, -12, and -13, three prototypic bovine neutrophil beta-defensins. Characterization of the corresponding cDNAs indicated that BNBD-4 (41 residues) derives from a 63-amino acid prepropeptide and that BNBD-12 (38 residues) and BNBD-13 (42 residues) derive from a common 60-amino acid precursor (BNBD-12/13). The peptides were found to be encoded by two-exon genes that are closely related to bovine epithelial beta-defensin genes. BNBD-4 and BNBD-12/13 mRNAs were most abundant in bone marrow, but were expressed differentially in certain non-myeloid tissues. In situ hybridization and immunohistochemical studies demonstrated that BNBD-4 synthesis is completed early in myelopoiesis. BNBD-12 was localized exclusively to the novel dense granules, organelles that also contain precursors of cathelicidins, antimicrobial peptides that undergo proteolytic processing during phagocytosis. In contrast to cathelicidins, Western blot analyses revealed that mature beta-defensins are the predominant organellar form in myeloid cells. Stimulation of neutrophils with phorbol myristate acetate induced secretion of BNBD-12, indicating that it is co-secreted with pro-cathelicidins. The exocytosis of BNBD-12 by activated neutrophils reveals different mobilization pathways for myeloid alpha- and beta-defensins.

Amino Acid Sequence↗
PubMed1999

Molecular cloning and characterization of rat genes encoding homologues of human beta-defensins.

beta-Defensins are cationic peptides with broad-spectrum antimicrobial activity that may play a role in mucosal defenses of several organs. They have been isolated in several species, and in humans, two beta-defensins have been identified. Here, we report the identification of two genes encoding beta-defensin homologues in the rat. Partial cDNAs were found by searching the expressed-sequence-tag database, and primers were designed to generate full-length mRNA coding sequences. One gene was highly similar to the human beta-defensin-1 (HBD-1) gene and mouse beta-defensin-1 gene at both the nucleic acid and amino acid levels and was termed rat beta-defensin-1 (RBD-1). The other gene, named RBD-2, was homologous to the HBD-2 and bovine tracheal antimicrobial peptide (TAP) genes. The predicted prepropeptides were strongly cationic, were 69 and 63 residues in length for RBD-1 and RBD-2, respectively, and contained the six-cysteine motif characteristic of beta-defensins. The beta-defensin genes mapped closely on rat chromosome 16 and were closely linked to the alpha-defensins genes, suggesting that they are part of a gene cluster, similar to the organization reported for humans. Northern blot analysis showed that both RBD-1 and RBD-2 mRNA transcripts were approximately 0.5 kb in length; RBD-1 mRNA was abundantly transcribed in the rat kidney, while RBD-2 was prevalent in the lung. Reverse transcription-PCR indicated that RBD-1 and RBD-2 mRNAs were distributed in a variety of other tissues. In the lung, RBD-1 mRNA expression localized to the tracheal epithelium while RBD-2 was expressed in alveolar type II cells. In conclusion, we characterized two novel beta-defensin homologues in the rat. The rat may be a useful model to investigate the function and contribution of beta-defensins to host defense in the lung, kidney, and other tissues.

Amino Acid Sequence↗
PubMed1999

Antimicrobial peptides as mediators of epithelial host defense.

Mammalian epithelial surfaces are remarkable for their ability to provide critical physiologic functions in the face of frequent microbial challenges. The fact that these mucosal surfaces remain infection-free in the normal host suggests that highly effective mechanisms of host defense have evolved to protect these environmentally exposed tissues. Throughout the animal and plant kingdoms, endogenous genetically encoded antimicrobial peptides have been shown to be key elements in the response to epithelial compromise and microbial invasion. In mammals, a variety of such peptides have been identified, including the well-characterized defensins and cathelicidins. A major source of these host defense molecules is circulating phagocytic leukocytes. However, more recently, it has been shown that resident epithelial cells of the skin and respiratory, alimentary, and genitourinary tracts also synthesize and release antimicrobial peptides. Both in vitro and in vivo data support the hypothesis that these molecules are important contributors to intrinsic mucosal immunity. Alterations in their level of expression or biologic activity can predispose the organism to microbial infection. The regulatory and developmental aspects of antimicrobial peptide synthesis are discussed from a perspective that emphasizes the possible relevance to pediatric medicine.

Amino Acid Sequence↗
PubMed1998

Isolation of human intestinal defensins from ileal neobladder urine.

We describe the isolation of naturally occurring human intestinal defensins HD-5 and HD-6 from ileal neobladder urine and ileal mucosa. Using an antibody-based detection assay, we found multiple N-terminally processed forms of HD-5. The predominant HD-5 forms in tissue were longer than those in neobladder urine (amino acid (aa) 23-94 and 29-94 versus aa 36-94, 56-94 and 63-94) suggesting that Paneth cells store prodefensin that is processed to mature defensin during or after degranulation. Search for mature HD-6 yielded aa 69-100 as the predominant form in both sources. The ileal neobladder is a promising model to study human Paneth cell secretion.

Amino Acid Sequence↗
PubMed1998

Enteric beta-defensin: molecular cloning and characterization of a gene with inducible intestinal epithelial cell expression associated with Cryptosporidium parvum infection.

A growing body of evidence suggests that endogenous antibiotics contribute to the innate defense of mammalian mucosal surfaces. In the cow, beta-defensins constitute a large family of antibiotic peptides whose members have been previously isolated from the respiratory and oral mucosa, as well as circulating phagocytic cells. A novel bovine genomic clone with beta-defensin-related sequence [corrected] related to those of these alpha-defensins was isolated and characterized. The corresponding cDNA was isolated from a small intestinal library; its open reading frame predicts a deduced sequence of a novel beta-defensin, which we designate enteric beta-defensin (EBD). Northern blot analysis of a variety of bovine tissues revealed that EBD mRNA is highly expressed in the distal small intestine and colon, anatomic locations distinct from those for previously characterized beta-defensins. EBD mRNA was further localized by in situ hybridization to epithelial cells of the colon and small intestinal crypts. Infection of two calves with the intestinal parasite Cryptosporidium parvum induced 5- and 10-fold increases above control levels of EBD mRNA in intestinal tissues. An anchored-PCR strategy was used to identify other beta-defensin mRNAs expressed in the intestine. In addition to that of EBD, several low-abundance cDNAs which corresponded to other beta-defensin mRNAs were cloned. Most of these clones encoded previously characterized beta-defensins or closely related isoforms, but two encoded a previously uncharacterized prepro-beta-defensin. Northern blot evidence supported that all of these other beta-defensin genes are expressed at levels lower than that of the EBD gene in enteric tissue. Furthermore, some of these beta-defensin mRNAs were abundant in bone marrow, suggesting that in enteric tissue their expression may be in cells of hematopoietic origin. Extracts of small intestinal mucosa obtained from healthy cows have numerous active chromatographic fractions as determined by an antibacterial assay, and one peptide was partially purified. The peptide corresponded to one of the low-abundance cDNAs. This study provides evidence of beta-defensin expression in enteric tissue and that the mRNA encoding a major beta-defensin of enteric tissue, EBD, is inducibly expressed in enteric epithelial cells. These findings support the proposal that beta-defensins may contribute to host defense of enteric mucosa.

Amino Acid Sequence↗
PubMed1998

Enteric defensin expression in necrotizing enterocolitis.

Immaturity of local innate defenses has been suggested as a factor involved in the pathophysiology of necrotizing enterocolitis (NEC). The mRNA of enteric human defensins 5 (HD5) and 6 (HD6), antibiotic peptides expressed in Paneth cells of the small intestine, have significantly lower levels of expression in fetal life compared with the term newborn and adult. In the current study, intracellular HD5 was demonstrated by immunohistochemistry at 24 wk of gestation, but at low levels, consistent with findings at the mRNA level. These data suggest that the low level enteric defensin expression, characteristic of normal intestinal development, may contribute to the immaturity of local defense, which predisposes the premature infant to NEC. To test if levels of defensin expression are altered in NEC, specimens from six cases of patients with NEC and five control subjects (four patients with atresia and one with meconium ileus) were analyzed to determine HD5 and HD6 mRNA levels by in situ hybridization. Compared with the control group, the level of enteric defensin expression per Paneth cell assessed by image analysis was increased 3-fold in cases of NEC (p = 0.02, analysis of variance and covariance). In addition, the number of Paneth cells was increased 2-fold in the small intestinal crypts of NEC specimens compared with those of control subjects (p < 0.01, covariance analysis). In healthy tissue, peptide levels within Paneth cells paralleled mRNA levels through development. In tissue from infants with NEC, the steady state level of intracellular peptide was not increased in conjunction with the observed rise in defensin mRNA. A straightforward interpretation of this finding is that HD5 is actively secreted in this setting and the Paneth cells maintain a constant steady state level of intracellular peptide, but the possibility of translational regulation of peptide expression is also consistent with these data. The associations between NEC and enteric defensin expression reported here offer support for future studies to address the role of these endogenous host defense factors in the pathophysiology of this disease.

Adult↗
PubMed1997

The mouse genome encodes a single homolog of the antimicrobial peptide human beta-defensin 1.

The cysteine-rich beta-defensin peptides are broad-spectrum bactericidal agents expressed in epithelial and myeloid tissues. The human beta-defensin-1 (hBD-1) gene maps adjacent to the human alpha-defensin cluster and is expressed in the respiratory, gastrointestinal and genitourinary tracts. Here, we characterize a mouse beta-defensin gene (mBD-1) which is: (1) closely related to hBD-1 both in sequence and gene organization; (2) expressed at high levels in the mouse kidney and at lower levels in brain, heart, lung, uterus, spleen, skeletal muscle, stomach, and small intestine; and (3) maps to mouse chromosome 8 at or near the location of the mouse alpha-defensin genes. These data indicate that mBD-1 is a close homolog of hBD-1, and suggest that analysis of its role in mouse host defense may provide significant insights into human epithelial innate immunity.

Amino Acid Sequence↗