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Biomedical subjects

D R Mack

Publications and source records attributed to D R Mack.

At least 19 recordsLinked to original sources
PubMed2003

Extracellular MUC3 mucin secretion follows adherence of Lactobacillus strains to intestinal epithelial cells in vitro.

BACKGROUND: Mucins are large complex glycoproteins that protect intestinal mucosal surfaces by limiting access of environmental matter to their epithelial cells. Several mucin genes have been described, including MUC3 that is a membrane associated mucin of the small intestine. Increased MUC3 mRNA transcription is induced by incubation of intestinal epithelial cells with a Lactobacillus strain known to be adherent to them. AIMS: To determine whether increased epithelial cell MUC3 mucin expression in response to Lactobacillus strains results in increased extracellular secretion of MUC3 mucins and the importance of epithelial cell adherence in modulation of MUC3 mucin expression. METHODS: HT29 cells grown to enhance expression of MUC3 mucins were incubated with selected Lactobacillus strains. Spent cell culture medium was collected for detection of secreted MUC3 mucins using dot blot immunoassay with a generated MUC3 antibody. Post-incubation HT29 cell RNA was collected for analysis of MUC3 expression by northern blot analysis using a MUC3 cDNA probe. In vitro binding studies using Lactobacillus strains incubated alone or coincubated with enteropathogenic Escherichia coli strain E2348/69 were used for adherence and inhibition of adherence studies, respectively. RESULTS: Lactobacillus strains with minimal ability to adhere to HT29 cells failed to induce upregulation of mucin gene expression. There was a direct correlation between upregulation of MUC3 mucin mRNA expression and extracellular secretion of MUC3 mucin. The same Lactobacillus strains that increased extracellular secretion of MUC3 mucin led to reduced adherence of enteropathogen E coli E2348/69 during coincubation experiments. CONCLUSION: Probiotic microbes induce MUC3 mucin transcription and translation with extracellular secretion of the MUC3 mucins. Epithelial cell adherence enhances the effects of probiotics on eukaryotic mucin expression.

Bacterial Adhesion↗
PubMed2001

Intrinsic bending and deformability at the T-A step of CCTTTAAAGG: a comparative analysis of T-A and A-T steps within A-tracts.

Introduction of a T-A or pyrimidine-purine step into a straight and rigid A-tract can cause a positive roll deformation that kinks the DNA helix at that step. In CCTTTAAAGG, the central T-A step has an 8.6 degrees bend toward the major groove. We report the structural analysis of CCTTTAAAGG and a comparison with 25 other representative crystal structures from the NDB containing at least four consecutive A or T bases. On average, more local bending occurs at the disruptive T-A step (8.21 degrees ) than at an A-T step (5.71 degrees ). In addition, A-tracts containing an A-T step are more bent than are pure A-tracts, and hence A-A and A-T steps are not equivalent. All T-A steps examined exhibit positive roll, bending towards the major groove, while A-T steps display negative roll and bend slightly towards the minor groove. This illustrates how inherent negative and positive roll are, respectively, at A-T and T-A steps within A-tracts. T-A steps are more deformable, showing larger and more variable deformations of minor groove width, rise, cup, twist, and buckle. Standard deviations of twist, rise, and cup for T-A steps are 6.66 degrees, 0.55 A, and 15.90 degrees, versus 2.28 degrees, 0.21 A, and 2.99 degrees for A-T steps. Packing constraints determine which local values of these helical parameters an individual T-A step will adopt. For instance, with CCTTTAAAGG and three isomorphous structures, CGATTAATCG, CGATATATCG, and CGATCGATCG, crystal packing forces lead to a series of correlated changes: widened minor groove, large slide, low twist, and large rise. The difference in helical parameters between A-T steps lying within A-tracts, versus A-T steps within alternating AT sequences, demonstrates the importance of neighboring steps on the conformation of a given dinucleotide step.

AT Rich Sequence↗
PubMed2001

Elevated extrahepatic expression and secretion of mammary-associated serum amyloid A 3 (M-SAA3) into colostrum.

Mammary-associated serum amyloid A 3 (M-SAA3) was secreted at highly elevated levels in bovine, equine and ovine colostrum and found at lower levels in milk 4 days postparturition. N-terminal sequencing of the mature M-SAA3 protein from all the three species revealed a conserved four amino acid motif (TFLK) within the first eight residues. This motif has not been reported to be present in any of the hepatically-produced acute phase SAA (A-SAA) isoforms. Cloning of the bovine M-Saa3 cDNA from mammary gland epithelial cells revealed an open reading frame that encoded a precursor protein of 131 amino acids which included an 18 amino acid signal peptide. The predicted 113 residue mature M-SAA3 protein had a theoretical molecular mass of 12,826Da that corresponded with the observed 12.8kDa molecular mass obtained for M-SAA3 in immunoblot analysis. The high abundance of this extrahepatically produced SAA3 isoform in the colostrum of healthy animals suggests that M-SAA3 may play an important functional role associated with newborn adaptation to extrauterine life and possibly mammary tissue remodeling.

Amino Acid Motifs↗
PubMed1999

Probiotics inhibit enteropathogenic E. coli adherence in vitro by inducing intestinal mucin gene expression.

Probiotic agents, live microorganisms with beneficial effects for the host, may offer an alternative to conventional antimicrobials in the treatment and prevention of enteric infections. The probiotic agents Lactobacillus plantarum 299v and Lactobacillus rhamnosus GG quantitatively inhibited the adherence of an attaching and effacing pathogenic Escherichia coli to HT-29 intestinal epithelial cells but did not inhibit adherence to nonintestinal HEp-2 cells. HT-29 cells were grown under conditions that induced high levels of either MUC2 or MUC3 mRNA, but HEp-2 cells expressed only minimal levels of MUC2 and no MUC3 mRNA. Media enriched for MUC2 and MUC3 mucin were added exogenously to binding assays and were shown to be capable of inhibiting enteropathogen adherence to HEp-2 cells. Incubation of L. plantarum 299v with HT-29 cells increased MUC2 and MUC3 mRNA expression levels. From these in vitro studies, we propose the hypothesis that the ability of probiotic agents to inhibit adherence of attaching and effacing organisms to intestinal epithelial cells is mediated through their ability to increase expression of MUC2 and MUC3 intestinal mucins.

Bacterial Adhesion↗
PubMed1998

Small bowel bacterial overgrowth as a cause of chronic diarrhea after liver transplantation in children.

Children who have undergone liver transplantation may develop chronic diarrhea for a number of reasons. Three children who underwent liver transplantation for liver failure, all of whom had had previous biliary and intestinal surgeries and whose postoperative course was marked by signs and symptoms of intestinal malabsorption including chronic diarrhea, are described. Duodenal aspirates showed a panoply of bacterial species, and duodenal histology featured villus atrophy in two: one associated with luminal gram-positive cocci and another with acute and chronic duodenitis. Oral antibiotics cleared the symptoms. Small bowel bacterial overgrowth may need to be considered in children with chronic diarrhea after liver transplantation, especially when previous intestinal surgery has taken place. Long-term antibiotic therapy may be required to effectively eradicate the offending organisms to suppress symptoms.

Administration, Oral↗
PubMed1998

Methotrexate in patients with Crohn's disease after 6-mercaptopurine.

OBJECTIVE: The objective of this study was to describe the clinical outcome of children with Crohn's disease treated with subcutaneous methotrexate. SUBJECTS/METHODS: Fourteen patients (10 boys) with extensive Crohn's disease diagnosed at a mean age of 10.6 +/- 3.6 years had previously received various medical therapies for 4.3 +/- 4.0 years. Because of the severity of their disease, 6-mercaptopurine had been introduced but discontinued because of the patients' failure to respond (n = 11) or the development of pancreatitis (n = 3). Subsequently, low-dose, weekly, subcutaneous methotrexate was initiated. Pediatric Crohn's Disease Activity Index scores and prednisone requirement were followed as outcome measures. RESULTS: Overall, 9 (64%) of the 14 patients showed improvement, including 6 (55%) of 11 patients who had previously received an adequate trial of 6-mercaptopurine and all three patients who were intolerant of 6-mercaptopurine. Improvement in clinical and laboratory measures occurred by 4 weeks and were similar whether (n = 8) or not (n = 6) the dose of corticosteroids was increased before the start of subcutaneous methotrexate. Three patients were tapered from their initial methotrexate dose after the minimization of corticosteroids and remain well. One patient receiving daily corticosteroids died suddenly after acute onset of illness. Among patients responding, methotrexate was discontinued because of side effects (n = 2) or electively (n = 2). Of the latter two patients, one has resumed methotrexate after disease relapse, whereas the other patient has had a sustained remission. CONCLUSIONS: Low-dose, weekly, subcutaneous methotrexate can induce remission in some pediatric patients with Crohn's disease who fail to adequately respond to other immunomodulator medications.

Adolescent↗
PubMed1998

Altered expression of sialylated carbohydrate antigens in HT29 colonic carcinoma cells.

To determine whether cell growth conditions impacted carbohydrate expression, HT29 cells were gradually transferred from a conventional glucose-containing media to a glucose-free galactose containing media. Indirect immunofluorescence on acetone fixed cells showed increased expression of sialyl Lewis A antigen (CA19-9), sialyl Lewis C (DUPAN2) and Tn/sialyl-Tn on the surface of HT29 cells grown in the glucose-free galactose containing media compared to those grown in the glucose containing media. Sialyltransferases responsible for the synthesis for these sialylated epitopes were Increased in the galactose-fed HT29 cells. Media overlying the cells was subjected to isopycnic ultracentrifugation in cesium chloride and the fractions derived from both glucose and galactose media with equivalent buoyant densities of 1.56 g/L, which are predicted to contain mucin glycoforms, were further separated by HPLC using a Mono-Q anion exchange column. The chromatograph of eluent from the sample derived from the cells growing in the galactose containing media showed an increased peak that reacted with the anti-sialyl Lewis A antibody, CA19-9. These results show that alteration of in vitro culture conditions may cause HT29 colonic carcinoma cells to alter the expression of sialylated carbohydrates.

Adenocarcinoma↗
PubMed1998

Ongoing advances in inflammatory bowel diseases, including maintenance therapies, biologic agents, and biology of disease.

Inflammatory bowel diseases remain a significant chronic disease affecting children and adolescents. Although corticosteroids remain the standard form of therapy for many patients, an era of biological agents for therapy in inflammatory bowel diseases is upcoming with human trials using these agents now forthcoming. In addition, studies on maintenance of remission are beginning to address the selection of those patients most likely to benefit from aminosalicylate therapies, the risks of relapse from using cyclooxygenase inhibitors, the lack of benefit from lipoxygenase inhibitors, and possible future methodologies to examine the effectiveness of the immuno-suppressive agent 6-mercaptopurine. Further development of the hypothesis that new-onset disease may be different than longstanding disease can be appreciated with reports of cytokine analysis in new-onset inflammation and the high risk of progression of disease in new-onset ulcerative proctitis in children. With more reports on the role of intestinal epithelial cells in intestinal diseases, it is now clear that this cell layer is not a passive bystander with regard to the interactions between the luminal contents and immune system components found within the lamina propria; new studies suggest that novel therapeutic strategies may be possible. This review summarizes recently reported aspects of Crohn's disease and ulcerative colitis, with an emphasis on issues-pertinent for younger patients.

Anti-Inflammatory Agents↗
PubMed1997

Posttransplant eosinophilic gastroenteritis in children.

The cause of eosinophilic gastroenteropathy in older children and adults is unknown. In this report, two post-liver transplantation children treated with low-dose cyclosporine A and alternate-day low-dose prednisone are described who were administered a single bolus administration of a lympholytic dose of corticosteroids without taper and who developed intestinal symptomatology several weeks later. Histologic examination of mucosal biopsy specimens from various regions of the gastrointestinal tract showed an intense eosinophilic infiltration of the mucosa and lamina propria. The patients recovered after corticosteroid administration was tapered. Post-transplant gastroenteric eosinophilic inflammation may need to be considered in patients on immunomodulatory medications who have chronic intestinal symptomatology.

Anti-Inflammatory Agents↗
PubMed1997

Intolerance to protein hydrolysate infant formulas: an underrecognized cause of gastrointestinal symptoms in infants.

The purpose of this study was to determine the effectiveness of an amino acid-based infant formula in infants with continued symptoms suggestive of formula protein intolerance while they were receiving casein hydrolysate formula (CHF). Twenty-eight infants, 22 to 173 days of age, were enrolled; each had received CHF for an average of 40 days (10 to 173 days) and continued to have bloody stools, vomiting, diarrhea, irritability, or failure to gain weight, or a combination of these symptoms. Sigmoidoscopy with rectal biopsy was performed in all infants. The infants then received an amino acid-based infant formula, Neocate, for 2 weeks. After 2 weeks of treatment, 25 of the infants demonstrated resolution of their symptoms and underwent challenge with CHF. Of the 25 who were challenged, eight tolerated the CHF and the remainder had recurrence of their symptoms. The histologic features in these infants varied from eosinophilic infiltration to normal. We conclude that not all infants with apparent formula protein-induced colitis respond to CHF and that these infants may have resolution of their symptoms when fed an amino acid-based infant formula.

Dietary Proteins↗
PubMed1997

Introduction of 6-mercaptopurine in Crohn's disease patients during the perioperative period: a preliminary evaluation of recurrence of disease.

BACKGROUND: Recurrence of Crohn's disease after surgery is a common occurrence, pointing to the need for a strategy to prevent recurrent disease. We report the postoperative course of 10 patients who required intestinal resections for complications related to Crohn's disease. METHODS: All patients had a Pediatric Crohn's Disease Activity Index score of 10 or greater. Among these patients, 5 began treatment with 6-mercaptopurine in the perioperative period. All 10 had received various combinations of prednisone and salicylate compounds. Patients who were given 6-mercaptopurine did not discontinue the medication until 2 years after the surgery. RESULTS: To date, none of the five patients who were placed on 6-mercaptopurine have had recurrence of their Crohn's disease (mean disease-free period 32.6 +/- 18.4 months). Among those five patients not receiving 6-mercaptopurine there have been three relapses (mean time to relapse 3.7 +/- 1.2 months). Log-rank sum analyses of Kaplan-Meier survival curves show benefit to patients receiving 6-mercaptopurine in preventing relapses after intestinal resection (p < 0.05). CONCLUSIONS: Although the underlying pathophysiologic reasons leading to the high relapse rate after intestinal surgery in Crohn's disease are unknown, we conclude that treatment with 6-mercaptopurine in the perioperative period may be warranted to help prevent the recurrence of Crohn's disease after surgery.

Adolescent↗
PubMed1997

Gastroenteric inflammation in children with ulcerative colitis.

This is a retrospective review of five pediatric cases of inflammatory bowel disease with gastroduodenal as well as pancolonic inflammation. The presumptive diagnosis was Crohn's disease in all. Three of five also had microscopic ileitis. Chronic active gastritis was present at diagnosis in all five and duodenitis in four of five. None ever had noncaseating granulomas in any location. Prolonged (mean, 22 months) and ineffective trials of multiple medical therapies were carried out before subtotal proctocolectomy, which allowed the diagnosis of ulcerative colitis to be made in all children. Surgery remained curative after follow-up of over 1 yr (mean, 16 months). This experience confirms that gastroduodenal inflammation occurs in children with ulcerative colitis. Presence of gastroduodenal inflammation does not ensure the diagnosis of Crohn's unless other characteristic features of Crohn's are present. Accurate discrimination between Crohn's and ulcerative colitis remains important in management of pediatric inflammatory bowel disease to facilitate timely surgical referral. Upper gastrointestinal tract inflammation in ulcerative colitis warrants further study.

Adolescent↗
PubMed1996

Influenza vaccination following liver transplantation in children.

Our objective was to determine the immunologic response to two influenza vaccine doses in 39 children who had undergone liver transplantation. Patients received two doses of trivalent inactivated influenza vaccine 4 weeks apart. Sera were collected 4 weeks after each dose and analyzed by a hemagglutination inhibition assay (HAI) for evidence of antibody response to the antigens A/Taiwan/1/86 (H1N1), A/Beijing/32/92 (H3N2), and B/Panama/45/95. Patients with HAI titers of 1:40 or greater were considered to have protective titers. Twenty-six (67%) patients showed a 1:40 or greater titer response to A/Beijing/32/92 1 month after the first vaccination. Only two additional patients were found to have similar titers after the second dose. A higher proportion of patients with protective titers were on smaller amounts of prednisone for body weight or alternate day low dose (< 10 mg/day) prednisone compared to patients on daily low dose or daily high dose prednisone. Patients with protective titers were significantly older (9.0 +/- 2.8 years) than those without protective titers (4.2 +/- 3.4 years, p = .002) following the first inoculation of the A/Beijing/32/92 vaccine component. Similar results were found for the second vaccination and with the H1N1 antigen. Cyclosporine level, gender, and body mass index were not associated with any outcome measures. We conclude that most liver transplant recipients had a protective antibody titer after a single influenza inoculation, but little further advantage was gained after an additional dose. Vaccination of household contacts of younger patients and those patients on daily prednisone or patient chemoprophylaxis may offer greater benefit in prevention of influenza in liver transplant recipients than multiple vaccine doses with current vaccine preparations.

Adolescent↗
PubMed1996

Shwachman syndrome: exocrine pancreatic dysfunction and variable phenotypic expression.

BACKGROUND & AIMS: Shwachman syndrome is an inherited condition with multisystemic abnormalities, including exocrine pancreatic dysfunction. The aim of this study was to evaluate the occurrence and progression of features in a large cohort of patients. METHODS: Clinical records of 25 patients with Shwachman syndrome were reviewed. RESULTS: Mean birth weight (2.92 +/- 0.51 kg) was at the 25th percentile. However, by 6 months of age, mean heights and weights were less than the 5th percentile. After 6 months of age, growth velocity was normal. Severe fat maldigestion due to pancreatic insufficiency was present in early life (fecal fat, 26% +/- 17% of fat intake; age, < 2 years). Serial assessment of exocrine pancreatic function showed persistent deficits of enzyme secretion, but 45% of patients showed moderate age-related improvements leading to pancreatic sufficiency. Neutropenia was the most common hematologic abnormality (88%), but leukopenia, thrombocytopenia, and anemia were also frequently encountered. Patients with hypoplasia of all three bone marrow cellular lines (n = 11) had the worst prognosis; 5 patients died, 2 of sepsis and 3 of acute myelogenous leukemia. Other findings included hepatomegaly and/or abnormal liver function test results and skeletal abnormalities. CONCLUSIONS: A wide and varied spectrum of phenotypic abnormalities among patients with Shwachman syndrome is described. Pancreatic acinar dysfunction is an invariable abnormality. Patients with severe bone marrow involvement may have a guarded prognosis.

Abnormalities, Multiple↗
PubMed1996

Preliminary experience with intestinal transplantation in infants and children.

OBJECTIVE: This report discusses the preliminary experience with intestinal transplantation in children at the University of Nebraska Medical Center. PATIENTS: During the past 4 years, 16 intestinal transplants have been performed in infants and children. Thirteen have been combined liver and bowel transplants, and the reminder were isolated intestinal transplants. Nearly half of the patients were younger than 1 year of age at the time of surgery, and the vast majority were younger than 5 years of age. All but one had short bowel syndrome. RESULTS: The 1-year actuarial patient and graft survival rates for recipients of liver and small bowel transplants were 76% and 61%, respectively. Eight of 13 patients who received liver and small bowel transplants remain alive at the time of this writing, with a mean length of follow-up of 263 (range, 7 to 1223) days. Six patients are currently free of total parenteral nutrition. All three patients receiving isolated intestinal transplants are alive and free of parenteral nutrition. The mean length of follow-up is 384 (range, 330 to 450) days. Major complications have included severe infections and rejection. Lymphoproliferative disease, graft-versus-host disease, and chylous ascites have not been major problems. CONCLUSIONS: Although intestinal transplantation is in its infancy, these preliminary results suggest combined liver and bowel transplants and isolated intestinal transplantation may be viable options for some patients with intestinal failure caused by short bowel syndrome or other gastrointestinal disease in whom long-term total parenteral nutrition is not an attractive option.

Actuarial Analysis↗
PubMed1996

Determination of prothrombin activation fragments in young patients with inflammatory bowel disease.

OBJECTIVE: To assess coagulation cascade activation as a potential index of thromboembolic risk in inflammatory bowel disease (IBD). STUDY DESIGN: Fifty plasma samples were obtained during consecutive outpatient encounters with 29 patients (male:female = 20:9) with either Crohn's disease (CD) (n = 23) or ulcerative colitis (UC) (n = 6). Disease activity for CD was determined using the Pediatric Crohn's Disease Activity Index (PCDAI) and for UC using signs/symptoms and mucosal histology. Patients were grouped as active, recently active (not currently active but had been active within the previous 2 months), or inactive. Prothrombin fragment 1.2 (F1.2) was determined by enzyme-linked immunosorbent assay on plasma samples. Lab parameters were compared using the Kruskal-Wallis test with pairwise comparisons made using Wilcoxian rank sum test. RESULTS: Forty-three percent of samples taken during active phases of disease (13 of 30) had elevated prothrombin cleavage byproduct F1.2. Similarly, five of eight encounters (63%) with recently active IBD had elevated F1.2 values. In contrast, none of the patients with inactive disease exhibited F1.2 elevation. Median F1.2 levels in both the active (0.85 nM/L) and recently active (1.4 nM/L) patient groups were greater than that of the inactive group (0.6 nM/L; p < 0.05). CONCLUSIONS: Evidence of coagulation cascade activation in patients with active and recently active IBD suggests an increased risk of thrombogenesis during active disease that extends for a period of time after commencement of medications to induce remission in their disease process. It may be prudent to counsel patients to avoid risk factors associated with thrombotic phenomenon around the time of active IBD.

Adolescent↗