Adenoviral-mediated gene transfer to murine small intestine is more efficient in neonates than adults

PURPOSE

The authors sought to assess the feasibility of in vivo gene transfer to the small intestine using recombinant adenovirus in neonatal and adult mice.

METHODS

H5.010CMVlacZ is a replication-defective, E1-deleted human type 5 adenovirus, which contains the lacZ gene under the control of a cytomegalovirus promoter and enhancer. The lacZ gene was used as a marker because its gene product, beta-galactosidase, is readily detected by X-gal histochemistry. Sixty neonatal (3 to 5 days old) and 45 adult (6 to 8 weeks old) C57BL/6 mice were investigated. Intestinal gene transfer was attempted with H5.010CMVlacZ by intraperitoneal (i.p.), intraluminal (IL), and intramural (i.m.) injection. Based on prior studies, the optimal dose of H5.010CMVlacZ was 1 x 10(8) plaque forming units (pfu/mL). Control animals received saline injections. Gene transfer on repeat administration of adenovirus has been shown to be prevented by neutralizing antibody. To determine if neonatal inoculation induced a humoral immune response, neonates (n = 5) that received i.p. injections were rechallenged with intravenous H5.010CMV alkphos, a similar adenoviral construct containing the alkaline phosphatase marker gene. Serum samples were analyzed by Western blot to detect the presence of adenoviral-specific antibody.

RESULTS

Gene transfer to neonatal small intestine was successful by IL gastric (n = 8/10), IL jejunal (n = 9/10) and i.p. (n = 10/10) routes 2 days after injection. Macroscopic staining was present in 90% of standardized 2-cm small bowel segments. Transgene expression was identified in intestinal smooth muscle, serosa, and epithelium. Gene transfer to the adult small intestine was successful by IL jejunal (n = 4/5), i.m. (n = 5/5), and i.p. (n = 1/5) injection of adenoviruslacZ with focal staining (< 5% of 2-cm segments) in epithelium including crypts, muscle, and serosa. Three weeks after i.p. H5.010CMVlacZ in neonates, intravenous injection with H5.010CMValkphos resulted in hepatic transgene expression (n = 4/5) that was indistinguishable from a primary intravenous inoculation; persistent, lacZ expression was not detectable in the liver or intestine (n = 0/5). Western blot analysis detected adenoviral-specific antibodies after adult IM but not after neonatal i.p. injection. Furthermore, 3 weeks after neonatal i.p. injection repeat administration by the i.m. route was successful (n = 4/ 4).

CONCLUSION

Gene transfer to neonatal and adult small intestine is feasible using recombinant adenovirus and is more efficient in neonates as indicated by increased surface area of marker gene expression, effectiveness of intraperitoneal delivery, and the ability to readminister recombinant adenovirus.

Fiber: effect on bacterial translocation and intestinal mucin content

Total parenteral nutrition (TPN) and elemental diet (ED) produce intestinal atrophy and increase bacterial translocation (BT) to mesenteric lymph nodes. The increased rate of BT may be due to alterations in mucosal structure, enzyme activity, or mucin content. Fiber improves intestinal structure and function in rats and may reduce the rate of BT. This study determined whether the addition of fiber to TPN or ED would maintain intestinal integrity and decrease BT to the mesenteric lymph nodes. Fifty-six adult male Sprague-Dawley rats underwent placement of jugular catheters and were assigned to one of five dietary groups: TPN, TPN+oral oat fiber (TPNF) 2 g/day, ED, ED+oral oat fiber (EDF) 2 g/day, or AIN-76 (control); they were pair-fed for 7 days. On day 8 the mesenteric lymph nodes were removed for bacterial cultures; and jejunal mucosal weight, DNA, protein, alkaline phosphatase, maltase, and jejunal mucin content were measured. Enteral nutrition significantly decreased BT when compared to parenteral feeding, and fiber significantly decreased BT when administered to rats receiving TPN or ED. Improvements in intestinal mucosal structure were not consistently associated with decreased rates of BT. Additionally, BT occurred independently of jejunal mucin concentration. Mechanisms other than maintenance of mucosal structure or mucin content are important in the mediation of fiber-induced decreased BT in rats receiving TPN or ED.

Butyrate increases colonocyte protein synthesis in ulcerative colitis

Butyrate promotes epithelial cell healing and improves symptoms when administered rectally in patients with distal ulcerative colitis (UC). It was hypothesized that butyrate may enhance healing in patients with UC by stimulating colonocyte proliferation and/or protein production. Mucosa from the descending colon was obtained from patients with UC (n = 5), Crohn's disease (n = 8), diverticulitis (n = 6), and cancer (normal tissue 10 cm from tumor; n = 10). Epithelial cells were isolated using dispase/collagenase and differential sedimentation and incubated for 4 hr at 37 degrees C with either Na butyrate (10 mM) or NaCl (10 mM). Protein synthesis was assessed by [14C]leucine incorporation and proliferation was determined with [3H]thymidine. Mean viability and purity were >88%. Spontaneous proliferation was significantly increased in UC when compared to diverticulitis and normal controls. Butyrate significantly increased protein synthesis in UC epithelial cells when compared to saline control. The therapeutic effects of butyrate in patients with UC may be due to its use by epithelial cells as a metabolic fuel to increase protein production and promote healing.

Identification of glucose response proteins in two biological models of beta-cell adaptation to chronic high glucose exposure

High resolution 2-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) combined with computerized analysis of gel images was used to search for proteins whose biosynthesis was induced or repressed in pancreatic islet cells chronically exposed to high glucose in an in situ and a tissue culture model of islet cell adaptation to excessive fuel load. The in situ model involved a 4-day intravenous infusion of either 50% glucose or 0.45% saline solution, followed by islet isolation, [35S]methionine labeling at 3 and 18 mM glucose for both groups, and protein analysis by 2-dimensional SDS-PAGE. The tissue culture model involved a 7-day culture of isolated rat islets in RPMI 1640 with 10% fetal calf serum containing either 3 or 30 mM glucose, followed by radiolabeling and 2-dimensional PAGE of proteins as in the in situ model. A small fraction of about 1.5% of the approximately 2000 identifiable proteins can be characterized as adaptive proteins. Of these altogether 58 proteins in the two models, 5 proteins were demonstrable in both models and two of these (proteins 1526 and 7622) are particularly noteworthy. Protein 1526 (Mr 57,000; pI 5.09) showed the same response pattern in both models and its expression was most enhanced when islets from chronically glucose-infused animals or those cultured for 7 days at 30 mM were radiolabeled at 18 mM glucose. Protein 7622 (Mr 68,000; pI 6.50) (also known as GSP-65; Collins, H.W., Buettger, C., and Matschinsky, F.M. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 5494-5498) showed a different labeling pattern in the two models: stimulation of [35S]methionine incorporation by 18 mM glucose both in control and experimental islets from the infusion study, but lack of such stimulation of radiolabeling in islets cultured for 7 days at 30 mM glucose in contrast to islets cultured at 3 mM. The experimental strategy and the methodology are evaluated and the significance of the results is discussed. Potentials of the approach and plans for future experiments are considered.

Biennial survey of clinical nutrition training programs

Three posttraining program surveys have been done by The American Society for Clinical Nutrition Committee on Subspecialty Training to evaluate the status of training programs in clinical nutrition. This survey updates demographic data about programs and determines which classes are offered or required as a part of basic nutrition-science requirements for nutrition training programs. In addition, the importance of board certification and accreditation of training programs is examined.

Biennial survey of physician clinical nutrition training programs

This is the third survey of physician clinical nutrition training programs. Current training programs were identified, descriptive information obtained, and training program content was compared with that recommended at the 1984 Conference on Clinical Nutrition Training. In general, goals as to the quantity of research, clinical, and teaching training are being met. Virtually all programs provide training in nutritional support activities. Most training programs are not as broad in scope of exposure to the less clinical aspects of nutrition nor to all the illness and age groups recommended by the 1984 conference. Consideration of broadening the scope of physician training programs or redefinition of training guidelines is warranted. A program-certifying agency may be helpful in identifying programs achieving certain minimal standards.

Utility of skin testing in nutritional assessment: a critical review

To evaluate the claim that delayed cutaneous hypersensitivity skin testing is useful in nutritional assessment of hospitalized patients, we reviewed the English language literature of the last 12 years. Although several hundred publications discussed delayed cutaneous hypersensitivity testing and nutritional status, only 15 provided new, objective data correlating these variables in hospitalized adults. Of these, only three provided age-matched control groups to control for antigen variability, lack of prior exposure, and other technical problems. The majority of reports took no account of diseases (cancer, immune disease, infection) or therapies (radiation, drugs, surgery) known to affect skin test response. In the reports specifying different degrees of malnutrition, the most important group, those with less than obvious malnutrition, were not abnormal by skin testing. Ten reports described serial skin testing during nutritional intervention. Non reported serially tested controls without nutritional intervention, important since serial testing alone can augment skin test response. Nonnutritional intercurrent therapy which might affect skin tests was seldom mentioned. In the few reports specifying that nutritional repletion was even achieved, repleted patients were not separated from unrepleted in subsequent analyses. No report examined skin testing for its predictive accuracy, cost/benefit ratio, or influence on outcome. Because of these problems in experimental design, the frequent lack of appropriate controls, and the low specificity of abnormal delayed cutaneous hypersensitivity responses, we conclude that the utility of skin testing in nutritional assessment remains unproved.