Barbara J. Sheppard

A tough biodegradable elastomer

Biodegradable polymers have significant potential in biotechnology and bioengineering. However, for some applications, they are limited by their inferior mechanical properties and unsatisfactory compatibility with cells and tissues. A strong, biodegradable, and biocompatible elastomer could be useful for fields such as tissue engineering, drug delivery, and in vivo sensing. We designed, synthesized, and characterized a tough biodegradable elastomer from biocompatible monomers. This elastomer forms a covalently crosslinked, three-dimensional network of random coils with hydroxyl groups attached to its backbone. Both crosslinking and the hydrogen-bonding interactions between the hydroxyl groups likely contribute to the unique properties of the elastomer. In vitro and in vivo studies show that the polymer has good biocompatibility. Polymer implants under animal skin are absorbed completely within 60 days with restoration of the implantation sites to their normal architecture.

Bacterial Infection Promotes Colon Tumorigenesis in ApcMin/+ Mice

The Min mouse, which has a germ line mutation in 1 allele of the Apc tumor suppressor gene, is a model for the early steps in human colorectal cancer. Helicobacter pylori infection, a known risk factor for gastric cancer in humans, causes chronic inflammation and increased epithelial cell proliferation in the stomach. Infection with the bacterium Citrobacter rodentium is known to increase epithelial cell proliferation and to promote chemically initiated tumors in the colon of mice. Min mice infected with C. rodentium at 1 month of age were found to have a 4-fold increase in the number of colonic adenomas at 6 months of age, compared with uninfected Min mice. Most of the colonic adenomas in the infected Min mice were in the distal colon, where C. rodentium-induced hyperplasia occurs. These data demonstrate that bacterial infection promotes colon tumor formation in genetically susceptible mice.

Isolation of Helicobacter cinaedi from the Colon, Liver, and Mesenteric Lymph Node of a Rhesus Monkey with Chronic Colitis and Hepatitis

ABSTRACT On the basis of biochemical, phenotypic, and 16S rRNA analyses,Helicobacter cinaedi was isolated from the colon, liver, and mesenteric lymph nodes of a 2-year-old rhesus monkey with chronic diarrhea. Histologically, the liver had mild to moderate biliary hyperplasia and hypertrophy with periportal inflammation and fibrosis. Colonic and cecal lesions consisted of diffuse chronic inflammation and glandular hyperplasia extending the length of the crypts. This is the first observation of H. cinaedi associated with active hepatitis and colitis in a nonhuman primate.

Helicobacter pylori Infection and High Dietary Salt Independently Induce Atrophic Gastritis and Intestinal Metaplasia in Commercially Available Outbred Mongolian Gerbils

Risk factors for development of gastric adenocarcinoma include high dietary salt and Helicobacter pylori infection. Few animal models exist for the laboratory investigation of these factors. We examined gastric pathology resulting from H. pylori infection and high dietary salt as independent variables in commercially available, outbred Mongolian gerbils. Gastric adenocarcinoma and its precursor lesion, intestinal metaplasia, have been previously reported in inbred Mongolian gerbils (MGS/Sea) infected either with clinical isolates of H. pylori or with the strain ATCC 43504. In contrast, we utilized outbred gerbils [Crl:(MON)] infected with the Sydney strain of H. pylori. After 37 weeks, five of five infected animals had atrophic gastritis and intestinal metaplasia. These lesions were similar in description and time of appearance to the lesions reported in inbred gerbils. Atrophic gastritis and intestinal metaplasia also developed in six of six uninfected, outbred gerbils fed a 2.5% salt diet for 56 weeks. In contrast to the H. pylori-infected animals, these lesions were present without concurrent gastric inflammation. The outbred Mongolian gerbil therefore provides an excellent animal model for the study of several gastric cancer risk factors.

Isolation and Characterization of a Helicobacter sp. from the Gastric Mucosa of Dolphins, Lagenorhynchus acutus and Delphinus delphis

ABSTRACT Gastric ulcerations in dolphins have been reported for decades. Some of these lesions were associated with parasitic infections. However, cases of nonparasitic gastric ulcers with no clearly defined etiology also have been reported in wild and captive dolphins. Considerable speculation exists as to whether dolphins haveHelicobacter-associated gastritis and peptic ulcer disease. The stomachs of seven stranded Atlantic white-sided dolphins,Lagenorhynchus acutus, and 1 common dolphin,Delphinus delphis, were assessed for the presence ofHelicobacter species. Novel Helicobacterspecies were identified by culture in the gastric mucosa of two of the eight dolphins studied and by PCR in seven of the eight dolphins. The gram-negative organisms were urease, catalase, and oxidase positive. Spiral to fusiform bacteria were detected in gastric mucosa by Warthin Starry staining. Histopathology revealed mild to moderate diffuse lymphoplasmacytic gastritis within the superficial mucosa of the main stomach. The pyloric stomach was less inflamed, and bacteria did not extend deep into the glands. The lesions parallel those observed inHelicobacter pylori-infected humans. Bacteria from two dolphins classified by 16S rRNA analysis clustered with gastric helicobacters and represent a novel Helicobacter sp. most closely related to H. pylori. These findings suggest that a novel Helicobacter sp. may play a role in the etiopathogenesis of gastritis and gastric ulcers in dolphins. To our knowledge this represents the first isolation and characterization of a novel Helicobacter sp. from a marine mammal and emphasizes the wide host distribution and pathogenic potential of this increasingly important genus.

Sexual dysfunction and sudden death in epileptic male EL mice: inheritance and prevention with the ketogenic diet.

Summary:  Purpose: The EL mouse is an animal model for multifactorial idiopathic epilepsy. Although EL mice have been studied extensively for >45 years, the etiology of male sudden death and its relation to seizures have not been defined. Here we investigated the cause of EL male sudden death and its relation to epilepsy.

Allele- and tir-independent functions of intimin in diverse animal infection models.

Upon binding to intestinal epithelial cells, enterohemorrhagic Escherichia coli (EHEC), enteropathogenic E. coli (EPEC), and Citrobacter rodentium trigger formation of actin pedestals beneath bound bacteria. Pedestal formation has been associated with enhanced colonization, and requires intimin, an adhesin that binds to the bacterial effector translocated intimin receptor (Tir), which is translocated to the host cell membrane and promotes bacterial adherence and pedestal formation. Intimin has been suggested to also promote cell adhesion by binding one or more host receptors, and allelic differences in intimin have been associated with differences in tissue and host specificity. We assessed the function of EHEC, EPEC, or C. rodentium intimin, or a set of intimin derivatives with varying Tir-binding abilities in animal models of infection. We found that EPEC and EHEC intimin were functionally indistinguishable during infection of gnotobiotic piglets by EHEC, and that EPEC, EHEC, and C. rodentium intimin were functionally indistinguishable during infection of C57BL/6 mice by C. rodentium. A derivative of EHEC intimin that bound Tir but did not promote robust pedestal formation on cultured cells was unable to promote C. rodentium colonization of conventional mice, indicating that the ability to trigger actin assembly, not simply to bind Tir, is required for intimin-mediated intestinal colonization. Interestingly, streptomycin pre-treatment of mice eliminated the requirement for Tir but not intimin during colonization, and intimin derivatives that were defective in Tir-binding still promoted colonization of these mice. These results indicate that EPEC, EHEC, and C. rodentium intimin are functionally interchangeable during infection of gnotobiotic piglets or conventional C57BL/6 mice, and that whereas the ability to trigger Tir-mediated pedestal formation is essential for colonization of conventional mice, intimin provides a Tir-independent activity during colonization of streptomycin pre-treated mice.

Poly(glycerol sebacate)—A Novel Biodegradable Elastomer for Tissue Engineering

Abstract : Biodegradable polymers have significant potential in biotechnology and bioengineering. However, for some applications, they are limited by their inferior mechanical properties and unsatisfactory compatibility with cells and tissues. A strong, biodegradable, and biocompatible elastomer could be useful for fields such as tissue engineering, drug delivery, and in vivo sensing 1,2. We designed, synthesized, and characterized a tough biodegradablc elastomer from biocompatible monomers. This elastomer forms a covalently crosslinked three-dimensional network of random coils with hydroxyl groups attached to its backbone. Both crosslinking and the hydrogen bonding interactions between the hydroxyl groups likely contributes to the unique properties of the elastomer. In vitro and in vivo studies show the polymer has good biocompatibility. Subcutaneous (SC) polymer implants are absorbed completely within 60 days with restoration of the implantation sites to their normal architecture.