Biomedical subjects

Linda K Johnson

Publications and source records attributed to Linda K Johnson.

6 recordsLinked to original sources

PubMed2006

Rat hepatocyte engraftment in severe combined immunodeficient x beige mice using mouse-specific anti-fas antibody.

BACKGROUND: Hepatocyte transplantation holds promise as a treatment for acute and chronic liver failure; however, robust model systems needed to study xenogeneic hepatocyte transfer are lacking. Severe combined immunodeficient x beige (SCID/bg) hybrid mice readily accept foreign tissue. Repopulation of C.B-17 SCID/bg mouse liver with rat hepatocytes was studied following induction of mouse hepatocyte apoptosis using an anti-mouse agonistic fas monoclonal antibody (Jo2 mAb) that does not engage xenogeneic fas. METHODS: SCID/bg mice were transplanted with 1 x 10(6) fresh adult rat hepatocytes intrasplenically and treated with various doses, routes and frequencies of Jo2 mAb. Rat cell repopulation was characterized by quantitative immunofluorescent antibody (q-IFA) staining specific for rat dipeptidyl peptidase type IV (DPP-IV) and leucine amino peptidase, amplification of rat genomic DNA using polymerase chain reaction and histopathological and serum biochemistry analyses. RESULTS: Analysis of liver sections from mice treated twice weekly for 12 weeks with 0.4 mg/kg Jo2 mAb intraperitoneally consistently demonstrated >50% rat hepatocytes in the parenchymal mass by q-IFA. Rat hepatocyte engraftment protected mice from Jo2 mAb-mediated liver hemorrhage and hepatocyte apoptosis. Serum liver enzyme levels did not increase in Jo2 mAb-treated mice that were highly engrafted with rat hepatocytes, in contrast to matched non-engrafted mice. At 12 weeks post-engraftment, minimal fibrosis and inflammation were apparent and liver architecture had returned to near normal. Jo2 mAb did not induce histopathological abnormalities in other tissues known to express fas antigen (i.e. heart, lung). CONCLUSIONS: This novel model represents a simple and robust system of xenogeneic hepatocyte transplantation that could be applied to studies of liver biology, regeneration and hepatocyte transplantation.

Animals↗

PubMed2004

Age-related differences in vincristine toxicity and biodistribution in wild-type and transporter-deficient mice.

The impact of mouse multidrug resistance genes mdrla/b and mrpl on age-related differences in the toxicity and biodistribution of vincristine (VCR) was evaluated in wild-type, mrpl(-/-), mdrla/b(-/-), and combined mdrla/b(-/-), mrpl(-/-) weanling and adult mice given a single IP dose of VCR ranging from 0.0625 to 6 mg/kg. Weanling mice of all four genotypes were more sensitive than adult animals as determined by survival rate, average time of death, and pathologic findings. Wild-type animals were the least sensitive and combined mdrla/b(-/-), mrpl(-/-) mice the most sensitive to VCR toxicity. Mdrla/b(-/-) and mrpl(-/-) genotypes exhibited intermediate sensitivities, with mdrla/b(-/-) mice being more sensitive than mrpl(-/-) animals to the vinca alkaloid. Administration of [3H]VCR to wild-type and mdrla/b(-/-), mrpl(-/-) animals revealed relatively greater accumulation of radioactive VCR equivalents in weanlings over adults in several tissues, with weanling mdrla/b(-/-), mrpl(-/-) lung and heart exhibiting the greatest enhanced accumulation of 26- and 15-fold over adults, respectively. A similar cardiopulmonary differential accumulation of VCR was not observed in wild-type weanlings to adults. Semiquantitative RT-PCR expression analyses of ABC transporter genes in weanling and adult tissues of wild-type and combined mdrla/b(-/-), mrpl(-/-) mice did not reveal major age-related differences in these ABC transporters that would explain the relatively greater toxicity observed in weanling mice. However, the greater cardiopulmonary accumulation of VCR equivalents seen in the combined mdrla/b(-/-), mrpl(-/-) weanlings over that of adults underscores the potential for unique organ and age-related toxicities of this agent in the setting of transporter deficiency.

ATP-Binding Cassette Transporters↗

PubMed2004

Pathogenesis of enterotropic mouse hepatitis virus in immunocompetent and immunodeficient mice.

Mouse hepatitis virus (MHV) is one of the most prevalent viruses infecting laboratory mice. Most natural infections are caused by enterotropic strains. Experiments were done to compare the pathogenesis of enterotropic strain MHV-Y in immunocompetent BALB/c and C57BL/6 mice with that in B and T cell-deficient mice. In situ hybridization was used to identify sites of virus replication, and reverse transcriptase-polymerase chain reaction analysis was used to detect viral RNA in feces and blood. MHV-Y caused acute subclinical infections restricted to the gastrointestinal tract in BALB/c and C57BL/6 mice. Viral RNA was detected in small intestine and associated lymphoid tissues of immunocompetent mice for 1 week and in cecum and colon for 2 weeks. Infected B cell-deficient mice developed chronic subclinical infection also restricted to the gastrointestinal tract. Viral RNA was detected in the small intestine, cecum, colon, and feces for 7 to 8 weeks. In contrast, infected T cell-deficient mice developed multisystemic lethal infection. During the first week, viral RNA was restricted to the gastrointestinal tract. However, by 2 weeks, mice developed peritonitis, and viral RNA was detected in mesentery and visceral peritoneum. Three to four weeks after virus inoculation, T cell-deficient mice became moribund and viral RNA was detected in multiple organ systems. These results suggest that B cells promote clearance of MHV-Y from intestinal mucosa and that T cells are required to prevent dissemination of MHV-Y from the gastrointestinal tract and associated lymphoid tissues.

Animals↗

PubMed2003

Characterization of Mycobacterium montefiorense sp. nov., a novel pathogenic Mycobacterium from moray eels that is related to Mycobacterium triplex.

The characterization of a novel Mycobacterium sp. isolated from granulomatous skin lesions of moray eels is reported. Analysis of the hsp65 gene, small-subunit rRNA gene, rRNA spacer region, and phenotypic characteristics demonstrate that this organism is distinct from its closest genetic match, Mycobacterium triplex, and it has been named M. montefiorense sp. nov.

Animals↗

PubMed2003

Pathogenesis of mouse hepatitis virus infection in gamma interferon-deficient mice is modulated by co-infection with Helicobacter hepaticus.

Gamma interferon-deficient (IFN-gamma KO) mice developed a wasting syndrome and were found to be co-infected with Helicobacter sp., and a new isolate of mouse hepatitis virus (MHV) designated MHV-G. The disease was characterized by pleuritis, peritonitis, hepatitis, pneumonia, and meningitis. Initial experiments used a cecal homogenate inoculum from the clinical cases that contained H. hepaticus and MHV-G to reproduce the development of peritonitis and pleuritis in IFN-gamma KO mice. In contrast, immunocompetent mice given the same inoculum developed an acute, self-limiting infection and remained clinically normal. This result confirmed the importance of IFN-gamma in preventing chronic infection and limiting viral dissemination. To understand the role of both agents in the development of peritonitis and pleuritis, IFN-gamma KO mice were infected with either agent or were co-infected with H. hepaticus and MHV-G. Infection with MHV-G induced a multisystemic infection similar to that described in the original cases, with multifocal hepatic necrosis, acute necrotizing and inflammatory lesions of the gastrointestinal tract, and acute peritonitis and pleuritis with adhesions on the serosal surfaces of the viscera. However, mice given H. hepaticus alone had minimal pathologic changes even though the organism was consistently detected in the cecum or feces. Although co-infection with H. hepaticus and MHV-G induced lesions similar to those associated with MHV-G alone, the pathogenesis of the MHV infection was modified. Helicobacter hepaticus appeared to reduce the severity of MHV-induced lesions during the acute phase of infection, and exacerbated hepatitis and meningitis at the later time point. We conclude that infection of IFN-gamma KO mice with MHV-G results in multisystemic infection with peritonitis, pleuritis, and adhesions due to the aberrant immune response in these mice. In addition, co-infection of these mice with H. hepaticus results in alterations in the pathogenesis of MHV-G infection.

Animals↗

PubMed2002

Predicting early breastfeeding attrition.

The Breastfeeding Attrition Prediction Tool (BAPT) is based on the theory of planned behavior, which explains behavior as a function of attitudes, subjective norm, and perceived control. The BAPT subscales are positive and negative attitudes toward breastfeeding, family and professional expectations, and perceived ability to be successful. The purpose of this study was to test the reliability and validity of the BAPT among 269 women who planned to breastfeed for at least 8 weeks. Subjects completed the BAPT in the hospital and during a telephone interview at 8 weeks. Based on factor analysis, several items were deleted. Using discriminant function analysis, the modified BAPT was an effective predictor of 78% of women who stopped breastfeeding before 8 weeks and 68% of those who were still breastfeeding. There is potential for the modified BAPT to be an adjunct for the clinician in identifying women at risk for early cessation of breastfeeding.

Adolescent↗