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Biomedical subjects

Martin G Martin

Publications and source records attributed to Martin G Martin.

5 recordsLinked to original sources
PubMed2006

Polymeric immunoglobulin receptor in intestinal immune defense against the lumen-dwelling protozoan parasite Giardia.

The polymeric Ig receptor (pIgR) is conserved in mammals and has an avian homologue, suggesting evolutionarily important functions in vertebrates. It transports multimeric IgA and IgM across polarized epithelia and is highly expressed in the intestine, yet little direct evidence exists for its importance in defense against common enteric pathogens. In this study, we demonstrate that pIgR can play a critical role in intestinal defense against the lumen-dwelling protozoan parasite Giardia, a leading cause of diarrheal disease. The receptor was essential for the eradication of Giardia when high luminal IgA levels were required. Clearance of Giardia muris, in which IgA plays a dominant role, was severely compromised in pIgR-deficient mice despite significant fecal IgA output at 10% of normal levels. In contrast, eradication of the human strain Giardia lamblia GS/M, for which adaptive immunity is less IgA dependent in mice, was unaffected by pIgR deficiency, indicating that pIgR had no physiologic role when lower luminal IgA levels were sufficient for parasite elimination. Immune IgA was greatly increased in the serum of pIgR-deficient mice, conferred passive protection against Giardia, and recognized several conserved giardial Ags, including ornithine carbamoyltransferase, arginine deiminase, alpha-enolase, and alpha- and beta-giardins, that are also detected in human giardiasis. Corroborative observations were made in mice lacking the J chain, which is required for pIgR-dependent transepithelial IgA transport. These results, together with prior data on pIgR-mediated immune neutralization of luminal cholera toxin, suggest that pIgR is essential in intestinal defense against pathogenic microbes with high-level and persistent luminal presence.

Animals↗
PubMed2006

Acute liver failure in children: the first 348 patients in the pediatric acute liver failure study group.

OBJECTIVES: To determine short-term outcome for children with acute liver failure (ALF) as it relates to cause, clinical status, and patient demographics and to determine prognostic factors. STUDY DESIGN: A prospective, multicenter case study collecting demographic, clinical, laboratory, and short-term outcome data on children from birth to 18 years with ALF. Patients without encephalopathy were included if the prothrombin time and international normalized ratio remained > or = 20 seconds and/or >2, respectively, despite vitamin K. Primary outcome measures 3 weeks after study entry were death, death after transplantation, alive with native liver, and alive with transplanted organ. RESULTS: The cause of ALF in 348 children included acute acetaminophen toxicity (14%), metabolic disease (10%), autoimmune liver disease (6%), non-acetaminophen drug-related hepatotoxicity (5%), infections (6%), other diagnosed conditions (10%); 49% were indeterminate. Outcome varied between patient sub-groups; 20% with non-acetaminophen ALF died or underwent liver transplantation and never had clinical encephalopathy. CONCLUSIONS: Causes of ALF in children differ from in adults. Clinical encephalopathy may not be present in children. The high percentage of indeterminate cases provides an opportunity for investigation.

Adolescent↗
PubMed2003

Varicella in pediatric liver transplant patients: a retrospective analysis of treatment and outcome.

BACKGROUND: Varicella is a common childhood disease that can cause morbidity and mortality among immunosuppressed patients. There have been few previous studies monitoring the course of pediatric liver transplant patients with acute varicella. The aim of this study was to evaluate the treatment, outcomes, and complications of pediatric liver transplant patients admitted with acute varicella infection. METHODS: A retrospective chart review was carried out based on discharge diagnoses of orthotopic liver transplant and varicella among pediatric patients (age range, birth-18 years) admitted to the UCLA Medical Center between 1985 and 2001. RESULTS: Five hundred fifty-six pediatric patients received liver transplantations between 1985 and 2001. Twenty-two of these patients were admitted to the UCLA Medical Center with varicella (11 females, 11 males). No patients were treated on an outpatient basis. Mean age of the patients was 6 years (range, 1-16 years). None of these patients received the varicella vaccine before hospitalization. On admission, 5 of 22 patients (23%) had received varicella zoster immunoglobulin within 96 hours of exposure. The mean length of hospitalization was 6 days (range, 2-11 days). All immunosuppression dosages were reduced during the admissions. None of the patients had been treated with high-dose corticosteroids for acute rejection before the onset of the varicella infection. Patients were treated until defervescence with intravenous acyclovir and until their varicella lesions crusted. Patients were discharged with oral acyclovir to complete a 10-day course (including the intravenous treatment). No patients had complications from the varicella infection. A complication of an elevated serum creatinine for one patient was noted with the intravenous acyclovir treatment. This patient had associated headache and nausea that resolved when the creatinine level returned to normal. CONCLUSIONS: There were no complications or dissemination of varicella infection among our pediatric liver transplant patients. Further prospective randomized trials are required to evaluate the management of pediatric liver transplant patients infected with varicella.

Acyclovir↗
PubMed2002

Molecular basis for glucose-galactose malabsorption.

Glucose-galactose malabsorption (GGM) is an autosomal recessive disease that presents in newborn infants as a life-threatening diarrhea. The diarrhea ceases within 1 h of removing oral intake of lactose, glucose, and galactose, but promptly returns with the introduction of one or more of the offending sugars into the diet. Our goal is to determine whether or not mutations in the sodium-glucose cotransporter gene (SGLT1) are responsible for GGM. We first isolated the human cDNA (hSGLT1), mapped the gene, and identified its chromosomal location (22q13.1). Our approach was then to screen GGM patients for mutations in hSGLT1 and then determine if these caused defects in sugar transport using the Xenopus laevis oocyte expression system. In 46 patients we have identified the mutations responsible for GGM. These included missense, nonsense, frame shift, splice site, and promoter mutations. In 30 patients, the same mutations were on both alleles, and the remaining 16 had different mutations on each allele (compound heterozygotes). Several mutations (e.g., C355S) were found in unrelated patients. The nonsense, frame shift, and splice site mutations all produce nonfunctional truncated proteins. In 22 out of the 23 missense mutations tested in the oocyte expression system, the proteins were translated and were stable in the cell, but did not reach the plasma membrane. In four of these mutants, an alanine residue was replaced by a valine, and in two, the trafficking defect was rescued by changing the valine to cysteine. One mutant protein (Q457R) did reach the plasma membrane, but it was unable to transport the sugar across the cell membrane. We conclude that mutations in the SGLT1 gene are the cause of glucose-galactose malabsorption, and sugar transport is impaired mainly because the mutant proteins are either truncated or are not targeted properly to the cell membrane.

Carbohydrate Metabolism, Inborn Errors↗