Biomedical subjects
Paul Martin
Publications and source records attributed to Paul Martin.
Methylenetetrahydrofolate reductase and thymidylate synthase genotypes and risk of acute graft-versus-host disease following hematopoietic cell transplantation for chronic myelogenous leukemia.
Methylenetetrahydrofolate reductase (MTHFR) and thymidylate synthase (TS) play key roles in intracellular folate metabolism. Polymorphisms in these enzymes have been shown to modify toxicity of methotrexate (MTX) after hematopoietic cell transplantation. In this study, we evaluated the risk of acute graft-versus-host disease (GVHD) associated with genetic variation in recipient and donor MTHFR and TS genotypes to assess whether genotype alters the efficacy of MTX in acute GVHD prophylaxis. Data on the transplantation course were abstracted from medical records for 304 adults who received allogeneic hematopoietic cell transplants. MTHFR (C677T and A1298C) and TS (enhancer-region 28-base pair repeat, TSER, and 1494del6) genotypes were determined using polymerase chain reaction/restriction fragment length polymorphism and TaqMan assays. Multivariable logistic regression was used to assess the associations between genotypes and risk of acute GVHD. Compared with recipients with the wild-type MTHFR 677CC genotype, those with the variant 677T allele showed a decreased risk of detectable acute GVHD (677CT: odds ratio, 0.8; 95% confidence interval, 0.4-1.6; 677TT: odds ratio, 0.4; 95% confidence interval, 0.2-0.8; P for trend = .01). The variant MTHFR 1298C allele in recipients was associated with an increased risk of acute GVHD compared with the wild-type MTHFR 1298AA genotype (1298AC: odds ratio, 2.0; 95% confidence interval, 1.1-3.9; 1298CC: odds ratio, 3.6; 95% confidence interval, 1.0-12.7; P for trend < .01). No association with risk of acute GVHD was observed for donor MTHFR genotypes or for recipient or donor TS genotypes, with the exception of an increase in acute GVHD among recipients whose donors had the TSER 3R/2R genotype (odds ratio, 3.0; 95% confidence interval, 1.3-7.2). These findings indicate that host, but not donor, MTHFR genotypes modify the risk of acute GVHD in recipients receiving MTX, in a manner consistent with our previously reported associations between MTHFR genotypes and MTX toxicity. A direct trade-off between drug toxicity and drug efficacy may play a role. Alternatively, the systemic folate environment, regulated by host tissues, might influence donor T-cell growth and activity.
Provider-patient in-office discussions of response to hepatitis C antiviral therapy and impact on patient comprehension.
BACKGROUND & AIMS: Providers need to communicate projected response rates effectively to enable patients with hepatitis C virus to make informed decisions about therapy. This study used interactional sociolinguistics (1) to evaluate how gastroenterologists and allied health professionals communicate information regarding response rates to antiviral therapy, (2) to determine how these discussions relate to where the patient is in the continuum of evaluation and treatment, (3) to assess whether patients were aligned with providers in their perceptions of response rates after office visits, and (4) to identify factors that improve provider-patient alignment. METHODS: Gastroenterologists, allied health professionals, and patients with hepatitis C virus were videotaped and audiotaped during regularly scheduled visits. Postvisit interviews were conducted separately with patients and providers. Visits and postvisits were transcribed and analyzed using validated sociolinguistic techniques. RESULTS: The phase of hepatitis C virus treatment shaped the benchmarks of response talk, although across the treatment continuum providers overwhelmingly made strategic use of positive statistics, providing motivation. In postvisit interviews, 55% of providers and patients were aligned on response rates. Patients with a favorable outcome and patients who asked response-related questions in the visit were more likely to be aligned with providers. Areas identified for improvement included the tendency to discuss response rates before an individualized assessment could be made, balancing motivation and accuracy, and assessing the patient's perspective before delivering any bad news, if necessary. CONCLUSIONS: Sociolinguistic analysis provides a powerful tool to evaluate provider-patient interactions and to identify ways to improve in-office communication regarding antiviral therapy.
A new single-dose hepatitis B vaccine versus a conventional vaccine in patients with end-stage renal disease.
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Entecavir for treatment of lamivudine-refractory, HBeAg-positive chronic hepatitis B.
BACKGROUND & AIMS: Lamivudine treatment is associated with frequent development of resistant hepatitis B virus (HBV) and loss of treatment benefit. In preclinical and phase II studies, entecavir demonstrated potent antiviral activity against lamivudine-resistant HBV. METHODS: In this phase III, double-blind trial, hepatitis B e antigen-positive patients who were refractory to lamivudine therapy (persistent viremia or documented YMDD mutations while receiving lamivudine) were randomized to switch to entecavir 1 mg daily (n = 141) or continue lamivudine 100 mg daily (n = 145) for a minimum of 52 weeks. Two coprimary end points were assessed at 48 weeks: histologic improvement and a composite end point (HBV branched DNA <0.7 MEq/mL and alanine aminotransferase [ALT] <1.25 times the upper limit of normal). RESULTS: Histologic improvement occurred in 55% (68/124) of entecavir-treated vs 28% (32/116) of lamivudine-treated patients (P < .0001). More patients on entecavir than lamivudine achieved the composite end point: 55% (77/141) vs 4% (6/145), respectively (P < .0001). Mean change from baseline in HBV DNA was -5.11 log(10) copies/mL for entecavir-treated patients and -0.48 log(10) copies/mL for lamivudine-treated patients (P < .0001). Virologic rebound because of entecavir resistance substitutions occurred in 2 of 141 of entecavir-treated patients, and genotypic evidence of resistance was detected in 10 patients. The safety profile of entecavir was comparable to lamivudine with fewer ALT flares on treatment. CONCLUSIONS: In patients with lamivudine-refractory chronic hepatitis B, switching to entecavir provides superior histologic improvement, viral load reduction, and ALT normalization compared with continuing lamivudine, with a comparable adverse event profile.
Pulsed-field gel electrophoresis of Listeria monocytogenes strains: the PulseNet Europe Feasibility Study.
A feasibility study on standardized subtyping of Listeria monocytogenes by pulsed-field gel electrophoresis (PFGE) was performed in 2003 in Europe. The aim of the project was to identify veterinary, food, and public health reference laboratories that were willing to participate in the molecular surveillance of Listeria infections in Europe, as is done with PulseNet USA, and to test if the participants could generate results that were comparable with each other. A panel of strains and the methodology were sent to European laboratories, and images of PFGE gels were transferred electronically, then analyzed visually and with image analysis software. Only nine out of 43 gels were not fully satisfactory at the visual evaluation step stage. Computerized analysis showed that only three out of 33 gels gave dendrograms totally different from the reference dendrograms. Thus, the objectives of the study were met: most human and food European laboratories concerned with typing L. monocytogenes participated, images were transmitted electronically, and the overall quality of the gels was good.
Living donor liver transplantation: histological abnormalities found on liver biopsies of apparently healthy potential donors.
OBJECTIVE: With the continued shortage of deceased donor grafts, living donor liver transplantation has become an option for adult liver transplant candidates. In the non-transplant setting, liver biopsy is typically carried out to evaluate clinical or biochemical hepatic dysfunction. In living donor liver transplantation, assessment of histological abnormalities that are undetectable by serological, biochemical and radiological methods might play an important role in donor and recipient outcome. METHODS: Seventy consecutive liver biopsies carried out as part of our evaluation of potential donor candidates for adult-to-adult or adult-to-child living donor liver transplants were analyzed. RESULTS: Of the 70 potential donor candidates who underwent liver biopsy for evaluation for living donor liver transplantation, 67% had an unexpected abnormality, of which steatosis was the most common abnormality (38.5%). A variety of other histopathological abnormalities were found including granulomas of unknown etiology (7%), chronic hepatitis (6%) and a microabscess. None of the histological abnormalities had been suspected despite extensive clinical, serological or radiological investigation. CONCLUSIONS: Among the 70 potential donor candidates for living donor liver transplantation, 34% had unremarkable liver biopsies. The most common abnormality was steatosis (38.5%). These findings suggest that all potential candidates for living donor liver transplants should undergo screening liver biopsies. The precise significance of these changes remains to be determined, including which of these changes are contraindications to liver transplantation. These findings may also have implications in the non-transplant setting as changes ascribed to specific etiologies for liver disease might include changes occurring in apparently healthy individuals.
Treatment alternatives for hepatitis B cirrhosis: a cost-effectiveness analysis.
BACKGROUND: Hepatitis B virus (HBV) patients with cirrhosis are at risk for developing costly, morbid, or mortal events, and therefore need highly effective therapies. Lamivudine is effective but is limited by viral resistance. In contrast, adefovir and entecavir have lower viral resistance, but are more expensive. The most cost-effective approach is uncertain. METHODS: We evaluated the cost-effectiveness of six strategies in HBV cirrhosis: (1) No HBV treatment ("do nothing"), (2) lamivudine monotherapy, (3) adefovir monotherapy, (4) lamivudine with crossover to adefovir on resistance ("adefovir salvage"), (5) entecavir monotherapy, or (6) lamivudine with crossover to entecavir on resistance ("entecavir salvage"). The primary outcome was the incremental cost per quality-adjusted life-year (QALY) gained. RESULTS: The "do nothing" strategy was least effective yet least expensive. Compared with "do nothing," using adefovir cost an incremental US dollars 19,731. Entecavir was more effective yet more expensive than adefovir, and cost an incremental US dollars 25,626 per QALY gained versus adefovir. Selecting between entecavir versus adefovir was highly dependent on the third-party payer's "willingess-to-pay" (e.g., 45% and 60% of patients fall within budget if willing-to-pay US dollars 10K and US dollars 50K per QALY gained for entecavir, respectively). Both lamivudine monotherapy and the "salvage" strategies were not cost-effective. However, between the two salvage strategies, "adefovir salvage" was more effective and less expensive than "entecavir salvage." CONCLUSION: Both entecavir and adefovir are cost-effective in patients with HBV cirrhosis. Choosing between adefovir and entecavir is highly dependent on available budgets. In patients with HBV cirrhosis with previous lamivudine resistance, "adefovir salvage" appears more effective and less expensive than "entecavir salvage."
Genotypes of Listeria monocytogenes strains isolated from 2000 to 2002 in Poland.
Pulsed field gel electrophoresis (PFGE), multiplex PCR and multilocus sequence typing (MLST) methods were used for genotyping study of seventy-three L. monocytogenes isolates collected in Poland between 2000 and 2002 from human, food, environment and a diseased goat. The multiplex PCR, which is an alternative method to classical serotyping, divided the isolates into four PCR groups, IIa (42.5%), IIb (27.4%), IIc (4.1%) and IVb (26%). The isolates displayed 33 distinct PFGE profiles. Twenty eight strains were further characterised by MLST based on sequence analyses of seven housekeeping genes. The combined sequence analyses revealed a total of 10 different allelic profiles from which 3 were not described earlier. It is intended that results obtained in this study will be the first data of a national database of L. monocytogenes genotypes in Poland.
Review of nursing in the community in Scotland.
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Comparative characterization of Listeria monocytogenes isolated from Portuguese farmhouse ewe's cheese and from humans.
In order to investigate the possible relationships between Listeria monocytogenes strains isolated from farmhouse ewe's cheese and clinical strains collected, in partially overlapping dates, from the same geographical area in Portugal, a total of 109 isolates from seven ewe's cheese manufactures (n=94) and from humans (n=15) were characterized by serotyping, RAPD, PFGE and allelic analysis of the virulent actA gene. Serotyping indicated the presence of four different serovars: 1/2a, 1/2b, 1/2c and 4b. The 15 clinical isolates were either serovar 4b (86.7%) or serovar 1/2b (13.3%). Among the 94 isolates from cheese and related environments the serovars prevalence was 1/2a (1.1%), 1/2b (17.0%), 1/2c (12.8%) and, unexpectedly, 4b (69.1%). Based on results obtained with PFGE typing of the strains, 25 genotypes were identified, 10 from farmhouses and 15 from human cases. Isolates from serovars 1/2a and 1/2c were assigned to single genotypes, respectively. Within serovars 1/2b and 4b three and 20 genotypes were established, respectively. RAPD typing of the isolates rendered 18 types indicating the lack of accuracy of the primers used in strain differentiation within serovar 4b. The actA gene typing of the strains showed a prevalence of actA gene type I (90.4%) compared with the rest of the strains that were all actA gene type II (9.6%). In spite of the fact that all the farmhouses were completely independent, the distribution of L. monocytogenes genotypes, intra and inter cheese manufactures, was relatively homogeneous, suggesting the existence of resident strains. In contrast, among human isolates there was a great genetic diversity. There was no common genotype between L. monocytogenes implicated in the cases of listeriosis and these cheese-related isolates, suggesting the absence of a causal relationship.
Inflammatory cells during wound repair: the good, the bad and the ugly.
Damage to any tissue triggers a cascade of events that leads to rapid repair of the wound - if the tissue is skin, then repair involves re-epithelialization, formation of granulation tissue and contraction of underlying wound connective tissues. This concerted effort by the wounded cell layers is accompanied by, and might also be partially regulated by, a robust inflammatory response, in which first neutrophils and then macrophages and mast cells emigrate from nearby tissues and from the circulation. Clearly, this inflammatory response is crucial for fighting infection and must have been selected for during the course of evolution so that tissue damage did not inevitably lead to death through septicemia. But, aside from this role, exactly what are the functions of the various leukocyte lineages that are recruited with overlapping time courses to the wound site, and might they do more harm than good? Recent knockout and knockdown studies suggest that depletion of one or more of the inflammatory cell lineages can even enhance healing, and we discuss new views on how regulation of the migration of inflammatory cells to sites of tissue damage might guide therapeutic strategies for modulating the inflammatory response.
Biodiversity: disease threat to European fish.
The deliberate introduction of new species can have unexpected negative consequences and we show here how a recently introduced fish, the invasive Asian cyprinid Pseudorasbora parva, is causing increased mortality and totally inhibiting spawning in an already endangered native fish, the European cyprinid Leucaspius delineatus. This threat is caused by an infectious pathogen, a rosette-like intracellular eukaryotic parasite that is a deadly, non-specific agent. It is probably carried by healthy Asian fish, and could decrease fish biodiversity in Europe, as well as having implications for commercial aquaculture.
Cell biology: master regulators of sealing and healing.
The protective layer of the epidermis in Drosophila (cuticle) and mice (stratum corneum) are structurally unrelated. Yet new evidence suggests a conserved transcription factor, Grainyhead, controls both their development and the means by which both structures repair themselves.
The small GTPase Rac plays multiple roles in epithelial sheet fusion--dynamic studies of Drosophila dorsal closure.
The coordinated migration and fusion of epithelial sheets is a crucial morphogenetic tool used on numerous occasions during the normal development of an embryo and re-activated as part of the wound healing response. Drosophila dorsal closure, whereby a hole in the embryonic epithelium is zipped closed late in embryogenesis, serves as an excellent, genetically tractable model for epithelial migration. Using live confocal imaging, we have dissected multiple roles for the small GTPase Rac in this process. We show that constitutive activation of Rac1 leads to excessive assembly of lamellipodia and precocious halting of epithelial sweeping, possibly through premature activation of contact-inhibition machinery. Conversely, blocking Rac activity, either by loss-of-function mutations or expression of dominant negative Rac1, disables the assembly of both actin cable and protrusions by epithelial cells. Movies of mutant embryos show that continued contraction of the amnioserosa is sufficient to draw the epithelial edges towards one another, allowing the zipper machinery to bypass non-functioning regions of leading edge. In addition to illustrating the key role of Rac in organization of leading edge actin, loss-of-function mutants also provide substantive proof that Rac acts upstream in the Jun N-terminal kinase (JNK) cascade to direct epithelial cell shape changes during dorsal closure.
Enhanced expression of the mannose receptor by endothelial cells of the liver and spleen microvascular beds in the macrophage-deficient PU.1 null mouse.
Mice null for the haematopoietic lineage-specific transcription factor PU.1 lack mature Mphi and are compromised in their ability to clear cellular debris from the blood circulation. We investigated the possibility that non-professional phagocytes may partially compensate for the lack of Mphi in clearance functions. In the absence of Kupffer cells (resident liver Mphi) in the PU.1 null mice, electron microscopy revealed ingested debris in sinusoidal endothelial cells and hepatocytes although debris was also seen free in blood vessels. To investigate whether an increased clearance function of non-professional phagocytes might be linked to expression of Mphi-associated phagocytic and pinocytic receptors by other cells in PU.1 null mouse, we examined expression of several candidate proteins by immunocytochemistry and Western blotting. We found mannose receptor (MR) comparably expressed in PU.1 null and PU.1+ mice liver and spleen whereas class A scavenger receptor was substantially reduced and complement receptor 3 was absent in PU.1 null animals. By morphometric analysis, liver and spleen sinusoidal endothelial cells were seen to express significantly more MR in the PU.1 null mouse. This study provides the first evidence of apparently compensatory alterations in the microvasculature of the Mphi-deficient PU.1 null mouse.
Treatment alternatives for chronic hepatitis B virus infection: a cost-effectiveness analysis.
BACKGROUND: Treatment options for chronic hepatitis B virus (HBV) infection have disparate risks and benefits. Interferon has clinically significant side effects, and lamivudine is associated with viral resistance. In contrast, adefovir is safe and has lower viral resistance but is more expensive. The most cost-effective approach is uncertain. OBJECTIVE: To determine whether and under what circumstances the improved efficacy of adefovir offsets its increased cost compared with lamivudine or interferon. DESIGN: Cost-utility analysis stratified by hepatitis B e antigen (HBeAg) status. DATA SOURCES: Systematic review of MEDLINE from 1970 to 2005. TARGET POPULATION: Patients with chronic HBV infection, elevated aminotransferase levels, and no cirrhosis. TIME HORIZON: Lifetime. PERSPECTIVE: Third-party payer. INTERVENTIONS: 1) No HBV treatment ("do nothing" strategy), 2) interferon monotherapy, 3) lamivudine monotherapy, 4) adefovir monotherapy, or 5) lamivudine with crossover to adefovir upon resistance ("adefovir salvage" strategy). OUTCOME MEASURE: Incremental cost per quality-adjusted life-year (QALY) gained. RESULTS OF BASE-CASE ANALYSIS: The "do nothing" strategy was least effective yet least expensive. Compared with the "do nothing" strategy, using interferon cost an incremental 6337 dollars to gain 1 additional QALY. Compared with interferon, the adefovir salvage strategy cost an incremental 8446 dollars per QALY gained. Both the lamivudine and adefovir monotherapy strategies were more expensive yet less effective than the alternative strategies and were therefore dominated. RESULTS OF SENSITIVITY ANALYSIS: In sensitivity analysis, interferon was most cost-effective in health care systems with tight budgetary constraints and a high prevalence of HBeAg-negative patients. LIMITATIONS: These results apply only to patients with chronic HBV infection, elevated aminotransferase levels, and no clinical or histologic evidence of cirrhosis. They do not apply to alternative populations. CONCLUSIONS: Neither lamivudine nor adefovir monotherapy is cost-effective in chronic HBV infection. However, a hybrid salvage strategy reserving adefovir only for lamivudine-associated viral resistance may be highly cost-effective across most health care settings. Interferon therapy may still be preferred in health care systems with limited resources, especially in those serving populations with a high prevalence of HBeAg-negative HBV.
Live imaging of wound inflammation in Drosophila embryos reveals key roles for small GTPases during in vivo cell migration.
Aa robust inflammatory response to tissue damage and infection is conserved across almost all animal phyla. Neutrophils and macrophages, or their equivalents, are drawn to the wound site where they engulf cell and matrix debris and release signals that direct components of the repair process. This orchestrated cell migration is clinically important, and yet, to date, leukocyte chemotaxis has largely been studied in vitro. Here, we describe a genetically tractable in vivo wound model of inflammation in the Drosophila melanogaster embryo that is amenable to cinemicroscopy. For the first time, we are able to examine the roles of Rho-family small GTPases during inflammation in vivo and show that Rac-mediated lamellae are essential for hemocyte motility and Rho signaling is necessary for cells to retract from sites of matrix- and cell-cell contacts. Cdc42 is necessary for maintaining cellular polarity and yet, despite in vitro evidence, is dispensable for sensing and crawling toward wound cues.