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Biomedical subjects

Paul Martin

Publications and source records attributed to Paul Martin.

At least 19 recordsLinked to original sources
PubMed2003

Wound healing in the PU.1 null mouse--tissue repair is not dependent on inflammatory cells.

Damage to neonatal and adult tissues always incites an influx of inflammatory neutrophils and macrophages. Besides clearing the wound of invading microbes, these cells are believed to be crucial coordinators of the repair process, acting both as professional phagocytes to clear wound debris and as a major source of wound growth factor signals. Here we report wound healing studies in the PU.1 null mouse, which is genetically incapable of raising the standard inflammatory response because it lacks macrophages and functioning neutrophils. Contrary to dogma, we show that these "macrophageless" mice are able to repair skin wounds with similar time course to wild-type siblings, and that repair appears scar-free as in the embryo, which also heals wounds without raising an inflammatory response. The growth factor and cytokine profile at the wound site is changed, cell death is reduced, and dying cells are instead engulfed by stand-in phagocytic fibroblasts. We also show that hyperinnervation of the wound site, previously believed to be a consequence of inflammation, is present in the PU.1 null wound, too.

Animals↗
PubMed2003

Nuclear gene sequences from a late pleistocene sloth coprolite.

The determination of nuclear DNA sequences from ancient remains would open many novel opportunities such as the resolution of phylogenies, the sexing of hominid and animal remains, and the characterization of genes involved in phenotypic traits. However, to date, single-copy nuclear DNA sequences from fossils have been determined only from bones and teeth of woolly mammoths preserved in the permafrost. Since the best preserved ancient nucleic acids tend to stem from cold environments, this has led to the assumption that nuclear DNA would be retrievable only from frozen remains. We have previously shown that Pleistocene coprolites stemming from the extinct Shasta sloth (Nothrotheriops shastensis, Megatheriidae) contain mitochondrial (mt) DNA from the animal that produced them as well as chloroplast (cp) DNA from the ingested plants. Recent attempts to resolve the phylogeny of two families of extinct sloths by using strictly mitochondrial DNA has been inconclusive. We have prepared DNA extracts from a ground sloth coprolite from Gypsum Cave, Nevada, and quantitated the number of mtDNA copies for three different fragment lengths by using real-time PCR. We amplified one multicopy and three single-copy nuclear gene fragments and used the concatenated sequence to resolve the phylogeny. These results show that ancient single-copy nuclear DNA can be recovered from warm, arid climates. Thus, nuclear DNA preservation is not restricted to cold climates.

Animals↗
PubMed2003

HLA-matched related hematopoietic cell transplantation for chronic-phase CML using a targeted busulfan and cyclophosphamide preparative regimen.

Allogeneic blood or marrow transplantation (BMT) is a curative therapy for chronic myeloid leukemia (CML). We have previously reported that the pharmacologic targeting of busulfan combined with cyclophosphamide (TBU/CY) can minimize regimen-related toxicity while preserving antileukemic effects. We report here on 131 consecutive chronic-phase CML patients treated with allogeneic related BMT using a TBU/CY preparative regimen, where the busulfan dose was targeted to achieve a steady-state plasma concentration of at least 900 ng/mL. The median age of the patients was 43 years (range, 14-66 years). Estimates of the probabilities of nonrelapse mortality, relapse, survival, and disease-free survival 3 years after transplantation were 14%, 8%, 86%, and 78%, respectively. Age had no statistically significant effect on survival. Although approximately 60% of the patients developed clinically extensive chronic graft-versus-host disease, the median Karnofsky score at last contact date among survivors was 95%. Of surviving patients, 11% were molecularly positive for the bcr-abl mRNA at last contact, with a median level of bcr-abl transcripts of 4.6 copies/microg RNA. These data suggest that TBU/CY is a very effective preparative regimen for CML in chronic phase, associated with an expected survival at 3 years of approximately 85%, with most patients being in molecular remission.

Adolescent↗
PubMed2003

Role for keratins 6 and 17 during wound closure in embryonic mouse skin.

Injury to adult skin triggers a response designed to restore its vital barrier function. A conserved aspect of this response is a rapid switch in gene expression whereby the type II keratin 6 (K6) and type I keratins 16 and 17 (K16, K17) are induced in epithelial cells at the wound edge. This induction occurs at the expense of the keratins normally expressed during terminal differentiation and correlates with the activation of epithelial cells at the wound edge, ahead of their migration into the wound site. Here, we show that the capacity to enact this switch is already acquired in E11.5 stage mouse embryos. Such early timing is well ahead of the onset of differentiation-specific gene expression (approximately E13.5) and the acquisition of barrier formation by developing epidermis (approximately E16.5). Induction of K6, K16, and K17 correlates with changes in the morphology of epithelial cells at the wound edge. The closure of embryonic wounds is significantly delayed in K17 null embryos, but not embryos null for K6. These observations significantly extend the correlation between K6, K16, and K17 expression and epithelial wound closure, and provide direct evidence that expression of these keratins, K17 in particular, is important for the timeliness of this process.

Animals↗
PubMed2003

6-thioguanine can cause serious liver injury in inflammatory bowel disease patients.

BACKGROUND & AIMS: Thioguanine (6-TG) has been studied as an alternative thiopurine in inflammatory bowel disease (IBD). Short-term safety and efficacy data were favorable. Experience with 6-TG in patients with acute lymphoblastic leukemia raised long-term safety concerns when implicated in nodular regenerative hyperplasia (NRH) of the liver and portal hypertension. The aim of this study was to describe the association between 6-TG and NRH in IBD. METHODS: Liver chemistries and complete blood counts were monitored, and patients were encouraged to undergo liver biopsy. Clinical data were collected by chart review, and associations were tested by univariate and multivariable analyses. Patients were classified based on the presence (group 1) or absence (group 2) of laboratory abnormalities. RESULTS: Laboratory abnormalities occurred in 29 of 111 patients (26%). Elevations of liver enzymes and a decrease in platelet counts (<200,000) were most commonly observed. Male gender (odds ratio, 2.9; 95% CI, 1.1-7.3; P < 0.03) and preferential 6-methylmercaptopurine production on 6-mercaptopurine/azathioprine (odds ratio, 3.0; 95% CI, 1.2-7.4; P < 0.04) were independently associated with laboratory abnormalities. No association was seen with duration of 6-TG treatment, cumulative dose, or 6-TG nucleotide levels. The median increase in alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase levels was 39, 30, and 75 U/L, respectively, in group 1, and the median decrease in platelet count was 115,000 in group 1 versus 7000 in group 2 (P < 0.001). NRH occurred in 76% of patients undergoing biopsy in group 1 and 33% in group 2. CONCLUSIONS: NRH is a common finding in 6-TG-treated patients with IBD. The progression or reversibility of NRH remains unknown. Our findings suggest that 6-TG should not be considered as therapy for patients with IBD.

Adolescent↗
PubMed2003

c-Jun regulates eyelid closure and skin tumor development through EGFR signaling.

To investigate the function of c-Jun during skin development and skin tumor formation, we conditionally inactivated c-jun in the epidermis. Mice lacking c-jun in keratinocytes (c-jun(Deltaep)) develop normal skin but express reduced levels of EGFR in the eyelids, leading to open eyes at birth, as observed in EGFR null mice. Primary keratinocytes from c-jun(Deltaep) mice proliferate poorly, show increased differentiation, and form prominent cortical actin bundles, most likely because of decreased expression of EGFR and its ligand HB-EGF. In the absence of c-Jun, tumor-prone K5-SOS-F transgenic mice develop smaller papillomas, with reduced expression of EGFR in basal keratinocytes. Thus, using three experimental systems, we show that EGFR and HB-EGF are regulated by c-Jun, which controls eyelid development, keratinocyte proliferation, and skin tumor formation.

Animals↗
PubMed2003

Conversion from intravenous to intramuscular hepatitis B immune globulin in combination with lamivudine is safe and cost-effective in patients receiving long-term prophylaxis to prevent hepatitis B recurrence after liver transplantation.

Recurrent hepatitis B infection after liver transplantation was previously frequent and associated with significant allograft failure and mortality. Recurrence rates of hepatitis B were improved with the use of passive immunoprophylaxis with hepatitis B immune globulin, and later, lamivudine monotherapy. Combination prophylaxis with intravenous hepatitis B immune globulin and lamivudine substantially decreased rates of hepatitis B recurrence, but intravenous administration of hepatitis B immune globulin was expensive and associated with significant adverse effects. In the current study, 59 patients receiving primary liver transplantation for chronic hepatitis B infection were prospectively followed up after converting from intravenous to intramuscular hepatitis B immune globulin in combination with lamivudine. All patients tolerated intramuscular hepatitis B immune globulin well. At a median follow-up of 511 days after conversion to intramuscular hepatitis B immune globulin, 58 of 59 patients (98.3%) were hepatitis B surface antigen-negative. Twenty-one patients (35.6%) required a median of one supplemental intravenous hepatitis B immune globulin infusion to maintain therapeutic antibody levels. Economic analysis showed an average cost-effectiveness ratio for combination intramuscular hepatitis B immune globulin plus lamivudine of $52,600 per recurrence prevented, which was far below the cost of lamivudine monotherapy and of intravenous hepatitis B immune globulin alone or in combination with lamivudine. These results suggest that intramuscular administration of hepatitis B immune globulin in combination with lamivudine offers a safe, effective, and cost-effective approach to preventing hepatitis B recurrence after orthotopic liver transplantation.

Adult↗
PubMed2002

Invasive aspergillosis in allogeneic stem cell transplant recipients: changes in epidemiology and risk factors.

The incidence of postengraftment invasive aspergillosis (IA) in hematopoietic stem cell transplant (HSCT) recipients increased during the 1990s. We determined risks for IA and outcomes among 1682 patients who received HSCTs between January 1993 and December 1998. Risk factors included host variables (age, underlying disease), transplant variables (stem cell source), and late complications (acute and chronic graft-versus-host disease [GVHD], receipt of corticosteroids, secondary neutropenia, cytomegalovirus [CMV] disease, and respiratory virus infection). We identified risk factors associated with IA early after transplantation ( 6 months after transplantation) was associated with chronic GVHD and CMV disease. These results emphasize the postengraftment timing of IA; risk factor analyses verify previously recognized risk factors (GVHD, receipt of corticosteroids, and neutropenia) and uncover the roles of lymphopenia and viral infections in increasing the incidence of postengraftment IA in the 1990s.

Adolescent↗
PubMed2002

Dynamic analysis of actin cable function during Drosophila dorsal closure.

Throughout development, a series of epithelial movements and fusions occur that collectively shape the embryo. They are dependent on coordinated reorganizations and contractions of the actin cytoskeleton within defined populations of epithelial cells. One paradigm morphogenetic movement, dorsal closure in the Drosophila embryo, involves closure of a dorsal epithelial hole by sweeping of epithelium from the two sides of the embryo over the exposed extraembryonic amnioserosa to form a seam where the two epithelial edges fuse together. The front row cells exhibit a thick actin cable at their leading edge. Here, we test the function of this cable by live analysis of GFP-actin-expressing embryos in which the cable is disrupted by modulating Rho1 signaling or by loss of non-muscle myosin (Zipper) function. We show that the cable serves a dual role during dorsal closure. It is contractile and thus can operate as a "purse string," but it also restricts forward movement of the leading edge and excess activity of filopodia/lamellipodia. Stripes of epithelium in which cable assembly is disrupted gain a migrational advantage over their wild-type neighbors, suggesting that the cable acts to restrain front row cells, thus maintaining a taut, free edge for efficient zippering together of the epithelial sheets.

Actins↗
PubMed2002

A humanized non-FcR-binding anti-CD3 antibody, visilizumab, for treatment of steroid-refractory acute graft-versus-host disease.

Visilizumab is a humanized anti-CD3 monoclonal antibody characterized by a mutated IgG2 isotype, lack of binding to Fcgamma-receptors, and ability to induce apoptosis selectively in activated T cells. To test pharmacokinetics, safety, and immunosuppressive activity of visilizumab, 17 patients with glucocorticoid-refractory acute graft-versus-host disease (GVHD) were enrolled in a phase 1 study. Six patients were given 7 doses of visilizumab (0.25 or 1.0 mg/m(2)) on days 1, 3, 5, 7, 9, 11, and 13. Because multiple doses of 1 mg/m(2) caused delayed visilizumab accumulation and prolonged lymphopenia, the next 11 patients received a single dose of 3.0 mg/m(2) on day 1. GVHD improved in all patients; 15 were evaluable through day 42. Multiple dosing resulted in 1 of 6 complete responses (CRs) and 5 partial responses (PRs), but all 6 patients died at a median of 87 days after starting visilizumab therapy. Single dosing resulted in 6 of 9 CRs, 3 PRs, and 7 of 11 patients surviving after 260 to 490 days (median, 359 days; P =.03). There were no allergic reactions and 3 grade 1 acute infusional toxicities. Plasma Epstein-Barr virus (EBV) DNA titers more than 1000 copies/mL and posttransplant lymphoproliferative disease (PTLD) developed in 2 of the first 7 patients. Based on rising EBV DNA titers, 5 of the next 10 patients were given the B cell-specific monoclonal antibody, rituximab. EBV DNA became undetectable and no overt PTLD developed. Visilizumab is well tolerated and has activity in advanced GVHD. A phase 2 study incorporating preemptive therapy for PTLD is warranted to determine the efficacy of visilizumab in GVHD.

Acute Disease↗
PubMed2002

Factors associated with outcome after unrelated marrow transplantation for treatment of acute lymphoblastic leukemia in children.

Acute lymphoblastic leukemia (ALL) is the most common indication for transplantation of marrow from unrelated donors in children. We analyzed results of this procedure in children with ALL treated according to a standard protocol to determine risk factors for outcome. From January 1987 to 1999, 88 consecutively seen patients with ALL who were younger than 18 years received a marrow transplant from an HLA-matched (n = 56) or partly matched (n = 32) unrelated donor during first complete remission (CR1; n = 10), second remission (CR2; n = 34), third remission (CR3; n = 10), or relapse (n = 34). Patients received cyclophosphamide and fractionated total-body irradiation as conditioning treatment and were given methotrexate and cyclosporine for graft-versus-host disease (GVHD) prophylaxis. Three-year rates of leukemia-free survival (LFS) according to phase of disease were 70% for CR1, 46% for CR2, 20% for CR3, and 9% for relapse (P <.0001). Three-year cumulative relapse rates were 10%, 33%, 20%, and 50%, respectively, and 3-year cumulative rates of death not due to relapse were 20%, 22%, 60%, and 41%, respectively, for patients with CR1, CR2, CR3, and relapse. Grades III to IV acute GVHD occurred in 43% of patients given HLA-matched transplants and in 59% given partly matched transplants (P =.10); clinical extensive chronic GVHD occurred in 32% and 38%, respectively (P =.23). LFS rates were lower in patients with advanced disease (P <.0001), age 10 years or older (P =.002), or short duration of CR1 (P =.007). Thus, in addition to phase of disease, age and duration of CR1 were predictors of outcome after unrelated-donor transplantation for treatment of ALL in children. Outcome was particularly favorable in younger patients with early phases of the disease.

Adolescent↗
PubMed2002

Effect of endothelin blockade on basal and stimulated forearm blood flow in patients with essential hypertension.

Endothelin receptor antagonism lowers blood pressure in patients with essential hypertension, but the contribution of the endothelin system to increased vascular tone in these patients remains controversial. We used strain-gauge venous plethysmography to measure changes in basal and metabolically stimulated (peak reactive hyperemia [PRH]) forearm blood flow (FBF) induced by continuous intrabrachial infusion of SB 209670, a dual endothelin type A/endothelin type B receptor antagonist (ETRA) in 11 patients with hypertension and 12 healthy age-matched control subjects. In both groups, ETRA caused significant vasodilation (increase in FBF compared with baseline over the last 30 minutes of ETRA infusion: 75+/-12% in control subjects, 40+/-13% in hypertension patients; P<0.01 for both groups). By repeated-measures ANOVA, there was no greater increase in FBF after ETRA in hypertension patients compared with control subjects. In addition, FBF responses to PRH, expressed as percent change from baseline (prePRH), were similar in both groups (control subjects: preETRA, 1381+/-222%; during ETRA, 921+/-178%; and hypertension patients: preETRA, 1232+/-221%: during ETRA, 865+/-285%). We conclude that basal and stimulated vasodilation induced by short-term ETRA infusion in the forearm vasculature of hypertension patients is not increased compared with that of control subjects. An enhanced contribution of the endothelin system to vascular tone in hypertension patients could not be demonstrated using this experimental approach.

Blood Flow Velocity↗
PubMed2002

Immediate early genes krox-24 and krox-20 are rapidly up-regulated after wounding in the embryonic and adult mouse.

Embryos show a remarkable capacity for perfect repair after injury. Wounding of embryonic skin triggers rapid activation of epithelial sweeping and mesenchymal contraction tissue movements that bear striking analogy to several naturally occurring morphogenetic tissue movements, but very little is known about the early molecular signals that might initiate such movements. Here, we describe the rapid and transient up-regulation of two immediate early genes, krox-24 and krox-20, after wounding of the embryonic mouse. Furthermore, we demonstrate that these signals are conserved, but of longer duration, in the neonate and adult wound situation. To further test the roles of these transcription factors in vivo, we performed wound healing studies on embryos lacking either Krox-24 or 20. Despite the dramatic up-regulation of these genes in response to injury, our studies reveal that neither of them on their own is essential for repair.

Age Factors↗
PubMed2002

Epithelial fusions in the embryo.

Morphogenesis in the embryo involves the bending, folding and fusing of epithelial tissues to create the final complex shapes of the various organs and structures in the body. One essential process that occurs frequently during development is the drawing together and fusion of epithelial edges. Drosophila dorsal closure is perhaps the most genetically tractable of this type of movement, and several recent advances have revealed much about the signals regulating the dynamic actin cytoskeletal machineries that underlie the zippering-closed of this hole in the embryonic fly. It is now clear that there are intriguing parallels with more complex morphogenetic tissue movements in vertebrates.

Actins↗
PubMed2002

Structures in focus--filopodia.

Filopodia are thin cell surface extensions filled with tight parallel bundles of actin filaments. They are highly dynamic structures which rapidly extend and retract as well as sweep up and down and from side to side, and can be found at the leading edge of many types of motile cells such as fibroblasts and keratinocytes, as well as the growth cone tips of migrating axons. Cells appear to use filopodia to explore the extracellular matrix (ECM) and surfaces of other cells, identifying appropriate targets for adhesion or in the case of a migrating growth cone, for sensing guidance cues that enable the axon to navigate to it's appropriate target. As well as this sensory role, filopodia have also recently been shown to play an important mechanical role in epithelial adhesion, and are likely to be key players in developmental processes that require migrating epithelial sheets to zipper and fuse to one another. Their dynamic properties as well as their tendency to be damaged or lost after fixation mean they are best analysed using live imaging techniques. As this field improves, the number of tissues in which filopodia are seen to be playing key roles is fast increasing.

Animals↗
PubMed2002

Dynamic analysis of dorsal closure in Drosophila: from genetics to cell biology.

Throughout development a series of epithelial bendings, sweepings, and fusions occur that collectively give shape to the embryo. These morphogenetic movements are driven by coordinated assembly and contraction of the actomyosin cytoskeleton in restricted populations of epithelial cells. One well-studied example of such a morphogenetic episode is dorsal closure in Drosophila embryogenesis. This process is tractable at a genetic level and has recently become the focus of live cell biology analysis because of the availability of flies expressing GFP-fusion proteins. This marriage of genetics and cell biology is very powerful and is allowing the dissection of fundamental signaling mechanisms that regulate the cytoskeletal reorganizations and contractions underlying coordinated tissue movements in the embryo.

Actins↗