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A P Martin

Publications and source records attributed to A P Martin.

At least 19 recordsLinked to original sources
PubMed2006

Successful staged kidney and liver transplantation for glycogen storage disease type Ib: A case report.

Glycogen storage disease type Ib is a rare metabolic disease caused by a defect of the G6P transporter. Patients suffer from hypoglycemic episodes; growth and developmental delay; osteoporosis; neutropenia; and tendency to infections, ovarian cysts, and liver adenomas. Terminal kidney disease is a rare complication. Liver transplantation has been performed to prevent malignant transformation of hepatic adenomas. We present the case of a female patient with glycogenosis type Ib who had severe hypoglycemic episodes and recurrent infections since early childhood. She became dialysis dependent at the age of 24 years. Kidney transplantation was performed at age 30, and liver transplantation 2 years later. The main indication for liver transplantation were the persistent, therapy-refractory hypoglycemic episodes. The transplanted kidney function is stable. The liver transplantation resulted in the disappearance of hypoglycemic episodes, with the patient leading a normal life and eating a normal diet. The neutropenia did not recover, but there were no more significant infectious episodes after liver transplantation. This is, to the best of our knowledge, the first communication of a dual kidney and liver transplant performed in a patient with glycogenosis type Ib. It confirmed the beneficial effect of liver transplantation on the quality of life of patients with severe hypoglycemia. The transplantation should be attempted earlier in the course of the disease to reduce complications and allow catch-up growth. Hepatocyte transplantation may be considered; however, long-term results seem to be rather poor in the few documented cases.

Adult↗
PubMed2006

Global phylogeography of the scalloped hammerhead shark (Sphyrna lewini).

Large marine fishes typically have little population genetic structure. The exceptions are associated with sedentary behaviour, disjunct distributions, or reproductive philopatry. Scalloped hammerhead sharks (Sphyrna lewini) incorporate the contrasting traits of oceanic habitat (usually associated with high dispersal) and possible fidelity to nursery grounds (for reproductive females). To evaluate the expectations of these contrasting behaviours, we examined the global genetic structure of S. lewini based on collections (n = 271 individuals) from 20 nursery areas. A 548-bp fragment of mitochondrial DNA control region revealed 22 polymorphic sites, 24 haplotypes, and three lineages distinguished by 2.56-3.77% sequence divergence. Coalescence analyses based on a provisional molecular clock indicate an origin in the Indo-West Pacific with late Pleistocene radiations into the central Pacific (Hawaii) and eastern Pacific (Central America), as well as recent interchange between oceans via southern Africa. Population subdivisions are strong (overall Phi(ST) = 0.749, P < 0.0001 and among oceans Phi(ST) = 0.598, P < 0.0098). Genetic discontinuity within oceans (Phi(ST) = 0.519, P < 0.0001) is primarily associated with oceanic barriers (migration across oceans M approximately 0), with much less structure along continental margins (M > 10). We conclude that nursery populations linked by continuous coastline have high connectivity, but that oceanic dispersal by females is rare. Although we cannot rule out philopatry to natal nurseries, oceanic barriers appear to have a much stronger influence on the genetic architecture of this species and may indicate a mechanism for recent evolutionary radiations in the genus Sphyrna.

Animals↗
PubMed2005

Sirolimus conversion after liver transplantation: improvement in measured glomerular filtration rate after 2 years.

METHODS: We reviewed our prospectively maintained database of 2005 liver transplantations. Therapy was either started de novo or converted from calcineurin inhibitors (CNIs) to sirolimus as the main immunosuppressive agent for nephrotoxicity or rejection. Glomerular filtration rate (GFR) was determined with iodine 125-labeled sodium isthalamate (Glofil-125), and serum creatinine concentration was obtained before and 3 months after transplantation, and yearly in both groups. Sirolimus levels were 10 to 15 ng/mL in patients at less than 3 months after transplantations and 5 to 10 ng/mL in the remaining patients. All patients received mycophenolate mofetil as maintenance therapy. RESULTS: Data for 29 patients in the de novo group and 35 in the conversion group were reviewed. Patients in the de novo group demonstrated an acute cellular rejection rate of 17.2%, 40% of which were steroid resistant. In this group, 48.2% discontinuation of sirolimus was necessary because of adverse effects. Patients in the conversion group demonstrated an acute cellular rejection rate of 2.8% and a 34.3% rate of sirolimus discontinuation. Seventeen (56.7%) patients at 1 year and 8 (44.4%) patients at 2 years demonstrated continued improvement in GFR. In the conversion group, case-control analysis did not demonstrate a significant difference in GFR and serum creatinine concentration (P > .05) at 1 and 2 years after conversion. At the time of review, no patients in the conversion group required hemodialysis. CONCLUSIONS: Conversion to sirolimus therapy is an effective strategy in improving renal function in patients with CNI-induced nephrotoxicity and can be done without increased rejection. Most of our patients (65.7%) tolerated sirolimus conversion. Of these, 56.7% and 44.4% demonstrated continued increase in GFR with the CNI-free regimen at 1 and 2 years, respectively. Long-term, large-population, prospective, randomized, controlled studies should further validate these results.

Creatinine↗
PubMed2005

An interspecific comparison of foraging range and nest density of four bumblebee (Bombus) species.

Bumblebees are major pollinators of crops and wildflowers in northern temperate regions. Knowledge of their ecology is vital for the design of effective management and conservation strategies but key aspects remain poorly understood. Here we employed microsatellite markers to estimate and compare foraging range and nest density among four UK species: Bombus terrestris, Bombus pascuorum, Bombus lapidarius, and Bombus pratorum. Workers were sampled along a 1.5-km linear transect across arable farmland. Eight or nine polymorphic microsatellite markers were then used to identify putative sisters. In accordance with previous studies, minimum estimated maximum foraging range was greatest for B. terrestris (758 m) and least for B. pascuorum (449 m). The estimate for B. lapidarius was similar to B. pascuorum (450 m), while that of B. pratorum was intermediate (674 m). Since the area of forage available to bees increases as the square of foraging range, these differences correspond to a threefold variation in the area used by bumblebee nests of different species. Possible explanations for these differences are discussed. Estimates for nest density at the times of sampling were 29, 68, 117, and 26/km2 for B. terrestris, B. pascuorum, B. lapidarius and B. pratorum, respectively. These data suggest that even among the most common British bumblebee species, significant differences in fundamental aspects of their ecology exist, a finding that should be reflected in management and conservation strategies.

Animals↗
PubMed2005

"Periapicitis".

Explore the source record for details and available documents.

Humans↗
PubMed2004

Spatial variation in Streptomyces genetic composition and diversity in a prairie soil.

Understanding how microbial genotypes are arrayed in space is crucial for identifying local factors that may influence the spatial distribution of genetic diversity. In this study we investigated variation in 16S rDNA sequences and rep-PCR fingerprints of Streptomyces stains isolated from prairie soil among three locations and four soil depths. Substantial variation in Streptomyces OTU (operational taxonomic unit) and BOX-PCR fingerprint diversity was found among locations within a limited spatial area (1 m2). Further, phylogenetic lineages at each location were distinct. However, there was little variation in genetic diversity among isolates from different soil depths and similar phylogenetic lineages were found at each depth. Some clones were found at a localized scale while other clones had a relatively widespread distribution. There was poor correspondence between 16S rDNA groupings and rep-PCR fingerprint groupings. The finding of distinct phylogenetic lineages and the variation in spatial distribution of clones suggests that selection pressures may vary over the soil landscape.

DNA Fingerprinting↗
PubMed2004

A Malthusian curb on spatial structure in microorganism populations.

That all organisms are born in the company of a parent but die alone is a fundamental biological asymmetry. It has been suggested that this provides a deep-rooted source of spatial pattern formation for microorganisms even at the scale of the population. Such a theory, however, neglects the strong influence in nature of the limited and spatially variable availability of food. The tendency, first recognized by Thomas Malthus in the 18th century, of a population to out-strip its food resources will eventually lead, through local starvation, to the suppression of a heterogeneity growing within a population. Using a generic model it is demonstrated that including local food limitation of breeding strongly dampens spatial structure otherwise resulting from birth and death. The extent of this damping is shown to be a function of the strength of the coupling between organisms and their food and of the total abundance of organic material. Moreover, this work provides an example of a density-dependent process acting to diminish spatial structure rather than to create it and highlights the rich variety of behaviour that is missed by continuum models which fail to represent such local dynamics.

Animals↗
PubMed2004

Molecular and metabolic characterization of cold-tolerant alpine soil Pseudomonas sensu stricto.

Alpine soils undergo dramatic temporal changes in their microclimatic properties, suggesting that the bacteria there encounter uncommon shifting selection gradients. Pseudomonads constitute important members of the alpine soil community. In order to characterize the alpine Pseudomonas community and to assess the impact of shifting selection on this community, we examined the ability of cold-tolerant Pseudomonas isolates to grow on a variety of carbon sources, and we determined their phylogenetic relationships based on 16S ribosomal DNA sequencing. We found a high prevalence of Pseudomonas in our soil samples, and isolates from these soils exhibited extensive metabolic diversity. In addition, our data revealed that many of our isolates form a unique cold-adapted clade, representatives of which are also found in the Swedish tundra and Antarctica. Our data also show a lack of concordance between the metabolic properties and 16S phylogeny, indicating that the metabolic diversity of these organisms cannot be predicted by phylogeny.

Altitude↗
PubMed2004

Integron diversity in heavy-metal-contaminated mine tailings and inferences about integron evolution.

Integrons are horizontal gene transfer (HGT) systems containing elements necessary for site-specific recombination and expression of foreign DNA. The overall phylogenetic distribution of integrons and range of genes that can be transferred by integrons are unknown. This report contains an exploration of integrons in an environmental microbial community and an investigation of integron evolution. First, using culture-independent techniques, we explored the diversity of integrons and integron-transferred genes in heavy-metal-contaminated mine tailings. Using degenerate primers, we amplified integron integrase genes from the tailings. We discovered 14 previously undescribed integrase genes, including six novel gene lineages. In addition, we found 11 novel gene cassettes in this sample. One of the gene cassettes that we sequenced is similar to a gene that codes for a step in a pathway for nitroaromatic catabolism, a group of compounds associated with mining activity. This suggests that integrons may be important for gene transfer in response to selective pressures other than the presence of antibiotics. We also investigated the evolution of integrons by statistically comparing the phylogenies of 16S rRNA and integrase genes from the same organisms, using sequences from GenBank and various sequencing projects. We found significant differences between the organismal (16S rRNA) and integrase trees, and we suggest that these differences may be due to HGT.

Bacteria↗
PubMed2000

Regional endemism and cryptic species revealed by molecular and morphological analysis of a widespread species of Neotropical catfish.

The lower Central American landscape was fully emergent approximately three million years ago, an event which marked the beginning of the Great American biotic interchange. Freshwater fishes participated in the biotic interchange. Because primary freshwater fishes are restricted to freshwater, they provide an excellent system for investigating the interplay of historical and recent processes on the assembly, structure and diversity of the regions' aquatic ecosystems. We focused on examining the history of diversification for a species of catfish (Pimelodella chagresi) whose distribution spans multiple, isolated drainage basins across the Isthmian landscape and into north-western South America. Analysis of mitochondrial DNA haplotypes and morphological traits indicated that P. chagresi, as currently recognized, comprises a species complex. In addition, along the Pacific slope of Panama, repeated dispersion, diversification, extinction and possibly hybridization are thought to underlie a complex distribution of haplotypes. Overall, the results underscore the tremendous importance of historical processes on regional biodiversity.

Animals↗
PubMed2000

Choosing among alternative trees of multigene families.

Estimation of gene trees is the first step in testing alternative hypotheses about the evolution of multigene families. The standard practice for inferring gene family history is to construct trees that meet some objective criteria based on the fit of the character state changes (nucleotide or amino acid changes) to the gene tree. Unfortunately, analysis of character state data can be misleading. In addition, this approach ignores information about the relationships of the species from which the genes have been sampled. In this paper I explore using statistics of fit between the character data and gene trees and the reconciliation of the gene and species trees for choosing among alternative evolutionary hypotheses of gene families. In particular, I advocate a two-pronged strategy for choosing among alternative gene trees. First, the character data are used to define a set of acceptable gene trees (i.e., trees that are not significantly different from the minimum length tree). Next, the set of acceptable gene trees is reconciled with a known species tree, and the gene tree requiring the fewest number of gene duplications and losses is adopted as the best estimate of evolutionary history. The approach is illustrated using three gene families: BMP, EGR, and LDH.

Animals↗
PubMed1999

Substitution rates of organelle and nuclear genes in sharks: implicating metabolic rate (again).

Rates of nucleotide substitution for nuclear genes are thought to be governed primarily by the number of germ line replication events (the so-called "generation time" hypothesis). In contrast, rates of mitochondrial DNA evolution appear to be set primarily by DNA damage pathways of mutation mediated by mutagenic by-products of oxidative phosphorylation (the so-called "metabolic-rate" hypothesis). Comparison of synonymous substitution rates estimated for the mitochondrial cytochrome b gene and nuclear-encoded dlx, hsp70, and RAG-1 genes in mammals and sharks shows that rates of molecular evolution for sharks are approximately an order of magnitude slower than those for mammals for both nuclear and mitochondrial genes. In addition, there is significant positive covariation of substitution rate for mitochondrial and nuclear genes within sharks. These results, interpreted in light of the pervasiveness of DNA damage by mutagenic by-products of oxygen metabolism to both nuclear and mitochondrial genes and coupled with increasing evidence for cross-genome activity of DNA repair enzymes, suggest that molecular clocks for mitochondrial and nuclear genes may be set primarily by common mutational mechanisms.

Animals↗
PubMed1998

Systematics and evolution of lower Central American cichlids inferred from analysis of cytochrome b gene sequences.

Central American cichlids allied to the genus "Cichlasoma" are thought to be of South American ancestry. The group has apparently undergone extensive morphological, ecological, and behavioral differentiation in Central America following colonization. Uncertainties regarding the systematics of the group and the timing of colonization complicate interpretation of the biological history of cichlids in Central America. We determined complete cytochrome b gene sequences for 54 individual cichlids representing 21 species to test hypotheses regarding the time of origin and pattern of diversification of lower Central American cichlids. The data also bear on issues relating to the systematics and taxonomy of heroine cichlids. Our results suggest that cichlids have been in Central America since the middle to late Miocene. Moreover, the data provide evidence of a rapid radiation early in the history of the group. Similar ecomorphological types have evolved multiple times. Inferences of convergent morphological evolution may, in part, explain a lack of concordance between the mitochondrial gene tree and previous inferences of phylogenetic relationships based on observable characteristics. Phylogenetic inferences based on the molecular data provide support for the recognition of "sections" [erected by Regan (1905) and others] as distinct genera and suggest that thorough revision of Central American cichlids is necessary before the extent of biological diversity within the group can be fully appreciated.

Animals↗
PubMed1998

Comparative mtDNA phylogeography of neotropical freshwater fishes: testing shared history to infer the evolutionary landscape of lower Central America.

Historical biogeography seeks to explain contemporary distributions of taxa in the context of intrinsic biological and extrinsic geological and climatic factors. To decipher the relative importance of biological characteristics vs. environmental conditions, it is necessary to ask whether groups of taxa with similar distributions share the same history of diversification. Because all of the taxa will have shared the same climatic and geological history, evidence of shared history across multiple species provides an estimate of the role of extrinsic factors in shaping contemporary biogeographic patterns. Similarly, differences in the records of evolutionary history across species will probably be signatures of biological differences. In this study, we focus on inferring the evolutionary history for geographical populations and closely related species representing three genera of primary freshwater fishes that are widely distributed in lower Central America (LCA) and northwestern Colombia. Analysis of mitochondrial gene trees provides the opportunity for robust tests of shared history across taxa. Moreover, because mtDNA permits inference of the temporal scale of diversification we can test hypotheses regarding the chronological development of the Isthmian corridor linking North and South America. We have focused attention on two issues. First, we show that many of the distinct populations of LCA fishes diverged in a relatively brief period of time thus limiting the phylogenetic signal available for tests of shared history. Second, our results provide reduced evidence of shared history when all drainages are included in the analysis because of inferred dispersion events that obscure the evolutionary history among drainage basins. When we restrict the analysis to areas that harbour endemic mitochondrial lineages, there is evidence of shared history across taxa. We hypothesize that there were two to three distinct waves of invasion into LCA from putative source populations in northwestern Colombia. The first probably happened in the late Miocene, prior to the final emergence of the Isthmus in the mid-Pliocene; the second was probably coincident with the rise of the Isthmus in the mid-Pliocene, and the third event occurred more recently, perhaps in the Pleistocene. In each case the geographical scale of the dispersion of lineages was progressively more limited, a pattern we attribute to the continuing development of the landscape due to orogeny and the consequent increase in the insularization of drainage basins. Thus, the fisheye view of LCA suggests a complex biogeographic history of overlaid cycles of colonization, diversification, sorting and extinction of lineages.

ATP Synthetase Complexes↗