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PubMed2003

Apoptotic susceptibility of cancer cells selected for camptothecin resistance: gene expression profiling, functional analysis, and molecular interaction mapping.

To study the molecular mechanisms by which drug resistance develops, we compared DU145 humanprostate cancer cells with a subline selected for resistance to camptothecin. Differences in gene expression level were assessed by hybridizing the two cell types against each other using quadruplicate "Oncochip" cDNA microarrays that included 1648 cancer-related genes. Expression levels differing by a factor of >1.5 were detected for 181 of the genes. These differences were judged statistically reliable on the basis of a stratum-adjusted Kruskal-Wallis test, after taking into account a dye-dependent variable. The 181 expression-altered genes included a larger than expected number of the "apoptosis-related" genes (P = 0.04). To assess whether this observation reflected a generalized resistance of RCO.1 to apoptosis, we exposed the cells to a range of stresses (cisplatin, staurosporine, UV, ionizing radiation, and serum starvation) and found greatly reduced apoptotic responses for RC0.1 (relative to DU145) using flow cytometric Annexin V and terminal deoxynucleotidyl transferase-mediated nick end labeling assays. We next examined the apoptosis-related genes in the context of a molecular interaction map and found expression differences in the direction "expected" on the basis of the apoptosis-resistance of RC0.1 for BAD, caspase-6, and genes that signal via the Akt pathway. Exposure of the cells to wortmannin, an inhibitor of the Akt effector phosphatidylinositol 3-kinase, provided functional support for involvement of the Akt pathway. However, closer examination of the molecular interaction map revealed a paradox: many of the expression differences observed for apoptosis-related genes were in the direction "contrary" to that expected given the resistance of RC0.1. The map indicated that most of these unexpected expression differences were associated with genes involved in the nuclear factor kappa B and transforming growth factor beta pathways. Overall, the patterns that emerged suggested a two-step model for the selection process that led to resistance in RC0.1 cells. The first hypothesized step would involve a decrease in apoptotic susceptibility through changes in the apoptosis-control machinery associated with the Bcl-2 and caspase gene families, and also in antiapoptotic pathways operating through Akt/PKB. The second step would involve changes in multifunctional upstream genes (including some genes in the nuclear factor kappa B and transforming growth factor beta pathways) that can facilitate apoptosis but that would also tend to contribute to cell proliferation in the presence of drug. Thus, we propose that a downstream blockade of apoptosis was "permissive" for the selection of upstream pathway changes that would otherwise have induced apoptosis. This model is analogous to one suggested previously for the relationship between oncogene function and apoptosis in carcinogenesis.

Androstadienes↗
PubMed1997

Genetic drift and gene flow in post-famine Ireland.

This study examines the genetic impact of the Great Famine (1846-1851) on the regional genetic structure of Ireland. The Great Famine resulted in a rapid decrease in population size throughout Ireland in a short period of time, increasing the possibility of genetic drift. Our study is based on migration and anthropometric data collected originally in the 1930s from 7211 adult Irish males. These data were subdivided into three time periods defined by year of birth: 1861-1880, 1881-1900, and 1901-1920. Within each time period the data were further subdivided into six geographic regions of Ireland. Estimates of Wright's FST were calculated from parent-offspring migration data and from 17 anthropometric variables (10 head measures, 7 body measures). Over time, the average population size decreased, but average rates of migration increased. The estimates of FST at equilibrium from migration matrix analysis suggest that the net effect of these opposite effects is a reduction in among-group variation. Closer examination shows that within each time period the rate of convergence to equilibrium is slow, meaning that the expected levels of genetic homogeneity revealed from migration matrix analysis are not likely to be seen over short intervals of time. Estimates of FST from anthropometric data show either relatively little change in microdifferentiation or some increase, depending on which variables are analyzed. Investigation of a simple model of demographic and genetic change shows that, given the demographic changes in post-Famine Ireland, FST could in theory increase, decrease, or remain the same over short intervals of time. Overall, the Great Famine appears to have had minimal impact on the genetic structure of Ireland on a regional level. Comparison with studies focusing on local genetic structure shows the opposite. It appears that the level of genetic impact depends strongly on the level of analysis; local populations are affected to a greater extent by demographic shifts than regional populations. We also provide formulas for the standard errors of FST from metric traits and related statistics.

Adolescent↗
PubMed1989

Effects of neuropeptides and capsaicin on tracheobronchial blood flow of the pig.

Blood flow changes upon systemic i.v. injections in the pig of various neuropeptides, capsaicin, bradykinin and histamine were directly monitored by a Transonic blood flowmeter in the superior laryngeal, bronchial and femoral arteries and indirectly in the larynx and skin using laser Doppler flowmetry. To minimize influence of compensatory reflexes and indirect effects, the pigs were pre-treated with atropine, guanethidine, chlorisondamine and capsaicin. Substance P (SP), vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), calcitonin gene-related peptide (CGRP), capsaicin, bradykinin and histamine all decreased vascular resistance, suggesting vasodilation in the superior laryngeal and bronchial arteries. All peptides and histamine when given i.v. exerted vasodilatory effects independent of autonomic motor nerves and capsaicin-sensitive afferents. SP was the most potent vasodilator agent tested in both tracheal and bronchial circulation, being about 1000-fold more active than histamine. VIP was about 10-fold more potent than PHI in decreasing vascular resistance and had a preferential action on the SLA compared to CGRP. In the femoral artery capsaicin and also SP in the highest dose increased vascular resistance. Capsaicin increased the laser Doppler signal in both laryngeal mucosa and skin, while i.v. peptides caused variable effects. In conclusion, SP and CGRP mimicked capsaicin-induced vasodilation in the tracheobronchial circulation while VIP had a preferential effect on the tracheal circulation.

Animals↗
PubMed1993

Analysis of the V kappa III variable regions of polyclonal rheumatoid factors arising during Epstein Barr virus induced infectious mononucleosis.

The mechanisms that govern autoantibody production are still under debate. In particular, auto-antibodies can appear as a consequence of a polyclonal activation of B cells or as a consequence of an antigen driven B cell expansion. The molecular analysis of the variable regions of auto-antibodies arising during different clinical situations can help to understand the origin of auto-antibodies. We recently described the main light chain variable regions of polyclonal rheumatoid factors occurring during rheumatoid arthritis and suggested that the mutation pattern of these regions could reflect an antigen driven process. Using the same approach, we now report the molecular analysis of the same light chain variable region containing a VKIII segment of rheumatoid factors originating from a polyclonal activation of B cells during an in vivo Epstein-Barr virus infection, infectious mononucleosis. The cDNA derived from rheumatoid factor synthetizing cells were amplified by two sets of polymerase chain reaction. The amplified products were cloned in M13mp19 phages and sequenced. The nucleotide analysis of the VKIII containing VK regions shows that: 1) the rheumatoid factor activity is associated with the 3 VKIII genes (Kv 325, Kv 328 and Vg) already known to encode for monoclonal and polyclonal rheumatoid factors, 2) there is a preferential use of Kv 328 and Vg, each one of these genes being poorly mutated, 3) the CDR mutation rates of these genes is no higher than the framework mutation rates, 4) there is a restriction of the JK usage; Kv 328 derived gene segments rearrange exclusively with JK1, Vg preferentially rearranges with JK1 and JK4. These results mainly suggest that naturally occurring polyclonal activation of autoreactive B cells produces poorly mutated autoantibodies.

Adult↗
PubMed1997

French multicentric evaluation of mdr1 gene expression by RT-PCR in leukemia and solid tumours. Standardization of RT-PCR and preliminary comparisons between RT-PCR and immunohistochemistry in solid tumours. French Network of the Drug Resistance Intergroup, and Drug Resistance Network of Assistance Publique-Hôpitaux de Paris.

Since there is no consensus on the techniques for multidrug resistance (MDR) phenotype evaluation, many discrepancies concerning the importance and frequency of mdr1 gene expression in leukemias and solid tumors are observed in the literature. In order to establish an inter-laboratory consensus in France, a multicenter study was carried out to propose further guidelines for MDR phenotype evaluation. The techniques used by the 38 laboratories participating in the trial were: immunodetection (immunohisto and/or cytochemistry, flow cytometry), functional tests, reverse transcription-polymerase chain reaction (RT-PCR) or Northern blot. We present the results obtained by 19 laboratories concerning the measurement of mdr1 gene expression assessed by RT-PCR or Northern blot in: (1)19 samples of tumor cells obtained from leukemic patients; (2) six solid tumor samples obtained at surgery; (3) eight cell lines exhibiting variable levels of resistance, and; (4)10 preparations of RNA and of cDNA obtained from solid tumors. Standardization of the RT-PCR technique and preliminary results comparing RT-PCR with immunohistochemistry in solid tumors are also reported.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Phylogeography of the California mountain kingsnake, Lampropeltis zonata (Colubridae).

The phylogeography of the California mountain kingsnake, Lampropeltis zonata, was studied using mitochondrial DNA sequences from specimens belonging to the seven recognized subspecies and collected throughout the range of the species. Maximum parsimony and maximum likelihood methods identified a basal split within L. zonata that corresponds to southern and northern segments of its distribution. The southern clade is composed of populations from southern California (USA) and northern Baja California, Mexico. The northern clade is divided into two subclades, a 'coastal' subclade, consisting of populations from the central coast of California and the southern Sierra Nevada Mountains of eastern California, and a 'northeastern' subclade, mainly comprised of populations north of the San Francisco Bay and from the majority of the Sierra Nevada. We suggest that past inland seaways in southwestern California and the embayment of central California constituted barriers to gene flow that resulted in the two deepest divergences within L. zonata. Throughout its evolutionary history, the northern clade apparently has undergone instances of range contraction, isolation, differentiation, and then expansion and secondary contact. Examination of colour pattern variation in 321 living and preserved specimens indicated that the two main colour pattern characters used to define the subspecies of L. zonata are so variable that they cannot be reliably used to differentiate taxonomic units within this complex, which calls into question the recognition of seven geographical races of this snake.

Animals↗
PubMed2003

American marten (Martes americana) in the Pacific Northwest: population differentiation across a landscape fragmented in time and space.

American marten (Martes americana) have a close association with mature temperate forests, a habitat that expanded throughout the Pacific Northwest as glaciers receded at the end of the Pleistocene. Similar to several other forest-associated mammals in North America (e.g. black bear), genetic analysis of the marten shows a deep phylogeographical subdivision that reflects populations with distinctive evolutionary histories. Using a suite of 14 microsatellite markers, we explored the genetic structure of marten populations in two reciprocally monophyletic clades in the Pacific Northwest identified previously as M. caurina and M. americana by mitochondrial haplotypes and morphology. Microsatellite phylogeographical patterns were congruent with mitochondrial analyses. These independent data sets shed light upon hybridization patterns, population structure and evolutionary histories. Hybridization between M. caurina and M. americana individuals was documented in two regions of sympatry (Kuiu Island in southeastern Alaska and southern Montana). Northern insular populations of M. caurina exhibited higher differentiation and lower variability relative to northern populations of M. americana. Greater divergence among M. caurina populations may reflect longer isolation and persistence in coastal forest habitat that was fragmented by rising sea level in the early Holocene. Lower differentiation among northern M. americana populations and close relationship to other continental M. americana populations may reflect more recent expansion into the Pacific Northwest and/or continued gene flow among populations. Differentiation among M. caurina populations was attributed to habitat fragmentation (i.e. rising sea level), as opposed to isolation-by-distance; oceanic straits pose significant barriers to gene flow among M. caurina populations and between populations of M. caurina and M. americana.

Animal Population Groups↗
PubMed2004

Genetic and morphological differentiation in Tephritis bardanae (Diptera: Tephritidae): evidence for host-race formation.

The fruit fly Tephritis bardanae infests flower heads of two burdock hosts, Arctium tomentosum and A. minus. Observations suggest host-associated mating and behavioural differences at oviposition indicating host-race status. Previously, flies from each host plant were found to differ slightly in allozyme allele frequencies, but these differences could as well be explained by geographical separation of host plants. In the present study, we explicitly test whether genetic and morphological variance among T. bardanae are explained best by host-plant association or by geographical location, and if this pattern is stable over a 10-year period. Populations of A. tomentosum flies differed significantly from those of A. minus flies in (i) allozyme allele frequencies at the loci Pep-A and Pgd, (ii) mtDNA haplotype frequencies and (iii) wing size. In contrast, geographical location had no significant influence on the variance estimates. While it remains uncertain whether morphometric differentiation reflects genotypic variability or phenotypic plasticity, allozyme and mtDNA differentiation is genetically determined. This provides strong evidence for host-race formation in T. bardanae. However, the levels of differentiation are relatively low indicating that the system is in an early stage of divergence. This might be due to a lack of time (i.e. the host shift occurred recently) or due to relatively high gene flow preventing much differentiation at loci not experiencing selection.

Analysis of Variance↗
PubMed2004

Recapitulation of B cell differentiation in the central nervous system of patients with multiple sclerosis.

Clonally expanded populations of B cells carrying somatic mutations of Ig variable (V) region genes have been detected in the CNS of subjects with multiple sclerosis (MS), suggesting that a process of B cell affinity maturation with ensuing production of potentially pathogenic autoantibodies may occur inside the CNS. Here, we have characterized the B cell subsets present in the cerebrospinal fluid (CSF) of MS patients and of individuals with other inflammatory neurological disorders by flow cytometry. CD19(+)CD38(high+)CD77(+), Ki67(+), Bcl-2(-) centroblasts, i.e., a B cell subset found exclusively in secondary lymphoid organs, were detected in the CSF but not in paired peripheral blood from both patient groups. CD27(+)IgD(-) memory B cells, i.e., cells with hyper-mutated IgV genes, were significantly increased in the CSF vs. paired peripheral blood and displayed up-regulation of the CD80 and CD86 costimulatory molecules and of CC chemokine receptor (CCR) 1, CCR2, and CCR4 in both patient groups. Lymphotoxin-alpha, CXC ligand (CXCL) 12, and CXCL13, key mediators of lymphoid neogenesis, were present in the CSF from patients with MS and other inflammatory neurological disorders and were expressed in MS brain tissue, with selective localization in the outer layer of the capillary vessel wall. In conclusion, this study suggests that a compartmentalized B cell response occurs within the CNS during an ongoing inflammatory reaction, through a recapitulation of all stages of B cell differentiation observed in secondary lymphoid organs. The presence of lymphotoxin-alpha, CXCL12, and CXCL13 in the CNS may provide favorable microenvironmental conditions for these events.

Antigens, CD↗
PubMed2003

On the pBuM189 satellite DNA variability among South American populations of Drosophila buzzatii.

The pBuM189 satellite DNA was analysed in Drosophila buzzatii populations that cover most of the species distribution in South America. This satDNA consists of A + T-rich monomers of 189 bp and previous studies showed a fast rate of evolutionary change of this component of D. buzzatii genome. A total of 63 pBuM189 repetition units from 14 D. buzzatii populations (9 from Brazil and 5 from Argentina) were studied. The average nucleotide variability among the 63 repeats is 4.2 %. At least one repeat (Juan/4) seems to be part of another pBuM189 satDNA subfamily. The nucleotide alignment of all 63 repeats revealed no specific nucleotide substitutions, or indels, that could discriminate each population or groups of geographically close populations. Such lack of satDNA interpopulational differentiation is congruent with previous mtDNA data that indicate a high gene flow and very little population differentiation throughout most of the D. buzzatii distribution in South America. Gene flow might have been possible during glaciation events in the Pleistocene, such as the one occurred between 13,000 and 18,000 years ago, when D. buzzatii probably had a more continuous distribution than what is observed today.

Animals↗
PubMed2004

Biodistribution of the RD114/mammalian type D retrovirus receptor, RDR.

BACKGROUND: The limited expression of viral receptors on target cells is a recognized barrier to therapeutic gene transfer. Previous analysis of receptor expression has been performed using indirect methods due to a lack of receptor-specific antibodies. METHODS: In this report we have used anti-RDR antiserum to provide direct histochemical and flow cytometric analysis of the expression of RDR, which is the cognate receptor for RD114-pseudotyped vectors as well as being a neutral amino acid transporter. RESULTS: RDR was present on a range of normal tissues with relevance to gene therapy including: colon, testis, ovary, bone marrow and skeletal muscle. It was also highly expressed on immature cells present in the squamous epithelia of skin, cervix, nasal mucosa, bronchus and tonsil. Of relevance to possible germline gene transfer, we demonstrated a lack of RDR expression on male or female germ cells. RDR expression on mature hemopoietic cell subsets showed up to 5-fold variability between individuals within each lineage-with some individuals expressing low levels of RDR across all blood lineages. Both myeloid and monocytic lineages contained the highest fraction of cells expressing RDR, whereas lymphoid lineages showed the lowest. Coexpression of CD34 and RDR ranged from 2.04 to 0.44% in G-CSF-mobilized peripheral blood samples. CONCLUSIONS: As a means to optimize gene transfer protocols, biodistribution studies such as these are fundamental to enable targeting of the virus receptor most abundantly expressed on relevant populations. The inter-individual variation of receptor expression seen here also raises the possible requirement for tailor-made gene therapy protocols.

3T3 Cells↗
PubMed1992

Investigations on the variability of blood group polymorphisms among sixteen tribal populations from Orissa, Madhya Pradesh and Maharashtra, India.

Sixteen tribal populations from Orissa, Madhya Pradesh and Maharashtra have been typed for the polymorphic blood group systems A1A2B0, MNSs, Rhesus, Kell, Duffy and Diego. The heterogeneity in the distribution of haplotype and allele frequencies, respectively, is partly considerable. It is supposed that this is due to the operation of several microevolutionary factors, such as genetic drift, social and geographic isolation and gene flow. This is discussed in detail.

Alleles↗
PubMed2003

Development of functional human monoclonal single-chain variable fragment antibody against HIV-1 from human cervical B cells.

A panel of novel recombinant single-chain variable fragment (scFv) antibody against human immunodeficiency virus type-1 (HIV-1) was isolated and characterized. We generated human scFvs using RNA harvested from cervical B lymphocytes of Kenyan prostitutes who are highly exposed to HIV-1, but remain persistently seronegative. The variable regions of the heavy (VH) and light (VL) chain antibody genes were selected as hybrids using guided-selection with the VL and VH, respectively, of a derivative of IgGb(12) using the phagemid vector pComb3X. IgGb(12) is a previously well-characterized HIV-1 neutralizing human monoclonal antibody (MAb). One of the hybrid scFv, IgA6/4L, neutralizes HIV-1 infectivity in in vitro cell culture assay. The cervical VH and VL chain antibody genes were connected by a DNA linker and subcloned in pComb3X. The cervical scFv clones were functional in recognizing HIV-1 gp120 by enzyme-linked immunosorbant assay (ELISA) and on cells in flow cytometry. Whole IgGb(12) does not inhibit binding of clones IgA6/5k nor IgA6/30lambda to gp120, which suggests that they bind different epitopes. Nucleotide sequence analysis of the cervical scFv show the clones are unique and reveal interesting characteristics of human cervical V gene pools. This work demonstrates, for the first time, cloning of a functional scFv MAb to a sexually transmitted disease pathogen from local cervical B-cell pools in exposed humans.

Amino Acid Sequence↗
PubMed1995

Preferential expansion and survival of B lymphocytes based on VH framework 1 and framework 3 expression: "positive" selection in appendix of normal and VH-mutant rabbits.

B cells with a rearranged heavy-chain variable region VHa allotype-encoding VH1 gene segment predominate throughout the life of normal rabbits and appear to be the source of the majority of serum immunoglobulins, which thus bear VHa allotypes. The functional role(s) of these VH framework region (FR) allotypic structures has not been defined. We show here that B cells expressing surface immunoglobulin with VHa2 allotypic specificities are preferentially expanded and positively selected in the appendix of young rabbits. By flow cytometry, a higher proportion of a2+ B cells were progressing through the cell cycle (S/G2/M) compared to a2- B cells, most of which were in the G1/G0 phase of the cell cycle. The majority of appendix B cells in dark zones of germinal centers of normal 6-week-old rabbits were proliferating and very little apoptosis were observed. In contrast, in 6-week-old VH-mutant ali/ali rabbits, little cell proliferation and extensive apoptosis were observed. Nonetheless even in the absence of VH1, B cells with a2-like surface immunoglobulin had developed and expanded in the appendix of 11-week-old mutants. The numbers and tissue localization of B cells undergoing apoptosis then appeared similar to those found in 6-week-old normal appendix. Thus, B cells with immunoglobulin receptors lacking the VHa2 allotypic structures were less likely to undergo clonal expansion and maturation. These data suggest that "positive" selection of B lymphocytes through FR1 and FR3 VHa allotypic structures occurs during their development in the appendix.

Animals↗
PubMed2000

Cell-surface exposure of phosphatidylserine correlates with the stage of fludarabine-induced apoptosis in chronic lymphocytic leukemia and expression of apoptosis-regulating genes.

BACKGROUND: Programmed cell death (PCD) is characterized by a sequence of tightly regulated events that result in the activation of caspases and in internucleosomal DNA cleavage. Late apoptotic events such as DNA-strand breaks can be assayed by in situ end labeling (ISEL) and DNA measurement (sub G1) using flow cytometry. Phosphatidylserine (PS) redistribution from the inner plasma membrane leaflet to the outer leaflet, an early event in PCD, can be detected by annexin V (AxV) binding to PS. AxV-fluorescein isothiocyanate (FITC) fluorescence intensity is variable and characterizes different cell populations, denoted here as AxV-negative (AxV(neg)), AxV-low-positive (AxV(lo)), and AxV-high-positive (AxV(hi)). METHODS: We investigate the correlation of three methods (ISEL, sub G1 DNA content, and AxV assay) for detecting apoptosis with focus on differences between populations with different levels of PS. We also examined the expression of PCD-regulating Bcl-2 family members in these cell populations by reverse transcription-polymerase chain reaction (RT-PCR). Chronic lymphocytic leukemia (CLL) cells exposed to fludarabine (FAMP) were used as an in vitro model. Cells with different PS/AxV levels were separated using fluorescence-activated cell sorting (FACS). RESULTS: Only purified AxV(hi) cells had high positivity in the ISEL and sub G1 assays (94 +/- 0.6%, 88.6 +/- 6.6%, and 98.6 +/- 0.6%, respectively), indicating that late apoptotic cells are detected equally by all three methods. In the AxV(lo) population, ISEL was positive in 21% +/- 13% and DNA sub G1 in 20% +/- 6.6% of cells, suggesting that AxV identifies early apoptotic cells better than the other assays. Anti-apoptotic Bcl-2 and Bcl-X(L) were upregulated by FAMP when cells entered apoptosis (AxV(lo)), as was pro-apo- ptotic Bcl-X(S), which was undetectable in nonapoptotic AxV(neg) cells. Pro-apoptotic Bax was only expressed in AxV(neg) and AxV(lo) cells. Late apoptotic AxV(hi) cells did not express Bcl-X(S) or Bax. RESULTS: (1) AxV staining is more sensitive than sub G1 or ISEL in detecting early apoptotic cells; (2) only late apoptotic cells are equally detected by all assays; (3) AxV is a valuable tool in the detection and isolation of apoptotic cells at different stages of PCD; and (4) pro-apoptotic Bcl-X(S) and Bax are expressed at early, not late, stages of apoptosis.

Annexin A5↗
PubMed1991

Genetic evidence for three species within Pseudoterranova decipiens (Nematoda, Ascaridida, Ascaridoidea) in the North Atlantic and Norwegian and Barents Seas.

Genetic variation of 1017 specimens of codworm, Pseudoterranova decipiens, collected from fish and seals at 23 sampling locations in the North Atlantic and Norwegian and Barents Seas, was analysed on the basis of 16 enzyme loci. Three reproductively isolated species, provisionally designated P. decipiens A, B and C, were detected, showing distinct alleles at the following loci: Mdh-1, 6Pgdh, Np, Pgm, Est-2 (between species A and B); Mdh-3, 6Pgdh, Np, Sod-1, Adk, Pgm, Est-2, Mpi (between A and C); Mdh-1, Mdh-3, Sod-1, Adk, Pgm, Est-2, Mpi (between B and C). One F1 hybrid was observed between P. decipiens A and B, but this apparently does not lead to any gene exchange between the two species, which do not show any evidence of introgression. No hybrids or introgressed individuals were observed between P. decipiens C and either A or B. Genetic distances among conspecific populations were low (average Nei's D 0.001-0.005), even though they were collected thousands of kilometres apart, indicating high levels of gene flow within each of the three species. The values of Nei's index D were 0.44 between P. decipiens A and B, 0.57 between B and C, and 0.79 between A and C. Estimated evolutionary divergence times, using Nei's formula, range from 2 to 4 million years. Differences between P. decipiens A, B and C were also found with respect to genetic variability, morphology, geographical distribution and hosts. Mean heterozygosity values of 0.08, 0.05 and 0.02 were obtained for P. decipiens A, B and C, respectively. Preliminary morphological examination of adult males, previously identified by multilocus electrophoresis, revealed differences in the relative size and pattern of caudal papillae. P. decipiens B is widespread in the study area, whereas P. decipiens A was found only in the North-East Atlantic and Norwegian Sea. In this area P. decipiens A is most common in the grey seal, Halichoerus grypus, while the common seal, Phoca vitulina, is the main host for P. decipiens B. In Canadian Atlantic waters, where P. decipiens A is apparently absent, P. decipiens B infects both grey and common seals; a few specimens were also found in the hooded seal, Cystophora cristata. The only definitive host so far identified for P. decipiens C is the bearded seal, Erignathus barbatus; P. decipiens C appears to be widespread, occurring in both the North-West Atlantic and Barents Sea.

Animals↗
PubMed2006

Phylogeography of human lymphatic filarial parasite, Wuchereria bancrofti in India.

Wuchereria bancrofti, a nematode parasite causing human lymphatic filariasis is widely distributed in India. The phylogeography of this parasite was studied by constructing RAPD profiles of parasite populations collected from 71 microfilaria carriers residing in different geoclimatic regions of India. The analysis showed that the phylogeography of W. bancrofti populations is complex, with a high genetic divergence and gene flow among populations. The total genetic diversity (H(T)) and genetic differentiation (G(ST)) estimated for all the parasite populations were 0.0926 and 0.5859, respectively. The gene flow (Nm) between different regions indicated that two strains of W. bancrofti were prevalent in the country, one in the eastern side and the other on the western side of the Western Ghats. A highly significant genetic differentiation (F(ST) [theta] = 0.7978) was estimated between these two strains (chi 2 = 308.2789; P < 0.001). The gene flow between these strains was very low (0.2338). These two strains appear to have drifted genetically because of their geographic isolation by this thickly forested mountain range. The strain in the eastern side was found to be monophyletic in origin and is undergoing genetic divergence as the major parasite population in the country, spanning from eastern peninsular region to the northern plains. The variable geoclimatic factors and the antifilarial chemotherapeutical pressure on the parasite, which is in place for the past half a century, might have contributed for the high genetic heterogeneity its strains/populations in the country. The route of entry of the parasite into Indian sub-continent possibly appeared to be from an ancient origin from the countries of the Southeast Asian archipelago, through the eastern coastal line of the southern peninsula.

Animals↗
PubMed2003

Molecular population genetic analysis of the spectacled bear (Tremarctos ornatus) in the northern Andean area.

Eighty-two Andean bear samples obtained in three South American Andean countries were analyzed using five hypervariable microsatellite markers. Neither the overall sample nor the samples coming from each of the countries analyzed were in Hardy-Weinberg equilibrium. This is attributable to the Wahlund effect caused by a fragmentation of the bear populations. The genetic variability levels found were in general low for this kind of molecular markers (H = 0.38 for the global population). The situation of the Ecuadorian bear population seems to be endangered (H = 0.24). This is the lowest level recorded for any bear population. The genetic heterogeneity among the three populations was large and highly significant (F(ST) = 0.39; R(ST) = 0.32-0.49). Likewise, the gene flow estimates were remarkably low among these populations (Nm = 0.2-0.3). This means that the populations are strongly isolated. Different methods were applied to determine the effective numbers in these populations. A significant spatial structure of the genotypes was analyzed with different procedures. In all cases, an isolation-by-distance structure was detected. This could be a consequence of the original South America colonization. There was no evidence for a recent genetic bottleneck. This could mean that the low heterozygosity and the population fragmentation could be explained by ancient events related to the bear colonization, with the arrival of humans beings in the Americas, and/or with the glacial maximum, 16.000-30.000 years ago.

Animals↗