¿Qué nos dicen los primates neotropicales bajo la mirada de la citogenética? / What do neotropical primates tell us under the look of cytogenetics?

RESUMEN Los estudios de citogenética en Primates Neotropicales (Primates: Platyrrhini) han demostrado que estos mamíferos comprenden un grupo heterogéneo a nivel cromosómico. La notable variedad de cariotipos descriptos provee evidencia significativa sobre el posible papel de los reordenamientos cromosómicos en su evolución. En el Grupo de Investigación en Biología Evolutiva (GIBE), la línea de investigación sobre el proceso de divergencia evolutiva en Platyrrhini considerando distintos aspectos de la organización del genoma se ha establecido y desarrollado de manera ininterrumpida desde hace más de 30 años. Entre los avances realizados en los últimos años se encuentra la cuantificación del tamaño del genoma en seis especies de monos caí (Cebus sp.) y dos especies de monos aulladores (Alouatta sp.) y la descripción de la composición de pares de bases en las regiones de heterocromatina constitutiva en los géneros Cebus y Ateles. Se concretaron las primeras descripciones del cariotipo y comportamiento meiótico en profase I temprana de dos especies de monos aulladores, Alouatta caraya y A. guariba clamitans. En esta última especie se identificó el primer sistema sexual de tipo pentavalente X1X2X3Y1Y2 en una especie de primate. Se caracterizó la organización de la eucromatina en términos del contenido y distribución de bases nucleotídicas AT y GC en tres especies de aulladores y en dos especies de monos caí. Estas investigaciones, entre otras, permitieron contribuir de forma original al conocimiento sobre la especiación en distintos niveles, así como sobre la arquitectura y dinámica del genoma de estos primates.

ABSTRACT Cytogenetics studies in Neotropical Primates (Primates: Platyrrhini) have shown that these mammals comprise a heterogeneous group at the chromosomal level. The remarkable variety of karyotypes described provides significant evidence on the possible role of chromosomal rearrangements in their evolution. In the Grupo de Investigación en Biología Evolutiva (GIBE), the line of research on the evolutionary divergence process in Platyrrhini considering different aspects of the organization of the genome has been established and developed uninterruptedly for more than 30 years. Among the advances made in recent years is the quantification of the genome size in six species of caí monkeys (Cebus sp.) and two species of howler monkeys (Alouatta sp.) and the description of the composition of base pairs in the constitutive heterochromatin regions in the genera Cebus and Ateles. The first descriptions were made of the karyotype and meiotic behavior in early prophase I of two species of howler monkeys, Alouatta caraya and A. guariba clamitans. In this last species, the first pentavalent-type sexual system X1X2X3Y1Y2 was identified in a primate species. The organization of euchromatin was characterized in terms of the content and distribution of AT and GC nucleotide bases in three species of howlers and in two species of caí monkeys. These, among other investigations, allowed contributing in an original way to the knowledge about speciation at different levels, as well as about the architecture and dynamics of the genome of these primates.

HEp-2 cell line as an experimental model to evaluate genotoxic effects of pentavalent inorganic arsenic / HEp-2 como modelo experimental para evaluar los efectos genotóxicos del arsénico inorgánico pentavalente

Early detection of toxic events induced by xenobiotics is necessary for a proper assessment of human risk after the exposure to those agents. The aim of this work was to evaluate the cell line HEp-2 as an experimental model to determine the genotoxic effects of sodium arsenate. To this end, we determined the metabolic activity cells by the MTT test on seven concentrations of arsenate that range from 27 to 135,000 μM, obtaining the median lethal concentration (LC50), the lowest observed effect concentration (LOEC), and the not observed effect concentration (NOEC) of sodium arsenate at 24 h of exposition. According to the cytotoxic response obtained, we evaluated the genotoxic effect of the 27 and 270 μM concentrations by using the micronucleus assay and chromosomal aberrations test. We found a statistically significant increase (p<0.05) in the frequency of micronuclei between control cultures and those exposed to the highest concentration of sodium arsenate. Furthermore, the frequencies of nucleoplasmic bridges and tripolar mitosis were significantly higher in cell cultures exposed to the above concentrations compared to the control cultures (p<0.05). The participation of the glutathione system as response to the arsenate exposition was also analyzed, and a statistically significant increase in the glutathione content was found in those cells exposed to 27 μM of arsenate. The Glutathione S-transferase activity did not increase in the exposed cells compared to control cells, suggesting that the arsenate reduction involved other metabolic pathways in the HEp-2 cells. These results confirm that, under the conditions carried out in this study, sodium arsenate is genotoxic for HEp-2 cells. Therefore, we suggest that this cell line would be a good model for the assessment of the cytotoxic and genotoxic effects of xenobiotics on human cells.

La detección temprana de eventos tóxicos inducidos por xenobióticos es necesaria para una adecuada evaluación del riesgo humano ante la exposición a dichos agentes. El objetivo de este trabajo fue evaluar a la línea celular HEp-2 como modelo experimental para determinar los efectos genotóxicos del arseniato de sodio. Para ello, se determinó la actividad metabólica de las células mediante el ensayo de MTT, en siete concentraciones de arseniato de sodio en el rango 27-135.000 μM, determinando la concentración letal media (LC50), la menor concentración de efecto observado (LOEC) y la mayor concentración de efecto no observado (NOEC) de arseniato de sodio para una exposición de 24 h. Teniendo en cuenta los datos de citotoxicidad, se evaluó el efecto genotóxico a las concentraciones 27 y 270 μM por medio del ensayo de micronúcleos y aberraciones cromosómicas, encontrando un aumento estadísticamente significativo en la frecuencia de micronúcleos entre el control y la mayor concentración arseniato de sodio ensayada. Además, la presencia de puentes nucleoplasmáticos y mitosis tripolar fue significativamente mayor en ambas concentraciones estudiadas con respecto al control. Se analizó la participación del sistema de glutatión como respuesta a la exposición al arseniato, encontrándose un aumento estadísticamente significativo en el contenido de glutatión en la concentración de arseniato de 27 μM. La actividad de la glutatión S-transferasa no aumentó, lo que sugiere que la reducción del arseniato implicó otra vía metabólica en las células HEp-2. Estos resultados confirman que el arseniato de sodio induce genotoxicidad en células HEp-2 en las condiciones realizadas en este estudio y por lo tanto este tipo de línea celular es un buen modelo para ensayos de citotoxicidad y genotoxicidad en los cuales se quiere evaluar el riesgo humano.

[SILS appendectomy for acute appendicitis - two-year experience]. / SILS apendektómia pre akútnu apendicitídu - dvojrocné skúsenosti.

INTRODUCTION: The study aims to present our two-year experience with SILS (Single Incision Laparoscopic Surgery) appendectomy in patients operated on for acute appendicitis symptoms. The results obtained were analysed and then compared with patients operated by standard laparoscopy, as well as with data available from the published literature with emphasis on safety and advantages of a new operating technique. MATERIAL AND METHODS: A retrospective analysis of patients operated on at the Third Department of Surgery, Slovak Medical University, the Kosice-Saca Hospital, a.s., in the past two years was performed. Age, sex, BMI, length of operation, post-operative hospitalization period, occurrence of pre- and post-operative complications were evaluated. RESULTS: In the period from 1 November 2009 to 31 October 2011, 116 patients were operated on by the authors, 47 of them by the SILS technique. The group included 26 males and 21 females with average age of 37.13 years (18-80) and average BMI 26.3 kg/m2 (18-47.1). Average length of the operation was 54.81 minutes (30-100). The length of post-operative hospital stay was 3.83 days (2-6). An abscess in the surgical wound was found in three patients. One patient had to be reoperated due to a pericaecal abscessed hematoma. Incisional hernia was not observed in our group. CONCLUSION: Our results are comparable with the data from international published literature and confirm that the SILS appendectomy is a safe method and represents an appropriate alternative to the standard laparoscopic technique. It is suitable for surgeons with advanced experience in laparoscopy. Apart from the excellent cosmetic effect, other advantages or disadvantages in comparison with standard laparoscopy will require confirmation by prospective randomized studies.

Genome size of two cebus species (primates: platyrrhini) with a fertile hybrid and their quantitative genomic differences.

Genome size or C-value is defined as the total amount of DNA contained within a haploid chromosome set and is regarded as a species-specific constant. Speciation among neotropical primates seems to be accompanied by marked quantitative changes in DNA content. A direct correlation between genome size and the presence of heterochromatin has also been proposed. In this work, we analyzed the genome of a female fertile hybrid between Cebus libidinosus and C. nigritus using interspecies comparative genomic hybridization (iCGH), in order to detect quantitative differences between the hybrid and the parental genomes. We also estimated the genome sizes of C. libidinosus and C. nigritus. Both species, considered subspecies of C. apella until 2001, have a highly homologous karyotype but are easily distinguishable at the chromosomal level due to the noncentromeric heterochromatin block on C. libidinosus chromosome 11. Our findings on C-value quantification support the species status for C. libidinosus and C. nigritus, each having a different genome size. The iCGH analysis of the hybrid revealed quantitative differences in comparison to both parental species. The hybrid genome contains a greater amount of DNA in the heterochromatic blocks related to those in the genomes of both parental species. In view of observations in previous and the present work, some hypotheses about genome dynamics of neotropical primates are proposed and discussed.

Chromosome painting in two genera of South American monkeys: species identification, conservation, and management.

Cytogenetic studies showed that a number of New World primate taxa, particularly the genera Alouatta, Aotus, and Callicebus, have highly derived karyotypes. Cytogenetics in these primates, at every level of analysis, has contributed to the recognition of species and revealed that their number was certainly underestimated by researchers relying solely on traditional morphological data. Further attention was drawn to Alouatta and Aotus because they are characterized by translocations of the Y chromosome to autosomes, generating multiple sex chromosome systems. Here we present a report on the hybridization of human chromosome-specific paints on metaphases from 4 individuals originally assigned to Alouatta caraya and 1 individual of Aotuslemurinus. This is only the third karyotype studied with chromosome painting out of more than 10 known karyomorphs in Aotus. The banded chromosomes matched those of karyotype II as defined by Ma et al. [1976a], and we were able to more precisely assign the origin of the sample to A. l. griseimembra. Our results on the Argentinean Alouatta caraya samples were generally comparable to the banding and hybridization pattern of previous studies of A. caraya including the presence of an X(1)X(1)X(2)X(2)/X(1)X(2)Y(1)Y(2) sex chromosome system. The karyotype of the Brazilian Alouatta sample labeled as A. caraya differs from the 3 Argentinean samples by at least 10 chromosome rearrangements. The diploid number, G banding, and hybridization pattern of this female cell line was almost identical to previous painting results on Alouatta guariba guariba. Therefore we must conclude that this cell line is actually from an A. guariba guariba individual. The contribution of cytogenetic tools in identifying species or in this case assigning individuals or cell lines to their precise taxonomic allocation is stressed. Gathering further molecular cytogenetic data on New World primates should be conservation and management priorities.

[SILS cholecystectomy--analysis of the first 100 patients]. / SILS cholecystektómia - analýza süboru prvých 100 pacientov.

AIM: The purpose of the study is to evaluate the results of the group of patients underwent SILS cholecystectomy and compare them with the literature evidence. MATERIAL AND METHODS: The retrospective analysis of the first 100 patients underwent cholecystectomy through single SILS port was performed. The operation was carried out with standard laparoscopic instruments. The average age, sex, BMI, mean operative time and the length of postoperative hospitalization were recorded. RESULTS: The sex ratio was approximately 3:1 for women. The mean age in the group was 49 years, BMI 26.8 kg/m2, operative time 63 minutes and the length of postoperative hospitalization was 2.2 days. Two intraoperative complications were observed - cystis artery bleeding and leasion of common hepatic duct. Four patients required conversion to a conventional laparoscopic cholecystectomy and one to open procedure. Three wound complications during the postoperative period was observed. CONCLUSION: The results of analysis show the SILS cholecystectomy to be a good and comparable alternative to multiport cholecystectomy in the rate of complications, the length of hospitalization and postoperative recovery. The ideal candidates for the procedure are younger patients with lower BMI without the signs of acute inflammation. The further advantages, except excellent cosmetis result, is needed to confirm in randomized studies.

Epidemiological study of pestiviruses in South American camelids in Switzerland.

BACKGROUND: In the context of the ongoing eradication campaign for bovine viral diarrhea virus (BVDV) in cattle in Switzerland, the role of South American camelids (SAC) as a possible virus reservoir needed to be evaluated. OBJECTIVE: To assess and characterize the prevalence of pestivirus infections in SAC in Switzerland. ANIMALS: Serum samples collected from 348 animals (40 herds) in 2008 and from 248 animals (39 herds) in 2000 were examined for antibodies against pestiviruses and for the presence of BVDV viral RNA. METHODS: Cross-sectional study using stratified, representative herd sampling. An indirect BVDV-ELISA was used to analyze serum samples for pestivirus antibodies, and positive samples underwent a serum neutralization test (SNT). Real-time RT-PCR to detect pestiviral RNA was carried out in all animals from herds with at least 1 seropositive animal. RESULTS: In 2008, the overall prevalence of animals positive for antibodies (ELISA) and pestiviral RNA or was 5.75 and 0%, respectively. In 2000, the corresponding prevalences were 3.63 and 0%, respectively. The seroprevalences (SNT) for BVDV, border disease virus or undetermined pestiviruses were estimated to be 0, 1.73, and 4.02% in 2008, and 0.40, 1.21, and 2.02% in 2000, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: At the present time, SAC appear to represent a negligible risk of re-infection for the BVDV eradication program in cattle in Switzerland.

Humoral response to 2 inactivated bluetongue virus serotype-8 vaccines in South American camelids.

BACKGROUND: Bluetongue virus serotype 8 (BTV-8) has caused disease in domestic ruminants in several countries of northern Europe since 2006. In 2008 a mass-vaccination program was launched in most affected countries using whole virus inactivated vaccines. OBJECTIVE: To evaluate 2 inactivated vaccines (Bovilis BTV 8; BTVPUR AlSap8) for immunogenicity and safety against BTV-8 in South American camelids (SAC) in a field trial. ANIMALS: Forty-two SAC (25 Alpacas, 17 Llamas) aged between 1 and 16 years. METHODS: The animals were vaccinated twice at intervals of 21 days. They were observed clinically for adverse local, systemic, or both reactions throughout the trial. Blood samples collected on days 0, 14, 21, 43, and 156 after vaccination were tested for the presence of BTV-8 virus by real time-polymerase chain reaction and of specific antibodies by competitive ELISA and a serum neutralization test. RESULTS: All vaccinated animals developed antibodies to BTV-8 after the 2nd administration of the vaccine. No adverse effects were observed except for moderate local swellings at the injection site, which disappeared within 21 days. Slightly increased body temperatures were only observed in the first 2 days after vaccination. The BTV was not detected in any of the samples analyzed. CONCLUSIONS AND CLINICAL IMPORTANCE: The administration of the 2 inactivated commercial vaccines was safe and induced seroconversion against BTV-8 in all vaccinated animals. The results of this study suggest that 2 doses injected 3 weeks apart is a suitable vaccination regimen for SAC.

Cebus paraguayanus and Cebus nigritus (Primates, Platyrrhini): a comparative genomic hybridization analysis.

Primate genomes show a great karyological variability while the DNA content variation is scarce. The biggest genome size occurs in Cercophitecus cephus (Catarrhini, Cercophitecidae) with 5.26 pg whereas the smallest one is described for Callicebus torquatus (Platyrrhini, Callithricidae) with 2.26 pg. Over the last 20 years different authors have been studying the Platyrrhini genomes on a chromosomal level. Among them, Cebus (Cebidae) being considered the most ancestral and conserved karyotype in relation to human karyotype has been extensively studied. Cebus genome sizes range from 3.40 to 3.98 pg. The species that inhabit Argentina, where they reach the most southern natural distribution, Cebus paraguayanus (CPA) and Cebus nigritus (CNI), have been extensively studied with classical cytogenetic comparisons focusing on banding pattern behavior. In the present study we performed comparative genomic hybridization (CGH) between these two closely related species with the aim of going a step further in the dissection of Cebus genomes. CGH evidenced that the DNA imbalances between them involved different genome regions, i.e. preferentially repetitive DNA in CPA and coding or very disperse DNA in CNI. Particularly, CNI showed species-specific DNA in more than 9 chromosomal pairs with a red/green (r/g) ratio ranging from 1.7 to 4, meaning that CNI presents at least twice as much DNA than CPA in those chromosomal segments. CPA showed species-specific DNA in the telomeric region of at least 3 chromosomal pairs with an r/g ratio of 0.5. They also showed a DNA gain in the chromosomal pairs with extracentromeric heterochromatin. Our findings modify the widespread idea of considering the heterochromatin proportion as the only difference between CPA and CNI. In Cebus then, the diversification process could be mediated by little changes in DNA content accompanied by a euchromatin-heterochromatin interaction although maintaining a minimum proportion like the one observed in CNI.

Serological survey of bluetongue virus serotype-8 infection in South American camelids in Switzerland (2007-2008).

BACKGROUND: Outbreak of bluetongue virus serotype-8 (BTV-8) infection in domestic ruminants in Northern Europe. OBJECTIVE: To investigate the South American camelids' (SAC) susceptibility to BTV-8 infection, their role in the epidemiology of the disease, and the use of currently available serological screening tests in SAC in an endemic region. ANIMALS: Three hundred and fifty-four unvaccinated and 27 vaccinated SAC (170 llamas, 201 alpacas), ranging in age from 1 month to 17 years between June and August 2008. The SAC originated from 44 herds throughout the country, representing 10% of the Swiss SAC population. METHODS: Prospective, observational study of a convenience sample of SAC. Serum samples were analyzed with 2 serological screening tests. When results diverged, a 3rd ELISA was carried out for confirmation (ID Screen Bluetongue Competition ELISA kit). RESULTS: All sera from the 354 unvaccinated animals were negative in the endemic region. Reliable seroconversion was observed after administration of 2 doses of vaccine. CONCLUSIONS AND CLINICAL IMPORTANCE: This study suggests a low susceptibility of SAC to BTV-8 despite the presence of the virus in the cattle and small ruminant population, indicating that SAC do not play a major role in the epidemiology of BTV-8. Furthermore, these results indicate that commercially available serological tests for BTV-8 can be used in SAC.

Genotoxicity of the herbicide formulation Roundup (glyphosate) in broad-snouted caiman (Caiman latirostris) evidenced by the Comet assay and the Micronucleus test.

The genotoxicity of pesticides is an issue of worldwide concern. The present study was undertaken to evaluate the genotoxic potential of a widely used herbicide formulation, Roundup (glyphosate), in erythrocytes of broad-snouted caiman (Caiman latirostris) after in ovo exposure. Caiman embryos were exposed at early embryonic stage to different sub-lethal concentrations of Roundup (50, 100, 200, 300, 400, 500, 750, 1000, 1250 and 1750microg/egg). At time of hatching, blood samples were obtained from each animal and two short-term tests, the Comet assay and the Micronucleus (MN) test, were performed on erythrocytes to assess DNA damage. A significant increase in DNA damage was observed at a concentration of 500microg/egg or higher, compared to untreated control animals (p<0.05). Results from both the Comet assay and the MN test revealed a concentration-dependent effect. This study demonstrated adverse effects of Roundup on DNA of C. latirostris and confirmed that the Comet assay and the MN test applied on caiman erythrocytes are useful tools in determining potential genotoxicity of pesticides. The identification of sentinel species as well as sensitive biomarkers among the natural biota is imperative to thoroughly evaluate genetic damage, which has significant consequences for short- and long-term survival of the natural species.

The karyotype of Alouattapigra (Primates: Platyrrhini): mitotic and meiotic analyses.

We describe for the first time the karyotype of the black howler monkey, Alouatta pigra. Conventional staining, G- and C-banding, and fluorescence in situ hybridization (FISH) with a peptide nucleic acid (PNA) pantelomeric probe were performed. Eight free ranging adult individuals, four males and four females, within the natural distribution of the species presented a diploid karyotype with 2n = 58. Mitotic analyses showed an autosomal complement composed of 6 submetacentric, 3 metacentric, and 19 acrocentric chromosome pairs for females, and 6 submetacentric, 3 metacentric, and 18 acrocentric pairs for males. Meiotic analyses in males revealed 27 autosomal bivalents and a quadrivalent composed of a submetacentric X(1) and acrocentric X(2), Y(1), and Y(2). The G-banded karyotype allowed us to identify pair #17 as the autosomal pair involved in the rearrangement and the morphology of the quadrivalent components. C-banding technique in metaphase I corroborated the structure of the quadrivalent showing four C+ centromeres. FISH analysis showed telomeric signals at the terminal regions of all chromosomes. No interstitial signals were detected. DNA sequence data were in accordance with those previously published for this species.

Caiman latirostris (broad-snouted caiman) as a sentinel organism for genotoxic monitoring: basal values determination of micronucleus and comet assay.

Caiman latirostris is one of the two crocodilian species that inhabit Argentina. In this country, as a consequence of agricultural frontiers expansion during the last years, many areas of the geographic distribution of the broad snouted caiman overlap with regions of intensive agricultural activity. Contaminants released to the environment may induce genetic alterations in wildlife, which could lead to mutations and/or carcinogenesis. Up to the moment, no studies had been made concerning the possibbility to apply biomarkers of genotoxic evaluation in C. latirostris. The aim of this study was to adapt two widely used genotoxic techniques, the comet assay and the micronucleus test, for their application in C. latirostris and to determine the baseline values in this species, in order to establish its suitability as a sentinel organism for future genotoxic monitoring of environmental pollutants. A total of 41 juvenile caimans of 4 months old (FMO) and 10 months old (TMO) were used. Genotoxic techniques were applied on peripheral blood erythrocytes introducing the necessary modifications required by the material, which are presented here. Our results show that baseline values of DNA damage are quite stable among juvenile caimans (MN: FMO animals 0.87+/-0.74 and TMO animals 1.04+/-0.92; DI: FMO animals 103.40+/-3.36 and TMO animals 120.08+/-11.33), being independent of the nest of origin, sex and size of the animals and confirm the potential value of both short term tests as accurate screening tools for the evaluation of genotoxic agents in C. latirostris. This is the first reference to the application of genotoxic techniques on C. latirostris and the second in crocodilians. Data provided here will be useful for future studies involving the biomonitoring of natural regions where C. latirostris occurs, employing this species as a sentinel organism for genotoxic assessment of environmental pollutants.

Karyological diagnosis of Cebus (Primates, Platyrrhini) in captivity: detection of hybrids and management program applications.

Genetic data are very important for conservation programs in wild population as well as in captive conditions. Primates in zoos or breeding centers are often maintained in groups without geographic origin or genetic heritage information. These lead to the incorrect assignment of species and introduce an artificial reproductive barrier, which in turn constitutes inadequate management of the colonies. A karyological analysis of specimens from a Primate Reproduction Center, considered as Cebus apella (Platyrrhini), was performed. Cell cultures were conducted from peripheral blood samples following standard cytogenetic methods. A fluorescence in situ hybridization (FISH) procedure was applied in mitotic metaphases using two probes: A specific probe of the extracentromeric heterochromatin (He+) of Cebus, and a human chromosome 21 probe. The latter was chosen due to the known homeology with the euchromatic region limiting with 11qHe+ of Cebus. The species status was determined for at least half of the animals and identified a hybrid specimen using this combined FISH protocol. This procedure is an accurate diagnostic methodology for taxonomic determinations and, therefore can be used for management of reproduction in colonies.

Genetic variability in four Alouatta species measured by means of nine DNA microsatellite markers: genetic structure and recent bottlenecks.

We used microsatellite DNA to study the population genetics of 4 Alouatta species from Central and South America. Our main findings include the following: (1) A. seniculus had the highest level of microsatellite variability while A. caraya and A. palliata had the lowest mean number of alleles per locus and the lowest expected heterozygosity, respectively; (2) the samples of A. seniculus and A. palliata came from different regions and were not in Hardy-Weinberg equilibrium (HWE) which may indicate a Wahlund effect and differentiated gene pools -- in contrast, A. macconnelli and A. caraya were in HWE; (3) the microsatellite genetic heterogeneity of the 4 Alouatta species was similar to the karyotype divergence found among these Alouatta species; the species pair with the lowest level of heterogeneity (genetic differentiation) was A. seniculus/A. caraya, while the Central American species, A. palliata, was highly differentiated from the other 3 South American species; (4) we recommend the establishment of a conservation plan to help protect A. caraya because the Cornuet and Luikart procedure demonstrated a recent bottleneck for this species.

Mitochondrial sequence diversity of the southernmost extant New World monkey, Alouatta caraya.

Variability in mitochondrial DNA sequences was analyzed in the howler monkey, Alouatta caraya, in order to delineate evolutionary relationships among populations in the most southerly distributed New World monkey. Based on new and previously published sequence data, fourteen cytochrome b haplotypes were observed among 33 howlers sampled in Argentina, Paraguay and Brazil, and grouped in two main haplogroups. In northeastern Argentina and southern Paraguay, new sequence data on 73 specimens sampled from six localities gave 34 control region haplotypes that also clustered in two main haplogroups. At this southern distribution, both mitochondrial markers revealed the presence of two sympatric and differentiated clades that we interpret to be the consequence of a secondary contact between previously allopatric populations. Given evidence for a demographic expansion at the beginning of the Holocene 15,500-7000 years ago (Fu's test, F(S)=-12.137; P<0.001), we suggest that atleast two populations of A. caraya have colonized the southernmost range since the Holocene employing forested corridors on the Paraná and Paraguay Rivers.

Chromosomal localization of the telomeric (TTAGGG)n sequence in eight species of New World Primates (Neotropical Primates, Platyrrhini).

Chromosomal localization of the telomeric sequence (TTAGGG)(n) in eight New World Primates (Platyrrhini) (Alouatta caraya, Alouatta palliata, Alouatta guariba clamitans, Aotus azarae, Ateles chamek, Cebus nigritus, Cebus paraguayanus, and Saimiri boliviensis) using Fluorescence In Situ Hybridization (FISH) with a peptide nucleic acid (PNA) pantelomeric probe and their possible relationship with the C-banding pattern were analyzed. FISH showed telomeric signals only at the terminal regions of chromosomes from all the species analyzed. Although all of them showed centromeric C+ bands and different size and location of extracentromeric C+ bands, none, except Aotus azarae exhibited (peri)centromeric interstitial telomere-like sequences (ITS). The presence of ITS in Aotus azarae was limited to one pair of submetacentric chromosomes and very likely represents telomeric sequences remaining after a fusion event of ancestral chromosomes during karyotype evolution. Therefore, our data indicate that the distribution of heterochromatin blocks do not correlate with the presence of ITS. However, we cannot rule out the possibility that simple ITS arrays with a few copies of the (TTAGGG)(n) sequence, not detectable by conventional FISH, might play a role in the karyotypic evolution of Ceboidea. Further FISH and molecular studies will be needed to confirm this hypothesis.

Genotoxic and aneugenic properties of an imidazole derivative.

To contribute to a more accurate characterization of the mutagenic and aneugenic effects of thiabendazole (TBZ), a widely used antiparasitic and food preservative drug, the induction of sister chromatid exchanges (SCEs) and mitotic spindle anomalies as cytogenetic end-points were investigated. Studies were carried out in Chinese hamster ovary (CHO) cells and human peripheral blood lymphocytes. A significant dose-dependent increase in SCE frequency was observed in CHO cells with S9-Mix (P < 0.01) in the 50-100 microg ml(-1) dose-range, while in the absence of S9-Mix, an enhancement of the SCE frequency was exhibited at the highest dose (P < 0.01). In CHO-K1 cells a significant increase in mitotic spindle anomalies (P < 0.01) was observed with the highest concentration assayed reflecting the specific effect of TBZ formulation at the microtubule level. Cell proliferation kinetics (CPK) were not modified by the addition of this pharmaceutical product. In human lymphocyte cultures, exposure to 100 microg ml(-1) TBZ formulation resulted in a significant decrease of the mitotic index (MI) (P < 0.003) and changes in the replication index (RI) (P < 0.05).

Heterochromatin and chromosome evolution: a FISH probe of Cebus apella paraguayanus (Primate: Platyrrhini) developed by chromosome microdissection

Neotropical Primate karyotypes are highly variable, particularly in the heterochromatic regions, not only regarding the amount of heterochromatin, but also the composition. G and C banding and FISH techniques provide useful information to characterize interspecific relationships. We used chromosome microdissection to develop a FISH probe of the chromosome 11 heterochromatic block (11qHe+) of Cebus apella paraguayanus (CAPp). Fragments of the 11qHe+ microdissected from fibroblast cell culture were collected in a PCR tube, amplified by degenerate oligonucleotide primer-PCR and subsequently labeled. The specificity of the FISH probe was confirmed in metaphases of some Ceboidea species. Signals were located in the He+ of chromosomes 4, 11, 12, 13, and 19 of CAPp and in the He+ of chromosomes 4, 12 and 13 of C. a. nigritus (CAPn); no signals were observed when other Ceboidea species were analyzed. We propose that the heterochromatin observed in CAPp and CAPn is specific for these species. We consider this C. apella heterochromatin identity as a possible key for the interpretation of chromosomal evolution in these Ceboidea.

Teratogenic evaluation of metronidazole and ornidazole using Drosophila melanogaster as an experimental model.

BACKGROUND: Drosophila and vertebrates show similarities that suggest that the mechanisms involved in the induction of developmental defects may be similar in both. Therefore, Drosophila has been proposed as a useful, rapid, and economical model in the preliminary screening for teratology studies. The objective of the present study was to investigate the effect of metronidazole (MTZ) and ornidazole (ONZ) on the developmental stages of Drosophila melanogaster. METHODS: Samarkand wild-type females were allowed to lay eggs for 24 hr in media containing MTZ or ONZ at concentrations of 0, 500, 1000, and 2000 microg/ml. When larvae completed their development, the emerging flies were counted and examined for morphological abnormalities. RESULTS: After the analysis of 400-1000 flies for each concentration, ONZ-treated flies did not show an incidence of malformations above control values, although a significant high number of individuals with reduced body size was observed (p < 0.005, chi2 test). On the other hand, the 1000- and 2000-microg/ml MTZ-treated series presented higher frequencies of total abnormalities than did concurrent and historic controls (p < 0.05, chi2 test), indicating an MTZ effect during developmental morphogenesis. CONCLUSIONS: These findings contribute to the characterization of both nitroimidazoles, which are widely used, especially in underdeveloped countries. At the same time, this Drosophila bioassay is sensitive enough to detect differential effects of MTZ and ONZ (abnormalities vs. growth effects), showing specificity and selectivity.