RESUMO
We investigated the relationship between satellite copy number and chromosomal evolution in tuco-tucos (genus Ctenomys), a karyotypically diverse clade of rodents. To explore phylogenetic relationships among 23 species and 5 undescribed forms, we sequenced the complete mitochondrial cytochrome b genes of 27 specimens and incorporated 27 previously published sequences. We then used quantitative dot-blot techniques to assess changes in the copy number of the major Ctenomys satellite DNA (satDNA), named RPCS. Our analysis of the relationship between variation in copy number of RPCS and chromosomal changes employed a maximum-likelihood approach to infer the copy number of the satellite RPCS in the ancestors of each clade. We found that amplifications and deletions of RPCS were associated with extensive chromosomal rearrangements even among closely related species. In contrast, RPCS copy number stability was observed within clades characterized by chromosomal stability. This example reinforces the suspected role of amplification, deletion, and intragenomic movement of satDNA in promoting extensive chromosomal evolution.
Assuntos
Cromossomos/genética , DNA Satélite/genética , Roedores/genética , Animais , Aberrações Cromossômicas , Grupo dos Citocromos b/genética , DNA/química , DNA/genética , DNA Mitocondrial/química , DNA Mitocondrial/genética , Evolução Molecular , Amplificação de Genes , Deleção de Genes , Dosagem de Genes , Dados de Sequência Molecular , Filogenia , Roedores/classificação , Análise de Sequência de DNA , Especificidade da EspécieRESUMO
Variation in the nucleotide sequence of the entire mitochondrial cytochrome b gene (1140 bp) was examined for 27 individuals representing 13 species of South American rodents of the genera Ctenomys, Octodontomys, Tympanoctomys, and Spalacopus. Representatives of the family Echimyidae, Euryzygomatomys and Mesomys, were used as outgroups to test the monophyly of the Octodontinae and Ctenomyinae. Relationships among species of tuco-tucos (genus Ctenomys) were also examined including representatives of the three described subgenera and the two sperm morphs. Reciprocal monophyly of the Octodontinae and Ctenomyinae is strongly supported. Several basal relationships among species of the genus Ctenomys are poorly resolved, suggesting the possibility of a hard polytomy due to a rapid and potentially simultaneous radiation early in the history of the genus. In other cases, clades within the Ctenomyinae previously identified on the basis of allozymes, chromosomes, parasites, or skull morphology were supported. Calibrations based on the fossil record suggest that the mitochondrial cytochrome b of these caviomorphs has evolved at a rapid rate, comparable to those proposed for Mus-Rattus, and three to four times higher than ungulate rates.
Assuntos
Evolução Molecular , Filogenia , Roedores/genética , Animais , Composição de Bases , Grupo dos Citocromos b/análise , Grupo dos Citocromos b/genética , DNA Mitocondrial/análise , DNA Mitocondrial/genética , Variação Genética , Dados de Sequência Molecular , RatosRESUMO
Genome size (the amount of DNA per cell) was measured by flow-cytometric analysis in seven species of a chromosomally variable rodent genus: Ctenomys boliviensis, C. conoveri, C. frater, C. leucodon, C. lewisi, C. opimus, and C. steinbachi. The mean genome size of these species was 7.19 pg DNA and little inter- and intra-specific variation was observed. Genome size was not correlated with diploid number, suggesting that chromosomal evolution at this level is independent of total DNA content. A hypothetical taxonomic unit optimization procedure was carried out using genome size change on a Wagner tree derived from allozyme data. Allozyme evolution and genome size change are linked by a weak, but significant, negative correlation suggestive of preferential genic evolution in the absence of genome size evolution.
Assuntos
Evolução Biológica , Genoma , Roedores/genética , Animais , Bolívia , Cromossomos , DNA/análise , DNA/genética , Variação Genética , Filogenia , Especificidade da EspécieRESUMO
Between 1970 and 1975, the incidence of new Schistosoma mansoni infections was reduced in 5 villages after each household was provided with its individual water supply and community laundry shower units were made available. In 1975, 1976, and 1977 chemotherapy with oxamniquine was offered to persons found to be infected. Transmission was reduced further and remained at a low level for the next 4 years, with no sign of an increase in spite of the reservoir of infection remaining after therapy and a poor level of sanitation in the villages.Thus, properly maintained water supplies appear to be effective in maintaining transmission at a low level during the maintenance phase of a schistosomiasis control programme, after chemotherapy. Sporadic new infections must be anticipated among children, but these will probably be of low intensity and associated with minimal morbidity.
Assuntos
Esquistossomose/prevenção & controle , Abastecimento de Água/normas , Adolescente , Adulto , Animais , Criança , Pré-Escolar , Humanos , Lactente , Pessoa de Meia-Idade , Oxamniquine/uso terapêutico , Saneamento , Schistosoma mansoni , Índias OcidentaisRESUMO
After an intensive area-wide mollusciciding campaign, over four and a half years, transmission of Schistosoma mansoni was reduced. A cheaper scheme suitable for the follow-up or consolidation stage of control was evaluated and two selective population chemotherapy campaigns using hycanthone (2 mg/kg b.w.) and oxamniquine (15 mg/kg b.w.) were mounted. Prevalence dropped to 6% and 3% in areas with previously high and low levels of transmission respectively. Calculations suggested that these figures were falsely low and that perhaps 20% of the population were still excreting S. mansoni ova in small numbers. The unco-operative groups in the population are probably more important in maintaining a reservoir of infection in the community than persons with light infections undetected by the sedimentation concentration stool examination technique used. The benefit of more sensitive but more costly examination techniques is not clear since the importance of very light infections in transmission is uncertain. Case detection absorbs an increasing proportion of the total cost of chemotherapy programmes with fewer cases being found amongst the same number screened. Using hycanthone (649 treated) the cost per person protected was $0.74 and using oxamniquine (264 treated) $0.94. The need to develop low cost consolidation or follow-up procedures for preventing a resurgence of transmission after successful control, when the infection is no longer of public health importance, is stressed.
Assuntos
Controle de Pragas/métodos , Esquistossomose/prevenção & controle , Fezes/parasitologia , Humanos , Hicantone/uso terapêutico , Moluscocidas , Oxamniquine/uso terapêutico , Controle de Pragas/economia , Schistosoma mansoni , Esquistossomose/transmissão , Índias OcidentaisRESUMO
A serological survey of a random sample of 541 of the population of St Lucia was undertaken. The prevalence of antibodies to dengue, herpes virus, VZ, rotavirus, rubella and syphilis is described and compared with other communities.
Assuntos
Anticorpos Antivirais/imunologia , Adolescente , Adulto , Fatores Etários , Idoso , Barbados , Criança , Pré-Escolar , Citomegalovirus/imunologia , Vírus da Dengue/imunologia , Feminino , Inquéritos Epidemiológicos , Herpesviridae/imunologia , Herpesvirus Humano 3/imunologia , Herpesvirus Humano 4/imunologia , Humanos , Técnicas Imunológicas , Lactente , Masculino , Pessoa de Meia-Idade , Rotavirus/imunologia , Vírus da Rubéola/imunologia , Sorodiagnóstico da Sífilis , Índias OcidentaisRESUMO
Plasma samples from St. Lucians were tested for the presence of antibodies which cooperate in vitro with normal human leukocytes in causing cytotoxic damage to schistosomula of Schistosoma mansoni. The in vitro antibody activity, which has been previously shown to depend on eosinophil effector cells was detected in 56% of the individuals with known, current S. mansoni infections and in 14% of control subjects from the same endemic area. Quantitatively, eosinophil dependent cytotoxic antibody (EDCA) activity, when expressed as the maximum amount of damage to schistosomula induced at high plasma concentration, correlated significantly with the intensity of S. mansoni infection as determined by fecal egg count, the highest levels of activity occurring in patients with stool counts of 60 eggs/ml or greater. In addition, plasma EDCA activity was found to correlate with the in vitro blastogenic responsiveness of patients' lymphocytes to three different parasite antigen preparations. In contrast, titrations of EDCA activity failed to reveal a relationship between EDCA titer and the most recent egg count performed on each subject. However, a significant correlation was observed when titers were compared to egg counts averaged over a 3-year period. Neither maximal EDCA activity nor titer was found to correlate with the duration of known schistosome infection.
Assuntos
Anticorpos/análise , Testes Imunológicos de Citotoxicidade , Eosinófilos/imunologia , Esquistossomose/imunologia , Humanos , Ativação Linfocitária , Contagem de Ovos de Parasitas , Schistosoma mansoni , Fatores de Tempo , Índias OcidentaisRESUMO
Control of Schistosoma mansoni transmission solely by treatment of all infected persons was attempted in Marquis Valley (population about 3,100), St. Lucia. Two-year results are reported. Excluding 26 pregnant patients, 709 to 729 persons who were found to be infected received treatment the first year. Most of these, 677, were given a single injection of hycanthone (2.5 mg/kg of body weight), and the same treatment was administered to 159 patients the second year. Side effects were not severe; the major side effect, vomiting, occurred in about 22% on both occasions. In villages with initially high transmission rates, the incidence of new infections in children 0 to 14 years fell from 20.8% before chemotherapy to 7.4% after 1 year and to 3.7% after 2 years. This pattern was significantly different from that in the comparison area where no control scheme exists. Chemotherapy alone appears to be a rapid, effective, and comparatively inexpensive method of controlling S. mansoni transmission in St. Lucia.
Assuntos
Hicantone/uso terapêutico , Niridazol/uso terapêutico , Nitroquinolinas/uso terapêutico , Oxamniquine/uso terapêutico , Esquistossomose/prevenção & controle , Tioxantenos/uso terapêutico , Adolescente , Adulto , Criança , Pré-Escolar , Custos e Análise de Custo , Feminino , Humanos , Lactente , Masculino , Schistosoma mansoni , Esquistossomose/tratamento farmacológico , Esquistossomose/epidemiologia , Índias OcidentaisAssuntos
Hicantone/uso terapêutico , Esquistossomose/tratamento farmacológico , Tioxantenos/uso terapêutico , Adolescente , Animais , Criança , Ensaios Clínicos como Assunto , Enzimas/sangue , Feminino , Humanos , Hicantone/efeitos adversos , Masculino , Contagem de Ovos de Parasitas , Schistosoma mansoni , Índias OcidentaisRESUMO
A relatively simple, standardized hatching test was devised, tested and used to estimate the Schistosoma mansoni hatching rate for 88 St Lucian subjects selected by age, sex and intensity of infection. The hatching rate was dependent on the intensity of infection and rose proportionately with it. The rate also decreased with increasing age of the subject. Sex alone had no direct effect but there was a suggestion of an interaction between sex and age. These results suggest that several hatching tests are necessary, before and after treatment in schistosomicidal drug trials, to permit valid conclusions to be drawn. The hatching data are used in conjunction with survey results to calculate the contamination potential of different age groups in a population. School children (5-14 years old) are about twice as important as young adults (15-29 years old) who, nevertheless, contribute over a quarter of the total contamination potential. However, whereas school children are fairly accessible for mass chemotherapy control programmes, young adults often are not and, furthermore, involve problems associated with the treatment of women of child-bearing age.