RESUMO
A synergistic effect in the somatotropic axis (GH1-GHR-IGF1) was observed in 736 young Nelore (Bos indicus) bulls under ad libitum grass feeding conditions on irrigated pasture in central Brazil. Stepwise substitution of shorter alleles of the promoter region of the growth hormone gene (GH1) and the P1 promoter of the GH1 receptor gene (GHR) with longer alleles was associated with significantly increased body weight gain (W550, weight at age 550 days; ADG, average daily gain) and fat accrual (FAT, rib eye fat thickness). A threshold effect on ADG was associated with allele size variation at the GH1. A best fit model indicated a 3- to 6-fold effect of GH1 variation on ADG, when compared to the variation at the GHR and a known microsatellite at the somatomedin gene (IGF1, insulin-like growth factor 1). A threshold effect on FAT was associated with substitution of the short GHR allele by the longer GHR alleles; the effect of the GHR variation on FAT was 10-fold that of the variation at the GH1 and IGF1 loci. Among the 10 GH1-GHR-IGF1 multi-genotypes identified, the predominant genotype was homozygous for the large GH1 promoter (long/long, G2/G2 or domestic type), short GHR promoter (short/short or wild type), and short IGF1 microsatellite (short/short or wild type). This predominant multi-genotype suggests that selection pressure in the Nelore breed has been directed towards high ADG and W550, and low FAT. Our results mirror previous findings in the oMtla-oGH transgenic mouse model, in which the level of somatotropic gene expression acts through a threshold mechanism, and low expression results in adipogenesis, while high expression increases body growth.
Assuntos
Adiposidade/genética , Bovinos/genética , Hormônio do Crescimento/genética , Regiões Promotoras Genéticas , Receptores da Somatotropina/genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Animais , Cruzamento , Bovinos/crescimento & desenvolvimento , Frequência do Gene , Estudos de Associação Genética , Variação Genética , Genótipo , Fator de Crescimento Insulin-Like I/genética , Masculino , Polimorfismo de Fragmento de Restrição , Aumento de Peso/genéticaRESUMO
Growth hormone (GH) is a part of the somatotropic axis that controls metabolism, growth, development and aging in a wide range of animals. Mutations that reduce GH signaling have been associated with extended life spans and increased longevity in ways similar to what is observed in dietary restriction (DR) models. However, the mechanism by which DR works is not well understood. Here, we show that DR works as a factor in the evolution of the genetic make-up of domestic cattle. In a series of 6864 bovines of seven Bos indicus and tropically adapted Bos taurus breeds, the frequency of a short, wild-type allele of the promoter region of the bovine GH gene, G1 allele, varied from 2.7 to 17.7%. The frequency of the long, domestic G2 allele increased from 88 to 95% along 20 calf crops of commercial Bos indicus cattle of the Nelore breed undergoing selection for increasing post-weaning weight gain with ad libitum nutrient intake. Under DR, however, the G1 allele sustained growth better than the G2 allele, as observed in a series of feeding tests. The G2 allele was even detrimental or abiotropic, as it caused rapid body decay under DR. We observed a reflection symmetry of GH allele substitution effects on body weight under different dietary schemes. The G2 allele is featured as the "demanding allele", because it is optimally fitted to ad libitum nutrient intake. The G1 allele is featured as the "thrifty allele" because it is optimally fitted to DR. Our results show that dietary regimens need not extend lifespan or increase longevity in the sense of age-specific fitness. Instead, adaptation to any particular dietary regimen is just as much a consequence of selection as its cause; dietary regimens work as do any selection force, optimizing genotypic fitness to nutritional conditions.
Assuntos
Hormônio do Crescimento/genética , Modelos Genéticos , Alelos , Animais , Peso Corporal/genética , Bovinos , Dieta , Genótipo , Análise dos Mínimos Quadrados , Funções Verossimilhança , Mutação , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , Aumento de PesoRESUMO
The aim of the present article was to study the population structure and genetic diversity of Nelore cattle and genetic relationships between Nelore and different taurine and zebu breeds raised in Brazil. DNA polymorphism analysis was carried out with 1976 animals of 16 zebu, taurine and synthetic breeds raised in Brazil. A higher genetic differentiation was observed in taurine than in zebu cattle. Gene flow was intense between the different zebu populations. Genetic affinity analysis within the most conspicuous Brazilian zebu beef cattle, the Nelore, was carried out in a group of 615 animals from 15 representative herds. This analysis revealed at least two major Nelore subtypes, named after some genotype-phenotype associations such as the "thrifty type" and the "demanding type". This study provides molecular genetic evidence that, despite selection based on the phenotype, gene flow and gene segregation still play a major role in maintaining genetic variability within the Nelore and zebu population as a whole in Brazil.
Assuntos
Bovinos/genética , Variação Genética , Animais , Brasil , Cruzamento , Fluxo Gênico , Genética Populacional , Genótipo , Repetições de Microssatélites , Fenótipo , Seleção GenéticaRESUMO
Levels of mtDNA(4977) deletions (DeltamtDNA(4977)) have been found to be lower in tumors than in adjacent non-tumoral tissues. In 87 cancer patients, DeltamtDNA(4977) was detected by multiplex polymerase chain reaction (PCR) amplification in 43 (49%) of the tumors and in 74 (85%) of the samples of non-tumoral tissues that were adjacent to the tumors. DeltamtDNA(4977) deletions were detected in 24% of the breast tumors, 52% of the colorectal tumors, 79% of the gastric tumors, and 40% of the head and neck tumors as compared with 77, 83, 100, and 90% of the adjacent respective non-tumoral tissues at the same DNA template dilution. Based on limiting dilution PCR of 16 tumors and their adjacent non-tumoral tissues, it was found that the amount of DeltamtDNA(4977) was 10- to 100-fold lower in the tumor than in the respective control non-tumoral tissues. Real-time PCR experiments were performed to quantify the number of DeltamtDNA(4977) deletions per cell, by determining the mitochondrial-to-nuclear DNA ratio. In all of the cases of breast, colorectal, gastric, and head and neck cancer the proportion of DeltamtDNA(4977) in tumors was lower than that of the respective non-tumoral tissue. Traces of DeltamtDNA(4977) in tumors were apparently due to contamination of tumor tissue with surrounding non-tumoral tissue, as evidenced by tumor microdissection and in situ PCR techniques, suggesting that tumors are essentially free of this mutation. Although the metabolic effect of DeltamtDNA(4977) may be minimal in normal (non-tumor) tissue, in tissue under stress, such as in tumors, even low levels of DeltamtDNA(4977) deletions may be intolerable.
Assuntos
Feminino , Humanos , Deleção de Sequência/genética , Mutação/genética , Neoplasias Colorretais/genética , Neoplasias Gástricas/genética , Neoplasias da Mama/genética , Neoplasias de Cabeça e Pescoço/genética , Estudos de Casos e Controles , DNA Mitocondrial/genética , Reação em Cadeia da Polimerase , Células Tumorais CultivadasRESUMO
We developed, and quantitatively and qualitatively evaluated an easily reproducible method for high yield purification of mitochondrial DNA (mtDNA) from human placentae by mechanical tissue disruption, differential centrifugation of mitochondria, enzymatic digestion, phenol extraction and ethanol precipitation. Average mtDNA yields were 2.5 microg/g tissue (without an RNAse treatment step) and 1.5 microg/g tissue (with an RNAse treatment step). This mtDNA migrated as a 16.5-kb isolated band in agarose gels; it yielded fragments of expected sizes after digestion with restriction enzymes; it successfully served as a template in long PCR for amplification of mtDNA sequences, and hybridized to an mtDNA probe in a predictable fashion. MtDNA yields of this method were 10-fold higher than those of previously reported ones for mtDNA purification from freshly obtained human cells and tissues, with the advantage that more placental tissue can be obtained for mtDNA purification than other types of tissue, at lower cost, and with minimal or no ethical issues
Assuntos
Humanos , DNA Mitocondrial/isolamento & purificação , Placenta , Sequência de Bases , Enzimas de Restrição do DNARESUMO
We developed a model system for testing gene vectors, based on the growth of murine tumors on the chorioallantoic membrane (CAM) of embryonic chickens. The ability of selected murine cells to grow on the CAM was rated according to the following criteria: i) formation of tumor masses; ii) metastasis formation; iii) reproducibility; iv) yield, indicated as the number of embryos surviving to assessment time with visible tumors on the CAM; v) maintainability of the cell, both in the original host and the embryonic chick, or 'shuttle maintainability'; vi) detection by the naked eye, and vii) cost/benefit relation. The murine melanoma cell lineage, B16F10, which efficiently forms distinct, pigmented tumor masses and metastases on the CAM, performed better in this model than the murine B61 cell line. In vitro transduction of B16F10 cells with a recombinant adenovirus carrying a construct of the E. coli LacZ gene followed by inoculation onto the CAM resulted in beta-galactosidase expression in the tumor mass growing on the CAM. This model is potentially applicable to preclinical evaluation of gene vectors, especially for gene therapy of cancer
Assuntos
Humanos , Animais , Adenoviridae/genética , Vetores Genéticos , Melanoma Experimental/patologia , Alantoide , Embrião de Galinha , Córion , Análise Custo-Benefício , Células Tumorais Cultivadas/patologia , Camundongos , Melanoma Experimental/genética , Reprodutibilidade dos TestesRESUMO
Gene therapy is the treatment of diseases based on the transfer of genetic information. Agents that carry or deliver DNA to target cells are called vectors (Latin vector: carrier, deliverer). Ideally, a vector should accommodate an unlimited amount of inserted DNA, lack the ability of autonomous replication of its own DNA, be easily manufactured, and be available in concentrated form. Secondly, it should have the ability to target specific cell types or to limit its gene expression to specific cell types, and to achieve sustained gene expression in the long term or in a controlled fashion. Finally, it should not be toxic or immunogenic. Such a vector does not exist and none of the DNA delivery systems so far available for in vivo gene transfer is perfect with respect to any of these points. Gene therapy and the means to promote it depend heavily on the development and improvement of new gene vector systems.
Assuntos
Técnicas de Transferência de Genes , Terapia Genética , Vetores Genéticos , Vírus/genética , DNARESUMO
Gene therapy is the treatment of diseases based on the transfer of genetic information. Agents that carry or deliver DNA to target cells are called vectors (Latin vector: carrier, deliverer). Ideally, a vector should accommodate an unlimited amount of inserted DNA, lack the ability of autonomous replication of its own DNA, be easily manufactured, and be available in concentrated form. Secondly, it should have the ability to target specific cell types or to limit its gene expression to specific cell types, and to achieve sustained gene expression in the long term or in a controlled fashion. Finally, it should not be toxic or immunogenic. Such a vector does not exist and none of the DNA delivery systems so far available for in vivo gene transfer is perfect with respect to any of these points. Gene therapy and the means to promote it depend heavily on the development and improvement of new gene vector systems
Assuntos
Técnicas de Transferência de Genes , Terapia Genética , Vetores Genéticos , Vírus/genética , DNARESUMO
Neuronal size and the incidence of neuritic plaques (NPs) and neurofibrillary tangles (NFTs) were morphometrically and quantitatively studied in the entorhinal cortex of 300 autopsied individuals without dementia in three geographically distinct series (Brazil, Germany and Japan), and an additional series including 30 clinically diagnosed Alzheimer's disease patients. The mean ages at onset of NPs and NFTs were similar between the three normal series, and the incidence of NPs and NFTs increased exponentially with age, but at different rates. A correlation was found between larger neuronal size and higher incidence of NPs and NFTs. Neuronal size distribution largely seemed to account for the differences between the series. While the onset of neurodegeneration may be tightly programmed, i.e., in a species-specific manner, our data support the idea that the incidence of NPs and NFTs and the progression from NPs to NFTs may vary remarkably, depending on neuronal size.
Assuntos
Envelhecimento/psicologia , Encéfalo/patologia , Neuritos/ultraestrutura , Emaranhados Neurofibrilares/patologia , Neurônios/ultraestrutura , Adulto , Idoso , Encéfalo/citologia , Encéfalo/ultraestrutura , Brasil , Núcleo Celular/ultraestrutura , Tamanho Celular , Feminino , Alemanha , Humanos , Japão , Masculino , Pessoa de Meia-Idade , Degeneração Neural/fisiologia , Tamanho do Órgão/fisiologiaRESUMO
This morphometric, quantitative and correlative multivariate study of the hippocampal formation in human brains from two distinct normal aging populations provides an additional support to the notion that neuritic plaques (NP) are an earlier stage of the pathological process underlying neurofibrillary tangle (NFT) formation. It is shown that the rate of transformation of NP-affected neurons into NFT-bearing neurons may vary remarkably between distinct populations. In addition, it is put forward that different rates of neuronal degeneration may be one of the explanations for the existence of conflicting hypotheses regarding pathogenesis of NP and NFT and the relationships of these important histological markers to psychical deterioration.