Testes genéticos em diagnóstico pré-natal: onde estamos, para onde vamos / Prenatal genetic testing: where we are at, where we are heading to

Este texto tem como objetivo apresentar uma revisão acerca do estado da arte da citogenética convencional e molecular aplicada ao diagnóstico pré-natal, discutindo as aplicações, vantagens e desvantagens dos diferentes métodos, em suas bases teóricas e históricas. Desde 1960, a citogenética convencional, com a análise microscópica dos cromossomos em divisão, vem sendo utilizada como padrão ouro. Entretanto, mesmo adotando essa abordagem, para uma significativa parcela de casos não é possível estabelecer diagnóstico sindrômico definitivo em cerca de metade dos pacientes que apresentam cariótipo normal, na presença de malformações. Para esse grupo, as técnicas moleculares que envolvem estudos em nível genômico poderiam permitir a identificação de novos microarranjos cromossômicos possivelmente responsáveis pelo fenótipo anormal, contribuindo para a caracterização molecular e estabelecimento de um diagnóstico mais preciso, uma abordagem perinatal mais adequada e um aconselhamento genético mais detalhado. Destaca-se o advento das técnicas de FISH, SKY, CGH e array CGH como promissoras aliadas, de forma complementar ao cariótipo convencional

This paper aims at presenting a review of the state of the art of conventional and molecular cytogenetics applied to prenatal diagnosis, the applications, pros and cons of different techniques and their historical and theoretical background. Since 1960, conventional cytogenetics, based on the analysis of chromosomes has been used as a gold standard. However, for a significant proportion of cases it is not possible to establish definitive syndromic diagnosis in about half of the patients with normal karyotype in the presence of malformations. For this group, molecular techniques at the genomic level might allow the identification of new chromosomal areas potentially responsible for the abnormal phenotype, contributing to the molecular characterization and establishment of a more accurate diagnosis and the most appropriate perinatal approach, including a more detailed genetic counseling. The advent of FISH techniques, SKY, CGH and array CGH will be discussed as promising tools to complement cytogenetic diagnosis based on conventional karyotyping

Principles of complementary medicine in terms of a suggested scientific basis.

In order to create a scientific basis of complementary medicine it is certainly necessary to add a more non-local approach to the molecular substance of orthodox "life-sciences". It should be able to explain strange phenomena like healing by homeopathy or acupuncture. A possible frame concerns oscillatory electromagnetic interactions as regulatory and - in case of disease--deregulatory impulses of the organisms. These couplings are found, for instance, in biological rhythms, external rhythmical influences (sun exposure, atmospheric disturbances), and vibrations of the body over a huge range of frequencies. One basic example is biophotons and "delayed luminescence".

Cytogenetic analysis and description of the sexual chromosome determination system ZZ/ZW of species of the fish genus Serrapinnus (Characidae, Cheirodontinae)

Four populations of Serrapinnus notomelas and one population of Serrapinnus sp.1, both belonging to the subfamily Cheirodontinae, were analyzed by Giemsa and silver nitrate impregnation techniques. We found 2n = 52 chromosomes for all populations, with interspecific differences in the karyotype formula; S. notomelas showed 16m + 22sm + 10st + 4a, with fundamental number (FN) = 100 for males, and 16m + 23sm + 10st + 3a, with FN = 101 for females. Serrapinnus sp.1 had 8m + 16sm + 4st + 24a, with FN = 80 for males, and 8m + 15sm + 4st + 25a, with FN = 79 for females. The difference in FN for the two sexes is due to a pair of heteromorphic chromosomes in the females of both species, which characterizes a ZZ/ZW-type mechanism of chromosome sexual determination. Interspecies differences were also found in nucleolus organizer regions (NORs). A simple NOR system was detected in three of four S. notomelas populations, while Serrapinnus sp.1 had two chromosome pairs with NOR. Although S. notomelas and Serrapinnus sp.1 have the same diploid number, differences in the karyotype structure indicate that these are different species. Apparently there was pericentric inversion during the karyotype evolution of these species.

Preponderance of GC-rich sites in silver-stained nucleolus organizing regions of Rita rita (Hamilton) and Mystus gulio (Hamilton) (Bagridae, Pisces), as revealed by chromomycin A3-staining technique and scanning electron microscopic studies

The karyotypes of two species of catfish, Rita rita (Hamilton) (2n = 54; 14m + 34sm + 6st; NF = 102) and Mystus gulio (Hamilton) (2n = 58; 30m + 12sm + 2st + 14t, NF = 100) were studied through Giemsa-, silver- and chromomycin A(3)-staining techniques. The silver-stained karyotypes in both sexes of R. rita and M. gulio revealed that the nucleolus organizing regions were located terminally at the shorter arms (Tp) of one pair of submetacentric chromosomes, placed at positions Nos. 2 and 1, respectively, which was confirmed by scanning electron microscopy. Staining with a GC-specific fluorochrome, chromomycin A(3), produced bright fluorescence in the Ag-positive nucleolus organizer regions, suggesting thereby that nucleolus organizing regions actually included GC-rich sites of active r-RNA genes in metaphase chromosomes of these two bagrids. Further such studies are needed due to the extreme paucity of data on fish.

Chromosome number in the Triatominae (Hemiptera-Reduviidae): a review

The chromosome numbers of 46 out of the 122 currently recognized species of Triatominae (Hemiptera, Reduviidae) are summarized. We present the number of autosomes, the sex mechanism and the first reference for each karyotype.

Detección de heterocigotos de ataxia telangiectasia por la sensibilidad a la radiación ionizante / Detection of heterocygotic with patients with ataxia telangiectasia show chromosomic rupture

Investigaciones recientes han demostrado que los pacientes homocigotos y heterocigotos de ataxia telangiectasia (AT) tienen rompimientos cromosómicos. De acuerdo con esta característica se diseñó el estudio inducido rompimientos cromosómicos en células granulocíticas de pacientes con diagnóstico de AT, heterocigotos obligados de AT y comparados con un grupo de individuos sanos. A todos los pacientes se les cuantificó el número de rompimientos cromosómicos con 14 dosis de radiación 125 kv, 125 mA. Los resultados sugieren diferencias significativas en el número de alteraciones estructurales cromosómicas inducidas por la radiación en los granulocitos de heterocigotos de ataxia telangiectasia similares a las alteraciones estructurales de los linfocitos de pacientes con AT y se demuestra que estas alteraciones se presentan preferentemente en un cromosoma del grupo C de homocigotos y heterocigotos de AT

Induction and characterization of premature chromosome condensation in Drosophila synkaryons and implications to dosage compensation.

Premature chromosome condensation (PCC) was induced in Drosophila melanogaster cell hybrids, with Drosophila mitotic cells and interphase cells at different phases (G1,G1-S,S,S-G2 of the cell cycle, and from male and female, using standard cell fusion technique with polyethylene glycol (PEG). A combination of Feulgen and autoradiography was used to enhance the resolution of the PCC plates. It was possible to identify the characteristics of PCC's at G1, S and G2, and the transitory intermediate phases, which are comparable with respect to the characteristics of PCC's previously described for other species. Using the combined Feulgen-autoradiography technique it was possible to critically resolve the different phases including the transitory intermediate phases in greater detail. Analysis and comparison of results obtained from M (female) x S (female/male) and M (female) x G2 (female/male) hybrids have revealed that the X chromosome from the male could be identified as a distinct acrocentric entity which showed clear allocyclic, heteropycnotic characteristics. The results thus lead us to suggest that the X chromosome in such synkaryons is indeed early replicating as is the X chromosome of male larval salivary gland of Drosophila. The X chromosome morphology is also distinctly at an advanced stage of the cell cycle. On the basis of these findings it is concluded that X chromosome is hyperactive in the normally dividing diploid cells.

Estudio citogenético en 22 adultos y tres niños con leucemia linfoblástica aguda / Cytogenetic study in 22 adults and therr children with acute lymphoblastic leukemia

Se presentan los resultados del estudio citogenético realizado en sangre periférica y/o médula ósea de 25 pacientes (22 adultos y 3 niños) con LLA estudiados entre 1987 a 1990. Todos los casos presentaron alteraciones cromosómicas (25/25), aunque en 23 pacientes (23/25) estaba presente una línea celular normal. Entre las aberriguaciones estructurales encontradas están t(17;19) (q11;p13), t(2;9;22)(q34;q34;q11), t(1;7)(p13;q33), t(6;11)(q26;p16), t(3;4)(q24-25;q26), t(1;12)(q23;q34), t(2;18)(q15;p12), t(2;4;)(q23;35) y t(4;11)(q21ñq23). Estos rearreglos fueron indicadores de riesgo y se correlacionaron con la respuesta al tratamiento y la supervivencia de los pacientes. Algunas de estas anomalías no habían sido previamente descritas en LLA; sin embargo, los puntos de ruptura coinciden con los observados en otras neoplasias hematológicas, lo cual suguiere que esas regiones son críticas en la patogénesis de estos desórdenes.

The chromosomes of Entamoeba histolytica I

Los cromosomas de Estamoeba histolytica I. Se cultivaron trofozoítos de E. Histolytica cepa IMSS-M1 en medio axénico por un método ya descrito y se cosecharon a las 24, 48 y 72 hs., se fijaron y se tiñeron por la reacción de Feulgen modificada para ADN, para identificar sus cromosomas, Se usaron como testigos cromosomas de linfocitos humanos. Se observaron aproximadamente 6 a 20 cromosomas filamentosos, dificilmente discernibles individualmente dado el límite de la resolución óptica del microscopio, dispuesto en forma paralela, en círculos, en cúmulos polarizados o dispersos en el citoplasma, frecuentemente arrosariados con microesférulas, y en ocasiones con microvesículas integradas, en sus extremos o aisladas. Esto demuestra condensación de ADN con produccipon de cromosomas filamentosos, macronúcleos lobulados y micronúcleos. Esta tinción puede aplicarse a otros protozoarios ya que es la primera vez que se utiliza para identificar cromosomas en Entamoeba histolytica. la duplicación nuclear amibiana en cultivo axénico óptimo ocurre en forma continua y probablemente debido a que el género Estamoeba ocupa un espacio evolutivamente primitivo, su mitosis corresponde a una transición entre procariotes y eucariotes.

Heterozygous puffing patterns in polytene chromosomes of a mosquito, Culex quinquefasciatus

Cromossomos politênicos de núcleos de túbulos de Malpighi em exemplares adultos de Culex quinquefasciatus exibem puffs heterozigotos. Aparentemente a heterozigosidade manifesta-se como uma diferença no tempo de formaçäo dos puffs entre os dois homólogos. Diferenças morfológicas na atividade de puffing de homológos podem ter um papel importante na evoluçäo de dípteros

Chromosome size variation occurs in cloned Plasmodium falciparum on in vitro cultivation

Variaçöes de tamanho nos cromossomos de linhagens de parasitos derivados de um clone de Plasmodium falciparum. Tais variaçöes desenvolveram-se durante períodos de muitos meses em parasitos haplóides na fase eritrocitária, mantidos in vitro. As variaçöes foram mais numerosas em populaçöes com resistência à mefloquina, induzida pelo cultivo sob pressäo de droga, do que em parasitas controles mantidos em meio de cultura sem droga. Em alguns casos, as modificaçöes de tamanho foram täo grandes que alteraram a ordem relativa das bandas de DNA cromossômico em separaçöes através de eletroforese em gel de "pulsed-field gradient". As regiöes subteloméricas dos cromossomos säo especialmente ativas, estando envolvidas em rearranjos responsáveis pelas alteraçöes de tamanho. O papel biológico destes rearrranjos näo é conhecido. Entretanto, sua ocorrência em experimentos controles, bem como sua frequente apariçäo em condiçöes de pressäo por mefloquina, sugerem que tais rearranjos reflititiam modificaçöes generalizadas da estrutura genômica em resposta às condiçöes ambientais

A Karyotype Study in Chiroptera (Bats)

The bat (Chiroptera) is the only mammal that is able to fly as birds do and forms a peculiar taxonomic group in that the diploid number of chromosomes seldom are of the same number in the same genus and the different species in contrast to the other eutherian mammals. At the present time, many karyological problems remain unsolved in Korean bats. It is easy enough to imagine that many interesting things have happened in the chromosomes of the Korean bats as well. The present study was designed in order to get karyotypic data on living species of Korean bats (Vespertilio superans THOMAS and Miniopterus schreibersii fuliginosus (HODGSON). The diploid number of chromosomes of the Vespertilio superans was 38. The autosomes consisted of 6 pairs of the large metacentric, a pair of the small submetacentric and 11 pairs of tile small acrocentric chromosomes. The X chromosome was medium sized and metacentric in type and the Y was a small acrocentric type. The fundamental number was 50. The diploid number of chrmosomes of the Miniopterus schreibersii fuliginosus was 46. The autosomes consisted of 8 pairs of the metacentric type including a pair of minute metacentric chromosomes. and 18 pairs of the small acrocentric type chromosomes. The X chromosome was medium-sized and submetacentric, and the Y was a small acrocentric chromosome. The fundamental number was 52.