摘要:

The linguistically hybrid terms nucleosome and nucleotype are synonymous of karyosome and karyotype, i.e. their linguistically pure forms. Because nucleosome and karyosome both mean nuclear body, similarly nucleotype and karyotype both mean nuclear type. In the current scientific terminology a rather dissimilar meaning, in part due to a lack of knowledge or to a non-consideration of terminological priorities, is attributed to the above mentioned synonyms. In the present work the author discusses and documents this terminologically chaotic state of affairs.

ISSN:0008-7114    

DOI:10.1080/00087114.1994.10797297

出版商:Taylor & Francis    

年代:1994

数据来源: Taylor

摘要:

We have studied the distribution of the Nucleolus Organizer Regions on the chromosome complements of three species of Mediterranean Mugilids:Liza aurata, Liza ramadaandChelon labrosus, by means of the silver nitrate staining method. Only one representative pair of NOR-chromosomes was detected in each species, the submetacentric or metacentric number 24, common to all of them. The terminal NOR position on the short arm as well as the lack of variation in size indicate the conservative nature of the NORs in the Family Mugilidae. A certain variation of the nucleoli number (1 to 4) in interphasic nuclei was detected. This may be explained by the selectivity of the silver staining for the transcriptionally active NORs. Associations involving the NOR-chromosomes reveal a slight deleting of argirofilic proteins attached to them.

ISSN:0008-7114    

DOI:10.1080/00087114.1994.10797298

出版商:Taylor & Francis    

年代:1994

数据来源: Taylor

摘要:

The early phases of basidiospore-derived infection ofMelampsora pulcherrima(Bub.) Maire on the leaves ofMercurialis annuaL. were studied by light microscopy, SEM and TEM. The fine morphology of the basidiospore germling penetration and intraepidermal infection structures is discussed in comparison with that of other rusts recently described. The direct penetration through the epidermal cell wall, characteristic of the rust basidiospore-derived germlings, is confirmed. The absence of an extrahyphal matrix around the intraepidermal vesicle and the presence of a collar around the vesicle neck are pointed out.

ISSN:0008-7114    

DOI:10.1080/00087114.1994.10797299

出版商:Taylor & Francis    

年代:1994

数据来源: Taylor

摘要:

Cytogenetic analysis of different populations ofBelostoma plebejum(2n= 14 + XY, male) has revealed the presence of two naturally occurring chromosome mutants: one heterozygous for an autosomal fusion, and the other with a sex chromosome fragmentation. Meiosis in both individuals is very regular. The fusion heterozygote (2n= 13 + XY) presented an autosomal trivalent at meiosis I, which divided reductionally at first anaphase; cells at meiosis II had 6 or 7 autosomes plus the XY pseudo-bivalent. The other chromosome mutant presented three sex chromosomes, which probably resulted from the fragmentation of the original X chromosome (2n= 14 + X1X2Y). The three sex chromosomes divided equationally at anaphase I and associated in a chain at metaphase II. Many authors are of the opinion that karyotype evolution in Heteroptera has proceeded principally by fusions and fragmentations. Particularly inBelostoma, it has been proposed that evolution from the ancestral number 2n= 26 + XY has occurred through autosomal fusions and an X chromosome fragmentation. The facts that these rearrangements have been found in natural populations ofB. plebejumand that they show a regular meiotic behaviour, seem to support the suggested hypothesis.

ISSN:0008-7114    

DOI:10.1080/00087114.1994.10797300

出版商:Taylor & Francis    

年代:1994

数据来源: Taylor

摘要:

The occurrence of natural triploidy in two specimens ofAstyanax scabripinniscollected in the Araquá river and in the Córrego das Pedras stream, respectively, is noticed. The triploid specimen from the Araquá river presented one macro B-chromosome and the triploid specimen from Córrego das Pedras stream presented two macro B-chromosomes. The C-banding performed in the specimen from the Araquá river confirmed the triploidy and showed that the macro B-chromosome was entirely heterochromatic. Ag-NOR characterization showed two chromosomes involved in the nucleolar activity in both specimens. Some aspects related to the origin of triploid fishes are described.

ISSN:0008-7114    

DOI:10.1080/00087114.1994.10797301

出版商:Taylor & Francis    

年代:1994

数据来源: Taylor

摘要:

C and ASG banding ofCeratitis capitata(Wied.) (Diptera Tephritidae) were carried out. Results obtained by ASG banding differ according to the length of slides treatment times. With longer times we obtained C bands, with shorter times we obtained G like bands. The C bands are similar to those obtained by C-banding method. These bands agree with the bands described by others authors for C-banding. This fact shows that the same classes of heterochromatin are involved in C-banding and in ASG banding with longer times. With shorter times of treatment we obtained G-like bands. Sometime the G-like bands present variations for the chromosomes N° 1 and N° 4.

ISSN:0008-7114    

DOI:10.1080/00087114.1994.10797302

出版商:Taylor & Francis    

年代:1994

数据来源: Taylor

摘要:

The cytological status of callus and regenerants ofPodophyllum hexandrumcultured in vitrofor over a period of 3 years is reported. Calli maintained both on lower (0.5 μM) and higher (10 μM) 2,4-D, remained cytologically stable up to 18 months. With the long term (3 years) culture on higher 2,4-D both numerical and structural changes in the chromosomes were observed. The calli maintained for 3 years on lower 2,4-D on the other hand retained both chromosome stability and regeneration potentiality. The regenerants in general showed normal mitotic complements. One of the regenerants from higher 2,4-D medium, however, showed structural chromosome changes.

ISSN:0008-7114    

DOI:10.1080/00087114.1994.10797303

出版商:Taylor & Francis    

年代:1994

数据来源: Taylor

摘要:

Karyotype analysis ofBalistes carolinensis, by means of C banding and silver nitrate staining, reveals: 44 acrocentric chromosomes in both males and females; a secondary constriction in the third pair corresponding to the NORs whose position is subcentromeric and C-positive; and a constitutive heterochromatin pattern being mainly distributed in pericentromeric areas of three chromosome pairs. The most important evolutionary implications of these characteristics are: the reduction of diploid number of the species in relation to the ancestral teleost coinciding moreover with the modal value of the group (2n= 44); the parallelism of this reduction with the taxonomical position of the balistids; the scarcity of constitutive heterochromatin in comparison with the most other teleostean species also reflecting a diminution; and the primitive disposition of the NORs. Such characteristics prove specialized among Teleosts but relatively generalized into the order Tetraodontiformes.

ISSN:0008-7114    

DOI:10.1080/00087114.1994.10797304

出版商:Taylor & Francis    

年代:1994

数据来源: Taylor

摘要:

Parallel polymorphisms for B chromosome and supernumerary segments on M6, S9and S10pairs have been detected in two Argentinian populations ofDichroplus elongatus, Raco (RA) and Tafi Viejo (TV) (Tucumán Province). All these polymorphisms seem to be temporally stable. In all samples of TV, it was observed a tendency towards an excess of the B + SS6class. SS6produces a total restriction of chiasma formation in proximal position in the involved pair in heterozygous and homozygous males. In TV a consistent dose effect of B chromosome on interstitial chiasma (Xi) frequency was detected in males. The Xifrequency vs. number of supernumeraries plot fits to a linear regression. In both populations, the individuals with B's showed a significant increase in macro- and microspermatid production. This effect is more marked at RA. The cytophotometric analysis of DNA content revealed that in both types of males, B and non B carriers, most macrospermatids are diploid suggesting a probably origin by cytokinesis blocking. However, spermatids with 3 to 5C contents in B carriers were also detected showing that other mechanism (i.e. cell fusion) may also account to explain the effects of B's on abnormal sperm formation.

ISSN:0008-7114    

DOI:10.1080/00087114.1994.10797305

出版商:Taylor & Francis    

年代:1994

数据来源: Taylor

摘要:

Chinese hamster Don cell line metaphase chromosomes were digested with Hae III restriction enzyme and examined by electron microscopy. The enzymatic digestions were carried out employing two different methods: digestion in suspension and transference of metaphases. The activity of Hae III induced a G-like banding pattern, but the mechanism of formation of bands is different depending on the treatment used. Furthermore, we observed that chromosomes 1, 2 and 9 from Don cell line showed the centromeres highly affected after the enzymatic treatment. The appearance of ghost-like structures led us to visualize swollen chromosomes in which only contour delineation could be well-differentiated. Such chromosomes appear as empty structures showing the greatest alteration of chromosomal structure.

ISSN:0008-7114    

DOI:10.1080/00087114.1994.10797306

出版商:Taylor & Francis    

年代:1994

数据来源: Taylor