The meiotic pairing of nine wheat chromosomes

Summary The meiotic identification of nine pairs of chromosomes at metaphase I of meiosis of Triticum aestivum (B genome, 4A and 7A) has been achieved using a Giemsa C-banding technique. As a result, the analysis of the pairing of each chromosome arm in disomic and monosomic intervarietal hybrids between Chinese Spring and the Spanish cultivar Pané 247 could be carried out. Differences in the chiasmata frequencies per chromosome arm cannot be explained on the basis of relative arm lengths only. Possible effects of arm-to-arm heterochromatic differences on meiotic pairing are discussed.     

Fine structure of anaphase bridges in meiotic chromosomes of the crane fly Pales

Chromatin bridges of autosomal bivalents in anaphase I were observed in spermatocytes of Pales ferruginea. The bridges are formed without simultaneous production of akinetochoric (akinetic) fragments. A bridge consists of a single fiber up to approximately. 500 Å in diameter. Filamentous substructures of approximately 100 Å diameter can be visualized. It is suggested that these bridges represent a low order coiling of the chromatid, and may be caused by non-separation of the terminal segments of the chromatids (telomeres).     

Microsporogenesis and meiotic behavior in nine species of the genus Pinus

The meiotic behavior of 10 taxa （nine species and one variety） of the genus Pinus was investigated using pollen mother cells （PMCs） to reveal the differentiation among karyotypes. Chromosome spreads were prepared by conventional squashing. The meiotic index and the average configuration were higher, whereas the frequency of aberrance （chromosomal bridges, fragments, or micronuclei） was lower, in all 10 taxa compared with other gynmosperms. The meiotic index, average configuration, and frequency of irregularity were found to be uniform among the species. It was shown that the genomes of the Pinus species investigated were highly stable, confirming results of previous mitotic analyses in this genus. However, slight differentiation of homologous chromosomes among genomes was revealed by analysis of meiotic configurations in Pinus nigra var. poiretiana. Quadrivalents were observed in 9.31% of PMCs in this species. This is the first time that quadrivalents have been observed in gymnosperms.     

The comparative germination ecology of nine Rumex species

The germination requirements, dormancy cycle and longevity of nine Rumexspecies were studied in field conditions and laboratory experiments to show theadaptations of the related species to their specific habitat. Within one genus,rather striking differences were observed in germination ecology. However, theclosely related species, R. acetosa and R.scutatus, are very similar: they fruit in early summer; theirseeds can germinate immediately after dispersal, and they are nondormant andshort-lived. R. acetosella also has fruits insummer, but the seeds do not germinate the first season after dispersal. Theyare long-lived, but buried seeds do not show a dormancy cycle; they mightgerminate in different seasons after exposure to light. Seeds of four species (R. conglomeratus,R. maritimus, R. sanguineus andR. crispus) are long-lived and undergo aseasonal dormancy cycle, with a low level of dormancy in winter and early springand a deep dormancy in summer as was already known for R.obtusifolius. These seeds are shed in the autumn, and they germinatemainly in the spring in consecutive years. R. maritimusalso germinates in summer and autumn on drying muddy soils. The seeds of R. hydrolapathum only germinate onwaterlogged soils, which explains its growth at the edge of streams and ponds.Its seeds are rather short-lived. The seeds of the species on very wetplaces require a higher temperature for germination.     

Fine structure of 33 258 H-treated chromosomes

Summary Metaphase chromosomes of mouse strain L cells show strikingly uncondensed pericentric heterochromatic regions after treatment of living cells with the benzimidazol-derivate 33258 Hoechst. In electron micrographs of total preparations after G-band staining the chromosomes are seen to be made up of irregularly folded fibrils of 200–400 Å in diameter. In the uncondensed regions only very few fibrils laid in loose loops are present, making it probable that only one fibril forms one chromatid.     

A comparative study of chromosome morphology among the nine annual species of Cicer L

Thirty-six accessions, representing the full complement of all the nine annual Cicer L. species, viz C. arietinum, C. reticulatum, C. echinospermum, C. pinnatifidum, C. judaicum, C. bijugum, C. chorassanicum, C. yamashitae and C. cuneatum, were subjected to karyotype analysis for the first time in a single comprehensive study. The detailed karyotype of C. chorassanicum was also investigated for the first time. A 12 h cold water pretreatment and 13 min 60 degrees C 1 N HCl hydrolysis confirmed a somatic chromosome number of 2n = 16 in all the species. Within species interchromosomal size variation was observed to be quite large in C. arietinum, C. reticulatum and C. echinospermum, but not in the remaining six species. Individual chromosome size ranged from 3.77 microns in C. echinospermum to 1.32 microns in C. arietinum while the haploid genome length ranged from 20.65 microns in C. echinospermum to 14.92 microns in C. cuneatum. Ample rearrangement of chromatin among chromosomes within a species was implied to have played a role in Cicer genome evolution. The nine species were classified in two groups based on karyotypic similarity, with the first group comprising the inter-crossable species C. arietinum, C. reticulatum and C. echinospermum, while the remaining species forming the second group. The first group species are also genetically close to each other as deduced by other morphological, biochemical and DNA based studies. Circumstantial evidence has lead to the speculation that perhaps karyotypic similarity and interspecific crossability are positively related to each other.     

Application of advanced fluorescence microscopy to the structure of meiotic chromosomes

Chromosomes undergoing meiosis are defined by a macromolecular protein assembly called the synaptonemal complex which holds homologs together and carries out important meiotic functions. By retaining the molecular specificity, multiplexing ability, and in situ imaging capabilities of fluorescence microscopy, but with vastly increased resolution, 3D-SIM and other superresolution techniques are poised to make significant discoveries about the structure and function of the synaptonemal complex. This review discusses recent developments in this field and poses questions approachable with current and future technology.     

The meiotic chromosomes of man

Summary Information was obtained on the chromosome number, and the behavior of autosomes as well as of the sex chromosomes in meiosis in human male germ cells derived from 25 Japanese patients, 4 to 79 years in age, who were hospitalized mostly due to epididymitis, prostate cancer, undescended testes or infertility.In 16 out of the 25 specimens, the chromosome numbers, 46 in 2n and 23 in n, were consistently established together with an XY sex-determining mechanism based on spermatogonial and spermatocyte divisions. No reliable counts were obtained from the remaining 9 cases, because of that they provided no cells for precise investigation.The X and Y chromosomes during the leptotene stage were observed as two separate heteropycnotic bodies lying along the inner wall of the nucleus, while at pachytene they formed a sex-vesicle after homologous pairing. At the diplotene, diakinesis and first metaphase the X and the Y appeared as an isopycnotic bivalent showing an end-to-end association, though there were some cells in which they remained as two separate entities free from contact. Evidence was presented that the X and the Y seemed to associate with each other at the distal end of the short arm of each element.One or sometimes two smallest autosomal bivalents tended to show rather precociously a chiasma-terminalization at the first metaphase.The metaphase chromosomes of the second spermatocytes were evident by the haploid number as well as by their widely diverged chromatids with a characteristic spiral configuration.The testicular materials under study contained in most cases polyploid cells with a considerable frequency in spermatogonia as well as in first and second spermatocytes. Giant sperm heads were observed not infrequently, mostly being abnormal in shape. No significant correlation was obtained between the frequency of polyploid cells and the age of patients so far studied.Contribution No. 679 from the Zoological Institute, Faculty of Science, Hokkaido University, Sapporo. — It is our pleasure to dedicate this paper to Professor Dr. Hans Bauer, Max-Planck-Institut für Meeresbiologie, Tübingen, in honor of his sixtieth birthday.     

Giemsa banding of meiotic chromosomes

Applying a Giemsa staining technique to the meiotic chromosomes of Anemone blanda demonstrates that Giemsa bands similar to those seen in the mitotic chromosomes are discernible at all the principal stages of meiosis. The bands are not a product of the Giemsa procedure since they can be seen in unstained preparations using phase-contrast optics as chromocentres in interphase nuclei and as condensed regions in prophase chromosomes. That the bands seem to be permanent features of the nucleus, whether it is dividing or otherwise is an important consideration for understanding their nature and function. Bands and chiasmata do not coincide indicating on the one hand that chiasmata are not responsible for differences in banding patterns and on the other hand that the conservation of bands is an indication that they are either inert regions or specialised regions with considerable adaptive significance. These alternatives can only be resolved by genetical studies of the banding phenomena.     

A comparative study of leucokinin-immunoreactive neurons in insects

Antisera were raised against leucokinin IV, a member of the leucokinin peptide family. Immunohistochemical localization of leucokinin immunoreactivity in the brain of the cockroach Nauphoeta cinerea revealed neurosecretory cells in the pars intercerebralis and pars lateralis, several bilateral pairs of interneurons in the protocerebrum, and a group of interneurons in the optic lobe. Several immunoreactive interneurons were found in the thoracic ganglia, while the abdominal ganglia contained prominent immunoreactive neurosecretory cells, which projected to the lateral cardiac nerve. The presence of leucokinins in the abdominal nerve cord was confirmed by HPLC combined with ELISA. Leucokinin-immunoreactive neurosecretory cells were also found in the pars intercerebralis of the cricket Acheta domesticus and the mosquito Aedes aegypti, but not in the locust Schistocerca americana or the honey bee Apis mellifera. However, all these species have leucokinin-immunoreactive neurosecretory cells in the abdominal ganglia. The neurohemal organs innervated by abdominal leucokinin-immunoreactive cells were different in each species.     

Fine structure of the chromosomes of hexaploid wheat antipodal cells

At the postendoreduplicative stage of chromosomes of antipodes are shown to be depolytenized and represented by solitary 0.1-0.3 micrometer chromonemas. Micropuffs and chromomer-like regions were found in the chromonemas. The chromonem puffing takes place independently of the nuclear membrane. A degradation of antipodal chromosomes begins in the zone of the nucleolus and spreads gradually over the whole nucleus. Later the cell is destructed but the nucleoli remain intact. Some of them are giant and vacuolized, others are similar to nucleoli of the usual low-ploidal nuclei.     

The study of joint inheritance of mutations impairing the structure of meiotic chromosomes in rye Secale cereale L

Genetic analysis has demonstrated that meiotic mutations mei8 (irregular condensation and fragmentation of meiotic chromosomes) and mei10 (chromosome overcompaction) are nonallelic. Mutation mei10 exhibits digenic inheritance (with a segregation ratio of 13:3) in the combinations of crosses studied. It is assumed that the phenotypic expression of mutation mei10 is suppressed by the effect of recessive gene lch1 or lch2 (long chromosomes), both of which have been revealed in one of the parental lines (Mc10). These genes determine weak condensation of meiotic chromosomes. In double mutants mei8 mei10, the mutations are expressed independently of each other. Gene mei10 is linked with gene mei8 (r = 36.8 +/- 5.38%); genes lch1 and lch2 are not linked either with them or with each other. Taking into account the data on the linkage between genes mei10 and sy10 and between mei8 and sy10, the order of genes in the linkage group is shown to the following: mei8-sy10-mei10.     

Oogenesis at subzero temperatures: a comparative study of the oocyte morphology in nine species of Notothenioids

Oogenesis was examined in nine species of Antarctic fish to verify the existence of morphological peculiarities. The analyses were carried out on specimens belonging to three different families of Notothenioids (Nototheniidae, Channichthyidae and Bathydraconidae), all captured in the Ross Sea, in front of the Italian Station of Terra Nova Bay. Following dissection, the ovaries were processed and examined at the light and electron microscopes to determine the oocyte gross and fine morphology. The attention, in particular, was focused on the presence of cytoplasmic round bodies and on the organization of the cortical alveoli and the vitelline envelope. Results reveal significant specie-specific differences that could be partly correlated to the phylogenetic radiation but not to the peculiar environmental conditions being essentially comparable to those observed among temperate species.     

A comparative study of the chromosomes of birds

Karyotype analysis and morphometric measurement of the chromosomes of eleven species of Indian birds are described. The unequivocal identification of W chromosome in the females of five species of the present investigation further strengthens the generalisation that, at least in Carinatae, the sex chromosome constitutions are of ZZ and ZW types in males and females respectively. — The chromosomes of different species of birds so far worked out in each order have been compared using quantitative methods and tentative conclusions have been drawn regarding chromosomal affinities between species of different taxonomic categories.