Cytogenetics of ticks (Acari: Ixodoidea)

Chromosomes and sex determination of 9 species of Haemaphysalis assigned to 4 subgenera are described. H. (tAlloceraea) kitaokai possesses an XX∶XO sex chromosome system with 18 autosomes plus XX in females; 18 plus X in males. H. (Kaiseriana) hystricis has 18 +XX and 18 + XY in females and males, respectively, in most specimens, but a supernumerary chromosome is present in some individuals. A supernumerary chromosome was also observed in 1 male H. (Aborphysalis) formosensis. These two species are the second and third species of ticks reported to have supernumerary chromosomes. H. formosensis, H. (Kaiseriana) bispinosa, H. (Haemaphysalis) campanulata, H. (H.) flava, H. (H.) megaspinosa, H. (H.) japonica, and H. (H.) pentalagi possess 20 autosomes plus 2 sex chromosomes in females and 20+1 sex chromosomes in males. Phylogenetic relationships within the genus Haemaphysalis are briefly discussed.     

Characterization of B chromosomes in Lilium hybrids through GISH and FISH

Supernumerary (B) chromosomes and small aberrant chromosomes were detected in Lilium hybrids and characterized through genomic in situ hybridization (GISH) and florescence in situ hybridization (FISH). Two small, supernumerary or B chromosomes were detected as extra chromosomes in a tetraploid plant derived from chromosome doubling of a hybrid (2n = 2x = 24) between a cultivar of the Longiflorum (L) and the Trumpet (T) group. When this tetraploid LLTT hybrid was crossed with a triploid LLO hybrid (O = Oriental), the B chromosome was transmitted to 73.4 % of the progenies. Based on GISH and FISH characterization, it was shown that the B chromosome consisted of two identical arms, with 5S rDNA hybridizing to the majority of it, which were flanked by normal telomeres, suggesting that this is an isochromosome. In another population, which is a backcross progeny between a F1 hybrid of Longiflorum × Asiatic (LA) and its Asiatic parent, the former produced functional 2n gametes which resulted in a triploid LAA progeny (2n = 3x = 36), in which three exceptional plants possessed 35 normal chromosomes and a small aberrant chromosome instead of the expected normal number of 36. In all three cases, the small aberrant chromosomes were isochromosomes which had obviously originated during the first backcross generation. These three chromosomes showed normal telomeres and mitosis. In addition, one of the new generated chromosomes possessed two 45S rDNA sites in the proximal positions. These new arisen isochromosomes were proposed to originate from centric breakage and fusion of two short arms of the missing chromosome in three genotypes, respectively, based on the comparison of arm lengths as well as rDNA loci. Their relevance to the origin of Bs is discussed.     

Cytotaxonomy ofCalliphoridae (Diptera)

A modification of the general system of classification ofCalliphoridae is proposed in this report. Information about the chromosome complements of about 90 species is provided including references to the earlier literature on chromosomes of this family. With one exception all species studied by us or by earlier investigators have 2n=12. The total complement length of 556 complements from 83 species averaged 66.4 μ. Most species have a short heteromorphic sex pair but the size and morphology vary considerably and one species,Hemipyrellia fernandica, seems to have a quadrivalent sex-chromosome complex in a 2n=14 complement. The autosomal pairs vary in both length and arm ratios between the species but seem to be more stable than the sex chromosomes. Only minor variations were found between different collections of the same species except for two collections ofCalliphora croceipalpis. Although presently available data on the chromosomes of Diptera species suggest that increases in total complement length accompany evolutionary progress, no such general trends were obvious in either the total complement lengths or chromosome morphology, either within or between the tribes ofCalliphoridae. Thus the karyotypical reorganizations in the family have apparently not been directly associated with changes in the general morphological features of the adults which may have responded in these respects more extensively to genetic mutations.     

Localization of rDNA in the chimpanzee (Pan troglodytes) chromosome complement

In situ hybridization was used to identify the sites of rDNA in the chromosome complement of the chimpanzee (Pan troglodytes). The rDNA was present in the satellite regions of chimpanzee chromosomes 14, 15, 17, 22 and 23. Four of these (14, 15, 22, 23) are homologous to human chromosomes carrying rDNA: 13, 14, 21 and 22.     

Chromosomal segregational mechanisms in ant-lions (Myrmeleontidae,Neuroptera)

In a single male specimen of Myrmeleon mexicanum Banks the sex chromosomes, normally X and Y, were replaced by what appeared to be X¹X² and Y. These segregated as expected on that interpretation in only half of the spermatocytes — in the other half, one X and the Y segregated from the other X. This atypical segregation is explicable on the assumption that one of the supposed Xs is a supernumerary, not a sex chromosome, and the diploid complement of the male comprises six pairs of autosomes plus a supernumerary and the X and Y sex chromosomes. The orientation of the X chromosomes at first metaphase was variable: kinetochoric activity may be localized midway the length of the chromosome, as in gonial mitosis, or terminally. Comparative study of three congeneric species, seven of Brachynemurus, one of Psammoleon, and one of Vella showed normal segregation in all, and no evidence for secondary kinetochoric activity. In nine of the species studied one pair of autosomes was unconjoined at first metaphase in 0.3%–1.2% of primary spermatocytes. These autosomes segregated precociously with the sex chromosomes in the central unit of the spindle. In one exceptional male of Brachynemurus hubbardi Currie all first meiotic metaphases showed this behavior, and a compound X¹X²/Y¹Y² system was thus simulated. Bivalent formation replaced distance segregation of sex chromosomes in 0.4%–3.2% of the spermatocytes in seven of the thirteen species studied. These sex-bivalents frequently displayed partial or complete failure in congression.     

Chromosome banding in the genusPinus

Somatic chromosomes ofPinus nigra var.maritima (2n=24) were sequentially stained with DNA binding base-specific fluorochromes, chromomycin A₃ (CMA) and DAPI. Many CMA- and DAPI-bands appeared at intercalary and/or proximal regions of most chromosomes. These banding patterns reversely related. Individual chromosomes were easily identified using these fluorescent banding patterns.     

BrdU-33258 Hoechst analysis of DNA replication in human lymphocytes with supernumerary or structurally abnormal X chromosomes

BrdU-33258 Hoechst techniques have been used to characterize DNA replication patterns in lymphocytes from human females with supernumerary or structurally abnormal X chromosomes. Fluorescence analysis permits identification of late replicating X chromosomes in a very high proportion of cells and affords a high resolution method for determining the interchange points of X-X and X-autosome translocations. Asynchrony among terminal replication patterns of multiple late replicating X chromosomes within an individual cell can occasionally be demonstrated. The arms of isochromosomes usually exhibit symmetrical fluorescence patterns, with replication terminating in bands Xq21 and Xq23 (predominant pattern) or in bands Xq25 and Xq27 (alternative pattern) in both arms. In the vast majority of lymphocytes containing a balanced X-13 or X-19 translocation, the normal X is late replicating. However, DNA synthesis in the translocation products occasionally appears somewhat delayed relative to that expected for an early replicating X, consistent with possible position effects on replication kinetics.     

Location of the genes coding for 18S and 28S ribosomal RNA in the human genome

³H-rRNA obtained from Xenopus laevis tissue cultured cells, or a ³H-cRNA made from Xenopus ribosomal DNA, was used for heterologous in situ hybridisation with human lymphocyte metaphase chromosomes. Prior to hybridisation, chromosome spreads were stained with Quinacrine and selected cells showing good Q-banding photographed; the same cells were then rephotographed after autoradiography and pairs of photographs for each cell were used to make dual karyotypes. The chromosomes within each karyotype were divided into equal sized segments (approx. 0.7 μ), with a fixed number of segments for each chromosome type. The distribution of silver grains between segments showed that the ³H-RNAs hybridised specifically to the nucleolar organising regions of the D and G group chromosomes with no other sites of localised labelling in the complement. Control experiments showed no localisation, with insignificant labelling, when metaphase spreads were incubated in a mixture containing Xenopus ³H-rRNA and competing cold human (HeLa) rRNA. Filter hybridisation experiments on isolated human DNA showed that the Xenopus derived ³H-RNAs hybridised to a fraction of human DNA which was on the heavy side of the main DNA peak and that these RNAs were competed out in the presence of excess cold human rRNA, confirming the specificity of the heterologous hybridisation. In situ hybridisation experiments were also carried out on cells from individuals with one chromosome pair showing heteromorphism for either a very long stalk (nucleolar constriction) subtending a satellite, or a large satellite. It was shown that the chromosome with the large stalk hybridised four times as much ³H-rRNA as its homologue, whereas differences in the sizes of the subtended satellites did not materially affect hybridisation levels indicating that rDNA is located in the stalks and not the satellites. The amount of ³H-rRNA hybridised differs between chromosomes and individuals; these differences are heritable and rDNA can be detected by in situ hybridisation in all three chromosomes number 21 in cells from Down's patients and in translocated chromosomes conta.ining a nucleolar constriction. Different D and G group chromosomes which hybridised equal amounts of ³H-rRNA participated in rosette associations at metaphase in a random fashion in some individuals and in a non-random fashion in others. In all individuals studied chromosomes with large amounts of rDNA were not found to be preferentially involved in association. It was therefore concluded that the probability of a chromosome being involved in the formation of a common nucleolus is not a simple function of its rDNA content and other possible factors are considered.     

C-banding and non-homologous associations in Gryllus argentinus

A comparative study of C-banded mitotic and meiotic chromosomes of Gryllus argentinus (Gryllidae) is reported. Improved cytological procedures were followed to establish karyotypes and to detect C-segments. Twenty-eight autosomes plus a sexual system XX, XO were found. Terminal C-heterochromatin in both arms and paracentric segments were detected in most of the chromosomes of the complement. Microdensitometric tracings confirmed the distribution of C-banded segments. Manifold connections through condensed terminal chromomeres were observed at pachytene occurring between two or more bivalents during meiosis. These heterologous associations involved the whole karyotype. End-to-end pachytene associations reacted intensely to the C-procedure. C-segments detected at diakinesis allowed the measurement of the centromere indices of bivalents which resulted in a more precise identification of given chromosome pairs. The relationship of the presence of terminal heterochromatin in mitotic chromosomes, the end-to-end associations through C-segments, the attachment of pachytene filaments to the nuclear membrane and their molecular implications is discussed.     

Chromosome location of the genes for 28S, 18S and 5S ribosomal RNA in Triturus marmoratus (Amphibia Urodela)

The localization of the 28S, 18S and 5S rRNA genes in the mitotic chromosomes, and of the 5S rRNA genes in the lampbrush chromosomes of Triturus marmoratus has been studied by RNA/DNA in situ hybridization. The 28S and 18S genes are located in a subterminal position, and the 5S genes in an intermediate position, on the long arm of mitotic chromosome X. In situ hybridization on lampbrush chromosomes has shown that the 5S genes are located at or near a dense matrix loop landmark. The cytogenetic implications of these findings are briefly discussed.     

Plasma-Derived Human C1-Esterase Inhibitor Does Not Prevent Mechanical Ventilation-Induced Pulmonary Complement Activation in a Rat Model of Streptococcus pneumoniae Pneumonia

Mechanical ventilation has the potential to cause lung injury, and the role of complement activation herein is uncertain. We hypothesized that inhibition of the complement cascade by administration of plasma-derived human C1-esterase inhibitor (C1-INH) prevents ventilation-induced pulmonary complement activation, and as such attenuates lung inflammation and lung injury in a rat model of Streptococcus pneumoniae pneumonia. Forty hours after intratracheal challenge with S. pneumoniae causing pneumonia rats were subjected to ventilation with lower tidal volumes and positive end-expiratory pressure (PEEP) or high tidal volumes without PEEP, after an intravenous bolus of C1-INH (200 U/kg) or placebo (saline). After 4 h of ventilation blood, broncho-alveolar lavage fluid and lung tissue were collected. Non-ventilated rats with S. pneumoniae pneumonia served as controls. While ventilation with lower tidal volumes and PEEP slightly amplified pneumonia-induced complement activation in the lungs, ventilation with higher tidal volumes without PEEP augmented local complement activation more strongly. Systemic pre-treatment with C1-INH, however, failed to alter ventilation-induced complement activation with both ventilation strategies. In accordance, lung inflammation and lung injury were not affected by pre-treatment with C1-INH, neither in rats ventilated with lower tidal volumes and PEEP, nor rats ventilated with high tidal volumes without PEEP. Ventilation augments pulmonary complement activation in a rat model of S. pneumoniae pneumonia. Systemic administration of C1-INH, however, does not attenuate ventilation-induced complement activation, lung inflammation, and lung injury.     

Fluorescent chromosome banding inLarix leptolepis (Pinaceae)

The somatic karyotype ofLarix leptolepis (2n=24) is composed of 12 large metacentric chromosomes and 12 small submetacentric chromosomes. Each CMA-band appeared at the interstitial region of four metacentric chromosomes. Each bright DAPI-band appeared at the proximal region of one side of the arms of nearly all chromosomes. However, two submetacentric chromosomes had no discriminable DAPI-bands. The CMA-bands coincided in position with the secondary constriction and the negative DAPI-bands.     

The chromosomal location of ribosomal DNA in the mouse

In situ hybridization of I¹²⁵-labelled ribosomal RNA to mouse chromosomes was used to determine the location of the rDNA loci. The results demonstrate the presence of rDNA sites on chromosomes 15, 18 and 19.     

A comparative banding analysis of chromosomes in three species of lemurs (Primates,Lemuridae)

Banded karyotypes were compared in 3 species of lemurs,Lemur catta (2n=56),L. f. fulvus (2n=60) andL. mongoz (2n=60). The karyotypes of the latter 2 species were indistinguishable from each other in both Q-band and G-band patterns, except thatL. mongoz had an unusually large Y chromosome. The karyotypic differences betweenL. catta and the other 2 species were mainly explained by centric fusions (or fissions) and pericentric inversions. Contrary to the general similarity in Q-band and G-band patterns, the C-band patterns were highly variable among the 3 species. All chromosomes ofL. fulvus had a distinctive C-band in the centromeric region, whileL. mongoz had only a few chromosomes with an apparent C-band.L. catta was remarkable by showing interstitial and terminal C-bands in some elements, in addition to the centromeric band which was observed in about 20 pairs.     

Variation in nucleolar organiser rRNA gene multiplicity in wheat and rye

In hexaploid wheat and diploid rye, different varieties have different numbers of ribosomal RNA genes as indicated by rRNA/DNA hybridisation. Wheat has four different chromosomes which carry nucleolar organisers. Analyses of DNA isolated from substitution lines in which each of these nucleolar organiser chromosomes of several varieties has been substituted one at a time into a common genetic background, have indicated that none of the four organiser chromosomes possess an invariant number of ribosomal RNA genes. The ribosomal RNA gene complement of the varieties investigated can be approximately accounted for by the sum of the ribosomal RNA genes on each of the four nucleolar organiser chromosomes.     

The chromosomal distribution of satellite DNA in the germ-line and somatic tissues of the gall midge,Heteropeza pygmaea

Somatic DNA from Heteropeza pygmaea separated in CsCl gradients into a main band DNA (?=1.685 g/cm³) and a satellite band (?=1.716 g/cm³) comprising 15% of the total DNA. The satellite melted sharply at 93.0°C in SSC, 10.4°C higher than the main band DNA. Satellite DNA reassociated rapidly, banding in CsCl heavier than native satellite but lighter than denatured satellite. The complementary strands of the satellite formed a single band in alkaline gradients and hence are apparently similar in G+T composition. — Filter hybridization experiments with Xenopus ribosomal RNA showed that the satellite band does not contain ribosomal cistrons. — Complementary RNA (cRNA) transcribed in vitro from isolated satellite bound extensively to satellite DNA but not to main band DNA. — The strain of Heteropeza used here contained about 58 chromosomes in germ-line cells and reproduced only paedogenetically. During early cleavage, the presumptive somatic nuclei eliminate most of their chromosomes (E-chromosomes) and retain only ten (S-chromosomes). In situ hybridizations with satellite-cRNA showed satellite DNA (prepared from predominately somatic tissues) to be localized in the centromeric heterochromatin of S- and E-chromosomes. Silver grain comparisons suggested that the amount of satellite is equivalent in both types of chromosomes. — Lastly we found that both diploid and polyploid cells contain similar amounts of satellite DNA. We interpreted this to mean that during polyploidization, as has been demonstrated during polytenization, satellite DNA does not replicate or replicates only slightly while other DNA fractions increase.