bluuebunny/crossref_metadata_2025 huggingface dataset:
Short‐term potentiation of mEPSCs requires N‐, P/Q‐ and L‐type Ca2+ channels and mitochondria in the supraoptic nucleus
Authors: Quinlan Michelle E. , Alberto Christian O. , Hirasawa Michiru
Published: May 2008

The glutamatergic synapses of the supraoptic nucleus display a unique activity‐dependent plasticity characterized by a barrage of tetrodotoxin‐resistant miniature EPSCs (mEPSCs) persisting for 5–20 min, causing postsynaptic excitation. We investigated how this short‐term synaptic potentiation (STP) induced by a brief high‐frequency stimulation (HFS) of afferents was initiated and maintained without lingering presynaptic firing, using in vitro patch‐clamp recording on rat brain slices. We found that following the immediate rise in mEPSC frequency, STP decayed with two‐exponential functions indicative of two discrete phases. STP depends entirely on extracellular Ca2+ which enters the presynaptic terminals through voltage‐gated Ca2+ channels but also, to a much lesser degree, through a pathway independent of these channels or reverse mode of the plasma membrane Na+–Ca2+ exchanger. Initiation of STP is largely mediated by any of the N‐, P/Q‐ or L‐type channels, and only a simultaneous application of specific blockers for all these channels attenuates STP. Furthermore, the second phase of STP is curtailed by the inhibition of mitochondrial Ca2+ uptake or mitochondrial Na+–Ca2+ exchanger. mEPSCs amplitude is also potentiated by HFS which requires extracellular Ca2+. In conclusion, induction of mEPSC‐STP is redundantly mediated by presynaptic N‐, P/Q‐ and L‐type Ca2+ channels while the second phase depends on mitochondrial Ca2+ sequestration and release. Since glutamate influences unique firing patterns that optimize hormone release by supraoptic magnocellular neurons, a prolonged barrage of spontaneous excitatory transmission may aid in the induction of respective firing activities.
Local subcutaneous and muscle pain impairs detection of passive movements at the human thumb
Authors: Weerakkody N. S. , Blouin J. S. , Taylor J. L. , Gandevia S. C.
Published: May 2008

Activity in both muscle spindle endings and cutaneous stretch receptors contributes to the sensation of joint movement. The present experiments assessed whether muscle pain and subcutaneous pain distort proprioception in humans. The ability to detect the direction of passive movements at the interphalangeal joint of the thumb was measured when pain was induced experimentally in four sites: the flexor pollicis longus (FPL), the subcutaneous tissue overlying this muscle, the flexor carpi radialis (FCR) muscle and the subcutaneous tissue distal to the metacarpophalangeal joint of thumb. Tests were conducted when pain was at a similar subjective intensity. There was no significant difference in the ability to detect flexion or extension under any painful or non‐painful condition. The detection of movement was significantly impaired when pain was induced in the FPL muscle, but pain in the FCR, a nearby muscle that does not act on the thumb, had no effect. Subcutaneous pain also significantly impaired movement detection when initiated in skin overlying the thumb, but not in skin overlying the FPL muscle in the forearm. These findings suggest that while both muscle and skin pain can disturb the detection of the direction of movement, the impairment is site‐specific and involves regions and tissues that have a proprioceptive role at the joint. Also, pain induced in FPL did not significantly increase the perceived size of the thumb. Proprioceptive mechanisms signalling perceived body size are less disturbed by a relevant muscle nociceptive input than those subserving movement detection. The results highlight the complex relationship between nociceptive inputs and their influence on proprioception and motor control.
Ca2+ microdomains near plasma membrane Ca2+ channels: impact on cell function
Authors: Parekh Anant B.
Published: May 2008

In eukaryotic cells, a rise in cytoplasmic Ca2+ can activate a plethora of responses that operate on time scales ranging from milliseconds to days. Inherent to the use of a promiscuous signal like Ca2+ is the problem of specificity: how can Ca2+ activate some responses but not others? We now know that the spatial profile of the Ca2+ signal is important Ca2+ does not simply rise uniformly throughout the cytoplasm upon stimulation but can reach very high levels locally, creating spatial gradients. The most fundamental local Ca2+ signal is the Ca2+ microdomain that develops rapidly near open plasmalemmal Ca2+ channels like voltage‐gated L‐type (Cav1.2) and store‐operated CRAC channels. Recent work has revealed that Ca2+ microdomains arising from these channels are remarkably versatile in triggering a range of responses that differ enormously in both temporal and spatial profile. Here, I delineate basic features of Ca2+ microdomains and then describe how these highly local signals are used by Ca2+‐permeable channels to drive cellular responses.
Recovery of mouse neuromuscular junctions from single and repeated injections of botulinum neurotoxin A
Authors: Rogozhin A. A. , Pang K. K. , Bukharaeva E. , Young C. , Slater C. R.
Published: May 2008

Botulinum neurotoxin type A (BoNT/A) paralyses muscles by blocking acetylcholine (ACh) release from motor nerve terminals. Although highly toxic, it is used clinically to weaken muscles whose contraction is undesirable, as in dystonias. The effects of an injection of BoNT/A wear off after 3–4 months so repeated injections are often used. Recovery of neuromuscular transmission is accompanied by the formation of motor axon sprouts, some of which form new synaptic contacts. However, the functional importance of these new contacts is unknown. Using intracellular and focal extracellular recording we show that in the mouse epitrochleoanconeus (ETA), quantal release from the region of the original neuromuscular junction (NMJ) can be detected as soon as from new synaptic contacts, and generally accounts for > 80% of total release. During recovery the synaptic delay and the rise and decay times of endplate potentials (EPPs) become prolonged approximately 3‐fold, but return to normal after 2–3 months. When studied after 3–4 months, the response to repetitive stimulation at frequencies up to 100 Hz is normal. When two or three injections of BoNT/A are given at intervals of 3–4 months, quantal release returns to normal values more slowly than after a single injection (11 and 15 weeks to reach 50% of control valuesversus6 weeks after a single injection). In addition, branching of the intramuscular muscular motor axons, the distribution of the NMJs and the structure of many individual NMJs remain abnormal. These findings highlight the plasticity of the mammalian NMJ but also suggest important limits to it.
The Right and the Good: Distributive Justice and Neural Encoding of Equity and Efficiency
Authors: Hsu Ming , Anen Cédric , Quartz Steven R.
Published: May 2008

Distributive justice concerns how individuals and societies distribute benefits and burdens in a just or moral manner. We combined distribution choices with functional magnetic resonance imaging to investigate the central problem of distributive justice: the trade-off between equity and efficiency. We found that the putamen responds to efficiency, whereas the insula encodes inequity, and the caudate/septal subgenual region encodes a unified measure of efficiency and inequity (utility). Notably, individual differences in inequity aversion correlate with activity in inequity and utility regions. Against utilitarianism, our results support the deontological intuition that a sense of fairness is fundamental to distributive justice but, as suggested by moral sentimentalists, is rooted in emotional processing. More generally, emotional responses related to norm violations may underlie individual differences in equity considerations and adherence to ethical rules.
The pharmaco-invasive approach to STEMI: when should fibrinolytic-treated patients go to the “cath lab”?
Authors: Edmond J J , Juergens C P , French J K
Published: May 2008

Although primary percutaneous coronary intervention (PCI) in clinical trials has lower rates of reinfarction, stroke and mortality than fibrinolytic therapy, because of system delays in routine practice, field triage and prehospital administration of fibrinolytic therapy may lead to similar clinical outcomes, especially in those patients who present in the first 2 h after symptom onset. Necessary for these outcomes is the liberal use of both rescue PCI and in-hospital revascularisation. Non-invasive prediction of failed reperfusion may be enhanced by the use of ST recovery, patient characteristics and troponin T levels, measured by point-of-care assays. This review focuses on the timing of, and indications for, an invasive strategy after fibrinolytic therapy, including that for failed pharmacological reperfusion.
Evolution of Drosophila insecticide resistance
Authors: Morton R. A.
Published: May 2008

The impact of insecticide resistance is well documented. It includes the toxic effects of pesticides on the environment and the cost of the increased amounts of insecticides required to effectively control resistant insects. Resistance evolves by the selection of genes that confer tolerance to insecticides. Several resistance genes have been identified and cloned in Drosophila, including genes for mutant target molecules and genes that increase insecticide degradation. Drosophila is a useful system to understand the evolution of quantitative traits in general as well as the population genetics of insecticide resistance. Through it, we may hope to understand the relationship between discrete genetic change and continuously varying characters. In addition, molecular genetic techniques developed using Drosophila can eventually be transferred to other insects in order to help control pest populations.Key words: insecticide resistance, evolution of tolerance, selection of resistant genes, molecular genetics, Drosophila.
Cytological basis of 2n pollen formation in a wide range of 2x, 4x, and 6x taxa from tuber-bearing Solanum species
Authors: Watanabe Kazuo , Peloquin Stanley J.
Published: May 2008

Cytological mechanisms of 2n pollen formation were investigated in microsporogenesis and sporad development in 2x, 4x, and 6x taxa of tuber-bearing Solanum species that were originally collected from Mexico, and Central and South America. Parallel spindles and tripoles were seen at anaphase II in the majority of genotypes observed. The occurrence of parallel spindles and tripoles were well correlated with the occurrence of dyads and triads at the sporad stage. Further, the frequency of 2n pollen predicted by frequencies of parallel spindles and tripoles and by frequencies of dyads and triads were also well correlated with observed 2n pollen frequencies. Premature cytokinesis at telophase I to prophase II was seen only in 2x and 4x species from series Conicibaccata. The frequency of premature cytokinesis corresponded well with the frequency of dyads leading to 2n pollen formation. It was concluded that the major mechanisms of 2n pollen formation in tuber-bearing Solanum species is parallel spindles.Key words: cytological mechanisms, parallel spindles, ploidy series, tuber-bearing Solanum species, 2n pollen.
Genetic and cytogenetic analyses of the A genome of Triticum monococcum. VIII. Localization of rDNAs and characterization of 5S rRNA genes
Authors: Kim Nam-Soo , Kuspira J. , Armstrong K. , Bhambhani R.
Published: May 2008

In situ hybridization with [3H]dCTP labelled pScT7 (5S rDNA) and pTa80 (18S + 26S rDNA) indicated that both hybridized to the terminal regions of two pairs of chromosomes in Triticum monococcum. When the hybridization was performed with a mixture of both probes, only two pairs of chromosome arms were labelled, which suggested that the loci of both genes were located in juxtaposition to one another. Both probes labelled one pair of sites more heavily than the other. Southern analysis of 5S with BamHI-digested DNA from 12 accessions of T. monococcum (including T. urartu) produced two superimposed ladders of approximate sizes of 500 and 330 bp, which differ from T. aestivum in which 500- and 420-bp ladders were found. The 500-bp ladder is derived from chromosome 5A (5SDna-A2) and the 330-bp ladder from chromosome 1A (5SDna-A1). The recognition site for SstI was present in the long spacer region but absent in the short spacer as in T. aestivum; however, unlike T. aestivum, there were HaeIII (GGCC) and HindIII (AAGCTT) recognition sites in the short spacer region. The TaqI recognition sites (TCGA) in the long and short spacer regions are probably more highly methylated in T. monococcum than in T. aestivum. The results have implications regarding the evolutionary changes that occurred in the A genome of the hexaploid compared with the diploid.Key words: Triticum monococcum, 5S rDNA, 18S + 26S rDNA, in situ hybridization, Southern hybridization, restriction fragments, methylation.
Mitochondrial DNA variation and genetic relationships of Populus species
Authors: Barrett John W. , Rajora Om P. , Yeh F. C. H , Dancik Bruce P. , Strobeck Curtis
Published: May 2008

We examined variation in and around the region coding for the cytochrome c oxidase I (coxI) and ATPase 6 (atp6) genes in the mitochondrial genomes of four Populus species (P. nigra, P. deltoides, P. maximowiczii, and P. tremuloides) and the natural hybrid P. × canadensis (P. deltoides × P. nigra). Total cellular DNAs of these poplars were digested with 16 restriction endonucleases and probed with maize mtDNA-specific probes (CoxI and Atp6). The only variant observed for Atp6 was interspecific, with P. maximowiczii separated from the other species as revealed by EcoRI digestions. No intraspecific mtDNA variation was observed among individuals of P. nigra, P. maximowiczii, P. × canadensis, or P. tremuloides for the CoxI probe. However, two varieties of P. deltoides were distinct because of a single site change in the KpnI digestions, demonstrating that P. deltoides var. deltoides (eastern cottonwood) and var. occidentalis (plains cottonwood) have distinct mitochondrial genomes in the region of the coxI gene. Populus × canadensis shared the same restriction fragment patterns as its suspected maternal parent P. deltoides. Nucleotide substitutions per base in and around the coxI and atp6 genes among the Populus species and the hybrid ranged from 0.0017 to 0.0077. The interspecific estimates of nucleotide substitution per base suggested that P. tremuloides was furthest removed from P. deltoides and P. × canadensis and least diverged from P. nigra. Populus maximowiczii was placed between these two clusters.Key words: mitochondrial DNA, poplars, phylogenetics, variation, restriction fragment length polymorphisms.
Genetic analysis of the foraging microregion of Drosophila melanogaster
Authors: Belle J. Steven de , Sokolowski Marla B. , Hilliker Arthur J.
Published: May 2008

The rover/sitter polymorphism in Drosophila melanogaster larval behaviour is a unique example of a genetically determined, naturally occurring behavioural polymorphism. Allelic variation at the foraging locus (for) accounts for the rover (long foraging paths) and sitter (short foraging paths) phenotypes. We previously developed lethal tagging and used deficiency mapping to place for in the 24A3-C5 interval on the polytene chromosome map, thereby defining the for microregion. Here, we subjected this microregion to mutational analysis to (i) isolate putative lethal foraging mutations and characterize their behavioural phenotypes to assess whether or not for is a vital locus, (ii) generate cytologically detectable chromosome rearrangements with breakpoints in or near for for more precise localization and for future molecular analysis of the for gene, and (iii) identify other gene loci in the immediate vicinity of the for locus. We recovered 10 gamma-induced and 33 ethyl methanesulfonate (EMS) induced new mutations that define seven complementation groups in 24A3-D4. Two new EMS-induced lethal for alleles and four gamma-induced rearrangements with breakpoints in for were identified, which allowed us to further localize for to 24A3-5. All lethal mutations in for resulted in an altered behavioural phenotype providing evidence that both vital and behavioural functions are encoded by for.Key words: behaviour, genetics, foraging microregion, Drosophila melanogaster, larvae.
Meiotic chromosome interactions in inbred autotetraploid rye (Secale cereale)
Authors: Chatterjee R. , Jenkins G.
Published: May 2008

Electron microscopy of whole-mount surface-spread synaptonemal complex complements and conventional light microscopy of chromosomes at first metaphase of meiosis were used to compare the relative frequencies of pairing configurations at the two stages in inbred autotetraploid rye (Secale cereale L.). Statistical tests showed significantly fewer multivalents at first metaphase than expectations based on random initiation of synapsis at each telomeric site within each group of four homologues. Direct observations of synaptic behaviour of chromosomes showed that this deviation is due primarily to a preponderance of bivalents during zygotene and pachytene. It is also the result of a significant drop in multivalent frequency from meiotic prophase to metaphase I, which is attributable both to a lack of chiasmata with which to consolidate multivalents and inhibition of chiasma formation in synaptonemal complex segments of multivalents that are nonhomologous.Key words: autotetraploid, rye, synaptonemal complex, multivalents, chiasmata.
Paraquat selection identifies X-linked oxygen defense genes in Drosophila melanogaster
Authors: Humphreys James M. , Hilliker Arthur J. , Phillips John P.
Published: May 2008

We have previously shown that homozygous mutants of Drosophila melanogaster deficient in the oxygen radical scavengers, CuZn superoxide dismutase or urate, are adult viable and yet hypersensitive to the oxygen radical-generating agent, paraquat. Thus, paraquat could be used as a selective agent to identify adult-viable mutants potentially defective in other, perhaps unknown, oxygen defense functions. Here we report the successful use of paraquat hypersensitivity in the isolation of X-linked, ethylmethanesulfonate-induced mutations affecting oxygen defense in Drosophila melanogaster. Two paraquat hypersensitive mutants were identified that, by complementation analysis, were shown to be new alleles of the maroon-like gene. In addition to paraquat hypersensitivity, both alleles confer a maternally affected dark brown eye color and a complete lack of enzymatically active xanthine dehydrogenase, both of which are characteristic phenotypes of known maroon-like alleles. We conclude that the lack of xanthine dehydrogenase in these mutants leads to the absence of urate, which is the proximate cause of paraquat sensitivity. Because our search for such mutants on the X chromosome revealed two alleles of only a single selectable gene, we anticipate that the total number of major oxygen defense genes in the complete Drosophila genome may not be large.Key words: paraquat, maroon-like, xanthine dehydrogenase, oxygen defense.
The effects of level of 2,4-D and time in culture on regeneration rate and chromosome numbers of regenerants from calli of the hybrid Triticum aestivum cv. Chinese Spring ph1b × Thinopyrum ponticum (2n = 10x = 70)
Authors: Bai D. , Knott D. R.
Published: May 2008

Thinopyrum ponticum (Podp.) Barkworth &D. R. Dewey (2n = 10x = 70) has excellent resistance for both leaf and stem rusts. Long-term callus cultures were established from the immature embryos of a hybrid between Triticum aestivum L. (2n = 6x = 42) × Th. ponticum. They were maintained in culture for over 2 years and continued to grow and have organogenetic capacity. With increasing time on a maintenance medium, the plant regeneration rates of the hybrid calli decreased when transferred to regeneration media containing 0.1, 0.2, or 0.5 mg/L 2,4-D, but the rate of decrease was much higher at 0.5 mg/L than at either 0.1 or 0.2 mg/L 2,4-D. After 3 months of subculture, the highest plant regeneration rate was obtained on the medium containing 0.5 mg/L 2,4-D (1.11 plantlets/callus), while on the 24th month of subculture the highest plant regeneration rate was obtained on the medium containing 0.1 mg/L 2,4-D (0.20 plantlets/callus). Thus, it was shown that as the calli aged it was important to reduce the level of 2,4-D in the regeneration medium. Over 2 years, a total of 667 regenerants were successfully transferred and grown to maturity. Chromosome numbers in root-tip cells were determined for 539 regenerants and ranged from 36 to 70. Telocentric chromosomes were frequent. A fertile plant was found among the regenerants after 15 months of subculture. It had 56 chromosomes with 2.15 (1–6) univalents, 22.76 (17–26) closed bivalents, 3.55 (1–9) open bivalents, and 0.41 (0–3) trivalents and was highly resistant to stem rust race 15B-1. Callus culture of wide hybrids can be used to introgress characters from alien species into wheat.Key words: wheat, callus culture, long-term regeneration, wide hybridization.
Conservation of a satellite DNA sequence (SATB) in the tilapiine and haplochromine genome (Pisces: Cichlidae)
Authors: Franck Jens P. C. , Wright Jonathan M.
Published: May 2008

We have cloned and sequenced a 1900-bp EcoRI fragment (SATB) from the tilapiine fish Oreochromis niloticus. The SATB sequence is highly reiterated in the tilapiine genome and organized in long tandem arrays. A 760-bp HindIII fragment, an internal component of SATB, has also been cloned and sequenced from the related tilapiine species Oreochromis hornorum. Hybridization of the radiolabeled 760-bp HindIII repeat detected the presence of the SATB repeat in the genomes of several tilapiine species as well as the haplochromine species Haplochromis (Protomelas) similis. The 760-bp HindIII fragment did not hybridize to genomic DNA of Etroplus maculatus (an Asian cichlid) or to that of Cichlasoma meeki (a South American cichlid). The SATB repeat sequence is 56% AT and constitutes 0.2–5% of the tilapiine genome depending on the species examined. Four imperfect 21-bp direct repeat sequences are present within the cloned 1900-bp EcoRI repeat. Alignment of the four direct repeats from the O. niloticus cloned 1900-bp DNA and the two homologous direct repeats from the O. hornorum 760-bp HindIII repeat revealed a core motif of 11 bp that exhibits 100% sequence identity between all of the direct repeats. The conservation of this motif in the SATB repeat suggests that this sequence may be under selective constraint.Key words: satellite DNA, Cichlidae, direct repeats.
Mammalian sex chromosomes. VI. Synapsis in the heterochromatin-rich X chromosomes of four rodent species, Mus dunni, Bandicota bengalensis, Mesocricetus auratus, and Nesokia indica
Authors: Singh Amar Pal , Raman Rajiva
Published: May 2008

This study analyzes the progression of chromosomal synapsis in female meiosis of four rodent species, Mus dunni, Bandicota bengalensis, Mesocricetus auratus, and Nesokia indica. Special attention has been paid to understand the mode of pairing between heterochromatin-rich X chromosomes. The ovaries were obtained from newborn individuals instead of fetuses. In all but M. auratus, day 0 ovaries provided almost all the prophase stages at varying frequencies. In B. bengalensis and M. dunni the entire X chromosomes were paired including the heterochromatin. In M. auratus and N. indica, the heterochromatic arms in a proportion of X bivalents, however, were only partially synapsed. It appears that in these two species heterochromatin association is either delayed or short lived.Key words: sex chromosomes, meiosis, heterochromatin, synapsis.
Distribution of TaqI sites along human chromosomes revealed by in situ enzyme-nick translation
Authors: Tagarro I. , Gonzalez-Aguilera J. J. , Fernandez-Peralta A. M. , Stefano G. F. de , Ferrucci L.
Published: May 2008

We have studied the relative richness of TaqI sites along human chromosomes by means of a nonradioactive in situ enzyme-nick translation procedure. Regions with a higher content of these sequences are shown to be the noncentromeric heterochromatin blocks, whereas within euchromatin, terminal R-bands are the domains more enriched in these sites. Results obtained suggest that the method of performing enzyme digestions using time as a variable, and then in situ nick translation, provides much more complete information about the distribution of enzyme sequences along chromosomes than standard enzyme digestions.Key words: TaqI, nick translation, biotin, T-bands, heterochromatin.
Phylogenetic relationships of the pigeonpea (Cajanus cajan) based on nuclear restriction fragment length polymorphisms
Authors: Nadimpalli Ram G. , Jarret R. L. , Phatak Sharad C. , Kochert Gary
Published: May 2008

Nuclear restriction fragment length polymorphisms (RFLPs) were used to determine phylogenetic relationships in the genus Cajanus using 15 random genomic probes and six restriction enzymes. Twenty-four accessions representing 12 species of four genera (Cajanus, Dunbaria, Eriosema, and Rhynchosia) were examined to determine phylogenetic relationships in the genus Cajanus. Eriosema parviflorum was selected as the out-group. Sufficient RFLP polymorphisms were detected among species to resolve in-group taxa into distinct clusters. Topologies of trees from parsimony and similarity matrix analyses were similar but not identical, and clustering patterns agreed broadly with published phylogenies based on seed protein data and, to a lesser extent, data from cytology and breeding experiments. Accessions of cultivated C. cajan shared more DNA fragments with C. scarabaeoides than with C. cajanifolia. Inconsistencies in taxonomic relationships based on data from morphology, cytology, crossability, and RFLPs are discussed.Key words: pigeonpea, systematics, taxonomy, evolution, germplasm.
Selective digestion of mouse chromosomes with restriction endonucleases. Oligonucleotide priming of single-stranded DNA produced with exonuclease III
Authors: Gosálvez J. , López-Fernández C. , Vega C. García de la , Mezzanotte R. , Fernández J. L. , Goyanes V.
Published: May 2008

L-929 mouse chromosomes prepared for electron microscopy have been treated with MspI, EcoRI, and HaeIII restriction endonucleases (REs). RE-induced nicks were amplified with exonuclease III to obtain single-stranded DNA (ss-DNA) motifs. The ss-DNA produced was enough to permit hybridization of a series of random oligonucleotides. These can be used as primers, which are extended by the Klenow fragment using non-isotopic labelled dUTP. The incorporation of biotinylated dUTP is detected with a gold-tagged streptoavidin as the reporter molecule. This allows, in mouse chromosomes, the detection of different rates of sensitivity to the digestion with specific REs in distinct intraheterochromatic DNA subsets. In addition, these results show that enzymatic production of ss-DNA seems to be adequate for electron microscopy work since the chromatin fiber is preserved better than in denatured DNA produced with heat, NaOH, or formamide.Key words: mammalian chromosomes, electron microscopy, chromosome structure, cytogenetics.
C-banding polymorphism and linkage of nonhomoeologous RFLP loci in the D genome progenitor of wheat
Authors: Hohmann U. , Lagudah E. S.
Published: May 2008

Chromosomes from four different accessions of Triticum tauschii, used as parents in generating F2 populations for RFLP genetic linkage map construction, were analyzed by C-banding. The accessions consist of the varietal taxa strangulata (AUS 21929) and meyeri (AUS 18911), and two genotypes of var. typica (AUS 18902 and CPI 110730 from Iran and Afghanistan, respectively). Chromosomes 1D and 7D of T. tauschii var. typica AUS 18902 are involved in a reciprocal interchange forming translocated chromosomes, T1DS.7DL and T7DS.1DL, with tbe breakpoints being located within the centrometric region. The formation of quadrivalent configuration in F1 hybrids provided further confirmation of the reciprocal translocation. Genetic linkage mapping of additional RFLP markers located on homoeologous group 1 and 7 chromosomes showed consistent linkage to a composite group of proximal markers on chromosomes 1D and 7D of a previously published map derived from the F2 progeny of AUS 18902 × AUS 18911. A high frequency of RFLP genotypes transmitted by the translocation parent was prevalent in the proximal regions of chromosomes 1D and 7D. Genotypic frequencies expected of the nontranslocated parental RFLP markers was evident only in the distal regions of these chromosomes.Key words: C-banding, genetic map, translocation heterozygote, RFLP, linkage.
Disomic and ditelosomic alien chromosome additions in beet (Beta vulgaris), carrying an extra chromosome of B. procumbens or telosome of B. patellaris
Authors: Lange W. , Bock Th. S. M. De , Speckmann G. J. , Jong J. H. De
Published: May 2008

Alien chromosome transmission through the female germ line as well as meiosis in pollen mother cells were studied in disomic and ditelosomic alien chromosome additions of beet. Beta vulgaris, carrying an extra pair of chromosomes or telosomes of B. procumbens or B. patellaris, respectively. The alien chromosomes carried genes for resistance to the beet cyst nematode, Heterodera schachtii, and screening for this resistance was used to select plants with or without the alien chromosomes. A great variation for alien chromosome transmission was recorded and plants carrying two extra alien chromosomes were recovered in the backcross progenies of the disomic or ditelosomic additions. However, in these progenies the average frequencies of plants without alien chromosomes (86%) did not clearly differ from that in similar progenies of the original monosomic or monotelosomic chromosome additions, indicating that doubling the number of the alien chromosome did not enlarge their transmission to the next generation. The alien chromosomes fully paired at pachytene and desynapsed again before diakinesis, indicating decreased chiasma formation. At second metaphase nearly 60% of the cells had one extra chromosome, and the remaining cells carried two or no extra chromosomes in about equal proportions. The tetrads looked fully normal. The expected relation between the average number of alien chromosomes in the germ cells and in the plants of the progenies did not show up, indicating a strong selection favouring the female gametes without alien chromosomes.Key words: disomic and ditelosomic alien chromosome additions, Beta vulgaris, Beta procumbens, Beta patellaris, chromosome transmission, meiosis.
Hybridization studies on Blattella germanica and B. asahinai (Dictyoptera: Blattellidae): species divergence and a possible influence of a major chromosome mutation
Authors: Ross Mary H.
Published: May 2008

An earlier study indicated that Blattella asahinai is separated from its close relative B. germanica by a non-reciprocal translocation that apparently involved the transfer of the nucleolus organizing region from the X chromosome of B. germanica or a B. germanica like ancestor to chromosome 12 in B. asahinai. Continued study on divergence of the two species included genetic analyses of fecundity, egg case hatch, nymphal hatch, sex ratios, and segregation of X chromosomes and the segment carrying the B. asahinai nucleolar organizing region in interspecific and backcross matings. Overall, a complex of maternally related disadvantages was associated with B. asahinai. The effects of cytoplasmic factors could not generally be distinguished from possible effects of X chromosome – cytoplasmic interactions. In two crossing systems, the data fit a hypothesis of lethal effects from the presence of an X chromosome in alien cytoplasm. Cytologic differences occurred frequently in backcrosses, especially with F1 hybrid females, but were limited to chromosomes and chromosome segments affected by the translocation. The possible relationship of the chromosome mutation to traits affecting reproduction and its role in species divergence are discussed.Key words: speciation, evolution, cockroach, cytogenetics.
Preliminary karyotype and chromosomal localization of ribosomal DNA sites in white spruce using fluorescence in situ hybridization
Authors: Brown Garth R. , Amarasinghe Vindhya , Kiss Gyula , Carlson John E.
Published: May 2008

We have localized the major ribosomal DNA (rDNA) loci on metaphase chromosomes and in interphase nuclei of white spruce (2n = 24) by fluorescence in situ hybridization. Hybridization sites of the biotin-labelled rDNA probe were detected using antibody–fluorochrome conjugates and a confocal laser scanning microscope. White spruce has at least 12, and possibly as many as 14, rDNA sites, 1 site present on each of seven separate chromosome pairs. This is one of the highest numbers of rDNA loci yet reported among plant species. The position of the rDNA loci together with secondary constriction patterns permit, for the first time, all homologous pairs of white spruce chromosomes to be distinguished. We discuss the application of molecular cytogenetics in studies relating to the organization and evolution of DNA sequences within conifer genomes.Key words: fluorescence in situ hybridization, Picea, rDNA, karyotype.
The trihybrid genome constitution of Bacillus lynceorum (Insecta Phasmatodea) and its karyotypic variations
Authors: Manaresi S. , Marescalchi O. , Scali V.
Published: May 2008

The standard karyotype and a wide array of repatterned cytotypes from 21 demes of the double-allotriploid thelytokous Bacillus lynceorum have been analyzed by means of Giemsa, C-banding, and silver-staining techniques. The present study substantially amends the first karyotype description and also analyzes in detail the chromosomal rearrangements to trace their most likely derivation. Bacillus lynceorum cytotypes also provide a well-documented instance of an intraspecific gain of centromeric function. The contribution of three different specific haplosets is particularly evidenced from centromeric heterochromatin pattern and satellite/Ag-NOR locations. In stick insects, both hybridogenetic and parthenogenetic Bacillus hybrids, including B. lynceorum, can utilize the rDNA of all available parental haplosets, although a hierarchical role of the B. rossius genome seems to emerge. Satellite/Ag-NOR patterns, besides clearly allowing the recognition of ancestral parental genomes, also suggest a polyphyletic origin for B. lynceorum, which, to our knowledge, represents the only described karyotype of a trihybrid invertebrate.Key words: Bacillus lynceorum, C-banding cytotypes, NOR hierarchy, centric fissions, thelytoky.
Alloplasmic wheat – Elymus ciliaris chromosome addition lines
Authors: Jiang Jiming , Chen Peidu , Friebe Bernd , Raupp W. John , Gill Bikram S.
Published: May 2008

Alloplasmic euploid wheat with the cytoplasm of Elymus ciliaris (2n = 4x = 28, ScScYcYc) is male sterile and has reduced vigor. However, alloplasmic plants with E. ciliaris chromosomes 1Sc or 1Yc marked by gliadin genes Gli-Sc1 and Gli-Ycl, respectively, are vigorous and fertile. The Rf genes on 1Sc and 1Yc are named Rf-Sc1 and Rf-Yc1. Two chromosome translocations involving 1Yc were isolated. The first involved the short arm of 1Yc translocated to the short arm of wheat chromosome 3B. The second involved the short arm of 1Yc translocated to the short arm of a chromosome, designated L, of E. ciliaris. The second line also has another E. ciliaris chromosome designated A and lacks wheat chromosome 6A. This line is resistant to Puccinia recondita. The relationship between fertility restoration and nucleolar organizing regions is discussed. Key words : Triticum aestivum, Elymus ciliaris, chromosome addition, Rf genes, nucleolar organizing regions.
Sequence analysis of cloned human satellite DNAs reveals nonrandom variations
Authors: Sol Katia , DuBow Michael S.
Published: May 2008

We have cloned, from the genome of HeLa cells, related 1.8-kb highly repetitive EcoRI satellite II (and III) DNA family members that displayed a high degree of TaqI and HinfI variations. Comparative sequence analysis of these cloned DNAs suggests that highly repetitive satellite DNAs may have evolved and diversified from the rapid amplification of a pentameric unit (5′ TTCCA 3′), by processes including random and non-random mutations. Base conservation, as well as mutational hotspots, were found associated with these related satellite II and III DNAs. The accumulation of C to G transversions within the pentamers, generating TaqI and HinfI sites, as well as C to T transitions at CpN dinucleotides, appear to be responsible for much of the microheterogeneity observed between related satellite II and III DNA family members.Key words: repetitive DNAs, heterochromatin, satellite DNAs, DNA sequence.
Cytogenetics of two novel compensating diploids in barley (Hordeum vulgare)
Authors: Singh R. J. , Tsuchiya T.
Published: May 2008

Novel compensating diploid plants are very rare in diploid species. The objective of this study was to describe the origin, identification, and meiotic and breeding behaviors of two compensating diploids of barley (Hordeum vulgare L.), isolated in a spring-type two-rowed cultivar, 'Shin Ebisu 16' (SE 16). A plant with 2n = 13 + 1 acro3L3S + 1 telo3S was identified cytologically in an F2 population from the cross 2n = 14 + 1 acro3L3S × yst 2 (yellow streak 2). In this plant, 1 acro3L3S and 1 telo3S compensated for one normal chromosome 3. The selfed population from this plant usually segregated three chromosomal types in a ratio of 1 (2n = 14): 2 (2n = 13 + 1 acro3L3S + 1 telo3S): (2n = 12 + 2 acro3L3S + 2 telo3S). A 1 (2n = 14): 1 (2n = 13 + 1 acro3L3S + 1 telo3S) ratio was observed when the plants with 2n = 13 + 1 acro3L3S + 1 telo3S were crossed with a diploid either as a male or female. At metaphase I, plants with 2n = 13 + 1 acro3L3S + 1 telo3S showed a 1 III + 6 II configuration in 84% of the sporotypes and the remaining (16%) sporocytes had a 6 II + I 11 (heteromorphic) + 1 I configuration. The chromosome arrangement in a trivalent was ∙3S–3S∙3L–3L3S. At anaphase I, a 7–8 (6 + 1 acro3L3S + 1 telo3S) chromosome separation was observed in 87.9% sporocytes. The second compensating diploid (2n = 12 + 2 acro3L3S + 2 telo3S) bred true and only produced plants with 2n = 13 + 1 acro3L3S + 1 telo3S when crossed with a diploid either as a male or female. At metaphase I, 97% of the sporocytes showed 8 II (6 II + I acro3L3S II + 1 telo3SII) and an 8–8 chromosome separation was recorded in 90% of the sporocytes at anaphase I. Morphologically, plants with 2n = 14, 2n = 13 + 1 acro3L3s + 1 telo3S, and 2n = 12 + 2 acro3L3S + 2 telo3S were indistinguishable.Key words: acrotrisomics, telotrisomics, heterochromatin.
Cytogenetics of an unstable trisomie in barley (Hordeum vulgare)
Authors: Singh R. J. , Tsuchiya T.
Published: May 2008

The origin, identification, meiotic chromosome behavior, and breeding behavior of an unstable trisomic barley were studied. The extra chromosome originated by breakage and fusion of an acrocentric chromosome 3 in a plant from an F2 population of a cross between acrotrisomic 3L3S (2n = 14 + 1 acro3L3S) and a balanced lethal stock, xc. (xantha) ac (albino). The F2 population segregated only for the albino trait. The genotypic constitution of the trisomic plant was ac ac (for both normal chromosome 3) and Ac (for the unstable metacentric chromosome). The unstable extra metacentric chromosome was designated as metacentric 3B (abbreviated as meta3B). Meiotic chromosome behavior in plants with 2n = 14 + 1 meta3B differed from plant to plant and within spikes. Some plants showed only trisomic cells with a chromosome configuration of 1 III + 6 II and 7 II + 1 I at metaphase I, whereas other plants showed both trisomie and disomic cells (7 II) that resulted from the elimination of the extra meta3B. The frequency of ring trivalents was low (6.8%). An average transmission rate of unstable meta3B ranged from 4.3 to 12.9%. The elimination of meta3B, and hence loss of the dominant Ac allele, resulted in albino seedlings as well as white stripes on plants, leaves, and spikes. Chromosome numbers of albino seedlings in the progeny of 2n = 14 + 1 meta3B were all diploid (2n = 14), while green seedlings contained 2n = 14 + 1 meta3B. However, progenies of some spikes of one trisomic plant showed a low frequency of green diploids and metatrisomics (2n = 14 + 1 meta3B), which was attributed to crossing-over.Key words: aneuploid, chromosome elimination, kinetochore, meta3B.
The molecular organization of the Star/asteroid region, a region necessary for proper eye development in Drosophila melanogaster
Authors: Higson Theodore S. , Tessiatore June E. , Bennett Sean A. , Derk Raymond C. , Kotarski Michael A.
Published: May 2008

The Star/asteroid (S/ast) region of Drosophila melanogaster has been cloned by P element transposon tagging using the snw chromosome as a source of defective P elements. In each mutation examined, the element integrated into the region was a 0.5-kb element from a region proximal to sn and not one of the head-to-head elements from the sn locus. Previously described spontaneous and X-ray induced mutations of S and ast were located on the molecular map by Southern analysis and restriction endonuclease mapping of genomic clones. S mutations are either large deletions of the cloned region or DNA breaks located near the P element insertions that cause ast mutations. Both S and ast mutations reduce the steady-state amounts of a 3.4-kb RNA. The molecular data, together with the phenotypic interactions observed for S and ast alleles, are consistent with the interpretation that S and ast mutations are lesions within the same gene or within genes that are functionally related.Key words: Drosophila, Star, asteroid, P elements.
Genome organization and restriction site map of the mitochondrial DNA of the housefly (Musca domestica)
Authors: Roehrdanz R. L.
Published: May 2008

A restriction map of the housefly mitochondrial DNA was constructed. The putative arrangement of the major coding regions was determined by two methods. In the first, Drosophila clones of known gene content were hybridized to housefly restriction fragments on Southern blots. In the second, rare restriction sites and clusters of restriction sites were used to align the housefly restriction map with that of Drosophila yakuba. Both methods produced the same apparent gene arrangement.Key words: mtDNA, restriction site map, Diptera, Muscidae, insect, evolution.
Karyotype evolution in Curimatidae (Teleostei, Characiformes) from the Amazon region. II. Centric fissions in the genus Potamorhina
Authors: Feldberg Eliana , Porto J. I. R. , Nakayama C. M. , Bertollo L. A. C.
Published: May 2008

Using cytogenetic analysis following Giemsa staining, nucleolar organizer region (NOR) staining, and C-banding, three distinct karyotypes in three species of curimatids belonging to the fish genus Potamorhina were identified: 2n = 54/44 M + 10 SM (P. pristigaster), 2n = 56/52 M + 2 SM + 2 ST (P. latior), and 2n = 102/2 M + 2 SM + 98 A (P. altamazonica). A 2n = 54 was considered to be the ancestral diploid number and the different karyotypes were probably the result of centric fissions. Both the NOR pattern and constitutive heterochromatin pattern are species specific.Key words: centric fissions, karyotypic evolution, Amazon fish, Curimatidae.
Variability among members of the Hor-2 multigene family
Authors: Kanazin Vladimir , Ananiev Evgeny , Blake Tom
Published: May 2008

The hordeins comprise the major prolamin storage proteins of barley. Two major and one minor gene families encode these alcohol-soluble proteins. The Hor-2 gene family encoding the B-hordeins has been estimated to contain 15–30 copies. Although several genes encoding B-hordeins have been cloned and sequenced, little is known about the mechanisms responsible for the generation of the enormous genetic variability at this locus. Polymerase chain reaction sequence amplification provided a simple technique that permitted the amplification of the Hor-2 gene family members from the genomes of several barley genotypes. Sequence analysis of clones permitted the identification of a region within the Hor-2 structural gene that appears to undergo recombinational and slippage-like gene conversion events. In this report we describe variability of the B-hordein genes, possible mechanisms responsible for it, and implications this may have on the evolution of prolamin-encoding gene families.Key words: barley, hordeins, polymerase chain reaction, polymorphism.
A genetic survey of the pathogenic fungus Ophiostoma ulmi across a Dutch elm disease front in Western Canada
Authors: Hintz W. E. , Jeng R. S. , Yang D. Q. , Hubbes M. M. , Horgen P. A.
Published: May 2008

The natural population structure of the Dutch elm pathogen Ophiostoma ulmi was determined for isolates collected from across a Western Canadian disease front through an analysis of restriction-site polymorphisms in the ribosomal DNA repeat, length mutations in the mitochondrial genomes, and through DNA fingerprinting of the nuclear genomes using a minisatellite DNA probe. The 8.8-kbp rDNA repeat was selected from a genomic library, and restriction-site and genic maps were constructed for the nonaggressive and aggressive subgroups of O. ulmi. There were only three restriction-site differences that distinguished these two subgroups and no intrasubgroup variation was detected. All of the isolates collected from the disease front were of the aggressive subgroup and were represented by two distinct nuclear and four mitochondrial genotypes. The majority of the isolates were of a single genotype (type A nuclear DNA; type I mtDNA), indicating the presence of a single very large clone extending across much of Manitoba and into Saskatchewan.Key words: Ophiostoma ulmi, Dutch elm disease, DNA fingerprinting, population biology.
Within-family selection at an otherwise unselected locus in dairy cattle
Authors: Gomez-Raya L. , Gibson J. P.
Published: May 2008

Identification of allelic variants with economic importance is feasible via molecular genetic techniques. This information can be used to increase the frequency of favourable alleles in dairy cattle. The effect of selection on the genotype within families in the early stages of life is examined. Three different strategies are considered: (1) random mating of bull sires with bull dams and with cows, with embryo selection of young bulls and all cows; (2) random mating of bull sires with bull dams, with embryo selection of young bulls only; (3) minimizing or avoiding matings between homozygotes for the unfavourable allele, with embryo selection of young bulls. Selection strategies assume the use of reproductive technologies such as embryo transfer to produce large family sizes for within-family selection to be practiced. All the three strategies increase the frequency of the favourable allele rapidly. Strategy 1 gives the fastest increase in the frequency of the favourable allele. The increase in the frequency of the favourable allele is slower under random mating (strategy 2) than under a negative assortative mating (strategy 3). This is a novel example of increased selection response with negative assortative mating.Key words: selection, breeding strategies, dairy cattle.
Replication banding patterns in Atlantic salmon (Salmo salar)
Authors: Pendás A. M. , Morán P. , García-Vázquez E.
Published: May 2008

Replication banding patterns have been obtained from in vivo treatment of Salmo salar using a modification of the 5-BrdU technique and in kidney cultures using the FPG staining method. Most of the chromosome pairs were identified in the karyotype based on the banding pattern, chromosome size, and centromere position. C-banding and replication banding patterns were compared.Key words: karyotype, replication banding, Salmo salar.