Enlarged euchromatic chromosomes (“megachromosomes”) in hybrids between Nicotiana tabacum and N. plumbaginifolia

The gigantic chromosomes (megachromosomes) described previously as occurring spontaneously in hybrid combinations between N. tabacum and species of the Tomentosae section of Nicotiana were due to an enlargement of heterochromatic segments introduced from the latter into a N. tabacum background. Only chromosomes with large heterochromatic segments became megachromosomes and the enlarged parts themselves showed at interphase and prophase the intense staining characteristic of heterochromatin. Euchromatic arms of the same chromosomes did not undergo enlargement.In contrast, megachromosomes described here for N. tabacum x N. plumbaginifolia hybrids originate from chromosomes which have no heterochromatic blocks. These megachromosomes are not recognizable at interphase and when distinguished at prophase are found to be stained lightly like the rest of the euchromatin.The mode of origin of megachromosomes is still unknown. Spontaneous chromosome breakage is frequent in all hybrids in which megachromosomes are found and is probably associated in some way with their formation, but an origin of megachromosomes by breakage and end-to-end fusion of broken strands is unlikely. This leaves as a possibility an origin by repeated replication from the same template.Other examples of very large chromosomes with characteristics of megachromosomes found in the literature are briefly discussed. They all arose in atypical situations of interspecific hydribization, exposure to mutagens or in tumors and cell cultures.Paper number 4748 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, North Carolina     

Highly asymmetric intergeneric nuclear hybrids between Nicotiana and Petunia: evidence for recombinogenic and translocation events in somatic hybrid plants after “gamma”-fusion

Summary Extremely asymmetric nuclear hybrids have been obtained via protoplast fusion in an intergeneric combination. Irradiated (cobalt⁶⁰,100 krad) kanamycinresistant Petunia hybrida mesophyll protoplasts were chemically fused with wild-type mesophyll protoplasts of Nicotiana plumbaginifolia. Eighty-six hybrid colonies were selected on kanamycin-containing medium, and twenty-four of these could be induced to regenerate numerous shoots. Cytological analysis of the regenerants showed the presence of a few chromosome fragments in some lines, and even a metacentric chromosome in yet another line. Besides additional chromosome fragments some lines only possessed typical Nicotiana chromosomes, and this at the diploid (2n = 2X = 20) as well as the tetraploid (2n = 2X = 40) level. Biochemical analysis showed that all regenerants had neomycin phosphotransferase activity (NPTII), which suggests that intergenomic recombination and or translocation events took place at least in those lines where no additional chromosome fragments could be detected. The presence of the NPTII gene was shown by Southern hybridization. All regenerants tested were fertile, and the segregation ratios for the kanamycin gene (for self and backcross pollinations to the recipient partner) for some of the regenerants correspond with Mendelian rules for a monogenic dominant marker. Most of the regenerants showed abnormal segregation ratios; in this case, no correlation could be made between segregation ratio and chromosome composition.Our results demonstrate the existence of intergenomic recombination and translocations evens in nuclear somatic hybrid plants obtained via gamma-fusion.     

Ecology of cryptic coral reef communities. II. Recovery from small disturbance events by encrusting bryozoa: The influence of “host” species and lesion size

Natural lesions in two species of encrusting, tropical Bryozoa (Steginoporella sp. and Reptadeonella sp.) are frequent and occur in a broad range of sizes. Since colonization of lesions by competitors is a potent threat to colonial organisms, recovery from such disturbances is an important component of colony survival. Regeneration of and settlement into experimentally placed lesions in these two bryozoan species varies with both lesion size and “host” species. As a result, the effects of predation or physically mediated disturbance will depend not only upon the absolute magnitude of damage, but also upon the species damaged and the sizes of the lesions produced.     

Response to comments by V. N. Manskikh: “Do external or internal factors lead to tumor development? It is still unknown”

The opinion is presented according to which the “bad luck” hypothesis (Tomasetti, C., and Vogelstein, B. (2015) Science, 347, 78–81), which has recently received experimental confirmation, has the right to exist, and its criticisms are largely unfounded.     

Comment to: “Spontaneous transformation of adult mesenchymal stem cells from cynomolgus macaques in vitro” by Z. Ren et al. Exp. Cell Res. 317 (2011) 2950-2957: Spontaneous transformation of mesenchymal stem cells in culture: Facts or fiction?

There is at present a controversy in the literature whether MSCs are susceptible to spontaneous in vitro transformation or not. Several groups have reported spontaneous transformation of MSCs from various species. However, some of these reports were not true transformations and later proven to be due to cross-contaminating cancer cells. To date there is no solid evidence that MSCs can undergo spontaneous transformation in culture. Only two groups used DNA fingerprinting to authenticate their transformed cells, and both groups later showed cross-contamination of cancer cells in their cultures. In this commentary, we address the paper "Spontaneous transformation of adult mesenchymal stem cells from cynomolgus macaques in vitro" by Z. Ren et al. Exp. Cell Res. 317 (2011) 2950-2957. In this article the authors characterize the transformed mesenchymal cells (TMCs) and claim to have verified their origin. We question the authentication of the TMCs made by the authors and we also believe it is in the interest of the scientific community, that a highly controversial finding, such as spontaneous transformation of MSCs, should be properly verified by stringent methods, preferably DNA fingerprinting, in order to validate if an actual transformation event has occurred.     

Materials towards the revision of the genus Triplophysa rendahl, 1933 (Cobitoidea: Balitoridae: Nemacheilinae): A revision of nominal taxa of Herzenstein (1888) described within the species “Nemachilus” stoliczkae and “N.” dorsonotatus, with the description of the new species T. scapanognatha sp. nova

This study reviews the nominal taxa within the species “Nemachilus” stoliczkae and “N.” dorsonotatus, described by Herzenstein (1888). N. dorsonotatus, N. d. retropinnis, and N. plagiognathus are reviewed within the species Triplophysa stoliczkae; it is suggested that this species is represented by at least 5 subspecies. N. stoliczkae brevicauda, N. s. leptosoma (synonym, N. s. productus), and N. s. crassicauda are considered as valid species, the last 2 are related to the group including the species T. tenuis, T. choprai, T. tenuicauda, and T. yasinensis rather than with T. stoliczkae. It was shown that the “stoliczkae” species group (sensu Prokofiev, 2001) should be divided into three species groups: “stoliczkae” (s. str.), “tenuis,” and “robusta”; their diagnoses and the species composition are presented. A new species from the “stoliczkae” group is described (T. scapanognatha sp. nova), related to T. tanggulaensis (Zhu, 1982). Original Russian Text ? A.M. Prokofiev, 2007, published in Voprosy Ikhtiologii, 2007, Vol. 47, No. 1, pp. 5–25.     

About the Book by S.A. Kuz'min and E.N. Gudimova, “Introduction of the Kamchatka Red King Crab into the Barents Sea: Specifics of Biology,Fishing Prospects” (Apatity: Kola Science Center RAS, 2002, 236 pp.)

Russian Journal of Marine Biology -     

Additions and corrections to “The Muscidae of Central Europe” III. A new species of <Emphasis Type="Italic">Coenosia</Emphasis> Meigen, 1826 from Central Europe (Diptera: Muscidae)

Coenosia bohemica sp. n. is described from the Bohemian Forest in the Czech Republic. Its relationships to similar species are discussed and its diagnostic characters are illustrated.