Heterochromatinization,chromatin elimination and haploidization in the parahaploid mite Metaseiulus occidentalis (Nesbitt) (Acarina: Phytoseiidae)

Embryogenic mitoses, mitoses in females and spermatogenesis are described in the predatory mite Metaseiulus occidentalis (Nesbitt). At 22° C, egg development lasts approximately 4 days. Six chromosomes are seen in mitotic metaphases and anaphases of 0–24 h eggs. Toward the end of this period some embryo squashes have patches of cells containing nuclei which are partially heteropycnotic. These patches of cells apparently increase in size with the age of the embryo. In approximately 1/2 of all 24–48 h-old eggs they encompass all or most cells of the embryo. In these embryos metaphases involved 6 chromosomes, anaphases 3. Either prior to, or following metaphase, a pairing of chromosomes appeared to take place to form 3 units which resembled meiotic diplotene chromosomes where there is opening out between homologues. At metaphase, two sets of 3 chromosomes were slightly differentially stained. One, designated the H set, was darker and slightly more contracted than the other, the E set. At anaphase, 3H and 3E chromosomes segregated in a reductional division retaining the differential contraction until telophase. No cytokinesis appeared. The H set appeared to remain contracted while the E set decontracted to assume the appearance of an interphase nucleus. Both of these entities, side-by-side, created the partially heteropycnotic nucleus mentioned above. The H set then appeared to be excluded from the cell. Mitotic meta and anaphases involving 6 chromosomes were noted in female deutonymphs. Spermatogenesis appeared to encompass an equational division of 3 chromosomes, with the formation of a binucleate spermatid. Two tail structures appeared juxtaposed at the edge of each spermatid and thereafter a separation into two individual sperms occurred. —While mitosis was not studied in known males, we believe that the embryos exhibiting heterochromatinization and elimination of chromosomes in most or all cells were in fact demonstrating parahaploidization.This paper is dedicated to the memory of Professor S.W. Brown and is presented to Professor H. Bauer in honor of his 75th birthday     

Responsibility for truth in research

For over half a century, cell cultures derived from animals and humans have served researchers in various fields. To this day, cross-contamination of cultures has plagued many researchers, often leading to mistaken results, retractions of results, cover-ups and some out-and-out falsification of data and results following inadvertent use of the wrong cells. Also, during years of examining cultures for purity we learned that many virologists were not too concerned about the specificity of the cultures they used to propagate the particular virus under study as long as the substrate (whatever it might have been) gave optimal virus yield. Polio virus propagates in primate cells, and much research has involved cells from man and various species of primates. In the 1950s a large number of chimpanzees were held in captivity in Africa for extensive studies of the efficacy of polio vaccine in production at the Wistar Institute in Philadelphia and elsewhere. Chimpanzee tissues, particularly kidneys, were thus readily available and could have also provided substrates for polio virus production, since little was known about the purity of substrates and little attention was paid to their specificity at that time.     

New observations on lecanoid spermatogenesis in the mealy bug,Planococcus citri

Summary A reexamination of the second spermatogenic division of the mealy bug, Planococcus citri (Risso), a lecanoid coccid, has revealed hitherto unknown spindle activity of the euchromatic set of chromosomes during anaphase II. An initial large half spindle elaborated by the heterochromatic chromosomes in early metaphase, gives way to a less pronounced, but clearly visible bipolar spindle involving both sets of chromosomes at early anaphase. There is no lengthening of the spindle or cell, but the separation of the chromosomes occurs around the periphery of the cell with the aid of interzonal activity. The active participation of the euchromatic chromosome during the separation is furthermore inferred by the formation of bridges resulting from euchromatic-heterochromatic translocations.     

Establishment of a lymphoblastoid cell line and isolation of an Epstein-Barr-related virus of gorilla origin.

A B-lymphoid cell line was established from a normal gorilla. The cells contained Epstein-Barr virus-related antigens, and herpesvirus particles were demonstrated by electron microscopy. DNA-DNA reassociation kinétics revealed 30 to 40% hybridization to Epstein-Barr virus with 50 genomes per cell. Examination of the viral nuclear antigen with gorilla sera showed this to be a unique isolate termed Herpesvirus gorilla. H. gorilla transformed gibbon B-lymphocytes in vitro.     

Establishment and characterization of a cell line derived from a spontaneous murinelung carcinoma (M109)

Summary The Madison lung (M109) tumor cell line, initiated from a “spontaneous”, anaplastic murine lung carcinoma, has been propagated continuously in vitro for more than 300 cell generations. Cytogenetic analysis revealed a mouse karyotype with a mode of 78 chromosomes (2n=40). Three distinct marker chromosomes were identified by trypsin-giemsa banding. The cells piled up in culture and had a short generation time and high plating efficiency. Electron microscopy revealed highly undifferentiated cells with little rough endoplasmic reticulum, an abundance of free polysomes, the presence of few and often oddshaped mitochondria, lipid bodies and phagocytic vacuoles. Virus particles of the C-type were found frequently. The subcutaneous transplantation of M109 cultured cells at a relatively low cell inoculum produced highly metastatic tumors in syngeneic BALB/c mice.     

Establishment and characterization of a cell line derived from a spontaneous murine lung carcinoma (M109).

The Madison lung (M109) tumor cell line, initiated from a "spontaneous", anaplastic murine lung carcinoma, has been propagated continuously in vitro for more than 300 cell generations. Cytogenetic analysis revealed a mouse karyotype with a mode of 78 chromosomes (2n = 40). Three distinct marker chromosomes were identified by trypsin-giemsa banding. The cells piled up in culture and had a short generation time and high plating efficiency. Electron microscopy revealed highly undifferentiated cells with little rough endoplasmic reticulum, an abundance of free polysomes, the presence of few and often odd-shaped mitochondria, lipid bodies and phagocytic vacuoles. Virus particles of the C-type were found frequently. The subcutaneous transplantation of M109 cultured cells at a relatively low cell inoculum produced highly metastatic tumors in syngeneic BALG/c mice.     

Clonal derivatives of a bovine kidney cell line (MDBK) and continuing preservation of total chromosomal material

Cells in clones of a permanent bovine kidney cell line (MDBK) revealed fluctuations in number and kinds of chromosomes concomitant with maintenance of chromosome arms. This inidcated the preservation of total chromosomal material through various combinations of species' characteristic telocentric autosomes and newly formed chromosomes with inserted centromeres and reflected the conditions which existed in the uncloned parental population as reported previously.

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Zusammenfassung Der Chromosomenbestand der Zellen einer aus Rinderniere stammenden Gewebekultur (Madin-Darby Bovine Kidney = MDBK) war nach früheren Untersuchungen durch eine der Robertsonschen Regel folgenden Variabilität gekennzeichnet. Mindestens sieben verschiedene Chromosomenbestände mit Kombinationen von den normalen telocentrischen Chromosomen und von neu entstandenen zweischenkligen Chromosomen traten dabei auf; die ursprüngliche (diploide) Zahl von Armen wurde aber beibehalten. Aus der Massenkultur durch Ein-Zell-Isolierung erhaltene Klone weisen, wie erwartet, spezifische cytologische Unterschiede in der Anzahl als auch der Kombination von ein- und zweischenkligen Chromosomen auf. Die cytologische Variabilität der Ursprungspopulation tritt in den Klonen wieder auf. Damit hat die Vermutung, daß nicht Translokation, sondern eine direkte Vereinigung (centric fusion) telocentrischer Chromosomen zur Entstehung von zweischenkligen Chromosomen führt, eine weitere Stütze bekommen.

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Supported by Contract No. PH 43-63-13 between the National Cancer Institute of the National Institutes of Health and the University of California. This report was presented in part at the 16th Annual Meeting of the Tissue Culture Association, Miami Beach, Fla., June, 1965.

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This report was presented in part at the 16th Annual Meeting of the Tissue Culture Association, Miami Beach, Fla., June, 1965.