Post-meiotic nucleo-cytoplasmic interaction in Cosmos bipinnatus

An interaction involving the nuclear envelope and spherical double-membrane bound inclusions takes place in the cytoplasm of post-meiotic male microspores of Cosmos (tribe Heliantheae, sub-tribe Coreopsidinae). The identity of the spherical inclusions has yet to be fully established, but they closely resemble profiles elsewhere in the cytoplasm, themselves presumably derived from the mitochondrial population of the premeiotic pollen mother cells. Both the cytoplasmic and nucleaar-associated inclusions regularly contain a central vesicle, formed by an ingagination of their bounding membranes. The interaction, which occurs immediately prior to the deposition of the primexine of the pollen wall, involves the adhesion of the inclusions to the nuclear surface. Experiments with osmotically disrupted cells reveal that the inclusions are firmly bound to the envelope and, at the points of contact, electron opaque granules are regularly present. Frequently elements of the chromatin may be observed in juxtapostion to these points of contact, but on the inner face of the envelope. The interaction in Cosmos is proposed to constitute part of the process by which the cytoplasm and its content are realigned to the new gametophylic style of growth.     

Damage and repair in mammalian cells after exposure to non-ionizing radiations : I. Ultraviolet and visible light irradiation of cells of the rat kangaroo (Potorous tridactylus) and determination of photorepairable damage in vitro

Cornea cells of the rat kangaroo or “potoroo” (Potorous tridactylus) were exposed to far-UV (254 or 302 nm) radiation, with or without subsequent illumination by near-UV or visible light. The DNA of these cells was extracted and tested for the presence of photoproducts binding yeast photoreactivating enzyme (PRE). The criterion for the latter was competitive inhibition of an in vitro photorepair system, consisting of UV-irradiated transforming DNA of Haemophilus influenzae and an extract containing yeast PRE. The effects on repair kinetics of the transforming DNA indicate that in UV-irradiated potoroo cornea cells up to approximately 90% of photorepairable DNA damage can be photorepaired within 15 min. However, the extent of cellular photorepair, assessed by the reduction in competitive inhibition of the in vitro repair system depends appreciably on experimental parameters during photoreactivating treatment. Control experiments with non-UV-irradiated cells indicated that, depending on specific conditions, the photoreactivating treatment itself produces a varying amount of DNA damage, which reacts with the PRE in vitro. To avoid most of this kind of damage, cells are nitrogen-gassed and kept at 5°C during illumination, and the photoreactivating light must not contain wavelengths shorter than 380–400 nm. Our results show that wavelengths >470 nm are still very effective, whereas wavelengths >555 nm are ineffective in photorepairing potoroo DNA. For unknown reasons, one particular strain of potoroo cornea cells lost its potential for photorepair. Treatment of unirradiated potoroo cells, or their extracted DNA, with hydrogen peroxide also results in competitive inhibition of photorepair in vitro, resembling that observed after near-UV illumination. Because of the occurrence of synergistic effects it is not clear whether the damage only interacts with PRE or can actually be photorepaired under appropriate conditions.

The results presented in this paper suggest that the expression of photorepair in mammalian cells, unlike that in prokaryotes, greatly depends on a number of experimental parameters, including the spectral composition of photoreactivating light. Apparently superposition of damage by the photoreactivating treatment itself is the critical factor. This may explain experimental discrepancies existing in different laboratories studying photorepair in UV-irradiated cells of placental mammals.     

Neolignans from Aniba burchellii

Seven neolignans, isolated from the benzene extract of Aniba burchellii Kosterm. (Lauraceae), included the hitherto unknown (2S,3S,5S)-5-allyl-5-methoxy-3-methyl-2-(3′,4′-methylenedioxyphenyl)-2,3,5,6-tetrahydro-6-oxobenzofuran and (1R,5R,6R,7R)-1-allyl-6-(4′-hydroxy-3′-methoxyphenyl)-3-methoxy-7-methyl-4,8-dioxobicyclo-[3,2,1]oct-2-ene. The former structure was previously assigned to a constituent of A. terminalis Ducke which is in fact the 5R-epimer. In addition to the latter constituent, all other previously described 4-oxobicyclo[3,2,1]oct-2-ene neolignans had their absolute configuration established.     

Structural abnormalities in chromosome 15 in cell lines with reduced expression of beta-2 microglobulin

Using somatic cell hybrids, the gene for beta-2 microglobulin has been assigned to human chromosome 15. We found it of interest to study a number of human lymphoid cell lines in light of this finding, to analyze whether spontaneously occurring loss or reduction of beta-2 microglobulin could be correlated with any aberration in chromosome 15. The Daudi cell line was shown to be devoid of any beta-2 microglobulin in total extracts. Chromosome analysis showed that one of the two chromosomes 15 was deleted in the region q14q21 on the long arm; in some metaphases, both chromosomes were deleted in this region. The K562 cell line was found to express very low (if any) membrane-associated beta-2 microglobulin. Chromosome analysis showed that this line was near-triploid, with two normal chromosomes 15 and one translocation chromosome t(15;18) involving the long arm of chromosome 15, whereby the segment proximal to the breakage point in band q15 was lost. The Namalwa cell line showed a reduction in membrane-associated and total beta-2 microglobulin. Chromosome analysis showed this line to contain one chromosome 15 which was shorter than its normal homolog. The deletion could be identified as such in the region q14q21 in Daudi cells, but is probably somewhat smaller than the one in Daudi cells. Since analyses of beta-2 microglobulin production and chromosomes 15 on several other human cells failed to reveal any abnormalities in either of these respects, we postulate that genes responsible for beta-2 microglobulin synthesis and membrane expression could be located in the region q14q21 on the long arm of chromosome 15. Since beta-2 microglobulin associated with the membrane was found to be absent in the K562 line, where total beta-2 microglobulin was nearly as high as in cell lines with normal membrane expression, it is suggested that membrane expression of beta-2 microglobulin can be regulated independentlyAbbreviations used in this paper are BSS Earle's balanced salt solution - Q banding bands obtained by fluorescence with Quinacrine Mustard - R banding bands obtained by fluorescence with Acridine Orange - FITC fluorescein isothiocyanate - EBV Epstein-Barr virus     

DNA-fluorometry of mammalian sperm

Summary The DNA-content of sperm and testicular cells was measured by pulse-cytophotometry with high resolution. From flat sperm symmetric and narrow fluorescence distributions were obtained. Enzymatic treatment with papain or pronase and staining with an ethidiumbromide-mithramycin dye solution generate stoichiometric DNA-staining including that of mature sperm with a coefficient of variation below 2%.     

Composition and photoinduced biosynthesis of the carotenoids of a protoplast-like Neurospora crass “slime” mutant

A spheroplast-like slime mutant of Neurospora crassa (lacking a rigid cell wall) was found to synthesize an identical spectrum of carotenoids as wild type strains except for -carotene. Furthermore strict photoregulation of the biosynthesis of these pigments as well as the characteristics of photoinduced carotenogenesis were also nearly identical in the mutant and in the wild type.     

Das Cellulassenzymsystem während Wachstum und Entwicklung von Acanthamoeba castellanii

Zusammenfassung In Extrakten wachsender Kulturen von Acanthamoeba castellanii konnte ein cellulose-abbauendes Enzymsystem nachgewiesen werden. Es besteht aus einer reduzierende Zucker abspaltenden Komponente mit einem pH-Optimum bei 4, einer viscositätsverändernden Komponente mit einem pH-Optimum bei 6 und einer -Glucosidase mit einem pH-Optimum von 3,5. Bei pH 4 sind die Celluloseabbauprodukte Cellobiose und Glucose, bei pH 6 höhermolekulare Oligosaccharide.Während der Entwicklung in einem nährstofffreien Salzmedium nehmen die Cellulaseaktivitäten ab: Vor dem Start der Cellulosesynthese sind noch etwa 30% der ursprünglich vorhandenen Celluloseaktivität nachzuweisen, fertige Cysten besitzen noch etwa 10% der Aktivität.Die Bedeutung des Cellulassenzymsystems wird ausgehend von der Tatsache diskutiert, daß die Excystierung ohne Abbau der Cystenwand, in die die Cellulose eingelagert ist, stattfindet.

---

The cellulase enzymes system during growth and development of Acanthamoeba castellanii

It could be shown that extracts of growing cultures of Acanthamoeba castellanii contained a cellulose degrading system. Reducing sugars are split off by one component of this system at an optimum of pH 4, another enzyme changes the viscosity at an optimum of pH 6, and a third component is a -glucosidase with an optimum at pH 3.5. At pH 4 the cellulose degradation products are cellobiose and glucose; at pH 6 higher molecular weight oligosaccharides are produced.During the development from trophozoites to cysts in a nutrient-free medium, the activities of both cellulases decline: Prior to the start of cellulose synthesis only 30%, and in cysts only 10% of the original existing activities are detectable.The biological function of the cellulase enzyme system is discussed together with a consideration of the fact that excystment takes place without digestion of the cyst wall in which the cellulose is deposited.

     

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.