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Biomedical subjects

A W Coleman

Publications and source records attributed to A W Coleman.

At least 37 records · Page 2Linked to original sources
PubMed1989

Cultivar variability for the presence of plastid DNA in pollen of Pisum sativum L.: implications for plastid transmission.

The mode of plastid transmission in the garden pea (Pisum sativum L.) was analyzed cytologically using the DNA-fluorochrome 4',6-diamidino-2-phenylindole (DAPI) in conjunction with epifluorescence microscopy. The reproductive cells of mature pollen obtained from 12 inbred lines and cv "Early Alaska" were examined for the presence or absence of DAPI-stained plastid DNA aggregates. Plastid DNA was detected in all 13 pea lines examined, although there was variability with regard to the percentage of pollen grains showing plastid DNA aggregates in generative cells (ranging from 3% in accession 82-12r to 65% in accession 82-14n). These cytological results may indicate genetic variability for plastid DNA inheritance in the garden pea.

Cell Count↗
PubMed1987

The solution to the cytological paradox of isomorphy.

Cells with polyploid nuclei are generally larger than cells of the same organism or species with nonpolyploid nuclei. However, no such change of cell size with ploidy level is observed in those red algae which alternate isomorphic haploid with diploid generations. The results of this investigation reveal the explanation. Nuclear DNA content and other parameters were measured in cells of the filamentous red alga Griffithsia pacifica. Nuclei of the diploid generation contain twice the DNA content of those of the haploid generation. However, all cells except newly formed reproductive cells are multinucleate. The nuclei are arranged in a nearly perfect hexagonal array just beneath the cell surface. When homologous cells of the two generations are compared, although the cell size is nearly identical, each nucleus of the diploid cell is surrounded by a region of cytoplasm (a "domain") nearly twice that surrounding a haploid nucleus. Cytoplasmic domains associated with a diploid nucleus contain twice the number of plastids, and consequently twice the amount of plastid DNA, than is associated with the domain of a haploid nucleus. Thus, doubling of ploidy is reflected in doubling of the size and organelle content of the domain associated with each nucleus. However, cell size does not differ between homologous cells of the two generations, because total nuclear DNA (sum of the DNA in all nuclei in a cell) per cell does not differ. This is the solution to the cytological paradox of isomorphy.

Cell Nucleus↗
PubMed1985

Applications of fluorochromes to pollen biology. I. Mithramycin and 4',6-diamidino-2-phenylindole (DAPI) as vital stains and for quantitation of nuclear DNA.

The two DNA-specific fluorochromes DAPI and mithramycin have been found to be extremely useful dyes in studies of pollen development and growth. Both fluorochromes stain nuclei brilliantly either in fixed or in living tricellular and bicellular angiosperm pollen, thereby permitting rapid scanning for pollen abnormalities and easy observation of nuclear details. These water soluble dyes can be incorporated into the germination medium for studies of pollen germination in vitro, facilitating observation of the movement of generative, sperm and tube nuclei during pollen growth. In fixed pollen, the fluorochromes bind quantitatively with DNA and thus may be used to quantitate ploidy changes and to study cell cycles during pollen development, germination and fertilization.

DNA↗
PubMed1984

Elucidation of fertilization and development in a red alga by quantitative DNA microspectrofluorometry.

Crucial nuclear events throughout the life histories of red algae have eluded researchers. Use of the DNA fluorochrome 4',6-diamidino-2-phenylindole (DAPI) and microspectrofluorometry has now resolved the problems. In the parasitic red alga Choreocolax polysiphoniae (= Leachiella pacifica), the amounts of nuclear DNA during the processes of meiosis and fertilization are documented as well as the transfer of the newly formed zygote nucleus to the adjacent accessory cell. In this organism, the G2 period predominates in the cell cycle of vegatative and reproductive cells; many nondividing vegetative cells become highly polyploid. The results indicate that the use of various fluorochromes combined with microspectrofluorometric measurements of individual nuclei is valuable for study of many developmental problems in lower eukaryotes where the relatively small nuclear DNA content has made study with conventional dyes impossible.

Cell Nucleus↗
PubMed1984

The fate of chloroplast DNA during cell fusion, zygote maturation and zygote germination in Chlamydomonas reinhardi as revealed by DAPI staining.

Chlamydomonas reinhardi, a haploid isogamous green alga, presents a classic case of uniparental inheritance of chloroplast genes. Since the molecular basis of this phenomenon is poorly understood, an examination of the cytology of the C. reinhardi plastid DNA was made in gametes, newly formed zygotes, maturing zygotes, and at zygote germination. The single plastid per cell of Chlamydomonas contains a small number of DNA aggregates ('nucleoids') which can be seen after staining with DNA-binding fluorochromes. In zygotes formed by pre-stained gametes, the fluorescing nucleoids disappear from the plastid of mating type minus (male) gamete plastids but not from the plastid of mating type plus (female) gamete plastids about 1 h after zygote formation. Subsequently, nucleoids aggregate slowly to a final average of two or three in the single plastid of the mature zygote. Quantitative microspectrofluorimetry indicates that gametes of both mating types have equal amounts of plastid DNA, and that zoospores arising from zygotes have 3.5 X as much as gametes. Assuming degradation of male plastid DNA, there must be a very major synthesis of plastid DNA between zygote formation and zoospore release when zygotes produce the typical 8-16 zoospores. That synthesis appears to occur at germination, where there is a massive increase in plastid DNA and nucleoid number beginning just prior to meiosis. The results support the theory that uniparental inheritance results from degradation of plastid DNA entering the zygote via the male gamete and suggest further studies, using mutants and altered conditions, which might explain how male plastid DNA sometimes survives.

Cell Fusion↗
PubMed1984

Transfer of nuclei from a parasite to its host.

During the normal course of infection, nuclei are transferred via secondary pit connections from the parasitic marine red alga Choreocolax to its red algal host Polysiphonia. These "planetic" nuclei are transmitted by being cut off into specialized cells (conjunctor cells) that fuse with an adjacent host cell, thereby delivering parasite nuclei and other cytoplasmic organelles into host cell cytoplasm. Within the foreign cytoplasm, planetic nuclei survive for several weeks and may be active in directing the host cellular responses to infection, since these responses are seen only in host cells containing planetic nuclei. The transfer and long-term survival of a nucleus from one genus into the cytoplasm of another through mechanisms that have evolved in nature challenge our understanding of nuclear-cytoplasmic interactions and our concept of "individual."

Journal Article↗
PubMed1984

Amplification of hypoxanthine-guanine phosphoribosyltransferase genes in chromosome-mediated gene transferents.

Hypoxanthine-guanine phosphoribosyltransferase (HPRT) enzyme activities may be elevated in genetically unstable chromosome-mediated gene transferents selected for transfer of the HPRT gene. Increased levels of HPRT polypeptides in unstable mouse L cell gene transferents were demonstrated by two-dimensional gel electrophoresis and immunoprecipitation. No additional polypeptides were found to be overexpressed. HPRT mRNA levels were elevated 10- to 15-fold in the unstable gene transferent GT427C. Southern blot hybridization experiments showed that overexpression of HPRT correlated with a 5- to 15-fold amplification of HPRT gene sequences in two unstable cell lines. Stabilized gene transferents displayed reduced HPRT copy numbers. The amplification of HPRT gene sequences in the unstable transferent GT427C was associated with the presence of multiple minute chromosome fragments. An average of 9.6 fragments was found per metaphase, but the variation was considerable, ranging from 0 to 53. We conclude that genomic DNA sequences may be amplified in unstable chromosome-mediated gene transferents and that such amplification may be associated with the occurrence of multiple chromosomal fragments.

Animals↗
PubMed1981

Mithramycin- and 4'-6-diamidino-2-phenylindole (DAPI)-DNA staining for fluorescence microspectrophotometric measurement of DNA in nuclei, plastids, and virus particles.

The properties of two DNA-specific fluorochromes, 4'-6-diamidino-2-phenylindole (DAPI) and mithramycin, have been analyzed as reagents to quantitate cellular DNA by fluorescence microspectrophotometry. Optimal staining conditions and concentrations, and the effects of other cellular materials to which the dyes bind, have been evaluated in measurements of the DNA of rat, chick, and yeast nuclei, Gonyostomum chloroplasts, and T4 particles. Use of either fluorochrome permits a high degree of resolution of different DNA quantities in nuclei and in cell organelles, and the DAPI-DNA complex is sufficiently fluorescent to permit quantitation of the DNA content in genomes as small as those of individual T4 bacteriophage particles. Fluorescence of mithramycin- or DAPI-stained DNA is proportional to DNA quantity when DNA of the same has composition is compared. Quantitation does not appear to be affected discernably by the state of the DNA, whether in different stages of the cell cycle, in condensed chromosomes, or in noncycling, differentiated nuclei. The use of chicken red blood cells is recommended as an internal monitor for variations in staining conditions.

Amidines↗
PubMed1981

Structure of the chloroplast and its DNA in chloromonadophycean algae.

The arrangement and ultrastructure of chloroplasts is described for the Chloromonadophycean algae gonyostomum semen Diesing and Vacuolaria virescens Cienkowsky. The chloroplasts are present in large numbers and are discoid structures approximately 3-4 micrometer in length by 2-3 micrometer in width. In Gonyostomum semen the chloroplasts form a single layer immediately interior to the cell membrane; frequently their longitudinal axis parallels the longitudinal axis of the cell. The chloroplasts in Vacuolaria virescens are more than I layer deep and do not appear to be preferentially oriented. In both organisms, chloroplast bands usually consist of 3 apposed thylakoids, although fusion and interconnections between adjacent bands frequently occur. External to the girdle band (the outermost thylakoids) is the chloroplast envelope. This is bounded by endoplasmic reticulum but there is no immediately apparent continuity between this endoplasmic reticulum and the nuclear envelope. Electron-dense spheres in the chloroplast stroma are thought to be lipid food reserve. Ring-shaped electron-translucent regions in the chloroplast contain chloroplast DNA. The DNA is distributed along this ring in an uneven fashion and, when stained, resembles a string of beads. Each plastid has I ring, and the ring is unbroken in the intact plastid.

Chloroplasts↗
PubMed1980

Characterization of the methylxanthine-induced propagated wave phenomenon in striated muscle.

Escalation is a propagated wave phenomenon readily observable in chick skeletal muscle fibers growing in culture. It occurs in fibers bathed in methylxanthines, halothane, or quinine, at concentrations associated with twitch potentiation. From the results of a variety of experiments, an explanation of the phenomenon is proposed. Cation requirements suggest that a wave may be initiated in conjunction with a spontaneous calcium influx or calcium spike; and drug concentration, temperature, and extracellular potassium effects support the theory that wave propagation occurs by calcium-induced calcium release from the sarcoplasmic reticulum. The optical effect may then reflect osmotic changes associated with the transient calcium release. Escalation is not restricted to cultured muscle, nor to chick. At appropriate temperatures and in the presence of methylxanthines, escalation has been observed in chick, frog, and rat skeletal muscle. This suggests that it is a subthreshold event, related to contraction, capable of providing further insight into excitation-contraction coupling. The superior visibility conditions and accessibility to experimental manipulation make cultured chick skeletal muscle fibers suitable subjects for such study.

Animals↗
PubMed1979

Use of the fluorochrome 4'6-diamidino-2-phenylindole in genetic and developmental studies of chloroplast DNA.

Use of the DNA-specific fluorochrome 4'6-diamidino-2-phenylindole (DAPI) makes it possible to examine in situ the structure of chloroplast DNA (chDNA) with the fluorescence microscope. This simplifies the study of genetic and developmental changes in chloroplast DNA. Three examples are presented. (a) Wild-type Euglena gracilis B contains several chloroplast DNA nucleoids per chloroplast. A yellow mutant lacking functional chloroplasts is similar, but such nucleoids are absent in an aplastidic mutant strain known from biochemical studies to have lost its chDNA. (b) In vegetative cells of the giant-celled marine algae Acetabularia and Batophora, only about a quarter of the chloroplasts have even one discernible chloroplast DNA particle, and such particles vary in size, showing a 30-fold variation in the amount of DNA-bound DAPI fluorescence detected per chloroplast. By contrast, 98% of chloroplasts in developing Acetabularia cysts contain chDNA, with as many as nine nucleoids per chloroplast. (c) DAPI-stained chloroplasts of chromophyte algae display the peripheral ring of DNA expected from electron microscope studies. However, these rings are not uniform in thickness, but are necklace-like, with the appearance of beads on a string. Since the multiple nucleoids in plastids of chlorophyte algae also appear to be interconnected throughout the chloroplast, a common structural plan may underlie chDNA morphology in both groups of algae.

Acetabularia↗
PubMed1978

Ultrastructure and mechanical activity expressed by striated muscle in culture.

Newly devised assay procedures for quantitating the mechanical capabilities of striated muscle fibers grown in cell culture have permitted the correlation of cytological features with the ability to respond mechanically to electrical and chemical stimuli during development. By developmental timing and by physiological characteristics, three distinct mechanical activities can be distinguished: : TWITCH, contracture and wave propagation (escalation). Parallel electron microscopy studies suggest that contracture and escalation require significantly greater internal membrane development than twitch. The assay procedures have revealed that fibers developed in culture from genetically dystrophic chick muscle cells display a heightened electrical threshold for a twich response, but are otherwise similar to normal fibers. Cultured chick fibers, whether of leg or breast origin, exhibit similar ultrastructural and mechanical properties; yet these are different from those of in vivo adult muscle and may represent the avian striated muscle archetype expressed in the absence of innervation. Primary or cell line cultures of rat muscle produce far fewer mechanically active fibers than do avian cell cultures. The influence of culture conditions and cell source, whether avian or mammalian, on the extent of differentiation expressed in culture is so great that our understanding of studies on cultured muscle fibers would benefit from some characterization of both morphological and contractile properties of the fibers being used.

Acetylcholine↗
PubMed1972

Methylxanthine-induced escalation: a propagated wave phenomenon observed in skeletal muscle developing in culture.

Relatively low concentrations of methylxanthines increase spontaneous twitching in cultured muscle fibers; they also cause a second activity, escalation, which is the initiation and undiminished propagation of visible waves. The effect on twitching is abolished by depolarizing concentrations of K(+) or by tetrodotoxin; the effect on escalation is not. Escalation is prevented by removal of external Ca(++) or by the addition of tetracaine.

Aminophylline↗