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R S Quatrano

Publications and source records attributed to R S Quatrano.

66 records · Page 4Linked to original sources
PubMed1977

Fine-structural studies of the gametes and embryo of Fucus vesiculosus L. (Phaeophyta). III. Cytokinesis and the multicellular embryo.

Condensation of the chromosomes during the first cell division following fertilization of the brown alga Fucus vesiculosus L. is accompanied by the almost complete disappearance of the nuclear envelope. Golgi vesicles and other small vesicles appear within the spindle, which has paired centrioles at each end. A large amount of rough endoplasmic reticulum is in the surrounding cytoplasm during mitosis, and many vesicles at the spindle margin are encircled by stacks of endoplasmic reticulum. Annulate lamellae are observed during mitosis. The envelope which initially reforms around the chromatin in telophase has unevenly spaced nuclear pores. Cytokinesis results primarily by vesicle addition to a centripetal furrow. Mitochondria and chloroplasts concentrate around the partition site, possibly in association with microfilaments. Fibrillar material is added rapidly to the space between the daughter cells from vesicle discharge of both cells and seems to spread into the older cell wall surrounding the embryo. The rhizoid daughter cell contains numerous mitochondria and hypertrophied Golgi bodies whose vesicles increasingly pack the cell. The thallus daughter cell is packed with a variety of vesicles, and the nucleus is surrounded by many dilated cisternae of rough endoplasmic reticulum. By the four-cell stage, chloroplasts of the rhizoid cells have weakly staining lamellae, while chloroplasts of the thallus cells are actively dividing with deeply staining lamellae.

Cell Division↗
PubMed1976

Cell wall assembly in fucus zygotes: I. Characterization of the polysaccharide components.

Fertilization triggers the assembly of a cell wall around the egg cell of three brown algae, Fucus vesiculosus, F. distichus, and F. inflatus. New polysaccharide polymers are continually being added to the cell wall during the first 24 hours of synchronous embryo development. This wall assembly involves the extracellular deposition of fibrillar material by cytoplasmic vesicles fusing with the plasma membrane. One hour after fertilization a fragmented wall can be isolated free of cytoplasm and contains equal amounts of cellulose and alginic acid with no fucose-containing polymers (fucans) present. Birefringence of the wall caused by oriented cellulose microfibrils is not detected in all zygotes until 4 hours, at which time intact cell walls can be isolated that retain the shape of the zygote. These walls have a relatively low ratio of fucose to xylose and little sulfate when compared to walls from older embryos. When extracts of walls from 4-hour zygotes are subjected to cellulose acetate electrophoresis at pH 7, a single fucan (F(1)) can be detected. By 12 hours, purified cell walls are composed of fucans containing a relatively high ratio of fucose to xylose and high levels of sulfate, and contain a second fucan (F(2)) which is electrophoretically distinct from F(1). F(2) appears to be deposited in only a localized region of the wall, that which elongates to form the rhizoid cell. Throughout wall assembly, the polyuronide block co-polymer alginic acid did not significantly vary its mannuronic (M) to guluronic (G) acid ratio (0.33-0.55) or its block distribution (MG, 54%; GG, 30%; MM, 16%). From 6 to 24 hours of embryo development, the proportion of the major polysaccharide components found in purified walls is stable. Alginic acid is the major polymer and comprises about 60% of the total wall, while cellulose and the fucans each make-up about 20% of the remainder. During the extracellular assembly of this wall, the intracellular levels of the storage glucan laminaran decreases. A membrane-bound beta-1, 3-exoglucanase is found in young zygotes which degrades laminaran to glucose. It is postulated that hydrolysis of laminaran by this glucanase accounts, at least in part, for glucose availability for wall biosynthesis and the increase in respiration triggered by fertilization. The properties and function of alginic acid, the fucans, and cellulose are discussed in relation to changes in wall structure and function during development.

Journal Article↗
PubMed1976

Fine-structural studies of the gametes and embryo of Fucus vesiculosus L. (Phaeophyta). I. Fertilization and pronuclear fusion.

In the marine brown alga, Fucus vesiculosus L., the sperm pronucleus is delimited by an envelope following penetration of the eff by the sperm. This envelope disintegrates as the pronucleus begins its migration through the cytoplasm of the egg. The highly condensed chromatin of the sperm pronucleus disperses slightly following disintegration of the envelope. Microtubules of unknown origin are associated with the sperm pronucleus during its migration. The flagellar microtubules remain in the peripheral cytoplasm but lose their tight 9 + 2 configuration. The sperm eyespot and mitochondria follow the pronucleus through the cytoplasm toward the egg pronucleus. The mitochondria of the sperm are distinguished from those of the egg by their longitudinally oriented cristae and by electron-opaque material in the intracristal space. The pronucleus of the egg becomes convoluted along the surface nearest to the advancing sperm pronucleus. Immediately prior to pronuclear fusion, many egg mitochondria aggregate in the vicinity of the sperm pronucleus. At this time, only the portion of the sperm pronucleus facing the egg pronucleus is surrounded by an envelope. The egg mitochondria disperse rapidly after pronuclear fusion. The sperm mitochondria and eyespot are still in the perinuclear region in 16-h-old embryos. At this time, the osmiophilia of the sperm eyespot has increased, and the sperm mitochondrial membranes are less distinct than in earlier stages. The fine-structural features of fertilization in Fucus are discussed in relation to the fertilization patterns in other cryptogams and marine invertebrates and to polar axis determination in the Fucaceae.

Cell Nucleus↗
PubMed1976

Fine-structural studies of the gametes and embryo of Fucus vesiculosus L. (Phaeophyta). II. The cytoplasm of the egg and young zygote.

Following fertilization, there are rapid changes in the appearance of the Fucus egg. Large electron-translucent vesicles (V1) accumulate fibrillar material, and following pronuclear fusion, they are largely electron-opaque. These vesicles (V1) are formed originally in unfertilized eggs by smooth endoplasmic reticulum (SER) after release of the eggs from the oogonium. Golgi complex hypertrophy follows fertilization, and this increased activity continues throughout early embryogenesis. Wall formation begins after penetration of the egg by the sperm. Vesicles (V2) of unknown origin, which have homogeneously fibrillar contents, and Golgi vesicles (V3) merge with SER-derived vesicles (V1) after wall formation begins. Osmiophilic bodies are a prominent feature of the egg and embryo. They are penetrated by SER, and subsequently there is a loss of electron-opaque material. Alternatively, they discharge concentrically whorled material into the cytoplasm. The nuclear surface of the egg is convoluted in the period close to fertilization, and electron-opaque material is segregated in the cytoplasmic matrix lying within the nuclear invaginations.

Cell Nucleus↗
PubMed1975

Isolation of Polysaccharides Sulfated during Early Embryogenesis in Fucus.

Beginning 10 hours after fertilization, zygotes of Fucus distichus L. Powell incorporate (35)S into polysaccharides as a sulfate ester of fucose. These sulfated polysaccharides are sequestered in only the rhizoid cell of the two-celled embryo and can serve as a marker of cellular differentiation. Zygotes were pulsed at different times after fertilization with Na(2) (35)SO(4) to identify and isolate the fucans localized within the region of cytoplasm destined to become the rhizoid cell. Low molecular weight pools of (35)S were saturated within 60 minutes, with the greatest incorporation into ethanol-soluble and insoluble fractions occurring with 0.1 mm Na(2)SO(4) in the artificial sea water medium. At the time of rhizoid formation, four fucose-containing polysaccharide fractions incorporated (35)S. When each fraction was subjected to diethylaminoethyl chromatography, two components were eluted with KCl that contained over 84% of the fucose and 93% of the (35)S of the particular fraction. Highvoltage paper electrophoresis of each fraction also resulted in the separation of these two major components. Both components from each of the four fractions behaved identically when separated by diethylaminoethyl chromatography and paper electrophoresis. By comparing the incorporation of (35)S into the polysaccharide fractions at 4 and 16 hours after fertilization, the fucan-sulfate components that are localized in the cytoplasm at the time of rhizoid formation were isolated. Although sulfated polysaccharides in brown algae are reported to be very heterogeneous in terms of their sugar composition and complexes with other heteropolymers, we propose that there are two major components that are sulfated during early embryogenesis in Fucus. The location of these two sulfated polysaccharides in different chemical fractions may reflect their subcellular localization (e.g., cytoplasmic vesicles or cell walls), or their association with other heteropolymers.

Journal Article↗