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Biomedical subjects

V S Polito

Publications and source records attributed to V S Polito.

8 recordsLinked to original sources
PubMed1991

Maintenance of turgor by rapid sealing of puncture wounds in leaf epidermal cells.

When leaf epidermal cells are puncture wounded with a glass microcapillary tip, a small droplet of fluid is discharged and then evaporates, leaving a solid residue on the cell surface. For puncture wounds of about 3.5 micrometers in diameter, this process is complete within 2 to 3 seconds. A second puncture wound also exhibits a similar discharge, indicating the persistence of some turgor pressure within the cell, despite damage to the cell wall. Direct measurement of turgor on the large epidermal cells of Tradescantia virginiana L. demonstrated that turgor was substantially maintained (91-96%) after puncture wounding. Anatomical and histochemical evidence suggests that the damaged portion of the cell wall was sealed with an amorphous plug of material comprised of pectinaceous polysaccharides. Rapid sealing of puncture wounds and the maintenance of turgor in epidermal cells may be an important functional component of plant adaptation to physical damage such as that caused by insect feeding.

Journal Article↗
PubMed1990

The initiation and organization of microtubules in germinating pear (Pyrus communis L.) pollen.

To study microtubule organization in germinating pear (Pyrus communis L., cv., Bartlett) pollen, we removed the pollen wall by freeze-fracturing before treating the resultant pollen protoplasts by conventional immunofluorescence procedures. Results reveal that axial bundles of microtubules are present in the generative cell of both inactivated and activated pollen grains. Microtubules are not present in the vegetative cells of inactivated pollen, but they are present in the vegetative cells of activated pollen grains. Microtubule nucleation occurs in the vegetative cell cortex. Subsequently, the microtubules grow as branching arrays through most of the vegetative cell cortex except at the apertures where they form localized converging or criss-cross patterns. Eventually, in a germinated pollen grain, the microtubules form network-like arrays through most of the pollen grain and a collar of short arrays at the base of the pollen tube. It is suggested that the role of vegetative cell microtubules in pollen germination is indirect through their mediation of the conformational changes in actin organization that are essential for pollen germination.

Fluorescent Antibody Technique↗
PubMed1989

Salinity stress increases cytoplasmic ca activity in maize root protoplasts.

High concentrations of NaCl immediately elevated cytoplasmic Ca activity in maize (Zea Mays L. cv Pioneer 3377) root protoplasts, as measured with the fluorescent probe Indo-1. The effect of salinity was inhibited by Li pretreatment but restored by inositol, suggesting that phosphoinositides mediate the stress response.

Journal Article↗
PubMed1988

Microfluorometry of pectic materials in the dehiscence zone of almond (Prunus dulcis [Mill.] DA Webb) fruits.

We examined the middle lamella and the primary and secondary walls in almond pericarp dehiscence zone cells using a fluorescent cytochemical method which permitted specific, quantitative detection of pectic cell wall materials. Glycol methacrylate-embedded sections were stained with coriphosphine and pectin-specific fluorescent emissions at 630 nm were quantified using green excitation (546 nm). Examination of sectioned material extracted with purified pecto-lytic enzyme preparations was used to demonstrate the relative specificity of the staining reaction for pectic substances.

Aminoacridines↗
PubMed1985

Zymolyase removes callose from germinating pollen and pollen tube walls.

The impermeable callosic wall that surrounds germinating pollen grains and pollen tubes is removed by brief treatment with Zymolyase, an enzyme preparation that hydrolyzes linear glucose polymers with beta-1,3 linkages. Zymolyase treatment does not interfere with pollen tube growth or cylosis in the vegetative cell.

Cell Wall↗
PubMed1985

Displacement of ca by na from the plasmalemma of root cells : a primary response to salt stress?

A microfluorometric assay using chlorotetracycline (CTC) as a probe for membrane-associated Ca(2+) in intact cotton (Gossypium hirsutum L. cv Acala SJ-2) root hairs indicated displacement of Ca(2+) by Na(+) from membrane sites with increasing levels of NaCl (0 to 250 millimolar). K(+)((86)Rb) efflux increased dramatically at high salinity. An increase in external Ca(2+) concentration (10 millimolar) mitigated both responses. Other cations and mannitol, which did not affect Ca(2+)-CTC chelation properties, were found to have no effect on Ca(2+)-CTC fluorescence, indicating a Na(+)-specific effect. Reduction of Ca(2+)-CTC fluorescence by ethyleneglycol-bis-(beta-aminoethyl ether) N,N'-tetraacetic acid, which does not cross membranes, provided an indication that reduction by Na(+) of Ca(2+)-CTC fluorescence may be occurring primarily at the plasmalemma. The findings support prior proposals that Ca(2+) protects membranes from adverse effects of Na(+) thereby maintaining membrane integrity and minimizing leakage of cytosolic K(+).

Journal Article↗