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R J Skaer

Publications and source records attributed to R J Skaer.

At least 19 recordsLinked to original sources
PubMed1981

A new en bloc stain for cell membranes: tannic methylamine tungstate.

A new stain is described that combines the mordanting and preservative effects of tannic acid with every strong staining, particularly of plasma membranes. The staining is sufficiently intense in some cell types to reveal frequent links between the outer and the inner leaflet of the plasma membrane.

Animals↗
PubMed1978

Transcription in the interbands of Drosophila.

Many interbands of Drosophila contain morphological evidence for transcription. Decondensed band material makes no detectable contribution to certain transcriptionally active interbands.

Animals↗
PubMed1977

Interband transcription in Drosophila.

Most puffs contain perichromatin ribonucleoprotein granules 30--40 nm in diameter; other puffs contain ribonucleoprotein granules 25 nm in diameter or mixtures of these and perichromatin granules. All puffs contain fragments of band material possibly from several bands. By examining progressively smaller puffs the transcriptionally active region is shown to lie within an interband. Some transcriptionally active interbands are so small that there can be no significant contribution of decondensed band material to the interband. Up to 33% of all interbands contain significant evidence of transcription. These findings are discussed in relation to the use of the terms heterochromatin and euchromatin to describe the banding pattern of polytene chromosomes.

Animals↗
PubMed1977

Chromatin-like artifacts from nuclear sap.

Nuclear sap, on fixation in glutaraldehyde, forms a fibrous network that resembles chromatin in its dimensions and staining properties. This artifactual network is easily confused with true chromatin fibres in sections of nuclei. With formaldehyde a homogeneous array of beads is produced. These are approximately 10 nm in diameter - the size of nucleosomes - and are interconnected by exceedingly fine fibrils. Each fixative and buffer imposes its own distinctive, reproducible pattern on nuclear sap. The structure of nuclear sap in life cannot be deduced from this range of patterns.

Animals↗
PubMed1977

The fixation of nuclei in glutaraldehyde.

The production of an artifactual network in the nuclear sap of the salivary glands of Drosophila has been investigated. Mechanical stress to the cells, 3% glutaraldehyde containing more than 4 mM calcium, tannins, or cacodylate buffer or whose temperature is above 10 degrees C all enhance this artifactual effect. Over the range pH 6.65-7.4 there is no significant effect of pH. The inclusion of sucrose, and adenine nucleotides or other 'chelating' agents in the fixative reduces the effect, especially at low temperature (6-10 degrees C). These influences are additive and can abolish the artifactual effect. So too can 8% glutaraldehyde, but this is irrespective of temperature.

Animals↗
PubMed1976

The fine structure of human chromosomes isolated by shearing-sieving.

Chromosomes isolated by the new technique of shearing-sieving, even if unstained, show a less degraded organisation than those prepared for the electron microscope by other techniques. The chromosomes are banded, may show more bands if stretched, and the centromere is a precisely defined structure. Appearances resulting from this technique are compared with those from other techniques.

Chromosomes↗
PubMed1976

The fixation of nuclei and chromosomes.

Chromosomes in the nuclei of living salivary glands of Simulium have been observed with Nomarski optics and polarized light before and during irrigation with various fixatives. All cause loss of chromosomal organization to some degree. The best fixative is redistilled glutaraldehyde; even so, although it leaves the nucleus visually unaltered, a network forms in the nuclear sap and birefringence is lost. Calcium ions in the fixative cause chromosomal movements. The fixatives may alter nucleoli and may dissolve them completely. New fixatives are needed for reliable fine-structural studies of chromosomal organization.

Acetates↗
PubMed1976

Platelet dense bodies: a quantitative microprobe analysis.

The electron microprobe shows that the dense bodies of human platelets have a mean P:Ca peak ratio of 1-2. After treatment with dry chloroform/methanol this falls to 0-89. These ratios vary slightly from patient to patient. The use of calcium and phosphorus standards enables these peak ratios to be converted to atomic ratios. The size of the phosphorus peak remaining after lipid extraction was given absolute terms with reference to the known quantities of adenine nucleotides and inorganic pyrophosphate in dense bodies. From the mean P:Ca atomic ratio of 1-76 the quantity of calcium in dense bodies was 0-6 mg/10(11) platelets or 2-97 mg Ca/g dry weight of platelets. This is within the published range for total platelet calcium. If all the phosphorus extracted by lipid solvents were phospholipid there would be 5-65 mg/10(11) platelets, and it would occupy most of the space inside dense bodies. The dense bodies of pig platelets contain both magnesium and calcium in a varying ratio to each other. These results are discussed in relation to control mechanisms that may influence aggregation.

Animals↗
PubMed1976

Intranuclear electrophoresis of the chromatin of living cells.

Intranuclear electrophoresis of living cells under appropriate conditions causes the chromatin and nucleoli to move rapidly into the anodal side of the nucleus. In pig kidney cells, chromatin lengths attached to the nuclear envelope are oriented by the current and freed from surrounding non-oriented chromatin. Individual chromatin strands isolated in this way are often long and have not been subjected to the trauma of isolation from the nucleus. This has allowed us to demonstrate oriented lines of up to 8 chromomeres in a strand, linked by fine single fibres. These chromomeres of chromatin have the same linear dimensions as the bands and interbands of polytene chromosomes. A very wide range of morphology of chromatin is revealed - from lines of nucleosomes in open array, to strands uniformly 25 nm thick. Doublet strands and multiple strands - often embedded in darkly staining material - are also seen. All morphological types may be seen in the same nucleus. Many of the oriented threads appear to be transcriptionally active. The variable morphology of these sites and their relation to peripheral heterochromatin is discussed. Histone nucleosomes are present in these apparently transcriptionally active regions. The method is useful for investigating the relationships between chromatin and the nuclear envelope. Approximately 1500 attachment sites per nucleus are found in these cells. Some nucleoli are attached to the nuclear envelope.

Cell Nucleolus↗
PubMed1975

Interpretation of the three-dimensional structure of living nuclei by specimen tilt.

A mechanism is described that enables a specimen to be tilted through a known angle and continuously observed under the highest power of the optical microscope. Objects can thus be localized accurately in space. This facility in conjunction with serial optical sectioning by Nomarski optics has been used to construct models of the arrangement of polytene chromosomes in nuclei of Drosophila, Simulium and Chironomus. Telomeres and chromocentre lie on the nuclear envelope. In Simulium they lie close to an equator of the nucleus. Despite these constraints, different nuclei in the same gland do not resemble each other closely.

Animals↗