Biomedical subjects

W T Jackson

Publications and source records attributed to W T Jackson.

At least 145 records · Page 8Linked to original sources

PubMed1984

Possible in vivo modulation of the immune system by the leukotriene, LTB4. I. Delayed suppression of cellular immunity.

Leukotriene B4 (LTB4) is a potent mediator of inflammation. Recently, reports have indicated that LTB4 may affect lymphocyte function in vitro. Therefore, we examined the effect of LTB4 following intrapleural injection to determine if LTB4, released at an inflammatory site, would affect rat mononuclear cell function. LTB4 appeared to have little effect on mitogen-induced lymphocyte transformation nor was any direct mitogenic effect observed at concentrations ranging from 10(-6)-10(-12) molar. However, a marked inhibition of a one-way mixed lymphocyte reaction was observed upon in vitro culturing of lymphocytes from animals examined 72-96 hr after a single intrapleural injection of LTB4. We conclude that LTB4 released at inflammatory sites may play a role in modulating immune function but it appears not to be a direct effect but rather, although the evidence is circumstantial, an indirect effect.

Animals↗

PubMed1983

Ionic changes in the mitotic apparatus at the metaphase/anaphase transition.

We have employed a series of permeant, nontoxic, fluorescent probes to detect changes in ionic conditions within the mitotic apparatus of living endosperm cells of Haemanthus during the transition from metaphase to anaphase. Fluorescence emission intensity measurements from the spindle for chlorotetracycline (CTC) decline before the onset of anaphase, indicating a reduction in the amount of membrane-associated Ca2+ and suggesting an efflux of Ca2+ from membrane compartments into the spindle. Subsequent to the onset of anaphase, we observe increases in fluorescence with both 8-anilino-1-naphthalene sulfonate (ANS) and 3,3'-dipentyl 2,2'-dioxacarbocyanine (diO-C5(3)), sensitive to cationic and anionic charges at membrane surfaces, respectively. The increases with ANS and diO-C5(3) suggest that redistributions of ions within the spindle accompany anaphase motion. During the metaphase/anaphase transition, spindle membrane content remains constant, as evidenced by unchanging fluorescence with the hydrophobic probe, N-phenyl-1-naphthylamine (NPN). Shifts in emission intensity from the nonspindle cytoplasm or from the spindle poles do not accompany the changes in fluorescence we observe in the spindle, suggesting that any ionic fluxes responsible for the changes in fluorescence are restricted to the spindle domain.

1-Naphthylamine↗

PubMed1982

Membrane distribution in dividing endosperm cells of Haemanthus.

Membranes in cell-wall-free dividing endosperm cells of Haemanthus were examined after postfixation with osmium tetroxide-potassium ferrocyanide. We found that preservation and staining of membranes in metaphase cells was highly variable. Even adjacent cells often showed different degrees of preservation of membrane. However, this method does reveal a much more extensive membrane system in the mitotic spindle of Haemanthus than has been revealed previously using glutaraldehyde-osmium fixation. At prometaphase a system of membranes becomes associated with the kinetochore bundles. By metaphase, membranes constitute a prominent feature of kinetochore bundles, terminating near the kinetichores. Minipoles, identified by converging microtubules and associated membranes, are distributed in a zone extending laterally across the polar regions of the cell. The microtubules appear to terminate at the minipoles, whereas the membrane system becomes oriented generally perpendicular to the spindle axis and interfaces distally with a region of amorphous electron-dense material, helical polyribosomes, and cell organelles. The role of this extensive membrane system, if any, in chromosome movement is unknown. However, its distribution is coincident with the distribution of calcium-rich membranes and kinetochore fibers at metaphase in these cells (Wolniak, S. M., P. K. Hepler, and W. T. Jackson, 1981, Eur. J. Cell Biol., 25:171-174). Thus, these membranes may function in creating calcium domains that, in turn, may play a regulatory role in chromosome movement.

Calcium↗

PubMed1982

Polarity of spindle microtubules in Haemanthus endosperm.

Structural polarities of mitotic spindle microtubules in the plant Haemanthus katherinae have been studied by lysing endosperm cells in solutions of neurotubulin under conditions that will decorate cellular microtubules with curved sheets of tubulin protofilaments. Microtubule polarity was observed at several positions in each cell by cutting serial thin sections perpendicular to the spindle axis. The majority of the microtubules present in a metaphase or anaphase half-spindle are oriented with their fast-growing or "plus" ends distal to the polar area. Near the polar ends of the spindle and up to about halfway between the kinetichores and the poles, the number of microtubules with opposite polarity is low: 8-20% in metaphase and 2-15% in anaphase cells. Direct examination of 10 kinetochore fibers shows that the majority of these microtubules, too, are oriented with their plus ends distal to the poles, as had been previously shown in animal cells. Sections from the region near the spindle equator reveal an increased fraction of microtubules with opposite polarity. Graphs of polarity vs. position along the spindle axis display a smooth transition from microtubules of one orientation near the first pole, through a region containing equal numbers of the two orientations, to a zone near the second pole where the opposite polarity predominates. We conclude that the spindle of endosperm cells is constructed from two sets of microtubules with opposite polarity that interdigitate near the spindle equator. The length of the zone of interdigitation shortens from metaphase through telophase, consistent with a model that states that during anaphase spindle elongation in Haemanthus, the interdigitating sets of microtubules are moved apart. We found no major changes in the distribution of microtubule polarity in the spindle interzone from anaphase to telophase when cells are engaged in phragmoplast formation. Therefore, the initiation and organization of new microtubules, thought to take place during phragmoplast assembly, must occur without significant alteration of the microtubule polarity distribution.

Anaphase↗

PubMed1981

Snapping scapholunate subluxation.

Three patients were treated for snapping scapholunate subluxation in four wrists, with disabling pain in three wrists. Conventional roentgenographic techniques were not helpful in diagnosing any of these wrist problems. No complete description of the precise abnormality encountered was found in the surgical or roentgenographic literature. Three of the involved wrists have had surgical correction with good early results.

Adolescent↗

PubMed1981

The coincident distribution of calcium-rich membranes and kinetochore fibers at metaphase in living endosperm cells of Haemanthus.

We have coupled chlorotetracycline (CTC) fluorescence with polarized light microscopic observations of living mitotic endosperm cells of Haemanthus in order to compare the spatial distributions of Ca2+-rich endomembranes in the spindle with that of the kinetochore fibers during metaphase. In either control cells or in those treated with the microtubule-stabilizing drug, taxol, the metaphase distribution of Ca2+-rich membranes (bright spindle fluorescence) coincides exactly with the distribution of kinetochore-fiber birefringence.

Calcium↗

PubMed1980

Detection of the membrane-calcium distribution during mitosis in Haemanthus endosperm with chlorotetracycline.

The distribution of membrane-associated calcium has been determined at various stages of mitosis in Haemanthus endosperm cells with the fluorescent chelate probe chlorotetracycline (CTC). CTC fluorescence in Haemanthus has two components: punctate, because of mitochondrial and plastid membrane-Ca++; and diffuse, primarily because of Ca++ associated with endoplasmic reticulum membranes. Punctate fluorescence assumes a polar distribution throughout mitosis. Cones of diffuse fluorescence in the chromosomse-to-pole regions of the metaphase spindle appear to coincide with the kinetochore fibers; during anaphase, the cones of fluorescence coalesce and this region of the spindle exhibits uniform diffuse fluorescence. Perturbation of the cellular Ca++ distribution by treatment with lanthanum, procaine, or EGTA results in a loss of diffuse fluorescence with no accompanying change in the intensity of punctate fluorescence. Detergent extraction of cellular membranes causes a total elimination of CTC fluorescence. CTC fluorescence of freshly teased crayfish claw muscle sarcoplasmic reticulum coincides with the A bands and is reduced by perfusion with lanthanum, procaine, and EGTA in a manner similar to that for diffuse fluorescence in the endosperm cells. These results are consistent with the hypothesis that a membrane system in the chromosome-to-pole region of the mitotic apparatus functions in the localized release of sequestered Ca++, thereby regulating the mechanochemical events of mitosis.

Animals↗

PubMed1980

Evaluating carpal instabilities with fluoroscopy.

In four patients with symptoms suggesting carpal instability (five wrists), fluoroscopic study of the wrists in motion was undertaken after plain film and arthrographic studies showed wither normal or nonspecific findings. Videotape recordings were made continuously of the fluoroscopic image. The examinations revealed that carpal instability can be due to a momentary subluxation that is demonstrable only by observation through a range of motion. Fluoroscopic observation of carpal motion is a useful supplement to static methods in the study of wrist injuries and in these cases gave decisive information not obtainable by other means.

Adolescent↗

PubMed1979

Actin in spindles of Haemanthus katherinae endosperm. I. General results using various glycerination methods.

We have studied actin-containing filaments in spindles in Haemanthus endosperm cells glycerinated by various methods; the actin-containing filaments were identified by their reaction with rabbit skeletal muscle heavy meromyosin (HMM) to form 'decorated' filaments. Actin-containing filaments in the spindle were seen in amongst microtubules in bundles (both non-kinetochore microtubule bundles and kinetochore microtuble bundles) and were also seen not associated with microtubules. There were very few extra-spindle actin-containing filaments in these cells. Actin-containing filaments seemed to interact with microtubules, because the filaments remained close to and parallel to microtubules even when the microtubules were sharply curved. Because of the close association between microtubules and actin-containing filaments we could not identify all the actin-containing filaments present in microtubule bundles: microtubules obscured actin-containing filaments. We studied Haemanthus endosperm cells as they were glycerinated. For some of these observations we used phase-contrast microscopy. Glycerination caused the cells to shrink, initially, and this was followed by rapid expansion, but the cells did not expand to as large a volume as before glycerination. Spindle structure was maintained despite these changes in cell size. Evidences for this are that relative chromosome positions were maintained during glycerination, that spindle birefringence was maintained during glycerination, and that individual chromosomal spindle fibres remained birefringent during glycerination. Electron-microscopic observations supported this in that kinetochore microtubule bundles and non-kinetochore microtubule bundle were maintained during glycerination, as was the helical arrangement of spindle ribosomes into polyribosomes. One-step glycerination procedures were used (cells were treated with mixtures containing 25% glycerol, Triton-X-100 and HMM), and such procedures might be of general use. Living cells were embedded in fibrin clots in making light-microscopic observations; this procedure, too, might be of general use.

Actins↗

PubMed1979

Actin in spindles of Haemanthus katherinae endosperm. II. Distribution of actin in chromosomal spindle fibres, determined by analysis of serial sections.

We have studied the arrangements of actin-containing filaments in 13 bundles of kinetochore microtubules in glycerinated, heavy meromyosin-treated Haemanthus endosperm cells: 7 bundles were in a cell at anaphase, and 6 were in a cell at metaphase. Actin-containing filaments were present in each of the 13 bundles of kinetochore microtubules: they were in amongst the microtubules in the bundle and seemed to be associated with the microtubules. Actin-containing filaments in each bundle seemed to terminate at the kinetochores. Actin-containing filaments associated with the kinetochore microtubules were of consistent polarity (the arrowheads pointed towards the kinetochores) whereas those associated with other microtubles and those not associated with microtubules did not have consistent polarity (some pointed towards the spindle pole, others pointed away from it). Roughly, there were as many individual stretches of actin-containing filaments identified per bundle of kinetochore microtubules as there were microtubules which terminated at the kinetochore. These data suggest that actin-containing filaments in spindles have a functional role. We used 2 glycerination procedures in our studies (one for each cell), and neither seemed to disrupt the basic microtubule arrangements: the arrangements of spindle microtubules seen after glycerination of Haemanthus endosperm were identical to those described previously by others in non-glycerinated glutaraldehyde-fixed Haemanthus endosperm. Thus we argue that spindle structure is not disrupted by the procedures, and therefore that the arrangements of actin-containing filaments are not artifacts of the glycerination procedures. The only difference between microtubules in glycerinated cells and microtubules in untreated cells is that there seem to be fewer in the glycerinated cells. The possible role of actin-containing filaments in the spindle is discussed.

Actins↗

PubMed1977

Animal welfare and the law.

A description of farm animal welfare legislation in Great Britain is given followed by a discussion of similar legislation in Europe. Methods of unifying legislation for the protection of animals in Europe and a summary of current activities are outlined.

Animals↗

PubMed1976

Design and farm animal welfare.

Farm animal welfare and the design of farm buildings and equipment are interrelated. The animals' requirements and preferences should first be estimated and ways in which this can be done are discussed, as are methods of assessment of their environment. Some examples of the influence which housing and equipment design can have are given. Attention is drawn to the difficulties inherent in the assessment of farm animal welfare and the postulation made that the veterinarian is well fitted to carry out such assessments.

Animals↗

PubMed1974