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Biomedical subjects

J R Kennedy

Publications and source records attributed to J R Kennedy.

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

Use of Peldri II (a fluorocarbon solid at room temperature) as an alternative to critical point drying for biological tissues.

A new chemical, Peldri II, is evaluated as a compound for drying soft biological tissues for scanning electron microscopy. Peldri II, a fluorocarbon, is a solid at room temperature and is a liquid above 25 degrees C. Cells or tissues are embedded in Peldri II by immersing them in the liquid form and allowing it to solidify. Once solidified, Peldri II will sublime with or without vacuum to dry tissues, probably without introducing surface tension. Several types of cells and tissues have been examined to compare preservation with Peldri II and critical point drying techniques. No differences were detected between the two techniques when normal surface structures were examined. Peldri II appears to be a significant improvement over hexamethyldisilazane as a drying agent for scanning electron microscopy. It is also very convenient for drying large numbers of samples.

Animals↗
PubMed1988

Utilization of digital image processing to study dynein arms (ATPase) in normal and immotile cilia.

Tracheal ciliary cross sections were examined with scanning transmission electron microscopy and the resultant images were digitized for image enhancement. A gray-scale histogram of each ciliary image was produced and manipulated to enhance the image for dynein arms. Tracheal epithelial tissue from the pig, rabbit, and dog, including dogs with immotile cilia syndrome, was examined by using this technique. Tissue from each animal was fixed with each of three different fixatives and sections were evaluated for preservation of dynein arms. The same fixative did not consistently provide optimal fixation for ciliary dynein arms in all three species examined. Each species, therefore, must be evaluated to determine the optimal fixative for preservation of normal ciliary ultrastructure. Digital image processing provides a mechanism for enhancing dynein arms in situ without the need for addition of special stains or the use of techniques such as image summation. With this technique it has been shown that about two-thirds of outer dynein arms are partially or completely missing on cilia from dogs with immotile cilia syndrome.

Adenosine Triphosphatases↗
PubMed1986

Calcium regulation of ciliary activity in rabbit tracheal epithelial explants and outgrowth.

Ciliated epithelial cells from rabbit trachea were employed to examine the role of Ca2+ in the regulation of ciliary motility. Tracheal explants and outgrowths were maintained in culture, and ciliary frequency was determined using a photomultiplier interfaced with a spectrum analyzer capable of Fast Fourier transform analysis. Relative cellular Ca2+ levels were determined by measuring 45Ca2+ uptake and efflux. Elevated cellular Ca2+, from exposure to 10(-5) M calcium ionophore A23187, led to an increase in ciliary frequency followed by inhibition of motility after prolonged treatment. A decrease in ciliary frequency was observed upon lowering intracellular Ca2+ by exposing the epithelium to 1 mM EGTA. Exposure of ciliated cells to 10(-4) M trifluoperazine resulted in inhibition of ciliary motility, a result suggesting a possible role for calmodulin- or phospholipid-sensitive Ca2+-dependent protein kinases in ciliary function. These results support the hypothesis that intracellular Ca2+ is actively involved in modulating the frequency of ciliary beat.

Animals↗
PubMed1986

The effects of gossypol on the ultrastructure and function of tracheal ciliated cells.

Gossypol acetic acid inhibits rabbit tracheal ciliary function in a concentration dependent manner. At concentrations of both 10(-4)M and 5 X 10(-5), ciliary beat is reduced to less than 2 beats/sec in approximately 60 min. At 10(-5)M, reduction of frequency is more gradual, requiring 120 min or longer to approach inhibition. The primary site in the cell showing morphological alteration is the mitochondrion, although extended exposure at lower concentrations does seem to cause increase in the amount of endoplasmic reticulum and Golgi. At the time of inhibition of ciliary beat, mitochondria have a washed out matrix, disrupted cristae and extensive infolding of the outer membrane. Some indication of mitochondrial swelling is also evident. Demembranated axonemes exposed to gossypol show the same dose-dependent response as intact ciliated cells. At 10(-4)M gossypol, axonemes are completely inhibited from reactivation. Axonemes can be reactivated in the presence of 10(-5)M gossypol but are quickly inhibited. 10(-6)M gossypol has no inhibitory effect on demembranated axonemes or intact ciliated cells. Gossypol may be acting initially as a direct but reversible inhibitor of axonemal function while damage to mitochondria may be responsible for the long term, non-reversible inhibition of ciliary function.

Animals↗
PubMed1984

Regulation of the synthesis of mucin glycoproteins in swine trachea explants.

Swine tracheal epithelium has been cultured as explants in a chemically defined medium for periods of up to 2 wk. The viability of the explants was shown by the preservation of the ultrastructural features of cells in the epithelial layer and by the active incorporation of radioactive glucosamine and sulfate into secreted mucin glycoproteins. The rate of secretion of mucin glycoprotein was about 0.035 mg per cm2 per d. After initial 24 h lag period was shown to be due to the equilibration of intracellular mucin glycoprotein pools with radioactive precursors. The rate of secretion of glycoprotein showed a linear dependence on the area of the explant, and maximal incorporation was observed at 200 microM glucosamine. A higher concentration of 35SO4, 1000 microM, was required for maximal incorporation of the precursor. Insulin at 0.1 to 1 microgram/ml increased the rate of secretion twofold, whereas 0.1 to 100 micrograms/ml of hydrocortisone and 0.1 to 100 micrograms/ml of epinephrine significantly decreased the rate of secretion. Vitamin A had little or no effect of normal trachea explants at low concentrations, and, at higher concentrations, 10(-5) M, it decreased the secretion of mucin glycoproteins. Vitamin A, at a concentration of 10(-9) M, increased the rate of synthesis of glycoprotein at least fourfold in trachea explants from vitamin A-deficient rats. Mucus secretions collected from the surface of swine trachea and from the culture medium of trachea explants were purified. The mucus was solubilized by reduction and carboxymethylation, and the high molecular weight mucin glycoproteins were purified by chromatography on Sepharose CL-6B columns under dissociating conditions in 2 M guanidine HCl. The mucin glycoproteins purified from swine trachea and from the culture medium of trachea explants were virtually indistinguishable. They showed the same properties when examined by gel electrophoresis and immunoprecipitation. The purified glycoproteins contained about 25% protein, and serine, threonine, and proline were the principal amino acids present. More than 80% of the carbohydride chains in both samples were released by treatment with alkaline borohydride. Nearly the same molar ratio of N-acetylgalactosamine, N-acetylglucosamine, galactose, fucose, sulfate, and sialic acid was found in both preparations.

Animals↗
PubMed1983

Morphology and quantitation of ciliated outgrowths from cultured rabbit tracheal explants.

Ciliated outgrowths from cultured rabbit tracheal epithelium have been characterized with scanning and transmission electron microscopy and the ciliary frequencies measured. Outgrowth surface cells change in morphology from columnar to cuboidal to squamous shapes in their progression away from the explant. The ciliated cells retain the organization of their cilia in a cluster usually centrally on the apical cell surface. Closest to the explant the nonciliated surface of ciliated cells develops extensive microvilli. Ciliary frequencies are comparable to those observed in fresh tracheal epithelium with means of 50 cells per explant ranging from 11 to 23 beats per second. For most cultures examined no correlation exists between ciliary frequency and cell distance from the explant. The goblet cells loose their ability to synthesize the characteristic mucus granules and can only be identified by the absence of cilia. Surface cells are supported by an underlying layer of discontinuous cells and connective tissue fibers. The characteristics of an outgrowth suggest that development occurs through migration of differentiated cells from the explant rather than differentiation of cell types from migrating basal cells.

Animals↗
PubMed1981

An improved system for studying the effect of Bordetella bronchiseptica on the ciliary activity of canine tracheal epithelial cells.

Ciliated epithelial cell outgrowths from canine tracheal explants were used to study the interaction between Bordetella bronchiseptica and canine respiratory cilia. A sensitive system for quantitating the ciliary beat frequencies of an individual cell was used to study the effects of B. bronchiseptica on ciliary function. Phase I and intermediate-phase B. bronchiseptica isolates produced significant reductions (greater than or equal to 50%) in ciliary beat frequencies within 5 min and nearly complete ciliostasis within 3 hr. A rough-phase isolate of B. bronchiseptica and heat- and formalin-killed preparations of the phase I isolate had no ciliostatic effect. Phase I and intermediate-phase isolates attached to cilia, whereas the rough-phase isolate did not. The ciliostatic effects of the phase I isolate could not be reproduced with endotoxin or culture supernatants from the organism. Thus, attachment alone does not produce ciliostasis; ciliostatic effects of Bordetella may require the close association between metabolically active organisms and cilia.

Animals↗
PubMed1981

Isolation of basal and mucous cell populations from rabbit trachea.

The application of a unit gravity sedimentation procedure to monodispersed rabbit tracheal cells resulted in the isolation of enriched (2-fold to 2.5-fold) basal and mucous cell populations. Cellular integrity was confirmed by a trypan blue dye exclusion index of 93%, [3H] leucine incorporation, and ultrastructural analysis. Unit gravity sedimentation is an affective and rapid procedure for obtaining viable, homogeneous preparations of basal and mucous cells that may be used for in vitro studies of cellular proliferation, differentiation, and glycoprotein biosynthesis in respiratory mucous epithelia.

Animals↗
PubMed1980

Cystic fibrosis serum effects on rabbit tracheal epithelium: an ultrastructural analysis.

The major variation in effect between undiluted cystic fibrosis and heterozygote sera on rabbit tracheal epithelium was in terms of the time after exposure at which changes occurred. Exposure to both types of sera for 3 min caused release of goblet cell mucus and ciliary resorption possibly by apical swelling of columnar cells. Fusion of cilia and loss of microtubule pairs increased markedly through 60 min exposure. After 60 min exposure to heterozygote sera, a thick mucus net formed over many regions of the ciliary surface trapping cilia. Cilia from these areas showed separation occurring between adjacent pairs of peripheral microtubules with individual microtubule pairs remaining intact. Prolonged exposure (60 min) to cystic fibrosis serum resulted in increased mucus secretion and massive columnar cell loss. Some columnar cells were extensively swollen and basal cells showed significant changes. Control serum had no effect on tracheal epithelium over the same time span. Such cystic fibrosis serum-induced changes are characteristic of what one would expect from cells undergoing extensive cytolysis and are much more severe than those induced by heterozygote sera.

Animals↗
PubMed1978

Crystalline inclusion bodies in rabbit embryos.

Crystalline inclusion bodies (CIB) may be found as prominent ultrastructural components of the trophoblast cells of rabbit blastocysts and of progestational uterine endometrium. In the work reported here we have sought to describe developmental steps in crystal formation, to correlate these events with embryonic age and to determine if the uterus is essential (either as a source or an environment) for crystal formation in the embryo. CIB, which are of a size and periodicity to make them appear to be clusters or packages of microtubules, are first detectable in embryos 4 days 6 h post coitum and by 41/2 days are well established in significant numbers. Another structural component, granular vesicles, may be seen in embryos as early as 21/2 days post coitum, and decrease in number during the same time the CIB are increasing. We believe that the CIB originate from the pre-existing granular vesicles and present electron micrograph evidence of crystal formation progressing from such vesicles. CIB formation does not occur in 41/2- to 5-day-old embryos which have been locked in the oviduct by a suture around the utero-tubal junction. However, when such tube-locked embryos are transplanted into the uterus, they develop crystals within 36 h thereafter. We conclude that the uterus is essential for CIB formation to occur in the rabbit embryo.

Animals↗
PubMed1977

Sport: assessing the risk.

Studies on the incidence of sports injuries are an integral part of sports medicine. A survey of three sports medicine journals showed a paucity of information in this area. In view of the need for well designed studies, a series of guidelines for studies is presented.

Athletic Injuries↗