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Biomedical subjects

L W Tice

Publications and source records attributed to L W Tice.

At least 19 recordsLinked to original sources
PubMed1984

Alteration of tight junctional permeability in the rat parotid gland after isoproterenol stimulation.

The permeability of junctional complexes to ultrastructural tracers of different molecular weight and the freeze-fracture appearance of junctional structure were investigated in the resting and stimulated rat parotid gland. Tracers were administered retrogradely via the main excretory duct, and allowed to flow by gravity (16 mmHg) into the gland for 15-60 min. Secretion was induced in some animals by intraperitoneal injection of isoproterenol. In resting glands, the tracers microperoxidase , cytochrome c, myoglobin, tyrosinase (subunits), and hemoglobin were restricted to the luminal space of the acini and ducts. In glands stimulated 1-4 h before tracer administration, reaction product for microperoxidase , cytochrome c, myoglobin, and tyrosinase was found in the intercellular and interstitial spaces, whereas hemoglobin was usually retained in the lumina. In contrast, horseradish peroxidase and lactoperoxidase appeared to penetrate the tight junctions and reaction product was localized in the extracellular spaces in both resting and stimulated glands. Diffuse cytoplasmic staining for horseradish peroxidase and lactoperoxidase was frequently observed in acinar and duct cells. The distribution of horseradish peroxidase was similar in both Sprague-Dawley and Wistar-Furth rats, and at concentrations of 0.1-10 mg/ml in the tracer solution. Freeze-fracture replicas of stimulated acinar cells revealed an increased irregularity of the tight junction meshwork, but no obvious gaps or discontinuities were observed. These findings indicate that (a) tight junctions in the resting rat parotid gland are impermeable to tracers of molecular weight greater than or equal to 1,900; (b) stimulation with isoproterenol results in a transient increase in junctional permeability allowing passage of tracers of molecular weight less than or equal to 34,500; (c) junctional permeability cannot be directly correlated with junctional structure; and (d) the behavior of horseradish peroxidase and lactoperoxidase in the rat parotid gland is inconsistent with their molecular weights. Cell membrane damage due to the enzymatic activity or binding of these two tracers may account for the observed distribution.

Animals↗
PubMed1980

Immunocytochemical localization of catechol-O-methyltransferase in the pregnant rat uterus.

Light microscopic immunocytochemical observations of catechol-O-methyl-transferase (COMT) localization in the pregnant rat uterus were made with a specific antibody to soluble rat liver COMT and the peroxidase-antiperoxidase technique. The changes in cellular localization of COMT were followed from the onset of pregnancy to 12 h after delivery of the last fetus. COMT first appeared on day 5 of pregnancy in endometrial epithelial cells of the uterus. On day 7, COMT appeared in the decidual cells on the antimesometrial side of the uterus close to the implanting blastocyst. Two morphologically distinct, COMT-positive, decidual cells were observed: polygonal cells and stellate cells. After parturition, COMT-positive decidual cells remained in the decidua basalis. The possible physiological roles of COMT in the pregnant uterus are discussed.

Animals↗
PubMed1979

Morphology of the granular secretory glands in skin of poison-dart frogs (Dendrobatidae).

The granular glands of nine species of dendrobatid frogs were examined using light and electron microscopy. The glands are surrounded by a discontinuous layer of smooth muscle cells. Within the glands proper the secretory cells form a true syncytium. Multiple flattened nuclei lie at the periphery of the gland. The peripheral cytoplasm also contains mitochondria, rough surfaced endoplasmic reticulum, the Golgi apparatus, and an abundance of smooth endoplasmic reticulum. Centrally, most of the gland is filled with membrane-bound granules surrounded by amorphous cytoplasm. Few other organelles are found in this region. Early in the secretory cycle, the central part of the gland is filled with flocculent material which appears to be progressively partitioned off by membranes to form the droplet anlage. As granules form, the structure of the contents becomes progressively more vesicular. Dense vesicles, which bud off from the Golgi apparatus, fuse with the granular membrane during the development of granules, and might contain enzymes involved in toxin synthesis. The granules at this point resemble multivesicular bodies. Their structure is similar in all species of dendrobatid frogs even though the different frogs secrete substances of different chemical structure and toxicity.

Animals↗
PubMed1979

Changes in tight junctions of rat intestinal crypt cells associated with changes in their mitotic activity.

The freeze-fracture appearance of tight junctions between rat duodenal crypt cells was studied in normal, mitotically suppressed, and mitotically enhanced animals. In normal animals crypt cell tight junctions present a pleomorphic appearance. The population includes junctions resembling postmitotic junctions of the intestinal villus, junctions composed largely or completely of particle chains, and regions at the cell apex in which junctions are absent for 3-4 micron distances laterally. Mitotic suppression by inhibition of DNA synthesis with cytosine arabinoside results in the disappearance of pleomorphism and crypt tight junctions progressively come to resemble those of the intestinal villus. With recovery from the drug and further synchronization with Colcemid, the crypt cells undergo a mitotic burst, and all varieties of unusual junctional configurations are observed with increased frequency.

Animals↗
PubMed1977

Tracer and freeze fracture observations on developing tight junctions in fetal rat thyroid.

The development of tight junctions in fetal rat thyroid from the sixteenth to the twentieth days of gestation was examined with conventional ultrastructural methods and freeze-fracture preparations. These results were compared with those obtained using lanthanum hydroxide and horseradish peroxidase (HRP) tracers. Tight junctions appear to arise on the plasma membranes of fetal thyroid cells by the aggregation and fusion of linear particle chains which appear at several discrete sites on the plasma membrane of developing follicular cells. Tracer studies show that they are effective barriers to the passage of HRP from the outset, are freely penetrated by La3+ at the sixteenth and seventeenth days of gestation, but progressively lose permeability to La3+ from the seventeenth to twentieth days of gestation. However, freeze-fracture observations suggest that La3+ must penetrate into the follicular lumen through the tight junction elements, for the follicular lumen, when it appears, is always completely surrounded by a continuous though sometimes rudimentary meshwork of tight junction elements. The results suggest that the tight junction forms an effective barrier to the passage of large macromolecules, e.g. thyroglobulin, from very early stages in its development. The La3+ results suggest that decreased resistance of the intercellular pathway, possibly related to the development of transepithelial potentials, may occur during this period in development.

Animals↗
PubMed1976

Gap junctions in thyroid epithelium of the rat.

Gap junctions were observed on the lateral plasma membrane of the typical thyroid epithelial cell in freeze-fracture preparations of rat thyroid gland. The gap junctions were 0.1 to 0.4 mum in diameter and were composed of closely packed, approximately 80 nm particles. They were located from 1 to 6 mum from the apical surface of the cell.

Animals↗
PubMed1975

Changes in tight junctions of thyroid epithelium with changes in thyroid activity.

The morphology of the tight junction of rat thyroid epithelium was examined in freeze-fractured material fixed in glutaraldehyde and briefly glycerinated. In normal thyroids the overall appearance of this junctional specialization resembled that of other cell types in many respects. Short-term changes in thyroid activity and hypophysectomy for 3 wk did not obviously affect the appearance of tight junctions. Feeding of the goitrogen, thiouracil, which stimulates secretion of thyroid-stimulating hormone, resulted in the appearance of some very narrow and some very wide, tight junctions or sometimes junctions with both wide and narrow regions within the same cell.

Animals↗
PubMed1975

Electron microscopic identification of adrenergic nerve endings on thyroid epithelial cells.

Electron microscopic observations were made of the microinnervation of the thyroids of normal mice and of mice given false adrenergic neurotransmitters, and the effects of the drugs on thyroidal norepinephrine uptake were measured. In addition to adrenergic nerve terminals on thyroid blood vessels, structures resembling nerve endings were seen in close apposition to the bases of thyroid epithelial cells. Because they take up false adrenergic neurotransmitters, and undergo degenerative change after administration of cytotoxic false neurotransmitters (6-hydroxydopamine and 5,7-dihydroxytryptamine), which also reduce thyroid norepinephrine uptake, they probably represent adrenergic nerve terminals on thyroid follicles. If so, they afford a morphological basis for the direct effects of catecholamines on thyroid function, which have been reported.

Animals↗
PubMed1967

Calcium activation of frog slow muscle fibres.

1. Skinned muscle fibres were prepared from the tonus bundle of the frog iliofibularis muscle and the contractile response elicited by applied calcium ions was studied. The fibre type was determined by electron microscopy.2. Fast fibres shortened many times more rapidly than slow fibres, indicating that the slow contraction of slow fibres is an inherent property of the contractile mechanism.3. The extent of spread of contraction following local calcium application was much greater in slow than in fast fibres, a difference which is consistent with the relative sparsity of the sarcoplasmic reticulum in slow fibres.4. The ability of the sarcoplasmic reticulum of slow fibres to accumulate calcium was demonstrated by the in situ immobilization of calcium when oxalate solutions were added to the skinned fibre.

Animals↗
PubMed1966

Cytochemistry of phosphatases of the sarcoplasmic reticulum. I. Biochemical studies.

A microsomal fraction was isolated from rabbit psoas muscle by a modification of Muscatello's method. The fraction contained a Mg-dependent ATPase which had a pH optimum of 7.5. Activity was further stimulated by addition of Na or K or other monovalent cations to the reaction mixture, but synergistic activation by Na and K, and ouabain inhibition, could not be demonstrated. The enzyme hydrolyzed only ATP (adenosine triphosphate) and ITP (inosine triphosphate) at appreciable rates, but Na or K stimulated activity only when ATP was used as substrate. Activity was inhibited by Ca and by low concentrations of Na deoxycholate, and was sensitive to inhibition by thiol group reagents. The enzyme could be distinguished from another enzyme, also present in the fraction, which was Ca-activated, and which exhibited a wider substrate specificity, different pH activation characteristics, lower specific activity, lack of stimulation by Na or K, and less sensitivity to inhibition by deoxycholate and by thiol group reagents. These findings formed the basis for demonstration of the Mg-dependent ATPase in situ.

Adenosine Triphosphatases↗