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J C Adams

Publications and source records attributed to J C Adams.

At least 55 records · Page 3Linked to original sources
PubMed1993

The National Temporal Bone, Hearing, and Balance Pathology Resource Registry.

The National Temporal Bone, Hearing, and Balance Pathology Resource Registry has been established with funding provided by the National Institute on Deafness and Other Communication Disorders of the National Institutes of Health. The registry is meant to serve as a national resource for researchers and the public to stimulate and facilitate human otopathologic research. It will maintain a computerized database of currently active and inactive temporal bone and auditory brain-stem collections throughout the United States. In addition, it will encourage human temporal bone research by disseminating pertinent information, developing and fostering temporal bone professional educational activities, implementing a national temporal bone acquisition network, and encouraging investigative collaborations in the study of the human temporal bone and brain structures. It will also identify otopathologic collections at risk of being discarded or lost and will develop mechanisms and strategies to conserve them.

Brain↗
PubMed1993

Identification and characterization of thrombospondin-4, a new member of the thrombospondin gene family.

A new member of the thrombospondin gene family, designated thrombospondin-4, has been identified in the Xenopus laevis genome. The predicted amino acid sequence indicates that the protein is similar to the other members of this gene family in the structure of the type 3 repeats and the COOH-terminal domain. Thrombospondin-4 contains four type 2 repeats and lacks the type 1 repeats that are found in thrombospondin-1 and 2. The amino-terminal domain of thrombospondin-4 has no significant homology with the other members of the thrombospondin gene family or with other proteins in the database. RNAse protection analysis establishes that the initial expression of Xenopus thrombospondin-4 is observed during neurulation. Levels of mRNA expression increase twofold during tailbud stages but decrease by the feeding tadpole stage. The size of the thrombospondin-4 message is 3.3 Kb and 3.4 Kb in the frog and human, respectively. Northern blot analysis of human tissues reveals high levels of thrombospondin-4 expression in heart and skeletal muscle, low levels in brain, lung and pancreas and undetectable levels in the placenta, liver and kidney. These data establish the existence of a new member of the thrombospondin gene family that may participate in the genesis and function of cardiac and skeletal muscle.

Amino Acid Sequence↗
PubMed1993

Diverse mechanisms for cell attachment to platelet thrombospondin.

Thrombospondin-1 is a component of the extracellular matrix which is thought to play important roles in cell migration and proliferation, during embryogenesis and wound repair. To understand the basis for these activities, we are mapping the regions of the molecule with cell adhesive activity. Here, we use antagonists of specific cell binding sites, adhesion-perturbing thrombospondin monoclonal antibodies and proteolytic fragments of platelet thrombospondin, to investigate the adhesive mechanisms used by G361 melanoma cells, human intestinal smooth muscle cells (HISM), epidermal keratinocytes and MG-63 osteosarcoma cells. When attached to the same preparations of platelet thrombospondin, HISM and MG-63 cells underwent spreading, whereas G361 cells and keratinocytes did not. Attachment of all four cell types involved the carboxyterminal domain. The type 1 repeats and the amino-terminal heparin binding domain were important for stable attachment of G361, HISM and MG-63 cells, but were not involved in keratinocyte attachment. GRGDSP peptide caused near complete inhibition of HISM and MG-63 cell attachment, partially inhibited G361 attachment, but did not inhibit keratinocyte attachment. Attachment of HISM and MG-63 cells involved the alpha v beta 3 integrin. The integrity of the thrombospondin molecule was important for its adhesivity towards G361, HISM, and MG-63 cells, whereas keratinocytes attached to the 140 kDa tryptic fragment as effectively as they did to the intact molecule. These results show that cell attachment to platelet thrombospondin typically involves multiple binding interactions, but the exact profile of interactions is cell type specific. Usage of particular cell-binding sites does not predict whether cells will undergo spreading or not. These data may, in part, explain some of the current controversies surrounding the mechanisms of cell attachment to thrombospondin.

Amino Acid Sequence↗
PubMed1993

Regulation of keratinocyte terminal differentiation by integrin-extracellular matrix interactions.

Suspension-induced terminal differentiation of human epidermal keratinocytes can be inhibited by fibronectin through binding to the alpha 5 beta 1 integrin. We have investigated the effect of fibronectin on expression of integrins and proteins of the actin cytoskeleton and have explored the nature of the differentiation stimulus by testing different combinations of anti-integrin monoclonal antibodies or extracellular matrix proteins in the suspension assay. Fibronectin prolonged cell surface expression of beta 1 integrins but did not overcome the inhibition of intracellular transport of integrins that occurs when keratinocytes are placed in suspension. Fibronectin did not prevent the suspension-induced decline in the level of mRNAs encoding the beta 1 integrin subunit, actin, filamin and alpha-actinin; furthermore, the inhibition of terminal differentiation did not depend on the state of assembly of microfilaments or microtubules. Terminal differentiation could be partially inhibited by an adhesion-blocking monoclonal antibody to the beta 1 integrin subunit or by a combination of adhesion blocking antibodies recognising the alpha subunits that associate with beta 1 (alpha 2, alpha 3 and alpha 5). Although laminin and type IV collagen do not inhibit terminal differentiation individually, they were inhibitory when added to cells in combination with a low concentration of fibronectin. We conclude that the proportion of keratinocyte beta 1 integrins occupied by ligand can regulate the initiation of terminal differentiation independently of the state of assembly of the actin cytoskeleton.

Actins↗
PubMed1993

The localization of synaptophysin in the organ of Corti of the human as shown by immunoelectron microscopy.

Synaptophysin, or p38, a polypeptide of molecular weight 38 kD, is a calcium-binding membrane protein found in synaptic vesicles of neurons and smooth surfaced vesicles of neuroendocrine cells. Six human neonatal and infant temporal bones were fixed in paraformaldehyde and glutaraldehyde, decalcified in EDTA and were than immunoreacted for synaptophysin (ICN Biomedicals) using the avidin-biotin reaction (ABC kit, Vector Labs). The tissue was then prepared for light microscopic surface preparation, radial sections of 5 microns, and serial section electron microscopy. At a light microscopic level, the inner spiral bundle, tunnel spiral bundle, upper tunnel crossing fibers and the base of outer hair cells were stained. At the base of outer hair cells, the immunoreactivity was seen to decrease from the base to the apex and from the first to third outer hair cells. At an electron microscopic level, immunoreactivity at the base of outer hair cells was limited to vesiculated efferent fibers. The degree of immunoreactivity between adjacent efferent fibers varied significantly. Immunoreactive vesiculated endings were also found in the supranuclear region of outer hair cells.

Hair Cells, Auditory↗
PubMed1993

Evidence against a major role for integrins in calcium-dependent intercellular adhesion of epidermal keratinocytes.

It is well established that integrins mediate keratinocyte adhesion to extracellular matrix proteins, but, in addition, there is some evidence that they mediate intercellular adhesion. We have investigated the role of integrins in keratinocyte-keratinocyte adhesion by adding anti-integrin antibodies to cells in three assays that differ according to the calcium ion concentration of the medium, the presence or absence of an adhesive substrate (glass or tissue culture plastic) and the timing of antibody addition. As previously reported by Larjava et al., (J. Cell Biol. 110:803-815), a monoclonal antibody to the beta 1 subunit perturbed cell-cell adhesion when added to adherent monolayers in low calcium medium (0.1 mM calcium ions), but did not prevent cell-cell adhesion or stratification induced by raising the level of calcium ions to 1.8mM (the concentration in standard medium). Monoclonal antibodies to both the alpha 3 and beta 1 subunits inhibited the attachment, spreading and motility of keratinocytes in low or standard calcium medium when added at the time of plating; however, they had only a modest effect on the accumulation of cells in adherent clusters. Aggregation of keratinocytes in suspension required a calcium ion concentration of greater than 0.1mM and was not inhibited by any of a large panel of anti-integrin antibodies, including three new antibodies that recognise alpha 2 beta 1. We conclude that any inhibitory effects of individual anti-integrin antibodies on cell-cell adhesion are abrogated by a calcium ion concentration above 0.1mM and that in low calcium medium at least some of the inhibition of cell-cell adhesion is a consequence of the inhibition of cell-substrate adhesion and motility.

Antibodies, Monoclonal↗
PubMed1992

GABAergic neurons in the mammalian inferior olive and ventral medulla detected by glutamate decarboxylase immunocytochemistry.

Neurons containing glutamic acid decarboxylase (GAD) (presumed GABAergic neurons) were mapped by immunocytochemistry in the ventral medulla of rat, rabbit, cat, rhesus monkey, and human, with emphasis on the inferior olive. In all species, three categories of GABAergic neurons were identified: periolivary neurons in the gray matter and the white matter surrounding the inferior olive, internuclear neurons located in the white matter between the subnuclei of the inferior olive, and intranuclear neurons located within the olivary gray matter. The intranuclear GABAergic neurons of the inferior olive had a characteristic morphology which differed from non-GABAergic olivary neurons; they were usually smaller, and, wherever their processes were stained, they had radiating, sparsely branching dendrites. They were also usually distinguished from the other GABAergic neurons by their smaller size. The intraolivary GABAergic neurons constituted only a minor proportion of the total olivary neuronal population, but they were concentrated in regions of the olive that varied by species. In the rat, they were situated in the rostral tip of the medial accessory olive and in the caudal subdivision of the dorsal accessory olive, while in the rabbit, they were located in the caudal two-thirds of the medial accessory olive, in the dorsal cap, and in the ventral lateral outgrowth. Such neurons were extremely rare in the cat; only a few were found in the rostral parts of the principal olive, the medial accessory olive, and the dorsal accessory olive. In the rhesus monkey, the principal olive and the lateral region of the rostral medial accessory olive contained most of the intranuclear GABAergic neurons, but some were also present in the dorsal accessory olive. In the human, such neurons occurred in the principal olive, the dorsal accessory olive and the rostral medial accessory olive, but as in the rhesus monkey, most were observed in the principal olive.

Animals↗
PubMed1992

Advance directives.

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Advance Directives↗
PubMed1992

Biotin amplification of biotin and horseradish peroxidase signals in histochemical stains.

A procedure is described for intensifying histochemical reactions by amplification of biotinylated sites. This is achieved by deposition of biotinylated tyramine on the tissue through the enzymatic action of horseradish peroxidase (HRP). The amplified biotin sites are subsequently visualized by binding them to avidin, to which a marker is attached. This amplification greatly increases the sensitivity of staining procedures that employ HRP (and/or biotin) in tissue. For neuroanatomical pathway tracing methods, the procedure greatly increases the detectability of the injected tracer. For lectin histochemistry and immunohistochemistry, the amplification requires that the lectin or primary antibody be greatly diluted. This dilution results in less background staining and yet strong signals are produced even when very dilute reagents are used. Alternatively, the amplification permits much shorter incubations in primary antibodies when dilutions are used that would ordinarily be used with conventional bridge techniques. The procedure is also useful for amplifying very weak signals, such as those of immunoreactions in glutaraldehyde-fixed tissue. The amplification procedure, together with the availability of avidin probes labeled with fluorochromes, colloidal gold, or enzyme systems other than HRP, provides a means of greatly increasing the versatility of a variety of histochemical reactions, including those for detecting in situ hybridization probes, in addition to increasing the sensitivity of the reactions.

Animals↗
PubMed1992

Effect of storage upon the toxicity of synfuel process waters to bacteria.

Storage of synfuel process waters at 4 degrees C for 8 years appeared to reduce the toxicity of these waters to indicator bacteria. When these waters were mixed in the amount of 10 percent process waters to 90 percent sewage, heterotrophic bacteria grew which indicate that storage or aeration may improve the treatability of these waters.

Bacteria↗
PubMed1991

Chemically distinct rat olivocochlear neurons.

We have produced a neurochemical map of the cell bodies of origin of the cochlear efferent terminals in rat by combining glutamic acid decarboxylase (GAD), choline acetyltransferase (ChAT), or calcitonin gene-related peptide (CGRP) immunocytochemistry with retrograde transport of horseradish peroxidase. The locations of cochlear efferent cell bodies are in general agreement with the medial and lateral systems described by White and Warr (J. Comp. Neurol. 219:203-214, 1983) with some minor modifications. The lateral system consists of at least two pools of chemically distinct neurons located within the lateral superior olive (LSO) ipsilateral to the injected cochlea. One pool immunostains with an antibody to GAD while the other immunostains with antibodies to ChAT and to CGRP. The medial efferent system consists of periolivary neurons that are almost exclusively large and ChAT-positive but CGRP-negative. They are located both ipsilateral and contralateral to the cochlea they project to. There are a few GAD-positive small neurons in the medioventral and rostral periolivary regions that project ipsilaterally, but these may prove tobe ectopic neurons. The ipsilateral lateroventral periolivary region (LVPO) contains some efferent neurons, all of which are ChAT-positive but CGRP-negative. Additional cochlear efferent neurons, some of which are ChAT-positive and others GAD-positive, are present within and immediately dorsal to the fiber capsule surrounding the medial limb, and to a lesser extent the lateral limb, of the ipsilateral LSO. Not all GAD-positive or ChAT-positive olivary cells project to the cochlea. We have complemented the results in the brainstem by demonstrating two immunocytochemically distinct populations of efferent terminals in the cochlea simultaneously, one CGRP-positive and the other GAD-positive. Approximately equal numbers of boutons immunoreactive for both markers are present beneath inner hair cells throughout the entire length of the cochlea. Surprisingly high numbers of GAD-positive and CGRP-positive boutons are also present on outer hair cells, with each class having its spatially and morphologically distinct features. The lack of CGRP-positive periolivary cells that are retrogradely labeled by cochlear injections of HRP suggests that the lateral olivocochlear system sends projections to outer hair cells. Our results raise questions about species differences in the organization of targets of the lateral and medial olivocochlear systems.

Animals↗
PubMed1991

Age-related changes in cochleas of mongolian gerbils.

The effects of aging on the gerbil cochlea were studied in 16 animals raised in a quiet environment. Animals were tested at ages ranging from 33 to 36 months, the approximate average lifespan of gerbils in our colony. Hearing sensitivity was assessed by measures of whole-nerve compound action potential (CAP) thresholds and surface preparations of the organ of Corti were subsequently examined by light microscopy for losses of sensory hair cells. These quiet-aged animals showed a wide range of hair-cell losses and threshold shifts. Outer hair cells often showed significant losses while inner hair cells were rarely absent. All animals had some threshold shift, especially at frequencies above 4 kHz. These shifts ranged from 1 to 68 dB. At high frequencies, threshold shifts often occurred without hair-cell losses at corresponding cochlear locations. At low frequencies, threshold shifts seldom reflected the losses of hair cells commonly found in the cochlear apex. Thus, the correlation of specific hair-cell losses and CAP threshold shifts at corresponding frequencies was poor. On the other hand, the total number of missing hair cells, irrespective of location, was a good, general indicator of the hearing capacity in a given ear. It appears that the factor or factors that makes cochleas susceptible to hair-cell loss with increasing age also affects other cochlear mechanisms that are necessary for normal functioning of the ear.

Action Potentials↗
PubMed1991

Expression of beta 1, beta 3, beta 4, and beta 5 integrins by human epidermal keratinocytes and non-differentiating keratinocytes.

We have compared the adhesive properties and integrin expression profiles of cultured human epidermal keratinocytes and a strain of nondifferentiating keratinocytes (ndk). Both cell types adhered to fibronectin, laminin, and collagen types I and IV, but ndk adhered more rapidly and at lower coating concentrations of the proteins. Antibody blocking experiments showed that adhesion of both cell types to fibronectin was mediated by the alpha 5 beta 1 integrin and to laminin by alpha 3 beta 1 in synergy with alpha 2 beta 1. Keratinocytes adhered to collagen with alpha 2 beta 1, but an antibody to alpha 2 did not inhibit adhesion of ndk to collagen. Both cell types adhered to vitronectin by alpha v-containing integrins. Immunoprecipitation of surface-iodinated and metabolically labeled cells showed that in addition to alpha 2 beta 1, alpha 3 beta 1, and alpha 5 beta 1, both keratinocytes and ndk expressed alpha 6 beta 4 and alpha v beta 5. ndk expressed all these integrins at higher levels than normal keratinocytes. ndk, but not normal keratinocytes, expressed alpha v beta 1 and alpha v beta 3; they also expressed alpha 1 beta 1, an integrin that was not consistently detected on normal keratinocytes. Immunofluorescence experiments showed that in stratified cultures of normal keratinocytes integrin expression was confined to cells in the basal layer; terminally differentiating cells were unstained. In contrast, all cells in the ndk population were integrin positive. Our observations showed that the adhesive properties of ndk differ from normal keratinocytes and reflect differences in the type of integrins expressed, the level of expression and the distribution of integrins on the cell surface. ndk thus have a number of characteristics that distinguish them from normal basal keratinocytes.

Antibodies↗
PubMed1991

Integrin expression during human epidermal development in vivo and in vitro.

In order to investigate the role of extracellular matrix receptors of the integrin family in establishing the spatial organization of epidermal kerotinocytes, we used immunofluorescence microscopy to examine the expression of a range of integrin subunits during development of human palm and sole skin. All of the integrins expressed during development were also present in mature epidermis and were largely confined to the basal layer of keratinocytes in a pericellular distribution. The alpha 3 and beta 1 subunits were expressed prior to the initiation of stratification and did not change in abundance or distribution during subsequent development. alpha 4 and beta 3 were not detected at any time in the epidermis. Every other subunit examined showed spatial or temporal changes in expression. Staining for alpha 1 was strong before stratification and until mid-development, but was greatly decreased in neonatal epidermis. alpha 2 was first detected in small patches of basal cells prior to stratification, and thereafter was found in the entire basal layer, with greater staining in developing sweat glands. alpha 5 was not expressed until mid-development, and then primarily in developing sweat glands, with faint expression in neonatal epidermis. alpha v was detected following stratification, in developing sweat glands, and occasionally in neonatal epidermis. alpha 6 and beta 4 were peribasally expressed before stratification, but thereafter became concentrated at the basal cell surface in contact with the basement membrane, co-localizing with hemidesmosomes as determined by staining with bullous pemphigoid antiserum. We also examined the distribution of three known ligands for keratinocyte integrins: laminin and collagen type IV were present in the basement membrane zone at all stages of development, whereas fibronectin was only evident there until about 13 weeks estimated gestational age. Finally, we found that the changes in integrin expression that occur on initiation of stratification in vivo could be reproduced in organ cultures of developing skin; such cultures therefore provided a useful experimental model for further studies of the role of integrins in epidermal stratification.

Embryonic and Fetal Development↗
PubMed1991

Production of scatter factor by ndk, a strain of epithelial cells, and inhibition of scatter factor activity by suramin.

ndk are a strain of human epidermal keratinocytes that do not undergo terminal differentiation and which grow as single cells rather than compact colonies. We show that ndk are motile and secrete an epithelial scatter factor that has the same biochemical and immunological properties as the scatter factor previously purified from ras-transformed 3T3 fibroblasts. We have found that suramin, a polyanionic detergent, will reverse the activity of scatter factor from either cell type in the standard MDCK activity assay. When added to ndk cultures, suramin causes the cells to grow in coherent patches. This morphological change is accompanied by alterations in the distribution of actin and integrins, but not by stratification or terminal differentiation. The effect is reversed upon removal of suramin. We propose that the motile phenotype of ndk is due, at least in part, to autocrine production of scatter factor and that suramin may be useful for further studies of scatter factor binding to the cell surface.

Actins↗
PubMed1990

Changes in keratinocyte adhesion during terminal differentiation: reduction in fibronectin binding precedes alpha 5 beta 1 integrin loss from the cell surface.

During terminal differentiation keratinocytes move out of the basal layer of the epidermis and thereby lose contact with the basement membrane. We show that terminal differentiation in culture involves loss of adhesiveness to fibronectin, laminin, and collagen types I and IV. The adhesive changes precede, by several hours, loss of the alpha 2 beta 1, alpha 3 beta 1, and alpha 5 beta 1 integrins from the cell surface. Keratinocyte adhesion to fibronectin is mediated by the alpha 5 beta 1 integrin, and the decrease in adhesion of intact cells to fibronectin is correlated with a decrease in the ability of alpha 5 beta 1 receptors to bind fibronectin. Thus modulation of integrin function early in terminal differentiation may be an early event determining cell migration out of the basal layer.

Cell Adhesion↗
PubMed1990

Immunocytochemical evidence for inhibitory and disinhibitory circuits in the superior olive.

Immunostaining of the cat superior olivary complex with antisera against glycine, calbindin, GABA, and its synthetic enzyme, glutamate decarboxylase (GAD) reveals considerable new information about neural connections that underlie processing of binaural signals. Antisera against glycine and calbindin immunostain principal cells and processes of the medial nucleus of the trapezoid body (MNTB). The extent of staining of fine processes afforded by the calbindin antisera reveals collateral processes of MNTB axons within the medial superior olive (MSO) and numerous terminals of these collaterals on neuronal somata and proximal dendrites. Electron microscopic immunocytochemistry of these terminals shows them to have the morphological features characteristic of inhibitory synapses, indicating that there can be considerable inhibitory inputs to MSO cells from the contralateral cochlear nucleus via the MNTB. Immunostaining for GAD and GABA shows some GABAergic inputs, mostly to dendrites within the MSO. Within the MNTB there are elaborate GABAergic endings that surround the principal cells. Electron microscopic immunocytochemistry of these terminals reveals the expected features characteristic of inhibitory synapses. The glycinergic inhibitory output of the MNTB cells is therefore subject to disinhibition by activity of these elaborate GABAergic inputs. Other endings that immunostain with antisera to leucine- enkephalin and neurotensin are found in modest amounts in both MSO and MNTB. Immunostaining of neuronal somata within the superior olivary complex suggests that the origins of the peptidergic and GABAergic endings in the MSO and MNTB may be periolivary cells. Whatever the origins, the results clearly indicate that control of the inhibitory GABAergic inputs to the MNTB can profoundly affect the inhibitory glycinergic MNTB outputs to other principal olivary nuclei. Investigations of the circumstances under which these circuits are activated will reveal much about neural processing that underlies binaural hearing.

Animals↗