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Biomedical subjects

J C Adams

Publications and source records attributed to J C Adams.

At least 73 records · Page 4Linked to original sources
PubMed1990

Tuning and suppression in auditory nerve fibers of aged gerbils raised in quiet or noise.

Mongolian gerbils were reared either in quiet or in a continuous noise field (85 dBA, 500-4000 Hz). The gerbils began the noise exposure at 8 months of age and, after the exposure, spent the remainder of their lives in the quiet vivarium with the quiet-aged group. The duration of the noise exposure was between 365 and 724 days. At the terminal experiment the ages of the animals varied between 24 and 43 months, with a mean age of about 36 months, an age representing the average life span of a gerbil in our colony. During the terminal experiment, tuning curves and boundaries of two-tone rate suppression were obtained from single fibers in the auditory nerve. Threshold shifts occurred in both groups of animals. The shift was largely confined to the tip of the tuning curve; i.e., the region around the characteristic frequency (CF) of the fiber. The CF shifts effectively reduced the tip-to-tail ratios of the tuning curves. Two-tone suppression areas above and below CF were present for all fibers in the quiet-aged animals, but were often absent for fibers in the noise-aged group. The presence of suppression was largely independent of fiber thresholds in both groups of animals. Indeed, fibers were found with clearly-defined suppression boundaries above and below CF despite threshold shifts of up to 60 dB. Moreover, in the noise-aged group suppression below CF was sometimes found without concomitant suppression above CF and vice versa, suggesting an independence between the two suppression areas. For fibers with CFs within the bandwidth of the noise, two-tone suppression above CF was always absent, even though suppression below CF was sometimes present. In sum, two-tone suppression was near normal in ears aged in quiet despite relatively large threshold shifts at the fiber CF. However, suppression, especially that above CF, was vulnerable to the effects of chronic noise. Taken with the results of other studies, our data suggest that the micromechanics of the cochlea are largely responsible for two-tone suppression, especially that above CF, and that different mechanisms may underlie suppression above and below CF.

Aging↗
PubMed1990

Immunolocalization of Na+,K(+)-ATPase and carbonic anhydrase in the gerbil's vestibular system.

The distribution of two ion transport enzymes in the vestibular system was investigated immunocytochemically. Immunostaining demonstrated abundant Na+,K(+)-ATPase in the basolateral plasmalemma of all dark cells and of cuboidal (transitional) cells bordering maculae and planum semilunatum cells bordering cristae. Na+,K(+)-ATPase was also present in nerve terminals impinging on vestibular hair cells and around nerve fibers and ganglion cells. Na+,K(+)-ATPase containing cells with fine intertwining processes were found within the perilymphatic stroma beneath maculae and cristae. These cells and interspersed nerves form a distinct, highly cellular plate that lies under neurosensory epithelium selectively. The catalytic alpha subunit of Na+,K(+)-ATPase in vestibular epithelia differs antigenically from the alpha subunit in nerves and from the alpha subunit in salivary gland and renal epithelium. Carbonic anhydrase (CA) isozyme II was localized in the apex of all supporting cells in neurosensory epithelia. In contrast, CA II immunostaining varied in vestibular dark cells showing heterogeneity in ion transport activity among these cells. Immunostaining evidenced CA II also in perilymphatic stromal cells which were presumably fibroblastic in nature and which correspond in location with the Na+,K(+)-ATPase positive cells under the vestibular neurosensory epithelium.

Animals↗
PubMed1989

Comparative study of glutamate decarboxylase immunoreactive boutons in the mammalian inferior olive.

An antiserum raised against rat glutamate decarboxylase was used to map GABAergic boutons in the inferior olive of rabbit, cat, rhesus monkey, and human. A description of the human periolivary region is also included. The inferior olive of each species contained a dense GABAergic innervation, but immunostaining intensities varied among regions. These intensities were evaluated visually and photometrically, and the sizes and frequencies of occurrence of boutons in various olivary subnuclei were measured. The beta nucleus in all species was intensely immunostained and contained the largest boutons. The caudal subdivision of the dorsal accessory olive stained with a lower intensity than the beta nucleus, but contained similarly large GABAergic boutons. By visual analysis, the rostral subdivision and the subnucleus a of the medial accessory olive and the principal olive were stained with an intermediate intensity, and these regions contained small GABAergic boutons. Photometric analysis of focal regions of the neuropil, however, revealed species differences in teh staining intensity of the principal olive, which was lowest in rabbits and highest in primates. In all species, the lowest immunostaining intensity was observed in the subnucleus b of the medial accessory olive. Species variations in bouton sizes and regional staining intensities were observed in the dorsal cap and the dorsomedial cell column. The heterogeneous staining pattern and regional variation of bouton size argue for the existence of separate GABAergic projections to discrete regions of the inferior olive. Since glutamate decarboxylase immunostaining patterns in the olive are largely similar across species, the afferent projections producing these patterns may also be similar.

Adolescent↗
PubMed1989

Fibronectin inhibits the terminal differentiation of human keratinocytes.

In the epidermis proliferation of keratinocytes is restricted to the basal layer, which is in contact with the basement membrane, and cells undergo terminal differentiation as they move upwards through the suprabasal layers. In stratified cultures of human keratinocytes, upward migration is a consequence, not a cause, of terminal differentiation and occurs because keratinocytes become less adhesive to their substratum and to one another. Most keratinocytes can be induced to differentiate to completion by placing them in suspension in methylcellulose: within 12 h DNA synthesis is irreversibly inhibited and by 24 h most cells express involucrin (ref 4; P. A. Hall, J.C.A. and F.M.W., unpublished observations). Here we report that when fibronectin is added to the methylcellulose, keratinocytes still withdraw from the cell cycle, but induction of involucrin expression is largely inhibited. The effect of fibronectin is concentration- and time-dependent and is mediated by a receptor of the integrin family. These results provide an explanation for why overt terminal differentiation is normally restricted to suprabasal cells, whereas cell-cycle withdrawal occurs within the basal layer; they also have important implications for the mechanism of epidermal wound healing. Furthermore, our data show that the binding of an extracellular matrix protein to its receptor can regulate differentiated gene expression in the absence of changes in cell shape.

Cell Differentiation↗
PubMed1989

Differences in phorbol-ester-induced down-regulation of protein kinase C between cell lines.

Down-regulation of protein kinase C induced by 12-O-tetradecanoylphorbol 13-acetate (TPA) was examined in Swiss 3T3, V79, MDBK and C6 cells by Western blotting. Variations in the rate of down-regulation caused by treatment with 100 nM-TPA were observed; TPA treatment for 5 h caused maximal down-regulation in V79 cells, whereas TPA treatment for 10 h or 30 h was needed for maximal down-regulation of protein kinase C in MDBK or Swiss 3T3 cells respectively. The decrease in amount of immunologically detectable protein kinase C was 30% in MDBK cells and 100% in V79 and Swiss 3T3 cells. MDBK and C6 cells could be completely depleted of protein kinase C by treatment with 250 nM-TPA. In C6 cells, after treatment with 500 nM-TPA, an 80% loss of protein kinase C was seen over 10 h. Measurement of the numbers of phorbol-ester-binding sites remaining in each cell line when protein kinase C was maximally down-regulated indicated that in MDBK and Swiss 3T3 cells loss of phorbol-ester-binding sites paralleled loss of protein kinase C, whereas in V79 and C6 cells no such correlation was observed.

Animals↗
PubMed1989

Use of nutrient response techniques to assess the effectiveness of chlorination of rapid sand filter gravel.

A direct viable counting method was used to rapidly assess the effectiveness of chlorination of biofilms on rapid sand filter gravel. A total of 50% of the cells were nutrient responsive after exposure to 0.5 mg of chlorine per liter, while this value was 25% after exposure to 25 mg of chlorine per liter. A large variation was seen in the numbers of nutrient-responsive cells on different rocks. More cells attached to the sandblasted side of marbles than to the smooth side, but there was no difference in eight of nine cases in the proportion of survival to chlorination between the two different sides. The effectiveness of chlorination appeared to be influenced by the species of bacterium in the biofilm.

Acridine Orange↗
PubMed1989

Comparison of methods for enumeration of selected coliforms exposed to ozone.

mT7 medium performed no better than m-Endo medium in enumerating cells of Escherichia coli and Citrobacter freundii exposed to ozone. Also, there was no difference in the plate count of heterotrophic bacteria in ozonated raw water determined on modified Henrici agar or R2A agar. Statistically significant differences were seen between bacteria and the type of water in which they were suspended during ozonation.

Citrobacter↗
PubMed1989

Immunohistochemical localization of vimentin in the gerbil inner ear.

Cells containing immunoreactive vimentin-type intermediate filaments (IF) were identified in paraffin sections and whole-mount preparations of the gerbil inner ear. Most connective tissue cells showed positive immunostaining, although one unusual class of stromal cell lacked vimentin. Several different types of epithelial cells contained high levels of vimentin. In the cochlea, Deiters' cells, inner phalangeal cells, Boettcher's cells, some outer sulcus cells, and the intermediate cells of the stria vascularis showed strong immunoreactivity. Strial basal cells exhibited weaker and less consistent staining. Neither inner nor outer hair cells were stained. In the vestibular system, hair cells with a morphology and location more characteristic of type I than of type II cells showed strong immunostaining for vimentin. Supporting cells in vestibular neurosensory epithelium stained with less intensity. These results were surprising because epithelial cells in vivo only rarely express vimentin-type IF. Although the functional significance of vimentin remains to be established, its presence in some but not other highly specialized cell types provides an excellent marker for investigating the lineage and morphogenesis of the complex inner ear tissues.

Animals↗
PubMed1989

Distribution of immunoreactive Na+,K+-ATPase in gerbil cochlea.

The distribution of Na+,K+-ATPase was mapped in cochleas of mature gerbils with normal hearing, using a specific and sensitive immunocytochemical method. Na+,K+-ATPase was abundant in the basolateral plasma membrane of marginal cells in the stria vascularis. Considerable levels of enzyme were also associated with the surfaces of spiral ganglion neurons and their central and peripheral processes. An unexpected finding was the detection of high levels of immunoreactive Na+,K+-ATPase in three different populations of cells lying in the inferior portion of the spiral ligament and at the medial and lateral border of the scala vestibuli just superior to the attachment of Reissner's membrane. Cells in these areas shared the morphological characteristics of cells specialized for active transport but appeared to be nonpolarized, suggesting a uniform distribution of Na+,K+-ATPase over their entire plasmalemma. The presence of these three distinct cell populations in the cochlea of several mammalian species suggests that they play an important role in cochlear function, perhaps that of regulating the cation content of perilymph. The absence of discrete concentrations of Na+,K+-ATPase-rich cells in the perilymphatic connective tissue of the bird cochlea and the mammalian vestibular system suggests further that these cells may be involved with generating and maintaining the high endolymphatic potential unique to the mammalian cochlea.

Animals↗
PubMed1988

How useful is gastroesophageal reflux scintigraphy in suspected childhood aspiration?

It has been suggested that gastroesophageal reflux scintigraphy (GRS) might be useful in assisting one in determining therapy for patients suspected of aspirating or becoming apneic secondary to gastroesophageal reflux. This, however, has not been our experience and in reviewing 23 patients with recurrent pneumonia and/or apnea who had GRS, we were able to detect aspiration in only one. This was especially significant since 13 (59%) of these patients had demonstrable reflux, and of these, eight were treated successfully for suspected aspiration even though none was demonstrated isotopically. To be sure, the demonstration of pulmonary aspiration with GRS had little influence on patient selection and response to therapy. For this reason we feel there is little justification in depending on the GRS for the specific purpose of trying to document pulmonary aspiration in infants and children who are refluxing.

Apnea↗
PubMed1988

An unusual strain of human keratinocytes which do not stratify or undergo terminal differentiation in culture.

We have characterized an unusual cell phenotype in third passage cultures of a human keratinocyte strain derived from newborn foreskin epidermis. The cells had the same DNA fingerprint pattern as the second passage, morphologically normal, keratinocytes; they formed desmosomes and expressed the keratin profile characteristic of normal keratinocytes in culture. However, unlike normal keratinocytes, the cells did not grow as compact colonies and did not stratify or undergo terminal differentiation, even after TPA treatment or suspension culture. For these reasons we named them ndk for "nondifferentiating keratinocytes." The ndk cells also differed from normal keratinocytes in that they did not require a feeder layer and were not stimulated by cholera toxin to proliferate. The ndk cells had an absolute requirement for hydrocortisone and their growth rate was increased when epidermal growth factor was added to the medium. Although ndk failed to undergo terminal differentiation in culture, they were not transformed, since they were still sensitive to contact inhibition of growth, did not proliferate in soft agar, and had a limited lifespan in culture. The appearance of the ndk phenotype was correlated with a doubling of chromosome number and the presence of a lp marker chromosome. We suggest that these cells are a useful experimental adjunct to cultures of normal keratinocytes, in which proliferation and terminal differentiation are tightly coordinated, because in ndk cells there appears to be a block in terminal differentiation.

Blotting, Western↗
PubMed1987

A possible neurotransmitter role for CGRP in a hair-cell sensory organ.

We report that calcitonin gene-related peptide (CGRP) increases the discharge rate of afferent fibers innervating hair cells in the lateral line organ of Xenopus laevis. We have localized CGRP-like immunoreactivity in small, presumably efferent, fibers innervating the lateral line organ. In addition to providing evidence for a neurotransmitter role for CGRP in a sensory system, these results may help explain the non-cholinergic excitatory effect seen with efferent stimulation in this and other hair cell organs such as the inner ear.

Action Potentials↗
PubMed1987

Patterns of glutamate decarboxylase immunostaining in the feline cochlear nuclear complex studied with silver enhancement and electron microscopy.

The cochlear nuclear complex of the cat was immunostained with an antiserum to glutamate decarboxylase (GAD), the biosynthetic enzyme for the inhibitory neurotransmitter GABA, and studied with different procedures, including silver intensification, topical colchicine injections, semithin sections, and immunoelectron microscopy. Immunostaining was found in all portions of the nucleus. Relatively few immunostained cell bodies were observed: most of these were in the dorsal cochlear nucleus and included stellate cells, cartwheel cells, Golgi cells, and unidentified cells in the deep layers. An accumulation of immunoreactive cells was also found within the small cell cap and along the medial border of the ventral cochlear nucleus. Immunostained cells were sparse in magnocellular portions of the ventral nucleus. Most staining within the nucleus was of nerve terminals. These included small boutons that were prominent in the neuropil of the dorsal cochlear nucleus, the granule cell domain, in a region beneath the superficial granule cell layer within the small cell cap region, and along the medial border of the ventral nucleus. Octopus cells showed small, GAD-positive terminals distributed at moderate density on both cell bodies and dendrites. Larger, more distinctive terminals were identified on the large cells in the ventral nucleus, in particular on spherical cells and globular cells. There was a striking positive correlation of the size, location, and complexity of GAD-positive terminals with the size, location, and complexity of primary fiber endings on the same cells. This correlation did not hold in the dorsal nucleus, where pyramidal cells receive many large GAD-positive somatic terminals despite the paucity of primary endings on their cell bodies. The GAD-positive terminals contained pleomorphic synaptic vesicles and formed symmetric synaptic junctions that occupied a substantial portion of the appositional surface to cell bodies, dendrites, axon hillocks, and the beginning portion of the initial axon segments. Thus, the cells provided with large terminals can be subjected to considerable inhibition that may be activated indirectly through primary fibers and interneurons or by descending inputs from the auditory brainstem.

Animals↗
PubMed1986

Neuronal morphology in the human cochlear nucleus.

Neuronal morphology in the human cochlear nucleus was studied with a Golgi method to better understand the organization of the nucleus. In ventral portions of the nucleus, three principal cell types and two small cell types previously seen in animals were found. In the dorsal portions of the nucleus, predominant cell types found in animals appear to be absent, indicating that cellular organization here is quite different from that in animals. On the other hand, cell morphology in the ventral nucleus suggests that signal processing here is fundamentally similar to that in animals. A review of the organization of these cells in animals is presented to provide a context of present results. The findings have great relevance in light of efforts to implant electrical prostheses in the nucleus.

Cell Nucleus↗
PubMed1986

Toxicity of granular activated carbon treated coal gasification water as determined by the Microtox test and Escherichia coli.

The Microtox assay and various parameters (growth, ATP concentration and electrochemical detection) of Escherichia coli were used to assess the toxicity of various levels of granular activated carbon treated coal gasification process water. The generation time of E. coli was statistically significantly slower at the level of 50 percent treatment than any other level of treatment. No differences were seen for ATP concentration per cell or in the electrochemical detection methods for any level treatment. There was a very high correlation between total organic carbon removal by GAC treatment and reduction in toxicity as measured by the Microtox system. However, even the treated water which had 91 percent of the TOC removed was still highly toxic.

Adenosine Triphosphate↗
PubMed1985

Nontoxicity of an oil shale process water to Escherichia coli.

The survival of Escherichia coli in the presence of an oil shale process water was studied over a five day period. The organism survived better in the presence of one or ten percent concentration of the process water than it did in distilled or tap water. Water chemistry of the diluent appeared to be important to the survival of the organism.

Escherichia coli↗