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Biomedical subjects

R Robb

Publications and source records attributed to R Robb.

16 recordsLinked to original sources
PubMed1992

HepG2 cells predominantly express the type II interleukin 1 receptor (biochemical and molecular characterization of the IL-1 receptor).

In this study we have characterized the cell surface interleukin 1 (IL-1) receptor in HepG2 hepatoma cells. We found that HepG2 cells bind both IL-1 alpha and beta with high affinity, KDs of 136 and 180 pM and receptor densities of 16,000 and 8500 binding sites/cell respectively. The binding sites appeared to be predominantly type II since phorbol ester treatment of the cells, which selectively downregulates type II IL-1 receptors, reduced binding by 68% while treatment of the cells with an inhibitory monoclonal antibody specific for the type I receptor had no significant effect on IL-1 binding. Competition studies with a modified IL-1 beta analog (Glu4) also revealed binding kinetics more consistent with binding to type II receptors than to type I. Crosslinking and ligand blotting with human 125I-IL-1 demonstrated the presence of two bands, a 78 kDa band typical of crosslinking to type II (p60) receptor, and a 98 kDa band, typical of crosslinking to the type I (p80) receptor. Low level expression of the type I receptor was consistent with molecular biological studies employing polymerase chain reaction (PCR) amplification which indicated that mRNA for the type I receptor was produced by the HepG2 cells. Functional receptors were demonstrated by the induction of IL-8 by IL-1 stimulated cells.

Animals↗
PubMed1992

Prescriptive hearing aid fitting by parameter adjustment and selection.

We describe the rationale for the development of a psychophysical procedure that allows individual listeners to adjust the frequency-gain characteristic of a programmable hearing aid on a unidimensional scale, based on a target-gain reference value. The listener's task is to adjust the frequency response and select the parametric value judged to optimize the intelligibility or quality of speech. Originally described as the Sliding Scale, the procedure has been modified for use in reliability and validity studies of hearing aid fitting at Michigan State University. The modified approach is referred to as the Parameter Adjustment and Selection (PAS) procedure. Primary immediate goals for the procedure are ease of use, high reliability, and rapid clinical administration. The procedure, which may offer potential advantages over a paired-comparison approach, appears to be generally applicable to the fitting of digitally programmable hearing aids.

Auditory Threshold↗
PubMed1989

Activation by saccharides of a cation-selective pathway on canine lingual epithelium.

Responses of isolated canine lingual epithelium in an Ussing chamber to D-glucose and fructose reveal events associated with taste transduction. With the use of isotopic flux studies, together with ion substitution and pharmacological and voltage clamp measurements, it was found that the stimulation of ion transport by D-glucose arises from an increase in the influx of cations through a cation-selective pathway. This influx of cations is completely inhibited by 0.1 mM amiloride. The stimulation of transport by fructose in 0.05 M KCl and by D-glucose in 0.05 M RbCl was also inhibited by amiloride, demonstrating that the saccharide-stimulated entry pathway was specific for neither hexose sugars nor for Na. Saccharide stimulation of canine lingual epithelia does not appear to be modulated by increases in intracellular levels of adenosine 3',5'-cyclic monophosphate, guanosine 3',5'-cyclic monophosphate, or Ca. The Na that enters taste cells on saccharide stimulation exits them via the ouabain inhibitable Na+-K+-adenosinetriphosphatase located in the serosal membranes.

Amiloride↗
PubMed1988

Transport pathways in rat lingual epithelium.

Measurements of ion transport across isolated lingual epithelium of rat were correlated with electrophysiological recordings from taste nerves. At hyperosmotic concentrations of NaCl, sodium ions enter the mucosal membrane of the isolated epithelium partially through an amiloride-inhibitable pathway and exit the serosal membrane through a Na+-K+-ATPase. At hyposmotic concentrations of KCl, potassium ions enter the mucosal membrane through a K+ pathway that is inhibited by 4-aminopyridine and exit at the serosal membrane through a K+ pathway that is inhibited by BaCl2. The inhibition of sodium transport by amiloride and potassium transport by 4-aminopyridine is consistent with previously published electrophysiological recordings from the chorda tympani nerve bundle (CT) and recordings from nucleus of the solitary tract (NST) obtained here. The responses to NaCl are greater than the responses to KCl at equimolar concentrations over the entire concentration range both in epithelial and neural measurements. At hyposmotic concentrations of NaCl the epithelial responses include inward sodium and outward chloride components. Isolated rat tongue is only slightly stimulated by D-glucose or sucrose as are the CT and NTS responses. These data suggest that events in taste transduction can be understood, in part, by measuring the epithelial responses of isolated rat tongue.

4-Aminopyridine↗
PubMed1988

Spatial map of salts and saccharides on dog tongue.

Front and rear regions of dog tongue were tested for spatial heterogeneity with respect to monovalent chloride salts (NaCl, KCl, and NH4Cl) and sweet tastants (sucrose, D-glucose, and L-glucose) by placing them in Ussing chambers where the open-circuit potential, Voc, and short-circuit current, Isc, were measured. The responses of Voc and Isc to 0.5 M NaCl were greater in the front of the tongue than in the rear, whereas the responses of Voc and Isc to 0.5 M sucrose were greater in the rear of the tongue than in the front. These results are similar to those of published neurophysiological measurements from the chorda tympani nerve and thalamus. These data suggest that the spatial heterogeneities seen in higher taste centers are present in the isolated lingual epithelium where primary taste transduction events occur.

Ammonium Chloride↗
PubMed1987

Autocrine growth of T cells independent of interleukin 2: identification of interleukin 4 (IL 4, BSF-1) as an autocrine growth factor for a cloned antigen-specific helper T cell.

Interleukin 4 (IL 4), formerly known as B cell stimulatory factor 1 (BSF-1), has recently been described as a growth factor for T cells. The role of IL 4 in the putatively IL 2-independent growth of certain cloned T helper cells is unclear. D10.G4.1 (D10) is a conalbumin-specific helper T cell that has been employed extensively in the analysis of T cell activation and as an assay for the detection of IL 1. Previously, it was thought that IL 1 induced the expression of IL 2 receptors on D10 cells, thereby permitting D10 to proliferate in response to endogenously produced IL 2. However, we cannot detect IL 2 mRNA or protein in D10 cells or their supernatants as determined by the following criteria: monoclonal antibodies that neutralize the in vitro activity of murine IL 2 do not block the IL 1-dependent proliferation of D10 cells; no competitive binding for high-affinity IL 2 receptors with 125I-labeled IL 2 can be detected with medium conditioned by activated D10 cells; and Northern blot analysis and S1 nuclease protection assays, performed with cDNA probes for IL 2, do not detect mRNA for IL 2 under a variety of different activation conditions that foster autocrine growth of D10 cells. In contrast, activated D10 cells produce both IL 4 mRNA and protein as judged by similar criteria. Purified IL 4 has significant TCGF activity as measured by proliferation of HT-2 cells. This activity can be blocked completely by a monoclonal antibody to IL 4 (11B11). The proliferation of D10 cells in the presence of 3D3 (a clonotype-specific monoclonal anti-T cell receptor antibody) and IL 1 can be blocked completely by 11B11 antibody. Highly purified IL 4 alone cannot induce the proliferation of resting D10 cells; however, equivalent amounts of IL 4 in the presence of recombinant IL 1 induce significant D10 proliferation. Therefore, IL 1 appears to render D10 cells responsive to their autocrine growth signal. These data indicate that IL 4 serves as the autocrine T cell growth factor for D10 cells, and that exogenous IL 1 is required for the transduction of this growth signal. This may represent a more broadly applicable mechanism for the growth of certain subsets of T helper cells.

Animals↗
PubMed1986

Epithelial responses of rabbit tongues and their involvement in taste transduction.

The response of rabbit tongue, placed in a modified Ussing chamber, to salts [KCl, NaCl, NH4Cl, tetraethylammonium chloride (TEACl)], sweeteners (D-glucose, sucrose), acid (HCl), and a bitter tastant, quinine, was investigated for the first time. These experiments were conducted to further explore the new paradigm of taste transduction that correlates changes in the electrical behavior of lingual epithelia with neural responses. In addition, the responses of rabbit tongue data were compared with previously published data on dog and frog tongues. When increases in short-circuit current (Isc) for rabbit tongue induced by hyperosmotic concentrations of several salts were compared, the following sequence was found: KCl greater than NH4Cl greater than NaCl greater than TEACl. These results are consistent with previously published integrated chorda tympani responses (ICTR) as well as behavioral studies that showed that rabbits prefer KCl to NaCl with their natural diet. Pharmacological studies using ouabain and amiloride suggest that K and Na are traversing rabbit tongue through different pathways. The maximal stimulation of Isc by D-glucose and sucrose (in 50 mM NaCl) was significantly smaller than those measured for KCl and NaCl. The rabbit tongue was sensitive to HCl at concentrations less than 1 mM in agreement with ICTR measurements.

Animals↗
PubMed1986

Transorbital penetrating injuries to the frontal lobe.

Three cases of transorbital penetrating trauma to the frontal lobe are reported. These cases are remarkable in that minimal ocular trauma was incurred and excellent vision was preserved. These cases underscore the importance of suspecting the possibility of intracranial injury when evaluating penetrating orbital trauma.

Adolescent↗
PubMed1977

Computerized image recognition for morphometry of nerve attribute of shape of sampled transverse sections of myelinated fibers which best estimates their average diameter.

A computerized image recognition method was used to measure various attributes of shape of cross-sections of myelinated nerve fibers. Measurements were made at intervals over 1/2 internode of each fiber on 20 fibers from each of 4 sural nerves from rats. Diameters were computed in 6 different ways from the computer measurements and compared for bias, precision, and accuracy between sections and to the diameter of an idealized cylinder reconstructed for each fiber from multiple actual cross sections. The diameter computed from cross-sectional areas of transversely sectioned myelinated fibers, converted into a circle, showed the highest precision, greatest accuracy and least bias. Fibers were classified by shape and the frequency was determined in defined regions (I1 = paranodal, I3= nuclear and I2=region between I1 and I3) of the 1/2 internode. A crenated shape is highly characteristic of the I1 region. The boomerang shape was found most frequently in I3 whereas the circular shape was found most frequently in I2. Epileptical and boomerang shapes of myelinated fibers within fascicles which have been orientated carefully to obtain transverse sections, are not due to obliquity of section. Therefore, using the minor axis to determine the diameter of such profiles, as we had done previously in our laboratory, is in error. We conclude from these studies, that in carefully orientated transverse sections of nerve trucks, the diameter calculated from measurement of area converted to a circular shape is the best among the various estimates of myelinated fiber diameter and is the most suitable one for use in computerized image recognition systems for nerve morphometry. It seems reasonable to extrapolate this general conclusion to myelinated fibers of man.

Animals↗
PubMed1977

Further structural studies of the heavy chain of HLA antigens and its similarity to immunoglobulins.

The papain-solubilized fragment of the heavy chain of HLA-B7, which is the NH2-terminal part of the whole polypeptide chain, can be divided into three regions by mild acid and cyanogen bromide cleavages. The first 100 amino acids terminating in a methionine residue contain the carbohydrate moiety; this segment is followed by two others of molecular weights 9,999 and 13,000, each containing an intrachain disulfide bridge. The two intrachain disulfide bridges are separated by a stretch of amino acids containing an acid-labile aspartyl-prolHLA-2, A28, and AW25 contain this acid-labile peptide bond in their larger subunit. Sequencing from the acid cleavage site of HLA-7 through the third half-cystine revealed consideralbe homology with amino acid sequences around a half-cystine in immunoglobulin variable regions.

Amino Acid Sequence↗
PubMed1977

Structure of HL-A A and B antigens isolated from cultured human lymphocytes.

From these data, a model was prepared which summarizes schematically our present knowledge of the structure and orientation of the HL-A antigenic molecule in the lymphocyte membrane (Fig. 3). It seems likely that the heavy chain spans the membrane, with the hydrophobic region inserted in the membrane and the hydrophilic C-terminus inside the cell. This C-terminal region bears one (possible two) SH residue which has the potential for forming interchain disulfides. Whether or not these are actually formed physiologically remains an interesting question. There is the attractive possibility that whatever the physiological functions of HL-A antigens are, structurally these molecules provide the potential for signaling from outside the cell to inside the cell because they span the membrane. It is even conceivable that this function might be expressed via the opening and closing of disulfide bridges.

Amino Acid Sequence↗