PubMed Health⌕ Search

Biomedical subjects

J E Schroeder

Publications and source records attributed to J E Schroeder.

10 recordsLinked to original sources
PubMed1998

Functional co-assembly among subunits of cyclic-nucleotide-activated, nonselective cation channels, and across species from nematode to human.

Cyclic-nucleotide-activated, nonselective cation channels have a central role in sensory transduction. They are most likely tetramers, composed of two subunits (alpha and beta or 1 and 2), with the former, but not the latter, being able to form homomeric cyclic-nucleotide-activated channels. Identified members of this channel family now include, in vertebrates, the rod and cone channels mediating visual transduction and the channel mediating olfactory transduction, each apparently with distinct alpha- and beta-subunits. Homologous channels have also been identified in Drosophila melanogaster and Caenorhabditis elegans. By co-expressing any combination of two alpha-subunits, or alpha- and beta-subunits, of this channel family in HEK 293 cells, we have found that they can all co-assemble functionally with each other, including those from fly and nematode. This finding suggests that the subunit members so far identified form a remarkably homogeneous and conserved group, functionally and evolutionarily, with no subfamilies yet identified. The ability to cross-assemble allows these subunits to potentially generate a diversity of heteromeric channels, each with properties specifically suited to a particular cellular function.

Animals↗
PubMed1997

Social anxiety and performance in an interpersonal perception task.

The Interpersonal Perception Task-15 videotape served as a criterion measure to test hypotheses about individual differences in interpersonal perception. 160 undergraduates completed the Personal Report of Communication Apprehension Scale, the Shyness and Sociability Scale, and the Interpersonal Perception Task-15. Scores on the Communication Apprehension Scale were negatively correlated with Interpersonal Perception Task-15 scores, as predicted. Scores on the Shyness scale were negatively correlated with scores on the Interpersonal Perception Task-15, while Sociability scale scores were positively correlated. These results underscore the association between social anxiety and interpersonal perception.

Adolescent↗
PubMed1993

Inhibition of Ca2+ currents by a mu-opioid in a defined subset of rat sensory neurons.

Activation of the endogenous opioid system can suppress pain without affecting other sensations, but the cellular mechanism of this selectivity is unclear. The analgesia might be due to inhibitory synapses arranged only on neurons whose activity leads to pain sensations. Alternatively, opioids might be released broadly, with neurons involved in pain sensation being especially sensitive. Therefore, we asked whether different subsets of rat dorsal root ganglion (DRG) sensory neurons vary in their sensitivity to opioids. Dissociated neurons were subdivided according to the spinal laminae to which they likely had projected, and whether they had innervated muscle. Using the patch-clamp method, we measured the inhibition of Ca2+ current by DAGO (Tyr-D-Ala-Gly-MePhe-Gly-ol), a peptide that selectively activates the mu (morphine) receptor. We also investigated the presence of different types of Ca2+ channels. In DRG neurons chosen at random, Ca2+ currents were inhibited by DAGO to widely varying degrees, with an average inhibition of 38%. Ca2+ currents in neurons in a subset that projects to laminae I and II had a lower average inhibition, and unlike the randomly selected cells, the responses were predictable and tightly distributed about the mean. This indicates that the variability of opioid sensitivity among DRG neurons reflects the presence of different subsets of cells. Since neurons projecting to laminae I and II, the projection site of nociceptive neurons, did not show high opioid sensitivity, there is no evidence that nociceptive neurons have stronger responses to opioids. But a firm conclusion is impossible because projection site does not strictly define sensory modality.

Amino Acid Sequence↗
PubMed1991

Activation of mu opioid receptors inhibits transient high- and low-threshold Ca2+ currents, but spares a sustained current.

Opioids and opiates decrease the duration of action potentials and the amount of neurotransmitter released from sensory neurons. The mu-type opioid receptor, the binding site for morphine, is thought to act exclusively on K+ channels. Here, we show that activation of the mu receptor inhibits Ca2+ channels in rat sensory neurons; the effect is blocked by a mu antagonist and is not mimicked by kappa or delta receptor agonists. Both low-threshold (T-type) and high-threshold Ca2+ currents are partially suppressed. omega-Conotoxin-sensitive and omega-conotoxin-insensitive, high-threshold Ca2+ currents are inhibited. The kinetic effect on high-threshold current is like that caused by diminished rest potential: the transient component is selectively lost, whereas the sustained component is spared.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1990

Two components of high-threshold Ca2+ current inactivate by different mechanisms.

High-threshold Ca2+ current triggers neurotransmitter release, but the existence, significance, and correct identification of different types of high-threshold Ca2+ channels remain controversial. We show selective inhibition of a rapidly inactivating component of high-threshold Ca2+ current in rat sensory neurons by bursts of brief pulses that mimic trains of action potentials and by prolonged depolarization just above the normal rest potential. In contrast, a slowly inactivating component decreases only when sufficient Ca2+ accumulates within the cell. Thus, there are physiologically important differences: whereas availability of the transient component depends on the value of the rest potential and the pattern of a prior stimulus, the sustained component seems to provide a baseline level of voltage-dependent Ca2+ entry that is lost only when intracellular Ca2+ rises.

Animals↗
PubMed1990

T-type calcium channels: heterogeneous expression in rat sensory neurons and selective modulation by phorbol esters.

We report selective inhibition of low-threshold, T-type calcium channels by a phorbol ester in rat sensory neurons. Cells were exposed, either acutely or with 15-60 min preincubations, to low concentrations of phorbol 12-myristate 13-acetate, (PMA), an activator of protein kinase C; if the temperature was 29 degrees C or higher, T-type Ca current was diminished without effect on high-threshold Ca current. In untreated cells, the amplitude of T-type Ca current varies widely among neighboring sensory neurons. T channels are absent in about 25% of cells, provide a small current near threshold for the majority of cells, and are a dominant pathway for calcium entry in a small subset of neurons. The results are of interest because, by selectively inhibiting a calcium channel expressed differently among subpopulations of sensory neurons, activation of protein kinase C might selectively suppress particular sensations.

Animals↗
PubMed1980

Imaginary representations of time cycles.

Two studies and 2 experiments, designed to investigate visual imaginary representations for day, week, and year time cycles, were reported. Incidence of such representations, incidence of subjective distortion, and two sources of suggestibility were also investigated. Finally, a relationship was sought between clearness of visual representations and performance on time-related tasks. Results indicated a high incidence of representations for all three time cycles. The representations were generally reported to be self-constructed as opposed to being taught. Subjective distortions were found in all three time cycles. Presence of an example increased the likelihood of a representation, indicating a possible source of suggestibility. Type of example was shown to have little influence on probability or content. Significant correlations were found between clearness of representation and self-reported accuracy of time estimation. This correlation was supposed by the finding that a group of subjects with clear visual representations out-performed a group of subjects with no representation on backward temporal calculations for months of the year. Results were discussed in terms of their implications for cognitive psychology and future research.

Humans↗
PubMed1978

Extroversion and reminiscence following a frustrating paired-associate task.

Two experiments were reported relating extroversion to reminiscence following a frustrating paired-associate (PA) task. In the first experiment a group of 30 male and female college students was randomly assigned to one of two tasks in which they learned a PA list of high or low stimulus similarity. All PA lists were mixed lists composed of half solvable and half unsolvable (randomized) stimulus-response items. Recall for solvable items was tested immediately, 15 min, and 30 min after criterion was reached. Results indicated a significant difference between high and low stimulus similarity with superior recall for low similarity. The predicted reminiscence effect for high stimulus similarity recall was present but not significant. Comparison of recall scores for extroverts and introverts indicated a significant difference in recall favoring the introverts. The second experiment made a similar test of recall for two groups of S s that had been established as extreme extroverts or introverts (N = 8 in each group). The superiority of recall for introverts was replicated, and a reminiscence effect was found for the extroverts. Results were discussed in relation to Eysenck's formulation and previous conflicting results.

Extraversion, Psychological↗