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V L Smith

Publications and source records attributed to V L Smith.

14 recordsLinked to original sources
PubMed1991

Gustatory neural coding in the monkey cortex: stimulus intensity.

1. We analyzed the activity of single neurons in gustatory cortex of alert cynomolgus monkeys in response to a range of stimulus intensities. Chemicals were deionized water, fruit juice, and several concentrations of the four prototypical taste stimuli: 10(-3)-1.0 M glucose, 10(-3)-1.0 M NaCl, 10(-4)-3 x 10(-2) M HCl, and 10(-5)-3 x 10(-3) M quinine HCl. 2. Taste-evoked responses could be recorded from a cortical gustatory area that measured 2.5 mm in its anteroposterior extent, 6.0 mm dorsoventrally, and 3.0 mm mediolaterally. Taste-responsive cells constituted 62 (3.7%) of the 1,661 neurons tested. Nongustatory cells gave responses associated with mouth movement (10.1%), somatosensory stimulation (2.2%), and approach or anticipation (0.9%). 3. Intensity-response functions were determined across 62 gustatory neurons. Neural thresholds for each stimulus quality conformed well to human psychophysical thresholds. Mean discharge rate was a direct function of stimulus concentration for glucose, NaCl, and quinine HCl. The most effective of the basic stimuli was glucose. 4. Power function exponents were calculated from the responses of neural subgroups most responsive to each basic stimulus. Those for glucose, NaCl, and quinine were within the range of psychophysically derived values. Thus the perceived intensity of each basic quality is presumably based on the activity of the appropriate neural subgroup rather than on the mean activity of all taste cells. 5. The mean breadth-of-tuning (entropy) coefficient for 62 gustatory neurons was 0.65 (range, 0.00-0.98). 6. There was no clear evidence of chemotopic organization in the gustatory cortex. 7. An analysis of taste quality indicated that sweet stimuli evoked patterns of activity that were clearly distinct from those of the nonsweet chemicals. Among the latter group, NaCl was differentiable from HCl and quinine HCl, whose patterns were closely related. 8. The response characteristics of cortical taste cells imply gustatory thresholds and intensity-response functions for the nonhuman primate that conform well to those reported in psychophysical studies of humans, reinforcing the value of this neural model for human taste intensity perception.

Action Potentials↗
PubMed1989

Rapid purification of the 30 kDa calcimedin using DNase I affinity chromatography.

The 30 kDa calcimedin was found to bind directly to phenyl-Sepharose in a calcium dependent manner similar to calmodulin. The 30 kDa calcimedin was also found to bind to and inhibit DNase I. This calcium-dependent binding was exploited to develop a two-step purification scheme for this calcimedin. In addition, affinity-purified antibodies to the 30 kDa calcimedin were used to examine its tissue distribution. The highest levels were found in lung, trachea and diaphragm while the lowest levels of the 30 kDa calcimedin were found in brain and skeletal muscle.

Actins↗
PubMed1989

Eyewitness accuracy and confidence: within- versus between-subjects correlations.

Previous researchers using between-subjects comparisons have found eyewitness confidence and accuracy to be only negligibly correlated. In this study, we examined the predictive power of confidence in within-subject terms. Ninety-six subjects answered, and made confidence ratings for, a series of questions about a crime they witnessed. The average between-subjects and within-subject accuracy-confidence correlations were comparably low: r = .14 (p less than .001) and r = .17 (p less than .001), respectively. Confidence is neither a useful predictor of the accuracy of a particular witness nor of the accuracy of particular statements made by the same witness. Another possible predictor of accuracy, response latency, correlated only negligibly with accuracy (r = -.09 within subjects), but more strongly with confidence (r = -.27 within subjects). This pattern was obtained for both between-subjects and within-subject comparisons. The theoretical and practical implications of these results are discussed.

Adult↗
PubMed1988

The expression of the 35- and 67-kDa calcimedins is dependent on thyroid hormone.

We have investigated the expression of the 35- and 67-kDa calcimedins and calmodulin during fetal and neonatal periods and in adulthood in rat liver, muscle, and brain. The 35- and 67-kDa calcimedin expression in liver and muscle increased during the perinatal period and correlated with the thyroid status of the developing rat. In fact, animals treated with thyroxine demonstrated a precocious appearance of the 35- and 67-kDa calcimedin in liver and muscle. Animals treated with methylthiouracil, an inhibitor of T4 and T3 synthesis, strongly suppressed the synthesis of the calcimedins in these tissues. Neither treatment influenced the levels of either the 35- and 67-kDa calcimedins in brain. In contrast, each tissue examined produced a unique pattern of calmodulin expression during development. None of the tissue calmodulin concentrations changed during hyper- or hypothyroid states. Collectively, these data support the concept that the intracellular calcium signal possesses multiple, independent molecular pathways of mediation. In addition, the variety of these pathways is influenced by hormonal preconditioning in that the cellular response to elevated cytosolic calcium is dependent upon the thyroid status of a tissue.

Animals↗
PubMed1987

Structure and sequence of the Drosophila melanogaster calmodulin gene.

A series of phage clones overlapping the single calmodulin gene locus of Drosophila melanogaster has been isolated and the exons of the gene positioned and sequenced within these clones. A calmodulin cDNA clone of the electric eel was used to identify these clones and to position the two major protein-coding exons of the gene. cDNA clones for D. melanogaster calmodulin were then isolated, characterized and used to identify the remaining exons. The gene consists of four exons separated by three introns of 3400 to 4300 bases in length. Exon 1 consists of the 5' untranslated region and the initiator ATG; exon 2 encodes amino acid residues 1 to 58.3; exon 3 encodes residues 58.3 to 139.3; and exon 4 encodes residues 139.3 to 148 and the 3' untranslated region. From the sequence of the 3' untranslated region and the lengths of the cDNA clones, two or three polyadenylation sites are indicated. Sequences potentially involved in the control of transcription of the gene and splicing of the mRNA product have been identified. Comparison of the intron-exon structures of the D. melanogaster calmodulin gene, the chick calmodulin gene, and other genes of the troponin C superfamily reinforces previous hypotheses that these genes arose from a common progenitor and permits identification of four introns that were probably present in the progenitor gene structure. The D. melanogaster calmodulin gene contains three of these introns, and the chick gene contains all four. These gene comparisons also indicate that the region of these genes encoding Ca2+-binding loop 3 is highly variable in structure. The chick and D. melanogaster calmodulin genes differ in this region, the chick gene containing a fifth intron here that is absent from the D. melanogaster gene.

Animals↗
PubMed1986

An immunological comparison of several novel calcium-binding proteins.

Polyclonal antibodies prepared against each of the calcimedins were utilized to determine their tissue distribution. The immunological survey of rat tissues revealed that the levels of the 35-kDa calcimedin varied, while the amount of the 67-kDa calcimedin was relatively constant in the tissues examined. A new immunoreactive species, 52 kDa, was detected with the antibody to the 35-kDa calcimedin; this protein appears to be the predominant immunoreactive species in the tissues examined. Antibodies to the 35-kDa calcimedin were also used to compare many other calcium-binding proteins in order to determine immunological relationships. These comparisons demonstrate that the epidermal growth factor receptor/kinase substrate (p35), the src kinase substrate (pp36), and calregulin are immunologically unrelated to the calcimedins. However, it was found that the 67-kDa calcimedin and the p70 calelectrin are identical, as are the 35-kDa calcimedin and the p32.5 calelectrin. The calimedins are a subset of the chromobindins. In addition, the antibody to the 35-kDa calcimedin also cross-reacts with synexin, which may be related to the new 52-kDa immunoreactive protein identified.

Amino Acid Sequence↗