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J V Pardo

Publications and source records attributed to J V Pardo.

28 records · Page 2Linked to original sources
PubMed1991

Does inter-subject variability in cortical functional organization increase with neural 'distance' from the periphery?

In mapping the functional anatomy of the human brain, anatomical variability is a recurring concern. The degree to which the functional organization of any one subject or group of subjects is more generally predictive is largely unknown. We have previously reported that the inter-subject variability of primary visual, somatosensory and motor cortices is small (4-8 mm). Many have suggested, however, that higher-order brain areas will be considerably more variable. For this reason we assessed the anatomical variability of several brain areas participating in language perception and production. In 10 anatomically normal subjects undergoing evaluation for partial complex epilepsy we applied a previously described battery of lexical tasks; intra-subject image averaging was used to minimize the effects of variations in response magnitude. We found inter-subject anatomical variability to be uniformly consistent, with no appreciable effect of distance from the neural periphery.

Adolescent↗
PubMed1990

The anterior cingulate cortex mediates processing selection in the Stroop attentional conflict paradigm.

Regional cerebral blood flow, an index of local neuronal activity, was measured using positron emission tomography (PET) during the performance of the classic Stroop color/word task in eight healthy right-handed subjects. In the first condition of this paradigm, subjects name the color of the words presented on a video monitor. All the words are the color names congruent to the color presented (e.g., the noun "red" displayed in red color). In the second condition, subjects also name the color of the words presented on the monitor. However, during these trials all words are color names incongruent to the color presented (e.g., the noun "red" displayed in green color). The difference in brain activity between these two conditions (i.e., incongruent minus congruent) could reveal brain systems involved in the attentionally mediated resolution of the conflict between the habitual response of reading words vs. the task demands of naming the color of the words--i.e., the Stroop interference effect. The most robust responses occurred in the anterior cingulate cortex. Other responses noted were in the left premotor cortex, left postcentral cortex, left putamen, supplementary motor area, right superior temporal gyrus, and bilateral peristriate cortices. These data provide support for the role of the anterior cingulate cortex in attentional processing through the selection and recruitment of processing centers appropriate for task execution. Furthermore, the extensive distributed network of activated regions suggests that the Stroop interference effect cannot be explained simply in terms of stimulus encoding or response interference.

Adult↗
PubMed1983

Gamma actin, spectrin, and intermediate filament proteins colocalize with vinculin at costameres, myofibril-to-sarcolemma attachment sites.

Localization of vinculin at the sarcolemma of striated muscle fibers defines an orthogonal lattice. The costameres of the lattice are the riblike bands of vinculin that run perpendicular to the long axis of the fiber, repeat in register with I bands of the subjacent myofibrils, and seem to couple the myofibril to the sarcolemma [Pardo et al 1982, 1983a]. The colocalization studies presented in this paper show that gamma actin, spectrin, and intermediate filament antigens are additional components of this lattice of costameres. In addition, the results show that gamma actin and spectrin are also components of the internal network of collars, first visualized with antibody to desmin [Granger and Lazarides, 1978], that connects the myofibrils to each other at the level of the Z line.

Actins↗
PubMed1983

Subcellular sorting of isoactins: selective association of gamma actin with skeletal muscle mitochondria.

We describe two subpopulations of actin antibodies isolated by affinity chromatography from a polyclonal antibody to chicken gizzard actin. One subpopulation recognizes gamma actins from smooth muscle and nonmuscle cells, but does not recognize alpha actin from skeletal muscle. The other subpopulation recognizes determinants that are common to alpha actin from skeletal muscle and the two gamma actin isotypes. Neither antibody recognizes cytoplasmic beta actin. Both antibodies recognize only actins or molecules with determinants that are also present in actins. By immunofluorescence we found that the anti-gamma actin colocalizes with mitochondria in fibers of mouse diaphragm, and that it does not bind detectably to the 1 bands of sarcomeres. The antibody that recognizes both alpha and gamma actins stains 1 bands intensely, as expected. We interpret these observations as preliminary evidence for selective association of gamma actin with skeletal muscle mitochondria and, more broadly, as evidence for subcellular sorting of isoactins.

Actins↗
PubMed1983

A vinculin-containing cortical lattice in skeletal muscle: transverse lattice elements ("costameres") mark sites of attachment between myofibrils and sarcolemma.

We have found that vinculin is localized at the sarcolemma of skeletal muscle cells in a two-dimensional orthogonal lattice. Perpendicular to the longitudinal axis of the cell, bands of vinculin encircle the muscle cell and repeat along its length with a periodicity corresponding to the subjacent sarcomeres. Because of their appearance and probable function, we call the transverse elements of the lattice "costameres" (Latin costa, rib; Greek meros, part). Costameres have a substructure consisting of densely clustered patches of vinculin; the patches are segregated into two rows which flank the Z line and overlie the I band of the underlying sarcomere. It is likely that the costameres are physically coupled to the underlying myofibrils because: (i) the costameres broaden and narrow in concert with the underlying I band in stretched and contracted muscle, and (ii) adjacent but misaligned myofibrils are mirrored by corresponding discontinuities in the overlying costameres. We hypothesize that the sarcolemmal lattice, detected because vinculin is one of its molecular components, integrates the contractile apparatus with the sarcolemma during lengthening and shortening of the muscle cells.

Actins↗
PubMed1983

Vinculin is a component of an extensive network of myofibril-sarcolemma attachment regions in cardiac muscle fibers.

Immunofluorescent staining of bovine and avian cardiac tissue with affinity-purified antibody to chicken gizzard vinculin reveals two new sites of vinculin reactivity. First, vinculin is organized at the sarcolemma in a striking array of rib-like bands, or costameres. The costameres encircle the cardiac muscle cell perpendicular to the long axis of the fiber and overlie the I bands of the immediately subjacent sarcomeres. The second new site of vinculin reactivity is found in bovine cardiocytes at tubular invaginations of the plasma membrane. The frequency and location of these invaginations correspond to the known frequency and distribution of the transverse tubular system in bovine atrial, ventricular, and Purkinje fibers. We do not detect tubular invaginations that stain with antivinculin in avian cardiocytes and, in fact, a transverse tubular system has not been found in avian cardiac fibers. Apparent lateral Z-line attachments to the sarcolemma and its invaginations have been observed in cardiac muscle by electron microscopy in the same regions where we find vinculin. On the basis of these previous ultrastructural findings and our published evidence for a physical connection between costameres and the underlying myofibrils in skeletal muscle, we interpret the immunofluorescence data of this study to mean that, in cardiac muscle, vinculin is a component of an extensive system of lateral attachment of myofibrils to the plasma membrane and its invaginations.

Animals↗
PubMed1979

alpha-Actinin localization in the junctional complex of intestinal epithelial cells.

We have used antibody to chicken gizzard alpha-actinin to identify and localize this molecule in chicken intestinal epithelium. The antibody binds only to alpha-actinin when tested against a crude extract of chicken gizzard. Extracts of purified epithelial cells contain a molecule which has a subunit molecular weight of 100,000 on sodium dodecyl sulphate gels and which is able to inhibit the interaction of alpha-actinin antibody and 125I-labeled chicken gizzard alpha-actinin. By indirect immunofluorescence, alpha-actinin is localized in the apical portion of chicken intestinal epithelial cells. Ethanol-fixed cryostat sections of intestine taken through the apical portion of the epithelial cells and in a plane perpendicular to the long axis of the cells show that alpha-actinin is organized in a polygonal pattern which corresponds to the outlines of the polygonally packed epithelial cells. We interpret the data as indicating that alpha-actinin is a component of the tight junction (zonula occludens) and/or the belt desmosome (zonula adherens), both of which are membrane structures known to encircle the cell and to be confined to its apical portion.

Actinin↗
PubMedDate not supplied

Practice-related changes in human brain functional anatomy during nonmotor learning.

Practice of a novel task leads to improved performance. The brain mechanisms associated with practice-induced improvement in performance are largely unknown. To address this question we have examined the functional anatomy of the human brain with positron emission tomography (PET) during the naive and practiced performance of a simple verbal response selection task (saying an appropriate verb for a visually presented noun). As a control state, subjects were asked to repeat the visually presented nouns. Areas of the brain most active during naive performance (anterior cingulate, left prefrontal and left posterior temporal cortices, and the right cerebellar hemisphere), compared to repeating the visually presented nouns, were all significantly less active during practiced performance. These changes were accompanied by changes in the opposite direction in sylvian-insular cortex bilaterally and left medial extrastriate cortex. In effect, brief practice made the cortical circuitry used for verbal response selection indistinguishable from simple word repetition. Introduction of a novel list of words reversed the learning-related effects. These results indicate that two distinct circuits can be used for verbal response selection and normal subjects can change the brain circuits used during task performance following less than 15 min of practice. One critical factor in determining the circuitry used appears to be the degree to which a task is learned or automatic.

Adult↗