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Biomedical subjects

D M Webster

Publications and source records attributed to D M Webster.

At least 19 recordsLinked to original sources
PubMed1997

Motivated language use in intergroup contexts: need-for-closure effects on the linguistic intergroup bias.

Two experiments examined the impact of the motivation for cognitive closure on the abstractness of linguistic communications in intergroup contexts. Participants described positive and negative behaviors attributed to either an in-group or an out-group member. Individuals high (vs. low) in need for closure exhibited greater linguistic abstraction when describing positive behaviors of in-group members and negative behaviors of out-group members. These differences disappeared for descriptions of negative behaviors of out-group members. The discussion relates these results to the interface of motivation, language, and social cognition.

Adult↗
PubMed1997

Psychological theory testing versus psychometric nay-saying: comment on Neuberg et al.'s (1997) critique of the need for closure scale.

S. L. Neuberg, T. N. Judice, and S. G. West (1997) faulted our work with the Need for Closure Scale (NFCS) on grounds that the NFCS lacks discriminant validity relative to S. L. Neuberg's and J. T. Newsom's (1993) Personal Need for Structure (PNS) Scale and is multidimensional, which, so they claim, renders the use of its total score inadmissible. By contrast, the present authors show that neither of the above assertions is incompatible with the underlying need for closure theory. Relations between NFCS and the PNS are to be expected, as these were designed to operationalize the very same construct (of need for closure). Furthermore, no unidimensionality of the NFCS has been claimed, and none is required to use its total score for testing various theoretically derived predictions. An instrument's ultimate utility hinges on theoretical considerations and empirical evidence rather than on questionable psychometric dogma unrelated to the substantive matters at hand.

Humans↗
PubMed1996

Motivated closing of the mind: "seizing" and "freezing".

A theoretical framework is outlined in which the key construct is the need for (nonspecific) cognitive closure. The need for closure is a desire for definite knowledge on some issue. It represents a dimension of stable individual differences as well as a situationally evocable state. The need for closure has widely ramifying consequences for social-cognitive phenomena at the intrapersonal, interpersonal, and group levels of analysis. Those consequences derive from 2 general tendencies, those of urgency and performance. The urgency tendency represents an individual's inclination to attain closure as soon as possible, and the permanence tendency represents an individual's inclination to maintain it for as long as possible. Empirical evidence for present theory attests to diverse need for closure effects on fundamental social psychological phenomena, including impression formation, stereotyping, attribution, persuasion, group decision making, and language use in intergroup contexts.

Cognition↗
PubMed1994

Antibody design: beyond the natural limits.

Dissection of antibody-antigen interactions requires a knowledge of antibody structure, the ability to model accurately the conformation of antibody-combining sites, and an understanding of the energetic factors governing the interactions. When this understanding has reached the point where the molecular shape and chemical character of a combining site necessary to define a particular specificity and binding requirement can be designed, the antibody repertoire will have been extended 'beyond the natural limits'.

Animals↗
PubMed1994

Individual differences in need for cognitive closure.

This article introduces an individual-difference measure of the need for cognitive closure. As a dispositional construct, the need for cognitive closure is presently treated as a latent variable manifested through several different aspects, namely, desire for predictability, preference for order and structure, discomfort with ambiguity, decisiveness, and close-mindedness. This article presents psychometric work on the measure as well as several validation studies including (a) a "known-groups" discrimination between populations assumed to differ in their need for closure, (b) discriminant and convergent validation with respect to related personality measures, and (c) replication of effects obtained with situational inductions of the need for closure. The present findings suggest that the Need for Closure Scale is a reliable and valid instrument of considerable potential utility in future "motivated social cognition" research.

Cognition↗
PubMed1993

Motivated augmentation and reduction of the overattribution bias.

Three experiments investigated whether the need to have (or avoid) cognitive closure affects observers' tendency to display attributional bias. Results of each experiment indicate that the overattribution bias was magnified under high need for cognitive closure and attenuated under high need to avoid closure. In Experiments 1 and 3, the relevant motivational state was manipulated situationally, whereas in Experiment 2 an individual-differences measure of the closure motivation was used. These divergent operationalizations yielded convergent results. Furthermore, when in Experiment 3 the task consisted of attributions to the situation, high need for closure augmented, and high need to avoid closure reduced, situational rather than dispositional overattributions. The results imply general motivational boundary conditions for inferential biases across judgmental contents.

Cognition↗
PubMed1993

Motivated resistance and openness to persuasion in the presence or absence of prior information.

Three experiments investigated the relation between need for cognitive closure and persuasion. In the 1st study, Ss high on an individual-differences measure of need for closure were more resistant to persuasion by their low need-for-closure counterparts than vice versa. In the 2nd study, Ss in a noisy environment, assumed to instill a relatively high need for closure, were more resistant to persuasion than Ss in a quiet environment, but only in presence of an initial informational base for an opinion. In its absence, Ss in the noisy (vs. quiet) environment were less resistant to persuasion. The interaction between need for closure and informational base was replicated in the 3rd experiment reverting to the individual-differences measure of need for closure. The discussion considered implications of these findings for further persuasion phenomena.

Acoustic Stimulation↗
PubMed1991

Funicular organization of avian brainstem-spinal projections.

The purpose of this study was to determine which reticulospinal projections need to be preserved to allow voluntary walking and to differentiate between those pathways descending within the ventrolateral funiculus versus the ventromedial funiculus. Retrogradely transported tracers (True Blue, Fast Blue, Diamidino Yellow dihydrochloride, fluorescein-conjugated dextran-amines) were used alone as discrete funicular injections (4-5 microliters) into the lumbar cord (L1), or in conjunction with a more rostral subtotal lesion of the low thoracic cord, to determine the trajectories of brainstem-spinal projections in adult ducks and geese. No difference was found between the species. The major components of the ventromedial funiculus include projections from the medullary reticular formation, pontine reticular formation, raphe obscurus and pallidus, lateral vestibular nucleus, and interstitial nucleus, and to a minor extent from the locus coeruleus, lateral hypothalamus, and nucleus periventricularis hypothalami. The components of the ventrolateral funiculus (VLF) include projections from the nucleus of the solitary tract, nucleus alatus, pontomedullary reticular formation, raphe pallidus, raphe magnus, locus coeruleus, subcoeruleus, lateral vestibular, and descending vestibular nuclei. The principal descending projections within the dorsolateral funiculus (DLF) arose from the red nucleus, the paraventricular nucleus, locus coeruleus, subcoeruleus, dorsal division of the caudal medullary reticular formation, and raphe magnus. The functional implications of the distribution of these descending pathways are discussed with regard to locomotion. Since birds were able to walk despite bilateral lesion of the DLF or VMF but were unable to walk following a bilateral lesion of the VLF, this suggests that medullary reticulospinal pathways coursing within the VLF are essential for the provision of locomotor drive.

Amidines↗
PubMed1991

Group members' reactions to opinion deviates and conformists at varying degrees of proximity to decision deadline and of environmental noise.

Four experiments examined freely interacting groups to investigate the determinants of group members' reactions to opinion deviates and conformists. In the 1st experiment, the deviate was rejected more when he or she articulated the dissenting opinion in close proximity to the group-decision deadline versus at an earlier point in the group discussion. In the 2nd, 3rd, and 4th experiment, the deviate was rejected more when the group discussion was carried out in a noisy versus a quiet environment. Furthermore, when the conformist's contributions to the group's attempts to reach consensus were made salient (in Experiment 4), he or she was evaluated more positively in a noisy versus a quiet environment. The results were discussed in terms of the notion that group members' tendency to denigrate a deviate or extol a conformist may be stronger when their need for collective cognitive closure is heightened.

Cognition↗
PubMed1990

Origins of descending spinal pathways in prehensile birds: do parrots have a homologue to the corticospinal tract of mammals?

In mammals, the supraspinal descending projections that influence distal limb muscles are the rubrospinal and corticospinal tracts. The former, which is found in other vertebrates, shows greater somatotopy in mammals that are 'dextrous' (e.g. monkeys) than those that are not (e.g. opossums). Similarly, the corticospinal tract, which is found only in mammals, has more extensive connections (i.e. direct corticomotoneural) in mammals that are dextrous than in mammals that are not. Descending spinal pathways have been described in 'non-dextrous' avian species (chickens, ducks, geese and pigeons), and the purpose of this study was to determine if there are any differences in the origins of descending projections to the spinal cord in 'dextrous' or prehensile parrots (sulphur-crested cockatoo, Cacatua galerita, and eastern rosella, Platycerus eximius). True Blue or wheat germ agglutinin-horseradish peroxidase was injected into the lumbar or cervical spinal cord. The distribution of retrogradely labelled cells was similar to that previously reported for non-prehensile birds. We found no evidence of any direct spinal projections from the telencephalon (including any pathway homologous to the corticospinal tract of mammals), nor any specialized anatomical organization of the descending pathways that could account for the pedal dexterity of these species.

Animals↗
PubMed1988

V region sequences of anti-DNA and anti-RNA autoantibodies from NZB/NZW F1 mice.

The V region sequences of two anti-DNA (A52, D42) and two anti-RNA (D44, D444) autoantibodies, derived from lupus prone NZB/NZW F1 female mice, were determined by mRNA sequencing. The sequences had the following features: 1) there was no clear sequence relationship between anti-DNA and anti-RNA antibodies; 2) there were no major similarities between any of the L chain sequences and each VL gene segment belonged to a different mouse VK subgroup; 3) the H chains of the two anti-RNA antibodies showed closely related sequences of VH gene segments and very similar third complementarity determining regions (CDR3); 4) the H chains of the two anti-DNA antibodies had VH segments belonging to different VH gene families but had a unique and similar combination of D segments and junctional sequences, suggesting a common recognition element for Ag and/or for idiotypic regulation in the H chain CDR3; and 5) the VH gene segment of one anti-DNA antibody (D42) was found to be very similar to the VH gene segment of a CBA mouse hybridoma antibody (6G6) which binds to the environmental Ag phosphocholine. The three-dimensional structure of the Fv-region of the anti-DNA antibody (D42) was modeled by computer and a stretch of poly(dT), ssDNA was docked to a cleft in the antibody combining site, formed by the three H chain CDR and by CDR1 and CDR3 of the L chain. The cleft is characterized by a preponderance of arginine and tyrosine residues, lining both the walls and base of the cleft.

Amino Acid Sequence↗
PubMed1988

Origins of brainstem-spinal projections in the duck and goose.

The purpose of this study was to determine the location of neuronal cell bodies with projections to the cervical or lumbar spinal cord in the adult duck and goose. Bilateral or unilateral injections (5-10 microliter) of the retrograde tracer dye True Blue (TB:5%) were made into the high cervical or high lumbar levels of the spinal cord. Similar results were obtained in both species. First, we found no evidence of retrogradely labelled cells in the telencephalon. In the brainstem, the distribution of TB cells was similar to those previously reported for the pigeon; however, the present study now demonstrates that some of these descending pathways project as far as the lumbar cord. We also discovered that there is a topographical representation of spinal projecting neurons within the avian medullary-pontine reticular formation.

Animals↗
PubMed1988

Engineering antibody affinity and specificity.

A combination of ab initio calculations, "knowledge-based prediction", molecular graphics and site-directed mutagenesis has enabled us to probe the molecular details of antibody:antigen recognition and binding and to alter the affinity and specificity of an antibody for its antigen. The significance of electrostatic hydrogen bonding, hydrophilic/hydrophobic patch matching and van der Waals interactions as well as CDR:CDR interactions are discussed in relation to the results of site-directed mutagenesis experiments on the anti-lysozyme antibody Gloop2. The ability to generate reconstructed antibodies, chimeric antibodies, catalytic antibodies and the use of modelled antibodies for the design of drugs is discussed.

Animals↗
PubMed1987

Stimulation of the pontomedullary reticular formation initiates locomotion in decerebrate birds.

The initiation and control of spinal locomotor mechanisms by supraspinal brainstem centers has been studied in many vertebrate species. However there is very little information regarding brainstem-spinal pathways involved in avian locomotion. To undertake these studies, birds (geese or ducks) were placed in a stereotaxic frame and decerebrated under halothane anesthesia. After anesthesia was discontinued, discrete brainstem regions were electrically stimulated. Locomotion could be evoked from several areas within the pontomedullary reticular formation. The stimulus threshold for evoking walking ranged from 25-50 microA at 30-80 Hz (pulse duration 0.5 ms). At slightly higher current strengths (50-100 microA) wing flapping ('flying') was initiated. Histological examination of the stimulation sites indicated that the predominant locomotor areas were restricted to the ventromedial gigantocellular reticular formation and a more dorsolateral location within the parvocellular reticular formation. To ascertain whether neurons in these regions of the avian brainstem project directly to the spinal cord, a retrograde fluorescent tracer dye, True blue, was injected into either the cervical or low thoracic spinal cord. Comparing the positions of the retrogradely labeled neurons and the effective locomotor stimulation sites indicated a high degree of overlap. The present results, when compared with previous studies, suggest strong similarities in descending brainstem control of locomotion for all vertebrates.

Animals↗
PubMed1986

Role of interferon in lymphocyte recruitment into the skin.

Large numbers of lymphocytes are recruited from the blood into sites of cutaneous DTH reactions. Our goal was to investigate the factors controlling this recruitment. 111In-labeled peritoneal exudate lymphocytes were injected iv and the accumulation of these cells in skin sites injected with a variety of stimuli, was used to measure lymphocyte recruitment in rats. Large numbers of lymphocytes migrated into vaccinia- and KLH-injected sites in sensitized animals, but only into the viral and not the KLH lesions in non-immune animals. Lymphocytes also migrated efficiently into sites injected with the alpha-interferon (IFN) inducers, uv-inactivated vaccinia virus and poly I:C, as well as into sites injected with IFN. In each case there was a dose-response relationship. Analysis of the kinetics of lymphocyte recruitment demonstrated that the peak rate of migration occurred most rapidly after the injection of IFN, later after poly I:C, and was slowest to be reached after vaccinia virus. Rabbit anti-IFN blocked the recruitment of lymphocytes by uv-inactivated vaccinia and by IFN. Histologically, all of these sites demonstrated a dense mononuclear cell infiltrate in the dermis. It is suggested that IFN may be an important mediator in the recruitment of lymphocytes into inflammatory reactions.

Animals↗
PubMed1986

Lymphocyte recruitment in vaccinia virus-induced cutaneous delayed-type hypersensitivity.

Our goal was to study the small lymphocytes that were recruited to cutaneous DTH lesions in order to determine if there existed a subset of small lymphocytes which preferentially migrated into cutaneous inflammatory sites rather than into lymphoid tissues. Lymphocytes were radiolabelled and injected i.v. into sensitized recipient rats on which DTH lesions were induced by the i.d. injection of vaccinia virus. Small lymphocytes, from unstimulated and antigen-stimulated LNs, migrated in large numbers to LNs but only to a modest extent to the DTH lesions. Lymphoblasts, from antigen-stimulated nodes, migrated to DTH lesions well, but poorly to normal LNs. The ratio of the radioactivity in the lesions to that in LNs was used as an index of the preferential migration of the cells. This ratio for small lymphocytes was 0.8:1, while that of lymphoblasts was 34:1. Lymphocytes from the blood and spleen were better at entering lesions than the small LNCs, and their ratio was higher. Peritoneal exudate lymphocytes induced by the i.p. injection of virus migrated very well to the DTH lesions and poorly into LNs, and produced a ratio of 130:1. The peritoneal lymphocytes that migrated into the lesions were primarily small lymphocytes. Negative selection for either surface Ig-, W3/25-, MRC OX-8- or MRC OX-6- cells had little effect on the accumulation of the cells within the DTH lesions. In conclusion, it is suggested that there exists a subset of small lymphocytes with receptors on their surfaces which cause them to migrate selectively to inflammatory sites rather than to LNs. An inflammatory exudate is a rich source of this subset of small lymphocytes, while only a small proportion of small LNCs being to this subset.

Animals↗
PubMed1985

Changes in isometric contractile properties of extensor digitorum longus and soleus muscles of C57BL/6J mice following denervation.

In this study, conducted on mice of the C57BL/6J+/+ strain, we investigated the differential effects of denervation on the isometric contractile properties of the extensor digitorum longus (EDL) and soleus (SOL) muscles. The contractile properties were studied at 1, 28, 84, and 210 days following unilateral section of the sciatic nerve at 12 weeks of age. When isometric tetanus tension was expressed relative to wet weight, the denervated SOL showed an earlier and more pronounced loss in tension generating capacity than the EDL. Both the denervated SOL and EDL showed potentiation of the twitch tension at 28 days postdenervation. The time to peak twitch tension (TTP) and the time to half-relaxation (1/2RT) were prolonged by 28 days postdenervation in both muscles. This trend continued to the oldest age-groups studied in the EDL, but reached an apparent plateau in the SOL at 84 days postdenervation. In response to fatigue, the denervated SOL showed a marked decrease in resistance to fatigue at 1 day but a relatively normal response thereafter, whereas the denervated EDL showed an increase in resistance to fatigue at and beyond the 28-day period. In spite of the fact that the total contraction time of both muscles increased following denervation, the predominantly oxidative SOL remained a slower contracting muscle than the more glycolytic EDL.

Animals↗