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Biomedical subjects

D G Perry

Publications and source records attributed to D G Perry.

At least 19 recordsLinked to original sources
PubMed2001

Gender identity: a multidimensional analysis with implications for psychosocial adjustment.

This study examined the relations between components of gender identity and psychosocial adjustment. The aspects of gender identity assessed were (a) feelings of psychological compatibility with one's gender (i.e.. feeling one is a typical member of one's sex and feeling content with one's biological sex), (b) feelings of pressure from parents, peers, and self for conformity to gender stereotypes. and (c) the sentiment that one's own sex is superior to the other (intergroup bias). Adjustment was assessed in terms of self-esteem and peer acceptance. Participants were 182 children in Grades 4 through 8. Felt gender compatibility (when operationalized as either self-perceived gender typicality or feelings of contentment with one's biological sex) was positively related to adjustment, whereas felt pressure and intergroup bias were negatively associated with adjustment. The results provide new insights into the role of gender identity in children's well-being, help identify sources of confusion in previous work, and suggest directions for future inquiry.

Adaptation, Psychological↗
PubMed1999

Clathrin-coated pit-associated proteins are required for alveolar macrophage phagocytosis.

During phagocytosis, phagocytic receptors and membrane material must be inserted in the pseudopod membrane as it extends over the phagocytic target. This may require a clathrin-mediated recycling mechanism similar to that postulated for leading edge formation during cell migration. To investigate this possibility, liposomes were used to deliver to intact rat alveolar macrophages (AMs): 1) Abs to clathrin, clathrin adaptor AP-2, and hsc70, and 2) amantadine. Phagocytosis was assayed by fluorometric and colorimetric techniques. Liposome-delivered Abs to clathrin and AP-2 inhibited AM phagocytosis of zymosan-coated, fluorescent liposomes from 16.3+/-0.3 to 5.8+/-0.3, and 10.1+/-0.9 to 4.8+/-0.2 liposomes/cell (p<0.01). Similarly, liposome-delivered Ab to clathrin also inhibited AM phagocytosis of IgG-opsonized RBCs from 11.7+/-1.7 to 3.8+/-0.7 RBCs/cell (p<0.01). Amantadine, which blocks the budding of clathrin-coated vesicles, inhibited phagocytosis from 13.8+/-0.8 to 5.7+/-0.6 (p<0.01). Ab blockade of hsc70, which catalyzes clathrin turnover, also inhibited phagocytosis from 9.1+/-0.5 to 4.3+/-0.2 (p<0.01). These findings suggest that clathrin-mediated receptor/membrane recycling is required for phagocytosis.

Adenosine Triphosphatases↗
PubMed1999

Skewed autonomy-relatedness in preadolescents' conceptions of their relationships with mother, father, and best friend.

Healthy adaptation within all close relationships--whether with parents, friends, or romantic partners--involves striking a balance between connectedness to and independence from the relationship partner. For some individuals, adaptation within one or more relationships is skewed, or characterized by either an excessive concern for closeness that impedes autonomy (preoccupied stance) or an excessive concern for autonomy that inhibits closeness (avoidant stance). In this study with boys and girls aged 9-14 years, children who reported a preoccupied or avoidant stance toward their mother displayed increased social impairment in the peer group over time. There were predictable associations among children's stances toward mother, father, and best friend. Children resembled their best friend in relationship stance. The study illustrates the advantages of applying common relationship constructs (e.g., autonomy-relatedness) to the study of diverse close relationships.

Adolescent↗
PubMed1999

Personal and interpersonal antecedents and consequences of victimization by peers.

This study was designed to determine whether the personal and interpersonal difficulties that characterize victimized children are antecedents of victimization, consequences of victimization, or both. Boys and girls in the 3rd through 7th grades (N = 173, mean age = 11.3 years) were assessed on victimization, personal variables (internalizing problems, externalizing problems, and physical strength), and interpersonal variables (number of friends and peer rejection). One year later children were assessed again on all variables. Internalizing problems, physical weakness, and peer rejection contributed uniquely to gains in victimization over time. Moreover, initial victimization predicted increases in later internalizing symptoms and peer rejection. These reciprocal influences suggest the existence of a vicious cycle that supports the strong temporal stability of peer victimization.

Child↗
PubMed1998

Does low self-regard invite victimization?

Two hypotheses were tested. The first was that low self-regard contributes over time to victimization by peers. The second was that behavioral vulnerabilities (e.g., physical weakness, manifest anxiety, poor social skills) are more likely to lead to victimization over time when children have low self-regard than when they are "self-protected" by healthy self-regard. Participants were 189 third-through 7th-grade boys and girls; data were collected in the fall and the spring of the school year. Both hypotheses were supported, especially when self-regard was assessed in terms of self-perceived peer social competence. In addition, the experience of being victimized led to diminished self-regard over time. Poor self-concept may play a central role in a vicious cycle that perpetuates and solidifies a child's status as a victim of peer abuse.

Adolescent↗
PubMed1998

Social-cognitive influences on change in aggression over time.

This study examined whether social cognitions that have been assumed to influence aggression actually forecast change in aggressive habits over time. Participants were 189 3rd- through 7th-grade boys and girls; data on social cognitions and social behaviors were collected in the fall and spring of the school year. Aggression-encouraging cognitions assessed in the fall indeed promoted aggression over the school year, but such developments hinged critically on child sex and on initial (fall) levels of aggression and victimization. Results illustrate the principle that cognitions affect behavioral development mainly when the child's transactions with the social environment support the use of the cognitions as guides for behavior.

Adolescent↗
PubMed1998

Victimization by peers: associations with children's reports of mother-child interaction.

Children who are chronically victimized by peers are at risk for personal difficulties. This study examined whether victimization is associated with mother-child interaction at home. Preadolescents (N = 184; mean age = 11.7 years) reported on their mother's child-rearing practices and on how they cope during conflicts with their mother. Peers reported on victimization at school. Sex-specific links between perceived family interaction and peer victimization were found. For boys, victimization was associated with perceived maternal overprotectiveness, especially when boys reported reacting with fear during mother-child conflict. For girls, victimization was associated with perceived maternal rejection and with girls' reports of aggressive coping during mother-child conflict. Results support the theory that parenting that hinders children's development of gender-salient competencies (autonomy for boys and communion for girls) places children at risk for peer victimization.

Adaptation, Psychological↗
PubMed1997

Individual risk and social risk as interacting determinants of victimization in the peer group.

This study evaluated the hypothesis that the behavior problems that place children at risk for victimization by peers are associated with victimization primarily when children are also at social risk for victimization. Social risk was defined as lacking supportive friends or as being rejected by the peer group. Participants were 229 boys and girls in the 3rd through 7th grades (M age = 11 years 2 months). As predicted, behavior problems (internalizing problems, externalizing problems, and physical weakness) were more strongly related to victimization when children had few friends, had friends who were incapable of fulfilling a protective function (e.g., were physically weak), or were rejected by peers than when children had more friends, had friends capable of defending them, or were better liked by peers. Results illustrate the principle that individual risk variables depend on social context for expression.

Child↗
PubMed1997

Nonimmune phagocytosis of liposomes by rat alveolar macrophages is enhanced by vitronectin and is vitronectin-receptor mediated.

Pulmonary alveolar macrophages (AMs) engulf diverse materials. The mechanisms allowing AMs to recognize, bind, and phagocytose these materials are poorly understood. To test the hypothesis that the adhesive glycoprotein vitronectin (Vn) acts as a nonimmune opsonin, we studied AM-Vn binding and AM phagocytosis of fluorescent liposomes under the following conditions: (1) pretreatment of AMs with Vn, followed by incubation of AMs with liposomes containing increased amounts of Vn; (2) inhibition of phagocytosis by gly-arg-gly-asp-ser (RGD) and gly-pen-gly-arg-gly-asp-ser-pro-cys-ala (GPen); and (3) antibody blockade of the alpha(v)beta3 vitronectin receptor (VnR). Pretreatment of AMs with 0.1, 1, and 2 microM Vn progressively enhanced AM-Vn binding from 23,622 +/- 3,328 cpm to 40,847 +/- 6,530 cpm, 57,149 +/- 2,789 cpm, and 124,852 +/- 42,930 cpm, respectively (P < 0.05). AM pretreatment also increased phagocytosis of Vn-enriched liposomes, but not empty liposomes (20.7 +/- 0.4 liposomes/cell versus 11.5 +/- 0.5 liposomes/cell, P < 0.05). Moreover, increased concentrations of Vn in liposomes progressively increased phagocytic activity (3.7 +/- 0.3, 6.5 +/- 0.2, 11.5 +/- 0.5, and 16.5 +/- 0.6 liposomes/cell with 0.01, 0.1, and 1 microM Vn, respectively, P < 0.05). RGD inhibited Vn-enhanced phagocytosis (8.1 +/- 0.4 liposomes/cell to 3.4 +/- 0.2, 2.4 +/- 0.4, and 2.2 +/- 0.2 liposomes/cell with 0.02, 0.2, and 2 mM RGD, respectively, P < 0.05), as did GPen (4.7 +/- 0.8 liposomes/cell versus control = 10.9 +/- 1.5 liposomes/cell, P < 0.05) and anti-VnR antibody (3.3 +/- 0.4 liposomes/cell versus control = 8.9 +/- 1.7 liposomes/cell, P < 0.05). We conclude that AMs employ Vn as a nonimmune opsonin to enhance the efficiency of phagocytosis.

Animals↗
PubMed1996

Assessment of in vivo attachment/phagocytosis by alveolar macrophages.

Alveolar macrophages (AMs) are recognized as an important first line of cellular host defense within the lung. Although mechanisms underlying AM response to microorganisms or particulates are well characterized in vitro, experimental approaches to the study of AMs in vivo are limited. To circumvent these limitations, a new assay was developed using fluorescently labelled liposomes or Pneumocystis carinii (PC) organisms which were administered intratracheally into mechanically ventilated rats. After 30 min, the lungs were lavaged and the percentage of administered liposomes or PC bound to AMs was determined by quantifying fluorescence. Factors known to enhance attachment/phagocytosis by AMs in vitro were assayed to determine their effect in vivo. For example, vitronectin (VN)-coated liposomes increased attachment from 25.2 +/- 2.4% to 47.2 +/- 3.0% (p < 0.001), while addition of VN increased the binding of PC to AMs from 16.5 +/- 1.7% to 24.5 +/- 2.2% (p < 0.05). Confocal laser microscopy of cells obtained by lavage provided morphologic evidence of attachment/phagocytosis by AMs. This model will permit the quantitative assessment of the interaction of fluorescently labelled liposomes or microorganisms with AMs in the lower respiratory tract of living animals.

Animals↗
PubMed1995

Fluorescent liposomes as quantitative markers of phagocytosis by alveolar macrophages.

A new phagocytic assay based on liposome ingestion by alveolar macrophages (AMs) is described. Fluorescent microspheres were encapsulated in liposomes, which allowed rapid enumeration by fluorometry. Liposomes made in the presence of vitronectin had the protein exposed on their outer surfaces, as determined by immunolabelling. Liposomes and rat AMs were incubated under conditions favorable for phagocytosis. Observation by light and electron microscopy showed AMs engulfing liposomes, with gradual transfer of fluorescent label from liposome to cell interior. This transfer was due to bona fide phagocytosis, as evidenced by (1) fluorescence of liposome-encapsulated dihydrofluorescein (DHF)-zymosan exclusively within AMs and (2) triggering of the respiratory burst by zymosan-associated liposomes only under conditions that allowed phagocytosis. Phagocytic activity was expressed as liposomes/cell, the average number of liposomes phagocytosed per macrophage. We used this technique to follow phagocytosis over time and to measure the effects of lipopolysaccharide (LPS) and vitronectin on AM phagocytosis.

Animals↗
PubMed1992

Neuromuscular junctions contain NP185: the multifunctional protein is located at the presynaptic site.

The NP185 polypeptide (AP3) is a multifunctional component isolated from brain endocytic vesicles, which binds to tubulin and clathrin light chains, decoated vesicles, synaptic vesicles, and the synaptosomal plasma membrane (Su et al., 1991). The NP185 molecules are expressed during avian cerebellar synaptogenesis and appear to function in CNS regions rich in synaptic terminals (Perry et al., 1991). In this report we describe double-labelling experiments with avian embryonic striated muscle fibers demonstrating the exclusive presence of the brain-specific protein at the neuromuscular junction. We used indirect rhodamine immunofluorescence labeling with a monoclonal antibody (mAb-8G8) to mark the location of NP185 in muscle combined with fluorescein-alpha-bungarotoxin to mark the postsynaptic location of the acetylcholine receptors (AChRs). We show that the distribution of both NP185 and AChRs has an overall correlation, but the location of NP185 is circumscribed to presynaptic structures adjacent but not overlapping with postsynaptic structures displaying the AchRs. To confirm the identity of NP185, the molecule was extracted from both tissues, partially purified, immunoprecipitated, and identified in Western blots with the mAb 8G8. The mAb reacted with an identical 185 kD protein band purified from both tissues. Based on its properties and specific neuronal location, the NP185 molecule may function in motor nerve terminals by screening membrane proteins, identifying areas of the synaptic plasma membrane, and to anchor these elements with structural proteins for their recycling and transport within the neuronal cellular compartments.

Adaptor Protein Complex 3↗
PubMed1991

Neuronal protein NP185 in avian and murine cerebellum: expression during development and evidence for its presence in nerve endings.

The neuronal protein NP185 is a neural tissue-specific protein isolated from clathrin-coated vesicles in brain. Using 8G8, a monoclonal antibody (MAb) characterized in our laboratory, we studied the expression and distribution of neuronal protein NP185 in developing avian cerebellum and in mature murine cerebellum. Furthermore, we compared these parameters to that of synapse-specific neuronal protein, synaptophysin, and an axon-specific (i.e., non-synaptic) neuronal protein, neurofilament NF68. We found that NP185 expression temporally and spatially corresponds to avian cerebellar synaptogenesis. In addition, NP185 distribution parallels synaptophysin distribution throughout development, while differing from that of either unassembled or filamentous forms of NF68. The evidence also suggests that embryonic NP185 expression coincides with synaptogenesis, and that NP185 remains concentrated in the terminal boutons of mature neurons. The synapse specificity of NP185 and the recent biochemical properties reported for this protein support the postulate that this molecule may trigger synaptic events and distinguish structurally and functionally active synapses.

Adaptor Proteins, Vesicular Transport↗
PubMed1990

Peers' perceptions of the consequences that victimized children provide aggressors.

Fourth- through seventh-grade children (mean age 11.5 years) estimated the likelihood that various consequences would occur following hypothetical acts of aggression toward victimized and nonvictimized classmates. Children also indicated how much they would care if the consequences were to occur. When contemplating aggression toward victimized classmates, children were more likely to expect tangible rewards, more likely to expect signs of victim suffering, and less likely to expect retaliation than when considering aggression against nonvictimized classmates. Also, when considering aggression toward victimized classmates, children cared more about securing tangible rewards but were less disturbed by the thought of hurting their victims or by the thought of their victims retaliating than when imagining aggression toward nonvictimized classmates. The foregoing pattern was stronger for boys than for girls. Implications for theories of aggression and for intervention with aggressive and victimized children are discussed.

Aggression↗
PubMed1986

Cognitive social learning mediators of aggression.

This research explored links between aggression in elementary school children and 2 classes of social cognitions that might influence children's decisions about whether to behave aggressively. Aggressive and nonaggressive children (mean age 11.3 years) responded to 2 questionnaires. One questionnaire measured children's perceptions of their abilities to perform aggression and related behaviors (perceptions of self-efficacy), and the other measured children's beliefs about the reinforcing and punishing consequences of aggression (response-outcome expectancies). Compared to nonaggressive children, aggressive subjects reported that it is easier to perform aggression and more difficult to inhibit aggressive impulses. Aggressive children also were more confident that aggression would produce tangible rewards and would reduce aversive treatment by others. There were negligible sex differences in perceived self-efficacy for aggression but large sex differences in anticipated social and personal consequences for aggression, with girls expecting aggression to cause more suffering in the victim and to be punished more severely by the peer group and by the self. It was concluded that children's knowledge of their capabilities and children's knowledge of the consequences of their actions are factors that need to be taken into account by cognitive models of aggression.

Aggression↗
PubMed1979

Interactive effects of cognitive involvement and response topography upon differential eyelid conditioning to conceptual discriminanda.

The purpose of the experiment was to determine some cognitive differences underlying the superior differential conditioning of voluntary-form (V) over conditioned-form (C) responders. Two cognitive activities were hypothesized to be jointly necessary for the superiority of Vs: first, an active development of reinforcement contingency awareness by the subject himself, and, second, an active use of acquired contingency knowledge in predicting UCS occurrences. The first variable was manipulated by asking half of the subjects to "figure out" the contingencies, while the other half were fully informed of them at the start. The second variable was assessed by requiring half of the subjects to engage in a button-pressing US prediction task on each trial. Conditioned discrimination indicated that, as predicted, both of these cognitive activities were required for good performance by Cs, supporting the hypothesis that Cs are normally deficient in these respects. An unpredicted deterioration in discrimination for Vs when both task manipulations were imposed suggested that competition between the Vs' spontaneous cognitive activities and the experimentally imposed ones developed in the high external demand situation.

Awareness↗