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Biomedical subjects

C L Martin

Publications and source records attributed to C L Martin.

At least 37 records · Page 2Linked to original sources
PubMed1997

Roles of temperamental arousal and gender-segregated play in young children's social adjustment.

The hypothesis that gender differences in children's adjustment is partially influenced by differences in temperament and interactions with same-sex peers was examined. Fifty-seven predominantly White, middle-class preschoolers (29 boys and 28 girls, M age = 54.5 months) participated. Measures were taken of children's arousability, problem behaviors, and tendencies to play with same-sex peers. A semester later, children's peer status was assessed. Analyses revealed that arousability and same-sex peer play interacted to predict problem behaviors. For boys high in arousability, play with same-sex peers increased problem behaviors. In contrast, arousable girls who played with other girls were relatively unlikely to show problem behaviors. Moreover, the interaction of arousability and same-sex peer play predicted boys' (but not girls') peer status, and this relation was partially mediated by problem behaviors. The role of gender-related processes is discussed.

Arousal↗
PubMed1997

A developmental perspective of self-construals and sex differences: comment on Cross and Madson (1997)

S. E. Cross and L. Madson (1997) proposed that women and men differ in self-construals, with women as interdependent and men as independent, and that these construals are seen to underlie many sex differences in social behavior. In this article, the authors address the issues of sex differences in self-construals, the stability of self-construals, and the centrality of interdependence-independence to sex differences. They examine the proposal next from a developmental perspective, suggesting that development of the self does not precede children's gender-related behavior. Evidence regarding the socialization processes that may contribute to sex differences in self-construals is largely inconclusive, especially regarding the differential treatment of boys and girls by parents. Their developmental perspective provides insights into ways that Cross and Madson's approach can be elaborated to explain sex differences in social behavior.

Adult↗
PubMed1996

T cell activation is regulated by voltage-dependent and calcium-activated potassium channels.

Membrane potential (Vm) is tightly controlled in T cells through the regulated flux of ions across the plasma membrane. To investigate the functional role of voltage-dependent (Kv) and calcium-activated (KCa) potassium channels in T cell activation, we compared the effects of two K+ channel blockers, namely kaliotoxin (KTX) and charybdotoxin (CHTX), on Vm, calcium influx, and cell proliferation. KTX potently inhibited Kv (ID50 = 3 nM) but not KCa (ID50 = 5 microM) currents in T cells. Resting T cells exposed to KTX (300 nM) depolarized from -56 mV to -50 mV. KTX had no effect on the transient membrane hyperpolarization that characteristically follows receptor-mediated T cell stimulation. However, T cells stimulated in the presence of KTX subsequently depolarized to -40 mV. KTX also reduced the steady state intracellular free calcium concentration ([Ca2+]i) in stimulated cells by 19% and inhibited T cell proliferation by 35%. CHTX potently inhibited both Kv and KCa currents (ID50 = approximately 1 nM). CHTX (300 nM) depolarized resting T cells to -48 mV, equivalent to the effect observed for KTX. In stimulated T cells, 300 nM CHTX completely blocked the induced hyperpolarization and subsequently depolarized the cells to -21 mV. These effects were associated with a 45% reduction in peak [Ca2+]i, a 60% decrease in steady state [Ca2+]i, and 63% inhibition of T cell proliferation. These results suggest that both Kv and KCa conductances contribute to the underlying mechanisms of T cell activation.

Calcium↗
PubMed1996

Comparison of bidisomide, flecainide and dofetilide on action potential duration in isolated canine atria: effect of isoproterenol.

Prolongation of action potential duration (APD) and the effective refractory period (ERP) is one mechanism to prevent reentrant atrial and ventricular arrhythmias. Because arrhythmias are usually associated with an elevated sympathetic tone and increase of circulating catecholamines, the potential influence of catecholamines on antiarrhythmic effects of an agent are critical to predicting the potential clinical response. In this study the effects of three different antiarrhythmic agents, bidisomide, flecainide and dofetillide, each of which prolongs atrial ERP, were compared before and after treatment with isoproterenol, a beta-adrenergic agonist. Standard intracellular microelectrode recording techniques were used to record action potentials from isolated canine atrial tissue. Bidisomide and flecainide elicited a 20 to 27 msec increase in APD and ERP that was independent of stimulation frequency (1-5 Hz). Dofetilide prolonged APD and ERP at 1 Hz (40 and 37 msec, respectively) but was completely ineffective at 5 Hz. After equilibration with the anti-arrhythmic agent, tissues were additionally exposed to isoproterenol. Only bidisomide prolonged APD and ERP in the presence of isoproterenol. In the converse series of experiments after treatment with isoproterenol, which caused a 20 to 30% reduction in APD and ERP, only bidisomide completely reversed the effect of 1 microM isoproterenol. Bidisomide was inactive in a functional beta-adrenergic antagonism assay, thus ruling out beta-adrenergic blockade as a potential mechanism. These results indicate that bidisomide, unlike flecainide and dofetilide was able to prolong APD and ERP in isolated canine atrium even at high stimulation frequencies and in the presence of isoproterenol. These data suggest that bidisomide would be effective in the presence of elevated sympathetic tone and on the agents studied, only bidisomide possessed a unique and desirable antiarrhythmic profile.

Action Potentials↗
PubMed1995

Treated delinquent boys' substance use: onset, pattern, relationship to conduct and mood disorders.

We describe relationships between substance use, conduct disorder (CD), depression, and history of self-injury or suicide attempts, in referred, delinquent, substance involved, adolescent males. Sixty youths (mean age 16.3 years) completed standardized assessments for substance use and other psychiatric disorders, aggressiveness, and social class. All boys met modified criteria for CD. Most had high aggression ratings. Twenty percent had depressive diagnoses. By age 13, 78% had begun regular substance use. Marijuana was the first substance for 42%. The boys had substance dependence on a mean of 3.2 different drugs (usually including alcohol and marijuana), with abuse of an average of one additional drug. CD symptoms began 3.6 years (mean) before regular use. CD symptom count correlated with number of dependence diagnoses, and both of those (but not depression) related significantly to suicide attempt and self-injury histories. Improved understanding of substance involvement in youths with CD may generate more rational prevention and treatment.

Adolescent↗
PubMed1995

Ophthalmic cyclosporine in equine keratitis and keratouveitis: 11 cases.

Topical cyclosporine A was safely used in a series of 11 cases of equine keratitis and keratouveitis and appeared to be an effective anti-inflammatory agent in 9 cases. The clinical diagnoses included interstitial keratouveitis, endotheliitis, multifocal punctate keratopathy and a melting stromal ulcer. In most cases, the presence or absence of insidious bacterial infection was not conclusively determined. Topical cyclosporine A had no deleterious effects in this series of cases. The authors suggest that topical cyclosporine in both aqueous and lipid base vehicles should be investigated and evaluated as an alternative mode of achieving ocular immunosuppression.

Administration, Topical↗
PubMed1995

Children's gender-based reasoning about toys.

The goal of these studies was to investigate how preschool children use gender-based reasoning in making judgments about toy preferences for themselves and for others. In Studies 1 and 2, children (n = 22, n = 71) were shown unfamiliar, non-sex-typed toys and asked to rate how much they, other girls, and other boys would like each toy. As expected, children made gender-based inferences: "What I like, children of my sex will also like, and children of the other sex will not like." Study 3 was designed to assess how children use gender-based reasoning to make decisions about attractive and unattractive toys when they are given gender labels. Children (n = 91) were shown unfamiliar toys varying in attractiveness that were given explicit gender labels (e.g., "this is a toy girls really like") or no label. With a different experimenter (to avoid demand characteristics), children rated their own and others' liking of the toys. Children used gender labels to guide their own preferences and their expectations for others. Even with very attractive toys, children liked toys less if they were labeled as being for the other sex, and expected other girls and boys to do the same. The role of gender-based reasoning in cognitive theories of gender and on children's play preferences is discussed.

Child, Preschool↗
PubMed1992

Contribution of delayed rectifier and inward rectifier to repolarization of the action potential: pharmacologic separation.

Outward potassium (K) currents contribute to the repolarization process of cardiac action potentials. There are, however, multiple K currents. Recently, two putatively specific K channel blockers have been developed as potential class III antiarrhythmic agents. E-4031 appears to block specifically a fast component of the delayed rectifier (IK), and RP 58866 is a reported inward rectifier current (IK1) blocker. In the present experiments, we examined the effects of E-4031 and RP 58866 on action potentials recorded from guinea pig papillary muscles to determine whether the properties of IK and IK1 measured in whole-cell experiments would be manifested in distinct effects. Both compounds prolonged the APD50 (action potential duration at 50% repolarization) and APD90 (action potential duration at 90% repolarization). However, RP 58866 did not significantly prolong the action potential at voltages of 0 mV and above, while E-4031 did. The results suggest that preferential IK1 block results in a change in action potential waveform that is distinct from that resulting from block of other outward K currents. This could thus be used as a simple first-pass screening tool in determining a preliminary mechanism of action of class III antiarrhythmics prior to more time-consuming but necessary whole-cell voltage clamp experiments.

Action Potentials↗
PubMed1991

The role of cognition in understanding gender effects.

Cognitive approaches, such as schematic processing theory, have been heuristic in a number of ways for bettering our understanding of how and why gender effects are so apparent in childhood. First, they provide a new and different perspective. Rather than concentrating on discovering all the instances of gendered information in our worlds and then assuming that this overwhelming amount of information accounts for children's behavior and thinking, cognitive theorists studying gender have reversed the emphasis. That is, we assume that thinking processes influence the world of information that is available to children. Furthermore, the nature of that world of information is then seen to influence behavioral choices. Second, cognitive approaches have been heuristic in providing some understanding of the mismatches that occur between available information and children's gender cognitions. More broadly stated, such approaches have been useful for discovering the reasons that gender cognitions are inaccurate--why some information is misperceived, misremembered, and selectively learned. Third, cognitive approaches have been useful for elaborating the development of children's gender knowledge. Finally, cognitive approaches have been useful for illustrating how cognition may influence behavior. If we go beyond gender for a moment, we see that cognitive approaches can also be useful for our understanding of the broader realm of all types of stereotypes. For instance, they are helpful in understanding the early origins of stereotypes. Why do children and adults develop stereotypes? Given the overwhelming amount of information we must deal with every day, how do we ever notice real but usually minor co-occurrences of group membership and attributes? Furthermore, why do stereotypes contain information that is not grounded in reality? To begin to answer these questions, we need to move cognitive approaches to a higher order of generality, that is, away from the specifics of gender and on to the broader case of concept formation about social groups. When cognitive notions are used in this way, children and adults appear to form higher order schemas concerning the nature of social groups. One such schema is the "if they differ in one way, they differ in other ways" schema. Another such schema represents the flip side: "If they are in the same group, they are the same in many other ways." Exposure to information about groups surely must lead to the formation of these higher order schemas. Once formed, they surely must influence how new information about specific groups is acquired by increasing perceivers' vigilance in noticing and creating supportive information.(ABSTRACT TRUNCATED AT 400 WORDS)

Child↗
PubMed1990

Pinacidil opens ATP-dependent K+ channels in cardiac myocytes in an ATP- and temperature-dependent manner.

Pinacidil is an antihypertensive agent that has been found to increase potassium conductance. This study examined the type of K channel affected by pinacidil in cardiac myocytes. Pinacidil shortened the action potential duration in papillary muscle. The effect was reversible upon addition of glyburide, a known IKATP blocker. The effect of pinacidil was temperature-dependent. Action potential duration was shortened more rapidly and to a greater extent at 37 degrees C than at 23 degrees C. Whole-cell experiments showed that I-V curves lost rectification after pinacidil treatment. As with the action potential experiments, the effect was more rapid at 37 degrees C than at 23 degrees C. Rectification was restored after exposure to glyburide. The I-V curve generated after pinacidil exposure was similar to that observed by others after treatment with metabolic inhibitors that activate IKATP. The effect of pinacidil was also ATP-dependent. Addition of 5 mM ATP to the internal solution prevented activation of IKATP. These data indicate that pinacidil activates IKATP.

Action Potentials↗
PubMed1990

The development of gender stereotype components.

Developmental research has been limited by a narrow concept of stereotypes. A more complex model is presented, and developmental changes in gender stereotypes were investigated using the new model. In 2 studies, children were told about several sex-unspecified children, each described as having 1 masculine or 1 feminine characteristic. The children then predicted the likelihood of each story child having other masculine and feminine characteristics. In Study 1, 56 children (4-6 years) were told about target children who liked either a masculine or feminine toy, and then children predicted the targets' interests in other toys. In Study 2, 76 older children (6, 8, 10 years) were told about target children with a masculine or feminine characteristic from 1 of 4 categories (appearance, personality, occupations, toys), and then they predicted the likelihood of targets having other masculine and feminine characteristics from the same and from different categories as the cue. 2 developmental trends emerged: (a) children appear first to learn associations among characteristics relevant to their own sex and, later, to learn them for the other sex, and (b) older children's stereotypic judgments are more extreme than those of younger children. The implications of these results for the development of stereotypes, assessing gender knowledge, and understanding social judgments are discussed.

Child↗
PubMed1990

The relation of gender understanding to children's sex-typed preferences and gender stereotypes.

Our goal was to explore how children's understanding of gender as a social category relates to their acquisition of sex-typed knowledge and preferences. Children's gender concepts, sex-typed preferences, and stereotyped knowledge were measured in 61 boys and girls (3-5 years). Gender concept measures included ability to identify and to discriminate the sexes, understanding gender group membership, temporal stability of gender, and gender consistency over situational changes. Children improved with age on most of the measures except gender consistency. With the exception of consistency, measures of gender concept understanding were found to be related to children's stereotyped toy and clothing knowledge and/or to their sex-typed toy preferences (with age controlled). It was shown that only rudimentary gender understanding is needed prior to children learning about sex stereotypes and prior to showing strong sex-typed preferences for peers or toys. The roles of gender identity, stability, consistency, and group membership in the sex-typing process are discussed.

Child↗
PubMed1989

Orbital neoplasia with enophthalmos in a cat.

A 9-year-old cat was evaluated for left-sided enophthalmos and protrusion of the third eyelid. A primary orbital fibrosarcoma was diagnosed. During the orbital exploration, normal periorbital fascia could not be identified in the lateral and ventral region, thus accounting for the enophthalmos.

Animals↗
PubMed1989

Distribution of cholinergic and adrenergic nerve fibers in the lacrimal glands of dogs.

The distribution of postganglionic autonomic nerve fibers in the lacrimal gland and gland of the third eyelid of dogs was studied by use of histochemical techniques. Adrenergic nerve distribution was identified by use of the sucrose-potassium phosphate-glyoxylic acid technique. A loose network of adrenergic nerves was found throughout the interstitium around acini and blood vessels and in vessel walls. Acetylcholinesterase staining was used to identify cholinergic nerve fibers. A cholinergic distribution pattern was found, although the cholinergic innervation appeared more dense than the adrenergic. In the gland of the third eyelid, mucus-secreting lobules and lipid-secreting lobules appeared to be equally innervated by parasympathetic fibers. These lobules could not be differentiated when the sucrose-potassium phosphate-glyoxylic acid technique was used. The techniques used in this study could not demonstrate whether direct contact was made by either cholinergic or adrenergic nerve fibers with secretory or myoepithelial cells. The presence of both nerve fiber types around acini suggests an interrelationship between the sympathetic and parasympathetic nervous system in lacrimal gland secretion in dogs.

Adrenergic Fibers↗