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P J Bauer

Publications and source records attributed to P J Bauer.

At least 37 records · Page 2Linked to original sources
PubMed1995

Effects of experience and reminding on long-term recall in infancy: remembering not to forget.

We examined whether some of the factors that facilitate recall in older children also extend to 1- to 2-years-olds. Using elicited imitation we assessed the efficacy of verbal (Experiment 1), and verbal plus nonverbal (Experiment 2) reminding on 15-month-olds' recall after a 1-week delay. Reminding ameliorated forgetting: Performance at delayed and immediate recall was equivalent. The addition of nonverbal information did not enhance recall above verbal information alone. In Experiment 3 we investigated the influence of verbal reminding, repeated experience, and mode of experience (i.e., imitate vs watch only) on recall after 1 month. The effects of reminding depended on event type: Reminding facilitated recall of events with enabling relations, but not of events lacking them. Repeated experience and the opportunity to imitate facilitated recall; children who watched events only once nevertheless recalled them. Results suggest that the strength of organization of an event representation, rather than retention interval, is a major determinant of remembering during the second year of life.

Attention↗
PubMed1995

One- to two-year-olds' recall of events: the more expressed, the more impressed.

The literature on stylistic differences in mother-child conversations about ongoing and past events can be interpreted to suggest that the opportunity to verbally elaborate on an event facilitates preschoolers' memory. In this research we examined whether similar effects would obtain in children who are just acquiring language and, thus, the opportunity for verbal encoding. Using elicited imitation, 12 groups, formed by a between-subjects crossing of 3 levels of age (13, 16, and 20 months) with 4 levels of delay (1-3, 6, 9, and 12 months), were tested for memory for specific laboratory events; children's event-relevant verbalizations also were recorded. The children remembered the events that they had experienced, regardless of their age at the time of exposure and of the delay interval imposed. Memories were demonstrated both nonverbally and verbally; nonverbal and verbal measures bore a modest relation with one another. Language ability at the time of exposure to the events predicted verbal expression of memory after the delay. Thus, the availability of a verbal mode of elaboration facilitated 1- to 2-year-olds' event memory.

Female↗
PubMed1995

The effects of task comprehension on preschoolers' and adults' categorization choices.

In experimental tasks in which subjects sort sets of objects with conflicting appearances and taxonomic relations, preschoolers often have been found to categorize according to appearance. The procedures used in past studies, however, may have biased preschoolers to attend to appearance instead of taxonomic relations. This possibility was examined in two experiments. In Experiment 1, children's preference for taxonomic- or appearance-based sorting was affected by both the training and the instructions they received. Adults in Experiment 1 were affected by instructions, but not by training. In Experiment 2 preschoolers sorted above chance according to the criterion for which they received training and instruction (taxonomic relations or appearance). Consistency data, children's justifications, and spontaneous labeling support the conclusions that training and instructions have a significant effect on children's preference to sort according to taxonomic relations or appearance, and that both criteria can be used systematically by children as young as four. Implications for task comprehension, flexibility, methodology, and education are discussed.

Adult↗
PubMed1994

Na(+)-Ca2+,K+ exchange in bovine retinal rod outer segments: quantitative characterization of normal and reversed mode.

Ca2+ homeostasis of bovine retinal rod outer segments is maintained through Na(+)-Ca2+,K+ exchangers and cGMP-gated channels in the plasma membrane. It has recently been demonstrated that both proteins are associated. This novel finding allowed us to investigate quantitatively normal and reversed mode Na(+)-Ca2+,K+ exchange in rod outer segment membrane vesicles and reconstituted proteoliposomes both containing exchangers in rightside-out and inside-out orientations. Addition of Na+ activated both normal and reversed mode exchange; if, however, initially Ca2+ from vesicles containing inside-out oriented exchangers has been released by activation of the associated channels, only normal mode exchange was observed upon addition of Na+. Using this approach, the fractions of vesicles containing rightside-out and inside-out oriented exchangers were about similar in these vesicle preparations. Normal and reversed mode exchange had similar Na+ concentrations of about 70 mM for half maximal activation (in the presence of 115 mM K+) and cooperativity parameters, nHill, of about 2.0. Furthermore, both modes were electrogenic, and showed only little Na(+)-Ca2+,K+ exchange in the absence of K+. The two modes of exchange differed, however, in the maximal exchange rate, the normal mode being about twice as fast as the reversed mode.

Animals↗
PubMed1994

After 8 months have passed: long-term recall of events by 1- to 2-year-old children.

The time course of development of the ability to remember specific past events is a matter of considerable curiosity and debate. Traditional and contemporary theories alike suggest that infants are unable to consolidate and stabilise event knowledge for recall after a long time period. In two experiments, we used elicited imitation, a nonverbal analogue to cued verbal recall, to test 21-, 24-, and 29-month-old children's recall of events they had experienced eight months previously. At the time of original exposure some of the events were novel, whereas others depicted activities familiar to 1-year-olds. At the eight-month retention test, performance of the experienced children was compared to that of matched naive controls. In both experiments the experienced children produced a greater number of the novel events; there were no differences between the groups on the familiar events. The results demonstrate long-term recall of specific past events by 1- to 2-year-olds. They thus challenge the suggestion that the absence of memories from infancy and early childhood is attributable to the inability to form memories that are enduring and accessible over time.

Analysis of Variance↗
PubMed1993

Increasing steps in recall of events: factors facilitating immediate and long-term memory in 13.5- and 16.5-month-old children.

Children late in the second year of life show patterns of event recall similar to those of older children: (a) well-ordered immediate and delayed recall, and (b) facilitation of recall by familiarity and by enabling relations. We used elicited imitation to test whether the patterns extend to children early in the second year. In Experiment 1, 13.5- and 16.5-month-olds accurately recalled familiar and novel 2-act sequences immediately and after a 1-week delay. For 16.5-month-olds, recall was facilitated by familiarity and by enabling relations; for 13.5-month-olds, only enabling relations facilitated recall. In Experiment 2, verbal cues were used to test immediate and 1-week delayed recall of 3-act sequences. For both ages, recall was facilitated by familiarity and by enabling relations. Experiment 3 verified that the verbal information served to cue recall of previously experienced events, not to "suggest" sequences that could be performed. Together the results demonstrate that children as young as 13 months can recall specific events after a delay. They also suggest development in sensitivity to factors that facilitate recall.

Attention↗
PubMed1993

Memory for gender-consistent and gender-inconsistent event sequences by twenty-five-month-old children.

Gender-schema theory predicts that, based on a rudimentary understanding of gender (e.g., self-labeling), children will invoke gender schemata in the processing of information. In older children, one indication of schematic processing is differential memory for schema-consistent versus schema-inconsistent material. Due to a lack of appropriate measures, evidence of very early use of gender schemata has been limited. In the present study, elicited imitation was used to assess 25-month-old girls' and boys' immediate and delayed recall of sequences depicting female-stereotyped, male-stereotyped, and gender-neutral activities. At immediate and delayed testing, girls showed equivalent levels of recall of all 3 sequence types. Boys showed superior recall of male- relative to female-stereotyped sequences; their recall of gender-neutral sequences was equivalent to that of male-stereotyped ones. Results indicate that, at least for boys, use of gender schemata is evident by 25 months of age. Possible explanations for the absence of a clear effect for girls are discussed.

Child Development↗
PubMed1992

Association of cyclic GMP-gated channels and Na(+)-Ca(2+)-K+ exchangers in bovine retinal rod outer segment plasma membranes.

1. Cyclic GMP-gated channels and Na(+)-Ca(2+)-K+ exchangers from bovine photoreceptors were examined by investigation of the Ca2+ fluxes from vesicles of rod outer segment (ROS) membranes and from proteoliposomes obtained by solubilization of the ROS membrane proteins and reconstitution in soy bean L-alpha-phosphatidylcholine (PC). 2. Whereas vesicles obtained by mild sonication of ROS membranes in a Ca(2+)-containing buffer yielded a maximal cyclic GMP-induced Ca2+ release of about 2.5% and a maximal Na(+)-induced Ca2+ release of about 7%, freezing and thawing of ROS membranes prior to sonication elevated these maximal Ca2+ releases to about 17% for cyclic GMP, and to about 34% for Na+. These observations are in agreement with the view that cyclic GMP-gated channels and Na(+)-Ca(2+)-K+ exchangers are localized only in the plasma membrane of the photoreceptors (which in bovine ROS makes up about 6% of the total membrane), whereas freezing and thawing results in fusion of disc and plasma membranes, thus leading to a distribution of these proteins over a much larger membrane area. 3. For fused ROS membranes, the cyclic GMP-releasable fraction of Ca2+ of 17% is an upper bound; assuming that the cyclic GMP-gated channels are randomly distributed we estimate that about 37% of the vesicles contain at least one cyclic GMP-gated channel. The mean diameter of the vesicles prepared by sonication was determined to be 0.12 +/- 0.04 micron, and therefore the fused ROS membranes contain about sixteen cyclic GMP-gated channels/microns 2. If all cyclic GMP-gated channels originated from the plasma membrane, we estimate that the plasma membrane contains about 270 cyclic GMP-gated channels/microns 2. 4. In vesicles prepared from fused ROS membranes, Na(+)-Ca2+ exchange after activation of the cyclic GMP-gated channels. On the other hand, after an exhaustive Na(+)-Ca2+ exchange, only little, if any, Ca2+ was released upon addition of cyclic GMP, demonstrating that cyclic GMP-gated channels and Na(+)-Ca(2+)-K+ exchangers occur on the same vesicle fraction. This observation suggests that Na(+)-Ca(2+)-K+ exchangers do not distribute independently of the cyclic GMP-gated channels upon membrane fusion but are apparently associated with the cyclic GMP-gated channels.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Ca2+ binding capacity of cytoplasmic proteins from rod photoreceptors is mainly due to arrestin.

Arrestin (also called S-antigen or 48-kDa protein) binds to photoexcited and phosphorylated rhodopsin and, thereby, blocks competitively the activation of transducin. Using Ca2+ titration in the presence of the indicator arsenazo III and 45Ca2+ autoradiography, we show that arrestin is a Ca2(+)-binding protein. The Ca2+ binding capacity of arresting-containing protein extracts from bovine rod outer segments is about twice as high as that of arrestin-depleted extracts. The difference in the Ca2+ binding of arrestin-containing and arrestin-depleted protein extracts was attributed to arrestin. Both, these difference-measurements of protein extracts and the measurements of purified arrestin yield dissociation constants for the Ca2+ binding of arrestin between 2 and 4 microM. The titration curves are consistent with a molar ratio of one Ca2+ binding site per arrestin. No Ca2+ binding in the micromolar range was found in extracts containing mainly transducin and cGMP-phosphodiesterase. Since arrestin is one of the most abundant proteins in rod photoreceptors occurring presumably up to millimolar concentrations in rod outer segments, we suggest that aside from its function to prevent the activation of transducin, arrestin acts probably as an intracellular Ca2+ buffer.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1990

Scripts or scraps: reconsidering the development of sequential understanding.

A growing literature attests to temporally ordered recall of events by children under 2 years of age. Other data suggest a developmental sequence wherein the ability to reproduce unfamiliar and/or arbitrarily ordered events, and familiar events in other than canonical order develops well after the first ordered productions of events. Early ordering is thus argued to be dependent upon familiarity, rather than upon general temporal principles. This suggestion was investigated by using elicited imitation to assess 21-month-olds' recall of familiar-canonical, familiar-reversed, novel-causal, and novel-arbitrary event sequences. Subjects reproduced canonical and both types of novel sequences in modeled order. On reversed sequences they vacillated between reproducing the events as modeled and "correcting" them to canonical order. The results suggest that temporal organization is not imposed upon an existing unordered event representation, but rather, is an integral aspect of the representation from its initial construction. It is suggested that young children's difficulty with reversed sequences may be attributed to a reluctance to reorganize existing representations, rather than to the absence of applicable temporal principles.

Attention↗
PubMed1988

Evidence for two functionally different membrane fractions in bovine retinal rod outer segments.

1. Cyclic GMP-induced and Na+-induced Ca2+ releases from Ca2+-containing photoreceptor membrane vesicles were investigated using the Ca2+-sensitive dye Arsenazo III. Bovine photoreceptor membrane vesicles were prepared by osmotic lysis and hypotonic wash of purified rod outer segments. 2. Calcium was entrapped into these vesicles either by utilizing their passive membrane permeability ('passive' Ca2+ loading), or by activating cyclic GMP-dependent channels (cyclic GMP-stimulated Ca2+ loading), or by Na+-Ca2+ exchange (Na+-stimulated Ca2+ loading). 3. After passive Ca2+ loading, cyclic GMP released at most about 23% of the total Ca2+ which could be released with the Ca2+ ionophore A23187 (Km = 6.5 +/- 0.92 microM (6); Hill coefficient 1.68 +/- 0.19 (6]. 4. Millimolar concentrations of Na+ also induce Ca2+ releases from passively Ca2+-loaded outer segment membrane vesicles of at most 26% of the total releasable Ca2+. 5. For passively Ca2+-loaded outer segment membrane vesicles, the sum of a partial cyclic GMP-induced Ca2+ release and a consecutive saturating Na+-induced Ca2+ release, or vice versa, the sum of a partial Na+-induced Ca2+ release and a consecutive saturating cyclic GMP-induced Ca2+ release, was about 25% of the total releasable Ca2+. 6. Both cyclic GMP-induced and Na+-induced Ca2+ release was greater than 25%, up to 50% of the total releasable Ca2+ if either cyclic GMP-stimulated or Na+-stimulated Ca2+ loading of outer segment membrane vesicles was employed. 7. When the outer segment membrane vesicles were mildly sonicated in a water bath, the maximal percentages of Ca2+ releasable by both cyclic GMP and Na+ dropped, reaching final values, after a 60 s sonication period, of 2.3% for the cyclic GMP-induced Ca2+ release and 7% for the Na+-induced Ca2+ release. 8. It is concluded from these results that outer segment membrane vesicles comprise two populations of vesicles, one which contains cyclic GMP-dependent channels and Na+-Ca2+ exchanging proteins, and another one which contains neither of these proteins. 9. The sonication experiments are interpreted as suggesting that these two vesicle populations correspond to plasma and disc membranes of the rod outer segments, respectively.

Animals↗
PubMed1987

The effect of ABO blood group on the diagnosis of von Willebrand disease.

In order to firmly establish a normal range for von Willebrand factor antigen (vWF:Ag), we determined plasma vWF:Ag concentrations in 1,117 volunteer blood donors by quantitative immunoelectrophoresis. The presence of the ABO blood group has a significant influence on vWF:Ag values; individuals with blood group O had the lowest mean vWF:Ag level (74.8 U/dL), followed by group A (105.9 U/dL), then group B (116.9 U/dL), and finally group AB (123.3 U/dL). Multiple regression analysis revealed that age significantly correlated with vWF:Ag levels in each blood group. We then performed reverse ABO typing on stored plasma from 142 patients with the diagnosis of von Willebrand disease (vWd). Of 114 patients with type I vWd, blood group O was found in 88 (77%), group A in 21 (18%), group B in 5 (4%), and group AB in none (0%), whereas the frequency of these blood groups in the normal population is significantly different (45%, 45%, 7% and 3%, respectively) (P less than .001). Patients with type II or III vWd had ABO blood group frequencies that were not different from the expected distribution. There may be a subset of symptomatic vWd patients with decreased concentrations of structurally normal vWf (vWd, type I) on the basis of blood group O. Some individuals of blood group AB with a genetic defect of vWF may have the diagnosis overlooked because vWF levels are elevated due to blood type.

ABO Blood-Group System↗
PubMed1986

Permeability of rod outer segment disk membranes as probed by Ficoll density gradient centrifugation and by turbidimetry.

Osmotic volume changes of isolated disks prepared from bovine rod outer segments were investigated utilizing the capacity of osmotically intact disks to float on 2.5% (w/v) Ficoll under hypotonic conditions. The amount of floating disks decreases steadily and approximately linearly when the osmolarity is increased stepwise with an osmotically active solute. The slope of the decrease becomes smaller for partially permeable substances and no decrease in observed for fully permeable solutes. All ions assayed by this method as well as sucrose were osmotically fully active to disk membranes. The buffer molecules Tris and imidazole partially penetrated the disk membranes at pH 7, whereas the zwitterionic buffer Hepes was impermeable. Ethanol showed absolutely no osmotic activity to disk membranes and, therefore, can easily penetrate these membranes. concurrent turbidimetric measurements and, therefore, can easily penetrate these membranes. Concurrent turbidimetric measurements confirmed these results. Upon prolonged exposure of disk membranes to 5% (w/v) Ficoll, a considerable modification of the osmotic properties of disk membranes is observed, indicating a significant interaction of 5% (w/v) Ficoll with disk membranes. No influence of 2.5% (w/v) Ficoll on the osmotic properties of disk membranes was detected. The restriction of the use of Ficoll for disk membrane preparative purposes will be discussed.

Animals↗
PubMed1984

Photoelectric signals generated by bovine rod outer segment disk membranes attached to a lecithin bilayer.

Purified bovine rod outer segment disk membranes were attached to a lecithin bilayer membrane. After photoexcitation with a 500-nm flash delivered by a dye laser, a negative photovoltage was observed on the bilayer under normal ionic strengths (100 mM KCl), which had a rise phase of 1-3 ms at 20 degrees C. The photoresponse was obviously due to bleaching of rhodopsin as it decreased for successive flashes of light. It originated most probably during the metarhodopsin-I metarhodopsin-II (meta-I-II) transition of rhodopsin because it was pH dependent at 2 degrees C but not at 20 degrees C. At 10 mM KCl, i.e., under hypotonic conditions, a positive photovoltage with slower kinetics than at high salt was observed. As the disk membranes were merely attached to the bilayer membrane, the photovoltage was apparently due to a light-induced transmembrane potential change in the disk membranes. Possible electrogenic mechanisms underlying the photosignal will be discussed.

Animals↗
PubMed1984

Comparison of the sensitivity of commercial APTT reagents in the detection of mild coagulopathies.

This study was undertaken to evaluate the precision and sensitivity of three different commercial APTT reagents containing the activators kaolin, micronized silica, or ellagic acid. These reagents varied greatly in their ability to detect mild coagulopathies. The ellagic acid reagent was able to detect the mildest deficiencies for the most common coagulopathies. This reagent was sensitive to 50% levels of Factor VIIIC, whereas the APTT with the kaolin reagent was not prolonged until levels of 35% or less were attained. The micronized silica reagent was the least sensitive to Factor IX deficiency, detecting levels of 12% or less. Precision was similar for all reagents when tested with normal and slightly abnormal plasmas. Since methods and instrumentation vary, each laboratory should evaluate their APTT reagent to determine its precision and sensitivity.

Blood Coagulation Disorders↗