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Biomedical subjects

S R Schmidt

Publications and source records attributed to S R Schmidt.

13 recordsLinked to original sources
PubMed2001

Memory for humorous cartoons.

Incidental memory for three types of cartoons was compared: original cartoons, literal translations of the originals, and weird cartoons created by inserting incongruous material into the literal translations. In Experiment 1, the three types of cartoons were mixed together in lists. In Experiment 2, each list contained only two cartoon types. In both experiments, original cartoons were remembered better than the literal and the weird cartoons, whereas the literal and the weird cartoons were equally well remembered. The detection of incongruities, or attempts to resolve those incongruities, cannot adequately explain the observed humor effects. The results were also inconsistent with both rehearsal and distinctiveness interpretations. Rather, humor per se appears to support good memory performance. Perhaps participants elaborated or gave sustained attention to humorous material at the expense of less humorous material.

Cartoons as Topic↗
PubMed2000

Organochlorine and metal contaminant exposure and effects in hatching black-crowned night herons (Nycticorax nycticorax) in Delaware Bay.

Pea Patch Island in Delaware Bay is the site of the largest heronry north of Florida. From 1989-93, the population of nine species of wading birds numbered approximately 12,000 pairs, but has recently declined to about 7,000 pairs. Because Delaware Bay is a major shipping channel and receives anthropogenic releases of toxic substances from agricultural, industrial, and municipal point and nonpoint sources, contaminant exposure and effects to the heronry have been an ongoing concern. In 1997, pipping (early hatching stage) black-crowned night herons (Nycticorax nycticorax) were collected from separate nests at Pea Patch Island and from a coastal reference site, Middle Island in Rehoboth Bay, Delaware. There was no evidence of malformations or hepatic histopathological lesions in embryos, and their body and liver weights did not differ between sites. Biomarkers of petroleum hydrocarbons, polyhalogenated contaminant, and metal exposure (cytochrome P450 induction and oxidative stress responses) did not differ (p > 0.05) between sites, although activities of benzyloxy-O-dealkylase and ethoxyresorufin-O-dealkylase were somewhat elevated in 3 of the 15 embryos collected from Pea Patch Island. Concentrations of 21 organochlorine pesticides and metabolites were relatively low at both sites, with p,p'-DDE values well below the threshold associated with eggshell thinning. Although total PCB concentration was modestly elevated (p < 0.05) in Pea Patch Island heron embryos, levels of arylhydrocarbon receptor-active PCB congeners, polychlorinated dibenzodioxins and dibenzofurans, and toxic equivalents were low and did not differ between sites. Concentrations of Cd and Mn in pipping embryos from Pea Patch Island were slightly greater (p < 0.05) than values observed in Middle Island embryos, but levels of these and the other metals and metalloids (e.g., Hg and Se) were below values associated with toxicity. In conclusion, it seems unlikely that chlorinated hydrocarbon and metal contaminant exposure constitutes a direct threat to the reproductive success of black-crowned night herons at Pea Patch Island. However, low-level exposure to these contaminants may constitute one of many stressors that in combination could adversely affect the stability of the wading bird population at this large heronry.

Animals↗
PubMed1997

Cloning of the homogentisate 1,2-dioxygenase gene, the key enzyme of alkaptonuria in mouse.

We determined 48 amino acid residues from five peptides from the homogeneous monomer of homogentisate 1,2-dioxygenase (HGO; E.C. 1.13. 11.15) of mouse liver. After digestion with trypsin, peptides were separated by reversed phase chromatography and amino acid sequenced. The deduced codon sequence of three peptides was used to derive degenerated oligomeres. By combining these oligos, we were able to amplify fragments from 100 to 300 bases (b) from mouse liver cDNA by polymerase chain reaction after reverse transcription (RT-PCR). A fragment of 200 b was cloned and used as a probe to screen a mouse liver cDNA library. One clone from this library contained the complete cDNA-insert for HGO as determined by sequencing. The cDNA encodes for a protein of 50 kDa, as predicted. The cDNA of mouse HGO has an overall identity of 41% to the corresponding gene hmgA from Aspergillus. Sequence similarities to human expressed sequence tags (EST) clones ranged from 70% to 20%. The positions of 122 conserved amino acids could be determined by multiple sequence alignment. We identified one first intron of 928 b in the mouse gene. The gene for HGO seems to be expressed in various tissues, as shown by RT-PCR on different cDNAs. FISH experiments with the whole murine cDNA as probe clearly revealed signals at the human chromosomal band 3q13. 3-q21. This corresponds well to the previous assignment of the locus for the human alkaptonuria gene (AKU) to the same chromosomal region by multipoint linkage analysis. We therefore conclude that the HGO cDNA encodes the gene responsible for alkaptonuria.

Alkaptonuria↗
PubMed1997

Molecular defects in alkaptonuria.

At the dawn of human genetics Sir Archibald Garrod used alkaptonuria as a paradigm to demonstrate the applicability of the Mendelian laws to men and to develop the concept of inborn errors of metabolism. The human cDNA for homogentisate 1,2 dioxygenase was identified due to its homology to the corresponding mouse enzyme and was screened for mutations in alkaptonuric patients from Slovakia. Homozygous mutations were found in four unrelated families and their segregation with the disease was demonstrated. One of the mutations, observed in two families, leads to a frame-shift and thus is unlikely to produce functional protein. The data formally establish the homogentisate 1,2 dioxygenase gene (HGD) as the molecular cause of alkaptonuria and allow for the development of molecular carrier tests in populations at risk.

Alkaptonuria↗
PubMed1996

Category typicality effects in episodic memory: testing models of distinctiveness.

Category typicality effects were investigated within the context of three models of distinctiveness: a univariate model, a fixed-multifeature model, and a weighted-multifeature model. High-typical, medium-typical, and atypical targets were embedded in lists containing a background set of medium- to high-typicality items. Atypical items were more poorly recalled than were medium- and high-typical items independently of list structure. In recognition, subjects who studied high-typical items had difficulty discriminating between high-typical items that were and were not presented as part of the list. However, item typicality had little effect on the recognition performance of subjects who did not study high-typical items. These findings were consistent with the weighted-multifeature model of distinctiveness.

Adult↗
PubMed1995

Murine liver homogentisate 1,2-dioxygenase. Purification to homogeneity and novel biochemical properties.

1. The murine liver enzyme homogenisate 1,2-dioxygenase (HGO) is purified 330-fold. The molecular mass, as determined by gel filtration, is approximately 149 kDa. SDS/PAGE under strongly reducing conditions reveals a single band at 49 kDa, whose concentration increases during the purification. 2. HGO has a pI = 8. The pH optimum for activity in vitro is 6.1. 3. The Km for its natural substrate HGA is 188 microM, whereas the Kd for the ferrous ion is determined at 19 microM. Fe2+ is an absolutely obligate cofactor and cannot be replaced by other divalent cations. Incubating the enzyme with Fe2+ plus one of other divalent cations Zn2+, Cu2+, Co2+ or Ni2+ in equimolar concentrations inhibits HGO, whereas addition of Ca2+ and Mn2+ has no effect. Ascorbate probably acts as a reducing agent, protecting Fe2+ from spontaneous oxidation or by reversing its oxidation. Ascorbate has a great potential to stabilize the assay system. 4. The activation energy determined by an Arrhenius plot is 24 kJ/mol. 5. HGO consists of a single type of subunit with no intermolecular disulfide bridges and requires Fe2+ as a cofactor. This emphazises that the enzyme is familiar with the class of extradiol dioxygenases.

Animals↗
PubMed1994

Effects of humor on sentence memory.

Memory for humorous and nonhumorous versions of sentences was compared. Humorous sentences were better remembered than the nonhumorous sentences on both free- and cued-recall tests and on measures of sentence recall and word recall. These effects persisted when subjects were warned that they were about to read a humorous sentence but were attenuated in incidental learning and limited to within-subjects manipulations. In incidental learning, recall was also scored as a function of subjective ratings of humor. Subjective humor affected memory in both within- and between-subjects designs. Attention, arousal, rehearsal, retrieval, and surprise explanations were explored. Results suggest that humorous material receives both increased attention and rehearsal relative to nonhumorous material.

Arousal↗
PubMed1991

Can we have a distinctive theory of memory?

The current status of the concept of distinctiveness an applied to memory research is discussed. In spite of the fact that distinctiveness is difficult to define, an increasing number of memory phenomena have been explained in terms of distinctiveness. These phenomena are grouped into four classes, which vary in how distinctiveness is operationalized. Distinctiveness has different effects on memory performance, depending on how it is defined, suggesting that the concept of distinctiveness has been overapplied. In addition, current theoretical explanations of the effects of distinctiveness on memory fail to specify what the different definitions of distinctiveness have in common, and fail to encompass adequately the broad range of phenomena to be explained. A limited theory of distinctiveness is proposed, in order to explain why conceptually incongruent material is remembered well.

Attention↗
PubMed1989

The negative generation effect: delineation of a phenomenon.

In four experiments employing between-list designs, generation was found to have negative effects on free recall of word pairs and on cued recall of the second word. In addition, generation had negative effects on measures of word-pair integration and on clustering in recall. In contrast, positive effects of generation were found on free recall of second words alone, and on a recognition test for memory of the second word. It was concluded that in between-list designs, generation led to greater individual-item processing of the generated term than reading, but this processing occurred at the expense of processing the relation between the words in a pair and processing the relations between different pairs in a list.

Association Learning↗
PubMed1985

Encoding and retrieval processes in the memory for conceptually distinctive events.

Memory for conceptually isolated (distinctive) words was investigated in two experiments. In Experiment 1, recognition of distinctive targets was compared with recognition of targets from homogeneous lists and with recognition of background information. Distinctive targets were better recognized than the same words presented in homogeneous lists. No effects of distinctiveness on the recognition accuracy of background items were observed. These results fail to support the hypothesis that distinctive information receives extra resources during encoding at the expense of surrounding background information. In Experiment 2 the effects of distinctiveness on recall were evaluated. Distinctive targets were more likely to be recalled than targets from homogeneous lists. However, unlike the effects found in recognition, background items were more poorly recalled from lists containing distinctive targets than from homogeneous lists. Organizational processes in recall were also evaluated. There was greater subjective organization for target and background items from lists containing distinctive targets than from lists containing nondistinctive targets. These results were discussed in terms of encoding and retrieval explanations of the effects of distinctiveness.

Adult↗
PubMed1975

Demonstration of a factor in the serum of homozygotes and heterozygotes for cystic fibrosis by a non-biological technique.

A factor has been isolated from serum of homozygotes and obligate heterozgotes for cystic fibrosis using isoelectric focusing and disc electrophoresis as analytical methods. The factor is focused within an IgG-fraction with an isoelectric point of pH 8 to 9 but differs from IgG in its lower molecular weight. It is thus similar to, if not identical with, the ciliary dyskinesia factor.

Blood Protein Electrophoresis↗