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Biomedical subjects

A M Freund

Publications and source records attributed to A M Freund.

14 recordsLinked to original sources
PubMed2001

Walking while memorizing: age-related differences in compensatory behavior.

This study investigated predictions of the life-span theory of selection, optimization, and compensation, focusing on different patterns of task priority during dual-task performance in younger and older adults. Cognitive (memorizing) and sensorimotor (walking a narrow track) performance were measured singly, concurrently, and when task difficulty was manipulated. Use of external aids was measured to provide another index of task priority. Before dual-task testing, participants received extensive training with each component task and external aid. Age differences in dual-task costs were greater in memory performance than walking, suggesting that older adults prioritized walking over memory. Further, when given a choice of compensatory external aids to use, older adults optimized walking, whereas younger adults optimized memory performance. The results have broad implications for systemic theories of cognitive and sensorimotor aging, and the costs and benefits of assistive devices and environmental support for older populations.

Adult↗
PubMed2001

[Effect of personal priorities on magnitude of stimulus preference: initial empirical findings].

This study examines whether setting priorities in personal life-investment is reflected in a heightened sensitivity towards thematically related stimuli. Two groups of adults (N = 47; M = 30 years; 53% female) were compared: (1) participants with a parallel goal structure (n = 12) who feel equally committed to the work and the family domain, both in the present and in the future, and (b) participants with a sequential goal structure (n = 24), who currently feel more involved in the work domain, but expect to be more engaged in the family domain in the future. Five tasks were used to assess preference, all of them simultaneously presenting work- and family-related stimuli. As hypothesized, individuals with a sequential goal structure showed a stronger preference for work-related stimuli than individuals with a parallel structure. There were clear differences in word detection, in the elaboration of work-related statements, and in the choice between work-related and family-related reading material. Results are discussed primarily in reference to models of action-regulation.

Adult↗
PubMed1999

Content and function of the self-definition in old and very old age.

Spontaneous self-definition was investigated in a heterogeneous sample of N = 516 participants of the Berlin Aging Study, aged between 70 and 103 years. The content of the self-definition revealed that old and very old persons view themselves as active and present-oriented. The self-definition also reflected an inward orientation, and central themes of life-review, health, and family. Participants generated more positive than negative evaluations in their self-definition, but the ratio of positive to negative evaluations was less favorable for the oldest old (> or = 85 years) than that of persons aged 70 to 84 years. Older individuals with more health-related constraints reported fewer and less rich self-defining domains (i.e., a less multifaceted self-definition). Positive emotional well-being was associated with naming more and richer self-defining domains. Multifacetness, however, did not buffer against the negative effect of low functional capacity on subjective well-being.

Aged↗
PubMed1998

Selection, optimization, and compensation as strategies of life management: correlations with subjective indicators of successful aging.

The usefulness of self-reported processes of selection, optimization, and compensation (SOC) for predicting on a correlational level the subjective indicators of successful aging was examined. The sample of Berlin residents was a subset of the participants of the Berlin Aging Study. Three domains (marked by 6 variables) served as outcome measures of successful aging: subjective well-being, positive emotions, and absence of feelings of loneliness. Results confirm the central hypothesis of the SOC model: People who reported using SOC-related life-management behaviors (which were unrelated in content to the outcome measures) had higher scores on the 3 indicators of successful aging. The relationships obtained were robust even after controlling for other measures of successful mastery such as personal life investment, neuroticism, extraversion, openness, control beliefs, intelligence, subjective health, or age.

Adaptation, Psychological↗
PubMed1989

Z-DNA-forming sequences are spontaneous deletion hot spots.

Z-DNA-forming sequences are shown to elicit a biological response in Escherichia coli. Plasmids containing sequences capable of adopting the Z conformation (GC and CA/GT) are shown to be hot spots for spontaneous deletions. All the deletions involve an even number of base pairs. The distribution of the deletion events shows that the process ends when the Z-DNA-forming sequence has been reduced to a size no longer capable of adopting the Z conformation at natural superhelical density.

Chromosome Deletion↗
PubMed1986

The secondary structure of salt-extracted ribosomal proteins from Escherichia coli as studied by circular dichroic spectroscopy.

Ribosomal proteins from Escherichia coli MRE600 have been obtained by a new, mild purification procedure. This involves extraction of the subunits with salt followed by chromatographic fractionation in the presence of salt. The use of urea or other denaturing agents and conditions is avoided. A survey of the secondary structure of the 30 S and 50 S proteins, as observed by circular dichroic spectroscopy, is presented. The spectra have been analysed by a new procedure which uses a library of 16 circular dichroic spectra of proteins with a known three-dimensional structure. This method provides a more reliable analysis, especially of the contribution from beta-sheet. The results show that most of the 30 S proteins have a high alpha-helix content, whereas the 50 S proteins are more diverse. The latter group shows a larger contribution from beta-sheet. The data presented here are compared with those already published for a number of proteins which were, with one exception, prepared in the presence of urea. In most cases we find higher alpha-helix and beta-sheet values for the salt-extracted proteins than for the corresponding urea-treated proteins. In those cases, however, where special care was taken to renature the urea-treated proteins agreement is found to within the expected experimental error. The results show that salt-extracted ribosomal proteins have a well-defined secondary structure with a relatively small contribution from unordered structure.

Circular Dichroism↗
PubMed1984

Carcinogen-induced mutation spectrum in wild-type, uvrA and umuC strains of Escherichia coli. Strain specificity and mutation-prone sequences.

Forward mutations induced by the ultimate carcinogen N-acetoxy-N-2-acetylaminofluorene (N-Aco-AAF) in the tetracycline resistance gene carried on plasmid pBR322 are shown to be dependent upon the induction of the host SOS functions in wild-type and umuC Escherichia coli cells. The mutation frequency in the umuC strain is equal to about 40% of the mutation frequency observed in the umu+ background. In the excision-repair-deficient uvrA mutant strain the mutagenic response is the same as in SOS-induced wild-type cells whether or not the uvrA bacteria are SOS-induced. Equal mutation frequencies are obtained in both the wild-type and the uvrA strains for equal modification levels although the survival of AAF-modified plasmid DNA is greatly reduced in the uvrA strain as compared to the wild-type strain. Sequence analysis of the mutations reveals that more than 90% of the N-Aco-AAF-induced mutations are frameshift mutations. Two types of mutational hotspots are observed occurring either at repetitive sequences or at non-repetitive sequences. Both types of mutants appear at similar locations and frequencies in both the wild-type and the uvrA strains. On the other hand, only the non-repetitive sequence mutants are obtained in the umuC background. These non-repetitive sequence mutants preferentially occur within the sequence 5' G-G-C-G-C-C 3' (the NarI restriction enzyme recognition sequence). The analysis of the -AAF binding spectrum to the same DNA fragment shows that there is no direct correlation between the modification spectrum and the mutation spectrum. We suggest that certain sequences are "mutation-prone" in the sense that only these sequences can be efficiently mutated as the result of an active processing mediated by specific proteins. When a sequence is said to be mutation-prone it probably corresponds to a particular structure that is induced within this sequence as a result of the binding to the DNA of the mutagen. This sequence-specific conformational change is the substrate for the protein(s) that fixes the mutation. The mutagenic processing pathway(s) is part of the cellular response to DNA-damaging agents (the so-called SOS response). Two pathways for frameshift mutagenesis are suggested by the data: an umuC-dependent pathway, which is involved in the mutagenic processing of lesions within repetitive sequences; an umuC-independent pathway responsible for the fixation of mutations within specific non-repetitive sequences.

2-Acetylaminofluorene↗
PubMed1983

Different levels of induction of RecA protein in E. coli (PQ 10) after treatment with two related carcinogens.

By means of an immunoradiometric assay the induction of protein RecA in E. coli PQ 10 was measured after treatment by two related carcinogens. On an adduct basis N-Acetoxy-N-2-acetylaminofluorene was shown to induce the protein RecA at a similar level as U.V. On the other hand, N-hydroxy-N-2-aminofluorene shows only a poor induction capacity of the RecA protein. The difference in the SOS inducing potential of the aminofluorene and acetylaminofluorene adducts is discussed in relation to the major difference in the local conformational change the two adducts induce in DNA.

2-Acetylaminofluorene↗
PubMed1982

Visualization of Z sequences in form V of pBR322 by immuno-electron microscopy.

Form V DNA has been prepared from pBR322 DNA by annealing covalently closed complementary single strands. Specific rabbit antibodies to Z-DNA were shown by radioimmunoassay and electron microscopy to react with form V DNA of pBR322. The bound antibodies were visualized either directly (on synthetic polynucleotides in Z-form), or after reaction with goat anti-rabbit immunoglobulin labeled with ferritin (on form V DNA).

Antigen-Antibody Complex↗
PubMed1979

Unwinding of supercoiled Col E1-DNA after covalent binding of the ultimate carcinogen N-acetoxy-N-2-acetylaminofluorene and its 7-iodo derivative.

The unwinding of superhelical Col E1-DNA was studied by means of gel electrophoresis and electron microscopy after covalent binding of N-acetoxy-N-2-[14C]acetylaminofluorene (N-Aco-[14C]AAF) and its 7-iodo derivative (N-Aco-[14C]AAIF). Studies with both compounds indicated that complete unwinding of the supercoiled DNA required the binding of hydrocarbon residue to about 3% of the bases. Thus the unwinding angle per residue of N-2-acetylaminofluorene (AAF) and its 7-iodo derivative was of 22 degrees +/- 3 and 18 degrees +/- 3 respectively. Our results are in good agreement with those obtained by Drinkwater et al. [9]. Precedent studies from this laboratory have shown that N-Aco-AAF and its 7-iodo derivative induce different local conformation change in native DNA (insertion-denaturation model and outside binding model respectively). The unexpected ability of the 7-iodo derivative to unwind supercoiled DNA is discussed.

2-Acetylaminofluorene↗
PubMed1979

Electron microscopic visualization of N-acetoxy-N-2-acetylaminofluorene binding sites in ColE1 DNA by means of specific antibodies.

ColE1 DNA has been allowed to react in vitro with N-acetoxy-N-2-[14C]acetylaminofluorene in the range of 0-15 N-2-[14C]acetylaminofluorene residues bound per molecule of DNA, at the C8 of guanine residues. Purified rabbit antibodies to both N-2-(guanosine-8-yl)-acetylaminofluorene and native DNA that had reacted with N-acetoxy-N-2-acetylaminofluorene were shown by electron microscopy to recognize specifically the acetylaminofluorene-modified ColE1 DNA. The antibodies bound to DNA were visualized either per se or after reaction with goat anti-rabbit immunoglobulins coupled with ferritin. There was a linear relationship between the average number of antibodies bound per DNA molecule and the number of N-2-(deoxyguanosine-8yl)-acetylaminofluorene residues per DNA molecule. The slope of this straight line was equal to 0.4. Due to the bivalence of the immunoglobulins one would expect a value of 0.5; we actually observed an important fraction of the bound antibodies crosslinking two parts of the same (or of another) DNA molecule.

2-Acetylaminofluorene↗
PubMedDate not supplied

Methodological comment: temporal stability of older person's spontaneous self-definition.

Open-ended tasks such as the "Who am I?" (Bugental & Zelen, 1950) or the Twenty Statement Test (Kuhn & McPartland, 1954) have facevalidity with regard to assessing content and dimensions of self-definition. Examined in the present study were questions about short-term temporal stability. Theory suggests that measures of the self may better reflect intraindividual variability than personality tests. Free-response and card-sort versions of the "Who am I?" were completed twice over an 8-week period by a volunteer sample of older persons (N = 104; age range: 69-92 years, M = 79). Low temporal stability of self-definition was found on an intraindividual level and on the level of interindividual differences. Measures of personality showed high stability. Although the "Who am I?" may not be the best instrument for assessing the content aspects of self-definition that are stable over time and across situations, it may provide a measure of situation-related variability.

Aged↗