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DNA binding in vivo: (6,7-\(^3\)H]ß-trenbolone (ß-TBOH) was administered p.o. and i.p. to rats. After 8 or 16 h, DNA was isolated from the livers and purified to constant specific radioactivity. Enzymatic digestion to deoxyribonucleotides and separation by HPLC revealed about 90% ofthe DNA radioactivity eluting in the form of possible TBOH-nucleotide adducts. The extent of this genotoxicity, expressed in units of the Covalent Binding Index, CBI = (~mol TBOH bound per mol nucleotide)/(mmol TBOH administered per kg body weight) spanned from 8 t~ 17, i. e. was in the range found with weak genotoxic carcmogens. Ames test: low doses of ß-TBOH increased the number of revertants in Salmonella strain TAl 00 reproducibly and m a dose-dependent manner. The mutagenic potency was 0.2 revertants per nmol after preincubation of the bacteria (20 min at 37° C) with doses between 30 and 60 \(\mu\)g per plate (47 and 94 \(\mu\)g/ml preincubation mixture). Above this dose, the number of revertants decreased to control values, accompanied by a reduction in survival. The addition of rat liver S9 inhibited the mutagenicity. DNA binding in vitro: calf thymus DNA was incubated with tritiated ß-TBOH with and without rat liver S9 Highest DNA radioactivities were determined in the absence of the "activation" system. Addition of inactive S9 (without cofactors) reduced the DNA binding by a factor of up to 20. Intermediate results were found with active S9. DNA binding in Salmonella: ß-TBOH was irreversibly bound to DNA isolated from S. typhimurium TA100 after incubation of bacteria with [\(^3\)H]ß-TBOH. Conclusions: Covalent DNA binding appears to be the mechanism of an activation-independent ("direct") mutagenicity of TBOH which is not easily detected because of the bactericidal activity. The genotoxicity risk arising from exposure of humans to trenbolone residues in meat was estimated using the in vivo data and compared to that from the exposure to unavoidable genotoxins aflatoxin B1 and dimethylnitrosamine. It ts concluded that trenbolone residues represent only a low genotoxic risk.
The effects of age, study time, and importance of text units on strategy use and memory for texts
(1988)
This study investigated study behavior and recall of a narrative text as a function of the reader's age, study time, and importance level of text units. Fifth graders, seventh graders, young- and older adults were asked to read a fairy tale, and do anything they liked to prepare for verbatim recall. Half of the subjects in each age group were assigned to an immediate recall condition; half were given additional study time. Examination of recall data showed that all subjects showed higher recall of important units in the text than unimportant units. This effect was independent of age and study time condition. Study behaviors varied significantly across age groups and study conditions: while adults underlined or took notes with equal frequency, children preferred note-taking as a study strategy. With additional study time, fifth graders, seventh graders, and older adults increased their strategic behavior; young adults did not.
Study of the 1s and 2s shell contributions to the isotropic hyperfine coupling constant in nitrogen
(1988)
The istropic part of the hyperfine coupling constant is investigated by means of multireference configuration interaction calculations employing Gaussian basis sets. A detailed study of the 1s and 2s spin polarisation in the nitrogen atom and the NH molecule shows that the structure of the lower-energy space of the unoccupied orbitals is essential for the results. A contraction of the Gaussian basis is possible without loss of accuracy if enough flexibility is retained to describe the main features of the original space of unoccupied functions. Higher than double excitations are found to be non-negligible for the description of α\(_{iso}\).
Stroke risk factors prepare rat brainstem tissues for a modified localized Shwartzman reaction
(1988)
Stroke risk factors such as hypertension, diabetes, advanced age, and genetic predisposition to stroke were demonstrated to prepare rat brainstem tissues for a modified local Shwartzman reaction. A single intracisternal injection of endotoxin provoked the reaction, and affected rats manifested neurologie deficits accompanied by pathologie lesions. Brainstem infarcts developed in only a small proportion of rats without recognized risk factors after intracisternal injection of endotoxin. Thus, stroke risk factors, whieh are ordinarily regarded as operating through acceleration of atherosclerosis, may predispose to brain ischemia by local effects on brain mierocirculation such as those thought to underlie preparation of a tissue for the local Shwartzman reaction.
Stability and Variability in Interactive Behavior as Measured by Methods of "Speech Chronemics"
(1988)
Dyadic interaction is modelled os an adaptive process between personality of the partners involved and the characteristics of the theme. The theme structure and the principles which control the adaptation process are referred to as "syntality". The material of the studies reported are the speech signals of the verbal interaction reduced to an on-off pattern. In a first study individual speech behavior was found to remain stable in dyads even if partners changed. The second study showed the stability of the speech patterns for different interaction themes even if dyads changed. These apparently contradictory results are reconciled by introducing the concept of "adaptive stability". Individual speech behavior does not happen at a stable activity level, but is characterized by a constant relationship (" less" or "more") to the respective activity of the other partner.