In vitro assessment of the toxicity of metal compounds

A review of in vitro mutagenesis assessment of metal compounds in mammalian and nonmammalian test systems has been compiled. Prokaryotic assays are ineffective or inconsistent in their detection of most metals as mutagens, with the notable exception of hexavalent chromium. Mammalian assay systems appear to be similarly inappropriate for the screening of metal compounds based upon the limited number of studies that have employed those compounds having known carcinogenic activity. Although of limited value as screening tests for the detection of potentially carcinogenic metal compounds, the well-characterized in vitro mutagenesis systems may prove to be of significant value as a means to elucidate mechanisms of metal genotoxicity.     

Different effects of serotonin antagonists on 3H-mianserin and 3H-ketanserin recognition sites

In minces prepared from the frontal cortex of rats treated with ketanserin (10 mg/kg i.p.) or mianserin (5 mg/kg i.p.) twice daily for 21 days, the Vmax of the adenylate cyclase stimulated by NE (100 microM) is attenuated, suggesting that ketanserin and mianserin share with a number of antidepressants the ability to attenuate the adenylate cyclase stimulation by NE. Ketanserin, given with the above mentioned dose schedule for 7 consecutive days, reduced the Bmax of 5HT2 recognition sites but failed to change either the Bmax or the apparent Kd of H-mianserin binding. A significant decrease in the Bmax of 5HT2 binding sites is elicited also by a single injection of mianserin (1). This drug also down-regulates its own binding when given twice daily for 3 weeks. From this and other information (2,3), it is concluded that ketanserin and mianserin bind to distinct recognition sites. The possibility that 5HT2 and mianserin recognition sites are functionally related and that serotonergic synapses are modulated by multiple chemical signals might be considered.     

Euclein: A new binaphthaquinone from Euclea pseudebenus

7-MethyljugIone, 8,8′-dihydroxy-4,4′-dimethoxy-6,6′-dimethyl-2,2′-binaphthyl-1,1′-quinone, 2-methylnaphthazarin, mamegakinone and euclein have been isolated from Euclea pseudebenus. Euclein is the 3,6′-dimer of 7-methyljuglone.     

N-Acetylsuccinimidylglutamate, a Cyclic Imide Form of the Peptide N-Acetylaspartylglutamate, Is Present in Low Micromolar Concentrations in Murine and Bovine CNS

Abstract: N -Acetylsuccinimidylglutamate [(asu)NAAG], a cyclic form of the peptide N -acetylaspartylglutamate (NAAG) in which the aspartyl residue is linked to glutamate via the α- and β-carboxylates, was identified and quantified by HPLC in the murine and bovine CNS. In the rat, the highest concentrations of (asu)NAAG were detected in the spinal cord (1.83 ± 0.15 pmol/mg of wet tissue weight) and brainstem (1.16 ± 0.08 pmol/mg wet weight), whereas the levels were below the limit of detection in cerebellum, hippocampus, and cerebral cortex. (Asu)NAAG was also detected in significant amounts in the superior colliculus and lateral genicutale nucleus (1.17 ± 0.05 and 0.82 ± 0.13 pmol/mg wet weight, respectively). Although the tissue content of (asu)NAAG was about three orders of magnitude lower than that of NAAG, levels of both peptides were positively correlated among different CNS regions ( r = 0.74, p < 0.003). In the rat spinal cord, (asu)NAAG levels progressively increased from week 2 to month 12 after birth. In bovine spinal cord, the contents of (asu)NAAG and NAAG were comparable in gray and white matter as well as in the dorsal and ventral horns. These results suggest that NAAG and (asu)-NAAG are closely related metabolically and raise the question of the physiological significance of such a cyclic peptide.     

Host interference with expression of the lambda N gene product

We have searched among E. coli M72 (D, bio11cI857H1) temperature resistant survivors and have found two bacterial mutants, gro100 and gro101 which block λiλ and λi⁴³⁴ phage development but allow growth of their N-independent derivatives λiλ nin and λi⁴³⁴nin. It is not known yet whether these two mutants interfere with the production of the N gene product or with its function. At least part of the gro genotype maps at 12′ of the E. coli genetic map and is co-transductible by Pl with the lac locus.     

Hemispheric asymmetries in cortical electrical activity during sleep. I

The hypothesis of a predominance of the right hemisphere in stage REM as compared to NREM has been tested through a spectral analysis of the EEG recorded from left (T3) and right (T4) temporal sites in 5 young healthy right-handed male subjects. Variations in the asymmetry coefficient R - L/R + L in different sleep stages have been analyzed by one way ANOVAs and Sheffé's tests. The hypothesis of a progressive increase in left hemisphere activity throughout different REM cycles as one approaches final awakenings have been investigated by comparing variations in the asymmetry coefficient for epochs of REM and stage 2 NREM sampled in different phases of the REM cycle. EEG results do not support either the hypothesized stage dependent or cycle dependent variation in EEG activity during sleep. We question whether variations in EEG amplitude and synchronization can be used as indices of hemispheric asymmetries during sleep.     

On the nature of chromophore in pig kidney diamine oxidase.

The nature of the 500-nm chromophore in pig kidney diamine oxidase was investigated by absorption spectroscopy and fluorescence in the presence of various chelating or carbonyl-specific reagents. From the spectroscopic measurements the following conclusions can be drawn. First, the 500-nm absorption band is not due to copper, the reduction of which is not related to the disappearance of this band. Second, phenylhydrazine and cycloserine give rise, upon reaction with the enzyme, to absorptions very similar to those of a pyridoxal enzyme, aspartate aminotransferase. Third, these enzyme derivatives are unexpectedly non-fluorescent. Copper removal, obtained after prolonged incubation of cycloserine-treated enzyme in the presence of reducing and chelating agents, leads to a fluorescence similar to that of cycloserine-aspartate transminase. It is proposed that copper is coordinated to the postulated pyridoxal phosphate of diamine oxidase through the pyridine nitrogen.