Binding of benzo[a]pyrene at the 1,3,6 positions to nucleic acids in vivo on mouse skin and in vitro with rat liver microsomes and nuclei

Loss of tritium from specific positions in [³H,¹⁴C] aromatic hydrocarbons can elucidate their binding site(s) to DNA and RNA and indicate the mechanism of activation. Studies of tritium loss from [6-³H,¹⁴C]benzo[a]pyrene(B[a]P), [1,3-³H,¹⁴C]B[a]P, [1,3,6-³H,¹⁴C]B[a]P, [6,7-³H,¹⁴C]B[a]P, and [7-³H,¹⁴C]B[a]P were conducted in vitro using liver nuclei and microsomes from 3-methylcholanthrene-induced Sprague-Dawley rats and in vivo on the skin of Charles River CD-1 mice. The relative loss of tritium from $\text{[}{}^3\text{H}\text{,}{}^{14}\text{C}\text{]}\text{B}\text{[a]}\text{P}$ was measured after binding to skin DNA and RNA, to nuclear DNA, and to native and denatured calf thymus and rat liver DNA's and poly(G) by microsomal activation. In skin, nuclei, and microsomes plus native DNA, virtually all B[a]P binding occurred at positions 1,3 and 6; while with microsomes plus denatured DNA or poly(G), B[a]P showed no binding at the 6 position and a small amount at the 1 and 3 positions. In vivo and with nuclei, binding at the 6 position predominated. Little loss of tritium from the 7 position was seen; this was expected because binding at this position is not thought to occur. This confirms the interpretation of loss of tritium as an indication of binding at a given position. These results demonstrate that the use of microsomes to activate B[a]P is not a valid model system for delineating the in vivo mechanism of B[a]P activation, and support previous evidence for one-electron oxidation as the mechanism of activation of hydrocarbons in binding to nucleic acids.     

The structure of two alanine containing ferrichromes: Sequence determination by proton magnetic resonance

Summary Metal coordination confers an extraordinary structural stability to the ferrichromes which, independent of their variable amino acid composition, results in a basically unperturbed conformation for all the homologous peptides in the series. The proton magnetic resonance (pmr) characteristics for Al³⁺ analogues (alumichromes) reflect this conformational isomorphism in usual solvents so that single site substitutions are clearly recognized in the pmr spectra. Thus, the substitution of glycine byl-alanine orl-serine introduce new resonances characteristic of the sidechains and alter the pattern of the amide NH pmr region in that doublets substitute for glycyl triplets at the same site. Since for glycine- andl-serine-containing alumichromes the resonances have already been identified, it is possible to unequivocally establish the primary structure of the twol-alanyl homologues ferrichrome C ( ) and sake colorant A ( ) on the basis of the comparative pmr spectra of their Al³⁺ analogues, namely, alumichrome C and alumisake. The resonance assignment, and hence the site occupancy, is substantiated by the temperature coefficients of the NH chemical shifts, rates of¹H-²H exchange and homonuclear proton spin decoupling experiments centered on the NH spectral region. Occupancy of site 1 by a glycine residue is observed for all known ferrichromes, which serves to conserve a hairpin turn. This method of obtaining sequence information should prove of general use for other systems of homologous polypeptides, provided their conformations are not affected by the residue substitutions.     

A factor analysis of morphogenetic fields in the human dentition

The traditional morphogenetic fields of the human dentition were evaluated by means of factor analysis of dental dimensions taken from a series of human crania. When crown length, crown width and crown index were considered separately, factors emerged which could be identified with the tooth group fields. But a combined crown length-crown width analysis generated factors which extended beyond the regional tooth groups. Crown width itself was revealed to be an important axis of morphologic intergration. It was concluded that univariate methods are not adequate for identifying morphogenetic fields; the teeth must be treated as multidimensional units where the correlation among dimensions is accounted for.     

Effects of ELF magnetic fields on biological magnetite

The effects of 60 Hz magnetic fields of 5 μT (50 mG) or less on biological structures holding magnetite (Fe₃O₄) are shown to be much smaller than that from thermal agitation; hence such interactions cannot be expected to be biologically significant. © 1993 Wiley-Liss, Inc.     

The identification of cholesterol and other steroids in Euphorbia pulcherimma

The 4-desmethyl tetracycles of the whole poinsettia plant (Euphorbia pulcherimma) less roots amounted to 0.07% of the wet wt and were shown by ¹H NMR spectroscopy to be steroids and not euphoids. The most abundant component was cholesterol, constituting half the mixture, followed in order of decreasing concentration by 24α-ethylcholesterol (sitosterol), 24α-methylcholesterol (campesterol) and 24β-methylcholesterol (22-dihydrobrassicasterol). The relative amount of cholesterol in this plant is the highest found so far in a tracheophyte. The 4,4-dimethyl compounds (0.1% of wet wt) included lanosterol (5%), 24-dihydrolansterol (5%), β-amyrin (25%), germanicol (50%), an unidentified pentacyclic triterpenoid (8%) and two or more (7%) unidentified components. Both the 4,4-dimethyl- and the 4-desmethylsterols were in the configurational series with a 20α-H-atom. Dihydrolanosterol and lanosterol are the probable intermediates from cycloartenol to cholesterol and 24-alkylcholesterol, respectively. Such a sequence would differ from that operating in most angiosperms, where the alkylation is thought to precede the opening of the 9,19-cyclopropane ring.     

Model for external influences on cellular signal transduction pathways including cytosolic calcium oscillations

Experiments on the effects of extremely-low-frequency (ELF) electric and magnetic fields on cells of the immune system, T-lymphocytes in particular, suggest that the external field interacts with the cell at the level of intracellular signal transduction pathways. These are directly connected with changes in the calcium-signaling processes of the cell. Based on these findings, a theoretical model for receptor-controlled cytosolic calcium oscillations and for external influences on the signal transduction pathway is presented. We discuss the possibility that the external field acts on the kinetics of the signal transduction between the activated receptors at the cell membrane and the G-proteins. It is shown that, depending on the specific combination of cell internal biochemical and external physical parameters, entirely different responses of the cell can occur. We compare the effects of a coherent (periodic) modulation and of incoherent perturbations (noise). The model and the calculations are based on the theory of self-sustained, nonlinear oscillators. It is argued that these systems form an ideal basis for information-encoding processes in biological systems. © 1995 Wiley-Liss, Inc.     

Bioresistance of poplar wood compressed by combined hydro-thermo-mechanical wood modification (CHTM): Soft rot and brown-rot

This work studied fungal bioresistance of combined hydro-thermo-mechanically modified (CHTM) poplar wood. The CHTM technique, introduced by Mohebby et al. (2009), is a combination of two wood modification techniques-hydrothermal wood modification and densification of wood. Blocks of poplar wood were initially treated hydrothermally at temperatures of 120, 150, and 180 °C for holding times of 0, 30, and 90 min. Afterwards, the treated blocks were compressed by a hot press (160 and 180 °C) for 20 min with a compression set of 60%. After the CHTM-treated blocks were dried, small specimens were cut for soft-rot and brown-rot decay tests according to ENV 807 and EN 113. Mass losses as well as metabolic moisture contents were determined in the decayed samples. Results revealed that the combination of wood modification techniques showed fungal suppression. It was also found that the hydrothermal treatment step could significantly reduce fungal attack in comparison with densification. Reduction of the mass losses was associated with the hydrothermal treatment temperature. Also, the level of metabolic moisture content was correlated with the mass losses for both fungi. Any reduction of the mass loss decreased the moisture content in the wood.     

Effects of pulsed magnetic stimulation on isolated crayfish heart

ABSTRACT

Cardiac muscular contraction of the neurogenic heart that could be excited by pulsed magnetic stimulation (PMS) was investigated using preparation of the isolated crayfish heart. When a figure-eight magnetic coil was set over the isolated heart, cardiac contraction induced by a single PMS was not observed. Cardiac arrest occurred immediately after repetitive PMS and persisted for dozens of seconds depending on the number of stimuli. We concluded that PMS caused neuronal modulation in the neuronal network in the cardiac ganglion.