Comparison of the relative sensitivity of human lymphocytes and mouse splenocytes to two spindle poisons

Aneugenic compounds act on non-DNA targets to exert genotoxicity via an indirect mechanism. In contrast to DNA-binding agents, these compounds are expected to possess threshold levels of activity. Therefore, the risk for adverse effects following human exposure to an aneugen could be minimal, if the threshold of activity has been clearly determined in vivo and in vitro and providing the human exposure level is below this threshold. Thus, the development of a single-cell model to allow comparisons between in vitro and in vivo threshold values for aneugenic compounds is of importance.The in vivo micronucleus test is one of the main assays used in genetic toxicology, and is often performed in the mouse. Thus, an extensive database is available in the literature. However, there are only few data concerning the in vitro micronucleus assay using mouse cells, as the majority of in vitro micronucleus assays have been performed using human lymphocytes. In addition, there is a lack of data concerning thresholds for any compound using this model.First, we evaluated whether the use of mouse splenocytes would be an acceptable alternative to that of human lymphocytes to identify aneugens. To allow valid comparisons, the two protocols were first harmonized. Thus, phytohemagglutinin (PHA) and concanavalin A were used as specific mitogens for human lymphocytes and mouse splenocytes, respectively, in order to achieve similar cell-proliferation rates. To achieve similar and sufficient numbers of binucleated cells, cytochalasin B was added 44 and 56 h after culture initiation of the human and mouse cells, respectively.Second, we compared the sensitivity of the mouse protocol with that of the human protocol by exposing the cells to the aneugens nocodazole and paclitaxel.There was good reproducibility of the cytotoxic/genotoxic responses of the two cell models following exposure to the aneugens. The sensitivity of the mouse splenocytes to paclitaxel was higher than that of the human lymphocytes. The two cell types were equally sensitive to nocodazole.     

EEG and behavioral effects of gamma-hydroxybutyrate in the rabbit

The effects of gamma-hydroxybutyrate (GHB) upon sleep wakefulness patterns and quantified nuchal muscle activity were examined in the rabbit in a dose-response paradigm (25–1,000 mg/kg). Relative to control (saline) values, there was no facilitation of sleep onset or epileptogenic activity at any of the dosages studied. However, at the higher GHB concentrations, slow wave sleep and tonic muscle activity were enhanced and a high amplitude, slow activity was superimposed on background EEG patterns. The highest concentration of GHB (1,000 mg/kg) was associated with depression of motor activity. An enhancement of paradoxical sleep observed at lower GHB levels in other species occured in attenuated form in the rabbit. The results indicate dose-related effects on both sleep and motor activation in the rabbit, but the absence of seizure activity for the concentrations of GHB studied.     

Kinetic studies on the lactate dehydrogenase isozymes of the brown trout, Salmo trutta L

Informative crosses have verified the genetic basis of a polymorphism at the Ldh-1 locus in brown trout and enzyme activity measurements indicate that the previously described polymorphism at this locus is best explained by a null allele. The LDH-1, LDH-2, LDH-3 and LDH-4 homotetrameric isozymes were purified and subjected to enzyme kinetic analysis. While LDH-1 and LDH-2 displayed catalytic equivalence, important kinetic differences were found between the LDH-3 and LDH-4 isozymes.     

Analgesic effects of dynorphin-A and morphine in mice

To investigate whether or not dynorphin-A is analgesic, the effect of this peptide was tested in comparison with that of morphine in mice. Dynorphin-A produced a potent analgesic effect in the acetic acid writhing and tail pinch tests, but a weak effect in the tail flick test when given by intracerebroventricular injection. In contrast, morphine caused a potent analgesia in all the tests. Dynorphin-A was more effective when given by intrathecal injection than by intracerebroventricular injection, whereas morphine was equipotent by both injection routes. The results suggest that dynorphin-A is analgesic and that its analgesia may be differentiated from that of morphine.     

Theoretical and experimental studies of the radiative properties of matter at high energy densities and their application to the problems of inertial confinement fusion

The paper presents the results of theoretical and experimental studies of the radiative properties of plasmas produced by heating and compression of various materials to high energy densities. The specific features of the theoretical plasma model known as the ion model, which is used to calculate the radiative characteristics of plasmas of complex chemical composition, are discussed. The theoretical approach based on this model is applied to the plasma produced during the explosion of the X-pinch wires. The theoretical estimate of the radiation efficiency is compared with the experimental data on the total energy yield from an X-pinch made of two different wires (NiCr and Alloy 188). The radiative characteristics of (C12 H16 O8) and (C8 H12 O6) plasmas are calculated for the temperature diagnostics of plasmas produced from porous targets employed in inertial confinement fusion experiments with the use of laser radiation and heavy-ion beams.     

The use of a mixture model in the analysis of count data

A mixture model is presented for the analysis of data on premature ventricular contractions. The analysis is shown to be straightforward and the conclusions relatively simple.     

Definition of meningococcal class 1 OMP subtyping antigens by monoclonal antibodies

The subtypes of meningococci are defined by antigenic determinants on the class 1 outer membrane proteins. The established subtypes, designated by P1 and a number according to the prototype reference strain on which they were first recognized by monoclonal antibodies, includes P1.2, P1.9, P1.15 and P1.16. We have investigated more prototype reference strains, using new monoclonal antibodies, and identified the new subtypes P1.1, P1.6 and P1.1,16. The P1.1,16 epitope is found on both the P1.1 and the P1.16 reference strains, but not on all P1.1 and P1.16 strains and can occur independently from the P1.1 and the P1.16 epitopes. It appears that class 1 outer membrane proteins contain at least two independent subtype-specific epitopes. For clarity, we now redefine P1.1,16 as P1.7, permitting thus the identification of strains of P1.1, P1.1,7, P1.7, P1.7,16 and P1.16 subtypes. It can clearly be expected that more class 1 outer membrane protein determinants will be recognized as more monoclonal typing antibodies are produced. The monoclonal antibodies now available to us can subtype 80-90% of group B and C meningococci; they also react with group A meningococci, but not with other Neisseriae. The immunological dissection of these subtyping antigens will improve our understanding of the relationship between components of the bacteria and the induction or prevention of disease.     

Polyproline binding is an essential function of human profilin in yeast.

Structural analysis of human profilin has revealed two tryptophan residues, W3 and W31, which interact with polyproline. The codons for these residues were mutated to encode phenylalanine and the mutant proteins overexpressed in Eschericia coli. The isolated proteins were diminished in their ability to bind polyproline, whereas phosphatidylinositol 4,5-bisphosphate (PIP2) binding remained unchanged. In many strains of Saccharomyces cerevisiae, disruption of the gene encoding profilin, PFY1, is lethal. It was found that expression of the gene for human profilin is capable of suppressing this lethality. The polyproline-binding mutant alleles of the human gene were cloned into various yeast expression vectors. Each of the mutant genes resulted in suppression of the lethality of pfy1Delta. It was observed that the mutant protein expression levels paralleled the growth rates of the strains. The severity of various morphological abnormalities of the strains was also attenuated with increased protein levels, suggesting that profilin polyproline-binding mutations are deleterious to cell growth unless overexpressed. Both tryptophan mutations were combined to give a third mutant allele that was found both unable to bind polyproline and to suppress the lethality of a pfy1 deletion. Immunoprecipitation experiments suggested that the mutants were unaltered in their affinity for actin and PIP2. These data strongly suggest that polyproline binding is an essential function of profilin.     

The thermal induced helix--beta transition of poly(N epsilon-methyl-L-lysine) and poly(N delta-ethyl-L-ornithine) in aqueous solution

Uncharged poly(N^ε-methyl-L -lysine) (PMLL) and its isomer, poly(N^δ-ethyl-L -ornithine) (PELO), in alkaline solution (pH ca. 12) undergo a helix-to-β transition upon mild heating at 50°C or higher in a manner similar to that of poly(L -lysine) (PLL). The rate of conversion follows the order: PMLL < PELO < PLL. The helix can be regenerated upon cooling near zero degrees, for instance, after more than 12 hr at 2°C. At concentrations less than 0.02% the β form is intramolecular, but at higher concentrations both intra- and intermolecular β forms are generated. Poly(N^δ-methyl-L -ornithine) (PMLO), an isomer of PLL, behaves like poly(L -ornithine); uncharged PMLO in alkaline solution is partially helical and becomes disordered at elevated temperatures.