FURTHER OBSERVATIONS ON THE GROWTH OF BACTERIA ON MEDIA CONTAINING VARIOUS ANILIN DYES, WITH SPECIAL REFERENCE TO AN ENRICHMENT METHOD FOR TYPHOID AND PARATYPHOID BACILLI

Several green dyes show a marked selective action for members of the typhoid-paratyphoid-colon group. This can be used for the enrichment of typhoid and paratyphoid bacilli present in feces. Forty dyes were tested with thirty strains covering all types of pathogenic bacteria. In general the dyes restrained the growth of the Gram-positive bacteria but had no effect on the growth of the Gram-negative group.

OBSERVATIONS ON THE GROWTH OF BACTERIA ON MEDIA CONTAINING VARIOUS ANILIN DYES

Gentian violet and allied anilin dyes have a similar influence on bacterial growth, dividing bacteria into two groups corresponding in general to their reaction to the Gram stain. Among Gram-negative bacteria a strain is occasionally encountered which will not grow on violet agar, differentiating it from other members of the same species or variety. The reaction is quantitative, although the quantitative character is more marked with some species than with others. The streptococcus-pneumococcus group differ from other Gram-positive bacteria in their ability to grow in the presence of amounts of dye sufficient to inhibit the other species. The dysentery bacillus group shows marked variation in the presence of dyes. In the case of fuchsin the variation approaches closely a specific difference between the dysentery and paradysentery groups. The variations of the latter groups with other dyes show no correlation with the common differential characteristics. A closer study might reveal variations in other characteristics which would parallel the different reactions to dyes. Decolorization with sodium sulphite robs the dyes of some of their inhibitive powers.

Universality in the entanglement structure of ferromagnets

Systems of exchange-coupled spins are commonly used to model ferromagnets. The quantum correlations in such magnets are studied using tools from quantum information theory. Isotropic ferromagnets are shown to possess a universal low-temperature density matrix which precludes entanglement between spins, and the mechanism of entanglement cancellation is investigated, revealing a core of states resistant to pairwise entanglement cancellation. Numerical studies of one-, two-, and three-dimensional lattices as well as irregular geometries showed no entanglement in ferromagnets at any temperature or magnetic field strength.

Pharmacodynamic and receptor binding changes during chronic lorazepam administration

To assess pharmacodynamic and neurochemical aspects of tolerance, lorazepam (2 mg/kg/day), or vehicle was administered chronically to male Crl: CD-1(ICR)BR mice via implantable osmotic pump. Open-field behavior, benzodiazepine receptor binding in vitro, receptor autoradiography, and muscimol-stimulated chloride uptake were examined at both 1 and 14 days. Open-field activity was depressed in lorazepam-treated animals on Day 1. On Day 14, open-field parameters were indistinguishable from those of vehicle-treated animals, indicating behavioral tolerance. Benzodiazepine binding, as determined by the specific binding of [125I]diazepam, was also decreased in cortex on Day 14. Hippocampal binding was unchanged following chronic lorazepam exposure. Apparent affinity in cortical membrane preparations was unchanged, indicating that altered ligand uptake was due to decreased receptor number. Muscimol-stimulated chloride uptake into cortical synaptoneurosomes from lorazepam-treated animals was not significantly different on Day 1 or Day 14 compared to vehicle-treated animals. These results confirm that down-regulation of benzodiazepine receptor binding is closely associated with behavioral tolerance to benzodiazepines. These observed changes in binding are not necessarily associated with robust changes in receptor function.

In situ hybridization histochemistry as a method to assess GABA(A) receptor subunit mRNA expression following chronic alprazolam administration

Previous work in our laboratory has demonstrated region-specific effects for chronic alprazolam on binding and function at the GABA(A) receptor. The present study evaluated regional changes in mRNA expression of several subunits of the GABA(A) receptor following chronic alprazolam administration that might underlie these effects. Mice received alprazolam (2 mg/kg/day) or vehicle via subcutaneously implanted osmotic pumps for 1, 7, 14 or 28 days. In situ hybridization histochemistry was performed on tissue sections using [35S]dATP oligonucleotide probes corresponding to the alpha1 and gamma2 subunits of the GABA(A) receptor. Specific hybridization was clearly demonstrated and alpha1 subunit mRNA expression in frontoparietal cortex (layers II-IV) on day 1 of infusion was reduced in animals receiving alprazolam compared to vehicle. On subsequent days, there were no alterations in the levels of alpha1 subunit mRNA in the frontoparietal cortex, hippocampus or dentate gyrus. Expression of gamma2 subunit mRNA was increased on day 1 in the frontoparietal cortex (layer VI), hippocampus and dentate gyrus. mRNA expression was also increased in the dentate gyrus on day 28 of infusion. Comparison of the present study with the results of chronic treatment with other benzodiazepines clearly demonstrates that the pattern of mRNA subunit alterations obtained is both treatment- and region-specific. This makes a definitive conclusion regarding benzodiazepines and their interactions with GABA(A) receptors difficult at best.

Lorazepam attenuates the behavioral effects of dizocilpine

To characterize the potential interaction between the excitatory and inhibitory neurotransmitter systems, the effects of dizocilpine, CPP, and lorazepam on open-field behavior and pentylenetetrazol-induced seizures were evaluated in mice. Dizocilpine (0.01-0.1 mg/kg), CPP (1-10 mg/kg), or vehicle was administered intraperitoneally 15 min prior to lorazepam (0.2-2 mg/kg) or vehicle. Behavioral monitoring began 25 min after the lorazepam injection. Upon completion of testing, unrestrained mice were infused intravenously with pentylenetetrazole until the onset of a full tonic-clonic seizure. The highest dose of dizocilpine by itself significantly increased the average distance traveled, the number of rears, and the number of stereotypies during the test period. Lorazepam alone dose dependently decreased activity on all behavioral parameters. Lorazepam also completely antagonized the hyperactivity produced by dizocilpine when the two compounds were coadministered. This antagonism is most likely due to an interaction in the regulation of dopaminergic tone which underlies motor activity. Lorazepam exerted a dose-dependent anticonvulsant effect. Dizocilpine alone had no effect on seizure induction and did not potentiate the anticonvulsive effect of lorazepam when coadministered with lorazepam. CPP reduced the number of rears and the number of stereotypies during the test period. CPP did not alter the pentylenetetrazol-induced seizure threshold and did not influence the anticonvulsant effect of lorazepam.

Effects of ketoconazole on triazolam pharmacokinetics, pharmacodynamics and benzodiazepine receptor binding in mice

We previously demonstrated that ketoconazole is a potent inhibitor of triazolam biotransformation in vitro and in vivo. Despite significant elevations in triazolam plasma levels with coadministration of ketoconazole, the pharmacodynamic enhancement was lower than predicted based on plasma levels of triazolam. The present study examines the effects of ketoconazole on benzodiazepine receptor binding in vitro as well as on open-field behavior in male CD-1 mice. Triazolam alone inhibited [3H]flunitrazepam binding with an IC50 value of 0.85 nM and a Ki value of 0.50 nM. Ketoconazole alone also competitively antagonized [3H]flunitrazepam binding in a concentration-dependent manner with an IC50 value of 1.56 microM and a Ki value of 1.17 microM. In the presence of 1, 3 or 9 microM ketoconazole, the IC50 value of triazolam was increased to 1.11, 1. 58 and 5.73 nM, respectively, whereas maximal binding was reduced by 36%, 69% and 89%. Coadministration of 50 mg/kg ketoconazole and triazolam (0.1-0.3 mg/kg) to intact animals significantly elevated plasma and brain triazolam levels. Ketoconazole could be measured in mouse brain at levels averaging 31% of those in plasma. Ketoconazole alone had minimal or no effect on open field activity, but it significantly potentiated the decreased activity seen with triazolam administration. The ability of ketoconazole to inhibit triazolam displacement of [3H]flunitrazepam binding may explain the muted pharmacodynamic effect of this benzodiazepine in the presence of ketoconazole. Based on these results, it is likely that ketoconazole acts as a neutral ligand at the benzodiazepine receptor.

Electroconvulsive shock alters GABAA receptor subunit mRNAs: use of quantitative PCR methodology

Electroconvulsive shock (ECS) may affect several neurotransmitter systems in brain, including the GABAergic inhibitory system. We used a quantitative PCR-based assay to evaluate mRNAs for five GABAa receptor subunits at 2 to 24 h after ECS. mRNAs for the alpha 1 and beta 2 subunits were significantly increased in cerebellum at 4 and 8 h after ECS, and returned to control levels at 24 h. No changes were observed in alpha 2, beta 3, gamma 1, or gamma 2 subunits, and no changes in any subunit evaluated were observed in cortex or hippocampus. These data corroborate prior results obtained for the alpha 1 subunit using Northern hybridization, and illustrate the utility of the PCR assay in quantitating low-abundance mRNAs.