Grayanotoxin-I-modified eel electroplax sodium channels. Correlation with batrachotoxin and veratridine modifications.

To probe the structure-function relationships of voltage-dependent sodium channels, we have been examining the mechanisms of channel modification by batrachotoxin (BTX), veratridine (VTD), and grayanotoxin-I (GTX), investigating the unifying mechanisms that underlie the diverse modifications of this class of neurotoxins. In this paper, highly purified sodium channel polypeptides from the electric organ of the electric eel were incorporated into planar lipid bilayers in the presence of GTX for comparison with our previous studies of BTX (Recio-Pinto, E., D. S. Duch, S. R. Levinson, and B. W. Urban. 1987. J. Gen. Physiol. 90:375-395) and VTD (Duch, D. S., E. Recio-Pinto, C. Frenkel, S. R. Levinson, and B. W. Urban. 1989. J. Gen. Physiol. 94:813-831) modifications. GTX-modified channels had a single channel conductance of 16 pS. An additional large GTX-modified open state (40-55 pS) was found which occurred in bursts correlated with channel openings and closings. Two voltage-dependent processes controlling the open time of these modified channels were characterized: (a) a concentration-dependent removal of inactivation analogous to VTD-modified channels, and (b) activation gating similar to BTX-modified channels, but occurring at more hyperpolarized potentials. The voltage dependence of removal of inactivation correlated with parallel voltage-dependent changes in the estimated K1/2 of VTD and GTX modifications. Ranking either the single channel conductances or the depolarization required for 50% activation, the same sequence is obtained: unmodified > BTX > GTX > VTD. The efficacy of the toxins as activators follows the same ranking (Catterall, W. A. 1977. J. Biol. Chem. 252:8669-8676).     

Interaction of neurotensin with prostaglandin E2 and prostaglandin synthesis inhibitors: effects on colonic temperature in mice

Neurotensin (NT) administered intracisternally (i.c.) to adult mice produced a marked hypothermia while prostaglandin E₂, administered by the same route, produced hyperthermia. When administered concurrently the effects of the two substances were neutralized. The prostaglandin synthesis inhibitors, indomethacin and acetylsalicylic acid, were injected subcutaneously 30 min prior to i.c. administered NT and/or thyrotropin-releasing hormone (TRH). Both inhibitors failed to potentiate the hypothermia induced by NT or alter its antagonism by TRH in mice kept at 26°C. When mice were kept at 6°C, pretreatment with indomethacin, but not acetylsalicylic acid, potentiated NT-induced hypothermia and prevented its antagonism by TRH. Because indomethacin inhibits synthesis of prostaglandins within the central nervous system (CNS) as well as in peripheral organs while acetylsalicylic acid acts only in the periphery, it appears that NT-induced hypothermia in a cold environment is enhanced by a reduction of prostaglandins in the CNS.     

Diterpenoids from Ajuga chamaepitys: Two neo-clerodane derivatives

From the whole plant of Ajuga chamaepitys two new neo-clerodane diterpenoids, ajugapitin and its dihydro derivative, have been isolated. Their     

Synthesis and relative stereochemistry of the four mercapturic acids derived from styrene oxide and N-acetylcysteine

The chemical reaction between (±)-styrene oxide and N-acetylcysteine produces both positional isomers ($\text{1}$ and $\text{2}$) as a mixture of diastereoisomers with a preference for the benzylic thioether isomer $\text{1}$ (2 : 1). Synthesis of the mercapturic acid conjugates from either (+)- or (?)-styrene oxide produces only two of the four possible stereoisomers. The single diastereoisomers of $\text{1}$ and $\text{2}$ were separated by high pressure liquid chromatography (HPLC) and identified by ¹H- and ¹³C-nuclear magnetic resonance (NMR). The relative stereochemistry at the benzylic carbon center of the mercapturic acid conjugates was assigned on the basis of the established chemical correlation between optically pure styrene oxide and its precursor mandelic acid, and considerations on the mechanism of ring opening of epoxides by sulfur nucleophiles. The stereochemical definition of the isomers $\text{3}$–$\text{6}$ should prove useful in investigations of the biotransformation of the glutathione (GSH) conjugates of styrene oxide.     

High mutagenicity and toxicity of a diol epoxide derived from benzo[a]pyrene

(±)-7β,8α-Dihydroxy-9β,10β-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BP 7,8-diol-9,10-epoxide) is a suspected metabolite of benzo[a]pyrene that is highly mutagenic and toxic in several strains of $\text{Salmonella}\text{typhimurium}$ and in cultured Chinese hamster V79 cells. BP 7,8-diol-9,10-epoxide was approximately 5, 10 and 40 times more mutagenic than benzo[a]pyrene 4,5-oxide (BP 4,5-oxide) in strains TA 98 and TA 100 of $\text{S.}\text{typhimurium}$ and in V79 cells, respectively. Both compounds were equally mutagenic to strain TA 1538 and non-mutagenic to strain TA 1535 of $\text{S.}\text{typhimurium}$. The diol epoxide was toxic to the four bacterial strains at 0.5–2.0 nmole/plate, whereas BP 4,5-oxide was nontoxic at these concentrations. In V79 cells, the diol epoxide was about 60-fold more cytotoxic than BP 4,5-oxide.     

Disparities in distribution of COVID-19 vaccines across US counties: A geographic information system–based cross-sectional study

BackgroundThe US Centers for Disease Control and Prevention has repeatedly called for Coronavirus Disease 2019 (COVID-19) vaccine equity. The objective our study was to measure equity in the early distribution of COVID-19 vaccines to healthcare facilities across the US. Specifically, we tested whether the likelihood of a healthcare facility administering COVID-19 vaccines in May 2021 differed by county-level racial composition and degree of urbanicity.Methods and findingsThe outcome was whether an eligible vaccination facility actually administered COVID-19 vaccines as of May 2021, and was defined by spatially matching locations of eligible and actual COVID-19 vaccine administration locations. The outcome was regressed against county-level measures for racial/ethnic composition, urbanicity, income, social vulnerability index, COVID-19 mortality, 2020 election results, and availability of nontraditional vaccination locations using generalized estimating equations.Across the US, 61.4% of eligible healthcare facilities and 76.0% of eligible pharmacies provided COVID-19 vaccinations as of May 2021. Facilities in counties with >42.2% non-Hispanic Black population (i.e., > 95th county percentile of Black race composition) were less likely to serve as COVID-19 vaccine administration locations compared to facilities in counties with <12.5% non-Hispanic Black population (i.e., lower than US average), with OR 0.83; 95% CI, 0.70 to 0.98, p = 0.030. Location of a facility in a rural county (OR 0.82; 95% CI, 0.75 to 0.90, p < 0.001, versus metropolitan county) or in a county in the top quintile of COVID-19 mortality (OR 0.83; 95% CI, 0.75 to 0.93, p = 0.001, versus bottom 4 quintiles) was associated with decreased odds of serving as a COVID-19 vaccine administration location.There was a significant interaction of urbanicity and racial/ethnic composition: In metropolitan counties, facilities in counties with >42.2% non-Hispanic Black population (i.e., >95th county percentile of Black race composition) had 32% (95% CI 14% to 47%, p = 0.001) lower odds of serving as COVID administration facility compared to facilities in counties with below US average Black population. This association between Black composition and odds of a facility serving as vaccine administration facility was not observed in rural or suburban counties. In rural counties, facilities in counties with above US average Hispanic population had 26% (95% CI 11% to 38%, p = 0.002) lower odds of serving as vaccine administration facility compared to facilities in counties with below US average Hispanic population. This association between Hispanic ethnicity and odds of a facility serving as vaccine administration facility was not observed in metropolitan or suburban counties.Our analyses did not include nontraditional vaccination sites and are based on data as of May 2021, thus they represent the early distribution of COVID-19 vaccines. Our results based on this cross-sectional analysis may not be generalizable to later phases of the COVID-19 vaccine distribution process.ConclusionsHealthcare facilities in counties with higher Black composition, in rural areas, and in hardest-hit communities were less likely to serve as COVID-19 vaccine administration locations in May 2021. The lower uptake of COVID-19 vaccinations among minority populations and rural areas has been attributed to vaccine hesitancy; however, decreased access to vaccination sites may be an additional overlooked barrier.

Inmaculada Hernandez and colleagues investigate the disparities in early-phase distribution of COVID-19 Vaccines across U.S. Counties.     

The effect of sample size and species characteristics on performance of different species distribution modeling methods

Species distribution models should provide conservation practioners with estimates of the spatial distributions of species requiring attention. These species are often rare and have limited known occurrences, posing challenges for creating accurate species distribution models. We tested four modeling methods (Bioclim, Domain, GARP, and Maxent) across 18 species with different levels of ecological specialization using six different sample size treatments and three different evaluation measures. Our assessment revealed that Maxent was the most capable of the four modeling methods in producing useful results with sample sizes as small as 5, 10 and 25 occurrences. The other methods compensated reasonably well (Domain and GARP) to poorly (Bioclim) when presented with datasets of small sample sizes. We show that multiple evaluation measures are necessary to determine accuracy of models produced with presence-only data. Further, we found that accuracy of models is greater for species with small geographic ranges and limited environmental tolerance, ecological characteristics of many rare species. Our results indicate that reasonable models can be made for some rare species, a result that should encourage conservationists to add distribution modeling to their toolbox.     

Genetic Network Analyzer: qualitative simulation of genetic regulatory networks

MOTIVATION: The study of genetic regulatory networks has received a major impetus from the recent development of experimental techniques allowing the measurement of patterns of gene expression in a massively parallel way. This experimental progress calls for the development of appropriate computer tools for the modeling and simulation of gene regulation processes. RESULTS: We present Genetic Network Analyzer (GNA), a computer tool for the modeling and simulation of genetic regulatory networks. The tool is based on a qualitative simulation method that employs coarse-grained models of regulatory networks. The use of GNA is illustrated by a case study of the network of genes and interactions regulating the initiation of sporulation in Bacillus subtilis. AVAILABILITY: GNA and the model of the sporulation network are available at http://www-helix.inrialpes.fr/gna.