Purine and pyrimidine synthesis differently affect the strength of the inoculum effect for aminoglycoside and ß-lactam antibiotics.

The inoculum effect has been observed for nearly all antibiotics and bacterial species. However, explanations accounting for its occurrence and strength are lacking. We previously found that growth productivity, which captures the relationship between [ATP] and growth, can account for the strength of the inoculum effect for bactericidal antibiotics. However, the molecular pathway(s) underlying this relationship, and therefore determining the inoculum effect, remain undiscovered. We show that nucleotide synthesis can determine the relationship between [ATP] and growth, and thus the strength of inoculum effect in an antibiotic class-dependent manner. Specifically, and separate from activity through the tricarboxylic acid cycle, we find that transcriptional activity of genes involved in purine and pyrimidine synthesis can predict the strength of the inoculum effect for ß-lactam and aminoglycosides antibiotics, respectively. Our work highlights the antibiotic class-specific effect of purine and pyrimidine synthesis on the severity of the inoculum effect and paves the way for intervention strategies to reduce the inoculum effect in the clinic.

Impact of training level on postplacental levonorgestrel 52 mg intrauterine device expulsion.

OBJECTIVE: To determine the association between provider training level and postplacental intrauterine device (IUD) outcomes following insertion instruction by email only. STUDY DESIGN: We conducted a single-center chart review of demographics, insertion and clinical outcomes within 6 months of delivery for 116 patients who underwent postplacental levonorgestrel 52 mg IUD placement from October 1, 2016, to March 31, 2017. RESULTS: We confirmed IUD retention, removal or expulsion in 87 of 116 (75.0%) patients by 6 months after delivery. Complete expulsion or removal for malposition occurred in 20 (23.0%) patients and more frequently after vaginal than cesarean delivery (30.2% vs. 4.2%, OR 9.93 [95% CI 1.25-78.96]) and when a postgraduate year (PGY) 1 physician placed the IUD compared to a PGY 2-4 or attending physician (37.5% vs. 14.5%, OR 3.52 [95% CI 1.25-9.94]). CONCLUSION: Postplacental levonorgestrel 52 mg IUD expulsion rates are associated with provider training level as well as delivery route, though the individual association of each of these factors is difficult to ascertain given the high degree of collinearity between these two variables in our study.

Colorado Medical Students' Attitudes and Beliefs About Marijuana.

BACKGROUND: Over the past two decades, state and local governments across the U.S. have been increasingly reforming marijuana laws. Despite growing support for marijuana as a medical treatment, little is known about medical students' perceptions of marijuana use. OBJECTIVE: To assess Colorado medical students' personal and professional opinions on current and future marijuana use in a healthcare setting. DESIGN: A voluntary, anonymous, online cross-sectional survey. PARTICIPANTS: Medical students (n = 624) at the University of Colorado School of Medicine between January and February 2014 were invited to participate. MAIN MEASURES: Numerical responses were quantified using counts and percentages, and Likert scale responses were collapsed for bivariate analysis. Items were gathered thematically and additively scored for each subscale. Internal consistency reliability statistics were calculated for each subscale to ensure that items were assessing similar constructs. Unadjusted t tests and one-way analysis of variance (ANOVA) were used to calculate mean differences in subscale scores between subgroups. KEY RESULTS: We received 236 responses (37%). Students indicated support for marijuana legalization (64%), and few believed that physicians should be penalized for recommending marijuana to patients (6%). Nearly all (97%) believed that further marijuana research should be conducted, and believed marijuana could play a role in the treatment of various medical conditions. Seventy-seven percent reported that they believed marijuana use had the potential for psychological harm, and 68% indicated concern for potential physical harm. Only a minority of students would recommend marijuana to a patient under current law (29%), or if it were legally available (45%). Acceptability of marijuana for treatment of approved conditions was not correlated with age or gender, but was positively correlated with living in Colorado prior to medical school (p < 0.001) and with prior marijuana use (p < 0.001). CONCLUSIONS: Medical students support marijuana legal reform, medicinal uses of marijuana, and increased research, but have concerns regarding risks of marijuana use, and appear hesitant to recommend marijuana to patients.

A Caenorhabditis elegans model of orotic aciduria reveals enlarged lysosome-related organelles in embryos lacking umps-1 function.

Gut granules are cell type-specific lysosome-related organelles found within the intestinal cells of Caenorhabditis elegans. To investigate the regulation of lysosome-related organelle size, we screened for C. elegans mutants with substantially enlarged gut granules, identifying alleles of the vacuolar-type H(+)-ATPase and uridine-5'-monophosphate synthase (UMPS)-1. UMPS-1 catalyzes the conversion of orotic acid to UMP; this comprises the two terminal steps in de novo pyrimidine biosynthesis. Mutations in the orthologous human gene UMPS result in the rare genetic disease orotic aciduria. The umps-1(-) mutation promoted the enlargement of gut granules to 250 times their normal size, whereas other endolysosomal organelles were not similarly affected. UMPS-1::green fluorescent protein was expressed in embryonic and adult intestinal cells, where it was cytoplasmically localized and not obviously associated with gut granules. Whereas the umps-1(-) mutant is viable, combination of umps-1(-) with mutations disrupting gut granule biogenesis resulted in synthetic lethality. The effects of mutations in pyr-1, which encodes the enzyme catalyzing the first three steps of de novo pyrimidine biosynthesis, did not phenotypically resemble those of umps-1(-); instead, the synthetic lethality and enlargement of gut granules exhibited by the umps-1(-) mutant was suppressed by pyr-1(-). In a search for factors that mediate the enlargement of gut granules in the umps-1(-) mutant, we identified WHT-2, an ABCG transporter previously implicated in gut granule function. Our data suggest that umps-1(-) leads to enlargement of gut granules through a build-up of orotic acid. WHT-2 possibly facilitates the increase in gut granule size of the umps-1(-) mutant by transporting orotic acid into the gut granule and promoting osmotically induced swelling of the compartment.