A Laboratory Exercise for Genotyping Two Human Single Nucleotide Polymorphisms

The dramatic decrease in the cost of sequencing a human genome is leading to an era in which a wide range of students will benefit from having an understanding of human genetic variation. Since over 90% of sequence variation between humans is in the form of single nucleotide polymorphisms (SNPs), a laboratory exercise has been devised in order to illustrate the importance of SNPs. Two separate SNPs are analysed, one of which has a significant effect on a person’s phenotype and one which does not. The genotyping protocol is relatively inexpensive and uses standard molecular biology reagents and equipment.     

PROPHYLACTIC PSYCHOTHERAPY BEFORE DESEXUALIZING OPERATIONS

To lessen the hazard of postoperative mental trauma, psychiatric preparation of patients with patently faulty psychic adjustment is advisable before operations entailing removal of genital organs.     

Two decades of tropical cyclone impacts on North Carolina’s estuarine carbon,nutrient and phytoplankton dynamics: implications for biogeochemical cycling and water quality in a stormier world

Coastal North Carolina (USA) has experienced 35 tropical cyclones over the past 2 decades; the frequency of these events is expected to continue in the foreseeable future. Individual storms had unique and, at times, significant hydrologic, nutrient-, and carbon (C)-loading impacts on biogeochemical cycling and phytoplankton responses in a large estuarine complex, the Pamlico Sound (PS) and Neuse River Estuary (NRE). Major storms caused up to a doubling of annual nitrogen and tripling of phosphorus loading compared to non-storm years; magnitudes of loading depended on storm tracks, forward speed, and precipitation in NRE-PS watersheds. With regard to C cycling, NRE-PS was a sink for atmospheric CO₂ during dry, storm-free years and a significant source of CO₂ in years with at least one storm, although responses were storm-specific. Hurricane Irene (2011) mobilized large amounts of previously-accumulated terrigenous C in the watershed, mainly as dissolved organic carbon, and extreme winds rapidly released CO₂ to the atmosphere. Historic flooding after Hurricanes Joaquin (2015) and Matthew (2016) provided large inputs of C from the watershed, modifying the annual C balance of NRE-PS and leading to sustained CO₂ efflux for months. Storm type affected biogeochemical responses as C-enriched floodwaters enhanced air–water CO₂ exchange during ‘wet’ storms, while CO₂ fluxes during ‘windy’ storms were largely supported by previously-accumulated C. Nutrient loading and flushing jointly influenced spatio-temporal patterns of phytoplankton biomass and composition. These findings suggest the importance of incorporating freshwater discharge and C dynamics in nutrient management strategies for coastal ecosystems likely to experience a stormier future.     

tRNA is a new target for cleavage by a MazF toxin

Toxin-antitoxin (TA) systems play key roles in bacterial persistence, biofilm formation and stress responses. The MazF toxin from the Escherichia coli mazEF TA system is a sequence- and single-strand-specific endoribonuclease, and many studies have led to the proposal that MazF family members exclusively target mRNA. However, recent data indicate some MazF toxins can cleave specific sites within rRNA in concert with mRNA. In this report, we identified the repertoire of RNAs cleaved by Mycobacterium tuberculosis toxin MazF-mt9 using an RNA-seq-based approach. This analysis revealed that two tRNAs were the principal targets of MazF-mt9, and each was cleaved at a single site in either the tRNA^Pro14 D-loop or within the tRNA^Lys43 anticodon. This highly selective target discrimination occurs through recognition of not only sequence but also structural determinants. Thus, MazF-mt9 represents the only MazF family member known to target tRNA and to require RNA structure for recognition and cleavage. Interestingly, the tRNase activity of MazF-mt9 mirrors basic features of eukaryotic tRNases that also generate stable tRNA-derived fragments that can inhibit translation in response to stress. Our data also suggest a role for tRNA distinct from its canonical adapter function in translation, as cleavage of tRNAs by MazF-mt9 downregulates bacterial growth.     

Adaptations to a high-fat diet that increase exercise endurance in male rats

Eighty-seven male Sprague-Dawley rats (245-300 g) were randomly assigned to one of two experimental groups. The first group consumed a diet high in fat and low in carbohydrate (LCD), whereas the second group ate a normal diet (ND). After either 1 or 5 wk on the diets, rats from each group were killed either before or after an exhausting run on a rodent treadmill (35 m X min-1, 0% grade). The LCD animals ran significantly longer before exhaustion at both week 1 (44.9 +/- 5.1 vs. 41.6 +/- 4.2 min) and week 5 (47.1 +/- 3.6 vs. 35.5 +/- 3.1 min) (P less than 0.05). Adaptations to the LCD included lower muscle and liver glycogen content, decreased rate of glycogen breakdown during exercise, decreased lactate production, and elevated blood ketone levels. In addition to these substrate changes, the LCD caused increased enzyme activities of muscular 3-hydroxyacyl-CoA dehydrogenase (35-110%) and citrate synthase (15-20%). These data indicate that rats exposed to a high-fat diet are capable of prolonged intense exercise in spite of limited glycogen stores. This improved capacity for exercise appears to be partially the result of muscular adaptations to the diet, which apparently increase the ability to oxidize fat and concomitantly spare glycogen.