Effects of Nitrate Supplementation on In Vivo Muscle Torque Recovery From BaCl2-Induced Injury

During repair from muscle injury, muscle satellite cells depend on nitric oxide production by immune cells to proliferate and differentiate. Nitrate supplementation has been shown to improve muscle endurance and oxygen consumption, but little is known about the ability of nitrate supplementation to interfere with muscle regeneration following injury. PURPOSE: To investigate whether nitrate supplementation affects muscle recovery of force after muscle injury produced by intramuscular injection of barium chloride. METHODS: Transgenic male mice (12 weeks old) that express Td-Tomato fluorescent protein in Pax7+ cells (i.e., satellite cells; Pax7CreER-Ai9 mice) were treated with tamoxifen (2 mg in corn oil, i.p.) once a day for 5 days. Four days after the last tamoxifen injection, both legs were subjected to stimulation of the peroneal nerve to evoke contractions of the anterior crural muscles at different frequencies of stimulation (1-200 Hz; i.e., Torque-frequency curve), followed by intramuscular injections of 1.2% BaCl2 (w/v) to produce injury of the tibialis anterior (TA) and extensor digitorum longus (EDL) muscles of the right leg. The contralateral leg served as a non-injured control. Torque-frequency curves were tested for both legs on days 2, 7, 14 and 21 post injury. At day 21, mice were euthanized, and muscles were dissected for histology (TA) and ex-vivo muscle contractility (EDL). A group of mice was treated with 1 g/L of NaNO3 in drinking water (nitrate group) 1 week before muscle injury, and a second group of mice was not treated (water group). RESULTS: Mice treated with NaNO3 (nitrate group) showed smaller torque in the non-injured leg compared to water group (103 ± 3 vs 84 ± 2 Nmm/kg, for water vs nitrate groups, respectively). However, the torque produced by the injured leg normalized by the torque developed by the non-injured leg was not different between groups on days 2 (28 ± 13% vs 25 ± 1%), 7 (41 ± 4% vs 35 ± 2%), 14 (81 ± 7% vs 87 ± 1%) and 21 (104 ± 3% vs 105 ± 3%) for water and nitrate groups respectively. CONCLUSION: The data suggest that nitrate supplementation decreases nerve-stimulated torque development in uninjured leg but does not change the recovery of torque after BaCl2 injury. Support: TRDRP grant # T29KT0397CA (to L.N.

Enabling violence: the ethics of writing and reading rape in South Africa

This thesis is concerned with describing the stakes of reading, writing and criticising fictional depictions of rape in a country plagued by high levels of sexual violence. I consider the capacity of rape representations to cause harm to women and rape survivors, and worsen the various injuries suffered by survivors as a direct or indirect consequence of rape. The possibility of such harm prompts me to examine the role and responsibilities of readers and critics in facilitating or preventing such harm. I further discuss the potential strategies of harm prevention that readers of novelistic portrayals of rape might adopt as well as the positive outcomes that such reading strategies make possible, and which might balance out the risks that accompany them. My description of the potential harm of rape representations combines postmodern critical feminist analysis with Miranda Fricker’s work on epistemic justice and Judith Herman’s work on trauma in order to illustrate the way that these representations shape our conception of rape in a manner that affects everything from how it is enacted to our treatment of survivors to the possibility of their recovery from posttraumatic stress disorder. In order to situate my analysis in the context of South African literature and to explore the notion of responsibility in relation to the writing of scenes of rape, I utilise a close reading of J.M. Coetzee’s Disgrace. Furthermore, I discuss the utility and limits of the critical feminist strategy of using a normative critical approach to rape representations in order to prevent harm. Ultimately, I argue that the use of such a strategy, along with the development of a purpose-honed adaptive critical style, is essential to the fulfilment of our responsibilities as readers and to the prevention of further suffering

Single-Leg Resistance Exercise Training in Mice Leads to a Fast Increase in In Vivo Torque of Anterior Crural Muscles

Resistance exercise is known to produce muscle hypertrophy. However, little is known about the role of muscle satellite cells in generating new myofibers or in incorporating satellite cells to live myofibers during exercise training. PURPOSE: To investigate whether single-leg resistance exercise training can activate the incorporation of muscle satellite cells in mice. METHODS: Transgenic male mice (12 weeks old) that express Td-Tomato fluorescent protein in Pax7+ (i.e., satellite cells) cells (Pax7CreER-Ai9) were treated with tamoxifen (2 mg in corn oil, i.p.) once a day for 5 days. Three days later, mice were single-leg exercise trained (i.e stimulation of the peroneal nerve of the right leg of each mouse to evoke fused tetanic contractions [100 Hz] of the anterior crural muscles), 3x per week for either 1 or 2 weeks. Each training session was composed of 3-s contractions with 7 s recovery between contractions, 10 contractions each set, 5 sets with 5 min rest between sets. Before the first training session and 3 days after the last training session (1 week or 2 weeks training), torque produced by the ankle was measured at different frequencies of pulse-stimulation (1-200 Hz), mice were euthanized, and muscles were frozen for histological measurements. RESULTS: During each session of training, peak torque developed at the last contraction was ~30% of the torque developed in the initial contraction of the session suggesting fatigue development. Between sessions of training, initial torque was not significantly different suggesting that muscle recovered function between sessions. Torque measurements at different frequencies of stimulation 3 days after 1 week or 2 weeks of training showed a ~50% increase in maximal tetanic torque relative to the mice body weight, after 1 week of training but there were no additional changes at 2 weeks of training. Tibialis anterior muscle cross sectional area and number of Td-tomato positive myofibers were also measured in these mice. CONCLUSION: Resistance exercise training in mice by using single-leg electrical stimulations leads to a fast (i.e., 1 week) increase in muscle force development

Meiosis in allopolyploid Arabidopsis suecica

Polyploidy is a major force shaping eukaryote evolution but poses challenges for meiotic chromosome segregation. As a result, first-generation polyploids often suffer from more meiotic errors and lower fertility than established wild polyploid populations. How established polyploids adapt their meiotic behaviour to ensure genome stability and accurate chromosome segregation remains an active research question. We present here a cytological description of meiosis in the model allopolyploid species Arabidopsis suecica (2n = 4x = 26). In large part meiosis in A. suecica is diploid-like, with normal synaptic progression and no evidence of synaptic partner exchanges. Some abnormalities were seen at low frequency, including univalents at metaphase I, anaphase bridges and aneuploidy at metaphase II; however, we saw no evidence of crossover formation occurring between non-homologous chromosomes. The crossover number in A. suecica is similar to the combined number reported from its diploid parents Arabidopsis thaliana (2n = 2x = 10) and Arabidopsis arenosa (2n = 2x = 16), with an average of approximately 1.75 crossovers per chromosome pair. This contrasts with naturally evolved autotetraploid A. arenosa, where accurate chromosome segregation is achieved by restricting crossovers to approximately 1 per chromosome pair. Although an autotetraploid donor is hypothesized to have contributed the A. arenosa subgenome to A. suecica, A. suecica harbours diploid A. arenosa variants of key meiotic genes. These multiple lines of evidence suggest that meiosis in the recently evolved allopolyploid A. suecica is essentially diploid like, with meiotic adaptation following a very different trajectory to that described for autotetraploid A. arenosa.ISSN:0960-7412ISSN:1365-313

CDKG1 Is Required for Meiotic and Somatic Recombination Intermediate Processing in Arabidopsis

The Arabidopsis (Arabidopsis thaliana) cyclin-dependent kinase G1 (CDKG1) is necessary for recombination and synapsis during male meiosis at high ambient temperature. In the cdkg1-1 mutant, synapsis is impaired and there is a dramatic reduction in the number of class I crossovers, resulting in univalents at metaphase I and pollen sterility. Here, we demonstrate that CDKG1 is necessary for the processing of recombination intermediates in the canonical ZMM recombination pathway and that loss of CDKG1 results in increased class II crossovers. While synapsis and events associated with class I crossovers are severely compromised in a cdkg1-1 mutant, they can be restored by increasing the number of recombination intermediates in the double cdkg1-1 fancm-1 mutant. Despite this, recombination intermediates are not correctly resolved, leading to the formation of chromosome aggregates at metaphase I. Our results show that CDKG1 acts early in the recombination process and is necessary to stabilize recombination intermediates. Finally, we show that the effect on recombination is not restricted to meiosis and that CDKG1 is also required for normal levels of DNA damage-induced homologous recombination in somatic tissues

Perceptions and experiences of medical student first responders: a mixed methods study

Context Medical Student First Responders (MSFRs) are volunteers who respond to emergency calls, managing patients before ambulance staff attend. The MSFR role provides opportunities to manage acutely unwell patients in the prehospital environment, not usually offered as part of formal undergraduate medical education. There are few previous studies describing activities or experiences of MSFRs or exploring the potential educational benefits. We aimed to investigate the activity of MSFRs and explore their experiences, particularly from an educational perspective. Methods We used a mixed methods design, combining quantitative analysis of ambulance dispatch data with qualitative semi-structured interviews of MSFRs. Dispatch data were from South Central and East Midlands Ambulance Service NHS Trusts from 1st January to 31st December 2019. Using propensity score matching, we compared incidents attended by MSFRs with those attended by other Community First Responders (CFRs) and ambulance staff. We interviewed MSFRs from five English (UK) medical schools in those regions about their experiences and perceptions and undertook thematic analysis supported by NVivo 12. Results We included 1,939 patients (median age 58.0 years, 51% female) attended by MSFRs. Incidents attended were more urgent category calls (category 1 n = 299, 14.9% and category 2 n = 1,504, 77.6%), most commonly for chest pain (n = 275, 14.2%) and shortness of breath (n = 273, 14.1%). MSFRs were less likely to attend patients of white ethnicity compared to CFRs and ambulance staff, and more likely to attend incidents in areas of higher socioeconomic deprivation (IMD – index of multiple deprivation) (p < 0.05). Interviewees (n = 16) consistently described positive experiences which improved their clinical and communication skills. Conclusion MSFRs’ attendance at serious medical emergencies provide a range of reported educational experiences and benefits. Further studies are needed to explore whether MSFR work confers demonstrable improvements in educational or clinical performance

Epidemiology and survival of the five stages of chronic kidney disease in a systolic heart failure population

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102653/1/ejhfhfq077.pd

LIM kinase function and renal growth: potential role for LIM kinases in fetal programming of kidney development

Aims Maternal dietary restriction during pregnancy impairs nephron development and results in offspring with fewer nephrons. Cell turnover in the early developing kidney is altered by exposure to maternal dietary restriction and may be regulated by the LIM-kinase family of enzymes. We set out to establish whether disturbance of LIM-kinase activity might play a role in the impairment of nephron formation. Main methods E12.5 metanephric kidneys and HK2 cells were grown in culture with the pharmacological LIM-kinase inhibitor BMS5. Organs were injected with DiI, imaged and cell numbers measured over 48 h to assess growth. Cells undergoing mitosis were visualised by pH 3 labelling. Key findings Growth of cultured kidneys reduced to 83% of controls after exposure to BMS5 and final cell number to 25% of control levels after 48 h. Whilst control and BMS5 treated organs showed cells undergoing mitosis (100 ± 11 cells/field vs 113 ± 18 cells/field respectively) the proportion in anaphase was considerably diminished with BMS5 treatment (7.8 ± 0.8% vs 0.8 ± 0.6% respectively; P < 0.01). This was consistent with effects on HK2 cells highlighting a severe impact of BMS5 on formation of the mitotic spindle and centriole positioning. DiI labelled cells migrated in 100% of control cultures vs 0% BMS5 treated organs. The number of nephrogenic precursor cells appeared depleted in whole organs and formation of new nephrons was blocked by exposure to BMS5. Significance Pharmacological blockade of LIM-kinase function in the early developing kidney results in failure of renal development. This is likely due to prevention of dividing cells from completion of mitosis with their resultant loss

Experimental validation of computerised models of clustering of platelet glycoprotein receptors that signal via tandem SH2 domain proteins

The clustering of platelet glycoprotein receptors with cytosolic YxxL and YxxM motifs, including GPVI, CLEC-2 and PEAR1, triggers activation via phosphorylation of the conserved tyrosine residues and recruitment of the tandem SH2 (Src homology 2) domain effector proteins, Syk and PI 3-kinase. We have modelled the clustering of these receptors with monovalent, divalent and tetravalent soluble ligands and with transmembrane ligands based on the law of mass action using ordinary differential equations and agent-based modelling. The models were experimentally evaluated in platelets and transfected cell lines using monovalent and multivalent ligands, including novel nanobody-based divalent and tetravalent ligands, by fluorescence correlation spectroscopy. Ligand valency, receptor number, receptor dimerisation, receptor phosphorylation and a cytosolic tandem SH2 domain protein act in synergy to drive receptor clustering. Threshold concentrations of a CLEC-2-blocking antibody and Syk inhibitor act in synergy to block platelet aggregation. This offers a strategy for countering the effect of avidity of multivalent ligands and in limiting off-target effects

High Resolution Images of Orbital Motion in the Trapezium Cluster: First Scientific Results from the MMT Deformable Secondary Mirror Adaptive Optics System

We present the first scientific images obtained with a deformable secondary mirror adaptive optics system. We utilized the 6.5m MMT AO system to produce high-resolution (FWHM=0.07'') near infrared (1.6 um) images of the young (~1 Myr) Orion Trapezium theta 1 Ori cluster members. A combination of high spatial resolution and high signal to noise allowed the positions of these stars to be measured to within ~0.003'' accuracies. Including previous speckle data (Weigelt et al. 1999), we analyze a six year baseline of high-resolution observations of this cluster. Over this baseline we are sensitive to relative proper motions of only ~0.002''/yr (4.2 km/s at 450 pc). At such sensitivities we detect orbital motion in the very tight theta 1 Ori B2B3 (52 AU separation) and theta 1 Ori A1A2 (94 AU separation) systems. Such motions are consistent with those independently observed by Schertl et al. (2003) with speckle interferometry, giving us confidence that these very small (~0.002''/yr) orbital motions are real. All five members of the theta 1 Ori B system appear likely gravitationally bound. The very lowest mass member of the theta 1 Ori B system (B4) has K' ~11.66 and an estimated mass of ~0.2 Msun. There was very little motion (4+/-15 km/s) detected of B4 w.r.t B1 or B2, hence B4 is possibly part of the theta 1 Ori B group. We suspect that if this very low mass member is physically associated it most likely is in an unstable (non-hierarchical) orbital position and will soon be ejected from the group. The theta 1 Ori B system appears to be a good example of a star formation ``mini-cluster'' which may eject the lowest mass members of the cluster in the near future. This ``ejection'' process could play a major role in the formation of low mass stars and brown dwarfs.Comment: To appear in the December 10, 2003 issue of the Astrophysical Journal 21 pages, 14 figures (some in color, but print OK in B&W