Faster top running speeds are achieved with greater ground forces not more rapid leg movements

We twice tested the hypothesis that top running speeds are determined by the amount of force applied to the ground rather than how rapidly limbs are repositioned in the air. First, we compared the mechanics of 33 subjects of different sprinting abilities running at their top speeds on a level treadmill. Second, we compared the mechanics of declined (-6 degrees ) and inclined (+9 degrees ) top-speed treadmill running in five subjects. For both tests, we used a treadmill-mounted force plate to measure the time between stance periods of the same foot (swing time, t(sw)) and the force applied to the running surface at top speed. To obtain the force relevant for speed, the force applied normal to the ground was divided by the weight of the body (W(b)) and averaged over the period of foot-ground contact (F(avge)/W(b)). The top speeds of the 33 subjects who completed the level treadmill protocol spanned a 1.8-fold range from 6.2 to 11.1 m/s. Among these subjects, the regression of F(avge)/W(b) on top speed indicated that this force was 1.26 times greater for a runner with a top speed of 11.1 vs. 6.2 m/s. In contrast, the time taken to swing the limb into position for the next step (t(sw)) did not vary (P = 0.18). Declined and inclined top speeds differed by 1.4-fold (9.96+/-0.3 vs. 7.10+/-0.3 m/s, respectively), with the faster declined top speeds being achieved with mass-specific support forces that were 1.3 times greater (2.30+/- 0.06 vs. 1.76+/-0.04 F(avge)/ W(b)) and minimum t(sw) that were similar (+8%). We conclude that human runners reach faster top speeds not by repositioning their limbs more rapidly in the air, but by applying greater support forces to the ground.

BACE knockout mice are healthy despite lacking the primary beta-secretase activity in brain: implications for Alzheimer's disease therapeutics

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by accumulation of amyloid plaques and neurofibrillary tangles in the brain. The major components of plaque, beta-amyloid peptides (Abetas), are produced from amyloid precursor protein (APP) by the activity of beta- and gamma-secretases. beta-secretase activity cleaves APP to define the N-terminus of the Abeta1-x peptides and, therefore, has been a long- sought therapeutic target for treatment of AD. The gene encoding a beta-secretase for beta-site APP cleaving enzyme (BACE) was identified recently. However, it was not known whether BACE was the primary beta-secretase in mammalian brain nor whether inhibition of beta-secretase might have effects in mammals that would preclude its utility as a therapeutic target. In the work described herein, we generated two lines of BACE knockout mice and characterized them for pathology, beta-secretase activity and Abeta production. These mice appeared to develop normally and showed no consistent phenotypic differences from their wild-type littermates, including overall normal tissue morphology and brain histochemistry, normal blood and urine chemistries, normal blood-cell composition, and no overt behavioral and neuromuscular effects. Brain and primary cortical cultures from BACE knockout mice showed no detectable beta-secretase activity, and primary cortical cultures from BACE knockout mice produced much less Abeta from APP. The findings that BACE is the primary beta-secretase activity in brain and that loss of beta-secretase activity produces no profound phenotypic defects with a concomitant reduction in beta-amyloid peptide clearly indicate that BACE is an excellent therapeutic target for treatment of AD.

Endothelin in human congestive heart failure

BACKGROUND

Although recent investigations report the elevation of plasma endothelin (ET) in congestive heart failure (CHF), it remains unclear if this elevation is that of the biologically active peptide ET-1 or of its precursor big-ET. Furthermore, it is unclear if such elevation is associated with increased myocardial ET and if the molecular form from cardiac tissue is altered ET. Last, it remains to be established whether circulating ET is increased at the earliest stage of CHF in patients with asymptomatic left ventricular dysfunction and correlates with the magnitude of ventricular dysfunction.

METHODS AND RESULTS

The present study was designed to investigate concentrations and molecular forms of ET in plasma and cardiac tissue in healthy subjects and CHF patients with New York Heart Association (NYHA) class I through IV using cardiac radionuclide angiogram, cardiac myocardial biopsy, radioimmunoassay, gel permeation chromatography (GPC), and immunohistochemical staining (IHCS). Plasma ET was increased only in patients with moderate (NYHA class III) or severe (NYHA class IV) CHF compared with healthy subjects and individuals with asymptomatic (NYHA class I) or mild (NYHA class II) CHF. The elevation of circulating ET in CHF showed a negative correlation with left ventricular ejection fraction and cardiac index and a positive correlation with functional class and left ventricular end-diastolic volume index. GPC demonstrated that immunoreactive plasma ET was ET-1 in healthy subjects and both mature ET-1 and its precursor big-ET in severe CHF patients, with big-ET the predominant molecular form. Cardiac tissue concentrations and IHCS revealed ET presence in healthy atrial and ventricular tissue, which were not different in severe CHF. GPC revealed that the molecular form of cardiac ET was ET-1 in both healthy and CHF hearts.

CONCLUSIONS

The present study establishes for the first time that the elevation of plasma ET in severe human CHF represents principally elevation of big-ET. Second, ET is present in healthy and failing myocardia, and its activity by both immunohistochemistry and radioimmunoassay is not changed in CHF. Furthermore, the elevated plasma ET is characteristic of severe CHF and not asymptomatic or mild CHF. In addition, the degree of plasma elevation of ET correlates with the magnitude of alterations in cardiac hemodynamics and functional class. The present study confirms and extends previous investigations of ET in human CHF and establishes the evolution of circulating and local cardiac ET in the spectrum of human CHF.

Identification of the genomic locations of duplicate nucleotide sequences in maize by analysis of restriction fragment length polymorphisms

While preparing a linkage map for maize based upon loci detected through the use of restriction fragment length polymorphisms (RFLPs), it was found that 62 of the 217 cloned maize sequences tested (29%) detected more than one fragment on genomic Southern blots. Thus, more than one nucleotide sequence is present within the maize genome which is in part homologous to each of these cloned sequences. The genomic locations of these ;;duplicate'' sequences were determined and it was found that they usually originated from different chromosomes. The process which produced them did not operate randomly as some pairs of chromosomes share many duplicate sequences while many other pairs share none. Furthermore, these shared duplicate sequences are generally arrayed in an ordered arrangement along these chromosomes. It is believed that chromosomal segments which contain several duplicate loci in a generally ordered arrangement must have had a common origin. The presence of these duplicated segments supports the idea that allopolyploidy may have been involved in the evolution of maize. Nevertheless, the duplicate loci do not primarily involve five pairs of chromosomes and thus, five pairs of homeologous chromosomes are not currently present within the maize genome. The data clearly indicate that maize is not a recent allotetraploid produced by hybridization between two individuals with similar genomic structures; however, the data are also consistent with the possibility of these shared duplicate chromosomal segments having been generated through internal duplication.

Benefits from adding the 5-lipoxygenase inhibitor zileuton to conventional therapy in aspirin-intolerant asthmatics

From bronchoprovocation studies and investigations of the acute effects of drugs that inhibit leukotrienes (LT), the hypothesis has emerged that leukotrienes are important mediators of airway obstruction and other symptoms in aspirin-intolerant asthma (AIA). However, it has yet not been shown if subjects with AIA respond favorably to clinical treatment with leukotriene inhibitors. Therefore, in a double-blind placebo-controlled crossover study, we examined the effects of 6 wk of treatment with the leukotriene-pathway inhibitor zileuton (600 mg, four times daily) in 40 patients with well-characterized AIA. The treatment was added to existing therapy, which included medium to high doses of inhaled (average daily dose 1,030 microg of beclomethasone or budesonide) or oral glucocorticosteroids (4 to 25 mg/d) for all but one of the patients. On top of this treated baseline, there were no significant effects of adding placebo, indicating that their asthma was kept relatively stable. However, there was an acute and chronic improvement in pulmonary function after treatment with zileuton, expressed both as increased FEV1 from baseline compared with placebo, and higher morning and evening peak expiratory flow rate (PEFR) values on zileuton treatment compared with placebo. The improvements occurred despite lower use of rescue bronchodilator with zileuton. Zileuton also diminished nasal dysfunction, which is one of the cardinal signs of AIA. There was a remarkable return of smell, less rhinorrhea, and a trend for less stuffiness and higher nasal inspiratory flow during treatment with zileuton. Zileuton caused a small but distinct reduction of bronchial hyperresponsiveness to histamine and inhibited aspirin-induced bronchoconstriction. Zileuton inhibited urinary excretion of LTE4 but did not change airway reactivity to inhaled LTD4, supporting that zileuton specifically inhibited leukotriene biosynthesis. The findings indicate that leukotrienes are important mediators of persistent airway obstruction and chronic nasal dysfunction in AIA. The study also suggests that addition of a leukotriene pathway inhibitor such as zileuton may bring about greater control of asthma than what is achieved by treatment with medium to high doses of glucocorticosteroids alone.

Sensitivity to titanium. A cause of implant failure?

Tissues from five patients who underwent revision operations for failed total hip replacements were found to contain large quantities of particulate titanium. In four cases this metal must have come from titanium alloy screws used to fix the acetabular component; in the fifth case it may also have originated from a titanium alloy femoral head. Monoclonal antibody labelling showed abundant macrophages and T-lymphocytes, in the absence of B-lymphocytes, suggesting sensitisation to titanium. Skin patch testing with dilute solutions of titanium salts gave negative results in all five patients. However, two of them had a positive skin test to a titanium-containing ointment.

Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study

BACKGROUND

No effective pharmacological or non-pharmacological interventions exist for patients with long COVID. We aimed to describe recovery 1 year after hospital discharge for COVID-19, identify factors associated with patient-perceived recovery, and identify potential therapeutic targets by describing the underlying inflammatory profiles of the previously described recovery clusters at 5 months after hospital discharge.

METHODS

The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a prospective, longitudinal cohort study recruiting adults (aged ≥18 years) discharged from hospital with COVID-19 across the UK. Recovery was assessed using patient-reported outcome measures, physical performance, and organ function at 5 months and 1 year after hospital discharge, and stratified by both patient-perceived recovery and recovery cluster. Hierarchical logistic regression modelling was performed for patient-perceived recovery at 1 year. Cluster analysis was done using the clustering large applications k-medoids approach using clinical outcomes at 5 months. Inflammatory protein profiling was analysed from plasma at the 5-month visit. This study is registered on the ISRCTN Registry, ISRCTN10980107, and recruitment is ongoing.

FINDINGS

2320 participants discharged from hospital between March 7, 2020, and April 18, 2021, were assessed at 5 months after discharge and 807 (32·7%) participants completed both the 5-month and 1-year visits. 279 (35·6%) of these 807 patients were women and 505 (64·4%) were men, with a mean age of 58·7 (SD 12·5) years, and 224 (27·8%) had received invasive mechanical ventilation (WHO class 7-9). The proportion of patients reporting full recovery was unchanged between 5 months (501 [25·5%] of 1965) and 1 year (232 [28·9%] of 804). Factors associated with being less likely to report full recovery at 1 year were female sex (odds ratio 0·68 [95% CI 0·46-0·99]), obesity (0·50 [0·34-0·74]) and invasive mechanical ventilation (0·42 [0·23-0·76]). Cluster analysis (n=1636) corroborated the previously reported four clusters: very severe, severe, moderate with cognitive impairment, and mild, relating to the severity of physical health, mental health, and cognitive impairment at 5 months. We found increased inflammatory mediators of tissue damage and repair in both the very severe and the moderate with cognitive impairment clusters compared with the mild cluster, including IL-6 concentration, which was increased in both comparisons (n=626 participants). We found a substantial deficit in median EQ-5D-5L utility index from before COVID-19 (retrospective assessment; 0·88 [IQR 0·74-1·00]), at 5 months (0·74 [0·64-0·88]) to 1 year (0·75 [0·62-0·88]), with minimal improvements across all outcome measures at 1 year after discharge in the whole cohort and within each of the four clusters.

INTERPRETATION

The sequelae of a hospital admission with COVID-19 were substantial 1 year after discharge across a range of health domains, with the minority in our cohort feeling fully recovered. Patient-perceived health-related quality of life was reduced at 1 year compared with before hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

FUNDING

UK Research and Innovation and National Institute for Health Research.

Choice making to promote adaptive behavior for students with emotional and behavioral challenges

Two analyses investigated the effects of choice making on the responding of elementary school students with emotional and behavioral challenges. In the first analysis, 2 participants were given choices from menus of academic tasks, all of which were pertinent to their educational objectives in English and spelling, respectively. Reversal designs showed that the choice-making conditions increased task engagement and reduced disruptive behavior for both students. An additional analysis was performed with a 3rd student in an effort to further distinguish the effects of choice making from preference. In this study, one of the no-choice phases was yoked to a previous choice-making condition. This analysis demonstrated that the choice-making condition was superior to baseline and yoked control phases as determined by levels of task engagement and disruptive behavior. The findings of the two analyses contribute information relevant to students with emotional and behavioral disorders, and to a growing literature on the desirable effects of choice making for students with disabilities and challenging behaviors.

Ocean circulation off east Antarctica affects ecosystem structure and sea-ice extent

Sea ice and oceanic boundaries have a dominant effect in structuring Antarctic marine ecosystems. Satellite imagery and historical data have identified the southern boundary of the Antarctic Circumpolar Current as a site of enhanced biological productivity. Meso-scale surveys off the Antarctic peninsula have related the abundances of Antarctic krill (Euphausia superba) and salps (Salpa thompsoni) to inter-annual variations in sea-ice extent. Here we have examined the ecosystem structure and oceanography spanning 3,500 km of the east Antarctic coastline, linking the scales of local surveys and global observations. Between 80 degrees and 150 degrees E there is a threefold variation in the extent of annual sea-ice cover, enabling us to examine the regional effects of sea ice and ocean circulation on biological productivity. Phytoplankton, primary productivity, Antarctic krill, whales and seabirds were concentrated where winter sea-ice extent is maximal, whereas salps were located where the sea-ice extent is minimal. We found enhanced biological activity south of the southern boundary of the Antarctic Circumpolar Current rather than in association with it. We propose that along this coastline ocean circulation determines both the sea-ice conditions and the level of biological productivity at all trophic levels.

DNA sequences required for regulated expression of beta-globin genes in murine erythroleukemia cells

We introduced into MEL cells rabbit beta-globin gene deletion mutants and two sets of hybrid genes constructed from the inducible human beta-globin gene and noninducible human gamma-globin gene or the murine H-2Kbm1 class I MHC gene. S1 nuclease analysis of gene transcripts before and after MEL differentiation showed that induction of the rabbit beta-globin gene did not require more than 58 bp of DNA 5' to the transcription initiation site. Hybrid genes were constructed with human beta-globin DNA sequences from either 5' or 3' of the translation initiation site linked to the complementary parts of the gamma or H2Kbm1 genes. Both types of constructs were inducible during MEL differentiation. The relative rates of transcription of the 5' gamma-3' beta and 5'H2-3' beta hybrid genes show that induction of the hybrid gene transcripts results at least in part from transcriptional activation of the genes. We suggest that DNA sequences that regulate beta-globin gene transcription during MEL differentiation are located both 5' and 3' to the translation initiation site.

Hyponatremia in ultradistance triathletes

PURPOSE

Hyponatremia ([plasma sodium] <135 mmol x L(-1)) is a potentially serious complication of ultraendurance sports. However, the etiology of this condition is still uncertain. This observational cohort study aimed to determine prospectively the incidence and etiology of hyponatremia in an ultradistance triathlon.

METHODS

The subjects consisted of 605 of the 660 athletes entered in the New Zealand Ironman triathlon (3.8-km swim, 180-km cycle, and 42.2-km run). Subjects were weighed before and after the race. A blood sample was drawn for measurement of plasma sodium concentration after the race.

RESULTS

Complete data on pre- and postrace weights and plasma sodium concentrations were available in 330 race finishers. Postrace plasma sodium concentrations were inversely related to changes in body weight (P = 0.0001). Women (N = 38) had significantly lower plasma sodium concentrations (133.7 vs 137.4 mmol x L(-1); P = 0.0001) than men (N = 292) and lost significantly less relative weight (-2.7 vs -4.3%; P = 0.0002). Fifty-eight of 330 race finishers (18%) were hyponatremic; of these only 18 (31%) sought medical care for the symptoms of hyponatremia (symptomatic). Eleven of the 58 hyponatremic athletes had severe hyponatremia ([plasma sodium] < 130 mmol x L(-1)); seven of these 11 severely hyponatremic athletes were symptomatic. The relative body weight change of the 11 severely hyponatremic athletes ranged from 2.4% to +5%; eight (73%) of these athletes either maintained or gained weight during the race. In contrast, relative body weight changes in the 47 athletes with mild hyponatremia ([plasma sodium] 130-134 mmol x L(1)) were more variable, ranging from -9.25% to +2.2%.

CONCLUSIONS

Hyponatremia is a common biochemical finding in ultradistance triathletes but is usually asymptomatic. Although mild hyponatremia was associated with variable body weight changes, fluid overload was the cause of most (73%) cases of severe, symptomatic hyponatremia.

Positive predictive value of the diagnosis of acute myocardial infarction in an administrative database

OBJECTIVE

To determine the positive predictive value of ICD-9-CM coding of acute myocardial infarction and cardiac procedures.

METHODS

Using chart-abstracted data as the standard, we examined administrative data from the Veterans Health Administration for a national random sample of 5,151 discharges.

MAIN RESULTS

The positive predictive value of acute myocardial infarction coding in the primary position was 96.9%. The sensitivity and specificity of coding were, respectively, 96% and 99% for catheterization, 95.7% and 100% for coronary artery bypass graft surgery, and 90.3% and 99. 7% for percutaneous transluminal coronary angioplasty.

CONCLUSIONS

The positive predictive value of acute myocardial infarction and related procedure coding is comparable to or better than previously reported observations of administrative databases.

Influence of conjugated linoleic acid (CLA) on establishment and progression of atherosclerosis in rabbits

OBJECTIVE

To determine effects of conjugated linoleic acid (CLA) on establishment and progression of experimentally-induced atherosclerosis in rabbits.

METHODS

For establishment of atherosclerosis, New Zealand White rabbits were fed a semipurified diet containing 0.1% to 0.2% cholesterol for 90 days. Some groups were fed diet and CLA. For effects on progression of atherosclerosis, rabbits with established atherosclerosis were fed a semipurified diet +/- CLA for 90 days.

RESULTS

At dietary levels as low as 0.1%, CLA inhibited atherogenesis. At dietary levels of 1%, CLA caused substantial (30%) regression of established atherosclerosis. This is the first example of substantial regression of atherosclerosis being caused by diet alone.

CONCLUSION

Dietary CLA is an effective inhibitor of atherogenesis and also causes regression of established atherosclerosis.

The pathogenesis of experimental neosporosis in pregnant sheep

Three groups of eight pregnant sheep were inoculated with tachyzoites of the NCl isolate of Neospora caninum at 45 (group 1), 65 (group 2) or 90 (group 3) days' gestation. A further six animals (group 4) served as controls. Fourteen of the infected ewes developed a fever, which in two cases was biphasic. In six ewes in group 1, the fetuses died and were resorbed, and in the other two the fetuses were aborted. In group 2, one ewe resorbed her fetus, six aborted dead fetuses and one produced a live lamb. In group 3, six ewes aborted and two produced one live and one stillborn lamb each. Thus, the stage of gestation influenced the outcome of infection. All but one of the ewes "seroconverted", as shown by enzyme-linked immunosorbent assay, and 10 of 13 fetal sera examined by an indirect immunofluorescent antibody test were positive. The polymerase chain reaction was also used to detect DNA of N. caninum in aborted tissues. Immunohistochemical examination showed that the parasite had invaded the placentas of all cases examined, displaying an apparent predilection for fetal chorionic epithelium and fetal placental blood vessels, as well as inducing thrombosis in some maternal caruncular blood vessels. Organisms were associated with fetal vasculitis, focal degeneration and inflammation of the chorioallantois, and widespread, severe focal necrosis in the placentome. Characteristic lesions were seen in the fetal brains, in addition to focal leucomalacia, thought to be due to anoxia resulting from the placental damage. The six control sheep in group 4 remained clinically healthy and produced normal uninfected lambs.