Crossbridge properties during force enhancement by slow stretching in single intact frog muscle fibres

The mechanism of force enhancement during lengthening was investigated on single frog muscle fibres by using fast stretches to measure the rupture tension of the crossbridge ensemble. Fast stretches were applied to one end of the activated fibre and force responses were measured at the other. Sarcomere length was measured by a striation follower device. Fast stretching induced a linear increase of tension that reached a peak and fell before the end of the stretch indicating that a sudden increase of fibre compliance occurred due to forced crossbridge detachment induced by the fast loading. The peak tension (critical tension, P _c) and the sarcomere length needed to reach P _c (critical length, L _c) were measured at various tensions during the isometric tetanus rise and during force enhancement by slow lengthening. The data showed that P _c was proportional to the tension generated by the fibre under both isometric and slow lengthening conditions. However, for a given tension increase, P _c was 6.5 times greater during isometric than during lengthening conditions. Isometric critical length was 13.04 ± 0.17 nm per half-sarcomere (nm hs⁻¹) independently of tension. During slow lengthening critical length fell as the force enhancement increased. For 90% enhancement, L _c reduced to 8.19 ± 0.039 nm hs⁻¹. Assuming that the rupture force of the individual crossbridge is constant, these data indicate that the increase of crossbridge number during lengthening accounts for only 15.4% of the total force enhancement. The remaining 84.6% is accounted for by the increased mean strain of the crossbridges.     

Observation of Bothrops atrox Snake Envenoming Blister Formation from Five Patients: Pathophysiological Insights

In the Brazilian Amazon, Bothrops atrox snakebites are frequent, and patients develop tissue damage with blisters sometimes observed in the proximity of the wound. Antivenoms do not seem to impact blister formation, raising questions regarding the mechanisms underlying blister formation. Here, we launched a clinical and laboratory-based study including five patients who followed and were treated by the standard clinical protocols. Blister fluids were collected for proteomic analyses and molecular assessment of the presence of venom and antivenom. Although this was a small patient sample, there appeared to be a correlation between the time of blister appearance (shorter) and the amount of venom present in the serum (higher). Of particular interest was the biochemical identification of both venom and antivenom in all blister fluids. From the proteomic analysis of the blister fluids, all were observed to be a rich source of damage-associated molecular patterns (DAMPs), immunomodulators, and matrix metalloproteinase-9 (MMP-9), suggesting that the mechanisms by which blisters are formed includes the toxins very early in envenomation and continue even after antivenom treatment, due to the pro-inflammatory molecules generated by the toxins in the first moments after envenomings, indicating the need for local treatments with anti-inflammatory drugs plus toxin inhibitors to prevent the severity of the wounds.     

The energy cost of level cross-country skiing and the effect of the friction of the ski

Summary Oxygen consumption [( ) in ml·kg^–1·min^–1], blood lactate concentration ([La] in mM) and dynamic friction of the skis on snow [(F) inN] were measured in six athletes skiing on a level track at different speeds [(v) in m·min^–1] and using different methods of propulsion. The increased withv andF, the latter depending mostly on snow temperature, as did [La]. The was very much affected by the skiing technique. Multiple regression equations gave the following results: with diagonal stride (DS), =–23.09+0.189v+0.62N; with double pole (DP), =–30.95+0.192v+0.51N; and with the new skating technique (S), =–32.63 +0.171+0.68N. In terms of DS is the most expensive technique, while S is the least expensive; however, asF increases, S, at the highest speed, tends to cost as much as DP. At speeds from 18 to 22 km·h^–1, the speeds measured in the competitions, theF for DS and DP can represent from 10% to 50% of the energy expenditure, withF ranging from 10 to 60N; with S this range increases to 20%–70%. This seems to depend on the interface between the skis and the snow and on the different ways the poles are used.     

A prospective,multicentre survey on antifungal therapy in neutropenic paediatric haematology patients

Invasive fungal infections are a frequent complication after intensive chemotherapy. The aims of this prospective study were to describe the use of antifungal therapy and to report which strategy was routinely adopted to guide the introduction of antifungal therapy. A total of 321 febrile episodes in 160 paediatric patients affected by acute leukaemia or non‐Hodgkin‐lymphoma were investigated. Antifungal therapy was used in 100 of 321 febrile episodes (31%), and classified as empiric in 73 episodes, diagnostic‐driven in 25 episodes and targeted in 2 episodes. Switching to a second‐line antifungal therapy was needed in 28 of 100 episodes (28%) and was classified as empiric in 10 episodes (36%), diagnostic‐driven in 17 episodes (61%) and targeted in 1 episode (4%). In 9 of 28 episodes (32%), switching to a third‐line antifungal therapy was performed and was classified as empiric in 2 episodes (22%), diagnostic‐driven in 6 episodes (67%) and targeted in 1 episode (11%). Invasive fungal infections was reported in 23 of 100 episodes: confirmed in 4 episodes, probable in 8 episodes, and possible in 11 episodes. Attributable mortality was 2.8%. Antifungal therapy was still used mostly empirically, whereas as fever persisted, its modification was guided by a diagnostic‐driven approach.     

Incidence, risk factors and clinical implications of venous thromboembolism in cancer patients treated within the context of phase I studies: the 'SENDO experience'

BackgroundTo investigate the incidence, risk factors and clinical implications of venous thromboembolism (VTE) in advanced cancer patients treated in phase I studies.Patients and methodsPatients enrolled and treated in phase I studies conducted by SENDO (Southern Europe New Drugs Organization) Foundation between 2000 and 2010 in 15 experimental centers were considered for the study. Clinical data, including adverse events, were prospectively collected during the studies and retrospectively pooled for VTE analysis.ResultsData of 1415 patients were considered for analysis. Five hundred and twenty-six (37.2%) patients were males, and median age was 57.3 years (range: 13–85). Eighty-five percent of patients had metastatic disease, while the remaining had locally advanced irresectable disease. For 706 (49.9%) of the patients, the study treatment was with cytotoxic agent(s) only, for 314 with target therapy(ies) only, while the remaining patients received a target therapy in combination with a cytotoxic drug. Fifty-six (3.96%) patients who developed a VTE, almost all (89.3%) during the course of treatment, the remaining during the follow-up. At univariate analysis, the Khorana score, the combination of an antiangiogenic agent with a cytotoxic drug, and the time from first cancer diagnosis to study entry (as continuous variable) were associated with a statistically significant increase of VTE occurrence. The multivariate analysis confirmed only a statistically significant association for the Khorana score. The hazard ratio of VTE occurrence was 7.88 [95% confidence interval (CI) 2.86–21.70) and 2.74 (95% CI 1.27–5.92) times higher for the highest (≥3) and intermediate (1–2) scores as compared with score = 0.ConclusionsVTE is a relatively common complication among patients treated in the context of phase I studies. The Khorana score predicts VTE development and can be used to identify patients at high of VTE.     

Human T-cell leukemia-lymphoma virus (HTLV): cloning of an integrated defective provirus and flanking cellular sequences.

Human T-cell leukemia-lymphoma virus (HTLV) is the first unequivocal human retrovirus. Seroepidemiological and virus isolation studies indicate that HTLV is etiologically associated with a subtype of adult T-cell malignancy. We have molecularly cloned approximately 1 kilobase of sequences derived from the 5' and 3' termini of the HTLV genome. Use of these clones as probes allowed isolation of a 9.8-kilobase EcoRI fragment from a genomic DNA library of an HTLV-infected neoplastic T-cell line (CR). Analysis of this clone revealed the presence of cellular sequences flanking approximately 5 kilobases of viral sequences including one long terminal repeat sequence. The 5' and 3' clones, as well as subclones derived from different regions of the genomic clone, were used as probes to compare integrated proviruses and viral RNA expression in different HLTV-infected neoplastic T cell lines. The results indicate that the infected cells are of clonal origin with respect to the virus integration sites and they express multiple viral mRNA species including a 35S RNA.     

Ocra Method: development of a new procedure for analysis of multiple tasks subject to infrequent rotation

In the Ocra methods (Ocra index and Ocra Checklist), when computing the final indices (Ocra index or checklist score), in the case of more than one repetitive task a "traditional" procedure was already proposed, the results of which could be defined as "time-weighted average". This approach appears to be appropriate when considering rotations among tasks that are performed very frequently, for instance almost once every hour (or for shorter periods). However, when rotation among repetitive tasks is less frequent (i.e. once every 1 1/2 or more hours), the "time-weighted average" approach could result in an underestimation of the exposure level (as it practically flattens peaks of high exposures). For those scenarios an alternative approach based on the "most stressful task as minimum" might be more realistic. This latter approach has already been included in the NIOSH approach for multiple sequential lifting tasks and, given the recent availability in the Ocra method of more detailed duration multipliers (practically one different Du(M) for each different step of one hour of duration of the repetitive task), it is now possible to define a particular procedure to compute the complex Ocra Multitask Index (cOCRA) and the complex Checklist Score (cCHESCO) for the analysis of two or more repetitive tasks when rotations are infrequent (rotations every 1 1/2 hours or more). The result of this approach will be at least equal to the index of the most stressful task considered for its individual daily duration and at the most equal to the index of the most stressful task when it is (only theoretically) considered as lasting for the overall daily duration of all examined repetitive tasks. The procedure is based on the following formula: Complex Ocra Multitask Index = Ocra(1(Dum1) + (Delta ocra1xK) where 1,2,3,...,N = repetitive tasks ordered by ocra index values (1 = highest; N = lowest) computed considering respective real duration multipliers (Dum(i)). ocra1 = ocra index of task, considering Dum(1). Dum(i) = duration multiplier for task(i) real duration. Dum(tot) = duration multiplier for total duration of all repetitive tasks. delta ocra1 = highest ocra index among N tasks considering Dum(tot) (ocra(i max)) - ocra index of task1 considering Dum1. K = (ocra(1 max)*FT1) + (ocra(2 max)*FT2) + ... + (ocra (N)*FT(N)) over (ocra(i max)). ocral,Nm(1,N MAX) = index of tasks 1 to Ncons idering Dum,, (tot)7=Fr(i) c tion of Time (values from 0 to 1) of task; wi(i)h respect to the total repetitive time.     

Reciprocal regulation of calcium‐/phosphate‐regulating hormones in cyclists during the Giro d'Italia 3‐week stage race

Calcium and phosphate are essential for cell functions, and their serum concentrations result from the balance between intestinal absorption, bony storage, and urinary excretion. Fibroblast growth factor 23 (FGF23), expressed by osteocytes and osteoblasts, acts in the kidney, leading to hypophosphatemia and low 1,25‐dihydroxycholecalciferol synthesis, but suppresses parathyroid function. The aim of this study was to explore the effects of a high‐energy demanding cycling race on this bone–kidney–parathyroid axis. We studied nine cyclists during the 2011 Giro d'Italia stage race. Pre‐analytical and analytical phases followed academic and anti‐doping recommendations. Serum parathyroid hormone (PTH), 25(OH)D, total calcium, inorganic phosphorus, and plasma FGF23 were measured on days ?1, 12, and 22 and corrected for changes in plasma volume. Dietary calcium and phosphorus, anthropometric parameters (height, weight, and body mass index) and indexes of metabolic effort (net energy expenditure, power output) were recorded. Dietary calcium and phosphorus intakes were kept at the same levels throughout the race. Twenty‐five (OH)D, PTH, and calcium concentrations remained stable. FGF23 increased 50% with a positive correlation with the indexes of metabolic effort and, consequently, phosphorous decreased, although only in the first half. The strong metabolic effort acts on the bone–kidney–parathyroid system, and the rise in FGF23 plasma concentration might be aimed at maintaining calcium and phosphorus homeostasis.     

A world apart: Inaccuracies of laboratory methodologies in antidoping testing

Antidoping testing is currently exclusively based on haematochemical analysis performed in specialized laboratories accredited by WADA (World Anti-Doping Agency). Many of the analytical methods used for the determination of the parameters considered, such as haematological parameters (haemoglobin, haematocrit and reticulocytes), proteins (soluble transferrin receptor and hepcidin) and hormones (erythropoietin and growth hormone) are often affected by lack of clear standardization and harmonization. The observed incongruity of the data deriving from different laboratories often results in the risk of false positive results in athletes.This review wants to provide additional proofs in support of the need to improve the antidoping methodology involving different research and clinical institutions and skills.