Does the adolescent patellar tendon respond to 5 days of cumulative load during a volleyball tournament?

Patellar tendinopathy (jumper's knee) has a high prevalence in jumping athletes. Excessive load on the patellar tendon through high volumes of training and competition is an important risk factor. Structural changes in the tendon are related to a higher risk of developing patellar tendinopathy. The critical tendon load that affects tendon structure is unknown. The aim of this study was to investigate patellar tendon structure on each day of a 5-day volleyball tournament in an adolescent population (16-18 years). The right patellar tendon of 41 players in the Australian Volleyball Schools Cup was scanned with ultrasound tissue characterization (UTC) on every day of the tournament (Monday to Friday). UTC can quantify structure of a tendon into four echo types based on the stability of the echo pattern. Generalized estimating equations (GEE) were used to test for change of echo type I and II over the tournament days. Participants played between eight and nine matches during the tournament. GEE analysis showed no significant change of echo type percentages of echo type I (Wald chi-square = 4.603, d.f. = 4, P = 0.331) and echo type II (Wald chi-square = 6.070, d.f. = 4, P = 0.194) over time. This study shows that patellar tendon structure of 16-18-year-old volleyball players is not affected during 5 days of cumulative loading during a volleyball tournament.

[Ouabain induces Rho-dependent rock activation and membrane blebbing incultured endothelial cells].

Small G protein Rho and its most studied effectors, ROCK I and ROCK II, are involved in several cellular fuctions including smooth muscle and non-muscle cell contractions, cell migration and apoptosis. Activation of ROCK I by caspase-3 and activation of ROCK II by granzyme B are essential for membrane blebbing in the execution phase of apoptosis. In contrast, it has been demonstrated that Rho signaling is critical for blebbing developed after serum removal. As it was shown by us previously, ouabain induces membrane blebbing and proteolitic cleavage of ROCK I and ROCK II via caspases in human umbilical endothelial cells. However, caspase inhibitors do not prevent ouabain-induced blebs. Ouabain induces concentration-dependent cell death and membrane blebbing in endothelial cells. The aim of this study was to identify the possible role of Rho in ouabain-induced membrane blebbing. Pretreatment of endothelial cells with a Rho inhibitor CT04 did not inhibit the ouabain-induced cell death but prevented the development ofbleb formation. These results indicate that bleb formation is dependent on Rho activity in ouabain-induced cell death in HUVECs. Taken together, these results suggest that the mechanism of membrane bleb formation might be different depending on cell type and cell death-stimuli.

Risk factors for patellar tendinopathy in basketball and volleyball players: a cross-sectional study.

Patellar tendinopathy (PT) has a multifactorial etiology, and many possible risk factors have been described in the literature. The findings are conflicting, though, and most research has been conducted on elite athletes. The aim of the current study is to determine the risk factors for PT in a large representative sample of basketball and volleyball players. Separate risk factors for men and women, basketball and volleyball players, and athletes with unilateral and bilateral PT were identified. All basketball and volleyball players between ages 18 and 35 from the Dutch Basketball Association and the Dutch Volleyball Association were invited to complete an online questionnaire on knee complaints and risk factors for PT. The logistic regression analyses included 2224 subjects. The risk factors for PT were age, playing at the national level, being male and playing volleyball (compared with playing basketball). The risk factors for men and women were comparable. Among volleyball players, outside hitters and middle blockers/hitters had an increased risk compared with setters. For basketball players, no risk factors could be identified. No differences in the risk factors were found between athletes with unilateral and bilateral PT. These findings should be taken into account for prevention and rehabilitation purposes.

Rho-associated protein kinase II (rock II) expression in normal and preeclamptic human placentas.

Rho-associated kinases are serine/threonine kinases that have several functions which might contribute to various physiological and pathological states in cells. There are two isoforms of these enzymes known as rho-associated kinase I (rock I, ROKbeta) and II (rock II, ROKalpha). It has been shown that rock II may be a potential mediator of apoptosis. In addition, rocks play a crucial role in the formation of microvilli-like structures. Increased placental apoptosis and microvilli shedding were shown in preeclampsia. We hypothesized that altered rock expression may lead to the pathologies seen in preeclampsia. Therefore in this study we compared placental rock II expression between normotensive and preeclamptic women using immunohistochemistry and Western blot. Immunohistochemistry and Western blot experiments revealed that rock II is mainly localized in syncytiotrophoblast cells of the placental villi and increased in preeclampsia. In addition to 160 kDa rock II molecule we also detected biologically relevant smaller active form of rock II in preeclamptic but not in normal placentas. We suggest that increased rock II expression in preeclamptic placentas may contribute to etiology or pathogenesis of this syndrome. However, it is considered that rock II expression may also increase to compensate for placental functions changing in preeclampsia.

Nitric oxide production by human umbilical vessels in severe pre-eclampsia.

OBJECTIVE: Pre-eclampsia is characterized by an increased vascular tone which might be related to an abnormal endothelial cell function. As representatives of the fetal circulation, we compared the nitric oxide (NO)-releasing capacity of human umbilical vessels from normal and pre-eclamptic pregnancies. METHODS: Normal and pre-eclamptic umbilical vessels were mounted in parallel in an organ chamber with three perfusion lines superfusing the same detector tissue (rubbed rat aortic ring). In this cascade system the capacity of the umbilical vessels to release NO was measured under basal conditions and after stimulation with histamine, bradykinin or calcium ionophore A23187. RESULTS: Relaxations dependent on basal NO release were found to be significantly higher in pre-eclamptic vessels (especially in veins) than in normal vessels. Conversely, stimulated NO release in response to histamine or bradykinin was significantly decreased in pre-eclamptic umbilical arteries, but not in veins, compared with normal vessels. However, there was no significant difference in the release of NO in response to A23187 between normal and pre-eclamptic vessels. CONCLUSIONS: The NO-releasing and NO-producing capacity in the vessels from fetal circulation is not diminished in pre-eclampsia. However, in pre-eclamptic umbilical arteries the NO release in response to certain stimuli (histamine or bradykinin) is diminished, probably as a result of alterations in the receptor function.

An exercise-based physical therapy program for patients with patellar tendinopathy after platelet-rich plasma injection.

OBJECTIVES: To describe a post platelet-rich plasma (PRP) injection, exercise-based physical therapy program, investigate feasibility and report the first results of patellar tendinopathy patients treated with PRP injection combined with the physical therapy program. STUDY DESIGN: Case-series. SETTING: A PRP injection followed by a physical therapy program seems promising for the treatment of patellar tendinopathy. However, descriptions of physical therapy programs are often limited and incomplete. PARTICIPANTS: Five patellar tendinopathy patients (six tendons) in the degenerative phase. MAIN OUTCOME MEASURE: VISA-P score. RESULTS: Muscle strength, endurance, power and retraining sport-specific function form the basis for the physical therapy program aiming to improve the load capacity of the knee. The program is characterised by gradually increasing intensity and difficulty of exercises. Five of the six tendons showed an improvement of at least 30 points on the VISA-P after 26 weeks. CONCLUSIONS: This study extensively describes, based on current knowledge, a physical therapy program after PRP injection for patellar tendinopathy patients. The combination treatment reported in this study is feasible and seems to be promising for patients in the late/degenerative phase of patellar tendinopathy.

Endothelium-dependent induction of vasorelaxation by Melissa officinalis L. ssp. officinalis in rat isolated thoracic aorta.

In the current study, vasorelaxant effect produced by the aqueous extract of Melissa officinalis L. ssp. officinalis (MOO) (Lamiaceae) and its possible mechanism in isolated rat aortic rings precontracted with phenylephrine were examined. In the first series of experiments, effect of MOO on the baseline and phenylephrine (10(-5)M) precontracted arteries was investigated, while in the second group of experiments, endothelium intact or endothelium denuded effect was determined. The agents used were N(omega)-nitro-L-arginine (L-NAME), an irreversible inhibitor of nitric oxide (NO) synthase, indomethacin (10 microM), a cyclooxygenase (COX) inhibitor, and glibenclamide (10 microM), an ATP-sensitive potassium channel blocker. The extract was found to exert a vasorelaxant effect and rosmarinic acid quantity, the characteristic compound of the plant, was analyzed by reversed-phase high-performance liquid chromatography (18.75%), and was further confirmed by LC-MS analysis giving a prominent [M(+1)] molecular ion peak at m/z 365. Total phenol amount in the extract was determined using Folin-Ciocalteau reagent (0.284 mg/mg extract). Vasorelaxant effect of the extract was entirely dependent on the presence of endothelium and was abolished by pretreatment with L-NAME, whereas pretreatment with indomethacin and glibenclamide reduced the relaxation to a minor extent. Rosmarinic acid was also tested in the same manner as the extract and was found to exert vasorelaxant effect. These results suggest that the aqueous extract of MOO vasodilates via nitric oxide pathway with the possible involvement of prostacycline and endothelium-derived hyperpolarizing factor (EDHF) pathways as well.

A newly described scorpion species, Leiurus abdullahbayrami (Scorpion: Buthidae), and the lethal potency and in vivo effects of its venom

Currently, medically significant scorpion species belong to the Buthidae family and are represented by the genera Androctonus, Buthus, Mesobuthus, Hottentotta, Parabuthus, Tityus, Centruroides, Leiurus. Although Leiurus was originally considered a monotypic genus, four additional species have since been described. Leiurus abdullahbayrami (previously identified as L. quinquestriatus in Turkey) was classified as a new Leiurus species. This is the first report conducted on the lethality and biologic effects of L. abdullahbayrami scorpion venom in mice. In this study, the electrophoretic protein pattern of its venom was also determined. Two protein bands with molecular masses of 4 and 6 kDa were more strongly detected than other protein bands in the venom sample. Electrophoresis showed that L. abdullahbayrami scorpion venom possesses both short- and long-chain neurotoxins. The median lethal dose of this venom was found to be 0.19 mg/kg by subcutaneous (SC) injection in mice. Animals experimentally envenomed with L. abdullahbayrami venom exhibited hyperexcitability, agitation, aggressive behavior, squeaking and fighting, tachypnea, weakness, convulsions, and death due to cardiac and respiratory failure. In further studies, the potency of antivenom should be investigated in relation to the scorpion venom. Molecular and pharmacological studies are also required to identify and characterize L. abdullahbayrami scorpion venom.(AU)

Does prevention of free radical reactions influence digoxin-arrhythmias?

In the present study, the possible role of oxygen-derived free radicals (OFR) on digoxin- (0.6 mg/kg(-1) IV bolus) induced arrhythmias of anesthetized guinea-pigs has been investigated. Guinea-pigs (300400 g) of either sex were anesthetized with urethane (1.5 g/kg(-1),IP), and their trachea for respiration, left common carotid artery for blood pressure monitoring, and right jugular vein for drug administration were cannulated. ECG and haemodynamics were recorded throughout the experiments. None of the agents used [N-acetyl-L-cysteine (20 mg/kg(-1)IV bolus), or SOD (30,000 IU/kg(-1) IV bolus) + catalase (15,000 IU/kg(-1) IV bolus)] significantly inhibited the arrhythmias except desferrioxamine which reduced the incidence of ventricular fibrillation and arrhythmia score. Desferrioxamine, by acting intracellularly unlike other agents used, might prevent the reduction of Fe(+3) by ascorbate and superoxide anion thus inhibiting the formation of cytotoxic hydroxyl radical in this experimental setting.

Effects of cyclooxygenase and lipoxygenase inhibitors on digoxin-induced arrhythmias and haemodynamics in guinea-pigs.

Effects of cyclooxygenase and lipoxygenase inhibitors of digoxin-induced arrhythmias and haemodynamics were studied in guinea-pigs. ECG, mean arterial blood pressure heart rate, pressure rate index and arrhythmias were recorded, starting 15 min before digoxin administration and continuing for 30 min afterwards. The cyclooxygenase inhibitor aspirin (50 mg kg-1) and the dual cyclooxygenase/lipoxygenase inhibitor BW 755C (0.25-10.0 mg kg-1) were found to produce a significant protection against the arrhythmias, whereas aspirin (100 mg kg-1) and CGS 8515 were found to be ineffective. SK&F 104 353, a potent and selective peptidoleukotriene receptor antagonist significantly attenuated the arrhythmias and mortality in a dose-dependent manner. It is concluded that production of both cyclooxygenase and lipoxygenase metabolites could favour the occurrence and/or the maintenance of digoxin-induced cardiac toxicity.