Theory in motion

Modeling studies are now a significant part of mainstream research in motor control. Novel and classical modeling techniques used in recent work on small and large motor systems illustrate the different roles that models play in furthering our understanding of motor systems. The models presented reveal single neuron short-term memory, unexpected effects of reciprocal inhibition and methods for decoding activity in large populations of neurons.     

LAITOR - Literature Assistant for Identification of Terms co-Occurrences and Relationships

Background  

Biological knowledge is represented in scientific literature that often describes the function of genes/proteins (bioentities) in terms of their interactions (biointeractions). Such bioentities are often related to biological concepts of interest that are specific of a determined research field. Therefore, the study of the current literature about a selected topic deposited in public databases, facilitates the generation of novel hypotheses associating a set of bioentities to a common context.     

大鼠放射性肺损伤模型的建立与动态观察

目的：建立并鉴定大鼠放射性肺损伤模型,摸索大鼠放射性肺损伤的病理变化规律,阐明氧化应激在其发生发展过程中的作用。方法：采用60Co源22Gy单次照射SD大鼠全肺。分别于照射前、照后1天,7天,15天,21天,30天,60天,120天活杀大鼠,计算肺系数,右肺行HE染色、Masson染色及天狼猩红染色,观察肺组织病理变化并对大鼠肺泡炎及纤维化程度进行评分,免疫组化法检测肺组织廿SMA表达情况;左肺进行羟脯氨酸含量测定;血清测定MDA含量、总SOD活力和TGF-β1含量。结果：（1）大鼠肺脏于照后15天开始出现明显大体改变,病理学表现为间质性渗出性炎症并随时间延长逐渐加重,照后60天至120天肺脏塌陷,表面可见纤维化病灶,病理改变以肺间隔内细胞增生和胶原纤维沉积为主;（2）血清T-SOD活力照后1天至7天短暂增加后其活力持续降低;血清MDA含量和TGF-β1含量随时间时间延长逐渐增高;（3）照后60天肺组织a-SMA表达明显增加,至照后120天最为显著。结论：成功建立了大鼠放射性肺损伤模型并阐述了其病理变化规律;氧化应激参与了放射性肺损伤的病理过程。为其防治提供了实验基础和理论依据。     

Influence of a natural and a synthetic inhibitor of factor XIIIa on fibrin clot rheology

We investigated the origins of greater clot rigidity associated with FXIIIa-dependent cross-linking. Fibrin clots were examined in which cross-linking was controlled through the use of two inhibitors: a highly specific active-center-directed synthetic inhibitor of FXIIIa, 1,3-dimethyl-4,5-diphenyl-2[2(oxopropyl)thio]imidazolium trifluoromethylsulfonate, and a patient-derived immunoglobulin directed mainly against the thrombin-activated catalytic A subunits of thrombin-activated FXIII. Cross-linked fibrin chains were identified and quantified by one- and two-dimensional gel electrophoresis and immunostaining with antibodies specific for the alpha- and gamma-chains of fibrin. Gamma-dimers, gamma-multimers, alpha(n)-polymers, and alpha(p)gamma(q)-hybrids were detected. The synthetic inhibitor was highly effective in preventing the production of all cross-linked species. In contrast, the autoimmune antibody of the patient caused primarily an inhibition of alpha-chain cross-linking. Clot rigidities (storage moduli, G') were measured with a cone and plate rheometer and correlated with the distributions of the various cross-linked species found in the clots. Our findings indicate that the FXIIIa-induced dimeric cross-linking of gamma-chains by itself is not sufficient to stiffen the fibrin networks. Instead, the augmentation of clot rigidity was more strongly correlated with the formation of gamma-multimers, alpha(n)-polymers, and alpha(p)gamma(q)-hybrid cross-links. A mechanism is proposed to explain how these cross-linked species may enhance clot rigidity.     

Sequence of a cDNA for mouse thymidylate synthase reveals striking similarity with the prokaryotic enzyme

We report the nucleotide sequence of a cloned cDNA, pMTS-3, that contains a 1-kb insert corresponding to mouse thymidylate synthase (E.C. 2.1.1.45). The open reading frame of 921 nucleotides from the first AUG to the termination codon specifies a protein with a molecular mass of 34,962 daltons. The predicted amino acid sequence is 90% identical with that of the human enzyme. The mouse sequence also has an extremely high degree of similarity (as much as 55% identity) with prokaryotic thymidylate synthase sequences, indicating that thymidylate synthase is among the most highly conserved proteins studied to date. The similarity is especially pronounced (as much as 80% identity) in the 44-amino-acid region encompassing the binding site for deoxyuridylic acid. The cDNA sequence also suggests that mouse thymidylate synthase mRNA lacks a 3' untranslated region, since the termination codon, UAA, is followed immediately by a poly(A) segment.      

Buchbesprechungen

Ohne Zusammenfassung     

Physiological comparisons between aquatic resistance training protocols with and without equipment

The purpose of the present study was to compare the physiological responses of oxygen uptake (VO(2)) and energy expenditure (EE) in two different aquatic resistance training protocols performed with three sets of 20 seconds (3 × 20) and six sets of 10 seconds (6 × 10) and with and without Speedo Resistance Equipment. Ten young healthy women volunteers, familiar with exercises in an aquatic environment, participated in this study. The four separate protocols were randomly selected and performed at a 48-hour interval by the same instructor. The total time of the 3 × 20 protocol was 34 minutes and that of the 6 × 10 protocol was 43 minutes, and all exercises were performed at maximal speed and amplitude. Although the protocols had different total times, they included one minute of stimulus per muscle group and the same time intervals. EE(gross) and EE(net) values were higher in the 6 × 10 protocol than in the 3 × 20 one. The variables VO(2) and EE(min) did not present significant difference between the protocols. VO(2), EE(gross), EE(net) and EE(min) values were higher when the equipment was used (W situation) than when it was not (WO situation). In the postexercise analysis, the W situation also showed higher VO(2) and EE(gross) values than the WO situation. Therefore, this study suggests the use of Speedo Resistance Equipment to increase VO(2) and EE, and it also suggests lengthier aquatic resistance training to obtain greater EE values per session.     

Cocontraction and economy of triathletes and cyclists at different cadences during cycling motion

The purpose of this study was to compare the cycling technique of triathletes and cyclists on the basis of the cocontraction of selected muscles of the lower limbs and economy at different cadences. The economy (EC) and percent cocontraction from nine triathletes and eight cyclists were compared at 60, 75, 90 and 105 rpm cadences. Tests were performed on two separate days. The maximal oxygen uptake was measured and the second ventilatory threshold (VO_2VT) was estimated on the first day using a stationary bicycle. On the second day the four different cadences were tested at approximately 5% below the VO_2VT. The EMG activity of the rectus femoris (RF), biceps femoris (BF) and vastus lateralis (VL) was recorded and the EMG signal was normalized using the 60 rpm dynamic contraction. The percent cocontractions were calculated from RF/BF and VL/BF muscles. The EC was also calculated. The results showed that cyclists were significantly more economic, indicating that they exerted more power with less VO₂, and presented significantly lower percent cocontraction than triathletes (p < 0.05). Thus, the results suggest that the cyclists had a better technique than the triathletes. The simultaneous use of the percent cocontraction and economy seems to be a good performance indicator for cyclists and triathletes.