The contribution of bovine Factor V and Factor Va to the activity of prothrombinase.

The rates of prothrombin activation under initial conditions of invariant concentrations of prothrombin and Factor Xa were studied in the presence of various combinations of Ca2+, homogeneous bovine Factor V, Factor Va, phosphatidylcholine-phosphatidylserine vesicles, and activated bovine platelets. Reactions were monitored continuously through the enhanced fluorescence accompanying the interaction of newly formed thrombin with dansylarginine-N-(3-ethyl-1,5-pentanediyl) amide. The complete prothrombinase (Factor Xa, Ca2+, phospholipid, and Factor Va) behaved as a "typical" enzyme and catalyzed the activation of prothrombin with an apparent Vmax of 2100 mol of thrombin/min/mol of Factor Va or Factor Xa, whichever was the rate-limiting component. Regardless of whether the enzymatic complex was composed of Factor Xa, Ca2+, and plasma Factor Va plus phospholipid vesicles, or activated platelets in the place of the latter components, similar specific activity values were observed. The combination of Factor Va, Ca2+, and phospholipid enhanced the rate of the Factor Xa-catalyzed activation of prothrombin by a factor of 278,000. Factor Va itself when added to Factor Xa, Ca2+, and phospholipid, enhanced the rate of prothrombin activation by a factor of 13,000. Unactivated Factor V appears to possess 0.27% of the procoagulant activity of thrombin-activated Factor Va. From the kinetics of prothrombinase activity, an interaction between Factor Xa and both Factor V and Factor Va was observed, with apparent 1:1 stoichiometries and dissociation constants of 7.3 x 10(-10) M for Factor Va and 2.7 x 10(-9) M for Factor V. The present data, combined with data on the equilibrium binding of prothrombinase components to phospholipid, indicate that the model prothrombinase described in this paper consists of a phospholipid-bound, stoichiometric complex of Factor Va and Factor Xa, with bound Factor Va serving as the "binding site" for Factor Xa, in concert with its proposed role in platelets.     

Effect of temperature on RNA synthesis in Escherichia coli CRT 266 (dna Bts) following infection with bacteriophage T3]

Infection of the temperature-sensitive E. coli CRT 266 (dnaBts) with T3-phages at the temperature of 30 degrees C and 35 degrees C, respectively, induced T3-specific RNA synthesis with a maximum rate at 7 min (30 degrees C) and 4.5 min (35 degrees C) after infection. At temperatures above 40 degrees C no T3-induced RNA synthesis could be observed. Infection of E. coli CR 34--45 (dnaB+) with T3 phages at 30 degrees C, 35 degrees C and at temperatures above 40 degrees C, however, produced T3-specific RNA synthesis. The maximum of T3-induced RNA synthesis could be observed between 7 min and 3 min depending on the temperature during infection. The inability to form T3-specific RNA after infection of E. coli CRT 266 at nonpermissive temperatures may be a cause for the absence of the formation of T3 phages and lysis of the host cells.     

New mechanical aid to physiotherapy in cystic fibrosis.

The force of impact and frequency of percussion by physiotherapists and parents of children with cystic fibrosis were analysed on a special test rig and incorporated in a prototype percussor. In adult volunteers and cadavers a maximum intrathoracic pressure could be achieved by a critical frequency of mechanical percussion which was higher than that reached by physiotherapists and parents. Consequently the percussor was redesigned to operate at this optimum frequency. It was then discovered that if the percussor was pressed firmly enough against the chest, this maximum intrathoracic pressure could be indicated by quivering of the voice. In a continuing study of intrathoracic pressures obtained mechanically and manually the Salford percussor''s produced higher pressures than the physiotherapists'' and maintained them constantly, while the physiotherapists'' efforts and results varied from one to another. Hospital and domiciliary use of the percussor have shown it to help in the first stage of the physiotherapy routine for patients with cystic fibrosis. The percussor should enable adolescents and adults to treat themselves and encourage twice-daily and more effective chest treatments. It is easy to apply and its speed and efficiency should enable parents to improve the quality of their chest therapy for younger children at home. Its long-term benefits are difficult to assess because of the nature of the disease.     

Laser light-scattering investigations of the teleost swimbladder response to acoustic stimuli.

When a laser pencil is directed through the teleost swimbladder fringe patterns can be seen in the far-field that are (a) highly sensitive to the orientation and position of the swimbladder with respect to the incident pencil and (b) a representation of contributions from each membrane through which the light passes. The fringe pattern fluctuates in intensity, and to some extent in position, in response to driving forces that distort the swimbladder. The spectrum of these very small distortions can be measured by standard light scattering techniques. This method was used to study the response of in situ swimbladders to imposed acoustic fields and evidence for a sharp roll-off of the response at frequencies above 1,000 Hz was found. Models for these effects are discussed.     

Cyclin D1 and cyclin D3 show divergent responses to distinct mitogenic stimulation

D‐type cyclins predominantly regulate progression through the cell cycle by their interactions with cyclin‐dependent kinases (cdks). Here, we show that stimulating mitogenesis of Swiss 3T3 cells with phorbol esters or forskolin can induce divergent responses in the expression levels, localization and activation state of cyclin D1 and cyclin D3. Phorbol ester‐mediated protein kinase C stimulation induces S phase entry which is dependent on MAPK activation and increases the levels and activation of cyclin D1, whereas forskolin‐mediated cAMP‐dependent protein kinase A stimulation induces mitogenesis that is independent of MAPK, but dependent upon mTor and specifically increases the level and activation of cyclin D3. These findings uncover additional levels of complexity in the regulation of the cell cycle at the level of the D‐type cyclins and thus may have important therapeutic implications in cancers where specific D‐cyclins are overexpressed. J. Cell. Physiol. 225: 638–645, 2010. © 2010 Wiley‐Liss, Inc.     

The relation of life to electricity

Conclusions and summary The experiments described in this paper tend to show that the relation between stainability and electromotive forces: + basophilic substance / acidophilic substance — holds not only for fats but likewise for esters, alcohols, hydrocarbons, etc., in short for a large number of substances which bear just a remote relationship to tissue constitutents. Exceptions to this rule are very rare and are hardly found prevailing in tissue.In these experiments esters, alcohol, and other substances were rendered basophilic by the addition of a water insoluble acid or else acidophilic by the addition of a water insoluble base; measurements of the electromotive force were made. The system measured was the following: The measurements were performed by combining each ester, alcohol, or other fluid with phenol using the apparatus described in part I of this report. The difference between two such measurements may be considered to be the electromotive force of such a cell. This was demonstrated previously be means of measurements with triacetin. The reason for this is that the electromotive forces of such battery systems, as those described, are located almost entirely at the phase boundary between the aqueous solution and the water immiscible fluid.To Dr. G. W.Crile the writers wish to express their appreciation for his kind interest in the progress of this work.     

Early Social Networks Predict Survival in Wild Bottlenose Dolphins

A fundamental question concerning group-living species is what factors influence the evolution of sociality. Although several studies link adult social bonds to fitness, social patterns and relationships are often formed early in life and are also likely to have fitness consequences, particularly in species with lengthy developmental periods, extensive social learning, and early social bond-formation. In a longitudinal study of bottlenose dolphins (Tursiops sp.), calf social network structure, specifically the metric eigenvector centrality, predicted juvenile survival in males. Additionally, male calves that died post-weaning had stronger ties to juvenile males than surviving male calves, suggesting that juvenile males impose fitness costs on their younger counterparts. Our study indicates that selection is acting on social traits early in life and highlights the need to examine the costs and benefits of social bonds during formative life history stages.