This study shows that at low hematocrit, the oxygen-delivering capacity of human red blood cells stored 5-6 wks is reduced compared with fresh cells and red blood cells stored for an intermediate period. Although red blood cells stored for 2-3 wks are completely devoid of 2,3-diphosphoglycerate, their oxygen-delivering capacity to the intestines was the same as fresh red blood cells. Our study showed that red blood cell deformability was preserved during storage, suggesting that other mechanisms may account for the observed decrease in oxygen delivery by red blood cells stored 2-3 wks.

In the present study we investigated the role of the fibronectin (FN)-and fibrinogen (FGN)-binding protein (FBPS) in the pathogenesis of Streptococcus suis serotype 2 in piglets. The complete gene encoding FBPS from S. suis serotype 2 was cloned in Escherichia coli and sequenced. The occurrence of the gene in various serotypes was analyzed by hybridization studies. The FBPS protein was expressed in E. coli and purified, and binding to human FN and FGN was demonstrated. The induction of antibodies in piglets was studied upon infection. An isogenic mutant unable to produce FBPS was constructed, and the levels of virulence of the wild-type and mutant strains were compared in a competitive infection model in young piglets. Organ cultures showed that FBPS was not required for colonization of the tonsils but that FBPS played a role in the colonization of the specific organs involved in an S. suis infection. Therefore, the FBPS mutant was considered as an attenuated mutant.Streptococcus suis causes severe infections in piglets. The bacterial infections include meningitis, septicemia, and arthritis, and the animals often do not survive the infection (6, 28). Occasionally, S. suis causes septicemia and meningitis in humans (3). The pathogenesis of an S. suis infection is rarely understood. Sows are symptomless carriers of S. suis on their tonsils and pass the bacteria on to their piglets. The piglets cannot cope with the bacterium and subsequently develop the specific symptoms of an S. suis infection. Until now, 35 capsular serotypes of S. suis have been described (26), but serotype 2 strains are most often isolated from diseased piglets. Capsule is an important virulence factor, since piglets infected with an acapsular mutant of S. suis serotype 2 strains do not develop any clinical symptoms (22). Bacterial proteins have been suggested to play a role in the pathogenesis as well (1,26). The expression of muramidase-released protein (MRP), extracellular factor (EF), and suilysin was shown to be strongly associated with pathogenic strains of S. suis serotype 2 (2, 29, 30). Since isogenic mutants lacking MRP and EF and isogenic mutants lacking suilysin were still pathogenic for young piglets, these proteins are not absolutely required for virulence (1,23). Recently, a new virulence factor was identified (21) by using a complementation approach. The function of this virulence factor in the pathogenesis has to be further investigated.Many important virulence factors are environmentally regulated and are induced at specific stages of the infection process (15). To identify these genes in S. suis, we cloned promoters and their downstream sequences that are "on" during experimental S. suis infection of piglets (20). Twenty-two in vivo-selected (ivs) genes were found. Two of the ivs genes were directly linked to virulence, since homology to genes in the database that encode for known virulence factors was found. One of these ivs genes (ivs-21) was identical to the epf gene of virulent S. suis serotype 2 strains (30). The other (i...

UV-C irradiation has been shown to be effective for pathogen reduction in platelet concentrates, but preliminary work indicated that UV-C irradiation of platelets can induce platelet aggregation. In this study, the mechanism underlying this phenomenon was investigated. Irradiation of platelets with UV-C light (1500 J/m 2 ) caused platelet aggregation, which was dependent on integrin ␣IIb␤3 activation (GPIIb/IIIa). This activation occurred despite treatment with several signal transduction inhibitors known to block platelet activation. UV-C also induced activation of recombinant ␣IIb␤3 in Chinese hamster ovary (CHO) cells, an environment in which physiologic agonists fail to activate. Activation of ␣IIb␤3 requires talin binding to the ␤3 tail, yet ␣IIb␤3-⌬724 (lacking the talin binding site) was activated by UV-C irradiation, excluding a requirement for talin binding. The UV-C effect appears to be general in that ␤ 1 and ␤ 2 integrins are also activated by UV-C. To explain these findings, we investigated the possibility of UV-C-induced photolysis of disulfide bonds, in analogy with the activating effect of reducing agents on integrins. Indeed, UV-C induced a marked increase in free thiol groups in platelet surface proteins including ␣IIb␤3. Thus, UV-C appears to activate ␣IIb␤3 not by affecting intracellular signal transduction, but by reduction of disulfide bonds regulating integrin conformation. (Blood. 2008;112:4935-4939) IntroductionViral and, especially, bacterial contamination of platelet concentrates remains an issue for platelet transfusions. 1 To minimize contamination of blood platelets, several pathogen reduction approaches have been developed that rely on irradiation with ultraviolet light (UV) in combination with a photosensitizer. [2][3][4] Recently, the possibility of using UV-C light without the addition of an exogenous sensitizer has been explored. 5,6 This approach uses UV-C at a wavelength of 254 nm, which is highly absorbed by nucleic acids, resulting in cyclobutane pyrimidine dimer formation and DNA degradation. 7,8 Since no photosensitizer needs to be added to the platelet concentrate, UV-C-based pathogen inactivation should be easier to implement in existing blood bank procedures.UV-based pathogen reduction in blood platelets has a few drawbacks, as some properties of platelets are affected by UV irradiation. Van Marwijk and colleagues observed that UV-B irradiation resulted in increased fibrinogen binding to platelets. 9 Furthermore, the UV-B-induced aggregation appeared to be dependent on PKC activation, signifying an important role for platelet signaling in UV-B-mediated activation of integrin ␣IIb␤3, the receptor binding fibrinogen.As a member of the integrin family, ␣IIb␤3 consists of a large type I transmembrane ␣/␤ heterodimer, which is capable of bidirectional signaling through the plasma membrane. On unstimulated platelets, ␣IIb␤3 resides in an inactive conformation on the plasma membrane, but it is rapidly switched to an "on" state when the platelet becomes activated after stimula...