Survival processing eliminates collaborative inhibition.

The present experiments examined the effect of processing words for their survival value, relevance to moving and pleasantness on participants' free recall scores in both nominal groups (non-redundant pooled individual scores) and collaborative dyads. Overall, participants recalled more words in the survival processing conditions than in the moving and pleasantness processing conditions. Furthermore, nominal groups in both the pleasantness condition (Experiment 1) and the moving and pleasantness conditions (Experiment 2) recalled more words than collaborative groups, thereby replicating the oft-observed effect of collaborative inhibition. However, processing words for their survival value appeared to eliminate the deleterious effects of collaborative remembering in both Experiments 1 and 2. These results are discussed in the context of the retrieval strategy disruption hypothesis and the effects of both expertise and collaborative skill on group remembering.

Surveillance of alloantibodies after transplantation identifies the risk of chronic rejection.

The monitoring of the levels of alloantibodies following transplantation might facilitate early diagnosis of chronic rejection (CR), the leading cause of renal allograft failure. Here, we used serial alloantibody surveillance to monitor patients with preoperative positive flow cytometric crossmatch (FCXM). Sixty-nine of 308 renal transplant patients in our center had preoperative positive FCXM. Blood was collected quarterly during the first postoperative year and tested by FCXM and single antigen bead luminometry, more sensitive techniques than complement-dependent cytotoxic crossmatching. Distinct post-transplant profiles emerged and were associated with different clinical outcomes. Two-thirds of patients showed complete elimination of FCXM and solid-phase assay reactions within 1 year, had few adverse events, and a 95% 3-year graft survival. In contrast, the remaining third failed to eliminate flow FCXM or solid-phase reactions directed against HLA class I or II antibodies. The inferior graft survival (67%) with loss in this latter group was primarily due to CR. Thus, systematic assessment of longitudinal changes in alloantibody levels, either by FCXM or solid-phase assay, can help identify patients at greater risk of developing CR.

Postmortem CT findings of gastromalacia: a trap for the radiologist with forensic interest.

Autolytic rupture of the stomach, so called gastromalacia, is a well recognized artifact at autopsy. A 50 year old Asian woman with a past history of alcoholism, head injury and posttraumatic epilepsy was found deceased at home following a 12 h period of feeling unwell, seizures and vomiting. Postmortem CT images of the abdomen showed free gas in the peritoneal cavity adjacent to the stomach and no other abnormality. There were no external or radiological features of putrefaction. Appearances were stated by a radiologist to be strongly suggestive of gastro-intestinal tract perforation. Autopsy revealed typical findings of autolytic gastric rupture without features of peritonitis. Cause of death was determined by the pathologist to be "complication of status epilepticus (posttraumatic)". This case demonstrates that gastromalacia may occur rapidly after death and can be detected on postmortem CT, even in the absence of external putrefactive features or CT findings of putrefaction such as gas within the anterior abdominal wall, cardiac chambers or hepatic vasculature. The radiologist with forensic interest must be aware of this postmortem CT artifact in order to avoid ascribing the presence of free intra-peritoneal gas to antemortem perforation of the bowel.

Escherichia coli L-serine deaminase requires a [4Fe-4S] cluster in catalysis.

L-Serine deaminases catalyze the deamination of L-serine, producing pyruvate and ammonia. Two families of these proteins have been described and are delineated by the cofactor that each employs in catalysis. These are the pyridoxal 5'-phosphate-dependent deaminases and the deaminases that are activated in vitro by iron and dithiothreitol. In contrast to the enzymes that employ pyridoxal 5'-phosphate, detailed physical and mechanistic characterization of the iron-dependent deaminases is limited, primarily because of their extreme instability. We report here the characterization of L-serine deaminase from Escherichia coli, which is the product of the sdaA gene. When purified anaerobically, the isolated protein contains 1.86 +/- 0.46 eq of iron and 0.670 +/- 0.019 eq of sulfide per polypeptide and displays a UV-visible spectrum that is consistent with a [4Fe-4S] cluster. Reconstitution of the protein with iron and sulfide generates considerably more of the cluster, and treatment of the reconstituted protein with dithionite gives rise to an axial EPR spectrum, displaying g axially = 2.03 and g radially = 1.93. Mössbauer spectra of the (57)Fe-reconstituted protein reveal that the majority of the iron is in the form of [4Fe-4S](2+) clusters, as evidenced by the typical Mössbauer parameters-isomer shift, delta = 0.47 mm/s, quadrupole splitting of Delta E(Q) = 1.14 mm/s, and a diamagnetic (S = 0) ground state. Treatment of the dithionite-reduced protein with L-serine results in a slight broadening of the feature at g = 2.03 in the EPR spectrum of the protein, and a dramatic loss in signal intensity, suggesting that the amino acid interacts directly with the cluster.

Subcellular localization of chlorosome proteins in Chlorobium tepidum and characterization of three new chlorosome proteins: CsmF, CsmH, and CsmX.

Chlorosomes are unique light-harvesting structures found in two families of photosynthetic bacteria. In this study, three chlorosome proteins (CsmF, CsmH, and CsmX) of the green sulfur bacterium Chlorobium tepidum were characterized by cloning and sequencing the genes which encode them, by overproducing the respective proteins in Escherichia coli, and by raising polyclonal antisera to the purified proteins. Three other proteins (AtpF, CT1970, and CT2144) which were identified in chlorosome fractions have similarly been characterized. The antisera were used to establish the distribution of each protein in various cellular fractions. Ten chlorosome proteins (CsmA, CsmB, CsmC, CsmD, CsmE, CsmF, CsmH, CsmI, CsmJ, and CsmX) copurified in a constant proportion together with bacteriochlorophyll c, and none of these 10 proteins was found in substantial amounts in other subcellular fractions. An antiserum to CsmH was highly effective in agglutinating chlorosomes, and antisera to CsmI, CsmJ, CsmX, and CsmA also immunoprecipitated chlorosomes to varying extents. However, an antiserum to CsmF did not agglutinate chlorosomes. The sequences of chlorosome proteins generally are not significantly similar to the sequences of other proteins in the databases. However, the N-terminal domains of three chlorosome proteins, CsmI, CsmJ, and CsmX, are related to adrenodoxin-type ferredoxins that ligate [2Fe-2S] clusters [Vassilieva, E. V., Antonkine, M. L., Zybailov, B. L., Yang, F., Jakobs, C. U., Golbeck, J. H., and Bryant, D. A. (2001) Biochemistry 40, 464-473]. The sequences of the C-terminal domains of these three proteins appear to be distantly related to CsmA and CsmE. The remaining chlorosome proteins can be divided into two additional structural families, CsmB/F and CsmC/D. CsmH is recovered in water-soluble form after overproduction in E. coli. Interestingly, this protein contains an N-terminal domain that is similar to CsmB/D, while its C-terminal domain is related to CsmC/D. The sequence relationships indicate that, although the protein composition of Chlorobium-type chlorosomes is superficially more complex than that of the chlorosomes of Chloroflexus aurantiacus, this heterogeneity is mostly produced by gene duplication and divergence among a small number of protein types.