Molecular characterization of cDNAs encoding low-molecular-weight heat shock proteins of soybean

Three cDNA clones (GmHSP23.9, GmHSP22.3, and GmHSP22.5) representing three different members of the low-molecular-weight (LMW) heat shock protein (HSP) gene superfamily were isolated and characterized. A fourth cDNA clone, pFS2033, was partially characterized previously as a full-length genomic clone GmHSP22.0. The deduced amino acid sequences of all four cDNA clones have the conserved carboxyl-terminal LMW HSP domain. Sequence and hydropathy analyses of GmHSP22, GmHSP22.3, and GmHSP22.5, representing HSPs in the 20 to 24 kDa range, indicate they contain amino-terminal signal peptides. The mRNAs from GmHSP22, GmHSP22.3, and GmHSP22.5 were preferentially associated in vivo with endoplasmic reticulum (ER)-bound polysomes. GmHSP22 and GmHSP22.5 encode strikingly similar proteins; they are 78% identical and 90% conserved at the amino acid sequence level, and both possess the C-terminal tetrapeptide KDEL which is similar to the consensus ER retention motif KDEL; the encoded polypeptides can be clearly resolved from each other by two-dimensional gel analysis of their hybrid-arrest translation products. GmHSP22.3 is less closely related to GmHSP22 (48% identical and 70% conserved) and GmHSP22.5 (47% identical and 65% conserved). The fourth cDNA clone, GmHSP23.9, encodes a HSP of ca. 24 kDa with an amino terminus that has characteristics of some mitochondrial transit sequences, and in contrast to GmHSP22, GmHSP22.3, and GmHSP22.5, the corresponding mRNA is preferentially associated in vivo with free polysomes. It is proposed that the LMW HSP gene superfamily be expanded to at least six classes to include a mitochondrial class and an additional endomembrane class of LMW HSPs.     

Phenylalanine 30 plays an important role in receptor binding of verotoxin-1

The homopentameric B subunit of verotoxin 1 (VT1) binds to the glycosphingolipid receptor globotriaosylceramide (Gb3). We produced mutants with alanine substitutions for residues found near the cleft between adjacent subunits. Substitution of alanine for phenylalanine 30 (Phe-30) resulted in a fourfold reduction in B subunit binding affinity for Gb3 and a 10-fold reduction in receptor density in a solid-phase binding assay. The interaction of wild-type and mutant B subunits with Pk trisaccharide in solution was examined by titration microcalorimetry. The carbohydrate binding of the mutant was markedly impaired compared with that of the wild type and was too weak to allow calculation of a binding constant. These results demonstrate that the mutation significantly impaired the carbohydrate-binding function of the B subunit. To ensure that the mutation had not caused a significant change in structure, the mutant B subunit was crystallized and its structure was determined by X-ray diffraction. Difference Fourier analysis showed that its structure was identical to that of the wild type, except for the substitution of alanine for Phe-30. The mutation was also produced in the VT1 operon, and mutant holotoxin was purified to homogeneity. The cytotoxicity of the mutant holotoxin was reduced by a factor of 10(5) compared to that of the wild type in the Vero cell cytotoxicity assay. The results suggest that the aromatic ring of Phe-30 plays a major role in binding of the B subunit to the Galalpha1-4Galbeta1-4Glc trisaccharide portion of Gb3. Examination of the VT1 B crystal structure suggests two potential carbohydrate-binding sites which lie on either side of Phe-30.     

Prediction of drinking outcomes for male alcoholics after 10 to 14 years

This study reports on the long-term outcomes of 360 men who were hospitalized for alcoholism during 1980 to 1984 and followed at 12 months and again 10 to 14 years later. At the 10/14-year follow-up, 96 (26.7%) men were confirmed as deceased; 255 (70.8%) men participated in the assessment/interview battery completed during baseline hospitalization. The battery consisted of psychosocial, alcohol-related, and psychiatric measures. Two distinct but highly correlated outcome measures were selected: a clinical rating scale and a factor score. Overall, predictors from baseline and 12-month follow-up included age at intake hospitalization, alcoholism severity, social stability, drinking days, and antisocial personality disorder. Approximately 37% of the assessed survivors were either totally abstinent or drinking nonabusively throughout the 10/14-year follow-up, whereas another 37% continued to drink abusively. Men who abstained or reduced alcohol intake reported better physical health at follow-up than those who continued to drink. Although our findings did not directly link alcoholism to death, they strongly indicate that chronic alcohol abuse may lead to premature death.     

Pentoxifylline inhibits hypoxia-induced upregulation of tumor cell tissue factor and vascular endothelial growth factor

The aim of this study was to compare the performance of CT and MRI in the diagnosis of longitudinal stress fracture of the tibia (LSFT). A retrospective study of imaging findings was performed in 15 patients with LSFT. The CT and MR images were compared for detection of fracture line, callus, bone marrow edema, and soft tissues changes. The CT and MRI techniques allowed the detection of the fracture line in 82 and 73 % of cases, respectively. The callus was always visualized with CT or MRI. The MRI technique had a markedly higher sensitivity than CT in the detection of bone marrow edema (73 vs 18 %) and soft tissue lesions (87 vs 9 %). This may cause a misleading aggressive appearance on MRI. Computed tomography remains the best imaging modality for diagnosis of LSFT. However, MRI findings should be known to obviate the performance of CT or bone biopsy.     

The role of PET-FDG in questionable diagnosis of relapse in the presence of radionecrosis of brain tumors

INTRODUCTION: Although CT and MR are sensitive techniques for the detection of cerebral tumours, both have limitations in distinguishing between tumour relapse (TR) and post-treatment radionecrosis (RN). PATIENTS AND METHODS: In this study we have determined the usefulness of metabolic imaging with PET-FDG in such situations. We assessed 70 patients with CNS tumours (22 low grade astrocytomas, 25 high grade astrocytomas, 3 oligodendrogliomas, 13 metastatic tumours and 7 other tumours. All had been treated with radiotherapy and other treatments such as radiosurgery, chemotherapy or different types of surgery, and presented clinical pictures which made it necessary to decide the differential diagnosis of relapse or radionecrosis. RESULTS: In the PET-FDG study visual and semiquantitative analysis was done by SUV (Standardized Update Value). Confirmation of the findings was obtained in 44 cases (24 TR and 20 RN). MR was doubtful or inconclusive in most cases, whilst with PET correct diagnosis was made in all cases. CONCLUSIONS: Metabolic imaging with PET-FGD is better than anatomostructural imaging techniques for differential diagnosis between tumour relapse and radionecrosis in CNS tumours which have been treated. Prospective studies are necessary for evaluation of SUV as a factor for prognosis of survival.     

Space-time adaptive reduced-rank multistage Wiener filtering for asynchronous DS-CDMA

An adaptive near-far resistant self-synchronizing receiver for asynchronous direct-sequence (DS) code-division multiple access (CDMA) systems with a J-element antenna array is presented in this paper. The primary requirement is prior knowledge of the spreading-code sequence of the desired user. A low-complexity version of the proposed receiver is developed that utilizes the concept of the reduced-rank multistage Wiener filter (MWF) introduced recently by Goldstein and Reed. This results in a self-synchronizing detection criterion that requires no inversion or eigen-decomposition of a covariance matrix. It also achieves a rapid adaptive convergence with only limited data support. Simulation results show that the proposed receiver provides superior performance both as an increasing function of the size of the J-element antenna array and the amount of sample support. As a consequence, this new self-synchronizing communications receiver significantly outperforms the conventional DS-CDMA receiver that uses a standard matched filter for acquisition. When compared with the MMSE-type receiver, the proposed receiver can accomplish a similar performance level without the requirement of known propagation delays.     

Impact of circuit resistance on the breakdown voltage of tantalum chip capacitors

Experiments are described in this paper whose results suggest a clear mathematical relationship between total circuit resistance (including the capacitor's ESR) and the voltage at which a capacitor is likely to break down. Specifically, the relationship defines how much each capacitor's (not precisely known) breakdown voltage is affected by changes in circuit resistance. Since a factor that strongly influences the reliability of a tantalum capacitor is the ratio of the capacitor's breakdown voltage to the applied voltage, if the impact of circuit resistance on breakdown voltage can be established, then, at least indirectly, the impact of circuit resistance on reliability can be inferred.The breakdown voltages of individual capacitors, drawn from large randomized samples, were determined for different values of circuit resistance. These data were analyzed and found to fit a specific mathematical relationship with a high degree of confidence. The relationship was found to hold for different, but similar, batches and part-types. The test methods employed to minimize statistical noise are described in the paper as is the resulting mathematical relationship. Implications of the relationship are explored and avenues of future research are suggested.     

Cooperative interception of neuronal apoptosis by BCL-2 and BAG-1 expression: prevention of caspase activation and reduced production of reactive oxygen species

Neuronally differentiated PC12 cells undergo synchronous apoptosis when deprived of nerve growth factor (NGF). Here we show that NGF withdrawal induces actinomycin D- and cycloheximide-sensitive caspase (ICE-like) activity. The peptide inhibitor of caspase activity, N-acetyl-Asp-Glu-Val-Asp-aldehyde, was more potent than acetyl-Tyr-Val-Ala-Asp-chloromethyl ketone in preventing NGF withdrawal-induced apoptosis, suggesting an important role for caspase-3 (CPP32)-like proteases. We observed a peak of reactive oxygen species (ROS) 6 h after NGF withdrawal. ROS appear to be required for apoptosis, because cell death is prevented by the free radical spin trap, N-tert-butyl-alpha-phenylnitrone, and the antioxidant, N-acetylcysteine. ROS production was blocked by actinomycin D, cycloheximide, and caspase protease inhibitors, suggesting that ROS generation is downstream of new mRNA and protein synthesis and activation of caspases. Forced expression of either BCL-2 or the BCL-2-binding protein BAG-1 blocked NGF withdrawal-induced apoptosis, activation of caspases, and ROS generation, showing that they function upstream of caspases. Coexpression of BCL-2 and BAG-1 was more protective than expression of either protein alone.