Mechanism of Pseudomonas aeruginosa persistence during treatment with broad-spectrum cephalosporins of lung infections in patients with cystic fibrosis.

Beta-lactam resistance in Pseudomonas aeruginosa detected only during ceftazidime therapy of cystic fibrosis patients was studied. Evaluation of resistant and susceptible isolates from one patient and resistant laboratory derivatives indicated that elevated beta-lactamase levels were the primary determinant of resistance. Susceptible isolates outgrew resistant isolates on antibiotic-free medium.     

Partial k-space reconstruction in single-shot diffusion-weighted echo-planar imaging.

Partial k-space sampling is frequently used in single-shot diffusion-weighted echo-planar imaging (DW-EPI) to reduce the TE and thereby improve the SNR. However, it increases the sensitivity of the technique to bulk rotational motion, which introduces a phase gradient across the tissue that shifts the echo in k-space. If the echo is displaced into the high spatial frequencies, conventional homodyne reconstruction fails, causing intensity oscillations across the image. Zero-padding, on the other hand, compromises the image resolution and may cause truncation artifacts. We present an adaptive version of the homodyne algorithm that detects the location of the echo in k-space and adjusts the center and width of the homodyne filters accordingly. The adaptive algorithm produces artifact-free images when the echo is shifted into the high positive k-space range, and reduces to the standard homodyne algorithm in the absence of bulk motion.     

Physico-chemical characterisation of rinderpest virus

Rinderpest virus grown in Vero cells was purified by equilibrium sedimentation in potassium tartrate gradients. The characteristics of the virus and its RNA dependend on the passage history of the virus. Undiluted passage virus had a density ofc 1.21 g/ml in potassium tartrate and contained RNA sedimenting atc. 20S and 5S. Virus obtained by dilute passage had a density ofc. 1.24 g/ml and contained 50S in addition to 20S and 5S RNA. Both diluted passage and undiluted passage viruses contained polypeptides with molecular weights of 98, 79, 75, 66, 48, 43 and 37×10³. Trace amounts of polypeptides with molecular weights of 29 and 20×10³ were also detected. The molecular weights of the major polypeptides are similar to those of the polypeptides present in measles and canine distemper viruses.     

Comparative genomic hybridization of 49 primary retinoblastoma tumors identifies chromosomal regions associated with histopathology,progression, and patient outcome

Forty-nine primary retinoblastoma (Rb) tumors were analyzed by the use of comparative genomic hybridization (CGH), and clinical/histological correlations were performed. Adverse histological factors were present in 13 patients. Chromosomal imbalance was a frequent phenomenon, seen in 96% of the tumors. Gain of 6p represented the most frequent event (69% of the tumors), whereas +1q was observed in 57%, confirming that these abnormalities are key secondary events in retinoblastoma tumor progression. Loss of 13q and 16 was significantly associated with tumors displaying adverse histo-prognostic factors, whereas -16q was significantly associated with tumors without adverse features. In three patients who developed an extra-ocular relapse, the tumors showed -13q and 2/3 had -5q, suggesting that these abnormalities may be associated with metastasis. Children >or= 36 months of age at enucleation tended to have more CGH abnormalities per tumor than children < 12 months (median numbers 11 vs. 3). In addition, +1q, +13q, -16, and -16q were more frequent in children with an older age at enucleation. Identical CGH changes were found in both tumors from one patient with bilateral tumors, suggesting a common origin. It is possible that tumors displaying loss of 13q and 5q indicate those patients who may suffer an adverse outcome and who would require alternative or more intensive therapy. CGH analysis on larger cohorts and in prospective clinical trials will be invaluable in determining whether a genetic classification of retinoblastoma represents a reliable measure of prognosis.     

HBs-Ag-negative hepatitis in a hemodialysis unit: relation to Epstein-Barr virus.

Eleven of 40 patients in a hemodialysis unit had clinical or biochemical evidence of hepatitis during a five-week period. The clinical disease was mild, being limited solely to dialysis patients. Epidemiologic investigation indicated that the incubation period was between 17 and 35 days and that 10 of 11 patients had been exposed to a single venous-pressure monitor before onset. Dried blood and evidence of blood reflux up the venous-pressure gauge suggested that cross-contamination of the blood of successive patients probably resulted in transmission of disease. No association with the hepatitis B surface antigen or anti-hepatitis B antibody was demonstrated, but 10 of the 11 patients with elevated transaminase levels had evidence of recent exposure, to Epstein-Barr virus as manifested either by Ox-cell hemolysin titers or rises in titers to viral capsid antigen.     

Maisonneuve fracture dislocation of the ankle

Ligamentous injuries of the ankle are usually benign and may be managed satisfactorily by nonoperative measures. This is not true, however, of the Maisonneuve variant. In this paper we present a case report of a high school athlete who sustained a Maisonneuve fracture dislocation of the ankle. The diagnosis was missed initially, because of an incomplete examination. The subsequent physical and radiographic examination revealed the proper diagnosis. Guidelines for the evaluation and appropriate treatment are discussed.     

Detection of human papillomavirus types 6 and 11 E4 gene products in condylomata acuminatum.

Polyclonal antiserum to an Escherichia coli-produced beta-galactosidase/E4 fusion protein of human papillomavirus type 6b (antiserum 256), and affinity purified HPV 11 anti-E4 antibodies were tested for reactivity in Western blots with bacterially expressed trpE/E4 fusion proteins of HPV types 6b, 11, 16, and 18. To further characterize the affinity purified anti-E4 antibodies, a dot-immunobinding assay was performed using overlapping synthetic HPV 11 E1E4 peptides as antigens. Protein extracts of condylomata acuminatum from 18 patients containing HPV type 6 or 11 DNA sequences were tested in Western blots using antiserum 256 or affinity purified HPV 11 anti-E4 antibodies. In the Western blots of the trpE proteins, antiserum 256 identified the HPV types 6b and 11 fusion proteins; the affinity purified HPV 11 anti-E4 antibodies identified only the HPV 11 fusion protein. In the dot-immunobinding assay, three HPV 11 peptides were recognized, each containing a shared 8 amino acid sequence that differs significantly from the corresponding sequences of HPV types 6b, 16, or 18. In the Western blots of protein extracts from 18 condylomata acuminatum samples shown to contain HPV types 6 or 11 DNA, putative E4 gene products were identified in six samples by antiserum 256. The affinity purified HPV 11 anti-E4 antibodies identified putative E4 gene products in one of these same six lesions, which was shown to contain HPV 11 sequences by the Southern blot method. All six samples containing E4 gene products were from women. Three of these women were pregnant, one had serum antibodies to the human immunodeficiency virus, and one was a renal transplant recipient receiving glucocorticoids.(ABSTRACT TRUNCATED AT 400 WORDS)     

Complement-dependent synergistic effects of rat monoclonal IgG antibodies in vivo

We describe studies aimed at maximizing the effector mechanisms responsible for eliminating target erythrocytes from the circulation in a fully homologous opsonization system in vivo. The effects on the subsequent fate of target erythrocytes were examined in both normal and decomplemented rats preinjected with a variety of rat IgG monoclonal antibodies (mAb) directed against different epitopes on the RTlA^a, the classical class I major histocompatibiliy complex antigen of the DA rat. In general, the clearance of both DA and (DA × PVG)F₁ erythrocytes in normal rats preinjected with various pairs of noncompetitive mAb was very rapid when compared with the overall clearance patterns seen with individual antibodies. With all mAb combinations containing IgG2b or IgG2a, an intact complement system was an essential requirement for augmenting the initial clearance and promoting hepatic sequestration of these target cells. The removal of (DA × PVG)F₁ erythrocytes, expressing half as much antigen, was considerably slower than the DA cells for each antibody pair tested although a notable degree of heterogeneity was observed in the overall behavior of both types of target cells with different mAb combinations. Our results suggest that the limiting effects of low antigen density on the target cells combined with the use of mAb of an isotype like the rat IgG2a can be overcome using pairs of mAb that recognize different epitopes on the same target antigen.     

Biochemical analyses of multiple fractions of PKR purified from Escherichia coli.

PKR is a cellular protein kinase activated by double-stranded RNA (dsRNA) that phosphorylates eukaryotic initiation factor alpha (eIF2alpha) and inhibits protein translation. Activation of PKR is accompanied by Ser/Thr autophosphorylation on multiple sites. Because PKR negatively regulates cell growth, overexpression and purification of PKR are difficult to achieve. Here, we describe overexpression and purification of recombinant PKR protein from Escherichia coli under native conditions at the milligram level. Affinity, ion exchange, and gel filtration chromatographies revealed multiple fractions of PKR with distinctive biochemical characteristics. During gel filtration, a small amount of PKR was found in a high molecular weight (>300 kDa) fraction that also contained endogenous bacterial RNA. The PKR in this fraction has a constitutive substrate phosphorylation activity. The majority of PKR is found in fractions of lower molecular weight and is free of RNA but is differentially phosphorylated as examined by isoelectric focusing electrophoresis and can be further separated by gradient anion exchange chromatography. PKR eluted with low salt has a lower level of basal autophosphorylation, and its kinase activity can be induced by dsRNA. With an increasing NaCl gradient, the purified PKR exhibits an increased level of autophosphorylation and constitutive kinase activity but reduced dsRNA inducibility. The highest salt eluent of PKR exhibits little dsRNA-induced activation. The inducible activation of high salt eluent PKR by dsRNA can be partially restored by treatment with protein phosphatase 1. The production of multiple fractions of PKR with different biochemical properties in E. coli suggests that the spectrum of PKR activity and regulation in mammalian cells is likely to be similarly complex.