Tanycytomas: a newly characterized hypothalamic-suprasellar and ventricular tumor.

We report five cases of tumors occurring in three children and in two adults. The tumors had unusual histomorphology and a mixture of ependymal and piloid-like astrocytic features and a myxoid stroma similar to myxopapillary ependymomas. MR imaging in three of the cases showed aggressive, intensely enhancing partially cystic hypothalamic-suprasellar masses near midline and near the floor of the third ventricle. In the three pediatric cases, the tumor encased the circle of Willis. This newly characterized tumor, the tanycytoma, has neoplastic cells with histomorphologic and ultrastructural characteristics similar to those of the tanycyte.

Postradiation gliosarcoma with osteosarcomatous components.

A 49-year-old man developed a gliosarcoma with prominent osteoid components 15 months after surgical resection and postoperative radiation and chemotherapy for a right frontal glioblastoma multiforme. The recurrent tumor was distinguished from the original lesion by the presence of dense ossification, visible on CT, at the original tumor site. The relevant literature is reviewed.

Analysis of mutations at residues A2451 and G2447 of 23S rRNA in the peptidyltransferase active site of the 50S ribosomal subunit.

On the basis of the recent atomic-resolution x-ray structure of the 50S ribosomal subunit, residues A2451 and G2447 of 23S rRNA were proposed to participate directly in ribosome-catalyzed peptide bond formation. We have examined the peptidyltransferase and protein synthesis activities of ribosomes carrying mutations at these nucleotides. In Escherichia coli, pure mutant ribosome populations carrying either the G2447A or G2447C mutations maintained cell viability. In vitro, the G2447A ribosomes supported protein synthesis at a rate comparable to that of wild-type ribosomes. In single-turnover peptidyltransferase assays, G2447A ribosomes were shown to have essentially unimpaired peptidyltransferase activity at saturating substrate concentrations. All three base changes at the universally conserved A2451 conferred a dominant lethal phenotype when expressed in E. coli. Nonetheless, significant amounts of 2451 mutant ribosomes accumulated in polysomes, and all three 2451 mutations stimulated frameshifting and readthrough of stop codons in vivo. Furthermore, ribosomes carrying the A2451U transversion synthesized full-length beta-lactamase chains in vitro. Pure mutant ribosome populations with changes at A2451 were generated by reconstituting Bacillus stearothermophilus 50S subunits from in vitro transcribed 23S rRNA. In single-turnover peptidyltransferase assays, the rate of peptide bond formation was diminished 3- to 14-fold by these mutations. Peptidyltransferase activity and in vitro beta-lactamase synthesis by ribosomes with mutations at A2451 or G2447 were highly resistant to chloramphenicol. The significant levels of peptidyltransferase activity of ribosomes with mutations at A2451 and G2447 need to be reconciled with the roles proposed for these residues in catalysis.

Crystal structure of the ribosome at 5.5 A resolution.

We describe the crystal structure of the complete Thermus thermophilus 70S ribosome containing bound messenger RNA and transfer RNAs (tRNAs) at 5.5 angstrom resolution. All of the 16S, 23S, and 5S ribosomal RNA (rRNA) chains, the A-, P-, and E-site tRNAs, and most of the ribosomal proteins can be fitted to the electron density map. The core of the interface between the 30S small subunit and the 50S large subunit, where the tRNA substrates are bound, is dominated by RNA, with proteins located mainly at the periphery, consistent with ribosomal function being based on rRNA. In each of the three tRNA binding sites, the ribosome contacts all of the major elements of tRNA, providing an explanation for the conservation of tRNA structure. The tRNAs are closely juxtaposed with the intersubunit bridges, in a way that suggests coupling of the 20 to 50 angstrom movements associated with tRNA translocation with intersubunit movement.

The 23 S rRNA environment of ribosomal protein L9 in the 50 S ribosomal subunit.

Ribosomal protein L9 consists of two globular alpha/beta domains separated by a nine-turn alpha-helix. We examined the rRNA environment of L9 by chemical footprinting and directed hydroxyl radical probing. We reconstituted L9, or individual domains of L9, with L9-deficient 50 S subunits, or with deproteinized 23 S rRNA. A footprint was identified in domain V of 23 S rRNA that was mainly attributable to N-domain binding. Fe(II) was tethered to L9 via cysteine residues introduced at positions along the alpha-helix and in the C-domain, and derivatized proteins were reconstituted with L9-deficient subunits. Directed hydroxyl radical probing targeted regions of domains I, III, IV, and V of 23 S rRNA, reinforcing the view that 50 S subunit architecture is typified by interwoven rRNA domains. There was a striking correlation between the cleavage patterns from the Fe(II) probes attached to the alpha-helix and their predicted orientations, constraining both the position and orientation of L9, as well as the arrangement of specific elements of 23 S rRNA, in the 50 S subunit.

Binocular three-dimensional perception through stereoscopic generation from rotating images.

RATIONALE AND OBJECTIVES: The authors evaluated the clinical utility and potential applications of a binocular three-dimensional (3D) image display in diagnostic radiology. MATERIALS AND METHODS: Rotating video displays of computed tomographic (CT), magnetic resonance (MR) angiographic, and digital subtraction angiographic (DSA) image data were used to generate stereoscopic image displays with a 3D appearance. Eight physicians viewed and scored eight skeletal and eight vascular-interventional studies with a planar display mode and a cathode ray tube. Each physician then viewed the 3D display of the same data and assessed the change in image findings, as well as any corresponding changes in level of diagnostic confidence. RESULTS: Image findings changed in 78 (61%) of the 128 studies after viewing the 3D displays. In 94 (73%) of all 128 studies, the interpreters reported increased confidence in their perception of the findings. Results for the vascular-interventional and skeletal cases were generally very similar. CONCLUSION: Binocular 3D stereoscopic displays from rotating images were reported to provide better image conceptualization and a higher degree of confidence in the findings on the images.

Near-field scanning optical microscopy in cell biology.

Near-field optics has produced the highest optical resolution that has ever been achieved. The methods involved lie at the interface of far-field optical microscopy and scanned probe microscopy. This article describes the principles behind near-field scanning optical microscopy (NSOM) and highlights its potential in cell biology.

Near-field optical photomask repair with a femtosecond laser.

We present a high-resolution near-field optical tool designed for repair of opaque defects in binary photomasks. Both instrument design and near-field imaging and patterning results will be presented. Designed for ablative processing of thin metal films, the MR-100 incorporates an industrial amplified femtosecond laser, third harmonic generator and built-in autocorrelator. The ultrashort duration of the femtosecond pulses enables the tool to remove chrome layers with negligible damage to the surrounding metal or the underlying quartz substrate. The micropipette based near-field writing head can deliver power densities of hundreds of GW/cm2 to spots of several hundred nanometres and below. Repairs on sample masks will be presented and the repair quality will be discussed.

Nanostructuring with spatially localized femtosecond laser pulses.

Spatially localized femtosecond pulses have been produced by a combination of scanning near-field optical microscopy with ultrashort pulse lasers. With these pulses direct ablative writing on metal surfaces is demonstrated. Possible applications of this technique for nanostructuring, repair, and production of lithographic masks are discussed.

Beyond the basics: monitoring with a pulmonary artery (Swan-Ganz) catheter.

Interpreting hemodynamic parameters requires both knowledge and practical experience. As emergency nurses care for more acutely ill patients during longer ED stays, an understanding of hemodynamic monitoring will be essential.

Near-field optical imaging of unstained bacteria: comparison with normal atomic force and far-field optical microscopy in air and aqueous media.

Simultaneous near-field scanning optical and atomic force imaging of bacteria is presented. The bacteria imaged in these studies were unstained. The near-field optical images had excellent signal-to-noise and showed excellent contrast even in these unstained specimens. The images obtained were interpreted in terms of the images that have been obtained by transmission electron microscopy and X-ray imaging. The results show that bacterial near-field optical imaging is going to be a very important tool in the arsenal of the bacteriologist both in terms of understanding the fundamental processes in the life cycle of bacteria with and without cytochemical staining and in terms of clinical diagnostic applications.

Dextro-naloxone counteracts amphetamine-induced hyperactivity.

The locomotor stimulating effect of d-amphetamine in mice was counteracted by the administration of l-naloxone [(-)-naloxone], a known opiate receptor antagonist. Mice injected with amphetamine reached a peak locomotor activity within 30 min. When treated simultaneously with amphetamine and l-naloxone, these subjects showed low motility. Furthermore, when mice were treated not with l-naloxone but with its mirror image, d-naloxone [(+)-naloxone], a compound that by itself does not antagonize opiates and does not affect spontaneous motility, they showed no amphetamine-induced hyperactivity. The finding that an enantiomer of naloxone, with no opiate antagonist activity, is able to block the excitatory action of amphetamine, suggests the existence of a hitherto unknown mechanism of counteracting some of the effects of stimulants and euphoriants like amphetamine and cocaine.

Ribosomal protein L15 as a probe of 50 S ribosomal subunit structure.

L15, a 15 kDa protein of the large ribosomal subunit, interacts with over ten other proteins during 50 S assembly in vitro. We have probed the interaction L15 with 23 S rRNA in 50 S ribosomal subunits by chemical footprinting, and have used localized hydroxyl radical probing, generated from Fe(II) tethered to unique sites of L15, to characterize the three-dimensional 23 S rRNA environment of L15. Footprinting of L15 was done by reconstituting purified, recombinant L15 with core particles derived from Escherichia coli 50 S subunits by treatment with 2 M LiCl. The cores migrate as compact 50 S-like particles in sucrose gradients, contain 23 S and 5 S rRNA, and lack a subset of the 50 S proteins, including L15. Using both Fe(II).EDTA and dimethyl sulfate, we have identified a strong footprint for L15 in the region spanning nucleotides 572-654 in domain II of 23 S rRNA. This footprint cannot be detected when L15 is incubated with "naked" 23 S rRNA, indicating that formation of the L15 binding site requires a partially assembled particle.Protein-tethered hydroxyl radical probing was done using mutants of L15 containing single cysteine residues at amino acid positions 68, 71 and 115. The mutant proteins were derivatized with 1-[p-(bromo-acetamido)benzyl]-EDTA. Fe(II), bound to core particles, and hydroxyl radical cleavage was initiated. Distinct but overlapping sets of cleavages were obtained in the footprinted region of domain II, and in specific regions of domains I, IV and V of 23 S rRNA. These data locate L15 in proximity to several 23 S rRNA elements that are dispersed in the secondary structure, consistent with its central role in the latter stages of 50 S subunit assembly. Furthermore, these results indicate the proximity of these rRNA regions to one another, providing constraints on the tertiary folding of 23 S rRNA.

Comparative value of urinalysis, urine cytology and urine sIL2R in the assessment of renal disease in patients with systemic lupus erythematosus (SLE).

Serial immunological testing has been recently proposed for monitoring patients with lupus nephritis as routine serological tests have shown sub-optimal correlation with clinical status. To assess the value of urine cytology and urine sIL2R in the evaluation of patients with SLE, in particular those with lupus nephritis, we conducted a prospective double-blind study of 31 patients with SLE, during an 18-month period. A comparison of routine urinalysis with urine cytology and urine sIL2R was performed in 84 samples: 15 from patients without a history of renal involvement and 69 from patients with a history of renal involvement. A high urine cytology score (> or = 6), particularly in the presence of lymphoblasts, plasma cells or monocytes, was significantly associated with lupus nephritis in relapse. Urine sIL2R levels were significantly elevated during all SLE relapses, unrelated to the presence of renal involvement. Fifteen urine specimens were obtained at the time of a kidney biopsy: 9 with active lesions and 6 with inactive renal disease. UC score was 2.0 +/- 1.89 for those with absent activity, 8.4 +/- 3.4 for mild activity and 11.0 +/- 2.4 for moderate/severe activity (p < 0.001 between active vs inactive disease). No urinalysis parameter alone permitted distinguishing the degree of renal disease activity. In the subgroup of patients with renal disease urinalysis was overall less accurate than urine cytology or urinary sIL2R levels for predicting renal disease activity defined by biopsy. Urine cytology and urine sIL2R proved to be reliable measures of lupus activity.

Prevention of cocaine-induced hyperactivity by a naloxone isomer with no opiate antagonist activity.

Dextro-naloxone [(+)-naloxone], an isomer with almost no opiate antagonist activity and no effect on spontaneous locomotor activity, can reduce cocaine-induced hyperactivity in mice. The classical opiate antagonist, levo-naloxone [(-)-naloxone], is known to counteract the excitatory motor effects of amphetamine and cocaine, but it has been tacitly assumed that this action of levo-naloxone is dependent on its ability to antagonize endogenous opioids. Our finding that a naloxone isomer with little or no opioid antagonist activity is also able to inhibit the cocaine effect on spontaneous motility, calls for a reconsideration of this assumption.

Directly probing rapid membrane protein dynamics with an atomic force microscope: a study of light-induced conformational alterations in bacteriorhodopsin.

This paper demonstrates that an atomic force microscope can be used to directly monitor rapid membrane protein dynamics. For this demonstration the membrane-bound proton pump, bacteriorhodopsin, has been investigated. It has been unequivocally shown that the light-induced dynamic alterations that have been observed do not arise from external artifacts such as heating of the sample by the incident light, but that these changes can be directly linked to the light-induced protein conformational alterations in this membrane. In essence, it has been shown that the light energy absorbed by bacteriorhodopsin is converted not only to chemical energy but also to mechanical energy. In summary a new ultrasensitive tool is described for monitoring the molecular dynamics of materials with wide applicability to fundamental and applied science.

A randomized double-blind placebo-controlled trial of cyclosporine in steroid-resistant idiopathic focal segmental glomerulosclerosis in children.

There is no generally accepted treatment for primary focal segmental glomerulosclerosis (FSGS). Steroids alone and steroids plus cyclophosphamide can be expected to induce a remission of the proteinuria in only 27% of patients. Probably the majority of FSGS patients will reach ESRD over the extended course of their disease. In addition to the work presented in this study, there have been many reports of the potential effectiveness of cyclosporine (CSA) on reducing the proteinuria of FSGS. This study was undertaken to test the efficacy and safety of a 6-month course of CSA in a double-blinded, prospectively randomized, placebo-controlled trial in children with corticosteroid-resistant FSGS. The potential inhibitory effect of hypercholesterolemia on the proteinuria-reducing actions of CSA was also assessed. Twenty-five patients with FSGS were randomized to receive either placebo or CSA for 6 months. Twelve of the 12 patients that received CSA experienced a diminution of their proteinuria as opposed to only two of the 12 placebo-treated patients. Proteinuria was significantly reduced from 151.7 +/- 162.4 mg/kg per 24 h at Week 0 to 36.9 +/- 42.3 at the end of the study in the group that received CSA (P < 0.05). There was no significant change in the proteinuria of the patients in the placebo group. A significant correlation between the percentage change of proteinuria over the 6 months of the study and the prestudy serum cholesterol levels (r = 0.79, P < 0.05) was seen in the CSA group. A partial correlation analysis controlling for the effects of serum cholesterol uncovered a significant relationship between average CSA level and proteinuria change (r = -0.76, P < 0.05). The fractional decline in GFR over the course of the study was not significantly different between the CSA and placebo-treated groups. In conclusion, CSA reduces proteinuria, increases serum albumin levels, and can be expected, therefore, to reduce the symptoms of nephrotic syndrome. Hypercholesterolemia antagonizes this effect of CSA.