The PapC usher forms an oligomeric channel: implications for pilus biogenesis across the outer membrane

Bacterial virulence factors are typically surface-associated or secreted molecules that in Gram-negative bacteria must cross the outer membrane (OM). Protein translocation across the bacterial OM is not well understood. To elucidate this process we studied P pilus biogenesis in Escherichia coli. We present high-resolution electron micrographs of the OM usher PapC and show that it forms an oligomeric complex containing a channel approximately 2 nm in diameter. This is large enough to accommodate pilus subunits or the linear tip fibrillum of the pilus but not large enough to accommodate the final 6.8-nm-wide helical pilus rod. We show that P pilus rods can be unraveled into linear fibers by incubation in 50% glycerol. Thus, they are likely to pass through the usher in this unwound form. Packaging of these fibers into their final helical structure would only occur outside the cell, a process that may drive outward growth of the pilus organelles. The usher complex appears to be similar to complexes formed by members of the PulD/pIV family of OM proteins, and thus these two protein families, previously thought to be unrelated, may share structural and functional homologies.     

Epirubicin has modest single-agent activity in head and neck cancer but limited activity in metastatic melanoma and colorectal cancer: phase II studies by the Eastern Cooperative Oncology Group

We present a case of synovial sarcoma involving the cutaneous tissue of the knee in an 18-year-old woman. The 2.5 cm tumor was locally excised and recurred six times over the following 24 years. The neoplasm involved the deep dermis with extension into the papillary dermis and superficial subcutis. The tumor was predominantly composed of spindle cells arranged in compact interdigitating fascicles and scattered epithelial nests were seen. Focal myxoid and hemangiopericytoma-like areas as well as numerous mast cells were identified. Spindle cells stained for vimentin, CAM 5.2, and epithelial membrane antigen, whereas epithelial nests only stained for CAM 5.2 and epithelial membrane antigen. Neither component was reactive for antibodies directed against desmin, muscle specific actin, smooth muscle actin, S-100 protein, CD-31, or CD-34. This newly reported location for this morphologically heterogeneous tumor creates potential diagnostic confusion with other primary neoplasms in these areas.     

Acute gouty arthritis is seasonal

OBJECTIVE: Information regarding effect of weather conditions on gout is sparse. We conducted a study in the USA to examine whether gout is seasonal. METHODS: We reviewed synovial fluid (SF) analyses from our laboratory during 1990-1995 and identified 359 patients who had acute gouty attacks. All fluids of patients with acute gout had intracellular monosodium urate crystals and SF leukocyte counts > 2000/mm3 or more than 10 leukocytes per high power field (HPF). Retrospective chart review of all patients was performed to confirm a clinical picture of acute gout. A control group included 76 patients with acute pseudogout whose SF were analyzed during the same period and who had intracellular calcium pyrophosphate crystals and inflammatory leukocyte counts as in patients with gout. RESULTS: Acute gout was most common during the spring; n = 115 (32%). Ninety (25%) patients had acute gout attacks in the fall; 81 (23%) had acute attacks during the summer; 73 (20%) had acute attacks in the winter. One-way analysis of variance (ANOVA) was used to compare the overall frequency of acute gout during the months and seasons. Using ANOVA, there was no overall statistically significant difference in the incidence of gout per season (p = 0.07), although it approached statistical significance. Acute gouty attacks were more common in the spring compared with winter (p = 0.002) and summer (p = 0.015). There was a trend but no statistically significant difference compared with fall. Winter was the season in which the fewest acute gouty cases were seen, although it was not statistically significant. No seasonal difference was seen in the pseudogout group. There was no correlation between either mean monthly temperature or humidity and the incidence of acute gouty attacks. CONCLUSION: Acute gout attacks are significantly more common in the spring. No seasonal variation was seen in patients with acute pseudogout attacks.     

Characterization and affinity applications of cellulose-binding domains

Cellulose-binding domains (CBDs) are discrete protein modules found in a large number of carbohydrolases and a few nonhydrolytic proteins. To date, almost 200 sequences can be classified in 13 different families with distinctly different properties. CBDs vary in size from 4 to 20 kDa and occur at different positions within the polypeptides; N-terminal, C-terminal and internal. They have a moderately high and specific affinity for insoluble or soluble cellulosics with dissociation constants in the low micromolar range. Some CBDs bind irreversibly to cellulose and can be used for applications involving immobilization, others bind reversibly and are more useful for separations and purifications. Dependent on the CBD used, desorption from the matrix can be promoted under various different conditions including denaturants (urea, high pH), water, or specific competitive ligands (e.g. cellobiose). Family I and IV CBDs bind reversibly to cellulose in contrast to family II and III CBDs which are in general, irreversibly bound. The binding of family II CBDs (CBD(Cex)) to crystalline cellulose is characterized by a large favourable increase in entropy indicating that dehydration of the sorbent and the protein are the major driving forces for binding. In contrast, binding of family IV CBDs (CBD(N1)) to amorphous or soluble cellulosics is driven by a favourable change in enthalpy which is partially offset by an unfavourable entropy change. Hydrogen bond formation and van der Waals interactions are the main driving forces for binding. CBDs with affinity for crystalline cellulose are useful tags for classical column affinity chromatography. The affinity of CBD(N1) for soluble cellulosics makes it suitable for use in large-scale aqueous two-phase affinity partitioning systems.     

Cobalt 60 radiotherapy for treatment of squamous cell carcinoma of the nasal cavity and paranasal sinuses in three horses

Three adult horses underwent aggressive treatment of squamous cell carcinoma of the nasal cavity and paranasal sinuses, using course-fractionated cobalt 60 radiotherapy. Squamous cell carcinoma of the nasal cavity and paranasal sinuses is not commonly diagnosed in horses. Historically, horses with this type of neoplasm have not been treated or have undergone some form of surgery. The prognosis for long-term survival or cure has been poor. Long-term results of cobalt 60 radiotherapy were good to excellent and exceeded those usually reported for horses treated surgically. On the basis of these results, use of radiotherapy for these neoplasms is recommended.     

Intrinsic hyperreactivity of mucosal T cells to interleukin-2 in pediatric Crohn''s disease

1. The basic etiology of Alzheimer's disease remains unknown, although four genes have so far been involved: beta-amyloid precursor protein, presenilin-1, presenilin-2 and apolipoprotein E genes. 2. The largest familial Alzheimer's disease (FAD) kindred so far reported belong to a point mutation in codon 280 that results in a glutamic acid-to-alanine substitution in presenilin-1 characterized in Antioquia, Colombia. 3. A hypothetical unified molecular mechanism model of cell death in FAD mediated by presenilin-1, beta-amyloid, and oxidative stress is proposed as an attempt to explain the mechanisms of neuronal loss in this neurodegenerative disorder.     

Short deceleration time of mitral inflow E velocity: prognostic implication with atrial fibrillation versus sinus rhythm

The present study retrospectively identified 367 patients who had restrictive physiology as defined by deceleration time < or = 130 msec; 293 were in sinus rhythm (SR) (194 men and 99 women; mean age 64 +/- 14 years) and 74 were in atrial fibrillation (AF) (51 men and 23 women; mean age 72 +/- 11 years; p < 0.001). Both groups had similar underlying diagnoses and no significant difference in Doppler indices (E wave, 96 +/- 23 vs 99 +/- 22 cm/sec in SR and AF, respectively; deceleration time, 116 +/- 12 vs 116 +/- 13 msec; and left ventricular outflow tract time velocity integral, 14.8 +/- 4.8 vs 14.5 +/- 4.4 cm). Left ventricular ejection fraction was significantly lower in SR patients (29% +/- 16% vs 39% +/- 20%; p = 0.0003). There were 120 deaths (41%) in the SR group and 35 (47%) in the AF group (median follow-up for both groups, 2.2 years). Restrictive physiology as defined by Doppler echocardiography (deceleration time < or = 130 msec) appears to predict a similar poor prognosis with AF as with SR.     

Luteinizing hormone secreting adrenal tumour as a cause of precocious puberty

OBJECTIVE: This study examined whether a selective serotonin reuptake inhibitor (paroxetine) had comparable efficacy but greater tolerability than a tricyclic antidepressant (imipramine) in depressed patients with HIV infection. METHOD: Seventy-five HIV-positive patients (45% of whom had AIDS) were blindly and randomly assigned to receive paroxetine (N = 25), imipramine (N = 25), or placebo (N = 25) in a 12-week trial. The Hamilton Anxiety Rating Scale, the Hamilton Depression Rating Scale, the Clinical Global Impression scale, and the SAFETEE general inquiry (for safety and tolerability) were administered at weeks 2, 4, 6, 8, and 12. RESULTS: Fifty-six (75%) of the 75 patients completed 6 weeks and 34 (45%) completed 12 weeks of the trial. The mean daily doses of both paroxetine (33.9 mg) and imipramine (162.5 mg) were significantly more effective than placebo; they were comparably effective at weeks 6, 8, and 12 according to the intent-to-treat analysis and at week 8 according to the analysis for the subjects who completed the trial (for them, only imipramine was superior to placebo at week 12). There were significantly more dropouts due to side effects from imipramine (48%) than from both paroxetine (20%) and placebo (24%). CONCLUSIONS: Depressed patients with HIV infection responded to imipramine or paroxetine at a higher rate than to placebo irrespective of severity of immunosuppression. Because paroxetine was much better tolerated than imipramine, its overall effectiveness may be greater. However, because of the small study group and the high attrition rate, these findings cannot be generalized and may need replication in a larger study group.     

Chlamydomonas kinesin-II-dependent intraflagellar transport (IFT): IFT particles contain proteins required for ciliary assembly in Caenorhabditis elegans sensory neurons

We previously described a kinesin-dependent movement of particles in the flagella of Chlamydomonas reinhardtii called intraflagellar transport (IFT) (Kozminski, K.G., K.A. Johnson, P. Forscher, and J.L. Rosenbaum. 1993. Proc. Natl. Acad. Sci. USA. 90:5519-5523). When IFT is inhibited by inactivation of a kinesin, FLA10, in the temperature-sensitive mutant, fla10, existing flagella resorb and new flagella cannot be assembled. We report here that: (a) the IFT-associated FLA10 protein is a subunit of a heterotrimeric kinesin; (b) IFT particles are composed of 15 polypeptides comprising two large complexes; (c) the FLA10 kinesin-II and IFT particle polypeptides, in addition to being found in flagella, are highly concentrated around the flagellar basal bodies; and, (d) mutations affecting homologs of two of the IFT particle polypeptides in Caenorhabditis elegans result in defects in the sensory cilia located on the dendritic processes of sensory neurons. In the accompanying report by Pazour, G.J., C.G. Wilkerson, and G.B. Witman (1998. J. Cell Biol. 141:979-992), a Chlamydomonas mutant (fla14) is described in which only the retrograde transport of IFT particles is disrupted, resulting in assembly-defective flagella filled with an excess of IFT particles. This microtubule- dependent transport process, IFT, defined by mutants in both the anterograde (fla10) and retrograde (fla14) transport of isolable particles, is probably essential for the maintenance and assembly of all eukaryotic motile flagella and nonmotile sensory cilia.