Biochemical basis of SOS-induced mutagenesis in Escherichia coli: reconstitution of in vitro lesion bypass dependent on the UmuD'2C mutagenic complex and RecA protein

Damage-induced SOS mutagenesis requiring the UmuD'C proteins occurs as part of the cells' global response to DNA damage. In vitro studies on the biochemical basis of SOS mutagenesis have been hampered by difficulties in obtaining biologically active UmuC protein, which, when overproduced, is insoluble in aqueous solution. We have circumvented this problem by purifying the UmuD'2C complex in soluble form and have used it to reconstitute an SOS lesion bypass system in vitro. Stimulated bypass of a site-directed model abasic lesion occurs in the presence of UmuD'2C, activated RecA protein (RecA*), beta-sliding clamp, gamma-clamp loading complex, single-stranded binding protein (SSB), and either DNA polymerases III or II. Synthesis in the presence of UmuD'2C is nonprocessive on damaged and undamaged DNA. No lesion bypass is observed when wild-type RecA is replaced with RecA1730, a mutant that is specifically defective for Umu-dependent mutagenesis. Perhaps the most noteworthy property of UmuD'2C resides in its ability to stimulate both nucleotide misincorporation and mismatch extension at aberrant and normal template sites. These observations provide a biochemical basis for the role of the Umu complex in SOS-targeted and SOS-untargeted mutagenesis.

Unusual lesions of the internal auditory canal

Acoustic neuromata (AN) account for nearly 90 per cent of internal auditory canal (IAC) and cerebello-pontine angle (CPA) tumours. The second most common tumour is meningioma. Rare lesions include primary cholesteatoma, facial neuroma, lipoma, angioma and various cysts. Two cases of IAC tumour are presented, one of hamartoma in which smooth muscle was prominent and the other of lymphangioma. Of interest are the specific clinical and radiological features associated with these lesions.

Novel method for processing respiratory specimens for detection of mycobacteria by using C18-carboxypropylbetaine: blinded study

A novel method for processing respiratory specimens to improve culture and acid-fast staining of mycobacteria is introduced. This new method utilized N,N-dimethyl-N-(n-octadecyl)-N-(3-carboxypropyl)ammonium inner salt (Chemical Abstract Service no. 78195-27-4), also known as C18-carboxypropylbetaine (CB-18). In a blinded, five-center study, CB-18-based processing was compared to the standard method combining NALC and NaOH (NALC/NaOH). A total of 573 respiratory specimens were tested. Individual specimens were split approximately equally; the host institutions processed half of each specimen by the NALC/NaOH method, while the other half was processed with CB-18 at Quest Diagnostics--Baltimore. A total of 106 specimens were culture positive for acid-fast bacilli (AFB). Replacement of the primary decontamination agent with CB-18 caused changes in all diagnostic parameters. Aggregate culture sensitivity improved by approximately 43% (P < 0.01), and smear sensitivity improved by approximately 58% (P < 0.01). The sensitivity of smear relative to that of M. tuberculosis isolates exceeded 93% (P < 0.01) when specimens were processed with CB-18. The average times to a positive result were reduced by 7.3 days in liquid culture (P < 0.01) and 5.3 days on solid media (P < 0.05); however, the CB-18 method had a 20.8% contamination rate in liquid culture versus a rate of approximately 7.5% with NALC/NaOH processing. There were also unusual reductions in liquid culture sensitivity and smear specificity among CB-18-processed specimens. The characteristics of the latter parameters suggested that refinement of the CB-18 processing method should allow further improvements in culture sensitivity. This study showed that the CB-18 method has the potential to improve both smear and culture detection for these important human pathogens.

Discriminating constant from variable angular velocities in structure from motion

We investigated accuracy in discriminating between constant and variable angular velocities for orthographic projections of three-dimensional rotating objects. The reported judgments of "constant" or "variable" angular velocity were only slightly influenced by the projected angular velocities, but they were greatly affected by the variations of the deformation, a first-order component of the optic flow. When viewing either a rotating ellipsoidal volume or a planar surface that accelerated and decelerated over the course of rotation, observers' tendencies to report a variable angular velocity were increased when the temporal phase of the acceleration pattern increased the range of variation of the median deformation; the tendencies were decreased when the same acceleration pattern was used to decrease the range of variation of the median deformation. These results provide evidence contrary to the hypothesis that the visual system performs a mathematically correct analysis of the optic flow.

Cisplatin- and paclitaxel-induced apoptosis of ovarian carcinoma cells and the relationship between bax and bak up-regulation and the functional status of p53

We investigated the roles of p53 and Bcl-2 homologues in the induction of apoptosis by cisplatin and paclitaxel in wild-type p53-expressing human ovarian carcinoma cells and cisplatin-resistant derivatives that have lost p53 function. Cisplatin induced apoptosis in parental A2780 but not in cisplatin-resistant A2780/cp70 cells, whereas paclitaxel induced apoptosis in both cell lines. Immunoprecipitation of p53 using antibodies specific for p53 conformation (pAb 1620 and pAb 240) showed that there were no relative changes in p53 conformation before and after cisplatin treatment in either cell line. A2780/cp70 cells have lost p53 function, yet they have wild-type p53 gene sequence. However, A2780/cp70 cells constitutively express more p53 in a form detected by pAb 240, an antibody that also detects mutant conformations of p53 that are transcriptionally inactive. There were no changes in levels of Bcl-2, Bcl-XL, or 24-kDa Bax over 72 hr after exposure to cisplatin or paclitaxel, but each agent led to up-regulation of Bak and 21-kDa Bax in A2780 cells. Paclitaxel, but not cisplatin, increased Bak and 21-kDa Bax levels in A2780/cp70 cells. These data suggest that apoptosis in A2780 and A2780/cp70 is associated with an increased level of Bak and 21 kDa Bax after drug-induced damage and that functional p53 may be required for this effect after cisplatin but not after paclitaxel.

Cationic lipids (lipofectamine) and disturbance of cellular cholesterol and sphingomyelin distribution modulates gamma-secretase activity within amyloid precursor protein in vitro

To study beta-amyloid protein generation we expressed different amyloid precursor protein (APP) isoforms in the human neuroblastoma cell line SY5Y (for details see (1)). Treatment with lipofectamine, an cationic lipid for eucaryotic cell transfection, inhibits gamma-secretase activity and stimulates the physiological APP cleavage by alpha-secretase activity. Beside the MDL inhibitor (2), this is the second agent that shows modulation of gamma-secretase activity in vitro. Further, we show that disturbance of cellular cholesterol and sphingomyelin distribution in transfected SY5Y cells results in an overproduction of beta-amyloid protein. This provides experimental evidence that membrane instability influenced the proteolytic activity of gamma-secretase within the APP molecule.

Activity of amoxicillin/clavulanate in patients with tuberculosis

Some beta-lactam antibiotics are active in vitro against Mycobacterium tuberculosis. There are anecdotal reports of successful treatment of tuberculosis caused by multiple-drug-resistant strains of M. tuberculosis with regimens that included amoxicillin/clavulanate. Reduction of M. tuberculosis in the sputum of patients with pulmonary tuberculosis during administration of amoxicillin/clavulanate was measured by a quantitative culture method to determine the activity in vivo. Patients were randomized to receive isoniazid, ofloxacin, or amoxicillin/clavulanate for 7 days. Isoniazid was the most effective agent, reducing M. tuberculosis after 2 days at a mean rate (+/- standard deviation) of 0.60 +/- 0.30 log10 cfu/mL per day, compared with 0.32 +/- 0.05 and 0.34 +/- 0.03 for ofloxacin and amoxicillin/clavulanate, respectively. The early bactericidal activity of amoxicillin/clavulanate was comparable to that reported for antituberculous agents other than isoniazid. Further studies of beta-lactam antibiotics with in vitro activity against M. tuberculosis are warranted to define their role in treatment of tuberculosis.

The TIR1 protein of Arabidopsis functions in auxin response and is related to human SKP2 and yeast grr1p

Genetic analysis in Arabidopsis has led to the identification of several genes that are required for auxin response. One of these genes, AXR1, encodes a protein related to yeast Aos1p, a protein that functions to activate the ubiquitin-related protein Smt3p. Here we report the identification of a new gene called TRANSPORT INHIBITOR RESPONSE 1 (TIR1). The tir1 mutants are deficient in a variety of auxin-regulated growth processes including hypocotyl elongation and lateral root formation. These results indicate that TIR1 is also required for normal response to auxin. Further, mutations in TIR1 display a synergistic interaction with mutations in AXR1, suggesting that the two genes function in overlapping pathways. The TIR1 protein contains a series of leucine-rich repeats and a recently identified motif called an F box. Sequence comparisons indicate that TIR1 is related to the yeast protein Grr1p and the human protein SKP2. Because Grr1p and other F-box proteins have been implicated in ubiquitin-mediated processes, we speculate that auxin response depends on the modification of a key regulatory protein(s) by ubiquitin or a ubiquitin-related protein.

The role of the psychologist in crisis/hostage negotiations

Over the past three decades, there has been a noted increase in hostage and barricade incidents involving perpetrators with a variety of emotional, economic, and political motives. A hostage incident may be defined as an incident in which (a) perpetrator(s) hold(s) one or more persons against their will in a location known to police. A barricade incident, on the other hand, is an incident without hostages in which a perpetrator is barricaded, also in a location known to police and refusing to surrender. Approximately 25 years ago, a theory of crisis/hostage negotiations was developed which has been continuously refined in field applications. This article will define the goal of crisis/hostage negotiation, review the history of hostage taking from biblical times to the present, review the utilization of psychologists and other mental health consultants by police crisis/hostage negotiation teams, and discuss the four roles and related functions of psychologists on crisis/hostage negotiation teams.

The cellular intake kinetics and acute biological effects of various oxovanadium species: a comparative study

It is well known that different oxovanadium species can have significantly different biopotencies, including hypoglycemic actions. The basis for the observed differences in the biopotency of different oxovanadium species: vanadate, vanadyl, 1,10-phenanthroline bisperoxovanadate (phen-bpv), 4-methyl 1,10-phenanthroline bisperoxovanadate (mpv) and 4,7-dimethyl 1,10-phenanthroline bisperoxovanadate (dpv), was examined in this study. The cellular uptake kinetics for these oxovanadium species was measured. Phen-bpv and vandyl had the most rapid cellular uptake. Mpv, dpv and vanadate exhibited a much slower uptake kinetics. Stimulation of protein tyrosine phosphorylation (PTP), both the time dependency and the dose dependency, was used as an index for biopotency. Although phen-bpv and vanadyl had the same cellular uptake kinetics, they differed markedly in their ability to stimulate PTP. Structurally similar oxovanadium species, phen-bpv, mpv and dpv demonstrated different uptake kinetics and effects on stimulating PTP. Bioavailability, both in term of cellular uptake and migration or transport to the active site, has been shown to be an important factor, in addition to intrinsic activity of the oxovanadium species, in determining the overall biopotency. Finally, this study demonstrates that variation of the chelating ligand has a profound effect on the physiochemical properties and biological effects of the oxovanadium species.

Activation of c-Src by receptor tyrosine kinases in human colon cancer cells with high metastatic potential

Recent data suggest that signal transduction may have a critical role in the development and regulation of the metastatic phenotype. Here, we investigated the role of c-Src activation in the process of human colon cancer metastasis to the liver. Our data, derived from two different sets of human colon cancer cell line metastatic variants, suggest that not only do highly-metastatic cells display constitutively elevated c-Src protein kinase activity when compared to poorly metastatic cells, but also that receptor tyrosine kinases participate in the ligand-activation of c-Src above basal levels. Specifically, the epidermal growth factor receptor (EGFR), p185HER2/Neu and the hepatocyte growth factor receptor (c-Met) appear to be linked to the process because they preferentially activate c-Src in highly-metastatic cells. EGFR was found to associate with c-Src in colon cancer cells and specific inhibitors of the EGFR resulted in a reduction of c-Src activity to basal levels. In addition, c-Src transfectants displayed partially-activated EGFRs, suggesting a feedback role for c-Src in the regulation of the EGFR. p185HER2/Neu was also identified in immunocomplexes of c-Src following ligand activation of the EGFR, but only in highly-metastatic cells. Collectively, these observations suggest a paradigm whereby c-Src interacts with multiple cell-surface growth factors in a catalytic fashion for the development of tumor cells with metastatic potential.

Effectiveness of a regional trauma system in reducing mortality from major trauma: before and after study

OBJECTIVE

To assess the effect of the development of an experimental trauma centre and regional trauma system on the survival of patients with major trauma.

DESIGN

Controlled before and after study examining outcomes between 1990 and 1993, spanning the introduction of the system in 1991-2.

SETTING

Trauma centre in North Staffordshire Royal Infirmary and five associated district general hospitals in the North West Midlands regional trauma system, and two control regions in Lancashire and Humberside.

SUBJECTS

All trauma patients taken by the ambulance services serving the regions or arriving other than by ambulance with injury severity scores > 15, whether or not they had vital signs on arrival at hospital.

MAIN OUTCOME MEASURES

Survival rates standardised for age, severity of injury, and revised trauma score.

RESULTS

In 1990, 33% of major trauma patients in the experimental region were taken to the trauma centre, and by 1993 this had risen to only 39%. Crude death rates changed by the same amount in the control regions (46.5% in 1990-1 to 44.4% in 1992-3) as in the experimental region (44.8% to 41.3%). After standardisation, the estimated change in the probability of dying in the experimental region compared with the control regions was -0.8% per year (95% confidence interval -3.6% to 2.2%); for out of hours care, the change was 1.6% per year (-2.3% to 5.6%), and, for multiply injured patients, the change was -1.6% (-6.1% to 2.6%).

CONCLUSION

Any reductions in mortality from regionalising major trauma care in shire areas of England would probably be modest compared with reports from the United States.

Actinomycosis oto-mastoiditis

Actinomycosis of the temporal bone is uncommon. There have only been 24 cases previously reported in the English literature. The responsible organism is Actinomyces israelii, an anaerobic filamentous Gram positive bacterium. While the cervico-facial region is the most common site of the disease, involvement of the temporal bone is rare. The diagnosis can sometimes be made clinically by identification of sulphur granules in a glue-like substrate but in all cases involving the temporal bone, the diagnosis has been made at histopathology. Effective therapy consists of surgery followed by the long-term administration of penicillin.

Assessment of health risks due to hazardous air pollutant emissions from electric utilities

Hazardous air pollutant (HAP) emissions from electric utilities were evaluated. Cancer risks, as well as noncancer effects, due to inhalation exposure were assessed for 67 HAPs. Also, cancer risks due to multipathway exposure to radionuclide emissions were assessed. In addition, an assessment of the fate of mercury (Hg) through various environmental media was included. Results suggest arsenic, chromium, and nickel are the HAPs that present the highest cancer risk due to inhalation exposure. For noncancer effects due to inhalation exposure, hydrogen chloride appears to present the greatest potential concern. The risks due to multipathway exposure to radionuclides are estimated to be of similar magnitude to the risks posed by inhalation of arsenic and nickel. Mercury is of potential concern for multipathway exposures because it persists in the environmental and bioaccumulates in the aquatic food web. The study suggests there is a plausible link between Hg emissions from utilities and the Hg found in soil, water, and freshwater fish.

Fidelity of Escherichia coli DNA polymerase III holoenzyme. The effects of beta, gamma complex processivity proteins and epsilon proofreading exonuclease on nucleotide misincorporation efficiencies

The fidelity of Escherichia coli DNA polymerase III (pol III) is measured and the effects of beta, gamma processivity and epsilon proofreading subunits are evaluated using a gel kinetic assay. Pol III holoenzyme synthesizes DNA with extremely high fidelity, misincorporating dTMP, dAMP, and dGMP opposite a template G target with efficiencies finc = 5.6 x 10(-6), 4.2 x 10(-7), and 7 x 10(-7), respectively. Elevated dGMP.G and dTMP.G misincorporation efficiencies of 3.2 x 10(-5) and 5.8 x 10(-4), attributed to a "dNTP-stabilized" DNA misalignment mechanism, occur when C and A, respectively, are located one base downstream from the template target G. At least 92% of misinserted nucleotides are excised by pol III holoenzyme in the absence of a next correct "rescue" nucleotide. As rescue dNTP concentrations are increased, pol III holoenzyme suffers a maximum 8-fold reduction in fidelity as proofreading of mispaired primer termini are reduced in competition with incorporation of a next correct nucleotide. Compared with pol III holoenzyme, the alpha holoenzyme, which cannot proofread, has 47-, 32-, and 13-fold higher misincorporation rates for dGMP.G, dTMP.G, and dAMP.G mispairs. Both the beta, gamma complex and the downstream nucleotide have little effect on the fidelity of catalytic alpha subunit. An analysis of the gel kinetic fidelity assay when multiple polymerase-DNA encounters occur is presented in the "Appendix" (see Fygenson, D. K., and Goodman, M. F. (1997) J. Biol. Chem. 272, 27931-27935 (accompanying paper)).

Design of the cyclops flap for chest-wall reconstruction

The cyclops flap is a little-known but not forgotten alternative in chest-wall reconstruction for women. Female patients having a large, pendulous breast with a contralateral adjacent defect may be reconstructed by this technique. The flap derives its name from the repositioning of the remaining nipple to the center of the chest. The design of the flap is described. By knowing the width and length of the defect, the surgeon can design incisions on the remaining breast tissue that will allow the flap to advance easily, reliably filling the defect. The flap is an axial-pattern flap nourished by the lateral thoracic artery and the variable external mammary artery. This arterial inflow will serve the medial portion of the flap. The operation is straightforward and predictable. In using this design scheme three times in the last two years, there have been no complications. There is little discomfort after surgery. Occasionally, patients will benefit from this reconstructive option.

v-Abl protein tyrosine kinase (PTK) mediated suppression of apoptosis is associated with the up-regulation of Bcl-XL

We demonstrated previously that the activation of v-Abl protein tyrosine kinase (PTK) in IC.DP murine pre-mast cells resulted in suppression of apoptosis after withdrawal of interleukin 3 (IL-3), that protein kinase C (PKC) translocated to the nucleus 6 h after v-Abl PTK activation and that inhibition of PKC restored apoptosis after IL-3 deprivation in the presence of v-Abl PTK activity. Here we demonstrate that v-Abl PTK activation is followed by an approximately twofold increase in mRNA level of Bcl-XL by 6 h and a corresponding increase in Bcl-XL protein level by 24 h. Bcl-xL RNA and protein decreased in IL-3 deprived cells in the absence of v-Abl PTK activity. Exposure of cells with v-Abl PTK active to the PKC inhbitor calphostin C (125 ng/ml) prevented the increase in Bcl-xL protein and resulted in apoptosis. No changes in Bax or Bcl-2 protein level were noted after IL-3 withdrawal and/or activation of v-Abl PTK. Bak was barely detectable and Bad protein level decreased in cells undergoing apoptosis. The data suggest that suppression of apoptosis by v-Abl PTK in the absence of IL-3 is associated with PKC signalling and the upregulation of Bcl-xL in IC.DP cells.

Acute renal failure due to indinavir crystalluria and nephrolithiasis: report of two cases

Two patients with oliguric acute renal failure (ARF) attributed to crystalluria and nephrolithiasis with obstructive uropathy caused by the human immunodeficiency virus protease inhibitor indinavir are described. In both patients, ARF resolved with administration of intravenous fluids. One patient required urologic intervention to relieve bilateral ureteral obstruction.