Interactions between DNA polymerase beta and the major covalent adduct of the carcinogen (+)-anti-benzo[a]pyrene diol epoxide with DNA at a primer-template junction

A molecular dynamics simulation has been carried out with DNA polymerase beta (beta pol) complexed with a DNA primer-template. The templating guanine at the polymerase active site was covalently modified by the carcinogenic metabolite of benzo[a]pyrene, (+)-anti-benzo[a]pyrene diol epoxide, to form the major (+)-trans-anti-benzo[a]pyrene diol epoxide covalent adduct. Thus, the benzo[a]pyrenyl moiety (BP) is situated in the single-stranded template at the junction between double- and single-stranded DNA. The starting structure was based on the X-ray crystal structure of the rat beta pol primer-template and ddCTP complex [Pelletier, H., Sawaya, M. R., Kumar, A., Wilson, S. H., and Kraut, J. (1994) Science 264, 1891-1903]. During the simulation, the BP and its attached templating guanine rearrange to form a structure in which the BP is closer to parallel with the adjacent base pair. In addition, the templating attached guanine is displaced toward the major groove side and access to its Watson-Crick edge is partly obstructed. This structure is stabilized, in part, by new hydrogen bonds between the BP and beta pol Asn279 and Arg283. These residues are within hydrogen bonding distance to the incoming ddCTP and templating guanine, respectively, in the crystal structure of the beta pol ternary complex. Site-directed mutagenesis has confirmed their role in dNTP binding, discrimination, and catalytic efficiency [Beard, W. A., Osheroff, W. P., Prasad, R., Sawaya, M. R., Jaju, M., Wood, T. G., Kraut, J., Kunkel, T. A., and Wilson, S. H. (1996) J. Biol. Chem. 271, 12141-12144]. The predominant biological effect of the BP is DNA polymerase blockage. Consistent with this biological effect, the computed structure suggests the possibility that the BP's main deleterious impact on DNA synthesis might result at least in part from its specific interactions with key polymerase side chains. Moreover, relatively modest movement of BP and its attached guanine, with some concomitant enzyme motion, is necessary to relieve the obstruction and permit the observed rare incorporation of a dATP opposite the guanine lesion.     

Expression of an exogenous eukaryotic DNA methyltransferase gene induces transformation of NIH 3T3 cells

Abnormal regional increases in DNA methylation, which have potential for causing gene inactivation and chromosomal instability, are consistently found in immortalized and tumorigenic cells. Increased DNA methyltransferase activity, which is also a characteristic of such cells, is a candidate to mediate these abnormal DNA methylation patterns. We now show that, in NIH 3T3 mouse fibroblasts, constitutive overexpression of an exogenous mouse DNA methyltransferase gene results in a marked increase in overall DNA methylation which is accompanied by tumorigenic transformation. These transformation changes can also be elicited by dexamethasone-inducible expression of an exogenous DNA methyltransferase gene. Our findings provide strong evidence that the increase in DNA methyltransferase activity associated with tumor progression could be a key step in carcinogenesis and provide a model system that can be used to further study this possibility.     

Intracoronary stent implantation using a single high-pressure perfusion balloon catheter

INTRODUCTION: A factory producing lead ingots, located in Ca?apava, caused lead and cadmium contamination of the environment, in the Paraiba Valley region of Southeastern, Brazil, through the discharge of industrial waste and the recycling of batteries. The factory, set in a rural, dairy cattle breeding area, worried sanitary authorities who envisaged the possibility of these metals' having entered the food chain. For the purpose of assessing the levels of contamination of the milk produced in the region, due to the cattle's possible consumption of contaminated grass and water, the amounts of cadmium and lead present in the milk were verified. MATERIAL AND METHOD: Major producers, covering an area of up to 20 km from the contaminated source, authorized collection of 218 samples of both pasteurized and non-pasteurized milk, which were analysed. Lead and cadmium levels were determined by flame atomic absorption spectrophotometry, the lead being pre-concentrated by complexation with APDC (ammonium 1-pyrrolidinecarbodithioate) and further extraction with isobutyl methylketone. RESULTS AND CONCLUSIONS: Of the total number of samples, 43 presented lead levels over the maximum limit of 0.05 mg/kg established by Brazilian legislation. The median value found for lead was 0.04 mg/L. The variance analysis, with 95% confidence level, found no significant difference among the types of milk studied with regard to lead levels. As for cadmium, all samples showed levels below the 0.02 mg/L quantification limit of the method. In spite of the environmental contamination, the levels of cadmium found in the milk were below the 1.0 mg/kg limit established by Brazilian legislation.     

Unilateral lobectomy for Hurthle cell adenoma

Considerable controversy exists regarding the ability to predict the biologic behavior of Hurthle cell tumors. Some have found the clinicopathologic criteria used to differentiate benign from malignant lesions to be unreliable and have advocated total thyroidectomy for all Hurthle cell neoplasms. From January 1980 to December 1995, 39 patients had surgery for Hurthle cell tumors of the thyroid. The surgical pathologic findings were reviewed by an experienced pathologist (JP). Eight patients had histologic findings of capsular or vascular invasion consistent with carcinoma and had total thyroidectomy. Four of these patients had postoperative evidence of residual disease and were treated by radiation ablation. No evidence of invasion was found in 31 patients diagnosed with Hurthle cell adenoma. Twenty-three of these patients had unilateral lobectomy; total thyroidectomy was done in the remaining 8 patients, 5 of whom were found to have an associated papillary carcinoma at the time of operation. There were no operative deaths or significant morbidity. Twenty-two adenomas (71%) were found in females, whereas males had malignant tumors in 6 of 8 cases (P = 0.025). The mean age of adenoma patients is 54.1 years, and that of the carcinoma patients is 55.8 years. Mean size of benign tumors was 2.8 cm and of malignant tumors 4.1 cm (P = 0.04). Four of seven (57%) carcinomas were larger than 4 cm as compared with 6 of 30 (20%) adenomas (P = 0.069). Follow-up has ranged from 1 month to 15 years, with a mean of 3.2 years. There have been no deaths, and no patients with Hurthle cell adenoma have had evidence of recurrence or metastases during follow-up. Our data suggest that carcinoma patients tend to be male and tumor size is larger. An association was found when trying to predict malignancy by using 4 cm as a threshold size. We conclude that pathologic evidence of capsular or angioinvasion can accurately differentiate benign from malignant tumors. Unilateral thyroid lobectomy is adequate therapy for the treatment of Hurthle cell adenoma, with total thyroidectomy reserved for those patients with histologically proven carcinoma.     

Basolateral amygdala stimulation evokes glutamate receptor-dependent dopamine efflux in the nucleus accumbens of the anaesthetized rat

Afferents from the basolateral amygdala and dopamine projections from the ventral tegmental area to the nucleus accumbens have both been implicated in reward-related processes. The present study used in vivo chronoamperometry with stearate-graphite paste electrodes in urethane-anaesthetized rats to determine how basolateral amygdala efferents to the nucleus accumbens synaptically regulate dopamine efflux. Repetitive-pulse (20 Hz for 10 s) electrical stimulation of the basolateral amygdala evoked a complex pattern of changes in monitored dopamine oxidation currents in the nucleus accumbens related to dopamine efflux. These changes were characterized by an initial increase that was time-locked to stimulation, a secondary decrease below baseline, followed by a prolonged increase in the dopamine signal above baseline. The effects of burst-patterned stimulation (100 Hz, 5 pulses/burst, 1-s interburst interval, 40 s) of the basolateral amygdala on the basal accumbens dopamine signal were similar to those evoked by 20 Hz stimulation, with the lack of a secondary suppressive component. Infusions of the ionotropic glutamate receptor antagonists (+/-)-2-amino-5-phosphonopentanoic acid (APV) or 6,7-dinitroquinoxaline-2,3-dione (DNQX) into the nucleus accumbens dose-dependently blocked or attenuated the initial and prolonged increases in the dopamine signal following 20 Hz or burst-patterned basolateral amygdala stimulation. Infusions of the metabotropic glutamate receptor antagonist (+)-alpha-methyl-4-carboxyphenylglycine selectively blocked the intermediate suppressive effect of 20 Hz basolateral amygdala stimulation on dopamine oxidation currents. Blockade of glutamate receptors or inhibition of dopamine neuronal activity via infusions of either APV + DNQX, lidocaine or gamma-hydroxybutyric acid, respectively, into the ventral tegmental area did not effect the pattern of changes in the accumbens dopamine signal evoked by basolateral amygdala stimulation. These data suggest that the glutamatergic basolateral amygdala inputs to nucleus accumbens dopamine terminals synaptically facilitate or depress dopamine efflux, and these effects are independent of dopamine neuronal firing activity. Moreover, these results imply that changes in nucleus accumbens dopamine levels following presentation of reward-related stimuli may be mediated, in part, by the basolateral amygdala.     

Advances in the management of Crohn's disease: economic and clinical potential of infliximab

New therapies for Crohn's disease are being developed based on improvements in our understanding of the disease's immune and inflammatory properties. One of these new therapies is infliximab, a monoclonal antibody directed against the proinflammatory cytokine tumor necrosis factor-alpha. Recent studies indicate that treatment of moderately to severely ill Crohn's disease patients with infliximab produces a rapid and profound reduction in the signs, symptoms, and severity of this disease. Beyond its clinical impact, Crohn's disease also carries significant economic consequences. Earlier reports on the costs of managing this disease estimated the average annual medical costs per patient at $9197, with the total annual cost of illness estimated to exceed $1.7 billion. Hospitalizations and surgeries represented 80% of these costs. Additional analyses have been conducted for this review to reflect more current treatment patterns. Assuming that proven increases in response and remission rates lead to diminished disease severity, infliximab can be expected to reduce the number of hospitalizations and surgeries in moderately to severely ill patients, with substantial cost savings. Moreover, improvement in disease status and quality of life may allow Crohn's disease patients to lead more productive lives.     

The cobbler's children: usability in the lab

Software and product designers regularly wrestle with the usability of their creations in user studies laboratories. The laboratories themselves, however, often languish for lack of the same scrutiny with respect to their own usability. In this article, we trace our efforts toward making a truly usable user studies laboratory. Our lab serves many purposes and many individuals, each requiring a slightly different configuration of equipment. The challenge was to design a user studies environment that would provide 'instant' configurations, obviating the need for users to connect components by hand. Toward this end, we purchased equipment that could be controlled directly or indirectly by a computer and designed the wiring plant to all run through a matrix switcher, also under computer control. Upon this technology, we designed a user interface in HyperCard that automatically configures the lab and provides the interface controls required for any one of a set of specific pre-designed tasks that the user may select. The interface also permits the user to customize and save sets of configurations and controls by copying and pasting among cards and also to create novel configurations by manipulating the matrix controller's software switches one by one.     

The major inherited disorders of cornification. New advances in pathogenesis

This article provides a synopsis of the major (most common) inherited disorders of cornification. It also reviews the recent advances that have been made for each disorder and their practical applications.     

Biochemical outcome after radical prostatectomy, external beam radiation therapy, or interstitial radiation therapy for clinically localized prostate cancer

CONTEXT: Interstitial radiation (implant) therapy is used to treat clinically localized adenocarcinoma of the prostate, but how it compares with other treatments is not known. OBJECTIVE: To estimate control of prostate-specific antigen (PSA) after radical prostatectomy (RP), external beam radiation (RT), or implant with or without neoadjuvant androgen deprivation therapy in patients with clinically localized prostate cancer. DESIGN: Retrospective cohort study of outcome data compared using Cox regression multivariable analyses. SETTING AND PATIENTS: A total of 1872 men treated between January 1989 and October 1997 with an RP (n = 888) or implant with or without neoadjuvant androgen deprivation therapy (n = 218) at the Hospital of the University of Pennsylvania, Philadelphia, or RT (n = 766) at the Joint Center for Radiation Therapy, Boston, Mass, were enrolled. MAIN OUTCOME MEASURE: Actuarial freedom from PSA failure (defined as PSA outcome). RESULTS: The relative risk (RR) of PSA failure in low-risk patients (stage T1c, T2a and PSA level < or =10 ng/mL and Gleason score < or =6) treated using RT, implant plus androgen deprivation therapy, or implant therapy was 1.1 (95% confidence interval [CI], 0.5-2.7), 0.5 (95% CI, 0.1-1.9), and 1.1 (95% CI, 0.3-3.6), respectively, compared with those patients treated with RP. The RRs of PSA failure in the intermediate-risk patients (stage T2b or Gleason score of 7 or PSA level >10 and < or =20 ng/mL) and high-risk patients (stage T2c or PSA level >20 ng/mL or Gleason score > or =8) treated with implant compared with RP were 3.1 (95% CI, 1.5-6.1) and 3.0 (95% CI, 1.8-5.0), respectively. The addition of androgen deprivation to implant therapy did not improve PSA outcome in high-risk patients but resulted in a PSA outcome that was not statistically different compared with the results obtained using RP or RT in intermediate-risk patients. These results were unchanged when patients were stratified using the traditional rankings of biopsy Gleason scores of 2 through 4 vs 5 through 6 vs 7 vs 8 through 10. CONCLUSIONS: Low-risk patients had estimates of 5-year PSA outcome after treatment with RP, RT, or implant with or without neoadjuvant androgen deprivation that were not statistically different, whereas intermediate- and high-risk patients treated with RP or RT did better then those treated by implant. Prospective randomized trials are needed to verify these findings.