DNA synthesis inhibition as an indirect mechanism of chromosome aberrations: comparison of DNA-reactive and non-DNA-reactive clastogens

Positive results in the in vitro assay for chromosome aberrations sometimes occur with test chemicals that apparently do not react with DNA, being negative in tests for mutation in bacteria, for DNA strand breaks, and for covalent binding to DNA. These chromosome aberrations typically occur over a narrow concentration range at toxic doses, and with mitotic inhibition. Indirect mechanisms, including oxidative damage, cytotoxicity and inhibition of DNA synthesis induced by chemical exposure, may be involved. Understanding when such mechanisms are operating is important in evaluating potential mutagenic hazards, since the effects may occur only above a certain threshold dose. Here, we used two-parameter flow cytometry to assess DNA synthesis inhibition (uptake of bromodeoxyuridine [BrdUrd]) associated with the induction of aberrations in CHO cells by DNA-reactive and non-reactive chemicals, and to follow cell cycle progression. Aphidicolin (APC), a DNA polymerase inhibitor, induces aberrations without reacting with DNA; 50 microM APC suppressed BrdUrd uptake during a 3-h treatment to <10% of control levels. Several new drug candidates induced aberrations concomitant with marked reductions in cell counts at 20 h (to 50-60% of controls) and suppression of BrdUrd uptake (<15% of control). Several non-mutagenic chemicals and a metabolic poison, which induce DNA double strand breaks and chromosome aberrations at toxic dose levels, also suppressed DNA synthesis. In contrast, the alkylating agents 4-nitroquinoline-1-oxide, mitomycin C, methylnitrosourea, ethylnitrosourea, methylmethane sulfonate and ethylmethane sulfonate, and a topoisomerase II inhibitor, etoposide, produced many aberrations at concentrations that were less toxic (cell counts >/=73% of controls) and gave little inhibition of DNA synthesis during treatment (BrdUrd uptake >/=85% of controls), although cell cycle delay was seen following the 3-h treatment. Thus, inhibition of DNA synthesis at the time of treatment is supporting evidence for an indirect mechanism of aberrations, when there is no direct DNA reactivity.     

Managed care and unintended pregnancy

This article assesses the adequacy of coverage of contraceptive services and supplies for US women in the various types of managed care plans, with special attention to Medicaid. Between 1993 and 1995, the percent of insured private-sector employees enrolled in managed care plans rose from 51% to 73%. By 1996, the health care of 40% of low-income Medicaid recipients was also under managed care administration. Although 84% of managed care plans cover oral contraceptives--a rate substantially higher than that for traditional indemnity plans, several logistic factors impede access to this and other reproductive health benefits. The requirement of preauthorization may delay access to care when timely presentation is essential to the prevention of unwanted pregnancy. Some plans restrict members to one visit per year with an obstetrician-gynecologist. Coordination of an enrollee's total health care through the primary care physician can raise confidentiality problems for those who seek sensitive reproductive health services. There are fewer restrictions on the access of Medicaid recipients to family planning providers and services, but treatment of sexually transmitted diseases may not be part of the reproductive health package. The explosion of managed care onto the US health care market has led to public sector regulation legislation--a process that is proceeding in a piecemeal rather than comprehensive way. Because of the importance of reproductive health care to the lives of women, communities, and the broader society, more systematic action on this front is essential.     

Bridging town and gown: building research partnerships between community-based professional providers and academia

Interleukin 1 (IL-1) is postulated to function in maintaining homeostasis, however, over-action of this cytokine may lead to disruption of homeostasis due to it's wide spectrum of activities. To understand the endogenous regulation of this cytokine, we examined the existence of IL-1 receptor antagonist (IL-1Ra) in tissues from healthy rabbits. IL-1Ra was constitutively produced in all tissues examined (lung, liver, spleen, thymus, caecum, skin, kidney, heart, and brain), as estimated by ELISA. Immunoprecipitation, RT-PCR and immunohistochemical studies indicated that all tissues produced secreted form of IL-1Ra (sIL-1Ra), whereas thymus, caecum, skin and kidney produced both sIL-1Ra and intracellular of IL-1Ra. All tissue IL-1Ra purified using anti-IL-1Ra IgG affinity chromatography had inhibitory activity on the IL-1-induced thymocyte proliferative response, and the activity was totally abolished by anti-IL-1Ra mAb. No IL-1 activity was detected in any tissues except skin and heart, however, after preincubation of the samples with anti-IL-1Ra, the activity was first visible in the tissues. Under these conditions, IL-1 activity in skin and heart was enhanced to 170% and 280%, respectively. Taken together, we conclude that tissue IL-1Ra is involved in health maintenance by masking co-existing IL-1 activity present in tissues.     

Anastrozole versus megestrol acetate in the treatment of postmenopausal women with advanced breast carcinoma: results of a survival update based on a combined analysis of data from two mature phase III trials. Arimidex Study Group

BACKGROUND: This report presents the results of a survival update based on the combined data from two studies that compared the efficacy and tolerability of anastrozole (1 or 10 mg once daily), a selective, nonsteroidal aromatase inhibitor administered orally, and megestrol acetate (40 mg 4 times daily) in the treatment of postmenopausal women with advanced breast carcinoma whose disease had progressed after treatment with tamoxifen. METHODS: Two randomized, parallel-group, multicenter trials were conducted, involving a total of 764 patients. The two trials were identical in design; both were double blind for anastrozole and open label for megestrol acetate. Overview analyses were conducted with the intent of strengthening the interpretation of results from each trial. The median follow-up duration for this survival update was 31 months. RESULTS: At the clinical dose of 1 mg daily, anastrozole demonstrated a statistically significant survival advantage over megestrol acetate, with a hazard ratio of 0.78 (P < 0.025)(0.60 < 97.5% confidence interval [CI] <1.0). The 1 mg anastrozole group also had a longer median time to death (26.7 months) compared with 22.5 months for the megestrol acetate group. The 10 mg anastrozole group also had a survival benefit over the megestrol acetate group, with a hazard ratio of 0.83 (P=0.09, not significant)(0.64 < 97.5% CI < 1.1). Higher 2-year survival rates were observed for both anastrozole treatment groups than for the megestrol acetate group (56.1%, 54.6%, and 46.3% for the groups given 1 mg anastrozole, 10 mg anastrozole, and megestrol acetate, respectively). CONCLUSIONS: This combined analysis of two trials of postmenopausal patients with advanced breast carcinoma has clearly demonstrated that, after disease progression with tamoxifen, treatment with anastrozole 1 mg once daily results in a statistically and clinically significant advantage over a standard treatment, megestrol acetate. This important benefit, in addition to the good tolerability profile of anastrozole, supports the use of this drug as a valuable new treatment option for this patient population.     

Differences in fine control of forces generated by the tongue, lips and fingers in humans

This study compared the fine control of forces generated by the tongue, lips and fingers in middle-aged adults. The aims were to determine whether (1) the articulatory organs (tongue, lips) and fingers differed in the manner of motor control, (2) force control of the various articulatory organs was similar, and (3) control of forces generated by males was different from that of forces generated by females. The relation among several variables of the ramp-and-hold force contraction and target force level was quantified for the articulatory organs and the fingers in 14 normal individuals (7 males and 7 females). Using visual feedback, participants produced ramp-and-hold compression forces as rapidly and accurately as possible to targets ranging from 0.25 to 2 N. The results showed differences in the profiles of forces generated by the articulatory organs and fingers. In particular, the forefingers were characterized by a greater accuracy of force control and precision of movement, a greater stability of the hold phase, but by slower velocities than the articulatory organs. Motor control of the lower lip differed from that of the upper lip and tongue. Mostly, the lower lip was characterized by a greater precision of contraction, faster development of the force, and greater stability of the hold phase than the upper lip and tongue. Gender was a distinguishing factor in the force task; males were able to produce forces with higher velocities and greater precision than females.     

Arachidonic acid activates a proton current in the rat glutamate transporter EAAT4

The excitatory amino acid transporter EAAT4 is expressed predominantly in Purkinje neurons in the rat cerebellum (1-3), and it participates in postsynaptic reuptake of glutamate released at the climbing fiber synapse (4). Transporter-mediated currents in Purkinje neurons are increased more than 3-fold by arachidonic acid, a second messenger that is liberated following depolarization-induced Ca2+ activation of phospholipase A2 (5). In this study we demonstrate that application of arachidonic acid to oocytes expressing rat EAAT4 increased glutamate-induced currents to a similar extent. However, arachidonic acid did not cause an increase in the rate of glutamate transport or in the chloride current associated with glutamate transport but rather activated a proton-selective conductance. These data reveal a novel action of arachidonate on a glutamate transporter and suggest a mechanism by which synaptic activity may decrease intracellular pH in neurons where this transporter is localized.     

Renal stone analysis: is there any clinical value?

OBJECTIVE: To provide national-level data concerning the percentage of pharmacies selling tobacco products, examine relationships between selling practices and pharmacy characteristic variables, and explore perceptions of conflicts between tobacco-selling activity and professional and personal values and the potential effects of such conflicts. DESIGN, SETTING, PARTICIPANTS: Data were collected from a geographically stratified systematic random sample of 899 pharmacies. Multiple mailings were sent to the attention of the pharmacy manager. A random sample of nonrespondents was also contacted by telephone, urging participation. MAIN OUTCOME MEASURES: Whether the pharmacy currently sold cigarettes and/or smokeless tobacco products, and if so, whether these practices differed from what respondents' personal or professional values tell them to do. Scales designed to measure job satisfaction, job-induced tension, and propensity to leave were also included. RESULTS: Slightly more than half (50.5%) of the pharmacies sold cigarettes and 35.4% sold smokeless tobacco products. Independents were less likely than chain pharmacies to sell tobacco products. For those respondents working in pharmacies where tobacco products were sold, 47.6% responded that this practice differs from what their personal values tell them to do and 63.9% replied that this practice differs from what their professional values tell them to do. Even when controlling for pharmacy type, respondents working in pharmacies that sold tobacco products had significantly lower levels of global job satisfaction, higher levels of job-induced tension, and a higher propensity to leave than did respondents working in pharmacies that did not. CONCLUSION: Decision makers in pharmacies where tobacco products are still sold should take a serious look at the justification for the continued availability of tobacco products in an environment that has a goal of promoting health.     

A double-blind randomized placebo cross-over controlled trial using the antioxidant vitamin E to treat reactive oxygen species associated male infertility

OBJECTIVE: To determine the effectiveness of the in vivo administration of vitamin E as treatment for reactive oxygen species-associated male infertility. SETTING: University-based center for reproductive medicine. DESIGN: Double-blind randomized placebo cross-over controlled trial. PATIENTS, PARTICIPANTS: Thirty healthy men with high levels of reactive oxygen species generation in semen and a normal female partner. INTERVENTIONS: Patients were allocated to two groups according to the blinded randomization. Each patient received either 600 mg/d of vitamin E (Ephynal, 300 mg tablets; F. Hoffman-La Roche Ltd., Basle, Switzerland) (order A) or identical placebo tablets (order B) for 3 months. Then after a 1-month wash-out period the patients were crossed-over to the other treatment. MAIN OUTCOME MEASURES: Improvement in the in vitro function of the spermatozoa measured by conventional semen analysis, computerized motility assessment, determination of reactive oxygen species generation, binding to the zona pellucida of the unfertilized human oocyte in a competitive zona binding assay, development of hyperactivated motility (both spontaneous and in the presence of 20% of the natural agonist, human follicular fluid) and pregnancy. RESULTS: Rise in the blood serum vitamin E levels after treatment accompanied by improvement in one of the sperm function tests: the zona binding assay. The zona binding ratio for order A improved from 0.2 (range 0 to 0.5) before treatment to 0.5 (range 0.1 to 1.0) after treatment, the corresponding values for order B were 0.2 (range 0 to 1.0) before treatment and 0.3 (range 0.1 to 0.7) after treatment. CONCLUSION: Oral administration of vitamin E significantly improves the in vitro function of human spermatozoa as assessed by the zona binding test.     

Synthesis and dopamine transporter affinity of 2-(methoxycarbonyl)-9-methyl-3-phenyl-9-azabicyclo[3.3.1]nonane derivatives

A series of 9-methyl-3 beta-phenyl-2-substituted-9-azabicyclo[3.3.1]nonane derivatives were synthesized and evaluated as cocaine-binding site ligands at the dopamine transporter (DAT). The conformation of the bicyclic structures and the stereochemistry of the substituents were determined by NMR and X-ray crystallography. The in vitro binding affinity (Ki) of the 9-azabicyclo[3.3.1]nonane derivatives was measured in rat caudate-putamen tissue, and they were found to be 100-fold (Ki = 2-14 microM) less potent than cocaine and other tropane analogs. From these results it is evident that the cocaine-binding site at the DAT is very sensitive to structural modifications of the unsubstituted methylene bridge [C(6)-C(7)] of cocaine and cocaine-like compounds.