Poly(methyl methacrylate) synthetic grit formulations sustain the delivery of nicarbazin, a contraceptive agent, in pest waterfowl.

Sixty-three mallards were fed one of ten poly(methyl methacrylate) based synthetic grit formulations containing varying concentrations of a proposed wildlife contraceptive (nicarbazin), plasticizer (acetyl tributylcitrate) and/or cross-linking agent (1,4-butanediol diacrylate). Release characteristics of the contraceptive agent were monitored for the purpose of developing a contraceptive formulation for control of pest waterfowl in urban settings. The addition of plasticizer increased the erosion rate (t(1/2)=0.97-2.85 days), cross-linking the polymer matrix slightly decreased the erosion rate (t(1/2)=4.45-5.05 days) and increasing the concentration of the contraceptive agent increased the erosion rate (t(1/2)=3.3 and 9.9 days at 60% and 7.5% active ingredient, respectively). The larger and smaller grit pieces had longer half lives at 11.0 and 11.6 days, respectively while the mid sized grit had a half life of 4.95 days. Control grit had a half life of 12.7 days based on weight loss. Analysis of blood and feces for monitoring release from the grit and approximate indirect plasma levels of the active ingredient proved feasible.     

Defining the practice population in fee-for-service practice.

OBJECTIVE: To develop and validate a technique for defining a practice population of discrete individuals based on multiyear family practice fee-for-service billings data. DATA SOURCES/STUDY SETTING: Nineteen family physicians in Ontario, Canada who converted from fee-for-service to capitation payment. Data sources were fee-for-service billings data for the three-year period prior to the conversion from fee-for-service to capitation payment and the rosters of enrolled patients for the first and third years after the change to capitation payment. STUDY DESIGN: The billings-based definition of the physician's practice population was compared against the Year 1 roster. We also compared the billings-based practice population and the Year 1 roster to the physician's Year 3 roster to identify patients who might have been missed during the roster development process. Our principal analyses were an assessment of the sensitivity of the billings-based definition of the practice population (EPP), the positive predictive value of EPP, and the agreement between EPP and the rostered patient population (RPP). We also examined the ratio between EPP and RPP to determine EPP's accuracy in estimating the practice denominator. DATA COLLECTION/EXTRACTION METHODS: The practice population for each physician at the time of conversion from fee-for-service to capitation payment was defined as (a) all persons for whom the physician billed the provincial health insurance plan for at least one visit during the year immediately prior to joining the capitation-funded program; and (b) all additional patients for whom the physician billed the plan for at least one service in each of the two preceding years. Data extraction was carried out within the Ministry of Health in order to preserve the anonymity of patients and physicians. Data were provided to the investigators stripped of patient and physician identifiers. PRINCIPAL FINDINGS: The mean sensitivity and positive predictive value of EPP were 95.3 percent and 87.4 percent, respectively. The level of agreement between EPP and RPP averaged 84.4 percent. The mean ratio of EPP to RPP was 1.21 (95 percent C.I. 1.030-1.213). Correction for roster false-negatives increased the sensitivity, positive predictive value, and agreement between EPP and the practice population, and reduced the mean ratio of EPP to the practice population to 1.068 (95 percent C.I. 1.010-1.127). CONCLUSIONS: The practice population can usefully be defined in fee-for-service family practice on the basis of multiyear fee-for-service billings data. Further research examining alternative encounter-based practice population definitions would be valuable.     

Structure-activity relationships of (+)-CC-1065 analogues in the inhibition of helicase-catalyzed unwinding of duplex DNA.

(+)-CC-1065 is a potent antitumor antibiotic produced by Streptomyces zelensis. Previous studies have shown that the potent cytotoxic and antitumor activities of (+)-CC-1065 are due to the ability of this compound to covalently modify DNA. (+)-CC-1065 reacts with duplex DNA to form a (N3-adenine)-DNA adduct which lies in the minor groove of DNA overlapping with a five base-pair region. As a consequence of covalent modification with (+)-CC-1065, the helix bends into the minor groove and also undergoes winding and stiffening. In the studies described here, we have constructed templates for helicase-catalyzed unwinding of DNA that contain site-directed (+)-CC-1065 and analogue DNA adducts. Using these templates we have shown that (+)-CC-1065 and select synthetic analogues, which have different levels of cytotoxicity, all produce a significant inhibition of unwinding of a 3'-tailed oligomer duplex by helicase II when the displaced strand is covalently modified. However, the extent of helicase II inhibition is much more significant for (+)-CC-1065 and an analogue which also produced DNA winding when the winding effects are transmitted in the opposite direction to the helicase unwinding activity. This observed pattern of inhibition of helicase-catalyzed unwinding of drug-modified templates was the same for a 3'-T-tail, for different duplex region sequences, and with the Escherichia coli rep protein. Unexpectedly, the gel mobility of the displaced drug-modified single strand was dependent on the species of drug attached to the DNA. Last, strand displacement by helicase II coupled to primer extension by E. coli DNA polymerase I showed the same pattern of inhibition when the lagging strand was covalently modified. In addition, the presence of helicase II on single-stranded regions of templates caused the premature termination of primer extension by DNA polymerase. These results are discussed from the perspective that (+)-CC-1065 and its analogues have different effects on DNA structure, and these resulting structural changes in DNA molecules are related to the different in vivo biological consequences caused by these drug molecules.     

Expression and capping of a proliferation-associated surface membrane p34 kDa antigen on different human hematopoietic cell lines

A novel surface membrane nonglycosylated acidic polypeptide (34 kDa), encoded by a structural gene on chromosome 11, has been identified using murine monoclonal antibody (MoAb) 53.6 (IgG2a). MoAb 53.6, raised against uninduced cells of a human erythroleukemia line (HEL), recognizes a surface membrane antigen that is displayed on proliferating (cell cycle phase G1, S, and M + G2 phase) human leukocytes. The expression and redistribution (i.e., patching and capping) of the p34 kDa antigen on 27 different long-term human hematopoietic cell (HHC) lines was defined by fluorescence microscopy. These lines had been established from patients with leukemia or healthy donors and included phenotypically defined populations of T cells, B cells, and myelomonocytic cells. Almost all (greater than 95%) of the leukocytes of the 27 lines reacted strongly with MoAb 53.6. The majority of the leukocytes displayed p34 kDa antigen patching (26/27 lines; patched cells, 96-100%); moreover, 20 of 27 lines exhibited p34 kDa antigen capping (capped cells, 8-96%). Presentation of the p34 kDa antigen on surface membrane ultrastructures, imaged with immunogold using an indirect antibody labeling procedure, was illustrated by scanning electron microscopy, and endocytosis of the gold-tagged antigen-antibody complex was studied by transmission electron microscopy. The HHC lines are thought to represent immortalized populations of different human leukocyte subsets that are in different stages of maturation and/or differentiation; thus these lines should prove useful as models for further characterizing this unique p34 kDa proliferation-associated antigen and for defining the mechanisms and significance of surface membrane antigen redistribution and modulation that has been associated with leukocyte activation and propagation.     

The effect of valproic acid on 65Zn distribution in the pregnant rat

The effect of valproic acid on the distribution of gavaged 65Zn in maternal and embryonic tissue of Sprague-Dawley rats was examined 24 h after gavaging of the drug on d 13 of pregnancy. Valproic acid treatment resulted in a significantly higher retention of 65Zn in maternal liver and lower amounts in uterus, placenta and embryos than in controls. Compared to controls, gel chromatography of maternal liver from valproic acid-treated dams showed higher 65Zn counts associated with a protein peak of molecular weight of 6,500, the approximate molecular weight of the Zn-binding protein metallothionein. These results support the idea that the teratogenicity of valproic acid is in part due to an induction of embryonic Zn deficiency secondary to a drug-induced sequestering of Zn into maternal liver that results in a decrease in maternal plasma Zn and subsequent reduction in embryonic Zn uptake.