Blood thymidine level and iododeoxyuridine incorporation and reutilization in DNA in mice given long-acting thymidine pellets. (1/1204)

A long-acting thymidine pellet consisting of 190 mg of cholesterol and 60 mg of thymidine has been developed for the study of thymidine metabolism and reutilization in vivo. Implantation of such a pellet s.c. in adult mice will maintain the blood plasma concentration of thymidine at levels between 40 and 8 X 10(-6) M, which are from 36 to 7 times those of normal mice, for periods up to 48 hr. During this period, in vivo uptake and reutilization of [125I]iododeoxyuridine, a thymidine analog, into intestinal and tumor DNA were almost completely suppressed. While iododeoxyuridine reutilization is not large in normal proliferative tissue even in the absence of pellet implants, reutilization of over 30% was measured in large, rapidly growing ascites tumors. The inhibition of iododeoxyuridine incorporation by elevated thymidine blood levels is directly proportional to serum concentration. This appears to be due to a thymidine pool in rapid equilibrium with blood thymidine. This pool is at least 10 times larger than the 4-nmole pool of extracellular thymidine.  (+info)

The effects of levonorgestrel implants on vascular endothelial growth factor expression in the endometrium. (2/1204)

Vascular endothelial growth factor (VEGF) expression and the microvascular density of the endometrium were studied in Norplant users and normal controls, using immunohistochemistry on formalin-fixed paraffin-embedded endometrial sections. The VEGF staining index was quantified using computerized image analysis. The VEGF staining index between stages of the menstrual cycle and between normal and Norplant endometria were compared. Norplant VEGF staining index was analysed for correlation with microvascular density, duration of Norplant use, the number of bleeding/spotting days in the reference period up to 90 days prior to biopsy, and the length of time since the last bleeding/spotting episode. The results showed that immunoreactive VEGF was detected predominantly in endometrial glands but weakly expressed in the stroma throughout the menstrual cycle, and also in Norplant users. Large variation in the VEGF staining index between individuals was observed and no significant difference in the VEGF staining index was detected between stages of the menstrual cycle for the glands and stroma. The glandular and stromal VEGF staining indices were significantly higher in Norplant than in normal endometrium (P<1x10(-4)). No correlation was found between the Norplant VEGF staining index and endometrial microvascular density, duration of Norplant use, the number of bleeding/spotting days in the reference period, and the length of time since the last bleeding/spotting episode. The VEGF staining index was higher in glands than stroma for both normal and Norplant endometrium. The results suggest a differential control of endometrial glandular versus stromal VEGF expression, and possible positive effects of levonorgestrel on VEGF expression.  (+info)

Ectopic bone morphogenetic proteins 5 and 4 in the chicken forebrain lead to cyclopia and holoprosencephaly. (3/1204)

Proper dorsal-ventral patterning in the developing central nervous system requires signals from both the dorsal and ventral portions of the neural tube. Data from multiple studies have demonstrated that bone morphogenetic proteins (BMPs) and Sonic hedgehog protein are secreted factors that regulate dorsal and ventral specification, respectively, within the caudal neural tube. In the developing rostral central nervous system Sonic hedgehog protein also participates in ventral regionalization; however, the roles of BMPs in the developing brain are less clear. We hypothesized that BMPs also play a role in dorsal specification of the vertebrate forebrain. To test our hypothesis we implanted beads soaked in recombinant BMP5 or BMP4 into the neural tube of the chicken forebrain. Experimental embryos showed a loss of the basal telencephalon that resulted in holoprosencephaly (a single cerebral hemisphere), cyclopia (a single midline eye), and loss of ventral midline structures. In situ hybridization using a panel of probes to genes expressed in the dorsal and ventral forebrain revealed the loss of ventral markers with the maintenance of dorsal markers. Furthermore, we found that the loss of the basal telencephalon was the result of excessive cell death and not a change in cell fates. These data provide evidence that BMP signaling participates in dorsal-ventral patterning of the developing brain in vivo, and disturbances in dorsal-ventral signaling result in specific malformations of the forebrain.  (+info)

Cephalosporin and aminoglycoside concentrations in peritoneal capsular fluid in rabbits. (4/1204)

To study the penetration of antibiotics into peritoneal tissue fluid, a subcutaneous tissue capsule model was modified by implanting multiple, perforated spherical capsules in the peritoneal cavity of rabbits. Capsules became vascularized, encased in connective tissue, and filled with fluid having a mean protein concentration of 3.6 g/100 ml. Capsular fluid was obtained by percutaneous needle aspiration and assayed for antibiotic by the disk plate bioassay technique. Cephalosporins were administered intramuscularly at a dose of 30 mg/kg. Mean peak concentrations of cephaloridine and cefazolin were significantly higher than cephalothin and cephapirin in capsular fluids, but the percent penetration (ratio of capsular mean peak to serum mean peak) ranged from 8.7 to 16.9% and was not significantly different among the cephalosporins. At 24 h the capsular concentration of cefazolin was significantly greater than for the other cephalosporins (P < 0.001). Lower rabbit serum protein binding observed at high in vivo concentrations may have enabled cefazolin to penetrate capsular fluid, but in vitro protein binding studies did not confirm a decrease in serum protein binding at high concentrations within the clinical range. Kanamycin and amikacin showed comparable capsular fluid peak concentrations as did gentamicin and tobramycin. The percent penetration ranged from 15.2 to 34.5% for the aminoglycosides. The only statistical difference was that amikacin penetration was significantly higher than that for tobramycin. Mean capsular concentrations of amikacin, cefazolin, and cephaloridine compared most favorably with the minimum inhibitory concentration of gram-negative bacilli at the dosages used in this study.  (+info)

Synchronization of estrus in beef cattle with norgestomet and estradiol valerate. (5/1204)

Fifty-six cows received a norgestomet implant and an injection of norgestomet and estradiol valerate; half (n = 28) received 500 IU equine chorionic gonadotrophin (eCG) at implant removal, 9 d later. A third group (n = 25) received 2 doses of cloprostenol (500 micrograms) 11 d apart. Estrous rate was higher (P < 0.05) for cows given norgestomet and estradiol plus 500 IU eCG (75.0%) than for those receiving cloprostenol (44.0%); for those receiving norgestomet and estradiol alone, it was intermediate (67.8%). Pregnancy rates to artificial insemination (after estrus or timed) were higher (P < 0.05) for cows given norgestomet and estradiol than for those given cloprostenol (23 of 28, 82.1% vs 13 of 25, 52.0%), and intermediate (67.8%) for those given norgestomet and estradiol plus eCG. In a second experiment, for heifers treated with norgestomet and estradiol plus eCG (n = 15) or with 2 doses of cloprostenol (n = 16), estrous rates were 66.7% vs 56.2% (P > 0.5), ovulation rates were 100.0% vs 81.2% (P = 0.08), intervals from implant removal or cloprostenol treatment to estrus were 48.0 +/- 4.4 hours vs 61.3 +/- 7.0 hours (P = 0.12) and to ovulation were 70.4 +/- 4.4 hours vs 93.2 +/- 7.5 hours (P < 0.01), respectively; pregnancy rates were 41.7 and 35.7%, respectively (P > 0.5). Norgestomet and estradiol were as good as (heifers) or superior to (cows) a 2-dose cloprostenol regimen. In cows given norgestomet and estradiol, injecting eCG at implant removal did not significantly improve estrous or pregnancy rates.  (+info)

Oral ganciclovir for patients with cytomegalovirus retinitis treated with a ganciclovir implant. Roche Ganciclovir Study Group. (6/1204)

BACKGROUND: The intraocular ganciclovir implant is effective for local treatment of cytomegalovirus retinitis in patients with the acquired immunodeficiency syndrome (AIDS), but it does not treat or prevent other systemic manifestations of cytomegalovirus infection. METHODS: Three hundred seventy-seven patients with AIDS and unilateral cytomegalovirus retinitis were randomly assigned to one of three treatments: a ganciclovir implant plus oral ganciclovir (4.5 g daily), a ganciclovir implant plus oral placebo, or intravenous ganciclovir alone. The primary outcome measure was the development of new cytomegalovirus disease, either contralateral retinitis or biopsy-proved extraocular disease. RESULTS: The incidence of new cytomegalovirus disease at six months was 44.3 percent in the group assigned to the ganciclovir implant plus placebo, as compared with 24.3 percent in the group assigned to the ganciclovir implant plus oral ganciclovir (P=0.002) and 19.6 percent in the group assigned to intravenous ganciclovir alone (P<0.001). As compared with placebo, oral ganciclovir reduced the overall risk of new cytomegalovirus disease by 37.6 percent over the one-year period of the study (P=0.02). However, in the subgroup of 103 patients who took protease inhibitors, the rates of new cytomegalovirus disease were low and of similar magnitude, regardless of treatment assignment. Progression of retinitis in the eye that initially received an implant was delayed by the addition of oral ganciclovir, as compared with placebo (P=0.03). Treatment with oral or intravenous ganciclovir reduced the risk of Kaposi's sarcoma by 75 percent (P=0.008) and 93 percent (P<0.001), respectively, as compared with placebo. CONCLUSIONS: In patients with AIDS and cytomegalovirus retinitis, oral ganciclovir in conjunction with a ganciclovir implant reduces the incidence of new cytomegalovirus disease and delays progression of the retinitis. Treatment with oral or intravenous ganciclovir also reduces the risk of Kaposi's sarcoma.  (+info)

17 beta-estradiol reduces glycoxidative damage in the artery wall. (7/1204)

Glycoxidative damage in the vasculature has been linked to atherosclerotic cardiovascular disease. Estrogens protect against the development and progression of atherosclerosis. Because estrogens are potent antioxidants that also effect glucose metabolism, part of their protection against atherosclerosis could be through attenuation of glycoxidative damage in the vascular wall. In this study, we tested the hypothesis that chronic estradiol administration is associated with decreased levels of glycoxidative damage in arterial walls. We harvested and examined iliac arteries from ovariectomized, 8-month-old rats that had been implanted for 6 months with 1 of the following subcutaneous hormone pellets: low estradiol (2.5 mg estradiol), high estradiol (25 mg estradiol), P4 (200 mg progesterone), low estradiol and P4, placebo (no hormone), or control (no implant). Using pentosidine as a biomarker of glycoxidative damage, we found that all vessels from rats receiving estradiol (low estradiol, high estradiol, and low estradiol+P4) exhibited a 50% reduction in glycoxidative damage compared with P4, placebo, and control vessels (P<0.05). Consistent with this finding, we observed that estradiol-treated rats had a 30% decrease in tissue levels of hydroperoxides, a marker of oxidative stress. Finally, estradiol-treated rats had a small, but significant, decrease in plasma glucose levels (P<0.01). In summary, we report the novel finding that chronic estrogen administration is associated with significant decreases in glycoxidative damage and oxidative stress in the arterial wall. It seems likely that these actions may constitute a mechanism by which estrogen attenuates the progression of atherosclerosis.  (+info)

Millimeter-scale positioning of a nerve-growth-factor source and biological activity in the brain. (8/1204)

Toxicity prevents the systemic administration of many therapeutic proteins, and attempts at protein targeting via the circulatory system (i.e., "magic bullets") have failed in all but a few special cases. Direct administration at the target site is a logical alternative, particularly in the central nervous system, but the limits of direct administration have not been defined clearly. Nerve growth factor (NGF) enhances survival of cholinergic neurons and, therefore, has generated considerable interest for the treatment of Alzheimer's disease. We tested the effectiveness of local delivery by implanting small polymer pellets that slowly released NGF into the central nervous system of adult rats at controlled distances from a target site containing transplanted fetal cholinergic cells. NGF-releasing implants placed within 1-2 mm of the treatment site enhanced the biological function of cellular targets, whereas identical implants placed approximately 3 mm from the target site of treatment produced no beneficial effect. Effective NGF therapy required millimeter-scale positioning of the NGF source, and efficacy correlated with the spatial distribution of NGF concentration in the tissue; this result suggests that NGF must be delivered within several millimeters of the target to be effective in treating Alzheimer's disease. Because the human brain is divided into functional regions that are typically several centimeters in diameter and often irregular in shape, new methods for sculpting larger-scale drug fields are needed. We illustrate a concept, called pharmacotectonics, in which drug-delivery systems are arranged spatially in tissues to shape concentration fields for potent agents.  (+info)