7-Oxo-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-c]pyridines as novel inhibitors of human eosinophil phosphodiesterase

High-throughput file screening against inhibition of human lung PDE4 led to the discovery of 3-ethyl-1-(4-fluorophenyl)-6-phenyl-7-oxo-4, 5,6,7-tetrahydro-1H-pyrazolo[3,4-c]pyridine (11) as a novel PDE4 inhibitor. Subsequent SAR development, using an eosinophil PDE assay, led to analogues up to 50-fold more potent than 11 with IC50 values of 0.03-1.6 microM. One such compound, CP-220,629 (22) (IC50 = 0.44 microM), was efficacious in the guinea pig aerosolized antigen induced airway obstruction assay (ED50 2.0 mg/kg, po) and demonstrated a significant reduction in eosinophil (55%), neutrophil (65%), and IL-1beta (82%) responses to antigen challenge in atopic monkeys (10 mg/kg, po).

Effect of interstitial and/or systemic delivery of tirapazamine on the radiosensitivity of human glioblastoma multiforme in nude mice

The purpose of this study was to investigate the feasibility and the efficacy of administering tirapazamine by a slow-releasing polymer disc that was implanted interstitially into a U251 (human glioblastoma multiforme) tumor grown in nude mice. Tumor-bearing animals, with a tumor nodule 0.8 cm3 in size, were distributed to groups receiving combinations of empty or drug-containing polymer implants in the tumor or contralateral leg, intraperitoneal (i.p.) drug, and/or irradiation. The drug (i.p.) alone (14 mg/kg x6) or in combination with tumor drug implant (2 mg) did not significantly increase the tumor volume doubling time compared to that of control animals. Given with 12 Gy of irradiation in twice a day 2-Gy fractions, combined i.p. drug and tumor drug implant significantly delayed tumor growth compared to irradiation alone, which was not achieved with either drug treatment alone added to irradiation. Toxicity, as manifested by transient weight loss, was primarily seen in animals receiving radiation and i.p. tirapazamine. These results indicated that a slow-releasing tirapazamine disc can be produced and the addition of an interstitially implanted tirapazamine disc further increased the effectiveness of i.p. tirapazamine.

Interindividual variation in the metabolic activation of heterocyclic amines and their N-hydroxy derivatives in primary cultures of human mammary epithelial cells

The heterocyclic amines, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) are pyrolysis products formed when meat is cooked and are rodent mammary carcinogens. They are thought to be metabolically activated by N-hydroxylation, catalysed by cytochrome P450 (CYP), followed by O-acetylation catalysed by N-acetyltransferases. Primary cultures of human mammary epithelial cells (HMECs) prepared from up to 26 individuals for each compound, were treated with IQ, MeIQ, or PhIP (500 microM) or with N-hydroxy-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-OH-PhIP) or N-hydroxy-2-amino-3-methylimidazo[4,5-f]quinoline (N-OH-IQ) (20 microM) and the levels of adduct formation in their DNA analysed by 32P-post-labelling. In order to investigate whether pharmacogenetic polymorphisms influence DNA adduct formation, the NAT2 genotype of each individual was determined by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method that distinguishes between the wild-type and four variant alleles. Presence of two variant alleles designates a slow NAT2 acetylator, whereas individuals with one or two wild-type alleles are designated fast NAT2 acetylators. Interindividual variations in total DNA adduct levels ranged for IQ from 0.64-63.1 DNA adducts per 10(8) nucleotides (mean 7.80), for MeIQ from 1.99-17.8 (mean 6.63), for PhIP from 0.13-4.0 (mean 0.96), for N-OH-PhIP from 6.32-497 (mean 176) and for N-OH-IQ from 0.92-30.6 (mean 9.24). The higher adduct levels observed in cells treated with the N-OH metabolites suggests that N-hydroxylation is the rate-limiting step in HMECs and this may be due to low CYP levels. In contrast, the Phase II reaction catalysed by N-acetyltransferases is probably the major step in the metabolic activation of heterocyclic amines that occurs in the breast. Higher mean levels of heterocyclic amine-DNA adduct formation were detected in the cells of NAT2 fast acetylators compared with slow acetylators, with mean adduct levels per 10(8) nucleotides following IQ treatment, of 12.74 and 3.57 respectively, following PhIP treatment, of 1.20 and 0.74, respectively, following MeIQ treatment, of 7.90 and 5.08, respectively and following N-OH-PhIP-treatment, of 243.1 and 130.0, respectively. However, due to the large variations in adduct levels, these differences in mean values were not statistically significant with the limited number of individuals studied. This appears to be the first pilot study to demonstrate interindividual variations in the metabolic activation of heterocyclic amines and their metabolic intermediates in primary cultures of HMECs in vitro.

Antibodies to recombinant Clostridium difficile toxins A and B are an effective treatment and prevent relapse of C. difficile-associated disease in a hamster model of infection

Clostridium difficile causes antibiotic-associated diarrhea and colitis in humans through the actions of toxin A and toxin B on the colonic mucosa. At present, broad-spectrum antibiotic drugs are used to treat this disease, and patients suffer from high relapse rates after termination of treatment. This study examined the role of both toxins in pathogenesis and the ability of orally administered avian antibodies against recombinant epitopes of toxin A and toxin B to treat C. difficile-associated disease (CDAD). DNA fragments representing the entire gene of each toxin were cloned, expressed, and affinity purified. Hens were immunized with these purified recombinant-protein fragments of toxin A and toxin B. Toxin-neutralizing antibodies fractionated from egg yolks were evaluated by a toxin neutralization assay in Syrian hamsters. The carboxy-terminal region of each toxin was most effective in generating toxin-neutralizing antibodies. With a hamster infection model, antibodies to both toxins A and B (CDAD antitoxin) were required to prevent morbidity and mortality from infection. In contrast to vancomycin, CDAD antitoxin prevented relapse and subsequent C. difficile reinfection in the hamsters. These results indicate that CDAD antitoxin may be effective in the treatment and management of CDAD in humans.

Comparison of North American Symptomatic Carotid Endarterectomy Trial and population-based outcomes for carotid endarterectomy

PURPOSE

The North American Symptomatic Carotid Endarterectomy Trial (NASCET) advocated the use of carotid endarterectomy (CEA) for transient ischemic attacks (TIAs), nondisabling strokes, and ipsilateral high-grade stenosis in highly selected patients. Whether similar results are achieved when CEA is applied to an entire geographically defined population is unknown but important if the NASCET recommendations are to be applied broadly to all community patients.

METHODS

To determine the survival rate to ipsilateral stroke after CEA for all symptomatic patients in a defined population, we reviewed the medical records of all patients residing in Olmsted County, Minn. (approximately 100,000), who underwent a CEA for TIA or nondisabling stroke between 1970 and 1995. Their outcomes were compared with the NASCET results.

RESULTS

In the community of Olmsted County, 297 patients (108 women and 189 men) underwent 322 CEAs during the study period. TIAs or nondisabling stroke was the indication in 254 patients (86%), whereas the remaining 14% had asymptomatic stenosis. After CEA for symptomatic lesions, survival rate free of ipsilateral stroke was 97% at 2 years, 93% at 5 years, and 92% at 10 years. These results are similar to the NASCET survival rates free of ipsilateral stroke at 2 years (91%). However, the 30-day postoperative stroke rate for patients older than 80 years was significantly higher than that for patients younger than 80 years.

CONCLUSIONS

When the NASCET results are compared with a population-based experience in which all symptomatic patients undergoing CEA were analyzed, the early outcomes were similar. Our population-based data also document the remarkably durable long-term results of CEA in preventing stroke and present another benchmark for carotid stent angioplasty.

Benzodiazepine receptor antagonists modulate the actions of ethanol in alcohol-preferring and -nonpreferring rats

The pyrazoloquinoline CGS 8216 (2-phenylpyrazolo-[4,3-c]-quinolin-3 (5H)-one, 0.05-2 mg/kg) and the beta-carboline ZK 93426 (ethyl-5-isopropyl-4-methyl-beta-carboline-3-carboxylate, 1-10 mg/kg) benzodiazepine receptor antagonists were evaluated for their capacity to modulate the behavioral actions of ethanol in alcohol preferring and -nonpreferring rats. When alcohol-preferring rats were presented with a two-bottle choice test between ethanol (10% v/v) and a saccharin (0.0125% g/v) solution, both antagonists dose-dependently reduced intake of ethanol by 35-92% of control levels on day 1 at the initial 15 min interval of the 4 h limited access. Saccharin drinking was suppressed only with the highest doses. CGS 8216 (0.25 mg/kg) and ZK 93426 (4 mg/kg) unmasked the anxiolytic effects of a hypnotic ethanol dose (1.5 g/kg ethanol) on the plus maze test in alcohol-preferring rats, but potentiated the ethanol-induced suppression in alcohol-nonpreferring rats. CGS 8216 (0.25 mg/kg) and ZK 93426 (4 mg/kg) attenuated the ethanol (0.5 and 1.5 g/kg)-induced suppression in the open field in alcohol-nonpreferring rats; however, CGS 8216 potentiated the depressant effects of the lower ethanol dose (0.5 g/kg) in alcohol-preferring rats. These findings provide evidence that benzodiazepine receptor antagonists may differentially modulate the behavioral actions of ethanol in alcohol-preferring and-nonpreferring rats. It is possible that the qualitative pharmacodynamic differences seen in the present study may be related to selective breeding for alcohol preference. The findings indicate the potential for development of receptor specific ligands devoid of toxic effects which may be useful in the treatment of alcohol abuse and alcoholism.

Overexpression of Rab3D enhances regulated amylase secretion from pancreatic acini of transgenic mice

Rab3D, a member of the ras-related GTP-binding protein Rab family, is localized to secretory granules of various exocrine tissues such as acinar cells of the pancreas, chief cells of the stomach, and parotid and lacrimal secretory cells. To elucidate the function of Rab3D in exocytosis, we have generated transgenic mice that over-express Rab3D specifically in pancreatic acinar cells. Hemagglutinin-tagged Rab3D was localized to zymogen granules by immunohistochemistry, and was shown to be present on zymogen granule membranes by Western blotting; both results are similar to previous studies of endogenous Rab3D. Secretion measurements in isolated acinar preparations showed that overexpression of Rab3D enhanced amylase release. Amylase secretion from intact acini of transgenic mice 5 min after 10 pM cholecystokinin octapeptide (CCK) stimulation was enhanced by 160% of control. In streptolysin-O-permeabilized acini of transgenic mice, amylase secretion induced by 100 microM GTP-gamma-S was enhanced by 150%, and 10 microM Ca2+-stimulated amylase secretion was augmented by 206% of that of the control. To further elucidate Rab3D involvement in stimulus-secretion coupling, we examined the effect of CCK on the rate of GTP binding to Rab3D. Stimulation of permeabilized acini with 10 pM CCK increased the incorporation of radiolabeled GTP into HA-tagged Rab3D. These results indicate that overexpression of Rab3D enhances secretagogue-stimulated amylase secretion through both calcium and GTP pathways. We conclude that Rab3D protein on zymogen granules plays a stimulatory role in regulated amylase secretion from pancreatic acini.

Stimulation of both CCK-A and CCK-B receptors activates MAP kinases in AR42J and receptor-transfected CHO cells

It was recently found that cholecystokinin (CCK) activates mitogen-activated protein kinases (MAPK) in isolated rat pancreatic acini. The present study evaluates whether one or both types of CCK receptors are capable of MAPK activation in pancreatic AR42J acinar cells as well as CHO cells transfected with CCK-A or CCK-B receptors. CCK significantly increased p44 MAPK and p42 MAPK activities in AR42J cells. Minimal, half-maximal, and maximal responses were observed at 30 and 500 pM and 10 nM, respectively, after CCK-8 stimulation and at 100 pM and 1.5 and 30 nM, respectively, after gastrin stimulation. Glycine-extended gastrin had no effect at 100 nM and a small but significant effect at 1 microM. The CCK-B receptor antagonist L365,260 almost totally blocked MAPK activation in AR42J cells after stimulation with gastrin and glycine-extended gastrin and substantially reduced the activation of both kinases by CCK-8, while the CCK-A receptor antagonist L364,718 was much less effective. The CCK-A-selective agonist A71376, however, was an effective stimulant of MAPK activity. In an alternative approach, stably transfected CHO cells bearing either CCK-A or CCK-B receptors were stimulated with CCK-8. Each receptor induced a time-dependent increase in activity of both MAPKs by five- to sixfold in CCK-A- and CCK-B-bearing cells. In conclusion, both CCK-A and CCK-B receptors activate MAPK in AR42J cells and in transfected CHO cells.

Cholecystokinin and EGF activate a MAPK cascade by different mechanisms in rat pancreatic acinar cells

The effects of activating the Gq protein-coupled cholecystokinin (CCK) receptor on different proteins/signaling molecules in the mitogen-activated protein kinase (MAPK) cascade in pancreatic acinar cells were analyzed and compared with the effects of activating the tyrosine kinase-coupled epidermal growth factor (EGF) receptor. Both EGF and CCK octapeptide rapidly increased the activity of the MAPKs [extracellular signal-regulated kinase (ERK) 1 and ERK2], reaching a maximum within 2.5 min when 3.9- and 8.5-fold increases, respectively, were observed. The EGF-induced increase of MAPK activity was transient, with only a slight elevation after 30 min, whereas CCK-stimulated MAPK remained at a high level of activation to 60 min. The protein kinase C inhibitor GF-109203X abolished the activation by phorbol ester and inhibited the effect of CCK by 78% but had no effect on EGF-activated MAPK activity. EGF and CCK activated both forms of MAPK kinase (MEK), with CCK having a much larger effect, activating MEK1 by 6-fold and MEK2 by 10-fold, whereas EGF activated both MEKs by only 2-fold. Immunoblotting revealed three different forms of Raf in pancreatic acinar cells. Of the total basal Raf kinase activity, 3.7% was Raf-A, 89.0% was Raf-B, and 7.3% was c-Raf-1. All three forms of Raf were stimulated to a greater extent by CCK than by EGF, which was especially evident for Raf-A and c-Raf-1. The effect of CCK in activating Rafs was at least partially mimicked by stimulation with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate. EGF significantly increased GTP-bound Ras by 183 and 164% at 2.5 and 10 min, respectively; CCK and TPA had no measurable effect. Our study suggests that CCK and EGF activate the MAPK cascade by distinct mechanisms in pancreatic acinar cells.

CCK-B receptors produce similar signals but have opposite growth effects in CHO and Swiss 3T3 cells

Rat cholecystokinin-B (CCK-B) receptors were transfected into Chinese hamster ovary (CHO)-K1 (CHO-CCK-B) and Swiss 3T3 (Swiss 3T3-CCK-B) cells, and the effects of receptor activation on cell proliferation and intracellular signaling were investigated. CCK octapeptide (CCK-8) treatment had no effect on cell growth in quiescent CHO-CCK-B cells but inhibited DNA synthesis, proliferation, and colony formation when the cells were grown in fetal bovine serum (FBS). In contrast, CCK-8 stimulated DNA synthesis in quiescent Swiss 3T3-CCK-B cells and had no effect when the cells were grown in FBS. These differences in growth responses were not due to differences in the level of receptor expression, as similar numbers of receptors were present in both cell types. To determine whether the different growth effects were due to differences in receptor coupling to common second messenger pathways, we investigated the effects of CCK-8 on several known intracellular signals. In both cell types, CCK-8 stimulated increases in intracellular Ca2+ concentration and polyphosphoinositide hydrolysis with similar potencies and efficacies. CCK-8 also stimulated arachidonate release from both cell types, although the potency was higher in the CHO cells. Adenosine 3',5'-cyclic monophosphate generation was observed at high agonist concentrations in both cell types and was much greater in cells with higher receptor density. In summary, receptor activation had opposite effects on growth parameters in CHO and Swiss 3T3 cells, but only minor differences were observed in the characteristics of CCK-B receptor coupling to specific second messengers in the two cell types. Thus cellular context is a principal determinant of the biological effects of CCK-B receptor activation, and differences in biological responses may occur independently of major differences in receptor coupling.

Regulation of macrophage cytokine production by prostaglandin E2. Distinct roles of cyclooxygenase-1 and -2

Prostaglandin E2 (PGE2) modulates a variety of physiological processes including the production of inflammatory cytokines. There are two cyclooxygenase (Cox) enzymes, Cox-1 and Cox-2, that are responsible for initiating PGE2 synthesis. These isozymes catalyze identical biosynthetic reactions but are regulated by different mechanisms in the cell. This report examines differences in the roles of Cox-1 and Cox-2 in regulating cytokine synthesis in macrophages. We employed agents that selectively modulate the activity of each isozyme and measured their effects on synthesis of interleukin (IL)-6, IL-1, and tumor necrosis factor-alpha by peritoneal macrophages. Among these three cytokines, only IL-6 synthesis was stimulated by production of endogenous PGE2. This effect was specifically linked to activation of Cox-2 and not Cox-1. The specificity derives, partly, from the timing of the production of PGE2 following stimulation of each isozyme and from induction of ancillary signals that control the response to PGE2. The experimental findings demonstrate that the effects of Cox-1 and Cox-2 activity on macrophage IL-6 synthesis are segregated. This provides a mechanism for IL-6 to be induced selectively during inflammation.

Fabrication of multipassband moiré resonators in fibers by the dual-phase-mask exposure method

We report on the fabrication of in-fiber moiré filters by dual exposure of a nondedicated chirped phase mask. This simple technique produces broadband filters whose structure depends only on an intermediate stretch between two identical UV exposures. We demonstrate moiré filters with as many as four narrow passbands within a 2-nm stopband.

Is the outcome of in-vitro fertilization and embryo transfer treatment improved by spontaneous or surgical drainage of a hydrosalpinx?

A pilot study was designed to examine whether the outcome of embryo transfer in women with a hydrosalpinx might be improved by surgical drainage of the hydrosalpinx at the time of oocyte collection for in-vitro fertilization treatment. A comparative, controlled but retrospective analysis of the results was performed of all women with infective tubal damage aged <40 years old, who had ovulatory cycles, a normal uterus and a partner with normal spermatozoa. A standardized treatment regimen was used. A maximum of three embryos were transferred. Hydrosalpinx was defined by prior hysterosalpingography and/or laparoscopy with transcervical dye injection. A total of 237 embryo transfer cycles in women with hydrosalpinges (tubal distension not visible in 151, visible but not drained in 30 and drained in 56) were compared with 705 embryo transfer cycles in women with tubal disease but no hydrosalpinx. Results were analysed in the first three cycles but also separately in the first cycle to check for bias. Success rates were higher in the first cycle, but did not significantly influence overall differences. Implantation rates were significantly reduced overall in the hydrosalpinx group (8.0 versus 13.2% for controls; P < 0.001), being 8.3% (P < 0.01) in the subgroup without evident tubal distension and 7.5% (not significant) in the drained hydrosalpinx group. This study shows that tubal damage with distal occlusion is associated with a marked reduction in embryo implantation, even in the absence of obvious fluid distension. Surgical drainage of distended hydrosalpinges appears to offer no benefit.

Immunoglobulin/Myc recombinations in murine Peyer's patch follicles

Immunoglobulin heavy chain (Igh)/Myc recombinations are a hallmark of pristane-induced mouse plasmacytomas but are also frequently found in non-tumorous tissues. Here we describe for the first time a PCR-based technique for detecting fusions between Igh mu or Igh alpha and Myc in situ. Igh/Myc recombinations were found in transplanted and primary plasmacytomas. In addition, the gut-associated lymphoid tissues of plasmacytoma-free BALB/c mice were investigated for the presence of Igh/Myc fusions. Igh/Myc rearrangements were detected in Peyer's patch follicles and in the intestinal lamina propria both in normal mice and in mice shortly after pristane treatment. The sequence analysis showed that i) three to five different Igh/Myc hybrid sequences were present in individual follicles, ii) Igh/Myc recombinations can be subjected to additional switch recombinations as shown by related sequences in neighboring cells, and iii) cells harboring these rearrangements migrate into the adjacent lamina propria. The results indicate that Peyer's patches are a hyper-recombinogenic tissue. Myc recombination-positive cells are present in at least 100-fold more frequently than expected if recombinations were random, which suggests that this kind of trans-chromosomal rearrangement may be targeted.

p70s6k is activated by CCK in rat pancreatic acini

The expression and activity of p70s6k-p85s6k in isolated rat pancreatic acini were revealed by Western blotting, immunoprecipitation, and kinase assay. Cholecystokinin (CCK) stimulation of p70s6k activity was biphasic, with an early phase maximum at 5 min and a late phase maximum at 60 min. The threshold concentration of CCK to increase p70s6k activity was 3 pM, and the maximal effect was seen at 1 nM CCK. Carbachol and bombesin, but not vasoactive intestinal peptide, also activated p70s6k. The protein kinase C (PKC) activator (12-O-tetradecanoylphorbol 13-acetate), the calcium ionophore (ionomycin), and a derivative of adenosine 3',5'-cyclic monophosphate induced only a slight increase in p70s6k activity. Rapamycin potently blocked both the basal and the CCK-stimulated p70s6k activity, and this inhibition was reversed by an excess of FK-506. The phosphatidylinositol 3-kinase inhibitor, wortmannin, potently inhibited p70s6k activation by CCK, whereas the tyrosine kinase inhibitor genistein had only a partial effect. Neither rapamycin nor wortmannin inhibited amylase release at concentrations that inhibited p70s6k activity. Thus the activation pathway of p70s6k by CCK is not mediated by PKC or mobilization of intracellular calcium but seems to be mediated by phosphatidylinositol 3-kinase. The effect of rapamycin to inhibit p70s6k activity is mediated by binding to the immunophyllin FK-506-binding protein of 12 kDa. The p70s6k is not involved in the secretion of digestive enzymes induced by CCK.

Heterotrimeric G-protein Gq/11 localized on pancreatic zymogen granules is involved in calcium-regulated amylase secretion

The heterotrimeric G-protein Gq/11 was identified on pancreatic acinar zymogen granules and its function in calcium-regulated exocytosis was examined. Western blotting showed alphaq/11, but not alphas or alphao, to be localized to the zymogen granule membrane along with G-protein beta-subunit; all three alpha subunits were present in a plasma membrane fraction and the alphaq/11 signal was 30-fold more enriched in the plasma membrane as compared with granule membrane. Neither CCK receptors nor alpha subunits of the sodium pump, both plasma membrane markers were present on granule membranes. Immunohistochemistry of pancreatic lobules showed that alphaq/11 localized to the zymogen granule-rich apical region of acinar cells together with a much stronger signal at the basolateral plasma membrane. When the substance-P-related peptide GPAnt-2a, an antagonist of Gq/11, was introduced into streptolysin-O permeabilized acini to bypass the plasma membrane, the amylase release induced by 10 microM free calcium was potentiated in a concentration-dependent manner. By contrast, another substance-P-related peptide, GPAnt-1, an antagonist of Go and Gi, showed no effect on calcium-induced amylase release from permeabilized acini. GPAnt-2a peptide also exerted an inhibitory effect on the total GTPase activity of the purified zymogen granules and a larger inhibitory effect on the GTPase activity of the Gq/11 protein immunopurified from zymogen granules. GPAnt-1, however, did not inhibit GTPase activity of either zymogen granules or immunopurified Gq/11. These results suggest that GPAnt-2a peptide augmented calcium-induced amylase release from permeabilized acini by inhibiting GTPase activity of the Gq/11 protein on zymogen granules. We conclude that Gq/11 protein on zymogen granules plays a tonic inhibitory role in calcium-regulated amylase secretion from pancreatic acini.

Novel Kinase Signaling Cascades in Pancreatic Acinar Cells

Pancreatic secretagogues that activate digestive enzyme secretion through classic intracellular mediators such as Ca2+ also activate novel signaling kinase cascades. The best defined of these is the MAP kinase cascade, but cholecystokinin also activates jun kinase, p38 MAP kinase, and S6 kinase. These novel pathways are likely involved with pancreatic growth and gene expression.

Induction of cytochrome P4503A by the antiglucocorticoid mifepristone and a novel hypocholesterolaemic drug

Rat liver microsomal testosterone (250 microM) hydroxylation and immunoreactive CYP3A protein were compared after administration of the antiglucocorticoid RU 486 (50 mg.kg-1.day-1 for 4 days) and the hypocholesterolaemic drug SR-12813 (150 mg.kg-1.day-1 for 4 days). Markers of CYP3A-mediated enzyme activity (testosterone 15 beta-, 6 beta-, and 2 beta-hydroxylation) were increased after administration of both drugs. Testosterone 6 beta-hydroxylation was increased 5-fold by RU 486 and 9-fold by SR-12813. Administration of dexamethasone alone at 150 mg.kg-1.day-1 or in combination with RU 486 induced testosterone 6 beta-hydroxylation 15- to 20-fold. The lack of antagonistic effect of RU 486 on dexamethasone-mediated CYP3A induction strengthens support for the hypothesis that the "classical glucocorticoid receptor" does not play a part in this process. The induction of CYP3A enzymes by the bisphosphonate SR-12813 suggests the existence of a new class of compounds with CYP3A inducing properties.

Silver and fluoride ion release from metal-reinforced glass-ionomer filling materials

This study was undertaken to examine whether a relationship exists between the composition of metal-containing glass-ionomer cements and ion release from these materials. Conflicting data on silver release from this type of material has been reported and it was felt that further investigation was desirable in view of the increasing use of these materials. In this study, the release of ions, particularly of silver and fluoride, into deionized water and artificial saliva was measured for up to one year. Low levels of silver and copper ions were found in both media. The amounts released from alloy-containing materials were dependent on the amount of alloy present; lesser amounts were leached from cermets. Fluoride ion release was less material-dependent but still lowest for cermets. The use of artificial saliva reduced ion release as did increasing the maturation time prior to immersion in either liquid.

Implantable biodegradable polymers for IUdR radiosensitization of experimental human malignant glioma

PURPOSE

The potential of halogenated pyrimidines for the radiosensitization of human malignant gliomas remains unrealized. To assess the role of local delivery for radiosensitization, we tested a synthetic, implantable biodegradable polymer for the controlled release of 5-iodo-2'-deoxyuridine (IUdR) both in vitro and in vivo and the resultant radiosensitization of human malignant glioma xenografts in vivo.

MATERIALS AND METHODS

In vitro: To measure release, increasing (10%, 30%, 50%) proportions (weight/weight) of IUdR in the polyanhydride [(poly(bis(p-carboxyphenoxy)-propane) (PCPP): sebacic acid (SA) (PCPP : SA ratio 20:80)] polymer discs were incubated (1 ml phosphate-buffered saline, 37 degrees C). The supernatant fractions were serially assayed using high performance liquid chromatography. To measure modulation of release, polymer discs were co-loaded with 20 microCi 5-125-iodo-2'-deoxyuridine (125-IUdR) and increasing (10%, 30%, or 50%) proportions of D-glucose. To test radiosensitization, cells (U251 human malignant glioma) were sequentially exposed to increasing (0 or 10 microM) concentrations of IUdR and increasing (0, 2.5, 5.0, or 10 Gy) doses of acute radiation. In vivo. To measure release, PCPP : SA polymer discs having 200 microCi 125-IUdR were surgically placed in U251 xenografts (0.1-0.2 cc) growing in the flanks of nude mice. The flanks were reproducibly positioned over a collimated scintillation detector and counted. To measure radiosensitization, PCPP : SA polymer discs having 0% (empty) or 50% IUdR were placed in the tumor or contralateral flank. After five days, the tumors were acutely irradiated (500 cGy x 2 daily fractions).

RESULTS

In vitro: Intact IUdR was released from the PCPP : SA polymer discs in proportion to the percentage loading. After 4 days the cumulative percentages of loaded IUdR that were released were 43.7 +/- 0.1, 70.0 +/- 0.2, and 90.2 +/- 0.2 (p < 0.001 ANOVA) for the 10, 30, and 50% loadings. With 0, 10, 30, or 50% D-glucose co-loading, the cumulative release of 125-IUdR from PCPP : SA polymers was 21, 70, 92, or 97% (p < 0.001), respectively, measured 26 days after incubation. IUdR radiosensitized U251 cells in vitro. Cell survival (log10) was -2.02 +/- 0.02 and -3.68 +/- 0.11 (p < 0.001) after the 10 Gy treatment and no (control) or 10 microM IUdR exposures, respectively. In vivo: 125-IUdR Release: The average counts (log10 cpm +/- SEM) (hours after implant) were 5.2 +/- 0.05 (0.5), 4.3 +/- 0.07 (17), 3.9 +/- 0.08 (64), and 2.8 +/- 0.06 (284). Radiosensitization: After intratumoral implantation of empty polymer or intratumoral 50% IUdR polymer, or implantation of 50% IUdR polymers contralateral to tumors the average growth delays of tumors to 4 times the initial volumes were 15.4 +/- 1.8, 20.1 + 0.1, and 20.3 + 3.6 (mean + SEM) days, respectively (p = 0.488 one-way ANOVA). After empty polymer and radiation treatments, no tumors regressed and the growth delay was 31.1 + 2.1 (p = 0.046 vs. empty polymer alone) days. After implantation of 50% IUdR polymers either contralateral to the tumors or inside the tumors, followed by radiation, tumors regressed; growth delays to return to the initial average volumes of 14.0 + 3.6 or 24.2 + 0.2 (p < 0.01) days, respectively.

CONCLUSIONS

Synthetic, implantable biodegradable polymers hold promise for the controlled release and local delivery of IUdR for radiosensitization of gliomas.

Energy-dependent polarity correction factors for four commercial ionization chambers used in electron dosimetry

The polarity effects of four commercially available ionization chambers were characterized and correction factors as a function of mean energy at depth were tabulated. These included a Farmer-type chamber, two parallel plate chambers, and one cylindrical chamber used in a scanning water phantom dosimetry system. Polarity effects were measured at representative depths along the depth dose curves of 6, 9, 12, 16, and 20 Me V electron beams. The term "polarity error" is introduced and is defined as the error which is introduced if polarity effects are ignored. Polarity errors for the four ionization chambers studied were shown to monotonically decrease with increasing mean energy at depth and were largely independent of the energy of the incident electron beam. Only at very low energies, that is, very near the end of the practical range, did the correction factors for beams of different incident energy diverge. Three of the four chambers studied had correction factors which were independent of field size, to within +/- 1/2%. One chamber showed an increase in correction factor with increasing field size which was shown to be mainly due to stem and cable irradiation.

Gene expression domains as markers in developmental toxicity studies using mammalian embryo culture

We are examining the hypothesis that expression domains of developmental control genes may be informative markers in mammalian embryo culture studies of developmental toxicity. Expression domains might be altered directly by chemical exposure, or might reflect developmental abnormality prior to any overt morphological defect. Whole-mount in situ hybridization using digoxygenin-labeled RNA probes was used to monitor the regions of expression of Hoxb-4, Pax-3 and Emx-2. These genes were selected because of their different restrictions within the developing CNS; Hoxb-4 for its anterior margin in the hindbrain, Pax-3 for its dorso-ventral pattern in the spinal cord, and Emx-2 for being restricted to a portion of the forebrain. Valproic acid was used as a prototype developmental toxicant because of its known actions on neural tube closure and on segmentation. For patterns of expression, we made three comparisons, between: rat in vivo developed embryos and published descriptions for mouse; rat cultured and in vivo; control and valproate exposed. For these genes, there were no differences between domains of expression in rat and mouse, nor between rat cultured and in vivo embryos. In valproate-exposed embryos, some domains were spatially abnormal, for example Pax-3 in the neural crest, but this was coincident with structural defects induced by the treatment. There was no indication, for these three genes, and this teratogen, that treatment caused any shifts in boundaries of expression, nor induced any ectopic domains, even though exposures induced overt malformation.

Effects of hyperosmolar mannitol on regional oxygen supply and consumption in the newborn pig

Previous work indicated that opening the blood-brain barrier with hyperosmotic mannitol decreased local venous O2 saturation and increased cerebral O2 consumption. This study was performed to assess the vascular effect of hypertonic mannitol on oxygen supply/consumption balance in the newborn pig and to determine the role of nitric oxide in mediating the effects of mannitol. Animals were anesthetized with alpha-chloralose and mechanically ventilated to maintain their blood gases within normal range. Retrograde catheterization of the right carotid artery was performed to inject 12 ml to 25% mannitol over a 30 sec interval. In one group of animals (n = 5), the blood-brain barrier transfer coefficient (Ki) to 14C-alpha aminoisobutyric acid or 14C-urea (n = 4) was measured 12 min after mannitol. In another group of animals (n = 9), regional cerebral blood flow and small vein O2 saturation was measured using 14C-iodoantripyrine and microspectrophotometry. Similar measurements were made in other groups of animals (n = 9) after pretreatment with 10 mg kg-1 i.v. of N-omega-nitro-L-arginine methyl ester (L-NAME), 20 min before mannitol injection. The mannitol injection did not increase Ki or local cerebral O2 consumption. It resulted in a decreased small vein O2 saturation in the ipsilateral cortex (46 +/- 3%) in comparison to the contralateral cortex (55 +/- 2%). The O2 supply/consumption ratio decreased in the ipsilateral cortex in the mannitol injected animals (2.14 +/- 0.23) in comparison to the contralateral cortex (2.76 +/- 0.28). Pretreatment with L-NAME abolished this effect of mannitol (small vein O2 saturation 59 +/- 2% in ipsilateral cortex and 58 +/- 2% in the contralateral cortex; O2 supply/consumption 2.68 +/- 0.17 in the ipsilateral cortex and 2.65 +/- 0.16 in the contralateral cortex). We conclude that hypertonic mannitol adversely affects O2 supply/consumption balance, without increasing blood-brain barrier transport, and this effect is blocked by L-NAME, a nitric oxide synthase antagonist.