bluuebunny/crossref_metadata_2025 huggingface dataset:
The injection of methadone and benzodiazepines among Sydney injecting drug users 1996–2000: 5‐year monitoring of trends from the Illicit Drug Reporting System
Authors: DARKE SHANE , TOPP LIBBY , ROSS JOANNE
Published: July 2002

Trends in the injection of methadone and benzodiazepines by injecting drug users (IDU) recruited in Sydney for the Illicit Drug Reporting System over the period 1996–2000 were examined. A total of 788 IDU were interviewed over the 5‐year period. The proportion of IDU reporting recent methadone injecting declined significantly over the study period, from a peak of 31% in 1997 to 13% in 2000. Unlike the injection of methadone, there was no significant difference between the proportions of IDU reporting recent benzodiazepine injecting over the study period, which ranged between 10% and 16%. A consistent minority (range 5–7%) of IDU reported having injected both methadone and benzodiazepines in all years of the study. There were no differences in the proportions of males and females reporting recent methadone or benzodiazepine injecting in any individual year. Both methadone and benzodiazepine injecting were independently associated with higher levels of injection‐related health problems. Given the substantial harms associated with these practices, continued monitoring of their prevalence is war ranted.
Immunotoxicology—Regulatory and Risk Assessment Concepts
Authors: Blank James A. , Luster Michael I. , Langone John J. , Wilson Susan D.
Published: July 2002

Disclaimer: This article was written by Susan D. Wilson in her private capacity. No official support or endorsement by the Food and Drug Administration is intended or should be inferred. Address correspondence to James Blank, Pfizer Central Research (Mailbox #8014), Eastern Point Road, Groton, CT 06340, USA. E-mail: james_a_blank@groton.pfizer.com This article provides a review of presentations given at the symposium on Immunotoxicology: Regulatory and Risk Assessment Concepts held at the American College of Toxicology meeting in Orlando, Florida, in November, 1998. Immune system alterations have typically been assessed by histopathology of select lymphoid tissue, clinical pathology, clinical chemistry, plaque forming cell assay for humoral immunity, and allergic contact hypersensitivity. Advances in immunology and molecular biology have led to various activities to optimize hazard identification and risk assessment processes and strategies for immunotoxicants. With such advances, regulatory agencies have been either implementing immunotoxicology guidance as part of the safety of medical devices, evaluating environmental chemicals, or considering immunotoxicologic criteria for nonclinical assessments. Reviews of the guidance document provided by the Food and Drug Administration (FDA)/Center for Device and Radiological Health and concepts being considered by the FDA/Center for Drug Evaluation and Research are presented. In addition, a review of the process for evaluation of the murine local lymph node assay by the Interagency Coordinating Committee on the Validation of Alternative Methods and the state of risk assessment for chemical-induced autoimmunity are presented.
Oral Toxicity of 1,2-Dithiole-3-Thione, a Potential Cancer Chemopreventive Agent, in the Rat
Authors: Brown Alan P. , Morrissey Robert L. , Tolhurst Thomas A. , Crowell James A. , Levine Barry S.
Published: July 2002

This study examined the toxicity of 1,2-dithiole-3-thione (D3T) in rats following 14 days of daily oral (gavage) administration. D3T, an extensive inducer of hepatic phase II drug-metabolizing enzymes, has demonstrated cancer preventive efficacy in rodent models of tumorigenesis and is a candidate drug for cancer prevention. Male and female CD rats (5/sex/dose group) received D3T at dose levels of 0 (corn oil vehicle control), 2, 6, 20, and 60 mg/kg/day. Oral administration of D3T for 14 days at 20 mg/kg/day resulted in decreased activity, lethargy, rough coat, and piloerection, and toxicologically significant lesions in the stomach, characterized by apoptotic necrosis and hyperplasia of the glandular mucosa. Administration of D3T at 60 mg/kg/day produced anemia in females, decreased body weight gain in males, and increased vacuolation of adrenal cortical cells. Increased liver weights, vacuolation of hepatocytes, and serum chemistry changes, indicative of altered liver function, were observed at 6 mg/kg/day, which were likely due to a pharmacologic effect of D3T on the liver and not considered to be toxicologically significant. Under the conditions of the study, the no-observed-adverse effect level (NOAEL) was 6 mg/kg/day.
Diet Restriction as a Protective Mechanism in Noncancer Toxicity Outcomes: A Review
Authors: Ramaiah Shashi K. , Apte Udayan , Mehendale Harihara M.
Published: July 2002

It is well documented that diet restriction (DR) increases life expectancy, slows aging, and decreases the incidence of a variety of age-associated diseases including cancer and chemical-induced carcinogenesis. With regard to chemical toxicity, very few studies have attempted to investigate the effects of DR on noncancer toxicity outcomes. This review summarizes the findings of how DR influences acute toxicity outcomes and mechanisms. DR-induced protection in ozone lung inflammation, acute toxicity of isoproterenol, ganciclovir-, aspirin-and acidified ethanol-induced gastric injury are discussed. Because similar physiologic mechanisms exist in humans, DR, if practiced as a fife-style option, may improve quality of life in addition to accruing savings in burgeoning health care costs. Finally, these studies may be of value in boosting research in the area of pharmacology and therapeutics in developing potential therapeutic and safety assessment tools in human and veterinary medicine.
Modulation of Urethane (Ethyl Carbamate) Carcinogenicity by Ethyl Alcohol: A Review
Authors: Benson R. Wayne , Beland Frederick A.
Published: July 2002

Urethane (ethyl carbamate) is a carcinogen that has been detected as a contaminant in certain foods and alcoholic beverages. The carcinogenicity of urethane appears to be mediated through a metabolic pathway involving sequential cytochrome P-450-catalyzed oxidation to vinyl carbamate and vinyl carbamate epoxide, the latter of which reacts with DNA to yield etheno-type DNA adducts. The interactions of ethanol on urethane metabolism and carcinogenicity are varied and complex. Urethane is oxidized by cytochrome P-450 IIE1, an isoform induced by ethanol, which suggests that chronic ethanol consumption could increase the oxidation of urethane to its epoxide derivative. On the other hand, ethanol coadministration is known to inhibit the elimination and hydrolysis of urethane. Ethanol has decreased the tumorigenicity of urethane in two bioassays, but did not have an effect in a third. While the results to date suggest that ethanol will decrease the metabolic activation of urethane, with a resultant decrease in tumorigenicity, additional studies are clearly necessary to elucidate the mechanisms by which ethanol influences the carcinogenicity of urethane.
Effect of Single Versus Repeated Exposure to 1,1,1-Trichloroethane on Rat Operant Behavior
Authors: Warren D. Alan , Reigle Thomas G. , Dallas Cham E.
Published: July 2002

A design feature of most dose-response studies involving schedule-controlled operant behavior is the repeated administration of different doses of the test substance to the same experimental animal. Repeated dosing raises the question of whether or not an animal's initial exposure to a chemical agent alters its behavioral response to subsequent exposures. To address this question, a dose-response curve for the effect of inhaled 1,1,1-trichloroethane (TRI) on the rate of lever-pressing for milk delivery was generated with repeatedly exposed rats (i.e., a within-subject design) and compared to dose-response data obtained from rats receiving a single inhalation exposure to TRI (i.e., a between-group design). Relative to that generated with singly exposed rats, the dose-response curve generated by repeated exposure was shifted to the left. This suggests that the behavioral effects of rate-decreasing concentrations of TRI are augmented by previous exposures. This residual effect is apparently not due to the accumulation of pharmacologically active substances or to the development of an aversion to responding, since TRI is rapidly eliminated following exposure and solvent-free responding was unaffected 24 h postexposure. Instead, the results of this study support the well-established belief that an animal's response to a drug or chemical agent can be modified by its prior behavioral and exposure history. Thus, comparisons of single and repeated exposures may be necessary for fully accurate interpretations of the behavioral consequences of solvent exposure.
Subchronic Neurotoxicity of Vaporized Diisopropyl Ether in Rats
Authors: Rodriguez S. C. , Dalbey W. E.
Published: July 2002

The neurotoxicity potential of diisopropyl ether (DIPE) during subchronic exposures was evaluated in rats using a functional observational battery (FOB), automated motor activity, and neuropathology. Sprague-Dawley rats were exposed 5 dl wk for 13 weeks by inhalation to either 0, 450, 3250, or 7060 ppm DIPE. Body weights were recorded weekly and clinical observations were recorded prior to each exposure. The FOB and a measurement of motor activity were performed before the first exposure. The FOB was repeated following 2, 4, 8, and 13 weeks of exposure, and motor activity was determined following 4, 8, and 13 weeks of exposure. After completion of the final evaluations, the animals were intravascularly perfused with phosphate-buffered 5% glutaraldehyde. Microscopic examination of the brain, spinal cord, gasserian and dorsal root ganglia, and sciatic nerve was performed on six animals/ group/ sex exposed to 0 or 7060 ppm DIPE. Motor activity in a figure-eight maze and unperturbed activity in the FOB were decreased at week 4 in females exposed to 7060 ppm; activity in the FOB was also decreased in females exposed to 450 ppm at week 4. Other changes in the FOB appeared to be minor, and none were observed during microscopic examination of tissues from the nervous system. In conclusion, inhalation exposures to DIPE at concentrations as high as 7060 ppm for 13 weeks resulted in few observable effects on the nervous system.
An Evaluation of the Phototoxicity of Tacrolimus (FK506) Ointment in Hairless Mice
Authors: Bekersky Ihor , Ohara Kaname , Dressier Dawna E. , Kuroda Yoshio , Sambuco Christopher P.
Published: July 2002

The acute phototoxic potential of tacrolimus (FK506) ointment was investigated in Crl:SKH1-hr hairless mice. Response toa series of ultravioletradiation (UVR) site exposures in males (five group) following a single topical administration of tacrolimus ointment (0%[vehicle], 0.03%, 0.1%, 0.3%, 1%, or 3%) indicated that tacrolimus ointment was neither photoprotective or phototoxic. However, a slight but dose-related decrease in body weight relative to the vehicle control was found at the end of the 4-day observation period in the tacrolimus ointment-treated groups. The same concentrations of tacrolimus ointment were applied to the back and sides of mice (five sex group; ∼40% of total body surface area) 5 days week in a 13-week range-finding study to assess the tolerance to the ointment and UVR exposure. Untreated animals served as a control group. Mice were exposed to 72 minutes of UVR from a 6.5-kW xenon lamp. Mortality occurred in the 0.3%, 1%, and 3% ointment groups. Application of 3% tacrolimus ointment was associated with reduced body weight. Mild to moderate erythema and/or edema were noted in all tacrolimus ointment-treated groups. Histopathologi-cal examination indicated a mild increase in the prominence of the stratum granulosum and mild acanthosis of the epidermis in both vehicle-treated and tacrolimus ointment-treated mice. Stomach, esophageal, and/ or abdominal cavity lesions, indicative of systemic toxicity and possibly associated with the in gestion of ointment vehicle during preening, were observed during necropsy. There was minimal photo-mediated dermal toxicity of tacrolimus ointment in the 13 weeks of exposure in the present study.
Serotonin transporter (5‐HTT) gene polymorphisms and susceptibility to cocaine dependence among African‐American individuals
Authors: Patkar Ashwin A. , Berrettini Wade H. , Hoehe Margaret , Hill Kevin P. , Sterling Robert C. , Gottheil Edward , Weinstein Stephen P.
Published: July 2002

Studies indicate that the serotonin system, particularly the serotonin transporter (5‐HTT), may modulate the central effects of cocaine. We investigated whether a polymorphism in the 5′ promotor region (5‐HTTLPR) of the 5‐HTT gene confers susceptibility to cocaine dependence. One hundred and ninety‐seven cocaine‐dependent African‐American subjects and 101 controls were studied. Polymerase chain reaction based genotyping of a biallelic repeat polymorphism in the 5′ promotor region yielded 2 alleles containing 484 (S) and 528 bp (L) repeats, respectively. There were no significant differences between controls of European background (n = 40) and African‐American controls (n = 61) in distribution of genotypes (European: LL = 32.5%, LS = 40.0%, SS = 27.5%; African‐American: LL = 27.9%, LS = 57.4%, SS = 14.7%) (χ2= 3.60, df = 2, p = 0.16) or allele frequencies (European: L = 52.5%, S = 47.5%; African‐American: L = 56.6%, S = 43.4%) (χ2= 2.21, df = 1, p = 0.13). When cocaine patients were compared to an ethnically diverse control group (n = 101), frequencies of the L variant (65.0%) were significantly higher while the S variant (35.0%) was less frequent among cocaine patients compared to controls (L = 53.9%, S = 46.1%) (χ2= 6.83, df = 1, p < 0.01). Similarly, there were more cocaine patients with the LL genotype (41.1%) and less with the SS genotype (11.2%) compared to controls (LL = 29.7%, SS = 21.8%) (χ2= 7.43, df = 2, p < 0.05). However, after restricting controls to African‐American individuals only (n = 61), cocaine subjects and controls did not differ significantly with respect to genotype distribution (χ2= 4.24, df = 2, p = 0.12) or allele frequencies (χ2= 2.83, df = 1, p = 0.10). In conclusion, although comparisons with a heterogeneous control group indicated a possible association between allelic variants of 5‐HTTLPR and cocaine dependence among African‐American cocaine subjects, this relationship was not observed when the control group was limited to African‐American people only. Our findings need to be confirmed on larger samples of ethnically matched individuals.
Alcohol exposure and paracetamol‐induced hepatotoxicity
Authors: RIORDAN STEPHEN M. , WILLIAMS ROGER
Published: July 2002

AbstractMost instances of hepatotoxicity due to paracetamol in the United Kingdom and Australia are the result of large overdoses of the drug taken with suicidal or parasuicidal intent. In contrast, serious hepatotoxicity at recommended or near‐recommended doses for therapeutic purposes has been reported, mainly from the United States and in association with chronic alcohol use, leading to the widely held belief that chronic alcoholics are predisposed to paracetamol‐related toxicity at relatively low doses. Yet the effects of alcohol on paracetamol metabolism are complex. Studies performed in both experimental animals and humans indicate that chronic alcohol use leads to a short‐term, two‐ to threefold increase in hepatic content of cytochrome P4502E1, the major isoform responsible for the generation of the toxic metabolite from paracetamol, although increased oxidative metabolism of paracetamol at recommended doses has not been demonstrated clinically. A reduced hepatic content of glutathione, required to detoxify the reactive metabolite, has been documented in chronic alcoholics, due probably to associated fasting and malnutrition, providing a metabolic basis for any possible predisposition of this group to hepatotoxicity at relatively low paracetamol doses. Simultaneous alcohol and paracetamol ingestion reduces oxidative metabolism of paracetamol in both rodents and humans, predominantly as a consequence of depletion in cytosol of free NADPH. The possibilities that chronic alcohol use may predispose to paracetamol‐related hepatotoxicity and that alcohol taken with paracetamol may protect against it, based on these metabolic observations, are examined in this review.
Gender differences in the pharmacology of nicotine addiction
Authors: Benowitz Neal L. , Hatsukami Dorothy
Published: July 2002

Smoking rates have declined in recent years less rapidly in women than in men. More adolescent girls than boys are currently smoking. Quitting smoking is reported in many studies to be more difficult in women than in men. These observations suggest that there may be gender differences in the nature of nicotine addiction. Gender differences in various pharmacological processes involved in nicotine addiction are reviewed. Women take in less nicotine from smoking per cigarette than men but, because of slower metabolism, nicotine levels in the body for a given number of cigarettes per day are similar in male and female smokers. Women tend to be less sensitive to the discriminative effects of nicotine and tend to regulate nicotine intake less precisely than men. On the other hand, women appear to be more sensitive to the effects of nicotine in reducing negative affect and reducing body weight. There is a strong association between depression and smoking, and this association appears to be stronger in women than in men. Women tend to respond more to environmental cues associated with smoking than do men. Thus, several lines of evidence suggest that nicotine addiction is different in women than in men. Understanding the basis for gender differences may be of utility in individualizing and optimizing smoking cessation therapy.
Coordinated Incorporation of Skeletal Muscle Dihydropyridine Receptors and Ryanodine Receptors in Peripheral Couplings of BC3H1 Cells
Authors: Protasi Feliciano , Franzini-Armstrong Clara , Flucher Bernhard E.
Published: July 2002

Rapid release of calcium from the sarcoplasmic reticulum (SR) of skeletal muscle fibers during excitation–contraction (e–c) coupling is initiated by the interaction of surface membrane calcium channels (dihydropyridine receptors; DHPRs) with the calcium release channels of the SR (ryanodine receptors; RyRs, or feet). We studied the early differentiation of calcium release units, which mediate this interaction, in BC3H1 cells. Immunofluorescence labelings of differentiating myocytes with antibodies against α1 and α2 subunits of DHPRs, RyRs, and triadin show that the skeletal isoforms of all four proteins are abundantly expressed upon differentiation, they appear concomitantly, and they are colocalized. The transverse tubular system is poorly organized, and thus clusters of e–c coupling proteins are predominantly located at the cell periphery. Freeze fracture analysis of the surface membrane reveals tetrads of large intramembrane particles, arranged in orderly arrays. These appear concomitantly with arrays of feet (RyRs) and with the appearance of DHPR/RyS clusters, confirming that the four components of the tetrads correspond to skeletal muscle DHPRs. The arrangement of tetrads and feet in developing junctions indicates that incorporation of DHPRs in junctional domains of the surface membrane proceeds gradually and is highly coordinated with the formation of RyR arrays. Within the arrays, tetrads are positioned at a spacing of twice the distance between the feet. The incorporation of individual DHPRs into tetrads occurs exclusively at positions corresponding to alternate feet, suggesting that the assembly of RyR arrays not only guides the assembly of tetrads but also determines their characteristic spacing in the junction.
AP-2/Eps15 Interaction Is Required for Receptor-mediated Endocytosis
Authors: Benmerah Alexandre , Lamaze Christophe , Bègue Bernadette , Schmid Sandra L. , Dautry-Varsat Alice , Cerf-Bensussan Nadine
Published: July 2002

We have previously shown that the protein Eps15 is constitutively associated with the plasma membrane adaptor complex, AP-2, suggesting its possible role in endocytosis. To explore the role of Eps15 and the function of AP-2/Eps15 association in endocytosis, the Eps15 binding domain for AP-2 was precisely delineated. The entire COOH-terminal domain of Eps15 or a mutant form lacking all the AP-2–binding sites was fused to the green fluorescent protein (GFP), and these constructs were transiently transfected in HeLa cells. Overexpression of the fusion protein containing the entire COOH-terminal domain of Eps15 strongly inhibited endocytosis of transferrin, whereas the fusion protein in which the AP-2–binding sites had been deleted had no effect. These results were confirmed in a cell-free assay that uses perforated A431 cells to follow the first steps of coated vesicle formation at the plasma membrane. Addition of Eps15-derived glutathione-S-transferase fusion proteins containing the AP-2–binding site in this assay inhibited not only constitutive endocytosis of transferrin but also ligand-induced endocytosis of epidermal growth factor. This inhibition could be ascribed to a competition between the fusion protein and endogenous Eps15 for AP-2 binding. Altogether, these results show that interaction of Eps15 with AP-2 is required for efficient receptor-mediated endocytosis and thus provide the first evidence that Eps15 is involved in the function of plasma membrane–coated pits.
Parathyroid Hormone–related Peptide (PTHrP)-dependent and -independent Effects of Transforming Growth Factor β (TGF-β) on Endochondral Bone Formation
Authors: Serra Rosa , Karaplis Andrew , Sohn Philip
Published: July 2002

Previously, we showed that expression of a dominant-negative form of the transforming growth factor β (TGF-β) type II receptor in skeletal tissue resulted in increased hypertrophic differentiation in growth plate and articular chondrocytes, suggesting a role for TGF-β in limiting terminal differentiation in vivo. Parathyroid hormone–related peptide (PTHrP) has also been demonstrated to regulate chondrocyte differentiation in vivo. Mice with targeted deletion of the PTHrP gene demonstrate increased endochondral bone formation, and misexpression of PTHrP in cartilage results in delayed bone formation due to slowed conversion of proliferative chondrocytes into hypertrophic chondrocytes. Since the development of skeletal elements requires the coordination of signals from several sources, this report tests the hypothesis that TGF-β and PTHrP act in a common signal cascade to regulate endochondral bone formation. Mouse embryonic metatarsal bone rudiments grown in organ culture were used to demonstrate that TGF-β inhibits several stages of endochondral bone formation, including chondrocyte proliferation, hypertrophic differentiation, and matrix mineralization. Treatment with TGF-β1 also stimulated the expression of PTHrP mRNA. PTHrP added to cultures inhibited hypertrophic differentiation and matrix mineralization but did not affect cell proliferation. Furthermore, terminal differentiation was not inhibited by TGF-β in metatarsal rudiments from PTHrP-null embryos; however, growth and matrix mineralization were still inhibited. The data support the model that TGF-β acts upstream of PTHrP to regulate the rate of hypertrophic differentiation and suggest that TGF-β has both PTHrP-dependent and PTHrP-independent effects on endochondral bone formation.
Component Specificity for the Thylakoidal Sec and Delta Ph–Dependent Protein Transport Pathways
Authors: Mori Hiroki , Summer Elizabeth J. , Ma Xianyue , Cline Kenneth
Published: July 2002

Prokaryotes and prokaryote-derived thylakoid membranes of chloroplasts share multiple, evolutionarily conserved pathways for protein export. These include the Sec, signal recognition particle (SRP), and Delta pH/Tat systems. Little is known regarding the thylakoid membrane components involved in these pathways. We isolated a cDNA clone to a novel component of the Delta pH pathway, Tha4, and prepared antibodies against pea Tha4, against maize Hcf106, a protein implicated in Delta pH pathway transport by genetic studies, and against cpSecY, the thylakoid homologue of the bacterial SecY translocon protein. These components were localized to the nonappressed thylakoid membranes. Tha4 and Hcf106 were present in ∼10-fold excess over active translocation sites. Antibodies to either Tha4 or Hcf106 inhibited translocation of four known Delta pH pathway substrate proteins, but not of Sec pathway or SRP pathway substrates. This suggests that Tha4 and Hcf106 operate either in series or as subunits of a heteromultimeric complex. cpSecY antibodies inhibited translocation of Sec pathway substrates but not of Delta pH or SRP pathway substrates. These studies provide the first biochemical evidence that Tha4 and Hcf106 are specific components of the Delta pH pathway and provide one line of evidence that cpSecY is used specifically by the Sec pathway.
Heterophilic Binding of L1 on Unmyelinated Sensory Axons Mediates Schwann Cell Adhesion and Is Required for Axonal Survival
Authors: Haney C.A. , Sahenk Z. , Li C. , Lemmon V.P. , Roder J. , Trapp B.D.
Published: July 2002

This study investigated the function of the adhesion molecule L1 in unmyelinated fibers of the peripheral nervous system (PNS) by analysis of L1- deficient mice. We demonstrate that L1 is present on axons and Schwann cells of sensory unmyelinated fibers, but only on Schwann cells of sympathetic unmyelinated fibers. In L1-deficient sensory nerves, Schwann cells formed but failed to retain normal axonal ensheathment. L1-deficient mice had reduced sensory function and loss of unmyelinated axons, while sympathetic unmyelinated axons appeared normal. In nerve transplant studies, loss of axonal-L1, but not Schwann cell-L1, reproduced the L1-deficient phenotype. These data establish that heterophilic axonal-L1 interactions mediate adhesion between unmyelinated sensory axons and Schwann cells, stabilize the polarization of Schwann cell surface membranes, and mediate a trophic effect that assures axonal survival.
In Vivo Release of Mitotic Silencing of Ribosomal Gene Transcription Does Not Give Rise to Precursor Ribosomal RNA Processing
Authors: Sirri Valentina , Roussel Pascal , Hernandez-Verdun Danièle
Published: July 2002

Nuclear RNA transcription is repressed when eukaryotic cells enter mitosis. Here, we found that the derepression of ribosomal gene (rDNA) transcription that normally takes place in telophase may be induced in prometaphase, metaphase, and anaphase mitotic HeLa cells, and therefore appears not to be dependent on completion of mitosis. We demonstrate for the first time that in vivo inhibition of the cdc2– cyclin B kinase activity is sufficient to give rise to okadaic acid–sensitive dephosphorylation of the mitotically phosphorylated forms of components of the rDNA transcription machinery, and consequently to restore rDNA transcription in mitotic cells. These results, showing that during mitosis the rDNA transcription machinery is maintained repressed by the cdc2–cyclin B kinase activity, provide an in vivo demonstration of the cell cycle–dependent regulation of rDNA transcription. Interestingly in mitotic cells, the newly synthesized 47S precursor ribosomal RNA (pre-rRNA) is not processed into the mature rRNAs, indicating that rDNA transcription and pre-rRNA processing may be uncoupled. Moreover this suggests that inhibition of the cdc2– cyclin B kinase is not sufficient to activate the 47S pre-rRNA processing machinery and/or to induce its relocalization at the level of newly synthesized 47S pre-rRNA. This in vivo approach provides new possibilities to investigate the correlation between pre-rRNA synthesis and pre-rRNA processing when the nucleolus reforms.
Accumulation of Caveolin in the Endoplasmic Reticulum Redirects the Protein to Lipid Storage Droplets
Authors: Ostermeyer Anne G. , Paci James M. , Zeng Youchun , Lublin Douglas M. , Munro Sean , Brown Deborah A.
Published: July 2002

Caveolin-1 is normally localized in plasma membrane caveolae and the Golgi apparatus in mammalian cells. We found three treatments that redirected the protein to lipid storage droplets, identified by staining with the lipophilic dye Nile red and the marker protein ADRP. Caveolin-1 was targeted to the droplets when linked to the ER-retrieval sequence, KKSL, generating Cav–KKSL. Cav–ΔN2, an internal deletion mutant, also accumulated in the droplets, as well as in a Golgi-like structure. Third, incubation of cells with brefeldin A caused caveolin-1 to accumulate in the droplets. This localization persisted after drug washout, showing that caveolin-1 was transported out of the droplets slowly or not at all. Some overexpressed caveolin-2 was also present in lipid droplets. Experimental reduction of cellular cholesteryl ester by 80% did not prevent targeting of Cav–KKSL to the droplets. Cav–KKSL expression did not grossly alter cellular triacylglyceride or cholesteryl levels, although droplet morphology was affected in some cells. These data suggest that accumulation of caveolin-1 to unusually high levels in the ER causes targeting to lipid droplets, and that mechanisms must exist to ensure the rapid exit of newly synthesized caveolin-1 from the ER to avoid this fate.
Rho Family Gtpase Cdc42 Is Essential for the Actin-Based Motility of Shigella in Mammalian Cells
Authors: Suzuki Toshihiko , Mimuro Hitomi , Miki Hiroaki , Takenawa Tadaomi , Sasaki Takuya , Nakanishi Hiroyuki , Takai Yoshimi , Sasakawa Chihiro
Published: July 2002

Shigella, the causative agent of bacillary dysentery, is capable of directing its movement within host cells by exploiting actin dynamics. The VirG protein expressed at one pole of the bacterium can recruit neural Wiskott-Aldrich syndrome protein (N-WASP), a downstream effector of Cdc42. Here, we show that Cdc42 is required for the actin-based motility of Shigella. Microinjection of a dominant active mutant Cdc42, but not Rac1 or RhoA, into Swiss 3T3 cells accelerated Shigella motility. In add-back experiments in Xenopus egg extracts, addition of a guanine nucleotide dissociation inhibitor for the Rho family, RhoGDI, greatly diminished the bacterial motility or actin assembly, which was restored by adding activated Cdc42. In N-WASP–depleted extracts, the bacterial movement almost arrested was restored by adding exogenous N-WASP but not H208D, an N-WASP mutant defective in binding to Cdc42. In pyrene actin assay, Cdc42 enhanced VirG-stimulating actin polymerization by N-WASP–actin-related protein (Arp)2/3 complex. Actually, Cdc42 stimulated actin cloud formation on the surface of bacteria expressing VirG in a solution containing N-WASP, Arp2/3 complex, and G-actin. Immunohistological study of Shigella-infected cells expressing green fluorescent protein–tagged Cdc42 revealed that Cdc42 accumulated by being colocalized with actin cloud at one pole of intracellular bacterium. Furthermore, overexpression of H208D mutant in cells interfered with the actin assembly of infected Shigella and diminished the intra- and intercellular spreading. These results suggest that Cdc42 activity is involved in initiating actin nucleation mediated by VirG–N-WASP–Arp2/3 complex formed on intracellular Shigella.
A class of differentiable toral maps which are topologically mixing
Authors: Sumi Naoya
Published: July 2002

We show that on the 2-torus

T

2

\mathbb {T}^{2}

there exists a

C

1

C^{1}

open set

U

\mathcal {U}

of

C

1

C^{1}

regular maps such that every map belonging to

U

\mathcal {U}

is topologically mixing but is not Anosov. It was shown by Mañé that this property fails for the class of

C

1

C^{1}

toral diffeomorphisms, but that the property does hold for the class of

C

1

C^{1}

diffeomorphisms on the 3-torus

T

3

\mathbb {T}^{3}

. Recently Bonatti and Diaz proved that the second result of Mañé is also true for the class of

C

1

C^{1}

diffeomorphisms on the

n
n

-torus

T

n

\mathbb {T}^{n}

(

n
≥
4

n\ge 4

).
Local boundary rigidity of a compact Riemannian manifold with curvature bounded above
Authors: Croke Christopher , Dairbekov Nurlan , Sharafutdinov Vladimir
Published: July 2002

This paper considers the boundary rigidity problem for a compact convex Riemannian manifold

(
M
,
g
)

(M,g)

with boundary

∂
M

\partial M

whose curvature satisfies a general upper bound condition. This includes all nonpositively curved manifolds and all sufficiently small convex domains on any given Riemannian manifold. It is shown that in the space of metrics

g
′

g’

on

M
M

there is a

C

3
,
α

C^{3,\alpha }

-neighborhood of

g
g

such that

g
g

is the unique metric with the given boundary distance-function (i.e. the function that assigns to any pair of boundary points their distance — as measured in

M
M

). More precisely, given any metric

g
′

g’

in this neighborhood with the same boundary distance function there is diffeomorphism

φ
\varphi

which is the identity on

∂
M

\partial M

such that

g
′

=

φ

∗

g

g’=\varphi ^{*}g

. There is also a sharp volume comparison result for metrics in this neighborhood in terms of the boundary distance-function.
Domain decomposition algorithms for mixed methods for second-order elliptic problems
Authors: Chen Zhangxin , Ewing Richard , Lazarov Raytcho
Published: July 2002

In this paper domain decomposition algorithms for mixed finite element methods for linear second-order elliptic problems in

R

2

\mathbb {R}^{2}

and

R

3

\mathbb {R}^{3}

are developed. A convergence theory for two-level and multilevel Schwarz methods applied to the algorithms under consideration is given. It is shown that the condition number of these iterative methods is bounded uniformly from above in the same manner as in the theory of domain decomposition methods for conforming and nonconforming finite element methods for the same differential problems. Numerical experiments are presented to illustrate the present techniques.
A human tissue‐engineered vascular media: a new model for pharmacological studies of contractile responses
Authors: L’HEUREUX NICOLAS , STOCLET JEAN‐CLAUDE , AUGER FRANÇOIS A. , LAGAUD GUY JEAN‐LOUIS , GERMAIN LUCIE , ANDRIANTSLTOHAINA RAMAROSON
Published: July 2002

Our method for producing tissue‐engineered blood vessels based exclusively on the use of human cells, i.e., without artificial scaffolding, has previously been described (1). In this report, a tissue‐engineered vascular media (TEVM) was specifically produced for pharmacological studies from cultured human vascular smooth muscle cells (VSMC). The VSMC displayed a differentiated phenotype as demonstrated by the re‐expression of VSMC‐specific markers and actual tissue contraction in response to physiological stimuli. Because of their physiological shape and mechanical strength, rings of human TEVM could be mounted on force transducers in organ baths to perform standard pharmacological experiments. Concentration‐response curves to vasoconstrictor agonists (histamine, bradykinin, ATP, and UTP) were established, with or without selective antagonists, allowing pharmacological characterization of receptors (H1,B2, and P2Y1, and pyrimidinoceptors). Sustained agonist‐induced contractions were associated with transient increases in cytosolic Ca2+ concentration, suggesting sensitization of the contractile machinery to Ca2+. ATP caused both Ca2+ entry and Ca2+ release from a ryanodine‐ and caffeine‐sensitive store. Increased cyclic AMP or cyclic GMP levels caused relaxation. This human TEVM displays many of functional characters of the normal vessel from which the cells were originally isolated, including contractile/relaxation responses, cyclic nucleotide sensitivity, and Ca2+ handling mechanisms comparable to those of the normal vessel from which the cells were originally isolated. These results demonstrate the potential of this human model as a versatile new tool for pharmacological research.—L Heureux, N., Stoclet, J.‐C., Auger, F. A., Lagaud, G. J.‐L., Germain, L., Andriantsitohaina, R. A human tissue‐engineered vascular media: a new model for pharmacological studies of contractile responses. FASEB J. 15, 515‐524 (2001)
TIF1β functions as a coactivator for C/EBPβ and is required for induced differentiation in the myelomonocytic cell line U937
Authors: Rooney John W. , Calame Kathryn L.
Published: July 2002

Representational difference analysis (RDA) cloning has identified transcriptional intermediary factor 1 beta (TIF1β) as a gene inducibly expressed early during myeloid differentiation of the promyelocytic cell lines HL-60 and U937. To assess the role of TIF1β, U937 cell lines were made that expressed antisense-hammerhead ribozymes targeted specifically against TIF1β mRNA. These cells failed to differentiate into macrophages, as determined by several criteria: a nonadherent morphology, a failure to arrest cell cycle, lowered levels of macrophage-specific cell surface markers, resistance toLegionella pneumophilainfection, a loss of the ability to phagocytose and chemotax, and decreased expression of chemokine mRNAs. One way TIF1β acts in macrophage differentiation is to augment C/EBPβ transcriptional activity. Furthermore, we show by EMSA supershifts and coimmunoprecipitation that C/EBPβ and TIF1β physically interact. Although TIF1β is necessary for macrophage differentiation of U937 cells, it is not sufficient, based on the inability of ectopically expressed TIF1β to induce or augment phorbol ester-induced macrophage differentiation. We conclude that TIF1β plays an important role in the terminal differentiation program of macrophages, which involves the coactivation of C/EBPβ and induction of C/EBPβ-responsive myeloid genes.
Scatter/primary in mammography: Monte Carlo validation
Authors: Boone John M. , Cooper Virgil N.
Published: July 2002

The purpose of this investigation was to compare and validate the performance of the SIERRA Monte Carlo simulation routines for the analysis of the scatter to primary ratio (SPR) in the mammography setting. Two Monte Carlo simulation methods were addressed, the direct method was a straightforward and geometrically accurate simulation procedure, and the convolution method uses idealized geometry (monoenergetic, normally incident delta function input to the scattering medium) to produce scatter point spread functions (PSFs). The PSFs were weighted by the x‐ray spectrum of interest and convolved with the field of view to estimate SPR values. The SPR results of both Monte Carlo procedures were extensively compared to five published sources, including Monte‐Carlo‐derived and physically measured SPR assessments. The direct method demonstrated an overall agreement with the literature of 3.7% accuracy and the convolution method demonstrated an average of 7.1% accuracy The comparisons were made over a range of parameters which included field of view, phantom thickness, x‐ray energy, and phantom composition. Limitations of the beam stop method were also discussed. The results suggest that the SIERRA Monte Carlo routines produce accurate SPR calculations and may be useful for a more comprehensive study of scatter in mammography.
Experimental evaluation of a simple algorithm to enhance the spatial resolution in scanned radiographic systems
Authors: Olivo A. , Rigon L. , Arfelli F. , Cantatore G. , Longo R. , Menk R. H. , Pani S. , Prest M. , Poropat P. , Tromba G. , Vallazza E. , Castelli E.
Published: July 2002

In order to ensure an early diagnosis of breast cancer, an imaging system must fulfil extremely stringent requirements in terms of dynamic range, contrast resolution and spatial resolution. Furthermore, in order to reduce the dose delivered to the patient, a high efficiency of the detector device should be provided. In this paper the SYRMEP/FRONTRAD (SYnchrotron Radiation for MEdical Physics/FRONTier RADiology) mammography project, based on synchroton radiation and a novel solid state pixel detector, is briefly described. Particular relevance is given to the fact that the radiographic image is obtained by means of a scanning technique, which allows the possibility of utilizing a scanning step smaller than the pixel size. With this procedure, a convolution between the real image and the detector point spread function (PSF) is actually acquired: by carefully measuring the detector PSF, it is possible to apply a post‐processing procedure (filtered deconvolution), which reconstructs images with enhanced spatial resolution. The image acquisition modality and the deconvolution algorithm are herein described, and some test object images, with spatial resolution enhanced by means of the filtered deconvolution procedure, are presented. As discussed in detail in this paper, this procedure allows us to obtain a spatial resolution determined by the scanning step, rather than by the pixel size.
Parallel cascades: New ways to describe noise transfer in medical imaging systems
Authors: Yao J. , Cunningham I. A.
Published: July 2002

A generalized approach to describing transfer of the noise power spectrum through medical imaging systems has been developed over the past several years in which image‐forming processes are represented in terms of a cascade of amplified point processes. Until recently, this approach has been restricted to serial cascades only. Here we develop a generalized expression for the cross covariance of amplified point processes and an expression for the cross spectral density for wide‐sense stationary conditions. These results extend the generalized transfer‐theory approach to include the description of more complex image‐forming processes involving parallel cascades of quantum amplification processes. This parallel‐cascade approach is used to develop a theoretical expression for noise‐power transfer in a simple radiographic screen that includes the effect of characteristic x‐ray reabsorption. The result confirms earlier work by Metz and Vyborny, who showed that reabsorption increases image noise and decreases the detective quantum efficiency at low spatial frequencies. Use of the transfer‐theory approach facilitates a straightforward generalization to many new digital imaging systems including conventional angiographic and active‐matrix flat‐panel systems.
Parametrization of mammography normalized average glandular dose tables
Authors: Sobol Wlad T. , Wu Xizeng
Published: July 2002

Data from existing tables of normalized glandular doses in mammography were parametrized to determine analytical expressions that match tabulated results within known uncertainties. The parametrization was performed for three different target/filter combinations (molybdenum target–molybdenum filter, molybdenum target–rhodium filter, and rhodium target–rhodium filter) and three different breast compositions (100% adipose, 50% adipose–50% glandular, and 100% glandular). The analytical expressions provide the normalized glandular dose for any breast composition within stated ranges of tabulated input parameters (kVp, half‐value layer, and breast thickness). The maximum difference between tabulated and parametrized data is 1.29%, which is smaller than the stated 2% uncertainty in tabulated dose data due to uncertainties in the x‐ray spectra models used to generate the tables. Analytical expressions are easily coded to create custom functions that return the normalized glandular dose for the set of input parameters. Examples of implementation are presented in Microsoft Visual Basic for Applications™ (VBA).
A method for quantifying SPECT uniformity
Authors: Madsen Mark T.
Published: July 2002

Field uniformity is an important parameter for monitoring the performance of SPECT imaging systems. However, it is difficult to apply objective measures of uniformity because of the large variance associated with reconstructed images. In the proposed method, annular sampling of the SPECT uniformity image is used to reduce the noise level without decreasing the magnitude of uniformity artifacts. The reconstructed uniformity image is sectioned into annular rings centered on the center of rotation to match the expected distribution of uniformity artifacts. Statistical fluctuations are reduced by averaging the counts within the annular rings, allowing the use of objective measures of field uniformity such as integral uniformity. Application of the annular sampling technique on simulated and phantom uniformity images showed that the technique could reliably quantify SPECT uniformity artifacts at acceptable count levels. As a result this method can be used to objectively evaluate SPECT field uniformity in systems which utilize parallel collimation and circular orbits.
Quantitative evaluation of radiochromic film response for two‐dimensional dosimetry
Authors: Zhu Yimin , Kirov Assen S. , Mishra Vivek , Meigooni Ali S. , Williamson Jeffrey F.
Published: July 2002

Radiochromic film (RCF) is attractive as a thin, high resolution, 2D planar dosimeter. We have studied the uniformity, linearity, and reproducibility of a commercially supplied RCF system (model MD‐55). Forty 12 cm long strips of RCF were exposed to uniform doses of 6 MV x rays. Optical density (OD) distributions were measured by a helium‐neon scanning laser (633 nm) 2D densitometer and also with a manual densitometer. All film strips showed 8%–15% variations in OD values independent of densitometry technique which are evidently due to nonuniform dispersal of the sensor medium. A double exposure technique was developed to solve this problem. The film is first exposed to a uniform beam, which defines a pixel‐by‐pixel nonuniformity correction matrix. The film is then exposed to the unknown dose distribution, rescanned, and the net OD at each pixel corrected for nonuniformity. The double exposure technique reduces OD/unit dose variation to a 2%–5% random fluctuation. RCF response was found to deviate significantly from linearity at low doses (40% change in net OD/Gy from 1 to 30 Gy); a finding not previously reported. To study the tradeoff between statistical noise and spatial resolution, OD was averaged over blocks of adjacent 50 μm pixels (ranging from 1×1 to 10×10 pixels). Reproducibility, defined as the standard deviation of repeated single‐pixel measurements on separate film pieces, was 2% at 30 Gy for a resolution of 0.25 mm. With careful correction for nonlinearity and nonuniformity, RCF is a promising quantitative 2D dosimeter for radiation oncology applications.
Detective quantum efficiency dependence on x‐ray energy weighting in mammography
Authors: Cahn R. N. , Cederström B. , Danielsson M. , Hall A. , Lundqvist M. , Nygren D.
Published: July 2002

An evaluation of the dependence of detective quantum efficiency (DQE) on the incident energy spectrum has been made for mammography. The DQE dependence on the energy spectrum has been evaluated for energy‐integrating detectors, photon‐counting detectors, and detectors that measure the energy of each photon. To isolate the effect of the x‐ray energy spectrum the detector has been assumed to be ideal, i.e., all noise sources are assumed to be zero except for quantum fluctuations. The result shows that the improvement in DQE, if the energy‐integrating detector is compared to a single‐photon counting detector, is of the order of 10%. Comparing the energy‐integrating detector and the detector measuring the energy for each photon the improvement is around 30% using a molybdenum anode spectrum typical in mammography. It is shown that the optimal weight factors to combine the data in the case the energy is measured are very well approximated if the weight factors are proportional to Another conclusion is that in calculating the DQE, a detector should be compared to one that uses ideal energy weighting for each photon since this provides the best signal‐to‐noise ratio. This has generally been neglected in the literature.