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Volume 48,
Issue 7,
1999
Volume 48, Issue 7, 1999
- Short Article
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Identification of clinically isolated vancomycin-resistant enterococci:comparison of API and BBL Crystal systems
More LessSummaryTwenty-eight phenotypically separate strains of clinically isolated vancomycin-resistant enterococci have been investigated with two API identification kit systems (20 Strep and Rapid ID 32 Strep) and two BBL Crystal kits (Gram Positive and Rapid Gram Positive). All strains were identified as Enterococcus faecium by a reference laboratory. The Rapid ID 32 kit positively identified 15 of 28 strains (54%), but only two (7%) were identified correctly: 11 were identified as ‘doubtful’ or ‘to genus level’ and two gave ‘unacceptable’ profiles. The API 20 Strep kit identified 27 strains (96%), but only 16 (57%) were identified correctly as E. faecium. The Rapid ID 32 kit erred by either positively misidentifying vancomycin-resistant E. faecium as E. casseliflavus or E. gallinarum, or indicated that this was the most likely identification, while the API 20 Strep kit more commonly produced a misidentification as E. casseliflavus. The Crystal Gram Positive and Rapid Gram Positive kits correctly identified 26 (93%) and 27 (96%) of the strains, respectively.
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Microbiology of retroperitoneal abscesses in children
More LessSummarySamples of pus from 41 children with retroperitoneal abscess treated between 1974 and 1994 yielded a total of 125 organisms (3.0 isolates/specimen); 58 isolates were aerobic and facultative species (1.4/specimen) and 67 were anaerobic (1.6/specimen). Aerobic bacteria only were isolated from 7 (17%) abscesses, anaerobic bacteria only from 3 (7%) and mixed aerobic and anaerobic bacteria from 31 (76%); 34 (83%) infections were polymicrobial. The predominant aerobic and facultative isolates were Escherichia coli (19 isolates) and Staphylococcus aureus (6), and the predominant anaerobes were Peptostreptococcus spp. (18 isolates), Bacteroides spp. (22) and Prevotella spp. (5).
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Use of a low nutrient culture medium for the identification of bacteria causing severe ocular infection
More LessSummaryA low nutrient culture medium was used to identify the pathogens in four cases of persisting ocular infection. Bacto R2A agar was used in addition to conventional liquid-and solid-phase media to culture pathogenic bacteria from one case of recurrent keratitis, one case of suture-related keratitis with endophthalmitis and two eyes (two patients) with post-operative endophthalmitis. In each case, a pathogen was identified solely with R2A agar after culture for 6 days. Species isolated were Pseudomonas aeruginosa (one), Propionibacterium acnes (two) and Staphylococcus aureus (one). Antibiotic therapy was tailored to conform to the sensitivity of the cultured organism in each case. The use of Bacto R2A low nutrient agar should be considered in culture negative eyes not showing clinical improvement, or for chronic cases where bacteria may have become adapted to more stringent ocular environments.
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- Editorial
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- Antimicrobial Agents
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In-vitro anti-chlamydial activities of free and liposomal tetracycline and doxycycline
More LessSummaryThe purpose of this study was to evaluate the anti-chlamydial activities in vitro of liposome-encapsulated doxycycline (Dox) and tetracycline (Tet) in comparison with free Dox and Tet. Dox and Tet encapsulated in cationic (CAL), anionic (ANL) and neutral (NTL) liposomes by sonication, were quantified by high-performance liquid chromatography. Anti-chlamydial activities were determined by addition of serial dilutions of antibiotics (MIC 0.12-0.007 mg/L; MBC 4-0.25 mg/L) to HeLa 229 cell monolayers inoculated with Chlamydia trachomatis L2/434/Bu (103 ifu/well). After incubation for 72 h at 37°, chlamydial inclusions were stained by the May-Grünwald Giemsa method to establish MICs. MBCs were determined in chlamydial agent-free medium after second passages. Dox-encapsulation efficiencies were 28.6 SEM 6.4% in cationic (CAL-Dox), 49.1 SEM 6.7% in anionic (ANL-Dox) and 21.0 SEM 0.8% in neutral (NTL-Dox) liposomes. Tet-encapsulation efficiencies were 3.5 SEM 0.3% in anionic (ANL-Tet) and 2.2 SEM 0.6% in neutral (NTL-Tet) liposomes; no Tet was detected in cationic (CAL-Tet) liposomes. MIC values were 0.06 mg/L for Dox, 0.12 mg/L for Tet, 0.03 mg/L for CAL-Dox, NTL-Dox and NTL-Tet, and 0.01 mg/L for ANL-Dox and ANL-Tet. MBCs were 4 mg/L for Tet, 0.5 mg/L for CAL-Dox and NTL-Dox, and 1 mg/L for Dox, ANL-Dox, ANL-Tet, NTL-Tet and NTL-Tet. For MICs, the relative increase in anti-chlamydial activity observed with liposomal formulations compared to the corresponding free antibiotic ranged from 2- to 6-fold with Dox and from 4- to 10-fold with Tet. For MBCs, the relative increases in anti-chlamydial activity were 2- and 4-fold with liposome-encapsulated Dox and Tet, respectively. Dox was better encapsulated than Tet in all liposomes. Liposome-encapsulated drugs showed greater anti-chlamydial activities than their free forms; thus, these drug formulations have potential in the treatment of chlamydial infections.
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- Epidemiological Typing
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Comparison of a commercial test for serotyping heat-stable antigens of Campylobacter jejuni with genotyping by pulsed-field gel electrophoresis
More LessSummaryA new commercial serotyping set based on heat-stable Penner's antigens was compared with pulsed-field gel electrophoresis (PFGE) with SmaI and SacII restriction endonucleases. Among 50 isolates of Campylobacter jejuni from Finnish patients, which represented predominant PFGE patterns selected from isolates from sporadic cases and isolates associated with small outbreaks, 11 different serotypes were demonstrated from 43 typable isolates. Several PFGE patterns could be found within one serotype; on the other hand, several serotypes could be demonstrated within one PFGE type. Most isolates originated from sporadic cases; however, some isolates were epidemiologically associated and showed identical serotypes and PFGE patterns. Although the new serotyping set would have been useful in the few epidemic cases studied, several isolates (14%) representing the major PFGE patterns remained untypable or gave weakly positive agglutination reactions only suggesting a plausible serotype (18%). This might restrict the use of the novel serotyping set, at least in Finland.
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- Correspondence
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- Bacterial Pathogenicity
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Investigation of the types and characteristics of the proteolytic enzymes formed by diverse strains of Proteus species
More LessSummaryMany diverse clinical isolates of Proteus mirabilis (48 strains), P. penneri (25), P. vulgaris biogroup 2 (48) and P. vulgaris biogroup 3 (21) from man were examined for their ability to produce proteolytic enzymes and the nature and characteristics of the proteases were studied. All the P. penneri isolates, most (94-90%) of the P. mirabilis and P. vulgaris biogroup 2 isolates, but only 71% of the P. vulgaris biogroup 3 isolates, secreted proteolytic enzymes. These were detected most readily at pH 8 with gelatin as substrate. A strong correlation was found between the ability of a strain to form swarming growth and its ability to secrete proteases. Non-swarming isolates invariably appeared to be non-proteolytic. However, some isolates, particularly of P. vulgaris biogroup 3, were non-proteolytic even when they formed swarming growth. Analysis of the secreted enzymes of the different Proteus spp. on polyacrylamide-gelatin gels under various constraints of pH and other factors showed that they were all EDTA-sensitive metalloproteinases. Analysis of the kinetics of production of the proteases revealed the formation of an additional protease of undefined type and function that was cell-associated and formed before the others were secreted. The secreted protease was subsequently modified to two isoforms whose mass (53-46 kDa) varied with the Proteus spp. and the strain. There was no evidence that the secreted proteases of strains of Proteus spp. were of types other than metalloproteinases.
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Fur and iron transport proteins in the Brazilian purpuric fever clone of Haemophilus influenzae biogroup aegyptius
More LessSummaryThe Brazilian purpuric fever (BPF) clone of Haemophilus influenzae biogroup aegyptius causes a fatal septicaemic disease, resembling fulminant meningococcal sepsis, in children. When isolate F3031 was grown under iron-limiting conditions, the presence of several iron-regulated proteins of 38-110 kDa was revealed by electrophoretic analysis and a Fur homologue was shown by immunoblotting. Dot-blot assays and immunoblotting indicated that BPF cells bound human transferrin and contained transferrin-binding proteins in the outer membrane. However, the binding activity and the biosynthesis of these proteins were detected even under iron-rich conditions. Immunoblot analysis demonstrated the presence of a periplasmic protein related to the ferric iron-binding protein A (FbpA), the major iron-binding protein described in Neisseria spp. However, the FbpA homologue in strain F3031 was constitutively expressed and was smaller than the periplasmic protein detected in H. influenzae type b strain Eagan. The periplasm of strain F3031 also contained a protein related to the Streptococcus parasanguis FimA protein which recently has been shown to be involved in iron acquisition in Yersinia pestis. Although the Eagan and F3031 FimA homologues had a similar mol. wt, of 31 kDa, the expression of the BPF fimA-like gene was not regulated by the iron concentration of the culture medium.
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Bactericidal activity of rat lung lavage fluid against Bordetella pertussis
More LessSummaryCell-free lung lavage fluid (LLF) from healthy normal rats killed phase I (wild-type, virulent) Bordetella pertussis at 37° in vitro. B. parapertussis was also killed by the LLF, but phase IV (avirulent mutant) B. pertussis and some other common bacterial species, including B. bronchiseptica, were not. Transmission electron microscopy of thin sections of the phase I B. pertussis showed extensive structural damage and cell lysis. None of the other mammalian species tested had LLF with bactericidal activity against B. pertussis as high as that of the rat. Rats killed with halothane yielded LLF with higher bactericidal activity than when CO2 was used. Ultracentrifugation of LLF at 55 000 g gave a surfactant (pellet) fraction that had c. 95% of the bactericidal activity and which was biochemically distinct from the 5% of activity in the supernate fraction. Phospholipids and fatty acids appeared to be involved in LLF bactericidal activity, but not complement or lysozyme. Arachidonic acid was the most active of the fatty acids tested. Artificial surfactant, as used in premature infants, had no bactericidal effect on B. pertussis.
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Evidence for the presence in Burkholderia pseudomallei of a type III secretion system-associated gene cluster
More LessSummaryBurkholderia pseudomallei, the causative agent of melioidosis, contains a cluster of putative genes homologous to those encoding HpaP, HrcQ, HrcR, HrcS and HrpV in the plant pathogen Ralstonia solanacearum. In R. solanacearum, these genes form part of a type III secretion-associated pathogenicity island. The order of the genes in B. pseudomallei is directly equivalent to that found in R. solanacearum. The B. pseudomallei proteins share 49.5% (HpaP), 52.6% (HrcQ), 80.0% (HrcR), 72.1% (HrcS) and 46.7% (HrpV) similarity, respectively, with their equivalent R. solanacearum proteins. The presence of type III secretion-associated genes in B. pseudomallei pathogens suggests a possible role for type III secretion systems in the pathogenicity of this organism.
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- Bacterial Taxonomy
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Analysis of fliC variation among clinical isolates of Burkholderia cepacia
SummaryPCR and restriction fragment length polymorphism (RFLP) typing of flagellin genes (fliC) from 57 clinical isolates of Burkholderia cepacia indicated that only type II flagellins were present. Twenty-two isolates previously identified as the epidemic UK cystic fibrosis strain were indistinguishable by this method, as were 11 isolates from a pseudo-outbreak in Senegal. Other clinical isolates, including 19 from disparate sources in Malaysia, were separated into nine fliC RFLP groups, exhibiting a large degree of divergence. When isolates were indistinguishable by fliC genotyping, their similarity was confirmed by whole genome macro-restriction analysis with pulsed-field gel electrophoresis following XbaI digestion. The variation in fliC sequences of B. cepacia was far greater than that with B. pseudomallei, supporting the view that ‘B. cepacia’ as currently defined, may comprise several different genomic species.
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- Mycology
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In-vitro resistance to azoles associated with mitochondrial DNA deficiency in Candida glabrata
SummaryA commercially available disk diffusion procedure was used in a large-scale study to evaluate the susceptibility of a wide range of Candida isolates to polyenes and azoles. With almost all isolates of C. glabrata resistant colonies were present within the inhibition zones for the azole compounds fluconazole, ketoconazole and miconazole, and less frequently for isoconazole, econazole and clotrimazole. Ten randomly selected isolates were cloned by limiting dilution and the susceptibility of the resulting strains to polyenes and azoles was determined. All strains presented a similar susceptibility pattern with sensitivity to polyenes and the presence of resistant colonies for all azole compounds except tioconazole. For each strain and each antifungal agent, one of these resistant colonies was subcultured and studied for antifungal susceptibility. All these colonies showed similar properties regardless of which antifungal agent allowed their selection, with increased sensitivity to polyenes and cross-resistance to the azole compounds except tioconazole. Similar results were obtained on Shadomy's modified medium and on synthetic medium. Likewise, determination of MICs by the Etest method confirmed the resistance to fluconazole. Comparative growth studies revealed a respiratory deficiency in the mutants caused by mitochondrial DNA (mtDNA) deletions. In addition, ‘petite’ mutants were obtained from a wild-type strain by exposure to ethidium bromide, and these respiratory mutants were shown to be resistant to azoles. These results demonstrate the relationship between mtDNA deficiency and resistance to azoles, and provide an interesting model to study the mechanisms of action of these antifungal agents.
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Role of dimorphism in the development of Candida albicans biofilms
More LessSummaryTwo model biofilm systems, involving growth on disks of catheter material or on cylindrical cellulose filters, were used to investigate the structure of Candida albicans biofilms. To assess the importance of dimorphism in biofilm development, biofilms produced by two wild-type strains were compared with those formed by two morphological mutants, incapable of yeast and hyphal growth, respectively. Scanning electron microscopy and thin sections of biofilms examined by light microscopy revealed that biofilms of the wild-type strains formed on catheter disks consisted of two distinct layers: a thin, basal yeast layer and a thicker, but more open, hyphal layer. The hypha- mutant produced only the basal layer, whereas the yeast- mutant formed a thicker, hyphal biofilm equivalent to the outer zone of the wild-type structures. Biofilms of the yeast- mutant were more easily detached from the catheter surface than the others, suggesting that the basal yeast layer has an important role in anchoring the biofilm to the surface. Biofilms formed on cylindrical cellulose filters were quite different in appearance. The hypha- mutant and both wild types produced exclusively yeast-form biofilms whereas the yeast- mutant generated a dense hyphal mat on the top of the filter. All these biofilms, irrespective of morphological form, were resistant to the antifungal agent, amphotericin B. Overall, these results indicate that the structure of a C. albicans biofilm depends on the nature of the contact surface, but that some surfaces produce biofilms with a layered architecture resembling to that described for bacterial systems.
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- Serodiagnosis
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Usefulness of rat-derived antigen in the serodiagnosis of Pneumocystis carinii infection
More LessSummarySera from patients with likely and possible Pneumocystis carinii pneumonia (PCP) on the basis of clinical information and laboratory investigations were tested by immunoblotting to assess the usefulness of trophozoites in the serodiagnosis of PCP. IgG antibodies to 50-60- kDa proteins were demonstrated with cyst antigen, but antibodies to additional proteins of 61, 70, 82, 95, 99 and 116 kDa were found with trophozoite antigen. These bands were not demonstrated with control sera. IgG antibody to the 116-kDa protein was found in 18 (46%) of 39 sera from patients with possible PCP compared with 5 (17%) of 30 sera from patients with likely PCP. There was no other significant difference between the two patient groups in detection of these proteins. Sera with higher indirect immunofluorescence assay (IFA) IgG titres were more likely to be immunoblot positive. Only 4 of 16 patients with likely PCP were IgG negative in the IFA; three of these were IgG immunoblot positive. In 4 of 10 patients with likely PCP and 6 of 15 patients with possible PCP, demonstration of IgM or IgA, or both, by IFA or immunoblotting provided evidence suggestive of current infection. This study confirms the usefulness of rat-derived antigen, especially trophozoite antigen, in PCP serology. The IgG IFA remains the most useful test, but IgM and IgA testing and immunoblotting can support the diagnosis.
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- Book Reviews
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Volumes and issues
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Volume 74 (2025)
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Volume 73 (2024)
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Volume 72 (2023 - 2024)
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Volume 71 (2022)
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Volume 70 (2021)
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Volume 69 (2020)
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Volume 68 (2019)
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Volume 67 (2018)
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Volume 66 (2017)
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Volume 65 (2016)
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Volume 64 (2015)
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Volume 63 (2014)
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Volume 62 (2013)
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Volume 61 (2012)
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Volume 60 (2011)
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Volume 59 (2010)
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Volume 58 (2009)
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Volume 57 (2008)
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Volume 56 (2007)
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Volume 55 (2006)
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Volume 54 (2005)
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Volume 53 (2004)
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Volume 52 (2003)
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Volume 51 (2002)
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Volume 50 (2001)
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Volume 49 (2000)
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Volume 48 (1999)
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Volume 47 (1998)
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Volume 46 (1997)
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Volume 45 (1996)
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Volume 44 (1996)
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Volume 43 (1995)
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Volume 42 (1995)
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Volume 41 (1994)
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Volume 40 (1994)
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Volume 39 (1993)
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Volume 38 (1993)
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Volume 37 (1992)
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Volume 36 (1992)
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Volume 35 (1991)
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Volume 34 (1991)
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Volume 33 (1990)
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Volume 32 (1990)
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Volume 31 (1990)
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Volume 30 (1989)
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Volume 29 (1989)
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Volume 28 (1989)
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Volume 27 (1988)
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Volume 26 (1988)
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Volume 25 (1988)
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Volume 24 (1987)
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Volume 23 (1987)
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Volume 22 (1986)
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Volume 21 (1986)
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Volume 20 (1985)
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Volume 19 (1985)
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Volume 18 (1984)
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Volume 17 (1984)
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Volume 16 (1983)
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Volume 15 (1982)
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Volume 14 (1981)
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Volume 13 (1980)
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Volume 12 (1979)
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Volume 11 (1978)
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Volume 10 (1977)
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Volume 9 (1976)
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Volume 8 (1975)
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Volume 7 (1974)
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Volume 6 (1973)
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Volume 5 (1972)
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Volume 4 (1971)
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Volume 3 (1970)
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Volume 2 (1969)
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Volume 1 (1968)
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