- Volume 2, Issue 3, 1969
Volume 2, Issue 3, 1969
- Articles
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Ultrastructural Characteristics of Mycobacterial Growth
More LessSUMMARYChanges in the morphology of Mycobacterium tuberculosis and Mycobacterium smegmatis were examined with the electron microscope during growth in liquid media in shaken cultures. Cells at the early stage of exponential growth are characterised by a surface layer of fibrillar material consisting of cell-wall lipopolysaccharide, by the peripheral distribution of both single and clustered ribosomes, and by a fine network of nuclear filaments.
Late exponentially growing cells show cell walls overlaid with an amorphous lipopolysaccharide material which differs chemically from the fibrillar layer. The ribosomes at this stage are scattered throughout the cytoplasm.
Fibrillae, possibly ribonucleic acid in nature, interconnect single ribosomal particles during all stages of exponential growth.
In stationary-phase cells the nuclear filaments are concentrated in the central portion of the cytoplasm. Fine networks and bundles of fibrils, varying in size, become detached from the cell walls. After maximal growth, ribosomal structures disappear and the plasma membrane becomes detached from the inner surface of the cell wall, as an initial sign of plasmolysis.
Morphological differences between the cell-wall structure of Myco. tuberculosis and that of Myco. smegmatis are noted near the stage of maximal growth. In the former species, the cell wall consists of a dense thick layer, possibly containing large amounts of free lipid. Cell walls in the latter species are composed of a thin dense layer which is separated from the plasma membrane by a moderately dense layer.
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Dwarf-Colony Variants of Staphylococcus Aureus Resistant to Aminoglucoside Antibiotics and to a Fatty Acid
More LessSUMMARYThe exposure of cultures of Staphylococcus aureus to linoleic acid selected variants that were resistant to aminoglucoside antibiotics. Variants with identical characters were isolated by exposure to an aminoglucoside antibiotic, paromomycin.
The variants grew on nutrient agar as small, intensely pigmented colonies, but tended to revert to the original colonial form. The revertants were sensitive to aminoglucoside antibiotics.
Some of the variants were stimulated to normal growth only by fructose, and others by fructose, acetate, pyruvate, oxaloacetate and aspartate. The latter variants exhibited satellitism around colonies of certain Gram-positive cocci.
Dwarf-colony variants persisted better than the parent staphylococci on normal skin. Their occurrence in vivo might be relevant to the survival of staphylococci on carriage sites, particularly in patients being treated with aminoglucoside antibiotics.
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Variation in the M-Antigen of Group-A Streptococci
More LessSUMMARYDuring the long-term study of sore throat caused by group-A streptococci in a village, M-positive members of type 12 disappeared and were replaced by streptococci that appeared to be M-negative variants of the original strain.
The new strain resembled the original M-type-12 streptococcus in possessing the T-antigen of type 12, but further investigation showed that it was not M-negative; it had a hitherto undescribed M-antigen. It also differed from the M-type-12 strain in having the ability to produce opacity in horse serum and in not being lysogenic for a phage active on the indicator strain K56.
A minority-population of the new strain was found in 7 of 11 cultures of the original M-type-12 streptococcus. This is taken as evidence that the new strain has arisen as a variant of the M-type-12 streptococcus.
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Cytotoxicity of Filtrates of Haemolytic Escherichia Coli
More LessSUMMARYThe diffusible haemolysin of Escherichia coli is highly cytotoxic to chick embryo cell cultures, but has no effect on monkey kidney and mouse embryo cell cultures. The cytotoxic effects are specific, as they can be neutralised by specific antisera. Culture fluids from non-haemolytic strains of E. coli are non-cytotoxic. The haemolytic activity is thermolabile, but cytotoxicity is thermostable. The antibodies prepared against heated or unheated haemolysins prevent cytotoxicity, but haemolytic activity is neutralised only by antisera prepared against unheated haemolysin. Fraction A of haemolysin is non-haemolytic and non-cytotoxic, whereas fraction B is non-haemolytic but is cytotoxic.
The haemolytic and cytotoxic factors of Escherichia coli appear, therefore, not to be identical.
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Geographical Variation in Serological types of Urinary Escherichia Coli
More LessSUMMARYComparison of the distributions of the O-groups of strains of Escherichia coli isolated from infected urines in eleven previous studies has shown that there are statistically significant differences in the frequency distributions of certain O-groups between the findings in America and those in Europe. It is considered that in spite of differences in the methods of patient selection, the bacteriological methods and the levels of serological refinement used in the different investigations, these apparent intercontinental differences in O-group distribution are probably real.
In a study of the O-groups of the E. coli strains isolated from the urines of domiciliary patients with symptomatic infection of the urinary tract in three centres in north-west London, we have confirmed the preponderance of O-groups O2, O4, O6, O18 and O75 in all three localities. Nevertheless, the frequency of occurrence of certain O-groups differed significantly in the three localities, indicating that geographical differences occur not only between different continents but also between regions separated by only a few miles. This geographical variation in the O-group distribution of urinary strains of E. coli is presumably a reflection of a similar geographical variation in the O-groups of E. coli strains in the faecal flora.
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A Study of Escherichia Coli Isolated from Chronic Urinary Infection
More LessSUMMARYTwo hundred and eighty strains of Escherichia coli isolated from 85 female patients with chronic urinary tract infections in one hospital were tested for their serological and biochemical reactions.
Biochemical and serological variations and degradation changes were observed in strains isolated repeatedly during the course of the disease in separate patients; their significance is discussed.
From 34.2 percent. of 38 patients the same sero- and bio-type of E. coli was repeatedly isolated, from 18.4 percent. degraded strains probably the same as the original infecting type were isolated, and in 47.4 percent. the sero-and bio-type changed during the course of the disease.
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The Thiacetazone Sensitivity of Mycobacterium Tuberculosis
More LessSUMMARYA statistical analysis of the results of a comparison of 4 measures of the thiacetazone sensitivity of 90 wild strains of the tubercle bacillus leads to the conclusion that the best measure is the drug concentration that inhibits growth of 20 colonies from a standard inoculum (MIC 20) after 28 days’ incubation.
There was no evidence of natural thiacetazone resistance among 30 British and 30 Sudanese strains; a few of the East African strains were apparently resistant to thiacetazone.
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Degradation of the Phospholipids of the Serum Lipoproteins by Leptospirae
More LessSUMMARYThe main types of phospholipids in serum lipoproteins, namely lysolecithin, lecithin, cephalin and sphingomyelin, are susceptible to degradation by specific enzymes of leptospirae. On the basis of their ability to attack lecithin and sphingomyelin the leptospirae can be divided into three groups: (A) strains degrading lecithin but not sphingomyelin, (B) strains degrading lecithin and sphingomyelin, and (C) strains degrading neither lecithin nor sphingomyelin. The saprophytic leptospirae belong to group A and the parasitic leptospirae to groups B and C.
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Susceptibility of Erythrocebus Patas Monkeys to Rubella Virus
More LessSUMMARYErythrocebus patas monkeys share with certain other species of monkey and man a susceptibility to wild and attenuated strains of rubella virus. Overt clinical signs of infection do not occur, however, in this species.
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A Capsulate Staphylococcus Aureus
More LessSUMMARYA capsulate staphylococcus designated strain M is described. Apart from the presence of a capsule, this strain has most of the biological properties of typical strains of Staphylococcus aureus.
Strain M differs from modal strains of S. aureus in its colonial morphology, resistance to bacteriophage, greater virulence for mice and failure to clump in plasma. These differences are attributed to the presence of a thick capsule.
Non-capsulate variants, produced by prolonged culture in nutrient broth, were indistinguishable from typical strains of S. aureus, but reverted to the parent capsulate form when passaged in mice.
Strain M is compared with three heavily capsulate strains previously described, and with staphylococcus strain “ Smith ”, and the “ Smith-like ” strains of S. aureus.
The capsulate strain M has been deposited in the National Collection of Type Cultures (no. 10649).
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Penicillinase Production and Intrinsic Resistance to Penicillins in Methicillin-Resistant Cultures of Staphylococcus Aureus
More LessSUMMARYThe hydrolysis of methicillin by the penicillinase produced by 108 epidemiologically distinct methicillin-resistant strains of Staphylococcus aureus has been investigated. In no case is there evidence for a variant enzyme with increased efficiency of hydrolysis of methicillin. Cultures of penicillinase-negative variants of methicillin-resistant strains are heterogeneous in their resistance to methicillin. In all but one case, organisms resistant to a high concentration of methicillin revert to a heterogeneous resistance pattern on subculture in the absence of methicillin. Methicillin-resistant strains do not grow slowly in the absence of methicillin, but are more resistant to methicillin when grown at low temperature or when grown in the presence of sodium chloride. The mucopeptide of methicillin-resistant cells does not differ from that of methicillin-sensitive cells either in amount or composition. Possible mechanisms of methicillin resistance are discussed.
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Failure of Passive Transfer of Homograft Sensitivity in Mice by Means of Extracts of Sensitised Lymphoid Cells
More LessSUMMARYThe claim that passive transfer of homograft sensitivity could be achieved by the “injection of the supernatant obtained from tissue-sensitized lymphoid cells ⃛ by sonic vibration” (Najarian and Feldman, 1963) has been investigated. We repeated the original experiments, but could not confirm the observation; furthermore, we could not transfer homograft sensitivity passively with extracts of sonicated sensitised lymphoid tissue from different sites (spleen or pooled lymph-nodes or draining lymph-nodes), or with extracts of lymphoid tissue of mice sensitised with grafts from several strains. In our hands, extracts of sonicated sensitised lymphoid tissue invariably failed to produce accelerated graft rejection.
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In-Vitro Sensitivity of Strains of Mycoplasmas from Human Sources to Antibiotics and to Sodium Aurothiomalate and Tylosin Tartrate
More LessSUMMARYThe results of in-vitro sensitivity tests of strains of Mycoplasma pneumoniae, M. hominis, M. fermentons, M. salivarium and M. orale type 1 to ampicillin, cephaloridine, chloramphenicol, erythromycin, kanamycin, lincomycin, methi- cillin, streptomycin, tetracycline, sodium aurothiomalate and tylosin tartrate
are reported. They confirm that M. pneumoniae and M. hominis are sensitive to tetracycline and chloramphenicol, but show that a number of strains of M. salivarium and M. orale type 1 are resistant to these drugs. Some of these strains were also resistant to kanamycin, but most were sensitive to tylosin tartrate.
All the mycoplasmas were resistant to ampicillin and methicillin, and to cephaloridine at concentrations of 25-100 μg per ml. Strains of M. pneumoniae were sensitive to erythromycin, but most of the other strains were resistant. The mycoplasmas were very variable in their sensitivity to sodium aurothiomalate.
It is suggested that tylosin tartrate is the agent most likely to prove useful for eradicating mycoplasmas from contaminated tissue cultures.
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Mixed Infective Endocarditis in a Heroin Addict
More LessSUMMARYA case of bacterial endocarditis with septic pulmonary embolism in a heroin addict, from whom four different bacterial species were isolated, is reported. Apparent bacteriological cure was achieved after 5 mth of intensive therapy. It seems that successful treatment was not achieved until an underlying infection with Bacteroides fragilis was detected and antibiotic therapy was adjusted accordingly.
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Effect of pH on the Haemolysis of Rabbit Erythrocytes by Staphylococcus Alphatoxin
More LessSUMMARYThe effect of toxin concentration on the kinetics of haemolysis of rabbit erythrocytes has been studied at pH values differing by about 0.5 pH units over the range 5.5 to 8.5 for both crude and partially purified toxin at concentrations of 2.5, 5.0, 10, 20, 30, 40, 60 MHD per ml and at 80 and 120 MHD per ml for the partially purified toxin.
Increased concentration of toxin caused a decrease in the prelytic lag time (τ) of the sigmoid haemolysis curves, a decrease in the time to reach 50 per cent, haemolysis (t1/2), and an increase in the maximum rate of haemolysis (Rm)
Plateaux in Rm-toxin concentration, τ-toxin concentration and t1/2-toxin concentration curves were found at all pH values : these were displaced to higher concentrations in plots drawn for the partially purified toxin.
The effect of pH on haemolysis is very marked, and pH profiles for the maximum rate of haemolysis were constructed : for the crude toxin, the shape of the profile changed as the toxin concentration was increased, while for the partially purified toxin the shape was independent of toxin concentration.
The pattern of the profiles indicates that the crude toxin contains a small concentration of impurity that is strongly lytic at pH 5.5 and less markedly so at 8.5; the impurity has no significant effect at intermediate pH values.
The reaction is first order with respect to toxin over a very small range of concentrations only, and the maximum rate of haemolysis is independent of toxin concentration at concentrations greater than 120 MHD per ml.
The reaction is first order with respect to erythrocytes at all pH values, and over all measurable concentrations.
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Pigment Production in Bacteroides
More LessSUMMARYChromogenesis by three members of the genus Bacteroides was studied. The species investigated were: Bacteroides melaninogenicus, B. fragilis and B. necrophorus. All were capable of pigment production, but each species required a different set of factors for chromogenesis. All needed cysteine and ferrous sulphate. These factors sufficed for pigment production by B. melaninogenicus. Additional vitamin K1 was essential for pigment production by both B. necrophorus and B. fragilis, but the latter also required haemin.
Pigment production by B. melaninogenicus was studied in two media: 5 per cent, horse blood agar, and an agar-free partially defined medium. The pigment was harvested from these media, purified and subjected to chemical analysis. This pigment, previously thought to be haemin, proved to be colloidal ferrous sulphide.
The pigment produced by two other Bacteroides species, B. fragilis and B. necrophorus, examined in the same way also proved to be colloidal ferrous sulphide.
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Laboratory Studies on the Varicella-Zoster Virus
More LessSUMMARYIn a study of varicella-zoster virus, one strain isolated from a patient with varicella and one strain from a patient with zoster were grown in a range of different cell cultures. The viruses grew in human amnion, human thyroid, human embryo lung, HeLa, rhesus monkey kidney, vervet monkey kidney and V3A cultures. They behaved identically, giving similar cytopathic changes in the same range of cell cultures. Neither virus could be readily obtained in a cell-free state. The isolation of varicella-zoster viruses in cell cultures was accomplished from vesicle fluids of 15 patients with chickenpox and one patient with zoster, and from lung tissue of a fatal case of chickenpox and a fatal case of zoster. Virus was not isolated from the urine of 23 patients with chickenpox and one patient with zoster, nor from the ganglia of the fifth cranial nerve of 66 elderly persons who had died from causes other than chickenpox and zoster. Both viruses in cell cultures were stored satisfactorily for several years at either —65° or — 184°C and human thyroid cultures were the most suitable cultures for their subsequent recovery.
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Malabsorption in Johne’s Disease in Cattle: An in-vitro Study of L-Histidine uptake by Isolated Intestinal Tissue Preparations
More LessSUMMARYRings of whole ileum or mucosal scrapings from clinical cases of Johne’s disease, or from subclinically infected animals, accumulate L-histidine at considerably less than the normal rate when incubated in Krebs-Ringer bicarbonate
solution containing this amino acid at a concentration of 20 mM. “ Active ” uptake of histidine against a concentration gradient can be abolished by the addition of 0.2 mM-2:4-dinitrophenol to the incubation medium. The proportion actively accumulated was about 61 percent, in normal mucosal scrapings, but only some 25 percent, in specimens obtained from clinically affected cattle.
In the same tissue preparations, the mean total rate of histidine accumulation was almost halved, but its passive uptake was virtually unaffected, indicating that, in infected cattle, histidine probably diffused into the mucosal cells normally. By direct microscopic measurement, it was found that the thickness of the mucosal tissue layer in the ileum was not significantly greater in clinically affected cattle than in healthy controls. The weight of ileum per unit length, however, was, on the average, increased almost four times on account of massive submucosal infiltration.
It is suggested that the marked reduction in the “ active ” uptake of histidine by the mucosa from infected animals is indicative of a malabsorption state. The part this factor plays in the pathogenesis of the terminal clinical phase of Johne’s disease is discussed.
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Bacteriological Observations in A Mechanically Ventilated Experimental Ward and in two Open-Plan Wards
More LessSUMMARYObservations were made on patients in a new type of subdivided hospital ward with controlled ventilation and in two older open-plan wards with natural ventilation.
The rate of acquisition in the nose of new strains of Staph, aureus was somewhat lower in the new ward than in the old wards, but the advantage was restricted to patients who stayed 2 wk or less, and there was no corresponding reduction in the rate of acquisition of tetracycline-resistant staphylococci or in the proportion of patients who became carriers of resistant strains.
No evidence was obtained that the risk of post-operative wound sepsis, or of acquired sepsis due to Staph, aureus, was less in the new ward than in the old wards.
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Isolation of Mycoplasms and other Organisms from the Placenta after Caesarean Section
More LessSUMMARYSwabs taken from the amniotic surface of the placenta in a series of 120 Caesarean sections were cultured for mycoplasms and bacteria; organisms of possible significance were isolated from 16 patients. In most of the patients, the membranes had been ruptured for more than 12 hr before Caesarean section, and in 10 of them there was pyrexia after the operation. Some of the babies showed evidence of neonatal infection.
The most frequently isolated micro-organisms in the series were T-strain mycoplasms. Two cases of infection by Mycoplasma hominis were encountered, and the clinical and serological findings in them are described. The possible importance of mycoplasms as a cause of infections in the puerperium is discussed.
We are indebted to Dr R. W. Burslem and Mr J. B. Jones for permission to study patients under their care, to the staff of the midwifery department at Withington Hospital for their help in collecting specimens, and to Mr P. Davis and Mr A. E. Eldridge for invaluable technical assistance. This work was made possible by a research grant from the Manchester Regional Hospital Board.
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Volumes and issues
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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)