Social impact projections for Qatar youth residents from 2022: The case of the IAAF 2019

While sport is playing an increasingly important role in society in the Middle East, there has been limited research on the perceived social impact of the hosting of major international events in this region. This study evaluates the main factors affecting youth residents' perceptions of hosting major international sport events, by measuring the psychic income in particular, generated within subgroups shaping their support toward hosting these events. Psychic income refers to the emotional and psychological benefit residents perceive they receive from hosting an international sport event. The study is of significance within the context of residents' perceptions studies given that the large majority of residents in Qatar are non-Qataris. Furthermore, the youth were the target population for this study given that they have been identified as the custodians of the next generation and as an essential force in molding national development; and extends the few residents' perception studies in Qatar which comprised the general population. Using the 2019 IAAF Athletics World championships as an example, a framework by Kim and Walker was adopted. Data were collected from 316 university students' from different nationalities residing in Qatar; a month after the event took place. After conducting confirmatory factor analysis, this study was subject to structural equation modeling. Overall, the results show that the perceived impact on Qatari youth nationals was higher compared to Arab youth, and non-Arab youth, respectively. Likewise, the perceived impact was higher for females compared to males. By evaluating the psychic income received by youth from different nationalities residing in Qatar, this study provides decision-makers and organizers with a better understanding of the outcome generated from hosting major international sport events, and how they can leverage these going forward. Of importance is that even if youth residents do not attend the event in person, these events may still generate positive psychic income which is particular relevant to the 2022 FIFA World Cup given the limitations related to purchasing tickets. With Qatar establishing itself as a regional sport hub by attracting a diverse range of international sport events, a cumulative approach to understanding psychic income is recommended.

Implementing a multi-faceted framework for proprietorship of hand hygiene compliance in a network of South African hospitals: leveraging the Ubuntu philosophy

BACKGROUND

Given the lack of hospital-wide ownership and shortage of nurses, the ideal model for large-scale implementation of hand hygiene (HH) behaviour change in low- and middle-income countries is unknown.

AIM

The aim of the multi-modal strategy was to engender hospital accountability for HH compliance.

METHODS

The quasi-experimental study was conducted in 50 South African hospitals (November 2015 to July 2017) and involved five overlapping phases: executive governance and corporate behaviour change; group-wide systematic situational analysis; development of an electronic-assisted direct-observed data collection and analysis application; launch and implementation; and accountable governance. Measurement of intra- and inter-hospital variance to six HH opportunities was calculated and data compliance dashboards were e-mailed weekly to hospital leadership teams to provide feedback of recorded HH compliance and behaviour to frontline teams. Baseline comparison (July 2016) of compliance was compared versus post-implementation (July 2017).

FINDINGS

Baseline HH compliance of ≤60% was documented for 16% (8/50) of hospitals, whereas overall, 48% (24/50) of hospitals demonstrated a significant improvement (P < 0.01). Over the 13-month observation period, 523,422 observations were recorded with a mean rate of 277 ± 223 observations per 1000 patient-days. The group mean composite compliance improved by 7.8% (P < 0.01) from 77.4% ± 12.8 to 85.2% ± 8.8 between July 2016 and July 2017, respectively.

CONCLUSION

Implementation of a multi-faceted HH model in a large, diverse group of South African hospitals translated into changes in the organizational systems and accountability, standardized HH compliance management and feedback that led to HH proprietorship.

FIDSSA 2017 Congress Abstracts Oral Presentations

No abstract available.

Stepwise introduction of the 'Best Care Always' central-line-associated bloodstream infection prevention bundle in a network of South African hospitals

BACKGROUND

Healthcare-associated infection (HCAI) remains a major international problem.

AIM

The 'Best Care Always!' (BCA) campaign was launched in South Africa to reduce preventable HCAI, including central-line-associated bloodstream infection (CLABSI).

METHODS

The intervention took place in 43 Netcare Private Hospitals, increasing later to 49 with 958 intensive care units (ICUs) and 439 high-care (HC) beds and 1207 ICUs and 493 HC beds, respectively. Phase 1, April 2010 to March 2011, ICU infection prevention and control (IPC) nurse-driven change: commitment from management and doctors and training of IPC nurses. Bundle compliance and infections per 1000 central-line-days were incorporated as standard IPC measures and captured monthly. Phase 2, April 2011 to March 2012, breakthrough collaborative method: multiple regional learning sessions for nursing leaders, IPC nurses and unit managers. Phase 3, April 2012 to May 2016: sustained goal-setting, benchmarks, ongoing audits.

FINDINGS

A total of 1,119,558 central-line-days were recorded. Bundle compliance improved significantly from a mean of 73.1% [standard deviation (SD): 11.2; range: 40.6-81.7%] in Phase 1 to a mean of 90.5% (SD: 4.7; range: 76.5-97.2%) in Phase 3 (P = 0.0004). The CLABSI rate declined significantly from a mean of 3.55 (SD: 0.82; range: 2.54-5.78) per 1000 central-line-days in Phase 1 to a mean of 0.13 (SD: 0.09; range: 0-0.33) (P < 0.0001).

CONCLUSION

This intervention, the first of its kind in South Africa, through considerable motivation and education, and through competition between hospitals resulted in significant decreases in CLABSI.

Genetic analysis in the asexual fungus Aspergillus niger

The genetics of A. niger has been developed since 1980. An overview is presented of the advances in developing methods and collecting data. Important tools have been a) the application of essentially different methods to isolate mutants, b) the adaptation to A. niger ofA. nidulans methodology for analysis of the parasexual cycle, c) the choice of marker genes, and in some cases the artificial introduction of such genes, to select homozygous segregants arising from mitotic recombination. With the use of parasexual recombination, a genetic linkage map of A. niger has been established. In total, 110 nuclear and 1 cytoplasmic (mitochondrial) markers are available. The application of A. niger genetics in applied research is illustrated by examples.

Isolation and characterization of sexual sporulation mutants of Aspergillus nidulans

For the genetic dissection of sexual sporulation in Aspergillus nidulans, we started a collection of ascosporeless mutants. After mutagenization of conidiospores with high doses of UV, we isolated 20 mutants with defects in ascospore formation. We crossed these mutants in two successive rounds with the wild-type strain. Eighteen of the 20 isolated mutants produced progeny with the original mutant phenotype in these crosses, and these mutants were further analyzed. All 18 analyzed mutations were recessive to wild type. We assigned them to 15 complementation groups, based on crosses between mutants. The mutants could be classified as follows according to their cytological phenotype: (1) no croziers, (2) arrest at prekaryogamy, (3) arrest in early meiotic prophase, (4) arrest in late meiotic prophase, (5) arrest in meiotic metaphase I, (6) defective postmeiotic mitosis and/or deliniation of ascospores, and (7) slow progression through the postmeiotic stages of ascospore formation. A large proportion of the mutants, namely 11 of 18, arrested in meiotic prophase or metaphase I. We discuss a possible approach for isolating the wild-type alleles of the genes that carry the sexual sporulation mutations.

Genetic analysis of resistance to fenpropimorph in Aspergillus niger

Resistance to the morpholine-fungicide fenpropimorph was studied in Aspergillus niger and A. nidulans. Mass selection of conidia of A. nidulans on agar amended with the fungicide at different concentrations did not yield of resistant mutants, even after UV-treatment of the conidia. In contrast, similar experiments with A. niger generated many fenpropimorph-resistant mutants. The mutants displayed cross-resistance to fenpropidin and generally showed wild-type sensitivity to the unrelated toxicants fenarimol and cycloheximide. Genetic analysis of fenpropimorph resistance in A. niger was carried out by means of the parasexual cycle. In the mutants tested, two genes located on linkage group II were involved in fenpropimorph resistance. Dominance tests showed that resistance to fenpropimorph in A. niger is recessive.

Cloning, sequencing, disruption and phenotypic analysis of uvsC, an Aspergillus nidulans homologue of yeast RAD51

We have cloned the uvsC gene of Aspergillus nidulans by complementation of the A. nidulans uvsC114 mutant. The predicted protein UVSC shows 67.4% sequence identity to the Saccharomyces cerevisiae Rad51 protein and 27.4% sequence identity to the Escherichia coli RecA protein. Transcription of uvsC is induced by methyl-methane sulphonate (MMS), as is transcription of RAD51 of yeast. Similar levels of uvsC transcription were observed after MMS induction in a uvsC+ strain and the uvsC114 mutant. The coding sequence of the uvsC114 allele has a deletion of 6 bp, which results in deletion of two amino acids and replacement of one amino acid in the translation product. In order to gain more insight into the biological function of the uvsC gene, a uvsC null mutant was constructed, in which the entire uvsC coding sequence was replaced by a selectable marker gene. Meiotic and mitotic phenotypes of a uvsC+ strain, the uvsC114 mutant and the uvsC null mutant were compared. The uvsC null mutant was more sensitive to both UV and MMS than the uvsC114 mutant. The uvsC114 mutant arrested in meiotic prophase-I. The uvsC null mutant arrested at an earlier stage, before the onset of meiosis. One possible interpretation of these meiotic phenotypes is that the A. nidulans homologue of Rad51 of yeast has a role both in the specialized processes preceding meiosis and in meiotic prophase I.

Polarity of meiotic gene conversion is 5' to 3' within the niaD gene of Aspergillus nidulans

We have examined polarity of meiotic gene conversion in the niiA-niaD gene cluster of Aspergillus nidulans in two-point crosses. The type and position of the mutations represented by the niaD alleles and the correlation between the relative frequency of gene conversion and the physical position of these mutations were determined. We show that polarity of meiotic gene conversion is 5' to 3' (transcribed strand) within the niaD gene. Additional crosses involving a niiA allele and a niaD allele show little polarity of gene conversion, which suggests that the recombination events leading to restoration of the niaD gene are initiated upstream of the coding region of the niaD gene but within the niiA-niaD gene cluster, possibly within the intergenic promoter region.

Molecular typing of Candida albicans in oral candidiasis: karyotype epidemiology with human immunodeficiency virus-seropositive patients in comparison with that with healthy carriers

Candida albicans organisms isolated from the oral cavities of healthy carriers (26 individuals) and compromised hosts (40 human immunodeficiency virus [HIV]-seropositive patients, all showing symptomatic oral candidiasis) were compared by resolving chromosome-sized DNA molecules into electrophoretic karyotypes. Seven- to 10-band electrophoretic patterns were obtained, with significant and reproducible differences in the distributions of the DNA bands. Seven distinct classes were identified and were designated type a (8 bands), type b (8 bands), type c (7 bands), type d (9 bands), type x (10 bands), type y (10 bands), and type z (9 bands). Four of these (types a to d) were the most representative within all of the isolated strains (95.5%), and the other three (types x to z) were observed only once in three HIV-seropositive individuals (4.5%). Only types b and c were isolated from healthy carriers, with the percentage of their isolation being 61.5 and 38.5%, respectively, while all the described karyotypes were isolated from HIV-seropositive patients, with type b being the most frequent (45%); this was followed by types c (25%), a (15%), and d (7.5%). The prevalence of type b and c karyotypes in HIV-infected individuals, as well as in healthy carriers, suggests that commensal strains in the oral cavities of healthy individuals may become the prevalent agents of subsequent oral candidiasis in compromised hosts. However, replacement of the original, commensal strain, if there is one, cannot be excluded in a compromised host, although strain replacement may be more reasonably hypothesized for types a and d, since only these types were isolated at a relative high percentage from the oral lesions of HIV-infected individuals.

The complete karyotype of Aspergillus niger: the use of introduced electrophoretic mobility variation of chromosomes for gene assignment studies

A method is described for unambiguous assignment of cloned genes to Aspergillus niger chromosomes by CHEF gel electrophoresis and Southern analysis. All of the eight linkage groups (LGs), with the exception of LG VII, have previously been assigned to specific chromosomal bands in the electrophoretic karyotype of A. niger. Using a LG VII-specific probe (nicB gene of A. niger) we have shown that LG VII corresponds to a chromosome of about 4.1 Mb. Furthermore, genetic localization of three unassigned genes (glaA, aglA and pepA) in strains in which these genes had been replaced by a selectable marker gene led to a revised karyotype for the chromosomes corresponding to LGs VIII and VI. The revised electrophoretic karyotype reveals only 5 distinct bands. The presence of three pairs of equally sized chromosomes precluded assignment of genes to one specific chromosome in the wild-type strain. However, unambiguous chromosome assignment of cloned genes using CHEF-Southern analysis was demonstrated using a set of A. niger strains with introduced chromosomal size variation. The availability of these tester strains obviates the need to isolate or construct mutant strains for the purpose of chromosome assignment.

Genetic maps of eight linkage groups of Aspergillus niger based on mitotic mapping

This paper provides a genetic map of Aspergillus niger. At present 84 markers have been assigned to eight linkage groups. The chromosomal location of 60 markers is presented in this paper. The allocation of markers is based on recombination due to mitotic crossing over. Various methods for selection and analysis of homozygous recombinants were applied, using colour, auxotrophic and resistance markers. In addition, transformants carrying the heterologous Aspergillus nidulans gene coding for acetamidase (amdS) were used for mitotic mapping of markers in several linkage groups. In most of the transformants the amdS insert appeared to be centromere-distal to all known genetic markers, thus extending the genetic map. The linear order of the markers in the eight linkage groups has been determined. On the basis of these and earlier experiments tentative genetic maps for the eight linkage groups are presented. Genetic markers were found on both arms of the chromosomes, except for chromosomes II and IV. The genetic distance between markers and the centromere varies from about 10(-4) (LG I, II, V) up to more than 10(-2) (LG III, VI, VIII). The total frequency of mitotic recombination per genome in this fungus has been estimated to be at least 1.2 x 10(-1).

Arginine and proline genes of Aspergillus niger

Aspergillus niger mutants defective in arginine or proline biosynthesis have been isolated and 12 genetic loci were identified. Mutation was induced by low doses UV, and mutants were isolated after filtration enrichment. The mutants were classified according to their phenotype in growth tests and were further characterized in complementation tests. The arginine auxotrophic mutants represent nine complementation groups. Three additional complementation groups were found for mutants that could grow on proline (two of them on arginine too). Linkage group analysis was done in somatic diploids obtained from a mutant and a master strain with genetic markers on six chromosomes. The arg genes belong to six different linkage groups and the pro genes to two. One arg-mutant could be complemented by transformation with the A. nidulans argB+ gene, and this A. niger gene thus appeared to be homologous to the A. nidulans argB. We isolated an A. niger strain with the argB gene tightly linked with the nicA1 marker. This strain is very suitable as acceptor for transformation with an argB-plasmid, because transformants with inserts on the homologous site can be recognized and analyzed genetically using the nicA1 marker gene.

Genetic localization of a series of genes affecting glucose oxidase levels in Aspergillus niger

A number of mutants of Aspergillus niger, affected in glucose oxidase (GOX) expression, are described. The overproducing mutants could be classified into seven complementation groups whereas two glucose oxidase-negative complementation groups were recognized. These nine gox loci were assigned to linkage groups using master strains with marked chromosomes. Three gox loci are in linkage group II, one is in III, two are in V and two are in linkage group VII. One weak glucose oxidase-overproducing mutant could not be assigned to one of the linkage groups. These genetically well characterized mutants will be used in a strain improvement program based on genetic recombination.

An electrophoretic karyotype of Aspergillus niger

An electrophoretic karyotype of Aspergillus niger was obtained using contour-clamped homogeneous electric field (CHEF) gel electrophoresis. Chromosome-sized DNA was separated into four bands. Seven of the eight linkage groups could be correlated with specific chromosomal bands. For this purpose DNA preparations from seven transformant strains of A. niger each carrying the heterologous amdS gene of Aspergillus nidulans on a different chromosome were analysed. Some of the assignments were confirmed with linkage group-specific A. niger probes. The estimated sizes of the A. niger chromosome range from 3.5 to 6.6 Mb, based on gel migration relative to the chromosomes of Schizosaccharomyces pombe strains, Saccharomyces cerevisiae and A. nidulans. The total genome size of A. niger significantly exceeds that of A. nidulans and is estimated to be about 35.5-38.5 Mb. Electrophoretic karyotyping was used to allocate non-mutant rRNA genes and to estimate the number of plasmids integrated in a high copy number transformant.

Genetic analysis of amdS transformants of Aspergillus niger and their use in chromosome mapping

The Aspergillus nidulans gene coding for acetamidase (amdS) was introduced into A. niger by transformation. Twelve Amd+ transformants were analysed genetically. The amdS inserts were located in seven different linkage groups. In each transformant the plasmid was integrated in only a single chromosome. Our (non-transformed) A. niger strains do not grow on acetamide and are more resistant to fluoroacetamide than the transformants. Diploids hemizygous for the amdS insert have the Amd+ phenotype. We exploited the opportunity for two-way selection in A. niger: transformants can be isolated based on the Amd+ phenotype, whereas counter-selection can be performed using resistance to fluoroacetamide. On this basis we studied the phenotypic stability of the heterologous amdS gene in A. niger transformants as well as in diploids. Furthermore, we mapped the plasmid insert of transformant AT1 to the right arm of chromosome VI between pabA1 and cnxA1, providing evidence for a single transformational insert. The results also show that the amdS transformants of A. niger can be used to localize non-selectable recessive markers and that the method meets the prerequisites for efficient mitotic mapping. We suggest the use of amdS transformants for mitotic gene mapping in other fungi.

Characterization of a glycerol kinase mutant of Aspergillus niger

A glycerol-kinase-deficient mutant of Aspergillus niger was isolated. Genetic analysis revealed that the mutation is located on linkage group VI. The phenotype of this mutant differed from that of a glycerol kinase mutant of Aspergillus nidulans in its ability to utilize dihydroxyacetone (DHA). The weak growth on glycerol of the A. niger glycerol kinase mutant showed that glycerol phosphorylation is an important step in glycerol catabolism. The mutant could still grow normally on DHA because of the presence of a DHA kinase. This enzyme, probably in combination with an NAD(+)-dependent glycerol dehydrogenase, present only in the mutant, is responsible for the weak growth of the mutant on glycerol. Enzymic analysis of both the mutant and the parental strain showed that at least three different glycerol dehydrogenases were formed under different physiological conditions: the NAD(+)-dependent enzyme described above, a constitutive NADP(+)-dependent enzyme and a D-glyceraldehyde-specific enzyme induced on D-galacturonate. The glycerol kinase mutant showed impaired growth on D-galacturonate.

Genetic analysis of Aspergillus niger: isolation of chlorate resistance mutants, their use in mitotic mapping and evidence for an eighth linkage group

This paper describes the use of chlorate resistant mutants in genetic analysis of Aspergillus niger. The isolated mutants could be divided into three phenotypic classes on the basis of nitrogen utilization. These were designated nia, nir and cnx as for Aspergillus nidulans. All mutations were recessive to their wild-type allele in heterokaryons as well as in heterozygous diploids. The mutations belong to nine different complementation groups. In addition a complex overlapping complementation group was found. Evidence for the existence of eight linkage groups was obtained. Two linked chlorate resistance mutations and two tryptophan auxotrophic markers, which were unlinked to any of the known markers, form linkage group VIII. We used the chlorate resistance mutations as genetic markers for the improvement of the mitotic linkage map of A. niger. We determined the linear order of three markers in linkage group VI as well as the position of the centromere by means of direct selection of homozygous cnxA1 recombinants. In heterozygous diploid cultures diploid chlorate resistant segregants appeared among conidiospores with a frequency of 3.9 x 10(-5) (cnxG13 in linkage group I) to 2.1 x 10(-2) (cnxD6 in linkage group III). The mean frequency of haploid chlorate resistant segregants was 1.3 x 10(-3). The niaD1 and niaD2 mutations were also complemented by transformation with the A. niger niaD+ gene cloned by Unkles et al. (1989). Mitotic stability of ten Nia+ transformants was determined. Two distinct stability classes were found, showing revertant frequencies of 5.0 x 10(-3) and 2.0 x 10(-5) respectively.

Mitotic mapping in linkage group V of Aspergillus niger based on selection of auxotrophic recombinants by Novozym enrichment

This paper describes a procedure which allows the quantitative selection of auxotrophs of the fungus Aspergillus niger by enzymatic killing of immobilized germinating prototrophic conidiospores. We have applied this procedure to linkage analysis on the basis of mitotic cross-over in this fungus. Starting with a heterozygous diploid strain, we could select auxotrophic homozygous diploid recombinants quantitatively. We estimated the frequency of crossing-over after correction for clonal distribution of recombinants, and localized four auxotrophic markers as well as the centromere on chromosome V of this fungus. The Novozym enrichment procedure proved to be useful in genetic analysis and for the construction of recombinant genotypes in the case of closely linked auxotrophic markers. The determination of gene order and the estimation of distances on the basis of benomyl-induced recombinant haploid segregants may lead to incorrect conclusions. Genetic analysis on the basis of homozygous recombinants, however, can provide reliable estimates of map distances.

Adenine and pyrimidine genes of Aspergillus niger and evidence for a seventh linkage group

Mutants of Aspergillus niger requiring adenine and one mutant requiring cytosine were isolated after low-dose mutagenesis and enrichment. In addition we had mutants of two genes involved in the pyrimidine biosynthesis isolated as 5-fluoro-orotic acid-resistant mutants. The fifteen adenine-less mutants could be placed in seven complementation groups. From each group a representative mutant was analyzed in order to determine the linkage group by analysis of the mutants in a heterozygous diploid carrying markers in six linkage groups. AdeF could not be assigned to any one of these linkage groups and proved to be linked to nicB, oliC and cnxC, none of which could be placed in a linkage group. Thus, conclusive evidence was obtained for a seventh linkage group. As pyrA was used as selection marker for transformation, we constructed a pyrA strain with a linked marker which can be used in the genetic analysis of transformations.

Tryptophan auxotrophic mutants in Aspergillus niger: inactivation of the trpC gene by cotransformation mutagenesis

Aspergillus niger tryptophan auxotrophic mutants have been isolated after UV irradiation of conidiospores. The mutants belong to two different complementation groups, trpA and trpB, which complement each other in heterokaryons. Neither of the mutations could be complemented with the cloned A. niger trpC gene. To obtain A. niger trpC mutants in a direct way, gene inactivation by cotransformation was performed. For this purpose an in-frame gene fusion between the A. niger trpC and Escherichia coli lacZ genes was constructed and shown to be functionally expressed after introduction into A. niger by cotransformation with the pyrA gene as selective marker. Among the beta-galactosidase expressing cotransformants, obtained with either circular or linearized vectors, no trpC mutants were detected, even after enrichment. Such mutants, however, could be obtained by cotransformation of A. niger with specific fragments of the fusion gene. Biochemical analysis of the cotransformants indicated that in nearly all cases the fusion gene had replaced the wild-type trpC gene. Genetic analysis showed that the trpC mutation is not linked to any of the A. niger loci described so far. The trpC mutants can be complemented by the cloned A. niger trpC gene as well as by the A. nidulans trpC gene.

Genetic analysis and the construction of master strains for assignment of genes to six linkage groups in Aspergillus niger

A start has been made on establishing a collection of Aspergillus niger colour and auxotrophic mutants with an isogenic background for use as a source of genetic markers. All strains have short conidiophores (csp A1), which makes them easy to handle on test plates. Genetic markers were combined stepwise by somatic recombination. Somatic diploids were obtained at frequencies of 10(-6) -10(-5) with conidiospores collected from a heterokaryon. The haploidization of heterozygous diploids was induced by benomyl. For unlinked markers, the frequency of recombinants varied from 35%-65%. Low frequencies of recombinants were found between markers on a same chromosome, but this was sometimes disturbed by mitotic crossing-over during an early stage of the diploid. Master strains were constructed having markers for six linkage groups.

Glycerol uptake mutants of the hyphal fungus Aspergillus nidulans

A new class of glycerol non-utilizing mutants, designated glcC, has been isolated. The glcC gene was mapped in linkage group VI and mutants were found to complement the reference strains glcA1 (linkage group V) and glcB33 (linkage group I) in diploids. The new mutants were unable to grow on glycerol. However, in contrast to the glcA and glcB phenotype these mutants did grow well on dihydroxyacetone and D-galacturonate. By in vivo 13C NMR spectroscopy it was shown that the glcC mutant did not take up glycerol but did take up dihydroxyacetone. The latter substrate was converted intracellularly into glycerol which was then catabolized as normal.

Cotransformation of Aspergillus nidulans: a tool for replacing fungal genes

When a non-selected DNA sequence was added during the transformation of amdS320 deletion strains of Aspergillus nidulans with a vector containing the wild-type amdS gene the AmdS+ transformants were cotransformed at a high frequency. Cotransformation of an amdS320, trpC801 double mutant strain showed that both the molar ratio of the two vectors and the concentration of the cotransforming vector affected the cotransformation frequency. The maximum frequency obtained was defined by the gene chosen as selection marker for transformation. Cotransformation was used to induce a gene replacement in A. nidulans. An amdS320 strain was transformed to AmdS+ and cotransformed with a DNA fragment containing a fusion between a non-functional A. nidulans trpC gene and the Escherichia coli lacZ gene. Ten AmdS+, LacZ+ transformants with a Trp- mutant phenotype were selected. All of these strains could be transformed with a functional copy of the A. nidulans trpC gene, but only two strains yielded TrpC+ transformants which, with a low frequency, had a LacZ- phenotype. These latter transformants had also lost the AmdS+ phenotype. Southern blotting analysis of DNA from these transformants confirmed the inactivation of the wild-type trpC gene, but revealed that amdS vector sequences were also involved in the gene replacement events.

Transformation of Aspergillus niger using the homologous orotidine-5'-phosphate-decarboxylase gene

A homologous transformation system for the filamentous fungus Aspergillus niger has been developed, based on the orotidine-5'-phosphate-decarboxylase gene. A. niger Pyr- mutants have been selected from 5-fluoro-orotic acid resistant mutants. These mutants were found to comprise two complementation groups, pyrA and pyrB. The A. niger OMP-decarboxylase gene was isolated from a gene library by heterologous hybridization with the Neurospora crassa pyr4 gene. The cloned gene is capable to transform A. nidulans pyrG mutants at high frequencies. Transformation of A. niger pyrA mutants occurs with moderate frequencies (about 50 transformants/micrograms DNA) whereas the pyrB mutants cannot be complemented with the cloned OMP-decarboxylase gene. Analysis of the DNA of the A. niger PyrA+ transformants showed that transformation resulted in integration of the vector DNA into the genome by homologous recombination. Both gene replacements and integration of one or more copies of the complete vector have been observed.

Genetic analysis of Aspergillus nidulans AmdS+ transformants

To correlate the genetic background of the Aspergillus nidulans amdS deletion strain MH1277 with the integrational behaviour of transforming vectors, classical genetic methods were used to construct AmdS- strains in which whole chromosomes had been exchanged with those of a master strain. Progeny strains were transformed to the AmdS+ phenotype with vector p3SR2. From Southern analysis it was concluded that transformants from all constructions contained tandemly repeated, multiple copy inserts of vector DNA as found for MH1277-derived AmdS+ transformants. AmdS+ transformants of MH1277 were analysed genetically to prove that the transformant phenotype is genome linked and that transformation by integration can take place on various chromosomes. In one case the AmdS+ property showed linkage to both chromosomes II and IV, due to a chromosomal translocation. Sexual analysis of two transformants with AmdS+ insertions on the same chromosome revealed a considerable instability of the AmdS+ phenotype in one of the strains upon selfing. Due to this instability no decisive answer could be given for the degree of linkage between the AmdS+ insertions in these transformants.

Feeder cell requirements for leukemia cell colony formation in cultures supplemented with phytohemagglutinin

The use of phytohemagglutinin-supplemented colony cultures has offered new opportunities recently for studying acute myeloid leukemia (AML) cell growth in vitro. The active stimulator cells for AML colony-forming cells have not been identified, although this could be important for optimal application of the technique and for elucidating differences in growth between normal and leukemic progenitor cells. In this study, feeder layers were prepared from subpopulations of normal peripheral blood leukocytes which were obtained by centrifugation through Ficoll-Isopaque, erythrocyte rosette sedimentation, and adherence separation. Underlayers containing lymphocytes (B, T, or B plus T) or adherent monocytes failed to stimulate AML colony formation. The colony stimulation capacity of total mononuclear cells was decreased significantly following depletion of T-lymphocytes. The highest AML colony numbers were obtained when adherent monocytes and T-lymphocytes in combination were added to phytohemagglutinin-containing cultures. Stimulation of AML colony formation depended on the quantitative interrelationship of monocytes and T-lymphocytes in the cultures. Thus, AML colony-forming cells, unlike normal marrow granulocyte-monocyte colony-forming cells, do not respond to monocyte stimulation alone and require for their proliferation an inducing factor derived from phytohemagglutinin-exposed T-lymphocytes and monocytes.

Acute myeloid leukemia colony growth in vitro: differences of colony-forming cells in PHA-supplemented and standard leukocyte feeder cultures

Bone marrow or blood of patients with acute myeloid leukemia was subjected to cell separation and the cells investigated for in vitro colony growth. Discontinuous albumin density gradient centrifugation and depletion of E-rosette-forming cells resulted in purified fractions of acute myeloid leukemia cells. From these fractions, growth of large leukemic colonies was obtained in the PHA-leukocyte feeder (PHA-LF) colony technique in 12 of 14 patients. The standard double agar layer techniques with a leukocyte feeder for granulocyte-macrophage colony forming cells (GM-CFC) supported colony formation in only four cases. The PHA-LF leukemic colony-forming cells (CFC) were found to be of low buoyant density (always less than or equal to 1.062 g.ml-1) when compared to normal marrow GM-CFC (peak at 1.065 g.ml-1). The density profile of PHA-LF CFC paralleled the distribution of the nucleated cells in 8 cases, but in 4 patients, the cFC peak was found at a distinctly lower density; this suggested that a specific leukemic subpopulation had a colony-forming capacity. In three of the four patients with colony growth in the double layer agar technique, it was evident that these CFC had density properties different from those of PHA-LF CFC. These findings suggest that cells giving rise to large colonies in the PHA-LF and double layer agar assays represent distinct leukemic subpopulations.

Karyotypically distinct subpopulations in acute leukemia with specific growth requirements

Bone marrow and blood cells of a patient with acute monoblastic leukemia with subclones marked with specific karyotypic abnormalities were investigated. In order to more precisely evaluate the proliferative abilities of these populations, leukemic cell enriched fractions were prepared and incubated in two colony assays. Colony forming cells of the disparate clones had growth advantages in different systems which shows that their proliferation depended on the presence of selective stimulatory factors in culture. In one assay, at diagnosis, colonies from the minor clone were demonstrated exclusively. It is suggested that the assays measured distinct cellular stages of myeloid differentiation and the findings indicate that prior to diagnosis the neoplasm had evolved into subsets with progressive dedifferentiation. Differences of growth in vitro correlated with the different roles of these clones in the clinical history of the disease. Approaches based on differential cloning of tumor stem cells as in this example, may be useful for discriminating biological properties of heterogeneous subpopulations within neoplasms, and may facilitate the cytogenetic recognition of minimal clones among composite malignant cell specimens.

Studies on chronic myeloid leukemia cell populations with colony-forming abilities in PHA-leukocyte feeder and Robinson assays

Investigation of leukemic colony-forming cells (CFC) in PHA-supplemented cultures requires removal of T lymphocyte precursors prior to culture. Using a method of discontinuous density gradient centrifugation with concurrent depletion of E-rosette forming cells, T lymphocytes were effectively separated from light density CML bone marrow and blood cell fractions. Consequently, in light density fractions (1.056 and 1.059 g/ml) pure leukemic colony growth was obtained in the PHA-leukocyte feeder (PHA-l.f.) assay. Fraction 1.062 g/ml also yielded pure leukemic colonies in most experiments. Comparison of the density distributions of leukemic PHA-l.f. CFC and Robinson CFC revealed that both CFC populations had congruent density profiles in most patients. In others PHA-l.f. CFC were found to be of somewhat higher density than Robinson CFC. The most striking divergence was apparent in a patient in blast crisis. The findings suggest that different subsets of precursor cells within the CML population proliferate in PHA-l.f. and Robinson colony methods. Both colony techniques are thus potentially useful for discriminating subpopulations of colony-forming cells in chronic myeloid leukemia.

Density profiles and purification of chronic myeloid leukemia cells forming colonies in the PHA-leukocyte feeder assay

Recently, PHA supplemented culture techniques have been introduced for growing colonies of myeloid leukemia cells. To prepare purified leukemic colony forming cell (CFC) suspensions for further studies, a discontinuous albumin density gradient separation method was applied to bone marrow and blood from patients with chronic myelocytic leukemia. It was found that the PHA-responding CFC were recovered, just as the leukocyte feeder layer stimulated CFC (Robinson CFC), from the light density fractions (1.056, 1.059 and 1.062 g/ml). Density profiles of the precursor cells forming colonies of Ph1 positive cells in the PHA-leukocyte feeder and Robinson assays appeared similar. T-lymphocyte progenitor cells, which also proliferate into colonies in the PHA-leukocyte feeder assay, were in majority harvested from the more dense fractions of the gradient. E-rosette tests and chromosome analysis were used to distinguish between leukemic and lymphocytic colonies. The density distributions of the PHA responsive leukemic CFC (Ph1 chromosome positive) and T-lymphocyte CFC (Ph1 negative) partially overlapped and a complete separation of leukemic and lymphocytic CFC was not achieved.

A characterization of T lymphocyte colony-forming cells (TL-CFC) in human bone marrow

T lymphocyte colony-forming cells (TL-CFC) present in the peripheral blood of healthy individuals have been studied by several investigators but an analysis of the properties of marrow TL-CFC is still lacking. The experiments reported here represent a first attempt to define some characteristic of marrow TL-CFC, in direct comparison with blood TL-CFC, using density gradients, rosette tests and stimulation of DNA synthesis. It was found that marrow TL-CFC and blood TL-CFC have different density properties. Both populations were characterized by distinct profiles with peaks at 1 . 07 g/ml and 1 . 065 g/ml respectively. In marrow as well as blood striking similarities between the density distributions of TL-CFC and E rosette-forming cells (E-RFC) were found. From E rosette Ficoll separation experiments it became clear that TL-CFC in bone marrow, as well as in blood, represent a subgroup of the E-RFC population. A marked dissociation was observed between the quantitative values of thymidine incorporation and colony responses following stimulation with PHA. The most prominent findings was that light-dense bone marrow-subfractions, which were virtually negative in PHA mitogen (DNA-synthesis) tests, still gave rise to relatively large numbers of T lymphocyte colonies after stimulation with PHA. On the contrary, in blood, T lymphocyte colonies could be grown exclusively from density fractions which were positive in PHA mitogen stimulation tests. Apparently, characteristics differences exist between marrow and blood TL-CFC.