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Biomedical subjects

P Vos

Publications and source records attributed to P Vos.

At least 37 records · Page 2Linked to original sources
PubMed1999

Leukocyte depletion during cardiac operation: a new approach through the venous bypass circuit.

BACKGROUND: Leukocyte depletion recently has been introduced for cardiac surgical patients to attenuate leukocyte-mediated inflammation and organ reperfusion injury. We evaluated the feasibility of a new leukocyte depletion method in which systemic leukocyte depletion is achieved through the venous side of the cardiopulmonary bypass circuit under low blood flow. METHODS: Forty cardiac surgical patients undergoing cardiopulmonary bypass were allocated randomly to a leukocyte depletion group (n = 20) and a control group (n = 20). In the depletion group, leukocyte filtration was achieved with two filter sets located between the venous drainage and the venous reservoir. Leukocyte filtration was commenced after the start of rewarming but before the release of the aortic cross-clamp, and it was driven by a spare roller pump of the heart-lung machine. RESULTS: All the episodes of filtration went smoothly within a period of 10 minutes and with a blood flow rate of 400 mL/min. The mean leukocyte removal rate calculated at the end of filtration was 69%. Circulating leukocytes were reduced by 38% in the depletion group compared with the control group at the moment of cross-clamp release (4.3x10(9)/L versus 6.8x10(9)/L, p<0.05). The postoperative inflammatory response also was reduced as indicated by less production of interleukin-8 (p<0.05). Clinically, there was no significant difference between the two groups in postoperative PaO2 or pulmonary hemodynamics. CONCLUSIONS: It is technically feasible to deplete circulating leukocytes through the venous side of the cardiopulmonary bypass circuit with a low blood flow rate. Future studies should focus on the duration and timing of leukocyte depletion to optimize the methodology of leukocyte depletion for cardiac surgical patients.

Aged↗
PubMed1999

Hepatosplenic candidiasis in patients with acute leukaemia.

A retrospective study of 23 patients with acute leukaemia and hepatosplenic candidiasis (HSC) was conducted to evaluate clinical treatment characteristics in terms of amount and duration of antifungal agents and to assess treatment outcome. Patients were admitted to two major tertiary care centres between 1990 and 1998. The diagnosis of HSC was based on clinical, blood cultures, histologic and imaging studies. Patients were treated with amphotericin B without interruption of the planned chemotherapy regimens. Serial magnetic resonance imaging (MRI) studies were the main tool for following patients' response and activity of the fungal lesions in conjunction with clinical and laboratory parameters. Treatment with amphotericin B was continued until resolution of all clinical symptoms and signs attributable to HSC, obtaining negative blood cultures and the appearance of at least healed lesions on MRI. Amphotericin B was discontinued in four patients because of severe nephrotoxicity (two patients), or continuous fever and persistent fungal lesions on MRI (two patients). Amphotericin B lipid complex (ABELCET) was successfully used as salvage therapy for these refractory patients. Four patients died with evidence of HSC despite treatment and supportive measures. The response rate for treatment of HSC was 82%. The mean total dose of amphotericin B including empirical treatment was 4 g and the median duration of treatment for responding patients was 112 d. The median number of days of anti- fungal treatment before the disappearance of fever was 19 d. Our results confirmed the need for protracted courses of antifungal agents for the successful eradication of HSC. Chemotherapy for the underlying disorder should not be interrupted or delayed in order to treat HSC.

Acute Disease↗
PubMed1998

Genetic and physical localization of the root-knot nematode resistance locus mi in tomato.

As part of a map-based cloning strategy designed to isolate the root-knot nematode resistance gene Mi, tomato F2 populations were analyzed in order to identify recombination points close to this economically important gene. A total of 21,089 F2 progeny plants were screened using morphological markers. An additional 1887 F2 were screened using PCR-based flanking markers. Fine-structure mapping of recombinants with newly developed AFLP markers, and RFLP markers derived from physically mapped cosmid subclones, localized Mi to a genomic region of about 550 kb. The low frequency of recombinants indicated that recombination was generally suppressed in these crosses and that crossovers were restricted to particular regions. To circumvent this problem, a population of Lycopersicon peruvianum, the species from which Mi was originally introgressed, that was segregating for resistance was developed. Screening of this population with PCR, RFLP and AFLP markers identified several plants with crossovers near Mi. Recombination frequency was approximately eight-fold higher in the Mi region of the L. peruvianum cross. However, even within the wild species cross, recombination sites were not uniformly distributed in the region. By combining data from the L. esculentum and L. peruvianum recombinant analyses, it was possible to localize Mi to a region of the genome spanning less than 65 kb.

Animals↗
PubMed1998

The tomato Mi-1 gene confers resistance to both root-knot nematodes and potato aphids.

Mi-1, a Lycopersicon peruvianum gene conferring resistance to the agricultural pests, root-knot nematodes, and introgressed into tomato, has been cloned using a selective restriction fragment amplification based strategy. Complementation analysis of a susceptible tomato line with a 100 kb cosmid array yielded a single cosmid clone capable of conferring resistance both to the root-knot nematode Meloidogyne incognita and to an unrelated pathogen, the potato aphid Macrosiphum euphorbiae. This resistance was stable. The Mi-1 gene encodes a protein sharing structural features with the nucleotide-binding site leucine-rich repeat-containing type of plant resistance genes.

Amino Acid Sequence↗
PubMed1998

Dissection of the fusarium I2 gene cluster in tomato reveals six homologs and one active gene copy.

The I2 locus in tomato confers resistance to race 2 of the soil-borne fungus Fusarium oxysporum f sp lycopersici. The selective restriction fragment amplification (AFLP) positional cloning strategy was used to identify I2 in the tomato genome. A yeast artificial chromosome (YAC) clone covering approximately 750 kb encompassing the I2 locus was isolated, and the AFLP technique was used to derive tightly linked AFLP markers from this YAC clone. Genetic complementation analysis in transgenic R1 plants using a set of overlapping cosmids covering the I2 locus revealed three cosmids giving full resistance to F. o. lycopersici race 2. These cosmids shared a 7-kb DNA fragment containing an open reading frame encoding a protein with similarity to the nucleotide binding site leucine-rich repeat family of resistance genes. At the I2 locus, we identified six additional homologs that included the recently identified I2C-1 and I2C-2 genes. However, cosmids containing the I2C-1 or I2C-2 gene could not confer resistance to plants, indicating that these members are not the functional resistance genes. Alignments between the various members of the I2 gene family revealed two significant variable regions within the leucine-rich repeat region. They consisted of deletions or duplications of one or more leucine-rich repeats. We propose that one or both of these leucine-rich repeats are involved in Fusarium wilt resistance with I2 specificity.

Amino Acid Sequence↗
PubMed1998

Perceptual grouping of strip dot patterns.

Grouping of one-dimensional (strip) dot patterns was investigated, using an adjustment procedure to evaluate the distance (adjusted gap) at which two patterns appear to merge in a single strip. The size of the patterns had only a scaling effect on the adjusted gap. The adjusted gap and the variance of the estimates were influenced by the number of dots and the regularity (similarity, symmetry) of the patterns in the pair. Models of proximal grouping failed to account for the results obtained. A two-stage process implying determination of dot location and evaluation of inter-dot separation by means of "eclectic units" (Morgan, Hole & Glennerster, 1990) was considered to explain the findings.

Adult↗
PubMed1997

AFLP-based fine mapping of the Mlo gene to a 30-kb DNA segment of the barley genome.

Resistance of barley (Hordeum vulgare) to the powdery mildew fungus Erysiphe graminis f.sp. hordei is conferred by several dominant genes, but also by recessive alleles of the Mlo locus mapping on the long arm of chromosome 4. In addition, this single-factor-mediated resistance is active against all known physiological races of the parasite. Thus the mechanism underlying mlo-mediated resistance should differ substantially from that mediated by the dominant genes. A positional cloning strategy to isolate the Mlo gene from the barley genome, the size of which is almost double the size of the human genome, has been designed. The AFLP technique was employed to identify markers tightly linked to the Mlo locus and to produce a local high-resolution genetic map. The use of this high-volume marker technology allowed the rapid screening of approximately 250,000 loci for linkage to Mlo. A large number of Mlo-linked AFLP markers were identified, one of which cosegregated with Mlo on the basis of more than 4000 meiotic events. A four-genome-equivalent barley YAC library (average insert size 480 kb) was constructed and screened with this cosegregating marker. Four YACs containing this marker were isolated and subsequent characterization by AFLP-based physical mapping allowed the physical delimitation of the Mlo locus to a DNA segment of 30 kb.

Chromosome Mapping↗
PubMed1997

The barley Mlo gene: a novel control element of plant pathogen resistance.

Mutation-induced recessive alleles (mlo) of the barley Mlo locus confer a leaf lesion phenotype and broad spectrum resistance to the fungal pathogen, Erysiphe graminis f. sp. hordei. The gene has been isolated using a positional cloning approach. Analysis of 11 mutagen-induced mlo alleles revealed mutations leading in each case to alterations of the deduced Mlo wild-type amino acid sequence. Susceptible intragenic recombinants, isolated from mlo heteroallelic crosses, show restored Mlo wild-type sequences. The deduced 60 kDa protein is predicted to be membrane-anchored by at least six membrane-spanning helices. The findings are compatible with a dual negative control function of the Mlo protein in leaf cell death and in the onset of pathogen defense; absence of Mlo primes the responsiveness for the onset of multiple defense functions.

Amino Acid Sequence↗
PubMed1997

The Arabidopsis NIM1 protein shows homology to the mammalian transcription factor inhibitor I kappa B.

The NIM1 (for noninducible immunity) gene product is involved in the signal transduction cascade leading to both systemic acquired resistance (SAR) and gene-for-gene disease resistance in Arabidopsis. We have isolated and characterized five new alleles of nim1 that show a range of phenotypes from weakly impaired in chemically induced pathogenesis-related protein-1 gene expression and fungal resistance to very strongly blocked. We have isolated the NIM1 gene by using a map-based cloning procedure. Interestingly, the NIM1 protein shows sequence homology to the mammalian signal transduction factor I kappa B subclass alpha. NF-kappa B/I kappa B signaling pathways are implicated in disease resistance responses in a range of organisms from Drosophila to mammals, suggesting that the SAR signaling pathway in plants is representative of an ancient and ubiquitous defense mechanism in higher organisms.

Amino Acid Sequence↗
PubMed1996

Strangulated urethral prolapse.

Urethral prolapse is rarely diagnosed. We describe the clinical findings in an 86-year-old woman. The treatment chosen was the excision of the urethral prolapse over an indwelling Foley catheter and suturing the mucosa edges to the vaginal skin. Etiology, differential diagnosis, and treatment modalities will be discussed.

Aged↗
PubMed1996

Cystic fibrosis hetero- and homozygosity is associated with inhibition of breast cancer growth.

Cystic fibrosis (CF) is the most common lethal recessive genetic disease of the Caucasian population. Although reports of cancer frequency in CF have emphasized an elevated observed-to-expected ratio of 6.5 for digestive tract cancers, these studies also show a significantly decreased observed-to-expected ratio for other malignancies including breast cancer. The cystic fibrosis transmembrane conductance regulator (CFTR) functions as an ATP channel. We found that heterozygous and homozygous CFTR knockout mice had elevated blood ATP concentrations. Elevated extracellular ATP is known to inhibit tumor growth in vivo and in vitro. Using double mutant mice created by F2 generation crosses of CFTR knockout and nude mice, we observed reduced breast tumor implantability in CFTR homozygous nude animals. Decreased tumor growth rate was observed in both CFTR heterozygous and homozygous nude animals. Extracellular ATP reduced human breast tumor cell growth rate in vitro, and a breast tumor transfected with human CFTR that had high extracellular ATP concentrations in vitro correspondingly had a slower growth rate in vivo. The results suggest that both CFTR heterozygosity and homozygosity suppress breast cancer growth and that elevated extracellular ATP can account for this phenomenon.

Adenosine Triphosphate↗
PubMed1996

Evaluation of the DNA fingerprinting method AFLP as an new tool in bacterial taxonomy.

We investigated the usefulness of a novel DNA fingerprinting technique, AFLP, which is based on the selective amplification of genomic restriction fragments by PCR, to differentiate bacterial strains at the subgeneric level. In totals, 147 bacterial strains were subjected to AFLP fingerprinting: 36 Xanthomonas strains, including 23 pathovars of Xanthomonas axonopodis and six pathovars of Xanthomonas vasicola, one strain of Stenotrophomonas, 90 genotypically characterized strains comprising all 14 hybridization groups currently described in the genus Aeromonas, and four strains of each of the genera Clostridium, Bacillus, Acinetobacter, Pseudomonas and Vibrio. Depending on the genus, total genomic DNA of each bacterium was digested with a particular combination of two restriction endonucleases and the resulting fragments were ligated to restriction halfsite-specific adaptors. These adaptors served as primer-binding sites allowing the fragments to be amplified by selective PCR primers that extend beyond the adaptor and restriction site sequences. Following electrophoretic separation on 5% (w/v) polyacrylamide/8.3 M urea, amplified products could be visualized by autoradiography because one of the selective primers was radioactively labelled. The resulting banding patterns, containing approximately 30-50 visualized PCR products in the size range 80-550 bp, were captured by a high-resolution densitoscanner and further processed for computer-assisted analysis to determine band-based similarity coefficients. This study reveals extensive evidence for the applicability of AFLP in bacterial taxonomy through comparison of the newly obtained data with results previously obtained by well-established genotypic and chemotaxonomic methods such as DNA-DNA hybridization and cellular fatty acid analysis. In addition, this study clearly demonstrates the superior discriminative power of AFLP towards the differentiation of highly related bacterial strains that belong to the same species or even biovar (i.e. to characterize strains at the infrasubspecific level), highlighting the potential of this novel fingerprinting method in epidemiological and evolutionary studies.

Acinetobacter↗
PubMed1995

AFLP: a new technique for DNA fingerprinting.

A novel DNA fingerprinting technique called AFLP is described. The AFLP technique is based on the selective PCR amplification of restriction fragments from a total digest of genomic DNA. The technique involves three steps: (i) restriction of the DNA and ligation of oligonucleotide adapters, (ii) selective amplification of sets of restriction fragments, and (iii) gel analysis of the amplified fragments. PCR amplification of restriction fragments is achieved by using the adapter and restriction site sequence as target sites for primer annealing. The selective amplification is achieved by the use of primers that extend into the restriction fragments, amplifying only those fragments in which the primer extensions match the nucleotides flanking the restriction sites. Using this method, sets of restriction fragments may be visualized by PCR without knowledge of nucleotide sequence. The method allows the specific co-amplification of high numbers of restriction fragments. The number of fragments that can be analyzed simultaneously, however, is dependent on the resolution of the detection system. Typically 50-100 restriction fragments are amplified and detected on denaturing polyacrylamide gels. The AFLP technique provides a novel and very powerful DNA fingerprinting technique for DNAs of any origin or complexity.

Base Sequence↗
PubMed1995

Combined mapping of AFLP and RFLP markers in barley.

AFLP marker technology allows efficient DNA fingerprinting and the analysis of large numbers of polymorphic restriction fragments on polyacrylamide gels. Using the doubled haploids from the F1 of the cross Proctor x Nudinka, 118 AFLP markers were mapped onto a barley (Hordeum vulgare L.) RFLP map, also including five microsatellite and four protein marker loci. The AFLP markers mapped to all parts of the barley chromosomes and filled in the gaps on barley chromosomes 2L, 4L and 6 in which no RFLP loci had been mapped. Interestingly, the AFLP markers seldom interrupted RFLP clusters, but grouped next to them. The combined map covers 1873 cM, with a total of 282 markers. The merging of AFLP and RFLP markers increased the total map length; 402 cM were added to the map at the tips of chromosomes or in regions corresponding to earlier gaps. Another 375 cM resulted from mapping AFLP markers near to RFLP clusters or in between non-clustered RFLP markers.

Base Sequence↗
PubMed1995

Identification of amplified restriction fragment polymorphism (AFLP) markers tightly linked to the tomato Cf-9 gene for resistance to Cladosporium fulvum.

Using the technique of amplified restriction fragment polymorphism (AFLP) analysis, and bulked segregant pools from F2 progeny of the cross Lycopersicon esculentum (Cf9) x L. pennellii, approximately 42,000 AFLP loci for tight linkage to the tomato Cf-9 gene for resistance to Cladosporium fulvum have been screened. Analysis of F2 recombinants identified three markers which co-segregated with Cf-9. The Cf-9 gene has recently been isolated by transposon tagging using the maize transposon Dissociation (Ds). Analysis of plasmid clones containing Cf-9 shows that two of these markers are located on opposite sides of the gene separated by 15.5 kbp of intervening DNA. AFLP analysis provides a rapid and efficient technique for detecting large numbers of DNA markers and should expedite plant gene isolation by positional cloning and the construction of high-density molecular linkage maps of plant genomes.

Base Sequence↗