An isoflavonoid-inducible efflux pump in Agrobacterium tumefaciens is involved in competitive colonization of roots

Agrobacterium tumefaciens 1D1609, which was originally isolated from alfalfa (Medicago sativa L.), contains genes that increase competitive root colonization on that plant by reducing the accumulation of alfalfa isoflavonoids in the bacterial cells. Mutant strain I-1 was isolated by its isoflavonoid-inducible neomycin resistance following mutagenesis with the transposable promoter probe Tn5-B30. Nucleotide sequence analysis showed the transposon had inserted in the first open reading frame, ifeA, of a three-gene locus (ifeA, ifeB, and ifeR), which shows high homology to bacterial efflux pump operons. Assays on alfalfa showed that mutant strain I-1 colonized roots normally in single-strain tests but was impaired significantly (P < or = 0.01) in competition against wild-type strain 1D1609. Site-directed mutagenesis experiments, which produced strains I-4 (ifeA::gusA) and I-6 (ifeA::omega-Tc), confirmed the importance of ifeA for competitive root colonization. Exposure to the isoflavonoid coumestrol increased beta-glucuronidase activity in strain I-4 21-fold during the period when coumestrol accumulation in wild-type cells declined. In the same test, coumestrol accumulation in mutant strain I-6 did not decline. Expression of the ifeA-gusA reporter was also induced by the alfalfa root isoflavonoids formononetin and medicarpin but not by two triterpenoids present in alfalfa. These results show that an efflux pump can confer measurable ecological benefits on A. tumefaciens in an environment where the inducing molecules are known to be present.     

Alteration of cartilage metabolism by cells from osteoarthritic bone

OBJECTIVE: To determine whether bone cells alter cartilage metabolism. METHODS: Bone cell cultures were established using explants obtained from the hip and knee joints of 9 patients with osteoarthritis (OA) and 6 subjects without arthritis (nonarthritic [NA]). NA human cartilage biopsy samples were incubated in the presence or absence of bone-derived cells, and the effects on glycosaminoglycan (GAG) release from cartilage were measured. RESULTS: Bone cell cultures secreted osteocalcin (OC) and did not contain cells expressing leukocyte common antigen. None of the 8 cultures established from NA bone, compared with 17 of 32 from OA bone, significantly altered GAG release from cartilage (P = 0.006). In knees with medial joint damage, 38% of the cultures derived from the medial side of the joint increased GAG release from cartilage. In contrast, 77% of the cultures derived from the lateral side of the joint had an effect on GAG, with 38% increasing and 38% decreasing GAG release. Seven cytokines were measured in OA bone cell supernatants. No significant difference was apparent in the concentration of any one cytokine when supernatants were compared according to their effects on GAG release. CONCLUSION: Bone cells from OA patients can influence cartilage metabolism. This might explain why increased subchondral bone activity can predict cartilage loss.     

Autoantibodies to human recombinant erythropoietin in patients with systemic lupus erythematosus: correlation with anemia

OBJECTIVE: To investigate the existence of circulating autoantibodies to erythropoietin (EPO) in sera from patients with systemic lupus erythematosus (SLE), and to correlate their presence with anemia and clinical activity. METHODS: Ninety-two consecutive patients with SLE, 80 patients with rheumatoid arthritis, and 42 normal individuals were studied. The patients with SLE were categorized into 3 groups according to hemoglobin (Hgb) level: group A (45 patients with Hgb > 12 gm/dl), group B (26 patients with Hgb 10.1-12 gm/dl), and group C (21 patients with Hgb < or = 10 gm/dl). In all patients with SLE, the disease activity was evaluated using the European Consensus Lupus Activity Measurement scale. Antibodies to EPO were detected using an enzyme-linked immunosorbent assay and purified recombinant human EPO as antigen. The specificity of the method was evaluated with homologous and cross-reactive inhibition assays. RESULTS: Antibodies to EPO were found in 15.2% of the SLE patient sera. The distribution of these antibodies among the 3 groups of SLE patients was as follows: 8.8% (4 of 45) from group A, 15.4% (4 of 26) from group B, and 28.6% (6 of 21) from group C. The prevalence of antibodies to EPO in patients with severe anemia (group C) was statistically significantly higher compared with patients without anemia (chi(2) = 4.31, P < 0.05). Patients with antibodies to EPO had higher disease activity scores (P < 0.005) and lower levels of the C4 component of complement (P < 0.05) compared with patients without antibodies to EPO. CONCLUSION: In this study, the presence of antibodies to EPO in the sera of SLE patients is demonstrated for the first time. The presence of these antibodies is associated with severe anemia and active disease.     

Magnetic resonance imaging demonstrates incomplete myelination in 18q- syndrome: evidence for myelin basic protein haploinsufficiency

Magnetic resonance imaging (MRI) and MRI relaxometry were used to investigate disturbed brain myelination in 18q- syndrome, a disorder characterized by mental retardation, dysmorphic features, and growth failure. T1-weighted and dual spin-echo T2-weighted MR images were obtained, and T1 and T2 parametric image maps were created for 20 patients and 12 controls. MRI demonstrated abnormal brain white matter in all patients. White matter T1 and T2 relaxation times were significantly prolonged in patients compared to controls at all ages studied, suggesting incomplete myelination. Chromosome analysis using fluorescence in situ hybridization techniques showed that all patients with abnormal MRI scans and prolonged white matter T1 and T2 relaxation times were missing one copy of the myelin basic protein (MBP) gene. The one patient with normal-appearing white matter and normal white matter T1 and T2 relaxation times possessed two copies of the MBP gene. MRI and molecular genetic data suggest that incomplete cerebral myelination in 18q- is associated with haploinsufficiency of the gene for MBP.     

The human 37-kDa laminin receptor precursor interacts with the prion protein in eukaryotic cells

Prions are thought to consist of infectious proteins that cause transmissible spongiform encephalopathies. According to overwhelming evidence, the pathogenic prion protein PrPSc converts its host encoded isoform PrPC into insoluble aggregates of PrPSc, concomitant with pathological modifications (for review, see refs. 1-3). Although the physiological role of PrPC is poorly understood, studies with PrP knockout mice demonstrated that PrPC is required for the development of prion diseases. Using the yeast two-hybrid technology in Saccharomyces cerevisiae, we identified the 37-kDa laminin receptor precursor (LRP) as interacting with the cellular prion protein PrPC. Mapping analysis of the LRP-PrP interaction site in S. cerevisiae revealed that PrP and laminin share the same binding domain (amino acids 161 to 180) on LRP. The LRP-PrP interaction was confirmed in vivo in insect (Sf9) and mammalian cells (COS-7). The LRP level was increased in scrapie-infected murine N2a cells and in brain and spleen of scrapie-infected mice. In contrast, the LRP concentration was not significantly altered in these organs from mice infected with the bovine spongiform encephalopathic agent (BSE), which have a lower PrPSc accumulation. LRP levels, however, were dramatically increased in brain and pancreas, slightly increased in the spleen and not altered in the liver of crapie-infected hamsters. These data show that enhanced LRP concentrations are correlated with PrPSc accumulation in organs from mice and hamsters. The laminin receptor precursor, which is highly conserved among mammals and is located on the cell surface, may act as a receptor or co-receptor for the prion protein on mammalian cells.     

Mature human hematopoietic cells in donor bone marrow complicate interpretation of stem/progenitor cell assays in xenogeneic hematopoietic chimeras

Xenogeneic hematopoietic chimeras have been used to assay the growth and differentiation of human stem/progenitor cells. The presence of human hematopoietic cells in immunodeficient mice transplanted with human marrow cells may be caused by proliferation and differentiation of early stem/progenitor cells and/or proliferation of mature cells. Unpurified human marrow mononuclear cells, T cell-depleted, or stem/progenitor cell-enriched (CD34+ or CD34+CD38-) populations were injected into sublethally irradiated NOD/LtSz scid/scid (NOD/SCID) mice. High levels of human cells were detected in mice (hu/mu chimeras) transplanted with each of the above human marrow populations. Large numbers of mature human T lymphocytes were found in marrow, spleens, and thymuses from hu/mu chimeras that had been transplanted with unpurified human mononuclear marrow cells. Human immunoglobulin was detected in sera from these chimeras, and some exhibited a clinical syndrome suggestive of graft-versus-host disease. In contrast, in hu/mu chimeras that had received T cell-depleted or stem/progenitor cell-enriched populations, multilineage hematopoiesis (myeloid, B lymphoid, and progenitor cells by immunophenotype) was detected but T lymphocytes and human immunoglobulin were not; in addition, no human cells were detected in the thymuses. Thus, injection of adult human marrow cells into immunodeficient mice can result in hematopoietic chimerism for at least 3 months after transplant. However, the types of cells present in hu/mu chimeras differ depending on the human cell population transplanted. This should be taken into account when hematopoietic chimeras are used to assess human stem/progenitor cell function.     

Major gene analysis for diseases and disorders of complex etiology

Genetic analysis of complex diseases is undergoing a paradigm shift as the DNA technology and computational resources for analysis become more precise. In this review we compare the old paradigm for genetic disease analysis with the new, more powerful and efficient methods, which rely on the application of genetically linked markers. To illustrate the utility of the new approach, we apply it in the study of ankylosing spondylitis.     

BMX, a novel nonreceptor tyrosine kinase gene of the BTK/ITK/TEC/TXK family located in chromosome Xp22.2

The Bmx sequence was identified and cloned during our search for novel tyrosine kinase genes expressed in human bone marrow cells. Bmx cDNA comprises a long open reading frame of 675 amino acids, containing one SH3, one SH2 and one tyrosine kinase domain, which are about 70% identical with Btk, Itk and Tec and somewhat less with Txk tyrosine kinase sequences. The amino terminal sequences of these four tyrosine kinases are about 40% identical and each contains a so-called pleckstrin homology domain. The 2.7 kb Bmx mRNA was expressed in endothelial cells and several human tissues by Northern blotting and an 80 kD Bmx polypeptide was detected in human endothelial cells. Immunoprecipitates of COS cells transfected with a Bmx expression vector and NIH3T3 cells expressing a Bmx retrovirus contained a tyrosyl phosphorylated Bmx polypeptide of similar molecular weight. The BMX gene was located in chromosomal band Xp22.2 between the DXS197 and DXS207 loci. Interestingly, chromosome X also contains the closest relative of BMX, the BTK gene, implicated in X-linked agammaglobulinemia. The BMX gene thus encodes a novel nonreceptor tyrosine kinase, which may play a role in the growth and differentiation of hematopoietic cells.     

Outcome after multiple colorectal tumours

BACKGROUND: Patients with primary colorectal cancers have a higher risk of development of second tumours synchronously or metachronously. This special group of patients raise a particular interest in their characteristics and outcome. METHODS: The records of 1009 patients with colorectal cancer were scrutinized. A group with multiple cancers was identified. Perioperative investigations, patterns of follow-up, pathological variables and outcome were noted. RESULTS: There were 22 patients with metachronous tumours and 39 with synchronous tumours following 'curative' operations in 20 and 28 respectively. There was no difference in Dukes classification between the two groups: Polyps were associated with metachronous lesions in ten of 22 patients and synchronous lesions in 17 of 39 patients. Five-year survival was 75 per cent for patients with metachronous tumours and only 18 per cent for those with synchronous tumours. CONCLUSION: In this study patients with metachronous tumours seemed to do very well while those with synchronous lesions did very badly. There were no identifiable demographic or clinical characteristics to account for this. There is a need to study this group of patients and identify factors like tumour biology or host resistance which prevent spread of tumour.