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Biomedical subjects

A Davidson

Publications and source records attributed to A Davidson.

At least 19 recordsLinked to original sources
PubMed1996

Induction of central tolerance by intrathymic inoculation of adenoviral antigens into the host thymus permits long-term gene therapy in Gunn rats.

Recombinant adenoviruses are highly efficient at transferring foreign genes in vivo. However, duration of gene expression is limited by the host antiviral immune response which precludes expression upon viral readministration. We tested the feasibility of prolonging gene expression by induction of central tolerance to adenoviral antigens in bilirubin-UDP-glucuronosyltransferase-1 (BUGT1)-deficient Gunn rats. Tolerance was induced by intraperitoneal injection of antilymphocyte serum, followed by intrathymic inoculation of one of the following: a recombinant adenovirus (Ad), adenovirus human UDP-glucuronosyltransferase (Ad-hBUGT1) carrying the hBUGT1 gene; a protein extract of the same virus; or viral infected hepatocytes. Controls received intrathymic injections of normal saline. After 12 d all groups were injected intravenously with 5 x 10(9) pfu of either Ad-hBUGT1 or adenovirus beta-galactosidase (Ad-LacZ) (expressing the Escherichia coli beta-galactosidase [LacZ] gene). In all three groups of tolerized rats, hBUGT1 was expressed in the liver after administration of Ad-hBUGT1, with glucuronidation of biliary bilirubin of above 95%. Serum bilirubin levels decreased from 7.2 to 1.8 mg/dl within 1 wk and remained low for 7 wk. Similar findings were observed following repeat injections given on days 45 and 112. In control rats serum bilirubin levels were reduced for only 4 wk, and viral readministration was ineffective. In all tolerized groups, but not in controls, there was a marked inhibition of appearance of neutralizing antibodies and cytotoxic lymphocytes against the recombinant adenovirus. Injection of wild type adenovirus-5 (Ad5) into the tolerized rats elicited a wild type-specific cytotoxic lymphocyte response. This is the first demonstration of Ad-directed long-term correction of an inherited metabolic disease following central tolerization with thymic antigen.

Adenoviridae↗
PubMed1996

An in vitro assay for detection of glomerular binding IgG autoantibodies in patients with systemic lupus erythematosus.

The deposition of anti-dsDNA antibodies in the glomerulus is believed to play a critical role in the pathogenesis of nephritis in SLE. However, an absolute correlation between serum levels of anti-dsDNA antibodies and renal disease has not been found. Recently a glomerular binding assay (GBA) has been developed to detect IgG binding to isolated rat glomeruli. We have used the GBA to study sera from four groups of SLE patients: (A) + anti-dsDNA antibodies, active nephritis; (B) - anti-dsDNA antibodies, active nephritis; (C) + anti-dsDNA antibodies, no nephritis; and (D) - anti-dsDNA antibodies, no nephritis. The serum anti-dsDNA antibodies in group A and group C patients could not be distinguished on the basis of isotype, charge, or cross-reactivity with histones. Nevertheless, the mean intensity of glomerular immunofluorescence was significantly higher in group A than in the three other patient groups and distinguished between patients with serum anti-dsDNA antibodies who had nephritis and those without clinically apparent nephritis. GBA reactivity was unaffected by DNase treatment of sera, but was partially inhibited by preincubation with dsDNA. These findings are consistent with the hypothesis that some anti-dsDNA antibodies cross-react with glomerular components and that the presence of this cross-reactivity is associated with, and may be responsible for, the development of nephritis. In addition, we have identified a group of SLE patients with renal disease and typical renal histopathology and immune deposits who do not have serum anti-dsDNA antibodies or antibodies that directly bind to glomeruli in the GBA. The mechanism of renal immune deposition in these patients remains to be determined.

Autoantibodies↗
PubMed1996

Retroviral gene transfer in autologous bone marrow transplantation for adult acute leukemia.

To evaluate whether marrow contributes to relapse after autologous bone marrow transplantation (AuBMT) for acute leukemia, transplanted marrow was marked with the G1N retroviral vector (Genetic Therapy Inc.) containing the neomycin phosphotransferase gene (neo). Between April 1992 and August 1993, 4 patients were transplanted for acute myeloid leukemia (AML) in second complete remission (CR) and 1 patient for acute lymphoid leukemia in first CR. An average of 12.4% (range 5-19%) of transplanted marrow mononuclear cells were exposed to G1N vector for 4 hr. In the vector-treated portion of the marrow, 4.9% of GM-CFU and 3.6% of erythroid burst-forming units (BFU-E) were resistant to G418 in vitro. In the 5 patients, the polymerase chain reaction (PCR) detected the neo sequence on only two occasions after AuBMT. Of 4 patients surviving 1 year after transplantation, only 1 had evidence of gene marked cells by PCR. Two AML patients have relapsed, one of whom had evidence of neo sequences in the bone marrow at day 100 but not at relapse 11 months after AuBMT. The second patient relapsed 18 months after AuBMT but never had PCR evidence of neo sequences before or after relapse. Our results indicate vector-transduced autologous bone marrow from heavily pretreated adults with acute leukemia mark with low efficiency, although vector sequences have been detected in bone marrow and peripheral blood up to 1 year after transplant. Of the 2 relapsed patients, no evidence of vector-marked leukemic blasts have been detected.

Acute Disease↗
PubMed1996

Rheumatoid factor idiotypic and antigenic specificity is strongly influenced by the light chain VJ junction.

The aim of this study was to define the structural basis for rheumatoid factor (RF) specificity and for the expression of the RF light chain-associated Ids, 4C9 and 6B6.6, by determining the reactivity of recombined heavy and light chains of Ig derived from monoclonal B cell lines of patients with rheumatoid arthritis and of light chains with site-directed mutations. We found that expression of the 4C9 and 6B6.6 Ids resulted from use of the VkIIIa genes Humkv 328 and Vg, but only in the presence of a permissive VJ junction. Expression of the Ids was independent of heavy chain use for the Humkv328-encoded light chains, but was highly dependent on the associated heavy chain for the Vg-encoded light chains. The RF specificity of the Abs was primarily heavy chain dependent, but the light chain VJ junction was critical in determining the relative avidity of the Abs for Fc. Our study points to the critical contribution of the somatically generated VJ junction to RF autoantibody specificity and to the expression of the two RF-associated Ids studied.

Amino Acid Sequence↗
PubMed1996

Regulation of VIP gene expression in general. Human lung cancer cells in particular.

Vasoactive intestinal peptide (VIP) is a neuropeptide of multiple functions affecting development and aging. In cancer, for example, VIP was found to function as an autocrine growth factor in nonsmall cell lung cancer (NSCLC) promotion. Furthermore, a VIP hybrid antagonist (neurotensin(6-11)-VIP(7-28)) was found to inhibit NSCLC growth. In the present study, the expression of VIP mRNA was studied using human lung cancer cells. RNA prepared from 19 cell lines was fractionated by 1% agarose gel electrophoresis followed by blotting onto nitrocellulose membranes and hybridization to a VIP-specific RNA probe. VIP mRNA was detected in about 50% of the cell lines tested with a greater abundance in NSCLC. Cultures of the NSCLC NCI-H727 cell line were treated with forskolin, an activator of cyclic AMP (cAMP), and separately with the tumor promoter phorbol 12-myristate 13-acetate (PMA). Northern blot hybridization analysis showed an increase in VIP mRNA levels after 4 h treatment with 50 microM forskolin. Incubation with PMA also showed a significant increase in the levels of VIP transcripts. Cultures were then incubated with PMA in the presence of actinomycin D, a transcription blocker. Results indicated that PMA treatment may induce both VIP mRNA synthesis as well as VIP mRNA stabilization, and suggested a 4-5 h half-life for the VIP mRNA in the absence of PMA. Thus, lung cancer tumor proliferation may be regulated, in part, at the level of VIP gene expression.

Animals↗
PubMed1996

Ex vivo expansion of murine hematopoietic progenitor cells generates classes of expanded cells possessing different levels of bone marrow repopulating potential.

The objective of ex vivo expansion of primitive hematopoietic progenitor cells (HPC) is to increase the number of progeny cells possessing hematopoietic potential similar to the original HPC. In the context of bone marrow (BM) transplantation in mice, this implies that expanding a number of HPC sufficient for long-term rescue of one lethally irradiated animal should generate enough cells to rescue more than one lethally irradiated recipient. In the present study, Sca-1+Lin- cells from male C57Bl/6 mice were expanded in vitro with stem cell factor (SCF), interleukin-1alpha (IL-1alpha), IL-3, and IL-6 and used to transplant lethally irradiated syngeneic female recipients. Expanded cells were tracked in vitro with the fluorescent membrane dye PKH2, which becomes evenly distributed among dividing daughter cells, and fractionated on day 7 into Sca-1+ cells which did not divide (Sca-1+PKH2bright), those which had divided 1 to 2 times (Sca-1+PKH2moderate), or those which had divided four or more times (Sca-1+PKH2dim). Grafts of expanded cells consisted of either the same number of fresh cells proven to rescue lethally irradiated animals [3X10(3) cells; referred to as one repopulating dose (1 RD)] or the expansion equivalent (EE) of these cells. One EE of cells represented 3X10(3) multiplied by the fold increase in the number of cultured cells on day 7. All animals transplanted with 3X10(3) freshly isolated Sca-1+Lin- cells survived long-term. Only 53% of animals receiving 1 EE of all cultured day-7 cells survived. One RD from all three PKH2 fractions (bright, moderate, and dim) of day-7 cultured Sca-1+ cells failed to rescue more than 30% of lethally irradiated recipients. Comparable survival rates were obtained when 1 EE of Sca-1+PKH2dim or only 4 RD of Sca-1+PKH2bright cells were used as grafts, suggesting that a larger frequency of long-term repopulating cells may have been retained within the fraction of Sca-1+ cells undergoing minimal or no proliferation in culture. Engraftment of male ex vivo expanded cells in recipients was confirmed by polymerase chain reaction (PCR) analysis with Y chromosome-specific primers. When analyzed for their cell cycle status, Sca-1+PKH2bright cells were mostly quiescent, whereas a higher percentage of Sca-1+PKH2dim cells were in active phases of cell cycle. These data suggest that ex vivo expansion does not augment the number of BM repopulating HPC and that ex vivo expansion generates classes of progenitor cells with different BM repopulating potentials depending on their proliferative history. These studies also suggest that the cell cycle status of graft cells may affect the ability of these cells to engraft in myeloablated hosts.

Animals↗
PubMed1996

Forced over-expression of the myeloid zinc finger gene MZF-1 inhibits apoptosis and promotes oncogenesis in interleukin-3-dependent FDCP.1 cells.

The myeloid zinc finger protein MZF-1 is important in hematopoiesis. Previous studies have found that reducing expression of MZF-1 inhibited G-CSF-driven human marrow colony formation assays. In this study we found that retrovirally overexpressing MZF-1 in IL-3-dependent FDCP.1 cells inhibited their apoptosis when IL-3 was withdrawn. The MZF-1-transduced FDCP.1 cells also formed tumors when injected into congenic mice, whereas control FDCP.1 cells did not.

Animals↗
PubMed1996

Lymphocytosis of donor origin in cerebrospinal fluid, and marrow aplasia after donor leukocyte infusion for EBV-lymphoproliferative disease.

A 29-year-old woman underwent a T cell-depleted unrelated donor transplant for CML in chronic phase. Sixty-three days after marrow infusion, the patient developed fevers and generalized lymphadenopathy. Lymph node biopsy was consistent with monoclonal EBV-associated immunoblastic lymphoma for which the patient received 10(5) CD3-positive donor leukocytes per kilogram. Six days after leukocyte infusion the patient developed mental status changes without focal neurological deficit. MRI revealed no mass lesions. Cerebral spinal fluid revealed a white blood cell count of 1650 cells/mm3 which were shown to be T lymphocytes of donor origin. The CSF was tested and found to be PCR positive for EBV virus interval repeat 1 sequence (IR1). The lymphocytosis and mental status changes resolved without specific intervention. Subsequently she developed marrow aplasia, which was believed to be secondary to the infusion of donor leukocytes. Possible mechanisms for these two previously unreported side-effects of donor leukocyte infusion are discussed.

Adult↗
PubMed1996

HLA-DRB1 and DQB typing of Hispanic American patients with rheumatoid arthritis: the "shared epitope" hypothesis may not apply.

OBJECTIVE: To determine whether the association of particular MHC class II alleles and the DRB1 "shared epitope" with disease susceptibility and severity in rheumatoid arthritis (RA) applies to ethnic groups other than Caucasian Americans. METHODS: 67 Hispanic American patients with RA and a similar number of ethnically matched controls were typed for DRB1 using polymerase chain reaction methods. DR4 subtype and DQB1 type were determined for the subjects positive for DR4. Disease severity in the patients with RA was assessed by clinical, radiographic and laboratory variables. RESULTS: The frequency of DR4 was significantly increased in the subjects with RA compared to the control group. However, the "shared" DRB1 amino acid sequence was relatively infrequent in the Hispanic American patients with RA, and there was no association of specific DR4 or DQ alleles with more severe disease or extraarticular manifestations. CONCLUSION: The HLA markers that predict poor prognosis and suggest that more aggressive clinical management may be appropriate in Caucasian American patients with RA may not be useful in other ethnic groups.

Arthritis, Rheumatoid↗
PubMed1995

Aberrant expression of the myeloid zinc finger gene, MZF-1, is oncogenic.

The zinc finger gene MZF-1 is preferentially expressed in primitive hematopoietic cells and plays an important role in regulating myelopoiesis. Regulators of development are potential targets for neoplastic transformation. This study investigated whether unregulated expression of MZF-1 could function as an oncogene. Retroviral transduction and subsequent overexpression of MZF-1 resulted in loss of contact inhibition, loss of substrate dependence, and more rapid cell cycling in NIH 3T3 cells. The MZF-1-transformed 3T3 cells formed aggressive tumors in athymic mice. Disruption of the tight lineage- and stage-specific regulation of MZF-1 can result in neoplastic transformation of embryonic fibroblasts. Therefore, MZF-1 represents a novel oncogene.

3T3 Cells↗
PubMed1995

Molecular characterization of monoclonal IgM derived from human B cell lines expressing the 4C9 rheumatoid factor associated idiotype.

Ten human monoclonal B cell lines that express the RF associated Id 4C9 were analyzed using an immunogenetic approach. Five of eight tested lines were also strongly positive for the 6B6.6 Id. We found that all the 4C9/6B6.6 positive lines expressed VkIIIa light chain genes. In contrast, 4C9 reactivity was also found on a cell line expressing a VkIIIb light chain gene and on a line expressing a V light chain gene. The two anti-Ids recognized a linear light chain determinant on Humkv328 encoded light chains but also a conformational determinant on Vg encoded light chains that appeared to be dependent on the presence of a heavy chain. Idiotypic reactivity occurred on both RF positive and RF negative antibodies. Within this idiotypic system, the basis for idiotypic reactivity and RF reactivity is complex, subject to both heavy and light chain gene usage and sensitive to small numbers of somatic mutations.

Amino Acid Sequence↗
PubMed1995

Superactive lipophilic peptides discriminate multiple vasoactive intestinal peptide receptors.

To distinguish vasoactive intestinal peptide (VIP) receptors in the brain-mediating neurotransmission and neurotrophism, potent VIP analogues were designed. Using a single amino acid substitution and the addition of a fatty acyl moiety, an analogue was devised that exhibited both a 100-fold greater potency than VIP and specificity for a VIP receptor associated with neuronal survival. This VIP agonist increased neuronal survival via a cAMP-independent mechanism. Identical chemical modification of a prototype VIP antagonist (Met-Hybrid, Neurotensin6-11-VIP7-28) also resulted in a 100-fold greater potency in blocking VIP-mediated increases in neuronal survival. Blockade of circadian activity rhythms was limited to VIP antagonists that could inhibit VIP-mediated increases in cAMP. These lipophilic peptides provide novel tools in receptor discrimination and drug design.

Amino Acid Sequence↗
PubMed1995

Managing constipation using a research-based protocol.

Constipation, a common health problem particularly for elderly and hospitalized patients, can cause abdominal pain, discomfort, gas, headaches, nausea, anorexia, a bad taste in the mouth, and potentially adds to functional loss and length of stay. As part of a quality improvement initiative, a research-based interdisciplinary protocol was developed to prevent constipation in hospitalized immobile vascular surgery patients. Using a combination of dietary fiber, increased fluid, and hygiene measures over a 3-year period, incidence of constipation was reduced from 59% to about 9%. The incidence of impaction was eliminated and requests for laxatives and enemas were reduced from 59% to about 8%.

Clinical Nursing Research↗
PubMed1994

Functional neurological outcome in leukaemic children receiving repeated cranial irradiation.

Long-term outcome defined by educational or employment history has been recorded in a group of children with acute lymphoblastic leukaemia (ALL) who received cranial radiotherapy at some stage prior to TBI conditioned bone marrow transplant (BMT). Median follow-up in 24 survivors of 69 consecutive patients was 4 years and 2 months. Individual risk factors for poor functional outcome were considered, including calculations of biological effective radiation doses. There was no incidence of CNS treatment-related mortality. All survivors are in normal school or employment, although three who had CNS relapse are receiving remedial teaching. No individual risk factors could be identified but the worst outcome was seen in children who were of young age at the time of initial treatment, who suffered CNS relapse and who had received the highest total dose of cranial irradiation.

Adolescent↗