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Biomedical subjects

C A Mullen

Publications and source records attributed to C A Mullen.

At least 55 records · Page 3Linked to original sources
PubMed1994

Tumors expressing the cytosine deaminase suicide gene can be eliminated in vivo with 5-fluorocytosine and induce protective immunity to wild type tumor.

Successful expression of the cytosine deaminase (CD) suicide gene in vivo is demonstrated in three weakly immunogenic murine tumor models: the 102 and 205 fibrosarcomas and the 38 adenocarcinoma. Normal mammalian cells do not contain cytosine deaminase, but tumor cells transduced with retroviral vectors containing the CD gene metabolize the relatively nontoxic prodrug 5-fluorocytosine to the highly toxic 5-fluorouracil. In vitro cells expressing the CD gene are killed by 5-fluorocytosine while unmodified cells are not. When injected into syngeneic mice, CD+ tumors can also be eliminated in vivo by systemic treatment with 5-fluorocytosine without significant toxicity to the host. Animals whose CD+ tumors were eliminated with prodrug treatment resist subsequent rechallenge with unmodified wild type tumor. This posttreatment immunity appears to be tumor specific. Applications of the CD system in gene therapy models are discussed.

Animals↗
PubMed1994

Metabolic suicide genes in gene therapy.

This article reviews uses of metabolic suicide genes in gene therapy. Suicide genes encode novel nonmammalian enzymes that can convert a relatively nontoxic prodrug into a highly toxic agent. Cells genetically transduced to express such genes essentially commit metabolic suicide in the presence of the appropriate prodrug. Three metabolic suicide genes are described: herpes simplex thymidine kinase, Escherichia coli cytosine deaminase and varicella zoster thymidine kinase. Transfer and expression of these genes into mammalian cells is described. Preclinical models of suicide gene therapy of cancer and human immunodeficiency virus are discussed, and several clinical trials employing suicide genes are described.

Animals↗
PubMed1994

A multiinstitutional survey of the Wiskott-Aldrich syndrome.

The Wiskott-Aldrich syndrome is an X-linked primary immunodeficiency originally characterized by the clinical triad of thrombocytopenia, eczema, and immunodeficiency. We collected clinical and laboratory information on 154 unselected patients with Wiskott-Aldrich syndrome to define better the clinical expression of this disorder. The classic triad of thrombocytopenia with small platelets, recurrent otitis media, and eczema was seen in only 27% of the study population; 5% of the study population had only infectious manifestations, and 20% of the study group had only hematologic manifestations before diagnosis. The results of immunologic evaluations varied from one patient to another and the course of the disorder varied tremendously, even within a single kindred. We conclude that many patients with Wiskott-Aldrich syndrome have an atypical presentation and that a panel of diagnostic tests is often required to establish the diagnosis. Two high-risk subgroups were identified in the study population: patients with platelet counts < 10 x 10(9)/L (< 10,000/mm3) at the time of diagnosis were at high risk of bleeding, and patients with autoimmune disorders were at increased risk of having a malignancy.

Adolescent↗
PubMed1994

Retroviral vectors containing chimeric promoter/enhancer elements exhibit cell-type-specific gene expression.

Retroviral vectors were constructed in which the U3 promoter/enhancer of Moloney murine leukemia (Mo-MLV) was replaced by the corresponding region from five related murine retroviruses--AKR murine leukemia virus (AKV), Harvey murine sarcoma virus (HaMSV), myeloproliferative sarcoma virus (MPSV), SL3-3, and the NZB-xenotropic virus (Xeno). In these vectors the chimeric long terminal repeat (chLTR) drives the expression of the chloramphenicol acetyl transferase (CAT) reporter gene that is followed by an internal SV40 virus early region promoter linked to the neomycin phosphotransferase II (NEO) gene. As an initial measure of the relative promoter/enhancer strength of the chLTR vectors, the murine NIH-3T3 cell line and the human JURKAT cell lines were transfected and assayed for CAT reporter activity. Relative to the MoMLV vector, the HaMSV construct was the most active in NIH-3T3 cells whereas the SL3-3 vector displayed the greatest activity in JURKAT cells. Retroviral vector producer cell populations and cell clones were established for each chLTR vector, and all were capable of yielding high vector titers (> 10(5) G418R cfu/ml on NIH-3T3). Supernatant from these cells was used to transduce both mouse and human cell lines and primary cells. In NIH-3T3 cells and two murine fibrosarcoma cell lines, the HaMSV chLTR vector was slightly more active than the MoMLV chLTR vector. In the human HepG2 and HeLa cell lines, the MPSV chLTR vector was the most active. Data from the human JURKAT T-cell line and a T cell line derived from an ADA-deficient severe combined immunodeficiency (SCID) patient demonstrate that the SL3-3 chLTR is the most active in these lymphoid cell lines. The greatest difference in the comparison of the different chLTR vectors was observed in primary human umbilical vein endothelial cells, where the MoMLV vector produced up to 100 times more CAT activity than the SL3-3 vector. These data suggest that the use of specific promoter/enhancer elements may lead to higher levels of gene expression following retroviral-mediated gene transfer into specific cell types and these observations may be useful in the design of human gene therapy experiments.

Animals↗
PubMed1994

Effects of IMP dehydrogenase inhibitors on the phosphorylation of ganciclovir in MOLT-4 cells before and after herpes simplex virus thymidine kinase gene transduction.

We have undertaken to characterize the role of cytoplasmic 5'-nucleotidase (EC 3.1.3.5) in the phosphorylation of the anti-herpes simplex virus and anti-human cytomegalovirus agent ganciclovir (GCV) in MOLT-4 cells, a human T cell line adapted to grow in suspension culture. The rate of formation of GCV triphosphate was found to be approximately doubled by preincubation of nontransfected MOLT-4 cells with agents that cause the accumulation of IMP, such as ribavirin (20 microM) and mycophenolic acid (1 microM), and the reaction rate was found to be unaffected by high levels of thymidine (100 microM). With herpes simplex virus-1 thymidine kinase (HStk) gene-transduced MOLT-4 cells, the rate of GCV phosphorylation was approximately 40-fold faster than that in uninfected cells and, in marked contrast to uninfected cells, the reaction was significantly inhibited both by IMP dehydrogenase inhibitors and by thymidine. These latter effects appear to be the result of 1) the accumulation of high levels of dTTP in IMP dehydrogenase inhibitor-treated cells, with consequent feedback inhibition of HStk, and 2) direct competitive substrate inhibition by thymidine of the HStk-catalyzed phosphorylation of GCV. Thus, agents that enhance 5'-nucleotidase-catalyzed phosphorylation of GCV in uninfected cells do not play a similar role in HStk-transfected cells, a consequence of the quantitative predominance of the viral thymidine kinase-catalyzed reaction over that attributable to endogenous cytoplasmic 5'-nucleotidase.

Cell Line↗
PubMed1993

Splenectomy and/or bone marrow transplantation in the management of the Wiskott-Aldrich syndrome: long-term follow-up of 62 cases.

This study describes the effects of two major treatment options, splenectomy and/or bone marrow transplantation, on the natural history of the Wiskott-Aldrich (WAS) syndrome. The records of 62 patients with the WAS evaluated at the National Institutes of Health Clinical Center from 1966 to 1992 were reviewed. Nineteen patients were treated with bone marrow transplantation (BMT) and the results were largely dependent on the source of the graft. Twelve of 12 patients receiving HLA-matched sibling marrow achieved satisfactory immunologic and hematologic reconstitution. By contrast, only 2 of 7 patients receiving haploidentical, parental, or matched unrelated marrow survived more than 1 year after BMT. Thirty-nine patients who lacked suitable bone marrow donors early in their course underwent splenectomy for management of their thrombocytopenia; most received prophylactic antibiotics to minimize the risk of sepsis. Nearly all these patients achieved normal platelet counts and the rate of serious bleeding was reduced nearly sevenfold. Median survival in the untransplanted splenectomy group was 25 years, compared with less than 5 years in unsplenectomized patients. We conclude that HLA-matched sibling donor BMT is the treatment of choice for patients with WAS and that splenectomy and daily prophylactic antibiotics provide a significant survival advantage to those boys without a matched sibling donor. Splenectomy should probably be used in preference to unmatched BMT until results with alternative donor BMT significantly improve or gene therapy becomes available.

Adolescent↗
PubMed1993

A study of the safety and survival of the adoptive transfer of genetically marked syngeneic lymphocytes in HIV-infected identical twins.

This phase I/II pilot project will evaluate the survival, tolerance, safety, and efficacy of infusions of activated, gene marked, syngeneic T lymphocytes obtained from HIV seronegative identical twins on the functional immune status of HIV infected twin recipients. T cells from each seronegative twin will be obtained by periodic apheresis, separated into CD4 and CD8 enriched populations by monoclonal antibody affinity binding techniques, induced to polyclonal proliferation with anti-CD3 and rIL-2 stimulation, transduced with distinctive neoR retroviral vectors, and expanded 10-1,000 fold in numbers during approximately 2 weeks of culture. These marked T cell fractions will then be infused into the seropositive twins and the survival of the uniquely marked T cell populations will be monitored by vector-specific PCR, while the recipients' functional immune status is monitored by standard in vitro and in vivo testing protocols. A total of 3 cycles of treatment will be given at intervals of 6 weeks between infusions.

Adolescent↗
PubMed1993

Strategies for gene therapy.

The use of retroviral-mediated gene transfer to introduce a DNA label into T cells (TIL) being used in the immunotherapy of patients with malignant melanoma finally opened the door to the clinical application of gene therapy for a wide variety of inherited and acquired diseases. The gene therapy trial for ADA deficiency SCID has demonstrated that long term stable expression of exogenous genes can be achieved in human T lymphocytes using retroviral vectors for ex vivo treatment and that significant immune reconstitution can be achieved in these patients following periodic infusions with ADA gene-corrected autologous T cells. Newer clinical applications include the insertion of genes into CD34 enriched stem cell populations, the testing of autologous tumor vaccines employing cytokine gene-modified tumor cells and the direct transfer of the herpes thymidine kinase gene into brain tumors in situ in order to render those tumors sensitive to treatment with the ordinarily non-cytotoxic drug ganciclovir.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Fibrosarcoma cells transduced with the IL-6 gene exhibited reduced tumorigenicity, increased immunogenicity, and decreased metastatic potential.

Murine fibrosarcoma cell lines transduced with retroviral vectors containing the murine interleukin 6 (IL-6) gene constitutively secreted IL-6. When injected s.c. into normal mice these IL-6-secreting tumors exhibited reduced tumorigenicity. This reduced tumorigenicity was not seen in nude or irradiated mice, implicating a T-cell-dependent, radiosensitive host response activated by the cytokine. Subcutaneous IL-6-secreting tumor did not retard the growth of distant deposits of wild-type tumor in the same host. However, animals rejecting IL-6-secreting tumors exhibited resistance to later challenge with wild-type tumor. When injected i.v. in an experimental metastasis model the IL-6-secreting tumors failed to or were extremely inefficient in giving rise to pulmonary nodules; this was observed in both normal and immunoincompetent mice, implicating a second, nonimmune mechanism affecting the growth of the tumor modified to secrete IL-6.

Animals↗
PubMed1992

Transfer of the bacterial gene for cytosine deaminase to mammalian cells confers lethal sensitivity to 5-fluorocytosine: a negative selection system.

Expression of the bacterial gene for cytosine deaminase (CD; EC 3.5.4.1) in mammalian cells was evaluated as a negative selection system or suicide vector for potential use in gene transfer studies and therapies. Mammalian cells, unlike certain bacteria and fungi, do not contain the enzyme CD and do not ordinarily metabolize cytosine to uracil. Nor do they metabolize the innocuous compound 5-fluorocytosine to the highly toxic compound 5-fluorouracil. The Escherichia coli CD gene underwent PCR oligonucleotide-directed mutagenesis to enhance its expression in a eukaryotic system and it was then cloned into an expression vector, pLXSN, that also contains a neomycin-resistance gene. Murine fibroblast lines were transfected with the plasmid and subjected to brief selection in the neomycin analogue G418. Lysates from these cell populations exhibited significant CD activity detected by conversion of radiolabeled cytosine to uracil. In clonogenic assays transfected cells expressing CD were selectively killed by incubation in 5-fluorocytosine, whereas control cell lines were not. Dose-response studies evaluating [3H]thymidine incorporation or cloning efficiency demonstrated profound inhibition at and above 65 micrograms of 5-fluorocytosine per ml. Mixed cellular assays showed that CD-positive cells could be eliminated without bystander killing of other cells. Retrovirus-mediated CD gene transfer into various tissues was also demonstrated. Thus CD, with its ability to produce the toxic antimetabolite 5-fluorouracil from 5-fluorocytosine, may be useful as a negative selection system for studies and treatments employing gene transfer techniques.

Animals↗
PubMed1991

Dual serotoninergic projections to forebrain in the rat: morphologically distinct 5-HT axon terminals exhibit differential vulnerability to neurotoxic amphetamine derivatives.

The cerebral cortex of the rat and other mammals is innervated by two morphologically distinct classes of serotoninergic (5-HT) axon terminals: fine axons with minute varicosities and beaded axons characterized by large, spherical varicosities. Fine and beaded 5-HT axons exhibit different regional and laminar distributions in forebrain and arise from separate brainstem nuclei, the dorsal and median raphe nuclei, respectively. The present neuroanatomic study, based on immunocytochemical methods to visualize 5-HT axons, demonstrates that the two axon types differ markedly in their vulnerability to the neurotoxic amphetamine derivatives, methylenedioxyamphetamine (MDA), and p-chloroamphetamine (PCA). While both drugs cause extensive degeneration of fine 5-HT axons throughout forebrain, beaded 5-HT axons are consistently spared. Fine 5-HT axons, which richly innervate most regions of dorsal forebrain in control rats, are rarely seen 2 weeks after treatment with MDA or PCA; this loss of fine axons reflects a marked denervation that persists for months after drug administration. The serotoninergic axon terminals remaining after MDA or PCA administration are almost entirely of the beaded type and appear to be unaffected by both drugs. Over a wide range of doses (2.5-40 mg/kg PCA) and survival times (2 weeks to 2 months), these spared 5-HT axons with large, spherical varicosities cannot be distinguished from the normal, beaded 5-HT axons in control rats by morphologic criteria. Moreover, beaded 5-HT axons exhibit a highly characteristic regional distribution which is the same in control as in MDA- and PCA-treated rats: these axons innervate specific zones or layers within parietal and occipital cortex, hippocampus, cingulate cortex, entorhinal cortex, and the olfactory bulb, among other forebrain areas, and they form a dense plexus lining the ventricular system. Taken together, the results of this study demonstrate that fine 5-HT axons are highly vulnerable to the neurotoxic effects of the amphetamine derivatives MDA and PCA, while beaded 5-HT axons are markedly resistant. These findings are consistent with the hypothesis that there are two anatomically and functionally distinct sets of serotoninergic neurons projecting to forebrain. While both of these neuronal systems utilize 5-HT as a neurotransmitter, they differ in several features: 1) origin from separate nuclei in the brainstem (the dorsal and median raphe), 2) two types of morphologically distinct axon terminals, 3) markedly different distribution and innervation patterns in forebrain, and 4) dissimilar pharmacological properties. The results further suggest that psychotropic amphetamine derivatives have a selective action upon fine serotoninergic axons that arise from the dorsal raphe nucleus.

3,4-Methylenedioxyamphetamine↗
PubMed1990

Early hospital discharge of children with cancer treated for fever and neutropenia: identification and management of the low-risk patient.

Children with leukemia and solid tumors are often hospitalized for empiric broad-spectrum antibiotic therapy because of fever during periods of chemotherapy-induced neutropenia. Conventional practice dictates that parenteral antibiotics be continued until the patient is afebrile and has recovered from neutropenia, ie, until the absolute neutrophil count (ANC) exceeds 500 cells per cubic millimeter. However, the practice in our center has been to discontinue parenteral antibiotic therapy and discharge many such patients before resolution of neutropenia. Since the feasibility and safety of this approach has not been studied, we reviewed the records of 114 consecutive hospitalizations for fever and neutropenia in 61 patients during a 13-month period. Seventy-seven children (68%) were discharged to their homes while still neutropenic after they had been afebrile for 1 to 2 days on parenteral antibiotics, had negative blood cultures, appeared well, and usually had some evidence of bone marrow recovery. Five patients (4.4%) developed recurrent fever and required rehospitalization within 7 days of discharge. Only three of the 77 patients (3.9%) who were sent home with neutropenia had recurrent fever. Each had a brief and uneventful second hospitalization. Two of the 37 children discharged with an ANC over 500 cells per cubic millimeter required rehospitalization. A declining ANC and advanced malignancy were risk factors in predicting recurrence of fever following discharge. A rising monocyte count was a predictor of imminent recovery from neutropenia. These results suggest that "early" discharge of an afebrile yet still neutropenic patient is safe when the patient is in remission, has no evidence of serious infection, appears clinically stable, and has indications of bone marrow recovery. The conventional approach of routinely continuing the hospitalization until resolution of neutropenia may be unnecessary in such low-risk patients.

Bacterial Infections↗
PubMed1990

Laryngospasm-induced pulmonary edema: case report.

Laryngospasm during the emergent phase of anesthesia is a respected complication well known to any PACU nurse. One complication of laryngospasm is noncardiac pulmonary edema (NCPE). NCPE can be a catastrophic complication of anesthesia. A case report is presented to illustrate the signs and symptoms of laryngospasm and NCPE. The physiology of hemoptysis and hypoxemia is reviewed. The mechanism of laryngospasm-induced pulmonary edema is described. The need for PACU nurses to comprehend the pathophysiology and implications of laryngospasm and hypoxemia is paramount when determining proper treatment. PACU nurses should be particularly alert to and aware of this complication.

Adult↗
PubMed1989

Highly immunogenic regressor tumor cells can prevent development of postsurgical tumor immunity.

Highly immunogenic malignant cells form small tumors that spontaneously regress after initial growth because the tumor induces specific immunity. However, variants may arise during the initial tumor growth that lose antigens, grow progressively, often become the predominant tumor population, and eventually kill the host. These progressively growing variants usually have not lost all tumor antigens and remain susceptible to rejection by T cells specific for antigens present on the parental tumor and retained by the progressively growing variants. Thus, it would seem logical for therapy to actively immunize with the parental highly immunogenic tumor (or sublines made similarly immunogenic by tumor heterogenization) after maximal surgical removal of the growing tumor. However, the present findings suggest that such a strategy may be ineffective and have adverse effects: the parental highly immunogenic tumor cells, either remaining or reintroduced, may perpetuate unresponsiveness to both the parental and the variant tumor. These findings suggest that unless tumor-induced suppression is first abrogated, immunization with highly immunogenic tumor cells may be counterproductive because this maneuver may maintain preexisting immune suppression and prevent development of postsurgical tumor immunity.

Animals↗
PubMed1987

Distribution of locus coeruleus axons in the rat spinal cord: a combined anterograde transport and immunohistochemical study.

The distribution of locus coeruleus axons in the rat spinal cord was studied by anterograde transport of Phaseolus vulgaris leucoagglutinin in combination with dopamine-beta-hydroxylase immunohistochemistry. Locus coeruleus axons were observed primarily in the superficial laminae of the dorsal horn. Few locus coeruleus fibers were seen in the vicinity of motoneuron pools or in the intermediolateral cell column of the thoracic spinal cord. The results of this study suggest a selective action of the coeruleo-spinal projection upon sensory inputs to the spinal cord.

Animals↗
PubMed1986

Immunoregulation by natural killer cells.

Polyinosinic-polycytidilic acid (poly (I:C], a synthetic analog of viral double-stranded RNA (dsRNA), activates natural killer (NK) cells and inhibits induction or promotes termination of the primary IgM response in vivo. Suppression of responses was reproduced in vivo by interferons (IFN) which activate NK cells and in vitro by cells enriched for NK cells. The likelihood that NK cells may be involved in the normal regulation of IgM responses is supported by the following observations: immunization itself induces NK activity at times appropriate to account for termination, NK cells activated by immunization suppress in vitro, mice with high NK activity induced by immunization with one antigen have reduced responses to immunization with a second antigen, and mice with induced loss of NK activity fail to down-regulate IgM antibody responses normally.

Animals↗