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D E Johnson

Publications and source records attributed to D E Johnson.

At least 55 records · Page 3Linked to original sources
PubMed2001

Chem-tox informatics: data mining using a medicinal chemistry building block approach.

Relating chemical structure to biological activity is not a new endeavor, however, the ability to do this on large datasets is just emerging. To cope with the enormous amounts of data being generated, an assortment of computational methods has been developed in the fields of chemoinformatics and computational toxicology. Many of the molecular descriptors used in these approaches are abstract, theoretical constructs that are difficult to understand and visualize. Having easily recognized chemical features, such as those in several new programs, will allow chemists to use toxicological information (or any biological information) when designing new libraries. These improved chem-tox informatics systems will have an impact on library design, hit and lead optimization, development candidate testing and regulatory review.

Animals↗
PubMed2001

Novel antineoplastic isochalcones inhibit the expression of cyclooxygenase 1,2 and EGF in human prostate cancer cell line LNCaP.

Experiments were conducted to determine the effects of novel anti-neoplastic isochalcones (DJ compounds), on cyclooxyegenase 1 and 2 (COX-1 and COX-2) enzyme expression in androgen receptor dependent human prostate cancer cell line LNCaP. Results from Western blot analysis and cell flow cytometry showed that DJ52 and DJ53 decreased the steady state levels of COX-1 and COX-2 protein levels in a dose dependent manner. In addition, DJ52 and DJ53 decreased the levels of epidermal growth factor (EGF) in LNCaP cells. In this study, we report that novel isochalcones decreased COX-1, COX-2 and EGF levels as well as LNCaP cellular growth in a dose responsive manner. Our findings indicate that relative decreases in COX-1, COX-2 and EGF expressions might serve as indicators of tumor growth inhibition in prostate neoplasms.

Antineoplastic Agents↗
PubMed2001

Neuropsychological performance deficits in adults with attention deficit/hyperactivity disorder.

Neuropsychological deficits in children diagnosed with attention deficit/hyperactivity disorder (ADHD) have been well documented utilizing various neuropsychological tests. Only recently has research begun to examine if similar deficits are present in adults with ADHD. A neuropsychological testing battery was constructed that assessed verbal learning and memory, psychomotor speed, and sustained attention--all demonstrated to be deficient in individuals with ADHD. Fifty-six self-referred nonmedicated adults with a DSM-IV diagnosis of ADHD and 38 normal comparison adults participated. ADHD adults demonstrated verbal and nonverbal memory deficits and decreased psychomotor speed compared to normal controls. Differences between ADHD and normal adults were not documented on traditional measures of executive functioning. A pattern of results emerged whereby ADHD adults' performance, particularly with regard to psychomotor speed, became more impaired as task complexity increased. This study's results largely corroborate similar neuropsychological testing results in ADHD children and recent ADHD adult findings, and support a frontal lobe dysfunction hypothesis of ADHD.

Journal Article↗
PubMed2000

Tumor-induced apoptosis of T cells: amplification by a mitochondrial cascade.

We have recently reported that apoptosis of T cells induced by squamous cell carcinoma of the head and neck (SCCHN) is partly Fas dependent. This tumor-induced T-cell death is mediated by the activities of caspase-8 and caspase-3 and is partially inhibited by antibodies to either Fas or Fas ligand. We report here that in contrast to apoptosis induced by agonistic anti-Fas antibody (Ab), the tumor-induced apoptotic cascade in Jurkat cells is significantly amplified by a mitochondrial loop. The involvement of mitochondria in tumor-induced apoptosis of T cells was demonstrated by changes in mitochondrial permeability transition as assessed by 3,3'-dihexiloxadicarbocyanine staining, by cleavage of cytosolic BID and its translocation to the mitochondria, by release of cytochrome c to the cytosol, and by the presence of active subunits of caspase-9 in Jurkat T cells cocultured with tumor cells. To further elucidate the significance of mitochondria in tumor-induced T-cell death, we investigated the effects of various inhibitors of the mitochondrial pathway. Specific antioxidants, as well as two inhibitors of mitochondria permeability transition, bongkrekic acid and cyclosporin A, significantly blocked the DNA degradation induced in Jurkat T cells by SCCHN cells. However, these inhibitors had no effect on cells triggered by anti-Fas Ab. Furthermore, a cell-permeable inhibitor of caspase-9, Ac-LEHD.CHO, which did not inhibit T-cell apoptosis induced by anti-Fas Ab, markedly inhibited apoptosis induced by etoposide or by coculture of Jurkat with SCCHN cells. These findings demonstrate that apoptotic cascades induced in Jurkat T lymphocytes by anti-Fas Ab or tumor cells are differentially susceptible to a panel of inhibitors of mitochondrial apoptotic events. It appears that besides the Fas-mediated pathway, additional mitochondria-dependent cascades are involved in apoptosis of tumor-associated lymphocytes. Inhibition of mitochondria-dependent cascades of caspase activation should be considered to enhance the success of immunotherapy or vaccination protocols in cancer.

Anti-Bacterial Agents↗
PubMed2000

Analysis of testes and semen from rabbits treated by intravenous injection with a retroviral vector encoding the human factor VIII gene: no evidence of germ line transduction.

In a phase 1 clinical trial, we are evaluating a murine leukemia virus (MuLV)-based retroviral vector encoding the human factor VIII gene [hFVIII(V)], administered intravenously, as a therapy for hemophilia A. Preclinical biolocalization studies in adult rabbits revealed vector-specific PCR signals in testis tissue at low levels. In follow-up animal studies we used PCR to (1) estimate the frequency with which a given cell in testis tissue is transduced, and (2) determine whether a positive PCR signal could be detected in semen samples from animals treated with hFVIII(V). Using the 99% confidence bound, results indicate that the probability that a given cell within the testis was transduced is less than 1/709,000 (97 days after treatment). This probability decreased with time after hFVIII(V) administration. Moreover, the rate of provector sequence detection in semen samples collected weekly throughout two cycles of spermatogenesis was 3/4281 reactions (0.07%), which is lower than the rate of false positives (1/800, 0.125%) observed for control animals. Using PCR assays with single-copy sensitivity, we have shown that the small number of transduced cells present in testis tissue does not give rise to detectable transduced cells in semen.

Animals↗
PubMed2000

Analysis of the role of conserved cysteine residues in the bcl-2 oncoprotein.

The Bcl-2 oncoprotein is an integral membrane protein localized primarily to the outer membrane of the mitochondria. The precise molecular mechanism responsible for the antiapoptotic action of Bcl-2 remains unknown. Two cysteine residues are found in Bcl-2 and these residues are well-conserved across species. The first cysteine (cys(155)) is located in the alpha5 domain, a region important for the ion channel properties of Bcl-2, while the second cysteine (cys(226)) is located in the carboxyl-terminal membrane anchor domain. In this study, we found that replacement of both cysteines with serine residues generated a mutant protein that retained the ability to homodimerize and heterodimerize with proapoptotic Bax protein in vitro. In whole cells, the mutant protein efficiently heterodimerized with Bax, but exhibited impaired homodimerizationrelative to wild-type Bcl-2. The mutant protein was also less efficient than wild-type Bcl-2 at suppressing caspase activation, DNA fragmentation, and loss of viability during IL-3 withdrawal-induced apoptosis. Together, the data indicate that the cysteine residues in Bcl-2 contribute, but are not absolutely essential, to the ability of Bcl-2 to homodimerize, heterodimerize with Bax, and suppress apoptosis.

Amino Acid Substitution↗
PubMed2000

Constitutive activation of Stat3 signaling abrogates apoptosis in squamous cell carcinogenesis in vivo.

Field cancerization predisposes the upper aerodigestive tract mucosa to the formation of multiple primary tumors, when exposed to environmental carcinogens. Up-regulation of epidermal growth factor receptor occurs early in squamous cell carcinogenesis and is critical for the loss of growth control in a variety of human cancers, including head and neck squamous cell carcinomas. In these tumor cells in culture, epidermal growth factor receptor stimulation initiates signaling via persistent activation of selective STAT proteins. To determine the timing of Stat3 activation in head and neck carcinogenesis, we studied the expression and constitutive activation of Stat3 in tumors and normal mucosa from patients with head and neck cancer compared with mucosa from controls without cancer. Stat3 was up-regulated and constitutively activated in both primary human head and neck tumors as well as in normal mucosa from these cancer patients compared with control normal mucosa from patients without cancer. In vivo liposome-mediated gene therapy with a Stat3 antisense plasmid efficiently inhibited Stat3 activation, increased tumor cell apoptosis, and decreased Bcl-x(L) expression in a head and neck xenograft model. These findings provide evidence that constitutively activated Stat3 is an early event in head and neck carcinogenesis that contributes to the loss of growth control by an anti-apoptotic mechanism.

Animals↗
PubMed2000

Inhibitor of apoptosis protein hILP undergoes caspase-mediated cleavage during T lymphocyte apoptosis.

Several endogenous or viral inhibitors of apoptosis, including Bcl-2, Bcl-xL, FLIP, p35, and CrmA, have been shown to be cleaved by caspases during apoptosis. In this study, we demonstrate that the endogenous inhibitor of apoptosis, hILP/XIAP, is also cleaved in apoptotic T lymphocytes, generating at least one prominent fragment of 29 kDa. This p29 cleaved fragment was detected in Jurkat cells induced to apoptose by anti-Fas antibody, staurosporin, or VP-16. The cleavage of hILP appears to be caspase mediated because the production of the p29 protein was inhibited by the pan-caspase peptide inhibitor, Z-VAD.FMK. In Jurkat cells engineered to overexpress CrmA, cleavage of hILP in response to anti-Fas antibody or staurosporin was inhibited, whereas overexpression of Bcl-2 abrogated the cleavage in response to VP-16. Cleavage of hILP was also observed in cell-free reactions using in vitro translated hILP and recombinant caspase-3 or -7. Moreover, we found that the p29 hILP fragment retained the ability to bind caspase-3 and -7, as shown previously for full-length or BIR-2 hILP. The p29 cleavage product was also detected during T-cell receptor-mediated apoptosis in peripheral blood lymphocytes from normal donors. Furthermore, tumor-associated T lymphocytes purified from ascites of patients with ovarian cancer expressed fragmented hILP, which was not detected in control T cells purified from peripheral blood of normal donors. Our results suggest that the cleavage of hILP represents an important event in apoptosis of T lymphocytes in both normal and pathological in vivo settings.

Amino Acid Chloromethyl Ketones↗
PubMed2000

Tumor-induced apoptosis of T lymphocytes: elucidation of intracellular apoptotic events.

Our recent studies suggest that human squamous cell carcinoma of the head and neck (SCCHN) is capable of activating an intrinsic mechanism of programmed-cell death in interacting lymphocytes in situ and in vitro. The current study used Jurkat T-cell line as a model to investigate intracellular apoptotic events in T cells interacting with SCCHN. Apoptosis induced in T lymphocytes by tumor cells was in part Fas-mediated, since it was partially, but significantly, inhibited in the presence of anti-Fas ligand Ab or in Fas-resistant Jurkat cells. The synthetic caspase inhibitors, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-FMK) and N-benzyloxycarbonyl-Asp-glu-Val-Asp-fluoromethyl ketone (Z-DEVD-FMK), effectively blocked apoptosis of Jurkat cells co-incubated with SCCHN cell lines, suggesting the involvement of caspases in tumor-induced apoptosis of lymphocytes. Overexpression of CrmA, an inhibitor of caspase-1 and caspase-8, partially inhibited tumor-induced T-cell death. Caspase-8 and caspase-3 were identified as effector molecules in the execution of tumor-induced T-cell death, since the proform enzymes were processed into active subunits during co-incubation of T cells with tumor cells. Furthermore, co-incubation with tumor cells resulted in cleavage of poly(ADP-ribose) polymerase (PARP), a common caspase-3 substrate, and in cleavage of TcR-zeta chain, shown by us to be a T-cell specific caspase-3 substrate. Overexpression of Bcl-2 did not provide protection of T cells from SCCHN-induced DNA degradation. Instead, the Bcl-2 protein was cleaved in the target T cells during their co-incubation with tumor cells. These findings demonstrate that tumor cells can trigger in T lymphocytes caspase-dependent apoptotic cascades, which are not effectively protected by Bcl-2. (Blood. 2000;95:2015-2023)

Apoptosis↗
PubMed2000

Inflammatory mechanisms in Alzheimer's disease: inhibition of beta-amyloid-stimulated proinflammatory responses and neurotoxicity by PPARgamma agonists.

Alzheimer's disease (AD) is characterized by the extracellular deposition of beta-amyloid fibrils within the brain and the subsequent association and phenotypic activation of microglial cells associated with the amyloid plaque. The activated microglia mount a complex local proinflammatory response with the secretion of a diverse range of inflammatory products. Nonsteroidal anti-inflammatory drugs (NSAIDs) are efficacious in reducing the incidence and risk of AD and significantly delaying disease progression. A recently appreciated target of NSAIDs is the ligand-activated nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma). PPARgamma is a DNA-binding transcription factor whose transcriptional regulatory actions are activated after agonist binding. We report that NSAIDs, drugs of the thiazolidinedione class, and the natural ligand prostaglandin J2 act as agonists for PPARgamma and inhibit the beta-amyloid-stimulated secretion of proinflammatory products by microglia and monocytes responsible for neurotoxicity and astrocyte activation. The activation of PPARgamma also arrested the differentiation of monocytes into activated macrophages. PPARgamma agonists were shown to inhibit the beta-amyloid-stimulated expression of the cytokine genes interleukin-6 and tumor necrosis factor alpha. Furthermore, PPARgamma agonists inhibited the expression of cyclooxygenase-2. These data provide direct evidence that PPARgamma plays a critical role in regulating the inflammatory responses of microglia and monocytes to beta-amyloid. We argue that the efficacy of NSAIDs in the treatment of AD may be a consequence of their actions on PPARgamma rather than on their canonical targets the cyclooxygenases. Importantly, the efficacy of these agents in inhibiting a broad range of inflammatory responses suggests PPARgamma agonists may provide a novel therapeutic approach to AD.

Alzheimer Disease↗
PubMed2000

Evaluation of E1-mutant adenoviruses as conditionally replicating agents for cancer therapy.

The oncolytic effect of adenoviruses may provide an efficient means to destroy tumor tissue if viruses could be developed with sufficient selectivity and efficacy. In this report we have characterized several adenoviruses, each with different mutations in the E1 region, for selective cytopathic effect in tumor cells in vitro and for their ability to inhibit tumor growth in vivo. Of the E1 mutants tested, we have identified one, E1Adl01/07, which preferentially induces cytopathic effects in a range of tumor cells versus primary cells. In addition, E1Adl01/07 significantly inhibited tumor growth and increased survival of mice in several models of human cancer. These results suggest that E1Adl01/07 might serve as an effective cancer therapeutic, combining both selectivity and efficacy.

Adenoviridae↗
PubMed2000

Assessment of a new transurethral balloon dilation catheter in the treatment of urethral stricture disease.

OBJECTIVES: To assess a newly designed balloon dilation catheter for the treatment of urethral stricture disease. The dilating capability of the catheter, the tolerability and safety of the procedure, and its short-term efficacy were evaluated. METHODS: Fifty-one patients with urethral strictures underwent dilation with the UrethraMax or a coude tip balloon dilation catheter. Efficacy parameters included measurement of the American Urological Association symptom score and maximum urinary flow rate 3, 6, and 12 months after treatment. The adequacy of dilation and the degree of mucosal trauma and hematuria were assessed endoscopically, and patient pain was measured using a visual analog scale. RESULTS: Forty-three patients (84.3%) were successfully dilated, achieving a urethral caliber of 20F or greater. Dilation resulted in statistically significant improvements in both the mean American Urological Association symptom score and mean maximum urinary flow rate at 3 and 6 months. Mucosal trauma was mild in all but 4 cases, and no patient developed significant hematuria. The mean visual analog pain score was 3.9 (range 0.1 to 9.4). CONCLUSIONS: Balloon dilation is a safe, well-tolerated, office-based procedure that theoretically offers several advantages over sequential rigid dilation and internal urethrotomy. It is associated with minimal complications, and its short-term efficacy is acceptable. We regard this as the dilation procedure of choice and first-line therapy for most strictures.

Adult↗