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Biomedical subjects

T L Brown

Publications and source records attributed to T L Brown.

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

Transforming growth factor beta induces caspase 3-independent cleavage of alphaII-spectrin (alpha-fodrin) coincident with apoptosis.

Transforming growth factor beta (TGF-beta) is a potent growth inhibitor and inducer of cell death in B-lymphocytes and is essential for immune regulation and maintenance of self-tolerance. In this report the mouse immature B cell line, WEHI 231, was used to examine the mechanisms involved in TGF-beta-mediated apoptosis. Induction of apoptosis is detected as early as 8 h after TGF-beta administration. Coincident with the onset of apoptosis, the cytoskeletal actin-binding protein, alphaII-spectrin (alpha-fodrin) is cleaved into 150-, 115-, and 110-kDa fragments. The broad spectrum caspase inhibitor (Boc-D-fmk (BD-fmk)) completely abolished TGF-beta-induced apoptosis and alphaII-spectrin cleavage. Caspase 3, although present in WEH1 231 cells, was not activated by TGF-beta, nor was its substrate, poly(ADP-ribose) polymerase. These results identify alphaII-spectrin as a novel substrate that is cleaved during TGF-beta-induced apoptosis. Our data provide the first evidence of calpain and caspase 3-independent cleavage of alphaII-spectrin during apoptosis and suggests that TGF-beta induces apoptosis and alphaII-spectrin cleavage via a potentially novel caspase. This report also provides the first direct evidence of caspase 3 activation in WEH1 231 cells and indicates that at least two distinct apoptotic pathways exist.

Animals↗
PubMed1999

TGF-beta induces fibronectin synthesis through a c-Jun N-terminal kinase-dependent, Smad4-independent pathway.

Transforming growth factor-beta (TGF-beta) exerts its effects on cell proliferation, differentiation and migration in part through its modulation of extracellular matrix components, such as fibronectin and plasminogen activator inhibitor-1 (PAI-1). Although the SMAD family of proteins recently has been shown to be a key participant in TGF-beta signaling, other signaling pathways have also been shown to be activated by TGF-beta. We report here that c-Jun N-terminal kinase (JNK), a member of the MAP kinase family, is activated in response to TGF-beta in the human fibrosarcoma HT1080-derived cell line BAHgpt. Stable expression of dominant-negative forms of JNK1 and MKK4, an upstream activator of JNK, results in loss of TGF-beta-stimulated fibronectin mRNA and protein induction, while having little effect on TGF-beta-induced levels of PAI-1. The human fibronectin promoter contains three CRE elements, one of which has been shown to bind a c-Jun-ATF-2 heterodimer. Utilizing a GAL4 fusion trans-reporting system, we demonstrate a decrease in transactivating potential of GAL4-c-Jun and GAL4-ATF-2 in dominant-negative JNK1- and MKK4-expressing cells. Finally, we show that TGF-beta-induced fibronectin synthesis is independent of Smad4. These results demonstrate that TGF-beta-mediated fibronectin induction requires activation of JNK which in turn modulates the activity of c-Jun and ATF-2 in a Smad4independent manner.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1999

Altered gene expression in melanocytes exposed to 4-tertiary butyl phenol (4-TBP): upregulation of the A2b adenosine receptor 1.

Exposure to phenolic agents contributes to the development of occupational vitiligo. Proposed as a causative factor for leukoderma in vivo, the para-substituted phenol 4-tertiary butyl phenol was chosen to investigate early cellular events responsible for selective disappearance of melanocytes from the epidermis of individuals sensitive to such agents. To this end, differential display of melanocyte mRNA isolated from three separate cultures was performed following a 12 h exposure of cells to 250 microM 4-tertiary butyl phenol or to vehicle alone. Fragments of cDNA representing differentially expressed messages were cloned and subsequently confirmed by reverse dot blotting. Alignment analysis revealed that the L30 ribosomal protein was upregulated by the treatment, potentially reflecting altered levels of protein synthesis in response to stress. In addition, a gene sequence upregulated following exposure to 4-tertiary butyl phenol was identified as the A2b receptor (a P1 receptor for adenosine). Differential expression of this gene was confirmed in an RNase protection assay. By reverse transcription-polymerase chain reaction, the gene was shown to be expressed in keratinocytes and fibroblasts as well. Flow cytometry confirmed differential expression in melanocytes and fibroblasts, but not in keratinocytes. Interestingly, it has been reported that P1 purinoceptor stimulation can induce apoptosis. This is in concordance with results reported elsewhere demonstrating induction of apoptosis by 4-tertiary butyl phenol in human melanocytes, as well as with morphologic changes observed in this study in cells exposed to 250 microM 4-tertiary butyl phenol for 72 h. In conclusion, differential display is useful to establish melanocyte components involved in the cellular response to phenolic agents.

Flow Cytometry↗
PubMed1999

Involvement of protein kinase C in Rickettsia rickettsii-induced transcriptional activation of the host endothelial cell.

Our laboratory has reported on a biphasic pattern of nuclear factor kappaB (NF-kappaB) activation in cultured human umbilical vein endothelial cells during infection with Rickettsia rickettsii, an obligate, intracellular bacterium, and the etiologic agent of Rocky Mountain spotted fever. Transcriptional activation of the tissue factor (TF) gene during this infection has been shown to involve NF-kappaB. To further understand the signal transduction events underlying these phenomena, we studied the role of protein kinase C (PKC), a ubiquitous family of phospholipid-dependent enzymes implicated in the regulation of a variety of cell signaling pathways. Two inhibitors of PKC, namely, bisindolylmaleimide I hydrochloride (BM-1) and calphostin C, which exhibit different inhibitory properties towards various isozymes of PKC, were used. Infection of cells with R. rickettsii in the presence of BM-1 (50 nM) did not significantly affect NF-kappaB, whereas calphostin C (2.5 microM) completely blocked the early phase of NF-kappaB activation. The late, sustained phase also was not affected by treatment with BM-1. Downregulation of phorbol ester-sensitive PKCs by long-term treatment with phorbol 12-myristate 13-acetate (PMA) did not inhibit NF-kappaB activation. Likewise, this downregulation had no effect on induction of TF activity. The activity of TF was, however, sensitive to BM-1 and calphostin C, whereas expression of TF mRNA was inhibited only by calphostin C. Overall, these results suggest the lack of involvement of classical PKC pathways in R. rickettsii-induced NF-kappaB activation but the possible involvement of a non-PMA-responsive PKC isoform in the posttranscriptional control of TF expression.

Cells, Cultured↗
PubMed1999

Reproductive potential after methotrexate treatment of ectopic gestation in a community hospital.

OBJECTIVE: To compare the rates of ipsilateral tubal patency after methotrexate treatment versus conservative surgical treatment in a small community hospital lacking personnel dedicated to methotrexate management. STUDY DESIGN: From hospital and clinic records, cases of ectopic gestation within a six-year interval were identified. Method of treatment and location of the ectopic gestation were documented by review of records and confirmed by patient interviews. Women desiring fertility were offered hysterosalpingography (HSG) to evaluate tubal patency. HSG was performed under fluoroscopy with water-soluble contrast medium. RESULTS: HSG was completed in 11 cases of linear salpingostomy and 11 cases of ectopic gestations treated by methotrexate. Ipsilateral patency was documented in 8 of 11 (72%) tubes treated by linear salpingostomy and 9 of 11 (81%) methotrexate-treated tubes. One methotrexate case had a prior ipsilateral ectopic treated by salpingostomy, and two additional cases had a prior contralateral ectopic removed by salpingectomy. Each of these three cases had ipsilateral tubal patency after methotrexate for the most recent ectopic gestation. CONCLUSION: Data from this study suggest comparable tubal patency rates after methotrexate and conservative surgery. Comparable tubal patency outcomes were obtained in our community hospital despite a less-rigorous-than normal follow-up protocol.

Abortifacient Agents, Nonsteroidal↗
PubMed1998

Visual half-field Stroop effects with spatial separation of words and color targets.

Past inconsistencies in the occurrence of differential visual half-field Stroop effects were addressed in two experiments using a visual half-field presentation technique incorporating brief displays (100 ms) and a fixation task designed to ensure proper eye fixation at display onset. Experiment 1 used displays in which distractor words and color targets were presented in contralateral visual fields. Experiment 2 compared contralateral with ipsilateral displays where words and color targets appeared one above the other in the same visual field. Stroop effects were larger whenever a word occupied the right as opposed to the left visual field, regardless of whether the color target was left or right. Results are consistent with the idea that words are processed more efficiently or automatically in right visual field/left hemisphere presentations.

Analysis of Variance↗
PubMed1998

Medication patterns of recurrent headache sufferers: a community study.

This community-based telephone survey determined medication patterns of 274 frequent headache sufferers who reported 12 or more headaches a year. Headaches were classified using the International Headache Society's (IHS) criteria. Participants reported on 465 types of headaches: 129 tension headaches, 158 migraine headaches, 8 chronic tension headaches, and 148 headaches which were unclassifiable using IHS criteria. Females (n = 133) reported an average of 1.9 types of headache and males (n = 141) reported 1.5 headache types. Fifty-six percent of respondents used acetaminophen for tension-type and 60% used acetaminophen for migraine. One percent used prescription medication for tension headache and 12% used prescriptions for migraine. The perceived effectiveness of over-the-counter medication was approximately 7 on a scale of 0-10 for tension headaches and 6 for migraine. Both tension-headache and migraine-headache sufferers waited about 1 h before taking any medication. Tension-headache sufferers waited until the headache was above 5 on a 0 to 10 scale (4.6 for migraine). It is possible that more aggressive use of medication might improve headache management.

Adolescent↗
PubMed1998

Steam pasteurization of commercially slaughtered beef carcasses: evaluation of bacterial populations at five anatomical locations.

A steam pasteurization process (patent pending) has been shown to effectively reduce pathogenic bacterial populations on beef tissue and to significantly reduce naturally occurring bacterial populations on commercially slaughtered beef carcasses. The objective of this study was to determine the effectiveness of the steam pasteurization treatment for reducing bacterial populations at several anatomical locations on commerically slaughtered carcasses. Before and after pasteurization treatment (82.2 degrees C, 6.5-s exposure time), a sterile sponge was used to sample 300 cm2 at one of five locations (inside round, loin, midline, brisket, or neck). Eighty carcasses (40 before treatment and 40 after treatment) were sampled per anatomical location over 2 processing days. Before treatment, aerobic plate counts (APCs) were found to be highest (P < or = 0.01) at the midline (4.5 log10 CFU/100 cm2), intermediate at the inside round, brisket, and neck (ca. 3.8 log10 CFU/100 cm2), and lowest at the loin (3.4 log10 CFU/100 cm2). After treatment, APCs at all locations were reduced significantly (P < or = 0.01). The inside round, loin, and brisket had the lowest (P < or = 0.01) APCs (ca. 2.6 log10 CFU/100 cm2), whereas the midline and neck had APCs of 3.1 and 3.3 log10 CFU/100 cm2, respectively. The lower reduction in APCs at the neck area indicated that the treatment may not be as effective there, possibly because of the design of the pasteurization equipment. Generic Escherichia coli populations were low at all locations before treatment, with populations on 32% of all carcasses sampled being less than the detection limit of the study (5.0 CFU/100 cm2). After treatment, E. coli populations were significantly lower (P < or = 0.01) than populations before treatment and 85% of all carcasses sampled had E. coli populations below the detection limit. The maximum E. coli population detected after treatment was 25 CFU/100 cm2. For enteric bacterial populations, no differences were observed in the effectiveness of the treatment among the five carcass locations.

Abattoirs↗
PubMed1998

Caspase inhibitor BD-fmk distinguishes transforming growth factor beta-induced apoptosis from growth inhibition.

Transforming growth factor beta (TGFbeta) is essential for immune regulation and growth control. TGFbeta has previously been shown to inhibit cell growth as well as induce cell death in lymphocytes, although the mechanisms controlling these processes are not well understood. The mouse pre-B lymphoma cell line WEHI 231 was used to examine the mechanisms of TGFbeta-mediated growth inhibition and apoptosis. TGFbeta inhibits the growth of WEHI 231 cells in a dose-dependent manner; however, a decrease in viability is also observed, which is indicative of increased cell death. TGFbeta induces oligonucleosomal DNA ladder formation in a dose-dependent manner, indicating the mechanism of cell death is via apoptosis. The broad spectrum caspase inhibitor BD-fmk, but not tetrapeptide inhibitors of specific caspases, completely blocks TGFbeta-induced apoptosis while maintaining cellular viability. BD-fmk, however, has no effect on TGFbeta-induced growth inhibition. The ability of TGFbeta to down-regulate cyclin A-associated kinase activity, postulated to mediate TGFbeta growth inhibition, is not affected by the caspase inhibitor BD-fmk. These results suggest that caspases do not regulate cell cycle mediators of growth and provide the first demonstration that a pharmacological inhibitor of TGFbeta-induced apoptosis is capable of distinguishing growth inhibitory from apoptotic pathways.

Animals↗
PubMed1997

Interferon action and apoptosis are defective in mice devoid of 2',5'-oligoadenylate-dependent RNase L.

2',5'-Oligoadenylate-dependent RNase L functions in the interferon-inducible, RNA decay pathway known as the 2-5A system. To determine the physiological roles of the 2-5A system, mice were generated with a targeted disruption of the RNase L gene. The antiviral effect of interferon alpha was impaired in RNase L-/- mice providing the first evidence that the 2-5A system functions as an antiviral pathway in animals. In addition, remarkably enlarged thymuses in the RNase L-/- mice resulted from a suppression of apoptosis. There was a 2-fold decrease in apoptosis in vivo in the thymuses and spleens of RNase L-/- mice. Furthermore, apoptosis was substantially suppressed in RNase L-/- thymocytes and fibroblasts treated with different apoptotic agents. These results suggest that both interferon action and apoptosis can be controlled at the level of RNA stability by RNase L. Another implication is that the 2-5A system is likely to contribute to the antiviral activity of interferon by inducing apoptosis of infected cells.

Adenine Nucleotides↗
PubMed1997

Multisystemic treatment of violent and chronic juvenile offenders: bridging the gap between research and practice.

The lack of communication between researchers and practitioners has hindered the development of effective interventions for children and adolescents. Recently, however, significant headway in bridging this researcher-practitioner gap has been made due to the emergence of multisystemic therapy (MST) as a treatment approach that combines the rigor of science and the "real world" aspects of clinical practice in treating violent and chronic juvenile offenders and their families in community-based settings. MST addresses the multiple known determinants of delinquency and delivers services in the family's natural environment, with considerable emphasis on treatment fidelity. This article describes MST and provides a case example of how MST treatment principles are applied.

Adolescent↗
PubMed1996

Mothers' attitudes and behavior toward medicating children's pain.

Studies on physicians', patients', and the public's attitudes toward using opioid pain medications in adults have shown that negative attitudes are associated with decreased prescription/use of opioids in the treatment of moderate to severe pain. Most of the pain that children experience is managed by parents, yet little is known about parents' attitudes toward using medication to treat children's pain. A 20-item scale was developed to examine mothers' attitudes to using acetaminophen to treat children's pain. During a structured telephone interview, 298 mothers responded to the attitude scale items. Mothers also responded to questions concerning their medicating behaviors. Mothers were concerned about tolerance and side effects from acetaminophen. Principal components factor analysis on the acetaminophen scale extracted four factors which accounted for 59% of the variance in responses. Mothers with more positive attitudes toward acetaminophen were more likely to medicate for common childhood pains and would give medication at lower levels of pain than would mothers with less positive attitudes. However, the moderate internal reliability of the attitude subscales somewhat limits the generalizability of these findings. Further scale development will be necessary in order to clarify mothers' attitudes and the relationship between their attitudes and behaviors. Studies using different pain contexts, and using fathers and older children and adolescents as respondents, will add to our understanding of attitudes toward using medication for children's pain.

Acetaminophen↗
PubMed1996

Apolipoprotein J/clusterin expression defines distinct stages of blastocyst implantation in the mouse uterus.

The endometrium is a dynamic tissue that responds to hormonal cues and growth factors to accommodate, regulate, and nurture developing embryos. To provide clues about the molecular mechanisms underlying the responsiveness of this tissue, we have begun to identify genes that are expressed at specific stages of early pregnancy. One such gene, apolipoprotein J (apoJ), encodes a secretory glycoprotein capable of binding lipids and membrane-active proteins. Uterine apoJ gene activity was not detected immediately following fertilization, but glandular epithelial expression of apoJ mRNA appeared just before the time of blastocyst implantation and persisted postimplantation. During implantation, uterine luminal epithelial cells also expressed apoJ, but expression was excluded from luminal cells adjacent to the sites of attached blastocysts. ApoJ protein accumulated in the glandular and uterine lumens in proximity to the epithelial cells that expressed apoJ mRNA. We suggest that apoJ expression is a marker of uterine receptivity to blastocyst implantation. Subsequent expression of apoJ message in uterine stromal cell types and in circular muscle myocytes coincided with the onset of decidualization. During this period the myocytes of the longitudinal muscle layer showed no evidence of apoJ mRNA. ApoJ protein was localized to nondecidualized tissue but was not evident in decidualized cells. In contrast, the protein was dispersed throughout both the circular and longitudinal myometrium. In the uteri of hormone-treated females stimulated with oil, apoJ was also expressed during decidualization in stromal cells and in circular myocytes, indicating that signals specifically transmitted from the embryo itself are not responsible for apoJ mRNA accumulation.

Animals↗
PubMed1996

Attentional selection and word processing in Stroop and word search tasks: the role of selection for action.

The time course of visual word processing was investigated in two tasks differing in whether words were "selected for action" (Allport, 1989). Using identical displays in which a square color patch appeared at fixation with either 2, 4, or 8 flanking words appearing at any of the 8 sides and corners, subjects performed either a Stroop color-naming task or a word search task requiring detection of a color name among the flanking words by either a manual presence/absence response (Experiment 1) or a vocal naming response (Experiment 2). The color-naming task produced Stroop effects indicating parallel word processing in multiword displays, whereas the word search task produced evidence consistent with serial, self-terminating search requiring allocation of spatial attention. The differences in word processing across tasks are reconciled using Allport's concept of selection for action and extended to neuropsychological evidence on attention.

Attention↗
PubMed1995

Local synthesis of apolipoprotein J in the eye.

Apolipoprotein J (apoJ), a secretory glycoprotein known to transport lipids and to regulate terminal complement function, is present in the human eye in both aqueous and vitreous, as well as in the retina. Ocular apoJ is the product of local synthesis, rather than plasma contamination, as demonstrated by its distinct structural properties and the presence of abundant apoJ mRNA in retina and retina pigment epithelium. ApoJ mRNA is also present in mouse eye, with a developmentally regulated pattern of expression. In fetal mouse, apoJ mRNA is present in retina, lens and cornea. In contrast, adult eye apoJ mRNA is present in retina and ciliary body. We propose that apoJ is important in tissue remodeling and in stabilizing hydrophobic molecules which are required for vision and/or which would otherwise be deleterious and membrane-active.

Aged↗