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L Thomas

Publications and source records attributed to L Thomas.

At least 181 records · Page 10Linked to original sources
PubMed1999

[Sheep, chills and "doughnut granuloma"--an atypical course of Coxiella infection].

Q fever usually presents with high fever, headache and an atypical pneumonia. A case report of a 47-year-old patient with an atypical course of a coxiella infection is described. The dominant clinical symptoms were a liver and bone marrow involvement, whereas pulmonary manifestations were absent. The diagnosis of Q fever in this patient was based on the detection of cytoplasmatic inclusion bodies in macrophages and granulocytes. Furthermore fibrin-ring granulomas ("doughnut lesions") were found in liver tissue specimen and epitheloid-cell granulomas were detected in bone marrow specimen. Complement-fixation antibody titers and PCR resulted unspecific or negative on different occasions during the course of the disease. A confirmation of the diagnosis by complement-fixation antibody test was possible only after recovery from the disease. In Q fever with atypical clinical and serological presentation the screening of blood cells for inclusion bodies and liver or bone marrow tissue for granulomas may be important for establishing the diagnosis.

Animals↗
PubMed1998

Interleukin-4 and -13 induce upregulation of the murine macrophage 12/15-lipoxygenase activity: evidence for the involvement of transcription factor STAT6.

When human monocytes or alveolar macrophages are cultured in the presence of interleukin (IL)-4 or IL-13, the expression of the reticulocyte-type 15-lipoxygenase is induced. In mice a 15-lipoxygenase is not expressed, but a leukocyte-type 12-lipoxygenase is present in peritoneal macrophages. To investigate whether both lipoxygenase isoforms exhibit a similar regulatory response toward cytokine stimulation, we studied the regulation of the leukocyte-type 12-lipoxygenase of murine peritoneal macrophages by interleukins and found that the activity of this enzyme is upregulated in a dose-dependent manner when the cells were cultured in the presence of the IL-4 or IL-13 but not by IL-10. When peripheral murine monocytes that do not express the lipoxygenase were treated with IL-4 expression of 12/15-lipoxygenase mRNA was induced, suggesting pretranslational control mechanisms. In contrast, no upregulation of the lipoxygenase activity was observed when the macrophages were prepared from homozygous STAT6-deficient mice. Peritoneal macrophages of transgenic mice that systemically overexpress IL-4 exhibited a threefold to fourfold higher 12-lipoxygenase activity than cells prepared from control animals. A similar upregulation of 12-lipoxygenase activity was detected in heart, spleen, and lung of the transgenic animals. Moreover, a strong induction of the enzyme was observed in red cells during experimental anemia in mice. The data presented here indicate that (1) the 12-lipoxygenase activity of murine macrophages is upregulated in vitro and in vivo by IL-4 and/or IL-13, (2) this upregulation requires expression of the transcription factor STAT6, and (3) the constitutive expression of the enzyme appears to be STAT6 independent. The cytokine-dependent upregulation of the murine macrophage 12-lipoxygenase and its induction during experimental anemia suggests its close relatedness with the human reticulocyte-type 15-lipoxygenase despite their differences in the positional specificity of arachidonic acid oxygenation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1998

Regulation of endosome sorting by a specific PP2A isoform.

The regulated sorting of proteins within the trans-Golgi network (TGN)/endosomal system is a key determinant of their biological activity in vivo. For example, the endoprotease furin activates of a wide range of proproteins in multiple compartments within the TGN/endosomal system. Phosphorylation of its cytosolic domain by casein kinase II (CKII) promotes the localization of furin to the TGN and early endosomes whereas dephosphorylation is required for efficient transport between these compartments (Jones, B.G., L. Thomas, S.S. Molloy, C.D. Thulin, M.D. Fry, K.A. Walsh, and G. Thomas. 1995. EMBO [Eur. Mol. Biol. Organ.] J. 14:5869-5883). Here we show that phosphorylated furin molecules internalized from the cell surface are retained in a local cycling loop between early endosomes and the plasma membrane. This cycling loop requires the phosphorylation state-dependent furin-sorting protein PACS-1, and mirrors the trafficking pathway described recently for the TGN localization of furin (Wan, L., S.S. Molloy, L. Thomas, G. Liu, Y. Xiang, S.L. Ryback, and G. Thomas. 1998. Cell. 94:205-216). We also demonstrate a novel role for protein phosphatase 2A (PP2A) in regulating protein localization in the TGN/endosomal system. Using baculovirus recombinants expressing individual PP2A subunits, we show that the dephosphorylation of furin in vitro requires heterotrimeric phosphatase containing B family regulatory subunits. The importance of this PP2A isoform in directing the routing of furin from early endosomes to the TGN was established using SV-40 small t antigen as a diagnostic tool in vivo. The role of both CKII and PP2A in controlling multiple sorting steps in the TGN/endosomal system indicates that the distribution of itinerant membrane proteins may be acutely regulated via signal transduction pathways.

Amino Acid Sequence↗
PubMed1998

PACS-1 defines a novel gene family of cytosolic sorting proteins required for trans-Golgi network localization.

We report the role of one member of a novel gene family, PACS-1, in the localization of trans-Golgi network (TGN) membrane proteins. PACS-1 directs the TGN localization of furin by binding to the protease's phosphorylated cytosolic domain. Antisense studies show TGN localization of furin and mannose-6-phosphate receptor, but not TGN46, is strictly dependent on PACS-1. Analyses in vitro and in vivo show PACS-1 has properties of a coat protein and connects furin to components of the clathrin-sorting machinery. Cell-free assays indicate TGN localization of furin is directed by a PACS-1-mediated retrieval step. Together, these findings explain a mechanism by which membrane proteins in mammalian cells are localized to the TGN.

Adaptor Protein Complex alpha Subunits↗
PubMed1998

alpha1-Antitrypsin Portland, a bioengineered serpin highly selective for furin: application as an antipathogenic agent.

The important role of furin in the proteolytic activation of many pathogenic molecules has made this endoprotease a target for the development of potent and selective antiproteolytic agents. Here, we demonstrate the utility of the protein-based inhibitor alpha1-antitrypsin Portland (alpha1-PDX) as an antipathogenic agent that can be used prophylactically to block furin-dependent cell killing by Pseudomonas exotoxin A. Biochemical analysis of the specificity of a bacterially expressed His- and FLAG-tagged alpha1-PDX (alpha1-PDX/hf) revealed the selectivity of the alpha1-PDX/hf reactive site loop for furin (Ki, 600 pM) but not for other proprotein convertase family members or other unrelated endoproteases. Kinetic studies show that alpha1-PDX/hf inhibits furin by a slow tight-binding mechanism characteristic of serpin molecules and functions as a suicide substrate inhibitor. Once bound to furin's active site, alpha1-PDX/hf partitions with equal probability to undergo proteolysis by furin at the C-terminal side of the reactive center -Arg355-Ile-Pro-Arg358- downward arrow or to form a kinetically trapped SDS-stable complex with the enzyme. This partitioning between the complex-forming and proteolytic pathways contributes to the ability of alpha1-PDX/hf to differentially inhibit members of the proprotein convertase family. Finally, we propose a structural model of the alpha1-PDX-reactive site loop that explains the high degree of enzyme selectivity of this serpin and which can be used to generate small molecule furin inhibitors.

ADP Ribose Transferases↗
PubMed1998

Absence of cytokine receptor-dependent specificity in red blood cell differentiation in vivo.

Erythropoietin (EPO) is required for red blood cell development, but whether EPO-specific signals directly instruct erythroid differentiation is unknown. We used a dominant system in which constitutively active variants of the EPO receptor were introduced into erythroid progenitors in mice. Chimeric receptors were constructed by replacing the cytoplasmic tail of constitutively active variants of the EPO receptor with tails of diverse cytokine receptors. Receptors linked to granulocyte or platelet production supported complete erythroid development in vitro and in vivo, as did the growth hormone receptor, a nonhematopoietic receptor. Therefore, EPOR-specific signals are not required for terminal differentiation of erythrocytes. Furthermore, we found that cellular context can influence cytokine receptor signaling.

3T3 Cells↗
PubMed1998

Systemic antibiotic prophylaxis in elective cesarean delivery.

OBJECTIVE: To test the value of using prophylactic antibiotics at elective cesarean delivery. METHOD: One-hundred and twenty women delivered by elective cesarean in the absence of labor and before the rupture of membranes were randomized to receive either 1.5 g of cefuroxime intravenously at cord clamping (n = 59) or no prophylaxis (control group, n = 61). RESULTS: Twelve women developed febrile morbidity (six study, six control, P = 0.09). Of these, five had endometritis (two study, three control, P = 0.09) and two had wound infection (one study, one control, P = 0.09). Ten more women had microbiological evidence of endometritis and wound infection (six study, four control, P = 0.08). There was no significant difference in the hospital stay (6.5 days study, 6.8 days control, P = 0.06). Staphylococcus aureus was the commonest pathogen accounting for 14 infection episodes. Amniotic fluid culture could not predict the development of infection. CONCLUSION: Administration of prophylactic antibiotics at elective cesarean deliveries was not associated with decreased postoperative morbidity.

Adult↗
PubMed1998

Quantitation of amphotericin B in plasma by second-derivative spectrophotometry.

A method is described for determining amphotericin B in plasma using second-derivative spectrophotometry after deproteinization. The assay was based on the absorbance at 407.5 nm. The second-derivative spectrum recorded between 350 and 450 nm allowed identification of the analyte and showed absence of drug interference. Only bilirubin interfered at high concentration (> or = 50 mumol l-1. The linear concentration ranges were 0.05 -5.0 mg l-1 (r = 0.999, slope = 2.731, intercept = 0.008). Between-day CV < or = 9.7%, within-day CV < or = 5.5%, analytical recovery close to 100% were suitable for clinical investigations. This method provides better specificity than direct absorbance, is simpler and faster than a high performance liquid chromatography assay and can be used routinely by any laboratory possessing a spectrophotometer with a derivative accessory.

Amphotericin B↗
PubMed1998

Peak mitral inflow velocity predicts mitral regurgitation severity.

OBJECTIVES: Mitral regurgitation (MR) is a common echocardiographic finding; however, there is no simple accurate method for quantification. The aim of this study was to develop an easily measured screening variable for hemodynamically significant MR. BACKGROUND: The added regurgitant volume in MR increases the left atrial to left ventricular gradient, which then increases the peak mitral inflow or the peak E wave velocity. Our hypothesis was that peak E wave velocity and the E/A ratio increase in proportion to MR severity. METHODS: We performed a retrospective analysis of 102 consecutive patients with varying grades of MR seen in the Adult Echocardiography Laboratory at the University of California, San Francisco. Peak E wave velocity, peak A wave velocity, E/A ratio and E wave deceleration time were measured in all patients. The reference standard for MR was qualitative echocardiographic evaluation by an expert and quantitation of regurgitant fraction using two-dimensional and Doppler echocardiography. RESULTS: Peak E wave velocity was seen to increase in proportion to MR severity, with a significant difference between the different groups (F = 37, p < 0.0001). Peak E wave velocity correlated with regurgitant fraction (r = 0.52, p < 0.001). Furthermore, an E wave velocity >1.2 m/s identified 24 of 27 patients with severe MR (sensitivity 86%, specificity 86%, positive predictive value 75%). An A wave dominant pattern excluded the presence of severe MR. The E/A ratio also increased in proportion to MR severity. Peak A wave velocity and E wave deceleration time showed no correlation with MR severity. CONCLUSIONS: Peak E wave velocity is easy to obtain and is therefore widely applicable in clinical practice as a screening tool for evaluating MR severity.

Adult↗
PubMed1998

Membranous subaortic stenosis presenting decades after surgical correction for tetralogy of Fallot.

Subaortic stenosis is rare in the middle-aged adult. Its association with tetralogy of Fallot is extremely rare. We report two middle-aged patients, presenting three decades after surgical repair of tetralogy of Fallot, with the rare association of subaortic stenosis. The clinical presentation in each patient mimicked residual pulmonary stenosis and insufficiency, but echocardiography revealed subaortic stenosis with associated valvular aortic regurgitation.

Adult↗
PubMed1998

[Managing cutaneous melanoma].

Cutaneous melanoma represents the main cause of death among skin cancers. Early diagnosis gives, for the time being, the only possibility for high rate of curative treatment. Diagnosis is based on pathological findings, and at primary tumor stage. Breslow thickness of the lesion is the best prognostic index. At local stage of the disease, treatment is precisely codified by international recommendations and consensus conferences. Follow-up after surgical treatment is also well codified. Treatment of lymph node invasion or metastatic disease is, on the other hand, less codified. Despite recent advances, especially in immunotherapy, treatment of advanced stages of melanoma remains difficult.

Combined Modality Therapy↗
PubMed1998

[Chemotherapy of soft tissue sarcoma in the adult].

The goal of postoperative treatment in adult soft tissue sarcoma is local control, and in high-risk patients prevention of distant failures. Radiation therapy is essential after non-radical surgery. The role of adjuvant chemotherapy on improvement of overall survival remains to be evidenced; however, recent meta-analysis data have confirmed its impact on both local and metastatic evolution of the disease. Because for both radiotherapy and chemotherapy, delay of treatment may be crucial for efficacy following tumor excision, concomitant radiochemotherapy should be considered. Review of the literature as well as personal results showed the feasibility of postoperative radiochemotherapy in adult soft tissue sarcoma, even when the chemotherapeutic associations used included an anthracycline. Prospective study of radiochemotherapy should be performed in order to assess its real impact in terms of efficacy and toxicity.

Adult↗
PubMed1998

Cigarette smoking and cervical dysplasia among non-Hispanic black women.

This is the first case-control study to determine whether smoking is associated with cervical dysplasia, after adjustment for human papillomavirus (HPV) infection, among a group of non-Hispanic black women. Subjects were interviewed and asked questions about smoking and other risk factors for cervical cancer. HPV infection was determined by hybrid capture. Thirty-two women with histologically confirmed incident dysplasia and 113 control women with normal cytologic smears were enrolled; all women were HIV negative. Smoking was more strongly associated with dysplasia among women with high-grade lesions than among all case women combined. After adjustment, women with high-grade lesions were roughly four times more likely to be ever (odds ratio [OR]: 3.8; 95% confidence interval [CI]: 0.76-18.4) or current (OR: 4.3; 95% CI: 0.83-21.9) smokers, compared with control women. Larger studies among black women that control for HPV infection are needed to confirm these findings and to explore associations among black women with low-grade lesions.

Adult↗
PubMed1998

Analysis of glycosphingolipids of human head and neck carcinomas with comparison to normal tissue.

Glycosphingolipids of head and neck carcinomas from six tumor-bearing patients were analyzed and compared to those of normal tissue from similar areas. The total glycosphingolipid content and the lipid-bound sialic acid were much higher in carcinomas than in normal tissue. Major neutral glycolipids were glucosylceramide, lactosylceramide, trihexosylceramide and paragloboside. Sulfatides were seen only in extracts from normal tissue which also showed a rather simple ganglioside pattern with #GM3 and GD3 as major species, whereas tumors showed additional species such as GM2 and GD2, along with a strong increase in LM1, GM1, GD1a and GT1b.

Biomarkers, Tumor↗