Biomedical subjects

P Nguyen

Publications and source records attributed to P Nguyen.

At least 55 records · Page 3Linked to original sources

PubMed2000

The hsp90-related protein TRAP1 is a mitochondrial protein with distinct functional properties.

The hsp90 family of molecular chaperones was expanded recently due to the cloning of TRAP1 and hsp75 by yeast two-hybrid screens. Careful analysis of the human TRAP1 and hsp75 sequences revealed that they are identical, and we have cloned a similar protein from Drosophila. Immunofluorescence data show that human TRAP1 is localized to mitochondria. This mitochondrial localization is supported by the existence of mitochondrial localization sequences in the amino termini of both the human and Drosophila proteins. Due to the striking homology of TRAP1 to hsp90, we tested the ability of TRAP1 to function as an hsp90-like chaperone. TRAP1 did not form stable complexes with the classic hsp90 co-chaperones p23 and Hop (p60). Consistent with these observations, TRAP1 had no effect on the hsp90-dependent reconstitution of hormone binding to the progesterone receptor in vitro, nor could it substitute for hsp90 to promote maturation of the receptor to its hormone-binding state. However, TRAP1 is sufficiently conserved with hsp90 such that it bound ATP, and this binding was sensitive to the hsp90 inhibitor geldanamycin. In addition, TRAP1 exhibited ATPase activity that was inhibited by both geldanamycin and radicicol. Thus, TRAP1 has functions that are distinct from those of hsp90.

Amino Acid Sequence↗

PubMed2000

High-output heart failure resulting from a remote traumatic aorto-caval fistula: diagnosis by echocardiography.

Congestive heart failure (CHF) due to high output states is known to occur in a variety of systemic illnesses and in patients with arterial-venous fistulas. This paper reports the case of a 45-year-old man admitted to the emergency room with a diagnosis of new onset atrial fibrillation and CHF, whose past medical history was not significant except for a gunshot wound to his abdomen 22 years previously. The etiology of his CHF together with the cardiomegaly and hyperdynamic left ventricular systolic function was unknown. A subcostal view routinely done during transthoracic echocardiography revealed a severely dilated inferior vena cava and the presence of an aorto-caval fistula by color doppler. The patient underwent successful corrective repair with dramatic improvement in symptoms and resolution of the atrial fibrillation, and cardiac size returned to normal. This rare case emphasizes that patients with refractory CHF must be closely examined with particular attention to palpation and auscultation over all scars, irrespective of the duration since any traumatic or surgical event.

Abdominal Injuries↗

PubMed2000

Breakthrough pain in cancer patients: new therapeutic approaches to an old challenge.

Breakthrough pain is a well recognized but ill-defined phenomenon that occurs commonly in the presence of otherwise stable, persistent pain. It is defined now as a "transient pain episode that occurs, or breaks through from the otherwise stable background pain." Breakthrough pain is usually associated with moderate to severe pain and may form a predictor of poor response to treatment with routine pharmacotherapy. Breakthrough pain is also associated with functional impairment and psychological distress. The assessment and treatment should be multidimensional. Although primary therapies such as chemotherapy, radiation treatment, and surgical options are explored, the mainstay of treatment is pharmacotherapy. Nonpharmacologic methods, such as orthotic devices and joint stabilizations along with behavioral methods, should be explored. Anesthetic and neurosurgical procedures are performed on a limited number of patients based on the prognosis, intractable nature of pain, and favorable risk/benefit ratio. Newer oral transmucosal fentanyl offers a favorable pharmacokinetic and pharmacodynamic profile and ease of administration.

Analgesics↗

PubMed2000

Endoscopic-guided direct endonasal approach for pituitary surgery.

BACKGROUND: Submucosal dissection of the nasal septum is often performed as part of the transseptal approach to the sella. To evaluate whether this submucosal dissection is a necessary component of this operation, we compared the morbidity of a direct transmucosal endonasal approach to that of the transseptal approach in patients undergoing pituitary surgery. METHODS: Forty-one consecutive patients undergoing pituitary surgery from January 1996 to March 1999 were included in this study. The first 21 patients underwent the standard transseptal operation through either a sublabial or columellar incision. The latter 20 patients were operated on through an endoscopically guided, direct endonasal exposure, without any submucosal dissection of the nasal septum. The operative morbidity, the duration of surgery, and the length of hospitalization for each group were compared. RESULTS: The sphenoid sinus exposure obtained through the endonasal route was comparable with the transseptal approach and was adequate for resection of most pituitary tumors. Although the morbidity of the two approaches was similar, patients undergoing the endonasal operation had less postoperative facial pain. Furthermore, the endonasal approach significantly decreased the length of the operation (116 minutes vs. 161 minutes, p = 0.002) and the duration of hospitalization (3.6 vs. 5.1 days, p = 0.003) as compared with the transseptal route. CONCLUSIONS: Morbidity of the endonasal approach to the sphenoid sinus is comparable to that of a conventional transseptal approach. By eliminating the submucosal dissection, the endonasal approach reduces postoperative facial discomfort and decreases length of surgery and hospitalization.

Adenoma↗

PubMed2000

Role of perforin in controlling B-cell hyperactivity and humoral autoimmunity.

To determine the role of perforin-mediated cytotoxic T lymphocyte (CTL) effector function in immune regulation, we studied a well-characterized mouse model of graft-versus-host disease (GVHD). Induction of acute GVHD using perforin-deficient donor T cells (pfp-->F1) initially resulted in features of acute GVHD, e.g., engraftment of both donor CD4(+) and CD8(+) T cells, upregulation of Fas and FasL, production of antihost CTL, and secretion of both Th1 and Th2 cytokines. Despite fully functional FasL activity, pfp donor cells failed to totally eliminate host B cells, and, by 4 weeks of disease, cytokine production in pfp-->F1 mice had polarized to a Th2 response. Pfp-->F1 mice eventually developed features of chronic GVHD, such as increased numbers of B cells, persistence of donor CD4 T cells, autoantibody production, and lupuslike renal disease. We conclude that in the setting of B- and T-cell activation, perforin plays an important immunoregulatory role in the prevention of humoral autoimmunity through the elimination of both autoreactive B cells and ag-specific T cells. Moreover, an ineffective initial CTL response can evolve into a persistent antibody-mediated response and, with it, the potential for sustained humoral autoimmunity.

Animals↗

PubMed2000

The nuclear receptor corepressor (N-CoR) contains three isoleucine motifs (I/LXXII) that serve as receptor interaction domains (IDs).

Unliganded thyroid hormone receptors (TRs) repress transcription through recruitment of corepressors, including nuclear receptor corepressor (N-CoR). We find that N-CoR contains three interaction domains (IDs) that bind to TR, rather than the previously reported two. The hitherto unrecognized ID (ID3) serves as a fully functional TR binding site, both in vivo and in vitro, and may be the most important for TR binding. Each ID motif contains a conserved hydrophobic core (I/LXXII) that resembles the hydrophobic core of nuclear receptor boxes (LXXLL), which mediates p160 coactivator binding to liganded nuclear receptors. Although the integrity of the I/LXXII motif is required for ID function, substitution of ID isoleucines with leucines did not allow ID peptides to bind to liganded TR, and substitution of NR box leucines with isoleucines did not allow NR box peptides to bind unliganded TR. This indicates that the binding preferences of N-CoR for unliganded TR and p160s for liganded TR are not dictated solely by the identity of conserved hydrophobic residues within their TR binding motifs. Examination of sequence conservation between IDs, and mutational analysis of individual IDs, suggests that they are comprised of the central hydrophobic core and distinct adjacent sequences that may make unique contacts with the TR surface. Accordingly, a hybrid peptide that contains distinct adjacent sequences from ID3 and ID1 shows enhanced binding to TR.

Amino Acid Motifs↗

PubMed2000

Use of the PFA-100 apparatus to assess platelet function in patients undergoing PTCA during and after infusion of c7E3 Fab in the presence of other antiplatelet agents.

The PFA-100 (Dade) is a new functional whole blood analyzer, the accuracy and reliability of which have been evaluated in von Willebrand disease and during acetyl salicylate acid therapy. This new test has the advantages of rapidity and simplicity. It may be useful to monitor new antiplatelet agents, such as GPIIb/IIIa receptor antagonists. The objective of this study was to assess the PFA-100 in comparison with aggregometry and with the percentage of blockaded receptors GPIIb/IIIa during and after c7E3 Fab infusion in fifteen patients undergoing PTCA. Our results showed a change of closure time values from normal to abnormal within a small margin of flow cytometric values (60-75% of blockaded receptors), and moreover a variable platelet response to long-term low dose aspirin treatment in agreement with aggregometry. No influence with heparin was observed. In conclusion, this study shows that PFA-100 may be helpful in the decision making for additional antiaggregant therapy before PTCA or in monitoring long-term GPIIb/IIIa receptor antagonist treatment.

Abciximab↗

PubMed2000

Plasma levels of tumor necrosis factor-alpha (TNF-alpha) are essentially dependent on visceral fat amount in type 2 diabetic patients.

TNF-alpha is considered as one of the potential determinants of insulin resistance. However several data suggest that TNF-alpha expression itself, could be modulated by the degree of adiposity and/or plasma insulin levels. To clarify the determinants of plasma TNF-alpha levels in type 2 diabetes mellitus, we studied the impact of intensive insulin treatment on plasma TNF-alpha levels in 16 type 2 diabetic subjects with failure to oral antidiabetic medication (HbA1c: 10.8 +/- 1.2 %). Furthermore, we analyzed the relationship between plasma TNF-alpha levels and total or regional body fat measurements using anthropometry, bienergetic absorptiometry and computed tomography in a cohort of 33 caucasian obese type 2 diabetic subjects (BMI: 32.2 +/- 4.4 kg/m(2) ). The plasma TNF-alpha level was neither affected by plasma glucose level variations nor intensive insulin treatment despite a 37 % decrease in daily insulin needs at the end of insulin therapy (total duration: 11.5 +/- 2.0 days). The plasma TNF-alpha level was similar in men and women and unrelated to age, fasting glycemia or HbA1c. A relationship was highlighted with BMI (r =0.39, p <0.02), but not with total fat mass. This relationship was only dependent on the intra-abdominal fat mass amount as assessed by the waist-to-hip circumference ratio (r =0.52, p <0.01) and the visceral adipose tissue area (r =0.56, p <0. 01). These results show that plasma TNF-alpha levels are essentially dependent on visceral fat amount, thus suggesting that TNF-alpha could be one of the factors mediating insulin resistance and cardiovascular risk in obese type 2 diabetic patients.

Absorptiometry, Photon↗

PubMed2000

[Determination of polymorphonuclear neutrophil adhesion receptors. Effect of pre-analytic factors].

UNLABELLED: Polymorphonuclear neutrophil (PMN) adherence receptors expression varies with leukocyte activation state. Their quantification need accurate and inter-laboratories reproducible methods, without artefactual activation. OBJECTIVE: The aim of this study was to study the influence of cell preparation on PMN adherence receptors expression. MATERIALS AND METHODS: It was proposed to quantify, using immunolabeling standard (QIFIKIT(R), Dako), surface expression of the main adherence receptors (L-selectin and B(2) integrins), from different preparations of PMN: total blood collected with EDTA, isolated PMN by density gradient Polymorphprep(TM) 1,113 (Nycomed Pharma) and formaldehyde fixed PMN. RESULTS: A decrease of all receptors was noted after isolation and fixation of PMN, in comparison with whole blood PMN analysis. These results differed from data previously reported since, in these studies, activated phenotypes (increased of B(2) integrins) were observed after isolation and fixation methods. CONCLUSION: The present study provides strong evidence that pre-analytical conditions are sources of biological variations and thus extreme care must be taken in the interpretation of results. It underlines the interest of consensual practices for these pre-analytic and analytic parameters in order to compare results in multicenter and longitudinal studies.

CD18 Antigens↗

PubMed2000

[Platelet-leukocyte interactions in coronary heart disease: pathophysiology, clinical relevance, pharmacological modulation].

The interactions between leukocytes and endothelial cells have been studied extensively under conditions of ischemia and reperfusion. In contrast, attraction of leukocytes by platelets at the site of damage is poorly understood. This recruitment facilitates inflammation and atherogenesis. Studies performed ex vivo in coronary artery disease show that neutrophil-platelet adhesion increases in unstable angina, coronary angioplasty and coronary artery bypass surgery, in comparison with stable angina. Experimental works have shown the major role of platelet P-selectin in platelet-leukocyte interactions, and of fibrinogen, which is the ligand of both platelets and leukocytes (B2 integrins). Studied performed in anti-GPIIb/IIIa-treated patients demonstrate a modulation, as inhibition, of platelet-leukocyte interactions. This new drug inhibits platelet function and coagulation, and moreover inflammation.

Abciximab↗

PubMed1999

Regulation of BRCA1 by protein degradation.

BRCA1, a tumor suppressor protein implicated in hereditary forms of breast and ovarian cancer, is transcriptionally regulated in a proliferation-dependent manner. In this study, we demonstrate a substantial role for proteolysis in regulating the BRCA1 steady-state protein level in several cell lines. N-acetyl-leu-leu-norleucinal (ALLN), an inhibitor of the proteasome, calpain, and cathepsins, caused BRCA1 protein to accumulate in the nucleus of several human breast, prostate, and melanoma cell lines which express low or undetectable basal levels of BRCA1 protein, but not in cells with high basal expression of BRCA1. Protease inhibition did not increase BRCA1 synthesis, nor change its mRNA level, but it dramatically prolonged the protein's half-life. In contrast to ALLN, lactacystin and PS341, two specific proteasome inhibitors, as well as calpastatin peptide and PD150606, two selective calpain inhibitors, had no effect on BRCA1 stability, whereas ALLM, an effective calpain and cathepsin inhibitor but weak proteasome inhibitor, did stimulate accumulation of BRCA1. Moreover, three inhibitors of acidic cysteine proteases, chloroquine, ammonium chloride and bafilomycin, were as effective as ALLN. These results demonstrate that degradation by a cathepsin-like protease in fine balance with BRCA1 transcription is responsible for maintaining the low steady-state level of BRCA1 protein seen in many cancer cells.

BRCA1 Protein↗

PubMed1999

Apparent MHC-independent stimulation of CD8+ T cells in vivo during latent murine gammaherpesvirus infection.

Like EBV-infected humans with infectious mononucleosis, mice infected with the rodent gammaherpesvirus MHV-68 develop a profound increase in the number of CD8+ T cells in the circulation. In the mouse model, this lymphocytosis consists of highly activated CD8+ T cells strikingly biased toward V beta 4 TCR expression. Moreover, this expansion of V beta 4+CD8+ T cells does not depend on the MHC haplotype of the infected animal. Using a panel of lacZ-inducible T cell hybridomas, we have detected V beta 4-specific T cell stimulatory activity in the spleens of MHV-68-infected mice. We show that the appearance and quantity of this activity correlate with the establishment and magnitude of latent viral infection. Furthermore, on the basis of Ab blocking studies as well as experiments with MHC class II, beta2-microglobulin (beta2m) and TAP1 knockout mice, the V beta 4-specific T cell stimulatory activity does not appear to depend on conventional presentation by classical MHC class I or class II molecules. Taken together, the data indicate that during latent infection, MHV-68 may express a T cell ligand that differs fundamentally from both conventional peptide Ags and classical viral superantigens.

Animals↗

PubMed1999

Cyclic AMP induces inhibition of cyclin A expression and growth arrest in human hepatoma cells.

Classical cytotoxic therapy has been minimally useful in the treatment of hepatocellular carcinoma. In an effort to develop a new approach to the treatment of this neoplasm, we have investigated the signal transduction pathways regulating the growth of human hepatoma cells. In the data reported here, cyclic AMP (cAMP), a negative growth regulator for many cells of epithelial origin, induced G1 synchronization and apoptosis in the HepG2 human hepatoma cell line. The effects of cAMP on the components of the G1/S transition were analyzed. There was no detectable effect of two different cAMP analogs, 8-bromo cAMP or dibutyryl cAMP on the level of the D-type cyclins, cyclin E, cyclin-dependent kinase 2, cyclin-dependent kinase 4, p53, or the cyclin-dependent kinase inhibitors p21 or p27. In contrast, the cAMP analogs induced a dramatic downregulation of cyclin A protein, cyclin A messenger RNA, and cyclin A-dependent kinase activity. Cyclin A-dependent kinase has been shown to be required for the G1-S transition. Furthermore, cyclin A deregulation has been implicated in the pathogenesis of hepatocellular carcinoma. The data reported here suggest a novel signal transduction-based approach to hepatoma therapy.

Apoptosis↗

PubMed1999

Regulation of actin cytoskeleton in lymphocytes: PKC-delta disrupts IL-3-induced membrane ruffles downstream of Rac1.

In the murine pre-B lymphoid cell line Baf3, the presence of IL-3 is required for the formation of membrane ruffles that intensely stain for actin and are responsible for the elongated cell phenotype. Withdrawal of IL-3 dissolves ruffled protrusions and converts the cell phenotype to round. Flow cytometric analysis of the cell shape showed that an inactive analog of Rac1 but not inactive RhoA or inactive cdc42 rounds the cells in the presence of IL-3. Constitutively activated Rac1 restores the elongated cell phenotype to IL-3-starved cells. We conclude that the activity of Rac1 is necessary and sufficient for the IL-3-induced assembly of membrane ruffles. Similar to the IL-3 withdrawal, phorbol 12-myristate 13-acetate (PMA) dissolves actin-formed membrane ruffles and rounds the cells in the presence of IL-3. Flow cytometric analysis of the cell shape demonstrated that in the presence of IL-3 the PMA-induced cell rounding cannot be abolished by constitutively active Rac1 but can be imitated by inactive Rac1. These data indicate that PMA disrupts the IL-3 pathway downstream of Rac1. Cells rounded by PMA return to the elongated phenotype concomitantly with PKC depletion. PMA-induced cell rounding can be reversed by the PKC-specific inhibitor GF109203X. Experiments with overexpression in Baf3 of individual PKC isoforms and a dominant negative PKC-delta indicate that activation of PKC-delta but not other PKC isoforms is responsible for disruption of membrane ruffles.

Actins↗

PubMed1999

A new spin on an old model: in vivo evaluation of disease progression by magnetic resonance imaging with respect to standard inflammatory parameters and histopathology in the adjuvant arthritic rat.

OBJECTIVE: To noninvasively examine the pathogenesis of rat adjuvant-induced arthritis (AIA) by magnetic resonance imaging (MRI), and to correlate MRI indices of disease progression with classic inflammatory parameters and histologic evaluation. METHODS: AIA was established in male Lewis rats following subcutaneous injection in the right hindpaw with 0.5 mg of heat-killed Mycobacterium butyricum suspended in light mineral oil. In vivo MRI evaluations of soft tissue and bony changes in AIA rats with matched histopathology were correlated with changes in left hindpaw volumes, circulating leukocytes, acute-phase reactants, and urinary collagen crosslinks throughout the disease process. RESULTS: MRI of arthritic tibiotarsal joints of the uninjected left hindpaws from AIA rats demonstrated 2 distinct phases of disease activity. The first phase, apparent between days 10 and 18, was characterized by periarticular inflammation with marked synovitis, synovial fibroplasia, and distension of the joint capsule into the surrounding tissue. The secondary phase, occurring between days 18 and 30, was marked by continued soft tissue inflammation, periostitis with osteolysis, and periosteal new bone formation progressing to a state of near complete ankylosis by day 30. These 2 phases of disease activity observed by MRI paralleled biochemical, cellular, and histologic markers of disease progression. CONCLUSION: MRI can be used to noninvasively detect, monitor, and quantify the chronic synovitis and progressive destruction of soft tissue and bone in live AIA rats, thereby improving the ability to evaluate disease progression in this preclinical animal model of rheumatoid arthritis.

Animals↗

PubMed1999

The benzoquinone ansamycin geldanamycin stimulates proteolytic degradation of focal adhesion kinase.

FAK is a nonreceptor tyrosine kinase involved in adhesion-mediated signal transduction whose level of expression is related to the invasiveness of malignant tumors. In seeking strategies to downregulate FAK, we treated various cell lines in vitro with the benzoquinone ansamycin geldanamycin (GA) which was previously described as a tyrosine kinase inhibitor, but recently has been shown to exert its effects by interfering with the chaperone function of members of the hsp90 family of heat-shock proteins. We evaluated the effects of benzoquinone ansamycins on FAK steady-state protein level and FAK half-life in breast and prostate carcinoma, Ewing's sarcoma, and 3T3 fibroblasts. Our data demonstrate that GA stimulates the proteolytic degradation of FAK in all cell lines examined and markedly reduces the half-life of newly synthesized FAK protein without significantly altering the level of FAK mRNA. These data demonstrate FAK to be another tyrosine kinase sensitive to the destabilizing effects of benzoquinone ansamycins and further show that small molecule-mediated pharmacologic modulation of FAK protein level is a feasible approach to the interdiction of FAK function.

3T3 Cells↗

PubMed1999

Endoscopic ultrasound (EUS) and EUS-guided fine-needle aspiration (FNA) of liver lesions.

BACKGROUND: Endoscopic ultrasonography (EUS) is not traditionally thought to be clinically applicable in liver imaging. EUS-guided fine-needle aspiration of the liver has not been well described. METHODS: A prospective study was conducted in which 574 consecutive patients with a history or suspicion of gastrointestinal or pulmonary malignant tumor undergoing upper EUS examinations underwent EUS evaluation of the liver. Fourteen (2.4%) patients were found to have focal liver lesions and underwent EUS-guided fine-needle aspiration. RESULTS: The median largest diameter of the liver lesions was 1.1 cm (range 0.8 to 5.2 cm). The mean number of passes was 2.0 (range 1 to 5 passes). All fine-needle passes yielded an adequate specimen. One of the 14 patients underwent EUS-guided fine-needle aspiration of 2 liver lesions. Fourteen of the 15 liver lesions sampled by means of EUS-guided fine-needle aspiration were malignant and one was benign. Before EUS, computed tomography (CT) depicted liver lesions in only 3 of 14 (21%) patients. Seven of 14 patients had a known cancer diagnosis. For the other 7, the initial diagnosis of cancer was made by means of EUS-guided fine-needle aspiration of the liver. There were no immediate or late complications. CONCLUSIONS: EUS can detect small focal liver lesions that are not detected at CT. Findings of EUS-guided fine-needle aspiration can confirm a cytologic diagnosis of liver metastasis and establish a definitive M stage that may change clinical management.

Adult↗

PubMed1999

Effect of intravenous glutamine on duodenal mucosa protein synthesis in healthy growing dogs.

To determine whether glutamine acutely stimulates protein synthesis in the duodenal mucosa, five healthy growing dogs underwent endoscopic biopsies of duodenal mucosa at the end of three 4-h primed, continuous intravenous infusions of L-[1-13C]leucine on three separate days, while receiving intravenous infusion of 1) saline, 2) L-glutamine (800 micromol. kg-1. h-1), and 3) isonitrogenous amounts of glycine. The three infusions were performed after 24 h of fasting, a week apart from each other and in a randomized order. Glutamine infusion induced a doubling in plasma glutamine level, and glycine caused a >10-fold rise in plasma glycine level. During intravenous infusions of [13C]leucine, the plasma leucine labeling attained a plateau value between 3.22 and 3.68 mole % excess (MPE) and [13C]ketoisocaproate ([13C]KIC) of 2.91-2. 84 MPE; there were no significant differences between glutamine, glycine, and saline infusion days. Plasma leucine appearance rate was 354 +/- 33 (SE), 414 +/- 28, and 351 +/- 35 micromol. kg-1. h-1 (not significant) during glycine, saline, and glutamine infusion, respectively. The fractional synthetic rate (FSR) of duodenal mucosa protein was calculated from the rise in protein-bound [13C]leucine enrichment in the biopsy sample, divided by time and with either plasma [13C]KIC or tissue free [13C]leucine as precursor pool enrichment. Regardless of the precursor pool used in calculations, duodenal protein FSR failed to rise significantly during glutamine infusion (65 +/- 11%/day) compared either with saline (84 +/- 18%/day) or glycine infusion days (80 +/- 15%/day). We conclude that 1) plasma [13C]KIC and tissue free [13C]leucine can be used interchangeably as precursor pools to calculate gut protein FSR; and 2) short intravenous infusion of glutamine does not acutely stimulate duodenal protein synthesis in well-nourished, growing dogs.

Aging↗