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Biomedical subjects

T T Huynh

Publications and source records attributed to T T Huynh.

At least 19 recordsLinked to original sources
PubMed2006

Mechanical stretch has contrasting effects on mediator release from bronchial epithelial cells, with a rho-kinase-dependent component to the mechanotransduction pathway.

INTRODUCTION: In vivo, the airway epithelium stretches and relaxes with each respiratory cycle, but little is known about the effect this pattern of elongation and relaxation has on bronchial epithelial cells. We have used a model of cell deformation to measure the effect of stretch on inflammatory cytokine release by the BEAS 2B cell line, and to examine the method of mechanotransduction in these cells. METHODS: BEAS 2B cells were cyclically stretched using the Flexercell system. IL-8 and RANTES protein and RNA levels were measured after different elongations, rates and duration of stretch. An inhibitor of Rho (Ras Homologous)-associated kinases was used, to assess the effect of blocking downstream of integrin signalling. Immunofluorescent staining of paxillin was used to study the effect of stretch on the distribution of focal contacts and the organisation of the actin cytoskeleton. RESULTS: IL-8 release by BEAS 2B cells was increased by cytokine stimulation and stretch, whereas RANTES levels in the cell supernatant decreased after stretch in a dose-, time- and rate-dependent manner. Thirty percent elongation at 20 cycles/min for 24h increased IL-8 levels by over 100% (P < 0.01). Blocking rho kinase using Y-27632 inhibited the effect of stretch on IL-8 release by the BEAS 2B cells. Immunofluorescent staining demonstrated that stretch caused dramatic disassembly of focal adhesions and resulted in the redistribution of paxillin to the peri-nuclear region. CONCLUSION: This study demonstrates a marked effect of stretch on bronchial epithelial cell function. We propose that stretch modulates epithelial cell function via the activation of rho kinases. The observation that stretch promotes focal adhesion disassembly suggests a mechanism whereby focal adhesion turnover (coordination of assembly and disassembly) is essential for mechanotransduction in bronchial epithelial cells.

Amides↗
PubMed2005

Expression of CXCR6 and its ligand CXCL16 in the lung in health and disease.

BACKGROUND: Chemokine receptors (CR) play an important role in T cell migration, but their contribution to lung trafficking is unclear. OBJECTIVE: We hypothesized that if a particular CR was involved in T cell homing its expression would be enriched on lung T cells compared with peripheral blood T cells (PBT). METHODS: We have measured the CR expression on BAL T cells from patients with sarcoid, other interstitial lung diseases (ILD), asthma and healthy volunteers. RESULTS: Of 14 CR studied in sarcoid, CXCR6 expression was the most markedly increased in the lung compared with the blood, a finding that was also seen in ILD patients. A striking although lesser increase was also seen in asthmatics and healthy controls. Analysis of expression of the CXCR6 ligand, CXCL16, by immunohistochemistry suggested that alveolar macrophages (AM) were the major source of CXCL16 in the lung. AM expressed mRNA for CXCL16 and released nanogram quantities after adhesion to plastic as shown by RT-PCR, Western blotting and ELISA. Bronchoalveolar lavage (BAL) fluid from all subjects contained large amounts of CXCL16. The full-length CXCL16 was the predominant isoform in AM lysates, supernatants and BAL. CONCLUSION: This data suggests that CXCR6 and CXCL16 may play a role in T cell recruitment to the lung.

Adult↗
PubMed2003

Kaempferol-induced growth inhibition and apoptosis in A549 lung cancer cells is mediated by activation of MEK-MAPK.

A vast variety of naturally occurring substances have been shown to protect against experimental carcinogenesis and an increasing amount of evidence suggests that kaempferol may have cancer chemopreventative properties. However, the precise underlying protective mechanisms are poorly understood. To elucidate these mechanisms, we challenged human lung cancer cell line A549 with kaempferol and investigated its effects upon cellular growth and signal transduction pathways. Treatment of A549 cells with kaempferol resulted in a dose- and time-dependent reduction in cell viability and DNA synthesis with the rate of apoptosis equivalent to 0.9+/-0.5, 5.2+/-1.5, 16.8+/-2.0, 25.4+/-2.6, and 37.8+/-4.5% on treatment with 0, 17.5, 35.0, 52.5, and 70.0 microM kaempferol, respectively. Concomitantly, kaempferol treatments led to a 1.2-, 2.7-, 3.3-, and 3.4-fold increase in Bax. Similar elevations were also observed in Bad which increased 1.2-, 3.3-, 3.7-, and 4.7-fold, respectively, as compared to control. Bcl-2 and Bcl-xL expression were inhibited in a dose-dependent fashion. While the Akt-1 and phosphorylated Akt-1 were inhibited, the mitogen-activated protein kinase (MAPK) was activated upon kaempferol treatment. Kaempferol induced apoptosis was associated with the cleavage of caspase-7 and poly ADP-ribose polymerase (PARP). Inhibition of MEK1/2 but not PI-3 kinase blocked kaempferol-induced cleavage of caspase-7, PARP cleavage, and apoptosis. The results suggest that inactivation of Akt-1 and alteration of Bcl-2 family of proteins are not sufficient for kaempferol to induce apoptosis and activation of MEK-MAPK is a requirement for kaempferol-induced cell death machinery in A549 cells.

Antineoplastic Agents↗
PubMed2002

Failure of steroid regulation of the MMTV promoter in a small cell lung cancer cell line is caused by a DNA sequence flanking the glucocorticoid response element.

We have previously described a panel of human small cell lung carcinoma (SCLC) cell lines that have profound glucocorticoid resistance, resulting from various molecular defects in glucocorticoid signalling. However, in one SCLC cell line, CORL103, the cause of the resistance is unknown. These cells are refractory to dexamethasone stimulation of MMTV even when exogenous wild-type glucocorticoid receptor (GR) is co-transfected. This is in contrast to cell lines DMS79 and CORL24 where resistance is overcome by transfection of the wild-type receptor. Sequencing of the GR from CORL103 cells revealed two point mutations, but neither of these induced dominant negative activity. Steroid hormone resistance extended to mineralocorticoid and progesterone receptor (MR, PR) activation of MMTV-luc, whereas oestrogen and thyroid hormone receptor transactivation were normal. A simpler reporter, TAT3-luc, containing three copies of the tyrosine aminotransferase glucocorticoid response element (GRE), was responsive when transfected into CORL103 cells with GR, MR and PR expression vectors and activated with their respective ligands. Similarly, pHH-luc and pAH-luc (truncated MMTV variants containing the GRE region, both derived from a different strain of MMTV), were effectively transactivated with dexamethasone. This suggests that the minor changes in the flanking sequence of the MMTV promoter are critically important in determining steroid responsiveness in CORL103 cells. We propose that minor differences in MMTV may determine recruitment of co-factors, which destabilise GR binding to the MMTV GREs. These findings represent a new, selective, model of glucocorticoid resistance that may explain specific cell and target gene differences in glucocorticoid sensitivity.

3' Flanking Region↗
PubMed2001

Staged repair of extensive aortic aneurysms: morbidity and mortality in the elephant trunk technique.

BACKGROUND: Extensive aortic aneurysms (ascending aorta, aortic arch, and descending or thoracoabdominal aorta) require innovative surgical techniques. Some surgeons advocate a single procedure with long periods of profound hypothermia, whereas others use a staged approach. We adopted a two-staged procedure (elephant trunk technique) in 1991 for elective repair of extensive aortic aneurysms. METHODS AND RESULTS: Between February 1991 and May 2000, we performed a total of 1146 aortic aneurysm operations. Of these, 182 (15.9%) operations were first- or second-stage elephant trunk procedures, performed in a total of 117 patients. Stage 1 was completed in all 117 patients. Stage 2 was completed in 65 (55.6%) of 117 patients. Thirty-day mortality rate for the first stage was 5.1% (6 of 117). Mortality rate during the interval between operations was 3.6% (4 of 111), of which 75% (3 of 4) were the result of aneurysm rupture. Thirty-day mortality rate for the second stage was 6.2% (4 of 65). A total of 43 patients did not return for second-stage repair. Among these patients, within an average period of 3.4 years (range, 1.5 months to 4.9 years), 13 of 43 (30.2%) died, 4 of 13 (30.8%) as the result of rupture. Two of 117 (1.7%) first-stage patients had postoperative stroke. No spinal cord dysfunction occurred in second-stage patients. CONCLUSIONS: Extensive aortic aneurysms can be repaired with acceptable morbidity and mortality rates through the use of the elephant trunk technique. Death was most commonly the result of rupture, both in interval patients awaiting scheduled second-stage repair and in patients who did not return. After the first stage, prompt treatment of the remaining segment is crucial to the success of staged repair.

Adolescent↗
PubMed2001

The genes of two G-proteins involved in protein transport in Pichia pastoris.

Members of the Rab protein family play essential roles in vesicle fusion during protein secretion and represent highly conserved GTP binding proteins. The Saccharomyces cerevisiae Sec4p and Ypt1p, promoting vesicle fusion at the plasma membrane and in ER-Golgi transport, respectively, are among the best characterised yeast members. We have here cloned the Pichia pastoris SEC4 homologue using a S. cerevisiae SEC4 probe. In addition we isolated a crosshybridising clone encoding another Rab-/Ypt-like protein. The deduced full-length PpSec4p comprises 204 amino acid residues with an over all identity of 64% to the Sec4p from S. cerevisiae and 72% to the Candida albicans Sec4p. The YPT-like gene encodes a 216 amino acid residue protein showing highest similarity to the S. cerevisiae Ypt10p and Ypt53p. Both PpSec4p and the Ypt-like protein carry a -Cys-Cys C-terminus, indicating that these proteins are targets for geranyl-geranylation by a type II prenyltransferase.

Amino Acid Motifs↗
PubMed2001

Descending thoracic aortic aneurysm: surgical approach and treatment using the adjuncts cerebrospinal fluid drainage and distal aortic perfusion.

BACKGROUND: Neurologic deficit (paraplegia or paraparesis) remains a significant morbidity in the repair of descending thoracic aortic aneurysm. METHODS: Between February 1991 and February 2000, we operated on 182 patients for descending thoracic aortic aneurysm. For the purpose of this study-to identify the impact of the combined adjuncts distal aortic perfusion and cerebrospinal fluid (CSF) drainage on neurologic outcome-we selected the 148 of 182 nonemergent patients who had received conventional treatment (simple cross-clamping with or without adjuncts). The mean patient age was 61 years, and 49 of the 148 (33%) patients were women. Nine of the 148 patients (6%) had acute type B dissections. We compared the results of 105 of the 148 patients (71%) who received the combined adjuncts of CSF drainage and distal aortic perfusion with the remaining 43 (29%) patients who underwent repair using the simple cross-clamp with or without the addition of a single adjunct. RESULTS: Overall 30-day mortality was 13 of 148 patients (8.8%). Overall early neurologic deficit was 4 of 148 (2.7%): 1 of 105 (0.9%) patients who had received distal aortic perfusion and CSF drainage, versus 3 of 43 (7%) in all other patients (p < 0.04). CONCLUSIONS: In our practice the use of the combined adjuncts of CSF drainage and distal aortic perfusion has all but eliminated the incidence of immediate postoperative neurologic deficit in nonemergent patients with aneurysms of the descending thoracic aorta.

Adolescent↗
PubMed2001

Neurologic outcome after thoracic and thoracoabdominal aortic aneurysm repair.

BACKGROUND: Neurologic deficit (paraparesis and paraplegia) after repair of the thoracic and thoracoabdominal aorta remains a devastating complication. The purpose of this study was to determine the effect of cerebrospinal fluid drainage and distal aortic perfusion upon neurologic outcome during repair of thoracic and thoracoabdominal aortic aneurysm (TAAA) repair. METHODS: Between February 1991 and March 2000, we performed 654 repairs of the thoracic and thoracoabdominal aorta. The median age was 67 years and 420 (64%) patients were male. Forty-five cases (6.9%) were performed emergently. Distribution of TAAA was the following: extent I, 164 (25%); extent II, 165 (25%); extent III, 61 (9%); extent IV, 95 (15%); extent V, 23 (3.5%); and descending thoracic, 147 (22%). The adjuncts cerebrospinal fluid drainage and distal aortic perfusion were used in 428 cases (65%). RESULTS: Thirty-day mortality was 14% (94 of 654). The in-hospital mortality was 16% (106 of 654). Early neurologic deficits occurred in 33 patients (5.0%). Overall, 14 of 428 (3.3%) neurologic deficits were observed in the adjunct group, and 19 of 226 (8.4%) in the nonadjunct group (p = 0.004). When the adjuncts were used during extent II repair, the incidence was 10 of 129 (7.8%) compared with 11 of 36 (30.6%) in the nonadjunct group (p < 0.001). Multivariate analysis demonstrated that risk factors for neurologic deficit were cerebrovascular disease and extent of TAAA (II and III) (p < 0.05). CONCLUSIONS: The combined adjuncts of distal aortic perfusion and cerebrospinal fluid drainage demonstrated improved neurologic outcome with repair of thoracic and TAAAs. In extent II aneurysms, adjuncts continue to make a considerable difference in the outcome and to provide significant protection against spinal cord morbidity. Future research should focus on spinal cord protection in patients with high-risk extent II aneurysms.

Adolescent↗
PubMed2001

Local treatment with recombinant tissue factor pathway inhibitor reduces the development of intimal hyperplasia in experimental vein grafts.

BACKGROUND: Tissue factor (TF)-initiated thrombin generation has been implicated in the development of intimal hyperplasia after arterial injury. An increase in intimal TF expression has been shown to precede the development of intimal hyperplasia in vein grafts. This study examines the effects of local treatment with recombinant human tissue factor pathway inhibitor (rTFPI) in experimental vein grafts. METHODS: Thirty-six male New Zealand white rabbits underwent bypass grafting of the carotid artery by use of the reversed ipsilateral jugular vein and were divided into four groups. Twenty animals had ex vivo incubation with rTFPI treatment (50 microg x mL(-1); n = 10) or placebo vehicle (control; n = 10). Sixteen animals received both ex vivo incubation and in vivo gel treatment with rTFPI (50 microg. mL(-1); n = 8) or without rTFPI (gel-control; n = 8). After operation, vein grafts were harvested at 3 days for immunohistochemical and Western analyses and at 28 days for histomorphologic study. RESULTS: Western analysis demonstrated a 6.2-fold reduction in the expression of TF protein with rTFPI treatment in comparison to without rTFPI treatment. CD-18 leukocyte staining was diminished, whereas Tie-2 endothelial staining was increased in all rTFPI-treated vein grafts, compared with control and gel-control vein grafts. Intimal thickness was reduced by 21% with ex vivo rTFPI treatment compared with placebo (69 +/- 4 versus 87 +/- 5 microm; P <.05) and by 30% with the addition of rTFPI in vivo compared with gel-control (60 +/- 4 versus 86 +/- 5 microm; P <.01). CONCLUSION: Local administration of rTFPI exerts early beneficial effects and limits the development of intimal hyperplasia in vein grafts. Therefore blocking TF-mediated pathway may offer new therapeutic options to reduce vein graft failure.

Animals↗
PubMed2001

Pheochromocytomas in von Hippel-Lindau syndrome and multiple endocrine neoplasia type 2 display distinct biochemical and clinical phenotypes.

This study examined the mechanisms linking different biochemical and clinical phenotypes of pheochromocytoma in multiple endocrine neoplasia type 2 (MEN 2) and von Hippel-Lindau (VHL) syndrome to underlying differences in the expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis, and of phenylethanolamine N-methyltransferase (PNMT), the enzyme that converts norepinephrine to epinephrine. Signs and symptoms of pheochromocytoma, plasma catecholamines and metanephrines, and tumor cell neurochemistry and expression of TH and PNMT were examined in 19 MEN 2 patients and 30 VHL patients with adrenal pheochromocytomas. MEN 2 patients were more symptomatic and had a higher incidence of hypertension (mainly paroxysmal) and higher plasma concentrations of metanephrines, but paradoxically lower total plasma concentrations of catecholamines, than VHL patients. MEN 2 patients all had elevated plasma concentrations of the epinephrine metabolite, metanephrine, whereas VHL patients showed specific increases in the norepinephrine metabolite, normetanephrine. The above differences in clinical presentation were largely explained by lower total tissue contents of catecholamines and expression of TH and negligible stores of epinephrine and expression of PNMT in pheochromocytomas from VHL than from MEN 2 patients. Thus, mutation-dependent differences in the expression of genes controlling catecholamine synthesis represent molecular mechanisms linking the underlying mutation to differences in clinical presentation of pheochromocytoma in patients with MEN 2 and the VHL syndrome.

Adolescent↗
PubMed2001

Vascular endothelial growth factor restores corporeal smooth muscle function in vitro.

PURPOSE: The therapeutic use of vasculogenic growth factors has been successfully demonstrated in models of organ ischemia. We determined whether vascular endothelial growth factor (VEGF) would reverse corporeal smooth muscle dysfunction in the hypercholesterolemic rabbit model of erectile dysfunction. MATERIALS AND METHODS: A total of 36 New Zealand White rabbits were fed a normal (12) or 1% cholesterol (24) diet and treated after 6 weeks with 0.9 mg. VEGF or vehicle. At 6 weeks 24 rabbits received a single intracavernous dose and 12 received a single intravenous bolus of either drug. Ten days after injection corporeal smooth muscle function was analyzed after relaxation to acetylcholine and sodium nitroprusside using isometric tension studies. Corporeal sections were assessed for smooth muscle content with f-actin staining and VEGF expression by immunohistochemical study and enzyme-linked immunosorbent assay. RESULTS: Endothelium dependent (acetylcholine) and nitric oxide mediated (sodium nitroprusside) smooth muscle relaxation were impaired in cholesterol fed animals (p = 0.021 and 0.003, respectively). Intracavernous VEGF treatment restored sodium nitroprusside mediated relaxation to normal (p = 0.015) and intravenous VEGF restored acetylcholine and sodium nitroprusside mediated relaxation (p = 0.014 and 0.018, respectively). Decreased smooth muscle content was noted in cholesterol fed animals versus normal diet controls (p = 0.008), which was not affected by VEGF treatment (p = 0.450). Corporeal endothelial cell content was increased after intracavernous but not intravenous VEGF treatment (p = 0.001 and 0.385, respectively). VEGF expression was augmented after treatment with recombinant VEGF (p <0.001). CONCLUSIONS: VEGF administration variably mitigated the impairment of corporeal smooth muscle relaxation in the hypercholesterolemic rabbit model of erectile dysfunction.

Animals↗
PubMed2000

Characterization of dopamine-mediated relaxation in experimental vein bypass grafts.

BACKGROUND: Dopamine is an endogenous inotropic agent commonly used during coronary artery surgery and in the medical therapy of a revascularized patient. In this study the responses of intimal hyperplastic vein grafts to dopamine are examined. METHODS: The in vitro isometric tension responses to dopamine of common carotid jugular vein bypass grafts in New Zealand White rabbits were determined. The responses were compared to those obtained in the jugular vein and in the common carotid artery. Both endothelialized and denuded vessels were precontracted with prostaglandin F(2alpha) and the responses to dopamine were assessed. The contributions of nitric oxide and prostanoids to the response were also determined. RESULTS: Each vessel showed a biphasic dose response to dopamine with relaxation at low concentrations followed by contraction at high concentrations. Dopamine relaxation in the jugular vein was endothelial independent while in the carotid artery it was endothelial dependent and decreased. The sensitivity of both vessels was significantly greater than the vein graft (6.62 +/- 0.12; P < 0. 05); however, after endothelial denudation, the sensitivity of dopamine-mediated relaxation of the vein graft (8.91 +/- 0.09) was significantly enhanced. Preincubation with L-NMMA (to block NO synthesis) inhibited vein graft relaxation to dopamine and preincubation with indomethacin (to block cyclooxygenase activity) inhibited carotid artery relaxation to dopamine. Addition of phenoxybenzamine, a broad alpha-adrenergic antagonist, enhanced dopamine relaxation in the jugular vein and depressed the relaxation in the carotid artery. There was no effect on the dopamine response in the vein graft. Jugular vein and carotid artery responded to dopamine with cholera toxin-sensitive (Galpha(s)) responses. In contrast, dopamine relaxation in the vein graft was enhanced by inhibition of Galpha(s). CONCLUSION: Dopamine relaxation in vein grafts is mediated in part by NO but not by either prostanoids or alpha-adrenergic receptor activation. It is diminished compared to native vessels due to an endothelium-dependent, Galpha(s)-mediated pathway.

Adjuvants, Immunologic↗
PubMed2000

Reversal of twice-delayed neurologic deficits with cerebrospinal fluid drainage after thoracoabdominal aneurysm repair: a case report and plea for a national database collection.

Delayed neurologic deficits are an uncommon yet devastating complication of thoracoabdominal aortic aneurysm repair. The mechanisms involved in the development of delayed spinal cord ischemia remain ill defined. We report a case of complete reversal of delayed neurologic deficits with postoperative cerebrospinal fluid (CSF) drainage. After a thoracoabdominal aneurysm extent I repair, the patient experienced delayed paraplegia at 6 hours and again at 34 hours after the operation, with elevated CSF pressure (>10 mm Hg) on both occasions. Prompt CSF decompression completely reversed the neurologic deficits within hours after onset. The findings in this case further support the role of CSF drainage in spinal cord protection for patients who undergo thoracoabdominal aneurysm repair and make a plea for a national database collection.

Aged↗
PubMed2000

Delayed onset of neurologic deficit: significance and management.

As contemporary adjuncts have substantially reduced the overall incidence of paraplegia and paraparesis after the surgical repair of thoracoabdominal aortic aneurysm, delayed-onset neurologic deficit has emerged as a significant clinical entity. It is generally agreed that neurologic deficits are attributable to the duration of spinal cord ischemia sustained during aortic cross-clamping. Factors known to increase the risk of spinal cord injury include the aneurysm extent, aortic cross-clamp time, aneurysm rupture, and associated acute aortic dissection. Clinically and experimentally, studies have shown different adjuncts to improve spinal cord protection, providing further insights into the pathophysiology of spinal cord ischemia. However, the pathophysiology of delayed-onset spinal cord deficit after thoracoabdominal aortic aneurysm repair remains largely controversial. This review discusses the significance and management of delayed-onset neurologic deficit.

Aortic Aneurysm↗
PubMed1999

Reduction of lipid peroxidation with intraoperative superoxide dismutase treatment decreases intimal hyperplasia in experimental vein grafts.

BACKGROUND: Vein graft failure is commonly attributed to the development of intimal hyperplastic lesions. Oxidative stress has been implicated in the initiation and progression of atherosclerosis. In this study we examined the effects of local intraoperative treatment with polyethylene glycolated superoxide dismutase (PEG-SOD) on lipid peroxidation and on the development of intimal hyperplasia in experimental vein grafts. MATERIALS AND METHODS: Forty-one New Zealand White male rabbits had a right carotid interposition bypass graft using the ipsilateral reversed jugular vein. Sixteen animals received local PEG-SOD (4,100 units) treatment; 9 animals received the polyethylene glycol (PEG) vehicle without SOD; 16 animals were used as controls. Postoperatively, malondialdehyde (MDA, a product of lipid peroxidation) concentration and SOD activity were assessed in 3-day vein grafts by colorimetric spectrophotometry. To determine wall dimensions and vasomotor function, morphometric and isometric tension studies were performed on 28-day vein grafts. RESULTS: MDA concentration was increased 5. 7-fold (P < 0.05) in 3-day control vein grafts compared to ungrafted jugular veins. Intraoperative PEG-SOD treatment raised SOD activity 5.0-fold (P < 0.05) and reduced MDA concentration 8-fold (P < 0.05) in 3-day vein grafts compared to controls. At 28 days, intimal thickness was reduced by 35% with PEG-SOD treatment (54 +/- 4 vs 83 +/- 5; P < 0.001) compared to control vein grafts, without a change in medial thickness (77 +/- 4 vs 88 +/- 5; P = ns). The vasomotor functions of 28-day PEG-SOD-treated vein grafts to norepinephrine, serotonin, bradykinin, nitroprusside, and acetylcholine were not significantly changed when compared to controls. Treatment with PEG alone did not significantly alter lipid peroxidation, wall dimensions, or vasomotor function of vein grafts. CONCLUSION: This study demonstrates that intraoperative local treatment of vein grafts with PEG-SOD increases SOD activity and decreases lipid peroxidation for at least 3 days, resulting in reduced intimal hyperplasia at 28 days. These findings further implicate oxidative stress in the hyperplastic response of vein grafts and suggest a potential therapeutic role for PEG-SOD in the prevention of vein graft failure.

Animals↗