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Biomedical subjects

H T Nguyen

Publications and source records attributed to H T Nguyen.

At least 109 records · Page 6Linked to original sources
PubMed1998

Drosophila mef2 expression during mesoderm development is controlled by a complex array of cis-acting regulatory modules.

The function of the Drosophila mef2 gene, a member of the MADS box supergene family of transcription factors, is critical for terminal differentiation of the three major muscle cell types, namely somatic, visceral, and cardiac. During embryogenesis, mef2 undergoes multiple phases of expression, which are characterized by initial broad mesodermal expression, followed by restricted expression in the dorsal mesoderm, specific expression in muscle progenitors, and sustained expression in the differentiated musculatures. In this study, evidence is presented that temporally and spatially specific mef2 expression is controlled by a complex array of cis-acting regulatory modules that are responsive to different genetic signals. Functional testing of approximately 12 kb of 5' flanking region of the mef2 gene showed that the initial widespread mesodermal expression is achieved through a 280-bp twist-dependent enhancer. The subsequent dorsal mesoderm-restricted mef2 expression is mediated through a 460-bp dpp-responsive regulatory module, which involves the function of the Smad4 homolog Medea and contains several binding sites for Medea and Mad. The analysis also showed that regulated mef2 expression in the caudal and trunk visceral mesoderm, which give rise to longitudinal and circular gut musculatures, respectively, is under the control of distinct enhancer elements. In addition, mef2 expression in the cardioblasts of the heart is dependent upon at least two distinct enhancers, which are active at different periods during embryogenesis. Moreover, multiple regulatory elements are differentially activated for specific expression in presumptive muscle founders, prefusion myoblasts, and differentiated muscle fibers. Taken together, the presented data suggest that specific expression of the mef2 gene in myogenic lineages in the Drosophila embryo is the result of multiple genetic inputs that act in an additive manner upon distinct enhancers in the 5' flanking region.

Animals↗
PubMed1998

Phylogenetic analysis of SIV and STLV type I in mandrills (Mandrillus sphinx): indications that intracolony transmissions are predominantly the result of male-to-male aggressive contacts.

Natural SIVmnd and STLVmnd infections of mandrills in a colony at the Centre International de Recherches Médicales de Franceville (CIRMF) in Gabon were investigated by genetic analysis to determine the extent of intracolony transmission. SIVmnd pol sequence analysis indicates that the six strains present in the colony belong to the SIVmnd lentivirus subgroup previously defined according to the only available prototype sequence (SIVmndGB1), which originated from the same colony. The intraanimal nucleotide diversity (1.1-3.1%) was similar in range to that reported in individuals infected by other HIV/SIVs. The interanimal diversity (0.5-4.3%) was not significantly different from that observed in each individual mandrill, indicating an epidemiological link among the SIVmnd isolates of distinct animals within the colony. Phylogenetic analysis of these isolates, together with seroepidemiological and behavior surveillance within the colony, indicates a predominant male-to-male transmission of SIVmnd that probably occurred during bouts of interanimal aggression. Moreover, our results suggest one case of vertical transmission of SIVmnd from a naturally infected founder female to one of her six offspring. The first genetic analysis of STLV isolates from mandrills is also reported here. Partial tax/rex sequences were used to evaluate the diversity between seven STLVmnd isolates and their phylogenetic relationships with other known strains of human and nonhuman primate T cell leukemia virus, types I and II (PTLV-I/II). They all belong to the PTLV-I subtype, but two genetically distinct STLVmnd groups were evidenced within the mandrill colony. The phylogenetic analyses of the STLVmnd isolates, together with seroepidemiological and behavior surveillance of the mandrills, indicate that intracolony transmissions of STLVmnd are also predominantly the result of male-to-male aggressive contacts.

Aggression↗
PubMed1998

Sensory evaluation of stored and rancid edible oils.

The sensory evaluation of stored and rancid edible oils is substantially influenced by tasting of the previous sample. Oil forms a film on walls of the oral cavity, modifying the access of active substances to taste receptors, and inhibiting the evaporation of volatiles to olfactory receptors. Intensities of different off-flavours decrease, while the flavour acceptancy increases. About 5-10 min after the first sensory test, the response of sensory receptors returns to the original sensitivity.

Brassica↗
PubMed1998

Aerosol delivery of lipid:DNA complexes to lungs of rhesus monkeys.

PURPOSE: The potential use of aerosol delivery for non-viral gene therapy was tested by nebulization of lipid:DNA complexes to the lungs of rhesus monkeys. METHODS: Four female rhesus monkeys were dosed with lipid:DNA formulations via aerosol inhalation, where the DNA coded for the human Cystic Fibrosis Transmembrane Conductance Regulator (hCFTR) protein. Delivery of DNA was determined in lung samples by polymerase chain reaction (PCR) by qualitative and quantitative methods. Transgene specific messenger RNA was measured by reverse transcriptase PCR (RT-PCR) and protein expression and localization were evaluated by immunohistochemistry (IHC). RESULTS: Approximately four mg of DNA, complexed with cationic lipid 1.2-dimyristoyl-sn-glycero-3-ethylphosphatidylcholine (EDMPC) and cholesterol were delivered to the lungs of animals by airjet nebulizer. Three days after dosing, tissue samples from the lung were collected and shown to have vector specific DNA, RNA and the presence of CFFR protein. Specifically, the hCFTR protein was distributed widely, although non-uniformly, throughout airway epithelium being located on the apical surface of epithelial cells. Importantly, no adverse clinical effects were observed and the lungs showed no histological abnormalities or signs of acute inflammation. CONCLUSIONS: This study shows that lipid:DNA formulations based on EDMPC and cholesterol can be administered to primates by nebulization resulting in measurable expression of the hCFTR protein. The absence of inflammation is also encouraging and such systems may have utility for delivery of genes to the lungs for the treatment of a variety of pulmonary diseases including cystic fibrosis.

Aerosols↗
PubMed1998

Observations on seminal vesicle dynamics in an in vivo rat model.

PURPOSE: To gain understanding of the seminal vesicle as a muscular organ, seminal vesicle compliance and contractile properties were quantified with an in vivo, microsurgical rat model. MATERIALS AND METHODS: Microsurgical dissection was performed on anesthetized rats to enable simultaneous organ filling and monitoring of intraluminal pressures. The reliability and reproducibility of post-ganglionic hypogastric nerve-induced ipsilateral (4 rats) and bilateral (5 rats) seminal vesicle contractile responses were assessed during repeated nerve stimulation. Seminal vesicle resting compliance was assessed during a constant saline infusion (10 rats). Functional performance curves were obtained at fixed fill-volumes by measuring organ contraction after nerve stimulation (4 rats). RESULTS: A reproducible seminal vesicle contractile response was obtained with a nerve stimulation interval > 15 minutes. Bilateral seminal vesicle responses were observed with unilateral nerve stimulation. The resting organ compliance curve with saline filling exhibited a characteristic, triphasic response. Functional performance studies revealed that contractile performance improves as the fill-volume increases until the distensibility limit of the organ is reached. CONCLUSIONS: A reliable, in vivo, rat model of seminal vesicle organ compliance and contractility is described. The seminal vesicle is a highly contractile, compliant smooth muscular organ with dynamic properties analogous to that of the urinary bladder. This experimental system may allow for the investigation of pharmacologic and other physiological influences on in vivo organ activity.

Animals↗
PubMed1998

Renal hemodynamic changes after complete and partial unilateral ureteral obstruction in the fetal lamb.

PURPOSE: Complete and partial ureteral obstruction decreases ipsilateral renal blood flow in neonatal and adult animals. However, the effects of obstruction that develops during gestation may be different from those in neonatal or adult animals. We determine whether complete or partial ureteral obstruction decreases ipsilateral renal blood flow in fetal sheep. MATERIALS AND METHODS: We positioned an ultrasonic flow transducer around both renal arteries in 21 fetal sheep at 123 to 125 days of gestation. Unilateral ureteral obstruction was created in 16 fetuses, including complete and partial obstruction in 7 and 9, respectively. There were 5 controls. Renal blood flow and arterial blood pressure were measured daily for a minimum of 7 days. RESULTS: All obstructed kidneys had hydronephrosis, partially obstructed kidneys had less obstruction and contralateral kidneys had none. Renal weight was similar in obstructed and contralateral kidneys in the sham operated, partial and complete obstruction groups. After partial ureteral obstruction renal blood flow in obstructed and contralateral kidneys was increased compared to that in sham operated kidneys up to 11 days after obstruction was created. After complete ureteral obstruction the blood flow in obstructed kidneys was significantly lower than in the unobstructed counterparts but it remained 124% of initial renal blood flow at 10 days. Elevated ureteral pressure was maintained in obstructed kidneys throughout the study period. CONCLUSIONS: In our experiment partial ureteral obstruction in the fetus did not decrease renal blood flow to the ipsilateral kidney even after 7 days. Complete obstruction decreased blood flow in the affected kidney but not to same magnitude as that in previous adult animal studies. Our findings suggest that during gestation renal blood flow is maintained in the presence of obstruction.

Animals↗
PubMed1998

Reduced expression of the renal calcium-sensing receptor in rats with experimental chronic renal insufficiency.

Chronic renal insufficiency is associated with elevated serum parathyroid hormone (PTH) levels (2 degrees HPT), deficiency of 1,25-dihydroxyvitamin D (1,25(OH)2D), and hypocalciuria. In chronic renal insufficiency, the 2 degrees HPT may result from reduced expression of the parathyroid gland extracellular Ca(2+)-sensing receptor (CaSR). Since the CaSR was cloned from rat and human kidney, this study examined in rats whether expression of the renal CaSR is altered in experimental chronic renal insufficiency. Four weeks after chronic renal insufficiency was induced by 5/6 nephrectomy (Nx) in Sprague Dawley rats, the serum creatinine concentration was 0.96+/-0.06 mg/dl compared with 0.35+/-0.02 mg/dl in sham-operated animals (P < 0.05). The serum total Ca2+ and phosphorus concentrations were not different. In the Nx group, the serum concentration of amino-PTH was higher (65+/-8 pg/ml), and the concentration of 1,25(OH)2D was significantly lower (47+/-5 pg/ml) compared with 45+/-5 pg/ml and 61+/-4 pg/ml (P = 0.05) in the sham group, respectively. In a subset of rats studied, the Nx group was hypocalciuric (1.4+/-0.5 mg/kg per d) compared with the sham group (3.7+/-0.5 mg/kg per d) (P < 0.05). In the Nx rats, CaSR mRNA expression and CaSR protein levels were found to be reduced by 35 and 38%, respectively, than those observed in controls. These results suggest that reduced renal CaSR expression in chronic renal insufficiency may play a role in disordered mineral ion homeostasis, including hypocalciuria.

Animals↗
PubMed1997

HIV and SIV envelope glycoproteins induce phospholipase A2 activation in human and macaque lymphocytes.

We investigated the early interactions between HIV-1, HIV-2, and simian immunodeficiency virus (SIV) envelope glycoproteins gp120(IIIB), gp105(ROD), and gp120(mac251), and human and macaque cells of the lymphocytic series. Our results demonstrate that the soluble viral glycoproteins induce a specific phospholipase A2 (PLA2) activation in lymphocytes through CD4. This PLA2 activation was induced after envelope glycoprotein-CD4 interaction and, because of its local membrane-destabilizing effect, may have important implications for preparing the lymphocyte membrane for fusion with the viral particle. However, this effect is not sufficient to accomplish fusion. These data indicate that the specific step of fusion may be downstream from PLA2 activation.

Animals↗
PubMed1997

Dyspedic mouse skeletal muscle expresses major elements of the triadic junction but lacks detectable ryanodine receptor protein and function.

The ry1(53) dyspedic mouse contains two disrupted alleles for ryanodine receptor type 1 (skeletal isoform of ryanodine receptor; Ry1R) resulting in perinatal death. In the present study, whole skeletal muscle homogenates and sucrose gradient-purified junctional sarcoplasmic reticulum from neonatal wild-type and dyspedic mice were assayed for biochemical and functional markers. Equilibrium binding experiments performed with 1-120 nM [3H]ryanodine reveal saturable high and low affinity binding to membrane preparations from wild-type mice, but not to preparations from dyspedic mice. Binding experiments performed with [3H]PN200 show a 2-fold reduction in [3H]PN200 binding capacity in dyspedic muscle, compared to age-matched wild-type muscle, with no change in receptor affinity. The presence or absence of proteins known to be critical for normal ryanodine receptor/Ca2+ channel complex function was assessed by Western blot analysis. Results indicate that FKBP-12, DHPRalpha1, triadin, calsequestrin, SERCA1 (sarco(endo)plasmic reticulum Ca2+ ATPase), and skeletal muscle myosin heavy chain are present in both dyspedic and wild-type muscle. Only wild-type membranes showed immunoreactivity toward Ry1R antibody. Neither dyspedic nor wild-type mouse muscle showed detectable immunoreactivity toward Ry2R or Ry3R antibodies, even after sucrose gradient purification of sarcoplasmic reticulum. These results indicate that proteins critical for ryanodine receptor function are expressed in dyspedic skeletal muscle in the absence of Ry1R. Ca2+ transport measurements show that membranes from wild-type controls, but not dyspedic mice, release Ca2+ upon exposure to ryanodine. Dyspedic mice and cells derived from them serve as excellent homologous expression systems in which to study how Ry1R structure relates to function.

Animals↗
PubMed1997

Plexiform neurofibroma involving the genitourinary tract in children: case reports and review of the literature.

We report extensive genitourinary neurofibroma in two children who presented with massive bilateral hydroureteronephrosis and a thick-walled bladder. The best radiologic technique to stage the disease and determine treatment is magnetic resonance imaging. Management of extensive genitourinary neurofibroma is controversial. Based upon our experience and a review of the literature, aggressive surgery should be approached cautiously.

Humans↗
PubMed1997

Hemodynamic changes after complete unilateral ureteral obstruction in the young lamb.

PURPOSE: We studied renal hemodynamic changes after complete acute unilateral ureteral obstruction in the young lamb. MATERIALS AND METHODS: Seven 4-week-old lambs underwent unilateral complete ureteral obstruction and renal blood flow was monitored in both kidneys with ultrasonic flow transducers. Ureteral and arterial blood pressure was measured. RESULTS: In the obstructed kidney renal blood flow was stable for 5 hours and then decreased thereafter to 71% of baseline at 5 days (p < 0.05). In the contralateral kidney the pattern of renal blood flow constituted a mirror image, although the magnitude of the increase was decreased (122% of baseline at 5 days, not statistically significant). Mean arterial blood pressure did not change in 5 days. Mean ureteral pressure increased from a baseline of 9 to 37 mm. Hg (p < 0.001) 2 hours after obstruction but gradually decreased to 24 mm. Hg after 24 hours and remained elevated for 5 days (p < 0.001). CONCLUSIONS: The pattern of renal blood flow and ureteral pressure response to obstruction in the young lamb is different from that previously reported. Renal blood flow does not increase after obstruction and it is relatively preserved at 5 days. This unexpected response may be a result of the compound caliceal sheep kidney, immaturity of the young vascular system or development differences in the mechanism of spontaneous decompression of the collecting system.

Age Factors↗
PubMed1997

Changing the technique of background subtraction alters calculated renal function on pediatric mercaptoacetyltriglycine renography.

PURPOSE: Although many operative decisions are based on apparent changes in function detected by serial diuretic renography, the reliability of relative renal function data has been questioned. We investigated the effect of background subtraction on calculated renal function. MATERIALS AND METHODS: We reviewed 23 pediatric mercaptoacetyltriglycine renograms. Regions of interest for background subtraction were redrawn and relative renal function values were recalculated. RESULTS: In patients with left hydronephrosis left differential renal function was consistently underestimated by 7.3% compared to the superior and 4.7% compared to the average background subtraction technique. In patients with right hydronephrosis, when considering lower pole background activity only, right differential renal function was consistently overestimated by 15.8% compared to the superior and 2.4% compared to the average background subtraction technique. In patients younger than 1 year at the time of study these differences were exaggerated. CONCLUSIONS: Because of overlapping hepatic background activity, the position of regions of interest for background subtraction may greatly influence calculated renal function. We recommend that the preferred method of calculating background subtraction to minimize error be based on a region of interest surrounding the whole kidney. This method is especially pertinent in patients with right hydronephrosis and in those younger than 1 year. Reported relative renal function data should be interpreted with caution.

Child↗
PubMed1997

Preoperative chemotherapy for stage IIIB extremity soft tissue sarcoma: long-term results from a single institution.

PURPOSE: To review a single institution's long-term results with doxorubicin-based preoperative chemotherapy for American Joint Committee on Cancer (AJCC) stage IIIB extremity soft tissue sarcoma (STS). PATIENTS AND METHODS: The records of all patients with AJCC stage IIIB extremity STS treated with preoperative chemotherapy between 1986 and 1990 at The University of Texas M.D. Anderson Cancer Center were reviewed to assess rates of response, local recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), disease-free survival (DFS), and overall survival (OS). RESULTS: Seventy-six patients with stage IIIB disease received preoperative chemotherapy. The median sarcoma size was 10 cm. Seventy-two patients (95%) had tumors located deep to the muscular fascia. Most patients received a median of three preoperative cycles of doxorubicin and dacarbazine (ADIC), cyclophosphamide and ADIC (CyADIC), or other doxorubicin-based regimens. Radiographic response rates were as follows: complete response (CR), 9%; partial response (PR), 19%; minor response, 13%; stable disease, 30%; and progression, 30%. The overall objective major response rate (CRs plus PRs) was 27%. At a median follow-up time of 85 months, 5-year actuarial rates of LRFS, DMFS, DFS, and OS with 95% confidence intervals (CIs) were 83% (CI, 73% to 94%), 52% (CI, 41% to 66%), 46% (CI, 35% to 60%), and 59% (CI, 48% to 72%), respectively. Comparison of responding patients (CRs plus PRs) and nonresponding patients did not show any significant differences in LRFS, DMFS, DFS, or OS. CONCLUSION: Preoperative doxorubicin-based chemotherapy was associated with response, DFS, and OS rates similar to those observed in randomized postoperative chemotherapy trials. Responding patients had rates of LRFS, DMFS, DFS, and OS comparable to those of nonresponders.

Adolescent↗
PubMed1997

Growth factors in bladder wound healing.

INTRODUCTION: Surgical and traumatic injuries to the bladder initiate a complex series of biological processes that result in wound healing. This process involves cellular proliferation, migration and differentiation; removal of damaged tissue; and production of extracellular matrix all of which may be controlled by growth factors. In skin, keratinocyte growth factor (KGF) is induced following incisional injury. We hypothesize that in bladder wound healing KGF and other growth factors are induced to modulate tissue repair. METHODS: We have created a model of surgical bladder injury in the rodent. At 12, 24 and 48 hrs and 5 and 7 days after injury, the bladder was bisected and total RNA extracted from the anterior or wounded half and posterior or non-wounded half. Histological analysis of the bladder wound was performed with Mason's Trichrome and immunohistochemistry against smooth muscle alpha actin. RNase protection assays were performed to examine the expression of KGF, transforming growth factor (TGF)alpha and TGF beta 2 and 3 as well as the receptors for KGF and epidermal growth factor (EGF). Lastly, the effects of the exogenous administration of KGF on the bladder was tested on neonatal mice by daily injections of 5 micrograms KGF per gram body weight for 5 days. RESULTS: At 12 hours after injury KGF mRNA expression in the anterior wounded bladder half and posterior non-wounded bladder half was 8 and 6 times higher respectively, compared to unoperated control bladders. A similar response was seen for TGF alpha, where the 12 hour mRNA expression was 4.5 times higher in the anterior wounded bladder half and 3.5 times higher in the posterior non-wounded bladder half compared to unoperated control bladders. The nadir mRNA expression for both KGF and TGF alpha occurred at 7 days after bladder injury and was the same as in unoperated control bladders. EGFR mRNA expression was approximately 2 times higher in both the anterior wounded and posterior non-wounded bladder halves compared to the nadir levels which occurred at 24 hours after injury. TGF beta 2 and beta 3 mRNA levels did not significantly change in either the anterior wounded or posterior non-wounded bladder halves. Exogenous KGF stimulation resulted in a marked urothelial proliferation when compared to age matched control animals. CONCLUSION: During the early phases of bladder wound healing (12-24 hours post injury), mRNA for KGF and TGF alpha increased, whereas TGF beta 2 and beta 3 and the KGFR and EGFR remain unchanged. Additionally, exogenous KGF has a direct effect on urothelial proliferation. KGF and TGF alpha warrant further study as potential mediators of bladder wound healing.

Animals↗
PubMed1997

Estimation of glomerular filtration rate in type II (non-insulin dependent) diabetes mellitus patients.

The aim of this research was to develop an estimation of glomerular filtration rates (GFRs) from a combination of simple parameters in a large group of type II diabetic patients. We selected 122 newly presenting, previously untreated, type II patients whose GFR was determined from the plasma clearance of 51Cr-ethylenediamine tetraacetic acid (51Cr-EDTA) and simultaneous measurements of demographic variables, including fasting plasma glucose concentration, HbA1c, blood pressure, lipids, age, weight, body-mass index, body surface area, urea, and plasma creatinine concentration. The actual GFR values were compared with estimated values obtained from multiple regression and the Cockroft-Gault equations. Out of all the demographic variables, only plasma creatinine concentration (r = -0.56, p < 0.001), age (r = -0.50, p < 0.001), urea (r = -0.28, p < 0.01), and systolic blood pressure (r = -0.21, p < 0.05) showed significant correlations with the actual GFR values, for which the mean and standard deviation were 117.5 +/- 22.0 ml min-1 x 1.73 m-2. The estimated values are highly correlated with the actual values (r = 0.70), having an identical mean value of 117 +/- 15.3 and an unbiased regression relation (y = 0.000 + 1.000x). As standard measurements of the GFR are very time consuming and expensive, the use of the simple equation GFR1 = 218.1 - 0.916 x Age - 0.635 x Creatinine is recommended. The classification of GFR values into three ranges has also revealed the nonlinear characteristics of GFR in relation to other demographic variables: age and creatinine are the dominant variables in the middle GFR range, while the body-mass index and urea are dominant in the high and low ranges, respectively.

Adult↗
PubMed1997

Sequence and phylogenetic analyses of HIV-1 infection in Vietnam: subtype E in commercial sex workers (CSW) and injection drug users (IDU).

More than 4,000 persons with human immunodeficiency virus type 1 (HIV-1) infection have been identified in Vietnam through sentinel surveillance since 1990, when the first case of HIV-1 infection was diagnosed in a young woman in Ho Chi Minh City. Currently, the estimated HIV-1 seroprevalences of 10% for injection drug users (IDU) and 3% for female commercial sex workers (CSW) in Vietnam are comparable to those observed in the same risk groups in Thailand five years ago. To clarify if concurrent epidemics with different HIV-1 subtypes (or clades) are occurring among different high-risk behavior groups in Vietnam, we conducted a genotypic analysis of HIV-1 by amplifying and sequencing a 325-nucleotide region spanning the principal neutralizing domain, or V3 loop, of the gp120-encoding env gene from genomic DNA extracted from dried, filter paper-blotted blood samples, collected in April/May and August/September 1995 from 8 HIV-1-seropositive CSW in Ho Chi Minh City, Can Tho and An Giang provinces and from 16 IDU in Ho Chi Minh City, Hanoi, Nha Trang and An Giang province. Sequence alignment and comparison with other HIV-1 subtypes indicated that the HIV-1 strains from CSW and IDU in Vietnam were genetically most similar to subtype E strains from Cambodia. The interstrain genetic variation among the Vietnam HIV-1 env sequences ranged from 0.3% to 9.0% (mean, 4.6%). Phylogenetic analysis verified that some of the Vietnam HIV-1 strains formed discrete clusters and were indistinguishable from other Southeast Asian strains. The demonstration of subtype E in both CSW and IDU in Vietnam contrasts sharply with the previously observed HIV-1 clade restriction in these high-risk behavior groups in nearby Thailand.

Adolescent↗