Biomedical subjects

T T Nguyen

Publications and source records attributed to T T Nguyen.

At least 73 records · Page 4Linked to original sources

PubMed2000

Evaluation of the effect of spinal cord injury on serum PSA levels.

OBJECTIVES: Prostatic structure and secretory activity are thought to be influenced by autonomic innervation of the prostate. Prostatic denervation is especially likely in patients with spinal cord injury (SCI) at the level of the cauda equina or the conus medullaris, where the peripheral nerve supply to the prostate may be specifically damaged. This may result in changes in serum prostate-specific antigen (PSA) levels, either directly or indirectly. Therefore, we measured serum PSA levels and also studied the influence of factors such as age, catheterization, duration of SCI, urinary tract infection, and history of cystitis on serum PSA values in men with SCI. METHODS: Serum PSA levels were determined in 79 men with SCI (age older than 40 years) using banked sera by the Abbott MEIA PSA assay. Variables such as age, catheterization, duration of SCI, urine culture results, and history of cystitis were obtained from a review of patient records. Comparisons were made with a randomly selected, non-SCI control population of 501 men, 40 to 89 years old, who underwent serum PSA determination at our institution. Statistical comparisons were performed using the Mann-Whitney U test (nonparametric), since the populations were not normally distributed. Multivariate logistic regression analysis was used to assess the correlation between the various factors and the serum PSA levels in men with SCI. RESULTS: No statistically significant differences were found in the median serum PSA values between the SCI group and the non-SCI control population. The age-specific PSA values obtained in the SCI group were also comparable to those reported for the general population at large. Age (P <0.03) and the presence of a catheter (P <0.0002) were the only two factors that were correlated with higher serum PSA values in the SCI group by regression analysis. CONCLUSIONS: Men with SCI tended to have serum PSA value distributions that were similar to those of the general population. However, those in the SCI group who had indwelling catheters were more likely to have higher PSA values at baseline, as were older men with SCI.

Adult↗

PubMed2000

Ammonia toxicity as a criterion for the evaluation of larval quality in the prawn Macrobrachium rosenbergii.

The feasibility of a short-term ammonia toxicity test as an evaluation criterion for larval quality was assessed in three trials. In each one, Macrobrachium rosenbergii larvae originating from the same spawn were nutritionally differentiated in two groups by feeding them either a nutrient-rich (Artemia nauplii enriched for 24 h with n-3 highly unsaturated fatty acids (HUFA) and ascorbic acid (AA)) or a nutrient-poor diet (Artemia nauplii starved for 24 h). Throughout their development, larvae from both treatments were exposed during 24 h to six concentrations of total ammonia (NH(4)(+)+NH(3)) and a control (no ammonia added). Based on mortality rates, the median lethal concentration for 50% of the population (LC(50)) was estimated. As expected from earlier work, larvae fed the optimal diet presented higher n-3 HUFA and AA contents as well as higher growth and metamorphosis rates. From the moment the effect of diet quality was analytically detectable in the tissues of the larvae, the ammonia test was able to distinguish both groups of larvae. Differences in ammonia tolerance were observed as early as larval stage 4 and remained evident throughout larval development. The short-term ammonia toxicity test proved to be a valuable, sensitive and reproducible criterion for the establishment of larval quality.

Age Factors↗

PubMed2000

Ultrasound-enhanced thrombolysis at 20 kHz with air-filled and perfluorocarbon-filled contrast bispheres.

BACKGROUND: Ultrasound (US) at low frequencies has been shown to enhance clot lysis by itself and in the presence of urokinase (UK). The comparative effects of air-filled versus perfluorocarbon-filled polymer bispheres in enhancing this effect have not been previously demonstrated. METHODS: Freshly drawn human blood was incubated at 37 degrees C for 2 hours, and the subsequent formed clot was dried and weighed. It was then exposed to saline control, saline + UK (10,000 IU), saline + UK + US, saline + UK + US + low shell-strength polymer bispheres (PB1), saline + UK + US + high shell-strength polymer bispheres (PB2), and perfluorocarbon-filled high shell-strength polymer bipsheres (PB3) for a total of 6 minutes. Clots were removed and weighed to determine the percentage of thrombolysis. RESULTS: The percentage of clot lysis for each study group was as follows: saline 18.5% +/- 4%, US alone 22.2% +/- 5%, UK alone 21.9% +/- 4%, US+UK 32.2% +/- 8% (P <.05 compared with UK alone), US+UK+PB1 36.9% +/- 8%, US+UK+PB2 34.3% +/- 8%, and US+UK+PB3 45.0% +/- 11% (P <.05 compared with US+UK, P <.05 compared with US+UK+PB2). CONCLUSION: Ultrasound at 20 kHz significantly enhances clot lysis. The addition of perfluorocarbon-filled bispheres increased this effect more significantly than did the addition of air-filled polymer bispheres.

Fluorocarbons↗

PubMed2000

Insulin-like growth factors and bone mineral density in African American and White girls.

OBJECTIVES: African American children have greater bone mineral density (BMD) and bone mineral content (BMC) than white children. We examined the hypothesis that differences in insulin-like growth factors (IGFs) are important determinants of BMD during childhood. METHODS: We measured IGFs and IGF binding proteins in 59 African American and 59 white girls matched for age, body mass index, socioeconomic status, and pubertal stage. BMD and BMC were determined by dual emission x-ray absorptiometry. RESULTS: African American girls had greater total BMD (P <.001), BMC (P <.01), total IGF-1 (P <.001), and free IGF-1 (P <.01) than white girls. IGFBP-1, IGFBP-2, and IGFBP-3 were similar in both groups or lower in African Americans. IGF-1 was positively correlated with IGF-2 in white girls (P =.012) but was negatively correlated with IGF-2 in African Americans (P =.015). IGF-1 and free IGF-1 were positively correlated with BMD/BMC. Multiple regression analyses showed 80% of the variance in BMC could be accounted for by the use of body weight, height, and IGF-1 in the model. When IGF-1 was included as a factor, race did not add to the model's predictive power. CONCLUSION: IGF-1 and free IGF-1 are greater in African American than in white girls and may contribute to the greater BMD of African Americans.

Black People↗

PubMed2000

DNA strand-break yields after post-irradiation incubation with base excision repair endonucleases implicate hydroxyl radical pairs in double-strand break formation.

PURPOSE: To determine the increases in SSB and DSB yields after post gamma-irradiation incubation of plasmid DNA with the Escherichia coli base excision repair endonucleases formamidopyrimidine-DNA N-glycosylase (FPG) and endonuclease III (endo III). MATERIALS AND METHODS: Aqueous solutions of plasmid DNA were irradiated with 137Cs gamma-rays in the presence of 10(-4) - 10(-1) mol dm(-3) formate. After irradiation, aliquots were treated with FPG and/or endo III. SSB and DSB yields were then determined using gel electrophoresis. RESULTS: Both SSB and DSB yields were found to increase after enzyme incubation, with the increase in the DSB yield being approximately equal to the square of the increase in the SSB yield. The correlation between the increases in the SSB and DSB yields was unaffected by the scavenger concentration during irradiation. CONCLUSION: Under the conditions used, the majority of DSB appear to be formed from two hydroxyl radical attacks.

DNA↗

PubMed2000

Associations between uncoupling protein 2, body composition, and resting energy expenditure in lean and obese African American, white, and Asian children.

BACKGROUND: Little is known about genes that affect childhood body weight. OBJECTIVE: The objective of this study was to examine the association between alleles of the mitochondrial uncoupling protein 2 (UCP2) gene and obesity because UCP2 may influence energy expenditure. DESIGN: We related UCP2 genotype to body composition and resting energy expenditure in 105 children aged 6-10 y. Overweight children and nonoverweight children of overweight parents were genotyped for a 45-base pair deletion/insertion (del/ins) in 3'-untranslated region of exon 8 and for an exon 4 C to T transition. RESULTS: Eighty-nine children were genotyped for the exon 8 allele: 50 children had del/del, 33 had del/ins, and 6 had ins/ins. Mean (+/-SD) body mass index (BMI; in kg/m(2)) was greater for children with del/ins (24.1 +/- 5.9) than for children with del/del (20.4 +/- 4.8; P < 0.001). BMI of ins/ins children (23.7 +/- 7.8) was not significantly different from that of del/ins children. A greater BMI in del/ins children was independent of race and sex. Body composition was also different according to UCP2 genotype. All body circumferences and skinfold thicknesses examined were significantly greater in del/ins than in del/del children. Body fat mass as determined by dual-energy X-ray absorptiometry was also greater in del/ins than in del/del children (P < 0.005). For 104 children genotyped at exon 4, no significant differences in BMI or body composition were found among the 3 exon 4 genotypes. Neither resting energy expenditure nor respiratory quotient were different according to UCP2 exon 4 or exon 8 genotype. CONCLUSIONS: The exon 8 ins/del polymorphism of UCP2 appears to be associated with childhood-onset obesity. The UCP2/UCP3 genetic locus may play a role in childhood body weight.

Asian People↗

PubMed2000

Difference in incidence of spontaneous mutations between Herpes simplex virus types 1 and 2.

Spontaneous mutations within the herpes simplex virus (HSV) genome are introduced by errors during DNA replication. Indicative of the inherent mutation rate of HSV DNA replication, heterogeneous HSV populations containing both acyclovir (ACV)-resistant and ACV-sensitive viruses occur naturally in both clinical isolates and laboratory stocks. Wild-type, laboratory-adapted HSV type 1 (HSV-1) strains KOS and Cl101 reportedly accumulate spontaneous ACV-resistant mutations at a frequency of approximately six to eight mutants per 10(4) plaque-forming viruses (U. B. Dasgupta and W. C. Summers, Proc. Natl. Acad. Sci. USA 75:2378-2381, 1978; J. D. Hall, D. M. Coen, B. L. Fisher, M. Weisslitz, S. Randall, R. E. Almy, P. T. Gelep, and P. A. Schaffer, Virology 132:26-37, 1984). Typically, these resistance mutations map to the thymidine kinase (TK) gene and render the virus TK deficient. To examine this process more closely, a plating efficiency assay was used to determine whether the frequencies of naturally occurring mutations in populations of the laboratory strains HSV-1 SC16, HSV-2 SB5, and HSV-2 333 grown in MRC-5 cells were similar when scored for resistance to penciclovir (PCV) and ACV. Our results indicate that (i) HSV mutants resistant to PCV and those resistant to ACV accumulate at approximately equal frequencies during replication in cell culture, (ii) the spontaneous mutation frequency for the HSV-1 strain SC16 is similar to that previously reported for HSV-1 laboratory strains KOS and Cl101, and (iii) spontaneous mutations in the laboratory HSV-2 strains examined were 9- to 16-fold more frequent than those in the HSV-1 strain SC16. These observations were confirmed and extended for a group of eight clinical isolates in which the HSV-2 mutation frequency was approximately 30 times higher than that for HSV-1 isolates. In conclusion, our results indicate that the frequencies of naturally occurring, or spontaneous, HSV mutants resistant to PCV and those resistant to ACV are similar. However, HSV-2 strains may have a greater propensity to generate drug-resistant mutants than do HSV-1 strains.

Drug Resistance, Microbial↗

PubMed2000

Familial splenomegaly: macrophage hypercatabolism of lipoproteins associated with apolipoprotein E mutation [apolipoprotein E (delta149 Leu)].

Splenomegaly with sea-blue histiocytes is not associated with dyslipidemia, except in severe cases of hypertriglyceridemia, Tangier disease, or lecithin cholesterol acyltransferase deficiency. We describe two kindreds in which the sea-blue histiocyte syndrome was associated with an apoE variant in the absence of severe dyslipidemia. Both patients presented with mild hypertriglyceridemia and splenomegaly. After splenectomy both patients developed severe hypertriglyceridemia. Pathological evaluation of the spleen revealed the presence of sea-blue histiocytes. A mutation of apoE was demonstrated, with a 3-bp deletion resulting in the loss of a leucine at position 149 in the receptor-binding region of the apoE molecule [apoE (delta149 Leu)]. Although both probands were unrelated, they were of French Canadian ancestry, suggesting the possibility of a founder effect. In summary, we describe two unrelated probands with primary sea-blue histiocytosis who had normal or mildly elevated serum triglyceride concentrations that markedly increased after splenectomy. In addition, we provide evidence linking the syndrome to an inherited dominant mutation in the apoE gene, a 3-bp deletion on the background of an apoE 3 allele that causes a derangement in lipid metabolism and leads to splenomegaly in the absence of severe hypertriglyceridemia.

Adult↗

PubMed2000

The CardioVision 2020 baseline community report card.

OBJECTIVE: To establish baseline data for the CardioVision 2020 program, a collaborative project in Olmsted County, Minnesota, organized to reduce cardiovascular disease rates by altering 5 health-related items: (1) eliminating tobacco use and exposure, (2) improving nutrition, (3) increasing physical activity, (4) lowering serum cholesterol level, and (5) controlling blood pressure. SUBJECTS AND METHODS: Data about tobacco use, diet, and physical activity were collected by random digit dial interview and follow-up questionnaire from a sample of the population. Blood pressure data were collected from medical records at Mayo Clinic, and serum cholesterol data were derived from the Mayo Clinic laboratory database. Data were stratified into 6 age groups. RESULTS: A total of 624 women and 608 men responded to the questionnaire. Population blood pressure data were available for 1,956 women and 1,084 men. Population serum cholesterol data were available for 17,042 women and 12,511 men. Except for women in the 30- to 39-year-old age group, less than 10% of the population sampled met 4 or 5 goals. Conversely, about 90% of the population met at least 1 goal, and about 80% met 1, 2, or 3 of the goals. CONCLUSION: The data from the Olmsted County population indicate considerable opportunity to reduce this population's burden of cardiovascular disease.

Adult↗

PubMed2000

The epidemiology of typhoid fever in the Dong Thap Province, Mekong Delta region of Vietnam.

A population-based surveillance for typhoid fever was conducted in three rural communes of Dong Thap Province in southern Vietnam (population 28,329) for a 12-month-period starting on December 4, 1995. Cases of typhoid fever were detected by obtaining blood for culture from residents with fever > or = 3 days. Among 658 blood cultures, 56 (8.5%) were positive for Salmonella typhi with an overall incidence of 198 per 10(5) population per year. The peak occurrence was at the end of the dry season in March and April. The attack rate was highest among 5-9 year-olds (531/10(5)/year), and lowest in > 30 year-olds (39/10(5)/year). The attack rate was 358/10(5)/year in 2-4 year-olds. The isolation of S. typhi from blood cultures was highest (17.4%) in patients with 5 to 6 days of fever. Typhoid fever is highly endemic in Vietnam and is a significant disease in both preschool and school-aged children.

Adolescent↗

PubMed2000

Inhibition of muscle glutamine formation in hypercatabolic patients.

Glutamine is synthesized primarily in skeletal muscle, and enables transfer of nitrogen to the liver, as well as serving other functions. There is increasing evidence for beneficial clinical effects of glutamine supplementation in critically ill patients. However, the response of endogenous glutamine formation to severe stress is poorly understood. The rates of net protein balance, leucine oxidative decarboxylation, and alanine and glutamine synthesis de novo were determined in leg skeletal muscle of 20 severely burned patients and 19 normal controls in the post-absorptive state. Patients were studied at 14+/-5 days post-burn, and their mean burn size was 66+/-18% of total body surface area. Methods were based on the leg arteriovenous balance technique in combination with biopsies of the vastus lateralis muscle. In the post-absorptive state, patients with severe burns, as compared with healthy control subjects, exhibited accelerated muscle loss (+150%) (i.e. proteolysis minus synthesis) and leucine oxidative decarboxylation (+117%), and depletion of the intramuscular free glutamine pool (-63%). The average rate of glutamine synthesis de novo was decreased by 48%, whereas net alanine synthesis de novo was increased by 174%, in skeletal muscle of burned patients. In conclusion, in severely hypercatabolic burned patients, muscle glutamine formation was suppressed, whereas alanine was the major vehicle for inter-organ nitrogen transport. These changes account for a decreased glutamine availability during prolonged severe stress.

Adult↗

PubMed1999

Expression and characterization of elastase inhibitors from the ascarid nematodes Anisakis simplex and Ascaris suum.

Two elastase inhibitors, ASPI-1 and ASPI-2, from the parasitic nematode Anisakis simplex, have been isolated and characterized. Because these inhibitors are similar in size (60 amino acids in length) and primary sequence (52 and 47% identical) to the Ascaris suum chymotrypsin/elastase inhibitor-1 (AsC/E-1), we suggest that these Anisakis elastase inhibitors belong to the same unique class of canonical inhibitors formed by the family of Ascaris inhibitors (Huang K, Strynadka NCJ, Bernard VD, Peanasky RJ, James MG. Structure 1994;2:679-689). To compare ASPI-1 with AsC/E-1, we expressed both inhibitors in Pichia pastoris and found that: (1) the association constant of rASPI-1 with porcine pancreatic elastase (PPE) is similar to native inhibitor (Ka = 4.5 x 10(9) and 6.4 x 10(9) M(-1), respectively); (2) rASPI-1 is a potent inhibitor of PPE and human leukocyte elastase (Ka = 1.6 x 10(9) M(-1)); and (3) it is only a very weak inhibitor of chymotrypsin (CHYM) (Ka = 1.2 x 10(6) M(-1)). In contrast to the Anisakis inhibitor, however, rAsC/E inhibitor-1 is a very strong inhibitor of both PPE (Ka = 3.5 x 10(10) M(-1)) and CHYM (Ka = 3.6 x 10(12) M(-1)). We also found that the determined reactive sites (P1-P'1) of rASPI-1 and rAsC/E-1, as recognized by PPE, are Ala 28-Met 29 and Leu 31-Met 32, respectively. These P1-P'1 residues of AsC/E-1 constitute the same reactive site as that also recognized by CHYM (Peanasky RJ, Bentz Y, Homandberg GA, Minor ST, Babin DR. Arch Biochem Biophys 1994;232:135-142). The difference in specificities of ASPI-1 and AsC/E-1 toward their cognate serine proteases may be attributed to the P1 and P'3 residues in the inhibitors. Elastase, which recognizes both alanine and leucine, canaccommodate both ascarid inhibitors, whereas chymotrypsin, which prefers bulky, hydrophobic residues, only recognizes the Ascaris C/E inhibitor-1.

Amino Acid Sequence↗

PubMed1999

Orally bioavailable nonpeptide vitronectin receptor antagonists containing 2-aminopyridine arginine mimetics.

A peptide RGD analog containing a novel 2-aminopyridine arginine mimetic was discovered to have good affinity and selectivity for the vitronectin receptor. Incorporation of the 2-aminopyridine arginine mimetic into the 3-oxo-1,4-benzodiazepine-2-acetic acid integrin antagonist series led to novel and potent nonpeptide vitronectin receptor antagonists with promising levels of oral bioavailability.

Administration, Oral↗

PubMed1999

Parental compliance with multiple immunization injections.

OBJECTIVE: To assess parents' (or caretakers') willingness to allow multiple immunization injections at a single visit. DESIGN: A survey of parental demographics and a medical record review to determine immunization status. SETTING: An inner-city pediatric clinic in Philadelphia, Pa. PARTICIPANTS: A convenience sample of 1059 patients who were due to receive 2 to 5 immunization injections at a single visit and their parents. Patients were excluded if parents had not previously witnessed at least 1 immunization. MAIN OUTCOME MEASURES: The number of immunizations due, the number of immunizations received, and the reasons for failure to immunize completely. RESULTS: Almost all (98.8%) of the children included in the study received all immunizations indicated at their visit. CONCLUSION: Despite potential parental resistance to multiple simultaneous immunization injections, this innercity population overwhelmingly complied with physicians' recommendations.

Adolescent↗

PubMed1999

Placental biogenic amine transporters: in vivo function, regulation and pathobiological significance.

The biogenic amine transporters are part of a large family of plasma membrane transporters. These carriers mediate the re-uptake of neurotransmitters from the synaptic cleft and plasma compartments. Re-uptake process is inhibited by drugs like cocaine, fluoxetine and tricyclic antidepressants. There are specific transporters for norepinephrine, epinephrine, dopamine and serotonin. The placenta expresses the norepinephrine and serotonin transporters, which is unusual as they are otherwise expressed predominantly in neuronal tissue. Fetal catecholamine clearance rate is higher than under any other physiological conditions and is mediated in large measure by the placental transporters. The high intrauterine catecholamine secretion and clearance rates are part of the unique fetal neuroendocrine milieu. They condition the fetus to a high capacity for catecholamine secretion in the early postnatal period when elevated sympathoadrenal system activity is vital for postnatal survival. Because of the prominent catecholamine clearance rate, the fetus is vulnerable to the adverse effects of re-uptake inhibitors. Understanding the mechanisms of expression and regulation of placental biogenic amine transporters is important to the pathobiology of fetal conditions associated with elevated catecholamine levels or intrauterine exposure to uptake inhibitors like cocaine.

Biogenic Monoamines↗

PubMed1999

A variety of gram-positive bacteria carry mobile mef genes.

The mefE gene codes for a membrane bound efflux protein, which confers resistance to macrolides, and has been identified in Streptococcus pneumoniae. A variety of gram-positive organisms were examined. Twenty-six isolates of S. pneumoniae carried mefE and were resistant to erythromycin (MIC of 2-16 mg/L). Two additional isolates of Emr S. pneumoniae carried both ermB and mefE(MIC of 16-128 mg/L). One Micrococcus luteus, one Corynebacterium jeikeium, three Corynebacterium spp., two viridans streptococci and seven Enterocccus spp. also carried mef genes. It was possible to move the mef gene from all 11 S. pneumoniae tested to susceptible S. pneumoniae and/or Enterococcus faecalis recipients. The addition of DNase (1 g/L) did not affect the gene transfer. It was also possible to move the mef gene from donor Enterococcus spp., viridans streptococci, M. luteus, C. jeikeium and Corynebacterium spp. to E. faecalis recipients. Transconjugant isolates were resistant to erythromycin (MIC = 16 mg/L). Hybridization with a labelled mef oligonucleotide probe against Southern blots and bacterial dot blots confirmed the presence of the mef genes. This is the first time that a mobile mef gene has been identified in four different genera, from three distinct geographical locations.

Anti-Bacterial Agents↗

PubMed1999

The cholesterol-lowering action of plant stanol esters.

Plant sterols and stanols derived from wood pulp and vegetable oils lower total and LDL cholesterol by inhibiting cholesterol absorption from the intestine in humans. Plant stanols are virtually unabsorbable, which makes them more ideal hypocholesterolemic agents than plant sterols. The esterification of plant stanols has allowed their incorporation into various foods such as margarine without changing the taste and texture of those foods. Plant stanol esters at a level of 2-3 g/d have been shown to reduce LDL cholesterol by 10-15% without side effects. Plant stanol esters appear to be a helpful dietary adjunct to a prudent diet to lower cholesterol.

Anticholesteremic Agents↗

PubMed1999

Negative electrostatic contribution to the bending rigidity of charged membranes and polyelectrolytes screened by multivalent counterions.

Bending rigidity of a charged membrane or polyelectrolyte screened by monovalent counterions is known to be enhanced by electrostatic effects. We show that in the case of screening by multivalent counterions the electrostatic effects reduce the bending rigidity. This inversion of the sign of the electrostatic contribution is related to the formation of two-dimensional strongly correlated liquids (SCL) of counterions at the charged surface due to strong lateral repulsion between them. When a membrane or a polyelectrolyte is bent, SCL is compressed on one side and stretched on the other so that thermodynamic properties of SCL contribute to the bending rigidity. Thermodynamic properties of SCL are similar to those of Wigner crystal and are anomalous in the sense that the pressure, compressibility and screening radius of SCL are negative. This brings about substantial negative correction to the bending rigidity. For the case of DNA this effect qualitatively agrees with experiment.

Cations↗