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Biomedical subjects

L Nguyen

Publications and source records attributed to L Nguyen.

At least 127 records · Page 7Linked to original sources
PubMed1993

Selected determinants of fertility in Vietnam: age at marriage, marriage to first birth interval and age at first birth.

Data from the 4172 women aged 15-49 interviewed in the 1988 Vietnamese Demographic and Health Survey were used to examine age at marriage, marriage to first birth intervals and age at first birth. Differences between urban and rural areas, northern and southern provinces and by education of the women were analysed. The majority of the women had their first birth before age 20, but women with secondary education had a significantly higher age at first birth than those with little or no education, and women from the north had a significantly higher age at first birth than women from the south. Rural women and those with little or no education married at significantly younger ages than urban women and those with secondary education; these education effects were confirmed in a rural subsample of women. Women from rural areas and from the north had significantly shorter marriage to first birth intervals than urban women and those from the south, but there were no significant effects related to education.

Adolescent↗
PubMed1993

A assessment of the plastic Thermafil obturation technique. Part 1. Radiographic evaluation of adaptation and placement.

Adaptation and placement of alpha-phase gutta-percha delivered with a plastic core-carrier, Thermafil, was compared to the lateral condensation of gutta-percha in a specific tooth model. Fifty-one mandibular molar roots with separate canals, patent canal orifices and curvatures greater than 15 degrees were cleaned and shaped with K-files and 2.5% sodium hypochlorite to a size 30 at the apex, and flared with Hedstrom files to create a continuously tapering funnel preparation. Canals were randomly obturated with Sealapex root canal sealer and either alpha-phase gutta-percha on a plastic Thermafil carrier, or standard beta-phase gutta-percha with lateral condensation. Roots were radiographed from the proximal and evaluated by three examiners, based on established criteria for overall material adaptation, apical adaptation, and filling material extrusion. Thermafil provided a statistically significant better overall canal obturation (P < 0.001), while, in the apical third, both techniques were not significantly different (P > 0.05). When the apical orifice was patent there was a significant propensity for the extrusion of filling materials beyond the apex (P < 0.001) with the Thermafil technique.

Evaluation Studies as Topic↗
PubMed1992

Carbachol potentiates isoprenaline-induced mucin secretion by rat submandibular gland.

We studied the effects of carbachol on isoprenaline-induced secretion of 3[H]glucosamine-labeled high molecular weight protein from in vitro fragments of rat submandibular gland. The concentration-response curve for isoprenaline was determined alone and in the presence of one of two concentrations of carbachol. Isobolic interaction indices were calculated from the resulting curves. The role of extracellular calcium on this interaction was assessed by examining the effect of increasing concentrations of [Ca2+]e on secretion induced by a fixed concentration of isoprenaline alone and in the presence of carbachol. Carbachol alone caused a small, but statistically significant, protein secretion. Carbachol markedly shifted the isoprenaline concentration-response curve to the left in a dose-dependent manner. In the absence of extracellular calcium, carbachol did not increase isoprenaline-induced secretion, but secretion increased as the [Ca2+]e was increased. The carbachol-induced increase in secretion reached a maximal level at approximately 2.0 mM [Ca2+]e. We conclude that carbachol's increase of isoprenaline-induced secretion of 3[H]glucosamine-labeled high molecular weight protein is not additive, but is true potentiation. This potentiation requires extracellular calcium, and may be maximal at physiological [Ca2+]e.

Animals↗
PubMed1992

Beta-endorphin blunts phosphatidylinositol formation during in vitro activation of isolated human lymphocytes: preliminary report.

We have previously described the regulatory effect of beta-endorphin on three human cytotoxic cell populations. We confirmed the variable nature of these effects on human natural killer cell (NK) activity, showed mixed effects on the generation of cytotoxic T lymphocyte (CTL) activity, and demonstrated the reproducible suppression of lymphokine-activated killer cell (LAK) activity. We and others also observed mixed effects of beta-endorphin on the proliferative response to mitogens and in mixed leukocyte reactions. In the study reported here, we test the effects of beta-endorphin on the formation of phosphatidylinositol during cell activation. 32P-radiolabeled peripheral blood mononuclear cells obtained from normal adult donors and CD2-depleted subpopulations were activated with phytohemagglutinin or in a NK, LAK, or CTL protocol in the absence or presence of recombinant beta-endorphin. The total lipidic extract was analyzed by thin-layer chromatography and autoradiography. The results of these studies indicate that beta-endorphin blunts the formation of phosphatidylinositol by about 20% in the four systems studied and in all the donors tested. This effect is dose-dependent and is blocked in part by the opioid antagonist, naltrexone, suggesting involvement of the opioid receptor.

Adolescent↗
PubMed1992

Elevated NMDA receptors in parkinsonian striatum.

Dopamine-glutamate interactions contribute to normal striatal function and have been implicated in neurotoxicity at nigrostriatal dopamine (DA) terminals. The present study examined the striata of idiopathic Parkinson's disease (PD) patients and age-matched controls for regional differences in the DA transporter and binding to N-methyl-D-aspartate (NMDA) receptors. [3H]Mazindol labeling of the DA transporter was reduced by 70-80% in the caudate and putamen of PD patients, with reductions being more extensive dorsally than ventrally. In contrast, L-[3H]glutamate binding to NDMA-sensitive receptors was 20-40% higher in PD cases than in controls. These findings raise the possibility that modifications occur within corticostriatal glutamate synapses of PD patients, possibly as a consequence of reduced nigrostriatal DA activity.

Aged↗
PubMed1992

Increased sitosterol absorption is offset by rapid elimination to prevent accumulation in heterozygotes with sitosterolemia.

Using plasma isotope-kinetic methods, we measured the absorption and turnover rates of cholesterol and sitosterol (24-ethylcholesterol) in two obligate heterozygotes (parents) and their homozygous daughter with sitosterolemia with xanthomatosis. Diets contained approximately 500 mg/day cholesterol and 100 mg/day sitosterol. In the homozygote, plasma cholesterol and apolipoprotein B concentrations were slightly higher, but sitosterol levels were 22 and 58 times higher than in her heterozygous parents. Cholesterol absorption was at the high end of the normal range in both heterozygotes (59% and 84%) and in the homozygote (62%) (value in the control subject 48%). In contrast, cholesterol synthesis was severely depressed in the homozygote (28% and 26% as great as in the heterozygotes and the control, respectively). Sitosterol absorption in the homozygote (34%) was 2.3 and 2.0 times greater than in the heterozygotes and 6.8 times greater than in the control. The sitosterol turnover rate, calculated independently by mathematical analysis of specific-activity decay curves, amounted to 15 and 24 mg/day in the heterozygotes compared with 27 mg/day in the homozygote and 7.9 +/- 2.3 mg/day in five control subjects. However, the total body sitosterol pool was 15 and 10.3 times larger in the homozygote (4,080 mg) than in her heterozygous parents because of extremely slow removal. The average sitosterol elimination constant in the heterozygotes (KA = 0.11 day-1) was 10 times that in the homozygote (KA = 0.01 day-1) but 35% less than that in the controls (KA = 0.17 day-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1992

Sitosterolemia.

Sitosterolemia is a rare inherited lipid storage disease characterized chemically by the accumulation of plant sterols and 5 alpha-saturated stanols in plasma and tissues. Very low cholesterol synthesis due to a deficiency of HMG-CoA reductase associated with increased intestinal plant sterol absorption and slow hepatic sterol removal are major biochemical features. Because cholesterol synthesis cannot up-regulate, bile acid malabsorption mobilizes body sterols for bile acid synthesis and dramatically lowers plasma and monocyte sterol concentrations and may halt the progression of the atherosclerotic process.

Cholesterol↗
PubMed1992

[Comparative efficacy of annual and semi-annual doses of ivermectin or diethylcarbamazine for the prevention of lymphatic filariasis].

A double blind randomized trial was performed on 58 healthy Polynesian Wuchereria bancrofti carriers, they were randomly allocated to treatments with repeated annual or semi-annual doses of ivermectin 100 mcg/kg or diethylcarbamazine (DEC) 3 mg/kg, or with repeated annual doses of DEC 6 mg/kg. After the 12-month treatment, the clearance of microfilaremia was complete in 7 of the 23 carriers treated with ivermectin and in 3 of the 35 treated with DEC. Nine months after that treatment, the lowest mean microfilaremia was observed in the carriers treated with 3 successive semi-annual doses of DEC 3 mg/kg. Adverse reactions were comparable in carriers treated with ivermectin and in those treated with DEC, and did not interfere with daily activities of treated subjects.

Adolescent↗
PubMed1992

Natural history of the minimally abnormal Papanicolaou smear.

OBJECTIVE: We sought to determine the natural history of the cytologic and colposcopic changes in patients with minimal abnormalities on their Papanicolaou smears (atypical squamous cells of undetermined significance or low-grade squamous intraepithelial lesion [SIL]). METHODS: Between November 1988 and November 1990, 632 women with abnormal Papanicolaou smears as listed above were evaluated at Los Angeles County-Olive View Medical Center. Each had review of cytology, repeat Papanicolaou smear, and colposcopy of the lower genital tract. We excluded those who were pregnant or had findings demonstrative of moderate dysplasia or worse, or had a cervical biopsy for any other indication. Women with symptomatic vaginal discharge were treated and remained in the study. Subjects were followed every 3 months with repeat Papanicolaou smear and colposcopy for a minimum of 9 months. If at any time the Papanicolaou smear or colposcopy was consistent with moderate dysplasia or worse, directed biopsies and endocervical curettage were performed, and treatment was given accordingly. Two hundred ninety-four patients fulfilled all inclusion criteria and had adequate follow-up data. RESULTS: Nine months after enrollment, 42 of 91 women (46.2%) with atypical squamous cells had persistent changes, none had progression, and 49 (53.8%) had regression to normal. In those with low-grade SIL, 37 of 203 cases (18.2%) persisted, seven (3.4%) progressed, and 159 (78.3%) regressed by 9 months. Patients in the first group were more likely to have persistence of the cytologic abnormalities than were those in the second (P less than .01). Only the latter group progressed to high-grade dysplasia during the 9-month study interval. CONCLUSION: The majority of women with confirmed minimal cytologic changes on Papanicolaou smear will have complete colposcopic and cytologic regression over a short interval.

Adult↗
PubMed1991

Differential effect of beta-endorphin on three human cytotoxic cell populations.

We have examined in vitro the effect of the proopiomelanocortin gene product, beta-endorphin (bE), on the cytotoxic activity of natural killer (NK) cells, lymphokine activated killer (LAK) cells and cytotoxic T-lymphocytes (CTL). Our studies show that bE reproducibly suppressed LAK cytotoxic activity in all donors tested. The effect of bE on the generation of CTL varied, and was negligible on CTL cytotoxic function. Our study also confirms the variable nature of the effects of bE on NK cytotoxicity. In all instances, the effects of bE were generally small, but could be blocked by opioid receptor antagonists, or by prior heat-inactivation of the peptide. The magnitude of the effects was greatest at low effector:target ratios in all of the three systems studied. These results support the emerging body of evidence that the neuroendocrine system may influence host defense mechanisms mediated by cytotoxic cells.

Adolescent↗
PubMed1991

Pituitary-adrenal-immune system in normal subjects and in patients with anorexia nervosa: the number of circulating helper T lymphocytes (CD4) expressing the homing receptor Leu8 is regulated in part by pituitary-adrenal products.

The association between plasma pituitary-adrenal (PA) hormones and the number of certain populations of peripheral blood lymphocytes (PBL) was examined in subjects with normal PA function and in patients with anorexia nervosa (AN). AN patients display several neuroendocrine dysfunctions, including hypercortisolemia. In the normal subjects there were positive correlations between adrenocorticotropic hormone (ACTH) and the number of PBL and helper T lymphocytes expressing the homing receptor Leu8 (CD4+Leu8+); there was a negative relationship between cortisol and these lymphocyte populations. These latter, inverse correlations did not occur in the AN patients, either while underweight or after weight recovery, with some persistence of hypercortisolemia. Administration of dexamethasone (DEX) suppressed cortisol levels and reduced, perhaps via a receptor-mediated mechanism, the number of circulating PBL and CD4+Leu8+ in the normal subjects but not in the AN patients. These results support the physiological relevance of PA-CMI interaction in subjects with normal PA function and indicate that the PA-CMI interrelationship is disrupted in AN patients with hypercortisolemia.

Adrenocorticotropic Hormone↗
PubMed1991

Polyamines in the anemia of end-stage renal disease.

The improvement in the anemia in patients with end-stage renal disease (ESRD) on continuous ambulatory peritoneal dialysis (CAPD) suggests that dialyzable substances present in the sera of uremic patients either inhibit erythropoiesis directly or inactivate erythropoietin (EPO). In the present study predialysis sera from patients with ESRD inhibited erythroid colony (CFU-E) (N = 10) formation to a significantly (P less than 0.01) greater degree than granulocyte-macrophage (CFU-GM) (N = 7) colony formation in mouse bone marrow (MBM) cultures. The polyamines spermine (SP) (18 to 560 nm/ml) and spermidine (SD) (4 to 648 nm/ml) exerted a more significant (P less than 0.05) inhibition of CFU-E (N greater than or equal to 5) than that of CFU-GM (N greater than or equal to 5) growth. Concentrations of 0.80, 1.0, and 1.5 nm/ml of putrescine (PU) were 92%, 85%, and 77% of erythroid colony (CFU-E) controls (N = 4) and 104%, 130%, and 127% of CFU-GM controls (N = 4). Putrescine (PU) at 1.5 nm/ml also produced a significant (P less than 0.05) inhibition of CFU-E, whereas CFU-GM were stimulated by PU. These data suggest that predialysis sera from uremic patients, as well as SP, SD, and PU, are selectively more inhibitory to CFU-E than CFU-GM growth. The immunoreactivity of EPO was not significantly changed when it was coincubated with SP, SD and PU and measured by radioimmunoassay. PU was found to inhibit noncompetitively the bioactivity of EPO in a CFU-E assay. These data support the hypothesis that polyamines may be important uremic toxins in the anemia of ESRD.

Anemia↗
PubMed1991

Cumulative mortality rates in Aedes polynesiensis after feeding on polynesian Wuchereria bancrofti carriers treated with single doses of ivermectin, diethylcarbamazine and placebo.

During a therapeutic trial, batches of 672 to 1979 laboratory-bred Aedes polynesiensis, the mosquito vector of lymphatic filariasis in French Polynesia, were fed on Wuchereria bancrofti carriers one, three and six months after they had been treated with either single doses of ivermectin at 100 mcg/kg, diethylcarbamazine (DEC) at 3 and 6 mg/kg or placebo. High mortality rates were observed during the 15-day period following the blood-meal in mosquitoes fed on carriers treated with microfilaricidal drugs and were significantly higher in mosquitoes fed on carriers treated with ivermectin than in those fed on carriers treated with DEC. Though its intensity decreased with the passage of time, the phenomenon was observed in mosquitoes fed on carriers up to six months after treatment, especially in those fed on carriers treated with ivermectin. By decreasing the number of mosquitoes able to transmit the infection, this lethal effect on Ae. polynesiensis might represent an additional advantage of ivermectin in lymphatic filariasis control programs.

Aedes↗
PubMed1991

Interleukin-1 beta stimulates bone resorption and inhibits bone formation in vivo.

Interleukin-1 beta (IL-1 beta) and several other cytokines, including IL-1 alpha, tumor necrosis factor (TNF), and lymphotoxin, stimulate bone resorption and also inhibit bone formation in vitro. These effects are consistent with an uncoupling function for these mediators, although the effect of in vivo regulatory mechanism(s) that couple resorption and formation cannot be adequately evaluated in vitro. In the present studies, the effect of IL-1 beta on bone resorption and formation was determined in adult rats in vivo. Resorption was assessed by serum and urinary calcium levels, osteoclast number, and active resorption surface. Bone formation was determined by measurement of serum osteocalcin levels, and by quantitation of bone apposition rate using tetracycline labeling. A modest dose of IL-1 beta (1 microgram/kg) was found to stimulate transient increases in serum calcium, and a persistent elevation of urinary calcium excretion. IL-1 beta treatment also resulted in decreases in serum iron levels and in the albumin/globulin ratio, well-established in vivo effects of IL-1. SGOT, SGPT, BUN, creatinine, and total protein were unaffected, indicating that IL-1 beta treatment did not compromise kidney or liver function, and that animals were systemically healthy. This was further evidenced by normal weight gain in IL-1 beta-treated animals. Low doses (50 micrograms/kg) of synthetic human parathyroid hormone (PTH 1-34) also stimulated resorption, as shown by a sustained increase in serum calcium without increased urinary excretion. Both IL-1 beta and parathyroid hormone (PTH) stimulated similar increases in osteoclast number (N.Oc) and active resorption surface [Oc.S(%)].(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

The treatment of microfilaremia due to Wuchereria bancrofti var. pacifica: ivermectin versus diethylcarbamazine.

In October 1989, a controlled, double-blind parallel group trial was implemented to compare both efficacy and tolerability of single doses of ivermectin and diethylcarbamazine (DEC). Fifty eight apparently healthy Wuchereria bancrofti carriers were hospitalized and randomly allocated to treatment with ivermectin 100 mcg/kg, DEC 3 or 6 mg/kg. Six months later, half of those initially treated with ivermectin 100 mcg/kg and DEC 3 mg/kg were given a second similar dose while the rest were given a placebo. After initial treatment, clearance of microfilaremia was complete in 22 of the 23 carriers treated with ivermectin and in one only of the 35 treated with DEC. Adjusted geometric mean microfilaremia was significantly lower (p less than 0.01) in carriers treated with ivermectin than in those treated with DEC at one, but neither at 3 (p = 0.26) nor at 6 months (p = 0.63). The comparison of adjusted geometric mean microfilaremia per group indicated that (i) regarding either ivermectin 100 mcg/kg or DEC 3 mg/kg, 2 successive doses resulted in higher efficacy than one annual dose and (ii) efficacy of 2 successive doses of ivermectin 100 mcg/kg or DEC 3 mg/kg were not significantly different. During the 3 days following initial treatment, adverse reactions were observed in 80% of the treated carriers of whom 14% suffered a grade 3 reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Double blind study on efficacy and safety of single doses of ivermectin and diethylcarbamazine for treatment of Polynesian Wuchereria bancrofti carriers. Results at six months.

In 1989, a double-blind trial was implemented in Tahiti to compare both efficacy and tolerability of single doses of ivermectin and diethylcarbamazine (DEC) for treatment of Wuchereria bancrofti carriers. Of 58 carriers, in whom microfilarial (mf) density was greater than or equal to 100 mf/ml, 23, 24 and 11 were randomly allocated to treatment with respectively ivermectin 100 mcg/kg, DEC 3 and DEC 6 mg/kg. One week after treatment, clearance of microfilaremia was complete in 22 of the 23 carriers treated with ivermectin and in one only of the 35 treated with DEC. Adjusted geometric mean for mf densities was significantly lower (p less than 0.001) in carriers treated with ivermectin than in those treated with DEC at one, but neither at 3 (p = 0.26) nor at 6 months (p = 0.63). At 3 and 6 months, mf levels were 14 and 28%, 21.6 and 19.4%, and 10.2 and 8.4% of pretreatment mf levels in carriers treated respectively with ivermectin 100 mcg/kg, DEC 3 and DEC 6 mg/kg. Side effects were experienced by 51 carriers (88%) of whom only 8 (14%) suffered a grade 3 reaction. Onset and intensity of side effects were significantly associated (p less than 0.01) with both pretreatment mf densities and peripheral blood parasite clearance. Efficacy of ivermectin single dose was superior to that of DEC single dose in terms of immediate mf clearance but not in terms of sustained mf decrease at 6 months.

Adult↗
PubMed1990

[Perpropionic and peracetic acids destroy HIV in suspension, but do not inhibit the virus in contaminated units of blood].

The virucidal activity of peracetic and perpropionic acids was evaluated against HIV in an attempt to inactivate the virus which might contaminate blood units collected from donors. The results showed first that doses of peracids as weak as 50 ppm were able to kill the virus in free suspension, but that the doses that did not adversely affect blood components did not inactivate the virus in those components.

Acetates↗