Search PubMed⌕ Search

Biomedical subjects

L Nguyen

Publications and source records attributed to L Nguyen.

At least 109 records · Page 6Linked to original sources
PubMed1996

Clonal distribution of penicillin-resistant Streptococcus pneumoniae 23F in France.

We studied the clonality of clinical isolates of Streptococcus pneumoniae 23F, the serotype most often associated with penicillin resistance in France. Clinical isolates obtained between November 1992 and April 1993 from nasopharyngeal samples from children with acute otitis media from different regions of the country were analyzed. The genetic polymorphism of penicillin-susceptible and -resistant 23F isolates (MIC, 2 mg/liter) was studied by pulsed-field gel electrophoresis. The resistant isolates were closely related, whereas the susceptible isolates were genetically heterogeneous. PCR amplification and restriction of the genes encoding penicillin-binding proteins (PBPs) 1A, 2B, and 2X also showed that the 24 resistant isolates had similar patterns which were very different from those of the susceptible isolates. All resistant isolates gave the same PBP pattern, with low affinities of PBPs for penicillin. Our results indicate that, in contrast to penicillin-susceptible 23F isolates, the penicillin-resistant 23F isolates have a single clonal origin, suggesting the rapid clonal spread of a resistant epidemic strain throughout the country.

Bacterial Proteins↗
PubMed1995

Selective trafficking of KNOTTED1 homeodomain protein and its mRNA through plasmodesmata.

Plasmodesmata are intercellular organelles in plants that establish cytoplasmic continuity between neighboring cells. Microinjection studies showed that plasmodesmata facilitate the cell-to-cell transport of a plant-encoded transcription factor, KNOTTED1 (KN1). KN1 can also mediate the selective plasmodesmal trafficking of kn1 sense RNA. The emerging picture of plant development suggests that cell fate is determined at least in part by supracellular controls responding to cellular position as well as lineage. One of the mechanisms that enables the necessary intercellular communication appears to involve transfer of informational molecules (proteins and RNA) through plasmodesmata.

Amino Acid Sequence↗
PubMed1995

Endogenous IL-10 protects mice from death during septic peritonitis.

IL-10 production during endotoxic shock is part of a protective mechanism that involves IL-10-induced inhibition of TNF synthesis. We sought to determine the role of IL-10 in septic peritonitis induced by cecal ligation and puncture (CLP). CLP led to a rapid induction of IL-10 mRNA in various organs of C57BI/6 mice. In liver, IL-10 mRNA was detectable within 1 h following CLP, while in spleen and lungs, IL-10 mRNA was detected from 2 to 4 h and onward. IL-10 protein became detectable in plasma 2 h after CLP, reaching peak concentrations after 12 h (12.7 +/- 5.7 ng/ml). Pretreatment (-2 h) with anti-IL-10 mAb resulted in higher plasma TNF levels following CLP when compared with mice treated with control mAb. Plasma IL-1 activity and IFN-gamma remained undetectable in virtually all mice. Anti-IL-10 enhanced mortality after CLP (p < 0.05 by log-rank test). Addition of anti-TNF mAb did not influence the increased mortality associated with anti-IL-10 treatment. Septic peritonitis is associated with sustained production of IL-10 in various organs, which serves to protect the host against lethality.

Animals↗
PubMed1995

Cucumber mosaic virus 3a protein potentiates cell-to-cell trafficking of CMV RNA in tobacco plants.

Contrary to a previous report, electron microscopic studies on the Fny strain of cucumber mosaic virus (CMV)-infected tobacco tissues revealed that plasmodesmata were not structurally modified during CMV infection, nor were virions ever observed in plasmodesmata connecting infected cells. To further explore the basis of CMV infection, experiments were performed on the CMV 3a ORF. The 3a protein of CMV was expressed in and purified from Escherichia coli. The purified protein was labeled with fluorescein isothiocyanate (FITC) and subsequently microinjected into mesophyll cells of mature leaves of Nicotiana tabacum cv. Turkish Samsun NN. Within a brief period (as little as 1 sec), the microinjected FITC-labeled CMV 3a protein moved into neighboring cells. Co-injection of unlabeled CMV 3a protein with 9.4-kDa fluorescein-conjugated dextran (F-dextran) resulted in extensive cell-to-cell movement (diffusion) of the F-dextran, indicating that the 3a protein can interact with and dilate plasmodesmata. Furthermore, co-injection of unlabeled 3a protein with fluorescently labeled infectious CMV RNA molecules resulted in rapid and extensive cell-to-cell transport. In contrast, a mutant form of the 3a protein was unable to traffic from cell to cell, to increase the size exclusion limit of plasmodesmata, or to potentiate cell-to-cell trafficking of CMV RNA molecules. Microinjection studies performed on transgenic tobacco plants expressing the CMV 3a protein indicated that fluorescently labeled CMV RNA moved out of the target cell into the surrounding mesophyll tissue. In addition, expression of the CMV 3a protein also potentiated the cell-to-cell movement of 9.4-kDa F-dextran. Collectively, these results provide direct experimental evidence that the CMV 3a protein functions as the movement protein of CMV. These findings are consistent with the hypothesis that CMV moves from cell-to-cell in the form of a ribonucleoprotein complex.

Base Sequence↗
PubMed1995

Repair of congenital diaphragmatic hernia after weaning from extracorporeal membrane oxygenation.

Stabilization and delayed operation for patients with congenital diaphragmatic hernia (CDH) is now widely accepted. When preoperative extracorporeal membrane oxygenation (ECMO) is needed, most centers have CDH repaired on ECMO to minimize the risk of postoperative deterioration. The authors adopted a policy of weaning from ECMO before repair in an effort to avoid hemorrhagic risks. They reviewed their experience with CDH patients who required ECMO for stabilization before repair but for whom post-ECMO repair was planned. The records of all high-risk CDH patients with a gestational age of at least 34 weeks were reviewed. Eighteen patients were identified. None of the eight who were stabilized and operated on without ECMO required bypass postoperatively; all survived. Ten were placed on bypass, nine for stabilization before repair. Of the nine, seven (78%) were weaned from ECMO to conventional ventilation. Repair of the diaphragmatic defect was performed an average of 3.8 days later; none of these patients had severe pulmonary hypertension postoperatively, and all survived. Two could not be weaned before repair, one of whom had a complex congenital heart defect. This patient died. The other patient had repair on ECMO because of intrathoracic gastric volvulus. Severe blood loss prompted decannulation, and the patient died. One patient who was placed on bypass was transferred 10 days after having had repair elsewhere (at 4 hours of age). Pulmonary hypertension did not resolve, and the postmortem examination showed alveolar capillary dysplasia, with focal misalignment of the pulmonary vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Extracorporeal Membrane Oxygenation↗
PubMed1994

Mechanism of virus-induced Ig subclass shifts.

Infection of mice with live viruses leads to a dramatic increase in the amount of IgG2a Ig with a consequent shift in the ratio of IgG1/IgG2a. To examine the Ig subclass shift induced by viral infection, we challenged mice with live virus, inactivated virus, or replication-defective mutant viruses that were able to infect cells and produce some viral proteins but were not able to complete a replicative cycle. While killed (or inactivated) virus was capable of inducing HSV-specific antibody, it did not stimulate a shift in the subclass of the total Ig. Replication-defective mutant viruses that fail to express a functional ICP8 or ICP27 protein, but not a mutant expressing a defective ICP4 protein, were able to stimulate the shift. Thus, only a portion of the lytic cycle is sufficient to induce the shift. At least part of the effect is mediated by IFN-gamma.

Animals↗
PubMed1994

Ultrasonic root-end preparation. Part 1. SEM analysis.

Preparations of apical cavities in resected root ends using rotary burs, with and without citric acid rinse, and ultrasonic tips were compared based on the presence or absence of superficial debris and smear layer. Three groups of 20 extracted teeth each were prepared as follows; I, a size 010 round bur was used to prepare an apical cavity 2-3 mm down the long axis of the root; II, treatment as per group I followed by a 60-s rinse with a solution of 10:3 (10% citric acid, 3% Fe2Cl3); and III, an ultrasonic retrotip was used to prepare a 2-3 mm deep apical cavity. Roots were grooved longitudinally, split and prepared for SEM analysis at x100 and x780 magnification. Examiners were calibrated to a standardized grading system. Extensive statistical analyses indicated statistically significant differences within and among the groups (P < 0.05). Root-end preparation with a bur created a heavy smear layer at all levels of the preparation. This layer was partially removed during ultrasonic preparation in the apical two-thirds. A greater removal of the smear layer was achieved with the citric acid rinse (P < 0.05). Coronally, root-end preparations were contaminated with moderate to heavy amounts of debris with all techniques.

Citrates↗
PubMed1994

Captopril inhibits proliferation of human lung fibroblasts in culture: a potential antifibrotic mechanism.

The angiotensin converting enzyme (ACE) inhibitor captopril, a free-thiol compound used widely as an antihypertensive agent, also inhibits radiation-induced pulmonary fibrosis in rats (Ward et al., Int J Radiat Oncol Biol Phys 19:1405, 1990). In an attempt to clarify the antifibrotic mechanism of captopril in vivo, the present study examined the effect of the drug on proliferation of human lung fibroblasts in culture. Captopril produced a drug dose-dependent reduction in fibroblast proliferation and 3H-thymidine incorporation during a 24-72-hr incubation. This cytostatic action of captopril was not the result of cytotoxicity as assessed by trypan blue exclusion, or by 51Cr or lactate dehydrogenase (LDH) release. Fibroblasts stimulated to proliferate by basic FGF were more sensitive to the antimitotic effect of captopril than were unstimulated cells. The ability of captopril to inhibit 3H-thymidine incorporation was not reversed by exogenous angiotensin 2, and was not mimicked by the nonthiol ACE inhibitor lisinopril. These data indicate that the cytostatic effect of captopril was not attributable to ACE inhibition. Penicillamine, a thiol compound with virtually no ACE inhibitory activity, also reduced fibroblast 3H-thymidine incorporation, indicating that the antimitotic action of captopril may represent a nonspecific sulfhydryl effect. This study suggests that the antifibrotic activity of captopril in irradiated lung may result in part from a direct inhibition of fibroblast proliferation, particularly in fibroblasts responding to mitogenic stimuli.

Angiotensin II↗
PubMed1994

[Drug-induced parkinsonian syndromes: a 10-year experience at a regional center of pharmaco-vigilance].

Besides classical neuroleptics, several drugs can induce parkinsonian symptoms. The present retrospective study investigates the characteristics of drug-induced parkinsonism notified to the Midi-Pyrénées Pharmacovigilance Centre between 1983 and 1992. Among 3,923 side effects spontaneously reported between 1983 and 1992 to the center, 53 (1.4%) were drug-induced parkinsonism. Mean age was 65 +/- 2 (s.e.m.) years (range 21-88). Drug-induced parkinsonism appeared after a mean treatment duration of 473 +/- 142 days (range 1 day to 15 years) and occurred most frequently in women (63%). The occurrence onset of drug-induced Parkinsonism exhibited a bimodal pattern with a first peak (between 0 and 6 months) mainly due to peripheral or central antidopaminergic drugs and a second one later (between 9 and 12 months) due mostly to calcium channel blockers. Involved drugs were mostly antidopaminergic agents: neuroleptics (antipsychotic drugs: 39%) but also agents used for nausea or vomiting (domperidone, metoclopramide, metopimazine or triethylperazine: 12%) or symptoms associated with menopause (veralipride: 6%). Other cases were related mainly to drugs with "calcium channel blocker" properties (flunarizine and cinnarizine: 30%), H1 antihistamine (1 case), fluoxetine (1 case), alphamethyldopa (1 case) or reserpine (1 case) whereas 3 cases were due to drug interactions. Imputability scores (according to the method of assessment of unexpected drug reactions used in France) were "doubtful" (11%), "plausible" (34%) and "probable" (53%). The complete triad (tremor, akinesia plus rigidity) was seen in 13 (25%) cases. Symmetrical symptoms occurred in 41 (77%) patients. A total disappearance of the clinical feature occurred in 39 (74%) patients whereas in 8 cases (15%), drug-induced parkinsonism led to the diagnosis of underlying idiopathic Parkinson's disease. The present study shows that around 80% of drug-induced parkinsonism are due to two pharmacological classes: central and peripheral antidopaminergic agents and calcium channel blockers.

Adult↗
PubMed1994

Recovery of antioxidants and reduction in lipid hydroperoxides in murine epidermis and dermis after acute ultraviolet radiation exposure.

In previous studies we have found that a single acute dose of ultraviolet radiation to murine skin causes a large degree of destruction of enzymic and non-enzymic antioxidants immediately after irradiation. In the present study, we wished to elucidate the recovery of antioxidants after a single dose of ultraviolet (UV) radiation. We measured antioxidants and lipid hydroperoxides (as a marker of membrane damage) in murine epidermis and the dermis at 0, 3, 12, 24, 72 and 120 h after exposure to UV radiation (25 J/cm2, UVA+UVB). Lipid hydroperoxides showed the highest values immediately after UV exposure and returned to control values within 24 h in both epidermis and dermis. The activities of catalase, glutathione peroxidase and glutathione reductase showed the lowest activities immediately after UV exposure; superoxide dismutase activities reached a minimum at 3 h postexposure. The pattern of recovery was different for each enzyme and for epidermis and dermis. The activities of superoxide dismutase and catalase decreased remarkably and recovered slowly. Superoxide dismutase in the dermis recovered full activity by 120 h and in the epidermis by 12 h. Catalase activity in both epidermis and dermis had returned to only 50% of control activity at 120 h, although the epidermis showed a temporary increase (to 93%) at 24 h. Glutathione peroxidase and glutathione reductase were slightly decreased immediately after irradiation, recovered to 100% at 3 h and then increased to 200-250% in both the epidermis and the dermis at various times; values had returned to 100% in epidermis by 120 h but remained elevated in dermis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Reduced density of adenosine A1 receptors and preserved coupling of adenosine A1 receptors to G proteins in Alzheimer hippocampus: a quantitative autoradiographic study.

Binding to adenosine A1 receptors and the status of their coupling to G proteins were studied in the hippocampus and parahippocampal gyrus of Alzheimer individuals and age-matched controls. The binding to A1 receptors was compared with binding to the N-methyl-D-aspartate receptor complex channel-associated sites (labeled with (+)-[3H]5-methyl-10,11-dihydro-5H- dibenzo[a,d]cyclohepten-5,10-imine maleate). In vitro quantitative autoradiography demonstrated a similar anatomical distribution of A1 receptors labeled either with an agonist ((-)-[3H]phenylisopropyladenosine) or antagonist ([3H]8-cyclopentyl-1,3-dipropylxanthine) in the brains of elderly controls. In Alzheimer patients, significant decreases in the density of both agonist and antagonist binding sites were found in the molecular layer of the dentate gyrus. Decreased A1 agonist binding was also observed in the CA1 stratum oriens and outer layers of the parahippocampal gyrus, while reduced antagonist binding was found in the subiculum and CA3 region. Reduced density of the N-methyl-D-aspartate receptor channel sites was found in the CA1 region and parahippocampal gyrus. The reductions in binding to adenosine A1 and N-methyl-D-aspartate receptors were due to a decrease in the density of binding sites (Bmax), and not changes in receptor affinity (KD). In both elderly control and Alzheimer subjects, GTP substantially reduced the density of A1 agonist binding sites with a concomitant increase in the KD values, whereas antagonist binding was unaffected by GTP. The results suggest that adenosine A1 receptor agonists and antagonists recognize overlapping populations of binding sites. Reduced density of A1 receptors in the molecular layer of the dentate gyrus most probably reflects damage of the perforant path input in Alzheimer's disease, while altered binding in the CA1 and CA3 regions is probably due to loss of intrinsic neurons. Similar effects of GTP on binding to A1 receptors in control and Alzheimer individuals suggest lack of alterations in coupling of A1 receptors to G proteins in Alzheimer's disease, thus supporting the notion of normal receptor coupling to their effector systems in Alzheimer's disease.

Adenosine↗
PubMed1993

Depressive symptoms among Vietnamese-American college students.

Fifty Vietnamese-American college students completed questionnaires measuring depressive symptoms, stressful life events, and acculturation to Vietnamese society versus U.S. society. In contrast to the findings of earlier studies, in which attention was limited to depressive symptoms specific to traditional Vietnamese culture, no gains in reliability or validity were apparent when analyses were limited to these symptoms. Acculturation to U.S. society was positively associated with increased reports of depressive symptoms, as was the occurrence of stressful life events. Implications of these findings are discussed in terms of the changing nature of the Vietnamese-American population.

Acculturation↗
PubMed1993

Chronic haloperidol treatment enhances binding to NMDA receptors in rat cortex.

Hyperactivity of the dopaminergic system and a hypoglutamatergic state have been hypothesized to underlie schizophrenia. It has also been proposed that neuroleptics may interact not only with the dopaminergic system but also with the glutamatergic system. We found that daily intraperitoneal injections of haloperidol (1 mg kg-1) for 21 days resulted in increased binding (10-20%) to the NMDA type of glutamate receptors in the outer layers of rat parietal cortex. Quantitative receptor autoradiography indicates that the action of haloperidol is regionally specific since no changes in NMDA receptors were found in the hippocampus and thalamus. Our data suggest that haloperidol may exert its antipsychotic effects by enhancement of glutamatergic functions as well as by the blockade of dopamine receptors.

Analysis of Variance↗
PubMed1993

An assessment of the plastic Thermafil obturation technique. Part 2. Material adaptation and sealability.

The short- and long-term apical seal of root canals obturated with softened alpha-phase gutta-percha on plastic core-carriers, Thermafil, was compared to that of laterally condensed, cold gutta-percha. Fifty-one roots from mandibular molars 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. Teeth were separated into three groups of 17 each and placed in black India ink for 24 h, 7 days or after 5 months storage in water. The teeth were demineralized, rendered transparent, and apical microleakage determined by the linear measurement of dye penetration. Significant differences in microleakage were noted between the 24 h and 5-month Thermafil groups (P < 0.05), 24-h and 7-day lateral condensation groups (P < 0.05), and 24-h and 5-month lateral condensation groups (P < 0.05). There were no significant differences between the two techniques at each time interval. It was concluded that both techniques demonstrated a significant increase in apical microleakage over a 5-month period.

Dental Leakage↗
PubMed1993

Alcoholism in Peru.

OBJECTIVE: Alcoholism is a problem of worldwide concern. Full appreciation of this international problem requires that adequate diagnostic measures be constructed and that comparable measures for different cultures be available so that valid differences in prevalence across cultures can be detected. A Spanish-language version of the Diagnostic Interview Schedule (DIS) has been used for epidemiologic studies of alcohol abuse and dependence in Los Angeles Mexican-Americans and mainland Puerto Ricans, and the authors used the same instrument to conduct a similar study in Peru. METHOD: A population sample (N = 815) from the Independencia district of Lima, Peru, was chosen for interviews with a revised form of the Spanish translation of the DIS. Lifetime prevalence rates of alcoholism and other DSM-III diagnoses were determined. RESULTS: The prevalence of alcohol abuse or dependence was higher among the men (34.80%) than among the women (2.46%), but the onset for women was earlier. Alcoholism was strongly associated with antisocial personality disorder and with drug abuse or dependence. CONCLUSIONS: The prevalence of alcoholism for the Peruvian men is higher than prevalences for men in U.S. studies, but the prevalence among the Peruvian women is one of the lowest reported. The high prevalence among men is likely due to cultural mores but may also be linked to the stresses found in impoverished societies undergoing rapid social, cultural, and economic change.

Adolescent↗
PubMed1993

Sedation and analgesia for gastrointestinal endoscopy.

We compared analgesia and sedation provided by one of four different opioids in combination with midazolam during gastrointestinal endoscopy. Patients were given 1-3 mg midazolam and meperidine 50-100 mg, fentanyl 50-100 micrograms, sufentanil 5-10 micrograms, or alfentanil 150-300 micrograms, plus additional opioid and/or midazolam if needed. No untoward effects (i.e., O2 saturation < 85%, nausea, vomiting, severe bradycardia) occurred. Sedation and analgesia were comparable in the upper gastrointestinal groups. The number of patients with amnesia for the examination was highest in the meperidine group. Recovery time generally was shorter with alfentanil and sufentanil. Recovery time of the lower gastrointestinal patients was significantly longer in the meperidine group than in the other groups; analgesia scores for sufentanil were significantly lower than for meperidine. Sedation scores for these patients were highest in the meperidine group. The number of patients given meperidine who were amnesic was significantly greater than for the other opioids. Meperidine was better than the other opioids with regard to patient comfort and amnesia during colonoscopy.

Adolescent↗