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Biomedical subjects

V K Nguyen

Publications and source records attributed to V K Nguyen.

At least 19 recordsLinked to original sources
PubMed2006

A longitudinal study to identify constraints to dairy cattle health and production in rural smallholder communities in Northern Vietnam.

The objective of the study was to investigate constraints to dairy cattle health and production in rural smallholder communities in northern Vietnam, one of the target areas of the Vietnam government's dairy development programme. A total of 99 dairy farms (11 per commune) were recruited from 9 of 32 communes in Ba Vi District, using random two-stage cluster sampling. After the initial questionnaire interviews were conducted, farms were visited at three monthly intervals over a period of 1 year. Information on several health and production parameters relating to the study cattle was collected. Using multiple indicator modelling, it was found that Fasciola infestation, farmers who had been involved in dairying for longer (not indicative of better management skills), larger herd size, and cattle being kept in a shed were linked to reduced reproductive performances.

Animal Husbandry↗
PubMed2006

Effects of drug resistance on viral load in patients failing antiretroviral therapy.

Previous studies on patients who develop drug resistant HIV-1 variants have shown that continued use of failing regimens might provide clinical benefit. However, the effect of long-term exposure to drug resistant variants may lead to emergence of compensatory mutations that may jeopardize this effect. In this study, we assess associations among type and number of drug resistant mutations, viral load and disease progression in patients with long-term follow up. Patients with genotypic testing performed at the time of treatment failure were enrolled. Comparison of viral load and CD4 cell count between different resistance groups was performed using analysis of variance. Multiple linear regression analysis was performed to assess the simultaneous effects of the presence of particular mutations and their accumulation on viral load. Data from 475 patients who were followed for a median of 43 months from October 1999 to July 2005 were studied. A "V shape" relationship was observed between the number of mutations and viral load. Specifically, in patients harboring up to five mutations, viral load was reduced by 0.8 log/copies when compared to wild-type variants. However, with more than six mutations viral load progressively increased. Certain reverse transcriptase mutations such as M184V/I, K70R, V108I, and protease mutations such as L33FIV, M84V, and M36I were associated with reduced viral load. Together, these findings suggest that long-term maintenance of a sub-optimal antiretroviral regimen may have deleterious consequences for the patient.

Adult↗
PubMed2006

Taenia solium taeniasis and cysticercosis in three communities in north Vietnam.

OBJECTIVES: (1) To investigate the response to a serum antigen-detecting ELISA for cysticercosis and a stool coproantigen test for taeniasis in two rural communities (mountainous and coastal areas) and one group of (peri-)urban factory workers; and (2) to examine clinical features of human cysticercosis in northern Vietnam. METHODS: Villagers and factory workers and their families were informed and invited to participate in the study. Blood and faecal samples were collected from the participants and a simple questionnaire on taeniasis/cysticercosis completed. Serum was examined for the presence of circulating cysticercus antigen by a monoclonal-based sandwich ELISA. Ag-ELISA positive persons underwent a clinical examination and a computed tomography (CT) scan. Stool samples were examined microscopically for the presence of Taenia eggs and for copro-antigens. Tapeworms were identified following therapeutic expulsion using morphology and PCR-RFLP. RESULTS: Circulating cysticercus antigens, suggesting active infection, were detected in 5.3% (16/303), 0.6% (1/175) and 0.0% (0/229) of the sampled individuals from the mountainous, coastal and urban regions, respectively. Clinical examination and CT scan of the cysticercus antigen positive persons showed that active cysticercosis did not cause severe disease in most cases. Taenia copro-antigens were found in 0.3% (1/297), 1.8% (3/166) and 0.0% (0/228) of the stool samples from the mountainous, coastal and urban communities, respectively. Three tapeworms were expelled after treatment: two Taenia solium and one Taenia saginata. CONCLUSION: This survey points to a focal distribution of taeniasis/cysticercosis and suggests that human cysticercosis is rather acquired due to close contact with a T. solium carrier and self-infection, than through infection from the environment.

Adolescent↗
PubMed2006

Prevalence of multiresistant Gram-negative organisms in a surgical hospital in Ho Chi Minh City, Vietnam.

OBJECTIVE: To determine resistance patterns of multiresistant Gram-negative organisms at a surgical hospital in Ho Chi Minh City, Vietnam, in order to guide appropriate antibiotic prescribing and improve infection control procedures. METHOD: All samples sent in for microbiological analysis over a 3-month period were included. A resource neutral double disc-diffusion test was introduced to detect the presence of extended-spectrum beta-lactamase (ESBL) production. RESULTS: We obtained 350 bacterial isolates from clinical specimens; 87.4% were Gram-negative bacteria (GNB). Of these, 88.9% were Enterobacteriaceae, of which 14.7% produced ESBL. Fifteen (37.5%) of these were isolated within 48 h of admission. Resistance to gentamicin and ciprofloxacin occurred in 70.0% and 72.5% of those organisms that produced ESBL and in 39.5% and 38.7% of those that did not. Resistance to third-generation cephalosporins was common: 36.7% of all GNB were resistant to ceftriaxone, 34.0% to cefotaxime, 19.6% to ceftazidime and 36.7% to cefoperazone. CONCLUSION: Multiresistant Gram-negative organisms are common and pose a challenge to antibiotic therapy. Successful implementation of a simple test to detect ESBL production allowed reporting of these organisms, appropriate antibiotic prescribing and infection control interventions. Development of antibiotic-prescribing guidelines must take into account these resistance patterns.

Anti-Bacterial Agents↗
PubMed2003

Emergence and evolution of functional heavy-chain antibodies in Camelidae.

Antibodies of jawed-vertebrates are composed of paired heavy (H) and light (L) polypeptide chains. Surprisingly, the sera of camelids, nurse shark and wobbegong shark, and possibly ratfish contain antibodies that lack L-chains. In camelids, these Heavy-chain antibodies (HCAbs) are gamma-isotypes, and are functional in antigen binding. In this review we focus on the dedicated immunoglobulin (Ig) genes that encode the HCAb in Camelidae (camels, dromedaries and llamas), about their origin, and how these camel immunoglobulins evolved and acquire a large and diverse repertoire of antigen binding sites in absence of the H-L combinatorial diversity.

Amino Acid Sequence↗
PubMed2000

Camel heavy-chain antibodies: diverse germline V(H)H and specific mechanisms enlarge the antigen-binding repertoire.

The antigen-binding site of the camel heavy-chain antibodies devoid of light chain consists of a single variable domain (V(H)H) that obviously lacks the V(H)-V(L) combinatorial diversity. To evaluate the extent of the V(H)H antigen-binding repertoire, a germline database was constructed from PCR-amplified V(H)H/V(H) segments of a single specimen of Camelus dromedarius. A total of 33 V(H)H and 39 V()H unique sequences were identified, encoded by 42 and 50 different genes, respectively. Sequence comparison indicates that the V(H)Hs evolved within the V(H) subgroup III. Nevertheless, the V(H)H germline segments are highly diverse, leading to a broad structural repertoire of the antigen-binding loops. Seven V(H)H subfamilies were recognized, of which five were confirmed to be expressed in vivo. Comparison of germline and cDNA sequences demonstrates that the rearranged V(H)Hs are extensively diversified by somatic mutation processes, leading to an additional hypervariable region and a high incidence of nucleotide insertions or deletions. These diversification processes are driven by hypermutation and recombination hotspots embedded in the V(H)H germline genes at the regions affecting the structure of the antigen-binding loops.

Amino Acid Sequence↗
PubMed1999

Protection of immunoreactivity of dry immobilized proteins on microtitration plates in ELISA: application for detection of autoantibodies in myasthenia gravis.

We show the ability of the BSA-trehalose film to convert normally fragile proteins such as mouse monoclonal antibody to the Alzheimer precursor protein A4 (APP695) and cell line TE671 acetylcholine receptor (AChRTE671) into a stable reagent, after its immobilization on microtitration plates. The remarkable property of the dry immobilized proteins are their stability under prolonged exposure to temperatures as high as 50 degrees C. Using the AChRTE671, the proposed method was applied for the measurement of anti-AChR autoantibodies in Myasthenia gravis by means of an enzyme-linked immunosorbent assay (ELISA). The test was shown to be specific and able to detect anti-AChR autoantibodies at concentrations as low as 3 nM. Using the same AchRTE671 as antigen, the results of examination of 34 serum samples for detection of anti-AChR autoantibodies by ELISA were compared with those of the conventional radioimmunoprecipitation assay (RIA). It was concluded that ELISA is another useful method for the diagnosis of M. gravis. The ELISA method offers a rapid, simple, safe and inexpensive means for mass screening of M. gravis.

Autoantibodies↗
PubMed1999

'LABNOTE', a laboratory notebook system designed for academic genomics groups.

We have developed a relational laboratory database system, adapted to the daily book-keeping needs of laboratories that must keep track of information acquired on hundreds or thousands of clones in an effective and user-friendly fashion. Data, whether final or related to experiments in progress, can be accessed in many different ways, e.g. by clone name, by gene, by experiment or through DNA sequence. Updating, import and export of results is made easier by specially developed tools. This system, in network version, serves several groups in our Institute and (over the Internet) elsewhere, and is instrumental in collaborative studies based on expression profiling. It can be used in many similar situations involving progressiveaccumulation of information on sets of clones or related objects.

Database Management Systems↗
PubMed1999

Loss of splice consensus signal is responsible for the removal of the entire C(H)1 domain of the functional camel IGG2A heavy-chain antibodies.

The molecular basis for the absence of the C(H)1 domain in naturally occurring heavy-chain antibodies of the camelids was assessed by determining the entire Camelus dromedarius gamma2a heavy-chain constant gene. The organization of the camel gamma2a constant heavy-chain gene obtained from a liver genomic library appears to be typical of all other mammalian gamma genes sequenced to date. It contains the switch, CH1, hinge, CH2, CH3, M1 and M2 exons. In contrast to the case in mouse and human heavy chain diseases, the camel gamma2a gene shows no major structural defect, and its equivalent CHI exon is intact. However, sequence analysis has revealed that the splicing site, immediately after the CH1 exon, is defective due to point mutations, especially the G(+1) to A(+1) transversion seems to be detrimental. It is concluded that the loss of the splice consensus signal is responsible for the removal of the entire CH1 domain in camel gamma2a heavy-chain immunoglobulins. Additionally, a closer analysis of the hinge exon suggests the possible involvement of transposons in the genetic variation of mammalian Cgamma hinges.

Amino Acid Sequence↗
PubMed1999

[Reactions of cells of nasal and sinusoidal mucosa of goats and sheep naturally infected by Oestrus ovis Linné 1758 (Diptera: Oestridae)].

OEstrosis is a very common myiasis of sheep and goats in mediterranean and tropical countries. Goats are suitable hosts for OEstrus ovis but the parasitic burden remain lower than in sheep. Cellular responses (mucous and serous mast cells, eosinophis and globules leucocytes) were measured in 30 infected and 30 non infected sheep and in 23 infected and 24 non infected goats. The presence of OEstrus ovis larvae led to an important inflammatory response in sheep and in goats as well. Furthermore, the intensity of the cellular response correlated with the larva burden, specially with globules leucocytes and eosinophils. Nevertheless, huge differences occurred between sheep and goats responses even in similar larval burden range. Infected sheep showed larger counts of mucous mast cells than goats, the differences were smaller in serous mast cells and eosinophils and no difference was detected in globules leucocytes (intraepithelial mast cells) counts between the two hosts species. These results were compared with those obtained in gastro-intestinal strongyles infections.

Animals↗
PubMed1998

The specific variable domain of camel heavy-chain antibodies is encoded in the germline.

The variable domains of the functional heavy-chain antibodies (VHHs) discovered in camels are related to the human VH subgroup III. They are nevertheless clearly distinguishable from the VHs of conventional four-chain immunoglobulins by the presence of important amino acid substitutions, located in the solvent-exposed surface normally covered by the variable domain of the light chain. The analysis of an unrearranged dromedary DNA library revealed that the specific VHH gene with its characteristic amino acid substitutions is encoded in the germline. Therefore, it is concluded that the VHHs do not arise through an ontogenic process of somatic hypermutation. The presence of putative DNA recombination signals that are more prevalent in the camel VHH, compared to the VH germline gene, might play a role in the formation and efficient expansion of the VHH repertoire.

Amino Acid Sequence↗
PubMed1996

[Mast cells and eosinophils of the respiratory mucosa of sheep with Oestrus ovis (Linné, 1761) infection].

Mast cells and eosinophils have been identified by differential stainings and counted in mucous membrane of nasal septum, turbinates and sinus of 77 ewes naturally infected with Oestrus ovis. Results have been compared with those of nine parasite free lambs. Anova tests indicate significant differences between infected and parasite-free sheep for the cell numbers and their distribution among the septum, the turbinates and the sinus and according to their position in mucous membrane, interglandular chorion of sub-mucosa. In infected sheep, the mean number of mast cells is twice the number present in parasite free animals. The burdens of eosinophils are multiplied by 17 for the septum, 29 for the turbinates and 58 for the sinus. The hypothesis of the development of an hypersensitivity phenomenon in ovine oestrosis is sustained by these results.

Animals↗
PubMed1993

Evaluation of an enzyme-linked immunosorbent assay for detection of antibodies to bovine leukemia virus in serum and milk.

The results of examination of 375 bovine serum and 150 bovine milk samples for detection of bovine leukemia virus infection by the immunodiffusion technique were compared with those of an enzyme-linked immunosorbent assay (ELISA). It was concluded that the ELISA is another useful method for the detection of antibodies to bovine leukemia virus in serum and milk. The ELISA provides a quantitative result and has the advantage of being more sensitive and less time-consuming than the conventional immunodiffusion technique.

Animals↗
PubMed1991

Immobilized enzyme electrode for creatinine determination in serum.

An immobilized enzyme electrode for continuous creatinine determination in blood serum is described. The enzymes creatinine amidohydrolase, creatine amidinohydrolase, and sarcosine oxidase are coimmobilized to the surface of the polypropylene membrane of a Clark-type electrode responsive to oxygen. The immobilized enzymes catalyze the decomposition of creatinine with the consumption of oxygen and thus permit the creatinine measurement. The whole assay takes less than 1 min. Effects of pH and temperature on electrode response are also described. The proposed technique offers a rapid, simple, and inexpensive means to determine creatinine in blood serum within the normal and abnormal ranges. The repeatability of the creatine determination in serum is 2.5% (relative standard deviation), and the detection limit is 3 x 10(-6) mol L-1. The results obtained by this method were compared to those obtained with the Technicon AutoAnalyzer SMAC system based on the Jaffé reaction; the correlation factor between the two methods was found to be r = 0.9997.

Amidohydrolases↗
PubMed1990

Enzyme immunoassay (ELISA) for detection of Clostridium difficile toxin B in specimens of faeces.

Antisera against Clostridium difficile toxin B were prepared in sheep and rabbit and were used in indirect and sandwich enzyme-linked immunosorbent assays (ELISA) for the detection of toxin B. Polyvinyl chloride and polystyrene microtitration plates were tested as solid phases for the assay. Both assays had a lower limit of detection for toxin B of 1 ng/ml. They were used to detect the presence of toxin B in 210 human faecal specimens and also in the culture supernatant fluids of C. difficile strains isolated from the faecal samples. There was a close correlation between the results of sandwich ELISA and those of cytotoxicity tests and isolation of C. difficile. Our sandwich ELISA method seems to be useful as a presumptive test for detection of C. difficile toxin B.

Bacterial Proteins↗
PubMed1989

Clostridium difficile toxin B: characterization and sequence of three peptides.

The cytotoxin, also named toxin B, was isolated from a toxigenic strain of Clostridium difficile, purified to homogeneity and partially characterized. The purification procedure included ultrafiltration followed by anion-exchange chromatography. We noticed that a non-specific nucleic material eluted with the protein during the purification. The presence of these nucleic acids appeared to be important for the toxic activity of the protein. Some characteristics of the cytotoxin were examined, especially the amino acid composition and the sequence of three tryptic fragments.

Amino Acid Sequence↗