Biomedical subjects

V Q Nguyen

Publications and source records attributed to V Q Nguyen.

11 recordsLinked to original sources

PubMed1996

Energy effects in collisional neutralization with organic molecules.

Neutralization-reionization of CH3OH+., CH3NH2+. and (CH3)2NH+. ions was studied under conditions of exothermic and endothermic electron transfer and distributions of internal energy in the reionized ions were determined. The internal energy deposited on neutralization at kiloelectronvolt collision energies is governed by Franck-Condon effects for the systems under study, whereas the endothermic or exothermic energy balance in electron transfer from molecular targets has only a small effect on the high-energy fraction of the molecules formed. Electron transfer from low-lying molecular orbitals of the organic donor is suggested to occur during random orientations of the ion-molecule collision pair. The internal energy of the precursor ions to be neutralized has a large effect on the relative abundances of survivor ions in the spectra. Vertical recombination energies of CH3OH+. and CH3NH2+. are found by Gaussian-2 level calculations to differ substantially from vertical ionization energies of the corresponding neutral molecules. Franck-Condon effects are analyzed for the vibrational modes that are affected most by vertical electron transfer.

Chemical Phenomena↗

PubMed1993

Anti-TAPA-1 antibodies induce protein tyrosine phosphorylation that is prevented by increasing intracellular thiol levels.

We studied the signal induced by the anti-TAPA-1 antibody and compared it to the signal induced by anti-IgM antibodies in a human B cell line, OCl-LY8. We found that exposure of these cells to either antibody resulted in a rapid increase in protein tyrosine phosphorylation which was prevented by inhibitors of tyrosine kinases. Tyrosine phosphorylation was an early event in the cascase leading to the antiproliferative effect of the anti-TAPA-1 antibody. However, 2-ME, a reducing agent that is not an inhibitor of tyrosine kinases, prevented both tyrosine phosphorylation and the antiproliferative effect of the antibody. Cells grown in low concentrations of 2-ME did not exhibit an increase in tyrosine phosphorylation in response to the anti-TAPA-1 antibody and were insensitive to the antiproliferative effect of the antibody. In contrast, the same cells maintained in 2-ME were able to induce tyrosine phosphorylation in response to anti-IgM. The use of 2-ME resulted in an increase in intracellular thiols, mostly glutathione. Moreover, compounds that block glutathione synthesis rendered cells susceptible to the antibody, even in the presence of 2-ME. These experiments demonstrate that tyrosine kinases are involved in propagating the antiproliferative signal initiated by the anti-TAPA-1 antibody and suggest that this signal is dependent upon the level of intracellular thiols.

Antigens, CD↗

PubMed1992

Unilateral diaphragmatic paralysis: a matter for concern.

A dilemma often faces the clinician who is asked to evaluate unilateral elevation of a hemidiaphragm that is identified on routine chest roentgenogram. The possibilities include neoplasm, infection, neuromuscular disease, trauma, or benign etiologies. We present an asymptomatic patient with this finding to provide some guidelines for the nature and extent of further investigation of unilateral diaphragmatic paralysis.

Biopsy, Needle↗

PubMed1992

DaCosta's syndrome: chronic symptomatic hyperventilation.

In 1871, DaCosta published his observation of somatic symptoms preceded by significant hyperventilation. More than a century later, the hyperventilation syndrome remains a poorly defined but common clinical condition. Although familiar to most practitioners of medicine when it presents as an acute phenomenon, the diagnosis may go unrecognized in its chronic form. The ability of a chronic hyperventilatory state to mimic a life-threatening cardiopulmonary disease is not always appreciated.

Adult↗

PubMed1991

Structure and membrane topology of TAPA-1.

TAPA-1 (the target of an antiproliferative antibody) is a 26-kDa cell surface protein expressed on most human cell lines. TAPA-1 is a member of an evolutionarily related family of cell surface proteins all of which contain four transmembrane domains. A model is proposed for topology of TAPA-1 based on proteolysis studies in the in vitro translated protein embedded into microsomal membranes. This analysis predicts that the amino and the carboxyl termini of the molecule are cytoplasmic and that the two hydrophilic regions of the molecule are extracellular. The antigenic epitope of the human TAPA-1 is contained within a subregion of the second extracellular domain of the protein. This is the only region in the protein that has not been tightly conserved in mammalian evolution.

Amino Acid Sequence↗

PubMed1991

Interleukin-2 enhances the translocation of Escherichia coli from the intestines to other organs.

To determine if interleukin-2 (IL-2) would inhibit gastrointestinal bacterial translocation, mice were gut-decontaminated and recolonized with Escherichia coli C25; some groups were pretreated with 200 mg/kg cyclophosphamide. IL-2 (1.68 mg/kg) or sterile diluent was injected twice daily for 3 or 5 days, and mice were sacrificed the next day. High cecal levels of E. coli C25 were present in all mice. The overall incidence of E. coli C25 translocation to mesenteric lymph nodes was not reduced by IL-2. The median numbers of translocated E. coli C25/g of mesenteric lymph node were significantly (P less than .005) higher after both 3 days (659 vs. 117) and 5 days (550 vs. 50) of treatment with IL-2 with cyclophosphamide and after 5 days (1784 vs. 225) of IL-2 without cyclophosphamide. IL-2 prevented neutropenia and exacerbated lymphopenia caused by cyclophosphamide. The in vitro growth of E. coli C25 was not affected by up to 10(5) units/ml IL-2. Ileal and cecal structures assessed by light and electron microscopy were not altered by IL-2. Thus, IL-2 unexpectedly enhanced the translocation of E. coli C25 from the gastrointestinal tracts of both cyclophosphamide-pretreated and normal mice.

Animals↗

PubMed1991

Bronchogenic carcinoma and the acquired immunodeficiency syndrome.

The majority of patients with the acquired immunodeficiency syndrome will develop clinical and radiographic pulmonary involvement during the course of their disease. Although opportunistic pathogens account for the majority of these intrathoracic abnormalities, pulmonary neoplasms are being encountered more often than would be expected for the age group under consideration. Clinicians need to be vigilant for the possibility of the early appearance of bronchogenic carcinoma in this subset of patients.

Acquired Immunodeficiency Syndrome↗

PubMed1988

Results of a prospective statewide reporting system for infective endocarditis.

To better understand the microbiology, anatomy, and demography of infectious endocarditis, we devised a prospective statewide reporting system to study these infections. Because our study design required accurate diagnosis, reliable case reporting, and a high probability of physician-to-case exposure, we enlisted the help of cardiologists, cardiovascular surgeons, and infectious disease specialists throughout Louisiana. All Louisiana members of the American College of Cardiology and the Infectious Diseases Society of America were invited to participate. Participants were supplied with a brief endocarditis report form and asked to complete the form as they saw patients with infective endocarditis. Seventy-five patients with infective endocarditis were reported for a case rate of 1.7 per 100,000 persons per year. This report analyzes the results from this one-year study.

Adolescent↗

PubMed1988

Pneumococcosuria in adults.

Pneumococcal bacteriuria is usually felt to indicate systemic pneumococcal infection, especially in children. To determine the frequency and significance of pneumococcosuria in adults, we reviewed the Shreveport Veterans Administration Medical Center microbiology laboratory log books for 1982 through 1985. During these 4 years, more patients had pneumococcal bacteriuria than bacteremia (38 versus 33), but only 2 patients had both. The medical records from 31 bacteriuric patients with 35 positive urine specimens were available for review. The collection technique was reliable for 23 (66%) urine specimens; the type of collection technique used was unknown for 12 (34%). The urine pH was less than or equal to 6 in 24 (68%) specimens, and the specific gravity was greater than 1.020 in 12 specimens (34%). A total of 24 specimens grew only Streptococcus pneumoniae, and 11 yielded mixed growth. All 31 patients were men, 25 (81%) were 60 years or older, and 13 (42%) had underlying genitourinary disorders. A total of 7 patients had genitourinary symptoms, 7 had fever, 5 had leukocytosis, and 12 had pyuria; however, these symptoms and signs were frequently accounted for by factors other than pneumococcosuria. Pneumococcosuria was an unexpected finding in all but two (6%) bacteremic patients. These were the only patients with systemic pneumococcal infections, and both died despite appropriate antibiotics. Among the 20 surviving patients with follow-up urine samples, pneumococcosuria resolved whether or not they had received antibiotics. Thus, pneumococcosuria in our patient population was frequently not accompanied by systemic pneumococcal infection and by itself did not require antibiotic therapy.

Adult↗

PubMed1988

Effect of photodynamic therapy on blood flow in normal and tumor vessels.

The aim of this series of experiments was to determine the dynamic blood flow changes that occur in normal and neoplastic tissues during photodynamic therapy. Mice bearing SMT-F tumors and rats with transplanted chondrosarcomas were injected with graded doses of dihematoporphyrin ether. Studies of changes in single-vessel and whole-tumor blood flow were carried out with 630 nm light activation. A helium neon laser Doppler velocimeter was used to stimulate dihematoporphyrin ether, as well as to measure changes in flow velocity in both single-vessel and whole-tumor models. There was a reduction of flow velocity in all vessels and tumors in animals injected with 1 to 40 mg/kg dihematoporphyrin ether intraperitoneally. The extent of flow reduction was related to drug dose administered. Decreases in blood flow began within 10 seconds of light stimulation and were maximal within 5 minutes. Both normal and tumor vessels responded similarly. We conclude that photodynamic therapy leads to significant microcirculatory changes that may be pertinent to the mechanism of tumor necrosis.

Animals↗

PubMed1987

Candida krusei infectious arthritis. A rare complication of neutropenia.

Candida krusei infections are increasing in neutropenic patients. This is the first report of a case of C. krusei arthritis in a neutropenic leukemic patient. The organism colonized the patient's respiratory tract and most likely seeded the right knee by hematogenous spread. Knee swelling and tenderness were minimal. Joint fluid Gram stain and fungal smears did not show the organism despite positive results on cultures. With therapy, the joint fluid converted from neutrophilic predominance to lymphocytic predominance. Despite sterilization of knee fluid, clinical relapse occurred after therapy with 256 mg of systemic amphotericin B; the infection was cured after a total dose of 456 mg.

Adult↗