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Biomedical subjects

A Louie

Publications and source records attributed to A Louie.

At least 19 recordsLinked to original sources
PubMed1995

Multiple determinants for growth of human immunodeficiency virus type 1 in monocyte-macrophages.

Attempts to define the genetic determinants required for efficient growth of human immunodeficiency virus type 1 (HIV-1) in monocyte-macrophages were made by constructing chimeras between two infectious clones of HIV-1 (HXB2 and LW/C), which despite only minor differences in their DNA sequence have striking differences in cell tropism. Although both of them replicate efficiently in peripheral blood mononuclear cells, HXB2 replicates extensively in permanent T cell lines but poorly in primary monocyte macrophages (T cell line tropic); the reverse is true for LW/C (macrophage tropic). The envelope proved to contain the major determinants of macrophage tropism. However, tropism determinants appeared to be scattered along the envelope. In particular, the V3 loop alone appeared to be neither necessary nor sufficient for growth in macrophages. Both vpr and nef genes appeared to play a less significant role to improve viral replication in macrophages, but only in the presence of the proper envelope sequences. HIV-1 macrophage tropism thus appears to result from the contribution of several different determinants.

Amino Acid Sequence↗
PubMed1995

Fluconazole and amphotericin B antifungal therapies do not negate the protective effect of endogenous tumor necrosis factor in a murine model of fatal disseminated candidiasis.

In systemic candidiasis, endogenously produced tumor necrosis factor (TNF)-alpha prolongs survival of the infected host. To determine whether endogenously produced TNF-alpha has a beneficial effect beyond that provided by antifungal therapy, survival was assessed in infected mice that received fluconazole or amphotericin B alone and in combination with anti-TNF-alpha antibody. Neutralization of serum TNF-alpha did not affect survival in fluconazole recipients; however, for amphotericin B recipients, it significantly shortened mean survival. For both fluconazole and amphotericin B recipients, colony counts in organs were significantly higher in animals that also received anti-TNF-alpha antibody. Administration of anti-TNF-alpha antibody with amphotericin B or fluconazole did not affect the morphology of fungi or the inflammatory response in kidneys. This study suggests that exogenous TNF-alpha and drugs that increase the endogenous production of TNF-alpha by the host may be useful adjuncts to fluconazole and amphotericin B for the treatment of systemic candidiasis.

Amphotericin B↗
PubMed1995

Growth of macrophage-tropic and primary human immunodeficiency virus type 1 (HIV-1) isolates in a unique CD4+ T-cell clone (PM1): failure to downregulate CD4 and to interfere with cell-line-tropic HIV-1.

Human immunodeficiency virus type 1 (HIV-1) isolates derived directly from clinical samples are usually unable to grow in cytokine-independent continuous cell lines, thus hindering the study of their biological features and their sensitivity to humoral and cellular protective immunity. To overcome these limitations, we have derived from the Hut78 T-cell line a CD4+ clone (PM1) characterized by a unique susceptibility to a wide range of HIV-1 isolates, including primary and biologically pure macrophage (M phi)-tropic isolates (e.g., HIV-1BaL), which are unable to infect other human T- or promonocytic cell lines. Both primary and M phi-tropic HIV-1 establish persistent infection in PM1, with sustained levels of virus replication for prolonged periods. Experiments with chimeric viruses containing envelope fragments of HIV-1BAL inserted into the genetic framework of HXB2, a molecular clone derived from the cell-line-tropic isolate HIV-1IIIB, showed the third hypervariable domain (V3) of gp120 to be a critical determinant of the cell line tropism of HIV-1. Nevertheless, the V3 loop of HIV-1BaL was not sufficient to confer on the chimeras a bona fide M phi tropism. The biological characteristics of HIV-1BaL and of a primary isolate (HIV-1(573)) were investigated by using the PM1 clone. Infection of PM1 by HIV-1BaL was critically dependent on the CD4 receptor, as shown by competition experiments with an anti-CD4 monoclonal antibody (OKT4a) or with soluble CD4. However, the amount of soluble CD4 required for inhibition of HIV-1BaL was approximately 100-fold higher than for HIV-1IIIB, suggesting that the affinity of HIV-1BaL for CD4 is significantly lower. Infection of PM1 with either HIV-1BaL or HIV-1(573) failed to induce downregulation of surface CD4 expression and syncytium formation. Analogous results were obtained with a chimeric virus (HXB2[BaL PvuII-BamHI]) encompassing a large portion of gp120 and gp41 of HIV-1BaL, indicating that the env genes contain critical determinants for CD4 downregulation and syncytium formation. Consistent with the lack of CD4 downregulation, persistent infection of PM1 by HIV-1BaL or HIV-1(573) failed to interfere with HIV-1IIIB superinfection, as revealed by the expression of a type-specific V3 loop epitope (M77) and by the induction of extensive syncytium formation. This lack of interference suggests that a direct viral interaction may occur in vivo between biologically diverse HIV-1 strains.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1994

Comparative capacity of four antifungal agents to stimulate murine macrophages to produce tumour necrosis factor alpha: an effect that is attenuated by pentoxifylline, liposomal vesicles, and dexamethasone.

The efficacy and toxicity of certain antifungal agents may be related to their ability to induce the production of cytokines by mononuclear phagocytes. The capacity of incremental concentrations of fluconazole, 5-fluorocytosine (5-FC), amphotericin B (AmB), and liposomal AmB (LAB) to stimulate murine peritoneal and RAW 264.7 macrophages to secrete tumour necrosis factor alpha (TNF alpha) after 3, 6 and 24 h incubation was assessed by L929 cytotoxic bioassay. Fluconazole (2.5-40 mg/L) and 5-FC (25-100 mg/L) did not have a stimulatory effect. However, AmB (0.25-10 mg/L) elicited TNF alpha production by macrophages. This response was concentration-dependent, and peak TNF alpha levels were detected between 3 and 6 h. This effect was attenuated by incorporation of AmB into liposomal vesicles and by pretreating macrophages with pentoxifylline or dexamethasone. AmB I mg/L in combination with 1 x 10(6) cfu of Candida albicans stimulated peritoneal macrophages to produce similar quantities of TNF alpha as AmB alone, and two- to four-fold more TNF alpha than C. albicans alone. Thus, this study suggests that: (1) the immunomodulatory activity and toxicities of AmB, in part, may be attributed to the capacity of this drug to stimulate macrophages to secrete TNF alpha, (2) the TNF alpha that is produced by macrophages in response to AmB may have clinical relevance even in the face of C. albicans infection, and (3) the failure of fluconazole, 5-FC, and LAB to elicit a TNF alpha response may explain their improved side-effect profiles.

Amphotericin B↗
PubMed1994

Tumor necrosis factor alpha has a protective role in a murine model of systemic candidiasis.

The role of tumor necrosis factor alpha (TNF-alpha) in host defense against systemic Candida albicans infection was evaluated in a murine model of systemic candidiasis in which uniform death occurred between 5 and 6 days after infection. TNF-alpha was first detected at 16 h postinfection and progressively increased thereafter. Peak levels (700 to 900 pg/ml) were measured in mice near death. Administration of 0.5 to 1.0 mg of polyclonal immunoglobulin G (IgG) TNF-alpha antibody (TNF-alpha Ab) to mice 2 h preinfection neutralized serum TNF-alpha for up to 30 h. However, this regimen shortened survival from a mean of 5.5 days for IgG controls to 3.4 days (P = 1.9 x 10(-12)). Semiquantitative cultures of spleen, lung, liver, and kidney conducted at 1, 2, and 3 days postinfection found colony counts of spleen and kidney to be significantly higher for TNF-alpha Ab recipients but only for the first 48 h. Administration of 1.5 and 1.0 mg of TNF-alpha Ab at 2 h before and 48 h after fungal injection, respectively, shortened the mean survival from 4.9 to 2.3 days (P = 5.2 x 10(-8)). This regimen neutralized serum TNF-alpha throughout infection. With this regimen, colony counts of all organs were significantly higher in TNF-alpha Ab recipients at 1, 2, and 3 days postinfection. Histopathologic studies showed an increase in the number and size of C. albicans foci in tissues. Peripheral leukocyte counts and inflammatory response in tissue were similar for TNF-alpha Ab and IgG sham recipients. In vitro, incubation of C. albicans with four to eight times the peak serum levels of TNF-alpha for up to 24 h did not inhibit the rate of germ tube or pseudohypha formation. Thus, TNF-alpha that was produced during infection with C. albicans augmented host resistance against this organism and prolonged survival. The protective effect of TNF-alpha was not mediated by increased leukocytes in blood or tissues nor by a direct anticandidal effect of TNF-alpha. This study suggests that the administration of exogenous TNF-alpha may enhance host resistance against systemic C. albicans infection and may improve host survival.

Animals↗
PubMed1994

Alteration of V3 loop context within the envelope of human immunodeficiency virus type 1 enhances neutralization.

Neutralization of a chimeric human immunodeficiency virus (HIV) type 1, containing the V3 loop of the MN isolate substituted within the HXB2 envelope, was enhanced up to 20-fold compared with the HXB2 or MN parental isolates by human HIV-positive sera. MN V3 loop-specific monoclonal antibodies were better able to recognize the chimeric virus compared with MN, staining a greater percentage of infected cells and exhibiting slight increases in relative affinity with a concomitant increase in neutralization titer. Competition analysis revealed that enhanced neutralization by human HIV-positive sera of the chimera was attributable in some cases to better reactivity with the linear V3 loop epitope but in others to conformational loop epitopes or previously cryptic or poorly recognized epitopes outside the loop region. Mice primed with a vaccinia virus-chimeric envelope recombinant and boosted with gp160 developed a spectrum of antibodies different from that of mice similarly immunized with HXB2 or MN recombinants or that of naturally infected humans. The chimeric envelope elicited antibodies with enhanced binding to the native MN V3 loop; however, the sites seen by the BALB/c mice were not neutralizing epitopes. Nevertheless, similar to the observations made with use of human sera, the chimeric virus was more readily neutralized by all of the immune mouse sera, an effect apparently mediated by non-V3 loop epitopes. These studies illustrate that not only the V3 loop sequence and conformation but also its context within the viral envelope influence neutralization.

AIDS Vaccines↗
PubMed1994

Emergency department screening for ectopic pregnancy: a prospective US study.

PURPOSE: To determine the effectiveness of pelvic sonography as a screening test for ectopic pregnancy. MATERIALS AND METHODS: Pelvic sonograms were prospectively analyzed in 1,427 consecutive patients with a serum level of the beta subunit of human chorionic gonadotropin of over 1,500 IU/L. RESULTS: Sonograms were diagnostic in 1,158 patients and indeterminate in 269. When indeterminate studies were considered falsely negative, the diagnostic accuracy was 81%. Twenty-four percent of patients with indeterminate studies were subsequently proved to have ectopic pregnancy. In ectopic pregnancy (n = 103), the most common finding was a complex adnexal mass (specificity = 92% [P < .001]). The sensitivity and specificity of screening sonography for ectopic pregnancy were 99% and 84%, respectively. CONCLUSION: Pelvic sonography is an effective screening test for ectopic pregnancy. Having a one in four chance of harboring an ectopic pregnancy, patients with indeterminate studies require close follow-up. The presence of a complex adnexal mass is a strong predictor of ectopic pregnancy.

Adult↗
PubMed1994

Relationship between Candida albicans epidermolytic proteinase activity and virulence in mice.

Five strains of Candida albicans with previously characterized epidermolytic acid proteinase activity were evaluated for virulence following intravenous (i.v.) injection in mice. Increased proteinase activity was associated with increased virulence in female, NYLAR mice receiving 10(6) cells i.v. Mean mortality times (1.25, 2.0, 2.0, 4.25 and 19.6 days, in groups of 20 mice for each of the five strains) correlated directly with degree of proteinase activity. Three of the strains were selected for additional in vivo study and the association between increased proteinase activity and increased mortality rates was confirmed in dose-response studies in two additional strains of mice. The mean survival times appeared to be independent of fungal growth rate in vitro. These results support the positive correlation between proteinase activity and virulence.

Animals↗
PubMed1993

Loss of a neutralizing epitope by a spontaneous point mutation in the V3 loop of HIV-1 isolated from an infected laboratory worker.

The third hypervariable region, or V3 loop, represents the principal neutralizing domain of the gp120 envelope glycoprotein of human immunodeficiency virus type 1 (HIV-1). Sequential viral isolates from a laboratory worker (LW) accidentally infected with HIV-1IIIB in 1985 were analyzed using type-specific neutralizing monoclonal antibodies directed to the V3 loop. A single amino acid substitution, Ala-->Thr at position 21 in the V3 loop of HIV-1LW isolated in 1987, was shown to determine the loss of the neutralizing epitope recognized by one of the monoclonal antibodies (M77). However, this antibody efficiently recognized linear V3 loop peptides containing either the Ala or Thr residue at position 21, indicating that a local change in conformation was responsible for the epitope loss in the native gp120. Molecular modeling studies, experimentally supported by different amino acid replacements at position 21, indicated that the Ala-->Thr substitution leads to a drastic change in the domain of the V3 loop, which contains the complementary surface for antibody binding. These results provide evidence for the first time that a conformation-dependent epitope within the V3 loop of HIV-1 is involved in the generation of neutralization escape mutants in vivo.

Acquired Immunodeficiency Syndrome↗
PubMed1993

A three-dimensional stereotactic device for computed tomography-guided invasive diagnostic and therapeutic procedures.

RATIONALE AND OBJECTIVES: A three-dimensional stereotactic technique is presented as an improvement in precision needle placement for percutaneous diagnostic and therapeutic procedures. METHODS: This method uses transaxial computed tomography (CT) imaging for the selection of the optimal target path, and it employs a three-dimensional stereotactic device designed to match precisely the CT parameters in a three-dimensional space. RESULTS: In selected cases, we reached targets as small as 1 to 2 cm while avoiding vital structures. CONCLUSIONS: In our hands, in selected cases, this has been a simple, safe, and accurate technique for improvement of percutaneous diagnostic and therapeutic procedures under CT guidance.

Aged↗
PubMed1992

The use of capillary electrophoresis in a micropreparative mode: methods and applications.

The ability to collect sufficient quantities of analytes from capillary electrophoresis for subsequent analyses is demonstrated. Fractions collected have been analyzed using the following techniques: capillary electrophoresis, mass spectrometry, and protein sequencing. Fractions can be collected directly into small volumes of buffer or directly onto membrane surfaces. Relevant parameters such as capillary diameter, mass loading, and separation parameters are addressed.

Amino Acid Sequence↗
PubMed1992

Mambin, a potent glycoprotein IIb-IIIa antagonist and platelet aggregation inhibitor structurally related to the short neurotoxins.

The purification, complete amino acid sequence, functional activity, and structural modeling are described for mambin, a platelet glycoprotein GP IIb-IIIa antagonist and potent inhibitor of platelet aggregation from the venom of the Elapidae snake Dendroaspis jamesonii (Jameson's mamba). Mambin is 59 residues in length and contains four disulfide linkages and an RGD amino acid sequence found in protein ligands that bind to GP IIb-IIIa. Mambin inhibits ADP-induced platelet aggregation (IC50 = 172 +/- 22 nM) and inhibits the binding of purified platelet fibrinogen receptor GP IIb-IIIa to immobilized fibrinogen (IC50 = 3.1 +/- 0.8 nM). Mambin has very little sequence similarity to the Viperidae family of platelet aggregation inhibitors, except for the RGD-containing region in the protein. However, mambin does have ca. 47% similarity to the short-chain postsynaptic neurotoxins found in other Elapidae venoms, which do not contain the RGD sequence and do not act as GP IIb-IIIa antagonists. On the basis of its circular dichroism spectrum, mambin has a beta-sheet structure characteristic of the neurotoxins. Molecular modeling of the mambin sequence onto the erabutoxin b structure predicts a very similar structure within the entire protein except for the loop containing the RGD sequence. Mambin may therefore represent a genetic hybrid of neurotoxic and hemotoxic proteins found in snake venoms.

Amino Acid Sequence↗
PubMed1991

Distinguishing mammalian sialidases by inhibition kinetics with novel derivatives of 5-acetamido-2,6-anhydro-3,5-dideoxy-D-glycero-D-galacto-non-2-enonic acid, an unsaturated derivative of N-acetylneuraminic acid.

Kinetic analysis of mammalian sialidases was carried out using analogs of the potent sialidase inhibitor, 5-acetamido-2,6-anhydro-3,5-dideoxy-D-glycero-D-galacto-non-2-enonic+ ++ acid (1). Substitutents at C-9 in place of the terminal hydroxyl group included a, 4-azido-2-nitrophenylthio group to give 5-acetamido-2,6-anhydro-9-S-(4-azido-2-nitrophenyl)-3,5, 9-trideoxy-9-thio-D-glycero-D-galacto-non-2-enonic acid (2), and an azide group to give 5-acetamido-2,6-anhydro-9-azido-3,5,9-trideoxy-D-glycero-D-galacto-non-2 -enonic acid (3). Competitive inhibition kinetics were observed when 1,2, and 3 were tested with the lysosomal sialidase (cultured fibroblasts) and the plasma membrane sialidase (adenovirus DNA-transformed, human embryonic kidney cells), giving a Ki of about 10 microM for both enzymes with all three compounds. In contrast, only 1 was a potent inhibitor of the microsomal sialidase (rat muscle).

Adenoviridae↗
PubMed1991

Stabilization of the Escherichia coli elongation factor Tu-GTP-aminoacyl-tRNA complex.

The effect of ammonium sulfate on the Escherichia coli elongation factor Tu-GTP-aminoacyl-tRNA complex has been studied. The half-lives of 12 E. coli aminoacyl-tRNA species were determined at 37 degrees C in the presence and absence of an equimolar amount of EF-Tu-GTP and in the presence and absence of 1.5 M ammonium sulfate. The results indicate that the addition of 1.5 M ammonium sulfate to the ternary complex increased the stability of all 12 complexes studied. In addition, the effects of various salts and crystallization agents on the stability of the E. coli EF-Tu-GTP-phenylalanyl-tRNA complex was studied in detail. Binding parameters were also measured under various conditions at 37 degrees C. The results indicate that the stability and the Kassoc of the ternary complex, using phenylalanyl-tRNA, can be increased by the presence of polyethylene glycol or ammonium sulfate.

Escherichia coli↗
PubMed1991

Comparative in-vitro susceptibilities of Pseudomonas aeruginosa, Xanthomonas maltophilia, and Pseudomonas spp. to sparfloxacin (CI-978, AT-4140, PD131501) and reference antimicrobial agents.

The susceptibility of sparfloxacin, a new broad spectrum fluoroquinolone, was determined for 72 clinical isolates of Pseudomonas aeruginosa, 15 Xanthomonas maltophilia, and 19 Pseudomonas spp. The activity of sparfloxacin was compared with that of ciprofloxacin and other reference antibiotics. Sparfloxacin was the most active antibiotic tested against X. maltophilia (MIC90 1 mg/l) and the most active quinolone against P. cepacia and P. putrifaciens. Ciprofloxacin, however, demonstrated greater activity than sparfloxacin against P. fluorescens and P. stutzeri. P. aeruginosa was most susceptible to ciprofloxacin with an MIC90 of 2 mg/l, compared with an MIC90 of 8 mg/l for sparfloxacin and ofloxacin. Although cross-resistance between quinolones was noted, cross-resistance between antibiotic classes was not seen. Aminoglycoside-resistant and aminoglycoside-susceptible P. aeruginosa strains were equally susceptible to sparfloxacin. Kill curves showed sparfloxacin to be rapidly bactericidal against P. aeruginosa at 1 x MIC. Sparfloxacin demonstrated greater bactericidal activity than ciprofloxacin at 1 x and 2 x their MICs. Unlike ciprofloxacin and gentamicin, sparfloxacin showed sustained bactericidal activity at greater than or equal to 1 MIC for 24 h.

Anti-Bacterial Agents↗
PubMed1991

Human T-cell leukemia-lymphoma virus type I (HTLV-I) expression in fresh peripheral blood mononuclear cells from patients with tropical spastic paraparesis/HTLV-I-associated myelopathy.

Tropical spastic paraparesis/human T-cell leukemia-lymphoma virus type I (HTLV-I)-associated myelopathy (TSP/HAM) is a chronic neurological illness epidemiologically associated with HTLV-I infection. We investigated the role of HTLV-I in the pathogenesis of this disease by studying viral expression in fresh uncultured peripheral blood mononuclear cells (PBMCs) of six patients of Caribbean origin with TSP/HAM. The PBMC genomic DNA of all the patients studied carried HTLV-I provirus, but viral expression was not detected by Northern (RNA) blot analysis of total cellular PBMC RNA. When the reverse transcriptase polymerase chain reaction technique was used with primers specific for the tax-rex mRNA, all of the samples were positive for this viral mRNA species, regardless of the duration of the illness (range, 2 to 13 years). The splice junctions for the tax-rex mRNA described in cases of HTLV-I-induced adult T-cell leukemia (position 5183 of the envelope and position 7302 of the pX region) were identical in three TSP/HAM cases studied. To ascertain whether viral expression occurred at a low level in many cells or at a high level in a few permissive cells, we performed in situ hybridization on fresh PBMCs from two patients (2 and 7 years after clinical diagnosis), seeking HTLV-I RNA sequences. Our finding indicated that in vivo HTLV-I expression occurred at a high level in a few cells (1 of every 5,000 PBMCs) in both cases studied. The fact that cells of all six patients with TSP/HAM were positive for viral expression, regardless of the time lag from diagnosis, suggests that persistent expression of a viral product(s) may be pivotal in the pathogenesis of TSP/HAM.

Adult↗
PubMed1991

Popliteal artery hemodynamics: MR imaging-US correlation.

Temporally resolved velocity measurements in the popliteal arteries of 11 healthy subjects were obtained by means of magnetic resonance (MR) imaging with use of the Fourier flow-encoding technique. Excellent agreement with corresponding Doppler ultrasonography (US) data (r = .97, slope = 0.99, intercept = -1.5 cm/sec) was demonstrated over the entire velocity range from 50 to -20 cm/sec. The method was rapid and its implementation straightforward. Further, MR imaging was shown to provide the intraluminal velocity distribution relevant for the determination of true flow rates, not obtainable with Doppler US.

Adult↗