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Biomedical subjects

L Fabry

Publications and source records attributed to L Fabry.

At least 19 recordsLinked to original sources
PubMed2001

Ultra-trace analytical monitoring of silicon wafer surfaces by capillary electrophoresis.

Several methods are presented for the routine ultra-trace analytical monitoring of inorganic and organic anions and cations on the surface and in the native oxide of silicon wafers--the wafer-surface water-extraction method, the vapor-phase-decomposition method, and the re-dissolving method. Electrokinetic injection, sample stacking, and electrolyte composition were, therefore, optimized and made robust. For electrokinetic injection with transient isotachophoretic preconcentration a linear range of 0.05 to 0.5 micromol L(-1) was obtained; for sample stacking the linear range was 0.5 to 10 micromol L(-1), even in the presence of up to 750 micromol L(-1) hydrofluoric acid. Inorganic anions and monovalent carboxylic acids are predominately dissolved in the aqueous layer on the wafer surface whereas dicarboxylic acids are chemically bonded to the silanol groups and form esters.

Coated Materials, Biocompatible↗
PubMed2000

Routine analysis of ultra pure water by ICP-MS in the low- and sub-ng/L level.

The chemical analysis with inductively coupled plasma-mass spectrometry (ICP-MS) can help to examine the purity of ultra pure water (UPW) down to 10 part per trillion (ng/L) and lower. For a proper determination of a high number of samples per week the analysis must be divided into two parts: the routine analysis and the reference water analysis. The routine analysis is done by direct measurement of the ultra pure water samples. Applying a standard addition method under particular clean conditions, the reference water analysis leads to the definition of the accurate zero. A quick evaluation scheme is also presented for the reference water analysis. The method is tested for its fitness for application by examining LOD (for relevant element < 2 ng/L), reproducibility and linearity of calibration. The ICP-MS was optimized according to the methodology of G. Taguchi to improve reproducibility and LOD.

Linear Models↗
PubMed2000

Efficacy and safety studies of a recombinant chimeric respiratory syncytial virus FG glycoprotein vaccine in cotton rats.

Several formulations of a recombinant chimeric respiratory syncytial virus (RSV) vaccine consisting of the extramembrane domains of the F and G glycoproteins (FG) were tested in cotton rats to evaluate efficacy and safety. The FG vaccine was highly immunogenic, providing nearly complete resistance to pulmonary infection at doses as low as 25 ng in spite of inducing relatively low levels of serum neutralizing antibody at low vaccine doses. Upon RSV challenge animals primed with FG vaccine showed quite mild alveolitis and interstitial pneumonitis, which were eliminated by the addition of monophosphoryl lipid A to the formulation.

Animals↗
PubMed1996

Accurate calibration of TXRF using microdroplet samples.

TXRF has been applied in combination with VPD to the analysis of trace impurities in the native oxide layer of Si wafer surfaces down to the range of 10(8) atoms. cm(-2). Proper quantification of VPD/TXRF data requires calibration with microdroplet standard reference wafers. The precision of calibration function has been evaluated and found to allow quantification at a high level of 3 sigma confidence with microdroplet standard reference.

Journal Article↗
PubMed1994

HIV-1 envelope-elicited neutralizing antibody titres correlate with protection and virus load in chimpanzees.

In an attempt to compare the protective effect of vaccination with two forms of envelope antigens, and to define immunological correlates of protection against HIV infection, chimpanzees were vaccinated with either recombinant gp160 or gp120. Homologous HIV challenge was performed 3 weeks after the fourth immunization. The animal with the highest level of serum neutralizing antibodies (gp160 immunogen) was protected against HIV infection. All other chimpanzees became infected, but displayed various levels of infected PBMCs. The postchallenge data gave rise to the following conclusions: (1) protection correlated with the level of the serological immune response, but not with the nature of immunogen (gp120 versus gp160); (2) the virus-neutralizing titre at day of challenge correlated with protection from infection; (3) the relative magnitude of the lymphoproliferative T-cell response at day of challenge did not correlate with any protective effect; (4) the peak numbers of virus-infected PBMCs in vaccinated animals were lower than those observed in control animals, and this effect was correlated with the intensity of the antibody response at day of challenge. This raises the possibility that a beneficial effect of HIV vaccination may be achieved in a situation where sterile immunity is not consistently obtained.

AIDS Vaccines↗
PubMed1994

Incomplete protection, but suppression of virus burden, elicited by subunit simian immunodeficiency virus vaccines.

We compared the efficacy of immunization with either simian immunodeficiency virus (SIV) Env glycoprotein (Env), Env plus Gag proteins (Gag-Env), or whole inactivated virus (WIV), with or without recombinant live vaccinia vector (VV) priming, in protecting 23 rhesus macaques (six vaccine and two control groups) from challenge with SIVmac251 clone BK28. Vaccination elicited high titers of syncytium-inhibiting and anti-Env (gp120/gp160) antibodies in all vaccinated macaques and anti-Gag (p27) antibodies in groups immunized with WIV or Gag-Env. Only WIV-immunized macaques developed anticell (HuT78) antibodies. After homologous low-dose intravenous virus challenge, we used frequency of virus isolation, provirus burden, and change in antibody titers to define four levels of resistance to SIV infection as follows. (i) No infection ("sterilizing" immunity) was induced only in WIV-immunized animals. (ii) Abortive infection (strong immunity) was defined when virus or provirus were detected early in the postchallenge period but not thereafter and no evidence of virus or provirus was detected in terminal tissues. This response was observed in two animals (one VV-Env and one Gag-Env). (iii) Suppression of infection (incomplete or partial immunity) described a gradient of virus suppression manifested by termination of viremia, declining postchallenge antibody titers, and low levels (composite mean = 9.1 copies per 10(6) cells) of provirus detectable in peripheral blood mononuclear cells or lymphoid tissues at termination (40 weeks postchallenge). This response occurred in the majority (8 of 12) of subunit-vaccinated animals. (iv) Active infection (no immunity) was characterized by persistent virus isolation from blood mononuclear cells, increasing viral antibody titers postchallenge, and high levels (composite mean = 198 copies per 10(6) cells) of provirus in terminal tissues and blood. Active infection developed in all controls and two of three VV-Gag-Env-immunized animals. The results of this study restate the protective effect of inactivated whole virus vaccines produced in heterologous cells but more importantly demonstrate that a gradient of suppression of challenge virus growth, reflecting partial resistance to SIV infection, is induced by subunit vaccination. The latter finding may be pertinent to studies with human immunodeficiency virus vaccines, in which it is plausible that vaccination may elicit significant suppression of virus infection and pathogenicity rather than sterilizing immunity.

Animals↗
PubMed1993

Dielectric spectroscopy of mammalian cells. 1. Evaluation of the biomass of HeLa- and CHO cells in suspension by low-frequency dielectric spectroscopy.

The capacitance of suspensions of CHO and HeLa cells (0.5-3 x 10(6) cells/ml) has been measured between 0.2 and 10 MHz. As frequencies decrease, there is a continuous increase in capacitance of both the cell suspension and the spent growth medium free of cells, a phenomenon which is partially attributed to an increased polarisation of the electrodes. At a given frequency, subtraction of the capacitance of the spent medium from that of the cell suspension allows one to determine the capacitance of the cells only. The intensity of this signal varies linearly with the biomass and cell size. At low frequencies such as those used in this study (0.25 MHz), where sensitivity is the highest, concentrations as low as 0.5 x 10(6) cells/ml can be accurately measured. Suggestions are made how to make these measures on-line, non-invasive and in real time.

Animals↗
PubMed1993

Dielectric spectroscopy of mammalian cells. 2. Simultaneous in situ evaluation by aperture impedance pulse spectroscopy and low frequency dielectric spectroscopy of the biomass of HTC cells on Cytodex 3.

Low-frequency dielectric spectroscopy has been used in situ, i.e. while the cells are still attached to their microsupport, to monitor the changes of biomass accompanying the growth of anchorage-dependent cells. This method, when compared to Aperture Impedance Pulse Spectroscopy (also called electronic sizing), is characterized by a somewhat lower degree of resolution. Suggestions are made on how to determine the capacitance of the spent growth medium alone, still keeping the probe inserted in the bioreactor. This will make dielectric spectroscopy the first truly in situ, on-line, in real time, non-invasive measure of the biomass.

Cell Division↗
PubMed1991

Structural and biological properties of human recombinant myeloperoxidase produced by Chinese hamster ovary cell lines.

The cDNA encoding human myeloperoxidase carries three ATG codons in frame; 144, 111 and 66 bp upstream from the proprotein DNA sequence. In order to determine the most efficient signal sequence, three cDNA modules starting at each of the ATG were cloned into an eucaryotic expression vector and stably expressed in Chinese hamster ovary cell lines. In all three cases, recombinant human myeloperoxidase (recMPO) was secreted into the culture medium of transfected cells, indicating that each of the signal peptides functions efficiently. One of the recombinant cell lines, which was amplified using methotrexate, overexpresses enzymatically active recMPO up to 6 micrograms.ml-1.day-1. The recombinant product was purified by a combination of ion-exchange and metal-chelate chromatography, and characterized in terms of molecular mass, amino-terminal amino acid analysis, glycosylation, physicochemical properties and biological activity. The data show that recMPO is secreted essentially as a monomeric, heme-containing, single-chain precursor of 84 kDa which exhibits peroxidase activity. Amino-terminal analysis indicated that cleavage of the signal peptide occurs between amino acids 48 and 49. In addition, recMPO appeared to be glycosylated up to the last stage of sialylation, to an extent similar to that of the natural enzyme. Specific activity measurements as well as stability data, in various pH, temperature, ionic strength and reducing conditions, indicated that the recombinant single-chain enzyme behaves essentially in the same way as the natural two-chain molecule. Finally, recMPO was shown to exert potent cytotoxicity towards Escherichia coli when provided with its physiological substrates, i.e. hydrogen peroxide and chloride ions.

Amino Acid Sequence↗
PubMed1988

Chromosome aberrations in mixed cultures of in vitro irradiated and unirradiated human lymphocytes.

Human whole blood samples were exposed to different doses (1, 2, 4, 6 or 10 Gy) of gamma-radiation and mixed with different volumes of non-irradiated blood before culturing to simulate partial body irradiations. Chromosome aberrations were analysed and the frequency of dicentrics was found to be lower than expected, particularly when irradiated blood was mixed with large volumes of non-irradiated blood and after exposure to high radiation doses. For the mixtures of irradiated and unirradiated blood the deviation from the Poisson distribution depends on the respective proportions and on the doses. The results can be correlated to in vivo aberration frequencies in case of therapeutical treatments, but the yields of aberrations are generally underestimated in vitro.

Chromosome Aberrations↗
PubMed1987

Shuttle transfer (or retrotransfer) of chromosomal markers mediated by plasmid pULB113.

The IncP1 plasmid pULB113 (RP4::miniMu) not only mediates the transfer of chromosomal markers in the classical direction (i.e. from the donor to the recipient cell) but also in the opposite direction (i.e. from the recipient bacterium to the donor). This phenomenon of retrotransfer was observed in homologous matings with Pseudomonas fluorescens, Alcaligenes eutrophus and Salmonella typhimurium. Retrotransconjugants could be discriminated from direct transconjugants by appropriate chromosomal and plasmid markers used to distinguish the mating partners not bearing pULB113. Retrotransfer of chromosomal markers occurred at frequencies equal to, or sometimes greater than, those observed for the direct mobilization, thus allowing the recovery of "recipient" recessive markers in the "donor" with linkage values similar to those found in the normal direction. Retrotransfer was also observed in heterospecific matings involving A. eutrophus and pULB113 bearing P. fluorescens: R-primes carrying different selected and unselected markers were recovered in both bacteria. "Retrotransfer" or "shuttle transfer" seems to be a specific trait of IncP1 plasmids.

Alcaligenes↗
PubMed1986

[Induction of chromosome anomalies in rabbit lymphocytes by weak doses of X-rays and neutrons].

The induction of dicentric aberrations has been studied in rabbit lymphocytes after exposure to low doses of X-rays or d(50) + Be neutrons. The aberrations have been analysed in first division cells collected after a 32 h culture time. In both cases, the dose response relationship is best fitted to a linear-quadratic model. Rabbit lymphocytes are less radiosensitive than human lymphocytes and RBE is lower in rabbit than in human cells. These discrepancies could be due to differences in the repair capacities for the lesions induced by X-rays and neutrons in rabbit and human lymphocytes.

Animals↗
PubMed1986

Dose response relationships for radiation induced chromosome aberrations in human lymphocytes in vivo and in vitro.

Chromosome aberrations have been analysed in cultured lymphocytes from a patient undergoing whole-body treatment with split doses of gamma-rays up to a cumulative dose of 1.4 Gy. The dependence on dose of the yield of dicentrics was best fitted to the linear-quadratic relationship with a linear component predominating in the low dose range (below 0.56 Gy). These observations were compared with the data obtained when blood samples were exposed in vitro to low acute doses of gamma-rays (from 0.05 up to 2.0 Gy). The frequencies of induced chromosome aberrations were similar in both cases and little deviation was found between the dose response curves (a/b ratio equal to 0.56 and 0.69 Gy, respectively in vivo and in vitro). These results confirm that in vitro calibration curves can be utilized confidently for the biological estimate of an in vivo absorbed dose.

Adult↗
PubMed1985

Study on the repair of the radioinduced lesions involved in the formation of chromosomal aberrations in G0 human lymphocytes after exposure to gamma-rays and fast neutrons.

Cytosine arabinoside (ara-C), an inhibitor of DNA synthesis and repair, has been used to study the mechanisms of formation of chromosomal aberrations after exposure to low- and high-LET radiation. When G0 human lymphocytes were exposed either to gamma-rays or to d(50 MeV)-Be neutrons and immediately treated with ara-C for increasing periods of time, the frequency of aberrations (dicentrics) increased sharply. For gamma-rays, the enhancement increased with the duration of the treatment up to 5 h, whereas for neutrons, an ara-C treatment lasting for 5 h was no more effective than treatment for 3 h. These results were confirmed by the second experiment in which ara-C was administered for 3 h with an increasing time delay following irradiation. Since no increase in the dicentric frequency was observed when ara-C was administered 5 h after gamma-irradiation, it is suggested that the induced breaks rejoined within that time. For neutrons, the data were conflicting since the repair was completed within 3 h after a dose of 0.5 Gy, and in approximately 5 h after a dose of 2.0 Gy. From both experiments, it appears that gamma-rays and fast neutrons produce similar types of lesions, as ara-C increased the frequencies of aberrations induced by both types of radiation. However, the ara-C treatment resulted in a smaller increase in aberrations following neutron irradiation. According to the enzymatic nature of break formation and the mode of action of ara-C on the polymerase activity, it is suggested that, in addition to double-strand breaks, single-strand breaks could be the lesions involved in the repair processes inhibited by ara-C. Single-strand breaks formed directly or by secondary reactions would, therefore, be one of the major lesions responsible for the aberrations produced by gamma and neutron radiations.

Cell Cycle↗
PubMed1985

[Chromosome aberrations produced in human lymphocytes by in vivo and in vitro irradiation].

The production of chromosome aberrations in vivo has been studied in lymphocytes from a patient undergoing a wholebody treatment with gamma-radiation up to a cumulative dose of 1.4 Gy. These results were compared with the observations performed on whole blood samples irradiated in vitro with doses from 0.05 up to 2 Gy of gamma-rays. The frequency of chromosome aberrations, particularly the dicentrics, was found to be similar in vivo and in vitro. The yield of dicentrics could be best related to the dose by using a linear-quadratic model in both cases, the ratio of the coefficients a/b being of 0.56 and 0.69 Gy, respectively in vivo and in vitro. These observations confirm that in vitro dose response curves may be used to evaluate accurately an in vivo absorbed dose.

Chromosome Aberrations↗
PubMed1985

Induction of chromosome aberrations in G0 human lymphocytes by low doses of ionizing radiations of different quality.

Human peripheral blood lymphocytes from two donors were exposed to low doses (0.05 to 2.0 Gy) of gamma rays, X rays, or fast neutrons of different energies. Chromosome aberrations were analyzed in metaphase of first-division cells after a culture time of 45-46 hr. At this time, less than 5% of the cells were found in second division. Different dose-response relationships were fitted to the data by using a maximum likelihood method; best fits for radiation-induced dicentric aberrations were obtained with the linear-quadratic law for all radiations. The linear component of this equation predominated, however, for neutrons in the range of doses studied, and the frequency of dicentrics induced by d(16)+Be neutrons up to 1.0 Gy could also be described by a linear relationship. The relative biological efficiency (RBE) of X rays and d(16)+Be, d(33)+Be, and d(50)+Be neutrons compared to 60Co gamma rays in the low dose range was calculated from the dose-effect relationships for the dicentrics produced. The RBE increased with decreasing neutron dose and with decreasing neutron energy from d(50)+Be to d(16)-+Be neutrons. The limiting RBE at low doses (RBEo) was calculated to be about 1.5 for X rays and 14.0, 6.2, and 4.7 for the d(16)+Be, d(33)+Be, and d(50)+Be neutrons, respectively.

Beryllium↗
PubMed1984

Mutagenicity of several derivatives of dipyrido[1,2-a:2',3'-d]imidazoles.

Different derivatives of dipyrido[1,2-a:2',3'-d]imidazoles have been investigated, as mutagens for Salmonella typhimurium. The nature of different substitution groups and their positions on the base ring influenced markedly the mutagenicity of these compounds. From this structure/effect relationship study, it was demonstrated that the 2 and 3 positions were of special interest. The 3-N-hydroxylated compound was the most active mutagen tested. We also observed that the frequently found frameshift mutagens were responsible for base-pair substitution. Metabolic activation by liver S9 mix increased the reversion rates of the strains tested. The SCE assays correlated poorly with the Salmonella/microsome mutagenicity test.

Cells, Cultured↗