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Biomedical subjects

A Franz

Publications and source records attributed to A Franz.

At least 55 records · Page 3Linked to original sources
PubMed2001

Measurement of the midrapidity transverse energy distribution from square root of [(s)NN] = 130 GeV Au + Au collisions at RHIC.

The first measurement of energy produced transverse to the beam direction at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory is presented. The midrapidity transverse energy density per participating nucleon rises steadily with the number of participants, closely paralleling the rise in charged-particle density, such that / remains relatively constant as a function of centrality. The energy density calculated via Bjorken's prescription for the 2% most central Au+Au collisions at square root[s(NN)] = 130 GeV is at least epsilon(Bj) = 4.6 GeV/fm(3), which is a factor of 1.6 larger than found at sqrt[s(NN)] = 17.2 GeV ( Pb+Pb at CERN).

Journal Article↗
PubMed2001

Best possible strategy for finding ground states.

Finding the ground state of a system with a complex energy landscape is important for many physical problems including protein folding, spin glasses, chemical clusters, and neural networks. Such problems are usually solved by heuristic search methods whose efficacy is judged by empirical performance on selected examples. We present a proof that, within the large class of algorithms that simulate a random walk on the landscape, threshold accepting is the best possible strategy. In particular, it can perform better than simulated annealing and Tsallis statistics. Our proof is the first example of a provably optimal strategy in this area.

Algorithms↗
PubMed2001

Centrality dependence of charged particle multiplicity in Au-Au collisions at square root of (s)NN = 130 GeV.

We present results for the charged-particle multiplicity distribution at midrapidity in Au-Au collisions at square root of [s(NN)] = 130 GeV measured with the PHENIX detector at RHIC. For the 5% most central collisions we find dN(ch)/d eta(vertical line eta = 0) = 622+/-1(stat)+/-41(syst). The results, analyzed as a function of centrality, show a steady rise of the particle density per participating nucleon with centrality.

Journal Article↗
PubMed2001

The effects of hydroxyethyl starches of varying molecular weights on platelet function.

We evaluated the effect of various hydroxyethyl starch (HES) solutions on platelet function. Blood was obtained before and after the IV infusion (10 mL/kg) of saline (n = 10), HES 70/0.5--0.55 (molecular weight in kD/degree of substitution; n = 10), HES 130/0.38--0.45 (n = 10), HES 200/0.6--0.66 (n = 10), or HES 450/0.7--0.8 (n = 10) in otherwise healthy patients scheduled for elective surgery. Collagen and epinephrine were used as agonists for assessment of platelet function analyzer closure times. Flow cytometry was used to assess agonist-induced expression of activated glycoprotein IIb/IIIa complex and P-selectin. Infusion of HES 450/0.7--0.8, HES 200/0.6--0.66, and HES 70/0.5--0.55 prolonged closure times and reduced glycoprotein IIb/IIIa expression, whereas saline and HES 130/0.38--0.45 had no significant effect on platelet variables. P selectin expression was not affected by any solution tested. In vitro experiments demonstrated a less inhibiting effect of HES 130/0.38--0.45 on closure times when compared with other HES solutions. This study shows that HES 450/0.7--0.8, HES 200/0.6--0.66, and HES 70/0.5--0.55 inhibit platelet function by reducing the availability of the functional receptor for fibrinogen on the platelet surface. Our data indicate that fluid resuscitation with HES 130/0.38--0.45 may reduce the risk of bleeding associated with synthetic colloids of higher molecular weight and degree of substitution.

Adult↗
PubMed2000

Antideuteron production in 158A GeV/c Pb + Pb collisions

The invariant cross section as a function of transverse momentum for antideuterons produced in 158A GeV/c per nucleon Pb+Pb central collisions has been measured by the NA44 experiment at CERN. This measurement, together with a measurement of antiprotons, allows for the determination of the antideuteron coalescence parameter. The extracted coalescence radius is found to agree with the deuteron coalescence radius and radii determined from two particle correlations.

Journal Article↗
PubMed2000

Influence of dental amalgam and heavy metal cations on in vitro interleukin-1beta production by human peripheral blood mononuclear cells.

The influence of dental amalgam and heavy metal cations on interleukin-1beta (IL-1beta) expression by peripheral blood mononuclear cells from healthy donors was studied. A marked decrease in the production of IL-1beta was caused by freshly prepared amalgam or amalgam-conditioned culture medium, but not by amalgam aged for 6 weeks. When metal cations were added as salts, Cu(2+), Hg(2+), and Ag(+) at high concentrations (33.3 and 333.3 microM) were highly inhibitory. Among other heavy metal cations, Au(3+), Pt(4+), Ni(2+), Pd(2+), but not Ga(3+) or Sn(2+), inhibited IL-1beta production in a concentration-dependent manner. Flow cytometry studies indicated that Hg(2+) and Ag(+) strongly reduced the percentage of CD14(+) cells containing IL-1beta intracellularly. As shown by Northern blot analysis, Hg(2+) inhibited the level of IL-1beta-specific mRNA by 28% at 3.3 microM and completely at 33.3 microM. Only slight inhibitory effects were induced by Cu(2+) at 33.3 microM. Interestingly, Ag(+) at a concentration of 3.3 microM increased twofold the amount of IL-1beta-specific mRNA. Our data show that IL-1beta production is altered at protein and mRNA levels by components released from fresh amalgam and by other heavy metal cations, suggesting a role of these cations in changes in the cell phenotype and IL-1-mediated cell functions.

Blotting, Northern↗
PubMed1998

Effects of dental amalgam and its components of histamine release from human basophils and tissue mast cells.

Recent studies have shown that metal ions can be released from dental amalgam or other dental materials, and can cause toxic effects on various cells. In this study, the effects of amalgam-conditioned culture medium (ACCM), components of amalgam (Ag+, Cu2+, Sn2+, Hg2+) and dental composite-conditioned culture medium (CCCM) on histamine release from human blood basophils (healthy subjects, n = 3) and tissue mast cells (n = 3) were analyzed. ACCM and CCCM were prepared using either fresh or 6-weeks-aged specimens. Of the metal ions tested, Ag+, and Hg2+ were found to induce histamine release from basophils (Ag+, 0.33 mM: 83 +/- 11% vs Hg2+, 0.33 mM: 100% vs control medium: 5 +/- 5%) and mast cells (Ag+, 0.33 mM: 91 +/- 16% vs Hg2+, 0.33 mM: 99 +/- 1% vs control: 2 +/- 1%), whereas no effects were seen with Cu2+ and Sn2+. Neither ACCM from freshly prepared amalgam nor ACCM from 6-weeks aged amalgam, produced histamine release in basophils or mast cells. Inductively coupled plasma atomic emission spectrometry (ICP) revealed that the Ag(+)- and Hg(2+)-concentrations in ACCM were below the range in which histamine release occurred. Similar to ACCM, no effects on basophils or mast cells were observed with CCCM. In summary, our data show that distinct metal ions present in dental amalgam, can induce (toxic) histamine liberation from basophils and mast cells. However, the amounts of metal ions released from amalgam apparently were too low, to cause histamine release.

Basophils↗
PubMed1998

Metal ion-induced toxic histamine release from human basophils and mast cells.

Recent data suggest that distinct metal ions can be released from dental alloys or other biomaterials, and may cause toxic effects on various cells. In this study, the effects of 14 metal ions on histamine release from human blood basophils (n = 4), isolated tissue mast cells (lung n = 8, uterus n = 2, skin n = 1, gingiva n = 1), the basophil cell line KU-812, and the mast cell line HMC-1 were analyzed. Of the 14 metal ions, Ag+ (0.33 mM) and Hg2+ (0.33 mM) were found to induce release of histamine in blood basophils, KU-812, mast cells, and HMC-1. The effects of Ag+ and Hg2+ were dose dependent and were observed within 60 min of incubation. In primary mast cells and basophils, AU3+ (0.33 mM) also induced histamine release, whereas no effects of Au3+ on HMC-1 or KU-812 cells were seen. The other metal ions showed no effects on primary or immortal cells within 60 min. However, Pt4+ (0.33 mM) induced histamine liberation in HMC-1 and lung mast cells after 12 h. The Ag+- and Hg2+-induced rapid release of histamine from HMC-1 was associated with ultrastructural signs of necrosis, but not apoptosis. In contrast, prolonged exposure to Pt4+ (0.33 mM, 14 h) induced apoptotic cell death in HMC-1 cells, as assessed by electron microscopy and DNA analysis. Together, certain metal ions induce distinct cytopathogenic effects in mast cells and basophils. Whereas Ag+, Hg2+, and Au3+ cause direct toxicity, Pt4 causes cell death through induction of apoptosis. Whether such effects contribute to local adverse reactions to metal-containing biomaterials in vivo remains to be determined.

Basophils↗
PubMed1998

Effects of dental amalgam and heavy metal cations on cytokine production by peripheral blood mononuclear cells in vitro.

The effects of dental amalgam on cytokine production by human peripheral blood mononuclear cells (PBMC) from healthy donors were analyzed. To induce cytokine production, PBMC were stimulated with lipopolysaccharide, phytohemagglutinin, or staphylococcal enterotoxin A and cultured for 48 h in the presence of either freshly prepared amalgam, aged amalgam, or amalgam-conditioned culture medium (ACCM). The concentrations of several cytokines were measured in PBMC supernatants by enzyme-amplified sensitivity immunoassays (EASIAs). Freshly prepared amalgam as well as ACCM induced a decrease in the production of interferon-gamma (IFN-gamma) and interleukin-10 (IL-10), and an increase in the concentrations of tumor necrosis factor-alpha (TNF-alpha). Both fresh amalgam and ACCM showed no effects on IL-2, IL-6, or granulocyte-macrophage colony-stimulating factor levels. Amalgam aged for 6 weeks did not affect the concentration of any of the above cytokines. To investigate which heavy metal cations released from amalgam caused the observed immunomodulatory effects, Cu2+, Hg2+, and Sn2+, which were detected in amalgam supernatants by inductively coupled plasma atomic spectrophotometry, were added as salts to the cultures. Cu2+ and Hg2+ induced a decrease in IFN-gamma and IL-10 levels, and Hg2+ an increase in TNF-alpha concentrations. Cytokine production was not significantly modulated by Sn2+. Under these experimental conditions, release of Ag+ into culture medium was not detectable. However, Ag+ markedly suppressed the production of IFN-gamma, IL-10, and TNF-alpha. In summary, our results show that fresh amalgam, but not amalgam aged for 6 weeks, causes changes in the cytokine pattern of PBMC in vitro, and that these effects are due to the release of Cu2+ and Hg2+.

Cations↗
PubMed1998

Cytotoxic effects of dental composites, adhesive substances, compomers and cements.

OBJECTIVES: Although research interest in biocompatibility of dental materials has been increasing, findings are frequently controversial and non-harmonized experimental approaches often lead to the production of contradictory results. The aim of this study was to compare the cytotoxic effects of six different light-cured dental composites, one compomer, one advanced glass-ionomer, two glass-ionomer cements, two zinc phosphate cements, one calcium hydroxide liner, one composite cement and one carboxylate cement with the same standardized cell-culture system. Two composites, one compomer and one advanced glass-ionomer were also tested in combination with the appropriate bonding substances and surface primers. METHODS: Specimens were added to the cultures immediately after production or after preincubation for 1, 2 or 7 days or 6 weeks under cell-culture conditions. Specimens were incubated with L-929 fibroblasts for 72 h and cell numbers determined by flow cytometry. RESULTS: All freshly prepared composite materials were cytotoxic. These effects diminished with increased preincubation times and were not significant after 7 days. Combinations of composites and bonding substances were still cytotoxic after preincubation for 7 days, but not after 6 weeks. Combinations of compomers and bonding substances demonstrated stronger toxicity than composites, although these effects were reduced earlier during preincubation. Glass-ionomer and phosphate cements showed similar effects to the composites with the exception of carboxylate cement, which demonstrated severe and persistent effects even after 6 weeks' preincubation. Together, our data provide evidence that all dental materials tested are cytotoxic immediately after production and that these effects are reduced after different preincubation periods in most cases. SIGNIFICANCE: Tested with a standardized cell-culture system, differences in toxicological potency between various commonly used dental materials were observed. Cytotoxicity data from standardized protocols should form the basis of screening the cytotoxic effects of new materials.

Adhesives↗
PubMed1997

Mycoplasmal arthritis in patients with primary immunoglobulin deficiency: clinical features and outcome in 18 patients.

A survey of 358 patients with primary antibody deficiency shows that mycoplasmal infection is the commonest cause of severe chronic erosive arthritis. We review our experience with 18 patients with confirmed or probable mycoplasmal arthritis. There was a broad spectrum of severity from a monoarthritis rapidly responding to tetracyclines to severe debilitating polyarthritis, sometimes with antibiotic-resistant organisms which in two cases were eliminated following hyperimmune animal serum therapy. Most patients had very low serum 1gG levels at the onset of arthritis, suggesting that maintaining levels within the normal range with immunoglobulin replacement may prevent infection. The unique susceptibility of these patients to mycoplasmal arthritis shows that antibodies play a crucial role in protection against these organisms.

Adolescent↗
PubMed1996

Detection, purification and partial characterization of beta-amylase from trophozoites of Entamoeba invadens.

Trophozoites of Entamoeba invadens were able to ingest glucopolysaccharides and metabolize them. An activity capable of degrading these substrates was purified to apparent homogeneity. The enzyme was identified as beta-amylase (alpha-1,4-D-glucan maltohydrolase EC 3.2.1.2): It was active against glycogen, amylose and amylopectin in a ratio of 100:198:133 and was also able to attack linear alpha-1,4-glucooligosaccharides with more than three glucose moieties. All degradation experiments yielded maltose as reaction product, and no free glucose could be detected. While amylose was completely degraded, amylolysis of glycogen and amylopectin yielded limit dextrins besides maltose. The enzyme was completely inactive against cyclohexaamylose, cycloheptaamylose and pullulan, indicating its lack of endo-glucosidase specificity. Hydrolysis of 4-nitrophenyl-maltoheptaoside resulted in the successive removal of maltose units from the non-reducing end yielding 4-nitrophenyl-maltopentaoside, -trioside and -glucoside. No 4-nitrophenyl-glycosides with even numbered glucose moieties were formed from this substrate. The enzyme exhibited a relative molecular mass of M(r) = 45,000 +/- 5% by gel filtration and sodium dodecyl sulfate (SDS) gel electrophoresis and the N-terminal sequence 1 VEVNVMLPL 9. Optimal hydrolysis was observed at pH 5.5 and a temperature of 42 degrees C. On the basis of inhibition by mercury ions and p-chloro-mercurybenzoate and abrogation of this effect by thiol reagents beta-amylase was identified as sulfhydryl-enzyme.

Animals↗
PubMed1996

Common variable immunodeficiency presenting as a Mycoplasma hominis septic arthritis.

A case is reported of common variable immunodeficiency (CVID) presenting as an acute septic arthritis due to Mycoplasma hominis. The diagnosis was not considered until the hypogammaglobulinaemia was discovered and the synovial fluid cultured specifically for mycoplasmas. The importance of diagnosing immunodeficiency states and searching for mycoplasmas in 'bacteriologically culture negative' cases is emphasized.

Adult↗
PubMed1996

Prevalence of hepatitis C in patients with primary antibody deficiency.

Concern over sporadic hepatitis C virus (HCV) infection from treatment with contaminated immunoglobulin in patients with immunodeficiency prompted use to screen serum from 44 patients for HCV RNA. We found no evidence of either horizontal or iatrogenic infection in our Clinic, except in two patients known to have received contaminated batches, and in one who had had regular plasma infusions. Thus, common variable immunodeficiency (CVID) patients in England do not have a high incidence of HCV infection despite exposure to various immunoglobulin products. This contrasts with the recently reported high prevalence in similar patients in Italy. Although our data reinforce the impression that both intramuscular and current licensed i.v. preparations in the UK are safe, manufacturers should be encouraged to PCR screen all batches of immunoglobulin for HCV.

Agammaglobulinemia↗
PubMed1995

Response of L-929 fibroblasts, human gingival fibroblasts, and human tissue mast cells to various metal cations.

Recent data suggest that under certain conditions, various metal cations are released from dental alloys. These ions may produce adverse effects in various cell types in vivo. In this study, the cytopathogenic effects of 13 metal cations on murine L-929 fibroblasts, human gingival fibroblasts, and human tissue mast cells were analyzed in vitro. Several metal cations (dose range, from 0.0033 to 1.0 mmol/L) were found to induce dose-dependent inhibition of 3H-thymidine incorporation into cultured fibroblasts. The rank order of potency (lowest observed effect level, LOEL) for L-929 fibroblasts was: Ag+ > Pt4+ > Co2+ > In3+ > Ga3+ > Au3+ > Cu2+ > Ni2+ > Zn2+ > Pd2+ > Mo5+ > Sn2+ > Cr2+. A similar rank order of potency was obtained for primary human gingival fibroblasts: Pt4+ > Ag+ > Au3+ > In3+ > Ga3+ > Ni2+ > Co2+ > Zn2+ > Cu2+ > Cr2+ > Pd2+ > Mo5+ > Sn2+. In primary human mast cells, Ag+ and Au3+ caused dose-dependent toxic histamine release, whereas the other metal cations were ineffective over the dose range tested. To investigate the mechanism of metal cation-induced effects, we performed DNA as well as electron microscopic analyses on cultured fibroblasts. Both the DNA pattern and the ultrastructure of L-929 cells and gingival fibroblasts after exposure to cytopathogenic metal cations revealed signs of necrosis but no signs of apoptosis. Together, our data provide evidence that various metal cations produce dose-dependent cytopathogenic effects in distinct cell types, including human gingival fibroblasts and human tissue mast cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗