Extinction: complexity of assessing risk.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
C Flemming
Publications and source records attributed to C Flemming.
Differentiation of Candida strains by lectin-mediated agglutination kinetics.
The lectin-mediated agglutination kinetics of Candida albicans, Candida tropicalis, Candida glabrata, Candida krusei, Candida kefyr, and Candida parapsilosis strains isolated from immunocompromised patients was investigated. The rate of the lectin-induced cell agglutination depends on the physiological state of the yeast cell population. Therefore, the Candida strains have to be cultivated and investigated under identical conditions. Lentil lectin (prepared from Lens culinaris), castor lectin, and concanavalin A were used. Different yeast species showed different agglutination behaviour. Furthermore, the lectin-mediated rate of agglutination is a strain-specific property which makes it possible to distinguish between different yeast strains of the same species. It is concluded that the lectin-mediated agglutination kinetics allows reproducible differentiation of yeast strains of the same species.
Agglutination↗
Comparative study of the in vitro behavior of cord blood subpopulations after short-term cytokine exposure.
We investigated the effect of short-term cytokine exposure on defined cord blood subpopulations. CD34+Thy1+, CD34+Thy1-, CD34+38-, CD34+38+, CD34+DR+, CD34+DR-, CD34+Rhodamine123 (Rh123)- and CD34+Rh123+ cells were incubated for 7 days in IMDM + 10% FCS + IL3 + IL6 + G-CSF + SCF (36GS) + flt3L. We evaluated LTHC-IC, immunophenotype and nucleated cell count for each cell population before and after cytokine exposure. Short-term exposure of CD34+38+, CD34+Thy1-, CD34+DR+, CD34+DR- and CD34+Rh123+ cells to 36GS causes a significant increase in cell number, whereas CD34+38-, CD34+Thy1+, and CD34+Rh123- cells show only a limited increase. CD34 status post cytokine incubation shows that CD34+38+, CD34+Thy1-, CD34+DR+, and CD34+Rh123+ fractions have a lower proportion of cells remaining CD34+ than CD34+38- CD34+Thy1+, CD34+DR- and CD34+Rh123- fractions. LTHC-IC analyses among input subpopulations show a higher frequency among CD34+38+, CD34+Thy1-, CD34+DR+, CD34+DR- and CD34+Rh123+ cells as compared with CD34+38-, CD34+Thy1+ and CD34+Rh123- cells. However, when LTHC-IC were evaluated after cytokine exposure, CD34+38-, CD34+Thy1+, and CD34+Rh123- cells showed a higher frequency of LTHC-IC as compared with other subpopulations. Addition of flt3L to 36GS doubled the numbers in all subpopulations without altering the proportion of CD34+ cells. Results suggest that CD34+38-, CD34+Thy1+ and CD34+Rh123- cells have a limited proliferative response to cytokines, the stem cell component of these populations is largely maintained and that expansion is derived from mature cell populations.
Cell Culture Techniques↗
Energy transfer and charge separation in photosystem I: P700 oxidation upon selective excitation of the long-wavelength antenna chlorophylls of Synechococcus elongatus.
Photosystem I of the cyanobacterium Synechococcus elongatus contains two spectral pools of chlorophylls called C-708 and C-719 that absorb at longer wavelengths than the primary electron donor P700. We investigated the relative quantum yields of photochemical charge separation and fluorescence as a function of excitation wavelength and temperature in trimeric and monomeric photosystem I complexes of this cyanobacterium. The monomeric complexes are characterized by a reduced content of the C-719 spectral form. At room temperature, an analysis of the wavelength dependence of P700 oxidation indicated that all absorbed light, even of wavelengths of up to 750 nm, has the same probability of resulting in a stable P700 photooxidation. Upon cooling from 295 K to 5 K, the nonselectively excited steady-state emission increased by 11- and 16-fold in the trimeric and monomeric complexes, respectively, whereas the quantum yield of P700 oxidation decreased 2.2- and 1.7-fold. Fluorescence excitation spectra at 5 K indicate that the fluorescence quantum yield further increases upon scanning of the excitation wavelength from 690 nm to 710 nm, whereas the quantum yield of P700 oxidation decreases significantly upon excitation at wavelengths longer than 700 nm. Based on these findings, we conclude that at 5 K the excited state is not equilibrated over the antenna before charge separation occurs, and that approximately 50% of the excitations reach P700 before they become irreversibly trapped on one of the long-wavelength antenna pigments. Possible spatial organizations of the long-wavelength antenna pigments in the three-dimensional structure of photosystem I are discussed.
Chlorophyll↗
Sequential biological immunosuppression. Induction therapy with rabbit antithymocyte globulin.
This paper describes 108 consecutively treated patients receiving 109 cadaveric (CD) and living donor (LD) renal allografts using a protocol of quadruple sequential immunosuppression with a rabbit anti-human thymocyte IgG (Thymoglobuline), azathioprine, tapering corticosteroids, and delayed introduction of cyclosporine A. The average length of induction was 6.1 d with an average Thymoglobuline dose of 2.0 mg/kg/d. The mean serum creatinine pre-transplant of the cohort was 877 +/- 263 (sd) mumol/L, 146 +/- 44 mumol/L by 3 months post-transplant, and 136 +/- 40 mumol/L at 1 yr. The overall 4-yr actuarial patient survival was 96.6%, and allograft survival was 88.6% at 2 yr and 83.6% at 4 yr. The incidence of acute rejection episodes defined by intention to treat was 32%. Additionally, eight patients in this series received retreatment with Thymoglobuline for a first acute rejection, and only one of these had a second rejection. This was in contrast to 5/11 recurrent rejections following steroid treatment only, and 5/13 recurrences following OKT3 treatment for the first rejection episode. The side-effect profile of Thymoglobuline was largely benign, and the biological agent was well tolerated with initial fever in 75%, chills in 27%, and leucopenia in 22% of the patients. All other drug-related adverse events had a prevalence of less than 3%, and clinical signs of meningismus were seen in only one patient. There were five associated episodes of CMV. We conclude that Thymoglobuline as part of a quadruple sequential immunosuppressive regimen for renal transplantation is well tolerated and can be associated with a good short- and long-term outcome of renal transplantation.
Actuarial Analysis↗
Use of thymoglobulin induction therapy in the prevention of acute graft rejection episodes following liver transplantation.
Explore the source record for details and available documents.
Acute Disease↗
Diagnosing salmonellosis in horses. Culturing of multiple versus single faecal samples.
Three rectal faecal samples were taken at 24-hour intervals from 136 horses in order to investigate whether multiple faecal cultures yield a greater number of Salmonella-positive horses compared to single faecal cultures. Of these 136 horses, 89 were suspected of salmonellosis on clinical grounds and 47 belonged to a control group. From the 'Salmonella suspected' group, 22 horses (25%) were Salmonella positive on one or more occasions. Only twelve of these 22 positive horses (55%) were positive at first sampling. Of the control group, only three horses (6%) were positive for Salmonella. Thirty-one (69%) of the 45 positive cultures from the 'Salmonella suspected' group were found only after enrichment in Selenite broth. From the results of the present study it is concluded that multiple faecal cultures are superior to single faecal cultures for diagnosing clinical salmonellosis in horses and that there is no relation between the course of the disease and whether the Salmonellae were cultured directly or indirectly, after enrichment in Selenite broth. Salmonellae were cultured from the faeces of horses treated with antibiotics before their referral, even when the isolated strain was sensitive to the antimicrobial drug used by the practitioner.
Animals↗
Determination of lectin characteristics by a novel agglutination technique.
A technique generally applicable for the determination of lectin characteristics is described. A sensitive light transmission/scattering method was adapted for the determination of lectin levels and lectin activity. Applying this procedure Geodia cydonium lectin-mediated agglutination was studied in an agglutimeter device using erythrocytes and even T-lymphocytes. In the Geodia lectin/T-lymphocyte system chosen, (i) a lectin concentration as low as 0.57 micrograms/ml could be measured accurately, (ii) the observed cell agglutination velocity constant with a maximal value of 0.75 min-1 was calculated, and (iii) the size of the agglutinates at a given lectin concentration and time period was estimated. The Geodia lectin activity was determined in parallel also in the erythrocyte system. Here, compared to the lectin/T-lymphocyte system the agglutination efficiency of the Geodia lectin-mediated agglutination was more than 10-fold higher and the lowest detectable lectin concentration was 0.06 micrograms/ml. Compared to the hemagglutination assay the lectin/erythrocyte system turns out to be more sensitive and to give much more information on agglutination behavior; this conclusion is supported by additional data using a second lectin isolated from Pellina semitubulosa. The superiority of the agglutination method described here over other known methods must be seen in its accuracy; moreover more lectin characteristics can be determined.
Agglutination↗
Determination of lectin-cell-binding parameters by a new agglutination technique.
We applied a recently described technique which is based on a light transmission/scattering method to determine the association characteristics of the Geodia lectin to sheep erythrocytes. The agglutination assays were performed in a total volume of 3 ml with 5.4 x 10(6) erythrocytes/ml. At a concentration of 360 ng/ml 50% of the lectin molecules were bound to the cells within the first 10 s of incubation. Scatchard analyses revealed an association constant (K(a)) of 0.9 +/- 0.1 x 10(8) M-1 and a number of 3.8 +/- 0.6 x 10(6) lectin binding sites on one erythrocyte. The method was also successfully applied to determine quantitatively the inhibitory potential of sugars competing with cell surface glycoproteins for the lectin binding site. At a lectin concentration of 360 ng/ml 1 mM of lactose or 70 mM of D-N-acetylgalactosamine are required to inhibit lectin-mediated agglutination by 50%. These analyses confirm the potential of the novel light absorption agglutination technique to evaluate lectin characteristics.
Animals↗
tri-n-Butyltin: a membrane toxicant.
Increased use of the biocidal compound tri-n-butyltin (TBT) in antifouling paints has prompted research aimed at determining the mechanism for TBT toxicity. Past investigations indicate that the primary cellular target for TBT is the cell membrane. Erythrocyte suspensions treated with TBT concentrations 2 greater than or equal to 5 microM undergo hemolysis described by a sigmoidal kinetic pattern. Transformation of cell shape from discocyte to echinocyte occurs at TBT concentrations greater than or equal to 0.1 microM, indicating that the compound enters the outer membrane bilayer. TBT at concentrations greater than or equal to 10 microM forms electron-dense aggregates that are intercalated within plasma membranes as viewed in ultrathin sections by transmission electron microscopy. Qualitative X-ray microanalysis of these aggregates confirms the presence of tin. The size of these structures can be modified by either 10 mM cyanide or 2,3-dimercaptopropanol (British Anti-Lewisite, BAL). Adding 10 mM cyanide to hemolytic TBT concentrations resulted in a synergistic stimulation of hemolysis attributable to high cyanide anion concentrations in or near the cell membrane. The elevated cyanide anion levels are thought to contribute to membrane lysis. The lipophilic dimercapto compounds BAL, dithiothreitol, and 2,3-dimercaptosuccinate are effective inhibitors of TBT-induced lysis. Water-soluble 2,3-dimercapto-1-propane sulfonate, a BAL analog, was largely ineffective as an inhibitor. The detailed molecular mechanism for TBT-induced membrane lysis is not yet clear. Cellular ATP depletion could be induced by TBT as well as by delipidation of anionic phospholipids or even formation of tributylstannylperoxy radicals, resulting in lipid peroxidation.
Chemical Phenomena↗
Organotin-induced hemolysis, shape transformation and intramembranous aggregates in human erythrocytes.
Organotin compounds examined in this study exhibited a relative order of potency for induction of in vitro hemolysis in human erythrocytes as follows: tri-n-butyltin greater than tri-n-propyltin greater than tetra-n-butyltin greater than triphenyltin chloride greater than tri-n-ethyltin bromide greater than dibutyltin dichloride greater than stannous chloride greater than tri-n-methyltin chloride = butyltin chloride dihydroxide. All of the organotin compounds induced erythrocyte shape transformation from the normal discocyte to an echinocyte and, in addition, triphenyltin chloride, tetra-n-butyltin and tri-n-ethyltin bromide also elicited stomatocyte formation at higher concentrations. Select organotin compounds also formed tin-containing aggregates within the plasma membrane. The relative order of effectiveness for organotin induction of intramembranous aggregates was tri-n-butyltin greater than tri-n-propyltin greater than tetra-n-butyltin greater than tri-n-ethyltin bromide, which was based upon the lowest concentration at which they were observed. These results support the previously suggested theory that organotins are membrane effectors because of their comparatively high hydrophobic, lipid partitioning properties. The relatively lipophilic compound, triphenyltin chloride, appeared to be anomalous because it did not readily promote hemolysis or induce the formation of intramembranous aggregates in human erythrocytes. A log-linear statistical model demonstrated an association of hemolysis with both tri-n-butyltin aggregate formation and shape transformation. Select organotin compounds should be useful probes in membrane studies because of their numerous effects.
Erythrocyte Aggregation↗
Inhibition of tributyltin mediated hemolysis by mercapto compounds.
Hydrophobic tributyltin (TBT) compounds at concentrations greater than 10 microM caused hemolysis of human erythrocytes and formed structures in plasma membranes. The mercapto compounds, beta-mercaptoethanol (beta MER), 2,3-dimercaptopropanol (BAL), 2,3-dimercapto-1-propane sulfonate (DMPS), DL-dithiothreitol (DTT), and meso-2,3-dimercaptosuccinic acid (DMSA) were examined for their ability to inhibit TBT mediated hemolysis. The relative order of effectiveness for inhibition of TBT mediated hemolysis was BAL greater than DTT greater than DMSA greater than DMPS greater than beta MER. A four-fold excess of BAL over TBT prevented hemolysis for 4 hrs and addition of BAL 0.5 hr after TBT reduced the rate of hemolysis. The number of membrane associated TBT aggregates observed per cell profile decreased as the BAL concentration increased from 0 to 100 microM. However, the mean diameter of TBT aggregates nearly doubled in erythrocyte suspensions at 100 microM BAL. Reactions of dimercapto compounds with lipophilic TBT aggregates may depend on their relative lipid solubilities. Also, conversion of the weak Lewis acid, TBT, from a four to a five or six-coordinate tin adduct by the dimercapto Lewis bases used could also be a factor slowing hemolysis rates.
Erythrocytes↗
[Interactions between lectins and microorganisms. 1. Determination of the rate of agglutination by measurement of extinction: agglutination of yeast cells (Saccharomyces cerevisiae H155) by concanavalin A].
A simple photometric method for the determination of the agglutination rate of cells by lectins in a continuously stirred suspension is presented. Besides the agglutination rate the method allows the estimation of an average degree of agglutination, i.e. the number of cells per aggregate. The influence of the Con A-concentration, cell number, temperature, and pH on the agglutination rate of Saccharomyces cerevisiae H155 have been studied. The results are of good reproducibility and, therefore, the methods is suitable to describe interactions between cell-bound receptors and receptor-specific proteins, e.g. lectins and antibodies.
Agglutination↗
[Isolation of a yeast cell-agglutinating component from normal serum by cell column chromatography].
By cell column chromatography a fraction of porcine serum has been obtained that specifically reacts to the surfaces of the yeast cells of Saccharomyces cerevisiae H155. This serum fraction agglutinates only the cells of Saccharomyces cerevisiae H155 but does not those of Candida maltosa EH15 and Yarrowia lipolytica EH59, respectively.
Agglutination↗
Interspecies variability in propylene glycol dinitrate-induced methemoglobin formation.
Interspecies variability of propylene glycol dinitrate (PGDN)-induced methemoglobin formation was studied in vitro employing erythrocytes from four separate species. The net rate of methemoglobin formation was significantly different among species with dog greater than guinea pig greater than rat greater than or equal to human. This order of susceptibility was maintained in stroma-free hemolysates, indicating that interspecies variability was not a reflection of differences in red cell membrane permeability or intracellular transport of PGDN. The erythrocytic enzymes, catalase, superoxide dismutase, glutathione peroxidase, 6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, methemoglobin reductase, and glutathione-S-transferase, were assayed by adaptation of existing methods to a centrifugal analyzer. The above enzymes were removed from hemoglobin derived from each species and the order of susceptibility to PGDN-induced methemoglobin formation remained essentially the same with dog greater than guinea pig greater than human = rat. However, the net rate of PGDN-mediated oxidation of hemoglobin to methemoglobin increased in purified hemoglobin preparations from each species. These results demonstrate that there is species variability in the net rate of PGDN-mediated methemoglobin formation. Total enzyme activity in erythrocytes may contribute to reduction in the net rate of methemoglobin formation. However, the primary determinant of the net rate of methemoglobin formation induced by PGDN appears to be the structure of each hemoglobin molecule.
Animals↗
"Natural antibodies" against yeast--a flow-microfluorometric approach.
Fluorescent labeling of antibodies in connection with flow-microfluorometry was applied to "natural antibodies" against yeast strains Candida maltosa and Yarrowia lipolytica, obtained by cell column chromatography. It is shown that "natural antibodies" against these yeast strains react in a specific manner with the surface of the cells.
Animals↗
Home care and adult protective services.
Explore the source record for details and available documents.
Adult↗
[Characterization of polygalacturonase covalently bonded to Sepharose].
For the soluble endo-polygalacturonase (EC 3.2.1.15.) from Aspergillus spec., investigated in the present work, the defined substrate turnover U at 50% loss of viscosity if 0.2% and is independent on the reaction temperature. In the case of the covalently-bonded enzyme, the following linear equation applies to U, depending on the specific activity A and in the limits from A = O [U] and Amax: U = [U] + S square root of A. U is influenced by the kind of linkage, the conditions of immobilization and the properties of the carrier: it is a measure of the postulated conformational change of the polygalacturonase. The characteristic limiting value for the substrate turnover at A = O [U] is also temperature-independent and proves to be a true increment of binding, whereas Amax depends essentially on the porosity of the carrier. Polygalacturonase-sepharose complexes with a real substrate turnover U of 3--20% were prepared by varying systematically the kind of linkage and the specific activity A. It was found that with increasing U these complexes were, as a rule, inhibited to a lesser extent by a non-competitive pectinase inhibitor than the soluble polygalacturonase. Furthermore, their ability to liberate or enrich oligomeric galacturonic acids with a degree of polymerization greater than 3 was markedly reduced.
Aspergillus↗