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Results for “differential selection”

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At least 127 records · Page 7Linked to original sources
PubMed2001

Development of a selective differential agar for isolation and enumeration of Campylobacter spp.

Direct plating is an effective technique for isolation and enumeration of Campylobacters from a variety of sample types; however, distinguishing Campylobacters from non-Campylobacter contaminants that frequently grow on many existing agars is difficult. In this study, it was determined that exposing Campylobacters to low levels (200 mg/liter) of triphenyltetrazolium chloride (TTC) was not inhibitory to growth yet was sufficient to give a deep-red to magenta color to the colonies. The new agars (Campy-Line agar [CLAI and Campy-Line blood agar [CLBA]) are translucent. The contrast of deep-red colonies on a translucent background greatly facilitates Campylobacter isolation and makes enumeration on light boxes or by electronic means possible. Direct plating of broiler carcass rinse samples (n = 20) was compared on Campy-Cefex agar and CLA. Recovery of Campylobacter populations was not significantly different between the agars (P < 0.05); however, enumeration was much less labor intensive with the CLA. No contaminants were observed on the CLA, whereas the Cefex agar supported the growth of approximately 14 contaminating (non-Campylobacter) CFU/ml. In a separate trial, recovery of Campylobacters from carcass rinses (n = 25) was similarly compared on Cefex, CLA, and CLBA. Again, recovery of Campylobacters was not significantly different between the agars (Pearson correlation coefficient = 0.988), whereas about nine contaminating (non-Campylobacter) CFU/ml were observed on Cefex agar and none on CLA or CLBA. Although some contaminants can still grow on CLA and CLBA and can present red colonies, most of these contaminants are easily distinguished from Campylobacter by differences in colony morphology.

Agar↗
PubMed1981

Differential selective toxicity of DMS-aureofacin components.

Trimethylammonium methyl esters (DMS) of polyene macrolides are products of the methylation of native polyene antibiotics with dimethyl sulfate. We isolated individual components of the DMS-aureofacin complex and characterized their toxicity and activity to induce permeability changes in cell membranes. The DMS-aureofacin complex contained five components readily separated by thin-layer chromatography on polygram cellulose plates. DMS-Aureofacin A, a major component of the complex (90%), showed poor selective toxicity between yeast cells and mammalian cells grown in culture. DMS-Aureofacin B (6%) and DMS-aureofacin E (4%) exhibited very high biological activities and differed qualitatively in selective toxicity. DMS-Aureofacin B was much more active for mammalian cells than for yeast cells. In contrast, DMS-aureofacin E was much more active for yeast cells than for mammalian cells. DMS-Aureofacin C and D were present in the complex in only minute quantities which did not permit their biological characterization.

Animals↗
PubMedDate not supplied

[Selective differentiation and proliferation of human eosinophils from umbilical cord blood: calcium fluxes and superoxide ion secretion].

Investigation of the physiologic mechanisms involved in the activation of eosinophils is crucial to comprehend their role in the pathogenesis of allergic reactions. To overcome the difficulty of obtaining large numbers of eosinophils, we differentiated in vitro eosinophils from human umbilical cord blood mononuclear cells. These cells responded to fMLP or PAF with an increase in [Ca2+]i, associated with O2 production. Deprivation or chelation of extracellular calcium induced a reduction of fMLP or PAF-induced [Ca2+]i rise and O2- production. Similar results were obtained with extracellular Ni2+ addition. Chelation of intracellular calcium induced an inhibition of fMLP- or PAF-induced [Ca2+]i rise and a decrease in O2- production. Our results indicate that fMLP- and PAF-dependent O2- production in eosinophils requires intra- and extracellular Ca2+ and that Ca2+ influx is necessary for optimal activation.

Calcium↗
PubMed1992

Polymorphism and differential selection for the sexes.

Various genetic models with different fitnesses for the sexes are investigated. Only a limited set of fitness values will result in a stable polymorphism, and the rate of approach to these equilibrium frequencies is extremely slow. These results indicate that there are problems associated with the interpretation of some human genetic traits by such models.

Albinism↗
PubMed1968

A selective-differential medium for detection of Streptococcus agalactiae.

A practical culture medium which allows direct plating of milk samples for detection and differentiation of Streptococcus agalactiae within 48 hours is described. Most other micro-organisms likely to be present in these samples are inhibited. Although some strains of Staphylococcus species and ofStreptococcus faecalis are able to grow, they may be differentiated on the basis of reaction in the medium surrounding the colonies.

Animals↗
PubMed1985

Differential selectivity of cholinephosphotransferase and ethanolaminephosphotransferase of Tetrahymena for diacylglycerol and alkylacylglycerol.

The glycerophospholipids of the ciliate protozoan Tetrahymena thermophila differ greatly in their content of alkylacylglycerol with phosphatidylcholine, phosphatidylethanolamine, and 2-aminoethylphosphonolipid containing 60, 4, and 53% glyceryl ether, respectively. This difference is achieved by differences in the selectivities of cholinephosphotransferase (EC 2.7.8.2) and ethanolaminephosphotransferase (EC 2.7.8.1) for alkylacylglycerol and diacylglycerol. When the two enzymes are assayed in vitro using only endogenous diglyceride as substrate, the newly formed phosphatidylcholine contains 37% glyceryl ether, while the newly formed phosphatidylethanolamine contains 5% glyceryl ether. The ethanolaminephosphotransferase is stimulated equally well by addition of diolein and dipalmitin, but the diacylglycerols have no effect on the glyceryl ether content of phosphatidylethanolamine. In contrast, the glyceryl ether content of newly formed phosphatidylcholine decreases to 16% when the cholinephosphotransferase is exposed to diolein or dipalmitin. The ethanolaminephosphotransferase is not stimulated by addition of a 60:40 mixture of alkylacylglycerol/diacylglycerol. The cholinephosphotransferase is stimulated by the mixture to the same extent as it is by the diacylglycerols, with the glyceryl ether content of the newly formed phosphatidylcholine increasing to 52%. With the addition of alkylacylglycerol alone, the glyceryl ether content of the newly formed phosphatidylethanolamine increases to 10%, while that of the newly formed phosphatidylcholine increases almost to 60%.

Animals↗
PubMed1980

[Treatment of trigeminal neuralgia using controlled differential selective thermorhizotomy].

Personal experience in 35 cases of controlled, partial, selective thermorhizotomy of the trigeminus is referred to in a discussion of its indisputable advantages (abolition of pain, preservation of tactile sensibility, simple method) by comparison with other techniques, and its theoretical basis: selective lesion of the "delta" A and C fibres by exploiting the vulnerability gradient of the nerve fibres to heat.

Adult↗
PubMed1996

Differential selectivity of M1 and M3 type muscarinic acetylcholine receptors in coupling with a G protein G01 alpha examined in Xenopus oocytes.

The coupling specificities between muscarinic acetylcholine receptors (porcine M1 and M3 subtypes) and a heterotrimeric GTP binding protein (bovine G01) were examined by analysing receptor-stimulated, phospholipase C (PLC)-mediated chloride current responses in Xenopus oocyte expression system. M1-stimulated responses were suppressed by G01 alpha, and this suppression was reversed by expressing exogenous G beta and G gamma, whereas M3-stimulated responses were enhanced by G01 alpha in the presence or absence of G beta and G gamma. G01 alpha itself, when activated directly by intracellular fluoride injection, efficiently activated PLC and stimulated chloride current responses. The results indicate that M1 receptor does not couple with G01, while M3 receptor activates G01 effectively.

Animals↗
PubMed1998

Differential selectivity of ligands for the C1a and C1b phorbol ester binding domains of protein kinase Cdelta: possible correlation with tumor-promoting activity.

Protein kinase C (PKC) represents the major, high-affinity receptor for the phorbol esters as well as for a series of structurally diverse natural products. The phorbol esters function by binding to the tandem C1a and C1b domains in PKC, leading to enzyme activation. Although the typical phorbol esters represent the paradigm for tumor promoters in mouse skin, it is now clear that different high affinity ligands for PKC have distinct biological effects. Thus, the daphnane analogue mezerein is a second-stage promoter, the macrolide bryostatin 1 is a partial antagonist, and certain 12-deoxyphorbol 13-monoesters also function as partial antagonists but with a different pattern of activity. The biochemical basis for these differences is an area of active investigation. In this report, we have examined the relative interaction of ligands differing in structure and pattern of biological response with the C1a and C1b domains of PKCdelta. We mutated either or both of the C1 domains of PKCdelta, expressed the constructs in NIH 3T3 cells, and monitored the interaction of the ligands by their ability to induce translocation of the mutated PKCdelta from the cytosol to the particulate fraction. We found that different ligands showed different dependence on the C1a and C1b domains for translocation. Whereas phorbol 12-myristate 13-acetate and the indole alkaloids indolactam and octylindolactam were selectively dependent on the C1b domain, selectivity was not observed for mezerein, for the 12-deoxyphorbol 13-monoesters prostratin or 12-deoxyphorbol 13-phenylacetate, or for the macrocyclic lactone bryostatin 1. Provocatively, the pattern of response corresponds with the activity of the compounds as complete tumor promoters.

3T3 Cells↗
PubMed1998

Helminth antigens selectively differentiate unsensitized CD45RA+ CD4+ human T cells in vitro.

Human filarial helminth infections are characterized by type 2 immune responses to parasite Ag that can persist for the life of the individual; one possible cause for this may be prenatal exposure to the blood-borne microfilarial (Mf) stage of the parasite. To examine the relationship between early exposure to filarial Ag and subsequent immune responsiveness, CD45RA+ CD4+ cells frp, normal unsensitized donors were stimulated in vitro with soluble microfilarial Ag (MfAg) from the filarial parasite Brugia malayi in the presence of APCs. MfAg alone induced proliferation and IFN-gamma and IL-5 production in unsensitized CD45RA+ CD4+ cells, demonstrating the ability of filarial Ags to prime naive T cells in the absence of exogenous cytokines and dendritic cells. Adding exogenous cytokine(s) (particularly IL-12 and IL-4) during priming was able to alter the MfAg-specific responses of CD45RA+ CD4+ cells as well as subsequent responses to Ag. Interestingly, priming solely with MfAg led to enhanced IL-5 production following Ag restimulation, suggesting that MfAg preferentially primes for type 2 responses. These data demonstrate that filarial Ags by themselves can specifically prime CD45RA+ CD4+ cells in vitro and do so in such a way as to deviate the immune response.

Animals↗