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At least 883 records · Page 49Linked to original sources
PubMed2005

Mice selectively bred for open-field thigmotaxis: life span and stability of the selection trait.

In 2 experiments, the authors examined 69 mice selectively bred for high or low levels of open-field (OF) thigmotactic behavior (high open-field thigmotaxis [HOFT] and low open-field thigmotaxis [LOFT], respectively). They found that the strains differed in defecation during the 60-min exposure to the OF. Furthermore, the strains differed with regard to their life spans: The more thigmotactic HOFT mice lived longer than the LOFT mice. The strains were not differentiated by food intake or excretion. The strain difference in thigmotaxis was not age dependent, and it persisted in the home-cage condition as well. Neither the location (center or wall) of the starting point nor the shape (circular or square) of the OF arena affected the difference in wall-seeking behavior between the two strains. The authors concluded that the difference in thigmotaxis (or emotionality) between the HOFT and LOFT mice is a stable and robust feature of these animals.

Age Factors↗
PubMed1996

Recommendation on mean molar activity coefficients and single ion activity coefficients of solutions for calibration of ion-selective electrodes for sodium, potassium, and calcium determination. IFCC Scientific Division Working Group on Selective Electrodes.

In principle, flame photometry measures substance concentration, and ion-selective electrodes (ISEs) measure ion activity. However, the situation regarding the comparison of results from the two techniques when applied to blood plasma is complex. The problem can be approached experimentally from the point of view of calibration of ISEs with concentration calibrators, and similar procedures are adopted for commercial ISE-based clinical analyzers. Nevertheless, there is interest in the evaluation of single ion activities in blood plasma and solutions simulating its ionic composition. Solutions are proposed for calibrating ISEs for the determination of sodium, potassium, and calcium. It is recommended that the values for single ion activities derived from the Pitzer treatment of mixed electrolyte solutions be adopted, because, although this has some empirical features, it has a sounder theoretical basis than the previously used Stokes-Robinson-Bates hydration approach.

Calcium↗
PubMedDate not supplied

Nurse manager selection process (Part 1). Survey of selection process (Part 2).

The Queen Elizabeth II Health Sciences Centre developed as a result of the merger of the five adult hospitals in Halifax, Nova Scotia. The merge involved 7000 staff members, 2700 of whom were nursing staff. Although mergers are becoming relatively common amongst health care organizations, there is a paucity of information in the literature to describe such an enormous human resource effort. This two-part article describes the hiring process for the selection and placement of 52 nurse managers over a concentrated time period of six weeks. Issues identified and resolved included: unionized and non unionized head nurses, the role of nurse managers, varying educational preparations, the time frame and organization of the process itself, options for unsuccessful incumbents, and multi unit and multi site management. The second part of the article reports on the results of a survey which was carried out to obtain feedback from the applicants and the interview panel members. The survey was conducted within eight weeks of the conclusion of the hiring process. Overall the process was deemed successful, albeit stressful. Some of the problems encountered are discussed.

Adult↗
PubMed1992

Selective reactivity of CD8-independent T lymphocytes to a cytotoxic T lymphocyte-selected H-2Kb mutant altered at position 222 in the alpha 3 domain.

To study the structural basis for specificity and affinity of cytotoxic T lymphocytes for major histocompatibility complex/peptide complexes, we have employed a cytotoxic T lymphocyte (CTL)-mediated immunoselection approach to obtain H-2Kb structural mutants which are resistant to lysis by a Kb-specific alloreactive CTL clone. In this study we describe the Kb structural mutant, designated R8.60.14, recovered following immunoselection using the CD8-dependent CTL clone 60 as a selective agent. Although serologically unaltered with respect to Kb expression, R8.60.14 is not recognized by CD8-dependent, Kb-specific CTL. DNA sequence analysis revealed a single Glu----Lys amino acid substitution at position 222 in the Kb alpha 3-domain of this variant. To determine if a direct correlation exists between CD8 dependence of a Kb specific CTL and its failure to respond to R8.60.14, we examined the lytic response against R8.60.14 by CD8-independent, Kb-specific CTL obtained from long-term culture in the presence of anti-CD8 monoclonal antibody, 3.155. CD8-independent CTL exhibit no difference in their response against the R8 parent and R8.60.14 variant. This study demonstrates unequivocally that Kb-specific recognition of R8.60.14 by CD8-independent CTL is unaltered, while the response by CD8-dependent CTL is completely abrogated. Thus, the sole basis for emergence of this variant in the CTL-mediated immunoselection approach used in this study resides in the alteration of a single CD8-binding site residue at position 222 in the Kb alpha 3 domain. The functional importance of this Glu222 residue for the interaction between the CD8 molecule on CD8-dependent CTL and the Kb alpha 3 domain is further reinforced by virtue of the recovery of the R8.60.14 variant on the basis of its resistance to lysis by a CD8-dependent CTL clone in this CTL-mediated immunoselection approach.

Animals↗
PubMed1994

Evidence for a selective and multi-step model of T cell differentiation: CD4+CD8low thymocytes selected by a transgenic T cell receptor on major histocompatibility complex class I molecules.

We have characterized a prominent (15-20%) thymocyte population expressing CD4 at a high and CD8 at a low level (CD4+8lo) in mice transgenic for a T cell receptor (TCR) restricted by major histocompatibility complex (MHC) class I molecules. The results demonstrate that the CD4+8lo population is an intermediate stage between immature CD4+8+ and end-stage CD4+8- thymocytes and that the survival of these cells crucially depends on the successful interaction of the transgenic TCR with self MHC class I molecules. In addition we demonstrate that the avidity of the interaction between TCR and self MHC class I molecules determines whether CD4+8lo thymocytes are found in significant numbers in this transgenic model. Our findings support a selective and multi-step model of T cell differentiation in the thymus.

Animals↗
PubMed2001

Fast selection of antibodies without antigen purification: adaptation of the protein fragment complementation assay to select antigen-antibody pairs.

We have adapted the protein fragment complementation assay (PCA) to the screening and selection of antibodies in the single-chain Fv (scFv) format. In this assay, two interacting proteins (target and antibody) are genetically fused to the two halves of the dissected enzyme dihydrofolate reductase. Binding of the two partners reassembles this enzyme and reconstitutes its activity, thus allowing growth on minimal medium. We have optimized this system with regard to linker length and orientation, and can reach an efficiency for antigen/antibody interactions similar to that with fused leucine zippers. Using several model antibodies specific for peptides and proteins, we show that cognate interactions give rise to about seven orders of magnitude more colonies than non-specific interactions. When transforming mixtures of plasmids encoding different antigens and/or antibodies, all colonies tested contained plasmids encoding cognate pairs. We believe that this system will be very powerful as a routine system for generating antibodies, especially in functional genomics, since it does not require purification and immobilization of the antigen. The identification of an antibody specific for a cDNA or EST-encoded protein will require only cloning, transformation and plating of bacteria.

Animals↗
PubMed1998

Coherence selection and excitation sculpting using RF-gradients in selective 1D experiments and nonselective 2D experiments

The B0 gradient pulses can be replaced with long high-power pulses (RF-gradients) in z-rotation composite sandwiches. By doing this, practically all B0 gradient-based pulse sequences can be performed with instruments lacking a field gradient accessory. We have implemented RF-gradients into selective 1D and nonselective 2D TOCSY and NOESY experiments. The spectral quality obtained with the RF-gradient method was comparable to that of the B0 method for small- to medium-sized molecules. There are also some advantages in using RF-gradients instead of B0 gradients. There is practically no shift or coupling evolution during RF-gradient pulses. This may be significant in some experiments. Copyright 1998 Academic Press.

Journal Article↗
PubMed1993

Is airways hyperreactivity selective or non-selective?

Airways hyperresponsiveness has often been termed "nonspecific" on account of close correlations between responses to histamine and methacholine. This relationship, however, does not apply to stimuli, such as exercise, hyperventilation, sulphur dioxide, and distilled water. We have shown that allergen causes a greater and more prolonged increase in responses to bradykinin than to methacholine adding support to the notion that airways hyperresponsiveness is a selective pathophysiologic abnormality.

Allergens↗
PubMed1988

Single anion-selective channel and its ion selectivity in the vascular smooth muscle cell.

The properties of voltage-gated Cl channels of cultured smooth muscle cell prepared from embryonic rat aorta were studied. In the excised patch (inside-out configuration), we observed the activity of channels, opening and closing spontaneously, when the membrane potential was held at around 0 mV. The channels were active at a potential range between +10 and -10 mV. A step change of the membrane potential from the active potential range in either a positive or a negative direction closed the channel to an apparently inactivated state. The time course of this inactivation process became faster as the amplitude of the step change was increased. Returning the membrane potential to 0 mV allowed the channel to recover from the inactivated state. The channel had at least two open conductance states. Ca ions at the cytoplasmic face were not required for the activation of the channel. Adenosine nucleotides at the same side of the membrane had no effect on channel activity. The channels were selective to anions rather than cations, and they had a large single channel conductance of 340.5 +/- 20.4 pS in symmetrical 150 mM TEA-Cl. The reversal potential of the channel was shifted by -15.2 +/- 2.6 and 17.0 +/- 1.7 mV, when the Cl concentration at the intracellular side was changed to 75 mM or 300 mM, respectively. The permeability sequence of halides was I- greater than Br- greater than Cl- greater than F- (1.4:1.3:1.0:0.7), whereas the conductance sequence was Cl- greater than Br- greater than F- greater than I- (1.00:0.89:0.86:0.83).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Improved selectivity and detection limit of the carbonate-selective electrode.

The properties of the carbonate neutral carrier 4-( n-hexadecyl)-3-nitro-1-trifluoroacetylbenzene were compared with those of a similar carrier, without a nitro group, studied previously. In spite of differences in the Hammett constant of the carbonyl group responsible for interaction with the analyte, the analytical characteristics of both carriers, measured under the same conditions, were comparable. Special care was taken to avoid the presence of an excessive carbon dioxide level in the diffusion layer at the membrane-solution interface. The internal reference solution was prepared without carbonate components; the external solution was protected from contact with atmospheric carbon dioxide. Under such conditions the detection limit of both electrodes was extended to 10(-11 )mol L(-1), and the selectivity towards salicylate, chloride, and acetate was significantly improved.

Journal Article↗
PubMed1997

Selective inhibition of oncogenic ras-p21 in vivo by agents that block its interaction with jun-N-kinase (JNK) and jun proteins. Implications for the design of selective chemotherapeutic agents.

We have obtained evidence that oncogenic and activated normal ras-p21 proteins utilize overlapping but distinct signal transduction pathways. Recently, we found that ras-p21 binds to both jun and its kinase, jun kinase (JNK). We now present evidence that suggests that oncogenic but not normal activated p21 depends strongly on early activation of JNK/jun. This early activation most likely involves direct interaction between oncogenic p21 and JNK/jun because p21 peptides that blocked the binding of p21 to JNK and jun strongly inhibited oncogenic p21-induced oocyte maturation while they did not inhibit insulin-activated normal cellular p21-induced maturation. Very similar results were also obtained for a newly characterized specific inhibitor of JNK which blocked oncogenic but not normal activated p21-induced oocyte maturation. We also found that both jun and JNK strongly enhanced oncogenic p21-induced oocyte maturation while they inhibited insulin-activated normal p21-induced oocyte maturation. These results suggest that the peptides and JNK inhibitor may be useful agents in selectively blocking the effects of oncogenic but not normal p21 in cells.

Animals↗
PubMed2006

Social phobia, anxiety, oppositional behavior, social skills, and self-concept in children with specific selective mutism, generalized selective mutism, and community controls.

We compared social phobia, anxiety, oppositional behavior, social skills, and self-concept in three groups: (1) 28 children with specific mutism (who did not speak to teachers but were more likely to speak to parents and peers at home and school); (2) 30 children with generalized mutism (whose speaking was restricted primarily to their homes); and (3) 52 community controls. Children with generalized mutism evidenced higher anxiety at school, and more separation anxiety, OCD, and depressive symptoms at home. Parents and teachers reported that the social phobia and anxiety scores of children in both the specific and generalized mutism subgroups were higher than controls. Children in both the specific and generalized mutism groups evidenced greater deficits in verbal and nonverbal social skills at home and school than controls. Teachers and parents did not report differences in nonverbal measures of social cooperation and conflict resolution and we found no evidence that selective mutism was linked to an increase in externalizing problems such as oppositional behavior or ADHD. Although children with specific mutism speak in a wider range of situations and appear less anxious to their teachers than children with generalized mutism, significant socially phobic behavior and social skills deficits are present in both groups.

Anxiety Disorders↗
PubMed2006

Selection of peptides for lipopolysaccharide binding on to epoxy beads and selective detection of Gram-negative bacteria.

Lipopolysaccharide (LPS)-binding peptides were enriched by using epoxy beads as a novel support to immobilize LPS for a phage displayed peptide library screening. The sequence of Phe-Ala-Pro-Trp (FAPW) was the most significant consensus motif of 10 selected clones, and Pro-Phe (PF) was the key dipeptide for binding at the apex of the loop to form a characteristic structure of CXXPFXXXC. Moreover, AWLPWAK, one of the highly conserved heptamer peptides, could detect specifically Gram-negative bacteria via a whole cell binding test at 10(6) cells ml(-1).

Bacterial Typing Techniques↗
PubMed1986

Selective inhibition and selective induction of multiple microsomal epoxide hydrolases.

The inhibition in vitro and induction in vivo of microsomal trans-stilbene oxide hydrolase have been studied. This microsomal epoxide hydrolase activity is distinguishable from the previously well-defined microsomal arene oxide hydrolase by a number of catalytic criteria. Two substituted chalcone oxides, 4-phenylchalcone oxide and 4'-phenylchalcone oxide, are potent inhibitors of microsomal trans-stilbene oxide hydrolase, but have no apparent activity against benzo[a]pyrene 4,5-oxide hydrolase. Conversely, compounds that are potent inhibitors of benzo[a]pyrene 4,5-oxide hydrolase, including styrene oxide, cyclohexene oxide, and trichloropropene oxide, inhibit microsomal trans-stilbene oxide hydrolase only at very high (millimolar) concentrations. The chalcone oxides inhibit microsomal trans-stilbene oxide hydrolase noncompetitively, and have micromolar or nanomolar affinity constants for the enzyme. Attempts were made to induce microsomal trans-stilbene oxide hydrolase in vivo. Compounds that induced microsomal benzo[a]pyrene 4,5-oxide hydrolase levels in mice did not simultaneously induce trans-stilbene oxide hydrolase levels. Clofibrate was an exception; it induced levels of both enzymes to a small but statistically significant degree. The two microsomal hydrolase activities have, therefore, very different catalytic sites and appear to be under separate genetic control. 4-Phenylchalcone oxide and 4'-phenylchalcone oxide are selective inhibitors of microsomal trans-stilbene oxide hydrolase and may prove to be very useful in assessing the involvement of this enzyme in the metabolism of endogenous or xenobiotic epoxides.

Animals↗
PubMed1980

Reactivity-selectivity properties of reactions of carcinogenic electrophiles and nucleosides: influence of pH on site selectivity.

6-Chloromethylbenzo[a]pyrene (6-CMBP) labeled with 13C in the chloromethyl group was used as a model for those carcinogens which form essentially free carbocations. Using 13C-NMR to identify products, the selectivity with which this electrophile modifies nucleosides was investigated. At pH 7, guanosine and deoxyguanosine are the most nucleophilic nucleosides toward the carbocation generated by solvolysis of 6-CMBP. Attack at N-7 predominates over attack at N-2. At higher pH, the nucleophilicity of guanosine and deoxyguanosines increases markedly. In addition, the site of modification changes to N-1 with secondary modification at O-6. The pH dependence of the rate of this reaction implicates a group with pK-value approx. 8.7 which was assigned to the hydrogen on N-1. The presence of a methyl group on the N-7 position of guanosine lowers this pK-value to approx. 7.2. Consequently, N7-methylguanosine shows the high nucleophilicity at physiological pH that guanosine has at high pH. These observations lead to the suggestion of a one base : two-site model for chemical carcinogenesis.

Benzopyrenes↗
PubMed1989

The logic of social exchange: has natural selection shaped how humans reason? Studies with the Wason selection task.

In order to successfully engage in social exchange--cooperation between two or more individuals for mutual benefit--humans must be able to solve a number of complex computational problems, and do so with special efficiency. Following Marr (1982), Cosmides (1985) and Cosmides and Tooby (1989) used evolutionary principles to develop a computational theory of these adaptive problems. Specific hypotheses concerning the structure of the algorithms that govern how humans reason about social exchange were derived from this computational theory. This article presents a series of experiments designed to test these hypotheses, using the Wason selection task, a test of logical reasoning. Part I reports experiments testing social exchange theory against the availability theories of reasoning; Part II reports experiments testing it against Cheng and Holyoak's (1985) permission schema theory. The experimental design included eight critical tests designed to choose between social exchange theory and these other two families of theories; the results of all eight tests support social exchange theory. The hypothesis that the human mind includes cognitive processes specialized for reasoning about social exchange predicts the content effects found in these experiments, and parsimoniously explains those that have already been reported in the literature. The implications of this line of research for a modular view of human reasoning are discussed, as well as the utility of evolutionary biology in the development of computational theories.

Adolescent↗
PubMed1992

Ubiquitin, a central component of selective cytoplasmic proteolysis, is linked to proteins residing at the locus of non-selective proteolysis, the vacuole.

Ubiquitin, an evolutionary highly conserved protein, is known to be involved in selective proteolysis in the cytoplasm. Here we show that ubiquitin-protein conjugates are also found in the yeast vacuole. Mutants defective in the major vacuolar endopeptidases, proteinase yscA and yscB, lead to accumulation of ubiquitin-protein conjugates in this cellular organelle.

Aspartic Acid Endopeptidases↗
PubMed1995

Co-selection of cognate antibody-antigen pairs by selectively-infective phages.

We have developed a chloramphenicol resistant derivative of fd phage with which cognate pairs of antibodies and antigens can be selected. The phage genome encodes a fusion of single-chain antibody to the C-terminal domain of gIIIp, rendering the phage non-infective. The antigen fused to the N-terminal domains of gIIIp is encoded in the same phage genome. Antigen and antibody fusion interact with each other in the periplasm of the phage-producing cell, restoring infectivity. This system has a very low background and will allow simultaneous randomisation of antibody and antigen.

Amino Acid Sequence↗