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PubMed1989

[Effects of longterm selection on the genetic structure of populations--a simulation study. I. Simulation models and selection responses].

Monte Carlo method has been utilized to investigate responses to longterm selection. The simulation involves 3 gene effect models (additive, dominant, and over-dominant), two population sizes, three linkage intensities, and three heritability levels, thus making 54 combinations. For each combination, 5 replicate populations are selected over 49 consecutive non-overlapping generations. The results demonstrate that under all the gene effect models, linkage is important only in the case of small populations and intense linkage, when it reduces responses significantly due to hampering the fixation of favourable alleles and accelerating their loss. Linkage has no apparent effect if it is not very tight or if the population is large. Much greater responses are achieved in the large populations than in the small ones, especially for traits with low heritability. Among those discussed are problems of crossing selected lines to obtain extra responses, and discrepancy of some theoretic results on selection limits.

Computer Simulation↗
PubMed2000

GAP1, a novel selection and counter-selection marker for multiple gene disruptions in Saccharomyces cerevisiae.

We report on the use of a new homologous marker for use in multiple gene deletions in S. cerevisiae, the general amino acid permease gene (GAP1). A GAP1 strain can utilize L-citrulline as the sole nitrogen source but cannot grow in the presence of the toxic amino acid D-histidine. L-citrulline as well as D-histidine uptake is mediated solely by the general amino acid permease, and a gap1 strain is therefore able to grow in the presence of D-histidine but cannot utilize L-citrulline. Gene disruption is effected by transforming a gap1 strain with a gene cassette generated by PCR, containing GAP1 flanked by short (60 bp) stretches of the gene in question. Through homologous recombination, the cassette will integrate into the target gene, which is thus replaced by GAP1, and mutants are selected for on minimal L-citrulline medium. When propagated under non-selective conditions, some cells will lose the GAP1 gene. This is caused by recombination between two Ashbya gossypii AgLEU2 [corrected] direct repeats embracing GAP1, and will result in a sub-population of gap1 cells. Such cells are selected on a medium containing D-histidine, and may subsequently be used for a second gene disruption. Hence, multiple gene disruptions can be made fast, cheaply and easily in a gap1 strain, with two positive selection steps for each disruption.

Amino Acid Transport Systems↗
PubMed1991

First step of selective motoneuron axonal growth: selective outgrowth at discrete sites in the spinal cord.

Selective axonal growth at a series of choice points along pathways is essential for the establishment of precise motoneuron projections. To reveal some of the molecules responsible for this selective growth of motoneuron axons, this study investigates the phenomenon of why motoneurons extend axons outside the spinal cord, whereas interneurons do not. Axonal growth in the chick embryonic spinal cord at early stages of development was examined immunohistochemically. MAb SC1 staining of serial sections selectively revealed the entire distribution of motoneuron axons in the embryo. In the cervical segments, some motoneurons, called dorsal motoneurons, extended axons outside the cord via the dorsal root entry zone. The axons of both dorsal and ventral motoneurons were distributed only in the anterior half of the sclerotome; inside the cord motoneuron cell bodies and axons were distributed evenly along the anterior-posterior axis. Motoneurons and interneurons extended axons during the same period, and although the growth cones of both were intermixed in the same locations, only motoneuron axons grew out from the cord. The outgrowth of all st 19 motoneurons from the cord through either the dorsal or ventral exit zone strongly suggests that extension of their axons outside the cord is a selective rather than random process.

Animals↗
PubMed1993

Co-selection of the rare T cell receptor-gamma B haplotype in mouse lines selected for low responsiveness to red blood cell antigens.

T cell receptor (TcR)-gamma haplotype was investigated in seven pairs of murine Biozzi lines selected for low and high antibody (Ab) response to different antigens (Ag). High-responder lines (H) express gamma A or gamma C haplotypes irrespective of the selecting Ag. In contrast, the gamma B haplotype, which is rare in laboratory mouse strains, is found in all low-responder lines (L) to sheep erythrocyte Ag (SE). However, the TcR-gamma B locus might only have a low penetrance in the control of the SE response. Moreover, investigations using LIVA mice, which were selected for low SE response from homozygous gamma A founder parents, indicate that the gamma B haplotype is neither necessary nor sufficient to achieve a low-responder phenotype. The gamma B haplotype might, thus, be co-selected to confer to L mice an improved resistance to bacterial infections mediated by gamma delta T cells compensating the profound and nonspecific immune perturbation associated with the low Ab response.

Animals↗
PubMed2006

Involvement of phosphatidylcholine-selective phospholipase C in activation of mitogen-activated protein kinase pathways in imidazoline receptor antisera-selected protein.

Imidazoline receptor antisera-selected protein (IRAS) is considered as a candidate for the I1-imidazoline receptor (I1R), but the signaling pathway mediated by IRAS remains unknown. In our study, the signal transduction pathways of IRAS were investigated in CHO cells stably expressing IRAS (CHO-IRAS), and compared to the native I1R signaling pathways. Rilmenidine or moxonidine (10 nM-100 microM), I1R agonists, failed to stimulate [35S]-GTPgammaS binding in CHO-IRAS cell membrane preparations, suggesting that G protein may not be involved in IRAS signaling pathway. However, incubation of CHO-IRAS with rilmenidine or moxonidine for 5 min could induce an upregulation of phosphatidylcholine-selective phospholipase C (PC-PLC) activity, and an increase in the accumulation of diacylglycerol (DAG), the hydrolysate of PC-PLC, in a concentration-dependent manner. The elevated activation of PC-PLC by rilmenidine or moxonidine (100 nM) could be blocked by efaroxan, a selective I1R antagonist. Cells treated with rilmenidine or moxonidine showed an increased level of extracellular signal-regulated kinase (ERK) phosphorylation in a concentration-dependent manner, which could be reversed by efaroxan or D609, a selective PC-PLC inhibitor. These results suggest that the signaling pathway of IRAS in response to I1R agonists coupled with the activation of PC-PLC and its downstream signal transduction molecule, ERK. These findings are similar to those in the signaling pathways of native I1R, providing some new evidence for the relationship between I1R and IRAS.

Animals↗
PubMed2003

Selective arterial spin labeling (SASL): perfusion territory mapping of selected feeding arteries tagged using two-dimensional radiofrequency pulses.

To date, most perfusion magnetic resonance imaging (MRI) methods using arterial spin labeling (ASL) have employed slab-selective inversion pulses or continuous labeling within a plane in order to obtain maps derived from all major blood vessels entering the brain. However, there is great potential for gaining additional information on the territories perfused by the major vessels if individual feeding arteries could be tagged. This study demonstrates noninvasive arterial perfusion territory maps obtained using two-dimensional (2D) selective inversion pulses. This method is designated "selective ASL" (SASL). The SASL method was used to tag the major arteries below the circle of Willis. A combination of 2D selective tagging and multislice readout allows perfusion territories to be clearly visualized, with likely applications to cerebrovascular disease and stroke.

Brain↗
PubMed2001

Spin-state-selective excitation in selective 1D inverse NMR experiments.

A general and very simple strategy for achieving clean spin-state-selective excitation with full sensitivity in carbon-selective gradient-enhanced 1D HMQC and HSQC pulse schemes is presented. The incorporation of an additional hard 90 degrees (13)C pulse applied along a specific orthogonal axis just prior to acquisition into the conventional sequences allows us to select a simultaneous coherence transfer pathway which usually is not detected. The superimposition of this resulting antiphase magnetization to the conventional in-phase magnetization gives the exclusive excitation of the directly attached proton showing only the alpha or beta spin state of the passive (13)C nucleus. The propagation of this particular spin state to other protons can be accomplished by adding any homonuclear mixing process just after this supplementary pulse. Such an approach affords a suite of powerful selective 1D (13)C-edited NMR experiments which are helpful for resonance assignment purposes in overcrowded proton spin systems and also for the accurate determination of the magnitude and sign of long-range proton-carbon coupling constants in CH spin sytems for samples at natural abundance. Such measurements are performed by measuring the relative displacement of relayed signals in the corresponding alpha and beta 1D subspectra.

Journal Article↗
PubMed1993

Development of a new transformant selection system for Penicillium chrysogenum: isolation and characterization of the P. chrysogenum acetyl-coenzyme A synthetase gene (facA) and its use as a homologous selection marker.

A new transformation system for the filamentous fungus Penicillium chrysogenum is described, based on the use of the homologous acetyl-coenzyme A synthetase (facA) gene as a selection marker. Acetate-non-utilizing (Fac-) strains of P. chrysogenum were obtained by positive selection for spontaneous resistance to fluoroacetate. Among these fac mutants putative facA strains were selected for a loss of acetyl-coenzyme A (CoA) synthetase activity. The facA gene, coding for the enzyme acetyl-CoA synthetase, was isolated from a P. chrysogenum genomic library using synthetic oligonucleotides derived from conserved regions from the corresponding genes of Aspergillus nidulans and Neurospora crassa. Vector pPC2-3, comprising a genomic 6.5 kb PstI fragment, was able to complement P. chrysogenum facA strains with frequencies up to 27 transformants.micrograms-1 DNA. Direct selection of transformants was accomplished using acetate and low amounts (0.001%) of glucose as carbon sources. About 50% of the transformants arose by integration of pPC2-3 DNA at the homologous facA locus and 50% by integration elsewhere in the genome. Determination of the nucleotide sequence of part of the cloned fragment showed the presence of an open reading frame of 2007 nucleotides, interrupted by five putative introns. Comparison of the nucleotide and the amino acid sequence of the facA gene of P. chrysogenum with the facA gene of A. nidulans reveals similarities of 80% and 89%, respectively. The putative introns present in the P. chrysogenum facA gene appear at identical positions as those in the A. nidulans facA gene, but show no significant sequence similarity.

Acetate-CoA Ligase↗
PubMed1984

Promoter selectivity of Escherichia coli RNA polymerase. II: Altered promoter selection by mutant holoenzymes.

Using the in vitro mixed transcription system (Kajitani and Ishihama (1983a, 1983b), we examined selective transcription of truncated DNA templates carrying lac(UV5), rrnE or rpsA promoters by RNA polymerase holoenzymes from pairs of wild-type parents and mutants with a mutation in one or more RNA polymerase subunit genes. The promoter selectivity of RNA polymerases from two sigma-subunit mutants carrying either rpoD2 or rpoD285 differed markedly from that of the respective wild-type enzymes. Both the parental RNA polymerases, however, exhibited abnormal promoter selectivity compared with holoenzymes from various wild-type E. coli strains. On the other hand, all the RNA polymerases from rpoB and/or rpoC mutants and the respective wild-type parents were similar, if not identical, in promoter selection at low temperature. At high temperature, however, RNA polymerases from mutants carrying rpoB2B7 and rpoC4, affecting the beta and beta' subunits, respectively, showed decreased transcription from the high-affinity slow-transcribable promoter rrnEp2 whereas the rpoC92 and rpoB906 X rpoC907 mutant enzymes both lost transcription activity from the strong promoter lacP(UV5). Taking all these observations together we conclude that not only the sigma subunit but also the beta and beta' subunits are involved in the recognition of promoters.

DNA-Directed RNA Polymerases↗
PubMed1990

Differential ability of selective and non-selective dopamine agonists to induce climbing in the rat indicates the involvement of both D-1 and D-2 receptors in this behaviour.

Approximately 50% of female Wistar rats examined exhibited a continuous climbing response to a screening dose of apomorphine. In animals identified as climbing, the mixed D-1/D-2 agonists apomorphine, pergolide and L-dopa, and the indirectly acting agonists nomifensine and (+)-amphetamine, induced a dose-related climbing response. The selective D-1 agonist SKF 38393 caused only minimal climbing, and the selective D-2 agonists bromocriptine, lisuride and LY 141865 induced a weak climbing response. All agonists examined, except SKF 38393, caused a dose-related stereotypy response. The selective D-1 antagonist SCH 23390, and the selective D-2 antagonist sulpiride, both produced maximum inhibition of apomorphine-induced climbing. SCH 23390 also inhibited stereotyped behaviour, but sulpiride was less effective. In animals identified as "non-climbers" using the screening dose of apomorphine, only L-dopa induced a marked climbing response. Nomifensine and bromocriptine produced weak or discontinuous climbing in this group, while the other agonists examined had little or no effect. In contrast all drugs examined, except SKF 38393, induced stereotyped behaviour of the same intensity observed in the "climbers". It is concluded that stimulation of both D-1 and D-2 receptors is necessary to induce a continuous climbing behaviour in rats. D-2, but not D-1 stimulation, alone can induce a weak or discontinuous climbing response, but concomitant stimulation of D-1 receptors potentiates this effect. Failure of some rats to climb does not appear to be related to relative degrees of D-1 and D-2 stimulation.

Amphetamine↗
PubMed2004

Co-transformation using a negative selectable marker gene for the production of selectable marker gene-free transgenic plants.

A negative selectable marker gene, codA, was successfully co-transformed with a GUS reporter gene to develop selectable marker gene-free transgenic plants. The pNC binary vector contained a T-DNA harboring the codA gene next to the nptII gene, while a second binary vector, pHG, contained a GUS reporter gene. Tobacco plants ( Nicotiana tabacum cv. Samsun NN) were co-transformed via the mixture method with Agrobacterium tumefaciens LBA4404 strains harboring pNC and pHG, respectively. Seeds harvested from the co-transformants were sown on germination media containing 5-fluorocytosine (5-FC). Analysis of the progeny by GUS staining and PCR amplification revealed that all of the 5-FC-resistant R(1) plants were codA free, and that the codA gene segregated independently of the GUS gene. Because codA-free seedlings developed normally on 5-FC-containing medium, we suggest that co-transformation with negatively selectable markers is a viable method for the production of easily distinguished, selectable marker gene-free transgenic plants.

Agrobacterium tumefaciens↗
PubMed2003

Selective versus non-selective suppression of nitric oxide synthase on regional hemodynamics in rats with or without LPS-induced endotoxemia.

The late phase of severe septic shock is associated with reduced cardiac output (CO) and activation of the inducible isoform of nitric oxide synthase (NOS). This study examined the effects of 1400 W (N-3-aminomethyl-benzyl-acetamidine), a new selective inhibitor of inducible NOS (iNOS), relative to those of N(G)-nitro-L-arginine (L-NNA, non-selective inhibitor of NOS) and the vehicle, on mean arterial pressure (MAP), CO, total peripheral resistance (TPR) and tissue blood flow (BF) in thiobutabarbital-anesthetized rats with lipopolysaccharide (LPS, 10 mg/kg, i.v.) induced endotoxemia. At 2.5 as well as 4 h after injection of LPS, MAP, CO, and BF of the stomach, skeletal muscle and skin were decreased, but TPR was increased, BF to the heart and kidneys were also decreased at 4 h after injection of LPS. Treatment of endotoxemic rats with 1400 W (3 mg/kg followed by 3 mg/kg/h, i.v.) at 2.5 h after endotoxin challenge prevented the late phase fall in MAP without exacerbating the decreases in CO and tissue BF. In contrast, treatment with L-NNA (8 mg/kg followed by 3 mg/kg/h, i.v.) at 2.5 h did not prevent the decline in MAP in the LPS-treated rats. Furthermore, CO drastically decreased, TPR markedly increased, and BF to the heart, brain, intestine and skeletal muscle were decreased at 4 h relative to the readings in saline- or 1400 W-treated endotoxemic rats. Therefore, selective inhibition of iNOS by 1400 W restores MAP without compromising CO, but non-selective inhibition of NOS is detrimental at the late stage of septic shock.

Amidines↗
PubMedDate not supplied

Variable selection and specification of robust QSAR models from multicollinear data: arylpiperazinyl derivatives with affinity and selectivity for alpha2-adrenoceptors.

Two QSAR models have been identified that predict the affinity and selectivity of arylpiperazinyl derivatives for alpha1 and alpha2 adrenoceptors (ARs). The models have been specified and validated using 108 compounds whose structures and inhibition constants (Ki) are available in the literature [Barbaro et al., J. Med. Chem., 44 (2001) 2118; Betti et al., J. Med. Chem., 45 (2002) 3603; Barbaro et al., Bioorg. Med. Chem., 10 (2002) 361; Betti et al., J. Med. Chem., 46 (2003) 3555]. One hundred and forty-seven predictors have been calculated using the Cerius 2 software available from Accelrys. This set of variables exhibited redundancy and severe multicollinearity, which had to be identified and removed as appropriate in order to obtain robust regression models free of inflated errors for the beta estimates - so-called bouncing betas. Those predictors that contained information relevant to the alpha2 response were identified on the basis of their pairwise linear correlations with affinity (-log Ki) for alpha2 adrenoceptors; the remaining variables were discarded. Subsequent variable selection made use of Factor Analysis (FA) and Unsupervised Variable Selection (UzFS). The data was divided into test and training sets using cluster analysis. These two sets were characterised by similar and consistent distributions of compounds in a high dimensional, but relevant predictor space. Multiple regression was then used to determine a subset of predictors from which to determine QSAR models for affinity to alpha2-ARs. Two multivariate procedures, Continuum Regression (the Portsmouth formulation) and Canonical Correlation Analysis (CCA), have been used to specify models for affinity and selectivity, respectively. Reasonable predictions were obtained using these in silico screening tools.

Models, Molecular↗
PubMedDate not supplied

Non-random selection of gene segment 3 and random selection of gene segment 5 observed in reassortants generated in vitro between rotavirus SA11 and RRV.

A total of 154 clones of reassortants between rotavirus RRV and SA11 were isolated in vitro in order to compare the selection modes of each RNA segment in reassortant formation with those in the in vivo experiment (carried out by Gombold and Ramig) using the same parent strains in which the occurrence of non-random selection of gene segments 3 and 5 was observed. In reassortants isolated from a cross RRV x SA11-L2 (66 isolates) and a cross RRV x SA11-S1 (88 isolates), 36 and 57 different genotypes were identified, respectively. Segregation rates of SA11 RNA segments 1, 5, 8, 9 and 11 were significantly different as compared with those previously reported in the in vivo experiment. While RNA segment 3 was preferentially selected from an SA11 parent, the segregation rate of SA11 gene 5 was relatively low in vitro. Thus, the selection mode of rotavirus RNA segments was found to be different between in vivo and in vitro reassortments.

Animals↗
PubMed2004

Accelerating sensory recovery after sciatic nerve crush: non-selective versus melanocortin MC4 receptor-selective peptides.

Melanocortin receptor ligands accelerate functional recovery after peripheral nerve crush. It is not known which mechanism is involved or via which melanocortin receptor this effect occurs, albeit indirect evidence favours the melanocortin MC4 receptor. To test whether the melanocortin MC4 receptor is involved in the effects of melanocortins on functional recovery, we used melanocortin compounds that distinguish the melanocortin MC4 receptor from the melanocortin MC1, MC3 and MC5 receptors on basis of selectivity and agonist/antagonist profile. Activation and binding studies indicated that the previously described peptides JK1 (Ac-Nle-Gly-Lys-D-Phe-Arg-Trp-Gly-NH2) and [D-Tyr4]melanotan-II ([D-Tyr4]MTII. Ac-Nle-c[Asp-His-D-Tyr-Arg-Trp-Lys]NH2) are selective for the rat melanocortin MC4 receptor as compared to the rat melanocortin MC3 and MC5 receptors, but are also potent on the melanocortin MC1 receptor. Both peptides did not accelerate sensory recovery in rats with a sciatic nerve crush, whereas the non-selective melanocortin agonist melanotan-II (MTII, Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]NH2) was effective. The melanocortin MC3/MC4 receptor antagonist SHU9119 (Ac-Nle-c[Asp-His-D-Nal(2)-Arg-Trp-Lys]NH2) also enhanced sensory recovery. This effect was probably not due to interaction with the melanocortin MC4 receptor, since JK46 (Ac-Gly-Lys-His-D-Nal(2)-Arg-Trp-Gly-NH2), a selective melanocortin MC4 receptor antagonist, was ineffective. Taken together, these data suggest that melanocortins do not accelerate sensory recovery via interaction with the melanocortin MC4 receptor. From the known melanocortin receptors, only the involvement of the melanocortin MC5 receptor in acceleration of recovery could not be excluded.

Animals↗
PubMed2006

Differential effects of selective and non-selective inhibition of nitric oxide synthase on the expression and activity of cyclooxygenase-2 during gastric ulcer healing.

Nitric oxide synthases (NOS) and cyclooxygenase-2 (COX-2) are important enzymes involved in ulcer healing but interactions between them have not been clearly defined. The aim of this study was to investigate the effects of selective or non-selective inhibition of NOS on the expression and activity of COX-2 during healing of acetic acid-induced gastric ulcers in rats. N-[3-(aminomethyl)benzyl] acetamidine (1400 W), a potent selective inhibitor of inducible nitric oxide synthase (iNOS), at a dose of 0.1 mg/kg/day, was found to reduce the ulcer sizes at day 3 and 7 post-ulcer induction. On the other hand, 15 mg/kg/day of NG-nitro-L-arginine methyl ester (L-NAME), a non-selective NOS inhibitor that suppresses both iNOS and endothelial nitric oxide synthase (eNOS), enlarged the ulcer sizes over the same time periods. The expression of COX-2 and COX activity, together with NF-kappaB activation in the ulcer tissues were down-regulated by L-NAME but not 1400 W. It is concluded that iNOS may contribute to ulcer formation while COX-2 and eNOS promote ulcer healing. eNOS enhances COX-2 expression possibly through the activation of NF-kappaB.

Acetic Acid↗
PubMed2004

In phase selective excitation of overlapping multiplets by gradient-enhanced chemical shift selective filters.

We have developed gradient-enhanced chemical shift selective filters (ge-CSSF) for inphase excitation of overlapping multiplets 1H. This method relies on the constructive addition of on resonance signal while off resonance magnetization is eliminated by destructive interference due to variable chemical shift evolution. This is achieved by co-addition of several FIDs acquired with a gradually incremented chemical shift evolution period. Two variable-time and one constant-time ge-CSSFs are proposed that can be combined with TOCSY, NOESY, and ROESY mixing schemes yielding highly selective 1D experiments. Analytical and numerical expressions are derived to calculate the excitation profiles of the ge-CSSFs and to examine the effects of spin-spin relaxation, the length of the CSSF increment, and selective inversion pulses. We demonstrate, both theoretically and experimentally, that CSSFs yield fast signal separation for compounds with a range of spin-spin relaxation times and chemical shift differences as small as 1-2 Hz. The use of pulsed field gradients ensures that very clean spectra are obtained. The main application of these techniques lies in analysis of mixtures where severe spectral overlap prevents the use of simple 1D selective methods.

Journal Article↗
PubMed2004

Extending the limits of the selective 1D NOESY experiment with an improved selective TOCSY edited preparation function.

Compared to its 2D counterpart, the selective 1D NOESY experiment offers greatly simplified spectral interpretation and is invaluable to the structure elucidation of small-to-medium sized molecules, although its application is limited to well-resolved resonances only. The doubly selective 1D TOCSY-NOESY experiment allows the 1D NOESY experiment to be extended to resonances within overlapped spectral regions. However, existing methods do not address the critical issue of zero-quantum interference, which leads to severe anti-phase distortions to the line shape of scalar coupled spins and often complicates the identification of weak NOE enhancements. In this communication, we describe an improved selective TOCSY edited preparation (STEP) function and its application to the selective 1D NOESY experiment. The STEP function incorporates a novel zero-quantum filter introduced by Thrippleton and Keeler [Angew. Chem. Int. Ed. 42 (2003) 3938], which permits essentially complete suppression of zero-quantum coherence in a single scan. Residual anti-phase distortions due to spin-state mixing are removed using the double difference methodology reported by Shaka et al. [45th Experimental NMR Conference, Pacific Grove, USA, 2004]. The combined use of these techniques ensures that the final spectra are free of distortions, which is crucial to the reliable detection of weak NOE enhancements. Although employed as an additional preparation period in the example demonstrated here, the STEP function affords a general editing tool for spectral simplification and can be applied to a range of experiments.

Ionophores↗