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At least 19 recordsLinked to original sources
PubMed1975

In vitro selection and extended culture of antigen-specific T lymphocytes. I. Description of selection culture procedure and initial characterization of selected cells.

Specific selection of antigen-responsive guinea pig peritoneal exudate lymphocytes (PELs) was achieved by a selection culture procedure. This procedure involved the addition of PELs from immune donors to monolayers of antigen-pulsed adherent peritoneal exudate cells from nonprimed syngeneic donors. PELs which failed to adhere were discarded at 24 and 48 h; after 1 wk of culture, lymphocytes were obtained which were highly responsive to the antigen for which they were selected but which demonstrated little or no response to other antigens to which the original donor of the lymphocyte was immune. These selected cells were largely T lymphocytes and could be maintained in culture for 2-5 wk in an antigen-responsive state and, in 20-30% of cases, for 8-10 wk in an antigen-independent state.

Albumins↗
PubMed1975

Determination of the environmental sensitivity of selection lines by the selection environment.

The parents chosen to continue 10 independent selection lines of Schizophyllum commune over eight successive generations of selection, along with unselected controls, have been retrospectively examined for their response to growth at 15 degrees, 20 degrees, 25 degrees, 30 degrees and 35 degrees C. The regression of rate of growth on temperature was essentially linear over the range 15 degrees to 30 degrees C for all lines in all generations as was also the regression of rate of growth on various biological assessments of the environments over the whole temperature range. Either regression, therefore, provided linear regression coefficients which adequately accounted for the relative sensitivities of the lines to temperature in each generation of selection. These measures of environmental sensitivity confirmed our earlier report that selection for high mean performance in a good environment or for low mean performance in a poor environment leads to selections that are more sensitive to environmental variation than selections for high mean performance in a poor environment or for low mean performance in a good environment. These differences in sensitivity emerge as correlated responses during selection and the magnitude of these correlated responses is higher in the good environment than in the poor environment irrespective of the direction of selection. The environmental sensitivity of selection lines can be modified in either direction as required by either selecting for sensitivity simultaneously with the selection for mean performance or by selecting for mean performance in an above or below average environment. The quality of environments in which artificial selection is usually carried out is likely to have led to high selections with maximum environmental sensitivity and low selections with minimum sensitivity.

Environment↗
PubMed2025

Evaluating selection at intermediate scales within genes provides robust identification of genes under positive selection in M. tuberculosis clinical isolates.

Multiple studies have reported genes in the M. tuberculosis (Mtb) genome that are under diversifying selection, based on genetic variants among Mtb clinical isolates. These might reflect adaptions to selection pressures associated with modern clinical treatment of TB. Many, but not all, of these genes under selection are related to drug resistance. Most of these studies have evaluated selection at the gene-level. However, positive selection can be evaluated on different scales, including individual sites (codons) and local regions within an ORF. In this paper, we use GenomegaMap, a Bayesian method for calculating selection, to evaluate selection of genes in the Mtb genome at all three levels. We present evidence that the intermediate analysis (windows of codons) yields the most credible list of candidate genes under selection (excluding PPE and PE_PGRS genes, which are predicted less reliably due to frequent sequencing errors). A further advantage of this approach is that it identifies specific regions within proteins that are under selective pressure, which is useful for structural and functional interpretation. In an analysis of two separate collections of Mtb clinical isolates (from Moldova; and a globally-representative set), we observed 53 and 173 significant genes under selection, with 36% overlap. The lists of genes under selection include many drug-resistance genes, as well as other genes that have previously been reported to be under selection (resR, phoR). The specific regions under selection identified within drug-resistance genes are shown to correspond to protein structural features known to be involved in resistance, supporting accuracy of the method. Positive selection in several ESX-1-related genes was also observed, suggesting adaptation to immune pressure.

adaptation↗
PubMed1975

Hybridization and selection for increased penicillin titre in wild-type isolates of Aspergillus nidulans.

Repeated hybridization and selection among wild-type isolates produced strains of Aspergillus nidulans with increased penicillin titre. Four independent selection lines were established, each originating from a sexual cross between two different heterokaryon-incompatible wild-type isolates. In each generation, two selected high-titre sister strains were crossed to produce the next generation. An initial increase in titre was obtained in each line, but after four or five generations of selection the genetic variation was considerably reduced and the rate of response to selection had decreased. From a base population of wild-type isolates with a mean titre of 8-6 units/ml the progeny mean titre was raised to between 16 and 20 units/ml in each line. The gradual nature of the response suggests that a number of genes determine penicillin titre in the wild-type isolates used. The gene action throughout the selection programme was predominantly additive.

Aspergillus nidulans↗
PubMed1975

In vitro selection and extended culture of antigen-specific T lymphocytes. II. Mechanisms of selection.

Functional selection of antigen-specific T lymphocytes can be achieved by culturing thymus-dependent (T) lymphocytes from immunized guinea pigs on "monolayers" of antigen-pulsed adherent peritoneal exudate cells (PEC) from nonimmune syngeneic donors. Several aspects of the in vitro selection of T lymphocyte-rich peritoneal exudate lymphocytes (PEL) were studied. It was shown that irradiated adherent PEC were equivalent to nonirradiated adherent PEC in supporting selection cultures, indicating that the lymphocytes harvested at the end of the selection culture derive from the immune donors of the PEL and not from the nonimmune donor of the adherent PEC. The relative importance of specific adherence and specific proliferation for achieving selection was determined by comparing the degree of selection obtained when nonadherent cells were discarded at 24 hr with that noted when the discard step was omitted. It was found that omitting the discard step markedly diminished the degree of selection. On the other hand, blocking proliferation with specific alloantisera after the discard step did not diminish the degree of selection, although it did diminish the cell yield. Thus, specific adherence to antigen-pulsed PEC appeared to be critical in the selection culture procedure. An estimate of the degree of enrichment obtained by the selection culture procedure was obtained by culturing selected cells in an excess of nonprimed PEL, so that auxiliary cells would not be limiting. Under these conditions, it appeared that selected cells were enrichied from 4- to 10-fold in antigen-responsive cells with respect to the initial cell population.

Animals↗
PubMed2026

Transition from Conventional to Genomic Selection (ssGBLUP) led to improve in accuracy gains and selection decisions in Sahiwal Cattle.

By using genome-wide markers to predict an individual's genetic potential, the introduction of Genomic Selection (GS) has transformed animal breeding. This greatly accelerated selection for complex traits by lowering reliance on drawn-out field trials, allowing for faster genetic gains in livestock. However, there is little research on the effects of genomic selection on Sahiwal cattle in India, and comparing it to the current culling or selection process is even more uncommon, particularly in nations with fewer genotyped animals. This study is an initial effort to address the aforementioned gaps in knowledge. Genomic selection was implemented in Sahiwal cattle for the 305 days milk yield using univariate animal model and the single-step Genomic Best Linear Unbiased Prediction (ssGBLUP) method. The Effective Population size (Ne) of the Sahiwal herd was calculated using genomic data and was reported for the previous generation to be 71.927. The heritability of 305 days milk yield was estimated as 0.177 ± 0.068. Genomic estimated breeding values (GEBVs) were predicted for each individual using ssGBLUP, yielding a mean prediction accuracy of 43.11%, compared with 40.88% obtained using conventional pedigree-based BLUP. Cross-validation further demonstrated superior predictive performance of ssGBLUP, with accuracies of 76.82% and 70.50% for ssGBLUP and PBLUP, respectively. To further check the effectiveness of the genomic selection methodology, we also compared the GEBVs obtained and compared it with the Expected Progeny Difference (EPD) which is being applied in our farm for culling decisions. It was seen that GEBVs obtained from ssGBLUP methodology were also in line with the conventionally used method of EPD. The use of genomic selection enables genetic studies with limited pedigree information. Additionally, the ssGBLUP methodology allows to check for pedigree errors, where family relationships are incorrectly recorded. The EPD and GEBVs were consistent with one another, indicating that genomic selection may also be utilised to support culling and selection decisions in a farm. Thus, in a conventional animal breeding program with constraint resources and an incomplete pedigree, we recommend employing the ssGBLUP model for regular genomic assessment and identification of suitable candidates to effectively carry out a genomic selection program.

Animals↗
PubMed2025

Positive selection and relaxed purifying selection contribute to rapid evolution of sex-biased genes in green seaweed Ulva.

BACKGROUND: The evolution of differences in gamete size and number between sexes is a cornerstone of sexual selection theories. The green macroalga Ulva, with incipient anisogamy and parthenogenetic gametes, provides a unique system to investigate theoretical predictions regarding the evolutionary pressures that drive the transition from isogamy to anisogamy, particularly in relation to gamete size differentiation and sexual selection. Its minimal gamete dimorphism and facultative parthenogenesis enable a rare window into early evolutionary steps toward anisogamy. RESULTS: By analyzing the expression profiles of sex-biased genes (SBGs) during gametogenesis, we found that SBGs evolve faster than unbiased genes, driven by higher rates of non-synonymous substitution (dN), indicating that SBGs are under stronger selective pressures. Mating type minus-biased genes (mt-BGs) exhibit higher dN/dS values than mating type plus-biased genes (mt+BGs), suggesting stronger selective pressures on mt-BGs, although this difference was not statistically significant (P = 0.08). Using branch-site and RELAX models, we found positive selection and relaxed purifying selection acting on a significant proportion of SBGs, particularly those associated with flagella function. CONCLUSIONS: This study highlights the selective pressures shaping anisogamy and provides insights into the molecular mechanisms underlying its evolution. The faster evolution of SBGs, particularly mt-BGs, and the positive selection on genes associated with motility, such as those related to flagella function, suggest the importance of enhanced gamete motility in the transition to anisogamy. These findings contribute to our understanding of sexual selection and the evolutionary forces that drive the differentiation of gamete size and number between sexes.

Selection, Genetic↗
PubMed1975

Population size and selection intensity effects on long-term selection response in mice.

Long-term response to within full-sib family selection for increased postweaning gain was evaluated in lines having different effective population sized (Ne) and selection intensities (i). Line designations were I4(4), I8(2), I16(2), M4(4), M8(2) and M16(2), where I and M indicate selection of the top 50% and 25%, respectively; 4, 8 and 16 represent the number of parental pairs per replicate and number of replicates is given in parentheses. Realized within full-sib family heritabilities (hR-2) in the first phase of selection (0-14 generations) were larger in 16-pair lines than in 4- and 8-pair lines. In the second phase of selection (greater than 14 generations), hR-2 declined significantly (P smaller than .01) in all lines, and only the I16 and M16 lines had hR-2 values significantly (P smaller than .01) greater than zero. Realized genetic correlations involving number born, 12-day litter weight, weaning weight and six-week weight tended to decline in the second phase of selection. The I16, M16 and control (C16) replicates were crossed in all combinations at generation 14. Crosses were then selected within litters for high postweaning gain. The hR-2 values in the crossbred lines were all larger than those in the second selection phase for M16-1. M16-2 and I16-1, but not for I16-2. Within each Ne level, total response was significantly (P smaller than .01) less for I lines compared with M lines. Total response increased as Ne increased, within each level of i. Relatively small differences in realized i values among Ne lines could not account for this result. The difference in total response among the Ne lines at a given selection intensity may be due to inbreeding depression and a combination of interactions involving "drift" and selection. By crossing replicates of the M lines with the C16 control, the effects of inbreeding depression were removed. Inbreeding depression and genetic drift, as defined herein, were equally important in accounting for differences among Ne lines in total response.

Animals↗
PubMed1977

Mutation-selection balance with stochastic selection.

Diffusion theory has been used to analyze a model of mutation-selection balance in which the selection process is assumed to be stochastic in time. The limiting outcome of the mutation-stochastic selection process is determined qualitatively by the geometric mean fitnesses of the genotypes, and the conditions for fixation or polymorphism are similar to those that determine the outcome of the mutation-selection process when selection is constant. However, in the case of a completely recessive allele, detailed numerical study of the polymorphism associated with stochastic selection has shown that the average allele frequency maintained is greater than the equilibrium frequency expected when selection is constant, even when the geometric mean fitness of the recessive homozygotes is identical in the stochastic and deterministic models. Thus, allele frequencies in natural populations that are too high to be plausibly explained by a balance between mutation and constant selection can be accounted for if selection is stochastic.

Alleles↗
PubMed1975

A controlled, randomized trial of highly selective vagotomy versus selective vagotomy and pyloroplasty in the treatment of duodenal ulcer.

The results of highly selective vagotomy without drainage and selective vagotomy with pyloroplasty for duodenal ulcer were compared in a randomized, controlled trial of a series of 100 patients. The frequency of dumping, diarrhoea, and epigastric fullness was significantly lower after highly selective (6, 6, and 8 percent) than after selective vagotomy (30, 20, and 28 percent) one year after the operations. Recurrent and persisting duodenal ulcers appearing from one to four years after the operations were significantly more frequent after highly selective (22 percent) than after selective vagotomy (8 percent). No significant relationships were found between recurrent ulceration and gastric acid secretion measurements after the two operations. The Hollander response was early positive in 28 percent and late positive in 30 percent of the patients subjected to highly selective vagotomy, while the corresponding figures after selective vagotomy were 26 and 32 percent. The overall clinical results of the two operations were not different according to the classification of Visick. Excluding the patients with recurrence resulted in significantly better clinical results after highly selective vagotomy.

Adult↗
PubMed1976

Selection for geotaxis in Drosophila melanogaster: heritability, degree of dominance, and correlated responses to selection.

Selection for geotaxis was carried out with flies from a natural population of Drosophila melanogaster; geotactic behavior was measured by means of a Hirsch classification maze. The population was initally almost neutral to gravity, and it responded to both positive (downward) and negative (upward) selection with a realized heritability of about 0.13. Stabilizing selection toward neutral gravity was carried out simultaneously. At generations 6, 9, and 10, all possibly hybrid crosses between pairs of the selected populations were generated and tested. The geotactic scores of hybrids in generations 6 and 9 were not significantly different from the midparent values, while the scores of hybrids in generation 10 deviated significantly from the midparent values in the direction of positive geotaxis. The frequencies of polymorphic inversions declined in every population during selection, but the population under neutral selection seemed to maintain a higher chromosomal polymorphism than those under positive or negative selection. There was no significant depression of productivity, measured as number of progeny, in any population during nine generations of selection.

Animals↗
PubMed1975

Selective and non-selective lymphocytotoxicity in human melanoma: observation on the effect of long-term culture and fetal bovine serum on target-cell sensitivity to lymphocytes.

In vitro cell mediated cytotoxicity (CMC) assays have been conducted in a human melanoma system with a 3H-proline retention technique. Melanoma target cells from long-term cultures ("cell lines") are found to exhibit increased susceptibility for lymphocyte cytotoxicity in comparison to the same target cells from short-term culture. The higher sensitivity of the "cell line" derived target cells is seen with lymphocytes, irrespective of diagnosis of the donor. In parallel experiments with the target cells grown in medium supplemented with fetal calf serum (FCS) and AB+ human serum (from a normal male doner), the melanoma target cells grown with FCS do not show any enhanced cytotoxicity, suggesting no causal relationship of such enhanced sensitivity of "cell line"-derived target cells to "heterologous melanoma antigens" that might have been acquired by the target cells following the use of FCS in tissue culture. In controlled assays of in vitro CMC, lymphocytes from melanoma patients (14/44) exhibited selective cytotoxicity (destruction of only one target-cell type) against the melanoma target cells, whereas only 3/97 control lymphocytes (other malignancies and normal donors) showed such melanoma-selective cytotoxicity. This difference is statistically significant at p less than 0.001. Non-selective cytotoxicity (destruction of two or more unrelated target cell types) was seen with lymphocytes from 9/44 melanoma patients, 13/51 patients with other malignancies and 8/46 normal donors. No correlation of selective cytotoxicity could be established with donors' age, sex, stage of disease, therapy or history of blood transfusion. Such a correlation may emerge as our series becomes larger. Despite the lack of any correlation between selective cytotoxicity and disease status, our study reaffirms the existence of selective cytotoxicity by melanoma patients' lymphocytes against melanoma target cells.

Animals↗
PubMed1975

Effects of truncal, selective, and highly selective vagotomy on glucose tolerance and insulin secretion in patients with duodenal ulcer. Part I-Effect of vagotomy on response to oral glucose.

An oral glucose tolerance test was performed in patients who had undergone truncal vagotomy and pyloroplasty, bilateral selective vagotomy and pyloroplasty, or highly selective vagotomy without a drainage procedure at least six months earlier. The results were compared with those from patients with chronic duodenal ulcer before operation. In all three groups of patients after vagotomy more rapid rates of rise of blood glucose and higher peak concentrations were observed than in patients who were tested before operation. These differences were statistically significant only in patients who had undergone truncal or selective vagotomy with pyloroplasty and were probably due to more rapid rates of gastric emptying after these operations. Plasma insulin concentrations were lower after truncal vagotomy than after selective or highly selective vagotomy, the difference between truncal vagotomy and highly selective vagotomy being statistically significant. Truncal vagotomy resulted in a diminished insulin response to oral glucose, which could have been due to vagal denervation of the pancreas or, more probably, impaired release of small-bowel hormones which normally augment the pancreatic insulin response.

Adult↗
PubMed1975

Effects of truncal, selective, and highly selective vagotomy on glucose tolerance and insulin secretion in patients with duodenal ulcer. Part II-Comparison of response to oral and intravenous glucose.

Paired oral and intravenous glucose tolerance tests were carried out in patients who had undergone truncal vagotomy and pyloroplasty, selective vagotomy and pyloroplasty, or highly selective vagotomy at least six months earlier. Intravenous glucose tolerance was similar in all three groups. Oral glucose elicited significantly higher concentrations of plasma insulin in patients who had undergone selective and highly selective vagotomy than in those treated by truncal vagotomy. When the same amount of glucose was given intravenously, however, plasma insulin concentrations were similar in all three groups of patients. The insulin secreted in response to intravenous glucose expressed as a percentage of that secreted in response to oral glucose was 112% for truncal vagotomy, 51% for selective vagotomy, and 52% for highly selective vagotomy. Truncal vagotomy thus led to a diminished insulin response to oral glucose, which was probably due to impaired release of small-bowel hormones.

Administration, Oral↗
PubMed1979

Quantitative structure-selectivity relationships: selective drug design.

The concept of complex selectivity (Scn) permits the investigation of quantitative structure--selectivity relationships in the presence of n side effects; Scn permits differentiation of the most selective molecules rather than the most active ones in a congener series. Selectivity quantification in the presence of n side effects facilitates molecular comparisons. The information provided by Scn and its changes with increasing n is discussed. The proposed mathematical model is applied to the study of the selectivity of some antibiotics and antibacterial agents.

Chemistry, Pharmaceutical↗
PubMed1979

Cardiovascular and adrenergic effects of cigarette smoking during immediate non-selective and selective beta adrenoceptor blockade in humans.

The cardiovascular and adrenergic responses to cigarette smoking during acute selective and non-selective beta adrenoceptor blockade were studied in seven young healthy volunteers in a double blind cross-over fashion. Heart rate, arterial blood pressure, forearm blood flow and plasma levels of adrenaline and noradrenaline were determined before and during the terminal 5 min period of 15 min smoking test. During smoking, plasma concentrations of adrenaline increased markedly and evenly by approximately 0.3 ng/ml in all three experimental sessions. Plasma concentrations of noradrenaline remained unchanged. Propranolol, a non-selective beta blocker, caused a marked rise in diastolic and mean blood pressure and forearm vascular resistance during smoking. This response was not seen in the control series or after selective beta-1 blockage with atenolol. This difference is attributable to propranolol's blockade of adrenaline's vasodilating effect mediated by beta-2 receptors in the resistance vessels. Furthermore, atenolol attenuated the systolic blood pressure and tachycardiac responses induced by cigarette smoking by comparison with placebo. This study suggests that selective beta-1 blockers are preferable in the management of patients who are habitual smokers.

Adult↗
PubMed1979

Secondary selective enrichment of salmonellae from naturally contaminated specimens by using a selective motility system.

A selective motility medium was used as a secondary selective enrichment medium to examine specimens naturally contaminated with salmonellae. The medium, incubated at 37 degrees C, was inoculated from either selenite brilliant green sulfa enrichment broth or Müller-Kauffman tetrathionate broth, both of which had been incubated at 42 degrees C. The use of the selective motility medium resulted in an increase in the number of positive specimens from 65 and 74% to 80 and 82%, when inoculated at 24 and 48 h, respectively, from tetrathionate broth. Tetrathionate broth, when used singly, was significantly better than selenite brilliant green sulfa broth, which detected 55% of positive specimens at both 24 and 48 h. The use of the selective motility medium of Harper and Shortridge (J. Hyg. 67: 181--186, 1969) for the further examination of specimens culturally negative on primary selective enrichment is advocated.

Animal Feed↗
PubMed1979

Selecting interspecific human-mouse and Chinese hamster-mouse hybrids using a new half-selection technique with a polyene antibiotic.

Interspecific human-mouse and Chinese hamster-mouse hybrids were isolated from polyethylene glycol fused cells by a new half-selection technique employing a structurally modified polyene macrolide antibiotic, amphotericin B methyl ester (AME), and HAT media. Unfused parental cells were killed as a result of innate sensitivity to AME or their genetic deficiency, absence of thymidine kinase (TK-) or hypoxanthine guanine-phosphoribosyl transferase (HGPRT-). In contrast, hybrid colonies were isolated after two to three weeks growth in three or four changes of HAT-AME media and subsequent growth in HAT media alone. The ability of hybrid cells to proliferate using this selective protocol indicates that genetic complementation resulted, and polyene antibiotic resistance was expressed as a dominant phenotypic property in the hybrids. Hybrid selection was dependent on: (1) the number of cells of each parental cell type co-cultivated; (2) the level of polyene antibiotic administered; and (3) the time interval before selection was initiated. The half-selection technique described in this report is simple to use, very effective in eliminating unfused parental cells and increases the potential types of hybrids which can be formed. Only one parental cell type need contain a biochemical defect, whereas the second parental type can be genetically normal.

Amphotericin B↗