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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↗

PubMed1979

Divergent selection on locomotor activity in Drosophila melanogaster. I. Selection response.

Selection for high and low locomotor activity has been applied in two base populations of Drosophila melanogaster of distinct geographical origin. From each base population a high and a low line were selected, in which anesthesia was performed with ether. In addition, from one of the base populations a high line and a low line were selected under CO2 narcosis. Locomotor activity was measured in an apparatus consisting of rows of 20 tubes in a line. Heritabilities in the base populations determined in progeny tests were approximately 10%. Divergent directional selection was successful with realized heritabilities of similar value.

Animals↗

PubMed1979

Divergent selection on locomotor activity in Drosophila melanogaster. II. Test for reproductive isolation between selected lines.

Tests for reproductive isolation between lines selected for locomotor activity were performed. Three sets of selection lines were used, each consisting of lines selected for low and high locomotor activity from the same base population. Females preferred high-activity males in almost every case. However, in one of the sets temporary sexual isolation was found between flies of the high and low lines. This was accompanied in the low-activity females with a higher fertility when they were mated with their own males. After further selection the partial isolation disappeared.

Animals↗

PubMed1975

Voluntary selection of and tolerance to 1,2 propanediol (propylene glycol) by high and low ethanol-selecting mouse strains.

Fifteen male mice from each of 4 inbred strains (C57BL/6J, BALB/cJ, CBA/J, and DBA/2J) were tested to determine their voluntary self-selection of a 10% solution of 1,2 propanediol (1,2 PD), A 3-carbon alcohol of low toxicity. As with ethanol, the C57BL/6J strain consumed significantly greater amounts that the 3 other low ethanol-selecting strains. A second experiment determined that the 3 low selecting strains suffered significantly greater depression of the central nervous system from 1,2 PD than the high selecting C57BL strain. It was also found that ethanol is a much more potent depressant that 1,2 PD. These results are discussed in terms of the possible role of neural sensitivity in regulating consumption levels of the 2 alcohols.

Alcohol Drinking↗

PubMed1976

Intercellular adhesive selectivity. III. Species selectivity of embryonic liver intercellular adhesion.

A species difference in the intercellular adhesive selectivity of mixtures of embryonic liver cells is reported. This is first quantitative assessment of species differences in the intercellular adhesive properties of embryonic cells. A collecting aggregate assay, a new double-label assay procedure, and histological and autoradiographic procedures were used to elucidate the intercellular adhesive selectivity of developing mammalian and avian liver cells. Evidence is presented that the reported adhesive differences are not due to the different cell types composing the respective embryonic mammalian and avian livers. Finally, such heterolgous-homotypic selectivity of adhesion is not a property of all tissues, since it is shown that developing brain cells (mesencephalon) do not exhibit the avove intercellular adhesive selectivity (mammalian vs. avian). These findings provide further support for the hypothesis that generic identity as well as cell type may play an important part in determining the intercellular adhesive behavior of heterologous-homotypic mixtures of embryonic cells. A possible evolutionary divergence of morphogenetic mechanisms is discussed.

Animals↗

PubMed1976

Selective versus non-selective His bundle pacing.

His bundle pacing was achieved in 10 anaesthetized open chest dogs by stimulation from bipolar electrode catheters positioned in the aortic root and right heart. Recordings were taken directly through plunge wires from the right atrium, high ventricular septum, and epicardial sites on the right and left ventricles. Six types of response were seen during A-V junctional stimulation: (1) low atrial pacing; (2) combined atrial and His bundle pacing; (3) His bundle pacing; (4) combined atrial, ventricular septal, and His bundle pacing; (5) combined septal and His bundle pacing; and (6) ventricular pacing. Pacing of the His bundle in combination with the atrium and/or ventricular septum is designated as non-selective, whereas stimulation of the His bundle alone is considered selective pacing. Non-selective His bundle pacing can be recognized from the surface leads by changes in onset and amplitude of the QRS with appreciable T-wave alterations. Although electrode position was an important determinant of the type of pacing achieved, a variety of patterns of stimulation resulted from variation in the modalities of the pacing stimulus, ie, polarity, intensity, and duration. Unless these factors are considered, selective His bundle pacing may not be achieved.

Animals↗

PubMed1975

Selection of early treatment of myelomeningocele: a retrospective analysis of selection procedures.

In an attempt to formulate a procedure for the selection of those children with open myelomeningocele most likely to benefit from early surgery, the records of 163 children have been reviewed. No physical findings, either singly or in combination, were found to distinguish accurately between children with good and poor prognoses, and an alternative selection procedure is proposed which takes into consideration the absence or presence of lacunar skull deformity (a finding strongly associated with mental retardation). Early surgery is not recommended for children with lacunar skull deformity and at least two of Lorber's major adverse neonatal criteria, or children with associated gross congenital anomalies. This selection procedure has been applied retrospectively to the 163 children reviewed and has been shown to predict the (known) outcome of these children much more reliably than existing selection criteria.

Follow-Up Studies↗

PubMed1992

T-helper functions in lines of mice selected for high or low antibody production (Selection III): modulation by anti-CD4+ monoclonal antibody.

T-helper function was evaluated in mice genetically selected for high (H) or low (L) antibody (Ab) responsiveness to Salmonella flagellar antigen (Ag) (Selection III). In this Selection as opposed to what was demonstrated in Selections I, II and IVA, the interline difference was not proven to be based upon the modification of Ag processing and presentation at macrophage level. CD4+/CD8+ lymph node ratio is similar in HIII and LIII mice, both lines being equally susceptible to in vivo depletion of CD4+ T cells by GK 1-5 monoclonal antibody (mAb) treatment. Nevertheless, the Ab responsiveness of the two lines was differently modulated by GK 1-5 mAb: the inhibition of Ab responses to various Ag required lower mAb doses and was long lasting in LIII as compared to the transient effect of higher mAb doses observed in HIII. LIII mice were also refractory to Salmonella-induced reversion of GK 1-5 mAb inhibition. Moreover, in vitro specific I proliferation was constantly lower in LIII, though its IL-2 production was unexpectedly similar to that of HIII T cells. Results of in vivo and in vitro experiments are thus consistent with a defective response of T-helper cells to immunogenic challenge in LIII mice.

Animals↗

PubMed1976

Specific selection of cytotoxic effector cells: the generation of cytotoxic T cells in rat thoracic duct lymphocyte populations positively or negatively selected for reactivity to specific strong histocompatibility alloantigens.

These studies consider the generation of cytotoxic T lymphocytes (CTL) from precursors (CTLP) present in rat thoracic duct lymphocytes after stimulation with strong alloantigens. Also, they explore the relationship between CTLP and "initiator" (I) lymphocytes responsible for specific GVH and MLI reactions. Positively selected TDL populations prepared in bulk MLI cultures show enriched GVH and MLI reactivity for the selecting major histocompatibility complex (MHC) haplotype, but no cytotoxic activity, raising the possibility that I and CTLP may belong to different subpopulations, and the latter failed to differentiate or to survive under these culture conditions. Restimulation of these cells in Marbrook culture vessels with the original priming haplotype under conditions suitable for generating killer cells in vitro resulted in greatly increased specific CTL activity with accelerated kinetics soon after priming and normal kinetics later. These findings indicate that "memory" killer cells can be generated in a previously stimulated lymphocyte population that had no overt cytotoxic activity. Restimulation with third party haplotypes failed to give CTL activity either to specific or to third party targets. Negatively selected TDL populations prepared by "filtration" through x-irradiated F1 rats, depleted of specific GVH and MLI responses, were also depleted of the ability to generate CTL in Marbrook cultures stimulated with the selecting haplotype. Stimulation with third party haplotypes, or with both third party and specific haplotypes together, gave CTL effective only against the third party target.

Animals↗

PubMed1992

Group selection, individual selection, and the evolution of genetic drift.

In a subdivided population, genetic drift affects variation between groups, and thus it can have an important effect on the outcome of evolution (Wright, 1978). The rate of genetic drift is determined, in part, by the behaviour of population members. This paper presents three mathematical models in which behavioural traits that affect the rate of genetic drift are allowed to coevolve with traits that are under selection at the group and individual levels. The results show that if group selection is strong relative to individual selection, then behavioural traits that enhance the rate of genetic drift will tend to increase in frequency. The strength of this effect depends, in part, on the way in which vacant sites are colonized.

Animals↗

PubMed1976

The unit of selection in Drosophila mercatorum. I. The interation of selection and meiosis in parthenogenetic strains.

An important problem in population genetics is the determination of the level of genetic organization to which fitness measures can be ascribed that yield an adequate description or prediction of the outcome of selection in populations. To study this problem, we used two strains of Drosophila merca torum (S-1-Im and O-3-Im) that are capable of both sexual and parthenogenetic reproduction, a feature that allows us to experimentally control many factors which affect genetic variability. Both S and O reproduce parthenogenetically by "pronuclear duplication," a mechanism that retains normal meiosis (and hence crossing over and assortment) but results in homozygosity for all loci in a single generation. Since an isozyme survey indicated that S and O differ at a third of their loci, we hypothesized that S and O have adapted in genetically distinct fashions to the genetic environment of total homozygosity. This is tested by breeding females that are S-O hybrids for 100%, 60% and 40% of their genetic backgrounds, and scoring their respective pathenogenetic progenies for four isozyme and two visible markers. The data collected gave evidence for a coadaptation to total homozygosity involving non-additive and non-multiplicative interactions between non-alleles. As the perturbation of the parental coadapted genotypes by meiosis increases (i.e., the greater the degree of S-O hybridity), the level of genetic material which behaves as an additive/multiplicative fitness unit becomes larger. Selective neutrality of genetic variation may be an artifact of our failure to measure the proper genetic unit of selection.

Animals↗

PubMedDate not supplied

Comparison of crossbred and purebred selection for a heterotic trait in highly selected populations of Tribolium.

Selection on the basis of crossbred performance (RRS) was compared for 11 generations to within-line selection based on purebred performance (WLS) for a heterotic trait, 13-day larval weight in Tribolium populations previously subjected to 30 generations of purebred selection. RRS crossbreds gained slightly less than crossbreds of WLS populations. RRS purebreds showed a much smaller composite populations were greater than those observed for the continued populations. A model for the genetic control of larval weight is suggested in which there are both dominant and overdominant loci and homozygotes are less fit than heterozygotes.

Animals↗

PubMed1979

[Survival of the mutant clone. III. Catastrophic selection. The inadequacy of the selection coefficient for assessing clone fate].

Majorant estimations of the probabilities pr for the surviving of the clone of the dividing cells have been obtained in the catastrophic situation (monotonous diminishing of the clone almost to zero during the period of time from t=0 to t=T, T approximately 100 generation). At t=0 the clone consisted of 10(6) individuals. Average selection coefficient (s) was found to determine pr only roughly, that is the clone with s greater than --0.09 survives almost in all cases, whereas the clone with s greater than --0.13 becomes extinct practically always. Within this interval ps-inversion can be observed, i.e. preferential surviving of the clone with a worse s value. Results of three communications lead to the conclusion that the mutants with small selective advantage practically cannot be selected.

Cell Survival↗

PubMed1979

Urinary MHPG levels and tricyclic antidepressant drug selection. A preliminary communication on improved drug selection in clinical practice.

The 24-hour urinary 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) output was used as the basis for selection of tricyclic antidepressant drug therapy for the depressed patient population treated by one psychiatrist over a period of ten months in a psychiatric clinic. Use of MHPG output level as the criterion for drug selection resulted in significantly better clinical results than had been obtained previously by the same psychiatrist using more traditional selection methods on a similar depressed patient population. A correlation was noted between patients' pretreatment MHPG output levels and three symptoms of depression (guilt, agitation, and diurnal variation) as measured on the Hamilton Rating Scale for Depression.

Adult↗

PubMed1978

A selective and sensitive assay for urinary metanephrine and normetanephrine using gas chromatography mass spectrometry with selected ion monitoring.

Vapor phase methodology for quantitative analysis of urine for metanephrine and normetanephrine as the pentafluoropropionyl derivative is described. The use of selected ion monitoring provided sufficient sensitivity and selectivity that milliliter aliquots of urine required only a simple scheme of sample processing; preliminary purification consisted of percolation through a column of XAD-2 followed by solvent extraction. The sample extracts were converted to the pentafluoropropionyl derivatives and analyzed by gas chromatography mass spectrometry with selected ion monitoring. Quantitative analysis was based on alpha[2H2]-beta-[2H1]metanephrine and alpha-[2H2]-beta-[2H1]normetanephrine which were added to the urine sample at the outset. The calibration plots for metanephrine and normetanephrine were linear from 10 ng ml-1 to 2000 ng ml-1 of urine permitting the detection of metanephrine and normetanephrine levels throughout the normal range and well into the subnormal range. Examples of application of the methodology to clinical investigation are described. The overall reproducibility of the sample processing methodology and instrumentation was assessed by replicate analyses of the same urine sample over a period of several weeks; the coefficient of variation was +/- 2.5% (n = 8).

Chromatography, Gas↗

PubMed1976

The selection of students for medical education: select bibliography, 1970-75.

The problems of student selection are constantly in the mind of medical school administrators and medical teachers. When reviewing current policies there is clearly a need to study the recent journal literature, but the term 'student selection' is not a subject heading in Index Medicus; consequently no convenient listing of journal articles on this important topic is readily available. To assist administrators and medical teachers a bibliography has now been prepared. The references are taken from Index Medicus 1970-75 and presented here in a quick-reference alphabetical format. To the list has been added World Health Organization publication EURO 6203 which is considered an important document on the subject. The bibliogrraphy therefore provides a concise reference to the recent literature on student selection for medical education.

Bibliographies as Topic↗

PubMed1992

[Usefulness of selective endoscopic retrograde pancreatography (selective ERP) and endoscopic pancreatic biopsy (EPB) in the diagnosis of mucin-producing tumor of the pancreas].

Selective ERP and EPB were employed in the diagnosis of mucin-producing tumor (MPT) of the pancreas and their usefulness was evaluated. Thirty five cases of MPTs were subdivided into three subtypes, i.e., 1) main duct type, 2) branch duct type and 3) peripheral type (mucinous cystadenoma/cystadenocarcinoma). Selective ERP was proved to be useful in demonstrating precise and whole pancreatograms, especially in revealing multiple lesions, when compared with standard ERP. Selective ERP could demonstrate communication between cystic tumors of the peripheral type and the pancreatic duct in seven (88%) of eight cases of the peripheral type, which suggests high frequency of the communication in the peripheral type. For preoperative tissue diagnosis, EPB was shown to be a useful method to yield sufficient tissue materials for histopathological evaluation and may be used as an adjunction method to diagnose the intraductal extent of the tumorous lesion.

Adenocarcinoma, Mucinous↗