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At least 883 records · Page 49Linked to original sources
PubMed2003

Effect of MON810 Bt field corn on Helicoverpa zea (Lepidoptera: Noctuidae) cannibalism and its implications to resistance development.

Pairs of Helicoverpa zea (Boddie) larvae reared on diet-incorporated MON810 transgenic leaf tissue of field corn (Zea mays L.) were observed in the laboratory to characterize effects of sublethal levels of Bacillus thuringiensis variety kurstaki (Bt) Cry1Ab endotoxins on cannibalistic behavior and mortality. Feeding on sublethal levels of Bt corn reduced the frequency of cannibalistic behaviors exhibited by H. zea when uneven instars were paired together. Exposure to the Bt endotoxin had no significant effect on when cannibalistic mortality occurred or the level of mortality as a result of cannibalism. Assuming that H. zea larvae reared on nonBt corn tissue behaved in a similar way that resistant larvae would if feeding on Bt tissue, sublethal effects of Cry1Ab intoxication may reduce the chances of successful cannibalism by susceptible larvae and thus play a disproportionate role in the survival of multiple ear infestations. Furthermore, cannibalistic encounters could result in partially resistant larvae feeding on nontoxic food, thus temporarily providing an escape from exposure to the Bt endotoxin. These behavior alterations could increase the selective differential between susceptible individuals and those carrying resistance genes.

Animals↗
PubMed2003

Mitochondrial diversity in new world house flies (Diptera: Muscidae).

Mitochondrial diversity in house flies was examined by using the single-strand conformation polymorphism method in house flies, Musca domestica L. sampled in six zoogeographical subregions in the New World. The number of haplotypes and haplotype diversities were homogeneous among subregions, but a strong spatial component was found in the distribution of particular haplotypes. Nei's differentiation index among subregions, GRT, was 0.53 and that among populations within subregions, GPR, was 0.31. Greater genetic differentiation was found among populations in the Nearctic than in the Neotropics. Haplotype frequency distributions in two of three Nearctic subregions deviated from that expected under the neutral infinite allele model, suggesting the existence of differential selection patterns.

Analysis of Variance↗
PubMed2002

Contextual control of stimulus generalization and stimulus equivalence in hierarchical categorization.

The purpose of this study was to determine whether hierarchical categorization would result from a combination of contextually controlled conditional discrimination training, stimulus generalization, and stimulus equivalence. First, differential selection responses to a specific stimulus feature were brought under contextual control. This contextual control was hierarchical in that stimuli at the top of the hierarchy all evoked one response, whereas those at the bottom each evoked different responses. The evocative functions of these stimuli generalized in predictable ways along a dimension of physical similarity. Then, these functions were indirectly acquired by a set of nonsense syllables that were related via transitivity relations to the originally trained stimuli. These nonsense syllables effectively served as names for the different stimulus classes within each level of the hierarchy.

Adolescent↗
PubMed1984

Foreign medical graduates in the 1980s: trends in specialization.

Secondary analysis of data collected by the American Medical Association and the Graduate Medical Education National Advisory Committee (GMENAC) suggests that measures to diminish the flow of alien Foreign Medical Graduates (FMGs) into the United States have been less effective than planned. Declining trends in the proportion of FMG house officers in the mid- to late-1970s have recently stabilized around 19 per cent. There has also been a dramatic increase in the number of US citizen Foreign Medical Graduates ( USFMGs ) in house officer positions. A pattern of alien FMG and USFMG house officer specialization correlates with specialties designated by the GMENAC as shortage areas by 1990 (r = -.49, p less than .05). Despite the GMENAC prediction of a surplus of physicians by 1990, differential selection of alien FMGs and USFMGs into shortage specialties may assure their substantial future presence in the US health care system.

Foreign Medical Graduates↗
PubMed1996

Vectors encoding alternative antibiotic resistance for use in the yeast two-hybrid system.

We have altered the antibiotic resistance of the reporter plasmids and the pJG4-5 activation-domain and pEG202 DNA binding-domain plasmids used in the Brent interaction trap/two-hybrid system. These plasmids were each previously ampicillin-resistant, resulting in an inefficient purification of any one plasmid from a yeast strain containing all three plasmids that constitute the complete interaction trap. By creating derivatives of each of these plasmids expressing either kanamycin or chloramphenicol resistance, along with the parent plasmids, we now have the option to use the interaction trap in yeast with three E. coli differentially selectable vectors. This will allow isolation of any one plasmid by purifying all of the interaction trap plasmids from yeast simultaneously and plating E. coli transformed with the plasmids onto the appropriate antibiotic plate to select the particular plasmid of interest.

Ampicillin Resistance↗
PubMed1998

Assessment of memory in multiple sclerosis patients using the Memory Assessment Scale.

Previous assessment of memory function in multiple sclerosis patients has yielded mixed findings regarding the type and severity of memory deficits, which may be due to (1) differential selection of scales for memory assessment; (2) limited, inconsistent or weak reliability and validity data for the memory scales employed; (3) poor standardization techniques; (4) lack of theoretical foundation for the measure; and (5) limited control of confounding variables, e.g., education, age and the use of nonverbal memory tests. The purpose of the present study was to assess memory function in multiple sclerosis subjects using the verbal subtests of the Memory Assessment Scale, a relatively new measure designed to overcome many of the aforementioned problems. Participants included 57 patients diagnosed as relapsing-remitting, 47 diagnosed as chronic progressive (two generally recognized types of multiple sclerosis), and 132 control participants. A multivariate analysis controlling for age and verbal IQ was significant (Wilks = 5.64, p < .001). One way follow-up tests showed both groups with multiple sclerosis had significantly diminished performance across all memory variables when compared with controls, with the exception of List Clustering Acquisition. This indicated that the patients used clustering (mentally grouping similar words together) as often as controls did. These findings provide support for the presence of significant and consistent verbal memory impairment in multiple sclerosis patients and the particular importance of using psychometrically sound measures in the assessment of this population.

Adolescent↗
PubMedDate not supplied

Human mast cell heterogeneity.

Mast cell neutral proteases are the most precise markers of heterogeneity among human mast cells. Two types of human mast cells have been recognized. MCTC cells contain tryptase together with chymase, cathepsin-G like protease, and mast cell carboxypeptidase; MCT cells contain tryptase, but lack the other neutral proteases present in MCTC cells. All mast cells develop from hemopoietic stem cells. In vitro procedures for studying mast cell growth have been developed, using the major human mast cell growth factor, stem cell factor (SCF, also called Kit-ligand). Cultures of hemopoietic progenitor cells in the presence of SCF alone result in selective differentiation to mast cells. The same progenitor cells can be induced to differentiate into other lineages when SCF is used with various lineage-specific colony-stimulating factors such as erythropoietin for erythrocytes. Mast cell development from hematopoietic progenitors may represent a "default pathway," occurring optimally in a permissive microenvironment such as skin, bowel, and lung. The presence or absence of certain cytokines in blood and bone marrow may create a non-permissive environment, thus the absence of granulated mast cells in such locations.

Animals↗
PubMed1991

Effects of inbreeding on reproduction and wool production of Rambouillet, Targhee, and Columbia ewes.

Because of a traditional interest in inbreeding as a tool for breed improvement, it was desirable to evaluate the effects of inbreeding on the most important products of the sheep industry, lamb and wool production. The data for this study were based on 13,807 ewe and 16,470 lamb records from Rambouillet (R), Targhee (T), and Columbia (C) sheep collected over 9 or 10 yr from 54 inbred lines. Average inbreeding of the lambs and ewes involved was near 25 and 20%, respectively. The combined effects of lamb's and dam's inbreeding reduced litter weight weaned at 120 d approximately .5 kg for each percentage of increase in inbreeding in every breed. For ewes and lambs of average inbreeding, the reductions relative to noninbred ewes amounted to 12.4, 10.3, and 11.3 kg for R, T, and C, respectively. The reductions constituted declines in weight weaned per ewe of 34, 25, and 28%. Similarly, net reproduction rate (lambs weaned per ewes put into breeding) was reduced more than one percentage point for each percentage of increase in inbreeding, with net declines at average inbreeding of 31.7, 23.5, and 25.7 percentage points for each breed, respectively. These reductions were equivalent to reductions in net rate of 29, 20, and 23%. The combined effect of lamb and dam inbreeding reduced weaning weight by 3.5, 2.6, and 2.2 kg, which constituted reductions of 10, 7, and 6%, respectively. Reduced weaning weight was approximately 30% as important as reduced net reproduction rate in contributing to the decline in litter weight weaned. Effects on fleece weight were curvilinear and amounted to reductions of .35, .18, and .00 kg, respectively, at levels of average inbreeding; however, Columbia fleece weights declined rapidly at levels exceeding 20% for ewes. Potential selection differentials were reduced 16% at inbreeding levels of 25 and 20% for lambs and dams, respectively, and 62% at levels of 55 and 50%. The average economic loss per ewe in value of production was estimated at $17 for average inbreeding and as high as $36 for inbreeding approaching 50%. It seems that the use of inbreeding as a tool for improving productive merit in sheep is much more certain to be a detriment, economically and genetically, than an advantage.

Animals↗
PubMed1991

Evaluation of performance-tested boars using a single-trait animal model.

Data structure designs for breeding value estimation of performance-tested boars using mixed-model methodology were compared. Computer models were based on estimates of parameters from the literature and from results of a survey of test station managers. Results were compared using accuracy (the correlation of true and estimated breeding values) and prediction error variance (PEV). The single-trait animal model included a fixed effect due to station-season, a random effect due to breeding value for ADG or backfat, and a random error term. Family size, number of families per test, and relationships among animals within and across tests were varied. Prediction error variance decreased faster for small families than for large ones as number of families increased, but increasing numbers of animals per pen was most important, especially if test size was optimized. With no other genetic ties, full-sibs were much more accurately evaluated than half-sibs. Designs that included sire ties among families within a station-season resulted in increased PEV. Increasing the number of full-sibs and(or) increasing the number of families per test would help to optimize PEV and correct this problem. Tying station-seasons with the relationship matrix improved the average accuracy of predicted breeding values. Placing full-sibs in different stations resulted in the greatest accuracy of evaluation, but a large number of half-sib (sire) ties resulted in comparable accuracies. Half-cousin ties did not improve accuracy of evaluation but could result in significant genetic progress by increasing the selection differential.

Adipose Tissue↗
PubMed1992

Classical and mixed-model analysis of an index selection experiment for fecundity in Drosophila melanogaster.

A comparison of three family indices to increase number of pupas from 3-d lay in Drosophila melanogaster is reported. The three indices were Id, based exclusively on dam's information; Ihd, based additionally on dam's full-sibs' and half-sibs' information; and Ihs, which also included the sire's full-sibs' and half-sibs' records. Three lines, D, HD, and HS, were selected, each according to one of the three indices: Id, Ihd, or Ihs. Each line consisted of 10 sires and 60 dams. Each dam contributed one male offspring and three female offspring. Seven generations of selection were performed in a two-replicate experiment. The expected advance of Ihs and Ihd over Id in the seventh generation was .38 and .15 phenotypic standard deviations, respectively. The experiment was analyzed in terms of both classical ordinary least squares (OLS) and mixed-model methodology (MMM). The phenotypic trends in the first replicate were 4.06 +/- 1.74, 1.42 +/- 1.76, and .26 +/- 1.94 pupas per generation for Lines D, HD, and HS, respectively, and in the second replicate 8.52 +/- 2.40, 6.16 +/- 3.21, and 4.21 +/- 2.60, respectively. The genetic trends in the first replicate were 2.18 +/- .61, 1.08 +/- .67, and .24 +/- .68 pupas per generation and, in the second replicate, 2.51 +/- .60, .16 +/- .61, and .05 +/- .64 for Lines D, HD, and HS, respectively. Despite theoretical expectations, the Id index was consistently better than the more complex indices. Several explanations for these results are possible: 1) smaller than expected selection differential, 2) inbreeding depression, and 3) incorrect heritability used to construct the indices.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1980

Inheritance of teat number and its relationship to maternal traits in swine.

The relationship of teat number to seven measures of female reproduction was evaluated in the University of Nebraska Gene Pool population. Teat number was recorded for 7,513 pigs, ovulation rate for 2,794 gilts and litter size and weight at birth and weaning (42 days) for 789 gilts. Paternal half-sib and full-sib analyses were used to estimate heritabilities for each trait and to estimate the genetic and phenotypic correlations of teat number with the measures of reproduction. The direct response to selection for ovulation rate and the correlated response in teat number were also evaluated from the regressions of line differences (Select-Control) on generation number (10 generations of selection) and cumulative selection differential for ovulation rate. The paternal half-sib heritabililty for teat number was .32, and the paternal half-sib heritabilities for ovulation rate and the litter traits were similar to previous estimates from this population. Most of the genetic and phenotypic correlations with teat number were negative and all were nonsignificant. The realized heritability for ovulation rate was .46 +/- .10. The regression of response in teat number on generation number number was .08 +/- .03 (P < .10). An estimate of .44 was obtained for the realized genetic correlation of teat number with ovulation rate.

Animals↗
PubMedDate not supplied

The ultrastructure and histogenesis of male germ neoplasia with emphasis on seminoma with early carcinomatous features.

The range of ultrastructural morphology was studied in 107 male germ cell neoplasm to assess relationships among tumor subtypes and to consolidate diagnostic criteria. Eighty-three pure-pattern neoplasms including 47 seminomas, 26 embryonal carcinomas, 10 endodermal sinus tumors, and 24 mixed germ cell tumors were analyzed. In the seminoma category, 4 cases showing cell surface specialization in keeping with early carcinomatous transformation were noted. The finding suggested a closer link between seminoma and nonseminomatous germ cell tumors than had been traditionally recognized and was in keeping with other clinical, histologic, biochemical, and xenograft observations. Subtypes of nonseminomatous germ cell tumors also exhibited a continuum of ultrastructural morphology with some types such as embryonal carcinoma and endodermal sinus tumor often blending together. At a practical level, electron microscopy has been of value in selected differential diagnoses such as seminoma versus lymphoma.

Choriocarcinoma↗
PubMed1995

Staining etched epoxy resin sections for light microscopy.

Staining of etched sections for light microscopy is described. Azan staining was successful after treatment with potassium dichromate and the use of concentrated dye solutions. To remove osmium for hematoxylin-eosin staining, removal by reduction with ferrocene was used instead of oxidation. Highly selective differentiation after hematoxylin staining was achieved using p-toluenesulfonic acid-DMSO. To enhance eosin staining, a 2-bromoethylamine link between eosin and the tissue was used. Ferrocene also facilitated counterstaining of nuclei with hematoxylin after the PAS reaction. Periodic acid-methenamine silver staining was carried out without modification.

Epoxy Resins↗
PubMed1980

Progeny tested sires compared with pedigree selected young sires.

First lactation records of 109,589 cows in 1,978 Holstein herds cooperating with three artificial insemination studs in young sire sampling were studied to compare performance of progeny of approximately the upper 15, 2, and 25% of sires, dams, and maternal grandsires for milk yield with selection differentials of +350, +2735, and +268 kg milk when the young sires entered sampling programs. The 315 young bulls were sired by 88 sires. Mean weighted Predicted Differences for sires proven through artificial insemination were 130 kg milk and 4.0 kg fat, whereas weighted averages for naturally proven sires were 13 kg milk and .4 kg fat. For young sires, pedigree index of sire, dam, and maternal grandsire averaged 347 kg milk and 11.8 kg fat, and for an index including sire and maternal grandsire averaged 242 kg milk and 7.6 kg fat. Annual trends for ancestors were +31.8 kg milk and +.9 kg fat for sires. Within herd-year-season, production of daughters of progeny tested sires exceeded that of daughters of young sires by 84 kg milk and 2.4 kg fat. Progeny of young sires produced 103 kg more milk than daughters of naturally tested bulls.

Animals↗
PubMed1991

Using embryo sexing within closed mixed multiple ovulation and embryo transfer schemes for selection on dairy cattle.

Two types of multiple ovulation and embryo transfer schemes that included bull progeny testing were compared. In the juvenile schemes, embryos were collected at 16 to 18 mo of age without sexing, whereas, in the adult schemes, donors were chosen based on their first lactation record, and their embryos were systematically sexed. With the latter schemes, natural calves obtained at the first two calvings could compete with embryo transfer calves to be replacements. The optimal structure of this scheme was derived algebraically for the same number of transferred embryos as in the juvenile schemes. Predicted asymptotic annual genetic gains, after stabilization of genetic parameters taking into account the Bulmer effect, were found to be slightly in favor of the adult schemes for a given set of parameters (overall number of transferred embryos, number of embryos per collection, and embryo survival rate). In the adult schemes, the nucleus sizes were much larger than in the juvenile schemes, which allowed a higher selection differential on male paths, thus compensating for the longer generation interval. Asymptotic rate of genetic gain for Monte Carlo simulations were about 10 and 7% lower for juvenile and adult schemes, respectively, but still higher (20%) than the predicted value for the corresponding conventional scheme. Consequently, adult schemes with embryo sexing can be an efficient alternative to juvenile schemes without embryo sexing.

Animals↗
PubMed2005

Relative roles of microsurgery and stereotactic radiosurgery for the treatment of patients with cranial meningiomas: a single-surgeon 4-year integrated experience with both modalities.

OBJECT: The authors sought to assess the respective roles of microsurgery and gamma knife surgery (GKS) in the treatment of patients with meningiomas. METHODS: The authors culled from a 4-year prospective database data on 74 cases of meningiomas. Thirty-eight were treated with GKS and 35 with microsurgery. Simpson Grade 1 or 2 resection was achieved in 86.1 % of patients who underwent microsurgery. Patients who underwent GKS received a mean margin dose of 16.4 Gy (range 14-20 Gy). The mean tumor coverage was 94.7%, and the mean conformity index was 1.76. Significant differences between the two treatment groups (GKS compared with microsurgery) included age (mean 60 compared with 50.7 years), volume (mean 7.85 cm3 compared with 44.4 cm3), treatment history (55.3% compared with 14.3%), and tumor location (cavernous sinus/petroclival, 14 compared with three). The median follow up was 21.5 months (range 1.5-50 months). In patients with benign meningiomas GKS tumor control was 96.8% with one recurrence at the margin. The recurrence rate was zero of 27 for Simpson Grade 1 or 2 resection and three of four for higher grades in those patients who underwent microsurgery. There was no procedure-related mortality or permanent major neurological morbidity. The mean Karnofsky Performance Scale score was maintained for both forms of treatment. Symptoms improved in 48.4% of patients undergoing microsurgery and 16.7% of those who underwent GKS. Transient and permanent cranial nerve morbidity was 7.9 compared with 2.9%, and 5.3 compared with 8.5% for GKS and microsurgery, respectively. In a patient satisfaction survey 93.1% of microsurgery patients and 91.2% of GKS patients were highly satisfied. CONCLUSIONS: Both GKS and microsurgery serve important roles in the overall management of patients with meningiomas. Both are safe and effective and provide high degrees of satisfaction when used for differentially selected patients.

Adolescent↗
PubMed1975

The nature of the polymeric serum IgA in man.

The nature and the amount of polymeric IgA in sera from normal, adult humans was investigated by means of three markers that selectively differentiate polymeric IgA: the capacity to bind secretory component; the presence of the J chain; and the reactivity with an antiserum that recognizes only the polymeric form of IgA. The results demonstrated that the sera of healthy adults contain only minimal amounts (less than 1% of the total serum IgA) of the true dimeric IgA. These conditions are valid for healthy individuals only. Pathological conditions at the secretory sites may result in increased values for the dimeric as well as for the secretory IgA in serum.

Adult↗
PubMed2001

Prevalence of Salmonella serovars in chickens in Turkey.

In this study, 151 (18.6%) of 814 ceca obtained during in-line processing of 28 broiler (Hybro G, Avian, Arbor acres, and Cobb breeds) and 5 layer (Ross, Tetra SL, Isa Brown, and Brown Nick breeds) flocks in Turkey were found to be contaminated with four different Salmonella serovars. Only Salmonella enterica subsp. enterica Serovar Enteritidis (Salmonella Enteritidis) was recovered from layer birds, whereas Salmonella Enteritidis (81.5%). Salmonella Agona (7.6%), Salmonella Thompson (10.1%), and Salmonella Sarajane (0.8%) were isolated from broiler birds. Isolations of Salmonella Agona and Salmonella Thompson from poultry are reported for the first time in Turkey. The isolation of Salmonella Sarajane from chickens is the first report in the world. The standard method of National Poultry Improvement Plan, U.S. Department of Agriculture, was used to detect Salmonella from chicken cecal samples. Primary and delayed secondary enrichments (PE and DSE) were done in tetrathionate-Hajna broth (TTHB). Two different agar media, xylose lysine tergitol 4 (XLT4) and brilliant green with novobiocin (BGN) were used to observe, and compared for their isolation and selective differentiation of, Salmonella-suspected colonies. Isolated salmonellae were then biotyped and serotyped. Ninety-one and 151 salmonellae were isolated with XLT4 agar after PE and DSE, respectively. From the same samples, BGN agar was able to detect only 50 and 131 Salmonella after PE and DSE, respectively. The isolation rate with XLT4 was 11.2% (P < 0.01) with PE, and this rate increased to 18.6% after DSE. Also, the PE isolation rate (11.2%) with XLT4 agar was significantly higher (P < 0.01) than PE with BGN agar (6.1%). Salmonella was isolated from 39.3% (11 of 28) of the broiler flocks and from 60.0% (3 of 5) of the layers. The detection sensitivity of the isolation method was determined as 1 CFU g(-1) experimentally. These data demonstrate the presence of Salmonella Enteritidis, Salmonella Thompson, Salmonella Agona, and Salmonella Sarajane in chicken flocks in Turkey.

Animals↗