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Biomedical subjects

S Beebe

Publications and source records attributed to S Beebe.

9 recordsLinked to original sources
PubMed2006

QTL analysis of yield traits in an advanced backcross population derived from a cultivated Andean x wild common bean (Phaseolus vulgaris L.) cross.

Advanced backcross QTL analysis was used to identify quantitative trait loci (QTL) for agronomic performance in a population of BC2F(3:5) introgression lines created from the cross of a Colombian large red-seeded commercial cultivar, ICA Cerinza, and a wild common bean accession, G24404. A total of 157 lines were evaluated for phenological traits, plant architecture, seed weight, yield and yield components in replicated trials in three environments in Colombia and genotyped with microsatellite, SCAR, and phaseolin markers that were used to create a genetic map that covered all 11 linkage groups of the common bean genome with markers spaced at an average distance of every 10.4 cM. Segregation distortion was most significant in regions orthologous for a seed coat color locus (R-C) on linkage group b08 and two domestication syndrome genes, one on linkage group b01 at the determinacy (fin) locus and the other on linkage group b02 at the seed-shattering (st) locus. Composite interval mapping analysis identified a total of 41 significant QTL for the eight traits measured of which five for seed weight, two for days to flowering, and one for yield were consistent across two or more environments. QTL were located on every linkage group with b06 showing the greatest number of independent loci. A total of 13 QTL for plant height, yield and yield components along with a single QTL for seed size showed positive alleles from the wild parent while the remaining QTL showed positive alleles from the cultivated parent. Some QTL co-localized with regions that had previously been described to be important for these traits. Compensation was observed between greater pod and seed production and smaller seed size and may have resulted from QTL for these traits being linked or pleiotropic. Although wild beans have been used before to transfer biotic stress resistance traits, this study is the first to attempt to simultaneously obtain a higher yield potential from wild beans and to analyze this trait with single-copy markers. The wild accession was notable for being from a unique center of diversity and for contributing positive alleles for yield and other traits to the introgression lines showing the potential that advanced backcrossing has in common bean improvement.

Chromosome Mapping↗
PubMed2003

Using molecular markers to assess the effect of introgression on quantitative attributes of common bean in the Andean gene pool.

Progress in bean breeding programs requires the exploitation of genetic variation that is present among races or through introgression across gene pools of Phaseolus vulgaris L. Of the two major common bean gene pools, the Andean gene pool seems to have a narrow genetic base, with about 10% of the accessions in the CIAT core collection presenting evidence of introgression. The objective of this study was to quantify the degree of spontaneous introgression in a sample of common bean landraces from the Andean gene pool. The effects of introgression on morphological, economic and nutritional attributes were also investigated. Homogeneity analysis was performed on molecular marker data from 426 Andean-type accessions from the primary centres of origin of the CIAT common bean core collection and two check varieties. Quantitative attribute diversity for 15 traits was studied based on the groups found from the cluster analysis of marker prevalence indices computed for each accession. The two-group summary consisted of one group of 58 accessions (14%) with low prevalence indices and another group of 370 accessions (86%) with high prevalence indices. The smaller group occupied the outlying area of points displayed from homogeneity analysis, yet their geographic origin was widely distributed over the Andean region. This group was regarded as introgressed, since its accessions displayed traits that are associated with the Middle American gene pool: high resistance to Andean disease isolates but low resistance to Middle American disease isolates, low seed weight and high scores for all nutrient elements. Genotypes generated by spontaneous introgression can be helpful for breeders to overcome the difficulties in transferring traits between gene pools.

Breeding↗
PubMed2000

Genetic selection for enhanced bioavailable levels of iron in bean (Phaseolus vulgaris L.) seeds.

The bioavailability of Fe from 24 select genotypes of bean (Phaseolus vulgaris L.) seeds containing a range of concentrations of Fe, myo-inositol pentaphosphate plus phytic acid (IP5+IP6), and tannins was studied using a rat model. Bean accessions, selected from field trials for their variations in Fe, phytate, and tannin seed concentrations, were grown in a greenhouse in nutrient solutions radiolabeled with (59)Fe. Mature seeds were autoclaved and lyophilized. Test meals (containing 1 g of dried bean, 0.5 g of sucrose, and 1 g of basal Fe-deficient diet) were fed to marginally Fe-depleted weanling rats over a 3-h period; rats were radioassayed in a gamma-spectrometer immediately after feeding and daily thereafter for the next 10 d. Radioiron retention data were used to calculate percent Fe absorption (i.e., Fe bioavailability) from the meals. Seed Fe concentrations ranged from 52 to 157 microg g(-)(1) dry weight. There was a tendency to also select for higher Zn concentrations in the beans when selecting for high Fe concentrations. The Fe bioavailability to rats from test meals depended on the genotype and varied from 53% to 76% of the total Fe. Bean genotypes with higher seed Fe concentrations resulted in increased amounts of bioavailable Fe to rats. There was no significant correlation between the Fe concentration in different bean genotypes and Fe bioavailability to rats attributable to variations in IP5+IP6 or tannins, even though these antinutrients varied widely (i.e., from 19.6 to 29.2 micromol of IP5+IP6 g(-)(1) and from 0.35 to 2.65 mg of tannins g(-)(1)) in the test meals. Other unknown seed factors (i.e., antinutrients or promoter substances) may be contributing factors affecting Fe bioavailability from bean seeds.

Animals↗
PubMed1989

Pairs of cyclic AMP analogs, that are specifically synergistic for type I and type II cAMP-dependent protein kinases, mimic thyrotropin effects on the function, differentiation expression and mitogenesis of dog thyroid cells.

The role of the two different isozymes of the cAMP-dependent protein kinase is still unclear. We have investigated the potential roles for each isozyme in dog thyroid cells, a model in which the function, expression of differentiation and proliferation are positively regulated by thyrotropin acting through cyclic AMP. The dog thyroid contains both type I and type II cAMP-dependent protein kinases. These isozymes were selectively activated in vitro by type-I-directed and type-II-directed analog pairs. In thyroid slices, both type-I directed and type II-directed analog pairs synergistically activated thyroid hormone synthesis, as measured by incorporation of 131I into proteins and thyroid hormone secretion as determined by the release of butanol-extractable 131I. In primary cultures of dog thyroid cells both isozyme-directed analog pairs synergistically enhanced iodide trapping, a marker of differentiation, and DNA synthesis, as measured by the percentage of cells incorporating [3H]thymidine into their nuclei. However, DNA synthesis was more sensitive to type-I-directed pairs. The results demonstrate that both cAMP-dependent protein kinase isozymes can mediate the action of cAMP on function, differentiation expression and cell proliferation in dog thyroid cells.

Animals↗
PubMed1988

Regulation of mRNA levels for cellular retinol binding protein in rat Sertoli cells by cyclic AMP and retinol.

The levels of mRNA for cellular retinol binding protein (CRBP) were studied in primary rat Sertoli cell cultures treated with cAMP analogues and retinol. In the presence of cyclic AMP analogues a dose- and time-dependent reduction (70-90%) of the levels of mRNA for CRBP was observed. Retinol concentrations above 10 nM induced a dose- and time-dependent increase (2-3 fold) in mRNA levels for CRBP. Assuming that CRBP is important for vitamin A action, our data indicate that both cAMP and retinol itself modulate the sensitivity of the Sertoli cells for retinol.

Animals↗
PubMed1988

Differential regulation of messenger ribonucleic acids for specific subunits of cyclic adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase by cAMP in rat Sertoli cells.

In the present study we have examined the effects of FSH, forskolin, and (Bu)2cAMP on messenger RNA (mRNA) levels for all known subunits of cAMP-dependent protein kinase in rat Sertoli cells, using newly developed complementary DNA (cDNA) probes. mRNAs for the three regulatory subunits [RI alpha, RII51, (RII beta), and RII54 (RII alpha)] and the catalytic subunit C alpha were shown to be present in cultured rat Sertoli cells, whereas mRNAs for the subunits designated RI beta and C beta were below the level of detection. A high-levelled, concentration-dependent increase in a 3.2 kilobase mRNA for RII51 was observed when cultured immature Sertoli cells were incubated with increasing concentrations of (Bu)2cAMP (10(-6) to 5 X 10(-3) M) for 16 h. Densitometric scanning indicated a maximal stimulation by (Bu)2cAMP of 30- to 40-fold. Incubation with forskolin (100 microM) and FSH (200 ng/ml) gave rise to a smaller but significant increase in mRNA for RII51. When cultured Sertoli cells were incubated in the presence of 10(-4) M (Bu)2cAMP for varying time periods, there was a biphasic regulation of mRNA for RII51. (Bu)2cAMP caused an initial increase in mRNA for RII51 with maximal levels obtained after 10-16 h, after which a time-dependent decrease was observed. For the other three subunits present in Sertoli cells (RI alpha, RII54, and C alpha) a smaller but significant stimulation by (Bu)2cAMP and forskolin (2-4 fold) was seen. The functional implications of these changes in mRNA levels for the different subunits of cAMP-dependent protein kinase have not yet been revealed. However, our data clearly demonstrate differential regulation of the various subunits of cAMP-dependent protein kinase in Sertoli cells. Furthermore, these results document the presence of distinct adaptational changes taking place at the level of cAMP-dependent protein kinase in response to long term elevation of cAMP.

Animals↗
PubMed1988

Molecular cloning and cell-specific expression of newly discovered subunits of cAMP-dependent protein kinases. Implications for different cellular responses to cAMP.

In recent years a multiplicity in isoforms of cAMP-dependent protein kinases has been revealed. Gene products for four different regulatory subunits (RI alpha, RI beta, RII alpha, RII beta) and two different catalytic subunits (C alpha, C beta) have been identified. We hereby present the molecular cloning of rat cDNAs for RII beta, as well as full-length human cDNAs for RII beta and RI alpha. The amino acid sequences deduced from the cDNAs of the regulatory subunits, revealed dissimilarities which were primarily confined to the N-terminal part of the protein. Based on the vital role in testicular function played by gonadotropin-induced activation of cAMP-dependent protein kinases, mRNA levels for the various subunits of cAMP-dependent protein kinase have been studied in rat testis. A clear pattern of cellular localization of mRNAs for the various subunits of cAMP-dependent protein kinase has been demonstrated. Furthermore, stimulation of Sertoli cells by FSH and cAMP elicited a differential response in mRNA levels for various subunits. A dramatic increase (30-40 fold) in the mRNA for RII beta (3.2 kb) was seen with cAMP stimulation, whereas such treatment had minor effects on mRNAs for RI alpha, RII alpha and C alpha. A distinct pattern of expression for various subunits of cAMP-dependent protein kinase was observed during germ cell differentiation. RI alpha and RI beta were expressed at high levels at early stages of spermatogenesis, whereas unique mRNAs for RII alpha and RII beta appeared in post-meiotic germ cells. Altogether, the present results demonstrate specific expression of mRNAs for different subunits of cAMP-dependent protein kinase in different cell types, during hormonal stimulation and during cellular differentiation. This indicates that the individual subunits may confer specific functional properties to the cAMP-dependent protein kinase holoenzyme and to the cAMP signal pathway of the cell.

Animals↗
PubMed1980

Spatial perspective-taking and pretend play.

To test the hypothesis that pretend play has a facilitatory effect on young children's spatial perspective taking, 45 children were individually engaged in fantasy or non-fantasy interactions with an adult, after which they were administered 3 standard perspective-taking tasks by a blind examiner. Evidence in support of the hypothesis was found.

Child↗