bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECT OF DIETARY AFLATOXIN CONCENTRATION ON THE ASSESSMENT OF GENETIC VARIABILITY OF RESPONSE IN A RANDOMBRED POPULATION OF CHICKENS
Authors: Lanza G M , Washburn K W , Wyatt R D , Marks H L 
Published: January 2021

ABSTRACT
The effect of graded levels of dietary aflatoxin on the assessment of genetic variability of body weight and gain and plasma protein response was tested utilizing the Athens-Canadian randombred population of chickens. Dietary aflatoxin was administered at levels of either 0, 1.25, 2.50 or 5.0 µg/g of diet ad libitum from 7 to 21 days of age to progeny from 58 sire families. Twenty-one-day body weights, gain and plasma protein concentration were used to assess the variation in response.—The administration of increasing levels of aflatoxin resulted in a dose-related decrease of gains and plasma protein concentrations. Plasma protein concentrations were significantly higher among males than females within the control group; however, this difference was reversed as the severity of the aflatoxin challenge increased. Heritability estimates for all responses increased as the level of aflatoxin administered increased. This change was most notable for total plasma protein concentration. Phenotypic correlations for plasma protein concentration and growth measurements tended to diminish with increasing levels of aflatoxin. A similar trend was noted for the genetic correlations; however, a moderate correlation between growth responses and plasma protein response was detected in the 5.0-µg/g aflatoxin treatment group. Genetic correlations were calculated for the same characters between the different levels of aflatoxin. Regardless of which aflatoxin challenges were compared, a very high genetic correlation for 21-day body weight and 7- to 21-day gain was estimated. This variation in growth potential in the toxic environment paralleled that observed in the control environment but at a lower plane. Genetic correlations for plasma protein response across aflatoxin levels diminished as the difference between the levels of aflatoxin administered increased. Plasma protein concentration in the control environment was positively correlated with plasma protein response in groups fed a low level of aflatoxin, but negatively correlated when an aflatoxin challenge of 2.5 µg/g or more was given, suggesting that selection for aflatoxin resistance using plasma protein response as a selection criterion should be made under an aflatoxin stress environment.
HOMOLOGOUS CHROMOSOME PAIRING REMAINS AN UNSOLVED PROBLEM: A TEST OF A POPULAR HYPOTHESIS UTILIZING MAIZE MEIOSIS
Authors: Maguire Marjorie P 
Published: January 2021

ABSTRACT
A recently proposed and popular model for the mechanism of meiotic homologue pairing relies on prior association of nonhomologous chromosome arms of most similar length. According to this model, the diploid complement is organized into two genomic linear chains, each containing the various heterologues in the same sequence. At meiosis, then, appression of the two genomic chains could presumably readily accomplish homologue pairing. This model fails in its simplest form when observations of meiotic pairing of homologues in heterozygotes for arm length alterations are compared with computer-simulated predictions of the model. Contrary to predictions of the model, heterozygotes for arm length changes were found to exhibit only small frequencies of homologue-pairing failure, and this only for a single homologue pair in each case. It is difficult to conceive of a reasonable modification of this model that would be consistent with the observations.
ALTERNATE-2 DISJUNCTION IN THE GERMAN COCKROACH
Authors: Cochran Donald G 
Published: January 2021

ABSTRACT
The evidence in support of two types of alternate disjunction in translocation heterozygotes from the German cockroach, Blattella germanica(L.), is reviewed. When unique cytomorphological features occur in the translocation figure, the two types of alternate disjunction are identifiable regardless of the angle of observation. Photographs supporting this contention are presented for alternate-1 and alternate-2 disjunction in T(7;12)/7;12. Other evidence in support of the existence of alternate-2 disjunction is also presented.
THE INTERACTIONS OF THREE WIDELY SEPARATED LOCI CONTROLLING CONVERSION PROPERTIES OF w LOCUS I IN ASCOBOLUS IMMERSUS
Authors: Helmi Shaker , Lamb Bernard C 
Published: January 2021

ABSTRACT
Gene conversion properties of white (w) ascospore locus I in the Pasadena strains of Ascobolus immersus are controlled by complex interactions between three separate conversion control factors (ccfs), which can give conversion frequencies at wI ranging from less than 1% up to 33%. ccf-2, which has three alleles, is very closely linked to wI but does not usually co-convert with it. ccf-2(K) and ccf-2(91) give lower conversion frequencies than ccf-2(P) and are incompletely dominant to ccf-2(P), with cis/trans position effects on conversion of wI. The "super" factor (Helmi and Lamb 1979) has two interacting but unlinked components, ccf-3E and ccf-4r, which approximately double the conversion frequency at wI. ccf-2 (linkage group VIII), ccf-3 (linkage group I) and ccf-4 are probably all unlinked but interact and specifically control conversion at wI. ccf-3E could code for a diffusible product that affects the action of different ccf-2 alleles, which probably act by controlling the frequency of initiation of hybrid-DNA, which spreads into the adjacent wI locus. ccf-4R could code for a diffusible inhibitor of ccf-3E product, or be an alternative binding site for ccf-3E product. The dominance of ccf-4R depends on which ccf-2 alleles are present in the cross.
SENSITIVITY OF TRYPTOPHAN, TYROSINE AND PHENYLALANINE MUTANTS OF SACCHAROMYCES CEREVISIAE TO PHENETHYL ALCOHOL
Authors: Meade James H , Manney Thomas R 
Published: January 2021

ABSTRACT
Phenethyl alcohol inhibits the growth of many microorganisms. It is believed that the growth inhibition is mediated by its effect on the cell membrane. Differences between sensitive and resistant strains are suggested to be due to alterations in membrane structure. We report that, in some strains, an unexpected relationship exists between auxotrophy for tryptophan, tyrosine and phenylalanine and sensitivity to phenethyl alcohol.
NULLISOMIC TETRAHYMENA. II. A SET OF NULLISOMICS DEFINE THE GERMINAL CHROMOSOMES
Authors: Bruns P J , Brussard T B , Merriam E V 
Published: January 2021

ABSTRACT
Crosses of a diploid Tetrahymena thermophila to a strain with a haploid germinal nucleus result in chromosome loss during meiosis in the haploid. The resulting monosomics can be made nullisomic by a special cross that induces homozygosis of a meiotic product of the germinal nucleus, but retention of the parental somatic nucleus. The creation and testing of single nullisomics for three of the five chromosome pairs and a triple nullisomic missing another pair is presented. Taken together, these strains make possible a series of crosses in which all but one of the chromosomes is missing in one parent. This set of nullisomics can, therefore, be used to map any mutation in Tetrahymena to a specific chromosome.
EFFECTS OF HIGH LEVELS OF DNA ADENINE METHYLATION ON METHYL-DIRECTED MISMATCH REPAIR IN ESCHERICHIA COLI
Authors: Pukkila Patricia J , Peterson Janet , Herman Gail , Modrich Paul , Meselson Matthew 
Published: January 2021

ABSTRACT
Two methods were used in an attempt to increase the efficiency and strand selectivity of methyl-directed mismatch repair of bacteriophage λ heteroduplexes in E. coli. Previous studies of such repair used λ DNA that was only partially methylated as the source of methylated chains. Also, transfection was carried out in methylating strains. Either of these factors might have been responsible for the incompleteness of the strand selectivity observed previously. In the first approach to increasing strand selectivity, heteroduplexes were transfected into a host deficient in methylation, but no changes in repair frequencies were observed. In the second approach, heteroduplexes were prepared using DNA that had been highly methylated in vitro with purified DNA adenine methylase as the source of methylated chains. In heteroduplexes having a repairable cI/+ mismatch, strand selectivity was indeed enhanced. In heteroduplexes with one chain highly methylated and the complementary chain unmethylated, the frequency of repair on the unmethylated chain increased to nearly 100%. Heteroduplexes with both chains highly methylated were not repaired at a detectable frequency. Thus, chains highly methylated by DNA adenine methylase were refractory to mismatch repair by this system, regardless of the methylation of the complementary chain. These results support the hypothesis that methyl-directed mismatch repair acts to correct errors of replication, thus lowering the mutation rate.
MEIOTIC DNA METABOLISM IN WILD-TYPE AND EXCISION-DEFICIENT YEAST FOLLOWING UV EXPOSURE
Authors: Resnick Michael A , Stasiewicz Stanley , Game John C 
Published: January 2021

ABSTRACT
The effects of UV irradiation on DNA metabolism during meiosis have been examined in wild-type (RAD+) and mitotically defined excision-defective (rad1-1) strains of Saccharomyces cerevisiae that exhibit high levels of sporulation. The rad1-1 gene product is not required for normal meiosis: DNA synthesis, RNA synthesis, size of parental and newly synthesized DNA and sporulation are comparable in RAD + and rad1-1 strains. Cells were UV irradiated at the beginning of meiosis, and the fate of UV-induced pyrimidine dimers as well as changes in DNA and DNA synthesis were followed during meiosis. Excision repair of pyrimidine dimers can occur during meiosis and the RAD1 gene product is required; alternate excision pathways do not exist. Although the rate of elongation is decreased, the presence of pyrimidine dimers during meiosis in the rad1-1 strain does not block meiotic DNA synthesis suggesting a bypass mechanism. The final size of DNA is about five times the distance between pyrimidine dimers after exposure to 4 J/m2. Since pyrimidine dimers induced in parental strands of rad1-1 prior to premeiotic DNA synthesis do not become associated with newly synthesized DNA, the mechanism for replicational bypass does not appear to involve a recombinational process. The absence of such association indicates that normal meiotic recombination is also suppressed by UV-induced damage in DNA; this result at the molecular level is supported by observations at the genetic level.
THE INFIDELITY OF CONJUGAL DNA TRANSFER IN ESCHERICHIA COLI
Authors: Kunz Bernard A , Glickman Barry W 
Published: January 2021

ABSTRACT
The accuracy of replication and transfer of a lacI gene on an F' plasmid was measured. Following conjugal transfer of the F', a small but reproducible increase (1.8-fold) in the frequency of lacI - mutations was detected. Among these, however, the frequency of nonsense mutations was 15-fold higher than in the absence of transfer. This corresponds to a 300-fold increase in the rate of base substitutions per round of replication compared with normal vegetative DNA replication. The amber mutational spectra revealed that, following conjugal transfer, mutation frequencies were increased markedly at all sites detected. In addition, an increase in G:C → A:T transitions was noted and was due almost entirely to an enhanced proportion of mutants recovered at the spontaneous hotspots (amber sites 6, 15 and 34). recA-dependent processes were not responsible for the increase in mutation, since similar results were observed with various recA - donor and recipient combinations. These results demonstrate that the fidelity of conjugal DNA replication is considerably lower than that of vegetative DNA replication.
MATERNAL-ZYGOTIC GENE INTERACTIONS DURING FORMATION OF THE DORSOVENTRAL PATTERN IN DROSOPHILA EMBRYOS
Authors: Simpson Pat 
Published: January 2021

ABSTRACT
Maternal-zygotic interactions involving the three genes dorsal (dl), twist (twi) and snail (sna) are described. The results suggest that all three are involved in the process by which the dorsoventral pattern of the Drosophila embryo is established. First, the lethal embryonic mutant phenotypes are rather similar. In homozygous twi or sna embryos invagination of the ventral presumptive mesodermal cells fails to occur, and the resulting embryos are devoid of internal organs. This is very similar to the dominant phenotype described for dl; in the case of dl, however, the effect is a maternal one dependent on the mutant genotype of the female. Second, a synergistic interaction has been found whereby dominant lethality of twi - or sna-bearing zygotes is observed in embryos derived from heterozygous dl females at high temperature. The temperature sensitivity of this interaction permitted definition of a temperature-sensitive period which is probably that of dl. This was found to extend from approximately 12 hr prior to oviposition to 2— 3 hr of embryogenesis. A zygotic action for the dl gene in addition to the maternal effect was revealed by the finding that extra doses of dl + in the zygotes can partially rescue the dominant lethality of heterozygous twi embryos derived from heterozygous dl females. Two possible interpretations of the synergism are considered: (1) twi and sna are activated in the embryos as a result of positional signals placed in the egg as a consequence of the functioning of the dl gene during oogenesis and, thus, play a role in embryonic determination. (2) The gene products of dl + and twi + (or sna +) combine to produce a functional molecule that is involved in the specification of dorsoventral pattern in the early embryo.
CONDITIONING MUTATIONS IN DROSOPHILA MELANOGASTER AFFECT AN EXPERIENCE-DEPENDENT BEHAVIORAL MODIFICATION IN COURTING MALES
Authors: Gailey Donald A , Jackson F Rob , Siegel Richard W 
Published: January 2021

ABSTRACT
One aspect of courtship in male Drosophila melanogaster has been reported to be experience dependent. Males that have courted fertilized females are virtually unresponsive to virgin females for 2-3 hr. Here, this response was utilized as an assay for the effects of conditioning mutations on experience-dependent courtship. Seven strains expressing conditioning mutations (previously isolated and characterized for learning or memory defects in an electrical shock-odor association paradigm, independent of courtship) were all found to be mutant in expression of this experience-dependent change in courtship behavior. By comparison, three control strains that were unselected for conditioning defects all expressed normal experience-dependent courtship. Other results indicate that males of the conditioning-defective strains are able to elicit necessary cues from fertilized females, yet do not then modify their courtship with virgin females. Thus, it is suggested that experience-dependent modification of courtship and the previously reported associative olfactory conditioning with electric shock share common elements of processing. The possibility that experience-dependent courtship represents adaptive behavior is discussed.
Longitudinal Within-Person Associations Between Quality of Social Relations, Structure of Social Relations, and Cognitive Functioning in Older Age
Authors: Luo Minxia , Edelsbrunner Peter Adriaan , Siebert Jelena Sophie , Martin Mike , Aschwanden Damaris 
Published: January 2021

Abstract

Objectives
Individuals’ social connections and interpersonal experiences can both shape and be shaped by cognitive functioning. This study examines longitudinal within-person associations between quality of social relations, structure of social relations, and cognitive functioning in older age.

Methods
We examined 16-year longitudinal data (3 waves) from 497 older adults (M = 66.07 years, SD = 0.83, range = 64–68 years) from the Interdisciplinary Longitudinal Study of Adult Development and Aging. Quality of social relations was measured by scales on perceived emotional support, instrumental support, and social integration. Structure of social relations was measured by self-reported number of leisure time partner types, indicating social network diversity. Cognitive functioning was assessed as a latent construct consisting of five cognitive tests (i.e., Information, Similarities, Letter Fluency, Picture Completion, Block Design). We used a random intercept cross-lagged panel model in the analysis.

Results
At the within-person level, prior quality of social relations, but not structure of social relations, was positively associated with subsequent cognitive functioning. Moreover, prior cognitive functioning was positively associated with subsequent structure of social relations, but not with quality of social relations.

Discussion
Quality of social relations is a protective factor of cognitive aging. Additionally, responding to prior lower cognitive functioning, social network diversity reduced, but quality of social relations did not seem to change. Overall, this study suggested that social relations and cognitive functioning mutually influence each other, but different aspects of social relations (i.e., quality, structure) might have different directional associations with cognitive functioning.
Dementia and Cognitive Decline in Older Adulthood: Are Agricultural Workers at Greater Risk?
Authors: Arora Kanika , Xu Lili , Bhagianadh Divya 
Published: January 2021

Abstract

Objectives
To examine whether long-term exposure to agricultural work is associated with dementia prevalence and the rate of cognitive change in older adulthood.

Method
We employed data from the Health and Retirement Study (1998–2014). Multiple logistic regression was used to determine whether a longest-held job in the agricultural sector was associated with differences in dementia prevalence. We examined if hearing impairment, depression, and physical health indicators mediated the relationship between agricultural work and cognitive functioning. Subgroup analyses were done by age, retirement status, job tenure, and cognitive domain. We employed growth curve models to investigate implications of agricultural work on age trajectories of cognitive functioning.

Results
Longest-held job in agriculture, fishing, and forestry (AFF) was associated with 46% greater odds of having dementia. The relationship between AFF exposure and cognitive functioning was not mediated by hearing impairment, depression, or physical health indicators. Results were stronger among younger and retired older adults as well as those with extensive job tenure. AFF exposure was associated with lower scores in working memory and attention and processing speed. Growth curve models indicated that while agricultural work exposure was associated with lower initial levels of cognitive functioning, over time, the pattern reversed with individuals in non-AFF jobs, showing more accelerated cognitive decline.

Discussion
Consistent with European studies, results from the United States also demonstrate a higher prevalence of dementia among agricultural workers. The cognitive reserve framework may explain the seemingly paradoxical result on age patterning of cognitive performance across older adults with different work histories.
Prpf31 is essential for the survival and differentiation of retinal progenitor cells by modulating alternative splicing
Authors: Li Jingzhen , Liu Fei , Lv Yuexia , Sun Kui , Zhao Yuntong , Reilly Jamas , Zhang Yangjun , Tu Jiayi , Yu Shanshan , Liu Xiliang , Qin Yayun , Huang Yuwen , Gao Pan , Jia Danna , Chen Xiang , Han Yunqiao , Shu Xinhua , Luo Daji , Tang Zhaohui , Liu Mugen 
Published: January 2021

Abstract
Dysfunction of splicing factors often result in abnormal cell differentiation and apoptosis, especially in neural tissues. Mutations in pre-mRNAs processing factor 31 (PRPF31) cause autosomal dominant retinitis pigmentosa, a progressive retinal degeneration disease. The transcriptome-wide splicing events specifically regulated by PRPF31 and their biological roles in the development and maintenance of retina are still unclear. Here, we showed that the differentiation and viability of retinal progenitor cells (RPCs) are severely perturbed in prpf31 knockout zebrafish when compared with other tissues at an early embryonic stage. At the cellular level, significant mitotic arrest and DNA damage were observed. These defects could be rescued by the wild-type human PRPF31 rather than the disease-associated mutants. Further bioinformatic analysis and experimental verification uncovered that Prpf31 deletion predominantly causes the skipping of exons with a weak 5′ splicing site. Moreover, genes necessary for DNA repair and mitotic progression are most enriched among the differentially spliced events, which may explain the cellular and tissular defects in prpf31 mutant retinas. This is the first time that Prpf31 is demonstrated to be essential for the survival and differentiation of RPCs during retinal neurogenesis by specifically modulating the alternative splicing of genes involved in DNA repair and mitosis.
Input associativity underlies fear memory renewal
Authors: Li Wei-Guang , Wu Yan-Jiao , Gu Xue , Fan Hui-Ran , Wang Qi , Zhu Jia-Jie , Yi Xin , Wang Qin , Jiang Qin , Li Ying , Yuan Ti-Fei , Xu Han , Lu Jiangteng , Xu Nan-Jie , Zhu Michael Xi , Xu Tian-Le 
Published: January 2021

Abstract
Synaptic associativity, a feature of Hebbian plasticity wherein coactivation of two inputs onto the same neuron produces synergistic actions on postsynaptic activity, is a primary cellular correlate of associative learning. However, whether and how synaptic associativity are implemented into context-dependent relapse of extinguished memory (i.e. fear renewal) is unknown. Here, using an auditory fear conditioning paradigm in mice, we show that fear renewal is determined by the associativity between convergent inputs from the auditory cortex (ACx) and ventral hippocampus (vHPC) onto the lateral amygdala (LA) that reactivate ensembles engaged during learning. Fear renewal enhances synaptic strengths of both ACx to LA and the previously unknown vHPC to LA monosynaptic inputs. While inactivating either of the afferents abolishes fear renewal, optogenetic activation of their input associativity in the LA recapitulates fear renewal. Thus, input associativity underlies fear memory renewal.
EFFECTS OF TEST-BOLUS AND LOW-DOSE SCAN ON CT PULMONARY ANGIOGRAPHY IMAGE QUALITY IN PATIENTS WITH DIFFERENT BODY MASS INDEXES
Authors: Liu Huijia , Fu Yan , Zhao Bo , Zhang Xuening , Li Guilai , Liu Meizhou , Li Hewen 
Published: January 2021

Abstract
This study aimed to investigate different methods of obtaining high-quality Computed Tomography pulmonary angiography (CTPA) images using low-dose scanning in patients with different body mass index (BMI) values. Sixty patients with suspected pulmonary embolism were grouped based on their BMI values (BMI &lt; 25, designated N, and BMI ≥ 25, designated O) and were assigned to receive either test bolus (TB) or bolus tracking (BT) at conventional (C) or low (L) dose. The effective dose (ED) in the N–TB–L group was lower than in the group N–TB–C (0.56 ± 0.05 vs. 3.78 ± 1.16, p &lt; 0.001), with similar image quality (4.90 ± 0.31 vs. 4.70 ± 0.47, p = 0.120). The ED in the O–TB–L group was lower than in the O–TB–C group (0.54 ± 0.03 vs. 5.14 ± 1.34, p &lt; 0.001), but the group O–TB–C’s image quality was higher (4.65 ± 0.59 vs. 3.95 ± 0.89, p = 0.006). Groups N–TB–L versus O–TB–L, groups N-TB-L versus N–BT-L and groups O–TB–C versus O–BT–C had similar EDs (all ps &gt; 0.05), but the image quality was different (all ps &lt; 0.05). In conclusion, the results showed that the image quality of low-dose CTPA scanning using TB was similar to that of the conventional-dose CTPA in patients with BMI &lt; 25 but was lower in patients with BMI ≥ 25. TB was better than BT for all patients, regardless of BMI, when receiving the same ED.