bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of exercise in the prevention of cancer therapy-related cardiac dysfunction in breast cancer patients undergoing chemotherapy: systematic review
Authors: Murray James , Bennett Hunter , Bezak Eva , Perry Rebecca 
Published: January 2021

Abstract

Aims
Breast cancer (BC) patients undergoing chemotherapy are at risk of developing cancer therapy-related cardiac dysfunction (CTRCD). Exercise has been proposed to prevent CTRCD; however, its effectiveness remains unclear. The aim of this systematic review was to establish the effect of exercise on global longitudinal strain (GLS) and left ventricular ejection fraction (LVEF) in BC patients undergoing chemotherapy, to determine if exercise can prevent the development of CTRCD.

Methods and results
Four databases (Medline, Scopus, eMbase, SPORTDiscus) were searched. Studies were eligible for inclusion if they measured GLS or LVEF prior to and following an exercise intervention of any length in BC patients undergoing chemotherapy and were published in English from 2000 onwards. Risk of bias was evaluated using the QUADAS-2 tool. Of the 398 studies screened, eight were eligible. Changes were similar in exercising (EX) and non-exercising (CON) groups for GLS (EX: pre: −19.6 ± 0.4, post: −20.1 ± 1.0, CON: pre: −20.0 ± 0.4, post: −20.1 ± 1) and LVEF (EX: pre: 58.5 ± 4.1%, post: 58.6 ± 2%, CON: pre: 56.6 ± 4.2%, post: 55.6 ± 4.6%). Exercise maintained or improved peak oxygen uptake (VO2peak) during chemotherapy, while declines were observed in non-exercising groups. The included studies were limited by methodological deficiencies.

Conclusion
The ability of exercise to prevent CTRCD is unclear. However, exercise positively impacts cardiorespiratory fitness in BC patients undergoing chemotherapy. Future research must address the methodological limitations of current research to understand the true effect of exercise in the prevention of CTRCD.
INTEGRATION EFFICIENCY IN DNA-INDUCED TRANSFORMATION OF PNEUMOCOCCUS. II. GENETIC STUDIES OF MUTANT INTEGRATING ALL THE MARKERS WITH A HIGH EFFICIENCY
Authors: Tiraby Gérard , Sicard Michel Armand 
Published: January 2021

ABSTRACT
Transformation of the pneumococcus mutant 401 by DNA's bearing the standard reference marker and several other markers belonging to two unlinked loci has shown that differences in the integration efficiencies of these markers were considerably reduced in this strain compared to the wild-type strain Cl 3. The sensitivities of mutant 401 to ultraviolet light and to X-ray irradiation are the same as those of Cl 3. However, in 401 all the markers tested are more resistant to inactivation as shown by transformation of 401 and Cl 3 by ultraviolet-irradiated DNA. The increase in resistance is greater for low efficiency (LE) markers than for high efficiency (HE) markers.—The decreased discrimination between LE and HE markers in strain 401 is not due to a mechanism related to modification of markers in the transforming DNA by the recipient cells, nor are the proteins inducing competence of the cells responsible for the differences in the integration efficiencies of various markers.—Genetic studies of the fate of recombinants as well as the measure of the amount of DNA taken up have shown that all the markers are integrated in strain 401 by the same recombination process, that specific to high efficiency markers.
INHERITED BIOCHEMICAL VARIATION IN DROSOPHILA MELANOGASTER: NOISE OR SIGNAL? I. SINGLE-LOCUS ANALYSES
Authors: Sing Charles F , Brewer George J , Thirtle Barbara 
Published: January 2021

ABSTRACT
A study was conducted using small effective population size as an experimental design to test selective neutrality of seven isozyme polymorphisms. Loci varied as to the degree to which the decay of heterozygosity over 21 generations was retarded. Selection for heterozygotes, overdominance, is implicated for at least four of seven loci. Of these ADH gave the largest heterozygote excess in the presence of inbreeding. An interaction between the small population size treatment and excess heterozygosity suggests that (1) the loci studied may be selectively neutral and linked to other loci which are under the influence of selection or (2) the selection coefficients for the loci studied are not independent of the background genotype. In either case four of the seven enzymes studied are signaling the operation of selection. The problem of distinguishing the effect of a single marker from that of a chromosome segment is emphasized. The identification of the genetic unit of selection is crucial to any interpretation of the meaning of enzyme polymorphisms.
ISOZYME GENOTYPE-ENVIRONMENT ASSOCIATIONS IN NATURAL POPULATIONS OF THE HARVESTER ANT, POGONOMYRMEX BADIUS
Authors: Tomaszewski Elizabeth K , Schaffer Henry E , Johnson F M 
Published: January 2021

ABSTRACT
Harvester ants (P. badius) were collected from 49 localities in the southeastern U.S. Amylase and naphthylamidase activities were assayed by gel electrophoresis, and the frequencies of alleles controlling electrophoretic variation were calculated. Soil samples were analyzed and plotted against allelic frequencies. Climatographic and genetic data were analyzed by the method of principal components. Statistically significant correlations were found to occur between the patterns of genetic variation, and between the genetic and environmental patterns. These correlations are consistent with a selective basis for the maintenance of isozyme polymorphisms.
RECOMBINATION AT THE BAR LOCUS IN AN INVERTED ATTACHED-X SYSTEM IN DROSOPHILA MELANOGASTER
Authors: Gabay Susan J , Laughnan John R 
Published: January 2021

ABSTRACT
Recombination at the Bar locus in Drosophila melanogaster was investigated in an inverted attached-X system which enhanced the frequency of homozygosis for the Bar region. Females among the progeny of homozygous B mothers were searched for changes of B to BB and to B+. Marker genes were followed and exceptional half-tetrads were analyzed in regard to two hypotheses: that of exchange between obliquely synapsed members of the duplication, which is associated with exchange of outside markers, and that of intrachromosomal exchange, which does not involve recombination of markers.—Recombinant exceptions of B+ /BB genotype, carrying the outside marker combinations predicted on the hypothesis of exchange between obliquely synapsed duplication members, were encountered repeatedly. It is established that B+ and BB strands are reciprocal products of the same event.—Twelve nonrecombinant exceptional strands were isolated; ten of these were B+ and two were BB. Only one of the nonrecombinant half-tetrads offered the opportunity to test the prediction of reciprocity of the intrachromosomal event. Analysis showed the exceptional female to be of the constitution BB/B, a type not expected on the hypothesis. While it could have arisen through some kind of copy error in the repair of a chromatid break, a valid test of the hypothesis of intrachromosomal exchange must rest on the isolation and analysis of more cases of the appropriate exceptional genotype.—In several cases Bar changes were found to be associated with aberrations; all but one of these involved spontaneous, cytologically identifiable deletions.
ASPARAGINE-REQUIRING TUMOR CELL LINES AND THEIR NON-REQUIRING VARIANTS: CYTOGENETICS, BIOCHEMISTRY AND POPULATION DYNAMICS
Authors: Colofiore Joseph , Morrow John , Patterson Manford K 
Published: January 2021

ABSTRACT
Asparagine-requiring Jensen and Walker rat tumor cells and their asparagine-independent variants have been analyzed. The following results were obtained: (1) Both cell lines have very low levels of asparagine synthetase, and non-requiring revertants isolated from these lines have elevated levels of the enzyme. (2) No differences in chromosome number were detected between the parent Jensen line and five Jensen non-requiring revertants isolated from it. (3) Both Jensen and Walker cells undergo asparagineless death when deprived of this amino acid, although the Jensen cells do so at a more rapid rate. (4) Jensen requiring lines are at a selective advantage when grown in competition with non-requiring variants in complete medium, and their growth rate is more rapid when grown separately. The selective coefficients for the variant with respect to the asparagine-requiring parent ASN- line were 0.94 for the competition experiments and 0.83 for growth rate estimates. (5) A somatic cell hybrid between Chinese hamster cells (which require asparagine at low densities, and posses measurable synthetase activity) and the Walker line was found to be asparagine-independent, and it possessed enzyme levels equivalent to the hamster parent. The results of these investigations suggest a parallel with microbial auxotrophic mutants and can be understood in terms of alterations within nuclear structural genes.
DERIVATION OF TK- CLONES FROM REVERTANT TK+ MAMMALIAN CELLS
Authors: Roufa D J , Sadow B N , Caskey C T 
Published: January 2021

ABSTRACT
In order to obtain a large collection of Chinese hamster cell clones defective in thymidine kinase (TK-), BrdUr selection experiments have been performed on wild-type and revertant TK+ cell lines. No clones (&lt; 10-9) were obtained from the wild-type TK+ cell line by single-step selection. In contrast, revertant TK+ clones readily gave rise to stable TK- derivatives (1 - 2 × 10-4). Both wild-type and revertant TK+ clones spontaneously yielded 8-AGr colonies with the same frequency (1 - 5 × 10-6), suggesting that the differences between wild-type and revertant cell lines specifically affected selection of the TK- phenotype. The increased frequency of TK- clones reflects perhaps the number (ploidy) or character of the autosomal TK loci in TK+ revertants, or perhaps the mechanisms which regulate expression of the TK genes. Several mutagens, EMS, MNNG and UV, stimulated the TK+ revertants' frequency of TK- subclones only slightly (&lt; 3-fold). Biochemical and genetic data indicated that the TK- clones derived from one revertant are phenotypically different. The phenotypes displayed by these cell lines are stable and do not depend upon the continued presence of the selective agent.
APPARENT SELECTION OF ENZYME ALLELES IN LABORATORY POPULATIONS OF DROSOPHILA
Authors: Powell Jeffrey R 
Published: January 2021

ABSTRACT
Twelve laboratory populations of recently collected Drosophila willistoni were begun with different frequencies of alleles at three enzyme loci, six populations at 25° and six at 19°. Periodic sampling of the populations allowed monitoring of the frequency changes in allozymes over time.—At Lap-5 (a locus coding for leucine amino peptidase), three alleles converged to the same frequencies in all populations at both temperatures. The apparent equilibrium frequency of the major allele was about.75; this is different from the frequency (.57) found in the natural population from which the experimental populations were begun. Allele frequency changes at the esterase-5 locus (Est-5) were slower but consistent in all cages. It is difficult to determine if an equilibrium has been reached. However, the frequency of the rare allele in all cages is about the same as in wild populations, 5%. Alleles at both Lap-5 and Est-5 are non-randomly associated with inversions in the chromosomes onto which they map. Because of these associations, it is impossible to unambiguously attribute the change in allele frequencies to selection at the loci being observed.—After one year, no significant gene frequency changes were detected at Est-7, the third locus studied.
LOW GENE VARIATION IN DROSOPHILA BUSCKII
Authors: Prakash Satya 
Published: January 2021

ABSTRACT
Study of allozyme variation in D. busckii at thirty loci gives the proportion of polymorphic loci =.166 and the proportion of loci heterozygous per individual =.044. D. busckii has a narrower seasonal and food niche than the other domestic species D. melanogaster which has more allozyme variation. It is suggested that the low gene variation in D. busckii might be due to adaptation of this species to a narrow niche.
CHROMOSOME MARKERS IN MUS MUSCULUS: STRAIN DIFFERENCES IN C-BANDING
Authors: Dev V G , Miller D A , Miller O J 
Published: January 2021

ABSTRACT
The mitotic chromosomes of several inbred strains of mice and a series of F1 hybrids have been analyzed by quinacrine staining and further characterized by the centromeric heterochromatin banding (C-banding). Inbred strains had the same amount of C-banding material on homologous chromosomes but showed variation in the amount on different chromosomes. F1 hybrids showed characteristics of each parent and it appears that the amount of C-banding on each chromosome is a simple inherited polymorphism. In this study 12 different chromosomes could be distinguished by their C-banding, and these can be used as normal chromosome markers.
AN EXPERIMENTAL EVALUATION OF GENETIC CORRELATION
Authors: Rutledge J J , Eisen E J , Legates J E 
Published: January 2021

ABSTRACT
Heritability and genetic correlations realized from both single-trait and antagonistic index selection were compared with paternal half-sib estimates. Primary attention was focused on the genetic correlation between six-week body weight and six-week tail length. Parameters realized from single-trait selection were in excellent agreement with paternal half-sib estimates. However, the realized genetic correlation between six-week body weight and six-week tail length obtained from index selection was significantly greater than the other estimates. Differential inbreeding levels and realized selection intensities were considered and rejected as being causative factors for these results. Linkage disequilibrium probably was not a factor either, as the base population had been randomly mated and randomly selected with a large effective population size for many generations. It was concluded that with antagonistic index selection, the pleiotropic effects of genes may be more powerful in retarding response in aggregate genotype than current theory would suggest. Replication of all selected and control lines allowed the use of between-line estimators of sampling variances of realized genetic parameters in the above comparisons. Generally, standard errors of realized genetic parameters were much smaller than corresponding paternal half-sib standard errors. Thus, selection was an efficient method of estimation.
NINETEEN PARACENTRIC CHROMOSOMAL INVERSIONS IN MICE
Authors: Roderick Thomas H , Hawes Norman L 
Published: January 2021

ABSTRACT
Using mutagens on sperm and spermatids we have produced nineteen chromosomal inversions in mice. The levels of radiation and chemical mutagen we used induced inversions in about one per cent of the animals screened. Nine inversions have been transmitted through successive generations, and the particular frequency of first meiotic anaphase bridges manifested by each inversion remained constant. The cytological properties of first meiotic anaphases varied considerably among the inversions. Chromosomal locations of five inversions are known. Four of the five are fully viable in homozygous condition.
DETECTION AND IDENTIFICATION OF TRANSLOCATIONS BY INCREASED SPECIFIC NONDISJUNCTION IN ASPERGILLUS NIDULANS
Authors: Upshall Alan , Käfer Etta 
Published: January 2021

ABSTRACT
A meiotic technique for visual detection of translocations has been applied to ten mitotically identified interchanges, and three new translocations were discovered using this method. Testcrosses between "standard" strains and potential translocation strains—e.g. strains with newly induced mutants or descendants from translocation crosses—are inspected for the frequency of abnormal-looking colonies. In all heterozygous translocation crosses "abnormals" are increased at least tenfold compared to the average control level of 0.15%. Most of these are disomics, and can be recognized by their characteristic phenotypes. Each translocation produces a few specific types, since nondisjunction is increased mainly in the linkage groups involved in the translocation (50–100-fold over control values). Therefore, translocations were not only detected but often tentatively assigned to linkage groups from the analysis of the disomic progeny in crosses. In addition, this technique allows reciprocal and nonreciprocal translocations to be distinguished, since only the latter produce one-third phenotypically abnormal duplication progeny. While results are clearcut in most cases, occasionally problems are encountered, e.g. when morphological mutants segregate in crosses, or when other genetic factors which increase or reduce the frequency of nondisjunction are present in certain strains.
DIVERGENT OPERONS AND THE GENETIC STRUCTURE OF THE MALTOSE B REGION IN ESCHERICHIA COLI K12
Authors: Hofnung Maurice 
Published: January 2021

ABSTRACT
Complementation and polarity suppression data are interpreted in terms of the genetic structure of the maltose B region. It is proposed that this region comprises two divergent operons. One operon includes malK, a cistron involved in maltose permeation, and lamB the only known cistron specifically involved in λ receptor synthesis. The other operon includes malJ1 and malJ2 which are most probably two different cistrons, both involved in maltose permeation*. It is further assumed that expression of the two operons is controlled by malT, the positive regulatory gene of the maltose system, located in the malA region. The target(s) for the action of the malT product is (are) most likely to be located between malJ1 and malK. There is an indication that the two operons might overlap in the region of their promoters. The structure of such an overlap as well as the possible function of the products of the different cistrons in malB are briefly discussed.
THE SUPPRESSION OF GENE CONVERSION AND INTRAGENIC CROSSING OVER IN ASCOBOLUS IMMERSUS: EVIDENCE FOR MODIFIERS ACTING IN THE HETEROZYGOUS STATE
Authors: Girard J , Rossignol J L 
Published: January 2021

ABSTRACT
Four distinct systems cv1, cv2, cv4 and cv6 behaving as monogenic factors have been found in the stock 28 of Ascobolus immersus. They each specifically suppress gene conversion in a spore pigmentation gene (respectively, b1, b2, b4 and b6). In the gene b2, where this phenomenon was studied in most detail, the effect of cv2 on the suppression of gene conversion is almost total; intragenic recombination is very strongly diminished and crossing over is also affected. In the genes b1, b2 and b4 the suppression of conversion is observed only when the corresponding modifier (cv1, cv2 and cv4) is in the heterozygous condition. It is likely that cv6 acts in the same way on b6. cv1 and b1 on one hand, cv2 and b2 on the other, are very closely linked; no recombination was observed between these modifiers and the corresponding spore pigmentation genes. The same genetic distance is observed between the linked genes b4 and b6 and between cv4 and cv6. This could indicate that these two modifiers are also closely linked to the corresponding genes. A possible effect of cv4 on intergenic recombination between b4 and b6 was shown: here again it acts by diminishing the frequency of recombination when cv4 is in the heterozygous state. The problem of the nature of the cv modifiers is discussed.
THE GENETIC STRUCTURE OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER. XI. GENETIC VARIABILITY IN A LOCAL POPULATION
Authors: Mukai Terumi , Yamaguchi Osamu 
Published: January 2021

ABSTRACT
Six hundred and ninety-one second chromosomes were extracted from a Raleigh, North Carolina population, and the following experimental results were obtained: (1) Salivary gland chromosomes of all lines were observed and the number of inversion-carrying chromosomes was 130, among which 76 carried In(2R)NS, 36 carried In(2L)t, 4 carried In(2L)t and In(2R)NS, and 14 carried different kinds of rare inversions. (2) Viabilities of homozygotes and heterozygotes were examined. The frequency of lethal-carrying chromosomes was 275/691 (or 0.398):70/130 (or 0.538) in inversion-carrying chromosomes and 205/561 (or 0.365) in inversion-free chromosomes. The former is significantly higher than the latter. The average homozygote viability was 0.4342 including lethal lines and 0.7163 excluding those, the average heterozygote viability being 1.0000. The detrimental load to lethal load ratio (D:L ratio) was 0.334/0.501 = 0.67. The average viability of lethal heterozygotes was less than that of lethal-free heterozygotes, significantly in inversion-free individuals but not significantly so in inversion-carrying individuals. Inversion heterozygotes seem to have slightly better viability than the inversion-free heterozygotes on the average, but not significantly so. (3) The average degree of dominance of viability polygenes was estimated to be 0.293 ± 0.071 for all heterozygotes whose component chromosomes had better viabilities than 0.6 of the average heterozygote viability, 0.177 ± 0.077 for inversion-free heterozygotes and 0.489 ± 0.082 for inversion heterozygotes. (4) Mutation rates of viability polygenes and lethal genes were estimated on the basis of genetic loads and average degrees of dominance of lethal genes and viability polygenes. Estimates were very close to those obtained by direct estimation. (5) Possible overdominance and epistasis were detected, but the magnitude must be very small. (6) The effective size of the population was estimated to be much greater than 10,000 by using the allelism rate of lethal-carrying chromosomes (0.0040) and their frequency.—On the basis of these findings and the comparison with the predicted result (Mukai and Maruyama 1971), the mechanisms of the maintenance of genetic variability in the population are discussed.
SAMPLING VARIANCES OF HETEROZYGOSITY AND GENETIC DISTANCE
Authors: Nei Masatoshi , Roychoudhury A K 
Published: January 2021

ABSTRACT
Mathematical formulae for the sampling variances of average heterozygosity and Nei's genetic distance are developed. These sampling variances are decomposed into their two components, i.e. the inter-locus and intra-locus variances. The relationship between the number of loci and the number of individuals per locus to be examined for estimating average heterozygosity and genetic distance is also discussed. The utility of the inter-locus variance of heterozygosity for studying the mechanism of maintenance of genetic variability in populations is indicated.
THE RELATIVE NUMBERS OF DIFFERENT GENES IN EXPONENTIAL MICROBIAL CULTURES
Authors: Painter P R 
Published: January 2021

ABSTRACT
It is shown that the results of the marker frequency analysis of Sueoka and Yoshikawa (1965) can be derived as very good approximations from a model where the rigid assumptions of their analysis are relaxed to take into account statistical variations in the timing of cell events. It is further shown that the expression for the amount of DNA per cell can be approximated by an elementary exponential function of the growth rate, and this result facilitates genetic mapping by DNA hybridization techniques. An analysis of recent data on gene frequencies in Escherichia coli corroborates a model of symmetric, bidirectional chromosome replication with a replication time of approximately thirty minutes.