bluuebunny/crossref_metadata_2025 huggingface dataset:
Electro-deposition synthesis of tube-like collagen–chitosan hydrogels and their biological performance
Authors: Li Ping , He Lang , Liu Xueling , Fan Shengxuan , Yuan Yifan , Zhang Juntao , Wang Haibo , Li Sheng
Published: January 2021

Electro-deposition is a smart, safe and efficient method for biomaterial manufacturing. Collagen, a functional protein with excellent biocompatibility and biosafety, is a promising candidate for tissue engineering and biomedical applications. However, there are few reports on electro-deposition of biomaterials using collagen without electrically or magnetically active nanoparticles. In this study, electro-deposition was employed to swiftly fabricate tube-like collagen–chitosan hydrogels in a mild environment. Fourier transform infrared spectroscopy was employed to analyze the ingredients of the tube-like hydrogels. The result showed that the hydrogels contained both collagen and chitosan. The distribution and content of collagen in the hydrogels was further measured by hematoxylin–eosin staining and hydroxyproline titration. Collagen was distributed homogeneously and its content was related to the initial collagen:chitosan ratio. The tension resistance of the composite gels and the thermal stability of collagen in the composites were obviously enhanced by the chitosan doping. Meanwhile, the tube-like hydrogels retained a good ability to promote cell proliferation of collagen. This method offers a convenient approach to the design and fabrication of collagen-based materials, which could effectively retain the bioactivity and biosafety of collagen and furnish a new way to enhance the stability of collagen and the tensile strength of collagen-based materials.
Symmetric discrete AKP and BKP equations
Authors: Li Shangshuai , Nijhoff Frank W , Sun Ying-ying , Zhang Da-jun
Published: January 2021

We show that when KP (Kadomtsev–Petviashvili) τ functions allow special symmetries, the discrete BKP equation can be expressed as a linear combination of the discrete AKP equation and its reflected symmetric forms. Thus the discrete AKP and BKP equations can share the same τ functions with these symmetries. Such a connection is extended to 4 dimensional (i.e. higher order) discrete AKP and BKP equations in the corresponding discrete hierarchies. Various explicit forms of such τ functions, including Hirota’s form, Gramian, Casoratian and polynomial, are given. Symmetric τ functions of Cauchy matrix form that are composed of Weierstrass σ functions are investigated. As a result we obtain a discrete BKP equation with elliptic coefficients.
Efficiency of the introduction of different Ca levels in broiler chicken diets as part of dietary fiber extrudates
Authors: Kholodilina T N
Published: January 2021

One of the main tasks of industrial poultry farming is the introduction of new technologies that reduce the cost of obtaining products through the use of non-traditional feed components. The aim of the research is to study the effectiveness of the technology of extrusion processing of feed components at the stage of interaction with the biome of the poultry digestive system. It was found that the inclusion of extruded bran in the diet is accompanied by a significant increase in the number of Lactobacillus. Moreover, the most significant growth was observed in the intestines of a bird receiving an extrudate with an input of 20 % calcium. This group was also characterized by a maximum growth of Escherichia 7.3 times in comparison with the control. The introduction of an extrudate with a content of 10 % calcium is associated with a decrease in the number of E. coli in the cecum of chickens. Thus, pretreatment of non-starch polysaccharides together with calcium in the extruder stimulates abdominal digestion of chickens, which indicates the possibility of their use in industrial production.
The influence of soil treatment and irrigation methods on tomato yield and quality in the lowlands of Dagestan
Authors: Kurbanov S A , Magomedova D S , Dzhambulatova A Z
Published: January 2021

A positive effect of irrigation of meadow-chestnut soil on soil fertility was described for the dry-steppe zone of Dagestan. The object of research was tomatoes (Gift variety) planted on irrigated lands of Dagestan. The subject of research is tillage and irrigation methods. The influence of agrotechnical methods on agrophysical soil properties, level and quality of tomatoes was determined. Maintaining the moisture of the active soil layer within 80…100 % NV can optimize agrophysical fertility indicators of the meadow-chestnut soil. In combination with tillage at a depth of 0.23…0.25 m, it ensures the tomato yield of 80…86 t/ha.
Tailoring surface plasmon-exciton polariton for high-performance refractive index monitoring
Authors: Srivastava Triranjita , Jha Rajan
Published: January 2021

We report coupling between surface plasmon polariton (SPP) and surface exciton polariton (SEP) as hybrid mode; surface plasmon exciton polariton (SPEP) that can be utilized for highly sensitive and accurate refractive index monitoring. The proposed structure comprises of a thin layer of organic semiconductor; J-aggregate cyanine dye (5,5′,6,6′-tetrachloro-1,10-diethyl-3, 30-di(4-sulfobutyl) benzimidazolo-carbocyanine (TDBC)) having, strong dipole moment resulting from linear chain-like structure, over plasmon active metal coated on prism. It is found that due to SPEP excitation, the sensitivity of the proposed refractometer is ∼84% higher as compared to that of conventional plasmonic sensor at λ = 532 nm and has high tolerance towards 10 nm of metal thickness. The wavelength dependent performance analysis of SPEP modes reveals that for high energy SPEP (mode-1 at λ = 532 nm), sensitivity as well as figure of merit (FOM) of the proposed refractometer is ∼80% and ∼200% respectively higher than low energy SPEP (mode-2 at λ = 633 nm). We believe that the study will open a new window for a diverse range of biochemical and gaseous sensing applications.
Twistronics: a turning point in 2D quantum materials
Authors: Hennighausen Zachariah , Kar Swastik
Published: January 2021

Moiré superlattices—periodic orbital overlaps and lattice-reconstruction between sites of high atomic registry in vertically-stacked 2D layered materials—are quantum-active interfaces where non-trivial quantum phases on novel phenomena can emerge from geometric arrangements of 2D materials, which are not intrinsic to the parent materials. Unexpected distortions in band-structure and topology lead to long-range correlations, charge-ordering, and several other fascinating quantum phenomena hidden within the physical space between the (similar or dissimilar) parent materials. Stacking, twisting, gate-modulating, and optically-exciting these superlattices open up a new field for seamlessly exploring physics from the weak to strong correlations limit within a many-body and topological framework. It is impossible to capture it all, and the aim of this review is to highlight some of the important recent developments in synthesis, experiments, and potential applications of these materials.
A Review of Ectoparasitic Fungi Associated With Termites
Authors: Wilson Megan , Barden Phillip , Ware Jessica
Published: January 2021

Termites and ectoparasitic fungi have been at odds for millions of years. Surprisingly, fungi rarely kill their host and termites are continuously parasitized, albeit at low rates. ‘Termitophilous’ fungi have succeeded in the difficult task of infiltrating the ecological fortress of social immunity that is the termite colony. Here we review 34 definitive ectoparasitic fungal species from nine genera specialized to infest the cuticle of 50 + termite species. In general, reports of fungal ectoparasites on termites are underestimated and the actual prevalence of infestation is likely much greater in nature. In this review, we synthesize >120 yr of reports and studies on ectoparasitic fungi and their termite hosts to present an update to where our knowledge rests and where the proceeding steps should be focused. In reviewing this material, we aim to unite knowledge from two disciplines, entomology and mycology, creating a literary source useful for entomologists and mycologists alike. We provide a comprehensive summary of all fungal genera, illustrations showing morphological distinctions and development on the termite host, a glossary of mycological terminology, and an updated chart of the biogeography of these groups. Additionally, we provide a phylogenetic summary of parasite lineages and their known hosts as well as the first review of molecular evidence obtained from these fungal species.
New Horizons in the impact of frailty on pharmacokinetics: latest developments
Authors: Hilmer Sarah N , Kirkpatrick Carl M J
Published: January 2021

Frail older people have a high prevalence of drug use and are susceptible to adverse drug reactions. The physiological changes of frailty are likely to affect pharmacokinetics and pharmacodynamics. We reviewed the methods and findings of published studies of pharmacokinetics in frailty. Nine studies describing pharmacokinetics and an additional three of pharmacokinetic pathways in frail older people were identified. Most pharmacokinetic studies investigated a single administration of a medication, dose or formulation, in small populations, often with limited representation of males or females, and applied variable definitions of frailty. Pharmacokinetic sampling designs generally utilised saturated sampling followed by analysis based on the trapezoidal rule for area under the curve, with more recent studies using sparser sampling and more sophisticated modelling to obtain individual and population values of all pharmacokinetic parameters. Overall, the pharmacokinetic studies reported only small changes in some parameters for some drugs with frailty, with the most consistent change reduced hepatic clearance in frail older people. Recommendations for future studies of pharmacokinetics in frailty include (i) standard objective definitions of frailty; (ii) larger studies including people with mild, moderate and severe frailty; (iii) population pharmacokinetic modelling to allow sparser sampling and consideration of multiple influences on pharmacokinetics; (iv) physiologically based modelling as the physiology of frailty emerges and (v) longitudinal pharmacokinetic studies of chronic drug therapy from middle to old age and from robust to pre-frail to frail, including pre-clinical studies. These data, accompanied by pharmacodynamics data in frailty, will inform safe, effective prescribing for frail older people.
Optimising the conservation of genetic diversity of the last remaining population of a critically endangered shrub
Authors: Thomas William J W , Anthony Janet M , Dobrowolski Mark P , Krauss Siegfried L
Published: January 2021

An understanding of genetic diversity and the population genetic processes that impact future population viability is vital for the management and recovery of declining populations of threatened species. Styphelia longissima (Ericaceae) is a critically endangered shrub, restricted to a single fragmented population near Eneabba, 250 km north of Perth, Western Australia. For this population, we sought to characterize population genetic variation and its spatial structure, and aspects of the mating portfolio, from which strategies that optimize the conservation of this diversity are identified. A comprehensive survey was carried out and 220 adults, and 106 seedlings from 14 maternal plants, were genotyped using 13 microsatellite markers. Levels of genetic variation and its spatial structure were assessed, and mating system parameters were estimated. Paternity was assigned to the offspring of a subsection of plants, which allowed for the calculation of realized pollen dispersal. Allelic richness and levels of expected heterozygosity were higher than predicted for a small isolated population. Spatial autocorrelation analysis identified fine-scale genetic structure at a scale of 20 m, but no genetic structure was found at larger scales. Mean outcrossing rate (tm = 0.66) reflects self-compatibility and a mixed-mating system. Multiple paternity was low, where 61 % of maternal siblings shared the same sire. Realized pollen dispersal was highly restricted, with 95 % of outcrossing events occurring at 7 m or less, and a mean pollen dispersal distance of 3.8 m. Nearest-neighbour matings were common (55 % of all outcross events), and 97 % of mating events were between the three nearest-neighbours. This study has provided critical baseline data on genetic diversity, mating system and pollen dispersal for future monitoring of S. longissima. Broadly applicable conservation strategies such as implementing a genetic monitoring plan, diluting spatial genetic structure in the natural population, genetically optimizing ex situ collections and incorporating genetic knowledge into translocations will help to manage the future erosion of the high genetic variation detected.
A comprehensive overview and critical evaluation of gene regulatory network inference technologies
Authors: Zhao Mengyuan , He Wenying , Tang Jijun , Zou Quan , Guo Fei
Published: January 2021

Gene regulatory network (GRN) is the important mechanism of maintaining life process, controlling biochemical reaction and regulating compound level, which plays an important role in various organisms and systems. Reconstructing GRN can help us to understand the molecular mechanism of organisms and to reveal the essential rules of a large number of biological processes and reactions in organisms. Various outstanding network reconstruction algorithms use specific assumptions that affect prediction accuracy, in order to deal with the uncertainty of processing. In order to study why a certain method is more suitable for specific research problem or experimental data, we conduct research from model-based, information-based and machine learning-based method classifications. There are obviously different types of computational tools that can be generated to distinguish GRNs. Furthermore, we discuss several classical, representative and latest methods in each category to analyze core ideas, general steps, characteristics, etc. We compare the performance of state-of-the-art GRN reconstruction technologies on simulated networks and real networks under different scaling conditions. Through standardized performance metrics and common benchmarks, we quantitatively evaluate the stability of various methods and the sensitivity of the same algorithm applying to different scaling networks. The aim of this study is to explore the most appropriate method for a specific GRN, which helps biologists and medical scientists in discovering potential drug targets and identifying cancer biomarkers.
Association Between Chronic Use of Immunosuppresive Drugs and Clinical Outcomes From Coronavirus Disease 2019 (COVID-19) Hospitalization: A Retrospective Cohort Study in a Large US Health System
Authors: Andersen Kathleen M , Mehta Hemalkumar B , Palamuttam Natasha , Ford Daniel , Garibaldi Brian T , Auwaerter Paul G , Segal Jodi , Alexander G Caleb
Published: January 2021

Background

It is unclear whether chronic use of immunosuppressive drugs worsens or improves the severity of coronavirus disease 2019 (COVID-19), with plausible mechanisms for both.

Methods

Retrospective cohort study in 2121 consecutive adults with acute inpatient hospital admission between 4 March and 29 August 2020 with confirmed or suspected COVID-19 in a large academic health system, with adjustment for confounding with propensity score–derived stabilized inverse probability of treatment weights. Chronic immunosuppression was defined as prescriptions for immunosuppressive drugs current at the time of admission. Outcomes included mechanical ventilation, in-hospital mortality, and length of stay.

Results

There were 2121 patients admitted with laboratory-confirmed (1967, 93%) or suspected (154, 7%) COVID-19 during the study period, with a median age of 55 years (interquartile range, 40–67). Of these, 108 (5%) were classified as immunosuppressed before COVID-19, primarily with prednisone (>7.5 mg/day), tacrolimus, or mycophenolate mofetil. Among the entire cohort, 311 (15%) received mechanical ventilation; the median (interquartile range) length of stay was 5.2 (2.5–10.6) days, and 1927 (91%) survived to discharge. After adjustment, there were no significant differences in the risk of mechanical ventilation (hazard ratio [HR], .79; 95% confidence interval [CI], .46–1.35), in-hospital mortality (HR, .66; 95% CI, .28–1.55), or length of stay (HR, 1.16; 95% CI, .92–1.47) among individuals with immunosuppression and counterparts.

Conclusions

Chronic use of immunosuppressive drugs was neither associated with worse nor better clinical outcomes among adults hospitalized with COVID-19 in one US health system.
The Duration of Protection from Azithromycin Against Malaria, Acute Respiratory, Gastrointestinal, and Skin Infections When Given Alongside Seasonal Malaria Chemoprevention: Secondary Analyses of Data from a Clinical Trial in Houndé, Burkina Faso, and Bougouni, Mali
Authors: Phiri Mphatso Dennis , Cairns Matthew , Zongo Issaka , Nikiema Frederic , Diarra Modibo , Yerbanga Rakiswendé Serge , Barry Amadou , Tapily Amadou , Coumare Samba , Thera Ismaila , Kuepfer Irene , Milligan Paul , Tinto Halidou , Dicko Alassane , Ouédraogo Jean Bosco , Greenwood Brian , Chandramohan Daniel , Sagara Issaka
Published: January 2021

Background

Mass drug administration (MDA) with azithromycin (AZ) is being considered as a strategy to promote child survival in sub-Saharan Africa, but the mechanism by which AZ reduces mortality is unclear. To better understand the nature and extent of protection provided by AZ, we explored the profile of protection by time since administration, using data from a household-randomized, placebo-controlled trial in Burkina Faso and Mali.

Methods

Between 2014 and 2016, 30 977 children aged 3–59 months received seasonal malaria chemoprevention (SMC) with sulfadoxine-pyrimethamine plus amodiaquine and either AZ or placebo monthly, on 4 occasions each year. Poisson regression with gamma-distributed random effects, accounting for the household randomization and within-individual clustering of illness episodes, was used to compare incidence of prespecified outcomes between SMC+AZ versus SMC+placebo groups in fixed time strata post-treatment. The likelihood ratio test was used to assess evidence for a time-treatment group interaction.

Results

Relative to SMC+placebo, there was no evidence of protection from SMC+AZ against hospital admissions and deaths. Additional protection from SMC+AZ against malaria was confined to the first 2 weeks post-administration (protective efficacy (PE): 24.2% [95% CI: 17.8%, 30.1%]). Gastroenteritis and pneumonia were reduced by 29.9% [21.7; 37.3%], and 34.3% [14.9; 49.3%], respectively, in the first 2 weeks postadministration. Protection against nonmalaria fevers with a skin condition persisted up to 28 days: PE: 46.3% [35.1; 55.6%].

Conclusions

The benefits of AZ-MDA are broad-ranging but short-lived. To maximize impact, timing of AZ-MDA must address the challenge of targeting asynchronous morbidity and mortality peaks from different causes.
Improving the Prediction of Relapse After Nucleos(t)ide Analogue Discontinuation in Patients With Chronic Hepatitis B
Authors: Song Do Seon , Jang Jeong Won , Yoo Sun Hong , Kwon Jung Hyun , Nam Soon Woo , Bae Si Hyun , Choi Jong Young , Yoon Seung Kew
Published: January 2021

Background

Current guidelines recommend rules for stopping nucleos(t)ide analogues (NAs) in patients with chronic hepatitis B (CHB), but off-therapy relapse is still high. This study aimed to identify predictors of off-therapy relapse and improve existing stopping rules.

Methods

This retrospective study included 488 patients with CHB (262 hepatitis B e antigen [HBeAg]–positive and 226 HBeAg-negative) who discontinued NAs. Posttreatment relapse was investigated.

Results

During the median follow-up period of 73.3 months, the cumulative 5-year and 10-year virologic relapse (VR) rates were 73.5% and 76.1%, respectively. In HBeAg-positive patients, end-of-therapy hepatitis B surface antigen (HBsAg) levels (hazard ratio [HR], 1.93 [95% confidence interval {CI}, 1.42–2.61]) and consolidation duration ≥2 years (HR, 0.31 [95% CI: .17–.58]) were independent predictors of VR. Consolidation ≥2 years and low HBsAg levels (≤560 IU/mL) significantly lowered VR rates. In HBeAg-negative patients, only the HBsAg level (HR, 1.61 [95% CI: 1.24–2.11]) was independently predictive of VR. Cirrhosis was significantly associated with higher VR rates in HBeAg-negative patients with low HBsAg levels (≤800 IU/mL). Combining end-of-therapy HBsAg levels with current stopping rules or consolidation duration further reduced off-therapy relapse, with 2-year VR rates of approximately 15%–25% in HBeAg-positive patients and 35% in HBeAg-negative patients.

Conclusions

End-of-therapy HBsAg levels, consolidation duration, and cirrhosis are key determinants of off-therapy relapse. Together with low HBsAg levels, extended consolidation therapy for ≥2 years should be ensured, and cirrhotic patients should continue NAs even if low HBsAg levels are achieved. A combination of these parameters will help identify individuals at low risk of relapse and significantly improve the predictive ability of the existing stopping rules.
The landscape of nutri-informatics: a review of current resources and challenges for integrative nutrition research
Authors: Chan Lauren , Vasilevsky Nicole , Thessen Anne , McMurry Julie , Haendel Melissa
Published: January 2021

Informatics has become an essential component of research in the past few decades, capitalizing on the efficiency and power of computation to improve the knowledge gained from increasing quantities and types of data. While other fields of research such as genomics are well represented in informatics resources, nutrition remains underrepresented. Nutrition is one of the most integral components of human life, and it impacts individuals far beyond just nutrient provisions. For example, nutrition plays a role in cultural practices, interpersonal relationships and body image. Despite this, integrated computational investigations have been limited due to challenges within nutrition informatics (nutri-informatics) and nutrition data. The purpose of this review is to describe the landscape of nutri-informatics resources available for use in computational nutrition research and clinical utilization. In particular, we will focus on the application of biomedical ontologies and their potential to improve the standardization and interoperability of nutrition terminologies and relationships between nutrition and other biomedical disciplines such as disease and phenomics. Additionally, we will highlight challenges currently faced by the nutri-informatics community including experimental design, data aggregation and the roles scientific journals and primary nutrition researchers play in facilitating data reuse and successful computational research. Finally, we will conclude with a call to action to create and follow community standards regarding standardization of language, documentation specifications and requirements for data reuse. With the continued movement toward community standards of this kind, the entire nutrition research community can transition toward greater usage of Findability, Accessibility, Interoperability and Reusability principles and in turn more transparent science.
New perspectives on the distribution of farm incomes and the redistributive impact of CAP payments
Authors: Piet Laurent , Desjeux Yann
Published: January 2021

We contribute to understanding the impact of potential drivers of farm income inequality and the redistributive impact of Common Agricultural Policy (CAP) payments. Our approach provides information at any quantile of the income distribution, in contrast to the widely used Gini coefficient. Income growth and inequality dynamics of French commercial farms between 2000 and 2017 are found to be explained by a change in both income levels and farm characteristics. Further, CAP payments are shown to participate in levelling off income inequalities, with Pillar 1 and 2 payments performing differently along the distribution. Our results may help inform on-going policy debates about fairness in the distribution of farm support and structural change implications for the future of European agriculture.
Social network characteristics as correlates and moderators of older adults’ quality of life—the SHARE study
Authors: Schmidt Tanja , Christiansen Lars B , Schipperijn Jasper , Cerin Ester
Published: January 2021

Background

The quality of life (QoL) of older adults is a key aspect of healthy ageing, and older adults’ socioeconomic status (SES), the neighbourhood they live in and their social networks (SN) are known to impact QoL. However, little is known about the interaction between these concepts. The aim was to examine how SN, SES and neighbourhood type are associated with QoL in older adults.

Methods

Wave 4 (year 2011) and wave 6 (year 2015) data from the longitudinal Survey of Health, Ageing and Retirement in Europe were used for the analysis. Multilevel regression models estimated the associations including 34 792 participants from wave 4 and 67 334 participants from wave 6 from 16 countries (mean age = 66.45 years). The outcome variable was QoL, independent variables were SES (education and making end meet) and neighbourhood type (housing type and housing area), and SN variables (satisfaction and size) were the moderators.

Results

SES and SN variables were positively associated with QoL. Living in a house or duplex was positively associated with QoL compared with living in a farmhouse. SN moderated the association between education and QoL. The effect of area type on QoL was moderated by SN size. SN satisfaction was an independent correlate of QoL.

Conclusion

Older adults’ satisfaction with their SN may be more important than having a large SN. Low SES older adults may be more prone to having weak SN. Maintaining and creating supportive SN may attenuate the negative effects of low SES or less favourable neighbourhood characteristics.
Seemingly trivial secondary factors may determine microbial competition: a cautionary tale on the impact of iron supplementation through corrosion
Authors: Stouten Gerben R , Hamers Kelly , van Tatenhove-Pel Rinke J , van der Knaap Eline , Kleerebezem Robbert
Published: January 2021

Microbial community engineering aims for enrichment of a specific microbial trait by imposing specific cultivation conditions. This work demonstrates that things may be more complicated than typically presumed and that microbial competition can be affected by seemingly insignificant variables, like in this case the type of acid used for pH control. Aerobic bioreactors pulse fed with acetate operated with hydrochloric acid resulted in the enrichment of Plasticicumulans acidivorans, and changing the pH controlling agent to sulfuric acid shifted the community towards Zoogloea sp. Further research demonstrated that the change in community structure was not directly caused by the change in acid used for pH control, but resulted from the difference in corrosive strength of both acids and the related iron leaching from the bioreactor piping. Neither system was iron deficient, suggesting that the biological availability of iron is affected by the leaching process. Our results demonstrate that microbial competition and process development can be affected dramatically by secondary factors related to nutrient supply and bioavailability, and is way more complex than generally assumed in a single carbon substrate limited process.
Porosity and the Transnational: Travelling Theory between Naples and Frankfurt (Walter Benjamin, Asja Lacis and Ernst Bloch)
Authors: Smith Douglas
Published: January 2021

Since its foregrounding in Walter Benjamin and Asja Lacis’s essay on Naples in 1925, the concept of porosity has become a topos in discussions of that city, of Italy and of urban planning in general, to the point of receiving criticism in some quarters for its imprecision and over-use. The aim of this article is to explore the background to the term and its possible relevance to more recent transnational models of culture. This involves tracing the emergence of porosity in the work of Germanophone intellectuals travelling in Italy in the 1920s and its relation to the paradigm of travelling theory developed by Edward Said, itself one of the precursors of current models of transnationalism. Ultimately, the history of porosity reveals weaknesses and strengths that anticipate some of the problems and opportunities encountered by present attempts to understand cultural identity and interaction in transnational terms.
ENZYME VARIABILITY IN THE DROSOPHILA WILLISTONI GROUP. IV. GENIC VARIATION IN NATURAL POPULATIONS OF DROSOPHILA WILLISTONI
Authors: Ayala Francisco J , Powell Jeffrey R , Tracey Martin L , Mourão Celso A , Pérez-Salas Santiago
Published: January 2021

We describe allelic variation at 28 gene loci in natural populations of D. willistoni. Seventy samples were studied from localities extending from Mexico and Florida, through Central America, the West Indies, and tropical South America, down to South Brazil. At least several hundred, and often several thousand, genomes were sampled for each locus. We have discovered a great deal of genetic variation. On the average, 58% loci are polymorphic in a given population. (A locus is considered polymorphic when the frequency of the most common allele is no greater than 0.95). An individual fly is heterozygous, on the average, at 18.4% loci.—Concerning the pattern of the variation, the most remarkable finding is the similarity of the configuration of allelic frequencies from locality to locality throughout the distribution of the species. Our observations support the conclusion that balancing natural selection is the major factor responsible for the considerable genetic variation observed in D. willistoni.
GENETIC MECHANISMS OF RARE MATINGS OF THE YEAST SACCHAROMYCES CEREVISIAE HETEROZYGOUS FOR MATING TYPE
Authors: Gunge Norio , Nakatomi Yasuo
Published: January 2021

Yeast heterozygous for mating type lacks the ability to conjugate as judged by the mass-mating technique and accordingly is designated "non-mater". However, the non-mater shows rare mating ability with a frequency of less than 10−6. In the present study, the RD auxotroph mating method was mainly employed with the intention of examining the rare mating ability of various non-maters, using lactate ethanol minimal medium as a selective medium for hybridization. Crosses of aα × a, aα × a, aaα × a, aαα × a, etc. resulted in the production of respective hybrids with a relatively high frequency of about 10−6 to 10−7, whereas crosses of aaα × a, aαα × α, aaαα × a, aaαα × α, etc. resulted in hybrids with an extremely low frequency of about less than 10−8. Genetic analyses revealed that the rare matings were mostly caused by the presence of cells derived from the non-maters in which mating type had converted to a homozygous genotype. Mitotic recombination was shown to be a likely explanation for most of the conversion, judging from associated exchange of an outside marker, thr4. By successive employment of the RD auxotroph mating method, it was possible to produce a series of polyploid yeasts, triploids to octoploids. The DNA content and the cell volume were observed to increase parallel to the elevated ploidy states.
DIRECTED EVOLUTION OF METABOLIC PATHWAYS IN MICROBIAL POPULATIONS. I. MODIFICATION OF THE ACID PHOSPHATASE pH OPTIMUM IN S. CEREVISIAE
Authors: Francis J C , Hansche P E
Published: January 2021

An experimental system for directing the evolution of enzymes and metabolic pathways in microbial populations is proposed and an initial test of its power is provided.—The test involved an attempt to genetically enhance certain functional properties of the enzyme acid phosphatase in S. cerevisiae by constructing an environment in which the functional changes desired would be "adaptive". Naturally occurring mutations in a population of 109 cells were automatically and continuously screened, over 1,000 generations, for their effect on the efficiency (Km) and activity of acid phosphatase at pH 6, and for their effect on the efficiency of orthophosphate metabolism.—The first adaptation observed, M1, was due to a single mutational event that effected a 30% increase in the efficiency of orthophosphate metabolism. The second, M2, effected an adaptive shift in the pH optimum of acid phosphatase and an increase in its activity over a wide range of pH values (an increment of 60% at pH 6). M2 was shown to result from a single mutational event in the region of the acid phosphatase structural gene. The third, M3, effected cell clumping, an adaptation to the culture apparatus that had no effect on phosphate metabolism.—The power of this system for directing the evolution of enzymes and of metabolic pathways is discussed in terms of the kinetic properties of the experimental system and in terms of the results obtained.
TEMPERATURE-SENSITIVE MUTATIONS IN DROSOPHILA MELANOGASTER. IX. DOMINANT COLD-SENSITIVE LETHALS ON THE AUTOSOMES
Authors: Rosenbluth Raja , Ezell Dean , Suzuki David T
Published: January 2021

Ethyl methanesulfonate-treated autosomes were screened for the presence of dominant cold-sensitive (DCS) lethal mutations in Drosophila melanogaster. None was found among 6,552 treated and 168 untreated third chromosomes. Twenty-three DCS-L chromosomes which caused death at 17°C but survived at 22°C and 29°C were recovered from 5,046 mutagenized chromosome 2's.—The DCS-L mutations all mapped around dp and appeared to be functionally allelic. Lethality of heterozygotes for most of the DCS-L's occurred over a prolonged interval from the embryonic through the larval instars. Prolonged incubation at 17°C did not demonstrate any maternal effect on zygotic survival.
DENSITY TRANSFER STUDIES OF DNA ISOLATED FROM BACILLUS SUBTILIS AFTER EXPOSURE TO PHENETHYL ALCOHOL
Authors: Zyskind J Weaver , Pattee P A
Published: January 2021

The aim of this study was to determine whether there are specific weak points in the Bacillus subtilis chromosome and if so whether the replication point is the site of breakage. To answer these questions, B. subtilis chromosomes were partially labeled with 5-bromodeoxyuridine (5-BUdR). Sheared or unsheared preparations of partially labeled chromosomes which may or may not contain replication forks were analyzed for the distribution of genetic markers in a CsCl density gradient. Two sets of experiments based upon the density transfer experiments of Yoshikawa and Sueoka (1963) were performed: (1) experiments in which the origin of the chromosome was labeled and (2) experiments in which the terminus of the chromosome was labeled. In the first experiment, strain 23 (thy-, his-) spores were germinated in the presence of 5-BUdR for various lengths of time and then transferred to fresh medium containing phenethyl alcohol (PEA) and thymidine (TdR). The DNA was isolated before and after transfer to PEA and TdR. In the second experiment strain 23 (thy-, his-) spores were germinated in the presence of TdR and then PEA was added. After various lengths of time transfer was made to fresh medium containing PEA and 5-BUdR. The DNA was extracted by an extremely gentle technique to avoid breakage and centrifuged in a CsCl density gradient. PEA was added to the germinated spores to prevent dichotomous replication, but PEA did not prevent dichotomous replication in any of these experiments. This contradicts the conclusion of others that PEA prevents the chromosome from entering a new round of replication, but allows the chromosome to complete the round of replication already begun. The following observations offer support for the hypothesis that the replication point is a weak point in the chromosome: (1) when conditions were created to obtain partially labeled chromosomes with replication points: (a) labeled markers appeared at the hybrid density, (b) unlabeled markers appeared at the light density, (c) shearing of the DNA had little effect on the CsCl density gradient, except on a small proportion of labeled markers which had not appeared at the hybrid density prior to shearing; (2) when conditions were created to obtain partially labeled chromosomes with no replication points: (a) the majority of DNA molecules appeared at an intermediate density between the hybrid and the light densities, (b) the labeled and unlabeled markers appeared in the intermediate peak with approximately the same ratio as in the DNA preparations, (c) the labeled markers were found in the intermediate peak except where dichotomous replication had occurred, (d) after shearing, the labeled markers appeared at the hybrid density and the unlabeled markers appeared at the light density. Thus it is concluded that the replication point is a weak point in the B. subtilis chromosome where breakage easily occurs.
FINE STRUCTURE ANALYSIS OF THE ade3 LOCUS IN SACCHAROMYCES CEREVISIAE
Authors: Jones Elizabeth W
Published: January 2021

Twenty-six spontaneous mutants at the ade3 locus of Saccharomyces cerevisiae have been mapped and characterized with respect to revertibility, osmotic remediability and temperature sensitivity. Twelve of the twenty-six are temperature sensitive, 25 of 26 are osmotic remedial and 21 of 26 revert. Two of the mutants map as deletions. At least five of the 26 are nonsense mutations but are also, unexpectedly, osmotic remedial. Three nonsense mutations are also temperature sensitive, again an unexpected result. The two multisite mutations are both temperature sensitive and osmotic remedial. For mutants at this locus osmotic remediability and temperature sensitivity cannot be considered diagnostic criteria for missense mutations.
GLUTAMATE OXALOACETATE TRANSAMINASE (GOT) GENETICS IN THE MOUSE: POLYMORPHISM OF GOT-1
Authors: Chapman Verne M , Ruddle Frank H
Published: January 2021

We have examined a polymorphism for the soluble glutamate oxaloacetate (GOT-1) isozyme system which was found in the Asian mouse Mus castaneus. Variants of GOT-1 segregate as though they are controlled by codominant alleles for a single autosomal locus which we have designated Got-1. No close linkage of genes for soluble and mitochondrial forms of the enzyme, GOT-1 and GOT-2 respectively, was observed. Furthermore, no close linkage of Got-1 and the loci c, Gpi-1, Mod-2, Mod-1, Ld-1, Gpd-1, Pgm-1 or Gpo-1 was observed. Our results demonstrate the utility of sampling Mus from diverse populations to extend the repertoire of polymorphic loci and the genetic linkage map.
GENETIC CHANGE OF RECOMBINATION VALUE IN DROSOPHILA MELANOGASTER. I. ARTIFICIAL SELECTION FOR HIGH AND LOW RECOMBINATION AND SOME PROPERTIES OF RECOMBINATION-MODIFYING GENES
Authors: Kidwell Margaret Gale
Published: January 2021

A high and low selection line were formed by individual selection of females on the basis of their recombination. In the high line, recombination between Gl and Sb was increased from 14.8 percent to about 30 percent in twelve generations, when a plateau was apparently reached. Realized heritability was 0.12. The absence of a response to selection for low recombination is attributed mainly to genetic random drift, and partially to directional dominance and directional gene frequencies. Natural selection was found to act against increases of recombination above a level of about twenty percent in the measured interval. High recombination tended to be recessive to low recombination. In both selected lines and unselected stocks, intervals proximal to the centromere tended to have a higher recombination variance than distal intervals.
GENETIC CHANGE OF RECOMBINATION VALUE IN DROSOPHILA MELANOGASTER. II. SIMULATED NATURAL SELECTION
Authors: Kidwell Margaret Gale
Published: January 2021

Selection of Gl-Sb coupling heterozygotes was carried out for more than one hundred generations commencing with six independent lines drawn from a common base population. Population sizes were eight, sixteen and forty-eight parents per generation. The effect of natural selection on recombination value was measured by sampling and testing females at varying intervals of time. There was a significant reduction in percentage recombination between Gl and Sb from fifteen to a level between five and ten in four out of six of the original lines. In most cases this reduction occurred rather rapidly after the initiation of the experiment. In the remaining two lines there was no significant decrease in recombination value; there was, however, a significant increase in at least one subline of this group. The rapid rate of change of recombination value is most readily explained by the presence of a recombination modifying gene which is linked to the modified region. Genetic random drift was again shown to have an important effect on changes in recombination value in small populations. High recombination was almost completely recessive to low recombination in the one case examined. Lethal genes were fixed in sheltered regions of unmarked third chromosomes in five lines or sublines. These results are discussed in relation to the mode of development of permanent heterozygosity in some species of plants.
EXPERIMENTALLY DETERMINED, TWO LOCUS FITNESSES OF DROSOPHILA MELANOGASTER MALES
Authors: Wilson Jerome
Published: January 2021

A pilot demonstration of experimental fitness estimation utilizing pedigree data from D. melanogaster was described. Fitnesses were obtained for the male segregants of the two "complex loci," spineless–spineless aristapedia and radius incompletus–inturned. A good fit between selection model and data was obtained, perhaps because the experimental design largely eliminated concerns of frequency or density-dependent selection and assortative mating. The selection model assumed that net fitness was divided into two components: an "early" component operative from conception to the time of observation in the generation interval, and a late component operative from the time of observation to the time of gamete pool formation. These fitness components were roughly descriptive of the physiological components viability and reproductive ability. No simple systematic relationship between the fitness of two-locus genotypes and the marginal one-locus fitness emerged. These conclusions were based on relatively precise (by current standards) fitness estimates. It was argued that pedigree data is highly desirable for fitness estimation.
GENETICS OF THE ST SEROTYPE SYSTEM IN TETRAHYMENA PYRIFORMIS, SYNGEN 1
Authors: Grass Frank S
Published: January 2021

Genetic analyses using lines of Tetrahymena pyroformis manifesting different serotypes indicate that the St serotypes are governed by alleles at a single genetic locus. These alleles are termed StA and StC. The St locus is not closely linked to any of the other well-studied loci examined. Differentiation in StA/StC heterozygotes follows a pattern very similar to that observed with lines heterozygous at the other loci. Initially both alleles are expressed, but as the synclone divides, lines develop that manifest one allele or the other but not both. The time of differentiation is very early in the clonal life cycle, and the output ratio is eccentric. The pattern of development of the St locus places it in a category with the mating type and H serotype loci.
AN INSERTIONAL TRANSLOCATION IN NEUROSPORA THAT GENERATES DUPLICATIONS HETEROZYGOUS FOR MATING TYPE
Authors: Perkins David D
Published: January 2021

In strain T(I⇉II)39311 a long interstitial segment is transposed from IL to IIR, where it is inserted in reversed order with respect to the centromere. In crosses of T x T essentially all asci have eight viable, black spores, and all progeny are phenotypically normal. When T(I⇉II)39311 is crossed by Normal sequence (N), the expected duplication class is viable while the corresponding deficiency is lethal; 44% of the asci have 8 Black (viable) spores and 0 White (inviable) spores, 41% have 4 Black: 4 White, and 10% have 6 Black: 2 White. These are the ascus types expected from normal centromere disjunction without crossing over (8B:0W and 4B:4W equally probable), and with crossing over between centromere and break point (6B:2W). On germination, 8B:0W asci give rise to only parental types—4 T and 4 N; 4B:4W asci usually give four duplication (Dup) progeny; and 6B:2W asci usually give 2 T, 2 N, 2 Dup. Thus one third of all viable, black ascospores contain duplications.—Recessive markers in the donor chromosome which contributes the translocated segment can be mapped by duplication coverage. Ratios of 2 Dominant: 1 Recessive νs. 1 Dominant: 2 Recessive distinguish location in or outside the transposed segment. Eleven loci including mating type have been shown to lie within the segment, and markers at four loci have been transferred into the segment by meiotic recombination. The frequency of marker transfer indicates that the inserted segment usually pairs with its homologue. Ascus types that would result from single exchanges within the insertion are infrequent, as expected if asci containing dicentric bridges usually do not survive.—Duplication ascospores germinate to produce distinctive inhibited colonies. Later these "escape" to grow like wild type, and genes that were initially heterozygous in the duplication segregate when escape occurs. As with duplications from pericentric inversion In(IL⇉IR)H4250 (Newmeyer and Taylor 1967), the initial inhibition is attributed to mating-type heterozygosity, and escape to a somatic event that makes mating type homoor hemizygous.—Twenty additional duplication-generating Neurospora rearrangements are listed and described briefly in an Appendix.
MEIOTIC CHROMOSOME BEHAVIOR OF AN INVERTED INSERTIONAL TRANSLOCATION IN NEUROSPORA
Authors: Barry Edward G
Published: January 2021

Cytological study of meiotic chromosomes heterozygous for the T(I⇉II)39311 translocation confirm genetic evidence (Perkins 1972) that a section of linkage group I including the mating type locus has been inserted into linkage group II. Pachytene chromosomes when fully paired show that a segment from chromosome 1 has been inserted into chromosome 6. When pairing fails between the translocated segment in 6 and its homologous region in chromosome 1, buckles or loops are formed at pachynema in the deletion or insertion areas of the bivalents.—Acentric fragments and anaphase bridges occur at both meiotic divisions and in the subsequent two mitotic divisions in the ascus. These provide supporting evidence that the translocated segment is inverted with respect to centromere in its new location.—Unexpectedly the acentric fragment, formed by crossing over in the inverted translocated segment, persists without degradation in a micronucleus, and it replicates and divides in synchrony with the centric chromosomes in adjacent nuclei.
CARBONIC ANHYDRASE POLYMORPHISM IN A NEW JERSEY POPULATION OF THE WHITE-FOOTED MOUSE PEROMYSCUS LEUCOPUS
Authors: Wilmot Patrick L , Underhill Donald K
Published: January 2021

Two electrophoretic forms of erythrocytic carbonic anhydrase were found to be controlled by one autosomal locus with two codominant alleles, CAf and CA8. The gene frequencies for the CAf and CA8 alleles were found to be.15 and.85, respectively, in a sample of 53 mice from Middlesex County, New Jersey. The observed genotypic frequencies indicated that the population was in Hardy-Weinberg equilibrium.
SPERM PREFERENCE IN DROSOPHILA MELANOGASTER
†
Authors: Childress D , Hartl D L
Published: January 2021

A mating is described in which the females appear actively to discriminate against one of the genotypes of sperm. The males in the mating carry T(1;4)B  S  , and the sperm type selected against is the B  S+4-bearing segregant. Prior exposure of the reproductive tract of the females to B  S+4-bearing sperm seems to enhance the ability of the females to subsequently discriminate against B  S+4-bearing sperm. Thus it appears that at least some females of Drosophila melanogaster do possess a mechanism whereby different types of sperm can be distinguished—the sperm preference observed in this system appears to be independent of the meiotic drive in the T(1;4)B  S males.