bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitive detection of colorectal cancer in peripheral blood by a novel methylation assay
Authors: Zhang Yunfeng , Wu Qian , Xu Linhao , Wang Hong , Liu Xin , Li Sihui , Hu Tianliang , Liu Yanying , Peng Quanzhou , Chen Zhiwei , Wu Xianrui , Fan Jian-Bing
Published: April 2021

Background

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. Early detection of CRC can significantly reduce its mortality rate. Current method of CRC diagnosis relies on the invasive endoscopy. Non-invasive assays including fecal occult blood testing (FOBT) and fecal immunological test (FIT) are compromised by low sensitivity and specificity, especially at early stages. Thus, a non-invasive and accurate approach for CRC screening would be highly desirable.

Results

A new qPCR-based assay combining the simultaneous detection of the DNA methylation status of ten candidate genes was used to examine plasma samples from 56 normal controls, 6 hyperplastic polys, 9 non-advanced adenomas (NAAs), 22 advanced adenomas (AAs) and 175 CRC patients, using 10 ng of cfDNA. We further built a logistic regression model for CRC diagnosis. We tested ten candidate methylation markers including twist1, vav3-as1, fbn1, c9orf50, sfmbt2, kcnq5, fam72c, itga4, kcnj12 and znf132. All markers showed moderate diagnostic performance with AUCs ranging from 0.726 to 0.815. Moreover, a 4-marker model, comprised of two previously reported markers (c9orf50 and twist1) and two novel ones (kcnj12 and znf132), demonstrated high performance for detecting colorectal cancer in an independent validation set (N = 69) with an overall AUC of 0.911 [95% confidence interval (CI) 0.834–0.988], sensitivity of 0.800 [95% CI 0.667–0.933] and specificity of 0.971 [95% CI 0.914–1.000]. The stage-stratified sensitivity of the model was 0.455 [95% CI 0.227–0.682], 0.667 [95% CI 0.289–1.000], 0.800 [95% CI 0.449–1.000], 0.800 [95% CI 0.449–1.000] and 0.842 [95% CI 0.678–1.000] for advanced adenoma and CRC stage I-IV, respectively.

Conclusion

kcnj12 and znf132 are two novel methylation biomarkers for CRC diagnosis. The 4-marker methylation model provides a new non-invasive choice for CRC screening and interception.
Intestinal helminthic infection and allergic disorders among school children enrolled in mass deworming program, Sululta, Ethiopia
Authors: Abera Dessie , Wordofa Moges , Mesfin Abiyot , Tadesse Gemechu , Wolde Mistire , Desta Kassu , Tsegaye Aster , Taye Bineyam
Published: April 2021

Background

Intestinal helminths have been proposed to have a protective role against allergic sensitization and atopic diseases. However, consistent data demonstrating this are lacking in Sub-Saharan countries. We aimed to assess the association between intestinal helminths and allergic disorders among school children enrolled in mass deworming program in Sululta, Ethiopia.

Methods

A cross sectional study was conducted among 526 school children aged 5 to 14 years old from primary government schools in Sululta district, Ethiopia. An interviewer-led questionnaire administered to parents provided information on demographic and lifestyle variables. Questions on allergic disease symptoms were collected using the International Study of Asthma and Allergies in Children (ISAAC) questionnaire 6 months following deworming treatments. Atopy was defined as a positive skin prick test reaction to one or both dust mite (Dermatophagoides) and German cockroach (Blatella germanica) allergens. Fresh stool samples were collected, processed, and examined by direct wet mount, Kato-Katz technique, and formol-ether concentration technique. Multivariate logistic regressions were used to assess the association between allergic disorder and helminths infection.

Results

Of the total 526 school children, 58.2% were females. Overall, 24% (126/526) had allergic symptoms, 5.1% (27/526) had atopy, and 16.9% (89/526) had intestinal helminths. There was no association between helminthic infection and self-reported allergic symptoms (P = 0.317), butAscaris lumbricoidesinfection was positively associated with atopy (AOR = 4.307, 95% CI 1.143–16.222, P = 0.031). Atopy was related to increased allergy symptoms (AOR = 2.787, 95% CI 1.253–6.197, P = 0.012), and family history of allergy was associated with increased childhood allergy (AOR = 2.753, 95% CI 1.565–4.841, P = 0.001). Deworming in the past 6 months showed a reduced odd of self-reported allergic symptoms (AOR = 0.581, 95% CI 0.366–0.954, P = 0.034).

Conclusion

While no significant association between self-reported allergy and helminths was found in this study, this may have been due to the low prevalence and intensity of helminthic infection in the sample. There was a positive association betweenAscaris lumbricoidesand atopy. To further examine the underlying mechanism behind this positive association, a longitudinal study is needed.
Osimertinib as neoadjuvant therapy in a patient with stage IIIA non-small cell lung cancer: a case report
Authors: Chen Caroline Y. , Fares Charlene M. , Shin Daniel Sanghoon
Published: April 2021

Introduction

Tyrosine kinase inhibitors (TKI) targeting epidermal growth factor receptor (EGFR) are approved for use in metastatic non-small cell lung cancer (NSCLC).

Case presentation

Here we present a case of a African American patient with stage IIIA NSCLC treated with osimertinib in the neoadjuvant setting with concurrent radiation, followed by resection. The patient remains disease-free 4 months after surgery.

Conclusion

This case report suggests that osimertinib may be effective as neoadjuvant therapy in resectable stage III disease. Additionally, we provide a summary of previous case reports and ongoing clinical trials for neoadjuvant EGFR inhibition in stage III NSCLC patients.
A Pliocene–Pleistocene continental biota from Venezuela
Authors: Carrillo-Briceño Jorge D. , Sánchez Rodolfo , Scheyer Torsten M. , Carrillo Juan D. , Delfino Massimo , Georgalis Georgios L. , Kerber Leonardo , Ruiz-Ramoni Damián , Birindelli José L. O. , Cadena Edwin-Alberto , Rincón Aldo F. , Chavez-Hoffmeister Martin , Carlini Alfredo A. , Carvalho Mónica R. , Trejos-Tamayo Raúl , Vallejo Felipe , Jaramillo Carlos , Jones Douglas S. , Sánchez-Villagra Marcelo R.
Published: April 2021

The Pliocene–Pleistocene transition in the Neotropics is poorly understood despite the major climatic changes that occurred at the onset of the Quaternary. The San Gregorio Formation, the younger unit of the Urumaco Sequence, preserves a fauna that documents this critical transition. We report stingrays, freshwater bony fishes, amphibians, crocodiles, lizards, snakes, aquatic and terrestrial turtles, and mammals. A total of 49 taxa are reported from the Vergel Member (late Pliocene) and nine taxa from the Cocuiza Member (Early Pleistocene), with 28 and 18 taxa reported for the first time in the Urumaco sequence and Venezuela, respectively. Our findings include the first fossil record of the freshwater fishesMegaleporinus,Schizodon,Amblydoras,Scorpiodoras, and the pipesnakeAnilius scytale, all from Pliocene strata. The late Pliocene and Early Pleistocene ages proposed here for the Vergel and Cocuiza members, respectively, are supported by their stratigraphic position, palynology, nannoplankton, and86Sr/88Sr dating. Mammals from the Vergel Member are associated with the first major pulse of the Great American Biotic Interchange. In contrast to the dry conditions prevailing today, the San Gregorio Formation documents mixed open grassland/forest areas surrounding permanent freshwater systems, following the isolation of the northern South American basin from western Amazonia. These findings support the hypothesis that range contraction of many taxa to their current distribution in northern South America occurred rapidly during at least the last 1.5 million years.
Metabolic engineering of Moorella thermoacetica for thermophilic bioconversion of gaseous substrates to a volatile chemical
Authors: Kato Junya , Takemura Kaisei , Kato Setsu , Fujii Tatsuya , Wada Keisuke , Iwasaki Yuki , Aoi Yoshiteru , Matsushika Akinori , Murakami Katsuji , Nakashimada Yutaka
Published: April 2021

Gas fermentation is one of the promising bioprocesses to convert CO2 or syngas to important chemicals. Thermophilic gas fermentation of volatile chemicals has the potential for the development of consolidated bioprocesses that can simultaneously separate products during fermentation. This study reports the production of acetone from CO2 and H2, CO, or syngas by introducing the acetone production pathway using acetyl–coenzyme A (Ac-CoA) and acetate produced via the Wood–Ljungdahl pathway in Moorella thermoacetica. Reducing the carbon flux from Ac-CoA to acetate through genetic engineering successfully enhanced acetone productivity, which varied on the basis of the gas composition. The highest acetone productivity was obtained with CO–H2, while autotrophic growth collapsed with CO2–H2. By adding H2 to CO, the acetone productivity from the same amount of carbon source increased compared to CO gas only, and the maximum specific acetone production rate also increased from 0.04 to 0.09 g-acetone/g-dry cell/h. Our development of the engineered thermophilic acetogen M. thermoacetica, which grows at a temperature higher than the boiling point of acetone (58 °C), would pave the way for developing a consolidated process with simplified and cost-effective recovery via condensation following gas fermentation.
The existence of nonnegative solutions for a nonlinear fractional q-differential problem via a different numerical approach
Authors: Samei Mohammad Esmael , Ahmadi Ahmad , Hajiseyedazizi Sayyedeh Narges , Mishra Shashi Kant , Ram Bhagwat
Published: April 2021

This paper deals with the existence of nonnegative solutions for a class of boundary value problems of fractional q-differential equation ${}^{c}\mathcal{D}_{q}^{\sigma }[k](t) = w (t, k(t), {}^{c} \mathcal{D}_{q}^{\zeta }[k](t) )$

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Associations between socioprovincial factors and self-reported mental disorders among students from grade 4 to 8 in rural China
Authors: Guan Ming
Published: April 2021

Background

The focus on child mental health in developing countries was increasing. However, little was known in China. This study aimed to explore the associations between socioprovincial factors and self-reported mental disorders in rural China.

Methods

Data were from a publicly available survey with 54,498 students from Grade 4 to 8 in rural China. Chi-square test was used for descriptive analysis. Self-reported mental disorders included overall mental disorder, study anxiety, personal anxiety, loneliness, guilt, sensitivity, symptomatic psychosis, phobia, and impulsivity. Multiple logistic regressions and errors-in-variables regression models were employed to explore the associations between socioprovincial factors and mental disorders. Poisson regressions and errors-in-variables regression models were adopted to reveal the associations between socioprovincial factors and number of self-reported mental disorders.

Results

Descriptive statistics showed that mental health was poor in rural adolescents in China. Logistic regression showed that the odds of overall mental disorder and study anxiety were 189% (AOR = 2.89, 95%CI: 2.76, 3.02) and 92% (OR = 1.92, 95%CI: 1.84, 2.00) in Gansu more than those in Anhui, while the odds of personal anxiety, guilt, sensitivity, symptomatic psychosis, and phobia were 92% (AOR = 0.08, 95%CI: 0.08, 0.09), 71% (AOR = 0.29, 95%CI: 0.27, 0.30), 88% (AOR = 0.12, 95%CI: 0.11, 0.13), 69% (AOR = 0.31, 95%CI: 0.29, 0.32), and 78% (AOR = 0.22, 95%CI: 0.21, 0.23) in Gansu less than those in Anhui. Moreover, Gansu (Poisson regression: IRR =1.45, 95%CI: 1.42–1.47; errors-in-variables regression: Coefficient = 0.26, 95%CI: 0.16, 0.36), Ningxia (Poisson regression: IRR =1.63, 95%CI: 1.60–1.67; errors-in-variables regression: Coefficient = 0.43, 95%CI: 0.32, 0.53), Qinghai (Poisson regression: IRR =1.65, 95%CI: 1.60–1.69; errors-in-variables regression: Coefficient = 0.44, 95%CI: 0.34, 0.55), and Shaanxi (Poisson regression: IRR =1.28, 95%CI: 1.25–1.30; errors-in-variables regression: Coefficient = 0.11, 95%CI: 0.00, 0.21) were significantly associated with the number of self-reported mental disorders.

Conclusion

Class and provincial disparities in self-reported mental disorders were reported among the students from Grade 4 to 8 in rural China. Mental health care supported by governments and schools could be an effective way to reduce the disparities in mental disorders among the adolescents.
Predictive distribution modeling of Swertia bimaculata in Darjeeling-Sikkim Eastern Himalaya using MaxEnt: current and future scenarios
Authors: Boral Debasruti , Moktan Saurav
Published: April 2021

Background

As global temperatures continue to rise, species distribution modeling is a suitable tool for identifying rare and endangered species most at risk of extinction, along with tracking shifting geographical range.

Methods

The present study investigates the potential distribution of Swertia bimaculata in the Darjeeling-Sikkim region of Eastern Himalaya in current and future climate scenarios of GFDL-CM3 (Geophysical Fluid Dynamics Laboratory-Climate Model 3) for the year 2050 and year 2070 through MaxEnt presence data modeling. Two sets of variables were used for modeling current scenario. The models were evaluated using AUC (area under the curve) values and TSS (true skill statistic).

Results

Habitat assessment of the species shows low and sporadic distribution within the study area. A significant decrease is observed in the possible range of the species in the future climate scenario with the habitat decreasing from 869.48 to 0 km2. Resultant maps from the modeling process show significant upward shifting of the species range along the altitudinal gradient. Still, results should be taken with caution given the low number of occurrences used in the modeling.

Conclusions

The results thus highlight the vulnerability of the species towards extinction in the near future.
Does a lower self-concept contribute to mental health disparities of diverse immigrant youth from middle childhood to late adolescence?
Authors: Busch J. , Claus C. , Schneider S. , Siefen R. G.
Published: April 2021

Background

Three out of ten children in Germany have immigrant backgrounds and this proportion is expected to further increase in subsequent years. While immigrant youth have been found more vulnerable to developing symptoms of depression and anxiety, the underlying mechanisms of how such disparities unfold during youth development are still understudied. Some previous research has found that immigrant youth are at risk of experiencing a less positive self-concept compared to non-immigrant youth. We investigated whether the self-concept mediates mental health disparities and explored variability in such associations from middle childhood to late adolescence.

Methods

Overall 1839 children and adolescents aged 6–21 years (M = 14.05 years, SD = 3.03, 49.8% female, n = 782 with immigrant status) participated in a cross-sectional self-report survey in classroom settings using scales from the Beck Youth Inventories II (Beck et al. in Beck Youth Inventories - Second Edition, Psychological Corporation, San Antonio, 2005) to assess self-concept and symptoms of depression and anxiety. Links between immigrant status, age, self-concept and symptom levels of depression as well as anxiety were examined using hierarchical regression and moderated mediation models.

Results

Immigrant youth reported higher symptom levels of depression and anxiety than their non-immigrant peers but did not differ in their self-concepts. Hypothesized moderated mediation models were not fully supported and self-concept neither mediated the link between immigrant status and depression nor immigrant status and anxiety. However, self-concept was a significant predictor for symptom levels of depression as well as anxiety, with stronger associations in adolescents.

Conclusions

Our study substantiates previous findings that immigrant youth in Germany have overall increased symptom levels of depression and anxiety compared to non-immigrant youth. Our study however does not support that immigrant youth have a more negative self-concept and that the self-concept mediates such internalizing mental health disparities. Findings match previous evidence that developing a positive attitude towards the self is linked to better mental health. Beyond that, our findings suggest that mental health interventions addressing the self-concept could be especially relevant when targeting adolescents. Further research is needed to deepen the understanding of the mediating processes between migration status and mental health variables.
Identification of selected genes associated with the SARS-CoV-2: a therapeutic approach and disease severity
Authors: Veerabathiran Ramakrishnan , Ragunath Barath , Kaviarasan Vaishak , Mohammed Vajagathali , Ahmed Shiek S. S. J.
Published: April 2021

Background

The ongoing pandemic of COVID-19 viruses takes its sole origin from the Wuhan Huanan seafood market, China. The first case was recorded as viral pneumonia and later became a worldwide pandemic (officially declared by WHO on March 11, 2020).

Main body

SARS-CoV-2 is an extremely infectious and transferrable virus that develops severe conditions like respiratory syndrome, high blood pressure and weakens the immune system. Coronavirus falls under the Coronaviridae family and Beta coronavirus genus. Affected individuals will encounter problems starting with fever followed by severe complications like SARS, ARDS, and many others. These SARS-CoV and MERS-CoV enter the host cells by the endosomal pathway, and about 16 non-structural proteins are involved in assembling the viral RNA synthesis complex. They possess a positive-sense single-stranded RNA, and about four major genes are mainly associated with the development of ASRD, SARS, and other respiratory problems.

Conclusion

Susceptibility of these four major genes such as ACE2, IL-2, 7 and 10, TNF, and VEGF is associated with COVID-19. This highlights the identification of the above-mentioned genes that can be used as potential biomarkers for early diagnosis and targeted drug delivery for treating the SARS-CoV-2 neurological symptoms and reducing inflammation in the brain.
A review of fire effects across South American ecosystems: the role of climate and time since fire
Authors: Giorgis Melisa A. , Zeballos Sebastian R. , Carbone Lucas , Zimmermann Heike , von Wehrden Henrik , Aguilar Ramiro , Ferreras Ana E. , Tecco Paula A. , Kowaljow Esteban , Barri Fernando , Gurvich Diego E. , Villagra Pablo , Jaureguiberry Pedro
Published: April 2021

Background

Fire is an important driver of ecosystem dynamics worldwide. However, knowledge on broad-scale patterns of ecosystem and organism responses to fires is still scarce. Through a systematic quantitative review of available studies across South America, we assessed fire effects on biodiversity and abundance of different organisms (i.e., plants, fungi, invertebrates, and vertebrates), plant fitness, and soil properties under four climate types, and time since the last fire (i.e., early and late post fire). We addressed: (1) What fire effects have been studied across South America? (2) What are the overall responses of biodiversity, abundance, fitness, and soil properties to fires? (3) How do climate and time since fire modulate those responses?

Results

We analyzed 160 articles reporting 1465 fire responses on paired burned and unburned conditions. We found no effect of fire on biodiversity or on invertebrate abundance, a negative effect on woody plant species and vertebrate abundance, and an increase in shrub fitness. Soil in burned areas had higher bulk density and pH, and lower organic matter and nitrogen. Fire effect was significantly more positive at early than at late post fire for plant fitness and for soil phosphorus and available nitrogen. Stronger negative effects in semiarid climate compared to humid warm climate suggest that higher temperatures and water availability allow a faster ecosystem recovery after fire.

Conclusions

Our review highlights the complexity of the climate–fire–vegetation feedback when assessing the response of soil properties and different organisms at various levels. The resilience observed in biodiversity may be expected considering the large number of fire-prone ecosystems in South America. The recovery of invertebrate abundance, the reduction of the vertebrate abundance, and the loss of nitrogen and organic matter coincide with the responses found in global reviews at early post-fire times. The strength of these responses was further influenced by climate type and post-fire time. Our synthesis provides the first broad-scale diagnosis of fire effects in South America, helping to visualize strengths, weaknesses, and gaps in fire research. It also brings much needed information for developing adequate land management in a continent where fire plays a prominent socio-ecological role.
Roles of bile acids in enteric virus replication
Authors: Kong Fanzhi , Saif Linda J. , Wang Qiuhong
Published: April 2021

Bile acids (BAs) are evolutionally conserved molecules synthesized in the liver from cholesterol to facilitating the absorption of fat-soluble nutrients. In the intestines, where enteric viruses replicate, BAs also act as signaling molecules that modulate various biological functions via activation of specific receptors and cell signaling pathways. To date, BAs present either pro-viral or anti-viral effects for the replication of enteric viruses in vivo and in vitro. In this review, we summarized current information on biosynthesis, transportation and metabolism of BAs and the role of BAs in replication of enteric caliciviruses, rotaviruses, and coronaviruses. We also discussed the application of BAs for cell culture adaptation of fastidious enteric caliciviruses and control of virus infection, which may provide novel insights into the development of antivirals and/or disinfectants for enteric viruses.
Geomechanical stress conditions to induce half-moon events during hydraulic fracturing
Authors: Boitz Nepomuk , Shapiro Serge A.
Published: April 2021

Half-moon events are a special type of microseismic source mechanism that is found at various hydraulic-fracturing sites, but hardly observed in natural seismicity. This event type can be explained either by a vertical slip on a nearly vertical fault plane or by a horizontal slip on a nearly horizontal fault plane. For this, special stress conditions are required, for instance, nearly equal horizontal and vertical compressional stresses and significant shear stresses. Such conditions are created during hydraulic stimulation as shown by our numerical simulations. By applying fracture pressure to the surface of the hydraulic fracture, the stress field in the vicinity of the hydraulic fracture can locally rotate and horizontal or vertical faults become optimally oriented. We found that such rotations can occur in locations where the elastic properties of rocks change (i.e., the fracture crosses a layer interface) or at the tips of the hydraulic fracture. Depending on the stress regime, our model explains half-moon events generated by slip on nearly horizontal fault planes in strike-slip environments and by slip on nearly vertical fault planes in normal faulting tectonics. Moreover, our models explain several common characteristics observed in multiple case studies. This includes the observation of the high portion of half-moon events and opposed shear senses in different depths and on opposite sides of the fracture.
Improved imaging of gas hydrate reservoirs and their plumbing system using 2D elastic full-waveform inversion
Authors: Djeffal Adnan , Pecher Ingo A. , Singh Satish C. , Crutchley Gareth J. , Kaipio Jari
Published: April 2021

Gas hydrates are ice-like crystalline materials that form under submarine environments of moderate pressure and low temperature. Another key factor to their formation is the abundance in gas supply from depth in addition to local biogenic gas. Detailed imaging and velocity analysis of the plumbing system of gas hydrates can provide confidence that amplitude anomalies in seismic data are related to gas hydrate accumulations. We have conducted 2D elastic full-waveform inversion (FWI) along a 14 km long segment of a 2D multichannel seismic profile to obtain a high-resolution velocity model of a hydrate system on the southern Hikurangi margin. We compare the FWI velocity model to previously published semblance- and tomography-based velocity models from the same data to explore how much more can be gained from the FWI. The FWI yielded a structurally more accurate velocity model that better delineated the low-velocity zone associated with free gas beneath the bottom simulating reflector (BSR) compared to the semblance- and tomography-based velocity models. Our results also find a lateral velocity inversion, that is, a narrow low-velocity zone surrounded by bands of higher velocities at a seaward-verging protothrust fault, which the two other methodologies failed to resolve. The FWI provides an improved lateral resolution making it an important tool when imaging the “plumbing” systems of gas hydrate reservoirs. In the southeastern limb of the anticline, our results find that the closely spaced landward-vergent protothrusts provide gas-charged fluids for hydrate formation above the BSR. Moreover, at the center of the anticline, our results find that a seaward-vergent protothrust fault appears to be acting as a conduit for gas-rich fluids into strata, although there is no accumulation of any significant hydrate above the BSR at the apex of the anticline. Our finding emphasizes the significance of densely spaced faults and fractures for providing gas for hydrate formation in the hydrate stability zone.
In vivoembryonic expression of laminin and its involvement in cell shape change in the sea urchinSphaerechinus granularis
Authors: McCarthy Robert A. , Burger Max M.
Published: April 2021

Laminin, a component of the embryonic sea urchin basal lamina, is recognized by monoclonal antibody BL1 (Mab BL1). Our results demonstrate that laminin is secreted into the blastcoel at the early blastula stage at a time when the blastomeres undergo a cell shape change and are organized into an epithelium. Laminin is present on the basal surfaces of ectodermal cells and is absent or reduced on migrating primary mesenchyme cells. Microinjection of a monoclonal antibody directed against laminin induces a morphological change in cell shape and a deformation of the embryonic epithelium. Investigation of selected stages of live embryos suggests that the distribution of laminin may be heterogeneous within the basal lamina during early development. The results implicate laminin as a mediator of cell shape change during early morphogenesis.
Mapping the mouse X chromosome: possible symmetry in the location of a family of sequences on the mouse X and Y chromosomes
Authors: Avner Philip , Bishop Colin , Amar Laurence , Cambrou Jacques , Hatat Didier , Arnaud Danielle , Mattei Marie-Geneviève
Published: April 2021

Major advances in our knowledge of the genetic organization of the mouse X chromosome have been obtained by the use of interspecific crosses involving Mus spretus-derived strains. This system has been used to study sequences detected by three probes 80Y/B, 302Y/B and 371Y/B isolated from a mouse Y-chromosome library which have been shown to recognize both male-female common and malefemale differential sequences. These patterns are due to the presence of a family of cross-reacting sequences on the mouse X and Y chromosomes. Detailed genetic analysis of the localization of the X-chromosome-specific sequences using both a somatic cell hybrid pane) and an interspecific mouse cross has revealed the presence of at least three discrete clusters of loci (Y-Y)A, (X-Y)B and (X-Y)C. Two of these clusters, (X-Y)B and (X-Y)C, lie distally on the mouse X chromosome, the other cluster (X-Y)A being situated close to the centromere. In situ hybridization shows a striking symmetry in the localization of the major sequences on both the X and Y chromosomes detected by these probes, hybridization being preferentially localized to a subcentromeric and subtelomeric region on each chromosome.

This striking localization symmetry between the X and Y chromosome sequences is discussed in terms of the extensive pairing of the X-Y chromosomes noted during meiosis.
Mapping the H-Y gene
Authors: Simpson Elizabeth , Chandler Phillip , Mclaren Anne , Goulmy Els , Disteche Christine M. , Page David C. , Ferguson-Smith Malcolm A.
Published: April 2021

This paper uses cytotoxic and proliferative T cell clones specific for H-Y and restricted by MHC molecules to type mice and humans inheriting incomplete portions of the Y chromosome. The data have allowed us to map the H-Y antigen gene Hya in mouse to a position closely linked with, but separable from, Tdy on the Sxr fragment and thus presumably to a position of the normal mouse Y chromosome near the centromere. The human H-Y gene maps between deletion intervals 4B and 7, separate from TDF which is on interval 1. We are currently testing cells from a number of additional patients who have inherited different portions of the Y chromosome to pinpoint the mapping more closely. It is of interest that in mouse a Y-linked gene controlling spermatogenesis (Spy) maps near Hya on the Sxr fragment: they could be the same or closely linked genes. In man, a gene controlling spermatogenesis maps to Yq and the data so far do not exclude that it could be coincident with the H-Y gene.
Evidence for the presence of testicular tissue and Sxs antigen in the absence of Y-derived sequences
Authors: Wiberg Ulf H. , Scherer Gerd
Published: April 2021

Eleven XX males and seven XX true hermaphrodites have been tested for the presence of Y-derived DNA sequences using six different probes. All eleven XX males were positive with at least one of the probes but none of the seven true hermaphrodites could be shown to possess any Y-DNA. Using a new sensitive test for serologically sex-specific (Sxs) antigen, we found that, despite their apparent lack of Y-DNA, the XX true hermaphrodites were positive for their expression of the Sxs antigen.
The use of specific DNA probes to analyse the Sxr mutation in the mouse
Authors: Bishop C. E. , Roberts C. , Michot J.-L. , Nagamine C. , Winking H. , Guénet J.-L. , Weith A.
Published: April 2021

The mouse Y chromosome plays a fundamental role in the control of primary sex determination and fertility. Both genetic and molecular biological evidence has shown that much of the necessary information is contained in a minute piece of the Y (the Sxr region) which has arisen by a duplication of the pericentric region of the normal Y and the transposition of one copy to the distal pseudoautosomal region. The present article describes the isolation of random Y-chromosome probes and their use to investigate this Sxr region at the molecular level. Total mouse Y-chromosome libraries were constructed from flow-sorted material and a Sxr regional library after specific microdissection and cloning. Transcription has been detected in the testis using both Sxr-specific and non Sxr-located genomic probes taken from these libraries. In addition, we have been able to confirm the presence of an active steroid sulphatase gene on the mouse Y. This gene is located in the distal portion of the pseudoautosomal region and is tightly linked to Sxr. Finally, using an .S’xr-specific probe we can define multiple Y-chromosome haplotypes in the mouse showing that the region is evolving very rapidly.
The mammalian Y chromosome: molecular search for the sex-determining gene - summary and perspectives
Authors: Craig Ian , Levy Elaine , Fraser Neil
Published: April 2021

Other presentations to this symposium have indicated that the search at the molecular level for the pivotal regulatory, or structural, gene responsible for determining the development of the undifferentiated gonad has been joined in earnest. It is also clear that genes on the Y chromosome are involved in processes other than primary determination of the testis. In this summary, we will review briefly ‘the molecular search for the sex-determining gene’ and consider the approaches that are available and the achievements that have been made in the areas relevant to an understanding of the roles and significance of other Y-located genes. The availability of molecular and physical mapping data also allow an examination of the evolutionary relationship of the mammalian X and Y chromosomes and a consideration of the possible homologies between the human and mouse Y chromosomes.
Cytocortical organization during natural and prolonged mitosis of mouse 8-cell blastomeres
Authors: Johnson Martin H. , Pickering Susan J. , Dhiman Arun , Radcliffe Graham S. , Maro Bernard
Published: April 2021

Late 8-cell blastomeres were harvested within the first 45 min after entering mitosis. Some mitotic cells were analysed within the ensuing 2 h for the organization of their surface in relation to their progress through mitosis. Whereas in most late interphase cells microvilli were restricted to a discrete polar region, in mitotic cells at all stages from early metaphase to immediately postcytokinesis microvilli were found to be present over more of the cell surface. Other mitotic cells were placed in nocodazole to arrest them in M-phase for up to 10 h. They were found to show an even more extensive distribution of microvilli over the whole surface, the longer periods of incubation yielding more extended coverage such that many cells no longer appeared to have any residual surface polarity. Removal from nocodazole at all time points from 1 to 10 h resulted in most cells completing mitosis to yield pairs of cells which, in most cases, resembled pairs derived from nonarrested blastomeres and in which a defined polar area of microvilli was restored. However, the percentage of differentiative divisions decreased after 6h arrest. If, instead of removing cells from nocodazole, they were placed in both nocodazole and cytochalasin D (CCD) for periods of up to 3h, most microvilli retracted to reveal a tight polar zone of CCD-resistant microvilli. This result suggests that a heterogeneity of cytocortical organization may still exist within the arrested mitotic cell. We propose a model to explain the origin of this heterogeneity of organization and its relationship to the generation of cell diversity.
The albino deletion complex and early postimplantation survival in the mouse
Authors: Niswander Lee , Yee Della , Rinchik Eugene M. , Russell Liane B. , Magnuson Terry
Published: April 2021

The albino deletion complex in the mouse represents 37 overlapping chromosomal deflciencies that have been arranged into at least twelve complementation groups. Many of the deletions cover regions of chromosome 7 that contain genes necessary for early embryonic development. The work reported here concentrates on two of these deletions (c6H, cIIDSD), both of which were known to be lethal around the time of gastrulation when homozygous. A detailed embryological analysis has revealed distinct differences in the lethal phenotype associated with the c6H and cIIDSD deletions. c6H homozygous embryos are grossly abnormal at day 7·5 of gestation, whereas C11DSD homozygous embryos appear abnormal at day 8·5 of gestation. There is no development of the extraembryonic ectoderm in homozygotes, whereas extensive development of this tissue type occurs in c11DSD homozygotes. The visceral endoderm is abnormally shaped and the parietal endoderm appears to be overproduced in c6H homozygotes; these structures are not affected in c11DSD homozygotes. The embryonic ectoderm is runted in both types of embryo and it is not possible to obtain homozygous embryo-derived stem-cell lines for either deletion. Mesoderm formation occurs in the C11DSD but not in the c6H homozygotes. The c11DSD deletion chromosome complements the c6H chromosome in that the lethal phenotype of the compound heterozygote is similar to that of the c11DSD homozygote. These results suggest that a gene(s) necessary for normal development of the extraembry-onic ectoderm is present in the c11080 but deficient in the c6H deletion chromosome.

The submitted manuscript has been co-authored by a contractor of the US Government under contract No. DE-AC05-840R21400. Accordingly, the US Government retains a nonexclusive, royalty-free licence to publish or reproduce the published form of the contribution, or allow others to do so, for US Government Purposes.
‘Early’ mammalian myoblasts are resistant to phorbol ester-induced block of differentiation
Authors: Cossu G. , Ranaldi G. , Senni M. I. , Molinaro M. , Vivarelli E.
Published: April 2021

Mesenchymal cells were isolated from somites and limbs of mouse embryos at different developmental stages. When grown in tissue culture, some of the cells underwent muscle differentiation as indicated by synthesis of sarcomeric myosin, acetylcholine receptor and, in the case of limb cells, fusion into multinucleated myotubes.

When the tumour promoter 12-O-tetradecanoyl phorbol 13-acetate (TPA) was added to these cultures, it caused differential effects, depending upon the age of the embryo from which cells were isolated. In cultures of somites or limb bud from embryos up to 12 days post coitum, TPA did not interfere with the appearance of differentiated muscle cells. When TPA was added to cultures from older embryos, it inhibited muscle differentiation with an efficiency which increased with the age of the embryo, reaching about 90 % inhibition at 15 days.

After this period, a new population of myogenic cells appeared in the limb, which were able to differentiate in the presence of TPA and represented the great majority of myoblasts after day 18 of embryonic development.

The simplest interpretation of these data can be based on the existence of three major classes of myogenic cell precursors, which appear sequentially during muscle histogenesis: ‘early’ myoblasts, which appear resistant to tumour promoters; ‘late’ myoblasts, whose differentiation is inhibited by tumour promoters and ‘satellite’ cells which, like early myoblasts, show no sensitivity to TPA.
Lithium dorsalizes but also mechanically disrupts gastrulation ofXenopus laevis
Authors: Regen Chester M. , Steinhardt Richard A.
Published: April 2021

The discovery that lithium treatment at blastula stages can induce axis formation suggested that it might act by respecifying the cytoplasmic rearrangement-generated dorsoventral pattern, so that ventral cells behave like their dorsal counterparts. We have studied the effects of Li+ treatment on the spatial layout of the cell-group movements of gastrulation to see whether this is the case. We find that involution of the chordamesoderm and associated archenteron roof is retarded by Li+, an effect which does not suggest dorsal respecification. However, in both migration of the leading edge mesoderm and convergent extension of the marginal zone, ventral regions clearly do show dorsal-type movement. Because of this, and because of examples where disruption of involution and effects on axis differentiation do not correlate, we propose that failure of involution represents a distinct effect of Li+ involving disruption of mechanical relationships at the blastopore. Thus archenteron formation poorly reflects the dorsoventral pattern. Extension of sandwich explants of the ventral marginal zone is proposed as a reliable quantitative assay for alterations to the dorsoventral pattern.
The growth and differentiation in vitro of leg and wing imaginal disc cells from Drosophila melanogaster
Authors: Currie Douglas A. , Milner Martin J. , Evans Clive W.
Published: April 2021

We have devised a new in vitro culture system in which cells from dissociated Drosophila leg and wing imaginal discs grow and differentiate. Primary cultures consist of epithelial and fibroblast-like cells, together with some lamellocyte-like cells. These cultures have given rise to continuously dividing leg and wing cell lines, in which epithelial, fibroblast-like, lamellocyte-like and distinct sickle-shaped cells are found. Vesicles composed of epithelial cells form in primary cultures and these differentiate imaginal cuticular structures under the influence of 20-hydroxyecdysone. Two types of cuticle-like material are formed spontaneously in established cultures. One type is present as thin, untanned sheets resembling apolysed pupal cuticle, while the other consists of thicker, tanned material similar to imaginal cuticle.
Retinoic acid alters EGF receptor expression during palatogenesis
Authors: Abbott B. D. , Adamson E. D. , Pratt R. M.
Published: April 2021

Various growth factors are necessary for normal embryonic development and EGF receptors are present in developing palatal shelves of embryonic/fetal mice at least from day 12 of gestation. The medial epithelium of the palatal shelf undergoes a series of developmental events which do not occur in the oral and nasal epithelia. In utero and in organ culture, the control palatal medial epithelium shows a developmental decline in EGF receptors, demonstrated both by a decrease in the binding of antibody to EGF receptors and a decrease in the binding of l25I-EGF; decreases which are not observed in cells of the adjacent oral or nasal epithelium. During this period, medial cells cease DNA synthesis and undergo programmed cell death. Medial epithelial cells exposed to all-trans-retinoic acid continue to express EGF receptors, bind EGF, proliferate, fail to undergo programmed cell death and exhibit a morphology typical of nasal cells. The data suggest that this disturbance by retinoic acid of EGF receptor localization and subsequent alterations in differentiation of the epithelial cells plays a role in the retinoic-acid-mediated induction of cleft palate.
The behaviour and function of bottle cells during gastrulation of Xenopus laevis
Authors: Hardin Jeff , Keller Ray
Published: April 2021

The behaviour of bottle cells in normal and microsurgically altered gastrulae and in cultured expiants of Xenopus laevis was analysed, using time-lapse micrography, scanning electron microscopy (SEM) and cell tracing with fluorescein dextran amine (FDA). The results shed new light on the function of bottle cells. Bottle cells forming in vivo show a predominantly animal-vegetal apical contraction and a concurrent apical-basal elongation, whereas those forming in cultured expiants show uniform apical contraction and remain rotund. Bottle cells forming in embryos with fewer subblastoporal cells contract more uniformly than those in normal embryos and release of normal bottle cells from supra- and subblastoporal cells results in immediate loss of the bottle shape. These results, and an analysis of the effects of bottle cell formation on the shapes and movements of surrounding tissues, show that unique shape of bottle cells and their probable function in development are not intrinsic properties but result from a modulation of the effect of a uniform and intrinsic apical contraction by the geometric and mechanical properties of the surrounding tissue. Mechanical simulations of bottle cell formation, using the finite element method, suggest how the site of bottle cell formation and the thickness and stiffness of adjacent tissues might change the effects of their formation. These results and FDA marking of prospective bottle cells and the adjacent deep mesodermal cells suggest that bottle cells function during their formation to initiate the involution of the prospective mesodermal mantle. Later they respread to deepen the archenteron and to form its peripheral wall.
Can retinal adhesion mechanisms determine cell-sorting patterns: a test of the differential adhesion hypothesis
Authors: Thomas William A. , Yancey Janet
Published: April 2021

Embryonic chick neural retina cells possess two classes of adhesion mechanism, one Ca2+-independent, one Ca2+-dependent, responsible for short-term cell aggregation. This study investigates the role of these mechanisms in the long-term cell sorting potentially relevant to in vivo histogenesis. Retina cells are prepared either with both (E cells) or with only one mechanism (TC cells, CD; LTE cells, CI), respectively. The two types of cell preparations are differentially labelled using fluorescein or rhodamine isothiocyanate, mixed and allowed to aggregate in the presence or absence of cycloheximide at 0·5 μg ml-1 to retard metabolic recovery of the removed adhesive mechanism. When observed by fluorescence and phase-contrast microscopy, the aggregates formed in cycloheximide show cell sorting, the cells with both mechanisms assuming a more interior position relative to those with a single adhesion mechanism. In parallel hanging-drop experiments, preformed aggregates of cells with a single adhesion mechanism are seen to spread upon aggregates of cells with both mechanisms. No sorting occurs amongst cells from a given stage prepared using any single dissociation protocol. The observed cell sorting would thus seem to derive exclusively from differential cell adhesiveness dependent upon the different dissociation conditions and maintained in the presence of cycloheximide. The experiments support the hypothesis that the dual CI and CD adhesion mechanisms in question can play a central role in governing cell-sorting behaviour during normal histogenesis.
Analysis of hsp 30, hsp 70 and ubiquitin gene expression inXenopus laevistadpoles
Authors: Krone Patrick H. , Heikkila John J.
Published: April 2021

Heat-induced accumulation of hsp 30 mRNA (1·1 kb) during early development of Xenopus laevis was first detectable at the tailbud stage (stage 30–34). This contrasts with heat-induced accumulation of hsp 70 mRNA (2·7 kb) and ubiquitin mRNA (size range = 1·7–3·1 kb), which was first detectable at the mid- to late-blastula stage. Continuous exposure of tadpoles to a 33 °C heat shock resulted in a coordinate, transient accumulation of hsp 30, hsp 70 and ubiquitin mRNA. A coordinate, temporal pattern was also observed for the decay of hsp 30, hsp 70 and ubiquitin mRNA in tadpoles recovering at 22°C following a Ih heat shock at 33°C. Thus, while hsp 30 genes are regulated differently during development compared with hsp 70 and ubiquitin genes, these genes all exhibit a coordinate heat-inducible pattern of expression at the tadpole stage. Levels of α-cardiac actin mRNA remained unchanged during continuous heat shock and recovery experiments.
Specific guidance of motor axons to duplicated muscles in the developing amniote limb
Authors: Victoria Stirling R. , Summerbell Dennis
Published: April 2021

The effect of alteration of limb pattern upon motor axon guidance has been investigated in chick embryos. Following grafting of the zone of polarizing activity (ZPA) into the anterior margin of the early limb bud, limbs develop with forearms duplicated about the anteroposterior axis. The position of motoneurones innervating the duplicated posterior forearm extensor EMU was mapped by retrograde transport of horse radish peroxidase (HRP). The motor pool labelled from injection into the anteriorly duplicated EMU muscle is consistently similar to that supplying the posterior EMU muscle on the unoperated side of the embryo. In those cases where the axons are well filled,their trajectories from the injection site are observed to change position within the radial nerve to specifically innervate the duplicated muscle. The axons modify their trajectories proximal to the level of limb duplication in a region where there is no change in the pattern of overt differentiation of the limb cells. This suggests that axons may use a cell’s positional value to navigate and provides significant support for the theory of positional information.