bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of rolling resistance on people’s willingness to cycle during wintertime
Authors: Fenre Mathis Dahl , Klein-Paste Alex
Published: April 2021

Harsh winters reduce utilitarian cycling in many cities. Using an online survey, we examined how increasing rolling resistance due to snow and ice affect people’s cycling willingness. The respondents (N = 1318) reported their willingness to cycle on various winter cycling conditions presented in photos. The answers were compared to the rolling resistance levels on the presented conditions, measured in a previous study. Respondents’ cycling willingness dropped from 91.2% at very low to 18.3% at very high rolling resistances. The cyclist’s age, gender, local climate, winter cycling experience and studded tire use affected the cycling willingness significantly. Electric bike usage did not affect cycling willingness. “Summer-only” cyclists did not cycle during the winter due to low temperatures (29%), lacked feeling of safety (27%), bicycle wear (17%), increased travel time (17%) and increased physical effort (10%). Hence, lower rolling resistance and increased use of studded tires can increase the cycling frequency of existing winter cyclists. To recruit new winter cyclists, the surface conditions should not only offer a low rolling resistance but should also be perceived as safe and comfortable.
Non-Western interventions for stress reduction and resilience
Authors: Gerbarg Patricia L. , Brown Richard P.
Published: April 2021

Complementary and integrative medicine provides safe, low-cost, effective treatments for conditions ranging from everyday stress to post-traumatic stress disorder. The evidence for herbs, nutrients and mind–body practices is growing, despite disproportionately small amounts of financial support compared with funding for expensive pharmaceuticals. The unsustainable cost of conventional treatments, the moral imperative to care for millions of uninsured and the impact of COVID-19 compel us to fully explore known and potential benefits of treatments being used by complementary and integrative practitioners.
Assessment of Brain Metastasis at Diagnosis in Non–Small-Cell Lung Cancer: A Prospective Observational Study From North India
Authors: Naresh Gundu , Malik Prabhat Singh , Khurana Sachin , Pushpam Deepam , Sharma Vinod , Yadav Mukesh , Jain Deepali , Pathy Sushmita
Published: April 2021

PURPOSE

The incidence of symptomatic brain metastasis at diagnosis in non–small-cell lung cancer (NSCLC) is 5%-10%, and up to 40% develop during the disease course. There is a paucity of data supporting the role of brain imaging at diagnosis in asymptomatic cases particularly from resource-constraint settings. Here, we present our experience of mandatory baseline brain imaging with contrast-enhanced computed tomography (CECT) scans of all patients with NSCLC.

MATERIALS AND METHODS

This was a prospective observation study of patients with NSCLC with mandatory baseline brain CECT and a CNS examination. All histology proven patients with NSCLC diagnosed between January 2018 and October 2019 were included irrespective of stage.

RESULTS

A total of 496 patients were enrolled. The median age was 57 years (range, 23-84) with majority being males (75%) and smokers (66%). The prevalence of epidermal growth factor receptor mutations and anaplastic lymphoma kinase fusions was 33.4% and 12%, respectively. Brain imaging leads to upstaging in 7% cases. The prevalence of brain metastases was 21% (n = 104), with half being asymptomatic (51%). Factors associated with higher proportion of brain metastasis were young age (≤ 40 years), adenocarcinoma histology, poor Eastern Cooperative Oncology Group performance status (3 and 4), and high neutrophil-lymphocyte ratio (NLR) (> 2.5). After a median follow-up of 10.8 months (95% CI, 7.33 to 12.73), the median overall survival was 7.46 versus 12.76 months (hazard ratio 0.67; 95% CI, 0.46 to 0.96; P = .03) in patients with and without brain metastases, respectively. On multivariate analyses, high NLR and molecular graded prognostic assessment affected the overall survival significantly.

CONCLUSION

In our study, 21% of patients had brain metastasis at diagnosis detected with a mandatory baseline brain imaging with CECT. NLR and molecular graded prognostic assessment are significant predictors of survival in patients with brain metastasis.
Patient-Reported Complications, Symptoms, and Experiences of Living With X-Linked Hypophosphatemia Across the Life-Course
Authors: Cheung Moira , Rylands Angela J , Williams Angela , Bailey Karen , Bubbear Judith
Published: April 2021

Context

X-linked hypophosphatemia (XLH) is a rare, genetic phosphate-wasting disease resulting in bone, muscular, and dental problems, beginning in childhood and increasing in adulthood.

Objective

This qualitative analysis aimed to explore patient-reported symptoms, complications, and experiences of XLH over the life-course, using data from a large multinational online survey.

Methods

Responses to 2 open-ended questions from 209 adults and 86 children/adolescents (proxy report) with self-reported XLH were analyzed in 8 age groups. Two researchers independently coded and analyzed the responses, using thematic analysis, with differences settled among a multidisciplinary group. Six themes were identified, with age subgroup analysis conducted on the 3 most common, according to coding frequency.

Results

Within theme 1, “Clinical Signs and Symptoms of XLH,” “Pain” was a dominant subtheme across the life-course, but “Skeletal Pathology” dominated the responses of children/adolescents. Within theme 2, “Impacts of Clinical Signs and Symptoms,” interference with “Physical Exertion” and “Emotional Wellbeing” (comprising depression/anxiety in adults and lack of self-esteem in children/adolescents) was reported across all ages. For theme 3, “Negative Treatment Experiences,” “Medication” was problematic for children, with adults reporting lack of “Access to Appropriate Treatment.” Three further themes were identified: “Resilience,” “Positive Treatment Experiences,” and “Information Needs.”

Conclusion

The multiple burdens imposed on people with XLH throughout their lifetime encompassed the physical, emotional, and social, although the most challenging symptoms or complications differed between ages. Burden was further exacerbated by adults’ lack of access to appropriate treatment, illustrating the need for age-appropriate multidisciplinary care.
Comparative Efficacy of 6 Topical Pharmacological Agents for Preventive Interventions of Postoperative Sore Throat After Tracheal Intubation: A Systematic Review and Network Meta-analysis
Authors: Wang Ge , Qi Yang , Wu LiNa , Jiang GuiChun
Published: April 2021

BACKGROUND:

Topical pharmacological agents typically used to treat postoperative sore throat (POST) after tracheal intubation include nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, lidocaine, Glycyrrhiza (licorice), and N-methyl-d-aspartate (NMDA) receptor antagonists (including ketamine and magnesium). However, the optimal prophylactic drug remains elusive.

METHODS:

The literature published before September 8, 2019 was searched on the PubMed, the Embase, the Web of Science, and the Cochrane Library. Randomized controlled trials (RCTs) covering topical prophylactic medications for patients with POST were included. Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system was used to assess the quality of evidence. The primary outcome is the risk of POST. Combining both direct and indirect evidence, a network meta-analysis was performed to assess odds ratios (ORs) between the topical pharmacological agents and surface under the cumulative ranking (SUCRA) curve for the treatment-based outcomes. This study is registered with PROSPERO, number CRD42020158985.

RESULTS:

Sixty-two RCTs (at least 73% of which were double blinded) that included a total of 6708 subjects and compared 6 categories of drugs and/or placebos were ultimately enrolled. All preventive interventions except lidocaine were more effective than placebo at the 4 time intervals. Lidocaine (OR: 0.35, 95% credible interval [CrI], 0.16-0.79) has a greater POST preventative intervention effect than the placebo at a time interval of only 2 to 3 hours after surgery. Relative to lidocaine, the risk of POST except 2 to 3 hours was lower for the following treatments: corticosteroids, ketamine, magnesium, NSAIDs, and Glycyrrhiza. The NMDA receptor antagonists studied here included ketamine and magnesium. Magnesium generally demonstrated greater benefit than ketamine at 24 hours postsurgery/extubation (OR: 0.41, 95% CrI, 0.18-0.92). Compared with ketamine, corticosteroids were associated with a reduced risk of POST during the 4 to 6 hours (OR: 0.40, 95% CrI, 0.19-0.83) and 24 hours (OR: 0.34, 95% CrI, 0.16-0.72) time intervals. During the 2 to 3 hours time interval, Glycyrrhiza (OR: 0.38, 95% CrI, 0.15-0.97) was more efficacious than magnesium.

CONCLUSIONS:

Our analysis shows that, among the 6 topical medications studied, lidocaine is not optimal for topical use to prevent POST. Glycyrrhizin, corticosteroids, NSAIDs, and NMDA receptor antagonists (ketamine and magnesium) are associated with a reduced postoperative pharyngeal pain across the 4 postsurgical time intervals studied, all of which can be chosen according to the clinical experience of the anesthesiologists and the patient preferences and are recommended for the reduction of postoperative throat pain.
Dissemination of Anesthesia Information During the Coronavirus Disease 2019 Pandemic Through Twitter: An Infodemiology Study
Authors: Gai Nan , So Delvin , Siddiqui Asad , Steinberg Benjamin E.
Published: April 2021

BACKGROUND:

Twitter is a web-based social media platform that allows instantaneous sharing of user-generated messages (tweets). We performed an infodemiology study of the coronavirus disease 2019 (COVID-19) Twitter conversation related to anesthesiology to describe how Twitter has been used during the pandemic and ways to optimize Twitter use by anesthesiologists.

METHODS:

This was a cross-sectional study of tweets related to the specialty of anesthesiology and COVID-19 tweeted between January 21 and October 13, 2020. A publicly available COVID-19 Twitter dataset was filtered for tweets meeting inclusion criteria (tweets including anesthesiology keywords). Using descriptive statistics, tweets were reviewed for tweet and account characteristics. Tweets were filtered for specific topics of interest likely to be impactful or informative to anesthesiologists of COVID-19 practice (airway management, personal protective equipment, ventilators, COVID testing, and pain management). Tweet activity was also summarized descriptively to show temporal profiles over the pandemic.

RESULTS:

Between January 21 and October 13, 2020, 23,270 of 241,732,881 tweets (0.01%) met inclusion criteria and were generated by 15,770 accounts. The majority (51.9%) of accounts were from the United States. Seven hundred forty-nine (4.8%) of all users self-reported as anesthesiologists. 33.8% of all tweets included at least one word or phrase preceded by the # symbol (hashtag), which functions as a label to search for all tweets including a specific hashtag, with the most frequently used being #anesthesia. About half (52.2%) of all tweets included at least one hyperlink, most frequently linked to other social media, news organizations, medical organizations, or scientific publications. The majority of tweets (67%) were not retweeted. COVID-19 anesthesia tweet activity started before the pandemic was declared. The trend of daily tweet activity was similar to, and preceded, the US daily death count by about 2 weeks.

CONCLUSIONS:

The toll of the pandemic has been reflected in the anesthesiology conversation on Twitter, representing 0.01% of all COVID-19 tweets. Daily tweet activity showed how the Twitter community used the platform to learn about important topics impacting anesthesiology practice during a global pandemic. Twitter is a relevant platform through which to communicate about anesthesiology topics, but further research is required to delineate its effectiveness, benefits, and limitations for anesthesiology discussions.
Regulation of human IGF-II transcription in fetal and adult tissues
Authors: Schofield Paul N. , Tate Valerie E.
Published: April 2021

The insulin-like growth factors are single-chain polypeptides which promote cell multiplication in vitro. Their role in mammalian development is uncertain, although they have been implicated as modulators of cell growth and differentiation. We present evidence that the human IGF-II gene has at least two promoters, and their expression may be developmentally controlled in the liver. Most of the IGF-II transcripts in the fetal organs examined are derived from a promoter which is different to that used for most adult liver IGF-II mRNAs. Steady-state levels of IGF-II transcripts are seen to be dramatically reduced in organs of adult rather than fetal origin. This observation is apparently not linked to promoter usage and therefore suggests a second level of transcriptional control.

In addition, we show that an alternative splicing event at an intron/exon boundary, which results in an mRNA with an altered coding potential, is not developmentally regulated. This variant IGF-II mRNA is coexpressed with the major species of IGF-II at a low, but constant, ratio in all fetal and adult organs examined.
The minor haemoglobins of primitive and definitive erythrocytes of the chicken embryo. Evidence for haemoglobin L
Authors: Cirotto C. , Panara F. , Arangi I.
Published: April 2021

A new minor haemoglobin, L, was isolated from the haemolysates of chicken embryos more than 7 days old. Electrophoresis in denaturing conditions and tryptic peptide maps of the globins show that the β-Mike globin of HbL is identical to that of the minor haemoglobin H(βH) while the α-like globin is very similar to that of the adult haemoglobin D (αD). HbL completes the description of the map of the minor chicken haemoglobins during embryonic development. In early embryos two minor haemoglobins, M and E, are produced which have the same βMike globin (ε) and differ in their α-like globins (αD and αA, respectively). The same two α -like globins will make up the minor haemoglobins of the late embryo, L and H, which differ from HbM and HbE on account of their β -like globin (βH).

The native tetramers L and M are hard to distinguish from each other. However the constituent ε globin can be easily separated from βH by electrophoresis on polyacrylamide gel in formic acid. With this method we found that the switch of the minor haemoglobins in the blood of chicken embryos starts at the 7th incubation day.

The two red cell populations, primitive and definitive, present in the blood of 7-day-old embryos were separated on an albumin gradient and their minor haemoglobins analysed. The haemoglobin couple M/E was found in the primitive erythroid cells whereas the L/H couple was found in the definitive ones. The disappearance of the early haemoglobin couple and its substitution by the late one during embryonic development correlates with the replacement of erythroid lines in the blood.
Patterns of mRNA prevalence and expression of B1 and B2 transcripts in early mouse embryos
Authors: Taylor Kent D. , Pikó Lajos
Published: April 2021

Considerable evidence indicates that the 2-cell stage is a critical period of mouse embryo development when a transition from maternal to zygotic genomic control takes place. The overall changes in the structure of the mRNA population as a result of this transition were explored using a random cDNA library of 69 clones derived from late 2-cell embryos. The prevalence of the cloned sequences was analysed by dot hybridization of the cDNA clones with labelled cDNA probes synthesized to poly(A)+ RNA from different stages of development from 1-cell through blastocyst. The number of copies of individual transcripts was quantitatively estimated by comparison to standard clones of known prevalence. About one half of the transcripts that gave a measurable reaction at the 2-cell and later stages were not represented detectably in egg RNA, suggesting that a large set of zygote-specific genes not included in the maternal gene set becomes transcriptionally active in the 2-cell embryo. Six of the cDNA clones represented Bl and B2 repeat sequences. As measured by hybridization with labelled cDNA, Bl and B2 transcripts were abundantly expressed throughout cleavage, being represented by about 105 to 106 copies per embryo. However, the developmental pattern of prevalence was different for the two transcripts suggesting that their expression is regulated independently. The results of this study corroborate previous evidence derived from protein synthetic patterns and in vitro translation experiments that a major qualitative shift in the mRNA population occurs in the 2-cell embryo.
The organization of mesodermal pattern inXenopus laevis:experiments using aXenopusmesoderm-inducing factor
Authors: Cooke Jonathan , Smith J. C. , Smith Emma J. , Yaqoob M.
Published: April 2021

In this paper, we study the mechanism by which a Xenopus cell line-derived mesoderm-inducing factor (MIF) might establish the spatial-pattern of cellular differentiation in the mesoderm. The effects of the factor on competent animal pole tissue are consistent with it being identical to the natural mesoderm-inducing factor. The signal can only act on those membrane domains of the animal pole that face the blastocoel, but it can be stably recorded there, such that axial mesoderm is formed, after 15 min exposure or less. This exposure can end some hours, or several cell cycles, before the onset of RNA synthesis yet nevertheless be fully effective, although competence to respond also extends well after the onset of transcription.

Exposure of the entire blastocoel lining of intact embryos to MIF causes a synchronous and sudden transformation of the behaviour and adhesive properties of all inner animal cap cells. This transformation mimics and is contemporaneous with the involution behaviour of normal mesoderm in the early gastrula marginal zone. Although high concentrations of MIF totally disorganize gastrulation, lower concentrations permit gastrulation to proceed. However, the pattern of mesoderm in these embryos is disrupted and ectopic mesoderm is formed around the blastocoel remnant.

When MIF is injected directly into blastomeres, rather than into the blastocoel, it has no effect. This suggests that the molecule is secreted from source cells and affects target cells through an extracellular receptor.

Finally, we show that small pieces of animal pole tissue recently exposed to MIF go on to produce morphogenetic signals perhaps distinct from MIF. We discuss the role of these signals in establishing and modifying the spatial pattern of cellular differentiation in the mesoderm of Xenopus.
Genetics of sex determination: what can we learn from Drosophila?
Authors: Nöthiger Rolf , Steinmann-Zwicky Monica
Published: April 2021

The combined efforts of genetics, developmental and molecular biology have revealed the principles of genetic control of sexual differentiation in Drosophila. In combination with maternal components, a quantitative chromosomal signal, provided by the ratio of X chromosomes to sets of autosomes (X:A), regulates a key gene (Sxl). The functional state, ON or OFF, of Sxl, via a few subordinate regulatory genes, controls a switch gene (dsx) that can express two mutually exclusive functions, M or F. These serve to repress either the female or the male set of differentiation genes, thus directing the cells either into the male or into the female sexual pathway.

Investigations of control genes and their regulation show that they have properties of homeotic genes. Their role is to select one of two alternative developmental programs. Their function, or lack of function, is required throughout development to maintain the cells in their respective sexual pathway.

Differentiation genes are under negative control by dsx. We discuss the cis- and trans-regulatory elements that are needed for sex-, tissue- and stage-specific expression of the differentiation genes.

A comparison of Drosophila to other organisms such as Caenorhabditis, mammals and other insects indicates similarities that we interpret as evidence for a basically invariant genetic strategy used by various organisms to regulate sexual development.
Testis-specific transcripts detected by a human Y-DNA-derived probe
Authors: Leroy P. , Seboun E. , Mattei M. G. , Fellous M. , Bishop C. E.
Published: April 2021

A genomic sequence ( 12f3), derived from the long arm of the human Y chromosome, detects a 1-6 kb mRNA, expressed in human and mouse testis, but not in other tissues tested by Northern blot analysis. Using 12f3 as a probe, a mouse cDNA, designated PL5, was isolated from an adult mouse testis cDNA library. The profile obtained by Southern blot analysis using PLS as probe under high-stringency conditions, reveals that 12f3 probably represents a Y-located pseudogene which was derived from an autosomally located gene. Southern blot analysis of different vertebrate species, using probe PL5, shows that this gene has been highly conserved during evolution. Preliminary in situ hybridizations on testis tissue sections indicate that PLS is expressed during the postmeiotic stages of male germ cell differentiation and thus may play a role during spermatogenesis. A second cDNA, also obtained from the testis cDNA library, weakly crossreacts with 12f3. This cDNA, designated PL10, detects a mRNA of approximately 4 kb which is highly expressed in mouse testis, but not in male or female mouse liver. The gene corresponding to this cDNA is also well conserved among vertebrates.
Mapping of testis-determining locus on Yp by the molecular genetic analysis of XX males and XY females
Authors: Müller Ulrich
Published: April 2021

Sex reversal in males with female karyotypes is likely to be caused by the presence of cytogenetically undetectable Y-chromosomal DNA sequences that include the testis-determining gene(s). Studying a total of sixteen 46,XX males and one 47,XXX male, we detected Y-chromosomal DNA in 13 of the XX males (i.e. 80 %) and in the 47,XXX male. The amount of Y-chromosomal DNA present in the patients varied between individuals. This allowed the construction of a molecular map of the Y-chromosome short arm. The putative testis-determining locus was assigned to the more distal portion of Yp, yet proximal to the pseudoautosomal region. Mapping of the testis-determining locus was complemented by molecular findings in 46,XY females. These individuals may carry microdeletions of the portion of Yp that appears to be required for normal male gonadogenesis. The deletions detected in 46,XY females always included those Y-chromosomal DNA sequences that were found in most 46,XX males. Furthermore, the same DNA sequences were missing in a female with a 46,X,dic(Y) karyotype. The observations suggest that some of our DNA probes hybridize with Y-chromosomal DNA sequences within a few million base pairs of the testis locus. Chromosome walking and pulsed-field gel electrophoresis investigations have been initiated in order to isolate those Y-chromosomal DNA sequences that are required for normal testicular development.
Normal and abnormal interchanges between the human X and Y chromosomes
Authors: Weissenbach Jean , Levilliers Jacqueline , Petit Christine , Rouyer François , Simmler Marie-Christine
Published: April 2021

A single obligatory recombination event takes place at male meiosis in the tips of the X- and Y-chromosome short arms (i.e. the pseudoautosomal region). The crossover point is at variable locations and thus allows recombination mapping of the pseudoautosomal loci along a gradient of sex linkage. Recombination at male meiosis in the terminal regions of the short arms of the X and Y chromosomes is 10- to 20-fold higher than between the same regions of the X chromosomes during female meiosis. The human pseudoautosomal region is rich in highly polymorphic loci associated with minisatellites. However, these minisatellites are unrelated to those resembling the bacterial Chi sequence and which possibly represent recombination hotspots. The high recombination activity of the pseudoautosomal region at male meiosis sometimes results in unequal crossover which can generate various sex-reversal syndromes.
Autogenous regulation of tubulin synthesis via RNA stability during sea urchin embryogenesis
Authors: Gong Zhiyuan , Brandhorst Bruce
Published: April 2021

When pluteus embryos of Lytechinus pictus were treated with colcemid, the incorporation of [35S]meth- ionine into tubulin declined by 5- to 15-fold within 4 h. This was mostly accounted for by a rapid decline in the concentration of α- and β-tubulin mRNA in the cytoplasm. Treatment with other microtubule depoly- merizing agents (colchicine, nocodazole, low concen- trations of vinblastine) had similar effects. Treatment of embryos with the microtubule-stabilizing agent, taxol, or high concentrations of vinblastine resulted in increased synthesis of tubulin. The concentration of tubulin mRNA increases during development and becomes increasingly sensitive to colcemid and de- creasingly sensitive to taxol. The transcriptional ac- tivity of tubulin genes, estimated by an RNA run-on assay in isolated nuclei, was not altered after colcemid treatment. On the other hand, the rate of decay of tubulin mRNA in prism embryos treated with actino- mycin D was increased several fold by colcemid treatment, while taxol treatment led to an increased half-life of tubulin mRNA. These observations suggest that tubulin synthesis is autogenously regulated at the level of mRNA stability by the level of unpolymerized tubulin. The increasing polymerization of micro- tubules and declining level of unpolymerized tubulin during embryogenesis would result in a stabilization of tubulin mRNA accounting for the increasing concen- tration of tubulin mRNA and rate of tubulin synthesis, as well as the increasing sensitivity of tubulin synthesis to microtubule-depolymerizing agents. Evidence is also presented for a rapid influence of the level of unpolymerized tubulin on the efficiency of translation of tubulin mRNA.
Developmental Biology
Authors: Walbot Virginia , Holder Nigel , Davidson Eric H.
Published: April 2021

Another new undergraduate biology text, the title of which includes the word ‘Development,’ has in recent years arrived on my desk every few months. Depending on one’s point of view, it either is or is not surprising that each has a distinctive character, a different concept of what the field of development encompasses, a particular flavour. Of course they all share certain features as well, e.g. photomicrographs of various well-known embryos, and a plethora of beautiful and informative diagrams, the sort with which the college biology texts of my undergraduate era were never endowed Their similarities make it nearly impossible in evaluating any one of these books to avoid comparison. Nor is it possible to discuss their dissimilarities of ‘flavour’ in a wholly objective fashion, reactions to flavours being essentially a personal matter.
Intercellular communication in the early embryo of the ascidian Ciona intestinalis
Authors: Serras F. , Baud C. , Moreau M. , Guerrier P. , Biggelaar J. A. M. Van Den
Published: April 2021

We have studied the intercellular communication pathways in early embryos of the ascidian Ciona intestinalis. In two different series of experiments, we injected iontophoretically the dyes Lucifer Yellow and Fluorescein Complexon, and we analysed the spread of fluorescence to the neighbouring cells. We found that before the 32-cell stage no dye spread occurs between nonsister cells, whereas sister cells are dye-coupled, possibly via cytoplasmic bridges. After the 32-cell stage, dye spread occurs throughout the embryo. However, electrophysiological experiments showed that nonsister cells are ionically coupled before the 32-cell stage. We also found that at the 4-cell stage junctional conductance between nonsister cells is voltage dependent, which suggests that conductance is mediated by gap junctions in a way similar to that observed in other embryos.
Proximodistal leg regeneration in Carausius morosus: growth, intercalation and proximalization
Authors: Bart A.
Published: April 2021

The proximodistal epidermal organization of the regenerated insect leg has been studied by grafting between corresponding and noncorresponding levels of the pro- and metathoracic femur and tibia. The results have been studied quantitatively (growth rates of the associated parts and of unsegmented intercalary structures) and qualitatively (nature, length, polarity of intercalary structures). In grafts between equivalent levels, no intercalary structure is formed, but a differential growth has been observed, the distal one fifth of segments growing about 1·5 to 2 times more than the proximal one. In grafts between different levels, unsegmented intercalary structures are formed from the distal part which thereby acquires proximal characteristics (proximalization). However, distal tibial cells do not form femur in this process under an hypothetical femoral influence: there is no ‘dominance’ of femur over tibia. Some segmented intercalary structures have also been observed, but their formation cannot be related clearly to differences in the healing process. To explain proximalization, an hypothesis is presented suggesting that distal cells, which grow faster, would be the first to enter a period when positional value becomes labile and would then adapt to the proximal cells’ value.
Neural cell adhesion molecules during embryonic induction and development of the kidney
Authors: Klein Gerd , Langegger Maria , Goridis Christo , Ekblom Peter
Published: April 2021

The neural cell adhesion molecules (N-CAM) are a family of related glycoproteins with Mr of 180,140 and 120 ×103 (180K etc.). In the embryo, they are often highly sialylated and migrate as a diffuse band of 170250K. N-CAM are found in non-neural tissues and we have now studied the expression of N-CAM in the developing mouse kidney. During kidney development, a unique conversion of a mesenchyme to an epithelium occurs and it is thought that this is mediated by an increase in cell adhesivity. By immunofluorescence, we show that N-CAM is present already at onset of kidney development on the cells of the uninduced nephrogenic mesenchyme. After induction, when the cells convert into an epithelium, they lose N-CAM gradually and instead begin to express uvomorulin, another primary CAM. By using an organ culture model, we could rather precisely show that N-CAM and uvomorulin are coexpressed for a short period, but, when epithelial cell polarization is evident, only uvomorulin is present on the epithelium, whereas N-CAM is confined to the surrounding mesenchyme.

Immunoblotting for N-CAM revealed that the ‘embryonic’ form of N-CAM, the broad 170 –250K band was not present in the embryonic kidney, which instead expressed the three distinct 180K, 140K and 120K bands typical of adult neurones. The 180K and 140K bands were gradually lost during development and were no longer detectable in adult kidneys. By using an N-CAM cDNA, we detected three different mRNAs of 7 ·4, 6 ·7 and 4 ·3 kb in the developing kidney, but this expression was restricted to the embryonic and early postnatal stages. No transcripts were detectable in adult kidneys. The studies do not support the hypothesis that N-CAM expression in the kidney is turned on by embryonic induction. Rather, we suggest that N-CAM are important adhesives for the predetermined, but not yet induced, nephrogenic mesenchyme.
An embryonic pineal body as a multipotent system in cell differentiation
Authors: Watanabe Kenji , Aoyama Hirohiko , Tamamaki Nobuaki , Sonomura Takako , Okada T. S. , Eguchi Goro , Nojyo Yoshiaki
Published: April 2021

The differentiating potency of pineal cells from 8-day quail embryos was studied with cell culture. It was found that the differentiation of striated muscle fibres occurred abundantly in the pineal cells cultured in hypertonic culture conditions. Muscle nature of these fibres was confirmed by utilizing the antiserum against the striated muscle type creatine kinase (MM – CK). When CO2, NAHCO3, NaCl, KC1 and MgCl2 were added in hypertonic concentrations, extensive myogenesis occurred in cultured pineal cells. Myogenesis in pineal cultures began as early as 2 days and, after 3 days in the medium with 75 mm additional NaCl, reached 100-fold when compared with that in the isotonic medium. Muscle fibres from pineal cells in culture were similar in morphology to the skeletal muscle fibres of mesodermal origin in situ. Myogenesis of pineal cells under hypertonic conditions was accompanied by the synthesis of a unique 56 × 103Mr protein, which was not found in the intrinsic muscle cells. Clonal cell culture revealed that about 80 % of clonable pineal cells were myogenic precursors. Pineal cells of 8-day quail embryos were not only myogenic but oculopotent (melanogenic and lentoidogenic) in cultures. This study examined whether multipotential progenitor cells with both potentials are present in the pineal or not. The results showed that at least 16 % of all clonable pineal cells were multipotent precursors. The embryonic pineal is considered to be a typical multipotent system in parallel with the pigmented and neural retina, the neural crest and the teratocarcinoma.
Mutant expression of male copulatory bursa surface markers in Caenorhabditis elegans
Authors: Link Christopher D. , Ehrenfels Christian W. , Wood William B.
Published: April 2021

In a search for molecular markers of male tail morphogenesis in C. elegans, we have detected two surface markers that are specifically observed in the copulatory bursa of adult males and the vulva of adult hermaphrodites. These markers are defined by binding of a monoclonal antibody (Abll7) and the lectin wheat germ agglutinin (WGA) to live intact animals. Expression of these markers is dependent on sex, stage and anterior-posterior position in the animal. Four of ten mutants with specific defects in bursal development show altered expression of one or both markers. Because the WGA marker can be expressed in intersexual animals with very little bursal development, posterior surface expression of this marker can serve as an indication of subtle masculinization of hermaphrodites. The timing of expression of these markers is not affected by heterochronic mutations that cause larval animals to express adult cuticles or adult animals to express larval cuticles, indicating that marker expression can be uncoupled from general cuticle development. Mutant lin-22 males, which have an anterior-to-posterior transformation of cell fates in the lateral hypodermis, ectopically express both markers in a manner consistent with a ‘posteriorization’ of positional information in these animals. These markers should be useful for the isolation and characterization of mutants defective in bursal and vulval development, sex determination and expression of anterior-posterior positional information.
Relocation and reorganization of germ plasm in Xenopus embryos after fertilization
Authors: Ressom R. E. , Dixon K. E.
Published: April 2021

In the unfertilized egg, germ plasm is widely distributed throughout the vegetal subcortex in small islets. Following fertilization or artificial activation, the location and organization changes, and by the 4- to 8-cell stage the germ plasm forms a small number of large patches overlying the vegetal pole. We distinguish three processes that produce these changes. The first of these is aggregation which involves the islets moving towards the vegetal pole to form large patches by coalescence. This phase requires microtubules but does not depend on cleavage or dynamic microfilaments. The second phase is ingression during which the patches of germ plasm move to the interior of the egg. The movement is due to a flow of cytoplasm from the vegetal pole internally and the cytoplasmic current does not require either microtubules or dynamic microfilaments. In the third phase, the germ plasm is trapped in the vegetal hemisphere by microtubular arrays - in normal development, the mitotic spindle.
The fate of fetal Leydig cells during the development of the fetal and postnatal rat testis
Authors: Kerr J. B. , Knell C. M.
Published: April 2021

The ultrastructure and developmental fate of the fetal generation of Leydig cells of the rat testis was studied from the 17th day of fetal life up to 100 days after birth. The number of fetal Leydig cells per testis was determined by light microscopic morphometric analysis of semithin plastic sections. In fetal testes (days 17–22 postconception), Leydig cells exhibited a characteristic ultrastructure, containing smooth endoplasmic reticulum, many lipid inclusions and glycogen. Testes of 17-day-old fetuses contained about 25 × 103 fetal Leydig cells, rapidly increasing to 90×103 per testis in 21-day-old fetuses. After birth, fetal Leydig cells per testis remained relatively constant up to 2 weeks (80–90×103 per testis) and were identified by light and electron microscopy which showed their numerous lipid inclusions, their tendency for clustering and their association with interstitial tissue fibroblasts which partly encapsulated the fetal Leydig cells. From 21–100 days after birth, fetal Leydig cell numbers were quite variable with a mean of 45–60 ×103 per testis. These results are the first to show that the fetal generation of Leydig cells persist in the adult testis and do not undergo early postnatal degeneration or dedifferentiation into other interstitial cells. The simultaneous occurrence of the fetal Leydig cells and the adult population of Leydig cells indicates that these cells are distinct cell generations which are developmentally unrelated.
Antibodies against mouse nerve growth factor interfere in vivo with the development of avian sensory and sympathetic neurones
Authors: Rohrer Hermann , Hofer Magdalena , Hellweg Rainer , Korsching Sigrun , Stehle August D. , Saadat Siawusch , Thoenen Hans
Published: April 2021

The monoclonal antibody 27/21 directed against mouse nerve growth factor (NGF) interferes in vivo with the survival of sensory dorsal root ganglion (DRG) neurones during the development of the quail embryo: the number of DRG neurones at embryonic day 11 (Ell) was reduced by about 30 % in embryos treated with the antibody between E3 and Ell. Neurone numbers in the nodose ganglion were not affected.

The effect of NGF antibodies on sympathetic neurones was assessed by determining the levels of the adrenergic marker enzyme tyrosine hydroxylase. Both total tyrosine hydroxylase activity and protein levels in sympathetic chains were reduced by about 30 % in embryos treated with 27/21 antibody but not in embryos treated with a control antibody.

The 27/21 antibody cross-reacts with chick NGF-like activity as shown in vitro by the ability of the antibody to partially block the survival activity of chick-embryo-fibroblast-conditioned medium for E9 chick DRG neurones.
A gradient of affinities for sensory bristles across the wing blade ofDrosophila melanogaster
Authors: Ripoll P. , Messal M. El , Laran E. , Simpson P.
Published: April 2021

The wing blade of Drosophila melanogaster is composed of dorsal and ventral surfaces covered with hairs and rows of morphologically distinct bristles round the margin. The mutant shaggy causes a complete transformation of hairs into bristles over the entire wing surfaces. Clones of mutant bristles have a tendency to line up into straight bristle rows. Clones are straight and orderly near the wing margin but form bundles and vesicles when a long distance from the margin. Furthermore the bristle cells move distally along the future wing blade in the general direction of the margin. From these studies, we postulate the existence of a gradient of cell affinities for bristle cells that is maximal at the dorsoventral wing margin and decreases with distance away from it. The bristle clones also move onto the wing veins and often induce the formation of new veins in the surrounding shaggy+ cells. These new veins run from the clone and join up to existing veins. We conclude that there is a close relationship between bristles and veins.
CpG methylation of an X-linked transgene is determined by somatic events postfertilization and not germline imprinting
Authors: Collick Andrew , Reik Wolk , Barton Sheila C. , Surani M. Azim H.
Published: April 2021

The process of X-inactivation in mammals requires at least two events, the initiation of inactivation and the maintenance of the inactive state. One possible mechanism of control is by methylation of DNA at CpG dinucleotides to maintain the inactive state. Further-more, the paternal X-chromosome is frequently inactivated in the extraembryonic membranes. The relationship between the parental origin of the chromosome, nonrandom inactivation and DNA methylation is not clear. In this paper, we report on the CpG methylation of an X-linked transgene, CAT-32. The levels of methylation in embryonic, extra-embryonic and germline cells indicates that the modifications of the transgene are broadly similar to those reported for endogenous X-linked genes. Interestingly, the methylation of CAT-32 transgene in extraembryonic tissues displays patterns that could be linked to the germline origin of each allele. Hence, the maternally derived copy of CAT-32 was relatively undermethylated when compared to the paternal one. The changes in DNA methylation were attributed to de novo methylation occurring after fertilization, most probably during differentiation of extraembryonic tissues. In order to determine whether or not the patterns of DNA methylation reflected the gennline origin of the X-chromosome, we constructed triploid embryos specifically to introduce two maternal X-chromosomes in the same embryo. In some of these triploid conceptuses, methylation patterns characteristic of the paternally derived transgene were observed. This observation indicates that the methylation patterns are not necessarily dependent on the parental origin of the X-chromosome, but could be changed by somatic events after fertilization. One of the more likely mechanisms is methylation of the transgene following inactivation of the X-chromosome in extraembryonic tissues.
Initial limb budding is independent of apical ectodermal ridge activity; evidence from a limbless mutant
Authors: Carrington Jill L. , Fallon John F.
Published: April 2021

Outgrowth of normal chick limb bud mesoderm is dependent on the presence of a specialized epithelium called the apical ectodermal ridge. This ectodermal ridge is induced by the mesoderm at about the time of limb bud formation. The limbless mutation in the chick affects apical ectodermal ridge formation in the limb buds of homozygotes. The initial formation of the limb bud appears to be unaffected by the mutation but no ridge develops and further outgrowth, which is normally dependent on the ridge, does not take place. As a result, limbless chicks develop without limbs. In the present study, which utilized a pre-limb-bud recombinant technique, limbless mesoderm induced an apical ectodermal ridge in grafted normal flank ectoderm. However, at stages when normal flank ectoderm is capable of responding to ridge induction, limbless flank ectoderm did not form a ridge or promote outgrowth of a limb in response to normal presumptive wing bud mesoderm. We conclude from this that the limbless mutation affects the ability of the ectoderm to form a ridge. In addition, because the limbless ectoderm has no morphological ridge and no apparent ridge activity (i.e. it does not stabilize limb elements in stage-18 limb bud mesoderm), the limbless mutant demonstrates that the initial formation of the limb bud is independent of apical ectodermal ridge activity.
Cytogenetic study of silver-staining NOR in 8-cell-stage mouse blastomeres fused to 1-cell-stage embryos
Authors: Dyban A. P. , Lee K. , O’Neill G. T. , Speirs S. , Kaufman M. H.
Published: April 2021

Isolated blastomeres from 8- to 16-cell-stage embryos were fused by standard micromanipulatory means with either unfertilized eggs or fertilized or haploid parthenogenetically activated pronuclear-stage embryos. The hybrid eggs/embryos were incubated overnight in the presence of Colcemid until they had entered the first cleavage division. Air-dried chromosome preparations were then stained with silver nitrate in order to detect active nucleolar organizing regions (NOR). While control unfertilized eggs and 1- cell-stage fertilized and parthenogenetically activated embryos showed no evidence of silver-staining NOR-positive regions, the metaphase plates from 8- to 16-cell embryos showed characteristic NOR-positive regions, while their interphase nuclei also showed a characteristic reticular staining appearance. When hybrids between blastomere nuclei and unfertilized eggs were examined, none of the blastomere nuclei entered mitosis. However, when hybrids between blastomere nuclei and fertilized embryos were examined, in two thirds of the embryos, a single blastomere-derived diploid metaphase plate was present in association with two pronuclear-derived haploid metaphase plates. In most instances, the blastomere-derived chromosomes did not display silver-nitratestaining NOR. Similar findings were observed when the blastomere-derived chromosomes in hybrids between blastomere nuclei and haploid parthenogenetic embryos were analysed. In the majority of cases, when blastomere nuclei remained in interphase, the characteristic silver-nitrate-staining fine reticular material either was not seen, or the nuclear contents were dispersed into clumps of chromatin-like material. Occasionally, the diploid chromosomes in the hybrids displayed morphological abnormalities. Our findings suggest that the cytoplasm of activated (but not nonactivated) 1-cell embryos is capable of influencing the nucleolar activity of the introduced 8- to 16-cell nuclei, effectively erasing from their chromosomes the memory of at least three previous rounds of rRNA synthesis.
Expression pattern of the FGF-related proto-oncogene int-2 suggests multiple roles in fetal development
Authors: Wilkinson David G. , Bhatt Sangita , Mcmahon Andrew P.
Published: April 2021

The FGF-related proto-oncogene int-2 is implicated in mouse embryogenesis, since it is expressed in specific tissues during gastrulation and neurulation (Wilkinson et al. 1988). Here, we describe the expression of this gene during subsequent fetal development, int-2 transcripts are restricted to Purkinje cells in the cerebellum and to regions of the developing retina containing early-stage differentiating cells. This high level expression is not detected in the mature cerebellum or retina. In addition, int-2 RNA is detected in the mesenchyme of the developing teeth and in sensory regions of the inner ear. This complex and dynamic pattern suggests multiple roles of this proto-oncogene during fetal development of the mouse.
Influence of diandric and digynic triploid genotypes on early mouse embryogenesis
Authors: Kaufman M. H. , Lee K. K. H. , Speirs S.
Published: April 2021

Standard micromanipulatory techniques were used to produce tripronucleate diandric and digynic triploid mouse conceptuses. When these were transferred to suitable recipients, most implanted. A wide range of embryonic stages from the primitive streak to the 15- to 25-somite stage were isolated in both triploid series in otherwise identical recipients. In the diandric triploid series, all of the embryos recovered appeared to be morphologically normal, but considerably smaller than fertilized embryos analysed at similar stages of development. This contrasts with the digynic triploid conceptuses which, though also ranging from the primitivestreak stage to about the 10- to 15-somite stage at the time of their isolation, generally showed poorer embryonic development than the diandric triploids, and were invariably morphologically abnormal. Unlike the situation observed in man, where the placentas of diandric triploid conceptuses commonly display widespread trophoblastic hyperplasia and form the characteristic ‘partial’ or ‘incomplete’ type of hydatidiform moles, the extraembryonic membranes of the diandric triploid mouse conceptuses (as well as the digynic triploids) did not appear to be grossly abnormal).