bluuebunny/crossref_metadata_2025 huggingface dataset:
Suppression of neuroinflammation by an allosteric agonist and positive allosteric modulator of the α7 nicotinic acetylcholine receptor GAT107
Authors: Mizrachi Tehila , Marsha Oshrit , Brusin Karen , Ben-David Yael , Thakur Ganesh A. , Vaknin-Dembinsky Adi , Treinin Millet , Brenner Talma
Published: April 2021

Background

The α7 nicotinic acetylcholine receptor (α7 nAChR) negatively regulates the synthesis and release of pro-inflammatory cytokines by immune cells. Our previous studies showed that in encephalitogenic T cells, α7 nAChR expression is upregulated and that activation of the cholinergic system can attenuate experimental autoimmune encephalomyelitis (EAE). GAT107 is an allosteric agonist and positive allosteric modulator (ago-PAM) of α7 nAChR that can produce persistent activation of this receptor. Therefore, in the present study, we investigated the effect of GAT107 on neuroinflammation in EAE, the animal model used for the study of multiple sclerosis (MS) via α7 nAChR, and the inflammatory pathways involved.

Methods

EAE was induced by administration of myelin oligodendrocyte glycoprotein (MOG35–55) in C57BL/6 mice. EAE mice were treated with the ago-PAM GAT107 or a placebo for 9 days, starting from the day of EAE induction. Clinical assessment and immunological evaluation of immune cells and cytokine production was performed.

Results

Following activation of the α7 nAChR by GAT107 during EAE, disease severity was significantly reduced by 70% and was correlated with a reduction in the extent of neuroinflammation in the CNS. The treatment reduced encephalitogenic T cell proliferation and the production of pro-inflammatory cytokines, as well as increased the production of the anti-inflammatory cytokine IL-10. Furthermore, the expression of immune cell markers was altered by GAT107 treatment, which induced a significant reduction in macrophages, dendritic cells, and B cells, as well as a reduction in anti-MOG35–55antibodies. Additionally, GAT107 was found to directly activate α7 nAChR in murine macrophage RAW264.7 cells and in human PBMCs derived from MS patients and healthy donors.

Conclusions

Our results show that GAT107 can be a useful molecule for harnessing the cholinergic anti-inflammatory pathway for long-lasting and wide-ranging modulation and downregulation of neuroinflammation in EAE.
Correction to: Psychiatric symptoms, risk, and protective factors among university students in quarantine during the COVID-19 pandemic in China
Authors: Sun Shufang , Goldberg Simon B. , Lin Danhua , Qiao Shan , Operario Don
Published: April 2021

An amendment to this paper has been published and can be accessed via the original article.
Design optimization of bidirectional arterial perfusion cannula
Authors: Abdel-Sayed Saad , Ferrari Enrico , Abdel-Sayed Philippe , Wilhelm Markus , von Segesser Ludwig-Karl , Berdajs Denis
Published: April 2021

Objectives

Determine if shortening the covered section of a self-expanding bidirectional arterial cannula, can enhance retrograde flow and thus reduce the risk of lower limb ischemia.

Methods

Outlet pressure vs flow rate was determined for three cannulas types: a 15F self-expanding bidirectional cannula having a covered section of 90 mm, the same cannula but with a shorter covered section of 60 mm, and a Biomedicus cannula as control. The performances of all the cannulas were compared using a computerized flow-bench with calibrated sensors and a centrifugal pump. Water retrograde flow was determined using a tank timer technique. Anterograde and retrograde flow rate versus outlet pressure were determined at six different pump speed.

Results

For each of the six pump speed, both bidirectional cannulas, 60-mm covered and 90-mm covered respectively, showed higher performance than Biomedicus cannula control, as demonstrated by higher flow rate and lower pressure. We also observed that for the bidirectional cannula with shorter covered section, i.e. 60 mm coverage, provides enhanced performance as compared to a 90-mm coverage. Finally, the flow rate and the corresponding pressure can be consistently measured by our experimental set-up with low variability.

Conclusions

The new configuration of a shorter covered section in a bidirectional self-expanding cannula design, may present an opportunity to overcome lower leg ischemia during extra-corporal life support with long term peripheral cannulation.
Aneuploid abortion correlates positively with MAD1 overexpression and miR-125b down-regulation
Authors: Zhao Juan , Li Hui , Chen Guangxin , Du Lijun , Xu Peiyan , Zhang Xiaoli , Xie Min , Cao Tiansheng , Li Haibo
Published: April 2021

Background

Aneuploidy is the most frequent cause of early-embryo abortion. Any defect in chromosome segregation would fail to satisfy the spindle assembly checkpoint (SAC) during mitosis, halting metaphase and causing aneuploidy. The mitotic checkpoint complex (MCC), comprising MAD1, MAD2, Cdc20, BUBR1 and BUB3, plays a vital role in SAC activation. Studies have confirmed that overexpression of MAD2 and BUBR1 can facilitate correct chromosome segregation and embryo stability. Research also proves that miR-125b negatively regulates MAD1 expression by binding to its 3′UTR. However, miR-125b, Mad1 and Bub3 gene expression in aneuploid embryos of spontaneous abortion has not been reported to date.

Methods

In this study, embryonic villi from miscarried pregnancies were collected and divided into two groups (aneuploidy and euploidy) based on High-throughput ligation-dependent probe amplification (HLPA) and Fluorescence in situ hybridization (FISH) analyses. RNA levels of miR-125b, MAD1 and BUB3 were detected by Quantitative real-time PCR (qRT-PCR); protein levels of MAD1 and BUB3 were analysed by Western blotting.

Results

statistical analysis (p < 0.05) showed that miR-125b and BUB3 were significantly down-regulated in the aneuploidy group compared to the control group and that MAD1 was significantly up-regulated. Additionally, the MAD1 protein level was significantly higher in aneuploidy abortion villus, but BUB3 protein was only mildly increased. Correlation analysis revealed that expression of MAD1 correlated negatively with miR-125b.

Conclusion

These results suggest that aneuploid abortion correlates positively with MAD1 overexpression, which might be caused by insufficient levels of miR-125b. Taken together, our findings first confirmed the negative regulatory mode between MAD1 and miR-125b, providing a basis for further mechanism researches in aneuploid abortion.
Mass transfer and flow characterization of novel algae-based nutrient removal system
Authors: Heyland Andreas , Roszell Jordan , Chau Jeremy , Chai Kevin , Eaton Andrew , Nolan Kathleen , Madden Kyle , Ahmed Wael H.
Published: April 2021

Background

Recirculating aquaculture systems (RAS) are an essential component of sustainable inland seafood production. Still, nutrient removal from these systems can result in substantial environmental problems, or present a major cost factor with few added value options. In this study, an innovative and energy-efficient algae based nutrient removal system (NRS) was developed that has the potential to generate revenue through algal commercialization. We optimized mass transfer in our NRS design using novel aeration and mixing technology, using air lift pumps and developed an original membrane cartridge for the continuous operation of nutrient removal and algae production. Specifically, we designed, manufactured and tested a 60-L NRS prototype. Based on specific airlift mixing conditions as well as concentration gradients, we assessed NRS nutrient removal capacity. We then examined the effects of different internal bioreactor geometries and radial orientations on the mixing efficiency.

Results

Using the start-up dynamic method, the overall mass transfer coefficient was found to be in the range of 0.00164–0.0074 $${\mathrm{s}}^{-1}$$

s

-
1

, depending on flow parameters and we confirmed a scaling relationship of mass transfer across concentration gradients. We found the optimal Reynolds number to be 500 for optimal mass transfer, as higher Reynolds numbers resulted in a relatively reduced increase of mass transfer. This relationship between mass transfer and Reynolds number is critical to assess scalability of our system. Our results demonstrate an even distribution of dissolved oxygen levels across the reactor core, demonstrating adequate mixing by the airlift pump, a critical consideration for optimal algal growth. Distribution of dissolved gases in the reactor was further assessed using flow visualization in order to relate the bubble distribution to the mass transfer capabilities of the reactor. We run a successful proof of principle trial using the green alga Dunaliella tertiolecta to assess mass transfer of nutrients across the membrane and biomass production.

Conclusions

Manipulation of the concentration gradient across the membrane demonstrates a more prominent role of airlift mixing at higher concentration gradients. Specifically, the mass transfer rate increased threefold when the concentration gradient was increased 2.5-fold. We found that we can grow algae in the reactor chamber at rates comparable to those of other production systems and that the membrane scaffolds effectively remove nutrients form the wastewater. Our findings provide support for scalability of the design and support the use of this novel NRS for nutrient removal in aquaculture and potentially other applications.
Cold-inducible RNA-binding protein (CIRP) potentiates uric acid-induced IL-1β production
Authors: Fujita Yuya , Yago Toru , Matsumoto Haruki , Asano Tomoyuki , Matsuoka Naoki , Temmoku Jumpei , Sato Shuzo , Yashiro-Furuya Makiko , Suzuki Eiji , Watanabe Hiroshi , Kawakami Atsushi , Migita Kiyoshi
Published: April 2021

Background

Gout is an autoinflammatory disease driven by interleukin-1 (IL-1) induction in response to uric acid crystals. IL-1β production is dependent on inflammasome activation, which requires a priming signal, followed by an activating signal. The cold-inducible RNA-binding protein (CIRP) has been recently identified as a damage-associated molecular pattern (DAMP). In this study, we evaluated the roles of CIRP in monosodium urate (MSU)-mediated IL-1β secretion using human neutrophils.

Methods

Human neutrophils were stimulated by MSU in the presence or absence of CIRP priming to determine NLRP3 inflammasome activation and subsequent caspase-1 activation and IL-1β production. Cellular supernatants were analyzed by enzyme-linked immunosorbent assay (ELISA) to determine the presence of IL-1β or caspase-1 (p20). The cellular supernatants and lysates were also analyzed by immunoblotting using anti-cleaved IL-1β or anti-cleaved caspase-1 antibodies.

Results

Neither CIRP nor MSU stimulation alone induced sufficient IL-1β secretion from neutrophils. However, MSU stimulation induced IL-1β secretion from CIRP-primed neutrophils in a dose-dependent manner. This MSU-induced IL-1β secretion from CIRP-primed neutrophils was accompanied by the induction of cleaved IL-1β (p17), which was inhibited by the pretreatment of MCC950, a specific inhibitor for NLRP3. Furthermore, cleaved caspase-1 was induced in the cellular lysates of CIRP/MSU-treated neutrophils. Additionally, CIRP stimulation induced the protein expression of pro-IL-1β in neutrophils.

Conclusions

Our data indicate that CIRP, an endogenous stress molecule, triggers uric acid-induced mature IL-1β induction as a priming stimulus for NLRP3 inflammasome in human neutrophils. We propose that CIRP acts as an important proinflammatory stimulant that primes and activates inflammasome and pro-IL-1β processing in response to uric acid in innate immune cells.
An access control model for the Internet of Things based on zero-knowledge token and blockchain
Authors: Song Lihua , Ju Xinran , Zhu Zongke , Li Mengchen
Published: April 2021

Information security has become a hot topic in Internet of Things (IoT), and traditional centralized access control models are faced with threats such as single point failure, internal attack, and central leak. In this paper, we propose a model to improve the access control security of the IoT, which is based on zero-knowledge proof and smart contract technology in the blockchain. Firstly, we deploy attribute information of access control in the blockchain, which relieves the pressure and credibility problem brought by the third-party information concentration. Secondly, encrypted access control token is used to gain the access permission of the resources, which makes the user's identity invisible and effectively avoids attribute ownership exposure problem. Besides, the use of smart contracts solves the problem of low computing efficiency of IoT devices and the waste of blockchain computing power resources. Finally, a prototype of IoT access control system based on blockchain and zero-knowledge proof technology is implemented. The test analysis results show that the model achieves effective attribute privacy protection, compared with the Attribute-Based Access Control model of the same security level, the access efficiency increases linearly with the increase of access scale.
Solving fuzzy $(1+ n)$-dimensional Burgers’ equation
Authors: Osman Mawia , Gong Zengtai , Mustafa Altyeb Mohammed , Yang Hong
Published: April 2021

In this paper, we study the comparison of fuzzy differential transform method (FDTM), fuzzy Adomian decomposition method (FADM), fuzzy homotopy perturbation method (FHPM), and fuzzy reduced differential transform method (FRDTM) to obtain the solutions of fuzzy$(1 + n)$(1+n)-dimensional Burgers’ equation under gH-differentiability. We have investigated many new results to solve the above problem, and the methods have been implemented. The four illustrative numerical examples are presented to demonstrate the effectiveness of the proposed methods and also to demonstrate the efficiency and simplicity of the ways they were developed and derived. The results also show that the methods are powerful mathematical tools for solving fuzzy$(1 + n)$(1+n)-dimensional Burgers’ equation.
Randomized observation periods for compound Poisson risk model with capital injection and barrier dividend
Authors: Yu Wenguang , Guo Peng , Wang Qi , Guan Guofeng , Huang Yujuan , Yu Xinliang
Published: April 2021

In this paper, we model the insurance company’s surplus by a compound Poisson risk model, where the surplus process can only be observed at random observation times. It is assumed that the insurer observes its surplus level periodically to decide on dividend payments and capital injection at the interobservation time having an $\operatorname{Erlang}(n)$
Erlang
(
n
)
distribution. If the observed surplus level is greater than zero but less than injection line $b_{1} > 0$

b
1

>
0
, the shareholders should immediately inject a certain amount of capital to bring the surplus level back to the injection line $b_{1}$

b
1

. If the observed surplus level is larger than dividend line $b_{2}$

b
2

($b_{2} > b_{1}$

b
2

>

b
1

), any excess of the surplus over $b_{2}$

b
2

is immediately paid out as dividends to the shareholders of the company. Ruin is declared when the observed surplus level is negative. We derive the explicit expressions of the Gerber–Shiu function, the expected discounted capital injection, and the expected discounted dividend payments. Numerical illustrations are also given to analyze the effect of random observation times on actuarial quantities.
Nearly constant Q models of the generalized standard linear solid type and the corresponding wave equations
Authors: Hao Qi , Greenhalgh Stewart
Published: April 2021

Time-domain seismic forward and inverse modeling for a dissipative medium is a vital research topic for investigating the attenuation structure of the earth. Constant [Formula: see text], also called the frequency independence of the quality factor, is a common assumption for seismic [Formula: see text] inversion. We have developed first- and second-order nearly constant [Formula: see text] dissipative models of the generalized standard linear solid type, using a novel [Formula: see text]-independent weighting function approach. The two new models, which originate from the Kolsky model (a nearly constant [Formula: see text] model) and the Kjartansson model (an exactly constant [Formula: see text] model), result in the corresponding wave equations in differential form. Even for extremely strong attenuation (e.g., [Formula: see text]), the quality factor and phase velocity for the two new models are close to those for the Kolsky and Kjartansson models, in a frequency range of interest. The wave equations for the two new models explicitly involve a specified [Formula: see text] parameter and have compact and simple forms. We provide a novel perspective on how to build a nearly constant [Formula: see text] dissipative model, which is beneficial for time-domain large-scale wavefield forward and inverse modeling. This perspective could also help obtain other dissipative models with similar advantages. We also discuss the extension beyond viscoacousticity and other related issues, for example, extending the two new models to viscoelastic anisotropy.
On tomography velocity uncertainty in relation with structural imaging
Authors: Messud Jérémie , Guillaume Patrice , Lambaré Gilles
Published: April 2021

Evaluating structural uncertainties associated with seismic imaging and target horizons can be of critical importance for decision making related to oil and gas exploration and production. An important breakthrough for industrial applications has been made with the development of industrial approaches to velocity model building. We have developed an extension of these approaches, sampling an equiprobable contour of the tomography posterior probability density function (PDF) rather than the full PDF, and using nonlinear slope tomography. Our approach allows for assessing the quality of uncertainty-related assumptions (linearity and Gaussian hypothesis within the Bayesian theory) and estimating volumetric migration positioning uncertainties (a generalization of horizon uncertainties), in addition to the advantages in terms of computational efficiency. We derive the theoretical concepts underlying this approach and unify our derivations with those of previous publications. Because the method works in the full model space rather than in a preconditioned one, we split the analysis into resolved and unresolved tomography spaces. We argue that resolved space uncertainties are to be used in further steps leading to decision making and can be related to the output of methods that work in a preconditioned model space. Unresolved space uncertainties represent a qualitative by-product specific to our method, strongly highlighting the most uncertain gross areas, thus useful for quality control. These concepts are developed on a synthetic data set. In addition, the industrial viability of the method is determined on two different 3D field data sets. The first one consists of a merge of different seismic surveys in the North Sea and indicates the corresponding structural uncertainties. The second one consists of a marine data set and indicates the impact of structural uncertainties on gross-rock volume computation.
Impact of Oral Chemotherapy Management Program on Capecitabine Toxicity Management
Authors: Nhean Salin , Kostoff Diana , Yang Jessica J. , Vogel Vishnuprabha , Rybkin Igor I.
Published: April 2021

PURPOSE:

Increasing use of oral chemotherapy has created unique challenges related to patient safety and compliance. To address this issue, the Henry Ford Cancer Institute at Henry Ford Health System developed and implemented a system-wide, multidisciplinary program named the Oral Chemotherapy Management Program (OCMP). The purpose of this study was to evaluate the impact of OCMP on patient outcomes in those receiving capecitabine.

METHODS:

This was a retrospective, quasi-experimental study that compared outcomes in patients receiving capecitabine before and after OCMP implementation. The co-primary outcomes were incidence(s) of grade 1-4 and grade 3-4 adverse effects (AEs) associated with capecitabine. Secondary outcomes were emergency department (ED) visits, hospitalizations because of toxicity, and adherence rate.

RESULTS:

OCMP patients had significantly lower overall incidence of AE of any grade (58.9% v 70.3%; 95% CI, 0.39 to 0.94; P = .03). OCMP implementation significantly lowered incidence of any grade and grade 3-4 nausea, vomiting, and/or diarrhea, and grade 3-4 hand-foot syndrome. It resulted in the decreased number of ED visits (8.9% v 18.9%; P = .005) and hospitalizations (6.3% v 17.1%; P = .002), as well as improved medication adherence rates (0.94 v 0.97; P = .03).

CONCLUSION:

Most patients who developed capecitabine-related AE required intervention by OCMP. Implementation of OCMP reduced the incidence of high-grade AE, decreased the number of ED visits and hospitalizations because of AE, and improved the medication adherence rate.
[18F]-FDG-PET/CT Correlates With the Response of Radiorefractory Thyroid Cancer to Lenvatinib and Patient Survival
Authors: Valerio Laura , Guidoccio Federica , Giani Carlotta , Tardelli Elisa , Puccini Giulia , Puleo Luciana , Minaldi Elisa , Boni Giuseppe , Elisei Rossella , Volterrani Duccio
Published: April 2021

Context

18F-fluoro-2-deoxy-D-glucose positron emission tomography–computed tomography ([18F]-FDG-PET/CT)–positive metastatic lesions in radioiodine-refractory differentiated thyroid cancer (RAI-R DTC) have a poor prognosis and lenvatinib represents the best therapy.

Objective

We investigated the role of [18F]-FDG-PET/CT in the evaluation of metabolic response and prediction of the outcome of RAI-R DTC patients treated with lenvatinib.

Methods

Patients (n = 33) with progressive metastatic RAI-R DTC who were treated with lenvatinib were investigated at baseline and during follow-up with biochemical (thyroglobulin and thyroglobulin antibodies), morphological (whole-body CT scan) and metabolic ([18F]-FDG-PET/CT) evaluation.

Results

Nineteen (57.6%) patients showed the greatest metabolic response at the first [18F]-FDG-PET/CT scan, performed after 4 weeks of lenvatinib, while 5/33 (15.1%) patients had this response later. Moreover, 66.7% of patients had both a metabolic response at the first [18F]-FDG-PET/CT scan and a morphological response at the first CT scan. We observed a correlation between the metabolic response at [18F]-FDG-PET/CT scan performed after 4 weeks of treatment and the biochemical response at the same time in 60.6% of patients. The median overall survival (OS) was significantly longer in patients with either a metabolic response at last [18F]-FDG-PET/CT (40.00 vs 8.98 months) or a morphological response at last CT scan (37.22 vs 9.53 months) than in those without response. Moreover, the OS was longer in patients with a metabolic response at [18F]-FDG-PET/CT performed after 4 weeks of treatment (36.53 vs 11.28 months).

Conclusions

Our data show that [18F]-FDG-PET/CT can early predict the response to lenvatinib and correlates with the OS of RAI-R DTC patients treated with this drug.
The Influence of Lens Antibodies on the Development of Lens Antigen-containing Tissues in the Chick Embryo
Authors: Maisel Jan Langman, Harry , Squires James
Published: April 2021

The purpose of this experiment was to analyse the effect of treatment with antibodies prepared against total lens or against alpha, beta, and gamma crystallin separately on the development of 24-, 32-, and 42-hour chick embryos. The following observations were made after an additional incubation period of 50-70 hours.

When 32-hour chick embryos were treated with the different antibodies, cellular degeneration and gross abnormalities such as anencephalus, rachischisis, and anophthalmia were observed only in embryos treated with total lens or with alpha crystallin antiserum, but not in those treated with beta or gamma crystallin antiserum. Since the result of treatment with total lens and with alpha crystallin antibodies was identical in nature, it is concluded that the antibody effect is due exclusively to the interaction of alpha crystallin antibodies and their corresponding cellular antigens. The cellular degeneration and gross abnormalities were restricted to brain and eye, that is those organs in which the presence of lens antigens had been demonstrated earlier by means of immunological and fluorescent antibody techniques. None of the other tissues and organs in the abnormal embryos showed any effect of antibody treatment, thus indicating a high specificity of the alpha crystallin antigen-antibody reaction. Abnormalities found in the 24-hour series were identical to those obtained in the 32-hour series, indicating that in both cases the alpha crystallin antibodies had interfered with the same developmental processes. Treatment of 42-hour embryos was ineffective, suggesting that at this stage of development the antigen-antibody interaction either has become impossible, or is no longer able to interfere with morphological development. Since in many of the grossly abnormal embryos no indication of cellular degeneration was found, it seems likely that an antigen-antibody interaction not necessarily leads to cellular degeneration and necrosis, but may also interfere with cell life in a less damaging manner, such as inhibition of growth and rechannelling of normal differentiation capacities.
Experimental analysis of the extension of the dorsal marginal zone in Pleurodeles waltl gastrulae
Authors: Shi De-Li , Delarue Michel , Darribére Thierry , Riou Jean-François , Boucaut Jean-Claude
Published: April 2021

The capacity for extension of the dorsal marginal zone (DMZ) in Pleurodeles waltl gastrulae was studied by scanning electron microscopy and grafting experiments. At the onset of gastrulation, the cells of the animal pole (AP) undergo important changes in shape and form a single layer. As gastrulation proceeds, the arrangement of cells also changes in the noninvoluted DMZ: radial intercalation leads to a single layer of cells. Grafting experiments involving either AP or DMZ explants were performed using a cell lineage tracer. When rotated 90° or 180°, grafted DMZ explants were able to involute normally and there was extension according to the animal–vegetal axis of the host. In contrast, neither single nor bilayered explants from AP involutes completely, and neither extends when grafted in place of the DMZ. Furthermore, when inside of the host, these AP grafts curl up and inhibit the closure of the blastopore. Once transplanted to the AP region, the DMZ showed no obvious autonomous extension. DMZs cultured in vitro showed little extension and this only from the late gastrula stage onward. Removal of blastocoel roof blocked involution to a varied extent, depending on the developmental stage of the embryos. From these results, it is argued that differences could well exist in the mechanism of gastrulation between anuran and urodele embryos. That migrating mesodermal cells play a major role in urodele gastrulation is discussed.
Abortive development in the crested newt Triturus cristatus
Authors: Wallace H.
Published: April 2021

Crested newts exhibit a balanced lethal system which causes development to abort in 50 % of tailbud embryos. The main features of arrested embryos are described, shown to be constant in a range of culture conditions and found to be unchanged by parabiosis or extirpation of the central nervous system or heart. Two categories of abortive embryos can be distinguished in some spawnings. A corresponding segregation of an easily identified marker chromosome confirms previous reports that chromosome 1 carries the recessive lethal factors. The marker chromosome is tentatively associated with the blistered form of abortive embryo.

Two possible modes of origin for the balanced lethal system are discussed, either from ancestral autosomes or from sex chromosomes. The latter is favoured because it involves fewer assumptions. The subsequent evolution of the system should inevitably lead to progressively earlier embryonic mortality by an accumulation of multiple recessive lethal factors on each chromosome variant.
Determinative properties of muscle lineages in ascidian embryos
Authors: Meedel Thomas H. , Crowther Robert J. , Whittaker J. R.
Published: April 2021

Blastomeres removed from early cleavage stage ascidian embryos and reared to ‘maturity’ as partial embryos often elaborate tissue-specific features typical of their constituent cell lineages. We used this property to study recent corrections of the ascidian larval muscle lineage and to compare the ways in which different lineages give rise to muscle. Our evaluation of muscle differentiation was based on histochemical localization and quantitative radiometric measurement of a muscle-specific acetylchol-inesterase activity, and the development of myofilaments and myofibrils as observed by electron microscopy. Although the posterior-vegetal blastomeres (B4.1 pair) of the 8-cell embryo have long been believed to be the sole precursors of larval muscle, recent studies using horseradish peroxidase to mark cell lineages have shown that small numbers of muscle cells originate from the anterior-vegetal (A4.1) and posterior-animal (b4.2) blastomeres of this stage. Fully differentiated muscle expression in isolated partial embryos of A4.1-derived cells requires an association with cells from other lineages whereas muscle from B4.1 blastomeres develops autonomously. Clear differences also occurred in the time acetylcholinesterase activity was first detected in partial embryos from these two sources. Isolated b4.2 cells failed to show any muscle development even in combination with anterior-animal cells (a4.2) and are presumably even more dependent on normal cell interactions and associations. Others have noted an additional distinction between the different sources of muscle: muscle cells from non-B4.1 lineages occur exclusively in the distal part of the tail, while the B4.1 descendants contribute those cells in the proximal and middle regions. During the course of ascidian larval evolution tail muscle probably had two origins: the primary lineage (B4.1) whose fate was set rigidly at early cleavage stages and secondarily evolved lineages which arose later by recruitment of cells from other tissues resulting in increased tail length. In contrast to the B4.1 lineage, muscle development in the secondary lineages is controlled less rigidly by.processes that depend on cell interactions.
Vasculogenesis in the early quail blastodisc as studied with a monoclonal antibody recognizing endothelial cells
Authors: Pardanaud Luc , Altmann Curtis , Kitos Paul , Dieterlen-Lievre Francoise , Buck Clayton A.
Published: April 2021

QH1, a monoclonal antibody that recognizes quail endothelial and haemopoietic cells, was applied to quail blastodiscs in toto, in order to analyse by immunofluorescence the emergence of the vascular tree. The first endothelial cells were detected in the area opaca at the headfold stage and in the area pellucida at the 1-somite stage. Single cells then interconnected progressively, especially in the anterior intestinal portal and along the somites building up the linings of the heart and dorsal aortas. This study demonstrates that endothelial cells differentiate as single entities 4h earlier in development than hitherto detected and that the vascular network forms secondarily. The horseshoe shape of the extraembryonic area vasculosa is also a secondary acquisition. A nonvascularized area persists until later (at least the 14-somite stage) in the region of the regressing primitive streak.
The formation of the area centralis of the retinal ganglion cell layer in the chick
Authors: Straznicky Charles , Chehade Mark
Published: April 2021

In adult domestic chickens, the neurones in the retinal ganglion cell layer are very unevenly disposed such that there is a sixfold increase in neurone density from the retinal edge to the retinal centre. The formation of the high ganglion-cell-density area centralis was studied on chick retinal wholemounts from the 8th day of incubation (E8) to 4 weeks after hatching (4WAH). The density of viable neurones and the number and the distribution of pyknotic neurones in the ganglion cell layer were estimated across the whole retina.

Between E8 and E10, the distribution of neurones in the ganglion cell layer was anisodensitic with 53000 mm-2 in the centre compared to 34000 mm-2 in the periphery of the retina. Thereafter, a progressively steeper gradient of neurone density developed, which decreased from 24000 mm-2 in the retinal centre to 6000 mm-2 at the retinal periphery by 4WAH. Neuronal pyknosis in the ganglion cell layer was observed between E9 and E17. From Ell onwards, consistently more pyknotic neurones were found in the peripheral than in the central retina. It was estimated that over the period of cell death approximately twice as many neurones died per unit area in the retinal periphery than in the centre. Retinal area measurements and estimation of neurone densities in the ganglion cell layer after the period of neurone generation and neurone death indicated differential retinal expansion, with more expansion in the peripheral than in the central retina.

These observations allow us to conclude that the formation of the area centralis of the chick retina involves (1) slightly higher cell generation in the retinal centre, (2) higher rate of cell loss in the retinal periphery and (3) differential retinal expansion.
Basal lamina is not a barrier to neural crest cell emigration: documentation by TEM and by immunofluorescent and immunogold labelling
Authors: Martins-Green M. , Erickson C. A.
Published: April 2021

One of the factors proposed to control initiation of migration of neural crest (NC) cells is disruption of the basal lamina (BL) that is presumed to exist over the dorsal portion of the neural tube. Previously, we discovered that, in the mouse embryo, a continuous BL is not deposited over the dorsal portion of the neural tube until emigration of the NC cells is terminated. Here, we show that the pattern of BL deposition in chick embryos is similar, but not identical, to that in the mouse. In particular, (i) patches of BL are deposited on the premigratory NC cells in the chick but not in the mouse and (ii) BL is thicker and more interstitial matrix is deposited at the same stage of development in the chick. In addition, immunofluor escent and immunogold labelling of collagen IV, laminin and fibronectin show that (i) patches of young BL contain all three molecules; (ii) collagen IV and laminin are present in BL throughout neurulation but fibronectin either disappears or becomes masked in more mature BL and (iii) collagen IV and especially fibronectin are present in the interstitial matrix, but the relative abundance of fibronectin changes with time. The simultaneous use of immunolabelling for both light and TEM sections has allowed us to determine unambiguously that presence of a basement membrane (light microscopy) does not necessarily imply presence of basal lamina. We conclude that, as in mouse, the BL cannot be involved in the timing of the initiation of migration of NC cells. Our evidence in both the mouse and the chick, together with work in the axolotl, suggests that the basic pattern of BL deposition during neurulation may be a general phenomenon in embryonic development. Moreover, these results, in conjunction with the work of others, suggest that the critical step for initiation of migration of NC cells may be the loss of adhesions between cells.
Cell fate, morphogenetic movement and population kinetics of embryonic endoderm at the time of germ layer formation in the mouse
Authors: Lawson Kirstie A. , Pedersen Roger A. , Geer Sara Van De
Published: April 2021

The fate of the embryonic endoderm (generally called visceral embryonic endoderm) of prestreak and early primitive streak stages of the mouse embryo was studied in vitro by microinjecting horseradish peroxidase into single axial endoderm cells of 6·7-day-old embryos and tracing the labelled descendants either through gastrulation (1 day of culture) or to early somite stages (2 days of culture).

Descendants of endoderm cells from the anterior half of the axis were found at the extreme cranial end of the embryo after 1 day and in the visceral yolk sac endoderm after 2 days, i.e. they were displaced anteriorly and anterolaterally. Descendants of cells originating over and near the anterior end of the early primitive streak, i.e. posterior to the distal tip of the egg cylinder, were found after 1 day over the entire embryonic axis and after 2 days in the embryonic endoderm at the anterior intestinal portal, in the foregut, along the trunk and postnodally, as well as anteriorly and posteriorly in the visceral yolk sac. Endoderm covering the posterior half of the early primitive streak contributed to postnodal endoderm after 1 day (at the late streak stage) and mainly to posterior visceral yolk sac endoderm after 2 days. Clonal descendants of axial endoderm were located after 2 days either over the embryo or in the yolk sac; the few exceptions spanned the caudal end of the embryo and the posterior yolk sac.

The clonal analysis also showed that the endoderm layer along the posterior half of the axis of prestreak- and early-streak-stage embryos is heterogeneous in its germ layer fate. Whereas the germ layer location of descendants from anterior sites did not differ after 1 day from that expected from the initial controls (approx. 90 % exclusively in endoderm), only 62 % of the successfully injected posterior sites resulted in labelled cells exclusively in endoderm; the remainder contributed partially or entirely to ectoderm and mesoderm. This loss from the endoderm layer was compensated by posterior-derived cells that remained in endoderm having more surviving descendants (8·4 h population doubling time) than did anterior-derived cells (10-5 h population doubling time). There was no indication of cell death at the prestreak and early streak stages; at least 93 % of the cells were proliferating and more than half of the total axial population were in, or had completed, a third cell cycle after 22 h culture.

We suggest that the visceral embryonic endoderm, derived from the primitive endoderm of the late blastocyst, is displaced onto the yolk sac by a new population of endoderm inserted from epiblast at the anterior end of the early primitive streak. This cell population has colonized the axial endoderm by the neural plate stage and contributes to the embryonic endoderm of the early somite embryo.
Genetics of sex determination in man and mouse
Authors: Goodfellow P. N. , Darling S. M.
Published: April 2021

The cytological evidence has revealed a visible mechanical basis for the production of males and females in equal numbers and irrespective of external conditions (Wilson, 1909).
Epithelial-mesenchymal interactions in the production of basement membrane components in the gut
Authors: Simon-Assmann P. , Bouziges F. , Arnold C. , Haffen K. , Kedinger M.
Published: April 2021

The production and deposition of extracellular matrix proteins and the cellular origin of type-IV collagen have been analysed immunocytochemically in cocultured or transplanted intestinal epithelial-mesenchymal cell associations.

In the first experimental model, rat intestinal endodermal cells were cultured on top of confluent monolayers of rat intestinal or skin fibroblastic cells. Under these conditions, interstitial matrix and basement membrane proteins were deposited within the fibroblastic layer over the whole culture period; interactions between the epithelial cells and the fibroblastic cell population, whatever their organ of origin, were required for the production of the basement membrane. In addition, its formation was progressive as assessed by the shift of a spot-like labelling to a continuous linear pattern at the epithelial–mesenchymal interface, and paralleled epithelial cell differentiation.

In the second experimental model, chick–rat epithelial-mesenchymal recombinants developed as intracoelomic grafts were used, and the immunocytochemical detection of a basement membrane protein, type-IV collagen, was performed with species-specific antibodies. The major role of the mesenchyme in the deposition of type-IV collagen is supported by the fact that anti-chick but not anti-mammalian antibodies stained this antigen in chick mesenchyme-rat endoderm recombinants.

These observations emphasize the role of tissue interactions in the formation of a basement membrane and show that the mesenchymal compartment is the principal endogenous source of type-IV collagen.
Isolation and expression of a new mouse homeobox gene
Authors: Sharpe P.T. , Miller J. R. , Evans E. P. , Burtenshaw M. D. , Gaunt1 S. J.
Published: April 2021

A homeobox-containing clone has been isolated from an adult mouse kidney cDNA library and shown by DNA sequence analysis to be a new isolate, Hox-6·1†. A genomic clone containing Hox-6.1 has been isolated and found to contain another putative homeobox sequence (Hox-6·2), within 7 kb of Hox-6·1. In situ hybridization of mouse metaphase chromosomes shows this Hox-6 locus to be located on chromosome 14 (14E2).

Hox-6.1 has been studied in detail and the predicted protein sequence of the homeobox is 100 % homologous to the Xenopus Xebl (formally AC1) homeobox and the human c8 homeobox (Carrasco et al. 1984; Boncinelli et al. 1985; Simeone et al. 1987). Southern blotting shows that the DNA sequence encoding Hox-6.1 is single copy.

Expression of Hox-6.1 has been studied in adult tissues and embryos by RNase protection assays, Northern blotting analysis and in situ hybridization. RNase protection assays show that Hox-6.1 transcripts are present in embryos between days and of gestation and in extraembryonic tissues at day . Adult expression is detectable in kidney and testis but not in liver, spleen and brain. One major transcript is detectable on Northern blots of kidney and day- embryo RNA. In kidney, this transcript is 2·7 kb whereas in embryos the major transcript is smaller at 1·9 kb, a much fainter band being visible at 2·7 kb. Localized expression of Hox-6.1 is observed in the spinal cord and prevertebral column of day- embryos, and in the posterior mesoderm and ectoderm of day-8) embryos. An anterior boundary of expression is located just behind the hindbrain whereas the boundary in the mesoderm is located at the level of the 7th prevertebra.
Cell-autonomous action of the testis-determining gene: Sertoli cells are exclusively XY in XX ↔XY chimaeric mouse testes
Authors: Burgoyne Paul S. , Buehr Mia , Koopman Peter , Rossant Janet , Mclaren Anne
Published: April 2021

The distribution of XX and XY cells in XX ↔XY chimaeric mouse testes was analysed by enzyme marker analysis of separated testicular tissues and by in situ DNA marker analysis of air-dried testicular cells and testis sections. XX cells contributed to the Leydig cells, the peritubular cells and the vascularized connective tissue of the tunica albuginea. The Sertoli cells, on the other hand, appeared to be exclusively XY. These results indicate that during the development of the testis, Sertoli cell differentiation is triggered by cell-autonomous activity of the Y chromosomal testis-determining gene Tdy. Subsequent steps in testis differentiation may be a consequence of Sertoli cell activity.
A developmental and ultrastructural study of the optic chiasma in Xenopus
Authors: Wilson M. A. , Taylor J. S. H. , Gaze R. M.
Published: April 2021

The structure of the optic chiasma in Xenopus tadpoles has been investigated by light and electron microscopy. Where the optic nerve approaches the chiasma, a tongue of cells protrudes from the periventricular cell mass into the dorsal part of the nerve. Glial processes from this tongue of cells ensheath fascicles of optic axons as they enter the brain. Coincident with this partitioning, the annular arrangement of axons in the optic nerve changes to the laminar organization of the optic tract.

Beyond the site of this rearrangement, all newly growing axons accumulate in the ventral-most part of the nerve and pass into the region between the periventricular cells and pia which we have called the ‘bridge’. This region is characterized by a loose meshwork of glial cell processes, intercellular spaces and the presence of both optic and nonoptic axons. In the bridge, putative growth cones of retinal ganglion cell axons are found in the intercellular spaces in contact with both the glia and with other axons.

The newly growing axons from each eye cross in the bridge at the midline and pass into the superficial layers of the contralateral optic tracts. As the system continues to grow, previous generations of axons, which initially crossed in the then existing bridge, are displaced dorsally and caudally, forming the deeper layers of the chiasma. At their point of crossing in the deeper layers, these fascicles of axons from each eye interweave in an intimate fashion. There is no glial segregation of the older axons as they interweave within the chiasma.
Localization of transcripts from the wingless gene in whole Drosophila embryos
Authors: Baker Nicholas E.
Published: April 2021

In situ hybridization has been used to detect transcription in whole Drosophila embryos. Improved results have been obtained by incubating the hybridized embryos in liquid emulsion prior to autoradiographic exposure. This technique has been used to map the distribution of transcripts from the segment-polarity gene wingless (wg), which is transcribed in a stripe in each segment of the trunk region. By the extended germband stage additional areas of transcription in the head and caudal regions define a total of 21 domains, comprising the foregut, six regions in the head, three thoracic and ten abdominal segments, and the hindgut. At the end of the extended germband stage, the pattern of wg transcription is no longer uniform in the dorsoventral axis: wg transcripts are absent from the lateral epidermis. This pattern of wg transcription is discussed with particular regard to the segmentation of the terminalia. Also it is suggested that the dorsoventral reorganization could be related to the specification of the imaginal disc primordia.
Analysis of germ line development in the chick embryo using an antimouse EC cell antibody
Authors: Urven Lance E. , Erickson Carol A. , Abbott Ursula K. , Mccarrey John R.
Published: April 2021

We have found that EMA-1, a monoclonal antibody originally raised against mouse embryonal carcinoma (Nulli SCC1) cells (Hahnel & Eddy, 1982), also labels chick primordial germ cells (PGCs). We have used this antibody in immunohistological studies to follow the development of PGCs in the chick embryo from the time of their initial appearance beneath the epiblast, through their migratory phase and subsequent colonization of the germinal epithelium. During hypoblast formation, individual EMA-l-labelled cells appeared to separate from the basal surface of the epiblast and enter the blastocoel, coincident with the appearance of morphologically identifiable PGCs in this same area. EMA-1 continued to label germ cells until the initiation of gametogenesis in each sex; specifically, labelling was absent by 7–8 days of incubation in females and started to decrease at 11 days of incubation in males. There was a recurrence of the epitope on oogonia at 15 days of incubation, but not on spermatogonia during the remainder of development through hatching. These observations are consistent with an epiblast origin for the avian germ line, and are strikingly similar to those reported for the early mouse embryo using the same antibody (Hahnel & Eddy,1986).