bluuebunny/crossref_metadata_2025 huggingface dataset:
Association between CCN1 gene polymorphism and acute coronary syndrome in Chinese Han and Uygur populations
Authors: Li Yan-Hong , Luo Jun-Yi , Fang Bin-Bin , Du Guo-Li , Tian Ting , Liu Fen , Li Xiao-Mei , Yang Yi-Ning
Published: April 2021

Background

CCN1 plays a crucial role in the modulation of cardiovascular diseases. However, whether CCN1 genetic variants are involved in the susceptibility of ACS remains unknown. Hence, the present study investigates the association between CCN1 polymorphisms and ACS among Han and Uygur populations in Xinjiang, China.

Results

In this case-control study, 1234 Han (547 ACS patients and 687 controls) and 932 Uygur (471 ACS patients and 461 controls) were genotyped using SNPscanTM for three single-nucleotide polymorphisms (SNPs, rs6576776, rs954353, and rs3753794) of the human CCN1 gene. In the Uygur population, we found that the detected frequencies of the C allele (25.3% vs. 18.3%, P<0.001) and CC genotype (6.4% vs. 3.0%, P=0.001) of rs6576776 were significantly higher in the ACS patients than in the control participants. Differences in rs6576776 regarding the dominant model (CC+CG vs. GG, 44.2% vs. 55.8%, P=0.001) and the recessive model (CC vs. CG+GG, 6.4% vs. 93.6%, P=0.016) were observed between the two groups. The frequencies of the GGC and AGC haplotypes in those with ACS were significantly higher than those in the control group (all P<0.05) in the Uygur population. After adjusting for hypertension, diabetes, lipids and smoking, all of which indicate that the rs6576776 C allele is associated with higher risk of ACS (odds ratio (OR)=1.798, 95% confidence interval (CI), 1.218-2.656, P=0.003). In Han population, neither the distribution of genotypes and alleles of the CCN1 gene three SNPs nor the distribution of haplotypes constructed with the three SNPs exhibited a significant difference between the ACS patients and control participants.

Conclusions

Our study document that the CCN1 gene rs6576776 C allele is associated with higher susceptibility of ACS and that the frequencies of GGC and AGC haplotypes are higher among the Uygur ACS patients.
Progress and challenges of implantable neural interfaces based on nature-derived materials
Authors: Redolfi Riva Eugenio , Micera Silvestro
Published: April 2021

Neural interfaces are bioelectronic devices capable of stimulating a population of neurons or nerve fascicles and recording electrical signals in a specific area. Despite their success in restoring sensory-motor functions in people with disabilities, their long-term exploitation is still limited by poor biocompatibility, mechanical mismatch between the device and neural tissue and the risk of a chronic inflammatory response upon implantation.

In this context, the use of nature-derived materials can help address these issues. Examples of these materials, such as extracellular matrix proteins, peptides, lipids and polysaccharides, have been employed for decades in biomedical science. Their excellent biocompatibility, biodegradability in the absence of toxic compound release, physiochemical properties that are similar to those of human tissues and reduced immunogenicity make them outstanding candidates to improve neural interface biocompatibility and long-term implantation safety. The objective of this review is to highlight progress and challenges concerning the impact of nature-derived materials on neural interface design. The use of these materials as biocompatible coatings and as building blocks of insulation materials for use in implantable neural interfaces is discussed. Moreover, future perspectives are presented to show the increasingly important uses of these materials for neural interface fabrication and their possible use for other applications in the framework of neural engineering.
Understanding the information content in gravity gradiometry data through constrained inversions for salt bodies
Authors: Maag-Capriotti Elizabeth , Li Yaoguo
Published: April 2021

Gravity gradiometry inversion can provide important knowledge about a salt body and can assist in subsalt imaging. However, such inversions are faced with difficulties associated with the lack of response from the nil zone in which the salt density is nearly identical to that of the background sediments and weak signals from the deeper portion of the salt. It is well understood that such difficulties could be alleviated by incorporating prior information, such as the top of salt from seismic imaging and petrophysical data, into the inversions. How to effectively incorporate such prior information is still a challenge, and what level of increased knowledge such constrained inversions can provide remains to be understood. We have investigated and compared the additional knowledge provided by incorporating different forms of prior information, such as a top-of-salt surface and an expected density contrast model. These different types of information are incorporated through different strategies of constrained inversion, including an inversion with bound constraints on the density contrast, inversion after a reduction-to-binary process, and discrete-valued inversion. We apply these strategies first to synthetic gravity gradiometry data calculated from the SEG/EAGE salt body and evaluate the improvements to the recovered salt provided from successive imposition of increased prior information. We further apply the strategies to a set of marine gravity gradiometry data collected in the Gulf of Mexico and examine the additional knowledge gained from the imaging of the salt in the region. We find that much more valuable knowledge about the salt can be obtained with the right prior information imposed through an effective strategy, and we determine that such gravity gradiometry data contain information about the salt body at depths much greater than previously recognized.
National Marrow Donor Program–Sponsored Multicenter, Phase II Trial of HLA-Mismatched Unrelated Donor Bone Marrow Transplantation Using Post-Transplant Cyclophosphamide
Authors: Shaw Bronwen E. , Jimenez-Jimenez Antonio Martin , Burns Linda J. , Logan Brent R. , Khimani Farhad , Shaffer Brian C. , Shah Nirav N. , Mussetter Alisha , Tang Xiao-Ying , McCarty John M. , Alavi Asif , Farhadfar Nosha , Jamieson Katarzyna , Hardy Nancy M. , Choe Hannah , Ambinder Richard F. , Anasetti Claudio , Perales Miguel-Angel , Spellman Stephen R. , Howard Alan , Komanduri Krishna V. , Luznik Leo , Norkin Maxim , Pidala Joseph A. , Ratanatharathorn Voravit , Confer Dennis L. , Devine Steven M. , Horowitz Mary M. , Bolaños-Meade Javier
Published: April 2021

PURPOSE

Hematopoietic cell transplantation (HCT) is curative for hematologic disorders, but outcomes are historically inferior when using HLA-mismatched donors. Despite unrelated donor registries listing > 38 million volunteers, 25%-80% of US patients lack an HLA-matched unrelated donor, with significant disparity across ethnic groups. We hypothesized that HCT with a mismatched unrelated donor (MMUD) using post-transplant cyclophosphamide (PTCy), a novel strategy successful in overcoming genetic disparity using mismatched related donors, would be feasible and increase access to HCT.

PATIENTS AND METHODS

We performed a prospective phase II study of MMUD bone marrow HCT with PTCy for patients with hematologic malignancies. The primary end point was 1-year overall survival (OS), hypothesized to be 65% or better. 80 patients enrolled at 11 US transplant centers (December 2016-March 2019). Following myeloablative or reduced-intensity conditioning–based HCT, patients received PTCy on days +3, +4, with sirolimus and mycophenolate mofetil starting on day +5. We compared outcomes to Center for International Blood and Marrow Transplant Research contemporary controls receiving PTCy.

RESULTS

Notably, 48% of patients enrolled were ethnic minorities. 39% of pairs were matched for 4-6 out of 8 HLA alleles. The primary end point was met, with 1-year OS of 76% (90% CI, 67.3 to 83.3) in the entire cohort, and 72% and 79% in the myeloablative and reduced-intensity conditioning strata, respectively. Secondary end points related to engraftment and graft-versus-host-disease were reached. Multivariate analysis comparing the study group with other mismatched HCT controls found no significant differences in OS.

CONCLUSION

Our prospective study demonstrates the feasibility and effectiveness of HCT with an MMUD in the setting of PTCy. Remarkably, nearly half of the study participants belonged to an ethnic minority population, suggesting this approach may significantly expand access to HCT.
Proust against the Monde
Authors: Weber Caroline
Published: April 2021

This essay examines the role of comedy in Marcel Proust’s À la recherche du temps perdu.
The Changing Inhibition of Early Differentiation and General Development in the Chick Embryo by 2 -Ethyl-5 -Methyl-Benzimidazole and Chloramphenicol
Authors: Blackwood Unabelle Boggs
Published: April 2021

Studies conducted during the past 10 to 15 years primarily in amphibian and chick embryos have led to a controversy over the identity of substances principally responsible for induction and early differentiation. That ribonucleoproteins are most directly involved is widely accepted. However, the question of which is most important ribonucleic acid (RNA) or protein has been the major point of disagreement. Brachet (1950) first suggested that RNA plays the primary role in induction and early differentiation. Several investigators studying the inductive properties of denatured ribonucleoprotein preparations from mammalian organs on amphibian gastrula ectoderm have concluded that protein is of greater importance than RNA (reviews, Barth, 1957; Yamada, 1958). Work with non-denatured thymus preparations led Niu (1958) to report that protein plays a role in differentiation but that RNA is the causal agent.
β-catenin signaling can initiate feather bud development
Authors: Noramly Selina , Freeman Allison , Morgan Bruce A.
Published: April 2021

Intercellular signaling by a subset of Wnts is mediated by stabilization of cytoplasmic β-catenin and its translocation to the nucleus. Immunolocalization of β-catenin in developing chick skin reveals that this signaling pathway is active in a dynamic pattern from the earliest stages of feather bud development. Forced activation of this pathway by expression of a stabilized β-catenin in the ectoderm results in the ectopic formation of feather buds. This construct is sufficient to induce bud formation since it does so both within presumptive feather tracts and in normally featherless regions where tract-specific signals are absent. It is also insensitive to the lateral inhibition that mediates the normal spacing of buds and can induce ectopic buds in interfollicular skin. However, additional patterning signals cooperate with this pathway to regulate gene expression within domains of stabilized β-catenin expression. Localized activation of this pathway within the bud as it develops is required for normal morphogenesis and ectopic activation of the pathway leads to abnormally oriented buds and growths on the feather filaments. These results suggest that activation of the β-catenin pathway initiates follicle development in embryonic skin and plays important roles in the subsequent morphogenesis of the bud.
Anterior cephalic neural crest is required for forebrain viability
Authors: Etchevers Heather C. , Couly Gérard , Vincent Christine , Douarin Nicole M. Le
Published: April 2021

The prosencephalon, or embryonic forebrain, grows within a mesenchymal matrix of local paraxial mesoderm and of neural crest cells (NCC) derived from the posterior diencephalon and mesencephalon. Part of this NCC population forms the outer wall of capillaries within the prosencephalic leptomeninges and neuroepithelium itself. The surgical removal of NCC from the anterior head of chick embryos leads to massive cell death within the forebrain neuroepithelium during an interval that precedes its vascularization by at least 36 hours. During this critical period, a mesenchymal layer made up of intermingled mesodermal cells and NCC surround the neuroepithelium. This layer is not formed after anterior cephalic NCC ablation. The neuroepithelium then undergoes massive apoptosis. Cyclopia ensues after forebrain deterioration and absence of intervening frontonasal bud derivatives. The deleterious effect of ablation of the anterior NC cannot be interpreted as a deficit in vascularization because it takes place well before the time when blood vessels start to invade the neuroepithelium. Thus the mesenchymal layer itself exerts a trophic effect on the prosencephalic neuroepithelium. In an assay to rescue the operated phenotype, we found that the rhombencephalic but not the truncal NC can successfully replace the diencephalic and mesencephalic NC. Moreover, any region of the paraxial cephalic mesoderm can replace NCC in their dual function: in their early trophic effect and in providing pericytes to the forebrain meningeal blood vessels. The assumption of these roles by the cephalic neural crest may have been instrumental in the rostral expansion of the vertebrate forebrain over the course of evolution.
Effects of heat shock and cycloheximide on growth and division of the fission yeast,Schizosaccharomyces pombe
Authors: Polanshek Mark M.
Published: April 2021

Effects of superoptimal temperature shock (HS) and the protein synthesis inhibitor, cycloheximide (CH), on growth and division of the fission yeast, Schizosaccharomyces pombe, were studied. Experiments on asynchronous cultures have shown that a 15-min HS of 41 °C inhibits RNA and protein synthesis and growth in cell length while delaying mitosis, division, and DNA synthesis. A 10-min CH pulse (100 μg/ml) inhibits protein and RNA synthesis briefly while delaying mitosis, division, and DNA synthesis. These single heat or CH pulses partially synchronize mitosis, division, and DNA synthesis.

Experiments in which either 15-min HS or 10-min CH pulses were applied at different times in selection-synchronized cultures have demonstrated several kinds and periods of sensitivity to these agents. During roughly the first two-thirds of the cell cycle (measured between divisions) mitosis, division, and DNA synthesis are delayed equally, delay increasing as a pulse is applied progressively later in the cycle. The magnitude of the delay from a heat shock is always greater than that from a CH pulse, but for both agents there is a period during which delay is greater in magnitude than pulse length. The pattern of delay from cultures synchronized by an induction method suggests that the period of increasing delay lies obligately within G2.

At 0 ·65 in the cycle the nature of the sensitivity to heat and CH changes. Between this transition point and the formation of a cell plate, CH has no effects on the timing of mitosis or cell plate stage. However, CH can block the final splitting of the cell plate, leading to a permanent cell plate and the formation of transient 4-celled pseudo-filaments upon resumed growth. HS following the transition point allows mitosis to be completed with normal timing to a stage in which daughter nuclei occupy terminal positions in the cell, but formation of the cell plate is delayed by about 30 min. Cells pulsed in the last third of the cycle may develop several morphological aberrations. The cell plate is sometimes oblique or positioned at one end of the cell, giving rise to daughter cells with 2 or no nuclei. Thus, it appears that some functions related to normal positioning of the cell plate occur during the last third of the cycle.

Recovery from a heat shock applied prior to 0 ·65 in the cycle includes a period in which there is increasing delay when a CH pulse is applied progressively later following the heat shock. However, applied together, CH plus HS produce roughly the amount of delay due to the HS alone. These facts are considered evidence for a common effect of both agents during the first two-thirds of the cycle.

The results are discussed with reference to possible controls over several events of the cell cycle.
Junctional structures in Hydra
Authors: Filshie B.K. , Flower N. E.
Published: April 2021

The sealing and communicating junctions present in hydra have been examined using conventional staining, lanthanum tracer and freeze-fracturing techniques. The presence of distinct types of gap and septate junctions has been confirmed. Combined lanthanum tracer and freezefracture results have provided a more detailed understanding of these junctional structures. A model has been constructed which demonstrates the various aspects of the junction seen at different sectioning angles.

The probable lengths of septa within septate junctions and the junctional ‘maze’ formed by them is discussed because of its bearing on the ‘sealing’ nature of the junction and also, to some extent, on its permeability to tracers such as lanthanum.
Plasma membrane intramembranous particle topography in 3t3 and sv3t3 cells: The effect of cytochalasin b
Authors: Scott Robert E. , Maercklein Peter B. , Furcht Leo T.
Published: April 2021

The topography of plasma membrane intramembranous particles in contact-inhibited and transformed cells is a topic of current controversy. We have reported that particles are aggregated in 3T3 cells and that they are randomly distributed in SV3T3 cells. Other investigators have, however, proposed that these differences result from the effect of cryoprotectants and are blocked by aldehyde fixation. The experiments described in this paper re-examine PMP topography in large samples of 3T3 and SV3T3 cells prepared by a variety of preparative methods. The results confirm that 3T3 cells contain aggregated intramembranous particles and that native SV3T3 cells do not, regardless of whether cells are prepared in glycerol, sucrose, tissue culture medium or following prefixation in paraformaldehyde.

Data presented in this paper also show that cytochalasin B induces dose -and time-dependent disaggregations of particles in contact-inhibited 3T3 cells. Particle disaggregation results from exposure of cells in situ for 1-3 h to 1-500 ng/ml cytochalasin B. Removal of the drug by washing with reincubation of cells in medium containing serum results in particle reaggregation within 1 to 3 h.

These observations suggest that intramembranous particles in 3T3 cells are aggregated in the native state and that membrane-active drugs modulate their distribution by a mechanism possibly involving disruption of linkages between membrane components and the cytoskeleton.
Ultrastructural and radioautographic investigation of the nucleolar cycle in Physarum polycephalum. characterization of dna-containing subunits
Authors: Lord A. , Nicole L. , Lafontaine J. G.
Published: April 2021

The present study has been mainly focused on the nucleolar cycle in the slime mould Physarum polycephalum. The ultrastructural characteristics of the interphase nucleolus, in this species, are quite similar to those of nucleoli in other organisms: it is essentially constituted of large particulate zones surrounding denser regions which are predominantly fibrillar in texture. The latter nucleolar zones, following fixation with osmium tetroxide, are characterized by the presence of opaque granules approximately 25 nm in diameter. Contrary to the situation which generally prevails in other eukaryotes, the late prophase nucleolus fragments into numerous globular bodies which are recognizable by the presence of opaque particles. These fibrillogranular nucleolar fragments persist during mitosis and are observed to become incorporated in the newly formed nucleolus. High-resolution radioautographic observations reveal that these nucleolar remnants contain DNA. The present observations together with recent biochemical data from other authors on the characteristics and mode of duplication of nucleolar DNA in P. polycephalum have led us to the hypothesis that the nucleolus, in this organism, contains several distinct globular subunits each containing ribosomal DNA as a key component. The existence of such morphological subunits appears to account for the unusual behaviour of the nucleolus during the cell cycle.
Brain endothelial tricellular junctions as novel sites for T cell diapedesis across the blood–brain barrier
Authors: Castro Dias Mariana , Odriozola Quesada Adolfo , Soldati Sasha , Bösch Fabio , Gruber Isabelle , Hildbrand Tobias , Sönmez Derya , Khire Tejas , Witz Guillaume , McGrath James L. , Piontek Jörg , Kondoh Masuo , Deutsch Urban , Zuber Benoît , Engelhardt Britta
Published: April 2021

The migration of activated T cells across the blood–brain barrier (BBB) is a critical step in central nervous system (CNS) immune surveillance and inflammation. Whereas T cell diapedesis across the intact BBB seems to occur preferentially through the BBB cellular junctions, impaired BBB integrity during neuroinflammation is accompanied by increased transcellular T cell diapedesis. The underlying mechanisms directing T cells to paracellular versus transcellular sites of diapedesis across the BBB remain to be explored. By combining in vitro live-cell imaging of T cell migration across primary mouse brain microvascular endothelial cells (pMBMECs) under physiological flow with serial block-face scanning electron microscopy (SBF-SEM), we have identified BBB tricellular junctions as novel sites for T cell diapedesis across the BBB. Downregulated expression of tricellular junctional proteins or protein-based targeting of their interactions in pMBMEC monolayers correlated with enhanced transcellular T cell diapedesis, and abluminal presence of chemokines increased T cell diapedesis through tricellular junctions. Our observations assign an entirely novel role to BBB tricellular junctions in regulating T cell entry into the CNS.

This article has an associated First Person interview with the first author of the paper.
More evidence for replication-transcription-coupling in Physarum polycephalum
Authors: Pierron GÉrard , Sauer Helmut W.
Published: April 2021

Endogenous RNA polymerase activity of isolated nuclei from Physarum polycephalum was determined at high (400 mM KC1) and low (5 – 100 rπM KC1) ionic strength.

The activity of RNA polymerase B (α-amanitin-sensitive UMP incorporation) and of RNA polymerase A (plus C) (α-amanitin-resistant UMP incorporation) was compared in accurately sized nuclear samples derived from macroplasmodia at distinct points of the mitotic cycle. Minimum total RNA polymerase activity was detected in metaphase nuclei. A constant level of RNA polymerase B activity was detected at all other stages of the mitotic cycle, if nuclei were assayed at high ionic strength. However, a high level in S-phase, a low level in G2-phase and again a high level in early prophase were measured, if nuclei were assayed at low ionic strength.

Inhibition of DNA synthesis by hydroxyurea in vivo had a selective and drastic effect on in vitro RNA polymerase activity of isolated nuclei derived from S-phase plasmodia, yielding up to 100% inhibition in early S-phase.
Red blood cell adhesion: II. Interferometric examination of the interaction with hydrocarbon oil and glass
Authors: Gingell David , Todd Ian
Published: April 2021

Using both living and glutaraldehyde-fixed red cells, we have examined adhesion to both oil/saline and glass/saline interfaces by interference reflection microscopy. At low ionic strength, 0 ·4 mM NaCl, fixed cells adherent to the oil/saline interface show first order whitish yellow zones of closest approach which indicate a separation of ∼ 100 nm. Quantitative interferometry in monochromatic light supports this conclusion. As the salt concentration is increased the separation decreases and the final image shows zero-order black which probably indicates molecular contact with the interface. Similar but less reproducible results were obtained with fixed and unfixed cells on glass. These observations show that physical interactions alone can be responsible for adhesion in dilute and concentrated salt solutions. It is not, however, believed that the results necessarily imply the existence of adhesion with a gap in physiological concentrations of salt.
Cell junctions in the excitable epithelium of bioluminescent scales on a polynoid worm: A freeze-fracture and electrophysiological study
Authors: Bilbaut A.
Published: April 2021

The bioluminescent scales of the polynoid worm Acholoe are covered by a dorsal and ventral monolayer of epithelium. The luminous activity is intracellular and arises from the ventral epithelial cells, which are modified as photocytes.Photogenic and non-photogenic epithelial cells have been examined with regard to intercellular junctions and electrophysiological properties. Desmosomes, septate and gap junctions are described between all the epithelial cells. Lanthanum impregnation and freeze-fracture reveal that the septate junctions belong to the pleatedtype found in molluscs, arthropods and other annelid tissues. Freeze-fractured gap junctions show polygonal arrays of membrane particles on the P face and complementary pits on the E face. Gap junctions are of the P type as reported in vertebrate, mollusc and some annelid tissues, d.c. pulses injected intracellularly into an epithelial cell are recorded in neighbouring cells. Intracellular current passage also induces propagated non-overshooting action potentials in all the epithelial cells; in photocytes, an increase of injected current elicits another response which is a propagated 2-component overshooting action potential correlated with luminous activity.

This study shows the coexistence of septate and gap junctions in a conducting and excitable invertebrate epithelium. The results are discussed in relation to the functional roles of intercellular junctions in invertebrate epithelia. It is concluded that the gap junctions found in this excitable epithelium represent the structural sites of the cell-to-cell propagation of action potentials.
Histochemical and ultrastructural characteristics of a cell line from human bone-marrow stroma
Authors: Lanotte Michel , Allen Terence D. , Dexter T. Michael
Published: April 2021

Morphological, enzymic and antigenic data are presented regarding a human bone-marrow stromal cell line maintained for 10 months and subcultured weekly. The main characteristics are a fibroblastoid morphology, diffuse growth in collagen gels, no colony formation in soft gel media, contact inhibition of growth and conversion to adipocytes when treated with hydrocortisone. The cells are non-phagocytic and membrane Fc receptors (i.e. aggregated human immunoglobulin G receptors) are absent, but they show diffuse cytoplasmic non-specific esterase activity, a strong acid phosphatase reaction, and a negative immunofluorescence (direct and indirect) against factor VIII antigen. Other cell lines also have been isolated and maintained in culture and present similar characteristics. These cell lines are thought to be derived from the acid-phosphatase-positive marrow stroma directly associated with bone trabecular matrix and probably represent a component of the haemopoietic inductive microenvironment. As such, they may provide a useful tool for studies in vitro of cell interactions and regulatory processes in the control of human bone-marrow haemopoiesis.
The role of the cytoskeleton in the motility of coccidian sporozoites
Authors: Russell D. G. , Sinden R. E.
Published: April 2021

The sporozoites of Eimeria tenella and Eimeria acervulina show bending, pivoting and gliding motility. All these types of motility occur intermittently and with decreasing frequency during the life of a sporozoite. Gliding is the only locomotive action expressed by these sporozoites and is only seen when the sporozoites are in contact with the substratum. All gliding sporozoites adopt a set pattern of body’ attitudes which suggests that locomotion involves a fixed body shape.

The microtubule inhibitors, colchicine, griseofulvin, vinblastine sulphate and nocodazole, have no effect on sporozoite motility. Ultrastructural examination reveals, in addition, that they have no effect on the subpellicular microtubules. The microfilament inhibitor, cytochalasin B, completely, and reversibly, inhibits pivoting and gliding but bending is only slightly depressed by the drug. High magnesium ion concentration inhibits all motility completely.

The cell membrane was readily labelled with fluorescein isothiocyanate-conjugated cationized ferritin, the label was rapidly capped and shed from the posterior of the sporozoite. This capping reaction takes place only during sporozoite locomotion. The membrane label was seen to ‘move’ backwards relative to the sporozoite at the same rate as the sporozoite moved forwards relative to the substratum. The substratum and the leading edge of the cap remained static relative to each other. Both capping and locomotion are sensitive to low temperature and cytochalasin B.

From these results a theory of sporozoite motility is postulated. The sporozoites adhere to the substratum by surface ligands. This ligand/substratum complex is then capped along the fixed spiral of the sporozoite body by a microfilament-based contractile system.

This proposed model for motility of coccidia sporozoites is consistent with all current observations on cell invasion by the sporozoa and therefore suggests that locomotion is an integral component of host cell invasion in this group of parasites.
Fertilization in brown algae: IV. appearance of sperm-specific antigens on fertilized eggs
Authors: Vithanage H. I. M. V. , Catt J. W. , Callow J. A. , Callow Maureen E. , Evans L. V.
Published: April 2021

Flagella antigens from sperm of Fucus serratus have been used to raise antibodies in rabbits. The immunoglobulin G fraction inhibits fertilization with some degree of species specificity. The antigens detected on sperm are not present on unfertilized egg membranes, but appear after fertilization. The common antigens on the fertilized egg can be distinguished from the cell wall material that is also released on fertilization.
Metabolism of palmitate by anoxic and reoxygenated heart cell cultures
Authors: Bailey Peter J. , Higgins Trevor J. C.
Published: April 2021

Under anoxic incubation conditions heart cell cultures showed enhanced uptake of [U-14C]pal-mitic acid into neutral lipids, while incorporation into phospholipids was unaltered. Fractionation of the neutral lipids showed greatest incorporation of radiolabel into the triglyceride fraction. Uptake of fatty acid in normoxic cultures may be dependent upon the supply of glycerol 3-phosphate from glycolysis, as 2-deoxyglucose and L-lactate, respectively, inhibited and stimulated incorporation of fatty acid into neutral lipid fractions.

When previously anoxic cultures were reoxygenated, oxidation of fatty acid was depressed and the mitochondrial function of anoxic cultures appeared to be more readily uncoupled by 2,4-dinitro-phenol, in comparison with cultures maintained under normoxic conditions. Similar behaviour was seen when oxidation of endogenous lipid or oxidation of glucose was examined. Previously anoxic cultures show a preference for oxidation of endogenous rather than exogenous lipid substrates.

The results suggest that anoxia-stimulated lipid accumulation may prove injurious to subsequent mitochondrial function and may be a contributory factor in the pathological processes associated with hypoxic injury of cardiac tissue.
Stochastic partitioning of chloroplasts at cell division in the alga Olisthodiscus, and compensating control of chloroplast replication
Authors: Hennis Annette S. , Birky C. William
Published: April 2021

We asked how chloroplasts in a unicellular marine alga are replicated and partitioned at cell division so that each daughter cell will receive the appropriate number of copies. The data were obtained simply by counting chloroplasts in pairs of daughter cells immediately after cell division. The results show that chloroplast partitioning is not always equal; however, it is equal much more often than predicted by the binomial distribution of chloroplast numbers that would be expected if partitioning were strictly random. The parental chloroplasts were partitioned equally in approximately 76% of the divisions, while in the remaining 24% the deviations from equality were very small. To maintain a reasonable range of chloroplast numbers in the face of unequal partitioning, there must be some form of compensating control of chloroplast replication. Our data suggest that daughter cells that receive very large numbers of chloroplasts go directly to the next division without replicating their chloroplasts, while cells with very small numbers of chloroplasts go through two rounds of chloroplast replication before dividing.
A revision of the Dictyostelium discoideum cell cycle
Authors: Weijer Cornelis J. , Duschl Gertrud , David Charles N.
Published: April 2021

We have reinvestigated the Dictyostelium discoideum cell cycle using fluorometric determinations of cellular and nuclear DNA contents in exponentially growing cultures and in synchronized cultures. Almost all cells are in G2 during both growth and development. There is no G1 period, S phase is less than 0·5 h, and G2 has an average length of 6·5 h in axenically grown cells. Mitochondrial DNA, which constitutes about half of the total DNA, is replicated throughout the cell cycle. There is no difference in the nuclear DNA contents of axenically grown and bacterially grown cells. Thus the long cell cycle in axenically grown cells is due to a lengthening of the G2 phase.
Distribution of protein sulphydryls and disulphides in fixed mammalian chromosomes, and their relationship to banding
Authors: Sumner A. T.
Published: April 2021

Fixed mammalian mitotic chromosomes, when stained with a variety of sensitive, sulphydryl-specific fluorochromes directly or following reduction of disulphide groups, show uniform fluorescence. Thus sulphydryl and disulphide groups are uniformly distributed along the length of the chromosomes, and do not show patterns related to chromosome bands. Performance of G- or C-banding procedures oxidizes sulphydryls to disulphides, but does not produce an inhomogeneous distribution of these groups. Cross-linking sulphydryl groups has no effect on G-, C- or Q-banding of chromosomes. Thus there appears to be no connection between chromosome bands and the distribution or state of oxidation of sulphur in chromosomal proteins.
Lesions induced in dna by ultraviolet light are repaired at the nuclear cage
Authors: Mccready S. J. , Cook P. R.
Published: April 2021

In mammalian cells, S-phase DNA synthesis occurs at sites fixed to a sub-nuclear structure, the nuclear matrix or cage. This is an ordered network of non-histone proteins, which maintains its essential morphology even in the absence of DNA. We show here that unscheduled DNA synthesis following exposure of HeLa cells to ultraviolet light also takes place at this sub-structure. We also show that ultraviolet irradiation grossly reorganizes nuclear DNA, arrestingS-phase synthesis at the cage and leaving the residual synthesis highly localized.
Identification of desmosomal surface components (desmocollins) and inhibition of desmosome formation by specific fab′
Authors: Cowin P. , Mattey D. , Garrodf D.
Published: April 2021

Specific antibodies against the components of desmosomes, the adhesive junctions of epithelial cells, have been used to determine which components are located on the cell surface. Three criteria have been used: fluorescent antibody staining, immuno-gold labelling and electron microscopy, and quantitative measurements of antibody binding using [125I]protein A. When these techniques were applied to living Madin-Darby bovine kidney (MDBK) cells, antibodies against only two des-mosomal components, glycoproteins of approximately 115×103.<Wr and 100×103Mr, bound to the cell surface. Antibodies against all other components, the 230 and 205×103Mr proteins (desmo-plakins), the 150×l3Mr glycoprotein and the 82 and 86×103Mr proteins reacted in fluorescent antibody staining only after cells had been fixed and made permeable.

MDBK cells were cultured in the presence of univalent fragments (Fab′) of anti-desmosomal antibodies for periods from 24 h to 72h. After these times cells were fixed, made permeable, and stained with anti-desmoplakin antibody to assay for desmosome formation. Fab′ derived from anti-100×103Mr protein specifically inhibited desmosome formation, whereas Fab′s from anti-desmoplakin, anti-150× 103Mr and anti-82 and 86×103Mr proteins were without effect.

We conclude that the 100×103Mr and the immunologically related 115 ×103Mr components are located on the cell surface and are directly involved in cell-cell adhesion. We have named them desmocollins to denote that they are involved in the adhesive function of desmosomes.

The modulation of desmocollin distribution during monolayer formation and establishment of epithelial polarity has also been studied. Fluorescent and immuno-gold labelling using Fab′ or IgG at 4 °C revealed that desmocollins were initially evenly dispersed over the cell surface. Staining with IgG at 37 °C caused the desmocollins to ‘patch’ but not to ‘cap’. With the establishment of con-fluency, desmocollins were gradually removed from the upper surfaces of the cells (or masked and rendered inaccessible to antibody) being confined to the lateral and probably basal regions of the cells. Treatment of confluent monolayers with 3mM-EGTA rendered the desmocollins stainable, probably by causing their release from lateral constraint. Desmocollin staining at the cell surface was not appreciably reduced during 5 h of EGTA treatment, suggesting that desmocollins, unlike desmosomal plaques, may not be internalized after junction breakdown.
Adhesion of neutrophil leucocytes under conditions of flow
Authors: Forrester J. V. , Lackie J. M.
Published: April 2021

By passing a suspension of polymorphonuclear leucocytes through a parallel-plate chamber their adhesiveness can be assessed by scoring the number of cells trapped on the lower plate, and the fluid shear stress can be defined for a given flow rate. Since the adhesiveness of the cell at the instant of collision must exceed the distractive shear if the cell is to stop, the kinetics of cell accumulation provide a measure of the adhesiveness of the leucocytes and the adhesive interaction can be quantified. This measure of adhesion does not suffer from the complication that the force required to remove the cells from the surface will be greater if the cells have the opportunity to spread before the distractive force is applied. The assay is described in detail and the results of modifying the surface of the flow chamber and altering the composition of the suspension medium are used to illustrate the method. Plasma proteins generally seemed to reduce the adhesiveness of neutrophil leucocytes, whether they were present as a coat of adsorbed protein or in the suspension medium during perfusion. Neutrophil leucocytes, unless suspended in relatively high concentrations of plasma, were considerably more adhesive than other cells that have been tested in this assay system.
Genomic in situ hybridization to sectioned nuclei shows chromosome domains in grass hybrids
Authors: Leitch A. R. , Mosgöller W. , Schwarzacher T. , Bennett M. D. , Heslop-Harrison J. S.
Published: April 2021

In situ hybridization using biotinylated total genomic DNA and avidin detection systems was adapted for examination of thin-sectioned plant material in the light and electron microscopes. Root tip material was preserved prior to sectioning, so that the in vivo disposition of the chromatin was maintained. Use of total genomic DNA from Secale africanum as a probe enabled the chromatin from the two parental genomes in the grass hybrid Hordeum chilense × S. africanum to be distinguished. The biotinylated probe preferentially labelled the chromosomes of S. africanum origin. DNA-DNA hybrids were visualized at the lightmicroscope level by Texas Red fluorescence and at the electron-microscope level by the enzymic precipitation of DAB (diaminobenzidine) or by colloidal gold particles. The use of thin sections allowed the location of probe hybridization to be established unequivocally in both metaphase and interphase nuclei. Analysis of interphase nuclei showed that chromatin originating from the two parental genomes did not intermix but occupied distinct domains.
Plasticity of the tubular lysosomal compartment in macrophages
Authors: Knapp Philip E. , Swanson Joel A.
Published: April 2021

Because bone marrow-derived macrophages differentiate in culture, their lysosomal compartment is largely devoid of the undigested particles that are common in macrophages removed from tissues. The morphology of this nearly vacant lysosomal compartment was observed, after labeling with fluorescent endocytic tracers such as Lucifer Yellow, to be an extensive, tubuloreticular network, which underwent extensive rearrangements in accommodating endocytic loads. It was converted to spherical organelles when the lysosomal compartment was loaded with osmotically active solutes such as sucrose or Acridine Orange. Enzymatic degradation of intravacuolar sucrose by pinocy-tosed invertase resulted in the shrinkage of vacuoles and the re-formation of the tubular network. After phagocytosis of opsonized erythrocytes or latex beads, tubular lysosomes wrapped around the phagosomes, then merged to form phagolysosomes. The disappearance of tubules was proportional to the total surface area of particles ingested. Degradation of the phagocytosed contents permitted shrinkage of the phagolysosome and concomitant re-formation of the tubuloreticular network. Non-degradable contents such as latex beads prevented re-formation of the tubular network. These rearrangements of the lysosomal compartment indicate that the organelle exhibits considerable plasticity and interconnectedness, and that maturation of lysosomes after endocytosis does not necessarily entail irreversible morphological changes.
Gap junction distribution in adult mammalian myocardium revealed by an anti-peptide antibody and laser scanning confocal microscopy
Authors: Gourdie R. G. , Green C. R. , Severs N. J.
Published: April 2021

A polyclonal antiserum, raised against a synthetic peptide matching part of the sequence of connexin43 (a rat cardiac gap-junctional protein), was used in combination with laser scanning confocal microscopy to investigate gap junction distribution in cardiac tissues from a range of mammalian species. Comparison of the localised punctate staining patterns obtained in ventricular tissue with the distribution of intercalated disks as viewed by conventional light microscopy and electron microscopy, and with the staining observed by standard light-microscope immunofluorescence using the same antiserum, demonstrated highly specific labelling of clearly resolved individual gap junctions. Laser scanning confocal microscopy of ventricular myocardium showed the immunostained gap junctions to be confined to well-defined intercalated disks bisecting the long axis of the muscle fibre, whereas in the atrial myocardium, gap junctions were commonly distributed widely over the lateral surfaces of the myocyte body. Rat atrial gap junctions were significantly larger (as measured by the longest axial lengths of fluorescent spots), and showed a narrower spread of sizes, than their counterparts in the ventricle. Ventricular myocardium from six mamalian species including man gave similar immunostaining patterns, indicating conservation both of the epitope(s) detected by the antiserum, and of the general organisation of the cell-to-cell pathways for electrical propagation, in the mammalian heart. Optical section series obtained by laser scanning confocal microscopy permitted the quantification and mapping of the three-dimensional distribution of gap junctions in ventricular intercalated disks with high clarity over substantial specimen depths. A consistent feature of gap junction organisation within disks of ventricular myocardium in all species studied was the presence of a conspicuous ring of large gap junctions around the periphery of the disk. Immunostained gap junctions lying within the interior zone delineated by the peripheral junctions generally occurred at lower numerical densities and were significantly smaller. In all species, less than 3 % of all immunolabelled gap junctions measured were >2 μm in maximal length, though a small proportion (0·06%? exceeded 4 μm. The numerical density of immunolabelled gap junctions in the disk was similar between species; however, within species there was a significant decrease in numerical density with increasing disk size. The new features of intercalated disk structure revealed in this study may have an important part to play in the intercellular communication and electrical propagation properties of the mammalian heart.
The Rapid Escape Response of the Earthworm Lumbricus Terrestris L.: Overlapping Sensory Fields of the Median and Lateral Giant Fibres
Authors: Moore M. J.
Published: April 2021

In undissected, freely mobile earthworms the sensory input for tactile stimulation to the MGF and LGF shows a region of overlap occupying a number of segments behind the clitellum. The average number of overlapping segments from a sample of 14 worms was 13 (range 0–28). The overlap zone consists of segments from which both LGF and MGF spikes can be elicited. Increasing stimulus intensity in the LGF field reduces the latency of the first spike until it reaches a minimum of 6 ms. This value is used to calculate conduction velocity of afferent impulses along the sensory pathway. It is suggested.on the basis of conduction velocity, that the large sensory neurones in the segmental nerves are those mediating afferent events in the rapid escape response.
Exponential Satisficing
Authors: Tyson Christopher J.
Published: April 2021

We propose the exponential satisficing model of boundedly rational decision-making, a general-purpose tool designed for use in typical microeconomic applications. The model posits that the preferences perceived and acted upon by the agent are a stochastic coarsening of his or her true, welfare-significant preferences. The decision-maker’s perceptual capabilities are controlled by a preference resolution parameter, which smoothly varies the impact of cognitive constraints on choice. To demonstrate the implementation of the model, it is applied to duopolistic price competition with satisficing consumers and to normal-form games with satisficing players. (JEL D01, D80, D90)
On Dokuzuncu Yüzyılın İlk Yarısında Osmanlılarda Medrese Çevrelerinde Modern Astronomi
Authors: Güneş Orhan
Published: April 2021

Teleskobun bilimsel amaçlarla kullanılması Güneş Sistemi’nin yapısına dair bilgimizi önemli ölçüde değiştirdi. On dokuzuncu yüzyılın ortalarına gelindiğinde kadim dönemlerden beri bilinen beş gezegene iki yeni gezegen, bir düzine asteroid ve onlarca uydu ilave edilmişti. Batı’da meydana gelen bu gelişmelere sırtını dönmeyen Osmanlı bilim çevreleri bunları eserlerine yansıttılar. Ancak güncel bilginin aktarımıyla ilgili temel tez, bu aktarımın esasen modern eğitim kurumları tarafından yapıldığı ve hızının da çok yüksek olmadığı yönündedir. Özellikle medrese çevresi söz konusu olduğunda bu iddia daha da güçlü bir şekilde dile getirilmektedir. Literatürde modern dönemde keşfedilen iki yeni gezegen olan Uranüs ve Neptün’den bahseden medrese çevrelerindeki ilk eserin 1857’den sonraki bir tarihte yazılan Abdullah Şükrî b. Abdülkerim Konevî’nin (ö. 19. Yüzyıl) Tenkîhu’l-İşkâl’i olduğu ifade edilir. Bu, Uranüs için 76, Neptün için ise en az 11 yıllık bir gecikme demektir. Bu makale Uranüs ve Neptün’den bahseden ilk çalışmaların modern eğitim kurumları kökenli olmadığını ayrıca bilgi aktarımında sözü edildiği kadar gecikmenin meydana gelmediğini göstermeyi amaçlamaktadır. Çalışmamızda Uranüs’ten bahseden ilk eserin medrese çevrelerinden Kuyucaklızâde Muhammed Âtıf’ın (ö. 1263/1847) 1831’de kaleme aldığı Teshîlü’l-idrâk, Neptün’den bahseden ilk çalışmanın ise yine medrese Hayâtîzâde Seyyid Şeref Halil’in (ö. 1267/1851) 1848 tarihinde basılan ancak 1847’de kaleme alınan Efkâru’l-ceberût adlı eseri olduğu gösterilmiştir. Böylelikle üzerinde büyük oranda ittifak bulunan tezin bu örneklerden hareketle sorgulanmaya başlaması umulmaktadır.