bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of the cytoskeleton in the motility of coccidian sporozoites
Authors: Russell D. G. , Sinden R. E. 
Published: April 2021

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.&lt;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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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 &gt;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

ABSTRACT
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.
A public health intervention package for increasing tuberculosis notifications from private practitioners in Bandung, Indonesia (INSTEP2): A cluster-randomised controlled trial protocol
Authors: Hadisoemarto Panji Fortuna , Lestari Bony Wiem , Sharples Katrina , Afifah Nur , Chaidir Lidya , Huang Chuan-Chin , McAllister Susan , van Crevel Reinout , Murray Megan , Alisjahbana Bachti , Hill Philip C 
Published: April 2021

Background. A significant proportion of tuberculosis (TB) patients globally make their initial visit for medical care to either an informal provider or a private practitioner, and many are not formally notified. Involvement of private practitioners (PPs) in a public–private mix for TB (TB-PPM) provides an opportunity for improving TB control. However, context-specific interventions beyond public–private agreements and mandatory notification are needed. In this study we will evaluate whether a tailored intervention package can increase TB notifications from PPs in Indonesia. Methods. This is a cluster-randomized trial of a multi-component public health intervention. 36 community health centre (CHC) areas will be selected as study locations and randomly allocated to intervention and control arms (1:1). PPs in the intervention areas will be identified using a mapping exercise and recruited into the study if they are eligible and consent. They will receive a tailored intervention package including in-person education about TB management along with bimonthly electronic refreshers, context-specific selection of referral pathways, and access to a TB-reporting app developed in collaboration with the National TB programme. The primary hypothesis is that the intervention package will increase the TB notification rate. The primary outcome will be measured by collecting notification data from the CHCs in intervention and control arms at the end of a 1-year observation period and comparing with the 1-year pre-intervention. The primary analysis will be intention-to-treat at the cluster level, using a generalised mixed model with repeated measures of TB notifications for 1 year pre- and 1 year post-intervention. Discussion. The results from this study will provide evidence on whether a tailored intervention package is effective in increasing the number of TB notifications, and whether the PPs refer presumptive TB cases correctly. The study results will guide policy in the development of TB-PPM in Indonesia and similar settings.
FAKTOR KUNCI KEBERHASILAN MANAJEMEN RANTAI PASOKAN PENANGANAN BENCANA ALAM DALAM PERSPEKTIF PEMERINTAH
Authors: Rini Poppy Laksita 
Published: April 2021

Disaster supply chain management is different from the supply chain management of commercial organization because of the high level of uncertainty. The high level of uncertainty significantly affects the availability of logistic supplies that are needed by the victims of the disaster. This study discovers the key success factors of the disaster supply chain management based on the perspective of the government. The re- search specifically study the Government of the D.I. Yogyakarta that are represented by Badan Penanggulangan Bencana Daerah (BPBD). Due the fact that Yogyakarta as one of the regions that have the high risk of catastrophic nature in Indonesia. The study will be carried out in a qualitative methodology by conducting deep interview with the Representative of Logistics Department in BPBD. The results of in-depth interviews with four representative of BPBD found that there are six key success factors of disasater management supply chain management which are : (1) Quality of the TRC Team Assessment Results; (2) BPBD Coordination with Government and Non-Government; (3) Effective Rules and Regulations; (4) Character and Attitude of the Community in Dealing with Disasters; (5) BPBD Warehouse Inventory Management; (6) Management Information Systems and Data Updates.
The structure of MgtE in the absence of magnesium provides new insights into channel gating
Authors: Jin Fei , Sun Minxuan , Fujii Takashi , Yamada Yurika , Wang Jin , Maturana Andrés D. , Wada Miki , Su Shichen , Ma Jinbiao , Takeda Hironori , Kusakizako Tsukasa , Tomita Atsuhiro , Nakada-Nakura Yoshiko , Liu Kehong , Uemura Tomoko , Nomura Yayoi , Nomura Norimichi , Ito Koichi , Nureki Osamu , Namba Keiichi , Iwata So , Yu Ye , Hattori Motoyuki 
Published: April 2021

MgtE is a Mg2+ channel conserved in organisms ranging from prokaryotes to eukaryotes, including humans, and plays an important role in Mg2+ homeostasis. The previously determined MgtE structures in the Mg2+-bound, closed-state, and structure-based functional analyses of MgtE revealed that the binding of Mg2+ ions to the MgtE cytoplasmic domain induces channel inactivation to maintain Mg2+ homeostasis. There are no structures of the transmembrane (TM) domain for MgtE in Mg2+-free conditions, and the pore-opening mechanism has thus remained unclear.
Here, we determined the cryo-electron microscopy (cryo-EM) structure of the MgtE-Fab complex in the absence of Mg2+ ions. The Mg2+-free MgtE TM domain structure and its comparison with the Mg2+-bound, closed-state structure, together with functional analyses, showed the Mg2+-dependent pore opening of MgtE on the cytoplasmic side and revealed the kink motions of the TM2 and TM5 helices at the glycine residues, which are important for channel activity. Overall, our work provides structure-based mechanistic insights into the channel gating of MgtE.