bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contraction waves in lymphocyte locomotion
Authors: Haston Wendy S. , Shields James M. 
Published: April 2021

ABSTRACT
In this paper we propose that the constriction ring, a prominent feature of moving leucocytes, is a major source of locomotive force. Analysis of time-lapse films of lymphocytes in suspension and moving through three-dimensional collagen gels, demonstrated that the constriction ring was the morphological manifestation of a wave of circular contraction that moved antero-posteriorly. In lymphocytes in suspension the wave moved, although the cells could not. Analysis of lymphocytes moving through a collagen gel revealed that the waves remained stationary with respect to the external environment while the cell appeared to move forward through them. Passage of a single equatorial contraction wave resulted in cell lengthening: a shortening of the region posterior to the constriction was observed in cells moving through collagen gels, but not in lymphocytes held in suspension, suggesting that attachment of cells to the collagen network was necessary for longitudinal contraction. Lymphocyte attachment to collagen gels was mediated through the rapid extension of bleb-like structures into the collagen network. Transmission electron microscopy (TEM) failed to demonstrate any organized structure at the constriction ring. NBD-Phallacidin staining of lymphocytes together with TEM demonstrated that F-actin was distributed evenly throughout the length of the cell. Cell polarity was clearly recognizable by the distribution of coated vesicles, microvilli, and all organelles to the rear, and Thy 1-2 to the front, of motile cells, but polarity could be reversed by the passage of a single contraction wave starting at the rear of the cell, without prior redistribution of these structures.
Alterations induced by glucose deprivation and tunicamycin in the kinetic parameters of hexose transport in hybrid cells
Authors: White M. K. , Bramwell M. E. , Harris H. 
Published: April 2021

ABSTRACT
Matched pairs of malignant and non-malignant hybrid cells were compared in their response to glucose deprivation and to tunicamycin. Glucose deprivation induced an increase in the maximum velocity in the malignant cells, but not in the non-malignant cells. The Michaelis constant of hexose uptake was largely unchanged by glucose deprivation except in the case of one melanoma derivative, PG19 G—, which showed a large increase in Michaelis constant when deprived of glucose. Tunicamycin increased the Michaelis constant of hexose uptake in both malignant and non-malignant cell lines. It is therefore possible that the Michaelis constant of hexose uptake is affected by the extent of glycosylation of one or more of the cell membrane glycoproteins
The morphology of the granule cells of the olfactory bulb
Authors: Price J. L , Powell T. P. S 
Published: April 2021

ABSTRACT
The granule cells of the olfactory bulb of the rat have been studied in material prepared by the Golgi-Kopsch method for examination with the light microscope, and in material examined with the electron microscope. With the Golgi method, the granule cells are found to have no process which can be identified as a typical axon, but from the superficial aspect of the somata stout peripheral processes arise and pass into the overlying external plexiform layer, while from the opposite side of the cell body several thinner deep dendrites extend towards the deeper parts of the bulb. Both types of processes, as well as the penkarya, have numerous spine-like appendages. On the distal portions of the peripheral processes in the external plexiform layer the appendages are much larger than on the deeper parts of the cell. The deep dendrites have localized swellings along their length which give them a varicose appearance, appendages often arise from these vancosities. The electron-microscopic features of the granule cells correspond well with the appearance of these cells in material impregnated with the Golgi method. The cell somata are small, with very little cytoplasm, and have a relatively large nucleus. The peripheral processes can be identified passing superficially from the penkarya of the granule cells; at their junction with the cell body their appearance is typically dendritic; all the cytoplasmic organelles found in the cytoplasm extend into these processes and none of the features of the initial segments of axons are found. In the external plexiform layer large spine-like appendages, which have been termed ‘gemmules’, arise from the distal portions of the peripheral processes, and participate in reciprocal synapses with the dendrites of mitral and tufted cells. The deep dendrites are much finer than the peripheral processes, and the vancosities which are seen in Golgi material may also be found with the electron microscope. Spines are found on all parts of the granule cells in the granule cell layer, including the peripheral processes, the penkarya and the deep dendrites. In addition to a spine apparatus, these spines commonly have numerous inclusions, including mitochondria, ribosomes, and vesicles which are the same size and shape as the synaptic vesicles present in the gemmules; no synapses oriented away from the spines have ever been found.
The response of human monocytes to interaction with immobilized immune complexes
Authors: Eccles M. Helen , Glauert Audrey M. 
Published: April 2021

ABSTRACT
The interaction between human peripheral blood monocytes and immobilized immune complexes has been monitored by morphological and biochemical criteria using an established model system previously used with human eosinophils. The model consists of an agar layer containing immune complexes. Monocytes flatten extensively on these layers and make very close contact with the agar surface; cells incubated on control layers, without antibody, are more loosely attached. After 15 min incubation on immobilized immune complexes there is a ‘pulse’ of lysosomal enzyme release from the monocytes and electron micrographs indicate that extracellular secretion occurs. Simultaneously, two proteins with apparent molecular weights of 50000 and 25 000 appear at the cell surface as a specific consequence of the interaction with immune complexes. These newly accessible proteins were detected by lactoperoxidase-catalysed iodination, and the major of the two (labelled M3) has similarities to a protein with an apparent molecular weight of 55 000 of human eosinophils (labelled protein 3), which has been shown to be closely associated with the eosonophil Fc receptor. It will be of interest to establish whether a similar association occurs in monocytes.
Regulation of cell shape in Euglena gracilis : II. the effects of altered extra- and intracellular ca2 + Concentrations and the effect of calmodulin antagonists
Authors: Lonergan Thomas A. 
Published: April 2021

ABSTRACT
When cultures of Euglena gracilis Z., normally grown in medium containing 180μM-Ca2+, are resuspended in Ca2+-free medium cells assume round shapes within 10 min, from which they recover slowly when Ca2+ is returned to the cultures. Cultures grown in 10 μM-Ca2+ do not display the typical circadian rhythm in cell shape even though the photosynthesis and cell division circadian rhythms are unaffected. Elevating intracellular Ca2+ levels by the addition of the Ca2+ ionophore A23187 prevents cells from undergoing the two daily shape changes characteristic of growth-synchronized cultures, but does not alter the ability to maintain the cell shapes found at the time of ionophore addition. When the calmodulin inhibitors trifluoperazine or chlorpromazine are added to cultures, the cells always respond by rounding. Cells are not able to maintain any cell shape other than spherical in the presence of these inhibitors and therefore cannot change shape throughout the daily cycle as is found in the control populations.
Extracellular matrix modulation of endothelial cell shape and motility following injury in vitro
Authors: Young William C. , Herman Ira M. 
Published: April 2021

ABSTRACT
We utilized fluorescence microscopy and affinity-purified antibodies to probe the form and function of cytoplasmic actin in endothelial cells (EC) recovering from injury and grown on extracellular matrices in vitro. Bovine aortic EC were seeded onto glass microscope coverslips that had been coated with either BSA, fibronectin, type I and III (interstitial) collagens, type IV (basement membrane) collagen or gelatin. After EC that had been grown on glass, glass-BSA or extracellular matrix-coated coverslips reached confluence, a 300–400μm zone of cells was mechanically removed to stimulate EC migration and proliferation. Post-injury EC movements were monitored with time-lapse, phase-contrast videomicrography before fixation for actin localization with fluorescence microscopy using affinity-purified antibodies. We found that the number of stress fibres within EC was inversely proportional to the rate of movement; and, the rates of movement for EC grown on glass or glass-BSA were approximately eight times faster than EC grown on gelatin or type IV collagen (X velocity = 0·5μm/min versus 0·06μm/min). EC movements on fibronectin and interstitial collagens were similar (X velocity = 0·2μm/min). These results suggest that extracellular matrix molecules modulate EC stress fibre expression, thereby producing alterations in the cytoskeleton and the resultant EC movements that follow injury in vitro. Moreover, the induction of stress fibres in the presence of basement membrane (type IV) collagen may explain the failure of aortic EC to migrate and repopulate wounded regions of intima during atherogenesis in vivo.
Adult, foetal and transformed fibroblasts display different migratory phenotypes on collagen gels: Evidence for an isoformic transition during foetal development
Authors: Schor S. L. , Schor A. M. , Rushton G. , Smith L. 
Published: April 2021

ABSTRACT
Data are presented indicating that the migration of fibroblasts into three-dimensional collagen gels is affected by cell density. We have defined a ‘cell density migration index’ (CDMI) to express this behavioural response in quantitative terms. The results of a survey of 77 different cell types indicate that the CDMI values expressed by normal adult skin fibroblasts and transformed cell lines fall into two distinct, non-overlapping groups. Measurement of the CDMI therefore provides an additional means of distinguishing between normal and transformed cells and may be used in conjunction with other commonly recognized criteria (e.g. anchorage-independent growth) to assess expression of a transformed phenotype in vitro. It is of interest to note that the CDMI values expressed by foetal cells define a group lying intermediate between normal and transformed cells. Both uncloned and cloned foetal cells have been observed to undergo a stable transition to expression of CDMI values characteristic of adult cells when followed throughout the duration of their in vitro lifespan. In addition to providing a novel means of distinguishing between normal adult and foetal cells, our results suggest that foetal fibroblasts undergo an ‘isoformic’ transition at some point in their developmental history, which is manifest in vitro by the expression of an adult CDMI.
An antigen of Plasmodium yoelii that translocates into the mouse erythrocyte membrane upon entry into the host cell
Authors: Murakami Kenji , Tanabej Kazuyuki 
Published: April 2021

ABSTRACT
Monoclonal antibodies against the rodent malaria parasite, Plasmodium yoelii, have been prepared and characterized by indirect immunofluorescence on acetone-fixed infected mouse erythrocytes. The antibody of clone K2 reacted strongly with late trophozoites and schizonts, whereas it did so weakly and diffusely with ring forms and early trophozoites. Strong fluorescence was confined to granular structures in schizonts and merozoites. Parasites that invaded erythrocytes in vitro lost the strong fluorescence. Instead, immunofluorescence appeared in the membranes of erythrocytes infected in vitro with merozoites. Erythrocytes infected with more than one merozoite had intensified immunofluorescence in their membranes. Staining of the invaded erythrocytes with 4’,6-diamidino-2-phenylindole (DAPI) hydrochloride demonstrated that membranes of all the invaded erythrocytes acquired the P. yoelii antigen. These results suggest that the P. yoelii antigen in merozoites is translocated into erythrocyte membranes upon entry into the host cell. Immunofluorescence continued to appear in membranes of infected erythrocytes throughout the intra-erythrocytic parasite growth. Staining of unfixed infected erythrocytes with the K2 antibody failed to detect the parasite antigen. In contrast, immunofluorescence was present in unfixed membranes of erythrocyte ghosts, which had been spontaneously formed after rupture of schizont-infected erythrocytes by merozoite release. No immunofluorescence appeared in either acetone-fixed or unfixed ghosts of normal erythrocytes. These results suggest the antigenic determinant of the P. yoelii antigen is exposed at the cytoplasmic surface of the infected erythrocyte membrane. Immunoprecipitation has revealed that the K2 antibody recognizes a 160×10’ MRP. yoelii antigen.
Ultrastructural characterization and morphometric analysis of human eosinophil degranulation
Authors: Henderson William R. , Chi Emil Y. 
Published: April 2021

ABSTRACT
Human eosinophil degranulation induced by the calcium ionophore A23187 was examined by transmission and scanning electron microscopy, and morphometric analysis. After incubation with A23187, eosinophil degranulation was characterized by granule movement to the cell periphery and pentalaminar membrane fusion between perigranular and plasma membranes. As adjacent granules fused they became swollen and vesiculated; their contents were released into large cytoplasmic vacuoles, which communicated extracellularly through surface pores. Extracellular release of eosinophil peroxidase without release of lactate dehydrogenase occurred after treatment with the ionophore. Morphometric analysis of the transmission electron micrographs indicated a significant reduction of cytoplasmic granules in the degranulated cells. There was a loss primarily of larger granules and alternatively an increase in the smaller-sized granules (less than 0·1 μm2), suggesting the possibility that exocytosis of mature granules is accompanied by new cytoplasmic granule formation.
Cytoskeletal reorganization and plasma membrane fusion in conjugating Tetrahymena
Authors: Wolfe Jason 
Published: April 2021

ABSTRACT
The conjugation junction of Tetrahymena is the specialized site where plasma membrane fusion occurs between two cells of complementary mating types. The junction is constructed through a series of cooperative interactions and morphogenetic steps. A contact-mediated interaction between free-swimming, sexually mature and mating-competent cells of two complementary mating types induces a morphological transformation of the anterior tips. Cells then join in pairs aligned by the apposition of their modified tips. Thin sections show that the plasma membranes of the tips are separated by ∼500Â of extracellular space, in which some strands of matrix material can be identified. The cytoplasmic face of the membrane is in contact with a junction-specific thick layer of electron-dense material. At hundreds of independent sites in this junction plasma membranes fuse in a limited manner, thereby establishing hundreds of separate membrane-ensheathed cytoplasmic channels that connect the two cells. At the same locations the thick submembrane layer is interrupted. Consequently, the junction appears to be a structure that is perforated with hundreds of pores. This study poses the question of whether the junction’s submembrane layer is, or includes, a skeletal element. Cells were extracted with the non-ionic detergent Triton X-100 under conditions that yield cytoskeletal frameworks (CFs) that maintain the morphological integrity of the cells. The CFs include chromatin and also cortical structures such as microtubule bands, basal bodies, ciliary axonemes, kinetodesmal fibres and fibrillar epiplasm. CFs of conjugant pairs are also paired, indicating that the junction contains a skeletal element that is responsible for integrating the individual CFs into a higher-order complex. At the ultrastructural level the skeletal structure of the junction includes membrane lamina and a submembrane scaffold, residues of the plasma membrane and thick submembrane layer, respectively, both of which are interrupted at the pores. However, the two separate scaffolds are joined at the rims of the pores. This provides a means by which the separate CFs become integrated. On the basis of images of junctional CFs, which show interruptions of the scaffold without concomitant membrane fusion, but where laminae are pressed close together, a specific model of membrane fusion is proposed. According to this model, the submembrane skeletal scaffold regulates membrane fusion by limiting its occurrence, and the extent of its occurrence.
Circadian rhythm of nucleoli in rat superior cervical ganglion neurons: The two types of fibrillar centres and their quantitative relationship with the nucleolar organizing regions
Authors: Pébusque Marie-Josèphe , Vio-Cigna M. , Aldebert Bernard , Seite Raymond 
Published: April 2021

ABSTRACT
A quantitative stereological analysis was undertaken in nucleoli of rat superior cervical ganglion neurons. In this model, two types of fibrillar centres were observed: (1) small-type fibrillar centres were observed during the light span; and (2) a single large-type fibrillar centre occurred during the dark span near the smaller ones. The present data showed that the drastic increase in the mean volume of fibrillar centres during the dark span involved the occurrence and the progressive enlargement of one single large-type fibrillar centre and a marked rise in the number of small-type centres from 18 ± 2 to 74 ± 5 at 1500 h and 0100 h corresponding to light and dark spans, respectively. The total number of these small-type fibrillar centres per nucleolus increased with the total volume whereas their unit volume remained unchanged. This enabled us to establish some relationship with nucleolar organizing regions (NORs).
Actin-regulating activities in cultured bhk cells
Authors: Koffer Anna , Daridan Myra 
Published: April 2021

ABSTRACT
A large proportion (60-85%) of the actin present in lysates of cultured baby hamster kidney (BHK) cells is monomeric at low temperature. All this G-actin is accounted for in the fractions obtained by high-speed centrifugation of the lysate in the presence or absence of non-ionic detergent; 98 (±7)% of it reacts as monomer in the deoxyribonuclease assay. The fractions nevertheless possess actin polymerization nucleating activity, as assayed by the fluorescence of extraneous pyrene-conjugated actin, reflecting the presence of capping proteins and their complexes with oligomeric actin, which dissociate during the deoxyribonuclease assay. Despite the enhanced nucleation, the total proportion of actin polymerized at equilibrium is reduced, relative to that of actin in the absence of cell extract, presumably because of the presence of ‘barbed’-end capping protein(s). With increasing concentrations of the supernatant material, the proportion of polymerized actin was progressively reduced and the presence of inhibitory activity against polymerization became apparent. On addition of micromolar concentrations of free calcium, nucleation by the supernatant fractions is greatly accelerated, but the extent of polymerization undergoes a further reduction, due to the elevated critical monomer concentration resulting from capping. Inhibition of polymerization by the supernatant fraction in the presence of calcium is much greater than by saturating concentrations of cytochalasin E. These observations are most simply interpreted as showing that the cytoplasm additionally contains a ‘pointed’-end capping protein. The plasma membranes were found to have nucleating activity largely residing in the Triton-insoluble fractions.
Actin cross-linking activity was assayed by adding small proportions of either the supernatant or membrane fractions to a large excess of F-actin and analysing the pellet resulting from a low-speed centrifugation. Supernatant fraction, containing Triton-soluble membrane-derived material, possessed much greater cross-linking capacity than the membrane-free supernatant prepared in the absence of detergent. The membrane fractions had practically no cross-linking activity on their own. Nevertheless, a non-ionic detergent extract of the membrane enhanced the cross-linking activity of the supernatant, indicating the participation of more than one species in a cross-linking process.
Effects of dietary fat on the growth of normal, preneoplastic and neoplastic mammary epithelial cells in vivo and in vitro
Authors: Carrington Christine A. , Hosick Howard L. 
Published: April 2021

ABSTRACT
In order to determine: (1) whether there is a growth-regulating interaction between the mammary fat pad and mammary epithelium; (2) whether this interaction could be modified by dietary fats; and (3) whether these effects could be demonstrated in vitro, the following experiments were performed. Virgin Balb/c mice had the left inguinal mammary fat pad cleared of epithelium and were then maintained on one of four fully defined diets. These diets contained the following proportions of fat by weight: 5% or 10% mixed fats; 20% saturated fat plus cholesterol; or 20% polyunsaturated fat. To test for effects in vivo, animals received subcutaneous injections into the cleared fat pad of tumorigenic mammary cells (WAZ-2T(+SA) or WAZ-2T (—SA)) or preneoplastic mammary cells (CL-S1). Dietary fat had little effect on the latent period of tumour formation, but a low-fat diet increased the invasive/metastatic potential of both tumorigenic cell lines. A high-saturated-fat diet inhibited the growth of normal and preneoplastic epithelium in vivo. To test for effects in vitro, CL-S1 cells were co-cultured with explants of cleared mammary fat pad embedded within collagen gels. CL-S1 cells co-cultured with adipose explants obtained from mice fed on a diet containing 20% polyunsaturated fat showed a threefold increase in incorporation of [3H] thymidine into trichloroacetic acid-precipitable material. These results imply that dietary fats may affect the growth of mammary epithelium in two ways: the inhibition of growth caused by the high-saturated-fat diet may be due to systemic effects as it was not apparent in vitro; the increase in growth seen in vitro and caused by a high-polyunsaturated-fat diet is due to a direct interaction between the mammary fat pad and mammary epithelial cells. This interaction may be masked by systemic effects in vivo.
Timing of sulphogalactolipid biosynthesis in the rat testis studied by tissue autoradiography
Authors: Lingwood Clifford A. 
Published: April 2021

ABSTRACT
The testicular synthesis of sulphatoxygalactosylacylalkylglycerol (SGG) has been studied in the rat by autoradiography of frozen tissue sections following in vivo metabolic labelling. The results are consistent with the synthesis of this major mammalian germ-cell glycolipid at the zygotene and early pachytene stages of spermatogenesis. Further synthesis of SGG is prevented by the appearance of an inhibitor of galactolipid sulphotransferase activity at the mid-pachytene stage.