bluuebunny/crossref_metadata_2025_split huggingface dataset:
A note on synaptic structure of the retina of Octopus vulgaris
Authors: Gray E. G. 
Published: April 2021

ABSTRACT
Electron microscopy of the octopus retina shows that both types of synapse (formed by the visual cell collaterals and the efferents respectively) have synaptic membrane specializations with associated aggregations of synaptic vesicles—features usually regarded as indicative of synaptic contact. These have hitherto been considered as absent from the octopus retina. Other details of the retinal synapses are described and in addition the grouped microtubules in the initial portions of the optic axons are seen to have in association a regular pattern of micro filaments.
The fine structure of obliquely striated body wall muscles in the earthworm, Lumbricus terrestris linn
Authors: Mill P. J. , Knapp M. F. 
Published: April 2021

ABSTRACT
The fine structure of obliquely striated muscle fibres from the body wall of the earthworm has been investigated. Certain details of the structure have been confirmed by cutting serial sections. The fibres contain both thick and thin myofilaments. The latter are attached to Z matenal and the 2 types of myofilament are arranged in interdigitating arrays to give rise to A- and I-bands and an H-zone similar to those in cross-striated muscle. The A-bands contain both thick and thin myofilaments and the I-bands only thin myofilaments. The Z-matenal is rod-shaped and these Z-rods, oriented perpendicular to the sarcolemma, are arranged in numerous parallel rows which run obliquely along the length of the fibre A line drawn parallel to the longitudinal fibre axis through a Z-rod in one row passes through a Z-rod in the next row. A thin, sheet-like array of myofilaments lies between 2 such Z-rods, forming a single sarcomere containing an A-band and 2 I-bands. The flat surfaces of neigh bouring sarcomeres are directly apposed to one another but, since the rows of Z-rods run diagonally along the length of the fibre, each sarcomere is displaced longitudinally with respect to the next, so that the A- and I-bands follow an oblique course, instead of a transverse course as in cross-striated muscle. Because of the regular stagger of the sarcomeres A- and I-bands are cut alternately in transverse sections. Also the sarcomeres are very narrow and are seen as bands lying perpendicular to the sarcolemma.
In the A-band a variable number of thin myofilaments (up to 12) surrounds each thick one. Cross-links have been seen between the 2 types of filaments.
In longitudinal sections an appearance similar to that seen in cross-striated muscle is obtained in one plane (perpendicular to the sarcolemma). In the plane at right angles to this (parallel to the sarcolemma) the A- and I-bands are at an acute angle to the longitudinal fibre axis. The thick myofilaments exhibit a banding of about 15 nm.
There is a system of transversely oriented tubules and peripheral vesicles with dyad-like structures occurring at the juxtaposition between the peripheral vesicles and the sarcolemma. It is concluded that this system is sarcoplasmic reticulum, and it is compared with tubular systems in other muscles.
Other cellular constituents are described, including a peripheral skeleton of fibrillar bundles.
Immunological and immuno fluorescent studies on keratin of the hair follicle
Authors: Kemp D. J. , Rogers G. E. 
Published: April 2021

ABSTRACT
Keratins from the differentiating cortical cells of the guinea-pig hair follicle have been studied by immunological and immunofluorescent procedures. Antisera were prepared to the unfractionated keratin proteins from the follicle and the specificity of these antisera examined by lmmunodifTusion and lmmunoelectrophoresis. The major follicle antigens were the ‘low sulphur’ keratins, and the antibodies were specific for these and related α-keratins. Use of the precipitin reaction as a quantitative immunoassay for follicle keratins has been demonstrated. The fluorescent antibody technique has been applied to the hair follicle and the follicle antigens have been localized by this procedure in the cytoplasm of the developing cortical cells. By this technique keratin could not be detected in the proliferative cells of the bulb region of the follicle supporting the view that keratin synthesis begins only when the cells enter the upper bulb region of the follicle.
The use of antibiotics in the preparation of amphibian cell cultures from highly contaminated material
Authors: Laskey R. A. 
Published: April 2021

ABSTRACT
Embryos and larvae of Xenopus laevis are contaminated with a wide range of micro-organisms from the maternal cloaca. Primary monolayer cultures prepared from them were usually destroyed by endogenous contaminants. Fungal contamination was readily eliminated by the usual procedures. The high incidence of bacterial contamination was not reduced by penicillin, streptomycin, tetracycline or combinations of the three. Contamination by Gram-negative bacilli, especially Proteus and Pseudomonas, remained. Treatment with carbenicillin, gentamicin or the combination of polymyxin E with kanamycin usually eliminated all infection. The cytotoxicity of effective antibiotics was tested.
The basic requirements of a method for eliminating endogenous bacterial contamination and the relative merits of the three effective treatments are discussed.
Electron-microscopic observations of polyoma virus-transformed mouse cells treated with specific immune serum
Authors: Negroni G. , Tilly Rita 
Published: April 2021

ABSTRACT
Transformed, non-malignant cells from a polyoma virus-induced mouse fibrosarcoma were treated with immune serum raised in isologous mice, and fresh guinea-pig serum (complement). Electron microscopy showed that reduction in cell viability in vitro was associated with damage to cell membranes. The extravasated cell organelles showed only minimal changes.
The surface structure of cultured rabbit kidney cells as revealed by electron microscopy
Authors: Dimmock Elizabeth 
Published: April 2021

ABSTRACT
An epithelioid line of rabbit kidney cells (RK 13), in which the distribution of blood group antigen A had previously been investigated by mixed agglutination, was chosen for studies of the structure of the cell surface. Cells were grown in monolayer culture, and thin sections were examined by electron microscopy after fixation in glutaraldehyde and osmium tetroxide and staining of the sections with lead, or uranyl and lead. Cells were also treated with ruthenium red incorporated in the osmium fixative. Other cells were fixed in lanthanum or potassium permanganate, and both stained and unstained sections were examined.
The morphology of RK 13 cell surfaces is described. There is apparently no great degree of cellular specialization. The treatment with ruthenium red resulted in dense staining of a layer of the cell surface that is not visible in conventional preparations, and sometimes in staining of the surfaces of intracellular organelles. Lanthanum permanganate fixation also revealed a dense layer on the surface of the plasma membrane; a less dense surface layer was distinguished in many cells fixed in potassium permanganate.
The reaction of ruthenium red with the cell surface is probably due to the presence of acidic glycoproteins, but the chemical specificity of the staining method is not yet clear. The nature of the material revealed by lanthanum and potassium permanaganates is also undefined. How-ever, these staining methods reveal that the cell surface is more complex than is apparent in cells prepared by conventional techniques. The additional surface layer is probably the site of many blood group substances and other compounds involved in the physiological reactions of the cell surface.
Membrane differentiation in the golgi complex of Micrasterias denticulata bréb. visualized by freeze-etching
Authors: Staehelin L. A. , Kiermayerf O. 
Published: April 2021

ABSTRACT
Freeze-etched dictyosomes of the alga Micrasterias denticulata (Bréb.) exhibit a gradual increase in the density of particles on the membranes of successive cisternae from the forming to the maturing face. At the maturing face a drop in particle numbers can be observed in the peripheral regions of the cisternae, where fenestration and the packaging of the secretory products takes place.
Subsidiary components of the flagella of Chlamydomonas reinhardii
Authors: Hopkins J.M. 
Published: April 2021

ABSTRACT
Some subsidiary components of flagella from the alga Chlamydomonas reinhardii have been studied in the electron microscope using frayed and partially dispersed material, negatively stained. In all, 5 distinct subsidiary structures have been observed, 3 of which are associated with the 9 pairs of outer tubules and 2 with the central pair of tubules.
Radial spokes, about 33 nm long and 5 nm in diameter, are attached at right angles to the A tubule of each outer pair and extend into the lumen of the flagellum in the direction of the central pair of tubules, but do not reach them. The spokes usually occur in pairs along the length of each A tubule. The interval between pairs is about 70 nm and that between the 2 members of each pair about 30 nm. ‘Secondary fibres’. The distal end of each spoke terminates in a hammerhead-like attachment some 10–20 nm by 5 nm with its axis parallel to the long axis of the flagellum. These hammerhead attachments are now identified with the so-called ‘secondary fibres’ previously deduced from micrographs of embedded and sectioned material. There is no evidence from the present work of a continuous secondary fibre throughout the length of the flagellum. Side arms are found attached to the A tubule of each outer pair. These arms, which occur in pairs, are roughly at right angles to the radial spokes which are also attached to the A tubules. The side arm material is distributed along the tubule at regular intervals of about 14 nm. The chemically more stable centre tubule has 2 longitudinal rows of projections, each projection being about 18 nm long with a repeat distance of about 16 nm. Occasionally, on the chemically less stable centre tubule, there is observed one row of projections which are somewhat similar to those on the other tubule.
New informationhas made it possible to reinterpret earlier work and to present a 3-dimensional picture of the external flagellum and its parts.
G and/or c-bands in plant chromosomes?
Authors: Schubert I. , Rieger R. , Döbel P. 
Published: April 2021

ABSTRACT
Similarities and differences become evident from comparisons of centromeric and noncentromeric banding patterns in plant and animal chromosomes.
Similar to C and G-banding in animals (at least most of the reptiles, birds and mammals), centromeric and nucleolus-organizing region bands as well as interstitially and/or terminally located non-centromeric bands may occur in plants, depending on the kind and strength of pretreatment procedures. The last group of bands may sometimes be subdivided into broad regularly occurring ‘marker’ bands and thinner bands of more variable appearance.
Non-centromeric bands in plants often correspond to blocks of constitutive heterochromatin that are rich in simple sequence DNA and sometimes show polymorphism; they thus resemble C-bands. However, most of these bands contain late-replicating DNA. Also they are sometimes rich in A·T base-pairs, closely adjacent to each other and positionally identical to Feulgen+ and Q+ bands, thus being comparable to mammalian G-bands.
Although banding that is reverse to the non-centromeric bands after Giemsa staining is still uncertain in plants, reverse banding patterns can be obtained with Feulgen or with pairs of A·T versus G·C-specific fluorochromes.
It is therefore concluded that not all of the plant Giemàa banding patterns correspond to C-banding of mammalian chromosomes. Before the degree of homology between different Giemsa banding patterns in plants and G and/or C-bands in mammals is finally elucidated, the use of the neutral term ‘Giemsa band’, specified by position (e.g. centromeric, proximal, interstitial, terminal), is suggested to avoid confusion.
Dissociation of insect malpighian tubules into single, viable cells
Authors: Satmary William M. , Bradley Timothy J. 
Published: April 2021

ABSTRACT
The Malpighian tubules of insects are generally composed of more than one cell type. In the hemipteran Rhodnius prolixus, the tubules are divided into two regions, termed the upper and lower tubules, each of which is composed of a distinct cell type. In the dipteran Aedes taeniorhynchus, primary and stellate cells are interspersed throughout the length of the tubules. We report here techniques for the dissociation of the Malpighian tubules of both of these species into single cells. Tubules are removed from the insect and placed for 1 h in insect Ringer containing elastase (Sigma, type III) at 4mg/ml. This treatment fully removes the basal lamella. Mild agitation by hand produces a suspension of single cells, which remain viable as determined by Trypan Blue exclusion. Isolated cells have been maintained in cell culture for one week. Using light and scanning electron microscopy, upper and lower tubule cells of Rhodnius and primary and stellate cells of Aedes can be distinguished on the basis of size, shape, microvillar length, and the presence or absence of intracellular crystals.
Endogenous β-galactoside-specific lectins in rabbit tissues
Authors: Harrison F. Lynne , Fitzgerald John E. , Catt James W. 
Published: April 2021

ABSTRACT
Soluble β-galactoside-specific lectins have been detected in many rabbit tissues and are relatively abundant in certain organs. These lectins are apparently identical to the lectin in rabbit bone marrow, which may be involved in inter-erythroblast associations during differentiation, and are very similar in structure and activity to lectins described in a number of species both in adult and embryonic tissues. The rabbit lectin is a monomer with a relative molecular mass of approximately 12000 and has a low specific activity in the haemagglutination of trypsinized rabbit erythrocytes relative to lectins from other species, which are predominantly dimeric. In addition to the major antigen two minor isoforms of the rabbit galaptin were detected in all tissues. Since these lectins are widely distributed, it seems probable that they are involved in cellular functions that are prominent during development and also maintained in certain differentiated tissues. Experimental evidence currently available suggests that these lectins may be involved in the organization of extracellular matrix components.
Immunolocalization of tissue inhibitor of metalloproteinases (timp) in human cells characterization and use of a specific antiserum
Authors: Hembry Rosalind M. , Murphy Gillian , Reynolds John J. 
Published: April 2021

ABSTRACT
A specific antiserum to pure human amniotic fluid metalloproteinase inhibitor (TIMP) was raised in a sheep. This antiserum was used to demonstrate: firstly, the immunological identity of the TIMP activities from amniotic fluid and culture medium of human foetal lung fibroblasts; and secondly, by indirect immunofluorescence, the secretion of TIMP by human foetal lung fibroblasts, chondrocytes, epithelial cells and smooth muscle cells. The phorbol ester, 12-O-tetra-decanoylphofbol-13-acetate, was used to stimulate secretion of TIMP by human foetal lung fibroblasts and the ionophore monensin was used to demonstrate intracellular accumulation of TIMP in the Golgi apparatus of these cells. These results are discussed in relation to other inhibitors of collagenase reported in the literature, which are probably identical to TIMP.
The specificity and stability of the triton-extracted cytoskeletal framework of gerbil fibroma cells
Authors: Gilbert Mark , Fulton Alice B. 
Published: April 2021

ABSTRACT
Cellular meshworks and topography of gerbil fibroma cells can be preserved by gentle extraction procedures using Triton X-100. We determined the stability and specificity of these cytoskeletal frameworks by measuring extraction rate and its sensitivity to exogenous protein. Two buffers were used, which mimicked the intracellular and extracellular ionic environments. With both buffers, extraction was nearly complete at 5 min..This pattern of extraction was seen both in 5- and 9-day-old cultures. The same pattern of extraction was seen when three different dilutions of cells were examined the second day after plating. Thus, extraction rate was largely independent of minor variations in ionic composition, age in culture, or cell density. Specificity of the cytoskeletal frameworks so produced was determined by competition with two different exogenous proteins (bovine serum albumin or ovalbumin), which did not remove any additional material from the cytoskeletal frameworks, even with over 10% exogenous protein in the extraction buffer. This pattern of extraction is not unique to gerbil fibroma cells. A similar pattern of extraction was seen for a series of cells: mouse 3T3 cells, 3T6 cells and SVPY 3T3 cells. These experiments indicate that the cytoskeletal framework produced by Triton extraction under appropriate conditions is stable after extraction for a period of 10 min or longer, and that the structures are specific, in that they are not disrupted by the presence of exogenous proteins.
Selective association of an endogenous lectin with connective tissues
Authors: Catt J. W. , Harrison F. Lynne 
Published: April 2021

ABSTRACT
Using indirect immunofluorescence we have localized an endogenous P-galactoside-specific lectin in resin-embedded rabbit tissue sections. The pattern of lectin distribution correlates well with biochemical estimations of lectin levels, being abundant in intestine, lung and heart tissue and relatively less abundant in skeletal muscle, liver and kidney. In all tissues lectin is found in connective tissue associated with fibroblasts and the extracellular matrix, and at the periphery of morphologically recognizable smooth muscle cells. The lectin is abundant in skin, intestine and blood vessels, where connective tissue forms the tissue architecture. It is also abundant in heart, where it is particularly associated with the capillaries and lung, where it is also found in alveolar cells. Discrete localization of lectin occurs in areas of connective tissue where epithelial elements are differentiating, such as the crypts of Lieberkuhns in the small intestine and hair follicles in the skin. From these observations we suggest that in cells of mesenchymal origin these endogenous lectins may play a role in the elaboration or organization of the extracellular matrix that regulates tissue differentiation in a number of embryonic and adult tissues.
A novel procedure for pattern analysis of features present on freeze-fractured plasma membranes
Authors: Appleyard S. T. , Witkowski J. A. , Ripley B. D. , Shotton D. M. , Dubowitz V. 
Published: April 2021

ABSTRACTWe have used statistical methods for the analysis of two-dimensional point patterns to derive quantitative descriptions of the distributions of caveolae on freeze-fractured muscle fibre membranes. One method was based on a quadrat analysis while the second was a new procedure that we have called the interpoint distance analysis. We show that the latter analysis can unambiguously distinguish random, clustered and dispersed patterns and that a single parameter can be derived that can be used to compare different distributions. It is readily applicable to patterns containing several hundred points. Practical details of the method are given and a simple algorithm that can be implemented on a microcomputer is provided. The interpoint distance analysis should prove generally useful in situations where the two-dimensional distribution of objects has to be quantified.
Responses of cultured cardiac myocytes to lysosomotropic compounds and methylated amino acids
Authors: Decker R. S. , Decker M. L. , Thomas V. , Fuseler J. W. 
Published: April 2021

ABSTRACT
Cardiac myocytes whose lysosomes had been pre-labelled with acridine orange were exposed to either L-amino acid methyl esters (L-leucine or methionine methyl ester) or to ‘lysosomotropic’ weak bases (chloroquine, methylamine, and NH4CI) for 1 h. Both types of interventions dilated lysosomes equally and inhibited proteolysis to varying degrees. The weak bases produced no apparent alterations in the acridine orange staining, whereas the methylated amino acids induced a marked redistribution of the fluorescent dye from lysosomes into the myoplasm, suggesting that they may have provoked a change in lysosomal membrane permeability. A brief exposure to weak bases failed to enhance acid proteinase secretion into the culture medium but apparently inactivated cellular cathepsin B activity. In contrast, methylated amino acids induced no alterations in acid proteinase activity or the cellular distribution of the two proteolytic enzymes. Lastly, weak bases markedly elevated intralysosomal pH as measured with fluorescein dextran, while only modest rises were observed after amino acid methyl ester treatment. The present observations imply that amino acid methyl esters represent a new class of reagents with actions distinctly different from those of chloroquine and NH4CI, and they may provide a unique and valuable means of studying secondary lysosomal function in cell culture.
Simultaneous ultrastructural localization of ag-nor (nucleolar organizer region) proteins and ribonucleoproteins during mitosis, in human breast cancerous tissues
Authors: Ploton D. , Menager M. , Adnet J. J. 
Published: April 2021

ABSTRACT
The simultaneous ultrastructural localization of the Ag-NOR proteins and ribonucleoproteins (RNP) was carried out during mitosis in human breast cancerous tissues using a one-step silver staining method followed by acetylation.
Owing to the good preservation of the cells and to the high precision of the Ag staining we were able to follow the behaviour of the argyrophilic nucleolar components from prophase to late telophase.
During all the phases of mitosis the Ag-NOR proteins were associated with fibrillar RNP component (without visible fibrillar centre), which originated, during prophase, from the dense fibrillar component of the nucleolus and then integrated within the periphery of some metaphasic chromosomes as irregular structures. The Ag staining of these structures was homogeneous but lower compared to those of nucleoli during prophase.
The RNP sheath that covered the chromosomes was never silver stained.
From anaphase to early telophase the argyrophilic RNP structures disposed within the periphery of the chromatin mass formed roundish and then spherical structures in which the Ag-NOR proteins were clustered as centrally localized spheres.
These findings showed the usefulness of our method for the precise study of the spatial relationship between the Ag-NOR proteins and the chromosomes. Thus we were able to show striking segregation of both the argyrophilic structures at the periphery of the chromatin mass and of the Ag-NOR proteins within these structures. This suggests that a high degree of the structural organization of the future nucleus is already present during anaphase. This could be related to the rapid resumption of ribosomal RNA synthesis.