Light and dark Purkinje cells (light microscopic and microautoradiographic studies]

The authors deal with the phenomenon of dualism of pale and dark ganglion cells in general, the phenomenon which, since FLEMMING (1882), still remains an actual problem of neurohistology. They deal with Purkinje cells from a special aspect with the aim to demonstrate the dualism through various staining methods. They directed their attention also to the question of the influence of perfusion and immersion fixation and length of staining with luxol-fast-blue on the production of luxol-positive (chromophilic) Purkinje cells. The authors have found that these methodologic circumstances do not influence the production of luxol-positive Purkinje cells, so it can be hardly spoken about an artifact. Examinations with the labelled leucine have shown that the increased metabolic activity can be observed in those Purkinje cells which in HE-picture are seen as pale ones. In the dark Purkinje cells leucine granulations are located on the surface of plasmatic membrane and they follow to some distance the main dendrite of those cells. The microautoradiographic method evidences for the increased leucine metabolism of the pale Purkinje cells as well.     

Insects, oxygen, and iron

Konrad Bloch developed an interest in insects because they are unable to make sterols, and in yeast because these cells need oxygen to make sterols and unsaturated fatty acids. Insects, like all other organisms, must deal with the toxic effects of oxygen in the presence of iron, which itself is a vital nutrient. They do so by making proteins with high affinity for ferric or ferrous ions. Two such proteins are transferrins and ferritins. Insects produce both of these proteins, but use them in different ways from most other organisms. Insect transferrins appear to be involved in innate immunity, perhaps by sequestering ferric ions to prevent pathogens and parasites from utilizing them. Insect ferritins, unlike those of any other group of organisms, are exported into the extracellular space (hemolymph). They may be involved in iron transport and/or protection against iron overload in the diet.     

Ontogenesis of 5-hydroxytryptamine-like immunoreactive cells and their relationship with bombesin in chicken proventriculus

By using a double-stain immunohistochemical procedure, the Aa. studied the onset, the behaviour and the possible interrelationship between the 5-HT-like and bombesin-like immunoreactive cells during the ontogenesis of chicken proventriculus and in adult animals. The 5-HT-like immunoreactive cells become evident from the 8th day of incubation and they reach their peak around the 16th day, then markedly decrease at hatching. In adult animal these cells are always present, but are not so numerous. Between the 14th and the 18th day many double-stained cells scattered among other only 5-HT or bombesin-like immunoreactive cells are present. They can also be observed in adults, but only occasionally.     

Structure of cryptic lambda prophages

When Escherichia coli cells lysogenic for bacteriophage lambda are induced with ultraviolet light, cells carrying cryptic lambda prophages are occasionally found among the apparently cured survivors. The lambda variant crypticogen (lambda crg) carries an insertion of the transposable element IS2, which increases the frequency of cryptic lysogens to about 50% of cured cells: 43 of these cryptic prophages have been characterized. They all contain substitutions that replace the early segment of the prophage genome (from the IS2 to near the cos site) with a duplicate copy of a large segment of the host chromosome. The right end of the substitution always results from recombination between the nin-QSR-cos region of the prophage and the homologous incomplete lambdoid prophage Qsr' at 12.5 minutes in the E. coli chromosome. The left end of the substitution is usually a crossover that recombines the IS2 element in the prophage with an E. coli IS2 at 8.5 minutes, near the lac gene, or with a second IS2 located counterclockwise from leu at 2 minutes, generating duplications of at least 200,000 bases. Five cryptic lysogens derived from cells lysogenic for a reference strain of lambda (which lacks the IS2 present in lambda crg) have been characterized. They contain substitutions whose right termini are generated by a crossover with the Qsr' prophage. The left termini of these substitutions are formed either by a crossover between the lambda exo gene and a short exo-homologous segment of Qsr' (2/5), or by a crossover between sequences to the left of attL and an unmapped distant region of the host chromosome (3/5). The large duplications carried by these cryptic lysogens are stable, unlike tandem duplications, and so may significantly influence the cell's evolutionary potential.     

On the Phloem of Mimosa pudica L.

The phloem of Mimosa pudica L. was examined in view of somereports that the sieve elements in this plant show featuresnot previously described for these cells in Leguminosae. Inthe present study only a usual dicotyledonous type of sieveelement was recognized. The sieve elements pass through stagesof differentiation involving development and dispersal of P-proteinbodies, disintegration of nuclei, and appearance of plastidsstoring a starch staining red with iodine. Callose occurs onthe transverse or moderately oblique sieve plates. The phloemcontains secretory cells. They are wide and long and have transverseor more or less inclined end walls. In younger cells the endwall bears in the centre a conspicuous pit to which the protoplastsof the superimposed cells are firmly attached. In many oldercells the pit region is replaced by a perforation so that thecontents of superimposed cells may be completely merged. Itremains to be determined whether the perforation is presentin an intact plant or results from a rupture during sampling.The secretory cells accumulate material that gives a positivetest for carbohydrates and a negative test for proteins.     

Light and electron microscopical observations on sperm cells of Guizotia abyssinica (Asteraceae)

The sperm cells of Guizotia abyssinica were studied during pollen development by light microscopy and at anther dehiscence by transmission electron microscopy. During development, the nuclei change shape from spherical to elongate, thread-like and banded. They are straight or folded, and rarely spiral-shaped when present in the pollen tube. Electron microscopy disclosed that the elongated sperm nuclei are apparently lobate. Intermittently, they are constricted and attenuated or convoluted. The major part of the sperm chromatin is condensed and peripheral, while a minor part is dispersed and central. The scanty sperm cytoplasm contains mitochondria and starch granules. The cytoplasm is mainly restricted to spaces adjoining constricted, lobed and convoluting nuclear sites. Some cytoplasmic patches become embayed in the nucleus at these sites. The periplasm bordering the sperm cells may originate from lucid dilations of the lumen between the plasma membranes of the sperm and vegetative cells. The periplasm is sometimes partially or entirely surrounded by double-membraned endoplasmic reticulum. Folded sperm cells with less coherent periplasm possibly represent a late stage preceding discharge into the pollen tube. The sperm cells always precede the vegetative nucleus into the pollen tube.     

Towards a structural biology of bacterial conjugation

Horizontal DNA transfer among bacteria (conjugation) requires the formation of secure intercellular contacts before DNA transfer can occur. The formation of such contacts among Gram-negative bacteria is mediated by conjugative pili. Like other pili, conjugative pili are filaments extending from the surface of donor cells. They are composed, in so far as is known, entirely of conjugative pilin subunits. Here, we review the structure of F-pilin, the subunit of which F-pili are composed. We emphasize recent studies suggesting a specific domain organization for F-pilin and present a model of how these domains might be arranged in filament subunits.     

The Langerhans' cell

Langerhans cells are antigen-presenting cells that play a key role in the initiation and regulation of immune response. They are localized in stratified epithelia, such as epidermis, and migrate to the lymphoid organs in order to present antigens introduced in the skin so that the T cell response can be initiated. Light and electron microscopy images of the cells demonstrate their morphology within the epidermis and as they migrate to the culture medium. Factors inducing migration are reviewed, as well as the therapeutic potential of these factors in regulating the immune response.     

Features and functions of nonlinear spatial integration by retinal ganglion cells

Ganglion cells in the vertebrate retina integrate visual information over their receptive fields. They do so by pooling presynaptic excitatory inputs from typically many bipolar cells, which themselves collect inputs from several photoreceptors. In addition, inhibitory interactions mediated by horizontal cells and amacrine cells modulate the structure of the receptive field. In many models, this spatial integration is assumed to occur in a linear fashion. Yet, it has long been known that spatial integration by retinal ganglion cells also incurs nonlinear phenomena. Moreover, several recent examples have shown that nonlinear spatial integration is tightly connected to specific visual functions performed by different types of retinal ganglion cells. This work discusses these advances in understanding the role of nonlinear spatial integration and reviews recent efforts to quantitatively study the nature and mechanisms underlying spatial nonlinearities. These new insights point towards a critical role of nonlinearities within ganglion cell receptive fields for capturing responses of the cells to natural and behaviorally relevant visual stimuli. In the long run, nonlinear phenomena of spatial integration may also prove important for implementing the actual neural code of retinal neurons when designing visual prostheses for the eye.     

Effects of dactinomycine (actinomycine D) on budless hydra and during its budding process.

The effect of dactinomycine (actinomycine D) is manifested in various ways, which depends upon its concentration and animal condition at the time of treatment. Dactinomycine is citotoxic in stronger concentations so hydra dies quickly. In thinner concentrations it stops the mitotic activity of the cell, but the basic metabolic processes continue as before. Interstitial cells differenciate into cnidoblasts for some time, the cnid production is not halted, but all of these cells disappear as well as zimogen cells which dedifferentiate into gastrodermal interstitial and into mucous cells. Such animals live longer but die eventually. The effect of dactinomycine is generally milder on animals with a larger cell mass, in hydras with the budding tendency where exist such reserves and in those hydras in which the budding process has begun. In these a part of mobile undamaged zimogen cells can remain. They keep their reproduction ability. These animals can survive and keep on growing normally.     

Biomarkers, regerons, and pathways to lethal cancer

Cancer is a disease of "outlaw" cells that become mutated in regulatory mechanisms. They have lost normal self controls and relationships to the whole organism. Cancers can progress by several pathways from a normal cell to malignant cancer, from bad to worse. Questions about advisability of treatment for some cancers arise from the possibility that they are arrested during progression and so never become lethal. Techniques could be developed to determine the degree of progression and possibility for successful treatment. This article is intended to suggest a way of looking at cancer. It is not a review so references to research articles are infrequent.     

Cells on microspheres: a new technique for flow cytometric analysis of adherent cells

Technical problems have previously prevented the application of fluorescence activated cell sorting to the study of adherent cell populations. We have developed a procedure for attachment of human monocyte-macrophages to 14-20 micrometer microspheres. These adherent cells on microspheres retained phagocytic capacity, could be stained for cell surface antigens using indirect immunofluorescence, and could be maintained in long-term culture. They could be examined and sorted on a fluorescence activated cell sorter while still in the adherent state. This technique facilitates the flow cytometric study of adherent cells and permits the isolation of subpopulations of these cells.     

Expression of epithelial antigens in primary cultures of normal human breast analysed with monoclonal antibodies

Abstract. Primary cultures of normal human breast were stained with monoclonal antibodies to see if antigens characteristic of luminal epithelial cells are retained in culture. Three monoclonal antibodies were used, LICR-LON-M8, LICR-LON-M18, and LICR-LON-M24, all specific for the cell surface of luminal epithelial as opposed to myoepithelial or stromal cells in the breast, and each staining a different subset of the epithelial cells in the intact tissue. Cultures were prepared from reduction mammoplasty samples by digestion with collagenase. The surface layer of cells was stained by immunofluorescence without fixation. (Cells underneath the surface layer were not accessible to this mode of staining). The antibodies stained patches of cells resembling flattened epithelium. These patches of cells cannot be distinguished by phase contrast microscopy without reference to the staining, in fact the boundaries of the cells are not usually resolved by phase contrast microscopy. Electron microscopy of sections through these cells show they are very flattened. They lie on top of the polygonal and elongated cells that dominate the phase contrast image. Two of the antibodies, M8 and M24, stain subsets of these epithelial-like cells at all stages of culture. The third antibody, Ml8, stains such cells initially, but after the first few days staining is predominantly found on the polygonal and elongated cells, then this also gradually disappears. It is possible that the cells stained by antibody Ml8 are converting from the epithelial-like morphology to the cuboidal and elongated morphology. Many cells are not stained by any of the antibodies, so appear either to by myoepithelial in origin or to have lost their luminal epithelial surface antigens at an early stage. This analysis draws attention to the variety of cell types in these cultures and the limitations of phase contrast microscopy as a means of analysing them.     

Expression of epithelial antigens in primary cultures of normal human breast analysed with monoclonal antibodies

Primary cultures of normal human breast were stained with monoclonal antibodies to see if antigens characteristic of luminal epithelial cells are retained in culture. Three monoclonal antibodies were used, LICR-LON-M8, LICR-LON-M18, and LICR-LON-M24, all specific for the cell surface of luminal epithelial as opposed to myoepithelial or stromal cells in the breast, and each staining a different subset of the epithelial cells in the intact tissue. Cultures were prepared from reduction mammoplasty samples by digestion with collagenase. The surface layer of cells was stained by immunofluorescence without fixation. (Cells underneath the surface layer were not accessible to this mode of staining). The antibodies stained patches of cells resembling flattened epithelium. These patches of cells cannot be distinguished by phase contrast microscopy without reference to the staining, in fact the boundaries of the cells are not usually resolved by phase contrast microscopy. Electron microscopy of sections through these cells show they are very flattened. They lie on top of the polygonal and elongated cells that dominate the phase contrast image. Two of the antibodies, M8 and M24, stain subsets of these epithelial-like cells at all stages of culture. The third antibody, M18, stains such cells initially, but after the first few days staining is predominantly found on the polygonal and elongated cells, then this also gradually disappears. It is possible that the cells stained by antibody M18 are converting from the epithelial-like morphology to the cuboidal and elongated morphology. Many cells are not stained by any of the antibodies, so appear either to by myoepithelial in origin or to have lost their luminal epithelial surface antigens at an early stage. This analysis draws attention to the variety of cell types in these cultures and the limitations of phase contrast microscopy as a means of analysing them.     

Generation of an environmental niche for neural stem cell development by the extracellular matrix molecule tenascin C

Stem cells in the embryonic mammalian CNS are initially responsive to fibroblast growth factor 2 (FGF2). They then undergo a developmental programme in which they acquire epidermal growth factor (EGF) responsiveness, switch from the production of neuronal to glial precursors and become localized in specialized germinal zones such as the subventricular zone (SVZ). Here we show that extracellular matrix molecules act as regulators of this programme. Tenascin C is highly expressed in the SVZ, and transgenic mice lacking tenascin C show delayed acquisition of the EGF receptor. This results from alterations in the response of the stem cells to the growth factors FGF2 and bone morphogenic protein 4 (BMP4), which normally promote and inhibit acquisition of the EGF receptor, respectively. Tenascin C-deficient mice also have altered numbers of CNS stem cells and these stem cells have an increased probability of generating neurones when grown in cell culture. We conclude that tenascin C contributes to the generation of a stem cell 'niche' within the SVZ, acting to orchestrate growth factor signalling so as to accelerate neural stem cell development.     

Novel microfluidic platform for culturing neurons: Culturing and biochemical analysis of neuronal components

Neurons, one of the most polarized types of cells, are typically composed of cell bodies (soma), dendrites, and axons. Many events such as electric signal transmission, axonal transport, and local protein synthesis occur in the axon, so that a method for isolating axons from somata and dendrites is required for systematically investigating these axonal events. Based on a previously developed neuron culture method for isolating and directing the growth of central nervous system axons without introducing neutrophins, we report three modified microfluidic platforms: (1) for performing biochemical analysis of the pure axonal fraction, (2) for culturing tissue explants, and (3) a design that allows high content assay on same group of cells. The key feature of these newly developed platforms is that the devices incorporate a number of microgrooves for isolating axons from the cell body. They utilize an open cellculture area, unlike the enclosed channels of the previous design. This design has extended the axonal channel so that a sufficient amount of pure axonal fraction can be obtained to perform biochemical analysis. The design also addresses the drawback of the previous neuron culture device, which was not adaptable for culturing thick neuronal tissues such as brain explants, neurospheres, and embryoid bodies, which are essential model tissues in neuroscience research. The design has an open cellculture area in the center and four enclosed channels around open area, and is suitable for multiple drug screening assays.     

An electron microscopical study of the development of peroxisomes during formation and germination of ascospores in the methylotrophic yeast Hansenula polymorpha

Ascospore formation was studied in liquid cultures of the yeast Hansenula polymorpha, previously grown under conditions in which the synthesis of alcohol oxidase was repressed (glucose as growth substrate) or derepressed (methanol, glycerol and dihydroxyacetone as growth substrates and after growth on malt agar plates). In ascospores obtained from repressed cells, generally one small peroxisome was present. The organelle probably originated from the small peroxisome, originally present in the vegetative cells. They had no crystalline inclusions and cytochemical experiments indicated the presence of catalase, urate oxidase and amino acid oxidase activities in these organelles. In ascospores obtained from derepressed cells, generally 1–3 crystalline peroxisomes were observed. These organelles also originated from the peroxisomes originally present in the vegetative cells by means of fragmentation or division. They contained, in addition to the enzymes characteristic for peroxisomes in spores from repressed cells, also alcohol oxidase. The latter enzyme is probably responsible for the crystalline substructure of these peroxisomes.Peroxisomes had no apparent physiological function in the process of ascosporogenesis. A glyoxysomal function of the organelles during germination of the ascospores was also not observed. Germination of mature ascospores in media containing different sources of carbon and nitrogen showed that the function of the peroxisomes present in ascospores of Hansenula polymorpha is probably identical to that in vegetative haploid cells. They are involved in the oxidative metabolism of different carbon and nitrogen sources. Their enzyme profile is a reflection of that of peroxisomes of vegetative cells and their presence may enable the formation of cells which are optimally adapted to environmental conditions extant during spore germination.     

The excretion of lactate dehydrogenase in human urine after ingestion of aspirin

1. Cells present in normal human urine contain 5-10% of the total lactate dehydrogenase excreted. The enzyme released from these cells by ultrasonication contained a distribution of isoenzymes similar to that found in the bulk of the urine and it is suggested that these cells are the main source of urinary lactate dehydrogenase. 2. Cells were thoroughly washed before examination so it is unlikely that the enzyme found in urinary sediment was simply adsorbed. In addition, full recoveries of added lactate dehydrogenase isoenzymes LDH(1) and LDH(5) showed that adsorption did not occur. 3. Most of the cells in normal urine are of the non-squamous epithelial type and their excretion is greatly increased after the ingestion by the subject of 3g. of aspirin. The possible origin of these non-squamous cells from the kidney is discussed. 4. Starch-block electrophoresis and relative activity measurements of lactate dehydrogenase excreted after the subject had taken aspirin show that the enzymes present in urine and cells are very similar, confirming the conclusion reached above (point 1). They have slightly more M subunits than the normal, shown particularly as an increase in isoenzyme LDH(2). The isoenzyme pattern is like that of the kidney medulla and the possible reasons for this are discussed in terms of the concentration of salicylic acid in various parts of the kidney. 5. The results confirm the previous suggestion that the kidney is the main source of urinary lactate dehydrogenase.