THE STRUCTURE AND BEHAVIOR OF THE NUCLEI IN SPORES AND GROWING HYPHAE OF MUCORALES: I. MUCOR HIEMALIS AND MUCOR FRAGILIS

1957 ◽  
Vol 3 (5) ◽  
pp. 771-789 ◽  
Author(s):  
C. F. Robinow
Keyword(s):  
Phase Contrast ◽  
Central Body ◽  
Gentian Violet ◽  
Metaphase Plate ◽  
Low Density ◽  
Mucor Hiemalis ◽  
The Past ◽  
New Findings ◽  
Contrast Microscopy ◽  
And Behavior

The behavior of the nuclei in resting and germinating spores and in growing hyphae of Mucor hiemalis has been followed during life with phase contrast microscopy. The nuclei consist of a dense central body, the nucleolus, surrounded by a shell of variable shape composed of optically uniform material of low density. The nuclei have been seen to divide by constriction. One half of the nucleolus and one half-shell of the low density material pass to each daughter nucleus.All phases of nuclear division have been recognized in fixed and stained preparations. The nucleolus is readily stained by iron hematoxylin or gentian violet but is Feulgen-negative. The shell of low density has no marked affinity for hematoxylin and other basic or acid stains although it consists largely of granules and filaments which are Feulgen-positive. In these elements the chromosomes of the nuclei must somehow be contained but the size, shape, and behavior of individual chromosomes cannot yet be described. Division of the mass of chromatinic elements is direct and involves neither spindle nor metaphase plate. It is tentatively proposed that the chromosomes in the resting nucleus are already divided and segregated to opposite sides and that the constriction of the nucleus is merely the consummation of a kind of endomitosis initiated during the terminal stages of the previous division. Supporting observations have been made on Mucor fragilis, several other Mucorales, and two species of Saprolegnia. Uncertainties and controversies of the past can be explained in the light of the new findings.

scholarly journals The control of amplitude in phase-contrast microscopy

1947 ◽  
Vol 190 (1022) ◽  
pp. 422-426 ◽  
Keyword(s):  
Phase Contrast ◽  
Living Cells ◽  
Differential Staining ◽  
Phase Contrast Microscopy ◽  
Living Tissue ◽  
The Past ◽  
Contrast Microscopy ◽  
Focus Image ◽  
Dark Ground ◽  
First Time

In the past the biologist has generally resorted to differential staining as a means of rendering visible slight non-homogeneities in his preparations. When such treatment was impracticable, as in the case of living cells, the alternatives were to study the out-of-focus image, to illuminate the specimen with very narrow' pencils (with a consequent loss of resolution), or to use dark-ground illumination. Phase contrast offers a means of converting slight changes of refractive index (with the consequent change of wave front) into corresponding changes of amplitude. The method possesses the advantages that the object is accurately focused, that the full aperture of the objective is used and that the eye is particularly sensitive to changes in amplitude. It also makes possible for the first time the detailed study at full aperture of transparent living tissue in place of the usual stained preparations which may have undergone considerable modification in the course of processing.

Diisopropylglutathione ester protects A549 cells from the cytotoxic effects of sulphur mustard

1998 ◽  
Vol 17 (11) ◽  
pp. 606-612 ◽  
Author(s):  
Christopher D Lindsay ◽  
Joy L Hambrook
Keyword(s):  
Phase Contrast ◽  
Gentian Violet ◽  
A549 Cells ◽  
Neutral Red ◽  
A549 Cell Line ◽  
Cytotoxic Effects ◽  
Sulphur Mustard ◽  
Culture Viability ◽  
Contrast Microscopy ◽  
Optimal Effect

The A549 cell line was used to assess the ability of diisopropylglutathione (DIPE) to protect against a 100 mM challenge dose of sulphur mustard (HD) using gentian violet (GV), thiazolyl blue (MTT) and neutral red (NR) assays as indicators of cell culture viability. As part of a continuing study of the efficacy of protective nucleophiles as candidate treatments for HD poisoning, several different combinations of protectant and HD were used to determine the optimal means of protecting A549 cells from the effects of HD. It was found that DIPE (4 mM) could protect cells against the effects of HD though for optimal effect, DIPE had to be present at the time of HD challenge. Cultures protected with DIPE were up to 2.9- fold more viable than HD exposed cells 48 h after HD challenge when using the GV, MTT and NR assays to assess viability. Observations by phase contrast microscopy of GV stained cultures confirmed these findings. Pretreating A549 cultures with DIPE for 1 h followed by its removal prior to HD challenge did maintain cell viability, though at a relatively low level (only up to 1.4- fold more viable than HD only exposed cells). DIPE was also able to protect HD exposed A549 cultures when added to cell cultures at intervals of up to 12 to 15 min after the initial HD exposure, though viability tended to decrease over this period, so that at 1 h, addition of DIPE did not maintain the viability of the cultures. This is the first such report of the anti-HD protectant properties of DIPE in A549 cells. It is concluded that the protection observed against HD is probably largely due to extracellular inactivation of HD by DIPE.

Mitosis in Aspergillus Nidulans

1969 ◽  
Vol 5 (2) ◽  
pp. 403-431 ◽  
Author(s):  
C. F. ROBINOW ◽  
C. E. CATEN
Keyword(s):  
Aspergillus Nidulans ◽  
Mitotic Spindle ◽  
Phase Contrast ◽  
Metaphase Plate ◽  
Acid Fuchsin ◽  
Central Spindle ◽  
Sister Chromatids ◽  
Region Division ◽  
Contrast Microscopy ◽  
The Individual

Mitosis in growing hyphae of haploid and diploid Aspergillus nidulans has been studied with the light microscope in Helly-fixed preparations. At the periphery of the nuleus a sharply defined granule is invariably found which has strong affinity for acid fuchsin. Mitosis begins with the duplication of this granule and the development inside the nucleus of a gradually lengthening fibre between the daughter granules. This fibre is also visibel in dividing nuclei of living hyphae examined by phase-contrast microscopy, when it appears as a grey bar traversing the non-nucleolar region. Division of the chromatin has been studied in preparations stained with aceto orcein, directly or after hydrolysis. It proceeds through four phases, beginning with the condensation of distinct chromosomes from the chromatin network of the resting nuclei. Later the chromosomes become arranged in two parallel rows of chromatinic masses in which individual chromosomes can no longer be distinguished. Division is completed by migration of the chromatin to the ends of each row, giving the appearance of a transverse break in the double bar. The chromatin accumulating at the ends of the double bar condenses to form the two daughter nuclei. The number of chromatinic elements appears to be the same in both haploid and diploid nuclei, although the individual elements are larger in the latter. Successive staining of the same dividing nucleus, first for the fibre (acid fuchsin) and then for the chromosomes (HCl-aceto orcein or HCl-Giemsa) has established that the fibre lies among the chromosomes, and that is elongation is closely related to the anaphase-telophase movements of the chromosomes. This suggests that the fibre is the equivalent of a mitotic spindle. That the fibre is connected with the chromosomes is further suggested by the observation that, in stained preparations, the fibre is considerably thicker in dividing diploid than in haploid nuclei. Electron microscopy of dividing nuclei has revealed that mitosis is carried out within the intact nuclear envelope. The mitotic spindle is composed of a bundle of fibrils which traverses the nucleus between two plaques of dense material associated with the envelope. In order to explain the configurations seen during the division of the chromatin it is proposed that the chromosomes become attached to the central spindle at various points along its length. With the elongation of the spindle the sister chromatids separate and pass, asynchronously, to opposite ends of the spindle along two preferred lines, thereby producing the characteristic double bar figure. The absence of a metaphase plate is thus accounted for by the scattered points of attachment of the chromosomes to the spindle and by their asynchronous division.

scholarly journals The Morphology and Behavior of Living Exoerythrocytic Stages of Plasmodium gallinaceum and P. fallax and Their Host Cells

1960 ◽  
Vol 7 (1) ◽  
pp. 93-102 ◽  
Author(s):  
Clay G. Huff ◽  
Alan C. Pipkin ◽  
A. B. Weathersby ◽  
Dinniemaud V. Jensen
Keyword(s):  
Phase Contrast ◽  
Nuclear Division ◽  
Time Lapse ◽  
Host Cells ◽  
Phase Contrast Microscopy ◽  
Tissue Cultures ◽  
Plasmodium Gallinaceum ◽  
Contrast Microscopy ◽  
And Behavior ◽  
Culture Phase

The morphology and behavior of living exoerythrocytic stages of Plasmodium gallinaceum and P. fallax were studied by the use of tissue cultures, phase contrast microscopy, and time-lapse cinephotomicrography. The morphology of exoerythrocytic stages of these two species was essentially that previously observed in fixed, stained material, with the following exceptions: (1) the presence of a filament on one end of the merozoite, (2) the absence of clefts in the cytoplasm of the large schizonts, and (3) the absence of a vacuole-like space around the parasite. The following behavior was observed either directly or in time-lapse sequences: (1) emergence of merozoites from mature schizonts, (2) progressive motility of free merozoites, (3) entry of merozoites, both actively and passively, into host cells, (4) nuclear division in the parasite, (5) the various stages of schizogony, including final production of merozoites, (6) massive infection of host cells, and (7) phagocytosis of merozoites and attempted phagocytosis of mature schizonts by macrophages. Exoerythrocytic stages of P. fallax differed from those of P. gallinaceum in that the merozoites of the former were (1) somewhat more curved in shape and (2) present in fewer numbers in mature schizonts. The use of tissue culture, phase contrast microscopy, and time-lapse cinephotomicrography promises to solve many of the remaining problems concerning exoerythrocytic stages of malarial parasites and their interrelationships with host cells.

Detachment of biofilm bacteria due to variations in nutrient supply

1998 ◽  
Vol 37 (4-5) ◽  
pp. 211-214 ◽  
Author(s):  
Linda K. Sawyer ◽  
Slawomir W. Hermanowicz
Keyword(s):  
Phase Contrast ◽  
Digital Image Analysis ◽  
Specific Growth ◽  
Nutrient Supply ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Nutrient Limitations ◽  
Contrast Microscopy ◽  
Biofilm Bacteria ◽  
Observable Parameter

Growth and detachment rates of an environmental isolate of Aeromonas hydrophila attached to a surface were determined under varying nutrient supply conditions in a complex medium. Growth and detachment of cells were observed in real time using phase contrast microscopy in glass parallel plate flow chambers. Surface shear stress was controlled in all experiments at 3 N m−2. Images were taken every 15 min. Digital image analysis was used to determine specific growth and detachment rates. An observable parameter proportional to the nutrient depletion at the surface due to transfer limitations was used to indicate nutrient limitations. Specific detachment rates increased as the depletion parameter increased, indicating that nutrient limitations cause this bacterium to detach at greater rates.

Brains as Engines of Association

2019 ◽  
Author(s):  
Dale Purves
Keyword(s):  
Neural Systems ◽  
Neural Function ◽  
Trial And Error ◽  
Nervous Systems ◽  
The Past ◽  
Sensing Systems ◽  
Lifetime Experience ◽  
Survival And Reproduction ◽  
Pros And Cons ◽  
And Behavior

Brains as Engines of Association seeks an operating principle of the human brain and is divided into four parts. The first part (“What Nervous Systems Do for Animals”) is intended to set the stage for understanding the emergence of neural systems as promoting what all organisms must accomplish: survival and reproduction. The second part (“Neural Systems as Engines of Association”) lays out the general argument that biological sensing systems face a daunting problem: they cannot measure the parameters of the world in the way physical instruments can. As a result, nervous systems must make and update associations (synaptic connections) on the basis of empirical success or failure over both evolutionary and individual time. The third part (“Evidence that Neural Systems Operate Empirically”) reviews evidence accumulated over the past 20 years that supports this interpretation in vision and audition, the sensory systems that have been most studied from this or any other perspective. Finally, the fourth part (“Alternative Concepts of Neural Function”) considers the pros and cons of other interpretations of how brains operate. The overarching theme is that the nervous systems of humans and every other animal operate on the basis associations between stimuli and behavior made by trial and error over species and lifetime experience.

Temporal Focus

2020 ◽  
Author(s):  
Abbie J. Shipp
Keyword(s):  
Well Being ◽  
Psychology Research ◽  
The Past ◽  
Research Areas ◽  
The Future ◽  
Behavior Based ◽  
The Individual ◽  
And Behavior ◽  
Temporal Focus

Temporal focus is the individual tendency to characteristically think more or less about the past, present, and future. Although originally rooted in early work from psychology, research on temporal focus has been steadily growing in a number of research areas, particularly since Zimbardo and Boyd’s (1999) influential article on the topic. This chapter will review temporal focus research from the past to the present, including how temporal focus has been conceptualized and measured, and which correlates and outcomes have been tested in terms of well-being and behavior. Based on this review, an agenda for research is created to direct temporal focus research in the future.

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