Quantitative studies on step-down photophobic response ofEuglena in an individual cell

PROTOPLASMA ◽  
1981 ◽  
Vol 106 (1-2) ◽  
pp. 37-48 ◽  
Author(s):  
T. Shimmen
Keyword(s):  
Individual Cell ◽  
Quantitative Studies ◽  
Photophobic Response ◽  
Step Down

scholarly journals A step-down photophobic response in coral larvae: implications for the light-dependent distribution of the common reef coral, Acropora tenuis

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yusuke Sakai ◽  
Kagayaki Kato ◽  
Hiroshi Koyama ◽  
Alyson Kuba ◽  
Hiroki Takahashi ◽  
...  
Keyword(s):  
Reef Coral ◽  
Benthic Organisms ◽  
Light Conditions ◽  
Coral Larvae ◽  
Mathematical Simulations ◽  
Photophobic Response ◽  
Acropora Tenuis ◽  
The Common ◽  
Step Down ◽  
Planktonic Larval Stage

Abstract Behavioral responses to environmental factors at the planktonic larval stage can have a crucial influence on habitat selection and therefore adult distributions in many benthic organisms. Reef-building corals show strong patterns of zonation across depth or underwater topography, with different suites of species aggregating in different light environments. One potential mechanism driving this pattern is the response of free-swimming larvae to light. However, there is little experimental support for this hypothesis; in particular, there are few direct and quantitative observations of larval behavior in response to light. Here, we analyzed the swimming behavior of larvae of the common reef coral Acropora tenuis under various light conditions. Larvae exhibited a step-down photophobic response, i.e. a marked decrease in swimming speed, in response to a rapid attenuation (step-down) of light intensity. Observations of larvae under different wavelengths indicated that only the loss of blue light (wavelengths between 400 and 500 nm) produced a significant response. Mathematical simulations of this step-down photophobic response indicate that larvae will aggregate in the lighter areas of two-dimensional large rectangular fields. These results suggest that the step-down photophobic response of coral larvae may play an important role in determining where larval settle on the reef.

scholarly journals Behavioural Responses to Light in Paramecium Bursaria in Relation to its Symbiotic Green Alga Chlorella

1988 ◽  
Vol 134 (1) ◽  
pp. 43-60
Author(s):  
KENJI IWATSUKI ◽  
YUTAKA NAITOH
Keyword(s):  
Green Alga ◽  
Paramecium Bursaria ◽  
Swimming Velocity ◽  
Behavioural Responses ◽  
Symbiotic Algae ◽  
Response System ◽  
Light Region ◽  
Photophobic Response ◽  
Green Alga Chlorella ◽  
Step Down

The behavioural responses to light in the ciliate Paramecium bursaria Focke, which normally contains hundreds of the symbiotic green alga Chlorella in its cytoplasm, were analysed quantitatively to clarify the mechanisms governing photoreception in the cell. P. bursaria was found to possess three kinds of photoreceptor systems for (1) the step-up photophobic response (system I), (2) the step-down photophobic response (system II), and (3) the photokinetic response (system III). Under the influence of light, the symbiotic algae inhibited systems I and III, but activated system II. Thus the cells showed the avoiding reaction when they encountered shade (the step-down photophobic response), and consequently gathered in the light region (photoaccumulation). Inhibition of system I and activation of system II were assumed to be mediated by products of the blue-light effect of the algae, while inhibition of system III was due to photosynthetic products of the algae. The cells whose algae were experimentally removed gathered in the shade (photodispersal) due to the avoiding reaction exhibited by them when they encountered a lighted region (the step-up photophobic response mediated by system I). Lowered swimming velocity and increased frequency of spontaneous changes in the swimming direction in the shade (photokinetic responses mediated by system III) also caused photodispersal.

PHOTOBEHAVIOR OF EUGLENA GRACILIS: ACTION SPECTRUM FOR THE STEP-DOWN PHOTOPHOBIC RESPONSE OF INDIVIDUAL CELLS

1979 ◽  
Vol 29 (5) ◽  
pp. 1015-1019 ◽  
Author(s):  
Corrado Barghigiani ◽  
Giuliano Colombetti ◽  
Barbara Franchini ◽  
Francesco Lenci
Keyword(s):  
Euglena Gracilis ◽  
Action Spectrum ◽  
Photophobic Response ◽  
Step Down

Residual Gas Reaction in the Electron Microscope: II The Design of a Gas-Control Chamber for Quantitative Observations

1969 ◽  
Vol 27 ◽  
pp. 82-83
Author(s):  
Chester J. Calbick ◽  
Richard E. Hartman
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Local Environment ◽  
Chamber Pressure ◽  
Objective Lens ◽  
Ion Pump ◽  
Quantitative Studies ◽  
Precise Knowledge ◽  
Differential Pumping ◽  
And Control

Quantitative studies of the phenomenon associated with reactions induced by the electron beam between specimens and gases present in the electron microscope require precise knowledge and control of the local environment experienced by the portion of the specimen in the electron beam. Because of outgassing phenomena, the environment at the irradiated portion of the specimen is very different from that in any place where gas pressures and compositions can be measured. We have found that differential pumping of the specimen chamber by a 4" Orb-Ion pump, following roughing by a zeolite sorption pump, can produce a specimen-chamber pressure 100- to 1000-fold less than that in the region below the objective lens.

Ultrastructure of myoepithelial cell in parotid gland

1988 ◽  
Vol 46 ◽  
pp. 342-343
Author(s):  
C. N. Sun
Keyword(s):  
Parotid Gland ◽  
Osmium Tetroxide ◽  
Individual Cell ◽  
Branching Processes ◽  
Muscle Cells ◽  
Myoepithelial Cells ◽  
Uranyl Acetate ◽  
Thin Sections ◽  
Gland Carcinoma ◽  
Parotid Gland Carcinoma

Myoepithelial cells have been observed in the prostate, harderian, apocrine, exocrine sweat and mammary glands. Such cells and their numerous branching processes form basket-like structures around the glandular acini. Their shapes are quite different from structures seen either in spindleshaped smooth muscle cells or skeletal muscle cells. These myoepithelial cells lie on the epithelial side of the basement membrane in the glands. This presentation describes the ultrastructure of such myoepithelial cells which have been found also in the parotid gland carcinoma from a 45-year old patient.Specimens were cut into small pieces about 1 mm3 and immediately fixed in 4 percent glutaraldehyde in phosphate buffer for two hours, then post-fixed in 1 percent buffered osmium tetroxide for 1 hour. After dehydration, tissues were embedded in Epon 812. Thin sections were stained with uranyl acetate and lead citrate. Ultrastructurally, the pattern of each individual cell showed wide variations.

Ratio imaging of intracellular ion concentration

1992 ◽  
Vol 50 (2) ◽  
pp. 1160-1161
Author(s):  
Stephen R. Bolsover
Keyword(s):  
Individual Cell ◽  
Video Camera ◽  
Field Of View ◽  
Ion Concentration ◽  
Fluorescence Signal ◽  
Ion Imaging ◽  
Ratiometric Fluorescence ◽  
Ratio Imaging ◽  
The Mean ◽  
The Many

The field of intracellular ion concentration measurement expanded greatly in the 1980's due primarily to the development by Roger Tsien of ratiometric fluorescence dyes. These dyes have many applications, and in particular they make possible to image ion concentrations: to produce maps of the ion concentration within living cells. Ion imagers comprise a fluorescence microscope, an imaging light detector such as a video camera, and a computer system to process the fluorescence signal and display the map of ion concentration.Ion imaging can be used for two distinct purposes. In the first, the imager looks at a field of cells, measuring the mean ion concentration in each cell of the many in the field of view. One can then, for instance, challenge the cells with an agonist and examine the response of each individual cell. Ion imagers are not necessary for this sort of experiment: one can instead use a system that measures the mean ion concentration in a just one cell at any one time. However, they are very much more convenient.

Comparative strengths and weaknesses of peroxidase and colloidal gold in pre- and post-embedding immunolabeling techniques

1987 ◽  
Vol 45 ◽  
pp. 1002-1005
Author(s):  
D. R. Abrahamson ◽  
P. L. St.John ◽  
E. W. Perry
Keyword(s):  
Electron Microscopy ◽  
Horseradish Peroxidase ◽  
Light Microscopy ◽  
Colloidal Gold ◽  
Light Microscope ◽  
Ultrastructural Localization ◽  
The Other ◽  
Quantitative Studies ◽  
Dense Suspension ◽  
Antigen Localization

Antibodies coupled to tracers for electron microscopy have been instrumental in the ultrastructural localization of antigens within cells and tissues. Among the most popular tracers are horseradish peroxidase (HRP), an enzyme that yields an osmiophilic reaction product, and colloidal gold, an electron dense suspension of particles. Some advantages of IgG-HRP conjugates are that they are readily synthesized, relatively small, and the immunolabeling obtained in a given experiment can be evaluated in the light microscope. In contrast, colloidal gold conjugates are available in different size ranges and multiple labeling as well as quantitative studies can therefore be undertaken through particle counting. On the other hand, gold conjugates are generally larger than those of HRP but usually can not be visualized with light microscopy. Concern has been raised, however, that HRP reaction product, which is exquisitely sensitive when generated properly, may in some cases distribute to sites distant from the original binding of the conjugate and therefore result in spurious antigen localization.

Rem Study of Current Effect on the Structure of Clean Si(111) Surface

1990 ◽  
Vol 48 (1) ◽  
pp. 306-307
Author(s):  
A. Yamanaka ◽  
H. Ohse ◽  
K. Yagi
Keyword(s):  
The Other ◽  
Current Direction ◽  
Clean Surface ◽  
Current Effect ◽  
Atomic Steps ◽  
Step Bunching ◽  
Terrace Width ◽  
Step Down ◽  
A Current

Recently current effects on clean and metal adsorbate surfaces have attracted much attention not only because of interesting phenomena but also because of practically importance in treatingclean and metal adsorbate surfaces [1-6]. In the former case, metals deposited migrate on the deposit depending on the current direction and a patch of the deposit expands on the clean surface [1]. The migration is closely related to the adsorbate structures and substrate structures including their anisotropy [2,7]. In the latter case, configurations of surface atomic steps depends on the current direction. In the case of Si(001) surface equally spaced array of monatom high steps along the [110] direction produces the 2x1 and 1x2 terraces. However, a relative terrace width of the two domain depends on the current direction; a step-up current widen terraces on which dimers are parallel to the current, while a step-down current widen the other terraces [3]. On (111) surface, a step-down current produces step bunching at temperatures between 1250-1350°C, while a step-up current produces step bunching at temperatures between 1050-1250°C [5].In the present paper, our REM observations on a current induced step bunching, started independently, are described.Our results are summarized as follows.(1) Above around 1000°C a step-up current induces step bunching. The phenomenon reverses around 1200 C; a step-down current induces step bunching. The observations agree with the previous reports [5].

Step-Down Tx Helpful in Refractory Gastroparesis

2006 ◽  
Vol 39 (20) ◽  
pp. 54
Author(s):  
SHERRY BOSCHERT
Keyword(s):  
Step Down

Understanding Why Older People Develop a Wish to Die

Crisis ◽  
2011 ◽  
Vol 32 (4) ◽  
pp. 204-216 ◽  
Author(s):  
M. L. Rurup ◽  
H. R. W. Pasman ◽  
J. Goedhart ◽  
D. J. H. Deeg ◽  
A. J. F. M. Kerkhof ◽  
...  
Keyword(s):  
Older People ◽  
Cohort Studies ◽  
Conceptual Framework ◽  
Life Events ◽  
Traumatic Life Events ◽  
Quantitative Studies ◽  
Wish To Die ◽  
Open Coding ◽  
Death Wishes ◽  
Depth Interviews

Background: Quantitative studies in several European countries showed that 10–20% of older people have or have had a wish to die. Aims: To improve our understanding of why some older people develop a wish to die. Methods: In-depth interviews with people with a wish to die (n = 31) were carried out. Through open coding and inductive analysis, we developed a conceptual framework to describe the development of death wishes. Respondents were selected from two cohort studies. Results: The wish to die had either been triggered suddenly after traumatic life events or had developed gradually after a life full of adversity, as a consequence of aging or illness, or after recurring depression. The respondents were in a situation they considered unacceptable, yet they felt they had no control to change their situation and thus progressively “gave up” trying. Recurring themes included being widowed, feeling lonely, being a victim, being dependent, and wanting to be useful. Developing thoughts about death as a positive thing or a release from problems seemed to them like a way to reclaim control. Conclusions: People who wish to die originally develop thoughts about death as a positive solution to life events or to an adverse situation, and eventually reach a balance of the wish to live and to die.

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