Protoplasmic Structure and Mitosis

1951 ◽  
Vol 28 (4) ◽  
pp. 417-433
Author(s):  
M. M. SWANN
Keyword(s):  
Integral Equation ◽  
Sea Urchin ◽  
Time Lapse ◽  
Mitotic Figure ◽  
Psammechinus Miliaris ◽  
Protoplasmic Structure ◽  
Mitotic Figures ◽  
Point To Point ◽  
Oriented Material ◽  
Time Lapse Photography

1. The present paper is the first of a series dealing with the birefringence of mitotic figures in the eggs of the sea-urchin Psammechinus miliaris. 2. Living eggs have been examined using time-lapse photography, and retardation curves for the mitotic figures constructed from densitometric measurements made on the film negatives. 3. In the case of the aster, an integral equation relating retardation and coefficient of birefringence can be formulated and solved exactly to give coefficient of birefringence. In the case of the spindle, coefficient of birefringence can only be calculated approximately. 4. In both asters and spindles, the coefficient of birefringence is nil at the centres,rises to a maximum at 5 or 6CL out, and then falls to a minimum at the equator of the spindle or the periphery of the aster. 5. The rise in coefficient of birefringence round the centre is not as sharp as might be expected, and there is some evidence that orientation is built up gradually over a distance of a few microns. 6. The fall in coefficient of birefringence away from the maximum is approximately an inverse square in the case of the spindle. In the aster it falls off somewhat more rapidly. Since the density of material does not vary from point to point, this fall must be due to changes in molecular and micellar arrangement, or to a decreasing proportion of oriented material. 7. The classical conception of the spindle and asters as structures built up of discrete fibrils radiating from the centres, would be expected, for geometrical reasons, to give an inverse square fall in proportion of oriented material. While, therefore, a homogeneous structure with varying molecular and micellar arrangement cannot be ruled out, it is possible that the mitotic figure consists of definite fibrils radiating from the centres. 8. Evidence from other sources supports this view, and suggests that the fibrils must be submicroscopic in size.

The Mechanism of Cell-division

1953 ◽  
Vol s3-94 (28) ◽  
pp. 369-379
Author(s):  
M. M. SWANN
Keyword(s):  
Carbon Monoxide ◽  
Cell Division ◽  
Sea Urchin ◽  
White Light ◽  
Time Lapse ◽  
Psammechinus Miliaris ◽  
Energy Store ◽  
Time Lapse Photography

1. Developing eggs of the sea-urchin Psammechinus miliaris were subjected to carbon monoxide inhibition, which was controlled by changing from green to white light. The behaviour of the eggs was recorded by time-lapse photography. 2. If inhibition is applied before the eggs enter mitosis, their first cleavage is delayed by a time which is roughly equal to the period of the inhibition. 3. If the inhibition is applied when the cells have already entered mitosis, they complete mitosis and cleave with little or no delay, but their second cleavage is delayed by a time which is roughly equal to the period of the inhibition. 4. It is suggested that the necessary energy for the second mitosis and cleavage is being stored up during the first mitosis and cleavage, and that this energy store operates like a reservoir which is continually being filled but siphons out when it is full. Once the energy has siphoned out, it carries mitosis and cleavage through, even though the reservoir is not filling up because of carbon monoxide inhibition.

Protoplasmic Structure and Mitosis

1951 ◽  
Vol 28 (4) ◽  
pp. 434-444
Author(s):  
M. M. SWANN
Keyword(s):  
Structural Change ◽  
Sea Urchin ◽  
Active Substance ◽  
Mitotic Figure ◽  
Contractile Mechanism ◽  
Spindle Poles ◽  
Sea Urchin Egg ◽  
Protoplasmic Structure ◽  
New Material ◽  
The Moment

1. The mitotic figure of the sea-urchin egg is most strongly birefringent at metaphase. During anaphase this birefringence decreases considerably, but the spindle and asters both grow in size. These changes have been investigated quantitatively by constructing curves of retardation and coefficient of birefringence across the mitotic figure, using techniques described in an earlier paper. 2. The decrease of birefringence in the spindle starts at the equator, and then moves, in the course of a few minutes, to either pole. Only when the decrease has reached the spindle poles does it begin in the asters, where it moves outwards from the centres. 3. These changes resemble the movements of the chromosomes, which also start at the equator in metaphase, and move in separate groups to the poles during t anaphase. By examining single eggs in qaphase up to the moment of fixation, and then staining them to show the chromosomes, it is established that the regons of, decreasing birefringence actually correspond to the position of the chromosomes. 4. Since the chromosomes are too small to be the direct cause of the decrease in birefringence, it is concluded that they are producing the decrease indirectly by initiating a structural change in the spindle and asters. 5. The possible mechanisms for this change are discussed. It is concluded that the chromosomes must be releasing an active substance, for which the term ‘structural agent’ is suggested. 6. The growth of the mitotic figure takes the form, in the spindle, of an increase in length, and in the asters, of an increase in size. It is accompanied by an increase in coefficient of birefringence, though this is to some extent masked by the decrease in birefringence referred to earlier. 7. The increase in coefficient of birefringence affects the whole mitotic figure from the very beginning of anaphase, and is not therefore relatable to the position of the chromosomes. For this reason it might be due to a number of merent mechanisms, but as it starts at the same moment as the decrease in birefringence, it is tentatively assumed to be due to the release of a second ‘structural agent’. 8. The increase in coefficient of birefringence is probably due to the orientation of new material. The decrease is more Uely to be due to changes in molecular and micellar arrangement; it would be consistent with a contractile mechanism in the spindle. 9. The implications of these findings are discussed in a concluding section.

scholarly journals The determination of glacier speed by time-lapse photography under unfavorable conditions

1992 ◽  
Vol 38 (129) ◽  
pp. 257-265 ◽  
Author(s):  
W.D. Harrison ◽  
K.A. Echelmeyer ◽  
D.M. Cosgrove ◽  
C. F. Raymond
Keyword(s):  
Time Lapse ◽  
Systematic Errors ◽  
Horizontal Motion ◽  
Limited Information ◽  
Glacier Surface ◽  
Alaska Range ◽  
Use Of Time ◽  
West Fork ◽  
Time Lapse Photography

AbstractTwo practical problems in the use of time-lapse photography for the measurement of speed were encountered during the recent surge of West Fork Glacier in the central Alaska Range, Alaska, U.S.A. The first is severe rotational camera instability; we show how natural, unsurveyed features on the valley wall can be used to make the necessary corrections. The second problem is the computation of absolute speed when many different, unsurveyed glacier-surface features are used as targets. We give a method for connecting the data obtained from different targets, and for determining the scale using limited information obtained by surveying. Severe systematic errors can occur unless the angle between the axis of the lens and the direction of horizontal motion is determined.

scholarly journals Dynamin-related Protein Drp1 Is Required for Mitochondrial Division in Mammalian Cells

2001 ◽  
Vol 12 (8) ◽  
pp. 2245-2256 ◽  
Author(s):  
Elena Smirnova ◽  
Lorena Griparic ◽  
Dixie-Lee Shurland ◽  
Alexander M. van der Bliek
Keyword(s):  
Mammalian Cells ◽  
Fluorescent Protein ◽  
Time Lapse ◽  
Subcellular Fractionation ◽  
Related Protein ◽  
Direct Role ◽  
Mitochondrial Division ◽  
Transfected Cells ◽  
Green Fluorescent ◽  
Time Lapse Photography

Mutations in the human dynamin-related protein Drp1 cause mitochondria to form perinuclear clusters. We show here that these mitochondrial clusters consist of highly interconnected mitochondrial tubules. The increased connectivity between mitochondria indicates that the balance between mitochondrial division and fusion is shifted toward fusion. Such a shift is consistent with a block in mitochondrial division. Immunofluorescence and subcellular fractionation show that endogenous Drp1 is localized to mitochondria, which is also consistent with a role in mitochondrial division. A direct role in mitochondrial division is suggested by time-lapse photography of transfected cells, in which green fluorescent protein fused to Drp1 is concentrated in spots that mark actual mitochondrial division events. We find that purified human Drp1 can self-assemble into multimeric ring-like structures with dimensions similar to those of dynamin multimers. The structural and functional similarities between dynamin and Drp1 suggest that Drp1 wraps around the constriction points of dividing mitochondria, analogous to dynamin collars at the necks of budding vesicles. We conclude that Drp1 contributes to mitochondrial division in mammalian cells.

Variation in the naturally occurring rhythm of the estuarine amphipod, Corophium volutator (Pallas)

1983 ◽  
Vol 63 (4) ◽  
pp. 833-850 ◽  
Author(s):  
Walter F. Holmström ◽  
Elfed Morgan
Keyword(s):  
Activity Rhythm ◽  
Time Lapse ◽  
Early Summer ◽  
Corophium Volutator ◽  
Use Of Time ◽  
Recording Conditions ◽  
Free Running ◽  
Endogenous Activity ◽  
Free Running Period ◽  
Time Lapse Photography

The endogenous activity rhythm of the estuarine amphipod Corophium volutator has been studied by direct observation and with the use of time lapse photography. The rhythm persists under constant conditions having a free running period of between 12 and 13 h, and with activity maxima occurring during the early ebb. Freshly collected animals show a rhythm which is modulated on a semi-lunar basis, the activity maxima being attenuated during the neap tide periods, and the rhythm has also been found to vary in definition throughout the year. The activity pattern is most clearly denned in early summer and autumn, the population becoming arrhythmic during the winter months. The rhythm is relatively unaffected by the ambient light intensity and temperature of the recording conditions, and is evident in all post-natal stages of development. The possibility of mutual entrainment is discussed.

Observations of the deep-sea floor from 202 days of time-lapse photography

Nature ◽  
1978 ◽  
Vol 272 (5656) ◽  
pp. 812-814 ◽  
Author(s):  
ALLEN Z. PAUL ◽  
EDWARD M. THORNDIKE ◽  
LAWRENCE G. SULLIVAN ◽  
BRUCE C. HEEZEN ◽  
ROBERT D. GERARD
Keyword(s):  
Deep Sea ◽  
Time Lapse ◽  
Sea Floor ◽  
Time Lapse Photography
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