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1.
Figure 5

Figure 5. Dynamics of FLIP formation and retraction. From: Shear flow-induced formation of tubular cell protrusions in multiple myeloma cells.

Phase-contrast images of ARH-77 type A cells under flow. Time indicates interval (in seconds) after initiation of FLIP formation. The FLIP shown is elongating at its tip (left panel), with concomitant slow, backwards retraction that occurs at its base (right panel). Direction of flow is marked by an arrow.

Ziv Porat, et al. J Cell Physiol. ;226(12):3197-3207.
2.
Figure 9

Figure 9. Lifespan of FLIPs: Single-cell analysis of the data from Figure 6. From: Shear flow-induced formation of tubular cell protrusions in multiple myeloma cells.

Cells that extended FLIPs were analyzed, according to their FLIP lifespan. The population could be roughly divided into two groups, separated by the vertical dashed line: Fast-retracting cells (left) that have a maximum FLIP lifespan of 12 minutes, and slow-retracting cells (right). This difference is not dependent on the level of force applied.

Ziv Porat, et al. J Cell Physiol. ;226(12):3197-3207.
3.
Figure 3

Figure 3. Transmission electron microscopy images of FLIP-forming cells. From: Shear flow-induced formation of tubular cell protrusions in multiple myeloma cells.

ARH-77 type A cells were fixed under flow, and processed for electron microscopy. (A, B) Examples of two cells under flow. Flow direction is denoted by the white arrows. (A1) Enlargement of the area marked in (A). (B1, B2) Higher magnification of the marked areas in (B). FLIPs are mostly devoid of organelles. (B1) The FLIP ‘neck’, marked by arrowhead, contains microfilaments. (B2) FLIPs often contain ER-like membranal structures, marked with arrowheads.

Ziv Porat, et al. J Cell Physiol. ;226(12):3197-3207.
4.
Figure 7

Figure 7. FLIP extension, but not retraction is affected by force level. From: Shear flow-induced formation of tubular cell protrusions in multiple myeloma cells.

ARH-77 type A cells were exposed to shear flow as indicated, time-lapse movies were taken, and FLIP formation was analyzed. At each time point, the numbers of FLIP formation and FLIP retraction events were counted. Shown here are the cumulative scores, indicated by the percentage of total numbers of FLIPs formed during 40 minutes of treatment for each force level. While higher levels of shear force increased the incidence of new FLIP formation, the FLIP retraction rate was not affected by changes in shear stress.

Ziv Porat, et al. J Cell Physiol. ;226(12):3197-3207.
5.
Figure 6

Figure 6. Shear force level affects FLIP formation. From: Shear flow-induced formation of tubular cell protrusions in multiple myeloma cells.

ARH-77 type A cells were placed inside the chamber, and shear forces of 4,12, 20, 28 or 36 dynes/cm2 were applied for 40 min. Time-lapse movies were taken, and the number of FLIP-forming cells was scored, and presented as a percentage. Black arrows indicate flow start and end times. Insert shows FLIP formation during the first two minutes after exposure to flow. It can be seen that the stronger the force, the higher the percentage of FLIP-producing cells, and the shorter the lag period.

Ziv Porat, et al. J Cell Physiol. ;226(12):3197-3207.
6.
Figure 1

Figure 1. ARH-77 type A multiple myeloma cells develop tubular protrusions (FLIPs) upon exposure to shear flow of >10 dynes/cm2. From: Shear flow-induced formation of tubular cell protrusions in multiple myeloma cells.

Cells were seeded and allowed to adhere to fibronectin-coated glass coverslips, placed in a flow chamber, and exposed to shear flow. Shown are phase-contrast images of (A) cells under stationary conditions; and (B) cells under shear flow of 20 dynes/cm2, for 8 minutes, forming numerous FLIPs. The insert shows a magnification of the marked area. White arrowheads point to induced FLIPs. Direction of flow is indicated by the arrow.

Ziv Porat, et al. J Cell Physiol. ;226(12):3197-3207.
7.
Figure 10

Figure 10. The force-responding cell population can be divided into highly sensitive, slow-retracting cells, and poorly sensitive, fast-retracting cells. From: Shear flow-induced formation of tubular cell protrusions in multiple myeloma cells.

(A) FLIP formation in individual cells for different force levels over time. Each cell is represented by a different colored line. Time, in minutes, is shown from the beginning of flow. (B) Plot showing the relative initiation times of FLIP formation, as a function of FLIP lifespan under different levels of shear stress. It is shown that FLIP extension is mainly force-dependent, as strong shear force induced FLIP formation in all cells. Sensitive cells also respond to weak forces, while insensitive cells require the stimulus of strong force. The insensitive subpopulation is also fast-retracting (B, solid diamonds), whereas the FLIPs formed by the sensitive cells display longer lifespans (B, empty squares).

Ziv Porat, et al. J Cell Physiol. ;226(12):3197-3207.
8.
Figure 8

Figure 8. FLIP suppression is induced by shear flow, yet is highly dependent on the duration, rather than the force, of the shear treatment. From: Shear flow-induced formation of tubular cell protrusions in multiple myeloma cells.

ARH-77 Type A cells were placed inside the flow chamber. A shear force of 4 dynes/cm2 was applied, and then increased in a stepwise fashion to 8, 12, 16, 20, 24, 28, and 32 dynes/cm2 (see Insert for force change). Each force level was applied for variable lengths of time, ranging from 1–8 min for each force step. Time-lapse movies were then taken, and FLIP formation was scored. It appears that the duration of exposure to flow plays a major role in the suppression of FLIP formation, as longer flow times resulted in a decrease in FLIP formation events.

Ziv Porat, et al. J Cell Physiol. ;226(12):3197-3207.
9.
Figure 2

Figure 2. The FLIP is a narrow tubular protrusion with a typical length of up to 20 μm, extending in the direction of flow. From: Shear flow-induced formation of tubular cell protrusions in multiple myeloma cells.

Scanning electron microscope images of ARH-77 type A cells under flow. Cells were fixed under flow, and processed for electron microscopy. (A) Control cells, not exposed to flow, showing numerous villi and lamellae on their entire surface. (B, C) Cells under flow (20 dynes/cm2), showing the formation of ‘matrix anchoring zones’ at the edges of the cells, facing the external flow (arrowheads) and reduction in surface microvilli and lamellae. All membrane protrusions localize to the end of the cell, in the direction of the flow. (D) Higher-magnification image of the FLIP shown in (C). The direction of flow is indicated by an arrow. Scale bar is 5μm.

Ziv Porat, et al. J Cell Physiol. ;226(12):3197-3207.
10.
Figure 4

Figure 4. Actin and tubulin localization in multiple myeloma cells exposed to shear flow. From: Shear flow-induced formation of tubular cell protrusions in multiple myeloma cells.

Fluorescence microscopy images of ARH-77 type A cells under flow. Cells were fixed and labeled with phalloidin-FITC (right panel), anti-α-tubulin antibody (middle panel) and DAPI (merge, left panel). (A–B) Control cells, not exposed to flow, show microtubule network with distinct perinuclear microtubule organizing center and numerous actin-rich lamellipodia and microvilli extensions formed throughout the cell surface. (C–D) Cells exposed to shear flow. The cell surface becomes smooth and free of microvilli and lamellae, and localization of FLIPs and other membrane extensions at the cell edge in the direction of flow can be seen. The FLIPs are rich in actin, located at the plasma membrane, and largely devoid of microtubules. An example of a FLIP with a single microtubule fiber is indicated by an arrowhead. Direction of flow is marked with an arrow. Scale bar is 10μm.

Ziv Porat, et al. J Cell Physiol. ;226(12):3197-3207.

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