Clocking the Lyme Spirochete

In order to clear the body of infecting spirochetes, phagocytic cells must be able to get hold of them. In real-time phase-contrast videomicroscopy we were able to measure the speed of Borrelia burgdorferi (Bb), the Lyme spirochete, moving back and forth across a platelet to which it was tethered. Its mean crossing speed was 1,636 µm/min (N = 28), maximum, 2800 µm/min (N = 3). This is the fastest speed recorded for a spirochete, and upward of two orders of magnitude above the speed of a human neutrophil, the fastest cell in the body. This alacrity and its interpretation, in an organism with bidirectional motor capacity, may well contribute to difficulties in spirochete clearance by the host

Directed cell movement and cluster formation : physical principles

The cell-cell interaction of migrating human leukocytes (granulocytes) was investigated. We have found that the attractive pair interaction of granulocytes tan be switched-off at high calcium concentrations and switched-on at low calcium concentrations. Through this experiment we established that the cells attracted each other and formed clusters containing actively moving cells : (i) the cluster formation was a function of the mean cell density, (ii) where no clusters were observed for small cell densities, $\rho_1$ (< 150-300 cells/mm$^2$ ; threshold behaviour), (iii) and the mean cluster size was a function of the mean cell density. (iv) In addition we established that the dynamic process of the cluster formation was a function of the mean cell density, and (v) the migrating cells were oriented towards the cluster's tenter. The cluster formation is discussed in the framework of a droplet model where two dynamic processes are observed : (a) the cells in a cluster attract further cells and (b) the cells at the boundary of the cluster have the possibility to move away. The droplet mode] in connection with the cell conservation law is confirmed by the experiments. The analogy between the liquid-gas transition of interacting molecules and the condensation of interacting cells is shown. The migrating and oriented cells of a cluster are in an orientational liquid crystal state of polar symmetry. The polar order is discussed in the framework of a polar mean field

Plunder of Human Blood Leukocytes Containing Ingested Material, by Other Leukocytes: Where Is the Fusagen That Allows Preservation of Membrane Integrity and Motile Function?

<div><p>In studying phagocytosis of zymosan particles by human blood monocytes in phase-contrast videomicroscopy, we found that monocytes loaded with zymosan particles became chemotactic for polymorphonuclear leukocytes (PMN) which closed on them and purloined their particle content. This despoliation usually occurred in monocytes that had begun to swell—prefiguring their death. The violent seizure of their contents by the aggressing PMN often tore the monocytes apart. However, some apparently healthy monocyte survived the removal of zymosan content by PMN or, more commonly, its removal by another monocyte. PMN—a much hardier cell in slide preparations—that were similarly loaded with zymosan particles, also attracted PMN. The latter could remove zymosan from the target cell without killing it. Thus, leukocytes were sacrificing significant portions of themselves without losing residual membrane integrity and motile function. Their behavior with respect to other particles (e.g., bacteria) will be of interest. We suggest that the membrane fusagen resides in the inner membrane leaflets when they are brought together in an extreme hourglass configuration. This event may be similar to the fragmentation of erythrocytes into intact pieces, the formation of cytokineplasts, the rear extrusion of content by migrating cells on surfaces, and the phagocytic process itself.</p></div

One simple interpretation of the membrane events associated with intercellular transfer of zymosan.

<p>In this formulation, the two cells briefly become one (B), a phagosome(s) moves from right to left, transporting 2 zymosan (C), and the separate cells reestablish themselves (D).</p

Monocyte containing zymosan attracts PMN which apparently dismantle it, taking up its zymosan themselves.

<p>A. Monocyte contains 9 zymosan. PMN approaching. B. +7 min, 7 sec: The monocyte swells (dying). The PMN continue to arrive. C. +19 min, 7 sec: PMN appear to enter the monocyte and take up its zymosan. D. +45 min, 5,sec: The monocyte is completely destroyed. Nuclear material is stretched out. PMN move away. (Monocytes and zymosan in 100% plasma, 2 hr, washed, and autologous PMN added. Substrate: methacrylate-coated glass.)</p

PMN can purloin a monocyte's zymosan without killing it.

<p><b>A. Monocyte (M) containing 6 zymosan.</b> A. deformed (trapped) erythrocyte is at 12 o'clock. Four PMN are approaching. B. +6 min, 55 sec: PMN are surrounding the monocyte. C. +27 min, 43 sec: A PMN, traversing the monocyte from left to right, takes up a zymosan. D. +6 min, 56 sec: The same PMN is now pressing into the body of the monocyte from the right. The monocyte is so far intact and motile. E. +4 min,19 sec: The PMN appears to have transected the monocyte. The nucleated portion (above, Mn) remains motile. F. +15 min,58 sec: Ma indicates the anucleate portion of the monocyte. The arc shows a clear area of its residual cytoplasm; at right its zymosan is being scavenged by PMN. Mn remains motile for 24 more minutes. (Monocytes and zymosan in 100% plasma, 1 hr, washed, and autologous PMN added. Substrate: plastic.)</p

PMN can purloin zymosan from other PMN without loss of motile function in aggressor or victims.

<p>A. Three PMN (N1–3), one with 2 prominent zymosan (N2) another with 4 zymosan (N3). B +1 min, 57′sec, and C +9 min, 23 sec. Aggressor PMN (N1) takes up 2 zymosan from N2. D +3 min, 20 sec. N1 moves to N3 and, in E +7 min, 15 sec, and F 15 min, 39 sec, takes up two more zymosan from the latter. All 3 PMN remain motile (N2 has left the field at lower right). (PMN and zymosan in 100% plasma, 30 min, washed, and autologous PMN added. Substrate: glass.)</p

Monocytes can purloin another a monocyte's zymosan without killing it.

<p>A. Target monocyte loaded with 13 zymosan; aggressor monocyte at left. B. +11 min, 7 sec. The latter extends a wide cytoplasmic tongue, C. +5 min, 43 sec, surrounds 2 zymosan from the target cell, and D. +16 min, 34 sec, incorporates them into its own cytoplasm. (Monocytes and zymosan in 100% plasma, 2 hr, washed, and autologous monocytes added. Substrate: plastic.)</p