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Biomedical subjects

A C Groom

Publications and source records attributed to A C Groom.

At least 37 records · Page 2Linked to original sources
PubMed1994

Overexpression of metalloproteinase inhibitor in B16F10 cells does not affect extravasation but reduces tumor growth.

It is widely accepted that a major role of matrix metalloproteinases in the metastatic process is degradation of basement membrane during cancer cell invasion. We tested the hypothesis that the reduction in metastatic potential which has been demonstrated for B16F10 melanoma cells genetically engineered to overexpress tissue inhibitor of metalloproteinase-1 (TIMP-1) is caused by a decrease in their ability to extravasate. Using intravital videomicroscopy of chick embryo chorioallantoic membrane, we studied extravasation of B16F10 cells and B16F10 cells transfected to overexpress TIMP-1. More than 800 cells in 36 chick embryos were analyzed for each cell line during 72 h postinjection. TIMP-1 upregulation had no effect on the time course of extravasation, virtually all cells from both cell lines having extravasated by 36 h. We also studied the morphology of micrometastases at days 3 and 7. Lack of contact between cancer cells within micrometastases at day 3 and reduction in size and number of tumors at day 7 were observed for TIMP-1 overexpressor cells compared to B16F10. Our findings illustrate that the imbalance between TIMP and metalloproteinases created by overexpression of TIMP-1 in B16F10 cells reduces their metastatic ability in vivo by affecting tumor growth postextravasation.

Animals↗
PubMed1994

Mammary carcinoma cell lines of high and low metastatic potential differ not in extravasation but in subsequent migration and growth.

We examined the extravasation and subsequent migration and growth of murine mammary tumor cell lines (D2A1 and D2.OR) which differ in their metastatic ability in lung and liver, invasiveness in vitro and expression of the cysteine proteinase cathepsin L. In light of the differences in invasiveness and cathepsin L expression, we hypothesized that during hematogenous metastasis the two cell lines would differ primarily in their ability to extravasate. We used in vivo videomicroscopy of mouse liver and chick embryo chorioallantoic membrane to examine the process and timing of extravasation and subsequent steps in metastasis for these cell lines. In contrast to our expectations, no differences were found between the cell lines in either the timing or mechanism of extravasation, at least 95% of cells having extravasated by 3 days after injection. However, after extravasation, the more metastatic and invasive D2A1 cells showed a greater ability to migrate to sites which favor tumor growth and to replicate to form micrometastases. These studies point to post-extravasation events (migration and growth) as being critical in metastasis formation.

Animals↗
PubMed1994

Heterogeneity of red blood cell perfusion in capillary networks supplied by a single arteriole in resting skeletal muscle.

Flow heterogeneity within capillary beds may have two sources: (1) unequal distribution of red blood cell (RBC) supply among arterioles and (2) unique properties of RBC flow in branching networks of capillaries. Our aim was to investigate the capillary network as a source of both spatial and temporal heterogeneity of RBC flow. Five networks, each supplied by a single arteriole, were studied in frog sartorius muscle (one network per frog) by intravital video microscopy. Simultaneous data on RBC velocity (millimeters per second), lineal density (RBCs per millimeter), and supply rate (RBCs per second) were measured continuously (10 samples per second) from video recordings in 5 to 10 capillary segments per network for 10 minutes by use of automated computer analysis. To quantify heterogeneity, mean values from successive 10-second intervals were tabulated for each flow parameter in each capillary segment (ie, portion of capillary between successive bifurcations), and percent coefficient of variation (SD/mean.100%) was calculated for (1) spatial heterogeneity among vessels (CVs) every 10 seconds and for the entire 10-minute sample and (2) temporal heterogeneity within vessels for every capillary segment and for the mean flow parameter. Analysis of these data indicates that (1) capillary networks are a significant source of both spatial and temporal flow heterogeneity, and (2) continuous redistributions of flow occur within networks, resulting in substantial temporal changes in CVs, although a persistent spatial heterogeneity of perfusion still exists on a 10-minute basis. In most networks, CVs decreased as supply rate within the network increased, thus indicating that rheology plays a significant role in determining the perfusion heterogeneity.

Animals↗
PubMed1993

Scanning and transmission electron microscopy and high resolution intravital video-microscopy of capillaries in the mouse exocrine pancreas, with special emphasis on endothelial cells.

Capillaries in the mouse exocrine pancreas were studied by scanning electron microscopy of microvascular corrosion casts, transmission electron microscopy of tissue sections, and high resolution intravital video-microscopy. Two types of capillaries were discerned by corrosion casting. The first type was rather straight, had a constant diameter of 5-6 microns, and its surface showed multiple circumferential furrows. The frequency of such constrictions was less in the second type, which was more undulated and had a diameter of 7-9 microns. In the second type, these constrictions defined bulged areas of the capillary cast. Corresponding tissue sections also showed two types of capillaries, fenestrated and non-fenestrated capillaries. Microtubules were abundant in all capillary endothelial cells, whereas bundles of microfilaments were scarce. Microtubules were arranged along the long axis of endothelial cells as well as parallel to endothelial cell border regions. Endothelial cells were joined by intermediate junctions along cell borders running both circumferentially and longitudinally. Flow reversal in capillaries and spontaneous endothelial contractions were documented in vivo. Endothelial cells bulged into the lumen, either at their nuclear region or distant from it. Spontaneous contraction of pericytes was not observed. These results suggest that contraction of capillaries is carried out by endothelial cells, representing an autonomous flow regulatory device. Capillary contraction in exocrine pancreas may be influenced by blood-borne agents, probably by those released in Langerhans islets.

Animals↗
PubMed1993

Early interactions of cancer cells with the microvasculature in mouse liver and muscle during hematogenous metastasis: videomicroscopic analysis.

Biomechanical interactions of cancer cells with the microvasculature were studied using high resolution intravital videomicroscopy. We compared initial arrest of murine B16F10 melanoma and D2A1 mammary carcinoma cells fluorescently labelled with calcein-AM, in low pressure (liver) vs high pressure (cremaster muscle) microvascular beds. Cells were arrested due to size restriction at the inflow side of the microcirculation, penetrating further and becoming more deformed in muscle than liver [median length to width ratios of 3.3 vs 1.3 for D2A1 cells, and 2.5 vs 1.2 for B16F10, at 1 min post-injection (p.i.)]. During the next 2 h many cells became stretched, giving maximum length to width ratios of 68 vs 22.1 (D2A1) and 28 vs 5.6 (B16F10) in muscle vs liver. Ethidium bromide exclusion demonstrated that over 97% of the cells maintained membrane integrity for > 2 h p.i. (In contrast, when an acridine orange labelling procedure was used, membrane disruption of B16F10 cells occurred within 15 min p.i.) Our experiments do not indicate the ultimate fate of the cancer cells, but if cell lysis occurs it must be on a time scale of hours rather than minutes. We report a process of 'clasmatosis' in cancer cells arrested in the microcirculation: large membrane-enclosed fragments (> 3 microns in diameter) became 'pinched off' from arrested cells, in both liver and muscle, often within minutes or even seconds of arrest. The significance of this process is not yet understood. In this study intravital videomicroscopy has thus provided a valuable clarification of the interactions of cancer cells with vessel walls during metastasis.

Animals↗
PubMed1993

Reduction of sunburn damage to skin by topical application of vitamin E acetate following exposure to ultraviolet B radiation: effect of delaying application or of reducing concentration of vitamin E acetate applied.

The skin of the skh-1 mouse after ultraviolet B (280-320 nm, UVB) irradiation shows the pathological changes typical of sunburn damage: spongiosis (edematous spaces) around some cells, necrosis of keratinocytes, giving rise to sunburn cells, inflammatory infiltration of polymorphonuclear leucocytes, etc. In our previous study, these were accompanied by erythema, increased skin sensitivity, and edematous swelling. The topical application of tocopherol acetate (TA) immediately after the UVB exposure decreased these changes. In this paper, multiple measurements of the skin thickness were made at different locations along the magnetic resonance imaging (MRI) cross-sectional image of the skin. This permits effects to be quantified with (if desired) the contralateral half of the back serving as an internal control, either exposed (positive control) or unexposed (negative control). Topical application of TA resulted in an increase in the concentration of free tocopherol in the skin. No qualitative differences in ultrastructural appearance of the UVB-irradiated, TA-treated skin could be discerned by careful examination. In vivo high resolution video microscopy of blood flow in venules of the irradiated mouse ear revealed a large (tenfold) but not statistically significant decrease in stationary lymphocytes adhering to the venule walls. The delaying of the application of TA up to 8 hours after the termination of UVB irradiation still offered statistically significant protection as did immediate application of 5% TA in diluent Myritol 318 (Delios S, Henkel).

Administration, Topical↗
PubMed1993

Comparative aspects of splenic microcirculatory pathways in mammals: the region bordering the white pulp.

Splenic microcorrosion casts prepared using minimal volumes of material show that most of the flow passes through the region bordering the white pulp. However, the nature of these microcirculatory pathways has received little attention. We have studied these in dog, cat, rat, mouse, and normal versus diseased human spleens. In all 5 species, a marginal sinus (MS) of anastomosing vascular spaces 5-10 microns thick lies between the white pulp and marginal zone (MZ). The morphology differs between species and the MS is absent in immune thrombocytopenia. The MS fills by circumferential flow before blood passes outward to the MZ. Many capillaries supply the MS and MZ, their arrangement and degree of branching differing among species. Capillaries never terminate within the reticulum of the white pulp. In immune thrombocytopenia, marked vascular hyperplasia occurs within white pulp and MZ. The perimarginal cavernous sinus plexus (PMCS), found in human, dog and rat, comprises large flattened spaces up to 300 microns x 1000 microns in area and 30-100 microns thick. It lies between the MZ and red pulp or directly adjacent to white pulp, and receives flow principally via the MZ. In sinusal spleens, the MS, MZ and PMCS are drained by open-ended venous sinuses. In non-sinusal spleens, the MS and MZ are drained by pulp venules. Approximately 90% of the splenic inflow passes through the region bordering the white pulp, bypassing the filtration beds of the red pulp. This suggests that immunologic functions of the spleen take precedence over the filtration of blood cellular elements in the red pulp.

Animals↗
PubMed1993

Ischemia-reperfusion induced microvascular dysfunction in skeletal muscle: application of intravital video microscopy.

Video microscopy of red cell flow in capillaries at the surface of skeletal muscle provided the opportunity to quantitate ischemia-reperfusion (I-R) induced microcirculatory changes, in vivo. Extensor Digitorum Longus (EDL) muscles of 22 male Wistar rats (300-400 g), anesthetized with sodium pentobarbital (Somnotol, 65 mg kg,-1 IP), were used to measure the number of perfused capillaries (CDper: mm-1) crossing lines drawn perpendicular to the muscle axis, and red blood cell velocity (VRBC: mm/s) within individual capillaries from controls (n = 6), and after 2 hr (n = 4), 3 hr (n = 4), and 4 hr (n = 5) of no-flow ischemia with the muscle temperature maintained at its normal value of 32 degrees C. Ischemia was induced by tightening a tourniquet placed around the limb above the EDL muscle. Measurements were made after 30, 60, and 90 min of reperfusion. To test the usefulness of this skeletal muscle model for evaluating proposed interventions in I-R, the effect of hypothermia (24 degrees C) on the microcirculation following 4 hr ischemia (n = 3) was measured. Edema formation was estimated from the wet/dry weight ratio of the ischemic and contralateral control EDL muscles. Capillary perfusion at the surface of the control muscles was remarkably stable over the 5 hr period studied, while significant changes occurred following the ischemic periods. Significantly lower CDper was measured 30 min following all periods of normothermic ischemia. However, unlike the 2 and 4 hr ischemic periods 3 hr normothermic ischemia resulted in a progressive decline in CDper throughout the reperfusion period. VRBC showed evidence of a hyperemic response following 2 hr normothermic ischemia (control: 0.12 mm/s +/- 0.19 compared to 0.26 mm/s +/- 0.03 following 90 min reperfusion; mean +/- sem). However, no such hyperemia was measured following either 3 or 4 hr normothermic ischemia (i.e., 3 hr control: 0.24 mm/s +/- 0.01 compared to 0.07 mm s +/- 0.003 following 90 min reperfusion). In fact, VRBC was essentially zero 90 min following 4 hr normothermic ischemia (0.01 mm/s +/- 0.01). However, when the muscle was allowed to cool to 24 degrees C during 4 hr ischemia no significant change in either VRBC or CDper was measured compared to pre-ischemic controls. Evidence of edema was found after 3 and 4 hr normothermic ischemia. This study establishes a skeletal muscle model of I-R, which may be useful in testing hypotheses regarding mechanisms of I-R injury, and effectiveness of proposed treatments of I-R.

Animals↗
PubMed1992

Early steps in hematogenous metastasis of B16F1 melanoma cells in chick embryos studied by high-resolution intravital videomicroscopy.

BACKGROUND: There are few techniques that permit direct observation of tumor metastasis. The ability to observe steps in this process as they occur in experimental animals would complement studies on molecular mechanisms. PURPOSE: We have developed a novel procedure using high-resolution intravital videomicroscopy to permit direct observation of cells as they arrest in the microcirculation, extravasate, and form micrometastases. We used this procedure to study early steps in experimental metastasis in immune-deficient chick embryos, permitting us to develop this technique in a relatively accessible respiratory organ and in the absence of host immune responses. Our goals were to develop techniques applicable to this host and to other hosts and to clarify the process of hematogenous tumor spread in this host. METHODS: We injected fluorescently labeled B16F1 melanoma cells into the circulation of 11- to 13-day chick embryos, and using intravital videomicroscopy, we observed the cells in the chorioallantoic membrane over time. RESULTS: The majority of injected cells were trapped initially in orifices to the chorioallantoic membrane capillary plexus or in tapering ends of arterioles leading to the plexus. During the first 2 hours, cells were found only in vessel lumina. After 8 hours, 83% of cells had extravasated, and the rest were in the process of extravasation. Cell shape changes and pseudopodial extensions were seen during extravasation and tumor development. Tumor cell division was seen only after extravasation. Tumors tended to develop near microvessels and were often wrapped around them. CONCLUSIONS: Intravital videomicroscopy can provide new information about steps in metastasis. This procedure is applicable to other hosts and can be used in future studies to test hypotheses about molecular mechanisms of tumor spread.

Animals↗
PubMed1992

Intravital videomicroscopy of the chorioallantoic microcirculation: a model system for studying metastasis.

The chick embryo is a useful model for studying hematogenous metastasis. Cancer cells injected into veins of the chorioallantoic membrane (CAM) circulate briefly through all tissues but form metastases predominantly in the CAM. This respiratory organ is particularly suitable for intravital microscope because of its accessibility without the need for surgery and the density and planar configuration of its vessels (which we confirmed by microcorrosion casting). Using an inverted microscope with oblique transillumination for high-resolution images and epifluorescence to identify labeled B16F1 melanoma cells, we studied successive stages of metastasis formation in the CAM in vivo. By 2 min postinjection (pi) all cancer cells had become arrested within the microvasculature. This initial arrest appeared to be due to size restriction, based on measurements of cell and vessel diameters. At 15-60 min pi, trapped cells were seen in tapering arterioles (27%), orifices from arterioles to the capillary plexus (61%), or in the plexus itself (12%). Some cells had extravasated into the underlying mesenchyme by 3 hr (pi), and at 24 hr all cancer cells had completed this process. The mean rate of migration out of capillary lumens was approximately 1 micron/hr. Micrometastases grew in a planar configuration just beneath the capillary plexus, with a cell doubling time of approximately 24 hr. Our technique is also applicable to other tumor types and host animals and provides a powerful tool to complement studies on the molecular basis of metastasis.

Allantois↗
PubMed1992

Evidence for Kupffer cell migration along liver sinusoids, from high-resolution in vivo microscopy.

Kupffer cells are generally considered fixed tissue macrophages of the liver. However, we have evidence that this opinion is incorrect. High-resolution in vivo video microscopy shows that Kupffer cells have the ability to migrate along sinusoidal walls. Images recorded from anesthetized mice show active locomotion of cells with or against the direction of blood flow or in the absence of flow. The size, changing morphology, and uptake of carbon or microspheres strongly suggest that these are Kupffer cells. Quantitative measurements were made on 29 migrating Kupffer cells. The mean speed of migration was 4.6 +/- 2.6 (SD) microns/min and was not significantly different whether migration occurred with or against the flow. When fluorescent microspheres were given in vivo as a phagocytic challenge, Kupffer cells containing few microspheres migrated more slowly (0.9 +/- 0.9 microns/min, n = 10), whereas those containing many microspheres were never seen to migrate. Individual Kupffer cells were able to move independently, i.e., in directions different from those of neighboring Kupffer cells. These findings may have major implications for the role of Kupffer cells in scavenging foreign particles and as antigen-presenting cells.

Animals↗
PubMed1991

Changes in splenic microcirculatory pathways in chronic idiopathic thrombocytopenic purpura.

The spleen plays a central role in the pathogenesis of chronic idiopathic thrombocytopenic purpura (ITP); it produces massive quantities of antiplatelet antibodies, leading to accelerated phagocytosis of platelets. Lymphoid hyperplasia typically occurs in the spleen, characterized by large numbers of lymphatic nodules with active germinal centers. Whether changes in splenic microcirculatory pathways also occur is not known. We have studied this question by scanning electron microscopy of corrosion casts, comparing spleens removed from patients with ITP with normal spleens obtained from organ transplant donors. The casts demonstrate two major changes in microcirculatory pathways in ITP. Firstly, a striking proliferation of arterioles and capillaries is found in the white pulp and marginal zone (MZ), seen as extensive vascularization in 92.3% of lymphatic nodules (n = 191) versus 0.6% (n = 224) in normal spleens. Secondly, the marginal sinus, a series of flattened, anastomosing vascular spaces between the white pulp and MZ, is absent in 89.4% of lymphatic nodules versus 4.9% in normal spleens. The cause of these microcirculatory changes, which may not be exclusive to ITP, is presently unknown. Absence of the marginal sinus may affect distribution of blood flow through the MZ such that platelets spend increased amounts of time in the proximity of macrophages. In the presence of antiplatelet antibodies found in ITP spleens, this delayed transit would lead to greatly increased platelet destruction.

Adult↗
PubMed1991

The high splenic hematocrit: a rheological consequence of red cell flow through the reticular meshwork.

The spleen concentrates blood to twice arterial hematocrit, but how it does so is poorly understood. We hypothesize that hemoconcentration results from percolation of blood through the reticular meshwork (RM) between capillary endings and venous channels. The RM has a large flow cross section, producing low shear rates, and an enormous surface area for red blood cell (RBC) adhesion. If these conditions cause slowing of RBCs with respect to plasma, increased hematocrits will occur (inverse Fahraeus effect). Movements of individual RBCs through the RM were studied from intravital microscopic videorecordings of Ringer-perfused mouse spleens. Analysis of three 70-microns paths showed characteristic "stop and go" motion, RBCs spending 0.015 to 9.71 see in any 7-microns segment, despite steady (+/- 15%) perfusate velocity. At some locations RBCs adhered to reticular cells/fibers by point attachment and at others they became caught over fibers. In general, RBCs were detained in the RM by surface interactions rather than by narrow channel. Perfusate ("plasma") velocity was estimated to be at least that of the fastest RBCs in each segment. Ratios of overall mean RBC and plasma velocities for three paths were 0.19, 0.20, and 0.37. Applying these velocity ratios to a feed hematocrit of 40% leads to predicted splenic hematocrits up to 78%. We conclude that this slowing of RBCs within the reticular meshwork provides the primary mechanism for generating the high intrasplenic hematocrit.

Animals↗
PubMed1991

Muscle capillary-to-fiber perimeter ratio: morphometry.

It is known that a substantial amount of capillary tortuosity is found in shortened muscles. However, the increased capillary length and surface area contributed by tortuosity and branching are seldom taken into account when capillarity is estimated and/or blood-tissue exchange is modeled in muscles. In this paper, we sought morphometric estimates of capillarity in transverse sections that incorporated data on capillary geometry. We derived equations to estimate capillary perimeter per fiber perimeter (i.e., capillary-to-fiber perimeter ratio) in transverse sections. We show how capillary-to-fiber perimeter ratio is related to capillary surface per fiber surface, i.e., to the amount of capillary surface available for exchange per muscle fiber surface area, and how it can be obtained by morphometry. Because capillary tortuosity and fiber perimeter are both a function of sarcomere length, the degree of extension or shortening of muscle samples obviously needs to be taken into account when capillary-to-fiber perimeter ratio is compared between muscles and/or samples. Using data currently available on capillary length and diameter with fiber shortening and extension, we show that it is a feature of capillary-to-fiber perimeter ratio to change relatively little with sarcomere length. As sarcomere length decreases from 2.80 to 1.58 microns in perfusion-fixed hindlimb muscles of rats, capillary and fiber perimeters in transverse sections increase substantially, whereas the ratio between the two variables, capillary-to-fiber perimeter ratio, changes only less than or equal to 10-15%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Microcirculatory pathways and blood flow in spleen: new insights from washout kinetics, corrosion casts, and quantitative intravital videomicroscopy.

The dynamics of splenic microcirculatory blood flow and the role of the spleen with respect to red blood cells (RBCs) have been elucidated by means of several different experimental approaches. First, the organ was treated as a 'black box' and input/output relationships were studied, such as the kinetics of RBC and plasma washout during Ringer perfusion. Second, microcorrosion casts were prepared from minimal amounts of injected material, such that 'fast' pathways for flow were selectively identified. Third, high-resolution video-microscopy was carried out in rat and mouse spleens transilluminated in vivo, with subsequent quantitative analysis of the data. New insights were obtained regarding fast and slow pathways for RBC flow; the origin of the high intrasplenic hematocrit; immature RBCs and the spleen; the pH, O2 tension and glucose concentration within the reticular meshwork; microcirculatory pathways bordering the white pulp; entry of blood into venous sinuses, both by open ends in the marginal sinus/zone and via interendothelial slits in sinus walls; spontaneous cyclic contractions of capillary walls in vivo, impeding RBC flow (i.e. endothelial contractility); and leukocyte interactions with walls of venous vessels. The different experimental approaches have provided complementary information and have clarified a number of important issues about which uncertainty existed in the literature. Exploiting the quantitative analysis of high-resolution intravital videomicroscopic recordings has an exciting potential for gaining new insights into the workings of this complex and neglected organ.

Animals↗
PubMed1990

Effect of sarcomere length on total capillary length in skeletal muscle: in vivo evidence for longitudinal stretching of capillaries.

It is generally assumed that when a muscle is shortened or extended the total length of capillaries does not change, implying that capillaries are nondistensible, longitudinally. On the basis of stereological estimates of capillary anisotropy versus sarcomere length, we propose that as long as capillaries are in a tortuous configuration muscle extension will merely decrease the tortuosity, leaving vessel length unaltered. Once capillaries have been pulled into a straight configuration, further extension of the muscle will cause the vessels to stretch. By means of intravital videomicroscopy we have demonstrated that stretching of individual capillaries does indeed occur over a sarcomere length range of 2.1 to 2.9 microns in rat extensor digitorum longus muscle. In vivo measurements of the lengths of six capillaries together with the sarcomere lengths of adjacent fibers were made in muscles positioned at various degrees of extension. Normalized data indicated that four capillaries stretched to the same degree as the muscle, one stretched more and another less. This may reflect differences in distensibility or tortuosity of capillaries in series with one another. The elastic stretching of capillaries during muscle activity may have important consequences in terms of shifts in permeability and increases in capillary surface area.

Animals↗
PubMed1990

Interactions of leukocytes with vessel walls and with other blood cells, studied by high-resolution intravital videomicroscopy of spleen.

Visualization of circulating leukocytes in vivo is difficult because their optical density differs so little from that of plasma. We have obtained intravital microscopic images of leukocytes at high resolution in spleens of rats and mice by means of an inverted microscope with a 100 x oil-immersion lens; oblique lighting gave improved contrast. Photographic evidence and quantitative data describing the behaviour of lymphocytes, polymorphonuclear leukocytes (PMNs), and macrophages within the microvasculature are presented. Mean numbers of marginated lymphocytes in venous vessels ranged from 0.1 to 4.5 per 1000 microns 2 of wall surface, and speeds of rolling from 11 to 20 microns/sec. Adherence times of leukocytes to vessel walls were log normally distributed, median values being 30, 130, and 560 sec, for lymphocytes, PMNs, and macrophages, respectively. Mean speeds of migration along luminal surfaces were similar (7-19 microns/min) for all three types of cells. Lymphocyte migration outward through the venular wall, observed on two occasions, took 1-2 min. Median values for duration of adherence of RBCs and lymphocytes to macrophages were 1 and 42 sec, respectively. Phagocytosis of a lymphocyte was observed and took 3 min. Macrophages often underwent dramatic changes in shape, including formation of a pseudopod up to 155 microns in length. High-resolution intravital videomicroscopy of spleen has great potential for studying leukocyte behaviour, e.g., homing and migration of lymphocytes, and immunologically related macrophage-lymphocyte interactions in vivo.

Animals↗