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PubMed2005

Transforming growth factor-beta3 increases gap-junctional communication among folliculostellate cells to release basic fibroblast growth factor.

Folliculostellate (FS) cells are known to communicate with each other and with endocrine cells via gap junctions in the anterior pituitary. We investigated whether TGFbeta3 and estradiol, known to regulate FS cell production and secretion of basic fibroblast growth factor (bFGF), increases gap junctional communication to alter bFGF secretion from FS cells. FS cells in monolayer cultures were treated with TGFbeta3 or vehicle alone for 24 h and then microinjected with Lucifer Yellow and high-molecular-weight Texas Red dextran. Ten minutes later the transfer of dye among adjacent cells was recorded with a digital microscope. TGFbeta3 increased the transfer of dye. The TGFbeta3-neutralizing antibody and the gap junction inhibitor octanol reduced the effect of TGFbeta3 on the transfer of dye. The TGFbeta3-induced transfer of dye was unaltered by simultaneous treatment with estradiol. The steroid alone also had no effect. TGFbeta3 increased total and phosphorylated levels of connexin 43. Estradiol treatment did not produce any significant changes on basal or TGFbeta3-induced increases in connexin 43 levels. The gap-junction inhibitor octanol reduced TGFbeta3-increased levels of bFGF in FS cells. Taken together, these results suggest that TGFbeta3 may act on FS cells to increase gap-junctional communication to maximize its effect on bFGF secretion.

Animals↗
PubMed1996

Tendon cells in vivo form a three dimensional network of cell processes linked by gap junctions.

Tendons respond to mechanical load by modifying their extracellular matrix. The cells therefore sense mechanical load and coordinate an appropriate response to it. We show that tendon cells have the potential to communicate with one another via cell processes and gap junctions and thus could use direct cell/cell communication to detect and/or coordinate their load responses. Unfixed cryosections of adult rat digital flexor tendons were stained with the fluorescent membrane dye DiI to demonstrate cell shape. Similar sections were immunolabelled with monoclonal antibodies to rat connexin 32 or connexin 43 to demonstrate gap junctions and counterstained with propidium iodide to show nuclei, or the membrane stain DiOC7 to show cell membranes. Sections were examined with a laser scanning confocal microscope and 3-dimensional reconstructions were prepared from optical section series to demonstrate cell shape and the position of connexin immunolabel. Cells had a complex interconnected morphology with gap junctions at points of contact with other cells. Cell bodies contained the nucleus and extended broad flat lateral cell processes that enclosed collagen bundles and interacted with similar processes from adjacent cells. They also had long thin longitudinal processes interacting with the cell process network further along the tendon. Connexin 43 occurred where cell processes met and between cell bodies, whereas connexin 32 was only found between cell bodies. The results indicate the presence of a 3-dimensional communicating network of cell processes within tendons. The intimate relationship between cell processes and collagen fibril bundles suggests that the cell process network could be involved in load sensing and coordination of response to load. The presence of 2 different types of connexins suggests that there could be at least 2 distinct communicating networks.

Animals↗
PubMed2004

Bifurcation geometry and the presence of cerebral artery aneurysms.

OBJECT: The angles of arterial bifurcations are governed by principles of work minimization (optimality principle). This determines the relationship between the angle of a bifurcation and the radii of the vessels. Nevertheless, the model is predicated on an absence of significant communication between these branches. The circle of Willis changes this relationship because the vessels proximal to the ring of vessels have additional factors that determine work minimization compared with more distal branches. This must have an impact on understanding of the relationship between shear stress and aneurysm formation. The authors hypothesized that normal bifurcations of cerebral arteries beyond the circle of Willis would follow optimality principles of minimum work and that the presence of aneurysms would be associated with deviations from optimum bifurcation geometry. Nevertheless, the vessels participating in (or immediately proximal to) the circle of Willis may not follow the geometric model as it is generally applied and this must also be investigated. METHODS: One hundred seven bifurcations of the middle cerebral artery (MCA), distal internal carotid artery (ICA), and basilar artery (BA) were studied in 55 patients. The authors analyzed three-dimensional reconstructions of digital subtraction angiography images with respect to vessel radii and bifurcation angles. The junction exponent (that is, a calculated measure of the division of flow at the bifurcation) and the difference between the predicted optimal and observed branch angles were used as measures of deviation from the geometry thought best to minimize work. The mean junction exponent for MCA bifurcations was 2.9 +/- 1.2 (mean +/- standard deviation [SD]), which is close to the theoretical optimum of 3, but it was significantly smaller (p < 0.001; 1.7 +/- 0.8, mean +/- SD) for distal ICA bifurcations. In a multilevel multivariate logistic regression analysis, only the observed branch angles were significant independent predictors for the presence of an aneurysm. The odds ratio (OR) (95% confidence interval) for the presence of an aneurysm was 3.46 (1.02-11.74) between the lowest and highest tertile of the observed angle between the parent vessel and the largest branch. The corresponding OR for the smallest branch was 48.06 (9.7-238.2). CONCLUSIONS: The bifurcation beyond the circle of Willis (that is, the MCA) closely approximated optimality principles, whereas the bifurcations within the circle of Willis (that is, the distal ICA and BA) did not. This indicates that the confluence of hemodynamic forces plays an important role in the distribution of work at bifurcations within the circle of Willis. In addition, the observed branch angles were predictors for the presence of aneurysms.

Angiography, Digital Subtraction↗
PubMed1975

Nonparoxysmal junctional tachycardia in acute myocardial infarction: computer-assisted detection.

Thirty consecutive patients with acture myocardial infarction had continuous magnetic tape recording of their stay in the coronary care unit. Analysis of the 24 hour tape recordings was implemented on a Honeywell model 316 digital computer. In the first 24 hours after admission to the coronary care unit, 12 of the 30 patients (40 percent) exhibited nonparoxysmal junctional tachycardia; in 5 the arrhythmia was not recognized by conventional monitoring techniques. For the subsequent 3 days, the incidence rate of the arrhythmia was 13 percent for the first 48 hours and 3 percent for 72 hours. Although the mortality rate in patients with nonparoxysmal junctional tachycardia was greater than in patients not demonstrating the arrhythmia (33 versus 6 percent), there was a greater percentage of patients with anterior infarction in the former group; therefore, mortality may have been related to site of infarction rather than being reflective of the arrhythmia or its associated pathophysiologic state. Of possible significance is the association of a greater degree of sinus arrhythmia with nonparoxysmal junctional tachycardia. The incidence of nonparoxysmal junctional tachycardia in this group of patients was greater than previously reported. It is possible that computer tape analysis may have provided more accurate recognition of the arrhythmia and, thus, more realistic incidence data. The association of nonparoxysmal junctional tachycardia with sinus arrhythmia could only have been recognized by computer technique. The computer system is not a diagnostic system but rather a tape review method.

Analog-Digital Conversion↗
PubMed2002

Abutment region dosimetry for the monoisocentric three-beam split field technique in the head and neck region using asymmetrical collimators.

Creating non-divergent field edges using asymmetric collimators and a single isocentre can improve matchline dosimetry owing to decreased reliance on operator skills and avoidance of couch movement. However, asymmetic jaws have an associated tolerance that can cause abutment to be misaligned. The matching area dose for monoisocentric three-beam split fields commonly used in head and neck cancer treatments using mismatched and matched collimators is the subject of this work. X-ray verification film was exposed in a solid-water phantom, and the dose at the matching area was evaluated using mismatched and matched collimators. In the case of mismatched (consistently overlapped) collimators, digital displays of an asymmetric collimator position within the tolerance indicated in the manufacturer's specifications were investigated for the three-beam split field technique. The effect of this technique on the junctional dose was also determined using matched collimators. Although the collimators showed a consistent overlap, a perfect dose distribution could be obtained at the matching area. The three-beam split field technique yielded an 8% overdose at the matchline using matched collimators. In conclusion, an awareness of the effects of the abutting technique and digital display tolerance is necessary to achieve good junction uniformity using asymmetric collimators.

Film Dosimetry↗
PubMed2003

Occlusion of the posterior communicating artery mimicking cerebral aneurysm: case report.

We report a rare case of posterior communicating artery occlusion mimicking a cerebral aneurysm. A 62-year-old man was admitted to Towakai Hospital with sudden onset of left motor weakness. He had developed thunderclap headache five days before. Computed tomographic scan and lumbar tap were negative for subarachnoid hemorrhage (SAH). Digital subtraction angiography and three-dimensional computed angiography showed aneurysmal protrusion at the junction of the right internal carotid (IC) artery and posterior communicating artery (PcomA). Because minor bleeding from IC-PcomA junction aneurysm was strongly suspected, a pterional craniotomy was performed. At surgery, there was no evidence of SAH but the PcomA was occluded at the peripheral portion. Several perforators arose from the proximal portion of the PcomA. An aneurysmal protrusion especially without a prominent PcomA does not always indicate an IC-PcomA aneurysm. In diagnosing protruding vascular lesions at the bifurcation between the IC-PcomA, not only infundibular dilatation but also occlusion of the PcomA should be considered if the PcomA is not visualized.

Angiography, Digital Subtraction↗
PubMed1989

[The evaluation of the marginal bone height on traditional and digitized panoramic radiographs].

The aim of the present study was to compare original and digitized panoramic radiographs (with a 512 X 512 digitization matrix) for the assessment of alveolar bone loss using intraoral radiographs as a reference. Intraoral radiographs of 2+, +5, and 6- and an orthopantomogram were obtained from each of 55 patients. Alveolar bone level was measured on the intraoral, the original panoramic, and the digitized panoramic radiographs using a Schei ruler as percentage of bone left from the cemento-enamel junction to the apex. Mean values between the separate observations of the two authors were used. A statistically significant reduction in bone level was observed when assessed by the panoramic methods compared to the intraoral radiographs (P less than 0.01 for all tooth groups). Similarly a significant reduction was observed in the digitized panoramic radiographs compared to the originals (P less than 0.05) except for the molar region. The results indicate that the 512 X 512 spatial resolution is not sufficient for the digitization of extraoral radiographs when fine-detail diagnostics are needed. It is suggested that extraoral radiographs are digitized in segments when working with this matrix.

Alveolar Process↗
PubMed1996

Seasonal prevalence of digital epiluminescence microscopy patterns in acquired melanocytic nevi.

BACKGROUND: Available information of the effect of sun exposure on the biologic activity and morphologic characteristics of nevi is based on a few cross-sectional studies. According to these, nevi excised in summer show a higher mitotic count, a greater extent of the junctional component, and more frequent regression and inflammation. OBJECTIVE: Our goals were to obtain data on the seasonal prevalence of digital epiluminescence microscopy (D-ELM) patterns in acquired melanocytic nevi (AMN) and to test the reliability of D-ELM as a substitute for histology in prospective studies of the morphologic response of AMN to sun exposure. METHODS: Two independent series of AMN located on intermittently sun-exposed body sites and undergoing D-ELM in winter (n=121) and in summer (n=116) were compared for the prevalence of major ELM patterns. RESULTS: Cases in the summer series showed a greater frequency of a broad and prominent pigment network; black dots with varied size, irregular distribution, and peripheral location; and peripheral depigmentation. CONCLUSION: On the basis of known histologic correlates of D-ELM features, our findings were consistent with studies of seasonal histologic changes in AMN. D-ELM may be a useful tool in the prospective evaluation of effects of sun exposure on AMN morphology.

Adolescent↗
PubMed1995

Median/ulnar premotor potential identification and localization.

A small negative waveform is known to precede the median and ulnar compound muscle action potentials when recorded with surface or concentric needle electrodes. This investigation documents that there are two distinct waveforms preceding the median compound muscle action potential (CMAP) depending upon the type of recording electrodes used (concentric needle versus surface) and their respective locations. The negative waveform originally described with a concentric needle electrode positioned within the substance of the distal thenar eminence and having a restricted zone of detection is referred to as the intramuscular nerve action potential (INAP). This potential is shown to be distinct from the premotor potential (the small negative waveform preceding surface recorded ulnar and median CMAPs). Detection of the median and ulnar premotor potentials at multiple locations about the hand with the same respective onset/peak latencies and amplitudes substantiates that this potential is a far-field potential. The median and ulnar premotor potentials most likely originate from a dipolar moment imbalance generated by digital sensory nerve action potentials as they cross the first and fifth metacarpophalangeal junctions, respectively. Applying far-field principles permits the documentation of additional far-field potentials as they are generated at the second through fourth metacarpophalangeal junctions following median nerve stimulation. Also, because the premotor potential is a far-field potential, caution must be exercised with respect to its diagnostic utility as joint position and other unknown factors may affect amplitude and onset/peak latency. The INAP following median nerve excitation, however, is documented to be a near-field potential distinct from the premotor potential arising from the recurrent branch of the median nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1998

The lumbrical muscle flap: anatomic study and clinical application.

This article describes the anatomy and clinical application of the lumbrical muscle flap. Anatomic and radiologic studies were performed in 20 fresh human cadaver hands injected with latex-lead-oxide solution. Only the 2 radial lumbrical muscles were found suitable for flap transposition. The vascular supply of the first and second lumbrical muscles is from branches originating in the superficial palmar arch and from the common palmar digital artery, respectively. The dominant branches invariably enter the muscle bellies at the junction of their proximal and middle thirds. Pedicled on these vessels, the lumbrical muscles can be transposed to reach the entire palm, up to the wrist flexion crease. The clinical use of the first and second lumbrical muscle flaps in 2 patients demonstrated the value of these flaps for coverage of the median nerve and its palmar branches.

Cadaver↗
PubMed1997

Advanced cement technique improves fixation in elbow arthroplasty.

An in vitro study was conducted to assess the efficacy of advanced cementing techniques in the fixation of the humeral stem in elbow arthroplasty. Sixteen fresh frozen cadaveric distal humeri were prepared to accept an acrylic sham humeral stem. Conventional cementing technique using doughy cement manually inserted and packed was performed in 8 specimens. The advanced cementing technique, consisting of canal irrigation, brushing and drying with gauze, canal plugging, and low viscosity cement pressurization with a delivery system was performed in the other specimens. All humeri subsequently were sectioned into 10 mm thick sections, photographed, and digitized to quantify the perimeter and area of the stem, cement mantle, corticocancellous junction, and cement voids. The degree of cement filling, determined from the area fraction of cement to the total available area within the corticocancellous junction, was significantly greater in the advanced group compared with the conventional group. Mechanical assessment of the specimens consisted of a push out load to failure test of the cement mantle from bone. For all locations in the distal humerus, the failure load and failure stress in the advanced group was significantly greater than the conventional group. It is concluded that development of an effective cement restrictor and application of advanced cement techniques in vivo should improve the initial fixation of the humeral component and may decrease the incidence of aseptic loosening associated with elbow arthroplasty.

Biomechanical Phenomena↗
PubMed2003

[Digital cineradiography of the pharynx and the oesophagus after total or partial laryngectomy].

PURPOSE: The aim of the present study is to report our experience using digital cineradiography to assess morphological and functional disorders of the pharynx in patients with prior partial or total laryngectomy. MATERIALS AND METHODS: From March 2000 to October 2002, 21 patients (18 males and 3 females) with prior total laryngectomy (12 patients), total laryngopharyngectomy (2 patients) and partial laryngectomy (7 patients) were examined. A digital cineradiography with 12 frames/second acquisition was performed in all patients. In four patients the procedure was interrupted for massive barium aspiration, without cough (silent aspiration). In 17 patients standing in the left posterior oblique position and prone in the right posterior oblique position the oesophagus and oesophagogastric junction were also examined. The water siphon test was performed at the end of the procedure. Small boluses (10 ml) of liquid (60% w/v) and high-density (250% w/v) barium, barium paste (110% w/v), and solid meal (obtained spreading a dry biscuit with barium paste) were used. RESULTS: All patients with prior total laryngectomy and total laryngopharyngectomy showed morphological and functional disorders of the neopharynx: parapharyngeal diverticulum (2 cases), submandibular pouch (6 cases), fistulas (2 cases), lumen narrowing and post-surgical stenoses (2 cases), tumour recurrence (1 case), prominent cricopharynx (5 cases) and rhinopharyngeal reflux (4 cases). All patients with prior partial laryngectomy (7 cases) presented silent aspiration. Eleven patients had an oesophageal motility disorder, which was very serious in three of them with decrease in oesophageal clearing and barium retention in the oesophagus. Oesophagogastric junction evaluation showed hiatus hernia in six cases, two of them with associated gastro-oesophageal reflux. CONCLUSIONS: Digital cineradiography appears able to identify the organic and functional postoperative complications of patient treated with partial or total laryngectomy. A special swallowing study can suggest to the speech therapist the best compensatory mechanism for improving patient swallowing and therefore quality of life.

Adult↗
PubMed2004

Modeling and characterization of the CEJ for optimization of esthetic implant design.

This study evaluated the dimensions and characteristics of the cementoenamel junction (CEJ) of maxillary anterior teeth; the natural CEJ was compared to current implant design and used for design optimization. Standardized digital images of 137 extracted human teeth (45 central incisors, 46 lateral incisors, and 46 canines) were used to measure cervical dimensions, CEJ curvature, and distance from zenith of CEJ to interdental contact on proximal views. The x- and y-coordinates of the CEJ contour were digitized before mathematic processing to allow the representation of a single average curve for buccal, palatal, mesial, and distal surfaces for each tooth type. These measurements were combined to existing data related to dentogingival and "implantomucosal" junction to extrapolate specific biologic landmarks around teeth and implants. Mean cervical dimensions, distance from zenith of CEJ to interdental contact, and CEJ curvature were compared. Cervical dimensions significantly differed, with a more symmetric cervical cross-section for central incisors, slightly more rectangular shape for lateral incisors, and distinctly rectangular shape for canines. CEJ curvature was statistically different between all tooth groups (centrals > laterals > canines); within groups, curvature value was always superior at the mesial aspect compared to distally (3.46 mm vs 3.13 mm for centrals, 2.97 mm vs 2.38 mm for laterals, and 2.55 mm vs 1.60 mm for canines). Tooth-implant biologic width discrepancies ranged from 4.10 to 5.96 mm and were different between all groups of teeth (centrals > laterals > canines); within groups, the discrepancy was always superior at the mesial aspect compared to distally. Current implant design featuring a flat, rotation-symmetric shoulder should be reconsidered in view of natural CEJ contour to improve biologic considerations and related esthetics.

Analysis of Variance↗
PubMed1998

Mechanism of mechanically induced intercellular calcium waves in rabbit articular chondrocytes and in HIG-82 synovial cells.

Intercellular communication through gap junctions allows tissue coordination of cell metabolism and sensitivity to extracellular stimuli. Intercellular Ca2+ signaling was investigated with digital fluorescence video imaging in primary cultures of articular chondrocytes and in HIG-82 synovial cells. In both cell types, mechanical stimulation of a single cell induced a wave of increased Ca2+ that was communicated to surrounding cells. Intercellular Ca2+ spreading was inhibited by 18alpha-glycyrrhetinic acid, demonstrating the involvement of gap junctions in signal propagation. In the absence of extracellular Ca2+, mechanical stimulation induced communicated Ca2+ waves similar to controls; however, the number of HIG-82 cells recruited decreased significantly. Mechanical stress induced Ca2+ influx both in the stimulated chondrocyte and HIG-82 cell, but not in the adjacent cells, as assessed by the Mn2+ quenching technique. Treatment of cells with thapsigargin and with the phospholipase C (PLC) inhibitor U73122 blocked mechanically induced signal propagation. These results provide evidence that in chondrocytes and in HIG-82 synovial cells, mechanical stimulation activates PLC, thus leading to an increase of intracellular inositol 1,4,5-trisphosphate. The second messenger, by permeating gap junctions, stimulates intracellular Ca2+ release in neighboring cells. It is concluded that intercellular Ca2+ waves may provide a mechanism to coordinate tissue responses in joint physiology.

Animals↗
PubMed2002

Behavior of junction channels between rat glomus cells during normoxia and hypoxia.

The activity of gap junction channels between cultured and clustered carotid body glomus cells of the rat was studied with dual voltage clamping during normoxia (PO(2) 300 Torr) and hypoxia induced by sodium dithionite (Na(2)S(2)O(4)) or 100% N(2). Na(2)S(2)O(4) reduced the saline PO(2) to approximately 10 Torr, whereas 100% N(2) reduced ambient O(2) to approximately 60 Torr. The following observations were made. 1) In normoxia, the intercellular macroconductance (G(j) = 3.0 +/- 1.01 ns, mean +/- SE) was changed unevenly (increased and decreased) under hypoxic conditions by either agent, although N(2) produced the largest changes. 2) The intercellular microconductances of the channels (g(j) = 104.44 +/- 10.16 pS under normoxic conditions) significantly decreased in 100% N(2) but showed depressions and enhancements in Na(2)S(2)O(4). 3) The conductance of single-junction channels (SChs), calculated as g(j) variance/mean g(j), yielded a mean of approximately 17.6 pS. Larger values were obtained with manual measurements of the data (approximately 34 pS). Hypoxic hypoxia (induced by 100% N(2)) significantly depressed the conductance of SChs when calculated from digitized records or from manual measurements. Hypoxia induced by Na(2)S(2)O(4) did not significantly change junctional conductance. 4) The number of intercellular channels, calculated as g(j)/SCh g(j), had a mean of approximately 452 (range 1 to 2,471). During N(2)-induced hypoxia, this number significantly decreased to approximately 84 but remained unchanged during Na(2)S(2)O(4) hypoxia. 5) The mean open time of junction channels varied from 4 to 30 ms in different experiments, having an overall mean of mu = 11.33 +/- 0.33 ms. This value was significantly reduced by 100% N(2) but was not changed by Na(2)S(2)O(4). 6) Intracellular calcium ([Ca(2+)](i)), 46.2 +/- 4.84 nM under normoxia, significantly increased to 77.32 +/- 11.27 nM with Na(2)S(2)O(4) and to 66.39 +/- 11.64 nM with 100% N(2). It is concluded that 100% N(2) uncouples glomus cells by significantly reducing intercellular macro- and microconductances. Hypoxia induced by Na(2)S(2)O(4) had variable effects. The coupling effects of hypoxia may depend on, or be aided by, increases in [Ca(2+)](i) and/or intracellular pH changes. However, secreted transmitters and ATP plus the effects of hypoxia on second messengers and other cytoplasmic components may also play an important role in this phenomenon.

Animals↗
PubMed1993

Validation of immunohistochemical quantification in confocal scanning laser microscopy: a comparative assessment of gap junction size with confocal and ultrastructural techniques.

Confocal scanning laser microscopy (CSLM) is increasingly being used to image antibody-labeled structures visualized with a fluorescent secondary antibody. Such digital images are routinely stored on computer and are well suited to quantitative analysis. Although theoretical aspects of CSLM imaging and resolution are well defined, information is lacking on the relationship observed between measurements of fluorescent antibody-labeled structures and the size of the same structures as determined by electron microscopy (EM). In the present study we examined this relationship for the cardiac gap junction. Data on the size of immunofluorescent-labeled gap junctions were acquired by two methods of analysis from CSLM images and compared statistically with measurements of gap junction size obtained by freeze-fracture EM. The freeze-fracture data were compared before and after exclusion of small junctions, corresponding to those that theoretically would not have been detected in CSLM analysis. The data obtained by the different methods were similar but not identical, reflecting the advantages and limitations of each technique. However, the comparison did indicate that with appropriate sample preparation and orientation, accurate and rapid analysis can be achieved by CSLM, particularly when digital semi-automated techniques are employed.

Animals↗
PubMed1994

Elastic deformation in tendons and myotendinous tissue: measurement by phase-contrast MR imaging.

PURPOSE: To determine whether phase-contrast magnetic resonance (MR) imaging can be used to measure stretch in the myotendinous junction and tendon. MATERIALS AND METHODS: Velocity-encoded cine MR images obtained during cyclic motion were used to measure strain in myotendinous tissue and indirectly in tendons in gastrocnemius muscle-tendon sutured to a motion phantom. Videotapes of the experiments were digitized and used as a standard of reference for validation of MR measurements. Strain, rotation, and translation of the myotendinous junction were calculated from the phase-contrast MR data and indirectly in the tendon. RESULTS: Strain as determined from the MR imaging experiments agreed with the measurements from the video reference, with linear correlation coefficients of .987 for tendon strain and .992 for strain in the myotendinous junction. CONCLUSION: Measurement of tendon and myotendinous stretch during movement may provide insight into tendon ability to store energy and a means of noninvasive measurement of muscle force.

Animals↗
PubMed1994

Interleukin-2 alters the positions of capillary and venule pericytes in rat cremaster muscle.

Interleukin-2 (IL-2) mediates regression of metastatic cancer, but its therapeutic efficacy has been limited by toxicities which occur secondarily to IL-2 induced macromolecular leakage from microvessels. Previous studies have indicated that pericytes function in an endothelial cell junction-dependent manner in lung capillaries and cremaster muscle venules, possibly to limit cellular and macromolecular leakage. The purpose of this investigation was to determine if pericyte positioning on skeletal muscle capillaries was junction-related, and if it was altered by IL-2. Anesthetized rats received intravenous injections of fluoroscein isothiocyanate conjugated to albumin. The cremaster muscle model of microcirculation was used in conjunction with intravital fluorescence microscopy to monitor changes in interstitial fluorescence which was used as an index of macromolecular leakage. IL-2 induced a progressive increase in interstitial albumin which started within 30 min of application and continued to increase until the end of the experiment at two hours. Cremaster muscle tissue was fixed and prepared for examination by transmission electron microscopy. A digitizing platter and morphometric software were used to quantify pericytes near vs away from endothelial cell junctions of capillaries and venules. In microvessels from animals in the control group, pericytes were randomly positioned on capillaries, and concentrated at endothelial cell junctions of venules. After treatment with IL-2, capillary pericytes were concentrated at junctions. Venular pericyte density also increased in endothelial junctional regions. IL-2 appears to alter the distribution of pericytes in the microcirculation, perhaps by induction of contraction.

Animals↗