Specific alterations in the expression of α3β1 and α6β4 integrins in highly invasive and metastatic variants of human prostate carcinoma cells selected by in vitro invasion through reconstituted basement membrane

Highly invasive cell subpopulations from a human prostate carcinoma cell line, PC-3, were selected for by allowing the parental PC-3 cells to invade through reconstituted basement membrane, Matrigel. These cells were collected, cultured and then selected further by repeated invasion through the in vitro invasion chamber. The invasive subpopulations (I-PC3 (2) and (3)) were found to be approximately 15-fold more invasive in vitro than the parental cells, had a distinct rounded morphology in culture, and proliferated more rapidly than the parental cells. When injected either subcutaneously or intraperitoneally into immunocompromised SCID mice, the I-PC3 cells were found to form tumors at the primary sites and to be highly invasive and metastatic. In contrast, the parental PC-3 cells formed tumors at the site of inoculation in these mice but failed to invade or metastasize. The I-PC3 cells attached equally as well as PC-3 cells to fibronectin, laminin, collagen type IV and vitronectin, but unlike the parental PC-3 cells these invasive variants failed to spread on any of these substrates. On Matrigel, the PC-3 cells became highly organized, whereas the I-PC3 cells remained rounded, clumped together and penetrated into the Matrigel. Biochemical analysis of the expression of adhesion proteins and integrins demonstrated that whereas the parental cells synthesized and secreted substantial amounts of fibronectin, the I-PC3 cell variants did not secrete any fibronectin. Although both PC-3 and I-PC3 cells expressed equivalent levels of cell surface v 3, 21 and 51 integrins, the expression of the 31 integrin, which is expressed at very high levels on the parental PC-3 cells, was drastically reduced on the invasive I-PC3 cells. This decrease in expression of 3 occurred also at the level of mRNA expression. Finally, whereas the PC-3 cells express 61, in the invasive I-PC3 cells the a6 subunit was associated mostly with the 4 subunit. Since the 64 integrin is analogous to the A9 tumor antigen which is associated with aggressive human squamous cell carcinomas, the apparent overexpression of 64 may also participate in the aggressive behavior of these variant prostate carcinoma cells. Alterations in the expression of the 31 and 64 integrins may thus allow these cells to become more invasive, and lead to an increased propensity for metastasis.     

Analysis of γδ+ T cells in peripheral blood of children with perinatal human immunodeficiency virus (HIV) infection

The present study examined CD8 antigen expression and variable (V) gene segment usage by T cell receptor (TCR)-⁺ lymphocytes in peripheral blood of symptomatic children with perinatal HIV infection. The relative number of ⁺, CD8⁺ T cells in most of the infected children was higher than that in uninfected children from HIV⁺ or HIV^– mothers and correlated with the immunodeficiency status of the patients. Infected infants and children over 1 year old also showed an increased proportion of V1-J1⁺ T lymphocytes. CD8 expression on those cells was higher in infected than in uninfected infants and children. Sequence analysis of the gene rearrangement of the predominant V1 family in peripheral blood of three HIV⁺ donors revealed extensive junctional diversity. These results suggest that the V skewing in the majority of HIV⁺ children reflects peripheral expansion of V1-J1⁺ T lymphocytes early in life, which might be involved in the mechanisms of HIV-induced immunodeficiency.     

Comparison of four commercial microdilution systems for susceptibility testing of anaerobic bacteria

The reliability of four commercially available broth microdilution systems (ATB ANA, MHK-Anaerob-Biotest, Dynatech MIC system, Sceptor Anaerobe MIC system) for routine susceptibility testing was evaluated using agar dilution and broth macrodilution as reference methods. Using the categories susceptible, moderately susceptible and resistant, the rate of essential agreement (complete agreement plus minor errors) of all four systems compared to the two reference methods was satisfactory, ranging from 93% (Dynatech system and agar dilution) to 98 % (Sceptor system and agar dilution). The rate of complete agreement compared to the agar dilution and broth dilution method respectively was 61 % and 60 % for the MHK-Anaerob-Biotest, 65 % and 63 % for the Dynatech system, 72 % and 72 % for ATB ANA, and 85 % and 80 % for the Sceptor system. The Sceptor system was thus superior to the other systems. The systems were easy to operate and inoculate, although arrangement of antimicrobial agents in the Dynatech panels was apt to be confusing.     

The significance of respiration for thoracic duct flow in relation to other driving forces of lymph flow

Experiments were performed to study the effect of respiratory intrathoracic pressure changes upon thoracic duct lymph propulsion as compared to other forces driving lymph flow in anaesthetized and artificially ventilated dogs. The effect of an open bilateral pneumothorax upon thoracic duct flow and protein composition was determined at rest, with passive limb movement and during saline infusion. The effect of hyperventilation was also tested.Thoracic duct flow was 30 l/min/kg, 45 l/min/kg and 60 l/min/kg at rest, with passive limb movement and saline infusion, respectively. These flows were decreased by opening the pneumothorax by 11 l/min/kg, 12 l/min/kg and 8 l/min/kg, respectively, and returned to the control level after the thorax was closed. The lymph protein concentration and lymph albumin to globulin ratio were not changed significantly. During hyperventilation, lymph flow was increased and showed a retarded decrease after hyperventilation had ceased. Lymph protein composition was not changed significantly by hyperventilation.The data confirm that lymph is propelled in anaesthetized dogs by respiratory intrathoracic pressure changes. The significance of this respiratory pump decreases, when lymph flow is increased by activation of the tissue pump or vis a tergo. Consequently, the respiratory pump may be assumed to play a secondary role in lymph propulsion in the conscious state when the other forces driving lymph flow are more predominant.Presented in part at the 48th meeting of the Deutsche Physiologische Gesellschaft [18]Supported by the Deutsche Forschungsgemeinschaft     

Secretin and VIP-stimulated adenylate cyclase from rat heart

Cardiac adenylate cyclase activity was normal in 3 weeks-old spontaneously hypertensive rats of the Wistar-Okamoto substrain. The hormone-sensitive adenylate cyclase activity was reduced in 10 weeks-old or older animals, and secretin- and VIP-activations were definitely more impaired (by 64% and 69%, respectively) than isoproterenol- and glucagonactivation (17% and 22%, respectively). By contrast, the fluoride- and p[NH]ppG-stimulations of the enzyme were unaffected. These alterations in the adenylate cyclase system coupled to secretin and VIP appeared specific to the heart as the isolated pancreatic acinar cells from spontaneously hypertensive animals responded normally to secretin, as a liver particulate fraction responded normally to secretin and VIP, and both brain synaptic membranes and a particulate fraction of anterior pituitary to VIP.Abbreviations VIP vasoactive intestinal peptide - cyclic AMP cyclic adenosine 35-monophosphate - p[NH]ppG guanosine 5-(, -imido)triphosphate - EGTA ethylene-glycol-bis-(2-amino-ether)-N,N,N,N-tetraacetic acid - IBMX 3-isobutyl-1-methylxanthine     

Identification and quantitation of cortisol metabolites in rat liver homogenate and -slices

Summary Cortisol-1, 2-H³ was incubated with rat liver homogenate and/or rat liver slices in the presence of a NADPH-generating system. The following metabolites could be identified in adult male rats: -cortol, allo--cortol, 3-allo--cortol, 20-hydroxy-cortisol, 11, 17, 20, 21-tetrahydroxy-5-pregnan-3-one, 3-allotetrahydrocortisol, tetrahydrocortisol, trace amounts of allotetrahydrocortisol and two highly polar metabolites only partly identified. In female rats only tetrahydrocortisol, allotetrahydrocortisol and allodihydrocortisol could be detected in significant amounts.The radioactive metabolites mentioned above were localized and quantitated on paper chromatograms by a 4-radiochromatogram scanner. A nearly perfect correlation was found between these results so obtained and those given by liquid-scintillation counting of each metabolite after its elution from the paper.Part of this work was supported by grant n° 695 of the National Fonds voor Wetenschappelijk Geneeskundig Onderzoek.Stagiair of the Nationaal Fonds voor Wetenschappelijk Onderzoek.     

Interferon-β-related DNA on human chromosome 4

A DNA subclone (pPE-4000) derived from the B4 interferon--related human genomic DNA clone was used as a probe in blot-hybridization experiments of DNA from a panel of human-rodent somatic cell hybrids containing overlapping subsets of human chromosomes. The DNA hybridization experiments showed that the B4 IFN- locus is localized to human chromosome 4. A provisional regional assignment to 4q12-qter was also obtained. Thus available hybridization data implicate human chromosomes 2, 4, and 9 in the human IFN- system while the available biological data also implicated human chromosome 5.     

Expression of an α-cardiac like myosin heavy chain in diaphragm,chronically stimulated,and denervated fast-twitch muscles of rabbit

An additional slow fibre type, type I, is detected in diaphragm and appears in fast-twitch hindlimb muscles of rabbit under the influence of altered neuromuscular activity. Type I fibres were delineated from fibres expressing myosin heavy chain I (type I) by immunohistochemistry with a monoclonal antibody raised against the -cardiac MHCI. When stained for mATPase after acid and alkaline preincubations, some type I fibres resembled type I and type IIA fibres, respectively. Some type I fibres displayed dissimilar mATPase staining, indicating heterogeneity of this fibre population. The appearance of numerous type I fibres in stimulated muscles, which in addition contain type IIA and type I fibres, suggested that they may be interspaced between types IIA and I. Electrophoresis under nondenaturing conditions disclosed an additional isomyosin both in normal diaphragm and stimulated muscles. This band displayed the same mobility as the slowest isomyosin in rabbit masseter muscle. It was recognized by the same monoclonal (anti-- cardiac MHC) antibody used for immunohistochemistry. Therefore, this isomyosin appeared to be very similar, but perhaps not identical to the -cardiac MHC-based isomyosin, probably resulting from discrete differences in the MHC complement. This assumption agrees with additional findings suggesting an even greater heterogeneity of the MHCs than generally assumed. In support of this, we show in atrium and masseter muscles the existence of an additional, electrophoretically distinct MHC isoform which migrates in close vicinity to MHCI     

Long-Term Effects of IFN-γ, IL-10, and TGF-β-Modulated Dendritic Cells on Immune Response in Lewis Rats

Increasing data have shown that IFN-, IL-10, and TGF--modulated dendritic cells (DC) provide a promising strategy in treatment of experimental allergic encephalomyelitis and experimental autoimmune myasthenia gravis through different manner. To explore the immune response status after long-term application of these cytokine-modulated-DC, Lewis rats were injected subcutaneously into naive DC and IFN-, IL-10, and TGF--modulated DC (i.e., IFN--DC, IL-10-DC, and TGF--DC) at does of 1 × 10⁶ cells/rat every month for continuous 18 months, respectively. No rats suffered from decreased vigor and activity as well as cachectic condition during 18-month observation, and no rats had body-weight loss after 18-month treatment. Exploratory laparectomy did not find any tumor in all rats. IL-10-DC and TGF--DC resulted in lower nonspecific (Con A-induced) and antigen specific (ovalbumin-stimulated) spleen mononuclear cells proliferation, accompanied by lower levels of IFN-, IL-10, and TNF-. On the contrary, IFN--DC did not suppress cell proliferation and IFN- and IL-10 production except only slightly decreased TNF- levels. These results suggest that IFN--DC seems to be a more ideal candidate in the treatment of autoimmune diseases without suppressing immune response.     

Harnsteroidprofile bei Cushing Syndrom und Tumoren der Nebennierenrinde

Summary The analysis of 24-h excretion profiles of urinary steroids in 18 patients suffering from Cushing's syndrome or adrenocortical tumors revealed typical patterns when compared to 37 healthy control persons, 24 patients with obesity, and 6 patients with hirsutism. The validation of eight criteria — increased excretion of free cortisol, 6-hydroxycortisol, 20-dihydrocortisol, 11-hydroxyandrosterone, and 3-hydroxy-5-en steroids, decreased ratio of tetrahydrocortisone (THE) to tetrahydrocortisol (THF), and increased ratios of THF to allotetrahydrocortisol (a-THF) and metabolites of androgens (AM) to metabolites of cortisol (CM) — afforded reliable detection of disorders in steroid biosynthesis. The analysis of urinary steroid profiles can therefore be recommended as a screening procedure in patients with clinical symptoms of disorders in steroid production and/or metabolism.

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Abkürzungen An Androsteron - Aet Aetiocholanolon - AM Androgenmetaboliten: An plus Aet - 11-O-An 11-Ketoandrosteron - 11-OH-An 11-Hydroxyandrosteron - 11-OH-Aet 11-Hydroxyaetiocholanolon - DHEA Dehydroepiandrosteron - 16-OH-DHEA 16-Hydroxydehydroepiandrosteron - 16-OH-DHEA 16-Hydroxydehydroepiandrosteron - A⁵T-16 Androsten-3,16,17-triol - P⁵T Pregnentriol-3-hydroxy-5-en Steroide: DHEA plus Androstendiole plus 16-OH-DHEA plus 16-OH-DHEA plus - P⁵D Pregnendiol plus A⁵T-16 plus 16-Hydroxypregnenolon plus P⁵T - THE Tetrahydrocortison - THF Tetrahydrocortisol - a-THF Allotetrahydrocortisol - CM Cortisolmetaboliten: THE plus THF plus a-THF. - -C,-C Cortole - -CL,-CL Cortolone - 6-OH-F 6-Hydroxycortisol - 20-OH-F 20-Dihydrocortisol - NNR Nebennierenrinde - CRF Corticotropin Releasing Hormon - ACTH Adrenocorticotropes Hormon - CPB Competitive Protein Binding - RIA Radioimmunoassay - HPLC High Pressure Liquid Chromatography - DHEAS Dehydroepiandrosteron-Sulfat. Mit Unterstützung der Deutschen Forschungsgemeinschaft, Ho-471/5-1     

Heat-shock proteins and the γδ T cell response in virus infections: Implications for autoimmunity

Conclusions Macrophages expressing hsp65 mRNA⁺ and TcR mRNA⁺ lymphocytes are found at high frequency late in the course of the pneumonia induced in mice by human influenza A viruses. The numbers of the two populations increase in parallel, after the time that infectious virus has been cleared from the lung. The range of TcR genes that are detected is consistent with, although not exclusive to, the pattern found by others for hybridoma cell lines that are reactive to hsp65. Secondary infection (in the absence of neutralizing antibody) greatly enhances both the rapidity and the magnitude of this T cell response for mice that are primed with a different type A influenza virus, but not with an influenza B virus. This could be taken to indicate that the initial infection has induced the generation of influenza A virus-specific T cell memory. However, when the primed T cells are depleted from such mice by treatment with mAb to CD4 and CD8, the accumulation of both the hsp65 mRNA⁺ macrophages and the TcR mRNA⁺ lymphocytes is greatly decreased.The results are consistent with the following hypothesis, which is highly speculative and based on limited data. The T cell response that mediates virus clearance induces high levels of hsp65 expression in macrophages, which in turn stimulates the involvement of hsp65-reactive T cells. Lymphokines/cytokines secreted by these T cells then function to maintain macrophage activation, and to retain these macrophages in the respiratory tract after the time that the virus has been eliminated and the T cells are no longer being stimulated. This serves to provide a nonspecific cover to protect the damaged lung from secondary bacterial infection during the process of tissue repair. If this model is correct, any virus-specific T cell response is likely to promote a local hsp65⁺ macrophage/ T cell circuit. Although normally a protective mechanism, such interactions could potentially exacerbate autoreactivity if occurring in sites (e. g., the joint) where inflammatory cells may not be readily cleared by normal, physiological processes.     

Hämofiltration — Differentialindikation zur Hämodialyse unter Berücksichtigung hämodynamischer und metabolischer Aspekte

Zusammenfassung Schwerwiegende, durch die herkömmlichen Dialyseverfahren bei einem Teil der Patienten kaum beherrschbare Komplikationen der chronischen Niereninsuffizienz bestehen in einer malignen Hypertonie sowie andererseits in einer Hypotonie trotz Hyperhydratation. Insbesondere bei älteren Patienten mit Gefäßsklerose und labilem Kreislaufverhalten, die diese Komplikationen aufweisen, sollte daher bevorzugt die Hämofiltration angewandt werden. Dieses Verfahren ermöglicht einen sehr schonenden Flüssigkeitsentzug sowie in den meisten Fällen auch eine Normalisierung des Blutdruckes ohne weitere medikamentöse Therapie. Bei vielen Patienten kann ein Absinken der Serum-Phosphatwerte bei gleichzeitiger Verminderung der Aluminiumhydroxyd-Therapie erreicht werden. Die Unabhängigkeit von großen Spülflüssigkeitsmengen und ein geschlossenes System gewährleisten darüberhinaus Mobilität und hygienische Sicherheit.     

Expression and ligand-binding function of the integrin α4β1 (VLA-4) on neural-crest-derived tumor cell lines

Human neural-crest-derived tumor cell lines, including three neuroblastomas, an astrocytoma, a glioblastoma, a rhabdomyosarcoma and a melanoma were screened for the expression of the integrin ₄₁ (VLA-4). The neuroblastomas IMR-32 and SK-N-SH, the astrocytoma 131-INI, the glioblastoma Fogerty and the rhabdomyosarcoma TE-671 expressed ₄₁ as determined by cytofluorometry and immunoprecipitation. Another neuroblastoma line, LA-N-1, did not express ₄₁. Analysis of immunoprecipitated ₄₁ showed that the ₄ subunit from the various cell types differed in relative molecular weight (M _r ). The variability in the observed M _r could be accounted for by differences in the levels of N-linked glycosylation. The observed variability in M _r did not appear to affect function since intact cells and solubilized ₄₁ bound to a synthetic peptide identical in sequence to the CS-1 region of the alternatively spliced IIICS domain of fibronectin, a known ₄₁, ligand.     

Tension development and calcium sensitivity in skinned muscle fibres of the frog

Calcium activated isometric tension development was measured in single skinned muscle fibres of the ileofibularis muscle of the frog. The experiments were carried out at 5°C, pH=6.9, 1 mM free Mg²⁺ and an ionic strength of 160 mM. A Hill curve was fitted to the isometrically developed tension at different Ca²⁺ concentrations by means of a non-linear least mean square approximation. At a sarcomere length of 2.15 m, the Ca²⁺ concentration for half maximum tension (K) was 1.6 M. This Ca²⁺ concentration decreased with increasing sarcomere length; at 2.7 m, K was 1.1 M and at 3.1 m, K was 0.9 M. Therefore, Ca sensitivity is increased at larger sarcomere lengths. Consequently, the optimal sarcomere length for tension development shifted to larger values when the Ca²⁺ concentration was lowered. Osmotic compression of the fibre at 2.15 m by means of 5% Dextran also caused an increase in Ca sensitivity (K was 1.0 M). At 2.7 m, addition of 5% Dextran hardly affected the Ca sensitivity. The possible role of the interfilament spacing in the explanation of these results discussed.     

DNA-Antiviral Vaccines: New Developments and Approaches—A Review

Current vaccines can be divided into live, recombinant and killed vaccines. Live vaccines are traditionally composed of attenuated viruses or bacteria, selected for their reduced pathogenicity. Recombinant vaccines, driven by a viral or bacterial vector express foreign antigens, or only recombinant proteins injected as antigen. Killed vaccines consist of inactivated whole pathogens. But all these traditional vaccines have some disadvantages: Attenuated live vaccine are able to undergo mutation and as mutated viruses or bacteria can now provoke the diseases against which the vaccine should protect the organism. A further disadvantage of live vaccines is the possibility of shedding which is a real problem especially in veterinary medicine. Clearly, there is a need for better vaccines to protect against diseases without the disadvantages associated with vaccines presently in use. Modern vaccines might be characterized as safe, no risk of reversion to pathogenicity, and they should be stable without the necessity of a cold chain. Production should be simple, standardized and inexpensive. Vaccine development has now been improved by the ability to use direct inoculations of plasmid DNA encoding viral or bacterial proteins. One of the major benefits of DNA-vaccines, variously termed DNA-, genetic- or nucleic acid-immunization, is the endogenous synthesis of the encoded protein. Therefore DNA vaccines mimic natural infection and provoke both strong humoral and cellular immune response. This review summarizes new developments and approaches of DNA vaccination and explains the construction of expression plasmids as well as possible mechanisms of immune responses.     

Phenotypic and epistatic grouping of hypo- and hyper-rec mus mutants in Aspergillus

The mutants musK to musS of Aspergillus nidulans are sensitive to methyl-methanesulfonate (MMS) and several of them are meiotic-defective and alter mitotic recombination frequencies. All were found to be cross-sensitive to 4-nitro-quinoline-N-oxide (4-NQO) but unexpectedly none of them was hypersensitive to -rays and few to UV light. Double mus;uvs mutants were constructed to test for interactions with uvs mutations of the four epistatic groups of Aspergillus, UvsF, UvsC, UvsI, and UvsB. All meiotic-defective mus mutations caused some lethal interactions, usually with uvsF. None of them showed epistasis with UvsF or UvsB group mutants and one, musO, may represent a new group. Three mus mutations that affect recombination were assigned to the UvsC group, namely musN and K, and also musL which is recombination-defective and closely resembles uvsC. While uvsC mutants are mutators and lack UV-mutagenesis, most mus mutants had no effects on mutation. Only musR, which appeared epistatic with uvsI, showed reduced UV-reversion frequencies similar to uvsI. The recombination-proficient mus mutants appeared to be epistatic with more than one group, but in several cases sensitivities were slight and overlaps insufficient to obtain corroborating results with MMS and 4-NQO.     

Yeast artificial chromosome cloning of the β-catenin locus on human chromosome 3p21–22

-Catenin has emerged as an important component of the adherens junctions between epithelial cells. As a result of studies of its interaction with theAPC gene product, it has been implicated in the development of colorectal cancer. -Catenin, -catenin, E-cadherin and APC appear to mediate contact inhibition in epithelia. As part of the study of the organization of the -catenin gene, we have isolated yeast artificial chromosomes (YACs) to characterize its intron/exon structure. YAC fluorescencein situ hybridization analysis and polymerase chain reaction analysis of somatic cell hybrid DNAs show that -catenin maps in the 3p21–22 region, the location of tumour-suppressor genes deleted in small-cell lung cancer (SCLC) and other disorders. -Catenin YACs will provide a source of microsatellite markers useful in loss of heterozygosity studies to assess the importance of -catenin deletions in SCLC.     

Acute and chronic inflammatory responses to local administration of recombinant IL-1α, IL-β, TNFα, IL-2 and Ifnγ in mice

The contention that cytokines are important mediators of inflammation prompted the present studies which were designed to compare acute and chronic pathological effects of locally-administered recombinant (r) IL-1, IL-1, TNF, IL-2 and Ifn. Acute (6 hr), resolving (48 hr) inflammation was induced by the following, in order of potency: rIL-1>rIL-1>rTNF>rIfn=BSA (control) following a single sc. injection. However, only rIL-1 and rIL-2 initiated and maintained chronic granulomatous reactions when delivered locally from a sc. ethylene vinyl acetate (EVA) slow-release polymer. The predominance of macrophages in EVA-rIL-1 lesions contrasted with the proliferative lymphoid granulomata induced by EVA-rIL-2 implants. These in vivo observations reinforce, the roles of both IL-1 and IL-2 as potent mediators of chronic immunoinflammatory disease.     

Modulation of Nav1.5 by β1- and β3-subunit co-expression in mammalian cells

Cardiac sodium channels (Na_v1.5) comprise a pore-forming -subunit and auxiliary -subunits that modulate channel function. In the heart, 1 is expressed throughout the atria and ventricles, whilst 3 is present only in the ventricles and Purkinje fibers. In view of this expression pattern, we determined the effects of 3 and 1 co-expression alone, and in combination, on Na_v1.5 stably expressed in Chinese hamster ovary cells. The current/voltage relationship was shifted –5 mV with either 1 or 3 co-expression alone and –10 mV with co-expression of both 1 and 3. In addition, 3 and 1/3 co-expression accelerated macroscopic current decay. There were significant hyperpolarizing shifts in equilibrium gating relationships with co-expression of 1 and 3 alone and in combination. Co-expression of 1/3 together resulted in a greater hyperpolarizing shift in channel availability, and an increase in the slopes of equilibrium gating relationships. Co-expression of 3 and 1/3, but not 1, slowed recovery from inactivation at –90 mV. Development of inactivation at –70 and –50 mV was accelerated by -subunit co-expression alone and in combination. -Subunit co-expression also reduced the late Na current measured at 200 ms. In conclusion, -subunits modulate Na_v1.5 gating with important differences between co-expression of 1 and 3 alone and 1/3 together.     

Remodeling of the Actin Cytoskeleton in the Contracting A7r5 Smooth Muscle Cell

It has been proposed that the reorganization of components of the actin cytomatrix could contribute to force development and the low energy cost of sustained contraction in contractile cells which lack a structured sarcomere (A.S. Battistella-Patterson, S. Wang and G.L. Wright (1997) Can J Physiol Pharmacol 75: 1287–1299). However, there has been no direct evidence of an apropos actin reorganization specifically linked to the contractile response in cells of this type. Remodeling of the - and -actin domains was studied in A7r5 smooth muscle cells during phorbol 12,13 dibutyrate (PDB)-induced contraction using immunohistologic staining and -actin-green fluorescent protein (-actin-GFP) fusion protein expression. Cell stained with phalloidin as well as cells expressing -actin-GFP showed densely packed actin stress cables, arranged in parallel and extending across the cell body. PDB caused approximately 85% of cells to contract with evidence of forcible detachment from peripheral adhesion sites seen in many cells. The contraction of the cell body was not uniform but occurred along a principal axis parallel to the system of densely packed -actin cables. During the interval of contraction, the -actin cables shortened without evidence of disassembly or new cable formation. The use of cytochalasin to inhibit actin polymerization resulted in the dissolution of the actin cables at the central region of the cell and caused the elongation of precontracted cells. In unstimulated cells, -actin formed cables similar in arrangement to the cell spanning -actin cables. Within a short interval after PDB addition; however, the majority of -actin cables disassembled and reformed into intensely fluorescing column-like structures extending vertically from the cell base at the center of clusters of -actin filaments. The -actin columns of contracting cells showed strong colocalization of -actinin suggesting they could be structurally analogous to the dense bodies of highly differentiated smooth muscle cells. The results indicate that the - and -actin domains of A7r5 cells undergo a highly structured reorganization during PDB-induced contraction. The extent and nature of this restructuring suggest that remodeling could play a role in contractile function.