Transient basophilia following the application of lymphatic pump techniques: a pilot study

Lymphatic pump techniques (LPTs) consisting of pectoral traction and splenic pump were performed on seven male medical students following blood collection for baseline value determinations. Blood was collected from each subject at 15, 30, 60, 120, and 240 minutes post-LPT. The samples were analyzed for serum chemistry and complete blood cell count. All subjects showed an increase in the percentage of basophils. There was variation in the time points for the initial occurrence of basophilia among the subjects. A separate cohort of five male medical students served as control subjects. The control group did not receive LPTs. Blood samples collected at the same time points as the experimental group did not show the basophilia.

Expression of intercellular adhesion molecule 3 (CDw50) on endothelial cells in cutaneous lymphomas. A comparative study between nodal and cutaneous lymphomas

Advances in the molecular definition of surface proteins (adhesion molecules) involved in tumor metastasis may help to explain the invasive behavior of malignant tumors, that is, the migration of tumor cells involving reversible adhesive contacts, their release in the circulation, and their extravasation into distant sites. Intercellular adhesion molecule-3 (ICAM-3), the third receptor for the lymphocyte function-associated antigen molecule-1 (LFA-1) was recently characterized. We investigated fresh frozen skin biopsies from 10 patients with mycosis fungoides, four with pleomorphic T-cell lymphoma, six with Sézary syndrome, 10 with primary cutaneous B-cell lymphoma, and 10 with eczematous lesions as controls. The biopsies were compared with lymph node biopsies of five patients with known cutaneous T-cell lymphoma (CTCL), 10 with primary nodal B-cell lymphoma, and 11 with lymph-node specimens showing dermatopathic lymphadenopathy as controls. The specimens were stained with ICAM-3 antibody (Bender Medical Science) using the alkaline phosphatase antialkaline phosphatase method. Using cytomorphologic criteria, neoplastic lymphocytes could be differentiated from smaller reactive cells. Staining intensities were classified semiquantitatively as follows: 4, strong expression in 75 to 100% of the tumor cells; 3, 50 to 75%; 2, 25 to 50%; 1, 5 to 25%; and 0 fewer than 5% of the tumor cells. The endothelial cells in skin biopsies of seven of 30 primary cutaneous lymphomas expressed ICAM-3. In contrast, no expression of ICAM-3 could be demonstrated on endothelial cells in lymph nodes infiltrated with tumor cells of CTCL. Finally, endothelial cells of lymph nodes infiltrated with primary nodal B-cell lymphomas showed expression of ICAM-3 in three of 10 patients. The endothelial cells in the 11 control patients presenting with both eczematous lesions and dermatopathic lymphadenopathy showed no staining for ICAM-3. Every patient who expressed ICAM-3 on endothelial cells showed systemic spread of this disease. The findings suggest that ICAM-3 expression may be induced on endothelial cells in late-stage cutaneous lymphomas, probably by a cytokine-mediated mechanism.

Evaluation of monoclonal antibodies for subtyping of currently circulating human type A influenza viruses

The hemagglutinin subtype specificities of six monoclonal antibodies (MAbs) to influenza type A viruses were evaluated in a rapid culture assay by immunoperoxidase staining. Confluent monolayers of MDCK cells in multiwell plates were inoculated with (i) 23 reference viruses, (ii) 200 isolates collected during the influenza season 1995 to 1996, and (iii) 28 clinical specimens previously found to be influenza virus positive. After overnight incubation, the cells were fixed and stained with MAbs IVA1/B10, IIF4/D3, 12L/5, 13L/6, 18L/1, or 18L/4. Type-specific MAbs were included as controls. All antibodies gave intensive cytoplasmic staining with infected cells in the absence of any reaction with uninfected cells. MAbs 12L/5, 13L/6, 18L/1, and 18L/4 exclusively reacted with viruses of the subtype H1, and the antibodies IVA1/B10 and IIF4/D3 exclusively reacted with viruses of the subtype H3. None of these MAbs reacted with viruses of the H2 subtype or with influenza type B viruses. Of the 200 recent isolates, 63 were identified as influenza virus type A, subtype H1, 95 were identified as type A, subtype H3, and 41 were identified as type B. One isolate contained a mixture of a type A (H3) and a type B influenza virus. Of the 28 previously positive clinical specimens, 15 contained an influenza virus A, subtype H3, 1 contained an influenza virus A, subtype H1, and 9 contained an influenza B virus. The subtype of a very weakly positive specimen could not be determined, and two specimens remained negative. The MAbs described here allow for a rapid typing and subtyping of influenza virus isolates and for the type- and subtype-specific detection of influenza viruses in clinical specimens.

Synthesis of octyl O- and S-glycosides related to the GPI anchor of Trypanosoma brucei and their in vitro galactosylation by trypanosomal alpha-galactosyltransferases

Octyl O- and S-glycosides of mono- to tri-saccharides related to the core structure alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->6)-alpha-D-Manp of the GPI anchor of Trypanosoma brucei have been prepared via regioselective protodesilylation and glycodesilylation of octyl O- and S-glycosides of 2-O-benzoyl-4,6-O-(1,1,3,3-tetraisopropyl-1,3-disiloxane-1, 3-diyl)-alpha-D-mannopyranoside. The synthetic saccharides have been used as substrates for enzymatic alpha-galactosylation with membrane fractions of bloodstream forms of T. brucei strain 427 variants MITat 1.4, MITat 1.2, and MITat 1.5, respectively.

Theoretical Study of Ethylene Oligomerization by an Organometallic Nickel Catalyst

The mechanism for ethylene oligomerization by (acac)NiH has been studied using density functional theory (DFT). The transition states for chain propagation and chain termination were optimized and the related reaction barriers calculated. Several possible mechanisms were considered for the chain termination step. Chain termination by beta-hydrogen elimination was found to be energetically unfavorable, and is not likely to be important. Instead, beta-hydrogen transfer to the incoming ethylene unit seems to be operative. The most favorable beta-hydrogen transfer pathway has two transition states. The first leads from a weak pi-complex between an incoming ethylene unit and (acac)NiCH(2)CH(2)R to an intermediate in which the two olefins C(2)H(4) and H(2)CCHR both are strongly pi-complexed to the nickel hydride (acac)NiH. The second barrier takes the intermediate to another weak pi-complex between (acac)NiCH(2)CH(3) and H(2)C=CHR from which the oligomer H(2)C=CHR can be released and the catalyst (acac)NiCH(2)CH(3) regenerated. Due to the mechanism of chain termination, the actual catalyst is proposed to be (acac)NiCH(2)CH(3) whereas (acac)NiH serves as a precursor or precatalyst.

Wheezing bronchitis in children. Incidence, viral infections, and other risk factors in a defined population

Risk factors for severe wheezing bronchitis were studied in children aged 4 months to 4 years in need of hospitalization. The children included in the study consisted of all cases generated from a geographically defined population, the catchment area of St Göran's hospital in Stockholm. The incidence was 3/1000 children and year, during the two years of observation, with the highest rate in boys under the age of 18 months (4.7/1000). Symptoms of a preceding upper respiratory tract infection were reported in 90% of the cases, but a viral etiology could only be demonstrated with virus isolation in 26%. Respiratory syncytial virus was the most common finding in younger children. Rhinovirus was primarily seen in older children with a history of previous wheezing. Regardless of whether the cases had a positive or negative virus isolation they showed the same seasonal distribution. Furthermore, there was no difference in risk factors between children with a positive and negative virus isolation. Children older than 18 months with negative virus isolation had higher IgE levels than those with positive isolation, suggesting that atopy is of greater importance in this group.

Gas phase detection of cocaine by means of immunoanalysis

Immunoanalytical techniques based on an indirect competitive ELISA to determine cocaine in the gas phase are described. A test-gas generator was developed and evaluated by determining saturation vapour pressures and the sublimation enthalpy of cocaine base. To achieve quantitative recovery of the drug, the saturated air stream was sucked through a retention fluid. For validation of the test gas generator, samples were analysed with a microtitre plate cocaine-ELISA based on monoclonal antibodies. To simplify the sampling and analysis procedures by analysing the retention fluid directly in the sampling vessel, particle-based immunoassay formats were developed. According to the ELISA format, avidin was immobilized on the particles. The application of various solid particles consisting of different materials with a wide range of diameters (0.5-550 microns) to the analysis of cocaine standards and gas samples showed good correlation with the results obtained with the microtitre plate ELISA with an average IC50 value (end-point of the test; concentration at 50% binding) of 9.7 ng ml-1. The particle-based assays showed IC50 values in the range of 5-54 ng ml-1 and signal background ratios ranging from 2 to 11. The application of particle-based assays for direct analysis of cocaine in the sample fluid was successfully performed with glass beads, precoated with avidin and a biotin-cocaine conjugate. Recovery of cocaine from the gas phase depended on the volume of sample fluid and on the geometry of the sample tube.

Synergistic effects of fluid shear stress and cyclic circumferential stretch on vascular endothelial cell morphology and cytoskeleton

The development of atherosclerosis is thought to be initiated by a dysfunctional state of the vascular endothelium. The proposal that mechanical forces play a role in the localization of this disease has led researchers to develop in vitro models to assess their effects on cultured endothelial cells. The arterial endothelium is exposed simultaneously to circumferential hoop stretch and wall shear stress, yet previous investigations have focused on the isolated effects of either cyclic stretch or shear stress. The influence of physiological levels of combined shear stress and hoop stretch on the morphology and F-actin organization of bovine aortic endothelial cells was investigated. Cells subjected for 24 hours to shear stresses higher than 2 dyne/cm2 or to hoop stretch greater than 2% elongated significantly compared with unstressed controls and oriented along the direction of flow and perpendicular to the direction of stretch. Exposure to more than 4% stretch significantly enhanced the responses to shear stress. Both shear stress and hoop stretch induced formation of stress fibers that were aligned with the cells' long axes. Simultaneous exposure to both stimuli appeared to enhance stress fiber size and alignment. These results indicate that shear stress and hoop stretch synergistically induce morphological changes in endothelial cells, which suggests that circumferential strain might modulate sensitivity of endothelial cells towards shear stress.

CD44v6 is a marker for systemic spread in cutaneous T-cell lymphomas. A comparative study between nodal and cutaneous lymphomas

Adhesion molecules are involved in leukocyte recruitment, lymphocyte recirculation, and in several aspects of tumour biology. Recent discoveries of surface proteins on tumour cells involved in tumour metastasis may explain the invasive behaviour, the migration involving reversible adhesive contacts, the release into the circulation and the extravasation of tumour cells. CD44 is a family of glycoproteins involved in cell-cell and cell-matrix interactions. The v6 (variant exon v6) form of CD44 confers a metastatic potential onto some carcinoma cells. In the present study, the expression of CD44v6 on skin biopsies of 10 inflammatory skin diseases, 30 cutaneous lymphomas (CL), 11 reactive lymph nodes, 10 primary nodal non-Hodgkin's lymphomas (NHL) and 5 secondary nodal NHL was investigated immunohistochemically. None of the 10 nodal NHL were CD44v6 positive for the neoplastic B- or T-cells, whereas 11/12 CL with systemic spread showed a distinct CD44v6 expression in the skin. CD44v6 was not expressed on the tumour cells of skin biopsies of patients without systemic spread (18 cases of CL). In conclusion, CD44v6 expression is connected to an aggressive behaviour of CL.

Hand ischemia in patients with hemodialysis access grafts: angiographic diagnosis and treatment

PURPOSE

To determine the cause of symptoms and efficacy of transcatheter therapy in a series of patients with dialysis grafts and hand pain referred for arteriography.

MATERIALS AND METHODS

Thirteen patients with 14 hemodialysis grafts underwent arteriography for possible hand ischemia. The sites of proximal graft anastomosis were the distal radial artery (n = 6) and the mid- to distal brachial artery (n = 6). Transcatheter therapy was performed via the graft or by antegrade brachical puncture.

RESULTS

The cause of symptoms was ischemia from obstructive arterial disease in seven cases (three with superimposed steal), graft steal alone in three, ischemic monomelic neuropathy in two, and carpal tunnel syndrome in two. Five arterial stenoses were treated with angioplasty, with improvement or resolution of symptoms in four patients.

CONCLUSION

In this group, symptoms were usually the result of inflow or outflow arterial disease, alone or in combination with graft steal. Transcatheter therapy (angioplasty or embolization) is effective in selected cases.

Elongation of confluent endothelial cells in culture: the importance of fields of force in the associated alterations of their cytoskeletal structure

Studies using either animal models or in vitro flow systems have shown that the shape of large-vessel endothelial cells (ECs) was sensitive to the amplitude of the flow imposed on them. In order to better understand the morphological changes experienced by ECs when exposed to physical forces such as shear stress, the mechanical integrity of confluent bovine aortic ECs (BAECs) was anisotropically perturbed using the five following types of experiments: (i) slicing and partial scraping of BAEC monolayers; (ii) culture of BAECs on narrow strips of adhesive plastic; (iii) incubation of confluent BAECs with media containing low Ca2+ concentrations; (iv) culture of ECs on top of rectangular collagen gels; and (v) exposure of BAECs to laminar steady shear stress. In all five experimental systems, BAECs exhibited an elongated morphology and aligned their major axes in specific directions. In addition, a preferential alignment of actin microfilaments, vimentin intermediate filaments, and streaks of vinculin with the major axes of the cells often occurred concomitantly with BAEC elongation. In all five systems, the elongation of ECs was analyzed in terms of a mechanical deformation borne by the cytoskeleton, and possibly caused by anisotropic distribution of the forces experienced by the cell structure. In addition, the strain-stress and stiffness-stress relationships characterizing the elongation of BAECs exposed to steady flow were qualitatively similar to those computed for the uniaxial deformation of a spherical geodesic. Our findings suggest that the cytoskeleton of ECs plays an important role in the transduction of those forces which cause an elongation of ECs.

Respiratory virus infections during anticancer treatment in children

To evaluate the occurrence and clinical significance of respiratory virus infections in children during anticancer treatment, we studied 75 consecutive episodes of febrile infection in 32 children during 17 months. Viral antigen detection for 7 respiratory viruses, viral culture for rhinoviruses and enzyme immunoassay serology were used. Evidence for respiratory virus infection was found in 28 (37%) cases. Rhinovirus was the most common virus detected in 13 (17%) episodes. The other etiologic agents were respiratory syncytial virus (6 episodes), parainfluenza virus type 3 (5 episodes), adenovirus (4 episodes), influenza A virus (3 episodes), and influenza B virus (1 episode). Respiratory virus infections were diagnosed as often in leukopenic as in non-leukopenic patients (37% vs. 38%). In 4 cases bacteremic infection was diagnosed. We found no difference in serum C-reactive protein values when episodes positive for respiratory viruses were compared with virus-negative episodes. Our observations show that respiratory virus infections are common in febrile children receiving anticancer treatment. Diagnostic tests for respiratory viruses should be used more often in evaluation of fever in these patients.

An endothelial cell-smooth muscle cell co-culture model for use in the investigation of flow effects on vascular biology

Flow and the associated shear stress have been shown to play an active role in the regulation of the structure and function of endothelial cells (EC) in vitro. Although cultured EC subjected to flow exhibit an elongated morphology and a decreased cell growth rate rather like those observed in vivo, there are differences in morphology and growth rate, as well as other characteristics, between in vitro and in vivo EC. This suggests that flow is only one of the many factors affecting EC differentiation in vivo. In this study, a co-culture model system was designed, which includes smooth muscle cells (SMC), a matrix of collagen type I, and a confluent monolayer of EC, and this simplified model of the arterial wall was subjected to a steady, laminar shear stress of 10 and 30 dyn/cm2. Under non-flow conditions, EC exhibited an elongated shape, but with a random orientation. In response to flow, there was an alignment with the direction of flow. This alignment occurred more rapidly at 30 dyn/cm2 than at 10 dyn/cm2. The collagen matrix was found to be primordial in the maintenance of a quiescent endothelium, even in the absence of SMC and flow, suggesting the importance of an organized extracellular matrix (ECM) in the differentiation of cells in vivo.

Short-term use of amoxicillin-clavulanate during upper respiratory tract infection for prevention of acute otitis media

We performed a randomized, double-blind, placebo-controlled study to determine whether acute otitis media could be prevented by antibiotic therapy initiated promptly after the appearance of symptoms of upper respiratory tract infection. One hundred four children aged 1 to 4 years received a 7-day course of either amoxicillin-clavulanate or placebo. Acute otitis media developed in 9 (18%) of the 50 children receiving amoxicillin clavulanate and in 12 (22%) of the 54 children receiving placebo (p = 0.59).

Type- and subtype-specific detection of influenza viruses in clinical specimens by rapid culture assay

A rapid culture assay which allows for the simultaneous typing and subtyping of currently circulating influenza A(H1N1), A(H3N2), and B viruses in clinical specimens was developed. Pools of monoclonal antibodies (MAbs) against influenza A and B viruses and MAbs HA1-71 and HA2-76, obtained by immunizing mice with the denatured hemagglutinin subfragments HA1 and HA2 of influenza virus A/Victoria/3/75, were used for immunoperoxidase staining of antigens in infected MDCK cells. MAb HA1-71 reacted exclusively with influenza A viruses of the H3 subtype, while MAb HA2-76 reacted with subtypes H1, H3, H4, H6, H8, H9, H10, H11, and H12, as determined with 78 human, 4 swine, and 10 avian influenza virus reference strains subtyped by the hemagglutination inhibition test. To determine if the technique can be used as a rapid diagnostic test, 263 known influenza virus-positive frozen nasal or throat swabs were inoculated into MDCK cells. After an overnight incubation, the cells were fixed and viral antigens were detected by immunoperoxidase staining. Influenza A viruses of the H1 and H3 subtypes were detected in 31 and 113 specimens, respectively. The subtypes of 10 influenza A virus-positive specimens could not be determined because they contained too little virus. Influenza B viruses were detected in 84 specimens, and 25 specimens were negative. We conclude that this assay is a rapid, convenient, non-labor-intensive, and relatively inexpensive test for detecting, typing, and subtyping influenza viruses in clinical specimens.

Interactions between aldehyde derivatives and the aldehyde binding site of bacterial luciferase

The interaction of triazine aldehydes with the aldehyde binding site of bacterial luciferases was investigated using a series of triazine aldehydes with different aldehyde chain length, and substituents on the s-triazine ring. Substrate activity was determined using luciferase from Photobacterium fischeri and Vibrio harveyi in a dithionite-based luciferases assay. The chain length optimum was determined for two triazine aldehyde classes to be C-10 and C-11, respectively. Only the substrate activity of 10-(4-chloro-6-methylthio-s-triazine-2-yl)aminodecanal (5) was as high as n-decanal, the reference aldehyde. All other triazine derivatives reduced light emission, probably by hindered binding of the substrates. The degree of activity reduction correlated with the volume of the triazine ring moiety. The triazine moiety volume of compound 5 was estimated to be 200 x 10(-30) m3. Triazine aldehydes which showed reduced light emission had an estimated volume of 228 x 10(-30) m3 or greater. All triazine aldehydes showed approximately 10-fold lower activities for Vibrio harveyi than for Photobacterium fischeri luciferase. Substrate specificity was the same for both luciferases. A schematic superposition of quinone aldehydes and triazine aldehydes which showed substrate activities equivalent to n-decanal, indicated potential interaction sites of aldehyde substrates with the aldehyde binding site of bacterial luciferases. The in vivo relevance of the results is discussed.

Synthetic studies toward pyruvate acetal-containing saccharides: en route to the efficient synthesis of Rhizobium-related exopolysaccharide fragments

The disaccharide building block benzyl O-(2,3-di-O-benzoyl-4,6-O-[(R)-1-(methoxycarbonyl) ethylidene]-beta-D-galactopyranosyl)-(1-->3)-2-O-benzoyl-4,6-O-[(S)-1- (methoxycarbonyl)ethylidene]-alpha-D-glucopyranoside (13), related to a Rhizobium exopolysaccharide, was prepared by coupling various 4,6-O-[(R)-1-(methoxycarbonyl)ethylidene]-D-galactosyl donors (benzoyl-protected chloride 1, pivaloyl-protected chloride 2, and benzoyl-protected fluorides 3 and 4, and trichloroacetimidate 5) with benzyl 2-O-benzoyl-4,6-O-[(S)-1- (methoxycarbonyl)ethylidene]-alpha-D-glucopyranoside (10) and the corresponding 2,3-O-tetraisopropyldisiloxane-protected glucoside 12. The best results, with respect to beta-selectivity and yield of the coupling, were obtained with 5 and 10 in dichloromethane. The beta-linked (13) and alpha-linked (14) disaccharides were efficiently converted via the 1-OH derivatives 17 and 21 into the corresponding trichloroacetimidates 18 and 22. The latter were used for the synthesis of the disaccharide ligands 4,6-(R)-pyruvate-beta-D-Galp-(1-->3)-4,6-(S)-pyruvate-beta-D-Glcp-O(CH2) 5NH2 (20), and 4,6-(R)-pyruvate-alpha-D-Galp-(1-->3)-4,6-(S)-pyruvate-beta-D-Glcp-O (CH2)5NH2 (24). The corresponding tri- and tetra-saccharide derivatives 4,6-(R)-pyruvate-beta-D-Galp-(1-->3)-4,6-(S)-pyruvate-beta-D-Glcp-(1-->4 )-beta- D-Glcp-O(CH2)5NH2 (28) and 4,6-(R)-pyruvate-beta-D-Galp-(1-->3)-4,6-(S)-pyruvate-beta-D-Glcp-(1-->4 )-beta- D-Glcp-(1-->4)-beta-D-Glcp-O(CH2)25NH2 (36) were obtained similarly.

Tissue engineering a blood vessel: regulation of vascular biology by mechanical stresses

Important to the tissue engineering of a substitute blood vessel is an understanding of those factors which regulate vascular biology. A major factor in this regulation is the mechanical environment imposed by the hemodynamics of the vascular system. In this the vascular endothelium plays a critical role, and over the past two decades much has been learned about the influence of hemodynamics on vascular endothelial biology, to a large degree using cell culture to study the effects of flow and cyclic stretch. In our laboratory, such studies are now being extended through the development of a model of the arterial wall involving the co-culture of endothelial cells and smooth muscle cells. The development of such a model and its use in the study of hemodynamic effects represents necessary steps in the evolution of approaches to tissue engineering a blood vessel.

Synthesis of the 5-aminopentyl glycoside of beta-D-Gal p-(1-->4)-beta-D-Glc p NAc-(1-->3)-L-Fuc p and fragments thereof related to glycopeptides of human Christmas factor and the marine sponge Microciona prolifera

The marine sponge Microciona prolifera and human coagulation factor IX (Christmas factor)-related mono- to tri-saccharide 5-aminopentyl glycosides beta-D-Gal p-R (5), beta-D-Glc pNAc-R (16), beta-D-Gal p-(1-->4)-beta-D-Glc p NAc-R (26), beta-D-Glc p NAc-(1-->3)-beta-L-Fuc p-R (39), beta-D-Glc pNAc-(1-->3)-alpha-L-Fuc p-R (43), beta-D-Gal p-(1-->4)-beta-D- Glc pNAc-(1-->3)-beta-L-Fuc p-R (45), and beta-D-Gal p-(1-->4)-beta-D-Glc p NAc-(1-->3)-alpha-L-Fuc p-R (47), where R is a 5-aminopentyloxy spacer moiety, which allowed the construction of glycoconjugates, were prepared. Thus, 3,4,6-tri-O-acetyl-2-deoxy-2-(2,2,2- trichloroethoxycarbonyl-amino)-alpha-D-glucopyranosyl trichloroacetimidate (10) and 1,3,4,6-tetra-O-acetyl-2-chloro-acetamido-2- deoxy-beta-D-glucopyranose (13) were condensed with N-Z-protected 5-amino-pentanol (2) followed by conversion of the coupling products into the corresponding N-acetylglucosamine derivatives, to give compound 16 after deblocking. Similarly, the donors 10 and 13 were coupled to position 3 of suitably protected aminopentyl beta- (32) and alpha- (37) -L-fucopyranosides, to give the disaccharides 39 and 43, respectively. Starting from lactose, O-(2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl)-(1-->4)-3,6-di-O- benzoyl-2-deoxy-2-(2,2,2-trichloroethoxycarbonylamino)-alpha-D-glu copyranosyl trichloroacetimidate (23) was prepared and used as an efficient disaccharide donor for the construction of ligand 26 from 2 and of the trisaccharide ligands 45 and 47 from fucosides 32 and 37, respectively.

Effect of flow on the process of endothelial cell division

In this study we investigated the effect of flow and the associated shear stress on the process of endothelial cell division. A shear stress of 7 N/m2 (70 dyne/cm2) was applied to a monolayer of bovine aortic endothelial cells (BAECs) by using a parallel-plate flow-chamber system. Dividing cells under flow conditions were qualitatively compared with those under static-culture conditions. In addition, the duration of some phases of the cell cycle (ie, mitosis and cytokinesis) was measured for both static and flow conditions. Dividing BAECs in static cultures bowed upward; however, when cells were preconditioned by at least 6 hours of exposure to flow, they stayed relatively attached to the substrate during the entire process of cell division. Cell area significantly decreased during division for both static-culture and flow conditions. Finally, although significant changes in the duration of phases were observed in single experiments during which cells were exposed to shear stress, any differences disappeared when the data for a large number of cells were combined. Hence, on average, flow and its associated shear stress did not affect the duration of the different phases of endothelial cell division.