Thiazolidine derivatives: In vitro toxicity assessment against promastigote and amastigote forms of Leishmania infantum and ultrastructural study.

Neglected diseases, such as Leishmaniasis, constitute a group of communicable diseases that occur mainly in tropical countries. Considered a public health problem with limited treatment. Therefore, there is a need for new therapies. In this sense, our proposal was to evaluate in vitro two series of thiazolidine compounds (7a-7e and 8a-8e) against Leishmania infantum. We performed in vitro evaluations through macrophage cytotoxicity assays (J774) and nitric oxide production, activity against promastigotes and amastigotes, as well as ultrastructural analyzes in promastigotes. In the evaluation of cytotoxicity, the thiazolidine compounds presented CC50 values between 8.52 and 126.83 µM. Regarding the evaluation against the promastigote forms, the IC50 values ranged between 0.42 and 142.43 µM. Compound 7a was the most promising, as it had the lowest IC50. The parasites treated with compound 7a showed several changes, such as cell body shrinkage, shortening and loss of the flagellum, intense mitochondrial edema and cytoplasmic vacuolization, leading the parasite to cell inviability. In assays against the amastigote forms, the compound showed a low IC50 (0.65 µM). These results indicate that compound 7a was efficient for both evolutionary forms of the parasite. In silico studies suggest that the compound has good oral bioavailability. These results show that compound 7a is a potential drug candidate for the treatment of Leishmaniasis.

Dissipation and residue of fosthiazate in tomato and cherry tomato and a risk assessment of dietary intake.

In this study, the safety and risk of fosthiazate as a nematicide against root-knot nematode in tomato and cherry tomato were evaluated. The dissipation and residue of fosthiazate for 28 days in tomatoes and cherry tomatoes were determined and studied by HPLC after simple, rapid pre-treatment. The mean recovery was 83.79~94.18%, and the relative standard deviations were 3.97~7.40%. Results showed that the half-lives of fosthiazate in tomatoes (4.81~5.37 days) were significantly lower than that in cherry tomatoes (5.25~5.73 days). At the pre-harvest interval (PHI) of 21 days, the residues of tomatoes and cherry tomatoes were 0.032~0.046 mg/kg, which were lower than the maximum residue level (MRL) established in China. The potential risks of fosthiazate exposure through the dietary intake of tomatoes and cherry tomatoes to different populations were also studied. According to the results of dietary risk assessment, the residual levels of fosthiazate were within the acceptable range of long-term dietary risk in different populations in China within the sampling interval of 21 days after the application of fosthiazate. Our results show that fosthiazate at 2250 g.a.i./ha in the field control of root-knot nematode has high safety and low risk, and can provide a reference for the safe and reasonable use of fosthiazate as a nematicide in the field.

Intrinsic Clearance and Metabolism Pathway of Fosthiazate in Rat and Cock Liver Microsomes: From Chiral Assessment View.

Chiral fosthiazate enters the organisms via environmental exposure and food web enrichment. Liver subcellular fractions of rats (RLM) and cocks (CLM) were prepared to explore the stereoselective metabolism of fosthiazate in vitro. The results indicated that fosthiazate exhibited different stereoselective metabolism behaviors in RLM and CLM. The clearance rate order of RLM to four fosthiazate stereoisomers was (1R,3R)-fosthiazate > (1S,3R)-fosthiazate > (1R,3S)-fosthiazate > (1S,3S)-fosthiazate. However, CLM showed a faster clearance rate to (1S,3S)-fosthiazate and (1S,3R)-fosthiazate than the other two stereoisomers. The molecular docking results revealed that the stereoselectivity was partially due to the stereospecific binding between fosthiazate stereoisomers and cytochrome P450 proteins. The main metabolism pathways of fosthiazate in RLM and CLM were oxidation and hydrolysis with five common metabolites including M299, M243, M227, M103, and M197 being identified by LC-TOF-MS/MS. The present study provides the accurate data on risk assessment of chiral fosthiazate.

[Efficacy of Saxagliptin for Blood Glucose Control in Hemodialysis Patients with Diabetes].

Studies on the drug saxagliptin (marketed in Japan since 2013) suggest favorable efficacy in hemodialysis patients, but included small sample sizes. Noting that some hemodialysis patients at our medical institution had been switched to saxagliptin 2.5 mg from treatment with other dipeptidyl peptidase-4 inhibitors, we decided to evaluate the effects of switching to saxagliptin on blood glucose control in these patients. The study included 11 patients. Before switching drugs, six of the patients used teneligliptin 20 mg and five used linagliptin 5 mg. Mean glycated albumin (GA) from before to 4 months after switching tended to increase in the previous users of teneligliptin 20 mg (18.4±3.0% to 19.5±2.7%) and tended to decrease in the previous users of linagliptin 5 mg (18.8±3.3% to 17.7±1.4%). Lack of a substantial change in GA when the previous users of teneligliptin 20 mg and linagliptin 5 mg were switched to saxagliptin 2.5 mg indicates that these three agents might have comparable antihyperglycemic profiles when used in patients on hemodialysis. Future research following from this pilot study must evaluate the risk of cardiac failure and incidences of adverse events in a larger population, to investigate the long-term efficacy and safety of switching to saxagliptin.

Residue dissipation, evaluation of processing factor and safety assessment of hexythiazox and bifenazate residues during drying of grape to raisin.

An analytical method for the simultaneous analysis of hexythiazox and bifenazate residues in grape and raisin was validated by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The extraction method involved liquid-liquid extraction with ethyl acetate and dSPE cleanup with primary secondary amine (PSA). The drying of grape to raisin may increase or decrease residues of pesticides. During the raisin making process, the dissipation of residue was evaluated and the processing factor (PF) was established for drying. Dissipation data were best fitted to 1st + 1st-order kinetics with a half-life ranging between 6-10 days for hexythiazox and 5-6 days for bifenazate. The PF value for overall raisin making was found to be 0.20-0.36 for hexythiazox and 0.14-0.15 for bifenazate indicating degradation of the residues. However, the PF value varies between 1.13-1.64 for hexythiazox and 0.94-1.12 for bifenazate during the drying process indicating concentration of the residues in drying. The dietary exposure on each sampling day was less than the respective maximum permissible intake (MPI). The residues in market samples of raisins were devoid of any risk of acute toxicity related to dietary exposure. The PF value generated will be useful for the field level management of residues in grape intended for raisin preparation.

Novel hybrids of benzothiazole-1,3,4-oxadiazole-4-thiazolidinone: Synthesis, in silico ADME study, molecular docking and in vivo anti-diabetic assessment.

A series of new benzothiazole-1,3,4-oxadiazole-4-thiazolidinone hybrid analogs (Tz1-Tz28) were synthesized in search of potential anti-diabetic agents. Molecular docking study was conducted with binding pocket of peroxisome proliferator activated receptor-gamma to elucidate the binding interactions of newly synthesized targets. Seven selected compounds with best docking scores were further screened for in vivo anti-hyperglycemic efficacy by oral glucose tolerance test in non-diabetic rats and on streptozotocin induced diabetic rat models. All the tested compounds demonstrated excellent to moderate reduction in blood glucose levels. Three of the compounds (Tz21, Tz7 and Tz10) showed excellent anti-diabetic effect by reducing concentration of glucose to 157.15 ±â€¯1.79 mg/dL, 154.39 ±â€¯1.71 mg/dL, 167.36 ±â€¯2.45 mg/dL, respectively better than the standard drug, pioglitazone, 178.32 ±â€¯1.88 mg/dL. Moreover, three derivatives Tz21, Tz4 and Tz24 with IC50 values of 0.21 ±â€¯0.01 µM, 9.03 ±â€¯0.12 µM and 11.96 ±â€¯0.40 µM respectively also showed better inhibitory activities on alpha-glucosidase even more than the standard acarbose (IC50 = 18.5 ±â€¯0.20 µM), indicating Tz21 has the highest inhibitory effect among the seven tested derivatives. Prediction of Drug like properties using molinspiration online software suggests that all the synthesized compounds have potential of becoming the orally active molecules. Thus, these novel hybrids could serve as potential candidates to become leads for the development of new drugs eliciting anti-hyperglycemic effect orally.

Teneligliptin: An Economic and Effective DPP-4 Inhibitor for the Management of Type-2 Diabetes Mellitus: A Comparative Study.

CONTEXT: Increasing diabetic burden worldwide is creating an alarming situation for the management and development of economic resources for it's treatment. Progressive nature of the disease requires allocation of a higher proportion of expenditure on health care initiative of any country. AIM: Present study is designed with an aim to determine the effectiveness of cost-effective DPP-4 inhibitor, Teneligliptin, over the other agent of the same class. MATERIAL AND METHOD: The study was carried out in Postgraduate Department of Medicine, S.N. Medical College, Agra and 112 patients were selected as subjects with a selected inclusion criterion. STATISTICAL ANALYSIS USED: Independent student's t-test was applied to compare the means. Mean standard deviation was calculated for quantitative data. All p values were two-tailed and values p<0.05 were considered statistically significant. RESULT: There was no significant difference in the levels of blood sugar or glycosylated hemoglobin (HbA1c) before and after the treatment of Teneligliptin. CONCLUSIONS: Teneligliptin offered an efficient second line treatment for the management of type-2 Diabetes Mellitus at a reduced average price of INR 39 per day, when compared to other DPP-4 inhibitors.

Actin- and Myosin-Dependent Vesicle Loading of Presynaptic Docking Sites Prior to Exocytosis.

Variance analysis of postsynaptic current amplitudes suggests the presence of distinct docking sites (also called release sites) where vesicles pause before exocytosis. Docked vesicles participate in the readily releasable pool (RRP), but the relation between docking site number and RRP size remains unclear. It is also unclear whether all vesicles of the RRP are equally release competent, and what cellular mechanisms underlie RRP renewal. We address here these questions at single glutamatergic synapses, counting released vesicles using deconvolution. We find a remarkably low variance of cumulative vesicle counts during action potential trains. This, combined with Monte Carlo simulations, indicates that vesicles transit through two successive states before exocytosis, so that the RRP is up to 2-fold higher than the docking site number. The transition to the second state has a very rapid rate constant, and is specifically inhibited by latrunculin B and blebbistatin, suggesting the involvement of actin and myosin.

On the use of propensity scores in case of rare exposure.

BACKGROUND: Observational post-marketing assessment studies often involve evaluating the effect of a rare treatment on a time-to-event outcome, through the estimation of a marginal hazard ratio. Propensity score (PS) methods are the most used methods to estimate marginal effect of an exposure in observational studies. However there is paucity of data concerning their performance in a context of low prevalence of exposure. METHODS: We conducted an extensive series of Monte Carlo simulations to examine the performance of the two preferred PS methods, known as PS-matching and PS-weighting to estimate marginal hazard ratios, through various scenarios. RESULTS: We found that both PS-weighting and PS-matching could be biased when estimating the marginal effect of rare exposure. The less biased results were obtained with estimators of average treatment effect in the treated population (ATT), in comparison with estimators of average treatment effect in the overall population (ATE). Among ATT estimators, PS-weighting using ATT weights outperformed PS-matching. These results are illustrated using a real observational study. CONCLUSIONS: When clinical objectives are focused on the treated population, applied researchers are encouraged to estimate ATT with PS-weighting for studying the relative effect of a rare treatment on time-to-event outcomes.

Facile synthesis of 1,3-thiazolidin-4-ones as antitubercular agents.

We have developed, highly efficient, one-pot, solvent-free, [Et3NH][HSO4] catalyzed multicomponent reaction protocol for the synthesis of 1,3-thiazolidin-4-ones in excellent yields. For the first time, the 1,3-thiazolidin-4-ones were evaluated in vitro for their antimycobacterial activity against Mycobacterium tuberculosis dormant MTB H37Ra and Mycobacterium bovis BCG strains. Among the synthesized basic 1,3-thiazolidin-4-ones, particularly the compounds 4c, 4d, 4e, 4f, 4h, 4i and 4j displays promising antitubercular activity along with no significant cytotoxicity against the cell lines MCF-7, A549 and HCT-116.

Experimental and computational assessment of F-actin influence in regulating cellular stiffness and relaxation behaviour of fibroblasts.

In biomechanics, a complete understanding of the structures and mechanisms that regulate cellular stiffness at a molecular level remain elusive. In this paper, we have elucidated the role of filamentous actin (F-actin) in regulating elastic and viscous properties of the cytoplasm and the nucleus. Specifically, we performed colloidal-probe atomic force microscopy (AFM) on BjhTERT fibroblast cells incubated with Latrunculin B (LatB), which results in depolymerisation of F-actin, or DMSO control. We found that the treatment with LatB not only reduced cellular stiffness, but also greatly increased the relaxation rate for the cytoplasm in the peripheral region and in the vicinity of the nucleus. We thus conclude that F-actin is a major determinant in not only providing elastic stiffness to the cell, but also in regulating its viscous behaviour. To further investigate the interdependence of different cytoskeletal networks and cell shape, we provided a computational model in a finite element framework. The computational model is based on a split strain energy function of separate cellular constituents, here assumed to be cytoskeletal components, for which a composite strain energy function was defined. We found a significant influence of cell geometry on the predicted mechanical response. Importantly, the relaxation behaviour of the cell can be characterised by a material model with two time constants that have previously been found to predict mechanical behaviour of actin and intermediate filament networks. By merely tuning two effective stiffness parameters, the model predicts experimental results in cells with a partly depolymerised actin cytoskeleton as well as in untreated control. This indicates that actin and intermediate filament networks are instrumental in providing elastic stiffness in response to applied forces, as well as governing the relaxation behaviour over shorter and longer time-scales, respectively.

Assessment of In Vitro Antioxidant activity of Some New Ferulic Acid Derivatives.

Aim: The in vitro antioxidant potential of new thiazolidin-4-one derivatives of ferulic acid was evaluated according to the total antioxidant activity and ferric reducing power assays. Material and Methods: The ferric reducing power assay was based on the reduction of ferricyanide to ferrocyanide, which form in the presence of ferric chloride a Perl Prussian blue color complex. The total antioxidant activity assay was assessed using phosphomolybdenum method. The results were expressed as effective concentration (EC50) values and ascorbic acid was used as positive control. All determinations were performed in triplicate. Results: It was found that the activity of the tested compounds is influenced by the substituents on phenyl ring of the thiazolidine-4-one moiety. The most active compound was 1i, which contains 2,3-diOH as substituent on phenyl ring. Conclusions: A total of 10 new thiazolidin-4-one derivatives of ferulic acid were investigated for their in vitro antioxidant activity. The most active compound 1i (R=2,3-diOH) proved to be about 4 times more active than ferulic acid and comparable to ascorbic acid in both antioxidant assays.

Microwave-assisted synthesis of novel 2H-chromene derivatives bearing phenylthiazolidinones and their biological activity assessment.

6-Hydroxy-2-oxo-2H-chromene-4-carbaldehyde (2), 6-chloro-2-oxo-2H-chromene-4-carbaldehyde (3) and 6-hydrazinyl-4-methyl-2H-chromen-2-one (5) were prepared as single-pharmacophore motif key intermediates. Compounds 2, 3 and 5 were incorporated in a series of multicomponent reactions (MCRs), under microwave assistance as well as conventional chemical synthesis processes, to afford a series of three and/or four-pharmacophoric-motif conjugates 8a,b, 11, 13, 16, 17, 19 and 20 in good yields. The newly synthesized compounds were characterized by IR, NMR, 13C-NMR, MS and elemental analyses. Finally the synthesized compounds have been screened for their biological activity whereupon they exhibited remarkable antimicrobial activity on different classes of bacteria and the fungus.

The novel dipeptidyl peptidase-4 inhibitor teneligliptin prevents high-fat diet-induced obesity accompanied with increased energy expenditure in mice.

Dipeptidyl peptidase-4 (DPP-4)-deficient mice exhibit prevention of obesity with increased energy expenditure, whereas currently available DPP-4 inhibitors do not induce similar changes. We investigated the impact of the novel DPP-4 inhibitor teneligliptin on body weight, energy expenditure, and obesity-related manifestations in diet-induced obese mice. Six-weeks-old C57BL/6N mice were fed a high-fat diet (60%kcal fat) ad libitum and administered teneligliptin (30 or 60mg/kg) via drinking water for 10 weeks. Mice fed a high-fat diet showed accelerated body weight gain. In contrast, compared with the vehicle group, the administration of teneligliptin reduced body weight to 88% and 71% at dose of 30mg/kg/day and 60mg/kg/day, respectively. Although there was no change in locomotor activity, indirect calorimetry studies showed that teneligliptin (60mg/kg) increased oxygen consumption by 22%. Adipocyte hypertrophy and hepatic steatosis induced by a high-fat diet were suppressed by teneligliptin. The mean adipocyte size in the 60-mg/kg treatment group was 44% and hepatic triglyceride levels were 34% of the levels in the vehicle group. Furthermore, treatment with teneligliptin (60mg/kg) reduced plasma levels of insulin to 40% and increased the glucose infusion rate to 39%, as measured in the euglycemic clamp study, indicating its beneficial effect on insulin resistance. We showed for the first time that the DPP-4 inhibitor prevents obesity and obesity-related manifestations with increased energy expenditure. Our findings suggest the potential utility of teneligliptin for the treatment of a broad spectrum of metabolic disorders related to obesity beyond glycemic control.

Microfluidics-based assessment of cell deformability.

Mechanical properties of cells have been shown to have a significant role in disease, as in many instances cell stiffness changes when a cell is no longer healthy. We present a high-throughput microfluidics-based approach that exploits the connection between travel time of a cell through a narrow passage and cell stiffness. The system resolves both cell travel time and relative cell diameter while retaining information on the cell level. We show that stiffer cells have longer transit times than less stiff ones and that cell size significantly influences travel times. Experiments with untreated HeLa cells and cells made compliant with latrunculin A and cytochalasin B further demonstrate that travel time is influenced by cell stiffness, with the compliant cells having faster transit time.

Determination of the active metabolite of moguisteine in human plasma and urine by LC-ESI-MS method and its application in pharmacokinetic study.

In this study, a sensitive and reproducible electro-spray ionization liquid chromatography-mass spectrometry (LC-ESI-MS) method was established to determine the concentration of M1, the main active metabolite of moguisteine in human plasma and urine. The analysis was performed on a Diamonsil® C18(2) column (150 mm × 4.6 mm, 5 µm) with the mobile phase consisting of 0.1% formic acid-acetonitrile (57:43, v/v, pH=3.0) at a flow rate of 0.8 mL min⁻¹. The pseudo-molecular ions [M+H]+ (m/z 312.2 for M1 and 446.3 for glipizide) were selected as the target ions for quantification in the selected ion monitoring (SIM) mode. Plasma samples were analyzed after being processed by acidification with formic acid and protein precipitation with acetonitrile. Urine samples were appropriately diluted with blank urine for analysis. Calibration curve was ranged from 0.02 to 8 µg mL⁻¹. The extraction recovery in plasma was over 90%. Both the inter- and intra-day precision values were less than 7.5%, and the accuracy was in the range from -6.0% to 6.0%. This is the first reported LC-ESI-MS method for analyzing M1 in human plasma and urine. The method was successfully applied to the pharmacokinetic study after oral administration of single-dose and multiple-dose of moguisteine tablets in healthy Chinese subjects.

Long-term clinical effects of epalrestat, an aldose reductase inhibitor, on progression of diabetic neuropathy and other microvascular complications: multivariate epidemiological analysis based on patient background factors and severity of diabetic neuropathy.

AIMS: The goal of the study was to evaluate the efficacy of epalrestat, an aldose reductase inhibitor, on diabetic retinopathy and diabetic nephropathy, based on analysis of the results of the Aldose Reductase Inhibitor-Diabetes Complications Trial, a 3-year multicentre comparative clinical trial of conventional therapy (control group) and epalrestat therapy (epalrestat group) in Japanese patients with mild diabetic neuropathy. METHODS: The subjects of the study were patients enrolled in the Aldose Reductase Inhibitor-Diabetes Complications Trial for whom data for major patient characteristics, severity of diabetic neuropathy at the end of the study and time-courses of diabetic retinopathy and diabetic nephropathy were available (57 and 52 patients from the control and epalrestat groups, respectively). Progression of diabetic retinopathy/nephropathy (a primary endpoint) in relation to major patient characteristics, severity of diabetic neuropathy at the end of the study (assessed from the mean of z-scores in four neurological function tests) and epalrestat treatment were analysed using univariate analysis and multiple logistic regression analysis. RESULTS: Progression of diabetic retinopathy/nephropathy was significantly inhibited in the epalrestat group compared with the control group (odds ratio = 0.323, P = 0.014) and was dependent on the severity of diabetic neuropathy at the end of the study (odds ratio = 2.131, P = 0.025). CONCLUSIONS: Epalrestat prevented progression of diabetic neuropathy and retinopathy/nephropathy. The effect on diabetic retinopathy/nephropathy may have occurred indirectly because of the prevention of progression of diabetic neuropathy, in addition to the inhibitory action of epalrestat on aldose reductase.

In vivo and in vitro assessment of the role of glutathione antioxidant system in anthracycline-induced cardiotoxicity.

The clinical usefulness of anthracycline antineoplastic drugs is limited by their cardiotoxicity. Its mechanisms have not been fully understood, although the induction of oxidative stress is widely believed to play the principal role. Glutathione is the dominant cellular antioxidant, while glutathione peroxidase (GPx) together with glutathione reductase (GR) constitutes the major enzymatic system protecting the cardiac cells from oxidative damage. Therefore, this study aimed to assess their roles in anthracycline cardiotoxicity. Ten-week intravenous administration of daunorubicin (DAU, 3 mg/kg weekly) to rabbits induced heart failure, which was evident from decreased left ventricular ejection fraction and release of cardiac troponins to circulation. However, no significant changes in either total or oxidized glutathione contents or GR activity were detected in left ventricular tissue of DAU-treated rabbits when compared with control animals. GPx activity in the cardiac tissue significantly increased. In H9c2 rat cardiac cells, 24-h DAU exposure (0.1-10 µM) induced significant dose-dependent toxicity. Cellular content of reduced glutathione was insignificantly decreased, oxidized glutathione and GR activity were unaffected, and GPx activity was significantly increased. Neither buthionine sulfoximine (BSO, glutathione biosynthesis inhibitor) nor 2-oxo-4-thiazolidine-carboxylic acid (OTC, glutathione biosynthetic precursor) had significant effects on DAU cytotoxicity. This contrasted with model oxidative injury induced by hydrogen peroxide, which cytotoxicity was increased by BSO and decreased by OTC. In conclusion, our results suggest that the dysfunction of glutathione antioxidant system does not play a causative role in anthracycline cardiotoxicity.

Impact of the socioeconomic status on the probability of receiving formulary restricted thiazolidine (TZDs).

BACKGROUND: In the province of Quebec, Canada, the reimbursement of thiazolidinediones (TZDs) is limited to patients who do not respond to doses of metformin and a sulfonylurea. OBJECTIVES: The objective of this research project was to study, in a real-life setting, the ârisk factorsâ for receiving these restricted drugs among patients who meet the reimbursement criteria. METHODS: Among patients eligible for drug coverage under the RAMQ between May 2000 and June 2005, we selected those who received six consecutive dispensations of high doses of both metformin and a sulfonylurea. The date of the sixth dispensation was set as the index date. The proportion of patients who received a TZD in the year following the index date was calculated and a logistic regression was used to estimate the impact of several factors on the probability of receiving a TZD. RESULTS: There were 4,836 patients in the cohort. A TZD was dispensed to 24.9% (95% CI: 23.7%;26.2%) of the patients. Compared to the oldest group of patients (65 years and more), the probability to receive a TZD was higher for patients aged 51 to 64 years (OR=1.33 95% CI: 1.11;1.59) and patients aged 19 to 50 years [OR=1.81 (95% CI: 1.40;2.33)]. Patients with the highest income were more likely to receive a TZD (OR=1.55 95% CI: 1.21;1.98) compared to patients with the lowest income. CONCLUSIONS: These findings suggest that the restricted access to TZDs probably results in social inequities, as individuals with lower incomes are less likely to receive these drugs. Key words: Restricted drugs, TZDs, diabetes.

Neutrophil-bead collision assay: pharmacologically induced changes in membrane mechanics regulate the PSGL-1/P-selectin adhesion lifetime.

Visualization of flowing neutrophils colliding with adherent 1-mum-diameter beads presenting P-selectin allowed the simultaneous measurement of collision efficiency (epsilon), membrane tethering fraction (f), membrane tether growth dynamics, and PSGL-1/P-selectin binding lifetime. For 1391 collisions analyzed over venous wall shear rates from 25 to 200 s(-1), epsilon decreased from 0.17 to 0.004, whereas f increased from 0.15 to 0.70, and the average projected membrane tether length, L(tether)(m), increased from 0.35 mum to approximately 2.0 mum over this shear range. At all shear rates tested, adhesive collisions lacking membrane tethers had average bond lifetimes less than those observed for collisions with tethers. For adhesive collisions that failed to form membrane tethers, the regressed Bell parameters (consistent with single bond Monte Carlo simulation) were zero-stress off-rate, k(off)(0) = 0.56 s(-1) and reactive compliance, r = 0.10 nm, similar to published atomic force microscopy (AFM) measurements. For all adhesion events (+/- tethers), the bond lifetime distributions were more similar to those obtained by rolling assay and best simulated by Monte Carlo with the above Bell parameters and an average of 1.48 bonds (n = 1 bond (67%), n = 2 (22%), and n = 3-5 (11%)). For collisions at 100 s(-1), pretreatment of neutrophils with actin depolymerizing agents, latrunculin or cytochalasin D, had no effect on epsilon, but increased L(tether)(m) by 1.74- or 2.65-fold and prolonged the average tether lifetime by 1.41- or 1.65-fold, respectively. Jasplakinolide, an actin polymerizing agent known to cause blebbing, yielded results similar to the depolymerizing agents. Conversely, cholesterol-depletion with methyl-beta-cyclodextrin or formaldehyde fixation had no effect on epsilon, but reduced L(tether)(m) by 66% or 97% and reduced the average tether lifetime by 30% or 42%, respectively. The neutrophil-bead collision assay combines advantages of atomic force microscopy (small contact zone), aggregometry (discrete interactions), micropipette manipulation (tether visualization), and rolling assays (physiologic flow loading). Membrane tether growth can be enhanced or reduced pharmacologically with consequent effects on PSGL-1/P-selectin lifetimes.