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Biomedical subjects

S Bhattacharya

Publications and source records attributed to S Bhattacharya.

At least 37 records · Page 2Linked to original sources
PubMed2005

In vitro fertilisation for unexplained subfertility.

BACKGROUND: In vitro fertilisation (IVF) is now a widely accepted treatment for unexplained infertility (RCOG 1998). However, with estimated live-birth rates per cycle varying between 13% and 28%, its effectiveness has not been rigorously evaluated in comparison with other treatments. With increasing awareness of the role of expectant management and less invasive procedures such as intrauterine insemination, concerns about multiple complications and costs associated with IVF, it is extremely important to evaluate the effectiveness of IVF against other treatment options in couples with unexplained infertility. OBJECTIVES: The aim of this review is to determine, in the context of unexplained infertility, whether IVF improves the probability of live-birth compared with (1) expectant management, (2) clomiphene citrate (CC), (3) intrauterine insemination (IUI) alone, (4) IUI with controlled ovarian stimulation, and (5) gamete intrafallopian transfer (GIFT). SEARCH STRATEGY: We searched the Cochrane Menstrual Disorders and Subfertility Group Trials Register (searched 23 March 2004), the Cochrane Central Register of Controlled Trials (Cochrane Library Issue 3, 2004), MEDLINE (1970 to August 2004), EMBASE (1985 to August 2004) and reference lists of articles. We also handsearched relevant conference proceedings and contacted researchers in the field. SELECTION CRITERIA: Only randomised controlled trials were included. Live-birth rate per woman was the primary outcome of interest. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed eligibility and quality of trials. MAIN RESULTS: Ten randomised controlled trials were identified. In two we could not extract data separately for unexplained infertility cases, two were non-randomised, one did not report valid rates (included in the review but not in the meta-analysis); leaving four trials for analysis. One trial compared two different interventions (IVF versus IUI with or without ovarian stimulation) and one study compared three interventions (IVF versus IUI with ovarian stimulation and GIFT). The numbers of trials assessing the effectiveness of IVF with the other treatments were as follows: IVF versus expectant management (two), IVF versus IUI (one), IVF versus IUI with ovarian stimulation (two) and IVF versus GIFT (three). Live-birth rate per woman was reported in three studies and three studies determined clinical pregnancy rate per woman. Multiple pregnancy rate was reported in three trials. Two studies reported ovarian hyperstimulation syndrome (OHSS) as an outcome measure. There were no comparative data for clomiphene citrate and no comparative data on live-birth rates for GIFT. There was no evidence of a difference in live-birth rates between IVF and IUI either without (OR 1.96; 95% CI 0.88 to 4.4) or with (OR 1.15; 95% CI 0.55 to 2.4) ovarian stimulation. There were significantly higher clinical pregnancy rates with IVF in comparison to expectant management (OR 3.24; 95% CI 1.07 to 9.80). There was no significant difference between IVF and GIFT for the one RCT that reported live-birth rates (OR 2.57; 95% CI 0.93 to 7.08). However, there was a significant difference in the clinical pregnancy rates between IVF and GIFT, with pregnancy rates greater for IVF (OR 2.14; 95% CI 1.08 to 4.2). There was no evidence of a difference in the multiple pregnancy rates between IVF and IUI with ovarian stimulation (OR 0.63; 95% CI 0.27 to 1.5), however, IVF had a higher rate than GIFT (OR 6.3; 95% CI 1.7 to 23). Clinical heterogeneity was present among the studies included. However, there was no evidence of statistical heterogeneity, which allowed the studies to be combined for statistical analysis. AUTHORS' CONCLUSIONS: Any effect of IVF relative to expectant management, clomiphene citrate, IUI with or without ovarian stimulation and GIFT in terms of live-birth rates for couples with unexplained subfertility remains unknown. The studies included are limited by their small sample size so that even large differences might be hidden. Live-birth rates are seldom reported. Periods of follow up are inadequate and unequal. Adverse effects such as multiple pregnancies and ovarian hyperstimulation syndrome have also not been reported in most studies. Larger trials with adequate power are warranted to establish the effectiveness of IVF in these women. Future trials should not only report rates per woman/couple but also include adverse effects and costs of the treatments as outcomes. Factors that have a major effect on these outcomes such as fertility treatment, female partner's age, duration of infertility and previous pregnancy history should also be considered.

Clomiphene↗
PubMed2005

A qualitative study of women's decision-making at the end of IVF treatment.

BACKGROUND: The decision not to pursue further in vitro fertilization (IVF) after one or more unsuccessful attempts is an important and often difficult one for couples. Relatively little is known about the woman's perception of this decision-making process. The aim of this study was to examine patients' perspectives of decision-making, including circumstances influencing it and satisfaction with the decision-making process. METHODS: Semi-structured interviews were conducted with a purposive sample of 25 women who had decided to end treatment after unsuccessful IVF treatment. Interviews were tape-recorded and transcribed by means of thematic analysis using the open coding technique. RESULTS: Women experienced difficulty in accepting that their infertility would remain unresolved. Many felt that they had started with unrealistic expectations of treatment success and felt vulnerable to the pressures of both the media and society. Although the decision to end treatment was difficult, it offered many women a way out of the emotional distress caused by IVF; however, the process of decision-making created a sense of 'confrontation' for the women in which they had to address issues they had previously avoided. Adoptive parents perceived less societal pressure than those who remained childless. CONCLUSIONS: Efforts to improve the psychological preparation of couples who decide to end IVF treatment should be directed towards examination of the existing system of consultation, which has certain limitations in terms of the quality of communication and the provision of post-treatment support. Further efforts to develop strategies, which facilitate the decision-making process, should be considered.

Adult↗
PubMed2005

Anti-ulcer activity of ethanol extract of Terminaliapallida Brandis. in Swiss albino rats.

Ethanol extract of Terminalia pallida Brandis. (EETP) was evaluated for its anti-ulcer activity against various models of ulcers, such as drug-induced ulcers, histamine-induced ulcers and ethanol-induced ulcers in Swiss albino rats. The EETP at the doses of 250 and 500 mg/kg per os (p.o.) exhibited significant protection against ulcers produced by indomethacin, histamine and the effect was comparable to that of the reference drug famotidine (30 mg/kg b.w) orally. The extract also afforded significant protection against ethanol-induced gastric ulceration. Meanwhile, EETP significantly lowered the elevated lipid peroxide level (thiobarbituric acid reactive substances (TBARS)) and restored the altered glutathione level in ethanol-induced gastric ulceration. The present investigation revealed that the EETP exhibited significant anti-ulcer activity by enhancing antioxidant potential of the gastric mucosa, thereby reducing mucosal damage.

Animals↗
PubMed2005

Decreased apoptosis in polyamine depleted IEC-6 cells depends on Akt-mediated NF-kappaB activation but not GSK3beta activity.

The PI3-kinase/Akt pathway promotes cell survival in many different cell types including intestinal epithelial cells. Increased AKT activation in polyamine depleted intestinal epithelial cells correlated well with the decrease in TNF-alpha-induced apoptosis. Increased Akt activation and GSK3beta (Ser 9) phosphorylation without significant effect on Bad (Ser136) phosphorylation indicate that Akt-mediated protection is independent of Bad phosphorylation but may depend on GSK3beta. Pretreatment of polyamine-depleted cells with LY294002 increased caspase-9 and caspase-3 activation and decreased basal levels of GSK-3beta phosphorylation. Inhibition of GSK3beta activity using AR-A014418 or lithium chloride or siRNA-mediated downregulation of its expression had no effect on apoptosis. Inhibition of PI3-kinase and over-expression of dominant negative Akt (DN-AKT), significantly increased apoptosis in polyamine depleted cells. DN-Akt expression reversed the protective effect of polyamine depletion on apoptosis. DN-Akt, as well as the PI3-kinase inhibitors, prevented Akt activation and subsequent translocation of NF-kappaB to the nucleus. Constitutively active Akt (CA-AKT) expression increased resistance to TNF-alpha-induced apoptosis. Constitutively active-Akt expression increased nuclear staining of NF-kappaB. Moreover, polyamine depletion of DN-Akt cells prevented basal and TNF-alpha-induced IkappaBalpha phosphorylation. Prevention of NF-kappaB activation in DN-IkappaBalpha-transfected cells increased apoptosis in control cells and restored it in polyamine-depleted cells to control levels. These data indicate that Akt regulates the mitochondrial pathway, preventing activation of caspase-9 and thereby caspase-3 via NF-kappaB and these effects are independent of GSK-3beta activity.

Androstadienes↗
PubMed2005

Immunological characterization of novel secreted antigens of Mycobacterium tuberculosis.

Proteins secreted by Mycobacterium tuberculosis are targets of host immune responses and as such are investigated for vaccine and immunodiagnostics development. Computer-driven searches of the M. tuberculosis H37Rv genome had previously identified 45 novel secreted proteins. Here, we report the characterization of these antigens in terms of specificity for the M. tuberculosis complex and the ability to induce human immune responses. BLAST homology searches and Southern hybridization identified 10 genes that were either specific for the M. tuberculosis complex or found in only two nontuberculous mycobacterial species of minor medical significance. Selected recombinant proteins were purified from Escherichia coli cells and tested for the ability to elicit antibody responses in tuberculosis patients. Reactivity of the serum panel was ' 36% with at least one of five novel proteins (Rv0203, Rv0603, Rv1271c, Rv1804c and Rv2253), 56% with the 38 kDa lipoprotein, a M. tuberculosis antigen known to be highly seroreactive, and 68% with a combination of Rv0203, Rv1271c and the 38 kDa antigen. Thus, at least five novel secreted proteins induce antibody responses during active disease; some of these proteins may increase the sensitivity of serological assays based on the 38 kDa antigen.

Antibodies, Bacterial↗
PubMed2005

Evaluation of endocervical, first-void urine and self-administered vulval swabs for the detection of Chlamydia trachomatis in a miscarriage population.

OBJECTIVE: To compare, in parallel, different approaches of opportunistically screening women with bleeding in early pregnancy for Chlamydia trachomatis. DESIGN: Prospective observational [corrected] study. SETTING: Early pregnancy assessment unit, University hospital, Scotland, UK. POPULATION: Over 200 consecutive women admitted to an early pregnancy assessment unit were recruited. All had a positive pregnancy test, a history of vaginal bleeding and were less than 24 weeks of gestation. Women with recent antibiotic use, heavy vaginal bleeding and cervical shock excluded. METHODS: Each women provided two or more of the following specimens: a self-administered vulval swab, first-void urine and/or endocervical swab. Following screening, each completed a semi-structured questionnaire assessing the acceptability of each method undertaken. MAIN OUTCOME MEASURE: Subjective rating of the screening methods; prevalence; method performance, including proportion requiring repeat testing. RESULTS: The majority accepted screening, with moderate prevalence rates (95% CI) 3.9% (2.0-7.4%) identified. All positive women were less than 30 years of age. Parallel screening exposed the potential of reduced test performance with urine. Non-invasive sampling was more acceptable, but more likely to require repeat testing. CONCLUSION: Both acceptability and the effect of bleeding on test performance need further assessment before a particular specimen can be recommended for screening this population of women for C. trachomatis.

Abortion, Spontaneous↗
PubMed2005

Primary mode of delivery and subsequent pregnancy.

OBJECTIVE: To investigate the relationship between primary mode of delivery and subsequent pregnancy and to compare the findings with a previous study conducted on an earlier cohort from the same population. DESIGN: Population cohort. SETTING: Aberdeen City, Scotland. POPULATION: Women who delivered their first singleton child in Aberdeen Maternity Hospital between 1980 and 1997. METHODS: Population-based data relating to the index and next pregnancy event, if any, were obtained from the Aberdeen Maternity Neonatal Databank. Subsequent pregnancy was compared across the three modes of delivery groups using log rank tests and Cox proportional hazards regression models. MAIN OUTCOME MEASURE: First subsequent pregnancy following index delivery. RESULTS: Women who delivered by caesarean section (CS) were less likely to have a subsequent pregnancy compared with those who had a spontaneous vaginal delivery (SVD), hazard ratio = 0.91 (95% CI 0.87, 0.95). This confirmed the findings of a previous study conducted on an earlier cohort of the same population. The median time to next pregnancy following CS was 36.3 months, 31.8 months following instrumental vaginal delivery (IVD) and 30.4 months following SVD. In contrast to the earlier study where women who had an instrumental delivery were found to be an intermediate group, we found no difference in subsequent pregnancy following IVD compared with SVD, HR = 1.0 (95% CI 0.96, 1.03). CONCLUSIONS: Following an initial delivery by CS, fewer women went on to have another pregnancy compared with SVD. The incidence of subsequent pregnancy is similar following instrumental and SVD.

Adult↗
PubMed2005

Blood culture in India: a proposal for a national programme for early detection of sepsis.

Septicaemia is a major contributor of mortality. Blood culture is the essential investigation for the management of sepsis. Due to lack of resources blood culture is an irregularly used investigation in India. A three-tier level of development is being proposed to develop the blood culture based national programme for early detection of sepsis. The plan envisages the establishment of manual blood culture based elementary system in the health centre and district hospital level (Level 1), direct Gram stain and direct antibiotic sensitivity testing from the "positive" blood culture broths at the medical college hospital level (Level 2) and development of automated methods, enhancement of quality control and safety measures, clinical liaison and re-orientation of microbiology training at the tertiary care centre level (Level 3).

Bacteremia↗
PubMed2005

Studies of the outbreaks of foot and mouth disease in West Bengal, India, between 1985 and 2002.

Foot and mouth disease (FMD) is the major disease constraint on international trade in livestock and their products. In the state of West Bengal, India, 1,082 FMD outbreaks were reported in the 18 years from 1985 to 2002. Of the prevalent four serotypes, O type FMD virus accounted for the most outbreaks (67%), followed by Asia-1 virus type (15%) and A virus type (14%). Outbreaks of the type C FMD virus were least prevalent (4%), and no cases have been recorded since 1996. The study shows clearly that incidences were highest during the winter months and in the alluvial agro-climatic zones. The distribution and density of the FMD-susceptible population in different districts of the state also played major role in disease incidences. Due to the unrestricted movements of animals among different cattle markets, the disease was transmitted either by direct contact or by aerosols from infected to healthy animals. Cattle suffered most from the disease, accounting for about 95% of the cases. The monitoring of the disease documented in this study provides information about the endemicity of the disease that can help to formulate an effective strategy for an FMD control programme.

Animals↗
PubMed2004

Number of embryos for transfer following in-vitro fertilisation or intra-cytoplasmic sperm injection.

BACKGROUND: The traditional reliance on the transfer of multiple embryos during in vitro fertilisation (IVF) in order to maximise the chance of pregnancy, has resulted in increasing rates of multiple pregnancies. Women undergoing IVF had a 20 - fold increased risk of twins and 400 - fold increased risk of higher order pregnancies (Martin 1998). The maternal and perinatal morbidity and mortality as well as national health service costs associated with multiple pregnancies is significantly high in comparison with singleton births (Luke 1992; Callahan 1994; Goldfarb 1996). Single embryo transfer is now being considered as an effective means of reducing this iatrogenic complication. This systematic review evaluates the effectiveness of elective two embryo transfer in comparison with single and more than two embryo transfer following IVF and ICSI (intra cytoplasmic sperm injection) treatment. OBJECTIVES: The aim of this review is to determine, whether in couples who undergo IVF/ICSI: (1) the elective transfer of two embryos improves the probability of livebirth compared with: (a) Single embryo transfer, (b) Three embryo transfer or (c) Four embryo transfer.(2) the elective transfer of three embryos improves the probability of livebirth compared with: (a) Single embryo transfer, or (b) Four embryo transfer, SEARCH STRATEGY: We searched the Cochrane Menstrual Disorders and Subfertility Group's trials register (searched June 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 4, 2003), MEDLINE (1970 to 2003), EMBASE (1985 to 2003) and reference lists of articles. We also handsearched relevant conference proceedings and contacted researchers in the field. SELECTION CRITERIA: Only randomised controlled trials were included. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed eligibility and quality of trials. MAIN RESULTS: We found no studies that compared a policy of transferring multiple embryos on one cycle versus a policy of cryo- preservation and transfer of a single embryo over multiple cycles. We also found no trials comparing transfer of two versus three embryos. Three small, poorly reported trials compared transfer of two versus one embryo in a single cycle, and one small, poorly reported trial compared transfer of two versus four embryos in a single cycle. The clinical pregnancy rate per woman/couple associated with two embryo transfer was significantly higher compared to single embryo transfer (OR 2.08, 95% CI 1.24 to 3.50; test for overall effect p = 0.006). The live birth rate per woman/couple associated with two embryo transfer was also significantly higher than that associated with single embryo transfer (OR 1.90, 95% CI 1.12 to 3.22, test for overall effect p=0.02). The multiple pregnancy rate was significantly lower in women who had single embryo transfer (OR 9.97, 95% CI 2.61 to 38.19; p = 0.0008). The effectiveness of double embryo transfer versus four embryo transfer was tested in a single trial. There was no statistically significant differences in the clinical pregnancy rate (OR 0.75, 95% CI 0.26 to 2.16; p=0.6), and multiple pregnancy rates (OR 0.44. 95% CI 0.10 to 1.97; p = 0.28) between the two groups. The livebirth rate in the four embryo transfer group was higher compared to the two embryo transfer group, but the results were not statistically significant (OR 0.35, 95% CI 0.11 to 1.05; p = 0.06). REVIEWERS' CONCLUSIONS: The results of this systematic review suggest that live birth and pregnancy rates following single embryo transfer are lower than those following double embryo transfer as are the chances of multiple pregnancy including twins. As such, it is unlikely that the conclusions are robust enough to catalyse a change in clinical practice. The studies included are limited by their small sample size, so that even large differences might be hidden. Cumulative livebirth rates are seldom reported. The data were inadequate to draw conclusions about single embryo transfer and first frozen single embryo transfer (1FZET) or subsequent single frozen embryo transfers. Until more evidence is available single embryo transfer may not be the preferred choice for all patients undergoing IVF/ICSI. Clinicians may need to individualise protocols for couples based on their risks of multiple pregnancy. A definitive pragmatic, large multi centre randomised controlled trial comparing single embryo versus double embryo transfer in terms of clinical and cost effectiveness as well as acceptability is required. The primary outcome measured should be cumulative livebirth per woman/couple.

Embryo Transfer↗
PubMed2004

A randomized comparison of alternative methods of information provision on the acceptability of elective single embryo transfer.

BACKGROUND: The purpose of this study was to assess the effect of alternative ways of providing information about the risks of twins on couples' perceptions about elective single embryo transfer (eSET). METHODS: Couples undergoing IVF were randomized into three groups. Group 1 received a standard information pack, group 2 an extra information leaflet about twin pregnancy, and group 3 an additional discussion session. The primary outcome measure was acceptability of a hypothetical policy of eSET. Data were collected by means of a questionnaire. RESULTS: eSET was acceptable to 17 (27%), 20 (30%) and 24 (32%) couples in groups 1, 2 and 3, if it meant a slight reduction in pregnancy rates, and to 51 (82%), 55 (83%) and 53 (87%) couples, respectively, if pregnancy rates were unchanged. A fixed charge for all fresh and frozen embryo transfers following a single oocyte retrieval led to acceptability rates of 35 (57%), 36 (55%) and 38 (65%). CONCLUSIONS: Additional information, involving an extra information leaflet and face to face discussion, did not changes couples' attitudes towards eSET. Maintaining existing rates of pregnancy and offering a fixed charge for all embryo transfers resulting from an oocyte recovery may encourage more couples to consider eSET.

Embryo Transfer↗
PubMed2004

Anatomical variations of the splenic artery and its clinical implications.

The variations in orgin, course, and terminal branching pattern of the splenic artery were studied in 320 cadavers. The artery originated from the coeliac trunk in the majority of cadavers (90.6%), followed by abdominal aorta (8.1%), and other sights (1.3%). A suprapancreatic course of the artery was commonly observed (74.1%) followed by enteropancreatic (18.5%), intrapancreatic (4.6%), and retropancreatic (2.8%) courses. In two cases (0.63%) the proximal part of the splenic artery made a loop that was embedded in the substance of the pancreas, which is an interesting and rare finding. In five cases (1.5%) the proximal part of the artery divided into two or more branches that had suprapancreatic and enteropancreatic courses. The splenic artery divided into terminal branches in 311 (97%) cadavers. In nine (2.8%) cadavers it passed through the hilum of spleen without dividing. Two terminal branches were the most common (63.1%) followed by four (18.8%), six (9.7%), and more than six (5.6%) branches. The present study clearly indicates that there is variation in origin, course, and terminal distribution pattern of the splenic artery. The knowledge of these variations are of significant importance during surgical and radiological procedure of upper abdominal region to avoid any catastrophic complications.

Aorta, Abdominal↗
PubMed2004

A new self-tuned PID-type fuzzy controller as a combination of two-term controllers.

The present paper is a venture into the domain of proportional-integral-derivative (PID) -type adaptive fuzzy logic controllers (FLC's) and proposes a new algorithm which is realized by a self-tuned PI-type FLC (in velocity form) in parallel with a self-tuned PD-type FLC (in position form). Each of these PI/PD controllers implements a supervisory static FLC for adaptive online modification of the output scaling factor (SF) of a static PI/PD FLC. The proposed scheme is developed with a view to having a PID-type FLC with an architecture, simple enough for practical implementation, which at the same time has substantially satisfactory performance for a wide class of processes. Simulation studies on a range of processes reveal that the proposed controller has better performance compared to many of its existing counterparts.

Journal Article↗
PubMed2004

Women's perceptions of decision-making about hysterectomy.

OBJECTIVE: To explore women's views of decision-making relating to hysterectomy. DESIGN: Structured questionnaire and in-depth interview surveys. SETTING: A teaching hospital and a district general hospital in northeast Scotland. SAMPLE: Women scheduled for hysterectomy for benign menstrual problems. METHODS: Pre-operative questionnaires were sent to a consecutive sample of women booked for hysterectomy. A purposive sample was interviewed post-operatively. MAIN OUTCOME MEASURES: Women's experiences of, and satisfaction with, information provision, communication and decision-making processes; the relationship between views of decision-making processes and decisions made. RESULTS: One hundred and four women (66%) returned questionnaires. Most responded positively to structured questions about the process by which the decision to have a hysterectomy was reached. Almost all (97%) reported satisfaction with the decision made. Twenty women were interviewed post-operatively. A number, including some who had responded positively on the questionnaire, described aspects of the decision-making process that were suboptimal. Women's perceptions of the decision-making process, including the way their doctors communicated with them, did impinge on their views of the course of action selected. Some women had residual doubts about the appropriateness of hysterectomy. CONCLUSIONS: In a significant minority of women, there are important shortcomings in current patterns of information provision and communication relating to decision-making. These are unlikely to be picked up by conventional structured patient feedback surveys. Further efforts are required to ensure that women are adequately informed and involved in decisions about gynaecological treatments.

Adult↗
PubMed2004

Inhibition of DMBA/croton oil-induced two-stage mouse skin carcinogenesis by diphenylmethyl selenocyanate.

Selenium, an essential micronutrient, is associated with antioxidant functions, physiological defence mechanisms against different diseases including several types of cancers. Search for new selenium compounds with more chemopreventive activities and lesser toxicities are in progress. In the present study, the antioxidative roles of a synthetic organoselenium compound, diphenylmethyl selenocyanate, were evaluated against 7,12-dimethylbenz(a)anthracene (DMBA)/croton oil-induced two-stage mouse skin carcinogenesis model. The compound was administered orally in carcinogen-induced mice in two different non-toxic doses: 2 mg/kg body weight and 3 mg/kg body weight. Significant inhibition in the incidence of papilloma formation (58-80%) as well as in the cumulative number of papilloma per papilloma-bearing mouse were observed in the treated groups as compared with the carcinogen control group. The compound was also found to significantly upregulate different phase II detoxifying enzymes in liver cytosol such as glutathione-S-transferase (P<0.01), catalase (P<0.01) and superoxide dismutase (SOD) (P<0.01) when measured after 15 days and also after 12 weeks of first DMBA treatment. Lipid peroxidation measured as the thiobarbituric acid reactive substances in liver microsomes was significantly inhibited (P<0.05) in a dose-dependent manner by diphenylmethyl selenocyanate. Thus the compound exerts its chemopreventive activity by reducing papilloma formation during chemically induced carcinogenesis, which in turn, may be through modulating the level of lipid peroxidation and phase II detoxifying enzyme system at the doses evaluated.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2004

Dynamics of membrane nanotubulation and DNA self-assembly.

A localized point-like force applied perpendicular to a vesicular membrane layer, using an optical tweezer, leads to membrane nanotubulation beyond a threshold force. Below the threshold, the force-extension curve shows an elastic response with a fine structure (serrations). Above the threshold the tubulation process exhibits a new reversible flow phase for the multilamellar membrane, which responds viscoelastically. Furthermore, with an oscillatory force applied during tubulation, broad but well-resolved resonances occur in the flow phase, presumably matching the time scales associated with the vesicle-nanotubule coupled system. These nanotubules, anchored to the optical tweezer also provide, for the first time, a direct probe of the real-time dynamics of DNA self-assembly on membranes. Our studies are a step in the direction of analyzing the dynamics of membrane self-assembly and artificial nanofluidic membrane networks.

Biosensing Techniques↗