Aspiration Pressure Research Articles

The assessment of oocyte retrieval and blastocyst formation by changing the aspiration pressure in women undergoing in an in vitro fertilization

We have recently developed a fine (23G) needle for follicular aspiration, instead of 22G needle, for pain-less and complication-less oocyte retrieval. We optimized the follicle aspiration pressure and tested whether the use of 23G needle improves blastocyst formation rate.

Silicon chips detect intracellular pressure changes in living cells

The ability to measure pressure changes inside different components of a living cell is important, because it offers an alternative way to study fundamental processes that involve cell deformation. Most current techniques such as pipette aspiration, optical interferometry or external pressure probes use either indirect measurement methods or approaches that can damage the cell membrane. Here we show that a silicon chip small enough to be internalized into a living cell can be used to detect pressure changes inside the cell. The chip, which consists of two membranes separated by a vacuum gap to form a Fabry-Pérot resonator, detects pressure changes that can be quantified from the intensity of the reflected light. Using this chip, we show that extracellular hydrostatic pressure is transmitted into HeLa cells and that these cells can endure hypo-osmotic stress without significantly increasing their intracellular hydrostatic pressure.

The Effect of Aspiration Pressure Over Endobronchial Ultrasound-Guided Transbronchial Needle Aspiration on the Diagnosis of Intrathoracic Lymphadenopathies

Data regarding the effect of aspiration pressure over endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) on the diagnosis of intrathoracic lymphadenopathies is limited. The aim of this study was to compare the effect of three levels of aspiration pressure over EBUS-TBNA on the diagnostic yield and numbers of diagnostic cells. A prospective study was conducted on 66 patients with enlarged intrathoracic lymph nodes. Three levels of aspiration pressure (0, 20, and 40 mL) were applied after the needle pierced the target and the needle's position was confirmed by EBUS images. The diagnostic yield and the numbers of diagnostic cells attained with each pressure from the same target were compared. The cellularity of the obtained diagnostic cells was classified into four grades (inadequate, minimal, moderate, and numerous) by a cytopathologist in a blinded study. The mean nodal size was 19.1 ± 6.2 mm. The final diagnoses included 53 malignant and 13 benign lymphadenopathies. Adequate lymph node samples were obtained in 63 patients (95.5%), and EBUS-TBNA revealed definite diagnosis for 58 patients (87.9%). Negative pressure of 40 mL provided a diagnostic yield similar to that of 20 mL (83.3 vs. 75.8%; p = 0.23), but both showed higher diagnostic yields than zero pressure. In terms of cellularity of the specimen, however, high negative pressure (40 mL) gave higher numbers of adequate cells than the comparators (p < 0.001). Negative pressure should be applied in an EBUS-TBNA procedure. Although the diagnostic yield was not different, high negative pressure was superior to low negative pressure in obtaining numbers of adequate cells.

The Effect of Pressure and Shear on Autologous Fat Grafting

Fat grafting has become routine in plastic surgery because of low donor-site morbidity, a low complication rate, and fast recovery time. The optimal technique, however, has yet to be defined. Two critical variables are pressure and shear, both defined as force divided by area. In this study, the authors examined the effect of pressure and shear on human fat grafts in a nude mouse model. For negative pressure, tumescent liposuction was performed on fresh panniculectomy specimens. Suction pressure was either -15 inHg or -25 inHg. Lipoaspirate was centrifuged at 1200 g and injected into the flanks of nude mice. For positive pressure, positive pressure was applied to lipoaspirate up to 6 atm for up to 3 minutes and then injected into nude mice. For shear stress, lipoaspirate was centrifuged at 1200 g for 3 minutes and then injected with a fast flow rate (3 to 5 cc/second) or slow flow rate (0.5 to 1 cc/second). After 4 weeks, the fat grafts were analyzed for weight and histology. For negative pressure, there were no differences in weight or histology with high versus low suction pressures. For positive pressure, application of positive pressures up to 6 atm for up to 3 minutes did not create a significant difference in graft weight or histology at 4 weeks. For shear stress, in vivo, a slow injection pressure yielded a 38 percent increase in weight (p < 0.001) compared with fast injection. Histology was similarly affected. Higher aspiration pressures up to -0.83 atm did not affect fat graft viability in vivo. Positive pressure up to 6 atm also did not affect fat graft viability. The degree of shear stress, which is a function of flow rate, did significantly affect fat graft viability. Fat grafts injected slowly with low shear stress significantly outperformed fat injected with high shear stress. These data suggest that shear stress is a more important variable regarding fat graft viability than pressure.

Selected Abstracts from the Voice of Europe Session of the 5th Annual Congress of the EASAPS

S EXPERIMENTAL/SPECIAL TOPICS Selected Abstracts from the Voice of Europe Session of the 5th Annual Congress of the EASAPS (Editorial Coordinator Cristino Suarez Lopez de Vergara) Kemal Findikcioglu • Radu Ionescu • Nicolae Antohi • Tiberiu Bratu • Dana Jianu • Maria Filipescu • Doru Chirita • Jesus Benito-Ruiz • Jose Carlos Parreira • Paul Harris • Reza Nassab • James Southwell-Keely • Rajiv Grover • Barry Jones • Cristino Suarez Lopez de Vergara Published online: 16 April 2013 Springer Science+Business Media New York and International Society of Aesthetic Plastic Surgery 2013 The Hinderer Award Winner 2012 The Impact of Breast Reduction Surgery on the Vertebral Column Kemal Findikcioglu (Gazi Universitesi Tip Fakultesi Plastik Rekonstruktif ve Estetik Cerrahi A.D. Turkey. email: kemaldoctor@yahoo.com) Background: Although many studies have shown that breast reduction surgery is effective in reducing neck, back and lumbar pain; most of these studies are subjective evaluations that usually provide data through pain scales. This study was undertaken to objectively evaluate the radiologic effects of breast reduction on the vertebral column. Methods: Thirty breast reduction patients were included in the study. A lateral thoracolumbar radiograph was taken preoperatively and three months postoperatively for each patient. The thoracic kyphosis, lumbar lordosis and sacral inclination angles were measured for each radiograph. The impact of breast reduction surgery on posture was evaluated according to the comparison of these angles preoperatively and postoperatively. Effect of the age, BMI and the total amount of removed tissue was also taken into account and the relationship between these parameters and their effects on the change in preoperative and postoperative angle measurements were evaluated. Results: There was a significant decrease in all three angles after breast reduction surgery. A significant correlation was determined between BMI and the total amount of removed tissue on the change in angle measurements while a definite relationship was not observed between the angles and the patient’s age. Conclusion: This study has shown the objective impact that breast reduction surgery has on the vertebral column. Even though the symtomatic relief of breast reduction surgery on the musculoskeletal system is widely accepted, the objective assessment of this relief will be beneficial in persuading health insurance companies and those who think of this surgery as a purely aesthetic procedure. Junior Section—Young Investigator Winner Stromal Vascular Fraction Isolation Manual Protocol: A Cheap and Easy Way of Controlling the Production of Adipose-Derived Stem Cells Authors: Radu Ionescu MD, Nicolae Antohi MD, Tiberiu Bratu MD FAT!!! and the discovery of adipose-derived stem cells put the plastic surgery in the front line of new frontiers of science, the place where we, with our ability for public relation and safeness of good practicing in lipotransfer, we develop a powerful marketing tool, maybe too powerful, performing this type of surgery with a certain lack of knowledge and scientific data, fact that can make the ADRC research to be estompated by a increased number of questions concerning the safety and efficacy of Adipose-Derived Stem Cells treatments. The main objective of this work is to standard the protocol of: Fat harvesting, SVF preparation, and Lipotransfer. Fat harvesting have to be performed using low aspiration pressure 0.35 bar, cannula of maximum 3 mm, tumescent or super wet, buffer solution for infiltration—with low dosage of xyline at 37 Celsius (see photo 1). Preparation of SVF is performed in the operation room on using GMP devices and drugs, in approx. 60 min, on a standard protocol of 9 steps (see photo 2). Collagenase is Serva NB6 a GMP approved, and K. Findikcioglu R. Ionescu N. Antohi T. Bratu D. Jianu M. Filipescu D. Chirita J. Benito-Ruiz J. C. Parreira P. Harris R. Nassab J. Southwell-Keely R. Grover B. Jones C. S. L. de Vergara (&) Santa Cruz de Tenerife, Avenida de la Asuncion, 30 2nd, 38007 Tenerife, Spain e-mail: cristinosuarez@gmail.com 123 Aesth Plast Surg (2013) 37:602–604 DOI 10.1007/s00266-013-0106-4

Abstract 3766: Mechanical properties of cancer cells: a possible biomarker for stemness.

Abstract There is evidence that mechanical properties and deformability can be used as a biomarker to distinguish between healthy and cancerous cells. A number of biophysical techniques such as atomic force microscopy (AFM), and optical tweezers have been used to measure the mechanical properties of cancer cells. Deformability of a whole cell, which depends on the properties of the cytoplasm, the cytoskeleton and the nucleus, can be defined in terms of the strain response of the cell to an applied stress. Two different cell mechanical behaviors have been observed: 1) circulating white blood cells behave as liquid drops with a cortical tension; 2) most tissue cells behave as viscoelastic solids. In this study, micropipette aspiration was used to investigate deformability differences between two breast cancer cell lines: BT-20 and Hs578T. Hs578T breast cancer cells have been reported to have a stem-like phenotype, whereas BT-20 cells are more recognized as being non-stem-like. Cancer cells were aspirated one-by-one at controlled pressures into small glass micropipettes with radius, Rp, while the length of the aspirated section of the cell inside the micropipette, L, was measured. Two different aspiration procedures have been developed: 1) ramp test and 2) creep test. In the ramp test, suction pressure was increased linearly using a syringe pump, while for the creep test, the pressure was increased rapidly and then kept constant during the experiment. Using the ramp test, graphs of cell deformation (L/Rp) versus applied pressure, showed a linear trend for small deformations for both BT-20 and Hs578T cells, while for large deformations, the graphs were no longer linear. One explanation for this, was that above a deformation threshold the cells were exhibiting liquid-like behavior. This was tested using a constant aspiration pressure in the creep test. It was seen that half of the cells fully entered the micropipettes at constant pressure, a character of liquid drops, while the rest reached an equilibrium position, which implies a viscoelastic behavior for the cells. It could be concluded that for small deformations, cells mostly have solid-like behavior, while for large deformations they could exhibit liquid-like or viscoelastic behaviors. We also found that stem-like cancer cells are softer than non-stem-like cells with no significant differences between the mechanical properties of their cytoplasmic and nuclear regions, which allows them to deform more easily while undergoing extravasation and intravasation processes during metastasis. Our hypothesis is that the stem-like or non-stem-like phenotype of cancer cells is correlated with differences in mechanical properties. If these differences are significant enough, mechanical properties could be used as a biomarker for stemness of cells, which could eventually lead to a new diagnostic method in cancer research. This work was supported by grant CBET-1106118 from the National Science Foundation. Citation Format: Ameneh Mohammadalipour, Fabian Benencia, Monica M. Burdick, David F. J. Tees. Mechanical properties of cancer cells: a possible biomarker for stemness. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3766. doi:10.1158/1538-7445.AM2013-3766

Minimally invasive vitreo retinal surgery: How small do we go?

The armamentarium of vitreo retinal surgeons has advanced tremendously with advances in physics and now the focus is on the maximum benefit that can be derived using micro incisions. The 23-G and 25-G systems have become fairly common and several studies have been done to determine the safety, advantages and disadvantages of small gauge sutureless surgery.[1] Though higher infusion and aspiration pressures are needed to remove the vitreous using small gauge probes, the corresponding damage on tissues is also substantially lower. My own experience with the small gauge vitrectomy system encouraged me to embrace this advancement in totality. My experience shows that the smaller gauge vitrectomy techniques shorten operating time and improve patient comfort. By minimizing surgically induced trauma, it decreases the post-operative inflammatory response and hastens recovery. Although higher pressures are needed for injection of silicon oil especially the heavy oil, the overall outcomes are much better. Various surgical procedures have been performed with microincision vitrectomy surgery (MIVS) but it is being advocated for macular holes and epiretinal membrane (ERM) surgery. Sandali et al. in their study[2] concluded that in ERM surgery 23-G and 25-G systems are as safe and effective as the 20-G system. They also noted that MIVS systems cause significant reduction in surgical time. Similar results have been reported by Haas et al.[3] I prefer a proportional mode vitrectomy for the separation of the membrane from the retina and it has given me excellent results. Concerns have been raised about the increased risk of endophthalmitis with 23-G and 25-G instrumentation. Oshima et al. in their study Multicenter survey with a systematic overview of acute-onset endophthalmitis after transconjunctival MIVS[4] found no significant difference in the incidence of post vitrectomy endophthalmitis between MIVS and 20-G vitrectomy similar results were observed by Bahrani et al.[5] Our experience is also similar as there have been no differences between the 20-G and MIVS in incidence of post-operative endophthalmitis. Nevertheless, the microsurgical task force came up with guidelines for minimizing endophthalmitis with vitrectomy surgery.[6] The advent of the 27-G instrument system, has given a totally new dimension to microsurgery.[7] For obvious reasons the fluid dynamics of the 27-G system are lower than 25-G MIVS. The pros and cons of the small gauge system will have to be weighed to decide how small we can go. The desired goal of surgery is to achieve optimal surgical results with minimal damage. Optimal utilization of the newer properties of machines in relation to the characteristics of the disease will have to be assessed to decide the risk benefit ratio of the MIVS system.[8] The risk of instrument bending, leading to lower stability and reduced cutting efficiency is a point for concern. This needs to be compared with improved wound healing and finer surgical results in select cases. I look at the future where further advances in technology will obviate the risks associated with the smaller gauge.

Mechanics of membrane–cytoskeleton attachment in Paramecium

In this paper we assess the role of the protein MKS1 (Meckel syndrome type 1) in the cortical membrane mechanics of the ciliated protist Paramecium. This protein is known to be crucial in the process of cilium formation, and we investigate its putative role in membrane–cytoskeleton attachment. Therefore, we compare cells where the gene coding for MKS1 is silenced to wild-type cells. We found that scanning electron microscopy observation of the cell surface reveals a cup-like structure in wild-type cells that is lost in silenced cells. Since this structure is based on the underlying cytoskeleton, one hypothesis to explain this observation is a disruption of membrane attachment to the cytoskeleton in the absence of MKS1 that should affect plasma membrane mechanics. We test this by probing the mechanics of wild-type and silenced cells by micropipette aspiration. Strikingly, we observe that, at the same aspiration pressure, the membrane of silenced cells is easily aspirated by the micropipette whereas that of wild-type cells enters only at a moderate velocity, an effect that suggests a detachment of the membrane from the underlying cytoskeleton in silenced cells. We quantify this detachment by measuring the deformation of the cell cortex and the rate of cell membrane entry in the micropipette. This study offers a new perspective for the characterization of membrane–cytoskeleton attachment in protists and paves the way for a better understanding of the role of membrane–cortex attachment in cilium formation.

The Effect of Pressure and Shear on Fat Grafting

INTRODUCTION: Fat grafting has become routine in Plastic surgery due to low donor site morbidity, low complication rate, and fast recovery time. Two critical variables are pressure and shear, both defined as force divided by area. In this study, we examined the role of pressure and shear on human fat grafts in a nude mouse model. METHODS: Negative Pressure: Liposuction was performed in the laboratory on panniculectomy specimens. Suction pressure was either -15 inches Hg (-0.5 atmosphere) or -25 inches Hg (-0.83 atmosphere). Lipoaspirate was centrifuged at 1200G and injected into the flanks of nude mice. Positive Pressure: Lipoaspirate was obtained and positive pressure was applied up to 6 atmospheres for up to 3 minutes and then injected into nude mice. Shear Stress: Lipoaspirate was centrifuged at 1200G for 3 minutes and then injected at two different speeds: fast flow rate (3-5 cc/sec) versus slow flow rate (0.5-1 cc/sec). After 4 weeks, the fat grafts were analyzed for weight and histology. RESULTS: Negative Pressure: There were no differences in weight or histology with high versus low suction pressures. Positive Pressure: Application of positive pressures up to 6 atmospheres for up to 3 minutes did not create a significant difference in graft weight or histology at 4 weeks. Shear Stress: In vivo, a slow injection pressure yielded a 38% increase in weight (p<0.001) compared to fast injection. Histology was similarly affected. CONCLUSION: Higher aspiration pressures up to -0.83 atm did not affect fat grafts viability in vivo. Positive pressure up to 6 atmospheres over time (up to 3 minutes) also did not affect fat graft viability. The degree of shear stress, which is a function of flow rate, did significantly affect fat graft viability. Fat grafts injected slowly with low shear stress significantly outperformed fat injected with high shear stress.

The Impact of Liposuction Cannula Size on Adipocyte Viability

Autologous fat transfer ("fat grafting") is widely used in cosmetic and reconstructive surgery, but long-term outcomes remain inconsistent. Each step in the transfer process can cause mechanical damage to the graft tissue. In particular, liposuction breaks aspirated adipose tissue into distinct globules and subjects it to shear forces, both of which can impact subsequent fat graft viability. The optimal size of the liposuction cannula for use in fat grafting is not known. METHODS AND TECHNIQUES: Controlled lipoaspirate samples were collected from adult female patients undergoing elective liposuction of the abdomen and flanks with uniform aspiration pressure (-25 in Hg) and either a 3- or 5-mm standard blunt-tip liposuction cannula. Individual grafts of 1.00±(0.01) gram were prepared and injected into the bilateral flanks of nude mice with a 14-gauge catheter. After six weeks, these grafts were explanted and analyzed by weight and histology. At six weeks, fat lobules in the 5-mm group retained 25% more weight than those in the 3-mm group [mean (SD), 0.70 (0.07) vs 0.56 (0.09) g, n=24/group, P<0.01). Histologic analysis revealed more intact, nucleated adipocytes in the 5-mm group than in the 3-mm group [4.42 (0.92) vs 3.10 (0.56) on a 1-5 rating scale]. The 5-mm group exhibited both less infiltrate [1.58 (0.17) vs 3.13 (0.70)] and less fibrosis [1.67 (0.45) vs 3.13 (0.89)] than the 3-mm group. In this controlled model of fat grafting with either a 5- or 3-mm aspiration cannula, the use of a larger aspiration cannula led to improved graft retention and quality. This finding has important implications for clinical applications of fat grafting.

Viscoelastic Cell Mechanics and Actin Remodelling Are Dependent on the Rate of Applied Pressure

BackgroundLiving cells are subjected to external and internal mechanical stresses. The effects of these stresses on the deformation and subsequent biological response of the cells remains unclear. This study tested the hypothesis that the rate at which pressure (or stress) is applied influence the viscoelastic properties of the cell associated with differences in the dynamics of the actin cytoskeleton.Principal FindingMicropipette aspiration was used to determine the instantaneous and equilibrium moduli and the viscosity of isolated chondrocytes based on the standard linear solid (SLS) model and a variation of this incorporating Boltzmann superposition. Cells were visualised for 180 seconds following aspiration to 7 cmH2O at 0.35, 0.70 and 5.48 cmH2O/sec. Cell recovery was then examined for a further 180 seconds once the pressure had been removed. Reducing the rate of application of pressure reduced the levels of cell deformation and recovery associated with a significant increase in modulus and viscosity. Using GFP transfection and confocal microscopy, we show that chondrocyte deformation involves distortion, disassembly and subsequent reassembly of the cortical actin cytoskeleton. At faster pressure rates, cell deformation produced an increase in cell volume associated with membrane bleb formation. GFP-actin transfection inhibited the pressure rate dependent variation in cell mechanics indicating that this behaviour is regulated by GFP-sensitive actin dynamics.ConclusionWe suggest that slower rates of aspiration pressure enable greater levels of cortical actin distortion. This is partially inhibited by GFP or faster aspiration rates leading to membrane bleb formation and an increase in cell volume. Thus the rate of application of pressure regulates the viscoelastic mechanical properties of living cells through pressure rate sensitive differences in actin dynamics. Therefore cells appear softer when aspirated at a faster rate in contrast to what is expected of a normal viscoelastic material.

Neutrophil motion in straight and tapering P‐selectin‐coated in vitro models of lung capillaries

Neutrophil sequestration in lung capillaries is a key step in the inflammatory response to lung infection. Neutrophils were aspirated into capillary‐sized glass microvessels of varying diameters and taper rates coated with soluble P‐selectin or BSA. Cell velocity distributions were measured for pressure differences thought to be present across single pulmonary capillary segments. A creeping motion was observed with velocity significantly lower on P‐selectin than BSA, and that decreased with increasing P‐selectin concentration. The gap width between neutrophil surface and microvessel wall decreased with increasing concentration of P‐selectin while the force exerted by the bonds on the cell increased. It was also shown that high concentrations of anti‐P‐selectin F(ab&amp;#900;)2 were effective to inhibit the P‐selectin mediated adhesion. These results demonstrate that even low densities of P‐selectin mediate neutrophil adhesion in the pulmonary capillary geometry. No mechanical arrest of neutrophils was observed in tapering vessels with taper angles of up to 9°, however, there is a transition point where cells slow down drastically, that does not depend on the P‐selectin concentrations, taper rate, or aspiration pressure. These results suggest that neutrophil arrest is primarily influenced by adhesion rather than mechanical trapping. This work was supported by grant BES‐0547165 from the NSF.

Investigation of mechanical properties of breast cancer cells using micropipette aspiration technique

Characterization of the mechanical properties of cancer cells is a promising diagnostic method for recognizing cancerous cells in the very early stages of the disease. In this study, the micropipette aspiration technique was used to investigate deformability differences between two types of breast cancer cell line: BT‐20 and Hs578T. Hs578T breast cancer cells have been reported having stem cell‐like properties, whereas BT‐20 cells are more recognized as non‐stem cell‐like cancer cells. Using a controlled aspiration pressure, a cancer cell was aspirated into a small glass micropipette while the length of the aspirated section of the cell inside the micropipette was measured. For a solid‐like cell, the Young's modulus can be calculated from the slope of a pressure versus aspiration length graph. The Hs578T cell line was found to have a Young's modulus larger than that of the BT‐20 cell line. This supports our hypothesis that the technique can be used for the characterization of cancer cells by their mechanical properties, which could lead to a new method of detecting circulating tumor cells. This work was supported by grant CBET‐1106118 from the National Science Foundation.

Mechanical characterization of adult stem cells from bone marrow and perivascular niches

Therapies using adult stem cells often require mechanical manipulation such as injection or incorporation into scaffolds. However, force-induced rupture and mechanosensitivity of cells during manipulation is largely ignored. Here, we image cell mechanical structures and perform a biophysical characterization of three different types of human adult stem cells: bone marrow CD34+ hematopoietic, bone marrow mesenchymal and perivascular mesenchymal stem cells. We use micropipette aspiration to characterize cell mechanics and quantify deformation of subcellular structures under force and its contribution to global cell deformation. Our results suggest that CD34+ cells are mechanically suitable for injection systems since cells transition from solid- to fluid-like at constant aspiration pressure, probably due to a poorly developed actin cytoskeleton. Conversely, mesenchymal stem cells from the bone marrow and perivascular niches are more suitable for seeding into biomaterial scaffolds since they are mechanically robust and have developed cytoskeletal structures that may allow cellular stable attachment and motility through solid porous environments. Among these, perivascular stem cells cultured in 6% oxygen show a developed cytoskeleton but a more compliant nucleus, which can facilitate the penetration into pores of tissues or scaffolds. We confirm the relevance of our measurements using cell motility and migration assays and measure survival of injected cells. Since different types of adult stem cells can be used for similar applications, we suggest considering mechanical properties of stem cells to match optimal mechanical characteristics of therapies.

Low‐ vs. high‐pressure suction drainage after total knee arthroplasty: a double‐blind randomized controlled trial

The aim of this study was to assess the efficacy of continuous low-pressure suction drainage compared with closed high-pressure suction following total knee arthroplasty. Closed wound drainage systems are used in surgical interventions to reduce the incidence of haematomas, promote wound healing and reduce infections. However, evidence shows that using a closed wound drainage system can increase transfusion requirements. A randomized, double-blind and parallel controlled trial was performed. Adult knee replacement patients recruited between May 2006 and March 2007 were assigned to receive low-pressure suction of 50 mmHg (experimental drainage) or high-pressure suction of 700 mmHg (comparator drainage). The primary outcome was total blood loss after surgery. Secondary outcomes were incidence of transfusion, complications and mortality. Statistical analysis was based on an intention-to-treat approach. Linear regression was performed to account for factors that could influence blood loss. A total of 169 patients were included. Mean age was 73 (±6) years, 128 women and 41 men. A total of 84 patients were randomized to the experimental drainage and 85 to the comparator drainage. Analysis showed a total postoperative blood loss of 541·8 mL in the experimental group and 524·4 mL in the comparator group (P = 0·734). The only factor that showed an association with blood loss was the length of surgery. Linear regression did not show differences between the groups. Continuous low-pressure suction of 50 mmHg is not more effective than the higher aspiration pressure system to diminish the blood loss in total knee arthroplasty. The results do not support any change in current nursing practice relating to the use of this drain system.

Mechanosensitive shivering of model tissues under controlled aspiration

During embryonic development and wound healing, the mechanical signals transmitted from cells to their neighbors induce tissue rearrangement and directional movements. It has been observed that forces exerted between cells in a developing tissue under stress are not always monotonically varying, but they can be pulsatile. Here we investigate the response of model tissues to controlled external stresses. Spherical cellular aggregates are subjected to one-dimensional stretching forces using micropipette aspiration. At large enough pressures, the aggregate flows smoothly inside the pipette. However, in a narrow range of moderate aspiration pressures, the aggregate responds by pulsed contractions or "shivering." We explain the emergence of this shivering behavior by means of a simple analytical model where the uniaxially stretched cells are represented by a string of Kelvin-Voigt elements. Beyond a deformation threshold, cells contract and pull on neighboring cells after a time delay for cell response. Such an active behavior has previously been found to cause tissue pulsation during dorsal closure of Drosophila embryo.

Comparison of diagnostic accuracy of endoscopic ultrasound-guided fine-needle aspiration with 22- and 25-gauge needles in the same patients.

BACKGROUND: Various factors, such as the optimal number of passes, aspiration pressure, and the use of 19-gauge and Trucut biopsy needles, have been studied to improve the diagnostic accuracy of endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA). We retrospectively compared the diagnostic accuracy of EUS-FNA between 25- and 22-gauge needles, which have been widely used recently. SUBJECTS AND METHODS: The study group comprised 47 consecutive patients who underwent EUS-FNA with both 22- and 25-gauge needles from October 2007 through March 2010. Their underlying diseases were pancreatic cancer in 24 patients, submucosal tumors in 11, other pancreatic tumors in 4, chronic pancreatitis in 4, enlarged lymph nodes in 3, and gall bladder cancer in 1. Tissue specimens, which were pushed out of the puncture needle, were placed into physiological saline solution. Gray-whitish, worm-like specimens were used for histologic diagnosis. The remaining specimen was centrifuged, and the sediment was plated on slides and examined by a cytopathologist to obtain the cytologic diagnosis. RESULTS: A total of 75 punctures (mean, 1.6) were performed with 25-gauge needles, and 69 punctures (mean, 1.4) were performed with 22-gauge needles. The overall tissue-sampling rate for cytology was 100% (47/47), which was significantly (p=0.01) superior to 83% (39/47) for histology. The overall diagnostic accuracy on the cytologic and histologic examinations was 79% (37/47) and 85% (33/39) (p=0.48). According to needle type, the tissue-sampling rate for cytology and histology on each puncture was 97% (73/75) and 56% (42/75) with 25-guage needles, and was 97% (67/69) and 58% (40/69) with 22-guage needles, the accuracy of cytologic diagnosis on each puncture was 73% (53/73) with 25-gauge needles and 66% (44/67) with 22-gauge needles (p=0.37); the accuracy of histologic diagnosis on each puncture was 60% (25/42) and 75% (30/40) (p=0.14), respectively. No patient had complications. CONCLUSIONS: The tissue-sampling rate and diagnostic accuracy did not differ significantly between 22- and 25-gauge needles in patients with pancreatic or gastrointestinal diseases who underwent EUS-FNA.

Abnormalities in Post-Ovulatory Aged Eggs Include Defective Cortical Mechanics and Are Partially Recapitulated by Perturbation of Myosin-II Function.

Attempting to conceive at increased times after ovulation, in vivo and in vitro, is associated with poor reproductive outcomes. Post-ovulatory aging of the egg is associated with multiple cellular, molecular, and functional abnormalities that contribute to a limited window of time for successful fertilization and initiation of development. In recent work, we presented the first characterization of cellular mechanics in mammalian eggs. By using micropipet aspiration (MPA), in which we assess the aspiration pressure required to induce a defined deformation in the cell and then perform calculations based on the Law of Laplace, we can measure the effective cortical tension in the cell, measured in nN/μm. These studies revealed that there are dramatic changes in cortical tension in mouse oocytes with progression through meiosis as well as mechanical polarity established at metaphase II arrest, which in turn is associated with spindle morphology and function. Given the abnormalities that develop during post-ovulatory aging, we hypothesized that cortical tension would be altered in aged eggs. We used MPA to measure the mechanical properties of young and eggs metaphase II mouse eggs, and found that cortical tension is reduced in both the microvillar domain (where sperm bind and fuse) and in the amicrovillar domain (where the metaphase II spindle is sequestered) in aged eggs. Microvillar tension is reduced ~50% and amicrovillar tension is reduced ~40%, which interestingly, is very similar to what we observed in eggs with myosin-II-based contractility impaired by treatment with ML-7, an inhibitor of myosin light chain kinase. We therefore examined the expression and localization of the active phosphorylated form of the myosin regulatory light chain (pMRLC), as well as a second protein that our past work implicated in oocyte cortical tension. This second protein is a family known as ERM, an acronym for the three members, ezrin, radixin, and moesin. We showed that the active, phosphorylated form of ERM (pERM) is localized in the microvillar domain, opposite of pMRLC in the amicrovillar domain, and that dominant-negative disruption of ERMs led to aberrant cortical tension and spindle function. Our studies of aged eggs revealed that 33% (24/72) aged eggs had abnormalities in pERM levels or localization, while 62% (80/130) aged eggs had abnormalities in pMRLC levels or localization. Based on this, we examined the effects of inhibition of myosin light chain kinase activity (through ML-7 treatment) on in vitro fertilization outcomes with ZP-free eggs and on membrane topography, two features of post-ovulatory aged eggs we have studied previously. These experiments demonstrated that ZP-free ML-7-treated eggs, like aged eggs, have an increased propensity to become polyspermic, but also a subset of ML-7-treated eggs are slow to fertilize or resistant to fertilization. Scanning electron microscopy analyses showed that ML-7-treated eggs had noteworthy differences from controls, including abnormal surface features and impaired sperm-induced membrane remodeling, similar to what has been observed in fertilized aged eggs. Taken together, these data points to impaired myosin-II function as a contributor to the cellular and functional abnormalities in post-ovulatory aged eggs. (platform)

Physico-mechanical characteristics of rose petals dealing with the pneumatic harvest of Rosa damascena

For the design of harvesting machines is important the study of characteristics dealing with the harvest of crops. This study focused on some physico-mechanical characteristics of rose petals, which are important for pneumatic harvest mechanization of Rosa damascena Mill. These characteristics are terminal velocity, picking force, mass, projection area, density, and drag coefficient of rose petals. The petals were handpicked at 06:30 a.m. (S1), 08:30 a.m. (S2), 10:30 a.m. (S3), and 12:30 p.m. (S4) at four different dates in 2009, June 5 (H1), June 11 (H2), June 17 (H3), and June 23 (H4), covering the potential flowering period. Terminal velocity of rose petals varied between 1.572 and 1.257 m s–1; the picking force from 0.501 to 1.005 N; the mass measured from 0.049 to 0.122 g; projection area from 13.830 cm2 for H1S4 to 7.071 cm2 for H4S1; drag coefficient from 0.790 for H2S1 to 0.287 for H1S4. The results of the study indicate that as far as terminal velocity of rose petals is concerned the harvest of R. damascena should be executed towards the end of H4 and S4. On the other hand, the magnitude of the picking force, the density, and the drag coefficient of rose petals decrease when the harvesting hour increases from H1 to H4 and the harvesting date increases from S1 to S4, which makes necessary to increase aspiration pressure.

Pressure transmitting device: a simple and safe method of continuous aspiration of subglottic secretions during orotracheal intubation

Many interventions are known to decrease the incidence of ventilator-associated pneumonia, which has great impact on mortality, length of stay and costs in intensive care units. One of them is the aspiration of the secretions that pool above the cuff of the endotracheal tube [1]. It is a simple device but its use is not free from complications [2], being, most of them, bleedings and obstructions due to lesions of tracheal mucosa. The maintenance of a constant suction, without wide pressure variation, is an important point to minimize these complications. The common manometers do not have enough precision to set an adequate aspiration pressure, because of its broad scale, and are not able to avoid or to limit pressure variations in case of partial occlusions, by secretion, for example, facilitating lesions occurrence. Pressure transmitting devices (Figure ​(Figure1),1), usually used for continuous aspiration of pleural drainage, have those helpful characteristics. It can be set in an adequate aspiration pressure (20 mmHg ~ 27 cmH2O) by setting the water column height. It avoids suction pressure variations since the air bubbles up on the water, balancing pressure inside the system. Figure 1 Methods Pressure transmitting devices were tested in 12 patients with subglottic aspiration on their orotracheal tubes. They were watched for complications and the findings are reported. The aspiration pressure used was set at 20 cmH2O.