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At least 1,585 records · Page 88Linked to original sources
PubMed2003

Measurement in vivo of the survival rate in autologous adipocyte transplantation.

Up until now, research on fat cells has been unable to prove their survival rate objectively in vivo. In this article, the first application of the cell surface marker PKH26 in the fat cells of rats is reported. In a study of 48 Lewis rats, this method enabled the objective stereometry of viable and necrotic grafts after variable follow-up times in groups of eight animals each. The best survival rate was 30.41 percent, and the best implantation site was the interscapular subcutis. During follow-up, a characteristic change in size of the viable fat cells matched the in vitro findings of various investigators. Because of the surface marking, it could be proved that the viable cells found after 6 months were transplanted cells that had undergone a cycle of fat deprivation and regaining. This is proof of the cell survival theory postulated by Peer in 1950.

Adipocytes↗
PubMed2006

Formation of focal adhesion-like structures in circulating human neutrophils after severe injury: triggering of a tissue-phase response in the vascular space.

Neutrophils play a key role in injury to the lung, kidney, liver, and gastrointestinal tract, often seen after major trauma. We evaluated the role of integrin-linked focal adhesions in the primed state, previously identified in peripheral blood neutrophils from severely injured patients. Immunoblot analysis of Triton-insoluble cell fractions revealed that total paxillin content was unchanged in comparison with that found in neutrophils from healthy volunteers, but phosphorylation of paxillin on tyrosine residue 118 was increased by more than 2-fold. Immunoprecipitation with antipaxillin and immunoblotting for proline-rich tyrosine kinase 2 (Pyk2) and for fgr showed significantly more colocalization. Densitometric analysis of total phosphotyrosine profiles also demonstrated significantly more in patient cells as compared with healthy cells. When allowed to adhere to fibronectin-coated plates, healthy and patient cells demonstrate a significant increase in tyrosine phosphorylation from that found in suspension-phase cells. Differential interference contrast microscopy of healthy neutrophils adherent to fibronectin matrices demonstrated rounded cells, without evidence of spreading; spreading was induced by addition of TNF-alpha. Patient neutrophils spread spontaneously, a response not further enhanced by TNF-alpha. Confocal imaging using anti-Pyk2 demonstrated aggregation of Pyk2 into punctate structures in patient but not in healthy cells. We conclude that neutrophils from severely injured patients are in a primed state, characterized by formation of focal adhesion-like structures. The identification of such structures in a clinical disease setting where they likely participate in unwanted consequences provides a novel area for study of regulation of neutrophil function.

Adult↗
PubMed2006

Wet but not slippery: Boundary friction in tree frog adhesive toe pads.

Tree frogs are remarkable for their capacity to cling to smooth surfaces using large toe pads. The adhesive skin of tree frog toe pads is characterized by peg-studded hexagonal cells separated by deep channels into which mucus glands open. The pads are completely wetted with watery mucus, which led previous authors to suggest that attachment is solely due to capillary and viscous forces generated by the fluid-filled joint between the pad and the substrate. Here, we present evidence from single-toe force measurements, laser tweezer microrheometry of pad mucus and interference reflection microscopy of the contact zone in Litoria caerulea, that tree frog attachment forces are significantly enhanced by close contacts and boundary friction between the pad epidermis and the substrate, facilitated by the highly regular pad microstructure.

Adhesiveness↗
PubMed1979

Differentiated regions of human placental cell surface associated with attachment of chorionic villi, phagocytosis of maternal erythrocytes and syncytiotrophoblast repair.

Scanning electron micrographs of human placental cell surface show: (1) Differentiated zones of trophoblast which may be covered by fewer 'microvilli' than the adjacent syncytial cell surface and which extend as a narrow, usually distal protrusion of the chorionic villus. This narrow outgrowth terminates as a fractured end. Presumably since preparations were obtained from therapeutic terminations of pregnancy or Caesarian deliveries these broken ends represent the yield point in the anchoring 'villi' ruptured as a result of surgery. Similar anchoring 'villi' with fractured ends were observed in unfixed material with the use of Nomarski interference contrast microscopy. (2) It appears that, during apparent phagocytic uptake of maternal erythrocytes by syncytiotrophoblast, cell surface lining the forming vacuole still retains an irregular microvillous surface. This observation indicates the potential location of phagocytosis receptors for red blood cells in the placental cell surface. (3) Areas of human placenta which appears to have been damaged and may be undergoing repair exhibit masses of cells with conspicuous microvillar cell surfaces. The origin of these cells is discussed in relation to the usual processes of syncytiotrophoblast formation.

Cell Membrane↗
PubMed1988

On the mechanism of a high-frequency force generator in outer hair cells isolated from the guinea pig cochlea.

Isolated mammalian outer hair cells elongate or shorten respectively by several micrometres when electrically hyperpolarized or depolarized. The experiments in this paper were designed to locate the force-generating mechanism that drives length changes in outer hair cells, and to determine some of its basic properties. The whole-cell mode of the patch-clamp technique was used to stimulate cells electrically and to perfuse them with specific drugs. The pattern of displacement of cellular organelles, and the relative displacements of the cell base and apex during electrical stimulation with the cell mechanically anchored at various points along its length, suggest that the force-generating mechanism is distributed throughout the length of the cell. Further experiments altering the shape, volume and intracellular pressure of outer hair cells suggest that the mechanism is closely associated with the plasma membrane. These experiments also demonstrate that the characteristic tubular shape of outer hair cells is maintained by membrane-associated structures with elastic properties that enable the cell to return to its original shape after deformation. The mechanism controlling length changes may, therefore, be composed of two elements in parallel, namely a force generating element and a passive elastic element. Inhibitors of ATP synthesis, or the presence of the non-hydrolysable ATP analogue AMP.PNP, perfused into outer hair cells, failed to inhibit length changes. Drugs against actin, including phalloidin, cytochalasin B and cytochalasin D, and against tubulin, including colchicine, nocodazole and colcemid, also failed to inhibit length changes. We conclude that the force-generating mechanism is, therefore, unlike most other forms of cell motility, and possible alternative hypotheses are briefly discussed.

Actins↗
PubMed2002

A review of recent work in sub-nanometre displacement measurement using optical and X-ray interferometry.

This paper reviews recent work in the field of displacement measurement using optical and X-ray interferometry at the sub-nanometre level of accuracy. The major sources of uncertainty in optical interferometry are discussed and a selection of recent designs of ultra-precise, optical-interferometer-based, displacement measuring transducers presented. The use of X-ray interferometry and its combination with optical interferometry is discussed.

Interferometry↗
PubMed1980

Colony morphology, ultrastructure and morphogenesis in Mycoplasma hominis, Acholeplasma laidlawii and Ureaplasma urealyticum.

Colonies of Mycoplasma hominis, Acholeplasma laidlawii (three strains) and Ureaplasma urealyticum were examined by light and electron microscopy and their characteristic morphology, ultrastructure and morphogenesis are described. Mycoplasma hominis and A. laidlawii, PG8 and oral strains, developed typical 'fried-egg' colonies which were remarkably heterogeneous in size. The colonies of A. laidlawii strain NCTC 10116 were more homogeneous and grew mainly on the surface of the agar showing a fine granular appearance. Ureaplasma urealyticum produced smaller, granular colonies which grew deeply embedded in the agar and generally without much surface growth. The cellular ultrastructure in these colonies was also examined. The results indicate that several aspects of colony morphogenesis and ultrastructure varied for each of the three species examined.

Acholeplasma laidlawii↗
PubMed2004

Candida bombiphila sp. nov., a new asexual yeast species in the Wickerhamiella clade.

Two yeast strains were isolated from a bumblebee and bumblebee honey. The strains were almost identical in their D1/D2 domain of the large-subunit rDNA and their physiological abilities. In both respects the strains resembled Wickerhamiella domercqiae. On the basis of these data, it is proposed that the strains represent a novel species with the name Candida bombiphila sp. nov. The type strain is CBS 9712T (= NRRL Y-27640T = MH268T).

Animals↗
PubMed2000

Adhesive switching of membranes: experiment and theory.

We report on a study of a model bioadhesion system: giant vesicles in contact with a supported lipid bilayer. Embedded in both membranes are very low concentrations of homophilic recognition molecules (contact site A receptors) competing with higher concentrations of repeller molecules: polyethylene glycol (PEG) lipids. These repellers mimic the inhibiting effect of the cell glycocalyx on adhesion. The effective adhesive interaction between the two membranes is probed by interferometric analysis of thermal fluctuations. We find two competing states of adhesion: initial weak adhesion is followed by slower aggregation of the adhesion molecules into small, tightly bound clusters that coexist with the regions of weak adhesion. We interpret our results in terms of a double-well intermembrane potential, and we present a theoretical analysis of the intermembrane interaction in the presence of mobile repeller molecules at a fixed chemical potential that shows that the interaction potential indeed should have just such a double-well shape. At a fixed repeller concentration we recover a conventional purely repulsive potential. We discuss the implications of our findings in terms of a general amplification mechanism of the action of sparse adhesion molecules by a nonspecific double-well potential. We also discuss the important role of the Helfrich undulation force for the proposed scenario.

Biophysical Phenomena↗
PubMed2001

Instability of myelin tubes under dehydration: deswelling of layered cylindrical structures.

We report experimental observations of an undulational instability of myelin figures. Motivated by this, we examine theoretically the deformation and possible instability of concentric, cylindrical, multilamellar membrane structures. Under conditions of osmotic stress (swelling or dehydration), we find a stable, deformed state in which the layer deformation is given by deltaR infinity r(square root[B(A)/(hB)]), where B(A) is the area compression modulus, B is the interlayer compression modulus, and h is the repeat distance of layers. Also, above a finite threshold of dehydration (or osmotic stress), we find that the system becomes unstable to undulations, first with a characteristic wavelength of order square root[xi(d)0], where xi is the standard smectic penetration depth and d0 is the thickness of dehydrated region.

Biophysical Phenomena↗
PubMed2006

Optical measurement of cell membrane tension.

Using a novel noncontact technique based on optical interferometry, we quantify the nanoscale thermal fluctuations of red blood cells (RBCs) and giant unilamellar vesicles (GUVs). The measurements reveal a nonvanishing tension coefficient for RBCs, which increases as cells transition from a discocytic shape to a spherical shape. The tension coefficient measured for GUVs is, however, a factor of 4-24 smaller. By contrast, the bending moduli for cells and vesicles have similar values. This is consistent with the cytoskeleton confinement model, in which the cytoskeleton inhibits membrane fluctuations [Gov et al., Phys. Rev. Lett. 90, 228101, (2003).

Biophysical Phenomena↗
PubMed1994

The response to gravity is correlated with the number of statoliths in Chara rhizoids.

In contrast to higher plants, Chara rhizoids have single membrane-bound compartments that appear to function as statoliths. Rhizoids were generated by germinating zygotes of Chara in either soil water (SW) medium or artificial pond water (APW) medium. Differential-interference-contrast microscopy demonstrated that rhizoids form SW-grown plants typically contain 50 to 60 statoliths per cell, whereas rhizoids from APW-grown plants contain 5 to 10 statoliths per cell. Rhizoids from SW are more responsive to gravity than rhizoids from APW because (a) SW rhizoids were oriented to gravity during vertical growth, whereas APW rhizoids were relatively disoriented, and (b) curvature of SW rhizoids was 3 to 4 times greater throughout the time course of curvature. The growth rate of APW rhizoids was significantly greater than that of SW-grown rhizoids. This latter result suggests that APW rhizoids are not limited in their ability for gravitropic curvature by growth and that these rhizoids are impaired in the early stages of gravitropism (i.e. gravity perception). Plants grown in APW appeared to be healthy because of their growth rate and the vigorous cytoplasmic streaming observed in the rhizoids. This study is comparable to earlier studies of gravitropism in starch-deficient mutants of higher plants and provides support for the role of statoliths in gravity perception.

Chlorophyta↗
PubMed2000

High throughput cellular localization of specific plant mRNAs by liquid-phase in situ reverse transcription-polymerase chain reaction of tissue sections.

Advances in high throughput DNA sequencing and bioinformatic gene discovery far outpace our ability to analyze gene function, necessitating development of more efficient means to examine expression at the cellular level. Here we present a polymerase chain reaction-based method to detect mRNA species in situ in which essentially all of the steps are carried out in liquid phase in a 96-well microtiter tray and only the final signal detection is performed on a microscope slide. We demonstrate the sensitivity of the method by the cellular localization of mRNA for the Tkn2 transcription factor in a wide variety of plant tissues, and its selectivity in discriminating a single gene family member by the in situ localization of rbcs3 transcripts. Furthermore, we demonstrate the utility of the in-well in situ method in detecting FDL and IFL1 transcripts in Arabidopsis sections, thus establishing the method as a tool to determine spatial expression pattern of sequences obtained from genomic sequencing projects. Being amenable to robotic processing, in-well in situ reverse transcription-polymerase chain reaction permits a great enhancement in the number of tissue samples that can be processed. Consequently, this method may become a powerful tool for functional genomics studies, permitting the cellular site of transcription of large numbers of sequences obtained from databases to be rapidly established.

Arabidopsis↗
PubMed2002

Fiber-optic confocal reflectance microscope with miniature objective for in vivo imaging of human tissues.

We have built a fiber-optic confocal reflectance microscope capable of imaging human tissues in near real time. Miniaturization of the objective lens and the mechanical components for positioning and axially scanning the objective enables the device to be used in inner organs of the human body. The lateral resolution is 2 micrometers and axial resolution is 10 micrometers. Confocal images of fixed tissue biopsies and the human lip in vivo have been obtained at 15 frames/s without any fluorescent stains. Both cell morphology and tissue architecture can be appreciated from images obtained with this microscope.

Biopsy↗
PubMed2003

Advanced optical tweezers for the study of cellular and molecular biomechanics.

Optical tweezers are an important tool for studying cellular and molecular biomechanics. We present a robust optical tweezers device with advanced features including: multiple optical traps, acousto-optic trap steering, and back focal plane interferometry position detection. We integrate these features into an upright microscope, with no compromise to its capabilities (differential interference contrast microscopy, fluorescence microscopy, etc.). Acousto-optic deflectors (AODs) steer each beam and can create multiple time-shared traps. Position detection, force calibrations and AOD performance are presented. The system can detect subnanometer displacements and forces below 0.1 pN.

Biomechanical Phenomena↗
PubMed2003

Toward virtual biopsy through an all fiber optic ultrasonic miniaturized transducer: a proposal.

The present generation of devices based on opto-acoustic and acousto-optic conversion lets us foresee the possibility of realizing complete miniaturized transmitting-receiving transducers, able to generate and detect wideband ultrasounds by laser light. In the present paper, a miniaturized ultrasonic transducer entirely based on fiber optic technology is proposed. Such a device springs from the conjunction between our research, which has produced a highly efficient fiber optic opto-acoustic source, with the results obtained by other researchers concerning the realization of an ultrasonic receiver based on optical interferometry. Making use of the thermo-elastic effect for ultrasound generation, a source of ultrasound can be obtained by coupling a fiber optic to pulsed laser, if a film capable of absorbing laser light is placed onto fiber end. Starting from these remarks, we propose an efficient opto-acoustic source, able to generate pressure pulses with amplitude of the order of 10(4) Pa and bandwidth extending up to 40 MHz and beyond by using graphite materials as absorbing film. This solution makes use of a low-power pulsed laser as optical source possible. An ultrasonic receiving element was realized placing a Fabry-Perot cavity over the tip of a fiber optic. The cavity thickness modulation induced by ultrasonic beam is detected by an interferometer optical technique. We have realized a prototype of a receiving device that exhibits a sensitivity comparable with that of piezoelectric devices (10-100 nV/Pa) and an almost flat bandwidth extending up to 20 MHz or more. The extreme miniaturization of the resulting ultrasonic transducer, together with its wide ultrasonic frequency bandwidth, is the first step toward ultrasonic tissue biopsy. In this paper, before discussing the problem of constructing a complete ultrasonic transducer composed by a transmitter and receiver, the results carried out in these fields during the last decade are reviewed.

Biopsy↗