Safety of aeromedical repatriation after myocardial infarction: a retrospective study.
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Aerospace Medicine↗
Biomedical subjects
F Morgan
Publications and source records attributed to F Morgan.
Instabilities of cylindrical bubble clusters.
Small bubbles in an experimental two-dimensional foam between glass plates regularly undergo a three-dimensional instability as the small bubbles shrink under diffusion or equivalently as the plate separation increases, and end up on one of the plates. The most recent experiments of Cox, Weaire, and Vaz are accompanied by Surface Evolver computer simulations and rough theoretical calculations. We show how a recent second variation formula may be used to perform exact theoretical calculations for infinitesimal perturbations for such a system, and verify results with Surface Evolver simulations.
Journal Article↗
Survival of Listeria monocytogenes during manufacture, ripening and storage of soft lactic cheese made from raw goat milk.
Soft lactic cheeses were manufactured with raw goat milk inoculated with Listeria monocytogenes. The physico-chemical and microbiological characteristics of curds and cheeses were determined after each processing step as well as during ripening and refrigerated storage. The fate of Listeria monocytogenes was evaluated by enumeration on PALCAM agar and by a qualitative detection after a double selective enrichment procedure. The results showed that the physico-chemical and microbiological characteristics of lactic cheeses caused a decrease of Listeria monocytogenes counts. However, this decrease did not lead to the complete disappearance of the pathogen and Listeria monocytogenes was able to survive in soft lactic cheeses made with raw goat milk.
Animals↗
Qualitative and quantitative analysis of monocyte transendothelial migration by confocal microscopy and three-dimensional image reconstruction.
A novel method for qualitative and quantitative analysis of monocyte transendothelial migration is described. By labeling monocytes and endothelial cells with different fluorophores, and utilizing confocal microscopy and three-dimensional image reconstruction, transmigrating monocytes were resolved and quantified within a subendothelial collagen gel. Comparison of monocyte migration across endothelial monolayers derived from human brain microvessels versus umbilical veins revealed diapedesis across brain endothelium to be significantly delayed. Inclusion of astrocytes within the subendothelial collagen gel resulted in the formation of an array of astrocytic processes that simulated the glia limitans surrounding brain microvessels in situ, thus yielding a more physiologic paradigm of the blood-brain barrier. By virtue of its unique capacity to provide information on the total number of migrating cells, this analytic approach overcomes significant caveats associated with sampling only aspects of the migration process. The potential adaptability of this method to computer-assisted analysis further enhances its prospective use in high-throughput screening.
Astrocytes↗
Formation of stable covalent dimer explains the high solubility at pH 4.6 of lactose-beta-lactoglobulin conjugates heated near neutral pH.
The solubility of lactose-beta-lactoglobulin conjugates at pH 4.6, after heating near neutral pH in phosphate buffer/0.116 M NaCI, was investigated by size exclusion chromatography and compared with unmodified protein. Heated conjugates in the temperature range 65-90 degrees C showed greater solubility at pH 4.6. The proportion of soluble protein increased with the number of bound lactose molecules. Total solubility was obtained for conjugates with nine lactose residues attached per monomer of beta-lactoglobulin. The protective effect of bound sugar toward precipitation was associated with the formation of soluble disulfide cross-linked dimers, highly accessible to trypsin digestion. These results suggested that bound lactose, through steric hindrance and high surface hydrophilicity, prevents the thiol-disulfide exchange reactions of the polymerization-aggregation process of lactose-beta-lactoglobulin conjugates.
Chromatography, Gel↗
Modification of bovine beta-lactoglobulin by glycation in a powdered state or in an aqueous solution: effect on association behavior and protein conformation.
The effect of glycation with lactose on the association behavior and conformational state of bovine beta-lactoglobulin (beta-LG) was studied, using size exclusion chromatography, polyacrylamide gel electrophoresis, proteolytic susceptibility, and binding of a fluorescent probe. Two modification treatments were used, i.e., aqueous solution glycation and dry-way glycation. The results showed that the latter treatment did not significantly alter the nativelike behavior of the protein while the former treatment led to important structural changes. These changes resulted in a specific denatured beta-LG monomer, which covalently associated via the free thiol group. The homodimers thus formed and the expanded monomers underwent subsequent aggregation into a high molecular weight species, via noncovalent interactions. The association behavior of glycated beta-LG is discussed with respect to the known multistep denaturation/aggregation process of nonmodified beta-LG.
Animals↗
Modification of bovine beta-lactoglobulin by glycation in a powdered state or in an aqueous solution: immunochemical characterization.
Bovine beta-LG was modified by glycation with lactose in a powdered state or in an aqueous solution. An immunological characterization was performed using monoclonal antibodies with defined epitopes. The results showed that the structural changes were confined to the AB loop region of the molecules when glycation was conducted in a restricted water environment and had little consequences on the association state of glycated beta-LG. The protein conformation was much more extensively modified when glycation was performed in an aqueous solution at 60 degrees C, despite a lower glycation extent. These structural changes were located at the dimer interface (AB loop, GH loop, beta-strand I, and alpha-helix). These results allowed us to establish a relationship between the conformational changes and the modification of the association state of the glycated protein (formation of disulfide bridges between the free thiol groups of two monomers), previously described.
Animals↗
Selective detection of lactolated peptides in hydrolysates by liquid chromatography/electrospray tandem mass spectrometry.
In food processing as well as in human nutrition and physiology, the increasing importance of the Maillard reaction has brought about the need for analytical means to detect and characterize the protein-bound Amadori products. In this paper, we describe a highly selective and sensitive method for detecting peptides glycated with lactose (lactolated peptides) from a complex hydrolysate using electrospray ionization tandem mass spectrometry. Protonated molecular ions of lactolated peptides gave a product-ion spectrum, with the dominant mode of decomposition including cleavage of the O-glycosidic bond followed by dehydration steps giving a characteristic neutral loss of 216 Da. Optimization of the ion marker [M + H]+ - 216, identified as a furylium ion, was investigated. It remained dominant regardless of the nature of the glycated peptides, the collision energy used, or the charge state of the parent ion. An approach for detecting lactolated peptides from protein digest was proposed during reverse-phase high-performance liquid chromatography (HPLC)/electrospray mass spectrometry and reverse-phase HPLC/tandem mass spectrometry using neutral loss scanning. This technique detected picomole amounts of lactolated peptides.
Amino Acid Sequence↗
Intracellular fluorescent probe concentrations by confocal microscopy.
A general method is described that takes advantage of the optical sectioning properties of a confocal microscope to enable measurement of both absolute and relative concentrations of fluorescent molecules inside cells. For compartments within cells that are substantially larger than the point spread function, the fluorescence intensity is simply proportional to the concentration of the fluorophore. For small compartments, the fluorescence intensity is diluted by contributions from regions outside the compartment. Corrections for this dilution can be estimated via calibrations that are based on the intensity distribution found in a computationally synthesized model for a cell or organelle that has been blurred by convolution with the microscope point spread function. The method is illustrated with four test cases: estimation of intracellular concentration of a fluorescent calcium indicator; estimation of the relative distribution between the neurite and soma of a neuronal cell of the InsP3 receptor on the endoplasmic reticulum; estimation of the distribution of the bradykinin receptor along the surface of a neuronal cell; and relative distribution of a potentiometric dye between the mitochondria and cytosol as a means of assaying mitochondrial membrane potential.
3T3 Cells↗
Augmented reality and its future in orthopaedics.
Augmented reality is a display technique that combines supplemental information with the real world environment. Augmented reality systems are on the verge of being used everyday in medical training, preoperative planning, preoperative and intraoperative data visualization, and intraoperative tool guidance. The basic technologies of augmented reality are discussed, augmented reality systems currently being used in the medical domain are examined, and some future uses of these systems in orthopaedic applications are explored.
Bone and Bones↗
The Otto Aufranc Award. Image guided navigation system to measure intraoperatively acetabular implant alignment.
There has been little clinical research to examine the effects of patient positioning and pelvic motion on the alignment of the acetabular implant during total hip replacement surgery. Until now, no tools were capable of accurately measuring these variables during the actual procedure. As part of a broader program in medical robotics and computer assisted surgery, a clinical system has been developed that includes several enabling technologies. The hip navigation system (HipNav) continuously and precisely measures pelvic location and tracks relative implant alignment intraoperatively. HipNav technology is used to gauge current clinical practice and provide intraoperative feedback to surgeons with the goal of improving the precision and accuracy of acetabular alignment during total hip replacement. This system provides surgeons with a new class of image guided measurement tools and assist devices. These tools successfully were introduced into the clinical practice of surgery with results showing the following: (1) There exist unpredictable and large variations in the initial position of patients' pelves on the operating room table and significant pelvic movement during surgery and during intraoperative range of motion testing; (2) current mechanical acetabular alignment guides do not account for these variations, and result in variable and in the majority of cases unacceptable acetabular alignment; and (3) press fitting oversized acetabular components influences the final cup orientation.
Anthropometry↗
Nonenzymatic lactosylation of bovine beta-lactoglobulin under mild heat treatment leads to structural heterogeneity of the glycoforms.
Lactose reacts nonenzymatically with beta-lactoglobulin (beta-LG), the major whey protein, under mild heat treatment and the formation of the complex may be monitored by mass spectrometry. Using Reverse Phase HPLC coupled with Electrospray Ionization MS (ESI-MS) we have measured the global extent of glycosylation and examined the distribution of lactose among the beta-LG glycoforms. Identification of lactosylated sites by trypsinolysis and Tandem MS indicate that, although the glycosylation reaction was non-specific and potentially involved all the reactive sites (alpha- and epsilon-amino groups), beta-LG appeared to have at least two populations of lysine with the distinct ability to react with lactose. These results underline the structural heterogeneity of beta-LG glycoforms, with respect to the number of lactose linked per molecule and to the binding sites involved, which could affect the biological function of beta-LG.
Amines↗
Babe the magnificent organ donor? The perils and promises surrounding xenotransplantation.
The number of xenotransplantations may increase despite the many concerns about the likelihood of spreading known and unknown infectious diseases. Regardless of the safety precautions employed in the early trials, the risks remain unknown. Zoonotic and even xenozoonootic diseases are not remote possibilities; they exist in various forms and come from various sources. The nature of transplantation requires the suppression of the immune system to levels where opportunistic infections may take route. Even if procedures to avoid increased levels of immunosuppression to the recipient were successful, risk to third parties, whose immune systems would not be equipped to fight off the infection, would remain. In this context, the PHS Guidelines provide a useful starting point, but they do not go far enough. First, the Guidelines are merely suggestions; this needs to be changed to require institutions undertaking xenotransplantation research and clinical trials to comply with the Guidelines. Second, every possible effort should be made to protect third parties from disease transmission. This requires and justifies placing restrictions on recipients that, in an ordinary context, would be unacceptable. Third, xenotransplantations should occur only after all other medical measures have been exhausted. Until the time when disease transmission risks are scientifically insignificant or cures for the transmitted diseases are found, mandatory guidelines with stringent requirements are the best means of balancing the interests of society against the potential beneficiaries of xenotransplantation.
Adult↗
Protein translation components are colocalized in granules in oligodendrocytes.
The intracellular distribution of various components of the protein translational machinery was visualized in mouse oligodendrocytes in culture using high resolution fluorescence in situ hybridization and immunofluorescence in conjunction with dual channel confocal laser scanning microscopy. Arginyl-tRNA synthetase, elongation factor 1a, ribosomal RNA, and myelin basic protein mRNA were all co-localized in granules in the processes, veins and membrane sheets of the cell. Colocalization was evaluated by dual channel cross correlation analysis to determine the correlation index (% colocalization) and correlation distance (granule radius), and by single granule ratiometric analysis to determine the distribution of the different components in individual granules. Most granules contained synthetase, elongation factor, ribosomal RNA and myelin basic protein mRNA. These results indicate that several different components of the protein synthetic machinery, including aminoacyl-tRNA synthetases, elongation factors, ribosomes and mRNAs, are colocalized in granules in oligodendrocytes. We propose that these granules are supramolecular complexes containing all of the necessary macromolecular components for protein translation and that they represent a heretofore undescribed subcellular organization of the protein synthetic machinery. This spatial organization may increase the efficiency of protein synthesis and may also provide a vehicle for transport and localization of specific mRNAs within the cell.
Amino Acyl-tRNA Synthetases↗
Three-dimensional organization of endoplasmic reticulum in the ventral photoreceptors of Limulus.
Living Limulus ventral photoreceptor cells were injected with long chain lipophilic carbocyanine fluorescent dyes to label the endoplasmic reticulum (ER). The purpose of this study was to examine the continuity, dynamic changes, and structure of the ER in the living cell, using laser scanning confocal microscopy and three-dimensional image reconstruction. In this highly polarized neuron, three lines of evidence indicate that the ER is a continuous network extending throughout both lobes of the cell. First, injection of DiO or DiI results in the labeling of ER throughout both lobes of the cell. Second, three-dimensional image reconstruction of the optical sections reveals a dispersed membrane meshwork which may be the structure that serves to interconnect the ER in the two lobes. Third, in cells fixed before dye injection, the pattern of labeling was similar to that in living cells, indicating that vesicle transport was not responsible for the spread of dye throughout the cell. The overall organization of the ER in the photoreceptor cell is relatively stable; however, the fine structure changes over time. This dynamic process appears to represent continual reorganization of the intracellular membranes in the cell. Three morphological types of ER were observed. The ER of the light-sensitive lobe, identified by coinjection of rhodamine-phalloidin to label the microvillar actin, is characterized by a concentration of stratiform membranes interconnected by thin tubular cross-bridges. The perinuclear ER is characterized by a tangle of convoluted tubules sometimes terminating in bulbous structures. Finally, there is a fine tubular reticulum dispersed throughout the cell.
Animals↗
Scanning concentration correlation spectroscopy using the confocal laser microscope.
Concentration correlation spectroscopy allows the assessment of molecular motions in complex systems. The technique generally monitors concentration fluctuations by means of some method such as the intensity of fluorescent molecules (fluorescence correlation spectroscopy). We describe here the use of scanning confocal laser microscopy to measure correlation functions in both space and time. This methodology offers two major advantages over conventional methods. First, collecting data from different regions of the sample significantly increases the signal-to-noise ratio. Second, molecular motions of colloidal gold can be analyzed by correlation methods with high temporal and spatial resolution. Using a MRC 600 laser scanning system, we collect data from an ensemble of 768 independent subvolumes and determine the space-time correlation function. We demonstrate the technique using two different types of samples, fluorescently labeled DNA molecules in solution and colloidal gold-tagged lipids in a planar bilayer. This approach, which we term "scanning concentration correlation spectroscopy," provides a straightforward means of performing high resolution correlation analysis of molecular motions with available instrumentation.
Biophysical Phenomena↗
Transport and localization of exogenous myelin basic protein mRNA microinjected into oligodendrocytes.
We have studied transport and localization of MBP mRNA in oligodendrocytes in culture by microinjecting labeled mRNA into living cells and analyzing the intracellular distribution of the injected RNA by confocal microscopy. Injected mRNA initially appears dispersed in the perikaryon. Within minutes, the RNA forms granules which, in the case of MBP mRNA, are transported down the processes to the periphery of the cell where the distribution again becomes dispersed. In situ hybridization shows that endogenous MBP mRNA in oligodendrocytes also appears as granules in the perikaryon and processes and dispersed in the peripheral membranes. The granules are not released by extraction with non-ionic detergent, indicating that they are associated with the cytoskeletal matrix. Three dimensional visualization indicates that MBP mRNA granules are often aligned in tracks along microtubules traversing the cytoplasm and processes. Several distinct patterns of granule movement are observed. Granules in the processes undergo sustained directional movement with a velocity of approximately 0.2 micron/s. Granules at branch points undergo oscillatory motion with a mean displacement of 0.1 micron/s. Granules in the periphery of the cell circulate randomly with a mean displacement of approximately 1 micron/s. The results are discussed in terms of a multi-step pathway for transport and localization of MBP mRNA in oligodendrocytes. This work represents the first characterization of intracellular movement of mRNA in living cells, and the first description of the role of RNA granules in transport and localization of mRNA in cells.
Animals↗
Visualizing cells in three dimensions using confocal microscopy, image reconstruction and isosurface rendering: application to glial cells in mouse central nervous system.
This paper describes a general method for visualizing individual cells in intact tissue in three dimensions. The method involves immunostaining intact tissue to label specific cells, "optical sectioning" the stained tissue by laser scanning confocal microscopy, computationally reconstructing a three dimensional image data set from the digitized confocal optical sections, delineating isosurfaces of specific intensity within the reconstructed image by a "marching cubes" algorithm to generate polygon meshes defining boundaries of cells, and displaying individual cells, identified as three dimensional objects enclosed by contiguous polygon meshes, using computer graphics techniques. Each of the components of this method has been described previously in conjunction with other applications. However the combination of these techniques to visualize a variety of different individual cell types in three dimensions in intact tissue represents a new approach. To illustrate the application of this method, we have visualized three different glial cell types in mouse CNS tissue. Oligodendrocytes, specifically stained with antibody to myelin basic protein, were used as an example of cells labelled with an internal membrane antigen. Astrocytes, specifically stained with antibody to glial fibrillary acidic protein, were used as an example of cells labelled with a cytoplasmic antigen. Microglia, specifically stained with Mac.1 antibody, were used as an example of cells labelled with an external membrane antigen. The images that are generated contain remarkably detailed volumetric and textural information that is not obtainable by conventional imaging techniques.
Algorithms↗