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PubMed2006

Plasma membrane polarization during mating in yeast cells.

The yeast mating cell provides a simple paradigm for analyzing mechanisms underlying the generation of surface polarity. Endocytic recycling and slow diffusion on the plasma membrane were shown to facilitate polarized surface distribution of Snc1p (Valdez-Taubas, J., and H.R. Pelham. 2003. Curr. Biol. 13:1636-1640). Here, we found that polarization of Fus1p, a raft-associated type I transmembrane protein involved in cell fusion, does not depend on endocytosis. Instead, Fus1p localization to the tip of the mating projection was determined by its cytosolic domain, which binds to peripheral proteins involved in mating tip polarization. Furthermore, we provide evidence that the lipid bilayer at the mating projection is more condensed than the plasma membrane enclosing the cell body, and that sphingolipids are required for this lipid organization.

Cell Membrane↗
PubMed2004

Functional imaging: new views on lens structure and function.

1. We have developed an experimental imaging approach that allows the distribution of lens membrane proteins to be mapped with subcellular resolution over large distances as a function of fibre cell differentiation. 2. Using this approach in the rat lens, we have localized precisely histological sites of connexin 46 cleavage, quantitatively mapped changes in gap junction distribution and fibre cell morphology and correlated these changes to differences in intercellular dye transfer. 3. Profiling of glucose transporter isoform expression showed that lens epithelial cells express GLUT1, whereas deeper cortical fibre cells express the higher-affinity GLUT3 isoform. Near the lens periphery, GLUT3 was located in the cytoplasm of fibre cells, but it underwent a differentiation-dependent membrane insertion. 4. Similarly, the putative adhesion protein membrane protein 20 is inserted into fibre cell membranes at the stage when the cells lose their nuclei. This redistribution is strikingly rapid in terms of fibre cell differentiation and correlates with a barrier to extracellular diffusion. 5. Our imaging-orientated approach has facilitated new insights into the relationships between fibre cell differentiation and lens function. Taken together, our results indicate that a number of strategies are used by the lens during the course of normal differentiation to change the subcellular distribution, gross spatial location and functional properties of key membrane transport proteins.

Animals↗
PubMed2002

Effect of bacteriocin-induced cell damage on the branched-chain amino acid transamination by Lactococcus lactis.

The effect of the bacteriocin lacticin 3147 on the branched-chain amino acid transamination by Lactococcus lactis IFPL359 was investigated. The bacteriocin provokes membrane permeabilisation of the cells, rendering them non-viable but metabolically active. Free diffusion of amino acids into the cell was facilitated. In addition, membrane permeabilisation promotes further cell lysis. Both facts render the enzymes more accessible to their substrates and hence increase branched-chain amino acid transamination. This research broadens the spectrum of technological applications of lacticin 3147 in the development of cheese flavour.

Amination↗
PubMed1969

Pulmonary gas transport time: larynx to alveolus.

The transport time of gas from the larynx to pulmonary alveolar capillary blood was directly measured by injecting a bolus of carbon monoxide into the inspired airstream of dogs and photoelectrically monitoring the formation of carboxyhemoglobin in the capillaries on the surface of the lung. The rapidity of transit (0.3 second) implies that gas transport during inspiration is facilitated by an interaction between bulk flow and diffusion.

Animals↗
PubMed2002

Fatty acid transport across membranes: relevance to nutrition and metabolic pathology.

Long-chain fatty acids are an important constituent of the diet and they contribute to a multitude of cellular pathways and functions. Uptake of long-chain fatty acids across plasma membranes is the first step in fatty acid utilization, and recent evidence supports an important regulatory role for this process. Although uptake of fatty acids involves two components, passive diffusion through the lipid bilayer and protein-facilitated transfer, the latter component appears to play the major role in mediating uptake by key tissues. Identification of several proteins as fatty acid transporters, and emerging evidence from genetically altered animal models for some of these proteins, has contributed significant insight towards understanding the limiting role of transport in the regulation of fatty acid utilization. We are also beginning to better appreciate how disturbances in fatty acid utilization influence general metabolism and contribute to metabolic pathology.

Adipose Tissue↗
PubMed1998

Respiratory and metabolic functions of carbonic anhydrase in exercised white muscle of trout.

Electrical stimulation of a trout saline-perfused trunk preparation resulted in metabolic and respiratory responses comparable to those occurring after exhaustive exercise in vivo. Recovery of intracellular acid-base status and glycogen resynthesis were faster than in vivo. Intracellular carbonic anhydrase (ICF CA) blockade elevated intracellular PCO2 relative to untreated postexercise controls, whereas extracellular CA (ECF CA) blockade did not, in contrast to previous work with muscle at rest. ECF CA blockade had only a transient effect on postexercise CO2 and ammonia efflux. The relatively small pool of membrane-associated CA appears to be overwhelmed by exercise-induced CO2 production in muscle. Transmembrane ammonia efflux appears to shift from diffusion primarily as NH3 at rest, which is facilitated by ECF CA, to movement predominantly as NH+4 after exercise, which is independent of CA. The postponed recovery of intracellular pH caused by either or both ECF and ICF CA inhibition was consistent with reduced metabolic acid and lactate excretion from muscle. Creatine phosphate resynthesis was delayed by CA inhibition, whereas ATP replenishment was not affected. Delayed glycogen recovery indicates that HCO-3-dependent pathway(s) may be involved in glyconeogenesis.

Acid-Base Equilibrium↗
PubMed1990

Concentration dependence of urea and thiourea transport in rat inner medullary collecting duct.

The vasopressin-dependent urea permeability of the rat terminal inner medullary collecting duct (IMCD) is much greater than can be explained by lipid-phase permeation or paracellular diffusion, suggesting the presence of vasopressin-stimulated facilitated transport pathway. We used the isolated perfused tubule technique to test whether the urea transport pathway exhibits saturation characteristics consistent with a facilitated pathway. When the luminal urea concentration was varied between 0 and 800 mM (no urea in peritubular bath), the relationship between the urea flux and the luminal concentration was linear with a y-axis intercept that was not significantly different from zero, indicating an absence of saturation in this concentration range. Higher concentrations of urea could not be tested due to technical limitations. However, when thiourea (a urea analogue that shares the urea transport pathway with urea) was substituted for urea in similar experiments, the apparent thiourea permeability fell with increasing thiourea concentration in the range 10-200 mM, indicative of saturation of the urea-thiourea transporter. When the urea concentration was varied in both bath and lumen, the lumen-to-bath urea flux approached a limiting value at 400-500 mM urea, consistent with saturation of the transporter. However, nonspecific inhibition of urea transport by bath urea could not be ruled out in those experiments. We conclude that the urea and thiourea transport pathway in the terminal IMCD exhibits saturation characteristics. However, the urea concentration required to saturate the pathway is apparently high, at least 400-500 mM in one set of experiments and probably greater than 800 mM in another.

Animals↗
PubMed2004

Ion channels and amino acid transporters support the growth and invasion of primary brain tumors.

The malignant growth of glial support cells causes gliomas, highly invasive, primary brain tumors that are largely resistant to therapy. Individual tumor cells spread by active cell migration, invading diffusely into the normal brain. This process is facilitated by Cl- channels that endow glioma cells with an enhanced ability to quickly adjust their shape and cell volume to fit the narrow and tortuous extracellular brain spaces. Once satellite tumors enlarge, their growth is limited by the spatial constraints imposed by the bony cavity of the skull and spinal column. Glioma cells circumvent this limitation by active destruction of peritumoral neural tissue through the release of glutamate, inducing peritumoral seizures and ultimately excitotoxic neuronal cell death. Hence, primary brain tumors support their unusual biology by taking advantage of ion channels and transporters that are designed to support ion homeostatic functions in normal brain.

Amino Acid Transport Systems↗
PubMed2003

Uptake of 5-hydroxytryptamine by equine digital vein endothelial cells: inhibition by amines found in the equine caecum.

REASONS FOR PERFORMING STUDY: 5-hydroxytryptamine (5-HT; serotonin) is a potent vasoconstrictor of equine digital blood vessels and has been implicated in the pathogenesis of acute laminitis. OBJECTIVES: The aims of this study were firstly to examine whether cells of the digital blood vessel wall exhibited an active uptake mechanism for 5-HT and to characterise its efficiency; and secondly, to study the potential inhibitory effect on this process of other amines, produced in the equine caecum. METHODS: Confluent monolayers of equine digital vein endothelial cells (EDVEC) and equine digital vein smooth muscle cells (EDVSMC) were incubated with [3H]5-HT (0.1-250 micromol/l) and the total and active uptake calculated. Equine pulmonary vein endothelial cells (EPVEC) were used as a positive control. RESULTS: Both EDVEC and EDVSMC showed uptake of [3H]5-HT by nonfaci litated diffusion; however, only EDVEC showed evidence of saturable facilitated uptake mechanism, with a Km of 41.6 +/- 9.3 micromol/l, which was significantly higher than that of EPVEC (9.9 +/- 2.1 micromol/l). All 6 caecally-derived amines examined (tyramine, spermine, isoamylamine, tryptamine, phenylethylamine and isobutylamine) inhibited the total uptake of [3H]5-HT in a concentration-dependent manner, tyramine having the lowest IC50 (3.7 x 10(-6) mol/l). CONCLUSIONS: These data suggest that facilitated uptake into the endothelium could play a role in moderating the vasoconstrictor response to 5-HT in the equine digital circulation. POTENTIAL CLINICAL RELEVANCE: The vasoconstrictor action of 5-HT could be potentiated by gut-derived amines, providing a feasible link between GI disturbances and the pathophysiology of laminits.

Amines↗
PubMed2000

Revascularization of femoropopliteal artery occlusion in Werner's syndrome. Report of a case and review of surgical literature in cardiovascular lesions.

A patient with Werner's syndrome suffering from a chronic ulcer on the right ankle joint underwent femoropopliteal bypass and patch angioplasty combined with endarterectomy of the distal popliteal artery. Postoperative angiography showed satisfactory graft patency and distal run-off, and the ulcer improved. Femoropopliteal occlusive disease in Werner's syndrome tends to have poor run-off and the internal diameter of the popliteal artery with diffuse arteriosclerotic lesion is often too small to facilitate distal anastomosis. Therefore, a conventional bypass procedure is not always effective and an aggressive attitude is essential to obtain sufficient ankle blood pressure and improve the leg ulcer in Werner' syndrome.

Anastomosis, Surgical↗
PubMed1989

Measurement of the villus surface area and its regional variation in the human full-term placenta.

The surface/volume ratio and the surface density of the chorionic villi in different cotyledonary regions of the human mature placenta were studied by stereologic methods. The villus surface/volume ratio showed a mean value of 812.3 cm2/cm3 (standard deviation = 89.2 cm2/cm3). There were no significant differences according to the site from which the sample was obtained. The villus surface density in normal mature placentae was (496.3 +/- 49.0) cm2/cm3. The last parameter showed no differences among regions. Despite the absence of significant differences of exchange surface areas among the cotyledonary regions considered, other important parameters, such as trophoblast thickness, frequency of vasculo-syncytial membranes, as well as the maximal gradient of concentration, facilitates the maternal-fetal transfer by simple diffusion mechanism in the central-parabasal region.

Chorionic Villi↗
PubMed1996

The effect of ultra-low sodium dialysate in CAPD. A kinetic and clinical analysis.

In peritoneal dialysis, sodium (Na) passes through the peritoneal membrane to a lesser extent than H2O and thus hypotonic fluid is removed indicating that Na removal is inefficient. Therefore we developed an ultra-low Na dialysate (ULNaD) [Na 98 mmol/liter, osmolality 340 mOsm/kg, glucose (G), 2.48%] to facilitate trans-peritoneal Na removal. The aim of the study was to examine (a) the fluid and Na kinetics of this solution, and (b) the clinical effect in the overhydrated patient. Regarding the former, in six cases, changes in the effluent Na levels during a 240-minute dwell of ULNaD were measured at 60-minute intervals. In eighteen cases, the transperitoneal net-Na removal (Na removal) and drained ultrafiltration (UF) volume after a 240-minute dwell of ULNaD were measured and compared to two types of standard Na dialysate (SNaD) [Na 132 mmol/liter, 1.36% G (348 mOsm/kg) and 2.27% G (396 mOsm/kg)]. The effluent Na levels increased gradually until the end of the dwelling. Drained UF volume of ULNaD (224 +/- 25 ml) was more than 1.36% G SNaD (77 +/- 33 ml, p < 0.01), but it was less than 2.27% G SNaD (341 +/- 32 ml, p < 0.01). However, a significant increase in Na removal by ULNaD (78.1 +/- 5.6 mmol) was found compared with both SNaD solutions (12.6 +/- 6.4 mmol in 1.36% G solution, p < 0.001; 27.8 +/- 5.1 mmol in 2.27% G solution, p < 0.001, respectively). Regarding the latter study aim, in six overhydrated patients with a Na excess, SNaD was replaced with ULNaD once a day for 7 consecutive days. At the end of the study as compared to the pre-values, a significant reduction in body weight (-2.5 +/- 1.0%, p < 0.05) and mean arterial pressure (-12.3 +/- 3.5%, p < 0.001) was observed. An increased drainage of daily UF volume (+86.5 +/- 31.1%, p < 0.05) and a markedly increased daily Na removal (+131.1 +/- 24.2%, p < 0.01) were also observed. The results of this study suggest that ULNaD actually facilitates trans-peritoneal Na removal mainly by diffusion force, and that ULNaD could benefit overhydrated patients with a Na excess.

Adult↗
PubMed1977

The association: scleroderma-silicosis or Erasmus' syndrome (author's transl).

Classically more common in women, scleroderma nevertheless affects with predilection men exposed to the inhalation of silica particles. The association scleroderma-silicosis is essentially a statistical finding. It has no particular clinical, radiological nor histological distinguishing characteristics, other than the syndromic juxtaposition of the stigmata of each of the two disorders. This serious pathological combination is not due merely to chance. It is the result of depressed cellular immunity, related to the cytotoxicity of silica and responsible for auto-immune reactions and the formation of circulating immune-complexes. In the presence of an underlying predisposition, the polyvisceral diffusion of inhaled toxic mineral particles could also facilitate the sclerodermic process by stimulating fibroblastic proliferation.

Female↗
PubMed1991

Application of charge-coupled device technology for measurement of laser light and fluorescence distribution in tumors for photodynamic therapy.

Laser and fluorescence light distributions with applications for photodynamic therapy were measured in mouse tumors using a non-invasive electronic optical imaging system. The system consists of a liquid-nitrogen-cooled, charge-coupled-device (CCD) array camera under computer control with 576 x 384 detection elements having dimensions of 23 microns x 23 microns. The available dynamic range of the array is approx. 10(3), and the effective wavelength range is 400-1000 nm. An interstitially placed cylindrical diffusing optical fiber was used to provide tumor illumination. The light distribution pattern from the fiber was determined by immersing the cylindrical diffusing tip in a fluorescing solution and recording the emission image. Fluorescence imaging facilitates an accurate measurement of light intensity distribution while avoiding problems associated with the directional nature of other detection methods used with diffusing fibers. Radiation-induced fibrosarcoma tumors on C3H mice were grown to about 1 cm diameter for in vivo recording of light distribution from the tumor volume and for determination of effective light penetration distance at 18 wavelengths in the range 458-995 nm. Endogenous tumor fluorescence and Photofrin II fluorescence intensity were measured over the wavelength range 585-725 nm to investigate the possible application of CCD imaging technology for drug distribution measurements. Model experiments were begun to evaluate the relative importance of potential distortions of light distribution measurements using this approach.

Animals↗
PubMed2003

Transbilayer lipid diffusion promoted by Bax: implications for apoptosis.

It is known that the proapoptotic protein Bax facilitates the formation of pores in bilayers, resulting in the release of proteins from the intermitochondrial space. We demonstrate that another consequence of the interaction of Bax with membranes is an increase in the rate of lipid transbilayer diffusion. We use two independent assays for transbilayer diffusion, one involving the formation of asymmetric liposomes by placing a pyrene-labeled lipid into the outer monolayer of preformed vesicles and another assay based on the initial preparation of liposomes having an asymmetric transbilayer distribution of lipids. With both methods we find that oligomeric BaxDeltaC or full-length Bax in the presence of tBid, but not monomeric full-length Bax, strongly promotes the rate of transbilayer diffusion. Although biological membranes exhibit rates of lipid transbilayer diffusion of minutes or less, they are able to maintain an asymmetric distribution of lipids across the bilayer. In the case of mitochondria, cardiolipin is sequestered on the inner leaflet of the inner mitochondrial membrane. However, during apoptosis this lipid translocates to the outer surface of the outer mitochondrial membrane. This phenomenon must involve an increase in the rate of transbilayer diffusion. The results of the present paper demonstrate that an activated form of Bax can cause this increased rate.

Apoptosis↗
PubMed2000

Diffusion MRI detects early events in the response of a glioma model to the yeast cytosine deaminase gene therapy strategy.

Detection of a therapeutic response early in the course of cancer treatment, before tumor growth delay or regression, is not currently possible in experimental models or clinical medicine. New interim measures of therapeutic response would be particularly useful in the development of cancer chemosensitization gene therapy by facilitating optimization of gene transfer protocols and prodrug dosing schedules. Diffusion MRI is a sensitive technique producing quantitative and noninvasive images of the apparent mobility of water within a tissue. We investigated the utility of diffusion MRI for detecting early changes associated with a refined cytosine deaminase (CD)/5-fluorocytosine (5FC) chemosensitization gene therapy paradigm in orthotopic 9L gliomas stably expressing the recently cloned S. cerevisiae CD gene. Mean tumor diffusion increased 31% within 8 days of initiating 5-FC treatment, preceding tumor growth arrest and regression. Complete regression of the intracranial tumor was observed in four of five treated animals, and recurrent tumor in the remaining animal exhibited water diffusion behavior similar to primary, untreated tumors. These results demonstrate the efficacy of the yCD/5FC strategy for glioma and suggest that increased tumor water diffusion is an indicator of active therapeutic intervention.

Animals↗
PubMed2007

Liquid crystalline phases and their dispersions in aqueous mixtures of glycerol monooleate and glyceryl monooleyl ether.

The aqueous phase behavior of mixtures of 1-glycerol monooleate (GMO) and its ether analogue, 1-glyceryl monooleyl ether (GME) has been investigated by a combination of polarized microscopy, X-ray diffraction, and NMR techniques. Three phase diagrams of the ternary GMO/GME/water system have been constructed at 25, 40, and 55 degrees C. The results demonstrate that the increasing amount of GME favors the formation of the reversed phases, evidenced by the transformation of the lamellar and bicontinuous cubic liquid crystalline phases of the binary GMO/water system into reversed micellar or reversed hexagonal phases. For a particular liquid crystalline phase, increasing the GME content has no effect on the structural characteristics and hydration properties, thus suggesting ideal mixing with GMO. Investigations of dispersed nanoparticle samples using shear and a polymeric stabilizer, Pluronic F127, show the possibility of forming two different kinds of bicontinuous cubic phase nanoparticles by simply changing the GMO/GME ratio. Also NMR self-diffusion measurements confirm that the block copolymer, Pluronic F127, used to facilitate dispersion formation, is associated with nanoparticles and provides steric stabilization.

Chemistry, Physical↗
PubMedDate not supplied

Community demonstration project initiative: technical support for program development at the community level.

Select population groups are at greater than average risk for cancer incidence and mortality. Lack of experience reaching high-risk populations, particularly those characterized by high proportions of the socioeconomically disadvantaged, presented a challenge to the American Cancer Society (ACS). A partial solution was to integrate outreach to high-risk populations into ACS national priorities and to fund community demonstration projects consistent with these priorities. Technical assistance (TA), which includes expert advice and problem solving, was provided during the first phase to facilitate the development of these projects into "model" projects to learn what initiatives can best be disseminated, or diffused, into target populations. TA also was used to assess how it can enhance the potential for replication. Evaluation of this initiative resulted in a plan to disseminate model projects to selected ACS divisions with varied resources and capabilities (e.g., outreach to high-risk populations, planning, program development, and evaluation) for replication. During the next phase, projects will be evaluated to document the role of TA in facilitating local empowerment and nationwide diffusion of effective cancer prevention and control programs.

Community Health Services↗