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At least 19 recordsLinked to original sources
PubMed1979

Simultaneous determination of polar and non-polar solvents in air using a two-phase desorption from charcoal.

A gas chromatographic procedure is described which is capable of measuring both polar and non-polar organic solvents present simultaneously in the work environment at concentrations between 1/100 and 1 times the Threshold Limit Values (TLV). Airborne organics are collected on a single activated charcoal tube for periods of 3 to 6 hours and desorbed with a two-phase (water/carbon disulfide) desorption mixture. Organic and aqueous phases are analyzed separately on the same gas chromatographic column packed with Oronite NIW on Carbopack B. Recoveries were determined for fifteen common solvents. Most recoveries were greater than 90% with all coefficients of variation being less than +/- 10%. Breakthrough was observed only when solvents were present at very high concentrations. Examples of field sampling are also presented. This procedure is generally applicable for monitoring complex mixtures of volatile organic compounds in air. Advantages include excellent recoveries for polar solvents such as acetone and ethanol, utilization of common analytical instrumentation under a single set of operating conditions and compatibility with TWA personnel monitoring methodology.

Air↗
PubMed1978

The visualization of actin filament polarity in thin sections. Evidence for the uniform polarity of membrane-associated filaments.

We have developed an improved method for visualizing actin filament polarity in thin sections. Myosin subfragment-1 (S-1)-decorated actin filaments display a dramatically enhanced arrowhead configuration when fixed in a medium which contains 0.2 % tannic acid. With the exception of brush borders from intestinal epithelial cells, the arrowhead periodicity of decorated filaments in a variety of nonmuscle cells is similar to that in isolated myofibrils. The periodicity of decorated filaments in brush borders is significantly smaller. Actin filaments which attach to membranes display a clear, uniform polarity, with the S-1 arrowheads pointing away from the plasma membrane, while those which comprise the stress fibers of myoblasts and CHO cells have antiparallel polarities. These observations are consistent with a sliding filament mechanism of cell motility.

Actins↗
PubMed1978

Comprehensive analytical procedures for the determination of volatile and non-volatile, polar and non-polar N-nitroso compounds.

The first comprehensive analytical procedures for the quantitative analysis of N-nitroso compounds are described. The scheme divides N-nitroso compounds into four major, overlapping categories: volatile (Class I), non-volatile, low polarity (Class II), non-volatile, non-ionic, high polarity (Class III) and non-volatile, ionic, high polarity (Class IV). Existing analytical techniques for each class of compound are integrated into an organized and logical sequence of analysis to allow all classes of compounds to be determined. TEA-GC is used for the volatile compounds and TEA-HPLC for the non-volatile. It is emphasized that the coincidence of retention time in either TEA-GC alone or TEA-HPLC alone cannot be taken as sufficient evidence for the identification of N-nitroso compounds, especially for samples from complex matrices. Independent techniques are required to confirm these results. The confirmatory techniques used frequently in our laboratory are: (1) spectroscopic analysis (IR, NMR, UV and MS), (2) formation and identification of derivatives, and (3) parallel TEA-GC/TEA-HPLC techniques. These procedures are now used at Thermo Electron for the comprehensive screening of environmental samples.

Chemical Phenomena↗
PubMed1977

The influence of polar and non-polar digoxin and digitoxin metabolites on the 86Rb-uptake of human erythrocytes and the contractility of guinea pig papillary muscles.

The potency of various digoxigenin and digitoxigenin derivatives with different polarity was tested in two biological systems: First, in an 86-Rb-erythrocyte assay which allows to determine the influence on active cation transport (measured as the glycoside concentration exerting half maximal inhibition of 86-Rb-uptake of human erythrocytes = IC50). Second, with isolated guinea pig papillary muscle, which allows to determine glycoside effects on contractile force (measured as the glycoside concentration exerting 100% increase of contractile force = C+100%). The IC50 of the substances covered a range from 3.2 to 4800 X 10(-9) M, the C+100% from 0.7 to 978 X 10(-6) M. In both assay systems the glucuronides of glycosides and genins were between 1.4 and 11 times less potent than the original substances. A highly significant correlation (p less then 0.0001) was found between IC50 and C+100% (r = 0.9996) and between log IC50 and log C+100% (r = 0.9819), the slope for the latter correlation being nearly unite (= 0.9912). The results support the hypothesis that inhibition of active cation transport is and important step in glycoside incuced posite-inotropic effect.

Animals↗
PubMed1979

Theoretical aspects of adsorption of polar substances from polar solvents.

The efficiency of adsorbents for hemoperfusion and dialysate regeneration can be increased if suitable catalysts are fixed on their surface in an appropriate density. Suitable catalysts are oxides and salts of the transition metals. The appropriate surface density of the catalysts depends on the molecular data of both catalyst and toxin to be removed, as well as on the distribution of the adsorption sites on the adsorbent surface area. The distribution of the adsorption sites is determined by means of photoelectron spectroscopy and adsorption and desorption measurements.

Adsorption↗
PubMed2026

Centrosome migration and apical membrane formation during epithelial polarization in MDCK cysts.

Polarization is crucial for the proper functioning of epithelial cells. Early hallmarks include the trafficking and enrichment of polarity molecules to form the apical membrane (AM) or cell-cell junctions, and the apical positioning of the centrosome. However, the dependencies among polarity molecules, AM formation, and centrosome positioning remain poorly understood. When cultured in Matrigel, de novo polarization of a single epithelial cell is often coupled with cytokinesis. During mitotic exit, centrosomes move to the future AM site, raising questions about their role in polarization. We perturbed centrosomes and polarity regulators in Matrigel-cultured cells and manipulated polarity direction using suspension culture to examine the relationships among polarization features. Surprisingly, centrosomal microtubules may not be necessary for centrosome positioning or AM formation, but their absence reduces the efficiency of AM formation. The polarity regulator Par3, rather than AM component trafficking, influences centrosome positioning. In suspension culture, centrosomes migrate in the direction opposite to AM formation. Taken together, our findings define the hierarchical relationships among several polarization features and show that centrosome-based polarity is not universal in epithelial cells, providing new insights into the mechanisms of epithelial polarization.

Animals↗
PubMed1976

Immunofluorescent polar tips of Rhizobium japonicum: possible site of attachment or lectin binding.

Rhizobium japonicum USDA 31 demonstrated marked polarity by binding homologous fluorescent antibody (FA) heavily on one end of the cell. FA prepared against R. japonicum strains 110 and 138, and against R. trifolii TA1 cross-reacted with strain 31 only in the polar tip region. No polar immunofluorescing tips could be seen with FA against two other strains of R. japonicum or with those against several unrelated microorganisms. Common antigens localized only in a polar region were seen in many rhizobia stained with R. japonicum 31 FA: 22 of 23 strains of R. japonicum, 10 of 17 strains of R. trifolii, 3 of 7 strains of R. melitolii, 3 of 6 strains of R. phaseoli, and 3 of 9 strains of R. leguminosarum had some cells with detectable polar tips. The proportion of R. japonicum 31 cells with polar tips was high throughout the growth cycle. Polar tip staining was not affected by drastic cell treatments. A function was proposed for the polar tip region as a site for attachment. R. japonicum 31 cells attached to each other in a tip-to-tip fashion and endwise to fungal hyphae with the polar tip in contact with the hyphal wall. Binding of fluorescein isothiocyanate-labeled soybean lectin to certain strains of R. japonicum gave additional evidence of polarity. Polar binding of both antibody and lectin may provide insights into relationships between rhizobia and roots of host legumes.

Antibodies, Bacterial↗
PubMed1978

Electron spin polarization in photosynthesis and the mechanism of electron transfer in photosystem I. Experimental observations.

Transient electron paramagnetic resonance (EPR) methods are used to examine the spin populations of the light-induced radicals produced in spinach chloroplasts, photosystem I particles, and Chlorella pyrenoidosa. We observe both emission and enhanced absorption within the hyperfine structure of the EPR spectrum of P700+, the photooxidized reaction-center chlorophyll radical (Signal I). By using flow gradients or magnetic fields to orient the chloroplasts in the Zeeman field, we are able to influence both the magnitude and sign of the spin polarization. Identification of the polarized radical and P700+ is consistent with the effects of inhibitors, excitation light intensity and wavelength, redox potential, and fractionation of the membranes. The EPR signal of the polarized P700+ radical displays a 30% narrower line width than P700+ after spin relaxation. This suggests a magnetic interaction between P700+ and its reduced (paramagnetic) acceptor, which leads to a collapse of the P700+ hyperfine structure. Narrowing of the spectrum is evident only in the spectrum of polarized P700+, because prompt electron transfer rapidly separates the radical pair. Evidence of cross-relaxation between the adjacent radicals suggests the existence of an exchange interaction. The results indicate that polarization is produced by a radical pair mechanism between P700+ and the reduced primary acceptor of photosystem I. The orientation dependence of the spin polarization of P700+ is due to the g-tensor anisotropy of the acceptor radical to which it is exchange-coupled. The EPR spectrum of P700+ is virtually isotropic once the adjacent acceptor radical has passed the photoionized electron to a later, more remote acceptor molecule. This interpretation implies that the acceptor radical has g-tensor anisotropy significantly greater than the width of the hyperfine field on P700+ and that the acceptor is oriented with its smallest g-tensor axis along the normal to the thylakoid membranes. Both the ferredoxin-like iron-sulfur centers and the X- species observed directly by EPR at low temperatures have g-tensor anisotropy large enough to produce the observed spin polarization; however, studies on oriented chloroplasts show that the bound ferredoxin centers do not have this orientation of their g tensors. In contrast, X- is aligned with its smallest g-tensor axis predominantly normal to the plane of the thylakoid membranes. This is the same orientation predicted for the acceptor radical based on analysis of the spin polarization of P700+, and indicates that the species responsible for the anisotropy of the polarized P700+ spectrum is probably X-. The dark EPR Signal II is shown to possess anisotropic hyperfine structure (and possibly g-tensor anisotropy), which serves as a good indicator of the extent of membrane alignment.

Chlorella↗
PubMed1979

Computer analysis of vectorcardiograms in myocardial infarction with special reference to polar vector and planarity of the QRS and T loops.

Spatial characteristics of the QRS and T loops in 110 patients with old myocardial infarction were analysed in comparison with 221 normal subjects. Measured were (1) QRS and T polar vectors, (2) initial 20- and 30-msec segmental QRS polar vectors, and (3) length, width, thickness, and ratios of width/length and thickness/length of the QRS and T loops in edgewise and broadside projections. Broadside and edgewise projections were obtained by transformation of the reference frame of the Frank lead system to a patient's own frame based on the polar vector. The recognition rates of abnormality in the QRS and T polar vectors were 66% and 60% of a total of 110 patients with myocardial infarction. The initial 30 msec segmental QRS polar vector showed the highest recognition rate of abnormality in myocardial infarction, i.e., 87% in anterior myocardial infarction, 100% in extensive anterior myocardial infarction and 78% in inferior myocardial infarction. The initial segmental QRS polar vector was abnormally deviated posteriorly and superiorly in inferior myocardial infarction. In anterior myocardial infarction, the initial segmental polar vector was directed inferiorly in more than 50% of the cases, while the vector in normal subjects was located superiorly and to the left. The QRS loop of anterior myocardial infarction was significantly smaller in the width and width/length ratio and significantly larger in the thickness and thickness/length ratio than those of the normal. Poor planarity of the QRS loop was one of the characteristics of myocardial infarction, especially of extensive anterior myocardial infarction. The T loop of myocardial infarction was significantly larger in the width/length ratio than that of the normal. More than 50% of the cases with anterior myocardial infarction showed abnormally wide T loops. The polar vector was a useful index to characterize the spatial orientation and sense of rotation of the spatial loop. In addition, the initial segmental QRS polar vector represented the mild localized abnormalities of the spatial loop. The loop configuration in space was characterized in edgewise and broadside projections.

Acute Disease↗
PubMed1977

Fluorescence polarization studies of rat intestinal microvillus membranes.

Rat intestinal microvillus membranes and lipid extracts prepared from them have been studied by fluorescence polarization with three lipid-soluble fluorophores: diphenylhexatriene, retinol, and anthroyl-stearate. The degree of fluorescence polarization of diphenylhexatriene, which provides an index of the "microviscosity" of the lipid regions of the membrane, is exceptionally high in microvillus membranes, the highest yet reported in normal biological membranes. Both the membrane proteins and lipids were found to contribute to the high values. With each of the three probes the polarization values are higher in ileal microvillus membranes as compared to membranes from proximal intestinal segments. Temperature-dependence studies of the fluorescence polarization of diphenylhexatriene and anthroylstearate demonstrate a phase transition in microvillus membranes and in liposomes prepared from their lipid extracts at approximately 26+/-2 degrees C. Ambient pH influences markedly the diphenylhexatriene fluorescence polarization in microvillus membranes but has little effect on that of human erythrocyte ghost membranes. The "microviscosity" of jejunal microvillus membranes is maximal at pH 6.5-7.0 and decreases as much as 50% at pH 3.0, an effect which depends largely upon the membrane proteins. Addition of calcium ions to suspensions of microvillus membranes increases the fluorescence polarization of retinol and anthroyl-stearate, but not that of diphenyl-hexatriene. This confirms the localization of the last compound to the hydrophobic interior of the membrane, relatively distant from the hydrophilic head groups of the polar lipids. Microvillus membrane proteins solubilized with Triton X-100 give relatively high fluorescence polarization and intensity values with retinol, suggesting the presence of binding proteins which could play a role in the normal absorptive mechanism for the vitamin.

Animals↗
PubMed1977

Flow cytometric measurement of the polarization of fluorescence from intracellular fluorescein in mammalian cells.

Based on the description of a laboratory-built flow cytometer, the necessary modifications of this instrument for the measurement of fluorescence polarization are described. At a maximum rate exceeding 1,000 cells/s, the instrument is capable of measuring simultaneously the horizontally and vertically polarized component of the fluorescence emitted from stained cells excited with vertically polarized light. By mathematical analysis of the accumulated data, the distribution of polarization values in the population is obtained. Various sources of instrumental error have been investigated. The large aperture of the detector optics leads to systematic underestimation of the polarization values. Other errors are negligible, and the instrument is shown to give results consistent with the theory of fluorescence polarization. Application of the instrument is illustrated by experiments with mammalian cells exposed to the fluorogenic substrate fluorescein diacetate (FDA). The polarization of the fluorescence from intracellular fluorescein produced by hydrolysis of FDA is measured, giving information on the cytoplasmic microviscosity. It appears that this microviscosity is constant over the cell cycle. On the other hand, it is significantly affected by the osmolarity of the medium.

Cell Division↗
PubMed1979

Polymerization of actin. VI. The polarity of the actin filaments in the acrosomal process and how it might be determined.

The polarity of the actin filaments which assemble from the nucleating body or actomere of Thyone and Pisaster sperm was determined using myosin subfragment 1 decoration. The polarity was found to be unidirectional with the arrowheads pointing towards the cell center. When polymerization is induced at low temperature with concentrations of actin near the critical concentration for polymerization, elongation of filaments occurs preferentially off the apical end. If the sperm are induced to undergo the acrosomal reaction with an ionophore, the polarity of the actin filaments attached to the actomere is the same as that already described, but the filaments which polymerize parallel to, but peripheral to, those extending from the actomere are randomly polarized. These randomly polarized filaments appear to result from spontaneous nucleation. When sperm are induced to undergo the acrosomal reaction with eggs, the polarity of the actin filaments is also unidirectional with the arrowheads pointing towards the cell center. From these results we conclude: (a) that the actomere, by nucleating the polymerization of actin filaments, controls the polarity of the actin filaments in the acrosomal process, (b) that the actomere recognizes a surface of the actin monomer that is different from that surface recognized by the dense material attached to membranes, and (c) that egg myosin could not act to pull the sperm into the egg. Included is a discussion of how the observation that monomers add largely to one end of a decorated filament in vitro relates to these in vivo observations.

Acrosome↗