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PubMed1976

Effect of gemfibrozil in vitro on fat-mobilizing lipolysis in human adipose tissue.

Fat-mobilizing lipolysis was studied in rat and human adipose tissue during incubation in vitro by following the release of glycerol into the incubation medium. Gemfibrozil as well as clofibrate consistently and readily inhibited basal as well as noradrenaline-stimulated fat-mobilizing lipolysis in rat fat. With human adipose tissue no effect was observed with gemfibrozil and clofibrate on basal lipolysis. This may be due to the comparatively low rate of the nonstimulated fat-mobilizing lipolysis in human tissue incubated in vitro. When lipolysis was stimulated with noradrenaline as well as isoprenaline, however, both gemfibrozil and clofibrate significantly reduced the fat-mobilizing lipolysis. This inhibition of lipolysis was however not observed in all studies. When lipolysis had been stimulated with theophylline, no inhibition of lipolysis was obtained with either compound. The possibility that reduced fat-mobilizing lipolysis in adipose tissue may cause a lowering of plasma triglycerides by reducing the flow of FFA to the liver is discussed in some detail. It is also suggested that inhibition of lipolysis may be accompanied by increased activity of lipoprotein lipase as well as an increase in the FIAT process. However, the pharmacological implication of the above-mentioned findings, particularly for gemfibrozil, must await further studies, as fairly large doses, around 1 mg/ml of incubation medium, were needed to obtain inhibition of fat-mobilizing lipolysis.

Adipose Tissue↗

PubMed1992

Oxidant-induced mobilization of zinc from metallothionein.

Neutrophils which accumulate at sites of inflammation secrete a number of injurious oxidants which are highly reactive with protein sulfhydryls. The present study examined the possibility that this reactivity with thiols may cause protein damage by mobilizing zinc from cellular metalloproteins in which the metal is bound to cysteine. The ability of the three principal neutrophil oxidants, hypochlorous acid (HOCl), superoxide (.O2-), and hydrogen peroxide (H2O2), to cleave thiolate bonds and mobilize complexed zinc was compared using two model compounds (2,3-dimercaptopropanol and metallothionein peptide fragment 56-61), as well as metallothionein. With all compounds, 50 microM HOCl caused high rates of Zn2+ mobilization as measured spectrophotometrically with the metallochromic indicator 4-(2-pyridylazo)resorcinol. Xanthine (500 microM) plus xanthine oxidase (30 mU), which produced a similar concentration of .O2-, also effected a rapid rate of Zn2+ mobilization which was inhibited by superoxide dismutase but not catalase, indicating that .O2- is also highly reactive with thiolate bonds. In contrast, H2O2 alone was much less reactive at comparable concentrations. These data suggest that HOCl and .O2- can cause damage to cellular metalloproteins through the mobilization of complexed zinc. In view of the essential role played by zinc in numerous cellular processes, Zn2+ mobilization by neutrophil oxidants may cause significant cellular injury at sites of inflammation.

Amino Acid Sequence↗

PubMed1976

Microviscosity parameters and protein mobility in biological membranes.

A fluorescence polarization technique with 1,6-diphenyl 1,3,5-hexatriene as a probe were employed to determine the microviscosity, n, in liposomes and biological membranes of different cholesterol to phospholipid mol ratio. From the temperature profile of n the flow activation energy, deltaE, and the unit flow volume, V, were derived. The increase of cholesterol/phospholipid ratio in liposomes is followed by a marked increase in n and a decrease in both deltaE and V. Liposomes of the same phospholipid composition as human erythrocyte membranes display in the extreme cases of cholesterol/phospholipid ratios 0 and 1.4 the values of n(25 degrees C) = 1.8 and 9.1 P, and deltaE = 15.0 and 6.5 kcal/mol, respectively. For most membranes studied the fluorescence polarization characteristics and the corresponding n values are similar to those obtained with these liposomes when the cholesterol/phospholipid level of the liposomes and the membranes were the same. However, unlike in liposomes deltaE of all membranes is in the narrow range of 6.5-8.5 kcal/mol, regardless of its cholesterol/phospholipid level. It is plausible that this is a general characteristic of biological membranes which originates from the vertical movement of membrane proteins to an equilibrium position which maintains constant deltaE and V values. This type of movement should affect the interrelation between lipid fluidity and protein mobility. Lipid microviscosity and the degree of rotational mobility of concanavalin A receptor sites in cell membranes were therefore determined. The examined cells were normal and malignant fibroblasts, as an example of cells that form solid tumours in vivo, and normal and malignant lymphocytes, as an example of cells that form ascites tumours in vivo. In both cell systems, opposite correlations between the lipid fluidity and the mobility of concanavalin A receptors were observed. In the fibroblasts the malignant cells possess a lower lipid fluidity but a higher receptor mobility, whereas in the lymphocytes the malignant cells possess a higher lipid fluidity but a lower receptor mobility. Thus, in these cell systems the degree of rotational mobility of concanavalin A receptors increases upon decreasing the lipid fluidity and decreases upon increasing the fluidity of the lipid core. This dynamic feature is in line with the above proposal according to which the concanavalin A receptor sites become more exposed to the aqueous surrounding upon increasing the microviscosity of the lipid layer and vice versa.

Animals↗

PubMed1976

Plasma chromatography of heroin and cocaine with mass-identified mobility spectra.

Plasma chromatography detects and identifies compounds in trace quantities at atmospheric pressure through characteristic positive and negative mobility spectra. To facilitate use of the technique to detect gas chromatographic effluents, a number of reference mobility spectra for different classes of compounds have been reported. Reference spectra for two more compounds, heroin and cocaine, are presented in this study. The primary ions found in these mobility spectra were determined to be M+, (M - H2)+, and (M - CH3CO2)+ for heroin and M+, (M - C6H5CO2)+ and (M - C6H5CO2 - CO2CH3)+ for cocaine using a directly interfaced plasma chromatograph-mass spectrometer. The identified ions agree closely with those predicted in the ion mobility spectra using mass-mobility correlation data coupled with chemical ionization mass spectrometry data. Also, an independent check demonstrating the reliability of reduced mobility values reported in earlier reference spectra was made.

Chromatography, Gas↗

PubMed1978

Change of electrophoretic mobility of purified alternative pathway factor D.

The electrophoretic mobility of factor D (D) of the alternative pathway of human complement activation was examined by the method of lysoelectrophoresis. Purified D was found to have beta-mobility, while D in fresh serum showed alpha-mobility. Addition of D-depleted serum to D induced a change of electrophoretic mobility from beta to alpha. Addition of guinea pig serum to D did not produce this change. The change of electrophoretic mobility of D was not due to complex formation between D and other known alternative factors, P, C3NeF, B and C3. The Factor(s), which mediated the change in the electrophoretic mobility of D, had pseudoglobulin properties and was distributed around the third peak on Sephadex G-200 gel filtration of human serum with a mol. wt. of 50,000-80,000. This phenomenon might be restricted to a semi-solid state reaction, because complexes containing D were not observed upon analyses by sucrose density gradient ultracentrifugation and isoelectrofocusing.

Animals↗

PubMed1979

Macrophage response to concanavalin A: effect of surface crosslinking on the electrophoretic mobility distribution.

Electrophoretic light scattering (laser Doppler electrophoresis) has been employed to study the effects of concanavalin A (Con A) and succinyl-Con A on the electrophoretic mobility distribution of resident guinea pig peritoneal macrophages. Con A, a tetrameric lectin, decreases slightly the mean mobility and increases by approximately 3-fold the width of the electrophoretic mobility distribution of resident macrophages. This effect can be abolished by alpha-methyl-D-mannoside, a hapten sugar of Con A. These effects were present in both low (0.010 M) and high (physiological, 0.15 M) ionic-strength media. Since lower ionic strengths correspond to a larger Debye screening distance, these data suggest that the alterations in the electrophoretic mobility distribution are not restricted to the outer portion of the glycocalyx. Succinyl-Con A, a dimeric derivative, was found to have no effect on the mobility distribution. However, the mean mobility decreased and the width increased over 4-fold when succinyl-Con A-treated macrophages were exposed to anti-Con A. These observations indicate that cross-linking of Con A receptors is an important process in the electrokinetic alterations of the macrophage surface. These results may have important consequences for the elucidation of the details of the endocytic mechanism.

Ascitic Fluid↗

PubMed1992

Artificial mobile DNA element constructed from the EcoRI endonuclease gene.

There exist several examples of mobile group I introns. These introns appear to use a straightforward mechanism to achieve highly site-specific and efficient insertion into homologous intronless genes. Because the only intron-specific function required by the prevailing model for the mechanism of intron mobility is the introduction of a site-specific double-stranded break in the intronless recipient DNA molecule, we reasoned that it should in principle be possible to construct artificially mobile DNA sequences. We have constructed an artificial mobile element from the gene for the restriction enzyme EcoRI that is capable of site-specific insertion at rates near those of authentic mobile introns. The generality of the mobility mechanism may enable high-efficiency targeted gene replacements or disruptions in a variety of organisms.

Bacteriophage lambda↗

PubMed1992

Osteoporosis in spinal cord injury: using an index of mobility and its relationship to bone density.

This study was undertaken to improve quantification of the extent of osteoporosis that accompanies spinal cord injuries (SCI) of various types, using single photon densitometry. In this study, we evaluated subjects with complete and incomplete SCI to determine whether there is a correlation between mobility and bone density. We created an index to rank the various levels of mobility among SCI subjects. Mobility index parameters ranged from 1, for complete immobility, to 9, for the full mobility of the uninjured control population. Incomplete SCI subjects (motor and/or sensory) ranked from 2 to 8 on the mobility scale. We also attempted to define clearly the mechanism of osteoporosis in those with predominantly unilateral SCI (Brown-Sequard syndrome). Using single photon absorptiometry (SPA), we found a strong correlation between our mobility index and observed bone density. These observations clearly show that osteoporosis is affected by the subject's level of physical activity. These observations also support the hypothesis that SCI individuals benefit from efforts to maintain a standing posture with some regularity. This effort to improve bone density slows the development of osteoporosis, a process that results in physical impairments in the SCI population.

Absorptiometry, Photon↗

PubMed1992

Iron mobilization from crocidolite asbestos greatly enhances crocidolite-dependent formation of DNA single-strand breaks in phi X174 RFI DNA.

The ability of the iron associated with asbestos to catalyze damage to phi X174 RFI DNA was determined and compared with iron mobilized from asbestos. Asbestos (1 mg/ml) suspended for 30 min in 50 mM NaCl containing 0.5 micrograms phi X174 RFI DNA, pH 7.5, did not catalyze detectable amounts of DNA single-strand breaks (SSB). However, addition of ascorbate (1 mM) resulted in 19, 26, 7 or 8% DNA with SSB for crocidolite, amosite, chrysotile or tremolite respectively. The percentage of DNA with SSB induced by each form of asbestos was directly related to its iron content. Inclusion of desferrioxamine B, which binds Fe(III) rendering it redox inactive, completely inhibited asbestos-dependent formation of DNA SSB, suggesting that iron was responsible for catalyzing the formation of DNA SSB. Mobilization of Fe(II) from crocidolite by citrate, EDTA or nitrilotriacetate (1 mM) in the absence of ascorbate resulted in 15, 33 or 63% DNA with SSB respectively. This activity was completely inhibited by compounds considered to be .OH scavengers, i.e. mannitol, 5,5-dimethyl-1-pyrroline N-oxide or salicylate (100 mM). Preincubation of crocidolite with citrate (1 mM) for 24 h resulted in mobilization of 52 microM iron and increased ascorbate-dependent induction of DNA SSB compared with crocidolite that was preincubated without citrate. Iron mobilized by citrate was entirely responsible for crocidolite-dependent formation of DNA SSB as evidenced by complete inhibition with desferrioxamine B. Therefore, the results of the present study strongly suggest that iron was responsible for asbestos-dependent generation of oxygen radicals, which resulted in the formation of DNA SSB. Mobilization of iron by chelators, followed by redox cycling, greatly enhanced crocidolite-dependent formation of DNA SSB. Thus, mobilization of iron in vivo by low mol. wt chelators may lead to the increased production of reactive oxygen species resulting in damage to biomolecules, such as DNA.

Asbestos↗

PubMed1979

Age-dependent changes in the electrophoretic mobilities of human blood lymphocytes.

The distribution of the anodic electrophoretic mobilities (EPM) of human peripheral blood lymphocytes was determined for lymphocytes isolated from umbilical cord blood and from blood of individuals 6 months to 93 years of age. The distribution was bimodal in infants up to 2 years of age and suggested a small percentage of cells with a mobility of 0.95 micrometer s-1 V-1 cm. this value was chosen to discriminate between low-mobility cells (LMCs) and high-mobility cells (HMCs). The relative percentage of LMCs increased from birth to 2 years and two types of LMCs could be distinguished. The distribution was unimodal and asymmetric in children and adults and nearly Gaussian in aged people. Substantial differences between the distributions of the lymphocyte EPMs were seen on comparison of the histograms for individuals of similar ages. The analysis of the distribution of the lymphocyte EPMs on cell suspensions enriched in, or depleted of T or B cells confirmed the mobility of most T cells to be higher than the mobility of most B cells, whatever the age of the individual. The distribution of lymphocyte EPMs determined in the same adult over a 6 year period showed minor variations.

Adolescent↗

PubMed1975

Interaction of a non-histone chromatin protein (high-mobility group protein 2) with DNA.

1. The interaction with DNA of the calf thymus chromatin non-histone protein termed the high-mobility group protein 2 has been studied by sedimentation analysis in the ultracentrifuge and by measuring the binding of the 125I-labelled protein to DNA. The results have been compared with those obtained previously by us [Eur. J. Biochem. (1974) 47, 263-270] for the interaction of high-mobility group protein 1 with DNA. Although the binding parameters are similar for these two proteins, high-mobility group protein 2 differs from high-mobility group protein 1 in that the former appears to change the shape of the DNA to a more compact form. 2. The molecular weight of high-mobility group protein 2 has been determined by equilibrium sedimentation and a mean value of 26 000 was obtained. 3. A low level of nuclease activity detected in one preparation of high-mobility group protein 2 has been investigated.

Animals↗

PubMed1992

Cadmium mobilization in vivo by intraperitoneal or oral administration of monoalkyl esters of meso-2,3-dimercaptosuccinic acid in the mouse.

The relative activities of a series of nine monoalkyl esters of meso-2,3-dimercaptosuccinic acid have been examined as agents for the mobilization of cadmium from mice one week after intraperitoneal administration of cadmium chloride. Eight of these are newly synthetized; all are of the type ROOCCH(SH)CH(SH)COOH, were R = Me, MMDMS; R = C2H5, MEDMS; R = (CH2)2CH3, Mn-PDMS; R = CHMe2, Mi-PDMS; R = (CH2)3CH3, Mn-BDMS; R = CH2CHMe2, Mi-BDMS; R = (CH2)4CH3, Mn-ADMS; R = (CH2)2CHMe2, Mi-ADMS; and R = (CH2)5CH3, Mn-HDMS. All are soluble in dilute sodium bicarbonate solutions and can be administered as aqueous solutions. Cadmium mobilization data were collected on each compound using mice previously loaded with cadmium; the monoesters were administered at a level of 0.40 mmol/kg intraperitoneally daily for five days. Data on whole body cadmium mobilization indicated that the monoester with the isoamyl group was the most effective under the conditions used. The relative whole body cadmium mobilization increased with the number of carbon atoms in the alkyl group of the monoester up to C5 and then decreased for the C6 compound. Cadmium removal from the kidneys and liver was also measured. It was found that the monoisoamyl ester was the most effective in removing cadmium from both the liver and the kidneys. The monoisoamyl ester also proved to be very effective in mobilizing cadmium from both the liver and the kidneys when given orally. This is the first compound which is reported capable of mobilizing cadmium in vivo from aged deposits after oral administration.

Animals↗

PubMed1992

Interactions between Ca2+ mobilizing mechanisms in cultured rat cerebellar granule cells.

1. The interactions between IP3 receptor-mediated and Ca(2+)-induced Ca2+ release were investigated in cerebellar granule cell bodies, using the techniques of microfluorimetry and image analysis. 2. The IP3-sensitive Ca2+ release mechanism was activated using acetylcholine (ACh) and the selective metabotropic glutamate receptor agonist 1-aminocyclopentane-1S,3R-dicarboxylic acid (ACPD). Caffeine was used to activate, and ryanodine to inhibit, the Ca(2+)-induced Ca2+ release process. Thapsigargin was used to deplete intracellular Ca2+ stores. 3. Transient applications of caffeine (5-50 mM), ACPD (50-500 microM) and ACh (0.05-1 microM) mobilized intracellular Ca2+ ([Ca2+]i). Ca2+ mobilizing responses to 50 mM caffeine and 1 microM ACh increased with time in culture until day 4. However, beyond this period the responsiveness of cells to caffeine, but not to ACh, declined markedly. 4. Responses induced by ACPD and ACh were inhibited in the presence of caffeine at concentrations below those which mobilized Ca2+ (1-5 mM). This effect was not due to Ca2+ pool depletion, elevation of cAMP or inhibition of phosphodiesterases. 5. Prior challenge with ACh or ACPD inhibited Ca2+ mobilization induced by caffeine (50 mM). Transient exposure to caffeine inhibited subsequent responses to ACh through a mechanism which involved store depletion. 6. Thapsigargin (0.1-1 microM) inhibited, to a similar extent, Ca2+ mobilization induced by caffeine, ACPD and ACh. 7. Ryanodine (10 microM) antagonized Ca2+ mobilization induced by caffeine, ACh and ACPD. However, the ability of ryanodine to block inositol 1,4,5-trisphosphate-linked agonist responses varied considerably between cells. The sensitivity of ACh-induced responses to ryanodine correlated with the sensitivity of the cells to caffeine. 8. The possible explanations for the pronounced interactions between IP3 receptor-mediated and Ca(2+)-induced Ca2+ release processes in cerebellar granule cells are discussed.

Acetylcholine↗

PubMed1992

Sequence analysis and characterization of the mobilization region of a broad-host-range plasmid, pTF-FC2, isolated from Thiobacillus ferrooxidans.

The nucleotide sequence of a 5,317-bp fragment which includes the region required for mobilization of broad-host-range plasmid pTF-FC2 was determined. A region of approximately 3.5 kb was required for plasmid mobilization, and oriT was localized on a 138-bp fragment. Polypeptides which corresponded in size and location to several of the open reading frames were detected in an in vitro transcription-translation system. Three open reading frames essential for plasmid mobilization and two which affect the mobilization frequency were identified. There was a distinct similarity in the sizes, amino acid sequences, and locations of the proteins from the mobilization region of pTF-FC2 and the Tra1 region of IncP plasmid RP4. Similarity in the structures and sequences of the oriT regions was also apparent. A sequence with 37-of-38-bp homology to the inverted repeated sequences of Tn21 and an open reading frame with strong homology to the MerR regulatory protein was identified outside of the region required for mobilization.

Amino Acid Sequence↗

PubMed1992

Cellular mechanisms of vasopressin and endothelin to mobilize [Mg2+]i in vascular smooth muscle cells.

The present study was undertaken to examine the effects of arginine vasopressin (AVP) and endothelin-1 (ET-1) on cytosolic free Mg2+ ([Mg2+]i) in cultured rat vascular smooth muscle cells (VSMC). [Mg2+]i was measured using the fluorescence indicator dye mag-fura-2. AVP and ET-1 at a concentration of 1 x 10(-9) M or higher induced the mobilization of [Mg2+]i and cytosolic free Ca2+ ([Ca2+]i) in a dose-dependent manner in rat VSMC. Atrial natriuretic peptide and sodium nitroprusside producing cellular guanosine 3',5'-cyclic monophosphate did not affect [Mg2+]i and [Ca2+]i. A diterpene activator of adenylate cyclase, forskolin, also did not alter [Mg2+]i and [Ca2+]i. The removal of extracellular Mg2+ enhanced the AVP-mobilized [Ca2+]i and did not change the AVP-mobilized [Mg2+]i. The Ca(2+)-free and nominally Mg2+/Ca(2+)-free states decreased the AVP-mobilized [Mg2+]i and [Ca2+]i. The Na(+)-free state enhanced the sustained, but not peak, level of the AVP-mobilized [Mg2+]i. These results indicate that AVP and ET-1 mobilize [Mg2+]i mediated through their intracellular second messenger [Ca2+]i and independent of extracellular Mg2+. Also, an increase in [Mg2+]i is indicated to stimulate the Na(+)-Mg2+ exchange to increase cellular Mg2+ efflux.

Animals↗

PubMed1978

The effects of ristocetin and von Willebrand factor on platelet electrophoretic mobility.

Ristocetin will induce the agglutination of platelets in the presence of von Willebrand factor. In previous studies, an electrostatic mechanism was proposed for this phenomenon wherein first the platelet's surface charge is reduced by the binding of ristocetin and then the von Willebrand factor acts as a bridge between platelets. To test this hypothesis, the effects of ristocetin and von Willebrand factor, singly and together, on the electrophoretic mobility of normal, trypsinized, and Bernard-Soulier platelets was measured. Ristocetin alone, at concentrations of 0.5 mg/ml or more, produced a statistically significant reduction in the electrophoretic mobility of fresh or fixed platelets. Control experiments showed that the reduction was not due to changes in the ionic milieu of the solution. Therefore, the decrease in platelet mobility is evidence for binding of ristocetin to the platelet surface. Bernard-Soulier and trypsinized platelets also had reductions in mobility with ristocetin, suggesting that ristocetin binds to the platelet at sites other than the binding site for von Willebrand factor. The presence of plasma from a patient with von Willebrand's disease did not alter the reduction in mobility of normal platelets by ristocetin. However, the reduction was markedly enhanced in the presence of normal plasma. This enhancement did not occur with Bernard-Soulier platelets and was inhibited by anti-Factor VIII/von Willebrand factor antiserum or trypsinization of the platelets. Thus, the enhanced reduction appears to be associated with the binding of von Willebrand factor to the platelet surface. These studies indicate that platelets undergo two changes with ristocetin and von Willebrand factor, both of which facilitate agglutination: reduction in net surface charge and binding of von Willebrand factor, a large molecule which can serve as a bridge between platelets. In parallel studies, bovine von Willebrand factor, without ristocetin, agglutinated and reduced the electrophoretic mobility of normal but not Bernard-Soulier or trypsinized platelets; this indicates a similar mechanism of agglutination.

Antibodies↗

PubMed1975

Effects of cytochalasin B on the aggregation, electrophoretic mobility and surface morphology of chick neural retina cells.

Over a concentration range of o-5-10 mug/cm-3, cytochalasin B caused a biphasic change in the electrophoretic mobility of disaggregated neural retina cells. An initial rise in anodal mobility at low concentrations of the drug was transformed into a reduction in the mobility below that of the control at a concentration of 10 mug/cm-3. The effect of cytochalasin B was found to be reversible by washing treated cells in cytochalasin B-free media. This was investigated at a concentration of cytochalasin at which the greatest difference existed between the mobilities of the control and experimental cell suspensions. Reaggregation of cell dispersions failed to show any significant difference in the rate of aggregation between cytochalasin B-treated cells and the control. Scanning electron microscopy of cells fixed while in suspension also showed little significant change in the surface morphology upon application of cytochalasin B. In high concentrations of the drug cells appeared somewhat smoother in outline, but no correlation was found between changes in surface morphology and the variations in cell electrophoretic mobility. It is concluded that the observed changes in electrophoretic mobility may be attributed to a binding of cytochalasin B to the cell membrane. This lends support to the hypothesis that the primary site of action of cytochalasin B may be the plasma membrane.

Animals↗

PubMed1977

Electrophoretic mobility of microsomes from rat liver.

The electrophoretic mobilities of rough and smooth microsomes were studied using free electrophoresis in a sucrose gradient. Rough microsomes have a higher net negative surface charge but removal of the ribosomes decreases their mobility to that of smooth microsomes. Treatment with neuraminidase and phospholipases C and D does not affect the mobility of total smooth microsomes, but this mobility is increased by approximately 20% after trypsin and papain treatment and by approximately 12% after phospholipase A treatment. Further treatment of trypsin-digested smooth microsomes with phospholipase C re-establishes the original mobility. This effect is not caused by the removal of lipid phosphate groups, but by the liberation of negatively charged protein species that are normally buried under trypsin-sensitive proteins. Low concentrations of trypsin also solubilize enzyme proteins from smooth liver microsomes of phenobarbital-treated rats, but the electrophoretic mobility is not increased, indicating structural differences between induced and control membranes.

Animals↗