Search PubMed⌕ Search

Biomedical subjects

J de Gier

Publications and source records attributed to J de Gier.

At least 19 recordsLinked to original sources
PubMed1998

Recovery of storage and emptying functions of the urinary bladder after spinal anesthesia with lidocaine and with bupivacaine in men.

BACKGROUND: The aim of this study was to evaluate and compare the effects of spinal anesthesia with lidocaine and with bupivacaine on urinary bladder function in healthy men who were scheduled for minor orthopaedic surgical procedures. METHODS: Twenty men were randomly allocated to receive either bupivacaine or lidocaine. Before spinal anesthesia, filling cystometry was performed with the patient in the supine position and a pressure flow study was done with the patient in the standing position. After operation, cystometric measurements were continued until the patient could void urine spontaneously. The levels of analgesia and of motor blockade were recorded. RESULTS: The urge to void disappeared immediately after injection of the local anesthetics. There was no difference in the duration of lower extremity motor blockade between bupivacaine and lidocaine. Detrusor blockade lasted significantly longer in the bupivacaine group (means +/- SD, 460 +/- 60 min) than in the lidocaine group (235 +/- 30 min). Total fluid intake and urine volume accumulated during the detrusor blockade were significantly higher in the bupivacaine group than in the lidocaine group. In the bupivacaine group, the total volume of accumulated urine (875 +/- 385 ml) was also significantly higher than cystometric bladder capacity (505 +/- 120 ml) with the risk of over distension of the bladder. Spontaneous voiding of urine did not occur until segmental sensory analgesia had regressed to the third sacral segment. CONCLUSIONS: Spinal anesthesia with lidocaine and with bupivacaine causes a clinically significant disturbance of bladder function due to interruption of the micturition reflex. The urge to void disappears quickly and bladder function remains impaired until the block has regressed to the third sacral segment in all patients. With long-acting local anesthetics, the volume of accumulated urine may exceed the cystometric bladder capacity. With respect to recovery of urinary bladder function, the use of short-acting local anesthetics for spinal anesthesia seems to be preferable.

Adult↗
PubMed1994

The cryoprotectant trehalose destabilises the bilayer organisation of Escherichia coli-derived membrane systems at elevated temperatures as determined by 2H and 31P-NMR.

In this study, 2H and 31P-NMR techniques were used to study the effects of trehalose and glycerol on phase transitions and lipid acyl chain order of membrane systems derived from cells of E. coli unsaturated fatty acid auxotroph strain K1059, which was grown in the presence of [11,11-2H2]-oleic acid or [11,11-2H2]-elaidic acid. From an analysis of the temperature dependence of the quadrupolar splitting it could be concluded that neither 1 M trehalose or glycerol generally had any significant effect on the temperature of the lamellar gel to liquid-crystalline phase transition. In the case of the oleate-containing hydrated total lipid extract, glycerol but not trehalose caused a 5 degrees C increase of this transition temperature. In general, both cryoprotectants induced an ordering of the acyl chains in the liquid-crystalline state. Trehalose and glycerol both decrease the bilayer to non-bilayer transition temperature of the hydrated lipid extract of oleate-grown cells by about 5 degrees C, but only trehalose in addition induces an isotropic to hexagonal (HII) phase transition. In the biological membranes, trehalose and not glycerol destabilised the lipid bilayer, and in the case of the E. coli spheroplasts, part of the induced non-bilayer structures is ascribed to a hexagonal (HII) phase in analogy with the total lipids. Interestingly, 1 mM Mg2+ was a prerequisite for the destabilisation of the lipid bilayer. In the hydrated total lipid extract of E. coli grown on the more ordered elaidic acid, both transition temperatures were shifted about 20 degrees C upwards compared with the oleate-containing lipid, but the effect of trehalose on the lipid phase behaviour was similar. The bilayer destabilising ability of trehalose might have implications for the possible protection of biological systems by (cryo-)protectants during dehydration, in that protection is unlikely to be caused by preventing the occurrence of polymorphic phase transitions.

Cell Membrane↗
PubMed1993

The membrane potential has no detectable effect on the phosphocholine headgroup conformation in large unilamellar phosphatidylcholine vesicles as determined by 2H-NMR.

In this study the effect of a transmembrane electrical potential on the phospholipid headgroup conformation was investigated using the 2H-NMR technique. Large unilamellar vesicles were prepared of dioleoylphosphatidylcholine, specifically 2H-labeled at the alpha- or beta-position of the choline group. No conformational change of the phosphocholine headgroup could be detected after induction of a valinomycin-induced K(+)-diffusion potential across the bilayer. However, this method could be used to measure the redistribution of tetraphenylphosphonium across the bilayer in response to delta psi, which reorients the phosphocholine headgroups in the opposite bilayer-water interfaces.

Benzothiazoles↗
PubMed1993

A novel property of a mitochondrial presequence. Its ability to induce cardiolipin-specific interbilayer contacts which are dissociated by a transmembrane potential.

A new property of the presequence of the mitochondrial precursor protein cytochrome oxidase subunit IV is presented. This mitochondrial presequence induces interbilayer contacts between large unilamellar vesicles consisting of phosphatidylcholine and cardiolipin. The presequence-vesicle aggregates can be dissociated by applying a membrane potential across the bilayers (negative inside). These effects require the presence of cardiolipin and are not observed for other negatively charged phospholipids. We propose a role for the presequence in the formation and dissociation of mitochondrial contact sites.

Amino Acid Sequence↗
PubMed1993

Osmotic behaviour and permeability properties of liposomes.

In this overview liposomes are described as bilayer-bounded vesicles which under defined conditions act as ideal osmometers according to the Boyle van't Hoff law. Investigations on osmotic volume changes, directly or indirectly by taking advantage of changes in light scattering, are considered and applications in permeability measurements are discussed. Solute-solvent interactions occurring in isotonic swelling experiments are analysed in view of an irreversible thermodynamic description. In a second part liquid crystalline lipid bilayers are characterized as highly selective permeability bilayers and the physical principles underlying this selectivity are considered. Attention is given to special physical and chemical conditions that may cause structural defects in the bilayer organization and can affect the selective permeability properties of the bilayer or completely deteriorate its barrier function. Finally an evaluation is given of intrinsic ionophoretic activity in lipid bilayers containing negatively charged lipids.

Cell Membrane↗
PubMed1991

The effect of a membrane potential on the interaction of mastoparan X, a mitochondrial presequence, and several regulatory peptides with phospholipid vesicles.

Recently the pH gradient evoked by a K+ diffusion potential was shown to translocate a synthetic monobasic amphipathic hexapeptide across the bilayer of lipid vesicles (De Kroon, A.I.P.M., Vogt, B., Van 't Hof, R., De Kruijff, B. and De Gier, J. (1991) Biophys. J. 60, in press). Here this observation is extended by studying the effect of a membrane potential on a set of bioactive peptides. The panel of peptides comprises the toxin mastoparan X, a tryptophan-containing analogue of the presequence of the mitochondrial protein cytochrome oxidase subunit IV (preCoxIV(1-25)W18), and the regulatory peptides ACTH(1-24), alpha-MSH, ACTH(1-10), dynorphin A, bombesin, and LHRH. The interaction of these peptides with phospholipid vesicles has been measured using the intrinsic tryptophan residue as fluorescent probe. In the absence of a K+ diffusion potential only mastoparan X and the presequence show considerable binding to vesicles consisting of phosphatidylcholine (PC). In contrast, under these conditions all peptides display affinity for vesicles consisting of the acidic phospholipid cardiolipin (CL), the extent of which depends on the net positive charge of the peptide. Application of a K+ diffusion potential to large unilamellar vesicles (LUV) consisting of PC results in a time dependent tryptophan fluorescence increase for mastoparan X, which is accelerated upon incorporating increasing amounts of CL into the LUV. A similar fluorescence increase in response to a K+ diffusion potential was observed for the above model peptide. Yet the mechanism resulting in the fluorescence increase of mastoparan X is completely different from that of the hexapeptide. Binding experiments indicate that a membrane potential-induced enhanced binding of the peptide to the outer surface of the vesicles contributes to the fluorescence increase. PreCoxIV(1-25)W18, dynorphin A, and ACTH(1-24) show fluorescence responses upon applying a membrane potential that are consistent with that of mastoparan X, whereas the other peptides tested do not respond up to a LUV CL content of 50%. The results tentatively suggest that the membrane potential only affects a peptide when it has the ability to adopt a stable membrane bound conformation.

Amino Acid Sequence↗
PubMed1991

The membrane interaction of amphiphilic model peptides affects phosphatidylserine headgroup and acyl chain order and dynamics. Application of the "phospholipid headgroup electrometer" concept to phosphatidylserine.

Deuterium nuclear magnetic resonance (2H NMR) was used to study the interaction of amphiphilic model peptides with model membranes consisting of 1,2-dioleoyl-sn-glycero-3-phospho-L-serine deuterated either at the beta-position of the serine moiety ([2-2H]DOPS) or at the 11-position of the acyl chains ([11,11-2H2]DOPS). The peptides are derived from the sequences H-Ala-Met-Leu-Trp-Ala-OH (AX, one-letter code with X = MLWA) and H-Arg-Met-Leu-Trp-Ala-OH (RX+) and contain a positive charge of +1 (AXme+) or +2 (RXme2+) at the amino terminus or one positive charge at each end of the molecule (AXetN2+). Upon titration of dispersions of DOPS with the peptides, the divalent peptides show a similar extent of binding to the DOPS bilayers, which is larger than that of the single charged peptide. Under these conditions the values of the quadrupolar splitting (delta vq) of both [2-2H]DOPS and [11,11-2H2]DOPS are decreased, indicating that the peptides reduce the order of both the DOPS headgroup and the acyl chains. The extent of the decrease depends on the amount of peptide bound and on the position of the charged moieties in the peptide molecule. The effects exerted by the peptides on the delta vq value of [2-2H]DOPS are consistent with the PS headgroup responding as a molecular electrometer to the surface charge resulting from the presence of the peptides in the lipid-water interface. The effects on the acyl chain deuterons are in agreement with a localization of the peptides intercalated in between the lipid headgrouops.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Ion gradient-induced membrane translocation of model peptides.

The K+ diffusion potential-induced association of synthetic model peptides carrying a single positive charge originating from the NH2-terminal amino function with large unilamellar vesicles (LUV) consisting of phosphatidylcholine (PC) has been reported previously (de Kroon, A. I. P. M., J. de Gier, and B. de Kruijff. 1989. Biochim. Biophys. Acta. 981:371-373). To determine the vesicle localization of the associated peptides, fluorescence measurements utilizing the peptides' tryptophan residue as intrinsic fluorescent probe were performed. The application in these measurements, of vesicles that exhibit an asymmetric transbilayer distribution of brominated PC which is a quencher of tryptophan fluorescence, unequivocally demonstrated that the peptide H3N(+)-AIMLWA-Ome (AIXme+) is accumulated in the interface of the inner leaflet of the vesicle membrane in response to the valinomycin-induced K+ diffusion potential (negative inside). The relative contributions of the membrane potential (delta psi) and the pH gradient (delta pH, acidic inside) induced by the K+ diffusion potential, to the process have been assessed. An analysis of the pH and delta pH dependencies of the process demonstrated that the K+ diffusion potential-induced peptide accumulation is largely determined by a redistribution of peptide according to the transbilayer pH gradient, in agreement with a translocation across the vesicle membrane of the neutral, deprotonated form of the peptide. The general validity of the mechanism proposed for the vesicle-uptake of AIXme+ has been examined by extending the experiments to peptide analogues with a single negative charge and to peptides with two positive charges, and by investigating the effect of incorporating the acidic phospholipid cardiolipin (CL) into the LUV. The incorporation of CL appeared not to affect the K+ diffusion, potential-induced vesicle uptake of AIXme+. The peptide H3N(+)-RMLWA-Ome (RXme2+) showed a small delta pH independent fluorescence response to the delta psi upon raising the CL content of the vesicles to 25%.

Amino Acid Sequence↗
PubMed1990

Gramicidin A induced fusion of large unilamellar dioleoylphosphatidylcholine vesicles and its relation to the induction of type II nonbilayer structures.

The fusogenic properties of gramicidin were investigated by using large unilamellar dioleoylphosphatidylcholine vesicles. It is shown that gramicidin induces aggregation and fusion of these vesicles at peptide to lipid molar ratios exceeding 1/100. Both intervesicle lipid mixing and mixing of aqueous contents were demonstrated. Furthermore, increased static and dynamic light scattering and a broadening of 31P NMR signals occurred concomitant with lipid mixing. Freeze-fracture electron microscopy revealed a moderate vesicle size increase. Lipid mixing is paralleled by changes in membrane permeability: small solutes like carboxyfluorescein and smaller dextrans, FD-4(Mr approximately 4000), rapidly (1-2 min) leak out of the vesicles. However, larger molecules like FD-10 and FD-17 (Mr approximately 9400 and 17,200) are retained in the vesicles for greater than 10 min after addition of gramicidin, thereby making detection of contents mixing during lipid mixing possible. At low lipid concentrations (5 microM), lipid mixing and leakage are time resolved: leakage of CF shows a lag phase of 1-3 min, whereas lipid mixing is immediate and almost reaches completion during this lag phase. It is therefore concluded that leakage, just as contents mixing, occurs subsequent to aggregation and lipid mixing. Although addition of gramicidin at a peptide/lipid molar ratio exceeding 1/50 eventually leads to hexagonal HII phase formation and a loss of vesicle contents, it is concluded that leakage during fusion (1-2 min) is not the result of HII phase formation but is due to local changes in lipid structure caused by precursors of this phase. By making use of gramicidin derivatives and different solvent conformations, it is shown that there is a close parallel between the ability of the peptide to induce the HII phase and its ability to induce intervesicle lipid mixing and leakage. It is suggested that gramicidin-induced fusion and HII phase formation share common intermediates.

Freeze Fracturing↗
PubMed1990

Protection by sugars against phase transition-induced leak in hydrated dimyristoylphosphatidylcholine liposomes.

The disaccharides trehalose and sucrose have small effects on temperature and enthalpy of the pre- and main phase transition in hydrated DMPC bilayers. In contrast, these sugars cause a considerable retention of carboxyfluorescein when large unilamellar vesicles of DMPC are heated through the main transition. This effect is sugar specific, as the monosaccharides glucose and fructose are less effective and ethyleneglycol has no effect at all.

Biological Transport↗
PubMed1989

Association of synthetic model peptides with phospholipid vesicles induced by a membrane potential.

Hydrophobic model peptides, consisting of 5 or 6 amino acids and carrying a net positive charge at the amino terminus, exhibit a dramatically increased association with large unilamellar egg-PC vesicles upon application of a valinomycin-induced K+ diffusion potential, negative inside. The association of the peptides is largely reversible, apparent from a release of peptide upon dissipation of the membrane potential.

In Vitro Techniques↗
PubMed1989

Interfacial properties of gramicidin and gramicidin-lipid mixtures measured with static and dynamic monolayer techniques.

Gramicidin films at the air/water interface are shown to exhibit a phase transition at 225 A2/molecule which might be caused by either cluster formation, reorientation of molecules, conformational changes or multilayer formation. It is further shown that coupling of a charged group on either NH2- or COOH-terminus or elongation of the peptide by two amino acids, only slightly affects the surface area characteristics whereas modification of the tryptophans or even replacement of a single tryptophan by phenylalanine leads to drastic alterations in the surface-area characteristics and a (partial) loss of the phase transition demonstrating that the tryptophans play an important role in the interfacial behavior of gramicidin. The lack of a solvent history effect on the interfacial behavior indicates a rapid conformational interconversion of the peptide at the air/water interface. Gramicidin in mixtures with dioleoylphosphatidylcholine and lysopalmitoylphosphatidylcholine shows a condensing effect whereas gramicidin shows ideal mixing with dioleoylphosphatidylethanolamine. The condensing effect most likely is related to the aggregational state of the peptides which is different in phosphatidylcholines and phosphatidylethanolamines.

Amino Acid Sequence↗
PubMed1988

Alterations in size, shape and osmotic behaviour of red cells after splenectomy: a study of their age dependence.

In whole blood from splenectomized subjects (n = 20), red cells showed a significant increase of mean surface area (MSA), mean cell volume (MCV), MSA/MCV-ratio and osmotic resistance, with the mean cell haemoglobin concentration (MCHC) being decreased. Studies on red cell populations of different cell age revealed that the increase of MSA affects younger and older cells, whereas the increase of MCV can mainly be ascribed to young cells with low density. The increased osmotic resistance is mainly determined by older cells due to a more favourable MSA/MCV-ratio. Shortly after splenectomy (n = 5) the MSA of younger and older cells increased, whereas the increase of MCV affected only young cells with a lowered density; moreover, the MSA/MCV-ratio increased in older cells in particular, resulting in a relatively greater increase of osmotic resistance. An impaired maturation of the reticulocyte may underlie the initial increase of MSA and MCV of young cells, but the present results contradict the current view that delayed maturation explains the changes in morphology and osmotic resistance of asplenic red cells.

Adult↗
PubMed1988

Vacuoles in red cells from splenectomized subjects originate during cell life: association with glycosylated haemoglobin?

Whole blood from splenectomized subjects (n = 8) contained a substantial percentage of vacuolated ('pitted') red cells (34.7 +/- 8.3%), while blood from controls revealed none. The percentage of haemoglobin A1 (HbA1) had increased significantly compared with controls (p less than 0.01). Fractionation on cell density revealed that the number of 'pitted' cells and the HbA1 percentage were associated with increased cell density. Fractionation on cell volume showed that 'pitted' cells are equally distributed in fractions with varying mean cell volume (MCV) and that decreasing MCV was associated with a linear rise of HbA1. It appeared that, shortly after splenectomy (n = 4), 'pits' develop early in cell life and that also older cells, after previous splenic contact, are capable of pit formation. A positive correlation found between the number of 'pitted' cells and the percentage of HbA1 might point to an impaired release of HbA1, manifest in the presence of 'pits'. The increased percentage of HbA1 in whole blood from splenectomized subjects may thus be explained.

Adult↗
PubMed1988

Reticulocyte crisis after splenectomy: evidence for delayed red cell maturation?

In whole blood from splenectomized subjects (n = 8) in a steady state an increased number of reticulocytes was observed (14.0 +/- 7.8% versus 3.6 +/- 2.4% controls: p less than 0.05). Cell fractionation on density showed that reticulocytes, as in normals, are more or less confined to the least dense fraction; cell fractionation on volume revealed that reticulocytes form a heterogeneous cell population with diverging volume, but sharing a low density. Immediately after splenectomy (n = 4), a reticulocytosis is observed, mainly manifest in the top fractions (262.0 +/- 49.0% versus 40.0 +/- 32.4% preoperatively; p less than 0.01). This reticulocytosis is not due to pre- or postoperative complications, but is associated with the splenectomy itself and probably is the consequence of a delayed, but ultimately occurring red cell maturation. The increase of reticulocytes is not accompanied by significant alterations in cell morphology, as far as cell volume is concerned.

Adult↗
PubMed1987

Solvent determined conformation of gramicidin affects the ability of the peptide to induce hexagonal HII phase formation in dioleoylphosphatidylcholine model membranes.

It is shown by 31P-NMR and small angle X-ray scattering that induction of an hexagonal HII phase in dioleoylphosphatidylcholine model membranes by external addition of gramicidin A' depends on the solvent which is used to solubilize the peptide. Addition of gramicidin from dimethylsulfoxide or trifluoroethanol solution leads to HII phase formation whereas addition of the peptide from ethanol does not. This solvent dependence is shown by circular dichroism to be correlated with the peptide conformation. The channel conformation appears to be responsible for HII phase formation by gramicidin.

Chemical Phenomena↗
PubMed1987

Gramicidin-induced hexagonal HII phase formation in erythrocyte membranes.

Using 31P nuclear magnetic resonance (NMR), small-angle X-ray scattering (SAXS), and freeze-fracture electron microscopic (FFEM) techniques, it is shown that gramicidin induces a hexagonal HII phase not only in liposomes prepared from total lipids extracted from human erythrocytes but also in isolated human erythrocyte membranes (white ghosts). A 37 degrees C, HII phase formation is detected at a gramicidin to phospholipid molar ratio exceeding 1:80. At a molar ratio of 1:5, about 30% of the phospholipid is organized in the HII phase. The gramicidin-induced HII phase exhibits a very small 31P chemical shift anisotropy [(CSA) approximately 10 +/- 1 ppm], indicating decreased head-group order, and it displays a temperature-dependent increase in tube diameter from 60.2 A at 4 degrees C to 64.2 A at 37 degrees C in ghosts and from 62.8 to 69.4 A at 37 degrees C in total lipid extracts, both in the presence of 1 mol of gramicidin/10 mol of phospholipid. This anomalous temperature-dependent behavior is probably due to the presence of cholesterol. 31P NMR data indicate that the HII phase formation by gramicidin is temperature dependent and show the gradual disappearance of the HII phase at low temperatures (less than 20 degrees C), resulting in a bilayer type of 31P NMR line shape at 4 degrees C, whereas SAXS and FFEM data suggest equal amounts of HII phases at all temperatures. This apparent discrepancy is probably the result of a decrease in the rate of lateral diffusion of the membrane phospholipids which leads to incomplete averaging of the 31P CSA in the HII phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythrocyte Membrane↗