Passive or active fluctuations in membranes containing proteins

We have experimentally investigated the effect of a transmembrane protein, the Ca2+-ATPase, on shape fluctuations of giant vesicles. By using the micropipette method, we have measured a substantial renormalization of the bending modulus due to the presence of proteins in the membrane. Moreover, we have produced the first quantitative measurement of the active force dipole associated with the amplification of the fluctuations when the proteins are activated by adenosine 5'-triphosphate (ATP).

Generic theory of active polar gels: a paradigm for cytoskeletal dynamics

We develop a general theory for active viscoelastic materials made of polar filaments. This theory is motivated by the dynamics of the cytoskeleton. The continuous consumption of a fuel leads to a non equilibrium state characterized by the generation of flows and stresses. Our theory can be applied to experiments in which cytoskeletal patterns are set in motion by active processes such as those which are at work in cells.

Fluid membranes exchanging material with external reservoirs

We investigate the dynamics of a single component fluid bilayer, which exchanges material with the surrounding fluid. We derive covariant equations of motion taking into account solvent permeation, exchange of lipids between solvent and the membrane and discuss the sources of noise in these equations. Different lipid concentrations on both sides of the membrane lead to a non-equilibrium state. We discuss steady states as well as shape instabilities which occur at a critical osmotic-pressure difference.

[Effect of fish protein on blood pressure, glycemia and plasma and urinary parameters in spontaneously hypertensive rats (SHR) and diabetic SHR]

Fish protein (FP) effect compared to casein (CAS) was studied on blood pressure (BP) evolution and glycemia in part, and on plasma lipid, angiotensine II and aldosterone concentrations and urinary aldosterone on the other hand, in SHR and in SHR with streptozotocin-induced diabetes (SHR-STZ). Two groups of rats (6 SHR and 6 SHR-STZ) were fed for 2 months diet containing 20% CAS or 20% FP. One month before sacrifice, diabetes was induced into one group of rats by a single intraperitonealy injection of streptozotocin (STZ). The results showed that FP diminished blood pressure (-9%) in SHR, compared with CAS. In contrast, FP enhanced significantly blood pressure in SHR-STZ vs SHR (p<0.01). There was no effect on glycemia with fish protein. FP compared to CAS involved a diminution (-41%) and (-17%) of total cholesterol and (-26%) and (-9%) of phospholipids in SHR and SHR-STZ, respectively. Moreover, a decrease of triacylglycerols (-21%) was noted in SHR-STZ with FP vs CAS. In SHR, plasma aldosterone and angiotensine II concentrations were reduced (-62%) and (-64%) and urinary aldosterone amounts were enhanced with FP compared to CAS (p<0.05). In SHR-STZ group, aldosterone value was fivefold lower in plasma and twofold higher in urine with FP compared to CAS. A significant enhancement of urinary aldosterone was noted in SHR-STZ vs SHR whatever diet-consumed. In conclusion, FP has a beneficial effect on blood pressure by modulating the hypertension markers i.e. plasma total cholesterol, angiotensine II and aldosterone, in SHR group, and on total cholesterol and triglycerids in SHR-STZ. FP reduces plasma aldosterone by its enhanced urinary excretion. It is necessary to specify the action mode of FP in order to propose it as nutritional complement in the degenerative diseases such as hypertension and diabetes.

Membranes with rotating motors: microvortex assemblies

We study collections of rotatory motors confined to 2-dimensional manifolds. The rotational motion induces a repulsive hydrodynamic interaction between motors leading to a non-trivial collective behavior. For high rotation speed, motors should arrange on a triangular lattice exhibiting crystalline order. At low speed, they form a disordered phase where diffusion is enhanced by velocity fluctuations. In confining geometries and under suitable boundary conditions, motor-generated flow might enhance left-right symmetry-breaking transport. All these effects should be experimentally observable for motors driven by external fields and for dipolar biological motors embedded into lipid membranes in a viscoelastic solvent.

Fish protein improves blood pressure but alters HDL2 and HDL3 composition and tissue lipoprotein lipase activities in spontaneously hypertensive rats

The two-month effects of dietary fish protein and casein on VLDL, HDL(2) and HDL(3) compositions and hepatic lipase (HTGL) and tissue lipoprotein lipase (LPL) activities were examined in spontaneously hypertensive rats (SHR) at 4 wk of age. After 2 mo of experiment, the fish protein diet induced lower blood pressure (-14 %) as compared to casein. Liver triacylglycerol and total cholesterol concentrations were 1.37- and 1.71-fold lower in the fish protein group than in the casein group, respectively. Total cholesterol concentration in plasma was also diminished by fish protein (-21 %) and was reflected in HDL(2) fraction (-44 %). SHR fed the fish protein diet as compared with those fed casein, showed a significantly low HDL(3) particle number, as measured by diminished HDL(3) mass and apo A-I. The consumption of fish protein did not affect VLDL particle number, but significantly decreased VLDL-triacylglycerol (-32 %) and adipose tissue total lipid concentrations as compared to casein. This was accompanied by diminished HTGL and adipose tissue LPL activities (-10%, -91%, respectively). These data demonstrate that fish protein plays an antihypertensive role and reduces plasma and tissue lipid concentrations. Thus, a fish protein intake might be beneficial for patients with hypertension.

Refined contour analysis of giant unilamellar vesicles

The fluctuation spectrum of giant unilamellar vesicles is measured using a high-resolution contour detection technique. An analysis at higher q vectors than previously achievable is now possible due to technical improvements of the experimental setup and of the detection algorithm. The global fluctuation spectrum is directly fitted to deduce the membrane tension and the bending modulus of lipid membranes. Moreover, we show that the planar analysis of fluctuations is valid for spherical objects, even at low wave vectors. Corrections due to the integration time of the video camera and to the section of a 3D object by the observation plane are introduced. A precise calculation of the error bars has been done in order to provide reliable error estimate. Eventually, using this technique, we have measured bending moduli for EPC, SOPC and SOPC: CHOL membranes confirming previously published values. An interesting application of this technique can be the measurement of the fluctuation spectra for non-equilibrium membranes, such as "active membranes".

Role of tensile stress in actin gels and a symmetry-breaking instability

It has been observed experimentally that the actin gel grown from spherical beads coated with polymerization enzymes spontaneously breaks the symmetry of its spherical shape, and yields a "comet" pushing the bead forward. We propose a mechano-chemical coupling mechanism for the initialization of this symmetry breaking. Key assumptions are that the dissociation of the gel takes place mostly in the region of the external surface, and that the rates of the dissociation depend on the tensile stress in the gel. We analyze a simplified two-dimensional model with a circular substrate. Our analysis shows that the symmetric steady state is always unstable against the inhomogeneous modulation of the thickness of the gel layer, for any radius of the circular substrate. We argue that this model represents the essential feature of three-dimensional systems for a certain range of characteristic lengths of the modulation. The characteristic time of the symmetry-breaking process in our model depends linearly on the radius of curvature of the substrate surface, which is consistent with experimental results, using spherical latex beads as substrate. Our analysis of the symmetry-breaking phenomenon demonstrates aspects of mechano-chemical couplings that should be working in vivo as well as in vitro.

Asters, vortices, and rotating spirals in active gels of polar filaments

We develop a general theory for active viscoelastic materials made of polar filaments. This theory is motivated by the dynamics of the cytoskeleton. The continuous consumption of a fuel generates a nonequilibrium state characterized by the generation of flows and stresses. Our theory applies to any polar system with internal energy consumption such as active chemical gels and cytoskeletal networks which are set in motion by active processes at work in cells.

Antioxidant status and levels of different vitamins determined by high performance liquid chromatography in diabetic subjects with multiple complications

Plasma vitamin A, C and E levels and erythrocyte antioxidant enzyme activities were investigated in type I and type II diabetic subjects with and without complications, i.e., hypertension, coronary artery disease and renal failure. Reverse phase HPLC was used to quantify vitamin A and E levels. We observed that the vitamin C levels were not significantly different between control and diabetic subjects. However, vitamin A and E levels were significantly lower in type I and type II diabetic subjects compared to controls. Superoxide dismutase (SOD) activity was significantly lower in type II, but not in type I, diabetic patients compared to controls. Interestingly, glutathione reductase and peroxidase activities were diminished in type I, but not in type II, diabetic subjects as compared to controls. Catalase activity was lower in both types of diabetic patients in comparison with their respective controls. Altogether these results suggest that diabetes mellitus may be associated with altered antioxidant status regardless to various complications.

Bidirectional cooperative motion of molecular motors

Recently, in a beautiful set of experiments, it has been shown that a Ncd mutant, NK11, which lacks directionality in its individual motion, was able to exhibit a new kind of directed motion in motility assays (Endow, S. A. & Higuchi, H. (2000) Nature (London) 406, 913-916): the filaments keep a given velocity for a while and then suddenly move in the opposite direction with similar velocity. We show that these observations nicely illustrate the concept of dynamic transitions in motor collections introduced earlier in the case of an infinite number of motors. We investigate the experimentally relevant case of a finite number of motors both when directionality is present (kinesins, myosins, Ncd) and absent (NK11). Using a symmetric two-state model, we demonstrate that bidirectional motion is the signature of a dynamic transition that results from the collective behavior of many motors acting on the same filament. For motors exhibiting directional bias individually, an asymmetric two-state model is appropriate. In that case, dynamic transitions exist for motor collections in the presence of an external force. We give predictions for the dependence of motion on ATP concentration, external forces, and the number of motors involved. In particular, we show that the reversal time grows exponentially with the number of motors per filament.

Active membrane fluctuations studied by micropipet aspiration

We present a detailed analysis of the micropipet experiments recently reported by J-B. Manneville et al., [Phys. Rev. Lett. 82, 4356 (1999)], including a derivation of the expected behavior of the membrane tension as a function of the areal strain in the case of an active membrane, i.e., containing a nonequilibrium noise source. We give a general expression, which takes into account the effect of active centers both directly on the membrane and on the embedding fluid dynamics, keeping track of the coupling between the density of active centers and the membrane curvature. The data of the micropipet experiments are well reproduced by our expressions. In particular, we show that a natural choice of the parameters quantifying the strength of the active noise explains both the large amplitude of the observed effects and its remarkable insensitivity to the active-center density in the investigated range.

Age-related changes in cholesterol metabolism in macrosomic offspring of rats with streptozotocin-induced diabetes

The aim of this study was to determine the impact of diabetic macrosomia on cholesterol and lipoprotein metabolism. Age-related changes in the activities of serum LCAT, hepatic HMG-CoA reductase, cholesterol 7alpha-hydroxylase, and ACAT, the major enzymes involved in cholesterol metabolism, were determined in macrosomic offspring of streptozotocin-induced diabetic rats. Hepatic, serum, and lipoprotein cholesterol contents were also examined. Mild hyperglycemia in pregnant rats was induced by intraperitoneal injection of streptozotocin (40 mg/kg body weight) on day 5 of gestation. Control pregnant rats were injected with citrate buffer. At birth, macrosomic pups had higher serum, LDL-HDL(1), and HDL(2-3) cholesterol levels (P < 0.05) associated with increased LCAT activity (+57%) compared with control values. At 1 and 2 months of life, serum and lipoprotein cholesterol concentrations in macrosomic rats were similar to those of controls, whereas LCAT activity remained elevated about 1.5-fold. In addition, there was no change in hepatic cholesterol contents but hepatic HMG-CoA reductase, cholesterol 7alpha-hydroxylase, and ACAT activities were higher in both macrosomic males and females than in their respective controls (P < 0.01). By 3 months, macrosomic rats had developed hypercholesterolemia with a rise in all lipoproteins. Enzyme activities were still increased in these mature macrosomic rats, and hepatic cholesteryl esters were higher only in macrosomic females. These data demonstrate an overproduction, combined with overutilization, of cholesterol during the phase of rapid growth in macrosomic rats. However, cholesterol oversynthesis exceeded its removal and was a major contributor to hypercholesterolemia in adult macrosomic rats. In conclusion, macrosomia was associated with alterations in cholesterol metabolism through adulthood.

Endoscopic treatment of urinary incontinence: long-term evaluation of the results

PURPOSE

We report on the use of polydimethylsiloxane for endoscopic treatment of urinary incontinence in children with neurogenic bladder and discuss our results to determine optimal criteria for patient selection.

MATERIALS AND METHODS

A total of 44 children (19 males) have been treated endoscopically for urinary incontinence since 1995. Etiology was spina bifida in 35 cases. Previous surgery had been performed on 24 patients, including bladder neck reconstruction with (17) or without bladder augmentation. Mean patient age at injection was 13 years (range 7 to 17). A single transurethral injection was given in 23 cases, 2 in 17 and 3 or more in 4. Mean volume at each injection was 3.5 cc and for each patient the total volume injected was 5.7 cc. Mean delay between 2 injections was 6 months (range 3 to 15).

RESULTS

Followup ranged from 6 to 53 months (median 28). Of the patients 15 (34%) are dry (continent greater than 4 hours, no urinary pad during the day), 11 (25%) are improved (continent 2 to 3 hours, occasional pad) and 18 had poor results. In the entire series only gender and preoperative hyperactivity influenced the results, as the best results were achieved in females with a stable bladder (44% of girls versus 21% of boys were cured). Good results persisted at 12-month followup in patients treated with only 1 injection (until 36 months for older patients) and after the last of 2 injections. Of the patients treated with 3 or more injections 1 was dry at 12-month followup and treatment failed in 3.

CONCLUSIONS

Injection of polydimethylsiloxane at the bladder neck achieved continence in 34% of neurogenic bladder cases. Results were better in girls with a stable bladder. Results deteriorated in the first 12 months of followup. No more than 3 injections are advised if a satisfactory result is not achieved.

Endoscopic treatment of urinary incontinence: long-term evaluation of the results

PURPOSE

We report on the use of polydimethylsiloxane for endoscopic treatment of urinary incontinence in children with neurogenic bladder and discuss our results to determine optimal criteria for patient selection.

MATERIALS AND METHODS

A total of 44 children (19 males) have been treated endoscopically for urinary incontinence since 1995. Etiology was spina bifida in 35 cases. Previous surgery had been performed on 24 patients, including bladder neck reconstruction with (17) or without bladder augmentation. Mean patient age at injection was 13 years (range 7 to 17). A single transurethral injection was given in 23 cases, 2 in 17 and 3 or more in 4. Mean volume at each injection was 3.5 cc and for each patient the total volume injected was 5.7 cc. Mean delay between 2 injections was 6 months (range 3 to 15).

RESULTS

Followup ranged from 6 to 53 months (median 28). Of the patients 15 (34%) are dry (continent greater than 4 hours, no urinary pad during the day), 11 (25%) are improved (continent 2 to 3 hours, occasional pad) and 18 had poor results. In the entire series only gender and preoperative hyperactivity influenced the results, as the best results were achieved in females with a stable bladder (44% of girls versus 21% of boys were cured). Good results persisted at 12-month followup in patients treated with only 1 injection (until 36 months for older patients) and after the last of 2 injections. Of the patients treated with 3 or more injections 1 was dry at 12-month followup and treatment failed in 3.

CONCLUSIONS

Injection of polydimethylsiloxane at the bladder neck achieved continence in 34% of neurogenic bladder cases. Results were better in girls with a stable bladder. Results deteriorated in the first 12 months of followup. No more than 3 injections are advised if a satisfactory result is not achieved.

[Correlation between Gleason score of prostatic biopsies and the one of the radical prostatectomy specimen]

The Gleason score obtained on prostatic biopsies is an essential element in the treatment decision for localized prostate cancer. The objective of this study was to evaluate the correlation between the biopsy Gleason score and the definitive Gleason score and to propose a classification into 3 groups in order to improve this correlation.

MATERIAL AND METHODS

One hundred radical prostatectomies were performed between 1995 and 1998. Eighty four of these patients underwent 6 biopsies. The Gleason score of the biopsies and operative specimens were compared. The concordance between the biopsy Gleason score and the operative specimen Gleason score was initially analysed score by score. The concordance was then established according to three groups, well differentiated tumours (score 2-4), moderately differentiated tumours (score 5-7), poorly differentiated tumours (score 8-10).

RESULTS

The concordance between the biopsy Gleason score and the operative specimen Gleason score was perfect in only 37% of cases. A 1-point difference of the score was observed in 35.7% of cases and a 2-point or greater difference was observed in 27.3% of cases. By classifying patients into 3 groups, the concordance increased from 37% to 72.6%.

CONCLUSION

The classification of patients into three distinct groups (well, moderately and poorly differentiated tumours) increases the concordance between the biopsy Gleason score and the definitive Gleason score. However, the limitations of the biopsy Gleason score must be kept in mind, particularly in the case of low-grade tumours.

Fetal macrosomia related to maternal poorly controlled type 1 diabetes strongly impairs serum lipoprotein concentrations and composition

AIMS

To determine the effects of fetal macrosomia related to maternal type 1 diabetes on the lipid transport system.

METHODS

Serum lipoprotein concentrations and composition and lecithin:cholesterol acyltransferase (LCAT) activity were investigated in macrosomic newborns (mean birth weight, 4650 g; SEM, 90) and their mothers with poorly controlled type 1 diabetes, in appropriate for gestational age newborns (mean birth weight, 3616 g; SEM, 68) and their mothers with well controlled type 1 diabetes, and macrosomic (mean birth weight, 4555 g; SEM, 86) or appropriate for gestational age (mean birth weight, 3290 g; SEM, 45) newborns and their healthy mothers.

RESULTS

In mothers with well controlled type 1 diabetes, serum lipids, apolipoproteins, and lipoproteins were comparable with those of healthy mothers. Similarly, in their infants, these parameters did not differ from those of appropriate for gestational age newborns. Serum triglyceride, very low density lipoprotein (VLDL), apolipoprotein B100 (apo B100), and high density lipoprotein (HDL) triglyceride concentrations were higher, whereas serum apo A-I and HDL3 concentrations were lower in mothers with diabetes and poor glycaemic control than in healthy mothers. Their macrosomic newborns had higher concentrations in all serum lipids and lipoproteins, with high apo A-I and apo B100 values compared with appropriate for gestational age newborns. In macrosomic infants of healthy mothers, there were no significant differences in lipoprotein profiles compared with those of appropriate for gestational age infants. LCAT activity was similar in both groups of mothers and newborns.

CONCLUSION

Poorly controlled maternal type 1 diabetes and fetal macrosomia were associated with lipoprotein abnormalities. Macrosomic lipoprotein profiles related to poor metabolic control of type 1 diabetes appear to have implications for later metabolic diseases.

Maternal and fetal serum lipid and lipoprotein concentrations and compositions in type 1 diabetic pregnancy: relationship with maternal glycemic control

The aim of this study was to determine maternal and fetal lipoprotein profiles in type 1 diabetic pregnancies differing in glycemic control. Serum lipid, apolipoprotein, and lipoprotein lipid concentrations were investigated in mothers with poorly controlled or well-controlled type 1 diabetes as reflected by hemoglobin A1c(HbA1c) concentrations performed by isolab column chromatography and in their macrosomic (body wt = 4650 +/- 90 g) or appropriate-for-gestational-age newborns (body wt = 3616 +/- 68 g), and these levels were compared with those in healthy mothers and in their control newborns (body wt = 3290 +/- 45 g). In mothers with well-controlled diabetes and in their infants, serum lipid, apolipoprotein, and lipoprotein lipid concentrations were comparable to those in control mothers and in their control newborns. Mothers with poorly controlled diabetes presented higher serum triglyceride and apoprotein B-100 (apo B-100) levels but lower apo A-I and HDL3 cholesterol and phospholipid levels as compared with control values. In their macrosomic newborns, all serum lipid, apolipoprotein, and lipoprotein lipid levels were higher than those in control newborns. Maternal HbA1c and triglyceride levels in late gestation were significant predictors of fetal lipids and lipoproteins in the poorly controlled diabetes group. In conclusion, when under good metabolic control, type 1 diabetes did not affect maternal and fetal lipid levels. However, when under poor metabolic control, type 1 diabetes is associated with maternal and fetal lipoprotein abnormalities.

An elastic analysis of Listeria monocytogenes propulsion

The bacterium Listeria monocytogenes uses the energy of the actin polymerization to propel itself through infected tissues. In steady state, it continuously adds new polymerized filaments to its surface, pushing on its tail, which is made from previously cross-linked actin filaments. In this paper we introduce an elastic model to describe how the addition of actin filaments to the tail results in the propulsive force on the bacterium. Filament growth on the bacterial surface produces stresses that are relieved at the back of the bacterium as it moves forward. The model leads to a natural competition between growth from the sides and growth from the back of the bacterium, with different velocities and strengths for each. This competition can lead to the periodic motion observed in a Listeria mutant.

Measurement of the elasticity of the actin tail of Listeria monocytogenes

We report biophysical experiments performed on the bacterium Listeria monocytogenes, a model system to study actin-based motility. Using optical tweezers and electrophoresis experiments, we find that the bacterium is firmly attached to its tail, and we demonstrate that the tail responds as an elastic gel when deformed. We have measured its elastic modulus at a value of 10(3)-10(4) Pa, which is 10 times higher than the rigidity of the eukaryotic cytoplasm. These results demonstrate that the bacterium and its tail form a very robust system, consistent with the steadyness of the motion observed in vivo. We propose an elastic model for the propulsion mechanism which takes into account the connection and thus the interaction between the actin filaments. It provides a generic description of the various aspects of actin-tail based movements.

Shape transitions of giant liposomes induced by an anisotropic spontaneous curvature

We explore how a magnetic field breaks the symmetry of an initially spherical giant liposome filled with a magnetic colloid. The condition of rotational symmetry along the field axis leads either to a prolate or to an oblate ellipsoid. We demonstrate that an electrostatic interaction between the nanoparticles and the membrane triggers the shape transition.

[Epidermoid cyst of the testis. Conservative surgery in 3 cases]

The authors report 3 cases of epidermoid cyst of the testis. Clinical, laboratory and ultrasound data were relatively nonspecific. Precise histological criteria were defined by PRICE in 1969. The diagnosis is based on frozen section examination after transnnguinal testicular exploration. The authors describe the most conservative therapeutic approach for a constantly benign testicular tumour.

Dietary protein level and origin (casein and highly purified soybean protein) affect hepatic storage, plasma lipid transport, and antioxidative defense status in the rat

The effects of different proportions (10, 20, and 30%) of dietary casein or highly purified soybean protein on lipid metabolism were studied in growing Wistar rats. Hepatic, plasma and lipoprotein lipid, and protein concentrations, plasma thiobarbituric acid-reactive substance (TBARS) levels, and resistance of red blood cells against free-radical attack were determined after a 4-wk dietary regimen. Compared with the 20% casein diet, the 20% soybean protein diet exhibited similar cholesterolemia but lower plasma triacylglycerol concentrations and very-low-density lipoprotein (VLDL) particle number, as measured by diminished contents of VLDL-triacylglycerol, VLDL-protein, and VLDL-apolipoprotein (Apo) B (B-100 and B-48). The soybean protein diet raised high-density lipoprotein (HDL)(2-3) particle number, as measured by enhanced concentrations of HDL(2-3) cholesterol, HDL-phospholipid, and HDL-ApoA-I. Increasing casein or soybean protein level (from 10 to 30%) in the diet involved higher VLDL-ApoB (B-100 and B-48), indicating an increase in the number of VLDL particles. Feeding the 30% casein or 30% soybean protein diet enhanced LDL-HDL(1) cholesterol contents. Despite similar HDL(2-3)-ApoA-I levels, the 30% casein diet enhanced the HDL(2-3) mass and its cholesterol concentrations. In contrast, feeding either the 10 or 30% soybean protein diet significantly lowered HDL(2-3) cholesterol and ApoA-I levels. These effects on cholesterol distribution in lipoprotein fractions occurred despite unchanged total cholesterol concentrations in plasma. Feeding 20% soybean protein versus 20% casein involved lower plasma TBARS concentrations. Decreasing casein or soybean protein levels in the diet were associated with higher plasma TBARS concentrations and had a lower resistance of red blood cells against free-radical attack. The present study shows that dietary protein level and origin play an important role in lipoprotein metabolism and the antioxidative defense status but do not affect total cholesterol concentrations in plasma.