Quantitative and qualitative antimicrobial usage patterns in farrow-to-finish pig herds in Belgium, France, Germany and Sweden

Data on sales of antimicrobials using a standardised methodology have shown that there are vast differences between countries in amounts of antimicrobials sold for food-producing animals, but these data do not provide insight on how sales are distributed by species and age groups. The aim of this study was to compare herd level antimicrobial usage for pigs by age category, antimicrobial class and administration route for farrow-to-finish herds in four EU countries. A cross-sectional study was conducted among 227 farrow-to-finish pig herds with at least 100 sows and 500 finishing pigs in Belgium (n=47), France (n=60), Germany (n=60) and Sweden (n=60). Detailed information about the antimicrobial consumption for breeding and growing pigs was collected. Antimicrobial usage was quantified as active substance expressed as mg and then converted to treatment incidence (TI) based on Defined Daily Doses Animal per 1000 pig-days at risk. TIs varied between and within countries, herds and age groups. The Swedish herds had the lowest and the German herds the highest overall use. Most treatments were applied to weaned piglets except in the Swedish herds where treatments of suckling piglets were most frequent. Antimicrobials were most often applied through feed or water except in the Swedish herds where parenteral treatments were most frequent. Aminopenicillins was the antimicrobial class most commonly used. Use of third and fourth generation cephalosporins constituted 11% of use for the Belgian herds, which was higher compared to the other countries. There was a significant (p<0.01) association between the within-herd antimicrobial use across different age categories. This study has shown that there were large differences in antimicrobial use for pigs between countries, herds and age groups in farrow-to-finish herds of similar size when actual consumption data were compared. Collecting detailed usage data can be used to efficiently target high users in order to reduce antimicrobial consumption.

Perceptions of antimicrobial usage, antimicrobial resistance and policy measures to reduce antimicrobial usage in convenient samples of Belgian, French, German, Swedish and Swiss pig farmers

We conducted a survey among convenient samples of pig farmers (N=281) in Belgium, France, Germany, Sweden and Switzerland. We identified some significant differences among the five investigated countries (independent variable) regarding farmers' antimicrobial usage compared to their own country and worries related to pig farming (dependent variables), but most of the differences were rather small. In general, farmers perceived their own antimicrobial usage to be lower than that of their peers in the same country and lower than or similar to that of farmers from other countries. This may be a consequence of our convenience sample, resulting in self-selection of highly motivated farmers. Farmers were significantly more worried about financial/legal issues than about antimicrobial resistance. They believed that a reduction in revenues for slaughter pigs treated with a large amount of antimicrobials would have the most impact on reduced antimicrobial usage in their country. Further, farmers who were more worried about antimicrobial resistance and who estimated their own antimicrobial usage as lower than their fellow countrymen, perceived more impact from policy measures on the reduction of antimicrobials. Our results indicated that the same policy measures can be applied to reduce antimicrobial usage in pig farming in all five countries. Moreover, it seems worthwhile to increase pig farmers' awareness of the threat of antimicrobial resistance and its relation to antimicrobial usage; not only because pig farmers appeared little worried about antimicrobial usage but also because it affected farmers' perception of policy measures to reduce antimicrobial usage. Our samples were not representative for the national pig farmer populations. Further research is therefore needed to examine to what extent our findings can be generalised to these populations and to farmers in other countries.

Effects of different antimicrobial treatments on serum acute phase responses and leucocyte counts in pigs after a primary and a secondary challenge infection with Actinobacillus pleuropneumoniae

The susceptibility to an initial challenge and a re-challenge inoculation with Actinobacillus pleuropneumoniae was analysed in pigs that were treated with antimicrobials of different efficacies following the first exposure to A pleuropneumoniae. In brief, 30 nine-week-old specific pathogen-free pigs were allocated to five groups of six. After acclimatisation, four groups were inoculated with A pleuropneumoniae serotype 2. At the onset of clinical signs, three of the groups of pigs were treated with enrofloxacin, tetracycline or penicillin. A fourth group served as the inoculated control and the fifth group as a control group that had not been inoculated. On day 28, all five groups were re-challenged with the same strain of A pleuropneumoniae serotype 2 as had been used in the first inoculation. No treatments were carried out at this time. The acute phase responses and differential leucocyte counts were monitored in detail after both inoculations. Leucocytosis and acute phase responses in the forms of serum amyloid A, pig-major acute phase protein and haptoglobin were recorded in all of the inoculated groups after the onset of clinical signs following the first inoculation. A porcine mannan-binding lectin-A response was less evident in the pigs. Acute phase responses resembling those of the first inoculation were observed in the pigs that had not previously been inoculated and in the pigs treated with enrofloxacin. Acute phase responses were not recorded in the other three groups, where the pigs had seroconverted to A pleuropneumoniae serotype 2 following the first inoculation.

Disease patterns and immune responses in the offspring to sows with high or low antibody levels to Actinobacillus pleuropneumoniae serotype 2

The serum antibody responses to Actinobacillus pleuropneumoniae and the secondary invader Pasteurella multocida were monitored from birth until slaughter in the offspring to sows with high or low levels of serum antibodies to A. pleuropneumoniae. Serum antibody concentrations to A. pleuropneumoniae were higher from birth to the age of 9 weeks in piglets delivered by high responding sows. In contrast, antibody levels to P. multocida were similar in both groups during this period. From the age of 20 and 15 weeks, antibody levels to A. pleuropneumoniae and P. multocida, respectively, were higher in the offspring to high responding sows. This implies that the offspring to sows with high levels of antibodies may be better protected during the first period of life because of a higher level of passively derived immunity. These piglets will also mount a higher antibody response when later infected, indicating a heritability of the humoral immune response.

Responses of pigs to a re-challenge with Actinobacillus pleuropneumoniae after being treated with different antimicrobials following their initial exposure

Four groups of six specific pathogen-free (SPF) pigs were inoculated intranasally with Actinobacillus pleuropneumoniae serotype 2 and treated with either enrofloxacin, tetracycline or penicillin at the onset of clinical disease, or left untreated. A fifth group was left uninoculated. The inoculated control and the penicillin-treated groups developed severe disease, but the groups treated with enrofloxacin and tetracycline recovered rapidly. All the inoculated pigs, except those treated with enrofloxacin developed serum antibodies to A pleuropneumoniae. On day 28, all five groups were challenged with A pleuropneumoniae without any subsequent treatment. The previously uninoculated control group and the enrofloxacin-treated group developed severe disease, but the three seropositive groups remained unaffected.

Antimicrobial susceptibility in Escherichia coli of human and avian origin--a comparison of wild-type distributions

In the present study, the antimicrobial susceptibilities of 97 Escherichia coli isolates from birds, and 100 clinical isolates from blood cultures, were determined by disk diffusion. The wild-type distributions were defined by the normalized resistance interpretation method. It is shown that the avian and clinical inhibition zone diameter distributions of wild-type E. coli are indistinguishable.

Transcriptional regulation and biological significance of the insulin like growth factor II gene

The insulin like growth factors I and II are the most ubiquitous in the mammalian embryo. Moreover they play a pivotal role in the development and growth of tumours. The bioavailability of these growth factors is regulated on a transcriptional as well as on a posttranslational level. The expression of non-signalling receptors as well as binding proteins does further tune the local concentration of IGFs. This paper aims at reviewing how the transcription of the IGF genes is regulated. The biological significance of these control mechanisms will be discussed.

Lameness in Piglets. Abrasions in Nursing Piglets and Transfer of Protection towards Infections with Streptococci from Sow to Offspring

A group of 175 newborn piglets were monitored with respect to development of abrasions and lameness. Lameness was diagnosed in 10.9% of the piglets. About every second litter was affected and around 75% of these diagnoses took place during the first 3 weeks of life. Skin lesions were present already on day 3. They increased in magnitude until day 10 and thereafter declined. They were generally bilateral and most commonly observed as abrasions over the carpal joints. Hocks, face and tails were affected in a similar way, but at lower magnitudes. Sole bruising was observed in 87% of the piglets on the third day of life, and moderate to severe lesions dominated until day 10. Thereafter the incidence decreased, indicating healing with time. Still 39% of the piglets were affected at day 17. There was a significant positive correlation between skin lesions of carpus and hock within all examination days in selected piglets with known identity (n = 48). Between day 10 and 17 significant positive correlations were found within all examination sites with exception of abdomen and teats. The offspring of sows treated against mastitis expressed more abrasions then piglets delivered by healthy sows and the mortality during the first 17 days postpartum was significantly higher among piglets delivered by sows treated for mastitis. The level of serum antibodies to Streptococcus equisimilis in eight dams decreased during the last month of gestation and a declining maternal immunity to S. equisimilis was demonstrated in all piglets (n = 47) during the first 5 weeks of life. During the first 2 weeks of life somewhat lower median levels of serum antibodies were recorded among the piglets that were treated against arthritis (n = 8).

Mutation frequency and biological cost of antibiotic resistance in Helicobacter pylori

Among the several factors that affect the appearance and spread of acquired antibiotic resistance, the mutation frequency and the biological cost of resistance are of special importance. Measurements of the mutation frequency to rifampicin resistance in Helicobacter pylori strains isolated from dyspeptic patients showed that approximately 1/4 of the isolates had higher mutation frequencies than Enterobacteriaceae mismatch-repair defective mutants. This high mutation frequency could explain why resistance is so frequently acquired during antibiotic treatment of H. pylori infections. Inactivation of the mutS gene had no substantial effect on the mutation frequency, suggesting that MutS-dependent mismatch repair is absent in this bacterium. Furthermore, clarithromycin resistance conferred a biological cost, as measured by a decreased competitive ability of the resistant mutants in mice. In clinical isolates this cost could be reduced, indicating that compensation is a clinically relevant phenomenon that could act to stabilize resistant bacteria in a population.

Comparative studies on neutralisation of primary HIV-1 isolates by human sera and rabbit anti-V3 peptide sera

IgG binding to V3 peptides and serum neutralising responses were studied in four HIV-1 infected individuals with progressive disease over a period of 31-70 months. The 18-20 mer peptides comprised residues 299-317 (numbering of HIV1 MN) in the N-terminal half of the V3 loop of the envelope glycoprotein gp120 and were derived from the sequences of autologous, as well as heterologous isolates. All four individuals studied lacked anti-V3 IgG binding to at least one autologous V3 sequence. V3 peptides to which autologous sera lacked binding IgG were all immunogenic in rabbits and induced antisera that were broadly cross-reactive by EIA and broadly cross-neutralising to primary HIV-1 isolates. This indicates that the peptides are immunogenic per se and that the respective human hosts have selective defects in recognising the corresponding V3 sequences. Despite the absence of antibody binding to autologous V3 peptides, the human sera had neutralising antibodies to autologous (three out of four cases), as well as heterologous isolates (all cases). Moreover, in vitro exposure of the patients' isolates to autologous neutralising serum or the homologous rabbit antiserum selected for variants with amino acid substitutions close to the crown of the V3 loop or in regions outside the sequence corresponding to peptides used for immunisation. The amino acid exchanges affected V3 positions known to be antigenic and which are also prone to change successively in infected persons. It is likely that neutralising antibodies recognise both linear and conformational epitopes in the V3 loop. Apparently, there are several, but restricted, numbers of ways for this structure to change its conformation and thereby give rise to neutralisation resistant viruses.

Critical dissolution tests of oral systems based on statistically designed experiments. III. In vitro/in vivo correlation for multiple-unit capsules of paracetamol based on PLS modeling

The main aims of the present study were to establish an in vitro/in vivo correlation for multiple-unit capsules of paracetamol by means of statistical prediction models and to investigate the effect of a number of in vitro variables on the discussion rate of paracetamol from the formulation. A fractional factorial screening design was used to investigate the effects of the variables agitation, pH, osmolality, viscosity, and the presence of bile salt on the dissolution rate of paracetamol. The effects were evaluated in two separate partial least-squares models, in which the responses were expressed as the cumulative percentage of paracetamol dissolved at specified time-points (model I) and as the shape (beta) and scale (eta) parameters according to the Weibull function (model II). It was concluded that agitation and viscosity had significant effects on the dissolution rate of paracetamol. Statistical models based on the responses from models I and II were then used to predict the in vitro conditions most closely correlated with the in vitro dissolution of paracetamol after administration of the formulation to 10 healthy volunteers. The predicted optimal in vitro conditions were similar for the two models and not too far from what is expected from the gastrointestinal tract. The experimental verification of the in vitro conditions showed that both models were equally good, and contributed to high degrees of correlation with the in vivo dissolution behavior of the formulation during 9 hr. The relationships obtained when plotting the percentage dissolved in vitro versus in vivo were y = 1.1x (r2 = 0.98) and y = 1.1x (r2 = 0.94) for models I and II, respectively. Based on these results, it is difficult to state a preference for one of the models. Finally, the use of statistical prediction models to develop critical in vitro tests is a successful approach in the establishment of associations between dissolution behavior in vitro and in vivo for oral extended-release systems.

Critical dissolution tests of oral systems based on statistically designed experiments. II. In vitro optimization of screened variables on ER-coated spheres for the establishment of an in vitro/in vivo correlation

The study was designed to optimize the effects of the screened in vitro dissolution variables agitation, temperature, osmolality, and polarity on the release of the neuroleptic compound remoxipride from extended release coated spheres. The variables were varied independently by means of a fractional factorial design. The in vitro tests were performed with the Basket method (USP). The polarity and the osmolality of the medium had significant effects on the dissolution rate of remoxipride. A statistical model was calculated based on the obtained dissolution in vitro. The model was then used to predict the in vitro conditions that most closely correlated with the dissolution rate of remoxipride in vivo, after administration of the formulation to 16 volunteers. The predicted in vitro conditions were experimentally verified, and an excellent association with the in vivo behavior of the formulation was found. Validation of the optimal in vitro conditions was performed on another batch of the formulation. The dissolution profile obtained showed a significant association with the corresponding dissolution profile in vivo. The use of statistically designed experiments in the development of critical dissolution tests for the establishment of in vitro/in vivo correlations seems to be a useful working approach, and supports further application to other oral solid systems.

Effect of head-group structure and counterion condensation on phase equilibria in anionic phospholipid-water systems studied by 2H, 23Na, and 31P NMR and X-ray diffraction

The phase equilibria, hydration, and sodium counterion association for the systems DOPA-2H2O, DOPS-2H2O, DOPG-2H2O, and DPG-2H2O were investigated with 2H, 23Na, and 31P NMR and X-ray diffraction. The following one-phase regions were found in the DOPA-water system: a reversed hexagonal liquid-crystalline (HII) phase up to about 35 wt % water and a lamellar liquid-crystalline (L alpha) phase between about 55 and 98 wt % water. The area per DOPA molecule was 36-65 A2 in the HII phase (10-40 wt % water) and 69 A2 in the L alpha phase (60 wt % water). DOPS and DOPG with 10-98 wt % water, and DPG with 20-95 wt % water formed an L alpha phase at temperatures between 25 and 55 degrees C. At temperatures above 55 degrees C, DPG with 20 and 30 wt % water formed a mixture of L alpha, HII, and cubic liquid-crystalline phases, the mole percent of lipid forming nonlamellar phases being smaller at 30 wt % water than at 20 wt % water. DPG with 10 wt % water probably formed a mixture of an L alpha phase and at least one nonlamellar liquid-crystalline phase at 25 and 35 degrees C, and a pure HII phase at 45 degrees C and higher temperatures. At water concentrations above about 50 wt % the 23Na quadrupole splitting was constant for all four lipid-water systems studied, implying that the counterion association to the charged lipid aggregates did not change upon dilution. These experimental observations can be described with an ion condensation model but not with a simple equilibrium model. The fraction of counterions located close to the lipid-water interface was calculated to be greater than 95%. The 2H and 23Na NMR quadrupole splittings of 2H2O and sodium counterions, respectively, indicate that the molecular order in the polar head-group region decreases for the L alpha phase in the order DOPA approximately DPG greater than DOPS greater than DOPG.

Changes in expression and organization of smooth-muscle-specific alpha-actin during fibronectin-mediated modulation of arterial smooth muscle cell phenotype

The spreading of freshly isolated arterial smooth muscle cells on a substrate of fibronectin is mediated by an integrin receptor on the cell surface. It is associated with organization of actin filaments in stress fibers and marked changes in cell morphology and function, collectively referred to as a transition from a contractile to a synthetic phenotype. To study further how extracellular matrix components affect smooth muscle phenotype, we have analyzed the expression and organization of smooth-muscle-specific alpha-actin in freshly isolated rat aortic smooth muscle cells cultured on a substrate of fibronectin under serum-free conditions. Northern-blot analysis showed that the expression of mRNA for smooth muscle alpha-actin, but not for nonmuscle actin, was strongly repressed during primary culture. On the other hand, the cellular content of alpha-actin was only moderately changed during the same period. Indirect immunofluorescence staining revealed that nonmuscle actin was rapidly organized in stress fibers, which did not stain with a monoclonal antibody against smooth muscle alpha-actin. Filament bundles containing alpha-actin were most prominent in the central parts of the cytoplasm and gradually disappeared as the spreading of the cells progressed. In contrast to the situation with nonmuscle actin, there was no apparent overlap in the staining for alpha-actin and the fibronectin receptor (alpha 5 beta 1), indicating that this receptor interacted with nonmuscle actin during the initial spreading process. Taken together, the results show that the expression and organization of smooth muscle alpha-actin are changed during interaction of the cells with fibronectin early in primary culture. They support the notion that integrin-mediated interactions between extracellular matrix components and arterial smooth muscle cells take part in the control of smooth muscle phenotype.

Expression of PDGF alpha- and beta-receptors in rat arterial smooth muscle cells is phenotype and growth state dependent

Adult rat arterial smooth muscle cells were shown to express mRNA for the platelet-derived growth factor (PDGF) alpha- and beta-receptors and to bind radioiodinated PDGF-AA and PDGF-BB in a phenotype-dependent and growth state-dependent manner. PDGF alpha-receptor mRNA was not detected in the intact aortic media, but appeared as the cells converted from a contractile to a synthetic phenotype during serum-free primary culture. PDGF beta-receptor mRNA was expressed already in vivo, and increased further as the cells were isolated and cultured in vitro. Exposure of the cells to human platelet PDGF resulted in increased PDGF alpha-receptor mRNA levels, decreased PDGF beta-receptor mRNA levels, and decreased binding of both PDGF-AA and PDGF-BB. Following removal of the exogenous mitogen, the content of PDGF alpha- and beta-receptor mRNA increased, as did the binding of PDGF-AA and PDGF-BB. Subsequently, the content of PDGF A-chain mRNA started to rise, and the cells retained a high rate of DNA synthesis in a serum-free medium. As a result of this autocrine stimulation, the PDGF receptors were down-regulated. Although smooth muscle cells in serum-free primary cultures bound the different PDGF isoforms to a varying extent (AA less than AB less than BB), the replicative response was of a similar magnitude. Subcultured cells bound the different PDGF isoforms in similar proportions as the primary cells. Contrary to the situation in primary cells, there was a direct correlation between the binding level and the DNA synthetic response. Moreover, the subcultured cells did not replicate in a serum-free medium. These observations support the idea that the phenotypic modulation of arterial smooth muscle cells in primary culture prepares the cells to activate autocrine growth mechanisms. When stimulated with an exogenous mitogen, they enter the cell cycle and are thereafter able to stimulate their own growth in an autocrine manner by production of PDGF-AA or a closely related molecule.

Suramin inhibits binding and degradation of platelet-derived growth factor in arterial smooth muscle cells but does not interfere with autocrine stimulation of DNA synthesis

During in vitro culture arterial smooth muscle cells of adult rats are able to produce a platelet-derived growth factor (PDGF)-like protein and to promote their own growth in an autocrine manner. Here, this process has been studied using suramin, a polyanionic drug that has been reported to interfere with the cellular binding of several growth factors. Our results indicate that suramin speeds up the transition of the cells from a contractile to a synthetic phenotype early in primary culture. It inhibits the binding of PDGF to the cells, displaces PDGF bound to the cell surface, and slows down the degradation of PDGF internalized by the cells. It reduces the specific activities of the lysosomal enzymes acid phosphatase, beta-N-acetylglucosaminidase and beta-glucuronidase, and gives rise to an accumulation of lysosomes with myelin-like inclusions. It blocks PDGF- and serum-induced DNA synthesis and cellular proliferation in secondary cultures, but lacks a distinct inhibitory effect on DNA synthesis in primary cultures under serum-free conditions. The results suggest that the PDGF-like protein produced by the smooth muscle cells under the latter conditions may bind to its receptor and exert its autocrine effect intracellularly, without prior release into the pericellular space.

Reversed hexagonal phase formation in lecithin-alkane-water systems with different acyl chain unsaturation and alkane length

Investigations of lipid-alkane systems are important for an understanding of the interactions between lipids and hydrophobic/amphiphilic peptides or other hydrophobic biological molecules. A study of the formation of nonlamellar phases in several phosphatidylcholine (PC)-alkane-2H2O systems has been performed. The PC molecules chosen in this work are dipalmitoyl-PC (DPPC), 1-palmitoyl-2-oleoyl-PC (POPC), dioleoyl-PC (DOPC), and dilinoleoyl-PC (DLiPC), lipids that in excess water form just a lamellar liquid-crystalline phase up to at least 90 degrees C. The addition of n-alkanes (C8-C20) to these PC-2H2O systems induces the formation of reversed hexagonal (HII) and isotropic phases. The water and dodecane concentrations required to form these phases depend on the degree of acyl chain unsaturation of the PC molecules and increase in the order DLiPC approximately DOPC less than POPC less than DPPC. The most likely explanation to this result is that the diameter of the lipid-water cylinders in the HII phase grows gradually larger with increased acyl chain saturation and more water and dodecane are consequently needed to fill the water cylinders and the void volumes between the cylinders, respectively. The ability of the alkanes to promote the formation of an HII phase is strongly chain length dependent. Although the number of alkane carbon atoms added per DOPC molecule in the DOPC-n-alkane-2H2O mixtures was kept constant, this ability decreased on going from octane to eicosane. The thermal history of a DPPC-n-dodecane-2H2O sample was important for its phase behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Chloroquine and monensin inhibit induction of DNA synthesis in rat arterial smooth muscle cells stimulated with platelet-derived growth factor

The weak base chloroquine and the Na+/H+ ionophore monensin were used to study the role of lysosomes in the induction of DNA synthesis by platelet-derived growth factor (PDGF) in rat arterial smooth muscle cells cultivated in vitro. The results show that PDGF initiates DNA synthesis in a defined, serum-free medium. This indicates that a single factor may control, directly or indirectly, the transition from the G0 to the G1 phase, the progress through the G1 phase, and the entrance into the S phase of the cell cycle. It is further demonstrated that PDGF has to be present throughout most of the prereplicative period (12-16 h) to induce DNA synthesis in the maximum number of cells, suggesting that one or more processes need to be stimulated continually or successively to push the cell into the S phase. Chloroquine and monensin inhibit induction of DNA replication by PDGF, with maximum effect at 50 microM and 5 microM, respectively. To be fully active, the drugs have to be added within 4-8 h after the growth factor, but a partial inhibition persists if they are added at any time during the prereplicative period. Both drugs reduce PDGF-stimulated RNA and protein synthesis, and suppress degradation of [3H]leucine-labeled cellular protein and [125I]-labeled PDGF. Fine-structurally, they give rise to an accumulation of lysosomes or prelysosomal vacuoles with inclusions of incompletely degraded material. These findings suggest that the mitogenic effect of PDGF is dependent on a normal function of lysosomes during the prereplicative phase, especially its first half (0-8 h).

Arterial smooth muscle cells express platelet-derived growth factor (PDGF) A chain mRNA, secrete a PDGF-like mitogen, and bind exogenous PDGF in a phenotype- and growth state-dependent manner

Adult rat arterial smooth muscle cells are shown to express platelet-derived growth factor (PDGF) A chain mRNA, to secrete a PDGF-like mitogen, and to bind exogenous PDGF in a phenotype- and growth state-dependent manner. In the intact aortic media, where the cells are in a contractile phenotype, only minute amounts of PDGF A chain and no B chain (c-sis) RNA were detected. After cultivation and modulation of the cells into a synthetic phenotype, the A chain gene was distinctly expressed, whereas the B chain gene remained unexpressed. Cells kept in serum-free medium on a substrate of plasma fibronectin showed high levels of A chain RNA and high PDGF receptor activity, but did not secrete detectable amounts of PDGF-like mitogen. After exposure to PDGF, which is itself sufficient to initiate DNA synthesis and mitosis in these cells, a PDGF-like mitogen was released into the extracellular medium. Concomitantly, the amount of A chain transcripts per cell and the ability of the cells to bind radioactive PDGF decreased. Similarly, smooth muscle cells initially grown in the presence of serum released more PDGF-like mitogen, contained fewer A chain transcripts, and bound more radioactive PDGF in proliferating than in stationary cultures. The findings confirm the notion that adult rat arterial smooth muscle cells are able to promote their own growth in an autocrine or paracrine manner. Furthermore, they reveal some basic principles in the control of this process.

Hydrophobic molecules in lecithin-water systems. I. Formation of reversed hexagonal phases at high and low water contents

The system dioleoylphosphatidylcholine (DOPC)-n-dodecane-2H2O was investigated with different nuclear magnetic resonance (NMR) techniques: (a) a tentative phase diagram was determined by 2H- and 31P-NMR, (b) translational diffusion coefficients were determined for the three components with the pulsed magnetic field gradient NMR technique, and (c) order parameters for perdeuterated n-dodecane were obtained by 2H-NMR. n-Dodecane induces the formation of reversed hexagonal (HII) phases at low and high water concentrations, and cubic phases at low water contents. The translational diffusion coefficients of n-dodecane in a cubic phase with 6 mol water per mol DOPC, and in an HII phase with 48 mol water per mol DOPC, were just approximately 2.5 times lower than in pure dodecane. Perdeuterated dodecane gave large quadrupole splittings in a lamellar phase, much smaller in an HII phase at low water contents, and a narrow single peak in an HII phase at high water contents. This latter observation indicates that a large fraction of the dodecane molecules is located in separate regions between the water cylinders. Our results support the model given by Gruner concerning the aggregation of membrane lipids in the presence of hydrophobic molecules.

Phase equilibria of membrane lipids from Acholeplasma laidlawii: importance of a single lipid forming nonlamellar phases

A basis for the reorganization of the bilayer structure in biological membranes is the different aggregate structures formed by lipids in water. The phase equilibria of all individual lipids and several in vivo polar lipid mixtures from acyl chain modified membranes of Acholeplasma laidlawii were investigated with different NMR techniques. All dioleoyl (DO) polar lipids, except monoglucosyldiglyceride (MGDG), form lamellar liquid crystalline (L alpha) phases only. The phase diagram of DOMGDG reveals reversed cubic (III), reversed hexagonal (HII), and L alpha phases. In mixtures of DOMGDG and dioleoyldiglycosyldiglyceride (DODGDG), the formation of an III (or HII) phase is enhanced by DOMGDG and low hydration or high temperatures. For in vivo mixtures of all polar DO lipids, a transition from an L alpha to an III phase is promoted by low hydration or high temperatures (50 degrees C). The phospholipids are incorporated in this III phase. Likewise, III and HII phases are formed at similar temperatures in a series of in vivo mixtures with different extents of acyl chain unsaturation. However, their melting temperatures (Tm) vary in an expected manner. All cubic and hexagonal phases, except the III phase with DOMGDG, exist in equilibrium with excess water. The maximum hydration of MGDG and DGDG is similar and increases with acyl chain unsaturation but is substantially lower than that for, e.g., phosphatidylcholine. The translational diffusion of the lipids in the cubic phases is rapid, implying bicontinuous structures. However, their appearances in freeze-fracture electron microscope pictures are different. The III phase of DOMGDG belongs to the Ia3d space group.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenotype modulation in primary cultures of smooth-muscle cells from rat aorta. Synthesis of collagen and elastin

Early in primary culture, arterial smooth-muscle cells undergo a transition from a contractile to a synthetic phenotype. This process includes the loss of myofilaments and of contractility. At the same time, an extensive rough endoplasmic reticulum and a large Golgi complex are formed, and active synthesis of DNA, RNA and proteins commences. In the present study, chemical and immunocytochemical methods were used to investigate the production of extracellular-matrix proteins in relation to this change in phenotypic properties. The results showed that the phase of rapid cellular proliferation that follows the structural modulation of smooth-muscle cells is associated with high rates of collagen and elastin synthesis, as measured by the incorporation of 3H-proline into 3H-hydroxyproline and 3H-valylproline, respectively. SDS-polyacrylamide gel electrophoresis and fluorography indicated that type-I collagen is the main collagen species synthesized by these cells. Smaller amounts of type-V collagen and (although not definitively identified) type-III collagen were also detected. Indirect immunofluorescence and immunoelectron microscopy demonstrated that smooth-muscle cells surround themselves with an incomplete basement membrane, containing laminin and type-IV collagen, and thin fibrils of type-I collagen. Adjacent to these fibrils, aggregates of amorphous, elastin-like material were also found. Our observations confirm and extend earlier notions of a close similarity between the behaviour of arterial smooth-muscle cells during in vitro cultivation and during the early stages of the formation of atherosclerotic lesions.

Rat skeletal myoblasts and arterial smooth muscle cells express the gene for the A chain but not the gene for the B chain (c-sis) of platelet-derived growth factor (PDGF) and produce a PDGF-like protein

It is shown here that the myogenic cell line L6J1, primary skeletal myoblasts, and primary adult arterial smooth muscle cells express the gene for the A chain but not the gene for the B chain (c-sis) of platelet-derived growth factor (PDGF). It is further demonstrated that conditioned media from L6J1 cultures contain material that (i) competes with 125I-labeled PDGF for binding to human fibroblasts, (ii) is specifically precipitated by antibodies against PDGF, and (iii) has a relative molecular mass comparable to that of PDGF and, after reduction, its constituent subunit chains. The secretion of PDGF-receptor-competing activity was at a maximum in exponentially growing cultures but remained at a high level also after the cells had become confluent, stopped dividing, and fused to form multinucleate myotubes. Similarly, it was previously demonstrated that adult rat arterial smooth muscle cells in primary culture produce a mitogenic protein with immunological and structural properties similar to PDGF. In accordance with these findings, it was recently shown that secretion of PDGF-like mitogens by a number of human tumor cell lines correlates with expression of the gene for the A chain rather than the B chain of PDGF. The results suggest that production of homodimers of PDGF A chains may stimulate proliferation of skeletal myoblasts and arterial smooth muscle cells in an autocrine or paracrine manner. This could fulfill important functions during myogenesis in the embryo as well as in tissue repair and atherogenesis in the adult.

The calcium antagonist nifedipine inhibits arterial smooth muscle cell proliferation

Migration of smooth muscle cells from the media to the intima of the arterial wall and proliferation of intimal smooth muscle are major early events in the formation of an atherosclerotic lesion. The start of proliferation requires that the cells have passed through a modulation from contractile to synthetic phenotype and that they are stimulated with growth factors. Here, we have examined the effects of the calcium antagonist nifedipine on phenotypic modulation and growth of isolated rat arterial smooth muscle cells cultivated in vitro. The results indicate that micromolar concentrations of nifedipine slow down the rate of transformation of the cells from a contractile to a synthetic phenotype and inhibit initiation of DNA synthesis as well as cellular proliferation. The inhibitory effect on DNA synthesis was seen both in cells stimulated with whole blood serum and with purified platelet-derived growth factor. The results raise the possibility that nifedipine may be used to prevent atherogenesis and to inhibit progression of fibromuscular lesions by interfering with the proliferation of arterial smooth muscle cells.

Phenotype modulation in primary cultures of arterial smooth-muscle cells: reorganization of the cytoskeleton and activation of synthetic activities

During primary culture, arterial smooth-muscle cells (SMCs) undergo transition from a contractile to a synthetic phenotype. As a consequence, they lose the ability to contract and, instead, acquire the ability to synthesize DNA, divide and produce extracellular-matrix components. In the present study, we used cytochemical and electron-microscopic methods to study the organization of the cytoskeleton in primary cultures of adult rat and human arterial SMCs. Freshly isolated cells were all in contractile phenotype and stained intensely with NBD-phallacidin, a fluorescent marker for F-actin. Diffuse, positive staining was also obtained using indirect-immunofluorescence microscopy with antibodies against tubulin and vimentin, which are subunit proteins of microtubules and intermediate filaments, respectively. Fine structurally, the cytoplasm of these cells was mainly filled with microfilament bundles coalescing in dense bodies. After a few hours in culture, the SMCs attached to the substrate and started to extend processes in various directions. These stained with antibodies to tubulin and vimentin, but not with NBD-phallacidin. Within 1-3 days of culture, the cells spread out on the substrate and developed a system of actin-containing stress fibre bundles spanning their entire length, as well as a radiating system of microtubules and vimentin filaments, originating in the juxtanuclear region. Fine structurally, these changes corresponded to a marked decrease in the number of microfilaments, an increase in the number of microtubules and intermediate filaments, and the formation of an extensive rough endoplasmic reticulum and a large Golgi complex. The morphological transformation of the cells was accompanied by the coordinated activation of DNA, RNA and protein synthesis.

Adult human arterial smooth muscle cells in primary culture. Modulation from contractile to synthetic phenotype

Smooth muscle cells were isolated enzymatically from adult human arteries, grown in primary culture in medium containing 10% whole blood serum, and studied by transmission electron microscopy and [3H]thymidine autoradiography. In the intact arterial wall and directly after isolation, each smooth muscle cell had a nucleus with a wide peripheral zone of condensed chromatin and a cytoplasm dominated by myofilament bundles with associated dense bodies. After 1-2 days of culture, the cells had attached to the substrate and started to spread out. At the same time, a characteristic fine-structural modification took place. It included nuclear enlargement, dispersion of the chromatin and formation of large nucleoli. Moreover, myofilament bundles disappeared and an extensive rough endoplasmic reticulum and a large Golgi complex were organized in the cytoplasm. This morphological transformation of the cells was completed in 3-4 days. It was accompanied by initiation of DNA replication and mitosis. The observations demonstrate that adult human arterial smooth muscle cells, when cultivated in vitro, pass through a phenotypic modulation of the same type as arterial smooth muscle cells from experimental animals. This modulation gives the cells morphological and functional properties resembling those of the modified smooth muscle cells found in fibroproliferative lesions of atherosclerosis. Further studies of the regulation of smooth muscle phenotype and growth may provide important clues for a better understanding of the pathogenesis of atherosclerosis.

Phenotype modulation in primary cultures of arterial smooth-muscle cells

The effects of prostaglandin E1 (PGE1) on the phenotypic state of enzymatically isolated arterial smooth-muscle cells in primary culture were studied by transmission electron microscopy, thymidine autoradiography, and cell counting. Early in culture (day 0-2), PGE1 stimulated conversion of the cells from contractile (less euchromatic nucleus and cytoplasm dominated by myofilament bundles) to synthetic state (more euchromatic nucleus and cytoplasm dominated by cisternae of rough endoplasmic reticulum and a large Golgi complex). The rate of entrance of the cells into DNA synthesis and mitosis was also increased at this time. Later on (day 3-6), when the majority of the cells had entered synthetic state, PGE1 inhibited DNA synthesis and cellular proliferation. These observations indicate that the effect of prostaglandins on arterial smooth muscle is dual in nature and dependent on the state of differentiation of the cells.

Phenotype modulation in primary cultures of arterial smooth muscle cells. On the role of platelet-derived growth factor

Smooth muscle cells were isolated from adult rat aorta by collagenase digestion, grown in primary culture in the presence of 10% whole blood serum (WBS), and studied by quantitative electron microscopy and thymidine autoradiography in order to correlate cellular fine structure and proliferation. On day 2-4, the cells passed through a structural transition from contractile to synthetic state. In the former they were characterized by predominance of cytoplasmic microfilament bundles and in the latter by an extensive rough endoplasmic reticulum (RER) and a large Golgi complex. The disappearance of the microfilament bundles was accompanied by a transient increase in lysosomal volume density but no signs of bulk autophagy. This suggests that microfilaments were disassembled into subunit proteins and that lysosomes were engaged in adjusting the pool of free subunits into a new equilibrium. RER cisternae grew out from the nuclear envelope and successively spread throughout the cytoplasm. Stacks of Golgi cisternae were organized in a circumscribed juxtanuclear region. The structural modulation occurred also in medium containing 10% plasma-derived serum (PDS). Its onset was delayed by addition of antibodies (50 micrograms/ml) against platelet-derived growth factor (PDGF) to 10% WBS-medium and speeded up by addition of purified PDGF (25 ng/ml) to 10% PDS-medium. Otherwise, the kinetics of the structural modulation was the same in all experimental groups. The observations could not be explained by overgrowth of contaminating fibroblasts since (1) successive steps in the process were clearly evident, (2) the cells surrounded themselves by an incomplete basement membrane, a characteristic feature of smooth muscle, and (3) mitomycin C blocked cell growth but not conversion from contractile to synthetic state. After 3-4 days of culture in 10% WBS-medium, active DNA synthesis and cellular proliferation were initiated as determined autoradiographically and by cell counting. Electron microscopic autoradiography showed that all cells were morphologically in the synthetic state at the time of entrance into S-phase. Initially, the cells grew at a lower rate in the presence of PDGF antibodies but after 5-6 days of culture attained a rate similar to that in the controls. No distinct proliferation was obtained in 10% PDS-medium unless purified PDGF (10 ng/ml) was added during the first days of culture. The results suggest that the structural modulation of the smooth muscle is an absolute but not sufficient prerequisite for cellular proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)

Application of optical diffractometry in studies of cell fine structure. Comparison of arterial smooth muscle cells in contractile and synthetic state

Arterial smooth muscle cells in contractile and synthetic state were analyzed by optical diffractometry. Cell sections (80-90 nm) were photographed in an electron microscope and diffraction patterns of the plates (negatives) were produced using a helium-neon laser. Radial and angular distributions of light intensity in the diffractograms were measured and digitized using an electronic detector plate consisting of ring- and wedge-shaped photosensitive elements; radial distributions provide information about size of structures and distances between them and angular distributions about spatial orientation of structures in the images. Micrographs of nuclei and cytoplasm were analyzed separately (40-50 plates in each group). Computerized statistical analysis of radial distributions of light intensity showed that the nuclear chromatin pattern differed between cells in contractile and synthetic state. The probability that the observed difference could have arisen purely by chance was less than 10(-5). Computer-aided classification to the a priori known cell group was correct in 96.5% of the cases. Analysis of radial distributions of light intensity similarly showed marked differences in cytoplasmic structure between cells in contractile state (dominated by bundles of myofilaments) and synthetic state (dominated by cisternae of rough endoplasmic reticulum). The probability that the observed difference could have arisen purely by chance was less than 10(-5). Computer-aided classification to the a priori known cell group was correct in 92.0% of the cases. In contrast, analysis of angular distributions of light intensity did not indicate any statistically significant differences between contractile and synthetic state cells. A likely reason is that both myofilaments and cisternae of rough endoplasmic reticulum were arranged in parallel. The results demonstrate that optical diffractometry is a useful method for image analysis in studies of cell fine structure. It provides information about size and orientation of structures with poorly defined shape and is particularly well suited for studies on cell differentiation and effects of pharmacological and other experimental treatments on cell fine structure. It represents an alternative and a complement to stereology for quantitative and objective evaluation of morphological data.