Thematic review series: The Pathogenesis of Atherosclerosis. An interpretive history of the cholesterol controversy: part II:the early evidence linking hypercholesterolemia to coronary disease in humans

The first in this series of historical reviews dealt with the pioneering animal model work of Anitschkow, implicating blood cholesterol in the pathogenesis of atherosclerosis, and the pivotally important work of Gofman, providing evidence that lipoprotein-bound cholesterol was a major factor in the human disease. This second installment reviews the early lines of evidence linking hypercholesterolemia in humans to the progression of atherosclerosis and the risk of coronary heart disease. The argument is made that by 1970, the evidence was already strong enough to justify intervention to lower blood cholesterol levels if all the available lines of evidence had been taken into account. Yet, it would be almost two decades before lowering blood cholesterol levels became a national public health goal. Some of the reasons the "cholesterol controversy" continued in the face of powerful evidence supporting intervention are discussed.

[Interaction between vecuronium and atracurium revisited by adapting an alternative method]

OBJECTIVES

Given that contradictory conclusions about the interaction between vecuronium and atracurium have been reached by previous investigators, the present study used an alternative method to analyze this interaction by way of the respective potencies of the two agents and the potency of their combination.

PATIENTS AND METHODS

Effective doses for each relaxant were first calculated by administering small amounts of the agents to 3 similar groups of patients anesthetized with intravenous drugs and ventilated with nitrous oxide. Depression of the first response to train-of-four stimulation was obtained during electromyographic monitoring. That information was used to estimate the mean potency for each individual by an alternative method based on prior knowledge of the slope of the dose-response curve. In another group of patients, fractions equipotent to the median effective dose (ED50) were administered and the same procedure was used to establish the theoretical and calculated potencies of fractionated doses. The algebraic sum of the ratios between the calculated and effective doses was used to define the type of interaction.

RESULTS

The ED50 and the doses giving 90% and 95% efficacy were 24, 38 and 45 microg x Kg(-1) for vecuronium and 144, 234 and 277 microg x Kg(-1) for atracurium. After combination, the new figures were 9, 14 and 17 microg x Kg(-1) for vecuronium and 57, 93 and 110 microg x Kg(-1) for atracurium. The algebraic sums of the ratios between calculated and effective doses were less than 1 for each level of effective dose (0.77, 0.76 and 0.77, respectively), denoting synergism.

CONCLUSIONS

The alternative method presented for analyzing the potency of the individual components of the vecuronium-atracurium interaction demonstrated that their effect is greater after combination and definitively synergistic.

Initial biofilm formation of Streptococcus sobrinus on various orthodontics appliances

Biofilms accumulate on hard and soft surface in the oral cavity. Accumulation of biofilms on orthodontic appliance bear scientific and clinical interest. The objection of this study was to examine the formation of dental biofilm by Streptococcus sobrinus on different types of orthodontics appliances, using a model consisting of host and bacterial constituents. The adsorption pattern of saliva to the orthodontics appliances was determined by means of gel electrophoresis coupled with computerized densitometry techniques. The amount of salivary proteins adsorbed onto the surfaces was measured using the Bradford method. Sucrose-dependent bacterial adhesion to the saliva-coated orthodontics appliances was tested by radioactive-labelled S. sobrinus. Our results show different adsorption patterns of salivary proteins to the various orthodontic appliances as modules, brackets, springs and intra oral elastics. Modules and brackets demonstrated the most affinity to salivary proteins. A surface dependent adhesion profile was recorded, showing a high affinity of albumin and amylase to modules. Bacterial accumulation was the highest on modules compared with springs which demonstrated the least bacterial adhesion. Our study demonstrates the specificity of biofilm formation on the different orthodontic appliances. Formation of a variety of dental biofilms has a significant impact on the progression of dental diseases associated with orthodontic treatment.

Thematic review series: the pathogenesis of atherosclerosis. An interpretive history of the cholesterol controversy: part I

This is the first of a series of reviews of the controversy that swirled around the "lipid hypothesis" of atherosclerosis for so many years. Today, in the era of the statins, there is no longer any doubt about the value of decreasing blood cholesterol levels. In fact, "the lower the better" is the position of many clinicians. However, getting to this point has been a long uphill battle marked by heated debate and sometimes violent disagreement. The history of this controversy is worth telling for its own sake and because remembering it may help us avoid similar mistakes in the future. The history of this controversy is worth telling for its own sake and because remembering it may help us avoid similar mistakes in the future.

[Rocuronium: onset time or speed of action?]

OBJECTIVE

Rocuronium has been said to have an initially rapid onset of action followed by a slower final approach to maximum effect, the supporting data showing only that time to 75% of blockade is more rapid. Expressions of velocity are derived from basic measures such as length and time. The aim of our study was to confirm the onset characteristics of rocuronium by using appropriate expressions of velocity.

PATIENTS AND METHODS

After consenting, 25 adults scheduled for elective surgery were anesthetized, using a bolus dose of rocuronium of 400 microg Kg(-1) for relaxation. Electromyography was used to determine maximal effect, time to reach 80% of a full neuromuscular block, onset time, the time interval between these two points, and the differential blockade produced during each period. Velocity for each period was calculated as the ratio between the percentage of block produced per amount of time elapsed (%/s) during each respective period. The ratio between time and blockade (s/%) was also calculated.

RESULTS

More blockade was produced per second (velocity) during the initial period of activity (0.55%/s) than during the final period (0.109%/s). The average velocity during the onset period overall (0.33%/s) lay between those two figures. Rocuronium requires less time (acting fast) to achieve an initial effect (1.95 s/%) than it does to reach the final effect (10.8 s/%). The ratio of early to late speed of onset was 5.8 +/- 3.5.

CONCLUSION

Using appropriate expressions and calculations, we can unequivocally conclude that rocuronium has a biphasic onset that is initially rapid and then slower. The rate of action is nearly 6 times faster at the beginning.

Bacteriophage isolation from human saliva

AIMS

To detect bacteriophages for Gram-positive oral pathogens in human saliva.

METHODS AND RESULTS

Saliva samples from 31 donors were screened for the presence of bacteriophages for Streptococcus sobrinus, Streptococcus mutans, Streptococcus salivarius, Actinomyces viscosus and Enterococcus faecalis. Bacteriophages for Enterococcus faecalis were found in seven samples. Enterococcus faecalis phages were still present in saliva re-collected from one donor one month, and one year after initial saliva collection.

CONCLUSIONS

The presence and stability of the Enterococcus faecalis bacteriophages in human saliva suggests a possible role of these bacteriophages in the oral ecosystem.

SIGNIFICANCE AND IMPACT OF THE STUDY

Phage therapy as a way to control oral bacteria might be considered.

Formulation, development and characterization of sustained release varnishes containing amine and stannous fluorides

This study describes properties of potential sustained release varnishes (SRV) containing amine fluoride or amine fluoride with stannous fluoride. The release kinetics, antibacterial properties and antiadhesion properties of two potential varnishes were tested. The varnish of ethylcellulose matrix was found to release fluoride for 4 h in vitro, while the formulation based on hydroxypropylmethylcellulose acetate succinate had a rapid release rate. Hydroxyapatite tablets coated with ethylcellulose-based SRV increased adhesion of Streptococcus mutans, while tablets coated with hydroxypropylmethylcellulose acetate succinate-based SRV decreased bacterial adhesion. Both types of SRV demonstrated a strong antibacterial effect on bacteria in biofilm.

Immobilization of fructosyltransferase from Streptococcus mutans on hydroxyapatite surfaces induces the formation of multimeric complexes

AIMS

To investigate the formation of fructosyltransferase (FTF) complexes on hydroxyapatite (HA) surfaces.

METHODS AND RESULTS

Cell-free extracellular FTF from Streptococcus mutans, purified from hyperproducing strain V-1995, was adsorbed onto HA and then eluted from the surface by means of a concentration gradient of potassium phosphate buffer. The FTF monomers loaded onto HA formed, upon adsorption, various complexes ranging from 200 to 700 kDa as demonstrated using native PAGE. All these complexes exhibited enzymatic activity.

CONCLUSIONS

Adsorption of FTF onto HA induced the formation of stable and enzymatically-active complexes.

SIGNIFICANCE AND IMPACT OF THE STUDY

The formation of these complexes may explain the change of FTF catalytic properties after adsorption onto HA. This study is another step in determining the properties of a-cellular constituents of the oral biofilm.

Correlation of antiphospholipid antibody recognition with the structure of synthetic oxidized phospholipids. Importance of Schiff base formation and aldol condensation

The oxidation of low density lipoproteins (LDL) has been correlated with atherogenesis through a variety of pathways. The process involves nonspecific fragmentation, oxidative breakdown, and modification of the lipids and protein of LDL. The process yields a variety of bioactive products, including aldehyde-containing phospholipids, which can cross-react with primary amines (i.e. peptides or phospholipid head groups) to yield Schiff base products. We also demonstrate that such oxidized phospholipid products may further react through a post-oxidation chemical pathway involving aldol condensation. EO6, an IgM monoclonal autoantibody to oxidized phospholipids, blocks the uptake of oxidized LDL (OxLDL) by macrophages. Because the epitope(s) of EO6 also blocks the uptake of OxLDL, a series of oxidized phospholipids, their peptide complexes, and their aldol condensates have been synthesized and characterized, and their antigenicity has been determined. This study defines structural motifs of oxidized phospholipids responsible for antigenicity for EO6. Certain monomeric phospholipids containing short chain fatty acids were antigenic whether oxidized or not in the sn-2 position. However, oxidized phospholipids containing sn-1 long chain fatty acids were not antigenic unless the sn-2 oxidized fatty acid contained an aldehyde that first reacted with a peptide yielding a Schiff base or the sn-2 oxidized fatty acid underwent an aldol type self-condensation. Our data indicate that the phosphorylcholine head group is essential for antigenicity, but its availability depends on the oxidized phospholipid conformation. We suggest that upon oxidation, similar reactions occur in phospholipids on the surface of LDL, generating ligands for macrophage recognition. Synthetic imine adducts of oxidized phospholipids of this type are capable of blocking the uptake of OxLDL.

Scavenger receptors, oxidized LDL, and atherosclerosis

Oxidized LDL (OxLDL) competes with oxidatively damaged and apoptotic cells for binding to mouse peritoneal macrophages, implying the presence of one or more common domains. However, the nature of the ligands involved has not been determined. Studies in this laboratory over the last several years provide evidence that oxidized phospholipids, present in OxLDL and also in the membrane of apoptotic cells, represent one such ligand. These oxidized phospholipids, either in the lipid phase of OxLDL or becoming attached covalently to apoprotein B during LDL oxidation, have been shown to play a major role in the binding of OxLDL to CD36 and to SR-B1 expressed in transfected cells. The lipid and protein moieties compete with each other to some extent, indicating that they are binding to at least one common site. A monoclonal antibody selected because of its reactivity with OxLDL proved to be an antibody against oxidized phospholipids (but not native phospholipids). This antibody (EO6) blocked the uptake of OxLDL by CD36 and by SR-B1 in transfected cells by as much as 80%; it also inhibited macrophage phagocytosis of apoptotic cells by about 40%. Thus, the persistence of receptors for OxLDL during evolution is probably accounted for by their role in recognition of ligands on the surfaces of oxidatively damaged or apoptotic cells. This has important implications in biology generally and specifically in atherogenesis, because apoptosis is a prominent feature of late lesions.

Effect of sodium hypochlorite and EDTA on mercury released from amalgam

OBJECTIVES

The effect of sodium hypochlorite (NaOCl) and EDTA on mercury released from dental amalgam was assessed in vitro.

STUDY DESIGN

Fifty-six samples of dental amalgam of similar size were prepared and exposed to a 10-mL solution of either 1% NaOCl, 3% NaOCl, 10% EDTA in 1% NaOCl, or 10% EDTA in 3% NaOCl for periods of 20, 40, and 60 minutes. Mercury concentrations in the solutions were measured by using a cold-vapor atomic absorption Mercury Analyzer System, and the differences between the groups were statistically analyzed.

RESULTS

All amalgam samples exposed to 1% NaOCl and 3% NaOCl-either alone or in combination with EDTA-released mercury into the solutions. Mercury release was significantly higher in the test groups than in the EDTA, distilled water, or phosphate buffer controls (P <.001). Increase in the mean concentration levels of mercury in solution was time-dependent and directly related to NaOCl concentration. The addition of EDTA caused a reduction in mercury levels detected in solution, which was more significant in amalgam samples exposed to 1% NaOCl combined with EDTA (P <.001).

CONCLUSIONS

NaOCl solutions commonly used for root canal cleaning and shaping cause mercury release from dental amalgam and may alter its chemo-physical properties as a sealant for root perforations.

[Effects of non-depolarizing muscle relaxants on the duration of mivacurium]

The interaction between Mivacurium and several muscle relaxants results in a slow recovery. We have previously described that small doses of d-tubocurarine prolong the duration of two successful administrations of Mivacurium. The present investigation was designed to uncover if such an effect could be observed after other neuro-muscular blocking drugs were administered, and if so, its consistency during the different methods of their use. Patients (n = 224) were anesthetized with Enflurane and randomly assigned to two control groups which received 100 micrograms/Kg-1 Mivacurium as a bolus or primed. Other groups received: Rocuronium (60 micrograms/Kg-1), Vecuronium (10 micrograms/Kg-1), Atracurium (60 micrograms/Kg-1), d-tubocurarine (50 micrograms/Kg-1) or Pancuronium (8 micrograms/Kg-1) before, after or as a mixture with 90 micrograms/Kg-1 of Mivacurium. The clinical effect was monitored by electromyography and the results show that all these agents prolong the duration of Mivacurium, the last three in a statistically significant fashion independently of the mode of administration. Current hypothesis are reviewed, but no definitive clues are obtained to explain the present results. Our conclusions must be considered as further research on the interaction between non-depolarizing muscle relaxants and a base for new theories on interactions.

Scavenger receptor class B type I as a receptor for oxidized low density lipoprotein

Scavenger receptor class B type I (SR-BI) has been established as the primary mediator of the selective transfer of lipids from HDL to mammalian cells. In addition to its role in cholesterol metabolism, SR-BI has been shown to bind apoptotic cells and thus could in theory also function as a scavenger receptor. We now show that SR-BI binds oxidized LDL (OxLDL) with high affinity (K(d) of 4.0 +/- 0.5 microg/ml) and mediates internalization and degradation to an extent comparable to that of other scavenger receptors, when normalized to binding activity. The best competitors for OxLDL binding to SR-BI were oxidized lipoproteins, whereas native or acetylated lipoproteins only competed for a small fraction of OxLDL binding. Both the isolated lipids and the isolated protein from OxLDL bound with high affinity to SR-BI and showed partial reciprocal competition. Monoclonal antibody EO6, an antibody against oxidized phospholipids, and 1-palmitoyl-2-(5-oxovaleroyl) phosphatidylcholine (POVPC) both competed effectively with intact OxLDL and with isolated lipids from OxLDL for SR-BI binding.Together, these results demonstrate a potential function of SR-BI, in addition to its role in selective uptake of lipids, to mediate internalization of OxLDL by macrophages and suggest a central role for oxidized phospholipids in this process.

Induction and 3D reconstruction of caries-like lesions in an experimental dental plaque biofilm model

The aim of this study was to examine an in vitro dental plaque model for volumetric assessment and 3D reconstruction of experimentally bacterial induced caries-like lesions. Twenty-three extracted, impacted human molars were coated with a varnish leaving a 3 x 3 mm window on the smooth surface. The teeth were coated with human saliva and Streptococcus sobrinus 6715 adhered onto the enamel via a sucrose dependent mechanism. The coated teeth were incubated for 1, 7, 14 and 28 days. At the end of each incubation period microhardness was measured on three sectioned teeth of each incubation period at the enamel surface and at 450 and 750 microm depth perpendicular to the enamel surface. The enamel surface was investigated by scanning electron microscopy (SEM) prior to embedding and serial sectioning of 12 other teeth. The serial sections were studied with polarization light microscopy to investigate subsurface demineralization. The outlines of the caries-like lesions were then traced consecutively on transparencies, digitized and three-dimensionally reconstructed to demonstrate the expansion of the lesion into enamel for volumetric assessment. Microhardness was significantly reduced on the enamel surface after 7, 14 and 28 days incubation. The SEM investigation showed a surface demineralization with dissolution of the prism cores after 28 days incubation. Polarization light microscopy demonstrated caries-like lesions with an irregular expansion into enamel. The results demonstrate that the described method produces caries-like lesions which can be used for further experimental studies regarding demineralization and remineralization processes.