Development of a model membrane system using stratum corneum lipids for estimation of drug skin permeability

Several model membrane systems have been reported to predict the skin permeability of drugs, but model membranes using stratum corneum (SC) lipids have never been reported. Thus, we developed a model membrane system for drug permeation study by fixing liposomes composed of SC lipids (ceramides, palmitic acid, cholesterol, and cholesterol-3-sulfate) onto a supporting filter, Biodyne B. The permeability of several drugs with different lipophilicities was investigated. Permeability increased with drug lipophilicity, estimated from the octanol/buffer solubility ratio of the drug. For relatively polar drugs, however, the permeability was almost constant, and very close to the value of a K+ ion, suggesting the membrane has both lipidic and aqueous pathways. Drug permeability through our system was compared with that through guinea pig skin. A good correlation (r = 0.880) was observed, although the former was one order of magnitude greater than the latter. Our model system will be useful not only for practical application, but also for basic studies, such as the elucidation of the relationships between SC lipid composition and drug permeability.

Effects of 1,2-diacylglycerol and cholesterol on the hydrolysis activity of phospholipase D in egg-yolk phosphatidylcholine bilayers

Effects of cholesterol (Chol) and 1,2-diacylglycerol (DAG) on the hydrolysis activity of phospholipase D (from Streptomyces chromofuscus) were studied in small unilamellar vesicles (SUV) of egg-yolk phosphatidylcholine (PC). 1,2-Diacylglycerol used here is derived from PC. Choline produced in the reaction was monitored by using a choline oxidase-oxygen electrode. Addition of 18.3 mol% Chol into SUV (2 mM PC) led to a small increase in the reaction rate. On the other hand, 18.3 mol% DAG in SUV brought about a 5-6-fold rate of choline production. The apparent maximum velocity, Vmax(app), increased by addition of DAG and Chol in SUV. In PC/Chol-SUV, the effect of increase in Vmax(app) was largely compensated by the increase in the apparent Michaelis constant, Km (app). The Chol and DAG molecules did not have significant effects on the kinetic parameters, when PC was solubilized in the micelles of heptaethylene glycol dodecyl ether. The effects of Chol and DAG are, therefore, not due to specific ones on the enzyme itself, but rather upon the bilayer-organization of the substrate. We discuss the activation of phospholipase D in terms of the influences of DAG and Chol on the structure of hydrophilic region and fluidity of the bilayers.

Significance of subclinical entrapment of nerves in lead neuropathy

We examined a left-handed 25-year-old man engaged for 2 years at a vinyl chloride resin factory where he had been exposed to lead stearate, a stabilizer of resin. Neurological examination revealed atrophy of small hand muscles, especially in the left dorsal interossei. Sensation of all modalities was intact. A nerve conduction study showed conduction block at the elbow, indicating possible cubital tunnel syndrome. Following CaEDTA therapy, continued recovery of conduction velocities, amplitude of compound muscle action potential, and diminution of conduction block at elbow were observed within a few months. In lead intoxication, nerves may incur mechanical damage. Subclinical entrapment may thus be an important factor leading to vulnerability of nerves in lead neuropathy.

Application of porcelain veneers following orthodontic treatment

To date, porcelain laminate veneers have been used primarily to solve esthetic problems. As bonding materials and veneer restoration techniques have improved, however, functional demand has now been accepted. Porcelain laminate veneers have been applied to compensate for the limitations of orthodontic treatment. In order to allow optimum functional movement of the mandible, anterior and lateral guidances are required in the maxillary dentition. These guidances provide pathways for the opposing mandibular teeth. Anterior and canine guidances have been established by means of veneer placement, and no broken restorations have been observed in the past four years. When diastema spaces have recurred subsequent to orthodontic space closure, they have been restored with porcelain veneers so effectively that no relapse has been observed. This paper also examines instances where small lateral incisors have caused a discrepancy in the tooth size ratio between the upper and lower arches. Porcelain veneers were placed to harmonize the tooth size and to stabilize the occlusion. Relapse sometimes occurs after orthodontic tooth alignment. Over correction, therefore, is usually applied for rotated teeth, anterior deep or open bite, and Class II or III molar relationships. Some malocclusions, however, cannot be over corrected. For example, the spacing between the teeth, such as diastema, can easily reopen because it is impossible to apply over correction once space closure has been achieved. The same is true of lateral open bites, because occlusal contact cannot be corrected properly. In these cases, the patient must wear a retainer for longer than usual, and/or permanent splints must be used to stabilize the occlusion. Another causal factor of relapse is dysfunctional occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of cyclodextrins on biological membrane. II. Mechanism of enhancement on the intestinal absorption of non-absorbable drug by cyclodextrins

The effects of two kinds of cyclodextrins (CyDs), alpha- and beta-CyD, on biological membranes were investigated by measuring changes in the absorption of a non-absorbable drug, sulfanilic acid (SA), from the rat small intestine, using in situ and in vitro experiments. After pretreatment with a mucolytic agent, N-acetyl-L-cysteine (N-Ac), only beta-CyD increased the absorption of SA significantly compared to the absorption without pretreatment. The mechanism of the enhancing effect of CyDs on the absorption of SA was discussed. Almost no morphological change in the small intestine was observed by pretreatment with N-Ac alone, N-Ac or alpha- or beta-CyD combinations. The liberation of membrane components differed among the CyDs, e.g., alpha-CyD selectively released phospholipid while beta-CyD released mainly cholesterol from the intestinal membrane. It is suggested that the interaction of membrane components with CyDs may be at least partly responsible for the enhanced absorption of SA. Moreover it was found from in vitro electrophysiological experiment, that the alteration in enhanced permeability caused by beta-CyD occurred primarily in the transcellular pathways, rather than in the paracellular pathways of the small intestine. These results suggest that the enhancement of intestinal absorption by beta-CyD, after removal of the mucin layer from the intestinal surface, is due to the interaction between the membrane components and CyD. This interaction would induce disorder in cell membrane lipid, resulting in the increased permeability of the transcellular route.

[Amounts of urinary metabolites of p-chloroaniline and their half lives in a patient with acute poisoning]

The aim of this study was to elucidate the time courses of amounts of urinary p-chloroaniline (p-CA) metabolites during acute poisoning and to establish a suitable method for biological monitoring of exposure to p-CA. Urinary p-CA metabolites which were previously identified in a patient with acute p-CA poisoning were determined quantitatively over time during admission of a patient by high-performance liquid chromatography (HPLC) and by the colorimetric method of diazo-positive metabolites (DPM). The data of urinary excretion of each p-CA metabolite were fitted to two-compartment model of pharmacokinetics. Major urinary metabolites of p-CA were conjugated p-CA and conjugated 2-amino-5-chlorophenol (2-A-5-CP), and the detected amounts of 2,4-dichloroaniline (2,4-DCA) and free p-CA were small. During the rapid phase for the disappearance of each metabolite, half lives of p-CA, 2-A-5-CP and 2,4-DCA were 2.4, 1.7 and 1.7 h, respectively, and during the slow phase, they were 4.5, 3.3 and 3.8 h, respectively. Urinary p-CA occupied about 62% of the total metabolites detected in the urine, 2-A-5-CP about 36%, and 2,4-DCA about 1%. 2-A-5-CP and p-CA were detected in the urine of the patient obtained on days 3 and 4, respectively, after the poisoning, but the amount of DPM after the second day of the poisoning was in the range of that of non-exposed persons.(ABSTRACT TRUNCATED AT 250 WORDS)

Lateral interactions of pig apolipoprotein A-1 with egg yolk phosphatidylcholine and with cholesterol in mixed monolayers at the triolein-saline interface

Interfacial tensions of egg yolk phosphatidylcholine (PC) and cholesterol monolayers adsorbed at the triolein-saline interface were measured in the presence and absence of pig apolipoprotein A-1 (apoA-1) in the saline phase. In the absence of apoA-1, the adsorptions of PC and cholesterol at the interface from the triolein phase are cooperative, showing large lateral attractive interactions between the PC molecules and the cholesterol molecules in the monolayer. In the presence of apoA-1, the PC adsorption is anti-cooperative, indicating strong lateral attractive interactions between the PC and the apoA-1 molecules, i.e., apparently, repulsive lateral interactions between the PC molecules. On the other hand, lateral interactions of very low magnitude are observed between the cholesterol and apoA-1 molecules in the monolayer. Values of the lateral interaction energy are evaluated from the adsorption data by the Defay-Prigogine-Flory theory of monolayers. The large difference in lateral interaction energy with apoA-1 between PC and cholesterol in a mixed monolayer is discussed in connection with current problems in lipoprotein catabolism: reverse cholesterol transport, alterations in affinity of lipid particles to apoA-1, and formation of high-density lipoproteins and abnormal lipoproteins.

[Excretion of p-chloroaniline metabolites into urine. Excretion of 2,4-dichloroaniline and p-chloroformanilide]

Previously, we identified by gas chromatography/mass spectrometry (GC/MS) urinary metabolites of p-chloroaniline (p-CA) in a patient with acute p-CA poisoning. Among these metabolites there is a possibility that 2,4-dichloroaniline (2,4-DCA) and p-chloroformanilide (p-CFA) are produced through some unknown metabolic pathways in human. In order to clarify whether 2,4-DCA and p-CFA were produced within the human body or not, an attempt was made to detect these metabolites in the patient's urine samples prepared by various pretreatments, using both GC/MS and high performance liquid chromatograph. In addition, the detection of these metabolites in non-exposed person's urine samples spiked with p-CA and 2-amino-5-chlorophenol was attempted by GC/MS using same the procedures in order to examine whether p-CA and 2-amino-5-chlorophenol excreted as metabolites were further changed to 2,4-DCA or p-CFA in the urine or not. 2,4-DCA was found abundantly in the ethereal extracts from the patient's urine samples hydrolyzed with hydrochloric, sulfuric and nitric acids, but only small amounts from intact urine samples by GC/MS. No 2,4-DCA was detected in the urine samples to which were added p-CA and 2-amino-5-chlorophenol. p-CFA was found in the ethereal samples which were extracted at acidic conditions from the patient's urine samples by GC/MS at the injection port temperature of 250 degrees C of the gas chromatograph, but the p-CFA peak disappeared at the injection port temperature of 150 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative study on interactions of alpha-aminoisobutyric acid containing antibiotic peptides, trichopolyn I and hypelcin A with phosphatidylcholine bilayers

Interactions of alpha-aminoisobutyric acid containing antibiotic peptides, trichopolyn I and hypelcin A with phosphatidylcholine bilayers were investigated to obtain some basic information on their bioactive mechanisms. Trichopolyn I as well as hypelcin A induced the leakage of a fluorescent dye, calcein, entrapped in sonicated egg yolk L-alpha-phosphatidylcholine vesicles. A quantitative analysis revealed that both the binding affinity and the 'membrane-perturbing activity' of trichopolyn I to the vesicles are about one-third of those of hypelcin A. The conformations and the orientations of the peptide and lipid molecules in the membranes were studied using polarized Fourier transform infrared-attenuated total reflection spectroscopy, circular dichroism, and differential scanning calorimetry. In phosphatidylcholine bilayers, both peptides mainly conformed to helical structures irrespective of the membrane physical state (gel or liquid-crystalline). The helix axes, penetrating the hydrophobic region of the bilayers, were oriented neither parallel nor perpendicular to the membrane normal. The disruption in the lipid packing induced by the peptide insertion seems to be responsible for the leakage by these peptides.

Interactions of an antimicrobial peptide, tachyplesin I, with lipid membranes

Tachyplesin I, isolated from the acid extracts of hemocytes of Tachypleus tridentatus, is a cyclic broad-spectrum antimicrobial peptide forming a rigid, antiparallel beta-sheet because of two intramolecular S-S linkages. The strong binding of the peptide to lipopolysaccharides cannot explain the susceptibilities of gram positive bacteria and fungi to the peptide. We found that tachyplesin I caused a rapid K+ efflux from Escherichia coli cells, concomitant with a reduced cell viability. This result suggests that the peptide-induced permeability enhancement of the bacterial membranes may be a plausible action mechanism. Thus, we studied the interactions of tachyplesin I with various large unilamellar vesicles (LUVs) to reveal the molecular machinery of the antimicrobial activity. Tachyplesin I induced the leakage of calcein, a trapped fluorescent marker, from LUVs of acidic phospholipids, especially phosphatidylglycerol (PG), but not from phosphatidylcholine LUVs. A detailed analysis found that the affinity of the peptide to the PG membranes is very strong and that the binding of one peptide molecule to approx. 200 lipid molecules leads to a significant leakage. The location of tachyplesin I in membranes was estimated by use of the Trp-2 fluorescence of the peptide. The presence of PG LUVs caused a blue shift of the maximum wavelength, an increase in the quantum yield, and a complete protection from fluorescence quenching by an aqueous quencher, acrylamide. Moreover, the degree of fluorescence quenching of the Trp residue by n-doxylstearates was in the order n = 5 greater than 7 greater than 12 approximately equal to 16. These results show that the Trp residue of tachyplesin I seems to locate in a hydrophobic environment near the surface of the PG bilayers.

[Identification of urinary metabolites in a patient of acute poisoning by p-chloroaniline]

In order to clarify urinary metabolites of p-chloroaniline (p-CA), urine samples of a patient acutely poisoned with p-CA were analyzed by gas chromatography/mass spectrometry. Urinary metabolites were extracted with diethylether at pH 1.0 and pH 10 from urine samples hydrolyzed with acid and base and from intact urine samples. Aliquots of the ethereal extracts were injected into the gas chromatography, and p-CA and its metabolites were identified by comparing their mass spectra and retention times to those of standards. Six substances identified were as follows: p-CA, 2-amino-5-chlorophenol, 2,4-dichloroaniline, p-chloroformanilide and traces of p-chloroacetanilide and 4-chloro-2-hydroxyacetanilide. Since p-CA was mainly detected in the hydrolyzed urine samples, p-CA was considered to form conjugates in the urine. N-Acetylation reactions of p-CA were suggested to be weak in human, because extremely minute amounts of p-chloroacetanilide and 4-chloro-2-hydroxyacetanilide were detected in the urine.

[The use of the maxillary protractor in the treatment of cleft lip and palate: a report of two cases]

The patients who underwent reconstruction of cleft lip and palate had clinically abnormal characteristics such as cicatricial contracture in the cleft area, narrow arches, missing teeth, and fistula. Most of those patients showed severe class III malocclusion with underdevelopment of the maxillary complex. In such patients, the treatment objectives in orthodontics were mainly anterior and lateral expansions of the maxillary arches, and inhibition of mandibular growth. In recent years, the maxillary protractor has been used positively in the treatment of the underdeveloped maxillary complex. In this study, we report on two patients with cleft lip and palate, and underdevelopment of the maxillary complex. Maxillary protractors were used beneficially at the period of the dento-craniofacial growth spurt. In these two cases, improvement of disharmony was obtained in the antero-posterior relationship between the maxilla and the mandible. The effects of the treatment were forward movement of the maxilla and growth inhibition of the mandible. Accordingly, the use of the maxillary protractor for cleft lip and palate patients with underdeveloped maxilla at the period of the dento-craniofacial growth spurt was shown to be important.

Physicochemical determinants for the interactions of magainins 1 and 2 with acidic lipid bilayers

Permeability enhancement of acidic lipid small unilamellar vesicles (dioleoylphosphatidylglycerol, DOPG; dipalmitoylphosphatidylglycerol, DPPG; bovine brain phosphatidylserine, PS) induced by magainins 1 and 2, basic antimicrobial peptides from Xenopus skin, was investigated at 30 degrees C based on leakage of calcein, an entrapped fluorescent marker. Both the peptide concentration and the lipid concentration dependencies of the leakage rate were analyzed to obtain the binding isotherms of the peptides to the membranes and the 'membrane-perturbing activities' of the membrane-bound peptides. For both peptides, the binding affinity was in the order DOPG greater than DPPG greater than PS, which coincided with the zeta potential order (-54, -39, and -9 mV, respectively). An increase in salt concentration of the medium reduced binding and leakage. Electrostatic interactions play a crucial role in the binding process. On the other hand, the membrane-perturbing activity is regulated by membrane fluidity: The fluid membranes (DOPG and PS) were leakier. A circular dichroism study suggested that at least 14 positively charged residues in the N-terminal regions can form amphiphilic helices which interact with the membranes. An even stronger binding of magainin 2 can be explained in terms of more positive charges in its N-terminal region. A tentative model for the magainin-lipid interactions is hypothesized.

[Orthodontic treatment of malocclusion with periodontitis]

Adults with untreated malocclusions suffer from more periodontal disease than if their malocclusion had been corrected orthodontically. What orthodontists can offer in the management of patients with periodontal disease, how they can help the periodontists and the patients, and how the periodontists can help the orthodontist make treatment safe and purposefully are widely discussed. The purpose of this study is, therefore, to discuss how orthodontic patients with severe periodontitis could be treated and what we should do for these patients during the treatment as well as at their initial visit. One case is presented as an example of treatment for malocclusion with sever periodontitis: The patient was a 23 years 8 months female with a chief complaint of protrusion of upper incisors. Since clinical examination revealed severe periodontitis, periodontal treatment was undertaken for one year prior to orthodontic treatment. From these observations, we are conviced of the importance again of the global approach and the team treatment method in treating malocclusions with periodontitis.

Effects of complete separation of condyle on the facial growth of growing rats

Normal mastication needs condylar support. Mandibular condyle is thought to be one of the factors which control facial growth. To determine which parts of the face are affected by unilateral complete condylotomy including surrounding connected soft tissues, thirty-nine male Wistar rats, 5 weeks of age, were divided into control, sham treated and experimental groups. The control animals received no treatment, where as the left mandibular condyles of the experimental animals were condylotomized. Soft X-rays of the animals of both groups were taken every two weeks, and all were killed six weeks after treatment. Roentgenografically, it was observed in the experimental animals that a functional condyle-like process generated to fill the condylar space of glenoid fossa. This process was smaller than normal condyle of the control anomals. Furthermore, ANOVA revealed significant differences (P less than 0.01) in some facial structures including facial height as well as mandibular length, which were still affected at six weeks after the surgery. The result of the present investigation suggests that unilateral condylotomy induced the production of a functional condyle-like process and caused some facial deformities.

Interactions of lecithin and pig apolipoproteins of high density lipoproteins at the surface monolayer of reconstituted very small particles

Cosonication of egg yolk lecithin and triolein with apolipoproteins isolated from pig high density lipoprotein (apoHDL) gave us reconstituted high density lipoprotein particles (r-HDLs) of 9 nm in average diameter. They were smaller than microemulsion particles (MEs) composed of the lipids (35 nm). The protein/egg yolk lecithin ratio in the fractionated r-HDLs was higher in the smaller particles. Binding of a hydrophobic probe, 2-p-toluidinylnaphthalene-6-sulfonate (TNS), to MEs, r-HDLs and apoHDL were evaluated on the basis of Halfman and Nishida's method. The reconstitution of apoHDL into MEs led to a 68% reduction in the binding of TNS and a small increase in the alpha-helix content as compared with free apoHDL. The binding experiments also showed the condensation of lecithin molecules at the r-HDL surface. The amphipathic helixes of apoHDL are located in the surface monolayer of egg yolk lecithin surrounding the triolein core. The intercalation of the hydrophobic residues of apoHDL between egg yolk lecithin molecules brings about a pronounced curvature of the surface and a decrease in the particle diameter.

[Effects of periodic tension on osteoblast-like cells for cell differentiation and alkaline phosphatase activity]

Bone remodeling requires bone resorption and formation. Bone formation involves osteoblastic activity. Both intermittent and continuous mechanical forces have been proved to affect osteoblast differentiation in vivo. It is evident in the present investigation that periodically applied tension alter cell division, protein synthesis and alkaline phosphatase activity. An initial seeding density of 50,000 cells/well was used for both the mechanically stimulated cells and controls. For the experimental cultures, the cells were subjected to different levels of tension applied at different frequencies; 1. Low frequency (0.3 cycles/minute) at moderate tension (17% elongation); 2. Moderate frequency (3 cycles/minute) at moderate tension (17% elongation); 3. High frequency (30 cycles/minute) at moderate tension (17% elongation); 4. Low tension (9% elongation at moderate frequency (3 cycles/minute); 5. High tension (22% elongation) at moderate frequency (3 cycles/minute). Cell numbers, protein synthesis and alkaline phosphatase activity were measured for each treatment combination, as well as for the unstressed controls. The cells were harvested at 24, 72, and 120 hours after the start of force application. Analysis of variance revealed that periodically applied tension stimulated cell activity in cultured UMR 106-01 cells: 1. Seventeen percent elongation at 3 and 30 cycles/minute was the optimum condition for stimulating osteoblastic cell division; and 2. High frequency stimulation at moderate tension and high tension at moderate frequency stimulated alkaline phosphatase activity. Given these findings, the following conclusions seem warranted: 1. There may be an optimal magnitude of tensional force that stimulates osteoblast activity. Beyond this optimal level, osteoblasts may lose potential to have cell divisions; 2. The optimal condition of tension might be different for cell division and other cell functions. Although high tension (22% elongation) did not stimulate cell division, alkaline phosphatase activity showed significantly high measurement at this condition; and 3. in the light of both the present study and previous investigations, periodically applied tension may stimulate both collagenase (a parameter of bone resorption) and alkaline phosphatase (a parameter of bone formation) production.

Effect of cyclodextrins on biological membrane. I. Effect of cyclodextrins on the absorption of a non-absorbable drug from rat small intestine and rectum

The effects of three kinds of cyclodextrins (CyDs), alpha-, beta- and gamma-CyD on biological membranes were investigated by changes in absorption of a non-absorbable drug, sulfanilic acid (SA), from the rat small intestine and rectum using an in situ perfusion technique. The absorption of SA from the intestine was slight and was not affected by the addition of CyDs. After pretreatment with a mucolytic agent, N-acetyl-L-cysteine (N-Ac), the absorption of SA was increased compared with SA alone in the presence of only beta-CyD. Similar treatment with sodium deoxycholate (SDC) and sodium lauryl sulfate (SLS) to gastro-intestinal membrane showed the enhanced absorption of SA by the addition of beta-CyD. The mucin layer on the surface of the gastro-intestinal membrane may play an important role in the absorption of drugs. On the other hand, enhanced absorption of SA from the rat rectum was not induced by beta-CyD with or without pretreatment with N-Ac, SDC or SLS. Simultaneously, the release of neutral sugars in the perfusate after treatment with adjuvants was also observed with N-Ac, SDC and SLS. These results indicate that the mucin layer works as a barrier to the increased absorption of SA by beta-CyD.

[Effect of PTH and periodic tension on osteoblast-like cells for collagenase synthesis]

The purpose of the present study was to determine whether cyclically applied tension stimulates osteoblast-like cells to produce collagenase as well as parathyroid hormone (PTH) does. Experimental evidences suggest that osteoblast growth can be altered by various extrinsic control factors, including continuous and intermittent mechanical forces. In the present study, morphological change and collagenase synthesis were observed for both cultures that were added PTH and under the periodic tension condition applied on osteoblast-like cells and their parallel controls. periodic tension was used because it was thought to more closely mimic the in vivo functional situation. An initial seeding density of 50,000 cells/well was used for both the PTH stimulated and mechanically stimulated cells and their controls. For the mechanically stimulated cultures, the cells were subjected to the following tension/relaxation combination; 3 cycles/minute at 17% elongation of tensional force. The cells were fixed at 24, 72, and 120 hours after the start of experiments and collagenase was stained immunohistochemically. The following results were obtained: 1. PTH stimulated collagenase production from the first through the fifth day; 2. Periodic tension changed cell morphology from round to stellate; and 3. Periodic tension increased collagenase production from the first through the fifth day.

Phospholipid monolayers at the triolein-saline interface: production of microemulsion particles and conversion of monolayers to bilayers

Interfacial tensions of phospholipid monolayer at the triolein (TO)-saline interface were measured. The adsorption isotherms and the interfacial pressure-molecular area curves were evaluated on the basis of the measurements. Phosphatidylcholine (PC) forms a highly condensed monolayer, with a large lateral attractive interaction; phosphatidylethanolamine (PE) and phosphatidylserine (PS) form expanded monolayers with smaller lateral interaction energies. At the lowest interfacial tension (the highest interfacial pressure), the mole fractions of PC, PE, and PS in the monolayers are estimated as 0.95, 0.73, and 0.88, respectively. Therefore, PC forms the most stable monolayer at the interface. These results are consistent with the finding that the stable TO particles in aqueous solution were produced by using PC as an emulsifier, and PE and PS did not stabilize the particles. The phase diagram of TO and PC mixtures in saline obtained from theoretical considerations predicts the equilibrium conversion of the monolayers on TO particles to bilayers. This process may be closely related to the transformations of very low density lipoproteins and chylomicrons to high-density lipoproteins in plasma. The particle sizes of the emulsion are calculated theoretically as a function of PC mole fraction in the TO-PC mixture and compared with the experimental values obtained from quasi-elastic light scattering (QLS) measurements.

[Root resorption of mandibular second molars by impacted third molars. A case report with some reviews]

A case is presented here in which mandibular third molars resorbed second molars bilaterally 4 years 9 months after orthodontic treatment was finished. The initial problem was open bite, which was treated by non-extraction followed by a period for observing the third molars. During that period, the mandibular third molars moved mesially to resorb the roots of the second molars. The injured second molars were, therefore, extracted and the third molars were uprighted. During adolescence, third molars are erupting. When the posterior space is not enough for the third molars, they often erupt buccally or lingually, or impact distally toward the second molars and cause root resorption. It is suggested that the third molars should be observed carefully till they erupt or are extracted.