Two pools of cholesterol in acetylcholine receptor-rich membranes from Torpedo.

The acetylcholine receptor (AChR)-containing electroplax membranes from Torpedo californica have a relatively high cholesterol content. Reconstitution studies suggest that this cholesterol may be important in preserving or modulating the function of the acetylcholine receptor-channel complex. We have manipulated cholesterol levels in intact Torpedo AChR-rich membrane fragments using small, unilamellar phosphatidylcholine liposomes. Conditions have been established that allow further subfractionation of sucrose gradient purified Torpedo electroplax membranes into AChR-rich and ATPase-rich populations and that, at the same time, achieve cholesterol depletion without phospholipid back exchange or fusion. The incubation of membranes with excess liposomes could only achieve about a 50% reduction in the molar ratio of cholesterol to phospholipid. In no case was the number of cholesterol molecules per AChR oligomer reduced below 36. The remaining cholesterol could not be depleted either by longer incubations or by multiple, sequential depletions. Cholesterol depletion was accompanied by a significant increase in bulk membrane fluidity as measured by electron spin resonance spectroscopy, but the equilibrium binding parameters of acetylcholine to its receptor were unaltered. This suggests strongly that there exist two pools of cholesterol in the AChR-rich Torpedo electroplax membrane: an easily depleted fraction that influences bulk fluidity, and a tightly-bound fraction perhaps surrounding the AChR oligomer.

Pressure reversal of the action of octanol on postsynaptic membranes from Torpedo.

Octanol increases the binding of [3H]-acetylcholine to the desensitized state of the nicotinic receptor in postsynaptic membranes prepared from Torpedo californica. This increase in binding results from an increase in the affinity of [3H]-acetylcholine for its receptor without any change in the number of sites or the shape of the acetylcholine binding curve. High pressures of helium (300 atm) decrease [3H]-acetylcholine binding by a mechanism that changes only the affinity of acetylcholine binding. Helium pressure reverses the effect of octanol on the affinity of [3H]-acetylcholine for its receptor. This pressure reversal of the action of octanol at a postsynaptic membrane is consistent either with pressure counteracting an octanol-induced membrane expansion or with independent mechanisms for the actions of octanol and pressure. The data do not conform with a mechanism in which pressure displaces octanol from a binding site on the receptor protein.

Microbiota associated with experimental peri-implantitis and periodontitis in adult Macaca mulatta monkeys.

This study examines the microbiota associated with the progression of experimental peri-implantitis and periodontitis induced concurrently in partially edentulous adult monkeys. Root-form and plate-form implants with fixed prosthesis in place for at least 12 months and their corresponding opposite molar teeth were ligated for 6 months. The microbiota in plaque around these ligated dental implants and molars were studied at 0, 1, 2, 3, and 6 months post-ligation. Plaque samples were analyzed by dark-field microscopy and selective and non-selective culture. Putative periodontal pathogens were detected as a major component of the microbiota cultured from plaque samples obtained from experimental peri-implantitis sites. Overall, the types and relative proportions of putative periodontal pathogens in plaque associated with ligature-induced peri-implantitis and ligature-induced periodontitis were similar. Only levels of anaerobic Actinomyces and spirochetes were significantly different between both sites. Spirochete levels were significantly higher at peri-implantitis sites when compared with levels at periodontitis sites after 6 months, and spirochete levels increased significantly between 0 and 6 months post-ligation at implant sites. Levels of spirochetes correlated significantly with probing depth and bone loss at peri-implantitis sites. Overall, Actinomyces levels were higher at periodontitis sites. Porphyromonas species were not detected continuously as part of the peri-implantitis microbiota. In conclusion, this study finds that the microbiota associated with the progression of experimental peri-implantitis and periodontitis occurring concurrently in partially edentulous mouths are similar.

Microbiota associated with consecutively placed loaded root-form and plate-form implants in adult Macaca mulatta monkeys.

This study describes the microbiota associated with consecutively placed root-form and plate-form implants placed in similar mandibular arches of rhesus (Macaca mulatta) monkeys and loaded with similar prostheses. The teeth and implants were maintained by monthly scaling and root planing. Twenty-four round (root-form) and 24 flat (plate-form) implants were placed in the loci of #18 and #31 in 36 adult monkeys. The microbiota around implants and mandibular molar teeth were studied quarterly from the day prostheses were loaded (Day 0) for 12 months. The microbiota were characterized by culture and dark field microscopy. Overall, levels of putative peri-implant pathogens studied declined or remained statistically unchanged at implant or mandibular molar sites. Levels of spirochetes and Porphyromonas species declined at mandibular molar teeth but increased at dental implant sites. Levels of A. actinomycetemcomitans declined significantly at implants and mandibular tooth sites during the period. No statistically significant difference was detected between levels of microorganisms colonizing root-form and plate-form implants. This study finds no significant increase in levels of putative peri-implant pathogens at root-form and plate-form implants sites in the first 12 months after prosthetic loading when maintained by monthly scaling.

Evaluation of consecutively placed unloaded root-form and plate-form implants in adult Macaca mulatta monkeys.

The present paper describes 18 consecutively-treated non-human primates (Macaca mulatta) as part of a balanced block design study of 36 animals to examine osseointegration in root- and plate-form implants prepared by atraumatic preparation of bone. Clinical measurements around selected teeth and digital radiology were utilized to monitor periodontal disease and bone deposition around the unloaded implants. Once a month scaling procedures were utilized as a means of preventing further advance of periodontal disease. Results indicate that once-monthly regimen of scaling and root planing can prevent attachment loss of natural teeth and will not interfere with the healing of either type of implant; once-monthly scalings produce significant reduction in redness (P < .05) and reduced probing depths (P = .01). A second finding is that both root and blade implants show radiographic evidence of osseointegration in this primate model. The quantitative analysis demonstrates bone gain is not stabilized until 6 months after healing. The data may indicate that occlusal loading of mandibular implants at 3 months may be premature.

Experimental peri-implantitis in consecutively placed, loaded root-form and plate-form implants in adult Macaca mulatta monkeys.

This study is part of an on-going project describing the character of round- and plate-form implants placed in a primate model. In this paper 20 loaded plate-form and 23 root-form implants were connected to prostheses and experimental peri-implantitis was induced by ceasing scaling procedures and placing braided silk ligature around the implants. Twenty-four prostheses utilizing natural teeth were studied for comparison. Clinical measurements were carried out monthly for 6 months and radiographic measurements at 3 and 6 months post-ligature placement and cessation of scaling. Both root-form implants and plate-form implants showed a significant loss of crestal bone height at 3 and 6 months after ligature placement (P < .001 after 6 months). The difference in bone loss between plate- and root-form implants, however, was not significant.

Guided bone regeneration of large mandibular defects in a primate model.

BACKGROUND: An earlier publication from our laboratory described the use of guided bone regeneration to fill large bone voids in the mandible created through en bloc resection in primates. The present report is an embellishment of this paper and describes bone regeneration experiments in 18 adult male Macaca mulatta monkeys to determine how long membranes must be in position to promote guided bone regeneration. METHODS: Thirty-six lesions were created in the mandibles of 18 monkeys in a standardized mandibular defect of 8 x 19 mm. Reinforced ePTFE membranes were placed in the animals and held in place with mini screws and sutures for anywhere from 1 to 12 months. No material was added to the defect. In addition to clinical studies, digital subtraction radiology and fluorescent labeling with tetracycline and histomorphometry are described. RESULTS: The results indicate that no bone gain was observed in membranes exposed for 1 month or less, but bone gain (approximately well over 90% of defects) was observed at 12 months when membranes were left in situ for 2 to 12 months (P <0.0001). No significant difference in the amount of bone gained at 12 months was observed for membranes left in place for intervals ranging from 2 to 12 months. A significant correlation between the amount of bone gain observed at 3 and 12 months was observed (P <0.0001). CONCLUSIONS: Data therefore suggest that membranes left in situ for 1 month or less result in minimal bone gain compared with membranes left in place from 2 to 12 months. In addition, labeling and stained sections clearly showed that the bone produced after 2 months of membrane placement is mature.

Implants in regenerated bone in a primate model.

BACKGROUND: Earlier publications from our laboratory described the use of guided bone regeneration to fill large bone voids in the mandible created through en bloc resection in primates. The present report describes placement of implants into the regenerated bone with subsequent prostheses construction and loading. METHODS: Lesions were created in the mandibles of 9 monkeys in a standardized mandibular defect of 8 x 19 mm. Reinforced expanded polytetrafluoroethylene membranes were placed in the animals and held in place with mini screws and sutures for anywhere from 1 to 12 months. No material was added to the defect. In each animal a root-form implant was placed 12 mm distal to the abutment teeth into the regenerated bone and was loaded with a prosthesis for 12 months. These implants were compared to original implants placed in the same monkeys years earlier in the same location in non-regenerated bone. Digital radiology and histomorphometry are described. RESULTS: The results show that root-form implants placed in regenerated bone show the same radiological and histomorphometric characteristics as in normal bone when loaded. In addition, the percentage of bone contact with implants seen in regenerated bone versus non-regenerated bone is the same when both are loaded (65 +/- 13% SD in regenerated bone versus 59 +/- 15% SD in non-regenerated bone). CONCLUSIONS: In a primate model root-form implants placed in regenerated bone and prosthetically loaded show no difference when compared to root-form implants placed in non-regenerated bone and prosthetically loaded.

Analysis of consecutively placed loaded root-form and plate-form implants in adult Macaca mulatta monkeys.

The present paper describes 36 consecutively treated non-human primates (Macaca mulatta) as part of a balanced block design study to examine osseointegration in root- and plate-form implants prepared by atraumatic preparation of bone. Clinical measurements around selected teeth and digital radiology were utilized to monitor periodontal disease and bone loss around root- and plate-form implants which were loaded with a fixed prosthesis. Results indicate that once monthly regimen of scaling and root planing can prevent attachment loss in natural teeth, serving as abutments of loaded bridges. Root-form implants exhibited a significant loss of crestal bone height during the first year (P < 0.03) while plate-form implants showed less loss in bone height. There was an increase in bone mass over time for root-form or plate-form implants. Both root-form and plate-form implants provided radiographic evidence of osseointegration in loaded bridges.

Effects of iron and ascorbic acid on acid phosphatases of the enamel organ of rat molars.

Protein extracts from 6- to 11-day-old rat enamel organs were applied to columns of carboxymethyl-52 cellulose. Protein eluted from the columns was assayed for acid phosphatase activity with substrates para-nitrophenylphosphate (p-NPP), beta-glycerolphosphate (beta-GP), ATP and phosphocasein. A weakly-bound peak of activity (A) emerged first which was insensitive to stimulation by iron and ascorbic acid. This enzyme hydrolysed only the phosphomonoester substrates (p-NPP and beta-GP). A strongly bound peak of activity (B) emerged later and was completely separated from the first activity. It hydrolysed all substrates except beta-GP, and was stimulated at least 10-fold by 0.1 mM ferrous ion (Fe2+) in the presence of a strong reducing agent (1.0 mM ascorbic acid). Both substances were more effective as stimulators when used together than they were when each was used separately. Dependency on these co-factors for the development of full activity increased with purification, especially when phosphocasein was substrate. The results were similar for each age of rat used. These properties of enzyme B are parallel with those of the acid phosphoprotein phosphatases of liver and spleen, and the tartrate-resistant acid phosphatase of rat bone. We conclude that enzyme B requires iron and a reducing agent for full activity and has properties that distinguishes it from the classical acid phosphatases (E.C. 3.1.3.2.).

Diagnostic stability of ADHD in a community sample of school-aged children screened for disruptive behavior.

A large school-based sample of children in Grades 1, 2, 3, and 4 were screened for disruptive behavior and subsequently assessed over a 5-year period for DSM-III-R symptoms of attention deficit hyperactivity disorder (ADHD) and other externalizing and internalizing behavior disorders. Parents completed structured diagnostic interviews in Years 1, 4, and 5, and teachers completed Behavioral Assessment for Children-Teacher Rating Scales behavioral ratings annually. For parent-derived diagnostic data, both inattention and hyperactivity/impulsivity symptom groups declined from Year 1 to Year 4, with hyperactivity showing more significant decline. For teacher-rated behavioral dimensions, the Attention Problems scale declined from Year 1 to Year 3 and stabilized thereafter. The Hyperactivity scale showed stability during the first 3 years before declining in Year 4. Of those children diagnosed with ADHD in Year 1, 69% still met criteria for ADHD in either Year 4 or 5. Persisters were more likely to exhibit coexisting conduct disorder in Year 1 and oppositional defiant disorder in Years 1, 4, and 5. Parents of persisters reported more psychosocial adversity on measures of parenting and marital satisfaction.

A multistudy analysis of socioeconomic status (SES) and the measures and outcomes of cognitive-behavioral treatment with children.

The relationship of the child's socioeconomic status (SES) to improvement and generalization from cognitive-behavioral treatment was investigated by comparing high and low SES groups on teacher ratings, performance measures, and judges' ratings of improvement and maintenance of positive change. Fifty-eight teacher-referred classroom problem children (grades 2-6) who had served as treated subjects in one of three treatment outcome studies were examined. SES data were collected by administration of a questionnaire to the head of each household. The judges' ratings were performed on clusters of teacher ratings and clusters of performance measures that were present in each study. Results indicated that, despite SES group variation in level of performance, improvement, when it occurred, was evident for both high and low SES groups. In addition, there were significant differences on a number of the performance measures at pretreatment, posttreatment, and follow-up. Initial SES group differences in verbal ability as measured by the Peabody Picture Vocabulary Test (PPVT) appear to have been an important factor in these performance differences.

School-based secondary prevention for children with disruptive behavior: initial outcomes.

First through fourth graders from 22 suburban elementary schools were screened for cross-setting disruptive behavior as eligibility criteria for participation in a longitudinal secondary prevention study aimed at reducing the risk for serious externalizing behavioral disorders. Three hundred nine subjects participated in either a multicomponent competence enhancement intervention (MCEI) or an information/attention control (IAC) condition over a 2-year period. Following baseline requirements, initial intervention effects were assessed at the end of intervention Year 1, at the beginning of intervention Year 2 (fall of the next school year), and at the end of intervention Year 2. Multisource assessments were not supportive of the efficacy of the MCEI over the IAC condition. Children in both groups rated themselves as improved over time in terms of increased adaptive skills and decreased school problems and internalizing symptoms. Teacher and parent ratings of externalizing behavior did not yield evidence of positive change, but teachers noted improved problem solving and observers noted a decrease in behavioral interference in both groups over time, possibly as a result of maturation.

Sialolithiasis in two chimpanzees.

Sialoliths were found in the duct of the submandibular salivary gland in 2 of 50 chimpanzees (Pan troglodytes) examined, and were surgically removed. Recovery was uncomplicated. Although sialoliths are uncommon in domestic, zoo, and laboratory animals, the signs of sialolithiasis may mimic other problems.

Soft tissue contouring as periodontal plastic surgery.

Many options are available today for treatment of the cosmetic dentistry patient. Composites, veneers, and porcelain crowns have become an art form, with the gingival tissue serving as the frame. Clinicians providing cosmetic dental services must keep aware of the different techniques available for soft tissue contouring. Only recently has periodontal plastic surgery been presented at dental meetings, and little information exists in the research literature. This review brings the practicing dentist up to date on scientific and clinically relevant articles on soft tissue contouring. By working with the shape and contour of the gingiva, a more complementary esthetic final result is possible.