Use of immediately loaded press-fit cylinder implants in oral reconstruction.

Press-fit implants can be used to meet the prosthetic needs of patients who require immediate loading of their implants. This procedure may be necessary because of a patient's unwillingness and/or inability to tolerate a removable prosthesis. The implants reported in this study had a similar success rate to those immediately loaded screw-type implants previously reported by others. The lack of large numbers of long-term immediately loaded implants dictates the need for detailed informed consent when using immediately loaded cylinder implants for dental reconstruction.

The posteromedial portal in knee arthroscopy: an analysis of diagnostic and surgical utility.

We reviewed 400 consecutive knee arthroscopy cases in a predominantly sports medicine practice to determine (1) the frequency of posteromedial portal usage under a prospectively established set of indications, and (2) the impact of posteromedial portal access on patient diagnosis and management. Diagnostic posteromedial portals were used in 22% of anterior cruciate ligament (ACL)-deficient knees, and in 11% of stable knees with nonpatellar (usually meniscal) lesions. When used, posteromedial portal visualization showed treatable lesions 64% of the time, the majority of which were repairable peripheral meniscus tears. In 63% of these cases, no definite lesion had been identified by initial routine anterior portal viewing and probing. Of the 22 patients with posteromedial meniscus tears that were discovered only via posteromedial portal access, 9 had recently undergone anterior portal arthroscopy by other surgeons, during which none of these tears were detected. Posteromedial surgical portals (19 cases) were most useful for synovectomy, posterior cruciate stump resection before arthroscopic reconstruction, and posterior horn medial meniscectomy in exceptionally tight knees. Posteromedial portal access is often useful diagnostically in cases where (1) posteromedial meniscal lesions are frequent (i.e., ACL-deficient knees) and/or suspected on the basis of preoperative symptoms or imaging studies, and (2) full, direct visualization of the entire superior meniscosynovial junction is not possible via standard anterior portals. The option of a surgical posteromedial portal should be entertained whenever frontal approaches for posteromedial instrument work prove inefficient or unsuccessful.

The use of gold chloride to stain developing and adult neuromuscular junctions in the insect.

Individual insect muscle fibers, whose neuromuscular junctions have been stained with a modification of Ranvier's gold chloride method, can be dissected free and mounted whole if the muscle is prefixed in aldehydes. The neuromuscular junctions along the length of the individual fibers are well delineated and can be measured and counted. Effective procedures include fixation with glutaraldehyde buffered to low pH with sodium citrate, or glutaraldehyde and paraformaldehyde combined in phosphate buffer at neutral pH, followed by exposure to citric acid and to gold chloride. The method is convenient, and could be useful for the study of arthropod neuromuscular junctions in general, since their nerve terminals do not release acetylcholine as a transmitter and cannot be stained by the more commonly used cholinesterase methods.

Scanning and freeze-fracture study of larval nerves and neuromuscular junctions in Manduca sexta.

The nerves and nerve terminals to tonic larval muscle fibers in third and fifth instar caterpillars were studied to compare them with those formed by the same motor neurons on phasic flight muscles in adult moths. Scanning micrographs showed a primary nerve branch running the length of each fiber, with secondary nerve branches extending from it at intervals. There was a great deal of variability in both the length of the branches and the distance from the nerve at which the neuromuscular junctions were formed. The rapid increase in muscle fiber size during larval development may be responsible for this variability. The nerves and junctions were often found to be obscure by overlying fibroblasts and tracheoblasts or entering the deep muscle clefts. Those examined were similar in appearance to the adult junctions formed by the same neurons, although some may have formed single branches instead of y-shapes. The membrane specializations of the synapse seen in freeze-fractured specimens were similar to those of the adult junction. However, the overall shape of the nerve terminal within the junction differed. The larval nerve terminals appeared varicose instead of having a uniform diameter. The spacing of the nerve plaques varied, in contrast with the relatively straight alignment and even spacing of plaques found in adult junctions. Such differences could result from an interaction between the motor neuron and the two different types of muscle fiber that it innervates, an intrinsic change in the motor neurons themselves that occurs with metamorphosis, or a plastic functional response that occurs as a result of the different types of motor patterns that are used in the two stages.

Affiliation of large numbers of fibroblasts with larval muscle fibers.

Muscle fibers from fourth and fifth instar caterpillars were examined with scanning and thin section electron microscopy. Scanning micrographs showed that early fifth instar specimens had a population of cells lying beneath the basal lamina over the surface of the muscle fiber and in conjunction with tracheoles and nerves. At least two cell types were present. One type could be categorized as tracheoblasts of their close association with the tracheoles and the presence of taenidia within the tracheoblast cytoplasm in sectioned material. A second cell type, characterized by long filamentous processes, contained extensive rough endoplasmic reticulum and cisternae swollen with an electron-dense substance similar in appearance to the basal lamina. This ultrastructural appearance is characteristic of vertebrate fibroblasts and certain types of insect hemocytes. Early and late fourth instar specimens had few cells on their muscle fiber surfaces. Measurements of the basal lamina thickness were taken from thin sections of nondigested muscle fibers of early fourth, late fourth, and early fifth instar animals. The results showed that the basal lamina underwent a large increase in thickness between the fourth and fifth instars. The proliferation of cells which appeared to be in an actively synthesizing state paralleled the increase in basal lamina thickness. This suggests the hypothesis that these cells are active in connective tissue formation, and contribute to the formation of the basal lamina that lies over both them and the muscle fiber.