A three-dimensional investigation of temporomandibular joint loading

A mathematical model of the muscle groups applied to the human mandible is developed to study the forces developed on the condyles during maximum unilateral occlusion. The results show that the reaction forces are in approximately a 2:1 ratio with the balancing side condyle carrying the greater load. Furthermore, the direction in which these condylar reactions occur is presented.     

Scaling analysis of coral reef systems: an approach to problems of scale

Dimensional analysis and scaling are related, semi-formal procedures for capturing the essential process(es) controlling the behaviour of a complex system, and for describing the functional relationships between them. The techniques involve the parameterization of natural processes, the identification of the temporal and spatial scales of variation of processes, and the evaluation of potential interactions between processes referenced to those scales using non-dimensional (scaled) parameters. Scaling approaches are increasingly being applied to a broad range of marine ecological problems, with the aims of assessing the relative importance of physical and biological parameters in controlling variation in process rates, and placing limits on the ability of one process to affect another. The value of the approach to coral reef research lies in the conceptualization of relationships between discipline-specific processes, and the evaluation of scale-dependent processes across the large range of spatial and temporal scales which pertain to coral reefs. Characteristic scales of physical, geological and biological processes exhibit different patterns of distribution along the temporal dimension. Scaling arguments based on examples from reef systems indicate that a large group of biological and biogeochemical processes are strongly influenced by hydrodynamic processe occuring at similar time scales within the range from about on hour to one year. We argue that scaling approaches to process-related problems are pre-requisite to interdisciplinary research on coral reefs.     

The complete amino acid sequence of human brain-derived acidic fibroblast growth factor

Acidic fibroblast growth factor is a potent mitogen for a variety of cells in culture, including vascular endothelial cells, and is angiogenic in vivo. The complete amino acid sequence of human brain-derived acidic fibroblast growth factor has been determined from amino terminal sequence analysis and carboxypeptidase A digestion of the whole protein and sequence analyses of peptides generated by tryptic, Staphylococcus aureus V8 protease and cyanogen bromide cleavages. A potential Asn-Gly-Ser glycosylation sequence is present in the human protein. The complete amino acid sequence is compared to that of the equivalent protein purified from bovine brain.     

Isolation and partial characterization of endothelial cell extracellular complexes

Human endothelial cells release components into the growth medium that stimulate cell-substratum adhesion. Several macromolecular components were isolated by ultracentrifugation of the endothelial cell conditioned medium. The components were heterogeneous, consisting of several sizes when examined by sedimentation velocity and gel filtration. When the extracellular components were evaluated by electron microscopy, structurally discrete particles were observed. The extracellular components and the complexes mediated cell-substratum adhesion to both human umbilical and arterial endothelial cells. The majority of the extracellular components that promote endothelial cell adhesion were pelleted by ultracentrifugation. Although the complexes contained fibronectin, antibodies to fibronectin did not inhibit cell adhesion to the complexes. Significant inhibition of endothelial cell adhesion was observed in the presence of heparin and heparan sulfate. The supernatant fraction following ultracentrifugation of the growth medium contained a component that suppressed endothelial cell adhesion to culture dishes coated with fibronectin, type I collagen, and endothelial cell complexes. SDS-polyacrylamide gel electrophoresis indicated that the complexes contained several components, and the majority of the large-molecular-weight components were pelleted by ultracentrifugation. The conditioned medium from human endothelial cells contains specific complexes that promote cell-substratum adhesion and components that suppress cell-substratum adhesion.     

Decreased HLA heterogeneity in parents of children with Down syndrome.

HLA-A and B antigens were determined in a study of 37 couples and their children with trisomy 21 Down syndrome (DS), using a standard microlymphocytotoxicity test. The comparison groups included 76 couples and their healthy children. All individuals were Caucasians from the same geographical area, and there was no history of consanguinity. The parents of children with DS did not show an association with a specific HLA antigen or haplotype. Sixteen of the 37 couples (43.24%) having children with DS share two or more antigens at the A and/or B locus. This was significantly higher than the proportion in the control group (6/76, or 7.88%). Of the 16 couples having children with DS and sharing two or more antigens, eight had a haplotype in common, in contrast with only two couples in the control group. The data suggest that sharing of parental HLA-A and B antigens may be related either to the occurrence of trisomy 21 zygotes or to prenatal survival of affected embryos and fetuses.     

Experimental studies of variation in hepaticae. I. Induced variation in lophocolea heterophylla

Quantitative analyses of eleven vegetative characters were obtained from five genetically distinct clones of the leafy hepatic,Lophocolea heterophylla, grown in pure culture in a variety of controlled environments.     

Rhesus monkey behavior during exposure to high-peak-power 5.62-GHz microwave pulses

Limits on the exposure to high-peak-power, short-duration microwave pulses have only recently been adopted. Additional data, however, are needed to understand the effects that may be produced by exposure to high-peak-power pulsed microwaves. Four male rhesus monkeys (Macaca mulatta) were trained on an operant task for food pellet reward to investigate the behavioral effects of very high-peak-power 5.62 GHz microwaves. The operant task required monkeys to pull one plastic lever on a variable interval schedule (VI-25 s) and then respond to color signals and pull a second lever to obtain food. The monkeys were conditioned to perform a color discrimination task using one of three colors displayed by a fiber-optic cable. A red signal was the discriminative stimulus for responding on the first lever. A response on the second lever when a green signal was presented (1 s duration) delivered a food pellet. If a response on the second lever was made in the presence of a white signal, a 30-s timeout occurred. While performing the behavioral task, the monkeys were exposed to microwave pulses produced by either a military radar (FPS-26A) operating at 5.62 GHz or the same radar coupled to a Stanford linear energy doubler (SLED) pulse-forming device (ITT-2972) that enhanced peak power by a factor of nine by adding a high power pulse to the radar pulse. The effects of both types of pulses were compared to sham exposure. Peak field power densities tested were 518, 1270, and 2520 W/cm² for SLED pulses and 56, 128, and 277 W/cm² for the radar pulses. The microwave pulses (radar or SLED) were delivered at 100 pps (2.8 μs radar pulse duration, ≈ 50 ns SLED pulse duration) for 20 min and produced averaged whole-body SARs of 2,4, or 6 W/kg. Compared to sham exposures, significant alterations of lever responding, reaction time, and earned food pellets occurred during microwave exposure at 4 and 6 W/kg but not 2 W/kg. There were no differences between radar or SLED pulses in producing behavioral effects. ©1994 Wiley-Liss, Inc.

1 This is a US Government work and, as such, is in the public domain in the United States of America.

     

Characterization of a chemotactic and cytotoxic proteinase from human skin.

A proteinase (EC 3.4.-.-) active at physiological pH has been isolated from human skin utilizing gel filtration and affinity chromatography techniques. The proteinase has a molecular weight of approx. 28 000 and it is inhibited by alpha 2-macroglobulin, alpha 1-antitrypsin, C-1 inactivatory, soybean trypsin inhibitor and diisopropyl fluorophosphate. 2njection of 1 ng of purified proteinase into rabbit skin induces polymorphonuclear leukocyte infiltration of the cutis. Inhibition of enzyme activity with diisopropyl fluorophosphate inhibits the chemotactic effect. Addition of 0.2 microgram/ml of purified proteinase to fibroblast cultures kills the cells within minutes. This proteinase may play a significant role in modulating the inflammatory response after cellular injury.