Highly crystalline MP‐1 hydroxylapatite coating Part II: In vivo performance on endosseous root implants in dogs

The in vivo integration strength and degree of bone apposition were compared for oral endosseous implants with different plasma-sprayed hydroxylapatite (HA) coatings. Pullout strength measurements and histological analysis were used to compare two different commercially available coating from the same manufacturer. One coating does not receive a post-plasma-spray treatment and contains about 75% crystalline HA. The other coating is treated with the MP-1 process, a pressurized hydrothermal post-plasma-spray process, which increases the coating composition to approximately 95% crystalline HA without changing the coating's adhesive or cohesive strength. Comparisons were made in dogs after healing times of 3 and 15 weeks in the mandible. No significant differences were found in either case between the two coatings. Two different methods were used to determine the degree of bone apposition at 15 weeks. Both methods confirmed that the MP-1 process does not affect the osseointegration rate of plasma-sprayed HA coatings. Qualitative histology data suggest that the treated coating is more stable than the control coating, especially in cases of direct soft tissue attachment to the implant. The present data suggest that extensive dissolution of calcium phosphate components into surrounding tissue is not a necessary precursor for direct apposition of bone to HA-coated implants.     

Derivation of human tumor cells in vitro without widespread genomic instability.

The majority of adult human epithelial cancers exhibit evidence of genetic instability, and it is widely believed that the genetic instability manifested by aneuploidy or microsatellite instability plays an essential role in the genesis of these tumors. Indeed, most experimental models of cancer also show evidence of genomic instability. The resulting genetic chaos, which has widespread effects on many genes throughout the genome, confounds attempts to determine the precise cohort of genetic changes that are required for the transformation of normal human cells to a tumorigenic state. Here we show that genetic transformation of human kidney epithelial cells can occur in the absence of extensive aneuploidy, chromosomal translocations, and microsatellite instability. These observations demonstrate that the in vitro oncogenic transformation of human cells can proceed without widespread genomic instability.     

CONCERNING THE RELATION OF THE COAGULATION TIME OF THE BLOOD TO THROMBOSIS IN PHLEBITIS

Positive results have been obtained in but a single set of experiments, namely those in which turpentine was employed. In so far as the results of this preliminary study go, one is led to the conclusion that thrombosis is most readily induced when active inflammatory lesions exist in the blood vessels, associated, probably in most instances, with secondary degenerative changes. Purely mechanical lesions are much less apt to be productive of conditions favorable to thrombosis as a sequence of phlebitis. Marked artificial increase or decrease in the coagulation time of the blood by the use of calcium lactate or citric acid, does not render animals abnormally prone to thrombosis incited by changes other than inflammatory. When true phlebitis exists, thrombosis is apt to be more extensive and less readily resolved, when the coagulation point of the blood has been shortened by the use of calcium lactate, and it is less extensive and more quickly absorbed when the coagulation time has been increased by the administration of citric acid. Experiments as yet incomplete appear to suggest that the increasing in rapidity or slowing of the general circulatory stream has but little bearing on the production of thrombosis in phlebitis, much less, indeed, than clinical and anatomical observations have generally led us to think. We have also been led to suspect that the presence or absence of anastomoses of abundant degree is largely concerned as a factor in determining the location and extent of thrombosis in phlebitis.     

Identification of pathology from diesel exhaust particles in the bladder in a rat model by aspiration of particles from the pharynx

To determine whether diesel exhaust particles (DEPs) could be a toxic agent to the bladder, rats were exposed to different concentrations of DEPs for one month or three months. When the rats were sacrificed, morphologic changes of the urothelium were investigated. The antioxidase activity and the levels of lipid peroxidation in the bladder were assayed. In the three-month group, DEPs at doses of 21.03 μg/μl insulted the structural integrity of surface glycosaminoglycans, widened the gap between urothelial cells, increased levels of lipid peroxidation, and decreased antioxidase activities in the urinary bladder (p < 0.05). Furthermore, DEPs at a dose of 5.61 μg/μl decreased glutathione, catalase, and glutathione peroxidase activities (p < 0.05). These results led to the conclusion that DEPs were a toxic agent in the bladder. The toxic effects might be attributed to oxidative damage mediated by pro-oxidant/antioxidant imbalance or excessive free radicals.     

An exploratory investigation into the usability and usefulness of training people with learning disabilities in a virtual environment

Purpose : Two studies sought to answer the following questions. Are people with learning disabilities capable of using a virtual environment? Are they motivated to learn using this training method? Do they show any benefit from using a virtual environment? Does any benefit transfer to improved real world performance? Method : In the first study, 30 students with learning disabilities were sequentially allocated to an active or a passive experimental group. Active participants explored a virtual bungalow searching for a toy car. Passive participants watched the exploration undertaken by the preceding active participant and searched for the toy car. All participants then performed spatial and object recognition tests of their knowledge of the virtual environment. In the second study, the errors of 45 participants on a real steadiness tester task were noted before they were randomly allocated to three groups--a real training group, a virtual training group and a no training group. After training, the participants performed a second test trial on the real steadiness tester. Results : The students were capable of using a virtual environment and were motivated to use this training method. Active exploration of a virtual environment was found to enhance their memory of the spatial layout of the bungalow but not their memory of the virtual objects. In the second study, virtual training was found to transfer to real task performance. Conclusions : These two laboratory-based studies provide answers to four important questions concerning virtual training of people with learning disabilities. Hopefully, the findings will encourage this training aid to be used more widely.