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Biomedical subjects

P J Sammon

Publications and source records attributed to P J Sammon.

10 recordsLinked to original sources
PubMed1994

An evaluation of electrodischarged prototype implants in rabbit tibia: a preliminary study.

This is the first in a series of biological investigations using a porous implant fabricated by a novel process known as electrodischarge compaction (EDC). This process uses Ti-6A1-4V powder and electrical energy to construct a beaded porous implant without any compromise in physical characteristics, often found with conventional sintering. The purpose of this study was to evaluate the bone response in rabbit tibia of a porous titanium prototype implant fabricated by this new technique. One hundred forty-four porous EDC-fabricated implants were placed into the tibia of 36 New Zealand rabbits. Animals were placed into one of six time periods (2, 4, 8, 12, 18, and 24 weeks). At the appropriate time period, animals were killed, and bone ingrowth was evaluated qualitatively by light and scanning electron microscopy. Bone/implant interface bond strength was also measured. Slight bone ingrowth was observed as early as the two-week time period and increased in depth at each time period for the duration of the study. Implant/bone bond strength was measurable at four weeks and continued until reaching a plateau at week 12. The results of this study suggest that this novel EDC implant may be suitable for continued development of an easily fabricated, cost-effective dental implant.

Aluminum↗
PubMed1986

Effects of diazepam on orthodontic tooth movement and alveolar bone cAMP levels in cats.

Cyclic AMP has been suggested as a possible intracellular mediator in bone remodeling during tooth movement. Accordingly, an increase in the level of this nucleotide should result in faster tooth movement. Breakdown of cAMP was inhibited by administration of diazepam in eight cats undergoing orthodontic tooth movement; another matched group of eight animals served as controls. Orthodontic appliances consisted of coil springs stretching between the right side maxillary and mandibular canines and third premolars. The data for tooth movement and cAMP concentrations were analyzed by repeated measures factorial analyses of variance. The results indicated that administration of diazepam increased the rate of tooth movement at P less than 0.0005 and, interestingly, although diazepam had no effect on undisturbed tissues, it lowered the cAMP levels in the periodontal tissues of orthodontically moved teeth at P less than 0.01. On the basis of these results, it was concluded that the concentration of cAMP did not correlate with bone remodeling in this model and perhaps should not be used as an index of periodontal-tissue response during orthodontic tooth movement.

Alveolar Process↗
PubMed1982

A case study of a nontraditional basic science curriculum.

This article presents a critical analysis of the ten-year experience of the Department of Oral Biology of the University of Kentucky College of Dentistry with a nontraditional basic science curriculum. The factors that led to the adoption of this curriculum are outlined, and its effects on students, faculty, and the college's administration are described. The pitfalls inherent in this approach and in the individualized self-instructional format for teaching the basic sciences to dental students are discussed. This critical evaluation is aimed at providing information for those contemplating similar sweeping curricular changes in the future to enable them to make rational decisions and to help them predict the effects of such changes on the educational program.

Curriculum↗
PubMed1975

The metabolism of labeled parathyroid hormone. II. Methodological studies.

Further studies on the preparation of 125I-labeled, biologically active parathyroid hormone have resulted in improvements in the procedure, in the storage of the labeled product, and in the establisment of the location of the label in the polypeptide chain. Approximately 95% of the label is on the single tyrosyl residue, amino acid 43, in the bovine hormone. New procedures have also been developed for the isolation and quantitative gel filtration of the labeled hormone deposited in tissues (liver, kidney and bone).

Amino Acid Sequence↗
PubMed1975

The metabolism of labeled parathyroid hormone. III. Studies in rats.

A series of experiments indicated that 125I-parathyroid hormone administered to the rat i.v. was deposited very rapidly in three organ systems only, bone, kidney and the liver. As indicated by increasing solubility in trichloracetic acid, the hormone seemed to be rapidly metabolized at the sites of deposition. The experiments were in part repeated employing quantitative extraction and gel filtration procedures. It was found that intact hormone predominated (82%) in the circulation but was cleared very rapidly: 91, 97, and 99% having left by 10, 30 and 60 minutes respectively after injection. The intact hormone was found at 10 minutes to be principally in kidney, bone, and liver. Although there was evidence of fragmentation preferentially to polypeptides of molecular weights of 6000, 4500 and 2500 these cannot be claimed to represent real molecular entities. By one hour, only a few per cent of the injected hormone remained intact, the bulk having been degraded to fragments of small molecular weight.

Animals↗
PubMed1975

The metabolism of labeled parathyroid hormone. IV. Autoradiographic studies.

Autoradiographs were prepared from tissues of rats sacrificed 10 minutes after injection of biologically active 125I-labeled parathyroid hormone. No radioactivity was seen in intestine and muscle. Deposition in liver was diffuse showing some sinusoidal concentrations. Depostion in kidney was high and, nearly all activity appeared in selected tubules (presumably proximal tubules) in the outer third of the cortex. Specific localization was also seen in bone particularly in the cellular layers of periosteum and endosteum adjacent to bony matrix and to some extent in osteocytes.

Animals↗
PubMed1975

The metabolism of labeled parathyroid hormone. V. Collected biological studies.

Biologically active 125I-labeled parathyroid hormone (125I-PTH) was used in a series of studies in dogs and chickens designed to confirm and augment earlier studies in rats. As in rats, a three exponential equation was required to describe disappearance of 125I-PTH from the blood in the dog. The first two "half-lives" (1.8 and 7 min) accounted for the bulk of the dose. Also as in rats, deposition of apparently intact hormone took place rapidly in kidney, liver and bone in both the dog and the chicken. Degradation occurred very rapidly in all three target organs. Three labeled hormones of different biological activities were compared in the rat. Inactive, oxidized hormone was rejected by the liver but showed markedly increased deposition in kidney and the higher the purity of the hormone the higher was its uptake by liver. Exploration of a wide range of dosages revealed few effects on distribution (smaller deposition in liver and kidney at highest dosages, 65 mug/rat). Fresh sera did not degrade hormone rapidly or extensively. There was no deposition of hormone in intestinal mucosa, marrow, and red cells. Nephrectomy increased deposition in liver and bone. Finally, the perfused liver was capable of extensive degradation of the hormone.

Animals↗