Sol Bernick

Vertebral End-Plate Changes With Aging of Human Vertebrae

The present study describes the sequential age changes within the growth and articular layers of the cartilaginous end-plates of vertebrae from humans varying in age from birth to 73 years. There is a gradual reduction in the width of the growth cartilage up to 16-20 years of age. During adulthood and progressing into old age (60-73 years), the end-plates consist of only articular cartilage which undergoes calcification followed by resorption and replacement by bone. Age changes are observed in the arterioles, capillaries, and venules found in the nutrient canals or spaces of the bone adjacent to the cartilage or disc. The calcification of the articular cartilage and vascular changes seen in the older vertebrae would impede the passage of nutrients from the blood to the disc proper. Collagen fibers are observed arising from the older vertebral end-plates to course into the midregion of the disc.

Effect of aging on the human pulp

Nonerupted, young functional, and old noncarious teeth obtained from individuals who varied in age from 15 to 75 years were studied to determine the changes in the collagenous fibers and ground substance during the aging process. It was noted that in the aging process, there is a progressive reduction in the size of the pulpal chamber and a progressive deposition of calcified masses that originate in the root pulp and progress into the coronal pulp. As a result of the calcification of the blood vessels and nerves in the pulp, there is a decrease in the number of blood vessels and nerves in the coronal pulp. However, their connective tissue sheaths persist and give the pulp a fibrotic appearance. The stroma of the pulp, regardless of age, consists of fine collagenous fibers and an abundant amount of alcianophilic ground substance.

AGE CHANGES TO THE ANULUS FIBROSUS IN HUMAN INTERVERTEBRAL DISCS

This study deals with age changes in the anulus fibrosus of the lumbar intervertebral discs of human individuals 21-83 years of age. The anular laminas from individuals less than 40 years of age consisted of obliquely orientated collagen fibers exhibiting a pennate arrangement. These fibers were intensely argyrophilic after silver nitrate impregnation. The fibers and surrounding substance appeared light pink after exposure to the periodicacid- Schiff (PAS) reaction and blue with alcian blue complex. Beginning during middle age and continuing into the eighth decade, there was a progressive degeneration of the laminas. The breakdown of the intact laminas was characterized by the fraying, splitting, and loss of collagen fibers. The newly formed spaces became filled with intense PAS-positive material. In addition, there was a continual deposition of chondroid substance in the anuluses of the aging discs. This phenomenon was not seen in the young disc. These age related changes lead to a loss of integrity to the disc, which may be a factor in disc pathology.

Biochemical differences between dystrophic calcification of cross-linked collagen implants and mineralization during bone induction

SummaryEctopic calcification of diseased tissues or around prosthetic implants can lead to serious disability. Therefore, calcification of implants of glutaraldehyde-cross-linked collagenous tissues and reconstituted collagen was compared with mineralization induced by demineralized bone matrix (DBM). Whereas implants of DBM accumulated large amounts of calcium and a bone-specific γ-carboxyglutamic acid protein (BGP or osteocalcin) following implantation in both young and older rats, implants of cross-linked pericardium calcified with only traces of BGP. Glutaraldehyde-cross-linked DBM failed to calcify after implantation in 8-month-old rats for 2–16 weeks. Implants of cross-linked type I collagen exhibited small calcific deposits 2 weeks postimplantation but calcium content eventually dropped to levels equal to those of soft tissues as the implants were resorbed. The calcium content of DBM implanted in 1- and 8-month-old rats reached comparable levels after 4 weeks, but the BGP content was approximately twice as high in the younger animals than in the older ones. Glutaraldehyde-cross-linked implants of DBM, tendon, and cartilage calcified significantly in young but not in old animals. This form of dystrophic calcification was associated with only trace amounts of BGP. Alkaline phosphatase activity was high in implants of DBM and undetectable in implants of cross-linked collagenous tissues. These results show that implants of glutaraldehyde-cross-linked collagenous tissues and reconstituted collagen calcify to different extents depending upon their origin and the age of the host, and that the mechanism of dystrophic calcification differs significantly from the process of mineralization associated with bone induction as reflected by alkaline phosphatase activity and BGP accumulation.

Osteogenesis in bone defects in rats: the effects of hydroxyapatite and demineralized bone matrix.

Hydroxyapatite (HA) and Demineralized Bone Matrix (DBM) are being investigated as potential osteogenic agents with hopes that these substances can be used to induce bone formation in non-union fractures. This study was done to determine the relative effects of HA and DBM implanted as moldable phospholipid composites in bone defects that result in non-unions. We studied 22 ten-month-old Long-Evans male rats with 5.0 mm unilateral radial defects implanted with HA, DBM, and a combination of both substances. Control defects were left unfilled. Eight weeks after implantation, the histological sections demonstrated a decrease in bone formation with HA relative to controls. The HA crystals were encapsulated by connective tissue stroma made up of collagenous elements, fibroblasts, and blood vessels. There were no indications of bone formation within the fibrous stroma. 45Calcium, alkaline phosphatase, and bone gla protein (BGP) assays demonstrated a 16% increase in bone formation in rats implanted with DBM, an 80% decrease in groups implanted with HA (p = 0.01) and an 80% decrease with DBM plus HA (p = 0.01). Radiologic analysis corresponds well with histological and biochemical results. We conclude that osteogenesis in non-union defects is enhanced by the implantation of DBM, while HA interferes with bone formation in the rat model. In the presence of both substances, HA appears to impede new bone growth, negating any positive effects seen with DBM.

Effect of Aging On the Nerve Supply To Human Teeth

Calcification of the pulp, diffuse or nodular, is a common occurrence in old teeth.1-3 A recent report4 compares the vascular supply of the pulps of young and old teeth. It shows that 90 percent of teeth from individuals more than 40 years of age have some degree of pulpal calcification, mainly involving the apically located blood vessels. Concomitant with the calcification of blood vessels, there is an apparent decrease in the number of demonstrable blood vessels supplying the coronal pulp. Because nerves are associated with the blood vessels in their course throughout the pulp, it becomes of interest to study the effects of aging on the nerves and their termination in the pulps of old teeth.

Innervation of teeth and periodontium after enzymatic removal of collagenous elements

Abstract 1. 1. The innervation of human and monkey teeth and their periodontium was studied by Pearsons silver gelatin method. The jaws and teeth were fixed in a formol-acetic acid-alcohol mixture, decalcified, dehydrated, and embedded in nitrocellulose in the usual manner. The embedded specimens were sectioned at 25 to 100 micra, and the cut sections were exposed to enzymatic hydrolysis before silver impregnation. 2. 2. The common pulpal nerve arises as a union of the branches of the various dental nerves which enter the apical periodontal membrane of all the surfaces surrounding the tooth. In the coronal portion of the pulp the common pulpal nerve breaks up into cuspal nerves which course toward the cuspal horns. The termination of these nerves is mainly in the odontoblastic layer; however, a few nerves enter the predentine, where they form a loop to return to the odontoblastic layer. 3. 3. The nerve supply to the periodontal membrane arises from the dental and interalveolar nerves, branches of the alveolar nerves. The dental nerve fibers supply the periapical region and pass gingivally to form a united bundle with the perforating branches of the interalveolar nerves. 4. 4. Two types of nerve endings are found in the periodontal membrane. (1) Nonmedullated nerve fibers may unite at their terminals to form an arborization. Fine delicate fibrils arise from this network to end as “free nerve endings” among the stroma cells, cementoblasts, and cementum. (2) Medullated fibers may lose their myelin sheath, and the naked fibrils terminate into an elongated spindlelike structure. 5. 5. Gingival innervation is derived from two sources: (1) fibers arising from the nerves of the periodontal membrane and (2) fibers originating from the labial or palatal nerves. As these fibers pass through the connective tissue, terminal twigs are given off which supply the tunica propria. Intrapapillary and intraepithelial nerve endings are scarce in the epithelial attachment and marginal gingiva. On the other hand, attached gingiva contains both types of nerve endings.

Ectopic bone formation is enhanced in senescent animals implanted with embryonic cells

Ectopic bone formation induced by the subcutaneous implantation of demineralized bone matrix (DBM) is very significantly reduced in older Fischer 344 rats. Cells originating from calvaria of 20-day-old embryo donors were introduced into cylinders of DBM sealed at the ends with a Millipore filter or collagen sponges prior to subcutaneous implantation. Cells within the chambers had access to vascular channels that could penetrate through the interstices of the DBM. After four weeks of implantation in 26-month-old rats, the cylinders were full of bone. This bone was assessed by histologic techniques, by calcium and bone gamma-carboxyglutamic acid (gla) protein (BGP) concentrations, and by alkaline phosphatase activity. Cylinders to which no cells were added produced no bone. Bone marrow cells enclosed in similar cylinders or injected weekly at the implantation site also enhanced new bone formation but to a much lesser extent. Embryonic muscle cells formed large amounts of cartilage and less bone. Fibroblasts were inactive in this system. Prior treatment of the DBM with trypsin inhibited the myoblast response but not that of calvaria cells.

The Pearson Silver-Gelatin Method for Light Microscopy of 0.5-2 μ Plastic Sections

Sections 0.5-2 μ thick of liver, kidney, lung, cartilage and brown fat embedded in Maraglas, Araldrite, Epon and Spurrs medium were deplasticized in alcoholic NaOH for 15 min. Following several alcohol rinses, the tissues were exposed to 2% AgNO3 at 50 C for 1-2 hr, and then developed in a solution containing 3% gelatin, 40 ml; 2% AgNO3, 10 ml; and 1% hydroquinone, 4 ml. Sections were then toned in 1% gold chloride (several dips), washed in water for 5 min and dipped in 2% oxalic acid. After a brief rinse in water the sections were placed in 5% Na2S2O3 for 5 min, washed in water for 5 min, dehydrated in alcohol, cleared and covered. Compared to similar sections retained in plastic and deplasticized sections stained in the routine manner with 1% toluidine blue, silver impregnated sections of all tissue free of plastic, displayed greater clarity of cellular detail. Especially clear were mitochondria of liver and brown fat cells. Type II cells of the lungs were exceptionally prominent as were podocyte foot ...

Studies on the Biology of the Periodontium of Marmosets: VIII. The Effect of Folic Acid Deficiency on the Marmoset Oral Mucosa

Marmoset oral mucosa has been shown to be extremely sensitive to folic acid deficiency induced experimentally by dietary and dietochemical means. Histologically, the most prominent deficiency-related changes were an interference with the maturation of the epithelial cells, impairment of keratinization, and an increased susceptibility to ulceration and secondary infection.