Bengt Engfeldt

Studies on mineralized dental tissues: I. A microradiographic and autoradiographic investigationof teeth and tooth germs of normal dogs

Summary This investigation was carried out in order to get further information onthe mineralized dental tissues. Two young normal dogs were injected, one with Na 2 S 35 O 4 , the other with Ca 45 Cl 2 . From selected parts of the lower jaws thin ground sections were prepared. These sections were studied by means of a combination of autoradiographic and microradiographic techniques. The autoradiographs revealed an uptake of both Ca 45 and S 35 in essentially the same locations of the bone and tooth tissues. There was thus a high uptake of isotopes in the periosteal areas and in young osteons and certain areas of the cancellous bone. In the deciduous teeth the labelling was most pronounced along the pulpo-dentinal border. In the tooth germs there was a high uptake of both isotopes along the pulpo-dentinal border in the same area. There was also a labelling along the enamel surface. In certain tooth germs, where the microradiographs indicated a high mineralization in the cusp tips, there was a diffuse labelling throughout the whole breadth of the enamel. These findings were interpreted as an expression of a secondary mineralization. The uptake of S 35 differed in certain respects from that of Ca 45 . In the tooth germs there was thus an uptake of S 35 along the dentino-enamel junction, and in the soft tissues, especially in the pulps of the tooth germs, there was also a marked labelling of S 35 only. Further, the labelling at the pulpodentinal border showed features differing from the autoradiographs obtained with Ca 45 . Thus the uptake of S 35 at this site was concentrated in two closely adjacent bands. It was concluded that the uptake of Ca 45 took place in the mineralized constituents of the tissues. However, as regards S 35 , one part was probably incorporated in the crystal lattice of the minerals, another being deposited with the organic matrix, presumably as mucopolysaccharides containing ester sulfuric acid. This latter conclusion refers to the uptake along the pulpo-dentinal border.

Stereological studies on the epiphyseal growth plate with special reference to the distribution of matrix vesicles.

The matrix vesicles in growth cartilage are considered to play an important role in the mineralization process and it has been claimed that the distribution of these vesicles corresponds to the pattern of subsequent apatite deposition. Employing modern stereological techniques the present investigation showed a different distribution pattern from that previously described in the literature, the highest volume density of matrix vesicles being found in the resting zone and the lowest in the zone of calcification. The volume—density differences are explained by differences in the number of vesicles between zones. The variation in mean caliper diameter was small. The possible biological significance of these findings is discussed in relation to the proposed theories on matrix vesicle origin. Our findings seem to support the view that most of the matrix vesicles are formed from degenerating chondrocytes, although the possible existence of small subpopulations of matrix vesicles of more specialized origin cannot be rejected.

Proteoglycans of dentine and predentine

A density gradient system is presented by which dentine and predentine are separated, leaving an intermediate fraction, which contains material from the mineralization front. From the fractions thus obtained the proteoglycans were extracted with 4 M guanidinium chloride and further purified in urea on a DEAE column. The glycosaminoglycans extracted from dentine appeared to be protein-bound, as judged from papain digestion experiments. The polydispersity of dentine proteoglycans seemed to depend, at least partly, upon the polydispersity of its glycosaminoglycans. The materials extracted from the three tissue fractions were eluted in a similar way from Sepharose 6 B, and the amino acid composition of the preparation was determined. The differing proteoglycan patterns of the three tissue fractions indicate a metabolism related to the mineralization front.

Lamellar structure of osteons demonstrated by microradiography.

Die Lamellen des Haverschen Systems wurden durch Röntgenmikroradiographie demonstriert. Lamellen mit hoher Röntgenabsorption wechseln mit solchen niedriger Absorption ab.

Renewal of phosphate in bone minerals. II. Radioautographic studies of the renewal of phosphate in different structures of bone.

Abstract 1. 1. Labelled phosphate, when injected intravenously, is unevenly distributed in bone tissue. 2. 2. Radioautographic and microradiographic examinations have shown that young Haversian systems have the highest uptake of radioactive phosphate. When a system becomes older and the amount of mineral salts approaches a maximum value the uptake of radioactive phosphate becomes very low. 3. 3. The main reason for the rapid initial uptake of labelled phosphate cannot be the occurrence of surface reactions throughout the whole bone tissue.

Analysis of dentine glycosaminoglycans using high-performance liquid chromatography

SummaryPuppy dentine was prepared using ultracentrifugation of tooth powder in organic density gradients. The glycosaminoglycans of the obtained tissue fraction were prepared after papain digestion andβ-elimination, using preparative chromatography on DEAE-cellulose and CPC-cellulose. These polysaccharide fractions were analyzed using highly sensitive HPLC procedures. One such HPLC procedure allowed hyaluronic acid to be determined in less than microgram amounts.The glycosaminoglycans thus prepared consisted only of chondroitin-4-sulfate, chondroitin-6-sulfate, and small amounts of highly hybridized dermatan sulfate, while the experiments failed to demonstrate even trace amounts of keratan sulfate, hyaluronic acid or heparan sulfate.

Analysis of the acid polysaccharides from squid cranial cartilage and examination of a novel polysaccharide

The polysaccharides of cranical cartilage were isolated by ethanol precipitation after papain digestion and beta-elimination procedures and were fractionated chromatographically on CPC-cellulose. In addition to the previously described, heavily oversulphated chondroitin sulphate, the tissue contained small amounts of hyaluronic acid, which, however, co-eluted with the chondroitin sulphate from the CPC-cellulose. Approx. 20% of the isolated polysaccharides consisted of an acidic polysaccharide which to our knowledge is not previously described. This polysaccharide consists mainly of glucuronic acid, galactose and mannose in a molar ratio of 1:2:1. Gel chromatography of the preparation indicated a polydisperse molecule with an apparent average molecular weight of 39 200 on weight basis (Mw) and 31 400 on number basis (Mn).

Fractionation of the glycosaminoglycans of human articular cartilage on ecteola cellulose in ageing and in osteoarthrosis.

Articular cartilage from the lower femoral epiphysis of human autopsy cases was collected in ten age groups from birth to 95 years and in osteoarthrosis of two grades of severity. By chromatography on Ecteola cellulose columns, the different glycosaminoglycans were separated and keratan sulphate was fractionated. The results are consistent with earlier studies using CPC-cellulose column technique, i.e. a higher content of total hexosamine and chondroitin sulphate was found in early childhood. Furthermore, normal articular cartilage in adults showed a higher content and a higher degree of heterogeneity of keratan sulphate than in childhood. In osteoarthrosis, a decreased content of total hexosamine due to a decrease both of chondroitin sulphate and keratan sulphate was found.

Primary vitamin-D resistant rickets. III. Biophysical studies of skeletal tissue.

Histological and biophysical studies of bone tissue in primary vitamin-D resistant rickets have shown structural features that in this disease differ from those found in ordinary human rickets. Compact bone has been found to show structural chagnes resembling those found in Pagets disease. These changes are characterized by an abnormal mosaiclike pattern of bone tissue which is not affected by large doses of vitamin D. Histological examination of the costochondral junction of these patients, however, reveal abnormalities similar to those found in ordinary vitamin-D deficiency rickets. It may be concluded that vitamin-D resistant rickets is a well defined, genetically determined clinical and pathological entity, different from ordinary rickets. Treatment with vitamin D in massive doses has no direct effect upon the skeleton in vitamin-D resistant rickets. Vitamin D improves the possibilities for a deposition of mineral salts in the skeleton by its hypercalcemic effect, but does not influence the morphology of the skeletal disorder and does not cure the disease.

Stereological studies on the epiphyseal growth plate in low phosphate, vitamin D-deficiency rickets with special reference to the distribution of matrix vesicles

SummaryIn low phosphate, vitamin D-deficiency rickets normal mineralization is reversibly arrested, and rickets is thus a suitable model for studying factors influencing the mineralization process. Partly on the basis of their distribution within the growth cartilage, the so-called matrix vesicles are considered to play an important role in the process of mineralization and it has been claimed that the distribution pattern is the same in rickets as in normal animals. With the use of modern stereological techniques, our group recently demonstrated a matrix vesicle distribution between the zones of the epiphyseal growth plate in normal rats different from that described earlier. The same bimodal distribution pattern was observed in rachitic rats in the present study, the highest volume density being found in the resting and upper hypertrophic zones and the lowest in the proliferative zone. The volume density differences are explained by differences in the number of vesicles between zones, the variation in mean caliper diameter being small. Our findings are discussed in relation to the proposed theories on matrix vesicle origin. The results seem to support the dynamic cell debris theory for matrix vesicle origin presented earlier, but the existence of subpopulations of matrix vesicles with a specialized function and origin cannot be ruled out.