Gerrit Bevelander

The Effect of the Administration of Tetracycline on the Development of Teeth

Several investigators1-0 have shown that the tetracyclines complex with several metallic ions. It has also been shown that tetracycline or a fluorophore of this drug is incorporated into growing bones.4-5 In our own studies6-7 it was shown that not only is the drug incorporated in developing skeletons, but that at appropriate levels a marked inhibition of skeletal development also occurs. The present study was designed to amplify our previous findings, to ascertain the effect of the administration of tetracycline on developing teeth. We selected young rats 2 weeks old for this purpose, since at this age both incisors and molars undergo rapid growth and mineralization-a situation somewhat comparable to that which obtains in the human when the deciduous and mixed dentition are being formed.

The effect of tetracycline on the development of the skeletal system of the chick embryo

Abstract Introduction of tetracycline into the yolk sac of the 8-day chick embryo results in a rapid and widespread distribution of the drug throughout the embryo. After 24 hours, the tetracycline fluorophore is localized exclusively in the skeletal system. Injection of 0.1–0.5 mg of the drug does not seriously impair growth of the embryo or mineralization of the bones. Increased amounts (2.5–5 mg), however, result in a marked reduction in the size of the embryo. The bones of these embryos are reduced in size, they appear bowed, mineralization is reduced, and an abnormal calcification of the cartilage of the matrix occurs. The tetracycline fluorophore is incorporated into the mineralized component of the bone exclusively. The inhibition of mineralization following injection of tetracycline is probably due to the reduction in the number of free cations which subsequently results in the formation of a bone deficient in minerals.

Correlation of lysosomal activity and ingestion by the mantle epithelium

1. Ingestion of particulate matter by the outer mantle fold of the calico clam, Macrocallista maculata, was studied. Following the introduction of carmine into the pallial space, dye particles were subsequently localized in the epithelia of the entire outer surface.2. In an attempt to identify the cell structure in which the dye particles were localized, histochemical tests to identify acid phosphatase, lipids and mucopoly-saccharides were employed. All of the above methods gave a positive reaction at the site corresponding to the locus in which the carmine was observed.3. Additional experiments were carried out in which colloidal gold was injected into the pallial fluid. Subsequent examination of epithelial cells showed that the colloidal gold was localized in organelles which, on the basis of fine-structure morphology and histochemical tests, we ascertain to be lysosomes.4. Pinocytosis, occurring as a result of the pinching-off of the bases of the microvilli is a prominent activity of these cells. The m...

The effect of diverse amounts of tetracyclineon fluorescence and coloration of teeth

The effects of tetracycline on fluorescence and visible coloration of the incisor teethof rats of different ages were investigated. The drug was administered (1) in diverse amounts, (2) in equivalent amounts as a single dose, and (3) in divided doses over a period of several days. Both fluorescence and visible coloration of enamel and dentin are enhanced as a result of increase in the amount of drug administered. This holds true whether the drug is administered as a single dose or in divided doses administered on several successive days. Coloration following administration of tetracycline is much more pronounced in young, incompletely mineralized teeth than in the teeth of older specimens.

A Comparison Between Dietary and Hormonal Factors in the Development of Dentin

From a study of the literature on the relation of Ca metabolism to hard tissues it is apparent that two factors, at least, are to be considered in the development of dentin and enamel. These are: first, the Ca content and Ca/P ratio of the diet; second, the amount of parathyroid hormone available to mediate the normal distribution of the dietary Ca and P throughout the body. Erdheim (1) and Toyofuku (2) produced severe lesions in the incisors of rats by removing the parathyroids of these animals. Similar results have been obtained by a number of subsequent investigators (3, 4, 5), so that it is now well established that parathyroidectomy is followed by abnormalities in the dentin laid down after operation. The diets used by the different investigators have apparently affected the results considerably, but data as to the mineral content of the rations are not available. In the present study we have undertaken a comparison of the effects of dietary and hormonal factors on the development of dentin. In two series we have observed the effects of variation in the Ca content and the Ca/P ratio of the diet. In another, lesions were produced by parathyroidectomy alone, the mineral content of the diet being kept normal, while in the fourth group parathyroidectomy was combined with a marked dietary Ca deficiency. In all groups, we have attempted to correlate the effect produced on the dentin with that other well known symptom of disturbed Ca metabolism, the serum-Ca level.

The Effect of Artificially Induced Fever On the Structure of the Developing Teeth of the Rat

The effect of fever on the development of teeth is a highly controversial question. The difficulties in obtaining accurate clinical evidence, and in following case histories for several years are undoubtedly the factors which are largely responsible for the lack of precise information on this subject. Stein (1) observed the teeth of several children who were known to have had fever during infancy and early childhood. He maintains that when he examined these teeth he observed enamel hypoplasia in several instances. Recently, three preliminary reports which deal with the effect of artificially induced fever on the structure of the developing tooth appeared simultaneously. Berman (2), working with rats and rabbits, exposed the animals to intense conditions of fever and reported changes in the structure of the dentin as a result of this treatment. Bevelander and Bernstein (3) subjected a number of rats to an increase in body temperature by means of exposure to short-wave emanations and reported certain changes in the pulpal tissues of the treated specimens. Garrison (4) subjected a number of rats to fever and also reported abnormal calcification of dentin and certain changes in the pulpal tissues. This paper deals with the observations made on a much more extended series of experiments than those previously reported. The problem with which we are concerned is this: Does fever produce deleterious effects on the developing tooth? By subjecting test animals under carefully controlled conditions to an increase in body temperature which may be induced either by short-wave emana-

A Histochemical and Cytological Study of the Calciferous Glands of Lumbricus terrestris

glands of the earthworm, as they are now more commonly known, have been the subject of numerous studies in the past. These early studies dealt in the main with numerous taxonomic and morphologic aspects (see Smith, 1954). It was not until Harrington (1889) published his extensive work on the finer structures of these glands that a clear and detailed description of the cyclic activity of the epithelial cells and their secretory function was clearly established. The common earthworm, Lumbricus terrestris, possesses three pairs of glands located in segments X, XI, and XII in intimate association with the esophagus and the seminal vesicles. According to Harrington (1889), the anterior glands serve as storage receptacles, while the two pairs of posterior glands elaborate calcium carbonate. The gland cavity is traversed by sinuses invested with epithelial cells. These cells are dissipated as a result of their cyclic activity. During the quiescent or spent phase, the cells appear flat and rectangular-shaped; with the onset of activity, the cells become clubor dome-shaped, and during this phase they elaborate numerous cytoplasmic inclusions. The final stage of cellular activity results in the extrusion of minute globular masses and various other cytoplasmic constituents.

Effects of DON (6-Diazo-5-Oxo-L-Norleucine) and Azaserine on the Sand-Dollar Embryo.

Summary 1. DON and azaserine interrupt the development of sand-dollar embryo at mid-blastula and early gastrula stages. The minimum dose of DON producing consistent effects is 3 milligamma/10 cc of sea-water; azaserine is approximately 1/32 as active. Large doses of DON up to 1 mg/10 cc of sea-water have no appreciable effect on fertilization, cleavage or early development. 2. Various physiological purines and derivatives will protect against the action of DON and azaserine, even when added up to 12 hours after fertilization. The most active ones are guanine, hypoxanthine and inosine. The protective action of these substances appears to be non-competitive, and they are not effective against large doses of DON and azaserine. 3. In view of the fact that DON and azaserine, acting as glutamine antagonists, apparently interrupt the de novo synthesis of purines, it is suggested that embryonic development in the sand-dollar is blocked at the time when DNA production, initially supplied by endogenous purine precursors, becomes dependent on de novo purine synthesis.