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Biomedical subjects

E J Reith

Publications and source records attributed to E J Reith.

At least 19 recordsLinked to original sources
PubMed1985

The pyroantimonate reaction and transcellular transport of calcium in rat molar enamel organs.

The distribution of calcium in the cells of the enamel organ of developing rat molar tooth germs was studied by the pyroantimonate method. It was found that there was a specific localization to the inner leaflet of the plasma membrane of both secretory and maturation phase ameloblasts. This information can be used to support the model for transcellular transport of calcium involving membrane fluidity, with phosphatidylserine as a carrier (Reith 1983). It can also support an alternative model involving movement of calcium ions over a surface of acidic phospholipids on the inner leaflet of the plasma membrane, without involving the necessity for membrane fluidity.

Animals↗
PubMed1984

Cyclical phenomena occurring during the maturation of the enamel of rat incisor teeth. Their manifestation during drying.

A pattern of obliquely oriented bands has been demonstrated at the surface of the maturation zone enamel of freshly dissected rat incisor teeth as they dry. This pattern, of which there is no evidence in the fresh, wet, or completely dry teeth, consists of up to 4 or 5 pale grey, translucent lines separated by wider, whiter, more opaque bands and has been shown to correlate directly with a similar pattern seen on the same teeth after staining with toluidine blue and previously described as the maturation cycle banding pattern (Boyde and Reith 1982). A second pattern comprised of much more closely spaced bands is also described. In this pattern, which again correlates with a similar pattern seen after toluidine blue staining, translucent and opaque bands cross the maturation zone more transversely and have a width of about 200 microns, approximating to 8 h tooth growth. It is postulated that these banding patterns reflect alternately different drying rates of the maturation zone enamel and that they may correspond to cyclical changes in the hydrophobicity and hydrophilicity of enamel matrix both on a daily basis and on a larger time scale.

Animals↗
PubMed1984

Rapid uptake of calcium in maturing enamel of the rat incisor.

Six rats were given intravascular injections containing 45Ca, killed by perfusion with fixative and the incisor teeth removed within 2 min. Direct autoradiography of the maturing enamel surface showed bands of 45Ca uptake at this short interval.

Animals↗
PubMed1983

Cyclical uptake pattern of tetracycline in post-secretory maturation phase enamel demonstrated in rooted teeth.

Uptake of tetracycline by enamel in the short-term was studied at an advanced stage of crown formation and after completion of crown formation in deciduous molars in the cat. Both secretory phase enamel and bands of postsecretory, maturation phase enamel labeled rapidly. The pattern of labeling mimicked that seen in the continuously growing, rootless incisor teeth of the rat, with narrow doublets fusing to form narrow bands with wide unlabeled intervals in the short term. This is a physiological demonstration which indicates that cyclical activity and changes may occur in vivo during the maturation phase of amelogenesis in rooted teeth. It is also noted that dentine did not, and that some circumscribed patches of bone did label in the same animals in the same time interval. Short-term tetracycline labels are lost following conventional histological processing, but are retained after freeze-drying or air-drying.

Ameloblasts↗
PubMed1982

In vitro histological and tetracycline staining properties of surface layer rat incisor enamel also reflect the cyclical nature of the maturation process.

Rat incisors cleaned of overlying enamel organ cells stain unevenly with several common histological stains producing two kinds of banding pattern. In one a pattern of widely spaced stained bands run in an oblique to transverse direction from a more apical level on the medial side to a more incisal level on the lateral side of each tooth. The pattern correlated directly with that produced by both in vivo and in vitro short-term tetracycline labelling in the same teeth: it also resembled the patterns previously demonstrated in a) horseradish peroxidase penetration into lateral intercellular spaces between maturation ameloblasts, b) the distribution of enamel labelling in vivo with 45Ca, c) of etching of enamel surfaces demineralized with EDTA with the glutaraldehyde fixed enamel organ in situ and d) in the distribution of smooth-ended and ruffled border types of cell specializations. We conclude that these bands demonstrate further and previously unrecognised aspects of the cyclical phenomena in enamel maturation-mineralization and show cyclical differences in the physico-chemical status of the organic matrix in the maturation process. A second, incremental growth type of banding pattern occurred at 200-225 micron intervals in the lower incisors and had the same distribution at the beginning and end of the maturation zone.

Animals↗
PubMed1982

Correlation of 45Ca incorporation with maturation ameloblast morphology in the rat incisor.

Rats were injected with 45Ca and horseradish peroxidase to determine the patterns of 45Ca incorporation into incisor enamel and the morphological types of the overlying maturation ameloblasts. 45Ca autoradiography showed no differences in the patterns of incorporation into enamel between routinely embedded and freeze-dried specimens. Enamel overlaid by ruffle-ended ameloblasts was much more heavily labeled while that overlaid by smooth-ended ameloblasts showed only moderate labeling. The observations lend further support to the hypothesis that the ruffle-ended cells are very active in mineralizing enamel and that the smooth-ended cells are in a passive, restorative phase.

Ameloblasts↗
PubMed1981

Innervation of rat molar teeth: I. Distribution of neuronal cell bodies in the trigeminal ganglion from a mandibular molar tooth.

The cell bodies of neurons innervating a rat mandibular molar tooth were examined with respect to their location in the trigeminal ganglion. The study sought to determine if these cell bodies were restricted to a specific somatotopic location within the mandibular territory of the ganglion or if they were distributed throughout the entire mandibular territory. Horseradish peroxidase (HRP) pellets were placed in the cavity preparation of right first mandibular molar teeth for a 24-hour period. The animals were then perfusion fixed, and the right trigeminal ganglion was removed, sectioned and processed by the tetramethyl benzidine neurohistochemical technic. The four trigeminal ganglia constituting this experimental series demonstrated 129, 185, 236, 318 HRP-positive cell bodies. These cell bodies were dispersed throughout the extent of the mandibular territory. It was concluded from these observations that the distribution of cell bodies innervating a rat mandibular molar tooth is not restricted to a specific region of the mandibular territory of the trigeminal ganglion, but rather the distribution of these cell bodies is throughout all parts of the mandibular territory.

Animals↗
PubMed1981

Display of maturation cycles in rat incisor enamel with tetracycline labelling.

Tetracycline was incorporated within seconds of intracardiac injection to form bright yellow fluorescent bands under UV irradiation in maturation zone enamel. The bands were narrow, widening with time. At several hours after subcutaneous injection, the fluorescent bands were wide and of low intensity. It is concluded that tetracycline enters maturing enamel opposite the narrow bands of non-striated border ameloblasts which are probably a main exit route for organic matrix remnants. Tetracycline distribution patterns at hours after injection reflect the diffusion of this substance within enamel and the pattern of its removal, which also occurs in relation to the non-striated border, smooth-ended maturation ameloblasts.

Aging↗
PubMed1981

Autoradiographic evidence of cyclical entry of calcium into maturing enamel of the rat incisor tooth.

Adult rats were injected intraperitoneally with radioactive calcium and allowed to survive for periods up to 60 min. Animals were then killed and the upper incisors were removed. Soft tissue was removed from the teeth by dissection and with Clorox. Teeth were then coated with photographic emulsion and, after 17 days, the emulsion on the specimens was developed. Black bands of reduced silver indicated areas of radioactivity where calcium had entered the enamel. These bands were separated by narrower bands of non-radioactive enamel. It was judged that calcium did not gain entry into the enamel in these areas of enamel at this particular time. The patterns made by the bands of calcium entry and restriction were similar to patterns which show where striated border and non-striated border maturation ameloblasts cover the maturing enamel. Maturation ameloblasts with a striated border cover a larger area of the maturing enamel than do maturation ameloblasts without a striated border. It is considered that the maturation ameloblasts with a striated border are engaged in calcium entry into the maturing enamel.

Ameloblasts↗
PubMed1981

The arrangement of ameloblasts on the surface of maturing enamel of the rat incisor tooth.

The location of striated border cells versus non-striated border cells during enamel maturation in the rat incisor was studied by light microscopy. Serial cross sections of the lower incisors were examined from a segment of the incisor in sections which also included the first molar tooth. In the series recorded here every cross section showed both striated and non-striated border cells. A map showing the distribution of cells on the enamel surface, as plotted from their position in each of the cross sections, reveals that the non-striated border cells traverse the enamel as oblique bands. Between the narrow bands of non-striated border cells were wide bands of striated border cells. The non-striated border cells were joined at their basal nuclear poles by contacts which appeared to separate the lateral inter-ameloblast space from the space between the papillary-ridge cells. Neither the striated border cells nor the non-striated border cells went entirely to the edge of the enamel organs. The above pattern of striated border cells and non-striated border cells is regarded to be a manifestation of the cyclical activity of maturation ameloblasts.

Ameloblasts↗
PubMed1979

A correlated scanning and transmission electron microscopic study of maturation ameloblasts in developing molar teeth of rats.

Maturation ameloblasts of developing molar teeth of the rate were studied by both scanning and transmission electron microscopy. After fixation, teeth were frozen and split. One face of the fractured tooth was used for SEM, the other for TEM. It was found that in some regions proximal junctional complexes separate the interameloblast space from the intercellular space of the papillary layer. Thereby an intercellular ameloblastic compartment is delineated which in some specimens contains a substance interpreted to be colloidal. Elsewhere the proximal junctions of ameloblasts are not present and free communication between the extracellular spaces is evident. The apical pole of ameloblasts varies in structure. Over some areas there is a distinct distal border zone with membranous infoldings which in some regions resembles a striated or ruffled border, but in other regions the membranes show whorl configurations. The distal border zone also contains granules with flocculent material. Elsewhere the ameloblasts display no distal border zone and the cells show a smooth membrane (except for pinocytotic vesicles and hemidesmosomes) facing the enamel surface. The lateral surface of ameloblasts exhibits a variety of surface configurations similar to but not as pronounced as those reported previously in rat incisor maturation ameloblasts.

Aging↗
PubMed1978

Intercellular attachments between calcified collagenous tissue forming cells in the rat.

Osteoblasts of the young rat cranium, and cementoblasts and odontoblasts of young rat molars were prepared by ethanol freeze-fracture prior to critical point drying for scanning electron microscopy (SEM) as well as conventional transmission electron microscopy (TEM) techniques. Critical point drying causes shrinkage which separates the lateral intercellular contacts between neighbours in the same sheet in the case of cementoblasts and osteoblasts, but not those between odontoblasts. These differences are considered to be of functional significance and need to be taken into consideration when formulating theories of calcium influx into the mineralizable matrix of the respective tissues.

Animals↗
PubMed1978

Histochemical and electron probe analysis of secretory ameloblasts of developing rat molar teeth.

Calcium was not found in secretory ameloblasts and stratum intermedium cells when treated with OsO4-pyroantimonate or when surfaces prepared by fracturing fresh, rapidly frozen, developing molar tooth germs were subject to electron probe X-ray analysis. Pyroantimonate reaction product, considered to be calcium, was found in mitochondria of enamel organ cells which were first placed in a bath containing calcium and potassium. The plasma membrane was disrupted in cells ehich showed mitochondrial localization of reaction product. The results provide no data which indicates that enamel organ cells have a direct, active role in the movement of calcium into the enamel. Rather, it is suggested that the secretory enamel organ might serve as a selective barrier in regulating the initial mineralization of enamel.

Ameloblasts↗
PubMed1978

Electron probe analysis of maturation ameloblasts of the rat incisor and calf molar.

Rapidly frozen upper incisor teeth of rats and molar teeth of calves were freeze fractured, freeze dried and dry dissected in preparation for energy dispersive x-ray emission microanalysis in the scanning electron microscope. Successive zones of ameloblasts adjacent to maturing rat incisor enamel were examined, beginning with cells adjacent to the least mature enamel and progressing to cells over increasingly more mature enamel. Pronounced Kalpha1,2 x-ray peaks were obtained for P, S, Cl, K and Fe but not for Ca. Ca levels were also very low compared with P, S, Cl and K in calf molar maturation ameloblasts, whereas they were high in the distal poles of the secretory odontoblasts in the same specimens. The findings indicate that both intra- and extracellular Ca levels are extremely low in maturation ameloblasts. It is concluded that Ca is neither stored nor concentrated in large amounts by the maturation ameloblasts prior to its entry into the enamel. The suggestion is made that the maturation ameloblasts might regulate entry of calcium into enamel by serving as a selective barrier.

Ameloblasts↗
PubMed1977

Scanning electron microscopy of rat maturation ameloblasts.

Post-secretory, maturation-phase ameloblasts were studied by scanning electron microscopy of freeze-fractured or dry-dissected rat incisors. These cells are in contact with the enamel which they secreted at an earlier time and which undergoes a process of continuing mineralization. The lateral intercellular compartment between maturation ameloblasts is sometimes continuous with the intercellular space of the papillary layer of the enamel organ, but often closed by basal ring contacts which correspond to terminal bars seen in transmission electron microscopy. The distal poles of the cells sometimes possess striated borders. Lateral cell surfaces may show longitudinal gutter-like depressions between ridges from which numerous intercellular connections arise; or a maze of lateral folds and ridges; or they may have mostly microvillous surface projections bordering a minimal intercellular space compartment. Preliminary correlations of groupings of basal, lateral and distal cell features indicate that "basal-closed plus distal striated border" cells may show every type of lateral surface. Cell without a striated border, whether open or closed basally, have ridge or maze lateral surfaces bordering a wide intercellular compartment. "Basal-open plus striated border" cells have microvillous or maze-like surfaces. These combinations of features are encountered a few times along the length of the maturation zone of individual incisors and suggest tha existence of cyclical changes in the type of activity of maturation ameloblasts.

Ameloblasts↗