Hamster Molars Research Articles

Cricetinae in the Quaternary fossil record of the Czech Republic and Slovakia (Rodentia: Cricetidae)

The paper surveys the Quaternary (MN17–Q4) fossil record of Cricetinae in the Czech Republic and Slovakia with particular attention to the current glacial cycle (Q4: Vistulian–Holocene) and immediate history of extant taxa. Vast majority of records were reexamined using standardized techniques of morphometric analysis (in total 625 molars of Cricetus, 805 molars of small hamsters). Cricetus cricetus, recorded in 130 Q4 fossil communities, exhibits almost continuous appearance since the beginning of Vistulian, possibly with considerable range regressions during LGM and middle Holocene. It was recorded also in 27 Early Pleistocene (MN17–Q2) and 6 Middle Pleistocene (Q3) assemblages, with a small-sized form (Cricetus cricetus nanus) in MN17–Q1 stage and a mosaic of Q2–Q3 records exhibiting mostly excessively large size (C. c. runtonensis), similarly as the Vistulian items which are clearly larger than those of the post-LGM and early Holocene age. The appearance of hamster in fossil record shows a mosaic character suggesting temporal spatial and abundance fluctuations: in most sites it absents and in general, it appears as a rather rare sub-recedent element (in Q4 communities with overall dominance of mere 0.55% and this is valid also for its appearance in Early and Middle Pleistocene assemblages). Small hamsters arranged here in the genus Cricetulus (incl. Allocricetus) represent a constant element of the Early and Middle Pleistocene assemblages (43 sites in the Czech Republic and Slovakia). The items of Q4 record (21 communities) clearly differ from the Early to Middle Pleistocene form Cricetulus bursae by a consistently smaller size corresponding to extant species Cricetulus migratorius. The gap is quite distinct conforming even to the possible extinction of C. bursae during the Eemian interglacial followed by early Vistulian expansion of the extant species from its Asiatic range suggested by molecular phylogeography. We examined a question of possible appearance of Phodopus among the Q4 record of small hamsters, yet in our material, we did not succeed to confirm it.

Parenteral monofluorophosphate (MFP) is a more potent inducer of enamel fluorotic defects in neonatal hamster molars than sodium fluoride

Supra-optimal intake of sodium fluoride (NaF) during early childhood results in formation of irreversible enamel defects. Monofluorophosphate (MFP) was considered as less toxic than NaF but equally cariostatic. We compared the potency of MFP and NaF to induce pre-eruptive sub-ameloblastic cysts and post-eruptive white spots and pits in developing hamster enamel. Hamster pups were injected subcutaneously with either NaF or MFP in equimolar doses of either 9 mg or 18 mg F/kg body weight. At 9 mg F/kg, MFP induced more but smaller sub-ameloblastic cysts with a collective cyst volume twice as large as that induced by NaF. Eight days after F injection, all F-injected groups had formed 4-6 white spots per molar, with an additional 2 pits per molar in the low MFP group. Twenty-eight days after injection, most white spots had turned into pits (5-6 per molar) and only the high MFP group still contained 2 white spots per molar. We conclude that parenterally applied MFP is more potent in inducing enamel defects than NaF. Most white spots formed turn into pits by functional use of the dentition. The higher potency of parenteral MFP may be associated with sustained elevated F levels in the enamel organ by enzymatic hydrolysis of MFP by alkaline phosphatase activity.

Enamel Pits in Hamster Molars, Formed by a Single High Fluoride Dose, Are Associated with a Perturbation of Transitional Stage Ameloblasts

Excessive intake of fluoride (F) by young children results in the formation of enamel subsurface porosities and pits, called enamel fluorosis. In this study, we used a single high dose of F administered to hamster pups to determine the stage of ameloblasts most affected by F and whether pit formation was related to F-related sub-ameloblastic cyst formation. Hamster pups received a single subcutaneous injection of either 20 mg or 40 mg NaF/kg body weight, were sacrificed 24 h later, and the number of cysts formed in the first molars were counted. Other pups were sacrificed 8 days after F injection, when the first molars had just erupted, to score for enamel defects. All F-injected pups formed enamel defects in the upper half of the cusps in a dose-dependent way. After injection of 20 mg NaF/kg, an average of 2.5 white spots per molar was found but no pits. At 40 mg NaF/kg, almost 4.5 spots per molar were counted as well as 2 pits per molar. The defects in erupted enamel were located in the upper half of the cusps, sites where cysts had formed at the transition stage of ameloblast differentiation. These results suggest that transitional ameloblasts, located between secretory- and maturation-stage ameloblasts, are most sensitive to the effects of a single high dose of F. F-induced cysts formed earlier at the pre-secretory stage were not correlated to either white spots or enamel pits, suggesting that damaged ameloblasts overlying a F-induced cyst regenerate and continue to form enamel.

Study on hypomineralized areas in hamster molars.

Hypomineralized area (HMA) scores were determined for hamster molars during tooth maturation and fluoride treatment. It was found that the molars were maturing until the animals were 45 days old, but from 45 to 74 days of age the HMA scores remained constant. Fluoride treatment decreased the HMA score. The group with the lowest HMA score was fed a cariogenic diet, inoculated with Streptococcus mutans and received topical fluoride treatment.

Quantitative analysis of fluoride-induced hypermineralization of developing enamel in neonatal hamster tooth germs

A procedure was developed for analysing the effect of fluoride on mineralization in the enamel of neonatal hamster molars during amelogenesis by means of the quantitative determination of the mineral content. In this procedure the distribution of calcium and mineral concentration was determined in sections containing developing tooth enamel mineral embedded in an organic epoxy resin matrix by means of the micro-PIXE technique. This allowed the determination of the calcium content along preselected tracks with a spatial resolution of 2 μm using a microprobe PIXE setup with a 3 MeV proton beam of 10 to 50 pA with a spot size of 2 μm in the track direction. In this procedure the X-ray yield is used as a measure for the calcium content. The thickness of each sample section is determined independently by measuring the energy loss of α-particles from a calibration source upon passing through the sample. The sample is considered as consisting of two bulk materials, allowing the correction for X-ray self-absorption and the calculation of the calcium concentration. The procedure was applied for measuring the distribution of mineral concentration in 2 μm thick sections taken from tooth germs of hamsters administered with NaF. The measurements indicated that a single intraperitoneal administration of 20 mg NaF/kg body weight to 4-to-5-day-old hamsters leads within 24 h to hypermineralization of certain focal enamel surface areas containing cystic lesions under transitional and early secretory ameloblasts. The mineral concentration there is substantially increased due to the fluoride treatment (35%, instead of 5 to 10% as in the controls), indicating that the normal mineralization process has been seriously disturbed. Furthermore it is found that using this technique the mineral concentration peaks at about 70% at the dentine-enamel junction, which is comparable to that reported for human dentine using other techniques.

Adriamycin alters the alkaline phosphatase activity in hamster molars during development in vitro.

The effect of a 2 hour exposure to adriamycin (1 mg/litre) on alkaline phosphatase (ALPase) activity of the golden hamster 4-5 day old second maxillary molars (M2) was investigated in vitro. The molars were grown in BGJb medium containing 15% fetal bovine serum, glutamine (200 micrograms/ml), vitamin C (250 micrograms/ml), penicillin G (50 micrograms/ml), and streptomycin sulphate (30 micrograms/ml). The gas phase contained 50% O2 + 5% CO2 + 45% N2. The molars were supported on cellulosic membrane filters and grown for 3, 5, and 7 days at the medium-gas interface in a closed humidified chamber. Biochemical analysis indicated a steady increase in ALPase activity throughout this study in the control samples. However, after adriamycin treatment no increase in ALPase activity could be observed. The histochemical data showed that the increased activity in the control was confined to the peripheral pulp, sub-odontoblastic layer, stratum intermedium, ameloblasts and odontoblasts. Although these layers showed a decreased activity after adriamycin treatment, the ameloblasts showed an increase in activity over the control. The data has shown that adriamycin caused a reduction in total ALPase activity in developing molars in vitro; osteodentin production by pulp cells; and appeared to produce an acceleration in the differentiation of ameloblasts.

Electron Probe X-Ray Microanalysis of Calcium and Phosphorus Distribution in Developing Hamster Tooth Germs in vitro and in vivo

The aim of the present study was to investigate the spatial distribution of Ca and P in dentin and enamel of developing first (M1) and second (M2) maxillary hamster molars (age: 3-5 days) in comparison with cultured molars. For culturing the germs were dissected from 3-day-old hamsters and incubated for 1 and 2 days, respectively, in a modified BGJb medium. Electron probe X-ray measurements were carried out on 3 regions extending in a vertical axis from cusp tip over cusp middle to cusp base next to the cervical loop region. Neither the in vivo nor the in vitro group was statistically different in the Ca and P concentration in the regions of dentin. In both groups the measurements in enamel showed a gradient with an increase in Ca and P from enamel surface towards dentin-enamel junction and a gradient with an increase from cusp base towards cusp tip. Direct comparison of the in vivo group with the in vitro group did not demonstrate a statistical difference between the mineral content of the 4-day-old germs and the 1-day culture germs, respectively the 5-day-old germs and the 2-day culture germs. The results indicate a high correspondence between the mineralization process of in vitro and in vivo tooth germ development.

An electron microscopic study on the epithelial attachment of golden hamster molars.

The fine structure of the junctional epithelium (JE) was studied by electron microscopy using molars of golden hamsters aged 10 days or 5 weeks. The following conclusions were obtained : 1. Primary epithelial attachment (PEA) The oral sulcular epithelium (OSE) adjoins the enamel organ at the top of the JE. Cells of the JE showed the same structure as those of the enamel organ at the pigmentation stage.2. Secondary epithelial attachment (SEA) In the cells directly connected with the adjoining enamel, the Golgi apparatus was located in the cytoplasm facing the enamel, and the rough endoplasmic reticulum was found in its vicinity. In other words, this cell type showed polarity, as in secretory cells. Cells located over the cells connected with the enamel contained small vacuoles with electron-dense material in the cytoplasm.3. Cell divisionA large number of mitotic figures were found in the basal layer and cells directly connected with the enamel of the JE, and these were very numerous in the infected JE. This finding was considered to indicate that there is a relationship between the deepening of pockets and bacterial infection.Polymorphonuclear leukocytes (PMN) were found mostly in the intercellular spaces between ameloblasts of the PEA, and in the papillary layer of the PEA. In the SEA, PMN were found mainly in the intercellular spaces between cells connected with the enamel and those of cells containing small vacuoles, as well as in the OSE. Very occasionally, PMN infiltrated the JE through the basal lamina at its apical end.

Carbonic anhydrase in developing hamster molars.

Carbonic anhydrase (CA) activity decreased slightly in hamster molars from one to four d after birth. It was inhibited by low concentrations of acetazolamide. Histochemically, the stratum intermedium and stellate reticulum showed an intense staining for CA, whereas ameloblasts increased and odontoblasts decreased their CA activity with age.

A histological and biochemical study of the effect of vitamin C-deficiency on induction of amelogenesis in hamster molars in vitro

Second maxillary molars of hamsters were cultured in the presence or absence of 250μg/ml vitamin C for periods up to 12 days. At various days, cultured expiants were studied with histological and biochemical methods to investigate effects of vitamin C-deficiency on matrix production and mineralization in vitro. As biochemical parameters for protein synthesis and mineralization, uptake and incorporation of [ 3H]-proline, 45Ca and 32PO 4 were used. To discriminate between synthesis of collagenous and non-collagenous proteins digestion of the [ 3H]-proline-labelled material by purified collagenase and its degree of hydroxylation were measured. Histologically, in control explants cultured with vitamin C, normal dentinogenesis, amelogenesis and mineralization in vitro were observed. In the vitamin C-deficient expiants, odontoblasts produced an abnormal predentine matrix and de-differentiated. Eventually, this matrix mineralized aspecifically. In the presence of this abnormal matrix, ameloblasts failed to differentiate, which suggests that a cell-matrix type of interaction is involved in the differentiation of the pre-ameloblasts. Biochemically, in the vitamin C-deficient explants protein synthesis and collagen synthesis were reduced by about the same extent; the in-vitro produced collagens appeared under-hydroxylated and could, in degraded form, easily be extracted in formic acid. An increase of [ 3H]-proline solubility in formic acid in the control explants, however, paralleled enamel matrix production and was attributed to the solubilization of proline-rich enamel matrix proteins. The production of acid insoluble phosphate was not affected by vitamin C-deficiency. The uptakes of 45Ca and 32PO 4 were retarded and the molar Ca:PO 4 uptake ratio was lower, reflecting the histologically observed aspecific mineralization.

Effect of developmental stage of explants on further in-vitro development of hamster molars

With morphometrical and biochemical methods the in-vitro development of 1–4-day-old 2nd maxillary molars was studied up to 10 days and compared with previously reported in-vivo development. Incorporation of [ 3H]-thymidine and increase in dry weight were used as biochemical parameters for cell proliferation and growth respectively specific alkaline phosphatase activity and uptake of 45Ca as the measure for mineralization. In expiants of 2–4-day-old hamsters, formation of dentine and enamel matrix was consistent; both mineralized. These expiants attained stages beyond enamel matrix formation, possibly the transitional stages of amelogenesis. The amounts of matrices produced appeared to be related to the final size the expiants attained. Best in-vitro development histologically was in expiants of 2 and 3-day-olds. Thus in-vitro development was qualitatively similar to in vivo.

A morphometric and biochemical study of the pre-eruptive development of hamster molars in vivo

Surface area measurements of cross-sections of M 1 and M 2 at 1–11 days were related to biochemical parameters for cell proliferation ([ 3H]-thymidine incorporation) and mineralization ( 45Ca uptake) and with increase in dry weight. The pre-eruptive development of molar tooth germs was divided into 4 phases which partly reflect the life cycle stages of the ameloblast. In phase 1 (proliferation phase, duration in M 2 about 5 days) mitotic activity and increase in total area were great; ameloblasts were undifferentiated or in a pre-secretory state. In phase 2 (differentiation phase, duration 2–3 days) the number of secretory ameloblasts increased and 45Ca uptake started and increased rapidly. At the end of phase 2, crown morphogenesis was completed and cell proliferation ([ 3H]-thymidine incorporation) became less. In phase 3 (secretion phase, duration 0.5–1 days) all ameloblasts throughout the tooth germ had differentiated into secretory ameloblasts and enamel matrix surface area increased about twice as fast as that of dentine. At the end of phase 3, the surface area of the enamel matrix almost attained its final value. In phase 4 (maturation phase, duration in M 1 till first eruption about 2–3 days), post-secretory ameloblasts increased in number and, in contrast to the surface area of the enamel matrix, that of the dentine continued to increase. The fast, linearly increasing total uptake of 45Ca during phase 4 which was attributed to the mineralization of both newly formed dentine and existing maturing enamel was the main cause of the rapid increase in dry weight of the whole tooth germ.

Fluoride Uptake and Caries Rate in Hamster Molars after Topical Fluoride Application Followed by Acidulation

Daily topical application of 2% NaF on hamster molars for 4 days in vivo, followed by acidulation (grapefruit beverage, pH 3.3) resulted in a lower caries rate than NaF followed by water application. Fluoride uptake was somewhat higher, but not significantly so in the acidulated group.

Influence of calcium, phosphate and complexing substances on inorganic pyrophosphatase in mineralizing hamster molars

The influence of calcium and phosphorus on PP i-ase activity in mineralizing hamster molars was studied in the presence and absence of several complexing substances. These complexing substances inhibited the PP i-ase activity. Only Zn 2+ completely reversed this inhibition. The Ca 2+ stimulation of the PP i-ase was substrate-dependent with an optimal activity at a Ca:PP i ratio of 1. At higher concentrations, Ca 2+ was strongly inhibitory, possibly by forming neutral salts with PP i. The influence of complexing substances on the enzyme was modified by Ca 2+, which changes the mol Ca 2+:PP i ratio or competes slightly with Zn 2+ for the complexing agent. There was a small inhibition of the PP i-ase activity by P i which was not influenced by the substrate used (PP i 4−, Mg-PP i 2−or Ca-PP i 2−. P i can reverse the inhibiting effects of complexing substances to a small extent, except for stronger inhibitions obtained for 0.1 mM EHDP and 2mM Cl 2 MDP. These small in-vitro effects of Ca 2+ and P i on the PP i-ase activity could not explain the great changes in PP i-ase activity in mineralizing molars during normal development and at P i depletion. This supports a stimulating role for the PP i-ase in mineralization. It was concluded that, during mineralization, different Ca 2+ and P i concentrations can modify the inhibitory effects of the complexing substances on the PP i-ase only to a very small extent.

Influence of Various Inhibitors on Alkaline Phosphatase in Calcifying Hamster Molars, Employing Paranitrophenyl Phosphate as Substrate

In mineralizing hamster molars, the influence of several inhibitors on p-NPP-ase has been demonstrated, and compared with their effect on PPi-ase, known to belong to the same enzyme. Whereas the latter activity is much more physiological, p-NPP is a better substrate to distinguish between the effects of bivalent cations on the enzyme or the substrate.

Effect of Strontium and Fluoride Administration on Caries Resistance of Hamster Molars

Effect of Strontium and Fluoride Administration on Caries Resistance of Hamster Molars

Caries-Promoting Properties of Fermented Milk Beverages Containing Live or Killed Lactobacillus

This paper describes the effects of fermented milk beverages, “Yakult”containing live Lactobacilli (Abbreviation: LL beverage), and“Calpis”containing killed Lactobacilli (KL beverage), on caries in hamsters and rats.Golden hamsters of NIH strain and Sprague-Dawley rats were used in the experiment. Microflora normally harboured in the mouth of the rodents were suppressed by providing penicillin in drinking solution for a few days before the experiment started. The animals, uninfected or infected with Streptococcus niutans K1-R, were reared on cariogenic diet #2000 and the beverages or deionized water as drinking fluid for 42 to 60 days. The raw or heat (100°C, 15min.) -treated LL beverage was used at original concentration, and the raw KL beverage at 5-fold diluted concentration. The diet and drinking solutions were continuously available. Molar dentitions of hamsters and rats were scored for dental caries by Keyes' method and the modified Takei's method, respectively.Uninfected hamsters and rats produced almost negligible carious lesions, whereas oral infection of K1-R induced moderate caries in the rodents of control groups receiving deionizd water. When the animals were provided with raw or heat-treated LL beverage continuously for 60 days, caries extents of both uninfected and infected animals became much more severe compared with those of respective controls. Administration of KL beverage also induced severe caries in hamsters reared on the cariogenic diet for 42 days. The ability of both beverages to promote caries with various severities were also demonstrated by analyzing individually the caries scores of 3 molars of hamsters and 14 pit-and-fissures of rat's molars, which were shown to have various caries susceptibilities. The caries development of infected hamsters, however, were reduced to the extent of infected control by providing the beverages intermittently, 3 days and/or 1 day per week. These results clearly indicate that the continuous administration of the beverages promotes various types of caries with various severities in the rodents.In addition, continuous administration of the beverages induced erosion-like lesions on the enamel of molar dentitions, particularly on the occulusal surface of 1st molar. The lesions might be caused by the highly acidic property of the beverages.Experimental animals receiving LL beverage were significantly lower, but not the groups receiving KL beverage, than control animals in body weight gain and diet consumption.

Effect of prenatal, preeruptive, and posteruptive strontium administration on dental caries in hamster molars.

Effect of prenatal, preeruptive, and posteruptive strontium administration on dental caries in hamster molars.

Predisposition to caries in hamsters following the Erosire effect of a commercial citrus beverage administered with and without supplemental fluoride.

A study was undertaken to investigate the effect of a citrus beverage on tooth erosion and predisposition to caries in hamster molars, and to determine if a supplement of 1.9 ppm fluoride to the beverage influences these systems. Results suggest that enamel erosion is a predisposing factor. The addition of physiological fluoride protects the enamel from erosion and caries.

Inorganic pyrophosphatase in mineralizing hamster molars

Inorganic pyrophosphatase contains both Zn2+ and Co2+ in the active center. The highest activity of the enzyme was obtained in the Zn2+ form. EDTA, diphosphonates and L-ascorbic acid are able to inhibit PPi-ase by complexing Zn2+ and Co2+.