František Tichý

Fate of the molar dental lamina in the monophyodont mouse.

The successional dental lamina (SDL) plays an essential role in the development of replacement teeth in diphyodont and polyphyodont animals. A morphologically similar structure, the rudimental successional dental lamina (RSDL), has been described in monophyodont (only one tooth generation) lizards on the lingual side of the developing functional tooth. This rudimentary lamina regresses, which has been proposed to play a role in preventing the formation of future generations of teeth. A similar rudimentary lingual structure has been reported associated with the first molar in the monophyodont mouse, and we show that this structure is common to all murine molars. Intriguingly, a lingual lamina is also observed on the non-replacing molars of other diphyodont mammals (pig and hedgehog), initially appearing very similar to the successional dental lamina on the replacing teeth. We have analyzed the morphological as well as ultrastructural changes that occur during the development and loss of this molar lamina in the mouse, from its initiation at late embryonic stages to its disappearance at postnatal stages. We show that loss appears to be driven by a reduction in cell proliferation, down-regulation of the progenitor marker Sox2, with only a small number of cells undergoing programmed cell death. The lingual lamina was associated with the dental stalk, a short epithelial connection between the tooth germ and the oral epithelium. The dental stalk remained in contact with the oral epithelium throughout tooth development up to eruption when connective tissue and numerous capillaries progressively invaded the dental stalk. The buccal side of the dental stalk underwent keratinisation and became part of the gingival epithelium, while most of the lingual cells underwent programmed cell death and the tissue directly above the erupting tooth was shed into the oral cavity.

Histotopography of Selected Enzymes in the Liver of Calves on Standard and Ca-deficient Diets

Tichy F., D. Horky; Histotopography of Selected Enzymes in the Liver of Calves on Standard and Ca-deficient Diets. Acta vet. Brno, 52, 1983: 131-143. Histochemical demonstration of enzymes in the liver of calves reared on a standard and a Ca-deficient diet is presented with regard to possible changes in the intensity of catalytic enzyme activity due to calcium deficiency. Liver tissue samples were collected from two calves fed a Ca-deficient diet and one animal fed a standard diet. The calves were 2 months old. By means of specific reactions the following enzymes were demonstrated: alkaline phosphatase (EC 3.1.3.1); acid phosphatase (EC 3.1.3.2), lactic dehydrogenase (EC 1.l.l.27), succinic dehydrogenase (EC 1.3.99.1), glycerophosphate dehydrogenase (EC l.1.1.8), and non-specific esterase (EC 3.1.1.1) Further, polysaccharides were determined by the PAS method. Besides the histotopographic determination of the above mentioned enzymes, semiquantitative comparison of intensity of their catalytic activities was made. Evaluation of these data indicated differences in liver enzyme endowment between the experimental and control animals, particularly as far as the catalytic activity of both phosphatases, lactate dehydrogenase and non-specific esterase are concerned. These enzymes seem to be affected by the calcium deficiency in the diet. There were no substantial differences in topography of the enzymes. Catalytic activity, enzymes, topography, Ca-deficiency, diet. Intensive research into the liver functions from the viewpoint veterinary diagnosis has been carried out since about 30 years. Major contributions to our knowledge are those of clinical biochemistry and pathological physiology. Histochemical evidence of enzymes has usually been mentioned with regard to experimental methods (Lojda 1966; Vacek 1972) or to biochemical quantitative determination of enzyme activities (Pojer et al. 1963). The majority of literature data have been oriented to clinical hepatology and differential diagnosis of liver diseases (Hegglin 1972; Pojer et al. 1968; Ganong 1978). In this work histochemical evidence of several enzymes in the liver is presented. Special attention was given to enzyme topography in the liver parenchyma. The data were obtained from calves fed different diets and the effect of the diets was considered, too. Materials and Methods Liver samples were collected from 2 calves fed a Ca-deficient diet from the age of 1 week until the day of sampling at the age of 2 months, and from one control calf of the same age fed a standard diet (see Table 1). The bioptic samples were immediately frozen and cut with a CRYO-CUT (American National Corporation).