High beta-galactosidase and ganglioside GM1 levels in the human parotid gland.

BACKGROUND: Ganglioside G(M1) is a membrane glycolipid typical of nerve cell membranes, where it partakes in neurotransmitter release and is catabolized by the lysosomal beta-galactosidase (GM1ase) (EC 3.2.1.23). After demonstrating a novel degenerative disease of the parotid gland in mice deficient in GM1ase, mimicking the human storage disease GM(1) gangliosidosis, we studied GM1ase and ganglioside G(M1) content in the human parotid glands. STUDY DESIGN: Levels of GM1ase and ganglioside G(M1) were determined in samples of parotid tissues and neighboring muscle (as a negative control) for 3 subjects. Tissues were also processed for histochemical demonstration of GM1ase. RESULTS: The mean specific activity of GM1ase was more than 6-fold higher in the healthy human parotid tissues (1.4 +/- 0.5 nmol of 4-methylumbelliferone per minute per milligram of protein) relative to the neighboring muscle tissue (0.23 +/- 0.07 nmol of 4-methylumbelliferone per minute per milligram of protein). Activity of GM1ase was histochemically localized mainly to striated duct and acinar cells of the parotid gland. Ganglioside G(M1) content in the parotid gland was on average 30-fold higher relative to muscle. CONCLUSIONS: Our results are consistent with previous findings reported in the mouse and the rabbit, and probably reflect a general property of the mammalian parotid glands. The novel mechanism we previously proposed for the mouse parotid saliva secretion, mimicking neurotransmitter release in ganglioside G(M1)-containing nerve cells, is probably applicable also to the human parotid gland. Similarly, the human parotid gland is probably also severely affected in GM(1) gangliosidosis.

Orthodontic, genetic, and periodontal considerations in the treatment of impacted maxillary central incisors: A study of twins.

Treatment of twins each with one impacted maxillary central incisor and a mesiodens is described. Treatment included rapid expansion, extraction of the mesiodens, surgical exposure of the impacted central incisor, and its forced eruption. The impacted incisor was brought into functional position in one patient but was lost in the other because of insufficient root length and high mobility. Orthodontic, genetic, and periodontal considerations of these 2 cases are evaluated.

Mechanism in inhibitory effects of vitamin K2 on osteoclastic bone resorption: in vivo study in osteopetrotic (op/op) mice.

Osteoclast deficiency in op/op mice was cured by a single injection of 5 micrograms recombinant human macrophage colony-stimulating factor (M-CSF). On d 5, the osteoclast number reached a maximum value. By d 15, the osteoclast number had decreased to about 70% of the maximum level. Moreover, by d 20, the osteoclast number had decreased to about 30% of its maximum level. On d 5, the osteoclast number of vitamin K2 12 h previously had decreased to about 30% of the M-CSF-only injected mice. Moreover, on d 5, the osteoclast number of the mice receiving a single injection of vitamin K2 24 h previously had decreased to about 15% that of mice injected only with M-CSF. These results indicate that vitamin K2 inhibits in vivo osteoclast formation. On d 20, the osteoclast number of the mice injected with a single dose of vitamin K2 12 or 24 h previously had decreased to 0% compared with those receiving only M-CSF. The present results suggest that the vitamin K2 "causes cell death" to mature osteoclasts and inhibits in vivo osteoclast formation.

High levels of GM(1)-ganglioside and GM(1)-ganglioside beta-galactosidase in the parotid gland: a new model for secretory mechanisms of the parotid gland.

A new model for the subcellular basis of parotid secretion is presented in this article. GM(1)-ganglioside, typically found in neural tissues, is shown to be abundant in the parotid gland. This ganglioside may play a central role in membrane turnover mechanisms underlying exocytosis/endocytosis in its role as a promoter of membrane fusion or a fusogen. The lysosome and lysosomal hydrolases also play a central role in this model in catabolism of GM(1)-ganglioside. Consequently, high levels of the lysosomal hydrolase acidic beta-galactosidase are demonstrated in the salivary gland. GM(1)-gangliosidosis of the parotid glands, as described in mice, appears to be the first single-gene heritable disease found so far in the salivary glands.

Lack of the bone remodeling in osteopetrotic (op/op) mice associated with microdontia.

Osteopetrosis is an inherited metabolic disease characterized by an excessive accumulation of bone. This is associated with an osteoclast deficiency. Osteopetrosis is always accompanied by the failure and/or delay of tooth eruption. The present study was conducted to examine in detail the morphological and histological changes of growth of the third molars in the osteopetrosis (op/op) mouse. At the age of 10 days, normal and op/op mice showed no detectable difference in the shape of the third molar follicles. However, the third molars in the op/op mouse became obscured by the proliferation of neighboring bone trabeculae. Moreover, no tartrate-resistant acid phosphatase-positive cells were detected on the bone surfaces of 10-day-old op/op mice. Ankylosis between the root dentin and proliferating bone trabeculae was a common feature in the 20- and 30-day-old op/op mice. The third molars erupted into the oral cavity before the age of 30 days in normal mice, and the crowns, roots, and periodontal ligaments appeared well developed. Throughout the experiment, it seemed that the primary cause of the microdontia and ankylosis of the developing root in the mutant mouse was a deficiency of osteoclasts, with attendant lack of bone remodeling.

High levels of GM1-ganglioside beta-galactosidase in the salivary glands and GM1-like-ganglioside storage in parotids of deficient mice.

We have previously demonstrated high levels of GM1-ganglioside beta-galactosidase (beta-gal) in the salivary glands of Swiss-Webster mice (Nowroozi et al., J Craniofac Genet Dev Biol 18:51, 1998), and suggested that this activity reflects an important role for the lysosome in catabolism of salivary glycoconjugates. Here, we characterized and compared activities of lysosomal glycosidases among the salivary glands, spleen, and muscle of C57BL/6 mice, beta-gal hexosaminidase, and beta-glucuronidase activities are high in all three glands relative to muscle. Enzyme activities in the sublingual gland were substantially higher than in the submandibular and parotid glands. Spleen displays levels of activity that are comparable or higher (for beta-glucuronidase) than those in the salivary glands, whereas muscle displays substantially lower levels of these lysosomal glycosidases. In order to investigate the role of beta-gal in the salivary glands, we further characterized the salivary phenotype of knock-out mice deficient in this enzyme, mimicking human GM1-gangliosidosis. In contrast with the relative levels of beta-gal specific-activity among the salivary glands, only the parotid developed severe, generalized, degenerative histopathological changes in beta-gal-deficient knock-out mice. GM1-like-ganglioside, typically found at high levels only in the nerve tissue, where its exact function is still not clear, was demonstrated in storage vacuoles of the parotid glands of the deficient mice by binding of cholera toxin subunit B. Thus, beta-gal activity observed in the parotid gland most likely reflects its role in GM1-ganglioside catabolism, and this ganglioside, never previously reported in the salivary glands, may have a role in parotid exocrine secretory functions. beta-gal may also serve in secretory glycoprotein catabolism in other salivary glands, but this function may be non-essential for these glands.

Two gene products for beta-galactosidase are differentially expressed in the mouse salivary glands.

The specific activity of GM1 ganglioside beta-galactosidase, also known as lysosomal or acidic beta-galactosidase, and the neutral beta-galactosidase were determined in the mouse three major salivary glands and compared to other tissues. Our data indicate that at pH 4.4, lysosomal beta-galactosidase activity in the submandibular gland and the sublingual gland of the mature male is the higher than in the parotid gland, kidney, and skeletal muscle. At pH 7.3, neutral beta-galactosidase activity is overall much lower and is higher in the submandibular gland compared to the sublingual and the parotid glands, kidney, and muscle. En bloc histochemical staining of tissues using x-gal as a substrate at pH 4.4 demonstrates high beta-galactosidase activity in all three salivary glands in comparison to skeletal muscle. At pH 7.3, the submandibular gland demonstrates higher activity, whereas the parotid appears negative and the sublingual gland demonstrates intermediate activity levels. En bloc staining using x-fucose (another substrate of lysosomal beta-galactosidase) demonstrates high activity in all three glands at pH 4.4, and no activity in any of the glands at pH 7.3. Microscopic histochemistry indicates that beta-galactosidase activity is localized to parenchymal cells. Thus, the two gene products for beta-galactosidase are differentially expressed in the salivary glands. These novel findings question the previous use of the bacterial beta-galactosidase (lacZ) as a reporter gene in the salivary glands. Endogenous beta-galactosidase activity in the salivary glands is probably related to glycoprotein metabolism, processing glycoconjugates containing a terminal beta-galactosidic linkage. Further studies of beta-galactosidase function and differential regulation in these tissues are needed.

Development, maturation, and aging of the alveolar bone. New insights.

Osteoblasts and bone tissue of the mandibular and maxillary alveolar processes substantially differ from osteoblasts and bone in other parts of the skeleton. These differences are apparent during embryonic development, maturation, and aging of these bones. The cellular and molecular basis for these differences is still not clear, but it is unfolding at record speed.

Endochondral and intramembranous fetal bone development: osteoblastic cell proliferation, and expression of alkaline phosphatase, m-twist, and histone H4.

We have previously studied the expression of alkaline phosphatase (ALP) and alpha2(I) collagen (two phenotypic markers of osteoblastic cell differentiation) during development of the rat mandible, and the spatial and temporal distribution of the respective transcripts. Our current studies utilize the rat mandible and hind foot as in vivo model systems to investigate the relationship between osteoblastic differentiation and proliferation during intramembranous and endochondral bone formation. Pregnant rats, at 15.17, and 19 days of gestation were intraperitoneally injected with various doses of [3H]-thymidine, and sacrificed at various time intervals in order to label dividing embryonic osteoblastic and preosteoblastic cells. Cross sections through the mid-body of 15-day embryos showed [3H-thymidine dose-dependent labeling of a relatively high percentage of cells in the liver (49 +/- 8% at 440 muCi) and a lower percentage of cells of the developing vertebral cartilage (29 +/- 6% at 440 muCi). ALP-positive condensed mesenchyme--consisting of mandibular preosteoblast (15 days of gestation) showed a relatively high (32 +/- 5%) level of [3H]-thymidine labeling, compared to surrounding ALP-negative loose mesenchymal cells (22 +/- 1%). Similar results were observed in the developing hind foot of 19-day embryos for ALP-positive cells (15 +/- 6%) and surrounding ALP-negative cells (13 +/- 5%). In both the hind foot and the mandible an overall decrease in labeling was observed during bone development. RNA samples from these tissues show increasing amounts of ALP mRNA, and decreasing amounts of histone H4 mRNA between days 15 and 19 of gestation. These data indicate that a general inverse correlation between osteoblastic differentiation and proliferation, similar to the correlation previously described in cultured osteogenic cells, is also present in developing bones in vivo. However, these results indicate that ALP-positive preosteoblasts, committed to the osteoblastic lineage, maintain their proliferative capacity. In an attempt to elucidate underlying molecular mechanisms, we further investigated the levels of expression of m-twist in these tissues. This member of the basic helix-loop-helix family of transcription regulators has been previously implied as playing a role in osteoblast differentiation in culture. Our results demonstrate a decrease in m-twist levels during bone development in both the mandible and the hind foot.

Dental patients' perceptions in a multiethnic environment.

Ethnic relations in multicultural metropolitan areas such as Los Angeles are extremely complex and are probably reflected, at least in part, in the relations between dental providers and their patients. The goals of this study were to determine whether dental services provided by providers of a different ethnic group and whether there was a direct relation between the level of patient anxiety and the level of preference for providers of the same ethnicity. Patients at the University of Southern California School of Dentistry were surveyed using a 29-item questionnaire. The survey included questions concerning preference for their provider's ethnicity and gender, dental anxiety, dental satisfaction, dental health, and socioeconomic status. The study focused on the four most common groups of patients at USCSD: Asians, Blacks, Caucasians and Hispanics, and their perceptions with regard to the dental providers of five potential ethnic backgrounds: Asian, Black, Caucasians, Hispanics and Middle Eastern. The majority of patients in all ethnic groups reported no preference for the ethnicity of their provider listed their own ethnicity. Moreover, the recorded preference levels for providers of the own ethnicity in the Hispanic group were consistently higher in correlation with higher dental anxiety, lower satisfaction with dental treatment, and poorer dental health. Our study suggests that ethnic relations are a significant factor in the dental office in Southern California.

Evaluation of horizontal and vertical differences in facial profiles by orthodontists and lay people.

A novel video image processing technique was used to evaluate changes in the facial profile mimicking the effects of various orthognathic surgical techniques. Incremental changes were introduced in male and female images simulating the effects of mandibular advancement or set-back, maxillary advancement or set-back, and maxillary impaction. Twenty-two clinicians and 22 lay people completed questionnaires evaluating their level of sensitivity to changes in the facial profiles and their preferences regarding alternative profiles. The results indicate that in judging realistic color video images, both orthodontists and lay people are sensitive to relatively small horizontal changes in the facial profile. In contrast, orthodontists are less sensitive to relatively large vertical changes but more sensitive to horizontal mandibular changes.