Invariant natural killer T cells: innate-like T cells with potent immunomodulatory activities.

Invariant natural killer T (iNKT) cells are a subset of T lymphocytes that react with glycolipid antigens presented by the major histocompatibility complex class I-related glycoprotein CD1d. Although iNKT cells express an antigen-specific receptor of the adaptive immune system, they behave more like cells of the innate immune system. A hallmark of iNKT cells is their capacity to produce copious amounts of immunoregulatory cytokines quickly after activation. The cytokines produced by iNKT cells can influence the level of activation of many cell types of the innate and adaptive immune systems as well as the quality of an adaptive immune response. As such, iNKT cells have emerged as important regulators of immune responses, playing a role in microbial immunity, autoimmunity, tumor immunity, and a variety of inflammatory conditions. Although several endogenous and exogenous glycolipid antigens of iNKT cells have been identified, how these glycolipids orchestrate iNKT-cell functions remains poorly understood. Nevertheless, iNKT cells hold substantial promise as targets for development of vaccine adjuvants and immunotherapies. These properties of iNKT cells have been investigated most extensively in mouse models of human disease using the marine sponge-derived agent alpha-galactosylceramide (alpha-GalCer) and related iNKT-cell antigens. While these preclinical studies have raised enthusiasm for developing iNKT-cell-based immunotherapies, they also showed potential health risks associated with iNKT cell activation. Although alpha-GalCer treatment in humans was shown to be safe in the short term, further studies are needed to develop safe and effective iNKT-cell-based therapies.

Evidence of sex-specific differences in masticatory jaw movement patterns.

The complexity of human oral functional movements has not been studied in detail quantitatively, and only recently have studies begun to evaluate whether such movements contain sex-specific characteristics. Therefore, the purposes of this study were: (1) to quantify in detail the jaw movements and associated masticatory electromyographic activity occurring during gum chewing, and (2) to explore these data for evidence of sex specificity. Fourteen male and 17 female subjects participated in the study. Approximately 11 right- and 11 left-sided chewing cycles and associated masticatory electromyographic activity were sampled from each subject. The samples were quantified into 165 variables per chewing cycle, averaged to create a single multivariate vector for each subject, and then analyzed by a step-wise discriminant analysis. With a combination of 6 variables, a jackknifed cross-validation test found the probability of correct classification to be 93.5%. These findings support the hypothesis that masticatory jaw movements contain sex-specific features.

Effects of diabetes and difluoromethylornithine treatment on hyperplasia, activity of MAP-kinase, and activity and association with cyclin B of p34cdc2 kinase in rat jejunal mucosa.

BACKGROUND: The different signal transduction pathways of rapidly proliferating cells of the intestine are not clearly understood. We report here a possible signaling pathway that involves regulation of activity of two closely related kinases, MAP-K (mitogen-activated protein kinase) and p34cdc2 kinase, during hyperplasia of diabetic jejunal mucosa. Our aim was to investigate the activity and phosphorylation of MAP-K and activity and association of p34cdc2 kinase with cyclin B during diabetes-induced jejunal mucosal hyperplasia in vivo. METHODS: We studied untreated and difluoromethylornithine (DFMO) treated control rats and rats with streptozotocin-induced type I diabetes. Assays were done 10 days after the induction of diabetes. In diabetic rats there was jejunal hyperplasia as indicated by increases in the jejunal mucosal weight/cm and DNA content as well as increased activities of MAP-K and p34cdc2 kinase and association of the latter with cyclin B as compared to corresponding values in control rats. Administration of DFMO, an irreversible inhibitor of the proliferation-associated enzyme ornithine decarboxylase (ODC), prevented diabetes-I induced jejunal hyperplasia and decreased all of the above enzymic parameters in both diabetic and control rats. In our previous in vivo study, DFMO administration also blocked diabetic jejunal hyperplasia and in addition decreased ornithine decarboxylase and tyrosine kinase activities jejunal and tyrosine phosphorylation of proteins. CONCLUSION: Thus the jejunal mucosal hyperplasia found in diabetes appears to involve activation of signal transduction pathways involving tyrosine kinases, MAP-K, p34cdc2 kinase, and cyclin B.

Role of tyrosine kinase, ODC, and p34cdc2 kinase and cyclin B-associated cdc2 in jejunal enterocyte proliferation, maturation, and exfoliation in diabetic and DFMO-treated rats.

BACKGROUND: Several signal transduction pathways involved in rapidly proliferating cells of the intestine are currently not well understood. In the jejunum, crypt enterocytes are constantly replicating, lower villi are maturing, and upper villi are constantly shed. Type I diabetes is associated with jejunal mucosal hyperplasia, and administration of diflouromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase (ODC), causes hypoplasia. Phosphorylation of proteins controls cellular proliferation and/or exfoliation. Cell division cycle kinase (p34cdc2) and cyclin B-associated p34cdc2 kinase regulate the cell cycle during the transition from G2-M phase. Our aims were to: 1) investigate the activities of tyrosine kinase, ODC, total p34cdc2 kinase, and cyclin B-associated p34cdc2 kinase and 2) phosphorylate proteins at tyrosine residues in jejunal upper villi, lower villi, and crypt enterocytes of DFMO-treated control and diabetic rats. METHODS: Diabetes was induced by streptozotocin. DFMO was administered in drinking water in both control and diabetic groups for 10 days after the induction of diabetes. Jejunal enterocytes were isolated and kept frozen at -70 degrees C until ready to process. RESULTS: Diabetic rats showed jejunal mucosal hyperplasia as indicated by increases in the jejunal mucosal weight/cm and DNA content compared to control rats. Diabetic crypt enterocytes showed significant increases in activities of tyrosine kinase, ODC, total p34cdc2 kinase, and cyclin B-associated cdc2 as well as increased phosphorylation of proteins at tyrosine residues compared to control rats. DFMO prevented diabetes-induced jejunal hyperplasia, and decreased the activities of these enzymes and phosphorylation of proteins at tyrosine residues in both diabetic and control rats. Phosphorylation of a 14 kd protein became prominent in crypt, upper villi, and lower villi enterocytes of DFMO-treated diabetic and control groups. CONCLUSION: Diabetic jejunal mucosal hyperplasia appears to involve activation of complex signal transduction pathways such as tyrosine kinase, ODC, p34cdc2 kinase, and cyclin B. These enzymes are involved in proliferation and/or exfoliation of jejunal enterocytes. Our results also suggest that tyrosine phosphorylation of a 14 kd protein may be involved in cell exfoliation and that jejunal mucosal hypoplasia may be a synergistic effect caused by down regulation of the above enzymes.

Altered expression and activity of G-proteins, mitogen activated protein kinases, and tyrosine kinases in aging kidney cortex.

BACKGROUND: Renal function declines with age and this may be related to changes in the expression or activity of various signal transduction proteins in the kidney. METHODS: The present study compared the expression and activity of G alpha i(1-3) and G alpha s phosphorylation of mitogen activated protein kinases (MAP-K) (44 and 42 kd) and the activity of tyrosine kinase in renal cortical homogenates of young (4-month-old) and aging (14-month-old) rats. RESULTS: The GTP/(GTP + GDP) binding ratio of G alpha s was significantly decreased in the kidney cortex of aging rats compared to young rats, while the GTP/(GTP + GDP) binding ratio of G alpha i(1-3) increased significantly in kidney cortex of aging rats. Tyrosine kinase activity and phosphorylation of MAP-K (44 and 42 kd) were also reduced in the kidney cortex of aging rats compared to young rats. CONCLUSIONS: These results suggest that diminished phosphorylation of MAP-K and tyrosine kinase activity as well as changes in the binding of GTP/(GTP + GDP) to G alpha i(1-3) and G alpha s may contribute to the age-related decline in renal tubular and vascular function seen in aging animals.

Comparative evaluation of microleakage of silorane-based composite and nanohybrid composite with or without polyethylene fiber inserts in class II restorations: an in vitro study.

AIM: To evaluate microleakage between nanocomposite and silorane composite in class II restorations with or without a polyethylene fiber insert. METHODOLOGY: Standardized class II cavities were prepared on extracted molars and randomly divided into 4 groups (n=20 each): group 1, Ceram X mono; group 2, Ceram X mono + Ribbond; group 3, Filtek P90; and Group 4, Filtek P90 + Ribbond. All specimens were subjected to a thermocycling regime, immersed in 2% methylene blue dye for 24 hours, sectioned longitudinally, and examined under a stereomicroscope to assess dye penetration on a six-point scale. The score data were subjected to statistical analysis whereby Kruskal-Wallis analysis of variance was used for multiple group comparisons and the Mann-Whitney test for groupwise comparisons at a significance level of p≤0.05. RESULTS: A statistically significant decrease in microleakage was found when Ribbond fiber was used with nanoceramic and silorane composite. A highly significant decrease in microleakage scores was found in silorane composite when compared to nanoceramic composite. CONCLUSION: Use of polyethylene fiber and silorane composite reduces microleakage in class II composite restorations with gingival margins below the cemento-enamel junction.

Intestinal mucosal ornithine decarboxylase and brush border membrane vesicle Na(+)-H+ exchange activities in diabetic rats.

To determine the possibility that intestinal mucosal ornithine decarboxylase activity can modulate mucosal brush border membrane Na(+)-H+ exchange activity, we studied the relationship between jejunal mucosal ornithine decarboxylase activity and mucosal brush border membrane Na(+)-H+ exchange activity in adolescent streptozotocin-diabetic and normal control rats. Diabetes was associated with enhanced intestinal mucosal ornithine decarboxylase and Na(+)-H+ exchange activities. Groups of diabetic and control rats were given difluoromethylornithine in drinking water to suppress intestinal mucosal ornithine decarboxylase activity. As expected, 10 days after induction of diabetes, intestinal mucosal weight (67.7 mg/cm vs 56.1 mg/cm), DNA (47.3 micrograms/mg protein vs 32.7 micrograms/mg protein), ornithine decarboxylase activity (1107 units/hr vs 654 units/hr), and brush border membrane vesicle Na(+)-H+ exchange activity, assessed as Vmax of 22Na+ uptake (32.5 nmol/mg protein/15 min vs 15.2 nmol/mg protein/15 min), were significantly greater in diabetic than in control rats. Treating diabetic and control rats with difluoromethylornithine suppressed jejunal mucosal growth by over 30%, ornithine decarboxylase activity by over 80%, and brush border membrane vesicle 22Na+ uptake by over 60%. Highly significant direct correlations (r > 0.900) were observed between jejunal DNA content, mucosal ornithine decarboxylase activity, and brush border membrane vesicle Na(+)-H+ exchange activity. The above findings suggest that jejunal mucosal ornithine decarboxylase activity can modulate mucosal epithelial proliferation and mucosal brush border membrane Na(+)-H+ exchange activity.

Polyamines and intestinal epithelial hyperplasia in streptozotocin-diabetic rats.

We measured specific activity of ornithine decarboxylase (ODC) and contents of putrescine and of the polyamines (spermidine and spermine) in isolated villus and crypt enterocytes from the jejunum of adolescent streptozotocin-diabetic and weight-matched control rats and diabetic and control rats treated with difluoromethyl ornithine (DFMO) 10 days after induction of diabetes. Consistent with previous observations by others of elevated ODC activity and contents of putrescine and of the polyamines in the intestinal epithelium undergoing hyperplasia, our studies showed elevated ODC activity and contents of putrescine and spermidine, but not of spermine, in the hyperplastic intestinal epithelium of diabetic rats. As in previous studies, suppression of ODC activity by DFMO prevented not only the jejunal epithelial hyperplasia in the diabetic rats, but also retarded jejunal epithelial growth in the control rats. DFMO administration lowered ODC activity by over 80% in both diabetic and control rat enterocytes and prevented the rise in enterocyte contents of putrescine and spermidine in the diabetic rat. The observation that, in both diabetic and control rats, treatment with DFMO lowered spermidine content in the crypt enterocytes but had no similar consistent effect on contents of putrescine or spermine suggested that spermidine could have been responsible for the intestinal epithelial hyperplasia in the diabetic rats and for the normal growth of the intestinal epithelium in control rats.

Relation of ornithine decarboxylase and tyrosine kinase activity in the jejunal mucosa in vivo.

Our aim was to study the relationship between jejunal mucosal activity of ornithine decarboxylase and tyrosine kinase during proliferation in adolescent rats in vivo. Their relationship in the proliferating intestinal mucosa under in vivo conditions has not been reported before. From the results of in vitro studies, it was speculated that tyrosine kinase activity modulated ornithine decarboxylase activity during colonic mucosal proliferation (Majumdar AP. Am J Physiol 259:G626-G630, 1990). Jejunal mucosal hyperplasia was induced by Type 1 diabetes and suppressed in both control and diabetic rats by administration of difluoromethylornithine. Jejunal mucosal weight and enzyme activity were determined after 3, 6, and 10 days, and tyrosine-specific phosphorylated proteins after 10 days of induction of diabetes. Difluoromethylornithine suppressed jejunal mucosal proliferation and tyrosine kinase activity after the 6- and 10- day study periods. After the 3-day study period although jejunal mucosal growth was suppressed, tyrosine kinase activity was not. Activity of tyrosine kinase and ornithine decarboxylase were highly significantly correlated at all time periods in both control and diabetic rats. Tyrosine-specific phosphorylated proteins of 34, 54, 80, and 200 kDa proteins were observed in jejunal mucosa of both control and diabetic rats. In the difluoromethylornithine-treated rats, phosphorylation of the above proteins was negligible while the phosphorylation of a 14-kDa protein was prominent. We speculate that in vivo ornithine decarboxylase activity may be modulating tyrosine kinase activity and that phosphorylation of a 14-kDa protein was associated with suppressed mucosal growth in difluoromethylornithine-treated rats.