A molecular analysis of the isolated rat posterior frontal and sagittal sutures: differences in gene expression

Although it is one of the most commonly occurring craniofacial congenital disabilities, craniosynostosis (the premature fusion of cranial sutures) is nearly impossible to prevent because the molecular mechanisms that regulate the process of cranial suture fusion remain largely unknown. Recent studies have implicated the dura mater in determining the fate of the overlying cranial suture; however, the molecular biology within the suture itself has not been sufficiently investigated. In the murine model of cranial suture fusion, the posterior frontal suture is programmed to begin fusing by postnatal day 12 in rats (day 25 in mice), reliably completing bony union by postnatal day 22 (day 45 in mice). In contrast, the sagittal suture remains patent throughout the life of the animal. Using this model, this study sought to examine for the first time what differences in gene expression--if any--exist between the two sutures with opposite fates. For each series of experiments, 35 to 40 posterior frontal and sagittal suture complexes were isolated from 6-day-old Sprague-Dawley rat pups. Suture-derived cell cultures were established, and ribonuicleic acid was derived from snap-frozen, isolated suture tissue. Results demonstrated that molecular differences between the posterior frontal and sagittal suture complexes were readily identified in vivo, although these distinctions were lost once the cells comprising the suture complex were cultured in vitro. Hypothetically, this change in gene expression resulted from the loss of the influence of the underlying dura mater. Significant differences in the expression of genes encoding extracellular matrix proteins existed in vivo between the posterior frontal and sagittal sutures. However, the production of the critical, regulatory cytokine transforming growth factor beta-1 was equal between the two suture complexes, lending further support to the hypothesis that dura mater regulates the fate of the overlying cranial suture.     

Effect of enzymatic treatment on calcium absorption by small intestine: a comparative study between rat and rabbit transport mechanisms

Calcium absorption by the small intestine of rat and rabbit reached steady state after 60 min of incubation with intracellular to extracellular ratio of 2.0. Trypsin and neuraminidase significantly inhibited (P less than 0.05) calcium accumulation in rat small intestine. These enzymes showed no significant effect (P greater than 0.05) on calcium transport across rabbit small intestine. The inhibitory action of trypsin and neuraminidase on calcium accumulation by the rat small intestine does not involve the influx of calcium into the intestinal cells.     

Direct branch of external carotid: a masseteric artery

An additional branch of the right external carotid in the form of an unusual direct artery to m. masseter is described. It arose as a terminal branch along with the maxillary and superficial temporal arteries, ran in the substance of the parotid gland to supply the muscle on its lateral aspect. The pertinent anatomical literature is reviewed.     

Interleukin 2 receptor expression by T cells in human aging

Aged individuals have depressed cell-mediated immunity and diminished T cell proliferation to mitogenic and antigenic stimuli. Because T cell responses depend on the surface expression and normal function of interleukin 2 receptors, we measured the quantities and affinities of cell surface IL-2R and the amount of soluble IL-2R alpha chain (p55) release in vitro in PHA-stimulated mononuclear cells from healthy aged (greater than or equal to 65 years old) and young (less than or equal to 39 years old) donors. At the peak of the PHA response, the fraction of cells expressing IL-2R alpha chain (CD25+) was lower in the aged (43% vs 56%, P = 0.033). Relative to the lower proliferation and CD25 expression, old donor cells released unexpectedly high quantities of soluble alpha chain into culture supernatants. However, the average affinities and the mean numbers of high- and low-affinity surface receptors per CD25+ cell were equivalent in cells from eight pairs of aged and young donors (1850 vs 1586 high affinity, and 20,655 vs 23,466 low affinity, P greater than 0.2 for both). The soluble IL-2R released by stimulated cells had no effect on proliferative responses, because addition of saturating doses of exogenous recombinant IL-2 did not increase cellular proliferation, and addition of soluble anchor-minus recombinant IL-2R alpha chain did not suppress it. These results indicate that in healthy older individuals, diminished numbers of T cells can be induced to express cell surface IL-2R following mitogenic stimulation, although aged CD25+ can express a normal complement of IL-2R molecules. In the aged, either CD25+ cells release excessive quantities or a subset of cells synthesizes and releases soluble IL-2R alpha chain into the extracellular environment without expressing it on the cell surface.     

Dose-dependent effect of radiation on angiogenic and angiostatic CXC chemokine expression in human endothelial cells

Blood vessel growth is regulated by angiogenic and angiostatic CXC chemokines, and radiation is a vasculogenic stimulus. We investigated the effect of radiation on endothelial cell chemokine signaling, receptor expression, and migration and apoptosis. Human umbilical vein endothelial cells were exposed to a single fraction of 0, 5, or 20 Gy of ionizing radiation (IR). All vasculogenic chemokines (CXCL1–3/5–8) increased 3–13-fold after 5 or 20 Gy IR. 20 Gy induced a marked increase (1.6–4-fold) in angiostatic CXC chemokines. CXCR4 expression increased 3.5 and 7-fold at 48 h after 5 and 20 Gy, respectively. Bone marrow progenitor cell chemotaxis was augmented by conditioned media from cells treated with 5 Gy IR. Whereas 5 Gy markedly decreased intrinsic cell apoptosis (0 Gy = 16% ± 3.6 vs. 5 Gy = 4.5% ± 0.3), 20 Gy increased it (21.4% ± 1.2); a reflection of pro-survival angiogenic chemokine expression. Radiation induces a dose-dependent increase in pro-angiogenic CXC chemokines and CXCR4. In contrast, angiostatic chemokines and apoptosis were induced at higher (20 Gy) radiation doses. Cell migration improved significantly following 5 Gy, but not 20 Gy IR. Collectively, these data suggest that lower doses of IR induce an angiogenic cascade while higher doses produce an angiostatic profile.     

Transforming growth factor-beta 1 modulates the expression of vascular endothelial growth factor by osteoblasts

Angiogenesis is essential to both normal and pathological bonephysiology. Vascular endothelial growth factor (VEGF) has been implicated in angiogenesis, whereas transforming growth factor-1 (TGF-1) modulates bone differentiation, matrixformation, and cytokine expression. The purpose of this study was toinvestigate the relationship between TGF-1 and VEGF expression inosteoblasts and osteoblast-like cells. Northern blot analysis revealedan early peak of VEGF mRNA (6-fold at 3 h) in fetal rat calvarial cellsand MC3T3-E1 osteoblast-like cells after stimulation with TGF-1 (2.5 ng/ml). The stability of VEGF mRNA in MC3T3-E1 cells was not increasedafter TGF-1 treatment. Actinomycin D inhibited the TGF-1-inducedpeak in VEGF mRNA, whereas cycloheximide did not. Blockade of TGF-1signal transduction via a dominant-negative receptor II adenovirussignificantly decreased TGF-1 induction of VEGF mRNA. Additionally,TGF-1 induced a dose-dependent increase in VEGF protein expressionby MC3T3-E1 cells (P < 0.01).Dexamethasone similarly inhibited VEGF protein expression. BothTGF-1 mRNA and VEGF mRNA were concurrently present in rat membranousbone, and both followed similar patterns of expression during ratmandibular fracture healing (mRNA and protein). In summary,TGF-1-induced VEGF expression by osteoblasts and osteoblast-likecells is a dose-dependent event that may be intimately related to bonedevelopment and fracture healing.