Angiostatin Inhibition of Vascular Endothelial Growth Factor– Stimulated Nitric Oxide Production in Endothelial Cells

Angiostatin (AS), a proteolytic fragment of plasminogen, is a potent antiangiogenic factor. It was reported that AS attenuates the vasodilatory response to vascular endothelial growth factor (VEGF) in isolated interventricular arterioles. Here, we investigated the effect of AS on nitric oxide (NO) production in human umbilical vein endothelial cells (HUVECs). AS inhibited VEGF-stimulated NO production in a dose-dependent manner, whereas AS alone did not affect basal NO production. Disruption of kringle structures by reduction of disulfide bonds resulted in the loss of the inhibitory effect of AS on VEGF-stimulated NO production. To elucidate how AS might impair VEGF activation of endothelial NO synthase (eNOS), we further examined whether AS would affect Ca²⁺-dependent and -independent pathways of eNOS activation. AS had no effect on the transient increase in cytosolic Ca²⁺ levels elicited by VEGF. In contrast, AS prevented VEGF-potentiated eNOS phosphorylation at Ser1177. These results clearly indicate that AS inhibits VEGF-stimulated NO production in HUVECs without affecting basal NO production. The kringle structures of AS are required for this effect, and impairment of Ser1177 phosphorylation of eNOS might be involved in the inhibition of VEGF-stimulated NO production by AS.     

Activation of STAT3, MAPK, and AKT in malignant astrocytic gliomas: correlation with EGFR status, tumor grade, and survival

Diffuse astrocytic gliomas are the most common human glial tumors with glioblastoma being the most malignant form. Epidermal growth factor receptor (EGFR) gene amplification is one of the most common genetic changes in glioblastoma and can lead to the activation of various downstream signaling molecules, including STAT3, MAPK, and AKT. In this study, we investigated the activation status of these 3 signaling molecules as well as wild-type (EGFRwt) and mutant (EGFRvIII) EGFR in 82 malignant astrocytic gliomas (55 glioblastomas and 27 anaplastic astrocytomas) using immunohistochemistry. The presence of EGFRwt, but not EGFRvIII, immunopositivity correlated significantly with prevalent EGFR gene amplification in glioblastomas. STAT3 and AKT activation correlated significantly with EGFR status, although the correlation for p-STAT3 was attributed exclusively to EGFRvIII. The distribution of these 3 activated molecules varied significantly with tumor grade; although activation of STAT3 was essentially identical between anaplastic astrocytomas and glioblastomas, an increase in the activation of MAPK and AKT appeared to correlate with the progression of anaplastic astrocytoma to glioblastoma. Finally, activated STAT3 and AKT were marginally predictive of improved and worse prognosis, respectively. Taken together, these findings begin to elucidate the interrelationship between these signaling pathways in astrocytic gliomas in vivo.     

Effects of CO2 laser debonding of a ceramic bracket on the mechanical properties of enamel

Objective:To investigate the effects of CO₂ laser debonding of a ceramic bracket on the mechanical properties of tooth enamel.Materials and Methods:Fifty-three human premolars were used in this study. The temperature changes of cross-sectioned specimens during laser irradiation were monitored with an infrared thermographic microscope system. Different laser output settings (3, 4, 5, and 6 W) were compared. The shear bond strength of brackets after laser irradiation was measured for specimens bonded with a conventional etch and rinse adhesive or with a self-etching adhesive, and the adhesive remnant index score was calculated. The hardness and elastic modulus of cross-sectioned enamel after laser irradiation were investigated by the nanoindentation test. Data were compared by one-way and two-way analysis of variance, followed by the Scheffé test.Results:The temperature of enamel increased by about 200°C under CO₂ laser irradiation with a relatively high output (5 and 6 W), and a temperature increase of about 100°C to 150°C was seen under laser irradiation with a low output (3 and 4 W). The bracket shear bond strength decreased under all laser irradiation conditions. The hardness and elastic modulus of enamel were not affected by CO₂ laser debonding.Conclusion:CO₂ laser debonding may not cause iatrogenic damage to enamel.     

A novel point mutation affecting the tyrosine kinase domain of the TRKA gene in a family with congenital insensitivity to pain with anhidrosis

A nerve growth factor receptor encoded by the TRKA gene plays an important part in the formation of autonomic neurons and small sensory neurons in dorsal root ganglia and in signal transduction through its intracytoplasmic tyrosine kinase domain. Recently, three mutations in the tyrosine kinase domain of TRKA have been reported in patients with congenital insensitivity to pain with anhidrosis, which is an autosomal recessive disorder characterized by recurrent fever due to absence of sweating, no reaction to noxious stimuli, self-mutilating behavior, and mental retardation. We examined the TRKA gene in five generations of a large Japanese family with many consanguineous marriages who live in a small remote island of the southern part of Japan. We found a novel point mutation at nucleotide 1825 (A-->G transition) resulting in Met-581-Val in the tyrosine kinase domain. Two of the three affected patients were homozygous for this mutation; however, the third affected patient was heterozygous. Further analysis revealed that the third patient was a compound heterozygote with the Met-581-Val mutation in one allele and with a single base C deletion mutation at nucleotide 1726 in exon 14 in the other allele, resulting in a frameshift and premature termination codon.     

A unique B2 B cell subset in the intestine

Over 80% of the body's activated B cells are located in mucosal sites, including the intestine. The intestine contains IgM(+) B cells, but these cells have not been characterized phenotypically or in terms of their developmental origins. We describe a previously unidentified and unique subset of immunoglobulin M(+) B cells that present with an AA4.1(-)CD21(-)CD23(-) major histocompatibility complex class II(bright) surface phenotype and are characterized by a low frequency of somatic hypermutation and the potential ability to produce interleukin-12p70. This B cell subset resides within the normal mucosa of the large intestine and expands in response to inflammation. Some of these intestinal B cells originate from the AA4.1(+) immature B2 cell pool in the steady state and are also recruited from the recirculating naive B cell pool in the context of intestinal inflammation. They develop in an antigen-independent and BAFF-dependent manner in the absence of T cell help. Expansion of these cells can be induced in the absence of the spleen and gut-associated lymphoid tissues. These results describe the existence of an alternative pathway of B cell maturation in the periphery that gives rise to a tissue-specific B cell subset.