Excellent performance of aromatic polyguanamines induced by multiple hydrogen bondable tetraazacalix[2]arene[2]-triazine ring in their main chain

A series of poly(guanamine) (c-PG)s containing tetraazacalix[2]arene[2]-triazine (mPDA₂CyC₂) were successfully prepared by solution polycondensation of mPDA₂CyC₂ with various aromatic diamines in an aprotic organic solvent with a lithium chloride additive (5 wt%) at 150 °C for 6 hours. The number-average molecular weights (M_n)s of these c-PG polymers reached up to 31 500, with a relatively broad molecular weight distribution (M_w/M_n) of 5.3. They showed good solubility in aprotic organic solvents, such as N-methylpyrrolidone and N,N-dimethylacetamide at a concentration of 2 mg mL⁻¹. The glass transition temperatures (T_g) of the c-PG polymers were in the range 359 °C–392 °C, approximately 160 °C higher than those of counterpart polymers (i.e., with no aza-calixarene-based PG (l-PG)). The coefficients of thermal expansion (CTEs) of the c-PG polymers were 29.7–48.1 ppm K⁻¹ (at 100 °C–150 °C), much lower than those of l-PG samples, i.e., 59.1–85.1 ppm K⁻¹. Transparent and almost colorless c-PG films were successfully prepared by a solution casting method, showing maximum tensile strength (σ_S), modulus (E_γ), and elongation at break (E_b) values of 151 MPa, 6.3 GPa, and 4.4%, respectively, for the c-PG polymer from mPDA₂CyC₂ and 4,4′-oxydianiline monomers. The corresponding l-PG film exhibited σ_S, E_γ, and E_b values of just 76 MPa, 5.4 GPa, and 1.6%, respectively. These outstanding thermal and mechanical properties of the c-PG polymers can be attributed to their multiple hydrogen bonding interaction between mPDA₂CyC₂ residues in the polymer backbone. This interaction was identified by infrared spectroscopy measurements at the broad absorption band around 3000–3400 cm⁻¹.

Poly(guanamine)s containing tetraazacalix[2]arene[2]triazine ring within the polymer main-chain show outstanding thermal and mechanical properties arisen from the multiple-hydrogen bond.

Selective intracellular vaporisation of antibody-conjugated phase-change nano-droplets in vitro

While chemotherapy is a major mode of cancer therapeutics, its efficacy is limited by systemic toxicities and drug resistance. Recent advances in nanomedicine provide the opportunity to reduce systemic toxicities. However, drug resistance remains a major challenge in cancer treatment research. Here we developed a nanomedicine composed of a phase-change nano-droplet (PCND) and an anti-cancer antibody (9E5), proposing the concept of ultrasound cancer therapy with intracellular vaporisation. PCND is a liquid perfluorocarbon nanoparticle with a liquid–gas phase that is transformable upon exposure to ultrasound. 9E5 is a monoclonal antibody targeting epiregulin (EREG). We found that 9E5-conjugated PCNDs are selectively internalised into targeted cancer cells and kill the cells dynamically by ultrasound-induced intracellular vaporisation. In vitro experiments show that 9E5-conjugated PCND targets 97.8% of high-EREG-expressing cancer cells and kills 57% of those targeted upon exposure to ultrasound. Furthermore, direct observation of the intracellular vaporisation process revealed the significant morphological alterations of cells and the release of intracellular contents.

Rapid synthesis and properties of segmented block copolymers based on monodisperse aromatic poly(N-methyl benzamide) and poly(propylene oxide)

Monodisperse aromatic N-methyl benzamide-based molecules (M_w/M_n = 1.02–1.04) with terephthalic acid at both sides (MABx–x) were rapidly prepared by a step-wise reaction using the reported one-pot dendrimer synthetic method.

Synthesis of highly refractive and highly fluorescent rigid cyanuryl polyimines with polycyclic aromatic hydrocarbon pendants

A series of rigid cyanuryl polyimines, polyguanamines (PGs) bearing polycyclic aromatic hydrocarbon pendants were successfully synthesized from 2-substituted 4,6-dichloro-1,3,5-triazine and aromatic diamine monomers.

Fatal tracheal aspergillosis during rituximab combined chemotherapy for diffuse large B-cell lymphoma that developed after lung transplantation

Invasive tracheal aspergillosis (ITA) is an infection that is unique to patients who have undergone lung transplantation (LT). Although the activity of this disease often appears on imaging, we encountered a case of ITA that became exacerbated, despite few computed tomography (CT) findings, during rituximab combined chemotherapy for diffuse large B-cell lymphoma. ITA developed during immunosuppressive therapy after LT. Because CT findings may show false-negative results, bronchoscopy is recommended for such cases.

Stress-induced ceramide generation and apoptosis via the phosphorylation and activation of nSMase1 by JNK signaling

Neutral sphingomyelinase (nSMase) activation in response to environmental stress or inflammatory cytokine stimuli generates the second messenger ceramide, which mediates the stress-induced apoptosis. However, the signaling pathways and activation mechanism underlying this process have yet to be elucidated. Here we show that the phosphorylation of nSMase1 (sphingomyelin phosphodiesterase 2, SMPD2) by c-Jun N-terminal kinase (JNK) signaling stimulates ceramide generation and apoptosis and provide evidence for a signaling mechanism that integrates stress- and cytokine-activated apoptosis in vertebrate cells. An nSMase1 was identified as a JNK substrate, and the phosphorylation site responsible for its effects on stress and cytokine induction was Ser-270. In zebrafish cells, the substitution of Ser-270 for alanine blocked the phosphorylation and activation of nSMase1, whereas the substitution of Ser-270 for negatively charged glutamic acid mimicked the effect of phosphorylation. The JNK inhibitor SP600125 blocked the phosphorylation and activation of nSMase1, which in turn blocked ceramide signaling and apoptosis. A variety of stress conditions, including heat shock, UV exposure, hydrogen peroxide treatment, and anti-Fas antibody stimulation, led to the phosphorylation of nSMase1, activated nSMase1, and induced ceramide generation and apoptosis in zebrafish embryonic ZE and human Jurkat T cells. In addition, the depletion of MAPK8/9 or SMPD2 by RNAi knockdown decreased ceramide generation and stress- and cytokine-induced apoptosis in Jurkat cells. Therefore the phosphorylation of nSMase1 is a pivotal step in JNK signaling, which leads to ceramide generation and apoptosis under stress conditions and in response to cytokine stimulation. nSMase1 has a common central role in ceramide signaling during the stress and cytokine responses and apoptosis.

Trisomy 8 and urogenital malformation in the ACI-rat

ACI-rats are considered as a model for studying urogenital abnormalities. In order to recognise cytogenetic changes related to these abnormalities 50 male ACI/Seg rats were examined by means of gross macroscopic, histological, and karyotypical investigations. In six of the examined animals (12%) unilateral agenesis of the kidney and ipsilateral hypoplasia of the testes and seminal vesicles were observed. Isochromosome 8 and trisomy 8 (i8, +8) were observed in 26.5% of karyotypes from the animals with kidney agenesis. Chromosome heteromorphisms such as 1p+, 3p+, 11p+, 12p+ were found in animals with and without apparent pathology. Because of the similarity between the phenotypical changes found in ACI-rats and in patients with familial renal agenesis (Potter's syndrome) and hereditary renal agenesis and aplasia (HRA), rat and human chromosomes associated with manifested renal malformations were examined by comparative cytogenetics and gene mapping.

Hemichrome formation observed in human haemoglobin A under various buffer conditions

AIM

To observe hemichrome formation in human haemoglobin A under various buffer conditions.

METHOD

Hemichrome formation of human oxyhaemoglobin A (HbO2) was studied spectrophotometrically in 0.1 m buffer at various temperatures and pH values.

RESULTS

Following autoxidation in ferrous HbO2, it was evident that formation of hemichrome, which tends to precipitate, occurred at various stages during the course of the autoxidation reaction namely at initial, intermediate or final stages, depending on temperature and pH of the solution. By varying temperature of the solution from 35 to 55 degrees C and pH from 4.5 to 10.5, it is shown here that HbO2 exhibits high susceptibility for hemichrome formation and its occurrence is a function of pH, temperature and progress of autoxidation of HbO2. Unlike HbO2 and its separated haemoglobin chains, monomeric bovine heart myoglobin (MbO2) did not easily form hemichrome.

CONCLUSION

These findings provide a clue on the crucial role of haemoglobin molecule for senescent cell recognition or homeostasis in the blood circulation.

Micro X-ray computed tomography analysis for the evaluation of asymmetrical condylar growth in the rat

OBJECTIVES

To investigate the influence of forced lateral bite on mandibular growth, micro X-ray computed tomography (CT) was used for the purpose evaluating condylar cartilage and cancellous bone formation in 10 male Wister rats (3 weeks of age). SETTINGS AND SAMPLE POPULATION: The rats were divided into two groups--experimental and control. In experimental group, an inclined crown was cemented onto the maxillary incisors to produce 2.5 mm shift toward the left side during mastication. Right-left differences in whole mandibular length, mandibular height, condylar size, trabecular structure of the condylar head and three-dimensional (3-D) finite element analysis were assessed using 3-D images reconstructed from micro X-ray CT scans when the mice had reached 21 weeks.

MEASUREMENTS AND RESULTS

Asymmetrical growth was found in the experimental group, in which the left condylar head became thicker and shorter than the right condylar head during development. When comparing the left and right condyles of the experimental animals, histomorphometric analysis from micro X-ray CT showed that the bone volume (BV) of the cancellous bone, the surface area of the cancellous bone (BS), the BS/BV ratio, the BV fraction (BV/TV), and the trabecular thickness and trabecular number were less for the right condyle than for the left condyle.

CONCLUSIONS

These findings suggested that artificial changes in the mastication do influence the growth of condylar head, condylar bone trabecular structure, and mineralization.

Measurement of mechanical strain on mandibular surface with mastication robot: influence of muscle loading direction and magnitude

OBJECTIVES

To investigate the mechanical effects of mastication on the mandible, we developed computational controlled mastication robot system with human dry skull and analyzed the strain distribution on the mandibular bone surface.

DESIGN

In the mastication robot, the mandible was suspended by eight wires, which simulated masticatory muscles. A non-linear spring damper generated viscoelastic properties, and tension sensors for simulation of jaw reflection to avoid unusual biting force were applied as a biological feedback mechanism. By using this robot system, various patterns of muscle loading (change of wire direction and magnitude) were performed.

RESULTS

From the results, significant differences in the amount of principal strain and its distribution were demonstrated in each condition (ANOVA, post hoc test, and p < 0.05). The value of maximum principal strain ranged from 79.66 x 10(-6) [at anterior border of ramus (Buccal side), 128 N] to -1.42 x 10(-6) [at foramen mentale (Buccal side), 32 N].

CONCLUSION

These results suggested that the muscle loading generated the mechanical strain on the mandibular bone surface and it was affected by the changes in loading direction and magnitude.

Renal blood flow measurement with contrast-enhanced harmonic ultrasonography: evaluation of dopamine-induced changes in renal cortical perfusion in humans

BACKGROUND

An accessible non-invasive method for evaluating renal regional blood flow in real time is highly desirable in the clinical setting. Recent progress in ultrasonography with microbubble contrast has allowed quantification of regional blood flow in animal models.

AIMS

Goal ofthis study was to establish a convenient contrast--enhanced harmonic ultrasonography (CEHU) method for evaluating renal cortical blood flow in humans.

METHODS

We carried out intermittent second harmonic imaging in 9 healthy volunteers. Pulse interval was progressively decreased from 4 s - 0.2 s during continuous venous infusion of the microbubble contrast agent.

RESULTS

Pulse interval versus CEHU-derived acoustic intensity plots provided microbubble velocity (MV) and fractional vascular volume (FVV) during renal cortical perfusion in humans. Low-dose dopamine infusion (2 microg/min/kg) resulted in a significant increase in MV which correlated well with the increase in total renal blood flow (RBF) determined by a conventional study of p-aminohippurate clearance (C(PAH)) (r = 0.956, p < 0.0001). Although FVV was not significantly increased, alterations in CEHU-derived renal cortical blood flow calculated by the products of MV and FVV were also correlated with alterations in total RBF (r = 0.969, p < 0.0001). Thus, low-dose dopamine infusion increases renal cortical blood flow observed in CEHU, mainly by increasing MV.

CONCLUSIONS

The present study shows that renal cortical blood flow in humans can be measured non-invasively by CEHU and that CEHU can be used for quantitatively evaluating changes induced by a therapeutic agent such as dopamine in flow velocity and in FVV.

Convenient synthesis of aliphatic polyesters by distannoxane-catalyzed polycondensation

A convenient synthesis of aliphatic polyesters by the distannoxane-catalyzed polycondensation of aliphatic dicarboxylic acids and aliphatic diols in solvents under azeotropic conditions was developed. To determine the optimum conditions for polycondensation of succinic acid with 1,4-butandiol, the effect of various types of catalyst and their concentration was investigated. By choosing the appropriate solvent, the polymerization was made to proceed in a two-phase system of solvent and molten polymer, and in the presence of 0.001 mol % of 1-chloro-3-hydroxy-1,1,3,3-tetrabutyldistannoxane (CHTD), poly(butylene succinate) (PBS) with a weight-average molecular weight of 277,000 was obtained. This method was then successfully applied to the synthesis of various aliphatic polyesters, such as poly(ethylene succinate), poly(1,4-cyclohexanedimethylene succinate), and poly(ethylene sebacate).

Evaluation of PCR primers to screen for Streptococcus pneumoniae isolates and beta-lactam resistance, and to detect common macrolide resistance determinants

Pneumococcal isolates (n = 148) from various countries (mostly from the USA) were tested by a primer set for PCR. Thirty-eight (86.4%) of the 44 penicillin G-susceptible isolates (MIC < or = 0.06 mg/L) had unaltered pbps, while six isolates (13.6%) had either one or two alterations in pbps. Of 47 penicillin G-resistant strains (MIC > or = 2 mg/L), 41 isolates (87.2%) had all three pbps altered, six isolates (12.8%) had altered pbp1a + 2x. Various combinations of altered pbp were seen in penicillin G-intermediate isolates. Prevalence of macrolide resistance genes mef(A) and erm(B) in isolates was clearly reflected by their MICs. All isolates were positive for lytA. The primers were useful for screening for Streptococcus pneumoniae and beta-lactam resistance, and for detection of common macrolide resistance determinants.

Angiotensin II signaling and HB-EGF shedding via metalloproteinase in glomerular mesangial cells

BACKGROUND

Angiotensin II (Ang II) has been implicated in the development of glomerulosclerosis by stimulating fibronectin (FN) synthesis. The processing and release of heparin binding-endothelin growth factor (HB-EGF) are activated by protein kinase C (PKC) and Ca2+ signaling. We studied the roles of HB-EGF and endothelial growth factor (EGF) receptor (EGFR) in Ang II-induced FN expression using mesangial cells.

METHODS

Mesangial cells were prepared from mouse kidneys by the explant method and cells were used at passages 4 and 5.

RESULTS

Ang II stimulated FN mRNA levels dose-dependently with a maximal increase (3.4-fold) after 12 hours of incubation. This action was completely inhibited by PKC inhibitors and slightly blocked by Ca2+ chelating agents. FN mRNA accumulation by Ang II was abolished by tyrosine kinase inhibitors, a specific inhibitor for EGFR (AG1478) and extracellular signal-regulated kinase (ERK) inactivation. Addition of neutralizing anti-HB-EGF antibody, as well as pretreatment with heparin or the metalloproteinase inhibitor batimastat abolished induction of FN expression by Ang II. In mesangial cells stably transfected with a chimeric construct containing HB-EGF and alkaline phosphatase (ALP) genes, ALP activity in incubation medium was rapidly increased by Ang II (1.7-fold at 0.5 min) and reached a 4.1-fold increase at two minutes. Ang II phosphorylated EGFR (maximal at 2 min) and ERK (maximal at 8 min) in a PKC- and metalloproteinase-dependent manner. Ang II stimulated the expression and release of transforming growth factor-beta (TGF-beta) via EGFR-mediated signaling, and the released TGF-beta also contributed to Ang II-mediated FN expression via EGFR transactivation.

CONCLUSIONS

Ang II-mediated FN expression was regulated by autocrine effects of HB-EGF and TGF-beta, suggesting a novel paradigm for cross-talk between Ang II and growth factor receptor signaling pathways.

Immunolocalization of vacuolar-type H+-ATPase, cathepsin K, matrix metalloproteinase-9, and receptor activator of NFkappaB ligand in odontoclasts during physiological root resorption of human deciduous teeth

To investigate the cellular mechanisms of physiological root resorption in human deciduous teeth, the authors examined the immunocytochemical localization of vacuolar-type H+-ATPase, a lysosomal cysteine proteinase, cathepsin K, matrix metalloproteinase-9 (MMP-9), and receptor activator of NFKB ligand (RANKL) in odontoclasts. H+-ATPase, cathepsin K, and MMP-9 are the most important enzymes for decalcification of apatite crystals and degradation of type-I collagen. In addition, RANKL is one of the key regulatory molecules in osteoclast formation and functions. Odontoclasts developed extensive ruffled borders and clear zones apposed to the resorbing root dentine surfaces. On immunoelectron microscopy, the expression of vacuolar-type H+-ATPase was detected along the limiting membranes of pale vacuoles and the ruffled border membranes of odontoclasts. Cathepsin K in odontoclasts was localized within pale vacuoles, lysosomes, the extracellular canals of ruffled borders, and the underlying resorbing dentine surfaces. MMP-9 localization in odontoclasts was similar to those of cathepsin K. RANKL was detected in both mononuclear stromal cells and odontoclasts located on resorbing dentine surfaces. These results suggest that (1) odontoclasts are directly involved in decalcification of apatite crystals by active extrusion of proton ions mediated by H+-ATPase and (2) extracellular degradation of dentine type-I collagen by both cathepsin K and MMP-9, and (3) odontoclast differentiation and activity are regulated, at least in part, by RANKL, possibly produced by mononuclear stromal cells and odontoclasts themselves in the resorbing tissues. Thus, the cellular mechanisms of physiological root resorption appear to be quite similar to those of osteoclastic bone resorption.

A successfully treated case of disseminated tuberculosis-associated hemophagocytic syndrome and multiple organ dysfunction syndrome

We report the case of a patient who presented with disseminated tuberculosis-associated hemophagocytic syndrome (HPS). A 40-year-old man was admitted because of fatigue, fever, and renal dysfunction. Chest radiograph and computed tomography scan showed diffuse reticulonodular shadow, and Mycobacterium tuberculosis was identified. Peripheral blood counts decreased rapidly, and bone marrow aspiration revealed hemophagocytosis by macrophages. Despite antituberculous and steroid pulse therapy, multiple organ dysfunction syndrome developed. After plasma exchange and continuous hemodiafiltration were started, hypercytokinemia and vital signs improved dramatically. Although disseminated tuberculosis-associated HPS carries a poor prognosis, acute blood purification may be an effective means of treating HPS involving multiple organ dysfunction syndrome.

Association of amino acid substitutions in penicillin-binding protein 3 with beta-lactam resistance in beta-lactamase-negative ampicillin-resistant Haemophilus influenzae

The affinity of [(3)H]benzylpenicillin for penicillin-binding protein (PBP) 3A was reduced in 25 clinical isolates of beta-lactamase-negative ampicillin (AMP)-resistant (BLNAR) Haemophilus influenzae for which the AMP MIC was > or =1.0 microg/ml. The affinities of PBP 3B and PBP 4 were also reduced in some strains. The sequences of the ftsI gene encoding the transpeptidase domain of PBP 3A and/or PBP 3B and of the dacB gene encoding PBP 4 were determined for these strains and compared to those of AMP-susceptible Rd strains. The BLNAR strains were classified into three groups on the basis of deduced amino acid substitutions in the ftsI gene, which is thought to be involved in septal peptidoglycan synthesis. His-517, near the conserved Lys-Thr-Gly (KTG) motif, was substituted for Arg-517 in group I strains (n = 9), and Lys-526 was substituted for Asn-526 in group II strains (n = 12). In group III strains (n = 4), three residues (Met-377, Ser-385, and Leu-389), positioned near the conserved Ser-Ser-Asn (SSN) motif, were replaced with Ile, Thr, and Phe, respectively, in addition to the replacement with Lys-526. The MICs of cephem antibiotics with relatively high affinities for PBP 3A and PBP 3B were higher than those of AMP and meropenem for group III strains. The MICs of beta-lactams for H. influenzae transformants into which the ftsI gene from BLNAR strains was introduced were as high as those for the donors, and PBP 3A and PBP 3B showed decreased affinities for beta-lactams. There was no clear relationship between 7-bp deletions in the dacB gene and AMP susceptibility. Even though mutations in another gene(s) may be involved in beta-lactam resistance, these data indicate that mutations in the ftsI gene are the most important for development of resistance to beta-lactams in BLNAR strains.

Angiotensin II type 2 receptor inhibits epidermal growth factor receptor transactivation by increasing association of SHP-1 tyrosine phosphatase

Angiotensin (Ang) II has 2 major receptor isoforms, Ang type 1 (AT(1)) and Ang type (AT(2)). AT(1) transphosphorylates epidermal growth factor receptor (EGFR) to activate extracellular signal-regulated kinase (ERK). Although AT(2) was shown to inactivate ERK, the action of AT(2) on EGFR activation remains undefined. Using AT(2)-overexpressing vascular smooth muscle cells from AT(2) transgenic mice, we studied these undefined actions of AT(2). Maximal ERK activity induced by Ang II was increased 1.9- and 2.2-fold by AT(2) inhibition, which was abolished by orthovanadate but not okadaic acid or pertussis toxin. AT(2) inhibited AT(1)-mediated EGFR tyrosine phosphorylation by 63%. The activity of SHP-1 tyrosine phosphatase was significantly upregulated 1 minute after AT(2) stimulation and association of SHP-1 with EGFR was increased, whereas AT(2) failed to tyrosine phosphorylate SHP-1. Stable overexpression of SHP-1-dominant negative mutant completely abolished AT(2)-mediated inhibition of EGFR and ERK activation. AT(1)-mediated c-fos mRNA accumulation was attenuated by 48% by AT(2) stimulation. Induction of fibronectin gene containing an AP-1 responsive element in its 5'-flanking region was decreased by 37% after AT(2) stimulation, corresponding to the results of gel mobility assay with the AP-1 sequence of fibronectin as a probe. These findings suggested that AT(2) inhibits ERK activity by inducing SHP-1 activity, leading to decreases in AP-1 activity and AP-1-regulated gene expression, in which EGFR dephosphorylation plays an important role via association of SHP-1.

Safety and availability of doxazosin in treating hypertensive patients with chronic renal failure

Hypertension accelerates the progression of renal disease in patients with chronic renal failure. Doxazosin, an alpha1-antagonist, is an antihypertensive agent with a long half-life. In this study, 15 patients with chronic renal failure were treated only with doxazosin and diuretics for 6 months and their blood pressure, renal parameters and lipid profile were measured. The initial dose of doxazosin was 2 mg/day and it was titrated until blood pressure was normalized. The average dose was 5.6 mg/day. As expected, systolic and diastolic blood pressure were decreased with treatment (165/91 mmHg to 135/73 mmHg). The drop in blood pressure was associated with an increase in glomerular filtration and a decrease in plasma BUN and creatinine levels. Reduction in mean blood pressure and decrease in proteinuria had a significant positive correlation (r=0.048, p=0.007). Proteinuria was decreased from 1.8 mg/day to 1.3 mg/day with doxazosin treatment and triglycerides also decreased, while HDL-cholesterol was increased. No side effects were observed. These results indicate that doxazosin is an efficient depressor agent with renal protective actions and that higher doses of doxazosin can be safely given to patients with chronic renal failure.

A three-dimensional, quantitative computed tomographic study of changes in distribution of bone mineralization in the developing human mandible

The three-dimensional distribution of highly mineralized cortical bone on the buccal surface of the mandible was evaluated using quantitative computed tomography. The study was completed in 34 living persons (21 females and 13 males) between the ages of 9 and 32 yr of age with symmetrical mandibles. The geometrical distribution of the highly mineralized areas (>1250 mg/cm(3)) was determined by three-dimensional reconstruction of images. The pattern of distribution was evaluated by superimposing a 9 by 9-mesh grid over the lateral view of the mandible and adapting it to the same anatomical landmarks for different aged participants. Individuals demonstrated four different patterns of distribution of highly mineralized buccal cortical bone. The youngest had highly mineralized bone in the corpus of the mandible and along the anterior ramal border. In older individuals, the mineralization changed to include the mid- and posterior ramus. Highly mineralized bone was not found within the condylar, coronoid, or gonial angle regions of any participant. A comparison of the mineralization pattern between the left and right lateral mandibular views showed bilateral symmetry with similar patterns of distribution. Comparison of the number of grids occupied by highly mineralized cortical bone with the age of the participant, mandibular length, gonial angle, and cross-sectional area of the masseter muscle produced the highest correlation coefficient with the size of the masseter muscle.

Cortical bone mineral density in asymmetrical mandibles: a three-dimensional quantitative computed tomography study

The three-dimensional distribution (3D) of the highest mineralized cortical bone was evaluated in 32 subjects between the ages of 8 and 30 years with asymmetrical mandibles using quantitative computed tomography (QCT). The geometrical distribution of the highest mineralized areas (> 1250 mg/cm3) representative of mandibular cortical bone was determined by 3D reconstruction of the images. The length of the mandible on each side was determined by defining a new linear measurement from the centre of the 3D reconstructed condyle to the midline of the symphysis as identified from a submental view. The cross-sectional areas of the masseter and medial pterygoid muscles were assessed from bilateral axial views through the middle of the muscles parallel to the Frankfort-Horizontal plane. Comparison between the lengths of the two mandibular sides (right-left = mm) indicated a range of asymmetries with an equal number of subjects with the left and right mandible longer. Comparison of the area of highest mineralized cortical bone between the right and left sides (R/L) to the ratio of the mandibular length (R/L) showed a high correlation coefficient (r = 0.629) suggesting that the shortest mandibular side had more highly mineralized bone. A comparison of the area of highest mineralized cortical bone between the right and left sides (R/L) to the ratio of cross-sectional areas of the muscles showed the highest correlation coefficient (r = 0.724) with the ipsilateral masseter muscle. These findings indicate that asymmetrical mandibles are associated with asymmetrical distributions of the highest mineralized cortical bone and that this is age dependent.

Growth hormone receptor gene variant and mandibular height in the normal Japanese population

This study was aimed at quantitatively evaluating the relationship between craniofacial morphology and the Pro561Thr (P56IT) variant in the growth hormone receptor gene (GHR), which is considered to be an important factor in craniofacial and skeletal growth. The subjects were unrelated individuals in a normal Japanese population and consisted of 50 men and 50 women. With the use of genomic DNA extracted from whole blood, the GHR gene P56IT variant was detected by the polymerase chain reaction-restriction fragment length polymorphism method (with the restriction enzyme StuI). The relationships of the genotypes to body height and 5 linear measurements from lateral cephalograms were examined for evaluation of craniofacial morphology. The normal Japanese population without P56IT had a significantly greater mandibular ramus length (condylion-gonion) than did those with P56IT. This suggests that the GHR gene P56IT variant may be associated with mandibular height growth and can be a genetic marker for it. Further studies about such genetic markers may expand our understanding of the genetic control in craniofacial morphological determinants and help in the prediction of craniofacial growth.

A clinical and histological evaluation of titanium mini-implants as anchors for orthodontic intrusion in the beagle dog

The aim of this study was to determine the anchorage potential of the titanium mini-implant for orthodontic intrusion of the mandibular posterior teeth. Six mini-implants were surgically placed around the mandibular third premolars on each side in 3 adult male beagle dogs. On the buccal site, three mini-implants were placed distal to the apex of the distal root of the third premolar, at the interradicular septa of the third premolar, and mesial to the apex of the mesial root of the third premolar, as linearly as possible. The same procedure was performed at the lingual site on both sides of the mandibular third premolars in each dog. Bilateral interradicular mini-implants on both the buccal and the lingual sites were used as the anchorage for the intrusion of the third premolars (loaded implants) and the other mini-implants were used as control (unloaded) implants. In 6 weeks, an intrusive force (150 g) was applied between the interradicular implants on the buccal and the lingual sites by closed coil springs run across the crowns of the third premolars. After 12 to 18 weeks of orthodontic intrusion, the animals were killed and their mandibles were dissected and prepared for histologic and fluorescent observation. The results indicated that the mandibular third premolars intruded 4.5 mm, on average, after 12 to 18 weeks of orthodontic force application, with mild root resorption at the furcation area as well as the root apex. All the mini-implants remained stable during orthodontic tooth movement without any mobility or displacement. The morphometrical findings indicated that the calcification of the peri-implant bone on the loaded implants was equal to or slightly greater than those of the controls. In addition, 6 of the 36 mini-implants were removed after tooth movement, and all of them were easily removed with a screwdriver. These findings suggest that mini-implants are effective tools for the anchorage of orthodontic intrusion in beagle dogs.

Effect of angiotensin II type 2 receptor on tyrosine kinase Pyk2 and c-Jun NH2-terminal kinase via SHP-1 tyrosine phosphatase activity: evidence from vascular-targeted transgenic mice of AT2 receptor

Angiotensin II (Ang II) has two major receptor isoforms, AT1 and AT2. AT1 transphosphorylates Ca(2+)-sensitive tyrosine kinase Pyk2 to activate c-Jun NH2-terminal kinase (JNK). Although AT2 inactivates extracellular signal-regulated kinase (ERK) via tyrosine phosphatases (PTP), the action of AT2 on Pyk2 and JNK remains undefined. Using AT2-overexpressing vascular smooth muscle cells (AT2-VSMC) from AT2-transgenic mice, we studied these undefined actions of AT2. AT1-mediated JNK activity was increased 2.2-fold by AT2 inhibition, which was abolished by orthovanadate. AT2 did not affect AT1-mediated Pyk2 phosphorylation, but attenuated c-Jun mRNA accumulation by 32%. The activity of src-homology 2 domain-containing PTP (SHP-1) was significantly upregulated 1 min after AT2 stimulation. Stable overexpression of SHP-1 dominant negative mutant in AT2-VSMC completely abolished AT2-mediated inhibition of JNK activation and c-Jun expression. These findings suggest that AT2 inhibits JNK activity by affecting the downstream signal of Pyk2 in a SHP-1-dependent manner, leading to a decrease in c-Jun expression.

[Beta-lactam and macrolide resistance in Streptococcus pneumoniae]

The resistance of beta-lactam antibiotics in penicillin-resistant Streptococcus pneumoniae (PRSP) is due to alterations in penicillin-binding proteins(PBPs). Recently, highly beta-lactam-resistant strains(MIC: > or = 4 micrograms/ml for penicillin, > or = 8 micrograms/ml for ampicillin, and > or = 4 micrograms/ml for cefotaxime) have been isolated. High resistance of these strains is caused by further alterations in pbp2x and pbp2b genes adjacent to conserved amino acid motifs, in addition to that detected in common PRSP. The resistant mechanisms of macrolides in S. pneumoniae is recognized as production of a 23s rRNA methylase encoded by ermB and efflux system mediated by mefA gene. We detected these genes by PCR in clinical isolates, and showed the relationship between the presence of each gene and the susceptibilities of 14-, 15-, 16-membered macrolides.

Localization of receptor activator of NFkappaB ligand, RANKL, in periodontal tissues during experimental movement of rat molars

The receptor activator of NFkappaB ligand, RANKL, is one of the key regulatory molecules in osteoclast formation and function. We examined RANKL localization in the periodontal tissues during experimental movement of rat molars. To produce orthodontic force, an elastic band was inserted between the upper first and second molars for 4 days, and the dissected maxillae were subjected to light and electron microscopic immunocytochemical examination for RANKL. Expression of RANKL protein was detected in osteoblasts, osteocytes, fibroblasts, and osteoclasts mostly located in resorption lacunae. In osteoblasts, osteocytes, and fibroblasts, RANKL localization was mainly observed in the cytoplasm, the cisternae of rough endoplasmic reticulum and along plasma membranes. In osteoclasts, RANKL was expressed along the ruffled, border membranes and in the cytoplasm, including the clear zone. These results suggest that during tooth movement, osteoclast differentiation and activation are regulated, at least in part, by RANKL, possibly produced by osteoblasts/stromal cells and osteoclasts themselves in the periodontal tissues.

Endosseous titanium implants as anchors for mesiodistal tooth movement in the beagle dog

The purpose of this study was to determine the anchorage potential of titanium implants (Branemark; 3.75 x 7 mm) with the use of a sectional arch wire technique for orthodontic mesiodistal tooth movement, as assessed by the osseointegration of implants and tooth movement. Two implants were surgically placed in healed mandibular extraction sites of the second and third premolars on each side in 4 adult male beagle dogs. The implants were surgically uncovered 18 weeks later, and second-stage abutments with soldered edgewise tubes were attached. Segmented edgewise rectangular archwires (0.017 x 0. 025 inch) with a T-loop or an L-loop were placed between the implants and the fourth premolars on both sides as the anchorage unit. One segment in each dog served as a loaded side, and the archwire was calibrated to produce 200 g of lateral force on the fourth premolar. The contralateral segment served as an unloaded side and was not subjected to orthodontic force. Sectional wires were activated biweekly 24, 28, 28, and 32 weeks, respectively, depending on the magnitude and the appearance of mesial tipping movement of the fourth premolar. After mandibular impressions were taken to measure the distance between the first molar and the fourth premolar, the animals were euthanized and dissected mandibles were prepared. The specimens were then embedded in polyester resin and cut to take backscattered electron images. On the basis of these images, the percentage of peri-implant bone volume was calculated and defined as an index of osseointegration. The differences between the initial and final fourth premolar to first molar distances varied (7.40, 8.85, 10.50, and 3.30 mm) on the loaded side, whereas the unloaded side showed no movement. Not only was there no statistical difference in the percent of peri-implant bone volume between the loaded and unloaded sides, but there was also no statistical difference between the compression and tension sides in both loaded and unloaded implants, which suggests that the implants maintained rigid osseointegration. In conclusion, the present study demonstrated that endosseous titanium implants can function as anchors for long-term orthodontic mesiodistal movement.

Cytochemical evaluation of localization and secretion of a heterologous enzyme displayed on yeast cell surface

A starch-utilizing Saccharomyces cerevisiae strain was constructed by cell surface engineering. Distribution of the heterologous glucoamylase-alpha-agglutinin fusion protein on the yeast cell was analyzed by indirect fluorescence microscopy using an anti-glucoamylase antibody. Most of the intense fluorescence was first localized in the small bud, then observed on the entire cell wall of the daughter and mother cells. Fluorescence also accumulated at the neck region. These observations suggest that the display of the heterologous protein on the cell surface is carried with other cell wall components to the areas in which the cell wall is newly synthesized; the distribution is controlled by the cell cycle. Then, the heterologous protein-encoding gene was expressed in a sec1 mutant, in which secretory vesicles accumulate under restrictive temperature, and the produced protein was detected by immunoelectron microscopy. Most of the gold particles that reacted with the fusion protein were not localized in vesicles but in expanding endoplasmic reticulum. This phenomenon may be due to overproduction of the heterologous protein which was designed to be displayed on the cell wall. Artificial production of heterologous protein may have caused a relative shortage of glycosyl phosphatidylinositol anchors.

Spontaneous formation of polypeptides in the interfacial thin films of amphiphilic amino acid esters: acceleration of the polycondensation and control of the structure of resultant polymers

For the purpose of elucidating the effects of molecular arrangements on the reaction rates and the structure of products, polycondensation of long-chain esters of alpha-amino acids in the monolayer on the water surface and the LB multilayers deposited on CaF2 plates were investigated by monitoring changes of the IR spectra. Spontaneous formation of the polypeptides occurs in the mono- and multilayers at room temperature without any catalyst. The rates of polycondensation in the monolayers are markedly influenced by the degree of molecular packing. Maximum polymerizability is obtained in the vicinity of the transition region from expanded to condensed films. The rates of polycondensation in the LB films are much higher than those in the bulk solids and the molten states. The polycondensation seems to be accelerated by regular arrangements of the monomer molecules in the LB films, where the functional groups are concentrated and situated more effectively for the reaction than in the bulk states. However, the polycondensation rates in the LB films are considerably slower when compared with those in the monolayers on the water surface kept at the optimum area or surface pressure, because the molecules in the LB films deposited under high compression are packed more closely than the optimum condition. Thus, suitably close packing of the monomer molecules, retaining a particular orientation together with some conformational freedom in the monolayer, is most favorable for the polycondensation. Two probable mechanisms for the polycondensation in the Y-type multilayers have been proposed. In the assembly of head-to-head double layers of the monomer molecules, the interlayer reaction propagates by sewing up the functional groups facing each other in the adjacent layers, and the polypeptide of a helical structure or random coil can be obtained. In contrast, for the alternating assembly of the amino acid ester and non-polymerizable octadecyl acetate, the polycondensation should proceed only in each single layer (intralayer reaction) and the polypeptide of the extended beta-form can be formed. In the case of dioctadecyl glutamate LB films, as well as the monolayer on water, the resultant polypeptide is the comb-like polymer with unreacted long-alkyl ester groups as side chains and abundant in the beta-form, indicating the dominant intralayer reaction. On the other hand, in the Y-type multilayer of the equimolar mixture of dioctadecyl glutamate (with two ester groups) and octadecyl ester of lysine (with two amino groups), both of the intra- and interlayer reactions occur effectively, resulting in a two-dimensional network structure of the polypeptide. In conclusion, not only the rate of polycondensation but also the higher-order structure of the resultant polypeptides can be controlled by organized arrangements of the monomer molecules in the interfacial thin films.

Transactivation of EGF receptor induced by angiotensin II regulates fibronectin and TGF-beta gene expression via transcriptional and post-transcriptional mechanisms

The signaling cascade elicited by angiotensin II (Ang II) resembles that characteristic of growth factor, and recent evidence indicates transactivation of epidermal growth factor receptor (EGF-R) by G protein-coupled receptors. Here, we report the involvement of EGF-R in Ang II-induced synthesis of fibronectin and TGF-beta in cardiac fibroblasts. Ang II stimulated fibronectin mRNA levels dose-dependently with a maximal increase (approximately 5-fold) observed after 12 h of incubation. Ang II-, or calcium ionophore-induced fibronectin synthesis was completely abolished by tyrosine kinase inhibitors and intracellular Ca2+ chelating agents. Ang II-induced fibronectin mRNA was not affected by PKC inhibitors or PKC depletion, whereas specific inhibition of EGF-R function by a dominant negative EGF-R mutant and tyrphostin AG1478 abolished induction of fibronectin mRNA. We isolated the rat fibronectin gene including the 5'-flanking region and found that the AP-1 binding site present in the promoter region was responsible for the Ang II responsiveness of this gene. Gel retardation assay revealed the binding of nuclear protein to the AP-1 site, which was supershifted with anti-c-fos and anti-c-jun but not anti-ATF-2 antibodies. Conditioned medium from Ang II-treated cells contained TGF-beta bioactivity and addition of neutralizing TGF-beta antibody modestly (46%) inhibited induction of fibronectin. Ang II-induced synthesis of TGF-beta was also abolished by inhibition of EGF-R function. The effect of TGF-beta was exerted by stabilizing fibronectin mRNA without affecting the promoter activity and required de novo protein synthesis. We concluded that Ang II-induced expression of fibronectin and TGF-beta is mediated by downstream signaling of EGF-R transactivated by Ca2+-dependent tyrosine kinase, and that Ang II-induced fibronectin mRNA expression is regulated by two different mechanisms; transcriptional control by binding of c-fos/c-jun complex to the AP-1 site, and post-transcriptional control by mRNA stabilization due to autocrine and/or paracrine effects of TGF-beta. Thus, this study suggested that the action of Ang II on extracellular matrix formation should be interpreted in association with the EGF-R signaling cascade.

Bisphosphonate administration alters subcellular localization of vacuolar-type H(+)-ATPase and cathepsin K in osteoclasts during experimental movement of rat molars

This study was designed to clarify the effects of bisphosphonate (BP) administration on structure and functions of osteoclasts in alveolar bone resorption during experimental movement of rat molars. To produce orthodontic force, elastic band was inserted between the upper first and second molars for 4 days, and dissected maxillae were then examined by means of light and electron microscopic immunocytochemistry for vacuolar-type H(+)-ATPase and lysosomal cystein proteinase, cathepsin K in osteoclasts. Vacuolar-type H(+)-ATPase and cathepsin K in osteoclasts are the most important enzymes for demineralization of apatite crystals and degradation of bone type-I collagen, respectively. At 1 day before elastic band insertion, BP was administered intraperitoneally. Control rats received the same volume of physiologic saline. In BP-administered rats, most osteoclasts exhibited either irregularly-formed ruffled borders and clear zones or only clear zones of various degrees of extension. Subcellular localization and expression of both vacuolar-type H(+)-ATPase and cathepsin K was significantly decreased in such osteoclasts with impaired ruffled borders and/or only clear zones by BP administration. In particular, cathepsin K secretion by osteoclasts towards resorption lacunae was markedly inhibited by BP administration. Our results indicate for the first time that BP administration significantly impair the osteoclast structure and reduces expression of both vacuolar-type H(+)-ATPase and cathepsin K in osteoclasts during tooth movement.

Angiotensin II initiates tyrosine kinase Pyk2-dependent signalings leading to activation of Rac1-mediated c-Jun NH2-terminal kinase

Ca(2+)-sensitive tyrosine kinase Pyk2 was shown to be involved in angiotensin (Ang) II-mediated activation of extracellular signal-regulated kinase (ERK) via transactivation of epidermal growth factor receptor (EGF-R). In this study, we tested the involvement of Pyk2 and EGF-R in Ang II-induced activation of JNK and c-Jun in cardiac fibroblasts. Ang II markedly stimulated JNK activities, which were abolished by genistein and intracellular Ca(2+) chelators but partially by protein kinase C depletion. Inhibition of EGF-R did not affect Pyk2 and JNK activation by Ang II. Stable transfection with a dominant negative (DN) mutant for Pyk2 (PKM) completely blocked JNK activation by Ang II. DN mutants of Rac1 (DN-Rac1) and MEK kinase (DN-MEKK1) also abolished it, whereas those of Cdc42, RhoA, and Ha-Ras had no effect. Induction of c-Jun gene transcription by Ang II was abolished in PKM, DN-Rac1, and DN-MEKK1, in which Ang II-induced binding of ATF2/c-Jun heterodimer to the activator protein-1 sequence at -190 played a key role. These results suggest that 1) in cardiac fibroblasts activation of JNK and c-Jun by Ang II is initiated by Pyk2-dependent signalings but not by downstream signals of EGF-R or Ras, 2) Rac1 but not Cdc42 is required for JNK activation by Ang II upstream of MEKK1, and 3) ATF-2/c-Jun binding to the activator protein-1 sequence at -190 plays a key role for induction of c-Jun gene by Ang II.

Linkage of autosomal recessive hereditary spastic paraplegia with mental impairment and thin corpus callosum to chromosome 15A13-15

To date, three loci for autosomal recessive hereditary spastic paraplegia (ARHSP) linked to chromosomes 8p12-q13, 16qter, and 15q13-15 have been characterized. We have clinically characterized 13 Japanese ARHSP families and performed genetic linkage analyses. All 13 families were classified as having the "complicated" form, which manifests with mental impairment and thin corpus callosum. Linkage to the 8p12-q13 and 16qter loci was excluded, although 10 of the 13 families showed marker data consistent with linkage to the 15q13-15 locus. The multipoint LOD score of the 10 families linked to chromosome 15 was above 9.00 in the 3-centimorgan segment flanked by D15S994 and D15S659, with a maximum multipoint LOD score of 9.68 at a position 1.2 centimorgans telomeric from D15S994 to D15S659. We have shown that ARHSP with thin corpus callosum, a subtype of recessive spastic paraplegia, maps to chromosome 15q13-15.

Cryofiltration and oral corticosteroids provide successful treatment for an elderly patient with cryoglobulinemic glomerulonephritis associated with hepatitis C virus infection

A 75-year-old man was admitted due to nephrotic syndrome, purpura on the legs, which was associated with hepatitis C virus (HCV), and type II mixed cryoglobulinemia. Renal biopsy revealed features of cryoglobulinemic glomerulonephritis. Since the patient was elderly and the HCV genotype was Ib, interferon-alpha for reducing HCV was not indicated. Four sessions of cryofiltration and the administration of corticosteroids improved the proteinuria and renal function strikingly without adverse effects. This case demonstrates that an elderly patient who has nephrotic syndrome caused by cryoglobulinemic glomerulonephritis associated with HCV can be treated safely by cryofiltration with low doses of oral corticosteroids.

Autophosphorylation of type I phosphatidylinositol phosphate kinase regulates its lipid kinase activity

Phosphatidylinositol phosphate kinases (PIPKs) have important roles in the production of various phosphoinositides. For type I PIP5Ks (PIP5KI), a broad substrate specificity is known. They phosphorylate phosphatidylinositol 4-phosphate most effectively but also phosphorylate phosphatidylinositol (PI), phosphatidylinositol 3-phosphate, and phosphatidylinositol (3,4)-bisphosphate (PI(3, 4)P(2)), resulting in the production of phosphatidylinositol (4, 5)-bisphosphate (PI(4,5)P(2)), phosphatidylinositol 3-phosphate, phosphatidylinositol (3,4)-bisphosphate (PI(3,4)P(2)), phosphatidylinositol (3,5)-bisphosphate (PI(3,5)P(2)), and phosphatidylinositol (3,4,5)-trisphosphate. We show here that PIP5KIs have also protein kinase activities. When each isozyme of PIP5KI (PIP5KIalpha, -beta, and -gamma) was subjected to in vitro kinase assay, autophosphorylation occurred. The lipid kinase-negative mutant of PIP5KIalpha (K138A) lost the protein kinase activity, suggesting the same catalytic mechanism for the lipid and the protein kinase activities. PIP5KIbeta expressed in Escherichia coli also retains this protein kinase activity, thus confirming that no co-immunoprecipitated protein kinase is involved. In addition, the autophosphorylation of PIP5KI is markedly enhanced by the addition of PI. No other phosphoinositides such as phosphatidylinositol phosphate, phosphatidylinositol bisphosphate, or phosphatidylinositol trisphosphate have such an effect. We also found that the PI-dependent autophosphorylation strongly suppresses the lipid kinase activity of PIP5KI. The lipid kinase activity of PIP5KI was decreased to one-tenth upon PI-dependent autophosphorylation. All these results indicate that the lipid kinase activity of PIP5KI that acts predominantly for PI(4,5)P(2) synthesis is regulated by PI-dependent autophosphorylation in vivo.

A critical role for a Rho-associated kinase, p160ROCK, in determining axon outgrowth in mammalian CNS neurons

We tested the contribution of the small GTPase Rho and its downstream target p160ROCK during the early stages of axon formation in cultured cerebellar granule neurons. p160ROCK inhibition, presumably by reducing the stability of the cortical actin network, triggered immediate outgrowth of membrane ruffles and filopodia, followed by the generation of initial growth cone-ike membrane domains from which axonal processes arose. Furthermore, a potentiation in both the size and the motility of growth cones was evident, though the overall axon elongation rate remained stable. Conversely, overexpression of dominant active forms of Rho or ROCK was suggested to prevent initiation of axon outgrowth. Taken together, our data indicate a novel role for the Rho/ROCK pathway as a gate critical for the initiation of axon outgrowth and the control of growth cone dynamics.

Changes in cortical bone mineralization in the developing mandible: a three-dimensional quantitative computed tomography study

Quantitative computed tomography (QCT) was completed in 34 subjects between the ages of 9 and 33 years with symmetrical mandibles in order to investigate the three-dimensional cortical bone mineral density (BMD) distribution in the mandible. The number and distribution of the pixels were determined at three levels: (1) representing the entire mandibular bone; (2) the cortical bone at 60% above the baseline defined as the segmentation level (around 1050 mg/cm3) and representative of only cortical bone; and (3) the highest mineralized cortical bone (>1250 mg/cm3). The geometrical distribution of the highest mineralized areas was evaluated by three-dimensional reconstruction of the images. The total number of pixels for the entire mandible increased significantly at each time point represented at four increasing ages groups (9-11 years of age, 12-14 years of age, 15-17 years of age, and >18 years of age). The male and female subjects had a similar total number of pixels for the entire mandible before the age of 11, but the male subjects showed a significantly larger total number of mandibular pixels after that age. Comparison of the number of pixels for pure cortical bone (60% segmentation level) and the highest mineralized cortical bone indicated a significant increase with maturation with the greatest change occurring between the 13-year and 16-year age groups. However, the ratio of cortical bone/total bone increased at a more rapid rate in the male subjects and reached a plateau by the 16-year age group, showing distinct differences in mineralization of the mandible between the sexes.

Type Ialpha phosphatidylinositol-4-phosphate 5-kinase mediates Rac-dependent actin assembly

Action polymerization is essential for a variety of cellular processes including movement, cell division and shape change. The induction of actin polymerization requires the generation of free actin filament barbed ends, which results from the severing or uncapping of pre-existing actin filaments [1] [2], or de novo nucleation, initiated by the Arp2/3 complex [3] [4] [5] [6] [7]. Although little is known about the signaling pathways that regulate actin assembly, small GTPases of the Rho family appear to be necessary [8] [9] [10] [11]. In thrombin-stimulated platelets, the Rho family GTPase Rac1 induces actin polymerization by stimulating the uncapping of actin filament barbed ends [2]. The mechanism by which Rac regulates uncapping is unclear, however. We previously demonstrated that Rac interacts with a type I phosphatidylinositol-4-phosphate 5-kinase (PIP 5-kinase) in a GTP-independent manner [12] [13]. Because PIP 5-kinases synthesize phosphatidylinositol-4,5-bisphosphate (PI(4,5)P(2)), a lipid that dissociates capping proteins from the barbed ends of actin filaments [14] [15] [16], they are good candidates for mediating the effects of Rac on actin assembly. Here, we have identified the Rac-associated PIP 5-kinase as the PIP 5-kinase isoforms alpha and beta. When added to permeabilized platelets, PIP 5-kinase alpha induced actin filament uncapping and assembly. In contrast, a kinase-inactive PIP 5-kinase alpha mutant failed to induce actin assembly and blocked assembly stimulated by thrombin or Rac. Furthermore, thrombin- or Rac-induced actin polymerization was inhibited by a point mutation in the carboxyl terminus of Rac that disrupts PIP 5-kinase binding. These results demonstrate that PIP 5-kinase alpha is a critical mediator of thrombin- and Rac-dependent actin assembly.

Angiotensin II type 2 receptor overexpression activates the vascular kinin system and causes vasodilation

Angiotensin II (Ang II) is a potent vasopressor peptide that interacts with 2 major receptor isoforms - AT1 and AT2. Although blood pressure is increased in AT2 knockout mice, the underlying mechanisms remain undefined because of the low levels of expression of AT2 in the vasculature. Here we overexpressed AT2 in vascular smooth muscle (VSM) cells in transgenic (TG) mice. Aortic AT1 was not affected by overexpression of AT2. Chronic infusion of Ang II into AT2-TG mice completely abolished the AT1-mediated pressor effect, which was blocked by inhibitors of bradykinin type 2 receptor (icatibant) and nitric oxide (NO) synthase (L-NAME). Aortic explants from TG mice showed greatly increased cGMP production and diminished Ang II-induced vascular constriction. Removal of endothelium or treatment with icatibant and L-NAME abolished these AT2-mediated effects. AT2 blocked the amiloride-sensitive Na(+)/H(+) exchanger, promoting intracellular acidosis in VSM cells and activating kininogenases. The resulting enhancement of aortic kinin formation in TG mice was not affected by removal of endothelium. Our results suggest that AT2 in aortic VSM cells stimulates the production of bradykinin, which stimulates the NO/cGMP system in a paracrine manner to promote vasodilation. Selective stimulation of AT2 in the presence of AT1 antagonists is predicted to have a beneficial clinical effect in controlling blood pressure.