Hierarchical assembly of the siliceous skeletal lattice of the hexactinellid sponge Euplectella aspergillum

Despite its inherent mechanical fragility, silica is widely used as a skeletal material in a great diversity of organisms ranging from diatoms and radiolaria to sponges and higher plants. In addition to their micro- and nanoscale structural regularity, many of these hard tissues form complex hierarchically ordered composites. One such example is found in the siliceous skeletal system of the Western Pacific hexactinellid sponge, Euplectella aspergillum. In this species, the skeleton comprises an elaborate cylindrical lattice-like structure with at least six hierarchical levels spanning the length scale from nanometers to centimeters. The basic building blocks are laminated skeletal elements (spicules) that consist of a central proteinaceous axial filament surrounded by alternating concentric domains of consolidated silica nanoparticles and organic interlayers. Two intersecting grids of non-planar cruciform spicules define a locally quadrate, globally cylindrical skeletal lattice that provides the framework onto which other skeletal constituents are deposited. The grids are supported by bundles of spicules that form vertical, horizontal and diagonally ordered struts. The overall cylindrical lattice is capped at its upper end by a terminal sieve plate and rooted into the sea floor at its base by a flexible cluster of barbed fibrillar anchor spicules. External diagonally oriented spiral ridges that extend perpendicular to the surface further strengthen the lattice. A secondarily deposited laminated silica matrix that cements the structure together additionally reinforces the resulting skeletal mass. The mechanical consequences of each of these various levels of structural complexity are discussed.

PTEN loss promotes rasHa-mediated papillomatogenesis via dual up-regulation of AKT activity and cell cycle deregulation but malignant conversion proceeds via PTEN-associated pathways

PTEN tumor suppressor gene failure in ras(Ha)-activated skin carcinogenesis was investigated by mating exon 5 floxed-PTEN (Delta5PTEN) mice to HK1.ras mice that expressed a RU486-inducible cre recombinase (K14.creP). PTEN inactivation in K14.cre/PTEN(flx/flx) keratinocytes resulted in epidermal hyperplasia/hyperkeratosis and novel 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted papillomas, whereas HK1.ras/K14.cre/PTEN(flx/flx) cohorts displayed a rapid onset of papillomatogenesis due to a synergism of increased AKT activity and extracellular signal-regulated kinase (ERK) elevation. High 5-bromo-4-deoxyuridine labeling in Delta5PTEN papillomas showed that a second promotion mechanism centered on failures in cell cycle control. Elevated cyclin D1 was associated with both HK1.ras/ERK- and Delta5PTEN-mediated AKT signaling, whereas cyclin E2 overexpression seemed dependent on PTEN loss. Spontaneous HK1.ras/Delta5PTEN malignant conversion was rare, whereas TPA promotion resulted in conversion with high frequency. On comparison with all previous HK1.ras carcinomas, such TPA-induced carcinomas expressed atypical retention of keratin K1 and lack of K13, a unique marker profile exhibited by TPA-induced K14.cre/PTEN(flx/flx) papillomas that also lacked endogenous c-ras(Ha) activation. Moreover, in all PTEN-null tumors, levels of ras(Ha)-associated total ERK protein became reduced, whereas phosphorylated ERK and cyclin D1 were lowered in late-stage papillomas returning to elevated levels, alongside increased cyclin E2 expression, in TPA-derived carcinomas. Thus, during early papillomatogenesis, PTEN loss promotes ras(Ha) initiation via elevation of AKT activity and synergistic failures in cyclin regulation. However, in progression, reduced ras(Ha)-associated ERK protein and activity, increased Delta5PTEN-associated cyclin E2 expression, and unique K1/K13 profiles following TPA treatment suggest that PTEN loss, rather than ras(Ha) activation, gives rise to a population of cells with greater malignant potential.

Synthesis of the bicyclic core of tagetitoxin

A synthesis of the 9-oxa-3-thiabicyclo[3.3.1]nonane ring system, which constitutes the core of the RNA polymerase inhibitor tagetitoxin, has been achieved through cyclisation of a thiol onto an electrophilic ketone.

Synthesis of Vinylogous Carbamates by Rhodium(II)-Catalyzed Olefination of Tertiary Formamides with a Silylated Diazoester

Treatment of tertiary formamides with a silylated diazoester in the presence of a rhodium(II) catalyst leads to the formation of 3-amino-2-silyloxyacrylates in good yield. No olefination is observed if a nonsilylated diazo compound is employed. [reaction: see text]

Influence of age and gender on the mechanism of supraventricular tachycardia

OBJECTIVES

The objective of this study was to determine the impact of age and gender on the mechanism of paroxysmal supraventricular tachycardia (PSVT).

BACKGROUND

Previous studies have indicated that PSVT mechanism may be influenced by age and gender, but contemporary data are limited.

METHODS

In 1,754 patients undergoing catheter ablation of 1,856 PSVTs between 1991 and 2003, the mechanism was classified as atrioventricular reentrant tachycardia (AVRT), atrioventricular nodal reentrant tachycardia (AVNRT), or atrial tachycardia (AT). Patients with inappropriate sinus tachycardia, atrial flutter, atrial fibrillation, and age <5 years were excluded.

RESULTS

The mean age was 45 +/- 19 years (range 5-96), and the majority were women (62%). Overall, AVNRT was the predominant mechanism (n = 1,042 [56%]), followed by AVRT (n = 500 [27%]) and AT (n = 315 [17%]). There was a strong relationship between age and PSVT mechanism; the proportion of AVRT in both sexes decreased with age, whereas AVNRT and AT increased (PM < .001 by ANOVA). The majority of patients with AVRT were men (273/500 [54.6%]), whereas the majority of patients with AVNRT and AT were women (727/1,042 [70%] and 195/315 [62%], respectively). The distribution of PSVT mechanism was significantly influenced by gender (P < .001). In women, 63% had AVNRT, 20% had AVRT, and 17.0% had AT. In men, 45% had AVNRT, 39% had AVRT, and 17% had AT. AVNRT replaced AVRT as the dominant PSVT mechanism at age 40 in men and at age 10 in women.

CONCLUSIONS

The mechanism of PSVT in patients presenting for ablation is significantly influenced by both age and gender.

An audit of pharyngeal pouch surgery using endoscopic stapling. The patient's viewpoint

We report an audit designed to assess patient satisfaction resulting from pharyngeal pouch surgery using an endoscopic stapler. A personal series of 16 patients all operated on by the senior author over a 3-year period is reported. Information was gathered using a retrospective telephone questionnaire to establish pre- and postoperative symptoms, complications of surgery and patient satisfaction. This showed endoscopic pharyngeal pouch surgery to be successful in the majority of cases. Eighty-seven percent of patients felt better as a result of surgery. Seventy-five percent had no symptoms postoperatively. This series shows that surgery on pharyngeal pouches results in significant improvement in patient symptoms with minimal morbidity and mortality.

Isoenzyme-selective regulation of SERCA2 gene expression by protein kinase C in neonatal rat ventricular myocytes

Patients with cardiac hypertrophy and heart failure display abnormally slowed myocardial relaxation, which is associated with downregulation of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2) gene expression. We previously showed that SERCA2 downregulation can be simulated in cultured neonatal rat ventricular myocytes (NRVM) by treatment with the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA). However, NRVM express three different PMA-sensitive PKC isoenzymes (PKCalpha, PKCepsilon, and PKCdelta), which may be differentially regulated and have specific functions in the cardiomyocyte. Therefore, in this study we used adenoviral vectors encoding wild-type (wt) and kinase-defective, dominant negative (dn) mutant forms of PKCalpha, PKCepsilon, and PKCdelta to analyze their individual effects in regulating SERCA2 gene expression in NRVM. Overexpression of wtPKCepsilon and wtPKCdelta, but not wtPKCalpha, was sufficient to downregulate SERCA2 mRNA levels, as assessed by Northern blotting and quantitative, real-time RT-PCR (69 +/- 7 and 61 +/- 9% of control levels for wtPKCepsilon and wtPKCdelta, respectively; P < 0.05 for each adenovirus; n = 8 experiments). Conversely, overexpression of all three dnPKCs appeared to significantly increase SERCA2 mRNA levels (dnPKCdelta > dnPKCepsilon > dnPKCalpha). dnPKCdelta overexpression produced the largest increase (2.8 +/- 1.0-fold; n = 11 experiments). However, PMA treatment was still sufficient to downregulate SERCA2 mRNA levels despite overexpression of each dominant negative mutant. These data indicate that the novel PKC isoenzymes PKCepsilon and PKCdelta selectively regulate SERCA2 gene expression in cardiomyocytes but that neither PKC alone is necessary for this effect if the other novel PKC can be activated.

PYK2 expression and phosphorylation increases in pressure overload-induced left ventricular hypertrophy

Proline-rich tyrosine kinase 2 (PYK2) is a member of the focal adhesion kinase (FAK) family of nonreceptor protein tyrosine kinases. PYK2 has been implicated in linking G protein-coupled receptors to activation of mitogen-activated protein kinase cascades and cellular growth in a variety of cell types. To determine whether PYK2 expression and phosphorylation is altered in left ventricular (LV) myocardium undergoing LV hypertrophy (LVH) and heart failure in vivo, suprarenal abdominal aortic coarctation was performed in 160-g male Sprague-Dawley rats. Immunohistochemistry and Western blotting were performed on LV tissue 1, 8, and 24 wk after aortic banding. Aortic banding produced sustained hypertension and gradually developing LVH. PYK2 levels were increased 1.8 +/- 0.2-, 2.7 +/- 0.6-, and 2.0 +/- 0.2-fold in 1-, 8-, and 24-wk banded animals compared with their respective sham-operated controls. The increase in PYK2 expression was paralleled by an increase in PYK2 phosphorylation, both of which preceded the development of LVH. Immunohistochemistry revealed that enhanced PYK2 expression occurred predominantly in the cardiomyocyte population. Furthermore, there was a high degree of correlation (R = 0.75; P < 0.001) between the level of PYK2 and the degree of LVH in 24-wk sham and banded animals. In contrast, FAK levels and FAK phosphorylation were not increased before the development of LVH. However, there was a high degree of correlation (R = 0.68; P < 0.001) between the level of FAK and the degree of LVH in 24-wk sham and banded rats. There was also a significant increase in the ratio of phosphospecific anti-FAK to FAK at this time point. These data are consistent with a role for PYK2 in the induction of pressure overload-induced cardiomyocyte hypertrophy, and suggest that PYK2 and FAK have distinctly different roles in LVH progression.

A ring expansion reaction of 1,3-oxathiolanes

1,3-Oxathiolanes are efficiently converted, via sulfur ylide intermediates, to 1,4-oxathianes by ring expansion with a silylated diazoacetate in the presence of a copper catalyst.

Polyamino acids as catalysts in asymmetric synthesis

The use of polyamino acids in asymmetric organic synthesis is reviewed. Particular emphasis is placed on the asymmetric epoxidation of alpha,beta-unsaturated ketones with hydrogen peroxide in the presence of polyalanine or polyleucine, and further transformations of the epoxide products.

Audit in the management of T3 fixed-cord laryngeal cancer

PURPOSE

To determine results of various treatments for T3 fixed-cord lesions and the subset T3 glottic cancer in Auckland from 1979 to 1995.

PATIENTS AND METHODS

Data were collected retrospectively from a departmental database, and the notes were reviewed. Because of the difficulty in determining the subsite of some fixed-cord lesions, the entire group of T3 fixed-cord lesions was examined, and those tumors that were considered to be definitely arising from the glottis were then analyzed as a specific subset.

RESULTS

Fixed-cord lesions were diagnosed in 75 patients (21 supraglottic, 54 glottic). Primary surgery (total laryngectomy) was performed on 46 patients, primary radical dose radiotherapy was undertaken on 25 patients, and four patients were treated palliatively. For T3 fixed-cord lesions, disease-specific survival for radiotherapy and surgery was 36% and 66%, respectively, and 32% and 67%, respectively, for T3 glottic lesions. For both T3 fixed-cord and T3 glottic lesions, surgery produced significantly better survival than did radiotherapy (<60 Gy; P = .0157). With radiotherapy greater than 60 Gy, cancer of the larynx has been controlled in seven of 13 patients, although only five patients are alive, with a median follow-up of 24 months (range, 12-49 months).

CONCLUSION

Radiotherapy less than 60 Gy produced markedly inferior results to surgery for T3 fixed-cord lesions and T3 glottis in Auckland. Radiotherapy at more than 60 Gy shows promise, but an ongoing audit is essential to ensure that survival is similar to surgery and to that reported by those promoting organ-preservation protocols.

Preservation of the great auricular nerve during parotidectomy

The great auricular nerve is routinely divided during the operation of parotidectomy, however, some surgeons have suggested that preserving the posterior branches reduces the area of post-operative anaesthesia. A prospective study was performed comparing the area of anaesthesia and hypoaesthesia in patients undergoing parotidectomy. In 20 patients the great auricular nerve was preserved and in 11 it was sacrificed. Mapping of the area of sensory loss at 2 weeks, 3, 6, 9 and 12 months showed that there was no difference between the two groups. The area of sensory loss decreased in an exponential fashion in both groups. The majority of the change occurred within 6 months. We conclude that preservation of the posterior branches of the great auricular nerve is unnecessary.

Manometric rhinometry: a new method of measuring the volume of the air in the nasal cavity

Almost all the pathological and physiological process that effect the nose will change the volume of the airspace within it. This volume has previously been difficult to measure but a new method that calculates this space has been developed. A mechanical model was built to test the physical parameters involved in making volume measurements. The model demonstrated that a model sinus could be detected if the ostium was only 0.5 mm in diameter. It also showed that a mathematical model which described the volume of the space could be constructed. In vivo experiments showed that nasal volume can be measured in children as young as 4. In children, nasal volume correlates with age, height, and weight. They had a low coefficient of variation (7.1%) and a high test-retest correlation (r = 0.94). Adult nasal volume averaged 138 ml. The method is sensitive enough to detect the decongestant effect of xylometazoline in a group of 17 healthy volunteers (p < 0.01). There is no significant difference in the sensitivity to detect the decongestant effect of xylometazoline when compared with active anterior rhinometry, nasal peak flow, and acoustic rhinometry (range 80-95%).