Use of paediatric donor tissue in Descemet stripping endothelial keratoplasty

AIMS

To evaluate the feasibility, efficacy and postoperative complications of Descemet stripping endothelial keratoplasty (DSEK) with paediatric donor tissue.

METHODS

Retrospective non-comparative interventional case series. Seven consecutive cases (seven eyes) of pseudophakic bullous keratopathy were treated with DSEK using paediatric donor tissue and followed up for 12 to 18 months. Data collected included best spectacle-corrected visual acuity, spherical equivalent refractive error, corneal astigmatism, corneal curvature and endothelial cell density.

RESULTS

DSEK was successfully performed in six out of seven eyes with paediatric donor graft; one paediatric donor graft perforated during dissection. All paediatric tissue was unfolded using the "hitch suture" technique and supported with plenty of air. No graft dislocation occurred. At 12 months postoperatively, the cornea was clear in all eyes; the best spectacle-corrected visual acuity ranged from 20/67 to 20/32; the average spherical equivalent refractive error was 1.9 (0.5) dioptres; the average corneal astigmatism was 2.2 (0.6) dioptres; the average corneal curvature was 45.2 (1.6) dioptres; and the average endothelial cell density was 2247.7 (74.3) cells/mm(2) (41.4 (3.7)% of endothelial cell loss).

CONCLUSION

With high postoperative endothelial cell counts, low graft dislocation rate and absence of high myopic shifts, paediatric donor tissue can be successfully used in DSEK.

Extracardiac lesions and chromosomal abnormalities associated with major fetal heart defects: comparison of intrauterine, postnatal and postmortem diagnoses

OBJECTIVES

The clinical outcome of prenatally diagnosed congenital heart defects (CHD) continues to be affected significantly by associated extracardiac and chromosomal abnormalities. We sought to: determine the frequency and type of major extracardiac abnormalities (with impact on quality of life) and chromosomal abnormalities associated with fetal CHD; and compare the extracardiac abnormalities detected prenatally to the postnatal and autopsy findings in affected fetuses, to find the incidence of extracardiac abnormalities missed on prenatal ultrasound.

METHODS

We reviewed the computerized database of the Division of Cardiology of the Hospital for Sick Children in Toronto to identify all cases of major CHD detected prenatally from 1990 to 2002. Medical records, fetal echocardiograms and ultrasound, cytogenetic and autopsy reports were reviewed. The types of CHD detected were grouped into categories and the frequencies of major extracardiac and chromosomal abnormalities in these categories were noted. Prenatal ultrasound findings were compared with those at autopsy or postnatal examination.

RESULTS

Of 491 fetuses with major structural CHD, complete data were obtained for 382. Of these, there were 141 (36.9%) with major extracardiac abnormalities at autopsy or postnatal exam, of which 46 had chromosomal abnormalities and 95 did not. In the absence of chromosomal abnormalities, the organ systems most affected were urogenital (12.2%) and gastrointestinal (11.6%). CHDs with the highest incidence of extracardiac abnormalities (>25%) included: heterotaxy, single left ventricle and tricuspid atresia, hypoplastic left heart syndrome and tetralogy of Fallot. Ninety-four of 334 (28.1%) fetuses tested had chromosomal abnormalities. The most common chromosomal abnormalities were trisomies 21 (43.6%), 18 (19.1%) and 13 (9.6%), monosomy X (7.4%) and 22q11.2 deletion (7.4%). Of 289 extracardiac abnormalities from the complete series, 134 (46.4%) were not identified prenatally. Of the missed extracardiac abnormalities, 65 were considered not detectable at prenatal ultrasound, so 23.9% (69/289) of detectable extracardiac abnormalities were missed prenatally.

CONCLUSIONS

Major extracardiac and chromosomal abnormalities are common in fetuses with major fetal CHD. Many important associated extracardiac abnormalities may be missed prenatally, which should be taken into consideration in the prenatal counseling for fetal CHD.

Direct observation of the transition state of ultrafast electron transfer reaction of a radiosensitizing drug bromodeoxyuridine

Replacement of thymidine in DNA by bromodeoxyuridine (BrdU) has long been known to enhance DNA damage and cell death induced by ionizing/UV radiation, but the mechanism of action of BrdU at the molecular level is poor understood. Using time-resolved femtosecond laser spectroscopy, we obtain the real-time observation of the transition state of the ultrafast electron transfer (ET) reaction of BrdU with the precursor to the hydrated electron, which is a general product in ionizing/UV radiation. The results show that the ET reaction is completed within 0.2 picosecond (ps) after the electronic excitation, leading to the formation of a transition state BrdU*- with a lifetime of approximately 1.5 ps that then dissociates into Br- and a high reactive radical dU*. The present results can greatly enhance our understanding not only of the mechanism of BrdU as a radio-/photosensitizer but of the role of prehydrated electrons in electron-initiated processes in biological and environmental systems.

Spectroscopic characterization of carbon chains in nanostructured tetrahedral carbon films synthesized by femtosecond pulsed laser deposition

A comparative study of carbon bonding states and Raman spectra is reported for amorphous diamondlike carbon films deposited using 120 fs and 30 ns pulsed laser ablation of graphite. The presence of sp(1) chains in femtosecond carbon films is confirmed by the appearance of a broad excitation band at 2000-2200 cm(-1) in UV-Raman spectra. Analysis of Raman spectra indicates that the concentrations of sp(1)-, sp(2)-, and sp(3)-bonded carbon are approximately 6%, approximately 43%, and approximately 51%, respectively, in carbon films prepared by femtosecond laser ablation. Using surface enhanced Raman spectroscopy, specific vibrational frequencies associated with polycumulene, polyyne, and trans-polyacetylene chains have been identified. The present study provides further insight into the composition and structure of tetrahedral carbon films containing both sp(2) clusters and sp(1) chains.

Thioredoxin reduces post-ischemic myocardial apoptosis by reducing oxidative/nitrative stress

BACKGROUND AND PURPOSE

Thioredoxin (Trx) is an oxidoreductase that prevents free radical-induced cell death in cultured cells. Here we assessed the mechanism(s) underlying the cardioprotective effects of Trx in vivo.

EXPERIMENTAL APPROACH

The effects of myocardial ischemia (30 min) and reperfusion were measured in mice, with assays of myocardial apoptosis, superoxide production, NOx and nitrotyrosine content, and myocardial infarct size. Recombinant human Trx (rhTrx, 0.7-20 mg kg(-1), i.p.) was given 10 min before reperfusion.

KEY RESULTS

Treatment with 2 mg kg(-1) rhTrx significantly decreased myocardial apoptosis and reduced infarct size (P<0.01). Nitrotyrosine content of cardiomyocytes was markedly reduced in rhTrx-treated animals (P<0.01). To further identify the mechanisms by which rhTrx may exert its anti-nitrative effect, iNOS expression and production of NOx and superoxide were determined. Treatment with rhTrx had no significant effect on iNOS expression or NOx content in the ischemic/reperfused heart. However, it markedly upregulated mSOD and reduced tissue superoxide content. To further establish a causative link between the anti- peroxynitrite effect and the cardioprotective effect of rhTrx, cultured adult cardiomyocytes were incubated with SIN-1, a peroxynitrite donor, (50 microM for 3 h) resulting in a nitrotyrosine content comparable to that seen in the ischemic/reperfused heart and causing significant cardiomyocyte apoptosis (P<0.01). Treatment with rhTrx markedly decreased SIN-1 induced apoptosis (P<0.01).

CONCLUSIONS AND IMPLICATIONS

These results demonstrate that Trx is a novel anti-apoptotic and cardioprotective molecule that exerts its cardioprotective effects by reducing ischemia/reperfusion-induced oxidative/nitrative stress.

Visual acuity in northern China in an urban and rural population: the Beijing Eye Study

AIM

To evaluate prevalence and demographic associations of visual impairment in an urban and rural population in northern China.

METHODS

In the Beijing Eye Study, a population based cohort study in northern China, visual acuity was assessed for 8876 eyes (4438 subjects) according to a response rate of 83.4%. The study was divided into a rural part (1972 subjects) and an urban part (n=2466). Mean age was 56.20 (SD 10.59) years (median 56 years; range 40-101 years).

RESULTS

Mean uncorrected visual acuity measured 0.72 (0.32) (median, 0.80), and mean best corrected visual acuity measured 0.91 (0.21) (median, 1.0). In a multiple regression analysis, best corrected visual acuity was significantly correlated with age (p<0.001), degree of nuclear cataract (p<0.001), amount of cortical cataract (p=0.014), amount of subcapsular cataract (p<0.001), educational background (p<0.001), and refractive error (p<0.001). Rural region versus urban region (p=0.34) and sex (p=0.053) were not statistically significantly associated with best corrected visual acuity.

CONCLUSIONS

In northern China, determinants of a low degree of best corrected visual acuity are age, cataract, low educational background, and myopia. Despite marked differences in educational background and family income, sex, and rural area versus urban area are not markedly associated with best corrected visual acuity.

Electron holography study on the microstructure of magnetic tunnelling junctions

Electron holography was applied to study the microstructure evolution of magnetic tunnelling junctions (MTJs) CoFe/AlO(x)/Co annealed at different temperatures. A mean inner potential barrier was observed in the as-deposited MTJ sample, while it was changed to a potential well after a 200 degrees C or a 400 degrees C annealing. It is suggested that the oxygen atoms were redistributed during the annealing, which left metallic atoms acting as acceptors to confine the electrons, leading to the decrease of the potential of the AlO(x) barrier layer. The results suggest that the electron holography may be a useful tool for the study of the microstructure of amorphous materials.

Characterization of phi8, a bacteriophage containing three double-stranded RNA genomic segments and distantly related to Phi6

The three double-stranded RNA genomic segments of bacteriophage Phi8 were copied as cDNA, and their nucleotide sequences were determined. Although the organization of the genome is similar to that of Phi6, there is no similarity in either the nucleotide sequences or the amino acid sequences, with the exception of the motifs characteristic of viral RNA polymerases that are found in the presumptive polymerase sequence. Several features of the viral proteins differ markedly from those of Phi6. Although both phages are covered by a lipid-containing membrane, the protein compositions are very different. The most striking difference is that protein P8, which constitutes a shell around the procapsid in Phi6, is part of the membrane in Phi8. The host attachment protein consists of two peptides rather than one and the phage attaches directly to the lipopolysaccharide of the host rather than to a type IV pilus. The host range of Phi8 includes rough strains of Salmonella typhimurium and of pseudomonads

The biosynthetic gene cluster for the microtubule-stabilizing agents epothilones A and B from Sorangium cellulosum So ce90

BACKGROUND

Epothilones are produced by the myxobacterium Sorangium cellulosum So ce90, and, like paclitaxel (Taxol((R))), they inhibit microtubule depolymerisation and arrest the cell cycle at the G2-M phase. They are effective against P-glycoprotein-expressing multiple-drug-resistant tumor cell lines and are more water soluble than paclitaxel. The total synthesis of epothilones has been achieved, but has not provided an economically viable alternative to fermentation. We set out to clone, sequence and analyze the gene cluster responsible for the biosynthesis of the epothilones in S. cellulosum So ce90.

RESULTS

A cluster of 22 open reading frames spanning 68,750 base pairs of the S. cellulosum So ce90 genome has been sequenced and found to encode nine modules of a polyketide synthase (PKS), one module of a nonribosomal peptide synthetase (NRPS), a cytochrome P450, and two putative antibiotic transport proteins. Disruptions in the genes encoding the PKS abolished epothilone production. The first PKS module and the NRPS module are proposed to co-operate in forming the thiazole heterocycle of epothilone from an acetate and a cysteine by condensation, cyclodehydration and subsequent dehydrogenation. The remaining eight PKS modules are responsible for the elaboration of the rest of the epothilone carbon skeleton.

CONCLUSIONS

The overall architecture of the gene cluster responsible for epothilone biosynthesis has been determined. The availability of the cluster should facilitate the generation of designer epothilones by combinatorial biosynthesis approaches, and the heterologous expression of epothilones in surrogate microbial hosts.