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Biomedical subjects

D Steel

Publications and source records attributed to D Steel.

At least 19 recordsLinked to original sources
PubMed2006

Managing 'suspicious glaucomatous discs' identified during digital-photography-based diabetic retinopathy screening.

PURPOSE: An audit to demonstrate the outcome of patients identified with suspicious glaucomatous discs within a digital-photography-based diabetic retinopathy screening programme. METHODS: Primary care based digital photographic screening was performed utilising mydriasis and two-field digital photography for all patients with diabetes. Patients identified with discs suspicious of glaucomatous optic neuropathy (GON) were initially referred to an accredited community-based optometrist for further assessment. Some patients were then referred to secondary care where appropriate. RESULTS: From 1st April 2002 to 31st March 2003 a total of 3868 patients were screened for diabetic retinopathy. This audit revealed that 55 subjects were identified by retinal screeners as having discs suspicious of glaucoma. A total of 29 were already under glaucoma clinic review. A total of 23/26 remaining were referred for an assessment by an accredited optometrist. Of these 13 were normal, 6 were referred to secondary care and 4 failed to attend. The three remaining were referred directly to secondary care. CONCLUSIONS: All nine referrals to secondary care were deemed appropriate by a glaucoma specialist. This suggests that the system described does not lead to over-referral of suspicious discs - although the issue of how many glaucomatous discs are missed during screening (false negatives) will only be answered in the longer term.

Aged↗
PubMed2005

Central scotoma associated with intraocular silicone oil tamponade develops before oil removal.

BACKGROUND: Unexplained sudden visual loss after removal of silicone oil from the eye has recently been described. We report the occurrence and features of unexplained central scotoma developing with silicone oil in situ in the vitreous cavity. METHODS: A retrospective case series of five patients (from two centres) who reported a central scotoma commencing during silicone oil tamponade was studied. All patients had vitrectomy for macula-on retinal detachment, with ultra-purified silicone oil tamponade (four out of five had giant retinal tear). Investigations included visual acuity, intraocular pressure, optical coherence tomography, fluorescein angiography, visual fields and electrophysiology. RESULTS: All patients reported a central scotoma that appeared during oil tamponade. Visual acuity fell by a mean of 0.93 LogMAR units after onset of the scotoma. After cataract extraction and oil removal, vision remained reduced by a mean of 0.8 units. The mean duration of oil in the eye was 2.7 months when the scotoma was noted by the patient. Investigations were performed after removal of oil. Fluorescein angiography (FFA) was performed in two cases and optical coherence tomography (OCT) in five patients. No abnormality was demonstrated. Electrophysiology was performed in five patients with pattern electroretinography suggestive of macular dysfunction in four patients. CONCLUSION: This is the first case series describing central scotoma associated with silicone oil in situ. Electrophysiology indicated macular dysfunction in most cases. We suggest that early removal of oil in cases with good visual potential should be considered to avoid this sight-threatening complication.

Adult↗
PubMed1999

The T-superfamily of conotoxins.

We report the discovery and initial characterization of the T-superfamily of conotoxins. Eight different T-superfamily peptides from five Conus species were identified; they share a consensus signal sequence, and a conserved arrangement of cysteine residues (- -CC- -CC-). T-superfamily peptides were found expressed in venom ducts of all major feeding types of Conus; the results suggest that the T-superfamily will be a large and diverse group of peptides, widely distributed in the 500 different Conus species. These peptides are likely to be functionally diverse; although the peptides are small (11-17 amino acids), their sequences are strikingly divergent, with different peptides of the superfamily exhibiting varying extents of post-translational modification. Of the three peptides tested for in vivo biological activity, only one was active on mice but all three had effects on fish. The peptides that have been extensively characterized are as follows: p5a, GCCPKQMRCCTL*; tx5a, gammaCCgammaDGW(+)CCT( section sign)AAO; and au5a, FCCPFIRYCCW (where gamma = gamma-carboxyglutamate, W(+) = bromotryptophan, O = hydroxyproline, T( section sign) = glycosylated threonine, and * = COOH-terminal amidation). We also demonstrate that the precursor of tx5a contains a functional gamma-carboxylation recognition signal in the -1 to -20 propeptide region, consistent with the presence of gamma-carboxyglutamate residues in this peptide.

Amino Acid Sequence↗
PubMed1998

Comparison of the time-resolved absorption and phosphorescence from the tryptophan triplet state in proteins in solution.

Measurement of the room temperature Trp triplet state lifetime in proteins by time-resolved phosphorescence can provide valuable information on the structure and dynamics of proteins in solution. Our time-resolved absorption measurements on the long-lived states resulting from electronic excitation of the chromophore demonstrate the presence of more complex behavior than revealed by time-resolved phosphorescence. To provide additional insight into this behavior, a comparative study of time-resolved transient absorption and time-resolved phosphorescence of proteins in solution was carried out. The results show that the time evolution of the long-lived states observed through transient absorption often differs considerably from that observed in time-resolved phosphorescence. In some proteins, the presence of competing reactions complicates the interpretation of the transient absorption measurements (which may affect the phosphorescence yield). A more complete characterization of these processes will likely prove useful in the study of protein structure and dynamics in solution.

Alkaline Phosphatase↗
PubMed1997

Messenger RNA deadenylylation precedes decapping in mammalian cells.

In yeast, the major mRNA degradation pathway is initiated by poly(A) tail shortening that triggers mRNA decapping. The mRNA is then degraded by 5'-to-3' exonucleolysis. In mammalian cells, even though poly(A) tail shortening also precedes mRNA degradation, the degradation pathway has not been elucidated. We have used a reverse transcription-PCR approach that relies on mRNA circularization to measure the poly(A) tail length of four mammalian mRNAs. This approach allows for the simultaneous analysis of the 5' and 3' ends of the same mRNA molecule. For all four mRNAs analyzed, this strategy permitted us to demonstrate the existence of small amounts of decapped mRNA species which have a shorter poly(A) tail than their capped counterparts. Kinetic analysis of one of these mRNAs indicates that the decapped species with a short poly(A) tail are mRNA degradation products. Therefore, our results indicate that decapping is preceded by a shortening of the poly(A) tail in mammalian cells, as it is in yeast, suggesting that this mRNA degradation pathway is conserved throughout eukaryotic evolution.

Animals↗
PubMed1992

Anterior subcapsular plaque cataract in hyperornithinaemia gyrate atrophy--a case report.

Hyperornithinaemia gyrate atrophy (HOGA) is a rare autosomal recessive disorder in which chorioretinal degeneration occurs with cataracts, myopia, and hyperornithinaemia. We report the case of an 18-year-old female who presented with the typical features of HOGA, including posterior subcapsular cataracts and elevated plasma ornithine. She later developed distorted vision in both eyes owing to wrinkling of the anterior lens capsules. Histological examination following lens extraction showed the wrinkling was caused by focal distortion from capsular fibrosis (anterior subcapsular plaque cataract). This specific lens change has not been linked previously with HOGA.

Adolescent↗
PubMed1988

Hereditary hemorrhagic telangiectasia. A family study.

The authors report a comprehensive evaluation of the hemostatic system in eight related patients with hereditary hemorrhagic telangiectasia (HHT). Unlike in previous reports, they could find no evidence for abnormalities in platelet aggregation or for qualitative abnormalities of the Factor VIII complex. The authors did identify a subgroup of the more severely affected patients in whom Factor VIIIc levels were increased, with shortened activated partial thromboplastin times (APTTs) associated with mild elevations of antithrombin III.

Adult↗
PubMed1987

Antagonism of N-methyl-D-aspartate (NMDA) evoked increases in cerebellar cGMP and striatal ACh release by phencyclidine (PCP) receptor agonists: evidence for possible allosteric coupling of NMDA and PCP receptors.

A comparison was made of the actions of phencyclidine receptor agonists and N-methyl-D-aspartate (NMDA) receptor antagonists in two well-defined neurochemical test systems. These included (i) [3H]acetylcholine release from striatal cholinergic interneurons in vitro, a system known to be positively modulated by corticostriatal excitatory amino acid inputs in vivo; and (ii) cerebellar cGMP levels in vivo, an indicator of cerebellar Purkinje cell activity, which is also modulated by excitatory amino acid inputs. Using these neuronal systems, we report that phencyclidine receptor agonists demonstrated a noncompetitive antagonism of NMDA receptor agonist actions.

Acetylcholine↗
PubMed1983

Effects of the Shearing posterior chamber intraocular lens on the corneal endothelium.

A consecutive group of 67 patients (70 eyes) with senile cataract underwent extracapsular cataract extraction and implantation of a Shearing posterior chamber intraocular lens. After two years of follow-up, there was an 11% +/- 2% decrease in central cell density (P less than .001), a 20% +/- 2% decrease in superior cell density (P less than .001), and a 5% +/- 3% decrease in inferior cell density (P less than .005). Complications included corneal edema requiring a corneal transplant (one patient), a sterile nonhealing ulcer that required a conjunctival flap (one patient), and secondary glaucoma (one patient). Nine patients had visual acuities poorer than 20/40 but none had cystoid macular edema. Primary or secondary capsulotomy did not significantly increase endothelial cell loss. Central endothelial cell loss from extracapsular cataract extraction with Shearing posterior chamber intraocular lens implantation was correlated with age, as well as with preoperative superior endothelial cell density (P less than .05).

Aged↗
PubMed1983

Analysis of incision depth following experimental radial keratotomy.

Eight-incision radial keratotomy was performed on a series of cadaver eyes using ultrasonic pachymetry and both metal and diamond blades. There were no statistically significant differences in mean corneal flattening (approximately 9.5 diopters) obtained with either the diamond or metal blades. Short diamond knife incisions produced less flattening that was statistically significant (5.8 diopters). Histologic analysis of incision depth revealed similar results with both the diamond (84%) and metal (86%) blades.

Cadaver↗
PubMed1981

Radial keratotomy in non-human primate eyes.

We performed a prospective study of the effects of radial keratotomy in the owl monkey. We compared a 16-incision and an eight-incision radial keratotomy, and followed the changes in corneal curvature, corneal thickness, endothelial cell counts, and intraocular pressure. We compared the results of the changes in these clinical factors with a histopathologic and ultrastructural analysis of the time-related changes after radial keratotomy in another group of animals. We found that the loss of initial corneal flattening following radial keratotomy corresponded with the contracture of the wound as demonstrated by histopathologic and ultrastructural study. This procedure results in a significant endothelial cell loss (14% to 15%), which is a result of the postsurgical inflammation associated with this surgery. Additionally, examination of the histopathologic structure of these corneas showed a high level of variability in the surgical incision depth, which we believe is responsible for the marked variations in the response to the surgical procedure.

Animals↗
PubMed1981

Radial keratotomy in fresh human cadaver eyes.

Radial keratotomy in fresh human cadaver eyes produced corneal flattening varying from 6 to 11 diopters (D). There was no significant difference in the effectiveness of the incisions to the incisions to the limbus compared to incisions through the limbus. Eighty to ninety percent of the flattening effect was obtained after the first eight incisions. The preoperative keratotomy reading was not helpful in predicting the final result. Histopathology of the incised corneas revealed considerable variation in incision depth and demonstrates the difficulty in achieving deep incisions safely.

Aged↗
PubMed1981

Preliminary study of keratomileusis in primates (Macaca speciosa).

Keratomileusis was investigated in five stumptail monkey eyes (Macaca speciosa). An arbitrary flattening of six diopters was selected and programmed in the computer for each eye. The actual flattening achieved two weeks after surgery ranged from -4.00 D to -6.00 diopters (D). One to 5 diopters of the initial effect was lost during the six-month observation period. Histopathology of two eyes demonstrated attenuation and/or loss of Bowman's membrane with overlying epithelial defects.

Animals↗
PubMed1981

Modification of corneal curvature following radial keratotomy in primates.

Radial keratotomy was performed on six stumptail monkey eyes (Macaca speciosa) and 22 owl monkey eyes (Aotus trivirgotus). Changes in keratometry, specular microscopy, and tonometry have been studied postoperatively for three to six months. Sixteen radial incisions in stumptail monkey eyes resulted in a significant mean corneal flattening of 2.75 diopters (P less than 0.005). This effect was stable with a mean 2.50 diopters flattening remaining six months after surgery. Sixteen radial incisions in ten owl monkey eyes resulted in a much greater short-term effect, with a mean 10.50 diopters of flattening present at two weeks postoperatively. This flattening deteriorated over the observation period, and no significant effect was noted three months after surgery. A comparison of 8 vs 16 incisions on owl monkey eyes demonstrated that these two procedures are equally effective in initially flattening the cornea. Complications and side effects encountered included perforations, irregular astigmatism, corneal neovascularization, transitory increase in pachometry, and decrease in central corneal endothelial cell density in isolated cases.

Animals↗