Search PubMed⌕ Search

Biomedical subjects

C Hudson

Publications and source records attributed to C Hudson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Influence of laser photocoagulation for clinically significant diabetic macular oedema (DMO) on short-wavelength and conventional automated perimetry.

The aim of the study was to determine the effect of laser photocoagulation for clinically significant diabetic macular oedema (DMO) on macular visual function as assessed by conventional and short-wavelength automated static threshold perimetry. The sample comprised 24 patients who required laser photocoagulation for clinically significant DMO (mean age 59.75 years, range 45-75 years). One eye of each patient was selected for the study. Patients underwent conventional and short-wavelength perimetry using programme 10-2 of the Humphrey Field Analyser on two separate occasions prior to treatment and subsequently within 1 week of, and at 1, 2, 4 and 12 weeks after, treatment. The pointwise pattern deviation plot was analysed for conventional perimetry and a pointwise horizontal and vertical hemifield asymmetry analysis was derived for short-wavelength perimetry (thereby negating the influence of pre-receptoral absorption). The extent of sensitivity loss was determined by counting the number of stimulus locations with statistical probability levels of p less than 0.05. Group mean log minimum angle of resolution (logMAR) visual acuity was largely unchanged over the course of the study. Conventional perimetry showed an increase in the group mean number of abnormal contiguous stimulus locations from 2.4 (SD 4.3, range 0-14) immediately prior to treatment, to 12.4 (SD 7.8, range 0-30) within 1 week of treatment; at 3 months post-treatment, the group mean number of abnormal contiguous stimulus locations was 8.1 (SD 6.5, range 0-20). A similar but less pronounced change was found for short-wavelength perimetry. The spatial position of the post-treatment localised sensitivity loss corresponded with the area of retinal photocoagulation. Despite proven benefit in the stabilisation of visual acuity, laser photocoagulation for clinically significant DMO invariably results in a localised loss of perimetric sensitivity within 10 degrees eccentricity of the fovea. Evidence for the value of laser therapy for clinically significant DMO must be re-examined.

Aged↗
PubMed1998

Xpat, a gene expressed specifically in germ plasm and primordial germ cells of Xenopus laevis.

cDNAs specific to vegetal poles of Xenopus gastrula embryos were used as a probe to screen a gastrula vegetal pole cDNA library. One of the novel clones isolated had an RNA expression pattern consistent with it being a component of germ plasm and it was thus named Xpat (Xenopus primordial germ cell associated transcript). The open reading frame encodes a 35 kDa protein with no clear homologies. The RNA is localised to the vegetal pole throughout oogenesis and early cleavage. During gastrulation cells containing this message move internally and at tailbud stages they migrate in an antero-dorsal direction. Xpat mRNA is not detectable once the dorsal mesentery forms. We show that the 3'-UTR is required and is sufficient for localisation of exogenous RNA to the vegetal pole of oocytes. We propose that Xpat UTR-containing transcripts can be localised by the Vg1 or late pathway of mRNA localisation during stage III of oogenesis, but endogenous Xpat appears to be localised earlier by a mitochondrial cloud mechanism similar to that proposed for Xcat-2.

Amino Acid Sequence↗
PubMed1998

Scanning laser tomography Z profile signal width as an objective index of macular retinal thickening.

AIMS: (i) To evaluate the relation between retinal thickness and the Z profile signal width of a scanning laser tomographer in selected patients exhibiting clinically manifest and circumscribed macular retinal thickening; (ii) to compare the Z profile signal width values of a group of age similar normal subjects with those of the patients with macular retinal thickening; and (iii) to present the methodology underlying the Z profile signal width derivation. METHODS: Three patients with the following conditions were selected: widespread diabetic macular oedema; localised diabetic macular oedema; and macular hole. The patients were selected because they exhibited clinically manifest and circumscribed macular retinal thickening. Patients underwent fundus photography and a clinical examination which included fundus biomicroscopy. Fourteen age similar normal subjects were also assessed. The Heidelberg retina tomograph (HRT) was utilised to acquire seven topographic images of each macula. Z profile signal width data were analysed using custom software. Signal width was measured at 50% of the maximum intensity. RESULTS: For each patient with macular retinal thickening, Z profile signal width analysis (after normalisation to reduce the influence of variation in reflectance intensity between successive images) revealed a significant (p < 0.0001) localised increase of signal width which agreed with the HRT topographic analysis of retinal height, and also the clinical assessment of retinal thickness. The mean normalised Z profile signal width for the normal subjects (assessed over the whole image) ranged from 0.278 (SD 0.039) to 0.444 (0.063); these values compared with those obtained from patients in areas of macular retinal thickening of 0.761 (0.224) to 0.953 (0.194). Z profile signal width test-retest data for the patient with localised diabetic macular oedema were plus or minus 0.159 which compared with a mean signal width value of 0.761. CONCLUSION: The evidence of this study, based upon three selected patients with macular retinal thickening and 14 normal subjects, would suggest that Z profile signal width analysis offers a non-invasive, objective, topographic, and reproducible index of macular retinal thickening. Studies employing larger sample sizes are required to determine the true clinical worth of the technique.

Aged↗
PubMed1997

Xsox17alpha and -beta mediate endoderm formation in Xenopus.

We have isolated two Xenopus relatives of murine Sox17 expressed in gastrula presumptive endoderm. Xsox17alpha and -beta expression can be induced in animal caps by activin, but not by FGF. Ectopic expression of these genes in animal caps induces the expression of endoderm markers; this induction is blocked by overexpression of a fusion of the Xsox17beta HMG domain to the Drosophila Engrailed repressor domain, as is induction of endoderm markers by activin and the expression of endodermal markers in whole embryos and isolated vegetal poles. These experiments, as well as the effects of the mRNAs on embryo phenotypes, suggest that the Xsox17 genes mediate an activin-induced endoderm differentiation pathway in animal caps and are involved in normal endoderm differentiation in embryos.

Activins↗
PubMed1997

Increased phospholipid breakdown in schizophrenia. Evidence for the involvement of a calcium-independent phospholipase A2.

BACKGROUND: Magnetic resonance spectroscopy studies have suggested above-normal turnover of membrane phospholipids in brains of patients with schizophrenia. One possible explanation for these findings is increased activity of the phospholipid-catabolizing enzyme phospholipase A2 (PLA2). However, attempts to demonstrate higher PLA2 activity in the serum of subjects with schizophrenia have led to conflicting results. We hypothesized that this was due to serum PLA2 activity consisting of a family of different enzymes, with each group of investigators measuring activity of different PLA2 forms. DESIGN: Activity of PLA2 in serum samples obtained from 24 individuals with schizophrenia was compared with serum obtained from 33 age- and sex-matched control subjects, using both fluorometric and radiometric assays with different substrates. Each method had previously yielded conflicting results concerning the status of the enzyme in schizophrenia. RESULTS: With the fluorometric assay, serum PLA2 activity in individuals with schizophrenia was markedly increased by 49% compared with control subjects (P < .001). In contrast, radiometric assay of the same serum samples resulted in PLA2 activity not significantly different between patients and control subjects. Further investigations demonstrated that, whereas the radiometric assay measured activity of a calcium-dependent enzyme, the fluorometric assay detected a calcium-insensitive enzyme possessing an acid-neutral pH optimum. CONCLUSIONS: Increased calcium-independent PLA2 activity was seen in the serum of patients with schizophrenia. This change, if present also in the brain, may well explain the increased levels of phosphodiesters observed using magnetic resonance spectroscopy and therefore may contribute to the pathophysiological features of the disorder.

Adult↗
PubMed1997

Cardiac pacemaker dysfunction in children after thoracic drainage catheter manipulation.

Two children underwent placement of permanent, epicardial-lead, dual-chamber, unipolar pacemaker systems for complete heart block. Postoperatively, both patients demonstrated subcutaneous emphysema-in the area of their pulse generators-temporally related to thoracic catheter manipulation. Acutely, each situation was managed with manual compression of the pulse generator, ascertaining appropriate pacemaker sensing and pacing. Maintenance of compression with pressure dressings, vigilant observation/monitoring, and education of the care givers resulted in satisfactory pacemaker function without invasive intervention.

Catheterization↗
PubMed1997

Objective morphological assessment of macular hole surgery by scanning laser tomography.

AIM: To assess the morphological change in retinal topography using a scanning laser tomographer following macular hole surgery. To compare the results of scanning laser tomography with clinical evaluation and visual function assessment. METHODS: The sample for this pilot study comprised four eyes exhibiting different stages of macular hole formation preoperatively. Subjects were assessed preoperatively and at 1 and 3 months postoperatively. Each assessment included visual acuity, letter contrast sensitivity, clinical examination (including automated static perimetry), and scanning laser tomography. The Heidelberg retina tomograph (HRT) was used to acquire digitised scanning laser tomography images of the macula (10 degrees and 20 degrees fields). Surgery essentially comprised vitrectomy, peeling of the posterior hyaloid face, if still attached, and intraocular gas tamponade. The magnitude and significance of topographic change were determined postoperatively using the HRT topographic difference facility. RESULTS: Topographic difference analysis of the right and left eyes of case 1 showed a significant reduction in the height of the retina postoperatively. Topographic difference analysis of case 2 showed no significant change in topography. Topographic difference analysis of case 3 showed a significant increase in the height of the retina postoperatively. Scanning laser tomography agreed with clinical assessment based upon fundus biomicroscopy in three of the four eyes studied; the postoperative closure of the stage 2 macular hole (as noted by clinical assessment) proved to be too small to reach statistical significance. Scanning laser tomography agreed with the assessment of visual function in two eyes; the agreement between scanning laser tomography and visual function depends, in part, on the stage of development of the macular hole. CONCLUSION: Scanning laser tomography provides an objective evaluation of the outcome of macular hole surgery. Studies employing larger sample sizes are required to fully determine the clinical worth of the technique.

Adult↗
PubMed1995

The attenuation of blue-on-yellow perimetry by the macular pigment.

PURPOSE: To determine the influence of macular pigment absorption on blue-on-yellow perimetry using a technique suitable for application with the Humphrey Field Analyzer. METHODS: The sample comprised one eye from each of 46 healthy subjects (age range, 20-80 years). Macular pigment absorption was assessed by measuring medium-wavelength sensitive cone sensitivity for 460- and 570-nm narrowband stimuli at the fovea, at 5.5 degrees and at 8 degrees eccentricity. The differences in sensitivities recorded between the fovea and 8 degrees eccentricity and between 5.5 degrees and 8 degrees eccentricity for the 460-nm stimulus relative to a value of zero at 570 nm were attributed to absorption by the macular pigment. Blue-on-yellow perimetry was undertaken using a 460-nm narrowband blue Goldmann size V stimulus and a yellow 330-cdm-2 background. RESULTS: Group macular pigment absorption (mean +/- standard error) was 0.40 +/- 0.03 log units foveally and 0.00 +/- 0.03 log units at 5.5 degrees eccentricity. The group mean foveal macular pigment absorption was significantly different from zero (P < 0.01). The coefficient of repeatability for the macular pigment absorption procedure (based on test-retest data for 16 subjects) was +/- 0.28 log units at the fovea and +/- 0.35 log units at 5.5 degrees eccentricity. CONCLUSION: The net effect of ocular media and macular pigment absorption relative to 460 nm was to attenuate the blue-on-yellow visual field at the fovea by approximately 0.80 log units and elsewhere by 0.40 log units.

Absorption↗
PubMed1995

Novel quinone antiproliferative inhibitors of phosphatidylinositol-3-kinase.

The inhibition of phosphatidylinositol-3-kinase (PtdIns-3-kinase), protein kinase C and c-Src protein tyrosine kinase by a series of halogenated naphthoquinones and quinoline quinones related to the plant-derived naphthoquinones juglone and methyljuglone, which inhibit protein kinase C, has been investigated. Some of the compounds inhibited PtdIns-3-kinase at micromolar concentrations and below. PtdIns-3-kinase inhibition was time dependent and could be prevented by endogenous thiol. The compounds were only weak inhibitors of PtdIns-4-kinase. Some of the compounds inhibited protein kinase C, but c-Src protein tyrosine kinase was only weakly inhibited. In intact cells, PtdIns-3-kinase was only partly inhibited by concentrations of the halogenated quinones that inhibited cell growth. Some halogenated quinones showed in vivo antitumor activity without accompanying toxicity, while methyljuglone was without in vivo antitumor activity. Halogenated quinones may have multiple biochemical effects in the cell that could contribute to their cytotoxic and antitumor effects. Inhibition of PtdIns-3-kinase by the halogenated quinones may provide a lead for the development of more potent and specific inhibitors.

Breast Neoplasms↗
PubMed1994

Risk identification for HIV infection in an inner London antenatal population.

This study was carried out to ascertain whether routine antenatal history taking is an effective means of identifying risk factors for HIV infection. Information about risk obtained at routine booking was compared with answers to selected questions obtained at a research interview. The study was conducted at St. Bartholomew's Hospital Homerton, and ran from February 1991 to March 1992. Of the 3729 women interviewed, 1671 had been hand booked (unstructured questionnaire) and 2058 had been computer booked (structured questionnaire). Hand booking failed to identify 77% of risk factors compared with 7% for computer booking. The findings highlight the underdetection of risk activity and confirm the need for intermittent, anonymous sampling to obtain background information against which a decision to implement universal testing may be made.

Female↗
PubMed1994

Fatigue effects during a single session of automated static threshold perimetry.

PURPOSE: To determine using a routine clinical program the time course of the fatigue effect in both eyes at a given examination, the influence of rest periods during the examination, and the differences in the fatigue effect between persons with ocular hypertension and age-matched normal subjects. METHODS: Perimetry was undertaken for both eyes of 20 normal persons and 20 persons with ocular hypertension using Program G1X (Interzeag AG, Schlieren, Switzerland) of the Octopus 1-2-3 perimeter. Global mean defect and loss variance were calculated for each of the eight individual stages and global SF was calculated for stages 5 to 8. The superoinferior and nasotemporal hemifield indices and those for within and beyond 17 degrees eccentricity were calculated separately to investigate the locus of the fatigue effect. RESULTS: Group mean mean defect and loss variance deteriorated over stages (P < 0.001) and between eyes for both groups (P < 0.001; P < 0.004). The deterioration in the mean defect was more marked peripherally (P < 0.001) and inferiorly with age and group (P < 0.001) whereas the localized loss was more pronounced peripherally (P < 0.001), superiorly (P < 0.010) and nasally (P < 0.001). A 1-minute break during the examination of a given eye and a 3-minute break between eyes was insufficient to overcome the fatigue effect. The performance of the two groups was almost indistinguishable. CONCLUSIONS: The deterioration in the visual field indices mean defect and loss variance challenges the currently accepted ideal length of a perimetric examination with the conventional algorithms. Confidence limits for the definition of abnormality with these algorithms should reflect the presence of the fatigue effect and be different for the second eye.

Aged↗
PubMed1993

Evaluation of FASTPAC: a new strategy for threshold estimation with the Humphrey Field Analyser.

A new strategy for threshold estimation, FASTPAC, has been introduced for the Humphrey Field Analyser with the aim of improving the efficiency of visual field examination without loss of accuracy. FASTPAC was compared to the standard 4-2 double staircase strategy in 98 normal volunteers (age 23-83 years). One eye of each subject was examined with both strategies on two visits using Program 30-2. The order of strategy was randomised. FASTPAC examination time was 43% faster than the standard algorithm, but the mean sensitivities were similar. Short-term fluctuation was 24% higher with FASTPAC (P < 0.001). Most parameters were adversely affected by increasing age. FASTPAC offers a valid alternative to the standard strategy in the examination of suspected normal fields and should always be considered as an alternative to the threshold-related screening strategies. The performance of the algorithm in the identification of field loss and in areas of reduced sensitivity awaits further study.

Adult↗
PubMed1993

An investigation of awareness of antenatal protocols.

Previous audit at the Homerton Hospital had revealed a poor level of compliance with established antenatal protocols mandated by risk factors detected at the booking visit. Medical staff were questioned as to their awareness of five of the most important protocols and their response was analysed by a new scoring system. The scores were generally low though consultants scored more highly than junior staff. Scores were related to the length of obstetric experience and duration of work in the obstetric unit but were not related to frequency of the use of the protocol manual nor to the last time that reference was made to the manual. To improve compliance within the unit, the following recommendations were made: (1) regular revision of protocols to incorporate the current views of senior clinicians and (2) improved dissemination of information. The scoring system described here should prove to be a simple and effective method for the assessment of protocols within any unit.

Awareness↗
PubMed1993

Maximizing the dynamic range of the humphrey field analyzer for blue-on-yellow perimetry.

The conditions employed for blue-on-yellow perimetry (i.e. a blue stimulus filter and a high luminance yellow background) are in conflict with those that allow a maximum dynamic range. A modification is described for increasing the dynamic range of the Humphrey Field Analyzer (HFA) for blue-on-yellow perimetry. The position of the HFA stimulus bulb was lowered by reducing the length of both terminals. A concave mirror with a 28 mm radius of curvature was positioned behind the lowered stimulus bulb to give a filament image partly above and partly overlapping the original filament profile within the confines of the size V stimulus patch diameter. The modification achieved a 60% increase in the light output on the default 0 dB value of 10,000 apostilbs and, therefore, a useable dynamic range for blue-on-yellow perimetry of 2.94 log units. The effective increase in voltage supply to the stimulus bulb permitted a filament life of 260 operating hours. Furthermore, the modification ensured the correct calibration of the instrument.

Color↗