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Biomedical subjects

L E Allen

Publications and source records attributed to L E Allen.

At least 19 recordsLinked to original sources
PubMed2006

Is optic nerve fibre mis-routing a feature of congenital stationary night blindness?

PURPOSE: To determine whether patients with congenital stationary night blindness (CSNB) have electrophysiological evidence of optic nerve fibre mis-routing similar to that found in patients with ocular albinism (OA). METHOD: We recorded the Pattern Onset VEP using a protocol optimised to detect mis-routing of optic nerve fibres in older children and adults. We tested 20 patients (age 15-69 yrs) with X-linked or autosomal recessive CSNB, 14 patients (age 9-56 yrs) with OA and 13 normally pigmented volunteers (age 21-66 yrs). We measured the amplitude and latency of the CI component at the occipital midline and over left and right occipital hemispheres. We also assessed the computed inter-hemispheric "difference" signal. Subjects with CSNB were classified as having the "complete" or "incomplete" phenotype on the basis of their ERG characteristics. Members of X-linked CSNB pedigrees underwent mutation screening of the NYX and CACNA1F genes. RESULTS: CI was significantly smaller over the ipsilateral hemisphere and more prominent over the contralateral hemisphere in OA patients compared with both controls and CSNB patients. In CSNB patients CI response amplitudes were not significantly different from controls but peak latency was prolonged at all three electrodes compared with controls. The inter-hemispheric "difference" signal was abnormal for the OA group but not for the CSNB group. Contralateral dominance of CI could be identified in the majority of OA patients and the "difference" signal was opposite in polarity for left compared with right eye stimulation in every patient in this group. Only 3 of 20 patients with CSNB showed significant inter-hemispheric asymmetry similar to that seen in the OA patients. All 3 CSNB patients with evidence for optic nerve fibre mis-routing had X-linked pedigrees: 2 had an identified mutation in the NYX gene but no mutation in either the NYX or CACNA1F genes was identified in the third. VEP evidence of optic nerve fibre mis-routing was present in 3 of the 11 subjects with "complete" phenotype and none of the 9 patients with "incomplete" phenotype CSNB. CONCLUSION: Mis-routing of optic nerve fibres does occur in CSNB but we found evidence of it in only 15% of our patients.

Adolescent↗
PubMed2004

Full-field ERG responses recorded with skin electrodes in paediatric patients with retinal dystrophy.

PURPOSE: Assess ERG responses recorded with skin electrodes in children with retinal dystrophies. METHOD: ERG responses were recorded using skin electrodes in 17 healthy children and 43 paediatric patients with retinal dystrophy. Subjects were aged 4-14 years. ERG responses were recorded to full-field stimuli similar to those recommended in the ISCEV standard. The type of retinal dystrophy was classified on the basis of standard clinical criteria and the ERG responses were compared with those of the age-matched controls. RESULTS: ERG responses were abnormal in every patient. The specific type of ERG abnormality was also consistent with the clinical findings in the majority of patients. Rod responses were abnormal in every patient with a rod-cone dystrophy and cone responses were also abnormal in the majority of patients. Those patients with cone dystrophy or rod monochromatism had normal or near normal rod responses but sub-normal or absent cone responses. Patients with CSNB or XLRS had a sub-normal b-wave but normal amplitude a-wave. CONCLUSION: ERGs can be recorded successfully with skin electrodes in paediatric patientsand responses can aid the diagnosis of the type of retinal dystrophy.

Adolescent↗
PubMed2003

Genotype-phenotype correlation in British families with X linked congenital stationary night blindness.

AIM: To correlate the phenotype of X linked congenital stationary night blindness (CSNBX) with genotype. METHODS: 11 CSNB families were diagnosed with the X linked form of the disease by clinical evaluation and mutation detection in either the NYX or CACNA1F gene. Phenotype of the CSNBX patients was defined by clinical examination, psychophysical, and standardised electrophysiological testing. RESULTS: Comprehensive mutation screening identified NYX gene mutations in eight families and CACNA1F gene mutations in three families. Electrophysiological and psychophysical evidence of a functioning but impaired rod system was present in subjects from each genotype group, although the responses tended to be more severely affected in subjects with NYX gene mutations. Scotopic oscillatory potentials were absent in all subjects with NYX gene mutations while subnormal OFF responses were specific to subjects with CACNA1F gene mutations. CONCLUSIONS: NYX gene mutations were a more frequent cause of CSNBX than CACNA1F gene mutations in the 11 British families studied. As evidence of a functioning rod system was identified in the majority of subjects tested, the clinical phenotypes "complete" and "incomplete" do not correlate with genotype. Instead, electrophysiological indicators of inner retinal function, specifically the characteristics of scotopic oscillatory potentials, 30 Hz flicker and the OFF response, may prove more discriminatory.

Base Sequence↗
PubMed1998

The treatment of encapsulated trabeculectomy blebs in an out-patient setting using a needling technique and subconjunctival 5-fluorouracil injection.

PURPOSE: Encapsulation of the trabeculectomy bleb is a common cause of drainage failure in the early post-operative period. The primary management of bleb encapsulation has previously been to restart medical therapy, but recent advances in the technique of needle manipulation and the introduction of adjunctive 5-fluorouracil (5-FU) have increased the popularity of early surgical bleb management. By reporting the results of bleb needling in a series of patients, we aim to illustrate its safety and efficacy. METHODS: We have reviewed a series of 32 eyes in which needling and 5-FU injection was performed for bleb encapsulation, and analysed the results over a follow-up period of 10.7 +/- 2.9 months. RESULTS: In 14 (43.7%) cases, primary needling was performed; in the other 18, needling was performed after conservative treatment had proved inadequate. The mean intraocular pressure (IOP) of the group decreased from 29.2 +/- 10.5 mmHg prior to needling to 15.9 +/- 4.0 mmHg at the most recent attendance (paired t-test p = 1.3 X 10(-7), with all eyes having a final IOP measurement of 22 mmHg or less. Twenty-three (71.9%) of the cases maintained a target IOP of 18 mmHg or less without additional treatment; 5 (15.6%) were qualified successes with an untreated IOP between 19 and 21 mmHg. The remaining 4 (12.5%) patients, whose IOPs ranged between 20 and 22 mmHg with one hypotensive agent, were considered needling failures. Choroidal detachment complicated the procedure in 2 cases; in each this resolved with conservative management and without long-term visual consequence. CONCLUSION: This technique is recommended as a safe and effective method of treating bleb encapsulation.

Adult↗
PubMed1998

The association between the oculocardiac reflex and post-operative vomiting in children undergoing strabismus surgery.

The oculocardiac reflex (OCR) is a potentially serious complication of ophthalmic surgery which is most commonly elicited during paediatric strabismus surgery. Post-operative vomiting (POV) is also extremely common after such procedures and may result in admission following planned day-case surgery. Although many factors play a part in the occurrence of POV, stimulation of the trigemino-vagal reflex arc is thought to explain the particularly high rate of vomiting after strabismus surgery. The OCR and the vaso-vagal response share this neuronal pathway, the bradycardia of the OCR often being the only objective feature of the vaso-vagal response while the patient is anaesthetised. The aim of this study was to investigate the possible association between the occurrence of the OCR and subsequent POV in children undergoing strabismus surgery. We have studied this relationship in 79 children, aged between 1 and 13 years, undergoing strabismus surgery under standardised anaesthetic conditions. A positive OCR was regarded as a drop in heart rate of 10% or more, or the onset of a dysrhythmia. An intraoperative OCR was elicited in 51 (64.6%) of the 79 children, whilst 29 (36.7%) developed POV in the subsequent 24 h period. There was a significant association between a positive intraoperative OCR and POV (p = 0.01): children with a positive OCR were 2.6 times more likely to vomit than those without the reflex. We conclude that there is an association between the occurrence of the OCR and POV and discuss possible preventive strategies.

Adolescent↗
PubMed1995

Survey of colour contrast sensitivity in non-ophthalmic users of blue-green wavelength argon lasers.

BACKGROUND: Previous studies have shown that ophthalmologists using blue-green argon laser may suffer subtle defects in their colour vision. A reduction in colour contrast sensitivity in the tritan colour confusion axis, an early manifestation of blue cone photoreceptor injury by the high energy photons of the laser, has been demonstrated and has prompted a reappraisal of laser safety in ophthalmology. Argon laser is also frequently used in scientific research, often at higher power output and for longer periods than is used in clinical practice. The scientists operating these lasers are at risk of developing similar phototoxic retinal injury. METHODS: The colour contrast sensitivity of 18 scientists who regularly use short wavelength argon laser was investigated. RESULTS: Eye protection was infrequently used and individuals had been subjected to between 580 and 7200 hours of cumulative laser exposure during the course of their research. CONCLUSION: The use of blue-green argon laser by the scientists investigated was not associated with a significant reduction in colour contrast sensitivity.

Adult↗
PubMed1995

Protein kinase C is increased in the liver of humans and rats with non-insulin-dependent diabetes mellitus: an alteration not due to hyperglycemia.

We tested the hypothesis that liver protein kinase C (PKC) is increased in non-insulin-dependent diabetes mellitus (NIDDM). To this end we examined the distribution of PKC isozymes in liver biopsies from obese individuals with and without NIDDM and in lean controls. PKC isozymes alpha, beta, epsilon and zeta were detected by immunoblotting in both the cytosol and membrane fractions. Isozymes gamma and delta were not detected. There was a significant increase in immunodetectable PKC-alpha (twofold), -epsilon (threefold), and -zeta (twofold) in the membrane fraction isolated from obese subjects with NIDDM compared with the lean controls. In obese subjects without NIDDM, the amount of membrane PKC isozymes was not different from the other two groups. We next sought an animal model where this observation could be studied further. The Zucker diabetic fatty rat offered such a model system. Immunodetectable membrane PKC-alpha, -beta, -epsilon, and -zeta were significantly increased when compared with both the lean and obese controls. The increase in immunodetectable PKC protein correlated with a 40% elevation in the activity of PKC at the membrane. Normalization of circulating glucose in the rat model by either insulin or phlorizin treatment did not result in a reduction in membrane PKC isozyme protein or kinase activity. Further, phlorizin treatment did not improve insulin receptor autophosphorylation nor did the treatment lower liver diacylglycerol. We conclude that liver PKC is increased in NIDDM, a change that is not secondary to hyperglycemia. It is possible that PKC-mediated phosphorylation of some component in the insulin signaling cascade contributes to the insulin resistance observed in NIDDM.

Adult↗
PubMed1993

Expression of basic fibroblast growth factor and its receptor in an invasive bladder carcinoma cell line.

Basic fibroblast growth factor (bFGF) is a multifunctional growth factor that can stimulate cell proliferation, production of proteases, and angiogenesis. Loss of mechanisms that regulate bFGF activity could result in tumor development. To test this idea, cells derived from an invasive bladder carcinoma (EJ) were compared with cells derived from a noninvasive bladder carcinoma (RT4) for the expression of bFGF and high and low affinity FGF receptors. bFGF was produced by the invasive EJ cells but not by the noninvasive RT4 cells, suggesting that bFGF could act in an autocrine fashion in the EJ cells to promote their invasion and growth in the surrounding tissue. The two cells lines also showed differences in FGF receptor expression. The EJ cells expressed both high and low affinity FGF receptors as determined by Scatchard analysis, whereas the RT4 cells expressed only high affinity receptors. The high affinity receptors on the RT4 cells were not recognized by an antibody to known FGF receptors. Furthermore, in contrast to the EJ cells, bFGF did not induce protein tyrosine phosphorylation in the RT4 cells. Thus these data suggest that the invasive potential of bladder carcinoma cells may be regulated by the expression of both bFGF and its receptors.

Binding, Competitive↗
PubMed1990

Rapid degradation of extracellular matrix proteins by normal human uroepithelial cells.

The degradation of subendothelial and smooth muscle matrices by normal and neoplastic uroepithelial cells grown under serum-free conditions was examined. Normal urothelial cells were compared with neoplastic cells derived from a low grade papillary tumor (RT4) and a more invasive carcinoma (EJ). Low levels of degradation were observed with all cell types in serum-free medium alone. Supplementing the medium with plasminogen increased the degradative activity of each cell type. Logarithmically growing normal urothelial cells degraded extracellular matrix proteins 6 to 14 times faster on a per cell basis than their transformed counterparts. Analysis of the residual matrix constituents revealed that, while the levels of glycoprotein breakdown by the normal and neoplastic cells were similar, the normal cells degraded more of the collagen components than the neoplastic cells. Epidermal growth factor and cell density were examined as possible regulators of degradative activity. The neoplastic cells were not responsive to cell density as a regulatory factor and were only slightly responsive to epidermal growth factor. However, epidermal growth factor increased the degradative activity of logarithmically growing normal urothelial cells in the presence of plasminogen and the activity of confluent cells was increased to an even greater extent. Gelatin substrate gel analysis confirmed that the normal urothelial cells elaborated a more diverse set of gelatinases than the tumorigenic cells. Although normal urothelial cells had higher degradative abilities than their malignant counterparts, it is significant that the neoplastic cells were less responsive to regulatory signals in our model system. Thus, loss of regulatory mechanisms for protease secretion and matrix degradation may be a more important determinant of invasive ability in vivo than protease secretion or matrix degradation in vitro.

Animals↗
PubMed1982

The surgical management of the enlarged clitoris.

In this study we compare the cosmetic and functional results of the common reconstructive techniques used in the management of patients with clitoral hypertrophy. We find impressive benefits in a surgical procedure that includes excision of the clitoral shaft with preservation of the glans and ventral mucosa combined with simple introitoplasty. We recommend reserving definitive vaginoplasty as needed until the age of puberty. Our experience is this clinical area is being offered with attention to the long-term followup of patients.

Adrenal Hyperplasia, Congenital↗