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Biomedical subjects

L A Wilson

Publications and source records attributed to L A Wilson.

At least 37 records · Page 2Linked to original sources
PubMed1997

The Endophthalmitis Vitrectomy Study. Relationship between clinical presentation and microbiologic spectrum.

PURPOSE: The authors determine if specific features of the clinical presentation of acute postoperative endophthalmitis correlated with the microbiologic culture results. METHODS: A total of 420 patients who had clinical evidence of endophthalmitis within 6 weeks after cataract surgery or secondary intraocular lens implantation were evaluated as part of a randomized clinical trial. Results of cultures performed on aqueous and vitreous specimens obtained at presentation were categorized as follows: gram-positive coagulase-negative micrococci, "other" gram-positive, gram-negative, and equivocal/no growth. RESULTS: Eleven features of the initial clinical presentation were associated with significant differences in the microbiologic spectrum (P < 0.05). Baseline factors correlating with higher rates of both gram-negative and other gram-positive isolates were: corneal infiltrate, cataract wound abnormalities, afferent pupillary defect, loss of red reflex, initial light perception-only vision, and symptom onset within 2 days of surgery. Gram-negative organisms did not grow in any eyes in which a retinal vessel could be visualized, and 61.9% of these eyes had equivocal or no growth. Diabetes mellitus was associated with a higher yield of gram-positive, coagulase-negative micrococci. Eye pain was not a discriminator for culture results. CONCLUSIONS: The presenting characteristics of acute endophthalmitis after cataract surgery may be helpful in predicting the most likely culture results. Such predictions do not appear sufficiently strong to guide the initial empiric choice of intravitreal antibiotics.

Acute Disease↗
PubMed1997

Variable clinical phenotype in merosin-deficient congenital muscular dystrophy associated with differential immunolabelling of two fragments of the laminin alpha 2 chain.

Approximately half the cases of classical congenital muscular dystrophy (CMD) have a pronounced deficiency or absence of the laminin alpha 2 chain of laminin-2 (merosin). This is caused by mutations in the LAMA2 gene that codes for laminin alpha 2, and all informative cases so far studied show linkage to the appropriate region on chromosome 6q. Most CMD patients with a deficiency of laminin alpha 2 have a severe phenotype that involves skeletal muscle, and the central and peripheral nervous system. We have identified four cases that have minimal reduction of laminin alpha 2 using a commercial antibody that only recognises a C-terminal 80 kDa fragment, but show a pronounced reduction using an antibody to the 300 kDa fragment. Haplotype analysis is compatible with linkage to the LAMA2 locus in three informative families, whilst the fourth family was not informative. Two of the affected children are ambulant and have a mild phenotype. The third case is unusual in having severe muscle weakness but does not show the white matter changes on magnetic resonance imaging of the brain that is usually seen in merosin-deficient cases of CMD; the fourth case has a severe phenotype, typical of merosin-deficient patients but shows good immunolabelling of the 80 kDa fragment of laminin alpha 2, corresponding to the C-terminal region. Our data show that there is a broad spectrum of phenotype and protein expression associated with a primary deficiency in laminin alpha 2, and that a wider range of clinical cases need to be screened for a deficiency of merosin. It is also important to study the expression of laminin alpha 2 with more than one antibody.

Antibody Specificity↗
PubMed1997

Expression of laminin chains in skin in merosin-deficient congenital muscular dystrophy.

Laminin-2 (merosin) is a heterotrimer composed of alpha 2, beta 1 and gamma 1 chains. Approximately half of the cases with the classical form of congenital muscular dystrophy (CMD) have a deficiency of the laminin alpha 2 chain, encoded by the LAMA2 gene on chromosome 6q22. This disorder is often termed merosin-deficient CMD. Skeletal and cardiac muscle, and the peripheral and central nervous systems, all express laminin alpha 2 and can be affected in merosin-deficient CMD. Normal skin also expresses all three chains of laminin-2 at the epidermal/dermal junction, around hair follicles and in the sensory nerves. Skin biopsies can therefore be used to assess merosin status in patients. We show here an absence of laminin alpha 2 in skin from four cases of CMD with a severe phenotype and abnormal magnetic resonance image (MRI) of the brain, in contrast to normal expression in one case of mild CMD with normal MRI, and in five controls. An additional case of CMD had a partial deficiency of laminin alpha 2 in the skin and severe motor disability, but a normal MRI. Sensory nerves in this case showed normal expression of laminin alpha 2, in contrast to its absence in the severe cases. The expression of laminin beta 1 was also reduced in skin from cases of merosin-deficient CMD. In contrast to human fetal muscle, the laminin alpha 2 protein was not detected in fetal skin up to 23 weeks of gestation. The laminin beta 1 and gamma 1 chains, and the mRNA for laminin alpha 2, however, were present. Studies of mRNA of cultured skin cells suggest that fibroblasts are the major source of laminin alpha 2, not keratinocytes. Our data show that skin is useful for the assessment of merosin status in patients with CMD and that skin fibroblasts may be a useful source of tissue-specific RNA. In addition, we show that there is a tissue-specific difference in the developmental expression of the laminin alpha 2 protein.

Adolescent↗
PubMed1996

Diagnosis of merosin (laminin-2) deficient congenital muscular dystrophy by skin biopsy.

BACKGROUND: The alpha2 chain of laminin-2 (merosin), encoded by a gene on chromosome 6q22, is deficient in about half the cases of congenital muscular dystrophy. Diagnosis of this condition has relied on immunocytochemical analysis of the alpha2 chain in muscle biopsy specimens. We have observed that normal skin also expresses laminin alpha2 in the basement membrane at the junction of the dermis and epidermis. Here we have investigated laminin alpha2 deficiency in skin biopsy specimens from two patients with congenital muscular dystrophy. PARTICIPANTS: Two patients with severe congenital muscular dystrophy gave informed consent to a skin biopsy. The girl was aged 10 and the boy was aged 7. The specimens were labelled with a commercially available mouse monoclonal antibody and a rat monoclonal antibody (4H8-2), which recognise an 80 and a 380 kDa fragment of the alpha2 chain, respectively. The antibodies were visualised by standard methods. A muscle biopsy specimen was available for each case, and was processed with the skin biopsy samples (from the girl a few months previously, from the boy at age 14 days). Skin biopsies were done on four controls with normal expression of laminin alpha2 on their skeletal muscle fibres. FINDINGS We did not detect laminin alpha2 in skin specimens from either case, although the controls were positive. The muscle biopsy specimens from the girl showed a few fibres, with traces of laminin alpha2; those from the boy showed no laminin alpha2. INTERPRETATION: Skin biopsy specimens will provide a useful alternative to muscle biopsy samples for the assessment of laminin-2 (merosin) status in congenital muscular dystrophy.

Biopsy↗
PubMed1996

Effect of adhered bacteria on the binding of Acanthamoeba to hydrogel lenses.

OBJECTIVES: To determine the effect of Pseudomonas aeruginosa and Staphylococcus epidermidis on the binding of Acanthamoeba species to hydrogel lenses. METHODS: Cells of amebae and bacteria were incubated with different types of hydrogel lenses. Densities of amebae that were bound to the lenses after rinsing were determined from direct counts with a cell detachment procedure and from scintillation counts of cells, which were radiolabeled with tritiated leucine. RESULTS: With both methods, amebae showed significantly increased binding to hydrogel lenses with attached P aeruginosa. The numbers of amebae that were retained on lenses with attached S epidermidis were not significantly different from those that were retained on lenses without bacteria. The binding of amebae to unworn hydrogel lenses, in contrast to the irreversible adherence of P aeruginosa, was tenuous. CONCLUSIONS: The binding of Acanthamoeba species to unworn hydrogel lenses was tenuous and appeared to be related to water content, surface tensions, and ionic charge. The presence of adhered P aeruginosa on the hydrogel lenses facilitated the binding of Acanthamoeba species. The cocontamination of lens systems with bacteria (eg, P aeruginosa) may be a prime factor in the development of amebic keratitis.

Acanthamoeba↗
PubMed1996

Effect of Staphylococcus epidermidis on hydrogel contact lens retention on the rabbit eye.

A slime-producing isolate of Staphylococcus epidermidis attached to FDA Group II hydrogel contact lenses persisted on rabbit eyes for up to 14 days, but except for minor redness of the eye no other effect was observed. Eye flora of eight representative New Zealand White rabbits included four different species of Staphylococcus including S. epidermidis and one species of Micrococcus, none of which produced overtly obvious biofilms. The slime-producing strain of S. epidermidis adhered more effectively to lenses than a non-slime-producing strain, and lenses challenged with the slime-producing strain remained on the rabbit eye for longer time periods than those with a non-slime-producing strain. Bacteria associated with the contact lens may affect the retention of the lens on the rabbit cornea during experimental studies.

Animals↗
PubMed1996

Intraocular dexamethasone produces a harmful effect on treatment of experimental Staphylococcus aureus endophthalmitis.

BACKGROUND: We created a standardized model of severe Staphylococcus aureus endophthalmitis in the aphakic rabbit eye to test various treatment strategies involving corticosteroid administration in addition to vitrectomy and antibiotic treatment. MATERIALS AND METHODS: In 71 aphakic New Zealand albino rabbit eyes, experimental endophthalmitis was created by injecting 10(5) colony-forming units of Staphylococcal aureus. The animals were divided into 5 groups. One control group was followed up without treatment, while 4 groups were treated with vitrectomy and intraocular cefazolin injection. Two groups were also treated with intramuscular methylprednisolone, 1 group beginning on the day of surgery and 1 group beginning on the following day. In the final group, dexamethasone, 400 micrograms, was injected into the vitreous cavity at the close of surgery. Culture results were compared on the first 2 days after surgery. Inflammatory scores, including development of total corneal opacity, were assessed over a 21-day follow-up period, and histopathologic grading was carried out at the conclusion of the clinical observations. RESULTS: Simultaneous administration of systemic corticosteroids beginning on the day of vitrectomy decreased inflammatory scores 1 week after institution of therapy but did not affect final scores. Delay of initiation of intramuscular corticosteroid until the first postoperative day negated the positive effects. Administration of intraocular corticosteroids was associated with an increase in inflammatory scores throughout the period of observation, an increase in percentage of eyes that developed opaque corneas, an increase in choroidal inflammation graded moderate or severe, and an increase in retinal necrosis compared with vitrectomy and cefazolin injection alone. CONCLUSIONS: This data suggest caution in the use of intraocular corticosteroids in treatment of severe endophthalmitis.

Animals↗
PubMed1996

Spectrum and susceptibilities of microbiologic isolates in the Endophthalmitis Vitrectomy Study.

PURPOSE: To determine the microbiologic spectrum and antibiotic susceptibilities of infecting organisms in postoperative endophthalmitis and to evaluate the effects of operative factors on the microbiologic spectrum. METHODS: Patients with bacterial endophthalmitis presenting within six weeks of cataract extraction or secondary intraocular lens implantation (IOL) were evaluated. Cultures and Gram stains were performed on intraocular specimens and susceptibility tests on the isolates. RESULTS: Confirmed microbiologic growth was demonstrated from intraocular specimens from 291 of 420 patients (69.3%). Gram-positive bacteria were isolated from 274 patients (94.2%) with confirmed growth and gram-negative bacteria from 19 (6.5%). Two hundred twenty-six of the 323 isolates obtained (70.0%) were gram-positive, coagulase-negative micrococci, 32 (9.9%) Staphylococcus aureus, 29 (9.0%) Streptococcus species, seven (2.2%) Enterococcus species, ten (3.1%) miscellaneous gram-positive species, and 19 (5.9%) gram-negative species. All gram-positive isolates tested were susceptible to vancomycin. Seventeen gram-negative isolates (89%) were susceptible to both amikacin and ceftazidime and two (11%) were resistant to both. Anterior chamber or secondary IOL implantations were associated with higher rates of infection with gram-positives other than coagulase-negative micrococci than were posterior chamber IOL implantations (P = .022) or primary cataract extractions (P = .024). CONCLUSIONS: Gram-positive, coagulase-negative micrococci predominated in this series. Vancomycin was active against all gram-positive isolates tested. Amikacin and ceftazidime showed equivalent activity against gram-negative isolates. Secondary or anterior chamber lens implantations were associated with a possible spectrum shift toward gram-positive organisms other than the coagulase-negative micrococci.

Anti-Bacterial Agents↗
PubMed1996

Effect of lactation on insulin signal transduction in sheep adipose tissue and skeletal muscle.

The molecular basis of the insulin resistance of adipocytes and skeletal muscle during lactation has been investigated in sheep. The number of insulin receptors per adipocyte or per unit membrane protein for skeletal muscle is unchanged by lactation. The ability of insulin to stimulate autophosphorylation of its beta-subunit was enhanced in adipocytes but not in skeletal muscle during lactation. This increased autophosphorylation was due, at least in part, to enhanced tyrosine phosphorylation and was found when both solubilised, immunoprecipitated insulin receptors and intact adipocytes were incubated with insulin. The ability of the insulin receptor kinase to phosphorylate other proteins did not appear to be altered by lactation; this was shown with lectin-purified insulin receptors using the artificial substrate, polyglutamyl tyrosine, and in intact adipocytes. Lactation had no effect on the ability of insulin to activate two key downstream kinases, mitogen-activated protein kinase and phosphatidyl inositol-3-kinase in adipocytes. The study thus shows that the insulin resistance of lactation in sheep is due to changes downstream of the receptor in both adipocytes and skeletal muscle.

Adipose Tissue↗
PubMed1996

Binding of Acanthamoeba to hydrogel contact lenses.

The numbers of Acanthamoeba binding to new hydrogel contact lenses of different polymer and water content were determined with two quantitative methods, a radiolabeled-cell method and a detaching-fluid method. Numbers of amoebae retained on nonionic lenses increased with increasing water content of the lenses. With both nonionic and ionic lenses numbers of associated amoebae decreased with successive rinsing steps. The retentions of amoebae on unworn hydrogel lenses, in contrast to the irreversible adhesion of bacteria, were tenuous and appeared to be effected mainly by surface tension, surface charge and water content.

Acanthamoeba↗
PubMed1996

Effects of polyhexamethylene biguanide and chlorhexidine on four species of Acanthamoeba in vitro.

We determined the relative minimal inhibitory and minimal amoebicidal concentrations of chlorhexidine digluconate and polyhexamethylene biguanide for four species of Acanthamoeba. The amoebae were grown in peptone-glucose-yeast extract broth for 72 h in tissue culture flasks. Either washed trophozoites (approximately 10(5)) or cysts (approximately 10(5)) were incubated in the enrichment broth in 96 well microtiter trays. Antimicrobial concentrations of the biguanides were determined from microscopic examinations of methylene blue uptake and from subcultures. In general, killing was time dependent. Minimal amoebicidal concentrations at 24 h ranged from 50 to 100 mg/ml and to as low as 25 mg/ml by 72 h. Trophozoites were killed more rapidly than cysts. Both biguanides had similar levels of activity. A synergistic combination of chlorhexidine and polyhexamethylene biguanide (total concentration 25 mg/ml) was most evident for A. castellanii and A. polyphaga. Cysts of A. culbertsoni and A. hatchetti stained more rapidly after exposure to the combination of biguanides than to the single biguanides, but there were no statistically significant differences in the final numbers of dead or stained cysts after exposure to the combination or to the single biguanides.

Acanthamoeba↗
PubMed1995

Expression of laminin subunits in congenital muscular dystrophy.

The expression of laminin subunits M, A, B1 and B2 was studied immunocytochemically in 25 cases of classical congenital muscular dystrophy (CMD), 11 hypotonic infants, 20 cases of a variety of inherited and acquired neuromuscular disorders, and 11 controls. Merosin, as indicated by labelling for the M chain, was deficient in 12 (48%) of the cases of classical CMD. Seven cases had no detectable labelling for the M chain whereas five showed traces, including three cousins from the same family. This suggests that very low expression may relate to a possible difference in the molecular defect, compared with cases completely devoid of the M chain. The A chain was abundant in regenerating fibres and in immature fibres expressing fetal myosin. In all merosin-deficient cases the A chain was over-expressed but this was not due to immaturity. A secondary reduction in sarcolemmal expression of the B1 chain occurred in five merosin-deficient cases, whilst expression in vascular tissue was normal. B1 was also reduced in one merosin-positive case of CMD, suggesting that other subunits may be involved in other forms of CMD. No differences in the expression of the B2 chain were observed in any of the cases studied. No abnormality in laminin subunits was found in controls or other neuromuscular disorders.

Adolescent↗