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Biomedical subjects

C R Dawson

Publications and source records attributed to C R Dawson.

At least 19 recordsLinked to original sources
PubMed1992

Fuchs' superficial marginal keratitis.

We studied three cases of Fuchs' superficial marginal keratitis, an uncommon condition that is characterized by intermittent, recurrent episodes of ocular irritation accompanied by marginal infiltrates and that is followed by progressive marginal superficial stromal thinning. Usually, it has an indolent course with spontaneous remission, and good visual acuity is preserved. In advanced cases, a pseudopterygium develops in the area of marginal thinning. The pseudopterygium encroaches onto the cornea over a period of years, but spares the central cornea. In two of our three cases, the degree of thinning beneath the pseudopterygium became marked. This led to corneal perforation during pseudopterygium excision in one case, and after blunt trauma in the other. These complications indicate the need for special precautions when caring for these patients.

Adult↗
PubMed1992

Comparison of the major outer membrane protein variant sequence regions of B/Ba isolates: a molecular epidemiologic approach to Chlamydia trachomatis infections.

The molecular evaluation of the chlamydial major outer membrane protein (MOMP) gene (omp1) can facilitate epidemiologic investigations of this pathogen. Genotyping of omp1 provides a more precise characterization of Chlamydia trachomatis than do current immunotyping techniques. Genetic omp1 variants of serovars that are responsible for ocular disease in Tunisia were identified. Archival conjunctival samples collected during 1972 and 1975 from trachoma patients in Douz were sequenced by automation along with additional B and Ba trachoma and genital isolates. Over 90% of the nucleotide changes resulted in an amino acid substitution. Different amino acid sequence changes in variable segments 1, 2, and 4 were found in the specimens collected in 1975 from those collected in 1972. Determination of omp1 genotypes responsible for trachoma will be useful for prospective, epidemiologic studies to identify chlamydial reservoirs within the host, evaluate transmission patterns, and determine the antigenic variation of MOMP for rational vaccine development.

Amino Acid Sequence↗
PubMed1992

Herpes simplex viral infection of the mouse trigeminal ganglion. Immunohistochemical analysis of cell populations.

Several distinct populations of sensory neurons in the ophthalmic region of the mouse trigeminal ganglion have been identified by their reactivity to antibodies raised against substance P (SP), calcitonin gene-related peptide (CGRP), cell-surface glycoconjugates SSEA3 and LD2, and the plant lectin, Bandeiraea simplicifolia lectin 1, isolectin 4 (BSIL4). Thirty-six percent of the neurons in the ophthalmic portion of the mouse trigeminal ganglion express CGRP and 17%, SP. All neurons that express SP also express CGRP. Forty percent of the neurons in the ophthalmic region of the ganglion are recognized by monoclonal antisera to SSEA3, and 66% of this population also express the neuropeptides SP or CGRP. The neuronal population recognized by BSIL4 is identical to the population with the LD2 epitope. This population of cells (BSIL4/LD2) does not express the SSEA3 glycoconjugate and is largely nonpeptidergic. All four populations of sensory neurons (SP, CGRP, SSEA3, and LD2/BSIL4) can be infected by herpes simplex virus (HSV). However, the relative proportion of SSEA3- and LD2/BSIL4-labeled cells that were infected productively with HSV was much less than expected based on the relative size of the populations of these neurons in the ophthalmic region of the ganglion.

Animals↗
PubMed1991

Latrine ownership as a protective factor in inflammatory trachoma in Egypt.

We investigated the association between inflammatory trachoma in children aged 1-5 and environmental and sociodemographic risk factors in a rural Nile Delta hamlet. Inflammatory trachoma clustered in households, emphasising the child-to-child nature of transmission in the hamlet. Multiple logistic regression analysis revealed three factors predicting inflammatory trachoma in children: the absence of a latrine in the household, school-age siblings with inflammatory trachoma, and additional same-age siblings (with or without disease) in the household. In the Egyptian setting the presence of pit latrines in all houses, even when full and unscreened, might result in a reduction in trachoma prevalence in this population from the current 49% to 35%. The construction of pit latrines may offer the simplest and most acceptable environmental method for reducing trachoma in this trachoma endemic area.

Child, Preschool↗
PubMed1991

Ultrastructural immunocytochemical localization of herpes simplex virus (type 1) in trigeminal ganglion neurons.

Four days after corneal inoculation of mice with herpes simplex (type 1) virus (HSV), infected trigeminal ganglion cells with and without calcitonin gene-related peptide (CGRP) antigenicity were examined by electron microscopy in sections treated with colloidal gold labeled antibodies. Cells that contain CGRP were identified by the dense gold labeling of small vesicles about 100 nm in diameter. Adjacent thin sections were stained using an indirect colloidal gold immunocytochemical technique to reveal HSV-1 antigens. In CGRP-positive neurons, HSV antigens were located over both nuclear and cytoplasmic compartments. HSV label was found over cytoplasmic vesicles that were significantly larger than those labeled with anti-CGRP antisera; the HSV-containing vesicles ranged in profile diameter from less than 170 to greater than 400 nm. There was no overlap in the distribution of the two labels. Thus, for this time period, the organelles involved in transport of the endogenous neuropeptide and HSV appear to remain discrete. Furthermore, there was no significant difference in the distribution of HSV in CGRP-reactive and CGRP-negative trigeminal ganglion cells. Thus, there is no indication of a preferential distribution or limited replication of HSV in CGRP-positive neurons.

Animals↗
PubMed1991

Design and organization of the herpetic eye disease study (HEDS).

The Herpetic Eye Disease Study (HEDS) includes three double-masked, placebo-controlled clinical trials for potentially blinding herpes simplex virus (HSV) eye infections. One study compares a tapering dosage of topical prednisolone or placebo eye drops for HSV stromal keratitis (HEDS-SKN). Two other trials compare oral acyclovir to placebo capsules for HSV stromal keratitis (HEDS-SKS) or iridocyclitis (HEDS-IRT) in patients on a tapering dosage of topical prednisolone drops. All medications are administered for 10 weeks. Outcome is judged by time to recurrent disease or treatment failure. This paper presents the design, estimated sample size and recruitment as of July 25, 1990.

Acyclovir↗
PubMed1990

The epidemiology of trachoma predicts more blindness in the future.

Trachoma is considered the world's leading preventable cause of blindness, with hundreds of millions of people affected and approximately 6 to 9 million blinded as a result of the disease. It was once endemic in much of the world. It disappeared from most of Europe and North America, coincident with the improvements in hygienic conditions that accompanied the expanding industrial revolution in the latter part of the 19th century. Common wisdom states that trachoma is disappearing from much of the world today as a result of improvement in the standard of living. Unfortunately, this is not a realistic perception. In some hyperendemic areas neither the standard of living nor hygienic conditions are improving. Deaths due to acute infections have been reduced and the population is both growing and aging. In some parts of the world, because of demographics, it is likely that there are more people being exposed to trachoma as children and more will survive to old age when trachomatous blindness develops. In these countries there will be larger numbers of blind individuals in the future than there are today. This will tax public health and economic systems in the involved communities.

Blindness↗
PubMed1979

Is trachoma an ocular component of a more generalised chlamydial infection?

In industrialised countries, inclusion conjunctivitis of the newborn is now known to be just one manifestation of a more generalised infection with Chlamydia trachomatis. Pneumonia and enteric infection can develop in perinatally infected infants. It is possible that trachoma in developing countries may reflect extraocular infection that may contribute to the high frequency of pneumonia and diarrhoea in infants in these countries. If true, this would explain the short-term effects of topical treatment, since children could reinfect their eyes by autoinoculation from other sites. Thus systemic treatment with macrolides would result in benefits beyond the temporary suppression of eye disease.

Administration, Oral↗
PubMed1979

Herpetic eye disease in rabbits after inoculation of autonomic ganglia.

Since herpes simplex virus (HSV) can cause persistent infection of autonomic ganglia of both humans and experimentally infected animals, we followed the pattern of eye disease and viral growth after HSV inoculation of one superior cervical ganglion in rabbits. Of 27 inoculated animals, eye disease or detectable virus developed in 18. Anterior uveitis was the most common clinical manifestation (94%), but conjunctivitis and dendritic keratitis were also frequent (60%). All 12 uveal-retinal specimens tested and five of seven ipsilateral superior cervical ganglia had detectable virus. If recurrent herpetic iritis in humans is associated with persistent infection of the superior cervical ganglion, autonomic mediators might trigger episodes of virus shedding. In patients with herpetic iritis, then, the use of epinephrine and other adrenergic agonists or antagonists should be avoided.

Animals↗
PubMed1979

Purulent ocular discharge in neonates: significance of Chlamydia trachomatis.

We obtained cultures for bacteria and chlamydiae from 100 infants with conjunctivitis that began during the first month of life. Sixty-nine infants were evaluated during well-child visits (group A); 31 were seen specifically for the ocular discharge (group B). Potentially pathogenic bacteria, predominantly Staphylococcus aureus, were cultured from one third of the infants in each group. Chlamydia trachomatis was recovered from three infants (4%) in group A and from ten (32%) in group B. Three infants with chlamydial conjunctivitis (two in group A, one in group B) had only mild inflammation. Initial treatment with topical antibiotics was unsuccessful in eliminating the organism from seven of 11 infants.

Conjunctivitis↗
PubMed1978

The effect of synthetic polymers on the electrical and permeability properties of lipid membranes.

1. The effect of two series of hydrophilic and hydrophobic polymers on the stability, conductivity and permeability towards water and leucine of black lipid membranes and liposomes is reported. 2. The changes in properties of these membrane preparations is related to bulk phase viscosity and dielectric measurements together with monolayer studies. 3. The hydrophobic polymers dramatically increase membrane stability, had no effect on conductivity, but increased the permeability coefficient of leucine. 4. The hydrophilic polymers produced minor, but significant changes to membrane properties. 5. It is concluded that not only basic polymers but also neutral and acidic macromolecules can interact strongly with lipid membranes.

Acrylic Resins↗
PubMed1978

The interaction of bee melittin with lipid bilayer membranes.

The influence of melittin and the related 8-26 peptide on the stability and electrical properties of bilayer lipid membranes is reported. Melittin, unlike the 8-26 peptide, has a dramatic influence on lipid membranes, causing rupture at dilute concentrations. The circular dichroism of melittin demonstrated that under physiological conditions, in water, melittin is in extended conformation, which is enhanced in aqueous ethanol. However in 'membrane-like' conditions it is essentially alpha-helical. Secondary structure predictions were used to locate possible alpha-helical nucleation centres and a model of melittin was built according to these predictions. It is postulated that melittin causes a wedge effect in membranes.

Bee Venoms↗
PubMed1978

The use of cycloheximide-treated cells for isolating trachoma agents under field conditions.

Standard procedures for the isolation of Chlamydia trachomatis require pretreatment of the tissue culture cells. We evaluated the use of cycloheximide, an antimetabolite that can be added to the cells with the inoculum. Cycloheximide-treated cells provided a sensitive system for isolating trachoma agents. This system was applicable to field studies as requirements for equipment were minimal and the cells were 2 weeks old when inoculated.

Chlamydia trachomatis↗