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Biomedical subjects

C R Dawson

Publications and source records attributed to C R Dawson.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1977

A spectroscopic and kinetic investigation of anion binding to ascorbate oxidase.

The binding of azide, fluoride, and cyanide to ascorbate oxidase has been investigated in detail. Both azide and fluorid inhibit the enzyme competitively with respect to ascorbic acid and noncompetitively with respect to oxygen. Cyanide inhibition is much more complex and also results in inactivation of the enzyme. The binding of azide and fluoride to the resting enzyme is partially competitive. Fluoride binds more strongly to the resting enzyme, while azide binds more strongly to the functioning enzyme. It is proposed that both azide and fluoride bind to type 2 copper and that this copper is also part of an ascorbate binding site. It seems likely that type 2 copper is a reductant binding site in all of the "blue" oxidases. This proposal is used to explain the effect of fluoride on the enzymes and also to suggest a mechanism for the internal electron transfer which is necessary for the reduction of oxygen to water.

Ascorbate Oxidase↗
PubMed1977

Herpesvirus in sensory and autonomic ganglia after eye infection.

In herpesvirus hominis (HVH) infections, virus harbored in the sensory ganglia is now thought to be the main source of recurrent infection at peripheral sites. Experimental HVH infection of the external eye in rabbits produces an acute infection and then latent infection of the trigeminal ganglion. In this study, acute infection of the automatic ganglia serving the eye (superior cervical and ciliary) as well as trigeminal ganglia occurred after HVH inoculation of rabbits' corneas with a herpes type 1 strain (RE). Latent virus infection was detected in the trigeminal ganglion of one of five animals tested six months after initial infection. Since the superior cervical and other autonomic ganglia serving the eye become infected during acute herpes simplex virus infection of the external eye in rabbits, it is possible that these ganglia are also sources of reinfection in recurrent herpetic disease of the eye. Following the initial eye disease with this virus strain, HVH shedding could not be demonstrated even after induction attempts by topically applied epinephrine or systemic use of cyclophosphamide. Thus, establishment of latent HVH infection in the ganglia and chronic shedding of virus into the external eye is not a constant feature of this animal model, but may depend on the specific strain of herpesvirus used.

Animals↗
PubMed1977

Concerning the metalloenzyme ascorbate oxidase.

Apoascorbate oxidase has been shown to have a molecular weight of 137,000 +/- 3,000 and essentially the same gross quaternary conformation as native ascorbate oxidase. The apoenzyme, however, lacks much of the conformational stability of the native enzyme. The removal of the copper from the oxidase protein, and the simultaneous reduction of the disulfide bonds results in an apoenzyme of lower structural stability than the native oxidase. The aging of apoascorbate oxidase has been found to involve a loss of ionizable tyrosine residues and a dissociation to subunits and component polypeptide chains, which was not observed with the more stable native and holo enzymes. The molecular weight of holoascorbate oxidase has been determined to be 285,000. An s020, w of 9.79 has been determined for the holoenzyme. Holoascorbate oxidase has been shown to have an electrophoretic mobility on polyacrylamide gels that is 23% lower than either the native or apoenzyme. Furthermore, electrophoresis of the holoenzyme, in buffers containing dodecyl sulfate, and also isoelectric focusing of the holenzyme, produce patterns of greater similarity to those of apoascorbate oxidase than the native enzyme.

Apoenzymes↗
PubMed1977

The induction of immune tolerance in delayed contact sensitivity by the use of chemically related substances of low immunogenicity.

Immune tolerance in delayed contact sensitivity to pentadecylcatechol can be induced by a series of derivatives substituted in the 6 position of the ring. Some of these derivatives have the property of being very poor sensitizers and having very low dermal toxicity. Thus, sensitization and tolerance have different biologic mechanisms and are associated with different properties of these chemicals.

Animals↗