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Biomedical subjects

J Duncan

Publications and source records attributed to J Duncan.

At least 145 records · Page 8Linked to original sources
PubMed1981

Penetrating keratoplasty for herpes simplex keratitis.

We conducted a retrospective longitudinal cohort study of 82 penetrating keratoplasties performed to treat herpes simplex keratitis. In 53 cases (65%) there was extensive corneal neovascularization or stromal ulceration and active intraocular inflammation, making the prognosis in these cases poor. Only 32 grafts (39%) were clear at the time of our analysis. Patients with active inflammation, active ulceration, perforation, or extensive neovascularization had particularly poor success rates. Conservative management of perforation before keratoplasty was highly successful (11 clear grafts in 13 eyes [85%]). Other categories with a good prognosis included disciform edema and scarred corneas in quiet eyes. We used a preliminary analysis of the data to build a model to predict the outcome of penetrating keratoplasty in herpes simplex keratitis. The model used preoperative ocular status and management technique as its terms. Testing of the model showed that there were significant differences in outcome between the groups in the sample.

Adult↗
PubMed1980

Randomized clinical trial of topically administered cromolyn sodium for vernal keratoconjunctivitis.

We performed a controlled, randomized, double-masked, double-crossover clinical trial topically administered cromolyn sodium (4%) in 11 patientas with atopy and vernal keratoconjunctivitis. Statistically significant differences were noted in conjunctival injection, superifcial punctate keratitis, mucous production, and itching when eyes treated with cromolyn were compared to those treated with a placebo. The drug was well tolerated by all patients.

Adolescent↗
PubMed1980

Molluscicides in schistosomiasis control.

Although mollusciciding can be a cost-effective method of controlling schistosomiasis transmission, only one organic molluscicide, niclosamide, is now being produced commercially, and only a few compounds are at present being tested in the laboratory. In future, improved cost-effective use of molluscicides will require more precise knowledge of schistosomiasis transmission patterns in each endemic area and improved application techniques. In snail control studies using controlled-release formulations only the organotins, especially tributyltin oxide (TBTO), have given satisfactory long-term results. However, large-scale field trials of organotin formulations have not been implemented and their use cannot be recommended as their chronic toxicity in mammals has not yet been determined. The development of molluscicides of indigenous plant origin deserves support. Endod, derived from the berries of the climbing plant Phytolacca dodecandra, is the most extensively tested plant molluscicide, but data on its chronic toxicity to non-target organisms are lacking. The mode of action of molluscicides has not been extensively studied, though knowledge of the properties required of molluscicidal molecules has contributed to the discovery and development of niclosamide and nicotinanilide. In general, molluscicides probably cause stress on the water balance system, which in gastropods in thought to be under neurosecretory control.

Drug Resistance↗
PubMed1979

Divided attention: the whole is more than the sum of its parts.

A divided attention situation is more than the sum of its component single tasks. Emergent aspects of the whole situation must also be considered. Three examples illustrate this. (a) When several complex stimuli (e.g., letters) are identified at once, their perceived components or features must be appropriately bundled together. Otherwise, components of two different stimuli may appear combined. This (emergent) problem is shown to depend on attention to multiple stimuli, not simply their presentation. (b) In the psychological refractory period (PRP) situation, especial difficulties arise when stimulus-response mappings are different for first and second reactions. It appears that for each reaction there is some (emergent) uncertainty over which mapping to use. This is only one of many possible emergent processes in the PRP situation. (c) When the two hands perform different actions (internally programmed sequences of taps), there is some tendency for each hand to carry out the action assigned to the other. This again is only a small part of the (emergent) problem of motor coordination. Thus the simple idea of competition for limited resources captures only a part of the problem of divided attention. Performance under divided attention will reflect an interaction between resource limitation, single task processes, and emergent aspects of the whole situation.

Adult↗
PubMed1977

Partial purification and characterization of a uracil DNA N-glycosidase from Bacillus subtilis.

A uracil specific DNA N-glycosidase activity has been partially purified from crude extracts of Bacillus subtilis. The enzyme has a molecular weight of approximately 24 000 with no subunit structure. It has no requirement for any known cofactors but is inhibited in the presence of Co2+, Fe2+, or Zn2+. The enzyme is specific for uracil in single- and double-stranded deoxyribonucleopolymers and does not release free uracil from RNA or from poly(rU):poly(dA). In addition, neither Udr, dUMP, nor dUTP is recognized as substrate. The enzyme will attack small poly(dU) oligomers but the minimum size recognized as substrate is (pU)4. This enzyme may have a role in the repair (by base excision) or uracil in DNA arising either by incorporation during DNA synthesis or by deamination of cytosine in DNA.

Bacillus subtilis↗