PubMed Health⌕ Search

Biomedical subjects

S L Franklin

Publications and source records attributed to S L Franklin.

7 recordsLinked to original sources
PubMed1996

Characterization of the metal-binding sites of the beta-lactamase from Bacteroides fragilis.

In an effort to better understand the structure and function of the metallo-beta-lactamase from Bacteroides fragilis, spectroscopic and metal-binding studies were performed on the native, metal-substituted, and mutant forms of the enzyme. Atomic absorption studies demonstrate that the native B. fragilis enzyme tightly binds 2 mol of Zn(II) and, along with mutagenesis studies, that the presence of both metal ions is required for full catalytic activity. EPR spectroscopy was used to confirm that the Co(II)-substituted beta-lactamase binds 2 mol of Co(II) per mole of enzyme, that the two Co(II)'s are highspin and probably uncoupled, with apparent g values of 6.5, 4.2, and 2.0, and that the coordination number of the Co(II) is 5 or 6. This number of ligands for the Co(II)-substituted enzyme is confirmed by UV-Vis spectra, which demonstrate the presence of very weak d-d transitions between 550 and 650 nm (epsilon approximately 30 M-1.cm-1) and an intense feature at 320 nm (epsilon approximately 1570 M-1.cm-1). The latter is assigned to a cysteine sulfur to Co(II) ligand-to-metal charge transfer band, and this assignment is confirmed by the disappearance of this band in the UV-Vis spectrum of a Co(II)-substituted C168S mutant. H NMR studies on the Co(II)-substituted enzyme suggest the presence of three histidine ligands bound to Co(II). Taken together, these studies support the sequence comparison study of Rasmussen et al., in which there is a catalytic metal-binding site with three histidines and one cysteine (C168). The remaining ligands are postulated to be water molecules involved in catalysis. Mutagenesis studies, in combination with activity assays and metal-binding studies, have been used to identify Asp61, Asp90, Asp152, and Asp183 as possible ligands to the second metal-binding site, with Asp90 and Asp152 having a pronounced effect on kcat. These results are discussed in light of the recent crystal structure of the metallo-beta-lactamase from B. cereus.

Bacteroides fragilis↗
PubMed1991

The acuityscope: a resolution test target projection ophthalmoscope.

The Acuityscope projects an image of a three bar resolution test target onto the patient's retina, where it is viewed and read by an observer. The test target consists of a series of three bar targets varying in size on a logarithmic scale. Individual targets are identified in the projected image by Bailey-Lovie log visual acuity equivalents. The projected image includes only those target sizes which are useful for estimating visual acuity. The Acuityscope is used for assessing the quality of retinal image formation, and is thus able to differentiate between poor visual acuity due to image degradation, (e.g. cataract or corneal disease) and poor visual acuity due to image handling defects (e.g. retinal or optic nerve disease). The use of the instrument is relevant to both clinical situations (e.g. pre-operative assessment of opacification of optical media) and experimental situations (e.g. clinical trials).

Equipment Design↗
PubMed1990

The transparency of the lens: a comparison between diabetic and non-diabetic patients.

The transparency of the lens of 485 eyes of 266 healthy volunteers were compared with 143 eyes of 83 diabetic patients. All the patients had well controlled diabetes. The transparency of the lens was measured with the opacity lensmeter 701. The concept of the instrument is based on the measurement of scattered light. The result revealed a similar transparency of the lenses of diabetic patients in relation to the normal volunteers. There was only a slight, and statistically not significant trend in the older age group versus a greater opacity for diabetic patients.

Adolescent↗
PubMed1988

Treatment of cataract in diabetics with and without retinopathy.

The results of cataract surgery in diabetic patients was reviewed. The visual outcome was good in the absence of retinopathy and was not significantly different from that of non-diabetic patients. Eyes with retinopathy achieved significantly worse visual results and the prognosis was related to the severity of retinopathy. Clinical cystoid macular oedema occurred significantly more frequently in eyes with retinopathy than without and there were significantly more eyes with retinopathy which became blind or partially sighted. The use of a Projectoscope for assessing the amount of degradation of an image was tested. A good correlation was found between the amount of blurring of the test target and the drop in visual acuity. The optimal type of cataract surgery is discussed and lines of management outlined.

Blindness↗
PubMed1968

ECHO-11 as a respiratory virus: quantitation of infection in man.

Through a series of controlled experiments in volunteers, quantitative aspects of infection, illness, and immunity to ECHO-11 virus were studied. ECHO-11 is a transmissable viral infection in man and equally infectious to the upper respiratory and the intestinal tracts. The rate of infection was directly related to the dose of virus exposure, but any infectious dose of virus produced illness in only about one-third of the infected subjects. The infectious dose for man varied over a billionfold range. Larger challenge doses caused no difference in the local symptoms at the portal of entry or in the peak severity of illness, but symptoms were more diverse and prolonged after a higher dose. Persons with asymptomatic infections became just as heavily infected as ill persons. In respiratory secretions from natural infection, the titer of infectious virus was found to be about 10(2) median infective doses in tissue culture (TCID(50))/ml. At this level, up to 40% of exposed contacts could be infected per milliliter of secretion. The observed rate of spread was 24%. This low-dose inoculum caused illness in 12% of volunteers but failed to elicit a significant antibody response in 93% or immunity to reinfection and another illness upon rechallenge. Larger doses of virus produced a longer excretion of virus and a significant increase in serum-neutralizing antibody. Nasal antibody was infrequently found. The principal effect of antibody was to decrease virus excretion and to shorten illness; it reduced the rate but did not prevent infection. Attempts to produce an asymptomatic enteric infection which would induce immunity failed.The characteristics of respiratory transmission with mild disease, recurrent infection, and illness without a detectable antibody response or solid immunity to reinfection, satisfy the epidemiologic conditions to establish ECHO-11 virus as one of the causes of the common cold.

Adult↗