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Biomedical subjects

C L McDonald

Publications and source records attributed to C L McDonald.

12 recordsLinked to original sources
PubMed2004

Physical properties of sulfur near the polymerization transition.

Acoustical measurements, electron spin resonance, and Raman spectroscopy have been employed to probe sulfur over the temperature range 80-180 degrees C, which includes the polymerization transition and the supercooled liquid state. Acoustical properties (sound velocity, absorption, and impedance) have been studied with both longitudinal and transverse waves at frequencies between 500 kHz and 22 MHz. The results confirm that polymeric sulfur is a solution of long chain molecules in monomeric solvent, and that the polymerization transition is not a second-order phase transition, as was proposed theoretically. Sulfur is a viscous liquid, but not viscoelastic, both below and above the polymerization transition temperature. It is shown that the classical Navier-Stokes theory is not applicable to the sound absorption in liquid sulfur in the highly viscous state.

Journal Article↗
PubMed2000

Phage display epitope mapping of human neutrophil flavocytochrome b558. Identification of two juxtaposed extracellular domains.

Despite extensive experimental and clinical evidence demonstrating the critical role of flavocytochrome b558 (Cyt b) in the NADPH-dependent oxidase, there is a paucity of direct structural data defining its topology in the phagocyte membrane. Unlike other Cyt b-specific monoclonal antibodies, 7D5 binds exclusively to an extracellular domain, and identification of its epitope should provide novel insight into the membrane topology of Cyt b. To that end, we examined biochemical features of 7D5-Cyt b binding and used the J404 phage display nonapeptide library to identify the bound epitope. 7D5 precipitated only heterodimeric gp91-p22phox and not individual or denatured Cyt b subunits from detergent extracts of human neutrophils and promyelocytic leukemia cells (gp91-PLB). Moreover, 7D5 precipitated precursor gp65-p22phox complexes from detergent extracts of the biosynthetically active gp91-PLB cells, demonstrating that complex carbohydrates were not required for epitope recognition. Epitope mimetics selected from the J404 phage display library by 7D5 demonstrated that (226)RIVRG(230) and (160)IKNP(163) regions of gp91phox were both bound by 7D5. These studies reveal specific information about Cyt b membrane topology and structure, namely that gp91phox residues (226)RIVRG(230) and (160)IKNP(163) are closely juxtaposed on extracytoplasmic domains and that predicted helices containing residues Gly(165)-Ile(190) and Ser(200)-Glu(225) are adjacent to each other in the membrane.

Amino Acid Sequence↗
PubMed1995

Revised interpretation of oxacillin MICs for Staphylococcus epidermidis based on mecA detection.

In 1992 and 1993, at The Ohio State University Medical Center, a larger proportion of Staphylococcus epidermidis strains required oxacillin MICs of 1 to 2 micrograms/ml than did Staphylococcus aureus strains. mecA genotype was correlated with antimicrobial susceptibility for selected clinical S. epidermidis strains. All 14 strains that required oxacillin MICs of < or = 0.25 microgram/ml and 2 of 5 strains that required oxacillin MICs of 0.5 microgram/ml were susceptible by 1-microgram oxacillin disk test and were mecA negative. Three of 5 strains that required oxacillin MICs of 0.5 microgram/ml and all 18 strains that required oxacillin MICs of > or = 1.0 microgram/ml were resistant by oxacillin disk test and were mecA positive. Current National Committee for Clinical Laboratory Standards MIC interpretive criteria may underestimate methicillin resistance among S. epidermidis strains.

Bacterial Proteins↗
PubMed1995

Use of UV ParaLens adapter for detection of acid-fast organisms.

Auramine-stained mycobacterial smears from 136 clinical specimens were interpreted by using the UV ParaLens adapter (Beckton Dickinson), and results were compared with smear interpretations using a traditional fluorescent microscope and culture. The sensitivity and specificity of the ParaLens were 84 and 93%, respectively. Smears yielding discrepant results were overstained by the Kinyoun method. Overall, the sensitivity of auramine-stained smears interpreted with the UV ParaLens was comparable to that of Kinyoun-stained smears.

Benzophenoneidum↗
PubMed1995

Rapid identification of Staphylococcus aureus from blood culture bottles by a classic 2-hour tube coagulase test.

The rapid, reliable identification of Staphylococcus aureus from positive blood cultures provides important information. While multiple methodologies for detection of S. aureus from blood culture broths exist, none is satisfactory. Immunologic tests have shown varied sensitivities, the thermonuclease test, while sensitive, is not practical for routine use, and probe tests are expensive. Few studies have addressed using the tube coagulase test (TCT). This study compared two immunologic methods, the Staph Latex kit (Remel Laboratories) and the Staphaurex kit (Wellcome Diagnostics), with a rabbit plasma TCT (Difco Laboratories) to identify S. aureus within 2 h directly from blood culture broths and pelleted supernatants from BACTEC (Johnston Laboratories) bottles. One hundred twelve unique clinical blood culture isolates consistent with a Gram stain for staphylococci and 68 negative blood culture bottles seeded with a variety of gram-positive organisms were evaluated. Sensitivity and specificity among clinical specimens for the 2-h TCT were 79.5 and 100%, respectively. Sensitivities for the immunologic methods were 12.8 and 10.2% for the Staphaurex and Remel Staph Latex, respectively, and specificities for both were 100%. These results contradict previously reported results for both immunologic and TCT methods and dictate that a specific as well as a sensitive method be employed. The 2-h TCT was found to be a cost-effective, reliable, and rapid method for identifying S. aureus from positive blood cultures.

Bacterial Typing Techniques↗
PubMed1994

Oerskovia xanthineolytica bacteremia in an immunocompromised patient with pneumonia.

Oerskovia species, which are Nocardia-like bacteria that have rarely been found to cause human disease, are usually found in association with a foreign body with removal of the infected focus being necessary for cure. We present a case of Oerskovia xanthineolytica bacteremia in a patient with metastatic breast cancer, community-acquired pneumonia, and a tunneled subcutaneous central venous catheter. Although the actual source of the bacteremia in this case is not proven, this patient's presentation with apparent lobar pneumonia and her improvement on antibiotics without catheter removal suggest that Oerskovia may be capable of causing primary pulmonary infection in the immunocompromised host.

Actinomycetales↗
PubMed1991

Effect of patella thickness on patella strain following total knee arthroplasty.

Patellar complications following total knee arthroplasty (TKA) have begun to emerge as a major cause of failure. In an effort to understand some of the mechanical factors that might contribute to patellar component failure, a biomechanical study was performed. Quadriceps force and anterior patellar strain were measured during dynamic flexion in 10 fresh, paired human cadaver knee joints. First, tests were performed in the intact knee, followed by either posterior cruciate ligament (PCL) retention or sacrifice of TKA without patellar resurfacing. Tests were then performed following patellar resurfacing with an overly thick, optimum and thin, bony patella. Patellar strain increased in each specimen (with flexion angles of up to 80 degrees), was most pronounced as the bony patella became thinner, was closest to the intact knee when the patella was not resurfaced, and was unaffected by PCL retention or sacrifice. Patellar osteotomy, resulting in a bony patellar thickness of less than 15 mm, resulted in significantly increased strain. TKA systems should include instrumentation that allows precise restoration of overall patellar thickness while maintaining a bony patellar thickness of at least 15 mm.

Cadaver↗
PubMed1990

Histopathologic correlation of magnetic resonance imaging signal patterns in a spinal cord injury model.

Magnetic resonance imaging (MRI) provides a noninvasive method of monitoring the pathologic response to spinal cord injury. Specific MR signal intensity patterns appear to correlate with degrees of improvement in the neurologic status in spinal cord injury patients. Histologic correlation of two types of MR signal intensity patterns are confirmed in the current study using a rat animal model. Adult male Sprague-Dawley rats underwent spinal cord trauma at the midthoracic level using a weight-dropping technique. After laminectomy, 5- and 10-gm brass weights were dropped from designated heights onto a 0.1-gm impounder placed on the exposed dura. Animals allowed to regain consciousness demonstrated variable recovery of hind limb paraplegia. Magnetic resonance images were obtained from 2 hours to 1 week after injury using a 2-tesla MRI/spectrometer. Sacrifice under anesthesia was performed by perfusive fixation; spinal columns were excised en bloc, embedded, sectioned, and observed with the compound light microscope. Magnetic resonance axial images obtained during the time sequence after injury demonstrate a distinct correlation between MR signal intensity patterns and the histologic appearance of the spinal cord. Magnetic resonance imaging delineates the pathologic processes resulting from acute spinal cord injury and can be used to differentiate the type of injury and prognosis.

Animals↗
PubMed1990

Management of inappetant sheep during export by sea.

In the first of 2 experiments, a simulated voyage was conducted to examine the effects of various treatments on bodyweight change and feeding frequency of inappetant sheep at the end of lot-feeding (non-feeders). The treatments, applied during simulated shipping, were: normal quantities of feed and length of troughs; extra trough length; extra feed. Adult Merino wethers (n = 108) were used in each treatment. A voyage to the Middle East was then conducted to establish whether shipboard mortality could be reduced by separating non-feeders (n = 305) from feeders (n = 5,620) late in the feedlot hase and housing the groups separately aboard ship. A control group of non-feeders (n = 215) mixed with feeders (n = 5,732) was used for comparison. Bars (marker bars), containing a coloured dye, were attached to feed troughs to mark sheep that fed. Most non-feeders (82%) began eating when placed in shipping pens in both studies. However, there was no significant difference in percentage of sheep that fed between non-feeders given extra trough length or extra feed compared with non-feeders given standard management at any stage of simulated shipping. There was no significant difference in mean bodyweights between treatment groups on days 1, 8 and 15 of simulated shipping. Differences in bodyweight on d 22 were probably associated with different levels of gut fill. Death rates were not significantly different in separated and control groups (1.1%, 0.9%, P = 0.6) in the voyage of 14 d to the Middle East.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗