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Biomedical subjects

M G Ryan

Publications and source records attributed to M G Ryan.

15 recordsLinked to original sources
PubMed2003

Reliance on stored water increases with tree size in three species in the Pacific Northwest.

In tall old forests, limitations to water transport may limit maximum tree height and reduce photosynthesis and carbon sequestration. We evaluated the degree to which tall trees could potentially compensate for hydraulic limitations to water transport by increased use of water stored in xylem. Using sap flux measurements in three tree species of the Pacific Northwest, we showed that reliance on stored water increases with tree size and estimated that use of stored water increases photosynthesis. For Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), water stored in xylem accounted for 20 to 25% of total daily water use in 60-m trees, whereas stored water comprised 7% of daily water use in 15-m trees. For Oregon white oak (Quercus garryana Dougl. ex Hook.), water stored in xylem accounted for 10 to 23% of total daily water use in 25-m trees, whereas stored water comprised 9 to 13% of daily water use in 10-m trees. For ponderosa pine (Pinus ponderosa Dougl. ex Laws.), water stored in xylem accounted for 4 to 20% of total daily water use in 36-m trees, whereas stored water comprised 2 to 4% of daily water use in 12-m trees. In 60-m Douglas-fir trees, we estimated that use of stored water supported 18% more photosynthesis on a daily basis than would occur if no stored water were used, whereas 15-m Douglas-fir trees gained 10% greater daily photosynthesis from use of stored water. We conclude that water storage plays a significant role in the water and carbon economy of tall trees and old forests.

Northwestern United States↗
PubMed2001

Developing a Respiratory Protection Program. Understanding the written elements.

1. Respirators can be the last defense for the estimated 5 million employees who use them for protection from dusts and fibers, fumes, mists, gases, vapors, and biological hazards. Because of these potentially lethal respiratory hazards, occupational and environmental health nurses need to be able to determine the need for, understand, develop, update, and implement an actionable respiratory protection program (RPP). 2. Regulated per 29 CFR 1910.134, a written RPP becomes the map or guideline process specific to the workplace that needs to be followed to ensure employee protection. 3. The nine required written elements of a RPP include respirator selection; fit testing; respirator use in routine and emergency situations; respirator maintenance and change schedules; ensuring adequate breathing air supply, quantity, and flow for atmosphere supplying respirators; regular evaluation of program effectiveness; medical evaluation; training employees in the respiratory hazards in routine and emergent situations; and training employees in proper use of the respirator. 4. Occupational and environmental health nurses are in a unique position to be a RPP program administrator, its designated licensed health care professional, or an active member of a team implementing the RPP process.

Equipment Design↗
PubMed2000

Isolation of a high affinity scFv from a monoclonal antibody recognising the oncofoetal antigen 5T4.

The oncofoetal antigen 5T4 is a 72 kDa glycoprotein expressed at the cell surface. It is defined by a monoclonal antibody, mAb5T4, that recognises a conformational extracellular epitope in the molecule. Overexpression of 5T4 antigen by tumours of several types has been linked with disease progression and poor clinical outcome. Its restricted expression in non-malignant tissue makes 5T4 antigen a suitable target for the development of antibody directed therapies. The use of murine monoclonal antibodies for targeted therapy allows the tumour specific delivery of therapeutic agents. However, their use has several drawbacks, including a strong human anti-mouse immune (HAMA) response and limited tumour penetration due to the size of the molecules. The use of antibody fragments leads to improved targeting, pharmacokinetics and a reduced HAMA. A single chain antibody (scFv) comprising the variable regions of the mAb5T4 heavy and light chains has been expressed in Escherichia coli. The addition of a eukaryotic leader sequence allowed production in mammalian cells. The two 5T4 single chain antibodies, scFv5T4WT19 and LscFv5T4, described the same pattern of 5T4 antigen expression as mAb5T4 in normal human placenta and by FACS. Construction of a 5T4 extracellular domain-IgGFc fusion protein and its expression in COS-7 cells allowed the relative affinities of the antibodies to be compared by ELISA and measured in real time using a biosensor based assay. MAb5T4 has a high affinity, K(D)=1.8x10(-11) M, as did both single chain antibodies, scFv5T4WT19 K(D)=2.3x10(-9) M and LscFv5T4 K(D)=7.9x10(-10) M. The small size of this 5T4 specific scFv should allow construction of fusion proteins with a range of biological response modifiers to be prepared whilst retaining the improved pharmacokinetic properties of scFvs.

Amino Acid Sequence↗
PubMed2000

Evidence that decomposition rates of organic carbon in mineral soil do not vary with temperature.

It has been suggested that increases in temperature can accelerate the decomposition of organic carbon contained in forest mineral soil (Cs), and, therefore, that global warming should increase the release of soil organic carbon to the atmosphere. These predictions assume, however, that decay constants can be accurately derived from short-term laboratory incubations of soil or that in situ incubations of fresh litter accurately represent the temperature sensitivity of Cs decomposition. But our limited understanding of the biophysical factors that control Cs decomposition rates, and observations of only minor increases in Cs decomposition rate with temperature in longer-term forest soil heating experiments and in latitudinal comparisons of Cs decomposition rates bring these predictions into question. Here we have compiled Cs decomposition data from 82 sites on five continents. We found that Cs decomposition rates were remarkably constant across a global-scale gradient in mean annual temperature. These data suggest that Cs decomposition rates for forest soils are not controlled by temperature limitations to microbial activity, and that increased temperature alone will not stimulate the decomposition of forest-derived carbon in mineral soil.

Carbon↗
PubMed1999

Use of a custom retrograde intramedullary rod for the management of distal femoral nonunion: a report of two cases.

Nonunion of the distal femur is a rare injury that is difficult to manage. A variety of surgical implants and techniques are available. We present an alternative mode of treatment for supracondylar femoral nonunion using a custom retrograde titanium femoral nail (Biomet; Warsaw, IN) to successfully achieve union in two cases. We believe the added length, custom modifications, and enhanced stability allowed better fixation in an osteopenic distal femur.

Adult↗
PubMed1998

Obsessional disorders during recovery from severe head injury: report of four cases.

Four cases of transient obsessional disorders following severe head injury are described within the context of recovery from acute traumatic brain injury (TBI). Obsessional features following TBI have important treatment implications in brain injury rehabilitation settings, since emergence of this disorder in the acutely brain injured patient poses a significant obstacle to interdisciplinary rehabilitation. Although the numbers of patients described here and in previous reports are too small to draw conclusions about the incidence of obsessional disorders following TBI, these cases illustrate the importance of correctly identifying and treating obsessional symptoms in the brain injured patient.

Adult↗
PubMed1998

One-stage treatment of congenital dislocation of the hip in children three to ten years old. Functional and radiographic results.

We reviewed the results of operative treatment of congenital dislocation of the hip in eighteen children (twenty-five hips) whose average age at the time of the index operation was six years and four months (range, three years to nine years and eleven months). None of the patients had had previous treatment of the dislocation. Preliminary traction was used for five patients (six hips), and open reduction and femoral shortening was performed in all hips. The functional result was assessed, according to the Iowa hip-rating system, after an average duration of follow-up of ten years and six months (range, six years and two months to sixteen years and ten months). Sixteen hips had an excellent result; seven, a good result; and two, a fair result. The average limb-length discrepancy was 0.8 centimeter (range, zero to four centimeters), and the average foot-progression angle was 11 degrees (range, 0 to 30 degrees) of external rotation. According to Severin's classification of the radiographic appearance, seven hips had an excellent result; eleven, a good result; four, a fair result; and three, a poor result. Four of eleven hips that had evidence of osteonecrosis of the proximal part of the femur had a severe deformity, and one patient had radiographic evidence of moderate degenerative osteoarthrosis when she was sixteen years old. On the basis of this review, we suggest that a one-stage operative procedure consisting of open reduction, femoral shortening, and pelvic osteotomy (if necessary) for previously untreated congenital dislocation of the hip in children who are three to ten years old can result in remodeling of the acetabulum and a functional hip.

Child↗
PubMed1996

The reductive half-reaction of xanthine oxidase. The involvement of prototropic equilibria in the course of the catalytic sequence.

The pH dependence and solvent isotope sensitivity of three discrete steps in the reductive half-reaction of xanthine oxidase have been investigated. The pH dependence of both kcat/Km from steady-state experiments and kred/Kdfrom rapid reaction experiments with xanthine as substrate indicate that enzyme reacts preferentially with the neutral form of substrate and that an ionizable group in the active site having a pKa of approximately 6.6 must be unprotonated for reaction to take place. The solvent kinetic isotope effect on kred/Kd is 2.4, once a uniform shift on going to D2O of approximately 1 unit for both pKa values is taken into account. The pH dependence of the formation and decay of Ered-P formed in the course the reaction of xanthine oxidase with lumazine has also been examined. Formation of this complex exhibits bell-shaped pH dependence, with pKa values of 6.5 and 7.8, consistent with the results obtained with xanthine. Decay of the Ered-P complex is base-catalyzed with a pKa > 11 and exhibits a small solvent kinetic isotope effect of 1.7 at pH/D 8.5. By contrast, the catalytic intermediate giving rise to the "very rapid" EPR signal that is transiently observed in the course of the reaction of enzyme with the substrate 2-hydroxy-6-methylpurine is found to undergo acid-catalyzed breakdown with an associated pKa < 6. Formation and decay of this species exhibit solvent kinetic isotope effects of 2.0 and 3.5 at pH 10. The results are discussed in the context of a specific reaction mechanism for the reductive half-reaction of xanthine oxidase, in which discrete ionizations associated with the molybdenum center of the active site play critical roles in determining the magnitude of the rate constants by which the Mo(IV)-P and Mo(V)-P intermediates form and decay.

Catalysis↗
PubMed1995

The molybdenum centers of xanthine oxidase and xanthine dehydrogenase. Determination of the spectral change associated with reduction from the Mo(VI) to the Mo(IV) state.

The UV-visible absorbance change associated with reduction of the molybdenum centers of xanthine oxidase and xanthine dehydrogenase has been determined using a double-difference technique. At pH 8.5, the Mo(VI) minus Mo(IV) difference spectrum seen with xanthine oxidase exhibits a positive feature at 420 nm, having an extinction change of approximately 3,000 M-1 cm-1 as well as evidence for a negative feature below 340 nm. In xanthine oxidase this change is found to exhibit a marked pH dependence, implicating protonation/deprotonation events associated with changes in the molybdenum oxidation state. Application of the double-difference protocol to the respective circular dichroism spectra of xanthine oxidase and xanthine dehydrogenase reveals appreciable CD changes at 420 and 580 nm associated with the reduction of the molybdenum center. The present results demonstrate a direct spectroscopic handle on the molybdenum centers of both xanthine oxidase and xanthine dehydrogenase.

Animals↗
PubMed1995

Carbon dioxide/digital subtraction arteriography-assisted transluminal angioplasty.

During a 62-month period, carbon dioxide was used to supplement or completely replace iodinated contrast agents in performing 27 transluminal angioplasties in 26 patients. The arterial segments addressed included the following: renal in two cases, iliac in five, femoral/popliteal in 15, infrapopliteal in two, and combined in three. Indications for intervention included lower extremity gangrene in 11 cases, ischemic ulceration in 10, rest pain in three, claudication in one, and ischemic nephropathy in two. Contraindications to iodinated contrast agents included renal insufficiency resulting from diabetes (n = 20) or ischemic nephropathy (n = 2) and congestive heart failure (n = 4). Eight procedures used carbon dioxide as the sole contrast agent, whereas 19 required supplementation of carbon dioxide with a mean of 39 ml of nonionic contrast medium. Technical success was achieved in 25 procedures with significant hemodynamic improvement in 20 patients. Complications included transient deterioration in renal function in two patients and myocardial infarctions in two. At 30 days 18 patients had demonstrated significant clinical improvement. Patients at high risk for iodinated contrast-related complications may undergo transluminal angioplasty using carbon dioxide/digital subtraction arteriography to reduce or eliminate the need for iodinated contrast agents.

Adult↗
PubMed1977

One hundred and eighty-seven cases of child abuse and neglect.

The case histories of 187 abused and neglected children, admitted to the Royal Alexandra Hospital for Children over a three-year-period, were reviewed. Multiproblem families from the lower socioeconomic groups predominated, reflecting the hospital's geographic catchment area. Eight children died and 30 were made state wards. A high proportion of mothers described problems during the pregnancy, a difficult delivery and neonatal problems. The majority of parents in this study were married and had small families. First-born male infants of young isolated mothers were found to be at greatest risk of child abuse and neglect.

Adolescent↗
PubMedDate not supplied

Connective tissue structures in clubfoot: a morphologic study.

A morphologic study of connective tissue structures in clubfoot, with special emphasis on the presence of myofibroblasts, was undertaken to investigate the theory of retracting fibrosis as an etiologic factor. Nine idiopathic clubfeet from six patients were studied. Specimens from the medial and lateral capsule, medial and lateral fascia, spring and lacinate ligaments, and flexor digitorum longus, flexor hallucis longus, posterior tibialis, and Achilles tendon sheaths were investigated. Fifty specimens were examined using light microscopy and hematoxylin and eosin staining, and 26 were examined by transmission electron microscopy. Light microscopy failed to reveal any myofibroblast-like cells or any qualitative differences between specimens from capsule, fascia, ligaments, and tendon sheath. Using transmission electron microscopy, the authors identified two cell types: fibroblasts and mast cells. Some fibroblasts contained a network of microfilaments but all lacked microbundles, basal lamina, or plasmalemmal attachment plaques seen in typical myofibroblasts. Mast cells were rarely identified in capsular specimens. The absence of myofibroblast-like cells or typical myofibroblasts in clubfoot connective tissue structures does not support the theory of retracting fibrosis as a likely cause of contracture in idiopathic clubfoot.

Clubfoot↗