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Biomedical subjects

R Lee

Publications and source records attributed to R Lee.

At least 163 records · Page 9Linked to original sources
PubMed1997

A randomized, controlled clinical trial of a treatment for shoulder pain.

BACKGROUND AND PURPOSE: The aim of this study was to evaluate the efficacy of a physical therapy approach to the treatment of shoulder pain. Subjects. Sixty-six volunteers with shoulder pain believed to be of local mechanical origin were randomly allocated to either a treatment group or a control group. METHODS: Subjects in the treatment group received 1 month of physical therapy aimed at restoring function of their shoulder muscles. Subjects in the control group received no treatment. Outcome measurements of pain intensity, range of motion (ROM), isometric muscle force, functional impairment, and self-perception of improvement were obtained by blinded assessment. RESULTS: Subjects in the treatment group showed improvement in pain-free abduction and flexion ROM, functional impairment, and self-perception of improvement. The control group deteriorated slightly over the experimental period in ROM and functional impairment measures. CONCLUSION AND DISCUSSION: These results suggest that the physical therapy approach used in this study is effective in improving shoulder function in subjects experiencing pain of mechanical origin. The results also provide little evidence of spontaneous recovery over a 1-month period.

Activities of Daily Living↗
PubMed1997

An STS-based radiation hybrid map of the human genome.

We have constructed a physical map of the human genome by using a panel of 83 whole genome radiation hybrids (the Stanford G3 panel) in conjunction with 10,478 sequence-tagged sites (STSs) derived from random genomic DNA sequences, previously mapped genetic markers, and expressed sequences. Of these STSs, 5049 are framework markers that fall into 1766 high-confidence bins. An additional 945 STSs are indistinguishable in their map location from one or more of the framework markers. These 5994 mapped STSs have an average spacing of 500 kb. An additional 4484 STSs are positioned with respect to the framework markers. Comparison of the orders of markers on this map with orders derived from independent meiotic and YAC STS-content maps indicates that the error rate in defining high-confidence bins is < 5%. Analysis of 322 random cDNAs indicates that the map covers the vast majority of the human genome. This STS-based radiation hybrid map of the human genome brings us one step closer to the goal of a physical map containing 30,000 unique ordered landmarks with an average marker spacing of 100 kb.

Animals↗
PubMed1997

Comparison of solution properties of human and rat ciliary neurotrophic factor.

The solution structure and stability of rat and human ciliary neurotrophic factor (CNTF) were examined by circular dichroism (CD), Fourier transform infrared (FTIR) and fluorescence spectroscopy and sedimentation equilibrium analyses. The secondary structure of both proteins, as assessed by CD and FTIR, consists primarily of alpha-helix, consistent with CNTF being a member of the four-helical bundle family of cytokines and neurokines, with rat CNTF containing slightly less helix (about 10% less) and slightly more disordered structure. The environment of the tyrosine and tryptophan residues, assessed by intrinsic fluorescence emission spectroscopy, appears to be the same in both proteins. Binding of anilinonaphthalene sulfonate is identical for both proteins, indicating that these two proteins have similar surface hydrophobicities in the native state. The thermal stability of the human CNTF is significantly less than that of the rat CNTF, yet their stabilities to guanidine HCl-induced denaturation are equivalent. This apparent discrepancy in stability between the two proteins may be explained by solubility differences upon thermal unfolding. Although the human protein precipitates as it is denatured by heat, the rat protein does not. It thus appears that the unfolded state of human CNTF is less soluble and more prone to aggregation than that of the rat protein upon heating, although their conformational stability is similar. Both proteins remain largely folded at pH 3.0. Sedimentation equilibrium analysis demonstrates that both rat and human CNTF exist primarily as monomers; however, significant dimer formation occurs as the protein concentrations are increased to greater than 3 mg/mL, particularly in the presence of ammonium sulfate.

Anilino Naphthalenesulfonates↗
PubMed1997

Analysis of mechanisms regulating expression of the ver-1 gene, involved in aflatoxin biosynthesis.

Previous studies have shown that ver-1A encodes an enzyme which is directly involved in the conversion of versicolorin A to demethylsterigmatocystin during aflatoxin B1 (AFB1) biosynthesis in the filamentous fungus Aspergillus parasiticus. In this study, two different tools were utilized to study the regulation of ver-1A expression at the level of transcription and protein accumulation. First, a ver-1A cDNA was expressed in Escherichia coli with the vector pMAL-c2. The resulting maltose-binding protein-Ver-1A fusion protein was purified and used to generate polyclonal antibodies. Western blot analyses showed that these antibodies specifically recognized the Ver-1 protein (approximately 28 kDa) in cell extracts of Aspergillus parasiticus SU1. Second, a GUS (uidA; encodes beta-glucuronidase) reporter system was developed by fusing the ver-1A promoter and transcription terminator to the GUS gene. Reporter constructs were transformed into A. parasiticus, resulting in a single copy of the ver-1A-GUS reporter integrated adjacent to the wild-type ver-1A gene (3' end) in the chromosome. Western blot analysis, Northern hybridization analysis, and a GUS activity assay were used to analyze transformants. The timing of appearance and pattern of accumulation of GUS transcript and GUS protein in transformants were consistent with the timing of appearance and pattern of accumulation of ver-1 transcript and Ver-1 protein. These data suggested that the GUS gene was under the same regulatory control as the wild-type ver-1 gene and confirmed that transcriptional regulation plays an important role in ver-1A expression. Integration of the ver-1A-GUS reporter construct at the niaD locus resulted in 500-fold-lower GUS activity, but the temporal pattern of accumulation of GUS activity was not affected. Therefore, chromosomal location can play a role in determining the level of gene expression in A. parasiticus and should be an important consideration when analyzing promoter function in this organism.

Aflatoxin B1↗
PubMed1997

Redistribution of villin to proximal tubule basolateral membranes after ischemia and reperfusion.

After ischemia and reperfusion, severe alterations in the cytoskeletal organization of renal tubular epithelial cells have been reported. These effects, accompanied by a modification in the polarized distribution of some membrane transport proteins, are especially evident in the proximal tubule. In normal proximal tubule cells, actin is concentrated in apical brush border microvilli, along with the actin-binding protein villin. Because villin plays an important role in actin bundling and in microvillar assembly but can also act as an actin-fragmenting protein at higher calcium concentrations, we examined the effects of ischemic injury and reperfusion on the distribution of villin and actin in proximal tubule cells of rat kidney. Using specific antibodies against villin and actin, we show that these proteins redistribute in parallel from the apical to the basolateral plasma membrane within 1 h of reperfusion after ischemia. Ischemia alone had no effect on the staining pattern. Repolarization of villin to the apical membrane begins within hours after reperfusion with enhanced apical localization over time during the period of regeneration. This apical repolarization of villin is accompanied by the migration of actin back to the apical membrane. These results show not only that villin may be involved in the initial disruption of the actin cytoskeleton during reperfusion injury but also that its migration back to the apical domain of these cells accompanies the reestablishment of a normal actin distribution in the brush border.

Actins↗
PubMed1997

Validation of current practice and a near patient testing method for oral-anticoagulant control in general practice.

When oral anticoagulant control is monitored in general practice, venous blood samples are usually transported to a central laboratory for determination of international normalized ratio (INR). An alternative is near patient testing by a commercial method. In a rural general practice 27 km from a central haematology laboratory, whole blood samples were drawn from patients receiving oral anticoagulants and analysed by three methods: after centrifugation, plasma separated and frozen in liquid nitrogen, transported to the laboratory, thawed and immediately analysed (control); courier transport of citrated sample to the laboratory for analysis (routine); near patient testing of whole blood sample (NPT). Maximum temperature achieved and time to analysis for routine samples were recorded. 306 complete sets of data were obtained. Comparison between the routine method and the control method revealed acceptable agreement. On multiple regression analysis, maximum temperature achieved did not contribute to differences observed but time to analysis of over 5 hours did make a significant contribution. Comparison between the NPT method and control method showed acceptable agreement, with persistent under-recording by the NPT method. The routine method for INR determination was validated as robust and reproducible with the proviso that needle-to-analysis time should be kept below 5 hours. The NPT method was valid under conditions of normal general practice. Strict quality control of NPT methods is essential if performance is to be comparable with that of established methods.

Anticoagulants↗
PubMed1997

Modeling seasonal changes in intracellular freeze-tolerance of fat body cells of the gall fly Eurosta solidaginis (Diptera, Tephritidae)

Although seasonal changes in the freeze-tolerance of third-instar larvae of Eurosta solidaginis have been well documented for the whole organism, the nature of this cold-hardiness at the cellular level has not been examined. Seasonal changes in the survival of fat body cells from E. solidaginis larvae were assessed using fluorescent vital dyes after freezing at -10, -25 or -80 &deg;C for 24 h both in vivo and in vitro. Cells frozen in vitro were frozen with glycerol, with sorbitol (both of which enhanced cell survival) or without cryoprotectants. Both cellular and organismal survival were low in August when larvae were not freeze-tolerant, then increased dramatically during September and October before leveling off from November to January. This observation for cells frozen without cryoprotectants indicates that the cells themselves have adapted. The single most important factor influencing cell survival, as determined by logistic regression modeling, was the time of larval collection, which reflects the level of cold-hardiness achieved by field acclimation. Cells frozen in vivo exhibited greater survival than did those frozen in vitro, even with the addition of cryoprotectants. Since no differences were observed between cells frozen with glycerol or sorbitol, the role of the multi-component cryoprotectant system present in E. solidaginis should be investigated.

Journal Article↗
PubMed1997

The effects of exposure to ammonia on ammonia and taurine pools of the symbiotic clam

The nutrition of the gutless clam Solemyareidi is supported by the activity of intracellular chemoautotrophic bacteria housed in its gill filaments. Ammonia (the sum of NH3 and NH4+) is utilized as a nitrogen source by the association and is abundant in the clam's environment. In the present study, clams were exposed to 0.01&shy;1.3mmoll-1 ammonia for 22&shy;23h in the presence of thiosulfate as a sulfur substrate. Ammonia exposure increased the ammonia concentration in the tissue pools of the gill, foot and visceral mass from 0.5 to 2&micro;molg-1wetmass, without added ammonia, to as much as 12&micro;molg-1wetmass in the presence of 0.7 and 1.3mmoll-1 external ammonia. Gill tissue ammonia concentrations were consistently higher than those in the foot and visceral mass. The elevation of tissue ammonia concentration compared with the medium may be due in part to an ammonia trapping mechanism resulting from a lower intracellular pH compared with sea water and greater permeability to NH3 compared with NH4+. Rates of ammonia incorporation into organic matter (assimilation) were determined using 15N as a tracer. 15N-labeled ammonia assimilation was higher in gill than in foot and increased as a function of 15N-labeled ammonia concentration in the medium. The size of the free amino acid (FAA) pool in the gill also increased as a function of ammonia concentration in the medium. This entire increase was accounted for by a single amino acid, taurine, which was the predominant FAA in both gill and foot tissue. Aspartate, glutamate, arginine and alanine were also abundant but their levels were not influenced by external ammonia concentration. Ammonia assimilation appeared to occur at rates sufficient to account for the observed increase in taurine level. These findings suggest that taurine is a major product of ammonia assimilation.

Journal Article↗
PubMed1997

Inorganic carbon acquisition by the hydrothermal vent tubeworm Riftia pachyptila depends upon high external PCO2 and upon proton-equivalent ion transport by the worm

Riftia pachyptila is the most conspicuous organism living at deep sea hydrothermal vents along the East Pacific Rise. To support its large size and high growth rates, this invertebrate relies exclusively upon internal chemosynthetic bacterial symbionts. The animal must supply inorganic carbon at high rates to the bacteria, which are far removed from the external medium. We found substantial differences in body fluid total inorganic carbon (CO2) both within and between vent sites when comparing freshly captured worms from a variety of places. However, the primary influence on body fluid CO2 was the chemical characteristics of the site from which the worms were collected. Studies on tubeworms, both freshly captured and maintained in captivity, demonstrate that the acquisition of inorganic carbon is apparently limited by the availability of CO2, as opposed to bicarbonate, and thus appears to be accomplished via diffusion of CO2 into the plume, rather than by mediated transport of bicarbonate. The greatly elevated PCO2 measured at the vent sites (up to 12.6 kPa around the tubeworms), which is a result of low environmental pH (as low as 5.6 around the tubeworms), and elevated CO2 (as high as 7.1 mmol l-1 around the tubes) speeds this diffusion. Moreover, despite large and variable amounts of internal CO2, these worms maintain their extracellular fluid pH stable, and alkaline, in comparison with the environment. The maintenance of this alkaline pH acts to concentrate inorganic carbon into extracellular fluids. Exposure to N-ethylmaleimide, a non-specific H+-ATPase inhibitor, appeared to stop this process, resulting in a decline in extracellular pH and CO2. We hypothesize that the worms maintain their extracellular pH by active proton-equivalent ion transport via high concentrations of H+-ATPases. Thus, Riftia pachyptila is able to support its symbionts' large demand for inorganic carbon owing to the elevated PCO2 in the vent environment and because of its ability to control its extracellular pH in the presence of large inward CO2 fluxes.

Journal Article↗
PubMed1997

Death and taxes: longer life, consumption, and social security.

We analyze in three steps the influence of the projected mortality decline on the long run finances of the Social Security System. First, on a theoretical level, mortality decline adds person years of life which are distributed across the life cycle. The interaction of this distribution with the age distribution of labor earnings minus consumption, or of taxes minus benefits, partially determines the corresponding steady state financial consequences of mortality decline. The effect of mortality decline on population growth rates also matters, but is negligible in low mortality populations. Second, examination of past mortality trends in the United States and of international trends in low mortality populations, suggests that mortality will decline faster than foreseen by the Social Security Administration's forecasts. Third, we combine the work of the first two parts in dynamic simulations to examine the implications of mortality decline and of alternative forecasts of mortality for the finances of the social security system. Also, we use stochastic population forecasts to assess the influence of uncertainty about mortality decline on uncertainty about finances; we find that uncertainty about fertility still has more important implications than uncertainty about mortality, contrary to sensitivity tests in the official forecasts.

Actuarial Analysis↗
PubMed1997

Lazaroid U-74500A for warm ischemia and reperfusion injury of the canine small intestine.

BACKGROUND: Although lazaroids have been shown to protect various organs from ischemia/reperfusion injury, results obtained in the small intestine have been conflicting. STUDY DESIGN: The canine small intestine was made totally ischemic for 2 hours by occluding the superior mesenteric artery and the superior mesenteric vein with interruption of the mesenteric collateral vessels. A lazaroid compound, U74500A, or a citrate vehicle was given intravenously to each of the six animals for 30 minutes before intestinal ischemia. Intestinal tissue blood flow, lipid peroxidation, neutrophil infiltration, adenine nucleotides and their catabolites, and histologic changes after reperfusion were determined. RESULTS: Lazaroid treatment attenuated decline of the mucosal and serosal blood flow after reperfusion. Accumulation of lipid peroxidation products and neutrophils in mucosal tissues was markedly inhibited by the treatment. Postischemic energy resynthesis was also augmented by lazaroid. Morphologically, mucosal architectures were better preserved with lazaroid treatment after reperfusion, and recovered to normal by postoperative day 3 in the treated group and by postoperative day 7 in control animals. CONCLUSIONS: Lazaroids protect the canine small intestine from ischemia/reperfusion injury by inhibiting lipid peroxidation and neutrophil infiltration. Dogs are tolerant of 2-hour normothermic complete intestinal ischemia.

Animals↗
PubMed1997

Attenuation of ischemic liver injury by monoclonal anti-endothelin antibody, AwETN40.

BACKGROUND: Enhanced production of endothelin-1 (ET-1), vasoconstrictive 21 amino acids produced by endothelial cells during ischemia and after reperfusion of the liver, is known to cause sinusoidal constriction and microcirculatory disturbances, which lead to severe tissue damage. Using a 2-hour hepatic vascular exclusion model in dogs, we tested our hypothesis that neutralization of ET-1 by monoclonal anti-ET-1 and anti-ET-2 antibody (AwETN40) abates vascular dysfunction and ameliorates ischemia/reperfusion injury of the liver. STUDY DESIGN: After skeletonization, the liver was made totally ischemic by cross-clamping the portal vein, the hepatic artery, and the vena cava (above and below the liver). Veno-venous bypass was used to decompress splanchnic and inferior systemic congestion. AwETN40, 5 mg/kg, was administered intravenously 10 minutes before ischemia (treatment group, n = 5). Nontreated animals were used as controls (control group, n = 10). Animal survival, hepatic tissue blood flow, liver function tests, total bile acid, high-energy phosphate, ET-1 levels, and liver histopathology were studied. RESULTS: Treatment with AwETN40 improved 2-week animal survival from 30% to 100%. Hepatic tissue blood flow after reperfusion was significantly higher in the treatment group. The treatment significantly attenuated liver enzyme release, total bile acid, and changes in adenine nucleotides. Immunoreactive ET-1 levels in the hepatic venous blood of the control group showed a significant increase and remained high for up to 24 hours after reperfusion. Histopathologic alterations were significantly lessened in the treatment group. CONCLUSIONS: These results indicate that ET-1 is involved in ischemia/reperfusion injury of the liver, which can be ameliorated by the monoclonal anti-ET-1 and anti-ET-2 antibody AwETN40.

Animals↗
PubMed1996

Glial cell line-derived neurotrophic factor: selective reduction of the intermolecular disulfide linkage and characterization of its disulfide structure.

Glial cell line-derived neurotrophic factor is a protein known to enhance the survival of dopaminergic neurons against several neurotoxins. It has been shown to have therapeutic potential in the treatment of Parkinson's disease and other neurodegenerative diseases. We have determined the inter- and intramolecular disulfide linkages of the dimeric molecule by a combination of direct peptide analysis and peptide analysis after either partial reduction or partial oxidation of the protein. Under an acidic condition, the interchain disulfide bond was selectively cleaved with tris(2-carboxyethyl)phosphine, revealing that Cys101 was involved in the intermolecular disulfide linkage. Three other disulfides, Cys68-Cys131, Cys72-Cys133, and Cys41-Cys102, were identified as intramolecular linkages. The determined disulfide structure is highly homologous to that of transforming growth factor beta 2. Since one intramolecular disulfide points through a ring consisting of eight amino acid residues based on the similarity with transforming growth factor beta 2, the disulfide-linked peptides were not purified by conventional methods. Only the peptides from an N-terminal region (residues -1 to 37) were liberated by proteolytic treatment with trypsin or endoproteinase Lys-C, resulting in a stable cystine-knot protein.

Amino Acid Sequence↗
PubMed1996

Enzymatic synthesis of UDP-galactofuranose and an assay for UDP-galactopyranose mutase based on high-performance liquid chromatography.

A method to prepare UDP-galactofuranose (UDP-Galf) free of UDP-galactopyranose (UDP-Galp) is described. The UDP-Galf is synthesized enzymatically from UDP-Galp using the enzyme UDP-galactopyranose mutase. Treatment of UDP-Galp with the enzyme yields an equilibrium mixture of UDP-Galp and UDP-Galf in which UDP-Galf is approximately 7%. In spite of its low yield, the UDP-Galf is readily purified from starting UDP-Galp using a Dionex PA-100 ion exchange HPLC column. The purified UDP-Galf was characterized by chemical degradations, by electrospray mass spectrometry, and by several nuclear magnetic resonance techniques. In addition, an HPLC assay for the enzyme UDP-galactopyranose mutase is presented that requires 0.5 microgram of UDP-Galf per assay and can be used for both qualitative and quantitative measurements of the enzyme activity. These procedures should thus aid in the characterization of the enzymes involved in galactofuranosyl biosynthesis for the cell walls of Mycobacteria, for the lipophosphoglycan of Leishmania, and for other microorganisms where galactofuranosyl residues are found.

Bacterial Proteins↗
PubMed1996

Crystalline Ropes of Metallic Carbon Nanotubes

Fullerene single-wall nanotubes (SWNTs) were produced in yields of more than 70 percent by condensation of a laser-vaporized carbon-nickel-cobalt mixture at 1200degreesC. X-ray diffraction and electron microscopy showed that these SWNTs are nearly uniform in diameter and that they self-organize into "ropes," which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms. The x-ray form factor is consistent with that of uniformly charged cylinders 13.8 +/- 0.2 angstroms in diameter. The ropes were metallic, with a single-rope resistivity of <10(-4) ohm-centimeters at 300 kelvin. The uniformity of SWNT diameter is attributed to the efficient annealing of an initial fullerene tubelet kept open by a few metal atoms; the optimum diameter is determined by competition between the strain energy of curvature of the graphene sheet and the dangling-bond energy of the open edge, where growth occurs. These factors strongly favor the metallic (10,10) tube with C5v symmetry and an open edge stabilized by triple bonds.

Journal Article↗
PubMed1996

High-performance liquid chromatographic method for the determination of mycophenolate mofetil in human plasma.

A method for the quantification of mycophenolate mofetil (MMF, CellCept) in plasma using solid-phase extraction and HPLC is described here. A solution of internal standard is added to a 0.5-ml plasma aliquot. The resulting sample is treated with water and dilute HCl and applied to a C18 solid-phase extraction column. After a water wash, the MMF and internal standard are eluted with methanol-0.1 M citrate-phosphate buffer, pH 2.6 (80:20, v/v). A 20-microliters aliquot of the eluate is injected onto a C18 column (5 microns particle size, 150 x 4.6 mm I.D.) and eluted at ambient temperature with acetonitrile-0.05 M citrate-phosphate buffer, pH 3.6, containing 0.02 M heptanesulfonic acid (41:59, v/v). Quantification is achieved by UV detection at 254 nm. The method is reproducible, accurate and specific for MMF. Using 0.5 ml of plasma for analysis, the quantification limit is 0.400 microgram/ml and the range is 0.400-20 micrograms/ml. Based on the stability profile of MMF in plasma, it is recommended that blood samples collected following intravenous infusion be immediately stored on ice and that plasma be prepared rapidly, immediately stored frozen at -80 degrees C and analyzed within four months of collection.

Chromatography, High Pressure Liquid↗
PubMed1996

Dynamic changes in the lymphocyte subpopulations of pig uterine lymph nodes.

Cell subpopulations in local lymph nodes draining the uterine tissue of non-pregnant and pregnant pigs were examined by one- and two-colour immunofluorescent staining and flow cytometry using a panel of monoclonal antibodies to pig leucocyte cell surface antigens. Significant changes were observed in the T and B lymphocyte subpopulations and in a subpopulation of non-T or B cells. Activation of lymphocytes in the uterine lymph nodes during cycling in non-pregnant gilts suggests a role for the local immune system in the normal physiology of the uterus. In non-pregnant sows there was evidence of an increase in the CD4/CD8H ratio and in the proportion of B cells in the uterine nodes when compared to gilts with no prior reproductive experience. Pregnancy was shown to induce further dramatic changes in the uterine lymph nodes with an escalation in the proportion of B cells from 48% to 88% and a further increase in the CD4/CD8H ratio. For the first time in swine, low-level CD2 expression is reported on a subpopulation of B cells which are activated during pregnancy. These results provide evidence that the local uterine immune system in pigs plays a role in reproduction and perhaps in the maintenance of normal pregnancy.

Animals↗