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At least 1,225 records · Page 68Linked to original sources
PubMed1998

High-resolution magnetic resonance imaging of articular cartilage: correlation with histology and pathology.

Current explanations of the link between magnetic resonance (MR) images and cartilage histology are reviewed. The influence of the three-dimensional cartilage matrix structure on T2 decay is emphasized and illustrated through the use of MR microimaging, T2 mapping, and correlative scanning electron microscopy (SEM). Special emphasis is given to the topics of T2 heterogeneity and orientation anisotropy. Common degenerative changes in the structure and biochemistry of cartilage are discussed and illustrated with examples of MR microimaging and T2 quantification with correlative SEM and light microscopy.

Cartilage, Articular↗
PubMed2001

Two B cell epitopes of HIV-1 Tat protein have limited antigenic polymorphism in geographically diverse HIV-1 strains.

HIV-1 Tat, a secreted virally encoded toxin, enhances chronic viral replication and induces immune suppression, activities blocked in vitro and in vivo by anti-Tat antibodies. We mapped HIV-1 Tat B cell epitopes, determined sequence variation within them in 350 Tat sequences in GenBank, and determined antigenic cross-reactions between significant amino acid polymorphs. Two of the four B cell epitope sequences identified had limited or no antigenic polymorphism within geographically diverse strains. For epitope 1 in primates, (V,I)4DP(R,K,S,N)7L(E,D)9PW(N,K)12, the most frequent antigenic polymorphs were VDPRLEPWK in B clades (75%) and VDPNLEPWN in non-B clades (64%), with five additional sequences occurring at lower incidence. Epitope 2 in primates, K41(G,A)42LGISYGRK50, had no antigenic polymorphism. These two epitopes have potential utility for the generation of universal vaccine immunogens and therapeutic antibodies.

Amino Acid Sequence↗
PubMed1998

Selective microvascular endothelial cell dysfunction in the small intestine following resuscitated hemorrhagic shock.

Following resuscitation (RES) from hemorrhagic shock (HEM), intestinal microvessels develop progressive vasoconstriction that impairs mucosal blood flow, despite central hemodynamic RES. These events might have clinical consequences secondary to occult intestinal ischemia. We hypothesized that the microvascular impairments were due to progressive endothelial cell dysfunction and an associated reduction in the dilator, nitric oxide (NO), following HEM/RES. Male Sprague-Dawley rats, were monitored for central hemodynamics and the terminal ileum was studied with in vivo videomicroscopy. HEM was 50% of baseline mean arterial pressure (MAP) for 60 min, and RES was with shed blood + 1 volume of normal saline (NS). Following HEM/RES, acetylcholine (10)(-7), 10(-5) M) was topically applied and ileal inflow (A1) and premucosal arteriolar diameters were measured to assess endothelial-cell function at 60 and 120 min post-RES. Normalization of MAP, cardiac output, and heart rate demonstrated adequate systemic resuscitation. Post-RES vasoconstriction developed in A1 (-25%) and premucosal (-28%) arterioles with an associated reduction in A1 flow (-47%). However, there was a selective impairment of endothelial-dependent dilation that was manifested only in the smaller premucosal arterioles and not in the inflow, A1 arterioles. This suggests that multiple mechanisms are involved in the development of the post-RES vasoconstriction. The premucosal response was likely mediated by endothelial cell dysfunction, while the A1 response was probably the result of enhanced vasoconstrictor forces. This early microvascular dysfunction might contribute to the late sequelae of intestinal ischemia and might alter microvascular responses to subsequent systemic insults.

Acetylcholine↗
PubMed2002

Mapping of the B1 field distribution of a surface coil resonator using EPR imaging.

Surface coil resonators have been widely used to perform topical EPR spectroscopy. They are usually positioned adjacent to or implanted within the body. For EPR applications these resonators have a number of important advantages over other resonator designs due to their ease of sample accessibility, mechanical fabrication, implementation of electronic tuning and coupling functions, and low susceptibility to sample motions. However, a disadvantage is their B(1) field inhomogeneity, which limits their usefulness for 3D imaging applications. We show that this problem can be addressed by mapping and correcting the B(1) field distribution. We report the use of EPR imaging (EPRI) to map the B(1) distribution of a surface coil resonator. We show that EPRI provides a fast, accurate, and reliable technique to evaluate the B(1) distribution. 3D EPRI was performed on phantoms, prepared using three different saline concentrations, to obtain the B(1) distribution. The information obtained from the phantoms was used to correct the images of living animals. With the use of this B(1) correction technique, surface coil resonators can be applied to perform 3D mapping of the distribution of free radicals in biological samples and living systems.

Animals↗
PubMed2001

Characterization of a maize chromosome 4 centromeric sequence: evidence for an evolutionary relationship with the B chromosome centromere.

Previous work has identified sequences specific to the B chromosome that are a major component of the B centromere. To address the issue of the origin of the B and the evolution of centromere-localized sequences, DNA prepared from plants without B chromosomes was probed to seek evidence for related sequences. Clones were isolated from maize line B73 without B chromosomes by screening DNA at reduced stringency with a B centromeric probe. These clones were localized to maize centromere 4 using fluorescence in situ hybridization. They showed homology to a maize centromere-mapped sequence, to maize B chromosome centromere sequences, and to a portion of the unit repeat of knobs, which act as neocentromeres in maize. A representative copy was used to screen a BAC library to obtain these sequences in a larger context. Each of the six positive BACs obtained was analyzed to determine the nature of centromere 4-specific sequences present. Fifteen subclones of one BAC were sequenced and the organization of this chromosome 4-specific repeat was examined.

Base Sequence↗
PubMed2006

Protein separation and characterization by np-RP-HPLC followed by intact MALDI-TOF mass spectrometry and peptide mass mapping analyses.

Because of their complexity, the separation of intact proteins from complex mixtures is an important step to comparative proteomics and the identification and characterization of the proteins by mass spectrometry (MS). In the study reported, we evaluated the use of nonporous-reversed-phase (np-RP)-HPLC for intact protein separation prior to MS analyses. The separation system was characterized and compared to 1D-SDS-PAGE electrophoresis in terms of resolution and sensitivity. We demonstrate that np-RP-HPLC protein separation is highly reproducible and provides intact protein fractions which can be directly analyzed by MALDI-TOF-MS for intact molecular weight determination. An in-well digestion protocol was developed, allowing for rapid protein identification by peptide mass fingerprinting (PMF) and resulted in comparable or improved peptide recovery compared with in-gel digestion. The np-RP sensitivity of detection by UV absorbance at 214 nm for intact proteins was at the low ng level and the sensitivity of peptide analysis by MALDI-TOF-MS was in the 10-50 fmol level. A membrane protein fraction was characterized to demonstrate application of this methodology. Among the identified proteins, multiple forms of vimentin were observed. Overall, we demonstrate that np-RP-HPLC followed by MALDI-TOF-MS allows for rapid, sensitive, and reproducible protein fractionation and very specific protein characterization by integration of PMF analysis with MS intact molecular weight information.

Animals↗
PubMed2004

Methotrexate enhances prostaglandin D2-stimulated heat shock protein 27 induction in osteoblasts.

As for the pathogenesis of rheumatoid arthritis (RA), prostaglandins (PGs) act as important mediators of inflammation and joint destruction. Among them, PGD2 is well recognized as a potent regulator of osteoblastic functions. We previously showed that PGD2 stimulates the induction of heat shock protein 27 (HSP27) via protein kinase C (PKC)-dependent p38 mitogen-activated protein (MAP) kinase and p44/p42 MAP kinase in osteoblast-like MC3T3-E1 cells. Therefore, it is a current topic to clarify how HSP27 plays a role for regulating osteoblastic functions in the lesion of RA. On the other hand, methotrexate (MTX) is one of the most effective medicines for the treatment of RA. Here, we examined the effect of MTX on PGD2-stimulated HSP27 induction in MC3T3-E1 cells. The cells were pretreated with various doses of MTX including therapeutic dosage for RA, and then stimulated by PGD2. MTX significantly enhanced the PGD2- increased levels of HSP27 in a dose-dependent manner, although MTX alone had no effect on the levels of HSP27. In addition, MTX amplified the PGD2-increased levels of HSP27 mRNA. On the contrary, MTX had little effect on PGD2-induced formation of inositol phosphates, PKC activation and phosphorylations of MAP kinases. Our results strongly suggest that MTX enhances PGD2-stimulated HSP27 induction at a point downstream from MAP kinases in osteoblasts.

Animals↗
PubMedDate not supplied

What are the acute cardiovascular effects of subcutaneous and topical epinephrine for hemostasis during burn surgery?

Although subcutaneous and topical epinephrine are widely used for hemostasis during burn surgery, the acute systemic cardiovascular effects of the epinephrine are neither well documented nor completely understood. The purpose of this work was to prospectively study the acute cardiovascular responses to epinephrine (epi) administered subcutaneously and topically during burn surgery. Consecutive patients who received subcutaneous and topical epi during burn surgery were monitored prior to the administration of epi, at 2-minute intervals during subcutaneous epi infiltration, and then after epi infiltration (during which time, topical epi was applied). This period of monitoring lasted up to 20 minutes and was referred to as an epinephrine event (EE). A total of 100 EEs from 38 operations in 24 patients (mean +/- SD: age 43 +/- 16 years, mean % TBSA burn 23 +/- 17%) were studied. The mean dose of subcutaneous epi was 30 +/- 30 microg/kg. Although all patients received topical epi, it was impossible to document the topical dose. There was no significant increase in heart rate from baseline, and no arrhythmias occurred. Mean arterial pressure (MAP) did acutely increase significantly by 17.0 +/- 14.1% from baseline (P =.009) and increased more than 10% from baseline in 64/100 EEs. However, the increase in MAP was independent of the dose of epi (r =.053). The increase in MAP was not clinically significant, did not require intervention, and did not appear to be related to the type of wound that received epi (donor site vs burn wound), or the depth of anesthesia, analgesia, or sedation. On the basis of these findings, the use of subcutaneous and topical epi appears to be safe and produces minimal acute cardiovascular effects.

Acute Disease↗
PubMed2003

Identification and characterization of the genes encoding human and mouse osteoactivin.

Osteoactivin (OA) is more highly expressed in the bones of osteopetrotic mutant rats (op/op) than in those of their normal littermates and is the homologue of human nmb, a cDNA more highly expressed in melanoma-derived cell lines of low metastatic potential, and of mouse DC-HIL, which has been implicated in endothelial cell adhesion. The human OA gene is found on chromosome 7p15.1 and consists of 11 exons spanning 28.3 kb. Murine OA is encoded by a highly similar gene of 11 exons spanning 20.2 kb on mouse chromosome 6. Human OA uses the same transcriptional initiation site in both bone and kidney as was reported for melanoma cells. OA is expressed in primary human and mouse osteoblast cultures at all stages of differentiation, with increased levels observed concurrently with the expression of osteoblast phenotype markers. OA is also expressed in a wide variety of human and mouse tissues as determined by RT-PCR analysis. Immunohistochemical investigation of OA expression in late mouse embryonic development showed very high, cell-specific expression in the nervous system, basal layer of the skin, germinal cells of hair follicles, and in the forming nephrons of the kidney. Continuing investigation of the cell-specific expression of OA in bone as well as in other tissues will lead to a better understanding of its function in the development of these cell types.

Amino Acid Sequence↗
PubMed2000

Using the fluorogenic 5' nuclease assay for high-throughput detection of (CA)n repeats in radiation hybrid mapping.

Here, the power of the 5' nuclease assay to detect PCR products containing (CA)n repeats was compared with that of the classical electrophoretic analysis. This assay, which relies on the use of a unique (CA)10 energy transfer-labeled probe and the 5' nuclease activity of Taq DNA polymerase, was used to construct a dog radiation hybrid map consisting of microsatellite markers. Data from over 7000 PCRs were analyzed in parallel by the fluorogenic assay and the conventional ethidium bromide-stained, agarose gel-based assay. We show that the fluorogenic assay provides a sensitive, reliable and specific method for detecting (CA)n amplimers. Moreover, as no processing is required after the PCR, the risk of carryover contamination and the time required for sample analysis are greatly reduced. All radiation hyrid (RH) assays can be performed using a single PCR protocol, and a standard analysis method has been developed that enables numerically automated data processing. On the whole, using this strategy greatly enhanced the rapidity, throughput and accuracy of the RH mapping of microsatellite markers.

5'-Nucleotidase↗
PubMed2001

MKP-7, a novel mitogen-activated protein kinase phosphatase, functions as a shuttle protein.

Mitogen-activated protein kinase (MAPK) phosphatases (MKPs) negatively regulate MAPK activity. In the present study, we have identified a novel MKP, designated MKP-7, and mapped it to human chromosome 12p12. MKP-7 possesses a long C-terminal stretch containing both a nuclear export signal and a nuclear localization signal, in addition to the rhodanese-like domain and the dual specificity phosphatase catalytic domain, both of which are conserved among MKP family members. When expressed in mammalian cells MKP-7 protein was localized exclusively in the cytoplasm, but this localization became exclusively nuclear following leptomycin B treatment or introduction of a mutation in the nuclear export signal. These findings indicate that MKP-7 is the first identified leptomycin B-sensitive shuttle MKP. Forced expression of MKP-7 suppressed activation of MAPKs in COS-7 cells in the order of selectivity, JNK p38 > ERK. Furthermore, a mutant form MKP-7 functioned as a dominant negative particularly against the dephosphorylation of JNK, suggesting that MKP-7 works as a JNK-specific phosphatase in vivo. Co-immunoprecipitation experiments and histological analysis suggested that MKP-7 determines the localization of MAPKs in the cytoplasm.

Active Transport, Cell Nucleus↗
PubMed1999

Frontiers of SLE: review of the 5th International Congress of Systemic Lupus Erythematosus, Cancun, Mexico, April 20-25, 1998.

OBJECTIVE: To review the recent advances in clinical and experimental research in systemic lupus erythematosus (SLE). METHODS: Review of the 5th International Congress of SLE that took place in Cancun, Mexico, on April 20-25, 1998. RESULTS: The main topics presented at the conference are summarized. These include new findings about the genetics of SLE due to fine mapping of the patients' genes and lupus mouse models, the nucleosome as a major autoantigen in SLE, serving as an immunogen for pathogenic T helper and B cells and contributing to the development of lupus nephritis, abnormalities of apoptosis as a cause of SLE, and apoptotic mechanisms as a cause of autoimmunization. Other topics included the pathophysiologic role of anti-endothelial cell antibodies in lupus with central nervous system involvement, vasculitis, the thrombotic diathesis associated with the antiphospholipid syndrome, induction of endothelial cell apoptosis and its regulation by the idiotypic network, the penetration of antinuclear antibodies to the cytoplasm and nucleus and the subsequent interaction with cellular organelles, and new aspects in the antiphospholipid syndrome, including animal models of the disease and the importance of antibodies to beta-2-glycoprotein-I and prothrombin. Advances in the clinical aspects of SLE included clinical manifestations, diagnosis, pregnancy and neonatal SLE, infections, hormones, and treatment. Additionally, four "Lectures of A Lifetime," entitled (1) What causes lupus? (2) From natural autoimmunity to autoimmune disease; (3) The idiotypic network and SLE; and (4) Late-stage morbidity and mortality in SLE-the role of accelerated atherosclerosis were presented. CONCLUSIONS: Recent advances provide new insights into the pathogenesis of SLE, as well as hope for novel therapeutic modalities and diagnostic measures. These offer the possibility of improving life quality and decreasing mortality from the disease and its complications.

Animals↗
PubMed1999

B-SPID: an object-relational database architecture to store, retrieve, and manipulate neuroimaging data.

We propose a hardware and software architecture to respond to crucial problems in the neuroimaging field: storage, retrieval, and processing of large datasets. The B-SPID project, here discussed, concerns the processing of neuroimages and attached components stored in an object-relational multimedia database management system (DBMS). Advanced bioinformation concepts are exploited in this project such as large scale data storage, high level graphical user interfaces and 3D graphical processing and display of data. Our database implementation is based on standard programming components, runs on several UNIX platforms and is written to be evolutive. Queries on this database are designed to obtain and display from neuroimaging data several types of results (pictures, text, or 3D graphical shapes) on heterogeneous systems.

Brain Mapping↗
PubMed2000

Proton mobility in protonated peptides: a joint molecular orbital and RRKM study.

The mobile proton model was critically evaluated by using purely theoretical models which include quantum mechanical calculations to determine stationary points on the potential energy surface (PES) of a model compound, and Rice-Ramsperger-Kassel-Marcus (RRKM) calculations to determine the rate constants of various processes (conformational changes, proton transfer reactions) which occur during mass analysis of protonated peptides. Extensive mapping of the PES of protonated N-formylglycinamide resulted in various minima which were stabilized by one or more of the following types of interaction: internal hydrogen bond, charge transfer interaction, charge delocalization, and ring formation. The relative energies of most of the investigated minima are less then 20 kcal mol(-1) compared with the most stable species. More importantly, the relative energies of the transition structures connecting these minima are fairly low, allowing facile transitions among the energetically low-lying species. It is demonstrated that a path can be found leading from the energetically most stable species, protonated on an amide oxygen, to the structure from which the energetically most favorable fragmentation occurs. It is also shown that the added proton can sample all protonation sites prior to fragmentation. The RRKM calculations applied the results of ab initio computations (structures, energetics, vibrational frequencies) to the reactions (internal rotations, proton transfers) occurring in protonated N-formylglycinamide, and clearly lend additional evidence to the mobile proton model. Based on the results of the PES search on protonated N-formylglycinamide, we also comment on the mechanism proposed by Arnot et al. (Arnot D, Kottmeier D, Yates N, Shabanowitz J, Hunt D F. 42(nd) ASMS Conference on Mass Spectrometry, 1994; 470) and Reid et al. (Reid G E, Simpson R J, O'Hair R A J. J. Am. Soc. Mass Spectrom. 1998; 9:945) for the formation of b(2)(+) ions. According to the high level ab initio results, the mechanism relying on amide oxygen protonated species seems to be less feasible than the one which involves N-protonated species.

Chemical Phenomena↗
PubMed2002

Genetic association mapping at the crossroads: which test and why? Overview and practical guidelines.

Until about a decade ago, genetic association testing essentially meant case control association analysis using genetic markers. Concerns about population stratification propelled family-based tests of association into widespread use and challenged the classic case control design. The literature now contains a vast collection of different family-based methods, most of which are based on the transmission/disequilibrium test (TDT). Some methods extend the original TDT to accommodate multiallelic markers, variable pedigree constellations, multiple loci, etc. Other methods go beyond the original design of the TDT to detect genetic association via haplotype sharing. Most recently, we have witnessed a revival of case control methods that control for population stratification. The purpose of this review is to help orient readers to the rapidly developing methods of association testing and enhance their understanding of the basic principles of these approaches. We present an overview of the development of genetic association tests, with practical guidelines on which test might be the most suitable for a given study.

Case-Control Studies↗