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Biomedical subjects

R Miller

Publications and source records attributed to R Miller.

At least 271 records · Page 15Linked to original sources
PubMed1998

[Dynamic surface tension of blood and synovial fluid in rheumatoid arthritis].

AIM: Assessment of the dynamic surface tension (DST) of blood serum (BS), synovial fluid (SF) in various courses of rheumatoid arthritis (RA). MATERIALS AND METHODS: Forty three patients with RA and 63 apparently healthy individuals were examined. DST of BS and SF was determined in the computer-aided tensiometer and some blood biochemical parameters were also measured. RESULTS: DST of BS in patients with RA were found to be higher than the normal values and some parameters c beta 2 and beta 3) of BS DST did not significantly differ from the normal values whereas others (beta 1 and gamma proved to be much lower. Depending on the disease course variants, there were some differences in these DST changes. There was a feedback between DST parameters and the levels of immunoglobulins, beta 2-microglobulin, and lipids in blood. CONCLUSION: Assessment of BS and SF DST may be useful in the differential diagnosis of RA, in the determination of its intensity and prognosis, and therapeutical efficiency.

Adolescent↗
PubMed1998

Review of counselling in a transfusion service: the London (UK) experience.

Donor (and recipient) counselling within the Transfusion Service in the UK has grown in volume and complexity over the last 10 years. The addition of new tests for donated blood and the growth of bone marrow transplantation have increased the demands on counselling staff. New initiatives, such as the HCV look-back programme, have required an extension of the skills and knowledge of staff involved in counselling.

Blood Donors↗
PubMed1998

Assessment of interlaboratory performance in external proficiency testing programs with a direct HDL-cholesterol assay.

Direct assays for the determination of HDL-cholesterol (HDL-C) have recently become available. The methods are precise, require small sample volume, and appear to be less affected by increased triglycerides than traditional precipitation methods. In this study, we describe the inter- and intralaboratory variability of the Boehringer Mannheim Corporation direct HDL-C assay and its performance in external proficiency testing surveys. A comparison study among three laboratories, using different analyzers and 85 serum specimens, showed a correlation coefficient (r) of 0.99. The direct HDL-C assay also showed good agreement with the ultracentrifugation-dextran sulfate-Mg2+ method (r = 0.98) and the Cholesterol Reference Method Laboratory Network-Designated Comparison Method (a = 0.98x + 4.75 mg/L, r = 0.98). Total error at medical decision levels ranged from -0.8% to +11.1%. Furthermore, this assay performed adequately in the College of American Pathologists and the ALERT surveys as well as the CDC Lipid Standardization Program and met all performance criteria of regulatory agencies.

Centers for Disease Control and Prevention, U.S.↗
PubMed1998

[Dynamic middle-phase tensiometry of blood and urine in female patients with malignant tumors of the reproductive organs].

An improved version of the MPT2 (LAUDA) computerized tensiometer (Germany) was used to measure dynamic surface tension (ST) of blood and urine by the maximum bubble pressure method in patients with tumors of the uterus, vagina and cervical canal. Relatively low blood and urine ST values at t-->infinity and serum at t = 1 s were registered. Combined radiotherapy involved oppositely-directed changes in the equilibrium (static) ST of the biological fluids as well as a urine ST inhibition in the surface short-life range (t = 0.01 s). The slope of blood serumtension curves by the end of treatment was close to that in healthy females.

Blood↗
PubMed1998

A graphical tool for ad hoc query generation.

Medical data are characterized by complex taxonomies and evolving terminology. Questions that clinicians, medical administrators, and researchers may wish to answer using medical databases are not easily formulated as SQL queries. In this paper we describe a graphical tool that facilitates formulation of ad hoc questions as SQL queries. This tool manages multiple attribute hierarchies and creates SQL query strings by navigating through the hierarchies. This interactive tool has been optimized using indexing to improve the overall speed of the query building and the data retrieval process. Indexed queries performed 5 to 100 times faster than query strings. However, query string generation time depends on the size of the taxonomies describing the hierarchies, while the index generation time depends on the size of the data warehouse.

Abstracting and Indexing↗
PubMed1998

Digital dynamic telepathology--the Virtual Microscope.

The Virtual Microscope is being designed as an integrated computer hardware and software system that generates a highly realistic digital simulation of analog, mechanical light microscopy. We present our work over the past year in meeting the challenges in building such a system. The enhancements we made are discussed, as well as the planned future improvements. Performance results are provided showing the system scales well, so that many users can be adequately serviced by an appropriately configured data server.

Computers↗
PubMed1997

Ab initio structure determination and refinement of a scorpion protein toxin.

The structure of toxin II from the scorpion Androctonus australis Hector has been determined ab initio by direct methods using SnB at 0.96 A resolution. For the purpose of this structure redetermination, undertaken as a test of the minimal function and the SnB program, the identity and sequence of the protein was withheld from part of the research team. A single solution obtained from 1 619 random atom trials was clearly revealed by the bimodal distribution of the final value of the minimal function associated with each individual trial. Five peptide fragments were identified from a conservative analysis of the initial E-map, and following several refinement cycles with X-PLOR, a model was built of the complete structure. At the end of the X-PLOR refinement, the sequence was compared with the published sequence and 57 of the 64 residues had been correctly identified. Two errors in sequence resulted from side chains with similar size while the rest of the errors were a result of severe disorder or high thermal motion in the side chains. Given the amino-acid sequence, it is estimated that the initial E-map could have produced a model containing 99% of all main-chain and 81% of side-chain atoms. The structure refinement was completed with PROFFT, including the contributions of protein H atoms, and converged at a residual of 0.158 for 30 609 data with F >or= 2sigma(F) in the resolution range 8.0-0.964 A. The final model consisted of 518 non-H protein atoms (36 disordered), 407 H atoms, and 129 water molecules (43 with occupancies less than unity). This total of 647 non-H atoms represents the largest light-atom structure solved to date.

Journal Article↗
PubMed1997

Incorporating tangent refinement in the Shake-and-Bake formalism.

Shake-and-Bake is a direct-methods procedure in which phase refinement and Fourier refinement are alternated repetitively, unconditionally and automatically. The traditional Shake-and-Bake approach invoked a parameter-shift routine to perform phase refinement in an effort to reduce the value of minimal function. In this paper, parameter shift is replaced with the tangent formula as a means of phase refinement. This study shows that the tangent formula is more efficient than parameter shift for small structures when the number of refinement cycles and number of applications of the tangent formula per Shake-and-Bake cycle are chosen very carefully. For larger structures, including the 400 non-H-atom crambin structure, the two methods generally perform with similar efficiency. However, only parameter shift has successfully produced recognizable solutions for the difficult 317 non-H-atom structure gramicidin A.

Algorithms↗
PubMed1997

Suitability of bone marrow from HIV-1-infected donors for retrovirus-mediated gene transfer.

Bone marrow samples from 21 human immunodeficiency virus type 1 (HIV-1)-infected subjects were evaluated for their suitability for retrovirus-mediated gene transduction with anti-HIV-1 genes. The percentages of CD34+ cells that could be isolated from the mononuclear fraction of bone marrow samples were determined. Fifteen of the 21 marrow samples had normal percentages of CD34+ cells isolated by immunomagnetic methods. All seven donors with CD4 counts > 100/mm3 had normal percentages of CD34+ cells; of 14 patients with low CD4 cell counts (< 100/mm3), 5 had reduced and 9 had normal percentages of CD34+ cells. Samples of the marrow were plated in a methylcellulose colony-forming unit (CFU) assay to determine the clonogenic capacity of the progenitor cells. Overall, the marrow samples from HIV-infected donors showed a 44% reduction in CFU derived from the mononuclear cell fraction and a 75% reduction in CFU derived from the isolated CD34+ cell fraction, when compared to marrow samples from uninfected donors. Isolated CD3+ cells were transduced with retroviral vectors containing various anti-HIV-1 genes to determine their susceptibility to gene transfer. Transduction of the clonogenic CD34+ cells by retroviral vectors did not differ among marrow samples from 13 HIV-1+ donors and 9 uninfected donors. Long-term bone marrow cultures established from the transduced CD34+ cells demonstrated equivalent survival of clonogenic progenitor cells from both HIV-1-infected and uninfected marrows. Toxicity from expression of the anti-HIV-1 genes was not observed; the percentages of clonogenic progenitor cells that survived in cultures transduced by vectors carrying anti-HIV-1 genes were similar to those transduced by the control LN vectors. Stromal cells cultured from marrow samples from HIV-1-infected donors showed similar growth kinetics, hematopoietic support function, and enhancement of retrovirus-mediated transduction of CD34+ cells as seen with stromal cells cultured from uninfected marrow donors. Semi-quantitative polymerase chain reaction (PCR) was performed before and after ex vivo transduction to determine the frequency of HIV-1-containing cells in the CD34+ cell preparations. Although HIV-1+ cells were present at low levels in the mononuclear cell fractions of some of the marrow samples, the CD34+ cell preparation from only one marrow sample contained detectable HIV-1 positive cells (< 1 positive cell/100,000 by PCR) prior to transduction. None of the CD34+ cell preparations contained detectable HIV-1 after transduction. These studies demonstrate that HIV-1-infected patients are candidates for retrovirus-mediated transduction of anti-HIV-1 genes in bone marrow gene therapy clinical trials.

Adolescent↗
PubMed1997

Adsorption Kinetics of Alkylphosphine Oxides at Water/Hexane Interface

A pendant drop technique has been used to study the adsorption of a nonionic surfactant, an alkyldimethylphosphine oxide (C13DMPO), at the water/hexane interface. The measured interfacial tensions exhibit a steep initial decrease, pass through a minimum, and then level off at a value which depends on the initial surfactant concentration in the drop. This time dependence of the interfacial tension can be interpreted by an adsorption with a subsequent transfer of the surfactant into the second bulk phase, hexane. Measurements of the distribution coefficient show that the solubility of C13DMPO is much higher in hexane than in water. A qualitative model is proposed which describes the observed dynamic interfacial tensions.

Journal Article↗
PubMed1997

Adsorption Kinetics of Alkylphosphine Oxides at Water/Hexane Interface

A theoretical model is presented to describe the adsorption of surfactant molecules at the water/oil interface for the case when transport across the interface must be considered due to the solubility of the surfactant in both liquid phases (aqueous solution drop in an oil phase). The theory is based on a diffusion-controlled adsorption model and a numerical difference scheme is used to solve the problem for closed finite systems. By simulating adsorption-desorption processes, the influence of the geometrical and thermodynamic parameters on the dynamic adsorption behavior is studied. In particular, the effects of the volume ratio, surfactant concentration, diffusion coefficients, and distribution coefficient on the process are analyzed. The model allows quantitative interpretation of the experimental data obtained for an alkyldimethylphosphine oxide at the water/hexane interface. The interfacial tension signals, presenting a minimum under some conditions, are fitted by the theoretical curves.

Journal Article↗
PubMed1997

Dynamic Adsorption Behavior of Polyethylene Glycol Octylphenyl Ethers at the Water/Oil Interface Studied by a Dynamic Drop Volume Technique

The dynamic drop volume technique has been used to measure the dynamic interfacial tensions of nonionic surfactants (Triton X-45, X-100, X-165, and X-405) at the water/nonane and water/butylbenzene interface. The measurements were performed under the conditions of equilibrium distribution of the surfactant between the two liquid phases established after a sufficiently high number of aqueous solution drops have been formed within a small volume of the oil phase under study. The diffusion kinetics model for the description of the adsorption at the surface of growing drops involves equilibrium surfactant distribution and adsorption from both adjacent phases. Two orientational states of adsorbed surfactant molecule at the interface were assumed in agreement with recently published results at the water/air interface. Good agreement between this theory and the experimental data was obtained.

Journal Article↗
PubMed1997

Accumulation of beta-amyloid precursor protein in HIV encephalitis: relationship with neuropsychological abnormalities.

The pathogenesis of neuropsychological abnormalities in patients with human immunodeficiency virus type 1 (HIV-1) encephalitis is obscure because neurons are not the target of infection and severe neuronal loss occurs only late during the disease. Moreover, there is evidence indicating that HIV dementia is not a homogeneous entity and could partially reverse after treatment with zidovudine. The finding that impaired axonal flow, evidenced by beta-amyloid precursor protein immunoreactivity, could contribute to the neuropsychological deficits prompted the present study. Brains of patients with full-blown acquired immunodeficiency syndrome (AIDS) were studied and findings compared with those of normal and abnormal control subjects. The presence of HIV-1 DNA was investigated by nested polymerase chain reaction; axonal abnormalities were detected by beta-amyloid precursor protein, ubiquitin immunohistochemistry, and silver staining. Accumulation of beta-amyloid precursor protein was observed in all the HIV encephalitis brains studied; the appearance of the immunostaining varied from globular structures to bundles of parallel formations. In 2 AIDS brains without pathological abnormalities, only the latter pattern was detected. The brains with trauma were strongly reactive with beta-amyloid precursor protein antibody and the different reactivity within them correlated with posttrauma survival, only globular structures being detected in the older cases. No correlation was found between the different pattern of beta-amyloid precursor protein reactivity and dementia in AIDS patients. These results show that widespread axonal injury is a constant feature in AIDS brains and suggest that it could play a role in the pathogenesis of the neuropsychological abnormalities of these patients.

AIDS Dementia Complex↗