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PubMed1993

Myocardial injury: the acute phase response and lipoprotein metabolism.

Myocardial infarction and other types of tissue injury generate changes in plasma proteins known as the acute phase response. Variations in lipid and lipoprotein levels after acute myocardial infarction are manifest within 24 to 48 h after the onset of chest pain. Maximal postinfarction reductions in total cholesterol occur at days 4 to 5 with levels 47% below baseline; low and high density lipoprotein cholesterol fractions decrease to their nadir on day 7 to concentrations that are 48% and 32% below baseline, respectively. Triglyceride levels increase after acute myocardial infarction to a maximal level that is 58% above baseline on day 7. These alterations in lipid and lipoprotein levels generally stabilize by 2 months after the acute event. Screening for dyslipidemias in survivors of myocardial infarction requires clinical decision-making based on accurate and reliable measurements. The clinician must be familiar with characteristic changes in acute phase lipids and lipoproteins to ensure that patients receive appropriate, potentially life-saving therapy.

Acute-Phase Proteins↗
PubMed1996

Electrically Induced Shear Waves in Colloidal Crystals

The static light scattering method is used for the detection of acoustic waves induced in colloidal crystals and liquids by low-frequency electric pulses. The method is sensitive to both density and shear modes and can be applied for the study of the liquid-crystalline phase transitions. At low fields the variations of light scattering intensity follow both the amplitude and the phase variations of the wave motion and enable the determination of resonance parameters, hence of viscoelastic parameters of the colloidal system.

Journal Article↗
PubMed1987

Twenty-four hour monitoring of deep body temperature with a novel flexible probe.

A portable thermomemory unit with a light, thin and flexible probe has been developed for the measurement of whole-day variations in deep body temperature. The probe consists of a thermistor, a heat-flow sensor and a heater. The probe detects heat flow from the skin; the heater then compensates for the heat lost and consequently the skin is effectively insulated from the ambient microenvironment. Skin temperature beneath the probe is therefore determined by the deep body temperature. The probe is 46 mm in diameter and 3 mm thick, its weight is 5 g. The probe is light and flexible and makes close contact with the skin. A 2 kbyte RAM in the unit enables up to 34 h of data to be collected with a sampling rate of once per minute. The device was applied to the chest and abdominal walls, and to the calf; the chest and abdominal deep body temperatures showed a significant dual phase diurnal variation, usually being low during sleep. In contrast, the calf showed a dynamic deep body temperature variation which depended on the amount of leg exercise. The device was found to be effective for analysing daily variations; measurements on the limbs suggested that it could be used for monitoring peripheral circulatory disorders.

Biomedical Engineering↗
PubMed1994

[Transvaginal pulsed color Doppler ultrasound in the study of the menstrual cycle].

Pulsed colour-Doppler imaging in the latest development in transvaginal sonography. Our objective is to study the uterine and ovarian perfusion during the menstrual cycle in normal fertile conditions. We studied 11 healthy volunteer women free of hormonal treatment. All studies were performed by the same operator, with the same sonograph. Measurements are made in the uterine arteries and their branches (arcuate, radial, spiral arteries) and in the ovarian vessels. The resistance index of Pourcelot (RI = [sequence: see text]) is used as reference. The statistic test is the non-parametric test of Kruskall-Wallis. The uterine and ovarian vascularization varied greatly during the menstrual cycle. Blood flow increased significantly in the luteal phase in the uterine arteries and their branches even in the active ovarian arteries. So, in the uterine artery, the RI was 0.43 in the follicular phase, 0.50 during the ovulatory peak, and 0.41 in the luteal phase. These variations were significant (p = 0.04). These results were the same all along the uterine artery. In the acurate arteries, the RI was respectively 0.75, 0.93, 0.72 at the same time of the menstrual cycle (p = 0.04). In an anovulatory cycle, blood flow remained unchanged and the arterial compliance remained stable. Quick and reproductible blood flow measurements are possible with transvaginal colour-Doppler. Millimetric vessels such as arcuate, radial and spiral arteries can be studied. This non-invasive technology can be used as a part of routine work in the management of infertility.

Adult↗
PubMed2006

Evaluation of PCDD/F partitioning between vapor and solid phases in MWI flue gases with temperature variation.

Partitioning of PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofuran) between vapor and solid phases in flue gas is affected by several factors including temperature variation. In this study, PCDD/F removal efficiencies achieved with activated carbon injection (ACI) and partitioning of vapor/solid phase PCDD/Fs in flue gases with temperature variation in a municipal waste incinerator (MWI) are evaluated via intensive flue gas sampling. Results indicate that most PCDD/Fs in flue gas downstream of the ACI+bag filter (BF) exist in vapor phase (over 90%) while the removal efficiencies of vapor and solid phase PCDD/Fs are 98.5-99.6% and 99.8-99.9%, respectively. The results of flue gas samplings also indicate that there is optimal operating temperature for PCDD/F removal achieved with ACI. Additionally, a pilot-scale adsorption system (PAS) is constructed in this study to evaluate the PCDD/F partitioning affected by temperature. The results of the PAS experimentation indicate that about 55% and 25% vapor phase PCDD/Fs passing through the filter cake (adsorbent) are transferred to solid phase at 150 and 200 degrees C, respectively. As the temperature is increased to 250 degrees C, filter cake (adsorbent) cannot effectively adsorb vapor phase PCDD/Fs and significant PCDD/Fs are formed via de novo synthesis.

Adsorption↗
PubMed1982

Pharmacokinetics of nalidixic acid in old and young volunteers.

Plasma levels of active naphthyridine were measured in healthy old (mean age 77.3 years) and young (mean age 25.4 years) subjects following oral administration of 1 Gm nalidixic acid. The plasma levels of active naphthyridine, i.e., nalidixic acid and its metabolite 7-hydroxynalidixic acid, were generally higher in the old group, particularly in the elimination phase. Significant variations in the pharmacokinetic parameters were obtained between the two groups of volunteers. The plasma half-life of active naphthyridine averaged 11.5 hours in old subjects and 2.7 hours in the younger group. Diminished renal function in the geriatric group may explain the slower elimination of the drug in the old subjects. The mean values of the other parameters calculated were: apparent volume of distribution, 0.55 (old) and 0.47 (young) liter/kg body weight; area under the curve, 327.7 (old) and 156.3 (young) micrograms/ml x hr; total body clearance 2.9 (old) and 8.3 (young) liters/hr; absorption rate constant, 0.29 (old) and 0.52 (young) hr. -1

Adult↗
PubMed2003

MRI detection of weak magnetic fields due to an extended current dipole in a conducting sphere: a model for direct detection of neuronal currents in the brain.

To investigate the feasibility of direct MR detection of neuronal activity in the brain, neuronal current flow was modeled as an extended current dipole located in a conducting sphere. The spatially varying magnetic field induced within the sphere by such a dipole was calculated, including its form close to and within the current source. The predicted field variation was experimentally verified by measurements of the variation in phase of the MR signal in a sphere containing a model dipole. The effects of the calculated magnetic field distributions on the phase and magnitude of the signal in MR images were explored. The minimum detectable dipole strength under normal experimental conditions was calculated to be about 4.5 nAm, which is similar in magnitude to dipole strengths from evoked neuronal activity, and is an order of magnitude smaller than dipole strengths expected from spontaneous activity. This minimum detectable dipole strength increases with increasing spatial extent of the primary current distribution. In the experimental work, the effects of a field of [1.1 +/- 0.5] x 10(-10) T strength were detected, corresponding to the maximum net field caused by a dipole of 6.3 nAm strength with a spatial extent of 3 x 3 x 2 mm(3).

Action Potentials↗
PubMed2006

B1-insensitive T2 preparation for improved coronary magnetic resonance angiography at 3 T.

At 3 T, the effective wavelength of the RF field is comparable to the dimension of the human body, resulting in B1 standing wave effects and extra variations in phase. This effect is accompanied by an increase in B0 field inhomogeneity compared to 1.5 T. This combination results in nonuniform magnetization preparation by the composite MLEV weighted T2 preparation (T2 Prep) sequence used for coronary magnetic resonance angiography (MRA). A new adiabatic refocusing T2 Prep sequence is presented in which the magnetization is tipped into the transverse plane with a hard RF pulse and refocused using a pair of adiabatic fast-passage RF pulses. The isochromats are subsequently returned to the longitudinal axis using a hard RF pulse. Numerical simulations predict an excellent suppression of artifacts originating from B1 inhomogeneity while achieving good contrast enhancement between coronary arteries and surrounding tissue. This was confirmed by an in vivo study, in which coronary MR angiograms were obtained without a T2 Prep, with an MLEV weighted T2 Prep and the proposed adiabatic T2 Prep. Improved quantitative and qualitative coronary MRA image measurement was achieved using the adiabatic T2 Prep at 3 T.

Adult↗
PubMed1984

Correlation between tumorigenicity and banding pattern of chromosome 15 in murine T-cell leukemia cells and hybrids of normal and malignant cells.

The most common chromosomal aberration in murine T-cell lymphomas is trisomy of chromosome 15. It has now been shown that the chromosomal region 15E exhibits a variant early replication banding pattern after 5-bromo-deoxyuridine labeling during part of the preceding S-phase. This variation is restricted to T-cell tumors. Plasmacytomas bearing the specific translocation t(12;15) show a normal early replication banding pattern of chromosome 15. In T-cell tumors all three chromosomes 15 of one cell are of the same variant banding type. In hybrids between tumor and nontumor cells, the number of cells expressing the variant early replication banding pattern is related to the degree of malignancy. Chromosomes 15 in one cell never expressed the variant and the normal banding pattern simultaneously. All five to six chromosomes 15 from one hybrid cell are of the same banding type irrespective of their parental origin. With respect to the type of early replication banding pattern, there is complete reversibility; tumor-parent-derived chromosomes 15 change to normal, and normal-parent-derived chromosomes 15 change to tumor.

Animals↗
PubMed1995

Mathematical analysis of a proposed mechanism for oscillatory insulin secretion in perifused HIT-15 cells.

Oscillatory secretion of insulin has been observed in many different experimental preparations ranging from pancreatic islets to the whole pancreas. Here we examine the mathematical features underlying a possible model for oscillatory secretion from the perifused, insulin-secreting cell line, HIT-15. The model includes the kinetics of uptake of glucose by GLUT transporters, the rate of glucose metabolism within the cell, and the effect of glucose on the rate of insulin secretion. Putative feedback by insulin on the rate of glucose transport into the cells is treated phenomenologically and leads to insulin oscillations similar to those observed experimentally in HIT cells. The resulting set of ordinary differential equations is simplified by time-scale analysis to a two-variable set of ordinary differential equations. Because of this simplification we can explore, in great detail, the characteristics of the oscillations and their sensitivity to parameter variation using phase plane analysis.

Animals↗
PubMed1982

The metabolism and toxicity of paracetamol in Sprague-Dawley and Wistar rats.

Urinary paracetamol metabolites from Sprague-Dawley and Wistar rats were analysed by reversed-phase HPLC. Variations in the metabolic profile were observed as a function of dose, age, sex, species and route of administration. In addition the effect of 3-methylcholanthrene as an inducer of cytochrome P450 mixed function oxidase on paracetamol metabolism was also studied. Increased oxidative metabolism which lead to the formation of 3-thiomethylparacetamol conjugates along with paracetamol mercapturic acid could be correlated with increased susceptibility to hepatic damage. Furthermore it appears that the length of time taken for excretion and the level of free drug excreted may be involved in the aetiology of chronic renal damage.

Acetaminophen↗
PubMed2001

Treatment regimen and hypnotic self-administration.

RATIONALE AND OBJECTIVES: Previous studies have shown that insomniacs self-administer hypnotics at high nightly rates. This study determined whether prior experience with different treatment regimens (i.e., instructions and capsule availability) would alter the previously observed high hypnotic self-administration rates. METHODS: Sixty-four healthy men and women with (n = 32) and without (n = 32) insomnia, 21-55 years, self administered placebo or triazolam (0.25 mg) after different prior treatment regimens. They received one of three different treatment regimens enforced for 11 nights: a capsule each night, a capsule as needed, or a capsule every third night. On 14 subsequent nights they choose to self-administer a capsule or not, placebo during 1 week and triazolam (0.25 mg) the other (counterbalanced in order). RESULTS: Insomniacs self-administered more capsules than normals and triazolam was self-administered more than placebo. For both groups, treatment regimen had a minimal effect on capsule self-administration. During the treatment phase, triazolam improved self-ratings of sleep relative to placebo. During the choice phase, nightly variations in self-rated sleep predicted self-administration of a capsule on the following night, regardless of whether the capsule was active drug or placebo. CONCLUSIONS: The data of this study are consistent with the view that hypnotic self-administration by insomniacs is therapy-seeking behavior and not drug abuse.

Adult↗
PubMed1995

The impact of jejunal transplant peristalsis on enteric flora.

The importance of phase III of the migrating myoelectric complex (MMC) for homeostasis of enteric flora is well documented. The goal of this study was to evaluate in an isogeneic rat model the effect of MMC changes on the self-purging capacity of the jejunal graft. The proximal 25% of the entire jejunoileum of Lewis rats was transplanted orthotopically. Electrodes were then fixed to the graft. Native bowel of five rats and five rats with analogue jejunal segmentation served as controls. Myoelectric recordings were carried out until day 21, when animals were killed for bacteriologic analysis of the segments analyzed myoelectrically and the of neighboring gut. MMCs were observed in all animals during all recordings. Phase III was irregular in transplants because of long-lasting periods of phase III absence alternating with phase III occurring more frequently. The variation coefficient of phase III periodicity calculated for grafts was 48.74, for native bowel 14.79, and for segmented jejunum 22.9. Enteric flora found in all specimens consisted of colonic-like microorganisms. Titers of microorganisms in grafts did not differ from control segments. These findings show that phase III periodicity is severely altered in jejunal grafts. Homeostasis of enteric flora, however, is not influenced by the transplant procedure.

Animals↗
PubMed1992

Kinetic studies of cellular metabolic activity, specific IgG production rate, IgG mRNA stability and accumulation during hybridoma batch culture.

During I.13.17. hybridoma batch cultivation, the levels of cytoplasmic mRNAs specifying immunoglobulin heavy (H) and light (L) chains peaked during the exponential phase and decreased significantly during the decline phase. This variation was found to parallel the rate of DNA synthesis and the total cytoplasmic RNA content. Moreover, we have investigated the possibility that the stability of H- and L-chain mRNAs could account for the observed difference in their levels throughout the batch culture. Using a transcription inhibitor (actinomycin D), we found that the differential accumulation of both mRNAs reflected transcript stability. However, at any growth stage of the culture, the specific monoclonal antibody production rate (pg IgG cell-1 h-1) was not reflected by the levels of H- or L-chain mRNAs, but could be partially correlated to the specific metabolic activity of the cells.

Carbohydrate Metabolism↗
PubMed1996

Pulsed laser treatment of plasma-sprayed hydroxyapatite coatings.

Plasma-sprayed hydroxyapatite (HA) coatings have complex microstructures. There are often variations in phase, structure and chemical composition among the starting material and coating. Some of these changes may not be acceptable for biomedical applications. Attaining all the requirements for a functional coating in a single spraying process is not easily achieved. Additional post-treatment may be necessary. This study examines the use of a pulsed laser to enhance the coating characteristics of plasma-sprayed HA coatings. Preliminary results show the laser-treated coatings having a modified microstructure with crack networks and pores in the size range 5-30 microns. The pores and cracks were quantified by an image analyser. The crack network is less significant in coatings that are treated at lower energy intensity and this could be interesting in that the laser can be used to alter the surface phase composition as well as the morphology. However, repetitive passes with the pulsed laser did not help to seal the cracks that formed.

Biocompatible Materials↗