The infectivity and host range of ground squirrel hepatitis virus (GSHV) have been further examined by animal inoculation experiments. Although carrier squirrel sera usually harbor 10(9) to 10(10) virions per ml as determined by physical measurements, titration of one such serum revealed that squirrel infectivity was lost following dilution of the sample over 10(6)-fold. Infectivity is markedly reduced by NP40 pretreatment of infected serum. GSHV infection cannot be readily transmitted to several related ground squirrel species, but chipmunks can be experimentally infected by GSHV virions or by cloned GSHV DNA, and the resulting infection closely resembles that seen in the normal host.

Animals↗

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Examples of marginal resolution of NMR relaxation peaks using UPEN and diagnostics.

The multiexponential inversion program UPEN by the authors [J. Magn. Reson. 1998; 132: 65-77; Ibid. 2000;147:273-85] employs negative feedback to a regularization penalty to implement variable smoothing when both sharp and broad features appear on a single distribution of relaxation times. This allows a good fit to relaxation data that correspond to a sum of decaying exponentials plus random noise, but it usually does not give a good fit to data that are distorted by systematic errors from instrument problems, which can cause erroneous "resolution" or erroneous non-resolution of peaks. UPEN provides a series of diagnostic parameters to help identify such data problems that can lead to interpretation errors, and, in particular, to warn when a close call on the resolution or non-resolution of nearby peaks might be questionable. Examples are given from a series of T(2) data sets from desiccated bone samples, with examples where the presence of two peaks is required by good data, examples where the presence of two peaks is negated by good data, and examples where the resolution or non-resolution of peaks cannot be trusted because of instrumental distortions revealed by UPEN diagnostic parameters. It is suggested that processing relaxation data with UPEN in nearly real time could permit retaking data while a sample is still available if the diagnostic parameters show instrumental problems.

Bone and Bones↗

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Effects of hydrophobic treatments of stone on pore water studied by continuous distribution analysis of NMR relaxation times.

The effects of protective hydrophobic products applied to porous media such as stone or mortar vary greatly with the product, the porous medium, and the mode of application. Nuclear Magnetic Resonance (NMR) measurements on fluids in the pore spaces of both treated and untreated samples can give information on the contact of the fluid with the internal surfaces, which is affected by all the above factors. Continuous distributions of relaxation times T(1) and T(2) of water in the pores of both synthetic and natural porous media were obtained before and after hydrophobic treatment. The synthetic porous media are ceramic filter materials characterized by narrow distributions of pore dimensions and show that the treatment does not produce large changes in the relaxation times of the water. For three travertine samples most of a long relaxation time component, presumably from the largest pores, remains after treatment, while the amplitude of an intermediate component is greatly reduced. For three pudding-stone samples, treatment leads to a substantial loss from the long component and an even greater loss from the intermediate component.

Calcium Carbonate↗

PubMedDate not supplied

A method for approximating fractional power average relaxation times without inversion of multiexponential relaxation data.

A method is presented for approximating fractional power averages of relaxation times for data equispaced in log time, without the need to invert multiexponential relaxation data. This form of average permits giving emphasis to short or long times depending on the choice of the p value, thus giving the possibility of representing different specific properties of porous media. This method has been tested on a large number of nuclear magnetic resonance (NMR) relaxation measurements in porous samples. This new algorithm appears to be robust with respect to both measurement and computation, and its major advantage is that it does not depend on a particular inversion method. Moreover, it permits a very fast computation.

Algorithms↗

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Estimates of permeability and irreducible water saturation by means of a new robust computation of fractional power average relaxation times.

In a suite of water-saturated sandstones, we have recently demonstrated that irreducible water saturation can be well estimated using relaxation time only, in the form of any of several "averages" giving more emphasis to short times than does the geometric mean time. The best estimate of permeability came from fits giving more emphasis to slightly longer times. In this paper we present estimates of irreducible water saturation and permeability using approximations (here called Robusta approximation) to the fractional power average relaxation time (Tp)1/p. The advantage of this approximation is that it does not involve previous computation of exponential components; therefore, it does not depend on the choice of the inversion method, and it permits a very fast computation. The Robusta approximation gives some of the best correlations using p = -0.55 for irreducible water saturation and p = +0.18 for permeability.

Fractals↗

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Examples of uniform-penalty inversion of multiexponential relaxation data.

When multiexponential relaxation data are inverted to give quasi-continuous distributions of relaxation times, the computed distribution is usually smoothed by means of an applied penalty function equal to a coefficient, C, times the integrated square of amplitude, slope, or curvature. When the distribution has a sharp peak and either a broad peak or long tail, smoothing with a fixed coefficient, C, widens the sharp peak and/or breaks up the broad peak or tail into two or more separate peaks. An iterative feedback procedure is used to generate a separate C value for each computed point in such a way as to give roughly equal contributions to the penalty function from each computed point. This permits adequate smoothing of broad features without oversmoothing sharp peaks. Examples are given for artificial data, for nuclear magnetic resonance in fluids in porous media, and for nuclear magnetic resonance in biological tissues.

Computer Simulation↗

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Development of an in vivo tumor-mimic model for learning radiofrequency ablation.

Radiofrequency ablation requires accurate probe placement using ultrasound guidance. The purpose of this study was to develop an in vivo tumor-mimic model for learning open and laparoscopic radiofrequency ablation. Tumor-mimics were created in ex vivo porcine livers by injecting a mixture of 3% agarose, 3% cellulose, 7% glycerol, and 0.05% methylene blue, which formed 1 cm hyperechoic, discrete lesions on ultrasound. Open and laparoscopic (using a box-trainer) ablation techniques were practiced. In vivo experiments were then conducted in 10 pigs. Three tumor-mimics were created in each animal using a laparoscopic approach. Lesions were characterized sonographically, ablated using an open (n = 5) or laparoscopic (n = 5) approach, and examined pathologically. An ablation in normal liver tissue was performed as a control. Tissue impedance was recorded. Target creation took 81 minutes per animal and 96% of injections were successful. Tissue impedance (48.8 +/- 5.8 vs. 49.6 +/- 5.4) and ablation size (25.1 +/- 3.4 vs. 24.3 +/- 5.1) were not significantly different for controls (n = 8) and tumor-mimics (n = 26), respectively. One animal died of a pulmonary embolism following injection of agarose into a hepatic vein. The agarose-based tissue-mimic creates realistic sonographic targets for learning ultrasound-guided open and laparoscopic radiofrequency ablation in an in vivo model.

Animals↗

PubMedDate not supplied

Maturation of binocular luminance interaction in normal young and adult rhesus monkeys.

PURPOSE: Our aim was to answer three questions 1) Do adult rhesus monkeys have binocular luminance interactions (BLIs) similar to those found in adult humans? 2) Is BLI in very young rhesus monkeys functionally mature? 3) If not, how does it change with age? METHODS: We recorded visually evoked potentials (VEPs) in response to sinusoidally modulated uniform fields. The fields were presented dichoptically by varying the relative temporal phase between the two eyes. Monkeys varied in age from 5.6 weeks to 5.25 years. RESULTS: VEPs were Fourier analyzed and the relative second harmonic amplitudes were taken as the response measure. The second harmonic amplitudes in adult monkeys had an asymmetrical 'V-shaped' function as interocular phase difference (IPD) varied from 0 degrees to 180 degrees, as had been observed previously in adult humans [1]. The youngest monkeys exhibited a symmetrical pattern which became more asymmetrical at older ages and was adult like by about 19 weeks. Asymmetry magnitude and log age correlated 0.97 (p < 0.05) in the monkeys younger than 19 weeks. CONCLUSIONS: The adult rhesus data are consistent with a model derived from humans which involves two types binocular luminance processing. One combines monocular responses nonlinearly (MNL) and a second combines monocular responses linearly followed by a binocular nonlinearity (MLBNL). These two processes have been associated with the parvocellular (P-) and magnocellular (M-) streams. Within this framework, the data from the youngest monkeys indicate that BLI in the P-stream is relatively less mature at birth than that in the M-stream and develops reaching functional maturity on these measures by around 19 weeks.

Adult↗

PubMedDate not supplied

Neurodynamics of relapse prevention: a neuronutrient approach to outpatient DUI offenders.

The central nervous system rewarding properties of ethanol, cocaine, and heroin may activate a common catecholaminergic reward system in the mesolimbic circuitry of the brain. Driving-under-the-influence (DUI) offenders with either alcohol- or cocaine-related problems were studied. The neuronutrients SAAVE and Tropamine significantly reduced relapse rates and enhanced recovery in these DUI outpatient offenders over a 10-week period. Follow-up on both the SAAVE and Tropamine groups after 10 months revealed a 73% and a 53% overall recovery rate, respectively. These clinical results favor the use of these neuronutrients as adjuncts to psychological therapeutic modalities.

Adult↗

PubMedDate not supplied

Purification of monospecific polyclonal antibodies from hyperimmune bovine whey using immunoaffinity chromatography.

Whey, a by-product of cheese production, is a potential source of proteins. Immunization of dairy cows in mid-lactation with mouse IgG and dinitrophenyl-keyhole limpet hemocyanin resulted in the formation of antibodies to these antigens in both blood serum and milk. The antibodies remained in whey during cheese making, and were isolated by immunoaffinity chromatography on matrices with immobilized antigens. The isolated monospecific antibodies were pure and retained their reactivity to antigens.

Animals↗

PubMedDate not supplied

Ion transport processes of crustacean epithelial cells.

Epithelial cells of the gut, antennal glands, integument, and gills of crustaceans regulate the movements of ions into and across these structures and thereby influence the concentrations of ions in the hemolymph. Specific transport proteins serving cations and anions are found on apical and basolateral cell membranes of epithelia in these tissues. In recent years, a considerable research effort has been directed at elucidating their physiological and molecular properties and relating these characteristics to the overall biology of the organisms. Efforts to describe ion transport in crustaceans have focused on the membrane transfer properties of Na+/H+ exchange, calcium uptake as it relates to the molt cycle, heavy metal sequestration and detoxification, and anion movements into and across epithelial cells. In addition to defining the properties and mechanisms of cation movements across specific cell borders, work over the past 5 yr has also centered on defining the molecular nature of certain transport proteins such as the Na+/H+ exchanger in gill and gut tissues. Monovalent anion transport proteins of the gills and gut have received attention as they relate to osmotic and ionic balance in euryhaline species. Divalent anion secretion events of the gut have been defined relative to potential roles they may have in hyporegulation of the blood and in hepatopancreatic detoxification events involving complexation with cationic metals.

Amino Acid Sequence↗

PubMedDate not supplied

Health after bereavement. A controlled study of young Boston widows and widowers.

Explore the source record for details and available documents.

Adult↗