Longitudinal study of a natural outbreak of heart and skeletal muscle inflammation in Atlantic salmon, Salmo salar L.

Heart and skeletal muscle inflammation (HSMI) is a transmissible disease of farmed Atlantic salmon, Salmo salar L. It is characterized by significant epi-, endo- and myocarditis, as well as myositis, particularly involving red skeletal muscle. The aetiology of HSMI is currently unresolved, though a viral cause is suspected. Since its discovery in 1999, HSMI has become an increasing problem for the Norwegian farming industry, with some farms experiencing yearly outbreaks and subsequent economic losses. In the present study an Atlantic salmon farm was studied from December 2003 to April 2005. Samples from apparently healthy as well as clinically diseased fish were collected monthly and examined histopathologically. The first fish to be diagnosed with HSMI was sampled in May, 8 months after transfer to sea. A clinical outbreak of HSMI followed in June, when all fish in the sample had lesions consistent with HSMI. Subsequent samples revealed that cardiac lesions decreased in severity 2 months after the start of the outbreak, but that multiple foci of cellular infiltration and necrosis persisted throughout the year. There appeared to be a shift in lesion location from being most severe in the compact myocardium in early stages of disease to a greater involvement of the atrium and spongy layer of the ventricle in later samples. Late samples also showed increased fibrosis of cardiac tissue. In conclusion, HSMI appears to be a severe disease with elevated mortality, morbidity close to 100% and prolonged duration.

Application of the chirp z-transform to MRI data.

A version of the chirp z-transform (CZT) enabling signal intensity and phase-preserving field-of-view scaling has been programmed. The algorithm is important for all single-point imaging sequences such as SPRITE when used with multiple data acquisition for T2* mapping or signal averaging. CZT has particular utility for SPRITE imaging of nuclei with short relaxation times such as sodium at high field. Here, a complete theory of the properties of CZT is given. This method operates entirely in k-space. It is compared with a conventional interpolation approach that works in image space after the application of a fast Fourier transformation.

A comparison of three SPRITE techniques for the quantitative 3D imaging of the 23Na spin density on a 4T whole-body machine.

Sodium density maps acquired with three SPRITE-based methods have been compared in terms of the resulting quantitative information as well as image quality and acquisition times. Consideration of factors relevant for the clinical implementation of SPRITE shows that the Conical-SPRITE variant is preferred because of a 20-fold reduction in acquisition time, slightly improved image quality, and no loss of quantitative information. The acquisition of a 3D data set (32x32x16; FOV=256x256x160 mm) for the quantitative determination of sodium density is demonstrated. In vivo Conical-SPRITE 23Na images of the brain of a healthy volunteer were acquired in 30 min with a resolution of 7.5x7.5x7.5 mm and a signal-to-noise ratio of 23 in cerebrospinal fluid and 17 in brain tissue.

Centric scan SPRITE magnetic resonance imaging: optimization of SNR, resolution, and relaxation time mapping.

Two strategies for the optimization of centric scan SPRITE (single point ramped imaging with T1 enhancement) magnetic resonance imaging techniques are presented. Point spread functions (PSF) for the centric scan SPRITE methodologies are numerically simulated, and the blurring manifested in a centric scan SPRITE image through PSF convolution is characterized. Optimal choices of imaging parameters and k-space sampling scheme are predicted to obtain maximum signal-to-noise ratio (SNR) while maintaining acceptable image resolution. The point spread function simulation predictions are verified experimentally. The acquisition of multiple FID points following each RF excitation is described and the use of the Chirp z-Transform algorithm for the scaling of field of view (FOV) of the reconstructed images is illustrated. Effective recombination of the rescaled images for SNR improvement and T*2 mapping is demonstrated.

Immunoglobulin genes and antibody responses in the spotted wolffish (Anarhichas minor Olafsen).

The spotted wolffish Anarhichas minor Olafsen is a promising new species in aquaculture in the cold waters of northern Norway. In this paper, some basic immunological studies of this marine species are reported. Of comparative interest are the cDNA sequences of the immunoglobulin transcript and the antibody responses to model antigens. Of more practical importance are the humoral immune responses and antibody specificities to potentially pathogenic bacteria. Full length cDNA clones encoding the immunoglobulin heavy and light chains in the spotted wolffish were sequenced demonstrating variable degrees of similarity to other teleost fish species. Also in the spotted wolffish the CH4 domain was deleted in the transmembrane form of the immunoglobulin heavy chain (IgH) as a receptor on B cells, with the transmembrane exon spliced directly to the CH3 domain. The antibody responses to various antigens like hapten-carrier molecules, protein antigens and bacterial pathogens were relatively high, but with some interesting exceptions. Anti-hapten responses to NIP and FITC were high while anti-DNS responses were low, but more surprisingly, there was hardly any B-cell response to the carrier molecule LPH. On the other hand, protein antigens like CGG and BSA were highly immunogenic in the spotted wolffish as were the bacterial antigens Vibrio anguillarum, V. salmonicida and Aeromonas salmonicida.

NMR stray-field analysis of oil drop size distribtuion in peanut cotyledons.

The technique of stray-field NMR has been applied to the study of an oil-bearing seed. It is found to provide additional information about the smallest size of oil drops within the cotyledon not easily measurable by other methods. A peanut was chosen as a convenient seed to investigate so as to allow comparison with previously published NMR pulsed field gradient data. We find a broad distribution of oil drop sizes ranging from a lower limit of order 0.26 microm up to a maximum of approximately 1.3 microm.

Diffusion-weighted imaging of bacteria colonies in the STRAFI plane.

Imaging colonies of bacteria in water suspension using NMR requires that the water inside the bacteria can be differentiated from the surrounding water. This is commonly carried out by using diffusion-weighted pulsed field gradient techniques. However, it is also possible to use the diffusion sensitivity inherent in stray field imaging (STRAFI). In STRAFI, the subject to be imaged is normally moved along the axis of a superconducting magnet so that it passes through the sensitive slice. However, by moving the sample in the transverse direction and by using a long copper strip in place of a surface induction coil, a diffusion-weighted one-dimensional projection profile can be obtained across the sensitive slice. Profiles from a water phantom and from a bacteria suspension show convincing discrimination between intracellular and extracellular water.

A three-dimensional NMR imaging scheme utilizing doubly resonant gradient coils.

A 3DFT gradient-echo technique has been developed which, in conjunction with series-resonant gradient-coil circuits, can produce three-dimensional NMR images with an echo time of less than 100 microseconds. The method involves a read-gradient waveform composed of two sinusoids of different frequencies. This is an improvement on previous imaging sequences using a single sinusoid where only half of k space was sampled and where the second half was calculated using conjugate symmetry. The inaccuracies involved in the necessary "cut and paste" of k space inevitably lead to artifacts in the final image. The important features of the new method are that with suitable phase encoding all octants of k space are sampled, the RF pulse is applied when the gradients are all zero, and the echo forms when the gradient is essentially constant. This method will allow more extensive application of solid imaging techniques to biological samples in vivo.

Diffusion and molecular mobility in microporous media: applications to rubber and zeolite 4A powders.

Broad-line magnetic resonance imaging using large oscillating field gradients has become a very useful and robust tool in the study of systems with a T2 of order 0.1-1 ms. Its use is illustrated with two examples involving microporous media: the ingress of decane into lightly cross-linked rubber and water transport in compacted zeolite 4A powder beds.

NMR studies of molecular mobility and diffusion in porous systems.

The uptake, partitioning, and release of ingredients such as water, oil, surfactant, and ions are important factors to understand and control in the design and manufacture of detergent and personal products. Although conventional pulse NMR (PNMR) spectroscopy continues to be used to analyse bulk molecular mobility and phase composition, more recently MR imaging techniques have created unique opportunities for gaining spatial information about these processes in ways that are noninvasive and potentially quantitative. This paper describes the evaluation of MRI and associated PNMR techniques to study transport in three relevant cases: ion diffusion (e.g., fluoride) in concentrated dispersions, oil transport through powders, and water ingress into porous powders (zeolite). Results are presented to illustrate the potential of multiple pulse and gradient echo MRI methods for dealing with the short T2 scenarios that represent a common problem in quantitative imaging of water in solid-containing composites involving, for instance, zeolite, or silica. Pore-size characterisation results are also presented.

Ingress of water into zeolite 4A powder plugs.

One dimensional profiles of the concentration of water absorbed from vapour diffusing into compacted type 4A zeolite powder have been obtained by broadline NMR imaging. After an induction period of approximately 6 h, a region of full hydration advances linearly with time into the zeolite plug. This behaviour is typical of Case II diffusion. A simple numerical simulation gives good agreement with the experimental results.

The measurement of drug consumption. Drugs for diabetes in Northern Ireland, Norway and Sweden.

The consumption of insulin and oral antidiabetic drugs was measured at the gross sales level in Sweden and Norway and at the prescription level in Northern Ireland. ""Agreed daily doses'' were used as units of comparison, which defined as follows: insulin 40 I.U., tolbutamide 1 g, acetohexamide 500 mg etc. Consumption was expressed as the number of ""agreed daily doses'' per 1,000 inhabitants per day. This provided a rough estimate of the number of subjects for whom the drug had been prescribed per 1,000 population. The data were collected during the three months April-June 1971. Marked differences in the consumption of antidiabetic drugs were found between the three countries and also between areas within each country. The consumption of insulin was similar in Norway and Northern Ireland (3.5 and 3.9 agreed daily doses per 1,000 inhabitants per day), but almost twice as high in Sweden. In Norway much lower use was found in certain rural areas. The variation in the consumption of oral antidiabetic drugs was even more marked. Surprisingly, consumption was considerably higher in Sweden (15.8) than in the nearby Norway (7.3), and was even lower in Northern Ireland (4.3). The major use was of sulphonylureas, especially chlorpropamide. Within the countries there was marked regional variation in the choice of individual biguanides and sulphonylureas. The data are discussed in relation to such factors as the incidence of diabetes, the sole use of dietary treatment etc. It is concluded that studies in depth, which link the actual use of drugs by patients to diagnosis, diabetic symptoms and clinical outcome of treatment are necessary in order to explore the reasons behind the marked geographical differences and to define a rational drug policy. However, the methods described in the study may be used for early detection of gross national differences in drug utilization, the further investigation of which may reveal to be of great public health interest.