Measurement of oxygen concentration for detection of subclinical mastitis.

INTRODUCTION: Subclinical mastitis is a frequent and economically important disease in cattle. Since the milk appears macroscopically normal the diagnosis depends on indirect parameters. In automatic milking systems ideally the measurements have to be automatized and completed during milking process. Oxygen concentration of the milk is a parameter which has not been used widely to date. Oxygen is consumed by cells in the milk, hence an increased number of cells results in decreased oxygen concentration. The main objectives of the study were to study the association of milk oxygen concentration with the number of cells and the electric conductivity and to assess the feasibility of oxygen concentration for detection of subclinical mastitis. The study was performed on five dairy farms using 690 macroscopically normal quarter milk samples. Oxygen concentrations (OC), somatic cell count (SCC) and electric conductivity (EC) were measured. The associations between the parameters were calculated and the diagnostic value of OC for detection of subclinical mastitis was estimated. Significant correlations were found between OC and SCC (rs =-0.28) and between OC and EC (rs = -0.20). SCC of the samples varied between 1,000 and 21,602,000 cells/ml. Out of the 690 milk samples 404 had SCC 200,000 cells/ml (subclinical mastitis). OC decreased whereas EC increased significantly with increasing SCC (P < 0.001). The threshold for OC to diagnose subclinical mastitis was 5.22% (sensitivity 84%, specificity 46%). The area under the curve describing the diagnostic value of OC was 0.72 (confidence interval 0.68-0.76). In conclusion OC has potential to be used as parameter to detect subclinical mastitis in dairy cattle. Currently the application is not suitable for routine use. Further research is necessary to improve measurement technology and diagnostic value of the parameter.

INTRODUCTION: La mammite subclinique est une maladie fréquente et économiquement importante chez les bovins. Puisque le lait apparaît macroscopiquement normal, le diagnostic dépend des paramètres indirects. Dans les systèmes de traite automatique, les mesures doivent idéalement être automatisées et effectuées pendant le processus de traite. La concentration en oxygène du lait est un paramètre qui n'a pas été largement utilisé à ce jour. L'oxygène est consommé par les cellules dans le lait, un nombre accru de cellules entraînant donc une diminution de la concentration en oxygène. Les principaux objectifs de l'étude étaient d'étudier l'association de la concentration d'oxygène du lait avec le nombre de cellules et la conductivité électrique et d'évaluer la praticabilité de la mesure de la concentration en oxygène pour la détection de la mammite subclinique. L'étude a été réalisée dans cinq fermes laitières à l'aide de 690 échantillons de lait de quartier macroscopiquement normaux. Des concentrations d'oxygène (OC), le nombre de cellules somatiques (SCC) et la conductivité électrique (EC) ont été mesurés. Les associations entre les paramètres ont été calculées et la valeur diagnostique de l'OC pour la détection de la mammite subclinique a été estimée. Des corrélations significatives ont été trouvées entre OC et SCC (rs= -0,28) et entre OC et EC (rs = -0,20). Le SCC des échantillons variait entre 1'000 et 21'602'000 cellules/ml. Sur les 690 échantillons de lait, 404 avaient un SCC de 200 000 cellules/ml (mammite subclinique). L'OC a diminué alors que l'EC a augmenté de façon significative avec l'augmentation du SCC (P - 0,001). Le seuil pour que l'OC permette un diagnostic de mammite subclinique était de 5,22 % (sensibilité 84 %, spécificité 46 %). La zone sous la courbe décrivant la valeur diagnostique de CO était 0.72 (intervalle de confiance 0.68-0.76). En conclusion, l'OC pourrait être utilisée comme paramètre pour détecter la mammite subclinique chez les bovins laitiers. Actuellement, l'application n'est pas adaptée à une utilisation de routine. D'autres recherches sont nécessaires pour améliorer la technologie de mesure et la valeur diagnostique du paramètre.

Selective immobilization and detection of DNA on biopolymer supports for the design of microarrays.

DNA immobilization for the manufacturing of microarrays requires sufficient probe density, low unspecific binding and high interaction efficiency with complementary strands that are detected from solutions. Many of these important parameters are affected by the surface chemistry and the blocking steps conducted during DNA spotting and hybridization. This work describes an alternative method to selectively immobilize probes and to detect DNA on biocompatible, hydrophilic cellulose coated supports with low unspecific binding, high selectivity and appropriate sensitivity. It takes advantage of a relatively selective adsorption of water soluble polysaccharides on a solid cellulose matrix. Single strands of DNA were conjugated to this soluble polysaccharide and subsequently micro-spotted on solid cellulose thin films that were coated on glass and polymer slides. This resulted in adsorptively bound DNA-probes that were used to detect complementary, labelled DNA strands with different lengths and sequences by hybridization. The interaction of the DNA-conjugates with cellulose surfaces and the selectivity of hybridization were investigated by a quartz crystal microbalance with dissipation monitoring (QCM-D) and fluorescence scanning. The method of non-covalent immobilization of DNA probes on an uncharged, non-reactive, hydrophilic support lowers the unspecific binding and the number of handling steps required to conduct the experiments for the detection of DNA on microarrays. Simultaneously selectivity, hybridization efficiency and detection limits are maintained.

Improvement of the hemocompatibility of PET surfaces using different sulphated polysaccharides as coating materials.

In this study, sulphated polysaccharides were investigated in respect to their blood compatibility properties (hemocompatibility). Pure chitosan was treated with sulphating agents such as SO(3)/pyridine complex and chlorosulfonic acid (HClSO(3)) to obtain 3,6-O-sulfochitosan with low and high concentration of sulfur. These synthetically derived materials and the commercially available sulphated polysaccharides heparin and dextran sulfate, both with high concentrations of sulfur, were coated onto PET foils to act as surfaces with strong antithrombotic activity. This treatment should lead to better blood compatibility properties of PET materials for medical applications. To examine this, the optimized free hemoglobin method was applied to determine the antithrombotic activity of these surfaces. Glass as the standard thrombotic surface and a heparin-coated PET surface as a surface well-known for its strong antithrombotic activity were used as internal references. The experiments showed that dextran sulfate and sulphated chitosan with high concentrations of sulfur demonstrated the same antithrombotic activity as heparin over the whole period of measurement time. In addition, a relationship between the sulfur concentration in these sulphated polysaccharides and their blood compatibility properties can be demonstrated in this article.

[Correlation between molecular parameters of hyaluronic acid and viscoelasticity of synovia]. / Zusammenhänge zwischen molekularen Parametern der Hyaluronsäure und der Viskoelastizität der Synovia.

The viscoelastic properties of hyaluronic acid solutions and synovial fluids were investigated by oscillating capillary rheology in a frequency range from 0.03 to 30 Hz. A clear dependency of these parameters, especially of the elastic component, on the molecular weight of the hyaluronic acid molecules was obtained. The addition of hyaluronic acid solutions to pathological synovial fluids improves the viscoelastic parameters depending on the applied dose. However, the rheological behavior of a "healthy synovial fluid" could not be reached by the procedure.

The viscoelasticity of blood and plasma in pig, horse, dog, ox, and sheep.

There is little data on blood viscosity in different animals. Therefore a comparison was performed between five species by an in-vitro method using oscillatory flow. At shear rates from 1 to 150/sec the viscous and the elastic component of the complex blood viscosity was highest in pig, followed by horse, dog, ox, and sheep. Plasma viscosity and plasma density were similar in dog and sheep and were higher in ox. The differences in whole blood viscosity were obviously related to the variable interspecies hematocrit, and may also be influenced by different aggregation tendencies. Aggregation in ox was low despite a high plasma fibrinogen. It seems that erythrocytes in sheep and ox remain separately suspended in a relative dense plasma. This may indicate that formation of microthrombi is less likely to occur in ox and sheep than in pig, horse, and dog.

Viscoelastic and transient network properties of hyaluronic acid as a function of the concentration.

Rheological measurements on a high molecular weight Hyaluronic Acid (from rooster combs) were performed to obtain information on the viscoelastic and temporary network characteristics of Hyaluronic Acid solutions as a function of the concentration. From rheological experiments, the critical concentration c* and the concentration dependency of the plateau modulus G degrees e were determined. Further on, structural parameters as Me, the average molecular weight of the polymer segments between entanglement points, and DN, the average distance between entanglement points, were estimated.

Rheology of synovial fluid.

After a discussion of the role of synovial fluid as a joint lubricant, rheological measurements are described with both normal (healthy) synovial fluids and pathological ones. Shear stress and first normal stress difference are measured as a function of shear gradient to calculate the apparent shear viscosity eta 1 and the apparent normal viscosity psi 7 as well as an apparent shear modulus G'. It is found, that in case of diseased synoviae all rheological parameters deteriorate. Most significant changes are observed with the zero shear viscosity eta 0, the shear modulus G', and a characteristic time theta 1, which is the reciprocal of the critical shear rate Dc which determines the onset of shear thinning. The rheological deterioration of synovial fluids is explained in terms of solute structure, whereby a molecular mass of the backbone hyaluronic acid of at least 10(7) g.mol-1 is required for satisfactory function. A theory of the rheological performance of normal synovial fluid as well as its pathological deterioration is proposed.

[Viscoelastic properties of normal human synovia and their relation to biomechanics]. / Viskoelastische Eigenschaften der intakten Human-Synovia und ihr Bezug zur Biomechanik.

The viscoelastic parameters of synovial fluid (SF) collected from donors with healthy joints were investigated in a shear rate range between D = 10(-3) to 10(+3) s-1. The rheological parameters obtained from these SF yielded a common Master-curve, which can be accepted as characteristic for healthy human FS: it shows high zero shear viscosity (6-60 Pa X s) and pronounced shear thinning with increasing shear rates. The shear module G, calculated from the first normal stress difference, shows a constant range with values between 1 and 5 Pa. The largest average relaxation times are observed in the range of 2 to 5 s, and they decrease linearly with increasing shear rate to values of 0.01 to 0.05 s. The above viscoelastic properties appear to be necessary for the formation of a fluid film to guarantee optimal joint lubrication and to protect the cartilage from mechanical damage.

Rheological discrimination between native, rigid and aggregated red blood cells in oscillatory flow.

The viscoelastic behaviour of hardened or aggregated red blood cells is compared with the flow pattern of native red blood cells, all suspended in buffer solution at a hematocrit of 45%. The rheological properties are investigated under oscillatory shear at the constant frequency of 2Hz. Variation of the amplitude covers a range of shear-rates from 0.5/s to 200/s. It can be seen that rigidification of the red cells by treatment with glutardialdehyde leads to changes of the flow properties in the range of shear-rates above 10/s, whereas aggregate formation due to addition of dextran distinctly alters the flow properties in the range of shear-rates below 10/s.

[Biorheological contribution to the problem of rheumatic joint diseases]. / Biorheologische Beiträge zum Problem der rheumatischen Gelenkserkrankungen.

The rheological properties of synovial fluids from patients with different rheumatic diseases are discussed. Viscosities of 73 samples were determined and are compared to a standard of "healthy" human synovial fluid p. m. and to bovine synovia. Typical differences between "healthy", degenerative and inflammatory synovial fluids could be discerned. These differences can be characterized with several rheological parameters. The mechanism of lubrication in joints and the role of synovial fluid as a lubricant are discussed. Rheological properties of polymere solutions which could serve as a substitute for sick synovial fluids are described and compared to the properties of healthy synovia. Several possibilities for molecular changes which could account for the deterioration of synovial fluids in patients with different rheumatic diseases are discussed.

[Viscosity of synovial fluid and possible artificial lubricants (author's transl)]. / Das rheologisch Verhalten von Synovialflüssigkeiten und möglichen Ersatzlösungen.

The viscosity of "normal" post mortem synovial fluid, and synovial fluid samples of knee joints affected by various joint diseases (inflammatory and non inflammatory) was investigated and compared with flow curves of Hyaluronic acid and Polyacrylamide solutions. The viscoelastic behaviours of synovial fluid seems to be of great importance for the lubrication mechanism of the joints. Differing results of the viscoelastic properties could be determined in different joint diseases. As a result of these changes the lubrication mechanism is impaired and this leads to cartilage wear. Solutions of Polyacrylamide and Hyaluronic acid have been investigated as model-substances, the former showing rheological properties similar to normal synovial fluid. Their application as an artificial lubricant has been investigated.