Factors associated with ruminal pH at herd level.

The objective of this study was to evaluate factors associated with ruminal pH at herd level. Four hundred and thirty-two cows of a Thuringian dairy herd were sampled before claw trimming using a rumen fluid scoop. Volume and pH of the rumen sample were measured, and lactation number, percentage of concentrates in the ration, days in milk (DIM), time of day, and daily milk yield were recorded. Rumen sampling was successful in 99.8% of the cows. The average sample volume was 25 mL. Rumen sample pH decreased with increasing percentage of concentrates in the ration. Ruminal pH decreased from calving to 77 DIM, and grew subsequently to 330 DIM. During the day, rumen pH followed a sinus curve, with maxima in the morning (0915 h) and afternoon (1533 h), and a minimum around noon (1227 h). Ruminal pH decreased with increasing daily milk yield. Lactation number interacted with daily milk yield on rumen pH. The percentage of concentrates in the ration, DIM, time of day, and daily milk yield were significant factors affecting ruminal pH at the herd level.

Kinetics of intracolloidal iodine in thyroid of iodine-deficient or equilibrated newborn rats. Direct imaging using secondary ion mass spectrometry.

The most significant impact of the Chernobyl accident is the increased incidence of thyroid cancers among children. In order to accurately estimate the radiation dose provided by radioiodines, it is important to examine how the distribution of newly incorporated iodine varies with time and if this distribution varies according to the iodine status. The kinetic distribution of intra colloidal newly organified iodine in the rat immature thyroid was recorded and analysed using the ionic nanoprobe NanoSims50. Our observations imply that in case of radioiodine contamination, the energy deposits vary (i) with time, (ii) from one follicle to another, and (iii) from one cell to another inside the same follicle regardless the iodine status. The kinetic heterogeneity of iodine distribution must be take in account in thyroid dose evaluation.

Randomised prospective study compares efficacy of five different stomach tubes for rumen fluid sampling in dairy cows.

The objective of the study was to compare the performance of five types of stomach tubes for rumen fluid sampling. Rumen fluid was sampled in rumen fistulated cows assigned to a 5×5 Latin square study design. The pH values of samples taken by stomach tubes and via fistulas were measured; the results were compared with indwelling sensor measurements. The practicability of the stomach tubes for regular use was tested in the field. Rumen fluid samples were obtained rapidly. Volumes for transfaunation could be obtained. The pH-values of samples taken with the four out of the five tubes (Dirksen, Geishauser, tube 4 and a simple water hose used with a gag) did not show significant differences to samples taken via rumen fistulas. Mean differences ranged between -0.02 and +0.09. Samples taken with tube 4 and the water hose showed also no significant differences to pH-sensor measurements. This study demonstrates that stomach tubes are suitable for rumen fluid sampling. Tube 4 seems to be the best probe for work in the field. It was well tolerated by the animals, saliva contamination is negligible. We, therefore, conclude that the evaluation of rumen acid base status in the field is possible.

An experimental model of acute encephalopathy after total body irradiation in the rat: effect of liposome-entrapped Cu/Zn superoxide dismutase.

PURPOSE: To develop an experimental model of acute encephalopathy following total body irradiation in rats and to define the therapeutic effect of liposome-entrapped Cu/Zn superoxide dismutase. METHODS AND MATERIALS: A total of 120 4-month-old rats received 4.5 Gy total body irradiation (TBI) while 120 rats received sham irradiation. A behavioral study based on a conditioning test of negative reinforcement, the one-way avoidance test, was performed 5 hours before irradiation and repeated the following days. Subcutaneous treatment was started 1 hour after irradiation and repeated daily for 2 weeks. In both the irradiated and sham group, three subgroups were defined according to the treatment received: liposome-entrapped Cu/Zn superoxide dismutase (0.5 mg/kg), liposomes only, normal saline. RESULTS: This work comprised two consecutive studies. In study A (90 rats) the one-way avoidance test was administered daily from day 0 to day 4 with a recall session at day 14. In study B (validation phase in 150 rats) the behavioral test was performed only from day 0 to day 6. Before irradiation, all rats showed a similar behavioral response. Study A (6 groups of 15 rats): Following TBI, irradiated rats treated with liposomes only or saline demonstrated a significant delay in learning the one-way avoidance test in comparison with sham-irradiated rats (0.05 < p <0.001 depending upon the day of evaluation and the subgroup type). In contrast, irradiated rats treated with liposome-entrapped Cu/Zn superoxide dismutase did not differ from sham-irradiated rats. Study B (6 groups of 25 rats): The results were the same as those in study A, demonstrating a significant delay in the learning of the test in the liposome and saline-treated irradiated rats in comparison with sham-irradiated rats (0.02 < p < 0.001). The irradiated rats, treated with liposome-entrapped Cu/Zn superoxide dismutase did not differ from the sham-irradiated controls. CONCLUSION: This study indicates that a relatively low dose of total body irradiation induces a substantial acute learning dysfunction in the rat. This effect is prevented by the administration of liposome-entrapped Cu/Zn superoxide dismutase.

Dosimetry at the cellular level of Kupffer cells after technetium-99m-sulphur colloid injection.

The radiation dose to Kupffer cells was estimated at the cellular level after intravenous injection of 99mTc labeled sulphur colloids in rats. The results were then compared with those obtained using macroscopic dosimetry. From the microscopy appearance observed using a "track" microautoradiographic method (MAR), it was shown that only 0.2% of the Kupffer cells were actually involved in the pinocytosis of radioactive colloids. For each electronic emission from 99mTc (Auger and internal conversion), the fraction of the emitted energy actually absorbed within the Kupffer cell was calculated using the values provided by Berger. About 15% of the total energy emitted by electrons was absorbed in 0.2% of the Kupffer cells. If these results are extrapolated to humans, the dose absorbed by the labeled cells can be estimated to be between 0.5 and 0.9 Gy/MBq. This represents about 15,000 times the average electron dose to the liver as estimated from macrodosimetric methods. In cases such as this one where an important distribution heterogeneity is expected, dosimetric estimations at a cellular level may be particularly useful.

Microautoradiographic study of technetium-99m colloid uptake by the rat liver.

A new microautoradiographic technique was developed to study the distribution of 99mTc-labeled radiopharmaceuticals. Using a thick emulsion, it is possible to get microscopically visible tracks of internal conversion and Auger electrons. The liver uptake of microscopic particles has been thought to occur in Kupffer cells but no direct evidence has been provided for technetium colloids. Using this method, 99mTc-labeled colloids were clearly identified in Kupffer cells in the sinusoidal areas of liver. "Track" microautoradiography using a thick emulsion layer may be used on any frozen tissue sections and may provide an important tool to assess the biodistribution of 99mTc radiopharmaceuticals.

Heterogeneous distribution of technetium-99m-labeled microspheres in rat lungs: microautoradiographic evidence and dosimetric consequences.

UNLABELLED: The heterogeneity of 99mTc-labeled microspheres distribution within rat lung was visualized and quantified using a microautoradiographic "track" method (MAR). METHODS: MAR was used to study the uptake of radioactivity by individual microspheres, thereby enabling calculation of the range of particle activity. MAR was also used to visualize in rat lung sections the intrapulmonary distribution of the microspheres within the lungs after intravenous administration. The mean doses delivered to the cells in close contact with the labeled microspheres were calculated taking only the 99mTc electron emissions into account. RESULTS: All the microspheres were labeled. Nevertheless, the spectrum of visible tracks varied by a factor of 10, inducing a variable activity per microsphere from < 36 Bq to 325 Bq (mean activity-94 Bq/microsphere). No correlation existed between the radioactivity uptake and the size of microspheres. A very heterogeneous tridimensional distribution of the microspheres within the lungs were demonstrated with interparticle distances ranging from 57-4400 microns. On the other hand, only 1 of 2000 rat lung capillaries was obstructed. Using the mean activity, calculated delivered doses were found to reach approximately 6 Gy for the closest endothelial cells and 2 Gy for epithelial cells. However, such high doses were delivered to only a few cells. CONCLUSION: The number of obstructed capillaries in human lungs is lower than in rat lungs; the distances between microspheres should be larger. Nevertheless, the individual doses absorbed by the pulmonary cells closest to the microspheres should be very important.

Immunoreactive beta-endorphin increases after an aspartame chocolate drink in healthy human subjects.

It has been claimed that sucrose intake induces a rise in beta-endorphins. In an attempt to discriminate between the sensorial and metabolic effects of sucrose intake in this process, the effects of two chocolate drinks were compared: one sweetened with 50 g of sucrose, the other with 80 mg of aspartame. Plasma beta-endorphin concentrations were more elevated after the aspartame drink than after sucrose or fasting, while insulin increased after drinking as much with aspartame as with sucrose. We suggest that the increase in beta-endorphin after aspartame edulcorated chocolate is related with insulin secretion in the absence of marked changes in blood glucose or with a direct effect of aspartame itself on beta-endorphin liberation.

Lack of plasmic beta-endorphin response to a gastronomic meal in healthy humans.

In order to study the relationship between the endogenous opiate system and food intake in man, plasma concentrations of beta-endorphin were measured in ten healthy subjects. Time course of beta-endorphinemia was compared under the following conditions: basal (fasting), after an injection of pentagastrin (6 micrograms/kg), or after a gastronomic meal. No changes in plasma beta-endorphin or ACTH concentrations were observed with pentagastrin nor after the meal, despite the combination of very high sensory pleasure with intake of a very large amount of food. It is concluded that blood beta-endorphin concentration is not a sensitive index of the effects of food intake on the endogenous opioid system in man.

Pharmacokinetics and tissue distribution of 99mTc-labelled enoxaparin in the rat: evaluation of dosimetry parameters.

A low molecular weight heparin, enoxaparin, was labelled with 99mTc and the characteristics of the labelled compound determined. In vitro the stability, and labelling efficiency (98%) of the labelled drug were excellent. Rats were injected with 99mTc-enoxaparin to study pharmacokinetics and distribution. The results were used to calculate dosimetric estimates which are a prerequisite for pharmacokinetic studies on labelled LMWH (low molecular weight heparin) in human subjects. Biodistribution studies showed preferential liver and spleen accumulation. But the doses absorbed by these target organs remained below the upper limits of the dose received by a patient undergoing hepatic scintigraphy.