Cryopreservation evaluated with mitochondrial and Z line ultrastructure in striated muscle

Single, intact, frog skeletal muscle fibres and whole frog hearts were quick-frozen on a polished, liquid-He-cooled copper block and examined in the electron microscope after freeze-substitution and freeze-fracture. In both kinds of striated muscle, collapse of the peripheral and intracristal membrane spaces in mitochondria was found to increase with increasing distance from the point of first impact (PFI) of the muscle cells on the cold copper block. The changes correlated with a previously described gradient of Z line and A band cryodamage occurring with distance from the PFI. The findings in thin sections from freeze-substituted preparations were confirmed by freeze-fracture preparations. It is concluded that, since the mitochondrial membrane changes are concurrent with, and follow the same spatial distribution of, other manifest cryoarte-facts, the cryoartefactual nature of the mitochondrial changes must be excluded before functional significance is attributed to them. The collapse of mitochondrial membrane spaces as a sensitive indicator of quality of cryopreservation may apply to non-muscle cells as well.     

Influence of adhesive and abrasive mechanisms on the tribological behaviour of thermoplastic polymers

Results of investigations on thermoplastic polymers are presented which can be interpreted by prevailing adhesive or abrasive mechanisms as well as by an overlap of different tribological processes.For polymer-polymer sliding pairs it was found that friction is decisively connected with adhesion. When data on the surface energy of the examined polymers were used, the experimentally determined friction values could be related to the adhesion energies of the different polymer-polymer sliding pairs.For polymer-steel sliding pairs the wear behaviour under prevailing abrasive mechanisms was studied. A relationship was established between the combined stresses in the interfacial area and the tensile or rupture strength of the polymers studied.The tribological behaviour of glass-fibre-reinforced polymers such as polyamides and poly(phenylensulphide) is determined by an overlap of different processes which are influenced by the orientation of the glass fibres with respect to the sliding area rather than by the percentage of the glass fibres added. Different investigation methods, e.g. scanning electron microscopy and energy-dispersive analysis of X-rays, revealed that numerous individual processes such as adhesion, material transfers, retransfers, abrasion, deformation and rupture processes as well as surface fatigue overlap in the complex wear behaviour of glass-fibre-reinforced polymers.     

Car driver behavior at flashing light railroad grade crossings

The behavior of car drivers at two Dutch railroad grade crossings with automatic flashing warning lights was analyzed. Car drivers were videotaped while approaching either the red flashing lights or the white flashing "safe"-signal. Approach speeds, positions, and time intervals were semiautomatically measured from videos of more than 900 drivers: 660 while confronted with the red lights and 272 while passing the white light. Of the latter group, head movements during the approach to the crossing were also registered. Red light compliance was relatively good, as no driver was observed to cross later than 6 seconds after the onset of the red lights, despite train-arrival times of well over 60 seconds. The level of red light compliance was further quantified in terms of both the deceleration and time-to-stopping-line as accepted by drivers. From a comparison with earlier research on red light compliance at signalized road intersections it appeared that red light compliance was better at railroad crossings than at road crossings. It is concluded that faulty red light compliance is not a major cause for car-train accidents and that emphasis should be placed on the ability of the present device to attract attention and to signal unambiguously. The high degree of compliance also causes unexpected driver actions, such as emergency braking and hesitations. A yellow phase may reduce these problems. Some drivers tended to proceed immediately after a train had cleared the road instead of waiting for the end of the red signal (typically some 3 to 5 seconds after the train had passed). This tendency might reveal a major cause of dramatic errors when a second train is approaching. Immediate extinction of the red signal is suggested, or even better, a separate signal to announce the arrival of the second train. Behavior during the white signal phase also showed indications of uncertainty. In some 10% of cases drivers tended to decelerate more strongly than necessary and to make extra head movements. It is recommended that the present white flashing signal be reconsidered.     

Effects of chronic environmental cold on growth, health, and select metabolic and immunologic responses of preruminant calves

The physiological response of the preruminant calf to sustained exposure to moderate cold has not been studied extensively. Effects of cold on growth performance and health of preruminant calves as well as functional measures of energy metabolism, fat-soluble vitamin, and immune responsiveness were evaluated in the present study. Calves, 3 to 10 d of age, were assigned randomly to cold (n = 14) or warm (n = 15) indoor environments. Temperatures in the cold environment averaged 4.7°C during the study. Frequent wetting of the environment and the calves was used to augment effects of the cold environment. Temperatures in the warm environment averaged 15.5°C during the study. There was no attempt to increase the humidity in the warm environment. Preventative medications or vaccinations that might influence disease resistance were not administered. Nonmedicated milk replacer (20% crude protein and 20% fat fed at 0.45 kg/d) and a nonmedicated starter grain fed ad libitum were fed to all calves. Relative humidity was, on average, almost 10% higher in the cold environment. Warm-environment calves were moderately healthier (i.e., lower respiratory scores) and required less antibiotics. Scour scores, days scouring, and electrolyte costs, however, were unaffected by environmental temperature. Growth rates were comparable in warm and cold environments, although cold-environment calves consumed more starter grain and had lower blood glucose and higher blood nonesterified fatty acid concentrations. The nonesterified fatty acid and glucose values for cold-stressed calves, however, did not differ sufficiently from normal values to categorize these calves as being in a state of negative-energy balance. Levels of fat-soluble vitamin, antibody, tumor necrosis factor-α, and haptoglobin were unaffected by sustained exposure to moderate cold. These results support the contention that successful adaptation of the dairy calf to cold is dependent upon the availability of adequate nutrition.     

Possible causes of a positive Haemoccult-II test in a population screening study for colorectal neoplasia

In the present paper, common disorders of the oral cavity and oropharynx are described with special emphasis on differential diagnostic aspects. The first part of this presentation covers different inflammatory diseases, mainly focusing on complications like peritonsillar, para- and retropharyngeal abscesses, and Ludwig's angina. These clinical entities can lead to further life-threatening complications, including deep neck infections and mediastinitis. The diagnostic value and necessity of modern imaging in these cases are emphasized. In the second part, the author reports on the incidence, etiology and clinical course of tumors of the oral cavity and oropharynx with special regard to malignancies. Tumors in these areas have been increasing in number over the past decades mainly due to changes in alcohol and nicotine consumption in the developed countries. Diagnostic management includes a thorough clinical evaluation as well as modern imaging for tumor delineation and possible bone infiltration, depending on the site of the original tumor. In addition, therapeutic considerations are discussed, focusing on surgical tumor removal and soft tissue replacement using different pedicled flaps and free flaps. It is also emphasized that postoperative radiotherapy is mandatory in most malignant tumors in this area.     

Effects of replacement of native fat in colostrum and milk with coconut oil on fat-soluble vitamins in serum and immune function in calves

Fat-soluble vitamins and their metabolites modulate immune function in a variety of animal species. The objective of the present study was to determine the role of fat-soluble vitamins in colostrum and milk in the development of specific aspects of immune function in the calf during the 1st wk postpartum. During this period, control calves (n = 6) were fed normal colostrum and milk, and calves in the treatment group (n = 6) were fed skimmed colostrum and skimmed milk supplemented with coconut oil. Treated calves did not experience the progressive increase in concentrations of retinol, beta-carotene, alpha-tocopherol, 1,25-dihydroxyvitamin D, or retinoic acids in serum that was observed in control calves. Acquisition of passive immunity, which is indicated by concentrations of immunoglobulin G1 in serum, was unaffected by treatment. Composition and functional capacities of populations of blood mononuclear leukocytes that were collected from birth to 7 d postpartum were also unaffected by treatment. Major changes in the function and composition of mononuclear leukocyte populations from all calves occurred during the experimental period and were unrelated to the concentrations of fat-soluble vitamins in serum. Populations of blood mononuclear leukocytes from calves were functionally hyporesponsive and compositionally different from populations of blood mononuclear leukocytes from adult nongravid cows. These differences likely reflected the immaturity of the immune system of the neonatal calf and may contribute to the increased susceptibility of the calf to infectious disease.