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Biomedical subjects

W Steffens

Publications and source records attributed to W Steffens.

At least 19 recordsLinked to original sources
PubMed1996

Protein sparing effect and nutritive significance of lipid supplementation in carp diets.

Although carp is in a position to utilize carbohydrates efficiently, lipids are an important energy source in carp diets. In general fat-enriched high-energy diets result in rapid growth and favourable feed conversion. Many authors emphasize the protein-sparing effect of lipid supplementation in carp diets. For efficient protein-utilization an optimal protein/energy ratio in feed is necessary. Good results may be obtained with diets containing 30-50% high-quality protein, > 14 MJ digestible energy/kg and a lipid level of at least 15%. Low protein-high energy diets bring about low nitrogen excretion which is important for maintenance water quality. Lipid-supplemented diets lead to increased lipid content in the carp. Fingerling carp with high fat deposits exhibit an improved overwintering ability. By using fish oil as lipid source it is possible to produce carp meat with high concentrations of n-3 polyunsaturated fatty acids which are beneficial for human health.

Animal Feed↗
PubMed1996

[Toxicologic evaluation of pyrethroids in indoor air: demonstrated with the example of cyfluthrin and permethrin].

Pyrethroids have varying activities depending on vehicle or route of administration (oral, dermal, inhalational). Specific features like the sensory irritation potential of the alpha-cyano-pyrethroids on the respiratory tract can only be quantified adequately by inhalation testing. Thus equitoxic dosages can vary between inhalative and oral application, especially for alpha-cyano-pyrethrolds. The no-effect values for chronic exposures derived for permethrin (type I pyrethroid) and cyfluthrin (type II pyrethroid) show clearly, that each pyrethroid has to be considered as an individual substance toxicologically, and that any extrapolation from the oral to the inhalative route should only be done after a thorough assessment of the specific toxicological profile. The study of simulated pest control measures on carpets pretreated with permethrin showed, that no significant enrichment of permethrin in total dust could be seen from a carpet additionally treated with pyrethroids. The missing correlation between absolute (mg pyrethroid/m3 air) and relative (mg pyrethroid/kg dust) concentrations in air-borne dust as well as the low degree of translocation of pyrethroids from carpets (only about 0.044% x m(-2) x h(-1) of the cyfluthrin applied to the carpet can be regarded as possibly respirable) prove, that analyses of pyrethroids in household sedimented dust ("vacuum cleaner bag analyses") without knowing the absolute surface concentration and respective air concentrations are of little value for risk assessment. The data allow the conclusion, that a scientific assessment of health risks is only possible based on absolute concentrations of pyrethroids in indoor air.

Air Pollution, Indoor↗
PubMed1996

[Nitrite formation and nitrosation potential of heterotrophic biological denitrification of drinking water in laboratory conditions].

In a laboratory construction for heterotrophic biological denitrification of drinking water treatment, the formation of nitrite, the potency of nitrosation and the genotoxic activity were tested. Parameter as nitrate concentration, the water flow rate in the system, nitrite and morpholine addition and the pH-value were checked. For testing the potency of nitrosation and formation of nitrite in the reactor we took morpholine, a fast nitrosing amine. The results show for the break down rate of nitrate, there is no influence of the initial nitrate concentration (80-195 mg/L), the nitrite addition (5-20 mg/L) and the water flow rate (45-100 min) in the system. pH-values below 5.5 showed a little break down rate of nitrate. There was no correlation between the starting point of nitrate concentration and the formation of nitrite, although there was a positive correlation between the length of stay and the formation of nitrite. Nitrite concentrations of 5 mg/L with morpholine concentrations of 5 and 10 mg/L didn't show detectable formation of nitrosomorpholine. The analyses of different watertests in the construction didn't show significant results for DNA damage by the sister-chromatid exchange (SCE). The results of the Salmonella microsome assay (tester strain TA1535) didn't show any mutagenic effects relating to the potency of nitrosation. According to our experiments the potency of generalising nitrosamides or nitrosamines by drinking water denitrification seems to be low. There is no final assessment of detriment to health by denitrifying drinking water.

Animals↗
PubMed1995

Effects of adding various oils to the diet on growth, feed conversion and chemical composition of carp (Cyprinus carpio).

The suitability of various vegetable and fish oils was tested as feed components for one-summer-old carp fingerlings. Five diets were used: a basal diet, which served as control feed, was supplemented with 10% corn-germ oil, 10% sunflower oil, 10% fish oil or 10% rapeseed oil, respectively. By means of the lipid supplementation the crude protein content decreased from 35.5% in the basal diet to 31.9% in the test diets, whereas the gross energy level increased from 16.3 to 18.9 MJ/kg. The diets were fed over a period of 84 feeding days and water temperature was 23 degrees C. Weight gain, feed conversion ratio and protein utilization were superior in all groups of carp which received the fat-enriched high energy diets. Considering the gain in % of the initial weight, the control fish reached less than 400% whereas all carp in the test groups, which consumed the oil-enriched diets, reached 455 to 485%. A significant influence of the kind of lipid on growth and feed conversion could not be recognized. The lipid-enriched diets with higher energy content resulted in increased fat levels of the carp. Fatty acid composition of the carp reflected that of the diets. In the control group and the fish oil group the levels of palmitic, palmitoleic, eicosapentaenoic and docosahexaenoic acid were especially high corresponding to the fatty acid profile of the diets. In carp fed the diets supplied with corn-germ oil and sunflower oil linoleic acid was dominant whereas the carp fed the rapeseed diet were characterized by a high level of oleic acid.

Aging↗
PubMed1993

[Significance of extruded feeds for trout nutrition and water protection].

Extruded feeds exhibit an improved starch digestibility and are more firmly bound due to the almost complete gelatinization of the starch. This results in fewer fines and longer water stability than pelleted feeds. Extruded pellets also have the advantage that they can soak up more oil than a conventional pellet. It is therefore possible to increase the maximum oil content to more than 20%. On the other hand extruding feeds is more expensive than steam pelleting. Gelatinized starch is a useful energy source in trout diets helping to reduce feed conversion ratios. Proportions up to 35-40% in the diet are tolerable. Using high dietary levels of both gelatinized starch and oil the non-protein energy of feed may be increased and thus a protein-sparing effect results. High-energy diets enable to reduce excretion of faeces and of nitrogen via gills. In addition a decrease of phosphorus level in feeds and thus of phosphorus excretion by fish is possible. Extruded high-energy diets therefore make a contribution to improve water quality.

Animal Feed↗
PubMed1990

Effect of thyrotropin-releasing hormone on immune functions of peripheral blood mononuclear cells.

The tripeptide thyrotropin-releasing hormone (TRH) works as a hypothalamic hormone, but is found also outside the brain in intrinsic nerve fibers of the gastrointestinal tract. There is evidence that TRH modulates the activity of immunocompetent cells, although there are only very few data on TRH-mediated immune effector functions. Since we could recently show that TRH inhibits monocyte activities we were also interested in other possible TRH modulated immune functions. Peripheral blood mononuclear cells (PBMC) from ten healthy subjects were cultured for 7 days and pulsed with 0.125 and 0.250 microgram/ml Pokeweed mitogen (PWM). 10(-12) to 10(-6) M TRH was added simultaneously with PWM. Lymphocyte proliferation [(3H]thymidine incorporation), interferon-gamma (IFN-gamma) activity (RIA) and immunoglobulin activities (IgG, IgM, IgA; ELISA) were determined in the supernatants. We could demonstrate a TRH-dependent decrease in PWM-pulsed IgG activity with significant (alpha = 0.05) values at 10(-8) and 10(-10) M (-29 +/- 6%/-16 +/- 3% for PWM 0.125 microgram/ml and -17 +/- 9%/-11 +/- 9% for PWM 0.250 microgram/ml). This inhibitory effect could be abolished by an anti-TRH antiserum. There was no TRH effect on IgM and IgA activities, IFN-gamma activity and lymphocyte proliferation compared with the PWM stimulated values alone. The described TRH effect on the polyclonal IgG response by PBMC gives further evidence for a functional link between the immune system and the endocrine system, although its underlying mechanism is not yet clear.

Enzyme-Linked Immunosorbent Assay↗
PubMed1987

Further results of complete replacement of fish meal by means of poultry by-products meal in feed for trout fry and fingerling (Salmo gairdneri).

By further experiment lasting 44 days trout fingerlings were fed with feed containing 50% poultry by-products meal in order to prove the possibility of using it as sole source of animal protein. Water temperature was 10-15 degrees C. The daily weight gain amounted to 2.17% with a feed conversion of 1.62 kg feed/kg gain. The control group being fed with standard feed (FB) containing 51.5% fish meal reached a daily weight gain of 2.33% with a feed conversion of 1.39 kg feed/kg gain. Due to higher lipid content of test diet the test group reached a higher fat content than the control group (10% compared to 5.9%). Suggested recipe makes it possible to use poultry by-products meal in pelleted feed for trout fingerlings.

Animal Feed↗
PubMed1986

[Use of solid fat in dry mixed feed for rainbow trout (Salmo gairdneri). 2. Fatty acid composition of feed and tissue lipids].

The effect of supplemental dietary fat on the fatty acid composition of some tissue lipids of rainbow trout fingerlings was studied. Data showed that dietary fatty acids were deposited nearly unchanged in the adipose tissue. The level of eicosapentaenoic acid, however, dropped significantly. Muscle showed remarkable capacity for deposition of dietary fat, while only minor changes were observed in the fatty acid composition of liver lipids. Levels of some polyenoic acid (e.g. 18: 2 omega 6, 20:4 omega 6, 20:5 omega 3, 22:6 omega 3) showed, that the fish converted lower unsaturated fatty acids to highly unsaturated fatty acids. It was observed that dietary acids had little effect on the fatty acid composition of tissue phospholipids. This result shows, that 17% fat in the diet are tolerated by trout, without alterations in the fat composition of the liver tissue. Probably the low rearing temperature (11 degrees C) had a more pronounced effect on the fatty acid composition of phospholipids than the diet.

Adipose Tissue↗
PubMed1979

[Reducing the proportion of animal protein in feed for rainbow trout (Salmo gairdneri). 2. Supplementation of methionine and lysine].

Continuing previous investigations, two test feedstuffs whose fishmeal content had been reduced to 5% and which were supplemented with 4.5 g methionine and 5.0 g lysine per kg resp. 6 g methionine and 6 g lysine per kg were proofed in comparison with a fattening feed for trout as customary in trade and with a fish meal content of 35%. The content of animal protein in the control feed was at least 75% (crude protein content 41%), in test feed I at most 35% (crude protein content 35.4%), in test feed II at most 17% (crude protein content 33.9%). All feedstuffs had the same energy content. The tests were made with rainbow trout (Salmo gairdneri) of 80...100 g at the beginning and at water temperatures of 11...12 degrees C. They were conducted over a period of 112 days. After giving the same amount of feed, growth of and feed expenditure for the fish feed with the test feedstuffs were less suitable than of those fish which had received the control feed. Concerning the protein efficiency ratio, the productive protein value and the energetic expenditure too, the best results were achieved with the control feed.

Animal Feed↗
PubMed1975

Influence of humidity and rain on uptake and metabolism of 14C-azinphos-methyl in bean plants.

In several experiments the influence of relative humidity and rain on uptake and metabolism of carbonyl-14C-azinphos-methyl was examined in bean plants under the following environmental conditions: Growth room with 35/80%, 65/85% and 95/95% (day/night) relative humidity and open field with and without rain. Increasing relative humidity had an enhancing effect on the rate of uptake and metabolism. A higher portion of water-soluble compounds was found in the bean tissue, although the azinphos-methyl itself is relatively non-polar. Low relative humidity and possible dry periods in summer will reduce the uptake and will leave the azinphos-methyl relatively persistent on the leaf surface. Rain or spray irrigation easily removed azinphos-methyl from the leaves. The rate of this removal seemed to depend on the intensity and time of rainfall after application. However, repeated wettings by rain may simultaneously stimulate uptake and metabolism of azinphos-methyl by the leaves.

Azinphosmethyl↗