Showing papers by "Swedish University of Agricultural Sciences published in 1981"

Protozoan grazing of bacteria in soil-impact and importance.

Abstract: Interactions between bacteria and protozoa in soil were studied over 2-week periods in the field and in a pot experiment Under natural conditions the total biological activity was temporarily synchronized by a large rainfall, and in the laboratory by the addition of water to dried-out soil, with or without plants In the field, peaks in numbers and biomass of bacteria appeared after the rain, and a peak of naked amoebae quickly followed Of the three investigated groups-flagellates, ciliates, and amoebae-only populations of the latter were large enough and fluctuated in a way that indicated a role as bacterial regulators The bacterial increase was transient, and the amoebae alone were calculated to be able to cause 60% of the bacterial decrease The same development of bacteria and protozoa was observed in the pot experiment: in the presence of roots, amoebic numbers increased 20 times and became 5 times higher than in the unplanted soil In the planted pots, the amoebic increase was large enough to cause the whole bacterial decrease observed; but in the unplanted soil, consumption by the amoebae caused only one-third of the bacterial decrease

Immunohistochemical studies on the effect of capsaicin on spinal and medullary peptide and monoamine neurons using antisera to substance P, gastrin/CCK, somatostatin, VIP, enkephalin, neurotensin and 5-hydroxytryptamine.

Abstract: After neonatal treatment of rats with capsaicin, the spinal cord, the spinal trigeminal nucleus and spinal and trigeminal ganglia were analysed with immunohistochemistry using antisera to several peptides and 5-hydroxytryptamine. A marked decrease was observed in substance P-, cholecystokinin-, somatostatin- and VIP-like immunoreactivity present in the central branches of primary sensory neurons in the spinal cord and in substance P- and somatostatin-like immunoreactivity in sensory ganglion cells. No definite depleting effect of capsaicin could be established on 5-hydroxytryptamine and peptides, such as enkephalin and neurotensin, present in centrally originating fibres in the dorsal horn of the spinal cord. The results demonstrate that the effects of capsaicin are not confined to substance P immunoreactive primary sensory neurons. The possibility is discussed that capsaicin effects specifically functioning rather than chemically specific primary sensory neurons.

Escherichia Coli Associated with Neonatal Diarrhoea in Piglets and Calves

Abstract: Enteric disease in man and animals caused by Escherichia coli can be classified into several forms (Moon, 1974).

Nutrition and growth of birch and grey alder seedlings in low conductivity solutions and at varied relative rates of nutrient addition

Abstract: Birch (Betula verrucosa Ehrh.) and grey alder (Alnus incana Moench) seedlings were grown with varied relative addition rates of all nutrients, up to optimum for vegetative growth. The root medium was basically distilled water to which the nutrients, contained in stock solutions in fixed proportions, were added every second hour and in exponentially increased amounts for consumption during the subsequent period. The nutrient weight proportions previously found to be required in birch (100 N:65 K:13 P) were used in all treatments. However, the nutrient proportions required in grey alder were found to be somewhat different (100 N:50 K:18 P). The use of the required proportions in the additions was important for maintenance of maximum growth, efficient nutrient utilization, and low concentrations in the root medium. Luxury consumption and inefficiency occurred at high concentrations. The results show that the nutrient requirements are sufficiently defined, for different relative growth rates, by the nutrient proportions and the relative addition rate. No clear relationships were found between conductivity or concentration in the root medium and the addition rate, net uptake rate, nutrient status, or relative growth rate. The results are in good agreement with data from low concentration and depletion experiments reported in the literature, showing that non-limited uptake rates occur down to very low concentrations. Thus, there is strong evidence that concentration has been incorrectly used when applied as the treatment variable for plant nutrition in plant science and cultivation practice. The dominant factors in sub-optimum and optimum nutrition are the amounts of nutrients available per unit of time, the growth rate, and the nutrient proportions. At low concentration levels, physical factors such as stirring and flow rate of nutrient solution and boundary layer effects are decisive for the rates with which the nutrients become available to the roots. Therefore, at low levels, concentration alone cannot be used as the factor determining nutrient uptake rate. At high levels, concentration is effective as a supra-optimum factor and increased internal percentage contents cause decreased uptake efficiency, thus counter-acting the concentration effect. Nitrogen effects dominated the stress indications when the internal nitrogen percentage content decreased from optimum to the level of the treatments in the beginning of the experiments. Leaf deficiency symptoms disappeared and the root/shoot ratio change ceased when nitrogen status stabilized. Strong linear regressions were found between any two of the variables: relative addition rate of nutrients, relative growth rate, and nutrient status.

Effect of energy restriction on total heat production, basal metabolic rate, and specific dynamic action of food in rats.

Abstract: Man and experimental animals are able to adapt to restricted levels of energy intake mainly by a reduction in basal metabolic rate (BMR) while the effects of energy restriction on the specific dynamic action (SDA) of food and the spontaneous activity are less well established. In this study, growing rats were fed ad libitum or restricted amounts of diet during 28-31 days. Then total heat production (THP) and BMR during 22 hours, as well as SDA of a test meal, were measured on individual rats by indirect calorimetry. After the calorimeter study rats were kept in metabolic cages for 6 days after which they were killed and analyzed for total body composition. The energy balance of the rats over the last 7 days of the study was calculated from changes in body composition and measurements of food intake during this period. During the calorimeter experiment an indirect estimation of the spontaneous activity of the rat was made. Results showed that THP, BMR and SDA of restricted rats were significantly lower than for ad libitum-fed rats. From body composition measurements, rats restricted in food intake before the calorimetry study were found to mobilize more protein and less fat compared to rats fed ad libitum until the calorimetry and body composition studies were carried out. No difference in spontaneous activity was observed between the two dietary treatments.

Tissue concentration and release of substance P-like immunoreactivity in the dental pulp.

Abstract: The concentration of substance P-like immunoreactivity (SPLI) was determined in dental pulps from cat, dog and man by radioimmunoassay. Pulps from mature cats showed the highest SPLI-levels (mean 32 pmol/g); these are comparable to or higher than those found in any other organ outside the central nervous system. The SPLI concentrations were lower in pulp from immature teeth. The immunological and chromatographic behav behaviour of the pulpal SPLI from cat and man resembled that of synthetic substance P (SP), indicating that the assayed substance is closely related to or identical with SP. Release of pulpal SPLI in canine teeth ws evoked by stimulation of the inferior alveolar nerve in anaesthetized cats. In 9 of 16 experiments the amounts of SPLI found in pulp suprafusates following stimulation (4–31 fmol) were larger than those in unstimulated controls (0–7 fmol). Stimulation also reduced the pulpat tissue concentration of SPLI to 60% of that in homologous control pulps. The high concentration of SPLI found in the dental pulp and the demonstration of nerve-induced release strengthen the hypothesis that SP serves some function in the dental pulp.

Effects of varied nitrogen stress on growth and nutrition in three Salix clones

Abstract: The ability of Salix aquatica Smith, S. fragilis L. and S. viminalis L. to absorb nitrogen at varied growth rates was investigated in nutrient solutions. The effects of five nitrogen addition rates on growth rates, nitrogen contents of the plants, nitrogen concentration of the media, and dry matter distribution between roots, stems and leaves, were studied. These clones are highly efficient in absorbing nitrogen at low concentrations in the root medium, independent of growth rate. Strong linear regressions were found between any two of the three factors: relative rate of nitrogen supply (RN), nitrogen content (plant), and relative growth rate (R). Dry matter production per unit nitrogen taken up and unit time (N-productivity) and per unit nitrogen taken up independent of time (N-efficiency) was closely correlated to the nitrogen status of the plant. Root development was favoured in the sub-optimum treatments, and leaf development in the optimum treatments. With regard to their ability to absorb nitrogen, these Salix clones appear satisfactory for efficient short rotation energy forestry.

Acyl exchange between oleoyl-CoA and phosphatidylcholine in microsomes of developing soya bean cotyledons and its role in fatty acid desaturation

Abstract: Microsomes of developing soya bean cotyledons transfer oleate from oleoyl-CoA to phosphatidylcholine (PC) by two different mechanisms: one in which oleate transfer is accompanied by the release of free CoA and another which results in the exchange of oleate from oleoyl-CoA for unsaturated 18-carbon fatty acids of PC. The acyl exchange can be demonstrated only when bovine serum albumin is present in the incubation medium. ATP-dependent acyl-CoA synthetase is not involved in the exchange process, which apparently does not require any cofactors. In light of this exchange process, the oleate desaturase system was reinvestigated in order to determine what the actual substrate for this system is. Upon incubation of microsomes with high concentrations of [14C] oleoyl-CoA, bovine serum albumin and NADH, it could be conclusively demonstrated that most oleic acid is desaturated while part of the PC molecule. The amounts of [14C] linoleoyl-CoA formed could be explained entirely by the acyl exchange. The physiological significance of the acyl exchange system is discussed. A new method for separation of acyl-CoA from other lipids and free CoA using reversed phase column chromatography also is described.

Hydrophobic adsorptive and hemagglutinating properties ofEscherichia coli possessing colonization factor antigens (CFA/I or CFA/II), type 1 pili, or other pili

Abstract: Hydrophobic and hemagglutinating activities of piliated enterotoxigenicEscherichia coli possessing colonization factor antigens (CFA)/I and putative CFA/II, strains with type 1 pili, and piliated strains of nonenterotoxigenicE. coli from urinary tract infections were compared. When passed through columns of hydrophobic Phenyl Sepharose in the presence of buffered ammonium sulfate, the strains with CFA adsorbed most strongly. Similarly, the CFA strains showed a tendency to autoagglutinate at a lower (NH4)2SO4 concentration than the other strains studied. The degree of hydrophobicity of the strains tested is in the order CFA/I>CFA/II>type 1 pili>urinary tract strains. Rough variants ofE. coli strains were more hydrophobic than their smooth parents. Electron microscopy showed large numbers of pili on CFA strains, whereas type 1 piliated strains possessed fewer pili. CFA-negative clones possessed few or no, pili and did not adsorb to the gel. A highly piliated mutant strain (PAK/2PfS) ofPseudomonas aeruginosa bound to the Phenyl Sepharose while the poorly piliated wild-type strains did not. Strains, lost their adsorptive capacity after blending, sonication, heating, or trypsin treatment. It is concluded that the hydrophobicity of enteric organisms, as measured by hydrophobic interaction chromatography, is a function of the type and number of pili on the cell surface.

Enterotoxigenic Bacteria in Food and Water from an Ethiopian Community

Abstract: Food and water samples from an Ethiopian community were screened for the presence of enterotoxin-producing bacteria. Using the Chinese hamster ovary cell assay, 40 of 213 isolates (18.8%) produced heat-labile (LT) enterotoxin. These LT-producing isolates comprised 33 of 177 (18.6%) strains from 24 of 68 food samples (35.3%) and 7 of 36 (19.4%) isolates of 4 of 17 water samples (23.5%). One LT-producing strain each of Salmonella emek and of Shigella dysenteriae was found. Three pseudomonads, all LT producers, produced heat-stable enterotoxin as gauged by the suckling mouse test. Two strains of LT-enterotoxigenic Escherichia coli O68 were found in water samples. No enterotoxigenic E. coli were isolated from food samples, but 13 of the LT-producing strains were Enterobacter, Klebsiella, Serratia, and Proteus species, and 7 food samples yielded more than one species of enterotoxigenic bacterium. Of the enterotoxigenic isolates from food, 15 were oxidase-positive strains of the genera Aeromonas, Pseudomonas, Achromobacter, Flavobacterium, and Vibrio. LT-enterotoxigenic Enterobacter, Acinetobacter, Klebsiella, Proteus, Providencia, and Serratia species represented 20 of the food and water isolates. Culture supernatant fluids of representative strains of oxidase-positive and oxidase-negative species giving positive reactions in Chinese hamster ovary cell tests induced fluid accumulation in rabbit ileal loops. Eight of the food samples and two of the water samples contained more than one isolate or species of enterotoxigenic bacterium. The stability of the LT production by oxidase-positive bacteria and non-E. coli strains was assessed by the rabbit skin and adrenal cell tests after 9 months and 1 year of storage, respectively, in Trypticase soy broth with glycerol at −70°C. Only 33% of the oxidase-positive strains were still LT enterotoxigenic. Of the oxidase-negative strains, 50 and 33% were LT producing at 9 months and 1 year, respectively. None of the E. coli isolates, both enterotoxigenic and nonenterotoxigenic, possessed K88, K99, or colonization factor antigen. The survey demonstrates the presence in food and water of enterotoxigenic bacteria of the same species as those isolated from cases of infantile diarrhea in the same community, although a correlation between these sources and infantile diarrhea remains to be established. Images

Diet of the golden eagle Aquila chrysaetos during the breeding season in Sweden

Abstract: During a five-year period, 1975–1979, a total of 2881 prey individuals of 65 prey species were collected at 162 golden eagle nests from northern Sweden and from the island of Gotland. In northern Sweden birds are taken in higher numbers than mammals but calculated as weight the two categories are of equal importance, The main prey during the breeding season are capercaillie, black grouse, willow grouse, ptarmigan, mountain hare and reindeer fawns which together form 91% of the total food biomass. The capercaillie and the black grouse are taken more in the southern part of the coniferous region than in the northern. In contrast, in northern areas, reindeer fawns are more preyed upon than in the South, Ptarmigan and willow grouse are the most commonly captured prey species in mountain areas. The total number of reindeer fawns taken (dead and/or alive) by the Swedish golden eagle population during one summer is estimated at 600 individuals. On Gotland the golden eagles take mammals more often than in its northern distribution area. Rabbit and hedgehog arc the most important species.

Nutritional aspects of Ascaris infection in young protein-deficient pigs

Abstract: Experiments were carried out to investigate the effects of Ascaris suum infection on the growth, food intake, nitrogen and fat utilization and intestinal function of young pigs receiving diets low in protein. An infection procedure was developed which provided relatively uniform and heavy infections in pigs under study. Ascaris -infected pigs showed statistically significant reduction in growth rate and food intake compared to uninfected controls. The reduction in growth rate was observed after the A. suum were mature and eggs were observed in the faeces of pigs. The degree of growth retardation was significantly correlated with worm burden. Infected pigs showed no consistent reduction in nitrogen and total solids digestibility compared to controls but fat digestion was reduced. The infected pigs showed reduced nitrogen retention compared to uninfected controls. Ascaris -infected pigs had heavier intestinal tracts with increased size of the tunica muscularis . Lactase activity in mucosa from infected pigs was significantly lower than in controls, whereas no consistent effect was observed in mucosal sucrase and maltase activity. When Ascaris -infected pigs were given an oral lactose load, blood glucose levels rose less than in control pigs, suggesting that the infection resulted in impaired lactose tolerance.

Occurrence and Ecology of Usnea Longissima in Central Sweden

Abstract: The past and present occurrence of Usnea longissima has been investigated at 31 localities in an area of eastern central Sweden. A marked decline was found which is due to different forestry practices, and, to a minor extent, air pollution. The species is confined to old spruce forests, mainly located on north-facing slopes with a slightly oceanic climate. The population size showed a large variation both within and between seven investigated localities. Specific habitat demands and low dispersal ability make U. longissima very sensitive to environmental disturbances.

Concentration of substance P-like immunoreactivity (SPLI) in tissues of dog, rat and mouse.

Abstract: The distribution of SPLI in various tissues from dog, rat and mouse was determined by radioimmunoassay. The gastrointestinal, urogenital and tracheobronchial tracts were found to contain SPLI with marked differences in levels in different parts of these tracts. Glandular tissues, such as salivary glands and pancreas, was well as eye, tongue and skin also contain SPLI. Species differences were encountered both in absolute amounts and the distribution of SPLI. The highest concentrations of SPLI were generally found in mouse followed by dog and rat. The present results are in agreement with those of previous studies in which SP was demonstrated by bioassay technique, but due to the greater sensitivity of the radioimmunoassay it was possible to show a much wider distribution of SP. Virtually all organs in which an effect of SP has been demonstrated also contain SPLI.

Partial Separation and Biochemical Characteristics of Periportal and Perivenous Hepatocytes from Rat Liver

Abstract: Suspensions of enzymatically prepared hepatocytes from starved rats were separated according to their buoyant density at 12°C in linear, isosmotic gradients of metrizamide, centrifuged at low speed for a relatively short time. The recovery of cell protein was 86%. Hepatocytes of high viability formed a single band around 1.10 g/cm3 and were recovered as four density populations (P1–P4) from low to high density, respectively. The content of protein was significantly lower in population P1, while the content of neutral fat or the average cell size was similar in the various populations. The specific activity of alanine aminotransferase increased in the order P1–P4. The distribution of this enzyme within the intact liver acinus obtained by others indicate that a partial separation of periportal and perivenous hepatocytes had occurred. The activity patterns of lactate dehydrogenase, glutamate dehydrogenase, isocitrate dehydrogenase (NADP+) and pyruvate kinase, also with known intra acinar distributions, supported this conclusion. The hepatocytes showed signs of shrinkage after separation, but since they retained a normal ultrastructure, most enzyme activities and viability, the present technique was regarded superior to previous procedures of hepatocyte separation by density. The degree of separation was calculated from an equation (see Appendix), and the periportal/perivenous ratio for parameters measured in density populations can be obtained. The specific activity of phosphofructokinase, alcohol dehydrogenase and aldehyde dehydrogenase showed no differences between populations. However, the ratio high-Km/lowa-Km aldehyde dehydr-benasc increased in the order P4–P1.

Binding to antithrombin of heparin fractions with different molecular weights

Abstract: The interaction between bovine antithrombin, a plasma proteinase inhibitor, and heparin species of different molecular weights was studied. A commercial heparin preparation was divided by gel chromatography into a number of fractions with average molecular weights ranging from 6000 to 34700. Each of these fractions was further fractionated by affinity chromatography on matrix-bound antithrombin. In the latter procedure, those heparin fractions that had molecular weights lower than about 14000 were separated into three peaks. The material in the first of these was not adsorbed on the column, and the other two peaks corresponded to the low-affinity and high-affinity peaks described previously. In contrast, high-molecular-weight heparin samples gave only the low-affinity and high-affinity fractions. U.v. difference absorption studies showed that the non-adsorbed heparin fraction bound to antithrombin in solution with a binding constant at physiological ionic strength only slightly lower than that of low-affinity heparin. The division between the two fractions thus is arbitrary and only dependent on the conditions selected for the affinity-chromatography experiment. Stoicheiometries and binding constants for the binding of several high-affinity heparin species to antithrombin were determined by fluorescence titrations. High-affinity heparin fractions of equal elution positions in the beginning of the peaks of the affinity chromatographies, but with different molecular weights, showed stoicheiometries that were not experimentally distinguishable from 1:1 and also had no appreciable differences in binding constants. However, the anticoagulant activities, calculated on a molar basis, of these fractions increased markedly with molecular weight, a behaviour that thus cannot be explained by differences in the binding of the fractions to antithrombin. In contrast, high-affinity samples of similar molecular weights, which were eluted at increasing ionic strengths from matrix-linked antithrombin, were found to have an increasing proportion of chains with two binding sites for antithrombin and also to have progressively higher binding constants. These binding properties at least partly explain the increasing anticoagulant activities that were observed for these fractions.

The Seasonal Course of Respiration and Photosynthesis in Strobili of Scots Pine

Abstract: The respiration of current and 1-year-old cones of Scots pine was investigated on excised cones during one season. The cones were collected in a 20-year-old stand of Scots pine in central Sweden. The respiration rate at 15oC showed pronounced seasonal variation and in light some of the carbon dioxide released in respiration was retixed. The average refixation capacity of 1-year-old cones was 60 percent and of current conelets 79 percent at light saturation. The seasonal performance of cone respiration was estimated, using records of air temperature and photon flux densities from the stand from which the cones were collected. The refixation of carbon dioxide reduced respiratory losses by 31 percent. Calculated on a carbon basis, the respiration cost of cone production was 50 percent of the final cone weight after correction for carbon refixation. Cones covered with aluminJure foil in mid-July had lower seed weight than the controls had when harvested in late October. FOREST SCI. 27:267-276. THE FEMALE STROBILUS IN SCOTS PINE (Pinus sylvestris L.) needs 2 years to develop into a mature cone. The strobili are first visible in late May or early June at the distal end of the 1-year-old shoots. Pollination occurs in the middle of June and the conelets grow to a diameter of approximately 5 mm during the first growing season. In May the following year the cone begins to increase in dry weight; the final weight is reached in late August. Fertilization occurs almost 13 months after pollination (Sarvas 1962), which in Central Sweden means late June or early July. The strobili of Scots pine are green throughout their development and turn brown during the last month of maturation. It has been reported by a number of authors that cone production depresses stem growth in conifers (cf. Els and others 1965). However, there is no agreement on the size of cone crop that causes a growth restriction, and its mechanism is not completely understood. Gas exchange studies in conifers have mainly concentrated on needle photo- synthesis; much less is known about the gas exchange of non-green parts of the tree (cf. Linder 1979), only a few reports are available concerning gas exchange in conifer strobili. Ching and Ching (1962) followed the development of Douglas-fir strobili from April until maturity in late September. They reported an increase in respiration

The antithrombin-binding sequence of heparin.

Abstract: Products obtained by partial depolymerization of pig mucosal heparin with nitrous acid were fractionated by affinity chromatography on immobilized antithrombin. A high affinity octasaccharide fraction was recovered and reduced with sodium [3H]borohydride, yielding terminal 2,5-anhydro-~-[l-~H]mannitol residues. Partial N-desulfation of this material by treatment with aqueous dimethylsulfoxide resulted in the formation of two distinct species, with low and medium affinity for antithrombin, respectively, in addition to components that retained a high affinity for the protein. The low and medium affinity fragments were converted into high affinity components by sulfation of free amino groups; N-acetylation was without effect. The N-substituents on the 2 glucosamine units at positions 4 and 6 (the 3H-labeled end group being at position 8) were defined by gel chromatography of the 3H-labeled oligosaccharides released on selective deamination of Nsulfated or N-unsubstituted D-glucosamine residues. In the high affinity fraction, both glucosamine residues, at positions 4 and 6, respectively, were N-sulfated. The medium affinity fraction contained an N-sulfated glucosamine unit in position 4 and an N-unsubstituted unit in position 6. The low affinity components were either N-unsubstituted in both positions or N-unsubstituted in position 4 and N-sulfated in position 6. It is concluded that high affinity binding of heparin to antithrombin requires the presence of two consecutive N-sulfated glucosamine residues in specific positions of the antithrombin-binding sequence; loss of either one of these N-sulfate groups (with or without subsequent N-acetylation) results in a distinct, and appreciable, decrease in binding affinity (and in anticoagulant activity).