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Biomedical subjects

J W Hansen

Publications and source records attributed to J W Hansen.

At least 37 records · Page 2Linked to original sources
PubMed1996

Plasma fatty acid responses, metabolic effects, and safety of microalgal and fungal oils rich in arachidonic and docosahexaenoic acids in healthy adults.

The effect of dietary supplementation with different amounts of a fungal oil containing arachidonic acid (AA, 20:4n--6) and a microalgal oil containing docosahexaenoic acid (DHA, 22:6n--3), blended to give a ratio of AA to DHA of 1.25:1.00, on plasma lipid AA, DHA, cholesterol, and triacylglycerols was evaluated in healthy men. Subjects (n = 8/group) were given 28.8 g fat/d containing 0 x (0 g AA, 0 g DHA), or 1 x (0.8 g AA, 0.6 g DHA), 3 x (2.2 g AA, 1.7 g DHA), or 5 x (3.6 g AA, 2.9 g DHA) the estimated intake of infants fed human milk with 0.5% AA and 0.4% DHA for 14 d. No clinically significant dose-related effects were seen on physical examination or from routine laboratory tests. The microalgal-fungal oil blend resulted in a significant, dose-dependent increase in plasma cholesterol and percentage phospholipid AA and DHA, and a decrease in percentage triacylglycerols and phospholipid linoleic acid. Plasma phospholipid AA and DHA increased approximately 18% and 50%, respectively, with the 1 x dose, similar to that expected at intakes provided by human milk. These oils appear to be safe dietary sources of AA and DHA for healthy adults at intakes equivalent to 0.8 g AA and 0.6 g DHA/d for > or = 2 wk.

Adult↗
PubMed1996

Effect of age on the intestinal absorption of vitamin D3-palmitate and nonesterified vitamin D2 in the term human infant.

This study was undertaken to investigate the utility of vitamin D3-palmitate as a nutritional supplement and thus define the intestinal absorption profile of vitamin D2 and vitamin D3 liberated after its cleavage from vitamin D3-palmitate in the human infant at various postnatal ages. The subjects for study consisted of 48 normal infants that were simultaneously administered 0.07 and 0.08 micromol/kg BW vitamin D as vitamin D3-palmitate and nonesterified vitamin D2 respectively, by orogastric tube. Blood samples were obtained before and 6, 12, and 24 h postadministration and analyzed simultaneously for vitamins D2 and D3. For data analysis, the infants were divided into two groups based on postnatal age: group 1, 1 day of age; and group 2, more than 10 days of age. Data were analyzed using the integrated peak area under the absorption curve for each subject. All subjects demonstrated the ability to absorb vitamin D after oral administration, although postnatal age as well as vitamin form had a profound effect on the absorption of vitamin D2 and vitamin D3 liberated from vitamin D3-palmitate. Nonesterified vitamin D2 is well absorbed both in very young and older infants, although absorption efficiency increases with age, perhaps due to increased bile acid secretion. Liberation of vitamin D3 from vitamin D3-palmitate was shown to increase, perhaps due to gastrointestinal tract maturation, beyond 10 days of age, probably coinciding with the secretion of intestinal esterases. Our data indicate that both forms of the orally administered vitamin approach equivalency in their abilities to elevate circulating vitamin D levels in the human infant at a postnatal age of approximately 89 days. Thus, vitamin D3-palmitate would appear not to be dietarily equivalent to free vitamin D as a nutritional source of vitamin D in the human neonate.

Aging↗
PubMed1994

Calciuria and aminoaciduria in very low birth weight infants fed a high-mineral premature formula with varying levels of protein.

To assess the influence of protein intake on renal excretion of calcium and amino acids and on bone mineralization in preterm infants, we randomly selected within weight group strata 27 infants who weighed < 1500 gm at birth (nine per group) to be fed a high-mineral (calcium, 940 mg/L; phosphorus, 470 mg/L) premature formula with one of the following protein contents: formula A, 3.0 gm/100 kcal; formula B, 2.7 gm/100 kcal; and formula C, 2.2 gm/100 kcal. Mean (+/- SD) daily weight gain was greater in infants receiving the higher protein intakes for the first 30 days (formula A, 24.8 +/- 5.1 gm; formula B, 20.5 +/- 3.8 gm; formula C, 16.2 +/- 5.9 gm (analysis of variance: p < 0.01; C < A, p < 0.05)). Bone mineral content did not differ at any time point, and all groups had a high prevalence of generalized aminoaciduria (4 weeks: formula A, 56%; formula B, 71%; formula C, 75%). Urinary calcium corrected for creatinine (in milligrams per milligram) increased as protein content decreased (2 weeks: formula A, 0.16 +/- 0.10; formula B, 0.20 +/- 013; formula C, 0.44 +/- 0.33 (C > A, C > B, p < 0.05); 4 weeks: formula A, 0.23 +/- 0.15; formula B,0.34 +/- 0.47; formula C, 0.49 +/- 0.22 (C > A, p < 0.01). We conclude that the high mineral content and other components of premature formulas result in a higher growth rate and may increase protein requirements. Failure to meet protein requirements may result in underutilization of absorbed calcium and increased renal excretion of calcium. In preterm infants, higher protein intake probably supports rather than jeopardizes bone mineral accretion, and reduces rather then increases calciuria.

Acetylglucosaminidase↗
PubMed1993

The anaerobic degradation of organic matter in Danish coastal sediments: iron reduction, manganese reduction, and sulfate reduction.

We used a combination of porewater and solid phase analysis, as well as a series of sediment incubations, to quantify organic carbon oxidation by dissimilatory Fe reduction, Mn reduction, and sulfate reduction, in sediments from the Skagerrak (located off the northeast coast of Jutland, Denmark). In the deep portion of the basin, surface Mn enrichments reached 3.5 wt%, and Mn reduction was the only important anaerobic carbon oxidation process in the upper 10 cm of the sediment. In the less Mn-rich sediments from intermediate depths in the basin, Fe reduction ranged from somewhat less, to far more important than sulfate reduction. Most of the Mn reduction in these sediments may have been coupled to the oxidation of acid volatile sulfides (AVS), rather than to dissimilatory reduction. High rates of metal oxide reduction at all sites were driven by active recycling of both Fe and Mn, encouraged by bioturbation. Recycling was so rapid that the residence time of Fe and Mn oxides, with respect to reduction, ranged from 70-250 days. These results require that, on average, an atom of Fe or Mn is oxidized and reduced between 100-300 times before ultimate burial into the sediment. We observed that dissolved Mn2+ was completely removed onto fully oxidized Mn oxides until the oxidation level of the oxides was reduced to about 3.8, presumably reflecting the saturation by Mn2+ of highly reactive surface adsorption sites. Fully oxidized Mn oxides in sediments, then, may act as a cap preventing Mn2+ escape. We speculate that in shallow sediments of the Skagerrak, surface Mn oxides are present in a somewhat reduced oxidation level (< 3.8) allowing Mn2+ to escape, and perhaps providing the Mn2+ which enriches sediments of the deep basin.

Adsorption↗
PubMed1993

Pathways of organic carbon oxidation in three continental margin sediments.

We have combined several different methodologies to quantify rates of organic carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH4+ and Sigma CO2 liberation sediment incubations were used with O2 penetration depths to conclude that O2 respiration accounted for only between 3.6-17.4% of the total organic carbon oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major carbon oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated organic carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mn-oxide were found (3-4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most important and of a similar magnitude. Overall, most of the measured O2 flux into the sediment was used to oxidized reduced inorganic species and not organic carbon. We suspect that the importance of O2 respiration in many coastal sediments has been overestimated, whereas metal oxide reduction (both Fe and Mn reduction) has probably been well underestimated.

Carbon↗
PubMed1993

Bacterial disproportionation of elemental sulfur coupled to chemical reduction of iron or manganese.

A new chemolithotrophic bacterial metabolism was discovered in anaerobic marine enrichment cultures. Cultures in defined medium with elemental sulfur (S) and amorphous ferric hydroxide (FeOOH) as sole substrates showed intense formation of sulfate. Furthermore, precipitation of ferrous sulfide and pyrite was observed. The transformations were accompanied by growth of slightly curved, rod-shaped bacteria. The quantification of the products revealed that S was microbially disproportionated to sulfate and sulfide, as follows: 4S + 4H(2)O --> SO(4) + 3H(2)S + 2H. Subsequent chemical reactions between the formed sulfide and the added FeOOH led to the observed precipitation of iron sulfides. Sulfate and iron sulfides were also produced when FeOOH was replaced by FeCO(3). Further enrichment with manganese oxide, MnO(2), instead of FeOOH yielded stable cultures which formed sulfate during concomitant reduction of MnO(2) to Mn. Growth of small rod-shaped bacteria was observed. When incubated without MnO(2), the culture did not grow but produced small amounts of SO(4) and H(2)S at a ratio of 1:3, indicating again a disproportionation of S. The observed microbial disproportionation of S only proceeds significantly in the presence of sulfide-scavenging agents such as iron and manganese compounds. The population density of bacteria capable of S disproportionation in the presence of FeOOH or MnO(2) was high, > 10 cm in coastal sediments. The metabolism offers an explanation for recent observations of anaerobic sulfide oxidation to sulfate in anoxic sediments.

Journal Article↗
PubMed1992

Comparison of anthelmintic control programs for sheep in Virginia.

Haemonchus contortus is the most serious parasitic problem encountered by sheep producers in southwestern Virginia. Four anthelmintic control programs for grazing lambs were tested. Group TR received monthly SC injections of ivermectin (200 micrograms/kg of body weight). Group SI received the same dose of ivermectin at 0, 3, 6, 9, and 12 weeks after the start of the grazing season. Group SL was given levamisole (8 mg/kg, PO) 0, 3, 6, 9, and 12 weeks after the start of the grazing season, and group TA received ivermectin (200 micrograms/kg) 0, 8, 16, 20, and 24 weeks after the beginning of grazing. None of the 4 programs provided satisfactory control of parasites as indicated by fecal egg counts and serum pepsinogen concentrations, although group-TR lambs gained significantly more weight than lambs in groups SI and TA. Group-TA lambs developed clinical haemonchosis in early August and required additional treatment at that time. These findings suggest that reliance on anthelmintics alone may not provide the most effective and economic control of parasitic infection.

Abomasum↗
PubMed1992

Comparative bacteriological studies on summer mastitis in grazing cattle and pyogenes mastitis in stabled cattle in Denmark.

A total of 143 secretions from clinical cases of summer mastitis (SM) in grazing cattle and from 89 cases of pyogenes mastitis (PM) in stabled cattle were examined bacteriologically. The typical bacteriological finding was a mixed flora in which the predominant organisms were Actinomyces pyogenes (SM-70%, PM-85%), Peptostreptococcus indolicus (54%, 54%), a microaerophilic coccus (Stuart-Schwan coccus) (26%, 25%), Fusobacterium necrophorum biovar B (22%, 12%), Bacteroides melaninogenicus (20%, 9%) and Streptococcus dysgalactiae (21%, 5%). All except six cases occurred in non-lactating animals or within three weeks after parturition. The majority of animals (about 90%) had only one quarter affected and no differences in quarter distribution were observed between the two groups.

Actinomyces↗
PubMed1992

Summer mastitis in heifers: studies on the seasonal occurrence of Actinomyces pyogenes, Peptostreptococcus indolicus and Bacteroidaceae in clinically healthy cattle in Denmark.

With the aim of investigating the seasonal occurrence of Actinomyces pyogenes, Peptostreptococcus indolicus, Bacteroides melaninogenicus ss. levii and Fusobacterium necrophorum, and thus the potential for development of summer mastitis, clinically healthy Danish Holstein-Friesian heifers due to calve in the autumn were sampled from the teat tip, the conjunctiva and the oral cavity at 2-6 week intervals from 1979 to 1981. The overall isolation rates of F. necrophorum, P. indolicus and B. melaninogenicus ss. levii, in order of significance, were significantly higher during the pasture period whereas no differences in isolation rates of A. pyogenes between housed and pastured animals were detected. F. necrophorum was recovered almost exclusively from the oral cavity, P. indolicus and A. pyogenes occurred most frequently in samples from the teat skin, whereas isolates of B. melaninogenicus ss. levii were evenly distributed between conjunctiva and teat tip samples. A distinct seasonal pattern of the isolation rates of summer mastitis pathogens was recorded, which corresponded closely to the seasonal activity of symbovine insects, in particular the headfly Hydrotaea irritans (Fallén). However, the high proportion of clinically healthy bacterial carriers as compared with the incidence of clinical disease strongly suggests that as yet unknown contributing or triggering factors, apart from the mere presence of the relevant bacterial species, are required for the establishment and development of clinical summer mastitis.

Actinomycosis↗
PubMed1991

The effect of parasite control on fertility in beef heifers.

The effect of anthelmintic treatment on the growth and conception rate in beef heifers was studied in southwestern Virginia, USA. Forty mixed-breed heifers were divided into two groups at weaning and placed on experimental pastures. Control heifers did not receive anthelmintic treatment, while animals in the treatment group were given ivermectin (200 micrograms kg-1) at the time of allocation to groups in October and again in April the following year. Supplemental feed was provided throughout the winter to ensure adequate weight gains. In May, the heifers were exposed to bulls for natural breeding for a period of 6 weeks. Weight gains, fecal egg counts, serum pepsinogen levels and pasture larvae counts were monitored throughout the experiment. No difference in conception rate was observed between the two groups, although the cumulative weight gain was significantly greater in treated than non-treated animals. Serum pepsinogen levels and fecal egg counts were also generally lower in treated than non-treated heifers.

Animals↗
PubMed1990

Attempted transmission of Ehrlichia risticii, causative agent of Potomac horse fever, by the ticks, Dermacentor variabilis, Rhipicephalus sanguineus, Ixodes scapularis and Amblyomma americanum.

Dermacentor variabilis, Rhipicephalus sanguineus, Amblyomma americanum, and Ixodes scapularis ticks were investigated for their ability to transmit Potomac horse fever. Larval and nymphal ticks were exposed to Ehrlichia risticii by feeding on mice inoculated with the organism. Molted exposed ticks were then allowed to feed on susceptible ponies or mice. No evidence of transmission, either clinically or by detection of antibodies to E. risticii in mice or ponies, was observed for any tick species examined.

Animals↗
PubMed1989

Epidemiology of Potomac horse fever: an investigation into the possible role of non-equine mammals.

A serological study of antibodies to Ehrlichia risticii was carried out on 10 species of wild and domestic mammals found on or near 21 horse farms in an area of the USA in which Potomac horse fever is endemic. No antibodies were found in 133 peridomestic rodents (Norway rats and house mice), nor in 108 wild rodents (white-footed mice and meadow voles) captured on farms. Three of the six domestic animal species examined, cats, pigs and a goat, showed serological evidence of exposure to E risticii. Seropositive animals were detected on three of the 21 premises. The eight seropositive cats (of 48 cats tested) were on two farms, and the three seropositive pigs (of 14 tested) were all on one farm which lay some 3 km from where the one seropositive goat (of three tested) was found. None of the 79 dogs, 75 cattle and seven sheep tested had antibodies to E risticii. The significance of these findings is discussed in the light of current understanding of the transmission of Potomac horse fever and of the epidemiology of other related ehrlichial diseases.

Animals↗
PubMed1989

The effect of stocking rate and parasite control on the performance of replacement beef heifers on pasture.

This study was designed to compare the animal production per unit area and per animal at 3 different stocking rates in combination with two deworming programs. Due to drought conditions, fecal egg output, serum pepsinogen levels and herbage larval counts were low throughout the grazing season. The beneficial effects of the strategic deworming program were, however, indicated by lower fecal egg counts and serum pepsinogen levels in the treated groups during most of the grazing season. Differences in weight gain, favoring the treated groups, were also observed and a clear effect of stocking rate was demonstrated. The lowest stocking rate groups continuously had the lowest egg output and serum pepsinogen levels and the highest average weight gain per animal. The experiment also clearly showed that the production per unit area increased with an increase in stocking rate. The medium and high stocking rate groups had a production per unit area exceeding that of the conventional stocking rate group by 15 and 45%, respectively.

Animals↗
PubMed1989

Molecular epidemiology of antibiotic resistant Haemophilus influenzae isolated in Denmark 1981-87.

The molecular basis of antibiotic resistance was studied in 32 epidemiologically unrelated Danish clinical isolates of Haemophilus influenzae. Both non-encapsulated and capsulated type b strains were represented as well as four different biotypes. Plasmid DNA was found in 11 strains, all of which were antibiotic resistant. Antibiotic resistance was transferred to an Rd Haemophilus influenzae recipient from 5 of 6 prospective donors. Ampicillin and chloramphenicol resistance were linked markers while tetracycline resistance--when unselected--was lost in 18% of the transconjugants. Loss of Tcr was associated with loss of a plasmid DNA segment. Restriction enzyme profiles of plasmid DNA lead to the conclusion that the drug resistance plasmids are derivatives of a common, not too distant, ancestor. There is evidence of both clonal spread and horizontal transmission of related drug resistance plasmids in H. influenzae in Denmark.

Ampicillin Resistance↗
PubMed1988

Grazing pressure and acquisition of Ostertagia ostertagi in calves.

The effect of stocking rate on the acquisition of Ostertagia ostertagi infection and performance of yearling calves grazing a marshland area in the southwest of Jutland (Denmark) was examined. During the early part of the grazing season, when grass growth was high and pasture infectivity low, there was little stocking rate effect on performance. However, during the late part of the grazing season (characterized by poorer grass growth and high pasture infectivity) gains were significantly lower at high, compared with moderate stocking. At both stocking rates, the beneficial effect of moving animals to aftermath in mid-summer was significant, but was most pronounced at the high stocking rate. Interactions between stocking rate and acquisition of parasitism are discussed in the light of grazing behaviour and climatic factors.

Animals↗