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Biomedical subjects

N A Jorgensen

Publications and source records attributed to N A Jorgensen.

At least 37 records · Page 2Linked to original sources
PubMed1981

Concentration of calcium, phosphorus, and 1,25-dihydroxyvitamin D in plasma of dairy cows during the lactation cycle.

Concentrations of calcium, phosphorus, and 1,25-dihydroxyvitamin D in plasma of four young, four nonparetic aged, and four paretic aged cows were measured during the lactation cycle. Concentration of 1,25-dihydroxyvitamin D in plasma was elevated significantly in paretic aged cows as compared to nonparetic aged and young cows from the day of calving to 3 days postcalving. In paretic aged cows, severe hypocalcemia and hypophosphatemia developed on the day of calving, whereas hypocalcemia and hypophosphatemia were only transient in nonparetic aged and young cows at this time. Changes were only minor in concentration of 1,25-dihydroxyvitamin D in plasma from 7 days postcalving to 7 days precalving in all cows.

Aging↗
PubMed1980

Intake, digestibility, and rate of passage of silages and hays from wet fractionation of alfalfa.

Fibrous products of alfalfa from various steps of the wet fractionation process were either ensiled or dried artificially. Two 4 X 4 Latin square digestion trials for silages and hays were to determine the effect of cell maceration and pressure fractionation on characteristics and acceptability of these products by ruminants. Silage treatments consisted of field wilted, chopped, and ensiled; direct cut and cell macerated; direct cut, cell macerated, and pressed; and repressed silage. Dry matter intake averaged 971, 914, 796, and 763 g/day, respectively. Digestion coefficients were: dry matter 60.1, 56.0, 55.6, and 54.3; cell wall constituents 49.8, 49.4, 49.9, and 50.8 for the treatments. Hay treatments were processed in the same manner as were silages but artificially dried. Dry matter intake averaged 1021, 990, 1025, and 980 g/day; digestibility of cell wall constituents was 44.6, 46.5, 51.4 and 52.7%; total mean retention time was 31.5, 41.8, 45.8, and 46.6 h for the hay treatments. When the fibrous residues were handled as hay, digestibility of fiber components was increased by cell maceration and pressure fractionation, while intake was maintained.

Animal Feed↗
PubMed1979

25-Hydroxyvitamin D3 26,23-lactone: a new in vivo metabolite of vitamin D.

A major vitamin D metabolite was isolated in pure form from the blood plasma of chicks either maintenance levels or large doses of vitamin D3. The isolation involved methanol-chloroform extraction and five column chromatographic procedures. The metabolite purification and elution position on these columns were followed by a competitive protein binding assay. The metabolite was identified, using high- and low-resolution mass spectrometry, 270-MHz proton nuclear magnetic resonance spectrometry, ultraviolet absorption spectrophotometry, Fourier transform infrared spectrophotometry, and specific chemical reactions, as 3 beta,-25-dihydroxy-9,10-seco-5,7,10(19)-cholestatrieno-26,23-lactone. The trivial names 25-hydroxyvitamin D3 26,23-lactone or calcidiol 26,23-lactone are suggested for this compound.

Animals↗
PubMed1979

Potential use of 1,25-dihydroxycholecalciferol for prevention of parturient paresis.

Twelve cows, at least third parity, were assigned randomly to either a control or treatment group. Treated cows received .4 mg of the vitamin D metabolite, 1,25-dihydroxycholecalciferol intramusculary in 5 ml corn oil. Intramuscular injections were started 5 days before predicted calving with reinjections every 5 days until calving. Incidence of parturient paresis was 0 and 33% (2 of 6) in the treated and control groups. Response to treatment was rapid with elevated calcium in serum approximately 12 h postinjection. Treatment maintained or elevated calcium and phosphorus concentrations in serum during the critical period, 24 h pre- to 48 h postpartum, when milk fever is most likely to occur. There was, however, no significant difference between treatments at 72 h postpartum. Based on these observations 1,25-dihydroxycholecalciferol holds promise as a preventative of parturient paresis; however, further studies are needed on application and safety.

Animals↗
PubMed1978

25-hydroxycholecalciferol for prevention of "milk fever" in dairy cows.

Intramuscular injections of 4 or 8 mg 25-hydroxycholecalciferol (25-OH D3) in 5 ml corn oil given three days before the predicted calving date and repeated at weekly intervals until calving effectively reduced the incidence of parturient paresis. Drug efficacy was improved in cows receiving low to normal recommended levels of dietary phosphorus prepartum. With proper management techniques, 25-OH D3 could prevent parturient paresis in dairy cattle.

Animals↗
PubMed1977

Adequate response of plasma 1,25-dihydroxyvitamin D to parturition in paretic (milk fever) dairy cows.

The concentration of 1,25-dihydroxyvitamin D was measured by means of a radioactive receptor assay in the plasma of cows during the period immediately prior to, during, and following parturition. Nonparetic cows showed initially a slight decrease in plasma 1,25-dihydroxyvitamin D which was followed by a significant increase during parturition and 2 days postpartum. The highest concentration achieved in the control or nonparetic cows was 100 picograms per milliliter. In the paretic animals the plasma 1,25-dihydroxyvitamin D concentration increased sharply during the day preceding calving and reached a maximum of 200 picograms per milliliter at parturition. This level was maintained during the ensuing 2.5 days. These results demonstrate that parturient paresis cannot be the result of insufficient synthesis or secretion of 1,25-dihydroxyvitamin D.

Animals↗
PubMed1977

Efficacy and safety of 1alpha-hydroxyvitamin D3 for prevention of parturient paresis.

Four trials involved intravenous or intramuscular injections of 1alpha-hydroxyvitavin D3 to test efficacy in preventing parturient paresis. Use of .1 mg intravenously afforded total protection compared with an incidence of 33% (2/6) in controls. Intramuscular injections of .1 mg in 2 ml propylene glycol and .3, .5, and 1.0 mg in 5 ml corn oil resulted in 0, 15.7, 20, and 0% incidence of parturient paresis compared with 33, 16.7, 37.5, and 37.5% incidence of parturient paresis in the controls. There was a rapid increase in serum calcium (12 to 24 h) in response to intravenous treatment, whereas the response to intramuscular injections was gradual but was maintained longer. To evaluate the safety of 1alpha-hydroxyvitamin D3, eight cows, two per treatment, were given intramuscular doses of .5, 1.0, 1.5, or 3.0 mg (three 1.0 mg injections) in 5 ml corn oil. No clinical or pathological evidence of hypervitaminosis C or soft tissue calcification was found. Tissue taken from the injection site 15 days after last injection contained 3 to 38 IU vitamin D activity per 100 g wet tissue compared with control of 8 to 15 IU per 100 g. Total vitamin D activity of milk taken the 11th milking postpartum from cows receiving .5 or 1.0 mg had a mean of 13.4 and 22.6 IU vitamin D activity per liter compared to 19 IU per liter for control milk. Milk from the 5th milking postpartum in the cows receiving .5 mg had a mean activity of 14.5 IU per liter. Milk from animals slaughtered for retention studies had a mean activity of 22 IU per liter.

Animals↗
PubMed1976

Calcium redistribution into subcutaneous fat at parturition in the dairy cow.

Blood samples and subcutaneous fat biopsies from six dairy cows at -14, 0, 14, and 28 days of parturition were analyzed to test the hypothesis that movement of calcium into subcutaneous fat contributes to hypocalcemia of parturient paresis. Plasma and subcutaneous fat calcium decreased while plasma free fatty acids increased at parturition. No trends were significant in magnesium or total lipid content of subcutaneous fat. Calcium content of subcutaneous fat was related positively to calcium concentration in plasma.

Adipose Tissue↗