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Biomedical subjects

M O Nielsen

Publications and source records attributed to M O Nielsen.

At least 19 recordsLinked to original sources
PubMed2005

Changes in freezing point of blood and milk during dehydration and rehydration in lactating cows.

We studied the influence of short-term changes in water intake in 4 lactating Holstein cows on diurnal fluctuation of packed cell volume (PCV), freezing point of blood (FPblood), freezing point of milk (FPmilk), and the relationship between changes in FPblood and FPmilk. The experiment lasted 108 h and was divided into 3 periods: 1) control (38 h); 2) dehydration/rehydration with 4 consecutive 12-h sequences: 8 h without water, 0.5-h access to water, 1.5 h without water, and 2-h access to water; and (3) 22 h for reconstitution. Cows were milked at 12-h intervals. Blood was sampled from the jugular vein hourly throughout the experiment, and at 0, 15, 30, 60, 90, 120, 150, 180, 210, and 240 min after initiated rehydration following the 8-h dehydration sequences. Intakes of free water and water in feed were recorded every hour. The PCV was negatively affected by water intake within the hour before sampling. Dehydration lowered FPblood steadily, whereas FPblood increased by 0.024 degrees C within 30 min following a large water intake in the rehydration period. The FPblood was not significantly influenced by actual water intake, but was highly correlated with the available water pool at time of blood sampling. The FPmilk correlated positively with the FPblood collected 1 h before milk sampling, indicating a delay in the transfer of water from plasma to milk. In summary, FPblood and FPmilk decrease during dehydration and increase during rehydration. Rehydration following a long dehydration period caused an increase in FPmilk within 1 h, but not above the initial level for FPmilk of the cow.

Animals↗
PubMed2005

The effects of dry period versus continuous lactation on metabolic status and performance in periparturient cows.

It has been argued that dairy cows with a high genetic milk production potential can maintain high milk production even with total omission of the dry period. Further, when omitting the dry period, cows are believed to experience fewer metabolic changes during the transition from late gestation to early lactation compared with cows having a traditional dry period. The performance and metabolic response to omission of the dry period for cows with an expected peak milk yield higher than 45 kg/d were studied in 28 Holstein dairy cows. The cows were followed in late gestation and in the subsequent 5 wk of early lactation. Fourteen cows were milked through late gestation (CM) and another 14 dairy cows underwent a 7-wk dry period (DRY). In the early lactation period, the cows had the same dry matter (DM) intake but cows in the CM group had a 22% reduction in milk yield compared with the cows in the DRY group. At calving, the experimental groups had the same average body weight and body condition score and there were no significant differences in body weight and body condition score changes in early lactation. However, the cows in the CM group compared with the cows in the DRY group had a higher plasma concentration of glucose and insulin and a lower plasma concentration of nonesterified fatty acids and beta-hydroxybutyrate in the following 5 wk of early lactation. Furthermore, the cows in the CM group had lower liver triacylglycerol concentration and higher liver glycogen concentration in the following early lactation. It is concluded that, even in dairy cows with an expected peak milk yield above 45 kg/d, omission of the dry period results in a relatively high reduction in milk yield in the following early lactation. Furthermore, these cows are in less metabolic imbalance in the following early lactation.

3-Hydroxybutyric Acid↗
PubMed2004

Mammary uptake and excretion of prostanoids in relation to mammary blood flow and milk yield during pregnancy-lactation and somatotropin treatment in dairy goats.

Mammary arterious-venous differences (A-V) and excretion into milk of four prostanoids were related to changes in milk yield and milk vein blood velocity (MBV) in goats at different stages of pregnancy and lactation, and during somatotropin (ST) treatment in mid-lactation. Arterial concentrations and mammary A-V for the vasodilators prostacyclin (PGI(2)) and prostaglandin (PG) E(2) (measured as 6-keto-PGF(1 alpha) and bicyclic PGE(2), respectively) decreased from late pregnancy to lactation. A-V were negatively correlated to MBV (r = -0.32 to -0.34). Arterial concentrations of the vasoconstrictors PGF(2 alpha) and TXA(2) (measured as TXB(2)) changed similarly, but no A-V across the mammary gland were found. The vasodilator to vasoconstrictor ratio in plasma was around 1:1, and in skimmed milk around 0.29-0.49 due to significantly higher TXB(2) levels in milk compared to plasma. Close linear correlations were established between milk yield and excretion of TXB(2) into milk (r = 0.80, P < 0.001), and between MBV and PGE(2) excretion into milk (r = 0.69, P < 0.001). ST treatment stimulated MBV and mammary prostanoid supply, and decreased prostanoid concentration in milk vein plasma. The high arterial levels of prostaglandins during pregnancy most likely reflected uterine synthesis. Our results support a role for PGI(2) and PGE(2) in local mammary blood flow regulation during lactation. Increased mammary uptake of these two prostanoids may be involved in the mammary blood flow response to ST. TXA(2) may be synthesized by mammary epithelial as well as vascular cells, and TXA(2) may be an important factor in regulation of mammary function.

Animals↗
PubMed2003

Leukocytes from heifers at different ages express insulin and insulin-like growth factor-1 (IGF-1) receptors.

The objectives of this study were to investigate if insulin receptors (IR) and insulin-like growth factor-1 receptors (IGF-1R) could be detected on bovine leukocytes using fluorescence antibodies and flowcytometry, and use this method to investigate whether the amount of receptors differed among heifers at different ages. Twenty Danish Holstein heifers in the following three age groups were included in the investigation: (1) heifers aged 25-45 days (n = 8), (2) heifers aged 185-205 days (n = 7), and (3) heifers aged 780-900 days (approximately one month prepartum; n = 5). Antibodies against human IR and IGF-1R were used for indirect immunofluorescence staining of cells, and were found to cross-react with the bovine receptors. IR were found on lymphocytes, monocytes, and neutrophils in all animals, while IGF-1R were found only on monocytes and neutrophils. The percentage of IR+ lymphocytes was almost doubled from stage 1 to 3 (34% versus 57%) and IR expression on lymphocytes and monocytes increased significantly (P<0.01) from 6.80 and 13.60 to 8.24 and 17.50 in heifers aged 185-205 days and heifers aged 780-900 days, respectively. No differences were observed for neutrophil IR or IGF-1R expression. In conclusion, surface IR and IGF-1R can be detected on bovine leukocytes by flowcytometry. Interestingly, the highest numbers of IR were found in heifers one month prepartum. The regulation of IR and IGF-1R expression on bovine leukocytes, and their role in host immunity, needs further investigation.

Aging↗
PubMed2002

Effect of energy density in the diet and milking frequency on hepatic long chain fatty acid oxidation in early lactating dairy cows.

The objective of this study was to examine the effects of diet energy density (high versus low) and increased milk yield, induced by increased milking frequency (two versus three times daily), on the hepatic status of triacylglycerol (TAG) and glycogen content and hepatic long chain fatty acid (LCFA) oxidation capacity in early lactation in a 2 x 2 factorial design. Forty multiparous Danish-Holstein dairy cows were used from 8 weeks before to 8 weeks after calving. Liver biopsies and blood samples were taken in weeks -2, 2, and 7 from calving. The cows fed the high energy density diet, compared with the cows fed the low energy density diet, had an 18 and 28% higher milk production and net energy intake, respectively. Milk yield was increased by 10% when the cows were milked three times compared with twice daily. Complete (CO2 production) and incomplete (ketone body production) LCFA oxidation capacity in the liver were 35 and 32% higher, respectively, and liver TAG content was 48% lower for the cows fed the high energy density diet compared with the low energy density diet. Overall there was no effect of milking frequency on liver parameters. However, a significant interaction between diet and milking frequency showed that the cows milked three times daily and fed the low energy density diet had the lowest liver LCFA oxidation (CO2 and ketone body) capacity. Furthermore, these cows had the numerically highest liver TAG content. The results for liver LCFA metabolism are discussed in relation to the plasma concentration of metabolites and insulin. In conclusion, cows in early lactation given a high energy density diet will, in general, have a lower risk of high TAG infiltration in the liver.

Animals↗
PubMed2002

Effects of hyperinsulinaemia under euglycaemic condition on liver fat metabolism in dairy cows in early and mid-lactation.

The objective was to examine the effects of insulin under euglycaemic conditions on liver long chain fatty acids (LCFA) metabolism with special focus on the aetiology of hepatic lipidosis in early lactation. A 4-day hyperinsulinaemic-euglycaemic clamp (clamp) was conducted on four dairy cows starting in weeks 4 and 17 postpartum. Insulin was infused continuously (1 microg/kg BW per h) and a 50% glucose solution was infused to maintain euglycaemia. Liver biopsies were taken 6 days before, the last day of, and 5 days after the clamp, and blood samples were taken in the same period. In the liver tissue, the relative triglyceride content decreased (P < 0.01) and the glycogen content increased (P < 0.0001) in response to the clamp. Hepatic in vitro palmitate oxidation capacity was lowest during the clamp period and could be explained by a significant decrease in incomplete oxidation (ketogenesis) (P < 0.04) and a tendency to a decreased complete oxidation of palmitate (P < 0.10). Plasma non-esterified fatty acids concentration was decreased during the clamp in early lactation (P < 0.05) but there was no effect on the mid-lactation clamp. The present study shows that increased insulin under euglycaemic conditions seems to depress hepatic LCFA oxidation capacity. However, in terms of preventing hepatic lipidosis, the anti-lipolytic effect of insulin on adipose tissue, which results in decreased mobilization of and hence hepatic load with LCFA, appears more important.

Animals↗
PubMed2001

Regulation of mammary glucose uptake in goats: role of mammary gland supply, insulin, IGF-1 and synthetic capacity.

Variations in mammary glucose uptake were measured during the normal pregnancy-lactation cycle in dairy goats. In addition mammary glucose uptake was studied in response to somatotropin (ST) treatment in mid-lactation and acute increases in glucose concentration induced by sodium-propionate challenge in early lactation. Mammary glucose uptake was independent of arterial glucose, insulin and Insulin-like Growth Factor-1 (IGF-1) concentrations during lactation and during acute increases in arterial glucose concentration. Glucose uptake in the lactating mammary gland of the goat must therefore be carried out by an insulin-independent carrier, possible GLUT1, and glucose supply is not a limiting factor for uptake under in vivo conditions. Extraction of glucose uptake changed markedly during the normal course of lactation, following the overall changes in milk yield. Concentrations of glucose in skimmed milk, believed to reflect intracellular glucose concentration, changed in opposite directions, resulting in decreasing ratios of arterial: skimmed milk glucose concentration with progressing lactation. Thus, mammary synthetic capacity also involves a capacity for glucose uptake, which may be influenced by variations in glucose carrier numbers, as well as mammary metabolic activity (intracellular glucose concentration). In contrast to the situation during the normal course of lactation, ST stimulated milk yield, despite less efficient glucose extraction.

Animals↗
PubMed1999

Responses to potential vasoactive substances of isolated mammary blood vessels from lactating sows.

The purpose of the investigation was to examine the response of the milk vein and the mammary artery to potential vasoactive substances in lactating sows. The response on artery and vein segments from the same sow was measured for the following substances: noradrenaline (NA), serotonin (5-HT), prostaglandin F2alpha (PGF2alpha), prostacyclin (PGI2), histamine (Hi) and potassium (K+). Interestingly, the contractile force in the mammary vein segments expressed per weight unit (mN/mg) was 1.5-2.5 fold larger than in the artery segments when NA, 5-HT and PGF2alpha were used, but similar for K+, Hi and PGI2. In vein segments, the order of sensitivity to the substances expressed by their pD2 values was 5-HT > NA = PGF2alpha > Hi > K+. The present findings suggest that NA, 5-HT, PGF2alpha, PGI2, and Hi are involved in mammary blood flow regulation in the sow, and the mammary venous system may be as important as the mammary arterial system in this regulation.

Adenosine↗
PubMed1995

The local differential effect of prostacyclin, prostaglandin E2 and prostaglandin F2 alpha on mammary blood flow of lactating goats.

Mammary blood flow (MBF) and milk yield are closely related in dairy ruminants, but little is known about the regulation of MBF in vivo. The local effects on MBF of injections or continuous infusions into the mammary artery of prostaglandins (PG) or indomethacin (an inhibitor of prostaglandins) respectively, were investigated in surgically prepared conscious goats. Prostacyclin (PGI2) was found to be a potent stimulator of MBF which increased linearly over the dose range 50-1000 ng. PGE2 was almost as potent as PGI2 at low doses, but tachyphylaxis occurred at doses at and above 100 ng. The response to repeated injections of PGE2 quickly declined depending on the dose. PGF2 alpha had no effect on MBF. During infusion of indomethacin into the mammary artery MBF was reduced markedly, showing that endogenous mammary prostaglandins are involved in the regulation of vasodilatation. The results indicate that PGI2 (and to a lesser extent PGE2) has an important role in the local regulation of vascular tone in the mammary gland.

Animals↗
PubMed1994

[Alternatives to acute admissions to a city hospital. Is it possible to reduce the number of acute admissions?].

The purpose of the study was to evaluate the number of inappropriate admissions to a smaller city hospital and find possible alternatives. Physicians and surgeons from three units (abdominal surgery, internal medicine and orthopaedic surgery) together with general practitioners, doctors on homecall duty and health personnel from the region contributed to the study. In all 421 consecutive patients were included during a three-week period. The patients' median age was 60.5 years. It was found that at least 13.6% of all patients seemed to have been admitted for an inappropriate reason. According to the admitting doctor 3.4% of the patients were not ill at all. The investigation implies that one out of seven acute admissions could be replaced by alternatives such as immediate care in residential homes, more flexible contact to the outpatient's clinic, better access to geriatric evaluation and improved laboratory service. We conclude that acute admission to hospital can be replaced by other alternatives, thereby achieving greater efficiency and better economics.

Adult↗
PubMed1994

Changes in mammary uptake of free fatty acids, triglyceride, cholesterol and phospholipid in relation to milk synthesis during lactation in goats.

Uptake of free fatty acids (FFA), triglycerides (TG), cholesterol (CHOL) and phospholipids (PL) was measured in both mammary glands of dairy goats during lactation. Arterial concentrations of TG, CHOL and PL as well as arterio-venous difference (AV) and extraction rate (E) for TG were highest in goats with the highest dietary feed intake. AV were linearly related to arterial concentrations for the four lipid classes, and arterial concentrations of CHOL were linearly related to output of lactose, protein and fat in milk. Arterial supply, and not mammary synthetic activity, is the main determinant of mammary FFA, TG and CHOL uptake.

Animals↗
PubMed1994

Studies on responses to potassium, noradrenaline, serotonin, histamine and prostaglandin F2 alpha, of isolated pudendal arteries from non-lactating goats.

The effects of potassium (K+), noradrenaline (NA), serotonin (5-HR), histamine (Hi) and prostaglandin F2 alpha (PGF2 alpha) were studied on isolated pudendal arteries from non-lactating goats. K+, NA, 5-HT, Hi and PGF2 alpha had concentration-dependent contractile effects on the arteries. The developed tensions were, in order of potencies, 5-HT > NA > PGF2 alpha > Hi > K+. NA induced a significantly higher maximal contractile force than K+, 5-HT, PGF2 alpha and Hi. Pretreatment with cocaine was without significant effect on the contractile response to NA. The contractile response to Hi was totally eliminated by mepyramine. Ca2+ had a concentration-dependent contractile effect on arteries depolarized by 125 mM K+. The results indicate that NA, 5-HT and PGF2 alpha may play essential roles in the regulation of goat mammary blood flow. The response to K+ is highly dependent on extracellular Ca2+. The contractile response to histamine may be mediated via H1-receptors. The in vitro method used is well suited to study the vascular reactivity in different regions of the mammary vascular bed.

Animals↗
PubMed1993

Changes in mammary glucose and protein uptake in relation to milk synthesis during lactation in high- and low-yielding goats.

1. Glucose and protein uptake were measured in both mammary glands of two low- and two high-yielding dairy goats during lactation. 2. Low-yielding goats tended to have higher arterial glucose concentrations, but approximately 40% lower arterio-venous differences (AV) and extraction rates (E) for glucose than high-yielding goats. 3. AV and E for glucose (but not protein) were linearly related to yields of both lactose, milk protein and fat. 4. Mammary uptake of glucose is determined primarily by mammary glucose metabolism, not glucose supply; lower intracellular glucose concentration in mammary cells of genetically superior animals thus explains the more efficient mammary uptake.

Animals↗
PubMed1990

Changes in mammary blood flow during the lactation period in goats measured by the ultrasound Doppler principle.

1. Mammary blood flow was measured during the lactation period in two low- and two high-yielding dairy goats (peak milk yields approx. 1.5 and 3.6 kg/day respectively), using the ultrasound Doppler principle for determination of blood velocity in both milk veins (subcutaneous abdominal veins) of the animals, and ultrasound scanning for measurement of cross-sectional area of the veins. 2. Milk vein cross-sectional area ranged from 0.11 to 0.38 cm2 in the four goats, with a close to significant (P = 0.06) difference between the veins in the two sides of the animals. Cross-sectional area remained constant during the lactation period. Changes in mammary blood flow was therefore caused by changes in blood velocity. 3. Milk vein blood velocities ranged from 4.4 to 34.7 cm/sec independently of the time of the day, and were of the same magnitude in the two sides of the animals. Except in one goat (P = 0.1), blood velocity decreased significantly (P less than 0.01) with progressing lactation, during which period also milk yield was declining. 4. In the two low-yielding goats, a positive linear relationship (R2 = 0.20) was found between milk yield and milk vein blood velocity, whereas a diminishing exponential relationship (R2 = 0.97) was found in the two high-yielding goats. At a given milk vein blood velocity, high-yielding goats obtained a higher milk yield and also responded to changes in blood velocity (up to approx. 15 cm/sec) with greater increases in milk yield than low-yielding goats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Insulin-like growth factor I (somatomedin C) in goats during normal lactation and in response to somatotropin treatment.

1. Two experiments were performed. In Experiment 1, IGF-I concentrations in serum were followed in four lactating dairy goats during normal lactation and before, during and after 14 days of daily administration of 10 IU recombinant bovine somatotropin, starting 10 weeks post-partum. In Experiment 2, IGF-I was measured in single blood samples obtained from 40 dairy goats in the first part of lactation. 2. Measured IGF-I concentrations ranged from 4.4-9.0 nM. Concentrations varied during the day with coefficients of variation from 8.9 to 18.4% in the four goats in Experiment 1. There were no systematic trends in the diurnal variations (P greater than 0.75). 3. Concentrations of IGF-I remained fairly constant in all goats in Experiment 1 during the lactational period, and were not related to the changes in milk yield (P greater than 0.65). Similarly, no relationship was found in Experiment 2 between level of milk production and IGF-I concentration in serum. 4. Somatotropin treatment stimulated milk yields by 14 +/- 2.9% (P less than 0.05) and IGF-I concentration by 27.9 +/- 6.7% (P less than 0.05). 5. IGF-I is the most likely factor which increases mammary gland synthetic capacity in response to somatotropin treatment, and thus is responsible for the galactopoietic effect of this hormone being exerted. 6. However, serum IGF-I may primarily be involved in regulation of nutrient partitioning during normal lactation, but a paracrine synthesis with local effect on the mammary gland cannot be ruled out.

Animals↗