Dietary intakes of polyunsaturated fatty acids and indices of oxidative stress in human volunteers.

OBJECTIVE: To assess whether nutritionally-relevant changes in polyunsaturated fatty acid (PUFA) intake alter indices of oxidative stress in human volunteers DESIGN: A split plot/change over dietary study where half the volunteers consumed a diet containing 5% PUFA (low PUFA) as food energy for 4 weeks and after a 6 week washout period consumed a 15% PUFA (high PUFA) diet for another 4 weeks. The second group of volunteers completed this protocol in reverse. Total fat, carbohydrate, protein and vitamin E contents of the diets were constant. SUBJECTS: 10 healthy, non-smoking, male volunteers aged 32.6 +/- 1.7 y RESULTS: There was a significant increase in whole blood oxidised glutathione (P < 0.05), an index of oxidative stress, after consumption of the high PUFA diet. Moreover, urinary thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation, significantly increased (P = 0.038) following consumption of the high PUFA diet and decreased (P = 0.031) after consuming the low PUFA diet. However, there was no change in non specific plasma indices of lipid peroxidation, conjugated dienes and TBARS, nor in red cell antioxidant enzymes glutathione peroxidase, glutathione reductase, and catalase. However, superoxide dismutase significantly decreased (13%, P=0.018) after consumption of the low PUFA diet. Total cholesterol increased by 13% (P=0.014) after consumption of the low PUFA diet. CONCLUSIONS: This study indicates that although increasing dietary levels of PUFA may favourably alter cholesterol profiles, the same dietary changes may adversely affect some indices of lipid peroxidation. Care should be taken when providing dietary advice on PUFA intake and an adequate intake of antioxidants to match any increased PUFA may be important for preventing oxidative stress.

Comparison of weight and height relations in boys from 4 countries.

Height and weight data from children in the United States, United Kingdom, Japan, and Singapore were analyzed to investigate differences in growth between the groups of children. An investigation into the adjusted weight indexes of the form index = weight/heightp for differing powers of p (Benn index) showed that the power of p required to produce a correlation of zero between the index and height varied with age. For the United States, Japan, and Singapore the p value was just below 3.0 for children aged 6 y, increased to approximately 3.5 for children aged approximately 10 y, and decreased to approximately 2.0 at age approximately 18 y. A consequence of the p value being mostly >2.0 is that BMI (wt/ht2) tends to be greater for tall children than for short children. The US data (from the second National Health and Nutrition Examination Survey) also contained information on skinfold thickness. Relating skinfold thickness to indexes of the same form for height and weight suggested that the best relation was achieved with p values of approximately 2.0 except for children aged 12-16 y, for whom the optimal values for p were higher. The highest value, 2.9, was achieved at ages 12-13 y. Overall, the use of BMI as an indicator of adiposity appears acceptable for children aged 6-7 and 17-18 y. However, BMI should be used with caution when assessing children aged 8-16 y.

Description and evaluation of an experimental model to examine changes in selection between high-protein, high-carbohydrate and high-fat foods in humans.

OBJECTIVE: To develop and test an experimental model designed to detect changes in selection between foods individually enriched in protein, carbohydrate and fat in human subjects. DESIGN: Randomised counterbalanced (Latin square) design. SETTING: The metabolic suite at the Rowett Research Institute's Human Nutrition Unit. SUBJECTS: 16 normal-weight men (mean BMI = 23.5). INTERVENTIONS: Subjects were each studied 4 times in a 2-day protocol. On day 1 subjects received a fixed maintenance diet; on day 2 they received a mandatory intake as breakfast (08.30) plus a drink at 10.30. This comprised 80% of resting energy requirements as high-protein (HP), high-carbohydrate (HC) or high-fat (HF) foods (60% of energy in each case) or an equal mixture (M) of macronutrients, 33% by energy. All mandatory treatments contained the same energy content and density. From 12.30 onwards, subjects had ad libitum access to a counter-balanced selection of three groups of familiar foods (10 HP, 10 HC and 10 HF; 30 foods in total). Most energy in each food was derived from one macronutrient (approximately 60%), the remainder being equally split between the other two macronutrients. RESULTS: Subjects were significantly less hungry before lunch on the HP and M (33% protein) treatments (F3.44 = 7.35; P < 0.001). At lunch, they ate more energy after the HF treatment than after any of the other treatment (F1,38 = 9.00; P = 0.005). This was largely in the form of fat and protein, and to a lesser extent carbohydrate. Subsequent energy intake (EI) were lower on the HF treatment, largely through selection of less fat in the afternoon (F1.42 = 6.90; P=0.012). Daily EIs were similar across treatments. CONCLUSION: This design appears sensitive meal-to-meal to changes in both nutrient and EIs.

Free-living energy expenditure of adult men assessed by continuous heart-rate monitoring and doubly-labelled water.

Free-living energy expenditure was estimated by doubly-labelled water (DLW) and continuous heart-rate (HR) monitoring over nine consecutive days in nine healthy men with sedentary occupations but different levels of leisure-time physical activity. Individual calibrations of the HR-energy expenditure (EE) relationship were obtained for each subject using 30 min average values of HR and EE obtained during 24 h whole-body calorimetry with a defined exercise protocol, and additional data points for individual leisure activities measured with an Oxylog portable O2 consumption meter. The HR data were processed to remove spurious values and insert missing data before the calculation of EE from second-order polynomial equations relating EE to HR. After data processing, the HR-derived EE for this group of subjects was on average 0.8 (SEM 0.6) MJ/d, or 6.0 (SEM 4.2) % higher than that estimated by DLW. The diary-respirometer method, used over the same 9 d, gave values which were 1.9 (SEM 0.7) MJ/d, or -12.1 (SEM 4.0) % lower than the DLW method. The results suggest that HR monitoring can provide a better estimate of 24 h EE of groups than the diary-respirometer method, but show that both methods can introduce errors of 20% or more in individuals.

Effect of frequency of follicle aspiration on oocyte yield and subsequent superovulatory response in cattle.

The effect of frequency of transvaginal follicular aspiration on oocyte yield and subsequent superovulatory response was studied in 2 experiments. In Experiment 1, 32 primiparous Hereford x Friesian cows were assigned to 4 treatments (n = 8 per treatment). Oocyte recovery was carried out once a week for 12, 8, 4 or 0 (control) wk. Embryo recovery for all animals was 7 wk after the completion of the aspiration schedules. In Experiment 2, the effects of oocyte recovery once or twice a week (n = 8 per treatment; control n = 18) for 12 wk and response to superovulation 4 wk after the last aspiration were compared using nulliparous purebred Simmental heifers. Increasing the period of once weekly aspirations from 4 to 12 wk (Experiment 1) did not affect the number of follicles observed per session (mean +/- SEM; 10.0 +/- 0.82) or aspirated (7.8 +/- 0.71), but the recovery rate of oocytes from follicles aspirated was greater for donors aspirated for either 4 or 8 wk than for 12 wk (32.3 +/- 3.73 vs 28.4 +/- 2.61 vs 20.1 +/- 2.13 %; P < 0.05). Following the last aspiration and prior to commencing superovulatory procedures, estrus or estrous activity was observed in 7 8 , 8 8 , 7 8 and 6 8 of the animals aspirated over 12, 8, 4 or 0 wk, respectively. Subsequent superovulatory responses and in vivo embryo recoveries were similar for all aspiration treatments and for control animals. Changing the frequency of oocyte recovery from once to twice weekly (Experiment 2) did not affect the numbers of follicles observed (9.1 +/- 0.63 vs 8.3 +/- 0.85), follicles aspirated (5.9 +/- 0.56 vs 6.2 +/- 0.69), oocytes recovered (1.7 +/- 0.27 vs 1.9 +/- 2.0) per session or the oocyte recovery rate (29.4 +/- 2.4 vs 30.4 +/- 2.4 %); nor was there any effect of frequency of aspiration on subsequent superovulatory response and embryo recovery. In conclusion, increasing the period of aspiration from 4 to 12 wk and the frequency from once to twice a week over 12 wk did not reduce the number of follicles observed or aspirated, or number of oocytes recovered per donor per session. Subsequent estrous cyclicity and responses to superovulation were unaffected by the periods or frequencies of oocyte recovery examined here.

Evidence for the utilization of peptides for milk protein synthesis in the lactating dairy goat in vivo.

Precursors for milk protein synthesis have been examined in lactating dairy goats using arteriovenous difference and isotope kinetic techniques. Certain amino acids, such as phenylalanine and histidine, are taken up by the mammary gland in quantities that are insufficient to account for their output in milk protein. Some amino acids have been shown to be present in significant quantities (10-30% of total non-protein-bound amino acids) as peptides (< 1,500 Da) in the arterial supply to the mammary gland, although methodological considerations make it difficult to accurately assess the extent of their uptake across the tissue bed. Indirect evidence for the utilization of peptides for milk protein synthesis in vivo has been obtained, however, by examination of the kinetics of milk casein labeling during long-term (24 h) systemic infusion of [1-13C]phenylalanine and [1-13C]leucine. Comparison of plateau enrichments for blood, plasma, and casein indicate that, although, for leucine, the plasma free pool seems to provide all the leucine for milk protein synthesis, sources other than the labeled plasma free amino acids contribute phenylalanine (10-20%) for casein biosynthesis. These findings raise questions relating to the type and source of amino acid precursors used by tissues for protein synthesis.

Salt intake and blood pressure in rural and metropolitan Mexico.

A selected group of 155 Mexican adults aged 20-64 years were studied to investigate the role of sodium (Na) intake in explaining blood pressure (BP) differences in a rural town and urban Mexico City. The subjects had their BP, height, weight and skinfolds measured and they collected 3 continuous 24 h urines. Adjusted for age differences, average BPs were significantly higher (p < .05) for the urban (112.7 systolic: 73.6 diastolic mmHg) than for the rural group (108.4 systolic: 70.8 diastolic mmHg). They were also higher for men (111.8 systolic: 74.3 diastolic mmHg) than for women (109.6 systolic: 70.2 diastolic mmHg), the diastolic BP difference being significant (p < 0.05). The average daily Na excretion was also higher in the urban (122.2 mmol/day) than in the rural community (98.0 mmol/day) (p < 0.01). Potassium excretion rates showed similar differences. The differences in sodium excretion and blood pressure among communities were particularly marked in those over 30 years of age. The means for the four community-sex groups had the same rank order for both BP and Na. However, although some large surveys have suggested that half the observed differences in BP might be explained by different Na intakes, in this study the relationship between Na excretion and BP did not achieve statistical significance. Differences in the body mass index (BMI) accounted for 41% of the observed variance in BP.

Validation of the doubly labeled water method in growing pigs.

The CO2 production (rCO2) of eight growing pigs was determined by continuous collection of CO2 over 21 days and simultaneously estimated using the doubly labeled water (DLW) method. The aim was to assess the accuracy of the method before and after correction for known sources of error and to test for any residual discrepancy arising from as yet unidentified sources of error. Mass spectrometer accuracy was verified by analyzing serial dilutions of the dose material in the form of an artificial decay curve; no significant bias was detected. The physiological errors were linearly dependent on weight gain. DLW-derived rCO2 (corrected only for fractionated water loss) underestimated the true value by 0.270 l CO2/g wt gain or -8% in the restricted (group R) and -16% in the ad libitum-fed (group AL) groups. Known sources of error accounted for -0.006 (methane), -0.032 (fecal 2H losses), -0.108 (fat synthesis), and -0.146 (changing pool size) l CO2/g wt gain. After correction for these sources of error the DLW-derived rCO2 differed from the true value by -2 +/- 3% in group R and 0 +/- 3% in group AL. Thus there was no significant bias in the DLW method after correction for known sources of error, even during rapid weight gain or at weight stability with or without correction. The precision estimates include both dose and background errors and uncertainty in the correction factors used. Strategies for optimizing precision are presented.

Vitamin E and coronary heart disease: the European paradox.

OBJECTIVE: To relate premature mortality from coronary heart disease (CHD) to national food and nutrient supplies. DESIGN: Descriptive correlational study. SETTING: Nineteen western European and five non-European countries. METHODS: Premature mortality from CHD in men below 65 years was related to recalculated Food and Agriculture Organization (FAO) food, antioxidant vitamins and other nutrient supply data in 24 developed countries for 1985-87. Longitudinal analyses of death rates from CHD and supplies between 1970 and 1987 were carried out for all the countries. Correlational analyses of supplies that preceded mortality by up to 10 years were also undertaken. RESULTS: In 17 western European countries the inter-country association of dairy product supply with CHD was of moderate strength (r = 0.5) and the principal saturated fatty acids derived from dairy products: butyric, caproic and myristic acids (C4:0, C6:0 and C14:0) were the most strongly related with CHD (r = 0.5, 0.5 and 0.4 respectively). The phenolic-antioxidant-rich foods, e.g. wine, vegetables and vegetable oils, were inversely related to CHD (r = -0.8, -0.7 and -0.6 respectively). Of the antioxidant vitamins, the alpha-tocopherol component of vitamin E was strongly related to CHD across Europe (r = -0.8). The major determinant of alpha-tocopherol supply was usually sunflowerseed oil. Vitamin C and beta-carotene gave moderate correlations (r = -0.6 and -0.5 respectively). Latency periods of 5 and 10 years between supplies and mortality rates did not markedly change the correlations. Longitudinal analyses of nutrient supplies and death rates within each country from 1970 to 1987 also showed that for the majority of countries there was an inverse association between supply of alpha-tocopherol and CHD. CONCLUSIONS: Dietary alpha-tocopherol may provide at least as good an explanation as does wine for the paradoxically low rates of CHD in several European countries which have a relatively high saturated fatty acid intake.

CNS monoamine cell groups projecting to pancreatic vagal motor neurons: a transneuronal labeling study using pseudorabies virus.

The CNS monoamine cell groups that project to the pancreatic parasympathetic preganglionic neurons were identified with the use of the viral retrograde transneuronal labeling method. Pseudorabies virus (PRV) was injected into the pancreas of C8 spinal rats and subsequently, transneuronally-labelled central monoamine neurons were mapped in brain tissue sections that had been stained by an immunohistochemical procedure that allowed for the visualization of PRV products and biogenic amine neurotransmitter enzymes or serotonin (5-HT) in the same neuron. The enzymes studied were tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), phenylethanolamine-N-methyltransferase (PNMT), and histidine decarboxylase. Pancreatic vagal motor neurons originate exclusively from the dorsal vagal motor nucleus and some of these may be dopamine neurons because they were TH immunopositive, but DBH and PNMT immunonegative. Transneuronally labeled aminergic neurons were found throughout the medulla oblongata. The adrenergic inputs arose from the C1, C2, and C3 cell groups. Noradrenergic inputs originated predominantly from the A5 cell group, with lesser contributions from the A1 and A2 cell groups as well as from the area postrema. None of the other CNS catecholamine cells were labeled, except for some weakly staining TH-immunoreactive neurons, presumably dopaminergic, in the paraventricular hypothalamic nucleus (PVN). The greatest number of 5-HT neurons that innervate the pancreatic vagal motor neurons come from the gigantocellular reticular nucleus, pars alpha with lesser inputs from the raphe magnus, obscurus, and pallidus nuclei. None of the CNS histaminergic cell groups were labeled.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of Crestar, a synthetic progestogen regime, for synchronising oestrus in maiden heifers used as recipients of embryo transfers.

Crestar consists of an ear implant containing 3 mg norgestomet combined with an intramuscular injection of 3 mg norgestomet and 5 mg oestradiol valerate. Its effectiveness for synchronising oestrus in embryo transfer recipients was evaluated in comparison with a progesterone-releasing intravaginal device (PRID) and prostaglandin regimen, using 334 maiden heifers. The treatment devices were inserted on day 1, prostaglandin was administered to the PRID-treated heifers on day 8 and the devices were removed on day 10. High proportions of the heifers were seen in oestrus within five days of the removal of the devices after both the PRID prostaglandin (90.4 per cent) and Crestar (86.2 per cent) treatments. The interval from the removal of the device to the onset of oestrus was significantly shorter for Crestar than for PRID prostaglandin-treated heifers (45 vs 51 hours, P < 0.001), and the duration of oestrus was significantly longer (13 vs 10 hours, P < 0.01). The PRID prostaglandin treatment resulted in a higher degree of synchrony than the Crestar treatment (74.1 per cent vs 61.8 per cent, P < 0.05). There were no significant differences between the treatments in the proportions of the heifers selected as embryo transfer recipients or in the proportions which became pregnant after embryo transfer.

Synchronization of estrus in embryo transfer recipients after using a combination of PRID or CIDR-B plus PGF2alpha.

The use of CIDR-B or PRID in combination with prostaglandin F2alpha (PGF2alpha) for synchronizing estrus in embryo transfer recipients was evaluated in 2 experiments. In Experiment 1, virgin heifers (n=263) were synchronized using either a PRID (including estradiol benzoate capsule) or a CIDR-B in a combined program in which devices were inserted on Day 1, an injection of prostaglandin was given on Day 6, and devices were withdrawn on Day 7. The interval from device removal to the onset of estrus was significantly shorter for CIDR-B than for PRID-treated animals (50.44 vs 55.50 hours; P<0.003). The CIDR-B treatment resulted in a similar degree of synchrony to the PRID treatment (74.0 vs 70.4%; P=0.68). InExperiment 2, cows (n=95) and heifers (n=93) were allocated at random to be synchronized using a PRID (excluding estradiol benzoate capsule) plus PGF2alpha or a CIDR-B device plus PGF2alpha. The devices were inserted on Day 1, an injection of prostaglandin was given on Day 10 and the devices were removed on Day 12. Estrus was observed earlier following the CIDR-B treatment (43.50 vs 47.04 hours; P=0.01), but the degree of synchrony was similar (76.2 vs 76.3%; P>0.10) for the CIDR-B and PRID-treated animals. In both experiments, there were no significant differences in the proportions of animals observed in estrus, selected as embryo transfer recipients, or which achieved pregnancy consequent on embryo transfer between those synchronized using CIDR-B or PRID regimens. We conclude that the CIDR-B is a suitable device for synchronizing estrus in embryo transfer recipients.

The effect of feed intake and body weight on purine derivative excretion and microbial protein supply in sheep.

Urinary excretion of purine derivatives (PD) was used to estimate the microbial N (MN) supply to sheep in three experiments designed to examine the effects of DMI and BW on the efficiency of microbial N supply (EMNS) to the host animal. In Exp. 1, four sheep of about 45 kg BW were given 328, 656, 984, and 1313 g of DM/d of a hay/concentrate diet in a Latin square design. Excretion of PD per kilogram of digestible organic matter intake (DOMI) increased with intake, and EMNS increased from 12.0 to 28.3 g of MN/kg of OM digested in the rumen (DOMR). In Exp. 2, 19 sheep ranging from 22 to 73 kg BW were all offered 820 g of DM/d of the same diet as that fed in Exp. 1. Although DM digestibility was relatively constant, PD excretion varied from 4.5 to 13.5 mmol/d and EMNS from 8 to 36 g of MN/kg of DOMR, both inversely related to animal BW. In Exp. 3, five sheep of 48 to 57 kg BW were given a different diet at 702, 966, or 1,237 g of DM/d. Purine derivative excretion per kilogram of DOMI increased with the DMI:BW ratio. Calculated EMNS ranged from 23 to 35 g of MN/kg of DOMR. Pooled data from all experiments showed EMNS to be related to the DMI:BW ratio. It is suggested that the DMI:BW ratio defines the ruminal digesta passage rate and hence outflow of microbial protein. The results imply that the EMNS for a given diet is not constant, but changes with intake.

Urea metabolism in sheep given conventional feeds or nourished by intragastric infusion.

A comparison has been made of the kinetics of urea metabolism in sheep given conventional feeds or maintained wholly by intragastric infusions of volatile fatty acids, buffer, mineral and casein solutions. Daily nitrogen supply was 13.2 g/day in 'fed' sheep and 6.0 g/day in 'infusion' sheep. On each feeding system measurements were made at the basal (maintenance) level of intake and when the basal level was supplemented with infusions of urea into the abomasum (125 mmol/day) or into the rumen (300 mmol/day). Additional measurements were made when ammonium carbonate (100 mmol/day) was infused into the rumen, when cassava (150 g/day) was added to the diet of 'fed' sheep or when the input of casein to 'infusion' sheep was reduced by half. Urea kinetics were measured by means of a single intravenous injection of [14C]urea. Urea irreversible loss rate, urea pool size, urinary urea excretion, plasma urea concentrations and rumen ammonia concentrations were all significantly higher in sheep given conventional feeds than in those nourished by infusion but urea degradation in the gastrointestinal tract did not differ between the two methods of feeding. Regression analysis indicated only minor differences between the two feeding systems in the relationships between the various indices of urea metabolism. It is concluded that most of these findings can be attributed to differences in the quantity and nature of the nitrogen supplied in the basal diets and that the sheep nourished by infusion would be a suitable model for the study of factors involved in the control of urea recycling.

Measurement of fractionated water loss and CO2 production using triply labelled water.

The doubly labelled water (DLW) method for measuring CO2 production has recently been the subject of much interest since no other technique gives integrated values for CO2 production over long periods by free-living subjects. The importance of evaporative water loss and fractionation factors to the calculation of CO2 production using this technique is described. Present methods of estimating evaporative water loss and the use of fractionation factors are summarized together with a discussion of their limitations. A novel technique is proposed whereby water labelled with three isotopes can be used to measure evaporative water loss and CO2 production in completely free-living subjects, and the feasibility of the method is tested in simulations using experimental data. This technique has three advantages over existing methods of estimating evaporative water loss: (1) it can be used in completely free-living subjects without any additional experimental procedures (e.g. water-balance studies or physical trapping of water vapour); (2) it gives a direct estimate of fractionated evaporative water loss in each subject, since non-fractionated water lost as vapour is automatically compensated for; and (3) the routes of water loss do not have to be known. The appropriate calculations are presented together with a discussion of the difficulties of measuring oxygen-17 by mass spectrometry. It is estimated that the maximum theoretical error on calculated CO2 production is +/- 0.3%. Practical ways of achieving this theoretical level of accuracy are suggested. We conclude that the proposed technique will allow correction for evaporative water loss to be made more exactly, thereby increasing the accuracy of the heavy water technique for measuring CO2 production in free-living subjects.