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J M Hopkinson

Publications and source records attributed to J M Hopkinson.

At least 19 recordsLinked to original sources
PubMed2001

Energy requirements of lactating women derived from doubly labeled water and milk energy output.

Instead of using an incremental approach to assess the energy requirements of lactation, a more comprehensive approach may be taken by measuring total energy expenditure (TEE), milk energy output and energy mobilization from tissue stores. The latter approach avoids assumptions regarding energetic efficiency and changes in physical activity and adiposity. The purpose of this study was threefold: to assess the energy requirements of lactation; to compare these estimates with energy requirements in the nonpregnant, nonlactating state and to test for energetic adaptations in basal metabolic rate (BMR) and physical activity during the energy-demanding process of lactation. Milk production and composition, body weight and composition, TEE, BMR and physical activity levels were measured in 24 well-nourished women during exclusive breastfeeding at 3 mo postpartum and after the cessation of breastfeeding at 18 or 24 mo postpartum. TEE was measured by the doubly labeled water method, milk production by 3-d test-weighing, milk energy by bomb calorimetry on a 24-h milk sample, body composition by dual-energy x-ray absorptiometry and BMR by room respiration calorimetry. TEE, BMR and physical activity level (physical activity level = TEE/BMR) did not differ between the lactating and nonlactating state (TEE 10.0 +/- 1.5 versus 10.6 +/- 2.1 MJ/d). Mean milk energy output was equivalent to 2.02 +/- 0.33 MJ/d. Total energy requirements were greater during lactation than afterward (12.0 +/- 1.4 versus 10.6 +/- 2.1 MJ/d, P: = 0.002). Energy mobilization from tissue stores (-0.65 +/- 0.97 MJ/d) resulted in net energy requirements during lactation of 11.4 +/- 1.8 MJ/d. Because adaptations in basal metabolism and physical activity were not evident in these well-nourished women, energy requirements during lactation were met primarily from the diet and only partially by mobilization of tissue stores.

Adult↗
PubMed2000

Energy requirements derived from total energy expenditure and energy deposition during the first 2 y of life.

BACKGROUND: Current recommendations for energy intake of children are derived from observed intakes. Deriving energy requirements on the basis of energy expenditure and deposition is scientifically more rational than is using the observational approach and is now possible with data on total energy expenditure (TEE), growth, and body composition. OBJECTIVES: The objectives of this study were 1) to define energy requirements during the first 2 y of life on the basis of TEE and energy deposition; 2) to test effects of sex, age, and feeding mode on energy requirements; and 3) to determine physical activity. DESIGN: TEE, sleeping metabolic rate, anthropometry, and body composition were measured in 76 infants. TEE was measured with doubly labeled water, sleeping metabolic rate with respiratory calorimetry, and body composition with a multicomponent model. RESULTS: Total energy requirements were 2.23, 2.59, 2.97, 3. 38, 3.72, and 4.15 MJ/d at 3, 6, 9, 12, 18, and 24 mo, respectively. Energy deposition (in MJ/d) decreased significantly over time (P: = 0.001) and was lower in breast-fed than in formula-fed infants (P: = 0.01). Energy requirements were approximately 80% of current recommendations. Energy requirements differed by age (P: = 0.001), feeding group (P: = 0.03), and sex (P: = 0.03). Adjusted for weight or fat-free mass and fat mass, energy requirements still differed by feeding group but not by age or sex. Temperament and motor development did not affect TEE. CONCLUSION: The TEE and energy-deposition data of these healthy, thriving children provide strong evidence that current recommendations for energy intake in the first 2 y of life should be revised.

Anthropometry↗
PubMed2000

Lactation delays postpartum bone mineral accretion and temporarily alters its regional distribution in women.

The objective of this work was to compare long-term changes in bone mineral in lactating (L) and nonlactating (NL) women for 2 y postpartum. The 40 L women (mean duration of breastfeeding 345 +/- 177 d) and 36 NL women were enrolled during late pregnancy. Subjects were healthy and nonsmoking with a mean age of 28.8 +/- 4.1 y. Bone mineral content (BMC) was measured at 0.5, 3, 6, 12, 18 and 24 mo by dual-energy X-ray absorptiometry set for total body scan with regional analysis. BMC adjusted for bone area, weight and height (adj-BMC) decreased in L women at the lumbar spine (-3.1%, P < 0. 001) and pelvis (-0.9%, P = 0.03) by 3 mo, and at the total body (-0. 9%, P = 0.05) by 6 mo. Losses were recovered following onset of menses. Adj-BMC at the lumbar spine, pelvis, thoracic spine and total body increased over baseline by 24 mo in L women. In NL women, adj-BMC increased over baseline within 3 mo and continued to increase thereafter. Net total-body gains were greater in the 27 NL women who completed the final measurement than in their 26 L counterparts (+2.3% vs. +0.6%, P = 0.001). Net regional gains differed at the head, legs, and ribs, but not at the lumber spine, pelvis or thoracic spine. Duration of breastfeeding, parity, onset of menses and maternal age affected bone changes in L women. These results indicate that lactation delays bone mineral accretion and temporarily alters its regional distribution in postpartum women.

Adult↗
PubMed2000

Body composition during the first 2 years of life: an updated reference.

Normative body composition during the first 2 y of life was derived from a prospective study of 76 children. We present 1) fat free mass (FFM) and its components, and fat mass (FM), 2) incremental growth rates partitioned into chemical components, and 3) age-specific and gender-specific constants for converting chemical and physical components into FFM for children during the first 2 y of life. A multicomponent model based on measurements of total body water (TBW), total body potassium (TBK) and bone mineral content (BMC) was used to estimate FFM and FM at 0.5, 3, 6, 9, 12, 18, and 24 mo of age. TBW was determined by deuterium dilution, TBK by whole body counting, and BMC by dual energy x-ray absorptiometry. FFM was higher in boys than girls between 0.5-18 mo of age (p < or = 0.05). Percent FM increased on average from 13 to 31% between 0.5 and 3-6 mo, and then gradually declined. Percent FM was significantly higher in girls than in boys at 6 and 9 mo of age (p < or = 0.02). The components of FFM on a percentage basis changed with age (p = 0.001), but not gender. The protein content of FFM increased gradually with age, while TBW declined (p = 0.001). As a percentage of FFM, osseous mineral increased from 2.0 to 3.4% in boys and from 2.1 to 3.3% in girls between 0.5 and 24 mo (p = 0.001). Density and potassium content of FFM increased gradually with age (p = 0.001). These normative body composition data provide an updated reference upon which to assess normal growth and nutritional status of pediatric populations representative of mixed feeding groups during the first 2 y of life.

Absorptiometry, Photon↗
PubMed2000

Infant feeding mode affects early growth and body composition.

BACKGROUND: Differences in the growth pattern of breastfed (BF) and formula-fed (FF) infants are well-recognized and have been attributed to differences in nutrient intake. However, the impact of qualitative and quantitative differences in nutrient intake on the body composition of BF and FF infants has been unclear. Furthermore, it is unknown whether putative differences in body composition persist beyond weaning. DESIGN: Prospective cohort study. METHODS: Repeated anthropometric and body composition measurements were performed on 40 BF and 36 FF infants at 0.5, 3, 6, 9, 12, 18, and 24 months of age. A multicomponent body composition model based on total body water by deuterium dilution, total body potassium by whole body counting, and bone mineral content by dual-energy x-ray absorptiometry was used to estimate fat-free mass (FFM) and fat mass (FM). Independent measurements of FFM and FM were made using total body electrical conductivity and dual-energy x-ray absorptiometry. By design, infants were either exclusively BF or FF from birth to 4 months of age; thereafter, the feeding mode was at the discretion of the parents. Infant food intake was measured at 3, 6, 12, and 24 months of age using 3-day weighed-intake records. Data were analyzed by repeated measures analysis of variance. RESULTS: Weight velocity was higher in FF than BF infants age 3 to 6 months, and higher in FF than BF girls 6 to 9 months of age. Adjusted for gender and baseline values, BF infants had lower total body water at 3 months, lower total body potassium at 3 to 24 months, and lower bone mineral content at 12 months. The multicomponent model indicated that FFM was lower in BF than FF infants at 3 months, and FM and %FM were higher in BF than FF infants at 3 and 6 months (boys only). Total body electric conductivity confirmed lower FFM in BF than FF infants at 3 months, as well as at 6 and 9 months; FM and %FM were higher in BF than FF at 3 and 6 months, and 9 months (boys only). Intakes of energy, protein, fat, and carbohydrate were lower in BF than FF infants at 3 and 6 months, and were positively correlated with weight gain and FFM gain, but not FM gain. No differences in nutrient intakes were observed at 12 or 24 months. CONCLUSION: Infant feeding mode is associated with differences in body composition in early infancy which do not persist into the second year of life.

Absorptiometry, Photon↗
PubMed1999

Adjustments in energy expenditure and substrate utilization during late pregnancy and lactation.

BACKGROUND: Metabolic adjustments occur during pregnancy and lactation to support fetal growth and milk synthesis; however, the effect of body composition and hormonal milieu on these changes is poorly understood. OBJECTIVE: We hypothesized that energy metabolism changes during pregnancy and lactation to support fetal growth and milk synthesis, and that body composition and hormonal milieu influence these alterations. DESIGN: We measured energy expenditure, body composition, and hormone, metabolite, and catecholamine concentrations in 76 women (40 lactating, 36 nonlactating) at 37 wk gestation and 3 and 6 mo postpartum. Total energy expenditure (TEE), basal metabolic rate (BMR), sleeping metabolic rate (SMR), and minimal SMR (MSMR) were measured with room calorimetry. Fat-free mass (FFM) and fat mass were estimated with a 4-component model. RESULTS: TEE, BMR, SMR, and MSMR were 15-26% higher during pregnancy than postpartum after being adjusted for FFM, fat mass, and energy balance. TEE, SMR, and MSMR were higher in lactating than in nonlactating women. Fasting serum insulin, insulin-like growth factor I, fatty acids, and leptin, and 24-h urinary free norepinephrine, epinephrine, and dopamine correlated positively with TEE, BMR, SMR, and MSMR. In nonlactating women, the respiratory quotient decreased over time, carbohydrate oxidation decreased, and fat oxidation increased. Substrate utilization was not influenced by body composition, fasting serum hormones, or 24-h urinary catecholamines. CONCLUSIONS: These results indicate increased energy expenditure and preferential use of carbohydrates during pregnancy and lactation. Elevated respiratory quotient and carbohydrate utilization during pregnancy continue during lactation, consistent with preferential use of glucose by the fetus and mammary gland.

Adolescent↗
PubMed1998

Body composition changes during lactation are highly variable among women.

Changes in body weight and composition in response to the metabolic load imposed by lactation are highly variable among and within diverse populations. In most reports, rates of weight loss did not differ between lactating and nonlactating women. Despite differences in the hormonal milieu between lactating and nonlactating women, only subtle short-term differences were observed in postpartum changes in body composition. Regional patterns of fat deposition and mobilization did not differ between lactating and nonlactating women in most studies. Changes in body composition during lactation are responses to a sequence of complex neuroendocrine and biochemical stimuli that may be significantly modified by environmental factors. Gestational weight gain was the strongest determinant of postpartum weight and fat mass change, which supports the premise that biological mechanisms are aimed at restoring prepregnancy body weight and composition.

Adipose Tissue↗
PubMed1997

Changes in fat-free mass and fat mass in postpartum women: a comparison of body composition models.

OBJECTIVES: (1) To compare 2-, 3- and 4-component models of body composition based on total body water (TBW), underwater weighing (UWW), skinfold thicknesses (SF), total body potassium (TBK), dual-energy X-ray absorptiometry (DXA) and total body electrical conductivity (TOBEC); (2) to compare postpartum changes in body composition estimated by the 2-, 3- and 4-component models and (3) to test for an effect of pregnancy or lactation on the hydration, density and potassium content of fat free mass (FFM) in postpartum women. DESIGN: Longitudinal measurements of body composition at 3, 6 and 12 months postpartum. SUBJECTS: Thirty-five healthy postpartum women, aged 30.2 +/- 3.5 y. MEASUREMENTS: Body composition was estimated by 2-component models based on TBW, UWW, SF, TBK, DXA or TOBEC; 3-component models based on TBW and UWW (Fuller 3, Siri 3); and a 4-component model (Fuller 4) based on TBW, UWW and bone mineral content. RESULTS: Systematic differences were seen among the various body composition models, with the following ranking from lowest to highest estimate of fat mass (FM): TOBEC, TBW, Fuller 3, Siri 3, Fuller 4, UWW, SF, TBK, and DXA. Estimated changes in FFM and FM were not significantly different among methods, except for the 3-6 months FFM and FM changes estimated from TBW, which differed from SF, DXA, and TOBEC. Pregnancy-induced changes in the hydration, density and potassium content of FFM were not evident by 3 months postpartum (0.73 +/- 0.02, 1.099 +/- 0.015 kg/l and 2.31 +/- 0.10 g/kg, respectively). CONCLUSION: In spite of systematic differences among body composition models for the measurement of FFM and FM, changes in FFM and FM did not differ significantly among the models. Since there was no apparent effect of pregnancy or lactation on the postpartum composition of FFM, 2-component models of body composition are acceptable for use in postpartum women beyond the puerperium.

Adult↗
PubMed1997

Body fat estimation in late pregnancy and early postpartum: comparison of two-, three-, and four-component models.

Accurate methods for determining body fat mass during reproduction are necessary to evaluate energy balance. However, determination of fat mass is complicated during pregnancy by the accretion of water, which invalidates assumptions underlying standard two-compartment models. The extent to which the variability in body water during pregnancy invalidates use of pregnancy-corrected two-compartment models for determination of fat mass in individual women is unknown. Moreover, it is unclear whether body water returns to nonpregnant values by 2 wk postpartum, which is frequently used as the baseline in studies of postpartum women. The present study uses a four-component model as a criterion for evaluating two- and three-component models. Fifty-six healthy, normotensive women between the ages of 19 and 35 y were studied at 36 +/- 1 wk gestation and 15 +/- 2 d postpartum. Total body water (TBW), total body potassium (TBK), body density, and bone mineral content were measured by deuterium dilution, whole-body potassium counting, hydrodensitometry, and dual-energy X-ray absorptiometry (postpartum only), respectively. At 2 wk postpartum, hydration and density of fat-free mass (FFM) had not returned to nonpregnant values, and differed between lactating and nonlactating women (P < 0.05). Accordingly, standard TBW and body density estimates of fat mass differed from four-component estimates at both time points (P < 0.005). Moreover, our data indicate that even when pregnancy-specific values for hydration or density of FFM are used in TBW and body density models, individual fat mass estimates may differ by > 3 kg from the four-component value. Fat mass by TBK may differ by > 10 kg from fat mass by the four-component model during pregnancy, and by 6 kg postpartum. Use of standard two-compartment models to estimate fat mass results in significant error both during pregnancy and at 2 wk postpartum. Pregnancy-corrected two-compartment models produce reliable mean fat mass estimates during pregnancy, but individual fat mass estimates may vary widely from four-component values.

Absorptiometry, Photon↗
PubMed1997

A comparison of acceleromyography and mechanomyography for determination of the dose-response curve of rocuronium in children.

In order to compare an acceleromyograph (TOF-Guard) with a mechanomyograph (Grass FT03), the dose-response relationship of rocuronium was simultaneously determined in both arms of 15 children aged 3-11 years during anaesthesia with thiopentone, alfentanil and nitrous oxide. Three subgroups of five children received rocuronium 120, 180 or 240 micrograms.kg-1 randomly. The effective doses to produce 50% and 95% depression of the first twitch of the train-of-four determined by acceleromyography were 206 and 337 micrograms.kg-1, respectively, while these values determined by mechanomyography were 151 and 331 micrograms.kg-1, respectively. The dose-response curve obtained by acceleromyography was steeper and shifted to the right compared with that obtained by mechanomyography (p < 0.0001). The difference between the effective dose producing 50% twitch depression determined by the two devices was highly significant (p < 0.0001). In 13 out of 15 children, the acceleromyograph control train-of-four ratio was significantly greater than unity. Although there was a good correlation (r = 0.85) between simultaneous pairs of measurements of neuromuscular block, the acceleromyograph exhibited a bias of -25% relative to the mechanomyograph with wide limits of agreement (-62 to +12%). We conclude that acceleromyographic and mechanomyographic measurements should not be used interchangeably when determining the potency of muscle relaxants.

Androstanols↗
PubMed1997

Dose-response relationship and effective time to satisfactory intubation conditions after rocuronium in children.

We assessed the neuromuscular blocking effects of, and intubation conditions following, rocuronium in 81 children aged 2-12 years. The study was conducted in three parts. Parts 1 and 2 were undertaken during anaesthesia with thiopentone, alfentanil and nitrous oxide. Neuromuscular blockade was evaluated by recording the force of contraction of the adductor pollicis in response to train-of-four stimulation at 2 Hz repeated every 10s. In Part 1 the potency of rocuronium was determined in 15 children using a single dose-response technique; in Part 2 onset and recovery times were determined in six children following rocuronium 0.6 mg.kg-1. In Part 3 of the study, intubation conditions were assessed in five groups of 12 children whose tracheas were intubated 30, 40, 50, 60 and 70s after rocuronium 0.6 mg.kg-1 during anaesthesia with thiopentone. The times to satisfactory intubation conditions in 50% and 90% of children were determined by probit analysis. The effective doses of rocuronium to produce 50% and 95% twitch depression were 151 micrograms.kg-1 (95% confidence intervals: 129-173 micrograms.kg-1) and 331 micrograms.kg-1 (95% confidence intervals: 249-543 micrograms.kg-1), respectively. The mean times (SD) to 90% and 100% depression of control twitch following rocuronium 0.6 mg.kg-1 were 42 (11.8) s and 60.3 (19.3) s, respectively. The times to 5%, 25%, 75% and 90% recovery were 20.5 (3.1) min, 26.1 (4.1) min, 35.1 (5.4) min, and 39.5 (6.4) min, respectively. Intubation conditions were satisfactory in 4/12 children at 30 s, 6/12 at 40 s, 8/12 at 50 s, 11/12 at 60 s and 12/12 at 70 s. The times to satisfactory intubation conditions in 50% and 90% of children after rocuronium 0.6 mg.kg-1 were 38 s (95% confidence intervals: 30-44 s) and 61 s (95% confidence intervals: 55-70 s), respectively.

Androstanols↗
PubMed1997

A comparative multicentre trial of spinal needles for caesarean section.

We studied 681 patients in a randomised, multicentre, double-blind, parallel group trial designed to assess the incidence of headache following spinal anaesthesia for Caesarean section using four different pencil point spinal needles. The needles used were: Whitacre 25G (n = 170), Polymedic 25G (n = 170), Sprotte 24G (n = 173) and Polymedic 24G (n = 168). The incidence of all headaches prior to discharge was 11.1%. Only five headaches (0.75%) were severe with features of post dural puncture headache (PDPH) and required an epidural blood patch: Whitacre 25G = 0, Polymedic 25G = 1 (0.6%), Sprotte 24G = 2 (1.2%), Polymedic 24G = 2 (1.2%). There was no statistically significant difference between the four groups for PDPH. We conclude that all four needles studied performed satisfactorily and comparably.

Adult↗
PubMed1997

Leptin in human reproduction: serum leptin levels in pregnant and lactating women.

Experiments in ob/ob female mice demonstrated that leptin injections not only reduced weight and fat mass, but also restored fertility and partial lactation. To explore factors regulating ob gene expression in reproductive women, we measured serum leptin, body fat, energy expenditure, and milk production in 65 women at 36 weeks of gestation, and at 3 and 6 months postpartum. Serum leptin was measured by solid-phase sandwich enzyme immunoassay, and serum insulin and PRL by solid-phase 125I RIA. Total body water by deuterium dilution, body volume by hydrodensitometry, and bone density by dual-energy x-ray absorptiometry were used to estimate body fat. Serum leptin per unit fat mass was significantly higher at 36 weeks of pregnancy than at 3 and 6 months postpartum (1.25 vs. 0.75, 0.73 ng.mL-1.kg-1). Postpartum normalization of leptin was associated with changes not only in weight and fat mass, but also serum insulin. Leptin was not different between lactating and nonlactating women. Leptin may have affected milk production indirectly through its negative effect on serum PRL. Adjusted for fat-free mass and fat mass, rates of energy expenditure were not significantly correlated with leptin. Our results provide evidence that factors other than fat mass alone modulate serum leptin in reproductive women.

Adult↗
PubMed1995

Mast cells in aural polyps: a preliminary report.

Mast cells are a rich source of potent biologically active mediators and are found in connective tissue, associated with blood vessels in many varied inflammatory conditions. Mast cells have been described in nasal polyps and turbinates and in adenoidal tissue in the upper aerodigestive tract. As the middle ear lining is contiguous with the nose and the nasopharynx, the presence of mast cells in aural polyps is interesting. This preliminary study investigated the presence of mast cells in inflammatory aural polyps using light microscopy. All patients presenting to the department in one year were included. Patients with previous ear disease or surgery and in whom cholesteatoma was suspected were excluded. Except for one patient mast cells were seen in all aural polyps. The implications of these findings is discussed. Further work is needed using electron microscopy.

Adolescent↗
PubMed1995

Energy requirements from infancy to adulthood.

To investigate how age and body composition affect energy requirements, the sedentary daily expenditure (SDE) and basal metabolic rate (BMR) of 101 infants, 82 girls, and 27 adults were measured. Energy expenditure was scaled for differences in body size to test the effects of age and body fatness. A power function was superior to linear models. For all subjects, WT0.63 (where WT is weight) or FFM0.63 (where FFM is fat-free mass) explained 94% of the variability in BMR, and WT0.70 or FFM0.70 explained 97% of the variability in SDE. The effects of height and fat mass (kg or % body wt) on BMR and SDE scaled for weight or fat-free mass were age dependent. Best-fitted exponents relating BMR or SDE to body size differed between children (0.40-0.52) and infants (1.04-1.30) (P = 0.001). Human energy requirements from infancy to adulthood appear to be a power, not a linear, function of body weight and composition.

Adolescent↗
PubMed1993

Disposition of olsalazine and metabolites in breast milk.

This study examined the disposition of olsalazine and its metabolites into breast milk after the ingestion of a single dose of 500 mg olsalazine. Blood and serum samples were obtained for 48 hours after the ingestion of 500 mg olsalazine in a 39-year-old lactating woman. Blood samples were obtained at .0, .5, 1, 2, 4,6, 24.5, 26, and 48 hours. Maternal milk samples were obtained at .0, .5, 2, 4, 6, 14, 24, 28, 36, and 48 hours. Olsalazine and olsalazine-S underwent high-pressure liquid chromatography analysis, and 5-ASA and Ac 5-ASA underwent fluorometric detection. Acetylated-5-ASA achieved concentrations of .8, .86, and 1.24 mumol/L in breast milk at 10, 14, and 24 hours, respectively. Olsalazine, olsalazine-S, and 5-ASA were undetectable in the breast milk for 48 hours after drug administration. Clinically significant drug exposure in the breast-fed infant is unlikely after a maternal single dose of olsalazine. Idiosyncratic hypersensitivity, however, remains a possibility even if the infant is exposed to only minute quantities.

Administration, Oral↗