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Biomedical subjects

L A Baur

Publications and source records attributed to L A Baur.

At least 55 records · Page 3Linked to original sources
PubMed1996

Changes in glucose and lipid metabolism following weight loss produced by a very low calorie diet in obese subjects.

OBJECTIVE: To study the effects of a very low calorie diet (VLCD) on glucose and lipid metabolism in obese subjects, in particular, the effects on insulin sensitivity and the activities of the key enzymes of glucose disposal, glycogen synthase (GS) and the pyruvate dehydrogenase complex (PDHC). DESIGN: Clinical dietary intervention study (1.67 MJ (400 kcal)/day) until weight loss of > 10%. SUBJECTS: 11 (seven male, four female) non-diabetic, obese subjects (age: 27-62 y; BMI: 40.5 +/- 1.4 kg/m2). MEASUREMENTS: Whole body glucose disposal (by euglycemic hyperinsulinemic clamp), respiratory quotient (RQ), resting energy expenditure (REE), glucose and lipid oxidation (by indirect calorimetry), insulin-stimulated PDHC and GS activity (in muscle biopsies) both before and immediately after VLCD (i.e. while still in a hypocaloric state), serum hormone and metabolite levels throughout the dietary period. RESULTS: Weight loss was accompanied by reduced insulin and elevated NEFA levels, improved insulin sensitivity due to increased nonoxidative glycolysis with no increase in PDHC or GS activities. The rate of weight loss was inversely related to the initial RQ. PDHCa was strongly age-related. CONCLUSION: A low RQ may be used as a predictor of the efficacy of VLCD treatment and that while VLCD improves nonoxidative glycolytic flux, changes in oxidative glucose disposal and muscle glucose storage are prevented by high NEFA availability during this catabolic phase of dietary intervention.

Adult↗
PubMed1995

Relationships between muscle membrane lipids, fiber type, and enzyme activities in sedentary and exercised rats.

Insulin resistance in skeletal muscle is associated with 1) relative increases in the proportion of glycolytic and fast-twitch muscle fibers and decreases in the proportion of more oxidative fibers and 2) a higher proportion of the saturated fatty acids in membrane structural lipids. Exercise is known to improve insulin action. The aims of the current studies were 1) to investigate the relationship between muscle fiber type and membrane fatty acid composition and 2) to determine how voluntary exercise might influence both variables. In sedentary Wistar rats in experiment 1, increased amounts of unsaturated fatty acids were found in the more oxidative insulin-sensitive red quadriceps and soleus muscles, whereas reduced levels of polyunsaturated fatty acids were found in primarily glycolytic white quadriceps muscles. In experiment 2, voluntary running-wheel exercise by adult female rats over 45 days resulted in reduced proportions of type IIb fibers (P = 0.01) and increased proportions of type IIa/IIx fibers (P = 0.03) in extensor digitorum longus muscle. The magnitude of these changes was related to the distance run (r = -0.73, P = 0.04; r = 0.79, P = 0.02, respectively). Exercise significantly increased oxidative capacity, as assessed by the proportion of intensely NADH-stained fibers (P = 0.0004) and citrate synthase (P = 0.003) and hexokinase (P = 0.04) activities. Citrate synthase activity was also increased by exercise in soleus muscle, where, as expected, no fiber type changes were detected. No significant differences in the fatty acid profile of soleus and extensor digitorum longus were found between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Skeletal muscle membrane lipid composition is related to adiposity and insulin action.

The cellular basis of insulin resistance is still unknown; however, relationships have been demonstrated between insulin action in muscle and the fatty acid profile of the major membrane structural lipid (phospholipid). The present study aimed to further investigate the hypothesis that insulin action and adiposity are associated with changes in the structural lipid composition of the cell. In 52 adult male Pima Indians, insulin action (euglycemic clamp), percentage body fat (pFAT; underwater weighing), and muscle phospholipid fatty acid composition (percutaneous biopsy of vastus lateralis) were determined. Insulin action (high-dose clamp; MZ) correlated with composite measures of membrane unsaturation (% C20-22 polyunsaturated fatty acids [r= 0.463, P < 0.001], unsaturation index [r= -0.369, P < 0.01]), a number of individual fatty acids and with delta5 desaturase activity (r= 0.451, P < 0.001). pFAT (range 14-53%) correlated with a number of individual fatty acids and delta5 desaturase activity (r= -0.610, P < 0.0001). Indices of elongase activity (r= -0.467, P < 0.001), and delta9 desaturase activity (r= 0.332, P < 0.05) were also related to pFAT but not insulin action. The results demonstrate that delta5 desaturase activity is independently related to both insulin resistance and obesity. While determining the mechanisms underlying this relationship is important for future investigations, strategies aimed at restoring "normal" enzyme activities, and membrane unsaturation, may have therapeutic importance in the "syndromes of insulin resistance."

Adipose Tissue↗
PubMed1994

Total body nitrogen in children with chronic renal failure and short stature.

OBJECTIVE: To directly assess the body protein content of children with chronic renal failure (CRF) and short stature. SETTING: A tertiary referral paediatric hospital. SUBJECTS: There were: (i) 17 patients (10 male, nine pre-pubertal; mean age 12.90 +/- 3.20 years) with CRF and height standard deviation (SD) score < -2.00, and (ii) 43 normal children (18 male, 27 pre-pubertal; mean age 10.34 +/- 3.34 years). INTERVENTIONS: CRF patients had the following measurements: anthropometry, total body nitrogen (TBN) by neutron capture analysis, 4 day weighed food record and serum albumin levels. Control subjects had TBN and anthropometric measurements only. RESULTS: Although older than the controls, the CRF patients had significantly lower TBN values (645 +/- 265 vs 930 +/- 365 g, P < 0.01). Mean values for TBN and TBN/height (percentages of expected) in the CRF patients were significantly reduced to 54% and 63% respectively, when predicted from age. However, their TBN predicted from height was 100% of expected. %TBN (predicted from age) correlated significantly with height SD score (r = 0.79), weight SD score (r = 0.87), upper arm muscle area percentile (r = 0.62) and serum albumin (r = 0.62). Mean oral energy and protein intakes were 65% and 172% of recommended dietary intake respectively. CONCLUSIONS: Children with CRF and short stature are significantly protein-depleted for age although not for height. Chronic energy deficiency may contribute to impaired protein deposition which, in turn, may be important in the pathogenesis of growth failure in CRF.

Adolescent↗
PubMed1991

A total body nitrogen facility for paediatric use.

The design, calibration and evaluation of a facility for in vivo prompt gamma neutron capture analysis of total body nitrogen in children is described. The patient is scanned in both supine and prone positions, across a vertically collimated beam from a 1 GBq 252Cf fission source. Two NaI(T1) detectors are placed on either side of the patient, perpendicular to both the neutron beam and the scanning direction. The effective dose equivalent delivered to a child during an 840 s scan is approximately 0.14 mSv (QF = 10). Correction factors for nitrogen background (width-dependent), hydrogen background (1-4% of hydrogen gamma ray peak) and the differential attenuation of nitrogen and hydrogen gamma rays (width-dependent) can be applied to the measured nitrogen-to-hydrogen gamma ray counts ratio. By using the mass of hydrogen (based on body mass and fat mass) as an internal standard, the nitrogen mass can then be determined. Measurements with a urea-containing box phantom show that the current precision (CV) of the net nitrogen counts and of the nitrogen-to-hydrogen counts ratio is +/- 2.0% and +/- 1.5%, respectively. Using small anthropomorphic and other phantoms, estimation of the mass of nitrogen has a precision of +/- 1.4 to 5.4% and an accuracy of 97.1 to 101.5%.

Australia↗
PubMed1991

Nitrogen deposition in malnourished children with cystic fibrosis.

To determine the protein nutritional status of 21 malnourished children with cystic fibrosis (CF), total body nitrogen (TBN) was measured and the results were compared with 21 control subjects. CF patients demonstrated a lower TBN (P less than 0.001). When matched for height (n = 10) or bone age (n = 13), the CF patients still had a depressed TBN/height or TBN/lean body mass (P less than 0.05). To assess nitrogen deposition during nutritional rehabilitation, repeat TBN measurements were performed on the 21 CF patients. Nitrogen deposition ranged from -230 to 550 g/y and correlated with weight velocity (r = 0.78, P less than 0.001). Increased nitrogen deposition (greater than 150 g/y) was generally associated with normal height gain (height velocity SD score greater than -2.00) and weight gain (greater than 2.0 kg/y). Decreased nitrogen deposition was associated with poor weight gain but did not preclude normal linear growth. These data suggest an important role for TBN estimations in defining protein nutritional status in children and indicate that skeletal growth can continue in the presence of minimal nitrogen deposition.

Adolescent↗
PubMed1990

Nutritional status, growth and development in children undergoing intensive treatment for cystic fibrosis.

Dietary intakes were measured over a period of 5 days in 36 malnourished and 36 well-nourished patients with cystic fibrosis. Both energy and protein intakes were significantly less in the malnourished patients for the two age groups studied: 4-9.99 years (p less than 0.01 for both parameters), and 10-16 years (p less than 0.05 and p less than 0.01, respectively). In both age groups and both patient groups, average protein intakes were well in excess of the recommended daily intake, but energy intake in the malnourished patients was below the recommended daily intake. Nutritional supplementation of 10 malnourished patients with a polymeric formula, infused overnight via a gastrostomy tube, resulted in a seven-fold increase in weight gain (p less than 0.001) and a doubling of linear growth velocity (p less than 0.01) over a period of 18 months, compared to the 18 months prior to gastrostomy feeding. Measurements of total body nitrogen in eight of these patients demonstrated a 38% increase in body nitrogen content over 12 months, indicating a replenishment of the protein deficit.

Adolescent↗
PubMed1990

Determination of total body water by Fourier transform infrared analysis.

A new technique for determining body water using deuterium isotope dilution and Fourier transform infrared (FTIR) analysis is described. The advantages of the FTIR over conventional dispersion and filter infrared instruments include greater flexibility through computer controlled operations and availability of 'on-line' analytical software. The technique was further improved by the development of a simple procedure for determining D2O concentration in untreated serum samples. A validation study of six normal adults showed that the fat-free-mass determined from the deuterium-space (total body water) correlated well with the results obtained by total body nitrogen (r = 0.997), total body potassium (r = 0.996) and anthropometric (r = 0.995) measurements.

Adult↗
PubMed1982

Interrelations of the rat's thalamic reticular and dorsal lateral geniculate nuclei.

Electrophysiological and neuroanatomical techniques have been used to study the properties of cells in the reticular nucleus of the thalamus (RNT) responsive to photic stimuli. In the rat these cells are located in a discrete region of the nucleus lying immediately rostral to the dorsal lateral geniculate nucleus (LGNd), where the visual field is represented in a retinotopic fashion. After injections of horseradish peroxidase (HRP) into this area, neurones labelled with reaction product were found in the LGNd and not in other thalamic relay nuclei. After HRP injections into the LGNd, labelled RNT cells were found only within the region which contains neurones responsive to photic stimuli. These observations suggest that there is a precise reciprocal relation between the two areas. Studies and comparisons of the responses of relay cells (P cells) in LGNd and cells in RNT to electrical shocks lead us to conclude that RNT cells receive their excitation mainly via those relay cells in LGNd which are themselves excited by fast-conducting retinal ganglion cell axons. Such cells in LGNd have phasic responses and concentric receptive fields while RNT cells have phasic responses and on/off fields and a comparison of the receptive field sizes of P cells and RNT cells suggests that only a small number of LGNd relay cells converge on to each RNT cells. Further, although a particular functional class of relay cells in LGNd (Y-type) is shown to provide the major input to visually responsive RNT cells, both Y type and W type relay cells are subject to their inhibitory control. These results furnish evidence that cells in the RNT have an important role in modulating the flow of visual information from the LGNd to cortex.

Animals↗
PubMed1981

Cortical projections to visual centres in the rat: an HRP study.

We have investigated the relationships of the visual cortex to other visual centres in the rat: namely the lateral geniculate nucleus, the visually responsive part of the thalamic reticular nucleus and the superior colliculus. We injected horseradish peroxidase iontophoretically so as to restrict the injectate to each of the regions, and reacted sections using 3 different procedures. Areas 17, 18 and 18a project to both dorsal and ventral lateral geniculate nucleus as well as to the visually responsive part of the thalamic reticular nucleus and superior colliculus. Pyramidal cells in lamina VI project to the dorsal lateral geniculate nucleus and to the thalamic reticular nucleus, whereas cells of origin of the projection to the superior colliculus lie in lamina V; cells in lamina V also project to ventral lateral geniculate nucleus. The implications of these findings are discussed, particularly in terms of the functional relationships between the visual cortex, lateral geniculate nucleus and visual thalamic reticular nucleus.

Animals↗
PubMedDate not supplied

The use of body mass index to predict body composition in children.

BACKGROUND: Simple anthropometric indices of body composition have particular appeal for use in children, and as such body mass index (BMI) has been used to predict percentage body fat in a number of studies. AIM: To evaluate the relationship between BMI and percentage body fat (%body fat) and a proposed, more appropriate relationship between BMI and fat mass/height(2) in a cohort of young children. SUBJECTS AND METHODS: Cross-sectional study of 109 children aged between 6 and 10 years residing in either Sydney or Brisbane, Australia. Weight and height were measured using standard methods. Body composition was measured using a stable isotope method to firstly determine total body water and subsequently fat free mass. RESULTS: The correlation between BMI and fat mass/height(2) was markedly greater than that between BMI and percentage body fat. In the entire group of children the R(2) (x100%) value for the relationship between BMI and fat mass/height(2) was 73.3% compared with 46.5% for the relationship between BMI and percentage body fat. CONCLUSIONS: We have shown that the use of BMI to predict fat mass/height(2), and consequently percentage body fat, is superior to the use of BMI to predict percentage body fat based directly upon the R(2) values of the above analysis.

Anthropometry↗
PubMedDate not supplied

Obesity in children and adolescents with acquired brain injury.

OBJECTIVES: To measure the prevalence of obesity and to assess associated clinical factors in children and adolescents with acquired brain injury (ABI). STUDY DESIGN: This cross-sectional study included 88 subjects aged between 2.4-17.7 years attending the Brain Injury Clinic at a tertiary paediatric hospital. Body mass index (BMI) and BMI z-scores were calculated. Obesity and overweight were defined using the International Obesity Taskforce cut-points. Associations were examined between BMI z-scores and the following: ABI severity, mobility level, duration from injury and presence of radiological injury. RESULTS: The prevalence of obesity in this population (obese = 15%) was higher than those in Australian children and adolescents (1995 National Nutrition Survey) while the prevalence of overweight (19.3%) was comparable. There was a linear trend for the participants to have a higher BMI z-score with increasing level of mobility (F = 6.91, df 1.70, p = 0.011). CONCLUSION: There is no data about obesity in children and adolescents with ABI. The study with limited statistical power suggests that obesity is prevalent in this population and increases with increasing level of mobility. Further studies are required to address the issue of obesity and related complications in this population.

Adolescent↗
PubMedDate not supplied

Outcomes of a nutrition audit in a tertiary paediatric hospital: implications for service improvement.

OBJECTIVE: To examine the process of anthropometric assessment of nutritional status in a tertiary paediatric hospital, to identify the barriers and to make recommendations for service improvement. METHODS: The accuracy of height and weight scales in wards was checked. Dietitians measured height and weight of a representative sample of 245 inpatients and checked whether these measurements had been recorded on bed charts. Patients were classified as overweight, obese or under-nourished. Diagnoses and procedures were obtained for each patient. Funding implications were modelled for inappropriate coding of nutritional status. RESULTS: The barriers to nutritional assessment and management of nutritional comorbidities were: (i) inaccurate height scales in seven out of 12 wards; (ii) under-recording of height and weight on patient bed charts (73% height missing, 12% both height and weight missing); (iii) under-reporting of obesity and under-nutrition in medical notes (one of eight obese patients, and none of 28 undernourished patients, reported); and (iv) low referral rate of obese or under-nourished children to dietetic services (two of 42 overweight/obese patients referred, five of 28 undernourished patients referred). Funding simulation showed that if under-nourished patients were correctly diagnosed then the potential facility reimbursement would have increased by $A52 326. CONCLUSIONS: Barriers to nutritional assessment can lead to failure to diagnose and treat both over- and under-nutrition, thereby affecting quality of patient care, and may have financial implications for hospitals. Suggestions for service improvement include provision of accurate equipment, adequate training of staff undertaking nutritional assessments and clear definitions of staff responsibilities in all aspects of the process.

Body Height↗