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Biomedical subjects

T Heim

Publications and source records attributed to T Heim.

At least 55 records · Page 3Linked to original sources
PubMed1981

Fatty acid utilization in perinatal de novo synthesis of tissues.

The fatty acid content of fetal tissues was utilized to estimate essential fatty acid accretion during intrauterine growth. These rates of essential fatty acid accretion were used to predict that 400 mg/kg of body weight for omega-6 fatty acids and 50 mg/kg of body weight for omega-3 fatty acids per day would be used for intrauterine de novo synthesis of tissues. For the high risk low birth weight infant of approx. 1300 g birthweight it can be calculated that extrauterine de novo tissue synthesis would utilize about 280 mg/kg of body weight for omega-6 fatty acids and about 35 mg/kg of body weight for omega-3 fatty acids based on projected growth rates that are similar in composition to intrauterine growth and amount to 17 g of gain per day. From fatty acid analysis of brown and white adipose tissue it was estimated that some 70 and 78% of these net whole body accretion rates for essential fatty acids represent omega-6 and omega-3 fatty acid accretion in the adipose organs. Fatty acid analysis of human milk at day 16 of lactation was utilized to estimate the low birth weight infants' daily intake of major essential and other fatty acids. For intake levels of 120 kcal/kg it was concluded that the essential fatty acid content of mothers' own milk provides 6650 +/- 345 mg of total fatty acids, 850 +/- 160 mg of omega-6 fatty acids and 140 +/- 17 mg of omega-3 fatty acids.

Adipose Tissue↗
PubMed1981

Fatty acid accretion in the development of human spinal cord.

Lumbar and cervical segments of fetal and infant spinal cord were examined to determine the deposition rate of individual fatty acids in the spinal cord during the last trimester of fetal development and first 16 weeks of life. Fatty acid accretion rates were determined by regression analysis of spinal cord fatty acids at varying developmental ages. During the last trimester of fetal growth, accretion of major tissue fatty acids occurred earlier in cervical segments of spinal cord and at a greater rate than observed in lumbar regions. Postnatal accretion of fatty acids in cervical regions of spinal cord was minimal on a per gram of tissue basis with the exception of moderate increases in total omega-9 and saturated fatty acids, reflecting myelination. Significant postnatal accretion of fatty acids in lumbar regions of the spinal cord occurred some 4 weeks postnatally at rates significantly in excess of in utero rates. These developmental changes in fatty acid accretion are quantitatively relevant to estimates of fatty acid incorporation into spinal cord and parallel known processes of myelination and increasing neuro-motor activity in the developing infant.

Fatty Acids↗
PubMed1981

Fatty acid accretion in fetal and neonatal liver: implications for fatty acid requirements.

The fatty acid content of liver was determined during the last trimester of infant growth and first 4 months of life in order to estimate fatty acid levels of developing liver and to assess minimal fatty acid requirements for tissue synthesis. Accretion rates were computed by regression analysis on fatty acid determinants of total liver lipid extracts from infants of varying developmental ages. During the last trimester of liver growth, accretion of most fatty acids paralleled increases in liver weight with the exception of C18:3, omega-3. This fatty acid remained at consistently low levels during the last trimester and represented less than 10% of total omega-3 fatty acids present in liver, even though significant accretion of longer chain omega-3 homologues occurred during the final trimester. For the term infants studied, significant increase in liver weight did not occur during the early weeks of life. However, liver levels of major fatty acids declined during the first five weeks of life apparently reflecting mobilization of saturated, omega-9 and omega-3 fatty acids from liver. During the first four months of life C18:2, omega-6 and total omega-6 fatty acid content of liver increased about 3.5- and 2-fold, respectively. After the initial 5 week lag net accretion of other fatty acid components also occurred in the developing liver. These developmental changes in fatty acid components of liver are quantitatively relevant to estimating the magnitude of the potential essential fatty acid reserve that may be present in liver of the developing human neonate.

Fatty Acids↗
PubMed1981

Influence of postnatal age, energy intake, and weight gain on energy metabolism in the very low-birth-weight infant.

The relative importance and interrelationship of postnatal age, energy intake, and weight gain on metabolic rate is evaluated in 28 studies in 13 formula-fed very low-birth-weight AGA infants. The relationships between metabolic rate, energy intake, weight gain, and age all follow a similar pattern, increasing in the first two weeks of life and subsequently stabilizing. Significant linear correlations are demonstrated between metabolic rate and both energy intake (r = 0.88, P less than 0.001) and weight gain (r = 0.86, P less than 0.001). For each gram of weight gain, 0.67 kcal (2.8 kj) are expended in addition to the maintenance energy requirement of 51 kcal/kg/day. The increase in metabolic rate in the early postnatal period appears to be a consequence of the energy cost of tissue synthesis. Changes in metabolic rate with postnatal age are modulated by increasing energy intake and weight gain.

Age Factors↗
PubMed1981

Relation between heart rate and energy expenditure in the newborn.

This study defines the relationship between heart rate and metabolic rate in newborn infants and evaluates the accuracy of prediction of metabolic rate from heart rate. Continuous measurements of oxygen uptake, CO2 production, respiratory quotient, and cumulative heart rate were performed using computerized, open-circuit indirect calorimetry and on-line electrocardiogram monitoring over periods of 1 to 24 hr (mean 4.5 hr). Metabolic rate was calculated from the individual oxygen uptake and respiratory quotient. Thirty-five studies were performed in 16 infants (birthweight 0.75 to 3.1 kg; gestational age, 26 to 42 wk; mean +/- S.D. age at study, 26.5 +/- 15.7 days; study weight, 1.78 +/- 0.5 kg). Metabolic rate (cal/kg . min) and heart rate (beats/min) were compared minute by minute (8269 measurements) and showed a close third degree polynomial relationship for heart rates of 110 to 230/min (y = -0.0000291x3 + 0.01685x2 -2.93x + 197; r = 0.99; P less than 0.001); however, at heart rates above 140 beats/min, a linear relationship was found (r = 0.997; P less than 0.001). From cumulated heart rate measurements, factors defining metabolic rate per heart beat were also determined: for each beat 51.8 +/- 6.8 microliter of oxygen/kg are consumed and 0.258 +/- 0.03 cal/kg (1.1 J/kg) are expended. Despite the wide variation in birthweight, gestational age, method of feeding, and clinical characteristics, there was a remarkable consistency in the heart rate-metabolic rate relationships. A further 10 studies were performed in a similar group of infants to assess the predictive value of the previously defined relationships and showed a mean percentage deviation of 5.7 +/- 4% from the measured value. We conclude that in the varied group of newborns studied, heart rate correlates closely with metabolic rate and that cumulative heart rate measurements enable the estimation of metabolic rate in newborn infants. This provides a method of monitoring energy expenditure and caloric requirements over long periods.

Energy Metabolism↗
PubMed1980

Intrauterine fatty acid accretion rates in human brain: implications for fatty acid requirements.

Fatty acid components of infant brain were determined to assess fatty acid requirements for synthesis of structural lipids in brain tissue during the last trimester of development in the fetus. Quantitative fatty acid analysis of cerebellum, frontal and occipital brain lobes indicated rapid accretion of chain elongation and desaturation products during the last trimester of brain growth. Frontal and occipital brain lobes were similar in fatty acid content. Fatty acid accretion rates were determined by regression analysis of tissue fat components at varying gestational ages. Tissue accretion of saturated and omega-9 fatty acids, as well as total fatty acid content, paralleled increases in whole brain weight. Levels of linoleic (C18:2, omega-6) and linolenic (C18:3, omega-3) acids were consistently low in brain during the last trimester of development, while marked substantial accretion of long chain desaturation products, arachidonic (C20:4, omega-6) and docosahexaenoic (C22:6, omega-3) acids occurred. Accretion of individual fatty acids of cerebellum also reflected changes in tissue total fatty acid content, with exception of the levels of C18:3, omega-3 and its chain elongation products present in cerebellum during the last trimester. These developmental changes and estimates of fatty acid incorporation into whole brain and cerebellum are quantitatively relevant to estimation of fatty acid requirements of the low birth weight neonate.

Brain↗
PubMed1980

Extrauterine fatty acid accretion in infant brain: implications for fatty acid requirements.

Total fatty acid content of infant brain was determined to assess minimal fatty acid requirements for synthesis of structural lipids in brain tissue during the first 13 weeks of life. Fatty acid accretion rates were determined by regression analysis of tissue fat components at varying postnatal ages. Quantitative fatty acid analysis indicated that postnatal accretion of long-chain polyenoic fatty acids in cerebellum, frontal and occipital brain lobes initially appeared to lag behind the rate of increase in brain weight and brain fat content. After a 4-week period total long-chain fatty acids increased at a rate similar to the increase in brain weight. Accretion of individual fatty acids in cerebellum also reflected changes in tissue total fatty acid content. These developmental changes in fatty acid components of whole brain and cerebellum are quantitatively relevant to estimation of the minimal extrauterine fatty acid requirements of the human neonate.

Brain↗
PubMed1980

Serum intralipid levels in neonates during parenteral nutrition: the relation to gestational age.

To detect hyperlipidemia, serum Intralipid levels have been monitored by nephelometry (light scanning index) in children on total parenteral nutrition with glucose, amino acids, and Intralipid during the past 2 yr. Sufficient data were available in 93 neonates to analyze the effect of an Intralipid dose on serum levels in infants of different gestational ages. Guided by monitoring, Intralipid was given by constant infusion at a dose varying between 0.5 to 6.0 g/kg/day. Median post natal age at the start of therapy was 7 days. Gestational age varied from 27 to 32 wk in 36 infants (Group I), 33 to 36 wk in 18 (Group II), and was more than 37 wk in 39 (Group III). Of Group I infants, 28% developed hyperlipidemia (Intralipid level greater than 100 mg/100 ml) as compared to an incidence of 7% in Groups II and III. Peak Intralipid levels were highest in Group I and regression analysis also indicated that Intralipid was least well tolerated by this group. The dose response during the first 48 hr of Intralipid therapy was not significantly different from dose response later. Similarly, diagnosis did not seem to affect the dose-response. Dose recommendations were based on analysis of dose response lines. Even using these guidelines monitoring of serum Intralipid is advisable to avoid hyperlipidemia during Intralipid therapy. It is recommended that measurements of serum Intralipid be made several times per week in very low birth weight infants (Group I), and weekly in more mature neonates after a safe maximum Intralipid dose is established.

Age Factors↗
PubMed1980

13C abundances of nutrients and the effect of variations in 13C isotopic abundances of test meals formulated for 13CO2 breath tests.

Unlike 14CO2 breath tests, 13CO2 breath tests are performed in the presence of a large background of naturally occurring isotope. Because the exact abundance of 13CO2 in breath can be changed by variations in diet, a study of the 13C abundance of dietary constituents and their effects on breath 13CO2 has been undertaken. Dietary constituents have been combusted to CO2 and the relative abundance of 13C analyzed by mass spectrometry. Breath CO2 was collected and isotopically analyzed after the ingestion of several dietary constituents and test meals. The 13CO2 abundance of breath CO2 was shown to change in response to the 13C abundance of the substrate being oxidized. Conversely, a test meal that closely approximates the 13C abundance of fasting breath CO2 from North Americans was shown not to alter the 13CO2 abundance in breath. Investigation of the breath 13CO2 response to individual 13C-labeled dietary constituents demonstrated that amino acids produced the earliest 13CO2 response followed in order by medium chain triglycerides, carbohydrates, and long chain triglycerides. Because of the variation in 13C abundances in nature, the 13C abundance of any unlabeled substrate ingested during a 13CO2 breath test must be considered in order to eliminate artifacts that may reduce the sensitivity of the breath test or produce erroneous results. Methods for correcting breath tests for changes in background 13CO2 abundance are also discussed.

Adult↗
PubMed1977

Tracer kinetic studies on in vivo fatty acid metabolism in white adipose tissue of well-fed and starving newborn rabbits during acute or prolonged exposure to cold.

Pool size (M), and specific radioactivities (SA) of lipids of white adipose tissue (WAT), as well as the flow rates (ms) of free fatty acids (FFA) from plasma into WAT were studied by injecting 14C-1-palmitate (20.10(6) cpm/100 g body weight) into 7-day-old rabbits reared in a thermoneutral (Group I) or a cold environment (Group II) or subjected to starvation at an ambient temperature (Ta) of 35 degrees C (Group III) or at Ta 20 degrees C (Group IV). Experiments were carried out at Ta 20 degrees C in all four groups of rabbits. The pool size of esterified and non-esterified fatty acids of WAT was reduced in both the well-fed animals raised in the cold and in the starving ones. The SA of tissue FFA and phospholipid fatty acid (PL-FA) was highest in Group III and Group IV indicating an increased FFA metabolism of WAT in animals subjected to starvation prior to acute exposure to cold. The flow rate (ms) of FFA between plasma and WAT increased twofold in Group IV but remained about one fifth that of the ms between plasma and brown adipose tissue (BAT) indicating that the contribution of WAT to cold-induced calorigenesis of the whole animal must be regarded as of secondary importance.

Adipose Tissue↗
PubMed1975

Studies on plasma free-fatty-acid metabolism and triglyceride synthesis of brown adipose tissue in vivo during cold-induced thermogenesis of the newborn rabbit.

Parameters of plasma free fatty acid metabolism (pool size, half time, disappearance rate, turnover time and absolute turnover rate), the influx of plasma free fatty acids into the glycerides of brown adipose tissue and the pathway of triglyceride synthesis in brown adipose tissue (glycerol-1-phosphate versus monoglyceride pathway) were examined after intravenous injection of [1-14C]palmitate in newborn rabbits. In the thermoneutral environment of 35 degrees C the turnover rate of plasma free fatty acids was 10.20 mumol/min per 100 g body weight and its flux into the glycerides of brown adipose tissue 0.367 mumol/min per 100 g body weight. Cold exposure at an ambient temperature of 20 degrees C caused a decrease to 5.84 mumol/min and 0.207 mumol/min per 100 g body weight, respectively. Both under basal conditions at an ambient temperature of 35 degrees C and under cold-induced thermogenesis at an ambient temperature of 20 degrees C triglyceride synthesis in brown adipose tissue ran through the glycerol 1-phosphate pathway.

Adipose Tissue, Brown↗
PubMed1975

[Uptake of serum free fatty acids by lipids of the brown adipose tissue].

The flow rate of serum free fatty acids (FFA) into the lipids of brown adipose tissue (BAT) of newborn rabbits was determined by intravenous injection of [14C]-1-palmitate. For a normal 7 day old animal during acute cold exposure the flow rate is (1 hour in 20 degrees C ambient temperature) 0.209 mumol/minute, that is 3.6% of the serum FFA turnover. Prolonged cold exposure only induced an increase in FFA influx if the lipid depot had been depleted (48 hours starvation in 20 degrees C). Consequently, the BAT takes up serum FFA for heat production only after mobilisation of its lipid stores. It is supposed that the mechanism of the uptake of serum FFA by the BAT is connected with their esterification to triglycerides. The phospholipids of BAT which are not only membrane bound lipids are characterized by a high metabolism.

Adipose Tissue, Brown↗
PubMed1975

[The effect of cold and hunger on the free fatty acid metabolism in the serum of newborn rabbits].

A tracer kinetic study with [14C]-1-palmitic acid was carried out to study the influence of acute exposure to cold and starvation on free fatty acid (FFA) metabolism in serum of newborn rabbits. The turnover rate of serum FFA was 10.20 mumol/min in well fed rabbits kept in a thermoneutral environment (normal conditions). Cold exposure as well as starvation either in a cold or thermoneutral environment resulted in a diminution of the turnover rate, being the consequence of a significantly reduced pool of FFA. It was 9.57 mumol under normal conditions. The disappearance rate (1.07 min-1), half time (0.65 min) and turnover time (0.94 min) of well nourished animals was slightly, but mostly not significantly, influenced by cold exposure and starvation. The cold induced increase in serum FFA concentration and the decrease following restoration of thermoneutrality did not run parallel with changes in the absolute turnover rate.

Animals↗