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Biomedical subjects

S H Zlotkin

Publications and source records attributed to S H Zlotkin.

At least 19 recordsLinked to original sources
PubMed2001

Fractional zinc absorption using a single isotope tracer.

BACKGROUND: Fractional absorption of zinc (Zn) has been measured using dual isotopes of Zn given simultaneously. An oral test dose and an intravenous (i.v.) reference dose are administered, followed by the measurement of the double isotopic enrichment (E) in urine 48 h after administration. We postulated that an estimate of the %E in urine for a given i.v. dose of Zn may be used to eliminate the need for venipuncture and the second Zn isotope. OBJECTIVES: To determine a constant (k) for the Zn enrichment of urine after i.v. administration of a dose of labeled Zn in Zn-replete subjects. To use 'k' to calculate fractional absorption of Zn, and to compare these values to values obtained using the standard dual isotope method. DESIGN: Single-arm cohort. SETTING: The Hospital for Sick Children, Toronto, Canada. SUBJECTS: Twenty-three healthy adults were recruited from the Metropolitan Toronto area. Seventeen subjects completed the study. INTERVENTIONS: A 2.29 mg i.v. dose of (67)Zn followed immediately by a 2.50 mg oral dose of (70)Zn. RESULTS: Population mean percentage enrichment (%E) of (67)Zn in urine was 1.43 (95% CI 1.26, 1.60). The ratio of the i.v. dose to mean %E in urine (k) was estimated to be 1.60 mg (95% CI 1.43, 1.82). There was no difference in the mean fractional absorption of Zn calculated using the single compared to the dual isotope method: 12.58% (95% CI 2.22, 22.94) vs 12.68% (95% CI 4.52, 20.85), respectively (P=0.89). The correlation coefficient between the two methods was 0.81 (P<0.0001). CONCLUSIONS: The dual isotope method may be replaced by using a constant (k) and a single oral dose of isotopic-enriched Zn to estimate fractional absorption of Zn within a population. SPONSORSHIP: Gerber Products Company, Fremont, MI.

Administration, Oral↗
PubMed2000

Discontinuation of enterostomy tube feeding by behavioral treatment in early childhood: a randomized controlled trial.

OBJECTIVE: To determine whether behavior therapy was more effective than nutritional therapy in obviating the need for enteral feeding in infants with resistance to feeding. STUDY DESIGN: Sixty-four children aged 4 to 36 months who were tube fed for at least 1 month and had resistance to feeding were randomly assigned to either behavioral or nutritional interventions (32 per group). For 7 consecutive weeks subjects and their primary feeders attended a weekly clinic with 1 of 2 dietitians followed by 4 follow-up visits. The nutritional intervention provided structured schedules and routines to stimulate the hunger/satiety cycle. The behavioral intervention provided the same schedules and routines plus behavioral therapy (extinction). The primary outcome measure was the proportion of successes, defined as infants no longer requiring tube feeding at the third follow-up visit in each group (4(1/2) months after start of trial). The decision to discontinue tube feeding was made by an independent observer who used criteria defined before the study commencement. RESULTS: Fifteen (47%) of 32 subjects in the behavioral group versus none in the nutritional group were successes (P <.001). CONCLUSION: Behavior therapy is more efficacious in eliminating the need for tube feeding than nutritional counseling alone.

Behavior Therapy↗
PubMed2000

Developing and implementing food-based dietary guidance for fat in the diets of children.

This article discusses the process by which a country can effectively solve health problems through recommended changes in the nutrient content of the diet. Each country must consider not only the development of scientific guidelines suitable for its population, but also strategies for effective food-based dietary guidance to achieve the goal. This is best done by integrating health and dietary goals when forming scientific guidelines and by developing effective partnerships among the many sectors that influence the food supply and food selection. Using fat intake in children as an example, this article describes the determinants of success in achieving the goals of science-based dietary guidelines through food-based dietary guidance.

Canada↗
PubMed1999

Iron is well absorbed by healthy adults after ingestion of double-fortified (iron and dextran-coated iodine) table salt and urinary iodine excretion is unaffected.

Severe deficiencies of iron (Fe) and iodine (I) affect more than one third of the world's population. A table salt, fortified with I and Fe, would be useful in areas in which anemia and goiter coexist. However, interactions between the two minerals have prevented their simultaneous use as fortificants. A method has been developed to coat I with dextran such that after spraying onto table salt, Fe and I do not interact. Our objective was to determine the absorption of Fe and the urinary excretion of I from table salt when provided in meals designed to significantly inhibit or enhance Fe absorption. Subjects (n = 16) ingested Fe-enhancing and Fe-inhibiting meals containing 5 g of table salt with 0.39 micromol dextran-coated I as potassium iodide and 1 mg of Fe (ferrous fumarate labeled with 59Fe) per gram of salt. Subjects also received a reference dose of 3 mg of ferrous fumarate labeled with 59Fe to "correct" for interindividual variation in iron absorption at a later date. Measured by whole-body counting, Fe-absorption from the Fe-enhancing meal (36.2 +/- 12.0%, corrected; 13.5 +/- 13.8% uncorrected) was significantly higher than that from the Fe-inhibiting meal (7.4 +/- 11.3%, corrected; 4.0 +/- 8.4%, uncorrected) (P < 0.0001). Urinary excretion of iodine at baseline and postingestion were not significantly different (0.89 +/- 0.5 vs. 1.06 +/- 0.39 micromol/L, P < 0.47) and were within the normal range. We conclude that Fe was well absorbed but influenced by the composition of the meal and that urinary excretion of iodine was maintained in the normal range with dextran-coated iodine.

Absorption↗
PubMed1998

Disparity of serum transferrin receptor measurements among different assay methods.

OBJECTIVE: To highlight differences in the quantification of transferrin receptor (TfR) concentration (a reliable index of iron deficiency) between three different assay methods. DESIGN: Methods comparison of TfR measurements in 'elevated' and 'normal' human sera using the Ramco, Quantikine and 'Lab' assays. SETTING: The Hospital for Sick Children, Toronto, Ontario, Canada. SUBJECTS: Pooled TfR for elevated and normal human sera obtained from the Ramco TfR assay kit. MAIN OUTCOME MEASURES: Differences between TfR concentrations in normal and elevated samples and repeatability for each assay method and limits of agreement in TfR quantification between assay methods. RESULTS: The mean TfR concentrations for the elevated reference serum samples was higher than the normal reference samples within each individual assay (P < 0.001); however, measurement agreement between methods was poor. CONCLUSIONS: Recognition of the relative differences in the values obtained from each of the assays should affect the interpretation of TfR concentration as an index of iron deficiency.

Humans↗
PubMed1997

Percentile estimates for transferrin receptor in normal infants 9-15 mo of age.

To establish percentile estimates of transferrin receptor (TfR) for healthy infants, plasma TfR was measured in 485 healthy infants 9-15 mo of age from Edmonton, Toronto, Montreal, and Halifax. Education and income of the sample families were reflective of the average family based on the 1991 census estimates. The mean (+/-SD) plasma TfR concentration was 4.4 +/- 1.1 mg/L. As expected in the infant population, there were no differences in TfR concentrations as a result of sex, and within this small age range there was no significant change across age. Furthermore, the TfR concentration in plasma was not associated with hemoglobin, serum ferritin, or free erythrocyte protoporphyrin. TfR has been shown to be a sensitive, quantitative measure of tissue iron deficiency not affected by inflammation and is potentially important in the diagnosis of iron deficiency, but there is a lack of normative data, particularly in infants, who are at highest risk of iron deficiency. If TfR proves useful in the diagnosis of iron deficiency, the current data will be useful as a reference standard for healthy infants.

Female↗
PubMed1996

Day-to-day variation of transferrin receptor and ferritin in healthy men and women.

To determine the total day-to-day intraindividual variability of ferritin and transferrin receptor (TfR), we collected venous serum and plasma and capillary serum and plasma samples during 10 nonconsecutive days over a 4-wk period from a group of healthy men (n = 10) and women (n = 11) aged 19-46 y. On the basis of a method previously established in younger and older adults, biological (sigma 2 day) and analytical (sigma 2 rep) variance components were computed and summed to obtain the total day-to-day intraindividual variability (sigma 2 tot). The total day-to-day intraindividual CV (CVtot) was lower for TfR than for ferritin measurements. One to two discrete blood samples are required to accurately determine capillary and venous TfR, whereas capillary and venous ferritin, which have a higher CVtot, require three to six samples. Results from the current study showing the low biological and analytical variability of TfR support the use of this new test for assessing a person's iron status.

Adult↗
PubMed1996

A review of the Canadian "Nutrition recommendations update: dietary fat and children.".

A joint Working Group from the Canadian Paediatric Society and Health Canada met in the early 1990s to consider the applicability of recommendations to restrict total and saturated fat in children > or = 2 y of age. The Group weighed information from the literature on the nutritional needs for growth and development against evidence relating diet to risk of nutrition-related diseases. The Group concluded that the efficacy of the fat-restricted diet could not be assumed. There was no evidence that implementation of the diet would reduce illness in later life or provide benefit to children as children. Regarding safety, some children consuming self-selected diets with low fat intakes have lower energy intakes and food patterns that may compromise the intake of certain key nutrients. The primary recommendations of the Group were that the provision of adequate energy and nutrients to ensure adequate growth and development remains the most important consideration in the nutrition of children and that during the preschool and childhood years, nutritious food choices should not be eliminated or restricted because of fat content. Once linear growth has stopped, fat intake as currently recommended (30:10) is appropriate.

Adolescent↗
PubMed1995

Determination of iron absorption using erythrocyte iron incorporation of two stable isotopes of iron (57Fe and 58Fe) in very low birthweight premature infants.

Due to limited erythropoiesis, iron needs for the premature infant during the first 2 months of life are low. With the potential for increased use of erythropoietin in the preterm infant, iron requirements may become markedly higher. The ability of the preterm infant to absorb iron, therefore, becomes crucial. Previous studies using single stable isotopes of iron without metabolic balances were unable to quantitatively determine iron absorption since the percentage of absorbed iron appearing in the erythrocyte could not be measured. The objective of the current study was to determine iron absorption using the method of erythrocyte iron incorporation of two stable isotopes of iron given by the enteral and parenteral route to very low birth weight (VLBW) infants. Results obtained were compared to iron absorption values from studies using single isotopes and metabolic balance techniques. Six VLBW premature infants (gestational age 26.8 +/- 1.7 weeks, postnatal age 3.6 +/- 1.9 weeks, birth weight 863 +/- 117 g) were studied. Iron dosages were (i.v.) 0.15 mg/kg (57FeSO4) and (enteral) 1.5 mg/kg (58FeSO4). Erythrocyte isotope ratios, 57Fe/54Fe and 58Fe/54Fe, were determined by inductively coupled plasma mass spectrometry (ICP/MS) from single blood samples (100 microliters) collected before and after concurrent enteral (58Fe) and parenteral (57Fe) administration of isotopes. Only 17.8% of the i.v.-infused iron dose was incorporated into hemoglobin on day 15. Using a correction factor based on the percentage of i.v. iron (57Fe) incorporated into erythrocytes, the corrected incorporation of 58Fe was calculated to be 26.3 +/- 13.0% of the enteral dose of 58FeSO4.

Absorption↗
PubMed1995

Trace elements in nutrition for premature infants.

Ten trace elements that are nutritionally essential include: zinc, copper, selenium, chromium, manganese, molybdenum, cobalt, fluoride, iodine, and iron. This article briefly reviews the biochemistry of these trace elements, describes clinical deficiency states, and provides a rationale for recommended enteral and parenteral intakes for preterm infants.

Copper↗
PubMed1991

The influence of zinc-binding ligands in fetal circulation on zinc clearance across the in situ perfused guinea pig placenta.

Although zinc is essential for normal fetal growth and development, little is known about factors that influence its transfer across the placenta. The in situ perfused guinea pig placenta model was used to study the influence of zinc-binding ligands in fetal circulation on maternofetal placental zinc transfer. A placenta of each anesthetized sow was perfused (on the fetal side) with a physiological perfusate via the umbilical vessels, with the fetus excluded. The sow was infused intravenously with 65Zn as a tracer of placental zinc clearance and with antipyrine as an indirect indicator of maternal placental blood flow. Maternal plasma and placental effluent samples collected at intervals were counted for 65Zn with a gamma counter, and the absorbance of nitrosated antipyrine was measured at 350 nm. The addition of physiological levels of zinc-binding ligands (albumin, L-histidine and L-cysteine) to the perfusate increased the relative maternofetal clearance of zinc across the placenta calculated as zinc clearance/antipyrine clearance [mean +/- SEM; 0.113 +/- 0.016 vs. 0.062 +/- 0.012; ligands vs. no ligands; n = 8; P less than 0.05]. The results suggest that the availability of zinc-binding ligands in fetal circulation is one determinant factor of placental zinc transfer.

Animals↗
PubMed1990

Hepatic sulfur amino acid metabolism in rats with chronic renal failure.

We recently demonstrated elevated plasma amino acid concentrations and abnormal responses to amino acid supplementation (e.g., elevated methionine and phenylalanine) in children with chronic renal failure (CRF). We also recently developed an improved model of CRF in which animals manifest abnormal tissue amino acid levels, marked anorexia and growth failure. The objective of the current study was to determine the etiology of elevations of sulfur amino acids in animals with chronic renal failure. Chronic renal failure, defined as creatinine clearance less than 30% of control values, was induced in male rats in a two-stage surgical procedure. Four groups were studied over 2, 4 and 6 wk: control (non-operated) control (sham-operated), pair-fed (sham-operated and pair-fed with uremics) and CRF. Animals with CRF were anorexic and growth-retarded. Although plasma sulfur amino acid levels tended to be lower in the uremic animals than in controls, hepatic tissue concentrations were higher. Methionine adenosyltransferase was higher, but cystathione synthase and cystathionase activities were not significantly different in rats with CRF compared to pair-fed controls. We conclude that uremia, not malnutrition, affected sulfur amino acid metabolism and that with CRF, a normal adaptive response to elevated methionine levels was occurring, sufficient to normalize sulfur amino acid pool size. Alternative causes of elevated sulfur amino acids must be sought.

Amino Acids, Sulfur↗
PubMed1990

The effect of zinc levels in fetal circulation on zinc clearance across the in situ perfused guinea pig placenta.

Although zinc is essential for normal fetal growth and development, little is known about factors that influence its transfer across the placenta. The in situ perfused guinea pig placenta model was used to study the influence of the zinc concentration of fetal circulation on maternofetal placental zinc transfer. A placenta of the anaesthetized sow was perfused (on the fetal side) with a physiological perfusate via the umbilical vessels, with the fetus excluded. The sow was infused intravenously with 65zinc as a tracer of placental Zn clearance, and with antipyrine as an indirect indicator of maternal placental blood flow. Maternal plasma and placental effluent samples collected at intervals were counted for 65zinc by gamma counter, and the absorbance of nitrosated antipyrine was measured at 350 nm. Varying the mean zinc concentration in the perfusate from 0.176 to 1.87 mg/L had no effect on relative zinc clearance calculated as zinc clearance/antipyrine clearance (mean +/- SEM; 0.085 +/- 0.010 vs. 0.114 +/- 0.018; n = 6; p greater than 0.05). The results suggest that short-term changes in fetal zinc status do not influence placental zinc transfer.

Animals↗
PubMed1989

Nutrient interactions with total parenteral nutrition: effect of histidine and cysteine intake on urinary zinc excretion.

Because cysteine and histidine, two amino acids included in total parenteral nutrition regimens, bind zinc and increase its renal ultrafilterability, my objective was to quantify the effects of infusion of amino acids, including cysteine and histidine, on urinary zinc excretion. The effect of the infusion of high amounts of cysteine and no cysteine (100 mg/kg/day vs none) and of high and low amounts of histidine (165 vs. 95 mg/kg/day) on urinary zinc excretion was determined in 14 newborn infants receiving total parenteral nutrition who had similar zinc intakes (approximately 7 mumol/kg/day). After a 72-hour adaptation period, each infant's urine was collected for two 48-hour periods. Urinary zinc excretion during the high-dose histidine and cysteine infusion periods was significantly elevated compared with that during the no-cysteine and low-dose histidine periods. Therefore concurrent intakes of specific amino acids may have to be considered when zinc dosages are calculated.

Cysteine↗