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Biomedical subjects

M Janghorbani

Publications and source records attributed to M Janghorbani.

At least 37 records · Page 2Linked to original sources
PubMed1992

Trends in mortality from stroke in Scotland, 1950-1986.

The Scottish Registrar General's Annual Reports have been used to study trends in mortality from stroke in Scotland during 1950-1986 in those aged 45 to 74. In 1950 the age-adjusted mortality rate was 347.4 per 100,000 population for men and 360.8 for women, falling to 199.6 for men and 155.8 for women in 1986. This downward trend has increased from 1976 for males. The average annual decline in age-adjusted mortality from stroke over the 37-year period was 4.0 per 100,000 in males and 5.5 in females. This reduction in death rates was proportionally higher for women compared with men in all age groups over 55 years. As with cardiovascular deaths, mortality from stroke was lower in the east than in the central region and west of Scotland. The reduction in mortality resulted in a substantial 'saving' of lives, estimated at 12,500 between 1980 and 1984.

Age Factors↗
PubMed1992

Iron absorption and incorporation into red blood cells by very low birth weight infants: studies with the stable isotope 58Fe.

Measurements of iron absorption and incorporation into RBCs were obtained with the stable isotope 58Fe, administered as a reference dose, in 11 premature infants with birth weights between 780 and 1,520 g and gestational ages between 24 and 33 weeks. Each study included a timed stool and urine collection, nasogastric tube administration of a single dose of about 228 micrograms of 58Fe/kg of body weight (as FeSO4, with 10 mg/kg of vitamin C) between feedings, and blood samples before 58Fe (day 1) and then 2 weeks (day 15) later. Gastrointestinal absorption of the 58Fe dose as measured by fecal isotope balance was 41.6 +/- 17.6% (mean +/- SD). However, only 12.0 +/- 9.6% of the 58Fe dose (28.7 +/- 22.3% of the absorbed 58Fe dose) was incorporated into RBCs on day 15. 58Fe absorption and 58Fe incorporation into RBCs on day 15 were significantly correlated with the hemoglobin concentration and reticulocyte count on day 1. Transfusion history did not affect 58Fe absorption or 58Fe incorporation into RBCs. We conclude that concurrent measurement of 58Fe absorption with fecal monitoring and of 58Fe incorporation into RBCs permits a better understanding of the fate of iron ingested by premature infants than either measurement alone.

Algorithms↗
PubMed1991

Correlation between the size of the selenite-exchangeable metabolic pool and total body or liver selenium in rats.

This study explored the quantitative relationship between the size of the selenite-exchangeable metabolic pool (WSe-EMP) and total body or liver Se in rats of varying age and past Se intake. We performed four experiments. In one, weanling rats were fed either a Se-deficient or Se-supplemented diet for 30 d, followed by measurement of WSe-EMP and total body Se. For the other experiments, rats were fed natural sources of Se without added selenite until adult age and then either subjected to acute Se restriction during the 7 d of measurements or maintained on a Se-sufficient diet. For the animals fed the selenite diet, the 7-d average ratio of WSe-EMP:total body Se (Se(end),0) was 0.370 +/- 0.009, which was not significantly different from the corresponding value (0.350 +/- 0.018, P greater than 0.05) for the Se-deficient group. When the group mean values of WSe-EMP were correlated with the corresponding mean values of Se(end),0 for all experiments, we obtained highly linear relations (r2 greater than 0.96). When WSe-EMP for each animal was correlated with the corresponding value of total body endogenous Se (Se(end)) or liver Se(end) (for t = 1 or 7 d), we found equally strong linear relations (r2 greater than or equal to 0.99). We concluded that WSe-EMP accurately reflected total body Se content or the Se content of such organs as liver, regardless of past Se intake, chemical form of Se or age and size of the animals.

Administration, Oral↗
PubMed1991

Selenium absorption and retention by very-low-birth-weight infants: studies with the extrinsic stable isotope tag 74Se.

Measurements of dietary selenium absorption and retention were obtained after administration of a single dose of the extrinsic stable isotope tag 74Se in 20 appropriate for gestational age premature infants with birth weights between 720 and 1,630 g and gestational ages between 26 and 33 weeks. Infants were assigned randomly to receive a standard premature formula (1.34 microgram of Se/dl) or a selenium-supplemented version of that formula (2.03 micrograms of Se/dl). Each study consisted of one feeding that had been extrinsically labeled with 74Se (1.03 microgram/kg) and a timed stool and urine collection. The percent 74Se absorption was 91.2 +/- 5.4% (mean +/- SD) from the standard formula and 86.2 +/- 3.0% from the selenium-supplemented formula (p less than 0.05), but the percent of the absorbed 74Se retained was not different, i.e., 96.6 +/- 2.1% and 95.0 +/- 2.8%, respectively. The percent net absorption and net retention were also not different between the standard and selenium-supplemented formulas; net absorption was 72.7 +/- 18.1% vs. 67.8 +/- 18.8% and net retention was 57.2 +/- 17.6% vs. 53.3 +/- 20.2%, respectively. The percent 74Se absorption and true selenium absorption were significantly correlated with the percent net selenium absorption and net selenium absorption, respectively. We conclude that an extrinsically administered dose of 74Se can be used to study selenium nutrition in growing premature infants.

Birth Weight↗
PubMed1991

Gender-related differences in iron absorption by preadolescent children.

In a study of absorption of iron from meals by preadolescent children (Tanner stage 1), we had noted that erythrocyte incorporation of the extrinsic iron label was somewhat greater by girls than by boys. Although the difference was not significant, the observation seemed to warrant further study. Study A: A precisely determined quantity of ferrous sulfate enriched with the stable isotope 58Fe was given without food to 15 boys and 15 girls (Tanner stage 1) after an overnight fast and was immediately followed by a dose of 70 mg of ascorbic acid. 58Fe enrichment of the erythrocytes was determined by inductively coupled plasma mass spectrometry at baseline and 14 and 42 d after administration of the 58Fe dose. Geometric mean erythrocyte incorporation of the 58Fe label was 35.2% of intake by boys and 45.0% of intake by girls. The difference was significant (analysis of covariance with serum ferritin as covariate, p = 0.035). Study B: Fifteen boys and 15 girls (Tanner stage 1) were fed a breakfast labeled with 58Fe. Geometric mean erythrocyte incorporation of the 58Fe label was 14.8% of intake by boys and 24.7% of intake by girls. The difference was significant (analysis of covariance with serum ferritin as covariate, p = 0.004). Because serum ferritin concentrations were similar in boys and girls, the gender-related difference in iron absorption (as reflected by erythrocyte incorporation of the label) does not appear to be explained by a difference in body stores of iron. We hypothesize that hormonal differences between boys and girls in Tanner stage 1 favor iron absorption by girls.

Ascorbic Acid↗
PubMed1990

Effect of Mg nutriture on the dynamics of administered 25Mg exchange in vivo in the rat.

The effect of Mg nutriture on Mg exchange and interorgan distribution was studied in adult rats ten days after a single I.P. dose of (25)Mg ( approximately 5 mg). First the effects of level of Mg intake (0.25, 0.05, or 0.01% Mg) on standard measures of Mg nutriture were studied for 62d to fully document the Mg status of the adult rats. The Mg-deficient diet led to a reduction in plasma, erythrocyte and urine Mg concentration but the only tissues affected were kidney and bone; no outward signs of deficiency were observed. At this point, the 4 remaining rats from each diet group received a single dose of (25)Mg and were killed 10d later. Unlike measures of total Mg content, Mg restriction was observed to significantly alter the distribution of isotope within the soft tissue compartment. The proportion of retained isotope accumulated by soft tissues other than skeletal muscle increased. Because this was not true for skeletal muscle, exogenous (25)Mg label was diverted to more metabolically active tissues during Mg restriction. The apparent Mg exchangeable pool (MgEP) size, determined by in vivo stable isotope dilution, reflected this difference in skeletal muscle (25)Mg accumulation; MgEP size was 39% lower in Mg restricted (0.01% Mg) compared to control (0.05% Mg) rats. The pool of exchangeable Mg in bone was also reduced by Mg restriction but, unlike the soft tissue compartment, the reduction in bone exchangeable Mg was quantitatively similar to the reduction in total Mg content.

Journal Article↗
PubMed1990

Effect of acute selenium restriction on whole body endogenous selenium and the selenite-exchangeable metabolic pool in the adult rat.

The time course of changes in whole body endogenous selenium (Se(end)) was investigated during a short-term (7-day) selenium restriction study in the adult rat. The method of continuous feeding with a stable isotope of selenium was used to permit normal intake of selenium while distinguishing between the dietary and endogenous components of body selenium. Additionally, the effect of short-term selenium restriction on the time course of the selenite-exchangeable metabolic pool (Se-EMP) was investigated. Two groups of adult male rats were intubated with the in vivo stable isotope (74)SeO(3)(2-), then fed a Torula yeast diet (selenium <0.02 microg/g) and either deionized water (-Se group) or deionized water containing selenium as (76)SeO(3)(2-) (0.1 microg selenium/ml) (+Se group). Three animals from each group were killed at 24-hour intervals. Whole body Se(end) and the estimated size of Se-EMP (W(Se-EMP)) were determined using hydride generation-inductively coupled plasma mass spectrometry for isotopic measurements. Whole body Se(end) decreased linearly in the +Se group (Se degrees (end): 54.4 microg; Se(end) at 3 days: 49.3 +/- 2.1; Se(end) at 7 days: 45.2 +/- 2.2). The decrease was exponential for the -Se group (Se degrees (end): 54.4 microg; Se(end) at 3 days: 42.9 +/- 0.3; Se(end) at 7 days: 42.2 +/- 0.7). The value of W(Se-EMP,pl) (microg) was 19.8 +/- 0.6 at 1 day and 19.7 +/- 1.0 at 7 days for the +Se group. The corresponding values for the -Se group were 15.7 +/- 1.5 and 18.8 +/- 0.4. All respective values of W(Se-EMP,pl) for the -Se group were significantly smaller than for the +Se group (P < 0.05), with the exception of values at days 6 and 7. The value of W(Se-EMP,urine) (microg) was 2.1 +/- 0.2 at 1 day, increasing rapidly to 23.5 +/- 1.5 at 7 days for the +Se group. The corresponding values for the -Se group were 3.0 and 23.1.

Journal Article↗
PubMed1990

Development of the stable isotope tracer approach for studies of copper turnover in the rat and mouse.

The stable isotope tracer approach was explored for long-term investigations of copper turnover in the adult rat and mouse, with inductively coupled plasma mass spectrometry for isotope measurements. The isotopic measurement method permitted precision and accuracy of <1.0%, with an overall sample blank of <0.05 microg copper. Rats were fed a copper-deficient diet and deionized water with (+Cu) or without (-Cu) copper (20 microg/ml). Both groups underwent a single-day replacement of drinking water with 20 microg/ml of (65)Cu. Compared with the baseline isotope ratio ((65)Cu/(63)Cu) of 0.462 +/- 0.002, blood plasma ratios for the +Cu group on days 2, 7, and 14 postdosing were 0.702 +/- 0.021, 0.557 +/- 0.004, and 0.474 +/- 0.001, respectively. The corresponding data for liver were 1.652 +/- 0.018, 0.560 +/- 0.005, and 0.482 +/- 0.001, respectively. For the -Cu group, respective plasma ratios were 1.580 +/- 0.04. 0.917 +/- 0.02, and 0.664 +/- 0.01 for days 2, 7, and 14 postdosing, and the ratios for liver were 0.987 +/- 0.02, 0.876 +/- 0.04, and 0.739 +/- 0.03. Mice previously made copper deficient to varying degrees were given a single-day replacement with the label. When the 24-hour postdosing isotope ratios in the livers of these mice were correlated with the activity of plasma ceruloplasmin, a negative correlation (r = -0.85) was observed. Isotope enrichment in both rats and mice was greater in the copper-deficient animals compared with the controls.

Journal Article↗
PubMed1990

The selenite-exchangeable metabolic pool in humans: a new concept for the assessment of selenium status.

An in vivo isotope-dilution approach is considered for assessment of selenium status in human subjects. The approach depends upon the dilution of a single dose of the stable isotope 74SeO3(2-) in the selenite-exchangeable metabolic pool. Data from six metabolic protocols, conducted with healthy North American males, are presented in order to analyze characteristics of this pool. Pool size (WSe-EMP) correlated positively with daily selenium intake in subjects consuming diets of known and variable selenium content. When subjects were given a selenium-adequate or -restricted diet for 30 d, WSe-EMP,7d decreased from 4.49 +/- 0.28 to 3.76 +/- 0.22 mg (p less than 0.05). The corresponding 24-h urinary selenium concentration dropped from 0.556 +/- 0.035 to 0.341 +/- 0.058 mumol/d (means +/- 1 SEM). Route of administration (iv vs po) had no apparent effect on WSe-EMP. In subjects of similar selenium status, the WSe-EMP was reproducible within the expected uncertainties of the method. This approach may be suitable for assessment of selenium status for a wide range of chronic intakes.

Adult↗
PubMed1990

Comparison of the magnitude of the selenite-exchangeable metabolic pool and whole body endogenous selenium in adult rats.

The quantitative relationship between the size of the selenite-exchangeable metabolic pool (WSe-EMP) and whole body endogenous selenium (Seend) was investigated in adult male rats. Two experiments based on multiple labeling with stable isotopes were performed. One focused on short-term (7 d, Expt. 1) and the other on long-term (60 d, Expt. 2) relationships. Rats were fed a Torula yeast diet and water supplemented with [76Se]selenite at 0.1 micrograms Se/mL; the in vivo [74Se]selenite tracer was administered orally. Groups of three or four animals were killed at timed intervals and whole carcass or selected organs were analyzed for the stable isotopes 74Se, 77Se and 82Se with hydride generation/inductively coupled plasma mass spectrometry. The value of WSe-EMP was determined from plasma or urine isotope ratios. In Experiment 1, with plasma as the sampling compartment, WSe-EMP at 24 h was 36.5 +/- 1.2% of the baseline value of whole body endogenous selenium (Seend) and 36.3 +/- 1.8% at 7 d. When urine was the sampling compartment, the corresponding values were 3.9 +/- 0.3% and 43.1 +/- 2.8%, respectively. In Experiment 2, WSe-EMP (plasma) was 38.9 +/- 1.3% of Seend at 7 d, increasing to 45.5 +/- 1.6% at 60 d. The corresponding values for urine as the sampling compartment were 45.5 +/- 2.0% (7 d) and 61.5 +/- 1.7% (60 d), respectively.

Animals↗
PubMed1990

Effect of chronic selenite supplementation on selenium excretion and organ accumulation in rats.

We examined the effect of chronic selenite supplementation on whole body and selected organ selenium (Se) accumulation, urine excretion of total Se and trimethylselenonium ion, and Se balance in adult male rats. Animals were housed in metabolic cages and given either deionized water or water containing 4 micrograms of Se/mL as selenite for 30 d. Absorption of selenite was nearly complete, with only approximately 10% of ingested Se appearing in feces. There was a rapid rise in urinary Se that reached a plateau within a few days and accounted for 54 +/- 2% of the intake. Excretion of trimethylselenonium ion (TMSe) in urine increased rapidly, representing 35-40% of urinary Se in the supplemented animals compared with only 2% for the control group. In one experiment, rats were killed at 30 d and total carcass Se was measured using isotope dilution analysis. Supplemented rats had only a modest increase in whole body Se (94 +/- 4 micrograms Se vs. 66 +/- 3 in controls). Calculation of Se balance in the supplemented rats showed that approximately 35% of ingested Se could not be accounted for by urine plus fecal losses combined with the portion retained in the carcass. The results from this study demonstrate that under the condition of supplementation at 4 micrograms of Se/mL of drinking water, pathways other than urinary and fecal excretion may account for a substantial portion of Se loss.

Absorption↗
PubMed1990

Feasibility of using the stable isotope 25Mg to study Mg metabolism in infants.

The feasibility of using isotopic techniques to study Mg absorption and metabolism was explored in three full-term human infants. 25Mg (98.8 atom %) was administered orally as an in vivo tracer. Fractional 25Mg absorption, isotope retention, endogenous fecal Mg losses, and apparent Mg exchangeable pool size were then determined under three conditions of isotope administration: 1) 20 mg 25Mg, with single feeding; 2) 20 mg 25Mg, distributed over a 24-h period; and 3) 60 mg 25Mg, over a 24-h period. Mg isotope ratios were determined by inductively coupled plasma mass spectrometry. Fractional absorption was increased in all three infants after distributed versus bolus administration at the 20 mg dose; mean (+/- SD) fractional absorption was 64.0 +/- 3.9 versus 54.3 +/- 5.9%, respectively. 25Mg retention was also more in all three infants after distributed administration (55.8 +/- 3.0 versus 44.3 +/- 1.3% of dose). At the 60-mg 25Mg dose, compared to 20 mg, fractional absorption was reduced but absolute isotope absorption more than doubled in all infants; urine isotope losses represented a similar fraction of the absorbed dose, thus, 25Mg retention also more than doubled. Compared to the results of the isotope studies, net Mg absorption and balance were uninfluenced by total Mg intake. Isotope retention with distributed isotope administration resulted in measurable isotopic enrichment of plasma and erythrocytes at 72 h (i.e. plasma isotope enrichment was 6.3-10.2 and 19.2-23.5% for the 20- and 60-mg dose, respectively). With these doses, apparent Mg exchangeable pool size ranged from 5.5 to 7.6 mmol/kg body wt; these values showed a decrease with age both within and between infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Feasibility Studies↗
PubMed1989

Comparison of pneumatic nebulization and hydride generation inductively coupled plasma mass spectrometry for isotopic analysis of selenium.

A comparative investigation between pneumatic nebulization and continuous hydride generation as sample introduction methods for inductively coupled plasma mass spectrometry was carried out for isotopic analysis of selenium in biological samples of interest to human metabolic studies. Experimental parameters known to affect the analytical performance of the system were evaluated: instrument operating parameters, analyte solution/NaBH4 flow rate, and NaBH4 concentration. Signal-to-background ratio was examined for the three stable isotopes 74Se, 77Se, and 82Se. While background count rates for the hydride system were 3-5 times larger than those for the nebulization method, the signal-to-background ratios, normalized for Se concentration, were 30-50 times greater for the hydride system. Absolute detection limits (3 sigma) for the two systems were 20-60 (nebulization) and 0.6-1.8 (hydride) ng of Se. Overall memory of the hydride system was evaluated. Measurable effects were observed within 400 s from switching to analyte solution with differing isotopic composition, only if the sequence of analysis was from high to low ratio (1-4% bias). However, if the sequence was from low to high ratio, precise and linear calibration plots could be obtained over the isotope ratio range of an order of magnitude or higher. While further improvements might lead to potential enhancement of sensitivity and precision of as much as an order of magnitude, the present performance of the hydride system was satisfactory in relation to the requirements of isotopic analysis for metabolic investigations employing 74Se as the in vivo stable isotope tracer.

Isotopes↗
PubMed1989

Isotopic determination of selenium in biological materials with inductively coupled plasma mass spectrometry.

A method for the isotopic determination of selenium in biological matrices is described. The method is based on hydride generation inductively coupled plasma mass spectrometry (ICP-MS). The development is specifically related to the requirements of stable isotope tracer studies in human subjects. The method is based on isotope dilution using 82Se as the in vitro spike and can quantify the 74Se and 77Se contents of samples. It involves wet oxidation (HNO3 - H2O2 or HNO3 - HClO4) of the 82Se-spiked matrix, reduction to selenite by boiling with HCl followed by measurement of the isotope ratios (82Se/77Se and 74Se/77Se) in the gas stream (H2Se) generated from on-line reduction of the sample selenite with NaBH4. Compared with the isotopic signal resulting from a selenite solution containing 5 ng ml-1 of Se, the total sample blank contributions at m/z = 74, 77 and 82 were less than 5% of the respective isotope signal. Worst-case absolute detection limits were 0.2-0.9 ng of Se, depending on the isotope used. Ion beam intensity ratios were measured with an over-all precision [relative standard deviation (RSD)] of 1% for both isotope pairs. Measured ratios (MRa/b) were stable during a given day's operation within the expected precision of the measurements but varied for different days. The magnitude of MRa/b was generally independent of the nature of the matrix. Highly linear relationships were found between ion beam intensity ratios (MRa/b) and the corresponding true isotope ratios for calibration solutions whose isotope ratios had been altered by as much as one order of magnitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Experimental selenium restriction in healthy adult humans: changes in selenium metabolism studied with stable-isotope methodology.

Mechanisms responsible for selenium homeostasis were investigated in healthy adult men receiving diets adequate or low in Se (eight subjects per group). The appearance of a stable isotope of Se, 74Se, in plasma, urine, and feces was measured after oral administration of 74Se-selenite. One group received a restricted level of Se (18 +/- 1 micrograms/d) for 30 d, which resulted in a decrease in urinary, fecal, and plasma Se content compared with the group that consumed 119 +/- 1 micrograms/d. Low Se intake also resulted in decreased urinary 74Se excretion (27.2 +/- 1.4% vs 32.5 +/- 2.3% of the absorbed dose for the adequate intake), increased body retention of 74Se (74.8 +/- 3.1% vs 67.6 +/- 3.8% of the absorbed dose for the adequate group), and a contracted selenite-exchangeable metabolic pool (Se-EMP) (9782 micrograms for adequate Se and 6314 micrograms for the low-Se group; p less than or equal to 0.05). Measurement of Se-EMP may provide an additional and sensitive approach for assessing Se nutriture in human subjects.

Absorption↗
PubMed1989

Ascorbic acid-selenite interactions in humans studied with an oral dose of 74SeO3(2-).

The interaction between dietary ascorbic acid at extremes of ascorbic acid intake and selenium in young adult male humans was investigated with a stable-isotope approach using 74Se-selenite. Measurements were made of 74Se in plasma, urine, and feces with neutron-activation analysis after oral administration of 74SeO3(2-). Urine excretion and total body retention of isotope and the selenite-exchangeable metabolic pool (Se-EMP) were calculated. Limiting dietary ascorbic acid to about 20 mg/d appeared to reduce the time-related retention of absorbed selenite and the size of Se-EMP. Compared with a diet providing 1 g ascorbic acid/d the low ascorbic acid intake was associated with a lower fractional absorption of the isotope, a reduced retention of the label, and a smaller Se-EMP. These data and those previously obtained in subjects with more usual ascorbic acid intakes point to a possible important role for ascorbic acid in the maintenance of Se homeostasis.

Absorption↗
PubMed1989

Determination of zinc and copper absorption at three dietary Zn-Cu ratios by using stable isotope methods in young adult and elderly subjects.

Nine young men and six elderly men and women ingested low-zinc, low-copper, and adequate diets for 2-wk periods. The Zn-Cu ratios averaged 2:1, 15:1, and 5:1. On day 8 of each period, subjects ingested doses of 70Zn and 65Cu so that net absorption could be determined. Zn absorption on the adequate diet was 39 +/- 3% (means +/- SEM) in young subjects and 21 +/- 1% (p less than 0.05) in the elderly subjects. During the low-Zn period, Zn absorption was higher as compared with that on the adequate diet in both young (64 +/- 5%, p less than 0.05) and elderly subjects (43 +/- 7%, p less than 0.05). Cu absorption on the adequate diet was 60 +/- 4% and 53 +/- 2% in young and elderly subjects, respectively. During the low-Cu period, Cu absorption was higher as compared with that on the adequate diet in the elderly subjects (67 +/- 4%, p less than 0.05). Cu absorption was higher in six of seven young subjects on the restricted Cu diet (p greater than 0.05). The effect upon absorption of the change in the Zn-Cu ratio was less than the effect of dietary restriction.

Absorption↗