Radiolabeled red cell viability. I. Comparison of 51Cr, 99mTc, and 111In for measuring the viability of autologous stored red cells

The simultaneous determination of autologous 99mTc red cell (RBC) and 51Cr RBC viability at 24 hours was measured in 19 normal volunteers whose RBCs had been stored in additive media (Nutracel) for 42 or 49 days. The ratio of the 51Cr:99mTc value was 1.23. In this experiment we also calculated 51Cr RBC viability by both the single-isotope method (extrapolation) and the double-isotope method (using 125I human serum albumin for an independent plasma volume) in the same volunteers. The corresponding viability values were not significantly different. The simultaneous determination of autologous 111In-oxine RBC and 51Cr RBC viability at 24 hours was measured in 19 other normal volunteers whose RBCs had been stored in citrate-phosphate-dextrose-adenine (CPDA-1) for 1 or 15 days. The ratio of the 51Cr:111In value was 1.1. Use of these 24-hour viability ratios as conversion factors permits direct comparison of 99mTc or 111In RBC viability with a 51Cr standard, and therefore expands the application of these newer RBC radiolabels.     

Inhibition of hypoxic pulmonary vasoconstriction by carbon monoxide in dogs

OBJECTIVE: We tested the hypothesis that carbon monoxide might participate in the modulation of hypoxic pulmonary vasoconstriction (HPV) by prostacyclin (PGI2) and nitric oxide. DESIGN: Prospective, interventional study. SETTING: University laboratory. SUBJECTS: Nineteen intact anesthetized mongrel dogs. INTERVENTIONS: Right heart catheterization for the measurements of mean pulmonary artery pressure (Ppa), left atrial pressure estimated from occluded Ppa (Ppao), pulmonary capillary pressure (Pcp) calculated from the Ppa decay curve after balloon occlusion, and cardiac output (Q); inferior vena cava balloon for the control of Q by manipulation of venous return; ventilation in hyperoxia (fraction of inspired O2, 0.4) or in hypoxia (Fio2, 0.1); inhibition of cyclooxygenase by indomethacin (Indo); inhibition of nitric oxide synthase by NG-nitro-l-arginine (L-NA); inhibition of heme oxygenase by mesoporphyrin IX (SnMP); inhalation of nitric oxide (20 ppm); and inhalation of carbon monoxide (100 ppm). MEASUREMENTS AND MAIN RESULTS: The first seven dogs were weak responders to hypoxia as assessed by a hypoxia-induced increase in the gradient between Ppa and Ppao, measured at one level of Q kept constant, by an average of only 2 mm Hg (p = NS). This HPV was markedly increased by the combined administration of Indo and L-NA. A further enhancement of HPV was observed after the addition of SnMP, leading to severe pulmonary hypertension with an average increase in Ppa to 39 mm Hg. Inhaled nitric oxide inhibited HPV only after the combined administration of Indo, L-NA, and SnMP. Inhaled carbon monoxide had no effect. The next 12 dogs were stronger responders to hypoxia, as assessed by a hypoxia-induced increase in the gradient between Ppa and Ppao, measured at several levels of Q, by an average of 3 mm Hg (p <.05). This HPV was of the same magnitude after administration of placebo (n = 6) or SnMP (n = 6). Addition of Indo enhanced HPV to the same extent in the placebo and in the SnMP groups. Addition of L-NA induced a further enhancement of HPV, which was, however, greater in the SnMP group. There was a slight increase in the capillary-venous segment relative to the arterial segment in hypoxic conditions, but the partitioning of pulmonary vascular resistance was otherwise unaffected by nitric oxide, carbon monoxide, or PGI2. CONCLUSIONS: Endogenous carbon monoxide modulates canine HPV only in the absence of nitric oxide. The vasodilation mediated by nitric oxide, PGI2, or carbon monoxide is essentially distributed between proximal and distal sites proportionally to the degree of constriction produced during hypoxia.     

红细胞寿命检测方法及其应用的研究进展

红细胞寿命(RBCS)检测有助于了解各类型贫血及红细胞破坏的原因,更是溶血性贫血的诊断“金标准”.然而,迄今仍无一项技术手段可广泛应用于临床RBCS检测.本文在简要介绍红细胞清除机制的基础上,对51Cr标记法、15N-甘氨酸标记法和生物素标记法等几种常见RBCS检测方法的原理、检测步骤、临床应用及其利弊作一综述,并且重点介绍一种具有临床应用前景的RBCS检测方法——一氧化碳(CO)呼气试验.     

Comparison of radioisotope methods and a nonradioisotope method to measure the RBC volume and RBC survival in the baboon

BACKGROUND: RBC volume, 24-hour posttransfusion survival, and life span can be measured with radio-isotopes and nonradioactive procedures. STUDY DESIGN AND METHODS: RBC volume was measured directly with autologous baboon RBCs labeled with biotin-X-N-hydroxysuccinimide (NHS), 51Cr, 99mTc, and 111In-oxine and indirectly from the 125I plasma volume and the total body Hct. Twenty-four-hour posttransfusion survival and life span were measured in autologous fresh baboon RBCs labeled with 51Cr, 111In-oxine, 99mTc, and biotin-X-NHS. RESULTS: Significantly larger RBC volumes were observed when the fresh autologous RBCs were labeled with 51Cr, 111In-oxine, or 99mTc than when they were labeled with the nonradioactive biotin-X-NHS. Twenty-four-hour posttransfusion survival values were significantly lower in the RBCs labeled with 111In-oxine or 99mTc than in the RBCs labeled with 51Cr. CONCLUSIONS: The greater in vivo elution of 51Cr, 111In-oxine, and 99mTc than that of biotin-X-NHS influenced the measurements of RBC volume, 24-hour posttransfusion survival, and life span of the fresh baboon RBCs.     

Studies with nonradioisotopic sodium chromate. II. Single- and double- label 52Cr/51Cr posttransfusion recovery estimations

A recently developed nonradioisotopic 52Cr technique was used to measure either red cell volume or posttransfusion recovery of stored red cells. The experimental method uses Zeeman electrothermal atomic absorption spectrophotometry to measure red cell chromium. Results from the 52Cr method were compared with those from 51Cr single-label and 125I-albumin/51Cr double-label procedures using 49-day AS-1 red cell concentrates drawn and prepared according to standard procedures. In the first group of five donors, red cell volume was estimated concurrently with both 52Cr-labeled fresh red cells and 125I-albumin. The latter measured plasma volume from which red cell volume was estimated on the basis of the hematocrit (125I red cell volume). 51Cr-labeled stored red cells were transfused to measure posttransfusion recoveries. The correlation between 52Cr and 125I red cell volumes was significant (r = 0.68, p less than 0.01), and, in this group, the differences were not significant (p less than 0.05). Twenty-four-hour posttransfusion recoveries of 51Cr-labeled stored red cells averaged 66 +/- 5 percent when measured with the 125I/51Cr technique and 69 +/- 8 percent when measured with the 52Cr/51Cr method. In the second group of five donors, red cell volume was estimated by the 125I-albumin technique, and the posttransfusion recovery of stored red cells was quantitated by 51Cr- and 52Cr-labeled stored cells simultaneously. In this group, posttransfusion recoveries with 125I/51Cr averaged 73 +/- 7 percent; with 125I/52Cr, they averaged 75 +/- 10 percent. Using the single-label method of calculation, recoveries averaged 76 +/- 7 and 75 +/- 10 percent for the 51Cr and 52Cr methods, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute effect of smoking on rebreathing carbon monoxide, breath-hold carbon monoxide and alveolar oxygen

1. The rise ('boost') in carboxyhaemoglobin (HbCO) on smoking has been studied with alveolar carbon monoxide measurements before and after smoking a cigarette. We re-examined this in 28 subjects with HbCO values compared with rebreathing carbon monoxide [FACO(Rb)] and breath-hold alveolar carbon monoxide and oxygen concentrations, obtained after a 20 s breath-hold [FACO(Bh) and FAO2(Bh), respectively]. Tests were done in the order FACO(Bh) and FAO2(Bh), FACO(Rb), FACO(Bh) and FAO2(Bh) before and after smoking a single cigarette, with HbCO being measured 1 min before and after smoking. 2. The changes were expressed as the relative boost: (Post value-pre value)/(Pre value + post value)/2 X 100 For HbCO the average value was 23.7%, but the FACO(Rb) boost was only 9.8%. The first post-smoking FACO(Bh) boost was 3.9% (5.0 min after smoking), rising to 8.5% 9.4 min later. 3. The FAO2(Bh) values fell from a mean of 15.4% before smoking to 14.3% (5.0 min after smoking) then recovered to 15.4% 9.4 min later, suggesting a transient effect on pulmonary gas exchange. Correction of the first post-smoke FACO(Bh) data for this effect increased the relative boost to 11.5%. Routine FAO2(Bh) measurements may be useful in further smoking studies. 4. We conclude that none of the alveolar sampling techniques gives a reliable measurement of the acute HbCO changes associated with smoking.     

Respiratory Function of the Placenta as Determined with Carbon Monoxide in Sheep and Dogs

A technique is described for studying the respiratory function of the placenta using carbon monoxide, a gas whose exchange across the placenta between the maternal and fetal circulations is limited by diffusion rather than blood flow.During the steady state before the introduction of CO, the normal concentration of carboxyhemoglobin in the ewe, [COHb](M), is approximately 0.90%, and that in the fetus is 2.9%, the ratio [COHb](F)/[COHb](M) being 3.2. In dogs the corresponding values are 1.9%, 4.8%, and 2.4%.After the introduction of CO into the mother animal, CO diffused across the placenta slowly with an equilibration half-time of approximately 2 hours.The average carbon monoxide diffusing capacity (D(Pco)) of the placenta during maternal to fetal exchange was 0.54 ml per (minute x mm Hg x kg fetal weight) (SD +/- 0.13) in sheep and 0.57 ml per (minute x mm Hg x kg) (SD +/- 0.18) in dogs.The fetal to maternal placental diffusing capacity in two sheep was 0.54 ml per (minute x mm Hg x kg).Calculations considering the relative rates of reaction of O(2) and CO with red cell hemoglobin and the relative rates of diffusion of the two gases suggest that the true D(Po2) should be about 1.2 to 2 times greater than the D(Pco) or 0.65 to 1.1 per (minute x mm Hg x kg). This is about 5 times greater than the reported value of D(Po2) calculated from measurements of P(O2) in the mixed uterine and umbilical venous blood. With a diffusing capacity of this magnitude the maternal and fetal placental end capillary P(O2) would approach equilibrium, becoming too small to measure, and the calculation of D(Po2) would be unreliable. We suggest that the apparent end capillary P(o2) gradients of 15 to 20 mm Hg, obtained from sampling uterine and umbilical venous blood, result from a combination of uneven distribution of maternal and fetal placental blood flow and from placental oxygen consumption.     

Single injection (51Cr)EDTA plasma clearance determination in children using capillary blood samples.

The reliability of a determination of the total [51Cr]EDTA plasma clearance (E) (and with it the glomerular filtration rate), by a simplified single injection method (injected dose: 4.5 muCi per kg b.w.) using capillary blood samples (0.2 ml), was investigated in twenty children. Clearance values determined from capillary blood samples did not differ significantly from those measured simultaneously from venous blood samples, the mean ratio +/-SD being 1.02 +/- 0.06 (n = 10). The reproducibility (total day-to-day variation) of E determined from capillary blood samples was 6.7% in children with decreased renal function (n = 3) and 6.9% in children with normal renal function (n = 7). The present data indicate that the use of capillary blood samples is an accurate and very precise approach for determination of E in children.     

A new approach for measuring the erythrocyte life span with a nonradioisotope

The possibility of substituting a nonradioactive isotope of chromium for 51Cr was studied. Blood, from five dogs with varying erythrocyte life spans, was labeled with 50Cr and 51Cr and transfused autologously. Erythrocyte-bound 50Cr was determined by inductively coupled argon plasma mass spectrometry and 51Cr by measuring radioactivity. Erythrocyte life span determination derived from the two isotopes did not differ significantly. Our results suggest that 50Cr can provide a nonradioactive alternative to 51Cr for labeling erythrocytes for life span studies.     

Estimation of transfused red cell survival using an enzyme-linked antiglobulin test

An enzyme-linked antiglobulin test (ELAT) method was developed to estimate survival of transfused red cells. This procedure is based on a principle analogous to that of the Ashby technique were antigenically distinct red cells are transfused and their survival studied. We compared the ELAT survival to the 51Chromium method (51Cr) in four patients. Three patients with hypoproliferative anemias showed T 1/2 by ELAT of 17.5, 18, and 17 days versus 18.5, 20, and 19 days by the 51Cr method. A fourth patient with traumatic cardiac hemolysis had two studies performed. In this case, the ELAT showed a T 1/2 of 10 and 8.1 days while 51Cr T 1/2 values were 11 and 10.5 days. The ELAT method for measuring red cell survival yielded data which agreed closely with the results of the 51Cr method. Although 51Cr is the accepted method for red cell survival, the ELAT method can be used to estimate transfused red cell survival.     

Volume of RBCs, 24- and 48-hour posttransfusion survivals, and the lifespan of (51)Cr and biotin-X-N-hydroxysuccinimide (NHS)-labeled autologous baboon RBCs: effect of the anticoagulant and blood pH on (51)Cr and biotin-X-NHS elution in vivo

BACKGROUND: The RBC injury that occurs during collection of the first few milliliters of blood into the pH 5.0 ACD (NIH, Formula A) is referred to as the lesion of collection. The RBC injury was evaluated by labeling the ACD RBCs with (51)Cr and measuring the 24-hour posttransfusion survival. The effect of the acidification of ACD blood on the in vivo elution of (51)Cr from the RBC has not been reported. STUDY DESIGN AND METHODS: Baboon blood was collected in heparin and in ACD and CP2D at different ratios of blood to anticoagulant. ACD blood with a pH of 5.7 to 6.9 was labeled with (51)Cr. Heparinized blood with a pH of 7.4 was labeled with biotin-X-N-hydroxysuccinimide (NHS). ACD blood with a pH of 5.9 was labeled with both (51)Cr and biotin-X-NHS. The RBC volumes, 24- and 48-hour posttransfusion survivals, and lifespans (T50) were measured. RESULTS: The RBC volume of ACD blood with a pH ranging from 5.7 to 6.9 was not affected by (51)Cr labeling. (51)Cr-labeled ACD blood with a pH of 6.9 had an RBC volume that was significantly greater than that seen in heparinized blood with a pH of 7.4 labeled with biotin-X-NHS. In vivo elution of (51)Cr from the RBCs prepared from the ACD blood with a pH of 5.7 to 6.9 and in vivo elution of biotin-X-NHS from RBCs prepared from ACD blood with a pH of 5.9 were associated with reductions in 24- and 48-hour posttransfusion survivals and T50. CONCLUSIONS: The anticoagulant and the pH of the medium in which the RBCs were labeled with (51)Cr or biotin-X-NHS affected in vivo elution of the label from the RBCs and may reduce posttransfusion survival values.     

Carbon monoxide and pulmonary circulation in an ovine model.

The direct pulmonary vasoconstrictive effects of inhaled carbon monoxide were evaluated in chronically instrumented and anesthetized sheep (1.7% halothane in air) (n = 8). The response to carbon monoxide (2%), which was applied for 8 minutes through a double-lumen tube alternately to the left or right lung of each animal, was compared with baseline values. The induced carboxyhemoglobin level (65%) led to increases in cardiac output, pulmonary arterial pressure, stroke volume index, and heart rate. Systemic vascular resistance decreased, and pulmonary vascular resistance and mean arterial pressure were unchanged. The changes in pressure and flow were equivalent no matter which lung was exposed to carbon monoxide. No diversion of blood from one lung to the other was observed during the test period. We conclude that carbon monoxide does not have a direct pulmonary vasoconstrictive effect. The increase in pulmonary arterial pressure is a result of the decrease in mixed venous oxygen content (stimulus for hypoxic pulmonary vasoconstriction) and the increase in cardiac output.     

Diurnal variation of biopyrrin excretion in random urine specimens is not corrected by creatinine

Circulating bilirubin is thought to function as a physiological antioxidant. One of the decomposition products of this process is the biopyrrins, which include two regioisomers: biotripyrrin-a (1,14,15,17-tetrahydro-2,7,13-trimethyl-1,14-deoxy-3-vinyl-16H-tripyrrin-8,12-dipropionic acid) and biotripyrrin-b (1,14,15,17-tetrahydro-3,7,13-trimethyl-1,14-deoxy-3-vinyl-16H-tripyrrin-8,12-dipropionic acid). We measured biopyrrins in random urine specimens and investigated whether the biopyrrin values obtained were valid when expressed as a ratio of the creatinine (Cr) concentrations. All of the random urine specimens collected over 48 hr were from presumably healthy adults. We measured the biopyrrins by means of an enzyme-linked immunosorbent assay (ELISA) using an anti-bilirubin monoclonal antibody. When the values were expressed in terms of the ratio to Cr, the within-day coefficient of variation (%CV) of the excretion of biopyrrins was reduced to 27%+/-10% (P<0.05) from 59%+/-27%. However, assay values on random or spot urine specimens were unreliable because of the large %CV. The biopyrrin concentrations only in the first-morning-urine specimens in terms of both absolute amounts and ratios to Cr significantly reflected those in a 24-hr urine specimen (P<0.001). Concentrations in a random urine specimen voided at the second collection or later did not correlate with the concentration in a 24-hr urine specimen (P>0.05), even if their values were corrected by Cr. The amounts of biopyrrins excreted in 24-hr urine specimens were significantly correlated with the 24-hr cortisol excretion (P<0.001) but not to uropepsin (P>0.05).     

Interactions of carbon monoxide and metabotropic glutamate receptor groups in the nucleus tractus solitarii of rats

Carbon monoxide has been shown to act as a neurotransmitter and neuronal messenger in the brain. Heme oxygenase catalyzes the conversion of heme to carbon monoxide and biliverdin. We have recently reported that carbon monoxide was involved in central cardiovascular regulation. Carbon monoxide modulated the baroreflex and may affect glutamatergic neurotransmission. In addition, metabotropic glutamate receptors may be coupled to the activation of heme oxygenase in the nucleus tractus solitarii of rats. The present study was designed to investigate the possible interactions of carbon monoxide and metabotropic glutamate receptor groups in the nucleus tractus solitarii. Unilateral microinjection of several agonists for metabotropic glutamate receptor groups such as (R,S)-3,5-dihydroxyphenylglycine (DHPG) (group I) (0.03 nmol), 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate (APDC) (group II) (0.3 nmol), and l-(+)-2-amino-4-phosphonobutyric acid (l-AP4) (group III) (0.3 nmol) produced a significant decrease in blood pressure and heart rate. Among the metabotropic glutamate receptor agonists, prior administration of zinc protoporphyrin IX, an inhibitor of heme oxygenase activity, significantly attenuated the cardiovascular effects of APDC and l-AP4, and failed to attenuate the cardiovascular responses of DHPG. These results indicated interactions between carbon monoxide and group II and III metabotropic glutamate receptors in central cardiovascular regulation.     

Accelerated removal of antibody-coated red blood cells from the circulation is accurately tracked by a biotin label

BACKGROUND: Safe, accurate methods to reliably measure circulating red blood cell (RBC) kinetics are critical tools to investigate pathophysiology and therapy of anemia, including hemolytic anemias. This study documents the ability of a method using biotin‐labeled RBCs (BioRBCs) to measure RBC survival (RCS) shortened by coating with a highly purified monomeric immunoglobulin G antibody to D antigen. STUDY DESIGN AND METHODS: Autologous RBCs from 10 healthy D+ subjects were labeled with either biotin or ⁵¹Cr (reference method), coated (opsonized) either lightly (n = 4) or heavily (n = 6) with anti‐D, and transfused. RCS was determined for BioRBCs and for ⁵¹Cr independently as assessed by three variables: 1) posttransfusion recovery at 24 hours (PTR₂₄) for short‐term RCS; 2) time to 50% decrease of the label (T₅₀), and 3) mean potential life span (MPL) for long‐term RCS. RESULTS: BioRBCs tracked both normal and shortened RCS accurately relative to ⁵¹Cr. For lightly coated RBCs, mean PTR₂₄, T₅₀, and MPL results were not different between BioRBCs and ⁵¹Cr. For heavily coated RBCs, both short‐term and long‐term RCS were shortened by approximately 17 and 50%, respectively. Mean PTR₂₄ by BioRBCs (84 ± 18%) was not different from ⁵¹Cr (81 ± 10%); mean T₅₀ by BioRBCs (23 ± 17 days) was not different from ⁵¹Cr (22 ± 18 days). CONCLUSION: RCS shortened by coating with anti‐D can be accurately measured by BioRBCs. We speculate that BioRBCs will be useful for studying RCS in conditions involving accelerated removal of RBCs including allo‐ and autoimmune hemolytic anemias.     

A simple carbon monoxide breath test to estimate erythrocyte turnover.

Carbon monoxide is stoichiometrically released when heme is converted to bilirubin. This report describes and validates a novel technique that permits the estimation of heme turnover and red blood cell survival from the carbon monoxide concentration of end-expiratory breath samples. The end-alveolar Pco of a subject was corrected for environmental carbon monoxide exposure with a simple device that equilibrates with atmospheric carbon monoxide at the same rate as does the subject. The resultant value (endogenous Pco) was tested for its ability to predict heme turnover and red blood cell survival. Red cell survival times of 32 healthy subjects, as calculated from the endogenous Pco, averaged 101 +/- 19 days, a value close to the expected 110-day survival time; 13 patients with clinical evidence of shortened red blood cell survival times had measured erythrocyte life spans ranging from 10 to 59 days. The endogenous Pco of each of seven patients increased after red blood cell transfusion, demonstrating that this technique detected the known rapid turnover of a small fraction of transfused cells. A good correlation (r = 0.91) was observed between heme turnover calculated from endogenous Pco and total fecal biliary pigment output. Carbon monoxide measurements reflect red blood cell destruction in both the marrow and the circulation, therefore yielding shorter life spans than did chromium 51 survival studies. This breath test appears to yield a rapid, semiquantitative assessment of heme turnover and red blood cell survival that is not provided by any other presently available technique. This simple, noninvasive carbon monoxide breath test may find widespread use in the evaluation of anemia and jaundice.     

Acute and long-term effects of fluosol-DA 20% on respiratory system mechanics and diffusion capacity in dogs

We evaluated the acute and cumulative effects of Fluosol-DA 20% (Fluosol, Alpha Therapeutics, Los Angeles) on respiratory system mechanics and the diffusing capacity for carbon monoxide (D_LCO) in six dogs. A total dose of 45 to 75 mL/kg was administered during a period of eight to 12 days. After a loading dose of 15 mL/kg was a dose of 10 mL/kg was administered intravenously on alternate study days in four dogs and on successive days in two dogs. There were no significant differences between the initial and final study day in total lung capacity (TLC), residual volume (RV), static lung compliance (C_STAT), dynamic lung compliance (C_DYN), the retractive force at 50% at TLC (P_{50 TLC}), and the diffusion capacity for carbon monoxide (C_LCO). Although there was a small increase in the total pulmonary resistance (R_TP, 0.8 to 1.8 cm H₂O/L/s; P < .05), its absolute value remained in the normal range. In contrast to the lack of chronic dose-dependent and time-dependent changes in lung mechanics and D_LCO, there was a transient decrease in CDYN, from 0.066 to 0.047 L/cm H₂O, and an increase in R_TP, from 1.44 to 4.83 cm H₂O/L/s (P < .001), immediately following the infusion of Fluosol. We conclude that an increase in pulmonary resistance to airflow is part of the idiosyncratic acute reaction after the administration of Fluosol, while the repeated administration of Fluosol has little effect on pulmonary gas transfer assessed by C_LCO and respiratory system mechanics.     

Estimation of lipid assimilation from faecal samples using 14C-triolein as tracer and 51CrCl3 as non-absorbable marker

14C-triolein was investigated as tracer of dietary lipids from faecal measurements in 48 consecutive gastrointestinal patients. Simultaneously, 51CrCl3 was investigated as non-absorbable marker. Faecal 51Cr was measured in a whole-body scintillation counter and faecal 14C by means of a combustion technique. This technique permitted accurate measurement of faecal 51Cr and faecal 14C in each stool collected over a 6-day period. The investigation showed that the transit time of 51Cr was slightly shorter than the transit time of 14C-triolein in patients with high faecal excretion of 14C. Nevertheless, total faecal 14C, estimated from the ratio between 14C and 51Cr in two stools, correlated very closely with measured, cumulative faecal 14C (r = 0.99, P less than 0.001). 51CrCl3 was therefore considered useful as a non-absorbable marker. The 14C-labelling of triolein was stable during gastrointestinal transit. Qualitatively, estimated faecal 14C agreed with faecal fat diagnosing steatorrhoea in 97% (95% confidence limits 90-100%) of the patients with quantitative faecal collections. Quantitatively, a significant correlation with faecal fat was found (r = 0.82, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Measurement of circulating red cell volume using biotin-labeled red cells: validation against 51Cr-labeled red cells

BACKGROUND: Anemia is a serious problem in the fetus and preterm infant. To investigate the physiology and pathophysiology of anemia and to assess responses to blood transfusions or erythropoietin therapy, measurement of circulating red cell volume would be useful. Because the standard 51Cr method exposes the subject to radiation, a method of measuring circulating red cell volume without radiation exposure, sufficiently sensitive for use in fetuses and infants, was developed. STUDY DESIGN AND METHODS: In 10 healthy adults whose body mass ranged from 56.8 to 115.9 kg, aliquots of autologous red cells were labeled with biotin or with 51Cr, mixed, and transfused intravenously. Circulating red cell volume was measured in posttransfusion blood by quantitating the in vivo dilution of biotinylated red cells. Biotinylated red cells were detected by two methods: 1) 125I-streptavidin and 2) fluorescein-labeled avidin with flow cytometry. RESULTS: Circulating red cell volume measured by 125I-streptavidin detection agreed well with that measured by 51Cr (slope = 1.07, y-intercept = -97, correlation = 0.987). Similarly, circulating red cell volume measured by flow cytometry agreed well with that measured by 51Cr (slope = 1.05, y-intercept = -20, correlation = 0.987). CONCLUSIONS: Circulating red cell volume measured by the use of biotin with either 125I-streptavidin or flow cytometry agrees with that measured by 51Cr. Each system provides a method of performing these studies without exposing the subject to radiation.     

正常人脑组织发育的磁共振质子波谱研究

目的 用＾１Ｈ－ＭＲＳ观察正常人脑组织主要代谢化合物随年龄变化规律。方法 应用场强为２．０Ｔ的磁共振成像系统对２３例正常人（年龄０．４～１０５６周）脑组织进行＾１Ｈ－ＭＲＳ采集。计算氮－乙酰天门冬胺酸（ＮＡＡ）与肌酸（Ｃｒ）的峰下面积比值以及胆碱复合物（ＣＨｏ）与肌酸（Ｃｒ）峰下面积的比值,并分别与年龄进行回归分析。结果 ＭＡＡ／Ｃｒ值随年龄增加而成指数曲线增长,Ｃｈｏ／Ｃｒ值随年龄增长而成递减指