Evaluation of the 13CO2 kinetics in humans after oral application of sodium bicarbonate as a model for breath testing

Abstract. The kinetics of ¹³CO₂ have been investigated following oral administration at five doses between 12.5 and 100 mg of ¹³C labelled sodium bicarbonate to 10 healthy subjects in a randomized study. Sodium bicarbonate in this study served as a model compound for carbon dioxide/bicarbonate generated in breath tests. Exhalation of ¹³CO₂ into breath was monitored by stable isotope ratio mass spectrometry. The kinetics of ¹³CO₂ were characterized by an apparent terminal elimination half-life of 1 h and a mean recovery of 0.630 of the dose administered. The kinetics were not dose-dependent. These results were in agreement with the findings reported previously after iv. application of sodium bicarbonate.     

The 13C-mixed triglyceride breath test in healthy adults: determinants of the 13CO2 response

Defects in lipolysis due to pancreatic insufficiency can be diagnosed by the mixed triglyceride (MTG) ¹³CO₂ breath test. However, the effects of various test conditions on the ¹³CO₂ response have only been partially elucidated. In healthy adults, we performed the ¹³CO₂ mixed triglyceride breath test and we compared (a) the inter- and intra-individual variation in the ¹³CO₂ response; (b) the effect of two different test meals; (c) the effect of an additional meal during the test; and (d) the effect of physical exercise during the test. Upon repeating the test in the same individual (test meal cream), repeatability coefficients were large, with respect to either time to maximum ¹³C excretion rate (3.8 h), maximum ¹³C excretion rate (4.9% ¹³C dose h^?1) or cumulative recovery of ¹³C over the 9-h study period (22.7% ¹³C dose). The cumulative ¹³C expiration over 9 h obtained with the test meal composed of cream was quantitatively similar to that obtained with bread and butter: 42.2 ± 8.4% and 47.7 ± 6.3% respectively. Fasting for 9 h during the test resulted in similar ¹³C expiration rates and cumulative ¹³C expiration (43.4% ± 7.2%) when compared with consumption of an additional meal 3 h after the start of the test (38.3 ± 5.3%). The ¹³CO₂ response increased in five out of seven subjects, but decreased in the other two, when moderate exercise was performed (bicycle ergometer, 50 W for 5 h). We conclude that the repeatability of the MTG test in healthy adults is low. The present results indicate that a solid and a liquid test meal, containing a similar amount of fats, give similar cumulative ¹³CO₂ responses, and that stringent prolonged fasting during the test is unnecessary. Standardization of physical activity seems preferable, since the unequivocal effects of moderate exercise on the ¹³CO₂ response were observed in the individuals studied.     

Comparison of bolus versus fractionated oral applications of [13C]-linoleic acid in humans

BACKGROUND: The endogenous conversion of linoleic acid into long-chain polyunsaturated fatty acids is of potential importance for meeting substrate requirements, particularly in young infants. After application of [13C]-linoleic acid, we estimated its conversion to dihomo-gamma-linolenic and arachidonic acids from only two blood samples. DESIGN: Oral tracer doses were given to five healthy adults as a single bolus. In four subjects the tracer was given in nine equal portions over 3 days. Concentration and 13C content of fatty acids from serum phospholipids were analysed by gas chromatography combustion isotope ratio-mass spectrometry. Areas under the tracer-concentration curves were calculated, and fractional transfer and turnover rates estimated from compartmental models. RESULTS: The median fractional turnover of linoleic acid was 93.7% per day (interquartile range 25.3) in the bolus group and 80. 0% per day (6.3) in the fraction group (NS). Fractional conversion of linoleic to dihomo-gamma-linolenic acid was 1.5% (0.9) vs. 2.1% (0.7) (bolus vs. fraction, P < 0.05), and fractional conversion of linoleic to arachidonic acid was 0.3% (0.3) vs. 0.6% (0.3) (bolus vs. fraction, NS). In the fraction group conversion was significantly higher based on areas under the curve. The ratio of tracer concentration in conversion products to linoleic acid 48 h after dosing correlated very well (r >/= 0.94, P < 0.05) with the ratio of areas under the curve. CONCLUSIONS: Using areas under the curve overestimates the conversion, because different residence times are not considered. Estimation of conversion intensity appears possible with only one blood sample obtained after tracer application.     

Tritium and 14C isotope effects using tracers of leucine and alpha-ketoisocaproate

Abstract. To test if different leucine tracers behave in an indistinguishable manner and, by implication, that their metabolism is identical to that of natural leucine, we measured whole body leucine turnover in dogs and humans and fibrinogen synthesis in dogs by simultaneously infusing either [1–¹⁴C]leucine or [4,5–³H]leucine or [I-¹⁴C]α-ketoisocaproate (KIC) and [4,5–³H]KIC. Whole body leucine fluxes calculated from the plasma specific activity of the transaminated product of the infused tracer (reciprocal pool model) were lower (dogs by 5.7%; humans by 6.4%, both P<0.02) when the plasma 'H specific activity compared to ¹⁴C specific activity were used with leucine tracers and were also lower (dogs by 4.4%, P<0.02; humans by 86%, P<0.06 ) using the KIC tracers. Using leucine or KIC tracers in dogs, the fractional rate of fibrinogen synthesis was 6.7% or 9.4% lower, respectively, (P<0.02) using the ³H versus the ¹⁴C tracer. The apparently lower incorporation of ³H into protein was only in part accounted for by detritiation (2.1%, P = 0.05) of [³H]leucine during acid hydrolysis of proteins. These results suggest that in vivo and/or in vitro differential isotope effects are small (˜5%), but should be considered when dual isotopes infusions are employed to partition amino acid metabolism.     

[13C]-Galactose breath test: correlation with liver fibrosis in chronic hepatitis C

BACKGROUND: The galactose elimination capacity test is a quantitative liver function test that has been shown to be a potential surrogate marker for death in advanced chronic liver diseases. However, this test lacks sensitivity in early liver disease. The goal of this study was to evaluate a [13C]-galactose breath test (GBT) in a population of patients with chronic hepatitis C. DESIGN: The GBT was performed in 10 control subjects and 50 patients with chronic hepatitis C; the results were compared with the METAVIR pathological scoring of liver biopsy specimens and with standard biochemical liver function tests. RESULTS: In 10 patients, oral vs. intravenous administration of galactose yielded similar results for the GBT (3.01% +/- 0.12% dose h-1 for oral galactose vs. 2.98 +/- 0.21 for intravenous). The GBT was then performed orally in the remaining 40 patients and 10 control subjects. A significant difference was observed between control subjects and patients (4.51% +/- 0.18% vs. 2.97% +/- 0.14% dose h-1, P < 0.0001). A significant difference for GBT results was observed between each fibrosis stage, but not with regard to the activity score. CONCLUSIONS: The GBT results are dependent on the severity of liver fibrosis in chronic hepatitis C. Further studies are needed to evaluate the usefulness of the GBT for the follow-up of chronic hepatitis C.     

Direct determination of leucine metabolism and protein breakdown in humans using L-[1-13C, 15N]-leucine and the forearm model

Abstract. We have used the forearm model to study protein metabolism in six normal healthy subjects in the fed state using L-[1 –¹³C, ¹⁵N]-leucine as the substrate tracer.
Deep venous and arterialized venous blood samples from the forearm were collected at 10-min intervals 2±5 h into a primed-continuous infusion of the dilabelled tracer. Arterialized venous blood was obtained using a 'hot-box' technique and forearm blood flow was measured by mercury strain-gauge plethysmography.
The concentration and isotope enrichment of leucine and its metabolites, α-ketoisocaproic acid and CO₂, in deep venous and arterialized venous blood were measured by gas chromatography-mass spectrometry and isotope ratio-mass spectrometry.
The rates of leucine deamination and reamination were 388 ± 24 (mean ± SEM) and 330 ± 23 nmol (100 ml)^-1 min^-1 respectively, whilst protein synthesis and breakdown rates were 127 ± 11 and 87 ± 10 nmol (100 ml)^-1 min^-1 respectively across the forearm in the fed state. We have demonstrated that the use of doubly labelled leucine as tracer and application of the mathematical model developed in this study, permits the comprehensive quantification of leucine kinetics including protein breakdown.     

5HT2 receptors in cerebral cortex of migraineurs studied using PET and 18F-fluorosetoperone

Since the brain 5HT₂ receptors might be implicated in migraine pathogenesis, we have used positron emission tomography and ¹⁸F-fluorosetoperone, a 5HT₂ specific radioligand, to investigate in vivo the cortical 5HT₂ receptors in migraine subjects. Nine migraineurs who had either migraine with and without aura ( n = 5) or only migraine without aura ( n = 4) were studied between attacks. Twelve unmedicated healthy subjects of similar mean age were used as controls. Brain radioactivity was measured after ¹⁸F-setoperone IV injection for 90 min. A decrease of the regional specific distribution volumes (SDV) of the ligand was observed both in migraineurs and in controls. The age adjusted group means of SDV did not differ between patients and controls for the whole and for the right or left frontal, temporal, parietal and occipital cortex. These results suggest that cortical 5HT₂ receptors may be unaltered between attacks in migraine sufferers.     

Primary hyperparathyroidism: evaluated by 47Calcium kinetics, calcium balance and serum bone-Gla-protein

Combined 47Calcium kinetic and calcium balance studies with correction for dermal calcium loss were performed in thirteen patients with primary hyperparathyroidism (PHP), in whom serum bone-Gla-protein (S-BGP) was measured, and in ten matched controls. Dietary calcium was normal in PHP but both net (7.9 +/- 1.4 mmol Ca day-1 in PHP v. 3.5 +/- 0.9 mmol Ca day-1 in normals (mean +/- SE] and true (11.1 +/- 1.6 v. 6.8 +/- 0.9 mmol Ca day-1) intestinal absorbed calcium were enhanced (P less than 0.05). The renal calcium excretion (10.9 +/- 0.8 v. 5.1 +/- 0.4 mmol Ca day-1, P less than 0.001) and the dermal calcium loss (2.5 +/- 0.3 v. 1.5 +/- 0.1 mmol Ca day-1, P less than 0.02) were increased in PHP. Both patients and controls were in a negative calcium balance (P less than 0.01 and P less than 0.001, respectively) without any difference between the groups (P greater than 0.10). Mineralization (12.0 +/- 1.7 v. 4.8 +/- 0.8 mmol Ca day-1, P less than 0.02) and resorption rates (17.6 +/- 2.5 v. 7.9 +/- 0.6 mmol Ca day-1, P less than 0.02) were increased in PHP and S-BGP correlated positively to both variables (r = 0.64, P less than 0.05 and r = 0.62, P less than 0.05, respectively). Serum immunoreactive parathyroid hormone correlated positively to serum calcium (r = 0.69, P less than 0.01) but not to the calcium kinetic data.     

Comparative Absorption of Ferri-Haemoglobin-59Fe/Ferro-Haemoglobin-59Fe and 59Fe3+/59Fe2+ in Humans with Normal and Depleted Iron Stores*

Abstract. The intestinal ⁵⁹Fe absorption from ferri- and ferro-haemogIobin-⁵⁹Fe and ⁵⁹Fe³⁺ and ⁵⁹Fe⁺ was calculated from whole body-⁵⁹Fe-retention measurements in subjects with normal and depleted iron stores. A ferri-haemoglobin-⁵⁹Fe/ferro-haemoglobin-⁵⁹Fe absorption ratio of 1.03 ±0.11 was observed for the absorption of ferri-haemoglobin-⁵⁹Fe (8.6± 0.77%) and ferro-haemogIobin-⁵⁹Fe (8.7±0.94%) in persons with normal iron stores. Depletion of iron stores caused a slight but significant higher rise of ferri-haemoglobin-⁵⁹Fe absorption (22 ± 1.7%) than the increase of ferro-haemoglobin-⁵⁹Fe absorption (18 ±0.9%) so that the absorption ratio was 1.24±0.073.—This remarkable iron valence independence of haemoglobin iron absorption is in considerable contrast to the well-established valence dependence of inorganic iron absorption which favours ferrous iron absorption especially with rising iron doses. The ⁵⁹Fe³⁺/⁵⁹Fe²⁺ absorption ratio for a diagnostic 0.56 mg Fe dose increased from 0.43 in subjects with normal iron stores to 0.74 in persons with depleted iron stores, whereas this absorption ratio was augmented only from 0.21 to 0.28 for the therapeutic 50 mg Fe-dose.—The different influence of iron valence on iron absorption from inorganic and haemoglobin iron supports other evidence for the existence of two separate mechanisms for ferrous iron and haem iron absorption in humans.     

Radioimmunoassay of Prostaglandins Fα, E1 and E2 in Human Plasma

Abstract. Antibodies against prostaglandins (PG)F₂α, E₁ and E₂ were obtained in rabbits immunized with respectively PG F₂α, PG E₁ and PG E₂ conjugated to bovine serum albumin by carbodiimide. A radioimmunoassay capable of measuring 7 pg of PG Fα, 2 pg of PG E₂ and 14 pg of PG Ej in human peripheral plasma is described. Plasma samples (pH 3, citric acid) are extracted with cyclohexane: ethyl acetate, 1:1 and then chromatographed on silicic acid columns to separate the prostaglandins into three fractions: fraction I, PG A, PG B and some unknown immunoraactive compounds; fraction II, PG E and fraction III PG Fα. The recovery is 80 %± 6. 2. Mean plasma levels iu adults of PG Fa and PG E, expressed in pg/ml: -PG Fα 12 ± 2. 8 (n = 25 men), 8 ± 2. 3 (n = 18 women, follicular phase), 7 ± 1. 4 (n = 18 women, luteal phase). -PG E₁ 40. 5 + 7. 6 (n = 13 men), 38 + 17. 1 (n = 10 women). -PG E₂ 4. 5 ± 1 (n = 12 adult subjects).
The major characteristics of the method described herein are the following: - a large volume of plasma has to be processed (10 ml or more for PG Fa and PG E₁, 5 ml or more for PG E₂). - a chromatographic step is necessary to separate the different prostaglandins which makes it possible to circumvent problems of immunological cross reactivity and interference with unknown immunoreactive compounds. - great care has been taken in collection of blood samples, especially to insure complete removal of blood cells namely platelets.     

Cisplatin-induced renal effects and thromboxane A2 receptor blockade

The aim of this study was to evaluate the renal protective effect of linotroban, a thromboxane A₂ receptor antagonist, in 25 patients with malignant tumours scheduled for cisplatin therapy. Cisplatin was administered 1 h after the start of a 24-h continuous infusion of linotroban or placebo. Glomerular filtration rate and effective renal plasma flow were measured. Infusions of cisplatin decreased glomerular filtration rate by 17 ± 25 mL min⁻¹ ( P  = 0.049 vs. baseline) and effective renal plasma flow by 94 ± 150 mL min⁻¹ ( P  = 0.049 vs. baseline) in the placebo group. In the linotroban group a decrease in glomerular filtration rate by 11 ± 18 mL min⁻¹ ( P  = 0.050 vs. baseline) and in effective renal plasma flow by 26 ± 63 mL min⁻¹ ( P  = 0.2 vs. baseline) was noted. However, no difference was noted between groups in response to treatment. Our findings indicate that linotroban may not be useful for prevention of cisplatin's acute nephrotoxic effects.     

α1 and α2-adrenergic control of large and small coronary arteries during exercise in conscious dogs under β-blockade

Summary— The aim of this study was to determine the relative roles of α₁-and α₂-adrenoceptors at the level of large epicardial and small resistance coronary arteries when sympathetic tone is increased by exercise in conscious dogs. The responses of left circumflex coronary artery diameter and blood flow were investigated at rest and during graded treadmill exercise (5, 10 and 12 km/h) in six chronically instrumented dogs during control conditions (saline) and after administration of propranolol (1 mg/kg) either alone or in combination with either prazosin (50 μg/kg), or idazoxan (300 μg/kg), or the association of prazosin + idazoxan (same doses). In control conditions, graded treadmill exercise resulted in a progressive increase in coronary artery diameter (+ 3.8 ± 0.6% from 3479 ± 80 μm) and in a decrease in coronary vascular resistance (- 46.0 ± 4.5% from 8.49 ± 1.51 mmHg/cm/s). Propranolol significantly constricted large (- 4.4 ± 0.6% from 3486 ± 87 μm) and limited dilation of small coronary arteries during exercise. These coronary effects of propranolol remained unchanged following additional α₂-adrenoceptor blockade by idazoxan but were abolished following α₁-adrenoceptor blockade by prazosin, given either alone or combined with idazoxan. Thus, α₁- but not α₂-adrenoceptors are responsible for propranolol-induced constriction of large coronary arteries and limitation of small coronary arteries dilation during exercise in conscious dogs.     

Effect of Paco2 variation on standard base excess value in critically ill patients

Purpose

The aim of this study was to investigate the impact of acute Paco₂ temporal variation on the standard base excess (SBE) value in critically ill patients.

Methods

A total of 265 patients were prospectively observed; 158 were allocated to the modeling group, and 107 were allocated to the validation group. Two models were developed in the modeling group (one including and one excluding Paco₂ as a variable determinant of SBE), and both were tested in the validation group.

Results

In the modeling group, the mathematical model including SIDai, SIG, l-lactate, albumin, phosphate, and Paco₂ had a predictive superiority in comparison with the model without Paco₂ (R² = 0.978 and 0.916, respectively). In the validation group, the results were confirmed with significant F change statistics (R² change = 0.059, P < .001) between the model with and without Paco₂. A high correlation (R = 0.99, P < .001) and agreement (bias = −0.25 mEq/L, limits of agreement 95% = −0.72 to 0.22 mEq/L) were found between the model-predicted SBE value and the SBE calculated using the Van Slyke equation.

Conclusions

Acute Paco₂ temporal variation is related to SBE changes in critically ill patients.     

Pharmacological control of the human gastric histamine H2 receptor by famotidine: comparison with H1, H2 and H3 receptor agonists and antagonists

Histamine 0.1 microM-0.1 mM increased adenylate cyclase activity five- to ten-fold in human fundic membranes, with a potency Ka = 3 microM. The histamine dose-response curve was mimicked by the H3 receptor agonist (R) alpha-MeHA, but at 100 times lower potency, Ka = 0.3 mM. Histamine-induced adenylate cyclase activation was abolished by H2, H1 and H3 receptor antagonists, according to the following order of potency IC50: famotidine (0.3 microM) greater than triprolidine (0.1 mM) thioperamide (2 mM), respectively. Famotidine has no action on membrane components activating the adenylate cyclase system, including the Gs subunit of the enzyme stimulated by forskolin and cell surface receptors sensitive to isoproterenol (beta 2-type), PGE2 and VIP. The Schild plot was linear for famotidine (P less than 0.01) with a regression coefficient r = 0.678. The slope of the regression line was 0.64 and differs from unity. Accordingly, famotidine showed a slow onset of inhibition and dissociation from the H2 receptor in human cancerous HGT-1 cells. The results demonstrate that famotidine is a potent and selective H2 receptor antagonist with uncompetitive actions in human gastric mucosa. Consequently, famotidine might be a suitable drug with long-lasting actions in the treatment of Zollinger-Ellison syndrome. The results also confirm and extend the previous observations that (R) alpha-MeHA and thioperamide are two selective ligands at histamine H3 receptor sites. In the human gastric mucosa, these drugs are respectively 330 and 6700 times less potent than histamine and famotidine on the adenylate cyclase system. The possible involvement of histamine H3 receptors in the regulation of gastric secretion is proposed.     

经后路伤椎置钉结合功能锻炼治疗胸腰椎骨折临床观察

[目的] 探讨经伤椎椎弓根钉内固定结合术后功能锻炼治疗胸腰椎骨折的方法及效果。[方法] 短节段经伤椎治疗胸腰椎骨折患者78例,72例获得随访,术后对伤椎前缘高度、伤椎Cobb角、椎管容积、腰背痛及神经功能恢复等方面进行评价。[结果] 获得随访的患者,术后伤椎前缘高度恢复至(95.2±3.5)％,脊柱Cobb角恢复至术后的(4.5±3.2)°,伤椎平均正中矢状径恢复至术后的(96.5±2.3)％,手术前后有显著性差异(P<0.05)。患者腰背痛症状明显缓解,VAS评分由术前的(9.4±0.6)分降到术后的(2.4±2.7)分。神经功能除术前4例A级的患者下肢感觉、运动无改善,剩下患者神经功能均有1~3级的恢复;术后随访出现一例患者椎弓根螺钉断裂现象。[结论] 经伤椎椎弓根钉内固定术对骨折复位满意,重建脊柱的稳定性,术后功能锻炼对腰背痛及术后神经功能恢复起到促进作用,减少术后并发症。     

Compared effects of ruthenium red and cis [Ru(NH3)4Cl2]Cl on the isolated ischaemic-reperfused rat heart

Summary— The sequence ischaemia-reperfusion is characterized by reperfusion damage. The calcium overload occurring at the beginning of reperfusion is one of the main mechanisms responsible for reperfusion damage. Ruthenium red, a blocker of the mitochondrial calcium uniport system, could prevent this damage by preserving the ATP synthesis in the mitochondria. We tested ruthenium red and another ruthenium compound, cis-tetrammine dichlororuthenium (III) chloride in our experimental model of ischaemic-reperfused rat hearts. After a 15 minute-stabilization period, the hearts were submitted to a 30 minute global ischaemia period and then reperfused for 45 minutes with the standard perfusion solution or with ruthenium red or cis-tetrammine dichlororuthenium (III) chloride at 1, 3 or 9 μM. Ruthenium red at 3 μM exerted a protective effect in our experimental conditions by showing a significant improvement of the contractility recovery at the end of reperfusion and a significant decrease of the malondialdehyde production, which reflects free radical production. The cis-tetrammine dichlororuthenium (III) chloride (containing 1 Ru ion per molecule) at 9 μM was slighty less efficient than ruthenium red at 3 μM (containing 3 Ru ions per molecule). The heart ruthenium binding was better for the ruthenium red than for the cis-tetrammine dichlororuthenium (III) chloride, suggesting a role of the ruthenium ion complexation in the crossing of the membrane, whereas the cardiac effect seemed to be linked to the ruthenium ion heart concentration, which was similar for the ruthenium red at 3 μM and for the cis-tetrammine dichlororuthenium (III) chloride at 9 μM. One can hope that ruthenium compounds would limit reperfusion damage and infarct size after ischaemia in in vivo models.     

呼吸末二氧化碳在危重病患者代谢性紊乱中预测价值

目的:探讨呼吸末二氧化碳(ETCO2)在急危重患者代谢性紊乱中的预测价值。方法:分析2011-06-2011-09急诊入住武汉大学人民医院重症医学科的100例患者,入院后使用碳酸波形图监测初始ETCO2值,ETCO2监测完毕以后迅速抽血做血气分析监测HCO3值。统计数据并分析ETCO2和HCO3值的关系,同时比较分析存活组和死亡组以及HCO3≤21mmol/L和HCO3>21mmol/L的病例ETCO2和HCO3值的关系。结果:ETCO2和HCO3中度相关(R=0.593),死亡组ETCO2和HCO3值较存活组均明显减低,HCO3≤21mmol/L组ETCO2较HCO3>21mmol/L组低,差异有统计学意义。ETCO2可反映HCO3的水平,ROC曲线下面积是0.754(95%CI:0.659～0.850),ETCO2=32.5mmHg时,灵敏度=0.65,特异度=0.85,Youden指数=0.5,阳性似然比=4.3,阴性似然比=0.5,ETCO236.5mmHg时,特异度均在95%以上,甚至等于1。结论:碳酸波形图监测的ETCO2值作为一种无创的诊断工具,可有效预测危重症患者代谢性紊乱的发生,为临床评估患者的危重程度提供有力的证据,并为临床治疗的时机提供及时性的指导。