Intestinal calcium absorption from different calcium preparations: Influence of anion and solubility

Not only is the calcium content of a preparation significant for providing adequate calcium supplementation for the prophylaxis and therapy of osteoporosis, but also its bioavailablity is of essential importance. In the present study, the bioavailability of calcium citrate and calcium lactogluconate/carbonate from a therapeutic dose (= 500 mg Ca²⁺) was compared in men aged between 45 and 60 years on an intra-individual basis. Calcium citrate was administered both as a solution and as a suspension to 18 healthy volunteers. Using a double-isotope method, the intestinal absorption from the three preparations was determined in randomized order at intervals of 2–4 weeks. The stable isotope⁴⁴Ca (20 mg), in highly enriched form, was added in each case to the ready-to-drink solutions and, at the same time, a sterile and pyrogen-free solution containing 5 mg of the stable isotope⁴²Ca was injected intravenously. The intestinal calcium absorption was then determined after 24 h on the basis of the ratio of the two isotopes in the plasma. There was a significantly higher absorption of 29% from the citrate solution than from the lactogluconate/carbonate solution (25%). Absorption from the citrate suspension was similar to that from the lactogluconate/carbonate solution. While no correlation was found between the measured values for calcium absorption from the three preparations and the plasma concentration of 1,25-dihydroxycholecalciferol, significant inverse correlations with the basal parathyroid hormone concentration were observed for the citrate and lactogluconate/carbonate solution. The results of this study show that quantitative data on intestinal calcium absorption can be obtained without employing radioactive isotopes in humans. Moreover, they show that calcium absorption is not determined only by the solubility and the degree of ionization of the calcium salt administered, but rather that it is of a complex nature.     

Double immunofluorescence staining of pokeweed mitogen differentiated plasma cells--a sensitive assay to ascertain purity of anti-human Ig reagents as each cell produces only one isotype

A simple, but highly sensitive assay is described for the determination of the specificity and purity of heterologous antibodies to human immunoglobulin isotypes. In this assay, cytocentrifuge cell preparations of normal pokeweed mitogen differentiated plasma cells are stained initially with an FITC conjugate of an antibody to 1 isotype and then restained with a TRITC conjugate of an antibody to another isotope. No double staining of intracytoplasmic immunoglobulin in plasma cells was observed when highly purified and specific reagents were used. However, some reagents from commercial laboratories, which used immunodiffusion assays and enzyme immunoassay techniques (ELISA) to determine specificity of antisera, were found to lack specificity by the double immunofluorescence technique. This technique of obtaining cultured plasma cells with a wide variety of isotypes is reproducible and utilizes reagents that are easily available. Hence, one need not depend on panels of myeloma plasma cells or spleen cells which can be difficult to obtain.     

WEIGHT LOSS IN PATIENTS WITH HEAD AND NECK CANCER: MALNUTRITION OR TUMOUR EFFECT?

Isotopic infusions, hormone assays and calorimetry have been used to test the hypothesis that weight loss in head and neck cancer (HNC) patients is not due to pure malnutrition, but that a large component of the weight loss in these patients is a consequence of the metabolic effects induced by the tumour on the host. Twelve patients with advanced HNC were compared with eight depleted patients (DEP) who did not have cancer. Both groups had lost more than 10% of well body weight. Neither patient group had an elevated rate of energy expenditure as determined by calorimetry. Both glucose production and plasma glucose clearance were not significantly different between the two groups. The percentage of glucose production undergoing recycling to lactate was elevated in the HNC patients compared with the DEP patients. In addition, the percentage of glucose undergoing oxidation to CO₂ was significantly lower in the HNC patients compared with the corresponding DEP value. The HNC patients were significantly more catabolic than the DEP patients and their serum cortisol concentration was also significantly elevated. Although the basal plasma insulin concentrations were similar in the two groups, the response to glucose infusion was markedly less in the HNC patients. It is concluded that patients with advanced HNC are metabolically different from starving patients, although both may lose a similar amount of weight. In particular, the adaptive response of protein conservation seen in simple starvation does not occur in the HNC patient.     

Muscle protein synthesis in steroid-induced proximal myopathy: a case report

A 51-year-old man with proven adenosquamous carcinoma of the lung presented with clinically acute steroid myopathy. Postabsorptive whole body leucine kinetics and fractional mixed muscle protein synthesis rate (MPSR) were determined by a steady-state approach during continuous L-(1-13C) leucine infusion. Plasma 13C alpha-ketoisocaproic acid enrichment was taken to represent labeling of the precursor pool. Postabsorptive whole body leucine flux and protein synthesis were less than the 1 in 500 confidence intervals of control values. Fractional MPSR was significantly reduced (P less than 0.01). Simultaneous calculation of MPSR from two adjacent sites was in excellent agreement (0.0372 and 0.0395% h-1). This is the first report that steroid myopathy is associated with reduced whole body protein synthesis and fractional MPSR in man.     

广东高本底和对照地区居民肺组织中钍同位素含量的测定

本文用放射化学分析和半导体α-谱仪测量的新技术分析测定了广东高本底地区和对照地区民肺蛆织中天然放射性钍同位索的舍量, 并估算了对肺组织的剂量。     

Long-term survival with thorotrast cervical granuloma

Thorium dioxide, a radioactive contrast material, was commonly used for cerebral angiography prior to recognition of its radiation hazard. Extravasation of the material into the extravascular tissue in the neck results in granuloma formation, thorotrastoma, long-term morbidity, and an increased incidence of benign and malignant tumors. We report our experience with the management of 2 patients who underwent cerebral angiography with thorotrast more than 25 years ago. Aggressive surgical excision of involved tissue is warranted to ameliorate symptoms and diminish the risk of malignancy.     

Long-term urinary excretion of methaqualone in a human subject

The urinary excretion rates of methaqualone and of one of its metabolites, 6-hydroxymethaqualone (free and conjugated), were determined in a normal male subject over a 30-day period by stable isotope dilution analysis using field ionization mass spectrometry. The excretion rates for methaqualone were fitted by computer to three-and four-exponential functions. The estimated terminal halflife for the drug was approximately 74 hr. 6-Hydroxymethaqualone excretion in the elimination phase was fitted to a single exponential decay curve. Estimated halflives obtained for the free and total (primarily conjugated) metabolite were 78 and 70 hr, respectively. The apparent difference between the latter two values was not statistically significant. The close similarity between the halflives of methaqualone and 6-hydroxymethaqualone indicates that elimination of these compounds is ratelimited by the same pharmacokinetic process. A similarly long halflife, 50 hr, was estimated in a previous study (5) of another subject in which excretion of the compounds was followed over an 11-day period. These results demonstrate that the half-life of methaqualone can be much longer than has been indicated by relatively short-term investigations.Supported by Contract DADA17-73-C-3063 from the U.S. Army Medical Research and Development Command.     

β-catenin在肝脏中的表达及对125I粒子治疗肝细胞癌的疗效评估

近年来,^125I粒子植入内照射治疗肝细胞癌（HCC）越来越被人们所接受,但其有效性一直未得到基因学研究证实。β-catenin是一种新近发现的存在于肝细胞的信号转导通路中的蛋白,其异常高表达能够在某种程度上早期提示HCC的发生。^125I粒子植入治疗HCC的疗效可能与β-catenin表达的程度存在相关性。本文对此进行综述。     

Isotopic evidence for the diets of European Neanderthals and early modern humans

We report here on the direct isotopic evidence for Neanderthal and early modern human diets in Europe. Isotopic methods indicate the sources of dietary protein over many years of life, and show that Neanderthals had a similar diet through time (≈120,000 to ≈37,000 cal BP) and in different regions of Europe. The isotopic evidence indicates that in all cases Neanderthals were top-level carnivores and obtained all, or most, of their dietary protein from large herbivores. In contrast, early modern humans (≈40,000 to ≈27,000 cal BP) exhibited a wider range of isotopic values, and a number of individuals had evidence for the consumption of aquatic (marine and freshwater) resources. This pattern includes Oase 1, the oldest directly dated modern human in Europe (≈40,000 cal BP) with the highest nitrogen isotope value of all of the humans studied, likely because of freshwater fish consumption. As Oase 1 was close in time to the last Neanderthals, these data may indicate a significant dietary shift associated with the changing population dynamics of modern human emergence in Europe.     

Metabolic fate of a large amount of 13C-glycerol ingested during prolonged exercise

We have shown that the oxidation rate of exogenous glycerol and glucose during prolonged exercise were similar when ingested in small amounts (0.36 g/kg) (J Appl Physiol 90:1685,2001). The oxidation rate of exogenous carbohydrate increases with the amount ingested. We, thus, hypothesized that the oxidation rate of exogenous glycerol would also be larger when ingested in large amount. The study was conducted on six male subjects exercising for 120 min at 64 (2)%VO₂max while ingesting 1 g/kg of ¹³C-glycerol. Substrate oxidation was measured using indirect respiratory calorimetry corrected for protein oxidation, and from V ¹³CO₂ at the mouth. The ¹³C enrichment of plasma glucose was also measured in order to follow the possible conversion of ¹³C-glycerol into glucose. In spite of the large amount of glycerol ingested and absorbed (plasma glycerol concentration = 8.0 (0.3) mmol/l at min 100), exogenous glycerol oxidation over the last 80 min of exercise [8.8 (1.6) g providing 4.1 (0.7)% of the energy yield] was similar to that observed when 0.36 g/kg was ingested. The comparison between the ¹³C enrichment of plasma glucose and the oxidation rate of ¹³C-glycerol showed that a portion of exogenous glycerol was converted into glucose before being oxidized, but also suggested that another portion could have been directly oxidized in peripheral tissues.