Dual-tracer Method Research Articles

The Developments and Achievements of Endoscopic Surgery, Robotic Surgery and Function-preserving Surgery

The breakthrough in laparoscopic surgery has been the development of a charge-coupled device camera system and Mouret performing cholecystectomy in 1987. The short-term benefits of laparoscopic surgery are widely accepted and the long-term benefit of less incidence of bowel obstruction can be expected. The important developments have been the articulating instrumentation via new laparoscopic access ports. Since 2007, single-incision laparoscopic surgery has spread all over the world. Not only single-scar but also no-scar operation is a current topic. In 2004, Kalloo reported the flexible transgastric peritoneoscopy as a novel approach to therapeutic interventions. In 2007, Marescaux reported transvaginal cholecystectomy in a patient. The breakthrough in robotic surgery was the development of the da Vinci Surgical System. It was introduced to Keio University Hospital in March 2000. Precision in the surgery will reach a higher level with the use of robotics. In collaboration with the faculty of technology and science, Keio University, the combined master-slave manipulator has been developed. The haptic forceps, which measure the elasticity of organs, have also been developed. The first possible sites of lymphatic metastasis are known as sentinel nodes. Otani reported vagus-sparing segmental gastrectomy under sentinel node navigation. This kind of function-preserving surgery will be performed frequently if the results of the multicenter prospective trial of the dual tracer method are favorable. Indocyanine green fluorescence-guided method using the HyperEye charge-coupled device camera system can be a highly sensitive method without using the radioactive colloid. 'Minimally invasive, function-preserving and precise surgery under sentinel node navigation in community hospital' may be a goal for us.

Parathyroid scintigraphy protocols in Finland in 2010

SummaryThe goal of this study was to describe current clinical parathyroid scintigraphy (PS) protocols in Finland. Methods: All departments of nuclear medicine in Finland were contacted, and instructions regarding PS were requested. Results: Instructions regarding PS were received from all of the departments that perform PS (n = 19). Seven hundred and sixtynine PS studies were performed in 2009 (between 7 and 209 per hospital). Three methods of PS were used. The dual-phase method with 99mTc-sestamibi is used in seven hospitals, the dual-tracer method with 123I/99mTc-sestamibi in eleven, and 99mTcO4/99mTc-sestamibi in one hospital. The activities of 99mTc-sestamibi, 123I and 99mTcO4 were 150–800 MBq, 10–30 MBq and 50 MBq, respectively. The anterior image with parallel-hole collimators, the anterior image with pinhole collimator, the oblique angles with pinhole collimator, SPECT and hybrid CT with SPECT were acquired in 84%, 26%, 16%, 63%, and 42% of the hospitals, respectively. Because the imaging techniques were combined, one to four acquisitions were performed per patient. Scatter and attenuation correction were used in five protocols. A correction for crosstalk of 123I and 99mTc gamma energies was not used, but the amount of crosstalk was decreased by using narrow or asymmetric energy windows in all dual isotope protocols. Conclusion: 19 hospitals used 18 different study protocols. Thus, significant variability exists in the current practice of PS in Finland. The protocols should be tested with known phantoms to determine any differences in sensitivities for detecting small active structures. Further studies with phantoms are needed to determine the optimal imaging techniques. The results of these phantom studies will provide guidelines for proposing national recommendations for PS.

Prospective multicenter trial of sentinel node mapping for gastric cancer

4518 Background: The sentinel node (SN) concept has revolutionized the approach to the surgical staging of both melanoma and breast cancer, and these techniques can yield patient benefit by avoiding various complications due to unnecessary prophylactic regional lymph node dissection in cases with negative SN for cancer metastasis. Clinical application of SN mapping for early gastric cancer had been controversial for years. However, single institutional results of SN mapping for early gastric cancer are almost acceptable results in terms of detection rate and accuracy to determine lymph node status. We hypothesized that SN mapping plays a key role to obtain individual information and allows modification of the surgical procedure for early gastric cancer. Methods: The Japan Society of Sentinel Node Navigation Surgery (JSNNS) has conducted a prospective multicenter trial of SN mapping by a dual tracer method with radioactive colloid and blue dye. Between September 2004 and March 2008, 433 patients with early gastric cancer were accrued at 12 comprehensive hospitals. Patients were enrolled under JSNNS and each institutional review board-approved protocols. Eligibility criteria were that patients had clinically T1N0M0 or T2N0M0 single tumor with diameter of primary lesion less than 4cm without any previous treatments. Technetium-99m tin colloid and isosulfan blue were utilized as dual tracers for SN mapping. Results: SN mapping has been performed for 397 patients with early gastric cancer. Detection rate of hot and/or blue node using our procedure was 97.5% (387/397). The mean number of sentinel nodes per case was 5.6. Fifty-three of 57 cases with lymph node metastasis showed positive sentinel nodes. The sensitivity to detect metastasis based on SN status was therefore 93% in our experience. Accuracy of metastatic status based on SN was 99% (383/387). In two of the four SN false-negative cases, the tumor involved to pT2, and only one case showed the metastatic lymph node beyond the SN basin. Conclusions: Our results suggest that SN concept for clinically N0 early gastric cancer could be validated, and minimized gastrectomy with individualized selective and modified lymphadenectomy for early gastric cancer with negative SN should become feasible and clinically useful as less invasive surgical procedures. No significant financial relationships to disclose.

A laser-induced fluorescence measurement for aqueous fluid flows with improved temperature sensitivity

This paper presents temperature-sensitive laser-induced fluorescence measurements of Fluorescein 27 dissolved in aqueous solutions. We show that Fluorescein 27, dissolved in water and excited by a 532-nm Nd:YAG laser pulse, yields improved temperature sensitivity over traditional organic dyes such as Rhodamine B. The high temperature sensitivity of Fluorescein 27 when excited at 532 nm is due primarily to a temperature-dependent shift of the absorption spectrum to longer wavelengths for increased temperatures. The linearity of the fluorescence signal with respect to the incident laser intensity and dye concentration is reported. In addition, Fluorescein 27 dissolved in an aqueous solution remains photo-stable for >105 laser pulses at both ambient and high temperatures (T > 60°C) when excited with low-irradiance laser pulses. Finally, we demonstrate that using a dual tracer (or ratiometric) technique in which the fluorescence from Fluorescein 27 and another dye (e.g., Rhodamine B or Kiton Red 620) are detected following the 532 nm excitation results in a significantly enhanced temperature sensitivity over a single tracer measurement and previously reported dual tracer methods. Such temperature sensitivity is useful in multi-dimensional temperature imaging and temporally resolved measurements.

Gas exchange rates measured using a dual-tracer (SF6 and3he) method in the coastal waters of Korea

Over a period of 5 days between August 12 and 17, 2005, we performed a gas exchange experiment using the dual tracer method in a tidal coastal ocean located off the southern coast of Korea. The gas exchange rate was determined from temporal changes in the ratio of3He to SF6 measured daily in the surface mixed layer. The measured gas exchange rate (k CO 2), normalized to a Schmidt number of 600 for CO2 in fresh water at 20°C, was approximately 5.0 cm h-1 at a mean wind speed of 3.9 m s-1 during the study period. This value is significantly less than those obtained from floating chamber-based experiments performed previously in estuarine environments, but is similar in magnitude to values obtained using the dual tracer method in river and tidal coastal waters and values predicted on the basis of the relationship between the gas exchange rate and wind speed (Wanninkhof 1992), which is generally applicable to the open ocean. Our result is also consistent with the relationship of Raymond and Cole (2001), which was derived from experiments carried out in estuarine environments using222Rn and chlorofluorocarbons along with measurements undertaken in the Hudson River, Canada, using SF6 and3He. Our results indicate that tidal action in a microtidal region did not discernibly enhance the measuredk CO 2 value.

Premotor circuits controlling eyelid movements in conjunction with vertical saccades in the cat: II. Interstitial nucleus of Cajal

Vertical saccadic eye movements are accompanied by concurrent eyelid movements in the same direction. The interstitial nucleus of Cajal (InC) controls eye position for vertical eye movements and may also control saccade-related lid position as well. This study investigates whether the InC serves as a premotor center for eyelid saccades, by employing dual-tracer methods in cats to label both the projections of the InC and the motoneurons supplying the levator palpebrae superioris (LPS) muscle, which lie in the caudal central subdivision (CCS) of the oculomotor complex. Injections of biotinylated dextran amine (BDA) into the InC anterogradely labeled axons that terminated bilaterally throughout the CCS and in the oculomotor nuclei proper. Labeled terminals lay in close association with labeled LPS motoneurons, which were retrogradely labeled following injections of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) into the muscle. Ultrastructural investigation revealed that most terminals contained spherical vesicles and formed asymmetric synaptic contacts with the labeled motoneurons. These results strongly suggest that the InC monosynaptically controls lid movements in conjunction with vertical eye movements, including saccades. To identify the neurons of origin for this pathway, WGA-HRP injections were centered in the CCS. These experiments indicate that lid and eye motoneurons may share a common source of bilateral InC input. Thus, a common vertical position signal may be employed to maintain the lid and eye at appropriate elevations during fixation, such that the lid sits just above the pupil, allowing unobstructed vision, but at the ready to protect the cornea.

Permeability properties of tumor surrogate blood vessels induced by VEGF-A

Malignant tumors generate new blood vessels by secreting growth factors, particularly members of the vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) family. Overall, the new blood vessels that form are hyperpermeable to plasma proteins, a property that is thought to be important for generating new stroma. However, tumor blood vessels are structurally heterogeneous and include microvessels of at least the following distinct types: mother vessels (MV), glomeruloid microvascular proliferations (GMP), arterio-venous-like vascular malformations and capillaries. Our goal was to determine whether macromolecular tracers leaked from all or from only a subset of these vessel types and to elucidate the extravasation pathways. As blood vessels are only a minor component of tumors, and therefore, difficult to study in situ, we used an adenoviral vector to express VEGF-A164, the most important member of the VPF/VEGF family, in mouse tissues. So expressed, VEGF-A164 induces large numbers of surrogate vessels of each type found in tumors in a highly reproducible manner. Overall permeability to plasma proteins was assessed qualitatively with Evan's blue dye and quantitatively with a dual tracer method employing radioactive albumin. Leaky vessels were identified by confocal microscopy (FITC-dextran) and by electron microscopy (ferritin). MV, and to a lesser extent GMP, were found to be hyperpermeable but capillaries and vascular malformations were not. Ferritin extravasated primarily by two trans-cellular routes, vesiculo-vacuolar organelles (VVOs) and fenestrae. This occurred despite a considerable reduction in VVO frequency as VVO membranes translocated to the plasma membrane during MV formation. However, reduction in the number and complexity of VVOs was offset by extensive endothelial cell thinning and a greatly shortened extravasation pathway. Extrapolating these findings to tumors predicts that only a subset of tumor vessels, MV and GMP, is hyperpermeable, and that measures of overall vessel permeability greatly underestimate the permeability of individual MV and GMP.

Assessment of postprandial glucose metabolism: conventional dual- vs. triple-tracer method

The dual-tracer method has been used conventionally for assessment of postprandial fluxes, i.e., appearance in plasma of ingested glucose (R(a meal)), endogenous glucose production (EGP), and disposal (R(d)). To quantify the magnitude of errors affecting the calculations and their dependence on model assumptions, this method was assessed and compared with the triple-tracer method, which provides model-independent estimates. For this purpose, the dual-tracer protocol was performed twice in eight normal subjects, with [1-(13)C]glucose to trace ingested glucose and [6,6-(2)H(2)]glucose constantly infused. A third tracer, [6-(3)H]glucose, was infused at variable rates to render the calculation of R(a meal) and EGP virtually model independent. The dual-tracer method analyzed with a one-compartment model performed poorly, since R(a meal) peak was significantly lower and delayed compared with triple-tracer reference, resulting in a significantly lower estimation of the amount of absorbed glucose (9,036 +/- 558 vs. 11,316 +/- 823 micromol/kg, P = 0.0117). EGP showed a paradoxical pattern, with an initial overshoot followed by a rapid decay to negative values, resulting in a significant underestimation of EGP suppression (57 +/- 3 vs. 65 +/- 4%, P = 0.0117). A two-compartment model performed better but did not overcome the limitations of the dual-tracer approach, since the amount of absorbed glucose was still significantly underestimated (10,231 +/- 661 vs. 12,169 +/- 838 micromol/kg, P = 0.0117) and EGP still showed a paradoxical behavior. R(d), estimated from R(a meal) and EGP, was significantly underestimated with the dual-tracer method, irrespective of adopted model. We conclude that three suitably infused tracers are required for accurate assessment of postprandial R(a meal), EGP, and R(d).

Rapid dual-tracer PTSM+ATSM PET imaging of tumour blood flow and hypoxia: a simulation study

Blood flow and hypoxia are interrelated aspects of physiology that affect cancer treatment and response. Cu-PTSM and Cu-ATSM are related PET tracers for blood flow and hypoxia, and the ability to rapidly image both tracers in a single scan would bring several advantages over conventional single-tracer techniques. Using dynamic imaging with staggered injections, overlapping signals for multiple PET tracers may be recovered utilizing information from kinetics and radioactive decay. In this work, rapid dual-tracer PTSM+ATSM PET was simulated and tested as a function of injection delay, order and relative dose for several copper isotopes, and the results were compared relative to separate single-tracer data. Time-activity curves representing a broad range of tumour blood flow and hypoxia levels were simulated, and parallel dual-tracer compartment modelling was used to recover the signals for each tracer. The main results were tested further using a torso phantom simulation of PET tumour imaging. Using scans as short as 30 minutes, the dual-tracer method provided measures of blood flow and hypoxia similar to single-tracer imaging. The best performance was obtained by injecting PTSM first and using a somewhat higher dose for ATSM. Comparable results for different copper isotopes suggest that tracer kinetics with staggered injections play a more important role than radioactive decay in the signal separation process. Rapid PTSM+ATSM PET has excellent potential for characterizing both tumour blood flow and hypoxia in a single, fast scan, provided that technological hurdles related to algorithm development and routine use can be overcome.

A rapid CBF/CMRO2 measurement with a single PET scan with dual-tracer/integration technique in human

CBF/CMRO2 may be quantified using PET with 15O-tracers, but the conventional three-step technique (3S) requires a long study period, attributed to need for separate acquisition for three radioactive tracers for CBF (H215O or C15O2), CMRO2 (15O2), and CBV (C15O). Simultaneous determination of CBF, CMRO2 and CBV from a single dynamic 15O2 scan is known to suffer from statistical uncertainty. We recently developed a rapid technique that allows sequential administration of two of three tracers (for CBF and CMRO2) in a single PET scan, and generates quantitative CBF/CMRO2 images with a dual-tracer integration method (DTI). This study asked whether this technique is feasible in normal human subjects and how accurate quantitative values it provides in comparison with the 3S and non-linear fitting method (NLM). Eight normal subjects (24.2+-2.6 y.o) participated in this study. The protocol of the study was approved by the local ethical committee. All subjects received three emission scans, i.e., a 4-min scan after short bolus administration of C15O, a 9.5-min scan with dual administration of C15O2 followed by 15O2, and a 9-min scan with 15O2 followed by H215O. With correction for blood volume using the first C15O scan data, CBF/CMRO2 images were generated by 3S using the first part of the second (CO2) and the third scan (O2), whereas those by DTI method were calculated using both part of PET data in each of the second or the third scan. The calculation used a mathematical formula derived from a single-tissue compartment model including a correction for blood volume and an assumed partition coefficient for water. Regional quantitative values of CBF/CMRO2 in the DTI was compared with those by 3S and NLM. We also compared by voxel-by-voxel CBF or CMRO2 images between the second and the third DTI scan to test the regional difference. Global CBF or CMRO2 values for the DTI did not differ from those by the 3S, and between the second and third DTI scans. The cortical regional values of the DTI neither differed significantly from those of 3S and NLM. In contrast, CMRO2 values of the white matter region in both 3S and DTI differed significantly from NLM, as was predicted from a simulation study for the error in the assumed partition coefficient. Voxel-based comparison of CBF images between the second and the third DTI scan showed significant difference at brain regions around nasal cavity, and at the somatosensory areas that may come from the difference in methodology (inhalation or venous-injection of CBF tracer) and physiology (sensation of intravenous injection), respectively. These were also seen when compared CMRO2 images, but at a lower height threshold. These results suggest that this DTI technique generates CBF/CMRO2 images with a considerably shortened scan period, which are comparable to those by 3S, in terms of quantitative accuracy and image quality. The technique may be of use for clinical studies in patients particularly with acute stroke, and also for investigation of metabolic coupling during neuronal activation or pharmacological challenges in human.

Calcium Absorptive Efficiency Is Positively Related to Body Size

Calcium absorption efficiency is a more important determinant of calcium balance than calcium intake itself. The sources of variability in absorptive performance are only partly elucidated. The aim of the study was to explore the relationship between body size and calcium absorption efficiency. Metabolic studies were performed on an inpatient metabolic unit in an academic health sciences center. One hundred seventy-eight women, with an average age of 50.2 yr, were studied from one to five times and yielded an aggregate data set containing 633 individual studies. Calcium absorption fraction was measured by the dual-tracer method. Observed values were expressed as residuals from predicted values for each woman's actual calcium intake, using the previously published relationship between intake and absorption. Absorption residuals were significantly positively correlated with height, weight, and surface area, and after adjusting for estrogen status, these body size variables accounted for approximately 4% of the total variability. The magnitude of the effect is such that a woman 1.8 m in height would absorb 30+% more calcium from a given intake than a woman 1.4 m tall.

Recent advances in sentinel node navigation for gastric cancer: A paradigm shift of surgical management

The sentinel node (SN) is defined as the first draining node from the primary lesion and it has proven to be a good indicator of the metastatic status of regional lymph nodes in solid tumors. In the past 5 years, the validity of SN concept for gastric cancer has been demonstrated by a number of single institutional studies. Using a dual tracer method as the optimal procedure, the radio-guided method allows us to confirm the complete harvest of SNs by gamma probing, while the dye procedure enables us to perform real time observation of the lymphatic vessels. From previous reports, clinically staged T1N0 gastric cancer seems to be a good entity on which to try to change the therapeutic approach based on SN biopsy. At present, two large scale prospective multicenter trials are on-going in Japan. To overcome some remaining issues, such as limited sensitivity of intra-operative diagnosis of metastasis, and technical difficulty in laparoscopic SN detection, further technical and instrumental developments will be required. During this transitional phase, focused lymph node dissection targeted to sentinel lymphatic basins and modified resection of the stomach is an acceptable approach. Although there are several remaining issues, SN navigation should provide a paradigm shift for the surgical management of early gastric cancer in near future.

Methodological considerations in measuring human calcium absorption: relevance to study the effects of inulin-type fructans

During the last 50 years, a variety of methods have been developed to estimate Ca absorption in man. Mass balances were initially used, but these were unable to accurately measure fractional Ca absorption because they cannot distinguish unabsorbed dietary Ca from endogenous faecal Ca excretion (excretion of previously absorbed Ca back into the gut). A number of isotopic methods have been developed that can measure true fractional Ca absorption, employing radioisotopes, stable isotopes, or both. Different methods involve collection of urine, faecal or plasma samples. Of the currently available methods, the dual isotope tracer method with a timed urine collection is probably the most precise and reliable. It is also relatively straightforward to carry out and avoids the need for a faecal collection. The purpose of the present paper is to discuss the general advantages and disadvantages of the different methods of Ca absorption. In addition, the limitations the different methods have in examining the possible effects of non-digestible oligosaccharides on Ca absorption will be discussed.

Laparoscopic Sentinel Lymph Node Mapping for Early Gastric Cancer

Sentinel lymph node (SLN) is known as the first possible site of metastasis along the route of lymphatic drainage from the primary cancerous lesion [1]. SLN mapping has been a focus of attention in management of various solid tumors to establish individualized minimally invasive surgery. In the fields of breast cancer and melanoma, several multicentric prospective randomized control trials for SLN biopsy are ongoing, and less invasive modified surgical approaches based on the SLN status have already been put into practice. However, the application of the SLN concept for gastrointestinal (GI) malignancies was not recognized until late 1990s because of high incidence of so-called skip metastasis. From the reports in recent years, we found that socalled skip metastases in GI cancers are attributed to the aberrant lymphatic drainage from the GI tract and the most of so-called skip metastases occurred in SLNs [2, 3]. Despite the multidirectional and complicated lymphatic flow from gastric mucosa, the anatomical situation of the stomach is better suited for SLN mapping than that of organs that are embedded in closed spaces, such as the esophagus and rectum. In particular, clinically T1N0 gastric cancer seems to be a good entity for which to try to modify the therapeutic approach. Several studies supporting the validity of the SLN concept for gastric cancers have been reported in the past 5 years in settings of open surgery [4,5,6]. Two major largescale clinical trials of SLN mapping for gastric cancer in open surgery have been started in Japan. The next important issue in this field is the introduction of laparoscopic SLN mapping for early gastric cancer, to establish novel minimally invasive surgery. Laparoscopic modified surgery based on SLN status would be the goal of a minimally invasive approach for pathologically nodenegative early gastric cancer. In this issue of World Journal of Surgery, Tonouchi and colleagues present a result of laparoscopic lymphatic mapping and SLN biopsy for early gastric cancer. It is reasonable to employ the dual-tracer method with blue dye and radioactive tracer for detection of SLNs in this study. Although there are several favorable reports of dye-guided SLN mapping for gastric cancer in open surgery, laparoscopic dye-guided SLN detection for gastric cancer is not feasible. Fast transit of blue dye (5–15 min for diffusion) is a restriction of dye-guided laparoscopic detection of multidirectional SLNs of gastric cancer. Technical errors using the single mapping agent approach are reduced by adding a different approach for lymphatic mapping. The radio-guided method allows us to confirm the complete harvest of SLNs with multidirectional and widespread distribution by gamma probing while the dye procedure enables us to perform real-time observation of the visualized lymphatic vessels. Therefore, we recommend a combination of dye and radioguided methods for systematic lymphatic mapping of gastric cancer as an optimal procedure at this moment. In the present study, the authors reported the case of a false negative study that resulted from a detection error [7]. Although the SLN concept was valid (the metastatic node was radioactive) in this case, the radioactive SLN was missed by laparoscopic gamma probing due to the shine-through effect. As shown in the article by Tonouchi, we have to pay attention to the remaining issues in laparoscopic application of this technology. Laparoscopic gamma probing is still under development, and there are several technical and material limitations. Available rigid-type laparoscopic gamma probes are fixed by entry-trocar, and the freedom to search for SLN and to avoid the shine-through effect from the injection site is seriously restricted. As we have seen several breakthroughs in the field of endoscopic surgery, development of new devices may provide a new frontier of this technology. Limitation of the sensitivity of intraoperative histological examination is another serious problem that can lead to false-negative studyies [8]. After overcoming these remaining issues, laparoscopic SLN mapping for early gastric cancer could be the leading model of individualized minimally invasive approaches for study of visceral solid tumors.

Zinc Supplementation Reduces Fractional Zinc Absorption in Young and Elderly Korean Women

Background: Adjustments in zinc losses and absorption are thought to maintain zinc homeostasis with changes in intake, but the capacity to make these adjustments appears to be affected by aging. Zinc status of the individual may also influence adjustments in fractional zinc absorption.Objective: The purpose of this study was to compare the effects of changes in zinc status due to zinc supplementation on fractional zinc absorption in young and elderly Korean women.Design: Zinc status and absorption were measured initially in 15 young (20–24 yr) and 15 elderly women (64–75 yr) confined to a metabolic unit and consuming a typical Korean diet. Upon discharge from the unit the women were supplemented with 22 mg zinc/d for 28 days. On d 20, the women returned to the unit for measurement of zinc status and absorption. Fractional zinc absorption (FZA) was estimated from the same typical Korean breakfast at both time points using the dual isotopic tracer method. Zinc stable isotopic ratios were measured in urine samples collected for 3 days following isotope administration.Results: Plasma and urinary zinc concentrations increased significantly with zinc supplementation in the young but not the elderly women. FZA decreased following zinc supplementation in the young women from 22 to 8% (p < 0.0001) and in the elderly women from 19 to 10% (p < 0.0001). The decline in young women was greater than that in elderly women (p < 0.05).Conclusions: Both young and elderly women reduced their efficiency of zinc absorption with zinc supplementation. But, plasma and urinary zinc concentrations did not increase in the elderly following zinc supplementation suggesting that age altered the use of the additional zinc.

A dual stable isotope tracer method for the measurement of surfactant disaturated-phosphatidylcholine net synthesis in infants with congenital diaphragmatic hernia.

The aim of the study was to measure for the first time in humans surfactant disaturated-phosphatidylcholine (DSPC) net synthesis and kinetics by using a novel, dual stable isotope tracer approach. Ten infants with congenital diaphragmatic hernia [CDH; birth weight, 3.4 +/- 0.2; gestational age, 39.8 +/- 0.4 wk] and 6 age-matched control subjects with no lung disease (birth weight, 3.2 +/- 0.3 kg; gestational age, 39.1 +/- 1.1 wk), all of whom were admitted to the neonatal intensive care unit (Padua, Italy), were studied. All infants received simultaneously an intratracheal (carbon-13 di-palmitoyl-phosphatidylcholine) and an i.v. (deuterated palmitic acid) stable isotope tracer. Isotopic enrichment curves of DSPC from sequential tracheal aspirates were analyzed by mass spectrometry. DSPC kinetic data were expressed as mean +/- SEM and compared by the Mann-Whitney test. DSPC net synthesis from plasma palmitate was nearly identical in infants with CDH and control subjects (8.6 +/- 2.2 and 8.1 +/- 1.5 mg. kg(-1). d(-1); P = 0.7). DSPC apparent pool size was 36.7 +/- 7.5 and 58.5 +/- 9.1 mg/kg (P = 0.07) and half-life was 26.7 +/- 4.5 and 50.3 +/- 9.7 h (P = 0.03) in infants with CDH and control subjects, respectively. Both DSPC turnover and percentage of catabolism/recycling significantly correlated with duration of mechanical ventilation. In conclusion, the measurements of net DSPC synthesis and catabolism/recycling were reported for the first time in humans. Mean net DSPC synthesis was approximately 8 mg. kg(-1). d(-1). No significant differences were found between control subjects and infants with CDH. DSPC turnover was faster in infants with CDH, presumably reflecting an increased DSPC catabolism/recycling. Whether this may ultimately lead to a secondary surfactant deficiency in infants with CDH is still to be ascertained.

Effects of background concentrations of Aureococcus anophagefferens (brown tide) on growth and feeding in the bivalve Mercenaria mercenaria

Much research on the toxic alga Aureococcus anophagefferens (brown tide) has focused on its effects on bivalve suspension feeding, but less is known about how brown tide influences bivalve growth. This study examined the extent to which background levels, defined as concentra- tions too low for toxicity to inhibit bivalve feeding, of A. anophagefferens influenced the growth and feeding physiology of northern quahogs Mercenaria mercenaria compared to other phytoplankton common to Long Island, New York, waters. Juvenile quahogs were fed either unialgal cultures of A. anophagefferens, non brown tide species, or diets mixed with background levels of brown tide. Absorption efficiency (AE) was determined using the 14 C: 51 Cr dual-tracer method, and growth was determined by overall biomass change. Results showed that unialgal diets resulting in the highest AE, specifically Isochrysis galbana and Thalassiosira pseudonana, were associated with rapid M. mercenaria growth. Conversely, Nitzschia closterium resulted in a comparatively low AE and a loss in quahog biomass. Diets mixed with brown tide resulted in a significantly lower AE than the cor- responding unialgal diet for all phytoplankton species except N. closterium. Additionally, mixed diets exerted a small negative influence on quahog growth compared to unialgal diets. These observations suggest that quahogs may suffer subtle, chronic effects when A. anophagefferens is present in the field at background levels. Moreover, the different responses of M. mercenaria to each experimental diet have broad implications for understanding how phytoplankton community composition may influence bivalve growth patterns in the field.

Use of a novel triple-tracer approach to assess postprandial glucose metabolism.

Numerous studies have used the dual-tracer method to assess postprandial glucose metabolism. The present experiments were undertaken to determine whether the marked tracer nonsteady state that occurs with the dual-tracer approach after food ingestion introduces error when it is used to simultaneously measure both meal glucose appearance (R(a meal)) and endogenous glucose production (EGP). To do so, a novel triple-tracer approach was designed: 12 subjects ingested a mixed meal containing [1-(13)C]glucose while [6-(3)H]glucose and [6,6-(2)H(2)]glucose were infused intravenously in patterns that minimized the change in the plasma ratios of [6-(3)H]glucose to [1-(13)C]glucose and of [6,6-(2)H(2)]glucose to endogenous glucose, respectively. R(a meal) and EGP measured with this approach were essentially model independent, since non-steady-state error was minimized by the protocol. Initial splanchnic glucose extraction (ISE) was 12.9% +/- 3.4%, and suppression of EGP (EGPS) was 40.3% +/- 4.1%. In contrast, when calculated with the dual-tracer one-compartment model, ISE was higher (P < 0.05) and EGPS was lower (P < 0.005) than observed with the triple-tracer approach. These errors could only be prevented by using time-varying volumes different for R(a meal) and EGP. Analysis of the dual-tracer data with a two-compartment model reduced but did not totally avoid the problems associated with marked postprandial changes in the tracer-to-tracee ratios. We conclude that results from previous studies that have used the dual-tracer one-compartment model to measure postprandial carbohydrate metabolism need to be reevaluated and that the triple-tracer technique may provide a useful approach for doing so.

Estimation of True Calcium Absorption in Men

When both calcium intake and calcium absorption are measured under controlled conditions, variation in absorption efficiency explains more of the interindividual differences in balance than does actual calcium intake (1). Small wonder, therefore, that interest in measuring absorption has remained high for nearly 40 years. True calcium absorption is defined as the quantitative, unidirectional flux of calcium from intestinal lumen into the blood. It is most accurately measured by a dual-tracer method, with one tracer labeling the oral calcium load and the other labeling the miscible calcium pool into which the absorbed calcium is introduced. This approach was first developed into a practicable human test by deGrazia et al. (2). As described, it is usually time-consuming and expensive. To reduce these barriers for widespread use, Heaney and Recker (3)(4) developed a single-tracer variant for women, requiring only a single blood sample, and calibrated it against a simultaneously performed double-tracer method. The single-tracer method has been used efficiently in thousands of women (5). However, because the calibration is empirical and based on body-size variables, it is not directly suitable for use in men who, with a typically higher proportion of fat-free mass than women, would be expected to distribute absorbed tracer in a larger mass of calcium. To fill this methodologic gap, we performed a small set of parallel measurements in adult men, using the female-based algorithm together wiketh a modified double-tracer approach. Participants in the study were 30 Caucasian men (age range, 20–60 years; weight range, 63.5–104 kg; height range, 1.67–1.93 m). All participants were free of known diseases affecting bone remodeling or calcium homeostasis, and tests were not performed if the individual had experienced any gastrointestinal disturbance in the preceding 5 days. Each gave informed consent after the procedures of the study were explained. Both the project …

Heterogeneous cardiac sympathetic innervation in heart failure after myocardial infarction of rats.

We examined cardiac neuronal function and beta-receptor with a dual-tracer method of [(131)I]meta-iodobenzylguanidine (MIBG) and [(125)I]iodocyanopindolol (ICYP) in rat heart failure after myocardial infarction (MI). In rats with MI, left ventricular (LV) systolic function decreased, and LV dimension and right ventricular (RV) mass increased gradually. MIBG accumulations of the noninfarcted LV (remote region) and RV decreased by 15% at 1 wk compared with sham-operated rats, and these accumulations were restored by 71% and 56%, respectively, at 24 wk compared with age-matched sham rats despite sustained depletion of myocardial norepinephrine contents in these regions. ICYP accumulation of the remote region and of the RV did not decrease at any stages. Myocardial MIBG distribution was heterogeneous at 1 wk when it was lower in the peri-infarcted region than in the remote region, associated with reduced ICYP accumulation in the peri-infarcted region. The heterogeneous distribution of both isotopes disappeared at 12 wk. Thus cardiac sympathetic neuronal alteration was coupled with downregulation of beta-receptors in rat heart failure after MI. The abnormal adrenergic signaling occurred heterogeneously in terms of ventricular distribution and time course after MI.