An Assessment of the “Radioactive Renogram” Using O-Iodohippurate Sodium (Hippuran) Labelled with Radioactive Iodine

A “radioactive renogram” using o-iodohippurate sodium (Hippuran)-I¹³¹ was performed in 57 patients who had either hypertension or various renal diseases. In longstanding essential hypertension, the initial uptake and secretory phases are often reduced below normal. In five hypertensive patients who were shown to have unilateral renal disease, the renogram showed significantly abnormal tracings on the affected side. In three patients suffering from ureteral obstruction, the excretory phase was significantly prolonged.On the basis of comparative albumin and iodohippurate renograms, the initial uptake can no longer be considered as a vascular phase, as previously believed.The iodohippurate-I¹³¹ renogram is a useful adjunct in the investigation of hypertension and renal disease, providing information about each kidney not so readily obtained by other means. Nevertheless, the test does not supplant any other investigative procedure and should not be depended upon as a screening procedure.     

Cadaver Renal Homotransplants: Initial Experiences

Four renal homotransplants were carried out between cadaver donors and four recipients, all of whom were in terminal chronic renal failure. Immune suppression was attempted with azathioprine (Imuran), actinomycin C and prednisone; no radiation was used, nor were the recipient''s kidneys, spleen or thymus removed. One patient died with disseminated histoplasmosis at two weeks; another with irreversible homograft rejection at 30 days; a third patient died of septicemia after 9½ weeks with stable renal function. The fourth patient, whose transplant had been ischemic for 190 minutes and had not functioned for 2½ weeks thereafter, eventually achieved good function which remained unchanged to 7½ months. Changes in urinary enzyme excretion and in the I¹³¹ renogram and meralluride scan were of value in assessing homograft rejection.     

USE OF THE ARTIFICIAL KIDNEY—Its Place in the Treatment of Acute Renal Failure

Of 57 patients with severe, but potentially reversible, acute renal failure who were observed during a recent four-year period, some had dialysis with an artificial kidney and some did not.Twenty survived with the standard “conservative” management alone; 19 survived with a combination of “conservative” and “intensive” (that is, artificial kidney) treatment; 18 patients died.One error that was made in the management of all 18 patients who died, was excessive delay in the use of the artificial kidney.Hemodialysis should be used whenever serious electrolyte abnormality exists, whenever the blood urea nitrogen exceeds 150 mg. per 100 cc. or whenever clinical signs of uremia first appear. One or more of these indications will usually, but not always, become evident between the fifth and the eighth day of virtual anuria.     

Long-Term Responses to Loss of Renal Mass: Control Mechanisms: The Role of Renal “Work” in Compensatory Kidney Growth

In a series of studies designed to test the role of renal “work” in compensatory kidney growth we examined the relationship between absolute sodium reabsorption—which constitutes the bulk of renal energy expenditure, and growth of the remaining kidney at various intervals after contralateral nephrectomy.The increase in weight of the remaining kidney preceded the rise in sodium reabsorption and these two processes took place at different rates between 24 hours and 21 days after uninephrectomy.Absolute sodium reabsorption did not change during the first hours after contralateral nephrectomy, at a time when biochemical alterations are known to occur.The rate of [¹⁴C] choline incorporation into renal phospholipid, an early biochemical indicator of compensatory kidney growth, increased significantly one hour after contralateral nephrectomy but remained unchanged after sham-nephrectomy, regardless of the magnitude or direction of the concomitant change in absolute sodium reabsorption (“kidney work”).These results indicate that renal work expended in the reabsorption of glomerular filtrate is neither the initiating, nor the primary controlling factor, of the compensatory kidney growth that follows unilateral nephrectomy.     

Orthotopic Kidney Transplantation in Mice: Technique Using Cuff for Renal Vein Anastomosis

Mouse renal transplantation is a technically challenging procedure. Although the first kidney transplants in mice were performed over 34 years ago and refined some years later, the classical techniques of mouse renal transplantation required clamping both vena cava and aorta simultaneously and carry out suture anastomoses of the renal artery and vein in a heterotopic position. In our laboratory, we have successfully developed mouse orthotopic kidney transplantation for the first time, using a rapid “cuffed” renal vein technique for vessel anastomosis, wherein the donor’s renal vein was inserted through an intravenous catheter, folded back and tied. During grafting, the cuffed renal vein was directly inserted into the recipient’s renal vein without the need for the clamping vena cava and suturing of renal vein. This technique allowed for the exact transplantation of the kidney into the original position, compared to the classical technique, and has significantly shortened the clamping time due to a quicker and precise anastomosis of renal vein as described. This also allowed for a quicker recovery of the lower extremity activity, reduction in myoglobinuria with resultant kidney graft survival of 88.9%. Thus we believe that the cuffed renal vein technique simplifies microvascular anastomoses and affords important additional benefits.     

Intérêt pronostique de la scintigraphie au 99mTc-MAG3 pour le succès à un an de la transplantation rénale

Because of the increasing use of marginal grafts, it remains a significant difference in terms of transplants half-life between living donor or cadaver donor. The main objective of this study was to assess the prognostic value of various isotopic parameters available on the same day than surgery for the one-year outcome after kidney transplantation. A retrospective study of 100 patients, who received a renal allograft at the University Hospital of Montpellier between 1999 and 2006, and who performed ^99mTc-MAG3 renal scintigraphy within 72 h after transplantation, was performed. Measurement of various isotopic parameters was performed for angiographic and tubular phases, over three different regions of interest. According to judgment criteria, namely the success or not of transplantation after the first year, previously obtained results were statistically compared. The results of our study confirmed the importance of vascular parameters, especially the Kirchner index, with a good correlation with renal function one year after tranplantation. As expected by the physiological models, a well-perfused graft had the most chances of short-term survival. Kirchner index has a negative predictive value of more than 90% for the one-year success after transplantation (VPP = 75%). Parameters assessing more specifically nephronic functional reserve (such as tubular function slope or uptake on perfusion peaks report) are independent risk factors for the failure during the first three months.     

Efficient Uptake of Blood-Borne BK and JC Polyomavirus-Like Particles in Endothelial Cells of Liver Sinusoids and Renal Vasa Recta

Liver sinusoidal endothelial cells (LSECs) are specialized scavenger cells that mediate high-capacity clearance of soluble waste macromolecules and colloid material, including blood-borne adenovirus. To explore if LSECs function as a sink for other viruses in blood, we studied the fate of virus-like particles (VLPs) of two ubiquitous human DNA viruses, BK and JC polyomavirus, in mice. Like complete virions, VLPs specifically bind to receptors and enter cells, but unlike complete virions, they cannot replicate. ¹²⁵I-labeled VLPs were used to assess blood decay, organ-, and hepatocellular distribution of ligand, and non-labeled VLPs to examine cellular uptake by immunohisto- and -cytochemistry. BK- and JC-VLPs rapidly distributed to liver, with lesser uptake in kidney and spleen. Liver uptake was predominantly in LSECs. Blood half-life (∼1 min), and tissue distribution of JC-VLPs and two JC-VLP-mutants (L55F and S269F) that lack sialic acid binding affinity, were similar, indicating involvement of non-sialic acid receptors in cellular uptake. Liver uptake was not mediated by scavenger receptors. In spleen, the VLPs localized to the red pulp marginal zone reticuloendothelium, and in kidney to the endothelial lining of vasa recta segments, and the transitional epithelium of renal pelvis. Most VLP-positive vessels in renal medulla did not express PV-1/Meca 32, suggesting location to the non-fenestrated part of vasa recta. The endothelial cells of these vessels also efficiently endocytosed a scavenger receptor ligand, formaldehyde-denatured albumin, suggesting high endocytic activity compared to other renal endothelia. We conclude that LSECs very effectively cleared a large fraction of blood-borne BK- and JC-VLPs, indicating a central role of these cells in early removal of polyomavirus from the circulation. In addition, we report the novel finding that a subpopulation of endothelial cells in kidney, the main organ of polyomavirus persistence, showed selective and rapid uptake of VLPs, suggesting a role in viremic organ tropism.     

Serial Non-Invasive Assessment of Antibody Induced Nephritis in Mice Using Positron Emission Tomography

Mouse models of experimental anti-glomerular basement membrane (anti-GBM) nephritis provide an analytical tool for studying spontaneous lupus nephritis. The potential of Positron Emission Tomography (PET) was evaluated using 2-deoxy-2-[¹⁸F]fluoro-d-glucose (FDG) as a probe to monitor the progression of anti-GBM induced nephritis in a mouse model. The imaging results were compared to conventional measures of renal function and pathological changes. Serum and urinary vascular cell adhesion molecule-1 (VCAM-1) levels were used as measures of endothelial cell activation and inflammation. Following a challenge with anti-glomerular antibodies, mice exhibited peak changes in serum creatinine, proteinuria, and glomerulonephritis score at 14 days post-challenge (p.c.). In contrast, VCAM levels peaked at day 7 p.c. On dynamic PET images (0–60 min) of day 7, kidneys of the anti-GBM nephritis mice demonstrated a unique pattern of FDG uptake. Compared to the time activity curve (TAC) prior to challenge, a rightward shift was observed after the challenge. By day 10 p.c., kidney FDG uptake was lower than baseline and remained so until the study ended at 21 days p.c. During this time frame measures of renal dysfunction remained high but VCAM-1 levels declined. These changes were accompanied by an increase in kidney volume as measured by Computed Tomography (CT) and intra-abdominal fluid collection. Our results suggest that FDG-PET-CT can be used as a non-invasive imaging tool to longitudinally monitor the progression of renal disease activity in antibody mediated nephritis and the magnitude of renal FDG retention correlates better with early markers of renal inflammation than renal dysfunction.     

Analysis of Minimal Functions of Simian Virus 40 II. Enhancement of Oncogenic Transformation in Vitro by UV Irradiation

After light UV irradiation (5,000 to 10,000 ergs/mm²) “complete” and “defective” simian virus 40 (SV40) showed an enhancement of oncogenic transformation capacity in Syrian hamster kidney cells in vitro up to 180 and 270% of the controls, respectively. Simultaneously with the enhancement of transformation, an increase in T-antigen induction was observed in CV-1 cells infected with light UV-irradiated SV40; infectivity, however, was correspondingly reduced by 1 log₁₀. After strong UV irradiation (10,000 to 80,000 ergs/mm²) of “complete” and “defective” SV40, transformation capacity in vitro proved to be the most resistant viral function. It was only slightly reduced in comparison with a 4 to 5 log₁₀ reduction of infectivity. T-antigen induction of SV40 was also equally resistant to strong UV irradiation. We found no evidence of “multiplicity reactivation” involved in the high resistance of transformation capacity of SV40 after UV irradiation. Syrian hamster kidney cells transformed in vitro by UV-irradiated SV40 contained the SV40-specific T-antigen and showed the same morphology and growth characteristics as cells transformed by non-irradiated “complete” or “defective” SV40. They induced malignant tumors after subcutaneous inoculation into Syrian hamsters.     

Seasonality and Paleoecology of the Late Cretaceous Multi-Taxa Vertebrate Assemblage of “Lo Hueco” (Central Eastern Spain)

Isotopic studies of multi-taxa terrestrial vertebrate assemblages allow determination of paleoclimatic and paleoecological aspects on account of the different information supplied by each taxon. The late Campanian-early Maastrichtian “Lo Hueco” Fossil-Lagerstätte (central eastern Spain), located at a subtropical paleolatitude of ~31°N, constitutes an ideal setting to carry out this task due to its abundant and diverse vertebrate assemblage. Local δ¹⁸O_PO4 values estimated from δ¹⁸O_PO4 values of theropods, sauropods, crocodyliforms, and turtles are close to δ¹⁸O_H2O values observed at modern subtropical latitudes. Theropod δ¹⁸O_H2O values are lower than those shown by crocodyliforms and turtles, indicating that terrestrial endothermic taxa record δ¹⁸O_H2O values throughout the year, whereas semiaquatic ectothermic taxa δ¹⁸O_H2O values represent local meteoric waters over a shorter time period when conditions are favorable for bioapatite synthesis (warm season). Temperatures calculated by combining theropod, crocodyliform, and turtle δ¹⁸O_H2O values and gar δ¹⁸O_PO4 have enabled us to estimate seasonal variability as the difference between mean annual temperature (MAT, yielded by theropods) and temperature of the warmest months (TWMs, provided by crocodyliforms and turtles). ΔTWMs-MAT value does not point to a significantly different seasonal thermal variability when compared to modern coastal subtropical meteorological stations and Late Cretaceous rudists from eastern Tethys. Bioapatite and bulk organic matter δ¹³C values point to a C₃ environment in the “Lo Hueco” area. The estimated fractionation between sauropod enamel and diet is ~15‰. While waiting for paleoecological information yielded by the ongoing morphological study of the “Lo Hueco” crocodyliforms, δ¹³C and δ¹⁸O_CO3 results point to incorporation of food items with brackish influence, but preferential ingestion of freshwater. “Lo Hueco” turtles showed the lowest δ¹³C and δ¹⁸O_CO3 values of the vertebrate assemblage, likely indicating a diet based on a mixture of aquatic and terrestrial C₃ vegetation and/or invertebrates and ingestion of freshwater.     

The Integrin β1 Subunit Regulates Paracellular Permeability of Kidney Proximal Tubule Cells

Epithelial cells lining the gastrointestinal tract and kidney have different abilities to facilitate paracellular and transcellular transport of water and solutes. In the kidney, the proximal tubule allows both transcellular and paracellular transport, while the collecting duct primarily facilitates transcellular transport. The claudins and E-cadherin are major structural and functional components regulating paracellular transport. In this study we present the novel finding that the transmembrane matrix receptors, integrins, play a role in regulating paracellular transport of renal proximal tubule cells. Deleting the integrin β1 subunit in these cells converts them from a “loose” epithelium, characterized by low expression of E-cadherin and claudin-7 and high expression of claudin-2, to a “tight” epithelium with increased E-cadherin and claudin-7 expression and decreased claudin-2 expression. This effect is mediated by the integrin β1 cytoplasmic tail and does not entail β1 heterodimerization with an α-subunit or its localization to the cell surface. In addition, we demonstrate that deleting the β1 subunit in the proximal tubule of the kidney results in a major urine-concentrating defect. Thus, the integrin β1 tail plays a key role in regulating the composition and function of tight and adherens junctions that define paracellular transport properties of terminally differentiated renal proximal tubule epithelial cells.     

Evaluation of kidney repair capacity using Tc-DMSA in ischemia/reperfusion injury models

Quantitative ^99mTc-DMSA renal uptake was studied in different renal ischemia/reperfusion (I/R) mice models for the assessment of renal repair capacity. Mice models of nephrectomy, uni- and bi-lateral I/R together with sham-operated mice were established. At 1 h, 1 d, 4 d, 1, 2 and 3 wk after I/R, ^99mTc-DMSA (27.7 ± 1.3 MBq) was injected via tail vein and after 3 h post-injection, the mice were scanned for 30 min with pinhole equipped gamma camera. Higher uptake of ^99mTc-DMSA was measured in normal kidneys of uni-lateral I/R model and nephrectomized kidney I/R model at 3 wk post-surgery. Comparing the restoration capacities of the affected kidneys of nephrectomy, uni- and bi-lateral I/R models, higher repair capacity was observed in the nephrectomized model followed by bi-lateral then uni-lateral models. The normal kidney may retard the restoration of damaged kidney in uni-lateral I/R model. Moreover, 3 wk after Uni-I/R, the size of injured kidney was significantly smaller than non-ischemic contralateral and sham operated kidneys, while nephrectomy I/R kidneys were significantly enlarged compared to all others at 3 wk post-surgery. Very strong correlation between ^99mTc-DMSA uptake and weight of dissected kidneys in I/R models was observed. Consistent with ^99mTc-DMSA uptake results, all histological results indicate that kidney recovery after injury is correlated with the amount of intact tubules and kidney sizes. In summary, our study showed good potentials of ^99mTc-DMSA scan as a promising non-invasive method for evaluation of kidney restoration after I/R injuries. Interestingly, mice with Bi-I/R injury showed faster repair capacity than those with uni-I/R.     

Mesenchymal Stem Cells Improve Medullary Inflammation and Fibrosis after Revascularization of Swine Atherosclerotic Renal Artery Stenosis

Atherosclerotic renal artery stenosis (ARAS) raises blood pressure and can reduce kidney function. Revascularization of the stenotic renal artery alone does not restore renal medullary structure and function. This study tested the hypothesis that addition of mesenchymal stem cells (MSC) to percutaneous transluminal renal angioplasty (PTRA) can restore stenotic-kidney medullary tubular transport function and attenuate its remodeling. Twenty-seven swine were divided into three ARAS (high-cholesterol diet and renal artery stenosis) and a normal control group. Six weeks after ARAS induction, two groups were treated with PTRA alone or PTRA supplemented with adipose-tissue-derived MSC (10×10⁶ cells intra-renal). Multi-detector computed tomography and blood-oxygenation-level-dependent (BOLD) MRI studies were performed 4 weeks later to assess kidney hemodynamics and function, and tissue collected a few days later for histology and micro-CT imaging. PTRA effectively decreased blood pressure, yet medullary vascular density remained low. Addition of MSC improved medullary vascularization in ARAS+PTRA+MSC and increased angiogenic signaling, including protein expression of vascular endothelial growth-factor, its receptor (FLK-1), and hypoxia-inducible factor-1α. ARAS+PTRA+MSC also showed attenuated inflammation, although oxidative-stress remained elevated. BOLD-MRI indicated that MSC normalized oxygen-dependent tubular response to furosemide (-4.3±0.9, −0.1±0.4, −1.6±0.9 and −3.6±1.0 s⁻¹ in Normal, ARAS, ARAS+PTRA and ARAS+PTRA+MSC, respectively, p<0.05), which correlated with a decrease in medullary tubular injury score (R² = 0.33, p = 0.02). Therefore, adjunctive MSC delivery in addition to PTRA reduces inflammation, fibrogenesis and vascular remodeling, and restores oxygen-dependent tubular function in the stenotic-kidney medulla, although additional interventions might be required to reduce oxidative-stress. This study supports development of cell-based strategies for renal protection in ARAS.     

Acute Kidney Injury Enhances Outcome Prediction Ability of Sequential Organ Failure Assessment Score in Critically Ill Patients

Introduction

Acute kidney injury (AKI) is a common and serious complication in intensive care unit (ICU) patients and also often part of a multiple organ failure syndrome. The sequential organ failure assessment (SOFA) score is an excellent tool for assessing the extent of organ dysfunction in critically ill patients. This study aimed to evaluate the outcome prediction ability of SOFA and Acute Physiology and Chronic Health Evaluation (APACHE) III score in ICU patients with AKI.

Methods

A total of 543 critically ill patients were admitted to the medical ICU of a tertiary-care hospital from July 2007 to June 2008. Demographic, clinical and laboratory variables were prospectively recorded for post hoc analysis as predictors of survival on the first day of ICU admission.

Results

One hundred and eighty-seven (34.4%) patients presented with AKI on the first day of ICU admission based on the risk of renal failure, injury to kidney, failure of kidney function, loss of kidney function, and end-stage renal failure (RIFLE) classification. Major causes of the ICU admissions involved respiratory failure (58%). Overall in-ICU mortality was 37.9% and the hospital mortality was 44.7%. The predictive accuracy for ICU mortality of SOFA (areas under the receiver operating characteristic curves: 0.815±0.032) was as good as APACHE III in the AKI group. However, cumulative survival rates at 6-month follow-up following hospital discharge differed significantly (p<0.001) for SOFA score ≤10 vs. ≥11 in these ICU patients with AKI.

Conclusions

For patients coexisting with AKI admitted to ICU, this work recommends application of SOFA by physicians to assess ICU mortality because of its practicality and low cost. A SOFA score of ≥ “11” on ICU day 1 should be considered an indicator of negative short-term outcome.     

Longitudinal Study of the Decline in Renal Function in Healthy Subjects

Background

Chronic kidney disease is an important concern in preventive medicine, but the rate of decline in renal function in healthy population is not well defined. The purpose of this study was to determine reference values for the estimated glomerular filtration rate (eGFR) and rate of decline of eGFR in healthy subjects and to evaluate factors associated with this decline using a large cohort in Japan.

Methods

Retrospective cross-sectional and longitudinal studies were performed with healthy subjects aged ≥18 years old who received a medical checkup. Reference values for eGFR were obtained using a nonparametric method and those for decline of eGFR were calculated by mixed model analysis. Relationships of eGFR decline rate with baseline variables were examined using a linear least-squares method.

Results

In the cross-sectional study, reference values for eGFR were obtained by gender and age in 72,521 healthy subjects. The mean (±SD) eGFR was 83.7±14.7ml/min/1.73m². In the longitudinal study, reference values for eGFR decline rate were obtained by gender, age, and renal stage in 45,586 healthy subjects. In the same renal stage, there was little difference in the rate of decline regardless of age. The decline in eGFR depended on the renal stage and was strongly related to baseline eGFR, with a faster decline with a higher baseline eGFR and a slower decline with a lower baseline eGFR. The mean (±SD) eGFR decline rate was ‒1.07±0.42ml/min/1.73m²/year (‒1.29±0.41%/year) in subjects with a mean eGFR of 81.5±11.6ml/min/1.73m².

Conclusions

The present study clarified for the first time the reference values for the rate of eGFR decline stratified by gender, age, and renal stage in healthy subjects. The rate of eGFR decline depended mainly on baseline eGFR, but not on age, with a slower decline with a lower baseline eGFR.     

Protein charge ladders reveal that the net charge of ALS-linked superoxide dismutase can be different in sign and magnitude from predicted values

This article utilized “protein charge ladders”—chemical derivatives of proteins with similar structure, but systematically altered net charge—to quantify how missense mutations that cause amyotrophic lateral sclerosis (ALS) affect the net negative charge (Z) of superoxide dismutase-1 (SOD1) as a function of subcellular pH and Zn²⁺ stoichiometry. Capillary electrophoresis revealed that the net charge of ALS-variant SOD1 can be different in sign and in magnitude—by up to 7.4 units per dimer at lysosomal pH—than values predicted from standard pK_a values of amino acids and formal oxidation states of metal ions. At pH 7.4, the G85R, D90A, and G93R substitutions diminished the net negative charge of dimeric SOD1 by up to +2.29 units more than predicted; E100K lowered net charge by less than predicted. The binding of a single Zn²⁺ to mutant SOD1 lowered its net charge by an additional +2.33 ± 0.01 to +3.18 ± 0.02 units, however, each protein regulated net charge when binding a second, third, or fourth Zn²⁺ (ΔZ < 0.44 ± 0.07 per additional Zn²⁺). Both metalated and apo-SOD1 regulated net charge across subcellular pH, without inverting from negative to positive at the theoretical pI. Differential scanning calorimetry, hydrogen-deuterium exchange, and inductively coupled plasma mass spectrometry confirmed that the structure, stability, and metal content of mutant proteins were not significantly affected by lysine acetylation. Measured values of net charge should be used when correlating the biophysical properties of a specific ALS-variant SOD1 protein with its observed aggregation propensity or clinical phenotype.     

Study of Na+ and Water Transport in the Pigeon and Chicken Kidney by Lithium Clearance Method under Conditions of Water and Salt Load: Regimes of Renal Net Reabsorption and Net Secretion of Li+

The water (intestinally) and salt (intravenously) loads of a sufficient intensity (about 120 ml water or 9 mmol NaCl per kg body mass) caused a reversible conversion (of duration of 30–40 min) in the renal Li transport, i.e., transition from net reabsorption of this ion (FE_Li = C_Li/GFR < 1) to its net secretion (FE_Li > 1), where C_Li—lithium clearance, GFR—glomerular filtration rate, ⁶⁵ZnDTPA clearance. Maximal values of the fractional lithium excretion (FE_Li) amounted to about 1.5 and 2.0 after the water and salt loads, respectively. A repeated salt load (4–5 NaCl injections by 9 mmol/kg at 20–40 min intervals) induced a long (2–3 h) net secretion of lithium in the chicken kidney. This regime of renal functioning was characterized by abundant urination (20–30 ml/kg/h) and a substantial increase of the Na⁺ concentration in blood plasma (from 138 ± 9 to 172 ± 10 mM, the mean ( standard deviation) and in urine (to 157 ± 19 mM). The data obtained were considered in terms of a hypothesis suggesting that the renal lithium secretion indicates the appearance of net water and Na⁺ secretion in the proximal tubule of the avian kidney in response to water and salt load. The fractional reabsorption of Na⁺ and water in the chicken kidney were calculated by means of lithium clearance during both the net reabsorption and the secretion of lithium in the kidney. In the former regime of renal functioning (FE_Li < 1), regardless of changes in lithium reabsorption (up to its complete cessation at FE_Li = 1), the kidney as a whole reabsorbs about 99% of filtered Na⁺, while distal reabsorption of this ion accounts for about 98%. The corresponding values for water reabsorption are about 96 and 92%, respectively. At FE_Li > 1, the fractional reabsorption of Na⁺ and water decrease significantly: the minimal values amount to about 60%, while the mean values, about 80%.     

Dynamics of photoassimilated carbon in douglas fir seedlings

The relations between CO₂ uptake, translocation, and carbon accumulation in several vegetative components of Douglas fir seedlings (Pseudotsuga menziesii [Mirb.] Franco) have been quantified using ¹⁴CO₂. Seedlings were exposed to a constant specific radioactivity of ¹⁴CO₂ and a repeating daily pattern of temperature and light for 4 consecutive days. Results of ¹⁴C analysis, which indicated a transitory pattern of photoassimilated carbon movement, were extrapolated to a “steady rate” using a compartment analysis. Accumulation rates of photoassimilated carbon, relative to tissue carbon, were new needles, 0.94%/day, old needles, 1.14%/day, new shoots 0.38%/day, stem, 0.16%/day, and roots, 0.50%/day. Therefore, the source of carbon, the needles, is also the strongest sink.