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Aspergillus niger produces citric acid during surface fermentation on inulin, a reserve carbohydrate of plant tubers. Citric acid yields can be improved by airflow over the surface of the fermentation but yields from inulin are 20-30% lower than from sucrose, the traditional commercial substrate.
Material injected into the cerebral ventricles can leave the cerebrospinal fluid (CSF) but remain in the cranial cavity. To analyze the disappearance of 3H- and of 14C-labelled material from the cranial cavity, such material was injected into the lateral ventricles together with a bulk flow marker, labelled with the other radionuclide. In the present pilot study 3H-PAH and 14C-inulin were used. Five microliter of a mixture was injected into each lateral cerebral ventricles in rats, which were killed at various intervals. The whole skull was analyzed without opening the CSF space after homogenization in the deep-frozen state. The samples were combusted and analyzed by liquid scintillation counting. Probenecid, injected intraperitoneally, inhibited the removal of 3H-PAH from the skull cavity, as anticipated. Immediately after the intraventricular injection, however, 3H-PAH was transiently retained, probably by uptake into actively transporting tissue. After injection of probenecid, this delay in removal was reduced. The difference in disappearance rate between 3H-PAH and 14C-inulin was estimated by comparing the 3H/14C ratio in the skulls with that in the injected solution, which appeared to be a better method than comparing the recovery of each compound.
We evaluated iohexol as a filtration marker in 150 children. The clearance of iohexol was compared with that of inulin or with a formula clearance. The single-sample clearance of iohexol showed a good correlation with the clearance of inulin (r = 0.834). The clearance of iohexol correlated well (r = 0.672) with the formula clearance. The optimal blood sampling time for iohexol clearance determinations appears to be between 120 and 180 min after injection, at least in patients with relatively normal filtration rates. We conclude that iohexol clearance is an accurate method of determining the glomerular filtration rate in clinical practice.
An animal model which permits sampling of arterial blood and bile from unanesthetized rats with uninterrupted enterohepatic circulation is described. Pharmacokinetic data concerning inulin (0.2 mumol kg-1) and terbutaline (1.8 mumol kg-1) after intraarterial injection are presented. The following values for inulin were obtained Vdbeta equals 0.25 ml g-1, plasma clearance equals 2.3 ml min-1 kg-1 and bile clearance equals 0.03-0.04 ml min-1 kg-1, which mainly are in agreement with data from the literature. For terbutaline the corresponding values were 0.58 ml g-1, 5.2 ml min-1 kg-1 and 0.12-0.98 ml min-1 kg-1, respectively.
The present study analyzed the brain uptake of the differently sized hydrophilic molecules 14C-inulin, 14C-sucrose and 14C-mannitol. constant tracer concentrations were maintained in blood plasma after renal ligation. Accumulation of the indicators was measured in brain cortex during the approach to steady-state. At the conclusion of infusion periods of 5, 10, 15, 30 and 60 min, samples of cerebral cortex were analyzed for radioactivity. Fractions attributable to blood in the tissue were subtracted and time-dependent apparent distribution volumes of the indicators in the tissue were estimated. The brain level did not rise to more than 1--2% of that in the plasma for inulin and sucrose and to 6--7% for mannitol. The explanation for this could be a combination of restricted penetration from blood into brain and a sink effect of cerebrospinal fluid (csf). to determine the removal of the indicators into csf, ventriculo-cisternal perfusion was performed during the period of tracer uptake in the the tissue; the rate of passage of the indicators into perfusion fluid was found to be negligible in comparison to the rates of uptake in the tissue. As diffusion in the extracellular space could limit uptake rates from blood to brain, estimates of diffusion limited half-times were also made. Calculations showed that the major hindrance to indicator uptake in the tissue is located in the wall of the brain capillaries; thus the uptake data permit calculation of brain capillary permeability. The half-times for the distribution of the indicators in their equilibrated tissue distribution spaces were used to estimate brain capillary permeability. By comparison with the aqueous diffusion coefficients of the indicators it is concluded that the substances in the molecular weight range of 182 to 5 500 daltons are subjected to restricted diffusion during the passage of the blood-brain barrier and that in addition non-discriminative transendothelial pathways are available.
Glomerular filtration rate (GFR) was assessed over a 2 h period by the clearance of inulin (Cin) and in the subsequent 2 h period by a single-injection technique using radiolabelled sodium iothalamate (Ciot) or chromium-EDTA (CEDTA). Regression analysis yielded a significant correlation (P less than 0.05) between the standard clearance technique and the single-injection method, with the relationship Ciot = -10.67 + 1.25Cin with a significant correlation coefficient of r = 0.71 (P less than 0.02). There was better agreement between clearance values of inulin measured on successive days than between values determined by the single-injection technique on successive days. Cin remains the method of choice in sheep.
1. The volume of distribution of [14-C]carboxyl inulin has been studied in slices of outer and inner medulla from rat kidney incubated in Krebs phosphate-bicarbonate Ringer, modified to render it iso-osmolal with the tissue fluids in these zones, under three conditions, (a) aerobically at 37 degrees C (control), (b) anoxically at 37 degrees C, and (c) aerobically at 0 degrees C. 2. Under control conditions near steady-state volumes of approximately 24 and 42 mul./100 mg wet weight slice were obtained for outer and inner medulla respectively during the period 10-30 min from the start of incubation. In the outer medulla the volumes of distribution in anoxic and hypothermic slices exceeded that in control slices during this time, but control values increased from 30 to 100 min so that after 100 min the distribution volumes were approximately 30 mul./100 mg under each set of conditions. 3. In the inner medulla control and anoxic slices had inulin distribution volumes of approximately 42 mul./100 mg during 10-30 min, rising to over 50 mul./u99 mg by 100 min. Slices incubated hypothermically reached a steady-state value of approximately 40 mul./100 mg by 30 min, which did not increase further for up to 100 min. 4. All slices lost about 10% of their initial weight during the first 3 min of incubation. Thereafter control slices maintained weight constancy for at least 30 min (outer medulla) or 100 min (inner medulla); slices incubated anoxically or hypothermically gained weight, the gains being greatest in anoxic outer and hypothermic inner medulla. 5. The K concentration within control slices (both zones), hypothermic outer and anoxic inner medulla attained equilibrium when slice [K] was approximately 8 times medium [K] (5-9 mM). In anoxic outer and hypothermic inner medullary slices [K] fell to a significantly greater extent, but interpretation of these findings in terms of slice K loss is subject to modification in respect of the increases in slice weight (water content) accompanying the [K] decreases. 6. There was a transient (1-3 min) rise in [Na] in all slices. This was followed by a [Na] decrease, which was most apparent in control slices, and finally a gradual increase towards medium [Na] (141 and 180 mM for outer and inner medulla respectively).
A continuous infusion method for measuring inulin clearance (and hence glomerular filtration rate) which does not require urine collection has been re-evaluated and found to give satisfactory results. In two non-oedematous and anephric patients the plasma level of inulin became virtually constant four hours after a single intravenous dose, and hence this is the minimum time required for the infusion with this method.
The in vivo transalveolar transport of three large polar solutes, sucrose, inulin, and dextran (mol wt 60,000-90,00), was compared with the transport of urea in saline-filled dog lung. Apparent permeability coefficents (p', in cm X sec-1 X 10(6)) were as follows; urea: 2.4 +/- 0.28 (SD) greater than sucrose: 0.64 +/- 0.31 (P less than 0.001) greater than inulin: 0.12 +/- .05 (P less than 0.001)--not different from dextran (mol wt 60,000-90,000): 0.08 +/- .02 (P greater then .01). Calculation of the resistance of the alveolar epithelium compared to total barrier resistance for the various solutes indicates that approximately 90% of the total resistance resides in the alveolar epithelium. Comparison of the ratio of permeability coefficients to the ratio of free-diffusion coefficients in water shows similar values for the three large polar solutes, suggesting that permeation through the alveolar epithelium occurs by means of water-filled channels. The values for permeability coefficients of alveolar epithelium fit into the spectrum of values reported for other epithelial structures (including gall bladder, frog skin, and toad bladder); it seems to have a system of channels with a small number of wide "pores" (greater than 80 A) that permit permeation of large polar solutes and is not a relatively homogeneous structure.
Measurements of the extracellular space (ECS) of the isolated swine thoracic aorta were performed with both [14C]inulin and transient measurements and appeared to have better access to available tissue water than the [14C]sucrose gave more consistent results in available tissue water than the [14C]inulin. With [14C]sucrose as the tracer, no significant difference in the ECS was found when the tissue was incubated for 1.5 h in the presence of oxygen and glucose as compared to an incubation in which both oxygen and glucose were absent. However, the ion contents were markedly altered by this change in incubation medium. When oxygen and glucose were present tissue K+ was significantly higher and tissue Na+ was significantly lower than when these metabolites were deleted from the medium. Thus, significant alteration in ion content did not lead to substantial cell damage or bursting.
Clearance values of urea, inulin, and p-aminohippurate (PAH) were measured in heat-acclimated (HA) rats exposed for 3 wk to 35 degrees C, in control rats (C) exposed to 23 degrees C, and in HA rats deacclimated (DA) for 3 wk. In HA rats, urea clearance was lower by 73%, inulin clearance by 61%, and PAH clearance by 56%, compared with C rats. The clearance values of these substances returned to the control values in DA rats. The data suggest that the low clearance values reflect both reduced renal blood flow and possible changes in the capacity of the glomeruli for filtration and the tubules for either reabsorption or secretion.
A fully enzymatic method for the determination of inulin in serum or plasma without deproteinization is described. The assay is carried out by means of a fructose determination after hydrolysis of inulin via inulinase and simultaneous oxidation of the native glucose using glucose oxidase and H2O2. This time-saving procedure of high specificity, sensitivity and accuracy requires only small sample volumes. The usefulness of the method is shown by analysis of blood levels in humans and rabbits after an intravenous administration of Inutest.
The ability of newborn and adult rats to eliminate p-aminohippuric acid and inulin from plasma was determined. The pattern of development is similar to that observed in vitro using renal cortical slices. The fact that function increases to a peak and then declines over the developmental period while organ weight and histology mature progressively suggests a divergence of functional and antomical maturation. Inulin elimination, unlike PAH, increased over the ages tested, and is apparently more closely related to organ growth.
A method to analyze in vivo metabolites in blood obtained from the hepatic vein after the intraportal injection of a drug was established. This method includes cannulation into the portal vein, hepatic vein and bile duct, followed by TLC-autoradioluminography of a non-extracted sample. Either [14C]diazepam, L-3,4-dihydroxyphenyL[3-(14)C]alanine or [14C]inulin was administered on the day following the surgical operation to avoid the influence of anesthesia. Radioactive concentrations of [14C]DOPA decreased rapidly in the first 1 min, then decreased gradually. The concentrations of [14C]diazepam increased within the first 1 min and then decreased gradually. The concentration of [14C]inulin was approximately 10 times higher than that of [14C]DOPA, and both decreased gradually. These results show that the uptake levels of the drugs to the liver varied depending on the drugs. The metabolites of [14C]diazepam and [14C]DOPA were detected as early as 5 s after administration. These results suggest that the in vivo hepatic first pass effect of drugs in the early period of injection (5 s) can be studied using these techniques.
The conformational studies of inulin oligomers from G-F2 to G-F9, which isolated from Platycodon grandiflorum, suggested a plausible conformational change between G-F7 and G-F8 from the trends in their chemical shift patterns and molecular rotation; the oligomers higher than G-F8 would form some secondary conformations more rigid than shorter oligomers. On the other hand, spin-lattice relaxation (T1) studies of the protons proposed through-space interactions of 2- and 4-H's of glucose moiety in G-F5, presumably with some atom(s) of the terminal fructose moiety. This would reflect that the inulin molecule adopts a 5/1 helix.
A method is described to assess the accuracy of quantitative collection of urine in small experimental animals using implanted Alzet osmotic pumps for continuous release of specific urinary markers. The nominal pumping rate (10.00 +/- 0.15 microliters/h; mean +/- SEM) of 10 osmotic pumps was verified (9.96 +/- 0.12 microliters/h) in a 10-day in vitro assay in isotonic saline at 39.0 degrees C. Ten adult female mink (1100 +/- 34 g) had a 2-ml osmotic pump implanted intraperitoneally for 7 days while maintained in metabolic cages on a conventional mink diet. In 5 mink the pumps contained [3H]-labelled p-aminohippuric acid (PAH) only. The remaining 5 animals received a pump containing [3H]-PAH and [14C]-labelled inulin. The experiment was well tolerated by all animals. In fed animals, the amount of urine collected per day was not influenced by the osmotic pumps, whereas 24 h of fasting (water allowed) caused a dramatic fall in urinary volume. In 4 consecutive 24-h collections of urine (n = 10 animals) the recovery of [3H]-PAH was 70.8 +/- 3.6% (range: 52.0-87.2%), and urinary plus faecal water (= total) recovery of [3H]-PAH averaged 77.0 +/- 3.7% (range: 60.3%-94.3%). For [14C]-inulin (n = 5 animals) the urinary and total recoveries were 68.4 +/- 2.2% and 77.2 +/- 2.4%, respectively. In urine the 14C to 3H counts-ratio was almost identical to that of the infusion solution, indicating that metabolic decomposition of the markers was negligible. The results indicate that the daily recovery of suitable urinary markers, released by implanted osmotic pumps, provides a reproducible and valid measure of the accuracy achieved in quantitative collection of urine in mink and probably also in other animal species. Hence, this technique may be useful in future studies on animal nutrition and/or drug disposition.
The use of stalks instead of tubers as a source of carbohydrates for ethanol production has been investigated. The inulin present in the stalks of Jerusalem artichoke was extracted with water and the effect of solid-liquid ratio, temperature, and acid addition was studied and optimized in order to attain a high-fructose fermentable extract. The maximum extraction efficiency (corresponding to 35 g/L) of soluble sugars was obtained at 1/6 solid-liquid ratio. Fermentations of hydrolyzed extracts by baker's yeast and direct fermentation by an inulinase activity yeast were also performed and the potential to use this feedstock for bioethanol production assessed. The results show that the carbohydrates derived from Jerusalem artichoke stalks can be converted efficiently to ethanol by acidic hydrolysis followed by fermentation with Saccharomyces cerevisiae or by direct fermentation of inulin using Kluyveromyces marxianus strains. In this last case about 30 h to complete fermentation was required in comparison with 8-9 h obtained in experiments with S. cerevisiae growth on acid extracted juices.
Renal inulin clearance remains the standard by which other methods of measuring glomerular filtration rate are judged. A fully automated enzymatic assay capable of use with linear configuration inulin was recently published (Summerfield AL, et al. Clin Chem 1993; 39:2333-7). Sinistrin, a readily soluble preparation of polyfructan with side branching, is more suitable for clinical use and far more widely used in Europe. By modifying the incubation phase of samples with inulinase, incorporating a kinetic modification to the method of fructose analysis, and increasing the buffer strengths, we report a fully automated system, with minimal sample prehandling capable of complete sinistrin hydrolysis, and adapted for use on the Cobas Mira.