Controllo dei parassiti nel rettilario del Bioparco di Roma

Poiché le infestazioni parassitarie dei rettili in cattività possono incidere sulla loro salute, è stato condotto uno studio sui parassiti intestinali e gli ectoparassiti su 213 rettili del Bioparco di Roma. In cattività, dove gli animali sono confinati in piccoli spazi, la concentrazione di parassiti può essere più alta. Alcuni di essi sono innocui, ma altri, specialmente in associazione allo stress, possono essere pericolosi, causare malattie e portare anche alla morte se non trattati. Inoltre, i rettili parassitati hanno una vita più breve, sono più suscettibili ad altre malattie, hanno scarsa fertilità, ridotta crescita ed alta mortalità. Tra Gennaio 2012 e Dicembre 2014 sono stati raccolti campioni da 213 rettili che non mostravano alcun segno clinico e che includevano 23 specie di sauri, 20 specie di cheloni, 20 specie di ofidi e 4 specie di alligatori. I campioni sono stati esaminati per la presenza di parassiti intestinali mediante copromicroscopia di tipo qualitativo previa sedimentazione e successiva flottazione, mentre la tecnica di Zihel-Neelsen è stata usata per la ricerca di oocisti di Cryptosporidium . I campioni di feci sottoposti ad esame copromicroscopico qualitativo sono risultati positivi per almeno una tipologia di endoparassiti nel 49% dei casi. Il 35% dei campioni è risultato positivo per ossiuri, il 22% per coccidi, l’1% per strongili ed il 5% per ascaridi. Degli strisci fecali colorati con la tecnica di Zihel-Neelsen, il 25% sono risultati positivi per Cryptosporidium spp. Ossiuri e coccidi sono stati più prevalenti nei sauri rispetto ai cheloni, agli ofidi e agli alligatori e nel 14% è stata osservata la presenza di entrambi. Inoltre, per quanto riguarda gli ectoparassiti, sono state rilevate uova di Myocoptes musculinus nel 24% dei rettili esaminati. Tutti gli strisci risultati positivi per Cryptosporidium spp. sono stati inviati all’Università di Santiago de Compostela per essere sottoposti alla tecnica PCR.

Strategie nutrizionali finalizzate alla modulazione del microbiota intestinale del cane e del gatto

Il microbiota intestinale riveste un ruolo importantissimo nell’influenzare la salute dell’ospite. È stato dimostrato come la composizione della dieta possa condizionare lo stato di benessere dell’animale, inducendo importanti cambiamenti tra le popolazioni batteriche che coabitano l’intestino; l’uso di prebiotici rappresenta una delle strategie maggiormente impiegate per modulare positivamente la composizione ed il metabolismo dell’ecosistema gastroenterico. Il presente progetto di dottorato si è proposto di indagare gli effetti sul microbiota intestinale del cane e del gatto di diete a diverso tenore proteico e contenenti proteine di diversa digeribilità in presenza o meno di sostanze prebiotiche. Inoltre, sono stati valutati gli effetti della presenza di un estratto di Yucca schidigera e di tannini sulla microflora intestinale del gatto. In ultima istanza, sono state valutate le conseguenze di dosi crescenti di lattosio sul benessere intestinale del cane. I risultati del presente studio hanno rilevato come le sostanze prebiotiche influiscono sulla composizione e sul metabolismo della microflora del cane e del gatto, e come l’impiego di diete ricche di proteine possa avere conseguenze negative sull’ambiente intestinale. Tuttavia, la presenza di oligosaccaridi non sembra contrastare gli effetti negativi che diete ad alto tenore proteico potrebbero avere sull’ecosistema intestinale dell’animale. Nella successiva prova è stato evidenziato come l’inclusione nella dieta di estratti di Yucca e tannini possa contribuire a mitigare l’emanazione di sostanze maleodoranti dalle deiezioni degli animali da compagnia. Nel corso dell’ultima prova, nonostante non siano state osservate differenze tra le popolazioni microbiche intestinali, la somministrazione di dosi crescenti di lattosio ha indotto una certa riduzione delle fermentazioni proteolitiche microbiche. Ulteriori studi sono necessari per stabilire in che misura la dieta e gli alimenti “funzionali” possano influire sul microbiota intestinale del cane e del gatto e come queste informazioni possono essere utilizzate per migliorare miratamente l’alimentazione e lo stato di salute degli animali da compagnia.

Untersuchungen zur biotischen Bildung von Methylquecksilber aus anorganischem Quecksilber durch intestinale Sulfat-reduzierende Bakterien und die Bestimmung alkylierter Quecksilberverbindungen mittels GC-ICP-MS und Isotopenverdünnungsanalyse

Alkylierte Quecksilberspezies sind hundertfach toxischer als anorganisches Quecksilber (Hg) und werden in der Nahrungskette mit zunehmender Trophieebene im Gewebe von Tieren und dem Menschen akkumuliert. Aufgrund der Relevanz für die Umwelt und den Effekt auf die menschliche Gesundheit kommt der biotischen Transformation von anorganischem Hg zu Monomethylquecksilber (MeHg) eine große Bedeutung zu. Es ist bekannt, dass Sulfat-reduzierende Bakterien zu den Hauptproduzenten von MeHg gehören. Darüber hinaus gibt es jedoch nur wenige Untersuchungen über die biologischen Mechanismen und die Zusammenhänge in terrestrischen und insbesondere in intestinalen Systemen. Die vorliegende Arbeit leistet daher einen wichtigen Beitrag zur Abschätzung des Potentials zur Hg-Methylierung durch intestinale Bakterien und vertieft die Kenntnisse zu der damit verbundenen Akkumulation der organischen Schwermetallverbindung im Gewebe des Kompostwurms Eisenia foetida (E. foetida). rnIm Rahmen dieser Arbeit wurde erstmals unter Anwendung der Gas Chromatographie mit induktiv gekoppelter Massenspektrometrie (GC-ICP-MS) und Isotopenverdünnungsanalyse verschiedene Kulturen intestinaler Sulfat-reduzierender Bakterien auf die Bildung von organischem Monomethylquecksilber aus Hg(II) untersucht. Da in komplexen bakteriellen Nährlösungen mit hohem Sulfidgehalt Matrixeffekte auftreten und die Analyse von MeHg im Ultraspurenbereich erschweren können, erfolgte die Probenvorbereitung mittels der Methanol-Kaliumhydroxid-Extraktion unter Verwendung eines Maskierungsreagenzes und der Derivatisierung mit Natriumtetrapropylborat. Das Detektionslimit für MeHg in bakteriellen Nährlösungen betrug 0,03 ng/mL. Die Wiederfindung von zertifiziertem Referenzmaterial ERM® CE-464 Tuna Fish war sehr gut und lag in einem Bereich zwischen 98 – 105%. rnDie Resultate der Untersuchung von 14 verschiedenen Rein- und Anreicherungskulturen Sulfat-reduzierender Bakterien zeigten, dass neun Kulturen innerhalb von 12 h nach einer Inkubation mit 0,1 mg/L Hg2+ im Durchschnitt 100 bis 1200 pg/mL MeHg produzierten. Darunter waren zwei Desulfovibrio sp. Stämme, die Spezies Desulfovibrio piger, Desulfovibrio giganteus, Desulfovibrio termitidis, Desulfotomaculum ruminis, Desulfobulbus propionicus sowie Anreicherungskulturen aus dem Intestinaltrakt einer Zygoptera-Larve Zy1 und E. foetida EF4. Die Fähigkeit zur Hg-Methylierung durch eine Spezies der Ordnung Desulfotomaculum aus der Gruppe der Gram-positiven Firmicutes wurde hiermit erstmals beobachtet.rnWeiterhin wurde gezeigt, dass im Intestinaltrakt von E. foetida im Gegensatz zu mikrobiellen Bodenproben eine signifikante biotische Methylierung von Hg(II) durchgeführt wird. Dass diese Transformationen in hohem Maße von der intestinalen Region ausgeht und somit zur Akkumulation von MeHg im Gewebe beiträgt, konnte durch weiterführende Experimente mittels Laserablations-ICP-MS an histologischen Gefrierschnitten des Invertebraten darge-stellt werden. rn

The NutriChip project--translating technology into nutritional knowledge

Advances in food transformation have dramatically increased the diversity of products on the market and, consequently, exposed consumers to a complex spectrum of bioactive nutrients whose potential risks and benefits have mostly not been confidently demonstrated. Therefore, tools are needed to efficiently screen products for selected physiological properties before they enter the market. NutriChip is an interdisciplinary modular project funded by the Swiss programme Nano-Tera, which groups scientists from several areas of research with the aim of developing analytical strategies that will enable functional screening of foods. The project focuses on postprandial inflammatory stress, which potentially contributes to the development of chronic inflammatory diseases. The first module of the NutriChip project is composed of three in vitro biochemical steps that mimic the digestion process, intestinal absorption, and subsequent modulation of immune cells by the bioavailable nutrients. The second module is a miniaturised form of the first module (gut-on-a-chip) that integrates a microfluidic-based cell co-culture system and super-resolution imaging technologies to provide a physiologically relevant fluid flow environment and allows sensitive real-time analysis of the products screened in vitro. The third module aims at validating the in vitro screening model by assessing the nutritional properties of selected food products in humans. Because of the immunomodulatory properties of milk as well as its amenability to technological transformation, dairy products have been selected as model foods. The NutriChip project reflects the opening of food and nutrition sciences to state-of-the-art technologies, a key step in the translation of transdisciplinary knowledge into nutritional advice.

Icatibant , the bradykinin B2 receptor antagonist with target to the interconnected kinin systems

INTRODUCTION: HOE-140/ Icatibant is a selective, competitive antagonist to bradykinin (BK) against its binding to the kinin B2 receptor. Substitution of five non-proteogeneic amino acid analogues makes icatibant resistant to degradation by metalloproteases of kinin catabolism. Icatibant has clinical applications in inflammatory and vascular leakage conditions caused by an acute (non-controlled) production of kinins and their accumulation at the endothelium B2 receptor. The clinical manifestation of vascular leakage, called angioedema (AE), is characterized by edematous attacks of subcutaneous and submucosal tissues, which can cause painful intestinal consequences, and life-threatening complications if affecting the larynx. Icatibant is registered for the treatment of acute attacks of the hereditary BK-mediated AE, i.e., AE due to C1 inhibitor deficiency. AREAS COVERED: This review discusses emerging knowledge on the kinin system: kinin pharmacological properties, biochemical characteristics of the contact phase and kinin catabolism proteases. It underlines the responsibility of the kinins in AE initiation and the potency of icatibant to inhibit AE formation by kinin-receptor interactions. EXPERT OPINION: Icatibant antagonist properties protect BK-mediated AE patients against severe attacks, and could be developed for use in inflammatory conditions. More studies are required to confirm whether or not prolonged and frequent applications of icatibant could result in the impairment of the cardioprotective effect of BK.

Acute trichinellosis increases susceptibility to Giardia lamblia infection in the mouse model

The intestinal protozoan parasite Giardia lamblia causes diarrhoea in humans and animals. In the present study, we used the C57BL/6 inbred mouse model to assess the impact of a nematode (Trichinella spiralis) infection on the course of a G. lamblia (clone GS/M-83-H7) infection. Acute trichinellosis coincided with transient intestinal inflammation and generated an intestinal environment that strongly promoted growth of G. lamblia trophozoites although the local anti-Giardia immunoglobulin (Ig) A production was not affected. This increased G. lamblia infection intensity correlated with intestinal mast cell infiltration, mast cell degranulation, and total IgE production. Furthermore, a G. lamblia single-infection investigated in parallel also resulted in intestinal mast cell accumulation but severe infiltration was triggered in the absence of IgE. Recently, intestinal mast cells emerging during a G. lamblia infection were reported to be involved in those immunological mechanisms that control intestinal proliferation of the parasite in mice. This anti-giardial activity was assumed to be related to the capacity of mast cells to produce IL-6. However, this previous assumption was questioned by our present immunohistological findings indicating that murine intestinal mast cells, activated during a G. lamblia infection were IL-6-negative. In the present co-infection experiments, mast cells induced during acute trichinellosis were not able to control a concurrent G. lamblia infection. This observation makes it feasible that the T. spiralis infection created an immunological and physiological environment that superimposed the anti-giardial effect of mast cells and thus favoured intestinal growth of G. lamblia trophozoites in double-infected mice. Furthermore, our findings raise the possibility that intestinal inflammation e.g. as a consequence of a 'pre-existing' nematode infection is a factor which contributes to increased susceptibility of a host to a G. lamblia infection. The phenomenon of a 'pre-existing' nematode infection prior to a G. lamblia infection is a frequent constellation in endemic areas of giardiasis and may therefore have a direct impact on the epidemiological situation of the disease.

Expanded polytetrafluoroethylene graft for bypass surgery using the excimer laser-assisted nonocclusive anastomosis technique

OBJECT: Patients with complex craniocerebral pathophysiologies such as giant cerebral aneurysms, skull base tumors, and/or carotid artery occlusive disease are candidates for a revascularization procedure to augment or preserve cerebral blood flow. However, the brain is susceptible to ischemia, and therefore the excimer laser-assisted nonocclusive anastomosis (ELANA) technique has been developed to overcome temporary occlusion. Harvesting autologous vessels of reasonable quality, which is necessary for this technique, may at times be problematic or impossible due to the underlying systemic vascular disease. The use of artificial vessels is therefore an alternative graft for revascularization. Note, however, that it is unknown to what degree these grafts are subject to occlusion using the ELANA anastomosis technique. Therefore, the authors studied the ELANA technique in combination with an expanded polytetrafluoroethylene (ePTFE) graft. METHODS: The experimental surgeries involved bypassing the abdominal aorta in the rabbit. Ten rabbits were subjected to operations representing 20 ePTFE graft-ELANA end-to-side anastomoses. Intraoperative blood flow, followup angiograms, and long-term histological characteristics were assessed 75, 125, and 180 days postoperatively. Angiography results proved long-term patency of ePTFE grafts in all animals at all time points studied. Data from the histological analysis showed minimal intimal reaction at the anastomosis site up to 180 days postoperatively. Endothelialization of the ePTFE graft was progressive over time. CONCLUSIONS: The ELANA technique in combination with the ePTFE graft seems to have favorable attributes for end-to-side anastomoses and may be suitable for bypass procedures.

Effects of a divided high loading dose of caffeine on circulatory variables in preterm infants

BACKGROUND: A single high loading dose of 25 mg/kg caffeine has been shown to be effective for the prevention of apnoea, but may result in considerable reductions in blood flow velocity (BFV) in cerebral and intestinal arteries. OBJECTIVE: To assess the effects of two loading doses of 12.5 mg/kg caffeine given four hours apart on BFV in cerebral and intestinal arteries, left ventricular output (LVO), and plasma caffeine concentrations in preterm infants. DESIGN: Sixteen preterm neonates of <34 weeks gestation were investigated one hour after the first oral dose and one, two, and 20 hours after the second dose by Doppler sonography. RESULTS: The mean (SD) plasma caffeine concentrations were 31 (7) and 29 (7) mg/l at two and 20 hours respectively after the second dose. One hour after the first dose, none of the circulatory variables had changed significantly. One hour after the second caffeine dose, mean BFV in the internal carotid artery and anterior cerebral artery showed significant reductions of 17% and 19% (p = 0.01 and p = 0.003 respectively). BFV in the coeliac artery and superior mesenteric artery, LVO, PCO2, and respiratory rate had not changed significantly. Total vascular resistance, calculated as the ratio of mean blood pressure to LVO, had increased significantly one and two hours after the second dose (p = 0.049 and p = 0.023 respectively). CONCLUSION: A divided high loading dose of 25 mg/kg caffeine given four hours apart had decreased BFV in cerebral arteries after the second dose, whereas BFV in intestinal arteries and LVO were not affected.

LRH-1-mediated glucocorticoid synthesis in enterocytes protects against inflammatory bowel disease

Liver receptor homolog-1 (LRH-1) is a nuclear receptor involved in intestinal lipid homeostasis and cell proliferation. Here we show that haploinsufficiency of LRH-1 predisposes mice to the development of intestinal inflammation. Besides the increased inflammatory response, LRH-1 heterozygous mice exposed to 2,4,6-trinitrobenzene sulfonic acid show lower local corticosterone production as a result of an impaired intestinal expression of the enzymes CYP11A1 and CYP11B1, which control the local synthesis of corticosterone in the intestine. Local glucocorticoid production is strictly enterocyte-dependent because it is robustly reduced in epithelium-specific LRH-1-deficient mice. Consistent with these findings, colon biopsies of patients with Crohn's disease and ulcerative colitis show reduced expression of LRH-1 and genes involved in the production of glucocorticoids. Hence, LRH-1 regulates intestinal immunity in response to immunological stress by triggering local glucocorticoid production. These findings underscore the importance of LRH-1 in the control of intestinal inflammation and the pathogenesis of inflammatory bowel disease.

Current concepts in the pathogenesis of meningitis caused by Streptococcus pneumoniae

In spite of improved antimicrobial therapy, bacterial meningitis still results in brain damage leading to significant long-term neurological sequelae in a substantial number of survivors, as confirmed by several recent studies. Meningitis caused by Streptococcus pneumoniae is associated with a particularly severe outcome. Experimental studies over the past few years have increased our understanding of the molecular mechanisms underlying the events that ultimately lead to brain damage during meningitis. Necrotic damage to the cerebral cortex is at least partly mediated by ischemia and oxygen radicals and therefore offers a promising target for adjunctive therapeutic intervention. Neuronal apoptosis in the hippocampus may represent the major pathological process responsible for cognitive impairment and learning disabilities in survivors. However, the mechanisms involved in causing this damage remain largely unknown. Anti-inflammatory treatment with corticosteroids aggravates hippocampal damage, thus underlining the potential shortcomings of current adjuvant strategies. In contrast, the combined inhibition of matrix metalloproteinase and tumour necrosis factor-alpha converting enzyme protected both the cortex and hippocampus in experimental meningitis, and may represent a promising new approach to adjunctive therapy. It is the hope that a more refined molecular understanding of the pathogenesis of brain damage during bacterial meningitis will lead to new adjunctive therapies.

Small is beautiful: why profundaplasty should not be forgotten

BACKGROUND: Surgical profundaplasty (SP)is used mainly as an adjunct to endovascular management of peripheral vascular disease (PAD) today. Results from earlier series of profundaplasty alone have been controversial, especially regarding its hemodynamic effect. The question is: Can profundaplasty alone still be useful? Our aim was to evaluate its role in the modern management of vascular patients. METHODS: This was a retrospective outcome study. A consecutive series of 97 patients (106 legs) from January 2000 through December 2003 were included. In 55 (52%) legs, the superficial femoral artery was occluded. These patients were included in the current analysis. Of these patients 14 (25%) were female. Mean age was 71 ((11) years. Nineteen (35%) were diabetic. The indication for operation was claudication in 29 (53%), critical leg ischemia (CLI) in 26 (47%), either with rest pain in 17 (31%), or ulcer/gangrene in 9 (16%). Endarterectomy with patch angioplasty with bovine pericardium was performed in all cases. Mean follow-up was 33 ( 14 months. Mean preoperative ankle brachial index (ABI) was 0.6. Sustained clinical efficacy was defined as upward shift of 1 or greater on the Rutherford scale without repeat target limb revascularization (TLR) or amputation. Mortality, morbidity, need for TLR, or amputation were separate endpoints. RESULTS: Postoperatively, ABI was significantly improved (mean = 0.7), in 24 (44%) by more than 0.15. At three years, cumulative clinical success rate was 80%. Overall, patients with claudication had a better outcome than those with CLI (p = 0.04). Two (4%) major amputations and 2 (4%) minor ones were performed, all in patients with CLI. None of the 9 (16%) ulcers healed. CONCLUSION: Profundaplasty is still a valuable option for patients with femoral PAD and claudication without tissue loss. It is a straightforward procedure that combines good efficacy with low complication rates. Further endovascular treatment may be facilitated. It is not useful for patients with the combination of critical ischemia and tissue loss.

Percutaneous left ventricular assist devices for treatment of patients with cardiogenic shock

PURPOSE OF REVIEW: This review will discuss the rationale and clinical utility of percutaneous left ventricular assist devices in the management of patients with cardiogenic shock. RECENT FINDINGS: Left ventricular assist devices maintain partial or total circulatory support in case of severe left ventricular failure. Currently, two percutaneous left ventricular assist devices are available for clinical use: the TandemHeart and the Impella Recover LP system. Compared with the intraaortic balloon pump, the TandemHeart has been shown to significantly reduce preload and to augment cardiac output. In a randomized comparison between the TandemHeart and intraaortic balloon pump support in patients with cardiogenic shock, the improved cardiac index afforded by the left ventricular assist device resulted in a more rapid decrease in serum lactate and improved renal function. There were, however, no significant differences with respect to 30-day mortality, and complications including limb ischemia and severe bleeding were more frequent with left ventricular assist devices than intraaortic balloon pump support. SUMMARY: The advent of percutaneous left ventricular assist devices constitutes an important advance in the management of patients with severe cardiogenic shock and may serve as bridge to recovery or heart transplantation in carefully selected patients. While improvement of hemodynamic parameters appears promising, it remains to be determined whether this benefit translates into improved clinical outcome.

Automated end-to-side anastomosis to the middle cerebral artery: a feasibility study

The treatment of complex cerebrovascular or skull base pathological conditions necessitates a microsurgical blood flow preservation or augmentative revascularization procedure as either an adjunctive safety measure or a definitive treatment. The brain is susceptible to ischemia, and procedure-related risks can be minimized by the reduction of occlusion time or the use of a nonocclusive technique. The authors therefore analyzed the feasibility of an automatic device (C-Port xA, Cardica) designed for constructing an end-to-side anastomosis with or without flow interruption for a middle cerebral artery (MCA) bypass in a human cadaveric model and in an in vivo craniotomy simulation model.

Crystalloids versus colloids for goal-directed fluid therapy in major surgery

INTRODUCTION: Perioperative hypovolemia arises frequently and contributes to intestinal hypoperfusion and subsequent postoperative complications. Goal-directed fluid therapy might reduce these complications. The aim of this study was to compare the effects of goal-directed administration of crystalloids and colloids on the distribution of systemic, hepatosplanchnic, and microcirculatory (small intestine) blood flow after major abdominal surgery in a clinically relevant pig model. METHODS: Twenty-seven pigs were anesthetized and mechanically ventilated and underwent open laparotomy. They were randomly assigned to one of three treatment groups: the restricted Ringer lactate (R-RL) group (n = 9) received 3 mL/kg per hour of RL, the goal-directed RL (GD-RL) group (n = 9) received 3 mL/kg per hour of RL and intermittent boluses of 250 mL of RL, and the goal-directed colloid (GD-C) group (n = 9) received 3 mL/kg per hour of RL and boluses of 250 mL of 6% hydroxyethyl starch (130/0.4). The latter two groups received a bolus infusion when mixed venous oxygen saturation was below 60% ('lockout' time of 30 minutes). Regional blood flow was measured in the superior mesenteric artery and the celiac trunk. In the small bowel, microcirculatory blood flow was measured using laser Doppler flowmetry. Intestinal tissue oxygen tension was measured with intramural Clark-type electrodes. RESULTS: After 4 hours of treatment, arterial blood pressure, cardiac output, mesenteric artery flow, and mixed oxygen saturation were significantly higher in the GD-C and GD-RL groups than in the R-RL group. Microcirculatory flow in the intestinal mucosa increased by 50% in the GD-C group but remained unchanged in the other two groups. Likewise, tissue oxygen tension in the intestine increased by 30% in the GD-C group but remained unchanged in the GD-RL group and decreased by 18% in the R-RL group. Mesenteric venous glucose concentrations were higher and lactate levels were lower in the GD-C group compared with the two crystalloid groups. CONCLUSIONS: Goal-directed colloid administration markedly increased microcirculatory blood flow in the small intestine and intestinal tissue oxygen tension after abdominal surgery. In contrast, goal-directed crystalloid and restricted crystalloid administrations had no such effects. Additionally, mesenteric venous glucose and lactate concentrations suggest that intestinal cellular substrate levels were higher in the colloid-treated than in the crystalloid-treated animals. These results support the notion that perioperative goal-directed therapy with colloids might be beneficial during major abdominal surgery.

Transport model of the human Na+-coupled L-ascorbic acid (vitamin C) transporter SVCT1

Vitamin C (L-ascorbic acid) is an essential micronutrient that serves as an antioxidant and as a cofactor in many enzymatic reactions. Intestinal absorption and renal reabsorption of the vitamin is mediated by the epithelial apical L-ascorbic acid cotransporter SVCT1 (SLC23A1). We explored the molecular mechanisms of SVCT1-mediated L-ascorbic acid transport using radiotracer and voltage-clamp techniques in RNA-injected Xenopus oocytes. L-ascorbic acid transport was saturable (K(0.5) approximately 70 microM), temperature dependent (Q(10) approximately 5), and energized by the Na(+) electrochemical potential gradient. We obtained a Na(+)-L-ascorbic acid coupling ratio of 2:1 from simultaneous measurement of currents and fluxes. L-ascorbic acid and Na(+) saturation kinetics as a function of cosubstrate concentrations revealed a simultaneous transport mechanism in which binding is ordered Na(+), L-ascorbic acid, Na(+). In the absence of L-ascorbic acid, SVCT1 mediated pre-steady-state currents that decayed with time constants 3-15 ms. Transients were described by single Boltzmann distributions. At 100 mM Na(+), maximal charge translocation (Q(max)) was approximately 25 nC, around a midpoint (V(0.5)) at -9 mV, and with apparent valence approximately -1. Q(max) was conserved upon progressive removal of Na(+), whereas V(0.5) shifted to more hyperpolarized potentials. Model simulation predicted that the pre-steady-state current predominantly results from an ion-well effect on binding of the first Na(+) partway within the membrane electric field. We present a transport model for SVCT1 that will provide a framework for investigating the impact of specific mutations and polymorphisms in SLC23A1 and help us better understand the contribution of SVCT1 to vitamin C metabolism in health and disease.