Continuous Systemic Infusion Research Articles

GHSR controls food deprivation-induced activation of CRF neurons of the hypothalamic paraventricular nucleus in a LEAP2-dependent manner.

Prolonged fasting is a major challenge for living organisms. An appropriate metabolic response to food deprivation requires the activation of the corticotropin-releasing factor-producing neurons of the hypothalamic paraventricular nucleus (PVHCRF neurons), which are a part of the hypothalamic-pituitary-adrenal axis (HPA), as well as the growth hormone secretagogue receptor (GHSR) signaling, whose activity is up- or down-regulated, respectively, by the hormones ghrelin and the liver-expressed antimicrobial peptide 2 (LEAP2). Since ghrelin treatment potently up-regulates the HPA axis, we studied the role of GHSR in mediating food deprivation-induced activation of the PVHCRF neurons in mice. We estimated the activation of the PVHCRF neurons, using immuno-staining against CRF and the marker of neuronal activation c-Fos in brain sections, and assessed plasma levels of corticosterone and glucose in different pharmacologically or genetically manipulated mouse models exposed, or not, to a 2-day food deprivation protocol. In particular, we investigated ad libitum fed or food-deprived male mice that: (1) lacked GHSR gene expression, (2) had genetic deletion of the ghrelin gene, (3) displayed neurotoxic ablation of the hypothalamic arcuate nucleus, (4) were centrally treated with an anti-ghrelin antibody to block central ghrelin action, (5) were centrally treated with a GHSR ligand that blocks ghrelin-evoked and constitutive GHSR activities, or (6) received a continuous systemic infusion of LEAP2(1-12). We found that food deprivation results in the activation of the PVHCRF neurons and in a rise of the ghrelin/LEAP2 molar ratio. Food deprivation-induced activation of PVHCRF neurons required the presence and the signaling of GHSR at hypothalamic level, but not of ghrelin. Finally, we found that preventing the food deprivation-induced fall of LEAP2 reverses the activation of the PVHCRF neurons in food-deprived mice, although it has no effect on body weight or blood glucose. Food deprivation-induced activation of the PVHCRF neurons involves ghrelin-independent actions of GHSR at hypothalamic level and requires a decrease of plasma LEAP2 levels. We propose that the up-regulation of the actions of GHSR associated to the fall of plasma LEAP2 level are physiologically relevant neuroendocrine signals during a prolonged fasting.

New Design of a Percutaneous Port System for Continuous Intraperitoneal Insulin Infusion.

Insulin-dependent diabetes mellitus is treated with intensive insulin therapy using multiple daily injections or continuous subcutaneous insulin infusion with insulin pumps. For people with diabetes who cannot achieve acceptable glycemic control despite the use of intensive insulin therapy and continuous glucose measurement, there exists the possibility of continuous intraperitoneal insulin delivery via an implantable pump or a percutaneous port system that is connected to an external insulin pump. In this article, the current second generation of the Accu-Chek® DiaPort system for continuous intraperitoneal insulin delivery with its improvements over the former generation is presented and discussed.

Bivalirudin and ECLS

Bivalirudin and ECLS

Anhydramnios in the Setting of Renal Malformations: The National Institutes of Health Workshop Summary.

Anhydramnios in the setting of severe malformations of the fetal kidney and urinary tract is associated with a high incidence of stillbirths and life-threatening complications, including severe pulmonary hypoplasia, umbilical cord compression, and perinatal asphyxia. To prevent such adverse outcomes, some centers in the United States and elsewhere are offering amniotic fluid restoration for women diagnosed with anhydramnios in the setting of fetal renal malformations. The procedures include infusions of amniotic fluid substitutes (normal saline), percutaneously or through an amnioport-an implanted system for serial or continuous infusion of normal saline to maintain the desired amniotic fluid volume. The procedures are intended to prevent pulmonary hypoplasia and allow the pregnancy to progress closer to term gestation, enabling postnatal renal management, including long-term dialysis and renal transplantation. However, these procedures have not been recommended as standard of care by the professional societies because there are many knowledge gaps, including few data on short-term and long-term renal outcomes. The available diagnostic methods do not provide reliable prognostic information, and the current maternal and fetal interventions have not been standardized. To address these unresolved issues and to propose a research agenda, the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the National Institute of Diabetes and Digestive and Kidney Diseases invited a panel of experts to a workshop in August 2016. This report provides a summary of that meeting.

Abstract 3769: Continuous, low intensity systemic dosing maximizes the therapeutic margin of Eg5/KSP inhibition in an orthotopic model of urothelial cell carcinoma

Abstract Urothelial Cell Carcinoma (UCC) is the fifth most common cancer, but no new generation molecularly targeted therapies have been registered to treat this disease. Non muscle-invasive bladder cancer can be treated by systemic or intravesical dosing routes. However, the urothelium is one of the most formidable permeability barriers in nature, and may limit the penetration of small molecules into tumour tissue from the intravesical location. Inhibitors of mitosis, including spindle proteins such as Eg5, are attractive targets for cancer therapy, but their efficacy when dosed systemically is severely limited by bone marrow toxicities such as neutropenia and thrombocytopenia. AZ9814, a very potent and selective small molecule inhibitor of Eg5, induces apoptosis and inhibits proliferation of UCC cells in culture with a GI50 of < 1 nM. We have developed an orthotopic model of bladder cancer in the nude rat coupled with a programmable mini-pump system to continuously infuse AZ9814 into the bladder, and compared the therapeutic index of this delivery route with systemic dosing schedules using intraperitoneal injection and continuous subcutaneous infusion using an osmotic mini-pump. Continuous intravesical infusion resulted in severe bladder toxicity including hydropic degeneration and ulceration of urothelium, mucosal erosion and bilateral hydronephrosis, with limited penetration of compound into the tumour, and no significant impact on tumour pharmacodynamics and growth. In contrast, continuous low intensity systemic dosing resulted in significant tumour pharamacodynamic activity and control of tumour growth, albeit with significant but non-lethal effects on bone marrow toxicity. Daily intraperitoneal injection of AZ9814 resulted in very modest anti-tumour effects which were limited by bone marrow toxicity. It is concluded that Eg5 inhibitors have potential to treat UCC, but continuous systemic infusion is the best dosing schedule to maximize therapeutic index. Citation Format: Leigh Williams, Rebecca Ellston, Dawn Trueman, Helen Musgrove, Linette Ruston, Brian Aquila, Elizabeth Pease, Stephanie Klein, Barry R. Davies. Continuous, low intensity systemic dosing maximizes the therapeutic margin of Eg5/KSP inhibition in an orthotopic model of urothelial cell carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3769.

Brain‐derived neurotrophic factor causes chloride gradient collapse in supraoptic neurons inducing vasopressin‐mediated blood pressure increase (LB847)

Vasopressin (VP), an antidiuretic hormone, is also a potent vasoconstrictor and has been found at high levels in salt‐sensitive hypertensives. Hypertension normally reduces VP secretion by MNCs in the SON, by GABA‐dependent synaptic inhibition of their firing activities. However, in rats under chronic hypernatremia, GABAA receptor‐mediated synaptic inhibition is abolished in SON neurons due to a depolarization in chloride reversal potential (ECl), suggesting that continued VP secretion despite BP elevations may underlie the development of salt‐dependent hypertension. In order to test this hypothesis, we measured the mean arterial pressure (MAP) by radio telemetry in freely moving rats made chronically hypernatremic by 2% saline drinking. MAP of these rats rose steadily rise during the course of the 7‐day SL treatment (basal BP: 97.7±1.9 mmHg; day 7: 113.5±2.1 mmHg; n=10; P<0.05), however remained stable in euhydrated rats over the same time period (basal BP: 98.3±2.5 mmHg; day 7: 100.6±2.2 mmHg; n=6; P=0.50). Furthermore, the SL‐mediated increase in MAP was significantly reduced by continuous systemic infusion of a VP receptor type 1 (V1R) antagonist (αday 7; +8.8±2.5 mmHg; n=6) when compared to SL controls (α15.1±1.0 mmHg; n=10; P<0.05). These findings confirm our hypothesis that circulating VP contributes to increases in BP during chronic hypernatremia. Brain‐derived neurotrophic factor (BDNF) is a high‐affinity TrkB agonist previously shown to be responsible for chloride gradient collapse. In order to investigate this possibility in the SON, we induced a specific knockdown of this protein in SL rats in vivo by stereotaxic injections of adeno‐associated virus (AAV) containing BDNF‐shRNA into the SON. ECl measurements via Gramicidin perforated patch‐clamp revealed that this treatment significantly hyperpolarized the ECl of SON neurons (‐56.2±5.4 mV; n=10) when compared to values measured in SL rats injected with control AAV containing a scrambled sequence of shRNA (‐40.1±2.4 mV; n=7; p<0.05). These results strongly suggest that BDNF is the TrkB agonist responsible for producing the chloride gradient collapse in SON neurons under chronic hypernatremia, a phenomenon which potentially underlie the development of salt‐sensitive hypertension. Funding source: Canadian Institutes of Health Research.Grant Funding Source: CIHR

Effects of the α2‐adrenergic receptor agonist dexmedetomidine on neural, vascular and BOLD fMRI responses in the somatosensory cortex

This article describes the effects of dexmedetomidine (DEX) - the active ingredient of medetomidine, which is the latest popular sedative for functional magnetic resonance imaging (fMRI) in rodents - on multiple unit activity, local field potential (LFP), cerebral blood flow (CBF), pial vessel diameter [indicative of cerebral blood volume (CBV)], and blood oxygenation level-dependent (BOLD) fMRI. These measurements were obtained from the rat somatosensory cortex during 10 s of forepaw stimulation. We found that the continuous intravascular systemic infusion of DEX (50 μg/kg/h, doses typically used in fMRI studies) caused epileptic activities, and that supplemental isoflurane (ISO) administration of ~0.3% helped to suppress the development of epileptic activities and maintained robust neuronal and hemodynamic responses for up to 3 h. Supplemental administration of N(2)O in addition to DEX nearly abolished hemodynamic responses even if neuronal activity remained. Under DEX + ISO anesthesia, spike firing rate and the delta power of LFP increased, whereas beta and gamma power decreased, as compared with ISO-only anesthesia. DEX administration caused pial arteries and veins to constrict nearly equally, resulting in decreases in baseline CBF and CBV. Evoked LFP and CBF responses to forepaw stimulation were largest at a frequency of 8-10 Hz, and a non-linear relationship was observed. Similarly, BOLD fMRI responses measured at 9.4 T were largest at a frequency of 10 Hz. Both pial arteries and veins dilated rapidly (artery, 32.2%; vein, 5.8%), and venous diameter returned to baseline slower than arterial diameter. These results will be useful for designing, conducting and interpreting fMRI experiments under DEX sedation.

Infusion-based manganese-enhanced MRI: a new imaging technique to visualize the mouse brain

Manganese-enhanced magnetic resonance imaging is a technique that employs the divalent ion of the paramagnetic metal manganese (Mn(2+)) as an effective contrast agent to visualize, in vivo, the mammalian brain. As total achievable contrast is directly proportional to the net amount of Mn(2+) accumulated in the brain, there is a great interest in optimizing administration protocols to increase the effective delivery of Mn(2+) to the brain while avoiding the toxic effects of Mn(2+) overexposure. In this study, we investigated outcomes following continuous slow systemic infusion of manganese chloride (MnCl(2)) into the mouse via mini-osmotic pump administration. The effects of increasing fractionated rates of Mn(2+) infusion on signal enhancement in regions of the brain were analyzed in a three-treatment study. We acquired whole-brain 3-D T1-weighted images and performed region of interest quantitative analysis to compare mean normalized signal in Mn(2+) treatments spanning 3, 7, or 14days of infusion (rates of 1, 0.5, and 0.25μL/h, respectively). Evidence of Mn(2+) transport at the conclusion of each infusion treatment was observed throughout the brains of normally behaving mice. Regions of particular Mn(2+) accumulation include the olfactory bulbs, cortex, infralimbic cortex, habenula, thalamus, hippocampal formation, amygdala, hypothalamus, inferior colliculus, and cerebellum. Signals measured at the completion of each infusion treatment indicate comparable means for all examined fractionated rates of Mn(2+) infusion. In this current study, we achieved a significantly higher dose of Mn(2+) (180mg/kg) than that employed in previous studies without any observable toxic effects on animal physiology or behavior.

Multicenter User Evaluation of ACCU-CHEK® Combo, an Integrated System for Continuous Subcutaneous Insulin Infusion

The aim of this study was to evaluate a newly developed system for insulin delivery incorporating a multifunctional blood glucose meter and a remotely controlled insulin pump (ACCU-CHEK® Combo system) in established pump users with type 1 diabetes. The technology was assessed both from device performance and subject usability perspectives. A multicenter, prospective, single group study was carried out in five centers in the Netherlands and four centers in the United Kingdom for more than 6 months. The study was divided into two phases: Phase 1 (4 weeks) for device validation purposes and phase 2 (22 weeks) to observe the impact of the system on metabolic control, patient satisfaction [using the Diabetes Treatment Satisfaction Questionnaire (DTSQ)] and device safety. Eighty subjects completed the planned study period. There were no unexpected device errors. Treatment satisfaction was high at baseline and further increased to study end (DTSQ change version: sum score, 10.6±7.2; scale score range, -18 to +18, p<0.0001). Hemoglobin A1c improved continuously over time, from 7.9% (±0.9%) to 7.7% (±0.8%) at month 3 (p<0.001) and 7.6% (±0.8%) at month 6 (p<0.0001). The frequency of severe hypoglycemia was 0.08 per patient years. There was no case of ketoacidosis. The new system was evaluated by experienced continuous subcutaneous insulin infusion users as safe in daily practice and associated with favorable treatment satisfaction and a modest improvement in glycemic control.

Benefit from jejunal levodopa in a patient with apomorphine pump

Swings of the bioavailability of orally administered levodopa are considered an important factor of motor fluctuations in Parkinson’s disease (PD) [1]. In this regard, a pump system for continuous jejunal levodopa infusion (Duodopa ) has been introduced in some countries for patients with PD who suffer from troublesome motor fluctuations [2–4]. Since systematic comparisons with deep brain stimulation (DBS) or continuous apomorphine are not available, opinions on how this treatment relates to therapeutic alternatives rely on the observation of case histories for the time being [3, 5–7]. In this regard, we consider of note the therapeutic gain of Duodopa in a patient who had been successfully treated with an Apomorphine pump for years but finally redeveloped extremely severe and unpredictable off-states. Our patient was 60 years of age and noticed first hypokinetic symptoms 20 years ago. Therapy with levodopa was started in 1994, ever since in different combinations with dopamine receptor agonists, amantadine, selegiline and acetylcholine antagonists. Already, in 1999 he underwent surgery for subthalamic DBS for increasing wearing-off and dyskinetic symptoms, but postoperatively developed a brain abscess from the left DBS-electrode, which consequently was removed. He fully recovered from this complication, but did not further pursue DBS. Instead, medication of oral drugs together with apomorphine was started, first given as subcutaneous ‘rescue’ injections (APO-go ) for intermittent akinetic periods. Since off-states became, however, increasingly frequent and prolonged, apomorphine was administered continuously via pump since 2003, effectively stabilizing the patient’s condition with off-time reduction to tolerable levels. Under this therapy further dopaminergic drugs could be reduced by about fifty percent, but comedication remained necessary. With disease progression the initial delivery of apomorphine during 16 h waking time had to be raised to 24 h with a final dosage of 200 mg/day to effectively suppress unpredictable and sudden off-states. Nonetheless, in 2008 he began to suffer from Yo-Yoing with dystonic and tremulous next to hypokinetic symptoms, alternating with strongly hyperkinetic on-periods, both progressive in duration, frequency and severity. At last, he intermittently was completely akinetic (with literally maximal UPDRS motor score). Such off-states did no longer respond to rescue injections of apomorphine or to other drugs in a predictable manner, occurred within minutes five to ten times per day, altogether covering some 10 h. Consequently, he was predominantly bedridden, but still experienced short good or hyperkinetic movement states. In this situation jejunal levodopa infusion was started as substitution of 200 mg apomorphine, 800 mg levodopa (plus 200 mg benserazide), 800 mg entacapone, 2.8 mg pramipexole and 400 mg amantadine sulphate per day (earlier on, levodopa was taken up to ten times daily; reduction to four times was tried under the idea that dyskinesias might partly have been biphasic so that lowering intake frequency would have flattened fluctuations; however, this was not the case and occurrence of motor changes remained temporally random). Under 5,000 mg/24 h jejunal levodopa as monotherapy less severe hypokinetic episodes remained around cassette changes, cumulating about 60 min/day. Apart from this, the patient was constantly in a slightly hyperkinetic state (UPDRS motor score of 25), since even with minor dose reductions he F. Klostermann (&) C. Jugel F. Marzinzik Department of Neurology, CBF, Charite, University Medicine Berlin, Berlin, Germany e-mail: fabian.klostermann@charite.de

Adipocytokine Orosomucoid Integrates Inflammatory and Metabolic Signals to Preserve Energy Homeostasis by Resolving Immoderate Inflammation

Orosomucoid (ORM), also called alpha-1 acid glycoprotein, is an abundant plasma protein that is an immunomodulator induced by stressful conditions such as infections. In this study, we reveal that Orm is induced selectively in the adipose tissue of obese mice to suppress excess inflammation that otherwise disturbs energy homeostasis. Adipose Orm levels were elevated by metabolic signals, including insulin, high glucose, and free fatty acid, as well as by the proinflammatory cytokine tumor necrosis factor-alpha, which is found in increased levels in the adipose tissue of morbid obese subjects. In both adipocytes and macrophages, ORM suppressed proinflammatory gene expression and pathways such as NF-kappaB and mitogen-activated protein kinase signalings and reactive oxygen species generation. Concomitantly, ORM relieved hyperglycemia-induced insulin resistance as well as tumor necrosis factor-alpha-mediated lipolysis in adipocytes. Accordingly, ORM improved glucose and insulin tolerance in obese and diabetic db/db mice. Taken together, our results suggest that ORM integrates inflammatory and metabolic signals to modulate immune responses to protect adipose tissue from excessive inflammation and thereby from metabolic dysfunction.

Deletion of the Glutamate Receptor 5 Subunit of Kainate Receptors Affects the Development of Morphine Tolerance

Previous reports utilizing pharmacological antagonists implicate kainate receptor (KAR) activation in the development of morphine tolerance, dependence, conditioned place preference (CPP), and locomotor sensitization, but the role of glutamate receptor (GluR) 5-containing KAR in these effects remains unclear because of limited selectivity of the inhibitors employed. Therefore, we examined responses to systemic morphine treatment in mice expressing a constitutive deletion of GluR5 [GluR5 knockout (KO)]. Unlike wild-type (WT) littermates, GluR5 KO mice do not develop tolerance after repeated morphine administration by subcutaneous injection or via subcutaneous pellet implantation. In contrast, GluR5 KO mice do not differ from WT with respect to thermal or mechanical nociceptive thresholds, acute morphine antinociception, morphine disposition in the central nervous system (CNS), morphine physical dependence as revealed by naloxone-precipitated withdrawal or development of place preference and locomotor hyperresponsiveness after chronic morphine administration. It is surprising that continuous subcutaneous infusion of the GluR2/GluR5-preferring antagonist LY293558 [(3S,4aR,6R,8aR)-6-[2-(1(2)H-tetrazole-5-yl)ethyl]decahydroisoquinoline-3-carboxylic acid] decreased the number of naloxone-precipitated jumps to a similar extent in WT and GluR5 KO mice. We observed opioid-induced hypersensitivity in both groups during morphine withdrawal as demonstrated by equivalent reductions in thermal and mechanical thresholds; however, this hypersensitivity was not evident during continuous systemic morphine infusion. These data collectively indicate that KARs containing the GluR5 subunit contribute to the development of morphine tolerance without affecting nociceptive thresholds, morphine analgesia, or disposition in CNS of morphine and its metabolite morphine-3-glucuronide. In addition, constitutive deletion of GluR5 does not alter the morphine-induced increase in locomotor activity or the acquisition of morphine reward as measured by a CPP paradigm.

Continuous Drug Infusion for Diabetes Therapy: A Closed-Loop Control System Design

While a typical way for diabetes therapy is discrete insulin infusion based on long-time interval measurement, in this paper, we design a closed-loop control system for continuous drug infusion to improve the traditional discrete methods and make diabetes therapy automatic in practice. By exploring the accumulative function of drug to insulin, a continuous injection model is proposed. Based on this model, proportional-integral-derivative (PID) and fuzzy logic controllers are designed to tackle a control problem of the resulting highly nonlinear plant. Even with serious disturbance of glucose, such as nutrition absorption at meal time, the proposed scheme can perform well in simulation experiments.

Brief, meal-contingent intravenous infusion of glucagon-like peptide-1 (GLP-1) decreases spontaneous meal size in rats.

Continuous systemic intravenous infusion of GLP-1 decreases food intake in rats and humans. We further characterized the effects of GLP-1 on feeding in rats by testing (1) the effects of brief, prandial GLP-1 infusions, designed to mimic meal-related GLP-1 secretion, on spontaneous feeding parameters, and (2) hepatic portal vein (HPV) vs. inferior vena cava (VC) infusions. Adult male Sprague-Dawley rats were equipped with HPV catheters or both HPV and VC catheters. Infusions (5 min, 0.2 ml/min) began 2 min into the first nocturnal spontaneous meal. First, we tested HPV infusions of 0.33, 1 and 3 nmol/kg GLP-1 in consecutive crossover tests vs. vehicle (V). The two larger doses both significantly decreased meal size, but there was no difference in their effects (mean V, 2.1 ± 0.2 g; GLP-1, 2.0 ± 0.3, 1.3 ± 0.1 and 1.2 ± 0.1 g, respectively). GLP-1 did not affect the following intermeal intervals or meal sizes. Next, we compared the effects of HPV and VC infusions of 1 nmol/kg GLP-1 were compared in a separate group of rats. HPV and VC GLP-1 decreased meal size similarly: (HPV: V and GLP-1, 2.7 ± 0.4 and 1.6 ± 0.2 g; VC: V and GLP-1, 2.3 ± 0.3 and 1.1 ± 0.1 g, both P

Effective treatment of 4T1 mammary adenocarcinoma by direct tumor injection and continuous systemic infusion of transferrin receptor antisense in mice

14113 Background: Transferrin receptors (TfR) on the cell surface are the major transporters of iron into cells. Tumor cells often have increased expression of TfR, compared to normal cells. TfR antibodies have been shown to inhibit the growth of tumor cells. We previously reported that human TfR antisense inhibited the proliferation of human breast cancer cell lines in vitro. Methods: In the present study, we used antisense oligonucleotides targeted to the mouse TfR gene to treat the 4T1 mammary adenocarcinoma mouse model. The antisense was either directly injected one time into the tumors or continuously infused systemically for 14 days through subcutaneous implantation of Alzet osmotic minipumps. The control group of mice received Hank’s balanced salt solution. Tumor sizes were measured twice a week. Tumor necrosis and metastasis were examined grossly at autopsy and by microscopy. Results: At 4, 7 and 10 days post- treatment, tumor volumes of treated groups, including direct injection and continuous infusion, were significantly smaller than the control group. At 14 days post-treatment, gross and microscopic pathology showed that the continuously systemically treated mice had significantly less lung metastases than the control group (p&lt;0.001 and p&lt;0.01, respectively). Although the group of mice treated with direct injection received an equal total dosage of TfR antisense as the continuously systemic treated mice, direct tumor injection of TfR antisense did not suppress lung metastasis. Primary tumors had varying degrees of necrosis in the treated and control groups, but there was no statistical difference between groups. Summary: TfR antisense effectively inhibited tumor growth and metastasis of 4T1 mammary adenocarcinoma in mice. Furthermore, continuously systemic administration of antisense was more effective than direct tumor injection. No significant financial relationships to disclose.

Regional citrate anticoagulation for continuous venovenous hemodiafiltration using calcium-containing dialysate

Background: Regional anticoagulation with trisodium citrate for continuous venovenous hemodiafiltration (CVVHDF) is an effective and safe alternative to heparin, especially in patients at high risk for bleeding. However, regional citrate anticoagulation is not used widely because current protocols are complex, labor intensive, and cumbersome. Existing protocols require the use of calcium-free dialysate with a continuous systemic calcium infusion to prevent hypocalcemia. We evaluated Anticoagulant Citrate Dextrose Formula A (ACD-A) solution for regional anticoagulation in CVVHDF in combination with a commercially available calcium-containing dialysis solution. Methods: Thirty-eight patients in the intensive care units underwent citrate-based CVVHDF using low-calcium peritoneal dialysis solution (calcium, 5.0 mg/dL [1.25 mmol/L]). ACD-A infusion rate was adjusted to maintain postfilter ionized calcium (iCa++) levels at 1.0 to 2.0 mg/dL (0.25 to 0.5 mmol/L). Calcium chloride (10%) solution was administered intravenously every 6 hours on an as-needed basis to maintain systemic serum iCa++ levels at 3.5 to 4.0 mg/dL (0.88 to 1.0 mmol/L). Results: CVVHDF was performed for a total of 394 days using 149 hemofilters. Mean hemofilter life span was 63.5 ± 27.1 hours. Seventy-five percent, 61%, and 49% of hemofilters were patent at 24, 48, and 72 hours, respectively. No patient experienced a change in clinical status caused by hypocalcemia and/or signs and symptoms of citrate toxicity. Four patients developed metabolic alkalosis requiring 0.1 N of hydrochloric acid infusion. Conclusion: Our simplified technique of regional citrate anticoagulation for CVVHDF using calcium-containing dialysate is not associated with increased hemofilter clotting and obviates the need for a continuous systemic calcium infusion and calcium-free dialysate.

Short term infusion of glycine-extended gastrin(17) stimulates both proliferation and formation of aberrant crypt foci in rat colonic mucosa.

Evidence is accumulating that gastrin precursors may act as growth factors for the colonic mucosa in vivo and for colorectal carcinoma cell lines in vitro. The effect of short term administration of synthetic gastrins on the colonic mucosa in vivo, however, has not been reported. The aim of our study was to determine whether continuous systemic infusion of glycine-extended gastrin(17) stimulated proliferation and accelerated carcinogenesis in the colorectal mucosa. A significant increase in colonic mucosal proliferation as assessed by metaphase index was seen in the caecum (23%, p < 0.02) and distal colon (27%, p < 0.001), but not the rectum, after treatment of intact rats with glycine-extended gastrin(17) for 1 week using implanted miniosmotic pumps. Defunctioning of the rectum reduced both the proliferative index and crypt height of the rectal mucosa of untreated rats. Treatment of rectally defunctioned animals with glycine-extended gastrin(17) for either 1 or 4 weeks resulted in a significant increase in both the proliferative index (40% and 93%, respectively) and crypt height (11% and 19%, respectively) of the rectal mucosa. The total number of aberrant crypt foci in intact rats treated with the procarcinogen azoxymethane plus glycine-extended gastrin(17) was increased by 48% compared to the value in controls treated with azoxymethane only (p = 0.01). We conclude that short term administration of glycine-extended gastrin(17) to mature rats not only has a proliferative effect upon colonic mucosa, but also increases the number of aberrant crypt foci formed in the colorectal mucosa after treatment with azoxymethane. Glycine-extended gastrin(17) could thus potentially act as a promoter of carcinogenesis.

A system for continuous production and infusion of [ 15O]H 2O for PET activation studies

A system for continuous production and infusion of [ 15O]H 2O has been designed for Positron Emission Tomography brain activation studies. The infusion system consists of two Horizon Nxt infusion pumps, a four-port-two-position valve and a sterile 50 ml vial. The line and the back check valve between the furnace and the reservoir were heated in order to reduce vapor condensation in the line. The variation of the production of [ 15O]H 2O was <1%. The activity delivered as measured by scanner counts varied <2% during the steady state period. The system has been demonstrated to be capable of delivering activity over a wide range of conditions.

Vascular access system for continuous arterial infusion of a protease inhibitor in acute necrotizing pancreatitis.

We used a vascular access system (VAS) for continuous arterial infusion (CAI) of a protease inhibitor in two patients with acute necrotizing pancreatitis. The infusion catheter was placed into the dorsal pancreatic artery in the first patient and into the gastroduodenal artery in the second, via a femoral artery approach. An implantable port was then connected to the catheter and was secured in a subcutaneous pocket prepared in the right lower abdomen. No complications related to the VAS were encountered. This system provided safe and uncontaminated vascular access for successful CAI for acute pancreatitis.

Leptin reverses insulin resistance and diabetes mellitus in mice with congenital lipodystrophy.

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder characterized by a paucity of adipose (fat) tissue which is evident at birth and is accompanied by a severe resistance to insulin, leading to hyperinsulinaemia, hyperglycaemia and enlarged fatty liver. We have developed a mouse model that mimics these features of CGL: the syndrome occurs in transgenic mice expressing a truncated version of a nuclear protein known as nSREBP-1c (for sterol-regulatory-element-binding protein-1c) under the control of the adipose-specific aP2 enhancer. Adipose tissue from these mice was markedly deficient in messenger RNAs encoding several fat-specific proteins, including leptin, a fat-derived hormone that regulates food intake and energy metabolism. Here we show that insulin resistance in our lipodystrophic mice can be overcome by a continuous systemic infusion of low doses of recombinant leptin, an effect that is not mimicked by chronic food restriction. Our results support the idea that leptin modulates insulin sensitivity and glucose disposal independently of its effect on food intake, and that leptin deficiency accounts for the insulin resistance found in CGL.