The impact of clay-based hypoxia mimetic hydrogel on human fibroblasts of the periodontal soft tissue.

Thixotropic clays have favorable properties for tissue regeneration. Hypoxia mimetic agents showed promising results in pre-clinical models for hard and soft tissue regeneration. It is unclear if clays can be used as carrier for hypoxia mimetic agent in a periodontal regenerative setting. Here, we tested the response of human fibroblasts of the periodontal soft tissue to synthetic clay hydrogels and assessed hypoxia mimetic agent release. Cells were cultured on synthetic clay hydrogels (5.00%-0.15%). We assessed viability and differentiation capacity with resazurin-based toxicity assays, MTT staining, Live-Dead staining, and alkaline phosphatase staining. To reveal the response of fibroblasts to hypoxia mimetic agent-loaded clay hydrogels, cells were exposed to clay supplemented with dimethyloxalylglycine, deferoxamine, l-mimosine, and CoCl2. Supernatants from hypoxia mimetic agent-loaded clay hydrogels were harvested and replaced with medium at hour 1, 3, 6, 24, 48, and 72. To reveal the hypoxia mimetic capacity of supernatants, vascular endothelial growth factor production in the fibroblasts was assessed in the culture medium. Our data show that clay did not induce relevant toxic effects in the fibroblasts which remained capable to differentiate into alkaline phosphatase-positive cells at the relevant concentrations. Fibroblasts cultured on clay hydrogel loaded with dimethyloxalylglycine, deferoxamine, l-mimosine, and CoCl2 remained vital, however, no significant increase in vascular endothelial growth factor levels was found in the culture medium. Only dimethyloxalylglycine-loaded clay supernatants taken in the first hours stimulated vascular endothelial growth factor production in fibroblasts. In conclusion no pronounced toxic effects of synthetic clay were observed. Supplementation with dimethyloxalylglycine leads to hypoxia mimetic activity. This pilot study provides first insights into the impact of synthetic clay on periodontal tissue.

3D-porous ß-tricalcium phosphate-alginate-gelatin scaffold with DMOG delivery promotes angiogenesis and bone formation in rat calvarial defects.

Hypoxia-inducible factor-1α (HIF-1α), a well-studied angiogenesis pathway, plays an essential role in angiogenesis-osteogenesis coupling. Targeting the HIF-1a pathway frequently leads to successful reconstruction of large-sized bone defects through promotion of angiogenesis. Dimethyloxalylglycine (DMOG) small molecule regulates the stability of HIF-1α at normal oxygen tension by mimicking hypoxia, which subsequently accelerates angiogenesis. The current study aims to develop a novel construct by seeding adipose derived mesenchymal stem cells (ADMSCs) onto a scaffold that contains DMOG to induce angiogenesis and regeneration of a critical size calvarial defect in a rat model. The spongy scaffolds have been synthesized in the presence and absence of DMOG and analyzed in terms of morphology, porosity, pore size, mechanical properties and DMOG release profile. The effect of DMOG delivery on cellular behaviors of adhesion, viability, osteogenic differentiation, and angiogenesis were subsequently evaluated under in vitro conditions. Histological analysis of cell-scaffold constructs were also performed following transplantation into the calvarial defect. Physical characteristics of fabricated scaffolds confirmed higher mechanical strength and surface roughness of DMOG-loaded scaffolds. Scanning electron microscopy (SEM) images and MTT assay demonstrated the attachment and viability of ADMSCs in the presence of DMOG, respectively. Osteogenic activity of ADMSCs that included alkaline phosphatase (ALP) activity and calcium deposition significantly increased in the DMOG-loaded scaffold. Computed tomography (CT) imaging combined with histomorphometry and immunohistochemistry analysis showed enhanced bone formation and angiogenesis in the DMOG-loaded scaffolds. Therefore, spongy scaffolds that contained DMOG and had angiogenesis ability could be utilized to enhance bone regeneration of large-sized bone defects.

Chronic cigarette smoke exposure induces systemic hypoxia that drives intestinal dysfunction.

Crohn's disease (CD) is a chronic inflammatory disease of the gastrointestinal tract (GIT). Cigarette smoke (CS) exposure and chronic obstructive pulmonary disease (COPD) are risk factors for CD, although the mechanisms involved are poorly understood. We employed a mouse model of CS-induced experimental COPD and clinical studies to examine these mechanisms. Concurrent with the development of pulmonary pathology and impaired gas exchange, CS-exposed mice developed CD-associated pathology in the colon and ileum, including gut mucosal tissue hypoxia, HIF-2 stabilization, inflammation, increased microvasculature, epithelial cell turnover, and decreased intestinal barrier function. Subsequent smoking cessation reduced GIT pathology, particularly in the ileum. Dimethyloxaloylglycine, a pan-prolyl hydroxylase inhibitor, ameliorated CS-induced GIT pathology independently of pulmonary pathology. Prior smoke exposure exacerbated intestinal pathology in 2,4,6-trinitrobenzenesulfonic acid-induced (TNBS-induced) colitis. Circulating vascular endothelial growth factor, a marker of systemic hypoxia, correlated with CS exposure and CD in mice and humans. Increased mucosal vascularisation was evident in ileum biopsies from CD patients who smoke compared with nonsmokers, supporting our preclinical data. We provide strong evidence that chronic CS exposure and, for the first time to our knowledge, associated impaired gas exchange cause systemic and intestinal ischemia, driving angiogenesis and GIT epithelial barrier dysfunction, resulting in increased risk and severity of CD.

Tumour blood vessel normalisation by prolyl hydroxylase inhibitor repaired sensitivity to chemotherapy in a tumour mouse model.

Blood vessels are important tissue structures that deliver oxygen and nutrition. In tumour tissue, abnormal blood vessels, which are hyperpermeable and immature, are often formed; these tissues also have irregular vascularisation and intravasation. This situation leads to hypoperfusion in tumour tissue along with low oxygen and nutrition depletion; this is also called the tumour microenvironment and is characterised by hypoxia, depleted nutrition, low pH and high interstitial pressure. This environment induces resistance to anticancer drugs, which causes an increase in anticancer drug doses, leading to increased side effects. We hypothesised that normalised tumour blood vessels would improve tumour tissue perfusion, resupply nutrition and re-oxygenate the tumour tissue. Chemotherapy would then be more effective and cause a decrease in anticancer drug doses. Here we report a neovascularisation-inducing drug that improved tumour vascular abnormalities, such as low blood flow, blood leakage and abnormal vessel structure. These results could lead to not only an increased chemo-sensitivity and tissue-drug distribution but also an up-regulated efficiency for cancer chemotherapy. This suggests that tumour blood vessel normalisation therapy accompanied by angiogenesis may be a novel strategy for cancer therapy.

Targeted delivery of the hydroxylase inhibitor DMOG provides enhanced efficacy with reduced systemic exposure in a murine model of colitis.

Targeting hypoxia-sensitive pathways has recently been proposed as a new therapeutic approach to the treatment of intestinal inflammation. HIF-hydroxylases are enzymes which confer hypoxic-sensitivity upon the hypoxia-inducible factor (HIF), a major regulator of the adaptive response to hypoxia. Previous studies have shown that systemic (intraperitoneal) administration of hydroxylase inhibitors such as dimethyloxalylglycine (DMOG) is profoundly protective in multiple models of colitis, however the therapeutic potential of this approach is limited due to potential side-effects associated with systemic drug exposure and the fact that orally delivered DMOG is ineffective (likely due to drug inactivation by gastric acid). In order to overcome these issues, we formulated DMOG in a liquid emulsion drug delivery system which, when coated with specific polymer coatings, permits oral delivery of a reduced dose which is released locally throughout the colon. This colon-targeted DMOG formulation demonstrated increased relative colonic bioactivity with reduced systemic exposure and provided a similar degree of protection to systemic (intraperitoneal) administration at a 40-fold lower dose in DSS-induced colitis. In summary, targeted delivery of DMOG to the colon provides local protection resulting in enhanced efficacy with reduced systemic exposure in the treatment of colitis. This novel approach to targeting hydroxylase inhibitors to specific diseased regions of the GI tract may improve it's potential as a new therapeutic in inflammatory bowel diseases such as ulcerative colitis.

Release kinetics of prolyl hydroxylase inhibitors from collagen barrier membranes.

Collagen barrier membranes are used in guided tissue regeneration to support healing. This strategy, however, relies on the healing capacity of the tissue. Pharmacological inhibitors of prolyl hydroxylases can support regeneration by enhancing angiogenesis and are therefore a promising tool for periodontology. Here we evaluate the release kinetics of the prolyl hydroxylase inhibitors dimethyloxalylglycine and L-mimosine from collagen barrier membranes. Dimethyloxalylglycine and L-mimosine were lyophilized onto the collagen barrier membranes. The morphology of the collagen barrier membranes was analysed using scanning electron microscopy. The release of prolyl hydroxylase inhibitors was assessed by colorimetric and spectroscopic methods. Their ability to induce a cellular response was assessed in bioassays with gingival and periodontal ligament fibroblasts based on vascular endothelial growth factor production, proliferation, and metabolic activity of the cells. We found that loading of collagen barrier membranes with prolyl hydroxylase inhibitors did not change the overall membrane morphology. Assessment of the release kinetics by direct measurements and based on vascular endothelial growth factor production showed that supernatants obtained from the collagen barrier membranes in the first 6 hours had a sufficient level of prolyl hydroxylase inhibitors to induce vascular endothelial growth factor production. A similar kinetic was found when cell proliferation was assessed. Changes in metabolic activity did not reach the level of significance in the MTT assay. In conclusion, collagen barrier membranes can release prolyl hydroxylase inhibitors thereby increasing the pro-angiogenic capacity of periodontal cells in vitro. These findings provide the basis for preclinical studies to evaluate the regenerative capacity of prolyl hydroxylase inhibitors in periodontology and oral surgery.

PHDs inhibitor DMOG promotes the vascularization process in the AV loop by HIF-1a up-regulation and the preliminary discussion on its kinetics in rat.

BACKGROUND: The Arterovenous Loop (AV Loop) model is a vascularization model in tissue engineering research, which is capable of generating a three dimensional in vivo unit with cells as well as the supporting vessels within an isolation chmaber. In our previous studies the AV loop in the isolation chamber was discovered to undergo hypoxia, characterized by Hypoxia Inducible Factor (HIF) up-regulation. The vascularization followed the increase of HIF-α temporally, while it was spatially positively correlated with the HIF-α level, as well. This study aims to prove that HIF-1a up-regulation is the stimulus for vascularization in the AV loop model. METHOD: The AV loop model in rats was created by interposing a femoral vein graft into the distal ends of the contralateral femoral artery and vein, and the loop was embeded in fibrin matrix and fixed in isolation chamber. PHD (prolyl hydroxylases) inhibitor DMOG (Dimethyloxallyl Glycine) was applied systemically in the rats in 40 mg/KG at day 0 and day 3 (DMOG-1), or in 15 mg/KG at day 8, day10 and day12 (DMOG-2). Two weeks later the specimens were explanted and underwent morphological and molecular evaluations. RESULTS: Compared to the control group, in the DMOG-2 group the HIF-1α positive rate was siginicantly raised as shown in immunohistochemistry staining, accompanied with a smaller cross section area and greater vessel density, and a HIF-1α accumulation in the kidney. The mRNA of HIF-1α and its angiogenic target gene all increased in different extends. Ki67 IHC demostrate more positive cells. There were no significant change in the DMOG-1 group. CONCLUSION: By applying DMOG systemically, HIF-1α was up-regulated at the protein level and at the mRNA level, acompanied with angiogenic target gene up-regulateion, and the vascularization was promoted correspondingly. DMOG given at lower dosage constantly after one week tends to have better effect than the group given at larger dosage in the early stage in this model, and promotes cell proliferation, as evidenced by Ki67 IHC. Thus, this study proves that HIF-1a up-regulation is the stimulus for vascularization in the AV loop model and that the process of the vessel outgrowth can be controlled in the AV Loop model utilizing this mechanism.

Systemic preconditioning by a prolyl hydroxylase inhibitor promotes prevention of skin flap necrosis via HIF-1-induced bone marrow-derived cells.

BACKGROUND: Local skin flaps often present with flap necrosis caused by critical disruption of the blood supply. Although animal studies demonstrate enhanced angiogenesis in ischemic tissue, no strategy for clinical application of this phenomenon has yet been defined. Hypoxia-inducible factor 1 (HIF-1) plays a pivotal role in ischemic vascular responses, and its expression is induced by the prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG). We assessed whether preoperative stabilization of HIF-1 by systemic introduction of DMOG improves skin flap survival. METHODS AND RESULTS: Mice with ischemic skin flaps on the dorsum were treated intraperitoneally with DMOG 48 hr prior to surgery. The surviving area with neovascularization of the ischemic flaps was significantly greater in the DMOG-treated mice. Significantly fewer apoptotic cells were present in the ischemic flaps of DMOG-treated mice. Interestingly, marked increases in circulating endothelial progenitor cells (EPCs) and bone marrow proliferative progenitor cells were observed within 48 hr after DMOG treatment. Furthermore, heterozygous HIF-1α-deficient mice exhibited smaller surviving flap areas, fewer circulating EPCs, and larger numbers of apoptotic cells than did wild-type mice, while DMOG pretreatment of the mutant mice completely restored these parameters. Finally, reconstitution of wild-type mice with the heterozygous deficient bone marrow cells significantly decreased skin flap survival. CONCLUSION: We demonstrated that transient activation of the HIF signaling pathway by a single systemic DMOG treatment upregulates not only anti-apoptotic pathways but also enhances neovascularization with concomitant increase in the numbers of bone marrow-derived progenitor cells.

Systemic pretreatment with dimethyloxalylglycine increases myocardial HIF-1α and VEGF production and improves functional recovery after acute ischemia/reperfusion.

BACKGROUND: Stem cells protect the heart from ischemic damage in part by the release of cytoprotective growth factors, particularly vascular endothelial growth factor (VEGF). Production of VEGF is regulated in part by levels of the transcription factor hypoxia inducible factor 1-α (HIF-1α). Dimethyloxalylglycine (DMOG) prevents the deactivation of HIF-1α and increases VEGF production. However, the effects of systemic DMOG treatment on myocardial tolerance for ischemia are unknown. We hypothesized that systemic pretreatment with DMOG would improve myocardial ischemic tolerance. METHODS: To study this hypothesis, adult male rats were randomly given an intraperitoneal injection of DMOG (40 mg/kg in 1 mL saline, n = 5) or saline (1 mL, n = 6) 24 h before cardiectomy and isolated heart perfusion. All hearts were subjected to 15 min equilibration, 25 min ischemia and 40 min reperfusion. Myocardial function was continuously monitored. Following reperfusion, myocardial homogenates were analyzed for HIF-1α and VEGF production. RESULTS: We observed that hearts in the DMOG group exhibited greater recovery of left ventricular developed pressure LVDP, +dP/dt and -dP/dt. Myocardial HIF-1α and VEGF levels were increased by DMOG therapy. CONCLUSION: In conclusion, systemic pretreatment with DMOG augments post-ischemic myocardial functional recovery through increased HIF-1α levels and greater VEGF production.

Prolyl hydroxylase inhibition during hyperoxia prevents oxygen-induced retinopathy.

Oxygen-induced retinopathy (OIR) in the mouse, like the analogous human disease retinopathy of prematurity, is an ischemic retinopathy dependent on oxygen-induced vascular obliteration. We tested the hypothesis that chemically overriding the oxygen-induced downregulation of hypoxia-inducible factor (HIF) activity would prevent vascular obliteration and subsequent pathologic neovascularization in the OIR model. Because the degradation of HIF-1alpha is regulated by prolyl hydroxylases, we examined the effect of systemic administration of a prolyl hydroxylase inhibitor, dimethyloxalylglycine, in the OIR model. Our results determine that stabilizing HIF activity in the early phase of OIR prevents the oxygen-induced central vessel loss and subsequent vascular tortuosity and tufting that is characteristic of OIR. Overall, these findings imply that simulating hypoxia chemically by stabilizing HIF activity during the causative ischemia phase (hyperoxia) of retinopathy of prematurity may be of therapeutic value in preventing progression to the proliferative stage of the disease.

Prolyl hydroxylase inhibitor treatment confers whole-animal hypoxia tolerance.

AIM: Recently a family of O(2)-dependent prolyl hydroxylase domain-containing enzymes (PHD) has been identified as a cellular oxygen-sensing mechanism. Reduced prolyl hydroxylase activity initiates a signalling cascade that includes the accumulation, as well as the activation, of hypoxia-inducible factor (HIF-1alpha). In turn the transcription factor HIF-1alpha, and other targets of the PHD, elicit a myriad of incompletely understood cellular responses. In these studies we have tested: (1) whether a small-molecule prolyl hydroxylase inhibitor (PHI) can effectively activate the oxygen-sensing pathway when administered systemically to mice, and (2) whether the activation of the PHD signalling pathway at the cellular level results in whole-animal hypoxic tolerance. METHODS: Mice received daily injections of the PHI, ethyl-3,4 dihydroxybenzoate (EDHB, 100-250 mg kg(-1)) or vehicle. Tissue levels of HIF-1alpha and the serum levels of the HIF-inducible gene, erythropoietin (EPO), were measured to evaluate PHD-pathway activation. To evaluate hypoxic tolerance, the endurance and survival ability of these animals was tested in sublethal (8% O(2)) and lethal hypoxia (5% O(2)) respectively. RESULTS: Systemic treatment of mice with the PHD inhibitor, EDHB, leads to elevated levels of HIF-1alpha in liver and HIF-inducible EPO in serum, indicating activation of the cellular oxygen-sensing pathway. Animals treated with EDHB display significantly increased viability and enhanced exercise performance in hypoxia. CONCLUSION: These results demonstrate a novel pharmacological strategy to induce hypoxic tolerance and are the first to demonstrate that the activation of the PHD oxygen-sensing pathway at the cellular level is sufficient to produce a hypoxic-tolerant phenotype at the physiological level of the whole animal.

Effects of L-glutamate transport inhibition by a conformationally restricted glutamate analogue (2S,1'S,2'R)-2-(carboxycyclopropyl)glycine (L-CCG III) on metabolism in brain tissue in vitro analysed by NMR spectroscopy.

(2S,1'S,2'R)-2-(Carboxycyclopropyl)glycine (L-CCG III) was a substrate of Na(+)-dependent glutamate transporters (GluT) in Xenopus laevis oocytes (IC50 to approximately 13 and to approximately 2 microM for, respec tively, EAAT 1 and EAAT 2) and caused an apparent inhibition of [3H]L-glutamate uptake in "mini-slices" of guinea pig cerebral cortex (IC50 to approximately 12 microM). In slices (350 microM) of guinea pig cerebral cortex, 5 microM L-CCG III increased both the flux of label through pyruvate carboxylase and the fractional enrichment of glutamate, GABA, glutamine and lactate, but had no effect on total metabolite pool sizes. At 50 microM L-CCG III decreased incorporation of 13C from [3-13C]-pyruvate into glutamate C4, glutamine C4, lactate C3 and alanine C3. The total metabolite pool sizes were also decreased with no change in the fractional enrichment. Furthermore, L-CCG III was accumulated in the tissue, probably via GluT. At lower concentration, L-CCG III would compete with L-glutamate for GluT and the changes probably reflect a compensation for the "missing" L-glutamate. At 50 microM, intracellular L-CCG III could reach > 10 mM and metabolism might be affected directly.

Facilitation and inhibition of retrieval in two aversive tasks in rats by intrahippocampal infusion of agonists of specific glutamate metabotropic receptor subtypes.

RATIONALE: The generic antagonist of glutamate metabotropic receptors (mGlus), MCPG, blocks retrieval of inhibitory avoidance when infused into the CA1 area of rat hippocampus. It was considered important to study the effect of agonists of different types of mGlus on retrieval both of this task and of a related one, contextual fear. OBJECTIVES: To measure the effect of three mGlu agonists (3HPG, which is selective to mGlu1; LCCG, which binds to mGlu2 and mGlu3; and LAP-4, which binds to mGlu4 and mGlu6), infused bilaterally into CA1, on the retrieval of one-trial inhibitory avoidance and contextual fear in rats. METHODS: Rats bilaterally implanted with cannulae in the CA1 region of the dorsal hippocampus were trained in one-trial step-down inhibitory avoidance or in a contextual fear task and tested for retention 24 h later. The drugs 3HPG, LCCG and LAP-4 were infused into CA1 at different concentration levels 10 min before retention testing. In addition, we studied the effect of these drugs on locomotor and exploratory activity measured in an open field, and on pro- and anti-conflict behaviour in an elevated plus-maze. RESULTS: 3HPG hindered, and LCCG and LAP-4 enhanced, retrieval of the two tasks. In all cases the effects were dose-dependent. The drugs had no effects on open field or plus maze behaviour. CONCLUSIONS: Retrieval of one-trial inhibitory avoidance and of contextual fear is regulated by mGlus in the CA1area of the rat hippocampus. The results suggest that mGlu2s, mGlu3s, mGlu4s and mGlu6s are necessary for retrieval and that mGlu1s play an inhibitory role. The effects are not explainable by nonspecific influences on locomotor or exploratory activity or anxiety levels.

Behavioural evidence supporting a differential role for group I and II metabotropic glutamate receptors in spinal nociceptive transmission.

Metabotropic glutamate receptors (mGluRs) have been shown to contribute to nociceptive processing in spinal cord. This study examined the effects of intrathecal treatment with group I and II mGluR compounds on withdrawal thresholds to noxious mechanical stimuli, in the absence of tissue damage or inflammation, in adult female sheep. Both the group I/II mGluR agonist (+/-)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (trans-ACPD; 5.2-520 nmol) and the group II agonist (2S,1S, 2S)-2-(carboxycyclopropyl)glycine (L-CCG-I; 620 nmol) significantly increased mechanical withdrawal thresholds between 5-15 min post-injection. These anti-nociceptive effects were blocked by co-administration of the mGluR antagonist (2S)-alpha-ethylglutamate (EGLU; 570 nmol; group II), but not (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA; 450 nmol; group I). Intrathecal administration of the group I-specific agonist (S)-3,5-dihydroxyphenylglycine ((S)-3,5-DHPG; 50 nmol) produced a significant reduction in mechanical thresholds, which was blocked by co-administration of the group I antagonist AIDA. In contrast, the highest dose of (S)-3,5-DHPG tested, 5 micromol, significantly elevated response thresholds. These results demonstrate that both group I and II mGluRs play crucial, but contrasting roles in mediating acute mechanical nociceptive events in spinal cord.

Effects of the selective metabotropic glutamate receptor agonist, L-CCG-I, on acquisition of a Morris task by rats.

L-Glutamate, a major excitatory neurotransmitter in the central nervous system, plays an important role in a variety of neuronal events associated with learning and memory, neuronal plasticity, neurotoxicity, and neurodegeneration. We assessed the effects of L-CCG-I ((2S,3S,4S)-alpha-(carboxycyclopropyl)glycine), a conformationally restricted glutamate analogue, in a standard Morris water escape task with young adult rats. L-CCG-I is considered to be a selective agonist of the metabotropic glutamate receptor. Vehicle, 5, 50, or 500 nmol L-CCG-I was injected intra-cerebroventricularly (i.c.v.) into the right lateral ventricle 30 min before the start of each of five daily acquisition sessions. The data indicate that L-CCG-I had a centrally mediated mode of action; rats treated with 500 nmol L-CCG-I were clearly impaired in acquiring the standard Morris water escape task. The no-effect dose was 5 nmol.

[Effects of parenterally administered dicarboxylic amino acids and their amides on the secretory function of the stomach]. / Vliianie parental'no vvedennykh dikarbonovykh aminokislot i ikh amidov na sekretornuiu funktsiiu zheludka.

The effect of dicarboxylic amino acids and their amides on gastric secretion stimulated by sham-feeding (100 g of raw meat), as well as of amides of dicarboxylic amino acids on the gastric secretory function was studied in 119 tests on 8 dogs with gastric fistulas according to Basov. The tests were started 16-18 h after feeding under neutral or alkaline reactions of gastric excretion. The tests demonstrated that dicarboxylic amino acids inhibited gastric secretion induced by sham-feeding. It was shown that dicarboxylic amino acid amines, in contrast to these amino acids, did not inhibit gastric secretion induced by sham-feeding. On the contrary, asparagine and glutamine administered into the blood are capable of inducing gastric secretion, per se.

Effects of a parenteral nutrition regimen containing dicarboxylic amino acids on plasma, erythrocyte, and urinary amino acid concentrations of young infants.

Plasma, erythrocyte, and urinary amino acid concentrations were measured in young infants infused with a solution containing glutamate and aspartate. Eight infants (1.2 to 2.8 kg) were fed parenterally (80 kcal/kg/day) with two regimens containing dextrose (15 g/kg/day), amino acids (2 g/kg/day), and lipid (2 g/kg/day) for successive 3-day periods in a cross-over design. The regimens differed only in the amino acid source. One regimen (I) provided glutamate (1.5 mmol/kg/day) and aspartate (1.0 mmol/kg/day), while the other regimen (II) did not. The mean (+/- SD) plasma glutamate concentration was slightly, but significantly higher (89.9 +/- 28.5 microM) during infusion of regimen I than regimen II (66.5 +/- 19.8 microM), but values did not differ significantly from values observed in normal, orally fed premature infants (107 +/- 36 microM). No significant differences were noted in either plasma or erythrocyte aspartate concentrations, or in erythrocyte glutamate concentration. Since plasma and erythrocyte levels of dicarboxylic amino acids remained within the normal range, the data indicate no hazard to young infants from infusion of dicarboxylic amino acids at this level.

Diet and uptake of aldomet by the brain: competition with natural large neutral amino acids.

The rise in levels of aldomet in the brains of rats after an injection of the alpha-methylated amino acid was depressed when large neutral amino acids, but not acidic amino acids, were coadministered with the drug. This result suggests that aldomet is transported into brain by the carrier for natural large neutral amino acids. The prior ingestion of a carbohydrate meal, which lowers levels of neural amino acids in the serum, enhanced the uptake of aldomet into brain; the consumption of a protein-containing meal inhibited the subsequent uptake of aldomet into the brain. Antecedent diet can thus affect the availability of aldomet to the central nervous system; the mechanism of this effect probably involves the blood-brain barrier uptake system for large neutral amino acids.