967-21 Long Term Results of Balloon Expandable Slotted-Tube Nitinol Stents in Canine Coronary Arteries

This study evaluated delivery performance, quantitative angiographic parameters, intravascular ultrasound appearance. long term patency and vascular histology of radio-opaque, slotted-tube nickel titanium (nitinoll stents permanently implanted in canine coronary arteries. Dogs were treated with aspirin for 1 month. Follow-up angiography and histology were performed at 0.5, 1, 3, and 6 months (number of vessels = 2, 4, 6, and 26, respectively).ResultsThirty-eight of 39 (97%) stents were successfully implanted in the mid LAD and LCX of 20 dogs. One stent, which was undersized, was successfully removed by thermal recovery. Tandem stents were placed in 2 dogs without difficulty. Intravascular ultrasound of 6 stents showed symmetrical expansion with good wall contact. Acute angiographic parameters:nominal stent size (mm)ANOVA p3.03.54.0number42212–inflation pressure (atm)5.5±056.1±1.45.9±1.60.47minimal diameter (mm)2.93±0.073.24±0.143.48±0.160.0003balloon to artery ratio1.23±0.031.25±0.101.25±0.080.65stent to artery ratio1.09±0.031.14±0.091.13±0.070.30percent recoil11.0±1.88.4±1.89.9±1.80.05At follow-up, all vessels and 9 of 9 stented sidebranches were patent. The mean percent stenosis at 3 to 6 months was –1.6±5.2 and the late loss was 0.2±0.3 mm. All struts were covered with neointima at 2 weeks. At 6 months the maximal neointimal thickness was 260±50 μm and was located adjacent to the struts. No thrombi and only occasional areas of granulation tissue with rare inflammatory cells were seen.ConclusionsA slotted tube nitinol stent has delivery performance characteristics and recoil similar to stainless steel slotted-tube stents. Nitinol stents endothelialize rapidly and intimal proliferation is insufficient to create a stenosis in this animal model. These data suggest that a slotted-tube, balloon expandable nitinol stent is sufficiently reliable and biocompatible to warrant clinical trials

Measurement of splanchnic photoplethysmographic signals using a new reflectance fiber optic sensor

Splanchnic organs are particularly vulnerable to hypoperfusion. Currently, there is no technique that allows for the continuous estimation of splanchnic blood oxygen saturation (SpO(2)). As a preliminary to developing a suitable splanchnic SpO(2) sensor, a new reflectance fiber optic photoplethysmographic (PPG) sensor and processing system are developed. An experimental procedure to examine the effect of fiber source detector separation distance on acquired PPG signals is carried out before finalizing the sensor design. PPG signals are acquired from four volunteers for separation distances of 1 to 8 mm. The separation range of 3 to 6 mm provides the best quality PPG signals with large amplitudes and the highest signal-to-noise ratios (SNRs). Preliminary calculation of SpO(2) shows that distances of 3 and 4 mm provide the most realistic values. Therefore, it is suggested that the separation distance in the design of a fiber optic reflectance pulse oximeter be in the range of 3 to 4 mm. Preliminary PPG signals from various splanchnic organs and the periphery are obtained from six anaesthetized patients. The normalized amplitudes of the splanchnic PPGs are, on average, approximately the same as those obtained simultaneously from the periphery. These observations suggest that fiber optic pulse oximetry may be a valid monitoring technique for splanchnic organs

Modulating GLUT1 Expression in Retinal Pigment Epithelium Decreases Glucose Levels in the Retina: Impact on Photoreceptors and Müller Glial Cells

The retina is one of the most metabolically active tissues in the body and utilizes glucose to produce energy and intermediates required for daily renewal of photoreceptor cell outer segments. Glucose transporter 1 (GLUT1) facilitates glucose transport across outer blood retinal barrier (BRB) formed by the retinal pigment epithelium (RPE) and the inner BRB formed by the endothelium. We used conditional knockout mice to study the impact of reducing glucose transport across the RPE on photoreceptor and Müller glial cells. Transgenic mice expressing Cre recombinase under control of the Bestrophin1 (Best1) promoter were bred with Glut1 flox/flox mice to generate Tg-Best1-Cre:Glut1 flox/flox mice (RPE∆Glut1). The RPE∆Glut1 mice displayed a mosaic pattern of Cre expression within the RPE that allowed us to analyze mice with ~50% (RPE∆Glut1 m ) recombination and mice with \u3e70% (RPE∆Glut1 h ) recombination separately. Deletion of GLUT1 from the RPE did not affect its carrier or barrier functions, indicating that the RPE utilizes other substrates to support its metabolic needs thereby sparing glucose for the outer retina. RPE∆Glut1 m mice had normal retinal morphology, function, and no cell death; however, where GLUT1 was absent from a span of RPE greater than 100 µm, there was shortening of the photoreceptor cell outer segments. RPE∆Glut1 h mice showed outer segment shortening, cell death of photoreceptors, and activation of Müller glial cells. The severe phenotype seen in RPE∆Glut1 h mice indicates that glucose transport via the GLUT1 transporter in the RPE is required to meet the anabolic and catabolic requirements of photoreceptors and maintain Müller glial cells in a quiescent state. © 2019, American Physiological Society. All rights reserved

Myosin 6 Is Required for Iris Development and Normal Function of the Outer Retina

PURPOSE. To determine the molecular basis and the pathologic consequences of a chemically induced mutation in the translational vision research models 89 (tvrm89) mouse model with ERG defects. METHODS. Mice from a G3 N-ethyl-N-nitrosourea mutagenesis program were screened for behavioral abnormalities and defects in retinal function by ERGs. The chromosomal position for the recessive tvrm89 mutation was determined in a genome-wide linkage analysis. The critical region was refined, and candidate genes were screened by direct sequencing. The tvrm89 phenotype was characterized by circling behavior, in vivo ocular imaging, detailed ERG-based studies of the retina and RPE, and histological analysis of these structures. RESULTS. The tvrm89 mutation was localized to a region on chromosome 9 containing Myo6. Sequencing identified a TC point mutation in the codon for amino acid 480 in Myo6 that converts a leucine to a proline. This mutation does not confer a loss of protein expression levels; however, mice homozygous for the Myo6 tvrm89 mutation display an abnormal iris shape and attenuation of both strobe-flash ERGs and direct-current ERGs by 4 age weeks, neither of which is associated with photoreceptor loss. CONCLUSIONS. The tvrm89 phenotype mimics that reported for Myosin6-null mice, suggesting that the mutation confers a loss of myosin 6 protein function. The observation that homozygous Myo6 tvrm89 mice display reduced ERG a-wave and b-wave components, as well as components of the ERG attributed to RPE function, indicates that myosin 6 is necessary for the generation of proper responses of the outer retina to light

Oncogenic PIK3CA Mutations Reprogram Glutamine Metabolism in Colorectal Cancer

Cancer cells often require glutamine for growth, thereby distinguishing them from most normal cells. Here we show that PIK3CA mutations reprogram glutamine metabolism by upregulating glutamate pyruvate transaminase 2 (GPT2) in colorectal cancer (CRC) cells, making them more dependent on glutamine. Compared with isogenic wild-type (WT) cells, PIK3CA mutant CRCs convert substantially more glutamine to alpha-ketoglutarate to replenish the tricarboxylic acid cycle and generate ATP. Mutant p110 alpha upregulates GPT2 gene expression through an AKT-independent, PDK1-RSK2-ATF4 signalling axis. Moreover, aminooxyacetate, which inhibits the enzymatic activity of aminotransferases including GPT2, suppresses xenograft tumour growth of CRCs with PIK3CA mutations, but not with WT PIK3CA. Together, these data establish oncogenic PIK3CA mutations as a cause of glutamine dependency in CRCs and suggest that targeting glutamine metabolism may be an effective approach to treat CRC patients harbouring PIK3CA mutations

Oncogenic PIK3CA Mutations Reprogram Glutamine Metabolism in Colorectal Cancer

Cancer cells often require glutamine for growth, thereby distinguishing them from most normal cells. Here we show that PIK3CA mutations reprogram glutamine metabolism by upregulating glutamate pyruvate transaminase 2 (GPT2) in colorectal cancer (CRC) cells, making them more dependent on glutamine. Compared with isogenic wild-type (WT) cells, PIK3CA mutant CRCs convert substantially more glutamine to alpha-ketoglutarate to replenish the tricarboxylic acid cycle and generate ATP. Mutant p110 alpha upregulates GPT2 gene expression through an AKT-independent, PDK1-RSK2-ATF4 signalling axis. Moreover, aminooxyacetate, which inhibits the enzymatic activity of aminotransferases including GPT2, suppresses xenograft tumour growth of CRCs with PIK3CA mutations, but not with WT PIK3CA. Together, these data establish oncogenic PIK3CA mutations as a cause of glutamine dependency in CRCs and suggest that targeting glutamine metabolism may be an effective approach to treat CRC patients harbouring PIK3CA mutations

Investigation of photoplethysmographic signals and blood oxygen saturation values obtained from human splanchnic organs using a fiber optic sensor

Objective A reliable, continuous method of monitoring splanchnic organ oxygen saturation could allow for the early detection of malperfusion, and may prevent the onset of multiple organ failure. Current monitoring techniques have not been widely accepted in critical care monitoring. As a preliminary to developing a continuous indwelling device, this study evaluates a new handheld fiber optic photoplethysmographic (PPG) sensor for estimating the blood oxygen saturation (SpO2) of splanchnic organs during surgery. Methods A fiber optic splanchnic PPG sensor, instrumentation system and virtual instrument were developed to facilitate PPG and SpO2 measurement from splanchnic organs. Following Local Research Ethics Committee approval, the sensor was evaluated on seventeen ASA 1 and 2 patients undergoing open laparotomy. PPG signals were obtained from the large bowel, small bowel, liver and stomach. Simultaneous PPG signals from the finger were also obtained using an identical fiber optic sensor. Results Good quality PPG signals with high signal-to-noise (SNR) ratios were obtained from all splanchnic sites under investigation. Analysis of the ac and dc amplitudes of the red and infrared PPG signals showed there to be a statistically significant difference between PPG signals obtained from splanchnic organs with those obtained from the finger (using fiber optic sensors). Estimated SpO2 values from the splanchnic organs show good agreement with those obtained from the finger using both a fiber optic sensor and a commercial device. Furthermore, the results of a Bland and Altman analysis indicate that fiber optic splanchnic pulse oximetry, particularly of the bowel, may provide a suitable method for monitoring splanchnic organ perfusion. Conclusion The evaluation of a new fiber optic sensor on anaesthetized patients undergoing laparotomy demonstrated that good quality PPG signals and SpO2 estimates can be obtained from splanchnic organs. Such a sensor may provide a useful tool for the intraoperative assessment of splanchnic perfusion

Pramipexole effects on startle gating in rats and normal men

Dopamine D3 receptors regulate sensorimotor gating in rats, as evidenced by changes in prepulse inhibition (PPI) of startle after acute administration of D3 agonists and antagonists. In this study, we tested the effects of the D3-preferential agonist, pramipexole, on PPI in normal men and Sprague–Dawley rats. Acoustic startle and PPI were tested in clinically normal men, comparing the effects of placebo vs. 0.125 mg (n = 20) or placebo vs. 0.1875 mg (n = 20) pramipexole, in double blind, crossover designs. These measures were also tested in male Sprague–Dawley rats using a parallel design [vehicle vs. 0.1 mg/kg (n = 8), vehicle vs. 0.3 mg/kg (n = 8) or vehicle vs. 1.0 mg/kg pramipexole (n = 8)]. Autonomic and subjective measures of pramipexole effects and several personality instruments were also measured in humans. Pramipexole increased drowsiness and significantly increased PPI at 120-ms intervals in humans; the latter effect was not moderated by baseline PPI or personality scale scores. In rats, pramipexole causes a dose-dependent reduction in long-interval (120 ms) PPI, while low doses actually increased short-interval (10–20 ms) PPI. Effects of pramipexole on PPI in rats were independent of baseline PPI and changes in startle magnitude. The preferential D3 agonist pramipexole modifies PPI in humans and rats. Unlike indirect DA agonists and mixed D2/D3 agonists, pramipexole increases long-interval PPI in humans, in a manner that is independent of baseline PPI and personality measures. These findings are consistent with preclinical evidence for differences in the D2- and D3-mediated regulation of sensorimotor gating

Breast Tumor Cells with PI3K Mutation or HER2 Amplification Are Selectively Addicted to Akt Signaling

Dysregulated PI3K/Akt signaling occurs commonly in breast cancers and is due to HER2 amplification, PI3K mutation or PTEN inactivation. The objective of this study was to determine the role of Akt activation in breast cancer as a function of mechanism of activation and whether inhibition of Akt signaling is a feasible approach to therapy.A selective allosteric inhibitor of Akt kinase was used to interrogate a panel of breast cancer cell lines characterized for genetic lesions that activate PI3K/Akt signaling: HER2 amplification or PI3K or PTEN mutations in order to determine the biochemical and biologic consequences of inhibition of this pathway. A variety of molecular techniques and tissue culture and in vivo xenograft models revealed that tumors with mutational activation of Akt signaling were selectively dependent on the pathway. In sensitive cells, pathway inhibition resulted in D-cyclin loss, G1 arrest and induction of apoptosis, whereas cells without pathway activation were unaffected. Most importantly, the drug effectively inhibited Akt kinase and its downstream effectors in vivo and caused complete suppression of the growth of breast cancer xenografts with PI3K mutation or HER2 amplification, including models of the latter selected for resistance to Herceptin. Furthermore, chronic administration of the drug was well-tolerated, causing only transient hyperglycemia without gross toxicity to the host despite the pleiotropic normal functions of Akt.These data demonstrate that breast cancers with PI3K mutation or HER2 amplification are selectively dependent on Akt signaling, and that effective inhibition of Akt in tumors is feasible and effective in vivo. These findings suggest that direct inhibition of Akt may represent a therapeutic strategy for breast and other cancers that are addicted to the pathway including tumors with resistant to Herceptin