Effect of hypohydration on gastric emptying and intestinal absorption during exercise

Dehydration and hyperthermia may impair gastric emptying (GE) during exercise; the effect of these alterations on intestinal water flux (WF) is unknown. Thus the purpose of this study was to determine the effect of hypohydration ( approximately 2.7% body weight) on GE and WF of a water placebo (WP) during cycling exercise (85 min, 65% maximal oxygen uptake) in a cool environment (22 degrees C) and to also compare GE and WF of three carbohydrate-electrolyte solutions (CES) while the subjects were hypohydrated. GE and WF were determined simultaneously by a nasogastric tube placed in the gastric antrum and via a multilumen tube that spanned the duodenum and the first 25 cm of jejunum. Hypohydration was attained 12-16 h before experiments by low-intensity exercise in a hot (45 degrees C), humid (relative humidity 50%) environment. Seven healthy subjects (age 26.7 +/- 1.7 yr, maximal oxygen uptake 55.9 +/- 8.2 ml . kg-1 . min-1) ingested either WP or a 6% (330 mosmol), 8% (400 mosmol), or a 9% (590 mosmol) CES the morning following hypohydration. For comparison, subjects ingested WP after a euhydration protocol. Solutions ( approximately 2.0 liters total) were ingested as a large bolus (4.6 ml/kg body wt) 5 min before exercise and as small serial feedings (2.3 ml/kg body wt) every 10 min of exercise. Average GE rates were not different among conditions (P > 0.05). Mean (+/-SE) values for WF were also similar (P > 0.05) for the euhydration (15.3 +/- 1.7 ml . cm-1 . h-1) and hypohydration (18.3 +/- 2.6 ml . cm-1 . h-1) experiments. During exercise after hypohydration, water absorption was greater (P < 0.05) with ingestion of WP (18.3 +/- 2. 6) and the 6% CES (16.5 +/- 3.7), compared with the 8% CES (6.9 +/- 1.5) and the 9% CES (1.8 +/- 1.7). Mean values for final core temperature (38.6 +/- 0.1 degrees C), heart rate (152 +/- 1 beats/min), and change in plasma volume (-5.7 +/- 0.7%) were similar among experimental trials. We conclude that 1) hypohydration to approximately 3% body weight does not impair GE or fluid absorption during moderate exercise when ingesting WP, and 2) hyperosmolality (>400 mosmol) reduced WF in the proximal intestine.     

Induction of apoptosis by a short-chain neuropeptide analog in small cell lung cancer

Small cell lung cancer (SCLC) cells express a variety of neuropeptides which act as autocrine growth factors. Although several neuropeptide analogs have been reported to antagonize SCLC proliferation, the development of these compounds has been limited by their low potency and the cytostatic nature of their effects. In the present study we evaluated the cytotoxic activity of four short-chain substance P analogs (NY3460, NY3238[-pHOPA], NY3238[Phe1], NY3238[Lys5]) against a panel of five SCLC cell lines. NY3460 was the most potent compound in all five SCLC cell lines (IC50 = 2.8-3.7 microM) as assessed by a MTT growth inhibitory assay. NY3238[Phe1] was also relatively active in all cell lines (IC50 = 3.5-11.2 microM), while NY3238[Lys5] and NY3238[-pHOPA] were substantially less active. NY3460 was the only agent to induce an increase in the percentage of cells with subdiploid DNA content suggestive of apoptosis by flow cytometric DNA content analysis. The induction of apoptosis was confirmed by fluorescent microscopy in NCI-H69, NCI-H82, NCI-H446, and NCI-H510 cells after exposure to 5.0 microM NY3460 for 48 h. These findings suggest that NY3460 is a relatively potent cytotoxic inhibitor of SCLC growth, and that short-chain neuropeptide analogs deserve further evaluation as anti-SCLC agents.     

Energy thresholds in brain mitochondria. Potential involvement in neurodegeneration

Decreases in mitochondrial respiratory chain complex activities have been implicated in neurodegenerative disorders such as Parkinson's disease, Huntington's disease, and Alzheimer's disease. However, the extent to which these decreases cause a disturbance in oxidative phosphorylation and energy homeostasis in the brain is not known. We therefore examined the relative contribution of individual mitochondrial respiratory chain complexes to the control of NAD-linked substrate oxidative phosphorylation in synaptic mitochondria. Titration of complex I, III, and IV activities with specific inhibitors generated threshold curves that showed the extent to which a complex activity could be inhibited before causing impairment of mitochondrial energy metabolism. Complex I, III, and IV activities were decreased by approximately 25, 80, and 70%, respectively, before major changes in rates of oxygen consumption and ATP synthesis were observed. These results suggest that, in mitochondria of synaptic origin, complex I activity has a major control of oxidative phosphorylation, such that when a threshold of 25% inhibition is exceeded, energy metabolism is severely impaired, resulting in a reduced synthesis of ATP. Additionally, depletion of glutathione, which has been reported to be a primary event in idiopathic Parkinson's disease, eliminated the complex I threshold in PC12 cells, suggesting that antioxidant status is important in maintaining energy thresholds in mitochondria. The implications of these findings are discussed with respect to neurodegenerative disorders and energy metabolism in the synapse.     

Retrograde coronary venous infusion of ethanol for ablation of canine ventricular myocardium

INTRODUCTION: Permanent cure of reentrant ventricular tachycardia (VT) associated with coronary artery disease is difficult to achieve. Retrograde coronary venous infusion of ethanol for ablation of ventricular myocardium associated with reentrant tachyarrhythmias has several potential advantages, including use of physiologic mapping techniques and production of deeper, wider necrotic zones. METHODS AND RESULTS: Nine anesthetized dogs had baseline hemodynamic measurement, left ventriculography, coronary arteriography, occlusive coronary venography, and programmed electrical stimulation of the right ventricular apex and outflow tract. A balloon-tipped infusion catheter was advanced into a distal coronary venous branch, the balloon slowly inflated, and pure ethanol infused at volumes of 1.5, 3, or 5 cc. Hemodynamic measurements, angiography, ventriculography, and programmed electrical stimulation were repeated immediately and 1 week following ablation. Formalin-perfused hearts were serially sectioned and lesion volumes determined. Histologic examination of ablation beds then was performed. No significant difference was found in any hemodynamic measurement before or after ablation. Coronary arteriograms and left ventriculograms were unchanged after ablation. Nonsustained VT occurred in eight dogs during ethanol infusion; however, VT was not inducible in any dog before or after ablation. Infusion volumes of 3 cc or more were required to produce transmural lesions. CONCLUSION: Retrograde coronary venous infusions of ethanol using a balloon-tipped infusion catheter were effective in ablating ventricular myocardium. Retrograde chemical ablation did not itself result in inducible VT or adversely affect hemodynamic measurements or coronary arteries. Transmural myocardial necrosis, necessary in the ablation of VT associated with coronary artery disease, can be produced by higher infusion volumes.     

Expression, characterization, and purification of C-terminally hexahistidine-tagged thromboxane A2 receptors

Thromboxane A2 (TxA2) receptors belong to the class of G-protein-coupled receptors. Knowledge of the relationship of structure to function for TxA2 receptors is limited because of their low levels of expression, lengthy purification procedures and poor recoveries. A C-terminal hexahistidine-tag (C-His) was ligated to the alpha-isoform of TxA2 receptors and expressed in COS-7 and Chinese hamster ovary cells. The C-His-TxA2 receptors bound the radioligands 125I-7-[(1R,2S,3S,5R)-6, 6-dimethyl-3-(4-benzenesulfonylamino)bicyclo[3.1. 1]hept-2-yl]-5(Z)-heptenoic acid, an antagonist, and 125I-[1S-1alpha, 2beta(5Z),3alpha(1E,3S*), 4alpha]-7-[3[(3-hydroxy-4-(4'-phenoxy)-1butenyl)-7-oxabicycl o-[2.2. 1]heptan-2-yl]-5-heptanoic acid, an agonist, with affinities not significantly different from those of the wild type (wt)-TxA2 receptors. LipofectAMINE transfection of the cDNAs resulted in high levels of expression (Bmax = 95 +/- 6 pmol/mg) of the C-His-TxA2 receptors. In competition binding studies the IC50 values of five different ligands were not significantly different between C-His-TxA2 and wt-TxA2 receptors. Agonist-induced stimulation of cAMP and total inositol phosphate formation were not significantly different between the two receptors. Purification on a Ni2+-NTA column resulted in a rapid (within 4 h) purification with a 36 +/- 2% recovery and a 30 +/- 6-fold purification (n = 5). The partially purified receptors were resolved on SDS-polyacrylamide gel electrophoresis, transferred to a nitrocellulose membrane, dissolved in acetone/trifluoroacetic acid/hexafluoroisopropanol/sinapinic acid, and successfully subjected to matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis. The results suggest that the combination of a high level of expression of C-His-TxA2 receptors and a rapid purification procedure followed by SDS- polyacrylamide gel electrophoresis may provide a useful approach for mass-spectrometry based structure-function and other studies of TxA2 receptors.