Structure-permeation relations of met-enkephalin peptide analogues on absorption and secretion mechanisms in Caco-2 monolayers

Due to the low effective permeabilities of peptides at many absorption sites, their structure-permeation relations are of high interest. In this work structure-permeation relations of Met-enkephalin analogues are presented using confluent Caco-2 cells as an in vitro permeation model. Four model peptides (Met-enkephalin, [D-Ala2]Met-enkephalin, [D-Ala2]Met-enkephalinamide, and metkephamid) were tested in terms of permeability, lipophilicity, charge, and molecular size. Permeability coefficients (P(eff)) across Caco-2 cells were low, 3.3 x 10(-8) to 9.5 x 10(-8) cm s-1, and were similar to typical paracellular markers. No correlation of permeability and the log(apparent octanol/buffer partition coefficient) was observed. A 40-fold increase of the permeability of metkephamid in the presence of 10 mM EDTA suggested a significant contribution of paracellular transport. Independent support for this conclusion was obtained by visualizing the pathway of the fluorescein isocyanate isomer I 1-metkephamid by confocal laser scanning microscopy (CLSM). The fluorophore-labeled peptide was observed in the intercallular space only. Metkephamid permeabilities were found to be direction-specific. Permeabilities from basolateral to apical (b-to-a) were significantly higher (ca. 4-fold) than in the opposite (a-to-b) direction. The addition of verapamil equalized the permeabilities in the a-to-b and b-to-a directions, suggesting the involvement of a P-glycoprotein-mediated secretion mechanism. Similar observations were obtained with [D-Ala2]Met-enkephalinamide, but not with Met-enkephalin and [D-Ala2]Met-enkephalin. In contrast to the other analogues, metkephamid and [D-Ala2]Met-enkephalinamide are positively charged at neutral pH, as demonstrated by their isoelectric points (pl = 8.6 for [D-Ala2]Met-enkephalinamide and metkephamid and 5.3 for [D-Ala2]Met-enkephalin and Met-enkephalin). The data is in agreement with the literature showing that most compounds secreted by the P-glycoprotein transporter carry a positive charge.     

The social consequences of expressive suppression.

At times, people keep their emotions from showing during social interactions. The authors' analysis suggests that such expressive suppression should disrupt communication and increase stress levels. To test this hypothesis, the authors conducted 2 studies in which unacquainted pairs of women discussed an upsetting topic. In Study 1, one member of each pair was randomly assigned to (a) suppress her emotional behavior, (b) respond naturally, or (c) cognitively reappraise in a way that reduced emotional responding. Suppression alone disrupted communication and magnified blood pressure responses in the suppressors' partners. In Study 2, suppression had a negative impact on the regulators' emotional experience and increased blood pressure in both regulators and their partners. Suppression also reduced rapport and inhibited relationship formation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A case of paraquat poisoning and subsequent fatality presenting to an emergency department

Paraquat (1,1'-dimethyl-4,4'-dipyridylium) is an herbicide associated with both accidental and intentional ingestion, leading to severe and often fatal toxicity. Prognosis is largely dependent on the amount of paraquat absorbed. Rapid identification of the symptoms of paraquat toxicity (burns or ulceration at the site of ingestion or injection, acute respiratory distress, and renal failure) can facilitate early treatment intervention to limit absorption. We report a case of a 71-year-old man with a suicidal ingestion of paraquat 2 days prior to presentation. Serum paraquat levels, time elapsed since ingestion, and clinical symptoms all indicated poor prognosis. The patient developed severe respiratory distress and progressive renal failure, and died 6 days after admission to the hospital.     

Beta-COP is essential for biosynthetic membrane transport from the endoplasmic reticulum to the Golgi complex in vivo

Experimental glomerulonephritis was induced in rats to investigate the consequence of the antigen-antibody interaction on the surface of glomerular endothelial cells (GENs). A lectin, Lens culinaris hemoagglutinin (LCH), was first planted in the left kidney by isolated perfusion of a left kidney, and then the circulation was reestablished. Rabbit anti-LCH antibodies were injected from the tail vein 3 minutes after the recirculation of the left kidney, and acute glomerulonephritis ensued. Fifteen minutes after the injection, rabbit immunoglobulin G (IgG), rat C3, and LCH were observed exclusively on the surface of GENs. Accumulation of platelets was prominent. Three hours later, the immune deposits were seen in the subendothelial space, and the polymorphonuclear cells were the dominant infiltrate in the glomeruli. Up to the seventh day, immune deposits were seen in the subendothelial space, and the widening of this area was increasingly observed. Fourteen days later, immune deposits containing rat IgG were observed in the subepithelial area, but they were only occasionally seen in the subendothelial space and in the mesangial area. No crescent formation was seen at day 14, but the mesangial area was expanded, with an increased number of cells. The number of nuclei in the cross-section of a glomerulus increased after the induction of glomerulonephritis, but the number of leukocyte common antigen-positive cells (infiltrating cells) decreased gradually from day 4 to day 14. The staining of Thy-1.1, a marker of mesangial cell, was markedly enlarged in the glomerulus at day 14. These data suggest that mesangial proliferative glomerulonephritis can be induced by the antigen-antibody interaction on the surface of GENs.     

Terlipressin (glypressin) versus somatostatin in the treatment of bleeding esophageal varices--final report of a placebo-controlled, double-blind study

One hundred and six episodes of bleeding from esophageal or gastric varices in 72 patients with cirrhosis of the liver were randomized to treatment either with intravenous terlipressin 2 mg initially and 1 mg every four hours for 24 hours together with bolus injection and continuous infusion of placebo, or with somatostatin 250 micrograms as a bolus and continuous infusion of 250 micrograms/h somatostatin for 24 hours and placebo injections. Standard treatment with transfusions, fluid and electrolyte correction, and lactulose was administered in both groups. In the terlipressin group, 48 out of 53 bleeding episodes (91%) and in the somatostatin group 43 out of 53 bleeds (81%) were initially stopped by the vasoactive drugs. Four of the five bleeds not arrested by terlipressin, and nine of the ten bleeds not arrested by somatostatin, were stopped by balloon tamponade. In one patient in each group variceal bleeding could not be stopped initially, and both patients died. The failure rate of the vasoactive treatment alone, including rebleeds within the study period, was 17% in the terlipressin, and 28% in the somatostatin, group. The initial hemostasis, including balloon tamponade, were 98%, and the definitive bleeding control rates were 89% in both groups. The hospital mortality rate was 21% (11/53) in the terlipressin, and 21% (11/53) in the somatostatin, group. Blood transfusions and duration of bleeding did not differ significantly. The study indicates that a large proportion of bleeds from esophageal and fundic varices can be stopped initially (86%) and definitively controlled (77%) by vasoactive drugs alone.