Thrombosis triggered by severe arterial lesions is inhibited by oral administration of a glycoprotein IIb/IIIa antagonist

Platelet aggregation and thrombosis play an important role in the onset of acute coronary events. Regardless of the stimulus for activation, platelet thrombus formation is ultimately regulated through the IIb/IIIa receptor complex. The effects of oral administration of xemilofiban, a non-peptide mimetic of the RGDF sequence of the IIb/IIIa receptor complex, on thrombus formation were evaluated in a canine model. Xemilofiban significantly reduced platelet deposition on severely damaged arterial wall. Platelet deposition was reduced at both low (13 ± 1 from 56 ± 18 × 10⁶ platelets cm⁻²; P  < 0.05) and high (23 ± 2 from 111 ± 21 × 10⁶ platelets cm⁻²; P  < 0.01) shear rates. Platelet deposition was reduced to a monolayer as seen by electron microscopy (platelet–vessel wall interaction). Therefore, the availability of an orally active IIb/IIIa antagonist for chronic use may have significant value in preventing thrombus formation in those clinical situations associated with severe arterial injury, such as atherosclerotic plaque disruption.     

Effect of meal volume on gastric emptying

Abstract While the volume of a liquid meal has been identified as the principal accelerator of gastric emptying of liquids, the relationship between meal volume and gastric emptying of solids has been controversial. With solid foods, the need to reduce solid foods into small particles (trituration) before passage might obscure the effect of meal volume on solid propulsion. To distinguish trituration from driving force as the rate-limiting factor for emptying, 75 (1.6 mm) nylon spheres were fed along with different amounts of steak meals (150, 300 and 600 g), or alternatively, 50, 100 or 200 (1.6 mm) nylon spheres were fed to six dogs with 300 g steak meals. To examine the effect of meal volume on gastric emptying, we studied the effect of different meal volumes on the speed of gastric emptying of liquids (150, 300, 600 and 1200 ml of phosphate buffer) and solids (150, 300 and 600 g of cooked beef steak) in five dogs with duodenal fistulas. Intestinal inhibition was eliminated by diverting all chyme through the fistulas. In the absence of intestinal feedback, we found that gastric emptying of steak and spheres were different in that steak emptying was independent of meal volume (g min^-1 was constant across 150–600 g) while sphere emptying was affected by the number of spheres in the stomach and that liquid emptying was dependent on the meal volume (ml min^-1 increased across 150–1200 ml). Thus, meal volume accelerated gastric emptying provided the process is not rate-limited by trituration.     

LONGITUDINAL COMPARISON OF CARBOHYDRATE-DEFICIENT TRANSFERRIN AND GAMMA-GLUTAMYL TRANSFERASE: COMPLEMENTARY MARKERS OF EXCESSIVE ALCOHOL CONSUMPTION

The utility of carbohydrate-deficient transferrin (CDT) andgamma-glutamyl transferase (GGT) as biochemical markers of excessivealcohol consumption was studied in alcohol-dependent subjects.Serum samples were collected once weekly from 10 male out-patientsundergoing a 6-month alcohol treatment programme. Frequencyof relapse into drinking (defined as any intake of alcoholicbeverage) was assessed by self-reports during patient interviewsthree times per week and by daily determination of the 5-hydroxytryptophollevel in urine. A marked decrease in mean CDT and GGT valueswas observed during the initial month. Only one patient remainedtotally abstinent throughout the observation period, while fourhad sporadic relapses (2–5 days with alcohol consumption).Both CDT and GGT remained below the respective reference limitsin those patients. The other five patients drank more frequently(range 22–57 days) and increased their mean levels ofCDT and GGT after the initial decrease. As determined from thevalues at admission and during the course of the study, CDTappeared to be the most sensitive marker in six out of the 10patients. In one patient, both markers were affected in a parallelway, whereas two of those with frequent relapses responded toalcohol consumption with a marked increase in GGT, but withno or only a slight increase in CDT. One patient did not showany abnormal CDT or GGT values. In 54 female and 60 male serumsamples collected at random from patients during admission atan alcohol detoxification unit, 35% and 58% of the CDT valuesexceeded the reference limits for females and males, respectively.For GGT, 59% of the female and 67% of the male values were abovecut-off. Carbohydrate-deficient transferrin and GGT were notsignificantly correlated. Taken together, the present resultsindicate that measurement of both CDT and GGT will increasethe possibility of identifying excessive alcohol consumption.By following changes in CDT and GGT values during a period ofalcohol withdrawal, the most sensitive individual marker canbe determined. This in turn allows for improved detection ofrelapse into heavy drinking dunng long-term monitoring of out-patients.     

Comparison of the photochemical behavior of four different photoactivatable probes

The most commonly used photoaffinity labeling probes are compared, which are aryl azides, aryl diazirines, α-diazocarbonyls and benzophenone-derivatives. The compounds were used under identical conditions and crosslinking efficiency, influence of water, irradiation requirements, and by-products were investigated. Using the pentapeptide thymopentin (TP5) as a model system, we synthesized four analogues by solid-phase peptide synthesis and partially N-terminal modification to obtain [p-(3-trifluoromethyl)diazirinophenylalanine⁵] TP5, [p-benzoylphenylalanine⁵] TP5, 4-azidobenzoyl-TP5 and 2-diazo-3, 3, 3-trifluoropropionyl-TP5. The peptides were characterized by HPLC and ion-spray mass spectroscopy. Irradiation of the peptides with two different ultraviolet sources was carried out in water, n-propanol and water/n-propanol to imitate both hydrophobic and hydrophilic peptide/protein-interactions as well as the influence of the aqueous environment. Analysis of the products with HPLC, ion-spray MS, HPLC-MS and HPLC-CID-MS revealed that (Tmd)Phe is a highly potent carbene-precursor, which can be transformed easily into uniform crosslinking products by smooth photolysis. However, the electrophilic nature of the intermediate causes a high tendency to react with water molecules. The 4-azidobenzoyl group showed comparable crosslinking efficiency, but the probability to create non-uniform irradiation products (e.g. through rearrangement) is higher, whereas the reaction with water is less dominant. In contrast, Bpa was found to have an extremely low affinity to react with water, whereas prolonged UV irradiation is needed to get complete rearrangement into a variety of products. As the absorption band of α-diazocarbonyls at around 350 nm possesses a low extinction coefficient, 2-diazo-3, 3, 3-trifluoropropionyl-TP5 could not be activated at all with the optimized irradiation conditions that we have chosen for our comparative studies. © Munksgaard 1997.     

Liver-infiltrating T helper cells in autoimmune chronic active hepatitis stimulate the production of autoantibodies against the human asialoglycoprotein receptor in vitro.

Autoantibodies against the human asialoglycoprotein receptor (ASGPR) occur in the sera of patients with autoimmune liver disorders. Liver-infiltrating T cell clones that specifically recognize the ASGPR have been described in patients with autoimmune chronic active hepatitis (AI-CAH) and primary biliary cirrhosis (PBC). Recently, we have shown that peripheral blood mononuclear cells (PBMC) from patients with AI-CAH or PBC but not chronic viral hepatitis secreted anti-ASGPR antibodies in vitro. In this study we characterized the influence of liver-infiltrating T cells on the secretion of ASGPR-specific autoantibodies by autologous B cells in cell culture supernatants. T cell clones from liver biopsies of three patients with chronic autoimmune liver disorders (one with AI-CAH, two with PBC) were isolated and investigated for their proliferative response to soluble ASGPR and their helper function provided to autoantibody-secreting B lymphocytes. PBMC from these patients secreted autoantibodies spontaneously in their cell culture supernatants and showed a proliferative response to ASGPR. T cell-depleted PBMC, however, lacked spontaneous antibody secretion. Four CD4+CD8- liver-infiltrating T cell clones showed a proliferative response to ASGPR and also induced spontaneous anti-ASGPR antibody production in cell culture supernatants when added to autologous T cell depleted PBMC. Activated supernatants of these T cell clones failed to induce antibody production. None of seven CD4+CD8- and two CD4-CD8+ T cell clones non-responding to ASGPR provided this help for antibody secretion. Anti-ASGPR secretion in vitro could not be inhibited by the addition of MoAbs raised against monomorphic determinants on HLA class II molecules. The addition of purified ASGPR or polyclonal-activating pokeweed mitogen showed no influence on the production of autoantibodies in these cultures. These data show that B lymphocytes require T cell help for the production of ASGPR-specific antibodies. This help can be provided by ASGPR-responsive T helper cells via cellular interactions.