Aggregation of Platelet Membrane Vesicles by ADP

The study was performed to examine biochemical and biophysical changes in platelet membrane vesicles(PMV) when aggregated by ADP. PMV was isolated from normal donors by using glycerol lysis technique, and was suspended in 10mM Tris, 0.15M NaCl buffer, pH 7,4. Aggregation of PMV was readily observed under phasecontrastmlcroscopy within 3 min after addition of ADP(5mM), while AMP, UDF or GDP was without effect. Light scattering Intensity of PMV suspension determined by Lasernepherometer increased with addition of ADPCJmM), reaching plateau within 2 to 3 min, also indicating that vesicles were rapidly aggregating in suspending medium. In electronmicroscopic observation, amorphous floccuent materials were seen between aggregated PMV by ADP. This PMV aggregation by ADP was inhibited by the treatment of PMV with either neuraminidase(0.1u/ml) or trypsin(20μg/ml) and was hardly observed in PMV from a patient with thrombasthenia.

The addition of ADF(10mM) to PMV suspension resulted in the reduction in electronhoretic mobility of PW(0.301±0.057μ·cm/sec·V, control ;1.194±0.037) and increase in membrane microviscositv (p value; 0.277, control; 0.255).

Changes in protein profiles in aggregated PMV were examined by SDS Polyacrylamide gel disc electrophoresis. One protein band(M.W. 200,000) disappeared and instead, there observed increased coomassie blue staining intensity at the top of the gel.

The results suggest that these biochemical and biophysical changes in PMV may in part explain the mechanisms of platelet aggregation By ADP.

Potentiation of the Anti-Aggregating Activities of Prostacyclin by Verapamil

Prostacyclin (PGI2), which is a potent inhibitor of platelet aggregation formed in vascular wall, is now considered to play a crucial role in the pathogenesis of thrombosis. Evidence was presented in this investigation that a coronary vasodilator, Verapamil (VP), markedly potentiates the anti-aggregating activities of PCI2. VP caused a dose dependent inhibition of serotonin release induced either by thrombin or by A23187 in the absence of extracellular calcium. Addition of 1 mM CaCl2, with A23187 or thrombin partially overcame this inhibition, while 1 mM CaCl2 alone caused no significant release in the absence of A23187 or thrombin. Minimal concentration of PGI2 (supplied from Hoechst Research Instituted West Germany) to cause 50% inhibition of collagen-induced platelet aggregation was 1 nM, while that of VP was 100 μM. Simultaneous addition of 0.125 nM PGI2 and 30 μM VP resulted in complete inhibition of aggregation. Similar synergistic effects between PGI2 and VP were observed in platelet aggregation induced by ADP, arachidonic acid and A23187. 8-(N-N-diethylamino)-octyl 3,4,5-trimethoxybenzoate (TMB-8), a compound recently show to act as an intracellular calcium antagonist (I. Charo, Bioch. Biophy. Res. Comm.), also potentiates the inhibitory effect of PCI2 on platelet aggregation.

Our results suggest that an intracellular calcium antagonist may possibly become an unique anti-platelet agent because of its ability to inhibit release reaction and to potentiate the anti-aggregating activity of PGI2.

The Role of Calcium ION in Platelet Aggregation

Calcium is required for platelet aggregation but the precise role of Ca++ is not yet known. We have investigated the role of Ca++ in platelet aggregation, performing an ultra-structural and biochemical analysis of Ca++ treated platelet membrane vesicles. Human platelet membrane vesicles isolated by glycerol lysis technique according to the method of Barber and Jamieson, were suspended in 10 mM tris buffered saline, pH 7.4. Aggregation of platelet membrane vesicles was clearly observed under the phase-contrast microscopy in the presence of 5 mM CaCl2. Aggregated membranes were solubilized in 1Ï SDS and 1% 2-mer-captoethanol, and electfophorcsed on 5% SDS-polyacrylamide gels. Comparison of polypeptides of aggregated and native membranes revealed that the polypeptide of molecular weight 200,000 Daltons disappeared, instead, coomassie blue staining became visualized at the top of the gel in aggregated membranes. Ultrastructural observations were performed after fixation of membrane vesicles with 2% glutaraldehyde for both thin-section and freeze-fracturing. Freeze-fractured image of native membranes exhibit a smooth surface with a random distribution of intramembranous particles (IMP). Membrane vesicles treated with 5 mM CaCl2 possess round depressions suggestive of areas of mutual contact. These circular attachment sites are free of IMP, which accumulated at the periphery. It is suggested that these ultrastructural changes induced by Ca++ may be regarded as crucial events in platelet aggregation.

Inhibition of platelet function by sulbenicillin and its metabolite

The effect of sulbenicillin and its major metabolite, alpha-sulfobenzylpenicilloic acid, on platelet function was investigated. Sulbenicillin caused inhibition of platelet aggregation and release reaction in the same manner as carbenicillin. alpha-Sulfobenzylpenicilloic acid was found to cause much stronger inhibition of platelet function. The results indicate that the strong inhibitory action of alpha-sulfobenzylpenicilloic acid may also take part in impaired platelet functions following administration of sulbenicillin to humans.

Antitumor effect of seaweeds. II. Fractionation and partial characterization of the polysaccharide with antitumor activity from Sargassum fulvellum

An almost purified antitumor polysaccharide fraction (SFPP) was obtained by fractional precipitation with ethanol from hot-water extract of Sargassum fulvellum. The fraction showed remarkable tumor-inhibiting effect against sarcoma-180 implanted subcutaneously in mice. The results of chemical and physical analyses suggested that the active substance may be either a sulphated peptidoglycuronoglycan or a sulphated glycuronoglycan.

Effects of noise on human placental lactogen (HPL) levels in maternal plasma

The levels of human placental lactogen (HPL) in the serum of expectant mothers both subjected to and not subjected to aircraft noise were measured. The HPL levels in the quiet reference area and in the noise area were similar before the 29th week of pregnancy. However, the HPL levels of subjects in the noise area tended to be lower than those in the reference area after the 30th week of pregnancy and the difference became significant after the 36th week of pregnancy. The lower HPL levels were associated with lower birth weight for infants of mothers who lived in the noise area.

Effect of chilling on platelet cyclic adenosine 3:5-monophosphate and adenylate cyclase activity

Exposure of platelets to 1 C led to a transient increase in cyclic AMP levels (determined either by a protein binding method or by radioimmunoassay) within five to ten minutes reaching a maximum 10 to 15 minutes after chilling was begun and returning subsequently to baseline values. Addition of EDTA to the platelet suspension medium prevented this increase. Rewarming at 37 C produced a sudden reduction in platelet cyclic AMP. To determine whether the cold-induced increase in cyclic AMP was due to a transient stimulation of platelet adenylate cyclase or a rapid inhibition of phosphodiesterase, these enzymes were assayed in ruptured platelet suspensions. Platelet adenylate cyclase activity was found to possess certain characteristics similar to those of the enzyme derived from other sources but there was a marked potentiation of fluoride-stimulated adenylate cyclase activity by 0.001 M EDTA. This effect was limited to low EDTA concentrations. Exposure of platelets to 1 C for up to 60 minutes did not increase adenylate cyclase activity but lowered it substantially compared with controls kept at room temperature. Phosphodiesterase activity at 1 C was depressed sooner and to a greater extent than was adenylate cyclase. The transient rise in cyclic AMP levels in chilled platelets appears to be due to a disproportionate reduction of cyclic nucleotide phosphodiesterase activity.

Distribution of free sulfhydryl and disulfide groups among platelet membrane proteins

Reactive sulfhydryl and disulfide groups were identified in platelet membrane proteins resolved by sodium dodecyl sulfate-polycrylamide gel electrophoresis. Platelet membranes treated with N-ethyl(1-14C)maleimide, phenyl(203Hg)mercuric acetate and p-chloro(203Hg)mercuribenzoate showed similar patterns of distribution of sulfhydryl groups among the sodium dodecyl sulfate-solubilized membrane proteins. Four major and two minor polypeptides ranging in molecular weight from greater than 200 000 to 20 000 were found to have reactive SH groups. Reduction of membrane proteins by sulfite coupled with subsequent mercaptide formation of the resultant monothiols led to the identification of four polypeptides with disulfide bonds. Reaction of platelet membranes with 14C-labeled 5,5'-dithio-bis(2-nitrobenzoic acid) resulted changes in the distribution profile of the solubilized membrane proteins suggestive of a polymerization process dependent upon, 5,5'-dithio-bis(2-nitrobenzoic acid)-induced intermolecular disulfide interchange.

Effect of lysozyme on ionic forms of spores of Clostridium perfringens type A

H spores of Clostridium perfringens type A (two strains) were more sensitive to germination by lysozyme than native spores. Resistance to lysozyme of H spores was restored by calcium loading.

[Clinical experiences of lividomycin on respiratory tract infections (author's transl)]

Clinical effects of a newly developed aminoglycoside antibiotic lividomycin, were investigated in 13 patients suffering from respiratory infections. 1. A total of 13 patients with the following infectious diseases was treated with 1 g/day of lividomycin for 3 to 11 days (average 6.7 days): Acute pneumonia 3 cases, bronchiectasis 3 cases, acute bronchitis 5 cases, suppurative diseases of the lung 1 case, and pyothorax 1 case. As the results, the antibiotic was effective in 5 patients, moderately effective in 4 patients and ineffective in 4 patients, and thus the global effective rate was 62.9% (9/13). 2. As in the case of kanamycin, lividomycin indicated fairly good sensitivity against a total of 17 strains comprising Staphylococcus aureus (7 strains), alpha-Streptococcus (2 strains), beta-Streptococcus (3 strains), gamma-Streptococcus (1 strain), Neisseria (2 strains) and Haemophilus (2 strains) which were isolated from sputum. 3. No side effects attributable to lividomycin were observed.