Prostaglandin A1 inhibition of chondrosarcoma growth

The effects of various prostaglandins (PG) on the in vitro synthesis of macromolecules by two transplantable chondrosarcomas were studied. Prostaglandin A₁ markedly inhibited the incorporation of radioactive precursors into chondromucoprotein, total protein, RNA and DNA of both a well differentiated rat chondrosarcoma and a poorly differentiated murine chondrosarcoma. PGE₁ and PGF_1α had no effects on the synthesis of macromolecules by either tumor. PGA₁ inhibitory effects occurred over a dose range of 1 to 25 μg/ml. PGA₁ had no effect on the synthesis of macromolecules by liver. The data indicate that malignant transformation of cartilage cells does not alter their responsiveness to PGA₁.     

Prostaglandin A2 and S uptake in connective tissue

Rats deficient in essential fatty acids (EFA) incorporated lesser amounts of radioactive sulfate into lung, kidney, spleen, heart, costal cartlidge, long bone and skull bone than did normal control animals. Administration of prostaglandin A₂ stimulated ³⁵S uptake by lung, kidney and aorta while ³⁵S levels in costal cartilage, tibial cap and long bone were strikingly reduced. Comments are presented suggesting that this metabolic mechanism may explain, in part, cartilage and bone resorption in areas of inflammation, such as arthritis, both rheumatoid arthritis and osteoarthritis.     

Prostaglandin A2 and 35S uptake in connective tissue

Rats deficient in essential fatty acids (EFA) incorporated lesser amounts of radioactive sulfate into lung, kidney, spleen, heart, costal cartlidge, long bone and skull bone than did normal control animals. Administration of prostaglandin A₂ stimulated ³⁵S uptake by lung, kidney and aorta while ³⁵S levels in costal cartilage, tibial cap and long bone were strikingly reduced. Comments are presented suggesting that this metabolic mechanism may explain, in part, cartilage and bone resorption in areas of inflammation, such as arthritis, both rheumatoid arthritis and osteoarthritis.     

Prostaglandin A1 induces differentiation in friend erythroleukemia cells

The effect of different prostaglandins and prostaglandin-metabolites on the growth and differentiation of Friend erythroleukemia cells (FLC) was evaluated. The prostaglandin-metabolites, thromboxane B₂ and 6-keto PGF₁α, were completely inactive, while PGE₁ inhibited slightly and PGF₂α stimulated the replication of FLC. PGA₁ was found to be the most active compound. It profoundly inhibited the replication of both DMSO-treated and undifferentiated FLC. Most importantly, PGA₁ alone induced differentiation in FLC, stimulating hemoglobin production over a five-day period. PGA₁-stimulated differentiation was completely suppressed by the addition of 10⁻⁶M hydrocortisone. Finally, treatment of DMSO-differentiated cells with PGA₁ (but no DMSO) prevented the return to the undifferentiated state.     

Metabolism of prostaglandins A1 and A2 by human whole blood

The effect of human blood on prostaglandin metabolism in vitro was studied at 37°C and 4°C. Labeled prostaglandins were incubated for up to one hour in whole blood or plasma. After extraction, the prostaglandins were purified by LH-20 Sephadex chromatography. Appropriate ¹⁴C labeled compounds, when available, were used to correct for losses. Metabolism was determined by comparison of incubated samples with zero time controls. There was no reduction in isotopic recovery of prostaglandins B₁, B₂ and E₁ after incubation with whole blood for up to one hour. In contrast, human whole blood, but not plasma, rapidly metabolized prostaglandins A₁ and A₂ at 37°C. The rate of metabolism was temperature dependent, but still continued at 4°C. The products of these reactions were not identified, but they appeared to remain in the aqueous solution after extraction with the neutral organic solvent.     

Biosynthesis of gibberellins A12, A15, A24, A36, and A37 by a cell-free system from Cucurbita maxima

GA₁₂-aldehyde obtained from mevalonate via ent-kaurene, ent-kaurenol, ent-kaurenoic acid and ent-7α-hydroxykaurenoic acid in a cell-free system from immature seeds of Cucurbita maxima was converted to GA₁₂ by the same system. When Mn²⁺ was omitted from the system GA₁₂-aldehyde and GA₁₂ were converted further to several products. Among these GA₁₅, GA₂₄, GA₃₆ and GA₃₇ were conclusively identified by GC-MS. With the exception of GA₃₇ these GAs have not previously been found in higher plants. Another biosynthetic pathway led from ent-7α-hydroxykaurenoic acid to very polar products via what was tentatively identified as ent-6α, 7α-dihydroxykaurenoic acid. An unidentified component with an MS resembling that of a dihydroxykaurenolide was also obtained from incubations with mevalonate.     

Preparation of 2- and 3-substituted gibberellins A9 and A4 for bioassay

To test the effects of preventing enzymatic 2β- and 3β-hydroxylation on the biological activities of gibberellins, the preparation of the following compounds is described: 2β-methyl- and 2,2-dimethyl-gibberellins A₄ and A₉; 2α-fluoro-, 2β-fluoro- and 2β-methoxy-gibberellin A₉; and 3β-chloro-, 3β-fluoro-, 3β-methoxy- and 3-methylene A₉.     

Work in progress. Occurence of phospholipase A1 and A2 in human decidua

Phospholipase A₂, an enzyme which may regulate the formation of polyunsaturated fatty acids utilized for prostaglandin synthesis, was found to have significant higher activity in decidual than in myometrial tissue. The major part of phospholipase A₂ in the decidua had an acid pH optimum, which indicates that most of the enzyme is stored in the lysosomes of this tissue. These findings, together with previous observations, lend further support to the view that lysosomal phospholipase A₂ released within decidual cells might be a trigger of abortion and parturition.     

The effect of orally administered prostaglandins A1, A2 and 15 Epi-A2 on human gastric acid secretion

Prostaglandins A₁, A₂ and 15 Epi-A₂ were administered orally to human male volunteers. Prostaglandin A₁ and 15 Epi-A₂ did not consistently affect gastric acid secretion either in terms of the pH values within individual tests or in respect of comparative control test data. Prostaglandin A₂ administration resulted in a transient inhibition of secretion in all 6 subjects tested, with the pH rising above 6 in every case.It is concluded that none of these compounds is likely to have therapeutic application to the peptic ulceration problem.     

Prostaglandin D2 inhibits the proliferation of human malignant tumor cells

The cytotoxic effect of prostaglandin (PG) D₂, PGE₁ and PGF_2α was examined on human osteosarcoma cells (KSu cell line) , and PGD₂ was most effective. DNA, RNA and protein syntheses of KSu cells were also found to be inhibited by PGD₂ at a concentration of 5μg/ml. Furthermore, the proliferation of various human malignant tumor cells was inhibited by PGD₂ without exception so far. These results suggest that PGD₂ shows an antineoplastic effect on a variety of human malignant tumor cells.     

Prostaglandin A1 and E1 inhibit the plating efficiency and proliferation of murine melanoma cells (Cloudman S-91) in soft agar

PGA₁ and PGE₁ reduced the plating efficiency and inhibited proliferation of Cloudman S-91 murine melanoma cells in a dose dependent manner, as assessed by their effects on colony formation in soft agar. PGF_2α did not reduce plating efficiency but was as effective as PGA₁ in raising cAMP and cGMP levels. This data suggests that the inhibition of Cloudman S-91 murine melanoma cell growth occurs via a non-cyclic nucleotide mechanism.     

Effect of prostaglandins A1, A2, B1, B2, E2 and F2α on human umbilical cord vessels

The effect of six naturally occurring prostaglandins on isolated umbilical arteries and veins has been studied. All six prostaglandins had a constricting effect on the umbilical vessels. On the umbilical artery preparations the potencies in decreasing order were A₂>B₂>F_2α>B₁>E₂>A₁. Prostaglandin B₂ was more potent than PGA₂ on the umbilical vein. Polyphloretin phosphate (PPP) antagonised the constricting effect of all six prostaglandins without altering responses to 5-hydroxytryptamine.     

Polarographic assay for phospholipase A2

A rapid, specific, and quantitative assay for phospholipase A₂ from Naja naja venom has been devised, in which phospholipid hydrolysis is measured as soybean lipoxidase-catalyzed oxygen incorporation into the ensuing unsaturated fatty acids. Under conditions where phospholipid was limiting, a linear relationship developed between the extent of oxygen uptake and the amount of egg lecithin metabolized. When phospholipase was rate limiting, the initial rate of oxygen consumption was a linear function of phospholipase concentration over a 14-fold range from 30 to 420 ng/ml. This linear relationship did not exist at higher phospholipase levels, probably due to the micellar nature of the phospholipid. Since this assay can readily detect as little as 17 ng/ml of phospholipase A₂ (Naja naja venom) and is insensitive to most potential interfering materials, it should be useful in a variety of applications.     

Presence of prostaglandins E2 and A2 in canine gastric secretions

The presence of prostaglandins (PGs) was determined in gastric juice obtained from 3 conscious dogs, provided with a chronic gastric fistula. Outputs of acid (mequiv min^?1) and PGs (pg min^?1) were measured in gastric secretions stimulated by pentagastrin (100 or 200 ng kg^?1min^?1). Prostaglandin activity was estimated, after extraction and thin layer chromatography, by radioimmuno-assay of the PGB formed by treatment with alkali. Tritiated PGs were added to gastric juice for the purpose of correcting for PGs recovery. Using this method, the minimum mass of PGB which could be satisfactorily distinguished from zero was 25 pg. Prostaglandins A₂ and E₂ were present in pentagastrin-activated gastric secretions and averaged (mean ± SE, n = 8) 200.7 ± 18.1 and 260.1 ± 18.0 pg min^?1 respectively. The identity of PGA₂ and PGE₂ was confirmed by gas liquid chromatography combined with mass spectrometry. The amount of PGE₂ converted to PGA₂ during extraction, separation and conversion procedures was estimated from the amount of [³H] PGA₂ found when only [³H] PGE₂ had been added to a sample of gastric juice and averaged 14.5% ± 2.0. Our preliminary results support the possibility that PGE₂ and PGA₂ may be of physiological importance in the regulation of canine gastric secretions.     

N49 phospholipase A2, a unique subgroup of snake venom group II phospholipase A2

A novel phospholipase A₂ (PLA₂) with Asn at its site 49 was purified from the snake venom of Protobothrops mucrosquamatus by using SP-Sephadex C25, Superdex 75, Heparin-Sepharose (FF) and HPLC reverse-phage C₁₈ chromatography and designated as TM-N49. It showed a molecular mass of 13.875 kDa on MALDI-TOF. TM-N49 does not possess enzymatic, hemolytic and hemorrhagic activities. It fails to induce platelet aggregation by itself, and does not inhibit the platelet aggregation induced by ADP. However, it exhibits potent myotoxic activity causing inflammatory cell infiltration, severe myoedema, myonecrosis and myolysis in the gastrocnemius muscles of BALB/c mice. Phylogenetic analysis found that that TM-N49 combined with two phospholipase A₂s from Trimeresurus stejnegeri, TsR6 and CTs-R6 cluster into one group. Structural and functional analysis indicated that these phospholipase A₂s are distinct from the other subgroups (D49 PLA₂, S49 PLA₂ and K49 PLA₂) and represent a unique subgroup of snake venom group II PLA₂, named N49 PLA₂ subgroup.     

Carbocyclic thromboxane A2: Aggrevation of myocardial ischemia by a new synthetic thromboxane A2 analog

$\text{In vitro}$ experiments indicate that thromboxane A₂ (TA₂) is a potent platelet aggregator and vascular constrictor. However, it is unclear what roles these specific actions may contribute in the pathophysiology of myocardial ischemia. Carbocyclic thromboxane A₂ (CTA₂), a TA₂ analog, constricts isolated perfused cat coronary arteries, but does not aggregate platelets, and thus appeared useful to clarify these separate actions of TA₂. In anesthetized cats, radioactive labeled microspheres were injected into the left atrium for measurement of cardiac output and tissue blood flows. Compared to control measurements, CTA₂ infusion (4.8 μg·kg^?1·min^?1 to 10 min) significantly decreased cardiac output from 347 ± 16 ml·min^?1 to 248 ± 16 ml·min^?1 (p<0.025). Furthermore, V7 CTA₂ also significantly reduced blood flow to the left ventricle by 33 ± 7%, but did not alter heart rate or MABP in the intact cat. In cats subjected to left anterior descending coronary artery occlusion, infusion of CTA₂ (1 μg·min^?1 for 120 minutes) 30 min after ligation resulted in a significantly reduced myocardial cellular integrity as measured by myocardial creatine kinase activity (p<0.01) or percent bound myocardial cathepsin D (p<0.01). Thus, these data suggest that activation of vascular thromboxane receptors as well as direct cellular damage may play a role in the pathophysiology of myocardial ischemia.     

Biological activities of new gibberellins A30-A35 and A35 glucoside

The plant growth-promoting activities of new gibberellins, GA₃₀, GA₃₀, GA₃₂, GA₃₃, GA₃₄, GA₃₅ and GA₃₅ glucoside were evaluated in seven bioassays. In general GA₃₀, GA₃₀, and GA₃₅ showed fairly high biological activities, whilst GA₃₃, GA₃₄ and GA₃₅ glucoside were almost inactive. GA₃₂ was highly active, behaving similarly to GA₃. It is suggested that the C-11β and C-12α hydroxyl groups have little influence on growth-promoting activity, although the C-12α hydroxyl group reduces activity in the cucumber hypocotyl assay.     

Prostaglandin E2 and muscle protein turnover inPseudomonas aeruginosa sepsis

Rats were injected intraperitoneally withPseudomonas aeruginosa (septic group) or sterile 0.9% NaCl (controls). Soleus muscles were excised 7 h later, and muscle prostaglandin E₂ release and tyrosine release were measured in vitro. Muscles of septic rats exhibited 226–326% higher release of prostaglandin E₂ and 54–84% higher net proteolysis than muscles of controls. Inclusion of aspirin or indomethacin in the incubation medium almost completely inhibited prostaglandin E₂ production, but had no effect on net proteolysis in muscles from either group. Inclusion of cycloheximide, a protein synthesis inhibitor, increased tyrosine release of control muscles by 42%, whereas no statistically significant increase was observed in muscles from infected rats. However, total proteolytic rate, indexed by tyrosine release in the presence of cycloheximide, was 22% higher in muscles of septic rats compared to that of control animals. Concomitantly, inclusion of cycloheximide inhibited prostaglandin E₂ release by muscles of infected rats by 91% and that of controls by 65%. It is concluded that (a) muscles of septic animals exhibit a pronounced stimulation of prostaglandin E₂ release and net proteolysis, combined with a small increase in total proteolytic rate, (b) the stimulation of net proteolysis is mainly due to inhibition of protein synthesis, (c) the increases in net and total proteolysis appear to be independent of prostaglandin E₂ production, (d) cycloheximide has a previously unrecognized inhibitory effect on muscle prostaglandin E₂ production.     

Prostaglandin endoperoxides and thromboxane A2 in thrombus formation in the hamster cheek pouch in vivo

Electrical stimulation in the presence of ADP of arterioles of the hamster cheek pouch caused endothelial damage and white thrombus formation. The thrombus formation was inhibited by cyclo-oxygenase inhibitors aspirin and sulphinpyrazone and its thioether derivative G 35671. Thromboxane synthetase inhibitors N-(7-carboxyheptyl) imidazole and butylimidazole failed to inhibit thrombus formation, although in the same doses both compounds inhibited serum levels of thromboxane. These results indicate that thromboxane is not important in thrombus formation in the hamster, but that prostaglandin endoperoxides are more significant. However, it is possible that the inhibition of white thrombus formation by aspirin, sulphinpyrazone and G 25671 may be mediated by a different mechanism altogether.