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P Needleman

Publications and source records attributed to P Needleman.

At least 145 records · Page 8Linked to original sources
PubMed1984

Atriopeptins: a family of potent biologically active peptides derived from mammalian atria.

Extracts of rat atria are potent stimulators of sodium and urine excretion, and relax vascular and intestinal smooth muscle preparations. The structures of six biologically active peptides obtained from atrial extracts are reported here. Ion exchange chromatography of a low molecular weight fraction obtained by gel filtration of atrial extracts produced two natriuretic fractions: the first induced relaxation of intestinal smooth muscle strips only, whereas the second also relaxed vascular strips as well. From the first fraction four pure biologically active peptides obtained by reverse phase HPLC have been sequenced: the 21 amino acid peptide, designated atriopeptin I, and three homologs (des- ser1 -, des- ser1 -ser2-, and des- ser21 - atriopeptin I). From the second fraction two pure biologically active peptides were obtained, which had C-terminal extensions of atriopeptin I: atriopeptins II (23 amino acid residues) and III (24 residues), having respectively phe-arg and phe-arg-tyr C-termini. These results suggest that this family of six peptides, sharing the same 17 membered ring formed by an internal cystine disulfide, is derived from a common high molecular weight precursor.

Amino Acid Sequence↗
PubMed1984

Kallikrein activation of a high molecular weight atrial peptide.

Mammalian atrial extracts contain bioactive peptides that exert profound effects upon renal function and isolated smooth muscle preparations. Gel filtration chromatography of rat atrial extract separates the activity into two peaks having apparent molecular weights of 20,000 to 30,000 and less than 10,000. Mild proteolytic treatment (trypsin 1 U/ml) of the high molecular weight fraction enhances the smooth muscle relaxant activity of this fraction and concomitantly reduces the apparent molecular weight of this fraction to less than 10,000. In this report we show that urinary and submaxillary kallikrein enhances the activity of rat atrial extracts in a similar fashion. Pretreatment of the high molecular weight fraction with either kallikrein (1 microgram/ml) enhances the smooth muscle relaxant activity of this fraction. Similar treatment of the low molecular weight fraction had no effect. The enhancement of the bioactivity of the high molecular weight substance(s) by the kallikreins was abolished by aprotinin but was unaffected by soybean trypsin inhibitor. These results suggest that exogenous addition of tissue kallikrein activates a high molecular weight peptide by limited proteolysis. Analysis of the kallikrein-treated high molecular weight peptide fraction by gel filtration indicates that the biological activity comigrates with the low molecular weight peptides present in the original atrial extract.

Animals↗
PubMed1984

Purification and sequence analysis of bioactive atrial peptides (atriopeptins).

Mammalian cardiac atria have several biologically active peptides that exert profound effects on sodium excretion, urine volume, and smooth muscle tone. In the present study two such peptides of low molecular weight were purified and separated from each other on the basis of differences in charge, hydrophobicity, and biological profile. The first peptide, designated atriopeptin I, exhibits natriuretic and diuretic activity and selectivity relaxes intestinal smooth muscle but not vascular smooth muscle strips. The second peptide, atriopeptin II, is a potent natriuretic and diuretic that relaxes both intestinal and vascular strips. Sequence analysis of atriopeptin I indicates that it is composed of 21 amino acids, of which serine and glycine residues predominate. The amino terminal sequence of atriopeptin II up to residue 21 is the same as that of atriopeptin I, with the addition of the Phe-Arg extension at the carboxyl terminus. Both peptides appear to be derived from a common high molecular weight precursor (designated atriopeptigen); their biological selectivity and potency may be determined by the site of carboxyl terminal cleavage.

Amino Acid Sequence↗
PubMed1984

Cellular interactions and exaggerated arachidonic acid metabolism in rabbit renal injury.

Cell cultures from explants of the rabbit hydronephrotic kidney (HNK) cortex consisted of fibroblasts and an esterase-positive cell that phagocytizes zymosan. Cortical cell cultures from the contralateral kidney (CLK) contained only the fibroblast. The HNK cultures exhibited an endotoxin-induced prostaglandin (PG) E2 (three - fourfold) release indicative of the presence of macrophages, whereas no response was observed in the CLK cultures. At bradykinin concentrations as low as 10(-9)M there was a 20-fold stimulation of PGE2 from the HNK cultures and a sevenfold stimulation in the CLK cultures. The heterogeneous population of cells in the HNK cultures was separated using a mild trypsin treatment which permits passage of only the fibroblasts. The HNK-passaged cultures contained no phagocytic cells and did not release PGE2 in response to endotoxin. The passaged HNK cultures released less PGE2 in response to bradykinin as compared to primary cultures and had a decreased cyclooxygenase activity as determined by exogenous arachidonic acid conversion to PGE2. Conditioned media from adherent rabbit peripheral blood mononuclear cells stimulated basal PGE2 production (two - threefold) from both the HNK and CLK cultures. These findings demonstrated the similarity of the PGE2 production by cultured HNK cortical cells as compared to the ex vivo perfused HNK.

Animals↗
PubMed1984

Renal arachidonic acid metabolism and cellular changes in the rabbit renal vein constricted kidney: inflammation as a common process in renal injury models.

The process of renal inflammation was examined using the partial renal vein constricted rabbit kidney ( RVC ) as a model. Forty eight hours of partial renal vein constriction in the rabbit was associated with an increase in prostaglandin (PG) and thromboxane (Tx) production. The ex vivo perfused RVC kidney showed an enhanced time-dependent increase in PG and Tx production in response to bradykinin stimulation when compared with the unaltered contralateral ( CLK ) or normal kidney. At 6 hrs of perfusion bradykinin stimulation released 2950 +/- 350 ng PGE2, 61 +/- 15 ng TxB2 from the RVC , and 225 +/- 85 ng PGE2 and undetectable TxB2 from the CLK . Histological examination of the RVC cortex showed an increase in fibroblast-like cells, a modest increase in the interstitial space and an appearance of macrophages and lymphocytes not seen in the normal or CLK . Endotoxin has been reported to stimulate macrophages in culture to produce PGE2 and TxB2. Endotoxin (100 ng) stimulation of the perfused RVC kidney caused an immediate, followed by a chronically increasing, release of PGs and Tx. Two hours after endotoxin injection 50 ml of effluent from the RVC contained 1450 +/- 107 ng PGE2 and 15.0 +/- 4.5 ng TxB2. Other animals of renal inflammation (e.g., the hydronephrotic kidney, chronic glomerulonephritis) also show the histological appearance of macrophages. In addition, hydronephrotic kidneys undergo fibroblast proliferation and changes in arachidonic acid metabolism similar to that we observed in the RVC . This work suggests that the inflammatory process (mononuclear cell infiltration, fibroblast-like cell proliferation, and accompanying changes in arachidonate metabolism is common among different forms of renal injury.

Animals↗
PubMed1984

Arachidonic acid metabolism by rabbit fetal membranes of various gestational ages.

The ability of rabbit fetal membranes to convert arachidonic acid to both lipoxygenase and cyclooxygenase products was studied by separation and identification of products derived from incubations of 1-14C-arachidonate with subcellular fractions obtained by differential centrifugation of tissue homogenates. Both amnion and splanchnopleure (the chorion-equivalent of the rabbit) produced a mixture of 11-, 12-, and 15-hydroxyeicosatetraenoic acids when stimulated by calcium ions; these products were produced in greater quantity in middle pregnancy (20-22d) than later (28-30d). Cyclooxygenase products included PGD2, PGE2, TxB2 and PGF2 alpha, all of which were made more actively in late pregnancy than the middle in both amnion (which was more active) and chorion-equivalent. These data suggest that arachidonate metabolism by rabbit fetal membranes in middle pregnancy is directed primarily toward production of monohydroxy fatty acids, but that as pregnancy nears term, the PG-producing enzymes are induced, preparing the uterine smooth muscle for parturition.

Amnion↗
PubMed1984

Macrophage-dependent arachidonate metabolism in hydronephrosis.

Unilateral ureteral obstruction in rabbits leads to an influx of macrophages into the kidney, a proliferation of interstitial cells, and an increase in arachidonic acid metabolism. The role of the macrophage in the metabolic changes of hydronephrosis was investigated by using endotoxin and nitrogen mustard. The in vivo administration of endotoxin, a macrophage agonist, 1 hour before perfusion of the hydronephrotic kidney markedly enhanced (fourfold to tenfold) the peptide-stimulated arachidonic acid metabolism of the perfused kidney. Nitrogen mustard made animals leukopenic and prevented the influx of macrophages into the hydronephrotic kidney. The peptide-stimulated arachidonic acid metabolism of these kidneys was suppressed, and no enhancement was seen with in vivo endotoxin administration. The macrophage thus appears to be an essential determinant of the enhanced arachidonic acid metabolism seen in experimental hydronephrosis. An inhibitory effect of prostaglandin E2 on macrophage function in this model of renal inflammation was also demonstrated. Hydronephrotic animals were given aspirin during the period of unilateral ureteral obstruction to prevent in vivo prostaglandin E2 production. In the perfused hydronephrotic kidney, the peptide-stimulated arachidonic acid metabolism, which appears to be a marker of macrophage function in this model, was enhanced by aspirin treatment.

Animals↗
PubMed1984

Proteolytic activation of a bioactive cardiac peptide by in vitro trypsin cleavage.

Mammalian cardiac atria possess several unidentified biologically active peptides. Fractionation of rat atrial extracts by gel filtration chromatography revealed two major fractions [apparent molecular weights of 20,000-30,000 (peak I) and less than 10,000 (peak II)], both of which were potent natriuretic agents (eliciting a 25-fold increase in sodium excretion) and smooth muscle relaxants. Vigorous treatment with trypsin (100 units/ml at 37 degrees C for 15 min) of both fractions abolished all biological activity. Further purification of the lower molecular weight fraction (peak II) by ion-exchange chromatography indicated two subfractions that possessed potent natriuretic activity and that preferentially relaxed either intestinal (designated peak IIA) or vascular (peak IIB) smooth muscle assay tissues. The similarity of the biological effect of the high (peak I) and low (peak II) molecular weight peptides led us to test the possibility of precursor-product relationship. Mild proteolytic treatment of the high molecular weight peptide with trypsin (1 unit/ml at room temperature) markedly enhanced the smooth muscle relaxant activity. Subsequent analysis of the trypsin (1 unit/ml)-treated high molecular weight peptide (peak I) by gel filtration and ion-exchange chromatography revealed that the peptide now resembled the low molecular weight peptides (peaks IIA and IIB) present in the original atrial extract. These data suggest that the cardiac atria contain a relatively inactive (smooth muscle relaxant) high molecular weight peptide and suggest that biologically active low molecular weight peptides can subsequently be generated by proteolytic cleavage.

Animals↗
PubMed1984

An atrial peptide is a potent renal vasodilator substance.

Renal intra-arterial administration of rat atrial extracts elicits a concentration dependent renal vasodilation (independent of prostaglandin or dopamine release) in anesthetized rats. The atrial extracts do not alter skeletal musculature (hindlimb) vascular resistance or systemic arterial blood pressure. The high molecular weight peptide fraction of atrial extracts obtained by gel filtration, reduces renal resistance intra-arterially only after proteolytic activation (in vitro) or following intravenous (i.e., systemic in vivo activation) administration. The low molecular weight peptide fraction of the atrial extract which is active intra-arterially as a renal vasodilator has been further purified to yield two major peptides. The 21 amino acid peptide, designated atriopeptin I, was previously demonstrated to be natriuretic and to relax intestinal but not vascular smooth muscle strips. This peptide exerted little or no intra-arterial effect on renal resistance. The 23 amino acid peptide (the phenylalanine-arginine C terminal extension of atriopeptin I), designated atriopeptin II, was natriuretic and spasmolytic (in vitro) on both intestinal and vascular strips and was a potent renal vasodilator in vivo. Thus, the renal vasodilator activity present in cardiac atrial extracts appears to derive from a proteolytic process which selectively generates the 23 amino acid peptide, atriopeptin II. Further cleavage with the loss of phenylalanine-arginine C-terminal, as occurs with atriopeptin I, markedly suppresses the renal vasodilation.

Animals↗
PubMed1984

Mechanism of enhanced fibroblast arachidonic acid metabolism by mononuclear cell factor.

Chronic inflammation is associated with an infiltration of mononuclear cells, fibroblast proliferation, and elevated levels of prostaglandin (PG) E2. Mononuclear cell conditioned factor (MNCF) medium (5%) stimulated a 100-fold increase in basal human dermal fibroblast PGE2 release over 48 h as compared with fibroblasts that were incubated with control medium (conditioned medium prepared without cells). The MNCF-induced PGE2 production was suppressed by protein synthesis inhibitors. Fibroblasts pretreated with control medium released PGE2 only modestly in response to 1 nM bradykinin for 1 h (basal, 50 +/- 7 pg PGE2/micrograms protein; stimulated, 104 +/- 12 pg PGE2/micrograms protein), whereas cells that had been pretreated with MNCF showed a greatly facilitated bradykinin-induced release of PGE2. (basal, 297 +/- 59 pg PGE2/micrograms protein; stimulated, 866 +/- 85 pg PGE2/micrograms protein). The exaggerated agonist response is not specific for bradykinin because platelet-derived growth factor elicits a similar response. Exogenous arachidonic acid conversion to PGE2 was also facilitated (two- to threefold) by MNCF pretreatment as compared with control. Both the enhanced agonist-stimulated and exogenous arachidonic acid-induced PGE2 release from the MNCF pretreated cells were inhibited by actinomyin D or cycloheximide. A kinetic study of microsomal cyclooxygenase prepared from fibroblasts pretreated with MNCF showed a threefold increase in the maximum velocity (Vmax) but the same Michaelis constant (Km) as control-treated cells. This augmented arachidonic acid metabolism and subsequent enhanced PGE2 production may play an important role in macrophage-fibroblast interactions at sites of inflammation.

Arachidonic Acid↗
PubMed1984

Atriopeptins: bioactive peptides derived from mammalian cardiac atria.

Mammalian atria possess bioactive peptides that are natriuretic-diuretic and potent relaxants of vascular and nonvascular smooth muscle. Characterization of the biological activity of rat atrial extracts indicates two major peaks, having apparent molecular weight of 20,000-30,000 (atriopeptigen) and less than 10,000 (atriopeptins). The amino acid sequence of atriopeptins I, II and III have been determined, and it has been found that their structures are only slightly different. Atriopeptin I (twenty-one amino acid residues); ser-ser-cys-phe-gly-gly-arg-ile-asp-arg-ile-gly-ala-gln-ser-gly-leu-gly- cys- asn-ser) relaxes intestinal but not vascular smooth muscle strips, and is natriuretic. Atriopeptins II and III (23 and 24 residues; the 21-sequence of I with the addition of phe-arg or phe-arg-tyr at the C-terminus, respectively) relax intestinal and vascular smooth muscle strips and are potent natriuretics. Since atriopeptigen and the atriopeptins exhibit similar biological effects the possibility of a precursor-product relationship was tested. Mild proteolytic digestion (1IU/ml trypsin) of atriopeptigen activates this peptide and reduces its apparent molecular weight. Examination of whether the atria of Krebs perfused isolated hearts released the bioactive atrial peptides revealed the presence in the cardiac effluent of a trypsin-labile substance that was natriuretic-diuretic and a smooth muscle relaxant. To determine which form of the atrial peptide (e.g. atriopeptigen or atriopeptin) is released by the atria the cardiac effluents were concentrated and partially purified. The cardiac effluent contained a substance(s) similar to atriopeptin, but did not appear to possess the less-active high molecular weight peptide, atriopeptigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Pharmacological manipulation of canine cyclooxygenase and thromboxane synthetase in vivo: differential renal and platelet recovery rates.

Aspirin (acetylsalicylic acid) was chronically infused i.v. into dogs at a low dose (0.1 mg/kg/hr) using a surgically implanted Alzet osmotic pump. The time course for inhibition of cyclooxygenase and for its recovery after removal of the pump were followed in washed platelet preparations and in kidney medulla microsomes using [14C]arachidonic acid metabolism. Chronic acetylsalicylic acid infusion inhibited platelet cyclooxygenase 60% after 1 day of treatment and 95% after 3 days. Recovery of platelet arachidonate metabolism after removal of the osmotic pump was very rapid (T 1/2 = 0.9 days). Renal cyclooxygenase was also completely inhibited after 3 days but showed a slower recovery rate (T 1/2 = 2.8 days). Therefore, canine platelets, unlike human platelets, recover more rapidly from acetylsalicylic acid inhibition than do the kidneys. We have also established a whole blood method to study the effective time course of thromboxane synthetase inhibitors. The relative potencies for inhibiting platelet thromboxane synthetase after i.v. bolus administration of the agents studied was OKY-1581 greater than OKY-046 = dazoxiben much greater than Ro 22-7878. The effective half-life of OKY-1581, OKY-046 and dazoxiben was 2 hr while the half-life of Ro 22-7878 was 0.5 hr.

Animals↗
PubMed1983

Bioactive cardiac substances: potent vasorelaxant activity in mammalian atria.

Mammalian atrial extracts possess natriuretic and diuretic activity. In experiments reported here it was found that atrial, but not ventricular, extract also causes relaxation of isolated vascular and nonvascular smooth muscle preparations. The smooth muscle relaxant activity of atrial extract was heat-stable and concentration-dependent and could be destroyed with protease. Rabbit aortic and chick rectum strips were used for the detection of atrial biological activity. The atrial activity was separated by column chromatography into two peaks having apparent molecular weights of 20,000 to 30,000 and less than 10,000. The atrial substance that copurified with the smooth muscle relaxant activity in both peaks caused natriuresis when injected into conscious rats. It appears that atria possess at least two peptides that elicit smooth muscle relaxation and natriuresis, suggesting an endogenous system of fluid volume regulation.

Animals↗
PubMed1983

Measurement of prostaglandin biosynthetic capacity in discrete areas of the rabbit hippocampal formation.

Assay conditions sensitive enough to measure prostaglandin (PG) biosynthetic capacity in discrete brain areas have been developed. Serial sections of the rabbit hippocampal formation were dissected from the brain, frozen, and 16 micron sections were cut and freeze dried. The assay was performed with 40-200 micrograms dry weight of tissue in a 30 microliter incubation volume containing high specific activity arachidonic acid. The whole hippocampal formation slice or its subdivisions (subiculum, dentate gyrus, and hippocampus) when assayed individually demonstrated the ability to produce approximately 30-50 pmol/mg dry weight PGF2 alpha, PGE2, and lesser amounts of PGD2 (in a ratio of 1:0.8:0.3). A modest yet significant increase in PGE2 production was measured in the dentate gyrus when compared to PGE2 formation in the subiculum or hippocampus. An intact PGE2 isomerase was confirmed in the hippocampal formation slice by incubations with PGH2 endoperoxide. These results demonstrate that quantitative histochemical techniques can be used to measure PG metabolism in microscopic regions of brain.

Animals↗
PubMed1983

Prostaglandin production by the pregnant and non-pregnant rabbit uterus.

We have studied the prostaglandin synthesis of the pregnant and non-pregnant rabbit uterus in a microsomal membrane preparation, and in an ex vivo perfused uterus preparation which retains agonist stimulated prostaglandin production. In both the microsomal and isolated perfused system, prostacyclin was the major arachidonic acid metabolite produced; PGE2 was also produced in substantial quantities while TxB2 and PGF2 alpha were not detectable. Moreover, oxytocin was a specific stimulus of PGE2 release. The steroid hormone milieu influenced the level of agonist stimulated prostaglandin release; in general, ovariectomized, estrogen treated animals were more responsive to agonist stimulation than those treated with estrogen followed by progesterone. The microsomal studies indicated that the pregnant animal had a greatly enhanced capacity to metabolize arachidonic acid when compared with the non-pregnant animal. However, this was not reflected in the ability of agonists to stimulate prostaglandin release in the ex vivo perfused preparation.

Animals↗
PubMed1983

Effects of prostacyclin on short-circuit current and water flow in the toad urinary bladder.

The effects of prostaglandins of the E series on sodium and water transport have been studied extensively. PGE2 has been shown to inhibit the increase in osmotic water flow produced by vasopressin and to stimulate short-circuit current (SCC) in the toad bladder. On the other hand, the effects of prostacyclin (PGI2), an arachidonic acid product, on sodium and water transport have not been extensively evaluated. The present studies describe the effects of PGI2 on basal and vasopressin-stimulated osmotic water flow and on SCC in the urinary bladder of the toad. Studies were performed in the absence or presence of indomethacin. PGI2 in the absence of indomethacin had no effect on basal or vasopressin-stimulated osmotic water flow. When indomethacin was present, thereby eliminating intrinsic prostaglandin biosynthesis, PGI2 inhibited basal but not vasopressin-stimulated osmotic water flow. PGI2 increased SCC in the presence or absence of indomethacin. 6-keto PGF1 alpha, the stable metabolite of PGI2, had no effect on SCC. PGI2 stimulated cAMP production in isolated toad bladder epithelial cells. 2',5'-Dideoxyadenosine, an inhibitor of cAMP production, blocked the increase in SCC produced by PGI2, suggesting that the effects of this compound on SCC are mediated via cAMP.

1-Methyl-3-isobutylxanthine↗