Analysis of the regulation of phosphatidylinositol-4,5-bisphosphate synthesis by arachidonic acid in exocrine pancreas

In pancreatic acinar cells prelabeled with either 32Pi or myo-[3H]inositol, arachidonic acid (10-50 microM) rapidly decreased the steady-state levels of [32P]phosphatidylinositol 4',5'-bisphosphate [( 32P]PtdIns4,5P2) and inhibited carbachol-stimulated accumulation of [3H]inositol trisphosphate [( 3H]InsP3). Both actions of arachidonic acid were rapidly reversed by bovine serum albumin (BSA). Indomethacin and nordihydoguaiaretic acid failed to block the inhibitory effects of arachidonic acid on [32P]PtdIns4,5P2 levels. Arachidonic acid (10-50 microM) also caused a prompt depletion of cellular ATP which was rapidly reversed by BSA. The ATP-depleting action of arachidonate paralleled in terms of concentration dependence and time course its inhibitory effects on [32P]PtdIns4,5P2 and [3H]InsP3 levels. Exposure of acinar cells to 50 microM arachidonic acid produced an increase in oxygen consumption which exceeded that elicited by either carbachol or ionomycin. Arachidonic acid (10-50 microM) also caused a concentration-dependent rise in cytosolic Ca2+, which was partially obtunded by Ca2+ deprivation. A proposed mechanism involving arachidonic acid as a negative feedback regulator of polyphosphoinositide turnover in exocrine pancreas is discussed.

Association between recurrent spontaneous abortions and circulating IgG antibodies to sperm tails in women

The isotype and regional specificity of antisperm antibodies in the circulation of women with recurrent spontaneous abortions was examined. There was a statistically significant association (P less than 0.005) between the presence of IgG tail-directed antisperm antibodies and a history of unexplained recurrent spontaneous abortion. These antibodies were detected in 36.4% of 44 women with recurrent abortions and 14.6% of 616 female partners of infertile marriages. In contrast, no differences in IgG sperm head-directed antibodies or in IgA and IgM antisperm antibodies were observed between the two groups. Husbands of women in the miscarriage or infertile groups had similar semen evaluations. Antisperm antibodies may be a marker for defective immunosuppression in women with recurrent miscarriages. Alternatively, exposure of sperm-sensitized pregnant women to sperm may activate the maternal immune system to respond to paternal antigens present on the embryo.

Relationship between delta-9-tetrahydrocannabinol-induced arachidonic acid release and secretagogue-evoked phosphoinositide breakdown and Ca2+ mobilization of exocrine pancreas

We have previously shown that addition of exogenous arachidonic acid to pancreatic acinar cells inhibits the incorporation of myo-[3H]inositol into membrane phosphoinositides and causes a reduction in the steady state levels of [32P]phosphatidylinositol-4,5-bisphosphate (PtdIns4,5P2). In the present study, delta-9-tetrahydrocannabinol (THC) was utilized to raise endogenous levels of arachidonic acid. In acinar cells simultaneously prelabeled with [3H]arachidonic acid and [32P]Pi, THC (1-20 microM) produced a concentration-dependent increase in free [3H]arachidonic acid release and a reduction in the steady state levels of [32P]Ptd-Ins4,5P2. THC (1-20 microM) also caused a concentration-dependent inhibition of myo-[3H]inositol trisphosphate accumulation, cytoplasmic Ca2+ level, and amylase secretion elicited by 0.1 microM caerulein. The findings that THC (20 microM) was unable to inhibit either the rise in [Ca2+]i elicited by ionomycin, or the secretory response to phorbol myristic acid or ionomycin, indicate that THC exerts a selective inhibitory effect on the phosphoinositide messenger system. These results support the postulate that endogenous arachidonic acid serves as a negative feedback regulator of phosphoinositide turnover in exocrine pancreas.

The effects of fatty acids on phosphoinositide synthesis and myo-inositol accumulation in exocrine pancreas

The effects of arachidonic acid (20:4) on phosphoinositide turnover were examined in rat pancreatic acinar cells prelabeled with myo-[3H]inositol. Arachidonic acid (50 microM) increased the accumulation of myo-[3H]inositol, but not that of [3H]inositol monophosphate, [3H]inositol bisphosphate, or [3H]inositol trisphosphate. By contrast, 10 microM carbamoylcholine increased the accumulation of all four compounds. A combination of arachidonic acid plus carbamoylcholine caused a selective and marked accumulation of myo-[3H]inositol, which was abolished by 10 mM LiCl. Arachidonic acid (10-100 microM) produced a concentration-dependent inhibition of myo-[3H]inositol incorporation into phosphoinositides and markedly depressed carbamoylcholine-induced increases in myo-[3H]inositol incorporation into inositol phospholipids. Several other unsaturated and saturated fatty acids failed to elicit a synergistic response with carbamoylcholine in stimulating myo-[3H]inositol accumulation and did not retard the incorporation of myo-[3H]inositol into phosphoinositides. The fact that eicosapentaenoic acid (20:5), but not arachidic acid (20:0), mimicked the depressant effect of arachidonate on phosphoinositide labeling suggests that the degree of unsaturation of the fatty acid, rather than chain length, is important for inhibition of phosphoinositide synthesis. The arachidonate-induced decrease in myo-[3H]inositol incorporation was accompanied by a reduction in the steady state level of [32P]phosphatidylinositol 4,5-bisphosphate. The mass of arachidonic acid liberated in response to carbamoylcholine was measured by gas chromatography-mass spectrometry, and the time course of stimulated arachidonate accumulation paralleled that of inositol phosphate accumulation and amylase release. These observations suggest that in exocrine pancreas, endogenous arachidonic acid serves as a negative feedback regulator of phosphoinositide turnover.

Fatal Salmonella septicemia after platelet transfusion

A thrombocytopenic, leukopenic patient with multiple myeloma who was given 7 units of platelets died 6 days later from complications of Salmonella heidelberg septicemia. A platelet donor who was asymptomatic at the time of donation had group B Salmonella on stool culture. His clinical history and the results of serologic studies and stool culture were consistent with a mild Salmonella gastroenteritis 5 days before donation. Antibiotic sensitivity patterns and plasmid profiles indicated that the organism (S. heidelberg) isolated from the donor's stool was identical to that isolated from the patient's blood and from the platelet bags. It is believed that low-grade, asymptomatic bacteremia in the donor was the source of infection in the recipient. Food and Drug Administration records contain reports of six septic deaths due to platelet transfusions since 1979, compared with none in the preceding 4 years. Increased use of platelet products and the standard practice of storage at room temperature may contribute to the risk of sepsis after platelet transfusion, particularly in immunocompromised patients.

Characteristics of P2 (nucleotide) receptors mediating contraction and relaxation of rat aortic strips: possible physiological relevance

ATP and ADP relaxed rat aortic strips precontracted with noradrenaline by an endothelium-dependent mechanism. 5'-AMP was much less potent and adenosine was essentially without effect. The metabolically stable analogues alpha,beta-methylene ATP and beta,gamma-methylene ATP further contracted precontracted aorta. Aortic strips, which had not been precontracted with noradrenaline, contracted when exposed to either ATP or alpha,beta-methylene ATP, the latter nucleotide being much more potent than the former. Removal of the endothelium increased the contractions to ATP. ANAPP3 had no effect on the endothelium-dependent relaxations produced by ATP but it antagonized contractions produced by alpha,beta-methylene ATP. These results provide evidence for the possible existence of two subtypes of P2 receptors in rat aorta; a P2 receptor mediating contraction residing on smooth muscle which can be antagonized by ANAPP3 and where alpha,beta-methylene ATP is more potent than ATP, and a P2 receptor mediating relaxation located on the endothelium which cannot be antagonized by ANAPP3 and where ATP is much more potent than alpha,beta-methylene ATP.

Mechanism and metabolic disposition of verapamil-evoked overflow of radioactivity from isolated atria preloaded with [3H]norepinephrine

In this study the mechanism and metabolic profile of verapamil-evoked release of radioactivity was investigated in the rat isolated atria preloaded with [3H]norepinephrine [( 3H]NE). Verapamil (10(-7) to 10(-3) M) caused a dose-related increase in the outflow (or the fractional release) of 3H. The fractional 3H-release produced by verapamil was reduced markedly in tissues which had been preloaded with [3H]NE in the presence of cocaine (10 microM) or after pretreatment of animals with reserpine (5 mg/kg i.p., 24 hr before sacrifice). Verapamil-evoked fractional 3H-release was unchanged in the presence of tetrodotoxin (5 X 10(-6) M) or in Ca++-free Krebs' medium containing 2 mM ethylene glycol bis(beta-aminoethyl ether)N,N'-tetraacetic acid. Whereas greater than 90% of tissue 3H-content consisted of unchanged [3H]NE, 60 to 75% of the spontaneous outflow and the verapamil-evoked overflow consisted of [3H]-3,4-dihydroxyphenylglycol and 2 to 10% was unchanged [3H]NE. When both cocaine (10 microM) and hydrocortisone (28 microM) (uptake-1 and uptake-2 blockers, respectively) were present, although the spontaneous outflow, as well as verapamil-evoked overflow, of radioactivity was increased, the metabolic profiles remained essentially unchanged. The addition of pargyline (10 microM), a monoamine oxidase inhibitor, in addition to the uptake-1 and uptake-2 blockers to the Krebs' solution significantly depressed both the spontaneous outflow and verapamil-evoked overflow of 3H; the verapamil-evoked overflow under this condition, however, consisted of unchanged [3H]NE (greater than 90%).(ABSTRACT TRUNCATED AT 250 WORDS)

Antagonism by the tetramine disulfide benextramine of the inhibitory effects mediated by prejunctional alpha 2-adrenoceptors and by postjunctional histamine H2 receptors in the mouse vas deferens

The actions of benextramine, which blocks postjunctional alpha-adrenoceptors noncompetitively and irreversibly (non-equilibrium type) on prejunctional alpha-adrenoceptors (alpha 2) and postjunctional histamine H2 receptors, were studied in the mouse vas deferens, using clonidine and histamine, respectively, as the agonists. Both agonists caused a dose-related inhibition of the electrically evoked twitch responses, an inhibition that their respective antagonists (yohimbine or phentolamine, and cimetidine) antagonized competitively. Benextramine, however, antagonized the agonists' inhibitory effect noncompetitively. At the concentrations used, while clonidine or yohimbine and phentolamine protected the prejunctional alpha-adrenoceptors (alpha 2) against the benextramine noncompetitive blockade, histamine or cimetidine failed to protect the histamine H2 receptor against benextramine blockade. Therefore, although benextramine acts prejunctionally to block the alpha 2-adrenoceptors in the mouse vas deferens either by interacting directly with the same site as clonidine or yohimbine and phentolamine, or allosterically with a site close to it, it does not appear to act irreversibly, either directly or allosterically, with the same site as histamine or cimetidine. The mechanism by which benextramine blocks the histamine-induced inhibition of the electrically evoked twitch response in the mouse vas deferens remains to be established.

Depletion of cardiac noradrenaline stores by the calcium-channel blocker D-600

The actions of the calcium-channel blocker D-600 on cardiac noradrenaline stores were investigated by giving rats the drug systemically and then using a high-performance liquid chromatograph equipped with an electrochemical detector to determine the noradrenaline content of their hearts. A single 5-mg/kg dose of D-600 caused a significant depletion of noradrenaline content of the ventricles (approximately 31%) but not of the auricles. However, when multiple doses of D-600 were given at 12-h intervals, the depletion of cardiac noradrenaline content was more marked and both the auricular and ventricular contents were significantly decreased. Depletion of noradrenaline content was maximal 4 h after administration of D-600. A partial recovery of noradrenaline content occurred 16 h after administration of D-600, indicating that this effect of D-600 is reversible. In in vitro studies, D-600 (10(-7) to 10(-3) M) evoked a dose-related increase in the basal outflow of tritium from the rat isolated atria preloaded with [3H]noradrenaline ([3H]NA), indicating that depletion of cardiac noradrenaline stores by D-600 may be due to a direct action on sympathetic nerves rather than to increased reflex sympathetic activity secondary to profound vasodilation caused by the drug. The metabolic profile of tissue 3H content and of D-600-evoked 3H overflow was also examined. Whereas greater than 90% of tissue 3H content consisted of unchanged [3H]NA, 60-70% of the D-600-evoked overflow consisted of [3,4-3H]dihydroxyphenylglycol, and approximately 5% was unchanged NA, thus indicating that D-600 causes release of [3H]NA intraneuronally.(ABSTRACT TRUNCATED AT 250 WORDS)

Tetrodotoxin-resistant release of ATP from superfused rabbit detrusor muscle during electrical field stimulation in the presence of luciferin-luciferase

The present study was carried out to assess the possible role of ATP in the noncholinergic, nonadrenergic transmission in the rabbit urinary bladder. When rabbit detrusor muscle strips were superfused with medium containing firefly luciferin-luciferase and stimulated transmurally at low stimulation parameters, tetrodotoxin-sensitive contractions were obtained but no release of ATP could be detected. However, at somewhat higher stimulation parameters, release of ATP was observed. This release of ATP was not diminished by tetrodotoxin indicating that ATP was not likely released as a result of propagated action potentials in nerves. Because contractions persisted in the presence of tetrodotoxin, it is possible that the ATP might have been released as a result of direct electrical stimulation of the muscle. These results do not support the idea that ATP is released as a neurotransmitter in the rabbit bladder.

Ultrastructure of the parotid duct. Cytochemical studies of the striated duct and papillary cystadenoma lymphomatosum of the human parotid gland

To our knowledge, there are currently no reports in the literature that discuss the fine structure of the striated ducts of the human parotid gland. Papillary cystadenoma lymphomatosum (Warthin's tumor) is a benigh neoplasm found almost exclusively in the parotid gland that represents about 16% of all neoplasms of the gland. This neoplasm is believed to arise from the striated and/or excretory ducts, but there are contradictions with regard to the proposed origin and the cellular composition of some Warthin's tumors. Tissue was obtained at the time of surgery and examined ultrastructurally and cytochemically for the localization of alkaline phosphatase and adenosine triphosphatase. Myoepithelial cells were found ultrastructurally and cytochemically on the proximal aspect of the striated duct, with their cell bodies situated at the junction of the striated and intercalated ducts. Two Warthin's tumors were observed with cells that were structurally and cytochemically similar to myoepithelial cells.

Selective intracavitary and coronary hypothermic cardioplegia for myocardial preservation.Clinical, physiologic, and ultrastructural evaluation

Intraoperative myocardial protection was evaluated in two groups of patients undergoing coronary surgery in whom different techniques for cardiac arrest were utilized. In group A, profound selective myocardial hypothermic (15 to 18 C) arrest was achieved by perfusing a coolant (7 to 10 C) into the left ventricular cavity and the coronary circulation. The average anoxic arrest time was 82.5 +/- 27 minutes. In group B, ventricular fibrillation and moderate hypothermia were used. Group A patients showed rapid physiologic recovery, low average myocardial creatinine phosphokinase (MB-CK) isoenzyme levels (7.8 IU) , and a well-preserved myocardial ultrastructure. In group B, three patients showed abnormal physiologic recovery; six patients needed postoperative inotropic support; and in seven patients, electron-microscopy revealed irreversible focal changes. The average MB-CK isoenzyme level was 85.6 IU. Analysis of our data demonstrates that when myocardial protection during coronary bypass grafting is achieved by selective profound intracavitary and coronary cooling, there is physiological, ultrastructural, and biochemical evidence of less intraoperative myocardial damage than when ventricular fibrillation is applied.

Hepatoma induced by thorium dioxide

A 74-year-old man complained of anorexia and weight loss. Twenty-six years earlier he had received an injection of Thorotrast. A needle biopsy of the liver showed thorium dioxide granules and periportal fibrosis. On laparotomy, a hepatoma of the left lobe of the liver was discovered. Hepatic malignancy should be suspected in any patient with abnormal results of liver function tests, particularly an elevated level of alkaline phosphatase, who previously has had an injection of Thorotrast.