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The characteristics of receptors for platelet-activating factor (PAF) on rabbit neutrophils are investigated in this report. The presence of PAF-specific binding to rabbit neutrophils was confirmed using radiolabeled ligand binding assays and a rabbit peritoneal neutrophil membrane preparation. Binding of PAF to the neutrophil membranes was reversible and reached equilibrium within 30 min. Scatchard analysis of PAF-specific binding to the rabbit neutrophil membranes revealed a dissociation constant (Kd) for PAF of 0.41 +/- 0.045 nM and a Bmax of 0.32 +/- 0.11 pmol of PAF receptor/mg of protein. The order of potencies of PAF receptor antagonists to inhibit the binding of 3H-PAF to rabbit peritoneal neutrophil membranes was determined. For the competition assays, 100 micrograms of neutrophil or platelet membrane protein, 0.18 nM 3H-PAF, and varying amounts of PAF antagonist were incubated at room temperature for 1 hr. PAF receptor antagonists tested were ONO-6240, brotizolam, kadsurenone, WEB-2086, L-652-731, BN-52021, CV-3988, triazolam, alprazolam, and verapamil. The orders of potencies of these PAF receptor antagonists were similar for inhibition of 3H-PAF binding to rabbit peritoneal neutrophil and platelet membranes (correlation coefficient, r = 0.97). PAF had a significantly higher affinity for rabbit neutrophil membranes (Kd = 0.41 +/- 0.045 nM), as compared with its affinity for rabbit platelet membranes (Kd = 0.87 +/- 0.092 nM). In addition, sodium was found to inhibit 3H-PAF specific binding to rabbit platelet membranes and not to affect 3H-PAF binding to neutrophil membranes. These data indicate that, although PAF receptors on rabbit platelets and neutrophils exhibit similar orders of potencies of PAF receptor antagonists to inhibit the binding of 3H-PAF, the disparity in Kd of PAF for the receptors and the effect of NaCl on the binding of 3H-PAF reveal subtle differences between the cell types.

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Two hundred and sixty-one intravenous (IV) drug users, distributed between a methadone maintenance program and a large detention facility in New York City, were interviewed about knowledge of AIDS, needle use practices, and risk-reduction efforts. Ninety-seven per cent of subjects recognized needle-sharing as an AIDS risk factor; subjects showed less awareness about the effectiveness of certain risk-reduction techniques and tended to over-estimate the risk of casual contact. Of those still sharing needles at the time of first becoming aware of AIDS, 63% reported having subsequently either stopped needle-sharing or ceased IV drug use entirely. Logistic regression analysis indicated that continued needle-sharing behavior was associated with the detention facility site and lower scores on an AIDS knowledge questionnaire; reduced needle-sharing was more evident among methadone program patients and among subjects with greater knowledge about AIDS. The most common reasons for continued needle-sharing among those who continued to share needles despite knowledge of risk were: 'need to inject drugs, with no clean needle available' and 'only share with close friend or relative', offered by 46 and 45% of subjects, respectively. Results suggest that certain subgroups of IV drug users have adopted risk-reduction measures in response to AIDS. Expanded educational programs, increased drug treatment capacity, and additional strategies addressing drug users' access to sterile injection equipment and the social context of needle-sharing may be necessary to curb the further spread of AIDS among IV drug users.

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Platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine or AGEPC) is a potent phospholipid mediator elaborated by a variety of mammalian cells. CV-3988 (a unique structural analog of AGEPC), L-652731 (a lignan derivative of a natural product) and two triazolobenzodiazepines (triazolam and alprazolam) were evaluated for their ability to selectively antagonize aggregation and secretion responses in washed, [3H]serotonin-labeled rabbit platelets stimulated with graded doses of AGEPC. When 0.2 nM AGEPC was used as the stimulus, the concentration of antagonist needed for 50% inhibition (IC50) of secretion was obtained at 0.05 uM, 0.15 uM, 0.6 uM and 2.5 uM, for L-652732, CV-3988, triazolam and alprazolam, respectively. The corresponding IC50 values for aggregation were obtained at 0.2 uM, 0.1 uM, 1.5 uM and 6.5 uM, respectively. The inhibitory effects could be overcome by increasing the amount of AGEPC used to stimulate the platelets. Of the four compounds tested, L-652731 was the most potent antagonist of AGEPC-induced activation of washed rabbit platelets.

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To test the hypothesis that cognitive impairment may be present early in the course of HTLV-III/LAV infection, intravenous drug abusers (IDVAs) without overt symptoms of AIDS related illness were tested with standard neuropsychological and psychosocial measures. This study is the baseline for a prospective longitudinal study of the natural history of HTLV-III/LAV infection in this high risk population. Of 211 subjects initially evaluated, 70 (33%) were HTLV-III/LAV seropositive and 141 (67%) were seronegative. At the baseline, by univariate analysis, the seropositive IVDAs were significantly (p less than .05) more impaired than seronegatives on 4 of 8 measures: Finger Tapping--dominant, hand, Digit Span Forward, Trail making A and WAIS-Similarities. However, by multivariate analysis the seropositives were significantly more impaired only on the WAIS-Similarities and Wechsler--Associative Learning tests. Multiple factors such as drug use and psychological stress may have influenced test performance. These preliminary results, however, suggest that seropositive IVDAs may show evidence of impaired neuropsychological function even in the absence of AIDS related symptoms and are consistent with the hypothesis of the early neurotropism of HTLV-III/LAV.

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Washed, [3H]serotonin-labeled platelets from rats and guinea pigs were stimulated in vitro with a novel protein extracted from rat submandibular salivary glands (RS-PAP) and with the phospholipid platelet- activating factor 1-0-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine (AGEPC). Rat platelets, which are refractory to AGEPC stimulation, underwent shape-change, aggregation and secretion of [3H]serotonin in response to graded doses of RS-PAP and AGEPC. Intradermal injections of histamine, RS-PAP and AGEPC caused a dose-related increase in local microvascular permeability in rats, as measured by the extravasation of plasma containing Evans blue dye. Similarly, histamine, RS-PAP and AGEPC increased cutaneous vascular permeability when injected intradermally in guinea pigs. The vascular permeability induced by histamine and RS-PAP, but not by AGEPC, was partially inhibited by pretreatment with an antihistamine (diphenhydramine HCl). Pretreatment of guinea pigs with captopril, an inhibitor of angiotensin-converting enzyme (ACE), partially inhibited cutaneous responses to subsequent intradermal injections of histamine, RS-PAP and AGEPC. Regardless of pretreatment with diphenhydramine or captopril, skin test sites injected with large amounts of RS-PAP became hemorrhagic within minutes and necrotic within 12 hours.

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The structure of the potent inflammatory mediator, platelet-activating factor, is 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC, PAF-acether). Human sera contain an acid labile factor (ALF) that is a Ca+2-independent 2-acylhydrolase-specific for AGEPC and AGEPC-like molecules. The enzyme functions by catalytically removing the sn-2 acetyl moiety from AGEPC, producing the biologically inactive sn-2 hydroxy form or 2-lyso-GEPC. Incubation of ALF with sn-2 acyl PAF analogs indicated that the enzyme hydrolyzes the sn-2 fatty acid only if the chain length is five carbons or less, the sn-1 position fatty acid length is greater than 10 carbon units, and at least one methyl group is present on the terminal amine of the choline group. The enzyme was active with either an ether or ester linkage at the sn-1 position. ALF is inactivated by heating to 65 degrees C for 30 min. It is pronase and trypsin sensitive but resistant to papain and papain with dithiothreitol. Further characteristics of human ALF indicated a broad pH range of activity with an optimum of pH 6.2 and an isoelectric point of 6.2 to 6.7. The specificity and Ca+2 independence of human ALF sets it apart from phospholipase A2. It is proposed that human ALF be called human serum PAF-acylhydrolase to distinguish it from other hydrolases currently known to exist.

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Platelet-activating factor (1-0-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine or AGEPC) is a small, extremely potent phospholipid mediator. CV-3988, a unique structural analogue of AGEPC, has recently been introduced as a selective antagonist of AGEPC-induced in vitro platelet activation and in vivo systemic hypotension. At concentrations greater than 5 X 10(-5) M, CV-3988 itself induced aggregation and secretion responses in washed rabbit platelets. CV-3988 inhibited AGEPC-induced platelet activation at concentrations as low as 10(-8) M, but also blocked platelet activation induced by collagen and calcium ionophore A23187 at concentrations between 10(-6) M and 10(-5) M. The mechanism of inhibition, however, did not depend on increased levels of intracellular 3',5'-cyclic adenosine monophosphate (cAMP). In fact, CV-3988, like AGEPC itself, appeared to lower cAMP levels in washed rabbit platelets.

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Among the various naturally occurring substances which induce platelet aggregation and secretion, considerable attention has been focused recently on the phospholipid platelet-activating factor (PAF) derived from a variety of mammalian cells. In this report, we describe a platelet-activating protein, designated RS-PAP, which was isolated and partially purified from the submandibular salivary glands of adult male rats. This material caused a dose-related in vitro activation of washed, [3H]serotonin-labeled platelets from rats, rabbits and humans. The biologic activity of RS-PAP was compared with that of 1-0-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine (AGEPC), a well-characterized representative of the phospholipid platelet-activating factors, and collagen, a potent platelet-stimulating protein. The activation of washed rabbit platelets by RS-PAP required extracellular calcium for both aggregation and secretion of [3H]serotonin, and was not inhibited by indomethacin. Furthermore, RS-PAP was not inhibited by pretreatment with phenylmethylsulfonyl fluoride, iodoacetate, hirudin or an acetylhydrolase which specifically degrades the phospholipid AGEPC. RS-PAP was completely inactivated by heating at 56 degrees C for 20 minutes, by trypsinization and by a phospholipid extraction procedure. Gel filtration on Sephacryl S-200 indicated an approximate molecular weight of 22,000 - 25,000 daltons. Thus RS-PAP appears to be a new platelet-stimulating protein which activates a variety of mammalian platelets.

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A procedure is given for estimating the ratio of the means of two populations using the data from two independent random samples when the observations are normally distributed with population variances that are related to the population means.

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Washed, [3H]serotonin-labeled chicken thrombocytes aggregated and secreted [3H]serotonin when stimulated in vitro with platelet-activating factor (PAF), collagen and calcium ionophore A23187. The effective dose causing a 25% secretion of [3H]serotonin (ED25) from washed chicken thrombocytes was 10(-8) M for PAF, 5 X 10(-8) M for collagen and 3 X 10(-7) M for A23187. Chicken thrombocyte activation by PAF required Ca2+ and appeared to be mediated through a specific receptor for PAF.

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Platelet-activating factor (PAF), a potent endogenous phospholipid released by a variety of mammalian cells, induces platelet activation in vivo and in vitro. Little is known, however, about the physiological modulation of its actions. We have examined the ability of two naturally occurring compounds which stimulate cAMP production, vasoactive intestinal peptide (VIP) and prostacyclin (PGI2), to inhibit PAF-induced platelet aggregation and secretion in vitro. Washed, [3H]serotonin-labeled, rabbit platelets were incubated 60 sec in the presence of VIP, PGI2 or 3-isobutyl-1-methylxanthine (IBMX) and subsequently stimulated with PAF. In separate studies, cAMP levels were determined in similar aliquots of platelets incubated for 30 sec with VIP, PGI2 or IBMX. VIP, PGI2 and IBMX inhibited platelet aggregation and secretion in a dose-dependent manner. Fifty percent inhibition was achieved at final concentrations of 1.7 X 10(6) M VIP, 3.6 X 10(6) M PGI2 and 6.5 X 10(5) M IBMX. IBMX potentiated the inhibitory effects of VIP and PGI2 on PAF-induced platelet activation. VIP and PGI2 elevated platelet cAMP levels four-fold and 50-fold, respectively, in the presence of 10(3) M IBMX. These findings demonstrate that VIP inhibits PAF-induced platelet activation, with a potency comparable to that of PGI2.

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Platelet-activating factor (PAF) is a phospholipid that activates platelets, induces inflammation, and causes profound alteration in the cardiopulmonary system. PAF from rabbit basophils and hog leukocytes is 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC). Human and other mammalian serums contain an acid-labile factor (ALF) that rapidly inactivates AGEPC. ALF is associated with low-density lipoproteins but can be dissociated from the lipoproteins with detergent followed by ultracentrifugation. Delipidated ALF has an isoelectric point of approximately 7.1, its molecular weight is unknown, and it will not react with goat anti-whole human serum, antialbumin, anti-alpha- or anti-beta-lipoproteins, or antiapolipoproteins A or B. ALF has the following characteristics: 1) is acid labile; 2) is Ca2+ independent; 3) has a pH optimum of 6.2; 4) can hydrolyze a four-carbon but not a six-carbon or longer chain fatty acid at the sn-2 position; 5) is independent of an ester or ether linkage at the sn-1 position; 6) is incapable of hydrolyzing sn-2-acetylphosphatidylethanolamine, which indicates the need for at least one methyl group on the choline moiety of AGEPC; 7) requires between 5 and 16 carbons at the sn-1 position to remove a three- or four-carbon fatty acid on the sn-2 position; 8) is inactivated by heating to 65 C for 30 min; 9) is pronase and trypsin sensitive but papain resistant; and 10) is a hydrophobic molecule and thus behaves like a membrane-associated enzyme. Thus, ALF is a specific phosphatide 2-acylhydrolase.

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This report describes PAF activity in normal human mixed saliva from each of 24 randomly selected donors. The human salivary PAF (HS-PAF) was similar to rabbit basophil PAF (acetyl glyceryl ether phosphorylcholine or AGEPC) with respect to the following characteristics: 1. HS-PAF co-chromatographed with the standard rabbit basophil AGEPC and with synthetic AGEPC. 2. HS-PAF and AGEPC were unaffected by hirudin, indomethacin, and creatine phosphate/creatine phosphokinase, the respective inhibitors of platelet activation induced by thrombin, arachidonic acid, and ADP. 3. HS-PAF and AGEPC were inactivated by a 5-min incubation with ALF, the acid-labile factor in normal human serum that rapidly destroys AGEPC. 4. HS-PAF was demonstrated to be functionally similar to AGEPC by cross-desensitization experiments. In the absence of Ca++, HS-PAF and AGEPC cross-desensitized washed rabbit platelets to subsequent stimulation by either HS-PAF or AGEPC after recalcification. 5. HS-PAF was demonstrated to be structurally similar to AGEPC by several simple chemical tests for functional groups.

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Guinea pigs exposed via the respiratory route to Ascaris suum extract in aerosol form became hypersensitive. The hypersensitivity was detectable by inhalational bronchial provocation testing using a noninvasive plethysmography, by chopped lung histamine release, and by passive cutaneous anaplylaxis. The antibody responsible for the hypersensitivity seems to be directly associated with pulmonary tissue. A locally produced cytotropic pulmonary antibody, probably IgG or IgE may be causal. Histopathology included only a moderate pulmonary eosinophilia. Individual variability in susceptibility to experimental allergic asthma may be controlled by both physiologic and immunologic reactivities.

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Population increase of Pratylenchus hexincisus on corn was tested over 3 months at 15, 20, 25, and 30 C in Marshall silt loam, Clarion silt loam, Buckner coarse sand, and Haig silty clay loam soils. The optimum temperature for increase was 30 C in all soils. The nematode population was significantly larger in Buckner coarse sand than in other soil types at 50 C. The recovered P. hexincisus populations equaled or exceeded initial inoculum levels at the two higher temperatures in Marshall silt loam and Haig silty clay loam and at 30 C in Clarion silt loam and Buckner coarse sand. P. hexincisus required 32,400 heat units in Haig silty clay loam and more than 40,000 heat units in the three other soil types to reach a level that is known to cause significant height and biomass reduction in corn under controlled condition.

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A simple noninvasive technique for measuring specific airway resistance (airway resistance X thoracic gas volume) in unanesthetized guinea pigs is described. Specific airway resistances measured by this technique correlated well (r = 0.81) with the resistances obtained using a pleural catheter pressure measurement over a wide range of airway resistances. This range of resistances was generated by exposing the pigs to an aerosolized histamine bronchial challenge. The average specific airways resistance in unchallenged pigs was 1.24 +/- 3.47 cmH2O/s, somewhat lower than found by others, probably reflecting in part our larger pigs and in part some uncertainty in the absolute value of resistance inherent in our measurement technique. This technique is particularly useful in bronchial challenge experiments because of its sensitivity to acute changes in airway resistance.

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Specific paw test reactivity to tumor cells was transferred to normal mice using lymphoid cells or serum from mice with a growing or surgically excised methylcholanthrene-induced transplantable sarcoma. When the donors had been sensitized to PPD and to tumor, normal recipients of lymphoid cells became reactive by specific paw test to tumor cells and PPD. Normal recipients of serum from the same donors also became reactive to tumor cells. Normal recipients of serum from tumor-bearing mice developed depressed PHA paw tests. Adoptive transfer with cells or serum of paw test reactivity to tumor and PPD was unsuccessful when recipients had large tumors. This was the case when the recipients had either tumor of the same line or that of a separate line that did not cross-react antigenically.

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