Leucocytic Pyrogen Research Articles

Elevation of body temperature in rabbits by X-irradiation of the trunk

Rabbits, irradiated with moderate doses of X-rays on their trunk exhibit a hyperthermic response. Evidence is presented that this temperature response is mediated by leucocytic pyrogen.

Myxovirus Pyrogenに関する研究 III

Studies were made on the physico-chemical properties of leucocytic pyrogens induced by influenza virus (V) and bacterial pyrogen of Escherichia coli (LPS) in rabbits. The following results were obtained.1. The fever curve of the virus (256HAU/kg, i.v.) was quite different in lag time from that of LPS (0.1μg/kg, i.v.). The fever curves of the leucocytic pyrogens were quite similar to each other.2. The chromatographic patterns over Sephadex (G-200) or Bio gel (P-150) of the two leucocytic pyrogens were shown to be the same as that of control leucocytic pyrogen.3. The immuno-diffusion patterns of both leucocytic pyrogens against antiserum of guinea pig were the same, showing two or three precipitating bands.From the results mentioned above, it was concluted that both pyrogens (V and LPS) might be mediated by the same leucocytic pyrogens.

Prosaglandin E1 fever induced in rabbits.

1. Micro-injections of prostaglandin E(1) (PGE(1)) into the anterior hypothalamus of the rabbit produced fever which was nearly immediate in onset. The prostaglandin sensitive region appears to be identical to that described as being fever sensitive to leucocytic pyrogen.2. Micro-injections of PGE(1) into the posterior hypothalamus and midbrain reticular formation of the rabbit did not produce fever.3. The febrile response to PGE(1) injected into the anterior hypothalamus was dose dependent over a range of 20-1000 ng.4. Ambient temperature influenced the thermoregulatory mechanism by which PGE(1) fever evolved. In the cold, PGE(1) fever was due to increased heat production while during heat exposure both evaporative and dry heat losses were reduced without significant changes in heat production. Vasoconstriction, confined mainly to the ears, was effective in producing fever in standard room environments (24-25 degrees C) along with a small increase in heat production.5. The preoptic anterior hypothalamic area retained its thermosensitivity during PGE(1) fever; heating this area attenuated, while cooling augmented the fever.6. The results support the view that PGE(1) is a mediator of pyrogen induced fever.

Extra-adrenal effect of ACTH on fibrinogen synthesis.

ARTICLESExtra-adrenal effect of ACTH on fibrinogen synthesisU Seligsohn, SI Rapaport, and PR KueflerU Seligsohn, SI Rapaport, and PR KueflerPublished Online:01 May 1973https://doi.org/10.1152/ajplegacy.1973.224.5.1172MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByBlood coagulation dynamics during adrenocorticotropic hormone therapy in pediatric patients with infantile spasmsBrain and Development, Vol. 44, No. 8A sustained increase of plasma fibrinogen in sudden sensorineural hearing loss predicts worse outcome independentlyAmerican Journal of Otolaryngology, Vol. 38, No. 4Hypofibrinogenemia caused by adrenocorticotropic hormone for infantile spasms: A case reportBrain and Development, Vol. 37, No. 1Hypofibrinogenemia Due to Combined Therapy with Valproic Acid and ACTHJournal of the Japan Epilepsy Society, Vol. 28, No. 3The Effect of Immunodepletion of Antithrombin III on the Response of Rabbits to Russell's Viper Venom–Induced Activation of Factor XArteriosclerosis, Thrombosis, and Vascular Biology, Vol. 17, No. 2High PAI activity with correlation to triglyceride and HDL cholesterol values in patients with coronary artery disease with no difference in survivors of myocardial infarctionAnnals of Hematology, Vol. 67, No. 5Adrenocorticotrophic hormone fails to alter plasma fibrinogen and fibronectin values in calves but does so in rabbitsVeterinary Research Communications, Vol. 16, No. 4Haemostasis and parturition revisited: Comparative profiles in mammalsComparative Haematology International, Vol. 1, No. 3Analysis of γ-γ Dimer and Factor XIII (Fibrin Stabilizing Factor, FSF) During Pregnancy and LaborCorrelation of baseline plasminogen activator inhibitor activity with patency of the infarct artery after thrombolytic therapy in acute myocardial infarctionThe American Journal of Cardiology, Vol. 64, No. 19HORMONAL REGULATION OF FIBRINOGEN SYNTHESIS IN CULTURED HEPATOCYTESAnnals of the New York Academy of Sciences, Vol. 408, No. 1 Molecular BioThe Coagulation SystemEffects of epinephrine on plasma fibrinogen levels in rats submitted to tissue injuryExperientia, Vol. 37, No. 7Effects of insulin on plasma fibrinogen levels in rats submitted to tissue injury or ACTH administrationExperientia, Vol. 35, No. 5Assessment of clotting by the determination of fibrinogen catabolismThe American Journal of Surgery, Vol. 135, No. 3Evaluation of hypercoagulability in users of oral contraceptivesKlinische Wochenschrift, Vol. 55, No. 4Plasma fibrinogen response in the rat after thyroid stimulating hormone therapyExperientia, Vol. 32, No. 11The effect of leucocytic pyrogen on rabbit fibrinogen. A third viewThrombosis Research, Vol. 9, No. 5In Vivo Behaviour of Homologous Urea-Soluble 131 I-Fibrin and 125 I-Fibrinogen in Rabbits: the Effect of Fibrinolysis InhibitionBritish Journal of Haematology, Vol. 33, No. 1The effect of leukocytic extract on fibrinogen synthesis in rabbitsThrombosis Research, Vol. 7, No. 1Regulation of Net Biosynthesis of Albumin, Fibrinogen, α1-Acid Glycoprotein, α2-(Acute Phase) Globulin, and Haptoglobin by Direct Action of Hormones on the Isolated Perfused LiverDelayed Incorporation of [ 75 Se]Selenomethionine into Fibrinogen: Its Effect upon Kinetic Studies of Fibrinogen with [ 75 Se]Selenomethionine in RabbitsBritish Journal of Haematology, Vol. 26, No. 4 More from this issue > Volume 224Issue 5May 1973Pages 1172-1179 Copyright & PermissionsCopyright © 1973 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1973.224.5.1172PubMed4349533History Published online 1 May 1973 Published in print 1 May 1973 Metrics

The hypothermic effect of tetrodotoxin in the unanaesthetized cat.

1. The hypothermic effect on unanaesthetized cats of tetrodotoxin injected I.V. or into the lateral cerebral ventricle was examined.2. At an ambient temperature (T(a)) of 22 degrees C, tetrodotoxin given intraventricularly was over 400 times more potent in lowering body temperature (T(b)) than when given I.V. The magnitude of the hypothermia was dose-dependent for both routes. Decreases in T(b) as great as 6.8 degrees C were induced by infusions or multiple injections of tetrodotoxin into the ventricle.3. Tetrodotoxin also lowered T(b) at T(a) = 13, 30 or 35 degrees C. Tachypnoea, which lasted for longer durations and which became more intense the higher the T(a), accompanied development of hypothermia. Shivering was observed only during recovery from hypothermia at 13 degrees C.4. During the tetrodotoxin-induced hypothermia, animals were still able to regulate against environmental thermal stresses.5. EDTA disodium salt, leucocytic pyrogen and prostaglandin E(1) antagonized the hypothermic effect of tetrodotoxin when they were administered during recovery from tetrodotoxin.6. Activation of heat-loss mechanisms, and the absence of compensatory shivering during development of hypothermia after tetrodotoxin administration, plus lowering of T(b) by tetrodotoxin at T(a) above as well as below the thermoneutral temperature, indicate that lowering of the thermoregulatory set-point is the mechanism by which centrally or peripherally administered tetrodotoxin lowers T(b). Further evidence for set-point lowering after intraventricular administration of tetrodotoxin is provided by persistence of the ability to regulate against both heat and cold stresses during hypothermia. The possibility that the decrease in set-point could be due to the well known action of tetrodotoxin to block transient increases in membrane sodium ion conductance is discussed in terms of a recent hypothesis regarding ionic control of the thermoregulatory set-point.

発熱性物質に関する研究(VI)

We could be able to obtain Leucocytic pyrogen (LP) from rabbit polymorphonuclear leucocytes (PMN) in vitro, and studied on some physiological properties in comparison with bacterial pyrogen. The following results have been obtained; (1) LP showed a mono-phasic fever curve which has no or short latent period, and did not show any dose-response over the limitted dose. (2) From the preliminary chemical analysis, crude LP consisted of protein, polysaccharide, sodium chloride, and trace of phosphorous and lipid. (3) LP did not cause fever tolerance as unlikely as bacterial pyrogen. (4) LP caused transient leucocytosis in rabbit, but bacterial pyrogen caused severe leucopenia. (5) In leucopenic rabbit response of bacterial pyrogen was decreased, but response of LP was almost unchanged.

Fever induced with leucocytic or bacterial pyrogen in young and adult goats

The action of a bacterial pyrogen (LPS E. coli 0111B4), leucocytic pyrogen (LP) and endogenous pyrogen (EP) was studied in adult and 5 to 10 days old goats, of which only some were allowed access to their mother's colostrum. After injection of LP, fever curves showed only differences in the period of defeverscence, attributable to difference in body surface/body weight ratio between young and adult animals. After injection of LP or EP, there was no difference in fever reaction between colostrum-fed and colostrum-deprived kids. Significant differences in heights and contours of the temperature curves obtained in the kids and their mothers after injection with bacterial pyrogen could only partially be explained by differences in rate of heat loss. There was no difference in pyrogenic response to bacterial pyrogen between colostrum-fed and colstrum-deprived kids. Gammaglobulins were detected in most of the 5 to 9 days old kids denied access to their mother's colostrum.

Effect of ACTH on biosynthesis of fibrinogen in the rabbit.

ARTICLESEffect of ACTH on biosynthesis of fibrinogen in the rabbitAC Atencio, and L LorandAC Atencio, and L LorandPublished Online:01 Nov 1970https://doi.org/10.1152/ajplegacy.1970.219.5.1161MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByThe Coagulation SystemFatty acids, fibrinogen and blood flow: A general mechanism for hyperfibrinogenemia and its pathologic consequencesMedical Hypotheses, Vol. 6, No. 5Effects of insulin on plasma fibrinogen levels in rats submitted to tissue injury or ACTH administrationExperientia, Vol. 35, No. 5Hematologic and serologic studies in 6‐sulfanilamidoindazole arthritis23 November 2005 | Arthritis & Rheumatism, Vol. 21, No. 6The site of synthesis and functions of acute phase plasma proteins: Close relation-ship with the reticulo-endothelial systemMedical Hypotheses, Vol. 3, No. 2Plasma fibrinogen response in the rat after thyroid stimulating hormone therapyExperientia, Vol. 32, No. 11The effect of leucocytic pyrogen on rabbit fibrinogen. A third viewThrombosis Research, Vol. 9, No. 5The role of sialic acid in determining the life-span of circulating cells and glycoproteinsExperientia, Vol. 32, No. 2Regulation of Net Biosynthesis of Albumin, Fibrinogen, α1-Acid Glycoprotein, α2-(Acute Phase) Globulin, and Haptoglobin by Direct Action of Hormones on the Isolated Perfused LiverDelayed Incorporation of [ 75 Se]Selenomethionine into Fibrinogen: Its Effect upon Kinetic Studies of Fibrinogen with [ 75 Se]Selenomethionine in RabbitsBritish Journal of Haematology, Vol. 26, No. 4Acute-Phase ReactantsEffect of Whole-body X-irradiation on Plasma-protein Synthesis: Role of Adrenals3 July 2009 | International Journal of Radiation Biology and Related Studies in Physics, Chemistry and Medicine, Vol. 23, No. 5Insulin transformation in the liverActa Diabetologica Latina, Vol. 9, No. 1Effect of spironolactone and phenobarbital on the plasma fibrinogen in ratsExperientia, Vol. 28, No. 11Fibrinogen catabolism in rats fed thrombogenic dietsAtherosclerosis, Vol. 16, No. 3 More from this issue > Volume 219Issue 5November 1970Pages 1161-1165 Copyright & PermissionsCopyright © 1970 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1970.219.5.1161PubMed4319643History Published online 1 November 1970 Published in print 1 November 1970 Metrics

Experimental fever induced with endogenous pyrogen or leucocytic pyrogen in goats.

Experimental fever induced with endogenous pyrogen or leucocytic pyrogen in goats.

Leucocytic pyrogen generated by endotoxin.

LEUCOCYTIC pyrogen is a low molecular weight protein synthesized by polymorphonuclear and mononuclear leucocytes in response to certain stimuli. The fever accompanying many bacterial and viral infections is thought to be caused by the release of this material from host leucocytes and its action at the thermoregulatory centre of the brain1. Pyrogen is not preformed in leucocytes. In in vitro experiments, it appears in the extracellular fluid only on incubating intact leucocytes at 37° C, when a potent stimulus is endotoxin or bacterial lipopolysaccharide2. The well known pyrogenicity of endotoxin is best explained by its action on circulating leucocytes, but the mechanism is not known. It is usually assumed that endotoxin liberates a bound form of pyrogen or converts a propyrogen to an active form without itself entering into pyrogen formation. We shall describe a leucocytic-type pyrogen generated by incubating endotoxin with inactive leucocytic pyrogen preparations, which suggests that endotoxin contributes a building block for the synthesis of leucocytic pyrogen.

Studies on the antipyretic action of salicylates.

SummarySodium salicylate is antipyretic in experimental endotoxin fevers in rabbits but is not significantly antipyretic in fevers induced by leucocytic pyrogen. The in vitro production of pyrogen by leucocytes is significantly decreased by salicylate. The accumulated evidence suggests that in rabbits the antipyretic effect of salicylate is not central on the hypothalamus but is peripheral on the leucocyte to inhibit formation or release of its pyrogen.

Interactions of gram-negative bacterial endotoxin with rabbit blood in vitro.

ARTICLESInteractions of gram-negative bacterial endotoxin with rabbit blood in vitroES Snell, and E AtkinsES Snell, and E AtkinsPublished Online:01 May 1967https://doi.org/10.1152/ajplegacy.1967.212.5.1103MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByOxygen-derived Free Radicals in the Pathogenesis of Parasitic DiseaseLa Fievre17 May 2016 | Acta Clinica Belgica, Vol. 41, No. 2Temperature Regulation and FeverLeukocytic Endogenous Mediator in Nonspecific Host DefensesRenal excretion of prostaglandin metabolites, arginine vasopressin, and sodium during endotoxin and endogenous pyrogen induced fever in the goatActa Physiologica Scandinavica, Vol. 120, No. 4Molecular mechanisms in endotoxin feverAgents and Actions, Vol. 13, No. 5-6Molecular basis of fever in humansThe American Journal of Medicine, Vol. 72, No. 5Thermoregulation: Its Change During Infection with Endotoxin-Producing Micro-organismsExogenous PyrogensPathogenesis of fever in delayed hypersensitivity: factors influencing release of pyrogen-inducing lymphokinesInfection and Immunity, Vol. 21, No. 3Mechanisms of leukocyte activation during the formation of leukocytic pyrogenBulletin of Experimental Biology and Medicine, Vol. 86, No. 2Influence of endogenous pyrogen on the cerebral prostaglandin-synthetase systemExperientia, Vol. 32, No. 11The effect of sodium salicylate on dibutyryl cyclic amp fever in the conscious rabbitNeuropharmacology, Vol. 15, No. 1Pyrogen and prostaglandin fever in the rabbit—I: Effects of salicylate and the role of cyclic AMPNeuropharmacology, Vol. 14, No. 5-6The Effects of Bacterial Pyrogens and Leucocytic Pyrogen Upon Gastric Motility and Heart Rate Frequency in Conscious Goats13 May 2010 | Zentralblatt für Veterinärmedizin Reihe A, Vol. 21, No. 8Studies on the Mechanism of Endogenous Pyrogen Production II. Role of Cell Products in the Regulation of Pyrogen Release from Blood LeukocytesInfection and Immunity, Vol. 10, No. 3Pyrogen and enzyme release from rabbit blood leukocytes promoted by endotoxin and polyinosinic polycytidylic acidBiochemical Medicine, Vol. 5, No. 3Immunologic and anatomic consequences of calf thymosin injection in ratsCellular Immunology, Vol. 1, No. 1 More from this issue > Volume 212Issue 5May 1967Pages 1103-1112 Copyright & PermissionsCopyright © 1967 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1967.212.5.1103PubMed6023867History Published online 1 May 1967 Published in print 1 May 1967 Metrics

Studies on the pyrogen. IV. Some factors influencing the production of leucocytic pyrogen from polymorphonuclear leucocytes in vitro.

Beeson (1) has first described on the pyrogenic effect of a substance obtained from polymorphonuclear leucocytes of rabbits which was designated as “leucocytic pyrogen”. Bennett (2) also stated that the nature and action of this substance markedly differed from endotoxin in certain respects. This leucocytic pyrogen has been shown to differ from the originally administered endotoxin in the following respects: 1) It was characterized by the rapid brief monophasic body temperature curve in normal rabbits. 2) Daily repeated injections of endogenous pyrogen did not elicite resistance to its fever producing action. 3) It was relatively heat labile and differed from lipopolysaccharide as bacterial pyrogen. On the other hand, it has been found that during the fever response of rabbit injected with endotoxin, there appeared a pyrogenic substance in the circulating blood stream of the rabbit, and it has been called as an endogenous pyrogen in the blood. The differences between endogenous pyrogen and leucocytic pyrogen were not clearly demonstrated (3). But the study of the releasing mechanism and localization of leucocytic pyrogen in leucocytes might be one step of the study for the pathogenesis of fever. Present report deals with the conditions of the production of leucocytic pyrogen from leucocytes of rabbits and some physico-chemical properties of leucocytic pyrogen in vitro.

PATHOGENESIS OF INFLAMMATION. I. THE PRODUCTION OF AN INFLAMMATORY SUBSTANCE FROM RABBIT GRANULOCYTES IN VITRO AND ITS RELATIONSHIP TO LEUCOCYTE PYROGEN.

Material obtained from the in vitro incubation of granulocytes from saline-induced peritoneal exudates of rabbits has been shown to produce inflammation and fever in rabbits. The supernatant material from cells incubated in saline has been termed granulocytic substance (GS) and is heat-labile. Its production is temperature dependent, occurring at 37 degrees C but not at 4 degrees C, requires viable cells, and is inhibited by potassium ions. A similar material is liberated when cells are incubated in a more physiologic medium. Freezing and thawing of granulocytes does not release GS and the active principle cannot be obtained from the incubation of lymphocytes. GS produces a delayed inflammatory response as measured by leucocyte sticking and emigration in the rabbit ear chamber and the leakage of protein-conjugated dye at the site of intradermal injection. The former response can be accurately quantitated by calculation of the inflammatory index from reactions observed in the ear chamber. The inflammatory reaction and the properties of GS distinguish it from a variety of previously described mediators of inflammation, but GS appears to be identical with leucocytic pyrogen. The possible role of GS in delayed and protracted inflammation and its relationship to the pathogenesis of fever are discussed.

Electron microscopic observations of rabbit leucocytic pyrogen

We have studied by electron microscopy a pyrogenic protein derived from rabbit leucocytes. Whether the pyrogen is in crude or purified form, the basic unit appears the same: a sphere 50 Å in diameter which has a central, densely osmiophilic core of about 25 Å diameter. The reasons for believing that these particles may represent the substance we know chemically as leucocytic pyrogen are: (1) they are consistently present in preparations known by biological or chemical assay to contain leucocytic pyrogen; they are consistently absent in nonpyrogenic controls. (2) The calculated molecular weight of the particulate material (50,000) is consistent with our knowledge of the chemical properties of the pyrogen. (3) We cannot find any preparative artifact or other substance that this particulate material might reasonably repesent. Quite obviously none of our 3 reasons constitutes proff that what we are seeing is really the pyrogen. Although it seems probable to us that we are visualizing the pyrogen, we must wait until we develop an antibody to the pyrogen before we can present more convincing evidence.

Studies on the pathogenesis of fever. XI. Quantitative features of the febrile response to leucocytic pyrogen.

Although the absolute febrile responses of trained individual rabbits injected intravenously with small to moderate doses of leucocytic pyrogen vary over an appreciable range, the relative responses of each rabbit to changes in dosage are satisfactorily reproducible. The quantitative dose-response relationship is characterized by a hyperthermic ceiling at which the intensity of the febrile reaction is relatively constant over a wide dosage range. Only at lower dose levels, where the dose-response curve is reasonably steep, is the magnitude of the fever produced proportional to the amount of pyrogen injected. When sufficiently large doses of LP are injected, the hyperthermic ceiling is exceeded. The fevers thus induced are biphasic in character and, in this way, resemble the usual response to bacterial endotoxin. Similar biphasic fevers result from continuous infusions of relatively low concentrations of LP at a constant rate. Repeated intermittent injections of moderate doses of LP likewise cause prolonged biphasic fevers, but, once the fever has become established, the reaction to each individual injection becomes markedly depressed. When large doses of LP are injected at daily intervals, the characteristic biphasic response occurs only following the first injection. Thereafter a state of tolerance intervenes in which the late secondary rise in temperature fails to occur. This form of tolerance lasts as long as the daily injections are continued but subsides within a few days after the injections are stopped. During the transient tolerance the rabbit's responsiveness to small doses of LP (in the sensitive range of the dose response curve) is depressed. In addition, the amount of endogenous pyrogen mobilized from the tissues by a large dose of LP is not as great as that generated in a normal rabbit. The relations of these findings to biphasic fevers, tolerance, and the accuracy of the conventional method of pyrogen assay are briefly discussed.

Chemical properties of leucocytic pyrogen: I. Partial purification of rabbit leucocytic pyrogen

Rabbit leucocytes, if properly stimulated, will yield an endogenous or leucocytic pyrogen that is chemically and biologically distinct from exogenous pyrogens such as bacterial endotoxins. Just how the leucocytic pyrogen is produced is not yet known but the present study was undertaken in an effort to learn more of its chemical properties. Crude leucocytic pyrogen, obtained from sterile peritoneal exudates, was dialyzed against distilled water, freeze-dried, and applied first to a DEAE column to remove much of the protein, then to a phosphorylated cellulose column which adsorbed leucocytic pyrogen while allowing virtually all of the remaining protein to be eluted. The leucocytic pyrogen in turn was eluted by a stepwise increase in pH with a resulting thirty-fold increase in pyrogenic activity per gram of protein as compared with the crude pyrogen. This pyrogenic protein material is inactivated by 60°C for 5 minutes and by trypsin digestion. It is electrophoretically homogenous at pH 5.0 and 8.0 and yields at least nine amino acids on hydrolysis. The methods outlined above enable rabbit leucocytic pyrogen to be obtained in a relatively pure form so that further chemical characterization is now possible.

Studies on the pathogenesis of fever. X. The effect of certain enzyme inhibitors on the production and activity of leucocvtic pvrogen.

The production of endogenous pyrogen by intact granulocytes obtained from acute peritoneal exudates is blocked by arsenite, iodoacetate, p-chloromercuribenzoate, and N-ethylmaleimide in concentrations of 2 x 10(-4)M. When the concentration of these sulfhydryl-reactive enzyme inhibitors is increased to 2 x 10(-2)M, only the iodoacetate inactivates the pyrogen molecule, whereas the arsenite, the p-chloromercuribenzoate, and the N-ethylmaleimide have no gross effect upon its thermogenic activity. Both diisopropyl fluorophosphate and dinitrofluorobenzene are even more potent inactivators of the pyrogen molecule than iodoacetate, although the action of the DFP cannot be blocked or reversed by known antagonists such as 2-pyridine aldoxime methiodide and hydroxylamine. Proteolytic enzymes, potentially capable of degrading leucocytic pyrogen, are released from polymorphonuclear leucocytes, along with the pyrogen, when the cells are incubated in normal salt solution. These enzymes are readily activated by a sufficient concentration of glutathione (2 x 10(-2)M). They are not present in preparations of partially purified leucocytic pyrogen from which much of the non-pyrogenic protein has been removed. Glutathione by itself, even at concentrations as high as 2 x 10(-1)M, does not affect in the gross the thermogenic activity of the purified pyrogen. The implications of these findings in relation to both the production and the chemical characteristics of leucocytic pyrogen are discussed.

Studies on the pathogensis of fever. IX. The production of endogenous pyrogen by polymorphonuclear leucocytes.

Determination of the dose-response curve for rabbit leucocytic pyrogen reveals a hyperthermic "ceiling" at which there is a marked insensitivity to dosage. This finding has important implications in relation to the quantitative assay of leucocytic pyrogen. Polymorphonuclear leucocytes separated from normal rabbit blood possess the capacity to produce less than 5 per cent of the pyrogen generated by the same number of rabbit granulocytes collected from acute peritoneal exudates. Blood granulocytes, separated in the cold from the buffy coat, contain no detectable preformed pyrogen. The amount of preformed pyrogen within exudate granulocytes represents but a small fraction of the pyrogen which the cells are capable of generating when incubated in normal saline at 37 degrees C. It is suggested that the active pyrogen is formed from an inactive precursor within the cells. Under the conditions tested, cell fragments of rabbit granulocytes fail to produce endogenous pyrogen. The fact that the production of pyrogen is blocked at 4 degrees C is in keeping with the hypothesis that it involves metabolic reactions within the cell.

Observations on the production of pyrogenic substances by rabbit and human leucocytes.

1. The mechanism of release of a pyrogen from leucocytes has been studied in cells obtained from sterile rabbit peritoneal exudates and from rabbit blood. Attempts were made to induce human leucocytes-from blood-to release a pyrogen. 2. Rabbit leucocytes, kept below 4 degrees C., were not pyrogenic and did not release any pyrogen when disintegrated. Incubating such cells, in various media, at 37 degrees C. led to the formation of a pyrogen which was heat-labile. The maximum yield was attained after 1(1/2) hours' incubation. 3. The formation of rabbit leucocytic pyrogen was prevented by freezing and thawing the leucocytes, by heating them to 56 degrees C. for half an hour before incubation, and by ageing them in the cold. 4. Nitrofurazone (5-nitro-2-furaldehyde semicarbazone) prevents the formation of leucocytic pyrogen when given by mouth to the cell-donor animals, or when added to leucocytes in intro. 5. Leucocytes from rabbit blood formed leucocytic pyrogen, on incubation in saline, and this formation was also inhibited by nitrofurazone. 6. No leucocytic pyrogen was released from human leucocytes subjected to mechanical, osmotic, or thermal damage, and it was not formed when the cells were incubated in saline. 7. The source of rabbit leucocytic pyrogen, the action of nitrofurazone on leucocytes, and the supposed role of leucocytic pyrogen in fever are discussed.