Bacterial Pyrogen Research Articles

Change in Format, Register and Narration Style in the Biomedical Literature: A 1948 Example

Scientific communication has evolved over time and the formats of scientific writing, including its stylistic modules, have changed accordingly. Research articles from the past fit a research world that had not been taken over by the internet, electronic searches, the new media and even the science mass production of today and reflect a reality where scientific publications were designed to be read and appreciated by actual readers. It is therefore useful to have a look back to what science looked like in the past and examine the biomedical literature from older archives because several features of those publications may actually harbor vital insights for today’s communication. Maintaining a vivid awareness of the evolution of science language and modalities of communication may ensure a better and steadfast progression and ameliorate academic writing in the years to come. With this goal in mind, the present commentary set out to review a 1948 scientific report by I.L. Bennett Jr, entitled “A study on the relationship between the fevers caused by bacterial pyrogens and by the intravenous injection of the sterile exudates of acute inflammation”, which appeared in the Journal of Experimental Medicine in September 1948.

Sex steroid levels near the term of pregnancy do not alter lipopolysaccharide-induced fever in oophorectomized rats.

What is the central question of this study? Do plasma concentrations of oestrogen and progesterone similar to those observed near the term of pregnancy alter basal core temperature or the core temperature response to bacterial pyrogen in oophorectomized rats? What is the main finding and its importance? Plasma concentrations of oestrogen and progesterone similar to those observed near the term of pregnancy do not alter basal core temperature or the overall febrile response to bacterial pyrogen in oophorectomized rats. Thus, our data do not support the hypothesis that sex steroids mediate the regulated decrease in basal core temperature or the attenuated/absent core temperature response to bacterial pyrogen observed in rats near the term of pregnancy. Fever, an important component of the host's defence response to infection, is absent or attenuated in rats near the term of pregnancy concurrent with major changes in blood concentrations of the sex steroids, oestrogen and progesterone. The present experiments were carried out to determine the potential role of oestrogen and progesterone in mediating the altered core temperature response to bacterial pyrogen. For the experiments, oestrogen and progesterone were administered alone or in combination to oophorectomized, non-pregnant rats in concentrations that mimicked plasma levels of these hormones measured in pregnant rats on days 17, 18, 19 and 20 of gestation. Treatment with oestrogen or progesterone alone or in combination did not alter basal core temperature or the overall febrile response (i.e. 12h fever index) to an EC50 dose of Escherichia coli lipopolysaccharide (i.e. 20μgkg(-1) ). Administration of oestrogen did, however, influence the early core temperature response and increase the latency to fever following administration of lipopolysaccharide. Thus, our data provide evidence that although oestrogen may influence the early core temperature response to lipopolysaccharide, sex steroids in concentrations similar to those observed late in gestation do not alter the overall febrile response and are therefore unlikely to mediate the attenuated or absent febrile response to bacterial pyrogen in rats near the term of pregnancy.

Brain kinins and fever induced by bacterial pyrogens in rabbits

Brain kinins and fever induced by bacterial pyrogens in rabbits

Rabbit responses to human threshold doses of a bacterial pyrogen.

Summary The scarcity and conflicting nature of the existing evidence on the relationship between effective doses of bacterial pyrogens in man and rabbit is pointed out. The dose/quantal response curve for man to a pyrogen prepared from P. vulgaris has been determined and the intravenous ED50 for this preparation is estimated to lie between 0·084 and 0·101 μg./kg. (P = 0·95). The dose/temperature response curves for the rabbit to the same pyrogen preparation, in a variety of different experimental circumstances, have been determined. The relative sensitivities of man and rabbit to this pyrogen have been calculated on a weight-for-weight basis. Taking as the criteria of pyrogenic response (a) a rise of 0·6° C. in the temperature of the rabbit and (b) shivering in man, it is found that the rabbit is one-third to 7 times as sensitive as man, depending on the experimental conditions. 5 The expected efficiencies of the B.P. and U.S.P. tests, in detecting a human ED5 of Pyrogen Test Preparation No. 1 in differing volumes of solution, have been calculated. 6 Some evidence that pyrogens may interact with other substances has been discussed.

Some effects of bacterial pyrogens and activated charcoal on polarographic maxima.

Journal Article Some effects of bacterial pyrogens and activated charcoal on polarographic maxima Get access I F Jones, I F Jones School of Pharmacy, Sunderland Polytechnic Search for other works by this author on: Oxford Academic Google Scholar R C Kaye R C Kaye Division of Pharmacy, Department of Pharmacology, University of Leeds, England Search for other works by this author on: Oxford Academic Google Scholar Journal of Pharmacy and Pharmacology, Volume 21, Issue Supplement_1, December 1969, Pages 169S–172S, https://doi.org/10.1111/j.2042-7158.1969.tb08369.x Published: 12 April 2011 Article history Received: 29 April 1969 Published: 12 April 2011

British Pharmaceutical Conference Aberdeen, 1955

Abstract Dr. Seibert: “I started to work with the pyrogen back in 1923 and I can really say that I have never found any more difficult work than the work with pyrogen. In fact, I used to call it my little blue devil because it was there and wasn't there. I was impressed with the elusiveness of it, and the fact that it might be everywhere. It appears in all your flasks, all your water and in everything you work with. I am wary of the possibility of contaminating what I am working with, with a pyrogen. I have to wash all my glassware with freshly distilled water, make all my chemical reagents up with freshly distilled water, and I have to use special filters in order to eliminate the pyrogen. Pyrogens exist in very small concentration and give such a tremendous reaction. I am so much impressed with all this work that is being done, but I wonder, has it been done that carefully? Are some of these pictures that you get mixtures, due partly to what you are giving but also due to contaminants?” Proceedings Research Conference on Activities of Bacterial Pyrogens at the University of Pennsylvania March 2, 1951, S. 58.

Liver function and pyrexia caused by a pyrogen from Escherichia coli, lysergic acid diethylamide and dinitrophenol.

Abstract Rabbits with liver damaged by carbon tetrachloride do not respond with hyperthermia to a lipopolysaccharide pyrogen from Escherichia coli or dinitrophenol, but lysergic acid diethylamide develops its usual effect. Rabbits with obstructive liver damage react with hyperthermia to all three pyrogenic factors. The results support the concept of a peripheral action of pyrogen. It is suggested that the liver plays a rôle in the process of transforming the bacterial pyrogen into the endogenous pyrogen.

The assay of bacterial pyrogens.

The assay of bacterial pyrogens.

Comparative observations on the production of fever by bacterial pyrogens and leucocytic pyrogen in goats and rabbits.

Summary After moderate doses of bacterial pyrogen the goat is just as sensitive as the rabbit according to the “fever index” and to the average of the individual temperature maxima. In goats tolerance to bacterial pyrogens can be rapidly induced and is almost complete, in contrast to this phenomenon in rabbits. In goats the presence of endogenous pyrogen is demonstrated in the blood during fever evoked by bacterial pyrogen. Incubation of peritoneal exudate with a high percentage of polymorphonuclear neutrophilic leucocytes isolated from goats released a pyrogen which seems to be identical with endogenous pyrogen. This crude leucocytic pyrogen has the same characteristic properties as leucocytic pyrogen isolated from rabbit exudate cells. In the goat, latency time for temperature rise and shivering can be used as a parameter to differentiate between the febrile response after bacterial pyrogen and leucocytic pyrogen (or endogenous pyrogen). Leucocytic pyrogen isolated from goat peritoneal exudate seems not to be species-specific. Zusammenfassung Vergleichende Untersuchungen uber bakterielle und leukozytare Pyrogene bei Ziegen und Kaninchen Nach dem “Fieberindex” ist die Ziege ebenso empfindlich fur masige Dosen von bakteriellen Pyrogenen wie das Kaninchen. Bei Ziegen kann sehr rasch eine fast absolute Toleranz gegenuber bakteriellen Pyrogenen induziert werden. Wahrend des durch bakterielle Pyrogene erzeugten Fiebers sind im Blut der Ziege endogene Pyrogene nachzuweisen. Die Inkubation eines Peritoneal-exsudates von Ziegen, welches einen hohen Gehalt an polymorphkernigen neutrophilen Leukozyten enthielt, fuhrte zur Freisetzung eines Pyrogens, das mit dem endogenen Pyrogen identisch sein durfte. Dieses ungereinigte Leukozytenpyrogen hat die gleichen Eigenschaften wie das Leukozytenpyrogen aus den Zellen des Kaninchenexsudates. Bei der Ziege kann die Latenzzeit bis zum Temperaturanstieg und Muskelzittern als Parameter zur Differenzierung zwischen bakteriellen und leukozytaren bzw. endogenen Pyrogenen verwendet werden. Das Leukozytenpyrogen aus dem Ziegenexsudat scheint nicht tierartspezifisch zu sein. Resume Observations comparatives sur l'effet febrile provoque par des pyrogenes bacteriens et leucocytaires chez les chevres et les lapins Selon P et les maxima de temperature individuels, la chevre est aussi sensible que le lapin a des doses moderees de pyrogene bacterien. Chez les chevres et a l'encontre des lapins, on obtient rapidement une tolerance presque absolue aux pyrogenes bacteriens. Chez les chevres, on met en evidence la presence de pyrogenes endogenes dans le sang, pendant la poussee de fievre provoquee par les pyrogenes bacteriens. L'incubation d'un exsudat peritoneal de chevres, contenant de nombreux granulocytes neutrophiles, mene a la liberation d'un pyrogene, qui semble identique au pyrogene endogene. Ce pyrogene leucocytaire impur a les memes proprietes que le pyrogene leucocytaire des cellules d'un exsudat de lapin. Chez la chevre, le temps de latence jusqu'a la hausse de la temperature et au frisson peut etre employe comme parametre dans une differenciation entre pyrogenes bacteriens et leucocytaires (ou pyrogenes endogenes). Le pvrogene leucocytaire, isole de l'exsudat de chevres, ne semble pas etre specifique a l'espece. Resumen Observaciones comparativas sobre la produccion de fiebre mediante pirogenos bacterianos y leucociticos en cabras y conejos Tras recibir dosis moderadas de pirogenos bacterianos, la cabra es igual de sensible que el conejo con respecto al llamado y los maximos medios individuales de temperatura. En cabras, se puede inducir con rapidez una tolerancia casi completa frente a los pirogenos bacterianos, en contraste con este fenomeno en los conejos. En cabras, la presencia de pirogenos endogenos se identifica en la sangre durante la fiebre evocada por pirogenos bacterianos. La incubacion de exudado peritoneal de cabras, que contenia muchos leucocitos polimorfonucleares neutrofilos, derivo en el aislamiento de un pirogeno, que parece ser identico al pirogeno endogeno. Este pirogeno leucocitico crudo tiene las mismas propiedades caracteristicas que el pirogeno leucocitico aislado a partir de celulas del exudado de conejo. En la cabra, el tiempo de latencia hasta la hipertermia y el principio de los calofrios se puede usar como un parametro para diferenciar entre los pirogenos bacterianos y los leucociticos (o pirogenos endogenos). Los pirogenos leucociticos, aislados del exudado peritoneal de cabras, no parecen ser especificos de especie.

The reaction of different animal species to bacterial pyrogens.

Summary After a review of the literature the reactions of the different animal species to the parenteral administration of a single batch of E. coli 0111 B 4 lipopolysaccharide are described. Special attention has been given to the effects on body temperature, circulating white blood cells and the gastrointestinal system (vomiting, diarrhoea, hypomotility of the rumen). It is concluded that for these effects and this pyrogen the following list of diminishing sensitivity can be given: rabbit, horse, goat, dog, cow, sheep, cat, swine and chicken. The mouse, rat and guinea pig take a separate place by the absence of a fever reaction or a leucocyte response. The development of tolerance to repeated injections was studied in the goat. Acknowledgements We acknowledge the technical assistance of Miss. C. Th. M. van Duin, P. I. Lagendijk, J. M. Eyndhoven and the help of the veterinary students J. Atsma, H. H. Stigter and W. de Haan. Animals and experimental facilities were provided by the Institute of Veterinary Physiology and the Clinics for Veterinary Obstetrics, Surgery and Internal Medicine of the Veterinary Faculty of the University of Utrecht, the Institute for Animal Physiology of the Agricultural University Wageningen, and the Hoorn Institute of Feeding Research. Zusammenfassung Die Reaktion verschiedener Tierarten auf bakterielle Pyrogene Nach der Besprechung der einschlägigen Literatur werden die Reaktionen verschiedener Tierarten auf die Applikation von E. coli 0111 B 4-Lipopolysaccharid beschrieben. Besondere Beachtung fanden hierbei: die Körpertemperatur, die Leukozyten im zirkulierenden Blut und das Verhalten des Magendarmtraktes (Erbrechen, Durchfall, herabgesetzte Pansenmotorik). Nach ihrer Empfindlichkeit — Reihenfolge entsprechend abnehmender Sensitivität — kann folgende Liste aufgestellt werden: Kaninchen, Pferd, Ziege, Hund, Rind, Schaf, Katze, Schwein und Huhn. Maus, Ratte und Meerschweinchen nehmen eine Sonderstellung ein, indem sie weder Fieber noch leukozytäre Reaktionen aufweisen. Résumé La réaction de différentes espèces animales aux pyrogènes bactériens Après un compte-rendu de la littérature concernant ce sujet, on décrit les réactions observées chez différentes espèces animales après application de lipopolysaccharide de E. coli 0111 B 4. On examine tout particulièrement la température du corps, les leucocytes dans la circulation sanguine et le comportement du tractus digestif (vomissements, diarrhée, motricité diminuée de le rumen). Par ordre décroissant de sensibilité, nous nommons lapin, cheval, chèvre, chien, boeuf, mouton, chat, porc et poule. Souris, rat et cobaye ont une position spéciale, car ils ne produisent ni fièvre, ni réactions leucocytaires. Resumen La reacción de diversas especies animales frente a diversos pirógenos bacterianos Tras discutir la bibliografía correspondiente, descríbense las reacciones de varias especies animales frente a la aplicación del lipopolisacárido de E. coli 0111 B 4. Consideración especial merecieron a este respecto: la temperatura corporal, los leucocitos en la sangre circulante y el comportamiento del tracto gastrointestinal (vómito, diarrea, movimientos rebajados de la panza). Con arreglo a su sensibilidad — sucesión correspondiendo a la sensitividad — se puede establecer la lista siguiente: conejo, caballo, cabra, perro, vaca, oveja, gato, cerdo y gallina. El ratón, rata y cobaya ocupan una posición un tanto especial, ya que no manifiestan fiebre ni reacciones leucocitarias.

The effects of bacterial pyrogens and leucocytic pyrogen upon gastric motility and heart rate frequency in conscious goats.

The effects of bacterial pyrogens and leucocytic pyrogen upon gastric motility and heart rate frequency in conscious goats.

Restraint increases afebrile body temperature but attenuates fever in Pekin ducks (Anas platyrhynchos)

In mammals, procedures such as handling, restraint, or exposure to open spaces induces an increase in body temperature (T(b)). The increase in temperature shares some characteristics with pyrogen-induced fever and so is often called "stress fever." Birds also respond to acute handling with a stress fever, which may confound thermoregulatory studies that involve animal restraint. We have measured the T(b) responses of Pekin ducks on days when they were restrained and compared them to days when the birds remained unrestrained. Restraint induced a 0.5 degrees C increase in T(b) that was sustained for the entire 8 h of restraint. To determine whether the restraint-induced increase in T(b) is mediated by prostaglandins (PGs) we compared the T(b) responses during restraint after intraperitoneal injection with saline to the responses during restraint after injection with diclofenac sodium (15 mg/kg). There was no difference in response, suggesting that restraint affects T(b) by a PG-independent mechanism. We also compared the T(b) response to intramuscular injection of lipopolysaccharide (LPS; 100 microg/kg), a bacterial pyrogen, when the ducks were restrained or unrestrained. Despite T(b) being higher at the time of LPS injection when the ducks were restrained, the maximum temperature reached after LPS injection was higher, and the period that T(b) remained elevated was longer when the ducks were unrestrained. We conclude that restraint should be considered as a potential confounder in thermoregulatory studies in birds and presumably other species too.

Brain adaptations for a successful pregnancy

Pregnancy has long been the focus of endocrinologists and reproductive biologists. Possibly because of this, most physiology textbooks with chapters devoted to pregnancy, lactation and fetal/maternal physiology pay considerable attention to alterations in the maternal circulation, respiratory system and metabolism. Similarly, the importance of the hypothalamic–pituitary axis is acknowledged in the obligatory role of oxytocin in milk letdown and its participation in labour, and the additional involvement of the hypothalamic–pituitary–adrenal axis in some species in the initiation of labour. However, it is becoming evident that the maternal brain also undergoes significant changes during pregnancy that equip the mother physiologically and behaviourally for a successful pregnancy, delivery and mothering. This issue of The Journal of Physiology highlights this theme, which is at the intersection of reproductive biology and neuroscience. The invited contributions represent proceedings of a recent symposium supported by The Journal of Physiology and the International Union of Physiological Sciences at the 7th International Brain Research Organization World Congress of Neuroscience in Melbourne Australia. The symposium, entitled ‘Brain Adaptations for a Successful Pregnancy’ featured talks by leading scientists in the field who demonstrated how the dramatic hormonal changes that occur throughout pregnancy, birth and lactation can alter the brain to redirect its role from that of preservation of self only, to that devoted to support of a fetus and newborn. This requires a fascinating, neurally orchestrated series of physiological compromises and redirection of resources and energy. Two of the reviews in this symposium issue report on the attenuation of stress responses during pregnancy. Paula Brunton and John Russell (Brunton & Russell, 2008) use the immune stimulant, interleukin 1β, a well known activator of the hypothalamic–pituitary–adrenal (HPA) axis, and show how the glucocorticoid responses are reduced during pregnancy. This is due to an up-regulation of opioid inhibition of ascending fibres to the corticotrophin releasing hormone neurons in the hypothalamic paraventricular nucleus and is brought about by the neurosteroid allopregnanolone, a progesterone metabolite whose levels peak shortly before parturition. Inga Neumann and colleagues (Slattery & Neumann, 2008) note that hormonal responses to behavioural stressors are similarly attenuated during pregnancy and lactation and show how up-regulated actions of oxytocin and prolactin within the brain are involved in this attenuated stress response. They postulate that this may be important in preventing excessive levels of glucocorticoids that could be detrimental to healthy prenatal development and postnatal maternal care. David Grattan and colleagues (Augustine et al. 2008) discuss the adaptations required for a pregnant mother to meet the needs of a growing fetus and to prepare for the metabolic demands of lactation. This requires an increase in appetite and food intake brought about by alterations in the sensitivity of the hypothalamus to the hormone leptin, thus circumventing its known appetite-suppressing function. Finally, Sarah Spencer and colleagues (Spencer et al. 2008) report on their studies with the bacterial pyrogen lipopolysaccharide, and show how both the generation of prostaglandins within the brain, and the actions of these prostaglandins on thermogenesis are reduced specifically at term. Thus, fever, an important component of the host defence response, is attenuated, and the possible survival value of this adaptation is discussed. Altogether, these papers reveal that the brain displays remarkable plasticity during pregnancy, just as remarkable as those alterations seen in the maternal circulatory, endocrine and metabolic axes; it is time for the ‘maternal brain’ to be featured in our physiology textbooks. Finally, it is possible that the pregnancy-altered brain may provide a physiologically relevant, accessible preparation to understand other types of plasticity in the nervous system.

Thermoregulation: Channels that Are Cool to the Core

TRP channels are molecular sensors that endow animals with the ability to sense external temperatures. Recent studies have provided strong evidence that at least one TRP channel, TRPV1, is also essential for the maintenance of internal body temperature.

LPS induced hypothermia in pregnant rats: A regulated thermoregulatory response

Intraperitoneal administration of E. coli LPS in doses that elicit half-maximal (EC 50 – 20 ug/kg) and maximal (EC 100 – 160 ug/kg) febrile responses in nonpregnant rats produce hypothermia in near-term pregnant rats. The present experiments have been carried out to determine if the hypothermia results from a “regulated” or “forced” thermoregulatory response. Chronically-instrumented pregnant rats were allocated to one of two experimental groups depending upon whether they were studied in an experimental apparatus configured as a metabolic chamber with a uniform ambient temperature of 25 °C or configured as a thermocline with a linear temperature gradient ranging from 10 °C to 40 °C. The pregnant rats developed hypothermia following intraperitoneal administration of 160 ug/kg of E. coli LPS when they were studied in the thermal gradient as well as when they were studied in the uniform thermoneutral environment. They did not attempt to prevent the hypothermia following administration of bacterial pyrogen by moving to a warmer region of the thermocline. Thus, our data provide evidence that the hypothermia which occurs following intraperitoneal administration of an EC 100 dose of E. coli LPS results from a regulated rather than a forced thermoregulatory response. The mechanism and consequences of this pregnancy-induced thermoregulatory response to bacterial pyrogen are unknown.

Mifepristone (RU38486) influences the core temperature response of term pregnant rats to intraperitoneal lipopolysaccharide

Pregnancy alters the cytokine, prostanoid and core temperature responses of rats to infectious stimuli at a time when blood levels of the endogenous glucocorticoid corticosterone are elevated. Given that glucocorticoids attenuate bacterial pyrogen-induced fever in rats, the present experiments were carried out to test the hypothesis that administration of RU38486, a glucocorticoid type II receptor antagonist, would restore the febrile response to E. coli lipopolysaccharide (LPS) in pregnant rats on day 21 of gestation. Pregnant rats were randomly allocated to one of four experimental groups depending upon whether they received RU38486 (20 mg kg(-1) intragastric) or vehicle followed by E. coli LPS (160 microg kg(-1)i.p.; a minimal dose that elicits maximal febrile response in non-pregnant rats) or vehicle. Basal core temperature was not altered by intragastric administration of RU38486 or vehicle. Following intragastric administration of vehicle, intraperitoneal administration of E. coli LPS produced a significant hypothermia with latency, duration and magnitude of 0.5 h, 2 h and -1.3 degrees C, respectively. Following intragastric administration of RU38486, however, intraperitoneal administration of E. coli LPS elicited only a minimal decrease in core temperature which was not significantly different from control values. Thus, our data provide evidence that endogenous glucocorticoids play a role in modulating the early core temperature response to a relatively large dose of bacterial pyrogen in rats at term of pregnancy.

Bacterial lipopolysaccharide fever is initiated via Toll-like receptor 4 on hematopoietic cells

Lipopolysaccharide (LPS), a well-known bacterial pyrogen, is recognized by several receptors, including the Toll-like receptor 4 (TLR4), on various cells. Which of these receptors and cells are linked to fever production is unknown. By constructing 4 mouse chimeras and studying their thermoregulatory responses, we found that all 3 phases of the typical LPS fever depend on TLR4 signaling. The first phase is triggered via the TLR4 on hematopoietic cells. The second and third phases involve TLR4 signaling in both hematopoietic and nonhematopoietic cells.

Attenuated fever response in mice lacking TRPV1

TRPV1, the capsaicin receptor, is expressed not only in nociceptive neurons, but also in other locations, including the hypothalamus. Studies involving systemic or intrahypothalamic capsaicin administration have suggested a role for TRPV1 in body temperature control. To explore this possibility, we examined thermoregulatory responses in TRPV1−/− mice. These mutant animals exhibited no obvious changes in circadian body temperature fluctuation, tolerance to increased (35 °C) or decreased (4 °C) ambient temperature or ethanol-induced hypothermia. In contrast, fever production in response to the bacterial pyrogen, lipopolysaccharide (LPS) was significantly attenuated in TRPV1−/− mice. Despite this finding, we detected no significant differences between TRPV1−/− and control mice in the extent of LPS-induced c-Fos expression in numerous fever-related brain subregions. These results suggest that TRPV1 participates in the generation of polyphasic fever, perhaps at sites outside the brain.

Characterization of the DialGuardTM Device for Endotoxin Removal in Hemodialysis

Bacterial pyrogens, capable of penetrating dialyzer membranes, are responsible for a systemic inflammatory reaction in hemodialysis patients. Dialyzer reuse, involving rinsing of the dialyzer with pyrogen-containing water, may exacerbate this situation. Studies of the mechanism of action of endotoxin suggest that it irreversibly damages the vascular endothelium. The novel endotoxin removal method described here, is based on affinity-binding of endotoxin by the adsorbent ClarEtox^TM, a USP Class VI-certified resin that is the active component of the medical device DialGuard^TM. Under standard hemodialysis operating conditions, challenge of DialGuard with Pseudomonas maltophilia supernatant-spiked dialysate, containing 35–193 EU/ml endotoxin, resulted in endotoxin levels below 0.05 EU/ml in the treated dialysate. DialGuard was able to decrease endotoxin concentrations in the dialysate from a range of 2.39–8.49 to <0.005 EU/ml. DialGuard supports high fluid velocities at low back pressures and can be sanitized using the heat sanitization cycle of hemodialysis machines. DialGuard offers a simple, user-friendly way to reduce the concentration of endotoxin in dialysate and water for dialysis at a low cost.

Differences in the permeability of high-flux dialyzer membranes for bacterial pyrogens.

The increasing use of high-flux membranes for hemodialysis has raised concerns that patients dialyzed with these membranes may be at higher risk of being exposed to cytokine-inducing bacterial substances in the dialysate than patients dialyzed with low-flux membranes. We investigated the permeability of various high-flux membranes for both purified E. coli lipopolysaccharide (LPS) as well as for LPS derived from Stenotrophomonas (Sten.) maltophilia. An in vitro dialysis circuit with saline in the blood compartment of 3 dialyzers containing different membranes (polysulfone, helixone and Diapes) was employed. The dialysate was challenged with increasing doses of sterile filtrates derived from Sten. maltophilia cultures or with purified LPS from E. coli. Samples from the blood compartment were tested for cytokine induction (IL-1beta, IL-6 and TNF) in mononuclear cells as well as for LPS by limulus amebocyte lysate test (LAL). IL-6 induction above sterile controls (< 0.02 ng/ml IL-6) was observed by samples from the blood side of DIAPES dialyzers (1.2 +/- 0.7 ng/ml IL-6) after challenging the dialysate with 4.1 +/- 3.6 U/ml E. coli LPS (9.9 +/- 4.5 ng/ml IL-6). In contrast, at the same challenge dose no significant IL-6 induction above sterile controls was observed by blood side samples of polysulfone (0.15 +/- 0.07 ng/ml) and helixone (0.09 +/- 0.05 ng/ml) dialyzers. Increasing the amount of E. coli LPS in the dialysate further augmented IL-6 induction by blood side samples of Diapes but not of polysulfone and helixone dialyzers. Similar results were obtained for IL-1beta and TNF. After challenging the dialysate with E. coli LPS as well as with cultures of Sten. maltophilia, significantly more LAL reactivity was observed in the blood compartment of Diapes compared to polysulfone and helixone. There are considerable differences between high-flux membranes regarding their permeability for cytokine-inducing substances from E. coli as well as for LPS derived from E. coli and Sten. maltophilia. Dialyzers that leak CIS under aqueous conditions in vivo should not be used unless the dialysate has passed through an ultrafilter.