Navigating Access to Cancer Care: Identifying Barriers to Precision Cancer Medicine

OBJECTIVE

Precision medicine is revolutionizing cancer treatment. However, there has been limited investigation of barriers patients endure to access precision cancer medicine. This study aims to report the experiences of underserved patient populations with limited access to genomic testing, clinical trials, and precision cancer treatment.

METHODS

A mixed-method study was employed to quantitatively evaluate patients (N=300) seeking precision cancer medicine between January 2014- August 2017. Qualitatively, we conducted semi-structured interviews with eight case managers who navigate the health care and health insurance systems to provide patients with access to precision cancer medicine care. All interviews were analyzed to identify themes.

RESULTS

Within our patient cohort, 69% were diagnosed in stage I of cancer disease. Overall, 27 patients (9%) were denied treatment as a final outcome of their case due to insurance denials, 35 patients (12%) died before gaining access to precision cancer medicine, and 6 patients (2%) received precision cancer medicine through clinical trials. Four broad thematic areas emerged from the qualitative analysis: 1) lack of patient, provider and insurer knowledge of precision cancer medicine; 2) barriers to clinical trial participation; 3) lack of patient health literacy; and 4) barriers to timely access to care.

CONCLUSION

Our combined analyses suggest that both system-level and patient-level barriers limit patient access to precision cancer medicine options. Additionally, we found that these barriers may exist not only for traditionally underserved patients, but also for resourced and insured patients trying to access precision cancer medicine.

Practices and Attitudes toward Returning Genomic Research Results to Low-Resource Research Participants

INTRODUCTION

Many research programs are challenged to accommodate low-resource research participants' (LRRP) ancillary care needs when returning genomic research results. We define LRRP as those who are low income, uninsured, underinsured, or facing barriers to act upon the results returned. This study evaluates current policies and practices surrounding return of results (RoR) to LRRP, as well as the attitudes of investigators toward providing ancillary care to LRRP.

METHODS

A semi-structured interview study was conducted with representatives of 35 genomic research programs nationwide. Eligible programs were returning, or planning to return, medically actionable genomic results to participants.

RESULTS

Three content categories emerged from this study, including: (1) RoR structures, (2) barriers to RoR to LRRP, and (3) solutions to meet community and LRRP needs. Three major structures of RoR emerged: (1) RoR Embedded in Clinical Care, (2) RoR Independent of Clinical Care, and (3) Reliance on Clinical Partnerships to Facilitate RoR. Inadequacy of program resources to address the needs of LRRP was commonly considered a significant obstacle. The attitudes and views of informants regarding responsibility to provide ancillary care for LRRP receiving genomic results were highly varied. Some informants believed that genomic sequencing and testing was not a priority for LRRP because of other pressing issues in their lives, such as housing and food insecurity. Research programs differ regarding whether clinical and social support for LRRP is considered within the purview of the research team. Some programs instituted accommodations for LRRP, including social work referral and insurance enrollment assistance.

CONCLUSION

Support to access downstream treatment is not readily available for LRRP in many genomic research programs. Development of best practices and policies for managing RoR to LRRP is needed.

Perspectives of Sickle Cell Disease Stakeholders on Heritable Genome Editing

Advances in CRISPR technology and the announcement of the first gene-edited babies have sparked a global dialogue about the future of heritable genome editing (HGE). There has been an international call for public input to inform a substantive debate about benefits and risks of HGE. This study investigates the views of the sickle cell disease (SCD) community. We utilized a mixed-methods approach to examine SCD stakeholders' views in the United States. We found SCD stakeholders hold a nuanced view of HGE. Assuming the technology is shown to be safe and effective, they are just as supportive of HGE as genetics professionals, but more supportive than the general public. However, they are also concerned about the potential implications of HGE, despite this support. As discourse surrounding HGE advances, it is crucial to engage disease communities and other key stakeholders whose lives could be altered by these interventions.

Some historical perspectives on thermoregulation

In this paper, selected historical aspects of thermoregulation and fever are presented as background to the application of molecular biology to thermoregulation. Temperature-sensing mechanisms, coordination of thermal information, thermoregulatory circuitry, efferent responses to thermal stimuli, set point mechanisms, and some of the mechanisms and consequences of fever and hyperthermia are highlighted. Neurotransmitters used in thermoregulatory circuits are also discussed. An attempt is made to include information from comparative physiological sources. Possible future avenues of research in the light of recent new technologies are also presented.

Submandibular glands: novel structures participating in thermoregulatory responses

Since submandibular glands participate in the regulation of cardiovascular and immunological responses to bacterial endotoxin, we examined their role as modulators of endotoxin-induced fever. Core body temperatures were measured by telemetry in rats that had either a sham operation or a sialadenectomy 1 week previously and that were maintained at 23-24 degrees C. The sialadenectomized rats showed a circadian variation in body temperature similar to sham-operated rats, although their daytime body temperature was 0.24 +/- 0.01 degree C lower. The fever elicited by intraperitoneal injection of Escherichia coli endotoxin was biphasic, with an initial phase occurring between 2 and 3 h, and a broader second phase peaking between 4 and 8 h after endotoxin injection. The initial fever was similar in the two groups of rats, but the second phase of fever was significantly higher by 0.28 +/- 0.09 and 0.26 +/- 0.07 degree C in sialadenectomized rats receiving 50 or 150 micrograms/kg of endotoxin, respectively. Intravenous treatment with a novel peptide, submandibular gland peptide-T (SGP-T; 100 micrograms/kg), 30 min before endotoxin injection did not affect the early fever response, but significantly suppressed by 0.37 +/- 0.10 degrees C the late-phase fever provoked by 150 micrograms/kg of endotoxin. These results suggest that the submandibular glands modulate thermogenic responses to inflammatory stimuli possibly through the endocrine release of hormones, such as SGP-T.

Salivary glands, their hormones, and thermoregulation

The effects of the removal of the submandibular glands (sialadenectomy) on the fever induced by bacterial lipopolysaccharide (LPS) were examined. Thermally sensitive radiotransmitters were implanted into the abdomens of adult male Sprague-Dawley rats that experienced at this time either a sham operation or a sialadenectomy, and one week later body temperatures were recorded by telemetry in these rats when conscious. The initial fever (up to 180 min following LPS) response, following the intraperitoneal injection of 150 micrograms/kg E. coli LPS, was similar in the two groups of rats, but the second phase of the fever (240 to 420 min post-LPS) was modestly, but significantly higher (mean = 0.26 degree C) in sialadenectomized rats. A submandibular gland peptide (compound T; 100 micrograms/kg), given one-half hour before the LPS, did not affect the early fever, but suppressed the late-phase fever by 0.37 degree C (mean). The submandibular glands, which form an integral part of the neuroendocrine mechanisms responsible for attenuating the responses of the immune system to inflammatory stimuli, also appear to modulate thermogenic responses to these stimuli.

Effect of potassium-induced cortical spreading depression on prostaglandin-induced fever in conscious and urethane-anesthetized rats

Potassium-induced cortical spreading depression (CSD) on prostaglandin E1 (PGE1) induced fever has been investigated in a dose-responsive experimental design in both conscious and urethane-anesthetized adult male Sprague-Dawley rats. While CSD in itself had no effect on nonfebrile body temperature even under cold ambient conditions, CSD significantly suppressed small but not large fevers induced by intracerebroventricular PGE1. The increased oxygen consumption during fever was also reduced. We also explored the possible involvement of the antipyretic peptide arginine vasopressin, in the CSD-induced suppression of fever. Long term castrated rats have significantly reduced ventral septal levels of this peptide, yet CSD was effective in suppressing the initial 40 min of PGE1 fever in these animals. Thus we conclude that increased release of ventral septal arginine vasopressin is probably not involved in the action of CSD on fever.

Some responses of the cardiovascular system to heat and fever

This review outlines the mechanisms of body temperature control and the validity of various sites of measurement of core temperature. The mechanism of fever in response to circulating endotoxins are discussed, and the roles of various peripherally generated pyrogenic cytokines are outlined together with the loci of their action in the brain. The cardiovascular consequences of exposure to heat, particularly the pooling of blood in the skin and the increase of heart rate due to heating of the sinoatrial node, are discussed. The consequences of blood pooling, such as syncope or diminished G tolerance, are very important. Heat exposure and exercise lead to complex circulatory interactions, such as a higher heart rate for a given exercise load in the heat compared with a cool environment. At high work loads there may be a relatively lower cardiac output in hot conditions. Blood lactate levels and rectal temperature tend to be higher in exercise in the heat than exercise in the cold. Fever causes a large renal vasodilation and hepatic vasodilation, which are humorally mediated and which effectively cause a splanchnic vascular shunt of some consequence if there is already heart failure or shock. Syncope during fever, endotoxin shock and the role of pyrogens in heat stroke are discussed.

Regulation of a voltage-dependent, calcium-activated K conductance by cyclic GMP in dissociated flounder enterocytes

Enterocytes from the winter flounder (Pseudopleuronectes americanus) were isolated by collagenase digestion and maintained in flounder Ringer's solution. Whole cell currents were studied using the amphotericin-perforated whole-cell patch clamp technique. The mean resting membrane potential and capacitance values or dissociated cells were -45 +/- 7 mV and 5 +/- 0.4 pF, respectively. Enterocytes held at -20 mV and treated with 1 mumol.l-1 ionomycin exhibited outward currents when cells were stepped through a series of voltages from -60 to +110 mV. The reversal potential of this current in flounder Ringer's solution was -55 mV and the voltage at which half-maximal activation occurred was +20 mV. Voltage-dependent inhibition of outward current was observed at +60 mV and above. When cells were bathed in symmetric K Ringer's solution the reversal potential shifted to zero mV and no inhibition of current was observed at voltages between -60 and 140 mV. When the holding potential of the cell was changed from -20 to -80 mV and stepped from -60 to +110 mV, a second [previously characterized, O'Grady et al. (1991)] K current with delayed-rectifier properties was identified. This observation demonstrated that the delayed rectifier K channel and the Ca(2+)-activated K channel described in this study exist in the same cell. Extracellular addition of 2 mmol.l-1 Ba2+ to cells bathed in symmetric K Ringer's solution resulted in nearly complete inhibition of outward current. Charybdotoxin produced only minor effects on this current.(ABSTRACT TRUNCATED AT 250 WORDS)

Lupus anticoagulant testing: effect of the platelet count on the activated partial thromboplastin time

The activated partial thromboplastin time (APTT) is often used as a test to diagnose patients with lupus anticoagulants. It is recommended that platelet-poor plasma be used in the APTT test. In this study the effects of residual platelet contamination on lupus anticoagulant and antiphospholipid antibody testing are described. In fresh samples the residual platelet contamination has no significant effect whereas in frozen samples the effect of residual platelet contamination can have a significant effect on the APTT testing.

A method for continuous blood sampling during cold water immersion

A technique, consisting of a pre-calibrated, catheter-peristaltic pump combination, for continuous blood sampling was tested using six volunteers during a 20 min immersion in cold water at 14.7 +/- 0.9 degrees C. The device offered the advantage of continued collection of blood samples from an antecubital vein during the experiment with little discomfort for the subjects and in sufficient volume for assay of plasma constituents eg. catecholamines.

Vasopressin perfusion within the medial amygdaloid nucleus attenuates prostaglandin fever in the urethane-anaesthetized rat

The antipyretic effect of arginine vasopressin (AVP) introduced into the ventral septal area (VSA) by push-pull perfusion was investigated in the urethane-anaesthetized rat. In addition, experiments were carried out to determine whether AVP could suppress fever when similarly perfused within the medial amygdaloid nucleus (meA). During push-pull perfusion of artificial cerebrospinal fluid within the VSA or meA, PGE1 injected intracerebroventricularly evoked fevers with respective magnitudes of 1.3 +/- 0.2 degrees C and 1.4 +/- 0.3 degrees C above baseline. Perfusion of AVP (6.5 micrograms/ml) within the VSA had significantly reduced the magnitude of PGE1 fever to 0.3 +/- 0.3 degrees C above baseline, while having no significant effect on afebrile colonic temperature. Perfusion of AVP (6.5 micrograms/ml) within the meA had significantly attenuated the magnitude of PGE1 fever to 0.7 +/- 0.2 degrees C above baseline, while having no significant effect on afebrile colonic temperature. These results support further the utility of the urethane-anaesthetized rat model for future investigations of the central control of fever and antipyresis. In addition, these data are consistent with the hypothesis that AVP may act within the meA as an endogenous antipyretic.

Fever response of sheep in the peripartum period to gram-negative and gram-positive pyrogens

We have measured body temperatures and serum iron concentrations of sheep in the peripartum period following administration of endotoxin and Staphylococcus aureus cell walls. Both the rise in rectal temperature and the fall in serum iron concentration following intravenous injection of S. aureus were the same immediately pre- and postpartum as they were 5 weeks after parturition. The rise in rectal temperature following intravenous endotoxin injection immediately pre- and postpartum was significantly less than that of the same ewes 5 weeks later. However, the fall in serum iron concentration following endotoxin injection was significantly suppressed only prepartum. We conclude that fever is not suppressed in sheep in the peripartum period, but the response to endotoxin is suppressed, through complex processes incidental to the mechanism responsible for the maintenance of gestation and induction of labour.

Cyclic GMP regulation of a voltage-activated K channel in dissociated enterocytes

Enterocytes from the intestinal epithelium of the winter flounder were isolated by collagenase digestion and incubated in flounder Ringer solution. Conventional whole-cell and amphotericin-perforated whole-cell recording techniques were used to characterize the properties of a voltage-activated K current present in dissociated cells. Resting membrane potentials and series resistances were significantly lower (from -23 to -39 mV and 29 to 13 M omega, respectively) when amphotericin was used to achieve the whole-cell configuration. When cells were placed in flounder Ringer solution, held at -80 mV and subsequently stepped to a series of depolarizing voltages (from -70 to 0 mV), an outward current was observed that exhibited inactivation at voltages above -20 mV. This current was sensitive to holding potential and was not activated when the cells were held at -40 mV or above. When cells were bathed in symmetric K Ringer solution and the same voltage protocol was applied to the cell, inward currents were observed in response to the negative intracellular potentials. Reversal potentials at two different extracellular K concentrations were consistent with K as the current-carrying ion. BaCl2 (2 mM) and CsCl (0.5 mM) both produced voltage-dependent blockade of the current when added to the bathing solution. Charybdotoxin (300 nM extracellular concentration) completely blocked the current. The IC50 for charybdotoxin was 50 nM. Cyclic GMP inhibited the voltage-activated current in flounder Ringer and in symmetric K Ringer solution. The cyclic GMP analog, 8-Br cGMP, lowered the threshold for voltage activation and potentiated inactivation of the current at voltages above -40 mV.(ABSTRACT TRUNCATED AT 250 WORDS)

Nucleus tractus solitarii lesions alter the metabolic and hyperthermic response to central prostaglandin E1 in the rat

1. Given that the nucleus tractus solitarii (NTS) may regulate the ability of brown adipose tissue to evoke non-shivering thermogenesis and that brown fat may mediate the rise in whole-body metabolism observed following central pyrogen administration, we assessed whether interruption of baroreceptor afferents coursing though the NTS would interfere with the ability of prostaglandin E1 to evoke a normal fever response profile. 2. Infusion of 150-600 ng of prostaglandin E1 (PGE1) into a lateral cerebral ventricle of the conscious rat resulted in a rise in core temperature, and also an increase in whole-body metabolic rate, brown adipose tissue temperature, arterial blood pressure and heart rate. 3. Following bilateral electrolytic lesions to the NTS, resting core and brown fat temperatures, metabolic rates, blood pressures and heart rates in the NTS-lesioned animals were comparable to control rats. However, the PGE1-evoked increase in metabolic rate, along with the rise in core and brown adipose tissue temperatures and heart rate were attenuated. The pressor response was, however, enhanced, possibly due to the demonstrated interference by the lesions with normal baroreflex control. 4. The findings suggest that the nucleus tractus solitarii region of the rats' brain may be important in mediating the thermogenesis evoked by central PGE1.

Modulation of brown adipose tissue-mediated thermogenesis by lesions to the nucleus tractus solitarius in the rat

Given that relatively little is known regarding the central control of brown adipose tissue (BAT)-mediated thermogenesis the present study assessed whether the direct pharmacological stimulation of beta- or alpha-adrenergic receptors located on the brown adipocytes would result in a typical thermogenic response following electrolytic lesions to the nucleus tractus solitarius (NTS). Bilateral electrolytic lesions to the NTS in the rat effectively disrupted the baroreceptor reflex arc. It was observed that the metabolic and temperature responses to either norepinephrine (1, 5, or 25 micrograms/kg/min) or to the beta-agonist isoproterenol (0.5 micrograms/kg/min) were significantly attenuated in the NTS-lesioned rats relative to the control animals with an intact baroreflex. Conversely, the cardiovascular effects of norepinephrine or of the alpha-agonist phenylephrine (10 micrograms/kg/min) were enhanced in the NTS-lesioned animals. The results suggest that the functional capacity of the brown adipocytes was reduced following NTS lesions and points to an alteration in the ability of beta-receptors to respond to pharmacological stimulation with a typical thermogenic response.

Contribution of brown adipose tissue to central PGE1-evoked hyperthermia in rats

The relative contribution of several effector systems to a prostaglandin E1-(PGE1) evoked hyperthermia was examined. Infusion of 150 ng of PGE1 into a lateral cerebral ventricle increased core temperature and whole body metabolic rate, brown adipose tissue temperature, systolic blood pressure, and heart rate. Pretreating the animals with a nonselective beta-antagonist propranolol (1 mg/kg iv in 0.3 ml followed by 3 mg.kg-1.h-1 in 0.3 ml/h) not only attenuated the rise in metabolism observed after the central administration of 150 ng PGE1 but also diminished the elevation in both core and brown fat tissue temperatures as well as the increase in heart rate. Pretreating the animals with the alpha-antagonist prazosin (2 mg/kg im followed by 50 micrograms.kg-1.h-1 iv in 0.3 ml/h) somewhat reduced the rise in whole body metabolism, suppressed the elevation in core temperature, but failed to alter the rise in brown adipose tissue temperature normally seen after the central administration of PGE1. Moreover, both the rise in systolic blood pressure and heart rate were attenuated when the PGE1 administration was preceded by prazosin. These results suggest that brown adipose tissue is an important effector organ responsible for mediating the hyperthermic response observed after the intracerebral injection of PGE1. In addition, the results indicate that alterations in vasomotor tone may also be important in producing or sustaining the elevated core temperature found after a pyrogen administration.

The effectiveness of arginine vasopressin and sodium salicylate as antipyretics in the Brattleboro rat

The infusion of either 30 micrograms/microliters (approx. 100 micrograms/kg/h) of sodium salicylate or 10 ng/microliters (10(-5) M) arginine vasopressin within the ventral septal area of the Brattleboro rat brain reduced a centrally induced prostaglandin E1 (PGE1) hyperthermia when compared with infusions of artificial cerebrospinal fluid. Conversely, the infusion of a related peptide, oxytocin (10 ng/microliters (10(-5) M), or 33 ng/kg/h) failed to alter the rise in core temperature following the PGE1 injection. These results suggest that the vasopressin receptors reported to be present in the Brattleboro rat may respond normally to exogenously administered vasopressin, thus allowing for the antipyretic action. Moreover, the antipyretic effects of sodium salicylate suggest that aspirin-like drugs may induce the release of alpha-melanocyte-stimulating hormone which, in turn, attenuates the PGE1-evoked fever. Given recent evidence, however, which suggests that the Brattleboro rat may contain vasopressin both peripherally and within the brain, the antipyretic action of sodium salicylate may be alternatively explained through the endogenous release of vasopressin.

Cerebrospinal fluid pressure in conscious rats during prostaglandin E1 fever

Intraperitoneal body temperature was monitored from groups of 10 conscious adult male Wistar rats. The daily body temperature rhythm was determined, and an intraperitoneal body temperature dose response relationship was established for prostaglandin E1 (PGE1) delivered into a lateral cerebral ventricle (LCV). Cerebrospinal fluid pressure was measured by direct cannulation of a LCV. Heart rate, arterial and central venous blood pressure, and blood gases were also measured in groups of 10 animals. It was found that there was a daily rhythm in intraperitoneal body temperature that was higher at night than during the day but stable between 0800 and 1600 h. A significant temperature dose (20-2,000 ng)-response relationship was established for administration of PGE1 into the LCV. Cerebrospinal fluid pressure when measured from the LCV increased significantly during the "chill" phase of the PGE1-induced fever. Carotid arterial blood pressure also significantly increased at this time as did central venous pressure, particularly so with vigorous shivering. There was a significant fall in arterial CO2 partial pressure, a slight rise in pH, and no change in arterial O2 partial pressure. These data support the hypothesis that a significant increase in cerebrospinal fluid pressure occurs during the chill phase of a PGE1-induced fever in the conscious rat.

Indomethacin-induced antipyresis in the rat: role of vasopressin receptors

Infusion of 15 micrograms/microliters (approximately 120 micrograms/kg/h) of indomethacin within the ventral septal area of the rat brain significantly reduced a centrally induced prostaglandin E1 (PGE1) hyperthermia when compared with infusions of artificial cerebrospinal fluid. A bolus injection of a V1 receptor antagonist, d(CH2)5Try(Me)AVP, (200, 2000, or 20,000 pmol) within the ventral septal area had no effect of body temperature alone but did suppress the PGE1-induced fever. Similar bolus injections of the V1 receptor antagonist within the ventral septal area failed to alter the antipyretic action of indomethacin on the hyperthermia resulting from centrally administered PGE1. Central injections of a V2 receptor antagonist failed to alter either the PGE1-induced fever or the indomethacin-evoked antipyresis. The results suggest that the V1 receptor antagonist may exert non-specific neurodepressant effects which may interfere with the expression or production of PGE1 hyperthermia and may further mask any contribution of arginine vasopressin to the antipyretic effects of indomethacin.

Sodium salicylate: alternate mechanism of central antipyretic action in the rat

Infusion of sodium salicylate (50.0 or 100.0 micrograms/microliters) into the ventral septal area (VSA) of the rat brain suppressed Prostaglandin-E1-induced hyperthermia. Infusion of artificial cerebrospinal fluid (aCSF) or 10.0 micrograms doses of salicylate did not. The suppression of intracerebroventricularly-induced (icv) Prostaglandin E1 (PGE1) hyperthermia was not due to a hypothermic action of salicylate since salicylate infusions given during cold exposure (10.0 degrees C) did not lower core body temperatures. A possible interaction between salicylate and endogenous arginine vasopressin (AVP) was investigated. Infusion of both salicylate (50.0 micrograms/microliters) and either AVP antiserum or AVP antagonist into the VSA resulted in PGE hyperthermias occurring at levels which were not different from control levels as opposed to enhanced hyperthermia (antiserum or antagonist alone) or suppressed hyperthermia (salicylate alone). These results are consistent with the notion that sodium salicylate infusions within the VSA enhance AVP action and thus bring about the attenuation of PGE-induced hyperthermia.

Acute changes in forearm venous volume and tone using radionuclide plethysmography

In this investigation blood pool scintigraphy was validated as a method to study acute changes in human forearm veins. Changes in regional forearm vascular volume (capacity) and the occluding pressure-volume (P-V) relationship induced by sublingual nifedipine (NIF) and nitroglycerin (GTN) were recorded in 16 patients with simultaneous data collection by the radionuclide and the mercury-in-rubber strain-gauge techniques. The standard error of estimate (Syx) between successive control measurements using the radionuclide method was 3.1% compared with 3.2% for the strain-gauge method. The venous P-V curves were highly reproducible using both techniques. Strain gauge and radionuclide measurements of acute changes in forearm venous volume correlated well (r = 0.86; Syx = 7%, n = 156). After 20 mg of NIF or 0.6 mg of GTN, mean heart rate increased from 71 +/- 10 to 77 +/- 9 and from 68 +/- 10 to 75 +/- 11 beats/min, respectively, and group systolic blood pressure decreased from 128 +/- 22 to 120 +/- 19 and from 136 +/- 18 to 126 +/- 23 mmHg, respectively (P less than 0.05). At venous occluding pressures of 0 and 30 mmHg, the forearm vascular volume did not change after NIF (2 +/- 4 and -1 +/- 4%; P greater than 0.05), whereas it increased after GTN (8 +/- 5 and 12 +/- 7%; P less than 0.001). The forearm venous P-V relationship did not change after NIF, whereas a significant rightward shift (venodilation, with an increase in unstressed volume) occurred after GTN.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in body temperature and vasopressin content of brain neurons, in pregnant and non-pregnant guinea pigs, during fevers produced by Poly I:Poly C

The synthetic polyribonucleotide pyrogen Poly I:Poly C (800 micrograms.kg-1) was injected intramuscularly on alternate days into pregnant and non-pregnant female guinea pigs. Pregnant animals, close to term, had smaller fevers in response to the pyrogen than did non-pregnant animals. Repeated injections of the pyrogen caused sequentially smaller fevers for the first 3-4 injections, particularly in non-pregnant animals, and this appeared to be like the tolerance usually developed to repeated injections of endotoxin. Continued pyrogen injections then caused, in non-pregnant animals, fevers of increasing magnitude until the original fever levels were reached, whereas in pregnant guinea pigs the fever responses remained reduced until parturition. The development of tolerance was associated with an increase in immunoreactivity for arginine vasopressin (AVP) in some neurons in the medial part of the paraventricular nucleus, and in terminals in the lateral septum and amygdala similar to changes found in these areas at term of pregnancy. These observations raise the possibility that AVP in these regions may have a role in the development of tolerance to pyrogens, and further quantitative studies of the AVP content of, and release from, nerve terminals projecting to the limbic system seem warranted.

Surmounting barriers in ionic channels

Biological cells are defined by the membrane that shields their vital molecules from the environment. The lipid bilayer of the membrane is an effective dielectric shield (Parsegian, 1969; Andersen, 1978; Honiget al.1986), preventing penetration by charged molecules: the lipid presents a large electrostatic energy barrier because it cannot neutralize the charge of solute molecules nearly as well as water. This energy barrier inhibits the permeation of solutes with local charge, even metabolites. Of course, metabolites do enter cells, and so physiologists have suspected (for a very long time, Hille, 1984, ch. 8) that the membrane shield is pierced by aqueous channels, through which solutes diffuse (with their local charge substantially neutralized) as they cross the membrane. These aqueous pores now have molecular reality (e.g. Nodaet al.1984; Miller, 1986). Each is formed by a specialized protein, integral to membranes, perhaps shaped like a thick-walled pipe, called ionic channels. Channels control the movement of many important molecules in and out of cells by the ‘gating’ mechanism that controls their opening and closing and by the selective properties of their open channel.

Physiological changes during thermoregulation and fever in urethan-anesthetized rats

Adult male Wistar rats were anesthetized with urethan (1.5 g/kg). They were unable to maintain body temperature (Tb) in a warm (32 degrees C) or cool (9 degrees C) environment or at a laboratory room temperature of 22 degrees C. Tb was allowed to fall to 35.8, 34.5, or 33.3 degrees C, and prostaglandin E1 (PGE1, 400 ng) was delivered into a lateral cerebral ventricle. An immediate feverlike rise in Tb resulted, accompanied by vigorous shivering. Animals were vasoconstricted throughout. When Tb was raised to and maintained at 38.3 or 39.5 degrees C, animals also responded with a fever; however, the magnitude of the fever diminished as the starting Tb increased. In a series of experiments in which Tb was maintained (36.8-37.4 degrees C) by means of a heating pad, PGE1 delivered into a lateral cerebral ventricle or into the anterior hypothalamus caused a dose-dependent change in Tb, which was similar in time of onset, magnitude, and duration to that observed in conscious animals. This fever was accompanied by shivering and increased O2 uptake, heart rate, arterial blood pressure, respiratory rate, and intracranial pressure during the rising phase of the fever, and vasodilation of the paws occurred during defeveresence. Animals were also able to develop a dose-dependent rise in Tb in response to purified human interleukin 1.

The effect of venous blood stream cooling on survival of bacterially infected rabbits

The effect of physical cooling on the mortality rate of rabbits infected with Pasteurella multocida was investigated. Rabbits were cooled for 48 hours after bacterial injection by passing cold fluid through small hollow metal cuffs which had been surgically implanted around the abdominal vena cavae of rabbits. The average body temperatures of the rabbits during the 24-hour period after the intravenous injection of live Pasteurella multocida was 40.92 +/- 0.20 degrees C in control rabbits and 38.98 +/- 0.71 degrees C in cooled rabbits. 90% of physically cooled rabbits survived compared with 46% of control rabbits 48 hours after bacterial injection, suggesting that thermoregulatory effector mechanisms involved in cold defense may enhance survival.

Evidence supporting a role for endogenous vasopressin in fever suppression in the rat

1. Infusion of human purified interleukin-1 into a lateral cerebral ventricle of the rat evoked a rise in core temperature which was abolished by heating the interleukin-1. 2. When the intracerebroventricular infusion of interleukin-1 was preceded by a bilateral injection of saline into the ventral septal area, the resulting febrile response was not different from that induced by interleukin-1 alone. However, when the vasopressin V1 antagonist, d(CH2)5Tyr(Me)AVP, was injected into the ventral septal area prior to interleukin-1, a fever was evoked which was significantly greater in magnitude and duration. This enhancement of fever by the V1 antagonist was dose related. 3. Injection of either saline or the V1 antagonist into the ventral septal area, in the absence of interleukin-1, did not evoke any consistent alteration in the core temperature of the rats. 4. The vasopressin V2 antagonist, d(CH2)5-D-ValVAVP, was injected into the ventral septal area to determine the effect of another vasopressin analogue on the fever evoked by interleukin-1. The V2 antagonist did not alter the time course of interleukin-1-induced fever or alter core temperature in the afebrile rat. 5. These data are consistent with the hypothesis that endogenous vasopressin, released in the ventral septal area, may be involved in limiting fever. In addition, these results indicate that the central receptor mediating the antipyretic action of vasopressin may resemble the V1 subtype of peripheral vasopressin receptor.

Vasopressin and fever: evidence supporting the existence of an endogenous antipyretic system in the brain

Vasopressin administered into the ventral septum exerts a dose-related antipyresis. This site of action is similar in a number of species. The fever-reducing properties of vasopressin are both site and neuropeptide specific. Evidence supporting a role for endogenous vasopressin in fever suppression is the demonstration that the release of the peptide from the ventral septal area is altered during fever: the amount released correlates negatively with febrile changes in body temperature. In addition, changes in the concentration of vasopressin in the septum and amygdala have been demonstrated immunocytochemically during fever: an activation of vasopressinergic neurons occurs which is similar to that observed in pregnant animals at term when fever is absent. Specific antibodies directed against vasopressin or specific vasopressin antagonist analogues (e.g., d(CH2)5Tyr(Me)AVP) enhanced the febrile response to a pyrogen challenge when injected into the ventral septum. The same antagonist also can antagonize the antipyretic effect of exogenously administered vasopressin. The use of relatively specific antagonists and agonists of vasopressin, directed against the V1 and V2 subtypes of the peripheral vasopressin receptor, suggests that the central receptor responsible for the antipyretic effect of vasopressin may resemble the V1 subtype. Recent experiments using electrophysiological techniques have demonstrated the existence of thermoresponsive units in the ventral septal area whose activity may be altered by vasopressin which is possibly derived from the paraventricular nucleus and bed nucleus of the stria terminalis.(ABSTRACT TRUNCATED AT 250 WORDS)

Blockade of prostaglandin E1 hyperthermia by sodium salicylate given into the ventral septal area of the rat brain

1. Sodium salicylate (30.0 micrograms microliter-1) or artificial cerebrospinal fluid (ACSF) was infused bilaterally into the ventral septal area (v.s.a.) of the unrestrained rat for 1 h before and 1 h after the injection of prostaglandin E1 at a concentration of 20.0 ng microliter-1 into a lateral cerebral ventricle. 2. During control (ACSF) infusions, 200.0 ng of prostaglandin E1 evoked a hyperthermic response (0.95 +/- 0.16 degrees C). During sodium salicylate infusions, the prostaglandin E1-evoked hyperthermia was significantly reduced (P less than 0.025) to 0.31 +/- 0.16 degrees C. 3. The fever index (degrees C h for 1.0 h) during the infusion of sodium salicylate was reduced 66% below that of control infusions (P less than 0.01). 4. These data indicate that sodium salicylate infused in the v.s.a. of rats can antagonize a prostaglandin E-evoked hyperthermia. This suggests that there may be an additional mechanism of action for sodium salicylate antipyresis other than inhibition of prostaglandin E synthesis.

A cation channel in frog lens epithelia responsive to pressure and calcium

Patch-clamp recording from the apical surface of the epithelium of frog lens reveals a cation-selective channel after pressure (about +/- 30 mm Hg) is applied to the pipette. The open state of this channel has a conductance of some 50 pS near the resting potential (-56.1 +/- 2.3 mV) when 107 mM NaCl and 10 HEPES (pH 7.3) is outside the channel. The probability of the channel being open depends strongly on pressure but the current-voltage relation of the open state does not. With minimal Ca2+ (55 +/- 2 microM) outside the channel, the current-voltage relation is nonlinear even in symmetrical salt solutions, allowing more current to flow into the cell than out. The channel, in minimal Ca2+ solution, is selective among the monovalent cations in the following sequence K+ greater than Rb+ greater than Cs+ greater than Na+ greater than Li+. The conductance depends monotonically on the mole fraction of K+ when the other ion present is Li+ or Na+. The single-channel current is a saturating function of [K+] when K+ is the permeant ion, for [K+] less than or equal to 214 mM. When [Ca2+] = 2 mM, the current-voltage relation is linearized and the channel cannot distinguish Na+ and K+.

Is prostaglandin E the neural mediator of the febrile response? The case against a proven obligatory role

We have reviewed the evidence in favor of a prostaglandin mediator of the thermal responses in fever and found that PGE injected into the hypothalamus does not always cause fever, that cerebrospinal fluid concentrations of PGE are not reliable reflections of hypothalamic events, and that antipyretic drugs may act in ways other than inhibiting PGE synthesis. Fever is not blocked by prostaglandin antagonists, nor by ablation of PGE-sensitive areas of the brain. There is poor correlation between the effects of pyrogens and of PGE on cerebral neurons. There is evidence that at least one prostanoid other than prostaglandin is a mediator of fever, but the prostanoid has not been identified yet. We conclude that PGE may contribute to the neural responses in fever but is not essential.

Induced changes in intracranial pressure in the anesthetized rat and rabbit

Intracranial pressure (ICP) was measured continuously in anesthetized, free-breathing, adult, male Sprague-Dawley rats and New Zealand White rabbits by means of a subarachnoid screw technique. The effect upon ICP of changing the volumes within the cranium by infusion of artificial cerebrospinal fluid into the lateral cerebral ventricle at various rates was examined. Results obtained demonstrated some of the elastic and compensatory aspects of cerebrospinal fluid dynamics. The effects upon ICP of the intravenous administration of urea, mannitol, acetazolamide, dimethyl sulfoxide, norepinephrine, epinephrine, isoproterenol, nitroglycerin, papaverine, histamine, angiotension II, pitressin, sodium nitroprusside, diazoxide, lidocaine, sodium pentobarbitone, as well as inhalation of amyl nitrate and carbon dioxide were examined in anesthetized rats. The effect upon ICP of the intravenous infusion of urea, as well as the bolus intravenous administration of epinephrine and pitressin was examined in the anesthetized rabbit. Results obtained from these animals demonstrate the action of these experimental interventions upon ICP as measured by means of the subarachnoid screw technique.

Fever and intracranial pressures

The effect of fever upon intracranial pressures was determined in the rabbit and cat. In the unanesthetized rabbit and cat, cerebrospinal fluid (CSF) pressure was measured via direct cannulation of the lateral cerebral ventricle. Intracranial pressure (ICP) was measured in the rabbit by a subarachnoid screw technique. In all cases, intravenous administration of bacterial pyrogen extracted from Salmonella abortus equi resulted in significant differences from controls in physiological variables measured during the initial "chill" phase of the fever. There was an increase in body temperature, a fall in CSF or ICP pulse rate, an increase in pulse pressure amplitude, and a small increase in mean CSF or ICP. In addition, venous and arterial blood pressures increased significantly and, consistent with heat conservation, there was a fall in respiratory rate as well as cutaneous vasoconstriction in the ears. The arterial carbon dioxide tension was unchanged during the prodrome but fell significantly during the chill and flush phases and rose again during defervescence. The results suggest that in these animals there is a slight increase in pressures within the cranium during the "chill" phase of a pyrogen induced fever, resulting from changes occurring in many body systems during this phase of the fever.

Neurotransmitter effects on body temperature are modified with increasing age

This study reports effects on body temperature, in two different age groups of Sprague Dawley rats, of intracerebroventricular (ICV) administration of prostaglandin E2, noradrenaline, serotonin, dopamine, and carbachol. Young animals (3-5 months) developed fevers in response to administration of prostaglandin E2 (+ 1.02 +/- 0.26 degrees C), while no significant changes in colonic temperature were observed in the older (15-18 months) group of rats. Noradrenaline (10.0 micrograms), caused a decrease in colonic temperature in the younger group of animals (-2.02 +/- 0.70 degrees C), but had no significant effects on the body temperature of the older group. Similarly, differences between the temperature responses of the young as compared with the older group of animals were observed following ICV administration of carbachol, dopamine and serotonin. These data suggest that the roles of these substances in the hypothalamic control of body temperature may be modified with increasing age.

Peripheral blood flow during rewarming from mild hypothermia in humans

During the initial stages of rewarming from hypothermia, there is a continued cooling of the core, or after-drop in temperature, that has been attributed to the return of cold blood due to peripheral vasodilatation, thus causing a further decrease of deep body temperature. To examine this possibility more carefully, subjects were immersed in cold water (17 degrees C), and then rewarmed from a mildly hypothermic state in a warm bath (40 degrees C). Measurements of hand blood flow were made by calorimetry and of forearm, calf, and foot blood flows by straingauge venous occlusion plethysmography at rest (Ta = 22 degrees C) and during rewarming. There was a small increase in skin blood flow during the falling phase of core temperature upon rewarming in the warm bath, but none in foot blood flow upon rewarming at room air, suggesting that skin blood flow seems to contribute to the after-drop, but only minimally. Limb blood flow changes during this phase suggest that a small muscle blood flow could also have contributed to the after-drop. It was concluded that the after-drop of core temperature during rewarming from mild hypothermia does not result from a large vasodilatation in the superficial parts of the periphery, as postulated. The possible contribution of mechanisms of heat conduction, heat convection, and cessation of shivering thermogenesis were discussed.

Vasopressin: its role in antipyresis and febrile convulsion

When pyrogenic substances are injected intravenously into experimental animals, a sequence of events is set in motion which involves the hypothalamus and perhaps other portions of the diencephalon to produce a febrile response. We now present evidence that the brain produces its own endogenous antipyretic which may serve as a means of controlling the extent of the fever. When arginine vasopressin is perfused through the lateral septal area of the hypothalamus of the sheep, fever is suppressed. Vasopressin alone does not lower normal body temperature when perfused through this region of the brain. In addition, evidence is provided to indicate that vasopressin is released within the lateral septal area during the febrile response. It is concluded that, in fever, arginine vasopressin may be released in the lateral septal area of the brain and serve as an endogenous antipyretic. Results indicate that, following an initial application of vasopressin into the brain itself, a subsequent similar administration of vasopressin produces seizure-like activity. Therefore, it is suggested that this release of arginine vasopressin may contribute to the production of febrile convulsion.

Changes in the hypothalamic mechanisms involved in the control of body temperature induced by the early thermal environment

The experiments reported in this study were designed to investigate the influence of the early thermal environment on the functional properties of certain putative thermoregulatory neurotransmitters within the hypothalamus of the Sprague-Dawley rat. The effects on body temperature of serotonin, dopamine, carbachol, PGE2 and endotoxin when microinjected into the anterior hypothalamic/preoptic region of the brain have been examined in warm-reared, control and warm-acclimated animals. Serotonin and PGE2 are shown to have different effects on body temperature in warm-reared as compared to warm-acclimated and control animals. The thermoregulatory effects of intrahypothalamic dopamine are shown to be changed by the normal acclimation process, while carbachol and endotoxin have similar effects on the body temperature of all 3 groups of animals. These data suggest that the thermal environment may significantly affect the roles which specific neurotransmitters play in the control of body temperature.

An investigation of the age-related deficits in the febrile response of the rabbit

The febrile response of the New Zealand White rabbit in animals less than 1 yr old was compared with that in 3-yr-old animals. A reduced febrile response to both endotoxin and live bacteria injected intravenously was observed in the older group of animals. Peripheral vasoconstriction was observed, suggesting the drive to increase body temperature remained. Plasma catecholamines increased significantly in both groups of animals during fever. However, significantly greater increases in plasma epinephrine were observed in the older animals. A significant deficit in catecholamine-induced thermogenesis was observed in the older group of rabbits. This deficit alone does not explain the reduced febrile response, as beta-adrenergic blockade does not suppress the febrile response of young animals. Thus it is suggested that the primary deficit resulting in a reduced febrile response in the 3-yr-old rabbits is due to other age-related changes in the thermoregulatory system.

Peptide neurohormones: their role in thermoregulation and fever

The neural elements of the rostral diencephalon in the mammal have been implicated in the regulation of body temperature. Moreover, it may be the neural elements within this region of the brain which activate the febrile mechanisms in response to pyrogen. Is it possible that the neuropeptides located within this area of the brain serve as neurochemical intermediaries involved in temperature regulation, fever, and (or) antipyresis? Central administration of several neuropeptides can elicit marked changes in the core temperature of an animal. Although most of these purative neuroregulators exert only a very minor influence on thermoregulation, a small number of the neuropeptides have been shown to have a profound effect on the system controlling this basic vegetative function. One of these peptides, arginine vasopressin (AVP) may play a role as an endogenous antipyretic. The neuroanatomical localization of this peptide, as well as its axonal projections, are consistent with such a role for this neurohypophyseal peptide in the mediation of antipyresis. In addition, current evidence suggests that AVP does function as a neurotransmitter. Examination of the febrile response to pyrogen in both the periparturient animal and the neonate indicates that an elevation in plasma levels of AVP is closely correlated with the diminution in the febrile response. Also, when AVP is perfused into punctate regions of the brain, a pyrogen-induced fever may be markedly suppressed AVP appears to act primarily within the septal area, 2- to 3-mm rostral to the anterior commissure. During the development of fever, the release of AVP is altered within these same loci. As body temperature decreases during the febrile state, there is a concomitant increase in the amount of AVP released into the extracellular fluid of these septal sites. Very recent findings suggest that AVP may have additional central neurochemical functions. For example, this peptide may be involved in the etiology of some forms of convulsive disorders. The precise manner in which body temperature is regulated by the central nervous system normally and during fever is not well understood.(ABSTRACT TRUNCATED AT 400 WORDS)

Vasopressin: a homeostatic effector in the febrile process

This review compares the physiological changes which accompany infection and fever with the effects of the peptide, arginine vasopressin (AVP). AVP may act as a neuromodulator, a releasing factor, or a hormone to induce responses which are opposite to those homeostatic changes accompanying fever. Since AVP is released into blood and brain during fever, it is hypothesized that AVP contributes to the maintenance of homeostasis in the infected organism.