Severe Hyperthermia Research Articles

Hybrid paclitaxel and gold nanorod-loaded human serum albumin nanoparticles for simultaneous chemotherapeutic and photothermal therapy on 4T1 breast cancer cells.

The use of human serum albumin nanoparticles (HSAPs) as a drug carrier system for cancer treatment has proven successful through current marketable clinical formulations. Despite this success, there is a current lack of multifunctional HSAPs, which offer combinational therapies of more than one proven technique. Gold nanorods (AuNRs) have also shown medicinal promise due to their photothermal therapy capabilities. In this study, a desolvation and cross-linking approach was employed to successfully encapsulate gold nanorods into HSAPs simultaneously with the chemotherapeutic drug paclitaxel (PAC); forming PAC-AuNR-HSAPs with desirable overall particle sizes of 299 ± 6 nm. The loading efficiency of paclitaxel into PAC-AuNR-HSAPs reached up to 3 μg PAC/mg HSA. The PAC-AuNR-HSAPs experienced photothermal heating; with the bulk particle solution reaching up to 46 °C after 15 min of near-IR laser exposure. This heat increase marked the successful attainment of the temperature necessary to cause severe cellular hyperthermia and necrosis. The encasement strategy facilitated a colloidal hybrid treatment system capable of enhanced permeability and retention effects, photothermal ablation of cancer cells, and release of the active paclitaxel of up to 188 ng (from PAC-AuNR-HSAPs created with 30 mg HSA) in a single 15 min irradiation session. When treated with PAC-AuNR-HSAPs containing 20 μg PAC/mL particle solution, 4T1 mouse breast cancer cells experienced ∼82% cell death without irradiation and ∼94% cell death after just one irradiation session. The results for PAC-AuNR-HSAPs were better than that of free PAC, which only killed ∼77% of the cells without irradiation and ∼80% with irradiation. The hybrid particle system also lends itself to future customizable external functionalities via conjugated targeting ligands, such as antibodies. Internal entrapment of patient tailored medication combinations are also possible with this combination treatment platform, which may result in improved quality of life for those undergoing treatment.

Ice water submersion for rapid cooling in severe drug-induced hyperthermia

Context. The optimal method of cooling hyperthermic patients is controversial. Although controlled data support ice water submersion, many authorities recommend a mist and fan technique. We report two patients with drug-induced hyperthermia, to demonstrate the rapid cooling rates of ice water submersion. Case details. Case 1. A 27-year-old man presented with a sympathomimetic toxic syndrome and a core temperature of 41.4°C after ingesting 4-fluoroamphetamine. He was submerged in ice water and his core temperature fell to 38°C within 18 minutes (a mean cooling rate of 0.18°C/min). His vital signs stabilized, his mental status improved and he left on hospital day 2. Case 2. A 32-year-old man with a sympathomimetic toxic syndrome after cocaine use was transported in a body bag and arrived with a core temperature of 44.4°C. He was intubated, sedated with IV benzodiazepines, and submerged in ice water. After 20 mins his temperature fell to 38.8°C (a cooling rate of 0.28°C/min). He was extubated the following day, and discharged on day 10. Discussion. In these two cases, cooling rates exceeded those reported for mist and fan technique. Since the priority in hyperthermia is rapid cooling, clinical data need to be collected to reaffirm the optimal approach.

Protection of intestinal injury during heat stroke in mice by interleukin-6 pretreatment.

Heat stroke afflicts thousands of humans each year, worldwide. The immune system responds to hyperthermia exposure resulting in heat stroke by producing an array of immunological proteins, such as interleukin-6 (IL-6). However, the physiological functions of IL-6 and other cytokines in hyperthermia are poorly understood. We hypothesized that IL-6 plays a protective role in conditions of heat stroke. To test this, we gave small IL-6 supplements to mice prior to exposing them to hot environments sufficient to induce conditions of heat stroke. Pretreatment with IL-6 resulted in improved ability to withstand heat exposure in anaesthetized mice, it protected the intestine from injury, reducing the permeability of the intestinal barrier, and it attenuated the release of other cytokines involved in inflammation. The results support the hypothesis that IL-6 is a 'physiological stress hormone' that plays an important role in survival during acute life-threatening conditions such as heat stroke. The role of interleukin-6 (IL-6) in hyperthermia and heat stroke is poorly understood. Plasma IL-6 is elevated following hyperthermia in animals and humans, and IL-6 knockout mice are more intolerant of severe hyperthermia. We evaluated the effect of IL-6 supplementation on organ injury following severe hyperthermia exposure in anaesthetized mice. Two hours prior to hyperthermia, mice were treated with 0.6 μg intraperitoneal IL-6, or identical volumes of saline in controls. Mice were anaesthetized, gavaged with FITC-dextran for measures of gastrointestinal permeability, and exposed to incremental (0.5°C every 30 min) increases in temperature. Heating stopped when maximum core temperature (Tc) of 42.4°C was attained (Tc,max). The mice recovered at room temperature (≈22°C) for 30 or 120 min, at which time plasma and tissues were collected. IL-6-treated mice, on average, required ≈25 min longer to attain Tc,max . Injury and swelling of the villi in the duodenum was present in untreated mice after 30 min of recovery. These changes were blocked by IL-6 treatment. IL-6 also reduced gastrointestinal permeability, assayed by the accumulation of FITC-dextran in plasma. Plasma cytokines were also attenuated in IL-6-treated animals, including significant reductions in TNFα, MCP-1 (CXCL2), RANTES (CCL5) and KC (CCL5). The results demonstrate that IL-6 has a protective influence on the pattern of physiological responses to severe hyperthermia, suggesting that early endogenous expression of IL-6 may provide a protection from the development of organ damage and inflammation.

Validity and reliability assessment of detailed scoring checklists for use during perioperative emergency simulation training.

Few valid and reliable grading checklists have been published for the evaluation of performance during simulated high-stakes perioperative event management. As such, the purposes of this study were to construct valid scoring checklists for a variety of perioperative emergencies and to determine the reliability of scores produced by these checklists during continuous video review. A group of anesthesiologists, intensivists, and educators created a set of simulation grading checklists for the assessment of the following scenarios: severe anaphylaxis, cerebrovascular accident, hyperkalemic arrest, malignant hyperthermia, and acute coronary syndrome. Checklist items were coded as critical or noncritical. Nonexpert raters evaluated 10 simulation videos in a random order, with each video being graded 4 times. A group of faculty experts also graded the videos to create a reference standard to which nonexpert ratings were compared. P < 0.05 was considered significant. Team leaders in the simulation videos were scored by the expert panel as having performed 56.5% of all items on the checklist (range, 43.8%-84.0%), and 67.2% of the critical items (range, 30.0%-100%). Nonexpert raters agreed with the expert assessment 89.6% of the time (95% confidence interval, 87.2%-91.6%). No learning curve development was found with repetitive video assessment or checklist use. The κ values comparing nonexpert rater assessments to the reference standard averaged 0.76 (95% confidence interval, 0.71-0.81). The findings indicate that the grading checklists described are valid, are reliable, and could be used in perioperative crisis management assessment.

Uncoupling of oxidative phosphorylation and ATP synthase reversal within the hyperthermic heart.

Heart failure is a common cause of death with hyperthermia, and the exact cause of hyperthermic heart failure appears elusive. We hypothesize that the energy supply (ATP) of the heart may become impaired due to increased inner‐mitochondrial membrane permeability and inefficient oxidative phosphorylation (OXPHOS). Therefore, we assessed isolated working heart and mitochondrial function. Ex vivo working rat hearts were perfused between 37 and 43.5°C and showed break points in all functional parameters at ~40.5°C. Mitochondrial high‐resolution respirometry coupled to fluorometry was employed to determine the effects of hyperthermia on OXPHOS and mitochondrial membrane potential (ΔΨ) in vitro using a comprehensive metabolic substrate complement with isolated mitochondria. Relative to 37 and 40°C, 43°C elevated Leak O2 flux and depressed OXPHOS O2 flux and ∆Ψ. Measurement of steady‐state ATP production from mitochondria revealed decreased ATP synthesis capacity, and a negative steady‐state P:O ratio at 43°C. This approach offers a more powerful analysis of the effects of temperature on OXPHOS that cannot be measured using simple measures such as the traditional respiratory control ratio (RCR) or P:O ratio, which, respectively, can only approach 1 or 0 with inner‐membrane failure. At 40°C there was only a slight enhancement of the Leak O2 flux and this did not significantly affect ATP production rate. Therefore, during mild hyperthermia (40°C) there is no enhancement of ATP supply by mitochondria, to accompany increasing cardiac energy demands, while between this and critical hyperthermia (43°C), mitochondria become net consumers of ATP. This consumption may contribute to cardiac failure or permanent damage during severe hyperthermia.

Modeling the inflammatory response in the hypothalamus ensuing heat stroke: Iterative cycle of model calibration, identifiability analysis, experimental design and data collection

Heat Stroke (HS) is a life-threatening illness caused by prolonged exposure to heat that causes severe hyperthermia and nervous system abnormalities. The long term consequences of HS are poorly understood and deeper insight is required to find possible treatment strategies. Elevated pro- and anti-inflammatory cytokines during HS recovery suggest to play a major role in the immune response. In this study, we developed a mathematical model to understand the interactions and dynamics of cytokines in the hypothalamus, the main thermoregulatory center in the brain. Uncertainty and identifiability analysis of the calibrated model parameters revealed non-identifiable parameters due to the limited amount of data. To overcome the lack of identifiability of the parameters, an iterative cycle of optimal experimental design, data collection, re-calibration and model reduction was applied and further informative experiments were suggested. Additionally, a new method of approximating the prior distribution of the parameters for Bayesian optimal experimental design based on the profile likelihood is presented.

Severe Hyperthermia, Hypernatremia, and Early Postoperative Death After Transethmoidal Cavitron Ultrasonic Surgical Aspirator (CUSA)‐Assisted Diencephalic Mass Removal in 4 Dogs and 2 Cats

To report clinical findings including severe hyperthermia and hypernatremia after transethmoidal Cavitron ultrasonic surgical aspirator (CUSA)-assisted diencephalic mass removal. Retrospective case series. Dogs (n = 4) and 2 cats. Medical records (1997-2003) of dogs and cats that had transethmoidal CUSA-assisted diencephalic mass removal were reviewed. Retrieved data were: history, signalment, blood work, neurologic examination findings, MRI results, histopathology, postoperative complications, pre- and postoperative medical therapy, and outcome. Tumor types included: meningioma (n = 3), choroid plexus papilloma (1), astrocytoma (1), and pituitary macroadenoma (1). Median onset of hyperthermia was 3.5 hours (range: 1-6 hours) after extubation; median high temperature at onset was 40.3°C, (range: 39.6-41.7°C). Median onset of hypernatremia (median, 172 mmol/L; range: 168-196 mmol/L) was 4.5 hours (range: 1-9 hours) after extubation. Median time of death after hyperthermia was 10.5 hours (range: 6-13 hours) and after extubation was 13.5 hours (range: 11-15 hours). Transethmoidal CUSA-assisted diencephalic mass removal is associated with early postoperative hyperthermia, hypernatremia, and death, and cannot be recommended.

Single-dose oral quercetin improves redox status but does not affect heat shock response in mice

Inflammation and oxidative stress are considered as likely contributors to heat injury. However, their roles in regulating the heat shock response in vivo remain unclear. We tested the hypothesis that acute quercetin treatment would improve redox status and reduce heat shock responses in mice. Mice underwent two heat tests before and after single oral administration of either quercetin (15 mg/kg) or vehicle. We measured physiologic and biochemical responses in mice during and 18 to 22 hours after heat tests, respectively. There were no significant differences in core temperature, heart rate, or blood pressure between quercetin and vehicle groups during heat exposure. Mice with relatively severe hyperthermia during the pretreatment heat test showed a significant trend toward a lower peak core temperature during the heat test after quercetin treatment. Compared with mice not exposed to heat, quercetin-treated mice had significantly lower interleukin 6 (P < .01) and higher superoxide dismutase levels (P < .01), whereas vehicle-treated mice had significantly lower total glutathione and higher 8-isoprostane levels in the circulation after heat exposure. Heat exposure significantly elevated heat shock proteins (HSPs) 72 and 90 and heat shock factor 1 levels in mouse liver, heart, and skeletal muscles, but no significant differences in tissue HSPs and heat shock factor 1 were found between quercetin- and vehicle-treated mice. These results suggest that a single moderate dose of quercetin is sufficient to alter redox status but not heat stress response in mice. Acute adaptations of peripheral tissues to heat stress may not be mediated by systemic inflammatory and redox state in vivo.

Acute heat stress responses of mice with sickle cell trait (1104.18)

It has been a long standing controversy about whether individuals with sickle cell trait (SCT) are vulnerable to injury or even sudden death during physical activity in hot climates. Experimental studies assessing susceptibility of SCT to heat stress are lacking. Our objective was to examine whether transgenic SCT mice had an altered thermoregulatory response to heat exposure. All SCT mice (n =16) and majority of age‐ and gender‐matched normal mice (29 of 45) completed two separate heat tests (2 hr each at 39.5 degree C) without severe hyperthermia (42.4 degree C). SCT mice had a significantly lower body weight than normal mice (n = 19) with similar peak core temperature (Tc). There was no difference in weight loss between SCT and normal mice during heat exposure. No significant correlations between peak Tc and body weight were found among SCT or normal mice. Compared to their normal counterparts, both non‐heat exposed (n = 9) and heat exposed SCT mice had significantly higher levels of heat shock protein 72 (HSP72) in various tissues, slightly lower hematocrit values, but similar plasma lactate dehydrogenase concentrations. No differences in plasma inflammatory and redox makers were found between SCT and normal mice following heat exposure. We conclude that SCT mice reveal neither thermoregulatory dysfunction nor increased oxidative/inflammatory stress when exposed to moderate heat. The physiological significance of increased tissue HSP72 remains to be determined.Grant Funding Source: Supported by The Office of Naval Research Grant N0001411MP2002 and USU Intramural Grant R091EH

Protective efficacy of Babesia gibsoni culture-derived exoantigens against the challenge infection in dogs.

The aim of this study is to determine the efficacy of exoantigens derived from Babesia gibsoni cultures to induce protective immunity against challenge exposure of virulent organisms. An attenuated B. gibsoni Oita strain was maintained in vitro by the microaerophilus stationary phase (MASP) method, and exoantigens-containing supernatant fluids were collected for preparation of the immunization. Two dogs received three subcutaneous immunizations with a 20-day interval of B. gibsoni exoantigens plus 0.5 mg saponin (Quil A). On day 68 after the prime immunization, the immunized dogs and control dogs were challenged intravenously with 2 × 10(8) virulent parasites of a homologous B. gibsoni strain. The results showed that exoantigens could induce a high degree of protection against virulent homologous challenge exposure. Two dogs immunized with exoantigens showed a lower parasitemia, accompanied by a slight decrease in the PCV that returned to normal values. Control dogs developed typical acute clinical signs, including severe anemia and hyperthermia. The immunization elicited humoral immune responses. In dogs immunized with exoantigens, the maximum antibody titer was 2,560 and 5,120 by indirect fluorescent antibody test (IFAT), respectively. Preliminary Western blot analysis of the immunogen revealed five dominant proteins of molecular weights of 18, 37, 43, 50, and 57 kDa. These results suggested that the culture-derived exoantigens were candidates for non-viable vaccine.

Cocaine-Induced Agitated Delirium

Cocaine use continues to be a major public health problem in the United States. Although many of the initial signs and symptoms of cocaine intoxication result from increased stimulation of the sympathetic nervous system, this condition can present as a spectrum of acuity from hypertension and tachycardia to multiorgan system failure. Classic features of acute intoxication include tachycardia, arterial vasoconstriction, enhanced thrombus formation, mydriasis, psychomotor agitation, and altered level of consciousness. At the extreme end of this toxidrome is a rare condition known as cocaine-induced agitated delirium. This syndrome is characterized by severe cardiopulmonary dysfunction, hyperthermia, and acute neurologic changes frequently leading to death. We report a case of cocaine-induced agitated delirium in a man who presented to our institution in a paradoxical form of circulatory shock. Rapid evaluation, recognition, and proper management enabled our patient not only to survive but also to leave the hospital without neurologic sequelae.

Carvedilol inhibits the cardiostimulant and thermogenic effects of MDMA in humans

We read with interest the study by Hysek and colleagues that investigated the cardiostimulant and thermogenic effects of carvedilol on 3,4-methylenedioxymethamphetamine (MDMA) (Hysek et al., 2012). Although we applaud the authors for performing a randomized placebo-controlled trial in humans, we have a concern about their study design. The study uses a relatively low dose of MDMA compared with those used by patients arriving to most hospitals. The average MDMA user often consumes greater doses than those used in this study, ranging up to 280 mg, whereas the study participants received a single oral dose of 125 mg (Morefield et al., 2011). Typical patients exhibit greater cardiostimulatory and thermogenic effects than the small changes noted in the study group. Additionally, it is unclear whether carvedilol would have an effect on severe hyperthermia as the temperature change reported in the placebo-MDMA group was no more than 0.5°C above baseline. This study's applicability would have been strengthened by demonstrating a more significant effect of MDMA prior to use of carvedilol. Because ethical considerations most likely prevent the ability of changing these parameters to reflect real-life patient presentations, the true utility of a clinically adequate dose of carvedilol given after a patient presents with significant MDMA toxicity remains unknown.

Carvedilol inhibits the cardiostimulant and thermogenic effects of MDMA in humans: Lost in translation

We greatly appreciate the comments offered by Drs Rolle, Takematsu, and Hoffman and the opportunity to put our work into a wider perspective. We share the view that our work does not reflect the clinical situation but rather provides a proof of mechanism study, which aims to help to translate preclinical findings (Sprague et al., 2005) into the clinic. As we noted in the discussion of our work (Hysek et al., 2012b) the primary goal of the study was to investigate the role of adrenoceptors in the mechanism of action of MDMA in humans. Therefore, the study provided only indirect support for the use of carvedilol in the treatment of stimulant toxicity in which carvedilol would be administered following the ingestion of Ecstasy or other stimulants. Furthermore, we noted the limitation that the MDMA-induced increase in body temperature in our study was moderate and we do not know whether carvedilol would also be effective in cases of severe hyperthermia following ecstasy use.

Voluntary muscle and motor cortical activation during progressive exercise and passively induced hyperthermia

This study examined whether central fatigue was exacerbated by an increase in muscle contractile speed caused by passive hyperthermia (PaH) and whether exercise-induced hyperthermia (ExH) combined with related peripheral fatigue influenced this response. The ExH was induced by cycling at 60% of maximal oxygen uptake in 38°C conditions and the PaH by sitting in a 48°C climate chamber. Ten men performed brief (≈ 5 s) and sustained (30 s) maximal voluntary isometric contractions (MVCs) of the knee extensors at baseline (CON, ∼37.1°C) and during moderate (MOD, ≈ 38.5°C) and severe (SEV, ∼39.5°C) hyperthermia. Motor nerve and transcranial magnetic stimulation were used to assess voluntary muscle and cortical activation level, along with contractile properties. Brief MVC force decreased to a similar extent during SEV-ExH (-8%) and SEV-PaH (-6%; P < 0.05 versus CON). Sustained MVC force also decreased during MOD-ExH (-10%), SEV-ExH (-13%) and SEV-PaH (-7%; P < 0.01 versus CON). Motor nerve and cortical activation were reduced on reaching MOD (≈ 3%) and SEV (≈ 5%) ExH and PaH during the brief and sustained MVCs (P < 0.01 versus CON). Peak twitch force decreased on reaching SEV-ExH and SEV-PaH (P < 0.05 versus CON). Following transcranial magnetic stimulation, during the brief and sustained MVCs the peak muscle relaxation rate increased in ExH and PaH (P < 0.01 versus CON). The increase was greatest during the sustained contraction in SEV-PaH (P < 0.01), but this did not exacerbate central fatigue relative to ExH. These results indicate that during fatiguing cycling exercise in the heat, quadriceps peak relaxation rate increases. However, the centrally mediated rate of activation appears sufficient to overcome even the largest increase in muscle relaxation rate, seen during SEV-PaH.

Difficult diagnosis of malignant hyperthermia during laparoscopic surgery

Difficult diagnosis of malignant hyperthermia during laparoscopic surgery

Modeling the Intra- and Extracellular Cytokine Signaling Pathway under Heat Stroke in the Liver

Heat stroke (HS) is a life-threatening illness induced by prolonged exposure to a hot environment that causes central nervous system abnormalities and severe hyperthermia. Current data suggest that the pathophysiological responses to heat stroke may not only be due to the immediate effects of heat exposure per se but also the result of a systemic inflammatory response syndrome (SIRS). The observation that pro- (e.g., IL-1) and anti-inflammatory (e.g., IL-10) cytokines are elevated concomitantly during recovery suggests a complex network of interactions involved in the manifestation of heat-induced SIRS. In this study, we measured a set of circulating cytokine/soluble cytokine receptor proteins and liver cytokine and receptor mRNA accumulation in wild-type and tumor necrosis factor (TNF) receptor knockout mice to assess the effect of neutralization of TNF signaling on the SIRS following HS. Using a systems approach, we developed a computational model describing dynamic changes (intra- and extracellular events) in the cytokine signaling pathways in response to HS that was fitted to novel genomic (liver mRNA accumulation) and proteomic (circulating cytokines and receptors) data using global optimization. The model allows integration of relevant biological knowledge and formulation of new hypotheses regarding the molecular mechanisms behind the complex etiology of HS that may serve as future therapeutic targets. Moreover, using our unique modeling framework, we explored cytokine signaling pathways with three in silico experiments (e.g. by simulating different heat insult scenarios and responses in cytokine knockout strains in silico).

12 ways to take a temperature

12 ways to take a temperature

Regional susceptibility to stress-induced intestinal injury in the mouse

Injury to the intestinal mucosa is a life-threatening problem in a variety of clinical disorders, including hemorrhagic shock, trauma, burn, pancreatitis, and heat stroke. The susceptibility to injury of different regions of intestine in these disorders is not well understood. We compared histological injury across the small intestine in two in vivo mouse models of injury, hemorrhagic shock (30% loss of blood volume) and heat stroke (peak core temperature 42.4°C). In both injury models, areas near the duodenum showed significantly greater mucosal injury and reductions in villus height. To determine if these effects were dependent on circulating factors, experiments were performed on isolated intestinal segments to test for permeability to 4-kDa FITC-dextran. The segments were exposed to hyperthermia (42°C for 90 min), moderate simulated ischemia (Po2 ∼30 Torr, Pco2 ∼60 Torr, pH 7.1), severe ischemia (Po2 ∼20 Torr, Pco2 ∼80 Torr, pH 6.9), or severe hypoxia (Po2 ∼0 Torr, Pco2 ∼35 Torr) for 90 min, and each group was compared with sham controls. All treatments resulted in marked elevations in permeability within segments near the duodenum. In severe hypoxia or hyperthermia, permeability was also moderately elevated in the jejunum and ileum; in moderate or severe ischemia, permeability was unaffected in these regions. The results demonstrate increased susceptibility of proximal regions of the small intestine to acute stress-induced damage, irrespective of circulating factors. The predominant injury in the duodenum may impact the pattern of acute inflammatory responses arising from breach of the intestinal barrier, and such knowledge may be useful for designing therapeutic strategies.

Regional changes in brain blood flow during severe passive hyperthermia: effects of PaCO2 and extracranial blood flow

We investigated 1) the regional distribution of cerebral blood flow (CBF), 2) the influence of end-tidal Pco2 (PetCO2) on CBF, and 3) the potential for an extracranial blood "steal" from the anterior brain region during passive hyperthermia. Nineteen (13 male) volunteers underwent supine passive heating until a steady-state esophageal temperature of 2°C above resting was established. Measurements were obtained 1) during normothermia (Normo), 2) during poikilocapnic hyperthermia (Hyper), and 3) during hyperthermia with PetCO2 and end-tidal Po2 clamped to Normo levels (Hyper-clamp). Blood flow in the internal carotid (Qica), vertebral (QVA), and external carotid (Qeca) arteries (Duplex ultrasound), blood velocity of the middle cerebral (MCAv) and posterior cerebral (PCAv) arteries (transcranial Doppler), and cutaneous vascular conductance on the cheek (cheek CVC; Doppler velocimetry) were measured at each stage. During Hyper, PetCO2 was lowered by 7.0 ± 5.2 mmHg, resulting in a reduction in Qica (-18 ± 17%), Qva (-31 ± 21%), MCAv (-22 ± 13%), and PCAv (-18 ± 10%) compared with Normo (P < 0.05). The reduction in QVA was greater than that in QICA (P = 0.017), MCAv (P = 0.047), and PCAv (P = 0.034). Blood flow/velocity was completely restored in each intracranial vessel (ICA, VA, MCA, and PCA) during Hyper-clamp. Despite a ∼250% increase in QECA and a subsequent increase in cheek CVC during Hyper compared with Normo, reductions in QICA were unrelated to changes in QECA. These data provide three novel findings: 1) hyperthermia attenuates QVA to a greater extent than QICA, 2) reductions in CBF during hyperthermia are governed primarily by reductions in arterial Pco2, and 3) increased QECA is unlikely to compromise QICA during hyperthermia.

Virulence attenuation of Babesia gibsoni by serial passages in vitro and assessment of the protection provided by the immunization against the passaged isolate in dogs

The virulence of the Babesia gibsoni Oita isolate was attenuated by serial passages in vitro by using the microaerophilus stationary phase (MASP) technique. After 400 serial passages, the virulence of the isolate was found to be attenuated. This was evidenced by the response of two dogs inoculated intravenously with 109B. gibsoni passaged isolate. Specific antibodies were produced at a titer of 1:20,480, as detected by the fluorescent antibody test (IFAT). These results suggested that the serial passages of B. gibsoni reduced its virulence while retaining its antigenicity.The dogs that were inoculated with the attenuated isolate (1 and 2) and two naïve dogs (3 and 4) were challenged by intravenous inoculation of 2×108 infected erythrocytes of the virulent Oita isolate. Protection afforded by exposure to the attenuated isolate was evidenced by a lower parasitemia in dogs 1 and 2 with a rapid decrease to nondetectable levels, accompanied by a slight decrease in the PCV that returned to normal values. Dogs 3 and 4 developed typical acute clinical signs, including severe anemia and hyperthermia. These results suggested that the attenuated isolate was a candidate for live vaccine.