The essential chaperone DNAJC17 activates HSP70 to coordinate RNA splicing and G2-M progression

Molecular chaperones including the heat-shock protein 70-kilodalton (HSP70) family and the J-domain containing protein (JDP) co-chaperones maintain homeostatic balance in eukaryotic cells through regulation of the proteome. The expansive JDP family helps direct specific HSP70 functions, and yet loss of single JDP-encoding genes is widely tolerated by mammalian cells, suggesting a high degree of redundancy. By contrast, essential JDPs might carry out HSP70-independent functions or fill cell-context dependent, highly specialized roles within the proteostasis network. Using a genetic screen of JDPs in human cancer cell lines, we found the RNA recognition motif (RRM) containing DNAJC17 to be pan-essential and investigated the contribution of its structural domains to biochemical and cellular function. We found that the RRM exerts an auto-inhibitory effect on the ability of DNAJC17 to allosterically activate ATP hydrolysis by HSP70. The J-domain, but neither the RRM nor a distal C-terminal alpha helix are required to rescue cell viability after loss of endogenous DNAJC17 . Knockdown of DNAJC17 leads to relatively few conserved changes in the abundance of individual mRNAs, but instead deranges gene expression through exon skipping, primarily of genes involved in cell cycle progression. Concordant with cell viability experiments, the C-terminal portions of DNAJC17 are dispensable for restoring splicing and G2-M progression. Overall, our findings identify essential cellular JDPs and suggest that diversification in JDP structure extends the HSP70-JDP system to control divergent processes such as RNA splicing. Future investigations into the structural basis for auto-inhibition of the DNAJC17 J-domain and the molecular regulation of splicing by these components may provide insights on how conserved biochemical mechanisms can be programmed to fill unique, non-redundant cellular roles and broaden the scope of the proteostasis network.

GATOR2-dependent mTORC1 activity is a therapeutic vulnerability in FOXO1 fusion-positive rhabdomyosarcoma

Oncogenic FOXO1 gene fusions drive a subset of rhabdomyosarcoma (RMS) with poor survival; to date, these cancer drivers are therapeutically intractable. To identify new therapies for this disease, we undertook an isogenic CRISPR-interference screen to define PAX3-FOXO1-specific genetic dependencies and identified genes in the GATOR2 complex. GATOR2 loss in RMS abrogated aa-induced lysosomal localization of mTORC1 and consequent downstream signaling, slowing G1-S cell cycle transition. In vivo suppression of GATOR2 impaired the growth of tumor xenografts and favored the outgrowth of cells lacking PAX3-FOXO1. Loss of a subset of GATOR2 members can be compensated by direct genetic activation of mTORC1. RAS mutations are also sufficient to decouple mTORC1 activation from GATOR2, and indeed, fusion-negative RMS harboring such mutations exhibit aa-independent mTORC1 activity. A bisteric, mTORC1-selective small molecule induced tumor regressions in fusion-positive patient-derived tumor xenografts. These findings highlight a vulnerability in FOXO1 fusion-positive RMS and provide rationale for the clinical evaluation of bisteric mTORC1 inhibitors, currently in phase I testing, to treat this disease. Isogenic genetic screens can, thus, identify potentially exploitable vulnerabilities in fusion-driven pediatric cancers that otherwise remain mostly undruggable.

Abstract A015: Biochemical and preclinical anti-tumor activity of a bi-steric mTORC1-selective inhibitor in fusion positive rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children. Although FOXO1 fusions portend a dismal prognosis for patients with both localized (5-year survival 65%) and metastatic (19%) disease, current therapy is largely agnostic to fusion status. The allosteric mTORC1 inhibitor temsirolimus delays disease progression in relapsed RMS but does not improve survival. We hypothesized that this incomplete response is due to inadequate suppression of critical downstream effectors of the mTORC1 complex. Recently described bi-steric mTORC1-selective inhibitors combine allosteric and catalytic modes of kinase inhibition, and have shown promise in diverse preclinical cancer models with early evidence of clinical activity. We therefore set out to compare the activity of the bi-steric mTORC1-selective inhibitor RMC-6272 to the allosteric mTOR inhibitor rapamycin in cell line and xenograft models of fusion positive RMS. Methods: We compared the in vitro anti-proliferative activity of RMC-6272 and rapamycin in FOXO1 fusion positive RMS cell lines at 72 and 144 hours. We assessed the ability of these inhibitors to suppress mTORC1 outputs, using immunoblot to quantify phosphorylation of p70S6K, RPS6, and 4EBP1, and m7-GTP pulldowns to assess repression of cap-dependent translation. In vivo studies were conducted in patient-derived xenograft (PDX) models subcutaneously implanted in NSG mice. We tested preclinical anti-tumor activity of RMC-6272 at two doses and used immunoblots and m7-GTP assays in tumors harvested from treated mice to assess target engagement. Results: We observed superior anti-proliferative effects of RMC-6272 when compared to rapamycin in vitro, with the latter having only modest effect. Biochemically, treatment of RMS cell lines with either RMC-6272 or rapamycin diminished phosphorylation of p70S6K and RPS6. However, RMC-6272 blocked 4EBP1 phosphorylation and cap-dependent translation much more potently than rapamycin. Based on these findings, we conducted in vivo studies using weekly intraperitoneal injections of RMC-6272 in PDX-harboring mice. Both doses were associated with tumor regressions in two fusion positive RMS PDX models: 2 CR and 1 PR at 8 mg/kg, and 3 CR, 1 PR, 1 SD, and 2 PD at 6 mg/kg. NSG mice treated at 8 mg/kg demonstrated more weight loss than those at 6 mg/kg, suggesting strain-specific determinants of tolerability. We confirmed in vivo suppression of p70S6K phosphorylation and cap-dependent translation in tumors. Conclusions: The mTORC1 inhibitor RMC-6272 exhibits greater anti-tumor activity than the allosteric inhibitor rapamycin in vitro, and is capable of inducing complete remissions as monotherapy in FOXO1 fusion positive RMS PDX. Increased anti-tumor activity was associated with suppression of cap-dependent translation as assessed by m7-GTP assays, nominating dephosphorylation of 4EBP1 as a potential response biomarker. Preclinical studies are ongoing to assess mechanism-informed combination therapeutic strategies incorporating this highly active agent in FOXO1 fusion positive RMS.

Citation Format: Jacqueline Morales, Kristen Kwong, W. Clay Gustafson, Amit J. Sabnis. Biochemical and preclinical anti-tumor activity of a bi-steric mTORC1-selective inhibitor in fusion positive rhabdomyosarcoma [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr A015.

A one-generation reproductive toxicity study of the mycotoxin ochratoxin A in Fischer rats

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium molds. Grain-based foods account for most human dietary exposures to OTA. OTA is a teratogen, but its reproductive and developmental effects are poorly understood. A one-generation reproductive toxicity study was conducted with groups of 16 male and 16 female Fischer rats exposed to 0, 0.026, 0.064, 0.16, 0.4 or 1.0 mg OTA/kg in diet. Dams exposed to 1.0 mg OTA/kg diet had statistically significant F1 pup losses between implantation and postnatal day (PND 4). Delays in preputial separation (PPS) and vaginal opening (VO) were indicative of delayed puberty in F1 rats. Mild renal lesions in nursing pups indicated that exposure prior to weaning impacted the kidneys. The developing kidney was more susceptible to OTA than the adult kidney. Significant increases in multi-oocyte follicles (MOFs) and proportional changes in resting and growing follicles were observed in F1 female ovaries. Plasma testosterone was reduced in F0 males, and there were negative effects on sperm quality in F0 and F1 male rats. The results confirm that continuous dietary exposure to OTA causes post-implantation fetotoxicity in dams, and renal and reproductive toxicity in their male and female offspring.

Failed eradication therapy of new onset Pseudomonas aeruginosa infections in cystic fibrosis children is associated with bacterial resistance to neutrophil functions

BACKGROUND

Antibiotics, such as inhaled tobramycin are used to eradicate new onset Pseudomonas aeruginosa (PA) infections in cystic fibrosis (CF) patients but frequently fail due to reasons poorly understood. We hypothesized that PA isolates' resistance to neutrophil antibacterial functions was associated with failed eradication in patients harboring those strains.

METHODS

We analyzed all PA isolates from a cohort of 39 CF children with new onset PA infections undergoing tobramycin eradication therapy, where N=30 patients had eradicated and N=9 patients had persistent infection. We characterized several bacterial phenotypes and measured the isolates' susceptibility to neutrophil antibacterial functions using in vitro assays of phagocytosis and intracellular bacterial killing.

RESULTS

PA isolates from persistent infections were more resistant to neutrophil functions, with lower phagocytosis and intracellular bacterial killing compared to those from eradicated infections. In multivariable analyses, in vitro neutrophil responses were positively associated with twitching motility, and negatively with mucoidy. In vitro neutrophil phagocytosis was a predictor of persistent infection following tobramycin even after adjustment for clinical risk factors.

CONCLUSIONS

PA isolates from new onset CF infection show strain-specific susceptibility to neutrophil antibacterial functions, and infection with PA isolates resistant to neutrophil phagocytosis is an independent risk factor for failed tobramycin eradication.

Surveys of rice sold in Canada for aflatoxins, ochratoxin A and fumonisins

Approximately 200 samples of rice (including white, brown, red, black, basmati and jasmine, as well as wild rice) from several different countries, including the United States, Canada, Pakistan, India and Thailand, were analysed for aflatoxins, ochratoxin A (OTA) and fumonisins by separate liquid chromatographic methods in two different years. The mean concentrations for aflatoxin B(1) (AFB(1)) were 0.19 and 0.17 ng g(-1) with respective positive incidences of 56% and 43% (≥ the limit of detection (LOD) of 0.002 ng g(-1)). Twenty-three samples analysed in the second year also contained aflatoxin B(2) (AFB(2)) at levels ≥LOD of 0.002 ng g(-1). The five most contaminated samples in each year contained 1.44-7.14 ng AFB(1) g(-1) (year 1) and 1.45-3.48 ng AFB(1) g(-1) (year 2); they were mostly basmati rice from India and Pakistan and black and red rice from Thailand. The average concentrations of ochratoxin A (OTA) were 0.05 and 0.005 ng g(-1) in year 1 and year 2, respectively; incidences of samples containing ≥LOD of 0.05 ng g(-1) were 43% and 1%, respectively, in the 2 years. All positive OTA results were confirmed by LC-MS/MS. For fumonisins, concentrations of fumonisin B(1) (FB(1)) averaged 4.5 ng g(-1) in 15 positive samples (≥0.7 ng g(-1)) from year 1 (n = 99); fumonisin B(2) (FB(2)) and fumonisin B(3) (FB(3)) were also present (≥1 ng g(-1)). In the second year there was only one positive sample (14 ng g(-1) FB(1)) out of 100 analysed. All positive FB(1) results were confirmed by LC-MS/MS.

Detection of undiagnosed and poorly controlled asthma in a hospital-based outpatient pediatric primary care clinic using a health risk assessment system

OBJECTIVE

To determine the rate of undiagnosed and poorly controlled asthma detected by a computerized health risk assessment (HRA) survey system in an urban pediatric hospital-based outpatient teaching clinic.

METHODS

A software-based HRA system uses survey answer patterns to identify children with (1) probable, (2) uncontrolled, and (3) moderate to severe asthma. Parents of patients > or = 2 years of age were asked by clinic staff to complete the touch screen computer survey before seeing their physician from August 2005 through July 2006.

RESULTS

The HRA survey predicted 26% (282/1,098) to have probable asthma. Of these, 51% (144/282) were controlled and the parents reported a previous diagnosis of asthma; 14% (40/282) were controlled and the parents did not report a previous diagnosis of asthma; 25% (71/282) were uncontrolled and the parents reported a previous diagnosis of asthma; and 10% (27/282) were uncontrolled and no previous diagnosis of asthma was reported by the parents. Among active cases completing the baseline version survey (N = 217), 68% reported emergency department (ED) visits / hospitalizations in the last 2 years (44% > or =2), while 59% reported missed school days during the previous year (23% > or =5 days). Impairment, as defined by the 2007 National Heart, Lung, and Blood Institute/National Asthma Education and Prevention Program (NHLBI/NAEPP) asthma guidelines, tended to be higher in patients without a previous diagnosis of asthma, per parental report, but this trend only achieved significance in two measures: daytime symptoms > or =2 days per week in the last 4 weeks (p = 0.028) and more than 5 missed school days in the past year (p = 0.001).

CONCLUSION

A previously validated HRA system can consistently identify a high rate of undiagnosed and poorly controlled asthma in an urban pediatric hospital-based teaching clinic. The utility of such a system would be to reduce missed opportunities for delivery of care and morbidity for the patients who currently have undiagnosed and/or uncontrolled asthma in the pediatric primary care outpatient setting.

Risk factors, sequential organ failure assessment and model for end-stage liver disease scores for predicting short term mortality in cirrhotic patients admitted to intensive care unit

BACKGROUND

Prognostic scores in an intensive care unit (ICU) evaluate outcomes, but derive from cohorts containing few cirrhotic patients.

AIMS

To evaluate 6-week mortality in cirrhotic patients admitted to an ICU, and to compare general and liver-specific prognostic scores.

METHODS

A total of 312 consecutive cirrhotic patients (65% alcoholic; mean age 49.6 years). Multivariable logistic regression to evaluate admission factors associated with survival. Child-Pugh, Model for End-stage Liver Disease (MELD), Acute Physiology and Chronic Health Evaluation (APACHE) II and Sequential Organ Failure Assessment (SOFA) scores were compared by receiver operating characteristic curves.

RESULTS

Major indication for admission was respiratory failure (35.6%). Median (range) Child-Pugh, APACHE II, MELD and SOFA scores were 11 (5-15), 18 (0-44), 24 (6-40) and 11 (0-21), respectively; 65% (n = 203) died. Survival improved over time (P = 0.005). Multivariate model factors: more organs failing (FOS) (<3 = 49.5%, > or =3 = 90%), higher FiO(2), lactate, urea and bilirubin; resulting in good discrimination [area under receiver operating characteristic curve (AUC) = 0.83], similar to SOFA and MELD (AUC = 0.83 and 0.81, respectively) and superior to APACHE II and Child-Pugh (AUC = 0.78 and 0.72, respectively).

CONCLUSIONS

Cirrhotics admitted to ICU with > or =3 failing organ systems have 90% mortality. The Royal Free model discriminated well and contained key variables of organ function. SOFA and MELD were better predictors than APACHE II or Child-Pugh scores.

Chronic smoking enhances tachykinin synthesis and airway responsiveness in guinea pigs

This study tests the hypothesis that the bronchial hyperreactivity induced by chronic cigarette smoke (CS) exposure involves the increased expression and release of tachykinins and calcitonin gene-related peptide (CGRP) from afferent nerve fibers innervating the airways. In guinea pigs chronically exposed to CS (20 min twice daily for 14-17 d), peak response in total lung resistance to capsaicin (1.68 microg/kg, intravenously) was significantly greater than that evoked by the same dose of capsaicin in control (air-exposed) animals. This augmented response in CS-exposed animals was abolished after treatment with CP-99994 and SR-48968, the neurokinin (NK)-1 and NK-2 receptor antagonists, suggesting the involvement of tachykinins in chronic CS-induced airway hyperresponsiveness (AHR). Further, substance P (SP)-like immunoreactivity (LI) and CGRP-LI in the airway tissue were significantly greater in the CS animals than in the control animals. Finally, beta-preprotachykinin (PPT, a splice variant from the PPT A gene encoding tachykinins including SP and NKA) messenger RNA levels as measured by in situ hybridization histochemistry displayed a significant increase in jugular ganglion neurons but not in dorsal root or nodose ganglion neurons. These data suggest that chronic CS-induced AHR is related to an increase in SP synthesis and release in jugular ganglion neurons innervating the lungs and airways.

The influence of "sputum-like gel" viscosity on crackle characteristics in a mechanically ventilated porcine lung model

This study investigated the influence of airway secretion viscosity on the characteristics of crackle sounds produced using a mechanically ventilated porcine lung model. Aqueous ultrasonic methylene blue stained gel solutions of viscosity 100, 150 and 200 P were prepared and instilled into 15 isolated, mechanically ventilated, porcine lungs immersed in water. Sound signals recorded by a hydrophone before and after instillation of gel were subjected to both fast Fourier transform and wave-form analysis. At the completion of sound recording, the main bronchi were dissected and the location of the stained gel was photographically recorded. Wave-form analysis demonstrated that expiratory phase crackle incidence and amplitude were both significantly higher than inspiratory phase data. This study demonstrates that crackle duration and amplitude are inversely related to gel viscosity and that electronic lung sound analysis can provide indirect evidence of sputum viscosity.

The effect on sound generation of varying both gas flow rate and the viscosity of sputum-like gel in a simple tubular model

Gas flows of 2, 3, and 4 L/min were directed through a sputum-like gel with viscosities of 100, 150, and 200 P and placed in a tube similar in diameter to a human segmental bronchus (4 mm), which was immersed in a bath of water. The sound produced by gas flow through the gel was recorded with a hydrophone. Sound data were subjected to time-expanded waveforms and fast Fourier transform (FFT) analysis. This study demonstrated that the number of crackles generated was directly related to the flow rate and inversely related to gel viscosity. The initial deflection width (IDW), two-cycle duration (2 CD), and peak-to-peak amplitude of crackles were significantly affected by the gas flow rate but not the viscosity of the gel. A lower gas flow rate generated crackles with longer IDW and 2 CD, but higher gas flow rates generated crackles with higher amplitude. Peak sound intensity measured from FFT increased as flow rate increased but decreased as the viscosity of the gel increased. At low gas flows, no gel-induced crackle sound was generated within the data capture window when the most viscous gel was examined. A digital video image of gas flow through the gel was captured, and this confirmed the absence of bubbles or slug formation at low flows through 200 P gel during the 3 seconds of data acquisition. This study describes some characteristics of crackles generated from different combinations of gas flow and gel viscosity and suggests that "coarse crackles" results from the explosion of gas bubbles in pulmonary secretions. Health care practitioners should consider the combined effect of rate of inspiratory gas flow and sputum viscosity during auscultation of patients' lungs.

Selective posterior rhizotomy: results of five pilot cases

We report on two patients with spastic quadriplegia and three patients with spastic diplegia who underwent selective posterior rhizotomy. The mean period of follow-up was 15 months (range, 12-21 months). The patients were assessed preoperatively and at 2 weeks, 3 months, 6 months, and 1 year after surgery. Tests included those for muscle tone (using a modified Ashworth scale), range of passive movement, functional status, and gait pattern. Muscle tone was reduced substantially after the procedure, and the range of passive movement was increased. Both the dependent and independent ambulators showed an increment in their walking velocity and stride length. There were no postoperative complications apart from mild fever and the treatment was well tolerated by both patients and parents. There was no return of spasticity in any of the patients during follow-up. The reduced spasticity resulted in better motor performance, and patients felt more comfortable with their daily activities. We conclude that selective posterior rhizotomy should be considered for those patients who have cerebral palsy and are disabled by spasticity.

Effect of positioning on recorded lung sound intensities in subjects without pulmonary dysfunction

BACKGROUND AND PURPOSE

Physical therapists often use positioning to assist in the reexpansion of collapsed lung segments. An increase in lung sound intensity on auscultation is considered indicative of lung expansion. This study was designed to examine whether clinical interpretation of auscultatory findings is warranted.

SUBJECTS

The subjects (5 male, 6 female) were young physical therapist students without pulmonary dysfunction (mean age=20.4 years, mean height=166.3 cm, mean weight=57.5 kg). Subjects with lung disease were excluded because pulmonary pathology is difficult to standardize.

METHODS

Lung sounds electronically recorded over the posterior chest wall of subjects in sitting and side-lying positions were compared. Measures included peak intensity, frequency at maximum power, and median frequency.

RESULTS

In the sitting position, inspiratory sounds recorded over the left posterior chest wall were louder than those recorded on the right side. In the side-lying positions, the sound intensity recorded from the dependent chest wall was louder than that recorded from the nondependent chest wall. In side-lying positions, the upper hemithorax is "nondependent," and the side in contact with the bed is "dependent." Sound intensities recorded over both posterior chest walls in the sitting position were louder than those recorded over the same lung area in the nondependent side-lying position. There was no difference in the sound intensity recorded between the sitting and dependent side-lying postures.

CONCLUSION AND DISCUSSION

When comparative auscultation of the chest wall is used by physical therapists to assess the adequacy of pulmonary ventilation, patient posture and regional differences in breath sound intensity can influence clinical interpretation.

Non-invasive in vivo mapping of tumour vascular and interstitial volume fractions

Non-invasive measurement of haemodynamic parameters and imaging of neovasculature architecture is of importance in determining tumour prognosis, in directing tissue sampling and in assessing treatment efficacy. In the current research we investigated a dual tracer nuclear magnetic resonance (NMR) technique to map the tumour vascular (VVF) and interstitial volume fraction (IVF) non-invasively in vivo. We hypothesised that a NMR signal emanating after intravenous administrations of a vascular paramagnetic probe (MPEG-PL-GdDTPA) can be maximised so that additional signal after administration of a second interstitial probe (GdDTPA) would only reflect the IVF but not the VVF. The method and its assumptions were verified and experimental conditions optimised both in phantoms and in C6 glioma bearing rats. Data derived from in vivo studies show tumoral VVF and IVF values that are consistent with histology data and literature values; the relative ranking order of values was tumour > muscle > brain. Image maps showed intratumoral and intertumoral heterogeneity of both parameters at submillimetre pixel resolution. The method is applicable to a wide variety of tumour models and can theoretically be performed repeatedly to study tumour growth or involution during therapy.

Activation of pulmonary C fibres by adenosine in anaesthetized rats: role of adenosine A1 receptors

1. Intravenous administration of adenosine (Ado) to patients can cause dyspnoea, chest discomfort and bronchoconstriction. To assess the role of vagal pulmonary C fibres in evoking these adverse reactions, the effect of Ado on single pulmonary C fibres was studied in anaesthetized and artificially ventilated rats. 2. Right-atrial injection of Ado (320 microg kg-1) activated 68 % (73/107) of pulmonary C fibres; the total number of action potentials during a period of 15 s increased from a baseline of 0.2 +/- 0.1 impulses to a peak of 16.4 +/- 2.6 impulses (P < 0.01, n = 107) after Ado. Inosine, the metabolite of Ado, did not activate any of eleven C fibres tested in six rats. Furthermore, C fibres were activated only by right-atrial and not by left-ventricular injection of the same dose of Ado. 3. Unlike the immediate and transient stimulation of C fibres by capsaicin, the C fibre stimulation by Ado had a latency of 6.5 +/- 0.3 s (range, 3-18 s) and lasted longer. 4. The stimulation of C fibres by Ado was significantly attenuated by pretreatment with aminophylline, a non-selective Ado receptor antagonist, was completely prevented by 1,3-dipropyl-8-cyclopentylxanthine, an Ado A1 receptor antagonist, but was unaffected by 3,7-dimethy-1-propargylxanthine, an A2 receptor antagonist. None of these Ado receptor antagonists prevented capsaicin-induced C fibre stimulation. 5. In conclusion, Ado stimulates pulmonary C fibre terminals through an activation of A1 receptors. The stimulation of pulmonary C fibres may play an important role in Ado-induced adverse respiratory effects.

Role of pulmonary C fibers in adenosine-induced respiratory inhibition in anesthetized rats

The clinical use of adenosine is commonly associated with pulmonary side effects, namely dyspnea, that suggest the possible involvement of bronchopulmonary sensory afferents. Our objective in this study was to characterize the effects of adenosine on breathing and to determine whether the vagal pulmonary afferents play a role in mediating these effects. We measured respiratory and cardiovascular changes in anesthetized, spontaneously breathing rats after bolus injections of adenosine at therapeutic doses. Right atrial injection of adenosine (0.04-0.6 mg/kg) elicits, in a dose-dependent manner, a pulmonary chemoreflex-like response consisting of a delayed apnea, bradycardia, and hypotension. In contrast, the classic capsaicin-elicited pulmonary chemoreflex occurs immediately after injection. Perineural capsaicin treatment of the cervical vagi blocked the adenosine-induced respiratory inhibition. Left ventricular administration of adenosine failed to elicit an apneic response. Pretreatment with the adenosine A1-receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine attenuated the adenosine-induced apnea. These results indicate that adenosine elicits a respiratory inhibition via stimulation of pulmonary C fibers and that activation of the A1-receptor is probably involved. It is unclear, however, what accounts for the exceedingly long latency in this response.

Relative blood volume measurements by magnetic resonance imaging facilitate detection of testicular torsion

RATIONALE AND OBJECTIVES

The authors determine the utility of relative blood volume measurements (rBV) using a blood pool marker for magnetic resonance imaging (MRI) in detection of early testicular torsion.

METHODS

Testicular torsion was induced in rats by counterclockwise 720 degrees rotation and fixation of the testis in the scrotum. MPEG-PL-DTPA-Gd enhanced MRI (30 mumol Gd/kg bolus injection) was performed 1 hour after torsion at 1.5 T using fat-suppressed three-dimensional fast spoiled gradient-recalled sequence for relative blood volume measurement and three-dimensional time-of-flight sequence for MR angiography (MRA).

RESULTS

The rBV of the torqued testes was significantly lower (13.3% +/- 13.5%) than that of testes with sham operation (97.7% +/- 5.3%; P < 0.05). Rats with testicular torsion showed larger regions of ischemia than did animals with sham operation (63.4% +/- 13.0% versus 4.0% +/- 2.8% of all pixels in testis; P < 0.01). The MRA of testicular torsion showed engorgement of the distal testicular vein as a sign of venous compression or total disappearance of the testicular vein, indicating arterial insufficiency.

CONCLUSIONS

The authors conclude that MPEG-PL-DTPA-Gd can be used to obtain functional (rBV), morphologic (tunica enhancement), and angiographic (venous engorgement, arterial compromise) findings that should improve the diagnosis of testicular torsion in the acute setting.

Stimulation of pulmonary C fibres by lactic acid in rats: contributions of H+ and lactate ions

1. The contributions of H+ and lactate ions to the stimulation of single pulmonary C fibres by lactic acid were examined in anaesthetized and artificially ventilated rats. 2. Lactic acid injected into the right atrium caused a transient decrease in arterial blood pH (pHa) and a short but intense burst of afferent activities in pulmonary C fibres, whereas sodium lactate had no effect. The fibre activity usually reached a peak within 1-1.5 s, with an onset latency of < 1 s, and returned to the baseline in 5 s. 3. The injection of hydrochloric acid at the same pH as that of lactic acid did not significantly decrease pHa, nor did it stimulate any C fibres studied. 4. Formic acid has a pKa value (the negative logarithm of the dissociation constant) almost identical to that of lactic acid; thus, its injection decreased pHa to the same degree as did the injection of lactic acid. However, the response of C fibres to lactic acid was 134% stronger than that to formic acid. 5. We conclude that H+ is primarily responsible for the activation of pulmonary C fibres by lactic acid, probably through a direct effect of H+ on these afferent endings. The lactate ion, by itself, does not activate C fibres, but it seems to potentiate the stimulatory effect of H+ on these afferents.

Evaluation of a 10 percent carbamide peroxide gel vital bleaching agent

A clinical study determined the whitening effect of a 10 percent carbamide peroxide gel on the teeth of 10 subjects. Histological evaluation of the effect of this agent on human tooth pulps and hamster cheek pouch tissues was also undertaken. The gel provided a modest, but unpredictable, whitening of discoloured teeth. A localised mild to moderate inflammatory response was found in some of the pulps of teeth that had been bleached. No soft-tissue changes were observed in the hamster cheek pouches.

Frontal sinusitis caused by Myriodontium keratinophilum

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