Severity of Megakaryocyte-Driven Osteosclerosis in Mpig6b-Deficient Mice Is Sex-Linked

Patients with chronic myelofibrosis often suffer from osteosclerosis, which is associated with bone pain and may lead to bone marrow failure. The pathogenesis of myelofibrosis is linked to aberrant megakaryocyte development and function. Null and loss-of-function mutations in MPIG6B, which codes for the inhibitory heparan sulfate receptor G6b-B, result in severe macrothrombocytopenia, large megakaryocyte clusters, and focal primary myelofibrosis in mice and humans. We investigated the development of osteosclerosis in Mpig6b null (Mpig6b^−/−) mice. Although male and female Mpig6b^−/− mice presented with elevated bone marrow megakaryocyte number and macrothrombocytopenia, female Mpig6b^−/− mice developed progressive splenomegaly starting at 8 weeks of age. Micro–computed tomography (μCT) of femurs showed that female Mpig6b^−/− mice had increased cortical thickness and reduced bone marrow area starting at 8 weeks of age and developed occlusion of the medullary cavity by trabeculae by 16 weeks of age. In contrast, male Mpig6b^−/− mice developed only a small number of trabeculae in the medullary cavity at the proximal diaphysis and demonstrated a temporary decrease in bone volume fraction and trabecular thickness at 16 weeks. Ovariectomy of 10-week-old female Mpig6b^−/− mice prevented the development of medullary cavity osteosclerosis, whereas orchiectomy of male Mpig6b^−/− mice did not exacerbate their disease. Importantly, ovariectomized female Mpig6b^−/− mice also demonstrated improvement in spleen weight compared to sham-operated Mpig6b^−/− mice, establishing estrogen as a contributing factor to the severity of the megakaryocyte-driven osteosclerosis. © 2021 American Society for Bone and Mineral Research (ASBMR).     

Structure–activity investigation of the potentiating effect of cyano substitution on nitroaniline mutagenicity in the ames test

2,6‐Dicyano‐4‐nitroaniline and 2‐cyano‐4‐nitroaniline (CNNA; 2‐amino‐5‐nitrobenzonitrile) are potent mutagens in the Ames test, even though unsubstituted nitroanilines (NAs) are no more than weak mutagens. These compounds are putative reduction products of many commercial azo dyes, including Disperse Blue 165, Disperse Blue 337, Disperse Red 73, Disperse Red 82, Disperse Violet 33, and Disperse Violet 63. We have examined the mutagenicity in strains TA98 and YG1024 of a series of commercially‐available isomers of CNNA, and some related compounds, to probe the relationship between structure and genotoxic activity in this class of compounds. The potentiating effect of the cyano substituent is seen in many cases; e.g. 2‐amino‐4‐nitrobenzonitrile is a much more potent mutagen than 3‐NA. 2,4‐Dinitrobenzonitrile is also highly mutagenic. Possible mechanisms for the “cyano effect” are considered, with respect to the likely structures of cyanonitroaniline‐DNA adducts and the roles of the enzymes (nitroreductase and acetyl CoA:arylamine N‐acetyltransferase) believed to be involved in the activation of nitroaromatic compounds. Environ. Mol. Mutagen. 59:114–122, 2018. © 2017 Wiley Periodicals, Inc.     

Angiotensin II-dependent chronic hypertension and cardiac hypertrophy are unaffected by gp91phox-containing NADPH oxidase

The gp91phox-containing NADPH oxidase is the major source of reactive oxygen species (ROS) in the cardiovascular system and inactivation of gp91phox has been reported to blunt hypertension and cardiac hypertrophy seen in angiotensin (Ang) II-infused animals. In the current study, we sought to determine the role of gp91phox-derived ROS on cardiovascular outcomes of chronic exposure to Ang II. The gp91phox-deficient mice were crossed with transgenic mice expressing active human renin in the liver (TTRhRen). TTRhRen mice exhibit chronic Ang II-dependent hypertension and frank cardiac hypertrophy by age 10 to 12 weeks. Four genotypes of mice were generated: control, TTRhRen trangenics (TTRhRen), gp91phox-deficient (gp91-), and TTRhRen transgenic gp91phox-deficient (TTRhRen/gp91-). Eight to 10 mice/group were studied. ROS levels were significantly reduced (P<0.05) in the heart and aorta of TTRhRen/gp91- and gp91-mice compared with control counterparts, and this was associated with reduced cardiac, aortic, and renal NADPH oxidase activity (P<0.05). Systolic blood pressure (SBP), cardiac mass, and cardiac fibrosis were increased in TTRhRen versus controls. In contrast to its action on ROS generation, gp91phox inactivation had no effect on development of hypertension or cardiac hypertrophy in TTRhRen mice, although interstitial fibrosis was reduced. Cardiac and renal expression of gp91phox homologues, Nox1 and Nox4, was not different between groups. Thus, although eliminating gp91phox-associated ROS production may be important in cardiovascular consequences in acute insult models, it does not prevent the development of hypertension and cardiac hypertrophy in a model in which the endogenous renin-angiotensin system is chronically upregulated.     

Advances in the molecular classification of pediatric brain tumors: a guide to the galaxy

Central nervous system (CNS) tumors are the most common solid tumor in pediatrics, accounting for approximately 25% of all childhood cancers, and the second most common pediatric malignancy after leukemia. CNS tumors can be associated with significant morbidity, even those classified as low grade. Mortality from CNS tumors is disproportionately high compared to other childhood malignancies, although surgery, radiation, and chemotherapy have improved outcomes in these patients over the last few decades. Current therapeutic strategies lead to a high risk of side effects, especially in young children. Pediatric brain tumor survivors have unique sequelae compared to age-matched patients who survived other malignancies. They are at greater risk of significant impairment in cognitive, neurological, endocrine, social, and emotional domains, depending on the location and type of the CNS tumor. Next-generation genomics have shed light on the broad molecular heterogeneity of pediatric brain tumors and have identified important genes and signaling pathways that serve to drive tumor proliferation. This insight has impacted the research field by providing potential therapeutic targets for these diseases. In this review, we highlight recent progress in understanding the molecular basis of common pediatric brain tumors, specifically low-grade glioma, high-grade glioma, ependymoma, embryonal tumors, and atypical teratoid/rhabdoid tumor (ATRT). © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Effects of ovarian hormones and aging on respiratory sinus arrhythmia and breathing patterns in women

We investigated the effect of ovarian hormones and aging on breathing pattern [pulmonary minute ventilation (V(E))], tidal volume (V(T)), breathing frequency (F(b)), and respiratory sinus arrhythmia (RSA) in women. Recordings of V(E) and electrocardiogram (ECG) were obtained from 23 healthy women (10 premenopausal, 13 postmenopausal) under resting, isocapnic hypoxia (IH), and euoxic hypercapnia (EH) conditions. Premenopausal women were tested on three different days, each day corresponding to a specific phase of the menstrual cycle (follicular, mid-cycle, and luteal); postmenopausal women (PMW) were tested on 1 day only. On each test day, subjects were challenged with IH and EH. The order of the two tests was randomized and separated by at least 1 hour. Due to the low F (b) of several PMW, the band limits for RSA analysis had to be adjusted. The spectral coherence between respiratory flow and ECG RR-interval was used to determine the spectral band. Within the spectral band, there was a consistent phase relationship between the two variables where high values of spectral coherence indicate a well-defined phase relationship between respiratory flow and RR-interval variability. The main findings in this study for RSA are fourfold. First, RSA did not change with different levels of ovarian hormones (progesterone, serum 17beta-estradiol) during the menstrual cycle. Second, RSA was not influenced by hormone replacement therapy. Third, RSA did not change with age. Fourth, RSA did not change with IH and EH-induced changes in breathing patterns. Finally, high individual variability of average RR-interval change per breath was found.     

Feasibility of neurocognitive outcome evaluations in patients with brain metastases in a multi-institutional cooperative group setting: results of Radiation Therapy Oncology Group trial BR-0018

PURPOSE: A multi-institutional trial was conducted by the Radiation Therapy Oncology Group (RTOG) to test the feasibility of performing a test battery consisting of five neurocognitive measures and a quality-of-life instrument in patients with brain metastases. METHODS AND MATERIALS: The major eligibility requirements included histologic proof of a primary malignancy, measurable single or multiple brain metastases, Zubrod performance status of 0-1, neurologic function status of 0-2, and "certification" for administration of neurocognitive assessments. This certification process required either attendance at an RTOG neurocognitive assessment training workshop or review of an instructional video, followed by submission of an audiotape of mock/simulated test sessions for central review. The test battery included the following measures: the Mini-Mental Status Examination, Hopkins Verbal Learning Test, Verbal Fluency/Controlled Word Association Test, Ruff 2 and 7 test, Trailmaking Test, and Profile of Mood States-Short Form. The primary objective of this trial was to establish whether patients were able to complete this test battery. Compliance was defined as successful completion of a test measure. The test battery was to be administered just before, at completion of, and 1 month after whole brain radiotherapy to 37.5 Gy at 2.5 Gy/fraction once daily. Fifty-nine patients were enrolled in the trial. RESULTS: The patient characteristics included 32% > or =65 years; 44% with Zubrod performance status of 0; and 81% with multiple brain metastases. The overall compliance rate for administration and completion of the five neurocognitive measures and a quality-of-life instrument before treatment, at treatment completion, and 1 month after treatment was > or =95%, > or =84%, and > or =70%. The most common causes of noncompliance were patient-related factors (e.g., performance status or inability to understand test instructions) and not institutional error. CONCLUSION: Neurocognitive evaluation of patients with brain metastases in a multi-institutional and cooperative group setting is feasible using the test battery and certification process used in this study. This battery and certification process will be incorporated into future RTOG brain tumor trials.