Hair Follicle Nevus Located on the Chin of an Infant: Case Report and Review of Literature.

Hair follicle nevi are rare, benign, congenital hamartomas that usually occur in the distribution of the first brachial arch. Histopathologically, the distinction between hair follicle nevus, trichofolliculoma, and accessory tragus has recently come into question, and it may be that they are all on a spectrum of the same condition. We report the case of a 7-day-old boy who presented with a "tag"-like lesion on his midline chin that had been present since birth. Biopsy of the lesion proved it to be a hair follicle nevus.

Methotrexate versus Acitretin in the Treatment of Chronic Hand Dermatitis.

BACKGROUND: Recent studies have produced treatment algorithms for hand dermatitis, but there are limited current indications of systemic treatments for chronic hand dermatitis. OBJECTIVE: To compare the efficacy and safety of methotrexate and acitretin in the treatment of chronic hand dermatitis. METHODS: A chart-retrospective review of all patients with hand dermatitis seen by the primary author at the University of North Carolina Dermatology and Skin Cancer Center from September 2007 to April 2013. RESULTS: Eighty-three hand dermatitis charts were reviewed. Twenty-nine patients received systemic therapy, of which 17 (26.5%) were treated systemically with acitretin and/or methotrexate. Of these 17 patients, four patients received courses of both acitretin and methotrexate independently after failing the alternative treatment course. At 6 months, acitretin achieved clearance/almost clearance in 44% of patients, compared to 0% of those treated with methotrexate. At 12 months, 100% of patients treated with acitretin achieved clearance/almost clearance compared to 40% of patients treated with methotrexate. Adverse effects were minimal and as expected. LIMITATIONS: This was a retrospective study, and the small sample size makes it difficult to generalize results. CONCLUSION: Systemic retinoids are a good alternative for the treatment of chronic hand dermatitis.

Extensively drug-resistant pseudomonas aeruginosa isolates containing blaVIM-2 and elements of Salmonella genomic island 2: a new genetic resistance determinant in Northeast Ohio.

Carbapenems are a mainstay of treatment for infections caused by Pseudomonas aeruginosa. Carbapenem resistance mediated by metallo-ß-lactamases (MBLs) remains uncommon in the United States, despite the worldwide emergence of this group of enzymes. Between March 2012 and May 2013, we detected MBL-producing P. aeruginosa in a university-affiliated health care system in northeast Ohio. We examined the clinical characteristics and outcomes of patients, defined the resistance determinants and structure of the genetic element harboring the blaMBL gene through genome sequencing, and typed MBL-producing P. aeruginosa isolates using pulsed-field gel electrophoresis (PFGE), repetitive sequence-based PCR (rep-PCR), and multilocus sequence typing (MLST). Seven patients were affected that were hospitalized at three community hospitals, a long-term-care facility, and a tertiary care center; one of the patients died as a result of infection. Isolates belonged to sequence type 233 (ST233) and were extensively drug resistant (XDR), including resistance to all fluoroquinolones, aminoglycosides, and ß-lactams; two isolates were nonsusceptible to colistin. The blaMBL gene was identified as blaVIM-2 contained within a class 1 integron (In559), similar to the cassette array previously detected in isolates from Norway, Russia, Taiwan, and Chicago, IL. Genomic sequencing and assembly revealed that In559 was part of a novel 35-kb region that also included a Tn501-like transposon and Salmonella genomic island 2 (SGI2)-homologous sequences. This analysis of XDR strains producing VIM-2 from northeast Ohio revealed a novel recombination event between Salmonella and P. aeruginosa, heralding a new antibiotic resistance threat in this region's health care system.

Metabolism-driven in vitro/in vivo disconnect of an oral ERɑ VHL-PROTAC.

Targeting the estrogen receptor alpha (ERα) pathway is validated in the clinic as an effective means to treat ER+ breast cancers. Here we present the development of a VHL-targeting and orally bioavailable proteolysis-targeting chimera (PROTAC) degrader of ERα. In vitro studies with this PROTAC demonstrate excellent ERα degradation and ER antagonism in ER+ breast cancer cell lines. However, upon dosing the compound in vivo we observe an in vitro-in vivo disconnect. ERα degradation is lower in vivo than expected based on the in vitro data. Investigation into potential causes for the reduced maximal degradation reveals that metabolic instability of the PROTAC linker generates metabolites that compete for binding to ERα with the full PROTAC, limiting degradation. This observation highlights the requirement for metabolically stable PROTACs to ensure maximal efficacy and thus optimisation of the linker should be a key consideration when designing PROTACs.

Advanced bone formation in mice with a dominant-negative mutation in the thyroid hormone receptor ß gene due to activation of Wnt/ß-catenin protein signaling.

Thyroid hormone (T(3)) acts in chondrocytes and bone-forming osteoblasts to control bone development and maintenance, but the signaling pathways mediating these effects are poorly understood. Thrb(PV/PV) mice have a severely impaired pituitary-thyroid axis and elevated thyroid hormone levels due to a dominant-negative mutant T(3) receptor (TRß(PV)) that cannot bind T(3) and interferes with the actions of wild-type TR. Thrb(PV/PV) mice have accelerated skeletal development due to unknown mechanisms. We performed microarray studies in primary osteoblasts from wild-type mice and Thrb(PV/PV) mice. Activation of the canonical Wnt signaling in Thrb(PV/PV) mice was confirmed by in situ hybridization analysis of Wnt target gene expression in bone during postnatal growth. By contrast, T(3) treatment inhibited Wnt signaling in osteoblastic cells, suggesting that T(3) inhibits the Wnt pathway by facilitating proteasomal degradation of ß-catenin and preventing its accumulation in the nucleus. Activation of the Wnt pathway in Thrb(PV/PV) mice, however, results from a gain of function for TRß(PV) that stabilizes ß-catenin despite the presence of increased thyroid hormone levels. These studies demonstrate novel interactions between T(3) and Wnt signaling pathways in the regulation of skeletal development and bone formation.

Human stem cell osteoblastogenesis mediated by novel glycogen synthase kinase 3 inhibitors induces bone formation and a unique bone turnover biomarker profile in rats.

Wnt activation by inhibiting glycogen synthase kinase 3 (GSK-3) causes bone anabolism in rodents making GSK-3 a potential therapeutic target for osteoporotic and osteolytic metastatic bone disease. To understand the wnt pathway related to human disease translation, the ability of 3 potent inhibitors of GSK-3 (AZD2858, AR79, AZ13282107) to 1) drive osteoblast differentiation and mineralisation using human adipose-derived stem cells (hADSC) in vitro; and 2) stimulate rat bone formation in vivo was investigated. Bone anabolism/resorption was determined using clinically relevant serum biomarkers as indicators of bone turnover and bone formation assessed in femurs by histopathology and pQCT/µCT imaging. GSK-3 inhibitors caused ß-catenin stabilisation in human and rat mesenchymal stem cells, stimulated hADSC commitment towards osteoblasts and osteogenic mineralisation in vitro. AZD2858 produced time-dependent changes in serum bone turnover biomarkers and increased bone mass over 28 days exposure in rats. After 7 days, AZD2858, AR79 or AZ13282107 exposure increased the bone formation biomarker P1NP, and reduced the resorption biomarker TRAcP-5b, indicating increased bone anabolism and reduced resorption in rats. This biomarker profile was differentiated from anabolic agent PTH1-34 or the anti-resorptive Alendronate-induced changes. Increased bone formation in cortical and cancellous bone as assessed by femur histopathology supported biomarker changes. 14 day AR79 treatment increased bone mineral density and trabecular thickness, and decreased trabecular number and connectivity assessed by pQCT/µCT. GSK-3 inhibition caused hADSC osteoblastogenesis and mineralisation in vitro. Increased femur bone mass associated with changes in bone turnover biomarkers confirmed in vivo bone formation and indicated uncoupling of bone formation and resorption.

First- versus Third-Generation EGFR Tyrosine Kinase Inhibitors in EGFR-Mutated Non-Small Cell Lung Cancer Patients with Brain Metastases.

Introduction: Up to 50% of non-small cell lung cancer (NSCLC) harbor EGFR alterations, the most common etiology behind brain metastases (BMs). First-generation EGFR-directed tyrosine kinase inhibitors (EGFR-TKI) are limited by blood-brain barrier penetration and T790M tumor mutations, wherein third-generation EGFR-TKIs, like Osimertinib, have shown greater activity. However, their efficacy has not been well-studied in later therapy lines in NSCLC patients with BMs (NSCLC-BM). We sought to compare outcomes of NSCLC-BM treated with either first- or third-generation EGFR-TKIs in first-line and 2nd-to-5th-line settings. Methods: A retrospective review of NSCLC-BM patients diagnosed during 2010-2019 at Cleveland Clinic, Ohio, US, a quaternary-care center, was performed and reported following 'strengthening the reporting of observational studies in epidemiology' (STROBE) guidelines. Data regarding socio-demographic, histopathological, molecular characteristics, and clinical outcomes were collected. Primary outcomes were median overall survival (mOS) and progression-free survival (mPFS). Multivariable Cox proportional hazards modeling and propensity score matching were utilized to adjust for confounders. Results: 239 NSCLC-BM patients with EGFR alterations were identified, of which 107 received EGFR-TKIs after diagnosis of BMs. 77.6% (83/107) received it as first-line treatment, and 30.8% (33/107) received it in later (2nd-5th) lines of therapy, with nine patients receiving it in both settings. 64 of 107 patients received first-generation (erlotinib/gefitinib) TKIs, with 53 receiving them in the first line setting and 13 receiving it in the 2nd-5th lines of therapy. 50 patients received Osimertinib as third-generation EGFR-TKI, 30 in first-line, and 20 in the 2nd-5th lines of therapy. Univariable analysis in first-line therapy demonstrated mOS of first- and third-generation EGFR-TKIs as 18.2 and 19.4 months, respectively (p = 0.57), while unadjusted mPFS of first- and third-generation EGFR-TKIs was 9.3 and 13.8 months, respectively (p = 0.14). In 2nd-5th line therapy, for first- and third-generation EGFR-TKIs, mOS was 17.3 and 11.9 months, (p = 0.19), while mPFS was 10.4 and 6.08 months, respectively (p = 0.41). After adjusting for age, performance status, presence of extracranial metastases, whole-brain radiotherapy, and presence of leptomeningeal metastases, hazard ratio (HR) for OS was 1.25 (95% CI 0.63-2.49, p = 0.52) for first-line therapy. Adjusted HR for mOS in 2nd-to-5th line therapy was 1.60 (95% CI 0.55-4.69, p = 0.39). Conclusions: No difference in survival was detected between first- and third-generation EGFR-TKIs in either first or 2nd-to-5th lines of therapy. Larger prospective studies are warranted reporting intracranial lesion size, EGFR alteration and expression levels in primary tumor and brain metastases, and response rates.

Combination of EGFR-Directed Tyrosine Kinase Inhibitors (EGFR-TKI) with Radiotherapy in Brain Metastases from Non-Small Cell Lung Cancer: A 2010-2019 Retrospective Cohort Study.

INTRODUCTION: Traditionally, brain metastases have been treated with stereotactic radiosurgery (SRS), whole-brain radiation (WBRT), and/or surgical resection. Non-small cell lung cancers (NSCLC), over half of which carry EGFR mutations, are the leading cause of brain metastases. EGFR-directed tyrosine kinase inhibitors (TKI) have shown promise in NSCLC; but their utility in NSCLC brain metastases (NSCLCBM) remains unclear. This work sought to investigate whether combining EGFR-TKI with WBRT and/or SRS improves overall survival (OS) in NSCLCBM. METHODS: A retrospective review of NSCLCBM patients diagnosed during 2010-2019 at a tertiary-care US center was performed and reported following the 'strengthening the reporting of observational studies in epidemiology' (STROBE) guidelines. Data regarding socio-demographic and histopathological characteristics, molecular attributes, treatment strategies, and clinical outcomes were collected. Concurrent therapy was defined as the combination of EGFR-TKI and radiotherapy given within 28 days of each other. RESULTS: A total of 239 patients with EGFR mutations were included. Of these, 32 patients had been treated with WBRT only, 51 patients received SRS only, 36 patients received SRS and WBRT only, 18 were given EGFR-TKI and SRS, and 29 were given EGFR-TKI and WBRT. Median OS for the WBRT-only group was 3.23 months, for SRS + WBRT it was 3.17 months, for EGFR-TKI + WBRT 15.50 months, for SRS only 21.73 months, and for EGFR-TKI + SRS 23.63 months. Multivariable analysis demonstrated significantly higher OS in the SRS-only group (HR = 0.38, 95% CI 0.17-0.84, p = 0.017) compared to the WBRT reference group. There were no significant differences in overall survival for the SRS + WBRT combination cohort (HR = 1.30, 95% CI = 0.60, 2.82, p = 0.50), EGFR-TKIs and WBRT combination cohort (HR = 0.93, 95% CI = 0.41, 2.08, p = 0.85), or the EGFR-TKI + SRS cohort (HR = 0.46, 95% CI = 0.20, 1.09, p = 0.07). CONCLUSIONS: NSCLCBM patients treated with SRS had a significantly higher OS compared to patients treated with WBRT-only. While sample-size limitations and investigator-associated selection bias may limit the generalizability of these results, phase II/III clinicals trials are warranted to investigate synergistic efficacy of EGFR-TKI and SRS.

Comparison of pharmacist managed anticoagulation with usual medical care in a family medicine clinic.

BACKGROUND: The beneficial outcomes of oral anticoagulation therapy are dependent upon achieving and maintaining an optimal INR therapeutic range. There is growing evidence that better outcomes are achieved when anticoagulation is managed by a pharmacist with expertise in anticoagulation management rather than usual care by family physicians. This study compared a pharmacist managed anticoagulation program (PC) to usual physician care (UC) in a family medicine clinic. METHODS: A retrospective cohort study was carried out in a family medicine clinic which included a clinical pharmacist. In 2006, the pharmacist assumed anticoagulation management. For a 17-month period, the PC group (n = 112) of patients on warfarin were compared to the UC patients (n = 81) for a similar period prior to 2006. The primary outcome was the percentage of time patients' INR was in the therapeutic range (TTR). Secondary outcomes were the percentage of time in therapeutic range within ± 0.3 units of the recommended range (expanded TTR) and percentage of time the INR was >5.0 or <1.5. RESULTS: The baseline characteristics were similar between the groups. Fifty-five percent of the PC group was male with a mean age of 67 years; 51% of the UC group was male with a mean age of 71 years. The most common indications for warfarin in both groups were atrial fibrillation, mechanical heart valves and deep vein thrombosis. The TTR was 73% for PC and 65% for UC (p < 0.0001). The expanded TTR for PC was 91% and 85% for UC (p < 0.0001). The percentage of time INR values were <1.5 was 0.7% for PC patients and 1.9% for UC patients (p < 0.0001), and >5 were 0.3% for PC patients and 0.1% for UC (p < 0.0001). CONCLUSION: The pharmacist-managed anticoagulation program within a family practice clinic compared to usual care by the physicians achieved significantly better INR control as measured by the percentage of time patients' INR values were kept in both the therapeutic and expanded range. Based on the results of this study, a collaborative family practice clinic using pharmacists and physicians may be an effective model for anticoagulation management with these results verified in future prospective randomized studies.

Delivering Robust Candidates to the Drug Pipeline through Computational Analysis of Arrayed CRISPR Screens.

Genome-wide arrayed CRISPR screening is a powerful method for drug target identification as it enables exploration of the effect of individual gene perturbations using diverse highly multiplexed functional and phenotypic assays. Using high-content imaging, we can measure changes in biomarker expression, intracellular localization, and cell morphology. Here we present the computational pipeline we have developed to support the analysis and interpretation of arrayed CRISPR screens. This includes evaluating the quality of guide RNA libraries, performing image analysis, evaluating assay results quality, data processing, hit identification, ranking, visualization, and biological interpretation.

A Novel Screening Approach for the Dissection of Cellular Regulatory Networks of NF-κB Using Arrayed CRISPR gRNA Libraries.

CRISPR/Cas9 is increasingly being used as a tool to prosecute functional genomic screens. However, it is not yet possible to apply the approach at scale across a full breadth of cell types and endpoints. In order to address this, we developed a novel and robust workflow for array-based lentiviral CRISPR/Cas9 screening. We utilized a ß-lactamase reporter gene assay to investigate mediators of TNF-α-mediated NF-κB signaling. The system was adapted for CRISPR/Cas9 through the development of a cell line stably expressing Cas9 and application of a lentiviral gRNA library comprising mixtures of four gRNAs per gene. We screened a 743-gene kinome library whereupon hits were independently ranked by percent inhibition, Z' score, strictly standardized mean difference, and T statistic. A consolidated and optimized ranking was generated using Borda-based methods. Screening data quality was above acceptable limits (Z' ≥ 0.5). In order to determine the contribution of individual gRNAs and to better understand false positives and negatives, a subset of gRNAs, against 152 genes, were profiled in singlicate format. We highlight the use of known reference genes and high-throughput, next-generation amplicon and RNA sequencing to assess screen data quality. Screening with singlicate gRNAs was more successful than screening with mixtures at identifying genes with known regulatory roles in TNF-α-mediated NF-κB signaling and was found to be superior to previous RNAi-based methods. These results add to the available data on TNF-α-mediated NF-κB signaling and establish a high-throughput functional genomic screening approach, utilizing a vector-based arrayed gRNA library, applicable across a wide variety of endpoints and cell types at a genome-wide scale.

Thyroid hormone excess rather than thyrotropin deficiency induces osteoporosis in hyperthyroidism.

Thyrotoxicosis is an important but under recognized cause of osteoporosis. Recently, TSH deficiency, rather than thyroid hormone excess, has been suggested as the underlying cause. To investigate the molecular mechanism of osteoporosis in thyroid disease, we characterized the skeleton in mice lacking either thyroid hormone receptor alpha or beta (TRalpha(0/0), TRbeta-/-). Remarkably, in the presence of normal circulating thyroid hormone and TSH concentrations, adult TRalpha(0/0) mice had osteosclerosis accompanied by reduced osteoclastic bone resorption, whereas juveniles had delayed endochondral ossification with reduced bone mineral deposition. By contrast, adult TRbeta-/- mice with elevated TSH and thyroid hormone levels were osteoporotic with evidence of increased bone resorption, whereas juveniles had advanced ossification with increased bone mineral deposition. Analysis of T3 target gene expression revealed skeletal hypothyroidism in TRalpha(0/0) mice, but skeletal thyrotoxicosis in TRbeta-/- mice. These studies demonstrate that bone loss in thyrotoxicosis is independent of circulating TSH levels and mediated predominantly by TRalpha, thus identifying TRalpha as a novel drug target in the prevention and treatment of osteoporosis.

Regulation of fibroblast growth factor receptor-1 (FGFR1) by thyroid hormone: identification of a thyroid hormone response element in the murine Fgfr1 promoter.

T(3) is essential for normal skeletal development, acting mainly via the TRalpha1 nuclear receptor. Nevertheless, the mechanisms of T(3) action in bone are poorly defined. Fibroblast growth factor receptor-1 (FGFR1) is also essential for bone formation. Fgfr1 expression and activity are positively regulated by T(3) in osteoblasts, and in mice that harbor a dominant negative PV mutation targeted to TRalpha1 or TRbeta, Fgfr1 expression is sensitive to skeletal thyroid status. To investigate mechanisms underlying T(3) regulation of FGFR1, we obtained primary calvarial osteoblasts from wild-type and TRbeta(PV/PV) littermate mice. T(3) treatment increased Fgfr1 expression 2-fold in wild-type cells, but 8-fold in TRbeta(PV/PV) osteoblasts. The 4-fold increased T(3) sensitivity of TRbeta(PV/PV) osteoblasts was associated with a markedly increased ratio of TRalpha1:TRbeta1 expression that resulted from reduced TRbeta1 expression in TRbeta(PV/PV) osteoblasts compared with wild-type. Bioinformatics and gel shift studies, and mutational analysis, identified a specific TR binding site 279-264 nucleotides upstream of the murine Fgfr1 promoter transcription start site. Transient transfection analysis of a series of Fgfr1 promoter 5'-deletion constructs, of a mutant reporter construct, and a series of heterologous promoter constructs, confirmed that this region of the promoter mediates a TR-dependent transcriptional response to T(3). Thus, in addition to indirect regulation of FGFR1 expression by T(3) reported previously, T(3) also activates the Fgfr1 promoter directly via a thyroid hormone response element located at positions -279/-264.

Contrasting skeletal phenotypes in mice with an identical mutation targeted to thyroid hormone receptor alpha1 or beta.

Thyroid hormone (T(3)) regulates bone turnover and mineralization in adults and is essential for skeletal development. Surprisingly, we identified a phenotype of skeletal thyrotoxicosis in T(3) receptor beta(PV) (TRbeta(PV)) mice in which a targeted frameshift mutation in TRbeta results in resistance to thyroid hormone. To characterize mechanisms underlying thyroid hormone action in bone, we analyzed skeletal development in TRalpha1(PV) mice in which the same PV mutation was targeted to TRalpha1. In contrast to TRbeta(PV) mice, TRalpha1(PV) mutants exhibited skeletal hypothyroidism with delayed endochondral and intramembranous ossification, severe postnatal growth retardation, diminished trabecular bone mineralization, reduced cortical bone deposition, and delayed closure of the skull sutures. Skeletal hypothyroidism in TRalpha1(PV) mutants was accompanied by impaired GH receptor and IGF-I receptor expression and signaling in the growth plate, whereas GH receptor and IGF-I receptor expression and signaling were increased in TRbeta(PV) mice. These data indicate that GH receptor and IGF-I receptor are physiological targets for T(3) action in bone in vivo. The divergent phenotypes observed in TRalpha1(PV) and TRbeta(PV) mice arise because the pituitary gland is a TRbeta-responsive tissue, whereas bone is TRalpha responsive. These studies provide a new understanding of the complex relationship between central and peripheral thyroid status.

The thyroid hormone receptor beta-specific agonist GC-1 selectively affects the bone development of hypothyroid rats.

UNLABELLED: We investigated the effects of GC-1, a TRbeta-selective thyromimetic, on bone development of hypothyroid rats. Whereas T3 reverted the IGF-I deficiency and the skeletal defects caused by hypothyroidism, GC-1 had no effect on serum IGF-I or on IGF-I protein expression in the epiphyseal growth plate of the femur, but induced selective effects on bone development. Our findings indicate that T3 exerts some essential effects on bone development that are mediated by TRbeta1. INTRODUCTION: We investigated the role of the thyroid hormone receptor beta1 (TRbeta1) on skeletal development of rats using the TRbeta-selective agonist GC-1. MATERIALS AND METHODS: Twenty-one-day-old female rats (n = 6/group) were rendered hypothyroid (Hypo) and treated for 5 weeks with 0.3 ug/100 g BW/day of T3 (1xT3), 5xT3, or equimolar doses of GC-1 (1xGC-1 and 5xGC-1). Serum triiodothyronine (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), and insulin-like growth factor (IGF)-I concentrations were determined by radioimmunoassay (RIA). BMD and longitudinal bone growth were determined by DXA. Trabecular bone histomorphometry and epiphyseal growth plate (EGP) morphometry were performed in the distal femur. Expressions of IGF-I protein and of collagen II and X mRNA were evaluated by immunohistochemistry and in situ hybridization, respectively. To determine hormonal effects on ossification, skeletal preparations of hypothyroid-, 5xGC-1-, and 5xT3-treated neonatal rats were compared. RESULTS: Hypothyroidism impaired longitudinal body growth and BMD gain, delayed ossification, reduced the number of hypertrophic chondrocytes (HCs; 72% versus Euthyroid [Eut] rats; p < 0.001), and resulted in disorganized columns of EGP chondrocytes. Serum IGF-I was 67% reduced versus Eut rats (p < 0.001), and the expression of IGF-I protein and collagen II and X mRNA were undetectable in the EGP of Hypo rats. T3 completely or partially normalized all these parameters. In contrast, GC-1 did not influence serum concentrations or EGP expression of IGF-I, failed to reverse the disorganization of proliferating chondrocyte columns, and barely affected longitudinal growth. Nevertheless, GC-1 induced ossification, HC differentiation, and collagen II and X mRNA expression and increased EGP thickness to Eut values. GC-1-treated rats had higher BMD gain in the total tibia, total femur, and in the femoral diaphysis than Hypo animals (p < 0.05). These changes were associated with increased trabecular volume (48%, p < 0.01), mineralization apposition rate (2.3-fold, p < 0.05), mineralizing surface (4.3-fold, p < 0.01), and bone formation rate (10-fold, p < 0.01). CONCLUSIONS: Treatment of hypothyroid rats with the TRbeta-specific agonist GC-1 partially reverts the skeletal development and maturation defects resultant of hypothyroidism. This finding suggests that TRbeta1 has an important role in bone development.

Chaotic collisionless evolution in galaxies and charged-particle beams.

Both galaxies and charged particle beams can exhibit collisionless evolution on surprisingly short time scales. This can be attributed to the dynamics of chaotic orbits. The chaos is often triggered by resonance caused by time dependence in the bulk potential, which acts almost identically for attractive gravitational forces and repulsive electrostatic forces. The similarity suggests that many physical processes at work in galaxies, although inaccessible to direct controlled experiments, can be tested indirectly via controlled experiments with charged particle beams, such as those envisioned for the University of Maryland electron ring currently nearing completion.

A thyrotoxic skeletal phenotype of advanced bone formation in mice with resistance to thyroid hormone.

Thyroid hormone (T3) regulates bone turnover and mineralization in adults and is essential for skeletal development during childhood. Hyperthyroidism is an established risk factor for osteoporosis. Nevertheless, T3 actions in bone remain poorly understood. Patients with resistance to thyroid hormone, due to mutations of the T3-receptor beta (TRbeta) gene, display variable phenotypic abnormalities, particularly in the skeleton. To investigate the actions of T3 during bone development, we characterized the skeleton in TRbetaPV mutant mice. TRbetaPV mice harbor a targeted resistance to thyroid hormone mutation in TRbeta and recapitulate the human condition. A severe phenotype, which includes shortened body length, was evident in homozygous TRbetaPV/PV animals. Accelerated growth in utero was associated with advanced endochondral and intramembranous ossification. Advanced bone formation resulted in postnatal growth retardation, premature quiescence of the growth plates, and shortened bone length, together with increased bone mineralization and craniosynostosis. In situ hybridization demonstrated increased expression of fibroblast growth factor receptor-1, a T3-regulated gene in bone, in TRbetaPV/PV perichondrium, growth plate chondrocytes, and osteoblasts. Thus, the skeleton in TRbetaPV/PV mice is thyrotoxic and displays phenotypic features typical of juvenile hyperthyroidism.

Thyroid hormone activates fibroblast growth factor receptor-1 in bone.

Thyroid hormone (T3) and the T3 receptor (TR) alpha gene are essential for bone development whereas adult hyperthyroidism increases the risk of osteoporotic fracture. We isolated fibroblast growth factor receptor-1 (FGFR1) as a T3-target gene in osteoblasts by subtraction hybridization. FGFR1 mRNA was induced 2- to 3-fold in osteoblasts treated with T3 for 6-48 h, and FGFR1 protein was stimulated 2- to 4-fold. Induction of FGFR1 was independent of mRNA half-life and abolished by actinomycin D and cycloheximide, indicating the involvement of an intermediary protein. Fibroblast growth factor 2 (FGF2) stimulated MAPK in osteoblasts, and pretreatment with T3 for 6 h induced a more rapid response to FGF that was increased in magnitude by 2- to 3-fold. Similarly, T3 enhanced FGF2-activated autophosphorylation of FGFR1, but did not modify FGF2-induced phosphorylation of the docking protein FRS2. These effects were abolished by the FGFR-selective inhibitors PD166866 and PD161570. In situ hybridization analyses of TRalpha-knockout mice, which have impaired ossification and skeletal mineralization, revealed reduced FGFR1 mRNA expression in osteoblasts and osteocytes, whereas T3 failed to stimulate FGFR1 mRNA or enhance FGF2-activated MAPK signaling in TRalpha-null osteoblasts. These findings implicate FGFR1 signaling in T3-dependent bone development and the pathogenesis of skeletal disorders resulting from thyroid disease.

Measuring spatial chirp in ultrashort pulses using single-shot Frequency-Resolved Optical Gating.

We show that the spatio-temporal distortion, spatial chirp, is naturally and easily measured by single-shot versions of second-harmonic generation frequency-resolved optical gating (SHG FROG) (including the extremely simple version, GRENOUILLE);. While SHG FROG traces are ordinarily symmetrical, a pulse with spatial chirp yields a trace with a shear that is approximately twice the pulse spatial chirp. As a result, the trace shear unambiguously reveals both the magnitude and sign of the pulse spatial chirp. The effects of spatial chirp can then be removed from the trace and the intensity and phase vs. time also retrieved, yielding a full description of the spatially chirped pulse in space and time.

Measuring pulse-front tilt in ultrashort pulses using GRENOUILLE.

We show that the spatio-temporal distortion, pulse-front tilt, is naturally, easily, and sensitively measured by the recently demonstrated, extremely simple variation of single-shot second-harmonic generation frequency-resolved optical gating (SHG FROG): GRENOUILLE. While GRENOUILLE traces are ordinarily centered on the zero of delay, a pulse with pulse-front tilt yields a trace whose center is shifted to a nonzero delay that is proportional to the pulse-front tilt. As a result, the trace-center shift reveals both the magnitude and sign of the pulse-front tilt-independent of the temporal pulse intensity and phase. The effects of pulse-front tilt can then easily be removed from the trace and the intensity and phase vs. time also retrieved, yielding a full description of the pulse in space and time.