The role of GDF5 in regulating enthesopathy development in the Hyp mouse model of XLH.

X-linked hypophosphatemia (XLH) is caused by mutations in PHEX, leading to rickets and osteomalacia. Adults affected with XLH develop a mineralization of the bone-tendon attachment site (enthesis), called enthesopathy, which causes significant pain and impaired movement. Entheses in mice with XLH (Hyp) have enhanced bone morphogenetic protein (BMP) and Indian hedgehog (IHH) signaling. Treatment of Hyp mice with the BMP signaling blocker palovarotene attenuated BMP/IHH signaling in Hyp entheses, thus indicating that BMP signaling plays a pathogenic role in enthesopathy development and that IHH signaling is activated by BMP signaling in entheses. It was previously shown that mRNA expression of growth/differentiation factor 5 (Gdf5) is enhanced in Hyp entheses at P14. Thus, to determine a role for GDF5 in enthesopathy development, Gdf5 was deleted globally in Hyp mice and conditionally in Scx + cells of Hyp mice. In both murine models, BMP/IHH signaling was similarly decreased in Hyp entheses, leading to decreased enthesopathy. BMP/IHH signaling remained unaffected in WT entheses with decreased Gdf5 expression. Moreover, deletion of Gdf5 in Hyp entheses starting at P30, after enthesopathy has developed, partially reversed enthesopathy. Taken together, these results demonstrate that while GDF5 is not essential for modulating BMP/IHH signaling in WT entheses, inappropriate GDF5 activity in Scx + cells contributes to XLH enthesopathy development. As such, inhibition of GDF5 signaling may be beneficial for the treatment of XLH enthesopathy.

X-linked hypophosphatemia (XLH) is a rare bone disorder that leads to short stature and poorly mineralized bones. As adults, patients with XLH often develop a mineralization of the bone-tendon attachment site, called enthesopathy, which results in significant pain. We previously showed that Achilles bone-tendon attachment sites (entheses) in mice with XLH (Hyp) have an enthesopathy characterized by increased bone morphogenetic protein (BMP) signaling. In the current studies, we show that treating Hyp mice with the BMP signaling inhibitor palovarotene prevents enthesopathy, demonstrating that the increased BMP signaling in Hyp entheses leads to enthesopathy development. We also reported that gene expression of Gdf5, which activates BMP signaling, is enhanced in Hyp entheses. Therefore, to determine if the enhanced Gdf5 expression leads to the increased BMP signaling seen Hyp entheses, Gdf5 was deleted from Hyp mice and also deleted specifically in the entheses of Hyp mice. In both mouse models, enthesopathy development was attenuated, demonstrating that the increased Gdf5 expression in Hyp entheses plays a role in enthesopathy development. These data indicate that blocking GDF5 and BMP signaling may prevent enthesopathy in patients with XLH.

Long-Term (>24 Months) Duration of Symptoms Negatively Impacts Patient-Reported Outcomes Following Anterior Cervical Discectomy and Fusion for Cervical Radiculopathy.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To investigate the impact of long symptom duration (>24 mo) on patient self-reported outcomes for pain, function, and quality of life following anterior cervical discectomy and fusion (ACDF) for cervical radiculopathy. SUMMARY OF BACKGROUND DATA: ACDF is an effective treatment to relieve the symptoms of cervical radiculopathy. However, there is no consensus on whether prolonged preoperative length of symptoms negatively impacts postoperative outcomes. METHODS: This study included consecutive patients who underwent ACDF for cervical radiculopathy from May 1, 2012 to Dec 1, 2019 by a single surgeon. Patients were stratified by short (<24 mo) and long (>24 mo) duration of symptoms. Outcomes including visual analog scale (VAS) neck and arm, neck disability index (NDI), EuroQol-5D (EQ-5D), and overall state of health (EQ-VAS) were compared between cohort both for absolute values and percentage of patients achieving minimal clinically important difference. RESULTS: A total of 111 consecutive patients were included in our study, including 59 patients in the short symptom duration group and 52 patients in the long symptom duration group. The mean age of the patients was 51.4±9.4 and 41 (36.9%) were female. The baseline VAS neck and arm, NDI, EQ-5D, and EQ-VAS were similar between groups. Patients in both long and short symptom duration groups had clinical improvement following surgery. However, patients with short symptom duration had better VAS Neck and EQ-5D outcomes, and were more likely to meet minimal clinically important difference for NDI, EQ-5D, or any outcome. Multivariate analysis confirmed symptom duration <24 months as an independent predictor for better patient-reported outcomes. CONCLUSION: We appreciated better clinical outcomes in patients with shorter symptom duration who received ACDF for cervical radiculopathy. On the basis of this data, we advocate for prompt treatment of cervical radiculopathy to avoid the potential for long-term impairment. LEVEL OF EVIDENCE: Level 3.

Pediatric intracranial tuberculoma: illustrative case.

BACKGROUND: Tuberculosis is an airborne disease caused by Mycobacterium tuberculosis. Intracranial tuberculoma is a rare complication of extrapulmonary tuberculosis due to hematogenous spread to subpial and subependymal regions. Intracranial tuberculoma can occur with or without meningitis. OBSERVATIONS: A 3-year-old male who had recently emigrated from Sudan presented to the emergency department with right-sided seizures lasting 30 minutes, which were aborted with levetiracetam and midazolam. Head computed tomography revealed a multilobulated left supratentorial mass with solid and cystic components and measuring 8.0 × 4.8 × 6.5 cm. The patient had successful resection of the mass, which was positive for M. tuberculosis. He was started on rifampin, isoniazid, pyrazinamide, ethambutol, and fluoroquinolone and was discharged home in stable condition. LESSONS: A literature review on pediatric intracranial tuberculoma was performed, which included 48 studies (n = 49). The mean age was 8.8 ± 5.4 years with a slight female predilection (59%). Predominant solitary tuberculomas (63%) were preferentially managed with both resection and antituberculosis therapy (ATT), whereas multifocal tuberculomas were preferentially managed with ATT. Intracranial tuberculoma is a rare but treatable cause of space-occupying lesions in children. Clinicians should maintain a high level of suspicion in patients from endemic regions and involve the infectious disease service early.

Assessing the robustness of negative vascular surgery randomized controlled trials using their reverse fragility index.

OBJECTIVE: The reverse fragility index (RFI) describes the number of event conversions needed to convert a statistically nonsignificant dichotomous outcome to a significant one. The objective of the present study was to assess the RFI of vascular surgery randomized controlled trials (RCTs) comparing endovascular vs open surgery for the treatment of abdominal aortic aneurysms (AAAs), carotid artery stenosis (CAS), and peripheral artery disease (PAD). METHODS: MEDLINE and Embase were searched for RCTs that had investigated AAAs, CAS, or PAD with statistically nonsignificant binary primary outcomes. The primary outcome for the present study was the median RFI. Calculation of the RFI was performed by creating two-by-two contingency tables and subtracting events from the group with fewer events and adding nonevents to the same group until a two-tailed Fisher exact test had produced a statistically significant result (P ≤ .05). RESULTS: Of 4187 reports, 49 studies reporting 103 different primary end points were included. The overall median RFI was 7 (interquartile range [IQR], 5-13). The specific RFIs for AAA, CAS, and PAD were 10 (IQR, 6-15.5), 6 (IQR, 5-9.5), and 7 (IQR, 5.5-10), respectively. Of the 103 end points, 42 (47%) had had a loss to follow-up greater than the RFI, of which 10 were AAA trials (24%), 23 were CAS trials (55%), and 9 were PAD trials (21%). The Pearson correlation demonstrated a significant positive relationship between a study's RFI and the impact factor of its publishing journal (r = 0.38; 95% confidence interval [CI], 0.20-0.54; P < .01), length of follow-up (r = 0.43; 95% CI, 0.26-0.58; P < .01), and sample size (r = 0.28; 95% CI, 0.09-0.45; P < .01). CONCLUSIONS: A small number of events (median, 7) was required to change the outcome of negative RCTs from statistically nonsignificant to significant, with 47% of the studies having missing data that could have reversed the finding of its primary outcome. Reporting of the RFI relative to the loss to follow-up could be of benefit in future trials and provide confidence regarding the robustness of the P value.

Open surgical repair of giant hepatic artery aneurysm.

Hepatic artery aneurysms (HAAs) are visceral artery aneurysms with a significant risk of mortality upon rupture. HAAs can be treated with open or endovascular repair. The choice of treatment modality depends on aneurysm anatomy, adequacy of visceral collaterals, and overall health status of the patient. This case report describes the successful repair of a giant 14.9-cm HAA through open aneurysm resection and end-to-end anastomosis of the distal common hepatic artery to the gastroduodenal artery. The patient recovered postoperatively with no complications and normal liver function. This case report also reviews other giant HAAs that have been reported in literature.

Stemless anatomic total shoulder arthroplasty: a systematic review and meta-analysis.

BACKGROUND: Stemless anatomic total shoulder arthroplasty (TSA) is used in the treatment of osteoarthritis of the shoulder joint and other degenerative shoulder diseases. It has several proposed advantages over stemmed TSA including increased bone preservation, decreased operative time, and easier removal at revision. METHODS: A systematic search was conducted using MEDLINE, Embase, PubMed, and CENTRAL (Cochrane Central Register of Controlled Trials) to retrieve all relevant studies. RESULTS: The literature search yielded 1417 studies, of which 22 were included in this review, with 962 patients undergoing stemless TSA. Stemless TSA led to significant improvements in range of motion and functional scores in all included studies. Meta-analysis of comparative studies between stemless and stemmed TSA identified no significant differences in postoperative Constant scores (mean difference [MD], 1.26; 95% confidence interval [CI], -3.29 to 5.81 points; P = .59) or complication rates (odds ratio, 1.79; 95% CI, 0.71-4.54; P = .22). Stemless TSA resulted in a significantly shorter operative time compared with stemmed TSA (MD, -15.03 minutes; 95% CI, -23.79 to -6.26 minutes; P = .0008). Stemless TSA also resulted in significantly decreased intraoperative blood loss compared with stemmed TSA (MD, -96.95 mL; 95% CI, -148.53 to -45.36 mL; P = .0002). CONCLUSION: Stemless anatomic TSA resulted in similar functional outcomes and complication rates to stemmed TSA with decreased operative time and lower blood loss. Further research is required to investigate the long-term durability of the stemless implant.

1,25-Dihydroxyvitamin D Maintains Brush Border Membrane NaPi2a and Attenuates Phosphaturia in Hyp Mice.

Phosphate homeostasis is critical for many cellular processes and is tightly regulated. The sodium-dependent phosphate cotransporter, NaPi2a, is the major regulator of urinary phosphate reabsorption in the renal proximal tubule. Its activity is dependent upon its brush border localization that is regulated by fibroblast growth factor 23 (FGF23) and PTH. High levels of FGF23, as are seen in the Hyp mouse model of human X-linked hypophosphatemia, lead to renal phosphate wasting. Long-term treatment of Hyp mice with 1,25-dihydroxyvitamin D (1,25D) or 1,25D analogues has been shown to improve renal phosphate wasting in the setting of increased FGF23 mRNA expression. Studies were undertaken to define the cellular and molecular basis for this apparent FGF23 resistance. 1,25D increased FGF23 protein levels in the cortical bone and circulation of Hyp mice but did not impair FGF23 cleavage. 1,25D attenuated urinary phosphate wasting as early as one hour postadministration, without suppressing FGF23 receptor/coreceptor expression. Although 1,25D treatment induced expression of early growth response 1, an early FGF23 responsive gene required for its phosphaturic effects, it paradoxically enhanced renal phosphate reabsorption and NaPi2a protein expression in renal brush border membranes (BBMs) within one hour. The Na-H+ exchange regulatory factor 1 (NHERF1) is a scaffolding protein thought to anchor NaPi2a to the BBM. Although 1,25D did not alter NHERF1 protein levels acutely, it enhanced NHERF1-NaPi2a interactions in Hyp mice. 1,25D also prevented the decrease in NHERF1/NaPi2a interactions in PTH-treated wild-type mice. Thus, these investigations identify a novel role for 1,25D in the hormonal regulation of renal phosphate handling.

Heterotopic ossification after total elbow arthroplasty: a systematic review.

BACKGROUND: Heterotopic ossification (HO) is a known complication that can arise after total elbow arthroplasty (TEA). In most cases, it is asymptomatic; however, in some patients, it can limit range of motion and lead to poor outcomes. The objective of this review was to assess and report the incidence, risk factors, prophylaxis, and management of HO after TEA. METHODS: A systematic search was conducted using MEDLINE, Embase, and PubMed to retrieve all relevant studies evaluating the occurrence of HO after TEA. The search was performed in duplicate, and a quality assessment of all included studies was performed. RESULTS: A total of 1907 studies were retrieved, of which 45 were included involving 2256 TEA patients. HO was radiographically present in 10% of patients and was symptomatic in 3%. Fewer than 1% of patients went on to undergo surgical excision of HO, with outcomes after surgery reported as good or excellent as assessed by range of motion and the Mayo Elbow Performance Score. HO appears more likely to develop in patients undergoing TEA because of ankylosis, primary osteoarthritis, and distal humeral fractures. Surgical intervention is more likely to be required in patients in whom HO develops after TEA performed for ankylosis and post-traumatic osteoarthritis. CONCLUSION: HO is an uncommon complication after TEA, with most patients in whom HO develops being asymptomatic and requiring no surgical management. Routine HO prophylaxis for TEA is not supported by the literature. The effectiveness of prophylaxis in high-risk patients is uncertain, and future studies are required to clarify its usefulness.

Hormonal Regulation of Osteocyte Perilacunar and Canalicular Remodeling in the Hyp Mouse Model of X-Linked Hypophosphatemia.

Osteocytes remodel their surrounding perilacunar matrix and canalicular network to maintain skeletal homeostasis. Perilacunar/canalicular remodeling is also thought to play a role in determining bone quality. X-linked hypophosphatemia (XLH) is characterized by elevated serum fibroblast growth factor 23 (FGF23) levels, resulting in hypophosphatemia and decreased production of 1,25 dihydroxyvitamin D (1,25D). In addition to rickets and osteomalacia, long bones from mice with XLH (Hyp) have impaired whole-bone biomechanical integrity accompanied by increased osteocyte apoptosis. To address whether perilacunar/canalicular remodeling is altered in Hyp mice, histomorphometric analyses of tibia and 3D intravital microscopic analyses of calvaria were performed. These studies demonstrate that Hyp mice have larger osteocyte lacunae in both the tibia and calvaria, accompanied by enhanced osteocyte mRNA and protein expression of matrix metalloproteinase 13 (MMP13) and genes classically used by osteoclasts to resorb bone, such as cathepsin K (CTSK). Hyp mice also exhibit impaired canalicular organization, with a decrease in number and branching of canaliculi extending from tibial and calvarial lacunae. To determine whether improving mineral ion and hormone homeostasis attenuates the lacunocanalicular phenotype, Hyp mice were treated with 1,25D or FGF23 blocking antibody (FGF23Ab). Both therapies were shown to decrease osteocyte lacunar size and to improve canalicular organization in tibia and calvaria. 1,25D treatment of Hyp mice normalizes osteocyte expression of MMP13 and classic osteoclast markers, while FGF23Ab decreases expression of MMP13 and selected osteoclast markers. Taken together, these studies point to regulation of perilacunar/canalicular remodeling by physiologic stimuli including hypophosphatemia and 1,25D. © 2017 American Society for Bone and Mineral Research.

Determinants of uptake of hepatitis B testing and healthcare access by migrant Chinese in the England: a qualitative study.

BACKGROUND: Global migration from hepatitis B endemic countries poses a significant public health challenge in receiving low-prevalence countries. In the UK, Chinese migrants are a high risk group for hepatitis B. However, they are an underserved population that infrequently accesses healthcare. This study sought to increase understanding of the determinants of hepatitis B testing and healthcare access among migrants of Chinese ethnicity living in England. METHODS: We sought to obtain and integrate insights from different key stakeholders in the system. We conducted six focus group discussions and 20 in-depth interviews with community members and patients identifying themselves as 'Chinese', and interviewed 21 clinicians and nine health service commissioners. Data were thematically analysed and findings were corroborated through two validation workshops. RESULTS: Three thematic categories emerged: knowledge and awareness, visibility of the disease, and health service issues. Low disease knowledge and awareness levels among community members contributed to erroneous personal risk perception and suboptimal engagement with services. Limited clinician knowledge led to missed opportunities to test and inaccurate assessments of infection risks in Chinese patients. There was little social discourse and considerable stigma linked to the disease among some sub-sections of the Chinese population. A lack of visibility of the issue and the population within the health system meant that these health needs were not prioritised by clinicians or commissioners. Service accessibility was also affected by the lack of language support. Greater use of community outreach, consultation aids, 'cultural competency' training, and locally adapted testing protocols may help. CONCLUSIONS: Hepatitis B among migrants of Chinese ethnicity in England can be characterised as an invisible disease in an invisible population. Multi-modal solutions are needed to tackle barriers within this population and the health system.

Vector-model-supported optimization in volumetric-modulated arc stereotactic radiotherapy planning for brain metastasis.

Long planning time in volumetric-modulated arc stereotactic radiotherapy (VMA-SRT) cases can limit its clinical efficiency and use. A vector model could retrieve previously successful radiotherapy cases that share various common anatomic features with the current case. The prsent study aimed to develop a vector model that could reduce planning time by applying the optimization parameters from those retrieved reference cases. Thirty-six VMA-SRT cases of brain metastasis (gender, male [n = 23], female [n = 13]; age range, 32 to 81 years old) were collected and used as a reference database. Another 10 VMA-SRT cases were planned with both conventional optimization and vector-model-supported optimization, following the oncologists' clinical dose prescriptions. Planning time and plan quality measures were compared using the 2-sided paired Wilcoxon signed rank test with a significance level of 0.05, with positive false discovery rate (pFDR) of less than 0.05. With vector-model-supported optimization, there was a significant reduction in the median planning time, a 40% reduction from 3.7 to 2.2 hours (p = 0.002, pFDR = 0.032), and for the number of iterations, a 30% reduction from 8.5 to 6.0 (p = 0.006, pFDR = 0.047). The quality of plans from both approaches was comparable. From these preliminary results, vector-model-supported optimization can expedite the optimization of VMA-SRT for brain metastasis while maintaining plan quality.

Vector-model-supported approach in prostate plan optimization.

Lengthy time consumed in traditional manual plan optimization can limit the use of step-and-shoot intensity-modulated radiotherapy/volumetric-modulated radiotherapy (S&S IMRT/VMAT). A vector model base, retrieving similar radiotherapy cases, was developed with respect to the structural and physiologic features extracted from the Digital Imaging and Communications in Medicine (DICOM) files. Planning parameters were retrieved from the selected similar reference case and applied to the test case to bypass the gradual adjustment of planning parameters. Therefore, the planning time spent on the traditional trial-and-error manual optimization approach in the beginning of optimization could be reduced. Each S&S IMRT/VMAT prostate reference database comprised 100 previously treated cases. Prostate cases were replanned with both traditional optimization and vector-model-supported optimization based on the oncologists' clinical dose prescriptions. A total of 360 plans, which consisted of 30 cases of S&S IMRT, 30 cases of 1-arc VMAT, and 30 cases of 2-arc VMAT plans including first optimization and final optimization with/without vector-model-supported optimization, were compared using the 2-sided t-test and paired Wilcoxon signed rank test, with a significance level of 0.05 and a false discovery rate of less than 0.05. For S&S IMRT, 1-arc VMAT, and 2-arc VMAT prostate plans, there was a significant reduction in the planning time and iteration with vector-model-supported optimization by almost 50%. When the first optimization plans were compared, 2-arc VMAT prostate plans had better plan quality than 1-arc VMAT plans. The volume receiving 35 Gy in the femoral head for 2-arc VMAT plans was reduced with the vector-model-supported optimization compared with the traditional manual optimization approach. Otherwise, the quality of plans from both approaches was comparable. Vector-model-supported optimization was shown to offer much shortened planning time and iteration number without compromising the plan quality.

Raf Kinases Are Essential for Phosphate Induction of ERK1/2 Phosphorylation in Hypertrophic Chondrocytes and Normal Endochondral Bone Development.

Hypophosphatemia causes rickets by impairing hypertrophic chondrocyte apoptosis. Phosphate induction of MEK1/2-ERK1/2 phosphorylation in hypertrophic chondrocytes is required for phosphate-mediated apoptosis and growth plate maturation. MEK1/2 can be activated by numerous molecules including Raf isoforms. A- and B-Raf ablation in chondrocytes does not alter skeletal development, whereas ablation of C-Raf decreases hypertrophic chondrocyte apoptosis and impairs vascularization of the growth plate. However, ablation of C-Raf does not impair phosphate-induced ERK1/2 phosphorylation in vitro, but leads to rickets by decreasing VEGF protein stability. To determine whether Raf isoforms are required for phosphate-induced hypertrophic chondrocyte apoptosis, mice lacking all three Raf isoforms in chondrocytes were generated. Raf deletion caused neonatal death and a significant expansion of the hypertrophic chondrocyte layer of the growth plate, accompanied by decreased cleaved caspase-9. This was associated with decreased phospho-ERK1/2 immunoreactivity in the hypertrophic chondrocyte layer and impaired vascular invasion. These data further demonstrated that Raf kinases are required for phosphate-induced ERK1/2 phosphorylation in cultured hypertrophic chondrocytes and perform essential, but partially redundant roles in growth plate maturation.

c-Raf promotes angiogenesis during normal growth plate maturation.

Extracellular phosphate plays a key role in growth plate maturation by inducing Erk1/2 (Mapk3/1) phosphorylation, leading to hypertrophic chondrocyte apoptosis. The Raf kinases induce Mek1/2 (Map2k1/2) and Erk1/2 phosphorylation; however, a role for Raf kinases in endochondral bone formation has not been identified. Ablation of both A-Raf (Araf) and B-Raf (Braf) in chondrocytes does not alter growth plate maturation. Because c-Raf (Raf1) phosphorylation is increased by extracellular phosphate and c-Raf is the predominant isoform expressed in hypertrophic chondrocytes, chondrocyte-specific c-Raf knockout mice (c-Raf(f/f);ColII-Cre(+)) were generated to define a role for c-Raf in growth plate maturation. In vivo studies demonstrated that loss of c-Raf in chondrocytes leads to expansion of the hypertrophic layer of the growth plate, with decreased phospho-Erk1/2 immunoreactivity and impaired hypertrophic chondrocyte apoptosis. However, cultured hypertrophic chondrocytes from these mice did not exhibit impairment of phosphate-induced Erk1/2 phosphorylation. Studies performed to reconcile the discrepancy between the in vitro and in vivo hypertrophic chondrocyte phenotypes revealed normal chondrocyte differentiation in c-Raf(f/f);ColII-Cre(+) mice and lack of compensatory increase in the expression of A-Raf and B-Raf. However, VEGF (Vegfa) immunoreactivity in the hypertrophic chondrocytes of c-Raf(f/f);ColII-Cre(+) mice was significantly reduced, associated with increased ubiquitylation of VEGF protein. Thus, c-Raf plays an important role in growth plate maturation by regulating vascular invasion, which is crucial for replacement of terminally differentiated hypertrophic chondrocytes by bone.

Phosphate interacts with PTHrP to regulate endochondral bone formation.

Phosphate and parathyroid hormone related peptide (PTHrP) are required for normal growth plate maturation. Hypophosphatemia impairs hypertrophic chondrocyte apoptosis leading to rachitic expansion of the growth plate; however, the effect of phosphate restriction on chondrocyte differentiation during endochondral bone formation has not been examined. Investigations were, therefore, undertaken to address whether phosphate restriction alters the maturation of embryonic d15.5 murine metatarsal elements. Metatarsals cultured in low phosphate media exhibited impaired chondrocyte differentiation, analogous to that seen with PTHrP-treatment of metatarsals cultured in control media. Because phosphate restriction acutely increases PTHrP expression in cultured metatarsals, studies were undertaken to determine if this increase in PTHrP plays a pathogenic role in the impaired chondrocyte differentiation observed under low phosphate conditions. In contrast to what was observed with wild-type metatarsal elements, phosphate restriction did not impair the differentiation of metatarsals isolated from PTHrP heterozygous or PTHrP knockout mice. In vivo studies in postnatal mice demonstrated that PTHrP haploinsufficiency also prevents the impaired hypertrophic chondrocyte apoptosis observed with phosphate restriction. To determine how signaling through the PTH/PTHrP receptor antagonizes the pro-apoptotic effects of phosphate, investigations were performed in primary murine hypertrophic chondrocytes. Receptor activation impaired phosphate-induced Erk1/2 phosphorylation specifically in the mitochondrial fraction and decreased levels of mitochondrial Bad, while increasing cytosolic phospho-Bad. Thus, these data demonstrate that phosphate restriction attenuates chondrocyte differentiation as well as impairing hypertrophic chondrocyte apoptosis and implicate a functional role for the PTH/PTHrP signaling pathway in the abnormalities in chondrocyte differentiation and hypertrophic chondrocyte apoptosis observed under phosphate restricted conditions.

Evaluation of radiation dose and image quality for the Varian cone beam computed tomography system.

PURPOSE: To compare the image quality and dosimetry on the Varian cone beam computed tomography (CBCT) system between software Version 1.4.13 and Version 1.4.11 (referred to as "new" and "old" protocols, respectively, in the following text). This study investigated organ absorbed dose, total effective dose, and image quality of the CBCT system for the head-and-neck and pelvic regions. METHODS AND MATERIALS: A calibrated Farmer chamber and two standard cylindrical Perspex CT dosimetry phantoms with diameter of 16 cm (head phantom) and 32 cm (body phantom) were used to measure the weighted cone-beam computed tomography dose index (CBCTDIw) of the Varian CBCT system. The absorbed dose of different organs was measured in a female anthropomorphic phantom with thermoluminescent dosimeters (TLD) and the total effective dose was estimated according to International Commission on Radiological Protection (ICRP) Publication 103. The dose measurement and image quality were studied for head-and-neck and pelvic regions, and comparison was made between the new and old protocols. RESULTS: The values of the new CBCTDIw head-and-neck and pelvic protocols were 36.6 and 29.4 mGy, respectively. The total effective doses from the new head-and-neck and pelvic protocols were 1.7 and 8.2 mSv, respectively. The absorbed doses of lens for the new 200° and old 360° head-and-neck protocols were 3.8 and 59.4 mGy, respectively. The additional secondary cancer risk from daily CBCT might be up to 2.8%. CONCLUSIONS: The new Varian CBCT provided volumetric information for image guidance with acceptable image quality and lower radiation dose. This imaging tool gave a better standard for patient daily setup verification.

Coupled transcription-splicing regulation of mutually exclusive splicing events at the 5' exons of protein 4.1R gene.

The tightly regulated production of distinct erythrocyte protein 4.1R isoforms involves differential splicing of 3 mutually exclusive first exons (1A, 1B, 1C) to the alternative 3' splice sites (ss) of exon 2'/2. Here, we demonstrate that exon 1 and 2'/2 splicing diversity is regulated by a transcription-coupled splicing mechanism. We also implicate distinctive regulatory elements that promote the splicing of exon 1A to the distal 3' ss and exon 1B to the proximal 3' ss in murine erythroleukemia cells. A hybrid minigene driven by cytomegalovirus promoter mimicked 1B-promoter-driven splicing patterns but differed from 1A-promoter-driven splicing patterns, suggesting that promoter identity affects exon 2'/2 splicing. Furthermore, splicing factor SF2/ASF ultraviolet (UV) cross-linked to the exon 2'/2 junction CAGAGAA, a sequence that overlaps the distal U2AF(35)-binding 3' ss. Consequently, depletion of SF2/ASF allowed exon 1B to splice to the distal 3' ss but had no effect on exon 1A splicing. These findings identify for the first time that an SF2/ASF binding site also can serve as a 3' ss in a transcript-dependent manner. Taken together, our results suggest that 4.1R gene expression involves transcriptional regulation coupled with a complex splicing regulatory network.

Protein 4.1R, a microtubule-associated protein involved in microtubule aster assembly in mammalian mitotic extract.

Non-erythroid protein 4.1R (4.1R) consists of a complex family of isoforms. We have shown that 4.1R isoforms localize at the mitotic spindle/spindle poles and associate in a complex with the mitotic-spindle organization proteins Nuclear Mitotic Apparatus protein (NuMA), dynein, and dynactin. We addressed the mitotic function of 4.1R by investigating its association with microtubules, the main component of the mitotic spindles, and its role in mitotic aster assembly in vitro. 4.1R appears to partially co-localize with microtubules throughout the mitotic stages of the cell cycle. In vitro sedimentation assays showed that 4.1R isoforms directly interact with microtubules. Glutathione S-transferase (GST) pull-down assays using GST-4.1R fusions and mitotic cell extracts further showed that the association of 4.1R with tubulin results from both the membrane-binding domain and C-terminal domain of 4.1R. Moreover, 4.1R, but not actin, is a mitotic microtubule-associated protein; 4.1R associates with microtubules in the microtubule pellet of the mitotic asters assembled in mammalian cell-free mitotic extract. The organization of microtubules into asters depends on 4.1R in that immunodepletion of 4.1R from the extract resulted in randomly dispersed microtubules. Furthermore, adding a 135-kDa recombinant 4.1R reconstituted the mitotic asters. Finally, we demonstrated that a mitotic 4.1R isoform appears to form a complex in vivo with tubulin and NuMA in highly synchronized mitotic HeLa extracts. Our results suggest that a 135-kDa non-erythroid 4.1R is important to cell division, because it participates in the formation of mitotic spindles and spindle poles through its interaction with mitotic microtubules.