Sea urchin histamine receptor 1 regulates programmed cell death in larval Strongylocentrotus purpuratus.

Settlement is a rapid process in many marine invertebrate species, transitioning a planktonic larva into a benthic juvenile. In indirectly developing sea urchins, this ecological transition correlates with a morphological, developmental and physiological transition (metamorphosis) during which apoptosis is essential for the resorption and remodelling of larval and juvenile structures. While settlement is initiated by environmental cues (i.e. habitat-specific or benthic substrate cues), metamorphosis is regulated by developmental endocrine signals, such as histamine (HA), thyroid hormones (THs) and nitric oxide (NO). In the purple sea urchin, Strongylocentrotus purpuratus, we found that suH1R mRNA levels increase during larval development and peak during metamorphic competence. SuH1R positive cell clusters are prominently visible in the mouth region of sea urchin larvae, but the protein appears to be expressed at low levels throughout the larval arms and epidermis. SuH1R knock-down experiments in larval stages show that the function of suH1R is in inhibiting apoptosis. Our results therefore suggest that suH1R is regulating the metamorphic transition by inhibiting apoptosis. These results provide new insights into metamorphic mechanisms and have implications for our understanding of settlement and metamorphosis in the marine environment.

Development of a Protocol for SPECT/CT in the Assessment of Wrist Disorders.

Background Single-photon emission computed tomography and computed tomography (SPECT/CT) is a hybrid diagnostic imaging modality that allows clinicians to integrate their diagnostic evaluations and deliver a definitive diagnosis in musculoskeletal disorders. Specifically, in identification of osseous pathology, the conventional bone scan delivers greater specificity compared with magnetic resonance imaging (MRI). However, use of SPECT/CT enhances the sensitivity and specificity. Use of this modality denotes the possibility to specify the lesion more accurately and precisely while grading the activity according to osseous structural changes. Purpose This study aimed to evaluate the clinical utility of SPECT/CT in the diagnoses and management of osseous wrist disorders. The objectives were to examine the value of SPECT/CT in the diagnosis of osseous-related wrist pain and whether the findings altered management. Patients and Methods A retrospective cohort study of 20 patients with such wrist pain was conducted. SPECT/CT was used in the diagnostic process for these patients. Results Following SPECT/CT imaging, the common final diagnoses were osteoarthritis (10; 50%) and avascular necrosis (5; 25%). Less common diagnoses included ulnar carpal impact syndrome, infection, malunion, complex regional pain syndrome, and carpal boss. Some presented with multiple pathologies. SPECT/CT changed the final diagnosis in 11 cases, resulting in nonoperative treatment (7; 63%) or surgery (4; 37%). Conclusion Findings from this study and the literature demonstrate the clinical utility of SPECT/CT in the assessment of osseous-related wrist disorders. We present an algorithm for the assessment of wrist pain with osseous pathology. This commences with clinical assessment and plane radiographs (first-line investigation). Some cases will require a second-line investigation (ultrasound, CT, and/or MRI). If the diagnosis remains unclear, SPECT/CT is recommended as a third-line investigation.