Biochemical and Structural Studies of the Carminomycin 4-O-Methyltransferase DnrK.

Structural and functional studies of the carminomycin 4-O-methyltransferase DnrK are described, with an emphasis on interrogating the acceptor substrate scope of DnrK. Specifically, the evaluation of 100 structurally and functionally diverse natural products and natural product mimetics revealed an array of pharmacophores as productive DnrK substrates. Representative newly identified DnrK substrates from this study included anthracyclines, angucyclines, anthraquinone-fused enediynes, flavonoids, pyranonaphthoquinones, and polyketides. The ligand-bound structure of DnrK bound to a non-native fluorescent hydroxycoumarin acceptor, 4-methylumbelliferone, along with corresponding DnrK kinetic parameters for 4-methylumbelliferone and native acceptor carminomycin are also reported for the first time. The demonstrated unique permissivity of DnrK highlights the potential for DnrK as a new tool in future biocatalytic and/or strain engineering applications. In addition, the comparative bioactivity assessment (cancer cell line cytotoxicity, 4E-BP1 phosphorylation, and axolotl embryo tail regeneration) of a select set of DnrK substrates/products highlights the ability of anthracycline 4-O-methylation to dictate diverse functional outcomes.

Pott's Puffy Tumor, a Forgotten Complication of Sinusitis: Report of Two Cases.

Pott's puffy tumor (PPT) is a life-threatening complication of infectious sinusitis/osteomyelitis of the frontal bone. It occurs due to infection or trauma and is often seen in late childhood and adolescence. If left untreated for a protracted period, intracranial complications such as epidural abscess, subdural empyema, meningitis, and a cerebral abscess may occur. The diagnosis is often confirmed with CT. Prompt medical and surgical treatment is mandatory as there is the potential for significant morbidity if not quickly diagnosed and treated. This paper presents two cases of PPT manifested in patients with hemi pansinusitis.

Enzyme-mediated bioorthogonal technologies: catalysts, chemoselective reactions and recent methyltransferase applications.

Transferases have emerged as among the best catalysts for enzyme-mediated bioorthogonal functional group installation to advance innovative in vitro, cell-based and in vivo chemical biology applications. This review introduces the key considerations for selecting enzyme catalysts and chemoselective reactions most amenable to bioorthogonal platform development and highlights relevant key technology development and applications for one ubiquitous transferase subclass - methyltransferases (MTs). Within this context, recent advances in MT-enabled bioorthogonal labeling/conjugation relevant to DNA, RNA, protein, and natural products (i.e. complex small molecule metabolites) are highlighted.

Temporomandibular Joint Imaging.

The temporomandibular joint (TMJ) is an anatomically and biomechanically complex structure. Understanding how this structure grows and functions is essential to accurate radiographic evaluation. This article discusses the anatomy, function, and growth and development of the TMJ and how growth changes can affect the morphology of the craniofacial structures. Accordingly, the radiographic appearance of the entities that may alter the TMJ are discussed, including developmental, degenerative, inflammatory, and traumatic changes. Both osseous imaging and soft tissue imaging are shown.

Squamous cell carcinoma arising within a maxillary odontogenic keratocyst: A rare occurrence.

Squamous cell carcinoma (SCC) arising within the lining of an odontogenic keratocyst (OKC) is a rare occurrence. Although potentially locally destructive, OKC is a benign odontogenic process that typically presents with clinical and radiographic features characteristic of a benign intraosseous neoplasm. We present the clinical and radiographic features of a maxillary mass that demonstrated SCC arising from the lining of an OKC. Although the initial clinical and radiographic presentation suggested an infection or malignant neoplasm, biopsies revealed an infiltrative well-differentiated SCC contiguous with and arising from the focus of a pre-existing OKC. The patient subsequently underwent a type II hemi-maxillectomy with neoadjuvant chemoradiation. This report discusses the clinical and radiographic features associated with intraosseous malignancies, especially those arising from an otherwise benign odontogenic lesion. While the majority of OKCs are benign, the current report illustrates the potential for carcinomatous transformation within the lining of an OKC.

Analyzing Dental Implant Sites From Cone Beam Computed Tomography Scans on a Tablet Computer: A Comparative Study Between iPad and 3 Display Systems.

PURPOSE: The aim of this study was to compare a medical-grade PACS (picture archiving and communication system) monitor, a consumer-grade monitor, a laptop computer, and a tablet computer for linear measurements of height and width for specific implant sites in the posterior maxilla and mandible, along with visualization of the associated anatomical structures. MATERIAL AND METHODS: Cone beam computed tomography (CBCT) scans were evaluated. The images were reviewed using PACS-LCD monitor, consumer-grade LCD monitor using CB-Works software, a 13″ MacBook Pro, and an iPad 4 using OsiriX DICOM reader software. The operators had to identify anatomical structures in each display using a 2-point scale. User experience between PACS and iPad was also evaluated by means of a questionnaire. RESULTS: The measurements were very similar for each device. P-values were all greater than 0.05, indicating no significant difference between the monitors for each measurement. The intraoperator reliability was very high. The user experience was similar in each category with the most significant difference regarding the portability where the PACS display received the lowest score and the iPad received the highest score. CONCLUSIONS: The iPad with retina display was comparable with the medical-grade monitor, producing similar measurements and image visualization, and thus providing an inexpensive, portable, and reliable screen to analyze CBCT images in the operating room during the implant surgery.

Prevalence of bony septa, antral pathology, and dimensions of the maxillary sinus from a sinus augmentation perspective: A retrospective cone-beam computed tomography study.

PURPOSE: Sinus elevation procedures have become a routine and reliable way to gain bone volume in the edentulous maxilla for dental implant placement. Presence of bony septations and pathology in the maxillary sinus often cause complications leading to graft or implant failure or both. The aim of this study was to retrospectively evaluate the prevalence of pathology, direction of the septa, and sinus width measured at 2 mm, 5 mm, and 10 mm from the sinus floor in maxillary sinuses using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Seventy-two sinuses from 36 random preoperative CBCT scans referred for implant therapy were retrospectively evaluated for the number, prevalence, and direction of bony septations and presence of pathology. Width of the sinus was also measured at 2 mm, 5 mm, and 10 mm from the sinus floor to account for the amount of bone available for implant placement. RESULTS: Maxillary sinus septa were found in 59.7%. Presence of a single septum was noted in 20 sinuses (27.7%), followed by two septa in 17 sinuses. The most common direction of the septum was the transverse direction. Retention pseudocyst and mucosal thickening were the most commonly seen abnormality/pathology. CONCLUSION: Based on the high prevalence of septa and sinus pathology in this sample, a preoperative CBCT scan might be helpful in minimizing complications during sinus augmentation procedures for dental implant therapy.

Artifacts in Cone Beam Computed Tomography Image Volumes: An Illustrative Depiction.

INTRODUCTION: The evolution of cone beam computed tomography (CBCT) has brought about a paradigm shift in radiographic evaluation of the maxillofacial skeleton. Because of its low cost, high resolution, and relatively low-radiation dose, CBCT is fast becoming the 3-D imaging modality of choice in dentistry. The ubiquitous availability of this new imaging modality poses unique challenges in understanding this technology and recognizing the associated artifacts that present themselves in the acquired image volumes. There are several artifacts that are inherent to CBCT scans by virtue of the physics behind their acquisition and image reconstruction algorithms. BACKGROUND: An image artifact may be defined as a visualized structure in the reconstructed data that was not originally present in the object or the imaged area of interest. It can be explained as any distortion or error in the image that is unrelated to the subject being studied. Artifacts are induced by discrepancies between the physical conditions of the measuring setup, which is usually the CBCT scanner's technical composition and position of the object under investigation. OBJECTIVE: The objective of this study is to present an illustrative depiction of the most commonly encountered CBCT artifacts with an explanation of how each artifact is caused and how it presents itself in CBCT image volumes. CONCLUSION: Because these artifacts cause significant image degradation and often misrepresent the region of interest, they should be recognized, understood, and taught along with normal CBCT anatomy to facilitate accurate evaluation of the image volumes and prevent inaccurate diagnoses.

Arrested pneumatization of the sphenoid sinus mimicking intraosseous lesions of the skull base.

Arrested pneumatization of the sphenoid sinus is a developmental variant that is not always well recognized and is often confused with other pathologies associated with the skull base. This report describes the case of a patient referred for cone-beam computed tomography (CBCT) imaging for dental implant therapy. CBCT demonstrated a well-defined incidental lesion in the left sphenoid sinus with soft tissue-like density and sclerotic borders with internal curvilinear opacifications. The differential diagnoses included intraosseous lipoma, arrested pneumatization of the sphenoid sinus, chondrosarcoma, chondroid chordoma, and ossifying fibroma. The radiographic diagnosis of arrested pneumatization was based on the location of the lesion, its well-defined nature, the presence of internal opacifications, and lack of expansion. Gray-scale CBCT imaging of the area demonstrated values similar to fatty tissue. This case highlighted the fact that benign developmental variants associated with the skull base share similar radiographic features with more serious pathological entities.

Using hand-held dental x-ray devices: ensuring safety for patients and operators.

BACKGROUND: Since the introduction of hand-held x-ray units in dentistry, a few inexpensive devices have emerged that lack the necessary safety measures and failed to meet U.S. Food and Drug Administration (FDA) standards. They are advertised actively and sold online in the United States. METHODS: The authors present several safety issues associated with an imported hand-held x-ray device that has not been cleared by the FDA and compare the device with an FDA-cleared unit. RESULTS: The authors found that the non-FDA-cleared device posed major safety hazards, including high radiation doses to patients and operators, lack of operator shielding, lower-than-acceptable kilovolt (peak) value, inadequate collimation, lack of an audible signal of x-ray generation and absence of a so-called dead-man switch. CONCLUSIONS AND PRACTICAL IMPLICATIONS: Dental professionals must be aware of unsafe x-ray equipment and use only those devices that have been cleared by the FDA to protect themselves and their patients.