Regulation of vesicle trafficking, transcription, and meiosis: lessons learned from yeast regarding the disparate biologies of phosphatidylcholine.

Phosphatidylcholine (PtdCho) is the major phospholipid present in eukaryotic cell membranes generally comprising 50% of the phospholipid mass of most cells and their requisite organelles. PtdCho has a major structural role in maintaining cell and organelle integrity, and thus its synthesis must be tightly monitored to ensure appropriate PtdCho levels are present to allow for its coordination with cell growth regulatory mechanisms. One would also expect that there needs to be coordinated regulation of PtdCho synthesis with its transport from its site of synthesis to cellular organelles to ensure organellar structures and functions are maintained. Each of these processes need to be intimately coordinated with cellular growth decision making processes. To this end, it has recently been revealed that ongoing PtdCho synthesis is required for global transcriptional regulation of phospholipid synthesis. PtdCho is also a major component of intracellular transport vesicles and the synthesis of PtdCho is intimately involved in the regulation of vesicle transport from the Golgi apparatus to the cell surface and the vacuole (yeast equivalent of the mammalian lysosome). This review details some of the more recent advances in our knowledge concerning the role of PtdCho in the regulation of global lipid homeostasis through (i) its restriction of the trafficking of intracellular vesicles that distribute lipids and proteins from their sites of synthesis to their ultimate cellular destinations, (ii) its regulation of specific transcriptional processes that coordinate lipid biosynthetic pathways, and (iii) the role of PtdCho catabolism in the regulation of meiosis. Combined, these regulatory roles for PtdCho ensure vesicular, organellar, and cellular membrane biogenesis occur in a coordinated manner.

Asymptomatic multilocular radiolucent lesion of the mandible.

The odontogenic keratocyst is an established pathologic entity. Dentists must be aware of its existence and understand its clinical characteristics. Because it is impossible to radiographically and clinically differentiate the keratocyst from more innocuous odontogenic cysts, all cystic lesions removed from patients should be submitted for histopathologic examination and diagnosis.

Implant of articular eminence for recurrent dislocation of the temporomandibular joint.

Hypermobility of the temporomandibular joint is often caused by trauma, by opening the mouth too wide, by having a mouth forced open during general anesthesia procedures, or by dental procedures. The capsule may be stretched to an extent that dislocation occurs more easily thereafter. An implant of Vitallium mesh attached to the zygoma to restrict anterior movement of the condyle is used to prevent recurrent dislocation of the temporomandibular joint.