Conjoined twins are rare and present a unique challenge to pediatric surgeons and radiologists. Planning of surgical separation is aided by accurate preoperative imaging. Such twins are classified according to the most prominent site of connection: the thorax (thoracopagus), abdomen (omphalopagus), sacrum (pygopagus), pelvis (ischiopagus), skull (craniopagus), face (cephalopagus), or back (rachipagus). The area of fusion largely determines the imaging modalities used. Thoracic conjunction is most common and requires cardiac assessment. Magnetic resonance imaging and computed tomography provide excellent anatomic and bone detail, demonstrating organ position, shared viscera, and limited vascular anatomy. Contrast material radiography allows evaluation of the gastrointestinal and urogenital tracts, and a shared liver requires assessment of anatomy, vascularization, and biliary drainage. Angiography helps define specific vascular supply, which is useful in determining the distribution of shared structures between the twins at surgery. Each set of conjoined twins is unique. An imaging strategy to accurately define anatomic fusion, vascular anomalies, and other associated abnormalities is important for surgical planning and prognostic information.

No abstract

No abstract

The sarcoplasmic reticulum (SR) is a fenestrated sheath of membranes between and around skeletal muscle myofibrils Abbreviation used: SR, sarcoplasmic reticulum. Vol. 17and regulates the Ca?+ distribution and thus contraction and relaxation inside muscle cells. In the absence of Ca", isolated SR vesicles catalyse low rates of a Mg"-dependent ATP hydrolysis (basal ATPase) and on the addition of Ca'+ the ATPase activity is several times increased (Ca? +-dependent ATPase) (Martonosi, 1084). For each molecule of ATP hydrolysed two Ca'+ atoms are transported into the interior of the SR (Hasselbach, 1978).