Background and Purpose-Distinguishing between symptoms of posterior circulation infarction (PCI) and anterior circulation infarction (ACI) can be challenging. This study evaluated the frequency of symptoms/signs in the 2 vascular territories to determine the diagnostic value of particular symptoms/signs for PCI. Methods-Neurological deficits were reviewed and compared from 1174 consecutive patients with a diagnosis of PCI or ACI confirmed by magnetic resonance imaging in the Chengdu Stroke Registry. The diagnostic value of specific symptoms/signs for PCI was determined by measuring their sensitivity, specificity, positive predictive value (PPV), and the OR.

The vitamin D hormone, 1α,25-dihydroxyvitamin D3 [1,25-(OH)2 D3 ], exerts its hormonal effects predominantly on intestine, bone, and kidney, where it plays a crucial role in calcium and phosphorus homeostasis and bone mineralization. In addition to its classical actions, 1,25(OH)2 D3 exerts pleiotropic effects in a wide variety of target tissues and cell types, often in an autocrine/paracrine fashion. These biological activities of 1,25(OH)2 D3 have suggested a multitude of potential therapeutic applications for the vitamin D hormone in the treatment of hyperproliferative disorders (e.g. cancer and psoriasis), immune dysfunction (autoimmune diseases), and endocrine disorders (e.g. hyperparathyroidism). However, the calcemic effects induced by 1,25(OH)2 D3--hypercalcemia, increased bone resorption, and soft tissue calcification--limit the use of the natural ligand in these clinical applications. Therefore, numerous 1,25(OH)2 D3 analogues have been synthesized with the intent of producing therapeutic agents devoid of hypercalcemic and hyperphosphatemic side effects. To this aim, much attention has been focused on the development of 19-nor-vitamin D3 derivatives that lack the ring-A exocyclic methylene group (C19). In this review, the 19-nor-1,25(OH)2 D3 analogues are classified according to modifications made at the A-ring, the side chain, or both the A-ring and side chain, as well as other positions. The biological activities of these 19-nor-1,25(OH)2 D3 analogues are summarized and their structure-activity relationships and binding features with the vitamin D receptor (VDR) are discussed.

The plethora of biological activities of 1,25(OH)(2)D(3) and its analogs suggests an enormous potential for vitamin D therapy in the treatment of hyperproliferative diseases (cancer, psoriasis), endocrine dysfunction (hyperparathyroidism), immune disorders (autoimmune diseases, transplant rejection), bone disorders (osteoporosis, Paget's bone disease). However, the therapeutic limitation of 1,25(OH)(2)D(3) is its calcemic and phosphatemic activities, since it can cause serious side effects such as hypercalcemia and hyperphosphatemia at super physiological levels. Therefore, numerous efforts have been made to find the new vitamin D analogs, that retain the therapeutically important properties of 1,25(OH)(2)D(3) but with greater selectivity, which allows more effective intervention with fewer toxic side effects. This review will focus on the biological activities of the 2-substituted analogs of 1,25(OH)(2)D(3). They were classified as 2α-, 2β-, 2,2-disubstituted analogs, and those with modifications in both the A-ring at the 2-position and the side chains. Their structure-activity relationships and binding features with the vitamin D receptor (VDR) were discussed.