Transgenic Expression of the Vitamin D Receptor Restricted to the Ileum, Cecum, and Colon of Vitamin D Receptor Knockout Mice Rescues Vitamin D Receptor-Dependent Rickets.

Although the intestine plays the major role in 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] action on calcium homeostasis, the mechanisms involved remain incompletely understood. The established model of 1,25(OH)2D3-regulated intestinal calcium absorption postulates a critical role for the duodenum. However, the distal intestine is where 70% to 80% of ingested calcium is absorbed.

Multi-Center Randomized Controlled Trial on the Effect of Triclosan-Coated Sutures on Surgical Site Infection after Colorectal Surgery.

Background: Surgical site infection (SSI) remains the most frequent complication after colorectal resection. The role of sutures coated with antimicrobial agents such as triclosan in reducing SSI is controversial.

Methods: This was a multi-center randomized controlled trial with patients and outcome assessors blinded to treatment.

Incarcerated hernia in a trocar site following laparoscopic gastric bypass.

This paper reports a case of small bowel occlusion due to the herniation of an ileal ansa at the site of the insertion of a 12-mm trocar. A 28-year-old obese female patient underwent laparoscopic surgery for gastric bypass, the skin incisions of the trocar insertion sites were closed with absorbable sutures. Small bowel occlusion occurred on post-operative day 6 and the patient again underwent laparoscopic surgery.

Vitamin D biology revealed through the study of knockout and transgenic mouse models.

Early studies identifying vitamin D as an antirachitic factor led to studies in vitamin D-deficient models that resulted in a basic understanding of the mechanism of action of vitamin D. Recent studies using genetically modified mice have provided important new insight into the physiological role of vitamin D at target tissues and the functional significance of vitamin D target proteins, as well as the functional significance of proteins involved in the transport and metabolism of vitamin D. Studies using these mice have played an increasingly important role in elucidating the mechanisms involved in the control of calcium homeostasis and have provided evidence for a role of vitamin D in extraskeletal health.

Vitamin D and intestinal calcium absorption.

The principal function of vitamin D in calcium homeostasis is to increase calcium absorption from the intestine. Calcium is absorbed by both an active transcellular pathway, which is energy dependent, and by a passive paracellular pathway through tight junctions. 1,25Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) the hormonally active form of vitamin D, through its genomic actions, is the major stimulator of active intestinal calcium absorption which involves calcium influx, translocation of calcium through the interior of the enterocyte and basolateral extrusion of calcium by the intestinal plasma membrane pump.

Active intestinal calcium transport in the absence of transient receptor potential vanilloid type 6 and calbindin-D9k.

To study the role of the epithelial calcium channel transient receptor potential vanilloid type 6 (TRPV6) and the calcium-binding protein calbindin-D9k in intestinal calcium absorption, TRPV6 knockout (KO), calbindin-D9k KO, and TRPV6/calbindin-D(9k) double-KO (DKO) mice were generated. TRPV6 KO, calbindin-D9k KO, and TRPV6/calbindin-D9k DKO mice have serum calcium levels similar to those of wild-type (WT) mice ( approximately 10 mg Ca2+/dl). In the TRPV6 KO and the DKO mice, however, there is a 1.

Vitamin D: molecular mechanism of action.

Vitamin D maintains calcium homeostasis and is required for bone development and maintenance. Recent evidence has indicated an interrelationship between vitamin D and health beyond bone, including effects on cell proliferation and on the immune system. New developments in our lab related to the function and regulation of target proteins have provided novel insights into the mechanisms of vitamin D action.

Prevention of glucocorticoid-induced apoptosis in osteocytes and osteoblasts by calbindin-D28k.

Unlabelled: This study show for the first time that calbindin-D28k can prevent glucocorticoid-induced bone cell death. The anti-apoptotic effect of calbindin-D28k involves inhibition of glucocorticoid induced caspase 3 activation as well as ERK activation.

Introduction: Recent studies have indicated that deleterious effects of glucocorticoids on bone involve increased apoptosis of osteocytes and osteoblasts.

Calcium transporter 1 and epithelial calcium channel messenger ribonucleic acid are differentially regulated by 1,25 dihydroxyvitamin D3 in the intestine and kidney of mice.

We examined the expression of calcium transporter 1 (CaT1) and epithelial calcium channel (ECaC) mRNA in the duodenum and kidney of mice. Intestinal CaT1 mRNA level increased 30-fold at weaning, coincident with the induction of calbindin-D(9k) expression. In contrast, renal CaT1 and ECaC mRNA expression was equal until weaning when ECaC mRNA is induced and CaT1 mRNA levels fall 70%.

New insights into the mechanisms of vitamin D action.

The biologically active metabolite of vitamin D, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is a secosteroid whose genomic mechanism of action is similar to that of other steroid hormones and is mediated by stereospecific interaction of 1,25(OH)(2)D(3) with the vitamin D receptor (VDR) which heterodimerizes with the retinoid X receptor (RXR). After interaction with the vitamin D response element (VDRE) in the promoter of target genes, transcription proceeds through the interaction of VDR with coactivators and with the transcription machinery. The identification of the steps involved in this process has been a major focus of recent research in the field.