Changes in extracellular zinc concentration participate in modulating fundamental cellular processes such as proliferation, secretion, and ion transport in a mechanism that is not well understood. Here, we show that a micromolar concentration of extracellular zinc triggers a massive release of calcium from thapsigarginsensitive intracellular pools in the colonocytic cell line HT29. Calcium release was blocked by a phospholipase-C inhibitor, indicating that formation of inositol 1,4,5-triphosphate is required for zinc-dependent calcium release. Zinc influx was not observed, indicating that extracellular zinc triggered the release. The Ca i 2؉ release was zinc specific and could not be triggered by other heavy metals. Furthermore, zinc failed to activate the Ca 2؉ -sensing receptor heterologously expressed in HEK293 cells. The zinc-induced Ca i 2؉ rise stimulated the activity of the Na ؉ ͞H ؉ exchanger in HT29 cells. Our results indicate that a previously uncharacterized extracellular, G protein-coupled, Zn 2؉ -sensing receptor is functional in colonocytes. Because Ca i 2؉ rise is known to regulate key cellular and signal-transduction processes, the zinc-sensing receptor may provide the missing link between extracellular zinc concentration changes and the regulation of cellular processes.Z inc is an essential micronutrient involved in structural and regulatory cellular functions. Zinc interacts with zinc-finger domains and acts as a cofactor of numerous enzymes (1, 2). Zinc ions also specifically bind to many membrane receptors, transporters, and channels, thereby modulating their activity (3). Therefore, it is not surprising that zinc deficiency affects multiple organs, including the digestive (4), immune (5), and neuronal (2) systems. A severe lack of zinc also is linked to the attenuation of growth and sexual development (2). Conversely, an excess of extracellular zinc is considered toxic. Indeed, brain ischemia is accompanied by a massive release of synaptic zinc permeating into neurons, leading to neuronal cell death (6-8). Furthermore, striking changes in plasma-zinc concentration occur during diverse pathophysiological syndromes including myocardial infarction, hepatic renal failure, and neoplastic processes (9). Despite the large fluctuations in extracellular zinc concentrations and their subsequent clinical importance, little is known about cellular signaling mechanisms that sense changes in extracellular-zinc concentration.The calcium-sensing receptor serves as an example for the importance of an ion-sensing mechanism. It is a G proteincoupled receptor that senses changes in extracellular calcium and regulates diverse cellular functions (10, 11). Although the existence of other ion-sensing mechanisms have been suggested (12), none have been characterized fully yet.Gastrointestinal pathology, manifested in severe diarrhea, is an important hallmark of zinc deficiency. Indeed, zinc has a major role in the duration and severity of diarrheal diseases (4). The morbidity and mortality caused by diarrheal diseas...

Background and Objective The purpose of this study was to determine irradiation parameters of a 780 nm low power CW diode laser (6.5 mW) leading to enhanced proliferation of cultured normal human keratinocytes (NHK). The possible role of reactive oxygen species (ROS) in this response was evaluated. Study Design/Materials and Methods: NHK were exposed to a single dose of 0 to 3.6 J/cm2 (0–180 sec) of irradiation. Proliferation parameters studied were: incorporation of 3H‐thymidine during 6–24 hr following irradiation; percentage of dividing cells and number of cells, 24 hr and 48 hr following irradiation, respectively. Results Proliferation of NHK exposed to 0.45–0.95 J/cm2 was significantly enhanced by 1.3–1.9‐folds relative to sham‐irradiated controls, as inferred from parameters studied. Exposure to other energy densities was considerably less affective in enhancing proliferation parameters. Added enzymatic antioxidants, superoxide dismutase or catalase, scavenging superoxide anions and H2O2, suppressed this enhanced proliferation. Added scavengers (α‐tocopherol acetate, scavenging lipid peroxidation, or sodium azide, histidine, mannitol, scavenging singlet oxygen, superoxide anions, and hydroxyl radicals, respectively), or N‐acetyl cysteine, the thiol‐reducing agent, suppressed the response, but to different extents. Conclusions The results indicate that 780 nm low power diode laser irradiation enhanced keratinocytes proliferation in vitro, with an apparent involvement of ROS in this response, and comparably, might be used to promote their proliferation in vivo to enhance wound healing. Lasers Surg. Med. 22:212–218, 1998. © 1998 Wiley‐Liss, Inc.

The survival of Salmonella montevideo during serum treatment depends on the presence of an 0 antigen (0-Ag) associated with the lipopolysaccharide molecule. In this organism, the 0 antigen is a polysaccharide composed of 0 to more than 55 subunits, each containing 4 mannose residues together with glucose and n-acetylglucosamine. We used a mutant strain of S. montevideo that smooth, enteric gram-negative bacteria is efficient, and the bactericidal C5b-9 complex is formed on the surface of such smooth cells (13). However, in contrast to the stable, hydrophobic interaction of C5b-9 with rough cells, the C5b-9 complex is bound by weak hydrophilic interactions to smooth cells and is released from the surface (14). Consequently, it is not bactericidal. We and others (13,14,36) have suggested that C5b-9 complexes are shed because complement activation takes place on long O-Ag side chains and that C5b-9 complexes formed are sterically inhibited from inserting into hydrophobic membrane domains. In a recent paper (12)

The syndrome of congenital hypoparathyroidism, mental retardation, facial dysmorphism and extreme growth failure (HRD or Sanjad-Sakati syndrome; OMIM 241410) is an autosomal recessive disorder reported almost exclusively in Middle Eastern populations. A similar syndrome with the additional features of osteosclerosis and recurrent bacterial infections has been classified as autosomal recessive Kenny-Caffey syndrome (AR-KCS; OMIM 244460). Both traits have previously been mapped to chromosome 1q43-44 (refs 5,6) and, despite the observed clinical variability, share an ancestral haplotype, suggesting a common founder mutation. We describe refinement of the critical region to an interval of roughly 230 kb and identification of deletion and truncation mutations of TBCE in affected individuals. The gene TBCE encodes one of several chaperone proteins required for the proper folding of alpha-tubulin subunits and the formation of alpha-beta-tubulin heterodimers. Analysis of diseased fibroblasts and lymphoblastoid cells showed lower microtubule density at the microtubule-organizing center (MTOC) and perturbed microtubule polarity in diseased cells. Immunofluorescence and ultrastructural studies showed disturbances in subcellular organelles that require microtubules for membrane trafficking, such as the Golgi and late endosomal compartments. These findings demonstrate that HRD and AR-KCS are chaperone diseases caused by a genetic defect in the tubulin assembly pathway, and establish a potential connection between tubulin physiology and the development of the parathyroid.