Expression patterns of loricrin in various species and tissues

Abstract. In this study we analyzed the expression patterns of loricrin in various species and tissues using immunohistochemistry, immunoblotting and Northern blots. Loricrin is a glycine-, serine- and cysteine-rich protein expressed very late in epidermal differentiation in the granular layers of normal mouse and human epidermis. Later on in differentiation, loricrin becomes cross-linked as a major component into the cornified cell envelope by the formation of N^ɛ -(γ-glutamyl)lysine isopeptide bonds. This process either occurs directly or by the intermediate accumulation in L-keratohyaline granules of mouse epidermis and human acrosyringia. Loricrin was identified in all mammalian species analyzed by virtue of its highly conserved carboxy-terminal sequences revealing an electric mobility of ∼60 kDa in rodents, rabbit and cow and of ∼35 kDa in lamb and human on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Loricrin is expressed in the granular layer of all mammalian orthokeratinizing epithelia tested including oral, esophageal and fore-stomach mucosa of rodents, tracheal squamous metaplasia of vitamin A deficient hamster and estrogen induced squamous vaginal epithelium of ovary ectomized rats. Loricrin is also expressed in a few parakeratinizing epithelia such as BBN [N-butyl-N-(4–hydroxybutyl)nitrosamine]-induced murine bladder carcinoma and a restricted subset of oral and single vaginal epithelial cells in higher mammals. Our results provide further evidence that the program of squamous differentiation in internal epithelia of the upper alimentary tract in rodents and higher mammals differ remarkably. In addition, we also have noted the distinct distribution patterns of human loricrin and involucrin, another major precursor protein of the cornified cell envelope.     

Ca2+ oscillations induced by hormonal stimulation of individual fura-2-loaded hepatocytes

Isolated rat hepatocytes were loaded with the Ca2+ indicator fura-2 to measure cytosolic free Ca2+ concentrations ([Ca2+]i) in individual cells by digital ratio imaging microscopy. Stimulation with 0.1 nM vasopressin, 0.5 microM phenylephrine, or 0.5 microM ATP caused repetitive spikes of high [Ca2+]i in a high percentage of cells, in agreement with Woods et al. (Woods, N. M., Cuthbertson, K. S. R., and Cobbold, P. H. (1986) Nature 319, 600-602), but unlike the results of Monck et al. (Monck, J. R., Reynolds, E. E., Thomas, A. P., and Williamson, J. R. (1988) J. Biol. Chem. 263, 4569-4575). Reduction in extracellular [Ca2+] decreased the frequency but not the amplitude of the spikes, suggesting that the spikes result from dumping of intracellular stores and that the entry of extracellular Ca2+ affects only the rate of replenishment of those stores. Membrane depolarization failed to elevate [Ca2+]i and had an effect similar to removal of extracellular Ca2+ in decreasing the frequency of agonist-evoked [Ca2+]i oscillations or inhibiting them altogether, arguing against any significant role for voltage-operated Ca2+ channels.     

Response of fishes and aquatic habitats to sand-bed stream restoration using large woody debris

Effects of habitat rehabilitation of Little Topashaw Creek, a sinuous, sand-bed stream draining 37 km² in northwest Mississippi are described. The rehabilitation project consisted of placing 72 large woody debris structures along eroding concave banks and planting 4000 willow cuttings in sandbars. Response was measured by monitoring flow, channel geometry, physical aquatic habitat, and fish populations. Initially, debris structures reduced high flow velocities at concave bank toes, preventing further erosion and inducing deposition. Physical response during the first year following construction included creation of sand berms along eroding banks and slight increases in base flow water width and depth. Fish collections showed assemblages typical of incising streams within the region, but minor initial responses to debris addition were evident. Progressive failure of the structures and renewed erosion were observed during the second year after construction.     

The influence of reduced photorespiration on long-term growth and development of wheat

The long-term role of photorespiration was investigated by comparing growth, development, gas exchange characteristics and mineral nutrition of a wheat crop ( Triticum aestivum L. cv. Courtot) cultivated in a culture chamber during a life cycle, either in 4% O₂ or in normal O₂ Low O₂ pressure reduced photorespiration, but CO₂ was controlled so that net photosynthesis remained the same as in the control crop. The growth and development of the low O₂ crop was slowed down. Ear appearance was 16 days late, but the rate of tillering was the same as in the control and was maintained longer so that the final number of tillers was doubled. Pigment, ribulose bisphosphate carboxylase (EC 4.1.1.39) and soluble sugar contents were similar. The response of photosynthesis to CO₂ and O₂ was not appreciably changed by the low O₂ treatment. There was almost no seed formation, and the senescence of the leaves was delayed. It appears that in non-stress conditions most of the photorespiration can be suppressed without damage to the photosynthetic apparatus. Retardation of development and inhibition of reproduction are likely due to other effects of O₂.