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.     

Cytology of induced systemic resistance of cucumber to Colletotrichum lagenarium

The infection of cucumber leaves by Colletotrichum lagenarium was studied using cytological methods. Its progress in untreated plants was compared with that in plants in which systemic resistance had been induced by pre-infecting the first true leaf with the same fungus. In induced plants, a reduction of fungal development was observed at the leaf surface, in the epidermis, and in the mesophyll. On the leaf surface, formation of appressoria was slightly reduced. In the epidermis, enhanced formation of papillae beneath appressoria, and possibly increased lignification of entire cells, correlated with reduced development of infection hyphae. Papillae contained callose, identified by staining with aniline-blue fluorochrome and digestion with -1,3-glucanase, as a main structural component. In the mesophyll, reduced fungal development provided evidence for the existence of an additional induced defence reaction. The results imply that preinfection elicited a systemic, multicomponent defence reaction of the host plant against the fungus.Dedicated to the memory of Professor H. Grisebach     

Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium

Single batrachotoxin-activated sodium channels from rat brain were modified by trimethyloxonium (TMO) after incorporation in planar lipid bilayers. TMO modification eliminated saxitoxin (STX) sensitivity, reduced the single channel conductance by 37%, and reduced calcium block of inward sodium currents. These effects always occurred concomitantly, in an all-or-none fashion. Calcium and STX protected sodium channels from TMO modification with potencies similar to their affinities for block. Calcium inhibited STX binding to rat brain membrane vesicles and relieved toxin block of channels in bilayers, apparently by competing with STX for the toxin binding site. These results suggest that toxins, permeant cations, and blocking cations can interact with a common site on the sodium channel near the extracellular surface. It is likely that permeant cations transiently bind to this superficial site, as the first of several steps in passing inward through the channel.     

Electron microscopy of crystalline micelles in cellulose elementary fibrils of Dictyostelium discoideum

Summary In negatively stained preparations the cellulose of Dictyostelium discoideum appears in the form of 35 Å wide fibrils of undetermined length. Upon mild acid hydrolysis a periodic pattern may be observed along the fibrils, in the form of fine, electron-dense bands across the full diameter of the fibril spaced apart from each other by electron-transparent segments approximately 100 Å long. We propose that the electron-transparent segments represent the crystalline micelles of the elementary cellulose fibril, whereas the electron-opaque bands represent the amorphous regions.Part of a thesis submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree, University of Hawaii.     

Ultrastructural Changes During Germination of Dictyostelium discoideum Spores

Spores of Dictyostelium discoideum undergo significant changes in fine structure during germination. The mitochondria progressively become less dense and lose their peripherally attached ribosomes, and the tubuli become more pronounced as germination proceeds. During this period, the three-layered spore wall breaks down in two stages: first, the outer and middle layers are ruptured as a unit, and, second, the inner wall is breached. Crystals and dark (lipid) bodies disappear shortly before or during emergence of the myxamoebae. Autophagic vacuoles are found in dormant spores and throughout the entire germination process. The addition of cycloheximide to germinating spores inhibited the loss of the crystals and dark (lipid) bodies. In addition, the drug inhibited the breakdown of the inner wall layer. Cycloheximide did not prevent the formation of the water expulsion vesicle or the apparent function of the autophagic vacuoles.     

The complete heart-lead relationship in the einthoven triangle

The relationship between the source strength and the “manifest vector” in the Einthoven Triangle is derived for a line and a point dipole source and confirmed experimentally. The result permits the interpretation of the standard ECG leads in absolute terms and corrected for body size. The manifest vector is shown to be approximately times what it would be in an otherwise similar circular slab which circumscribes the triangle.     

Relative apparent synapomorphy analysis (RASA). I: The statistical measurement of phylogenetic signal

We have developed a new approach to the measurement of phylogenetic signal in character state matrices called relative apparent synapomorphy analysis (RASA). RASA provides a deterministic, statistical measure of natural cladistic hierarchy (phylogenetic signal) in character state matrices. The method works by determining whether a measure of the rate of increase of cladistic similarity among pairs of taxa as a function of phenetic similarity is greater than a null equiprobable rate of increase. Our investigation of the utility and limitations of RASA using simulated and bacteriophage T7 data sets indicates that the method has numerous advantages over existing measures of signal. A first advantage is computational efficiency. A second advantage is that RASA employs known methods of statistical inference, providing measurable sensitivity and power. The performance of RASA is examined under various conditions of branching evolution as the number of characters, character states per character, and mutations per branch length are varied. RASA appears to provide an unbiased and reliable measure of phylogenetic signal, and the general approach promises to be useful in the development of new techniques that should increase the rigor and reliability of phylogenetic estimates.      

Identification of pro-thymocytes in murine fetal blood: T lineage commitment can precede thymus colonization.

Phenotype and commitment of thymus-colonizing precursors are unknown. Here we report the identification of T lineage-committed precursors (designated prothymocytes) in murine fetal blood at day 15.5 of development. Fetal blood pro-thymocytes are Thy-1+c-kit(low)CD3- in contrast to fetal blood-derived pluripotent hematopoietic progenitors which are Thy-1-c-kit+. Upon transfer into the thymus, fetal blood pro-thymocytes generate a single wave of CD4+CD8+ thymocytes and subsequently mature TCR alpha beta+ peripheral T cells. However, fetal blood pro-thymocytes lack multipotent progenitor potential since they fail to reconstitute B lymphocytes and myeloid and erythroid lineages. In contrast, T and B lymphocytes as well as myeloid and erythroid lineages are reconstituted from fetal blood-derived pluripotent progenitors. Pro-thymocytes are equally present in peripheral blood of athymic fetal mice, suggesting that this novel precursor population is T lineage-committed prior to thymus colonization and represents the earliest T lineage precursor identified.     

Variation in heat-shock proteins among species of desert fishes (Poeciliidae, Poeciliopsis)

Analysis of the heat-shock proteins (hsps) of six closely related species of Poeciliopsis demonstrated the existence of biochemical diversity in the hsp100, hsp70, hsp60, and hsp30 protein families among species. Each species expressed five to seven hsp70-related isoforms. Constitutive 70-kD isoforms were identical among species, but four different patterns of heat-inducible isoforms were seen in these six species. Members of the hsp70 family of molecular chaperones are included among the most highly conserved proteins known, and the possibility of variation in hsp70 among closely related species has rarely been addressed. The hsp30 family is known to be less conserved than the hsp70 family, and, as expected, the Poeciliopsis hsp30 patterns showed more variation. Most of the hsp30 isoforms characteristic of a particular species were unique to that species. Hsp100 and hsp60 were identical in five of the species, but alternate isoforms were found in P. monacha. The small size and limited geographical distribution of the P. monacha population have probably contributed to the uniqueness of the monacha pattern. Two of the species were shown to acquire thermotolerance, the ability to withstand normally lethal temperatures when subjected to a gradual temperature increase. Rapid-heating protocols commonly used to establish critical thermal maxima of organisms do not include this inducible component of thermoresistance and therefore do not adequately assess an organism's capacity to withstand thermal stress.