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The effect of concanavalin A on the rat electro-olfactogram. Differential inhibition of odorant response.

When the rat olfactory mucosa is treated with concanavalin A, it subsequently shows diminished sensitivity towards 60% of the 112 odorants tested (as judged by the amplitude of the electro-olfactogram response). Odorants containing four to six carbon atoms tend to show the largest (absolute) diminutions, suggesting a receptor for this kind of odorant, although the structural specificity is weak. The receptor seems to be of particular importance in the detection of thiols, carboxylic acids and hydrocarbons of the above size, since these compounds loose the highest proportion of their original signal. The concanavalin A appears to be binding to the glycan of one or more cell-surface proteins. The binding may be at, or close to, at least one odorant receptor.     

A more accurate method for measurement of tuberculocidal activity of disinfectants.

The current Association of Official Analytical Chemists method for testing tuberculocidal activity of disinfectants has been shown to be inaccurate and to have a high degree of variability. An alternate test method is proposed which is more accurate, more precise, and quantitative. A suspension of Mycobacterium bovis BCG was exposed to a variety of disinfectant chemicals and a kill curve was constructed from quantitative data. Data are presented that show the discrepancy between current claims, determined by the Association of Official Analytical Chemists method, of selected commercially available products and claims generated by the proposed method. The effects of different recovery media were examined. The data indicated that Mycobacteria 7H11 and Middlebrook 7H10 agars were equal in recovery of the different chemically treated cells, with Lowenstein-Jensen agar having approximately the same recovery rate but requiring incubation for up to 3 weeks longer for countability. The kill curves generated for several different chemicals were reproducible, as indicated by the standard deviations of the slopes and intercepts of the linear regression curves.     

Norway spruce somatic embryogenesis: high-frequency initiation from light-cultured mature embryos

Somatic embryos and rooted plantlets have been regenerated from light-initiated embryogenic callus derived from mature embryos of Picea abies. Under a 16 h photoperiod, mature zygotic embryos were cultured on a modified half-strength Murashige & Skoog medium without NH₄NO₃ and supplemented with 5 mM glutamine, 4.5 M N6-benzyladenine and 10.7 M naphthaleneacetic acid or 10 M 2,4-dichlorophenoxyacetic acid. White translucent embryogenic callus, proliferating from the callusing hypocotyl region after 3 weeks incubation, was isolated from the green non-embryogenic tissue and subcultured for over 12 months. Upon transfer of the embryogenic callus through a specific sequence of media, somatic embryos proceeded to mature, elongating and forming rings of cotyledonary leaves similar to those of zygotic embryos. Transferred to medium without growth regulators, the somatic embryos germinated and produced plantlets with green cotyledons, elongated hypocotyls and primary roots.     

Concanavalin A reveals olfactory receptors which discriminate between alkane odorants on the basis of size.

For certain odorants, the amplitude of the rat electro-olfactogram is reduced if the olfactory epithelium is treated with the lectin concanavalin A. When normal and cycloalkanes of one to ten carbon atoms are used as odorants at equimolar concentration, the maximum reduction in amplitude is found to correlate with the size of the stimulus molecule. This observation is consistent with the notion that concanavalin A disables an olfactory receptor molecule which normally responds to the alkyl moiety of odorants in a particular size range. That moiety may thus represent a 'primary' quality-determining component in odour discrimination.     

Control of early seedling growth in varietal lines of hexaploid wheat (Triticum aestivum), durum wheat (Triticum durum), and barley (Hordeum vulgare) in response to the phthalimide growth regulant,AC 94,377

AC 94,377 caused elongation of seedlings of Triticum aestivum, Triticum durum, and Hordeum vulgare when applied to the soil, or the soil plus seed at planting. Affected were the leaf sheathes and the coleoptiles, and at high compound rates there was premature elongation of the stem internodes. As exemplified by the response of T. aestivum var. Fidel, the influence on coleoptile elongation was greatest under conditions whereby the coleoptile was naturally stimulated to elongate, i.e., when growth was in the dark and temperatures were cool (15°C). All of the stem internodes were capable of elongation except the one below the coleoptile node. The effect on leaf sheath elongation was prolonged when compared to activity of gibberellic acid.Several varieties of the three cereal species were examined in the greenhouse for sensitivity to AC 94,377 in order to evaluate the extent of the response. All of the barley varieties examined were sensitive to AC 94,377, elongating regardless of the planting conditions. Two such conditions were established, including incubation under warm (28/20°C) conditions following planting the grains 1 cm deep, and incubation under cool (22/16°C) conditions following planting the grains 6 cm deep. Wheat varieties distributed into two general categories, those which were sensitive and those which were not. The insensitivity correlated well to the presence of the reduced height (Rht) and GA-insensitive (Gai) genes in Triticum aestivum and Triticum durum, respectively. Thus, AC 94,377 can be used conveniently to evaluate varietal lines for the presence of this phenotype. This correlation also lends support to the notion that the Rht/Gai mutations in wheat are either at the level of a gibberellin receptor or at a step in the signal transduction pathway.     

Effect of amino acid substitutions and deletions on the thermal stability, the pH stability and unfolding by urea of bovine calbindin D9k

The influence of amino acid substitutions and deletions on the stability of bovine calbindin D9k, the smallest protein known with a pair of EF-hand calcium-binding sites, has been studied using circular dichroism and ultraviolet absorption spectroscopy. The five modifications are confined to one of the two Ca2+ -binding sites. The Ca2+-loaded forms of the wild-type and mutant calbindins are too stable to be significantly denatured by heating at 90 degrees C or by adding 8 M urea. For the Ca2+-free (apo) forms thermal unfolding appears to be only half complete at 90 degrees C, while denaturation is complete in 7-8 M urea. Four of the mutant proteins show reduced resistance towards unfolding by urea, but one of the modified proteins (Glu-17----Gln) shows an increased stability, presumably because of a reduced electrostatic repulsion in the native state. According to X-ray crystallographic data the OH group of the single tyrosine of calbindin (Tyr-13) is hydrogen-bonded to the carboxyl group of Glu-35, thus linking the two alpha helices flanking the N-terminal Ca2+ site. The pK of ionization of the Tyr-13 hydroxyl group was over 13 for calcium forms of the wild-type protein, between 12.3 and 12.8 for the calcium form of three mutants and between 11.5 and 11.7 for the apoproteins. Significant differences in pH stability between wild type and mutants were observed in the calcium forms, but were not apparent in the apo forms.     

Regulation of proliferation and differentiation of respiratory tract epithelial cells by TGFβ

In this paper we examined the effects of transforming growth factor β (TGFβ) on the proliferation and differentiation of rabbit tracheal epithelial cells in primary culture. Treatment of these cells with TGFβ inhibits cell proliferation in a time- and dose-dependent manner; concentrations as low as 1 pM are able to inhibit cell growth. Concomitantly, TGFβ causes cells to accumulate in the G0/G1 phase of the cell cycle and a sharp reduction in the ability of the cells to form colonies after subculture at clonal density. These results indicate that TGFβ induces terminal cell division in these cells. The inhibition of cell growth is accompanied by changes in cell morphology and a stimulation of the formation of cross-linked envelopes. TGFβ enhances the levels of transglutaminase activity and cholesterol sulfate, two markers of squamous differentiation. Our results indicate that TGFβ induces terminal squamous cell differentiation in rabbit tracheal epithelial cells. Retinoic acid (RA) does not affect the commitment to terminal cell division induced by TGFβ, but inhibits the expression of the squamous phenotype. Growth of normal human bronchial epithelial cells was affected by TGFβ in a way similar to that of rabbit tracheal epithelial cells. Several carcinoma cell lines tested were quite resistant to TGFβ, whereas growth of one carcinoma cell line was stimulated by TGFβ. These results indicate that a modified response to TGFβ could be one mechanism involved in the aberrant growth control of malignant cells.     

Behavioral treatment of irritable bowel syndrome: A 1-year follow-up study

Sixteen clients afflicted with irritable bowel syndrome (IBS) were reassessed 1 year following completion of a multicomponent treatment package incorporating progressive muscle relaxation, thermal biofeedback, cognitive therapy, and IBS education. For the 14 patients who kept a 2-week symptom diary, significant reductions in ratings of abdominal pain and tenderness, diarrhea, and flatulence were obtained comparing pretreatment and follow-up symptom-diary ratings. Eleven of 14 clients were improved over pretreatment levels, 57% met the criteria for clinical improvement of at least a 50% reduction in major symptom scores, and all but 1 of 16 rated themselves as subjectively improved.