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.     

Genetic analysis of murine strains C57BL/6J and C3H/HeJ to confirm the map position ofAth-1, a gene determining atherosclerosis susceptibility

Previous results suggested that strains C57BL/6J and C3H/HeJ differed in a single gene for atherosclerosis susceptibility, calledAth-1. Based on data from recombinant inbred strainsAth-1 was tentatively assigned to chromosome 1 linked toAlp-2. In this report, a cross between C57BL/6 and C3H/HeJ was carried out in order to test whether the tentative map position was correct. Parental strains and F₁ and F₂ progeny were examined. Susceptible alleles ofAth-1, found in C57BL/6, are associated with relatively low levels of high-density lipoprotein (HDL)-cholesterol in animals fed an atherogenic diet; resistant alleles ofAth-1 are associated with relatively high levels of HDL-cholesterol. F₁ progeny have HDL levels that are intermediate between these of the two parental strains. Among the F₂ progeny,Alp-2 andAth-1 cosegregated, providing confirmatory evidence thatAth-1 is linked toAlp-2 on chromosome 1. Three mice recombinant forAlp-2 andAth-1 were found among the 60 chromosomes tested, giving an estimated map distance between these two genes of 5.0±2.8 (SE) cM. The phenotypic characteristics ofAth-1 resemble a genetic trait in humans, hyperalphalipoproteinemia, which is characterized by elevated levels of HDL-cholesterol, reduced risk of heart disease, and increased longevity.This work was supported by Grant HL-32087 from the Heart, Lung, and Blood Institute, National Institutes of Health, Grant 1858 from the Council for Tobacco Research, Grant 86-1387 from the American Heart Association with funds contributed in part by the Alameda, Orange, and Santa Barbara County Chapters, and Grants 85-N132A and 85-N136A from the California Affiliate of the American Heart Association.     

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.     

Identification of a single nucleotide change in a mutant gene for hypoxanthine-guanine phosphoribosyltransferase (HPRTAnn Arbor)

Summary HPRT_{Ann Arbor} is a variant of hypoxanthine (guanine) phosphoribosyl-transferase (HPRT: EC 2.4.2.8), which was identified in two brothers with hyperuricemia and nephrolithiasis. In previous studies, this mutant enzyme was characterized by an increased K_m for both substrates, a normal V_max, a decreased intracellular concentration of enzyme protein, a normal subunit molecular weight and an acidic isoelectric point under native isoelectric focusing conditions. We have cloned a full-length cDNA for HPRT_{Ann Arbor} and determined its complete nucleotide sequence. A single nucleotide change (TG) at nucleotide position 396 has been identified. This transversion predicts an amino acid substitution from isoleucine (ATT) to methionine (ATG) in codon 132, which is located within the putative 5-phosphoribosyl-1-pyrophosphate (PRPP)-binding site of HPRT.     

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.     

The AXB and BXA set of recombinant inbred mouse strains

The recombinant inbred (RI) set of strains, AXB and BXA, derived from C57BL/6J and A/J, originally constructed and maintained at the University of California/San Diego, have been imported into The Jackson Laboratory and are now in the 29th to 59th generation of brother-sister matings. Genetic quality control testing with 45 proviral and 11 biochemical markers previously typed in this RI set indicated that five strains had been genetically contaminated sometime in the past, so these strains have been discarded. The correct and complete strain distribution patterns for 56 genetic markers are reported for the remaining RI strain set, which consists of 31 living strains and 8 extinct strains for which DNA is available. Two additional strains, AXB 12 and BXA 17, are living and may be added to the set pending further tests of genetic purity. The progenitors of this RI set differ in susceptibility to 27 infectious diseases as well as atherosclerosis, obesity, diabetes, cancer, cleft palate, and hydrocephalus. Thus, the AXB and BXA set of RI strains will be useful in the genetic analysis of several complex diseases.     

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.