Heat treatment results in a loss of transgene-encoded activities in several tobacco lines.

Heat treatment (37 degrees C) of transgenic tobacco (Nicotiana tabacum) plants led to a reversible reduction or complete loss of transgene-encoded activities in about 40% of 10 independent transformants carrying the luciferase-coding region fused to the 355 cauliflower mosaic virus or the soybean small subunit promoter and the nopaline synthase promoter driving the neomycin phosphotransferase gene, whereas the other lines had temperature-tolerant activities. Temperature sensitivity or tolerance of transgene-encoded activities was heritable. In some of the lines, temperature sensitivity of the transgene-encoded activities depended on the stage of development, occurring in either seedlings (40% luciferase and 50% neomycin phosphotransferase) or adult plants (both 40%). The phenomenon did not correlate with copy numbers or the homo- or hemizygous state of the transgenes. In lines harboring a temperature-sensitive luciferase activity, reduction of bioluminescence was observed after 2 to 3 h at 37 degrees C. Activity was regained after 2 h of subsequent cultivation at 25 degrees C. Irrespective of the reaction to the heat treatment, the level of luciferase RNA was slightly increased at 37 degrees C. Only in lines showing temperature sensitivity of transgene-encoded activities was the amount of luciferase and neomycin phosphotransferase strongly reduced. In sterile culture, heat treatment for 15 d did not cause visible damage or changes in plant morphology. In all plants tested a slight induction of the heat-shock response was observed at 37 degrees C.     

On feeding and nutrition in Fungiacava eilatensis (Bivalvia, Mytilidae), a commensal living in fungiid corals

The enlarged inhalant siphon of Fungiacava eilatensis opens into the coelenteron of species of fungiid corals with which it lives in commensal association. Material consisting of mucus, zooxanthellae, nematocysts, plankton and inorganic matter, is taken exclusively from the coelenteron. The very mobile foot possibly assists in food collection and in the removal of pseudofaeces; but, with large ctenidia, the bivalve is a typical ciliary feeder. Experiments with labelled zooxanthellae reveal that these are taken into the gut of Fungiacava with subsequent metabolic incorporation of products derived from them. The other prime source of food must be phytoplankton carried in with the feeding currents of the coral, itself carnivorous so that there is no competition for food between commensal and host. The Fungia zooxanthella– Fungiacava association operates as a "Troika" the productivity of which is autoregulated in proportion to the number of bivalves present. The inorganic wastes of the bivalve (as well as those of the coral) are utilized by the zooxanthellae, resultant increase in the algal component becoming available as food to the bivalve. Losses in the cycle are balanced by intake of exogenous food.     

Phosphorylation of the acetylcholine receptor by protein kinase C and identification of the phosphorylation site within the receptor delta subunit

Purified acetylcholine receptor is rapidly and specifically phosphorylated by partially purified protein kinase C, the Ca2+/phospholipid-dependent enzyme. The receptor delta subunit is the major target for phosphorylation and is phosphorylated on serine residues to a final stoichiometry of 0.4 mol of phosphate/mol of subunit. Phosphorylation is dose-dependent with a Km value of 0.2 microM. Proteolytic digestion of the delta subunit phosphorylated by either protein kinase C or the cAMP-dependent protein kinase yielded a similar pattern of phosphorylated fragments. The amino acids phosphorylated by either kinase co-localized within a 15-kDa proteolytic fragment of the delta subunit. This fragment was visualized by immunoblotting with antibodies against a synthetic peptide corresponding to residues 354-367 of the receptor delta subunit. This sequence, which contains 3 consecutive serine residues, was recently shown to include the cAMP-dependent protein kinase phosphorylation site (Souroujon, M. C., Neumann, D., Pizzighella, S., Fridkin, M., and Fuchs, S. (1986) EMBO J. 5, 543-546). Concomitantly, the synthetic peptide 354-367 was specifically phosphorylated in a Ca2+- and phospholipid-dependent manner by protein kinase C. Furthermore, antibodies directed against this peptide inhibited phosphorylation of the intact receptor by protein kinase C. We thus conclude that both the cAMP-dependent protein kinase and protein kinase C phosphorylation sites reside in very close proximity within the 3 adjacent serine residues at positions 360, 361, and 362 of the delta subunit of the acetylcholine receptor.     

The estrogenic responses to clomiphene in the different cell types of the rat uterus: morphometrical evaluation

The present study was designed to investigate the dose-response of clomiphene on several estrogenic responses in the immature rat uterus and to compare it to available data on estradiol-17 beta. A dissociation was demonstrated among the different estrogenic responses induced by clomiphene. Very high doses of clomiphene were needed to induce the 6-h uterine eosinophilia and deep endometrial edema, and maximal response levels were not reached at any dose studied. On the contrary, many genomic responses were induced with much lower doses of clomiphene, and maximal response levels were reached with at least the two highest doses of clomiphene. This dissociation is in agreement with the existence of separate groups of responses that are mediated by multiple and independent mechanisms of estrogen action involving different kind of receptors. Luminal epithelial, glandular epithelial, and myometrial hypertrophies were also found to differ with regard to the dose needed to induce this response in each cell type. The dissociation between genomic responses of the different uterine cell types supports the hypothesis of different estrogen receptors for each kind of cell. Clomiphene induces mitoses in the different cell types, but the proportion of mitoses in the cell types was different from that described for estradiol. It is suggested that these differences are also due to differences between receptors involved in cell proliferation.     

Microdissection of the Prader-Willi syndrome chromosome region and identification of potential gene sequences

The Prader-Willi syndrome chromosome region on the long arm of human chromosome 15 was microdissected and microcloned from 20 GTG-banded metaphase chromosomes, and 5000 recombinant clones were obtained. Of these clones, 39% identify single-copy human DNA sequences, most of which map to the dissected chromosome region and are evolutionarily conserved in other species. Three of eleven clones studied in detail are deleted in several patients with Prader-Willi syndrome. The microclones will be useful for the physical characterization of the Prader-Willi syndrome chromosome region and the identification of the affected genes in this disease.