Snare protein expression and adenoviral transfection of amphicrine AR42J.

The amphicrine AR42J acinar cell line is an excellent model to study both exocrine and neuroendocrine exocytotic mechanisms. As a first step toward this goal, we determined the specific isoforms of the v- and t-SNARE and Munc18 families expressed in these cells. In addition, we show that dexamethasone-induced differentiation toward the exocrine phenotype causes an upregulation of several of these proteins. AR42J is notoriously difficult to transfect, limiting its usefulness as a model. However, we have now overcome this obstacle by acheiving high efficiency expression of a beta-galactosidase reporter gene and truncated SNAP-25 gene using adenoviral infection techniques. The AR42J cells can now be used to pursue and elucidate the distinct functions of individual SNARE isoforms used in endocrine and exocrine secretion within a single cell line.     

Relationship between immunoglobulin levels and extremes of solar activity

The possible relationship between epidemics and extremes of solar activity has been discussed previously. The purpose of the present study was to verify whether differences in the levels of immunoglobulins (IgA, IgG, IgM) could be noted at the highest (July 1989) and lowest (September 1986) points of the last (21st) and present (22nd) 11-year solar cycle. The work was divided into a 1-month study (covering the month of minimal or maximal solar activity), a 3-month study (1 month before and after the month of minimal or maximal solar activity) and a 5-month study (2 months before and after the month of minimal or maximal solar activity). A trend of a drop-off for all three immunoglobulins was seen on the far side of the maximal point of the solar cycle. Statistical significance was achieved in the 5-month study for IgM (P=0.04), and a strong trend was shown for IgG (P=0.07). Differences between the sexes were also noted.     

The yeast Ski complex is a hetero-tetramer

The yeast Ski complex assists the exosome in the degradation of mRNA. The Ski complex consists of three components; Ski2, Ski3, and Ski8, believed to be present in a 1:1:1 stoichiometry. Measuring the mass of intact isolated endogenously expressed Ski complexes by native mass spectrometry we unambiguously demonstrate that the Ski complex has a hetero-tetrameric stoichiometry consisting of one copy of Ski2 and Ski3 and two copies of Ski8. To validate the stoichiometry of the Ski complex, we performed tandem mass spectrometry. In these experiments one Ski8 subunit was ejected concomitant with the formation of a Ski2/Ski3/Ski8 fragment, confirming the proposed stoichiometry. To probe the topology of the Ski complex we disrupted the complex and mass analyzed the thus formed subcomplexes, detecting Ski8-Ski8, Ski2-Ski3, Ski8-Ski2, and Ski8-Ski8-Ski2. Combining all data we construct an improved structural model of the Ski complex.     

Multidrug-resistant tumor cells with decreased malignancy: a role for integrin alphavbeta3

We studied whether acquisition of multidrug resistance (MDR) by tumor cells can alter their integrin profile and malignant behavior. Hamster fibroblast cell line HET-SR-2SC-LNM was selected for MDR, yielding the 2SC/20 subline. Compared with the parental cells, the 2SC/20 subline weakly adhered to denatured collagen (dCol) which correlated with decreased expression of alphavbeta3, a dCol receptor. Importantly, 2SC/20 subline demonstrated significantly decreased activity of collagenase MMP-2, lower ability to invade Matrigel, and attenuated metastasis in syngeneic animals. We provide evidence for the first time that selection for MDR can be associated with down-regulation of alphavbeta3 integrin, supporting our recent proof of the pro-apoptotic role of this integrin (Oncogene 20 (2001) 4710). Lack of alphavbeta3 expression may link cell survival under toxic conditions with decreased malignancy of the resulting drug resistant tumor.     

Codon usage in Xanthophyllomyces dendrorhous (formerly Phaffia rhodozyma)

By sequence analysis of 96 randomly selected clones in a cDNA library of Xanthophyllomyces dendrorhous, ten novel, full-length clones encoding cytoplasmic ribosomal proteins (rp) were found. The deduced amino acid sequences showed significant homology to their counterparts from eukaryotic origin including mammals, fungi and plants. Some ribosmal protein encoding cDNAs appeared several times, but by Southern blot analysis it was shown they are encoded by a single copy gene. The nucleotide sequences of ten full length cDNAs were used to investigate the codon usage in X. dendrorhous.     

The Effect of Chilling of the Physiological and Simulated Apex of 2- and 3-leaf Plants of Pisum sativum L. cv. Alaska on Lateral Shoot Growth, C-14 IAA Movement and P-32 Accumulation

The apex of a 3-leaf pea plant was chilled in cold chambers maintained at 5–7°C. The lateral shoots 1 through 5 grew, and shoot 5 eventually dominated other lateral shoots. The apex when returned to the ambient temperature did not reimpose apical dominance. The growing lateral shoots competed with the stem apex. The apices of 2- and 3-leaf plants were chilled and P-32 distribution in these plants was studied in the entire plant, at various intervals of time. Phosphorus-32 accumulation followed the growth pattern of the plant. The lateral shoots accumulated P-32 activity and very little activity was accumulated by the apex. The dominating shoots 2 and 5 accumulated the maximum amount of activity in 2- and 3-leaf plants, respectively. Labeled-IAA moved basipetally through the stem when applied to the cut stump simulating the apex. By cold treatment the translocation of IAA was influenced more than its absorption. The plant seems to metabolize this compound in the later periods of application. The plant now becomes “insensitive” to auxin and the lateral shoots grow.