Nucleotide sequence of the split tRNAUAALeu gene from Vicia faba chloroplasts: evidence for structural homologies of the chloroplast tRNALeu intron with the intron from the autosplicable Tetrahymena ribosomal RNA precursor

Summary The gene encoding the tRNA _UAA ^Leu from broad bean chloroplasts has been located on a 5.1 kbp long BamHI fragment by analysis of the DNA sequence of an XbaI subfragment. This gene is 536 bp long and is split in the anticodon region. The 451 bp long intron shows high sequence homology over about 100 bp from each end with the corresponding regions of the maize chloroplast tRNA _UAA ^Leu intron. These conserved sequences are probably involved in the splicing reaction, for they can be folded into a secondary structure which is very similar to the postulated structure of the intron from the autosplicable ribosomal RNA precursor of Tetrahymena. Very little sequence conservation is found in the 5-and 3-flanking regions of the broad bean and maize chloroplast tRNA _UAA ^Leu genes.     

Extraction and Partial Characterization of Enkephalin-Like Peptides from Splanchnic Nerve

A method is described for the extraction of enkephalin-like peptides from peripheral nerve using chloroform and acidic methanol to facilitate a differential extraction of peptides and lipid. Porcine splanchnic nerve contains enkephalin-like peptides in low amounts compared to porcine adrenal medulla and striatum. Gel filtration chromatography reveals the presence of enkephalin-like peptides in both processed and cryptic forms. This is the first reported isolation and partial characterization of these peptides in splanchnic nerve. The presence of these peptides in this nerve provides support for the contention that the splanchnic nerve can modulate catecholamine release from the adrenal medulla through an effect on opiate receptors located on chromaffin cells.     

Sequence of Guinea Pig Myelin Basic Protein

This paper proposes a tentative amino acid sequence of guinea pig myelin basic protein obtained by comparison of peptide fragments of the guinea pig and bovine proteins. Analyses of the tryptic peptides confirmed the known sequence differences in the NH2-terminal half of the molecule and showed that in the COOH-terminal half of the guinea pig protein Ser131 was missing, Ala136 - His137 was deleted, Leu140 was replaced by Phe, and an extra Ala was inserted somewhere within sequence 142-151 (tryptic peptide T23 ). Sequence determination of guinea pig tryptic peptides corresponding to residues 130-134 ( T20 ), 135-138 ( T21 ), and 142-151 ( T23 ) of the bovine protein confirmed the above sequence changes and placed the extra Ala between Gly142 and His143 . The sequence of the region corresponding to bovine residues 130-143 is thus Ala-Asp-Tyr-Lys-Ser-Lys-Gly-Phe-Lys-Gly-Ala-His. No species differences were observed in the amino acid compositions of the remaining tryptic peptides obtained from the COOH-terminal half of the molecule. Based upon these results, the guinea pig basic protein contains 167 amino acid residues and has a molecular weight of 18,256.     

Ordination of vegetation change in Guadalupe Mountains,New Mexico,USA

Vegetation change over a nine-year period was studied in Guadalupe Mountains, New Mexico. Permanent transects in desert shrub vegetation were sampled in 1972 and 1980. Emphasis was given to shrubs because of their importance to big game diets. Univariate paired t-tests and reciprocal averaging ordination were used to detect and display coordinated changes in species composition over time. Despite apparently less browsing pressure in desert shrub vegetation in 1980 there were few significant changes in species composition. In addition, preferred forage species showed reduced reproduction while species of intermediate and poor forage value dis-played increased reproduction during this time. These data do not support traditional rangeland succession theory which states that enhanced reproduction of preferred species should follow grazing or browsing pressure reduction.     

Detection of noncontingent feedback in EMG biofeedback

Noncontingent feedback is frequently used as a placebo control procedure in biofeedback research. Researchers, however, have criticized this procedure for lacking credibility because of easy detection. The present study examined detection of false feedback in biofeedback with EMG. Contingent feedback (CF), truly random false feedback (FF), and controlled false feedback (CFF) groups were compared for changes in EMG levels, report of inaccurate feedback, and report of learning muscle activity reduction. The results indicated that FF procedures are easily detected; therefore, differences found between the FF and CF groups may be influenced by extraneous variables. The CFF group did not detect false feedback, but subjects reported some suspicions in later trials. With more trials, CFF may have also been detected. These results indicate a need for more attention to appropriate placebo control procedures in evaluating the parameters and efficacy of biofeedback.     

Ammonium release by zooplankton in suspensions of heat-killed algae and an evaluation of the flow-cell method

The maximum excretion rate of NH₄ (39 nmol mg dry wt^–1h^–1) was directly measured for Daphnia pulex by measuringNH₄ accumulation in bottles containing D. pulex and dense, satiatingsuspensions of heat-killed algae. Ammonium release rates inthe algal suspensions were compared to those of individual animalsremoved from the suspension and placed in flow cells. Ammoniumrelease rate, R (nmol mg dry wt^–1 h^–1). in the flowcell decreased very rapidly with time, t (min), after removalaccording to the relation R = 26 + 25e^–0.16t. Ammoniumexcretion obtained by the flow cell method after extrapolationto time zero was not significantly different from that obtainedin the bottles. The considerable experiment-to-experiment variationin NH₄ excretion was in large part correlated (r² = 0.73) withthe feeding rate on the algae.     

The proα2 (V) collagen gene (COL5A2) maps to 2q14→2q32, syntenic to the proα1 (III) collagen locus (COL3A1)

Summary A recombinant probe specific for the pro2 chain of human Type V collagen has been used for the localization of the corresponding gene (COL5A2) to chromosome 2. Regional mapping by in situ hybridization and analysis of DNA from humanxrodent cell lines indicated that COL5A2 is confined within the segment 2q142q32, thus syntenic to the pro1 (III) collagen gene (COL3A1).     

The possession of coli surface antigen CS6 by enterotoxigenicEscherichia coli of serogroups O25, O27, O148, and O159: a possible colonization factor?

A total of 134 enterotoxigenicEscherichia coli (ETEC) of serogroups O25, O27, O148, and O159 were tested in the enzyme-linked immunosorbent assays for the colonization factor antigens I (CFA/I), CFA/II (coli surface antigens CS1, 2 and 3) and putative colonization factor (PCF) 8775 (CS4, 5 and 6). CS6 was detected without CS4 or CS5 in 94% of the strains of serogroup O25, 86% of strains of serogroup O27, 87% of strains of serogroup O148, and 29% of strains of serogroup, O159. The frequency with which CS6 occurs in ETEC of common serotypes without the antigens CS4 or CS5 suggests that it might be a colonization factor.     

Elucidation of a minimal immunoreactive site of vertebrate calmodulin

The heptapeptide AsnTyrGluGluPheValGlnNH₂ corresponding to residues 137–143 of vertebrate calmodulin is as immunoreactive as the entire 148-residue protein. A reproducible and rapid procedure for producing antisera against vertebrate calmodulin has been previously described (L. J. Van Eldik and D. M. Watterson (1981) J. Biol. Chem.256, 4205–4210). Most of the antisera elicited by this method react with a major immunoreactive region (residues 127–144) in the COOH-terminal domain of vertebrate calmodulin. In this report, the minimum segment of calmodulin required for reactivity with an antiserum that readily distinguishes various types of calmodulins is defined. These studies demonstrate that a linear segment of seven amino acid residues shows a competition curve in radioimmunoassay resembling the competition curve of intact calmodulin. This heptapeptide is the smallest calmodulin segment and the only sevenresidue segment in the 135–145 region that shows quantitative immunoreactivity with the anti-calmodulin serum. These data demonstrate that this heptapeptide is a major immunoreactive site of calmodulin. However, when this immunoreactive site heptapeptide is conjugated to a carrier and injected into rabbits, it does not elicit antisera that react with the native protein. These studies demonstrate that quantitative immunoreactivity of antisera produced in animals can be found in small peptide segments and that, for calmodulin, the requirements for production of anti-peptide antibodies that react with the native protein molecule are not as simple as surface exposure of the peptide region.