Ecological patterns of relative clutch mass in snakes

Summary Data on the relative clutch mass of snakes are summarized for over 100 populations. RCM was significantly lower in live bearing versus egg laying forms. We suggest that the longer reproductive season of viviparous snakes results in higher overall mortality compared to oviparous species; by reducing RCM, viviparous snakes may reduce this risk of mortality. Unlike lizards, no differences in RCM were found between categories of either escape behavior or foraging mode, possibly because detailed information on these behaviors are lacking for most snakes. In four populations examined, RCM did not vary among years. When compared to lizards, snakes demonstrate significantly higher RCM, perhaps owing to a more energetically efficient means of locomotion. Our data support the contention that RCM should be considered a separate and distinctive life-history characteristic of reptiles.     

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.     

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).     

Phage lambda and plasmid expression vectors with multiple cloning sites and lacZ alpha-complementation

Two new lambda vectors were constructed which permit cloning of genes that are potentially lethal if cloned in analogous plasmid vectors. lambda DL10 and lambda DL11 contain the alpha-complementing fragment of lacZ and multiple cloning sites found in the polylinker region of M13mp10 and M13mp11, respectively. DNA cloned into the unique cloning sites of these vectors can be detected by inactivation of alpha-complementation. These lambda vectors provide a lac promoter for expression of foreign genes as well as the ability to make fusion proteins. Two plasmid expression vectors, pPR110 and pPR111, were constructed from lambda DL10 and lambda DL11 respectively, and pCQV2. These plasmids, which express lacZ alpha-complementing activity from the lambda PR promoter, contain multiple cloning sites immediately downstream of the PR promoter. They allow cloning of genes under the control of the PR promoter and the plasmid-encoded thermosensitive (cI857) repressor, and allow easy detection of inserted fragments by inactivation of alpha-complementation.     

A new radioenzymatic assay for histamine using purified histamine N-methyltransferase

Radioenzymatic assays for histamine (Hm) have found wide application. However, these procedures may lack the sensitivity necessary to quantify Hm in certain biological samples, such as human plasma. Purification of histamine N-methyltransferase (HNMT) has permitted the development of a new and highly sensitive radioenzymatic assay for Hm. HNMT was purified by sequential ion exchange, hydrophobic and molecular exclusion chromatography. The use of purified HNMT in the Hm assay has allowed the inclusion of high specific activity tritiated S-adenosyl-L-methionine ([3H]SAME) and the development of a simplified solvent extraction product isolation procedure. This assay has a sensitivity of approximately 2 picograms and is specific for Hm. Hm was easily quantified in human plasma and was found to be 303 +/- 81 pg/ml (mean +/- SD) in 8 male subjects. Substantial blank reduction and increased product conversion occur when purified HNMT is utilized in the Hm radioenzymatic assay, thus, increasing the sensitivity and possibly improving the specificity of this procedure.     

Photoaffinity Labeling of Benzodiazepine Receptors in Rat Brain with Flunitrazepam Alters the Affinity of Benzodiazepine Receptor Agonist But Not Antagonist Binding

Abstract: Recently, it was proposed that β-carbolines interact with a subset of benzodiazepine (BZD) binding sites in mouse brain. This postulate was based upon evidence showing changes in binding properties of the BZD receptor following photoaffinity labeling of membranes with flunitrazepam (FLU). Under conditions in which 80% of specific [³H]diazepam binding was lost in photolabeled membranes, specific [³H]propyl β-carboline-3-carboxylate ([³H]PCC) binding was spared. In this study, the binding of the BZD antagonists [³H]PCC, [³H]Ro15 1788 and [³H]CGS 8216 was examined in rat brain membranes following photoaffinity labeling with FLU. No significant changes in the apparent K_D and small reductions in the B_max of ³H antagonist binding were observed. However, in the same membranes, up to 89% of specific [³H]FLU binding was lost. When [³H]PCC (0.05 nM) was used to label the receptors in control and photolabeled membranes, the ability of BZD receptor agonists to inhibit [³H]PCC binding was greatly diminished in the photolabeled membranes. In contrast, the potency of BZD antagonists remained the same in both control and treated membranes. Based upon PCC/[³H]Ro15 1788 competition experiments, the ability of PCC to discriminate between BZD receptor subtypes was unaffected by photoaffinity labeling of cortical membranes. Overall, these findings suggest that β-carbolines do not interact with a subset of BZD binding sites per se, but may be a consequence of the differential interaction of BZD agonists and antagonists with BZD binding sites that have been photoaffinity labeled with FLU. A possible mechanism underlying this phenomenon is discussed. The ability of photolabeled membranes to differentiate between BZD agonists and antagonists provides a potential screen for agonist and antagonist activity in compounds that interact with the BZD receptor.