Effect of habitable space on substrate selection by Paragnetina media (Walker) (Plecoptera: Perlidae)

A biological measure of space available within substrates was used as an index to examine substrate selection by the stonefly nymph Paragnetina media (Walker). Physical measures, such as total surface area of substrate, have not worked well in the past in explaining distribution of aquatic invertebrates. Although analysis of habitable space within substrate did not explain selection completely, the technique provided a precise measure and might be a more rigorous means by which substrate selection could be examined.     

Drug Potencies on Partially Purified Brain D2 Dopamine Receptors

To examine the sensitivities of partially purified dopamine receptors to various dopaminergic agonists and antagonists, canine brain striatum dopamine receptors were enriched by isoelectric focusing. The digitonin-solubilized receptors were prelabelled with [3H]spiperone and focused for two time periods. After 5 h (incomplete focusing), radioactive peaks were detected at pH 6 and 9-11. Only the pH 6 peak revealed drug sensitivities expected of D2 receptors. Receptor recovery of the pH 6 peak was 79% with purification being sevenfold. After focusing overnight to equilibrium, the pH 6 peak further separated into peaks at pH 4.6 and 6.8. The receptor was identified only in the pH 4.6 fraction. The recovery of receptors in the pH 4.6 peak was low (10%), indicating little enrichment of the receptor. The rank order of binding of neuroleptics and dopamine agonists to the purified material was similar to that of the original preparation of soluble receptors. Dopamine did not bind to the purified pH 4.6 fraction unless the phosphate buffer (used during focusing) was replaced with Tris buffer. The absence of receptors in the pH 6.8 and pH 10 fractions, although both contained prelabeled [3H]spiperone, indicates the importance of testing agonists and antagonists on each fraction at each step in purification.     

A rapid naphthol yellows method for measuring the cellular protein content of anchorage cultures

Summary A rapid method has been developed for measuring the cellular protein content of mono- and multilayered anchorage cultures. Fixed or air dried cultures are stained for 30 min with 0.2% Naphthol Yellow S (NYS) dissolved in 1% acetic acid. Unbound dye is removed by a series of four 2.5 min washes in 1% acetic acid, and protein-bound dye extracted with 10 mM unbuffered Tris base for spectrophotometric optical density determination at 433 nm. The NYS method exhibited a least-squares correlation coefficient of 0.99997 with the Oyama-Eagle Lowry method.     

A simple and rapid method for screening bacteria for type II restriction endonucleases: enzymes in Aphanothece halophytica

A method is described which allows a large number of bacterial strains to be rapidly and easily screened for the presence of site-specific endonucleases. The method involves selective permeabilization of the bacterial cell and analysis of the exuded material. Type II restriction endonucleases from cyanobacteria and Gram-negative eubacteria have been detected and new enzymes have been found. The method should be widely applicable and easy to modify for use in genera other than those tested. Three-site-specific endonuclease activities, detected by this method in Aphanothece halophytica PCC 7412, were purified and their recognition and cleavage specificities were determined AhaI and AhaII recognise and cleave the same DNA sequences as CauII and AcyI respectively; the specificity of AhaIII (TTTAAA) has been reported previously (Whitehead and Brown, 1982, FEBS Letters 143:296–300).Abbreviations Brij-58 20 cetyl ether - Pu purine nucleoside - Py pyrimidine nucleoside     

DNA probe localization at 18p113 band by in situ hybridization and identification of a small supernumerary chromosome

Summary Recombinant plasmid clone B74 (also named D18S3) containing a human single-copy DNA segment of 6 kilobases (kb) was localized by in situ hybridization on band p113 of chromosome 18. This probe was then used in cytogenetic diagnosis to identify precisely a small supernumerary chromosome as an isochromosome i(18p).     

Differential hormonal action of the bag cell neurons on the arterial system ofAplysia

Summary The peptide-secreting bag cell neurons ofAplysia californica activate a long-lasting, complex behavior called egg laying. During egg laying some organ systems (reproductive) are more active than others (digestive) suggesting that blood flow to these tissues may change in accordance with their activities during egg laying. To examine this possibility we used a semi-intact preparation of the three major arteries innervated by the abdominal ganglion. We found that electrically stimulated bursts of bag cell activity triggered a long-lasting (>1 h) increase in contractile activity in two arteries, the anterior and gastroesophageal, but did not affect contractions of the third (abdominal) artery. The arterial responses were not affected either in form or duration by denervation of the arteries, suggesting that the increase in contractile activity was mediated by hormonal actions of bag cell transmitters on vasoconstrictor muscles. In intact animals this differential action on the arterial system may cause a long-term decrease in blood flow to relatively inactive tissues (digestive and locomotory organs) while increasing circulation to tissues involved in egg production (ovotestis and oviduct).Abbreviations ASW artificial sea water - BCA bag cell activation - ELH egg laying hormone     

Lectin-induced modulation of the antibody response to type III pneumococcal polysaccharide

Several lectins were tested for their capacity to alter the antibody response to type III pneumococcal polysaccharide (SSS-III). The antibody response was enhanced by concanavalin A (Con A), phytohemagglutinin (PHA), as well as lectins from Phytolacca americana (Pa-2), Pisum sativum (PSA), and Lens culinaris (LCH), when these lectins were given 2 days after immunization with SSS-III; however, suppression was obtained when Con A and Pa-2 were given at the time of immunization. By contrast the lectins from Vicia villosa (VVL) and Bauhinia purpurea (BPA) did not alter the antibody response. Since the lectins PSA and LCH bind to the same monosaccharide as Con A, whereas the other lectins bind to different monosaccharides, these findings indicate that there is no relationship between nominal monosaccharide specificity and the capacity to modulate the antibody response. Substantial increases in the magnitude of the IgG₁ antibody response was noted after the administration of Con A whereas profound enhancement of IgG_2a antibody response was noted after PHA was given.     

Location of O-acetyl groups in the acidic d-xylan of mimosa scabrella (bracatinga). A study of O-acetyl group migration

Extraction with dimethyl sulfoxide of wood-meal of the stem of bracatinga (Mimosa scabrella), a south Brazilian hardwood, that was defatted and delignified by treatment with aqueous chlorine at 0–5° followed by extraction with cold ethanol, gave a soluble O-acetylated 4-O-methyl-d-glucurono-d-xylan having (1→4)-linked β-d-xylopyranosyl residues that were unsubstituted (65%) and 2-O-(14%), 3-O- (16%), and 2,3-di-O-acetylated (5%), as determined by methylation analysis. Another preparation obtained by use of refluxing ethanol in the delignification process showed neither removal nor migration of acetyl groups. By comparison with synthetic, partly O-acetylated d-xylans of known composition, ¹³C-n.m.r. spectroscopy indicated that O-acetyl group migration does not occur during treatment with cold aqueous chlorine, refluxing ethanol, or water at 70°. Methyl 2-O-acetyl-4-O-methyl-β-d-xylopyranoside (6) was also unaffected by aqueous chlorine. O-Acetyl group migration took place more readily in aqueous and dimethyl sulfoxide solutions of 6 than of O-acetyl-d-xylans. The lowest temperatures at which migration was observed in monosaccharides was at 50 and 70° for solutions in D₂O and (CD₃)₂SO, respectively.     

Nonvisual feeding in a visual planktivore,Xenomelaniris venezuelae

Summary Studies of the diel feeding patterns of the planktivorous fish, Xenomelaniris venezuelae, in Lake Valencia, Venezuela, revealed that, although the fish is primarily a diurnal feeder, it consumes substantial numbers of Chaoborus larvae and pupae at night. A number of fish species are known which feed on plankton at night, but these fish are filter feeders and their diets largely consist of relatively small, nonevasive prey. Chaoborus, however, is large and agile. Predation by Xenomelaniris in the dark was also studied experimentally. Captured fish were placed in completely darkened aquaria with zooplankton from Lake Valencia. After several hours the plankton was removed and examined for evidence of feeding. The fish were found to consume Chaoborus pupae and fourth instar larvae but not other types of prey. The mode of feeding by Xenomelaniris in the dark is unknown.