Functional and morphological evidence for the existence of neurites from abdominal ganglion bag cell neurons in the head-ring ganglia of Aplysia

Summary Three lines of evidence are presented indicating that axons of the Aplysia neuroendocrine bag cells extend into the head-ring ganglia of the CNS. When the abdominal ganglion was bisected longitudinally, separating the two bag cell clusters, an afterdischarge induced in one cluster generated an afterdischarge in the other via activity through the head-ring ganglia to which each half abdominal ganglion was attached by connective nerves. This suggests that some axons of bag cells in each cluster communicate through the head-ring ganglia. Retrograde labelling of bag cells occurred when rhodamine-onjugated latex microspheres were injected into the cerebral or either pleural ganglion, a direct demonstration that bag cell axons extend into these ganglia. Finally, cell LP1 in the left pleural ganglion was inhibited during a bag cell afterdischarge, an action mimicked by application of alpha-bag cell peptide (BCP). Since BCP can act only close to its site of release due to susceptibility to peptidase activity, it is likely that LP1 inhibition is dependent on the local release of BCP from bag cell neurites in the pleural ganglion. These results open new possibilities for how bag cell afterdischarges may be initiated and broaden the distribution of their effects.Abbreviations ASW artificial sea water; -BCP -bag cell peptide - ELH egg-laying-hormone - IR immunorective - PB phosphate buffer - PVC pleurovisceral connective     

Collagen metabolism and spicule formation in sea urchin micromeres

The role of collagen or collagen-like protein(s) in the in vitro formation of the sea urchin embryonic skeleton was investigated using isolated micromeres of Strongylocentrotus purpuratus. Micromeres were cultured in sea water containing 4% horse serum on tissue culture plastic or an extracellular matrix of type I collagen. The effect of proline analogs and an inhibitor of collagen hydroxylation on in vitro spicule formation in both culture systems was monitored. When micromeres are cultured in the presence of proline analogs l-azetidine-2-carboxylic acid and l-3,4-dehydroproline which disrupt collagen metabolism, spicule formation is significantly less inhibited on a collagen substratum than on plastic. Culturing micromeres on plastic in the presence of α,α′-dipyridyl, an inhibitor of collagen hydroxylation, resulted in almost complete inhibition of spicule formation. The inhibition by α,α′-dipyridyl can be overcome by culturing micromeres on collagen substratum. These results do not support the idea of collagen being the calcified organic matrix of the spicule. Rather, they suggest that micromeres synthesize a collagen-like extracellular matrix which is necessary for spicule formation. Inhibition of this activity by proline analogs or a collagen processing inhibitor can be overcome by providing the cells with a previously deposited extracellular matrix.     

Thermal denaturation of mononucleosomes in the presence of spermine,spermidine, N1-acetylspermidine,N8-acetylspermidine or putrescine: implications for chromosome structure

Putrescine (a diamine) raises the thermal denaturation temperature of mononucleosomes but produces only minor changes in the overall shape of the thermal denaturation curve. This is similar to the effect of sodium ions and is consistent with nonspecific binding to the DNA of the nucleosome. At very low levels of spermidine or spermine the same simple rise in thermal denaturation temperature is seen but at higher levels (above 1 M for total spermidine concentration) the thermal denaturation curve becomes substantially sharper and the premelt region of the curve diminishes in area. The acetylspermidines display intermediate effects. The change in shape of the thermal denaturation curve was resolved into components (R1 and R2) due to mononucleosomes in their original conformation plus a component (T) induced by the presence of spermidine or spermine. The proportion of component T was substantially reduced with acetylspermidine, compared to equivalent concentrations of spermidine. Hence, we suggest that spermidine acetylationin vivo has the potential to partially destabilise the nucleosome structure, possibly in coordination with histone acetylation.     

Antenna organization in green photosynthetic bacteria. 1. Oligomeric bacteriochlorophyll c as a model for the 740 nm absorbing bacteriochlorophyll c in Chloroflexus aurantiacus chlorosomes

Bacteriochlorophyll (BChl) c was extracted from Chloroflexus aurantiacus and purified by reverse-phase high-pressure liquid chromatography. This pigment consists of a complex mixture of homologues, the major component of which is 4-ethyl-5-methylbacteriochlorophyll c stearyl ester. Unlike previously characterized BChls c, the pigment from C. aurantiacus is a racemic mixture of diastereoisomers with different configurations at the 2a chiral center. Diluting a concentrated methylene chloride solution of BChl c with hexane produces an oligomer with absorption maxima at 740-742 and at 460-462 nm. Both the absorption spectrum and the fluorescence emission spectrum (maximum at 750 nm) of this oligomer closely match those of BChl c in chlorosomes. Further support for this model comes from the ability of alcohols, which disrupt BChl c oligomers by ligating the central Mg atom, to convert BChl c in chlorosomes to a monomeric form when added in low concentrations. The lifetime of fluorescence from the 740 nm absorbing BChl c oligomer is about 80 ps. Although exciton quenching might be unusually fast in the in vitro BChl c oligomer because of its large size and/or the presence of minor impurities, this result suggests that energy transfer from the BChl c antenna in chlorosomes must be very fast if it is to be efficient.     

Properties of the reaction center of the thermophilic purple photosynthetic bacterium Chromatium tepidum

Reaction centers were purified from the thermophilic purple sulfur photosynthetic bacterium Chromatium tepidum. The reaction center consists of four polypeptides L, M, H and C, whose apparent molecular masses were determined to be 25, 30, 34 and 44 kDa, respectively, by polyacrylamide gel electrophoresis. The heaviest peptide corresponds to tightly bound cytochrome. The tightly bound cytochrome c contains two types of heme, high-potential c-556 and low-potential c-553. The low-potential heme is able to be photooxidized at 77 K. The reaction center exhibits laser-flash-induced absorption changes and circular dichroism spectra similar to those observed in other purple photosynthetic bacteria. Whole cells contain both ubiquinone and menaquinone. Reaction centers contain only a single active quinone; chemical analysis showed this to be menaquinone. Reaction center complexes without the tightly bound cytochrome were also prepared. The near-infrared pigment absorption bands are red-shifted in reaction centers with cytochrome compared to those without cytochrome.     

Isolation and cDNA sequence of human postheparin plasma hepatic triglyceride lipase

Hepatic triglyceride lipase (H-TGL) was isolated from human postheparin plasma by column chromatography on heparin-Sepharose and phenyl-Sepharose and immunoaffinity chromatography with monoclonal antibodies. The purified enzyme had an apparent molecular weight of 65,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and an amino-terminal sequence of Leu-Gly-Gln-Ser-Leu-Lys-Pro-Glu. Partial amino acid sequences of seven cyanogen bromide peptides were obtained. A human hepatoma cDNA library was screened with synthetic oligonucleotides derived from the partial protein sequence. The cloned H-TGL cDNA of 1569 nucleotides predicts a mature protein of 477 amino acids plus a leader sequence of 22 amino acids. Blot hybridization analysis of poly(A)+ mRNA with a putative H-TGL cDNA clone gave a single hybridizing band of 1.7 kilobases. The protein contains four consensus N-glycosylation sequences based on the cDNA sequence. Comparison of the enzyme sequence with that of other lipases reveals highly conserved sequences in regions of putative lipid and heparin binding. The carboxyl terminus of H-TGL contains a highly basic sequence which is not reported to be present in rat H-TGL or other members of the lipase gene family.     

Effect of soil temperature and drought on peanut pod and stem temperatures relative to Aspergillus flavus invasion and aflatoxin contamination

Peanut stem and pod temperatures of plants growing in irrigated, drought, drought-heated soil, and drought-cooled soil treatments were determined near the end of the growing season. Mean soil temperatures of the treatments during this period were 21.5°, 25.5°, 30° and 20 °C, respectively. Peanut stem temperatures in all drought treatments reached a maximum of ca. 40 °C and for 6–7 h each day were as much as 10 °C warmer than irrigated peanut stems. Pod temperatures in drought-heated soil and drought treatments were ca. 34 °C and 30 °C, respectively, for several hours each day. As pod temperatures approached the optimum for A. flavus growth (ca. 35 °C), the proportion of kernels colonized and aflatoxin concentrations increased. Increased plant temperature without accompanying pod temperature increases (drought-cooled soil) resulted in colonization percentages and aflatoxin concentrations only slightly higher than those of the irrigated peanuts.     

Deletions in the genomes of pseudorabies virus vaccine strains and existence of four isomers of the genomes

As part of a study designed to identify the genes responsible for the virulence of pseudorabies virus, we have mapped the genomes of two independently derived vaccine strains (Bartha and Norden) by restriction enzyme analysis. The structures of these genomes have been compared with that of the genome of a laboratory strain previously mapped, of restriction fragments which had been cloned. The genome of the Bartha strain was found to be very similar to that of other pseudorabies virus strains, except that a deletion of approximately 2.7 X 10(6) daltons was found in the unique short (US) region. This deletion was also observed in the genome of the Norden vaccine strain but was not observed in the genomes of any other pseudorabies virus strains that have been studied (more than 20). The genome of the Norden strain differs from that of other pseudorabies virus strains in several other respects as well. The most important difference is that in contrast to all other pseudorabies virus strains analyzed to date, which contain a type 2 herpesvirus DNA molecule (in which the US region only inverts itself relative to the unique long [UL] region), the genome of the Norden strain is a type 3 molecule in which both the US and the UL regions of the genome invert themselves, giving rise to four isomeric forms of the genome. The ability of the UL region to invert itself is probably related to the fact that a sequence normally present in all other pseudorabies virus strains at the end of the UL only is found also in inverted form at the junction of the UL and the internal inverted repeat in the Norden strain.     

Responses of Spotted Hyenas to Lions Reflect Individual Differences in Behavior

Competition among mammalian carnivores can be particularly intense and can influence population dynamics at lower trophic levels. One strategy employed by carnivores to minimize potentially costly interspecific competition is avoidance of dominant species. Recent research has highlighted the importance of consistent individual differences in behavior (i.e. temperament traits) in understanding behavioral variation during predator–prey interactions and intraspecific interactions. However, the importance of such individual differences to interspecific competition has received little attention. Here, we examined the responses of spotted hyenas (Crocuta crocuta) to their primary competitors, African lions (Panthera leo), to (1) determine whether hyenas avoid lions and (2) evaluate the potential importance of individual differences in behavior during interspecific competition. Spotted hyenas and lions co‐occur throughout much of Africa and are vigorous competitors. Whereas lions sometimes kill hyenas and steal their food, lions also represent a source of food for hyenas via scavenging. Using audio playback experiments, we found that hyenas do not uniformly avoid potential encounters with lions. Indeed, we noted considerable variation among individuals in their responses to lion roars, and this variation reflected consistent individual differences in risk‐taking and vigilance tendencies. Individual differences in vigilance behavior were specific to interactions with lions. We conclude that individual differences in behavior have the potential to play an important role in determining the nature and outcome of interspecific competition.