Comparative larval energetics of an ophiuroid and an echinoid echinoderm

The morphologically convergent larvae of the echinoderm classes Ophiuroidea and Echinoidea have been suggested to be functionally dissimilar when it comes to their capacities to feed, but little is known about whether these larvae are similar in terms of energetics. Here, we compare the energetics of early development of a tropical ophiuroid, Ophiocoma alexandri, and a temperate to tropical echinoid, Arbacia punctulata, two species with similarly sized eggs. Measurements of respiration and constituent analyses were performed on eggs and unfed larvae of both species. Members of both species showed an increase in oxygen consumption during morphogenesis followed by a lower, static rate once morphogenesis was complete (3 d for O. alexandri and 1.3 d for A. punctulata). Compared to the echinoid larvae, the ophiuroid larvae developed more slowly and had peak respiration rates that were 3.1× lower. Eggs of O. alexandri contained significantly more protein and significantly less triacylglycerol than eggs of A. punctulata. Energy utilization, as calculated via respiration measurements, closely matched decreases in energy content from the eggs to larvae as measured with biochemical constituent assays. Larvae of A. punctulata used 1.4× more energy to reach the pluteus stage than larvae of O. alexandri, and used 4× more energy during the first 9 d of larval life. These data suggest that echinoid larvae require more energy to develop to the feeding stage than ophiuroid larvae, and likewise have higher requirements for maintenance metabolism. Ophiuroid larvae may be more tolerant of low food levels due to their very low metabolic rates, but this advantage may be offset by their slower rate of development.     

Solvent-tolerance of fungi located on an interface between an agar plate and an organic solvent

While 6 by 20 of type culture fungi could grow on an interface between organic solvent (log P, 4.12) and agar plate, 13 by 20 of strains could form a large colony after the removal of more toxic solvent, such as styrene (log P, 2.95) and tert-butyl acetate (log P, 1.76) because of viability of spores on the interface.     

Multipole representation of an eccentric dipole and an eccentric double-layer

Recently a theorem for representing current generators in a volume conductor by the superposition of a central dipole, quadrupole, octopole, etc., has been established by G. C. K. Yeh, J. Martinek, and H. de Beaumont (Bull. Math. Biophysics,20, 203–16, 1958). This theorem makes possible the representation of any discrete or line, surface- or volume-distributed current source by a unique model which can be determined for each given case by surface potential measurements and closed form analysis. In this paper the multipole representations of an eccentric dipole and an eccentric double-layer are obtained in terms of the various parameters of the assumed singularities, and the contributions to surface potentials due to each of the multipoles are compared. Certain numerical results corresponding to those of E. Frank (Amer. Heart J.,46, 364–78, 1953) are carried out and compared. Furthermore, the multipole representation of a partially damaged double-layer is also determined and compared with that of an undamaged one. It is concluded that within the range of parameters corresponding to human subjects the higher-order multipoles can contribute significantly to the surface potentials compared with the dipole. This investigation was supported by the National Heart Institute under a research grant H-2263(c).     

Obesity and microbiota: an example of an intricate relationship

It is widely accepted that metabolic disorders, such as obesity, are closely linked to lifestyle and diet. Recently, the central role played by the intestinal microbiota in human metabolism and in progression of metabolic disorders has become evident. In this context, animal studies and human trials have demonstrated that alterations of the intestinal microbiota towards enhanced energy harvest is a characteristic of the obese phenotype. Many publications, involving both animal studies and clinical trials, have reported on the successful exploitation of probiotics and prebiotics to treat obesity. However, the molecular mechanisms underlying these observed anti-obesity effects of probiotics and prebiotic therapies are still obscure. The aim of this mini-review is to discuss the intricate relationship of various factors, including diet, gut microbiota, and host genetics, that are believed to impact on the development of obesity, and to understand how modulation of the gut microbiota with dietary intervention may alleviate obesity-associated symptoms.     

Dynamics and metamorphosis of an identifiable peptidergic neuron in an insect

Eclosion hormone (EH) is a 7000 Da peptide that triggers ecdysis behavior in insects. In the moth, Manduca sexta, EH is found in two pairs of ventromedial (VM) cells in the brain which send their axons down the ventral nerve cord to a neurohemal site in the proctodeal nerve in the larva and pupa. During adult development, these cells send axon collaterals to the corpora cardiaca where they form a new release site used for adult eclosion. Studies of bioassayable peptide during the 5th larval instar and the larval-pupal transformation revealed that after depletion at ecdysis, the VM cells showed a transient increase in EH found in their cell bodies and axons. By contrast, their terminals in the proctodeal nerve showed a gradual accumulation of peptide followed by a release of over 90% of the stored material at pupal ecdysis. In situ hybridization analysis on whole mounts of the brains showed that the VM cells always contained EH mRNA with increased accumulation during the larval and pupal molting periods with a slight decline just before ecdysis. High levels of EH mRNA were found in brains of diapausing pupae. During the first two-thirds of adult development, mRNA accumulated to high levels, then slowly declined until ecdysis. EH mRNA levels up to 3 days after adult eclosion. At no time was EH mRNA found in the lateral neurosecretory cell cluster previously reported to produce EH for adult eclosion. 1994 John Wiley & Sons, Inc.     

Purification and properties of an endo-inulinase from an Arthrobacter sp.

Extracellular endo-inulinase of Arthrobacter sp. S37 was purified 63-fold, giving a single band on PAGE with activity staining. The Mr was estimated as 75 kDa by SDS-PAGE. The first 31 amino acids of the N-terminal sequence was determined. The endo-inulinase hydrolyzed inulin mainly into inulo-triose (F3), inulo-tetraose (F4) and inulo-pentaose (F5) optimally at pH 7.5 and 50°C. © Rapid Science Ltd. 1998     

Growth and antimicrobial activity of an association of an actinomycete and a green alga

During joint cultivation of the actinomycetes Streptomyces griseus (strains 65 and 744) isolated from the soil and the green algae Chlorella vulgaris larger amount of biomass as compared with solitary axenic culture have been shown. The relation of biomass of actinomycetes S. griseus strain 65 and S. griseus strain 744 and algae in the lichen-like experimentally formed thallom make up 42:1 and 40:1 relatively, i. e. the mass of actinomycetes forms 97-98% from the mass of thalloms. Actinomycetes in the associations with the algae accumulate larger amount of biomass that in the axenic cultures on corresponding medium, whereas the algae produce the same amount of the biomass as the axenic culture under the same conditions. The associations have the antimicrobic properties differed from the axenic cultures established.     

Phloretin - an uncoupler and an inhibitor of mitochondrial oxidative phosphorylation

The effect of phloretin on respiration by isolated mitochondria and submitochondrial particles was studied. In submitochondrial particles, both NADH- and succinate-dependent respiration was inhibited by phloretin. 50% maximum inhibition was reached at phloretin concentrations of 0.1 mM (NADH oxidation) and 0.7 mM (succinate oxidation). In isolated mitochondria, phloretin inhibited glutamate oxidation in both State 3 and State 4; 50% maximum inhibition occurred at about 30 microM. Succinate oxidation is inhibited in State 3 by phloretin, inhibition being half its maximum value at 0.5 mM, but in State 4 it is stimulated about 2-fold by phloretin at a concentration of 0.6 mM. Ascorbate oxidation is stimulated in both State 3 and State 4, maximum stimulation being equal to that obtained with an uncoupler of oxidative phosphorylation. Under all circumstances, phloretin lowered the transmembrane electrical potential difference in isolated mitochondria. These results are discussed in terms of mosaic non-equilibrium thermodynamics. We conclude that phloretin is both an uncoupler and an inhibitor of oxidative phosphorylation.     

Purification and characterization of an amidase from an acrylamide-degrading Rhodococcus sp.

A constitutively expressed aliphatic amidase from a Rhodococcus sp. catalyzing acrylamide deamination was purified to electrophoretic homogeneity. The molecular weight of the native enzyme was estimated to be 360,000. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the purified preparation yielded a homogeneous protein band having an apparent molecular weight of about 44,500. The amidase had pH and temperature optima of 8.5 and 40 degrees C, respectively, and its isoelectric point was pH 4.0. The amidase had apparent K(m) values of 1.2, 2.6, 3.0, 2.7, and 5.0 mM for acrylamide, acetamide, butyramide, propionamide, and isobutyramide, respectively. Inductively coupled plasma-atomic emission spectometry analysis indicated that the enzyme contains 8 mol of iron per mol of the native enzyme. No labile sulfide was detected. The amidase activity was enhanced by, but not dependent on Fe(2+), Ba(2+), and Cr(2+). However, the enzyme activity was partially inhibited by Mg(2+) and totally inhibited in the presence of Ni(2+), Hg(2+), Cu(2+), Co(2+), specific iron chelators, and thiol blocking reagents. The NH2-terminal sequence of the first 18 amino acids displayed 88% homology to the aliphatic amidase of Brevibacterium sp. strain R312.     

Development of an immunological response and changes in the activity of an ectogalactosyltransferase

Ectoglycosyltransferases have been postulated to play a role in intercellular recognition and association. Since considerable interaction among immunocompetent cells is required for the generation of the immune response, it was of interest to examine the involvement of these enzymes in this reaction. Thymic and splenic lymphocytes prepared from normal mice were capable of transferring galactose from uridine diphosphogalactose to endogenous acceptors. The transfer required the presence of Mn²⁺; the optimal concentration was 0.04 M. The K_M values for UDP-galactose were calculated to be 10^?5M for thymic lymphocytes and 0.7 × 10^?5M for splenic lymphocytes. After immunizing the mice with DNP₃-ovalbumin, thymic lymphocytes, but not splenic lymphocytes, showed a significant increase in their ability to catalyze the transfer of galactose as compared with those from nonimmunized mice. Whether the increase in activity can be related to some intercellular reaction of the immune response remains to be determined.     

Identification and characterization of an anterior fat body protein in an insect

We purified a novel protein with a molecular mass of 34 kDa from the Sarcophaga larval fat body. This protein, named AFP (anterior fat body protein), was restricted almost exclusively to the anterior fat body. The AFP content decreased after pupation on disintegration of the fat body tissue. cDNA analysis revealed that this protein consists of 306 amino acid residues and exhibits significant structural similarity with mammalian regucalcin (senescence marker protein-30), a calcium-binding liver protein. However, AFP did not seem to exhibit strong affinity with calcium. These results suggested that a seemingly uniform fat body tissue exhibits a regional difference in its function along the anterior-posterior axis.     

Amplification and transport of an endemic fish disease by an introduced species

The introduction of American shad from the Atlantic to the Pacific coast of North America in the late 1800’s and the subsequent population expansion in the 1980’s resulted in the amplification of Ichthyophonus sp., a Mesomycetozoean parasite of wild marine fishes. Sequence analysis of the ribosomal DNA gene complex (small subunit and internal transcribed spacer regions) and Ichthyophonus epidemiological characteristics indicate a low probability that Ichthyophonus was co-introduced with American shad from the Atlantic; rather, Ichthyophonus was likely endemic to marine areas of the Pacific region and amplified by the expanding population of a highly susceptible host species. The migratory life history of shad resulted in the transport of amplified Ichthyophonus from its endemic region in the NE Pacific to the Columbia River watershed. An Ichthyophonus epizootic occurred among American shad in the Columbia River during 2007, when infection prevalence was 72%, and 57% of the infections were scored as moderate or heavy intensities. The epizootic occurred near the record peak of shad biomass in the Columbia River, and corresponded to an influx of 1,595 mt of infected shad tissues into the Columbia River. A high potential for parasite spillback and the establishment of a freshwater Ichthyophonus life cycle in the Columbia River results from currently elevated infection pressures, broad host range, plasticity in Ichthyophonus life history stages, and precedents for establishment of the parasite in other freshwater systems. The results raise questions regarding the risk for sympatric salmonids and the role of Ichthyophonus as a population-limiting factor affecting American shad in the Columbia River.