Territorial defense against various food competitors in the Tanganyikan benthophagous cichlid <Emphasis Type="Italic">Neolamprologus tetracanthus</Emphasis>

Territorial defense of nonbreeding female Neolamprologus tetracanthus, a shrimp-eating Tanganyikan cichlid, was investigated. Females defended territories (=home ranges, ca. 1m across) against a variety of intruding fishes. Conspecific females were usually attacked outside the territories, heterospecific benthivores (shrimp eaters) and omnivores near the border of the territories, and piscivores, algae and detritus feeders, and herbivores inside the territories. Females used some parts of the sandy substrate in the territories for foraging (foraging areas). Territorial defense prevented most of the conspecific females and benthivores from intruding into the foraging areas. In omnivores, piscivores, and algae and detritus feeders, about half the intruders were repelled from the foraging areas, although herbivores were infrequently repelled in the areas. Soon after removal of the resident females, many food competitors invaded the foraging areas and eagerly devoured prey, suggesting that the territories are maintained for food resource protection from these competitors. Females are likely to discriminate intruding fishes and change their territorial defense primarily on the basis of the degree of dietary overlap, resulting in monofunctional serial territories.     

Synthesis and possible applications of biotin-linked copper clusters

The trifunctional aziridine XAMA-7 (CAS 57116-45-7) has been used to form crosslinks between a deep red-violet copper cluster of the type Cu(I)8Cu(II)6pen12Cl5- (pen=penicillamine) and molecules with biological activity such as d-biotin and proteins. A complex containing biotin, bovine serum albumin and the copper cluster displayed activity toward affinity columns of avidin on Agarose, and the red-violet pigment was immobilized on the gel. This interaction was completely blocked in gels which had been pretreated with d-biotin carboxylic acid. The free and biologically active versions of the cluster have some potential for biomedical applications. For example, the short-lived positron emitter 64Cu (suitable for positron tomography) may be carried in the cluster's structure. The cluster is paramagnetic, but it is a relatively weak effector of water proton spin-lattice relaxation. Other members of this structural group of inorganic compounds may have better magnetic properties, and the crosslinking reaction with aziridines appears to be generally applicable to the group.     

The interaction of mammalian medium-chain hydrolase with yeast fatty acid synthetase

The prolipoprotein, a secretory precursor of the outer membrane lipoprotein of Escherichia coli, is known to be accumulated in the cell envelope when cells are grown in the presence of a cyclic antibiotic, globomycin. The prolipoprotein was localized in the cytoplasmic membrane when it was separated from the outer membrane by sucrose-density gradient centrifugation. However, when the envelope fraction was treated with sodium sarcosinate, the prolipoprotein was found almost exclusively in the sarcosinate-insoluble outer membrane fraction. The prolipoprotein separated in the cytoplasmic membrane by sucrose-density gradient centrifugation was soluble in sarcosinate and could not form a complex with the outer membrane once solubilized in sarcosinate. Labeling of the two lysine residues at positions 2 and 5 of the prolipoprotein with [3H]dinitrophenylfluorobenzene was enhanced 26-fold when the cells were disrupted by sonication. On the other hand, a tryptic fragment of the ompA protein, which is known to exist in the periplasmic space, increased its susceptibility to [3H]dinitrophenylfluorobenzene only 5.3-times upon disruption of the cell structure. These results indicate that the prolipoprotein accumulated in the presence of globomycin is translocated across the cytoplasmic membrane and interacts with the outer membrane. At the same time, it is attached to the cytoplasmic membrane with its amino-terminal signal peptide in such a way that the amino-terminal portion of the signal peptide containing two lysine residues is left inside the cytoplasm.     

Seahawk: moving beyond HTML in Web-based bioinformatics analysis

Background  

Traditional HTML interfaces for input to and output from Bioinformatics analysis on the Web are highly variable in style, content and data formats. Combining multiple analyses can therfore be an onerous task for biologists. Semantic Web Services allow automated discovery of conceptual links between remote data analysis servers. A shared data ontology and service discovery/execution framework is particularly attractive in Bioinformatics, where data and services are often both disparate and distributed. Instead of biologists copying, pasting and reformatting data between various Web sites, Semantic Web Service protocols such as MOBY-S hold out the promise of seamlessly integrating multi-step analysis.     

Linear acceleration-evoked cardiovascular responses in awake rats.

It has been well documented that vestibular-mediated cardiovascular regulation plays an important role in maintaining stable blood pressure (BP) during postural changes. But the underlying neural mechanisms remain to be elucidated. In particular, because the vestibular stimulation employed in previous animal studies activated both semicircular canals and otolith organs, the contributions of the otolith system has not been studied selectively. The goal of the present study was to characterize cardiovascular responses to natural otolith stimulation in awake rats that were subjected to pure linear motion. In any of the four directions tested, transient linear motion produced a short-latency ( approximately 520 ms) increase in mean BP with a peak of 8.27 +/- 0.66 mmHg and was followed by a decrease in BP. There was an initial small biphasic response in heart rate (HR) that was followed by a longer duration increase. The short-latency increase in BP was absent in rats that were pentobarbital sodium anesthetized or that were labyrinthectomized bilaterally, but it was unaffected by baroreceptor denervation, indicating that it was of otolith origin. The increase in BP was linear acceleration intensity dependent and was not affected by absence of visual cues. Furthermore, the BP response was attenuated by inactivation of the medial and inferior vestibular nuclei by microinjections of muscimol, indicating that the otolith-driven cardiovascular responses are mediated by the neurons in these areas. These results not only demonstrate the otolith specific influences on the cardiovascular system but also they establish the first rodent model for examining the neural mechanisms underlying the otolith-mediated cardiovascular regulation.     

Implication of histidine at the active site of exo-beta-(1-3)-D-glucanase from Basidiomycete sp. QM 806

The enzyme, exo-beta-(1-3)-D-glucanase, (EC 3.2.1-) obtained from a culture filtrate of Basidiomycete sp. QM 806, has been obtained in a highly purified form and preliminary investigations on its mechanism of action have been reported (Peterson, D. R., and Kirkwood, S. (1975) Carbohydr. Res. 41, 273-283). Studies reported in this paper, have provided strong evidence for the role of histidine in the catalytic site of this carbohydrase. Chemical modifications of the amino acid residues in the enzyme with diazotized 5-amino-1H-tetrazole or tetranitromethane caused irreversible loss of enzyme activity which varied according to the time of exposure to, or concentration of the inhibitor. Prior incubation of the enzyme with a substrate considerably reduced the extent of this inhibition. Amino acid analysis of the enzyme treated in these ways clearly indicated that the substrate protected histidine residues from chemical modification by the diazotized 5-amino-1H-tetrazole. Chemical modification of both histidine and tyrosine residues were effected by incubating the enzyme with the inhibitors described above. Although evidence is presented to suggest that tyrosine is not directly involved in the active site of the enzyme (the catalytic site or the binding site), the role of this residue in the maintenance of the enzyme conformation is discussed. Enzyme assays carried out either in aqueous or deuterated buffer systems provided further evidence which is consistent with the proposed enzyme mechanism.