Response and place learning in crayfish spatial behavior.

Previous studies have demonstrated that animals use both environmental cues and egocentric information when orienting in mazes or nature. These two strategies have been examined separately in some species, yielding information on the specific properties associated with each. We examined spatial learning in crayfish (Orconectes rusticus) using an apparatus that required animals to orient under four different conditions: using egocentric (response) cues alone, response cues with inconsistent external (place) cues present, place cues with inconsistent response cues present, and place cues with consistent response cues present. Results demonstrated that crayfish could successfully learn a maze task using response cues alone and when external visual and tactile cues provided inconsistent information. Animals were markedly less successful at learning the task using place cues while disregarding inconsistent response information. We also found that more animals learned successfully when response and external cues were presented in a redundant format where both cues indicated the correct turn. Finally, we found that some crayfish were able to learn a single reversal when trained using response information alone and when response and external cues were presented in the redundant format. We consider these results in the light of findings from other species, and ideas on learning strategy properties, ecological relevance of strategies, and the possible role of stress coping style in crayfish learning.

TRAP transporters: a new family of periplasmic solute transport systems encoded by the dctPQM genes of Rhodobacter capsulatus and by homologs in diverse gram-negative bacteria.

The dct locus of Rhodobacter capsulatus encodes a high-affinity transport system for the C4-dicarboxylates malate, succinate, and fumarate. The nucleotide sequence of the region downstream of the previously sequenced dctP gene (encoding a periplasmic C4-dicarboxylate-binding protein) was determined. Two open reading frames (ORFs) of 681 bp (dctQ) and 1,320 bp (dctM) were identified as additional dct genes by insertional mutagenesis and complementation studies. DctQ (24,763 Da) and DctM (46,827 Da) had hydropathic profiles consistent with the presence of 4 and 12 potential transmembrane segments, respectively, and were localized in the cytoplasmic membrane fraction after heterologous expression of the dctQM ORFs in Escherichia coli. DctP, DctQ, and DctM were found to be unrelated to known transport proteins in the ABC (ATP-binding cassette) superfamily but were shown to be homologous with the products of previously unidentified ORFs in a number of gram-negative bacteria, including Bordetella pertussis, E. coli, Salmonella typhimurium, Haemophilus influenzae, and Synechocystis sp. strain PCC6803. An additional ORF (rypA) downstream of dctM encodes a protein with sequence similarity to eukaryotic protein-tyrosine phosphatases, but interposon mutagenesis of this ORF did not result in a Dct- phenotype. Complementation of a Rhizobium meliloti dctABD deletion mutant by heterologous expression of the dctPQM genes from R. capsulatus demonstrated that no additional structural genes were required to form a functional transport system. Transport via the Dct system was vanadate insensitive, and in uncoupler titrations with intact cells, the decrease in the rate of succinate transport correlated closely with the fall in membrane potential but not with the cellular ATP concentration, implying that the proton motive force, rather than ATP hydrolysis, drives uptake. It is concluded that the R. capsulatus Dct system is a new type of periplasmic secondary transporter and that similar, hitherto-unrecognized systems are widespread in gram-negative bacteria. The name TRAP (for tripartite ATP-independent periplasmic) transporters is proposed for this new group.

Excited States of gold(i) compounds, luminescence and gold-gold bonding.

It has long been established by Khan that the superoxide anion, O(2) (-), generates singlet oxygen, O(2) (1)Delta(g), during dismutation. Auranofin, gold-phosphine thiols, beta-Carotene, and metal-sulfur compounds can rapidly quench singlet O(2). The quenching of the O(2) (1)Delta(g), which exists at 7752 cm(-1) above the ground state triplet, may be due to the direct interaction of the singlet O(2) with gold(I) or may require special ligands such as those containing sulfur coordinated to the metal. Thus we have been examining the excited state behavior of gold(I) species and the mechanisms for luminescence. Luminescence is observed under various conditions, with visible emission ranging from blue to red depending on the ligands coordinated to gold(I). Triplet state emission can be found from mononuclear three coordinate Au(I) species, including species which display this behavior in aqueous solution. A description is given of the luminescent three coordinate TPA (triazaphosphaadamantane) and TPPTS (triphenylphosphine-trisulfonate) complexes, the first examples of water soluble luminescent species of gold(I).

Physiology of turkey embryos during pipping and hatching I. Hematology.

Blood samples were collected from turkey embryos during pipping and hatching, an age which corresponds to a time of elevated embryonic mortality. Samples were analyzed for erythrocyte counts (RBC), packed cell volume (PCV), hemoglobin concentration (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). An increase in RBC was significant (P less than .05) during piping and hatching. The PCV increased significantly (P less than .01) until pipping occurred and then declined significantly through hatching. The Hb concentration also increased significantly (P less than .05) as pipping and hatching occurred. The MCV declined significantly as development proceeded. Both MCH and MCH declined significantly (P less than .05) until the onset of pipping at which time both increased significantly (P less than .05) through hatching.

Physiology of turkey embryos during pipping and hatching II. selected blood parameters.

Blood samples from turkey embryos taken at days 24 to 28 of incubation, a time of great embryonic mortality were analyzed for plasma calcium, magnesium, potassium, total plasma protein, lipid, and glucose concentrations. Plasma calcium increased significantly (P less than .05) until pipping, after which it declined until hatching. Plasma magnesium declined significantly (P less than .01) only at hatching. Potassium concentration declined significantly (P less than .01) as the hatched state approached. Plasma total protein concentration decreased until the onset of pipping, after which the concentration increased significantly (P less than .01) until hatching. Plasma total lipid concentrations decreased significant (P less than .01) during pipping, but the concentration remained constant while the poult emerged from the shell. Plasma glucose concentration increased significantly (P less than .01) prior to pipping and again at hatching.