Sign tracking in cuttlefish (Sepia officinalis).

Two groups of cuttlefish (Sepia officinalis) were used to demonstrate classical conditioning in this species and to determine whether the resulting approach response would be that of sign tracking or goal tracking. For cuttlefish in the paired condition, a flashing light was presented at one end of a long tank followed by food dropped into the center of the tank. For cuttlefish in the unpaired condition, food was dropped into the center of the tank either before or after the flashing-light stimulus. Paired cuttlefish oriented to the light, positioned themselves within striking distance, and occasionally attacked the light. Unpaired cuttlefish showed no reliable response to either stimulus. The results demonstrate that cuttlefish are capable of signal learning and that, under the conditions tested, cuttlefish sign tracked. This study begins a comparative analysis of learning in cuttlefish and offers a possible ecological advantage for sign-tracking behavior.

Upstream regulatory elements controlling expression of the Entamoeba histolytica lectin.

Entamoeba histolytica genomic organization and putative promoter elements appear to be distinct from both metazoan and better characterized protozoan organisms. The recent development of DNA-mediated transfection for E. histolytica enabled characterization of cis-acting promoter elements required for gene expression. A deletion and replacement analysis was conducted on the promoter of an E. histolytica gene encoding the heavy subunit of the N-acetyl-beta-D-galactosamine-specific adhesin (hgl5). Deletion of the DNA from -1000 bases to -272 bases upstream from the start of transcription of hgl5 did not decrease reporter gene expression. Subsequent nested deletions and 10-bp replacement mutagenesis identified four positive upstream regulatory elements between bases -219 to -200, -189 to -160, -69 to -60, and -49 to -40. A negative upstream regulatory element between bases -89 to -80 was conserved upstream of three other E. histolytica genes. Mutation of the previously unidentified 'GAAC' element conserved within the putative core promoter decreased reporter gene expression by 75%. Site directed mutagenesis of the putative TATA element decreased reporter gene expression by greater than 50%, while mutation of the putative initiator element resulted in a more modest decrease. This analysis suggests that E. histolytica promoters are unlike other protozoan promoters, with AT-rich upstream regulatory elements, a non-consensus TATA element, the "GAAC' element, and an unusual initiator element.

Physical mapping and expression of gene families encoding the N-acetyl D-galactosamine adherence lectin of Entamoeba histolytica.

Adherence of the enteric protozoan parasite Entamoeba histolytica is mediated by an N-acetyl D-galactosamine (GalNAc)-specific lectin, a heterodimer of heavy (170 kDa) and light (35/31 kDa) subunits. The gene families encoding the lectin subunits were characterized using clamped homogeneous electric field (CHEF) gel electrophoresis in the strain HM1:IMSS. The heavy subunit was shown to be encoded by a family of five hgl genes, which were physically mapped to five distinct HindIII restriction fragments. The light subunit was shown to be encoded by a family of lgl genes located at six loci in the genome. Heavy and light subunit genes did not appear to be linked. Partial sequences of new members of the hgl and lgl gene families were obtained. Several different strains of E. histolytica were found to contain multiple hgl loci in their genomes. Expression of hgl and lgl genes in HM1:IMSS trophozoites was examined under different growth conditions using the reverse transcription-polymerase chain reaction (RT-PCR). mRNA transcripts were detected from three hgl genes and three lgl genes, with no significant differences between cultured amoebae and amoebae from liver abscesses. The complexity of GalNAc lectin gene expression observed suggests distinct biological functions for the products of the individual genes during pathogenesis.

Animal research in psychology. More than meets the eye of the general psychology student.

The general psychology course provides a unique opportunity to present the science of psychology to a wide audience. Informing the general public about the importance of animal research in psychology is especially important given contemporary concerns about animal rights and animal welfare. A study of 8 leading introductory psychology textbooks indicated that with the exception of principles of conditioning and learning, the contributions of animal research to psychology were often not explicitly acknowledged. In addition, major findings from animal research were frequently presented as if they had been obtained with humans. In obscuring the contributions of animal research, introductory psychology textbooks miss the opportunity to ensure that public policy be based on accurate information about the significance of this research to many areas of psychological science.

Transient transfection of the enteric parasite Entamoeba histolytica and expression of firefly luciferase.

Development of DNA-mediated transfection in Entamoeba histolytica will facilitate basic research toward the control of this protozoan parasite. A transient transfection system was established by using the firefly luciferase gene ligated to the 5' and 3' flanking regions of the amebic hgl1 gene. The optimal construct tested encoded an hgl1-luciferase fusion protein and contained 1 kb of 5' flanking sequence with 16 bases of coding sequence from the hgl1 gene ligated in-frame to the luciferase start codon and 2.3 kb of 3' flanking sequence from hgl1 ligated 3' to the luciferase stop codon. Optimal electroporation conditions in strain HM-1:IMSS trophozoites when using this construct were 500 microF and 500 V/cm, which resulted in luciferase activity up to 5000-fold above background 9-12 hr after electroporation. Constructs that contained the luciferase gene without amebic flanking sequences or that contained a simian virus 40 promoter, enhancer, and polyadenylylation signal produced only background levels of luciferase activity. The ability to introduce and express genes in amebae will now permit a genetic analysis of the virulence of this organism, which remains a serious threat to world health.

Analysis of the gene family encoding the Entamoeba histolytica galactose-specific adhesin 170-kDa subunit.

The 170-kDa or heavy subunit of the galactose binding adhesin of Entamoeba histolytica is seminal in target cell binding and lysis. To determine the existence and complexity of the 170-kDa subunit gene family, hgl, an amebic genomic library in lambda phage was hybridized with DNA fragments from the 5' or 3' ends of hgl1. Termini from three distinct heavy subunit genes were identified including hgl1, hgl2, and a third, unreported gene designated hgl3. The open reading frame of hgl3 was sequenced in its entirety. Non-stringent hybridization of a genomic Southern blot with heavy subunit specific DNA labeled only those bands predicted by hgl1-3. The amino acid sequence of hgl3 was 95.2% identical to hgl1 and 89.4% identical to hgl2. All 97 cysteine residues present in the heavy subunit were conserved in hgl1-3. Analysis of amebic RNA showed that all three heavy subunit genes were expressed in the amebae and that hgl message became less abundant as the amebae entered a stationary growth phase.

Contributions to the history of psychology: XCV. Possible relations between theories of evolution and animal learning.

It is proposed that the dominance of continuity learning theory as set against noncontinuity learning theory during the middle third of the 20th century rested importantly on its derivation from Darwin's theory of evolution. The kinship is shown in several ways. First, Thorndike and Hull echoed the principle of natural selection in their belief that behaviors underwent gradual modification because acts that were attended steadily by favorable consequences tended to occur with increasing frequency. Second, they denied both nonphysical explanations of behavior and a priori purposes which might guide that behavior. Third, the laws of learning were said to hold for all organisms. It is argued that the continuity approach may have enjoyed success because it was consistent with the Darwinian world view. Had punctualist, rather than gradualist, explanations of evolution come to the fore in the late 19th century, learning theories might have proceeded quite differently with the dominance of non-continuity approaches.

Danger at the waterhole.

The effects of declining accessibility of water and risk of electric shock on drinking patterns in rats were examined. Rats chose between two conditions to obtain their daily intake of water. In one condition, accessibility of water decreased systematically. In the other condition, water was readily accessible, but responses occasionally were followed by electric shock. Both variables affected drinking patterns similarly. As accessibility to water decreased, the number of drinking bouts initiated decreased but the quantity of water consumed increased. In response to risk of electric shock, the number of drinking bouts decreased but bout size increased. Results are considered in light of findings by Fanselow, Lester, and Helmstetter, (1988), Collier, Hirsch, and Hamlin (1972), and Marwine and Collier (1979).

New estimate for storage time in sensory memory.

Sperling in 1960 reported information in sensory storage remained for about one sec. In 1974 Phillips reported that information in sensory storage passed on to short-term visual memory after 100 msec. To distinguish between these alternatives, 55 subjects received 36 trials in which two matrices of letters, familiar shapes, or non-familiar shapes were presented successively in a recognition task. The interstimulus interval varied systematically. Results showed that as the interval increased, performance decreased. Further, memory for letters and familiar shapes was superior. Finally, there were no differences among letters, familiar shapes, and non-familiar shapes at the .25-sec. interval. At the .5-sec. interval, performance for familiar shapes was superior to performance for non-familiar shapes. It was concluded that information transfers to short-term visual storage after .25 sec.

Immediate and long-term retention for pictorial and verbal stimuli.

Although nouns of high imagery are generally recalled better than nouns of low imagery, both Palermo and Yuille have shown that retention for the former decreases with time. The present study tested the hypothesis that this decreased effectiveness occurs because images stored in long-term memory are accessible only through their verbal labels. 64 subjects were presented pictures and later asked to draw them or provide one-word descriptions. Other subjects were presented words and asked to recall them or draw representational pictures. Recall was tested immediately and 48 hr. later. Regardless of recall mode, subjects viewing pictures showed significantly greater recall than subjects viewing words, and for all subjects immediate recall was better.

Growth orientation of heart cells on nylon monofilament. Determination of the volume-to-surface area ratio and intracellular potassium concentration.

A new method is described for orienting the growth of embryonic chick heart cells as thin annuli about nylon monofilament. Analytical measurements of cell water, intracellular potassium, cell volume, and cell surface area incorporate several new techniques and provide the quantitative basis for characterizing the respective cell types in the preparation. The measurements support the hypothesis that tissue culture methodology does not alter the morphological and physiological properties of cardiac muscle cells. The preparations are ideally suited for radiotracer studies since tissue mass can be increased while retaining a relatively short diffusional distance.

Synthetic strands of cardiac muscle. Formation and ultrastructure.

Spontaneously active bundles of cardiac muscle (synthetic strands) were prepared from isolated cells of 11-13-day old embryonic chick hearts which were disaggregated with trypsin. Linear orientation of the cells was obtained by plating them on agar-coated culture dishes in which either grooves were cut in the agar film or a thin line of palladium was deposited over the agar. The influence of cell-to-cell and cell-to-substrate interactions was observed with time lapse cinematography and the formation of the synthetic strand was shown to involve both random and guided cell movements, enlargement of aggregates by accretion and coalescence, and the compact linear arrangement of cells along paths of preferential adhesion. Electron microscope investigations of these strands showed that a dispersed population of heart cells organized into an inner core of muscle cells and an outer sheath of fibroblast-like cells. The muscle cells contained well-developed, but widely spaced myofibrils, a developing sarcoplasmic reticulum associated in part with the myofibrils and in part with the sarcolemma, an abundance of nonmembrane bound ribosomes and glycogen, and a prominent Golgi complex. Numerous specialized contacts were observed between the muscle cells in the strand, e.g., fasciae adherentes, desmosomes, and nexuses. A distinct type of muscle cell characterized by its pale appearance was regularly observed in the strand and was noted to be similar to Purkinje cells described in the adult avian conduction system and in developing chick myocardium. The present findings were compared with other observations of the developing myocardium, in situ, and it was concluded that, by a number or criteria, the muscle cells of the strand were differentiating normally and suitably organized for electrophysiological studies.

Synthetic strands of cardiac muscle: growth and physiological implication.

Cardiac muscle cells obtained fronm disaggregated embryonic chick hearts were cultured on difjerentially treated oriented substrata. Subsequent cell reaggregation, growth, and attachmwent produced linearly organized strands of cardiac muscle with dimensions suitable for electrophysiological analysis. Along the strand, areas that contained few muscle cells demonstrated reduced conduction velocity and were subject to propagation failure.