Biomedical subjects

A Catena

Publications and source records attributed to A Catena.

6 recordsLinked to original sources

PubMed1998

Object-based perceptual grouping affects negative priming.

In 5 experiments the authors examine the role of object-based grouping on negative priming. The experiments used a letter-matching task with multiple letters presented in temporally separated prime and probe displays. On mismatch trials, distractor letters in primes were repeated as targets in probes, or distractor and target letters were completely different. Negative priming was shown by slowed responses when distractors were repeated as targets relative to when the stimuli differed. This occurred both when only letters were presented (Experiments 1 and 4) and when letters were surrounded by boxes (Experiment 5). Experiments 2, 3, and 4 showed that negative priming was affected by the grouping of target and distractor letters in prime displays. Negative priming was reduced when 1 of the distractor letters was placed in the target box and 1 was left outside the box; facilitatory priming was observed when both distractor letters appeared in the target box. The data were accounted for in terms of there being (a) object-based competition for visual selection, (b) inhibition of distractor objects that compete for selection with target objects, and (c) activation or inhibition of the identities of all component elements within target or distractor objects.

Adult↗

PubMed1994

Discrimination between and among schizophrenics and other pathologies using a Spanish version of the Whitaker Index of Schizophrenic Thinking.

A Spanish version of Forms A and B of the Whitaker Index of Schizophrenic Thinking (WIST) was administered to two sets of subjects. In the first study, the WIST was administered to 147 subjects of both sexes grouped into one of six categories: acute paranoid schizophrenic, acute nonparanoid schizophrenic, chronic paranoid schizophrenic, chronic nonparanoid schizophrenic, normal, and university student. Results revealed significant group differences; schizophrenics scored significantly higher. Further, chronic schizophrenics, regardless of the existence of paranoia, scored higher than acute subjects. In the second study, a heterogenous group of schizophrenics was compared to heroin addicts and depressed subjects (total N = 93). Significant group differences again were noted; the schizophrenics scored higher than the two other clinical samples.

Adult↗

PubMed1992

Successive negative contrast in one-way avoidance learning in rats.

In three experiments, successive negative contrast was examined in one-way avoidance learning. Reward magnitude in first (pre-shift) and second (post-shift) phases was manipulated by time spent in the safe compartment. Experiment 1 demonstrated that when time in the danger compartment was held constant, a group shifted from a large reward--30 sec spent in the safe compartment--to a small reward--1 sec--showed poor performance and longer response latency than a group conditioned with the small reward in both phases. Experiment 2 replicated this effect with a less intense shock and also demonstrated that a group shifted from large to small reward performed more poorly than a group exposed to large reward--30 sec--in both phases. Finally, Experiment 3 showed that changes in intertrial interval, defined as total time spent in the safe compartment and the danger compartment before the onset of the warning signal, were not responsible for this contrast effect. These results suggest that time spent in a safe place can act as appetitive incentive during one-way avoidance learning.

Animals↗

PubMed1985

In vitro adherence of Lactobacillus species to vaginal epithelial cells.

Because of the reported use of yogurt douches for the treatment of vaginitis, the adherence of Lactobacillus species to normal human vaginal epithelial cells was tested by in vitro methods. L. acidophilus and L. bulgaricus isolated from three commercial yogurts were compared to L. acidophilus, L. fermentum, L. cellobiosus, and L. casei isolated from clinical specimens and from American Type Culture Collection cultures. L. acidophilus isolated from Lactinex tablets was also tested. No significant difference was found among the 19 clinical isolates, the American Type Culture Collection cultures, and the Lactinex isolate, but all showed significantly higher (p less than 0.01) adherence than any Lactobacillus isolated from yogurt. The presence of Gardnerella vaginalis, which adheres strongly to vaginal epithelial cells, was found to interfere with the adherence of lactobacilli from all sources studied.

Adhesiveness↗

PubMed1980

Antigenic relationships and rapid identification of Peptostreptococcus species.

Antisera against whole cells of each Peptostreptococcus species (P. anaerobius, P. micros, P. parvulus, and P. productus) were produced in rabbits. When these antisera were reacted against sonically disrupted cells and culture supernatant fluids in Ouchterlony tests, lines of identity were obtained among the antigens from all the species and uninoculated culture medium. When the antisera were subsequently absorbed with the dehydrated culture medium used to grow the peptostreptococci, all cross-reactions in heterologous antigen-antibody combinations were eliminated, leaving only species-specific precipitin arcs. These absorbed antisera, specific for each Peptostreptococcus species by Ouchterlony tests, were used for rapid identification studies. Staphylococcus aureus-bearing protein A was sensitized with each absorbed antiserum. These reagents produced specific coagglutination reactions with suspensions of each Peptostreptococcus reference strain and with 16 clinical isolates. No cross-reactions occurred with the Streptococcus intermedius, Peptococcus magnus, or Peptococcus asaccharolyticus strains tested.

Agglutination Tests↗

PubMed1970

Physiological and kinetic studies with anthranilate synthetase of Bacillus alvei.

Anthranilate synthetase from Bacillus alvei was partially purified by ammonium sulfate fractionation and was stabilized by glycerol. The reaction mechanism of the enzyme was found to be sequential with respect to substrate, and the enzyme formed a hydroxamic acid in the absence of Mg(++). The K(m) for chorismic acid was 1.25 x 10(-4)m, and the K(m) for l-glutamine was 5.5 x 10(-4)m. Enzyme activity was inhibited by tryptophan noncompetitively with respect to chorismic acid and uncompetitively with respect to l-glutamine. An analysis of the inhibition patterns indicated that tryptophan may act as a dead end inhibitor and bind at the catalytic site. Enzyme activity could be completely inhibited in vitro and in vivo under the appropriate conditions, and enzyme synthesis was sensitive to repression by tryptophan. A sedimentation coefficient of 5.5S and an estimated molecular weight of 90,000 were obtained for the enzyme.

Bacillus↗