Autonomous learning based on cost assumptions: theoretical studies and experiments in robot control

Autonomous learning techniques are based on experience acquisition. In most realistic applications, experience is time-consuming: it implies sensor reading, actuator control and algorithmic update, constrained by the learning system dynamics. The information crudeness upon which classical learning algorithms operate make such problems too difficult and unrealistic. Nonetheless, additional information for facilitating the learning process ideally should be embedded in such a way that the structural, well-studied characteristics of these fundamental algorithms are maintained. We investigate in this article a more general formulation of the Q-learning method that allows for a spreading of information derived from single updates towards a neighbourhood of the instantly visited state and converges to optimality. We show how this new formulation can be used as a mechanism to safely embed prior knowledge about the structure of the state space, and demonstrate it in a modified implementation of a reinforcement learning algorithm in a real robot navigation task.     

Effects of elevated cytoplasmic calcium and protein kinase C on endoplasmic reticulum structure and function in HEK293 cells

In human embryonic kidney (HEK) cells stably transfected with green fluorescent protein targeted to the endoplasmic reticulum (ER), elevation of intracellular Ca2+ ([Ca2+]i) altered ER morphology, making it appear punctate. Electron microscopy revealed that these punctate structures represented circular and branched rearrangements of the endoplasmic reticulum, but did not involve obvious swelling or pathological fragmentation. Activation of protein kinase C with phorbol 12-myristate 13-acetate (PMA), prevented the effects of ionomycin on ER structure without affecting the elevation of [Ca2+]i. These results suggest that protein kinase C activation alters cytoplasmic or ER components underlying the effects of high [Ca2+]i on ER structure. Treatment of HEK cells with PMA also reduced the size of the thapsigargin-sensitive Ca2+ pool and inhibited Ca2+ entry in response to thapsigargin. Thus, protein kinase C activation has multiple actions on the calcium storage and signalling function of the endoplasmic reticulum in HEK cells: (1) reduced intracellular Ca2+ storage capacity, (2) inhibition of capacitative Ca2+ entry, and (3) protection of the endoplasmic reticulum against the effects of high [Ca2+]i.     

Retinol-induced elevation of ornithine decarboxylase activity in cultured rat Sertoli cells is attenuated by free radical scavenger and by iron chelator

We investigated retinol effects in ornithine decarboxylase activity in Sertoli cells. We also tested the hypothesis that free radical scavengers and iron chelators may attenuate the effect of retinol. Sertoli cells isolated from 15-day-old Wistar rats were previously cultured for 48 h and then treated with retinol by 24 h with or without mannitol (1 mM) or 1,10 phenanthroline (100 M). We measured ornithine decarboxylase and catalase activities and malondialdehyde concentrations in response to retinol treatment. In response to 7 M retinol treatment ornithine decarboxylase activity increased 30%. Retinol-induced ornithine decarboxylase activity was significantly decreased by addition of free radical scavenger (mannitol) or iron chelator (1,10 phenanthroline). In addition the same effect was observed in catalase increased activity and in malondialdehyde concentrations. These results suggest that retinol treatment induced ornithine decarboxylase and catalase activity and increased malondialdehyde concentration. These effects appear to be mediate by ROS.     

Salt-tolerant phenol-degrading microorganisms isolated from Amazonian soil samples

Two phenol-degrading microorganisms were isolated from Amazonian rain forest soil samples after enrichment in the presence of phenol and a high salt concentration. The yeast Candida tropicalis and the bacterium Alcaligenes faecoalis were identified using several techniques, including staining, morphological observation and biochemical tests, fatty acid profiles and 16S/18S rRNA sequencing. Both isolates, A. faecalis and C. tropicalis, were used in phenol degradation assays, with Rhodococcus erythropolis as a reference phenol-degrading bacterium, and compared to microbial populations from wastewater samples collected from phenol-contaminated environments. C. tropicalis tolerated higher concentrations of phenol and salt (16 mM and 15%, respectively) than A. faecalis (12 mM and 5.6%). The yeast also tolerated a wider pH range (3-9) during phenol degradation than A. faecalis (pH 7-9). Phenol degradation was repressed in C. tropicalis by acetate and glucose, but not by lactate. Glucose and acetate had little effect, while lactate stimulated phenol degradation in A. faecalis. To our knowledge, these soils had never been contaminated with man-made phenolic compounds and this is the first report of phenol-degrading microorganisms from Amazonian forest soil samples. The results support the idea that natural uncontaminated environments contain sufficient genetic diversity to make them valid choices for the isolation of microorganisms useful in bioremediation.     

Structure and division of the Golgi complex in Trichomonas vaginalis and Tritrichomonas foetus.

We present observations on the fine structure and the division process of the Golgi complex in the protists Trichomonas vaginalis and Tritrichomonas foetus, parasites of the urogenital tract of humans and cattle, respectively. The Golgi in trichomonads is a prominent structure, associated with striated parabasal filaments to which this organelle seems to be connected. We followed by immunofluorescence and electron microscopy the Golgi in interphasic and mitotic cells. Ultrastructural studies were performed using fast-freezing fixation, immunocytochemistry using antisera to the known adhesins AP65 and AP51, cytochemistry (acid phosphatase, Ca++-ATPase, zinc iodide-osmium tetroxide technique (ZIO), for analysis of distribution of the endoplasmic reticulum and Golgi complex, and Thiéry's techniques), routine and serial thin-sections. Three-dimensional reconstruction, NBD-ceramide, fluorescent lectin (WGA) and nocodazole treatments were also used. We demonstrate that: (1) the Golgi in trichomonads is a single-copy organelle; (2) presents a fenestrated structure; (3) is formed by 8-12 saccules; (4) is connected to the parabasal filaments by thin filamentous bridges; (5) by cytochemistry, presents a positive reaction for the lectin WGA, Ca++-ATPase, acid phosphatase, ZIO and Thiéry's techniques; (6) does not appear to break down at any point of the cell cycle; (7) elongates during the cell cycle by lateral growth; (8) is labeled by anti-glutamylated tubulin antibodies, but it is not fragmented by nocodazole treatment; (9) before mitosis, the already elongated Golgi ribbon undergoes progressive medial fission, cisternae by cisternae, starting at the cisternae adjacent to the cell surface and ending with the cis-most cisternae; (10) the Golgikinesis originates two small Golgi ribbons; (11) the Golgi is intensely labeled with the antisera to the AP65 and AP51 adhesins in T. vaginalis, thus seeming to be a key station in the production of adhesins.     

Genetic variation in remnant populations of Dalbergia nigra (Papilionoideae), an endangered tree from the Brazilian Atlantic Forest

BACKGROUND AND AIMS: Dalbergia nigra, known as Brazilian rosewood, is an endangered tree species restricted to the Brazilian Atlantic Forest and has been intensively logged for five centuries due to its high-quality wood. The objective of the present study was to assess the genetic variation and structure in adults and saplings of the species from a large reserve of the Atlantic Forest, the Rio Doce State Park, and from two small surrounding fragments, one better preserved and another with a high degree of anthropogenic disturbance. METHODS: Analyses of genetic variation and structure were conducted by studying allozyme markers. Seven putative enzymatic loci were resolved, five of them being polymorphic. KEY RESULTS: The mean numbers of alleles per locus (A) were 1.93 and 1.73, while the percentages of polymorphic loci (P) were 93 and 73 % for adults and saplings, respectively. Saplings from the fragment with high anthropogenic disturbance exhibited the lowest values of A and P. The fragment that constitutes a conservation area exhibited genetic variation similar to the population from the large reserve. The observed (H(o)) and expected (H(e)) heterozygosities were not significantly different among the three populations. Only sapling populations showed F(ST) values (divergence among populations) significantly different from zero over all studied loci. The fragment with high anthropogenic disturbance exhibited considerable genetic divergence in relation to the above-cited populations. CONCLUSIONS: The evaluated populations displayed mean levels of genetic variation intermediate to those expected for narrow and widespread species. The results suggest that fragments with similar area and geographical distance from a large protected reserve can exhibit different levels of genetic variation, depending on the degree of anthropogenic disturbance. The considerable genetic variation in the protected fragment points to the importance of adequate conservation of small fragments for the preservation of genetic variation in D. nigra.     

Propolis: anti-Staphylococcus aureus activity and synergism with antimicrobial drugs

Propolis is a natural resinous substance collected by bees from tree exudates and secretions. Its antimicrobial activity has been investigated and inhibitory action on Staphylococcus aureus growth was evaluated. The in vitro synergism between ethanolic extract of propolis (EEP) and antimicrobial drugs by two susceptibility tests (Kirby and Bauer and E-Test) on 25 S. aureus strains was evaluated. Petri dishes with sub-inhibitory concentrations of EEP were incubated with 13 drugs using Kirby and Bauer method and synergism between EEP and five drugs [choramphenicol (CLO), gentamicin (GEN), netilmicin (NET), tetracycline (TET), and vancomycin (VAN)] was observed. Nine drugs were assayed by the E-test method and five of them exhibited a synergism [CLO, GEN, NET, TET, and clindamycin (CLI)]. The results demonstrated the synergism between EEP and antimicrobial drugs, especially those agents that interfere on bacterial protein synthesis.     

Prevalence of diarrheagenic Escherichia coli in children with diarrhea in Salvador, Bahia, Brazil

We report the frequency of the different diarrheagenic Escherichia coli (DEC) categories isolated from children with acute endemic diarrhea in Salvador, Bahia. The E. coli isolates were investigated by colony blot hybridization with the following genes probes: eae, EAF, bfpA, Stx1, Stx2, ST-Ih, ST-Ip, LT-I, LT-II, INV, and EAEC, as virulence markers to distinguish typical and atypical EPEC, EHEC/STEC, ETEC, EIEC, and EAEC. Seven of the eight categories of DEC were detected. The most frequently isolated was atypical EPEC (10.1%) followed by ETEC (7.5%), and EAEC (4.2%). EHEC, STEC, EIEC, and typical EPEC were each detected once. The strains of ETEC, EAEC, and atypical EPEC belonged to a wide variety of serotypes. The serotypes of the others categories were O26:H11 (EHEC), O21:H21 (STEC), O142:H34 (typical EPEC), and O:H55 (EIEC). We also present the clinical manifestations and other pathogenic species observed in children with DEC. This is the first report of EHEC and STEC in Salvador, and one of the first in Brazil.     

Microscopical study of experimental wound healing in <Emphasis Type="Italic">Notothenia coriiceps</Emphasis> (Cabeçuda) at 0°C

Notothenia coriiceps (Cabeçuda) is an Antarctic benthic fish frequently found with lesions in the tegument caused by seal predation. We have investigated epidermal repair in these animals by means of a microscopic study of experimental wound healing at 0°C. At 24–48 h after wound induction, mucous exudate and necrotic lining cells covered the wound. At 7–14 days, an epidermal tongue could be discerned, folded at the tip, with intercellular oedema between the tip and the wound border. After 23–30 days, the wound was completely closed and the migrating epidermis, with intercellular oedema, was reduced. By 45–90 days, melanocytes progressively increased in the epidermis but no scales were formed. The inflammatory infiltrate was mainly composed of neutrophils after 7 days, at which time they were mostly replaced by macrophages; lymphocytes and plasma cells were also present. The border epidermis slid towards the centre, folding at the tip and finally fusing to form a diaphragm. The cells of the epidermis began to multiply only after complete closure of the wound. The lack of scale formation on induced and naturally found wounds, even after 90 days, suggests that different mechanisms in wound repair occur at 0°C from those in fish from temperate and tropical environment. This is the first report of successful wound repair at polar temperatures, indicating the adaptation of N. coriiceps to the Antarctic environment.The financial support from CNPq (68.0047/00-0 and 48.0262/00-4 grants), PROANTAR, SECIRM and FAPESP is greatly appreciated. Professor E.L. Cooper is partially supported by funds from the Hewlett Foundation to the Latin American Center, UCLA.