Implicit sequence learning in people with Parkinson\u27s disease

Implicit sequence learning involves learning about dependencies in sequences of events without intent to learn or awareness of what has been learned. Sequence learning is related to striatal dopamine levels, striatal activation, and integrity of white matter connections. People with Parkinson’s disease (PD) have degeneration of dopamine-producing neurons, leading to dopamine deficiency and therefore striatal deficits, and they have difficulties with sequencing, including complex language comprehension and postural stability. Most research on implicit sequence learning in PD has used motor-based tasks. However, because PD presents with motor deficits, it is difficult to assess whether learning itself is impaired in these tasks. The present study used an implicit sequence learning task with a reduced motor component, the Triplets Learning Task (TLT). People with PD and age- and education-matched healthy older adults completed three sessions (each consisting of 10 blocks of 50 trials) of the TLT. Results revealed that the PD group was able to learn the sequence, however, when learning was examined using a Half Blocks analysis (Nemeth et al., 2013), which compared learning in the 1st 25/50 trials of all blocks to that in the 2nd 25/50 trials, the PD group showed significantly less learning than Controls in the 2nd Half Blocks, but not in the 1st. Nemeth et al. (2013) hypothesized that the 1st Half Blocks involve recall and reactivation of the sequence learned, thus reflecting hippocampal-dependent learning, while the 2nd Half Blocks involve proceduralized behavior of learned sequences, reflecting striatal-based learning. The present results suggest that the PD group had intact hippocampal-dependent implicit sequence learning, but impaired striatal-dependent learning. Thus, sequencing deficits in PD are likely due to striatal impairments, but other brain systems, such as the hippocampus, may be able to partially compensate for striatal decline to improve performance

Effect of sodium arsenite on peripheral lymphocytes in vitro: individual susceptibility among a population exposed to arsenic through the drinking water

Arsenic (As) contamination in ground water has affected more than 19 countries. Approximately 36 million people in the Bengal delta alone are exposed to this toxicant via drinking water (>50 mg/l) and are at potential health risk. Chronic ingestion of As via drinking water is associated with occurrence of skin lesions, cancer and other arsenicinduced diseases in West Bengal, India. An in vitro cytogenetic study was performed utilizing chromosomal aberrations (CA) in lymphocytes treated with sodium arsenite (0±5 mM) in six symptomatic (having arsenicrelated skin lesions) individuals, six age- and sex-matched As-exposed asymptomatic (no arsenic-related skin lesions) individuals and six control individuals with similar socioeconomic status residing in non-affected districts of West Bengal with no evidence of As exposure. The mean As content in nails and hair was 9.61 and 5.23 mg/g in symptomatic, 3.48 and 2.17 mg/g in asymptomatic and 0.42 and 0.33 mg/g in the control individuals, respectively. The main aim of our study was to determine whether genotoxic effects differed in the lymphocytes of the control (no exposure to arsenic), asymptomatic and symptomatic individuals after in vitro treatment with sodium arsenite. Although both the exposed groups had chronic exposure to As through the drinking water, individuals with skin lesions accumulated more As in their nails and hair and excreted less in urine (127.80 versus 164.15 mg/l). The results show that sodium arsenite induced a signiÆcantly higher percentage of aberrant cells in the lymphocytes of control individuals than in the lymphocytes of both the exposed groups. Within the two exposed groups As induced higher incidences of CA in the symptomatic than the asymptomatic individuals. These results suggest that asymptomatic individuals have relatively lower sensitivity and susceptibility to induction of genetic damage by As compared with the symptomatic individuals

Chromosomal Aberrations in Arsenic-Exposed Human Populations: A Review With Special Reference to a Comprehensive Study in West Bengal, India

For centuries arsenic has played an important role in science, technology, and medicine. Arsenic for its environmental pervasiveness has gained unexpected entrance to the human body through food, water and air, thereby posing a great threat to public health due to its toxic effect and carcinogenicity. Thus, in modern scenario arsenic is synonymous with “toxic” and is documented as a paradoxical human carcinogen, although its mechanism of induction of neoplasia remains elusive. To assess the risk from environmental and occupational exposure of arsenic, in vivo cytogenetic assays have been conducted in arseniasis-endemic areas of the world using chromosomal aberrations (CA) and sister chromatid exchanges (SCE) as biomarkers in peripheral blood lymphocytes. The primary aim of this report is to critically review and update the existing in vivo cytogenetic studies performed on arsenic-exposed populations around the world and compare the results on CA and SCE from our own study, conducted in arsenic-endemic villages of North 24 Parganas (district) of West Bengal, India from 1999 to 2003. Based on a structured questionnaire, 165 symptomatic (having arsenic induced skin lesions) subjects were selected as the exposed cases consuming water having a mean arsenic content of 214.96 Ìg/l. For comparison 155 age-sex matched control subjects from an unaffected district (Midnapur) of West Bengal were recruited. Similar to other arsenic exposed populations our population also showed a significant difference (P ! 0.01) in the frequencies of CA and SCE between the cases and control group. Presence of substantial chromosome damage in lymphocytes in the exposed population predicts an increased future carcinogenic risk by this metalloid

Precancerous and Non-Cancer Disease Endpoints of Chronic Arsenic Exposure: The Level of Chromosomal Damage and XRCC3 T241M Polymorphism

Genetic variants are expected to play an important role in arsenic susceptibility. Our previous study revealed de.cient DNA repair capacity to be a susceptibility factor for arsenicism. T241M polymorphism in XRCC3 (a homologous recombination repair pathway gene) is widely studied for its association with several cancers. We have investigated the association of XRCC3 T241M polymorphism with arsenicinduced precancerous and non-cancer disease outcomes. The present study evaluated the association of T241M polymorphism with arsenic-induced skin lesions, peripheral neuropathy (neurodegenerative changes), conjunctivitis and other ocular diseases. A case-control study was conducted in West Bengal, India, involving 206 cases with arsenic-induced skin lesions and 215 controls without arsenicinduced skin lesions having similar arsenic exposure. XRCC3T241Mpolymorphism was determined using conventional PCR-sequencing method. Chromosomal aberration assay, arsenic-induced neuropathy and ocular diseases were also evaluated. The data revealed that presence of at least one Met allele (Met/Met or Thr/Met) was protective towards development of arsenic-induced skin lesions [OR = 0.45, 95% CI: 0.30–0.67], peripheral neuropathy [OR = 0.49; 95%CI: 0.30–0.82] and conjunctivitis [OR = 0.60; 95%CI: 0.40–0.92]. A signi.cant correlation was also observed between protective genotype and decreased frequency of chromosomal aberrations. Thus the results indicate the protective role of Met allele against the arsenic-induced skin lesions, chromosomal instability, peripheral neuropathy and conjunctivitis

Perfluoroalkane Functionalization of NU-1000 via Solvent-Assisted Ligand Incorporation: Synthesis and CO₂ Adsorption Studies

A new functionalization technique, <u>s</u>olvent-<u>a</u>ssisted <u>l</u>igand <u>i</u>ncorporation (SALI), was developed to efficiently incorporate carboxylate-based functionalities in the Zr-based metal–organic framework, <b>NU-1000</b>. Unlike previous metal node functionalization strategies, which utilize dative bonding to coordinatively unsaturated metal sites, SALI introduces functional groups as charge compensating and strongly bound moieties to the Zr₆ node. Utilizing SALI, we have efficiently attached perfluoro­alkane carboxylates of various chain lengths (C₁–C₉) on the Zr₆ nodes of <b>NU-1000</b>. These fluoro­alkane-functionalized mesoporous MOFs, termed herein <b>SALI-<i>n</i></b>, were studied experimentally and theoretically as potential CO₂ capture materials