Nucleus accumbens dopamine depletion impairs both acquisition and performance of appetitive Pavlovian approach behaviour: implications for mesoaccumbens dopamine function

The involvement of mesoaccumbens dopamine in adaptive learning and behaviour is unclear. For example, dopamine may act as a teaching signal to enable learning, or more generally modulate the behavioural expression, or selection, of an already-learned response. The present study investigated the involvement of the mesoaccumbens dopamine system in a fundamental form of learning: Pavlovian conditioning. In this case, the temporal association of a previously neutral visual stimulus and a biologically significant unconditioned stimulus (US), subsequently led to the production of the conditioned response (CR) of discriminated approach behaviour directed toward the conditioned stimulus (CS+), relative to a control (CS-) stimulus. 6-hydroxydopamine lesions of the nucleus accumbens (NAcc), leading to approximately 80% reductions in tissue dopamine, were made at varying time points in four experimental groups of rats, either before or subsequent to the acquisition of the CR. NAcc dopamine depletion produced long-term neuroadaptations in dopamine function 2 months after surgery, and profoundly impaired discriminated Pavlovian approach regardless of when the lesion was made. Thus, NAcc dopamine not only plays a role in conditioned behavioural activation, but also in making the appropriate discriminated response i.e. the direction of response. Further, acquisition lesions produced a far greater impact on discriminated approach than performance lesions. This difference in lesion-induced impairment implies that mesoaccumbens dopamine may play differential roles in the learning and performance of preparatory Pavlovian conditioning.     

Neurological manifestations and neuroradiological presentation of Erdheim-Chester disease: report of 6 cases and systematic review of the literature

Erdheim-Chester disease (ECD) is a rare, non-Langerhans form of histiocytosis of unknown etiology that affects multiple organs. We report 6 cases of ECD with neurological involvement and neuroradiological abnormalities on brain MRI. A literature review revealed 60 other cases of ECD with neurological involvement. We therefore analyzed 66 ECD patients with neurological involvement. Cerebellar and pyramidal syndromes were the most frequent clinical manifestations (41% and 45% of cases), but seizures, headaches, neuropsychiatric or cognitive troubles, sensory disturbances, cranial nerve paralysis or asymptomatic lesions were also reported. Neurological manifestations were always associated with other organ involvement, especially of bones (at least 86%) and diabetes insipidus (47%). Neurological involvement was responsible for severe functional handicaps in almost all patients and was responsible for the death of 6 of the 66 patients (9%). Neuroradiological findings could be separated into three patterns: the infiltrative pattern (44%), with widespread lesions, nodules or intracerebral masses, the meningeal pattern (37%), with either thickening of the dura mater or meningioma-like tumors, and the composite pattern (19%), with both infiltrative and meningeal lesions. Received in revised form: 21 October 2005     

Angioimmunoblastic T-cell lymphoma: clinical and laboratory features at diagnosis in 77 patients

We retrospectively analyzed 77 patients with pathologically diagnosed angioimmunoblastic T-cell lymphoma from a single city. There were 43 men and 34 women; the median age was 64.5 years (range, 30-91 yr). Average time between first symptoms of the disease and diagnosis was 3.6 months. At diagnosis, peripheral nodes were present in all but 1 patient, and were generalized in 90% of cases. Constitutional symptoms were reported in 77% of cases and spleen enlargement in 51%. A cutaneous eruption--morbilliform, urticarial, or more polymorphic--was present in 45% of patients; in one-third of them, the eruption occurred after drug administration. Other clinical manifestations included pleuritis (22%); arthralgia or arthritis (17%); ear, nose, and throat involvement (14%); central or peripheral neurologic manifestations (10%); and ascites (5%). Most patients presented with advanced disease at diagnosis (bone marrow involvement in 60% of cases).The main laboratory abnormalities were elevated lactate dehydrogenase levels (71%), inflammatory syndrome (67%), hypergammaglobulinemia (50%), anemia (51%), and lymphopenia (52%). Auto- or disimmune manifestations were reported in one-third of patients: autoimmune hemolytic anemia was present at diagnosis in 19% of patients and thrombocytopenic purpura in 7%. Documented vasculitis was described in 12% of cases. Clonality was analyzed in lymph nodes in 47 patients: T-cell and B-cell clones were found in 45 (96%) and 20 (45%) patients, respectively. Chromosomal abnormalities were identified in 62% of cases: trisomies 3, 5, 18, 19, additional X chromosome, and deletion of chromosome 7 were the most common abnormalities. The current study underlines the diversity of presenting manifestations of angioimmunoblastic T-cell lymphoma.     

Effects of selective excitotoxic lesions of the nucleus accumbens core,anterior cingulate cortex,and central nucleus of the amygdala on autoshaping performance in rats

The nucleus accumbens core (AcbC), anterior cingulate cortex (ACC), and central nucleus of the amygdala (CeA) are required for normal acquisition of tasks based on stimulus-reward associations. However, it is not known whether they are involved purely in the learning process or are required for behavioral expression of a learned response. Rats were trained preoperatively on a Pavlovian autoshaping task in which pairing a visual conditioned stimulus (CS+) with food causes subjects to approach the CS+ while not approaching an unpaired stimulus (CS-). Subjects then received lesions of the AcbC, ACC, or CeA before being retested. AcbC lesions severely impaired performance; lesioned subjects approached the CS+ significantly less often than controls, failing to discriminate between the CS+ and CS-. ACC lesions also impaired performance but did not abolish discrimination entirely. CeA lesions had no effect on performance. Thus, the CeA is required for learning, but not expression, of a conditioned approach response, implying that it makes a specific contribution to the learning of stimulus-reward associations.     

Les effets thermiques associés à la transition vetreuse de films de poly(téearéphatalate d'éthylène)

Differential scanning calorimetry and thermomechanical analysis are used for examining the thermal behaviour of amorphous poly(ethylene terephthalate) films in the glass-transition range. By variation of the heating rate between 0,2 and 100 K. · min^?1, it is possible to obtain either an exotherm associated with a shrinkage, or an endotherm, or both of these phenomena. It is found that very low heating rates not only give rise to a retardation mechanism but also to a molecular rearrangement.     

Hepatitis C virus infection in cameroon: A cohort-effect

A hepatitis C virus (HCV) serological study conducted in 2003 on 1,434 individuals in Yaounde and other HCV seroepidemiological studies on 2,066 sera sampled between 1993 and 1997 in four geographically distinct rural areas (Ntem, Mekas, Yokadouma, and Nditam) in Cameroon, are described. Two patterns of HCV seroprevalence were observed. The first pattern, represented by Nditam and Yokadouma populations, showed low HCV seroprevalence rates (2.9% and 3.3%, respectively) increasing moderately with age (9.0% and 16.7% after age 50). The second pattern showed high seroprevalence rates (6.9% for Yaounde, 14.4% and 16.7% for Ntem and Mekas, respectively). These rates increased dramatically with age (32.8%-49.5% after age 50). The age-specific anti-HCV prevalence curve of the 1993 Mekas survey paralleled those of the 1997 Ntem and 2003 Yaounde surveys. Using the year of birth as the x-axis, the three curves closely matched each other. This clearly indicates a cohort effect for which the seroprevalence trends are clearly related with the year of birth, rather than the age. The highest prevalence was observed among people born around 1940.     

The prevalence of hairy leukoplakia in HIV seropositive and HIV seronegative immunocompromised patients.

The prevalence of hairy leukoplakia was determined among 176 symptomatic HIV seropositive patients seen at the outpatient department of the Institute of Tropical Medicine in Antwerp, Belgium. Moreover, systematic tongue biopsies were performed during postmortem examination of 21 patients with AIDS, 100 HIV seronegative immunocompromised patients with haematologic or other malignancies and 100 HIV seronegative non-immunocompromised patients who died at the University Hospital Antwerp. Hairy leukoplakia was observed in 52 (29.5%) of the outpatients, but only in one (5%) of the AIDS patients in the postmortem study (P = 0.03). An explanation for this difference may be that significantly more AIDS patients who died had received either acyclovir or ganciclovir during the 3 months prior to the postmortem examination than the HIV seropositive outpatients during the 3 months prior to examination. Hairy leukoplakia occurred more often in Caucasian homosexual men with HIV infection (38%) than among heterosexual Africans with HIV infection (17%) (P = 0.06). Hairy leukoplakia was observed in none of the HIV seronegative patients.