Online data visualization using the neural gas network.

A high-quality distance preserving output representation is provided to the neural gas (NG) network. The nonlinear mapping is determined concurrently along with the codebook vectors. The adaptation rule for codebook positions in the projection space minimizes a cost function that favors the trustworthy preservation of the local topology. The proposed visualization method, called OVI-NG, is an enhancement over curvilinear component analysis (CCA). The results show that the mapping quality obtained with OVI-NG outperforms the original CCA, in terms of the trustworthiness, continuity, topographic function and topology preservation measures.     

GABA and its neural regulation in rat brown adipose tissue

Summary By using a radioreceptor assay GABA was detectable in rat interscapular brown adipose tissue (IBAT), the levels being 1% those of CNS and 10-fold those of peripheral plasma. Injection of the glutamic acid decarboxylase (GAD) inhibitor 3-mercaptopropionic acid lowered IBAT GABA levels by about half while injection of the GABA transaminase inhibitor -acetylenic GABA increased them by 230%. Rats kept at 4C for 14 days exhibited IBAT GABA levels that were about half those found at 22C. Accumulation of IBAT GABA after -acetylenic GABA increased by 2-fold in cold-exposed rats. Sympathetic denervation of IBAT prevented the effect of the cold environment on GABA content and impaired that on GABA accumulation. GAD activity was detectable in IBAT homogenates and isolated brown adipocytes. Exposure of rats to cold increased V_max of GAD without modifying its Km, regardless of intactness of innervation. In binding studies with³H-GABA as a ligand, two types of sites were uncovered of K_D=14 and 146 nM, respectively. In the presence of 2.5 mM Ca²⁺ bicuculline and baclofen were 57 and 46% as effective as GABA to displace³H-GABA from IBAT binding sites. The results indicate existence, possible synthesis and type A and B receptors of GABA in rat IBAT.     

Response to Dr. Nicholas Foray’s commentary on the paper by Rousseau et al. entitled “Efficacy of intracerebral delivery of cisplatin in combination with photon irradiation for treatment of brain tumors”

Journal of Neuro-Oncology -     

Locoregional intravenous anesthesia]

OBJECTIVE: To analyse current data on intravenous regional anaesthesia (IVRA), its benefits and drawbacks. DATA SOURCES: Articles were obtained from a Medline search using the following search terms: 'intravenous regional anaesthesia', alone or combined with 'local anaesthetic agents', 'toxicity'. STUDY SELECTION: Following articles in English and in French have been selected: main articles, original articles, update and review articles, letters to the editor and recent editorials. DATA EXTRACTION: Physiopathological and pharmacological data were extracted for involved mechanisms and means for improving this technique. DATA SYNTHESIS: IVRA is a reliable and efficient technique with a lower cost than general anaesthesia and well adapted for limb surgery in the ambulatory patient. Depending on the site of the surgical field, the pneumatic tourniquet is set either on the arm, forearm or wrist for the upper limb or thigh, calf or ankle for the lower limb. When set in periphery, less local anaesthetic agent is required. A wide tourniquet requires a lower inflation pressure than a double cuff tourniquet. A single cuff is as efficient as a dual cuff if shape, size and inflating pressure are appropriate. The limb occlusion pressure (LOP) is the minimal pressure required to occlude blood flow. It is assessed with either a pulse oximeter or Doppler for determination of the lowest cuff inflating pressure. The cuff is inflated to 50 mmHg above LOP. Oozing in the surgical field can be decreased by the re-exsanguination technique. Currently, lidocaine is the only local anaesthetic released in France for IVRA. Addition of a muscle relaxant, a NSAID or clonidine allows the dose of local anaesthetic agent to be decreased and improves postoperative analgesia.     

Different evaluations of the health related quality of life in dialysis patients

BACKGROUND: Sometimes patients on dialysis treatment cannot express their health-related quality of life (HRQoL); and therefore, it is necessary to use the assessment made by their carers. The purpose of this study was to evaluate the agreement between dialysis patients' HRQoL and the assessment made by their carers, and to investigate which variables were associated with the differences found. METHODS: Two hundred and twenty-two pairs of patients and carers were selected from 14 dialysis units. Patients' HRQoL was evaluated by the patients themselves and by their family carer (FAM), nurse (NUR) and physician (PH) using the Karnofsky scale (KS) and the EuroQOL5D (EQ5D) scale. Patients and their family carers answered the Medical Outcome Survey 36-Item Short Form Health Survey (SF-36), and the family carers answered the Zarit burden interview. Physicians scored the patients' comorbidity index and nurses evaluated the Barthel index (BI). RESULTS: The intraclass correlation coefficients (ICC) between the ratings provided by patients and their carers were: KS: 0.80(FAM), 0.76(NUR) and 0.62(PH); EQ5D: 0.42(FAM), 0.48(NUR) and 0.29(PH). The agreement between the EQ5D dimension scores varied from moderate for mobility and self-care to insignificant for pain and anxiety/depression. The variables associated to the size of the differences found were the Zarit burden interview score and the mental component score (MCS) (SF-36) of the carer, the physical component score (PCS) (SF-36), the BI score and patient comorbidity, and the physician's age and experience. CONCLUSIONS: Family carers and health care providers of dialysis patients are reasonably aware of the patient's level of function and well being and can be useful sources of proxy HRQoL information. Nevertheless, discrepancies can occur, depending in part on the different characteristics of patients and their caregivers.     

Feasibility of synchrotron radiation computed tomography on rats bearing glioma after iodine or gadolinium injection

The purpose of this work was to demonstrate the feasibility of a new imaging technique called synchrotron radiation computed tomography (SRCT). This technique leads to a direct assessment of the in vivo concentration of an iodine- or gadolinium-labeled compound. Rats bearing C6 glioma were imaged by MRI prior to the SRCT experiment. The SRCT experiments were performed after a 1.3 g I/kg (n = 5) or a 0.4 g Gd/kg (n = 5) injection. Finally, brains were sampled for histology. The SRCT images exhibited contrast enhancement at the tumor location. Ten minutes after injection, iodine and gadolinium tissular concentrations were equal to 0.80 ( ± 0.40) mg/cm³ and 0.50 ( ± 0.10) mg/cm³, respectively in the peripheral area of the tumor (respective background value: 0.20 ± 0.02 to 0.10 ± 0.01). Correlation to MRI and histology revealed that the contrast uptake occurred in the most vascularized area of the tumor. The present study summarizes the feasibility of in vivo SRCT to obtain quantitative information about iodine and gadolinium-labeled compounds. Beyond brain tumor pathology, the SRCT appears as a complementary approach to MRI and CT, for studying iodine- and gadolinium-labeled compounds by the direct achievement of the tissular concentration value in the tissue. Received: 8 September 1999; Revised: 3 May 2000; Accepted: 4 May 2000