Astrocytes control GABAergic inhibition of neurons in the mouse barrel cortex.

Astrocytes in the barrel cortex respond with a transient Ca2+ increase to neuronal stimulation and this response is restricted to the stimulated barrel field. In the present study we suppressed the astrocyte response by dialysing these cells with the Ca2+ chelator BAPTA. Electrical stimulation triggered a depolarization in stellate or pyramidal 'regular spiking' neurons from cortex layer 4 and 2/3 and this response was augmented in amplitude and duration after astrocytes were dialysed with BAPTA. Combined blockade of GABAA and GABAB receptors mimicked the effect of BAPTA dialysis, while glutamate receptor blockers had no effect. Moreover, the frequency of spontaneous postsynaptic currents was increased after BAPTA dialysis. Outside the range of BAPTA dialysis astrocytes responded with a Ca2+ increase, but in contrast to control, the response was no longer restricted to one barrel field. Our findings indicate that astrocytes control neuronal inhibition in the barrel cortex.

Gliomas induce and exploit microglial MT1-MMP expression for tumor expansion.

Diffuse infiltration of glioma cells into normal brain tissue is considered to be a main reason for the unfavorable outcomes of patients with malignant gliomas. Invasion of glioma cells into the brain parenchyma is facilitated by metalloprotease-mediated degradation of the extracellular matrix. Metalloproteases are released as inactive pro-forms and get activated upon cleavage by membrane bound metalloproteases. Here, we show that membrane type 1 metalloprotease (MT1-MMP) is up-regulated in glioma-associated microglia, but not in the glioma cells. Overexpression of MT1-MMP is even lethal for glioma cells. Glioma-released factors trigger the expression and activity of MT1-MMP via microglial toll-like receptors and the p38 MAPK pathway, as deletion of the toll-like receptor adapter protein MyD88 or p38 inhibition prevented MT1-MMP expression and activity in cultured microglial cells. Microglial MT1-MMP in turn activates glioma-derived pro-MMP-2 and promotes glioma expansion, as shown in an ex vivo model using MT1-MMP-deficient brain tissue and a microglia depletion paradigm. Finally, MyD88 deficiency or microglia depletion largely attenuated glioma expansion in 2 independent in vivo models.

The risk of radiation-induced cerebrovascular disease in Chernobyl emergency workers.

The paper deals with estimating radiation risks of non-cancer diseases of the circulatory system among the Chernobyl emergency workers based on data from the Russian National Medical and Dosimetric Registry. The results for the cohort of 61,017 people observed between 1986 and 2000 are discussed. These are essentially updated results for the similar cohort that was studied by authors earlier in 1986-1996. Newly discovered is the statistically significant dose risk of ischemic heart disease [ERR Gy = 0.41, 95% CI = (0.05; 0.78)]. Confirmation is provided for the existence of significant dose risks for essential hypertension [ERR Gy = 0.36, 95% CI = (0.005; 0.71)] and cerebrovascular diseases [ERR Gy = 0.45, 95% CI = (0.11; 0.80)]. In 1996-2000, the assessed ERR Gy for cerebrovascular diseases was 0.22 with 95% CI = (-0.15; 0.58). Special consideration is given to cerebrovascular diseases in the cohort of 29,003 emergency workers who arrived in the Chernobyl zone during the first year after the accident. The statistically significant heterogeneity of the dose risk of cerebrovascular diseases is shown as a function of the duration of stay in the Chernobyl zone: ERR Gy = 0.89 for durations of less than 6 wk, and ERR Gy = 0.39 on average. The at-risk group with respect to cerebrovascular diseases are those who received external radiation doses greater than 150 mGy in less than 6 wk [RR = 1.18, 95% CI = (1.00; 1.40)]. For doses above 150 mGy, the statistically significant risk of cerebrovascular diseases as a function of averaged dose rate (mean daily dose) was observed: ERR per 100 mGy d = 2.17 with 95% CI = (0.64; 3.69). The duration of stay within the Chernobyl zone itself, regardless of the dose factor, had little influence on cerebrovascular disease morbidity: ERR wk = -0.002, with 95% CI = (-0.004; -0.001). The radiation risks in this large-scale cohort study were not adjusted for recognized risk factors such as excessive weight, hypercholesterolemia, smoking, alcohol consumption, and others.

Nitric oxide signals parallel fiber activity to Bergmann glial cells in the mouse cerebellar slice.

Stimulation of parallel fibers in the cerebellar cortex triggers a transient calcium increase in Bergmann glial cells, a special form of astrocytes. Using patch-clamping and imaging techniques we have found that this form of neuron-glia interaction is mediated by nitric oxide (NO) since the response is blocked by the NO-synthase inhibitor N omega-nitro-l-arginine and mimicked by NO donors. None of the neurotransmitter receptors of Bergmann glia identified so far participates in or interferes with this signaling cascade. The NO-triggered increases in [Ca(2+)](i), as studied in Bergmann glial cells in the slice or in cultured astrocytes, are due to Ca(2+) influx and not to release from cytoplasmic stores. Thus, NO released from parallel fibers serves as a signaling substance to the neighboring glial elements.

Distribution and transport of cholesterol in Caenorhabditis elegans.

Cholesterol transport is an essential process in all multicellular organisms. In this study we applied two recently developed approaches to investigate the distribution and molecular mechanisms of cholesterol transport in Caenorhabditis elegans. The distribution of cholesterol in living worms was studied by imaging its fluorescent analog, dehydroergosterol, which we applied to the animals by feeding. Dehydroergosterol accumulates primarily in the pharynx, nerve ring, excretory gland cell, and gut of L1-L3 larvae. Later, the bulk of dehydroergosterol accumulates in oocytes and spermatozoa. Males display exceptionally strong labeling of spermatids, which suggests a possible role for cholesterol in sperm development. In a complementary approach, we used a photoactivatable cholesterol analog to identify cholesterol-binding proteins in C. elegans. Three major and several minor proteins were found specifically cross-linked to photocholesterol after UV irradiation. The major proteins were identified as vitellogenins. rme-2 mutants, which lack the vitellogenin receptor, fail to accumulate dehydroergosterol in oocytes and embryos and instead accumulate dehydroergosterol in the body cavity along with vitellogenin. Thus, uptake of cholesterol by C. elegans oocytes occurs via an endocytotic pathway involving yolk proteins. The pathway is a likely evolutionary ancestor of mammalian cholesterol transport.

Glutamate-triggered calcium signalling in mouse bergmann glial cells in situ: role of inositol-1,4,5-trisphosphate-mediated intracellular calcium release.

The mechanisms of glutamate-induced changes in intracellular free calcium concentration in Bergmann glial cells in mouse cerebellar slices were investigated by Fura-2-based microfluorimetry. Extracellular applications of glutamate, quisqualate and kainate triggered an increase in cytoplasmic calcium concentration, whereas N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate were ineffective. The calcium elevation triggered by kainate was completely blocked by removal of calcium ions from the external solutions or by slice incubation with 6-cyano-7-nitroquinoxaline-2,3-dione. Conversely, both glutamate- and quisqualate-induced intracellular calcium transients were only slightly attenuated by slice incubation with either 6-cyano-7-nitroquinoxaline-2,3-dione or calcium-free solution, suggesting the intracellular origin for calcium ions. The glutamate-triggered cytosolic calcium increases were inhibited by slice incubation with thapsigargin, the inhibitor of intracellular calcium pumps, or by intracellular perfusion of Bergmann glial cells with heparin, the antagonist of inositol-1,4,5-trisphosphate-gated calcium release channels. Therefore the calcium release from inositol-1,4,5-trisphosphate-sensitive intracellular stores plays the major role in glutamate-induced calcium signalling. We concluded that Bergmann glial cells express calcium permeable ionotropic glutamate receptors, which might be important for generation of fast calcium signals. However, slow glutamate-evoked calcium signals are mostly determined by inositol-1,4,5-trisphosphate-dependent intracellular signalling chain.

Microdomains for neuron-glia interaction: parallel fiber signaling to Bergmann glial cells.

Astrocytes are considered a reticulate network of cells, through which calcium signals can spread easily. In Bergmann glia, astrocytic cells of the cerebellum, we identified subcellular compartments termed 'glial microdomains'. These elements have a complex surface consisting of thin membrane sheets, contain few mitochondria and wrap around synapses. To test for neuronal interaction with these structures, we electrically stimulated parallel fibers. This stimulation increased intracellular calcium concentration ([Ca2+]i) in small compartments within Bergmann glial cell processes similar in size to glial microdomains. Thus, a Bergmann glial cell may consist of hundreds of independent compartments capable of autonomous interactions with the particular group of synapses that they ensheath.

Leukaemia and thyroid cancer in emergency workers of the Chernobyl accident: estimation of radiation risks (1986-1995).

This work focuses on the direct epidemiological assessment of the risks of radiation-induced leukaemia and thyroid cancer in emergency workers (EW) after the Chernobyl accident. The Russian National Medical Dosimetric Registry (RNMDR) contains data for 168,000 EW as of January 1, 1996. The analysis relates to 48 leukaemias and 47 thyroid cancers, diagnosed and verified. Radiation risks are estimated by comparing the EW data with national data for a male population of the same age distribution. For leukaemia, an excess relative risk per Gy (ERR/Gy) of 4.30 (95% CI: 0.83, 7.75) is obtained, while the excess absolute risk per 10(4) person-years (PY) Gy (EAR/10(4)PY Gy) is found to be 1.31 (95% CI: 0.23, 2.39); for thyroid cancer an ERR/Gy of 5.31 (95% CI: 0.04, 10.58) is obtained, and an EAR/10(4)PY Gy of 1.15 (95% CI: 0.08, 2.22).

Thyroid cancer among "liquidators" of the Chernobyl accident.

In 1986, immediately after the Chernobyl accident, the USSR Ministry of Health adopted a large scale programme of establishing an All-Union Distributed Registry of persons affected by radiation due to the accident. The registry was based at the Medical Radiological Research Centre of the Russian Academy of Medical Sciences (MRRC RAMS). In 1992, when the USSR was dissolved, this registry database contained information on 659,000 persons, including 284,000 Chernobyl accident emergency workers ("liquidators"). Currently, the Russian National Medical Dosimetric Registry (RNMDR) contains data on 435,276 persons, including 167,862 liquidators. This paper reviews the data for 47 verified thyroid cancers in the liquidator subgroup of the RNMDR. Analyses show that there is an excess relative risk of thyroid cancer per Gy of 5.31 (95% confidence intervals 0.04 and 10.58) and an excess absolute risk of thyroid cancer per 10(4) person-years per Gy of 1.15 (95% confidence intervals 0.08 and 2.22).