Transient Synaptic Enhancement Triggered by Exogenously Supplied Monocarboxylate in Drosophila Motoneuron Synapse

Current evidence suggests that glial cells provide C3 carbon sources to fuel neuronal activity; however, this notion has become challenged by biosensor studies carried out in acute brain slices or in vivo, showing that neuronal activity does not rely on the import of astrocyte-produced L-lactate. Rather, stimulated neurons become net lactate exporters, as it was also shown in Drosophila neurons, in which astrocyte-provided lactate returns as lipid droplets to be stored in glial cells. In this view, we investigate whether exogenously supplied monocarboxylates can support Drosophila motoneuron neurotransmitter release (NTR). By assessing the excitatory post-synaptic current (EPSC) amplitude under voltage-clamp as NTR indicative, we found that both pyruvate and L-lactate, as the only carbon sources in the synapses bathing-solution, cause a large transient NTR enhancement, which declines to reach a synaptic depression state, from which the synapses do not recover. The FM1-43 pre-synaptic loading ability, however, is maintained under monocarboxylate, suggesting that SV cycling should not contribute to the synaptic depression state. The NTR recovery was reached by supplementing the monocarboxylate medium with sucrose. However, monocarboxylate addition to sucrose medium does not enhance NTR, but it does when the disaccharide concentration becomes too reduced. Thus, when pyruvate concentrations become too reduced, exogenously supplied L-lactate could be converted to pyruvate and metabolized by the neural mitochondria, triggering the NTR enhancement. SIGNIFICANCE STATEMENT: The question of whether monocarboxylic acids can fuel the Drosophila motoneuron NTR was challenged. Our findings show that exogenously supplied monocarboxylates trigger a large transient synaptic enhancement just under extreme glycolysis reduction but fail to maintain NTR under sustained synaptic demand, still at low frequency stimulation, driven to the synapses to a synaptic depression state. Glycolysis activation, by adding sucrose to the monocarboxylate bath solution, restores the motoneuron NTR ability, giving place to a hexoses role in SV recruitment. Moreover these results suggest exogenously supplied C3 carbon sources could have an additional role beyond providing energetic support for neural activity.

Macropinocytosis and Cell Migration: Don't Drink and Drive…

Macropinocytosis is a nonspecific mechanism by which cells compulsively "drink" the surrounding extracellular fluids in order to feed themselves or sample the molecules therein, hence gaining information about their environment. This process is cell-intrinsically incompatible with the migration of many cells, implying that the two functions are antagonistic. The migrating cell uses a molecular switch to stop and explore its surrounding fluid by macropinocytosis, after which it employs the same molecular machinery to start migrating again to examine another location. This cycle of migration/macropinocytosis allows cells to explore tissues, and it is key to a range of physiological processes. Evidence of this evolutionarily conserved antagonism between the two processes can be found in several cell types-immune cells, for example, being particularly adept-and ancient organisms (e.g., the social amoeba Dictyostelium discoideum). How macropinocytosis and migration are negatively coupled is the subject of this chapter.

Early profiles of clinical evolution after intravenous thrombolysis in an unselected stroke population

BACKGROUND

Intravenous recombinant tissular plasminogen activator (rt-PA) is the only approved pharmacological treatment for acute ischaemic stroke. The authors aimed to analyse potential causes of the variable effect on early course and late outcome.

METHODS AND RESULTS

136 patients (42% women, 58% men) treated with intravenous rt-PA within 3 h of stroke onset in an acute stroke unit over a 3-year period, were included. Early clinical profiles of evolution at 48 h were divided into clinical improvement (CI) (decrease >4 points in the National Institute of Health Stroke Scale (NIHSS)); clinical worsening (CW) (increase >4 points NIHSS); clinical worsening after initial improvement (CWFI) (variations of >4 points in the NIHSS). Patients with clinical stability (no NIHSS modification or <4 points) were excluded. The patients showed in 66.9% CI, 13.2% CW 8.1 % CWFI and 11.8% remained stable. Female sex, no hyperlipaemia and peripheral arterial disease were associated with CW. Male sex and smoking were associated with CI. Absence of arterial occlusion on admission (28.4%) and arterial recanalisation at 24 h were associated with CI. Main causes of clinical deterioration included symptomatic intracranial haemorrhage (sICH), persistent occlusion and cerebral oedema. 23.5% developed ICH, 6.6% of which had sICH. At 3 months, 15.5% had died. Mortality was increased in CW, mainly related to sICH and cerebral oedema. The outcome of CWFI was intermediate between CW and CI.

CONCLUSIONS

Early clinical profiles of evolution in thrombolysed patients vary considerably. Even with CI, it is critical to maintain vessel permeability to avoid subsequent CW.

Perfusion computed tomography-guided subacute endovascular reperfusion in a patient with carotid occlusion

Most patients with symptomatic internal carotid artery occlusion have a single minor or major hemispheric stroke. A minority of patients have ipsilateral retinal ischemia, recurrent strokes, or transient ischemic attacks. Whereas spontaneous carotid recanalization is rare, acute surgical recanalization has been attempted, with mixed results. Recently, acute endovascular recanalization has been performed and described as feasible and relatively safe. We describe a patient with symptom recurrence related to hemodynamic factors after occlusion of the carotid artery who was successfully treated 14 days after symptom onset.

Adaptation of pregnant ewes to an exclusive onion diet

A diet consisting entirely of cull onions fed to pregnant ewes produced Heinz body hemolytic anemia in all sheep after 21 d. After 28 d of daily consumption of 20 kg of onions/ewe, the anemia stabilized, and for the remaining 74 d the packed cell volume increased in the majority of sheep, although it did not return to normal. Compared to control ewes fed an alfalfa and grain diet, the onion-fed ewes had comparable body condition scores and fleece weights. There was no significant difference (alpha = 0.05) in pregnancy or lambing rate, number of lambs born/ewe exposed, or number of lambs born/ewe lambing. Greater numbers of sulfate-reducing bacteria (Desulfovibrio spp) and more ruminal hydrogen sulfide were present in onion-fed sheep compared to controls. Although an average 27% reduction in packed cell volume and Heinz body anemia developed in the onion-fed ewes, on the basis of this study it appears that pregnant ewes may be fed a pure onion diet with minimal detrimental effects. This adaptation to a pure onion diet is in part likely due to the apparent ability of the sheep's rumen to quickly develop a population of sulfate-reducing bacteria that decrease the toxicity of onion disulfides.

The Irish cystic fibrosis database

We have found records of 1014 Irish cystic fibrosis patients alive by December 1994, belonging to 883 families. Prevalence in the population is 1/3475 and incidence at birth 1/1461, with a gene frequency of 2.6%. Twenty percent of the patients are aged over 20 years, but at present survival rate falls rapidly after that age. We have identified 85% of the mutations on the CFTR gene in a sample of 29% of the families (506 CF chromosomes). Mutation delta F508 is found in 72% of Irish CF chromosomes, G551D in 6.9%, and R117H in 2%. These are the highest frequencies reported for the latter two mutations world wide. Another seven mutations are found in an additional 4% of CF families. We present new microsatellite haplotype data that could be useful for genetic counselling of CF families bearing some of the 15% of CF mutations still unidentified, and comment on possible uses of our database.