Hypothalamic and basal ganglia projections to the posterior thalamus: possible role in modulation of migraine headache and photophobia.

Migraine attacks are typically described as unilateral, throbbing pain that is usually accompanied by nausea, vomiting, and exaggerated sensitivities to light, noise and smell. The headache phase of a migraine attack is mediated by activation of the trigeminovascular pathway; a nociceptive pathway that originates in the meninges and carries pain signals through meningeal nociceptors to the spinal trigeminal nucleus and from there to the cortex through relay neurons in the thalamus. Recent studies in our lab have identified a population of trigeminovascular neurons in the posterior (Po) and lateral posterior (LP) thalamic nuclei that may be involved in the perception of whole-body allodynia (abnormal skin sensitivity) and photophobia (abnormal sensitivity to light) during migraine. The purpose of the current study was to identify sub-cortical areas that are in position to directly regulate the activity of these thalamic trigeminovascular neurons. Such process begins with anatomical mapping of neuronal projections to the posterior thalamus of the rat by performing discrete injections of the retrograde tracer Fluorogold into the Po/LP region. Such injections yielded retrogradely labeled neurons in the nucleus of the diagonal band of Broca, the dopaminergic cells group A11/A13, the ventromedial and ventral tuberomammillary nuclei of the hypothalamus. We also found that some of these neurons contain acetylcholine, dopamine, cholecystokinin and histamine, respectively. Accordingly, we speculate that these forebrain/hypothalamic projections to Po and LP may play a role in those migraine attacks triggered by disrupted sleep, skipping meals and emotional reactions.

[Landscape components favouring the occurrence of anthrax in the Flooding Pampa grasslands (Buenos Aires province, Argentina)]. / Componentes del paisaje que favorecen la aparición de carbunco en la Pampa Deprimida (provincia de Buenos Aires, Argentina).

The authors studied the landscape components that favour the occurrence of anthrax in the Flooding Pampa grasslands (Buenos Aires province, Argentina). They made spatial locations of anthrax outbreaks diagnosed by registered veterinary laboratories in the study area's zone of influence. As variables for study, they differentiated areas that are flooded for 20% of the time or more from primary and secondary runoff channels. They also identified areas with low-productivity pasture. Logistic regression analysis of farm populations revealed that landscape components favouring the occurrence of anthrax outbreaks are shared runoff channels (odds ratio (OR) = 2.3; confidence interval (CI) = 1.2; 4.7) and > or = 40% low-productivity pasture (OR = 5.4; CI = 3.5; 8.3). Contrary to initial assumptions, susceptibility to flooding was not a significant variable (OR = 1.1; CI = 0.5; 2.1). The authors concluded that the first step in decision-making and ensuring more efficient implementation of future anthrax control and eradication plans was to identify risk variables.

Central nervous system networks involved in the processing of meningeal and cutaneous inputs from the ophthalmic branch of the trigeminal nerve in the rat.

This study analysed the organization of central nervous system networks involved in the processing of meningeal inputs in the male, Sprague-Dawley rat. We injected the anterograde tracer, biotin dextran, into areas of the medullary trigeminal nucleus caudalis (Sp5C), which receive inputs from the ophthalmic division of the trigeminal nerve. Double-labelling immunohistochemical studies were then performed to compare calcitonin gene-related peptide (CGRP) or serotonin 1D (5HT1(D)) receptor distributions in the areas innervated by Sp5C neurons. Dense, topographically organized intratrigeminal connections were observed. Sp5C neurons projected to the commissural subnucleus of the solitary tract, A5 cell group region/superior salivatory nucleus, lateral periaqueductal grey matter, inferior colliculus and parabrachial nuclei. Trigeminothalamic afferents were restricted to the posterior group and ventroposteromedial thalamic nuclei. Some of these areas are also immunoreactive for 5HT1(D) and CGRP and thus remain potential central targets of triptan molecules and other antimigraine drugs.

Short report: analysis of clonal relationship among Shigella sonnei isolates circulating in Argentina.

Thirty-five isolates of Shigella sonnei from patients with diarrhoea in three geographic regions of Argentina were examined for genetic diversity by pulsed-field gel electrophoresis (PFGE) and plasmid profile. PFGE of XbaI and BlnI DNA digests confirmed the occurrence of outbreaks in two regions caused by two separate predominant clones of S. sonnei. The third region was characterized by three circulating clones, one of which was possibly associated with an outbreak. Similar plasmids were found in distinct clones and in one outbreak clone five different plasmid profiles were identified. Antimicrobial resistance of the isolates varied from fully susceptible to the agents tested, to resistance to cotrimoxazole, ampicillin and ciprofloxacin. Antibiotic resistance did not correlate with plasmid content. This information will form the basis for active surveillance of shigellosis in Argentina and elsewhere in the region through the PulseNet International Network.