Ongoing outbreak of an acute muscular Sarcocystis-like illness among travellers returning from Tioman Island, Malaysia, 2011-2012.

As of 4 November, 2012, 100 patients with an acute muscular Sarcocystis-like illness associated with travel to Tioman Island, Malaysia, have been identified. Thirty-five travelled there mostly during July and August 2011 and 65 mostly during July and August 2012, suggesting an ongoing outbreak. Epidemiological investigations are ongoing. Public health agencies and practicing clinicians should be aware of this rarely-reported disease in humans and consider it as differential diagnosis in travellers returning from Tioman Island.

Tyrosine phosphorylation of the delta-opioid receptor. Evidence for its role in mitogen-activated protein kinase activation and receptor internalization*.

The internalization of G-protein-coupled receptors (GPCRs), including the delta opioid receptor (delta-OR), has been shown to involve the phosphorylation of serine and threonine residues. However, recent studies suggest that these residues may not be the only ones phosphorylated in response to prolonged opioid exposure. Tyrosines also appear important for delta-OR signalling, but it remains unclear whether they undergo phosphorylation. We examined whether the delta-OR, stably expressed in Chinese hamster ovary (CHO-K1) cells, was tyrosine-phosphorylated during prolonged agonist treatment. The epitope-tagged delta-OR was purified by immunoprecipitation, and the presence of phosphorylated tyrosines was detected using anti-phosphotyrosine antibodies. Tyrosine residues in the delta-OR were phosphorylated after exposure to the high-affinity agonist [d-Thr(2)]-Leu-enkephalin-Thr (DTLET) in a time- and concentration-dependent manner. Tyrosine phosphorylation of the delta-OR appeared to require the actions of a Src-like protein tyrosine kinase, since the Src inhibitor 4-amino-5-(4-methylphenyl)-7-(t-butyl)-pyrazolo-[3,4-d]-pyrimidine (PP1) attenuated this response. PP1 also attenuated the DTLET-mediated activation of mitogen-activated protein kinase, as well as rapid delta-OR internalization, but not receptor down-regulation. Finally, only opioid agonists that induce receptor internalization via the clathrin-dependent endosomal pathway stimulated significant tyrosine phosphorylation of the delta-OR protein. Evidence is presented that the delta-OR is tyrosine-phosphorylated, and we suggest how this may have an active role in opioid receptor signalling and regulation.

Mutation of tyrosine 318 (Y318F) in the delta-opioid receptor attenuates tyrosine phosphorylation, agonist-dependent receptor internalization, and mitogen-activated protein kinase activation.

Opioid receptors are known for their ability to activate diverse second messenger systems. Previously, we showed that selective delta-opioid agonists were able to induce the rapid tyrosine phosphorylation of delta-opioid receptors (delta-ORs) through Src. Src-dependent tyrosine phosphorylation of delta-ORs appears to be important for activation of the mitogen-activated protein kinase cascade and for receptor sequestration into clathrin-coated endosomes, as the Src antagonist, PP1, inhibited both. In an attempt to clarify the role of tyrosine phosphorylation in delta-OR signalling and regulation, we constructed a mutant receptor in which the tyrosine located in the conserved NPXXY motif of the C-terminus was replaced by a phenylalanine (Y318F-delta-OR). Mutation of Y318 resulted in a receptor that was comparable to the wild type in its expression level in HEK-293 cells and in its affinity for opioid ligands. Both receptors showed effective coupling to G proteins and were capable of inhibiting forskolin-stimulated cAMP accumulation with similar potencies. However, the mutant receptor was able to stimulate (35)S-GTPgammaS binding with a lower EC(50) than the wild type receptor. The stimulation of tyrosine phosphorylation in delta-ORs by [D-Thr(2)]-Leu-enkephalin-Thr (DTLET) was significantly less in cells expressing the Y318F-delta-OR than in cells expressing the wild type. In addition, both rapid receptor internalization and down-regulation were markedly attenuated in the mutant. Finally, the mutant receptor was unable to induce a robust activation of the MAPK pathway, suggesting that tyrosine phosphorylation of the delta-OR protein is important for this signalling pathway. These findings implicate tyrosine phosphorylation of Y318 in receptor signalling and agonist-mediated regulation.

The epidemiology of tuberculosis among North Carolina migrant farm workers.

Although tuberculosis (TB) has been recognized as a significant health problem of migrant farm workers, the nature and extent of the problem have been poorly defined. We report the first population-based study of TB in a random sample of farm workers (n = 543) and the first use of recall antigens in an epidemiologic study of TB. Purified protein derivative positivity ranged from 33% in Hispanics to 54% in US-born blacks and 76% in Haitians. Active tubercular disease occurred in 3.6% of US-born blacks and 0.47% of Hispanics. Among US-born blacks, risk factors associated with farm work were most significant. Blacks born in the United States also had the highest prevalence of anergy. The use of recall antigens made possible a better description of the epidemiology of TB by excluding false negatives and clarifying associations between infection and risk factors. We conclude that TB among farm workers represents a serious public health problem with previously unrecognized risk factors. Additional resources for migrant health care, improvements in health care access, and fundamental changes in the system of migrant labor are all necessary to reduce the transmission of TB.