Cloning and characterization of a trypsin-encoding cDNA of the human body louse Pediculus humanus.

From a cDNA library of the whole insect, a trypsin gene of Pediculus humanus has been cloned and sequenced. The 908 bp clone has an open reading frame of 759 bp, which encodes a pre-proenzyme with 253 amino acid residues. A sixteen-residue N-terminal signal peptide is followed by a twelve-residue activation peptide with putative cleavage sites at Gly16 and Tyr28. The deduced amino acid sequence has several features typical of trypsin proteases and an overall identity of 35-43% with the trypsins of several haematophagous Diptera. The 1.0 kb genomic trypsin gene contains three introns of 102, 79 and 80 nucleotides following the codons for Gly16, Gln74 and Ala155, respectively. Only a single gene seems to be present. In Northern blot analysis, unfed first instar larvae have an identical or slightly lower level of trypsin mRNA than fed adult lice, and in adults 2-24 h after the bloodmeal this gene shows a constitutive expression. After in vitro transcription and translation, the activation peptide is cleaved by chymotrypsin, a so far unreported phenomenon in trypsin activation.

Activation of basal ganglia loops in idiopathic Parkinson's disease: a PET study.

Patients with idiopathic Parkinson's syndrome (IPS) show dysexecutive deficits which are not related to dementia. We investigated whether these deficits may be caused by a disturbed interaction of prefrontal cortex and selective basal ganglia loops. 5 healthy right-handed volunteers and 5 non demented IPS patients were studied with FDG PET while performing a gambling task paradigm. Control subjects and patients showed consistent bilateral activation of the dorsolateral prefrontal cortex (DLPFC) and the left caudate. Only controls activated the right cingulate, mesial prefrontal and frontoorbital cortex. Patients significantly deactivated the right thalamus. Thus missing frontoorbital and frontomesial activity may indicate an impairment of the basal ganglia loop in IPS, connecting those regions to the thalamus via the ventral striate. The connections between DLPFC and Thalamus via the left caudate remained intact. This impairment may be the neuroanatomical correlate for dysexecutive syndromes in IPS more related to misjudgement than cognitive impairment.

Plasticity of language networks in patients with brain tumors: a positron emission tomography activation study.

We investigated plasticity of language networks exposed to slowly evolving brain damage. Single subject 0-15-water language activation positron emission tomography studies were analyzed in 61 right-handed patients with brain tumors of the left hemisphere, and 12 normal controls. In controls, activations were found in left Brodmann's Area (BA)44 and BA45, superior posterior temporal gyrus bilaterally, and right cerebellum. Patients additionally activated left BA46, BA47, anterior insula, and left cerebellum. Superior temporal activation was less frequent, and activations in areas other than posterior temporal gyrus were found bilaterally. Frontolateral activations within the nondominant hemisphere were only seen in patients (63%) with frontal or posterior temporal lesions. Laterality indices of frontolateral cortex showed reversed language dominance in 18% of patients. Laterality indices of the cerebellum were negatively correlated with language performance. Two compensatory mechanisms in patients with slowly evolving brain lesions are described: An intrahemispheric mechanism with recruitment of left frontolateral regions other than classic language areas; and an interhemispheric compensatory mechanism with frontolateral activation in the nondominant hemisphere. The latter one was only found in patients with frontal or posterior temporal lesions, thus supporting the hypothesis that right frontolateral activations are a disinhibition phenomenon.