Dopamine Selectively Sensitizes Dopaminergic Neurons to Rotenone-Induced Apoptosis

Among various types of neurons affected in Parkinson’s disease, dopamine (DA) neurons of the substantia nigra undergo the most pronounced degeneration. Products of DA oxidation and consequent cellular damage have been hypothesized to contribute to neuronal death. To examine whether elevated intracellular DA will selectively predispose the dopaminergic subpopulation of nigral neurons to damage by an oxidative insult, we first cultured rat primary mesencephalic cells in the presence of rotenone to elevate reactive oxygen species. Although MAP2⁺ neurons were more sensitive to rotenone-induced toxicity than type 1 astrocytes, rotenone affected equally both DA (TH⁺) neurons and MAP2⁺ neurons. In contrast, when intracellular DA concentration was elevated, DA neurons became selectively sensitized to rotenone. Raising intracellular DA levels in primary DA neurons resulted in dopaminergic neuron death in the presence of subtoxic concentrations of rotenone. Furthermore, mitochondrial superoxide dismutase mimetic, manganese (III) meso-tetrakis (4-benzoic acid) porphyrin, blocked activation of caspase-3, and consequent cell death. Our results demonstrate that an inhibitor of mitochondrial complex I and increased cytosolic DA may cooperatively lead to conditions of elevated oxidative stress and thereby promote selective demise of dopaminergic neurons.     

Conformation of the HMG17-nucleosome complex

The nucleosome core binds more than two molecules of HMG17 at low ionic strength (8.9 mM Tris-HCl/8.9 mM boric acid/0.25 mM Na2EDTA, pH 8.3). Circular dichroism of the complexes showed only minor conformational changes of the nucleosome core DNA on binding of HMG17, with no detectable change in the histone secondary structure. The fluorescence of N-(3-pyrene) maleimide bound to -SH groups at Cys-110 of H3 histones in the core particle suggested that the structure of the histone octamer assembly changed little upon binding of HMG17 to the nucleosome. These observations support the idea that even a high level of HMG17 binding, e.g., four HMGs per nucleosome, alone, does not open up the core particle.     

Identification of proteins encoded in Escherichia coli hydA, hydB and analysis of the hydA locus

The hydB gene of Escherichia coli, which is related with the expression of hydrogenase activity, was cloned into the plasmid (pES1). Using the maxicell protein-labeling method, the molecular weight of hydB gene product was estimated. Comparing between the gene products from the mutant strains and that of the hydB genes cloned strains, the molecular weight of the gene product was 35,000 Mr. Similarly, the molecular weight of the gene product of hydA, which had been previously cloned, was determined by maxicell analysis. The molecular weight of hydA gene product was estimated to be 80,000 Mr. Using deletion analysis and Tn1000 insertional inactivation of hydA's function, the hydA coding region was estimated between 2.2 kb and 2.8 kb in a 3.1 kb EcoRI-MluI fragment on the recombinant plasmid pEH3.     

Characterization of the heredity of kininogen deficiency in brown Norway Katholiek strain rats.

Brown Norway rat strain has been studied for mode of inheritance of its congenital deficiency in plasma high molecular weight (HMW)-kininogen and low molecular weight (LMW)-kininogen, and low plasma level of prekallikrein. We examined the genetics of the deficiency by performing a mixed breeding experiment between B/N-Katholiek (B/N-Ka, deficient) and B/N-Kitasato (B/N-Ki, normal) strains. Incidence of the deficiency was judged by the plasma level of HMW-kininogen. Plasma level of HMW-kininogen was around 50% of the normal level in all F1 generations of the hybrid between male B/N-Ka and female B/N-Ki (Exp. 1), and between female B/N-Ka and male B/N-Ki (Exp. 2). Incidence of deficiency (plasma HMW-kininogen level less than 5%) in Exp. 1 was 23.8% in male F2 and 20.0% in female F2 generations. By Exp. 2 also the incidence was 25.0% in male and 30.0% in female F2 generations. There was no significant difference of the incidence between the two experiments or sexes. These results indicate the inheritance of the kininogen-deficiency to be Mendelian autosomal recessive, the same as for the reported cases of human kininogen deficiency. Gel filtration study suggests that prekallikrein in the B/N-Ka plasma may be free form, while that in the B/N-Ki plasma may form complex with HMW-kininogen.     

Emergence of artemisinin-resistant Plasmodium falciparum with kelch13 C580Y mutations on the island of New Guinea

The rapid and aggressive spread of artemisinin-resistant Plasmodium falciparum carrying the C580Y mutation in the kelch13 gene is a growing threat to malaria elimination in Southeast Asia, but there is no evidence of their spread to other regions. We conducted cross-sectional surveys in 2016 and 2017 at two clinics in Wewak, Papua New Guinea (PNG) where we identified three infections caused by C580Y mutants among 239 genotyped clinical samples. One of these mutants exhibited the highest survival rate (6.8%) among all parasites surveyed in ring-stage survival assays (RSA) for artemisinin. Analyses of kelch13 flanking regions, and comparisons of deep sequencing data from 389 clinical samples from PNG, Indonesian Papua and Western Cambodia, suggested an independent origin of the Wewak C580Y mutation, showing that the mutants possess several distinctive genetic features. Identity by descent (IBD) showed that multiple portions of the mutants’ genomes share a common origin with parasites found in Indonesian Papua, comprising several mutations within genes previously associated with drug resistance, such as mdr1, ferredoxin, atg18 and pnp. These findings suggest that a P. falciparum lineage circulating on the island of New Guinea has gradually acquired a complex ensemble of variants, including kelch13 C580Y, which have affected the parasites’ drug sensitivity. This worrying development reinforces the need for increased surveillance of the evolving parasite populations on the island, to contain the spread of resistance.     

First report that the wasp Gronotoma guamensis (Hymenoptera: Figitidae: Eucoilinae) parasitizes the orchid‐feeding fly Japanagromyza tokunagai in Japan

Compared with mycorrhizal relationships, the relationships between mycoheterotrophic plants and insects have rarely been studied. Here we report a previously unknown tripartite interaction among an endangered mycoheterotrophic orchid, an orchid‐feeding fly, and a parasitoid wasp. The flowers and stems of Eulophia zollingeri were heavily attacked by Japanagromyza tokunagai (Sasakawa) (Diptera: Agromyzidae), and the parasitoid wasp Gronotoma guamensis (Yoshimoto) (Hymenoptera: Figitidae) was reared from these J. tokunagai individuals. Considering the high infestation rate of J. tokunagai, G. guamensis could be important in suppressing the J. tokunagai population, and positively affect the reproductive success of E. zollingeri.