Isolated and repeated stroke-like episodes in a middle-aged man with a mitochondrial ND3 T10158C mutation: a case report

Background

Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome, is the most common phenotype of mitochondrial disease. It often develops in childhood or adolescence, usually before the age of 40, in a maternally-inherited manner. Mutations in mitochondrial DNA (mtDNA) are frequently responsible for MELAS.

Case presentation

A 55-year-old man, who had no family or past history of mitochondrial disorders, suddenly developed bilateral visual field constriction and repeated stroke-like episodes. He ultimately presented with cortical blindness, recurrent epilepsy and severe cognitive impairment approximately 6 months after the first episode. Genetic analysis of biopsied biceps brachii muscle, but not of peripheral white blood cells, revealed a T10158C mutation in the mtDNA-encoded gene of NADH dehydrogenase subunit 3 (ND3), which has previously been thought to be associated with severe or fatal mitochondrial disorders that develop during the neonatal period or in infancy.

Conclusion

A T10158C mutation in the ND3 gene can cause atypical adult-onset stroke-like episodes in a sporadic manner.

     

Establishment and functional characterization of a tracheal epithelial cell line RTEC11 from transgenic rats harboring temperature-sensitive simian virus 40 large T-antigen

A tracheal epithelial cell line RTEC11 was established from transgenic rats harboring temperature-sensitive simian virus 40 large T-antigen. The cells grew continuously at a permissive temperature of 33 degrees C but not at a non-permissive temperature of 39 degrees C. Morphological and functional investigations demonstrated that the cells were polarized epithelial cells maintaining a regulated permeability barrier function. Interestingly, the expression levels of Muc1 (mucin 1) and Scgb1a1 (uteroglobin), non-ciliated secretory cell markers, and Tubb4 (tubulin beta 4), a ciliated cell marker, were significantly increased under the cell growth-restricted condition. Global gene expression and computational network analyses demonstrated a significant genetic network associated with cellular development and differentiation in cells cultured at the non-permissive temperature. The tracheal epithelial cell line RTEC11 with unique characteristics should be useful as an in vitro model for studies of the physiological functions and gene expression of tracheal epithelial cells.     

Common Functions or Only Phylogenetically Related? The Large Family of PLAC8 Motif-Containing/PCR Genes

PLAC8 motif-containing proteins form a large family and members can be found in fungi, algae, higher plants and animals. They include the PCR proteins of plants. The name giving PLAC8 domain was originally found in a protein residing in the spongiotrophoblast layer of the placenta of mammals. A further motif found in a large number of these proteins including several PCR proteins is the CCXXXXCPC or CLXXXXCPC motif. Despite their wide distribution our knowledge about the function of these proteins is very limited. For most of them two membrane-spanning α-helices are predicted, indicating that they are membrane associated or membrane intrinsic proteins. In plants PLAC8 motif-containing proteins have been described to be implicated in two very different functions. On one hand, it has been shown that they are involved in the determination of fruit size and cell number. On the other hand, two members of this family, AtPCR1 and AtPCR2 play an important role in transport of heavy metals such as cadmium or zinc. Transport experiments and approaches to model the 3_D structure of these proteins indicate that they could act as transporters for these divalent cations by forming homomultimers. In this minireview we discuss the present knowledge about this protein family and try to give an outlook on how to integrate the different proposed functions into a common picture about the role of PLAC8 motif-containing proteins.     

Transgenic mice expressing mutant (N279K) human tau show mutation dependent cognitive deficits without neurofibrillary tangle formation

Mutations in the tau gene, which is located on chromosome 17, were found causative for autosomal dominantly inherited frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). To determine if cognitive deficits could be caused by tau mutations, two transgenic mouse lines were generated expressing a four-repeat isoform of human tau or its mutant, containing one of the FTDP-17 mutations (WILD mice and N279K mice). In open field test, N279K mice showed hyperactivity in locomotion and rearing. In prepulse inhibition test, N279K mice but not Wild mice showed significant deficits. Both transgenic mice, especially N279K mice, showed impairment in acquisition of spatial learning in Morris water maze. Although both N279K mice and Wild mice acquired passive avoidance as well as non-transgenic mice, N279K mice but not Wild mice showed severe deficits in acquisition of active avoidance. Histological analysis of the present mutant mice did not show any signs of neurofibrillary tangle formations in the brain, and cognitive dysfunction seemed to precede such neuropathological changes or occur independently from them. The behavioral phenotype of N279K mice mimics features of human FTDP-17 and provides a basic model for elucidating mechanisms underlying cognitive deficits in not only FTDP-17, but also diverse tauopathies.     

Hypoxic up-regulation of triosephosphate isomerase expression in mouse brain capillary endothelial cells

A protein with a molecular mass of 27kDa was induced by hypoxia in a mouse brain capillary endothelial cell line and identified as triosephosphate isomerase (TPI) by amino-terminal sequencing. Hypoxia caused an elevation of the TPI protein level, concomitant with an increase of the TPI mRNA level. However, hypoxia resulted in an insufficient elevation of TPI activity level, compared to an increase of TPI protein level. When cells expressing the recombinant TPI protein with histidine tag were exposed to hypoxia and the TPI protein was affinity-purified, the catalytic activity (specific activity) of the TPI protein purified from hypoxic cells was substantially lower than that obtained from normoxic cells. In addition, three TPI isoforms with an electrophoretic multiplicity were found; two of the three isoforms were substantially increased in response to the hypoxia, but the level of the most acidic isoform was barely changed. The induction of TPI gene expression by hypoxia was suppressed by (1) a chelator of intracellular Ca(2+), (2) a blocker of non-selective cation channels, (3) a blocker of Na(+)/Ca(2+) exchangers, (4) an inhibitor of Ca(2+)/calmodulin-dependent protein kinases, and (5) an inhibitor of c-jun/AP-1 activation.     

Effect of magnetic field exposure on calcium channel currents using patch clamp technique

Calcium influxes through the membrane of PC-12D cells were measured under exposure to DC biased AC magnetic fields in resonant conditions of the ion cyclotron and the ion parametric resonance hypotheses and compared with influxes in cells without exposure to the magnetic field. After cancellation of the geomagnetic field, the cells were exposed to the horizontal fields generated by a current sheet, a planar sheet of conductor which generated a satisfactorily homogeneous horizontal magnetic field on the stage of a microscope without hindering treatment of a cell under observation. At or near any resonant conditions, no change in calcium influx could be detected under standard patch clamp conditions.     

Protective and therapeutic efficacy of Lactobacillus casei against experimental murine infections due to Mycobacterium fortuitum complex

A bacterial immunopotentiator, LC 9018 (heat-killed Lactobacillus casei), was studied for its protective and therapeutic efficacies against Mycobacterium fortuitum and M. chelonae infections in mice. This agent reduced the incidence of spinning disease and gross renal lesions and enhanced the elimination of organisms at the site of infection in the host mice, when administered intramuscularly six times a week (0.1 mg dry weight per injection, one injection on each day of treatment) from 1 week before to 2 weeks after infection. The LC 9018 injections in this protocol caused a marked increase in the phagocytic function, O2- -producing ability and chemiluminescence of host peritoneal macrophages. Moreover, LC 9018 injections using the same schedule resulted in an enhancement of interleukin-1-producing function of the macrophages, particularly in the infected mice. These findings indicate that LC 9018 administration with the present protocol can activate macrophage functions, in particular those related to microbicidal activity. This would partly explain the protective and therapeutic efficacy of LC 9018 against infection due to M. fortuitum complex.     

Trypanosome alternative oxidase as a target of chemotherapy

Parasites have developed a variety of physiological functions necessary for their survival within the specialized environment of the host. Using metabolic systems that are very different from those of the host, they can adapt to low oxygen tension present within the host animals. Most parasites do not use the oxygen available within the host to generate ATP, but rather employ systems anaerobic metabolic pathways. The enzymes in these parasite-specific pathways are potential targets for chemotherapy.Cyanide-insensitive trypanosome alternative oxidase (TAO) is the terminal oxidase of the respiratory chain of long slender bloodstream forms of the African trypanosome, which causes sleeping sickness in human and nagana in cattle. TAO has been targeted for the development of anti-trypanosomal drugs because it does not exist in the host. Recently, we found the most potent inhibitor of TAO to date, ascofuranone, a compound isolated from the phytopathogenic fungus, Ascochyta visiae.     

Neurogranin controls the spatiotemporal pattern of postsynaptic Ca2+/CaM signaling

Neurogranin (Ng) is a postsynaptic IQ-motif containing protein that accelerates Ca²⁺ dissociation from calmodulin (CaM), a key regulator of long-term potentiation and long-term depression in CA1 pyramidal neurons. The exact physiological role of Ng, however, remains controversial. Two genetic knockout studies of Ng showed opposite outcomes in terms of the induction of synaptic plasticity. To understand its function, we test the hypothesis that Ng could regulate the spatial range of action of Ca²⁺/CaM based on its ability to accelerate the dissociation of Ca²⁺ from CaM. Using a mathematical model constructed on the known biochemistry of Ng, we calculate the cycle time that CaM molecules alternate between the fully Ca²⁺ saturated state and the Ca²⁺ unbound state. We then use these results and include diffusion of CaM to illustrate the impact that Ng has on modulating the spatial profile of Ca²⁺-saturated CaM within a model spine compartment. Finally, the first-passage time of CaM to transition from the Ca²⁺-free state to the Ca²⁺-saturated state was calculated with or without Ng present. These analyses suggest that Ng regulates the encounter rate between Ca²⁺ saturated CaM and its downstream targets during postsynaptic Ca²⁺ transients.     

Roles of reactive nitrogen intermediates and transforming growth factor-beta produced by immunosuppressive macrophages in the expression of suppressor activity against T cell proliferation induced by TCR stimulation

The suppressor activity of splenic macrophages induced by Mycobacterium intracellulare infection (MI-M phi s) against T cell concanavalin A (Con A) mitogenesis is mediated by MI-M phi's mediators, such as reactive nitrogen intermediates (RNIs), phosphatidylserine, free fatty acids, prostaglandin E(2) and to a minor extent TGF-beta. Here, we have compared the roles of RNIs and TGF-beta in the expression of MI-M phi's suppressor activity against Con A mitogenesis and anti-CD3 monoclonal antibody (mAb)- and anti-CD28 mAb-induced mitogenesis (TCR signal-induced mitogenesis) of the target T cells, and have found the following. First, N(G)-monomethyl-L-arginine (NMMA) inhibited MI-M phi's suppressor activity against TCR signal-induced mitogenesis as well as Con A mitogenesis. Second, anti-TGF-beta mAb weakly restored the MI-M phi-mediated suppression only in the case of Con A mitogenesis, under limited conditions, such as very low cell densities of MI-M phi s. Third, the blocking effects of NMMA plus anti-TGF-beta mAb were somewhat more prominent in the case of Con A mitogenesis than in the case of TCR signal-induced mitogenesis. Fourth, Con A- or TCR signal-stimulated MI-M phi s secreted significant amounts of the latent TGF-beta but not the active one. These findings indicate that RNIs, but not TGF-beta, play important roles in the MI-M phi-mediated suppression of TCR signal-induced mitogenesis, as well as Con A mitogenesis, of the target T cells.