Effect of dietary copper on colonic tumor production and aortic integrity in the rat

Gastrointestinal malignancy has been associated with aortic aneurysmal disease in humans, while metabolic derangement of copper has been incriminated as a possible promotor of aneurysmal development of the aorta. An animal model utilizing the carcinogen 1,2-dimethylhydrazine (DMH) was selected to evaluate levels of dietary copper on both colonic tumor production and morphologic changes in the rat aorta. Six groups, each including 10 Sprague-Dawley rats, received 16 weekly doses (20 mg/kg) of DMH beginning at 4 weeks of age. Groups were maintained on either normal (25 ppm), low (0.6 ppm), or high (100 ppm) copper chow during the entire experimental period. After 25 weeks, all animals were sacrificed to assess colonic tumor production and to perform scanning (SEM) and transmission electron microscopic (TEM) studies of the rat aorta. Results showed a significant increase in colonic tumor production (3.14 +/- 0.39 tumors per centimeter colon) in rats treated with low-copper chow and DMH when compared with rats on normal chow and DMH (0.74 +/- 0.07 tumors per centimeter colon) and animals maintained on high-copper diets and DMH (0.76 +/- 0.08 tumors per centimeter colon). In addition, morphologic study showed disruption of the intima and media in rats maintained on low-copper diet alone, and also on low-copper diet plus DMH. The results of this study showed that DMH and low dietary copper significantly increase (P less than 0.001) the yield of colonic tumors and produce loss of aortic integrity when studied morphologically. Copper levels may be important in the association of neoplasia and aneurysm formation in the clinical setting.     

Stress proteins may provide a link between the immune response to infection and autoimmunity

Stress proteins are frequently the target of humoral and cell-mediatedimmune responses to infection. These proteins belong to highlyconserved gene families and there is substantial sequence homologybetween antigens produced by pathogenic organisms and the correspondingproteins from mammalian cells. Human T cells from sites of infectiousand autoimmune lesions proliferate in response to stress proteins,and mapping of antigenic determinants on a mycobacterial stressprotein shows that both species specific and highly conserved,‘self-like’, regions of the molecule can take partin immune recognition. It is proposed that the lymphocyte populationinduced in response to stress proteins of pathogens during infectionincludes cells capable of autolmmune recognition of the correspondingself protein. Local accumulation of self stress proteins—inresponse to viral infection, for example—may subsequentlyprovide a stimulus for proliferation of such autoreactive lymphocytes,thereby triggering a cycle of events which may contribute tothe pathological damage associated with autoimmune disease.     

TREM2 is required for microglial instruction of astrocytic synaptic engulfment in neurodevelopment

Variants in the microglial receptor TREM2 confer risk for multiple neurodegenerative diseases. However, it remains unknown how this receptor functions on microglia to modulate these diverse neuropathologies. To understand the role of TREM2 on microglia more generally, we investigated changes in microglial function in Trem2^−/− mice. We found that loss of TREM2 impairs normal neurodevelopment, resulting in reduced synapse number across the cortex and hippocampus in 1-month-old mice. This reduction in synapse number was not due directly to alterations in interactions between microglia and synapses. Rather, TREM2 was required for microglia to limit synaptic engulfment by astrocytes during development. While these changes were largely normalized later in adulthood, high fat diet administration was sufficient to reinitiate TREM2-dependent modulation of synapse loss. Together, this identifies a novel role for microglia in instructing synaptic pruning by astrocytes to broadly regulate appropriate synaptic refinement, and suggests novel candidate mechanisms for how TREM2 and microglia could influence synaptic loss in brain injury and disease.     

Platelet adhesion to damaged coronary arteries: Comparison in normal and von Willebrand disease swine.

The early response to coronary artery injury was investigated in normal swine and in swine with von Willebrand disease (vWD). Thirty minutes after coronary endothelial denudation, a monolayer of platelets was adherent to areas of simple injury in both bleeder and normal swine. The number of adherent platelets was not significantly different in the two phenotypes. Injury involving the media of the vessel produced platelet-fibrin thrombi. Platelet activation, as judged by pseudopod formation and platelet spreading over areas of simple injury, was significantly less in bleeder animals than in normal animals. These studies suggest that chemotaxis and initial contact adhesion of platelets to injured arterial wall is independent of the von Willebrand factor. On the other hand, the spreading and activation of platelets on the subendothelium appear to be dependent on the presence of plasma von Willebrand factor. Through this mechanism von Willebrand factor may contribute to arterial thrombosis and atherogenesis.     

Alterations in beta-amyloid production and deposition in brain regions of two transgenic models

Mutations in the amyloid precursor protein (APP) gene are associated with altered production and deposition of amyloid beta (Abeta) peptide in the Alzheimer's disease (AD) brain. The pathways that regulate APP processing, Abeta production and Abeta deposition in different tissues and brain regions remain unclear. To address this, we examined levels of various APP processing products as well as Abeta deposition in a genomic-based (R1.40) and a cDNA-based (Tg2576) transgenic mouse model of AD. In tissues, only brain generated detectable levels of the penultimate precursor to Abeta, APP C-terminal fragment-beta. In brain regions, holoAPP levels remained constant, but ratios of APP C-terminal fragments and levels of Abeta differed significantly. Surprisingly, cortex had the lowest steady-state levels of Abeta compared to other brain regions. Comparison of Abeta deposition in Tg2576 and R1.40 animals revealed that R1.40 exhibited more abundant deposition in cortex while Tg2576 exhibited extensive deposition in the hippocampus. Our results suggest that AD transgenic models are not equal; their unique characteristics must be considered when studying AD pathogenesis and therapies.     

Cross-species chromosome painting in bats from Madagascar: the contribution of Myzopodidae to revealing ancestral syntenies in Chiroptera

The chiropteran fauna of Madagascar comprises eight of the 19 recognized families of bats, including the endemic Myzopodidae. While recent systematic studies of Malagasy bats have contributed to our understanding of the morphological and genetic diversity of the island’s fauna, little is known about their cytosystematics. Here we investigate karyotypic relationships among four species, representing four families of Chiroptera endemic to the Malagasy region using cross-species chromosome painting with painting probes of Myotis myotis: Myzopodidae (Myzopoda aurita, 2n = 26), Molossidae (Mormopterus jugularis, 2n = 48), Miniopteridae (Miniopterus griveaudi, 2n = 46), and Vespertilionidae (Myotis goudoti, 2n = 44). This study represents the first time a member of the family Myzopodidae has been investigated using chromosome painting. Painting probes of M. myotis were used to delimit 29, 24, 23, and 22 homologous chromosomal segments in the genomes of M. aurita, M. jugularis, M. griveaudi, and M. goudoti, respectively. Comparison of GTG-banded homologous chromosomes/chromosomal segments among the four species revealed the genome of M. aurita has been structured through 14 fusions of chromosomes and chromosomal segments of M. myotis chromosomes leading to a karyotype consisting solely of bi-armed chromosomes. In addition, chromosome painting revealed a novel X-autosome translocation in M. aurita. Comparison of our results with published chromosome maps provided further evidence for karyotypic conservatism within the genera Mormopterus, Miniopterus, and Myotis. Mapping of chromosomal rearrangements onto a molecular consensus phylogeny revealed ancestral syntenies shared between Myzopoda and other bat species of the infraorders Pteropodiformes and Vespertilioniformes. Our study provides further evidence for the involvement of Robertsonian (Rb) translocations and fusions/fissions in chromosomal evolution within Chiroptera.     

Structure of a Venezuelan equine encephalitis virus assembly intermediate isolated from infected cells

Venezuelan equine encephalitis virus (VEEV) is a prototypical enveloped ssRNA virus of the family Togaviridae. To better understand alphavirus assembly, we analyzed newly formed nucleocapsid particles (termed pre-viral nucleocapsids) isolated from infected cells. These particles were intermediates along the virus assembly pathway, and ultimately bind membrane-associated viral glycoproteins to bud as mature infectious virus. Purified pre-viral nucleocapsids were spherical with a unimodal diameter distribution. The structure of one class of pre-viral nucleocapsids was determined with single particle reconstruction of cryo-electron microscopy images. These studies showed that pre-viral nucleocapsids assembled into an icosahedral structure with a capsid stoichiometry similar to the mature nucleocapsid. However, the individual capsomers were organized significantly differently within the pre-viral and mature nucleocapsids. The pre-viral nucleocapsid structure implies that nucleocapsids are highly plastic and undergo glycoprotein and/or lipid-driven rearrangements during virus self-assembly. This mechanism of self-assembly may be general for other enveloped viruses.     

Characterization of the putative cholesterol transport protein metastatic lymph node 64 in the brain

Intracellular management of cholesterol is a critical process in the brain. Deficits with cholesterol transport and storage are linked to neurodegenerative disorders such as Neimann-Pick disease type C and Alzheimer's disease. One protein putatively involved in cholesterol transport is metastatic lymph node 64 (MLN64). MLN64 localizes to late endosomes which are part of the cholesterol internalization pathway. However, a detailed pattern of MLN64 expression in the brain is unclear. Using immunocytochemical and immunoblot analyses, we demonstrated the presence of MLN64 in several tissue types and various regions within the brain. MLN64 immunostaining in the CNS was heterogeneous, indicating selective expression in discrete specific cell populations and regions. MLN64 immunoreactivity was detected in glia and neurons, which displayed intracellular labeling consistent with an endosomal localization. Although previous studies suggested that MLN64 may promote steroid production in the brain, MLN64 immunoreactivity did not colocalize with steroidogenic cells in the CNS. These results demonstrate that MLN64 is produced in the mouse and human CNS in a restricted pattern of expression, suggesting that MLN64 serves a cell-specific function in cholesterol transport.     

Physiological and biochemical characteristics of skeletal muscles in sedentary and active rats

Laboratory rats are sedentary if housed in conditions where activity is limited. Changes in muscle characteristics with chronic inactivity were investigated by comparing sedentary rats with rats undertaking voluntary wheel running for either 6 or 12 weeks. EDL (type II fibers) and soleus (SOL) muscles (predominantly type I fibers) were examined. When measured within 1–2 h post-running, calcium sensitivity of the contractile apparatus was increased, but only in type II fibers. This increase disappeared when fibers were treated with DTT, indicative of oxidative regulation of the contractile apparatus, and was absent in fibers from rats that had ceased running 24 h prior to experiments. Specific force production was ~?10 to 25% lower in muscle fibers of sedentary compared to active rats, and excitability of skinned fibers was decreased. Muscle glycogen content was ~?30% lower and glycogen synthase content?~?50% higher in SOL of sedentary rats, and in EDL glycogenin was 30% lower. Na⁺, K⁺-ATPase α1 subunit density was ~?20% lower in both EDL and SOL in sedentary rats, and GAPDH content in SOL?~?35% higher. There were no changes in content of the calcium handling proteins calsequestrin and SERCA, but the content of CSQ-like protein was increased in active rats (by ~?20% in EDL and 60% in SOL). These findings show that voluntary exercise elicits an acute oxidation-induced increase in Ca²⁺ sensitivity in type II fibers, and also that there are substantial changes in skeletal muscle characteristics and biochemical processes in sedentary rats.