Polarised Asymmetric Inheritance of Accumulated Protein Damage in Higher Eukaryotes

Disease-associated misfolded proteins or proteins damaged due to cellular stress are generally disposed via the cellular protein quality-control system. However, under saturating conditions, misfolded proteins will aggregate. In higher eukaryotes, these aggregates can be transported to accumulate in aggresomes at the microtubule organizing center. The fate of cells that contain aggresomes is currently unknown. Here we report that cells that have formed aggresomes can undergo normal mitosis. As a result, the aggregated proteins are asymmetrically distributed to one of the daughter cells, leaving the other daughter free of accumulated protein damage. Using both epithelial crypts of the small intestine of patients with a protein folding disease and Drosophila melanogaster neural precursor cells as models, we found that the inheritance of protein aggregates during mitosis occurs with a fixed polarity indicative of a mechanism to preserve the long-lived progeny

Neuronal Circuitry and Neurotransmitters in the Pretectal and Accessory Optic Systems

This chapter focuses on data obtained primarily from the nucleus of the optic tract (NOT) and accessory optic system (AOS) nuclei of mammals. The pretectal nuclear complex of mammals consists of several different nuclei situated between the superior colliculus and the dorsal thalamus. GABAergic and non-GABAergic neurons are scattered throughout the NOT with no specific topography. GABA is the major inhibitory neurotransmitter in the brain and plays a prominent role in the NOT and AOS pathways mediating visual-vestibular interaction. Opioid peptides have profound sensory effects, and are known to severely disrupt visual and oculomotor behavior in man, such as reduced visual sensitivity, diminished gain of smooth pursuit, and hypometric saccades with reduced velocities. The question of mismatch of neurotransimitter/neurotransmitter receptor appears to be quite relevant to the terminal AOS nuclei as studied in the rat. The functional relationship between opioid receptors and putative neurotransmitters in the AOS has yet to be determined.</p

Microvascular changes in estrogen-α sensitive brainstem structures of aging female hamsters

Structural neuronal plasticity is present in the nucleus para-retroambiguus (NPRA) and the commissural nucleus of the solitary tract/A2 group (NTScom/A2) in female hamsters. Both brainstem nuclei play a role in estrous cycle related autonomic adaptations. We investigated how aging affects the capillary condition in these adaptive brainstem regions. Senescent female hamsters (±95 weeks) were tested weekly for their 4-day estrous cycle. Subsequently morphological changes of NPRA and NTScom/A2 were compared with those of young (±20 weeks) females in an ultrastructural study. The medial tegmental field served as control area. In 841 capillaries (n = 319 capillaries, young females (N = 3); n = 522 capillaries, aged females (N = 4)) vascular aberrations were classified into 3 categories: endothelial and tight junction, basement membrane and pericyte aberrations. In old animals, capillaries showed marked endothelial changes, disrupted tight junctions, and thickening and splitting of basement membranes. Aberrations were found in 40–60% of all capillaries. About 70% of the pericytes contained degenerative inclusions. Despite this generalized vascular degeneration, the reproductive cycle of female hamsters was unaffected by vascular senescence. Perivascular fibrosis as reported in aging rats was never observed, which suggests the existence of species differences.

Different intrahepatic distribution of phosphatidylglycerol and phosphatidylserine liposomes in the rat

Liposomes with diameters of 200 to 400 nm containing phosphatidylserine (PS) or phosphatidylglycerol (PG) were injected intravenously into rats, Two hours after injection, T5% of the injected dose of PS liposomes was found in the liver and only 10% found in the spleen, while 35% of the PG liposomes was found in the liver and as much as 40% was found in the spleen. Cell-isolation experiments revealed the following remarkable difference in the intrahepatic distribution between the two liposome formulations: the PS liposomes distributed in about equal amounts to Kupffer cells and hepatocytes, despite their size (200-400 nm) exceeding that of the endothelial fenestrae (average 150 Mt), whereas the PG liposomes were only taken up by the Kupffer cells and not at all by the hepatocytes, Double-label studies, using liposomes in which the lipid-moiety was radio labeled with [H-3]cholesteryloleylether ([H-3]CE) and the water phase with [C-14]sucrose, showed that the liposomes were taken up as intact particles. These observations were confirmed through electron microscopy by determining the in situ localization of liposome-encapsulated colloidal gold particles in thin sections of liver and spleen. The differences in organ distribution are ascribed to differences in opsonization patterns of the two liposomal surfaces. For the difference in intrahepatic distribution, we offer the following two explanations: the exploitation of the blood cell-mediated forced sieving concept and the indication of a PS-specific pharmacological effect on the dimensions of the fenestrations (HEPATOLOGY 1997;26:416-423.)

Polyglutamine Aggregates Are Inherited by De Novo Generated Neuroblast Cells after Mitosis in <i>D. Melanogaster</i>

<div><p>(A) Expression of Htt-Q128 (red) and Pon-GFP (green) was assessed by confocal laser scanning microscopy in whole embryos (Stage 11, in which anterior is at the top). Occasionally, Htt-Q128 aggregates were observed (inset).</p> <p>(B) During mitosis, the aggregated protein Htt-Q128 is associated with only one of the poles in metaphase, anaphase, and telophase, opposing the Pon-GFP crescent, indicative of asymmetric inheritance to de novo generated neuroblast.</p> <p>(C) Spindle pole–associated aggregates were more clearly visualised after α-tubulin (red) staining in Htt-Q128 (cyan), Pon-GFP (green) neuroblasts. DNA is stained with DAPI (blue).</p></div

Polyglutamine-Expanded Proteins Form Aggresomes in Hamster O23 Cells and Human HEK293 Cells

<div><p>(A) Percentage of cells containing inclusions 24 h after transfection with a fluorescently tagged huntingtin fragment containing a stretch of either 74 (O23: EGFP-HDQ74) or 119 (HEK293: HDQ119-EYFP) glutamines.</p> <p>(B) Fraction of cells showing either aggresome-like inclusions or non–aggresome-like inclusions (nuclear and/or multiple scattered inclusions). Bars represent standard errors of the mean.</p> <p>(C) Aggresome-like inclusions are either close to (upper panel) or co-localise (lower panel) with the centrosomes (decorated with γ-tubulin antibodies) in interphase O23 cells (likewise in HEK293 cells, <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0040417#pbio-0040417-sg001" target="_blank">Figure S1</a>).</p> <p>(D) Vimentin microfilaments are redistributed in a cage-like manner around the inclusion, consistent with aggresome morphology. Note that also microtubules (decorated with α-tubulin antibodies) showed partial redistribution to the aggresome.</p> <p>(E) Sequential confocal planes of an aggresome showing both co-localisation with the centrosome and the cage of vimentin. For a full image of this cell see <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0040417#pbio-0040417-sg001" target="_blank">Figure S1</a>B. DNA is stained with DAPI (blue) and only shown in the overlay images. Bars in (C) and (D) represent 10 μm. Bar in (E) represents 2 μm.</p></div