Avian dark cells

Dark cells (DCs) of mammalian and non-mammalian species help to maintain the homeostasis of the inner ear fluids in vivo. Although the avian cochlea is straight and the mammalian cochlea is coiled, no significant difference in the morphology and/or function of mammalian and avian DCs has been reported. The mammalian equivalent of avian DCs are marginal cells and are located in the stria vascularis along a bony sheet. Avian DCs hang free from the tegmentum vasculosum (TV) of the avian lagena between the perilymph and endolymph. Frame averaging was used to image the fluorescence emitted by several fluorochromes applied to freshly isolated dark cells (iDCs) from chickens (Gallus domesticus) inner ears. The viability of iDCs was monitored via trypan blue exclusion at each isolation step. Sodium Green, BCECF-AM, Rhodamine 123 and 9-anthroyl ouabain molecules were used to test iDC function. These fluorochromes label iDCs ionic transmembrane trafficking function, membrane electrogenic potentials and Na+/K+ ATPase pump's activity. Na+/K+ ATPase pump sites, were also evaluated by the p-nitrophenyl phosphatase reaction. These results suggest that iDCs remain viable for several hours after isolation without special culturing requirements and that the number and functional activity of Na+/K+ ATPase pumps in the iDCs were indistinguishable from in vivo DCs. Primary cultures of freshly iDCs were successfully maintained for 28 days in plastic dishes with RPMI 1640 culture medium. The preparation of iDCs overcomes the difficulty of DCs accessability in vivo and the unavoidable contamination that rupturing the inner ear microenvironments induces.

Concentration-dependent differential induction of necrosis or apoptosis by HIV-1 lytic peptide 1

The mechanism by which human immunodeficiency virus type 1 induces depletion of CD4+ T-lymphocytes remains controversial, but may involve cytotoxic viral proteins. Synthetic peptides (lentivirus lytic peptide type 1) corresponding to the carboxyl terminus of the human immunodeficiency virus type 1 transmembrane glycoprotein induce cytopathology at concentrations of 100 nM and above. At these concentrations lentivirus lytic peptide type 1 disrupts mitochondrial integrity of CD4+ T-lymphoblastoid cells and induces other changes characteristic of necrosis. In contrast, at concentrations of 20 nM, lentivirus lytic peptide type 1 potently induces apoptosis. Thus, the mechanism by which human immunodeficiency virus type 1 mediates cell death, necrosis or apoptosis, may depend, in part, on the tissue concentration of transmembrane glycoprotein.

Both necrosis and apoptosis contribute to HIV-1-induced killing of CD4 cells

BACKGROUND

Data currently available on HIV-1-induced cytopathology is unclear regarding the mechanism of cell killing.

OBJECTIVE

To clarify the extent to which apoptosis or necrosis is involved in HIV-1-induced cell death in view of conflicting existing data.

METHODS

T lymphoblastoid cells or peripheral blood mononuclear cells were infected by various strains of HIV-1 and the numbers of apoptotic or necrotic cells were quantified at various times after infection using video-image analysis techniques; the results were compared with the amount of fragmented DNA using a quantitative method. Measurement of mitochondrial transmembrane potential (deltapsi(m)) and intracellular calcium concentrations [Ca2+]i was performed with fluorescent probes and fluorescence concentration analysis (FCA).

RESULTS

Although lymphoblastoid and monocytoid cells acutely infected by HIV-1 had increased levels of fragmented DNA, a marker of apoptotic cell death, few (<12%) had condensed chromatin and fragmented nuclei, the morphological features of apoptosis. The predominant alterations in acutely infected cells were distended endoplasmic reticulum and abnormal mitochondria; these ultrastructural changes are consistent with necrosis, although some infected cells simultaneously displayed features of both necrosis and apoptosis. Viability of cells persistently infected by HIV-1 was only minimally reduced from that of uninfected cells. This reduction was accounted for by an increased propensity of the persistently infected cells to die by apoptosis. Alterations in [Ca2+]i and deltapsi(m) occurred in both acutely and persistently infected cells.

CONCLUSION

Both necrosis and apoptosis contribute to HIV-1-induced killing of CD4 cells.

Acridine-induced subcellular and functional changes in isolated human hepatocytes in vitro

Acridines are nucleic acid intercalating compounds with properties relating to the complexity of their structure. Tetrahydroaminoacridine (tacrine, Cognex), a simple acridine, is a reversible inhibitor of cholinesterase activity available for the symptomatic treatment of Alzheimer's disease. Tacrine therapy causes sporadic elevations of aminotransferases in humans, and tacrine alters protein synthesis and ribosomal structure under short-term in vitro exposures in isolated hepatocytes from humans and other species. There is no clear relationship between transaminase elevation and liver damage in humans, and prolonged drug exposure to animals does not result in hepatic insult. Subcellular alterations have been described in isolated human and rodent hepatocytes, including degranulation and vesiculation of the endoplasmic reticulum (ER), aggregation of electron-dense structures within the ER, altered nuclei and nucleoli and detrimental structural and functional effects to mitochondria. Whether these changes in hepatocyte morphology and function are unique to tacrine or not is unknown, as human hepatocytes exposed to more complex acridines have not been characterized. In this study, we extended the results of in vitro studies with tacrine to acridine orange, 9-aminoacridine, quinacrine and proflavin. In primary human hepatocytes, these compounds caused a similar reduction of mitochondrial membrane potential with parallel ultrastructural changes. The 1-hydroxy and 7-hydroxy tacrine metabolites, acridine hydrochloride and acridine 9-carboxylic acid, and the non-acridine cholinesterase inhibitor eserine, did not induce characteristic subcellular ER changes but damaged mitochondria structure, reduced mitochondrial membrane potential and were cytotoxic. These data indicate that the tacrine-like subcellular changes in hepatocytes are reproducible with other acridines and cause mitochondrial dysfunction in human hepatocytes.

A synthetic peptide corresponding to the carboxy terminus of human immunodeficiency virus type 1 transmembrane glycoprotein induces alterations in the ionic permeability of Xenopus laevis oocytes

The carboxy-terminal 29 amino acids of the human immunodeficiency virus type 1 transmembrane glycoprotein (HIV-1 TM) are referred to as lentivirus lytic peptide 1 (LLP-1). Synthetic peptides corresponding to LLP-1 have been shown to induce cytolysis and to alter the permeability of cultured cells to various small molecules. To address the mechanisms by which LLP-1 induces cytolysis and membrane permeability changes, various concentrations of LLP-1 were incubated with Xenopus laevis oocytes, and two-electrode, voltage-clamp recording measurements were performed. LLP-1 at concentrations of 75 nM and above induced dramatic alterations in the resting membrane potential and ionic permeability of Xenopus oocytes. These concentrations of LLP-1 appeared to induce a major disruption of plasma membrane electrophysiological integrity. In contrast, concentrations of LLP-1 of 20-50 nM induced changes in membrane ionic permeability that mimic changes induced by compounds, such as the bee venom peptide melittin, that are known to form channel-like structures in biological membranes at sublytic concentrations. An analog of LLP-1 with greatly reduced cytolytic activity failed to alter the electrophysiological properties of Xenopus oocytes. Thus, by altering plasma membrane ionic permeability, the carboxy terminus of TM may contribute to cytolysis of HIV-1-infected CD4+ cells.

Use of antipolymer antibody assay in recipients of silicone breast implants

BACKGROUND

Local complications (encapsulation, rashes, rupture, and leakage) can occur after placement of silicone gel-containing breast implants (SBI). Whether SBI exposure results in systemic manifestations in some recipients is controversial. We have carried out a blinded study to assess whether there is any difference between SBI recipients and non-exposed controls in the proportions positive for serum antibodies directed against polymeric substances.

METHODS

We recruited female SBI recipients (including those without symptoms) who presented to a single rheumatology clinic. A physician global assessment was used to classify SBI recipients who did not meet criteria for specific autoimmune diseases according to the severity of local and systemic signs and symptoms. Controls were recruited from among clinic staff and their acquaintances. Results of the antipolymer antibody (APA) assay were compared with those of an assay for antinuclear antibodies (ANA) and with the severity of the signs and symptoms.

FINDINGS

Positive APA results were found in one (3%) of 34 SBI recipients with limited symptoms, two (8%) of 26 with mild symptoms, seven (44%) of 16 with moderate symptoms, and 13 (68%) of 19 with advanced symptoms. Four (17%) of 23 healthy non-SBI-exposed controls and two (10%) of 20 non-exposed women with classic autoimmune diseases were positive for APA. Thus, women with moderate or advanced symptoms were significantly more likely than those with limited or mild symptoms, or non-exposed controls to have APA (p < 0.001). The proportion with positive ANA results was higher for women with classic autoimmune diseases 14 (70%) of 20 than for any SBI-exposed subgroup (0-33%).

INTERPRETATION

The APA assay can objectively contribute to distinguishing between SBI recipients with limited or mild signs and symptoms. SBI recipients with more severe manifestations, and patients with specific autoimmune diseases. Further studies will be needed to define the signs and symptoms associated with exposure to SBI.

Human immunodeficiency virus infection of T-lymphoblastoid cells reduces intracellular pH

Alterations in plasma membrane function are induced by many cytopathic viruses, including human immunodeficiency virus type 1 (HIV-1). These alterations can result in changes in the intracellular content of ions and other small molecules and can contribute to cytolysis and death of the infected cell. The pH-sensitive fluorescent probe 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein-acetoxymethyl ester was used to quantitate intracellular pH (pHi) in HIV-1-infected T cells. Infection of cells from the CD4+ T-lymphoblastoid line HUT-78 (RH9 subclone) with HIV-1 strain LAI resulted in a significant decrease of pHi, from approximately 7.2 in mock-infected cells to below 6.7 by day 4 after infection, when cells were undergoing acute cytopathic effects. The pHi in persistently infected cells that survived the acute cytopathic effects of HIV-1 was approximately 6.8 to 7.0. Studies with amiloride, an inhibitor of the Na+/H+ exchange system, suggest that HIV-1-induced intracellular acidification in lymphocytes is due, in part, to dysfunction of this plasma membrane ion transport system. The alterations in pHi may mediate certain cytopathic effects of HIV-1, thereby contributing to depletion of CD4+ T lymphocytes in patients with AIDS.

Comparison of DNA fragmentation and color thresholding for objective quantitation of apoptotic cells

Apoptosis is a process of cell death characterized by distinctive morphological changes and fragmentation of cellular DNA. Using video imaging and color thresholding techniques, we objectively quantitated the number of cultured CD4+ T-lymphoblastoid cells (HUT78 cells, RH9 subclone) displaying morphological signs of apoptosis before and after exposure to gamma-irradiation. The numbers of apoptotic cells measured by objective video imaging techniques were compared to numbers of apoptotic cells measured in the same samples by sensitive apoptotic assays that quantitate DNA fragmentation. DNA fragmentation assays gave consistently higher values compared with the video imaging assays that measured morphological changes associated with apoptosis. These results suggest that substantial DNA fragmentation can precede or occur in the absence of the morphological changes which are associated with apoptosis in gamma-irradiated RH9 cells.