Search PubMed⌕ Search

Biomedical subjects

I I Kruman

Publications and source records attributed to I I Kruman.

At least 19 recordsLinked to original sources
PubMed2000

Homocysteine elicits a DNA damage response in neurons that promotes apoptosis and hypersensitivity to excitotoxicity.

Elevated plasma levels of the sulfur-containing amino acid homocysteine increase the risk for atherosclerosis, stroke, and possibly Alzheimer's disease, but the underlying mechanisms are unknown. We now report that homocysteine induces apoptosis in rat hippocampal neurons. DNA strand breaks and associated activation of poly-ADP-ribose polymerase (PARP) and NAD depletion occur rapidly after exposure to homocysteine and precede mitochondrial dysfunction, oxidative stress, and caspase activation. The PARP inhibitor 3-aminobenzamide (3AB) protects neurons against homocysteine-induced NAD depletion, loss of mitochondrial transmembrane potential, and cell death, demonstrating a requirement for PARP activation and/or NAD depletion in homocysteine-induced apoptosis. Caspase inhibition accelerates the loss of mitochondrial potential and shifts the mode of cell death to necrosis; inhibition of PARP with 3AB attenuates this effect of caspase inhibition. Homocysteine markedly increases the vulnerability of hippocampal neurons to excitotoxic and oxidative injury in cell culture and in vivo, suggesting a mechanism by which homocysteine may contribute to the pathogenesis of neurodegenerative disorders.

Animals↗
PubMed1999

ALS-linked Cu/Zn-SOD mutation increases vulnerability of motor neurons to excitotoxicity by a mechanism involving increased oxidative stress and perturbed calcium homeostasis.

We employed a mouse model of ALS, in which overexpression of a familial ALS-linked Cu/Zn-SOD mutation leads to progressive MN loss and a clinical phenotype remarkably similar to that of human ALS patients, to directly test the excitotoxicity hypothesis of ALS. Under basal culture conditions, MNs in mixed spinal cord cultures from the Cu/Zn-SOD mutant mice exhibited enhanced oxyradical production, lipid peroxidation, increased intracellular calcium levels, decreased intramitochondrial calcium levels, and mitochondrial dysfunction. MNs from the Cu/Zn-SOD mutant mice exhibited greatly increased vulnerability to glutamate toxicity mediated by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors. The increased vulnerability of MNs from Cu/Zn-SOD mutant mice to glutamate toxicity was associated with enhanced oxyradical production, sustained elevations of intracellular calcium levels, and mitochondrial dysfunction. Pretreatment of cultures with vitamin E, nitric oxide-suppressing agents, peroxynitrite scavengers, and estrogen protected MNs from Cu/Zn-SOD mutant mice against excitotoxicity. Excitotoxin-induced degeneration of spinal cord MNs in adult mice was more extensive in Cu/Zn-SOD mutant mice than in wild-type mice. The mitochondrial dysfunction associated with Cu/Zn-SOD mutations may play an important role in disturbing calcium homeostasis and increasing oxyradical production, thereby increasing the vulnerability of MNs to excitotoxicity.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1999

Evidence that Par-4 participates in the pathogenesis of HIV encephalitis.

Progressive neuronal degeneration in brain regions involved in learning and memory processes is a common occurrence in patients infected with human immunodeficiency virus type 1 (HIV-1). We now report that levels of Par-4, a protein recently linked to neuronal apoptosis in Alzheimer's disease, are increased in neurons in hippocampus of human patients with HIV encephalitis and in monkeys infected with a chimeric strain of HIV-1 and simian immunodeficiency virus. Par-4 levels increased rapidly in cultured hippocampal neurons following exposure to the neurotoxic HIV-1 protein Tat, and treatment of the cultures with a Par-4 antisense oligonucleotide protected the neurons against Tat-induced apoptosis. Additional findings show that Par-4 participates at an early stage of Tat-induced neuronal apoptosis before caspase activation, oxidative stress, and mitochondrial dysfunction. Our data suggest that Par-4 may be a mediator of neuronal apoptosis in HIV encephalitis and that therapeutic approaches targeting the Par-4 apoptotic cascade may prove beneficial in preventing neuronal degeneration and associated dementia in patients infected with HIV-1.

Animals↗
PubMed1999

Pivotal role of mitochondrial calcium uptake in neural cell apoptosis and necrosis.

Perturbed cellular calcium homeostasis has been implicated in both apoptosis and necrosis, but the role of altered mitochondrial calcium handling in the cell death process is unclear. The temporal ordering of changes in cytoplasmic ([Ca2+]C) and intramitochondrial ([Ca2+]M) calcium levels in relation to mitochondrial reactive oxygen species (ROS) accumulation and membrane depolarization (MD) was examined in cultured neural cells exposed to either an apoptotic (staurosporine; STS) or a necrotic (the toxic aldehyde 4-hydroxynonenal; HNE) insult. STS and HNE each induced an early increase of [Ca2+]C followed by delayed increase of [Ca2+]M. Overexpression of Bcl-2 blocked the elevation of [Ca2+]M and the MD in cells exposed to STS but not in cells exposed to HNE. The cytoplasmic calcium chelator BAPTA-AM and the inhibitor of mitochondrial calcium uptake ruthenium red prevented both apoptosis and necrosis. STS and HNE each induced mitochondrial ROS accumulation and MD, which followed the increase of [Ca2+]M. Cyclosporin A prevented both apoptosis and necrosis, indicating critical roles for MD in both forms of cell death. Caspase activation occurred only in cells undergoing apoptosis and preceded increased [Ca2+]M. Collectively, these findings suggest that mitochondrial calcium overload is a critical event in both apoptotic and necrotic cell death.

Amino Acid Chloromethyl Ketones↗
PubMed1998

HIV-1 protein Tat induces apoptosis of hippocampal neurons by a mechanism involving caspase activation, calcium overload, and oxidative stress.

Patients infected with HIV-1 often exhibit cognitive deficits that are related to progressive neuronal degeneration and cell death. The protein Tat, which is released from HIV-1-infected cells, was recently shown to be toxic toward cultured neurons. We now report that Tat induces apoptosis in cultured embryonic rat hippocampal neurons. Tat induced caspase activation, and the caspase inhibitor zVAD-fmk prevented Tat-induced neuronal death. Tat induced a progressive elevation of cytoplasmic-free calcium levels, which was followed by mitochondrial calcium uptake and generation of mitochondrial-reactive oxygen species (ROS). The intracellular calcium chelator BAPTA-AM and the inhibitor of mitochondrial calcium uptake ruthenium red protected neurons against Tat-induced apoptosis. zVAD-fmk suppressed Tat-induced increases of cytoplasmic calcium levels and mitochondrial ROS accumulation, indicating roles for caspases in the perturbed calcium homeostasis and oxidative stress induced by Tat. An inhibitor of nitric oxide synthase, and the peroxynitrite scavenger uric acid, protected neurons against Tat-induced apoptosis, indicating requirements for nitric oxide production and peroxynitrite formation in the cell death process. Finally, Tat caused a delayed and progressive mitochondrial membrane depolarization, and cyclosporin A prevented Tat-induced apoptosis, suggesting an important role for mitochondrial membrane permeability transition in Tat-induced apoptosis. Collectively, our data demonstrate that Tat can induce neuronal apoptosis by a mechanism involving disruption of calcium homeostasis, caspase activation, and mitochondrial calcium uptake and ROS accumulation. Agents that interupt this apoptotic cascade may prove beneficial in preventing neuronal degeneration and associated dementia in AIDS patients.

AIDS Dementia Complex↗
PubMed1997

Acridine orange as an indicator of the cytoplasmic ribosome state.

In hippocampal neurons of ground squirrels and neuroblastoma culture the ribosome state was analyzed by staining with acridine orange (AO), labeling with radioactive amino acids, and electron microscopy. Electron microscopy indicated that the extent to which ribosomes associated in polysomes varied from 25% in brain cells of torpid ground squirrels up to 93% in growing neuroblastoma cells. In control rat neurons, it was 75%. The fluorescence of the AO-rRNA complex in ribosomes changed with the polysome/monosome ratio. The red fluorescence of AO-single-stranded rRNA complex as well as ribosome association in polysomes decreased greatly as a function of the shift from polysomes to monosomes. The green fluorescence of AO intercalated in the double-stranded rRNA changed insignificantly. As a result, the ratio of red to green fluorescence intensity, Kalpha, changed more than 3-fold with the changing polysome/monosome ratio. Protein labeling also showed strong positive correlation with Kalpha. Thus, rRNA showed different accessibility for AO binding in active and inactive ribosomes. A possible mechanism of partial rRNA shielding with proteins is proposed. AO fluorescence in the cytoplasm, i.e., AO binding to rRNA in ribosomes, is presumed to reflect adequately the profound changes in the state of cell protein synthesizing system that can be regulated by both functional activity and stress factors.

Acridine Orange↗
PubMed1996

A role for T cell CD4 in contact mediated T dependent B cell activation.

Using a monoclonal antibody to CD4 we have shown that occupation of CD4 on T cells induces a strong dose dependent inhibition of in vitro IgM plaque forming cell (PFC) response of spleen cells to the T dependent antigen (Ag), sheep red blood cells (SRBC), in Mishell-Dutton cultures. This inhibitory effect is not due simply to nonspecific perturbation or Fc binding, since F(ab) fragments of anti-CD4 are as potent as the intact antibodies, whereas antibodies to class I molecules or T cell CD5 have no effect. The anti-CD4 antibody appears to block contact dependent interaction between T and B cells and this inhibitory effect cannot be overcome by cytokines. Anti-CD4 did not inhibit the PFC response to the T independent antigen, trinitrophenylated lipopolysaccharide. The anti-CD4 antibody prevented the interaction of preactivated fixed SRBC specific T helper cells with B cells, suggesting that CD4 had a role in contact mediated interactions between T cells and B cells. Surprisingly, antibodies to CD40L failed to inhibit the SRBC specific PFC response. Thus CD4 appears to be an important molecule required for cognate interactions between T and B cells that are needed to generate an Ag specific PFC response.

Animals↗
PubMed1993

Differentiation and apoptosis of murine neuroblastoma cells N1E115.

The mode and the kinetics of differentiation and death of murine N1E115 neuroblastoma cells induced by dimethyl sulfoxide and other nonspecific factors in vitro were investigated. After morphological differentiation neuroblastoma cells die by apoptosis which is indicated by characteristic morphological features and by internucleosomal DNA fragmentation. Durations of both differentiation and apoptosis are dependent on the nature of stimuli used. Protein synthesis inhibitor cycloheximide does not prevent differentiation and apoptosis of neuroblastoma cells induced by dimethyl sulfoxide and even accelerates both processes. The relationship between cell death and differentiation is discussed.

Animals↗
PubMed1992

Apoptosis of murine BW 5147 thymoma cells induced by cold shock.

Exposure of thymoma BW 5147 cells to cold (0-2 degrees C) followed by rewarming at 37 degrees C (cold shock) resulted in internucleosomal DNA cleavage. Sensitivity to cold shock-induced cell death was critically dependent on the serum concentration in the medium and limited to serum-deficient medium (2% serum concentration), whereas cells in the complete growth medium (10%) were completely resistant. RNA/protein-synthesis inhibitors (cycloheximide and actinomycin D) had no effect on cold shock-induced DNA cleavage in BW 5147 cells. The DNA fragmentation seems to be independent of increase in the cytosolic Ca2+ level. Moreover, reduction in the calcium content of the external medium by EGTA induced DNA cleavage. Incubation of BW 5147 cells in the presence of colchicine and cytochalasin B led to the apoptosis. The latter suggests that the internucleosomal DNA cleavage induced by cold shock may be concerned with the disruption of some cytoskeletal network caused by cooling. The results are discussed in relation to cell proliferation.

Animals↗
PubMed1992

Comparative analysis of cell replacement in hibernators.

1. Cell renewal in hibernators undergoes seasonal rhythm independent of the hibernation state. 2. We propose that seasonal depression of cell renewal in tissues of hibernators is caused by seasonal involution of thymus in these animals. 3. The latter is known to be involved in the control of cell proliferation. 4. The state of hibernation per se has also an effect on cellular proliferation. 5. It induces the block of cells in the permitotic phase. It is suggested that the blockage of cells in renewing tissues of hibernators under natural deep hypothermia throughout a period of torpidity represents the adaptive reaction of the organism.

Animals↗
PubMed1992

[The programmed cell death of murine BW5147 thymoma under the action of dexamethasone].

By flow cytometry, imitation modelling and biochemical analysis, the mode and kinetics of dexamethasone-treated T-lymphoma cell death were studied. The hormone was shown to induce delays in pre- and postsynthetic phases of the cell cycle and the death of part of cells. A short exposure to dexamethasone reveals its cytostatic rather than cytolytic effect. Following G2/M delay and cytokinesis, part of cells dies. A reduced serum concentration (2%) causes shorter delays in the cell cycle and a more rapid cell death. Dexamethasone stimulates apoptosis which is indicated by internucleosomal DNA fragmentation, and by a coincidence in time of the processes of DNA degradation and increase in the other membrane permeability. These results are discussed in relation to the cell death and proliferation.

Animals↗
PubMed1992

[The cellular apoptosis of murine BW5147 thymoma during cold shock].

The mode of T-lymphoma cell death induced by cold shock was studied. The rewarming of cells at 37 degrees C following a brief period of cold (0 degrees C) resulted in internucleosomal DNA fragmentation. The cells underwent cold shock-mediated apoptosis only at a reduced (2%) serum concentration. The apoptosis was not blocked by macromolecular synthesis inhibitors such as cycloheximide and antinomycin D, or by Quin-2. EGTA per se was responsible for the initiation of cell death. Colchicine also induced internucleosomal fragmentation of DNA. Our findings suggest that cold shock induced apoptosis is associated with low temperature mediated disruption of microtubules. The role of Ca2+ and growth factors in cold shock induced cell death is discussed.

Animals↗
PubMed1991

Apoptosis of murine BW 5147 thymoma cells induced by dexamethasone and gamma-irradiation.

The mode and the kinetics of the death of T-thymoma cells upon dexamethasone treatment and gamma-irradiation (10Gy) have been studied using flow cytometry and biochemical analysis. It has been shown that the hormone and gamma-irradiation induce cell death by apoptosis. In both cases the cells are initially blocked in G2/M and die only after overcoming the blockage and cytokinesis. A short exposure to dexamethasone results in a cytostatic effect, whereas a cytotoxic effect is absent. Reducing serum concentration to 2% causes more rapid death both following gamma-irradiation and dexamethasone. These results are discussed in relation to cell death and proliferation.

Animals↗
PubMed1991

[The role of changes in the cytoplasmic concentration of Ca2+ in dexamethasone-induced thymocyte death].

The putative role of changes in cytosolic Ca2+ concentration ([Ca2+]i) in the dexamethasone (DM) induced thymocyte death was investigated. Incubation of rat thymocytes with 10(-7) M DM for different time intervals from 0.1 to 8 h did not change the basal [Ca2+]i level ca 100 nM as measured with Ca(2+)-fluorescent probe Quin-2. Ca2+ influx measured by the rate of 45Ca2+ uptake was also just the same in DM treated and control cells. At the same time a 6-8 h incubation of cell suspension with 10(-7) M DM results in significant increase in DNA fragmentation and pyknosis, and a 24 h incubation is associated with the decrease in the percentage of cells not staining with Trypan blue. Thus, the results obtained indicate that 10(-7) M DM induces thymocyte death without any significant and constant [Ca2+]i rise during the first 8 h after hormone application.

Animals↗
PubMed1988

The intestinal epithelial cells of ground squirrel (Citellus undulatus) accumulate at G2 phase of the cell cycle throughout a bout of hibernation.

1. The mitotic index was found to be greatly reduced in the intestinal crypt cells of ground squirrel during bout of hibernation. The percentage of mitosis rose abruptly at least 2 hr after arousal. 2. An increase in the number of G2 cells was found in the intestinal tract of ground squirrel during bouts of hibernation. 3. The conclusion can be drawn that the cells are progressing steadily through the cell cycle. The cells accumulate at G2 in hibernation. 4. It was assumed that the block in G2 prevents the cells from possible damage in mitosis under hypothermia accompanying hibernation and, therefore, it represents an adaptive reaction.

Animals↗
PubMed1988

Seasonal variations of DNA-synthesis in intestinal epithelial cells of hibernating animals--2. DNA-synthesis in intestinal epithelial cells of ground squirrel (Citellus undulatus) during autumn and late hibernation season.

1. DNA-synthesis was found to be gradually reduced in the intestinal crypt cells of ground squirrel during autumn at the time of preparation for hibernation and gradually rose during late hibernation season in February-March at the time of preparation for arousal. 2. A conclusion is made on the seasonal variations in cell replacement of true hibernators.

Animals↗
PubMed1986

Seasonal variations of DNA synthesis in intestinal epithelial cells of hibernating animals--I. DNA synthesis in intestinal epithelial cells of ground squirrel (Citellus undulatus) during deep hibernation.

The conditions for obtaining crypt cells from ground squirrel small intestine were chosen which allow flow-through cytofluorometric analysis of the DNA synthesis of this tissue. DNA synthesis was found to be greatly reduced in the intestinal crypt cells of ground squirrel during deep hibernation in torpid animals, in animals during spontaneous arousals and in animals prevented from hibernation. The conclusion is made about endogenous control of the DNA synthesis in the cells of true hibernators.

Acclimatization↗