PubMed Health⌕ Search

Biomedical subjects

R F Itzhaki

Publications and source records attributed to R F Itzhaki.

At least 19 recordsLinked to original sources
PubMed1998

Mechanisms of uptake of gallium by human neuroblastoma cells and effects of gallium and aluminum on cell growth, lysosomal protease, and choline acetyl transferase activity.

We have studied the uptake and removal of gallium, used as an analogue of aluminum, and the effects of aluminum itself on cultured human neuroblastoma cells treated with soluble metal complexes. The prohibitively high cost of measurement of the only available radioisotope of aluminum (26Al) precluded its usage, and so we considered that gallium, which is chemically extremely similar, would be the most suitable model. Gallium has been used thus in a number of previous biological studies and has been found to behave like aluminum in many respects. We have previously shown that Al-EDTA treatment results in uptake of aluminum and expression of hyperphosphorylated tau, a key component of Alzheimer's disease paired helical filaments. Here we demonstrate that gallium uptake can occur by two separate methods, both leading to physiologically relevant intracellular metal concentrations. Uptake from medium containing bovine transferrin occurred mainly by pinocytosis, but in the presence of human transferrin (hTf), uptake by transferrin-mediated endocytosis occurred also, despite a very low level of hTf saturation, indicating that Tf-mediated uptake is a very effective method of Ga internalization. The intracellular gallium is relatively stable, though partially removable by (1 mM) EDTA, desferrioxamine, or 1,2-dimethyl-3-hydroxypyrid-4-one. Aluminum and gallium treatment were found to increase the overall activity of lysosomal proteases, enzymes implicated in amyloid precursor protein cleavage. No effects were detected on choline acetyl transferase activity, cell growth, or tritiated thymidine incorporation or on the structure of the cells, as judged by light or electron microscopy.

Aluminum↗
PubMed1998

Location of aluminium and gallium in human neuroblastoma cells treated with metal-chelating agent complexes.

The subcellular location of aluminium is unknown, probably because of difficulties in investigating aluminium biochemistry and the use of varied experimental approaches of uncertain sensitivity. We have studied levels of uptake and the localization of gallium and of aluminium in cultured human neuroblastoma cells treated with soluble metal complexes (mainly Al- or Ga-EDTA), radiolabeled with 26Al or 67Ga, respectively. Crude nuclei and cytoplasm were obtained by two separate methods, and DNA, RNA, and proteins were prepared from the nuclei by centrifugation in high salt; also, cytosol and noncytosol were separated using a nondissociating method. Levels of uptake were of similar order for the two metals-on average about 50 pmol/10(6) cells for aluminium and 120 pmol/10(6) cells for gallium, after 4 to 8 days treatment at 250 microM, and approximately 50 to 70% of the metal was found in the cytosol. About 20% of the aluminium and 10 to 25% of the gallium was associated with nuclear protein. A lower proportion was bound to DNA and to nuclear RNA. In cells treated with gallium-citrate/transferrin mixtures, 30 to 35% of the gallium in the cytosol was bound to protein, at least 35 being loosely bound; the main gallium-associated protein was probably intracellular transferrin. The remaining 65 to 70% of the metal in the cytosol was in low-molecular-weight form, and we suggest that the latter metal could affect structures such as the cytoskeleton and also metabolic processes in the cytoplasm. The similarity in distribution of the two metals supports the use of gallium as a "surrogate" for aluminium, at least in cell culture studies.

Aluminum↗
PubMed1997

Herpes simplex virus type 1 in brain and risk of Alzheimer's disease.

BACKGROUND: The apolipoprotein E epsilon 4 (APOE-epsilon 4) allele is a risk factor for Alzheimer's disease (AD), but it is neither essential nor sufficient for development of the disease. Other factors-genetic or environmental-must therefore have a role. By means of a PCR we have detected herpes simplex virus type 1 (HSV1) in latent form in brains of elderly people with and without AD. We have postulated that limited reactivation of the virus causes more damage in AD patients than in elderly people without AD because of a difference in the hosts. We now report the APOE genotypes of AD patients and non-AD sufferers with and without HSV1 in brain. METHODS: DNA was extracted from 84 samples of brain from 46 AD patients (39 temporal lobe, 39 frontal lobe, three hippocampus) and from 75 samples of brain from 44 non-AD elderly people (33 temporal lobe, 36 frontal lobe, six hippocampus). PCR amplification was used to detect HSV1 thymidine kinase gene and the host APOE gene. FINDINGS: By multiple logistic regression, the APOE-epsilon 4 allele frequency was significantly higher in the patients positive for HSV1 in brain than in the HSV1-negative AD group, the HSV1-positive non-AD group, or the HSV1-negative non-AD group (52.8% vs 10.0%, 3.6%, and 6.3%, respectively). The odds ratio for APOE-epsilon 4 in the HSV1-positive AD group compared with HSV1-negative non-AD group was 16.8 (95% CI 3.61-77.8) and in the HSV1-negative AD group, 1.67 (0.21-13.4). We also compared APOE genotypes of 40 people who had recurrent cold sores and 33 non-sufferers; the APOE-epsilon 4 allele frequencies were 36% and 9%, respectively (p < 0.0001). INTERPRETATION: These findings suggest that the combination of HSV1 in brain and carriage of an APOE-epsilon 4 allele is a strong risk factor for AD, whereas either of these features alone does not increase the risk of AD. The findings in people with cold sores support our hypothesis that APOE-epsilon 4 and HSV1 together are damaging in the nervous system.

Aged↗
PubMed1997

Neurotropic viruses and Alzheimer's disease: a search for varicella zoster virus DNA by the polymerase chain reaction.

BACKGROUND: In studies on the possible role of viruses in the aetiopathogenesis of Alzheimer's disease, herpes simplex virus type 1 (HSV1) DNA was detected by the polymerase chain reaction (PCR) in a high proportion of normal elderly people and of patients with Alzheimer's disease. The combination of HSV1 and a host factor, the type 4 allele of the gene for apolipoprotein E, is a strong risk factor for the disease. METHODS: Brain specimens were examined for another herpes virus, varicella zoster (VZV), which, like HSV1, is neurotropic, has a predilection for residing latently in the peripheral nervous system, and can reactivate. RESULTS: Using primers for sequences in the VZV origin of replication gene or thymidine kinase gene, VZV DNA was not found in any of 24 samples (18 HSV1 positive), from 17 patients with Alzheimer's disease, nor in 20 samples (12 HSV1 positive from 12 aged normal people. Hybridisation of the PCR products with a radiolabelled oligonucleotide probe capable of detecting less than 10 copies of the target sequence, confirmed the absence of VZV DNA. CONCLUSION: The presence of one neurotropic virus--HSV1--and the absence of another--VZV--in aged human brains is consistent with a role for HSV1 in the aetiology of Alzheimer's disease.

Aged↗
PubMed1994

Chromosome studies in Alzheimer's disease patients: distribution of dicentric breakpoints in lymphocytes irradiated in vitro.

A previous study showed a significant increase in dicentric frequency in lymphocytes irradiated in vitro from non-familial Alzheimer's disease patients compared to normal age-matched controls. This study examined the distribution of the chromosome breakpoints involved in the dicentric formation and found a non-specific increase in all chromosomes.

Alzheimer Disease↗
PubMed1993

DNA double-strand breaks measured by pulsed-field gel electrophoresis in irradiated lymphocytes from normal humans and those with Alzheimer's disease.

We have previously found that radiation-induced chromosome aberrations (dicentrics) are more numerous in lymphocytes from Alzheimer's disease (AD) patients than in those from age-matched normal individuals (Tobi et al. 1990). To investigate this further, we have examined double-strand breaks (dsb) produced by gamma-irradiation in the DNA of AD and normal lymphocytes by using pulsed-field gel electrophoresis. The percentage of DNA migrating into the gels is an indirect measure of the number of dsb; we have assayed the DNA content of sequential slices of the gel by direct fluorometry and have found that the percentage migrating is dose dependent. Our results show that the level of damage is similar in AD and normal lymphocytes and preliminary assays of the rate of repair suggest that the half-time is also similar, the value being > 1 h. The latter is consistent with the known rate of rejoining of chromosome fragments in interphase lymphocytes (Pantelias and Maillie 1985). The results suggest that at a gross level dsb repair is not impaired in AD cells; however, we cannot exclude the possibility that there is misrepair or non-repair of a small fraction of the dsb, which might account for the greater radiosensitivity of the AD cells.

Aged↗
PubMed1993

Alkylation damage and repair in Alzheimer's disease lymphocytes.

We have previously shown that lymphocytes from Alzheimer's disease (AD) patients are hypersensitive to ionising radiation, as revealed by their higher levels of dicentrics than those from age-matched, normal individuals. We have now examined the sensitivity of these cells to N-methyl-N-nitrosourea or methyl methanesulphonate, using a variety of assays, namely unscheduled DNA synthesis, viability, sister chromatid exchange and, via high performance liquid chromatography, level of methylation and repair of the adducts, 7-methylguanine, 0(6)-methylguanine and 3-methyladenine. We have found that AD lymphocytes and age-matched normal lymphocytes respond similarly to methylation damage, as assessed by all these techniques.

Adult↗
PubMed1992

Herpes simplex virus type 1 DNA is present in specific regions of brain from aged people with and without senile dementia of the Alzheimer type.

We have investigated the possible involvement of viruses, specifically Herpes simplex virus type 1, in senile dementia of the Alzheimer type (SDAT). Using the highly sensitive polymerase chain reaction, we have detected the viral thymidine kinase gene in post-mortem brain from 14/21 cases of senile dementia of the Alzheimer type and 9/15 elderly normals. The temporal cortex and hippocampus were usually virus-positive; in contrast, the occipital cortex was virus-negative in 9/9 SDAT cases and 5/5 elderly normals. Temporal and frontal cortex from younger normals (five infants and five middle-aged) were negative. Thus, the presence of Herpes simplex virus type 1 DNA is a region-dependent feature of the aged brain.

Aged↗