Incidence of mutations in the PARK2, PINK1, PARK7 genes in Polish early-onset Parkinson disease patients.

BACKGROUND AND PURPOSE: Parkinson disease (PD) is a complex disease, comprising genetic and environmental factors. Despite the vast majority of sporadic cases, three genes, i.e. PARK2, PINK1 and PARK7 (DJ-1), have been identified as responsible for the autosomal recessive form of early-onset Parkinson disease (EO-PD). Identified changes of these genes are homozygous or compound heterozygous mutations. The frequency of PARK2, PINK1 and PARK7 mutations is still under debate, as is the significance and pathogenicity of the single heterozygous mutations/variants, which are also detected among PD patients. The aim of the study was to analyze the incidence of autosomal recessive genes PARK2, PINK1, PARK7 mutations in Polish EO-PD patients. MATERIAL AND METHODS: The analysis of the PARK2, PINK1 and PARK7 genes was performed in a group of 150 Polish EO-PD patients (age of onset < 45 years). Mutation analysis was based on sequencing and gene dosage abnormality identification. RESULTS: Mutations were identified only in the PARK2 and PINK1 genes with the frequency of 4.7% and 2.7% of subjects, respectively. In PARK2, point mutations and exons' rearrangements, and in PINK1 only missense mutations were detected. In both genes mutations were found as compound heterozygous/homozygous and single heterozygous. EO-PD patients' genotype-phenotype correlation revealed similarities of clinical features in mutation carriers and non-carriers. CONCLUSIONS: The frequency of the PARK2, PINK1, PARK7 mutations among Polish EO-PD patients seems to be low. The role of single heterozygous mutations remains a matter of debate and needs further investigations.

Hemiparkinsonism-hemiatrophy syndrome - report on two cases and review of the literature.

Hemiparkinsonism-hemiatrophy (HPHA) is a rare neurological syndrome. The main clinical features of HPHA consist of atrophy of one side of the body (face, trunk, limbs), ipsilateral hemiparkinsonism (bradykinesia, rigidity, tremor) and in many cases dystonia. There are no data on prevalence of HPHA as the condition is rare. The mean age of parkinsonism onset is earlier than in idiopathic Parkinson disease (43.7 years, range: 15-63). Changes in magnetic resonance imaging (MRI) (cortical, basal ganglia atrophy contralaterally to the side of clinical presentation) are described in 30% of patients. The pathogenesis of HPHA is unknown, but in many cases a history of prenatal injuries was reported. We present two male patients with HPHA - 45 and 55 years old, with left-sided parkinsonism, dystonia and hemiatrophy (to our knowledge, the first Polish cases). Both patients had no atrophic changes in MRI and levodopa treatment was ineffective. In the discussion the authors review current literature on HPHA.

[Importance of expression of DNA repair proteins in non-small-cell lung cancer]. / Význam stanovovania expresie DNA reparacných mechanizmov u nemalobunkového karcinómu plúc.

BACKGROUND: Proteins XRCC1 and ERCC1 are involved in DNA repair. XRCC1 plays a role in DNA base excision repair and ERCC1 in nucleotide excision repair pathway. Higher expression profile of both proteins in cancer cells may contribute to development of drug resistance. ERCC1 is involved in removal of platinum adducts and might be a potential predictive and prognostic marker in NSCLC (non-small-cell lung cancer) treated with a cisplatin-based regimen. The purpose of study was determination of XRCC1 and ERCC1 levels and their correlation with basic clini-copathological parameters in NSCLC. PATIENTS AND METHODS: In this study, 107 tumor samples diagnosed as NSCLC were immunohistochemically examined for expression of XRCC1 and ERCC1 proteins. Our results were compared to basic clinicopathological parameters: type of tumor, tumor grade and stage of disease. For statistical analysis, the chi-square test was used. RESULTS: In squamous cell carcinoma and large cell carcinoma samples, the XRCC1 protein level was twofold higher (60% of positive samples) than in adenocarcinoma samples (35.5% of positive samples). We have found statistical correlation between XRCC1 protein expression and type of tumor (p = 0.0306). On the other hand, the statistical importance between the protein level versus grade and stage was not found. In the case of the ERCC1 protein, we observed the highest protein level in adenocarcinoma (64.5%) and squamous cell carcinoma (62.5%) samples. Next, we determined a significant difference in content of XRCC1 versus ERCC1 (35.5% vs 64.5%) in adenocarcinoma samples. Statistical chi-square test did not reveal any correlation between ERCC1 status and clinicopathological parameters. CONCLUSION: According to our results, XRCC1 represents an important mechanism of DNA repair in squamous cell and large cell carcinomas. Besides that, expression of XRCC1 was in correlation with type of tumor. In patients with adenocarcinoma and squamous cell carcinoma, we could assume increased resistance to platinum-based therapy because of high expectation of ERCC1 protein expression. However, its levels did not correlate with monitored clinicopathological parameters. The ERCC1 protein will be possibly an independent prognostic factor in NSCLC. To prove a true survival benefit of patients with expression of ERCC1, prospective validation of ERCC1 before clinical implication is needed in the future.

Mouse sarcoma L1 cell line holoclones have a stemness signature.

Accumulating data suggest that cancers contain a fraction of cells called cancer stem cells (CSCs), that may be responsible for upkeep and relapses of disease. In experimental settings, CSCs are regarded as most effective at tumour initiation in in vivo assays. Since the first isolation of cancer stem cells from acute myeloid leukaemia in 1994, cancer stem cells have been identified in human solid tumours and they have also been found in the established cell lines, based on ability of CSCs to form in vitro colonies of a specific morphology, called holoclones. Our study examined the ability of a mouse sarcoma cell line, derived from a lung metastasis of a BALB/c mouse and established as a stably growing line (L1), to produce holoclones in vitro. We aimed to verify a stemness signature of the holoclone cells. The L1 cell line was found to form holoclone colonies in vitro, which were shown to contain a percentage of CSC-like cells. A fraction of the L1 cells was able to repopulate the original cell line, and presented an increased clonogenic and metastatic potential (18th passage). In addition, MTT assay and flow cytometry of the side population fraction revealed that these cells were more resistant to chemotherapeutic drugs than the original cell line, and over-expressed the anti-apoptotic genes, GRP78 and GADD153. We conclude that mouse L1 sarcoma cell line contains CSC-like cells.

Erythropoietin concentration in serum and cerebrospinal fluid of patients with amyotrophic lateral sclerosis.

Erythropoietin (EPO) acts as a neuroprotective factor and is upregulated after neuronal injury. It has been reported that in cerebrospinal fluid (CSF) of amyotrophic lateral sclerosis (ALS) patients, the EPO concentration is decreased. In this study, EPO levels in serum and CSF of 30 patients with ALS and in 15 controls, using an ELISA technique, were estimated. EPO level in serum was decreased, especially in patients with bulbar onset ALS. A trend toward a progressive EPO decline with the duration of the disease in the mild + moderate ALS cases was observed. In severe cases, a tendency towards a positive correlation of EPO and duration of the disease was present. Serum EPO values were age related only in mild + moderate ALS in patients below 40 years of age. In CSF, the EPO levels were significantly decreased. Lower EPO values in the bulbar onset ALS when compared with the spinal onset ALS were present. The EPO decrease did not correlate with the severity and duration of the disease. Age relation of the EPO level only in the mild + moderate ALS cases more than 40 years was present. Lack of differences in EPO levels between patients with ALS of rapid and slow progression indicates that EPO concentration cannot be used as a prognostic factor. Nevertheless, the decreased serum and CSF EPO concentration and the known EPO neuroprotective action may indicate that EPO administration can be a new promising therapeutic approach in ALS.

Matrix metalloproteinases and their tissue inhibitors in serum and cerebrospinal fluid of patients with amyotrophic lateral sclerosis.

BACKGROUND AND PURPOSE: Matrix metalloproteinases (MMPs) are implicated in the pathogenesis of motor neuron degeneration in amyotrophic lateral sclerosis (ALS). We investigated the expression of MMPs and tissue inhibitors of matrix metalloproteinases (TIMPs) in serum and cerebrospinal fluid (CSF) correlating the results with age, disease duration and the clinical course. METHODS: The material consisted of 30 ALS patients and 15 age-matched healthy controls. ELISA method to determine the expression of MT-MMP-1, MMP-2, MMP-9, TIMP-1 and TIMP-2 in serum and CSF was used. MMP-2 and MMP-9 by zymography was also tested. RESULTS: In serum MT-MMP-1, MMP-2, MMP-9 and TIMP-1 expression was increased, especially in mild ALS cases. TIMP-2 values were normal. In CSF MT-MMP-1, MMP-2 and TIMP-1 level was either increased or normal, that of MMP-9 was decreased. TIMP-2 did not change. No correlation of MMPs and TIMP-1 expression in serum and CSF and the age of the patients was found. A correlation was observed between MMPs and TIMPs and disease duration. CONCLUSIONS: Increased level of MMPs and TIMP-1 of ALS patients may reflect the degeneration process of motor neurons and skeletal muscles and/or is associated with tissues remodeling. The low level of MMP-9 in CSF may result from impaired balance between MMP-9 and TIMP-1 and/or its increased intrathecal degradation and physical clearance. Although the role of changed MMPs/TIMPs level in the pathogenesis of ALS is not clear their analysis in serum may be used as prognostic factor and a potential marker for monitoring treatment effects.

Evaluation of matrix metalloproteinases in serum of patients with amyotrophic lateral sclerosis with pattern recognition methods.

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases, which are present in central and peripheral nervous system. They are considered to be involved in the pathogenesis of several neurological diseases, as multiple sclerosis, Alzheimer disease, and amyotrophic lateral sclerosis (ALS). The aim of the present study was to evaluate the application of the pattern recognition methods for the assessment of MMPs in serum of patients with ALS. Thirty patients with amyotrophic lateral sclerosis (ALS), in two subgroups: (i) with mild and (ii) severe progressing ALS, and 15 control healthy subjects were studied. The metalloproteinases MT-MMP-1, MMP-2, MMP-9 were examined. Additional variables (age of subjects and disease duration) were also analyzed by using a standard, parallel and hierarchical classifiers. Our results indicate that: (i) MMP-2 in serum may be an important marker for the evaluation of ALS progress; (ii) the set of two features {MT-MMP-1, MMP-9} may be helpful in differentiation between ALS and healthy subjects; (iii) the error rates obtained for the pair-wise linear classifier were similar to those received for the classifiers (standard, parallel, and hierarchical) based on k-NN rule. We conclude that the pattern recognition methods may be useful for the evaluation of significance MMPs as markers in neurodegenerative diseases, such as ALS.

[Revision knee arthroplasty due to aseptic loosening]. / Revizní náhrada kolena po aseptickém uvolnení.

PURPOSE OF THE STUDY: Anatomic changes associated with aseptic loosening make conditions for revision of total knee arthroplasty more diffi-cult. The aim of this study was to evaluate the results of revision total knee replacement at an average follow-up of 6.1 years. MATERIAL AND METHODS: A total of 97 revision knee replacements due to aseptic loosening carried out in the years 1992 to 2003 were evalua-ted. The group included 46 men and 51 women at an average age of 66.8 years. The average preoperative Knee Society Score (KKS) was 31 points and the Functional Score (FS) was 22 points. There were 41 minor operations for AORI type I defects, 49 moderately serious procedures for AORI type II defects and seven major operations for AORI type III defects. In minor procedures standard components were implanted in 14 patients, standard components with cemented stems with extension were used in nine, and polyethylene plateau exchange was carried out in 18 patients. For moderately serious procedures, posterior stabilized components with extended cemented stems were used in 15 patients, revision implants with cementless stems in 26 patients and standard components with cemented stems in eight patients. In seven patients with major surgery, the hinged type of prosthesis was employed. Radiographic results were evaluated on the basis of Ewald's classification. RESULTS: Clinical findings showed improvement of the average KKS from 31 to 74 points at follow-up of 6.1 years. Functional out-comes improved, as shown by the average FS, from 22 to 67 points. Fifteen patients were not satisfied with the outcome of surgery, the causes being aseptic loosening in four, deep infection in eight and pain due to progression of radiolucent lines of the tibia in three patients. DISCUSSION: The results of revision surgery with component replacement because of aseptic loosening are worse in comparison with those of primary total knee replacement. The average KSS score after revision surgery was 74 points at 6.1-year follow--up, whereas after primary surgery it was 92 points at 6.5 years. The average FS score after revision was 67 points, as compared with 86 points at 6.5 years after primary surgery. Complications involving infection occurred in 8.2 % of the revi-sion cases, but only in 0.8 % of the primary operations. The authors used modular systems because these provide more options. Good outcomes were achieved with morselized bone grafting for filling cavitary defects. In patients with large defects in tibial or femoral metaphyses, posterior stabilized components and cementless intramedullary stems were used with good results. CONCLUSIONS: The authors recommend to avoid filling large bone defects with bone cement. They prefer bone grafting. In the case of good quality metaphyseal bone, they use standard components or posterior stabilized components with or without additi-onal cemented or cementless short stem extensions. In the case of poor quality metaphyseal bone with defects, they use revision implants with cementless long stems. The authors have achieved good results with off-set stems.

Effect of transfection with a gene coding for the fibronectin FNIII/10 fragment upon contact inhibition of C3H10T1/2 fibroblasts.

The density-dependent growth inhibition of non-transformed cells may be associated with inefficient transduction of the proliferative signal from cell adhesion molecules. To verify this concept, the C3H10T1/2 fibroblasts were stably transfected with the gene coding for the fibronectin fragment III/10 (FNIII/10). This resulted in differences in gene's expression between original C3H10T1/2 cells and their FNIII/10 transfectants. No significant differences in growth properties were observed in the original or in the transfected cells. C3H10T1/2 cells and their transfectants, when co-cultured, displayed more cells at confluence than the cells cultured alone. Moreover, co-cultured C3H10T1/2 cells and their transfectants showed elevated levels of phospho-ERK1/2 compared to homogenous cultures. Results obtained indicate that cellular homogeneity is responsible for density-dependent growth inhibition.

Cellular quiescence induced by contact inhibition or serum withdrawal in C3H10T1/2 cells.

Either confluence or serum withdrawal may cause growth arrest of cultured non-transformed cells. Here, we compared sparsely populated and confluent C3H10T1/2 cells with and without serum-containing medium. The following proliferation-relevant end points were examined: cell-cycle distribution, Ki-67 antigen presence, the level of the von Hippel-Lindau (VHL) protein, and gene expression, determined using a microarray approach. In sparse/logarithmic cultures, the fraction of cells in G(0)/G(1) phase increased from 55 to 85% following serum withdrawal. Moreover, the fraction of Ki-67 positive cells dropped from 89 to 47%. In confluent cultures, the majority of cells (80%) were in G(0)/G(1) phase and only 25-30% were Ki-67 positive, regardless of serum presence. In both serum-deprived and contact-inhibited cultures, significant and distinct changes in gene expression were observed. Serum deprivation of sparsely cultured cells resulted in significant over-expression of several transcription factors, while confluent cells showed elevated expression of genes coding for Wnt6, uPar, Tdag51, Egr1, Ini1a and Mor1. These results indicate that contact inhibition and serum withdrawal lead to cellular quiescence through distinct genetic and molecular mechanisms.

Serum IgM anti-GM1 ganglioside antibodies in lower motor neuron syndromes.

Lower motor neuron syndromes (LMNS) are heterogenous conditions, which include patients with progressive lower motor neuron disease (LMND) and cases with the clinical phenotype of motor neuropathy (MN). The aim of this study was to estimate the IgM anti-GM1 ganglioside antibodies titer and the ratio of the light chains in order to define the presence of autoimmunity process in particular cases with LMNS. Twenty-eight patients were diagnosed with LMND and 15 patients were diagnosed with MN (10 patients with multifocal motor neuropathy with conduction block, five patients with MN without conduction block). Total of 103 patients with classical amyotrophic lateral sclerosis (ALS) and 50 healthy, age-matched persons were also tested. The IgM anti-GM1 ganglioside titer and the ratio of lambda/kappa light chains in serum were determined using the ELISA technique. High titer of IgM anti-GM1 antibodies were detected in serum of 46% LMND patients, 80% of MN patients, and 18% of the classical ALS cases. An elevated ratio of lambda/kappa light chains appeared in 18% of LMND patients, and in 67% of the MN cases. The lambda/kappa light chains ratio was normal in all ALS patients. The presence of elevated titer of IgM anti-GM1 ganglioside antibodies and the changed ratio of the light chains supports the presence of autoimmune process in LMNS and may provide clues for their management.

Effect of Riluzole on serum amino acids in patients with amyotrophic lateral sclerosis.

OBJECTIVES: There is evidence that an imbalance between glutamatergic and inhibitory neurotransmission may contribute to selective neurodegeneration in amyotrophic lateral sclerosis (ALS). The efficacy of Riluzole in prolonging the survival of patients with ALS has been demonstrated in two large controlled trials. It is believed that Riluzole is a glutamate antagonist, but the exact mode of its action is not known. Data on the effects of Riluzole treatment on excitotoxic amino acid levels in serum are not available. MATERIAL AND METHODS: We prospectively studied 17 patients with ALS (diagnosed according to the El Escorial criteria), who received long-term treatment with Riluzole (100 mg/day). The subjects were evaluated at baseline (before treatment) and after 6, 12 and 18 months on drug. Assessments included the functional status of the patients and serum levels of amino acids. Analysis of the serum amino acids was performed using high performance liquid chromatography techniques at baseline, and after 6, 12 and 18 months of the treatment. RESULTS: At baseline, glutamate, GABA and total amino acid concentration in serum of the ALS patients, mainly in those with severe course of the disease, were increased. During the first 6 months of Riluzole treatment there was a significant decrease of glutamate and total amino acids, afterwards the values returned to the initial high values, or even an 'overshooting' in their levels appeared. We did not observe a similar effect of Riluzole on glutamate and other amino acids in patients with less advanced ALS. CONCLUSIONS: It is suggested that the positive clinical effect of Riluzole in ALS patients may be related, at least partly, to its influence on amino acid metabolism in neural tissues.

Glassy and fluidlike behavior of the isotropic phase of n-cyanobiphenyls in broad-band dielectric relaxation studies.

It is shown that the temperature behavior of peaks f p, of dielectric loss curves in the isotropic phase of n-cyanobiphenyls n = 8, 9, 10 with isotropic-nematic and isotropic-smectic A transitions exhibits features characterisic for both supercooled, glass-forming liquids and critical, binary mixtures. The behavior of f p T can be portrayed by the Vogel-Fulcher-Tamman relation and the "critical-like", mode-coupling theory (MCT) equation. The latter is supported by the novel analysis of electric conductivity σ T . The obtained f p T and σT dependencies can be related by using the fractional Debye-Einstein-Stokes law. For all tested mesogens the static dielectric permittivities ɛ(') T and T are described by dependencies resembling those applied in the homogeneous phase of critical mixturesbut with specific-heat critical exponent α≈ 0.5. This behavior agrees with the novel fluidlike description for the isotropic-nematic transition (P.K. Mukherjee, Phys. Rev. E 51, 5745 (1995); A. Drozd-Rzoska, Phys. Rev. E 59, 5556 (1999)). The obtained glassy features of dielectric relaxation support the recent simulation analysis carried out by M. Letz et al.Phys. Rev. E 62, 5173 (2000)).

[The effect of selegiline and vitamin E in the treatment of ALS: an open randomized clinical trials]. / Ocena skutecznosci selegiliny i witaminy E w leczeniu SLA: otwarta randomizowana próba kliniczna.

A role for oxidative stress in the etiology or progression of amyotrophic lateral sclerosis (ALS) and other neurodegenerative diseases has been recently proposed. We conducted the 18-month, randomized treatment trial with oral vitamin E (600 IU daily) and selegiline (10 mg daily) in 67 patients with sporadic ALS. Thirty five patients were randomly assigned to receive antioxidative therapy (vitamin E plus selegiline) and the remaining 32 patients were the ALS controls who received symptomatic treatment. The primary end point was survival and functional status. At the end of 18-month study, 13 patients in the treatment group and 14 in the control group died or were tracheostomized. A decline in functional disability was also similar in both groups. Long-term antioxidative treatment did not benefit patients with ALS.

[Neurotoxic activity of serum and cerebrospinal fluid of amyotrophic lateral sclerosis patients against some enzymes of glutamate metabolism]. / Neurotoksyczne dzialanie surowicy krwi i plynu mózgowo- rdzeniowego chorych na stwardnienie boczne zanikowe na aktywnosc niektórych enzymów przemiany glutaminianu.

One of the hypotheses in amyotrophic lateral sclerosis (ALS) indicates on excitatory amino acids as the cause of neuronal death. Changes in their concentration in the tissues and body fluids may be the consequence of a defect in their transport, as well as abnormal activities of glutamate metabolizing enzymes. Abnormal synthesis/degradation of these enzymes and/or influence of activators/inhibitors should be taken into account. The activity of enzymes of glutamate metabolism of rat spinal cord in vitro in the presence of serum and cerebrospinal fluid (CSF) of 20 patients with ALS and 20 healthy controls was tested. In the presence of serum of the ALS patients glutaminase was significantly stimulated, instead of being inhibited; the inhibition of GABA aminotransferase, glutamate decaboxylase and aspartate aminotransferase was less evident than in the controls, glutamate dehydrogenase lost its activity more than in control conditions, the inhibition of glutamine synthetase was comparable to that when normal serum was applied. The activity of the enzymes in the presence of CSF of ALS patients was generally similar to that of normal CSF, except of glutaminase which was stimulated and GABA aminotransferase, which was inhibited stronger than in the presence of normal CSF. This study indicates, that changes in glutamate concentration in tissues and body fluids in ALS may be caused, at least partly, by abnormalities in the activity of glutamate metabolism enzymes, which are in turn induced by neurotoxic agents present in body fluids of ALS patients.

[The role of mitochondrial respiratory chain in the pathogenesis of ALS]. / Rola mitochondrialnego lancucha oddechowego w patogenezie SLA.

Mitochondrial dysfunction and abnormal electron chain transport (ECT) may be involved in the pathogenesis of ALS. The aim of this study was to investigate the effect of cerebrospinal fluid (CSF) from ALS patients on the activity of ECT enzymes in mitochondrial cerebral crude preparations in the rats. We found that CSF inhibited the activity of complex I-III in 20%, complex II-III in 12% and complex IV in 33% of the ALS patients. CSF from the controls did not affect the activity of complex I-III and II-III. The effect of the CSF ultrafiltrates with cut off below 5000 daltons on the activity of ECT enzymes was also investigated. The CSF ultrafiltrates inhibited the activity of complex I-III, complex II-III and complex IV in 38%, 44% and 53% of the ALS patients, and in 80%, 53% and 43% of the controls, respectively. The results of this study and our previously reported experiments on the sera of ALS patients may indicate that neurotoxic effects of body fluids from ALS patients could be mediated by inhibition of the respiratory chain enzymes. This confirms an important role of mitochondrial dysfunction in the pathogenesis of ALS.

Low-frequency dielectric relaxation in rubber.

A rubber sample is investigated by dielectric spectroscopy in the frequency range from 10(-2)

In vitro and in vivo study of the expression vector encoding vascular endothelial growth factor.

Vascular endothelial growth factor (VEGF) is an angiogenic cytokine with potential therapeutic applications in human diseases. It is a mitogen primarily for endothelial cells. The transfer of the cDNA encoding VEGF to ischemic tissues, which cannot be revascularized otherwise, represents a novel and promising approach to the treatment of vascular disorders. In this work the VEGF165 cDNA was cloned into the expression vector pSecTag2B. The activity of the construct was studied in cell culture as well as in vivo. Western blotting study showed that the cells transfected with the vector secreted significantly higher amounts of VEGF to the culture medium than the non-transfected cells. In vivo study revealed an increased number of new vessels in animals injected with vector encoding VEGF as compared with empty plasmid. Also, tumor cells transfected with the VEGF plasmid exhibited extensive vascularization.

Caffeine-inhibitable control of the radiation-induced G2 arrest in L5178Y-S cells deficient in non-homologous end-joining.

The two L5178Y (LY) sublines bear a heterozygous Tp53 mutation that affects its transactivation function. LY-S (radiation-sensitive) cells are deficient in double strand break (DSB) repair by non-homologous end-joining (NHEJ) and do not express p21WAF1 (Cdkna1) either constitutively or after x-irradiation, in contrast to their radiation-resistant counterpart LY-R cells, which express p21WAF1 constitutively. Radiation-induced G2 arrest in LY-S cells is very long (11 h/Gy) but 2 mM caffeine treatment shortens it, decreases the fraction of G2 cells and increases the fraction of apoptotic cells. The treatment also increases the DNA damage that is estimated with the comet assay 18 h after irradiation with 5 Gy (ca. 23% of the initial value for x-rays and ca. 47% for x-rays plus caffeine). This indicates that either the repair has not been completed or the apoptotic DNA fragmentation has been initiated (or both). The same treatment applied to x-irradiated (5 Gy) LY-R cells (G2 arrest, 4 h/Gy) has no radiosensitising effect, induces no apoptosis and does not alter the amount of DNA damage left unrepaired (ca. 28%). The results are compatible with the assumption that inhibition of the Atm-dependent homologous recombination repair by caffeine, brings differential effects in LY sublines because of the defect of the alternative DNA repair system (NHEJ) in LY-S cells.

Signal transduction in confluent C3H 10T1/2 cells. The role of focal adhesion kinase.

The activities of extracellular signal-regulated kinases (ERK1/ERK2) is required for proliferation of several types of cells. The performed analysis showed stimulation of ERK's by fetal calf serum (FCS) or fibronectin in the C3H 10T1/2 cell cultures at logarithmic phase of growth. The ERKs activity was not stimulated in confluent cells. This could not be accounted for a partial down regulation of ERK since its level was stable in both types of cells regardless of their density and kind of stimulation. Searching for ERK up-stream elements we studied the integrin receptor gene transcript by RT-PCR and focal adhesion kinase (FAK) by Western blotting and phosphorylation assays. It was found that FCS and fibronectin stimulated phosphorylating activity of FAK in the cells at the logarithmic phase of growth, but were inefficient in the confluent cells. RT-PCR showed the presence of alpha5 and beta1 integrin transcripts, and p125FAK was at the same level regardless of the type of stimulation. These data indicate that the ability of FAK to be activated plays an important role in ERK regulation and, in consequence in proliferation and growth inhibition during confluence.