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Biomedical subjects

Y Ziv

Publications and source records attributed to Y Ziv.

At least 19 recordsLinked to original sources
PubMed2001

Telomeric protein Pin2/TRF1 as an important ATM target in response to double strand DNA breaks.

ATM mutations are responsible for the genetic disease ataxia-telangiectasia (A-T). ATM encodes a protein kinase that is activated by ionizing radiation-induced double strand DNA breaks. Cells derived from A-T patients show many abnormalities, including accelerated telomere loss and hypersensitivity to ionizing radiation; they enter into mitosis and apoptosis after DNA damage. Pin2 was originally identified as a protein involved in G(2)/M regulation and is almost identical to TRF1, a telomeric protein that negatively regulates telomere elongation. Pin2 and TRF1, probably encoded by the same gene, PIN2/TRF1, are regulated during the cell cycle. Furthermore, up-regulation of Pin2 or TRF1 induces mitotic entry and apoptosis, a phenotype similar to that of A-T cells after DNA damage. These results suggest that ATM may regulate the function of Pin2/TRF1, but their exact relationship remains unknown. Here we show that Pin2/TRF1 coimmunoprecipitated with ATM, and its phosphorylation was increased in an ATM-dependent manner by ionizing DNA damage. Furthermore, activated ATM directly phosphorylated Pin2/TRF1 preferentially on the conserved Ser(219)-Gln site in vitro and in vivo. The biological significance of this phosphorylation is substantiated by functional analyses of the phosphorylation site mutants. Although expression of Pin2 and its mutants has no detectable effect on telomere length in transient transfection, a Pin2 mutant refractory to ATM phosphorylation on Ser(219) potently induces mitotic entry and apoptosis and increases radiation hypersensitivity of A-T cells. In contrast, Pin2 mutants mimicking ATM phosphorylation on Ser(219) completely fail to induce apoptosis and also reduce radiation hypersensitivity of A-T cells. Interestingly, the phenotype of the phosphorylation-mimicking mutants is the same as that which resulted from inhibition of endogenous Pin2/TRF1 in A-T cells by its dominant-negative mutants. These results demonstrate for the first time that ATM interacts with and phosphorylates Pin2/TRF1 and suggest that Pin2/TRF1 may be involved in the cellular response to double strand DNA breaks.

Amino Acid Sequence↗
PubMed2001

Effect of electrocautery vs. scalpel on fascial mechanical properties after midline laparotomy incision in rats.

BACKGROUND: The method of midline laparotomy incision and closure remains a complex surgical problem. OBJECTIVE: To compare the mechanical properties at the interface of midline laparotomy incision made by scalpel versus electrocuting current in rats. METHODS: A sharp midline laparotomy incision was made in 60 Wistar female rats using a scalpel or electrocautery to open the fascia. The fascial and skin wounds were closed separately with a continuous nylon. Fascial specimens were analyzed for mechanical properties at the midline incision using a loading machine. The load-extension curve was recorded during tensile loading at a steady extension rate of 15 mm/min. RESULTS: There was no statistically significant difference between the two groups in either wound-bursting force (PPEAK) or the strain energy spent until the point of measured PPEAK. Each load-extension curve showed a characteristic pattern in all rats. Tissue stiffness was greater in the scalpel group than in the electrocautery group (P = 0.02). Correlations were found between tissue stiffness and strain energy, between tissue stiffness and bursting force, and between bursting force and strain energy. CONCLUSIONS: While tissue stiffness was greater when a scalpel was used compared to electrocuting to incise the midline abdominal fascia in rats, there was no difference in the bursting force required to disrupt the wound.

Abdomen↗
PubMed2000

Utilization of oriented peptide libraries to identify substrate motifs selected by ATM.

The ataxia telangiectasia mutated (ATM) gene encodes a serine/threonine protein kinase that plays a critical role in genomic surveillance and development. Here, we use a peptide library approach to define the in vitro substrate specificity of ATM kinase activity. The peptide library analysis identified an optimal sequence with a central core motif of LSQE that is preferentially phosphorylated by ATM. The contributions of the amino acids surrounding serine in the LSQE motif were assessed by utilizing specific peptide libraries or individual peptide substrates. All amino acids comprising the LSQE sequence were critical for maximum peptide substrate suitability for ATM. The DNA-dependent protein kinase (DNA-PK), a Ser/Thr kinase related to ATM and important in DNA repair, was compared with ATM in terms of peptide substrate selectivity. DNA-PK was found to be unique in its preference of neighboring amino acids to the phosphorylated serine. Peptide library analyses defined a preferred amino acid motif for ATM that permits clear distinctions between ATM and DNA-PK kinase activity. Data base searches using the library-derived ATM sequence identified previously characterized substrates of ATM, as well as novel candidate substrate targets that may function downstream in ATM-directed signaling pathways.

Amino Acid Motifs↗
PubMed2000

Functional link of BRCA1 and ataxia telangiectasia gene product in DNA damage response.

BRCA1 encodes a familial breast cancer suppressor that has a critical role in cellular responses to DNA damage. Mouse cells deficient for Brca1 show genetic instability, defective G2-M checkpoint control and reduced homologous recombination. BRCA1 also directly interacts with proteins of the DNA repair machinery and regulates expression of both the p21 and GADD45 genes. However, it remains unclear how DNA damage signals are transmitted to modulate the repair function of BRCA1. Here we show that the BRCA1-associated protein CtIP becomes hyperphosphorylated and dissociated from BRCA1 upon ionizing radiation. This phosphorylation event requires the protein kinase (ATM) that is mutated in the disease ataxia telangiectasia. ATM phosphorylates CtIP at serine residues 664 and 745, and mutation of these sites to alanine abrogates the dissociation of BRCA1 from CtIP, resulting in persistent repression of BRCA1-dependent induction of GADD45 upon ionizing radiation. We conclude that ATM, by phosphorylating CtIP upon ionizing radiation, may modulate BRCA1-mediated regulation of the DNA damage-response GADD45 gene, thus providing a potential link between ATM deficiency and breast cancer.

Animals↗
PubMed2000

Functional link between ataxia-telangiectasia and Nijmegen breakage syndrome gene products.

Ataxia-telangiectasia (A-T) and Nijmegen breakage syndrome (NBS) are recessive genetic disorders with susceptibility to cancer and similar cellular phenotypes. The protein product of the gene responsible for A-T, designated ATM, is a member of a family of kinases characterized by a carboxy-terminal phosphatidylinositol 3-kinase-like domain. The NBS1 protein is specifically mutated in patients with Nijmegen breakage syndrome and forms a complex with the DNA repair proteins Rad50 and Mrel1. Here we show that phosphorylation of NBS1, induced by ionizing radiation, requires catalytically active ATM. Complexes containing ATM and NBS1 exist in vivo in both untreated cells and cells treated with ionizing radiation. We have identified two residues of NBS1, Ser 278 and Ser 343 that are phosphorylated in vitro by ATM and whose modification in vivo is essential for the cellular response to DNA damage. This response includes S-phase checkpoint activation, formation of the NBS1/Mrel1/Rad50 nuclear foci and rescue of hypersensitivity to ionizing radiation. Together, these results demonstrate a biochemical link between cell-cycle checkpoints activated by DNA damage and DNA repair in two genetic diseases with overlapping phenotypes.

Ataxia Telangiectasia↗
PubMed2000

Structured triacylglycerol emulsion, containing both medium- and long-chain fatty acids, in long-term home parenteral nutrition: a double-blind randomized cross-over study.

Structured lipid emulsion, an innovative approach in which both medium-chain and long-chain fatty acids are esterified to the same glycerol backbone, has been recently shown to be a safe and efficient way of providing energy to patients requiring parenteral nutrition. As yet, no assessment has been made of its safety and effect on liver functions during long-term treatment. Twenty-two home parenteral nutrition patients with Crohn's disease or short bowel syndrome were enrolled in a double-blind randomized, cross-over study. Twenty patients who completed the study were treated for 4 wk with a structured lipid emulsion and for 4 wk with long-chain triacylglycerol emulsion. Determined every 1 or 2 wk were blood pressure, body weight, respiratory rate, blood count, liver functions, albumin, transferrin, plasma lipids, free fatty acids (FFAs), and, at the end of each treatment period (weeks 4 and 8), plasma dicarboxylic acids and 3-OH-fatty acids. No differences were observed between the groups or within the groups between the two treatments with respect to either clinical safety and adverse event occurrence or laboratory assessments. Plasma dicarboxylic acids and 3-OH-fatty acids were similar and within normal range. No alteration of liver function occurred in any of the patients treated with the structured lipid emulsion, whereas two of the patients receiving long-chain triaclyglycerol emulsion developed abnormal liver function, which resolved after switching to the structured lipid emulsion. In conclusion, structured triacylyglycerols containing both medium- and long-chain fatty acids appear to be safe and well tolerated on a long-term basis in patients on home parenteral nutrition, and it may be associated with possible reduction in liver dysfunction.

Adolescent↗
PubMed2000

Emotional availability in the mother-infant dyad as related to the quality of infant-mother attachment relationship.

Dyadic emotional availability and infant-mother attachment relationship were examined in 687 Israeli dyads. Concurrent assessments used the Strange Situation procedure (Ainsworth, Blehar, Waters, & Wall, 1978) for evaluating infants' attachment relationship, and the Emotional Availability Scales (Biringen, Robinson, & Emde, 1993) for evaluating the quality of mother-child interaction. It was found that higher scores on the Emotional Availability Scales were associated with infant attachment security. In addition, it was found that the Emotional Availability Scales discriminated between insecure-ambivalent and secure attachment classification, but were not informative about unique characteristics of emotional availability in dyads with avoidant and disorganized infants. Our findings contribute to the cross-cultural validation of Emotional Availability Scales against infants' attachment security.

Emotions↗
PubMed1999

Targeting double-strand breaks to replicating DNA identifies a subpathway of DSB repair that is defective in ataxia-telangiectasia cells.

The critical cellular defect(s) and basis for cell killing by ionizing radiation in ataxia-telangiectasia (A-T) are unknown. We use the topoisomerase I inhibitor camptothecin (CPT), which kills mainly S-phase cells and induces DSBs predominantly in replication forks, to show that A-T cells are defective in the repair of this particular subclass of DSBs. CPT-treated A-T cells reaching G2 have abnormally high levels of chromatid exchanges (viewed as prematurely condensed G2 chromosomes); aberrations in normal cells are mostly chromatid breaks. Transfectants of A-T cells with the wild-type ATM cDNA are corrected for CPT sensitivity, chromatid aberrations, and the DSB repair defect. These data suggest that in normal cells ATM, the A-T protein, probably recognizes DSBs in active replicons and targets the repair machinery to the breaks; in addition, the ATM protein is involved in the suppression of low-fidelity, adventitious rejoining between replication-associated DSBs. The loss of ATM functions therefore leads to genome destabilization, sensitivity to DSB-inducing agents and to the cancer-promoting illegitimate exchange events that follow.

Ataxia Telangiectasia↗
PubMed1999

Embolization--an optional treatment for intractable hemorrhage from a malignant rectovaginal fistula: report of a case.

PURPOSE: Patients rarely have intractable hemorrhage from rectovaginal fistulas, which usually require surgical intervention. This report presents our experience with nonsurgical treatment of a high-risk patient with uncontrolled hemorrhage originating from a malignant rectovaginal fistula. METHODS: A 74-year-old female developed uncontrolled hemorrhage from a malignant rectovaginal fistula. Because of her poor physical condition, an embolization with metal clips of the right and left hypogastric arteries was performed, distal to the superior gluteal artery. RESULTS: Embolization was successful in controlling the rectovaginal bleeding, allowing the patient to live 12 months. She refused adjuvant radiotherapy or chemotherapy. CONCLUSIONS: Selective angiography and embolization is a worthwhile alternative in patients with uncontrolled bleeding from a malignant rectovaginal fistula who are poor candidates for surgical intervention.

Adenocarcinoma↗
PubMed1999

Diverticulitis: the effect of age and location on the course of disease.

To examine the effect of patient's age and the location of diverticular disease on the course of the acute disease we retrospectively collected demographic data, symptoms, laboratory findings, imaging techniques, type of treatment (conservative vs. surgical), early and late complications, and follow-up data on 119 patients with acute diverticulitis (74 women, 45 men; mean age 64+/-14 years; follow-up 7-102 months, median 40). Patients were divided by their age into two groups (42 aged 60 years or younger, 77 aged over 60) and on the location of their disease (108 to the left of the middle transverse, 11 to the right). Lower abdominal pain, abdominal tenderness, and fever were the most common complaints (70-97%). In the younger patients we found a significantly greater preponderance in the right colon (P = 0.02) than in older patients. Abdominal abscesses and fistulas were more common in right-sided diverticulitis (P = 0.01). Patients with right-sided colon diverticulitis were treated surgically (82%) and on an emergency basis more often than patients with left-side colon diverticulitis (25%; P = 0.001). Older patients treated conservatively suffered more than younger patients (61% and 33% respectively; P = 0.04) from recurrent abdominal pain but not from recurrent, confirmed diverticulitis. Patients with right-sided diverticulitis treated conservatively suffered more from recurrent diverticulitis episodes than patients with left-sided diverticulitis (P = 0.05). Younger patients thus do not have a more aggressive form of diverticulitis than older patients. Patients with acute diverticulitis in the right colon are likely to be operated earlier and for mistaken diagnoses than patients with left-sided diverticulitis.

Adult↗
PubMed1999

Emotional availability and attachment representations in kibbutz infants and their mothers.

Three components of the attachment transmission model were examined in 48 kibbutz dyads from 2 kibbutz sleeping arrangements: communal and home-based. Concurrent assessments used the Strange Situation procedure (M. D. Ainsworth, M. C. Blehar, E. Waters, & S. Wall, 1978) for infants' attachment relations, the Adult Attachment Interview (C. George, N. Kaplan, & M. Main, 1985) for mothers' attachment representations, and the Emotional Availability Scales (Z. Biringen, J. L. Robinson, & R. N. Emde, 1993) for emotional availability in the dyads. Security of infants' attachment relations as well as autonomy of mothers' attachment representations were associated with higher emotional availability scores. In addition, significantly poorer emotional availability was found in dyads in which infants were insecurely attached and mothers were nonautonomous. Results also indicate that in the ecology of collective sleeping, the associations between the experience of emotional availability in the dyads and infants' and mothers' attachment may have been disrupted.

Adult↗
PubMed1998

Defective potassium currents in ataxia telangiectasia fibroblasts.

Similarities exist between the progressive cerebellar ataxia in ataxia telangiectasia (AT) patients and a number of neurodegenerative diseases in both mouse and man involving specific mutations in ion channels and/or ion channel activity. These relationships led us to investigate the possibility of defective ion channel activity in AT cells. We examined changes in the membrane potential of AT fibroblasts in response to extracellular cation addition and found that the ability of AT fibroblasts to depolarize in response to increasing concentrations of extracellular K+ is significantly reduced when compared with control fibroblasts. Electrophysiological measurements performed with a number of AT cell lines, as well as two matched sets of primary AT fibroblast cultures, reveal that outward rectifier K+ currents are largely absent in AT fibroblasts in comparison with control cells. These K+ current defects can be corrected in AT fibroblasts transfected with the full-length ATM cDNA. These data implicate, for the first time, a role for ATM in the regulation of K+ channel activity and membrane potential.

Ataxia Telangiectasia↗
PubMed1998

Enhanced phosphorylation of p53 by ATM in response to DNA damage.

The ATM protein, encoded by the gene responsible for the human genetic disorder ataxia telangiectasia (A-T), regulates several cellular responses to DNA breaks. ATM shares a phosphoinositide 3-kinase-related domain with several proteins, some of them protein kinases. A wortmannin-sensitive protein kinase activity was associated with endogenous or recombinant ATM and was abolished by structural ATM mutations. In vitro substrates included the translation repressor PHAS-I and the p53 protein. ATM phosphorylated p53 in vitro on a single residue, serine-15, which is phosphorylated in vivo in response to DNA damage. This activity was markedly enhanced within minutes after treatment of cells with a radiomimetic drug; the total amount of ATM remained unchanged. Various damage-induced responses may be activated by enhancement of the protein kinase activity of ATM.

Adaptor Proteins, Signal Transducing↗
PubMed1998

ATM binds to beta-adaptin in cytoplasmic vesicles.

Inherited mutations in the ATM gene lead to a complex clinical phenotype characterized by neuronal degeneration, oculocutaneous telangiectasias, immune dysfunction, and cancer predisposition. Using the yeast two-hybrid system, we demonstrate that ataxia telangiectasia mutated (ATM) binds to beta-adaptin, one of the components of the AP-2 adaptor complex, which is involved in clathrin-mediated endocytosis of receptors. The interaction between ATM and beta-adaptin was confirmed in vitro, and coimmunoprecipitation and colocalization studies show that the proteins also associate in vivo. ATM also interacts in vitro with beta-NAP, a neuronal-specific beta-adaptin homolog that was identified as an autoantigen in a patient with cerebellar degeneration. Our data describing the association of ATM with beta-adaptin in vesicles indicate that ATM may play a role in intracellular vesicle and/or protein transport mechanisms.

Adaptor Protein Complex 3↗
PubMed1998

Identification of ATM mutations using extended RT-PCR and restriction endonuclease fingerprinting, and elucidation of the repertoire of A-T mutations in Israel.

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder characterized by neurodegeneration, immunodeficiency, cancer predisposition, and radiation sensitivity. The responsible gene, ATM, has an extensive genomic structure and encodes a large transcript with a 9.2 kb open reading frame (ORF). A-T mutations are extremely variable and most of them are private. We streamlined a high throughput protocol for the search for ATM mutations. The entire ATM ORF is amplified in a single RT-PCR step requiring a minimal amount of RNA. The product can serve for numerous nested PCRs in which overlapping portions of the ORF are further amplified and subjected to restriction endonuclease fingerprinting (REF) analysis. Splicing errors are readily detectable during the initial amplification of each portion. Using this protocol, we identified 5 novel A-T mutations and completed the elucidation of the molecular basis of A-T in the Israeli population.

Ataxia Telangiectasia↗