Biomedical subjects

Y Ziv

Publications and source records attributed to Y Ziv.

At least 37 records · Page 2Linked to original sources

PubMed1997

Recombinant ATM protein complements the cellular A-T phenotype.

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder characterized by neurodegeneration, immunodeficiency, cancer predisposition, genome instability and radiation sensitivity. The cellular phenotype of A-T points to defects in signal transduction pathways involved in activation of cell cycle checkpoints by free radical damage, and other pathways that mediate the transmission of specific mitogenic stimuli. The product of the responsible gene, ATM, belongs to a family of large proteins that contribute to maintaining genome stability and cell cycle progression in various organisms. A recombinant vector that stably expresses a full-length ATM protein is a valuable tool for its functional analysis. We constructed and cloned a recombinant, full-length open reading frame of ATM using a combination of vectors and hosts that overcame an inherent instability of this sequence. Recombinant ATM was stably expressed in insect cells using a baculovirus vector, albeit at a low level, and in human A-T cells using an episomal expression vector. An amino-terminal FLAG epitope added to the protein allowed highly specific detection of the recombinant molecule by immunoblotting, immunoprecipitation and immunostaining, and its isolation using immunoaffinity. Similar to endogenous ATM, the recombinant protein is located mainly in the nucleus, with low levels in the cytoplasm. Ectopic expression of ATM in A-T cells restored normal sensitivity to ionizing radiation and the radiomimetic drug neocarzinostatin, and a normal pattern of post-irradiation DNA synthesis, which represents an S-phase checkpoint. These observations indicate that the recombinant, epitope-tagged protein is functional. Introduction into this molecule of a known A-T missense mutation, Glu2904Gly, resulted in apparent instability of the protein and inability to complement the A-T phenotype. These findings indicate that the physiological defects characteristic of A-T cells result from the absence of the ATM protein, and that this deficiency can be corrected by ectopic expression of this protein.

Animals↗

PubMed1997

The ataxia-telangiectasia gene product, a constitutively expressed nuclear protein that is not up-regulated following genome damage.

The product of the ataxia-telangiectasia gene (ATM) was identified by using an antiserum developed to a peptide corresponding to the deduced amino acid sequence. The ATM protein is a single, high-molecular weight protein predominantly confined to the nucleus of human fibroblasts, but is present in both nuclear and microsomal fractions from human lymphoblast cells and peripheral blood lymphocytes. ATM protein levels and localization remain constant throughout all stages of the cell cycle. Truncated ATM protein was not detected in lymphoblasts from ataxia-telangiectasia patients homozygous for mutations leading to premature protein termination. Exposure of normal human cells to gamma-irradiation and the radiomimetic drug neocarzinostatin had no effect on ATM protein levels, in contrast to a noted rise in p53 levels over the same time interval. These findings are consistent with a role for the ATM protein in ensuring the fidelity of DNA repair and cell cycle regulation following genome damage.

Antibodies↗

PubMed1996

Identification and chromosomal localization of Atm, the mouse homolog of the ataxia-telangiectasia gene.

Atm, the mouse homolog of the human ATM gene defective in ataxia-telangiectasia (A-T), has been identified. The entire coding sequence of the Atm transcript was cloned and found to contain an open reading frame encoding a protein of 3066 amino acids with 84% overall identity and 91% similarity to the human ATM protein. Variable levels of expression of Atm were observed in different tissues. Fluorescence in situ hybridization and linkage analysis located the Atm gene on mouse chromosome 9, band 9C, in a region homologous to the ATM region on human chromosome 11q22-q23.

Amino Acid Sequence↗

PubMed1996

A human gene (DDX10) encoding a putative DEAD-box RNA helicase at 11q22-q23.

A human gene encoding a putative RNA helicase, designated DDX10, was identified 400 kb telomeric to the ataxia-telangiectasia gene at chromosome 11q22-q23. The predicted amino acid sequence shows very high similarity to a subgroup of DEAD-box RNA helicases involved in ribosome biogenesis. This novel gene encodes a 3.2-kb transcript in a variety of human tissues. A processed pseudogene of DDX10 was detected at chromosome 9q21-q22. We observed a rare trinucleotide repeat length polymorphism within the coding sequence of DDX10.

Amino Acid Sequence↗

PubMed1996

Genomic Organization of the ATM gene.

The ATM gene was recently identified and found to be responsible for the genetic disorder ataxiatelgiectasia. The major ATM transcript is 13 kb. Using long-distance PCR, we determined the genomic structure of this gene and identified all of its exon-intron boundaries. The ATM gene spans approximately 150 kb of genomic DNA and consists of 66 exons. The initiation codon falls within exon 4. The last exon is 3.8 kb and contains the stop codon and a 3'-untranslated region of about 3600 nucleotides.

Ataxia Telangiectasia↗

PubMed1996

Results after restorative proctocolectomy and ileal pouch-anal anastomosis in patients with familial adenomatous polyposis and coexisting colorectal cancer.

Although the operation of choice for patients with familial adenomatous polyposis (FAP) is restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA), its place in the management of patients with FAP and cancer has not been defined. The authors have reviewed their experience with these patients to determine the safety of IPAA and its efficacy as a cancer operation. The records of 55 patients with FAP who had undergone IPAA were examined. Follow-up studies included an annual questionnaire and physical examination. Eight patients had FAP with coexisting colorectal cancer. Median age at diagnosis was 25 (range 13-46) years, and at operation 33 (range 22-36) years. Of the eight patients (four men), four had colonic cancer and four had rectal cancer. Synchronous colorectal carcinoma was found in two patients. Staging according to the tumor node metastasis classification showed that five patients had stage 1 tumour, two had stage 2 and one had stage 3. Tumours were well, moderately or poorly differentiated in one, five and two patients respectively. During a median follow-up of 56 (range 14-98) months, metastasis developed in the liver of one patient 66 months after surgery. Two patients suffered complications: one had small bowel obstruction and the other mucosal prolapse. Tubular adenomas were found in the pouch of two patients and in the anal transitional zone of one. Pouch function is good to excellent in all surviving patients. Restorative proctocolectomy for patients with FAP and coexisting colorectal cancer can be undertaken with a favourable prognosis and function. It is compatible with curative intent.

Adenomatous Polyposis Coli↗

PubMed1996

Effect of systemic steroids on ileal pouch-anal anastomosis in patients with ulcerative colitis.

BACKGROUND: Long-term steroid therapy predisposes to postsurgical complications, especially in patients with inflammatory bowel disease. PURPOSE: This study was undertaken to determine incidence of early septic complications after ileal pouch-anal anastomosis (IPAA) in patients who are undergoing prolonged steroid therapy. METHODS: We reviewed charts of 692 patients undergoing restorative proctocolectomy and IPAA to treat ulcerative colitis. Incidence of early (within 30 days) septic complications and sepsis-related reoperations, in patients who were having high-dose (>20 mg of prednisone per day) and low-dose steroid therapy (<20 mg of prednisone per day) for more than one month before surgery, was compared with patients who were not receiving steroid therapy. Follow-up included an annual questionnaire and physical examination. RESULTS: Patients without steroid dose data recorded were excluded (n = 21). Of the 671 remaining patients, 310 received no steroids, 169 received low-dose steroids, and 192 received high-dose steroids. These three groups were similar in gender composition, age at surgery, types of anastomosis (stapled or handsewn), and incidence of diabetes mellitus, peripheral vascular disease, and obesity. Early septic complications were found in 18 (6 percent), 14 (8 percent), and 12 (6 percent) patients without steroid therapy, those having low-dose steroid therapy, and those having high-dose steroid therapy (P = 0.57), respectively. Sepsis- related reoperation rate (P = 0.73) and number of sepsis-related pouch excisions (P = 0.79) did not differ between groups. In patients undergoing IPAA without ileostomy, early septic complications were found in one (3.8 percent), two (20 percent), and five (50 percent) patients without steroid treatment, low-dose steroid therapy, and high-dose steroid therapy (P = 0.004), respectively. CONCLUSION: In patients who are undergoing IPAA with diversion for ulcerative colitis, prolonged systemic steroid therapy before surgery is not associated with increased septic complications.

Adolescent↗

PubMed1996

Stapled ileal pouch anal anastomoses are safer than handsewn anastomoses in patients with ulcerative colitis.

BACKGROUND: One of the theoretic advantages of using a stapled versus handsewn ileal pouch anal anastomosis (IPAA) in restorative proctocolectomy is a reduction in septic complications. We performed this study to compare the incidence of early septic complications in patients undergoing restorative proctocolectomy with stapled or handsewn IPAA. PATIENTS AND METHODS: A chart review of 692 patients undergoing restorative proctocolectomy for treatment of ulcerative colitis was performed. The incidence of early septic complications in patients having stapled IPAA was compared to that in patients having handsewn IPAA. Follow-up studies included an annual questionnaire and physical examination. RESULTS: Of the 692 patients, 238 had handsewn IPAA and 454 had stapled IPAA; these two groups were similar in sex, duration of disease, age at surgery, and type of surgical procedure performed. In the handsewn IPAA group, 25 patients (10.5%) had 32 septic complications, and 24 required 89 reparations. In 7 patients, the pouch was excised. In the stapled IPAA group, 21 patients (4.6%) had 23 septic complications, and 14 required 40 reparations. One patient needed pouch excision. There were more patients (P=0.0001) with early septic complications, and more (P<0.0001) pouch excisions because of these complications, in patients with handsewn IPAA than in patients with stapled IPAA. The sepsis-related reoperation rates did not differ significantly. CONCLUSIONS: The stapled technique for IPAA has fewer septic complications and results in fewer sepsis-related pouch excisions, in our hands, than the handsewn technique technique, for treating patients with ulcerative colitis.

Adolescent↗

PubMed1996

Ataxia-telangiectasia: founder effect among north African Jews.

The ATM gene is responsible for the autosomal recessive disorder ataxia-telangiectasia (A-T), characterized by cerebellar degeneration, immunodeficiency and cancer predisposition. A-T carriers were reported to be moderately cancer-prone. A wide variety of A-T mutations, most of which are unique to single families, were identified in various ethnic groups, precluding carrier screening with mutation-specific assays. However, a single mutation was observed in 32/33 defective ATM alleles in Jewish A-T families of North African origin, coming from various regions of Morocco and Tunisia. This mutation, 103C-->T, results in a stop codon at position 35 of the ATM protein. In keeping with the nature of this mutation, various antibodies directed against the ATM protein failed to defect this protein in patient cells. A rapid carrier detection assay detected this mutation in three out of 488 ATM alleles of Jewish Moroccan or Tunisian origin. This founder effect provides a unique opportunity for population-based screening for A-T carriers in a large Jewish community.

Africa, Northern↗

PubMed1996

Predominance of null mutations in ataxia-telangiectasia.

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder involving cerebellar degeneration, immunodeficiency, chromosomal instability, radiosensitivity and cancer predisposition. The responsible gene, ATM, was recently identified by positional cloning and found to encode a putative 350 kDa protein with a Pl 3-kinase-like domain, presumably involved in mediating cell cycle arrest in response to radiation-induced DNA damage. The nature and location of A-T mutations should provide insight into the function of the ATM protein and the molecular basis of this pleiotropic disease. Of 44 A-T mutations identified by us to date, 39 (89%) are expected to inactivate the ATM protein by truncating it, by abolishing correct initiation or termination of translation, or by deleting large segments. Additional mutations are four smaller in-frame deletions and insertions, and one substitution of a highly conserved amino acid at the Pl 3-kinase domain. The emerging profile of mutations causing A-T is thus dominated by those expected to completely inactivate the ATM protein. ATM mutations with milder effects may result in phenotypes related, but not identical, to A-T.

Amino Acid Sequence↗

PubMed1995

A single ataxia telangiectasia gene with a product similar to PI-3 kinase.

A gene, ATM, that is mutated in the autosomal recessive disorder ataxia telangiectasia (AT) was identified by positional cloning on chromosome 11q22-23. AT is characterized by cerebellar degeneration, immunodeficiency, chromosomal instability, cancer predisposition, radiation sensitivity, and cell cycle abnormalities. The disease is genetically heterogeneous, with four complementation groups that have been suspected to represent different genes. ATM, which has a transcript of 12 kilobases, was found to be mutated in AT patients from all complementation groups, indicating that it is probably the sole gene responsible for this disorder. A partial ATM complementary DNA clone of 5.9 kilobases encoded a putative protein that is similar to several yeast and mammalian phosphatidylinositol-3' kinases that are involved in mitogenic signal transduction, meiotic recombination, and cell cycle control. The discovery of ATM should enhance understanding of AT and related syndromes and may allow the identification of AT heterozygotes, who are at increased risk of cancer.

Amino Acid Sequence↗

PubMed1995

A high-density microsatellite map of the ataxia-telangiectasia locus.

The locus of the autosomal recessive disorder ataxia-telangiectasia (A-T) has been assigned by linkage analysis with biallelic markers to a 4-Mb interval on chromosome 11q22-23, between GRIA4 and D11S1897. We have undertaken to saturate the A-T region with highly polymorphic microsatellite markers. To this end, we have identified seven new polymorphic CA-repeats in this region, and have mapped to it five new markers generated by Genethon and the Cooperative Human Linkage Center. These markers are in addition to 12 others that we have previously mapped or generated at the A-T locus. All 24 markers have been integrated into a high-density microsatellite map spanning some 6 Mb DNA. This map, which contains the A-T locus and flanking sequences, allows the construction of extensive, highly informative haplotypes.

Ataxia Telangiectasia↗

PubMed1995

Surgery for the teenager with familial adenomatous polyposis: ileo-rectal anastomosis or restorative proctocolectomy?

Increasing numbers of polyposis registries have led to more young patients being diagnosed with familial adenomatous polyposis (FAP). To provide guidelines for selecting the appropriate surgical procedure in teenagers (10-19 years), we compared the results of colectomy and ileo-rectal anastomosis (IRA, n = 17 patients) to the results of restorative proctocolectomy and ileal pouch-anal anastomosis (IPAA, n = 7 patients). Charts were reviewed to obtain data on the operative technique, blood loss and transfusions, hospital stay (including the time for ileostomy closure), and early (within 30 days of surgery) and late complications. Functional results (bowel movements per 24 h, use of antidiarrheal drugs, seepage, and fecal incontinence) and quality of life were evaluated prospectively with a questionnaire and physical examination. The median follow-up time was 49 months (range, 6 to 95 months) after IRA, and 36 months after IPAA (range, 4 to 87 months). Although restorative proctocolectomy and IPAA, is a longer (5.75 vs 3.1 hours), more bloody (500 vs 300 mL blood loss), and more complex operation with a longer hospital stay (12 vs 7 days) than IRA (P = 0.008, P = 0.006, P = 0.02, respectively), no significant difference (P > 0.05) was found between groups concerning the complication rate or quality of life. For teenagers with FAP and rectal carpeting, large rectal adenomas, curable cancer in the upper two-thirds of the rectum, or who are unavailable for follow-up, we recommend a restorative proctocolectomy and IPAA. For the other patients, the decision whether to perform IRA or restorative proctocolectomy with IPAA depends on the patient's desire and the surgeon's skill.

Adenomatous Polyposis Coli↗

PubMed1995

Anal canal inflammation after ileal pouch-anal anastomosis. The need for treatment.

UNLABELLED: One technique used during restorative proctocolectomy to prevent loss of continence involves preservation of the anal canal. This technique retains a small amount of colonic mucosa and transitional mucosa that may become inflamed or develop dysplastic or neoplastic changes. PURPOSE: This study was designed to determine the presence and severity of anal canal inflammation and the need for treatment. METHOD: Records of 217 patients with mucosal ulcerative colitis who underwent restorative proctocolectomy with a stapled ileal pouch-anal anastomosis without anal mucosectomy from 1987 through 1990 were retrospectively reviewed. RESULTS: Anal canal inflammation was evident on both endoscopy and biopsy in 48 patients (22.11 percent); 18 patients (8.29 percent) had a normal ileal pouch (9 had symptoms; 5 required topical treatment), and 30 patients (13.82 percent) had associated ileal pouch inflammation (23 with symptoms requiring systemic treatment because of pouchitis; 10 patients had concomitant topical treatment). CONCLUSION: Symptomatic inflammation of the retained mucosa occurred in 32 (14.7 percent) patients. Nine (4.1 percent) patients had inflammation of the anal canal alone, and 23 (10.6 percent) had pouchitis in addition. The need for treatment occurred in 28 (12.9 percent) of the total ((2.3 percent) patients with anal canal inflammation and 23 (10.6 percent) with anal canal inflammation plus pouchitis).

Administration, Rectal↗

PubMed1995

Safety of urgent restorative proctocolectomy with ileal pouch-anal anastomosis for fulminant colitis.

PURPOSE: Subtotal colectomy with ileostomy is the operation of choice for patients with fulminant colitis. Restorative proctocolectomy (RPC) with ileal pouch-anal anastomosis (IPAA) is preferred for patients who undergo elective surgery for ulcerative colitis. We retrospectively evaluated the safety of RPC with IPAA in patients with a moderate form of fulminant colitis. METHODS: A chart review of 737 patients who underwent RPC with IPAA for ulcerative and indeterminate colitis from 1983 through 1992 was performed. Moderate fulminant colitis was defined as acute disease requiring hospitalization and parenteral steroid therapy, but without hypotension (systolic blood pressure, < 100 mmHg), tachycardia (> 120 beats/min), or megacolon. RESULTS: Twelve patients with moderate fulminant colitis underwent urgent surgery (1.6 percent). They had been treated preoperatively for 5.1 +/- 2.3 days with intravenous high-dose steroids, total parenteral nutrition, and antibiotics. These patients had a shorter length of disease (P = 0.01), lower hemoglobin, hematocrit, and albumin (P = 0.001), and higher temperature (P = 0.002) and leukocyte count (P = 0.007) than patients undergoing elective surgery. No early septic complications occurred, although perianal abscess occurred in one patient and pouch-anal fistula in another patient, 13 and 14 months after surgery, respectively. CONCLUSION: In carefully selected, hemodynamically stable patients with fulminant colitis and without megacolon, RPC with IPAA can be safely performed.

Acute Disease↗

PubMed1995

Human cDNA clones that modify radiomimetic sensitivity of ataxia-telangiectasia (group A) cells.

Genes responsible for genetic diseases with increased sensitivity to DNA-damaging agents can be identified using complementation cloning. This strategy is based on in vitro complementation of the cellular sensitivity by gene transfer. Ataxia-telangiectasia (A-T) is a multisystem autosomal recessive disorder involving cellular sensitivity to ionizing radiation and radiomimetic drugs. A-T is genetically heterogeneous, with four complementation groups. We attempted to identify cDNA clones that modify the radiomimetic sensitivity of A-T cells assigned to complementation group [A-T(A)]. The cells were transfected with human cDNA libraries cloned in episomal vectors, and various protocols of radiomimetic selection were applied. Thirteen cDNAs rescued from survivor cells were found to confer various degrees of radiomimetic resistance to A-T(A) cells upon repeated introduction, and one of them also partially influenced another feature of the A-T phenotype, radioresistant DNA synthesis. None of the clones mapped to the A-T locus on chromosome 11q22-23. Nine of the clones were derived from known genes, some of which are involved in cellular stress responses. We concluded that a number of different genes, not necessarily associated with A-T, can influence the response of A-T cells to radiomimetic drugs, and hence the complementation cloning approach may be less applicable to A-T than to other diseases involving abnormal processing of DNA damage.

Antibiotics, Antineoplastic↗

PubMed1995

The complete sequence of the coding region of the ATM gene reveals similarity to cell cycle regulators in different species.

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder involving cerebellar degeneration, immunodeficiency radiation sensitivity, and cancer predisposition. A-T heterozygotes are moderately cancer prone. The A-T gene, designated ATM, was recently identified in our laboratory by positional cloning, and a partial cDNA clone was found to encode a polypeptide with a PI-3 kinase domain. We report here the molecular cloning of a cDNA contig spanning the complete open reading frame of the ATM gene. The predicted protein of 3056 amino acids shows significant sequence similarities to several large proteins in yeast, Drosophila and mammals, all of which share the PI-3 kinase domain. Many of these proteins are involved in the detection of DNA damage and the control of cell cycle progression. Mutations in their genes confer a variety of phenotypes with features similar to those observed in human A-T cells. The complete sequence of the ATM gene product provides useful clues to the function of this protein, and furthers understanding of the pleiotropic nature of the A-T mutations.

Amino Acid Sequence↗

PubMed1995

Ileal pouch-anal anastomoses complications and function in 1005 patients.

BACKGROUND: Restorative proctocolectomy and ileal pouch-anal anastomosis (IPAA) has become an established surgery for patients with chronic ulcerative colitis and familial adenomatous polyposis. PURPOSE: The authors report the results of an 11-year experience of restorative proctocolectomy and IPAA at a tertiary referral center. METHODS: Chart review was performed for 1005 patients undergoing IPAA from 1983 through 1993. Preoperative histopathologic diagnoses were ulcerative colitis (n = 858), familial adenomatous polyposis (n = 62), indeterminate colitis (n = 75), and miscellaneous (n = 10). Information was obtained regarding patient demographics, type and duration of diseases, previous operations, and indications for surgery. Data were collected on surgical procedure and postoperative pathologic diagnosis. Early (within 30 days after surgery) and late complications were noted. Follow-up included an annual function and quality-of-life questionnaire, physical examination, and biopsies of the pouch and anal transitional zone. RESULTS: Of the 1005 patients (455 women), postoperative histopathologic diagnoses were as follows: ulcerative colitis (n = 812), familial adenomatous polyposis (n = 62), indeterminate colitis (n = 54), Crohn's disease (n = 67), and miscellaneous (n = 10). During a mean follow-up time of 35 months (range 1-125 months), histopathologic diagnoses were changed for 25 patients. The overall mortality rate was 1% (n = 10 patients, early = 4, late = 6); one death (0.1%) was related to pouch necrosis and sepsis. The overall morbidity rate was 62.7% (1218 complications in 630 patients; early, n = 27.5%; late, n = 50.5%). Septic complication and reoperation rates were 6.8% and 24%, respectively. The ileal pouch was removed in 34 patients (3.4%), and it is nonfunctional in 11 (1%). Functional results and quality of life were good to excellent in 93% of the patients with complete data (n = 645) and are similar for patients with ulcerative colitis, familial adenomatous polyposis, indeterminate colitis, and Crohn's disease. Patients who underwent operations from 1983 through 1988 have similar functional results and quality of life compared with patients who underwent operations after 1988. CONCLUSION: Restorative proctocolectomy with an IPAA is a safe procedure, with low mortality and major morbidity rates. Although total morbidity rate is appreciable, functional results generally are good and patient satisfaction is high.

Adenomatous Polyposis Coli↗