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Biomedical subjects

A Miron

Publications and source records attributed to A Miron.

At least 19 recordsLinked to original sources
PubMed2000

Testing for hereditary breast and ovarian cancer in the southeastern United States.

OBJECTIVES: To detail characterization of mutations and uncharacterized variants in the breast cancer susceptibility genes BRCA1 and BRCA2, as observed in a population of breast cancer patients from the southeastern United States, and to examine baseline characteristics of women referred for counseling and testing and provide a preliminary look at how counseling and testing affected intentions toward prophylactic surgery. BACKGROUND: Mutations in the BRCA1 and BRCA2 genes give rise to a dramatically increased risk of developing breast or ovarian cancer or both. There are many reports about special populations in which deleterious mutations are present at a high frequency. It is useful to study these genes in more heterogeneous populations, reflecting different geographic regions. Interest in preventive surgery for gene carriers is high in women and their surgeons. METHODS: Women were recruited through a prospective clinical trial of counseling and free genetic testing. BRCA1 and BRCA2 were screened for mutations using standard techniques, and results were given to participants. Baseline questionnaires determined interest in preventive surgery at the beginning of the study. Follow-up questionnaires for those who completed testing surveyed interest in prophylactic surgery after counseling and receiving test results. RESULTS: Of 213 women who completed counseling and testing, 44 (20.6%) had 29 separate mutations; there were 11 Jewish women carrying three founder mutations. Twenty-eight women (13.1%) had uncharacterized variants in BRCA1 or BRCA2; nine were not previously reported. Women overestimated their chances of possessing a deleterious gene mutation compared to a statistical estimate of carrier risk. A number of women changed their intentions toward preventive surgery after genetic counseling and testing. CONCLUSIONS: Hereditary breast cancer due to mutations in BRCA1 and BRCA2 was a heterogeneous syndrome in the southeastern United States. Most mutations were seen just once, and uncharacterized variants were common and of uncertain clinical significance. In general, positive test results tended to reinforce intentions toward prophylactic surgery. In contrast, women not interested in surgery at the time of entry tended to remain reluctant after testing and counseling.

Attitude to Health↗
PubMed2000

Identification of a novel E2F3 product suggests a mechanism for determining specificity of repression by Rb proteins.

The tumor suppressor function of Rb is intimately related to its ability to interact with E2F and repress the transcription of E2F target genes. Here we describe a novel E2F product that specifically interacts with Rb in quiescent cells. This novel E2F, which we term E2F3b, is encoded by a unique mRNA transcribed from an intronic promoter within the E2F3 locus. The E2F3b RNA differs from the previously characterized E2F3 RNA, which we now term E2F3a, by the utilization of a unique coding exon. In contrast to the E2F3a product that is tightly regulated by cell growth, the E2F3b product is expressed equivalently in quiescent and proliferating cells. But, unlike the E2F4 and E2F5 proteins, which are also expressed in quiescent cells and form complexes with the p130 protein, the E2F3b protein associates with Rb and represents the predominant E2F-Rb complex in quiescent cells. Thus, the previously described specificity of Rb function as a transcriptional repressor in quiescent cells coincides with the association of Rb with this novel E2F product.

Base Sequence↗
PubMed1999

Isolation and initial characterization of the BRCA2 promoter.

The hereditary breast cancer susceptibility gene, BRCA2, is considered to be a tumor suppressor gene that may be involved in the cellular response to DNA damage. The transcript for this gene is cell cycle regulated with mRNA levels reaching a peak just before the onset of DNA synthesis. In order to define the mechanisms by which BRCA2 is transcriptionally regulated, we have begun to study upstream regulatory sequences. In this report, we define a minimal promoter region that has strong activity in human breast epithelial cells. Deletions of this sequence narrowed the strong basal activity to a region extending from -66 to +129 with respect to the BRCA2 transcriptional start site. This sequence demonstrated cell cycle regulated activity with kinetics similar to the endogenous transcript. Examination of the sequence revealed several consensus binding sites for transcription factors including an E-box, E2F and Ets recognition motifs. Electrohoretic mobility shift assays revealed specific protein binding to two sequences upstream of the start site; the palindromic E-box and an Ets/E2F site. Site-directed mutagenesis of either of these sites reduced both the basal activity in log phase cells and the cell cycle regulated activity of the promoter. Mutational inactivation of both sites within the same construct effectively eliminated promoter activity. Antibodies to candidate transcription factors used in super shift experiments revealed specific interactions between the BRCA2 promoter and the basic region/helix - loop - helix containing USF-1 and 2 proteins and Elf-1, an Ets domain protein. Binding of these factors depended upon the presence of intact recognition sequences. The USF factors were shown to bind predominantly as a heterodimeric complex of USF-1 and 2 while Elf-1 bound the promoter when it was not occupied by USF. Co-transfection studies with USF proteins and the varicella zoster IE62 protein provide evidence for the involvement of endogenous and exogenous USF in the activation of the BRCA2 promoter. We propose that interactions between USF-1, USF-2 and Elf-1 play an important role in the transcriptional regulation of the BRCA2 gene.

BRCA2 Protein↗
PubMed1998

RGSZ1, a Gz-selective regulator of G protein signaling whose action is sensitive to the phosphorylation state of Gzalpha.

Regulators of G protein signaling (RGS) are a family of proteins that attenuate the activity of the trimeric G proteins. RGS proteins act as GTPase-activating proteins (GAPs) for the alpha subunits of several trimeric G proteins, much like the GAPs that regulate the activity of monomeric G proteins such as Ras. RGS proteins have been cloned from many eukaryotes, and those whose biochemical activity has been characterized regulate the members of the Gi family of G proteins; some forms can also act on Gq proteins. In an ongoing effort to elucidate the role of Gzalpha in cell signaling, the yeast two-hybrid system was employed to identify proteins that could interact with a mutationally activated form of Gzalpha. A novel RGS, termed RGSZ1, was identified that is most closely related to two existing RGS proteins termed RetRGS1 and GAIP. Northern blot analysis revealed that expression of RGSZ1 was limited to brain, and expression was particularly high in the caudate nucleus. Biochemical characterization of recombinant RGSZ1 protein revealed that RGSZ1 was indeed a GAP and, most significantly, showed a marked preference for Gzalpha over other members of the Gialpha family. Phosphorylation of Gzalpha by protein kinase C, an event known to occur in cells and that was previously shown to influence alpha-betagamma interactions of Gz, rendered the G protein much less susceptible to RGSZ1 action.

Amino Acid Sequence↗
PubMed1998

Overestimation of hereditary breast cancer risk.

OBJECTIVE: To find out how women with breast or ovarian cancer rate their chances of carrying hereditary factors for these cancers and to determine the extent to which they overestimate their risk. SUMMARY BACKGROUND DATA: BRCA1 and BRCA2 are genes that cause breast and ovarian cancer when they are inherited in families. Testing for disease-associated mutations in these genes is now available commercially. Previous studies have shown that women overestimate their chances of carrying mutations. However, women's perceptions of risk have not been compared to objective estimates or to actual BRCA1 and BRCA2 testing results. METHODS: This study examines estimates of carrying BRCA1 and BRCA2 mutations among women participating in a randomized trial comparing alternative precounseling educational materials. Estimates were provided by participants in a baseline mailed survey. Estimates given by participants were compared to those given by an expert panel and by a statistical model. Testing was offered free of charge and was done in an academic laboratory using standard techniques. Baseline estimates of participating women were compared to the estimates of the expert panel, to the carrier probability provided by the statistical model, and to actual testing results. RESULTS: Women who have a personal history of breast or ovarian cancer significantly overestimate their risk of carrying hereditary factors for breast and ovarian cancer. Self-estimates exceeded the estimates of experts and a statistical model. One hundred women completed testing, and 21 mutations in BRCA1 or BRCA2 were found. Many test-negative women also overestimated their hereditary risk. Some women with a high carrier probability were negative for BRCA1 and BRCA2 mutations. CONCLUSIONS: Overestimation of hereditary factors is common among affected women with a family history of cancer. Pretest education and counseling should reduce these high-risk perceptions. Better estimates of carrier probability will direct more intensive clinical services and research.

Adult↗
PubMed1998

Frequency of germline and somatic BRCA1 mutations in ovarian cancer.

Germline mutations in the BRCA1 tumor suppressor gene are thought to be the most common cause of hereditary ovarian cancer. The aim of this study was to explore further the role of BRCA1 alterations in the development of ovarian cancers. We sought to determine whether somatic BRCA1 mutations are ever present in ovarian cancers and whether mutation is always accompanied by loss of the wild-type allele. The entire coding region and intronic splice sites of BRCA1 were sequenced using genomic DNA samples from 103 unselected ovarian cancers. Thirteen clearly deleterious BRCA1 mutations and two variants of uncertain significance were found. Blood DNA was available in all but two cases and demonstrated that 4 of 13 mutations and both variants of uncertain significance were germline alterations, whereas in seven cases the mutation was a somatic change present only in the cancer. Using four microsatellite markers, loss of heterozygosity at the BRCA1 locus was found in all 15 ovarian cancers with BRCA1 sequence alterations, compared with only 58% of ovarian cancers that did not have BRCA1 mutations. BRCA1-associated ovarian cancers were characterized by serous histology and moderate histological grade. These data confirm prior reports suggesting that germline mutations in BRCA1 are present in about 5% of women with ovarian cancer. In addition, somatic mutations in BRCA1 occur in the development of some sporadic cases. The finding that both germline and somatic BRCA1 mutations are accompanied by loss of heterozygosity, suggests that loss of this tumor suppressor gene is a critical event in the development of these cancers.

Adult↗
PubMed1997

Distinct roles for E2F proteins in cell growth control and apoptosis.

E2F transcription activity is composed of a family of heterodimers encoded by distinct genes. Through the overproduction of each of the five known E2F proteins in mammalian cells, we demonstrate that a large number of genes encoding proteins important for cell cycle regulation and DNA replication can be activated by the E2F proteins and that there are distinct specificities in the activation of these genes by individual E2F family members. Coexpression of each E2F protein with the DP1 heterodimeric partner does not significantly alter this specificity. We also find that only E2F1 overexpression induces cells to undergo apoptosis, despite the fact that at least two other E2F family members, E2F2 and E2F3, are equally capable of inducing S phase. The ability of E2F1 to induce apoptosis appears to result from the specific induction of an apoptosis-promoting activity rather than the lack of induction of a survival activity, because co-expression of E2F2 and E2F3 does not rescue cells from E2F1-mediated apoptosis. We conclude that E2F family members play distinct roles in cell cycle control and that E2F1 may function as a specific signal for the initiation of an apoptosis pathway that must normally be blocked for a productive proliferation event.

Animals↗
PubMed1995

E2F-1 accumulation bypasses a G1 arrest resulting from the inhibition of G1 cyclin-dependent kinase activity.

Numerous experiments have defined a critical role for the G1 cyclins and associated kinases in allowing a normal progression of cells from a quiescent state, through G1, and into S phase. We now demonstrate that G1 cyclin-dependent kinase activity is critical for the accumulation of E2F activity late in G1. Moreover, E2F-1 overexpression can overcome a G1 arrest caused by the inhibition of G1 cyclin-dependent kinase activity, consistent with E2F activation being an important consequence of the action of G1 cyclins. E2F-1 also overcomes a G1 block caused by gamma irradiation and leads to an apparent complete replication of the cellular genome and entry into mitosis. This E2F-1-mediated induction of S phase and mitosis is not accompanied by the rise in either cyclin D-associated kinase activity or cdk2 activity that is normally observed during the G1 phase of the cell cycle. We conclude that one key function for G1 cyclin-dependent kinase activity is the activation of E2F-1, that the accumulation of E2F activity may be sufficient to allow initiation and completion of S phase, but that additional events, including G1 cyclin kinase activity, are likely necessary for a normal proliferative event.

Blotting, Western↗
PubMed1995

[Pancreatoduodenectomy with pancreaticogastric anastomosis].

There is not general agreement concerning the ideal way of preventing pancreatic leakage after duodenopancreatectomy. The aim of the present study is to present the experience of a three years period of performing a pancreatogastroanastomosis (PGA) after duodenopancreatectomy (DPC) in 12 consecutive patients. In 7 cases PGA was performed after closure of the gastric stump using a transverse incision of the posterior wall of the stomach. A total layer of nylon 9 points was doubled by an interrupted serocapsular suture. In one case only the seromuscular layers of the stomach were cut, adjusted to the size of the pancreatic section with a central hole for the duct of Wirsung. Four nylon 10 points were used to anastomose the latter to the gastric mucosa. PGA was performed in one layer interrupted suture between the pancreatic capsule and the seromuscular of the stomach. In 4 cases, after closure of the gastric stump an anterior gastrotomy was associated to the posterior incision of the gastric wall in order to perform PGA using an intragastric route. The postoperative follow-up showed a good evolution with only one anastomotic leakage that necessitated reintervention in the 10th day. PGA might be elective after DPC when appropriate dissection and mobilisation of the pancreas is possible.

Adenocarcinoma↗
PubMed1995

[The surgical treatment of pancreatic cysts and pseudocysts].

Pancreatic cysts and pseudocysts are now being detected more often as a result of wide use of abdominal echography and CT scan. Surgical strategy advocates resection whenever possible for true cysts and internal drainage for pseudocysts. The present study retrospectively analyses 8 cases of true cysts and 23 cases of pseudocysts submitted to surgery in a twenty years period. Conservative treatment and ultrasonography-guided percutaneous drainage were not discussed. Four true cysts with positive benign structure were treated by internal drainage and only two adenocarcinomas were resected. In two more malignancies internal drainage was done as a palliative procedure followed by lethal outcome. Pseudocysts were secondary to acute pancreatitis in 7 cases, chronic pancreatitis in 6 cases, abdominal trauma in 4 cases and were idiopathic in 6 cases. Caudal pancreatectomy was performed whenever distal localisation was diagnosed. External drainage imposed in 5 emergency situations but internal drainage was elective in 13 cases. In conclusion according to our experience internal drainage should be preferred as the main surgical treatment in all mature pseudocysts and also when benign true cysts are certified. Posterior transgastric cystogastroanastomosis is the procedure of choice.

Cystadenocarcinoma↗
PubMed1994

Multiple pathways of copy control of gamma replicon of R6K: mechanisms both dependent on and independent of cooperativity of interaction of tau protein with DNA affect the copy number.

The ability of a replication initiator protein to promote intermolecular pairing of two replication origins resulting in the turning off of the origin pair has been called handcuffing. We have endeavored to test the validity of the handcuffing model by isolating two mutant forms of the tau initiator protein of R6K that elicit high copy number phenotype. We have discovered that one mutant called tau 113 yielded a 3.6-fold increase in copy number of a gamma replicon with a concomitant impairment of its ability to loop DNA and to pair binding sites (iterons) in comparison with normal tau, thus supporting the handcuffing model. A second mutant called tau 108, on the other hand, elicited a 3-fold increase in copy number without showing any measurable loss in its ability to loop and pair gamma iterons. Both mutant forms of the wild-type tau protein showed no detectable differences in their affinity of binding to the gamma iterons. Thus, the phenotype of tau 108 is consistent with the proposition that copy number control involves macromolecular interactions other than cooperativity at a distance of tau or interaction of tau with the primary binding sites at gamma. Taken together, the results are consistent with the notion that tau-mediated handcuffing is a mechanism, but not the only mechanism, of copy control in R6K. Interaction of tau with host proteins is likely to provide additional facets of the copy control mechanism.

Amino Acid Sequence↗
PubMed1993

A 27 kd protein of E. coli promotes antitermination of replication in vitro at a sequence-specific replication terminus.

We have discovered a 27 kd protein of E. coli that binds to a terminator site (tau)-terminator protein (ter) complex and abrogates the replication fork-arresting activity of ter protein in vitro. The 27 kd protein also neutralizes the contrahelicase activity of ter protein, allowing dnaB helicase to unwind DNA past a tau-ter complex. The stimulatory activity of low levels of ter protein on helicase II is also abolished by the 27 kd protein. The binding of the 27 kd protein to a tau-ter complex does not appear to dissociate the ter protein from the DNA. Although the in vivo function of the 27 kd protein is unknown at this time, it has the major attributes of a novel replication antiterminator in vitro.

Bacterial Proteins↗
PubMed1993

[A surgical cure of inguinal hernias by the Shouldice procedure].

Shouldice procedure became an elective technique in inguinal hernia repair as a consequence of the spectacular results of the Shouldice Hospital in Toronto (less 1% recurrence rate) and of other surgical centres in USA or western Europe. In the present study 73 cases of uncomplicated inguinal hernias who underwent a Shouldice herniotomy are analysed within a period of three years. Cremaster resection was routinely performed preserving a one inch proximal fragment which was used to calibrate the inguinal ring after reconstruction. Two continuous nonresorbable stitches were used to reinforce the posterior wall, as described by the author. Short postoperative follow-up showed good results in 64 cases but only 21 patients were reviewed within 6 and 12 month. Nevertheless no recurrence was reported in 3 years by any patient. According to these encouraging results Shouldice procedure might be considered as the procedure of choice in the treatment of inguinal hernias but much more data are necessary for pertinent conclusions.

Abdominal Muscles↗
PubMed1992

Activation of distant replication origins in vivo by DNA looping as revealed by a novel mutant form of an initiator protein defective in cooperativity at a distance.

We have isolated mutants of the pi initiator protein of the plasmid R6K that are defective in DNA looping in vitro but retain their normal DNA binding affinity for the primary binding sites (iterons) at the gamma origin/enhancer. One such looping defective mutant called R6 was determined to be a proline to leucine change at position 46 near the N terminus of the pi protein. Using a set of genetic assays that discriminate between the activation of the gamma origin/enhancer from those of the distantly located alpha and beta origins, we show that the looping defective initiator protein fails to activate the alpha and beta origins but derepresses initiation from the normally silent gamma origin in vivo. The results conclusively prove that DNA looping is required to activate distant replication origins located at distances of up to 3 kb from the replication enhancer.

Autoradiography↗
PubMed1991

Replication of plasmid R6K origin gamma in vitro. Dependence on dual initiator proteins and inhibition by transcription.

We have developed a more efficient in vitro replication system for the plasmid R6K with the objective of dissecting the mechanism of activation of replication origins at a distance. Using this in vitro system we have shown that the activation of replication origin gamma of R6K is absolutely dependent on two exogenously added initiator proteins: namely the host-encoded DnaA and the plasmid-encoded Pi proteins. Replication was inhibited by novobiocin, suggesting a requirement for DNA gyrase. Surprisingly, rifampicin stimulated in vitro replication significantly, and this stimulation was manifested in the quantitative enhancement of replication without any noticeable qualitative change in the reaction products. This result suggests that transcription at or near the gamma origin keeps it repressed. Replication intermediates that were allowed to accumulate by dideoxynucleoside triphosphate incorporation were analyzed both by restriction enzyme digestion and by electron microscopy, and both sets of analyses revealed initiation from the gamma origin resulting in theta-type replication intermediates. Further development of this system should help us to understand how DNA-protein interaction at the gamma origin/enhancer activates the distal origins alpha and beta.

Autoradiography↗
PubMed1991

[Complicated postbulbar duodenal ulcers: the characteristics of the diagnosis and of the surgical procedure and management].

The paper reports on the authors' experience used on 164 patients with complicated postbulbar ulcers (12% of the duodenal ulcers) with hemorrhage (52 cases), perforation (9 cases), duodenal stenosis (13 cases), stenosis and penetration (36 cases) and pancreatic-biliary penetrations (36 cases). The frequency of hemorrhagic complication was of 31%. As the hemorrhage due to postbulbar ulcer is favoured by vascular fistula, the severe character of the hemorrhage and the frequency of the recurrence, mainly the cataclysmic one, impose the radical surgery as early as possible. The following were used: large Reichel-Polya's gastrectomy (26 cases with 7 deaths) Péan's gastro-duodenectomy (12 cases), Péan's hemigastrectomy+vagotomy (4 cases), gastrectomy for exclusion with hemostasis in situ and ligature of gastroduodenal artery (8 cases, of which 1 with vagotomy and 2 deaths) and pyloroplasty with vagotomy and hemostasis (2 cases). The postsurgical mortality was of 17%. In 9 cases with perforation: Reichel-Polya's gastrectomy in 5 patients (1 death), Péan's gastrectomy in 2 cases, excision pyloroplasty and suture of the perforation in one case, respectively, were used. In the postbulbar ulcers penetrating into the pancreas or into the hepatic pedicle associated with stenosis (36 cases) the following were performed: Reichel-Polya's gastrectomy (7 cases), Péan's gastrectomy (7 cases of which 2 with vagotomy) gastrectomy for exclusion of ulcer in 19 cases, of which 5 with vagotomy, Péan's hemigastrectomy+vagotomy (3 cases). The 36 cases of ulcers penetrating into pancreas were solved as follows: gastrectomy for exclusion (16 cases of which 5 with vagotomy), Reichel-Polya's gastrectomy (10 cases of which 1 with vagotomy), Péan's gastrectomy (10 cases of which 2 with vagotomy). In 13 patients with stenosed ulcers, Reichel's-Polya's gastric resection (10 cases), Péan's gastrectomy, gastrectomy for exclusion and gastrojejunostomy (in one case each) were performed. The conclusions may be drawn that the postbulbar ulcers are complicated ulcers that require differentiated surgical treatment, as early as possible, for diminishing the postsurgical morbidity and mortality (7.5% mortality).

Duodenal Ulcer↗
PubMedDate not supplied

[Palliative total gastrectomy].

Gastric cancer, because of lymphonodulary and local extension, often allows only palliative surgery. This study tries to present the total gastrectomy as an alternative meant to improve the life of the patients who cannot hope to radical cure. Thirty-one patients were submitted to this operation during the last five years. The main indication for surgery was cancer extended to the gastric corpus, mainly on the posterior aspects and almost reaching the cardia. Because of lymphonodulary invasion over N2, hepatic and pancreatic and colonic invasion over N2, hepatic and pancreatic and colonic invasion and because of the metastases, the resections were palliative. The operations consisted of total gastrectomy and omentectomy, without trying to reach lymphatic stations over NI. All cases presented evidence of restant cancerous tissue involving the pancreas, the liver or the other lymphatic stations, but the main purpose was the ablation of the gastric tumor. Postoperatively we recorded 3 deaths, 9 anastomotic fistulae and an average survival of 9 months (6-13 months).

Aged↗