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Biomedical subjects

J Weinstein

Publications and source records attributed to J Weinstein.

At least 19 recordsLinked to original sources
PubMed2001

Asymmetrical segregation of chromosomes with a normal metaphase/anaphase checkpoint in polyploid megakaryocytes.

During differentiation, megakaryocytes increase ploidy through a process called endomitosis, whose mechanisms remain unknown. As it corresponds to abortive mitosis at anaphase and is associated with a multipolar spindle, investigation of chromosome segregation may help to better understand this cell-cycle abnormality. To examine this variation, a new method was developed to combine primed in situ labeling to label centromeres of one chromosome category and immunostaining of tubulin. Human megakaryocytes were obtained from normal bone marrow culture. By confocal microscopy, this study demonstrates an asymmetrical distribution of chromosomes (1 or 7) either between the spindle poles at anaphase stage of endomitosis and between the different lobes of interphase megakaryocyte nuclei. The metaphase/anaphase checkpoint appears normal on the evidence that under nocodazole treatment megakaryocytes progressively accumulate in pseudo-metaphase, without spontaneous escape from this blockage. Immunostaining of p55CDC/hCDC20 with similar kinetochore localization and dynamics as during normal mitosis confirms this result. HCdh1 was also expressed in megakaryocytes, and its main target, cyclin B1, was normally degraded at anaphase, suggesting that the hCdh1-anaphase-promoting complex checkpoint was also functional. This study found the explanation for these unexpected results of an asymmetrical segregation coupled to normal checkpoints by careful analysis of multipolar endomitotic spindles: whereas each aster is connected to more than one other aster, one chromosome may segregate symmetrically between 2 spindle poles and still show asymmetrical segregation when the entire complex spindle is considered.

Anaphase↗
PubMed2001

Left anterior descending artery length in left and right coronary artery dominance.

BACKGROUND: Coronary stenosis of the left anterior descending artery (LAD) is respected by cardiologists because of its negative influence on morbidity and mortality. An important anatomical consideration is the length of the LAD. OBJECTIVE: To investigate the relationship between length of LAD and coronary dominance. DESIGN: Retrospective comparison of 100 consecutive angiograms with left coronary dominance with 100 consecutive angiograms with right coronary dominance. The relationship between the length of the LAD and coronary dominance was analyzed. METHODS: We retrospectively compared 100 consecutive angiograms with left coronary dominance (the posterior descending artery being supplied by the circumflex artery) with 100 consecutive angiograms with right coronary dominance (the posterior descending artery being supplied by the right coronary artery). LADs were categorized into three types: type A, LAD terminating before the cardiac apex; type B, LAD reaching the apex but not supplying the inferoapical segment of the left ventricle; and type C, LAD wrapping around the apex and supplying the inferoapical segment. LAD typing was also analyzed in relation to gender. RESULTS: It was found that the LAD wrapped around the apex in 87% of cases of left coronary dominance but only in 47% of patients with right coronary dominance, and that the long LADs were more frequently seen in women than in men, irrespective of coronary dominance. CONCLUSIONS: We found that the LAD in left coronary dominance is usually long and wraps around the apex, and believe that angiographic interventions in such cases have important clinical significance.

Coronary Angiography↗
PubMed2001

Celiac sprue: another autoimmune syndrome associated with hepatitis C.

OBJECTIVE: Celiac sprue is being diagnosed with increasing frequency by screening individuals with epidemiologically associated autoimmune syndromes. We sought to test our hypothesis that hepatitis C also may predispose to celiac sprue because it can trigger autoimmune reactions. METHODS: Two hundred fifty-nine consecutively evaluated patients with chronic hepatitis C infection, 59 with autoimmune liver disease, 137 with other hepatic diseases, 356 with various GI syndromes, and 221 normal volunteers underwent serologic screening for celiac sprue. Patients with antigliadin, antiendomysial, and antitissue transglutaminase antibodies in serum underwent duodenoscopy and biopsy. RESULTS: There was a statistically significantly higher prevalence of antigliadin antibody in all groups of patients with liver disease compared with GI controls and normal controls. However, only patients with hepatitis C (n = 3; 1.2%) or autoimmune liver disease (n = 2; 3.4%) had antiendomysial/antitissue transglutaminase antibody in serum. One of 221 normal volunteers (0.4%) was antigliadin, antiendomysial, and antitissue transglutaminase positive; this individual also was found to have hepatitis C (previously undiagnosed). Each of these six individuals had mild intestinal symptoms, duodenal histopathology consistent with celiac sprue, and the celiac-associated HLA-DQ2 allele. Five of the six followed a prescribed gluten-free diet and experienced symptomatic improvement. CONCLUSION: Celiac sprue is epidemiologically associated with chronic hepatitis C infection and with autoimmune liver disease. Because hepatitis C is much more frequently encountered than autoimmune liver disease, hepatitis C appears to be the most common hepatic disease associated with the development of celiac sprue.

Adult↗
PubMed2000

p55CDC/hCDC20 is associated with BUBR1 and may be a downstream target of the spindle checkpoint kinase.

Eukaryotic cells have evolved a mechanism that delays the progression of mitosis until condensed chromosomes are properly positioned on the mitotic spindle. We have been studying genes that regulated the spindle checkpoint in human cells. Enforced expression of human BUBR1, but not a BUBR1 mutant allele, enhances accumulation of mitotic cells. Yeast two-hybrid system and GST-pulldown analyses show that p55CDC/hCdc20, a protein known to link spindle checkpoint components such as MAD2 to anaphase promoting complex (APC), interacts with BUBR1. In addition, p55CDC is capable of pulling down BUBR1 in sf-9 cells infected with both p55CDC and His6-BUBR1 recombinant baculoviruses but not in the cells infected with p55CDC baculoviruses or with the baculoviral vector alone. Moreover, immunoprecipitation followed by Western blot analyses confirmed that native p55CDC is associated with BUBR1 in HeLa cells. Spindle checkpoint activation by nocodazole treatment enhances the association between p55CDC and His6-BUBR1. In nocodazole-arrested mitotic cells, both CDC16 and hyperphosphorylated CDC27, two APC components, preferentially associate with His6-BUBR1 resins, but not the control resins. Furthermore, BUBR1 phosphorylates p55CDC in vitro, and the phosphorylation of p55CDC by BUBR1 appears to be correlated with spindle checkpoint activation. Together, our studies strongly suggest that BUBR1 may target APC via p55CDC.

Alleles↗
PubMed2000

Involving patients in clinical decisions: impact of an interactive video program on use of back surgery.

BACKGROUND: Back surgery rates are rapidly rising in the United States. This surgery is usually elective, so patient preferences are important in the treatment decision. OBJECTIVES: The objective of this study was to determine the impact on outcomes and surgical choices of an interactive, diagnosis-specific videodisk program for informing patients about treatment choices. RESEARCH DESIGN: This was a randomized, controlled trial at 2 sites comparing the interactive video plus a booklet with the booklet alone. SUBJECTS: Elective surgery candidates (n = 393) included 171 patients with herniated disks, 110 with spinal stenosis, and 112 with other diagnoses. MEASURES: Mailed questionnaires were used to assess outcomes and satisfaction; surgery rates were determined by questionnaires and automated records. RESULTS: Symptom and functional outcomes at 3 months and 1 year were similar between study groups. The overall surgery rate was 22% lower in the videodisk group (26% versus 33%, P = 0.08). Among patients with herniated disks, those in the video group underwent significantly less surgery (32% versus 47%, P = 0.05 by Kaplan-Meier test). Among patients with spinal stenosis, surgery rates in the video group were higher (39% for the video group, 29% for the booklet group; P = 0.4). There was little effect on patient satisfaction, but patients in the video group felt better informed. CONCLUSIONS: The program appears to facilitate decision making and may help to ensure informed consent. For patients with herniated disks, it reduced the surgery rate without diminishing patient outcomes. Its impact on costs of care depends on the proportion of patients with various diagnoses and on local surgery rates.

Decision Making↗
PubMed2000

A multicenter, randomized trial of daily high-dose interferon-alfa 2b for the treatment of chronic hepatitis c: pretreatment stratification by viral burden and genotype.

OBJECTIVES: The aim of this study was to determine prospectively whether an intensive regimen of daily, high-dose interferon would improve the response rate for the treatment of chronic hepatitis C in patients with unfavorable virological characteristics. METHODS: A total of 104 patients with chronic hepatitis C were randomized at eight centers to receive interferon alfa-2b at a dose of 5 million units (MU) daily or 3 MU t.i.w. for a period of 24 wk. Patients were prospectively randomized by low or high viral burden and stratified by genotype. HCV RNA was measured by quantitative polymerase chain reaction, and response rates were compared between the dosage regimens. RESULTS: HCV RNA levels dropped more rapidly to lower levels in the group treated with 5 MU daily. In this group, the initial virological response (IR) at wk 12 and the end-of-treatment response (ETR) at wk 24 were double that of patients treated with standard interferon (66% vs 33% and 48% vs 24%, p < 0.01). Sustained response rates were low for both dose groups (14% vs 4%, p = 0.08). Genotype-related differences in initial response rates were present in the standard dose group (63% non-1 genotype vs 24% genotype 1; p = 0.005) but not in those treated with 5 MU daily (66% vs 67%, p = NS). Using multivariate analysis, only the interferon dose was associated with IR and ETR (p = 0.002). CONCLUSIONS: Daily, high dose interferon rapidly dropped HCV RNA and increased initial and end-of-treatment response rates when compared to t.i.w. regimens. This effect, independent of viral burden and genotype, suggests that patients with unfavorable viral characteristics might benefit from an intensive regimen that promotes rapid viral clearance. These data support further study of the use of high-dose induction regimens. However, improvements in sustained response rates will require additional therapeutic maneuvers such as prolonged therapy or the adjunctive use of ribavirin.

Adult↗
PubMed1999

Analogs of 4-(3-bromo-8-methyl-10-methoxy-6,11-dihydro-5H-benzo[5,6]-cyclo hepta[1,2-b]pyridin-11-yl)-1-(4-pyridinylacetyl)piperidine N-oxide as inhibitors of farnesyl protein transferase.

A series of 3-substituted analogs 3 of 4-(3-bromo-8-methyl-10-methoxy-6,11-dihydro-5H-benzo[5,6]-cyclohepta[1,2 b]pyridin-11-yl)-1-(4-pyridinylacetyl)piperidine N-oxide 2 was prepared and evaluated as FPT inhibitors. The objective of this study was to identify other substituents at C3 in this series of FPT inhibitors that would have the FPT potency enhancement similar to that found for a C3 bromo substituent. The 3-methyl analog 17b was found to be tenfold less active than 2, and other C3 substituents having more steric bulk were found to cause a further reduction in activity.

Alkyl and Aryl Transferases↗
PubMed1999

Analogues of 1-(3,10-dibromo-8-chloro-6,11-dihydro-5H-benzo-[5,6]-cyclohepta [1,2-b]pyridin-11-yl)piperidine as inhibitors of farnesyl protein transferase.

The synthesis of several 4-pyridylacetyl N-oxide derivatives of 4-(3-bromo-6,11-dihydro-5H-benzo[5,6]-cyclohepta[1,2-b]-pyridin-11-yl)pi perazine/piperidine 3 is described. This study was aimed at identifying fomesyl protein transferase (FPT) inhibitors in these two series of tricycles containing different phenyl ring substituents. The in vitro activity profile of the initial group of compounds 7a-7g led to the synthesis of the 8-methyl-10-methoxy and 8-methyl-10-bromo analogues 7i, 13i, and 13j. The 11R(-) enantiomers of these compounds were found to exhibit potent in vitro FPT inhibition activity.

Alkyl and Aryl Transferases↗
PubMed1998

Selective chemical modifications of polymyxin B.

Polymyxin B (1) monohydrochloride was converted to the tetra-BOC derivatives 1b and 1c by reaction with di-tert-butyl dicarbonate. The structures of these protected intermediates were established utilizing a degradative sequence that afforded 3 and 5. A method for the deprotection 2,4-dinitrophenylamines to the free amine, utilizing a strongly basic ion-exchange resin, was developed for use in the degradative sequence. The tetra-BOC derivatives 1b and 1c were used to prepare several Polymyxin B derivatives 6-27 at the DAB1 and DAB9-gamma-amine. The antibacterial activity of these selectively functionalized derivatives is reported here.

Anti-Bacterial Agents↗
PubMed1998

Synthesis and antibacterial activity of 2-alkoxy penems.

The phosphite mediated Oxalimide cyclization reaction was extended to 4-dithiocarbonates of N-oxalyl-2-azetidinones to synthesize 2-alkoxy penems 3. In general, the in vitro antibacterial potency of compounds 3 was weak compared to the highly potent 2-alkylthiopenems 2.

Anti-Bacterial Agents↗
PubMed1998

Inhibitors of farnesyl protein transferase. Synthesis and biological activity of amide and cyanoguanidine derivatives containing a 5,11-dihydro[1]benzthiepin, benzoxepin, and benzazepin [4,3-b]pyridine ring system.

Bioisosteric replacement of the C-6 carbon atom in piperidine I and piperazine II with S, O, and N heteroatoms is described. Amide and cyanoguanidine derivatives of these compounds were evaluated in vitro and found to be good inhibitors of farnesyl-protein transferase. An improved method of preparing the 5,11-dihydro-[1]-benzthiepin nucleus 6 was accomplished in high yield and with excellent regioselectivity using an AlCl3 melt protocol.

Alkyl and Aryl Transferases↗
PubMed1998

Mammalian p55CDC mediates association of the spindle checkpoint protein Mad2 with the cyclosome/anaphase-promoting complex, and is involved in regulating anaphase onset and late mitotic events.

We have investigated the function of p55CDC, a mammalian protein related to Cdc20 and Hct1/Cdh1 in Saccharomyces cerevisiae, and Fizzy and Fizzy-related in Drosophila. Immunofluorescence studies and expression of a p55CDC-GFP chimera demonstrate that p55CDC is concentrated at the kinetochores in M phase cells from late prophase to telophase. Some p55CDC is also associated with the spindle microtubules and spindle poles, and some is diffuse in the cytoplasm. At anaphase, the concentration of p55CDC at the kinetochores gradually diminishes, and is gone by late telophase. In extracts prepared from M phase, but not from interphase HeLa cells, p55CDC coimmunoprecipitates with three important elements of the M phase checkpoint machinery: Cdc27, Cdc16, and Mad2. p55CDC is required for binding Mad2 with the Cdc27 and Cdc16. Thus, it is likely that p55CDC mediates the association of Mad2 with the cyclosome/anaphase-promoting complex. Microinjection of anti-p55CDC antibody into mitotic mammalian cells induces arrest or delay at metaphase, and impairs progression of late mitotic events. These studies suggest that mammalian p55CDC may be part of a regulatory and targeting complex for the anaphase-promoting complex.

Anaphase↗
PubMed1998

Genomic organization, 5' flanking enhancer region, and chromosomal assignment of the cell cycle gene, p55Cdc.

p55Cdc is a mammalian homologue of a family of cell cycle proteins from widely divergent species, which contains WD repeats and has been implicated in cell cycle-regulated ubiquitin-mediated proteolysis. p55Cdc is highly expressed in proliferating but not in differentiated or growth-arrested cells. The expression, phosphorylation, and degradation of this protein have been shown to be cell cycle-regulated. We analyzed a 5.3-kb genomic region that contains the entire rat p55Cdc gene. The gene contains 10 exons ranging in size from 97 to 373 bp. The promoter region has a TAT box, four E-box consensus sequences, and potential binding sites for cell cycle-specific transcription factors. In transient transfection assays, a construct containing a 1000-nucleotide p55Cdc promoter region upstream of the chloramphenicol acetyltransferase reporter gene demonstrated a 12-fold increase in transcriptional activity. Finally, using radiation hybrid mapping techniques, we localized this gene to the human chromosome, 9q13-21.

Animals↗
PubMed1998

Analysis of cell death in myeloid cells inducibly expressing the cell cycle protein p55Cdc.

p55Cdc, a cell cycle protein is expressed in cycling mammalian cells and is required for normal cell division. Expression of this protein is regulated during the cell cycle, peaking in late G1 and S. We have previously shown that constitutive expression of p55Cdc results in inhibition of granulocyte differentiation. Degradation of p55Cdc is also required for apoptosis in growth factor and serum starved cells. In the present study we prepared stably transfected cells conditionally expressing p55Cdc in response to zinc stimulation to investigate the role of inducible p55Cdc expression in apoptosis of myeloid cells. We report that inducible expression of p55Cdc in the myeloid leukemic cell line 32Dc13 resulted in increased cell death. p55Cdc overexpression led to a statistically significant decrease in the viability of 32Dc13 cells compared with that of control cells. Furthermore, cell staining and flow cytometry analysis revealed that p55Cdc-overexpressing 32Dc13 cells progressed to apoptosis much earlier than uninduced cells. These results suggest that inducible expression of p55Cdc leads to earlier increases in cell death in the absence of growth factor and serum in myeloid leukemic cells.

Animals↗
PubMed1997

Cell cycle-regulated expression, phosphorylation, and degradation of p55Cdc. A mammalian homolog of CDC20/Fizzy/slp1.

p55Cdc is a mammalian protein that shows high homology to the cell cycle proteins Cdc20p of Saccharomyces cerevisiae and the product of the Drosophila fizzy (fzy) gene, both of which contain WD repeats and are thought to be required for the metaphase-anaphase transition. The fzy mutants exhibit a metaphase arrest phenotype, which is accompanied by stabilization of cyclins A and B, leading to the hypothesis that fzy function is required for cell cycle-regulated ubiquitin-mediated proteolysis. p55Cdc expression was initiated at the G1/S transition and steady state levels of p55Cdc were highest at M and lowest in G1. Inhibition of the 26 S proteasome prevented both mitotic exit and loss of p55Cdc at the M/G1 transition, suggesting that p55Cdc degradation was mediated by the cell cycle-regulated proteolytic pathway. Immune complexes of p55Cdc obtained at different cell cycle stages showed a variety of proteins with dramatic differences observed in the pattern of associated proteins during the transition from G2 to M. Immunolocalization of p55Cdc demonstrated dynamic changes in p55Cdc localization as the cells transit mitosis. p55Cdc appears to act as a regulatory protein interacting with several other proteins, perhaps via its seven WD repeats, at multiple points in the cell cycle.

Carrier Proteins↗