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M Dabrowski

Publications and source records attributed to M Dabrowski.

At least 37 records · Page 2Linked to original sources
PubMed1996

[Phosphate sites of RNA-ligands interacting with ribosome at different stages of translation. Thiophosphate method of analysis].

A novel footprinting method was recently developed which identifies phosphate groups of RNA involved in strong RNA-RNA and RNA-protein interactions. The method is based on iodine-dependent RNA cleavage at phosphothioate groups as long as these groups are not protected from iodine. Our recent studies of mRNA and tRNA regions protected in active ribosomes are summarized; initiation state of ribosomes as well as two elongation states in pre- and post-translocational states were analyzed. Only one phosphate group of mRNA, which was two positions upstream of the decoding codons, was weakly protected in longation complexes, whereas this group and the phosphate groups in the Shine-Dalgarno sequence were protected in the initiation complex. No protection was observed downstream of the decoding codons. On the contrary, numerous phosphate residues of tRNA were protected by the ribosome. The tRNA protection patterns significantly varied between two tRNAs simultaneously bound to the ribosome. The protection pattern of an individual tRNA was not significantly affected by translocation. The data indicate that both tRNA molecules are tightly bound to the ribosome, whereas mRNA is fixed predominantly by two tRNAs via codon-anticodon interaction. A possible translocation mechanism is suggested.

Base Sequence↗
PubMed1995

Interaction of tRNAs with the ribosome at the A and P sites.

In vitro transcribed tRNA(Phe) analogues from Escherichia coli containing up to four randomly distributed A, G, U or C phosphorothioated nucleotides were used to investigate contact patterns with the ribosome in the A and P sites. The tRNAs were biologically active. Molecular iodine (I2) can trigger a break in the sugar-phosphate backbone at phosphorothioated positions of the ribosomal bound tRNAs if contacts with ribosomal components do not prevent access of the iodine. Highly differentiated protection patterns were found which were strikingly different in the A and P sites, respectively. Strong protections accumulated in the T psi C loop and no protection was seen in the extra-arm region in both sites, whereas the phosphates in the anticodon loop are more strongly protected in the A site. Strong common protections in both the A and P sites were found neighbouring universally or semi-universally conserved bases in prominent regions of the tertiary structure of tRNAs: Y11, Y32, U33, psi55, C56, A58 and Y60. These bases are therefore candidates for 'identity elements' in ribosomal tRNA recognition. The data further indicate that tRNAs change their conformations upon binding to either ribosomal site.

Acetylation↗
PubMed1995

Self-coded 3'-extension of run-off transcripts produces aberrant products during in vitro transcription with T7 RNA polymerase.

More than 70% of the RNA synthesized by T7 RNA polymerase during run-off transcription in vitro can be incorrect products, up to twice as long as the expected transcripts. Transcriptions with model templates indicate that false transcription is mainly observed when the correct product cannot form stable secondary structures at the 3'-end. Therefore, the following hypothesis is tested: after leaving the DNA template, the polymerase can bind a transcript to the template site and the 3'-end of the transcript to the product site and extend it, if the 3'-end is not part of a stable secondary structure. Indeed, incubation of purified transcripts with the polymerase in transcription conditions triggers a 3'-end prolongation of the RNA. When two RNAs of different lengths are added to the transcription mix, both generate distinct and specific patterns of prolonged RNA products without any interference, demonstrating the self-coding nature of the prolongation process. Furthermore, sequencing of the high molecular weight transcripts demonstrates that their 5'-ends are precisely defined in sequence, whereas the 3'-ends contain size-variable extensions which show complementarity to the correct transcript. Surprisingly, a reduction of the UTP concentration to 0.2-1.0 mM in the presence of 3.5-4.0 mM of the other NTPs leads to faithful transcription and good yields, irrespective of the nucleotide composition of the template.

Bacteriophage T7↗
PubMed1994

Transfection of vitamin D receptor cDNA into the monoblastoid cell line U937. The role of vitamin D3 in homotypic macrophage adhesion.

A 2-kB cDNA for the vitamin D receptor (VDR) was cloned in sense orientation into the plasmid pMEP4 (containing a cadmium-inducible metallothionein II promoter and a hygromycin-resistance selection gene) and transfected into monoblastoid U937 cells. The resultant cell line, DH39, expressed two species of VDR mRNA: 4.6-kb wild-type mRNA (present in native U937 cells or cells transfected with pMEP4 alone) and 2-kb transfected mRNA, which increased with cadmium treatment. Binding studies (using the active vitamin D metabolite, 1,25-dihydroxycholecalciferol (1,25-DHCC)) showed that DH39 cells contained five times more VDR per cell than controls, and ten times more after cadmium treatment. DH39 were sensitive to 1,25-DHCC: adding cadmium with 100 nM 1,25-DHCC for 72 h completely inhibited proliferation and induced concomitant differentiation. Unlike control cells, differentiation of DH39 by 1,25-DHCC led to homotypic cell-cell adhesion and formation of macrophage clusters. FACS analysis showed that 1,25-DHCC increased the number of cells expressing CD11b in both DH39 and controls, and the number of cells expressing CD11c in DH39. There was a quantitative increase in mean fluorescence intensity of expression of CD11a and CD18 in DH39. Northern blotting showed increased CD11a and CD18 mRNA in DH39. Ab inhibition of 1,25-DHCC-induced homotypic adhesion showed that CD11a/18 mediated the cell-cell clustering. CD50 expression was decreased on DH39, but the CD11a/18 ligand implicated was CD54. DH39 provides a model system not only for investigating the VDR role in 1,25-DHCC anti-proliferative effects, but also for regulation of homotypic macrophage adhesion mechanisms that are important in disease pathogenesis.

Blotting, Northern↗
PubMed1994

Reversal of ischaemic systolic and diastolic left ventricular dysfunction by successful coronary angioplasty in patients with non-Q wave anterior myocardial infarction.

The effect of PTCA on global and regional left ventricular systolic function, isovolumic relaxation, chamber and muscle stiffness were studied in 30 patients with angina pectoris, previous non-Q wave anterior myocardial infarction (AMI) and significant stenosis of the left anterior descending coronary artery (LAD). In 11 of the 30 patients the condition was stable, but it was unstable in 19. Left ventricular angiograms were obtained before and 4.85 +/- 3.67 months after PTCA. The RAO was in the 30 degree projection, with the silhouette of the left ventricle sliced into 90 regions; changes in left ventricular volume, pressure and anterior wall thickness during the full cardiac cycle, together with dp/dt were demonstrated. After PTCA, global ejection fraction increased from 68.77 +/- 5.96% to 76.57 +/- 3.18%, P < 0.001. Impaired contractility was found in 29/90 (32.2%) regions before PTCA and in 5/90 (5.6%) after PTCA, P < 0.001. The time constant of the isovolumic pressure fall decreased after PTCA (52.56 +/- 17.40 ms vs 39.61 +/- 11.26 ms, P < 0.01). Elastic chamber stiffness coefficient decreased (0.022 +/- 0.003 vs 0.008 +/- 0.004, P < 0.001) and peak rate of left ventricular filling increased (319.0 +/- 107.9 ml.min-1 vs 396.8 +/- 201.4 ml.min-1, P < 0.05) after PTCA. The muscle stiffness coefficient was within normal values before and did not change after PTCA. The study findings show that in patients with persistent angina pectoris after non-Q wave AMI, complex systolic and diastolic ischaemic dysfunction occurs. This dysfunction can be reversed after successful PTCA of LAD.

Adult↗
PubMed1994

Long term follow up after percutaneous mitral commissurotomy with the Inoue balloon-incidence of restenosis.

UNLABELLED: The long term outcome of 300 consecutive patients following percutaneous mitral commissurotomy (PMC) with the Inoue balloon was analyzed with regard to the incidence of restenosis. There were 256 females and 44 males (mean age 44.4 +/- 9.9 years, range 18-69 years), 52 had previous surgical commissurotomy, 96 were in atrial fibrillation, and 16 had a history of embolism. PCM was carried out with a success rate of 84% (no significant mitral regurgitation and mitral valve area (MVA) > 1.5 cm2). Two hundred and seventy patients were available for clinical and serial echocardiographic studies at six months, 12 months and once a year thereafter (18 patients operated on for mitral regurgitation less than six months after PMC, three patients lost to follow up, nine patients refused to return). MVA increased with PMC from 1.18 cm2 +/- 0.3 to 2.0 +/- 0.3 cm2 and then decreased to 1.8 +/- 0.3 at a mean follow up of 24.0 +/- 13.5 months (range 6-55). Echocardiographic restenosis (RS) (MVA at follow up < 1.5 cm2 with a 50% loss of the initial gain) was found in 38 patients (14%). Twenty-five (66%) of them remained in NYHA class I or II. Restenosis free survival according to the Kaplan-Mayer curve was 93%, 86%, 77% and 73% at 12,24,36 and 55 months respectively. None of the 24 clinical, hemodynamic, echocardiographic or procedural variables used on the Cox proportional hazard regression analysis identified predictors of restenosis free survival. CONCLUSIONS: The overall incidence of echocardiographic restenosis post PMC is low (12.6%) in patients followed for a mean period of two years and often occurs without worsened clinical symptoms. It may be difficult to define clinical, echocardiographic or procedural factors as significant predictors of restenosis free survival.

Adolescent↗
PubMed1994

[Long term observations of patients after percutaneous inferior vena cava filter placement for recurrent pulmonary embolism].

Pulmonary embolism remains an important cause of mortality despite recent advances in medical therapy. The inferior vena cava filter has been devised for treatment of pulmonary embolism. The Gunter inferior vena cava filter was inserted percutaneously in 6 patients with recurrent pulmonary embolism despite anticoagulation therapy. No complications were observed during this procedure. Two patients died after filter placement (one after six weeks one after 1.5 year) because of right heart failure observed before procedure. The other four patients showed no signs of pulmonary embolism during four years follow-up. We conclude that percutaneous insertion of the Gunter filter is a safe and effective technique for prevention of recurrent pulmonary embolism.

Adult↗
PubMed1993

[Surgical course in patients with diabetes].

A retrospective analysis is presented of 388 patients with diabetes mellitus treated in a gastrointestinal surgery department in the years 1975-1988. In the patients 473 diseases were diagnosed which could be the basis for surgical treatment. Our of 388 patients, 254 were treated surgically and 375 operations were performed in them; 46 patients had multiple operations. The highest per cent of deaths was found in the group of patients with diabetic gangrene of the lower limbs which reached 10.4%, while in all patients the mortality was 4.3%. Finally it is suggested that only the approach to the diabetic patients as to high-risk patients enables obtaining of a satisfactory result of surgical treatment.

Aged↗
PubMed1993

[Percutaneous coronary angioplasty and levels of endothelin-1 in blood].

UNLABELLED: The aim of this study was to assess plasma endothelin-1 (ET) concentrations during percutaneous transluminal coronary angioplasty (PTCA) of the left anterio descending coronary artery (LAD). We also examined relations between plasma concentrations of ET and diameter of the PTCA-balloon. Plasma levels of ET determined by radioimmunoassay were measured in 24 patients (pts) without previous myocardial infarction undergoing PTCA of LAD. The pts were divided into two groups. In group 1 (12 pts) plasma ET levels were measured in the right atrium and in the forearm vein 24 hours before PTCA, and 5 minutes after the last balloon deflation. In group 2 (12 pts) concentrations of ET were measured only in venous blood: 24 hours before PTCA, just before PTCA, 5 minutes after last balloon deflation and 24 hours later. We compared the diameter of the inflated balloon with the diameter of the dilated artery [balloon/artery ratio /b/a ratio/] and correlated it with plasma ET concentration rise in every case. [table: see text] The mean b/a ratio correlated with plasma ET concentrations after PTCA (r = 0.677 p < 0.001). CONCLUSIONS: Plasma ET concentrations do not rise after non complicated PTCA procedure. Because plasma ET levels depend on b/t ratio it is very important that the diameter of the dilating balloon should correspond with the diameter of the coronary artery to avoid overdilation.

Angioplasty, Balloon, Coronary↗
PubMed1992

[Complications of percutaneous transluminal coronary angioplasty (PTCA)].

Between 1981 and 1990, 714 patients underwent 756 percutaneous transluminal coronary angioplasty (PTCA) procedures. A total of 52 patients (6.9%) had major in-hospital complications: 5 patients (0.66%) died, Q-wave or non Q-wave myocardial infarction were observed in 13 patients (1.66%) during procedure and in 8 (1%) outside the catheterization laboratory, before discharge. Because of periprocedural occlusion 11 patients (1.5%) were managed with bypass surgery, 8 (1%) had a transient occlusion that was reopened with PTCA. 21 patients (2.8%) were not ++re-dilated but managed pharmacologically. Dissection, intracoronary thrombus and previous thrombolytic treatment were often associated with occlusion. The risk of dissection was related to lesion morphology. Long-(more than 1 cm) lesion, eccentric stenosis and tortuosity of the vessel segment undergoing dilatation were risk factors for occlusive dissection. There was a high risk of side branch occlusion if its take-off was narrowed and side branch originated from the target lesion. One of the most important risk predictors is the amount of jeopardized myocardium supplied by the target coronary artery. Acute closure of an artery supplying large amount of myocardium may cause abrupt hemodynamic collapse. Hypotension secondary to the artery occlusion may cause a decrease of the flow in the other coronary arteries, leading to cardiogenic shock. Although it is important to note that patients with unstable angina, intracoronary thrombus, long and complex lesion, severe multivessel disease and compromised left ventricular function are at higher risk of acute complication, PTCA is a relatively safe procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1992

Percutaneous mitral commissurotomy with the Inoue balloon for severe mitral stenosis during pregnancy.

Percutaneous mitral commissurotomy using the Inoue balloon was performed in seven pregnant women between May 1990 and November 1991. The mean age of the group was 31.5 years (range 28-35 years). The mean gestation time was 29 weeks (range 20-38 weeks). All patients presented with severe symptoms; two had a recent history of pulmonary oedema, the rest exhibited marked shortness of breath, and mild exercise and paroxysmal nocturnal dyspnea. All were in sinus rhythm. Two patients had previously undergone closed mitral valvulotomy five and 14 years before their recent hospitalization. Echocardiographic examination revealed severe mitral stenosis, with the mitral valve area being less than 1.2 cm2 in all but one patient. None of the patients had left atrial thrombi or mitral regurgitation as seen on two-dimensional and Doppler echocardiography. Four patients (two with restenosis) had severe lesions of the subvalvular apparatus with thickening and marked shortening of the chordae, as assessed by echocardiography. Successful percutaneous mitral valvulotomy was completed in all seven patients using 25-28 mm Inoue balloons. There was one, transient maternal complications. Fetal complication did not occur. It is concluded that percutaneous, transseptal, mitral balloon valvulotomy during pregnancy with the Inoue balloon is a safe procedure, which can be recommended for suitable clinical cases.

Adult↗
PubMed1992

Development of antiserum against veiled (dendritic) cells of canine afferent lymph: implications for transplantation biology.

A method is described for production of anti-veiled cell serum against veiled cells (VC) or dendritic cells obtained from canine skin lymph. By use of discontinuous Percoll gradient, VC from lymph were enriched to about 50% of the entire lymph cell population. After immunization of rabbits with the priming total dose of 10(7) VC (intramuscular, subcutaneous, intracutaneous) and with the same total booster injection (intravenous), the sera obtained were cytotoxic mainly for VC, with cytotoxin titer 1:16-1:32 and for agglutinin 1:256-1:512, respectively. Antisera used in vitro blocked the Ia and CD1 antigens of VC on smears and inhibited the accessory function of VC in cell response to phytohemagglutinin (PHA) and their stimulatory activity in mixed leukocyte reaction (MLR). In vivo, the local, intracutaneous administration of antisera led to transient depletion of VC from afferent lymph, and to reduction of mononuclear cells in the T-dependent areas in regional lymph nodes.

Animals↗
PubMed1992

[Percutaneous transluminal coronary angioplasty in patients with high risk bypass surgery].

The purpose of this study was to assess the immediate and long-term results of incomplete percutaneous transluminal coronary angioplasty (PTCA) in high-risk coronary artery bypass surgery (CABG) patients. 24 pts (male-22, female-2, age - 39-60 years) were divided into 2 groups: I-8 pts with unstable angina pectoris who were definitely not CABG candidates because of very low ejection fraction (LVEF < 24%) and/or diffuse coronary atherosclerosis; II-16 pts selected for CABG only after failed PTCA. From this group 12 pts with unstable angina pectoris and history of myocardial infarction were at higher CABG risk because of LVEF < 40% and diffuse coronary atherosclerosis. 4 pts were poor surgical candidates because of coexistent medical disorders. The strategy of PTCA was to dilate first the most critical (culprit) lesion, responsible for the patient symptoms, usually situated in the artery supplying large area of viable myocardium. We did not achieve: complete revascularization in all our pts (incomplete revascularization by intent). Initial success rate of the PTCA in both groups was 100%. There were no serious complications. During follow-up (6 months--4 yrs) long-term clinical improvement was observed in 7 pts from group I (87.5%) and 14 pts from group II (87.5%). We conclude, that in most pts with unstable angina pectoris and with high-risk of CABG good immediate and long-term results of incomplete PTCA can be achieved.

Adult↗
PubMed1991

Difference in size of bone islands formed by isolated bone cells transplanted intramuscularly under various conditions.

Bone cells isolated from the whole calvaria (2 x 10(6)) from either central or peripheral parts of parietal bones (1 x 10(6)) and from scapulas (2 x 10(6)) were allowed to adhere to devitalized calvarial bones in the number indicated in brackets and transplanted intramuscularly (supported transplants). Whole calvaria bone cells (2.4 or 8 x 10(6) cells per transplant) were also injected intramuscularly as free transplants. Calvarial cells produced solid bone islands with small intraosseous cavities, while bone formed by scapular cells contained large medullary spaces. The size of bone islands formed in transplants and the shortest distance between the neighbor islands were measured. The results of these measurements were similar in all groups of free transplants. The size of bone islands formed in supported transplants of cells from the whole calvaria or from central and peripheral parts of parietal bones was also roughly similar, but the shortest distance between islands was larger than in the free transplants. Furthermore, in these groups of transplants bone islands considerably larger than the largest islands in free transplants were present. Scapular bone cells formed islands much larger than those produced by calvarial cells. Bone islands formed by calvarial cells in free transplants were separated by bands of fibrous tissue which was absent in supported transplants. It appears that this tissue could limit growth and/or fusion of neighbor bone islands and in this manner influence their size. The population of transplanted scapular cells contained numerous stromal elements which could form an exclusion area inaccessible to local cells from the site of transplantation and thus favour formation of large bone islands within this area.

Animals↗