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Biomedical subjects

J Michalski

Publications and source records attributed to J Michalski.

At least 55 records · Page 3Linked to original sources
PubMed1991

New synthetic approach to nucleoside phosphorofluoridates and fluoridites. Novel type of phosphitylating reagents containing 4-nitrophenoxy group.

New DNA analogues which have -OP(O)F-O internucleotide linkage are prepared by two methods. One route is based on transformation of a deoxynucleoside phosphoroimidazolidate by benzoylfluoride into the corresponding phosphorofluoridate. Alternative route begins with condensing of a new type of phosphoroamidites containing 4-nitrophenoxy group: N,N,N',-tetraisopropyl-O-4-nitrophenylphosphorodiamidite 9 to yield the dideoxynucleoside-4-nitrophenylphosphites which are readily converted into the corresponding dideoxynucleoside phosphorofluoridates and their sulfur analogues. Second part of this paper illustrates application of the N,N-diisopropyl-O-methyl-O-4-nitrophenylphosphoroamidite 12 and N,N-diisopropyl-O-4-nitrophenyl-P-methylphosphonoamidite 16 in efficient synthesis of dideoxynucleotides and their thio- and selenoanalogues.

Amides↗
PubMed1991

[Changes in electrical potentials of gastric mucosa during various types of experimental hypoxia].

In experiments performed on anaesthetized male and female Wistar rats the effects of different types of hypoxia on the electrical potential difference (PD) between the inner and the outer sides of the gastric wall were examined. The PD was determined by mean of the Digital Multimeter VC-10T, Unitra, and the calomel electrodes connected with the KCl-agar bridges. There were four series of experiments carried out in which hypoxia was produced by: I--low atmospheric pressure (hypobaric hypoxia) corresponding with the altitudes of 2500, 5500, 8500 and 10,500 m above sea level, II--1 min. nitrogen breathing (anoxic anoxia), III--bleeding ca. 1% of the body weight (anemic hypoxia), IV--the gastric vessels ligation (ischemic hypoxia). There were also performed the adequate control experiments of each series. In all types of hypoxia (I--IV) a decrease in the PD was observed. The value and rate of this decrease were dependent on the type, grade, duration and rate of hypoxia. In the conditions of the hypobaric hypoxia simulated altitude 10,500 m only evoked the statistically significant PD drops, by 31%. The nitrogen breathing caused the PD decrease by 23% and the anemic hypoxia by 18%. In the ischemic hypoxia the total disappearance of the potential difference (PD = 0 mV) was observed. In the control experiments small non significant fluctuations, not exceeding 4%, occurred only. The decrease in the PD of the gastric wall observed during hypoxia could be explained by the changes in the membrane transport e.g. the back-diffusion of Na+, Cl-, and H+ ions.

Animals↗
PubMed1990

Transposon-induced non-motile mutants of Vibrio cholerae.

Non-motile mutants of Vibrio cholerae were isolated after transposon insertion mutagenesis with either Tn5 on a plasmid or Tn10ptac mini-kan in bacteriophage lambda. The physical location and number of transposon insertions was determined. Eighteen Tn5 insertion mutants and 11 Tn10ptac mini-kan insertion mutants had single unique insertion sites. The 18 Tn5 insertions were contained within six different EcoRI fragments and the 11 Tn10ptac mini-kan insertions were contained within eight different fragments of V. cholerae chromosomal DNA. These data suggest that multiple genes are involved in motility. Immunoblot analysis of non-motile mutants with antibody to wild-type flagellar core protein indicated that two of the non-motile mutants made flagellar core protein. Three additional mutants reacted weakly with the antibodies. However, these mutants with immunopositive reactions did not produce any structures which resembled flagella by transmission electron microscopy. In addition, none of the other non-motile mutants produced wild-type flagella. However, five mutants which did not react in the immunoblot produced a structure which resembled a flagellar sheath without the internal flagellar core. In addition to having no filamentous core, the sheaths often extended from the sides of the bacteria, rather than from the poles where the flagellum is normally located. The data suggest that sheath formation is independent of flagellar filament formation, but that proper positioning of the sheath may require the flagellar filament.

DNA Transposable Elements↗
PubMed1986

Hemolysin production and cloning of two hemolysin determinants from classical Vibrio cholerae.

The hemolytic activity of 20 classical and 3 El Tor strains of V. cholerae O1 was examined phenotypically and genetically. The El Tor strains lysed bovine, chicken, human, rabbit, and sheep erythrocytes (RBCs), while the classical strains lysed only chicken and rabbit RBCs. The assay was done with RBCs in Tris-NaCl buffer, since phosphate-buffered saline was found to inhibit hemolytic activity. Hemolytic activity in culture supernatants from El Tor strains was more sensitive to heat inactivation than that in supernatants from the classical strain 395. A gene library of strain 395 was examined for hemolytic activity, and two distinct hemolytic clones were identified. One clone appeared identical to the previously cloned hemolysin structural gene from El Tor V. cholerae, while the other did not hybridize to the El Tor hemolysin probe, had a unique restriction enzyme digestion pattern, and encoded a hemolysin whose activity differed from that of the El Tor hemolysin clones. We suggest that the hemolysin specified by the determinant originally cloned from an El Tor vibrio be designated hemolysin I and the second hemolysin, cloned from the classical vibrio, be designated hemolysin II.

Animals↗
PubMed1986

Persistence of cholera in the United States: isolation of Vibrio cholerae O1 from a patient with diarrhea in Maryland.

A case of cholera was identified in Baltimore County, Md., in October 1984. The Vibrio cholerae O1 isolate from the patient was hemolytic, biotype El Tor, serotype Inaba, and was toxigenic by the Y-1 adrenal cell assay; on Southern blot analysis, the strain had a unique HindIII restriction site in the cholera toxin gene identical to that of other U.S. V. cholerae O1 isolates. Two days before he became ill, the patient had eaten meat from crabs harvested along the Texas coast.

Aged↗
PubMed1984

Synthesis and reactions of a nucleoside derivative of phosphoric sulfonic anhydride. Studies related to the mechanisms of coupling reactions in the chemical synthesis of oligodeoxyribonucleotides by phosphotriester procedures.

The synthesis of a model compound, diphenylphosphoric toluene-p-sulfonic anhydride, an arylsubstituted phosphoric sulfonic mixed anhydride, is described. Using the same procedure a thymidyl substituted derivative was prepared. The phosphoric sulfonic anhydride is the presumed intermediate in oligonucleotide coupling reactions involving phosphodiester activation by arenesulfonyl derivatives. This mixed anhydride reacts with a variety of nucleophiles. It can be converted to phophotriester derivatives in the presence of simple alcohols. Phosphotriester formation using the 5'-hydroxyl of a thymidine derivative requires additionally a catalyst such as N-methylimidazole. The reactive intermediate produced upon the addition of N-methylimidazole to the phosphoric sulfonic anhydride has been observed spectroscopically using 31P-NMR.

Chemical Phenomena↗
PubMed1983

Clinical symptoms and signs useful in the early diagnosis of ankylosing spondylitis.

Seventy patients between the ages of 18 to 30 with early spondylitis (eAS), with bilateral grade II-III sacroiliitis without syndesmophytes were examined. The control group comprised 32 patients of the same age range with lumbar disc disease (LDD) confirmed by radiculography, without changes in the sacroiliac joints. In both groups the same clinical parameters were evaluated, calculating for each the specificity, sensitivity and Youden index. Statistical analysis was done using Student's t-test and/or the chi-square test. A complex of simple clinical features was isolated suggesting presence of eAS in young subjects with persistent low back pain but without a clear-cut radiological appearance of the sacroiliac joints. The complex included: a history of morning back stiffness, swelling of knee joints, thoracic pain, clinical evidence of limited chest expansion below 5 cm, swelling of joints of lower extremities, positive Mennell's sign, and in laboratory investigations presence of raised ESR and HLA B27-antigen.

Adolescent↗
PubMed1978

Levamisole maintains cyclophsophamide-induced remission in murine lupus erythematosus.

Antibodies to DNA in 14 month old male NZB/W F1 mice were markedly decreased after 4 weeks of cyclophosphamide therapy. A group of these mice and untreated controls subsequently received levamisole for 12 weeks. Antibodies to DNA returned to pretreatment levels within 8 weeks in animals receiving only cyclophosphamide, whereas levamisole treatment after cyclophosphamide delayed the reappearance of these antibodies. Glomerular immunoglobulin deposition and the degree of lymphocytic tissue infiltrate were decreased in animals receiving cyclophosphamide followed by levamisole as compared with non-treated control animals or those receiving cyclophosphamide or levamisole alone. In vitro T-cell mitogen reactivity was inversely correlated with the final DNA antibody titres of individual mice, suggesting a relationship between decreased autoantibody production and augmented cellular immunity. We discuss possible mechanisms by which levamisole may delay the reappearance of autoantibodies and decrease the histological evidence of lupus nephritis when given to New Zealand mice first treated with cyclophosphamide.

Animals↗