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Biomedical subjects

J Siedlecki

Publications and source records attributed to J Siedlecki.

At least 19 recordsLinked to original sources
PubMed2005

Human red blood cells' physiological water exchange with the plasma.

In the present paper, fundamental issues related to the mechanisms of human red blood cells' physiological water exchange with the plasma (for the stationary conditions) have been discussed. It has been demonstrated, on the basis of mechanistic transport equations for membrane transport that red blood cells are capable of exchanging considerable amounts of water with the plasma. Water absorption is osmosis-driven, and its removal occurs according to the hydromechanics principle, i.e. is driven by the turgor pressure of red blood cells. This newly-acquired knowledge of these issues may appear highly useful for clinical diagnosis of blood diseases and blood circulation failures.

Animals↗
PubMed2000

Fapyadenine is a moderately efficient chain terminator for prokaryotic DNA polymerases.

Hypoxanthine¿xanthine oxidase¿Fe3+¿ethylenediaminetetraacetate (EDTA) was used to modify ss M13 mp18 phage DNA. The dominant base modifications found by GC/IDMS-SIM were FapyGua, FapyAde, 8-hydroxyguanine, and thymine glycol. Analysis of in vitro DNA synthesis on oxidatively modified template by three DNA polymerases revealed that T7 DNA polymerase and Klenow fragment of polymerase I from Escherichia coli were blocked mainly by oxidized pyrimidines in the template whereas some purines that were easily bypassed by the prokaryotic polymerases constituted a block for DNA polymerase beta from calf thymus. DNA synthesis by T7 polymerase on poly(dA) template, where FapyAde content increased 16-fold on oxidation, yielded a final product with a discrete ladder of premature termination bands. When DNA synthesis was performed on template from which FapyAde, FapyGua, and 8OHGua were excised by the Fpg protein new chain terminations at adenine and guanine sites appeared or existing ones were enhanced. This suggests that FapyAde, when present in DNA, is a moderately toxic lesion. Its ability to arrest DNA synthesis depends on the sequence context and DNA polymerase. FapyGua might possess similar properties.

Animals↗
PubMed1994

[Changes in levels of glucose, insulin, c-peptide, glucagon and potassium in serum of patients with bronchial asthma during stimulation with b2-adrenergic fenoterol].

The study was carried out on 40 patients with bronchial asthma (20 with atopic and 20 with non-atopic) and 20 healthy subjects as controls. After fenoterol stimulation in asthmatic and control groups an increase of glucose level and decrease of potassium concentration were documented. Moreover, a slight increase of insulin, C-peptide and glucogene++ release was suggested.

Adolescent↗
PubMed1993

Inhibition of reverse transcriptase activity by extracts of cultured blue-green algae (cyanophyta).

Lipophilic and hydrophilic extracts of over 900 strains of cultured blue-green algae (cyanophyta) were examined in vitro for their ability to inhibit the reverse transcriptases (RT) of avian myeloblastosis virus (AMV) and human immunodeficiency virus, type 1 (HIV-1). Eighteen (2.0%) aqueous extracts showed activity against AMV and HIV RTs. The maximal level of RT inhibition achieved by some of the active extracts was equivalent to that measured for 3'-azido-2',3'-di-deoxythymidine (AZT) at 668 ng/ml. Examination of partially purified fractions prepared by C18 column chromatography demonstrated that the RT inhibition observed could not be attributed entirely to the degradation of transcript DNA, template RNA, or enzyme protein in the reaction mixture. Thus, these results indicate that cultured blue-green algae may represent a novel source of compounds that inhibit RT activity, including that of HIV-1.

Antiviral Agents↗
PubMed1993

[Can administration of trasylol in reduced Hammersmith dosage with simultaneous transfusion of autologous blood meet the requirements of open heart surgery?].

PROBLEM: The general positive effect of the proteinase inhibitor trasylol on blood loss and transfusion demand in cardiac surgery has been demonstrated in several placebo-controlled studies. Given the possibility of cardiac and renal side effects associated with a high dose of trasylol (Hammersmith dosage: 6 x 10(6) kallikrein inactivator units KIU), the question of a dose reduction was raised. METHODS: Being designed as a randomized double-blind comparative group study, the investigation included 120 patients with elective primary cardiac surgery from November 1990 to April 1992. One characteristic aspect of this study was the combined administration of trasylol and autologous blood transfusions. To compare the efficacy and safety of different doses of trasylol, two groups, each with 60 patients, were created: the former with the full Hammersmith dose (high dose group = HD group), the latter with half of the Hammersmith dose (los dose group = LD group). A placebo group had to be excluded for ethical reasons. RESULTS: The trasylol plasma levels showed a good dose correlation for the complete interval. The intra-operative bleeding tendency, as judged by the surgeons in charge, did not show any statistical significant difference between the HD group and the LD group. As to the post-operative blood loss via thoracic drainage, the early collection periods did not show any difference between both study groups. Starting at 6 hours post-operatively, the drainage losses showed a tendency towards lower volumes in the HD group. This difference was statistically significant for the time period "6-12 hours post-operatively". The analysis of the post-operative complications did not show any difference. SUMMARY: In this study with a high percentage of autologous blood transfusions, a lower dose of trasylol seemed to be nearly as effective as a full Hammersmith dose. However, such a reduced dose did not demonstrate any advantage regarding the complication rate in comparison with the conventional high dose.

Aprotinin↗
PubMed1992

[A case of functional hyperprolactinemia].

A case is presented of a 27-year-old woman in whom galactorrhoea and amenorrhoea occurred simultaneously with the signs of acute neurosis. The determination of prolactin concentration after the administration of metoclopramide made possible the diagnosis of functional hyperprolactinaemia. Other causes of hyperprolactinaemia were excluded. The signs and symptoms regressed completely after several months of treatment with parlodel. Control investigation done after 18 months showed that the concentration of prolactin after administration of metoclopramide was slightly lower than before, but was still high.

Adult↗
PubMed1983

Characterization of a prokaryotic topoisomerase I activity in chloroplast extracts from spinach.

A topoisomerase I activity has been partially purified from crude extracts of spinach chloroplasts. This activity relaxes the supercoiled covalently closed circular DNA of pBR322. The enzyme requires Mg++, but not ATP, and has an apparent molecular weight of about 115,000. It catalyzes a unit change in the linkage number of supercoiled DNA but cannot relax positive supercoiled DNA. These characteristics of the topoisomerase suggest it is of the prokaryotic type and would tend to support the endosymbiotic theory of plastid origin and evolution.

Chloroplasts↗
PubMed1982

Inhibition of calf thymus DNA polymerase alpha and of normal and cancer cell growth by butylanilinouracil and butylphenylguanine.

6-(p-n-Butylanilino)uracil and N2-(p-butylphenyl)guanine inhibited the activity of DNA polymerase alpha from calf thymus but had no effect on other eukaryotic polymerases (DNA polymerases beta and gamma) or Escherichia coli DNA polymerase I. Inhibition was competitive with deoxyguanosine 5'-triphosphate and did not occur in the reaction of DNA polymerase alpha with a template that did not contain cytosine residues. The results support a mechanism which involves hydrogen bonding of inhibitors with cytosines in the DNA template and binding with an inhibitor specific site on the enzyme. A screen of inhibitor effects on normal and cancer cell growth in culture showed that cells were not uniformly sensitive to these compounds, a mouse lymphoma line being least sensitive and a human lung cancer line being most sensitive. It is suggested that these inhibitors may be useful to probe possible structural differences among DNA polymerases alpha.

Animals↗