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Biomedical subjects

M Vrana

Publications and source records attributed to M Vrana.

At least 19 recordsLinked to original sources
PubMed1990

[Effects of ethmozine on ventricular fibrillation threshold in acute occlusion of the coronary artery in dogs].

In experiments on dogs with acute left descending coronary artery occlusion, ethmozine (3 mg/kg) was tested for effects on the threshold of ventricular fibrillation occurring as a result of high-frequency electric stimulation. Two hours after occlusion, the fibrillation threshold became significantly lower than the control values. Ethmozine used in this period enhanced the ventricular fibrillation threshold in some experiments and diminished it in the others. Four hours following the occlusion, the fibrillation threshold did not differ from the control ones. Ethmozine given in this period caused a significant increase in the ventricular fibrillation threshold. It was concluded that 4 hours after the onset of experimental myocardial infarction are the minimal time period following which administration of ethmozine failed to decrease electric stability of the heart.

Animals↗
PubMed1989

The antifibrillatory effect of fentanyl, sufentanil and carfentanil in the acute phase of local myocardial ischaemia in the dog.

To determine the effect of strong analgesics on electrical instability (vulnerability to ventricular fibrillation), we examined the action of fentanyl (60 micrograms/kg), sufentanil (10 micrograms/kg) and carfentanil (3 micrograms/kg) on the ventricular fibrillation threshold (VFT) in a dog model of coronary artery occlusion. The effect of strong analgesics was compared with that of the first-generation beta-blocker propranolol (1.2 mg/kg) and the third-generation beta-blocker celiprolol (3 mg/kg). In the 5th minute of ischaemia, VFT declines in all groups of dogs. VFT values rise significantly from the 23rd to the 60th minute of ischaemia after opiate analgesic administration. The mean increase in VFT after opiate analgesics is less pronounced than after beta-blockers. Administration of opioid analgesics is followed by strong prevalence of vagal drive to the heart. Sympathetic drive to the heart after propranolol administration disappears and is depressed after the administration of celiprolol only. Blockers of the beta-receptors apparently intervene directly in the ischaemic focus and affect the "substrate" of electrical instability. The opioid analgesics probably exert their effect through a change in "substrate" modulation. There is an ongoing search for drugs that would stabilize the heart electrically in acute myocardial infarction, thus preventing sudden death. Our experimental results favour a combination of strong analgesics with other electrostabilizing drugs.

Adrenergic beta-Antagonists↗
PubMed1988

Trends in exploitation of packed red blood cells.

The following trends aim to a more efficient exploitation of packed red blood cells (PRBC): 1. Improvement of the operative distribution of PRBCs for transfusions before expiration. 2. Prolongation of the expiration time by monitoring the biochemical and physical processes during banking. Maintenance of native hemoglobin and restoration or substitution of substances involved in transport of energy and of oxygen are of utmost importance. Enzymic conversion of RBCs of blood group A, B to 0 is not supposed to leave laboratory scale soon. While cryo-conservation of RBCs with glycerine is known, freeze-drying of PRBCs remains a speculation. 3. Use of PRBCs after expiration as a raw material for products applicable in medicine and biochemistry. Stroma-free hemoglobin variants (SFH) are known as effective infusable oxygen carriers in experimental animal models. However, there is little convincing evidence on the metabolism and innocuity of SFH variants in human organism. Therefore, systemic infusion of SFH solutions is not yet acceptable to clinicians even in emergency situations. On the other hand, a broader use of SFH and its variants is anticipated and regarded as prospective in organ perfusion, cardioplegy and transplantation as well as in analytical biochemistry.

Blood Banks↗
PubMed1981

[Sodium thiosulfate in the treatment of early postischemic disorders].

Experiments were made in dogs weighing 15-25 kg with experimental tourniquet shock (35 dogs) and experimental myocardial infarction (29 dogs). Intravenous injection of sodium thiosulfate (500 mg/kg) exerted a marked therapeutic effect on cardio- and central hemodynamics under acute circulatory disturbances both in tourniquet shock and myocardial infarction. Sodium thiosulfate increased cardiac discharge, minute blood flow volume, the first derivative, the threshold of ventricular fibrillation, improved the heart work, decreased and normalized the general peripheral resistance. This effect is likely to be related to the stimulation of intracellular metabolism and antidote action of sodium thiosulfate against ischemic toxin.

Animals↗
PubMed1978

Sequence variation among heavy chains from inulin-binding myeloma proteins.

The entire sequences of the variable region of four heavy chains from BALB/c inulin-binding myeloma proteins have been determined. Among the four proteins there are six amino acid differences, all of which occur in the framework portion of the variable region. All of the six amino acid substitutions can be explained by single base mutations at the DNA level. The pattern of diversity in these proteins is compared to a previously reported group of heavy chains from phosphorylcholine-binding myeloma proteins. Unlike the phosphorylcholine-binding proteins, which (with the exception of two that are identical) have size and sequence differences in their complementarity regions, the inulin-binding heavy chains all have identical complementarity regions with H3 being extremely short. The pattern of variation observed in the anti-inulin heavy chains appears to be most easily explained by a somatic mutation mechanism. However, because none of the substitutions occur in complementarity-determining regions, they presumably would have no selective advantage and would not alter binding specificity. These proteins have further been shown to have crossreacting antigenic determinants (idiotypes). Five of the six sequence differences observed occur at positions that are internal in the molecule and thus presumably would not account for the idiotypic differences. These results suggest that most of the observed idiotypic crossreactivities will be due to differences in the light chains of the anti-inulin proteins.

Amino Acid Sequence↗
PubMed1977

Idiotypes of inulin-binding myeloma proteins localized to variable region light and heavy chains: genetic significance.

Idiotypes of inulin-binding myeloma proteins (InuBMP) were determined primarly by variable region light chains (VL) or by variable region heavy chains (VH) but needed both chains to be expressed. Recombinant molecules were used to show that individual idiotypes (IdI) of U61, E109, T957, and A4 InuBMP and cross-specific idiotypes (IdXB) of U61 were primarily determined by VL while cross-specific idiotype (IdXA) of A4 was determined mainly by VH. The assignment of genes controlling idiotypes to VH based on allotype linkage (e.g., IdXB) is dubious until the role of the L chain in determining that idiotype is assessed. IdXB has been shown to be a VL-VH marker which presumably is controlled by two unlinked genes. However IdXB can be used as a L chain marker in combinations of strains differing in their L chain genes but having the same permissive H chain genes. Conversely IdXB can be used as a H chain marker in strains having the same permissive L chain genes but differing in their H chain genes.

Animals↗
PubMed1977

Heavy-chain variable-region sequence from an inulin-binding myeloma protein.

The entire variable-region sequence of the heavy chain from ABE-47N, a BALB/c inulin-binding myeloma protein, has been determined. This protein is unusual in that the third complementarity region (H3) is extremely short, consisting of at the most three and probably only one amino acid. A comparison of the heavy-chain hypervariable regions from mouse, human, and rabbit proteins shows that the variability in length of H3 is greater than that seen in the first or second hypervariable regions. This variability in H3 length suggests a specialized function for this region.

Amino Acid Sequence↗
PubMed1975

Multiple individual and cross-specific indiotypes on 13 levan-binding myeloma proteins of BALB/c mice.

13 leven-binding myeloma proteins (LBMP) of BALB/c origin were classified into two groups with different binding specificities; one group of 11 proteins bound beta2 leads to 1 fructosans, a second group of two proteins bound fructosans probably of beta2 leads to 6 linkage. Anti-idiotypic sera prepared to 10 of the proteins in the appropriate strains of mice identified numerous idiotypic determinants. Each protein used for immunization had its own unique individual idiotypic specificities (IdI) and in addition most of the proteins carried two-nine cross-specific or shared idiotypes (IdX) that were found only among LBMP, and not found in 106 non-LBMP. Most of the IdX determinants and only four of the IdI determinants of the beta2 leads to 1 fructosan binding group were located in the antigen-binding site. The multiplicity of antigenic differences in this functionally related group of immunoglobulins reveals an unexpected degree of heterogeneity in V-regions that appears to be unrelated to binding.

Animals↗