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Biomedical subjects

R Alexandrescu

Publications and source records attributed to R Alexandrescu.

26 records · Page 2Linked to original sources
PubMedDate not supplied

[Study of purified aldolase from Saccharomyces cerevisiae, using irradiated fructose-1,6-diphosphate].

The interaction of an electromagnetic field with the enzymatic substrate-- the sodium salt of fructose-1,6-disphosphate--induces in the latter a new type of physical transition S leads to S. The enzyme, in this case Saccharomyces cerevisiae aldolase, is able to reveal this new state of the substrate by an increase in its specific activity within well established irradiation times. Each enzyme is characterized by the tm (minimal irradiation time of the substrate) a tau (fixed time period) parameters that delimit the two signals. Purified S. cerevisiae aldolase has tm=5 sec. and tau=20 sec., in contrast to muscle aldolase (represented by class I aldolase) which has tm=15 sec. and tau=30 sec. This may be attributed to the fact that most of the enzymatic systems in S. cerevisiae are made up of several distinct molecular forms, involved in more metabolic pathways than in the animal tissue, therefore with various responses to the phenomenon of perturbation of the substrates.

Culture Media↗
PubMedDate not supplied

The variations of the serum IgD and of the circulant immune complexes in diabetic patients.

The levels of serum IgD and of the circulating immune complexes (CIC) were determined in 168 diabetic patients, of whom 78 with type 1, 59 with type 2 and 31 with the so-called "intermediary" type of the disease, in comparison with 124 non-diabetic subjects for IgD and 100 for CIC. The results revealed very low IgD titres (less than 1 mg%, considered undetectable) in almost 3/4 of the cases; values over 1 mg% were recorded mostly in the cases of type 1, followed by those of "intermediary" and of type 2 diabetes. The mean CIC values of 67.13 +/- 36.53 optic density units (O.D.U.) were significantly higher than in the non-diabetic controls. Certain differences with respect to age, diabetes type, duration of the disease and of the insulin therapy were also recorded. The data are interpreted with caution, further investigations being necessary to the assertion of definite conclusions.

Adult↗
PubMedDate not supplied

[Quantitative and qualitative changes in the immunoglobulins of HIV-infected children].

In HIV-infected children impairment of B lymphocytes appears to precede the T cell deficiency, elevated but dysfunctional immunoglobulins being a hallmark of pediatric infection. Electrophoretic and immunochemical data obtained with samples from 91 cases of AIDS in children aged 7-36 months in P2 clinical stage are reported. In 21 children successive samples were obtained at each 3-4 months for a one-year follow-up. In electrophoresis low albumin level and marked increase of globulins level were noted. In immunodiffusion all Ig classes but especially IgG were increased. HI measles antibodies titers in all these samples were negative or very low in spite of measles vaccination positive record. Distinct from adult AIDS where absolute number of pan T and CD4 positive lymphocytes are good predictive markers, in pediatric AIDS estimation of quantitative and qualitative changes of immunoglobulins is useful for clinical diagnosis and follow-up of patients.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

The significance of the peroxides increase in the plasma of the patients with liver failure.

200 patients with varied types of liver failure were biochemically and clinically investigated. Beside the usual biochemical analyses (transaminases, glutamyl transpeptidase, triglycerides, bilirubin), some special parameters such as lipid peroxides, glutathione, ceruloplasmin and the total antioxidative capacity of plasma were measured. High levels of lipid peroxides appear especially in severe cases of liver failure such as acute viral hepatitis, coma. The persistence of a high level of peroxides in plasma suggests the presence of severe, irreversible lesions. The increase of peroxides in the plasma is mainly due to the overridden production of antioxidative systems, localized especially in the liver. In severe liver failure, the mechanism of the increased formation of peroxides seems to involve bilirubin, due to induction of liver heme oxygenase. The data presented showed inverse correlations between the increase of peroxides and the decrease of glutathione and ceruloplasmin.

Alanine Transaminase↗
PubMedDate not supplied

Studies on the intermolecular forces involved in the antibody-antigen interactions, using V3 synthetic peptides and sera from HIV1 seropositive patients.

The nature of physical forces responsible for the antibody-antigen (Ab-Ag) reaction was analyzed in an original system, represented by synthetic peptides derived from the V3 consensus sequences of some HIV1 subtypes gp 120 and HIV1 positive human serum. For locating antigenic determines, flexibility, hydrophilicity and hydrophobicity profiles of the V3 peptides were analysed. The hydrophilicity indicates that V3 apex borders are involved in the first stage of the reaction. The flexibility and hydrophobicity suggest that the apex of the V3 loop (GPGR/Q) is involved in the stabilization of the complex by hydrophobic interactions. Further, we followed up the influence of the dielectric constant and of the pH upon the forces established between Ab and Ag. Modifications in the dielectric constant and pH reveal a significant contribution of electrostatic and van der Waals forces in securing the intermolecular complementarity. D2O produces the highest augmentation of the antibody affinity for the most hydrophilic peptides, while a very slight one was recorded for the most hydrophobic sequence. A high affinity of antibodies for the peptides MN, R and Z was registered at an acid pH, when their His residue was protonated. On the contrary, no influence was recorded in the case of the peptide A, which does not contain any His residue.

Amino Acid Sequence↗
PubMedDate not supplied

Considerations about the prophylactic role of T cell vaccination in HIV infection.

The AIDS epidemic in Romania has properties that are both common to countries of Eastern Europe and unique to Romania. The unique aspects include the large number of cases in children infected parenterally and a relatively low but steadily increasing number of HIV infected adults. Other groups of children and adults were also exposed at risk to acquire HIV by transfusion with unscreened blood or by multiple parenteral treatments with potentially contaminated needles. Our hypothesis was that a substantial number of people in area of high endemicity was "silently" infected but did not undergo specific immune response or clinical signs. In an attempt to explore the possibility that immunization with autologous proteins (consequence of multiple transfusions) can play a role in the protection from HIV infection or in slowing down the progression of disease, we compared the incidence of autoantibodies (anti-nuclear, smooth muscle and anti-HEp-2) in a group of long survivors children with AIDS, in HIV infected children with rapid evolution and in adults at risk for parenteral acquisition of blood borne viral disease. We analyzed also the incidence of some blood borne viral infections and the presence of anti-HLA antibodies in the same groups of patients. Our results do not support the suggestion that HIV infection or AIDS can be prevented, respectively, delayed by T-cell vaccination.

Adolescent↗
PubMedDate not supplied

Preliminary results of HIV screening in sentinel facilities in Romania.

In the first months of 1994, 393 patients (random consecutive clinic attenders) from three sentinel clinics were tested for anti-V3 loop antibodies in ELISA with a branched synthetic peptide reproducing eight copies of full V3 sequence. Compared with a commercial HIV 1/2 ELISA kit the sensitivity of anti-V3 assay was 97.6% and the specificity 89.7%. The seroprevalence in women attending prenatal clinic was 7.54% and in children with multiple hospitalization record, 3.82%. Both heterosexual and parenteral transmission through unsafe medical practices fuel actual AIDS epidemic in Romania.

Adult↗