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Biomedical subjects

S Perez

Publications and source records attributed to S Perez.

At least 73 records · Page 4Linked to original sources
PubMed1989

Patterns of adenosine deaminase, ecto-5'-nucleotidase, poly(A)polymerase and surface light chain expression in chronic lymphocytic leukemias.

The levels of activity of three enzymes have been measured in the circulating malignant lymphocytes of 47 patients with B chronic lymphocytic leukemia (CLL). These were the purine degradative enzymes, adenosine deaminase (ADA) and ecto-5'-nucleotidase (5'NT) and the enzyme responsible for the polyadenylation of mRNA, poly(A) polymerase. The patterns of activity of the above enzymes and the expression of surface immunoglobulin light chains were examined. A heterogeneity in the specific activity of the enzymes was observed which could not be attributed to variations of the percentage of B lymphocytes. A positive correlation was found between ADA and poly(A)polymerase activity (r = 0.383, p less than 0.01). Furthermore, the expression of immunoglobulin light chain phenotype was inversely related to 5'NT specific activity; CLL cases in which less than 20% of the cells expressed lambda chain phenotype, presented 5'NT specific activity of 16.7 +/- 3.3 (S.E.) nmol/h/10(6) cells, whereas in CLL cases with more than 20% of the cells expressing this phenotype the enzyme specific activity was 4.8 +/- 1.6 (S.E.) nmol/h/10(6) cells (p less than 0.02). These findings suggest that the simultaneous determination of enzymatic activities and immunological markers, might be useful in defining subsets in CLL and the subsequent clinical treatment.

5'-Nucleotidase↗
PubMed1989

Hydrophobic cluster analysis of the primary sequences of alpha-amylases.

The amino acid sequences of 18 alpha-amylases have been compared by hydrophobic cluster analysis. The method was first calibrated with two alpha-amylases (Aspergillus oryzae and pig pancreas) whose three-dimensional structures are known. It was then applied to the other alpha-amylases resulting in straightforward sequence alignments which could be used for structure prediction. It was found that all alpha-amylases which were investigated display the same basic super-secondary structure with a (beta alpha)8 barrel. Most of the secondary structure elements of the protein cores could be assigned to segments of the amino acid sequences. In addition, six sub-families could be identified, based upon specific similarities occurring in the variable regions of alpha-amylases.

Amino Acid Sequence↗
PubMed1989

Effect of a uridine 5'-diphosphate glucose analogue on herpes simplex keratitis in rabbits and vaginal infection in guinea pigs.

A uridine 5'-diphosphate glucose analogue, active in vitro against herpes simplex type 1 and 2 viruses, was assayed in rabbit infected corneas with the above viruses. The infected eyes were treated by drug instillation thrice daily and evaluation of ocular lesion was performed by slit-lamp biomicroscopy. The compound [[[5'-(2'',3'',4'',6''-tetra-O-benzoyl-alpha-D-glucopyranosyl)oxy] carbonyl]amino)sulfonyl]uridine shows a moderate antiviral activity, resulting in a reduction in the severity of clinical illness during acute infection. Vaginal infection of guinea pigs with herpes simplex type 2 virus was treated topically by instillation twice daily with the compound. The effect on clinical evolution was related to viral shedding from the genital tract, and a moderate reduction of both parameters in respect to the infected untreated controls was observed.

Animals↗
PubMed1987

A colorimetric assay for the determination of 5'-nucleotidase activity.

A rapid, simple, quantitative and sensitive assay for the determination of 5'-nucleotidase has been developed. The method can be applied to both soluble and membrane bound forms of the leukocyte enzyme. Enzyme activity is determined by colorimetric estimation of NH3 released from adenosine, the product of 5'-nucleotidase activity in the presence of adenosine deaminase. The assay may be performed in microtitre plates and read with an automatic multiscan spectrophotometer. Thus it can be applied to a large number of samples for routine medical and research purposes.

5'-Nucleotidase↗
PubMed1987

Immunoregulatory effects of fraction 5 thymus peptides. I. Thymosin alpha 1 enhances while thymosin beta 4 suppresses the human autologous and allogeneic mixed lymphocyte reaction.

Thymosin alpha 1 and thymosin beta 4, two peptides isolated from preparations of calf thymus fraction 5, were tested in the human mixed lymphocyte reaction (MLR). Thymosin alpha 1 was found capable of enhancing both the allogeneic and autologous MLR. On the contrary, thymosin beta 4 suppressed MLR proliferative responses. Study of the responses of the T cell subpopulations revealed that T4+ (helper/inducer) cells but not T8+ (suppressor/cytotoxic) are responsible for the enhanced, proliferative response to allo- and autoantigens in the presence of thymosin alpha 1. Both the autologous and the allogeneic proliferative responses of either T4+ cells or T8+ cells were not influenced by the addition of thymosin beta 4 in the cultures. However, when T4+ and T8+ subsets were cocultured, thymosin beta 4 was capable of activating T8+ cells to suppress the allogeneic and the autologous proliferative response of T4+ cells. These studies show that thymosin fraction 5 peptides exert immunoregulatory effects on the human MLR proliferative responses in vitro.

Humans↗
PubMed1987

Effect of two thymosin fraction 5 polypeptides on human peripheral blood lymphocytes.

Thymosin fraction 5 polypeptides beta 4 and alpha 1 were tested for their ability to affect certain immunological parameters of human peripheral blood lymphocytes (PBL). PBL were cultured with various concentrations of the peptides for 24 hours. Thymosin beta 4 was found to induce a significant decrease in the expression of the Fc alpha receptors of PBL, as well as in their ability to express antibody dependent cellular cytotoxic (ADCC) activity. In addition, this peptide had the ability to increase the percentage of T4 lymphocytes in normal and immunosuppressed donors and to decrease the percentage of T8 positive cells in normal donors. Finally, beta 4 peptide caused a small increase in the capacity of peripheral blood lymphocytes to form sheep red blood cell (SRBC) rosettes (ER). In parallel experiments thymosin alpha 1 was found inactive. The results presented here indicate that thymosin beta 4 may be used as an immunoregulatory molecule in patients with immunodeficiencies.

Adjuvants, Immunologic↗
PubMed1987

Polyadenylic acid metabolizing enzyme levels during induction of differentiation in a human leukemia T-cell line with phorbol ester.

Induction of differentiation of MOLT3 cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) was found to affect the activity levels of the polyadenylic acid [poly(A)] metabolizing enzymes. TPA administration at a concentration of 16 nM resulted in an increase of poly(A) exonuclease and poly(A) polymerase activities after 2 and 2.5 hours, respectively, and in a decline to control levels thereafter. Cordycepin, an inhibitor of poly(A) polymerization, prevented the increasing binding of OKT11A monoclonal antibody induced by TPA treatment, whereas TPA-induced reduction in OKT6 monoclonal antibody binding persisted. The alterations in the poly(A) metabolizing enzyme activities following treatment of the cells with TPA, as well as the inhibitory effect of cordycepin, may suggest that these enzymes may be involved in the regulation of the differentiation process.

Antibodies, Monoclonal↗
PubMed1986

Dexamethasone caused alterations in poly(A) polymerase levels of a human leukemic cell line.

The effect of glucocorticosteroids upon the poly(A) synthetic and degrading activity has been studied in steroid sensitive and resistant human leukemic cell lines. At least a two-fold increase in the levels of poly(A) polymerase activity was found in soluble, cytoplasmic extracts from the steroid sensitive human malignant T-cells of the MOLT3 line after 24-h treatment with dexamethasone. Longer exposure time of the cultured cells to the steroid resulted in a gradual decrease of the poly(A) polymerase activity level. Pretreatment of the cells with progesterone, a competitive inhibitor of dexamethasone, prevented the dexamethasone induced increase in the level of poly(A) polymerase activity, while progesterone alone had no effect on the enzyme level. In contrast, the levels of poly(A) nucleases activity remained constant following steroid treatment. In the steroid resistant human leukemic B-cell line Daudi no alterations in the poly(A) metabolizing enzymes could be measured in response to dexamethasone. Thus we suggest that poly(A) polymerase levels may be used to predict sensitivity of leukemic cells to glucocorticosteroid treatment.

B-Lymphocytes↗
PubMed1985

Thymosin beta 4 induced phenotypic changes in Molt-4 leukemic cell line.

Thymosin beta 4 was tested for its ability to induce phenotypic changes in the human T-cell line Molt-4. Cells were cultured with nanogram concentrations of thymosin beta 4 for up to 16 days and were analyzed with a panel of monoclonal antibodies, sheep erythrocyte rosetting, peanut agglutinin binding (PNA) and an antibody to the enzyme, terminal deoxynucleotidyl transferase (TdT). Thymosin beta 4 induced Molt-4 cells to reduce the expression of a T-cell lineage specific antigen, with preferential expression on T blast-cells, detected by WT 1 monoclonal antibody. Thymosin beta 4 also induced an increase in sheep erythrocyte rosettes and PNA binding as well as an increased expression of OKT 11 A and OKT 8 in Molt-4 cells. TdT was found to be unchanged, however. Analysis of thymosin beta 4-treated cells with other monoclonal antibodies (OKT 3, OKT 6, OKT 9) showed no change when compared to controls. These results showed that thymosin beta 4 is capable of inducing phenotypic changes in Molt-4 cells. Such changes may represent a differentiation process of these cells through the early stages of the maturation process of thymus-dependent lymphocytes, albeit not to the stage of mature T cells.

Adult↗
PubMed1985

Establishment and characterization of a B-cell line from a patient with acute lymphoblastic leukemia.

A permanent lymphoblastoid cell line was established from the peripheral blood of a child with acute lymphoblastic leukemia. The cell line, designated SDK, grows in a stationary suspension culture, forming aggregates, in RPMI medium supplemented with 10% FCS, with a doubling time of 50-60 h. Immunologic markers and cytological features suggested that the SDK cells should be identified as being of B-cell origin. The cells failed to form rosettes with sheep erythrocytes, did not express T-cell antigens as defined by monoclonal antibodies, and exhibited surface and cytoplasmic immunoglobulin determinants. Chromosome analysis revealed the presence of three cell populations with (a) 46XY; (b) t(8q-; 14q+) or 2p-; 14q+) and (c) cells with unidentifiable markers. SDK demonstrated susceptibility to TPA-induced differentiation toward plasma cells.

Acid Phosphatase↗
PubMed1985

The biological effect of three thymosin fraction 5 polypeptides in the murine mixed lymphocyte reaction.

The biological effects of three thymosin fraction 5 polypeptides, designated as beta 10, beta 4, and alpha 1 were tested in the MLR of mouse splenocytes, lymph node cells and thymocytes against syngeneic or allogeneic stimulators. It was found that all three polypeptides, after in vivo and in vitro treatment of the responder cell population, could enhance the allogeneic MLR. These polypeptides were also able to induce significant syngeneic MLR in systems where responder cells were used against irradiated syngeneic splenocytes. In addition, while beta 4 was shown to have a weak stimulatory effect on allogeneic MLR utilizing thymocytes as the responder cell type, alpha 1 could strongly induce such responses when syngeneic splenocytes were included into the culture system. Preincubation of purified mature T cells or thymocytes with alpha 1 has shown these cells to be the target of this polypeptide action. Thus, it appears that thymosin fraction 5 polypeptides not only initiate differentiation processes of immature T cells, but also exert their effects on mature T lymphocytes.

Animals↗
PubMed1982

Imide derivatives of 3-nitro-1.8-naphthalic acid: their inhibitory activity against DNA viruses.

The antiviral action of a new drug, 5-amino-2-(dimethylaminoethyl)-benzo-[de]-isoquinolin-1.3-dione has been studied against herpes simplex type 2 (HSV-2) and adenovirus type 5 (Ad-5) grown in Vero cells. The concentration of the drug which gives a 5 log10 reduction in virus titer was 4 micrograms/ml (maximum tolerated concentration) for HSV-2. The anti-HSV-2 activity of this compound was one log. more powerful than that of iododeoxyuridine (IDU). At this concentration the drug shows virucidal activity against HSV-2. No inhibition was found when the drug was tested against Ad-5. The inhibition of virus production has been studied depending upon the amount of drug or virus, and drug addition-time after infection. Reversibility of inhibition after drug removal, and drug resistance in the presence of the drug have also been determined.

Adenine↗
PubMed1977

The inotropic memory of amphibian myocardium.

(1) Experimentally observed changes of contractile force induced by changes in the pattern of stimulation of frog ventricular myocardium were compared with predictions computed on the basis of a model for the contractile conditioning, proposed in a previous paper. (2) For this purpose, two functions (Potentiation and Inhibition) which describe in the model the effect of previous contractions, were determined experimentally. (3) It is shown that the model adequately predicts : force-frequency curve Inotropic Effect Curves at different basal frequencies, effect of the suppression of a contraction in a sequence of definite frequency, frequency-staircases, and strength-interval curves. (4) The formal characteristics of the model are discussed, and it is suggested that the potentiation mechanism results from the recirculation of activator calcium in two types of compartments, from which calcium passes to the myofilaments during the contractions or is lost to the exterior with first order kinetics during the rest period. Possible locations for these compartments are proposed. Various hypothesis on the nature of the inhibitory mechanism are considered.

Animals↗
PubMedDate not supplied

A ten-laboratory study of lomefloxacin (NY-198 or SC 47111) antimicrobial activity in Argentina.

The antimicrobial activity of a new fluoro-quinolone, lomefloxacin (NY-198, SC47111), was evaluated by standardized susceptibility testing methods at ten laboratories in Argentina. Lomefloxacin was found to be the most active drug against 1,316 recent clinical isolates compared directly to norfloxacin, co-trimoxazole, and gentamicin. Only 1.4% of Enterobacteriaceae were lomefloxacin-resistant (MIC greater than 4 micrograms/ml), and the lomefloxacin MIC90 for all staphylococci was 2 micrograms/ml, including methicillin-resistant isolates. Streptococci, enterococci, and some Pseudomonads (9% resistance) were less susceptible to lomefloxacin. Lomefloxacin was the most active against Neisseria gonorrhoeae strains compared to penicillin, cefuroxime, and spectinomycin. Among the tested Mycobacteria, only the nontuberculosis, slow growers had lomefloxacin MICs of greater than 4 micrograms/ml.

4-Quinolones↗